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ASN.1 Compiler Version 6.2 C/C++ User`s Manual Objective

1. generate C code C generate C cod c generate C code java generate Java code xsd lt filename gt generate XML schema definitions encoding rule options ber generate BER encode decode functions cer generate CER encode decode functions der generate DER encode decode functions per generate PER encode decode functions xer generate XER encode decode functions xml generate XML encode decode functions basic options asnstd lt std gt set standard to be used for parsing ASN 1 source file Possible values x208 x680 mixed default is x680 compact generate compact code compat lt version gt generate code compatible with previous compiler version lt version gt format is x x for example 5 3 config lt file gt specify configuration file depends compile main file and dependent IMPORT items I lt directory gt set import file directory lax do not generate constraint checks in code laxsyntax do not do a thorough ASN 1 syntax check Running ASNIC from the Command line list generate listing noContaining do not generate inline type for CONTAINING lt type gt nodecode do not generate decode functions noencode do not generat ncode functions noIndefLen do not generate indefinite length tests noObjectTypes do not gen types for items embedded in info objects noOpenExt do not generate open extension e
2. The My ops constraint on the opcode element specifies an information object set not shown that constrains the element value to one of the values in the object set The My ops opcode constraint on the argument element goes a step further it ties the type of the field to the type specified in the row that matches the given opcode value ASNIC generates an in memory table either an array or a list of structures for each of the items in the information object sets defined in a specification In the example above a table would be generated for the My ops information object set The code generated for the type would then use this table to verify that the given items in a structure that reference this table match the constraints The C or C type generated for the SEQUENCE above when tables is specified would be as follows typedef struct Invoke 108 Additional Code Generated with the tables option OSINT32 invokeID OPERATION_operationCode opcode ASN1Object argument Invoke This is almost identical to the type generated in the simple case The difference is the ASN1 Object type or ASNI TObject for C that is used instead of ASN OpenType This type is defined in the asn type h run time header file as follows typedef struct ASN10Object ASN10penTyp ncoded void decoded OSINT32 index This holds the value to be encoded or decoded in both encoded or decoded form The wa
3. if stat berDecStrmPeekTagAndLen amp ctxt amp tag amp len 0 rtxErrPrint amp ctxt return stat if msgtag TV_PersonnelRecord Step 4 Call decode function note last two args should always be ASNIEXPL and 0 stat asnlBSD_PersonnelRecord amp ctxt employee ASNIEXPL 0 155 Generated Streaming C Decode Method Format and Calling Parameters Step 5 Check return status if stat 0 process received data in employee variable else error processing er check for other known message types Need to reset all memory for next iteration rtxMemReset amp ctxt end of loop Step 6 Close the stream rtxStreamClose amp ctxt Remember to release dynamic memory when done rtFreeContext amp ctxt The only changes were the addition of the for loop and the call to rtxMemReset that was added at the bottom of the loop This function resets the memory tracking parameters within the context to allow previously allocated memory to be reused for the next decode operation Optionally rtxMemFree can be called to release all memory This will allow the loop to start again with no outstanding memory allocations for the next pass Generated Streaming C Decode Method Format and Calling Parameters Generated C streaming decode functions are invoked through the C class interface by calling the generated
4. Normally this would result in the addresses element being pulled out and used to create a temporary type with a name equal to SomePDU addresses as follows SomePDU addresses SEQUENCE OF AliasAddress 61 SET OF SomePDU SEQUENCE addresses SomePDU addresses However when the SEQUENCE OF element references a simple defined type as above with no additional tagging or constraint information an optimization is done to reduce the size of the generated code This optimization is to generate a common name for the new temporary type that can be used for other similar references The form of this common name is as follows _SeqOf lt elementProdName gt So instead of this SomePDU addresses SEQUENCE OF AliasAddress The following equivalent type would be generated _SeqOfAliasAddress SEQUENCE OF AliasAddress The advantage is that the new type can now be easily reused if SEQUENCE OF AliasAddress is used in any other element declarations Note the illegal use of an underscore in the first position This is to ensure that no name colli sions occur with other ASN 1 productions defined within the specification Some SEQUENCE OF elements in constructed types are inlined In other words no temporary type is created instead either the OSRTDList reference for linked list or the array definition is inserted directly into the generated C struc t
5. As per X 694 ASNIC generates a special type that acts as a container for all the different possible elements in the substitution group This is a choice type with the name lt BaseElement gt _group where lt BaseElement gt would be replaced with the name of the subsitution group head element MyBaseElement in this case The generated C type definitions for the above XSD definitions follow typedef const OSUTF8CHAR MyBaseElement typedef const OSUTF8CHAR MyExtendedElement define T_MyBaseElement_group_myBaseElement 1 define T_MyBaseElement_group_myExtendedElement 2 typedef struct EXTERN MyBaseElement_group int t union ADRENAL hy MyBaseEKlement myBaseElement ZEE 2 A MyExtendedElement myExtendedElement u MyBaseElement_group 101 Substitution Groups typedef struct EXTERN MyType MyBaseElement_group myBaseElement MyType typedef MyType MyElement In this case if My Element or MyType is used it can be populated with either base element or extended element data 102 Generated Encode Decode Function and Methods Encode Decode Function Prototypes If BER or DER encoding is specified a BER encode and decode function prototype is generated for each production DER uses the same form there are only minor differences between the two types of generated functions These prototypes are of the
6. C or cpp None Generate C source code cer None This option instructs the compiler to generate functions that implement the Canonical Encoding Rules CER as specified in the X 690 ASN 1 standard cfile lt filename gt This option allows the specification of a C or C source c or cpp file to which all of the generated encode de code functions will be written If not specified the default is to write to a series of c or cpp files based on the ASN 1 module name s of the documents being compiled compact None This option instructs the compiler to generate more com pact code at the expense of some constraint and error checking This is an optimization option that should be used after an application is thoroughly tested compat lt versionNumber gt Generate code compatible with an older version of the compiler The compiler will attempt to generate code more closely aligned with the given previous release of the com piler lt versionNumber gt is specified as x x for example com pat 5 2 config lt filename gt This option is used to specify the name of a file containing configuration information for the source file being parsed A full discussion of the contents of a configuration file is provided in the Compiler Configuration File section depends None This option instructs the compiler to generate a full set of header and source files t
7. Step 4 Check the return status note the test is gt 0 because the returned value is the length of the encoded message component if msglen gt 0 Step 5 If encoding is successful call xe_getp to fetch a pointer to the start of th ncoded message msgptr xe_getp amp ctxt 127 Generated C Encode Method Format and Calling Parameters else rtxErrPrint amp ctxt return msglen In general static buffers should be used for encoding messages where possible as they offer a substantial performance benefit over dynamic buffer allocation The problem with static buffers however is that you are required to estimate in advance the approximate size of the messages you will be encoding There is no built in formula to do this the size of an ASN 1 message can vary widely based on data types and the number of tags required If performance is not a significant issue then dynamic buffer allocation is a good alternative Setting the buffer pointer argument to NULL in the call to xe_setp specifies dynamic allocation This tells the encoding functions to allocate a buffer dynamically The address of the start of the message is obtained as before by calling xe_getp Note that this is not the start of the allocated memory that is maintained within the context structure To free the memory the rt MemFree run time macro must be called The following code fragment illustrates encoding using a
8. class S1AP_ELEMENTARY PROCEDURES public enum TVALUE T_UNDEF_ T_handoverPreparation T_handoverResourceAllocation T_pathSwitchRequest a In this case the type number identifier is not needed because the class name provides for unambiguous enumerated item names Generated Helper Methods For C special asnlAppend_ lt name gt and asn1GetIE_ lt name gt functions were generated to help a user append information elements IE s to a list and get an indexed IE respectively For C these are added as methods to the generated control class for the list type For example for the HandoverRequired_protocolIEs type the following methods are added to the control class class EXTERN ASN1C_HandoverRequired_protocolIEs public ASN1CSeqOfList Append IE 1 with value type ASNIT_MME_UE_S1AP_ID to list int AppendIE1 ASN1T_MME_UE_S1AP_ID value 81 Legacy Table Constraint Model Append IE 2 with value type ASN1T_HandoverType to list int AppendIE2 ASN1T_HandoverType value Get IE using id key value ASN1T_HandoverRequired_protocollIEs_element GetIE ASN1T_ProtocolIE_ID id i T T Legacy Table Constraint Model The legacy table constraint model exists in ASN1C v6 1 and older and supports a wider variety of uses of table constrains than the 3GPP model This model also may be used with 3GPP specifications as well The pri
9. lt perEncoding gt lt perEn hex data This variable allows a user to substitute a known binary coding gt PER encoding for the given element This encoding will be inserted into the encoded data stream on encoding and skipped over on decoding Its purpose is the production of more compact and faster code for PER by bypassing run time calculations needed to encode or decode variable data lt storage gt lt storage gt dynamic static list array The definition is the same as for the global case except or dynamicArray keyword that the specified storage type will only be applied to the generated C or C type for this element Compiler Error Reporting Errors that can occur when generating source code from an ASN 1 source specification take two forms syntax errors and semantics errors Syntax errors are errors in the ASN 1 source specification itself These occur when the rules specified in the ASN 1 grammar are not followed ASNIC will flag these types of errors with the error message Syntax Error and abort compilation on the source file The offending line number will be provided The user can re run the compilation with the I flag specified to see the lines listed as they are parsed This can be quite helpful in tracking down a syntax error The most common types of syntax errors are as follows e Invalid case on identifiers module name must begin with an uppercase letter productions types must be
10. ASN 1 specific Status Messages The following table describes status messages that may arise during the course of encoding or decoding an ASN 1 message The errors below indicate that while the system was able to read the data successfully it was unable to decode it properly Error Code Error Name Description 2 ASN_OK_FRAG Fragment decode success status This is returned when de coding is successful but only a fragment of the item was decoded User should repeat the decode operation in order to fully decode message 100 ASN_E_BASE Error base ASN 1 specific errors start at this base number to distinguish them from common and other error types ASN_E_BASE ASN_E_BASE 1 ASN_E_INVOBJID ASN_E_INVLEN Invalid object identifier This error code is returned when an object identifier is encountered that is not valid Possi ble reasons for being invalid include invalid first and sec ond arc identifiers first must be 0 1 or 2 second must be less than 40 not enough subidentifier values must be 2 or more or too many arc values maximum number is 128 Invalid length This error code is returned when a length value is parsed that is not consistent with other lengths in a BER or DER message This typically happens when an inner length within a constructed type is larger than the outer length value ASN_E_BASE 2 ASN_E BADTAG Bad tag value This error code is returned when a tag value is pars
11. if out getStatus 0 printf Encoding failed Status i n out getStatus out printErroriInfo return 1 if trace printf Encoding was successful n Generated BER Decode Functions NOTE This section assumes standard memory buffer based decoding is to be done If stream based decoding is to be done specified by adding stream to the ASN1C command line see the Generated BER Streaming Decode Functions section for correct procedures on using the stream based functions 139 Generated C Function Format and Calling Parameters For each ASN 1 production defined in an ASN 1 source file a C decode function is generated This function will decode an ASN 1 message into a C variable of the given type If C code generation is specified a control class is generated that contains a Decode method that wraps this function This function is invoked through the class interface to decode an ASN 1 message into the variable referenced in the msgData component of the class Generated C Function Format and Calling Parameters The format of the name of each decode function generated is as follows asnlD_ lt prefix gt lt prodName gt where lt prodName gt is the name of the ASN 1 production for which the function is being generated and lt prefix gt is an optional prefix that can be set via a configuration file setting The configuration setting used to set the prefix is the lt typePrefix gt element
12. Test DEFINITIONS BEGIN A NULL END The usual class definition for this specification looks like this class EXTERN ASNIC_A public ASN1CType protected public 39 Generated Encode Decode Function and Methods ASNIC_A ASN1C_A OSRTMessageBufferIF amp msgBuf ASNIC_A OSRTContext amp context standard encode decode methods defined in ASNICType base class int Encode int Decode stream encode decode methods int EncodeTo OSRTMessageBufferIF amp msgBuf int DecodeFrom OSRTMessageBufferIF amp msgBuf 5 It is very similar to the Symbian class definition class ASNI1C_A public ASN1CType protected public EXTERN ASNIC_A EXTERN ASNIC_A OSRTMessageBufferIF amp msgBuf EXTERN ASN1C_A OSRTContext amp context standard encode decode methods defined in ASNICType base class int Encode int Decode stream encode decode methods EXTERN int EncodeTo OSRTMessageBufferIF amp msgBuf EXTERN int DecodeFrom OSRTMessageBufferIF amp msgBuf a Note the use of EXTERN in the generated code it prefixes the constructors and the encoding and decoding functions but not the class declaration These prefixes are repeated in the implementation EXTERN ASN1C_A ASN1C_A ASN1CType Users should not have to modify generated code for use on the Symbia
13. lt ModuleName gt Table h lt ModuleName gt Table c cpp In this definition lt ModuleName gt would be replaced with the name of the ASN 1 module in which the information object is defined C Code Generation For C a global variable is generated to hold the information object definition This is very similar to the code generated for a value definition An example of an information object definition that is derived from the ASN 1 ATTRIBUTE class above is as follows name ATTRIBUTE WITH SYNTAX VisibleString ID 011 This results in the generation of the following C constant ATTRIBUTE name Code generated in information object initialization function name TypeSize sizeof _name_Type 87 Legacy Table Constraint Model name encodeType amp asnlE__name_Type name decodeType amp asnlD__name_Type name id numids 3 name id subid 0 O name id subid 1 1 name id subid 2 1 C Code Generation The C classes generated for ASN 1 information objects are derived from the ASN 1 class objects The constructors in these classes populate the fixed type field member variables with the values specified in the information object The classes also implement the virtual methods generated for the information object type fields All non optional methods are required to be implemented The optional methods are only implemented if they are defined in the information object definition An
14. 2 Create a variable of that type and assign a pointer to it to the Asn Object decoded member variable as void 3 Follow the common BER PER DER encode procedure A complete example showing how to assign an open type value is as follows Test DEFINITIONS BEGIN 111 General Procedure for Table Constraint Encoding r ATTRIBUTE CLASS amp Type amp id OBJECT IDENTIFIER UNIQU WITH SYNTAX WITH SYNTAX amp Type ID amp id GI name ATTRIBUTE WITH SYNTAX VisibleString ID 011 name ATTRIBUTE WITH SYNTAX INTEGER ID 012 SupportedAttributes ATTRIBUTE name commonName Invoke SEQUENCE opcode ATTRIBUTE amp id SupportedAttributes argument ATTRIBUTE amp Type SupportedAttributes opcode END In the above example the Invoke type contains a table constraint Its element opcode refers to the ATTRIBUTE id field and argument element refers to the ATTRIBUTE Type field The opcode element is an index element for the Invoke type s table constraint The argument element is an open type whose type is determined by the opcode value In this example opcode is the key field The opcode element can have only two possible values 0 1 1 or 0 1 2 If the opcode value is 0 1 1 then argument will have a VisibleString value and if the opcode value is 0 1 2 then argument will have an INTEGER value Any other
15. Running ASNIC from the Command line Option Argument Description The lt filename gt argument to this option is option al If not specified the functions will be written to lt modulename gt Test c where lt modulename gt is the name of the module from the ASN 1 source file hfile lt filename gt This option allows the specification of a header h file to which all of the generated typedefs and function pro totypes will be written If not specified the default is lt modulename gt h where lt modulename gt is the name of the module from the ASN 1 source file lt directory gt This option is used to specify a directory that the compil er will search for ASN 1 source files for IMPORT items Multiple I qualifiers can be used to specify multiple di rectories to search java None Generate Java source code See the ASNIC Java User s Guide for more information on Java code generation lax None This option instructs the compiler to not generate code to check constraints When used in conjunction with the compact option it produces the smallest code base for a given ASN 1 specification laxsyntax None This option instructs the compiler to not do a thorough syntax check when compiling a specification and to gen erate code even if the specification contains non fatal syn tax errors Use of the code generated in this case can have unpredictable results however
16. The calling sequence for the generated C class method is as follows len lt object gt Encode In this definition lt object gt is an instance of the control class i e ASN1C_ lt prodName gt generated for the given production The function result variable len returns the length of the data actually encoded or an error status code if encoding fails Error status codes are negative to tell them apart from length values Return status values are defined in the asnItype h include file Procedure for Calling C Encode Functions This section describes the step by step procedure for calling a C BER or DER encode function This method must be used if C code generation was done This method can also be used as an alternative to using the control class interface if C code generation was done Note that the procedures described here cannot be used if stream based encoding is to be done specified by the use of the stream ASN1C command line option In this case the procedures described in the Generated BER Streaming Encode Functions section Before any encode function can be called the user must first initialize an encoding context This is a variable of type OSCTXT This variable holds all of the working data used during the encoding of a message The context variable is declared as a normal automatic variable within the top level calling function It must be initialized before use This can be accomplished by using the rtInitContext f
17. canonical XER flag 174 Procedure for Using the C Control Class Encode Method OSBOOL aligned TRUE Employee employee typedef generated by ASNIC Initialize context and set encode buffer pointer if rtInitContext amp ctxt 0 return 1 xerSetEncBufPtr amp ctxt msgbuf sizeof msgbuf cxer Populate variable with data to be encoded mployee name givenName John Encode data stat asnlXE_Employee amp ctxt amp employee 0 0 if stat 0 msglen xerGetMsgLen amp ctxt else error processing rtFreeContext amp ctxt release the context pointer After encoding is complete msgbuf contains the XML textual representation of the data By default a UTF 8 encoding is used For the ASCII character set this results in a buffer containing normal textual data Therefore the contents of the buffer are represented as a normal text string and can be displayed using the C printf run time function or any other function capable of displaying text Procedure for Using the C Control Class Encode Method The procedure to encode a message using the C class interface is as follows 1 Instantiate an ASN 1 XER encode buffer object ASNIXEREncodeBuffer to describe the buffer into which the message will be encoded Constructors are available that allow a static message buffer to be specified and or canon ical encoding to b
18. int Decode stream encode decode methods int EncodeTo ASN1MessageBufferIF amp msgBuf int DecodeFrom ASN1MessageBufferIF amp msgBuf EXTERN int asnlE_EmployeeNumber OSCTXT pctxt ASN1T_EmployeeNumber pvalue ASNl1TagType tagging EXTERN int asnlD_EmployeeNumber OSCTXT pctxt ASN1T_EmployeeNumber pvalue ASNl1TagType tagging int length Note the two main differences between this and the C version 1 The use of the ASN T_ prefix on the type definition The C version uses the ASN T_ prefix for the typedef and the ASN C_ prefix for the control class definition 2 The inclusion of the ASN1C_EmployeeNumber control class As of ASNIC version 5 6 control classes are not automatically generated for all ASN 1 types The only types they are generated for are those determined to be Protocol Data Units or PDU s for short A PDU is a top level message 34 Header h File type in a specification These are the only types control classes are required for because the only purpose of a control class is to provide the user with a simplified calling interface for encoding and decoding a message They are not used in any of the ASNIC internally generated logic the exception to this rule is the XER XML encoding rules where they are used internally and still must be generated for all types A type is determined to be a PDU in two different ways 1 If it is explicitly declared
19. ASN1I1 Check return status employee EXPL 0 variable Remember to release dynamic memory when done rtFreeContext amp Ctxt 0 154 Generated Streaming C Function Format and Calling Parameters Decoding a Series of Messages Using the Streaming C Decode Functions The above example is fine as a sample for decoding a single message but what happens in the more typical scenario of having a long running loop that continuously decodes messages It will be necessary to put the decoding logic into a loop A code fragment showing a way to do this is as follows include employee h include file generated by ASNIC include rtxsrc rtxStreamFile h main ASNITAG msgtag int msglen stat OSCTXT ctxt PersonnelRecord employee const char filename message dat Step 1 Initialize a context variable for decoding if berStrmInitContext amp ctxt 0 initialization failed could be a license problem printf context initialization failed check license n return 1 Step 2 Open the input stream to read data stat rtxStreamFileCreateReader amp ctxt filename if stat 0 rtxErrPrint amp ctxt return stat for Step 3 Test message tag for type of message received note this is optional the decode function can be called directly if the type of message is known
20. Add a header guard prefix Add a C namespace Table Constraint Options I Generate code to Fully encode decode items with table constraints tables I Enable strict constraint checks on all table constraint items strict Generate code optimized for 3GPP specifications Event Handler Options I7 Generate code to invoke event handler callback Functions events Generate pure parser event handler callbacks with no types notypes r Output File Options Output code to c h files based on module names Max lines per file Output each generated function to a separate source file maxcfiles Output all code to a single c hfile c A The Generate static elements option is used to add static elements to CHOICE constructs instead of pointer values The compiler automatically attempts to resolve name collisions when items in different modules have the same names If it is necessary to have unique non generated item names uncheck Automatically create unique names for duplicate items Click on Help to get a summary of what each of these options do or read the section Running ASNIC from the Command line All of these items are optional Some items will be grayed out if they are not applicable to the encoding tules or language previously selected 21 C C Code Generation Options The final C C code generation options window follows ASNIC compiler Objective
21. As with other constructed types the lt t ype gt variable can reference any ASN 1 type including other ASN 1 con structed types Therefore it is possible to have a SEQUENCE OF SEQUENCE SEQUENCE OF CHOICE etc When a constructed type or type that maps to a C structured type is referenced a temporary type is generated for use in the final production The format of this temporary type name is as follows lt prodName gt _element In this definition lt prodName gt refers to the name of the production containing the SEQUENCE OF type For example a simple and very common single level nested SEQUENCE OF construct might be as follows A SEQUENCE OF SEQUENCE a INTEGER b BOOLEAN In this case a temporary type is generated for the element of the SEQUENCE OF production This results in the following two equivalent ASN 1 types A element SEQUENCE a INTEGER b BOOLEAN A SEQUENCE OF A element These types are then converted into the equivalent C or C t ypede fs using the standard mapping that was previously described SEQUENCE OF Type Elements in Other Constructed Types Frequently a SEQUENCE OF construct is used to define an array of some common type in an element in some other constructed type for example a SEQUENCE An example of this is as follows SomePDU SEQUENCE addresses SEQUENCE OF AliasAddress
22. msgptr encodeBuffer getMsgPtr len encodeBuffer getMsgLen else printf Encoding failed n encodeBuffer printErroriInfo exit 0 return 0 Encoding a Series of PER Messages using the C Inter face When encoding a series of PER messages using the C interface performance can be improved by reusing the message processing objects to encode each message rather than creating and destroying the objects each time A detailed example of how to do this was given in the section on BER message encoding The PER case would be similar with the PER function calls substituted for the BER calls As was the case for BER the encode message buffer object init method can be used to reinitialize the encode buffer between invocations of the encode functions Generated PER Decode Functions PER encode decode functions are generated when the per switch is specified on the command line For each ASN 1 production defined in the ASN 1 source file a C PER decode function is generated This function will parse the data contents from a PER encoded ASN 1 message and populate a variable of the corresponding type with the data If C code generation is specified a control class is generated that contains a Decode method that wraps this function This function is invoked through the class interface to encode an ASN 1 message into the variable referenced in the msgData component of the class 166 Generated C Function
23. The difference between the two is the C version includes constructors that initialize the value and methods for setting the value The ASN 1 DynBitStr type i e the type used in the C mapping is defined in the asn1type h header file as follows typedef struct ASN1DynBitStr OSUINT32 numbits const OSOCTET data ASN1IDynBitStr The ASNITDynBitStr type is defined in the asn CppTypes h header file as follows struct ASNITDynBitStr public ASN1DynBitStr ctors 45 BIT STRING ASN1TDynBitStr numbits 0 ASNITDynBitStr OSUINT32 _numbits OSOCTET _data j ASN1TDynBitStr ASN1IDynBitStr _bs ASNITDynBitStr Note that memory management of the byte array containing the bit string data is the responsibility of the user The wrapper class does not free the memory on destruction nor deep copy the data when a string is copied Static sized BIT STRING ASN 1 production lt name gt BIT STRING SIZE lt len gt Generated C code typedef struct OSUINT32 numbits OSOCTET data lt adjusted_len gt lt name gt Generated C code typedef struct lt name gt OSUINT32 numbits OSOCTET data lt adjusted_len gt ctors ASN1T_ lt name gt ASN1T_ lt name gt OSUINT32 _numbits const OSOCTET _data ASNIT_ lt name gt T lt adjusted_len gt lt len gt 1 8 1 For example the following ASN 1 production BS PR
24. else 143 Generated C Decode Method Format and Calling Parameters handle error for offset lt msglen xd_setp amp ctxt msgbuf offset msglen offset amp msgtag amp len Decode if tag TV_PersonnelRecord Call compiler generated decode function stat asnlD_PersonnelRecord amp ctxt amp employee ASN1EXPL 0 if stat 0 decoding successful data in employee else error handling return 1 else printf unexpected tag hx received n tag offset ctxt buffer byteIndex rtxMemReset amp ctxt Generated C Decode Method Format and Calling Pa rameters Generated decode functions are invoked through the class interface by calling the base class Decode method The calling sequence for this method is as follows status lt object gt Decode In this definition lt object gt is an instance of the control class i e ASN1C_ lt prodName gt generated for the given production An ASNIBERDecodeBuffer object reference is a required argument to the lt object gt constructor This is where the message start address and length are specified The message length argument is used to specify the size of the message if it is known In ASN 1 BER or DER encoded messages the overall length of the message is embedded in the first few bytes of the message so this variable is not required It is used as a test mechanism t
25. An xsd anyAttribute declaration is the attribute equivalent to the xsd any wildcard element declaration described earli er The main difference is that a single xsd anyAttribute declaration indicates that any number of undeclared attributes may occur whereas xsd any without a maxOccurs facet indicates that only a single wildcard element may occur at that position X 694 models xsd anyAttribute as a SEQUENCE OF UTFSString in ASN 1 Each string in the sequence is expected to be ina name value format The generated C type for this is simply a linked list of character strings For example lt xsd complexType name MyType gt lt xsd anyAttribute processContents lax gt lt xsd complexType gt results in the following C type typedef struct EXTERN MyType List of const OSUTF8CHAR OSRTDList attr MyType To populate a variable of this type for encoding one would add name value strings to the list for each attribute For example MyType myVar rtxDListInit amp myVar attr rtxDListAppend amp ctxt amp myVar attr OSUTF8 attrl valuel 98 xsd simpleContent rtxDListAppend amp ctxt amp myVar attr OSUTF8 attr2 value2 and so on xsd simpleContent The xsd simpleContent type is used to either extend or restrict an existing simple type definition In the case of exten sion the common use is to add attributes to a simple type ASNIC will generate a C st
26. For this reason run time helper functions are provided that allow the user to control the size increment of buffer expansions See the C C Run Time Library Reference Manual for a description of these functions In either case after a message is encoded it is necessary to get the start address and length of the message Even in the static buffer case the message start address may be different then the buffer start address see the section on encoding BER messages For this reason each set of encoding rules has a run time C function for getting the message start address and length See the C C Run Time Library Reference Manual for a description of these functions The C message buffer classes contain the getMsgPtr getMsgCopy and getMsgLength methods for this purpose A stream message buffer can be used for BER encoding This type of buffer is used when the stream option was used to generate the encode functions See the section on BER stream encoding for a complete description on how to set up an output stream to receive encoded data 123 124 Generated BER Functions Generated BER Encode Functions Note This section assumes standard memory buffer based encoding is to be done If stream based encoding is to be done specified by adding stream to the ASNIC command line see the Generated BER Streaming Encode Functions section for correct procedures on using the stream based encode functions For each ASN 1 produc
27. Name gt lt xsd sequence gt lt xsd element name givenName type xsd string gt lt xsd element name initial type xsd string minOccurs 0 gt lt xsd element name familyName type xsd string gt 92 xsd all lt xsd sequence gt lt xsd complexType gt would result in the creation of the following C type definition typedef struct EXTERN Name struct unsigned initialPresent 1 m const OSUTF8CHAR givenName const OSUTF8CHAR initial const OSUTF8CHAR familyName Name xsdzall The xsd all type is similar to an ASN 1 SET in that it allows for a series of elements to be specified that can be transmitted in any order However due to some technicalities with the type it is modeled in X 694 to be a SEQUENCE type with a special embedded array called order This array specifies the order in which XML elements were received if XML decoding of an XML instance was done If this information were then retransmitted in binary using BER or PER the order information would be encoded and transmitted followed by the SEQUENCE elements in the declared order If the data were then serialized back into XML the order information would be used to put the elements back in the same order in which they were originally received The mapping to C type would be the same as for xsd sequence above with the addition of the special order array An example of this is as follows lt xsd complexType name Name g
28. PROCEDURE information objects union p uj Init procedureCode id HandoverPreparation criticality reject HandoverRequired handoverPreparation procedureCode id HandoverResourceAllocation criticality reject HandoverRequest handoverResourceAllocation procedureCode id HandoverNotification criticality ignore HandoverNotify handoverNotification CEC ilatingMessage Generated C Type Definitions for Information Element IE Types In addition to message types another common pattern in 3GPP specifications is protocol information element IE types The general form of these types is a list of information elements as follows lt ProtocollEsType gt lt ProtocollE ContainerType gt lt ObjectSet gt lt ProtocollIE ContainerType gt lt Class gt lt ObjectSetParam gt SEQUENCE SIZE lt size gt OF lt ProtocollIE FieldType gt ObjectSetParam lt ProtocollIE FieldType gt lt Class gt lt ObjectSetParam gt SEQUENCE T 78 3GPP Table Constraint Model lt element1l gt lt Class gt amp lt fixed type field gt ObjectSetParam lt element2 gt lt Class gt amp lt fixed type field gt ObjectSetParam element1 lt element3 gt lt Class gt amp lt Type field gt ObjectSetParam element1 There are a few different variations of this but the overall patter
29. The pct xt argument is used to hold a context pointer to keep track of decode parameters This is a basic handle variable that is used to make the function reentrant so it can be used in an asynchronous or threaded application The user is required to supply a pointer to a variable of this type declared somewhere in his or her program The pvalue argument is a pointer to a variable to hold the decoded result This variable is of the type generated from the ASN 1 production The decode function will automatically allocate dynamic memory for variable length fields within the structure This memory is tracked within the context structure and is released when the context structure is freed The function returns the status of the decode operation Status code zero indicates the function was successful A negative value indicates decoding failed Return status values are defined in the rtvErrCodes h include file The reason text and a stack trace can be displayed using the rtxErrPrint function Procedure for Calling C Decode Functions This section describes the step by step procedure for calling a C XML decode function This method must be used if C code generation was done This method can also be used as an alternative to using the control class interface if C code generation was done These are the steps involved calling a compiler generated decode function 1 Prepare a context variable for decoding 2 Open an input stream for the XML document
30. There are three different types of message buffers that can be described 1 static this is a fixed size byte array into which the message is encoded 2 dynamic in this case the encoder manages the allocation of memory to hold the encoded message 3 stream in this case the encoder writes the encoded data directly to an output stream The static buffer case is generally the better performing case because no dynamic memory allocations are required However the user must know in advance the amount of memory that will be required to hold an encoded message There is no fixed formula to determine this number ASN 1 encoding involves the possible additions of tags and lengths and other decorations to the provided data that will increase the size beyond the initial size of the populated data 122 Accessing Encoded Message Components structures The way to find out is either by trial and error an error will be signaled if the provided buffer is not large enough or by using a very large buffer in comparison to the size of the data In the dynamic case the buffer description passed into the encoder is a null buffer pointer and zero size This tells the encoder that it is to allocate memory for the message It does this by allocating an initial amount of memory and when this is used up it expands the buffer by reallocating This can be an expensive operation in terms of performance especially if a large number of reallocations are required
31. This can be used to prevent name clashes if multiple modules are involved in a compilation and they all contain common names lt enumPrefix gt lt enumPre prefix text This is used to specify a prefix that will be applied to all generated enumerated identifiers within a module This can be used to prevent name clashes if multiple modules are involved in a compilation note this attribute is nor mally not needed for C enumerated identifiers because they are already wrapped in a structure to allows the type name to be used as an additional identifier This is a flag variable an empty element in XML termi nology that specifies that this production will be used to store an integer larger than the C or C int type on the given system normally 32 bits A C string type char will be used to hold a textual representation of the value This qualifier can be applied to either an integer or con structed type If constructed all integer elements within the constructed type are flagged as big integers fix gt lt isBigInteger gt n a lt isPDU gt n a This is a flag variable that specifies that this production represents a Protocol Data Unit PDU This is defined as a production that will be encoded or decoded from with in the application code This attribute only makes a differ ence in the generation of C classes Control classes that are only used in the application code are only generated for type
32. by both interfaces is used to accomplish this Decoding a Series of Messages Using the C Control Class Inter face The above example is fine as a sample for decoding a single message but what happens in the more typical scenario of having a long running loop that continuously decodes messages The logic shown above would not be optimal from a performance standpoint because of the constant creation and destruction of the message processing objects It would be much better to create all of the required objects outside of the loop and then reuse them to decode and process each message A code fragment showing a way to do this is as follows include employee h include file generated by ASN1C main OSOCTET msgbuf 1024 ASNITAG msgtag int msglen status Create message buffer ASNIT and ASNIC objects ASNIBERDecodeBuffer decodeBuffer msgbuf len ASN1T_PersonnelRecord employeeData ASN1C_PersonnelRecord employ decodeBuffer employeeData for logic to read message into msgbuf status decodeBuffer ParseTagLen msgtag msglen if status 0 handle error Now switch on initial tag value to determine what type of message was received switch msgtag case TV_PersonnelRecord compiler generated constant if status employee Decode 0 146 Generated C Decode Method Format and Calling Parameters decoding successful da
33. const qname bi The main differences between the BER DER PER control class definition and this are 1 The class generated for XER inherits from the ASNIXERSAXHandler base class and 2 The class implements the standard SAX content handler methods This allows an object of this class to be registered as a SAX content handler with any SAX compliant XML parser The parser would be used to read and parse XML documents The methods generated by ASN1C would then receive the parsed data via the SAX interface and use the results to populate the data variables with the decoded data Note that for XML code generation xml command line option the SAX handler interface is not generated That is because XML decoders use a pull parser instead of SAX code to parse the XML input stream Generated Methods For each production an EncodeFrom and DecodeTo method is generated within the generated class structure These are standard methods that initialize context information and then call the generated C like encode or decode function If the generation of print functions was specified by including print on the compiler command line a Print method is also generated that calls the C print function For XER additional methods are generated to implement a SAX content handler interface to an XML parser This includes a startElement characters and endElement method An init and finalize method may also be generated to initialize a variable prior to p
34. employee h include file generated by ASNIC include rtxsrc rtxStreamFile h main ASNITAG msgtag int msglen OSCTXT ctxt PersonnelRecord employee const char filename message dat Step 1 Initialize a context variable for decoding 153 Generated Streaming C Function Format and Calling Parameters if berStrmInitContext initialization failed printf context return 1 amp ctxt could be a license problem initialization failed PO ef check license n Step 2 Open the input stream to read data stat rtxStreamFileCreateReader amp ctxt filename if stat 0 rtxErrPrint amp ctxt JE if if return stat Step 3 Test message tag for typ note this is optional r received called directly if the type of messag stat berDecStrmPeekTagAndLen amp ctxt rtxErrPrint amp ctxt return stat msgtag TV_PersonnelRecord of messag the decode function can be is known amp tag amp len Af ap Step 4 Call decode function note last two args should always be ASNIEXPL and 0 status asnlBSD_PersonnelRecord amp ctx amp employee Step 5 if status process else error processing else check for other known message types Step 6 Close the stream rtxStreamClose amp Ctxt received data in A alt
35. figuration items see the Compiler Configuration File sec tion for more details Previous versions of the compiler did not generate unique names by default The compiler option uniquenames has been deprecated in favor of nouniquenames This option is used to specify the name of a directory to which all of the generated files will be written lt directory gt This option is used to specify the name of a directory to which only the generated header files h will be written param lt name gt lt value gt This option is used to instantiate all parameterized types with the ASN 1 modules that are being compiled with the given parameter value In this declaration lt name gt refers to the dummy reference in a parameterized type definition and lt value gt refers to an actual value pdu lt typeName gt Designate given type name to be a Protocol Definition Unit PDU type This will cause a C control class to be generated for the given type By default PDU types are determined to be types that are not referenced by any other types within a module This option allows that behavior to be overridden The wildcard character may be specified for lt type Name gt to indicate that all productions within an ASN 1 module should be treated as PDU types per None This option instructs the compiler to generate functions that implement the Packed Encoding Rules PER as spec ified in the
36. lt color gt e The special REAL values lt PLUS INFINITY gt and lt MINUS INFINITY gt are represented as INF and INF re spectively e GeneralizedTime and UTCTime values are transformed into the XSD representation for dateTime Y YY Y MMD DTHH MM SS SSSS Zl l HH MM when encoded to XML When an XML document is decoded the time format is transformed into the ASN 1 format e An unnamed element in a SEQUENCE OF construct will be wrapped with the fixed keyword element In XER the non parameterized type name is used For example in the employee sample program the following element exists in the PersonnelRecord construct children 3 IMPLICIT SEQUENCE OF ChildInformation In XER this is encoded as follows lt children gt lt ChildInformation gt lt ChildInformation gt In XML it is as follows lt children gt lt element gt lt element gt It is done this way in order to match the XML schema generated for the ASN 1 specification Also if code is generated by compiling XML schema specifications the generated XML will contain features defined in the schema which cannot be specified using plain ASN 1 such as attributes and namespaces Note that it is possible to support these items if ASN 1 with Extended XER notation E XER is used but this is not supported by ASNIC Its method of supporting these constructs is the direct compilation of XML schema files It is also important to note tha
37. lt typel gt and lt type2 gt are the equivalent C types representing the ASN 1 types lt element 1 t ype gt and lt el ment 2 type gt respectively lt tempName1 gt and lt tempName2 gt represent the names of temporary types that may have been generated as the result of using nested constructed types within the definition Choice alternatives may be unnamed in which case lt element name gt is derived from lt element type gt by making the first letter lowercase One needs to be careful when nesting CHOICE structures at different levels within 63 CHOICE other nested ASN 1 structures SEQUENCES SETs or other CHOICEs A problem arises when CHOICE element names at different levels are not unique this is likely when elements are unnamed The problem is that generated tag constants are not guaranteed to be unique since only the production and end element names are used The compiler gets around this problem by checking for duplicates If the generated name is not unique a sequential number is appended to make it unique The compiler outputs an informational message when it does this An example of this can be found in the following production C CHOICE 0 INTEGER 1 CHOICE 0 INTEGER 1 BOOLEAN This will produce the following C code define T_C_alInt define T_C_aChoice define T_C_aInt_1l define T_C_aBool NO RPN FR typedef struct int t union OSINT3
38. prefix text setPrefix gt This is used to specify a prefix that will be applied to all generated items in a module derived from an ASN 1 In formation Object Set definition lt noPDU gt n a Indicates that this module contains no PDU definitions This is normally true in modules that are imported to get common type definitions for example Information Framework This will prevent the C version of the compiler from generating any control class definitions for the types in the module lt intCType gt byte intl6 uintl6 int32 uint32 int64 string This is used to specify a specific C integer type be used for all unconstrained integer types By default ASNIC will use the int32 32 bit integer type for all unconstrained in tegers lt arcCType gt int32 int64 The is used to specify a specific C integer type be used for the arc types in Object Identifier definitions By default int32 32 bit integer arc values are generated lt namespace gt pace gt lt names namespace URI This is used to specify the target namespace for the given module when generating XSD and or XML code By de fault the compiler will not include a targetNamespace di rective in the generated XSD code i e all items will not be assigned to any namespace This option only has mean ing when used with the xml xsd command line options Production Level These attributes can be applied at the pro
39. return 0 rtCmpTCOID amp id pvalue bi This assumes that only BER or DER was specified as the encoding rules type First notice that member variables have been generated for the fixed type fields in the definition These include the id field Information object classes derived from this definition are expected to populate these fields in their constructors Also virtual methods have been generated for each of the type fields in the class These include the Type fields The method generated for Type is abstract and must be implemented in a derived information object class The method generated for the ParameterType field has a default implementations that does nothing That is because it is a optional field Also generated are Equals methods for the fixed type fields These are used by the generated code to verify that data in a generated structure to be encoded or data that has just been decoded matches the table constraint values This method will be generated only if it is required to check a table constraint OPTIONAL keyword Fields within a CLASS can be declared to be optional using the OPTIONAL keyword This indicates that the field is not required in the information object An additional construct is added to the generated code to indicate whether an optional field is present in the information object or not This construct is a bit structure placed at the beginning of the generated structure This structure always has varia
40. value declaration is as follows ASN 1 production lt name gt lt EnumType gt lt value gt Generated code OSUINT32 lt name gt lt value gt Binary and Hexadecimal String Value Binary and hexadecimal string value specifications cause two global C variables to be generated a numoct s variable describing the length of the string and a data variable describing the string contents The mapping for a binary string is as follows note BIT STRING can also be used as the type in this type of declaration ASN 1 production lt name gt OCTET STRING lt bstring gt B Generated code 72 Character String Value OSUINT32 lt name gt _numocts lt length gt OSOCTET lt name gt _data lt data gt A hexadecimal string would be the same except the ASN 1 constant would end in a H Character String Value A character string declaration would cause aC or C const char declaration to be generated ASN 1 production lt name gt lt string type gt lt value gt Generated code const char lt name gt lt value gt In this definition lt string type gt could be any of the standard 8 bit characters string types such as A5String Printa bleString etc Note Code generation is not currently supported for value declarations of larger character string types such as BMPString is currently Object Identifier Value Specification Object identifier values result in a structure bei
41. 66 Time String Lyp si senere a ee a a e E E E E A EES TS 67 EXTERNA D o u E E EE V EE E E E EE EE E O EEE R SS 68 EMBEDDED PPV orati eds sereasdseects ade rests RO a NEEE A A AaS EENIA O SEEE E PRA ERES TESA EEOSE SSR 68 Parameterized Types isseire e E A E ts Geckos E EEE E E EE EEEE aeea Ee 69 Value Mappings eerren attest E E E A EE EEEE E aE SE EEE 70 BOOLEAN Valte posos eo arero o eSEE ne jester ETE EEEE E K dees EEE TE IEE 71 INTEGER Valle vests acces sc issncs aces da nanara Ssa E OPR AA OER PESER SEEE E SO OaS EEE NTER ESEA 71 READ Valte os iera E E EE E A EE E EEAS ERES ES EE eG 72 Enumerated Valtle Specification sss scssi iiine e a E sss bea dade ET E ES T2 Binary and Hexadecimal String Value 0 0 0 0 cece cece eee cence cece nneceneeeeeeeeseeeeeeeaesea sees sean scans 72 Character String Valle ss cosscsescecevgssccee sds seccssassccsn eds saseangsseosa ess EEPE ASET SAPE EPESI SPENDE ES PESES ede 73 iii ASNIC Object Identifier Value Specification eorpora eee cee cece ee E pe SEE ESENE To EEP AREE pE SN EE e 73 Constructed Type Values e na a a E Sere de Bae Sas be E nade dues ace E OA eae 73 Table Constraint Related Structures sinusno naene a EE des egaeetvonteanibel oes E a S EETAS 76 3GPP Table Constraint Model sis ener ar E R e E E EE E E R ERR 76 Legacy Table Constramt Mod l nasiona ene e ea e E E T E a a mens en 82 XSD TO C CH TYPEMAPPINGS ireid ee cas tect E E E E T E E teat E EEES 91 XSD SiMplesLY Pes
42. C class to hold the values The name of the header and source file are of the following format lt ModuleName gt Table h lt ModuleName gt Table c cpp 88 Legacy Table Constraint Model In this definition lt ModuleName gt would be replaced with the name of the ASN 1 module in which the information object is defined C Code Generation A C global variable is generated containing a static array of values for the ASN 1 CLASS definition Each structure in the array is the equivalent C structure representing the corresponding ASN 1 information object An example of an Information Object Set definition that is derived from the ASN 1 ATTRIBUTE class above is as follows SupportedAttributes ATTRIBUTE name commonName E This results in the generation of the following C constant ATTRIBUTE SupportedAttributes int SupportedAttributes_Size 2 ay Code generated in the Information Object Set initialization function SupportedAttributes 0 TypeSize sizeof _name_Type SupportedAttributes 0 ncodeType amp asnlE__name_Type SupportedAttributes 0 decodeType amp asnlD__name_Type SupportedAttributes 0 id numids 3 SupportedAttributes 0 id subid 0 0 SupportedAttributes 0 id subid 1 1 SupportedAttributes 0 id subid 2 1 SupportedAttributes 1 TypeSize sizeof _commonName_Type SupportedAttributes 1l ncodeType amp asnlE__commonName_Type Support
43. Ff AsciiString asciiString LOSES 2 AT EBCDICString eBCDICString u String To set the AsciiString choice value one would first declare an AsciiString variable populate it and then plug the address into a variable of type String structure as follows AsciiString asciiString String string asciiString Hello string t T_String_AsciiString string u asciiString amp asciiString It is also possible to allocate dynamic memory for the CHOICE union option variable but one must be careful to release this memory when done with the structure If the built in memory management functions macros are used rtxMem all memory used for the variables is automatically released when rtxMemFree is called Open Type Note The X 680 Open Type replaces the X 208 ANY or ANY DEFINED BY constructs An ANY or ANY DE FINED BY encountered within an ASN 1 module will result in the generation of code corresponding to the Open Type described below An Open Type as defined in the X 680 standard is specified as a reference to a Type Field in an Information Object Class The most common form of this is when the Type field in the built in TYPE IDENTIFIER class is referenced as follows TYPE IDENTIFIER amp Type See the section in this document on Information Objects for a more detailed explanation The Open Type is converted into a C or C structure used to model a dynamic OCTET STRING type This structure contains a poin
44. Format and Calling Parameters cece cece ceeecc ence eeeeeeeeeeeeeeeneeenes 125 Generated C Encode Method Format and Calling Parameters ce cceceeeceeeceeeceeeeeeeeee es 126 Generated BER Streaming Encode Functions 2 0 0 0 0 cceceee cece nce nece eee ecceeeeeeeeeeceeseaesea sees ecaneeae esas 133 Generated Streaming C Function Format and Calling Parameters ccc cece eeee eee eeeeeeeee 133 Generated Streaming C Encode Method Format and Calling Parameters e cece 137 Generated BER Decode Functions osiris seein ia EN E i i a essa eeaa seas cea N a Ei 139 Generated C Function Format and Calling Parameters ssseeesseeresrrsrrreesrrrresreresrrerrsrrerreees 140 Generated C Decode Method Format and Calling Parameters sse sseeeneseerrrrrerrerrrrrerrreeere 144 BER Decode Performance Enhancement Techniques cceceeeceeeceeece seca ceca seca eeae eeu ceneeeeeeeenees 148 Dynamic Memory Management cece cece cece cece cece eee ce cen een ceeeeeeeeeeeeeseeseaeeeaeeeaeeaeeeges 148 Compact Code Generation isya a n E patenco shen goopee andes paaeeate E EAS EEES 149 Decode Fast Copy o rescos a Sie Gas ah A EE ae Gas US R O E AAE 149 Using Initialization PUNCHONS aisre en e a E E EE A EAA E NEE NEEE NFE 150 BER DER Deferred Decoding e e a e E N E a ara dba A wees A A E Eae rE 150 Generated BER Streaming Decode Functions ssessesseesserrsrrerrsrrerrererrre
45. Format and Calling Parameters Generated C Function Format and Calling Parameters The format of the name of each generated PER decode function is as follows asnlPD_ lt prefix gt lt prodName gt where lt prodName gt is the name of the ASN 1 production for which the function is being generated and lt prefix gt is an optional prefix that can be set via a configuration file setting The configuration setting used to set the prefix is the lt typePrefix gt element This element specifies a prefix that will be applied to all generated typedef names and function names for the production The calling sequence for each decode function is as follows status asnlPD_ lt name gt OSCTXT pctxt lt name gt pvalue In this definition lt name gt denotes the prefixed production name defined above The pct xt argument is used to hold a context pointer to keep track of decode parameters This is a basic handle variable that is used to make the function reentrant so it can be used in an asynchronous or threaded application The user is required to supply a pointer to a variable of this type declared somewhere in his or her program The pvalue argument is a pointer to a variable to hold the decoded result This variable is of the type generated from the ASN 1 production The decode function will automatically allocate dynamic memory for variable length fields within the structure This memory is tracked within the context structure and is releas
46. Instantiate an ASN1C_TypeName object to decode the message This class associates the message buffer object with the object that is to receive the decoded data The results of the decode operation will be placed in the variable declared in step 2 4 Invoke the ASN1C_TypeName object Decode method This method initiates and invokes the XML parser s parse method to parse the document This in turn invokes the generated SAX handler methods 5 Release dynamic memory that was allocated by the decoder All memory associated with the decode context is released when both the ASN1 XERDecodeBuffer and ASN1C_TypeName objects go out of scope A program fragment that could be used to decode an employee record is as follows int main int argc char argv const char filename employee xml int stat steps 1 2 and 3 instantiate an instance of the XER decoding classes This example specifies an XML file 180 Procedure for Interfacing with Oth er C and C X ML Parser Libraries as the message input source ASN1T_PersonnelRecord employee ASN1IXERDecodeBuffer decodeBuffer filename ASN1C_PersonnelRecord employeeC decodeBuffer employee step 4 invoke the decode method stat employeeC Decode if 0 stat employeeC Print employee else decodeBuffer printErrorinfo step 5 dynamic memory is released when employeeC and decode buffer objects go out o
47. Manual for a full description of these functions For C the ASN TSeqOfList class is used or in the case of PDU types the ASNJTPDUSegqOfList class The ASNITSeqOfList extends the C OSRTDList structure and adds constructors and other helper methods The ASNITPDUSeqOfList is similar except that it also extends the ASNJTPDU base class to add additional memory man agement capabilities needed by PDU types to automatically release memory on destruction See the ASNI CSeqOfList section in the C C Common Run time Reference Manual for details on all of the methods available in this class Populating Linked List Structures Populating generated list based SEQUENCE OF structures for the most part requires the use of dynamic memory to allocate elements to be added to the list note that it is possible to use static elements for this but this is unusual The recommended method is to use the built in run time memory management facilities available within the ASN1C runtime library This allows all list memory to be freed with one call after encoding is complete In the case of C the rtxMemAlloc or rtxMemAllocType function would first be used to allocate a record of the element type This element would then be initialized and populated with data The rtxDListAppend function would then be called to append it to the given list For C the compiler generates the helper methods NewElement and Append in the generated control class for a SEQUENCE OF type An i
48. Procedure for Table Constraint Decoding Test_init amp ctxt Step 3 Populate the structure to b ncoded msgData opcode numids 3 msgData opcode subid 0 0 msgData opcode subid 1 1 msgData opcode subid 2 1 note opcode value is 0 1 1 so argument must be ASN1IVisibleString type ASN1VisibleString argument objsys msgData argument decoded void amp argument Step 4 Call the generated encode function msglen asnlE_Invoke amp ctxt amp invoke ASNI1EXPL Step 5 Check the return status note the test is gt 0 because the returned value is the length of the encoded message component if msglen gt 0 Step 6 If encoding is successful call xe_getp to fetch a pointer to the start of th ncoded message msgptr xe_getp amp ctxt else error processing General Procedure for Table Constraint Decoding The general procedure to decode an ASN 1 message with table constraints is the same as without table constraints The only difference will exist in the decoded data for open type fields within the message In this case the Asn Object AsnITObject s decoded member variable will contain the original decoded type and the encoded member variable will contain the original data in encoded form Refer to the BER DER PER decoding procedure for further information The procedure to retrieve the value for op
49. This element specifies a prefix that will be applied to all generated typedef names and function names for the production The calling sequence for each decode function is as follows status asnlD_ lt name gt OSCTXT pctxt lt name gt pvalue ASNiTagType tagging int length In this definition lt name gt denotes the prefixed production name defined above The pct xt argument is used to hold a context pointer to keep track of decode parameters This is a basic handle variable that is used to make the function reentrant so it can be used in an asynchronous or threaded application The user is required to supply a pointer to a variable of this type declared somewhere in his or her program The variable must be initialized using the rtInitContext run time function before use The pvalue argument is a pointer to a variable of the generated type that will receive the decoded data The tagging and length arguments are for internal use when calls to decode functions are nested to accomplish decoding of complex variables At the top level these parameters should always be set to the constants ASNIEXPL and zero respectively The function result variable status returns the status of the decode operation The return status will be zero if decoding is successful or negative if an error occurs Return status values are defined in the asn1type h include file Procedure for Calling C Decode Functions This section describes the step by ste
50. a pointer to a variable of this type declared somewhere in his or her or her program The value argument contains the value to be encoded or holds a pointer to the value to be encoded This variable is of the type generated from the ASN 1 production The object is passed by value if it is a primitive ASN 1 data type such as BOOLEAN INTEGER ENUMERATED etc It is passed using a pointer reference if it is a structured ASN 1 type value in this case the name will be pvalue instead of value Check the generated function prototype in the header file to determine how this argument is to be passed for a given function The elemName and attributes arguments are used to pass the XML element name and attributes respectively The elemName argument is the name that will be included in the lt name gt lt name gt brackets used to delimit an XML item There are three distinct ways this argument can be specified 1 If it contains standard text this text will be used as the element name 173 Generated C Encode Method Format and Calling Parameters 2 If it is null a default element name will be applied Default names for all of the built in ASN 1 types are defined in the 2002 X 680 standard For example lt BOOLEAN gt is the default element name for the BOOLEAN built in type 6699 3 If the name is empty i e equal to is applied to the encoded data a zero length string not to be confused with null then no element name Th
51. and c are complete The name of the element is once again passed to the event handling callback function 3 contents methods A series of virtual methods are defined to pass all of the different types of primitive values that might be encountered when parsing a message see the event handler class definition below for a complete list 4 error This event will be fired when a parsing error occurs It will provide fault tolerance to the parsing process as it will give the user the opportunity to fix or ignore errors on the fly to allow the parsing process to continue 203 How to Use It These events are defined as unimplemented virtual methods in two base classes Asn NamedEventHandler the first 3 events and Asn ErrorHandler the error event These classes are defined in the asn CppEvtHndlr h header file The start and end element methods are invoked when an element is parsed within a constructed type The start method is invoked as soon as the tag length is parsed in a BER message or the preamble length is parsed in a PER message The end method is invoked after the contents of the field are processed The signature of these methods is as follows virtual void startElement const char name int index 0 virtual void endElement const char name int index 0 The name argument is used pass the element name The index argument is used for SEQUENCE OF SET OF constructs only It is used to pass the index of the item
52. and print to stream These allow the contents of generated types to be printed to the standard output a string or a stream such as a file or socket To reduce the code footprint several other options may be selected Do not generate indefinite length processing code Do not generate code to save restore unknown extensions Do not generate code to check constraints and Generate compact code may all be used to reduce the amount of generated code at the expense of some error checking Generate compact code cannot be used in conjunction with Generate compatible code Checking Generate compatible code will activate a drop down menu from which the compiler version may be selected No guarantee is made that the generated code will align exactly with what would be generated by the previous version but it will be similar This is useful in situations where upgrading the software may introduce test faults More C C options follow 20 C C Code Generation Options ASNIC compiler Objective Systems Inc objective SYSTEMS INC C C Code Generation Options Generated C C Type Modifiers Generate static member variables in choice constructs static Generate short Form of type names shortnames I Use Fully qualified enums JV Automatically create unique names for duplicate items Treat all types as Protocol Data Units PDU s pdu Generate code compatible with Symbian OS for DLLs
53. class derived from the Asn NamedEventHandler base class as follows 204 How to Use It class PrintHandler public AsnlNamedEventHandler protected const char mVarName int mIindentSpaces public PrintHandler const char varName PrintHandler void indent virtual void startElement const char name int index 1 virtual void endElement const char name int index 1 virtual void boolValue OSBOOL value other virtual contents method declarations In this definition we chose to add the mVarName and mIndentSpaces member variables to keep track of these items The user is free to add any type of member variables he or she wants The only firm requirement in defining this derived class is the implementation of the virtual methods We implement these virtual methods as follows In startElement we print the name equal sign and opening brace void PrintHandler startElement const char name int index indent printf s n name mindentLevelt t In this simplified implementation we simply indent this is another private method within the class and print out the name equal sign and opening brace We then increment the indent level Note that this is a highly simplified form We don t even bother to check if the index argument is greater than or equal to zero This would determine if a x should be appended to the element name In the
54. context initialization failed check license n return 1 rtxStreamInit amp ctxt Initialize stream The next step is to create a stream object within the context This object is an abstraction of the output device to which the data is to be encoded and is initialized by calling one of the following functions e rtxStreamFileOpen e rtxStreamFileAttach e rtxStreamSocketAttach e rtxStreamMemoryCreate e rtxStreamMemoryAttach The flags parameter of these functions should be set to the OSRTSTRMF_INPUT constant value to indicate an input stream is being created see the C C Common Run Time Library Reference Manual for a full description of these functions A decode function can then be called to decode the message If the return status indicates success 0 then the message will have been decoded into the given ASN 1 type variable The decode function may automatically allocate dynamic memory to hold variable length items during the course of decoding This memory will be tracked in the context structure so the programmer does not need to worry about freeing it It will be released when the context is freed The final step of the procedure is to close the stream and free the context block The function to free the context is rtFreeContext A program fragment that could be used to decode an employee record is as follows include employee h include file generated by ASNIC main int stat OSCTXT ctxt Pe
55. decoded message contents Note that the decoder may have allocated dynamic memory and stored pointers to objects in the C structure After processing on the C structure is complete the run time library function rtxMemFree should be called to free the allocated memory A program fragment that could be used to decode an employee record is as follows include employee h include file generated by ASNIC main OSOCTET msgbuf 1024 ASNITAG msgtag int msglen OSCTXT ctxt PersonnelRecord employee logic to read message into msgbuf Step 1 Initialize a context variable for decoding if rtInitContext amp ctxt 0 initialization failed could be a license problem printf context initialization failed check license n return 1 xd_setp amp ctxt msgbuf 0 amp msgtag amp msglen Step 2 Test message tag for type of message received note this is optional the decode function can be called directly if the type of message is known if msgtag TV_PersonnelRecord Step 3 Call decode function note last two args should always be ASNIEXPL and 0 status asnilD_PersonnelRecord amp ctxt amp employee ASNIEXPL 0 Step 4 Check return status if status 0 141 Generated C Function Format and Calling Parameters process received data in employee variable Remember to release dynamic memo
56. defined above The pvalue argument is used to pass a pointer to a variable of the item to be initialized Generated Memory Free Functions The genFree option causes functions to be generated that free dynamic memory allocated using the ASN1C run time memory management functions and macros rtxMem By default all memory held within a context is freed using the rtxMemFree run time function It is also possible to free an individual memory item using the r MemFreePtr function But it is not possible to free all memory held within a specific generated type container For example a SEQUENCE type could contain elements that require dynamic memory These elements in turn can reference other types that require dynamic memory The generated memory free functions make it possible to release all memory held within a variable of the type with a single call Generated memory free functions are written to the main lt module gt c file This file contains common constants global variables and functions that are generic to all type of encode decode functions If the cfile command line option is used the functions are written to the specified c or cpp file along with all other generated functions If maxcfiles is specified each generated function is written to a separate c file The format of the name of each generated memory free function is as follows asnlFree_ lt prefix gt lt prodName gt 193 Generated Print Functions where lt pr
57. example of an information object definition that is derived from the ASN 1 class above is as follows name ATTRIBUTE WITH SYNTAX VisibleString ID 011 This results in the generation of the following C class GI a class EXTERN name public ATTRIBUT public name virtual int encodeBERType OSCTXT pctxt ASN1TObject amp object virtual int decodeBERType OSCTXT pctxt ASN1ITObject amp object ba The constructor implementation for this class not shown sets the fixed type fields id to the assigned values 0 1 1 The class also implements the virtual methods for the type field virtual methods defined in the base class These methods simply call the BER encode or decode method for the assigned type this example assumes ber was specified for code generation other encode rules could have been used as well Generated Type Assignments If the information object contains an embedded type definition it is extracted from the definition to form a new type to be added to the generated C or C code The format of the new type name is as follows _ lt ObjectName gt _ lt FieldName gt where lt Ob ject Name gt is replaced with the information object name and lt FieldName gt is replaced with the name of the field from within the object Information Object Set Table constraint processing code to support Information Object Sets is generated in a header and source file with a C struct
58. filename gt This option allows the specification of a C or C source c or cpp file to which generated print to stream func tions will be written Print to stream functions are sim ilar to print functions except that the output is written to a user provided stream instead of stdout The stream is in the form of an output callback function that can be set within the run time context making it possible to redirect output to any type of device The lt filename gt argument to this option is option al If not specified the functions will be written to lt modulename gt Print c where lt modulename gt is the name of the module from the ASN 1 source file genTables tables lt filename gt This option is used to generate additional code for the han dling of table constraints as defined in the X 682 standard See the Generated Information Object Table Structures section for additional details on the type of code generated to support table constraints genTest lt filename gt This option allows the specification of a C or C source c or cpp file to which generated test functions will be written Test functions are used to populate an instance of a generated PDU type variable with random test data This instance can then be used in an encode function call to test the encoder Another advantage of these functions is that they can act as templates for writing your own pop ulation functions
59. following C typedef is generated typedef struct Aseq struct unsigned xPresent 1 unsigned anIntPresent 1 m OSINT32 xX AnInt anint Aseq 56 SEQUENCE When this structure is populated for encoding the developer must set the xPresent and anIntPresent flags accordingly to indicate whether the elements are to be included in the encoded message or not Conversely when a message is decoded into this structure the developer must test the flags to determine if the element was provided in the message or not The generated C structure will contain a constructor if OPTIONAL elements are present This constructor will set all optional bits to zero when a variable of the structured type is declared The programmer therefore does not have to be worried about clearing bits for elements that are not used only with setting bits for the elements that are to be encoded DEFAULT keyword The DEFAULT keyword allows a default value to be specified for elements within the SEQUENCE ASNIC will parse this specification and treat it as it does an optional element Note that the value specification is only parsed in simple cases for primitive values It is up to the programmer to provide the value in complex cases For BER encoding a value must be specified be it the default or other value For DER or PER it is a requirement that no value be present in the encoding for the default value For integer and boolean default values the co
60. function is generated This function will parse the data contents from an XML message of the corresponding ASN 1 or XML schema type and populate a variable of the C type with the data If C code generation is specified a control class is generated that contains a DecodeFrom method that wraps this function This function is invoked through the class interface to encode an ASN 1 message into the variable referenced in the msgData component of the class Generated C Function Format and Calling Parameters The format of the name of each generated XML decode function is as follows lt namespace gt XmlDec_ lt prefix gt lt prodName gt where lt namespace gt is an optional C namespace prefix lt prodName gt is the name of the ASN 1 production for which the function is being generated and lt prefix gt is an optional prefix that can be set via a configuration file setting The configuration setting used to set the prefix is the lt typePrefix gt element This element specifies a prefix that will be applied to all generated typedef names and function names for the production lt namespace gt is set using the ASNIC namespace command line argument Note that this should not be confused with the notion of an XML namespace The calling sequence for each decode function is as follows status lt ns gt XmlDec_ lt name gt OSCTXT pctxt lt name gt pvalue In this definition lt name gt denotes the prefixed production name defined above
61. general the generation logic for C is similar to the logic for C Instead of the c file extension cpp is used 37 Generated C files lt moduleName gt cpp Common definitions and functions for example asnlFree_ lt type gt and or global value constant defini tions This file also contains constructors destructors and all methods for ASN1C_ lt Type gt and ASN1T_ lt Type gt control classes lt moduleName gt Enc cpp C encode functions and C encode methods lt moduleName gt Dec cpp C decode functions and C decode methods If additional options are used such as genPrint genCopy etc additional files will be generated Filename Description lt moduleName gt Copy cpp copy functions generated if genCopy is specified lt moduleName gt Print cpp print functions generated if genPrint is specified lt moduleName gt Compare cpp comparison functions generated if genCompare is spec ified lt moduleName gt PrtToStr cpp print to string functions generated if genPrtToStr is specified lt moduleName gt PrtToStrm cpp print to stream functions generated if genPrtToStrm is specified lt moduleName gt Table cpp table constraint functions generated if genTable option is specified lt moduleName gt Test cpp test functions generated if genTest is specified The maxcfiles option for C works very similar to how it wor
62. gt _ lt element namel gt _ lt elementname2 gt _ lt element nameN gt For example in the definition above two temporary types would be generated A_x and A_y A_yis generated because a static OCTET STRING maps to a C struct type The general form is as follows 53 SEQUENCE ASN 1 production lt name gt SEQUENCE lt elementil name gt lt elementl type gt lt element2 name gt lt element2 type gt Generated C code typedef struct lt typel gt lt elementl nam lt type2 gt lt element2 name gt v lt name gt or typedef struct scene typedef struct renane typedef struct lt tempName1 gt lt element1 name gt lt tempName2 gt lt element2 name gt lt name gt The lt typel gt and lt type2 gt placeholders represent the equivalent C types for the ASN 1 types lt ele ment1 type gt and lt element2 type gt respectively This form of the structure will be generated if the internal types are primitive lt tempName1 gt and lt tempName2 gt are formed using the algorithm described above for pulling structured types out of the definition This form is used for constructed elements and elements that map to structured C types The example above would result in the following generated C typedefs typedef struct A x OSINT32 al OSBOOL a2 A_x typedef struct A y OSUINT32 numocts OSOCTET data 10 Ay typedef st
63. if a user know that certain parts of a specification are not going to be used thip op tion can save time list None Generate listing This will dump the source code to the standard output device as it is parsed This can be useful for finding parse errors maxcfiles None Maximize number of generated C files This option in structs the compiler to generate a separate c file for each generated C function In the case of C a separate cpp file is generated for each control class type and C func tion This is a space optimization option it can lead to smaller executable sizes by allowing the linker to only link in the required program module object files maxlines lt number gt This option is used to specify the maximum number of lines per generated c or cpp file If this number is exceed ed a new file is started with a _n suffix where n is a sequential number The default value if not specified is 50 000 lines which will prevent the VC Maximum line numbers exceeded warning that is common when com piling large ASN 1 source files Note that this number is approximate the next file will not be started until this number is exceeded and the com pilation unit that is currently being generated is complete 10 Running ASNIC from the Command line Description noContaining When used in conjunction with the genMake com mand line option the generated makefile
64. in the array This argument is set to 1 for all other constructs There is one contents method for passing each of the ASN 1 data types Some methods are used to handle several different types For example the charValue method is used for values of all of the different character string types 1A5String NumericString PrintableString etc as well as for big integer values Note that this method is overloaded The second implementation is for 16 bit character strings These strings are represented as an array of unsigned short integers in ASNIC All of the other contents methods correspond to a single equivalent ASN 1 primitive type The error handler base class has a single virtual method that must be implemented This is the error method and this has the following signature virtual int error OSCTXT pCtxt ASNICCB pCCB int stat 0 In this definition pCtxt is a pointer to the standard ASN 1 context block that should already be familiar The pCCB structure is known as a Context Control Block This can be thought of as a sub context used to control the parsing of nested constructed types within a message It is included as a parameter to the error method mainly to allow access to the seqx field This is the sequence element index used when parsing a SEQUENCE construct If parsing a particular element is to be retried this item must be decremented within the error handler How to Use It To define event handlers two things m
65. initializing the context and populating a variable of the structure to be encoded an encode function can be called to encode the message to the stream The stream must then be closed by calling the rtxStreamClose function A program fragment that could be used to encode an employee record is as follows include employee h include file generated by ASNIC 134 Generated Streaming C Function Format and Calling Parameters int main int stat OSCTXT ctxt Employee employee typedef generated by ASNIC const char filename message dat Step 1 Initialize the context and stream if berStrmInitContext amp ctxt 0 initialization failed could be a license problem printf context initialization failed check license n return 1 Step 2 create a file stream object within the context stat rtxStreamFileCreateWriter amp ctxt filename if stat 0 rtxErrPrint amp ctxt return stat Step 3 Populate the structure to b ncoded mployee name SMITH Step 4 Call the generated encode function stat asnlBSE_Employee amp ctxt amp employee ASNIEXPL Step 5 Check the return status and close the stream if stat 0 error processing rtxStreamClose amp ctxt In general streaming encoding is slower than memory buffer based encoding However in the case of streami
66. is 50000 do not generate initialization functions set output directory for header files generate static elements not pointers add a C namespace to generated cod nerated files C only Windows onl C C makefile project options genMake lt filename gt generate makefile to build generated cod vcproj lt version gt generate VC 6 0 project files for use with lt version gt dll generate makefile project to use DLL s mt generate makefile project to use multithreaded libs w32 generate code for Windows O S default GNU Java options compare dirs genbuild genant genjsources getset pkgname lt text gt generate comparison functions output Java code to module name dirs generate build script generate ant build xml script generate lt modulename gt mk for list of java files generat Java package name get set methods and protected member vars Running ASNIC from the Command line pkgpfx lt text gt Java package prefix java4 generate code for Java 1 4 C options nspfx lt text gt C namespace prefix namespace lt text gt C namespace name dirs output C code to module name dirs gencssources generate lt modulename gt mk for list of C files genMake generate makefile to build generated cod pro options 3gpp generate special code for 3GPP specifications events generate code to invoke SAX lik vent handlers stream
67. is derived from the context pointer reference within the class and the pvalue argument is obtained from the msgData reference contained within the class Print Format The prtfmt option can be used in conjunction with any of the genPrint options documented above to alter the format of the printed data There are two possible print formats details and bracetext The details format prints a line by line display of every item in the generated structure For example the following is an excerpt from a details display Employee name givenName John Employee name initial P Employee name familyName Smith Employee number 51 Employee title Director The alternative format bracetext provides a C like structure printout This is a more concise format that will omit optional fields that are not present in the decoded data An example of this is as follows Employee 196 Generated Compare Functions name givenName John initial P familyName Smith number 51 title Director As of ASNIC version 6 0 and higher bracetext is the default format used if prtfmt is not specified on the commandline Previous versions of ASNIC had details as the default setting Generated Compare Functions The genCompare option causes comparison functions to be generated These functions can be used to compare the contents of two generated type variables If an output file is not specified with the
68. is done Example 2 An Error Handler Despite the addition of things like extensibility and version brackets ASN 1 implementations get out of sync For situations such as this the user needs some way to intervene in the parsing process to set things straight This is faulttolerance the ability to recover from certain types of errors The error handler interface is provided for this purpose The concept is simple Instead of throwing an exception and immediately terminating the parsing process a user defined callback function is first invoked to allow the user to check the error If the user can fix the error all he or she needs to do is apply the appropriate patch and return a status of 0 The parser will be none the wiser It will continue on thinking everything is fine This interface is probably best suited for recovering from errors in BER or DER instead of PER The reason is the TLV format of BER makes it relatively easy to skip an element and continue on It is much more difficult to find these boundaries in PER Our example can be found in the cpp sample_ber errorHandler subdirectory In this example we have purposely added a bogus element to one of the constructs within an encoded employee record The error handler will be invoked when this element is encountered Our recovery action will simply be to print out a warning message skip the element and continue As before the first step is to create a class derived from the Asn Err
69. is specified on the command line A configuration setting is also available to further disambiguate duplicate enumerated item names This is the enum prefix setting that is available at both the module and production levels For example the following would cause the prefix h225 to be added to all enumerated identifiers within the H225 module lt module gt lt name gt H225 lt name gt lt enumP refix gt h225 lt enumPrefix gt lt module gt The fgenum fully qualified enum option may also be used to make C names unique When specified enumerated identifiers will be automatically prefixed with the enclosing type name In the specification above each of the iden tifiers would have the form lt name gt _ lt id gt This can be useful in situations where common identifiers are often re peated in different types This is not a problem in C because the identifiers are wrapped in a struct declaration which provides a namespace for the values see the C section below for more details In addition to the generated type definition helper functions are also generated to make it easier to convert to from enumerated and string format The signatures of these functions are as follows const OSUTF8CHAR lt name gt _ToString OSINT32 value int lt name gt _ToEnum OSCTXT pctxt const OSUTF8CHAR value lt name gt pvalue The first function would be used to convert an enumerated value into string form The second would do the o
70. is used to generate special code for table constraints in ASN 1 specifications that have a common pattern as found in many of the 3rd Generation Partner ship Project 3GPP specifications Specifications having this pattern include NBAP RANAP SIAP and X2AP ASNI1C can take advantage of this common pattern to gen erate more efficient code appInfo lt items gt This option only has meaning when generating an XML schema definitions XSD file using the xsd option It instructs the compiler to generate an XSD application information section lt appinfo gt for certain ASN 1 only items The items are specified as a comma delimited list Valid values for items are tags enum and ext lt items gt is an optional parameter If it is not specified it is assumed that application information should be produced for all three item classes ASN 1 tags ASN 1 enumera tions and extended elements asnstd x208 This option instructs the compiler to parse ASN 1 syntax x680 conforming to the specified standard x680 the default mixed refers to modern ASN 1 as specified in the ITU T X 680 X 690 series of standards x208 refers to the now depre cated X 208 and X 209 standards This syntax allowed the ANY construct as well as unnamed fields in SEQUENCE SET and CHOICE constructs This option also allows for parsing and generation of code for ROSE OPERATION and ERROR macros and SNMP OBJECTTYPE macros The mixed option i
71. method PrintErrorInfo can be invoked to get a textual explanation and stack trace of where the error occurred 6 Release dynamic memory that was allocated by the decoder All memory associated with the decode context is released when both the ASNJ PERDecodeBuffer and ASNIC_ lt ProdName gt objects go out of scope A program fragment that could be used to decode an employee record is as follows include employee h include file generated by ASNIC main 169 Decoding a Series of Messages Us ing the C Control Class Interface OSOCTET msgbuf 1024 int msglen stat OSBOOL aligned TRU GI logic to read message into msgbuf step 1 instantiate a PER decode buffer object ASN1PERDecodeBuffer decodeBuffer msgbuf msglen aligned step 2 instantiate an ASNIT_ lt ProdName gt object ASN1T_PersonnelRecord msgData step 3 instantiate an ASN1IC_ lt ProdName gt object ASN1C_PersonnelRecord employ decodeBuffer msgData step 4 decode the record stat employee Decode step 5 check the return status if stat 0 process received data else error processing decodeBuffer PrintErroriInfo step 6 free dynamic memory will be done automatically when both the decodeBuffer and employ objects go out of scope Decoding a Series of Messages Using the C Control Class Interface The above example is fine as a sample f
72. name will be pvalue instead of value Check the generated function prototype in the header file to determine how this argument is to be passed for a given function The elemName and nsPrefix arguments are used to pass the XML element name and namespace prefix respectively The two arguments are combined to form a qualified name QName of the form lt nsPrefix elemName gt If elemName is null or empty then no element tag is added to the encoded content If nsPrefix is null or empty the element name is applied as a local name only without a prefix The function result variable st at returns the status of the encode operation Status code zero indicates the function was successful A negative value indicates encoding failed Return status values are defined in the rtxErrCodes h include file The error text and a stack trace can be displayed using the rtvErrPrint function In addition to the XML encode function generated for types a different type of encode function is generated for Protocol Data Units PDU s These are types in an ASN 1 specification that are not referenced by any other types In an XML schema specification these are global elements that are not reference within any other types or global elements The format of the a PDU encode function is the same name format as above with the suffix _PDU This function does not contain the elemName and nsPrefix arguments these are built into the function as defined in the schema For this re
73. populated C variable of the given type into an XER encoded ASN 1 message i e an XML document If C code generation is specified a control class is generated that contains an Encode method that wraps this function This function is invoked through the class interface to encode an ASN 1 message into the variable referenced in the msgData component of the class Generated C Function Format and Calling Parameters The format of the name of each generated XER encode function is as follows asn1lXE_ lt prefix gt lt prodName gt where lt prodName gt is the name of the ASN 1 production for which the function is being generated and lt prefix gt is an optional prefix that can be set via a configuration file setting The configuration setting used to set the prefix is the lt typePrefix gt element This element specifies a prefix that will be applied to all generated typedef names and function names for the production The calling sequence for each encode function is as follows status asnlXE_ lt name gt OSCTXT pctxt lt name gt value const char elemName const char attributes In this definition lt name gt denotes the prefixed production name defined above The pct xt argument is used to hold a context pointer to keep track of encode parameters This is a basic handle variable that is used to make the function reentrant so it can be used in an asynchronous or threaded application The user is required to supply
74. the generation of application lan guage types corresponding to ASN 1 types embedded within information object definitions noOpenExt This option instructs the compiler to not add an open ex tension element extElem1 in constructs that contain ex tensibility markers The purpose of the element is to col lect any unknown items in a message If an application does not care about these unknown items it can use this option to reduce the size of the generated code notypes This options suppresses the generation of type definitions It is used in conjunction with the events options to gener ate pure parser functions noxmlns None This option instructs the compiler not to insert XML namespace entries in generated XML documents This in cludes xmlns attributes and prefixed names nouniquenames This option instructs the compiler not to automatically generate unique names to resolve name collisions in the generated code Name collisions can occur for example if two modules are being compiled that contain a produc tion with the same name A un ique name is generated by 11 Running ASNIC from the Command line Option Argument Description lt directory gt prepending the module name to one of the productions to form a name of the form lt module gt _ lt name gt Note that name collisions can also be manually resolved by using the typePrefix enumPrefix and valuePrefix con
75. the selected output code is C or C In general C will add some additional items such as a control class definition onto what is generated for C The following items are generated for each ASN 1 production e Tag value constant e Choice tag constants CHOICE type only e Named bit number constants BIT STRING type only e Enumerated type option values ENUMERATED or INTEGER type only e C type definition e Encode function prototype e Decode function prototype e Other function prototypes depending on selected options for example print e C control class definition C only A sample section from a C header file is as follows BRK KKK KKK HH KKK KK KH KK KKK HK KKK KK HK KKK KKK KKK KKK KKK KK KK KKK KK KKK KKK ass aA EmployeeNumber uk aw BRK KKK KKK HK HK IKK KKK KKK KK KKK IKK KKK KKK KK KKK KKK KKK KKK KKK KKK KKK k k k define TV_EmployeeNumber TM_APPL TM_PRIM 2 typedef OSINT32 m mployeeNumber EXTERN int asnlE_EmployeeNumber OSCTXT pctxt EmployeeNumber pvalue ASN1iTagType tagging EXTERN int asnlD_EmployeeNumber OSCTXT pctxt EmployeeNumber pvalue ASN1TagType tagging int length This corresponds to the following ASN 1 production specification EmployeeNumber APPLICATION 2 IMPLICIT INTEGER In this definition TV_EmployeeNumber is the tag constant Doing a logical OR on the class form and identifier fields forms this co
76. then the actual extension elements will be present in addition to the extElem element These elements will be treated as optional elements whether they were declared that way or not The reason is because a version 1 message could be received that does not contain the elements Additional bits will be generated in the bit mask if version brackets are present These are groupings of extended elements that typically correspond to a particular version of a protocol An example would be as follows TestSequence SEQUENCE item code INTEGER 0 254 item name TA5String SIZE 3 10 OPTIONAL dle urgency ENUMERATED normal high DEFAULT normal alternate item cod INTEGER 0 254 alternate item nam TA5String SIZE 3 10 OPTIONAL In this case a special bit flag will be added to the mask structure to indicate the presence or absence of the entire element block This will be of the form _v ExtPresent where would be replaced by the sequential version number 57 SET In the example above this number would be three two would be the version extension number of the urgency field Therefore the generated bit mask would be as follows struct unsigned item_namePresent 1 unsigned urgencyPresent 1 unsigned _v3ExtPresent 1 unsigned alternate_item_namePresent 1 m In this case the setting of the _v3ExtPresent flag would indicate
77. to be PDU via the lt isPDU gt configuration setting or pdu command line option 2 If no explicit declarations exist a type is determined to be a PDU if it is not referenced by any other types In the employee sample program EmployeeNumber would not be considered to be a PDU because it is referenced as an element within the Employee production For the purpose of this discussion we will assume EmployeeNumber was explicitly declared to be a PDU via a configuration setting or command line specification ASNIC_EmployeeNumber is the control class declaration The purpose of the control class is to provide a linkage be tween the message buffer object and the ASN 1 typed object containing the message data The class provides methods such as EncodeTo and DecodeFrom for encoding and decoding the contents to the linked objects It also provides other utility methods to make populating the typed variable object easier ASNIC always adds an ASN C_prefix to the production name to form the class name Most generated classes are derived from the standard ASN CType base class defined in asn1 Message h The following ASN 1 types cause code to be generated from different base classes BIT STRING The generated control class is derived from the ASN CBitStr class SEQUENCE OF or SET OF with linked list storage The generated control class is derived from the ASN1ICSeqOfList base class Defined Type The generated control class for defined types is der
78. to it are handled in the same way as defined type references This can lead to a significant reduction in generated code in cases where a parameterized type is referenced over and over again For example consider the following often repeated pattern from the UMTS 3GPP specs ProtocollIE Field RANAP PROTOCOL IES IEsSetParam SEQUENCE id RANAP PROTOCOL IES amp id IEsSetParam criticality RANAP PROTOCOL IES amp criticality IEsSetParam id value RANAP PROTOCOL IES amp Value IEsSetParam id In this case EsSet Param refers to an information object set specification that constrains the values that are allowed to be passed for any given instance of a type referencing a Protocol IE Field The compiler does not add any extra code to check for these values so the parameter can be discarded note that this is not true if the tables compiler option is specified After processing the Information Object Class references within the construct refer to the section on Information Objects for information on how this is done the reduced definition for Protocol lE Field becomes the following ProtocolIE Field SEQUENCE id ProtocollIE ID criticality Criticality value ASN 1 OPEN TYPE References to the field are simply replaced with a reference to the Protocol ID Field typedef If tables is specified the parameters are used and a new type i
79. used only a pointer to the data in the message buffer is stored so large copies of data are avoided The data within the deferred decoding open type container can be fully decoded later by using a special decode function generated by the ASNIC compiler for this purpose The format of this function is as follows asn1lD_ lt ProdName gt _ lt ElementName gt _OpenType OSCTXT pctxt lt ElementType gt pvalue Here lt ProdName gt is replaced with name of the type assignment and lt ElementName gt is replaced with name of the element In this function the argument pctxt is used to pass the a pointer to a context variable initialized with the open type data and the pvalue argument will hold the final decoded data value In following example decoding of the element id is deferred Identifier SEQUENCE id INTEGER oid OBJECT IDENTIFIER The following configuration file is required to indicate the element id is to be processed as an open type i e that it will be decoded later lt asniconfig gt lt module gt lt name gt modulename lt name gt lt production gt lt name gt Identifier lt name gt lt element gt lt name gt id lt name gt lt isOpenType gt lt element gt lt production gt lt module gt lt asnilconfig gt In the generated code the element id type will be replaced with an open type Asn OpenType for C or Asn TOpenType for C and the foll
80. used with these strings with some type casting Utility functions are provided for working with UTF 8 string data The UTF 8 encoding for a standard ASCII string is simply the string itself For Unicode strings represented in C C using the wide character type wchar_t the run time functions rt xUTF8ToWCS and rt xWCSToUTF8 can be used for converting to and from UTF 8 format The function rtxValidateUTF8 can be used to ensure that a given UTF 8 encoding is valid See the C C Run Time Library Reference Manual for a complete description of these functions Time String Types The ASN 1 GeneralizedTime and UTCTime types are mapped to standard C C null terminated character string types The C version of the product contains additional control classes for parsing and formatting time string values When C code generation is specified a control class is generated for operating on the target time string This class is derived 67 EXTERNAL from the ASN CGeneralizedTime or ASNICUTCTime class for GeneralizedTime or UTCTime respectively These classes contain methods for formatting or parsing time components such as month day year etc from the strings Objects of these classes can be declared inline to make the task of formatting or parsing time strings easier For example ina SEQUENCE containing a time string element the generated type will contain a public member variable containing the ASNIT type that holds the message data If one
81. value is specif NamedType identifier type type END This MACRO does not need to be defined in the ASN 1 specification to be parsed In fact any attempt to redefine this MACRO will be ignored Its definition is hard coded into the compiler The compiler uses this definition to parse types and values out of OPERATION definitions An example of an OP ERATION definition is as follows login OPERATION ARGUMENT SEQUENCE username IA5String password IA5String RESULT SEQUENCE ticket OCTET STRING welcomeMessage IA5String 211 ROSE OPERATION and ERROR ERRORS authenticationFailure insufficientResources 1 In this case there are two embedded types an ARGUMENT type and a RESULT type and an integer value 1 that identifies the OPERATION There are also error definitions The ASNIC compiler generates two types of items for the OPERATION 1 It extracts the type definitions from within the OPERATION definitions and generates equivalent C C structures and encoders decoders and 2 It generates value constants for the value associated with the OPERATION e the value to the right of the in the definition The compiler does not generate any structures or code related to the OPERATION itself for example code to encode the body and header in a single step The reason is because of the multi layered nature of the protocol It is assumed that the user of such a
82. value of the opcode element will be violation of the Table Constraint If the SupportedAttributes information object set was extensible indicated by a at the end of the definition then the argument element may have a value of a type that is not in the defined set In this case if the index element value is outside the information object set then the argument element will be assumed to be an Asn OpenType The Invoke type encode function call will use the value from argument encoded data field i e it will have to be pre encoded because the encode function will not be able to determine from the table constraint how to encode it A C program fragment that could be used to encode an instance of the Invoke type is as follows include TestTable h include file generated by ASNI1C main const OSOCTET msgptr OSOCTET msgbuf 1024 int msglen step 1 construct ASNIC C generated class this specifies a static encode message buffer ASNIBEREncodeBuffer encodeBuffer msgbuf sizeof msgbuf step 2 populate msgData structure with data to be encoded 112 General Procedure for Table Constraint Encoding ASN1T_Invoke msgData ASN1C_Invoke invok encodeBuffer msgData msgData opcode numids 3 msgData opcode subid 0 0 msgData opcode subid 1 1 msgData opcode subid 2 1 ASN1VisibleString argument objsys msgData argument decoded void
83. wanted to operate on the time string contained within that element they could do so by using one of the time string classes inline as follows ASN1CGeneralizedTime gtime msgbuf lt seqVar gt lt element gt gtime setMonth ASN1CTime November In this example lt seqVar gt would represent a generated SEQUENCE variable type and lt element gt would represent a time string element within this type See the ASN1CTime ASN1CGeneralizedTime and ASN1CUTCTime subsections in the C C Run Time Li brary Reference Manual for details on all of the methods available in these classes EXTERNAL The ASN 1 EXTERNAL type is a useful type used to include non ASN 1 or other data within an ASN 1 encoded message This type is described using the following ASN 1 SEQUENCE EXTERNAL UNIVERSAL 8 IMPLICIT SEQUENCE direct reference OBJECT IDENTIFIER OPTIONAL indirect reference INTEGER OPTIONAL data value descriptor ObjectDescriptor OPTIONAL encoding CHOICE single ASN1 type 0 ABSTRACT SYNTAX amp Type octet aligned 1 IMPLICIT OCTET STRING arbitrary 2 IMPLICIT BIT STRING The ASNIC compiler is used to create a meta definition for this structure This code will always be generated in the AsnlExternal hand AsnlExternal c cpp files The code will only be generated if the given ASN 1 source specification requires this definition The resulting C structure is populate
84. will be encoding There is no built in formula to do this the size of an ASN 1 message can vary widely based on data types and other factors If performance is not a significant issue then dynamic buffer allocation is a good alternative Using the form of the ASNIPEREncodeBuffer constructor that does not include buffer address and size arguments specifies dynamic buffer allocation This constructor only requires a Boolean value to specify whether aligned or unaligned encoding should be performed aligned is true The following code fragment illustrates PER encoding using a dynamic buffer include employee h include file generated by ASN1C main OSOCTET msgptr int msglen stat OSBOOL aligned TRU GI Create an instance of the compiler generated class This example does dynamic encoding no message buffer is specified 165 Encoding a Series of PER Mes sages using the C Interface ASN1PEREncodeBuffer encodeBuffer aligned ASN1T_PersonnelRecord msgData ASN1C_PersonnelRecord employ encodeBuffer msgData Populate msgData within the class variable msgData name givenName SMITH Encode if stat employee Encode 0 printf Encoding was successful n printf Hex dump of encoded record n ncodeBuffer hexDump printf Binary dump n encodeBuffer binDump employee Get start of message pointer and length
85. 1 The next step is to create a stream object within the context This object is an abstraction of the output device to which the data is to be encoded and is initialized by calling one of the following functions e rtxStreamFileOpen e rtxStreamFileAttach e rtxStreamSocketAttach e rtxStreamMemoryCreate e rtxStreamMemoryAttach The flags parameter of these functions should be set to the OSRTSTRMF_INPUT constant value to indicate an input stream is being created see the C C Common Run Time Library Reference Manual for a full description of these functions A simplified version of the Open functions are the CreateReader functions e rtxStreamFileCreateReader e rtxStreamMemoryCreateReader e rtxStreamSocketCreateReader After initializing the context and populating a variable of the structure to be encoded a decode function can be called to decode a message from the stream If the return status indicates success the C variable that was passed as an argument will contain the decoded message contents Note that the decoder may have allocated dynamic memory and stored pointers to objects in the C structure After processing on the C structure is complete the run time library function rtxMemFree should be called to free the allocated memory After stream processing is complete the stream is closed by invoking the rtxStreamClose function A program fragment that could be used to decode an employee record is as follows include
86. 2 context level which applies to print streams associated with a particular context For registering a global callback use rtxSetGlobalPrintStream rtxPrintCallback myCallback void pStrmInfo For registering a context level callback use rtxSetPrintStream OSCTXT pctxt rtxPrintCallback myCallback void pStrmInfo Once the callback function is registered the calling of each generated print to stream function will result in output being directed to the callback function The print to stream functions are declared as follows asnlPrtToStrm_ lt name gt OSCTXT pctxt const char name lt name gt pvalue The name and pvalue arguments are the same as they were in the print case The pctxt argument is used to specify an ASNIC context If a valid context argument is passed and there is a context level callback registered then that callback will be used If there is no context level callback registered or the pctxt argument is NULL then the global callback will be used If there is no global callback registered the default callback will be used which writes the print output to stdout If C code generation is specified setPrintStream and toStream methods are added to the ASNIC control class for the type The setPrintStream method takes only myCallback and pStrmInfo arguments the pctxt argument is obtained from the context pointer reference contained within the class The toStream method takes only a name argument the pctxt argument
87. 2 alInt struct int t union OSINT32 alInt OSBOOL aBool u aChoice C Note that _1 was appended to the second instance of T_C_aInt Developers must take care to ensure they are using the correct tag constant value when this happens Populating Generated Choice Structures Populating generated CHOICE structures is more complex then for other generated types due to the use of pointers within the union construct As previously mentioned the use of pointers with C can be prevented by using the static command line option If this is done the elements within the union construct will be standard inline variable declarations and can be populated directly Otherwise the methods listed below can be used to populate the variables The recommended way to populate the pointer elements is to declare variables of the embedded type to be used on the stack prior to populating the CHOICE structure The embedded variable would then be populated with the data to be encoded and then the address of this variable would be plugged into the CHOICE union pointer field Consider the following definitions AsciiString PRIVATE 28 OCTET STRING EBCDICString PRIVATE 29 OCTET STRING String CHOICE AsciiString EBCDICString Open Type This would result in the following type definitions typedef OSDynOctStr AsciiString typedef OSDynOctStr EBCDICString typedef struct String int t union PR E b
88. 3647 OSINT32 int signed 32 bit integer 0 4294967295 OSUINT32 unsigned int unsigned 32 bit integer The C type that is used to represent a given integer value can also be altered using the lt ctype gt configuration variable setting This allows any of the integer types above to be used for a given integer type as well as a 64 bit integer type The values that can be used with lt ctype gt are byte int16 uint16 int32 uint32 and int64 An example of using this setting is as follows Suppose you have the following integer declaration in your ASN 1 source file APPLICATION 1 INTEGER MyIntType You could then have ASNIC use a 64 bit integer type for this integer by adding the following declaration to a config uration file to be associated with this module lt production gt lt name gt My Int Type lt name gt lt intCType gt int 64 lt intCType gt lt production gt The lt intCType gt setting is also available at the module level to specify that the given C integer type be used for all unconstrained integers within the module Large Integer Support In C and C the maximum size for an integer type is normally 64 bits or 32 bits on some older platforms ASN 1 has no such limitation on integer sizes and some applications security key values for example demand larger sizes In order to accommodate these types of applications the ASN1C compiler allows an integer to be declared a big integer via a
89. 78 The compiler generates code for two of the items specified in this MACRO definition 1 The ASN 1 type that is specified using the SYNTAX command and 2 The assigned OBJECT IDENTIFIER value For an example of the generated code we can look at the following definition from the UDP MIB udpInDatagrams OBJECT TYPE SYNTAX Counter32 MAX ACCESS read only STATUS current DESCRIPTION The total number of UDP datagrams delivered to UDP users udp 1 In this case a type definition is generated for the SYNTAX element and an Object Identifier value is generated for the entire item The name used for the type definition is lt name gt _SYNTAX where lt name gt would be replaced with the OBJECT TYPE name i e udpInDatagrams The name used for the Object Identifier value constant is the OBJECTTYPE name So for the above definitions the following two C items would be generated typedef Counter32 udpInDatagrams_SYNTAX ASNI1OBJID udpInDatagrams 8 1 3 6 1 2 1 7 1 bi 214 Appendix A Runtime Status Codes This appendix describes status code messages returned by the ASNIC C C runtime libraries When deploying applications linked against optimized runtime libraries ASN1C by default does not include a stacktrace instead only an error code is provided These codes are described more fully in this appendix The descriptions are derived from the contents of rtxsrc rtxErrCodes h and rtsrc asnlErrC
90. 9 Using Initialization Functions Simple a 123 Simple b numocts 3 Simple b data ptr Message buffer J or m fo fos fo om The pointer stored in the data structure points directly at data in the message buffer No memory allocation or copy is done The user must keep in mind that if this technique is used the message buffer containing the decoded message must be available as long as the type variable containing the decoded data is in use This will not work in a producer consumer threading model where one thread is decoding messages and the next thread is processing the contents The producer thread will overwrite the buffer contents and therefore data referenced in the decoded message type variable that the consumer is processing This will also not work if the message buffer is an automatic variable in a function and the decoded result type is being passed out The result type variable will point at data in the buffer variable that has gone out of scope To set fast copy the rtSetFastCopy function must be invoked with the initialized context variable that will be used to decode a message This should be done once prior to entering the loop that will be used to decode a stream of messages Using Initialization Functions Initialization functions are generated by the ASN1C compiler when the gen nit option is added to the ASNIC com mand line These functions can be used as an alternative to memset ing a variable t
91. A program fragment that could be used to decode an employee record is as follows include employee h include file generated by ASNIC main OSOCTET msgbuf 1024 ASNITAG msgtag int msglen status logic to read message into msgbuf Use the ASNIBERDecodeBuffer class to parse the initial tag length from the message ASNIBERDecodeBuffer decodeBuffer msgbuf len status decodeBuffer ParseTagLen msgtag msglen if status 0 handle error Now switch on initial tag value to determine what type of message was received switch msgtag case TV_PersonnelRecord compiler generated constant ASN1T_PersonnelRecord msgData ASN1C_PersonnelRecord employ decodeBuffer msgData if status employee Decode 0 decoding successful data in msgData process received data else error processing 145 Generated C Decode Method Format and Calling Parameters case TV_ handle other known messages Note that the call to free memory is not required to release dynamic memory when using the C interface This is because the control class hides all of the details of managing the context and releasing dynamic memory The memory is automatically released when both the message buffer object ASNIBERMessageBuffer and the control class object ASN1C_ lt ProdName gt are deleted or go out of scope Reference counting of a context variable shared
92. ASN 1 standards prtfmt bracetext details Sets the print format for generated print functions The de tails option causes a line by line display of all generated fields in a generated structure to be printed The bracetext option causes a more concise printout showing only the relevant fields in a C like brace format As of release ver sion 6 0 bractext is the default details was the default or only option in previous versions shortnames None Generate a shorter form of an element name for a deeply nested production By default all intermediate names are used to form names for elements in nested types This can lead to very long names for deeply nested types This op tion causes only the production name and the last element name to be used to form a generated type name static None This has the same effect as specifying the global lt stor age gt static lt storage gt configuration item The compiler 12 Running ASNIC from the Command line Option Argument Description will insert static elements instead of pointer variables in some generated structures stream None This option instructs the compiler to generate stream based encoders decoders instead of memory buffer based This makes it possible to encode directly to or decode di rectly from a source or sink such as a file or socket In the case of BER it will also cause forward encoders to be generated w
93. D complex types and selected simple types are mapped to equivalent ASN 1 constructed types In some cases simplifications are done to make the generated code easier to work with The following are mappings for specific XSD complex types xsd sequence The XSD sequence type is normally mapped to an ASN 1 SEQUENCE type The following items describe special processing that may occur when processing a sequence definition If the resulting SEQUENCE type contains only a single repeating element it is converted into a SEQUENCE OF type This can occur if either the sequence declaration has a maxOccurs attribute with a value greater than one or if the single element inside has a similar maxOccurs attribute If the sequence contains an element that has a minOccurs 0 attribute declaration the element is mapped to be an OPTIONAL element in the resulting ASN 1 SEQUENCE assignment If the sequence contains a repeating element denoted by having a maxOccurs attribute with a value greater than one then a SEQUENCE OF type for this element is used in the ASN 1 SEQUENCE for the element If attributes are defined within the complex type container containing the sequence group attributes are defined these attribute declarations are added to the resulting ASN 1 as element declarations as per the X 694 standard In XML encodings these appear as attributes in the markup in binary encodings they are elements Example lt xsd complexType name
94. Decode From method The calling sequence for this method is as follows status lt object gt DecodeFrom lt inputStream gt In this definition lt object gt is an instance of the control class i e ASN1C_ lt prodName gt generated for the given production The lt inputStream gt placeholder represents an input stream object type This is an object derived from an ASN1DecodeStream class The function result variable st at returns the completion status Error status codes are negative Return status values are defined in the rtxErrCodes h include file Another way to decode message using the C class interface is to use the gt gt stream operator lt inputStream gt gt gt lt object gt 156 Generated Streaming C Decode Method Format and Calling Parameters Exceptions are not used in ASNIC C therefore the user must fetch the status value following a call such as this in order to determine if it was successful The getStatus method in the ASN DecodeStream class is used for this purpose Also the method Decode without parameters is supported for backward compatibility In this case it is necessary to create a control class object i e ASN1C_ lt prodName gt using an input stream reference as the first parameter and a reference to a variable of the generated type as the second parameter of the constructor Procedure for Using the Streaming C Control Class Decode Method Normally the receiving mess
95. EGER The ASN 1 INTEGER type is converted into one of several different C types depending on constraints specified on the type By default an INTEGER with no constraints results in the generation of an OSINT32 type In the global include file osSysTypes h OSINT32 is defined to be an int which is normally a signed 32 bit integer value on most computer systems ASN 1 production lt name gt INTEGER Generated C code typedef OSINT32 lt name gt Generated C code typedef OSINT32 ASN1T_ lt name gt Value range constraints can be used to alter the C type used to represent a given integer value For example the following declaration from the SNMP SMI specification would cause an OSUINT32 type mapped to a C unsigned int to be used Counter APPLICATION 1 IMPLICIT INTEGER 0 4294967295 In this case an OSINT32 could not be used because all values within the given range could not be represented Other value ranges would cause different integer types to be used that provide the most efficient amount of storage The following table shows the types that would be used for the different range values 43 INTEGER Min Lower Bound Max Upper Bound ASNIC Type C Type 128 127 OSINT8 char signed 8 bit int 0 299 OSUINTS8 unsigned char un signed 8 bit number 32768 32767 OSINT16 short signed 16 bit int 0 65535 OSUINT16 unsigned short un signed 16 bit int 2147483648 214748
96. EGER opcode OPERATION amp operationCode argument OPERATION amp ArgumentType T This is a very simple case that purposely omits a lot of additional information such as Information Object Set constraints that are typically a part of definitions such as this The reason this information is not present is because we are just interested in showing the items that the compiler is concerned with We will use this type to demonstrate the simple form of code generation We will then add table constraints and discuss what changes when the tables command line options is used The opcode field within this definition is an example of a fixed type field reference It is known as this because if you go back to the original class specification you will see that operationCode is defined to be of a specific type namely a choice between a local and global value The generated typedef for this field will contain a reference to the type from the class definition The argument field is an example of a variable type field In this case if you refer back to the class definition you will see that no type is provided This means that this field can contain an instance of any encoded type note in practice 107 Simple Form Code Generation table constraints can be used with Information Object Sets to limit the message types that can be placed in this field The generated typedef for this field contains an open type A
97. FUNCHODS 4 5 5 ss5cesecssvadssaneee diss deans sekdesnvesa teed peuaeees Wen ebos EENEN TEEPEE S 194 Print to Standard Output co s sca epee hai aa See ae ee 194 Pintto Stins sy esecns sites te sel a ser deen tens son thee a ued cosets Soageu ed oeacyedl ea awe reeed A NEES 195 Pintto Steam ear hed eek eda S oer ish ees Seed tae cc ee a eee ee 195 Print Format isa senser tests Sve e desks vote se yen des odes ae sedy Sea E by sae ok SenTeeaphswaesses Dea tren ated 196 Generated Compare FUNCTIONS sic secs cascun see tad etc e E aa tele R ede oY a 197 Generated Copy Functions senesine ges gsbeadeesewes haan tee inent sent dsa debe teedsved beds dey A a Ea EERS 197 Generated Test PUTEA OS a itet eee eee absentee reel ee irae tee Sh ee eae 200 Event Handler Interface onsi p ea EE R E EEE N NE E SEE ENE 203 How it Works oa are epa rota R Se eed A O E R R diss ed A E E S E 203 How to Use Tt reie a a a e e a e e ae Os A E a ea a a E EEE NAR 204 IMPORT EXPORT Of Types E E E T E E a A ee ea ieee EE A N EENS 209 ROSE and SNMP Macro S Uppoft siscs snecesee sudeceey seagesh REE e EE Eo RES E RER EPRE EEE Sa E 211 ROSE OPERATION and ERROR fs cecedade ee ar en E e R E E O ERE 211 ASNIC SNMP OBJECT TY PE r cosescessweessgatecadeeeneaase ph vee thshpeuaysen vie cgbepeeen dgsav eed ebe be season E ESPEIA EN 214 AS RuntimesStatus Codes ners arot e ce fe Gaara E EES eh ibe ath cathe das Shane eee dey ae ah ase RRS 215 ASNIC Errore Messages as
98. IVATE 220 BIT STRING SIZE 42 Would translate to the following C typedef typedef struct BS OSUINT32 numbits OSOCTET data 6 BS In this case six octets would be required to hold the 42 bits eight in the first five bytes and two in the last byte In the case of small sized strings less than or equal to 32 bits a built in type is used rather than generating a custom type This built in type is defined as follows typedef struct ASNIBitStr32 OSUINT32 numbits OSOCTET data 4 ASNIBitStr32 The C variant ASN1TBitStr32 adds constructors for initialization and copying 46 BIT STRING Note that for C ASNIC generates special constructors and assignment operators to make populating a structure easier In this case two constructors were generated a default constructor and one that takes numbits and data as arguments Named Bits In the ASN 1 standard it is possible to define an enumerated bit string that specifies named constants for different bit positions ASNIC provides support for this type by generating symbolic constants and optional macros that can be used to set clear or test these named bits These symbolic constants equate the bit name to the bit number defined in the specification They can be used with the rtBitSet rtBitClear and rtBitTest run time functions to set clear and test the named bits In addition generated C code contains an enumerated constant added to the cont
99. If XML functions are generated using the xml switch the function prototypes are as follows int XmlEnc_ lt ProdName gt OSCTXT pctxt lt ProdName gt value const OSUTF8CHAR elemName const OSUTF8CHAR nsPrefix int XmlDec_ lt ProdName gt OSCTXT pctxt lt ProdName gt pvalue In this case the encode function contains an argument for XML element name e emName and also namespace prefix nsPrefix Generated C Control Class Definition A control class definition is generated for each defined production in the ASN 1 source file that is determined to be a Protocol Data Unit PDU By default any type defined in an ASN 1 source file that is not referenced by any other type is a PDU This default behavior can be overridden by using a configuration file setting lt isPDU gt or a command line option pdu to explicitly declare that certain types are PDU s The generated control class is derived from the ASN CType base class This class provides a set of common attributes and methods for encoding decoding ASN 1 messages It hides most of the complexity of calling the encode decode functions directly BER DER or PER Class Definition The general form of the class definition for BER DER or PER encoding rules is as follows class ASN1C_ lt name gt public ASNI1CType protected ASN1T_ lt name gt amp msgData public ASN1C_ lt name gt ASNIT_ lt name gt amp data ASN1C_ lt name gt ASN1MessageBufferIF amp msgB
100. K status indicating encoding was successful A negative value indicates encoding failed Return status values are defined in the asnltype h include file The error text and a stack trace can be displayed using the rtErrPrint function Generated C Encode Method Format and Calling Pa rameters Generated encode functions are invoked through the class interface by calling the base class Encode method The calling sequence for this method is as follows stat lt object gt Encode 161 Populating Generated Structure Variables for Encoding In this definition lt object gt is an object of the class generated for the given production The function result variable stat returns the status value from the PER encode function This status value will be 0 0 if encoding was successful or a negative error status value if encoding fails Return status values are defined in the asnltype h include file The user must call the encode buffer class methods getMsgPtr and getMsgLen to obtain the starting address and length of the encoded message component Populating Generated Structure Variables for Encoding See the section Populating Generated Structure Variables for Encoding for a discussion on how to populate variables for encoding There is no difference in how it is done for BER versus how it is done for PER Procedure for Calling C Encode Functions This section describes the step by step procedure for calling a C PER encode funct
101. OBJID oidl 3 0 1 1 ASN1OBJID oid2 3 0 1 2 if msgData opcode oidl argument is a VisibleString ASN1VisibleString pArg ASN1VisibleString msgData argument decoded else if msgData opcode oid2 argument is an INTEGER OSINT32 arg OSINT32 msgData argument decoded else error processing In this case the type of the decoded argument can be determined by testing the key field value In the example as shown the SupportedAttributes information object set is not extensible therefore the type of the argument must be one of the two shown If the set were extensible indicated by a in the definition then it is possible that an unknown opcode could be received which would mean the type can not be determined In this case the original encoded message data would be present in msgData argument encoded field and it would be up to the user to determine how to process it The decoding procedure for C requires one additional step This is a call to the module initialization functions after context initialization is complete All module initialization functions for all modules in the project must be invoked The module initialization function definitions can be found in the lt ModuleName gt Table h file A C program fragment that could be used to decode the Invoke example is as follows 115 General Procedure for Table Constraint Decoding include Test
102. ObjId ASNIT_ lt name gt A RELATIVE OID is identical to an OBJECT IDENTIFIER except that it does not contain the restriction on the initial two arc values that they fall within a certain range see the X 680 standard for more details on this REAL The ASN 1 REAL type is mapped to the C type OSREAL In the global include file osSysTypes h OSREAL is defined to be a double ASN 1 production ASN 1 production Generated C code typedef OSREAL lt name gt Generated C code typedef OSREAL ASN1T_ lt name gt SEQUENCE This section discusses the mapping of an ASN 1 SEQUENCE type to C The C mapping is similar but there are some differences These are discussed in the C Mapping of SEQUENCE subsection at the end of this section An ASN 1 SEQUENCE is a constructed type consisting of a series of element definitions These elements can be of any ASN 1 type including other constructed types For example it is possible to nest a SEQUENCE definition within another SEQUENCE definition as follows A SEQUENCE x SEQUENCE al INTEGER a2 BOOLEAN y OCTET STRING SIZE 10 In this example the production has two elements x and y The nested SEQUENCE x has two additional elements al and a2 The ASNIC compiler first recursively pulls all of the embedded constructed elements out of the SE QUENCE and forms new internal types The names of these types are of the form lt name
103. PROCEDURE amp InitiatingMessage S1AP ELEMENTARY PROCEDURES procedureCode In this definition procedureCode and criticality are defined to be a enumerated fixed types and value is defined to be an open type field to hold variable content as defined in the object set definition In the legacy model defined below a loose coupling would be defined for the open type field using the built in ASN10b ject structure This structure uses a void pointer to hold a link to a variable of the typed data structure This is inconvenient for the developer because he would need to consult the object set definition within the ASN 1 specification in order to determine what type of data is to be used with each procedure code It is also error prone in that the void pointer provides for no type checking at compile time In the new model the generated structure is designed to be similar as to what is used to represent a CHOICE type That is to say the structure is a union with a choice selector value and all possible types listed out in a union structure This is the general form typedef struct lt Type gt lt ElementlType gt lt element1 gt lt Element2Type gt lt element2 gt information object selector lt SelectorEnumType gt t lt ObjectSet gt information objects union lt element1 gt lt object1l element1 value gt lt element2 gt lt o
104. PersonnelRecord_PDU amp ctxt amp data if stat 0 process received data else error processing rtxErrPrint amp ctxt can check for other possible tag matches here step 5 free the context rtFreeContext amp ctxt Generated C Decode Method Format and Calling Pa rameters Generated decode functions are invoked through the class interface by calling the base class Decode or DecodeFrom methods The calling sequence for this method is as follows status lt object gt Decode In this definition lt object gt is an object of the class generated for the given production An OSXMLDecodeBuffer object must be passed to the lt object gt constructor prior to decoding This is where the message stream containing the XML document to be decoded is specified Several constructors are available allowing the specification of XML input from a file memory buffer or another stream The function result variable status returns the status of the decode operation The return status will be zero if decoding is successful or a negative value if an error occurs Return status values are documented in the C C Common Functions Reference Manual and in the rtxErrCodes h include file Procedure for Using the C Control Class Decode Method The following are the steps are involved in decoding an XML message using the generated C class 189 Procedure for Using the C Contr
105. Prefix gt element This element specifies a prefix that will be applied to all generated typedef names and function names for the production The calling sequence for each encode function is as follows status asnlPE_ lt name gt OSCTXT pctxt lt name gt value In this definition lt name gt denotes the prefixed production name defined above The pct xt argument is used to hold a context pointer to keep track of encode parameters This is a basic handle variable that is used to make the function reentrant so it can be used in an asynchronous or threaded application The user is required to supply a pointer to a variable of this type declared somewhere in his or her program The value argument contains the value to be encoded or holds a pointer to the value to be encoded This variable is of the type generated from the ASN 1 production The object is passed by value if it is a primitive ASN 1 data type such as BOOLEAN INTEGER ENUMERATED etc It is passed using a pointer reference if it is a structured ASN 1 type value Check the generated function prototype in the header file to determine how the value argument is to be passed for a given function The function result variable st at returns the status of the encode operation Status code 0 0 indicates the function was successful Note that this return value differs from that of BER encode functions in that the encoded length of the message component is not returned only an O
106. R or XER encode or decode message buffers or for a BER or XER encode or decode stream The ASNIT_ lt name gt argument is used to specify the data variable containing data to be encoded or to receive data on a decode call The procedure for encoding is to declare a variable of this type populate it with data and then instantiate the ASNIC_ lt name gt object to associate a message buffer object with the data to be encoded The Encode or Encode To method can then be called to encode the data On the decode side a variable must be declared and passed to the constructor to receive the decoded data Note that the ASN C_ class declarations are only required in the application code as an entry point for encoding or decoding a top level message or Protocol Data Unit PDU As of ASNIC version 5 6 control classes are only generated for ASN 1 types that are determined to be PDU s A type is determined to be a PDU if it is referenced by no other types This differs from previous versions of ASN1C where control classes were generated for all types This default behavior can be overridden by using a configuration file entry or the pdu command line switch to explicitly declare the PDU types The lt isPDU gt flag is used to declare a type to be a PDU in a configuration file An example of this is as follows lt asnlconfig gt lt module gt lt name gt H323 MESSAGES lt name gt lt production gt lt name gt H323 UserInformation lt name gt lt isPD
107. RO that is built into the compiler The definition of this MACRO is as follows ROSE Layer ERROR MACRO BEGIN TYPE NOTATION Parameter VALUE NOTATION value VALUE INTEGER Parameter PARAMETER NamedType empty NamedType identifier type type END In this definition an error is assigned an identifying number as well as on optional parameter type to hold parameters associated with the error An example of a reference to this MACRO for the authenticationFailure error in the login operation defined earlier would be as follows applicationError ERROR PARAMETER SEQUENCE errorText IA5String The ASNIC compiler will generate a type definition for the error parameter and a value constant for the error value The format of the name of the type generated will be lt name gt _PARAMETER where lt name gt is the ERROR name 213 SNMP OBJECT TYPE applicationError in this case with the first letter set to uppercase The name of the value will simply be the ERROR name SNMP OBJECT TYPE The SNMP OBJECT TYPE MACRO is one of several MACROs used in Management Information Base MIB def initions It is the only MACRO of interest to ASN1C because it is the one that specifies the object identifiers and data that are contained in the MIB The version of the MACRO currently supported by this version of ASNIC can be found in the SMI Version 2 RFC RFC 25
108. SN1 OpenType reference to hold a previously encoded component to be specified in the final message Simple Form Code Generation In the simple form of information object code generation the Invoke type above would result in the following C or C typedefs being generated typedef struct Invoke SEQUENCE OSINT32 invokeID OPERATION_operationCode opcode ASN1OpenType argument The following would be the procedure to add the Invoke header type to an ASN 1 message body 1 Encode the body type 2 Get the message pointer and length of the encoded body 3 Plug the pointer and length into the numocts and data items of the argument open type field in the Invoke type variable 4 Populate the remaining Invoke type fields 5 Encode the Invoke type to produce the final message In this case the amount of code generated to support the information object references is minimal The amount of coding required by a user to encode or decode the variable type field elements however can be rather large This is a tradeoff that exists between using the compiler generated table constraints solution as we will see below and using the simple form Table Form Code Generation If we now add table constraints to our original type definition it might look as follows Invoke SEQUENCE invokeID INTEGER opcode OPERATION amp operationCode My ops argument OPERATION amp ArgumentType My ops opcode
109. SN1C main OSOCTET msgptr int msglen construct encodeBuffer class with no arguments ASNIBEREncodeBuffer encodeBuffer ASN1T_PersonnelRecord msgData ASN1C_PersonnelRecord employ encodeBuffer msgData populate msgData structure msgData name SMITH call Encode method if msglen employee Encode gt 0 encoding successful get copy of message msgptr encodeBuffer getMsgCopy delete msgptr free the dynamic memory 131 Generated C Encode Method Format and Calling Parameters Encoding a Series of Messages Using the C Control Class Inter face A common application of BER encoding is the repetitive encoding of a series of the same type of message over and over again For example a TAP3 batch application might read billing data out of a database table and encode each else error processing of the records for a batch transmission If a user was to repeatedly instantiate and destroy the C objects involved in the encoding of a message performance would suffer This is not necessary however because the C objects can be reused to allow multiple messages to be encoded As example showing how to do this is as follows include employee h include file generated by ASNIC main const OSOCTET msgptr OSOCTET msgbuf 1024 int msglen ASNIBEREncodeBuffer encodeBuffer msgbuf sizeof msgbuf ASN1T
110. SN1C_PersonnelRecord employ encodeBuffer msgData steps 4 and 5 encode and check return status if stat employee Encode 0 printf encoded XML message n printf const char msgbuf printf ONNE step 6 get start of message pointer and message length start of message pointer is start of msgbuf call getMsgLen to get message length msgptr encodeBuffer getMsgPtr will return amp msgbuf len encodeBuffer getMsgLen else printf Encoding failed n encodeBuffer printErroriInfo exit 0 msgptr and len now describe fully encoded messag Generated XML Decode Functions A major difference between generated XER decode functions and generated XML decode functions in ASNIC version 6 0 and later is that the XML functions no longer use the Simple API for XML SAX interface Instead the XML runtime now uses an XML pull parser developed in house for improved efficiency The pull parser also provides a 186 Generated C Function Format and Calling Parameters similar interface to that of binary encoding rules such as BER or PER meaning easier integration with existing encoding rules Finally the pull parser interface does not require integration with any 3rd party XML parser software XML decode functions are generated when the xml switch is specified on the command line For each ASN 1 pro duction defined in the ASN 1 source file a C XML decode
111. Systems Inc objective SYSTEMS INC C C Code Generation Options Makefile Options JV Generate Makefiles f Windows nmake GNU J Generate Visual Studio Project file vs 2003 v5 2005 M S 2008 Library Options f Generate static libraries Generate multi threaded libraries Generate shared libraries Sample Program Generation Options I Generate writer sample program writer I Generate reader sample program reader Other Options Enter other command line options not available in GUI oo Cancel Help These options provide convenient means for compiling and testing the target application by generating makefiles or Visual Studio project files and configuring them to use different library types as needed Click Help for additional details on these options Special command line options not present in the GUI may be specified in the Other Options box These options will be inserted at the end of the compilation command 22 C C Code Generation Options When all options have been specified the final screen may be used to execute the compilation command ASNIC compiler Objective Systems Inc iof x objective SYSTEMS INC ASN1C compiler command c acv620 bin asnle c acv620 cpp sample_ber empLoyee employee asn asnstd x680 c ber per xml compact genmake w32 ez i lt Back Next gt Finished Help Included in the window are the compiler comman
112. T data ASN1DynOctStr The ASNITDynOctStr type is defined in the ASN TOctStr h header file This class extends the C ASNIDynOctStr class and adds many additional constructors and methods See the C C Common Run time Reference Manual for a complete description of this class Static sized OCTET STRING ASN 1 production lt name gt OCTET STRING SIZE lt len gt Generated C code typedef struct OSUINT32 numocts OSOCTET data lt len gt 49 ENUMERATED lt name gt Generated C code typedef struct OSUINT32 numocts OSOCTET data lt len gt ctors ASN1T_ lt name gt ASN1T_ lt name gt OSUINT32 _numocts const OSOCTET _data ASN1T_ lt name gt const char cstring assignment operators ASN1T_ lt name gt amp operator const char cstring ASNIT lt name gt Contents Constraint It is possible to specify a contents constraint on an OCTET STRING type using the CONTAINING keyword This indicates that the encoded contents of the specified type should be packed within the OCTET STRING container An example of this type of constraint is as follows ContainingOS OCTET STRING CONTAINING INTEGER ASNIC will generate a type definition that references the type that is within the containing constraint In this case that would be INTEGER therefore the generated type definition would be as follows typedef OSINT32 ContainingOS
113. T32 elementTwo OSXSDAny elem MyType As per the X 694 standard the element was given the standard element name elem XML Attribute Declarations XML attribute declarations in XSD are translated into ASN 1 elements that are added to a SEQUENCE type In binary encodings there is no way to tell encoded attributes apart from encoded elements They just represent data fields in ASN 1 For XML special logic is added to the generated XML encoders and decoders to encode and decode the items as attributes An example of an attribute being added to an xsd sequence declaration is as follows lt xsd complexType name Name gt lt xsd sequence gt lt xsd element name givenName type xsd string gt lt xsd element name initial type xsd string gt lt xsd element name familyName type xsd string gt lt xsd sequence gt lt xsd attribute name occupation type xsd string gt lt xsd complexType gt This results in the following C type definition being generated typedef struct EXTERN Name struct unsigned occupationPresent 1 m const OSUTF8CHAR occupation const OSUTF8CHAR givenName const OSUTF8CHAR initial const OSUTF8CHAR familyName Name The attribute is marked as optional hence the occupationPresent flag in the bit mask since XML attributes are optional by default The attribute declarations also occur before the element declarations in the generated structure Attributes can also
114. T_PersonnelRecord amp getCopy ASN1IT_PersonnelRecord pDstData 0 The pDstData argument is used to pass the pointer to a destination variable where the value will be copied It may be null in this case the new ASNIT_ lt name gt variable will be allocated via a call to the rtxMemAlloc function e A newCopy method that will create a new dynamically allocated copy of the referenced ASNIT_ data member variable e An assignment operator This is used to copy one instance of a control class to another one 198 Generated Copy Functions inline ASN1C_ lt name gt amp operator ASN1C_ lt name gt amp srcData srcData getCopy amp msgData return this For example inline ASN1C_PersonnelRecord amp operator ASN1C_PersonnelRecord amp srcData srcData getCopy amp msgData return this Finally the class declaration might look as follows class EXTERN ASN1C_PersonnelRecord public ASN1CType protected ASN1T_PersonnelRecord msgData public ASN1C_PersonnelRecord ASN1MessageBuffer amp msgBuf ASN1IT_PersonnelRecord amp data ASN1C_PersonnelRecord ASN1C_PersonnelRecord original ASN1T_PersonnelRecord amp getCopy ASN1T_PersonnelRecord pDstData 0 ASN1T_PersonnelRecord newCopy inline ASN1C_PersonnelRecord operator ASN1C_PersonnelRecord amp srcData srcData getCopy amp msgData return this 3 The generated ASN T lt name gt structure will a
115. Table h include file generated by ASNIC main OSOCTET msgbuf 1024 ASNITAG msgtag int msglen OSCTXT ctxt Invoke invoke ASNIOBJID oidl 3 0 1 1 ASNIOBJID oid2 3 0 1 2 logic to read message into msgbuf Step 1 Initialize a context variable for decoding if rtInitContext amp ctxt 0 initialization failed could be a license problem printf context initialization failed check license n return 1 xd_setp amp ctxt msgbuf 0 amp msgtag amp msglen step 2 call module initialization functions Test_init amp ctxt Step 3 Call decode function status asnlD_Invoke amp ctxt amp invoke ASNIEXPL 0 Step 4 Check return status if status 0 process received data in invoke variable if rtCmpTCOID amp invoke opcode amp o0idl 0 argument is a VisibleString ASN1VisibleString pArg ASN1VisibleString msgData argument decoded else if rtCmpTCOID amp invoke opcode amp 0id2 0 argument is an INTEGER OSINT32 arg OSINT32 msgData argument decoded Remember to release dynamic memory when done ASNIMEMFREE amp ctxt 7 else error processing 116 General Procedures for Encoding and Decoding General Procedures for Encoding and Decod ing Encoding functions and methods generated by the ASN1C compiler are design
116. The generated encoders and decoders would handle the extra packing and unpacking required to get this to and from an OCTET STRING container This direct use of the containing type can be suppressed through the use of the noContaining command line argument In this case a normal OCTET STRING type will be used and it will be the users responsibility to do the necessary packing and unpacking operations to encode and decode the variable correctly ENUMERATED The ASN 1 ENUMERATED type is converted into different types depending on whether C or C code is being generated The C mapping is either a C enum or integer type depending on whether or not the ASN 1 type is extensible or not The C mapping adds a struct wrapper around this type to provide a namespace to aid in making the enumerated values unique across all modules C Mapping ASN 1 production lt name gt ENUMERATED lt idl gt lt vall gt lt id2 gt lt val2 gt Generated code typedef enum idl vall id2 val2 lt name gt _Root typedef OSUINT32 lt name gt 50 ENUMERATED The compiler will automatically generate a new identifier value if it detects a duplicate within the source specification The format of this generated identifier is id_n where id is the original identifier and n is a sequential number The compiler will output an informational message when this is done This message is only displayed if the warnings qualifier
117. U gt lt production gt lt module gt lt asnliconfig gt This will cause only a single ASN C_ control class definition to be added to the generated code for the H323 User Information production If the module contains no PDUs 1 e contains support types only the lt noPDU gt empty element can be specified at the module level to indicate that no control classes should be generated for the module XER Class Definition For the XML encoding rules XER the generated class definition is as follows class ASN1C_ lt name gt public ASN1CType ASN1XERSAXHandler protected ASN1IT_ lt name gt amp msgData additional control variables public ASN1C_ lt name gt ASN1T_ lt name gt amp data ASN1C_ lt name gt ASN1MessageBufferIF amp msgBuf ASN1T_ lt name gt amp data 105 Generated Methods standard encode decode methods defined in ASNICType base class int Encode int Decode stream encode decode methods int EncodeTo ASN1MessageBufferIF amp msgBuf int DecodeFrom ASN1MessageBufferIF amp msgBuf SAX Content Handler Interface virtual void startElement const XMLCh const uri const XMLCh const localname const XMLCh const qname const Attributes amp attrs virtual void characters const XMLCh const chars const unsigned int length virtual void endElement const XMLCh const uri const XMLCh const localname const XMLCh
118. X 683 The compiler is also capable of using table constraints as defined in ITU T X 682 to generate single step encoders and decoders that can encode or decode multi part messages in a single function call This release of the compiler contains a special command line option asnstd x208 that allows compilation of dep recated features from the older X 208 and X 209 standards These include the ANY data type and unnamed fields in SEQUENCE SET and CHOICE types This version can also parse type syntax from common macro definitions such as the OPERATION and ERROR macros in ROSE Using the Compiler Running ASN1C from the Command line The ASNIC compiler distribution contains command line compiler executables as well as a graphical user interface GUD wizard that can aid in the specification of compiler options This section describes how to run the command line version the next section describes the GUI To test if the compiler was successfully installed enter asn1c with no parameters as follows note if you have not updated your PATH variable you will need to enter the full pathname asnic You should observe the following display or something similar ASN1C Compiler Version 6 2 x Copyright c 1997 2009 Objective Systems Inc All Rights Reserved Usage asnlc lt filename gt lt options gt lt filename gt ASN 1 or XSD source filename s Multiple filenames may be specified and wildcards are allowed language options
119. _PersonnelRecord msgData ASN1C_PersonnelRecord employ encodeBuffer msgData Encode loop starts here this will repeatedly use the objects declared above to encode the messages for logic here to read record from some source database flat file socket etc populate structure with data to sbe encoded msgData name SMITH invoke Encode method if msglen employee Encode gt 0 encoding successful get pointer to start of message smsgptr encodeBuffer getMsgPtr do something with th ncoded messag else error processing 132 Generated BER Streaming Encode Functions Call the init method on th ncodeBuffer object to prepare the buffer for encoding another message encodeBuffer init Generated BER Streaming Encode Functions BER messages can be encoded directly to an output stream such as a file network or memory stream The ASNIC compiler has the stream option to generate encode functions of this type For each ASN 1 production defined in the ASN 1 source file a C stream encode function is generated This function will encode a populated C variable of the given type into an encoded ASN 1 message and write it to a stream If the return status indicates success 0 the message will have been encoded to the given stream Streaming BER encoding starts from the beginning of the message until the message is
120. a E E E E EEA E A EESE 105 Generated Methods os urne e E ea a a EA BS a eo Wee ASET 106 Generated Information Object Table Structures 2 0 0 0 cece cee cee cee ceeeeeeecaeeca cena eeae eens eeueceneeeeneeeees 106 Simple Form Code Generation esses oean e aea EEr ce ccce cece EEEE a Eee EEA EEE S EET seas eeaes 108 Table Form Code Generation en err ee e E Ea EER RNE T Eo EE EEEE AERES 108 Additional Code Generated with the tables option sesessseesresrssrerrsrrerreresrreresrerrsrrerrsreseese 109 General Procedure for Table Constraint Encoding sseseseseesereerseerrtrerreerrrerererreerresrrsrerese 111 General Procedure for Table Constraint Decoding cee e cece cece cece cece cece cena eeneeeneeenneeeees 114 General Procedures for Encoding and Decoding 0 2 0 0 0 cee eeeceeecc ence ence eeceeeeeeeeaeeeaeeea seen eeu eeaneees 117 Dynamic Memory Management ccsecceeseceeeeeceeececeeeaseceeaseceeaseeecasereeeseeeeeseresenereeeees 117 Populating Generated Structure Variables for Encoding cccecesseeceeececeeecenneeeeeeceeneseeneeees 121 Accessing Encoded Message Components ce ceeceeeceeeceeece seen eeea ceca seen eens een eeneeeneeeenees 122 Generated BER Functions ses ney suse e vdass dy osddy ses aE veSon see py stance gy veTeuey Sunde AE Ea SS 125 Generated BER Encode Functions ic cte dein teed peck a lk dein aed tree aah Sane need eds tae ee Mune eos 125 Generated C Function
121. a lower threshold and not exact A complete compilation unit for example a function will not be split because of this threshold The way it works is the threshold is checked before the output of a compilation unit If it is found to be exceeded a new file is started at that time Therefore a user should plan for a reserve to be in place above the limit to compensate for this overflow The reason for having this limit is because some C C compilers have problems with very large c files For example one product will not allow the debugger to work on lines in a file over the 64k threshold Use of the maxcfiles Option The maxcfiles option allows generation of more compact code by putting each encode decode copy compare etc function into a separate file This allows the linker to link in only the required functions as opposed to all functions in a compiled object module This option might be useful for applications that have minimal space requirements for example embedded systems 36 Generated C files Note Some sophisticated linkers have the capability to pull individual functions out of an object module directly for final inclusion in the target executable or shared object file In this case the maxcfiles option does not provide any advantage in reducing the size of the application program To achieve the best results it is necessary to put all compiled object files into an object library a or lib file and include t
122. a static message buffer ASNIPEREncodeBuffer encodeBuffer msgbuf sizeof msgbuf aligned step 2 populate msgData with data to be encoded ASN1T_PersonnelRecord msgData msgData name givenName SMITH step 3 instantiate an instance of the ASN1C_ lt ProdName gt 164 Procedure for Using the C Control Class Encode Method class to associate th ncode buffer and message data ASN1C_PersonnelRecord employ encodeBuffer msgData steps 4 and 5 encode and check return status if stat employee Encode 0 printf Encoding was successful n printf Hex dump of encoded record n ncodeBuffer hexDump printf Binary dump n encodeBuffer binDump employee step 6 get start of message pointer and message length start of message pointer is start of msgbuf call getMsgLen to get message length msgptr encodeBuffer getMsgPtr will return amp msgbuf len encodeBuffer getMsgLen else printf Encoding failed n encodeBuffer printErrorinfo exit 0 msgptr and len now describe fully encoded messag In general static buffers should be used for encoding messages where possible as they offer a substantial performance benefit over dynamic buffer allocation The problem with static buffers however is that you are required to estimate in advance the approximate size of the messages you
123. age can be one of several different message types It is therefore necessary to deter mine the type of message that was received so that the appropriate decode function can be called to decode it The ASNIBERDecodeStream class has standard methods for parsing the initial tag length from a message to determine the type of message received These calls are used in conjunction with a switch statement on generated tag constants for the known message set Each switch case statement contains logic to create an object instance of a specific ASN1C generated control class and to invoke and then to invoke that object s decode method A program fragment that could be used to decode an employee record is as follows include Employee h include file generated by ASNIC include rtbersrc ASNIBERDecodeStream h include rtxsrc OSRTFileInputStream h main ASNITAG tag int i len const char filename message dat OSBOOL trace TRUE Decode ASN1IBERDecodeStream in new OSRTFileInputStream filename if in getStatus 0 in printErroriInfo return 1 if in peekTagAndLen tag len 0 printf peekTagAndLen failed n in printErroriInfo return 1 Now switch on initial tag value to determine what type of message was received switch msgtag case TV_PersonnelRecord compiler generated constant ASN1T_PersonnelRecord msgData ASN1C_PersonnelRecord employ m
124. aint decode function as defined above is invoked This function will verify all fixed type values match what is defined in the information object definition and will fully decode all type fields and store pointers to the decoded type variables in the ASN TObject decoded fields 3 If a match is not found and the information object set is not extensible then a table constraint error status will be returned If the information object set is extensible a normal status is returned Simple Table Constraint 1 This function will verify all the fixed type values match what is defined in the table constraint object set If an element value does not exist in the table i e the information object set and the object set is not extensible then a table constraint violation exception will be thrown General Procedure for Table Constraint Encoding The general procedure to encode an ASN 1 message with table constraints is the same as without table constraints The only difference is in the open type data population procedure The tables option will cause ASN TObject fields to be inserted in the generated code instead of Asn OpenType declarations Refer to the BER DER PER encoding procedure for further information The procedure to populate the value for an ASNITObject item is as follows 1 Check the ASN 1 specification or generated C code for the type of the type field value in the information object set that corresponds to the selected key field value
125. alues defined in the enu meration facet 5 RTERR_SETDUPL Duplicate element in set This status code is returned when decoding an ASN 1 SET or XSD xsd all construct It is raised if a given element defined in the content model group occurs multiple times in the instance being decoded 6 RTERR_SETMISRQ Missing required element in set This status code is re turned when decoding an ASN 1 SET or XSD xsd all con struct and all required elements in the content model group are not found to be present in the instance being decoded 7 RTERR_NOTINSET Element not in set This status code is returned when en coding or decoding an ASN 1 SET or XSD xsd all con 217 General Status Messages Error Code Error Name Description struct When encoding it occurs when a value in the gen erated _order member variable is outside the range of in dexes of items in the content model group It occurs on the decode side when an element is received that is not defined in the content model group 8 RTERR_SEQOVFLW Sequence overflow This status code is returned when de coding a repeating element ASN 1 SEQUENCE OF or XSD element with minmaxOccurs gt 1 and more instances of the element are received the content model group 9 RTERR_INVOPT Invalid option in choice This status code is returned when encoding or decoding an ASN 1 CHOICE or XSD xsd choice construct When encoding it occurs when a value in t
126. an aligned argument This form is used to specify dynamic encoding Instantiate an ASN1T_ lt ProdName gt object and populate it with data to be encoded Instantiate an ASN1C_ lt ProdName gt object to associate the message buffer with the data to be encoded Invoke the ASNIC_ lt ProdName gt object Encode method Check the return status The return value is a status value indicating whether encoding was successful or not Zero indicates success If encoding failed the status value will be a negative number The encode buffer method printErrorInfo can be invoked to get a textual explanation and stack trace of where the error occurred If encoding was successful get the start of message pointer and message length The start of message pointer is obtained by calling the getMsgPtr method of the encode buffer object If static encoding was specified i e a message buffer address and size were specified to the PER Encode Buffer class constructor the start of message pointer is the buffer start address The message length is obtained by calling the getMsgLen method of the encode buffer object A program fragment that could be used to encode an employee record is as follows include employee h include file generated by ASNIC main const OSOCTET msgptr OSOCTET msgbuf 1024 int msglen stat OSBOOL aligned TRUE step 1 instantiate an instance of the PER encode buffer class This example specifies
127. an alternative to using the control class interface if C code generation was done Before any encode function can be called the user must first initialize an encoding context This is a variable of type OSCTXT This variable holds all of the working data used during the encoding of a message The context variable is within the top level calling function It must be initialized before use This can be accomplished by using the berStrmInitContext function OSCTXT ctxt if berStrmInitContext amp ctxt 0 initialization failed could be a license problem printf context initialization failed check license n return 1 The next step is to create a stream object within the context This object is an abstraction of the output device to which the data is to be encoded and is initialized by calling one of the following functions e rtxStreamFileOpen e rtxStreamFileAttach e rtxStreamSocketAttach e rtxStreamMemoryCreate e rtxStreamMemoryAttach The flags parameter of these functions should be set to the OSRTSTRMF_OUTPUT constant value to indicate an output stream is being created see the C C Common Run Time Library Reference Manual for a full description of these functions It is also possible to use a simplified form of these function calls to create a writer interface to a file memory or socket stream rtxStreamFileCreate Writer e rtxStreamMemoryCreate Writer rtxStreamSocketCreate Writer After
128. anagement works is that a large block of memory is allocated up front on the first memory management call This block is then subdivided on subsequent calls until the memory is used up A new block is then started The default value is 4K 4096 bytes The value can be set lower for space constrained systems and higher to improve performance in systems that have sufficient memory resources To set the block size the following run time function should be used void rtxMemSetDefB1lkSize OSUINT32 blkSize This function must be called prior to context initialization C Memory Management In the case of C the ownership of memory is handled by the control class and message buffer objects These classes share a context structure and use reference counting to manage the allocation and release of the context block When a message buffer object is created a context block structure is created as well When this object is then passed into a control class constructor its reference count is incremented Then when either the control class object or message buffer object are deleted or go out of scope the count is decremented When the count goes to zero i e when both the message buffer object and control class object go away the context structure is released What this means to the user is that a control class or message buffer object must be kept in scope when using a data structure associated with that class A common mistake is to try and pass a data var
129. are generated for the productions within the given ASN 1 source file Instead only a set of parser functions are generated that invoke the event handler callback functions This gives the user total control over what is done with the message data Data that is not needed can be discarded and only the parts of the message needed for a given application need to be saved How it Works Users of XML parsers are probably already quite familiar with the concepts of SAX Significant events are defined that occur during the parsing of a message As a parser works through a message these events are fired as they occur by invoking user defined callback functions These callback func tions are also known as event handler functions A diagram illustrating this parsing process is as fol Parser ASN 1 decode function lows The events are defined to be significant actions that occur during the parsing process We will define the following events that will be passed to the user when an ASN 1 message is parsed 1 startElement This event occurs when the parser moves into a new element For example if we have a SE QUENCE a b c construct type names omitted this event will fire when we begin parsing a b and c The name of the element is passed to the event handling callback function 2 endElement This event occurs when the parser leaves a given element space Using the example above these would occur after the parsing of a b
130. arene daveaned sect tac dhe a ea A ated a AERE hea pteeeses see Sa deeds 215 General Status Messages niae e E E EE tec E Se pie o a EE E E pE Re O E S E tee Sa 217 ASN 1 specific Status Messages Vi Overview of ASN1C The ASNIC code generation tool translates an Abstract Syntax Notation 1 ASN 1 or XML Schema Definitions XSD source file into computer language source files that allow ASN 1 data to be encoded decoded This release of the compiler includes options to generate code in four different languages C C C or Java This manual discusses the C and C code generation capabilities The ASNIC Java User s Manual discusses the Java code generation capability The ASN C C User s Manual discusses the C code generation capability Each ASN 1 module that is encountered in an ASN 1 source file results in the generation of the following two types of C C language files 1 An include h file containing C C typedefs and classes that represent each of the ASN 1 productions listed in the ASN 1 source file and 2 A set of C C source c or cpp files containing C C encode and decode functions One encode and decode function is generated for each ASN 1 production The number of files generated can be controlled through com mand line options These files when compiled and linked with the ASN 1 low level encode decode function library provide a complete package for working with ASN 1 encoded data ASNIC works with
131. argument note opcode value is 0 1 1 so argument must be ASN1VisibleString type step 3 invoke Encode method if msglen invoke Encode gt 0 encoding successful get pointer to start of message msgptr encodeBuffer getMsgPtr else error processing The encoding procedure for C requires one extra step This is a call to the module initialization functions after context initialization is complete All module initialization functions for all modules in the project must be invoked The module initialization function definitions can be found in the lt ModuleName gt Table h file The format of each module initialization function name is as follows void lt ModuleName gt _init OSCTXT pctxt Here ModuleName would be replaced with name of the module A C program fragment that could be used to encode the Invoke record defined above is as follows include TestTable h include file generated by ASNIC int main OSOCTET msgbuf 1024 msgptr int msglen OSCTXT ctxt Invoke invoke typedef generated by ASNIC Step 1 Initialize the context and set the buffer pointer if rtInitContext amp ctxt 0 initialization failed could be a license problem printf context initialization failed check license n return 1 xe_setp amp ctxt msgbuf sizeof msgbuf step 2 call module initialization functions 113 General
132. arsing and to complete population of a variable with decoded data Generated Information Object Table Structures Information Objects and Classes are used to define multi layer protocols in which holes are defined within ASN 1 types for passing message components to different layers for processing These items are also used to define the 106 Generated Information Object Table Structures contents of various messages that are allowed in a particular exchange of messages The ASN1C compiler extracts the types involved in these message exchanges and generates encoders decoders for them The holes in the types are accounted for by adding open type holders to the generated structures These open type holders consist of a byte count and pointer for storing information on an encoded message fragment for processing at the next level The ASNIC compiler is capable of generating code in one of two forms for information in an object specification 1 Simple form in this form references to variable type fields within standard types are simply treated as open types and an open type placeholder is inserted 2 Table form in this form all of the classes objects and object sets within a specification result in the generation of code for parsing and formatting the information field references within standard type structures The second form is selected by specifying the tables command line option To better understand the support in
133. ason calling PDU functions is usually more convenient than calling the equivalent function for the referenced type 183 Procedure for Calling C Encode Functions Procedure for Calling C Encode Functions This section describes the step by step procedure for calling C XML encode functions This procedure is similar to that for the other encoding methods except that some of the functions used are specific to XML Before an XML encode function can be called the user must first initialize an encoding context block structure The context block is initialized by calling rtXmlInitContext to initialize a context block structure The user then must call the rtXmlSetEncBufPtr function to specify a message buffer to receive the encoded message Specification of a dynamic message buffer is possible by setting the buffer address argument to null and the buffer size argument to zero An encode function can then be called to encode the message If the return status indicates success then the message will have been encoded in the given buffer XML encoding starts from the beginning of the buffer and proceeds from low memory to high memory until the message is complete This differs from BER where encoding was done from back to front Therefore the buffer start address is where the encoded XML message begins If a dynamic message buffer was used the start address of the encoded message can be obtained by calling the rtX mlEncGetMsgPtr function Since the e
134. atus The return value is a status value indicating whether encoding was successful or not Zero indicates success If encoding failed the status value will be a negative number The encode buffer method printErrorInfo can be invoked to get a textual explanation and stack trace of where the error occurred 6 If encoding was successful get the start of message pointer and message length The start of message pointer is obtained by calling the getMsgPtr method of the encode buffer object If static encoding was specified i e a message buffer address and size were specified to the XML Encode Buffer class constructor the start of message pointer is the buffer start address The message length is obtained by calling the getMsgLen method of the encode buffer object A program fragment that could be used to encode an employee record is as follows include employee h include file generated by ASNIC 185 Generated XML Decode Functions main OSOCTET msgbuf 4096 int msglen stat step 1 instantiate an instance of the XML encode buffer class This example specifies a static message buffer OSXMLEncodeBuffer encodeBuffer msgbuf sizeof msgbuf step 2 populate msgData with data to be encoded ASN1T_PersonnelRecord msgData msgData name givenName SMITH step 3 instantiate an instance of the ASN1C_ lt ProdName gt class to associate th ncode buffer and message data A
135. ax Compatability Options J Generate code compatible with compiler version Next gt Cancel Help This dialog permits users to modify the code that is generated by the compiler by adding or subtracting functionality or by applying certain optimizations to the output Basic encoding rules are selected by default Only one of BER DER and CER can be checked at any time XML and XER are also mutually exclusive options C C Code Generation Options By default encoding decoding and initialization functions are generated by the compiler If the target application does not require encoding or decoding capabilities for example if it is only intended to read messages and does not need to write them unchecking the corresponding checkbox will reduce the amount of code generated Initialization functions produce extra code but usually improve overall performance Other functions may also be generated if desired Memory Free Copy Compare Test and Named bit macros all supply extra functionality or control of generated types Check Stream to modify generated encode and decode functions to use streams instead of memory buffers This allows encoding and decoding to a source or sink such as a file or socket Stream based encoding and decoding cannot be combined with buffer based As an aid to debugging Print functions may also be generated Three different different types exist print to stdout print to string
136. be added to a choice group In this case an ASN 1 SEQUENCE is formed consisting of the attribute elements and an embedded element choice for the choice group An example of this is as follows lt xsd complexType name NamePart gt lt xsd choice gt lt xsd element name givenName type xsd string gt lt xsd element name initial type xsd string gt lt xsd element name familyName type xsd string gt lt xsd choice gt lt xsd attribute name occupation type xsd string gt lt xsd complexType gt This results in the following C type definitions being generated 97 xsd any Attribute define T_NamePart_choice_givenName 1 define T_NamePart_choice_initial 2 define T_NamePart_choice_familyName 3 typedef struct EXTERN NamePart_choice int t union t 1 const OSUTF8CHAR givenName t 2 const OSUTF8CHAR initial t 3 const OSUTF8CHAR familyName u NamePart_choice typedef struct EXTERN NamePart struct unsigned occupationPresent 1 m const OSUTF8CHAR occupation NamePart_choice choice NamePart In this case occupation attribute declaration was added as before But the choice group became a separate em bedded element called choice which the ASNIC compiler pulled out to create the NamePart_choice temporary type This type was then referenced by the choice element in the generated type definition for NamePart xsd anyAttribute
137. bject1 element2 value gt lt object1 element3 type gt lt objectl name gt lt elementl gt lt object2 element1 value gt lt element2 gt lt object2 element2 value gt lt object2 element3 type gt lt object2 name gt In this definition the first two elements of the sequence would use the equivalent C or C type as defined in the fixed type field in the information object This is the same as in the legacy model The open type field element3 would be expanded into the union structure as is shown The lt SelectorEnumType gt would be an enumerated type that is generated to represent each of the choices in the referenced information object set The union then contains an entry for each of the possible types as defined in the object set that can be used in the open type field Comments are used to list the fixed type fields corresponding to each open type field An example of the code that is generated from the S1AP sample ASN 1 snippet above is as follows 77 3GPP Table Constraint Model typede be os Tbs Tl 3 ete SLAR f enum handoverPreparation handoverResourceAllocation pathSwitchRequest ELEMENTARY_PROCEDURE_TVALUE 7 typedef struct InitiatingMessage ProcedureCode procedureCode Criticality criticality information object selector S1AP_ELEMENTARY_PROCEDURE_TVALUE t S1AP ELEMENTARY
138. ble name m and contains single bit elements of the form lt fieldname gt Present as follows struct unsigned lt field namel gt Present 1 unsigned lt field name2 gt Present 1 m In this case the fields included in this construct correspond to only those fields marked as OPTIONAL within the CLASS If a CLASS contains no optional fields the entire construct is omitted 85 Legacy Table Constraint Model For example we will change the CLASS in the previous example to make one field optional ATTRIBUTE CLASS amp Type OPTIONAL amp id OBJECT IDENTIFIER UNIQUE In this case the following C typedef is generated in C struct or C class definition struct unsigned TypePresent 1 m When this structure is populated for encoding the information object processing code will set TypePresent flag ac cordingly to indicate whether the field is present or not In C code generation an additional method is generated for an optional field as follows OSBOOL is lt FieldName gt Present if m lt FieldName gt Present return TRUE else return FALSE e This function is used to check if the field value is present in an information object definition Generation of New ASN 1 Assignments from CLASS Assignments During CLASS definition code generation the following new assignments are created for C or C code generation 1 A new Type Assignment is
139. c realloc_func OSFreeFunc free_func The malloc realloc and free functions must have the same prototype as the standard C functions Some systems do not have a realloc like function In this case realloc_func may be set to NULL This will cause the malloc_func free_func pair to be used to do reallocations This function must be called before the context initialization function rtInitContext because context initialization requires low level memory management facilities be in place in order to do its work Note that this function makes use of static global memory to hold the function definitions This type of memory is not available in all run time environments most notably Symbian In this case an alternative function is provided for setting the memory functions This function is rtxJnitContextExt which must be called in place of the standard context initialization function rtInitContext In this case there is a bit more work required to initialize a context because the ASN 1 subcontext must be manually initialized This is an example of the code required to do this int stat rtxInitContextExt pctxt malloc_func realloc_func free_func if 0 stat Add ASN 1 error codes to global table rtErrASNlInit 119 Dynamic Memory Management Init ASN 1 info block stat rtCtxtInitASNlInfo pctxt Memory management can also be tuned by setting the default memory heap block size The way memory m
140. code is generated for the Information Object Sets defined within a specification in the form of a global array of structures Each structure in the array is an equivalent C structure representing the corresponding ASN 1 information object Additional encode and decode functions are also generated for each type that contains table constraints These functions have the following prototypes BER DER int asnlETC_ lt ProdName gt OSCTXT pctxt lt ProdName gt pvalue int asnlDTC_ lt ProdName gt OSCTXT pctxt lt ProdName gt pvalue 109 Additional Code Generated with the tables option PER int asnlPETC_ lt ProdName gt OSCTXT pctxt lt ProdName gt pvalue int asnlPDTC_ lt ProdName gt OSCTXT pctxt lt ProdName gt pvalue The purpose of these functions is to verify the fixed values within the table constraints are what they should be and to encode or decode the open type fields using the encoder or decoder assigned to the given table row Calls to these functions are automatically built into the standard encode or decode functions for the given type They should be considered hidden functions not for use within an application that uses the API C Code Generation For C code is generated for ASN 1 classes information objects and information object sets This code is then referenced when table constraint processing must be performed Each of the generated C classes builds on each other First th
141. complete This is sometimes referred to as forward encoding This differs from regular BER where encoding is done from back to front Indefinite lengths are used for all constructed elements in the message Also there is no permanent buffer for streaming encoding all octets are written to the stream The buffer in the context structure is used only as a cache If C code generation is specified a control class is generated that contains an EncodeTo method that wraps the stream encode C function This function is invoked through the class interface to convert a populated msgData attribute variable into an encoded ASN 1 message Generated Streaming C Function Format and Calling Pa rameters The format of the name of each generated streaming encode function is as follows asnlBSE_ lt prefix gt lt prodName gt where lt prodName gt is the name of the ASN 1 production for which the function is being generated and lt prefix gt is an optional prefix that can be set via a configuration file setting The configuration setting used to set the prefix is the lt typePrefix gt element This element specifies a prefix that will be applied to all generated typedef names and function names for the production The calling sequence for each encode function is as follows stat asnlBSE_ lt name gt OSCTXT pctxt lt name gt pvalue ASNiTagType tagging In this definition lt name gt denotes the prefixed production name defined ab
142. config gt section Name lt events gt lt events gt Values defaultValue keyword Description This configuration item is for use with Event Handling as described in a later section in this document It is used to include a special event that is fired when a PER message is being parsed This event occurs at the location a value should be present in the message but is not and a default value has been specified in the ASN 1 file for the element In this case the normal event sequence startElement con tents endElement is executed using the default value lt storage gt lt storage gt dynamic Static list array or dynamicArray keyword If dynamic it indicates that dynamic storage i e point ers should be used everywhere within the generated types where use could result in lower memory consumption These places include the array element for sized SE QUENCE OF SET OF types and all alternative elements within CHOICE constructs If static it indicates static types should be used in these places In general static types are easier to work with If list a linked list type will be used for SEQUENCE OF SET OF constructs instead of an array type If array an array type will be used for SE QUENCE OF SET OF constructs The maxSize attribute can be used in this case to specify the size of the array vari able for example lt storage maxSize 12 gt array lt stor age gt If dynamicArray a dynamic a
143. configuration file variable the lt isBigInteger gt setting is used to do this see the section describing the configuration file for full details When the compiler detects this setting it will declare the integer to be a character string variable instead of a C int or unsigned int type The character string would then be populated with a character string representation of the value to be encoded Supported character string representations are hexadecimal strings starting with Ox octal strings starting with 0o and decimal no prefix For example the following INTEGER type might be declared in the ASN 1 source file INTEGER SecurityKeyType APPLICATION 2 Then in a configuration file used with the ASN 1 definition above the following declaration can be made lt production gt lt name gt SecurityKeyType lt name gt lt isBigInteger gt lt production gt This will cause the compiler to generate the following type declaration BIT STRING typedef const char SecurityKeyType The SecurityKeyType variable can now be populated with a hexadecimal string for encoding such as the following SecurityKeyType secKey 0xfd09874da875cc90240087cd12fd Note that in this definition the 0x prefix is required to identify the string as containing hexadecimal characters On the decode side the decoder will populate the variable with the same type of character string after decoding There are also a number of run
144. created for a TypeField s type definition as follows _ lt ClassName gt _ lt FieldName gt lt Type gt Here ClassName is replaced with name of the Class Assignment and FieldName is replaced with name of this field Type is the type definition in CLASS s TypeField This type is used as a defined type in the information object definition for an absent value of the TypeField It is also useful for generation of a value for a related Open Type definition in a table constraint 2 A new Type Assignment is created for a Value Field or Value Set Field type definition as follows if the type definition is one of the following ConstraintedType ENUMERATED NamedList BIT STRING SEQUENCE SET CHOICE SEQUENCE OF SET OF _ lt ClassName gt _ lt FieldName gt lt Type gt Here ClassName is replaced with the name of the CLASS assignment and FieldName is replaced with name of the ValueField or ValueSetField Type is the type definition in the CLASS s ValueField or ValueSetField This type will appear as a defined type in the CLASS s ValueField or ValueSetField This new type assignment is used for compiler internal code generation purpose It is not required for a user to understand this logic 3 Anew Value Assignment is created for a ValueField s default value definition as follows _ lt ClassName gt _ lt FieldName gt _default lt Type gt lt Value gt Here ClassName is replaced with name of the Class Assignment and Fie
145. cri a a E R e a e a E eed lath E eed ead 91 XSD Complex Py pes seysete Feces eis see a ce ei E Sa ee tS cae See ete a 92 xsd Seguente eiye E E E E R E sun dseal sea EE EA EEE EE E 92 xsd all eaaa E E ae My oan ace bee E ee ee sed ae ees cea 93 XSi ChOmCe and Xs Union saei neen a ae nase gee tevebaes See e Saves E yawn Bee teceeded Sonu NE REES 93 Repeating Groups s eer n e EE e E N E E E A Deuce amt oven sd ube eh E ok one E aN 94 Repeating Elements spiesen oaee a detec suche sume E RE ea ae EEA EER EEE E 95 paa E S E EESE S E E dehusse au dale ddeted ei Na ode aeeeaeeNs 96 XSCIAMY essare a cee A R A E aces E E E ESSES 96 XML Attribute Declarations a 2a yee ck pease dei E e N eed oh E E EEA R ieee 97 xsd any Attribute anye e N ph ven dosh ese sphee a ees Asse yeen Shek vaeme cep ESER NE SN 98 xXSdisimpleContent E Asda Ae SO aah an eden aad Stee ee das sen ade dea eds 99 XSi ComplexContent 34 4 s ances seas does tawesysdegacdonu eden seas ages a Saneadent root dm dan etuwetuouetaseys 100 Substitution Groups ea ee a E EE E N wee tape teleae poner eet eed 101 Generated Encode Decode Function and Methods sssesrseeerssessrrrrssrrresrrsrrsrrerrrrerrrrresreersrrerrsresrreees 103 Encode Decode Function Prototypes ce rana aa e r E a E a ES 103 Generated C Control Class Definition sii esns e E E eens S EEE AS 104 BER DER or PER Class Definition seiis ea T EE E EE EECa EN EE ES 104 XER Class Definition sisser ee a saun
146. ctions are generated when the xml switch is specified on the command line These are similar to the XER encode functions described earlier Like XER this function allows data in a populated variable 181 Generated XML Encode Functions to be formatted into an XML document Unlike the XER variant this function will produce XML that adheres more closely to the Worldwide Web Consortium W3C XML conventions In particular the following differences exist e Lists of numbers enumerated tokens and named bits are expressed in space separated list form instead of as indi vidually wrapped elements or value lists For example the ASN 1 specification A SEQUENCE OF INTEGER with value 1 2 3 would produce the following encoding in XER lt A gt lt INTEGER gt 1 lt INTEGER gt lt INTEGER gt 2 lt INTEGER gt lt INTEGER gt 3 lt INTEGER gt lt A gt in XML it would be the following lt A gt I 2 3 lt A gt The values of the BOOLEAN data type are expressed as the lower case words true or false with no delimiters In XER the values are lt TRUE gt and lt FALSE gt e Enumerated token values are expressed as the identifiers themselves instead of as empty XML elements i e ele ments wrapped in lt gt For example a value of the ASN 1 type Colors ENUMERATED red blue green equal to red would simply be lt color gt red lt color gt instead of lt color gt lt red gt
147. ctions are used These can be changed by calling the rtMemSetAllocFuncs function This function takes as arguments function pointers to the allocate reallocate and free functions to be used in place of the standard C functions Another run time memory management function that can improve performance is 7tMemReset This function is useful when decoding messages in a loop It is used instead of rtMemF ree at the bottom of the loop to make dynamic memory available for decoding the next message The difference is that rtMemReset does not actually free the dynamic memory It instead just resets the internal memory management parameters so that memory already allocated can be reused Therefore all the memory required to handle message decoding is normally allocated within the first few passes of the loop From that point on that memory is reused thereby making dynamic memory allocation a negligent issue in the overall performance of the decoder A more detailed explanation of these functions and other memory management functions can be found in the C C Common Run Time Library Reference Manual Compact Code Generation Using the compact code generation option compact and lax validation option lax can also improve decoding performance The compact option causes code to be generated that contains no diagnostic or error trace messages In addition some status checks and other non critical code are removed providing a slightly less robust but fast
148. d an option to save the project and the output from compilation Selected options are reflected in the command line Click Finish to terminate the program The wizard will ask whether or not to save any changes made whether a new project has been created or not 23 Compiling and Linking Generated Code Compiling and Linking Generated Code C C source code generated by the compiler can be compiled using any ANSI standard C or C compiler The only additional option that must be set is the inclusion of the ASN 1 C C header file include directory with the I option When linking a program with compiler generated code it is necessary to include the ASN 1 run time libraries It is necessary to include at least one of the encoding rules libraries asn1ber asn per or asn1xer as well as the common run time functions library asnIrt See the ASNIC C C Run time Reference Manual for further details on these libraries For static linking on Windows systems the name of the library files are asnI ber_a lib asnIper_a lib or asnIxer_a lib for BER DER CER PER XER or XML respectively and asn rt_a lib for the common run time components On UNIX Linux the library names are libasnIber a libasnIper a libasnIxer a libasn1xml a and libasnIrt a The library files are located in the lib subdirectory For UNIX the L switch should be used to point to the subdirectory path and lasn ber lasn1 per lasn1xer lasn1xml and or lasnIrt us
149. d is faster as it simply returns a pointer to the actual start of message that is maintained within the message buffer object The getMsgCopy method will return a copy of the message Memory for this copy will be allocated using the standard new operator so it is up to the user to free this memory using delete when finished with the copy A program fragment that could be used to encode an employee record is as follows This example uses a static encode buffer include employee h include file generated by ASNIC main const OSOCTET msgptr OSOCTET msgbuf 1024 130 Generated C Encode Method Format and Calling Parameters int msglen step 1 construct ASNIC C generated class this specifies a static encode message buffer ASNIBEREncodeBuffer encodeBuffer msgbuf sizeof msgbuf ASN1T_PersonnelRecord msgData ASN1C_PersonnelRecord employ encodeBuffer msgData step 2 populate msgData structure with data to be encoded msgData name SMITH step 3 invoke Encode method if msglen employee Encode gt 0 encoding successful get pointer to start of message msgptr encodeBuffer getMsgPtr else error processing The following code fragment illustrates encoding using a dynamic buffer This also illustrates using the getMsgCopy method to fetch a copy of the encoded message include employee h include file generated by A
150. d just like any other compiler generated structure for working with ASN 1 data Note NOTE It is recommended that if a specification contains multiple ASN 1 source files that reference EXTER NAL all of these source files be compiled with a single ASN1C call in order to ensure that only a single copy of the Asn1External source files are generated EMBEDDED PDV The ASN 1 EMBEDDED PDV type is a useful type used to include non ASN 1 or other data within an ASN 1 encoded message This type is described using the following ASN 1 SEQUENCE EmbeddedPDV UNIVERSAL 11 IMPLICIT SEQUENCE identification CHOICE syntaxes SEQUENCE abstract OBJECT IDENTIFIER transfer OBJECT IDENTIFIER ca na 68 Parameterized Types syntax OBJECT IDENTIFIER presentation context id INTEGER context negotiation SEQUENCE presentation context id I transfer syntax OBJECT IDENTIFIER transfer syntax OBJECT IDENTIFIE fixed NULL 7 Ww data value descriptor ObjectDescriptor OPTIONAL data value OCTET STRING WITH COMPONENTS data value descriptor ABSENT The ASNIC compiler is used to create a meta definition for this structure This code will be always generated in the AsnlEmbeddedPDV h and AsnlEmbeddedPDV c cpp files The code will only be generated if the given ASN 1 source specification req
151. d to model an ASN 1 CLASS contains member variables for each of the fields within the class Derived information object classes are required to populate these variables with the values defined in the ASN 1 information object specification The C class also contains virtual methods representing each of the type fields within the ASN 1 class specification If the field is not defined to be OPTIONAL in the ASN 1 specification then it is declared to be abstract in the generated class definition A class generated for an ASN 1 information object that references this base class is required to implement these abstract virtual methods For each of the following CLASS fields a corresponding member variable is generated in the C class definition as follows For a Value Field definition the following member variable will be added Also an Equals method will be added if required for table constraint processing lt TypeName gt lt FieldName gt inline OSBOOL idEquals lt TypeName gt pvalue For a Type Field definition a virtual method is added for each encoding rules type to call the generated C encode and decode functions If print is specified a print method is also generated virtual int encode lt ER gt lt FieldName gt OSCTXT pctxt ASN1ITObject amp object return 0 virtual int decode lt ER gt lt FieldName gt OSCTXT pctxt ASN1TObject amp object return 0 virtual void print lt FieldName gt ASN1Co
152. ding a Series of Messages Using the Streaming C Control Class Interface Encoding a series of messages using the streaming C control class is similar to the C method of encoding All that is necessary is to create a loop in which EncodeTo or Encode methods will be called or the overloaded lt lt streaming operator It is also possible to call different EncodeTo methods or Encode or operator lt lt one after another An example showing how to do this is as follows include employee h include file generated by ASN1C include rtbersrc ASNIBEREncodeStream h include rtxsrc OSRTFileOutputStream h 138 Generated BER Decode Functions int main const OSOCTET msgptr OSOCTET msgbuf 1024 int msglen const char filename message dat step 1 construct stream object ASN1IBEREncodeStream out new OSRTFileOutputStream filename if out getStatus 0 out printErrorInfo return 1 step 2 construct ASNIC C generated class ASN1T_PersonnelRecord msgData ASN1C_PersonnelRecord employ msgData for step 3 populate msgData structure with data to be encoded note this uses the generated assignment operator to assign a string msgData name SMITH step 4 invoke lt lt operator or EncodeTo method out lt lt employee or employee EncodeTo out can be used here step 5 fetch and check status
153. ding or decoding date values when the month or day value is not within the legal range 1 12 for month and 1 to whatever the max days is for a given month 15 RTERR_TOODEEP Nesting level too deep This status code is returned when a preconfigured maximum nesting level for elements within a content model group is exceeded 16 RTERR_CONSVIO Constraint violation This status code is returned when constraints defined the schema are violated These include XSD facets such as minmaxOccurs minmaxLength pat terns etc Also ASN 1 value range size and permitted alphabet constraints 218 General Status Messages Error Code Error Name Description 17 18 RTERR_ENDOFFILE RTERR_INVUTF8 Unexpected end of file error This status code is returned when an unexpected end of file condition is detected on decode It is similar to the ENDOFBUF error code de scribed above except that in this case decoding is being done from a file stream instead of from a memory buffer Invalid UTF 8 character encoding This status code is re turned by the decoder when an invalid sequence of bytes is detected in a UTF 8 character string 19 RTERR_OUTOFBND Array index out of bounds This status code is returned when an attempt is made to add something to an array and the given index is outside the defined bounds of the array RTERR_INVPARAM Invalid parameter passed to a function of method This
154. duction level by including them within a lt production gt section Name Values Description lt name gt module name This attribute identifies the module to which this section lt name gt applies It is required lt ctype gt byte int16 uintl6 int32 This is used to specify a specific C integer or character uint32 int64 string charar ray string type be used in place of the default definition gener ated by ASNIC In the case of integers ASN1C will nor mally try and use the smallest integer type available based on the value or value range constraint on the integer type If the integer is not constrained the int32 32 bit integer 29 Compiler Configuration File Name Values Description type will be used For character string ASNIC will use a character string pointer char by default The chararray item can be used on strings with size constrains to specify a static character array variable be used lt storage gt lt storage gt dynamic Static list array or dynamicArray keyword The definition is the same as for the global case except that the specified storage type will only be applied to the generated C or C type for the given production lt typePrefix gt lt typePrefix gt prefix text This is used to specify a prefix that will be applied to all generated C and C typedef names note for C the prefix is applied after the standard ASN1T_ prefix
155. dynamic buffer include employee h include file generated by ASNIC main OSOCTET msgptr int msglen OSCTXT ctxt Employee employee typedef generated by ASNIC if rtInitContext amp ctxt 0 initialization failed could be a license problem printf context initialization failed check license n return 1 xe_setp amp ctxt NULL 0 mployee name givenName SMITH Eal msglen asnlE_Employee amp ctxt amp employee ASN1EXPL if msglen gt 0 msgptr xe_getp amp ctxt rtxMemFree amp ctxt don t call free msgptr else error processing 128 Generated C Encode Method Format and Calling Parameters Encoding a Series of Messages Using the C Encode Functions A common application of BER encoding is the repetitive encoding of a series of the same type of message over and over again For example a TAP3 batch application might read billing data out of a database table and encode each of the records for a batch transmission If a user was to repeatedly allocate free memory and reinitialize the C objects involved in the encoding of a message performance would suffer This is not necessary however because the C objects and memory heap can be reused to allow multiple messages to be encoded As example showing how to do this is as follows include employee h include file generated by ASNIC ma
156. e Note that this usage summary shows all options for the pro version of ASN1C Some of these options are not available in the basic version Running ASNIC from the Command line To use the compiler at a minimum an ASN 1 or XSD source file must be provided The source file specification can be a full pathname or only what is necessary to qualify the file If directory information is not provided the user s current default directory is assumed If a file extension is not provided the default extension asn is appended to the name Multiple source filenames may be specified on the command line to compile a set of files The wildcard characters and are also allowed in source filenames for example the command asnlc asncode gt will compile all ASN 1 files in the current working directory The source file s must contain ASN 1 productions that define ASN 1 types and or value specifications This file must strictly adhere to the syntax specified in ASN 1 standard ITU T X 680 The asnstd x208 command line option should be used to parse files based on the 1990 ASN 1 standard x 208 or that contain references to ROSE macro specifications The following table lists all of the command line options and what they are used for The options are shown in alpha betical order Note that the Java and C options are not shown here They are shown in their respective documents Option Argument Description 3gpp None This option
157. e C malloc and free functions These functions are very expensive in terms of per formance The large blocks of memory are tracked through the ASN 1 context block OSCTXT structure For C this means that an initialized context block is required for all memory allocations and deallocations All allocations are done using this block as an argument to routines such as rtxMemAlloc All memory can be released at once when a user is done with a structure containing dynamic memory items by calling rtxMemFree Other functions are available for doing other dynamic memory operations as well See the C C Run time Reference Manual for details on these High Level Memory Management API The high level memory management API consists of C macros and functions called in gemerated code and or in application programs to allocate and free memory within the ASNIC run time At the top level are a set of macro definitions that begin with the prefix rtxMem These are mapped to a set of similar functions that begin with the prefix rtxMemHeap A table showing this basic mapping is as follows Macro Function Description rtxMemAlloc rtxMemHeapAlloc Allocate memory rtxMemAllocZ rtxMemHeapAllocdzZ Allocate and zero memory rtxMemRealloc rtxMemHeapRealloc Reallocate memory rtxMemF ree rtxMemHeapFreeAl1 Free all memory in context rtxMemFreePtr rtxMemHeapFreePtr Free a specific memory block 117 Dynamic Memory Manag
158. e a variable of the generated ASN 1C_ lt name gt class specifying the item created in 2 as an argument to the constructor 5 Invoke the EncodeTo method or lt lt operator A program fragment that could be used to encode an employee record is as follows This example uses a file output stream include employee h include file generated by ASNIC include rtbersrc ASN1IBEREncodeStream h include rtxsrc OSRTFileOutputStream h 137 Generated Streaming C Encode Method Format and Calling Parameters main int msglen const char filename message dat step 1 construct output stream object ASN1BEREncodeStream out new OSRTFileOutputStream filename if out getStatus 0 out printErrorInfo return 1 step 2 construct ASNIC C generated class ASN1T_PersonnelRecord msgData ASN1C_PersonnelRecord employ msgData step 3 populate msgData structure with data to be encoded note this uses the generated assignment operator to assign a string msgData name SMITH step 4 invoke lt lt operator or EncodeTo method out lt lt employee or employee EncodeTo out can be used here step 5 check status of the operation if out getStatus 0 printf Encoding failed Status i n out getStatus out printErrorInfo return 1 if trace printf Encoding was successful n Enco
159. e classes generated that correspond to ASN 1 CLASS definitions form the base class foundation Then C classes derived from these base classes corresponding to the information objects are generated Finally C singleton classes corresponding to the information object sets are generated Each of these classes provides a container for a collection of C objects that make up the object set Additional encode and decode functions are also generated as they were in the C code generation case for interfacing with the object definitions above These functions have the following prototypes BER DER int asnlETC_ lt ProdName gt OSCTXT pctxt lt ProdName gt pvalue lt ClassName gt pobject int asnlDTC_ lt ProdName gt OSCTXT pctxt lt ProdName gt pvalue lt ClassName gt pobject PER int asnlPETC_ lt ProdName gt OSCTXT pctxt lt ProdName gt pvalue lt ClassName gt pobject int asnlPDTC_ lt ProdName gt OSCTXT pctxt lt ProdName gt pvalue lt ClassName gt pobject These prototypes are identical to the prototypes generated in C code generation case except for the addition of the pobject argument This argument is for a pointer to the information object that matches the key field value for a given encoding These functions have different logic for processing Relative and Simple table constraints The logic associated with each case is as follows On the encode side Relative Table Constraint 1 Th
160. e function result variable stat returns the status of the encode operation Status code zero indicates the function was successful A negative value indicates encoding failed Return status values are defined in the rtxErrCodes h include file The error text and a stack trace can be displayed using the rtvErrPrint function Generated C Encode Method Format and Calling Pa rameters Generated encode functions are invoked through the class interface by calling the base class Encode method The calling sequence for this method is as follows stat lt object gt Encode In this definition lt object gt is an object of the class generated for the given production The function result variable stat returns the status value from the XER encode function This status value will be zero if encoding was successful or a negative error status value if encoding fails Return status values are defined in the rtxErrCodes h include file The user must call the encode buffer class methods getMsgPtr and getMsgLen to obtain the starting address and length of the encoded message component Procedure for Calling C Encode Functions This section describes the step by step procedure for calling C XER encode functions This procedure is similar to that for the other encoding methods except that some of the functions used are specific to XER Before an XER encode function can be called the user must first initialize an encoding context block structure The c
161. e gt lt FieldName gt For TypeField definitions an encode and decode function pointer and type size field is generated to hold the informa tion of the type for the OpenType If the print option is selected a print function pointer is also added int lt FieldName gt Size int encode lt FieldName gt int decode lt FieldName gt void print lt FieldName gt For an Object Field lt ClassName gt lt FieldName gt For an ObjectSetField definition an array of class definitions is generated to hold the list of information objects lt ClassName gt lt FieldName gt In each of these definitions lt FieldName gt would be replaced with the name of the field without the leading amp lt TypeName gt would be replaced with the C type name for the ASN 1 Type lt ClassName gt would be replaced with the C type name of the class for the Information Object As an example consider the following ASN 1 class definition ATTRIBUTE CLASS amp Type amp id OBJECT IDENTIFIER UNIQU WITH SYNTAX amp Type ID amp id GI This would result in the following definition in the C source file GI typedef struct ATTRIBUTE int TypeSize int encodeType OSCTXT void ASN1TagType int decodeType OSCTXT void ASNiTagType int ASNI1OBJID id 83 Legacy Table Constraint Model C Code generation The C abstract class generate
162. e is a choice between the base type and all derivations of that base type It will be used wherever the base type is referenced This makes it possible to use an instance of the extended type in these places The case of restriction is handled in a similar fashion In this case instead of creating a new type with additional elements a new type is created with all restrictions implemented This type may be identical to the base type definition Substitution Groups A substitution group is similar to a complex content type in that it allows derivations from a common base In this case however the base is an XSD element and the substitution group allows any of a set of elements defined to be in the group to be used in the place of the base element A simple example of this is as follows lt xsd element name MyElement type MyType gt lt xsd complexType name MyType gt lt xsd sequence gt lt xsd element ref MyBaseElement gt lt xsd sequence gt lt xsd complexType gt lt xsd element name MyBaseElement type xsd string gt lt xsd element name MyExtendedElement type xsd string substitutionGroup MyBaseEle In this case the global element MyElement references MyType which is defined as a sequence with a single element reference to MyBaseElement MyBaseElement is the head element in a substitution group that also includes MyExtendedElement This means MyType can either reference MyBaseElement or MyExtendedElement
163. e lookupObject method is invoked on the object set instance to find the class object for the data in the populated type variable to be encoded 110 General Procedure for Table Constraint Encoding 2 If a match is found the table constraint encode function as defined above is invoked This function will verify all fixed type values match what is defined in the information object definition and will encode all type fields and store the resulting encoded data in the ASNI TObject encoded fields 3 If a match is not found and the information object set is not extensible then a table constraint error status will be returned If the information object set is extensible a normal status is returned Simple Table Constraint 1 This function will verify all the fixed type values match what is defined in the table constraint information object set If an element value does not exist in the table i e the information object set and the object set is not extensible then a table constraint violation exception will be thrown The normal encode logic is then performed to encode all of the standard and open type fields in the message On the decode side the logic is reversed The normal decode logic is performed to populate the standard and open type fields in the generated structure Relative Table Constraint 1 The lookupObject method is invoked on the decoded key field value to find an object match 2 If a match is found the table constr
164. e turned on canonical encoding removes all encoding options from the final message to produce a single encoded representation of the data The default constructor specifies use of a dynamic encode buffer and canonical encoding set to off 2 Instantiate an ASN1T_ lt type gt object and populate it with data to be encoded 3 Instantiate an ASN1IC_ lt type gt object to associate the message buffer with the data to be encoded 4 Invoke the ASN1C_ lt type gt object Encode method 5 Check the return status The return value is a status value indicating whether encoding was successful or not Zero indicates success If encoding failed the status value will be a negative number The encode buffer method printErrorInfo can be invoked to get a textual explanation and stack trace of where the error occurred 6 If encoding was successful get the start of message pointer and message length The start of message pointer is obtained by calling the getMsgPtr method of the encode buffer object If static encoding was specified i e a message buffer address and size were specified to the XER Encode Buffer class constructor the start of message 175 Procedure for Using the C Control Class Encode Method pointer is the buffer start address The message length is obtained by calling the getMsgLen method of the encode buffer object A program fragment that could be used to encode an employee record is as follows include employee h inc
165. e type exists The following table summarizes these mappings XSD Simple Type ASN 1 Type anyURI UTF8String base64Binary OCTET STRING boolean BOOLEAN byte INTEGER 128 127 date UTF8String datetime UTF8String decimal UTF8String double REAL duration UTF8String ENTITIES SEQUENCE OF UTF8String ENTITY UTF8String float REAL gDay UTF8String gMonth UTF8String gMonthDay UTF8String gYear UTF8String gYearMonth UTF8String hexBinary OCTET STRING ID UTF8String IDREF UTF8String IDREFS SEQUENCE OF UTF8String integer INTEGER int INTEGER 2147483648 2147483647 language UTF8String long INTEGER 9223372036854775808 9223372036854775807 Name UTF8String NCName UTF8String negativelnteger INTEGER MIN 1 91 XSD Complex Types XSD Simple Type ASN 1 Type NMTOKEN UTF8String NMTOKENS SEQUENCE OF UTF8String nonNegativelnteger INTEGER 0 MAX nonPositiveInteger INTEGER MIN 0 normalizedS tring UTF8String positiveInteger INTEGER 1 MAX short INTEGER 32768 32767 string UTF8String time UTF8String token UTF8String unsignedByte INTEGER 0 255 unsignedShort INTEGER 0 65535 unsignedInt INTEGER 0 4294967295 unsignedLong INTEGER 0 18446744073709551615 The C C mappings for these types can be found in the section above on ASN 1 type mappings XSD Complex Types XS
166. each type for example aJnt is used for INTEGER There is one caveat however ASNIC cannot handle multiple unnamed elements in a SEQUENCE or SET with the same type names Element names must be used in this case to distinguish the elements So for the example above the generated code would be as follows typedef OSINT32 AnInt typedef struct Aseq OSINT32 x AnInt anInt Aseq OPTIONAL keyword Elements within a sequence can be declared to be optional using the OPTIONAL keyword This indicates that the element is not required in the encoded message An additional construct is added to the generated code to indicate whether an optional element is present in the message or not This construct is a bit structure placed at the beginning of the generated sequence structure This structure always has variable name m and contains single bit elements of the form lt element name gt Present as follows struct unsigned lt element namel gt Present 1 unsigned lt element name2 gt Present 1 m In this case the elements included in this construct correspond to only those elements marked as OPTIONAL within the production If a production contains no optional elements the entire construct is omitted For example the production in the previous example can be changed to make both elements optional Aseq PRIVATE 2 SEQUENCE Xx INTEGER OPTIONAL AnInt OPTIONAL T In this case the
167. eceived message The only other change was the call to employee memFreeAll that was added at the bottom of the loop Since the objects are not deleted to automatically release allocated memory we need to do it manually This call will free all memory held within the decoding context This will allow the loop to start again with no outstanding memory allocations for the next pass 159 160 Generated PER Functions Generated PER Encode Functions PER encode decode functions are generated when the per switch is specified on the command line For each ASN 1 production defined in the ASN 1 source file a C PER encode function is generated This function will convert a populated C variable of the given type into a PER encoded ASN 1 message If C code generation is specified a control class is generated that contains an Encode method that wraps this function This function is invoked through the class interface to encode an ASN 1 message into the variable referenced in the msgData component of the class Generated C Function Format and Calling Parameters The format of the name of each generated PER encode function is as follows asnlPE_ lt prefix gt lt prodName gt where lt prodName gt is the name of the ASN 1 production for which the function is being generated and lt prefix gt is an optional prefix that can be set via a configuration file setting The configuration setting used to set the prefix is the lt type
168. ecoded producing information on the OPERATION type based on the MACRO definition and message type Invoke Result etc The invoke identifier would also be available for use in session management In our example we would know at this point that we got a login invoke request ROSE OPERATION and ERROR 2 Based on the information from step 1 the ROSE layer would know that the Open Type field contains a pointer and length to an encoded Login ARGUMENT component It would then route this information to the appropriate processor within the Application Layer for handling this type of message 3 The Application Layer would call the specific decoder associated with the Login ARGUMENT It would then have available to it the username password the user is logging in with It could then do whatever applicationspecific processing is required with this information database lookup etc 4 Finally the Application Layer would begin the encoding process again in order to send back a Result or Error message to the Login Request A picture showing this is as follows Application Layer Call specific function to decode Login ARGUMENT and process data A Encoded message pointer and length Decode ROSE header message structure Invoke Open type structure contains message pointer and length of encoded Login ARGUMENT A Encoded ROSE message The login OPERATION also contains references to ERROR definitions These are defined using a separate MAC
169. ect TYPE HandoverType PRESENCE mand Generated IE Append Function A user would need to allocate objects of this structure populate them and add them to the protocol IE list In order to make this easier helper functions are generated assist in adding information items to the list The general format of these append functions is as follows int asnlAppend_ lt ProtocollEsType gt _ lt n gt OSCTXT pctxt lt ProtocollEsType gt plist lt ValueType gt value In this definition lt ProtocollEsType gt refers to the main list type SEQUENCE OF defining the information element list lt n gt is a sequence number that is a 1 based index to each of the different type field options in the associated information object set lt ValueType gt is the type of the value for the indexed information object set item An example of this type of function from the S1AP definitions is as follows Append IE 1 with value type MME_UE_S1AP_ID to list int asnlAppend_HandoverRequired_protocollIEs_1 OSCTXT pctxt HandoverRequired_protocollIEs plist MME_UE_S1AP_ID value Generated IE Get Function In addition to the list append function a second type of helper function is generated to make it easier to find an item in the list based on the key field The general format for this type of function is as follows lt ProtocollE FieldType gt asnlGet_ lt ProtocollEsType gt lt KeyFieldType gt lt key gt lt ProtocollEsTy
170. ects performance vcproj 2003 2005 2008 This option instructs the compiler to generate Visual C 6 0 compatible project files to compile generated source code This is a Windows only option By passing one of the listed years the compiler will generate a project that links against libraries provided for those versions of Vi sual Studio For example specifying 2008 will generate a project that links against libraries in the _vs2008 di rectory Not specifying a year will cause the compiler to link against libraries compiled for Visual Studio 6 0 warnings None Output information on compiler generated warnings Xer None This option instructs the compiler to generate functions that implement the XML Encoding Rules XER as spec ified in the X 693 ASN 1 standard Using the GUI Wizard to Run ASNIC Option Description xml xsd lt filename gt This option instructs the compiler to generate functions that encode decode data in an XML format that is more closely aligned with World Wide Web Consortium W3C XML schema The xsd option can be used in con junction with this option to generate a schema describing the XML format This option instructs the compiler to generate an equiv alent XML Schema Definition XSD for each of the ASN 1 productions in the ASN 1 source file The definitions are written to the given filename or to lt modulename gt xsd if the fil
171. ed for this purpose The dynamicArray keyword can be used at the global module or production level to specify that dynamic memory i e a pointer is used for the array The syntax of this qualifier is as follows lt storage gt dynamicArray lt storage gt The array keyword is used to specify that a static array is to be generated to hold the data In this case if the SE QUENCE OF production does not contain a size constraint the maxSize attribute must be used to specify the maximum size of the array For example lt storage maxSize 100 gt array lt storage gt If maxSize is not specified and the ASN 1 production contains no size constraint then a dynamic array is used The list keyword can also be used in a similar fashion to specify the use of a linked linked structure to hold the elements lt storage gt list lt storage gt See the section entitled Compiler Configuration File for further details on setting up a configuration file Dynamic SEQUENCE OF Type ASN 1 production lt name gt SEQUENCE OF lt type gt Generated C code typedef struct OSUINT32 n lt type gt elem lt name gt Generated C code typedef struct public ASNITPDU OSUINT32 n lt type gt elem ASN1T_ lt name gt ASN1T_ lt name gt ASNIT_ lt name gt Note that parsed values can be accessed from the dynamic data variable just as they would be from a static array variable i e an array subscri
172. ed to be similar in use across the different encoding rule types In other words if you have written an application to use the Basic Encoding Rules BER and then later decide to use the Packed Encoding Rules PER it should only be a simple matter of changing a few function calls to accomplish the change Procedures for such things as populating data for encoding accessing decoded data and dynamic memory management are the same for all of the different encoding rules This section describes common procedures for encoding or decoding data that are applicable to any of the different encoding rules Subsequent sections will then describe what will change for the different rules Dynamic Memory Management The ASN1C run time uses specialized dynamic memory functions to improve the performance of the encoder decoder It is imperative to understand how these functions work in order to avoid memory problems in compiled applications ASNI1C also provides the capability to plug in a different memory management scheme at two different levels the high level API called by the generated code and the low level API that provides the core memory managment functionality The ASNIC Default Memory Manager The default ASN1C run time memory manager uses an algorithm called the nibble allocation algorithm Large blocks of memory are allocated up front and then split up to provide memory for smaller allocation requests This reduces the number of calls required to th
173. ed to link with the libraries For Windows the LIBPATH switch should be used to specify the library path There are several other variations of the C C run time library files for Windows The following table summarizes what options were used to build each of these variations Library Files Description asnilrt_a lib Static single threaded libraries These are built without MT multithreading asnlber_a lib and MD dynamic link libraries options These are not thread safe How asnlper_a lib ever they provide the smallest footprint of the different libraries asnlxer_a lib asnlxml_a lib asnirt lib DLL libraries These are used to link against the DLL versions of the run time asnlber lib libraries asn rt dll etc asnlper lib asnlxer lib asnlxml lib asnirtmt_a lib Static multi threaded libraries These libraries were built with the MT option asnlbermt_a lib They should be used if your application contains threads and you wish to link asnlpermt_a lib with the static libraries note the DLLs are also thread safe asnlxermt_a lib asnilxmimt_a lib asnilrtmd_a lib DLL ready multi threaded libraries These libraries were built with the MD asnlbermd_a lib option They allow linking additional object modules in with the ASNIC run asnlpermd_a lib time modules to produce larger DLLs asnlxermd_a lib asnlxmlimd_a lib For dynamic linking on UNIX Linux a shared object versi
174. ed when the context structure is freed The function result variable st at returns the status of the decode operation Status code 0 0 indicates the function was successful A negative value indicates decoding failed Return status values are defined in the asn type h include file The reason text and a stack trace can be displayed using the rtErrPrint function described later in this document Generated C Decode Method Format and Calling Pa rameters Generated decode functions are invoked through the class interface by calling the base class Decode method The calling sequence for this method is as follows status lt object gt Decode In this definition lt object gt is an object of the class generated for the given production An ASNIPERDecodeBuffer object must be passed to the lt object gt constructor prior to decoding This is where the message start address and length are specified A Boolean argument is also passed indicating whether the message to be decoded was encoded using aligned or unaligned PER The function result variable status returns the status of the decode operation The return status will be zero 0 if decoding is successful or a negative value if an error occurs Return status values are documented in the C C Common Functions Reference Manual and in the rtxErrCodes h include file Procedure for Calling C Decode Functions This section describes the step by step procedure for calling a C PER decode f
175. ed with an identifier code that is too large to fit in a 32 bit integer variable 222 ASN 1 specific Status Messages Error Code Error Name Description ASN_E_BASE 3 ASN_E_BASE 4 ASN_E_INVBINS ASN_E_INVINDEX Invalid binary string This error code is returned when de coding XER data and a bit string value is received that contains something other than 1 or 0 characters Invalid table constraint index This error code is returned when a value is provided to index into a table and the value does not match any of the defined indexes ASN_E_BASE 5 ASN_E_INVTCVAL Invalid table constraint value This error code is returned when a the value for an element in a table constrained message instance does not match the value for the element defined in the table ASN_E_BASE 6 ASN_E_CONCMODF Concurrent list modification error This error is returned from within a list iterator when it is detected that the list was modified outside the control of the iterator ASN_E_BASE 7 ASN_E_BASE 8 ASN_E_ ILLSTATE ASN_E_ NOTPDU Illegal state for operation This error is returned in places where an operation is attempted but the object is not in a state that would allow the operation to be completed One example is in a list iterator class when an attempt is made to remove a node but the node does not exist This error is returned when a control class Encode or De code method i
176. edAttributes 1 decodeType amp asnlD__commonName_Type SupportedAttributes 1 id numids 3 SupportedAttributes 1 id subid 0 O SupportedAttributes 1 id subid 1 1 SupportedAttributes 1 id subid 2 1 SupportedAttributes 1 id subid 3 1 C Code Generation In C ASN 1 information object sets are mapped to C classes In this case a C singleton class is generated This class contains a container to hold an instance of each of the ASN 1 information object C objects in a static array The class also contains an object lookup method for each of the key fields Key fields are identified in the class as either a fields that are marked unique or b fields that are referenced in table constraints with the notation The generated constructor initializes all required values and information objects An example of an information object set that uses the information object class defined above is as follows SupportedAttributes ATTRIBUTE name commonName This results in the generation of the following C class class EXTERN SupportedAttributes protected ATTRIBUTE mObjectSet 2 const size_t mNumObjects 89 Legacy Table Constraint Model static SupportedAttributes mpInstance SupportedAttributes OSCTXT pctxt public ATTRIBUTE lookupObject ASN1ITObjJId _id static SupportedAttributes instance OSCTXT pctxt 3 The mOb ject Set array is the container for the informa
177. efile is generated it is assumed that the ASNIC project exists within the ASNIC installation directory tree The generation logic tries to determine the root directory of the installation by traversing upward from the project directory in an attempt to locate the rtsrc subdirectory which is assumed to be the installation root directory The makefile variable OSROOTDIR is then set to this value A similar traversal is done to locate the platform mk and xmlparser mk files These paths are then set in the makefile If the project directory is located outside of the ASNIC directory tree the user must set the OSROOTDIR environment variable to point at the ASNIC root directory in order for the makefile generation to be successful If this is done it is assumed that the platform mk and xmlparser mk files are located in this directory as well If the compiler is unable to determine the root directory using any of the methods described above an error will be generated and the user will need to manually edit the makefile to set the required root directory parameters and makefile include file paths Generated VC Project Files The vcproj option causes Microsoft Visual Studio project and workspace files to be generated that can be used to build the generated code The files are compatible with Visual Studio version 6 0 but higher versions of Visula Studio can convert these files to the newer formats This option can be used with the dll option that will generate
178. efixed production name defined above The name argument is used to hold the top level name of the variable being printed It is typically set to the same name as the pvalue argument in quotes for example to print an employee record a call to asnJPrint_Employee employee amp employee might be used 194 Print to String The pvalue argument is used to pass a pointer to a variable of the item to be printed If C code generation is specified a Print method is added to the ASNIC control class for the type This method takes only a name argument the pvalue argument is obtained from the msgData reference contained within the class Print to String The genPrtToStr option causes functions to be generated that print the contents of variables of generated types to a given text buffer This buffer can then be used to output the information to other mediums such as a file or window display It is possible to specify the name of a c or cpp file as an argument to this option to specify the name of the file to which these functions will be written This is an optional argument If not specified the functions are written to separate files for each module in the source file The format of the name of each file is lt module gt PrtToStr c If an output filename is specified after the genPrtToStr qualifier all functions are written to that file The calling sequence for each generated print to string function is as follows asnlP
179. ement See the ASNIC C C Common Runtime Reference Manual for further details on these functions and macros It is possible to replace the high level memory allocation functions with functions that implement a custom memory management scheme This is done by implementing some or all of the C rtxMemHeap functions defined in the following interface note a default implementation is shown that replaces the ASN1C memory manager with direct calls to the standard C run time memory management functions include lt stdlib h gt include rtxMemory h Create a memory heap int rtxMemHeapCreate void ppvMemHeap return 0 Allocate memory void rtxMemHeapAlloc void ppvMemHeap int nbytes return malloc nbytes Allocate and zero memory void rtxMemHeapAllocZ void ppvMemHeap int nbytes void ptr malloc nbytes if 0 ptr memset ptr 0 nbytes return ptr Free memory pointer void rtxMemHeapFreePtr void ppvMemHeap void mem_p free mem_p Reallocate memory void rtxMemHeapRealloc void ppvMemHeap void mem_p int nbytes_ return realloc mem_p nbytes_ Clears heap memory frees all memory reset all heap s variables void rtxMemHeapFreeAll void ppvMemHeap should remove all allocated memory there is no analog in standard memory management Frees all memory and heap structure as well if was allocated void rtxMemHeapRelease void p
180. en type fields is as follow 1 Check the possible Type in the Information Object Set from index element value 2 Assign or cast the Asn Object decoded member variable void to the result type 3 The Asn1 Object encoded field will hold the data in encoded form For the above complete example the Invoke type s argument element will be decoded as one of the types in the SupportedAttributes information object set i e either as a VisibleString or INTEGER type If the SupportedAttributes information object set is extensible then the argument element may be of a type not defined in the set In this case the decoder will set the Asn Object encoded field as before but the Asn1Object decoded field will be NULL indicating the value is of an unknown type 114 General Procedure for Table Constraint Decoding A C program fragment that could be used to decode the Invoke example is as follows include Test h include file generated by ASNIC main OSOCTET msgbuf 1024 ASNITAG msgtag int msglen status step 1 logic to read message into msgbuf step 2 create decode buffer and msg data type ASNIBERDecodeBuffer decodeBuffer msgbuf len ASN1T_Invoke msgData ASN1C_Invoke invok decodeBuffer msgData step 3 call decode function if status invoke Decode 0 decoding successful data in msgData use key field value to set type of message data ASN1
181. ename argument is not pro vided Using the GUI Wizard to Run ASN1C ASNIC includes a graphical user interface GUI wizard that can be used as an alternative to the command line version It is a cross platform GUI and has been ported to Windows and most UNIXes The GUI makes it possible to specify ASN 1 files and configuration files via file navigation windows to set command line options by checking boxes and to get online help on specific options The Windows installation program should have installed an ASN1C Compiler option on your computer desktop and an ASNIC option on the start menu The wizard can be launched using either of these items The UNIX version should be installed in ASN1C_INSTALL_DIR bin no desktop shortcuts are created so it will be necessary to create one or to run the wizard from the command line The wizard is navigated by means of Next and Back buttons Following is the initial window 14 Using the GUI Wizard to Run ASNIC ASNIC compiler Objective Systems Inc objective SYSTEMS INC ASN1C Project Wizard Create a new project ASNIC 6 2 0 z Open an existin i z F Op g Registered to project Name Company Email Next gt Cancel Help The Project Wizard will allow you to save your compilation options and file settings into a project file and retrieve them later If you wish to make a new project click the icon next
182. er code base The ax option causes all constraint checks to be removed from the generated code Performance intensive applications should also be sure to link with the compact version of the base run time libraries These libraries can be found in the ib_opt for optimized subdirectory These run time libraries also have all diag nostics and error trace messages removed as well as some non critical status checks Decode Fast Copy Fast Copy is a special run time flag that can be set for the decoder that can substantially reduce the number of copy operations that need to be done to decode a message The copy operations are reduced by taking advantage of the fact that the data contents of some ASN 1 types already exist in decoded form in the message buffer Therefore there is no need to allocate memory for the data and then copy the data from the buffer into the allocated memory structure As an example of what fast copy does consider a simple ASN 1 SEQUENCE consisting of an element a an INTEGER and b an OCTET STRING Simple SEQUENCE a INTEGER b OCTET STRING Assume an encoded value of this type contains a value of a 123 hex 7B and b contains the hex octets 0x01 0x02 0x03 The generated variable for the OCTET STRING will contain a data pointer So rather than allocate memory for this string and copy the data to it fast copy will simply store a pointer directly to the data in the buffer 14
183. erived from an ASNIEncodeStream class The function result variable st at returns the completion status Error status codes are negative Return status values are defined in the rtxErrCodes h include file Another way to encode a message using the C classes is to use the lt lt streaming operator lt outputStream gt lt lt lt object gt Exceptions are not used in ASNIC C therefore the user must fetch the status value following a call such as this in order to determine if it was successful The getStatus method in the ASN EncodeStream class is used for this purpose Also the method Encode without parameters is supported for backward compatibility In this case it is necessary to create control class i e ASN1C_ lt prodName gt using an output stream reference as the first parameter and msgdata reference as the second parameter of the constructor Procedure for Using the Streaming C Control Class Encode Method The procedure to encode a message directly to an output stream using the C class interface is as follows 1 Create an OSRTOutputStream object for the type of output stream Choices are OSRTFile OutputStream for a file OSRTMemory OutputStream for a memory buffer or OSRTSocketOutputStream for an IP socket connection 2 Create an ASNIBEREncodeStream object using the stream object created in 1 as an argument 3 Create a variable of the ASN T_ lt name gt type and populate it with the data to be encoded 4 Creat
184. es This mapping is defined as follows ASN 1 production lt name gt INTEGER lt value gt Generated code define ASN1V_ lt name gt lt value gt For example the following declaration ivalue INTEGER 5 will cause the following statement to be added to the generated header file 71 REAL Value define ASN1V_ivalue 5 The reason the ASN1V_ prefix is added is to prevent collisions with INTEGER value declarations and other declara tions such as enumeration items with the same name REAL Value The REAL type causes a de fine statement to be generated in the header file of the form ASN1V_ lt valueName gt where lt valueName gt would be replaced with the name in the ASN 1 source file By generating def ine statements the symbolic names can be included in the source code making it easier to adjust the boundary values This mapping is defined as follows ASN 1 production lt name gt REAL lt value gt Generated code define ASN1V_ lt name gt lt value gt For example the following declaration rvalue REAL 5 5 will cause the following statement to be added to the generated header file define ASN1V_rvalue 5 5 The reason the ASN1V_ prefix is added is to prevent collisions with other declarations such as enumeration items with the same name Enumerated Value Specification The mapping of an ASN 1 enumerated value declaration to a global C or C
185. es within productions it is generally not con sidered good style to define productions this way It is much better to manually define the constructed types for use in the final production definition For example the production defined at the start of this section can be rewritten as the following set of productions X SEQUENCE al INTEGER a2 BOOLEAN Y OCTET STRING A SEQUENCE X x Y y This makes the generated code easier to understand for the end user Unnamed Elements Note As of X 680 unnamed elements are not allowed elements must be named ASNIC still provides backward compatibility support for this syntax however In an ASN 1 SEQUENCE definition the lt element name gt tokens at the beginning of element declarations are optional It is possible to include only a type name without a field identifier to define an element This is normally done with defined type elements but can be done with built in types as well An example of a SEQUENCE with unnamed elements would be as follows AnInt PRIVATE 1 INTEGER 55 SEQUENCE Aseq PRIVATE 2 SEQUENCE x INTEGER AnInt In this case the first element x is named and the second element is unnamed ASNIC handles this by generating an element name using the type name with the first character set to lower case For built in types a constant element name is used for
186. ext section instead of XER XML is more closely aligned with W3C standard XML and XML schema The code generated to decode XML messages is different than that of the other encoding rules This is because off theshelf XML parser software is used to parse the XML documents to be decoded This software contains a common interface known as the Simple API for XML or SAX that is a de facto standard that is supported by most parsers ASNIC generates an implementation of the content handler interface defined by this standard This implementation receives the parsed XML data and uses it to populate the structures generated by the compiler The default XML parser used is the EXPAT parser http www expat org This is a lightweight open source parser that was implemented in C The C SAX interface was added by adapting the headers of the Apache XERCES C XML Parser http xml apache org to work with the underlying C code These headers were used to build a common C SAX interface across different vendor s SAX interfaces unlike Java these interfaces are not all the same The ASNIC XER SAX C and C libraries come with the EXPAT parser as the default parser and also include plug in interfaces that allow the code to work with the Microsoft XML parser MSXML The GNOME libxml parser and the XERCES XML parser Interfacing to other parsers only requires building an abstraction layer to map the common interface to the vendor s interface A diagram s
187. f context initialization failed check license n return 1 stat rtxStreamFileCreateWriter amp ctxt filename if stat 0 rtxErrPrint amp ctxt return stat for Step 2 Populate the structure to b ncoded mployee name SMITH Step 3 Call the generated encode function stat asnlBSE_Employee amp ctxt amp employee ASNIEXPL Step 4 Check the return status and break the loop if error occurs if stat 0 error processing break Step 5 Close the stream rtxStreamClose amp ctxt 136 Generated Streaming C Encode Method Format and Calling Parameters Generated Streaming C Encode Method Format and Calling Parameters C code generation of stream based encoders is selected by using the c and stream compiler command line options In this case ASNIC generates an EncodeTo method that wraps the C function call This method provides a more simplified calling interface because it hides things such as the context structure and tag type parameters The calling sequence for the generated C class method is as follows stat lt object gt EncodeTo lt outputStream gt In this definition lt object gt is an instance of the control class i e ASN1C_ lt prodName gt generated for the given production The lt outputStream gt placeholder represents an output stream object type This is an object d
188. f scope return stat Procedure for Interfacing with Other C and C X ML Parser Libraries As mentioned previously the Expat XML Parser library is the default XML parser library implementation used for decoding XER messages It is also possible to use the C SAX handlers generated by ASN1C with other XML parser library implementations The XER Run Time Library ASN1XER provides a common interface to other parsers via a common adapter interface layer There is a special XML interface object file for each of the following supported XML parsers e RTXMLLIBXML2IF interface to LIBXML2 e RTXMLMSXMLIF interface to MSXML e RTXMLXERCESIF interface to XERCES e RTXMLEXPATIF interface to EXPAT The XER Run Time Library is completely independent from the XML readers because the adapter layer within these libraries defines a common SAX API If an application is linked statically then the static variant of one of these interface objects their names have suffix _ A should be linked cooperatively with the XML parser ASNIXER and ASNIRT libraries If the application is linked dynamically using dynamically linked libraries DLL in Windows or shared objects SO or SL in UNIX Linux then it is necessary to link the application with the dynamic variant of the interfaces without suffix _A dynamic version of the XML parser ASN1XER and ASNIRT dynamic libraries Generated XML Encode Functions XML C encode and decode fun
189. fer amp ctxt msgbuf msglen aligned step 2 initialize the data variable asnlInit_PersonnelRecord amp employee step 3 call the decode function stat asnlPD_PersonnelRecord amp ctxt amp employee if stat 0 process received data else error processing rtxErrPrint amp ctxt step 4 free the context rtFreeContext amp ctxt Procedure for Using the C Control Class Decode Method The following are the steps are involved in decoding a PER message using the generated C class 1 Instantiate an ASN 1 PER decode buffer object ASN PERDecodeBuffer to describe the message to be decoded The constructor takes as arguments a pointer to the message to be decoded the length of the message and a flag indicating whether aligned encoding was used or not 2 Instantiate an ASN1T_ lt ProdName gt object to hold the decoded message data 3 Instantiate an ASN1C_ lt ProdName gt object to decode the message This class associates the message buffer object with the object that is to receive the decoded data The results of the decode operation will be placed in the variable declared in step 2 4 Invoke the ASN1C_ lt ProdName gt object Decode method 5 Check the return status The return value is a status value indicating whether decoding was successful or not Zero 0 indicates success If decoding failed the status value will be a negative number The decode buffer
190. fied in the X 682 standard This includes the generation of structures and classes for Information Object Classes Information Objects and Information Object Sets as specified in the X 681 standard Most of the additional items that are generated are read only tables for use by the run time for data validation purposes However generated structures for types that use table constraints are different than when table constraint code gener ation is not enabled These differences will be pointed out There are two models currently supported for table contraint generation 3GPP and Legacy These are documented in the following sections 3GPP Table Constraint Model The 3GPP table constraint model takes advantage of common patterns in a series of ASN 1 specifications in use in 3rd Generation Partnership Project GPP standards These standards include Node Application Part B NBAP Radio Access Network Application Part RANAP and Radio Network Subsystem Application Part RNSAP in the current 3G network and in S1AP and X2AP protocols in the newer 4G network LTE standards While this model was built by studying the patterns in these specifications it should be possible to extend it to fit other table constraint usage patterns as well This was introduced in version 6 1 3 and will become the default model in future versions The existing model the legacy model described below will be maintained for backward compatibility only Generated C Type Def
191. following general form int asnlE_ lt ProdName gt OSCTXT pctxt lt ProdName gt pvalue ASN1TagType tagging int asnlD_ lt ProdName gt OSCTXT pctxt lt ProdName gt pvalue ASNiTagType tagging int length The prototype with the asn E_ prefix is for encoding and the one with asn1D_ is for decoding The first parameter is a context variable used for reentrancy This allows the encoder decoder to keep track of what it is doing between function invocations The second parameter is for passing the actual data variable to be encoded or decoded This is a pointer to a variable of the generated type The third parameter specifies whether implicit or explicit tagging should be used In practically all cases users of the generated function should set this parameter to ASN EXPL explicit This tells the encoder to include an explicit tag around the encoded result The only time this would not be used is when the encoder or decoder is making internal calls to handle implicit tagging of elements The final parameter decode case only is length This is ignored when tagging is set to ASNI EXPL explicit so users can ignore it for the most part and set it to zero In the implicit case this specifies the number of octets to be extracted from the byte stream This is necessary because implicit indicates no tag length pair precedes the data therefore it is up to the user to indicate how many bytes of data are present If PER encoding is s
192. for Calling C Decode Functions cececseecenseeceesceceeeeeueeeeeeeceuueeeeueceaueeeeaeeeees 167 Procedure for Using the C Control Class Decode Method cece cc eecc neces ceeeeeeeenees 169 Decoding a Series of Messages Using the C Control Class Interface cee ceeeeeeeeeceeneeeene es 170 Performance Considerations Dynamic Memory Management ce cece cece ceeeceece eee eene eens 171 Generated XML Funct Ons osssescessdencsaieb cnaaseny Sen soos vooedee so EN E a RAE E SEEPI ES 173 Generated XER Encode Functtons morena is ede teek Gs c eats E EE E E Lee A ee 173 Generated C Function Format and Calling Parameters 0 cceceee cece ceeee cece eeneeeneeeneeeeeeeees 173 Generated C Encode Method Format and Calling Parameters 0 ecceceeeceeeceeeceeeeeeeeee ee 174 Procedure for Calling C Encode Functions cccesececseeccuneeceeececeeeeeuececeeseeueeeeescenaeseenaes 174 Procedure for Using the C Control Class Encode Method cece eeceeeeeeeneceeeeeeeeenees 175 Generated XER Decode FUNCIONS pissen yes kas niveddentdeet See qabhad ee teed dos AE eyed baodeeteden gens desegehoncn stubs 177 Procedure for Using the C Interface 2 0 0 0 cieeeeeeceeeececneeceeeceeeeeceaeeeeeececaeeeeaeeeeeesceanereeee ees 177 Generated C Function Format and Calling Parameters ce cceceeeceeeceeees cece cen eeneceneeeneeee es 177 Procedure for Calling C Decode Functi
193. genCompare qualifier the functions are written to separate c files for each module in the source file The format of the name of each file is lt module gt Compare c If an output filename is specified after the genCompare qualifier all functions are written to that file The format of the name of each generated compare function is as follows asnlCompare_ lt prefix gt lt prodName gt where lt prodName gt is the name of the ASN 1 production for which the function is being generated and lt prefix gt is an optional prefix that can be set via a configuration file setting The configuration setting used to set the prefix is the lt typePrefix gt element This element specifies a prefix that will be applied to all generated typedef names and function names for the production The calling sequence for each generated compare function is as follows OSBOOL asnlCompare_ lt name gt const char name lt name gt pvalue lt name gt pCmpValue char errBuff int errBufSize In this definition lt name gt denotes the prefixed production name defined above The name argument is used to hold the top level name of the variable being compared It is typically set to the same name as the pvalue argument in quotes for example to compare employee records a call to asn1 Compare_Employee employee amp employee etc might be used The pvalue argument is used to pass a pointer to a variable of the item to the first item to be compa
194. generate stream based encode decode functions tables generate table constraint functions strict do strict checking of table constraint conformance param lt name gt lt value gt create types from param types using given value prtToStr lt filename gt generate print to string functions C C prtToStrm lt filename gt generate print to stream functions C C genTest lt filename gt generate sample test functions domTest lt filename gt generate test functions that use XML DOM reader generate sample reader program writer generate sample writer program compare lt filename gt generate comparison functions C C copy lt filename gt generate copy functions C C maxcfiles generate separate file for each function C C XSD options appinfo lt items gt generate appInfo for ASN 1 items lt items gt can be tags enum and or ext ex appinfo tags enum ext default all if lt items gt not given attrs lt items gt generate non native attributes for lt items gt lt items gt is same as for appinfo targetns lt namespace gt Specify target namespace lt namespace gt is namespace URI if not given no target namespace declaration is added useAsnlxXsd reference types in asnl xsd schema Symbian options symbian lt items gt generate code for Symbian OS lt items gt can be dll e g symbian dll default symbian application style cod
195. gin with an uppercase letter and element names within constructors SEQUENCE SET CHOICE must begin with lowercase letters e Elements within constructors not properly delimited with commas either a comma is omitted at the end of an element declaration or an extra comma is added at the end of an element declaration before the closing brace Invalid special characters only letters numbers and the hyphen character are allowed The use of the underscore character _ in identifiers is not allowed in ASN 1 but is allowed in C Since C does not allow hyphens in identifiers ASNIC converts all hyphens in an ASN 1 specification to underscore characters in the generated code Semantics errors occur on the compiler back end as the code is being generated In this case parsing was successful but the compiler does not know how to generate the code These errors are flagged by embedding error messages directly in the generated code The error messages always begin with an identifier with the prefix ASN soa search can be done for this string in order to find the locations of the errors A single error message is output to stderr after compilation on the unit is complete to indicate error conditions exist 31 32 Generated C C Source Code Header h File The generated C or C include file contains a section for each ASN 1 production defined in the ASN 1 source file Different items will be generated depending on whether
196. gram execution These failures do not arise from ASN 1 specific features such as an invalid PER encoding but instead comprehend such failures as buffer overflows invalid socket options or closed streams Error Code Error Name Description 0 RT_OK Normal completion status 2 RT_OK_FRAG Message fragment return status This is returned when a part of a message is successfully decoded The application should continue to invoke the decode function until a zero status is returned 1 RTERR_BUFOVFLW Encode buffer overflow This status code is returned when encoding into a static buffer and there is no space left for the item currently being encoded 2 RTERR_ENDOFBUF Unexpected end of buffer This status code is returned when decoding and the decoder expects more data to be available but instead runs into the end of the decode buffer 3 RTERR_IDNOTFOU Expected identifier not found This status is returned when the decoder is expecting a certain element to be present at the current position and instead something different is en countered An example is decoding a sequence container type in which the declared elements are expected to be in the given order If an element is encountered that is not the one expected this error is raised 4 RTERR_INVENUM Invalid enumerated identifier This status is returned when an enumerated value is being encoded or decoded and the given value is not in the set of v
197. h the name of the module being imported and extension asn or xsd Additional directories can be searched for these files by adding them here User defined configuration files are specified in the third pane These allow further control of the compilation process They are optional and are only needed if the default compilation process is to be altered for example if a type prefix is to be added to a generated type name See the Compiler Configuration File section for details on defining these files There are also two options to generate extra compilation information Check Generate Listing if you want the compiler to echo the specification as it compiles it Check Output Warning Messages to output potential problems that occurred during compilation The next window is as follows Using the GUI Wizard to Run ASNIC ASNIC compiler Objective Systems Inc objective SYSTEMS INC Code Generation Options m Input File Type f Modern ASN 1 1997 based on X 680 standard Legacy ASN 1 based on obsolete x 208 standard with ROSE or SNMP macros XML Schema 5D Lax Syntax Check Application Language Ty p__ApPPPPB Ba a a a pa ap ma ec C C o C Java None syntax check only m dditional Translations I Generate equivalent XML schema X5D file I Use 45N 1 types in XSD translation J Generate 45N 1 file based on 694 X5D input only I Generate code for a
198. hars OSUNICHAR data Asnll 6BitCharString The OSUNICHAR type used in this definition represents a Unicode character UTF 16 and is defined to be a C un signed short type See the rt BMPToCString rtBMPToNewCString and the rt CToBMPSt ring run time function descriptions for information on utilities that can convert standard C strings to and from BMP string format The UniversalString type is a 32 bit character string for which the following structure is used typedef struct OSUINT32 nchars OS32BITCHAR data Asn1l32BitCharString The OS32BITCHAR type used in this definition is defined to bea C unsigned int type See the rtUCSToCString rtUCSToNewCSt ring and the rt CToUCSSt ring run time function descriptions for information on utilities that can convert standard C strings to and from Universal Character Set UCS 4 string format See also the rt UCSToWCSSt ring and rtWCSToUCSSt ring for information on utilities that can convert standard wide character string to and from UniversalString type The UTF8String type is represented as a string of unsigned characters using the OSUTF 8CHAR data type This type is defined to be unsigned char This makes it possible to use the characters in the upper range of the UTF 8 space as positive numbers The contents of this string type are assumed to contain the UTF 8 encoding of a character string For the most part standard C character string functions such as strcpy strcat etc can be
199. hat contain only the productions in the main file being compiled and items those productions depend on from IMPORT files Running ASNIC from the Command line Option Description der dll None This option instructs the compiler to generate functions that implement the Distinguished Encoding Rules DER as specified in the X 690 ASN 1 standard When used in conjunction with the genMake com mand line option the generated makefile uses dynami cally linked libraries DLLs in Windows or so files in UNIX instead of statically linked libraries domTest lt filename gt Selecting this option instructs the compiler to generate test functions that populate data structures with data from XML documents The generated functions use the libxm12 DOM parsing code to construct aDOM tree and then pop ulate the structures with data from that tree The lt filename gt argument to this option is option al If not specified the functions will be written to lt modulename gt Test c where lt modulename gt is the name of the module from the ASN 1 source file events None This option instructs the compiler to generate a build script when producing Java source code The generated build script is either a batch file Windows or a shell script UNIX genCompare compare lt filename gt This option allows the specification of a C or C source c or cpp file to which generated co
200. he generated t member variable is outside the range of indexes of items in the content model group It occurs on the decode side when an element is received that is not defined in the content model group 10 RTERR_NOMEM No dynamic memory available This status code is re turned when a dynamic memory allocation request is made and an insufficient amount of memory is available to sat isfy the request 11 RTERR_INVHEXS Invalid hexadecimal string This status code is returned when decoding a hexadecimal string value and a charac ter is encountered in the string that is not in the valid hex adecimal character set 0 9A Fa f or whitespace 12 RTERR_INVREAL Invalid real number value This status code is returned when decoding a numeric floating point value and an in valid character is received i e not numeric decimal point plus or minus sign or exponent character 13 RTERR_STROVFLW String overflow This status code is returned when a fixed sized field is being decoded as specified by a size con straint and the item contains more characters or bytes then this amount It can occur when a run time function is called with a fixed sixed static buffer and whatever oper ation is being done causes the bounds of this buffer to be exceeded 14 RTERR_BADVALUE Bad value This status code is returned anywhere where an API is expecting a value to be within a certain range and it not within this range An example is the enco
201. he standard The types of MACRO definitions that are supported are ROSE OPERATION and ERROR and SNMP OBJECT TYPE ROSE OPERATION and ERROR ROSE stands for Remote Operations Service Element and defines a request response transaction protocol in which requests to a conforming entity must be answered with the result or errors defined in operation definitions Variations of this are used in a number of protocols in use today including CSTA and TCAP The definition of the ROSE OPERATION MACRO that is built into the ASN1C is as follows OPERATION MACRO BEGIN TYPE NOTATION Parameter Result Errors LinkedOperations VALUE NOTATION value VALUE INTEGER Parameter ArgKeyword NamedType empty ArgKeyword ARGUMENT PARAMETER Result RESULT ResultType empty Errors ERRORS ErrorNames empty LinkedOperations LINKED LinkedOperationNames empty ResultType NamedType empty ErrorNames ErrorList empty ErrorList Error ErrorList Error Error value ERROR shall reference an error value type shall reference an error type if no error value is specified LinkedOperationNames OperationList empty OperationList Operation OperationList Operation Operation value OPERATION shall reference an operation va type shall reference an operation ty if no operation
202. her common example of parameterization is the substitution of a given type inside a common container type For example security specifications frequently contain a signed parameterized type that allows a digital signature to be applied to other types An example of this is as follows SIGNED ToBeSigned SEQUENCE toBeSigned ToBeSigned algorithmOID OBJECT IDENTIFIER 69 Value Mappings params Params signature BIT STRING An example of a reference to this definition would be as follows SignedName SIGNED Name where Name would be another type defined elsewhere within the module The compiler performs the substitution to create the proper C typedef for SignedName typedef struct SignedName Name toBeSigned ASN1OBJID algorithmOID Params params ASN1DynBitStr signature SignedName When processing parameterized type definitions the compiler will first look to see if the parameters are actually used in the final generated code If not they will simply be discarded and the parameterized type converted to a normal type reference For example when used with information objects parameterized types are frequently used to pass information object set definitions to impose table constraints on the final type Since table constraints do not affect the code that is generated by the compiler the parameterized type definition is reduced to a normal type definition and references
203. hich will use indefinite lengths for all con structed elements in a message Note that stream and memory buffer based encode decode functions cannot be used combined in any way The two are mutually exclusive If the stream option is selected then only stream based run time functions can be used with the generated code strict None This option instructs the compiler to generate code for strict validation of table constraints By default generated code will not check for value field constraints It should be noted that real world messages typically do not strictly follow value field table constraint definitions Therefore this option should be used with care targetns lt namespace gt This option only has meaning when generating an XML schema definitions XSD file using the xsd option It allows specification of a target namespace lt names pace gt is a namespace URI if it is not provided no target namespace declaration is added to the generated XSD file trace None This option is used to tell the compiler to add trace diag nostic messages to the generated code These messages cause print statements to be added to the generated code to print entry and exit information into the generated func tions This is a debugging option that allows encode de code problems to be isolated to a given production pro cessing function Once the code is debugged this option should not be used as it adversely aff
204. his library in the link command The genMake option when used in conjunction with maxcfiles will generate a makefile that will compile each of the generated files and add them to a library with a name based on the name of the ASN 1 module being compiled lt moduleName gt lib for Windows or lib lt moduleName gt a for NIX The format of each generated c file name is as follows asnl lt suffix gt _ lt prodname gt c where lt suffix gt depends on encoding rules and the function type encode decode free etc and lt prodname gt is the ASN 1 production name For example consider one type definition within the employee asn ASN 1 specification Employee DEFINITIONS BEGIN Name APPLICATION 1 IMPLICIT SEQUENCE givenName IA5String initial IA5String familyName IA5String AJ END By default the following c files would be generated note this assumes no additional code generation options were selected Employee c EmployeeEnc c EmployeeDec c If maxcfiles was selected as in the following command line asnlc employee asn c ber trac maxcfiles Running ASNIC with the maxcfiles option the following c files for this type would be generated for the Name type asnlD_Name c asnlE_Name c These contain the functions to decode Name and encode Name respectively Similar files would be generated for the other productions in the module as well Generated C files In
205. howing the components used in the XML decode process is as follows Step 1 Generate code Step 2 Build Application ASNIC generates code to implement the following methods defined in the SAX content handler interface startElement characters endElement The interface defines other methods that can be implemented as well but these are sufficient to decode XER encoded data Procedure for Using the C Interface The ASNIC compiler generates XER decode functions for C for constructed types in a specification These can be invoked in the same manner as other decode functions In this case they install the generated SAX content handler functions and invoke the XML parser s parse function to parse a document The procedure to call these generated functions is described below Generated C Function Format and Calling Parameters The format of the name of each generated C XER decode function is as follows 177 Procedure for Calling C Decode Functions asn1lXD_ lt prefix gt lt prodName gt where lt prodName gt is the name of the ASN 1 production for which the function is being generated and lt prefix gt is an optional prefix that can be set via a configuration file setting The configuration setting used to set the prefix is the lt typePrefix gt element This element specifies a prefix that will be applied to all generated typedef names and function names for the production The calling sequence for each decode f
206. iable out of a method and use it after the control and message buffer objects go out of scope For example consider the following code fragment ASN1T_ lt type gt func2 ASNIT_ lt type gt p new ASNIT_ lt type gt ASNIBERDecodeBuffer decbuf ASN1C_ lt type gt cc decbuf p cc Decode After return cc and decbuf go out of scope therefore all memory allocated within struct p is released return p void funcl ASN1T_ lt type gt pType func2 pType is not usable at this point because dynamic memory has been released As can be seen from this example once func2 exits all memory that was allocated by the decode function will be released Therefore any items that require dynamic memory within the data variable will be in an undefined state An exception to this rule occurs when the type of the message being decoded is a Protocol Data Unit PDU These are the main message types in a specification The ASN1C compiler designates types that are not referenced by any other types as PDU types This behavior can be overridden by using the pdu command line argument or lt isPDU gt configuration file element 120 Populating Generated Structure Variables for Encoding The significance of PDU types is that generated classes for these types are derived from the ASNITPDU base class This class holds a reference to a context object The context object is set by Decode and copy meth
207. ifies dynamic allocation This tells the encoding functions to allocate a buffer dynamically The address of the start of the message is obtained after encoding by calling the run time function pe_GetMsgPrtr The following code fragment illustrates PER encoding using a dynamic buffer include employee h include file generated by ASNIC main OSOCTET msgptr int msglen stat OSCTXT ctxt OSBOOL aligned TRUE Employee employee typedef generated by ASNIC GI mployee name givenName SMITH stat rtInitContext amp ctxt if stat 0 printf rtInitContext failed check license n rtxErrPrint amp ctxt return stat pu_setBuffer amp ctxt 0 0 aligned if stat asnlPE_Employee amp ctxt amp employee 0 msgptr pe_GetMsgPtr amp ctxt amp msglen else 163 Procedure for Using the C Control Class Encode Method error processing Procedure for Using the C Control Class Encode Method The procedure to encode a message using the C class interface is as follows l Instantiate an ASN 1 PER encode buffer object ASN1PEREncodeBuffer to describe the buffer into which the message will be encoded Two overloaded constructors are available The first form takes as arguments a static encode buffer and size and a Boolean value indicating whether aligned encoding is to be done The second form only takes the Boole
208. ify a list of type names to be included in the generated code for a particular module the following would be used lt include types TypeNamel TypeName2 TypeName3 gt 26 Compiler Configuration File The following are some examples of configuration specifications lt asnlconfig gt lt storage gt dynamic lt storage gt lt asnliconfig gt This specification indicates dynamic storage should be used in all places where its use would result in significant memory usage savings within all modules in the specified source file lt asnlconfig gt lt module gt lt name gt H323 MESSAGES lt name gt lt sourceFile gt lt typePrefix gt H225 lt typePrefix gt lt module gt lt asniconfig gt h225 asn lt sourceFile gt This specification applies to module H323 MESSAGES in the source file being processed For IMPORT statements involving this module it indicates that the source file h225 asn should be searched for specifications It also indicates that when C or C types are generated they should be prefixed with H225 This can help prevent name clashes if one or more modules are involved and they contain productions with common names The following tables specify the list of attributes that can be applied at all of the different levels global module and individual production Global Level These attributes can be applied at the global level by including them within the lt asnl
209. in const OSOCTET msgptr OSOCTET msgbuf 1024 int msglen OSCTXT CEXE PersonnelRecord data Init context structure if stat rtInitContext amp ctxt 0 printf rtInitContext failed stat d n stat return 1 Encode loop starts here this will repeatedly use the objects declared above to encode the messages for xe_setp amp ctxt msgbuf sizeof msgbuf logic here to read record from some source database flat file socket etc populate structure with data to be encoded data name SMITH call encode function if msglen asnlE_PersonnelRecord amp ctxt amp data ASNIEXPL gt 0 encoding successful get pointer to start of message msgptr xe_getp amp ctxt do something with th ncoded message 129 Generated C Encode Method Format and Calling Parameters else error processing Call rtxMemReset to reset the memory heap for the next iteration Note all data allocated by rtxMemAlloc will become invalid after this call rtxMemReset amp ctxt rtFreeContext amp ctxt The rtxMemReset call does not free memory instead it marks it as empty so that it may be reused in the next iteration Thus all memory allocated by rtxMemAlloc will be overwritten and data will be lost Procedure for Using the C Control Class Encode Method The procedure to encode a me
210. initial 2 define T_NamePart_familyName 3 typedef struct EXTERN NamePart int t union t 1 const OSUTF8CHAR givenName f t 2 F const OSUTF8CHAR initial fe CoS BL AS const OSUTF8CHAR familyName u NamePart Similar to xsd choice is xsd union The main difference is that xsd union alternatives are unnamed As specified in X 694 special names are generated in this case using the base name alt The generated name for the first member is alt names for successive members are alt n where n is a sequential number starting at 1 An example of this naming is as follows lt xsd simpleType name MyType gt lt xsd union memberTypes xsd int xsd language gt lt xsd simpleType gt This generates the following C type definition define T_MyType_alt 1 define T_MyType_alt_l 2 typedef struct EXTERN MyType int t union t 1 OSINT32 alt Y ie eee ae const OSUTF8CHAR alt_l u MyType Repeating Groups Repeating groups are specified in XML schema definitions using the minOccurs and maxOccurs facets on sequence or choice definitions These items are converted to ASN 1 SEQUENCE OF types 94 Repeating Elements An example of a repeating group is as follows lt xsd complexType name Names gt lt xsd sequence maxOccurs unbounded gt lt xsd element name givenName type xsd string gt lt xsd element name initial type x
211. initions for Message Types The standard message type used within these specifications is usually a SEQUENCE type with elements that use a relational table constraint that uses fixed type and type fields The general form would be as follows lt Type gt SEQUENCE lt element1l gt lt Class gt amp lt fixed type field gt lt ObjectSet gt lt element2 gt lt Class gt amp lt fixed type field gt lt ObjectSet gt element1 lt element3 gt lt Class gt amp lt type field gt lt ObjectSet gt element1 In this definition lt Class gt would be replaced with a reference to an Information Object Class lt fixed type field gt would be a fixed type field wtihin that class and lt t ype field gt would be a type field within the class lt ObjectSet gt would be a reference to an Information Object Set which would define all of the possibilities for content within the message The first element lt element1 gt would be used as the index element in the object set relation An example of this pattern from the S1AP LTE specification is as follows InitiatingMessage SEQUENCE procedureCode S1AP ELEMENTARY PROCEDURE amp procedureCode SLAP ELEMENTARY PROCEDURES criticality S1AP ELEMENTARY PROCEDURE amp criticality 76 3GPP Table Constraint Model S1LAP ELEMENTARY PROCEDURES procedureCode value S1AP ELEMENTARY
212. into account the possibility of out of order elements This is handled by using a loop to parse each element in the message Each time an item is parsed an internal mask bit within the decoder is set to indicate the element was received The complete set of received elements is then checked after the loop is completed to verify all required elements were received SEQUENCE OF The ASN 1 SEQUENCE OF type is converted into one of the following C C types e A doubly linked list structure OSRTDList for C or ASN1TSeqOfList a class derived from OSRTDList for C e A structure containing an integer count of elements and a pointer to hold an array of the referenced data type a dynamic array e A structure containing an integer count of elements and a fixed sized array of the referenced data type a static array The linked list option is the default for constructed types An array is used for a sequence of primitive types The allocation for the contents field of the array depends on how the SEQUENCE OF is specified in the ASN 1 definition If a size constraint is used a static array of that size is generated otherwise a pointer variable is generated to hold a 58 SEQUENCE OF dynamically allocated array of values The decoder will automatically allocate memory to hold parsed SEQUENCE OF data values The type used for a given SEQUENCE OF construct can be modified by the use of a configuration item The lt storage gt qualifier is us
213. ion This method must be used if C code generation was done This method can also be used as an alternative to using the control class interface if C code generation was done Before a PER encode function can be called the user must first initialize an encoding context block structure The context block is initialized by calling the rtInitContext to initialize the block The user then must call pu_setBuffer to specify a message buffer to receive the encoded message Specification of a dynamic message buffer is possible by setting the buffer address argument to null and the buffer size argument to zero The pu_setBuffer function also allows for the specification of aligned or unaligned encoding An encode function can then be called to encode the message If the return status indicates success 0 then the message will have been encoded in the given buffer PER encoding starts from the beginning of the buffer and proceeds from low memory to high memory until the message is complete This differs from BER where encoding was done from back to front Therefore the buffer start address is where the encoded PER message begins The length of the encoded message can be obtained by calling the pe_GetMsgLen run time function If dynamic encoding was specified i e a buffer start address and length were not given the run time routine pe_GetMsgPtr can be used to obtain the start address of the message This routine will also return the length of the encoded me
214. ion even if they are not actually used But still the size of the final application created with maxcfiles option should be less than the size of the application created without this option 38 Generated C C files and the compat Option Generated C C files and the compat Option ASNIC 5 6 and below did not generate separate files for common definitions encode and decode functions lt moduleName gt c cpp lt moduleName gt Enc c cpp lt moduleName gt Dec c cpp All code was generated in a single file with the name lt moduleName gt c cpp If it is necessary to maintain this behavior then use the compat 5 6 option Also the behavior of the cfile option is slightly changed in ASNIC 5 7 and above In 5 6 and below the cfile option did not have any effect for files containing copy print compare etc functions For ASN1C 5 7 and above cfile causes everything to be output to one file unless specific filename parameters are specified with genPrint genCopy etc Once again to maintain the previous behavior the compat 5 6 option can be used Generated C files and the symbian Option ASNIC version 6 1 introduced the symbian option to generate code that targets the Symbian platform While an exhaustive discussion of the differences between Symbian C and standard C is impractical for this User s Guide the differences in generated code are relatively minimal Two principle areas of concern are writable
215. ith the following code NamedBS bs memset amp bs 0 sizeof bs rtxSetBit bs data 10 NamedBS_bitOne The statement to clear the bit using rtxClearBit would be as follows rtxClearBit bs data 10 NamedBS_bitOne Finally the bit could be tested using rtxTestBit with the following statement if rtxTestBit bs data 10 NamedBS_bitOne bit is set Note that the compiler generated a fixed length data array for this specification It did this because the maximum size of the string is known due to the named bits it must only be large enough to hold the maximum valued named bit constant Contents Constraint It is possible to specify a contents constraint on a BIT STRING type using the CONTAINING keyword This indicates that the encoded contents of the specified type should be packed within the BIT STRING container An example of this type of constraint is as follows ContainingBS BIT STRING CONTAINING INTEGER ASNIC will generate a type definition that references the type that is within the containing constraint In this case that would be INTEGER therefore the generated type definition would be as follows typedef OSINT32 ContainingBS The generated encoders and decoders would handle the extra packing and unpacking required to get this to and from a BIT STRING container This direct use of the containing type can be suppressed through the use of the noContaining command line argument In this case a nor
216. ived from the generated base class for the reference type For example if we have A INTEGER and B A then B is a defined type and would inherit from the base class generated for A class ASN1C_B public ASNIC_A These intermediate classes are also derived from the ASN CType base class Their purpose is the addition of func tionality specific to the given ASN 1 type For example the ASNI CBitStr control class provides methods for setting clearing and testing bits in the referenced bit string variable In the generated control class the msgData member variable is a reference to a variable of the generated type The constructor takes two arguments an Asn 1 MessageBufferlF message buffer interface object reference and a reference to a variable of the data type to be encoded or decoded The message buffer object is a work buffer object for encoding or decoding The interface reference can also be used to specify a stream Stream classes are derived from this same base class The data type reference is a reference to the ASN T_ variable that was generated for the data type EncodeFrom and DecodeTo methods are declared that wrap the respective compiler generated C encode and decode stream functions Standard Encode and Decode methods exist in the ASNI CType base class for direct encoding and decoding to a memory buffer Command line options may cause additional methods to be generated For example if the print command line argument wa
217. ks for C The only differences are a few additional files are generated and the cpp extension is used instead of c Additional files are generated to hold ASNJC_ lt Type gt and ASNIT_ lt Type gt control classes The format of the filenames of these files is as follows asnl lt suffix gt _ lt prodname gt cpp ASN1C_ lt prodname gt cpp ASN1T_ lt prodname gt cpp where lt suffix gt depends on the encoding rules and function type selected encode decode free etc and lt prod name gt is the ASN 1 production name For the example presented previously in the C Files section the following files would be generated for the Name production in the employee asn file asnlD_Name cpp asnlE_Name cpp ASN1IT_Name cpp ASN1C_Name cpp These contain the functions to decode Name and encode Name respectively The ASNIT_Name cpp file contains the type class methods and the ASN C_Name cpp files contains the control class methods Note that not all productions have a control class only PDU types do for BER or PER therefore the ASN1C_ lt type gt cpp file may not be generated Similar files would be generated for the other productions in the module as well Note that for C the code reduction effect is less than that for pure C This is because most of the linkers cannot omit virtual methods even if they are not being used by the application These virtual methods refer to separate C functions and these functions are being linked into the applicat
218. ks simply output a textual representation of the data as they do in the print handler case The only difference in reader cpp from the other examples is that 1 There is no declaration of an employee variable to hold decoded data because no type for this variable was generated and 2 The Parse method is invoked instead of the Decode method This is the generated method definition for a pureparser If one examines the generated class definitions they will see that no Encode or Decode methods were generated Compiling and running this program will show the encoded PER message written to stdout as an XML message The resulting message is also saved in the message xmil file 208 IMPORT EXPORT of Types ASNIC allows productions to be shared between different modules through the ASN 1 IMPORT EXPORT mecha nism The compiler parses but ignores the EXPORTS declaration within a module As far as it is concerned any type defined within a module is available for import by another module When ASNIC sees an IMPORT statement it first checks its list of loaded modules to see if the module has already been loaded into memory If not it will attempt to find and parse another source file containing the module The logic for locating the source file is as follows 1 The configuration file if specified is checked for a lt sourceFile gt element containing the name of the source file for the module Note that the lt oid gt configuration item ca
219. ldName is replaced with name of this ValueField Value is the default value in the Class s ValueField and Type is the type in Class s ValueField 86 Legacy Table Constraint Model This value is used as a defined value in the information object definition for an absent value of the field This new value assignment is used for compiler internal code generation purpose It is not required for user to understand this logic ABSTRACT SYNTAX and TYPE IDENTIFIER The ASN 1 ABTRACT SYNTAX and TYPE IDENTIFIER classes are useful ASN 1 definitions These classes are described using the following ASN 1 definitions TYPE IDENTIFIER CLASS amp id OBJECT IDENTIFIER UNIQUE amp Type WITH SYNTAX amp Type IDENTIFIED BY amp id ABSTRACT SYNTAX CLASS amp id OBJECT IDENTIFIER UNIQUE amp Type property BIT STRING handles invalid encoding 0 DEFAULT WITH SYNTAX amp Type IDENTIFIED BY amp id HAS PROPERTY amp property The ASNIC compiler generates code for these constructs when they are referenced in the ASN 1 source file that is being compiled The generated code for these constructs is written to the RtClass h and c cpp source files Information Object Information Object code will be generated in a header and source file with a C struct C class to hold the values The name of the header and source file are of the following format
220. le time For example an OCTET STRING that does not contain a size constraint can be an indeterminate number of bytes in length ASNIC does two things by default to reduce dynamic memory allocations and improve decoding performance 1 Uses static variables wherever it can Any BIT STRING OCTET STRING character string or SEQUENCE OF or SET OF construct that contains a size constraint will result in the generation of a static array of elements sized to the max constraint bound 2 Uses a special nibble allocation algorithm for allocating dynamic memory This algorithm allocates memory in large blocks and then splits up these blocks on subsequent memory allocation requests This results in fewer calls to the kernel to get memory The downside is that one request for a few bytes of memory can result in a large block being allocated 148 Compact Code Generation Common run time functions are available for controlling the memory allocation process First the default size of a memory block as allocated by the nibble allocation algorithm can be changed By default this value is set to 4K bytes The run time function rMemSetDefBlkSize can be called to change this size This takes a single argument the value to which the size should be changed It is also possible to change the underlying functions called from within the memory management abstraction layer to obtain or free heap memory By default the standard C malloc realloc and free fun
221. lements notypes do not generate type definitions noxmlins do not generate XML namespaces for ASN 1 modules 0o lt directory gt set output file directory pdu lt type gt designate lt type gt to be a Protocol Data Unit PDU lt type gt may be to select all type definitions usepdu lt type gt specify a Protocol Data Unit PDU type for which sample reader writer programs and test code has to ted by print nerated names be generated print lt filename gt generate print functions prtfmt details bracetext format of output genera shortnames reduce the length of compiler g trace add trace diag msgs to generated cod no UniqueNames resolve name clashes by generati default on use noUniqueNames ng unique names to disable warnings nodatestamp C C options hfile lt filename gt cfile lt filename gt genBitMacros genFree hdrGuardPfx maxlines lt num gt noInit oh lt directory gt static cppNs lt namespace gt output compiler warning messages do not put date time stamp in g C vor Crt default header h filename is lt ASN 1 Module Name gt h C or C source c or cpp filename default is lt ASN 1 Module Name gt c generate named bit set clear test macros generate memory free functions for all types h files limit of number of lines per source file add prefix to header guard defines in set default value
222. ll dependent imported type definitions The Code Generations Options window permits users to specify the input language type target application language and additional translations if necessary Certain options will be inactive greyed out depending on the file type selected For example if an XSD file is selected the option Generate ASN 1 file based on X 694 will be active and the option Generate equivalent XML schema XSD file will be inactive Checking Generate code for all dependent imported type definitions will cause the compiler to search and generate code for modules specified in the IMPORTS statement of an ASN 1 specification 18 C C Code Generation Options C C Code Generation Options The following windows describe the options available for generating C or C source code ASNIC compiler Objective Systems Inc 9 objective SYSTEMS INC C C Code Generation Options Select Encoding Rules JV BER DER CER IV PER XER JV XML select aligned or unaligned PER at run time Select Function Types to be Generated IV Encode Copy J Print to MW Decode I Compare stdout string f stream JV Initialization Test I Memory Free Stream Named Bit Macros m Space Optimization Options T Do not generate indefinite length processing code noIndefLen Do not generate code to save restore unknown extensions noOpenExt 7 Do not generate code to check constraints l
223. lso contain an additional copy constructor if C is used and PDU generation is not disabled A destructor is also generated if the type contains dynamic memory fields This destructor will free the dynamic memory upon destruction of the type instance For example typedef struct EXTERN ASN1T_PersonnelRecord public ASNITPDU ASN1T_PersonnelRecord m uniPresent 0 m seqOfseqPresent 0 199 Generated Test Functions ASN1T_PersonnelRecord ASN1C_PersonnelRecord amp srcData ASN1T_PersonnelRecord ASNIT_PersonnelRecord This constructor is used to create an instance of the ASNIT_ lt name gt type from an ASNIC_ lt name gt control class object Memory Management of Copied Items Prior to ASNIC version 5 6 dynamic memory of decoded or copied items would only be available as long as the control class instance and or the message buffer object used to decode or copy the item remained in scope or was not deleted This restriction no longer exists as long as the type being copied is a Protocol Data Unit PDU The copied item will now hold a reference to the context variable used to create the item and will increment the item s reference count This reference is contained in the ASN TPDU base class variable from which PDU data types are now derived The dynamic memory within the item will persist until the item is deleted Generated Test Functions The genTest option causes test functions to be gene
224. lude file generated by ASNIC main const OSOCTET msgptr OSOCTET msgbuf 1024 int msglen stat OSBOOL canonical FALSI GI step 1 instantiate an instance of the XER encode buffer class This example specifies a static message buffer ASNIXEREncodeBuffer encodeBuffer msgbuf sizeof msgbuf canonical step 2 populate msgData with data to be encoded ASN1T_PersonnelRecord msgData msgData name givenName SMITH step 3 instantiate an instance of the ASN1C_ lt ProdName gt class to associate th ncode buffer and message data ASN1C_PersonnelRecord employ encodeBuffer msgData steps 4 and 5 encode and check return status if stat employee Encode 0 printf encoded XML message n printf const char msgbuf printf n step 6 get start of message pointer and message length start of message pointer is start of msgbuf call getMsgLen to get message length msgptr encodeBuffer getMsgPtr will return amp msgbuf len encodeBuffer getMsgLen else printf Encoding failed n encodeBuffer printErroriInfo exit 0 176 Generated XER Decode Functions msgptr and len now describe fully encoded messag Generated XER Decode Functions NOTE XER is maintained as a legacy XML format for ASN 1 New applications should consider using XML as described in the n
225. ly large number of different types that can be represented in the table constraint used to constrain a type field to a given set of values The index member of the type is for internal use by table constraint processing functions to keep track of which row in a table is being referenced If the 3gpp command line option is used in conjunction with tables a more specialized type of structure is generated This structure makes use of a common pattern used in a certain class of Third Generation Partnership Program 3GPP ASN 1 specifications In this case instead of a void pointer being used to hold an instance of a type containing data to be encoded all entries from the referenced Information Object Set are used in a union structure in much the same way as is done in a CHOICE construct If code is being generated from an XML schema file and the file contains an lt xsd any gt wildcard declaration a special type of any structure is inserted into the generated C C code This is the type OSXSDAny which is defined in the osSysTypes h header file This structure contains a union which contains alternatives for data in either binary or XML text form This makes it possible to transfer data in either binary form if working with binary encoding rules or XML form if working with XML Character String Types All 8 bit character character string types are derived from the C character pointer const char base type This pointer is used to hold a null termina
226. mal BIT STRING type will be used and it will be the users responsibility to do the necessary packing and unpacking operations to encode and decode the variable correctly ASN1CBitStr Control Class When C code generation is specified a control class is generated for operating on the target bit string This class is derived from the ASN1CBitStr class This class contains methods for operating on bits within the string Objects of this class can also be declared inline to make operating on bits within other ASN 1 constructs easier For example in a SEQUENCE containing a bit string element the generated type will contain a public member variable containing the ASNIT type that holds the message data If one wanted to operate on the bit string contained within that element they could do so by using the ASN1CBitStr class inline as follows ASNICBitStr bs lt seqVar gt lt element gt bs set 0 In this example lt seqVar gt would represent a generated SEQUENCE variable type and lt element gt would represent a bit string element within this type See the section on the ASN CBitStr class in the ASNIC C C Common Run time User s Manual for details on all of the methods available in this class 48 OCTET STRING OCTET STRING The ASN 1 OCTET STRING type is converted into a C structured type containing an integer to hold the number of octets and an array of unsigned characters OCTETs to hold the octet string contents The number
227. mary difference as to what a user sees and works with lies in the representation of open type elements that contain a table constraint The standard form of an open type element constrained with a table constraint within a SEQUENCE container is as follows lt Type gt SEQUENCE lt element gt lt Class gt amp lt type field gt lt ObjectSet gt index element If tables is not specified on the command line a standard open type structure is used to hold the element value typedef struct lt Type gt ASN1OpenType lt element gt The ASN10penType built in type holds the element data in encoded form The only validation that is done on the element is to verify that is a well formed tag length value TLV structure if BER encoding is used or a valid length prefixed structure for PER If the tables command line option is selected the code generated is different In this case ASN1OpenType above is replaced with ASN1Object or ASN1TOb ject for C This is defined in asnlt ype h as follows typedef struct generic table constraint value holder ASN10penTyp ncoded void decoded OSINT32 index table index ASN1Object This allows a value of any ASN 1 type to be represented in both encoded and decoded forms Encoded form is the open type form shown above It is simply a pointer to a byte buffer and a count of the number of byes in the encoded message component The decoded form is a
228. method This status code is returned by decode or val idate method when the used message buffer instance has type different from OS MessageBufferlF XMLDecode RTERR_DECELEMFAIL Element decode failed This status code and parameters are added to the failure status by the decoder to allow the specific element on which a decode error was detected to be identified RTERR_DECATTRFAIL Attribute decode failed This status code and parameters are added to the failure status by the decoder to allow the specific attribute on which a decode error was detected to be identified RTERR_STRMINUSE Stream in use This status code is returned by stream func tions when an attempt is made to initialize a stream or cre ate a reader or writer when an existing stream is open in the context The existing stream must first be closed be fore initializaing a stream for a new operation RTERR_NULLPTR Null pointer This status code is returned when a null pointer is encountered in a place where it is expected that the pointer value is to be set RTERR_FAILED General failure Low level call returned error RTERR_ATTRFIXEDV AL Attribute fixed value mismatch The attribute contained a value that was different than the fixed value defined in the schema for the attribute RTERR_MULTIPLE Multiple errors occurred during an encode or decode op eration See the error list within the context structure for a full list of all erro
229. mpare functions will be written Compare functions allow two variables of a given ASN 1 type to be compared for equality The lt filename gt argument to this option is option al If not specified the functions will be written to lt modulename gt Compare c where lt modulename gt is the name of the module from the ASN 1 source file genCopy copy lt filename gt This option allows the specification of a C or C source c or cpp file to which generated copy functions will be written Copy functions allow a copy to be made of an ASNIC generated variable For C they cause copy constructors and assignment operators to be added to gen erated classes The lt filename gt argument to this option is option al If not specified the functions will be written to lt modulename gt Copy c where lt modulename gt is the name of the module from the ASN 1 source file genFree None This option instructs the compiler to generate a memory free function for each ASN 1 production Normally mem ory is freed within ASNIC by using the rtMemFree run time function to free all memory at once that is held by a context Generated free functions allow finer grained con trol over memory freeing by just allowing the memory held for specific objects to be freed genMake None This option instructs the compiler to generate a portable makefile for compiling the generated C or C code If Running ASNIC from
230. mpiler automatically generates code to handle this requirement based on the value in the structure For other values an optional present flag bit is generated The programmer must set this bit to false on the encode side to specify default value selected If this is done a value is not encoded into the message On the decode side the developer must test for present bit not set If this is the case the default value specified in the ASN 1 specification must be used and the value in the structure ignored Extension Elements If the SEQUENCE type contains an open extension field i e a at the end of the specification or a in the middle a special element will be inserted to capture encoded extension elements for inclusion in the final encoded message This element will be of type OSRTDList and have the name extElem1 This is a linked list of open type fields Each entry in the list is of type ASN1 OpenType The fields will contain complete encodings of any extension elements that may have been present in a message when it is decoded On subsequent encode of the type the extension fields will be copied into the new message The noOpenExt command line option can be used to alter this default behavior If this option is specified the extElem1 element is not included in the generated code and extension data that may be present in a decoded message is simply dropped If the SEQUENCE type contains an extension marker and extension elements
231. mset or by calling the ASNIC generated initialization function A decode function can then be called to decode the message If the return status indicates success 0 then the message will have been decoded into the given ASN 1 type variable The decode function may automatically allocate dynamic memory to hold variable length variables during the course of decoding This memory will be tracked in the context structure so the programmer does not need to worry about freeing it It will be released when the context is freed The final step of the procedure is to free the context block This must be done regardless of whether the block is static declared on the stack and initialized using rt nitContext or dynamic created using rtNewContext The function to free the context is rtf reeContext A program fragment that could be used to decode an employee record is as follows include employee h include file generated by ASNIC main OSOCTET msgbuf 1024 ASNITAG msgtag int msglen stat OSCTXT ctxt OSBOOL aligned TRUE PersonnelRecord employee logic to read message into msgbuf This example uses a static context block step 1 prepare the context block stat rtInitContext amp ctxt if stat 0 printf rtInitContext failed check license n rtErrPrint amp ctxt return stat 168 Procedure for Using the C Control Class Decode Method pu_setBuf
232. msglen offset int curlen int msglen offset status decodeBuffer ParseTagLen msgtag curlen if status 0 handle error Now switch on initial tag value to determine what type of message was received switch msgtag 147 BER Decode Performance Enhancement Techniques case TV_PersonnelRecord compiler generated constant if status employee Decode 0 decoding successful data in employeeData process received data else error processing break default handle unknown message type her switch get new offset offset decodeBuffer getByteIndex Need to reinitialize objects for next iteration if it is not last iteration if offset lt msglen mployee memFreeAll end of loop BER Decode Performance Enhancement Tech niques There are a number of different things that can be done in application code to improve BER decode performance These include adjusting memory allocation parameters using compact code generation using decode fast copy and using initialization functions Dynamic Memory Management By far the biggest performance bottleneck when decoding ASN 1 messages is the allocation of memory from the heap Each call to new or malloc is very expensive The decoding functions must allocate memory because the sizes of many of the variables that make up a message are not known at compi
233. n be used to distinguish modules that have the same names but different object identifiers 2 If this element is not present the compiler looks for a file with the name lt ModuleName gt asn where module name is the name of the module specified in the IMPORT statement In both cases the I command line option can be used to tell the compiler where to look for the files The other way of specifying multiple modules is to include them all within a single ASN 1 source file It is possible to have an ASN 1 source file containing multiple module definitions in which modules IMPORT definitions from other modules An example of this would be the following ModuleA DEFINITIONS BEGIN IMPORTS B From ModuleB Bs CB END oduleB DEFINITIONS BEGIN B INTEGER END This entire fragment of code would be present in a single ASN 1 source file 209 210 ROSE and SNMP Macro Support The ASNIC compiler has a special processing mode that contains extensions to handle items in the older 1990 version of ASN 1 i e the now deprecated X 208 and X 209 standards This mode is activated by using the asnstd x208 command line option Although the X 208 and X 209 standards are no longer supported by the ITU T they are still in use today This version of ASNIC contains logic to parse some common MACRO definitions that are still in widespread use despite the fact that MACRO syntax was retired with this version of t
234. n is similar in all cases A parameterized type is used as a shorthand notation to pass an information object set into a container type The container type holds a list of the IE fields The structure of an IE field type is similar to a message type the first element is used as an index element to the remaining elements That is followed by one or more fixed type or variable type elements In the case defined above only a single fixed type and variable type element is shown but there may be more An example of this pattern from the S1AP LTE specification follows HandoverRequired SEQUENCE protocollEs ProtocollIE Container HandoverRequiredIEs ProtocoLTI E Container S1AP PROTOCOL IES IEsSetParam SEQUENCE SIZE 0 maxProtocollIEs OF ProtocollIE Field IEsSetParam ProtocolIE Field S1lAP PROTOCOL IES IEsSetParam SEQUENCE id S1AP PROTOCOL IES amp id IEsSetParam criticality S1AP PROTOCOL IES amp criticality IEsSetParam id value SIAP PROTOCOL IES amp Value IEsSetParam id In this case standard parameterized type instantiation is used to create a type definition for the protocollEs element This results in a list type being generated List of HandoverRequired_protocolIEs_element typedef OSRTDList HandoverRequired_protocollEs The type for the protocol IE list element is crea
235. n platform but should be aware of these particular differences when writing Symbian applications Generated Encode Decode Function and Meth ods Generated Makefile The genmake option causes a portable makefile to be generated to assist in the C or C compilation of all of the generated C or C source files This makefile contains a rule to invoke ASN1C to regenerate the c and h files if any of the dependent ASN 1 source files are modified It also contains rules to compile all of the C or C source files Header file dependencies are generated for all the C or C source files 40 Generated VC Project Files Two basic types of makefiles are generated 1 AGNU compatible makefile This makefile is compatible with the GNU make utility which is suitable for compiling code on Linux and many UNIX operating systems and 2 A Microsoft Visual Studio compatible makefile This makefile is compatible with the Microsoft Visual Studio nmake utility A GNU compatible makefile is produced by default the Microsoft compatible file is produced when the w32 com mand line option is specified in addition to genmake Both of these makefile types rely on definitions in the platform mk make include file This file contains parameters specific to different compiler and linker utilities available on different platforms Typically all the needs to be done to port to a different platform is to adjust the parameters in this file When a mak
236. na ors TEESE PESSE KERESSE Tii 25 Compiler Configuration File teisese e erene e coos e a i oeira i e ETE NEEE 26 Compiler Error Reporting errereen ease e e a a a e E vedas E ET E ETE a AEE ES SS 31 Generated C C Source Code rar Ee EEE se sie EEEE EINE EEE ET EEOAE os ves TEST RS 33 lo lava lra A nD a I EE E loa E E AN EAE E E AE E AE 33 Ge ner ted C Source Piles esarri noei E EE bake sia leh coed AO Liege EERE EESE EESTE 36 Maximum Mines per File sesine aai anes e e a E yes pated a a aaa iGS 36 Use of the maxcfilesS Option spises nises kirri oie eo e EEE EE E E E E i 36 Generated CA E il EEE E E EE E sa nesgecv ete 37 Generated C C files and the compat Option sssssesessserrsresrrrrerrrrrsrrerrsrrerrererrereerrerrerteerseeseeet 39 Generated C files and the symbian Option cece cece ceee cece en eeca cece cece eene een eeneeeeeeeeeeeeeeeeeeaees 39 Writable Static Data 5cccctiiteees sees coke hese ees Te E Mes we EES E EE EEE ETE EE e i 39 Extern Link ge ir rere iee e cas signees o A EEEE EE dieses E EEAS TS EEEE SEEE EEUN S OSEE THRE 39 Generated Encode Decode Function and Methods sseessesesserrssrerreresrrrrrrreresrreerrereereeerrreeerreeen 40 Generated Makefile lt s0tc 0 jssste sss in a bande e egos EEE See se boa Dae eh ee ates eek E RE aS ag daa R 40 Generated VC Project Piles 2c c55 cssie eek eee in nE scons ES EEEE O cases cube doses yecss 41 ASNT To C C Mappings sssscns sac
237. ncoded XML message is nothing more than a null terminated string in a memory buffer the standard C library function strlen can be used to obtain the length A program fragment that could be used to encode an employee record is as follows include employee h include file generated by ASNIC int main int argc char argv PersonnelRecord employee OSCTXT CExXt OSOCTET msgbuf 4096 int stat Initialize context and set encode buffer pointer stat rtXmlInitContext amp ctxt if 0 stat printf context initialization failed n rtxErrPrint amp ctxt return stat rtXmlSetEncBufPtr amp ctxt msgbuf sizeof msgbuf Populate variable with data to be encoded mployee name givenName John Encode data stat XmlEnc_PersonnelRecord_PDU amp ctxt amp employee if stat 0 Note message can be treated as a null terminated string in memory printf encoded XML message n puts char msgbuf printf n 184 Generated C Encode Method Format and Calling Parameters else error processing rtFreeContext amp ctxt release the context pointer Generated C Encode Method Format and Calling Pa rameters When C code generation is specified using the xml switch the generated EncodeTo and DecodeFrom methods in the PDU control class are set up to encode complete XML documents including the start docume
238. nction name defined above The pct xt argument is used to hold a context pointer to keep track of dynamic memory allocation parameters This is a basic handle variable that is used to make the function reentrant so that it can be used in an asynchronous or threaded application The user is required to supply a pointer to a variable of this type declared somewhere in his or her program The variable must have been previously initialized using the rt nitContext run time function The pvalue argument is a pointer to hold the populated data variable This variable is of the type generated for the ASN 1 production The test function will automatically allocate dynamic memory using the run time memory management for the main variable as well as variable length fields within the structure This memory is tracked within the context structure and is released when the context structure is freed 200 Generated Test Functions In the case of C a method is added to the generated control class for test code generation The name of this method is genTestInstance The prototype is as follows lt typeName gt pvalue lt object gt genTestInstance where lt typeName gt is the ASN1T_ lt name gt type name of the generated type and lt object gt is an instance of the ASN1IC_ lt name gt generated control class Generated DOM Test Functions A new command line option added in ASNIC version 6 0 is domtest This is similar to gentest excpet
239. nd Calling Parameters Encode buffer size 1K Buffer start Start of Encode this way End of Buffer address Message 0x500 0x100 0x200 In this example a 1K encode buffer is declared which happens to start at address 0x100 When the context is initialized with a pointer to this buffer and size equal to 1K it positions the internal encode pointer to the end of the buffer address 0x500 Encoding then proceeds from back to front until encoding of the message is complete In this case the encoded message turned out to be 0x300 768 bytes in length and the start address fell at 0x200 This is the value that would be returned by the xe_getp function A program fragment that could be used to encode an employee record is as follows include employee h include file generated by ASNIC int main OSOCTET msgbuf 1024 msgptr int msglen OSCTXT ctxt Employee employee typedef generated by ASNIC Step 1 Initialize the context and set the buffer pointer if rtInitContext amp ctxt 0 initialization failed could be a license problem printf context initialization failed check license n return 1 xe_setp amp ctxt msgbuf sizeof msgbuf Step 2 Populate the structure to b ncoded mployee name givenName SMITH Step 3 Call the generated encode function msglen asnlE_Employee amp ctxt amp employee ASNIEXPL
240. ng encoding it is not necessary to implement code to write or send the encoded data to an output device The streaming functions also use less memory because there is no need for a large destination memory buffer For this reason the final performance of the streaming functions may be the same or better than buffer oriented functions Encoding a Series of Messages Using the Streaming C Encode Functions A common application of BER encoding is the repetitive encoding of a series of the same type of message over and over again For example a TAP3 batch application might read billing data out of a database table and encode each of the records for a batch transmission 135 Generated Streaming C Function Format and Calling Parameters Encoding a series of messages using the streaming C encode functions is very similar to encoding of one message All that is necessary is to set up a loop in which the asn BSE_ lt name gt functions will be called It is also possible to call different asn BSE_ lt name gt functions one after another An example showing how to do this is as follows include employee h include file generated by ASNIC int main int stat OSCTXT CEXE Employee employee typedef generated by ASNIC const char filename message dat Step 1 Initialize the context and stream if berStrmInitContext amp ctxt 0 initialization failed could be a license problem print
241. ng populated in the C or C source file ASN 1 production lt name gt OBJECT IDENTIFIER lt value gt Generated code ASNI1OBJID lt name gt lt value gt For example consider the following declaration oid OBJECT IDENTIFIER ccitt b 5 10 This would result in the following definition in the C or C source file ASNIOBJID oid 3y 0 Bp 0 4 3 To populate a variable in a generated structure with this value the rt Set OID utility function can be used see the C C Run Time Library Reference Manual for a full description of this function In addition the C base type for this construct ASN1TOb4jId contains constructors and assignment operators that allow direct assignment of values in this form to the target variable Constructed Type Values ASNIC will generate code for following remaining value definitions only when their use is required in legacy table constraint validation code 73 Constructed Type Values SEQUENCE e SET e SEQUENCE OF e SET OF e CHOICE Note SEQUENCE SET SEQUENCE OF SET OF and CHOICE values are available only when the tables option is selected The values are initialized in a module value initialization function The format of this function name is as follows init_ lt ModuleName gt Value OSCTXT pctxt Where lt ModuleName gt would be replaced with the name of the module containing the value specifications The only re
242. nly difference in this API with what is described above is that tracking of allocated memory is done through the context This makes it possible to provide an implementation of the rtxMemHeapFreeAll function as described above This memory management scheme is slower than the default manager i e nibble based but has a smaller code footprint This form of memory management is enabled by defining the MEMCOMPACT C compile time setting This can be done by either adding D_MEMCOMPACT to the C compiler command line arguments or by uncommenting this item at the beginning of the rttMemory h header file Uncomment this definition before building the C or C run time libraries to enable compact memory management This will have a smaller code footprint than the standard memory management however the performance may not be as good a define _MEMCOMPACT Low Level Memory Management API It is possible to replace the core memory management functions used by the ASNIC run time memory manager This has the advantage of preserving the existing management scheme but with the use of different core functions Using different core functions may be necessary on some systems that do not have the standard C run time functions malloc free and realloc or when extra functionality is desired To replace the core functions the following run time library function would be used void rtxMemSetAllocFuncs OSMallocFunc malloc_func OSReallocFun
243. nstCharPtr name ASN1ITObject amp object For an Object Field class lt ClassName gt lt FieldName gt In each of these definitions lt FieldName gt would be replaced with the name of the field without the leading amp lt TypeName gt would be replaced with the C type name for the ASN 1 Type lt ClassName gt would be replaced with the C type name of the class for the Information Object lt ER gt would be replaced by an encoding rules type BER PER or XER As an example consider the following ASN 1 class definition ATTRIBUTE CLASS amp Type amp ParameterType OPTIONAL amp id OBJECT IDENTIFIER UNIQUE WITH SYNTAX amp Type ID amp id This would result in the following definition in the C source file class EXTERN ATTRIBUT protected GI 84 Legacy Table Constraint Model ASNITObjId id ATTRIBUTE public virtual int encodeBERType OSCTXT pctxt ASN1TObject amp object 0 virtual int decodeBERType OSCTXT pctxt ASN1TObject amp object 0 OSBOOL isParameterTypePresent if m ParameterTypePresent return TRUE else return FALSI Gl e virtual int encodeBERParameterType OSCTXT pctxt ASN1TObject amp object return 0 virtual int decodeBERParameterType OSCTXT pctxt ASN1ITObject amp object return 0 inline OSBOOL idEquals ASN1TObjId pvalue
244. nstance is created in accordance with the rules above Value Mappings ASNIC can parse any type of ASN 1 value specification but it will only generate code for following value specifi cations 70 BOOLEAN Value e BOOLEAN e INTEGER e REAL e ENUMERATED e Binary String e Hexadecimal String e Character String e OBJECT IDENTIFER All value types except INTEGER and REAL cause an extern statement to be generated in the header file and a global value assignment to be added to the C or C source file INTEGER and REAL value specifications cause define statements to be generated BOOLEAN Value A BOOLEAN value causes an extern statement to be generated in the header file and a global declaration of type OSBOOL to be generated in the C or C source file The mapping of ASN 1 declaration to global C or C value declaration is as follows ASN 1 production lt name gt BOOLEAN lt value gt Generated code OSBOOL lt name gt lt value gt INTEGER Value The INTEGER type causes a define statement to be generated in the header file of the form ASN1V_ lt valueName gt where lt valueName gt would be replaced with the name in the ASN 1 source file The rea son for doing this is the common use of INTEGER values for size and value range constraints in the ASN 1 specifi cations By generating def ine statements the symbolic names can be included in the source code making it easier to adjust the boundary valu
245. nstance of this class can be created using the list element within a generated structure as a parameter The helper methods can then be used to allocate and initialize an element and then append it to the list after it is populated See the cpp sample_ber employee writer cpp file for an example of how these methods are used In this program the following logic is used to populate one of the elements in the children list for encoding 60 SEQUENCE OF ASN1T_ChildInformation pChildInfo ASN1C__SeqOfChildInformation listHelper encodeBuffer msgData children pChildiInfo listHelper NewElement fill_Name amp pChildInfo gt name Ralph T Smith pChildInfo gt dateOfBirth 19571111 listHelper Append pChildInfo In this example msgData is an instance of the main PDU class being encoded PersonnelRecord This object contains an element called children which is a linked list of ChildInformation records The code snippet illustrates how to use the generated control class for the list to allocate a record populate it and append it to the list ASNIC also generates helper methods in SEQUENCE SET and CHOICE control classes to assist in allocating and adding elements to inline SEQUENCE OF lists These methods are named new_ lt elem gt _element and append_to_ lt elem gt where lt elem gt would be replaced with the name of the element they apply to Generation of Temporary Types for SEQUENCE OF Elements
246. nstant This constant can be used in a comparison operation with a tag parsed from a message The following line 33 Header h File typedef OSINT32 EmployeeNumber declares EmployeeNumber to be of an integer type note OSINT32 and other primitive type definitions can be found in the osSysTypes h header file asnlE_EmployeeNumber and asnID_EmployeeNumber are function prototypes for the encode and decode functions respectively These are BER function prototypes If the per switch is used PER function prototypes are generated The PER prototypes begin with the prefix asn PE_ and asn PD_ for encoder and decoder respectively XER function prototypes begin with asn XE_ and asn1XD_ A sample section from a C header file for the same production is as follows BRR KK HH KI KKK HK KKK KK HH KK KKK KKK KKK KKK KKK KK HHH KKK KKK KKK KK KKK KKK as EmployeeNumber A a Ai BRR KKK KH HK IK KK HK KI KKK HH KI KKK KKK KKK KKK KIKI K KKK KKK KKK KKK KK KKK KKK define TV_EmployeeNumber TM_APPL TM_PRIM 2 typedef OSINT32 ASN1T_EmployeeNumber class EXTERN ASN1C_EmployeeNumber public ASN1CType protected ASN1IT_EmployeeNumber amp msgData public ASN1C_EmployeeNumber ASN1T_EmployeeNumber amp data ASN1C_EmployeeNumber ASN1MessageBufferIF amp msgBuf ASN1T_EmployeeNumber amp data standard encode decode methods defined in ASNICType base class int Encode
247. nt header as well as namespace attributes in the main element tag Generated encode functions are invoked through the class interface by calling the base class Encode method The calling sequence for this method is as follows stat lt object gt Encode In this definition lt object gt is an object of the class generated for the given production The function result variable stat returns the status value from the XML encode function This status value will be zero if encoding was successful or a negative error status value if encoding fails Return status values are defined in the rtxErrCodes h include file The user must call the encode buffer class methods getMsgPtr and getMsgLen to obtain the starting address and length of the encoded message component Procedure for Using the C Control Class Encode Method The procedure to encode a message using the C class interface is as follows 1 Instantiate an XML encode buffer object OSXMLEncodeBuffer to describe the buffer into which the message will be encoded Constructors are available that allow a static message buffer to be specified The default constructor specifies use of a dynamic encode buffer 2 Instantiate an ASN1T_ lt type gt object and populate it with data to be encoded 3 Instantiate an ASN1C_ lt type gt object to associate the message buffer with the data to be encoded 4 Invoke the ASN1C_ lt type gt object Encode or EncodeTo method 5 Check the return st
248. nternal use when calls to decode functions are nested to accomplish decoding of complex variables At the top level these parameters should always be set to the constants ASNIEXPL and zero respectively The function result variable status returns the status of the decode operation The return status will be zero if decoding is successful or negative if an error occurs Return status values are defined in the rtvErrCodes h include file Procedure for Calling Streaming C Decode Functions This section describes the step by step procedure for calling a streaming C BER decode function This procedure must be followed if C code generation was done This procedure can also be used as an alternative to using the control class interface if C code generation was done Before any decode function can be called the user must first initialize a context variable This is a variable of type OSCTXT This variable holds all of the working data used during the decoding of a message The context variable is declared as a normal automatic variable within the top level calling function It must be initialized before use This can be accomplished by using the berStrmInitContext function OSCTXT ctxt context variable 152 Generated Streaming C Function Format and Calling Parameters if berStrmInitContext amp ctxt 0 initialization failed could be a license problem printf context initialization failed check license n return
249. o determine if a corrupt or partial message was received If the parsed message length is greater than this value an error is returned If the value is specified to be zero the default then this test is bypassed The function result variable status returns the status of the decode operation The return status will be zero if decoding is successful or a negative value if an error occurs Return status values are defined in Appendix A of the C C Common Functions Reference Manual and online in the asn1type h include file 144 Generated C Decode Method Format and Calling Parameters Procedure for Using the C Control Class Decode Method Normally when a message is received and read into a buffer it can be one of several different message types So the first job a programmer has before calling a decode function is determining which function to call The ASNIBERDecodeBuffer class has a standard method for parsing the initial tag length from a message to determine the type of message received This call is used in conjunction with a switch statement on generated tag constants for the known message set in order to pick a decoder to call Once it is known which type of message has been received an instance of a generated message class can be instantiated and the decode function called The start of message pointer and message length if known must be specified either in the constructor call or in the call to the decode function itself
250. o zero to prepare it to receive decoded data The advantage is that the initialization functions are smarter and know exactly what within the structures needs to be zeroed as opposed to blindly clearing everything So for example large byte arrays used to hold OCTET STRING data will not be zeroed This can add up to significant performance improvements in the long run particular in complex deeply nested ASN 1 types If initialization functions are generated the generated decode logic will use them wherever it can in place of calls to zero memory BER DER Deferred Decoding Another way to improve decoding performance of large messages is through the use of deferred decoding This allows for the selective decoding of only parts of a message in a single decode function call When combined with the fast copy procedure defined above this can significantly reduce decoding time because large parts of messages can be skipped Deferred decoding can be done on elements defined within a SEQUENCE SET or CHOICE construct It is done by designating an element to be an open type by using the lt isOpenType gt configuration setting This setting causes the 150 Generated BER Streaming Decode Functions ASNIC compiler to insert an Asn OpenType placeholder in place of the type that would have normally been used for the element The data in its original encoded form will be stored in the open type container when the message is decoded If fast copy is
251. occur one or two times If minOccurs is absent its default value is 1 X 694 specifies that a SEQUENCE OF type be formed for this element and then the element renamed to fami lyName list to reference this element The C code produced by this transformation is as follows typedef struct EXTERN Name const OSUTF8CHAR givenName const OSUTF8CHAR initial struct OSUINT32 n const OSUTF8CHAR elem 2 familyName_list Name In this case an array was used to represent familyName_list In others a linked list might be used to represent the repeating item 95 xsd list xsd list Another way to represent repeating items in XSD is by using xsd list This is a simple type in XSD that refers to a space separated list of repeating items When the list is converted to ASN 1 it is modeled as a SEQUENCE OF type For example lt xsd simpleType name MyType gt lt xsd list itemType xsd int gt lt xsd simpleType gt results in the generation of the following C type typedef struct EXTERN MyType OSUINT32 n OSINT32 elem MyType Special code is added to the generated XML encode and decode function to ensure the data is encoded in spaceseparated list form instead of as XML elements xsd any The xsd any element is a wildcard placeholder that allows an occurence of any element definition to occur at a given location It is similar to the ASN 1 open type and can be modeled as such howe
252. ocess received data else error processing break default handle unknown message type here switch Need to reinitialize objects for next iteration rtxMemReset amp ctxt The only changes were the addition of the for loop and the call to rtxMemReset that was added at the bottom of the loop This function resets the memory tracking parameters within the context to allow previously allocated memory to be reused for the next decode operation Optionally rxMemF ree can be called to release all memory This will allow the loop to start again with no outstanding memory allocations for the next pass The example above assumes that logic existed that would read each message to be processed into the same buffer for every message processed inside the loop i e the buffer is reused each time In the case in which the buffer already contains multiple messages encoded back to back it is necessary to advance the buffer pointer in each iteration main OSOCTET msgbuf 1024 ASN1TAG msgtag int offset 0 msglen len OSCTXT ctxt PersonnelRecord employee FILE fp Step 1 Initialize a context variable for decoding if rtInitContext amp ctxt 0 initialization failed could be a license problem printf context initialization failed check license n return 1 if fp fopen filename rb msglen fread msgbuf 1 sizeof msgbuf fp
253. odName gt is the name of the ASN 1 production for which the function is being generated and lt prefix gt is an optional prefix that can be set via a configuration file setting The configuration setting used to set the prefix is the lt typePrefix gt element This element specifies a prefix that will be applied to all generated typedef names and function names for the production The calling sequence for each generated memory free function is as follows asnlFree_ lt name gt OSCTXT pctxt lt name gt pvalue In this definition lt name gt denotes the prefixed production name defined above The pctxt argument is used to hold the context pointer that the memory to be freed was allocated with This is a basic handle variable that is used to make the function reentrant so it can be used in an asynchronous or threaded application The user is required to supply a pointer to a variable of this type declared somewhere in his or her or her program The pvalue argument is used to pass a pointer to a variable of the item that contains the dynamic memory to be freed Generated Print Functions The following options are available for generating code to print the contents of variables of generated types print This is the standard print option that causes print functions to be generated that output data to the standard output device stdout genPrtToStr This option causes print functions to be generated that write their output to a memory b
254. odes h Users may always look at these two files or the documentation generated from them for a fully updated list of error messages and their descriptions ASN1C Error Messages The following table describes error messages that ASN1IC may report during the course of code generation not during runtime These include syntax errors import warnings type resolution failures and others Users should note that there are several classes of status messages in this list errors ASN E messages warnings ASN W messages and informational notices ASN I messages Error Code Error Description ASN E NOTYPE ASN E UNDEFTYPE No type was defined for the referenced element in a SEQUENCE or SET The type referenced was not defined within the context of this module ASN E NOTAG The object must be tagged in this context This usually occurs when context specific tags are required to disambiguate elements in a SE QUENCE or SET ASN W DUPLICATE The referenced type or value was previously defined ASN W DUPLTAG ASN E UNRECTYP The referenced tag was previously defined in a CHOICE or SET this happens when an contextual tag is provided more than once The type described is not recognized by the compiler ASN E MULTDEF A choice tag has multiple definitions ASN E UNDEFVAL The referenced value is not defined or cannot be found ASN E INVTYPNAM ASN E UNDEFTAG Invalid type name This i
255. oding loop and the modification of step 6 in the procedure The decoding loop is an infinite loop to continuously read and decode messages from some interface such as a network socket The decode calls are the same but before in step 6 we were counting on the message buffer and control objects to go out of scope to cause the memory to be released Since the objects are now being reused this will not happen So the call to the memFreeAll method that is defined in the ASN1C_Type base class will force all memory held at that point to be released Performance Considerations Dynamic Memory Manage ment Please refer to Performance Considerations Dynamic Memory Management in the BER Decode Functions section for a discussion of memory management performance issues All of the issues that apply to BER and DER also apply to PER as well 171 172 Generated XML Functions Generated XER Encode Functions XER stands for XML Encoding Rules a form of XML specified in the X 693 standard for use with ASN 1 NOTE XER is maintained as a legacy XML format for ASN 1 New applications should consider using XML as described in the next section instead of XER XML is more closely aligned with W3C standard XML and XML schema XER C encode functions are generated when the xer switch is specified on the command line For each ASN 1 prouc tion defined in the ASN 1 source file a C XER encode function is generated This function will convert a
256. ods Thus even if control class and message buffer objects go out of scope the memory will not be freed until the destructor of an ASNITPDU inherited class is called The example above will work correctly without any modifications in this case Another way to keep data is to make a copy of the decoded object before it goes out of scope A method called newCopy is also generated in the control class for these types which can be used to create a copy of the decoded object This copy of the object will persist after the control class and message buffer objects are deleted The returned object can be deleted using the standard C delete operator when it is no longer needed Returning to the example above it can be made to work if the type being decoded is a PDU type by doing the following ASN1T_ lt type gt func2 ASNIT_ lt type gt msgdata ASNIBERDecodeBuffer decbuf ASN1C_ lt type gt cc decbuf msgdata cc Decode Use newCopy to return a copy of the decoded item return cc newCopy Populating Generated Structure Variables for Encoding Prior to calling a compiler generated encode function a variable of the type generated by the compiler must be pop ulated This is normally a straightforward procedure just plug in the values to be encoded into the defined fields However things get more complicated when more complex constructed structures are involved These structures fre quently contain pointer type
257. of octets integer specifies the actual number of octets in the contents field The allocation for the contents field depends on how the octet string is specified in the ASN 1 definition If a size constraint is used a static array of that size is generated otherwise a pointer variable is generated to hold a dynamically allocated string The decoder will automatically allocate memory to hold a parsed string based on the received length of the string For C constructors and assignment operators are generated to make assigning variables to the structures easier In addition to the default constructor a constructor is provided for string or binary data An assignment operator is generated for direct assignment of a null terminated string to the structure note this assignment operator copies the null terminator at the end of the string to the data Dynamic OCTET STRING ASN 1 production lt name gt OCTET STRING Generated C code typedef ASN1DynOctStr lt name gt Generated C code typedef ASN1TDynOctStr ASN1T_ lt name gt In this case different base types are used for C and C The difference between the two is the C version includes constructors assignment operators and other helper methods that make it easier to manipulate binary data The ASN DynOctStr type i e the type used in the C mapping is defined in the asn type h header file as follows typedef struct ASN1DynOctStr OSUINT32 numocts const OSOCTE
258. of the target system In general the following parameters will need to be adjusted a CC C compiler executable name b CCC C compiler executable name c CFLAGS_ Flags that should be specified on the C or C command line The platform w32 and platform gnu files in the root directory of the installation are sample files for Windows 32 Visual C and GNU compilers respectively Either of these can be renamed to platform mk for building in either of these environments 6 Invoke the makefile in the build_lib subdirectory 25 Compiler Configuration File If all parameters were set up correctly the result should be binary library files created in the lib subdirectory Compiler Configuration File In addition to command line options a configuration file can be used to specify compiler options These options can be applied not only globally but also to specific modules and productions A simple form of XML is used to format items in the file XML was chosen because it is fairly well known and provides a natural interface for representing hierarchical data such as the structure of ASN 1 modules and productions The use of an external configuration file was chosen over embedding directives within the ASN 1 source itself due to the fact that ASN 1 source versions tend to change frequently An external configuration file can be reused with a new version of an ASN 1 module but internal directives would have to be reapplied to the new
259. oint number was used as part of a SIZE constraint ASN E INVRANGE ASN E IMPORTMOD This indicates an invalid range specification for example when the lower bound is greater than the upper bound This indicates that the specified import module object was not found ASN E NOTSUPP This indicates that the requested functionality is not supported by the compiler Most often the error is raised when generating test code for complex value definitions ASN E IDNOTFOU This indicates the compiler was unable to look up the specified iden tifier ASN E NOFIELD ASN E DUPLNAME This indicates that the specified field could not be found in the named class This indicates the specified name is already defined ASN W UNNAMED This warning is raised when specifications use unnamed fields These fields not allowed in X 680 but ASNIC supports them for purposes of backwards compatibility with X 208 ASN E UNDEFOBJ This indicates that the named object is not defined within context of the requested module ASN E ABSCLSFLD ASN E UNDEFCLAS This indicates that the specified field is absent in an information object definition This indicates that the specified class is not defined within context of the module that uses it ASN E INVFIELD This indicates the specified class field is not valid it must be defined ASN E UNDEFOSET This indicates that ASN1C was unable to find the specified object se
260. ol Class Decode Method Instantiate an XML decode buffer object OSXMLDecode Buffer to describe the message to be decoded There are several choices of constructors that can be used including one that takes the name of a file which contains the XML message one the allows a memory buffer to be specified and one that allows an existing stream object to be used Instantiate an ASN1T_ lt ProdName gt object to hold the decoded message data Instantiate an ASN1C_ lt ProdName gt object to decode the message This class associates the message buffer object with the object that is to receive the decoded data The results of the decode operation will be placed in the variable declared in step 2 Invoke the ASNIC_ lt ProdName gt object Decode or DecodeFrom method Check the return status The return value is a status value indicating whether decoding was successful or not Zero indicates success If decoding failed the status value will be a negative number The decode buffer method printErrorInfo can be invoked to get a textual explanation and stack trace of where the error occurred Release dynamic memory that was allocated by the decoder All memory associated with the decode context is released when both the OSXMLDecodeBuffer and ASNIC_ lt ProdName gt objects go out of scope A program fragment that could be used to decode an employee record is as follows include employee h include file generated by ASNIC main con
261. olding pointers to the now out of scope variables this type of error is commonly known as dangling pointers Using the second technique i e using C malloc and free can solve this problem In this case the memory for each of the elements can be safely freed after the encode function is called But the downside is that a free call must be made for each corresponding malloc call For complex structures remembering to do this can be difficult thus leading to problems with memory leaks The third technique uses the compiler run time library memory management functions to allocate and free the memory The main advantage of this technique as opposed to using C malloc and free is that all allocated memory can be freed with a single rtxMemFree call The rtxMemAlloc macro can be used to allocate memory in much the same way as the C malloc function with the only difference being that a pointer to an initialized OSCTXT structure is passed in addition to the number of bytes to allocate All allocated memory is tracked within the context structure so that when the rtxMemFree function is called all memory is released at once Accessing Encoded Message Components After a message has been encoded the user must obtain the start address and length of the message in order to do further operations with it Before a message can be encoded the user must describe the buffer the message is to be encoded into by specifying a message buffer start address and size
262. on of each run time library is included in the lib subdirectory This file typically has the extension so for shared object or sl for shared library See the documentation for your UNIX compiler to determine how to link using these files Compiling and linking code generated to support the XML encoding rules XER is more complex then the other rules because XER requires the use of third party XML parser software This requires the use of additional include directories when compiling and libraries when linking The C sample programs that are provided use the EXPAT XML parser http www expat org All of the necessary include files and binary libraries are included with the distribution for using this parser If a different parser is to be used consult the vendor s documentation for compile and link procedures 24 Porting Run time Code to Other Platforms See the makefile in any of the sample subdirectories of the distribution for an example of what must be included to build a program using generated source code Porting Run time Code to Other Platforms The run time source version of the compiler includes ANSI standard source code for the base run time libraries This code can be used to build binary versions of the run time libraries for other operating environments Included with the source code is a portable makefile that can be used to build the libraries on the target platform with minimal changes All platform specific item
263. ons ccececseeceeseeceeececueeeeeeeeeeeeceuneseeeececueseeaneeees 178 Procedure for Using the C Interface meieni e e aaa a a essen ceaeesenen sees 180 Procedure for Interfacing with Other C and C X ML Parser Libraries 0 cece eee ee ee 181 Generated XML Encode FUNCIONS ssrin ses sep veuese spore e p an A peswmess cavedav ess suadsee e S ee A ors 181 Procedure for Calling C Encode Functions 0 cceceee cece cece n E TEE 184 Generated C Encode Method Format and Calling Parameters cecceeceeeceeeceeeceeeeeeeene ee 185 Procedure for Using the C Control Class Encode Method ccecceeeceee cece eeceeeceneeeeeeeenees 185 Generated XML Decode FUNCtions sess peene e eE eR EEEE REE PEA EA E seem aeepeneens 186 Generated C Function Format and Calling Parameters se sseesseeesserrsererrreerrrrrsrrerrsrrerreresre 187 Procedure for Calling C Decode Functions ccececseeceneeeceeececueeeeueceeceeceaueeeeueceeueseeaneeees 187 Generated C Decode Method Format and Calling Parameters sesseeereseesrerrrrrerrrrrerrereere 189 Procedure for Using the C Control Class Decode Method ssneseeseeersseerrsrerrrrresrrrrerrerrese 189 Additonal Generated FUNCIONS 22 0 2 a nn EE E AE A EEE E TE E a E E O tee 193 Generated Initialization Functions sisena a E E E E E a E N SE 193 Generated Memory Free Functions ineen eea AE EEE A Ea E E EEEO EEE NE 193 Generated Print
264. ontext block is initialized by calling rtInitContext to initialize a context block structure The user then must call the xerSetEncBufPtr function to specify a message buffer to receive the encoded message Specification of a dynamic message buffer is possible by setting the buffer address argument to null and the buffer size argument to zero This function also also allows specification of whether standard XER or canonical XER encoding should be done An encode function can then be called to encode the message If the return status indicates success 0 then the message will have been encoded in the given buffer XER encoding starts from the beginning of the buffer and proceeds from low memory to high memory until the message is complete This differs from BER where encoding was done from back to front Therefore the buffer start address is where the encoded XER message begins The length of the encoded message can be obtained by calling the xerGetMsgLen run time function If dynamic encoding was specified i e a buffer start address and length were not given the run time routine xerGetMsgPtr can be used to obtain the start address of the message This routine will also return the length of the encoded message A program fragment that could be used to encode an employee record is as follows include employee h include file generated by ASNIC main OSOCTET msgbuf 4096 int msglen stat OSCTXT ctxt OSBOOL cxer FALSE
265. or decoding a single message but what happens in the more typical scenario of having a long running loop that continuously decodes messages The logic shown above would not be optimal from a performance standpoint because of the constant creation and destruction of the message processing objects It would be much better to create all of the required objects outside of the loop and then reuse them to decode and process each message A code fragment showing a way to do this is as follows include employee h include file generated by ASNIC main 170 Performance Considerations Dy namic Memory Management OSOCTI msgbuf 1024 int msglen stat OSBOOL aligned TRU ea FH Gl step 1 instantiate a PER decode buffer object ASNIPERDecodeBuffer decodeBuffer msgbuf msglen aligned step 2 instantiate an ASNIT_ lt ProdName gt object ASN1T_PersonnelRecord msgData step 3 instantiate an ASNIC_ lt ProdName gt object ASN1C_PersonnelRecord employ decodeBuffer msgData loop to continuously decode records for logic to read message into msgbuf stat employee Decode step 5 check the return status if stat 0 process received data else error processing decodeBuffer PrintErroriInfo step 6 free dynamic memory mploy memFreeAll The only difference between this and the previous example is the addition of the dec
266. orHandler base class This class is as follows class MyErrorHandler public AsnlErrorHandler public The error handler callback method This is the method that the user must override to provide customized error handling virtual int error OSCTXT pCtxt ASNICCB pCCB int stat 5 Simple enough All we are doing is providing an implementation of the error method 206 How to Use It Implementing the error method requires some knowledge of the run time internals In most cases it will be necessary to somehow alter the decoding buffer pointer so that the same field isn t looked at again If this isn t done an infi nite loop can occur as the parser encounters the same error condition over and over again The run time functions xd_NextElement or xd_OpenType might be useful in the endeavor as they provide a way to skip the current element and move on to the next item Our sample handler corrects the error in which an unknown element is encountered within a SET construct This will cause the error status ASN_E_NOTINSET to be generated When the error handler sees this status it prints information on the error that was encountered to the console skips to the next element and then returns an 0 status that allows the decoder to continue If some other error occurred i e status was not equal to ASN_E_NOTINSET then the original status is passed out which forces the termination of the decoding process The f
267. ove The pct xt argument is used to hold a context pointer to keep track of encode parameters This is a basic handle variable that is used to make the function reentrant so it can be used in an asynchronous or threaded application The user is required to supply a pointer to a variable of this type declared somewhere in his or her program This variable must be initialized using both the rt nitContext and rtStreamBuflnit run time library functions see the C C Common Run Time Library Reference Manual for a description of these functions The pvalue argument holds a pointer to the data to be encoded and is of the type generated from the ASN 1 pro duction 133 Generated Streaming C Function Format and Calling Parameters The tagging argument is for internal use when calls to encode functions are nested to accomplish encoding of complex variables It indicates whether the tag associated with the production should be applied or not implicit versus explicit tagging At the top level the tag should always be applied so this parameter should always be set to the constant ASNIEXPL for EXPLICIT The function result variable st at returns the completion status of the operation 0 0 means the success Procedure for Calling Streaming C Encode Functions This section describes the step by step procedure for calling a streaming C BER encode function This method must be used if C code generation was done This method can also be used as
268. owing additional function is generated EXTERN int asniD_Identifier_id_OpenType OSCTXT pctxt OSINT32 pvalue In the Identifier decode function element id is decoded as an open type Generated BER Streaming Decode Functions BER messages can be directly read and decoded from an input stream such as a file network or memory stream using BER streaming decode functions The ASN1C compiler stream option is used to generate decoders of this type For each ASN 1 production defined in an ASN 1 source file a C streaming decode function is generated This function will decode an ASN 1 message into a C variable of the given type If C code generation is specified a control class is generated that contains a DecodeFrom method that wraps this function This function is invoked through the class interface to decode an ASN 1 message into the variable referenced in the msgData component of the class 151 Generated Streaming C Function Format and Calling Parameters In this version there are three types of streams file socket and memory The most useful are file and socket streams It is possible to decode data directly from a file or socket without intermediate copying into memory If the full amount of data is not available for reading then the behavior of these streams will be different the file and memory input streams will report an error the socket input stream will block until data is available or an I O error occurs for e
269. p procedure for calling a C BER or DER decode function This method must be used if C code generation was done This method can also be used as an alternative to using the control class interface if C code generation was done Before any decode function can be called the user must first initialize a context variable This is a variable of type OSCTXT This variable holds all of the working data used during the decoding of a message The context variable is declared as a normal automatic variable within the top level calling function It must be initialized before use This can be accomplished as follows OSCTXT ctxt if rtInitContext amp ctxt 0 140 Generated C Function Format and Calling Parameters initialization failed could be a license problem printf context initialization failed check license n return 1 The next step is the specification of a buffer containing a message to be decoded This is accomplished by calling the xd_setp run time library function This function takes as an argument the start address of the message to be decoded The function returns the starting tag value and overall length of the message This makes it possible to identify the type of message received and apply the appropriate decode function to decode it A decode function can then be called to decode the message If the return status indicates success the C variable that was passed as an argument will contain the
270. p rriective SYSTEMS INC ASNIC ASN 1 Compiler Version 6 2 C C User s Manual Objective Systems Inc version 6 2 May 2009 The software described in this document is furnished under a license agreement and may be used only in accordance with the terms of this agreement Copyright Notice Copyright 1997 2009 Objective Systems Inc All rights reserved This document may be distributed in any form electronic or otherwise provided that it is distributed in its entirety and that the copyright and this notice are included Author s Contact Information Comments suggestions and inquiries regarding ASN1C may be submitted via electronic mail to info obj sys com Table of Contents Overview Of ASNI G jn sa2scts testis a e a R E a E a E ss Sancta a E R E a pa EEE 1 Using the Compiler sie eie betes hess ets Ee EEE es Neg aS See EEEE EI EE EE eSATA eA 3 Running ASNIC from the Command line 2 0 0 0 onise ri nei cc eeceeeceeeceeeeeeeceeseaeeea EE ESEESE EPES ER eE 3 Using the GUI Wizard to Run ASNIC 200 cece cece cc ne ce eeceeeceeeceeeceeecaeecaeeea sean seas eeneeneeeeeeeees 14 C C Code Generation Options sinceron 503 batasaes catia sek Dae ea tases ook E Sota saa See ato ag asa betes 19 Compiling and Linking Generated Code 00 00 00 cece cece cc ence ence ence eeceeeeaeeea ceca sean eens seas eeneeeeeeenes 24 Porting Run time Code to Other Platforms 20 0000 cece cece cece eee cee ce cece cena ce
271. pe to be used in a message An example of this is as follows lt xsd complexType name MyType gt lt xsd sequence gt lt xsd element name ElementOne type xsd string gt lt xsd element name ElementTwo type xsd int gt lt xsd sequence gt lt xsd complexType gt lt xsd complexType name MyExtendedType gt lt xsd complexContent gt lt xsd extension base MyType gt lt xsd sequence gt lt xsd element name ElementThree type xsd string gt lt xsd element name ElementFour type xsd int gt lt xsd sequence gt lt xsd extension gt lt xsd complexContent gt lt xsd complexType gt The base type in this case is MyType and it is extended to contain two additional elements in MyExtendedType The resulting C type definitions for MyType MyExtendedType and the special derivations type are as follows typedef struct EXTERN MyType const OSUTF8CHAR elementOne OSINT32 elementTwo MyType typedef struct EXTERN MyExtendedType const OSUTF8CHAR elementOne OSINT32 elementTwo const OSUTF8CHAR elementThree OSINT32 elementFour MyExtendedtType define T_MyType_derivations_myType 1 define T_MyType_derivations_myExtendedType 2 typedef struct EXTERN MyType_derivations int t union 100 Substitution Groups be Eas LAE MyType myType PE SZ A MyExtendedType myExtendedType u MyType_derivations The derivations typ
272. pe gt plist In this definition lt ProtocollEsType gt refers to the main list type SEQUENCE OF definiing the information element list lt ProtocolIE FieldType gt is the type of an element within this list and lt KeyFieldType gt is the type of index key field 80 3GPP Table Constraint Model An example of this type of function from the S1AP definitions is as follows Get IE using id key value HandoverRequired_protocollIEs_element asnilGet_HandoverRequired_protocoll ProtocolIE_ID id HandoverRequired_protocollEs plist GI n Generated C Classes and Methods This section discusses items that are generated idfferently for C for 3GPP table constraints Choice Selector TVALUE Type For C an enumerated type is generated for each of the options in a type field union These correspond to each of the items in the information object set associated with the union For example the TVALUE type generated for SI1AP_ELEMENTARY_PROCEDURES is as follows typedef enum T1_UNDEF_ Tl_handoverPreparation Tl_handoverResourceAllocation Tl_pathSwitchRequest S1AP_ELEMENTARY_PROCEDURES_TVALUE Note the number 1 following the leading T in each of these enumeration items That number is a sequential type number used to ensure that no name clashes occur between enumerations with common names For C this type is generated as a class with TVALUE as a public member inside
273. pecified the format of the generated prototypes is different The PER prototypes are of the fol lowing general form int asnlPE_ lt ProdName gt OSCTXT pctxt lt ProdName gt value int asnlPD_ lt ProdName gt OSCTXT pctxt lt ProdName gt pvalue In these prototypes the prefixes are different a P character is added to indicate they are PER encoders decoders and the tagging argument variables are omitted In the encode case the value of the production to be encoded may be passed by value if it is a simple type for example BOOLEAN or INTEGER Structured values will still be passed using a pointer argument If XER encoding is specified function prototypes are generated with the following format int asnlXE_ lt ProdName gt OSCTXT pctxt lt ProdName gt value const char elemName const char attributes int asnlXD_ lt ProdName gt OSCTXT pctxt lt ProdName gt pvalue The encode function signature includes arguments for the context and value as in the other cases It also has an element name argument elemName that contains the name of the element to be encoded and an attributes argument attributes 103 Generated C Control Class Definition that can be used to encode an attributes string The decode function is generated for PDU types only decoding of internally referenced types is accomplished through generated SAX handler callback functions which are invoked by an XML parser
274. pointer to a variable of a specific type The pointer is void because there could be a potentially large number of different types that can be represented in the table constraint used to constrain a type field to a given set of values The index member of the type is for internal use by table constraint processing functions to keep track of which row in a table is being referenced In addition to this change in how open types are represented a large amount of supporting code is generated to support the table constraint validation process This additional code is described below Note that it is not necessary for the average user to understand this as it is not for use by users in accomplishing encoding and decoding of messages It is only described for completeness in order to know what that additional code is used for CLASS specification All of the Class code will be generated in a module class header file with the following filename format 82 Legacy Table Constraint Model lt ModuleName gt Class h In this definition lt ModuleName gt would be replaced with the name of the ASN 1 module name for this class def inition C Code generation The C structure definition generated to model an ASN 1 class contains member variables for each of the fields within the class For each of the following class fields the corresponding member variable is included in the generated C structure as follows For a Value Field lt TypeNam
275. pposite convert from string to enumerated C Mapping ASN 1 production lt name gt ENUMERATED lt idl gt lt vall gt lt id2 gt lt val2 gt Generated code struct lt name gt enum Root idl vall id2 val2 enum Ext extidl extvall typedef OSUINT32 ASN1T_ lt name gt The struct type provides a namespace for the enumerated elements This allows the same enumerated constant names to be used in different productions within the ASN 1 specification An enumerated item is specified in the code using the lt name gt lt id gt form 51 NULL Every generated definition contains a Root enumerated specification and optionally an Ext specification The Root specification contains the root elements of the type or all of the elements if it is not an extended type and the Ext specification contains the extension enumerated items The form of the typedef following the struct specification depends on whether or not the enumerated type contains an extension marker or not If a marker is present it means the type can contain values outside the root enumeration An OSUINT32 is always used in the final typedef to ensure a consistent size of an enumerated variable and to handle the case of unknown extension values NULL The ASN 1 NULL type does not generate an associated C or C type definition OBJECT IDENTIFIER The ASN 1 OBJECT IDENTIFIER type is converted into a C or C
276. project files to compile all generated code into a DLL and mt that will add multi threaded compilation options to generated projects Because there are several different versions of Visual Studio the vcproj option takes an optional argument the release year of the version of Visual Studio used This modifies the resulting project to link against the appropriate set of libraries distributed with ASNIC If no year is specified the project will link against the usual c and cpp directories If 2003 is specified the project will us the c_vs2003 and cpp_vs2003 directories If 2005 is specified c_vs2005 and cpp_vs2005 will be used Likewise if 2008 is specified c_vs2008 and cpp_vs2008 will be used 41 42 ASN 1 To C C Mappings Type Mappings BOOLEAN The ASN 1 BOOLEAN type is converted into a C type named OSBOOL In the global include file osSysTypes h OSBOOL is defined to be an unsigned char ASN 1 production lt name gt BOOLEAN Generated C code typedef OSBOOL lt name gt Generated C code typedef OSBOOL ASN1T_ lt name gt For example if B PRIVATE 10 BOOLEAN was defined as an ASN 1 production the generated C type definition would be typedef OSBOOL B Note that the tag information is not represented in the type definition It is handled within the generated encode decode functions The only difference between the C and C mapping is the addition of the ASN1T_ prefix on the C type INT
277. protocol would be most interested in doing the processing in multiple stages hence no single function or structure is generated Therefore to encode the login example the user would do the following _ At the application layer the Login ARGUMENT structure would be populated with the username and password to be encoded N The encode function for Login ARGUMENT would be called and the resulting message pointer and length would be passed down to the next layer the ROSE layer W At the ROSE layer the Invoke structure would be populated with the OPERATION value invoke identifier and other header parameters The parameter numocts value would be populated with the length of the message passed in from step 2 The parameter data field would be populated with the message pointer passed in from step 2 D The encode function for Invoke would be called resulting in a fully encoded ROSE Invoke message ready for transfer across the communications link The following is a picture showing this process Application Layer Populate specific message structure Login ARGUMENT and encode Vv Encoded message pointer and length Populate ROSE header message structure Invoke and encode Open type structure contains message pointer and length from previous step Vv Final encoded message On the decode side the process would be reversed with the message flowing up the stack ROSE Layer 1 At the ROSE layer the header would be d
278. pt can be used ex elem 0 elem 1 In the case of C a constructor is generated to initialize the element count to zero If the type represents a PDU type either by default by not referencing any other types or explicitly via the pdu command line option the ASV TPDU base class is extended and a destructor is added This destructor ensures that memory allocated for elements is freed upon destruction of the object Static sized SEQUENCE OF Type ASN 1 production lt name gt SEQUENCE SIZE lt len gt OF lt type gt 59 SEQUENCE OF Generated C code typedef struct OSUINT32 n lt type gt elem lt len gt lt name gt Generated C code typedef struct OSUINT32 n lt type gt elem lt len gt ASNIT_ lt name gt List based SEQUENCE OF Type A doubly linked list header type OSRTDList is used for the type definition if the list storage configuration setting is used see above This can be used for either a sized or unsized SEQUENCE OF construct The generated C or C code is as follows Generated C code typedef OSRTDList lt name gt Generated C code typedef ASN1TSeqOfList ASN1T_ lt name gt The type definition of the OSRTDList structure can be found in the osSysTypes h header file The common run time utility functions beginning with the prefix rtxDList are available for initializing and adding elements to the list See the C C Common Run time Reference
279. ptional prefix that can be set via a configuration file setting The configuration setting used to set the prefix is the lt typePrefix gt element This element specifies a prefix that will be applied to all generated typedef names and function names for the production lt namespace gt is set using the ASNIC namespace command line argument Note that this should not be confused with the notion of an XML namespace The calling sequence for each encode function is as follows status lt ns gt XmlEnc_ lt name gt OSCTXT pctxt lt name gt value const OSUTF8CHAR elemName const OSUTF8CHAR nsPrefix In this definition lt ns gt is short for lt namespace gt and lt name gt denotes the prefixed production name defined above The pct xt argument is used to hold a context pointer to keep track of encode parameters This is a basic handle variable that is used to make the function reentrant so it can be used in an asynchronous or threaded application The user is required to supply a pointer to a variable of this type declared somewhere in his or her or her program The value argument contains the value to be encoded or holds a pointer to the value to be encoded This variable is of the type generated from the ASN 1 production The object is passed by value if it is a primitive ASN 1 data type such as BOOLEAN INTEGER ENUMERATED etc It is passed using a pointer reference if it is a structured ASN 1 type value in this case the
280. pvMemHeap should free all memory allocated free memory heap object if exists In most cases it is only necessary to implement the following functions rtxMemHeapAlloc rtxMemHeapAllocZ rtxMemHeapFreePtr and rtxMemHeapRealloc Note that there is no analog in standard memory management for ASNIC s rtxMemFree macro i e the rtxMemHeapFreeAll function A user would be responsible for freeing all items in a generated ASNIC structure individually if standard memory management is used The rtxMemHeapCreate and rtxMemHeapRelease functions are specialized functions used when a special heap is to be used for allocation for example a static block within an embedded system In this case rtxMemHeapCreate must 118 Dynamic Memory Management set the ppvMemHeap argument to point at the block of memory to be used This will then be passed in to all of the other memory management functions for their use through the OSCTXT structure The rtxtMemHeapRelease function can then be used to dispose of this memory when it is no longer needed To add these definitions to an application program compile the C source file it can have any name and link the resulting object file OBJ or O in with the application Built in Compact Memory Management A built in version of the simple memory management API described above i e with direct calls to malloc free etc is available for users who have the source code version of the run time The o
281. quired argument is an initialized context block structure used to hold dynamic memory allocated in the creation of the value structures If the value definitions are used in table constraint definitions then the generated table constraint processing code will handle the initialization of these definitions otherwise the initialization function must be called explicitly SEQUENCE or SET Value Specification The mapping of an ASN 1 SEQUENCE or SET value declaration to a global C or C value declaration is as follows ASN 1 production lt name gt lt SeqType gt lt value gt Generated code lt SeqType gt lt name gt The sequence value will be initialized in the value initialization function For example consider the following declaration SeqType SEQUENCE id INTEGER name VisibleString value SeqType id 12 name abc This would result in the following definition in the C or C source file SeqType value Code generated in value initialization function would be as follows 74 Constructed Type Values value id 12 value name abc SEQUENCE OF SET OF Value The mapping of an ASN 1 SEQUENCE OF or SET OF value declaration to a global C or C value declaration is as follows ASN 1 production lt name gt lt SeqOfType gt lt value gt Generated code lt SeqOfType gt lt name gt The sequence of value will be initialized in the value initiali
282. r type RTERR_INVCHAR Invalid character This status code is returned when a char acter is encountered that is not valid for a given data type For example if an integer value is being decoded and a non numeric character is encountered this error will be raised RTERR_XMLSTATE RTERR_XMLPARSE XML state error This status code is returned when the XML parser XML parser error This status code in returned when the underlying XML parser application by default this is Ex pat returns an error code The parser error code or text is 219 General Status Messages Error Code Error Name Description returned as a parameter in is not in the correct state to do a certain operation RTERR_SEQORDER Sequence order error This status code is returned when decoding an ASN 1 SEQUENCE or XSD xsd sequence construct It is raised if the elements were received in an order different than that specified the errInfo structure within the context structure RTERR_FILNOTFOU File not found This status code is returned if an attempt is made to open a file input stream for decoding and the given file does not exist RTERR_READERR Read error This status code if returned if a read IO error is encountered when reading from an input stream associated with a physical device such as a file or socket 30 RTERR_WRITEERR Write error This status code if returned if a write IO error is enco
283. rated These functions can be used to populate variables of gen erated types with random test data The main purpose is to provide a code template to users for writing code to pop ulate variables This is quite useful to users because generated data types can become very complex as the ASN 1 schemas become more complex It is sometimes difficult to figure out how to navigate all of the lists and pointers Using genTest can provide code that simply has to be modified to accomplish the population of a data variable with any type of data The generated test functions are written to a c or cpp file with a name of the following format lt asnlModuleName gt Test c where lt asn1ModuleName gt is the name of the ASN 1 module that contains the type definitions The format of the name of each generated test function is as follows asnlTest_ lt prefix gt lt prodName gt where lt prodName gt is the name of the ASN 1 production for which the function is being generated and lt prefix gt is an optional prefix that can be set via a configuration file setting The configuration setting used to set the prefix is the lt typePrefix gt element This element specifies a prefix that will be applied to all generated typedef names and function names for the production The calling sequence for each generated test function is as follows lt typeName gt pvalue lt testFunc gt OSCTXT pctxt In this definition lt testFunc gt denotes the formatted fu
284. reated Unnamed elements names are automatically generated from the type name by making the first character of the name lowercase One difference between temporary types used in a SEQUENCE and in a CHOICE is that a pointer variable will be generated for use within the CHOICE union construct ASN 1 production 62 CHOICE lt name gt CHOICE lt elementl name gt lt elementl type gt lt element2 name gt lt element2 type gt Generated C code define T_ lt name gt _ lt elementil name gt 1 define T_ lt name gt _ lt element2 name gt 2 typedef struct int t union lt typel gt lt element1 name gt lt type2 gt lt element2 name gt u lt name gt or typedef struct eee typedef struct PORT E E typedef struct int t union lt tempNamel gt lt elementl name gt lt tempName2 gt lt element2 name gt u lt name gt If the static command line option or lt storage gt static lt storage gt configuration variable is set for the given production then pointers will not be used for the variable declarations Note This is true for the C case only for C pointers must be used due to the fact that the generated code will not compile if constructors are used in a non pointer variable within a union construct The C mapping is the same with the exception that the ASN1T_ prefix is added to the generated type name
285. red The pCmp Value argument is used to pass the second value The two items are then compared field by field for equality The errBuff and errBuffSize arguments are used to describe a text buffer into which information on what fields the comparison failed on is written These arguments specify a fixed size buffer if the generated text is larger than the given buffer size the text is terminated The return value of the function is a Boolean value that is true if the variables are equal and false if they are not Generated Copy Functions The genCopy option causes copy functions to be generated These functions can be used to copy the content of one generated type variable to another 197 Generated Copy Functions If no output file is specified with the genCopy qualifier the functions are written to separate c cpp files for each module in the source file The format of the name of each file is lt module gt Copy c cpp where lt module gt would be replaced with the name of the ASN 1 module If an output filename is specified after the genCopy qualifier all functions are written to that file The format of the name of each generated copy function is as follows asnlCopy_ lt prefix gt lt prodName gt where lt prodName gt is the name of the ASN 1 production for which the function is being generated and lt prefix gt is an optional prefix that can be set via a configuration file setting The configuration setting used
286. rerreresrrerrsrrrereresreeeerreees 151 Generated Streaming C Function Format and Calling Parameters s sseeeeeeeserrereerrsrrerreees 152 ASNIC Generated Streaming C Decode Method Format and Calling Parameters cee 156 Generated PER Functions oneee e eE ii used KAES Bare ete gal E AA EE E ha Gali 161 Generated PER Encode Functions 0 065 cos ough st dhs tose aha ssdu eu daew sees hes tea ohne eden EE EE A EEEE 161 Generated C Function Format and Calling Parameters 00 cce cece cece ceeec cece cena eeneeeneeeeeeeeees 161 Generated C Encode Method Format and Calling Parameters eceeceeeceeceeeeeeeeeeeeee ee 161 Populating Generated Structure Variables for Encoding cee ceeeecee ce eece ence ence eeeeeeeeeeeneeeaes 162 Procedure for Calling C Encode Functions cccseceeseeccseecceececueeeeueeeceeseeaeeeeeeseeaueeeenees 162 Procedure for Using the C Control Class Encode Method cece ccceceee cece eceneceneeeeeeenees 164 Encoding a Series of PER Messages using the C Interface eee cee ceeeee teen eeenes 166 Generated PER Decode Functions orisii eo oie ee bibs ee ert deh Gan ge tbe eceosh essed aly eb ea gto d 166 Generated C Function Format and Calling Parameters ccc ce cece ceee cece cece cena eeneeeneeeeeeeeees 167 Generated C Decode Method Format and Calling Parameters cece eeeeeeeeeeeee eter eens 167 Procedure
287. rint functions generated if genPrint is specified lt moduleName gt Compare c comparison functions generated if genCompare is spec ified lt moduleName gt PrtToStr c print to string functions generated if genPrtToStr is specified lt moduleName gt PrtToStrm c print to stream functions generated if genPrtToStrm is specified lt moduleName gt Table c table constraint functions generated if genTable option is specified lt moduleName gt Test c test functions generated if genTest is specified If genCopy genPrint etc have a filename parameter then the code will be written to the given file instead of the default one If the cfile lt filename gt option is used and genCopy genPrint etc options do not have parameters then all code will be placed in one source file with name lt filename gt Maximum Lines per File In each of the cases above it is possible to specify an approximate maximum number of lines that each of the gener ated c files may contain This is done using the maxlines option If maxlines is specified with no parameter a default maximum number of lines 50 000 will be set otherwise the given value will be used If the given maximum lines limit is surpassed in a file a new file will be started with an _1 appended for example lt moduleName gt Enc_l c Additional files will be numbered sequentially if necessary _2 _3 etc Note that this limit is
288. rod gt Other attributes within the production section apply only to the referenced production and nothing else A complete list of attributes that can be applied to individual productions is provided in the table at the end of this section When an attribute is specified in more than one section the most specific application is always used For example assume a lt t ypePrefix gt qualifier is used within a module specification to specify a prefix for all generated types in the module and another one is used to a specify a prefix for a single production The production with the type prefix will be generated with the type prefix assigned to it and all other generated types will contain the type prefix assigned at the module level Values in the different sections can be specified in one of the following ways 1 Using the lt name gt value lt name gt form This assigns the given value to the given name For example the fol lowing would be used to specify the name of the H323 MESSAGES module in a module section lt name gt H323 MESSAGES lt name gt 2 Flag variables that turn some attribute on or off would be specified using a single lt name gt entry For example to specify a given production is a PDU the following would be specified in a production section lt isPDU gt 3 An attribute list can be associated with some items This is normally used as a shorthand form for specifying lists of names For example to spec
289. rol class with an entry for each of the bit numbers These entries can be used in calls to the methods of the ASN CBitStr class to set clear and test bits The genBitMacros command line option can be used to generate macros to set clear or test the named bits in a bit string structure These macros offer better performance then using the run time functions because all calculations of mask and index values are done at compile time However they can result in a large amount of additional generated code For example the following ASN 1 production NamedBS BIT STRING bitOne 1 bitTen 10 Would translate to the following if genBitMacros was specified Named bit constants define NamedBS_bitOne 1 define SET_BS3_bitOne bs lt code to set bit gt define CLEAR _BS3_bitOne bs lt code to clear bit gt define TEST_BS3_bitOne bs lt code to test bit gt define NamedBS_bitTen 10 define SET_BS3_bitTen bs lt code to set bit gt define CLEAR _BS3_bitTen bs lt code to clear bit gt define TEST_BS3_bitTen bs lt code to test bit gt Type definitions typedef struct ASNIT_NamedBS OSUINT32 numbits OSOCTET data 2 NamedBS 47 BIT STRING The named bit constants would be used to access the data array within the ASN T_NamedB3S type If bit macros were not generated the rtxSerBit function could be used to set the named bit bitOne w
290. rray will be used for SEQUENCE OF SET OF constructs A dynamic array is an array that uses dynamic storage for the array elements 27 Compiler Configuration File Module Level These attributes can be applied at the module level by including them within a lt module gt section values names gt are specified as an attribute Name Values Description lt name gt module name This attribute identifies the module to which this section lt name gt applies Either this or the lt oid gt element attribute is re quired lt oid gt module OID object identi This attribute provides for an alternate form of mod fier ule identification for the case when module name is not unique For example a given ASN 1 module may have multiple versions A unique version of the module can be identified using the OID value lt include types names ASN 1 type or value names This item allows a list of ASN 1 types and or values to be included in the generated code By default the compiler generates code for all types and values within a specifi cation This allows the user to reduce the size of the gen erated code base by selecting only a subset of the types values in a specification for compilation Note that if a type or value is included that has dependent types or values for example the element types in a SEQUENCE SET or CHOICE all of the dependent types will be automati cally included as well Thi
291. rs RTERR_NOTYPEINFO This error is returned when decoding a derived type def inition and no information exists as to what type of data is in the element content When decoding XML this nor mally means that an xsi type attribute was not found iden tifying the type of content 221 ASN 1 specific Status Messages Error Code Error Name Description 52 RTERR_ADDRINUSE Address already in use This status code is returned when an attempt is made to bind a socket to an address that is already in use 53 RTERR_CONNRESET Remote connection was reset This status code is returned when the connection is reset by the remote host via ex plicit command or a crash 54 RTERR_UNREACHABLE Network failure This status code is returned when the net work or host is down or otherwise unreachable 55 RTERR_NOCONN Not connected This status code is returned when an oper ation is issued on an unconnected socket 56 RTERR_CONNREFUSED Connection refused This status code is returned when an attempt to communicate on an open socket is refused by the host 57 RTERR_INVSOCKOPT Invalid option This status code is returned when an in valid option is passed to socket 58 RTERR_SOAPFAULT This error is returned when the decoded SOAP envelope is a fault message 59 RTERR_MARKNOTSUP This error is returned when an attempt is made to mark a stream position on a stream type that does not support it
292. rsonnelRecord employee ASN1ConstCharPtr filename message xml Step 1 Init context structure if rtInitContext amp ctxt 0 return 1 rtxStreamInit amp ctxt Step 2 Open a stream stat rtxStreamFileOpen amp ctxt filename OSRTSTRMF_INPUT if stat 0 rtErrPrint amp ctxt errInfo return 1 179 Procedure for Using the C Interface Step 3 decode the record stat asnlXD_PersonnelRecord amp ctxt amp employee if stat 0 if trace printf Decode of PersonnelRecord was successful n printf Decoded record n asnlPrint_PersonnelRecord Employee amp employee else printf decode of PersonnelRecord failed n rtxErrPrint amp ctxt rtxStreamClose amp ctxt return 1 Step 4 Close the stream and free the context rtxStreamClose amp ctxt rtFreeContext amp ctxt return 0 Procedure for Using the C Interface SAX handler methods are added to the C control class generated for each ASN 1 production The procedure to invoke the generated decode method is similar to that for the other encoding rules It is as follows 1 Instantiate an ASN 1 XER decode buffer object ASNIXERDecodeBuffer to describe the message to be decoded Constructors exist that allow an XML file or memory buffer to be specified as an input source 2 Instantiate an ASN1T_TypeName object to hold the decoded message data 3
293. rtToStr_ lt name gt const char name lt name gt pvalue char buffer int bufSize The name and pvalue arguments are the same as they were in the print case The buffer and bufSize arguments are used to describe the memory buffer the text is to be written into These arguments specify a fixed size buffer If the generated text is larger than the given buffer size as much text as possible is written to the buffer and a 1 status value is returned If the buffer is large enough to hold the text output all text is written to the buffer and a zero status is returned For C a toString method is generated in the control class that calls the generated print to string function In addition to the name argument this method also takes a buffer and bufSize argument to describe the buffer to which the text is to be written Print to Stream The genPrtToStrm option causes functions to be generated that print the contents of variables of generated types to an output stream via a user defined callback function The advantage of these functions is that a user can register a callback function and then the print stream is automatically directed to the callback function This makes it easier to support print to file or print to window type of functionalities It is possible to specify the name of a c or cpp file as an argument to this option to specify the name of the file to which these functions will be written This is an optional argument If no
294. ruct A A_X X A_y yi A In this case elements x and y map to structured C types so temporary typedefs are generated 54 SEQUENCE In the case of nesting levels greater than two all of the intermediate element names are used to form the final name For example consider the following type definition that contains three nesting levels X SEQUENCE a SEQUENCE aa SEQUENCE x INTEGER y BOOLEAN bb INTEGER In this case the generation of temporary types results in the following equivalent type definitions X a aa SEQUENCE x INTEGER y BOOLEAN X a SEQUENCE aa X a aa bb INTEGER X SEQUENCE X a a Note that the name for the aa element type is X a aa It contains both the name for a at level 1 and aa at level 2 The concatanation of all of the intermdeiate element names can lead to very long names in some cases To get around the problem the shortnames command line option can be used to form shorter names In this case only the type name and the last element name are used In the example above this would lead to an element name of X aa The disadvantage of this is that the names may not always be unique If using this option results in non unique names an _n suffix is added where n is a sequential number to make the names unique Note that although the compiler can handle embedded constructed typ
295. ructure in this case with an element called base that is of the simple type being extended An example of this is as follows lt xsd complexType name SizeType gt lt xsd simpleContent gt lt xsd extension base xsd integer gt lt xsd attribute name system type xsd token gt lt xsd extension gt lt xsd simpleContent gt lt xsd complexType gt this results in the following generated C type definition typedef struct EXTERN SizeType struct unsigned system_Present 1 m const OSUTF8CHAR system_ OSINT32 base SizeType In this case the attribute syst em was added first note the name change to syst em_ which was the result of system being determined to be a C reserved word The base element is then added and is of type OSINT32 the default type used for xsd integer In the case of a simple content restriction the processing is similar A complete new separate type is generated even if the result of the restriction leaves the original type unaltered i e the restriction is handled by code within the generated encode and or decode function This proves to be a cleaner solution in most cases than trying to reuse the type being restricted For example lt xsd complexType name SmallSizeType gt lt xsd simpleContent gt lt xsd restriction base SizeType gt lt xsd minInclusive value 2 gt lt xsd maxInclusive value 6 gt lt xsd attribute name system type xsd token use required g
296. ry when done rtxMemFree amp ctxt else error processing else check for other known message types Decoding a Series of Messages Using the C Decode Functions The above example is fine as a sample for decoding a single message but what happens in the more typical scenario of having a long running loop that continuously decodes messages It will be necessary to put the decoding logic into a loop main OSOCTET msgbuf 1024 ASNITAG msgtag int msglen OSCTXT ctxt PersonnelRecord employee Step 1 Initialize a context variable for decoding if rtInitContext amp ctxt 0 initialization failed could be a license problem printf context initialization failed check license n return 1 for logic to read message into msgbuf xd_setp amp ctxt msgbuf 0 amp msgtag amp msglen Step 2 Test message tag for type of message received note this is optional the decode function can be called directly if the type of message is known Now switch on initial tag value to determine what type of message was received switch msgtag case TV_PersonnelRecord compiler generated constant status asnlD_PersonnelRecord amp ctxt 142 Generated C Function Format and Calling Parameters amp employee ASNIEXPL 0 if status 0 decoding successful data in employee pr
297. s a parsing failure all type names must begin with an uppercase letter The referenced type must be tagged in this context ASN E UNKNOWN Undocumented error occurred in routine A status value is provided with this error message to help locate the cause of the failure ASN I NOCASE A case statement for the named object was not generated ASN E IMPFILOPN ASN E IMPFILPAR The compiler was unable to open the named import file The compiler was unable to parse the named imported module ASN E IMPNOTFOU The named type was not found in the import module as specified in the IMPORT statement ASN E INVCNSTRNT Invalid constraint specification ASN W INVOBJNAM ASN E SETTOOBIG Invalid object name The object name must begin with a lowercase letter Set contains more than 32 elements ASN E DUPLCASE This tag was used in a previous switch case statement 215 ASNIC Error Messages Error Code Error Description ASN E AMBIGUOUS ASN E VALTYPMIS This indicates a general ambiguity in the specification such as multiple embedded extensible elements This indicates the value specified does not match the type it is asso ciated with ASN E RANGERR This indicates the value is not within defined range for its associated type ASN E VALPARSE This indicates a general failure to parse a value definition It would be raised for example if a floating p
298. s are isolated in the platform mk file in the root directory of the installation The procedure to port the run time code to a different platform is as follows note this assumes common UNIX or GNU compilation utilities are in place on the target platform 1 Create a directory tree containing a root directory the name does not matter and lib src rt src and build_lib subdirectories note in these definitions is a wildcard character indicating there are multiple directories matching this pattern The tree should be as follows pe build lib 2 Copy the files ending in extension mk from the root directory of the installation to the root directory of the target platform note if transferring from DOS to UNIX or vice versa FTP the files in ASCII mode to ensure lines are terminated properly 3 Copy all files from the src and the different rt src subdirectories from the installation to the sre and rt src directories on the target platform note if transferring from DOS to UNIX or vice versa FTP the files in ASCII mode to ensure lines are terminated properly 4 Copy the makefile from the build_lib subdirectory of the installation to the build_lib subdirectory on the target platform note if transferring from DOS to UNIX or vice versa FTP the files in ASCII mode to ensure lines are terminated properly 5 Edit the platform mk file in the root subdirectory and modify the compilation parameters to fit those of the compiler
299. s called on a non PDU Only PDUs have implementations of these methods ASN_E_BASE 9 ASN_E_UNDEFTYP Element type could not be resolved at run time This er ror is returned when the run time parser module is used AsnIRTProd to decode a type at run time and the type of the element could not be resolved ASN_E_BASE 10 ASN_E_INVPERENC Invalid PER encoding This occurs when a given element within an ASN 1 specification is configured to have an expected PER encoding and the decoded value does not match this encoding 223 224
300. s form of the include directive tells the compiler to only include types and or values in the generated code that are imported by the given module s list lt include importsFrom ASN 1 module name s name gt specified as an attribute list lt exclude types names ASN 1 type or values names values names gt are specified as an attribute list This item allows a list of ASN 1 types and or values to be excluded in the generated code By default the compiler generates code for all types and values within a specifi cation This is generally not as useful as in include direc tive because most types in a specification are referenced by other types If an attempt is made to exclude a type or value referenced by another item the directive will be ig nored lt storage gt lt storage gt dynamic Static list array or dynamicArray keyword The definition is the same as for the global case except that the specified storage type will only be applied to generated C and C types from the given module lt sourceFile gt lt sourceFile gt source file name Indicates the given module is contained within the given ASN 1 source file This is used on IMPORTs to instruct the compiler where to look for imported definitions lt typePrefix gt lt typePrefix gt prefix text This is used to specify a prefix that will be applied to all generated C and C typedef names note for C the prefix is applied af
301. s specified a Print method is generated to wrap the corresponding C print function Specification of the XML encoding rules option xer causes a number of additional methods to be generated for constructed types These additional methods are implementations of the standard Simple API for XML SAX con tent handling interface used to parse content from XML messages The startElement characters and endElement methods are implemented as well as additional support methods The control class is also defined to inherit from the ASNIXERSAXHandler base class as well as ASNI CType or one of its descendents The equivalent C and C type definitions for each of the various ASN 1 types follow 35 Generated C Source Files Generated C Source Files By default the ASN1C compiler generates the following set of c source files for a given ASN 1 module note the name of the module would be substituted for lt moduleName gt lt moduleName gt c common definitions and functions for example asnlFree_ lt type gt and or global value constant defini tions lt moduleName gt Enc c encode functions asn1E_ lt type gt lt moduleName gt Dec c decode functions asn1D_ lt type gt If additional options are used such as genPrint genCopy etc additional files will be generated lt moduleName gt Copy c copy functions generated if genCopy is specified lt moduleName gt Print c p
302. s used to specify a source file that contains modules with both X 208 and X 680 based syn tax attrs lt items gt This option only has meaning when generating an XML schema definitions XSD file using the xsd option It instructs the compiler to generate non native attributes for certain ASN 1 only items that cannot be expressed in Running ASNIC from the Command line Option Argument Description XSD The items are specified as a comma delimited list Valid values for items are tags enum and ext lt items gt is an optional parameter If it is not specified it is assumed that application information should be produced for all three item classes ASN 1 tags ASN 1 enumera tions and extended elements ber None This option instructs the compiler to generate functions that implement the Basic Encoding Rules BER as spec ified in the X 690 ASN 1 standard bitMacros None This option instructs the compiler to generate additional macros to set clear and test named bits in BIT STRING constructs By default only bit number constants are gen erated Bit macros provide slightly better performance be cause mask values required to do the operations are com puted at compile time rather than runtime C None Generate C source code c or csharp None Generate C source code See the ASNIC C User s Guide for more information and options for generating C code
303. s which means memory management issues must be dealt with There are three alternatives for managing memory for these types 1 Allocate the variables on the stack and plug the address of the variables into the pointer fields 2 Use the standard malloc and free C functions or new and delete C operators to allocate memory to hold the data and 3 Use the rxtMemAlloc and rtxMemFree run time library functions or their associated macros Allocating the variables on the stack is an easy way to get temporary memory and have it released when it is no longer being used But one has to be careful when using additional functions to populate these types of variables A common mistake is the storage of the addresses of automatic variables in the pointer fields of a passed in structure An example of this error is as follows assume A B and C are other structured types typedef struct A a B by Cr Ce Parent void fillParent Parent parent A aa B bb 121 Accessing Encoded Message Components CCC logic to populate aa bb and cc parent gt a amp aa parent gt b amp bb parent gt c amp CC main Parent parent fillParent amp parent encodeParent amp parent error pointers in parent reference memory that is out of scope In this example the automatic variables aa bb and cc go out of scope when the fillParent function exits Yet the parent structure is still h
304. s with this attribute set Element Level These attributes can be applied at the element level by including them within an lt element gt section Name Values Description lt name gt element name This attribute identifies the element within a SEQUENCE lt name gt SET or CHOICE construct to which this section applies It is required lt ctype gt chararray This is used to specify a specific C type be used in place of the default definition generated by ASNIC In the case of elements the only supported customization is for charac ter string types which would normally be represented by a character pointer type char to be changed to use static 30 Compiler Error Reporting Name Values Description character arrays This can only be done if the string type contains a size constraint lt isOpenType gt n a This flag variable specifies that this element will be decod ed as an open type i e skipped Refer to the section on deferred decoding for further information Note that this variable can only be used with BER CER or DER encod ing rules lt notUsed gt n a This flag variable specifies that this element will not be used at all in the generated code It can only be applied to optional elements within a SEQUENCE or SET or to elements within a CHOICE Its purpose is for production of more compact code by allowing users to configure out items that are of no interest to them
305. sample program that is included with the compiler distribution the implementation is complete In endElement we simply terminate our brace block as follows void PrintHandler endElement const char name int index mindentLevel indent printf n Next we need to create an object of our derived class and register it prior to invoking the decode method In the reader cpp program the following lines do this Create and register an event handler object PrintHandler pHandler new PrintHandler employee decodeBuffer addEventHandler pHandler The addEventHandler method defined in the Asn MessageBuffer base class is the mechanism used to do this Note that event handler objects can be stacked Several can be registered before invoking the decode function When this is 205 How to Use It done the entire list of event handler objects is iterated through and the appropriate event handling callback function invoked whenever a defined event is encountered The implementation is now complete The program can now be compiled and run When this is done the resulting output is as follows employee name givenName John initial p n familyName Smith This can certainly be improved For one thing it can be changed to print primitive values out in a name value format i e without the braces But this should provide the general idea of how it
306. sd string gt lt xsd element name familyName type xsd string gt lt xsd sequence gt lt xsd complexType gt in this case ASNIC pulls the group out to form a type of form lt name gt element where lt name gt would be replaced with the complex type name In this case the name would be Names element ASEQUENCE OF type is then formed based on this newly formed type SEQUENCE OF Names element The generated C code corresponding to this is as follows typedef struct EXTERN Names_element const OSUTF8CHAR givenName const OSUTF8CHAR initial const OSUTF8CHAR familyName Names_element List of Names_element typedef OSRTDList Names This generated code is not identical to the code generated by performing an X 694 translation to ASN 1 and compiling the resulting specification with ASNIC it is much simpler The generated encoder and decoder make the necessary adjustments to ensure that the encodings are the same regardless of the process used Repeating Elements It is common in XSD to specify that elements within a composite group can occur a multiple number of times For example lt xsd complexType name Name gt lt xsd sequence gt lt xsd element name givenName type xsd string gt lt xsd element name initial type xsd string gt lt xsd element name familyName type xsd string maxOccurs 2 gt lt xsd sequence gt lt xsd complexType gt In this case the familyName element may
307. secases savceesigesdesseessopae eh tosis eas sestenddeedsassassoobeas ESSE CEES EPOE ROSP esa EEO PEISEN 43 Type Mappings sorait nesir Scala eed egos tes Seas ech nish oa ee Bas ees 43 BOOLEAN eoori ote cumttan yas a A E E E a E mieaeta ses E T oat 43 INTEGER iite ereo ere EE EE EEE OT EET e EEE ees E TEE E EE EEIE EE Es 43 BIT STRING eea e oeer EEEa Caa SEEE AES a AET EEAO SERE PE PIERIS EET EERS SS 45 OCTET STRING bsg eh ha ei as see lel EEE EE EOE E EE del tahoe 49 ENUMERATED se sci tose tea piisg sa bas hencattiea se batee des stay aa banches aitinbstberwane eitta ses ba waa amteaa ss Datee eR 50 NULG perete noorena ease Ses hoes os aeine Sages teen cues eee g geste ETE E EE se eee E S de 52 OBJECT IDENTIFIER er ee oaran seske seavdeac is tes borse sds Deen sage AEE a SEESI E OA O E EEEE EIERS 52 RELATIVE OID ea es Seo ashes La a a e E es e N aeS TES 52 READ a E eE AE E A TAI E E L E E E EE L EA E E E E T E 53 SEQUENCE hrener AA e eai Eoee Ee EEEE etek eee EEEE Ee Sele EEE EEE REE T oan 53 S m EE E TE E E 58 SEQUENCE OP i eera e Rea out ods EE EE EE E SEE Me EIRE EEEE Doles EE AE EENT 58 SET OB E E dates sos batvanyedatagesbates Saansauss Satdeet asta aa ents 62 CHOICE orhoi oreo a ties ERE tad nce E bakes selec oh wnt EES E yeas geass Seegs BUR ES deed gasses EE EAN 62 Open Dy Pe dss ses igo E ssovas dase se adeennesndae E csntesdgesteaegs verte ade i abasdsys 65 Character String Types iseci isesi ee E EAE E E E eteds loc eeds le EE aee eve
308. ser is required to supply a pointer to a variable of this type declared somewhere in his or her program The variable should be initialized using the rt nitContext run time library function see the C C Common Run Time Library Reference Manual for a complete description of this function The pvalue argument holds a pointer to the data to be encoded and is of the type generated from the ASN 1 pro duction The tagging argument is for internal use when calls to encode functions are nested to accomplish encoding of complex variables It indicates whether the tag associated with the production should be applied or not implicit versus explicit tagging At the top level the tag should always be applied so this parameter should always be set to the constant ASNIEXPL for EXPLICIT The function result variable len returns the length of the data actually encoded or an error status code if encoding fails Error status codes are negative to tell them apart from length values Return status values are defined in the asniltype h include file 125 Generated C Encode Method Format and Calling Parameters Generated C Encode Method Format and Calling Pa rameters When C code generation is specified the ASN1C compiler generates an Encode method in the generated control class that wraps the C function call This method provides a more simplified calling interface because it hides things such as the context structure and the tag type parameters
309. sgData 157 Generated Streaming C Decode Method Format and Calling Parameters in gt gt employee if in getStatus 0 printf decode of PersonnelRecord failed n in printErroriInfo return 1 or employee DecodeFrom in break case TV_ handle other known messages return 0 Note that the call to free memory and the stream close method are not required to release dynamic memory when using the C interface This is because the control class hides all of the details of managing the context and releasing dynamic memory The memory is automatically released when both the input stream object ASN BERDecodeStream and derived classes and the control class object ASNJC_ lt ProdName gt are deleted or go out of scope Reference counting of a context variable shared by both interfaces is used to accomplish this Decoding a Series of Messages Using the C Control Class Inter face The above example is fine as a sample for decoding a single message but what happens in the more typical scenario of having a long running loop that continuously decodes messages The logic shown above would not be optimal from a performance standpoint because of the constant creation and destruction of the message processing objects It would be much better to create all of the required objects outside of the loop and then reuse them to decode and process each message A code fragment showing a way to do
310. sing a required attribute value as defined in the XML schema 37 RTERR_HOSTNOTFOU Host name could not be resolved This status code is re turned from run time socket functions when they are un able to connect to a given host computer 38 RTERR_HTTPERR HTTP protocol error This status code is returned by func tions doing HTTP protocol operations such as SOAP func tions It is returned when a protocol error is detected De 220 General Status Messages Error Code Error Name Description tails on the specific error can be obtained by calling rtx ErrPrint 39 RTERR_SOAPERR SOAP error This status code when an error is detected when tryingto execute a SOAP operation RTERR_EXPIRED Evaluation license expired This error is returned from evaluation versions of the run time library when the hard coded evaluation period is expired RTERR_UNEXPELEM Unexpected element encountered This status code is re turned when an element is encountered in a position where something else for example an attribute was expected RTERR_INVOCCUR Invalid number of occurrences This status code is re turned by the decoder when an XML instance contains a number of occurrences of a repeating element that is out side the bounds minOccursmaxOccurs defined for the element in the XML schema RTERR_INVMSGBUF Invalid message buffer has been passed to decode or vali date
311. ssage A program fragment that could be used to encode an employee record is as follows include employee h include file generated by ASNIC main OSOCTET msgbuf 1024 int msglen stat OSCTXT ctxt OSBOOL aligned TRUE Employee employee typedef generated by ASNIC Populate employee C structure mployee name givenName SMITH Allocate and initialize a new context pointer stat rtInitContext amp ctxt if stat 0 printf rtInitContext failed check license n 162 Procedure for Calling C Encode Functions rtxErrPrint amp ctxt return stat pu_setBuffer amp ctxt msgbuf msglen aligned if stat asnlPE_Employee amp ctxt amp employee 0 msglen pe_GetMsgLen amp ctxt else error processing In general static buffers should be used for encoding messages where possible as they offer a substantial performance benefit over dynamic buffer allocation The problem with static buffers however is that you are required to estimate in advance the approximate size of the messages you will be encoding There is no built in formula to do this the size of an ASN 1 message can vary widely based on data types and other factors If performance is not a significant issue then dynamic buffer allocation is a good alternative Setting the buffer pointer argument to NULL in the call to pu_setBuffer spec
312. ssage using the C class interface is as follows 1 Create a variable of the ASN1T_ lt name gt type and populate it with the data to be encoded 2 Create an ASNIBEREncodeBuffer object 3 Create a variable of the generated ASN1C_ lt name gt class specifying the items created in 1 and 2 as arguments to the constructor 4 Invoke the Encode method The constructor of the ASN1C_ lt type gt class takes a message buffer object argument This makes it possible to specify a static encode message buffer when the class variable is declared A static buffer can improve encoding performance greatly as it relieves the internal software from having to repeatedly resize the buffer to hold the encoded message If you know the general size of the messages you will be sending or have a fixed size maximum message length then a static buffer should be used The message buffer argument can also be used to specify the start address and length of a received message to be decoded After the data to be encoded is set the Encode method is called This method returns the length of the encoded message or a negative value indicating that an error occurred The error codes can be found in the asn type h run time header file or in Appendix A of the C C Common Functions Reference Manual If encoding is successful a pointer to the encoded message can be obtained by using the getMsgPtr or getMsgCopy methods available in the ASN BEREncodeBuffer class The getMsgPtr metho
313. st char filename message xml OSBOOL verbose FALSE trace TRUE int i stat logic to read message into msgbuf step 1 instantiate an XML decode buffer object OSXMLDecodeBuffer decodeBuffer filename step 2 instantiate an ASNIT_ lt ProdName gt object ASN1T_PersonnelRecord msgData step 3 instantiate an ASNIC_ lt ProdName gt object ASN1C_PersonnelRecord employ decodeBuffer msgData step 4 decode the record stat employee Decode step 5 check the return status if stat 0 process received data else error processing 190 Procedure for Using the C Control Class Decode Method decodeBuffer PrintErroriInfo step 6 free dynamic memory will be done automatically when both the decodeBuffer and employ objects go out of scope 191 192 Additional Generated Functions Generated Initialization Functions As of ASNIC version 6 0 initialization functions are automatically generated in previous versions it was necessary to use the genJnit option to force this action If for some reason a user does want initialization functions to be generated the nolnit switch can be used to turn initialization function generation off The use of initialization functions are optional a variable can be initialized by simply setting its contents to zero for example by using the C run time memset function The advan
314. sta tus code is returned by a function or method when it does an initial check on the values of parameters passed in If a parameter is found to not have a value in the expected range this error code is returned RTERR_INVFORMAT RTERR_NOTINIT Invalid value format This status code is returned when a value is received or passed into a function that is not in the expected format For example the time string parsing function expects a string in the form nn nn nn where n s are numbers If not in this format this error code is re turned Context not initialized This status code is returned when the run time context structure OSCTXT is attempted to be used without having been initialized This can occur if rtxInitContext is not invoked to initialize a context vari able before use in any other API call It can also occur is there is a license violation for example evaluation license expired RTERR_TOOBIG Value will not fit in target variable This status is returned by the decoder when a target variable is not large enough to hold aa decoded value A typical case is an integer value that is too large to fit in the standard C integer type typ ically a 32 bit value on a given platform If this occurs it is usually necessary to use a configuration file setting to force the compiler to use a different data type for the item For example for integer the lt isBigInteger gt setting can be used to force use of a big intege
315. static data WSD and extern linkage Writable Static Data Writable static data are per process data that exist throughout the lifetime of the process The use of WSD complicates memory management in many cases especially in shared libraries A minimum of four kilobytes is allocated for WSD every single time a DLL is loaded even if less space is required If 50 bytes were needed for example 4046 bytes would be wasted every time the DLL was loaded For this reason the use of WSD is highly discouraged In practice WSD are globally scoped variables declared outside of a function struct or class and static variables declared in functions WSD may be eliminated by modifying primitive types with const Complex types i e classes or structs with non trivial constructors will be marked as WSD whether marked const or not It is common in generated code to use lookup tables for some types e g ENUMERATED These tables are composed of simple types and marked as const to avoid being marked as WSD by Symbian compilers Extern Linkage Most common compilers support applying external linkage to an entire class but Symbian s does not Symbian also requires that both prototype and implementation be marked with the appropriate linkage When the symbian option is specified generated code is modified to accommodate these requirements The following specification will demonstrate the differences between code generated with Symbian and without
316. structured type to hold the subidentifier values that make up the object identifier ASN 1 production lt name gt OBJECT IDENTIFIER Generated C code typedef ASNIOBJID lt name gt Generated C code typedef ASNITObjId ASNIT_ lt name gt In this case different base types are used for C and C The difference between the two is the C version includes constructors and assignment operators that make setting the value a bit easier The ASNJOBJID type i e the type used in the C mapping is defined in asn type h to be the following typedef struct OSUINT32 numids number of subidentifiers OSUINT32 subid ASN_K_MAXSUBIDS subidentifier values ASNIOBJID The constant ASN_K_MAXSUBIDS specifies the maximum number of sub identifiers that can be assigned to a value of the type This constant is set to 128 as per the ASN 1 standard The ASNITObjId type used in the C mapping is defined in ASNITObjId h This class extends the C ASNIOBJID structure and adds many additional constructors and helper methods See the ASNIC C C Common Run time Ref erence Manual for more details RELATIVE OID The ASN 1 RELATIVE OID type is converted into a C or C structured type that is identical to that of the OBJECT IDENTIFIER described above ASN 1 production lt name gt RELATIVE OID 52 REAL Generated C code typedef ASNIOBJID lt name gt Generated C code typedef ASNIT
317. t lt xsd restriction gt lt xsd simpleContent gt lt xsd complexType gt This applies a restriction to the SizeType that was previously derived In this case the generated C type is as follows typedef struct EXTERN SmallSizeType const OSUTF8CHAR system_ OSINT32 base SmallSizeType In this case the type definition is almost identical to the original SizeType The only exception is that the bit mask field for optional elements is removed a consequence of the use required attribute that was added to the 99 xsd complexContent systemattribute declaration The handling of the minInclusive andmaxInclusive attributes is handled inside the generated encode and decode function in the form of constraint checks xsd complexContent The xsd complexContent type is used to extend or restrict complex types in different ways It is similar to deriving types from base types in higher level programming languages such as C or Java A common usage pattern in the case of extension is to add additional elements to an existing sequence or choice group In this case a new type is formed that contains all elements those declared in the base definition and those in the derived type Also generated is a new type with the name lt baseType gt _derivations which is a choice of all of the different derivations of the base type This is used wherever the complex content base type is referenced to allow any derivation of the ty
318. t lt xsd all gt lt xsd element name givenName type xsd string gt lt xsd element name initial type xsd string gt lt xsd element name familyName type xsd string gt lt xsd all gt lt xsd complexType gt would result in the creation of the following C type definition typedef struct EXTERN Name struct OSUINT32 n OSUINT8 elem 3 _order const OSUTF8CHAR givenName const OSUTF8CHAR initial const OSUTF8CHAR familyName Name In this case the _order element is for the order element described earlier Normally the user does not need to deal with this item When the generated initialization is called for the type or C constructor the array will be set to indicate elements should be transmitted in the declared order If XML decoding is done the contents of the array will be adjusted to indicate the order the elements were received in xsd choice and xsd union The xsd choice type is converted to an ASN 1 CHOICE type ASNIC generates exactly the same code For example 93 Repeating Groups lt xsd complexType name NamePart gt lt xsd choice gt lt xsd element name givenName type xsd string gt lt xsd element name initial type xsd string gt lt xsd element name familyName type xsd string gt lt xsd choice gt lt xsd complexType gt in this case the generated code is the same as for ASN 1 CHOICE define T_NamePart_givenName 1 define T_NamePart_
319. t in the context of the module in which it s used ASN E INVV ALELM ASN E MIS VALELM An invalid value was supplied for an element in a type This indicates that a non optional element is missing a value when it should have one ASN E INVLIDENT This indicates that an invalid identifier was specified in an enumera tion ASN E FILNOTFOU This indicates that the requested file was not found ASN E INVSIZE ASN E UNRESOBJ This indicates that an invalid size specification for a type was provid ed check size constraints for base types This indicates that the specified information object could not be re solved within the context of the named module ASN E TOOMANY This indicates that too many sub elements for the specified type were provided 216 General Status Messages Error Code Error Description ASN E LOOPDETECTED ASN E INVXMLATTR This indicates a loop was detected in the course of code generation typically this is raised during test code generation This indicates that the specified attribute type must be a simple type ASN E INTERNAL This indicates that internal structures used for generating code are in consistent ASN E NOPDU This indicates that a PDU type was not found for generating a reader or writer program General Status Messages The following table contains both system and validation failures that may occur during pro
320. t specified the functions are written to separate files for each module in the source file The format of the name of each file is lt module gt PrtToStrm c If an output filename is specified after the genPrtToStrm qualifier all functions are written to that file Before calling generated print to stream functions a callback function should be registered Otherwise a default call back function will be used that directs the print stream to the standard output device The callback function is declared as void rtxPrintCallback void pPrntStrmInfo const char fmtspec va_list arglist The first parameter is user defined data which will be passed to each invocation of the callback function This parameter can be used to pass print stream specific data for example a file pointer if the callback function is to output data to a file The second and third parameters to the callback function constitute the data to be printed in the form of format specification followed by list of arguments A simple callback function for printing to file can be defined as follows 195 Print Format void writeToFile void pPrntStrmInfo const char fmtspec va_list arglist FILE fp FILE pPrntStrminfo vfprintf fp fmtspec arglist GI Once the callback function is defined it has to be registered with the runtime library There are two types of registrations possible 1 global which applies to all print streams and
321. t the xsd switch is complementary to the xml switch when generating XML encoders and decoders This is because the XML schema produced from the ASN 1 specification using the xsd switch can be used to validate the XML messages generated using the XML encode functions Similarly an XML instance can be validated using the generated XML schema prior to decoding XML C encode functions are generated when the xml switch is specified on the command line For each ASN 1 production defined in the ASN 1 source file a C XML encode function is generated In the case of XML schema a C 182 Generated XML Encode Functions encode function is generated for each type and global element declaration This function will convert a populated C variable of the given type into an XML encoded message i e an XML document If C code generation is specified a control class is generated that contains an Encode method that wraps this function This function is invoked through the class interface to encode an ASN 1 message into the variable referenced in the msgData component of the class Generated C Function Format and Calling Parameters The format of the name of each generated XML encode function is as follows lt namespace gt XmlEnc_ lt prefix gt lt prodName gt where lt namespace gt is an optional C namespace prefix lt prodName gt is the name of the ASN 1 production for which the function is being generated and lt prefix gt is an o
322. ta in employeeData process received data else error processing break default handle unknown message type her switch Need to reinitialize objects for next iteration if isLastIteration employee memFreeAll end of loop This is quite similar to the first example Note that we have pulled the ASN T_Employee and ASNIC_Employee object creation logic out of the switch statement and moved it above the loop These objects can now be reused to process each received message The only other change was the call to employee memFreeAll that was added at the bottom of the loop Since we can t count on the objects being deleted to automatically release allocated memory we need to do it manually This call will free all memory held within the decoding context This will allow the loop to start again with no outstanding memory allocations for the next pass If the buffer already contains multiple BER messages encoded back to back then it is necessary to modify the buffer pointer in each iteration The getByteIndex method should be used at the end of loop to get the current offset in the buffer This offset should be used with the decode buffer object s setBuffer method call at the beginning of the loop to determine the correct buffer pointer and length OSUINT32 offset 0 for offset lt msglen set buffer pointer and its length to decode decodeBuffer setBuffer amp msgbuf offset
323. tage of initialization function is that they provide smarter initialization which can lead to improved application performance For example it is not necessary to set a large byte array to zero prior to its receiving a populated value The use of memset in this situation can result in degraded performance Generated initialization functions are written to the main lt module gt c file This file contains common constants global variables and functions that are generic to all type of encode decode functions If the cfile command line option is used the functions are written to the specified c or cpp file along with all other generated functions If maxcfiles is specified each generated initialization function is written to a separate c file The format of the name of each generated initialization function is as follows asnlInit_ lt prefix gt lt prodName gt where lt prodName gt is the name of the ASN 1 production for which the function is being generated and lt prefix gt is an optional prefix that can be set via a configuration file setting The configuration setting used to set the prefix is the lt typePrefix gt element This element specifies a prefix that will be applied to all generated typedef names and function names for the production The calling sequence for each generated initialization function is as follows asnlInit_ lt name gt lt name gt pvalue In this definition lt name gt denotes the prefixed production name
324. ted C string for encoding decoding For encoding the string can either be static i e a string literal or address of a static buffer or dynamic The decoder allocates dynamic memory from within its context to hold the memory for the string This memory is released when the rt xMemF ree function is called The useful character string types in ASN 1 are as follows UTF8String es UNIVERSAL 12 IMPLICIT OCTET STRING NumericString a UNIVERSAL 18 IMPLICIT IA5String PrintableString oS UNIVERSAL 19 IMPLICIT IA5String T61String Heroes UNIVERSAL 20 IMPLICIT OCTET STRING VideotexString ees UNIVERSAL 21 IMPLICIT OCTET STRING TA5String oe UNIVERSAL 22 IMPLICIT OCTET STRING UTCTime yeas UNIVERSAL 23 IMPLICIT GeneralizedTim 66 Time String Types GeneralizedTim UNIVERSAL 24 IMPLICIT IA5String GraphicString 3S UNIVERSAL 25 IMPLICIT OCTET STRING VisibleString en UNIVERSAL 26 IMPLICIT OCTET STRING GeneralString T UNIVERSAL 27 IMPLICIT OCTET STRING UniversalString f UNIVERSAL 28 IMPLICIT OCTET STRING BMPString LIES UNIVERSAL 30 IMPLICIT OCTET STRING ObjectDescriptor UNIVERSAL 7 IMPLICIT GraphicString Of these all are represented by const char pointers except for the BMPString UniversalString and UTF8String types The BMPString type is a 16 bit character string for which the following structure is used typedef struct OSUINT32 nc
325. ted in much the same way as the main message type was above typedef struct HandoverRequired_protocollIEs_element ProtocolIE_ID id Criticality criticality struct information object selector HandoverRequiredIEs_TVALUE t HandoverRequiredIEs information objects sal A union id id MME UE S1AP ID criticality reject presence mandatory MME_UE_S1AP_ID _HandoverRequiredIEs_1 79 3GPP Table Constraint Model id id HandoverType criticality reject presence mandatory HandoverType _HandoverRequiredIEs_2 id id Cause criticality ignore presence mandatory u value HandoverRequired_protocolIEs_element In this case the protocol IE id field and criticality are generated as usual using the fixed type field type definitions The open type field once again results in the generation of a union structure of all possible type fields that can be used Note in this case the field names are automatically generated _HandoverRequiredIEs_n The reason for this was the use of inline information object definitions in the information object set as opposed to defined object definitions This is a sample from that set HandoverRequiredIEs S1AP PROTOCOL IES ID id MME UE S1AP ID CRITICALITY reject TYPE MME UE S1AP ID PRESENCE mand ID id HandoverType CRITICALITY rej
326. ter and length field The pointer is assumed to point at a string of previously encoded ASN 1 data When a message containing an open type is decoded the address of the open type contents field is stored in the pointer field and the length of the component is stored in the length field The general mapping of an Open Type to C C is as follows ASN 1 production lt name gt ANY 65 Character String Types Generated C code typedef ASN10OpenType lt name gt Generated C code typedef ASN1TOpenType lt name gt The difference between the two types is the C version contains constructors to initialize the value to zero or to a given open type value If the tables command line option is selected and the ASN 1 type definition references a table constraint the code generated is different In this case ASN OpenType above is replaced with ASN Object or ASNITObject for C This is defined in asn type h as follows typedef struct generic table constraint value holder ASN10penTyp ncoded void decoded OSINT32 index table index ASN1Object This allows a value of any ASN 1 type to be represented in both encoded and decoded forms Encoded form is the open type form shown above It is simply a pointer to a byte buffer and a count of the number of byes in the encoded message component The decoded form is a pointer to a variable of a specific type The pointer is void because there could be a potential
327. ter the standard ASN1T_ prefix This can be used to prevent name clashes if multiple modules are involved in a compilation and they all contain common names lt enumPrefix gt lt enumPre prefix text fix gt This is used to specify a prefix that will be applied to all generated enumerated identifiers within a module This can be used to prevent name clashes if multiple modules are involved in a compilation note this attribute is nor mally not needed for C enumerated identifiers because 28 Compiler Configuration File Name Values Description they are already wrapped in a structure to allows the type name to be used as an additional identifier lt valuePrefix gt lt valuePre prefix text This is used to specify a prefix that will be applied to all fix gt generated value constants within a module This can be used to prevent name clashes if multiple modules are in volved that use a common name for two or more different value declarations lt classPrefix gt lt classPre prefix text This is used to specify a prefix that will be applied to fix gt all generated items in a module derived from an ASN 1 CLASS definition lt objectPrefix gt lt objectPre prefix text fix gt This is used to specify a prefix that will be applied to all generated items in a module derived from an ASN 1 In formation Object definition lt objectsetPrefix gt lt object
328. that data for the test variables is not random it is extracted from an XML Document Object Model DOM tree at run time In order to use this capability it is necessary to have the libxml2 http xmlsoft org XML parser installed on your system Call are then made to parse a given XML document and create a DOM tree Data from the DOM tree will then be transfered to data varaibles of generated structures This has the same end result as decoding the XML documents using the XML decoder Generated Sample Programs In addition to test functions it is possible to generate writer and reader sample programs These programs contain sample code to populate and encode an instance of ASN 1 data and then read and decode this data respectively These programs are generated using the genwriter and genreader command line switches 201 202 Event Handler Interface The events command line switch causes hooks for user defined event handlers to be inserted into the generated decode functions What these event handlers do is up to the user They fire when key message processing events or errors occur during the course of parsing an ASN 1 message They are similar in functionality to the Simple API for XML SAX that was introduced to provide a simple interface for parsing XML messages The notypes option can be used in conjunction with the events option to generate pure parsing functions In this case no C types or encode or decode functions
329. the Command line Option Argument Description used with the w32 command line option a makefile that is compatible with the Microsoft Visual Studio nmake util ity is generated otherwise a GNU compatible makefile is generated genPrint print lt filename gt This option allows the specification of a C or C source c or cpp file to which generated print functions will be written Print functions are debug functions that allow the contents of generated type variables to be written to stdout The lt filename gt argument to this option is optional If not specified the print functions will be written to lt modulename gt Print c where lt modulename gt is the name of the module from the ASN 1 source file genPrtToStr prtToStr lt filename gt This option allows the specification of a C or C source c or cpp file to which generated print to string func tions will be written Print to string functions are simi lar to print functions except that the output is written to a user provided text buffer instead of stdout This makes it possible for the use to display the results on different out put devices for example in a text window The lt filename gt argument to this option is option al If not specified the functions will be written to lt modulename gt Print c where lt modulename gt is the name of the module from the ASN 1 source file genPrtToStrm prtToStrm lt
330. the presence or absence of the entire version block Note that it is also possible to have optional items within the block alternate item name C Mapping of SEQUENCE The C mapping of an ASN 1 SEQUENCE type is very similar to the C mapping However there are some important differences 1 As with all C types the prefix ASN1T_ is added before the typename to distinguish the data class from the control class the control class contains an ASN1C_ prefix 2 A default constructor is generated to initialize the structure elements This constructor will initialize all elements and set any simple default values that may have been specified in the ASN 1 definition 3 If the genCopy command line switch was specified a copy constructor will be generated to allow an instance of the data contained within a PDU control class object to be copied 4 Also if genCopy was specified a destructor is generated if the type contains dynamic fields This destructor will free all memory held by the type when the object is deleted or goes out of scope SET The ASN 1 SET type is converted into a C or C structured type that is identical to that for SEQUENCE as described in the previous section The only difference between SEQUENCE and SET is that elements may be transmitted in any order in a SET whereas they must be in the defined order in a SEQUENCE The only impact this has on ASNIC is in the generated decoder for a SET type The decoder must take
331. the rtxErrCodes h include file The reason text and a stack trace can be displayed using the rtxErrPrint function Procedure for Calling C Decode Functions This section describes the step by step procedure for calling a C XER decode function This method must be used if C code generation was done This method cannot be used as an alternative to using the control class interface if C code generation was done Use the C procedure instead There are four steps to calling a compiler generated decode function 1 Prepare a context variable for decoding 2 Open a stream 3 Call the appropriate compiler generated decode function to decode the message 4 Free the context after use of the decoded data is complete to free allocated memory structures Before a C XER decode function can be called the user must initialize a context variable This is a variable of type OSCTXT This variable holds all of the working data used during the decoding of a message The context variable is declared as a normal automatic variable within the top level calling function It must be initialized before use This can be accomplished by using the rt nitContext function Also the context must be initialized for streaming operations by calling the rtxStreamInit function OSCTXT ctxt context variable if rtInitContext amp ctxt 0 initialization failed could be a license problem 178 Procedure for Calling C Decode Functions printf
332. the version of ASN 1 specified in ITU T international standards X 680 through X 683 It generates code for encoding decoding data in accordance with the following encoding rules e Basic Encoding Rules BER Distinguished Encoding Rules DER or Canonical Encoding Rules CER as pub lished in the ITU T X 690 standard e Packed Encoding Rules PER as published in the ITU T X 691 standard Both aligned and unaligned variants are supported via a switch that is set at run time e XML Encoding Rules XER as published in the ITU T X 693 standard Additional support for XML is provided in the form of an option to generate an equivalent XML Schema Definitions XSD file for a given ASN 1 specification Encoders and decoders can then be generated using the xml option to format or parse XML documents that conform to this schema This level of support is closer to the W3C definition of XML then is the ITU T X 693 XER definition As of release version 6 0 it is possible to compile an XML schema definitions XSD file and generate encoders decoders that can generate XML in compliance with the schema as well as binary encoders encoders that implement the ASN 1 binary encoding rules BER DER CER or PER The compiler is capable of parsing all ASN 1 syntax as defined in the standards It is capable of parsing advanced syntax including Information Object Specifications as defined in the ITU T X 681 standard as well as Parameterized Types as defined in ITU T
333. this area the individual components of Information Object specifications are examined We begin with the CLASS specification that provides a schema for Information Object definitions A sample class specification is as follows OPERATION CLASS amp 0perationCode CHOICE local INTEGER global OBJECT IDENTIFIER amp ArgumentType amp ResultType amp Errors ERROR OPTIONAL Users familiar with ASN 1 will recognize this as a simplified definition of the ROSE OPERATION MACRO using the Information Object format When a class specification such as this is parsed information on its fields is maintained in memory for later reference In the simple form of code generation the class definition itself does not result in the generation of any corresponding C or C code It is only an abstract template that will be used to define new items later on in the specification In the table form if C is specified an abstract base class is generated off of which other classes are derived for information object specifications Fields from within the class can be referenced in standard ASN 1 types It is these types of references that the compiler is mainly concerned with These are typically header types that are used to add a common header to a variety of other message body types An example would be the following ASN 1 type definition for a ROSE invoke message header Invoke SEQUENCE invokeID INT
334. this is as follows include Employee h include file generated by ASNIC include rtbersrc ASNIBERDecodeStream h include rtxsrc OSRTFileInputStream h int main ASNITAG tag int i len const char filename message dat OSBOOL trace TRUE Decode ASNIBERDecodeStream in new OSRTFileInputStream filename if in getStatus 0 in printErroriInfo return 1 158 Generated Streaming C Decode Method Format and Calling Parameters ASN1T_PersonnelRecord msgData ASN1C_PersonnelRecord employ msgData for if in peekTagAndLen tag len 0 printf peekTagAndLen failed n in printErroriInfo return 1 Now switch on initial tag value to determine what type of message was received switch msgtag case TV_PersonnelRecord compiler generated constant in gt gt employee if in getStatus 0 printf decode of PersonnelRecord failed n in printErroriInfo return 1 or employee DecodeFrom in case TV_ handle other known messages Need to reinitialize objects for next iteration mploy memFreeAll end of loop return 0 This is quite similar to the first example Note that we have pulled the ASN T_Employee and ASNIC_Employee object creation logic out of the switch statement and moved it above the loop These objects can now be reused to process each r
335. time functions available for big integer support This set of functions provides an arbitrary length integer math package that can be used to perform mathematical operations as well as convert values into various string forms See the ASNI C C C Common Run time User s Manual for a description of these functions BIT STRING The ASN 1 BIT STRING type is converted into a C or C structured type containing an integer to hold the number of bits and an array of unsigned characters OCTETs to hold the bit string contents The number of bits integer specifies the actual number of bits used in the bit string and takes into account any unused bits in the last byte The type definition of the contents field depends on how the bit string is specified in the ASN 1 definition If a size constraint is used a static array is generated otherwise a pointer variable is generated to hold a dynamically allocated string The decoder will automatically allocate memory to hold a parsed string based on the received length of the string In the static case the length of the character array is determined by adjusting the given size value which represents the number of bits into the number of bytes required to hold the bits Dynamic Bit String ASN 1 production lt name gt BIT STRING Generated C code typedef ASN1DynBitStr lt name gt Generated C code typedef ASN1ITDynBitStr ASN1T_ lt name gt In this case different base types are used for C and C
336. tion defined in the ASN 1 source file a C encode function is generated This function will convert a populated C variable of the given type into an encoded ASN 1 message If C code generation is specified a control class is generated that contains an Encode method that wraps this function This function is invoked through the class interface to convert a populated msgData attribute variable into an encoded ASN 1 message Generated C Function Format and Calling Parameters The format of the name of each generated encode function is as follows asnlE_ lt prefix gt lt prodName gt where lt prodName gt is the name of the ASN 1 production for which the function is being generated and lt prefix gt is an optional prefix that can be set via a configuration file setting The configuration setting used to set the prefix is the lt typePrefix gt element This element specifies a prefix that will be applied to all generated typedef names and function names for the production The calling sequence for each encode function is as follows len asnlE_ lt name gt OSCTXT pctxt lt name gt pvalue ASN1iTagType tagging In this definition lt name gt denotes the prefixed production name defined above The pct xt argument is used to hold a context pointer to keep track of encode parameters This is a basic handle variable that is used to make the function reentrant so it can be used in an asynchronous or threaded application The u
337. tion object classes These objects are created and this array populated in the class constructor Note that this is a singleton class as evidenced by the protected constructor and instance methods Therefore the object set array is only initialized once the first time the instance method is invoked The other method of interest is the LookupObject method This was generated for the id field because it was identified as a key field This determination was made because id was declared to be UNIQUE in the class definition above A field can also be determined to be a key field if it is referenced via the notation in a table constraint in a standard type definition For example in the following element assignment argument OPERATION amp Type SupportedAttributes opcode the opcode element s ATTRIBUTE class field is identified as a key field 90 XSD TO C C TYPE MAPPINGS ASNIC can accept as input XML schema definition XSD specifications in addition to ASN 1 specifications If an XSD specification is compiled the compiler does internal translations of the XSD types into equivalent ASN 1 types as specified in ITU T standard X 694 The following sections provide information on the translations and the C C type definitions generated for the different XSD types XSD Simple Types The translation of XSD simple types into ASN 1 types is straightforward in most cases a one to one mapping from XSD simple type to ASN 1 primitiv
338. to Create a New Project Previously saved projects may be recalled by clicking the icon next to Open an Existing Project The status window will display the version of the software you have installed as well as report any errors upon startup that occur such as a missing license file 15 Using the GUI Wizard to Run ASNIC ASNIC compiler Objective Systems Inc 9 objective iA SYSTEMS INC Select Files and Directories ASN 1 XSD Fles Appa aa ee Browse Remove Include Import Directories Browse Eee rae Remove Configuration Filefs Browse Output Directory Browse I Generate Listing J Output Warning Messages lt Back Next gt ni Help In this window the ASN 1 file or files to be compiled are selected This is done by clicking the Add button on the right hand side of the top windows pane A file selection box will appear allowing you to select the ASN 1 or XSD files to be compiled Files can be removed from the pane by highlighting the entry and clicking the Remove button ASN 1 specifications and XML Schema Documents must not be compiled in the same project Once an asn file has been added no xsd files may be added 16 Using the GUI Wizard to Run ASNIC Include directories are selected in a similar manner in the middle pane These are directories the compiler will search for import files By default the compiler looks for files in the current working directory wit
339. to be decoded 187 Procedure for Calling C Decode Functions 3 Decode the initial tag value to figure out what type of message was received optional 4 Call the appropriate compiler generated decode function to decode the message 5 Free the context after use of the decoded data is complete to free allocated memory structures Before a C XML decode function can be called the user must first initialize a context block structure The context block structure is initialized by calling the rtXmlInitContext function An input stream is then opened using one of the rtxStream functions If the data is to be read from a file the rtxStream FileCreateReader function can use used Similar functions exist for opening a memory or socket based stream If the user knows the type of XML message that is to be processed he can directly call the decode function at this point If not the user may call the rtXmlpMatchStartTag method to match the initial tag in the message with a known start tag The user can continue to do this until a match is found with one of the expected message types Note that the rtXmlpMarkLastEvent function must be called if the tag is to be reparsed to attempt another match operation A decode function can then be called to decode the message If the return status indicates success 0 then the message will have been decoded into the given ASN 1 type variable The decode function may automatically allocate dynamic memory to hold
340. to set the prefix is the lt t ypePrefix gt element This element specifies a prefix that will be applied to all generated typedef names and function names for the production The calling sequence for each generated copy function is as follows void asnlCopy_ lt name gt OSCTXT pctxt lt name gt pSrcValue lt name gt pDstValue In this definition lt name gt denotes the prefixed production name defined above The pointer to the context structure pctxt provides a storage area for the function to store all variables that have been copied The pSrcValue argument is used to pass a pointer to a variable to be copied The pDstValue argument is used to pass the pointer to the destination value The source value is then copied to the destination value field by field Memory will be allocated for dynamic fields using calls to the rtxMemAlloc function If C is used cpp option is specified and PDU generation is not disabled lt noPDU gt config option is not used then the control class ASN1C_ lt name gt additionally will contain e A copy constructor that can be used to create an exact copy of the class instance The calling sequence is as follows ASN1C_ lt name gt ASN1C_ lt name gt amp orginal For example ASN1C_PersonnelRecord ASN1C_PersonnelRecord original e A getCopy method that creates a copy of the ASNIT_ lt name gt variable ASN1IT_ lt name gt amp getCopy ASN1IT_ lt name gt pDstData 0 For example ASN1
341. uf ASN1T_ lt name gt amp data standard encode decode methods defined in ASNICType base class int Encode int Decode stream encode decode methods int EncodeTo ASN1MessageBufferIF amp msgBuf int DecodeFrom ASN1MessageBufferIF amp msgBuf 3 The name of the generated class is ASN C_ lt name gt where lt name gt is the name of the production The only defined attribute is a protected variable reference named msgData of the generated type Two constructors are generated The first is for stream operations and allows the control class to be created using only a reference to a variable of the generated type The EncodeTo and DecodeFrom methods can then be used to encode or decode directly to and from a stream The lt lt and gt gt stream operators can be used as well 104 XER Class Definition The second constructor is the legacy form that allows a message buffer to be associated with a data variable at the time of creation The Encode and Decode methods defined in the ASN1CType base class can be used with this construction form to encode and decode to the associated buffer The constructor arguments are a reference to an ASN1MessageBufferlF message buffer interface type and a reference to an ASNIT_ lt name gt type The message buffer interface argument is a reference to an abstract message buffer or stream class Implementations of the interface class are available for BER DER PE
342. uffer genPrtToStrm This option causes print functions to be generated that write their output to an output stream via a userdefined print callback function Print to Standard Output The print option causes functions to be generated that print the contents of variables of generated types to the standard output device It is possible to specify the name of a c or cpp file as an argument to this option to specify the name of the file to which these functions will be written This is an optional argument If not specified the functions are written to separate files for each module in the source file The format of the name of each file is lt module gt Print c If an output filename is specified after the print qualifier all functions are written to that file The format of the name of each generated print function is as follows asnlPrint_ lt prefix gt lt prodName gt where lt prodName gt is the name of the ASN 1 production for which the function is being generated and lt prefix gt is an optional prefix that can be set via a configuration file setting The configuration setting used to set the prefix is the lt typePrefix gt element This element specifies a prefix that will be applied to all generated typedef names and function names for the production The calling sequence for each generated print function is as follows asnlPrint_ lt name gt const char name lt name gt pvalue In this definition lt name gt denotes the pr
343. uires this definition The resulting C structure is populated just like any other compil er generated structure for working with ASN 1 data Note NOTE It is recommended that if a specification contains multiple ASN 1 source files that reference EM BEDDEDPDYV all of these source files be compiled with a single ASNIC call in order to ensure that only a singled copy of the Asnl1EmbeddedPDV source files are generated Parameterized Types The ASNIC compiler can parse parameterized type definitions and references as specified in the X 683 standard These types allow dummy parameters to be declared that will be replaced with actual parameters when the type is referenced This is similar to templates in C A simple and common example of the use of parameterized types is for the declaration of an upper bound on a sized type as follows SizedOctetString INTEGER ub OCTET STRING SIZE 1 ub In this definition ub would be replaced with an actual value when the type is referenced For example a sized octet string with an upper bound of 32 would be declared as follows OctetString32 SizedOctetString 32 The compiler would handle this in the same way as if the original type was declared to be an octet string of size 1 to 32 That is it will generate a C structure containing a static byte array of size 32 as follows typedef struct OctetString32 OSUINT32 numocts OSOCTET data 32 OctetString32 Anot
344. ull text of the handler is as follows int MyErrorHandler error OSCTXT pCtxt ASNICCB pCCB int stat This handler is set up to look explicitly for ASN_E_NOTINSET errors because we know the SET might contain some bogus elements if stat ASN_E _NOTINSET Print information on the error that was encountered printf decode error detected n rtErrPrint pCtxt printf n Skip element xd_NextElement pCtxt Return an OK status to indicate parsing can continue return 0 else return stat pass existing status back out Now we need to register the handler Unlike event handlers only a single error handler can be registered The method to do this in the message buffer class is setErrorHandler The following two lines of code in the reader program register the handler MyErrorHandler errorHandler decodeBuffer setErrorHandler amp errorHandler The error handlers can be as complicated as you need them to be You can use them in conjunction with event handlers in order to figure out where you are within a message in order to look for a specific error at a specific place Or you can be very generic and try to continue no matter what Example 3 A Pure Parser to Convert PER encoded Data to XML A pure parser is created by using the notypes option along with the events option In this case no backing data types to hold decoded data are generated Instead parsing f
345. unction This method must be used if C code generation was done This method can also be used as an alternative to using the control class interface if C code generation was done 167 Procedure for Calling C Decode Functions Unlike BER the user must know the ASN 1 type of a PER message before it can be decoded This is because the type cannot be determined at run time There are no embedded tag values to reference to determine the type of message received The following are the basic steps in calling a compiler generated decode function 1 Prepare a context variable for decoding 2 Initialize the data structure to receive the decoded data 3 Call the appropriate compiler generated decode function to decode the message 4 Free the context after use of the decoded data is complete to free allocated memory structures Before a PER decode function can be called the user must first initialize a context block structure The context block is initialized by either calling the rtNewContext function to allocate a dynamic context block or by calling rtInitContext to initialize a static block The pu_setBuffer function must then be called to specify a message buffer that contains the PER encoded message to be decoded This function also allows for the specification of aligned or unaligned decoding The variable that is to receive the decoded data must then be initialized This can be done by either initializing the variable to zero using me
346. unction as follows OSCTXT ctxt if rtInitContext amp ctxt 0 initialization failed could be a license problem printf context initialization failed check license n return 1 The next step is to specify an encode buffer into which the message will be encoded This is accomplished by calling the xe_setp run time function The user can either pass the address of a buffer and size allocated in his or her program referred to as a static buffer or set these parameters to zero and let the encode function manage the buffer memory allocation referred to as a dynamic buffer Better performance can normally be attained by using a static buffer because this eliminates the high overhead operation of allocating and reallocating memory After initializing the context and populating a variable of the structure to be encoded an encode function can be called to encode the message If the return status indicates success positive length value the run time library function xe_getp can be called to obtain the start address of the encoded message Note that the returned address is not the start address of the target buffer BER encoded messages are constructed from back to front i e starting at the end of the buffer and working backwards so the start point will fall somewhere in the middle of the buffer after encoding is complete This is illustrated in the following diagram 126 Generated C Encode Method Format a
347. unction is as follows status asnlXD_ lt name gt OSCTXT pctxt lt name gt pvalue In this definition lt name gt denotes the prefixed production name defined above The pct xt argument is used to hold a context pointer to keep track of decode parameters This is a basic handle variable that is used to make the function reentrant so that it can be used in an asynchronous or threaded application The user is required to supply a pointer to a variable of this type declared somewhere in his or her program The variable must be initialized using the rt nitContext run time function before use C XER decoding is stream oriented To perform streaming operations the context pointer pctxt must also be initialized as a stream by using the rtxStreamlInit run time library function see the C C Common Run Time Library Reference Manual for a description of the run time stream C functions The pvalue argument is a pointer to a variable to hold the decoded result This variable is of the type generated from the ASN 1 production The decode function will automatically allocate dynamic memory for variable length fields within the structure This memory is tracked within the context structure and is released when the context structure is freed The function result variable st at returns the status of the decode operation Status code zero indicates the function was successful A negative value indicates decoding failed Return status values are defined in
348. unctions are generated that store the data internally within local 207 How to Use It variables inside the parsing functions This data is dispatched to the callback functions and immeditely disposed of upon return from the function It is up to the user to decide inside the callback handler what they want to keep and they must make copies at that time The result is a very fast and low memory consuming parser that is ideal for parsing messages in which only select parts of the messages are of interest Another use case for pure parser functions is validation These functions can be used to determine if a PER message is valid without going through the high overhead operation of decoding They can be used on the front end of an application to reject invalid messages before processing of the messages is done In some cases this can result in significantly increased performance An example of a pure parser can be found in the cpp sample_per per2xmlEH directory This program uses a pure parser to convert PER encoded data into XML The steps in creating an event handler are the same as in Example 1 above An implementation of the Asn NamedEventHandler interface must be created This is done in the xmlHandler h and xmlHandler cpp files A detailed discussion of this code will not be provided here What it does in a nutshell is adds the angle brackets lt gt around the element names in the startElement and endElement callbacks The data callbac
349. untered when attempting to output data to an output stream associated with a physical device such as a file or socket 31 RTERR_INVBASE64 Invalid Base64 encoding This status code is returned when an error is detected in decoding base64 data 32 RTERR_INVSOCKET Invalid socket This status code is returned when an at tempt is made to read or write from a scoket and the given socket handle is invalid This may be the result of not hav ing established a proper connection before trying to use the socket handle variable 33 RTERR_INVATTR Invalid attribute This status code is returned by the de coder when an attribute is encountered in an XML instance that was not defined in the XML schema 34 RTERR_REGEXP Invalid regular expression This status code is returned when a syntax error is detected in a regular expression val ue Details of the syntax error can be obtained by invoking rtxErrPrint to print the details of the error contained within the context variable 35 RTERR_PATMATCH Pattern match error This status code is returned by the decoder when a value in an XML instance does not match the pattern facet defined in the XML schema It can also be returned by numeric encode functions that cannot format a numeric value to match the pattern specified for that value 36 RTERR_ATTRMISRQ Missing required attribute This status code is returned by the decoder when an XML instance is mis
350. ure This is particularly true when XSD files are being compiled SET OF The ASN 1 SET OF type is converted into a C or C structured type that is identical to that for SEQUENCE OF as described in the previous section CHOICE The ASN 1 CHOICE type is converted into a C or C structured type containing an integer for the choice tag value t followed by a union u of all of the equivalent types that make up the CHOICE elements The tag value is simply a sequential number starting at one for each alternative in the CHOICE A define constant is generated for each of these values The format of this constant is T_ lt name gt _ lt element name gt where lt name gt is the name of the ASN 1 production and lt element name gt is the name of the CHOICE alternative If a CHOICE alternative is not given an explicit name then lt element name gt is automatically generated by taking the type name and making the first letter lowercase this is the same as was done for the ASN 1 SEQUENCE type with unnamed elements If the generated name is not unique a sequential number is appended to make it unique The union of choice alternatives is made of the equivalent C or C type definition followed by the element name for each of the elements The rules for element generation are essentially the same as was described for SEQUENCE above Constructed types or elements that map to C structured types are pulled out and temporary types are c
351. uses mul ti threaded libraries This option suppresses the generation of inline code to support the CONTAINING keyword Instead a normal OCTET STRING or BIT STRING type is inserted as was done in previous ASNIC versions nodecode This option suppresses the generation of decode functions noencode This option suppresses the generation of encode functions noIndefLen noInit This option instructs the compiler to omit indefinite length tests in generated decode functions These tests result in the generation of a large amount of code If you know that your application only uses definite length encoding this option can result in a much smaller code base size This option instructs the compiler not to generate an ini tialization function for each ASN 1 production A vari able of a generated structure can always be initialized by memset ing the variable to zero However this is not usu ally the most efficient way to initialize a variable because if it contains large byte arrays a significant amount of pro cessing is required to set all bytes to zero and they don t need to be Initialization functions provide a smart alter native to memset ing in that only what needs to be set to zero actually is Note that previous versions of the compiler did not gener ate initialization functions by default The genJnit switch has been deprecated in favor of nolnit noObjectTypes This option suppresses
352. ust be done 1 One or more new classes must be derived from the Asn NamedEventHandler and or the Asn ErrorHandler base classes All pure virtual methods must be implemented 2 Objects of these classes must be created and registered prior to calling the generated decode method or function The best way to illustrate this procedure is through examples We will first show a simple event handler application to provide a customized formatted printout of the fields in a PER message Then we will show a simple error handler that will ignore unrecognized fields in a BER message Example 1 A Formatted Print Handler The ASNIC evaluation and distribution kits include a sample program for doing a formatted print of parsed data This code can be found in the cpp sample_per eventHandler directory Parts of the code will be reproduced here for reference but refer to this directory to see the full implementation The format for the printout will be simple Each element name will be printed followed by an equal sign and an open brace and newline The value will then be printed followed by another newline Finally a closing brace followed by another newline will terminate the printing of the element An indentation count will be maintained to allow for a properly indented printout A header file must first be created to hold our print handler class definition or the definition could be added to an existing header file This file will contain a
353. variable length variables during the course of decoding This memory will be tracked in the context structure so the programmer does not need to worry about freeing it It will be released when the context is freed The final step of the procedure is to free the context block The function to free the context is rtFreeContext A program fragment that could be used to decode an employee record is as follows include employee h include file generated by ASNIC main PersonnelRecord data OSCTXT ctxt OSBOOL trace TRUE verbose FALSE const char filename message xml int i stat logic to read message into msgbuf This example uses a static context block step 1 initialize the context block stat rtXmlInitContext amp ctxt ASNIC V6 1 205 if stat 0 rtxErrPrint amp ctxt return stat step 2 open an input stream stat rtxStreamFileCreateReader amp ctxt filename if stat 0 rtxErrPrint amp ctxt 188 Generated C Decode Method Format and Calling Parameters return 1 step 3 attempt to match the start tag to a known value if 0 rtXmlpMatchStartTag amp ctxt OSUTF8 Employee Note that it is necessary to mark the last event active in the pull parser to that it can be parsed again in the PDU decode function rtXmlpMarkLastEventActive amp ctxt step 4 call the decode function stat XmlDec_
354. ver ASNIC uses a special type for these items OSXSDAny that allows for either binary or xml textual data to be stored This allows items to be stored in binary form if binary encoding rules are being used and XML text form if XML text encoding is used The definition of the OSXSDAny type is as follows typedef enum OSXSDAny_binary OSXSDAny_xmlText OSXSDAnyAlt typedef struct OSXSDAny OSXSDAnyAlt t union OSOpenType binary const OSUTF8CHAR xmlText u OSXSDAny The t value is set to either OSXSDAny_binary or OSXSDAny_xmlText to identify the content type If binary decoding is being done BER DER CER or PER the decoder will populate the binary alternative element if XML decoding is being done the xml Text field is populated It is possible to perform XML to binary transcoding of a multi part message for example a SOAP message by decoding each part and then reencoding in binary form and switching the content type within this structure An example of a sequence with a single wildcard element is as follows lt xsd complexType name MyType gt lt xsd sequence gt lt xsd element name ElementOne type xsd string gt lt xsd element name ElementTwo type xsd int gt lt xsd any processContents lax gt lt xsd sequence gt lt xsd complexType gt 96 XML Attribute Declarations The generated C type definition is as follows typedef struct EXTERN MyType const OSUTF8CHAR elementOne OSIN
355. version of the ASN 1 code At the outer level of the markup is the lt asnlconfig gt lt asnlconfig gt tag pair Within this tag pair the spec ification of global items and modules can be made Global items are applied to all items in all modules An example would be the lt storage gt qualifier A storage class such as dynamic can be specified and applied to all productions in all modules This will cause dynamic storage pointers to be used for any embedded structures within all of the generated code to reduce memory consumption demands The specification of a module is done using the lt module gt lt module gt tag pair This tag pair can only be nested within the top level lt asnlconfig gt section The module is identified by using the required lt name gt lt name gt tag pair or by specifying the name as an attribute for example lt module name MyModule gt Other attributes specified within the lt module gt section apply only to that module and not to other modules specified within the specification A complete list of all module attributes is provided in the table at the end of this section The specification of an individual production is done using the lt production gt lt production gt tag pair This tag pair can only be nested within a lt module gt section The production is identified by using the required lt name gt lt name gt tag pair or by specifying the name as an attribute for example lt production name MyP
356. xample the remote side closes the connection Generated Streaming C Function Format and Calling Pa rameters The format of the name of each streaming decode function generated is as follows asnlBSD_ lt prefix gt lt prodName gt where lt prodName gt is the name of the ASN 1 production for which the function is being generated and lt prefix gt is an optional prefix that can be set via a configuration file setting The configuration setting used to set the prefix is the lt typePrefix gt element This element specifies a prefix that will be applied to all generated typedef names and function names for the production The calling sequence for each decode function is as follows status asnlBSD_ lt name gt OSCTXT pctxt lt name gt pvalue ASNIiTagType tagging int length In this definition lt name gt denotes the prefixed production name defined above The pct xt argument is used to hold a context pointer to keep track of decode parameters This is a basic handle variable that is used to make the function reentrant so it can be used in an asynchronous or threaded application The user is required to supply a pointer to a variable of this type declared somewhere in his or her program The variable must be initialized using the berStrmInitContext run time function before use The pvalue argument is a pointer to a variable of the generated type that will receive the decoded data The tagging and length arguments are for i
357. y a user uses this to encode a value of this type is as follows 1 Populate a variable of the type to be used as the argument to the invoke type 2 Plug the address of this variable into the decoded void pointer in the structure above 3 Populate the remaining Invoke type fields 4 Encode the Invoke type to produce the final message Note that in this case the intermediate type does not need to be manually encoded by the user The generated encoder has logic built in to encode the complete message using the information in the generated tables Additional Code Generated with the tables option When the tables command line option is used additional code is generated to support the additional processing required to verify table constraints This code varies depending on whether C or C code generation is selected The C code is designed to take advantage of the object oriented capabilities of C These capabilities are well suited for modeling the behavior of information objects in practice The following subsections describe the code generated for each of these languages The code generated to support these constraints is intended for use only in compiler generated code Therefore it is not necessary for the average user to understand the mappings in order to use the product The information presented here is informative only to provide a better understanding of how the compiler handles table constraints C Code Generation For C
358. zation function For example consider the following declaration SeqgOfType SEQUENCE OF SIZE 2 INTEGER value SeqOfType 1 2 This would result in the following definition in the C or C source file SeqOfType value Code generated in the value initialization function would be as follows value n 2 value element 0 1 value element 1 2 CHOICE Value The mapping of an ASN 1 CHOICE value declaration to a global C or C value declaration is as follows ASN 1 production lt name gt lt ChoiceType gt lt value gt Generated code lt ChoiceType gt lt name gt The choice value will be initialized in the value initialization function For example consider the following declaration ChoiceType CHOICE oid OBJECT IDENTIFIER id INTEGER value ChoiceType id 1 This would result in the following definition in the C or C source file ChoiceType value 75 Table Constraint Related Structures Code generated in the value initialization function would be as follows value t T_ChoiceType_id value u id 1 Table Constraint Related Structures The following sections describe changes to generated code that occur when the tables option is specified on the command line or when Table Constraint Options are selected from the GUI This option causes additional code to be generated for items required to support table constraints as speci

ASN.1 Compiler Version 6.2 C/C++ User`s Manual Objective

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