PICA programmer manual
Contents
1. In Windows in order to attempt this task they use GetIpStatistics a function provided by the Iphlpapi library Forwarding and TTL information are stored in structure MIB_IPSTAT therefore in order to change the forwarding status or the TTL value it is necessary to change forwarding and or TTL values and then call SetIpStatistics with this structure altered according to the new settings Since in Linux all settings are stored on file this function reads and writes the appropriate files to get and set their values respectively Since these files are system files pica must be executed with root priviledges int PICAisForwarding int true_false int PICAsetForwarding int on off int PICAdefaultTTL int set_get int ttl 5 3 3 Sending and receiving packets management In Windows these functions use primitives provided by winpcap Hence to understand the code for Windows please consult winpcap s documentation Linux code relies on socket functionality for this task However it is necessary explicate wince 3 0 code int PICAopenDevice char device PICA IO DEVICE iodev LINUX open a socket and bind int PICAframe int mode PICA_IO DEVICE iodev void packet int packetsize int read int PICAcloseDevice PICA_IO DEVICE iodev int PICAcreatePacket char addr unsigned char data int datasize unsigned char packet int packetsize2. ie PICAS comidos RPICAOIjOS sla void Jour imc louiisiwe amie datasize In order to write data on a pipe both Linux and Windows operating systems use the same functions used to read a file int PICAclosePipe PICApipe pipe This function frees pipe resources 5 2 Process Management primitives 5 2 1 Timer management PICA provides multiple timers by means of a priority queue In this queue all events make use of the same timer in a way that only the first to happen event affected will be used to set the value of the timer To perform this task PICA employs the following data structures struct itimerval struct priogent struct timeval it interval AAA el struct timeval it value UINT64 tv void callback void void data ron REGA struct priogent pqe struct priogent pqe Figure 5 2 data structures definition for timer By starting the up timer the global variable pq with type prioq is allocated Each PICAtimer call with parameter action equal to SET adds a new element of type priorquent to the timer queue with fields set in this way e tv will be set according to the value of parameter time e callback will point to the function to call when tv time is expired e data will point to data to used as a parameter for the function e pque will point to the next el
3. 5 3 4 Routing management WINDOWS these functions are wrapper operating system one LINUX uses a socket on AF_INET domani and a ioctl call with command SIOCADDRT int PICAaddRoute UINT32 dest UINT32 mask UINT32 gateway int metric char device int PICAdelRoute UINT32 dest UINT32 mask UINT32 gateway char device int PICAgetRoutingTable RTInfo rti 5 3 5 Socket These functions are only wrapper operating system ones The different between Windows and Linux are the command to make socket no blocking int PICAcreateSocket PICAsocket sd int domain int type int protocol int block int PICAcloseSocket PICAsocket sd 5 4 PICA data structures and costants This paragraph resume all data types provided by PICA See file PICA data structure doc PICA defines following constants DEVS define MAXDEVS 32 define MAXDEVSIZE 128 IPF WD define FWD_ON 1 define FWD_OFF 0 define TTL_SET 1 define TTL_GET 0 LOG defin eal gt DF 0 EADF_WRITEF 2 define R define WRITEF 1 R C defin REATE_CLEAN 0 define APPEND 1 MEM PACKET define PICA_SEND 0 define PICA_RECEIVE 1 define PROMISCUOUS 0 define ALL_LOCAL 1 PICASPEC define PICA_WINDOWS_NT define PICA VE
4. File_1 h with the directive tinclude File 1 h PICA Linux version internal structure is the same shown above but without references to Libpcap Some functions provided by PICA need special libraries in order to interact with operating system and drivers hence these libraries depend on operating system 2 1 windows based operating systems timer user packet teres Iphipapi Figure 3 1 PICA internal structure on Windows operating systems The figure 3 1 shows relevant libraries referred by PICA library for all operating systems based on windows The only difference between Windows XP or 2000 and Windows CE is the respectively porting of Libpcap Winpcap for first type and Packet32 for the second Figure 4 5 reports only libraries does not use ordinarily Internet Protocol Helper AP phlpapi assists network administration of the local computer by enabling applications to retrieve information about the network configuration of the local computer and to modify that configuration IP Helper also provides notification mechanisms to ensure that an application is notified when certain aspects of the local computer network configuration change This library is used by PICA in order to get information about available network interfaces to manage time to live TTL and forwarding settings to send and to receive pac
5. Windows and Linux this function is a wrapper of the one made available by the operating system int PICAselect int time PICAdescList dl PICAselResult res In Linux any resource is identified by an integer descriptor Therefore since the select function provided by Linux works with resource descriptors it can be use for all sorts of resources On the contrary for Windows operating systems descriptors are generally represented by a specific data type called HANDLE while integers are only used for sockets The PICA library obviates this problem by emulating Linux s behaviour The fundamental idea of the algorithm used for the Windows version of PICA is to separate socket descriptors from others using a thread that calls the Windows select function on those sockets inserted in the list simultaneously the main application perform a select on the other descriptors The thread can communicate its results to the main application through a pipe The code in detail The first while loop divides descriptors contained in dl in two lists in the first one named sock we have all socket descriptors while in the second one called handles there are all remaining descriptors whose type is PICA_PIPE_TYPE and PICA_OTHER_TYPE After exiting this loop the function creates a new event to be added to the second list This event corresponds to a thread
6. directory containing all header files for the packet32 library d Verify that in PICA dependences are defined IPhlpapi lib winsock lib packet32 lib and pktdrv lib e Build the pica solution to create PICA s dynamic link library pica dll and static link library pica lib How to work with PICA on Windows CE 5 0 The winpcap port for Windows CE 5 0 is not yet available Hence only these steps must be performed a Open the solution file with the appropriate tool and verify that in the project dependencies winsock lib and IPhlpapi lib are defined b Build the pica solution to create pica s dynamic link library pica d11 and static link library pica lib 5 PICA s primitives This paragraph shows and describes PICA s primitives divided in three logical groups e memory management primitives e process management primitives e communication management primitives On each of them PICA sS primitives are separated by their functionality 5 1 Memory management primitives 5 1 1 In order to write the log file In order to unify the file descriptor PICA uses FDesc that in Windows is a HANDLE type while in Linux it corresponds to the int type These functions are wrappers those of the operating system In Windows file permission are generic while in Linux these are NN rr Iw Y 14 In windows it is important to notice that
7. s write on the pipe Before creating the thread Windows select function is called with timeout 0 in order to check if any of the sockets is ready In such case the function scans the sock list until it finds the first signalled socket and then sets variable res whose type is PICAselResult with the values of the correspondent fields of the signalled socket descriptor and finally returns If there are no ready sockets the function creates pipe and thread This executes the code of the sock select function This is a simple Windows select function call with the timeout value set as parameter time of PICAselect Hence there is a parallel execution of the thread and the main application Notice that while the thread waits on sockets the main application waits on other types of descriptors In order to attempt to do this task the main application uses the WaitForMultipleObjects function Since this function required an array of objects on which to wait upon the second while loop copies the handle list in handleArr array f PICAselect is called with PICA WAIT FOREVER as the actual parameter of time the WaitForMultipleObjects is invoked with an infinite timeout Otherwise it uses the value of parameter time If the call to WaitForMultipleObjects has success then it returns an integer i
8. Mutex management sac mass gemmes mod eue des dense ms cane 22 4 4 3 En order to manage PICA LiDary en Lindos du bis a ae ee 23 4 5 Communication management primitives 24 4 5 1 In order to get information on available devices 24 4 5 2 Management forwarding information 25 d OS Sending and receiving packets management 25 4 5 4 Routing Management sr nee esa ours Sea ee Se ee ere 26 4 525 SOCKET 2 re dam OS eae Owe poe du die YS Bee eee Ee ee oe 26 4 6 TCA data Structures and COSTANES eese ce eee ge dense te 26 1 Introduction Since PICA is released under the GNU General Public Licence any programmer can improve PICA This document was been created to make this task easier here all the functionality of PICA s code is explained and differences between operating systems and how PICA copes with them are pointed out Moreover in this document the programmer can find all the data structures and constant definitions Appendix A Some data structures have different definitions for each platform since Linux and Windows operating systems provide different data types for example a file is identified by a integer in Linux and by a HANDLE a special type in Windows In this document the data structures ar presented for the Windows version If they are defined in different way in Linux it is point
9. PICA programmer manual This document gives details about the PICA library and describes its internal code for each platform on which is available Index CA Programmer mantedes r side ed Li des ne Vase ed oR bee HbA Ve le ees 1 TOOK os oct A eb we be Geb ES ae ee at ee a ee 2 MELO GUGINO e ote tat Oe eee Se ee Se Re dant OS ee ae Sa de 3 like Termino log a heer edd bre ane e eel ES Sees eed QT dard re ed GE res 3 PICA Library internal Structure ssh dre ae sie eae nes 3 Zal windows based operating systems 9 232 TD TASC oly he di ne do aa rite tn BG atta ha he Soe Ss as nh ae a a ln a ea 6 Requirements in terms of tools and libraries 7 y HOW tO USE FG Pics 6 x Goch ua 26 cet as el lot ch aay a and aps Cored abe ces sae de Garr ade asi sated doy ct Sereda es eur 7 4 1 DPN Kew fais ee ne a a Ee ee Bw ee ee ew 8 4 2 Windows Operating SVSECMS utc seek me SRA same Rest de Sea 8 CALS PETMIELVES a sk ae NI a Ss A AS ARAS A Bie 10 4 3 Memory management P TMICIVOS coda Mis ees huis eae awe en 10 dul In Order Lo write Elbe TOO fae taa o alta ai d die A 10 4 3 2 Management packet buffer ercuemsosionsraterean esters 11 leas aes Papen MmanagemMmenEe s See Sees Stee eee Oe ae See See eee oaks 12 4 4 Process Management Primitives 2 ads dus e add hod a eek 14 4 4 1 Tiner Management Hi Siu eile Pies dle Pai a 14 4 4 2
10. RSION 0x010000 version 1 0 0 E define PICA_ERR_BUF_SIZE 100 RTMANAGER define BUFSIZE 3000 SOCK define NO_BLOCK 0 THR define PICA_SOCKET_TYPE 0 define PICA_PIP T TYPE 1 define PICA_OTHER_TYPE 2 define PICA_TIMEOUT_TYP GI 255 define PICA_WAIT_FOREVER 1 define MUTEX_ACQUIRE 0 define MUTEX RELEASE 1 define MUTEX_ACQ_NO_BLOCK 2 define SEMAPHORE_ACQUIRE 0 E define SEMAPHORE_RELEASE 1 define SEMAPHORE_ACQ_NO_BLOCK 2 T TIMER define TIME_DIV 100 E Linux define TIME_DIV 10 define T_SET 0 define T_STOP 1 define T_STARTUP 2 define T_KILL 3 USER define IS_ADM 1 define IS _NOT_ADM 0
11. ction PICAsemaphore p_sem int count The only thing to notice in this function s code is about its action when the action parameter takes the value SEMAPHORE ACQUIRE PICAsemaphoreAction calls count times operating systems function that allows increment semaphore value because neither Linux neither Windows offer functionality to increment that count int PICAdestroyMutex PICAmutex mut int PICAdestroySemaphore PICAsemaphore p sem In order to get user information int PICAisAdministrator int true false 5 2 3 In order to manage PICA libary ine PIrCAstarcupolint Flags y Both Linux and Windows initilize global variables by using the respectiv system functions but it necessary to point out that Windows needs to call The WSAStartup function This initiates use of the Winsock DLL by a process lie PICAcIleanu s WOE y The following functions are used to manage errors in the PICA library The first one is used in PICA s code each time an error occurs When this happens the message and error codes are saved in the global variables defined in PICAspec c file err_buf and err_code respectively Both functions use a mutex to access them thereby avoiding concurrent access problems void P_ERROR char message int code AS Sica charik err OE 5 3 Communication management primitives In Linux all PICA primitives related to network
12. d event of PICApipe was added Hence PICA provides a pipe data structure and primitives to manage it in order to cope with this difference In fact in Windows PICApipe is declared as typedef struct PICApipe typedef int PICApipe HANDLE pipe HANDLE event PICApipe Figure 5 1 PICApipe structure definitions left Windows right Linux int PICAmakePipe PICApipe in PICApipe out Both in Windows and in Linux functions the PICA pipe function called the respective on made available by the operating systems It is important to aw notice that in Windows the system function createPipe is called using the SECURITY_ATTRIBUTES structure as the last parameter which must have the bInheritHandle field set true this way theads can inherit it Moreover this function creates an event shared by the in and out pipe im PiCAsencioPipe PICASIpPS QUE voile dara int size int written In order to write data on a pipe both Linux and Windows operating systems use the same functions used for writing on a file In Windows in order to signal writes and reads on pipe it is necessary use the OVERLAPPED structure as the last parameter of the Windows write function By setting the OVERLAPPED structure s field named hEvent with the event of pipeOut the thread waiting to read on the pipe is informed about the write
13. der to use libpcap functionalities to interact with network adapter but subsequently PICA designers opted for using socket feature in place of libpcap Sine socket Linux allows a direct interaction with network adapters PICA designers prefer use it even if it is a little bit slowly instead of bind PICA to an other library augmenting code size and make it dependent on other code and its new released versions 3 Requirements in terms of tools and libraries In this paragraph we list the necessary tools to manage PICA s code along with the essential libraries to run PICA Win2000 XP WINCE 3 0 WINCE 5 0 Linux Winpcap Packet 32 Library winsock winsock2 winsock ActiveSync 4 2 Microsoft ActiveSync 3 5 Visual Studio Tool Visual Studio EmbeddedVisul Net 2005 Net 2003 c 3 0 Obviously if the programmer does not use PocketPC solely relying on the simulator provided by development nvironment the ActiveSync tool is not necessary Moreover ActiveSync 4 2 is back compliant therefore if the programmer uses it they can develop code both for Windows CE 3 0 and for Windows CE 5 0 Tests on PICA were done with the tools versions shown in the table above th user can pick a different version but optimum functionality is not guaranteed 4 How to use PICA The provided PICA package contains these directories e Linux e Windo
14. descList dl int type int mode void desc 5 2 2 Mutex management Windows and Linux manage mutexes and semaphores in different way Besides having different types of mutex and semaphore descriptors Linux does not allow setting the maximum value for a semaphore which is a feature available in Windows PICA provides this functionality In order to accomplish this it was necessary create a new data structure for semaphores in the Linux version typedef struct _PICAsemaphore sem_t sem pthread_mutex_t sem_mutex int max_count PICAsemaphore Figure 5 4 PICAsemaphore structure definition for Linux In this structure the first field is the real Unix semaphore the second is a mutex used to allow secure access to max_count field that stores the maximum semaphore value The PICAcreateSemaphore consists of a call to the sem_init function functionality provided by Linux in order to initialize semaphores and setting all field of p_sem its first parameter int PICAcreateMutex PICAmutex mut int PICAcreateSemaphore PICAsemaphore x p_sem int initial_count int max_count This function consists of two system calls to initialize semaphores and mutexes sem_init and pthread_mutex_init respectively and in setting the p_sem variable according to the values of its parameters int PICAmutexAction int action PICAmutex mut int PICAsemaphoreAction int a
15. ed out in the description In this manual the programmer can find necessary instruction to install and use chapter 4 and code description of all PICA primitives These are divided in three logical group memory management Section 5 1 process management chapter 5 2 and communication management Section 5 3 1 1 Terminology Since the biggest difference between operating systems is between Linux and Windows related families of kernels in the document the word Windows is to be interpreted as the Windows operating system s family including both desktop and compact editions In the case it is necessary to be more precise we will clearly state the version of Windows being analyzed 2 PICA library internal structure This paragraph shows PICA project internal structure for each platform on which PICA is available PICA project is constituted from eleven files of code and each of them includes a header file The figure 4 4 shows the general internal structure of PICA project and the relationships between header files and used library Devs Iphfwd manager Figure 2 1 PICA internal structure In this figure a white rectangle is a single PICA header file while the yellow rectangle is used for Libpcap porting header file Arrows are used as follows for example when we draw In this case File 2 h includes
16. ement The elements in the queue are in increasing order the first one has the lowest timeout value Therefore lement are inserted in queue according to their timeout value maintaining the required ordering Moreover it is important to notice that only the Windows version of PICA defines the itimerval structure because it is already defined in the Linux header file time h All operations on the timer queue are performed by using a mutex avoiding racing conditions Therefore even in multi threaded environments it is possibl us the same timer queue without synchronization problems UINT64 PICAgetCurrTime void As expected Linux and Windows get current time information using different procedures Windows uses GetLocalTime function that returns a structure containing all the information about current time Windows documentation suggests converting this structure into another one and this to an unsigned integer of 64 bits in order to perform arithmetic operations on its value Therefore Windows code is not a sample call of Windows system functions but contains all the necessary instructions to perform this conversion In Linux PICA s code calls the appropiate system s function and transforms its result into an unsigned long integer in order to unify types with Windows int PICAtimer int action UINT64 time void function void data This function i
17. f this library from www winpcap org install default htm b Open the solution file with appropriate tool and verify that in the project dependences are defined ws2_32 1ib and IPhlpapi lib c Build pica solution to create the pica dynamic link library pica dll and static link library pica lib How to work with PICA on Windows CE 3 0 a to install the necessary libraries download them from http www winpcap org install default htmt The download consists of a zip file that contains a project developed with Microsoft Embedded Visual Studio c This solution contains three projects named i DLL ii Driver 111 SampleApply While the first two projects consist of code to allow direct interaction with network interface the third is a small application that demonstrates the functionality of the first two libraries In order to obtain the packet32 library it is sufficient to build the DLL project and download it to the PocketPc Since it is dependent on the Driver project the same action must be performed on this library also Notice that output files of packet32 project are packet32 d11l for DLL and pktdrv dll Since the winpcap s developer does not guarantee its correct functioning on all devices it is advisable execute SampleApply to check if the driver is suitable to be used on the PocketPC c In PICA s project directory there is an MSinclude
18. functionality are implemented by invoking the ioctl function which manipulates the underlying device parameters of special files In particular many operating characteristics of special character files e g terminals may be controlled through ioctl requests The first parameter the ioctl function is a descriptor file while the second represents a command that selects the control function to be performed and shall depend on the STREAMS device being addressed Therefore in Linux these PICA functions are implemented by invoking the ioctl function on a socket and with different commands in order to get or set the necessary information 5 3 1 In order to get information on available devices In Windows these two functions are implemented by calling GetAdaptersWindows provided by the IPhlpapi library The Windows primitive is invoked twice The first call is used to find the number of available devices while the second is used to obtain information about the device n PICAgetAvailableDevices the information concerns devices names while in PICAgetDeviceAttrs it consists of IP and MAC addresses In Linux int PICAgetAvailableDevices DEVLIST devs int PICAgetDeviceAttrs char dev DevAttrs attrs 5 3 2 Management forwarding information These functions provide information about forwarding and TTL also allowing to change their states
19. hread is quite similar for both Linux and Windows environments First of all the thread creates the timer It then enters an infinite loop where it performs the following tasks a check if the timeout value for the first element is close to the current time It is obvious that it is impossible to activate an event at its exact timeout value since it is expressed with microsecond precision Therefore PICA actives an event if its timeout is in the range between its timeout plus or less 100 microseconds b If the previous checking returns true then the thread executes the event s function and afterwards deletes it from queue c Re start the loop If action s value is T_STOP the function searches th lement identified by its other parameter this task is performed by pg_getfromqueue and pqdeleteen The first element found that matches the criteria is deleted Finally PICAtimer calls the updatetimer function If the action s value is T_KILL the function frees the memory allocated for all the variables used by the timer by calling pqa cleanup In Linux this function calls thread in a different moment while in Windows it is created on the first call of PICAtimer with T_ SET in Linux it is created in a PICAtimer call with T_START this different does not change this function s behavior but
20. in order to implement file opening functionalities in append mode it is essential to shift the pointer file to the end using the SetFilePointer function provided by Windows before starting to write int PICAopenFile FDesc file char name int read write int flags int PICAwriteToFile FDesc file void data unsigned int datasize int PICAreadFile FDesc file void buf int buffersize int datasize int PICAcloseFile FDesc file 5 1 2 Management packet buffer Relatively to memory management PICA s architecture is based on offering the possibility to easily manage a data structure to handle a set of queues int PICAinitBuffer PICAbuffer ibuf int num queues For Windows operating systems it is important notice that in order to create a mutex that can be inherited by threads the CreateMutex function must be called with the first parameter set to a pointer to a SECURITY_ATTRIBUTES structure where field bInheritHandle is set to true On Windows XP this function creates a PICAbuffer with a number of queues equal to num queues in order to allocate the queues and an array of mutexs it uses the GlobalAlloc primitive in place of the classic malloc function since Windows XP can generate errors on memory management when an application tries to access a memory location allocated by a library Obviously it is necessary use GlobalFree primitives
21. its due to differences in terms of thread and resource management for the different operating systems Thread management The fork call is of common use in Unix environments to manage processes The Windows OS though does not offer this function PICA adopts a combination of the threads approximation along with the semaphore and mutex abstractions as an alternative to processes without generating too much extra code Although the Posix standard doesn t allow thread suspension and resuming the PICA library allows to use such functions in the Linux operating system by means of the SIGUSR1 and SIGUSR2 signals PICA s Windows functions focusing on threads merely wrap the operating system s primitives but it is important to notice that the Windows functions called in PICASuspendThread and PICAResumeThread are primarily designed for use by debuggers and they are not intended to be used for thread synchronization PICA s Linux functions are quite more complicated than than those for Windows since Linux does not provide thread suspend and resume functionality Before analyzing each PICA function code concerned thread here we report the fundamental idea on which these functions are based Since Linux does not admit thread suspending and resuming it does not provide a way to store information about which threads are suspended in order to call the resum functio
22. kets Ws2_32 Windows socket library version 2 uses the sockets paradigm that was first popularized by Berkeley Software Distribution BSD UNIX It was later adapted for Windows in Windows Sockets 1 1 with which Windows Sockets 2 applications are backward compatible 2 2 Linux pani FE G Z Si Devs Iphfwd rtmanager sock thr mem 4 j user pacto Figure 2 2 PICA internal structure for Linux PICA Linux version s based on Pthread library Historically hardware vendors have implemented their own proprietary versions of threads These implementations differed substantially from each other making it difficult for programmers to develop portable threaded applications In order to take full advantage of the capabilities provided by threads a standardized programming interface was required For UNIX systems this interface has been specified by the IEEE POSIX 1003 1c standard 1995 Implementations which adhere to this standard are referred to as POSIX threads or Pthreads Pthreads are defined as a set of C language programming types and procedure calls implemented with a pthread h header include file and a thread library though the this library may be part of another library such as libc It is fundamental notice that PICA Linux version does not need libpcap In the first time PICA was designed based on lipcap in or
23. n on them alone Therefore PICA faces up this problem using a global dynamic array named array of type Victim t a new type introduced by PICA typedef struct int inuse pthread_t id Victim_t Figure 5 3 Victim_t structure definition The first field is used to know if array element are in use or not By default PICA defines array with 10 elements but if necessary this array can easily grow in size Obviously The id field identifies the thread Moreover PICA uses global semaphore variables in order to allow the thread to communicates to the main process its entry in the suspend state int PICAstartThread THRID thr void func void arg This function creates a detached thread that is its thread ID and other resources can be reused as soon as the thread terminates int PICAsuspendThread THRID thr First of all PICAsuspendThread initializes all the necessary data structures and variables for thread suspension by invoking pthread_once This function calls suspend_init_routine that allocates an array variable initializes the semaphore and installs the signal handlers for suspending and resuming through an sigaction call It important to notice that suspend_init_routine is called only once by definition of the pthread_once function Afterwards PICAsuspendThread checks if the thread identified by thr i
24. ncluded between WAIT_OBJECT_O and WAIT_OBJECT_O plus handlerArr elements number If the value is equal to WAIT_OBJECT_O it means that the pipe used for intercommunication between the thread and the main application sends a signal because its descriptor was been saved as the first element of handleArr array In this case PICAselect can find on the pipe th index of the socket that has been signalled and then set th res variable field with the signalled socket value If WaitForMultipleObjects has success and the returned valued said i is bigger than WAIT_OBJECT_O the fields of the res variable will be set with the descriptor values at the ie position in the handle list In Linux the PICAselect function is a simple call to the select function provided by o s Before invoking the select function PICAselect cleans the set of signalled descriptors by using the FD_ZERO function and then creates a new set with all descriptors contained in dl list by invoking FD_SET The time rule is the same on as for Windows if PICAselect is called with PICA WAIT FOREVER then the select function is invoked with the last parameter set to null in order to return only when a descriptor is signalled If time is other number this value represents the timeout for the select function int PICAaddDesc PICA
25. s already suspended by searching thr in array If thr is not already suspended this function sends SIGUSRI to the thread to suspend it and then enter an wait state on semaphore The main process stays in the wait state until the thread enters in suspend state Hence the thread executes suspend_signal_handler the routine assigned to the SIGUSR1 signal in the previous initialization phase suspend_signal_handler suspends all signals for the thread except for SIGUSR2 and communicates its entering in suspend mode to the main process by calling sem post on the global semaphore When the main process receives this communication it exits from the wait state and continue its execution int PICAresumeThread THRID thr First of all this function calls pthread_once for more details see the previous function Subsequently it checks if the thread identified by thr is in the suspend state In the negative case it returns with error otherwise it sends the SIGUSR2 signal to the thread through the pthread_kill function invocation and then returns successfully When the thread receives that signal it executes resume_signal_handler This handler is a sample return but it is necessary in order to force sigsusped function called by the thread when it is entering the suspend state to return int PICAkillThread THRID thr In both
26. s implemented in the same way both in Windows and Linux but system calls are different obviously Here we describe the code for the Windows version and if here is some differences towards the Linux version they are pointed out Behaviour of this function depends on the value of parameter action like it is explained in PICA s user manual chapter x x If action s value is STARTUP the function initializes the global variable pg by malloc invocation and by setting its value to NULL In addition the Linux version of PICA starts the thread that manages timer If action s value is T_SET the function calls the pq_insert function pq_insert handles the insertion of a priogent element in the list and also calls pq updatetimer This function creates the thread identified by timerHandle that manages timer Afterwards it sets the timer value depending on these situations e if the queue does is empty the timer is set to zero Fh the queue contains one or more elements x if the first event timeout is lower than the current time then the timer s value is of one microsecond this is the case that the event has just happened x otherwise the timeout value is the differences between its timeout and the current time The function named TimerThrFunc that is executed by the t
27. to free previously allocated memory Since in Linux no such problems with memory allocation where detected PICA uses malloc primitives to allocate memory int PICAaddToBuffer PICAbuffer buf int queue id void data int data size int PICAgetFromBuffer PICAbuffer buf int queue id int num packets PICApacket packets int avail packets int PICAkillBuffer PICAbuffer buf This function un allocates the memory allocated with PICAinitBuffer First of all it blocks all mutexes in order to prevent the concurrent access problem Since mutexs are contained in the structure the function does a copy of the mutex array and blocks copy so that it can free the whole memory allocated for the buffer Afterwards for each queue the function un allocates each packet data and then the whole packet Finally after freeing the whole buffer data structure the functions frees the mutex array copy 5 1 3 Pipe management Windows unlike Linux leaves pipe event management to the programmer When a thread writes on a pipe it signals this action to the thread waiting for this event in Linux operating system delivers signal to resource waiting for that is this mechanism is transparent to programmer Instead in Windows programmer must set an event for in and out pipe in order to allow waiting thread on in pipe is advised when something is written on out pipe For this reason fiel
28. ws e WinCe 3 0 e WinCe 5 0 In each directory there is the source code and the necessary files to work with the tools specified above 4 1 Linux In this directory there are all the PICA files and the Makefil This file can be used by programmer to compile and install the PICA library in order to use it in other applications Respectively the commands are a make b make install By default the PICA library is installed in usr local lib and PICA header files in usr include PICA Obviously it is possible change PICA s directory of installation by changing the paths defined on the Makefile All PICA based applications must include the following code line finclude lt PICA pica h gt And can be compiled with this command gcc lt your stuff gt lpica 4 2 Windows operating systems In order to work with the Windows versionof PICA it is necessary to open each project using the solution file and be sure that the right references to essential libraries are defined in the project settings Moreover in order to work with Pocket PC Windows CE it is necessary to be sure that the development tool downloads all the libraries on the device and that they are in the same directory How to work with PICA on Windows XP a Install Winpcap executing winpicap_setup exe the user can download a up to date version o
Download Pdf Manuals
Related Search