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Annotation of os2sdk/demos/examples/signal/signal.c, revision 1.1

1.1     ! root        1: /*
        !             2:  * signal.c
        !             3:  *
        !             4:  * This example shows the useage of the signal handling capabilities of
        !             5:  * OS/2.  The signal handler is declared as a far pascal routine.  It
        !             6:  * expects two paramters on the stack: the signal number and, optionally,
        !             7:  * a user defined argument.  The latter has meaning only when the signal was
        !             8:  * generated by a DOSFLAGPROCESS api call.
        !             9:  *
        !            10:  * In general the signal handler can be thought of as an interrupt to
        !            11:  * the current running thread of a process.  Thread scheduling is still
        !            12:  * active.
        !            13:  *
        !            14:  * After a signal has been caught, the handler must "acknowledge" the signal
        !            15:  * before a second one can be handled.
        !            16:  */
        !            17: 
        !            18: #include <doscalls.h>
        !            19: #include <subcalls.h>
        !            20: #include <stdio.h>
        !            21: 
        !            22: #define SIGINTR 1
        !            23: #define SIGTERM 3
        !            24: #define SIGBREAK 4
        !            25: #define CATCH_SIG 2
        !            26: #define SIG_ACK 4
        !            27: 
        !            28: void pascal far sig_handler();
        !            29: 
        !            30: void main() {
        !            31:     
        !            32:     char       c;
        !            33:     void       (pascal far *address)();
        !            34:     unsigned   oldaction;
        !            35:     unsigned   result;
        !            36: 
        !            37:     if (result = DOSSETSIGHANDLER(sig_handler,
        !            38:                                  (unsigned long far *) &address,
        !            39:                                  (unsigned far *) &oldaction,
        !            40:                                  CATCH_SIG, SIGINTR))
        !            41: 
        !            42:        fprintf(stderr,"dossetsighandler failed %d\n", result);
        !            43: 
        !            44:     if (result = DOSSETSIGHANDLER(sig_handler,
        !            45:                                  (unsigned long far *) &address,
        !            46:                                  (unsigned far *) &oldaction,
        !            47:                                  CATCH_SIG, SIGTERM))
        !            48: 
        !            49:        fprintf(stderr,"dossetsighandler failed %d\n", result);
        !            50: 
        !            51:     if( DOSGETMACHINEMODE( &c))
        !            52:        if (result = DOSSETSIGHANDLER(sig_handler,
        !            53:                                      (unsigned long far *) &address,
        !            54:                                      (unsigned far *) &oldaction,
        !            55:                                      CATCH_SIG, SIGBREAK))
        !            56: 
        !            57:            fprintf(stderr,"dossetsighandler failed %d\n", result);
        !            58: 
        !            59:     do
        !            60:        printf("Type an SPACE to terminate demo\n");
        !            61:     while(getchar() != 0x20);
        !            62: 
        !            63:     fprintf(stderr,"Program terminating\n");
        !            64:     exit(0);
        !            65: }
        !            66: /*
        !            67:  * The signal handler routine must ACKNOWLEDGE the signal before it can
        !            68:  * capture another (of the same number).  Since this routine runs as
        !            69:  * thread 0 it can be preempted by another.  If it is
        !            70:  * important that all signals be caught, then Thread 0 should be run as
        !            71:  * a high priority thread and always snoozing. Of course, the
        !            72:  * acknowlegement should be the first thing done in the handler.
        !            73:  */
        !            74: void pascal far sig_handler(sig_arg, sig_num)
        !            75: unsigned sig_arg, sig_num;
        !            76: {
        !            77:     unsigned signum, sigarg;
        !            78:     long address;
        !            79:     int count;
        !            80: 
        !            81:     fprintf(stderr, "signum %u sigarg %u\n", sig_num, sig_arg);
        !            82: 
        !            83:     if (count = DOSSETSIGHANDLER( (void (far *)())0L,
        !            84:                                  (unsigned long far *) &address,
        !            85:                                  (unsigned far *) &sigarg,
        !            86:                                  SIG_ACK, sig_num))
        !            87: 
        !            88:        fprintf(stderr,"dossetsighandler failed %d\n", count);
        !            89: }

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