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Annotation of os2sdk/demos/examples/signal/signal.c, revision 1.1.1.2

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
1.1.1.2 ! root        8:  * generated by a DosFlagProcess api call.
1.1       root        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.
1.1.1.2 ! root       16:  *
        !            17:  * Created by Microsoft Corp. 1986
1.1       root       18:  */
                     19: 
1.1.1.2 ! root       20: #define INCL_DOSSIGNALS
        !            21: #define INCL_DOSMISC
1.1       root       22: 
1.1.1.2 ! root       23: #include <os2def.h>
        !            24: #include <bse.h>
        !            25: #include <stdio.h>
1.1       root       26: 
1.1.1.2 ! root       27: void APIENTRY sig_handler();
1.1       root       28: 
                     29: void main() {
                     30:     
1.1.1.2 ! root       31:     char         c;
        !            32:     PFNSIGHANDLER address;
        !            33:     USHORT       oldaction;
        !            34:     unsigned     result;
        !            35: 
        !            36:     if (result = DosSetSigHandler(sig_handler, &address,
        !            37:                                  &oldaction, SIGA_ACCEPT, SIGA_IGNORE))
1.1       root       38: 
                     39:        fprintf(stderr,"dossetsighandler failed %d\n", result);
                     40: 
1.1.1.2 ! root       41:     if (result = DosSetSigHandler(sig_handler, &address,
        !            42:                                  &oldaction, SIGA_ACCEPT, SIGA_ERROR))
1.1       root       43: 
                     44:        fprintf(stderr,"dossetsighandler failed %d\n", result);
                     45: 
1.1.1.2 ! root       46:     if( DosGetMachineMode( &c))
        !            47:        if (result = DosSetSigHandler(sig_handler, &address,
        !            48:                                      &oldaction, SIGA_ACCEPT,
        !            49:                                      SIGA_ACKNOWLEDGE ))
1.1       root       50:            fprintf(stderr,"dossetsighandler failed %d\n", result);
                     51: 
                     52:     do
1.1.1.2 ! root       53:        printf("Type a SPACE to terminate demo\n");
1.1       root       54:     while(getchar() != 0x20);
                     55: 
                     56:     fprintf(stderr,"Program terminating\n");
                     57:     exit(0);
                     58: }
                     59: /*
                     60:  * The signal handler routine must ACKNOWLEDGE the signal before it can
                     61:  * capture another (of the same number).  Since this routine runs as
                     62:  * thread 0 it can be preempted by another.  If it is
                     63:  * important that all signals be caught, then Thread 0 should be run as
                     64:  * a high priority thread and always snoozing. Of course, the
                     65:  * acknowlegement should be the first thing done in the handler.
                     66:  */
1.1.1.2 ! root       67: void APIENTRY sig_handler(sig_arg, sig_num)
        !            68: USHORT sig_arg, sig_num;
1.1       root       69: {
1.1.1.2 ! root       70:     USHORT signum, sigarg;
        !            71:     PFNSIGHANDLER address;
1.1       root       72:     int count;
                     73: 
                     74:     fprintf(stderr, "signum %u sigarg %u\n", sig_num, sig_arg);
                     75: 
1.1.1.2 ! root       76:     if (count = DosSetSigHandler( (void (pascal far *)())0L,
        !            77:                                  &address,
        !            78:                                  &sigarg, SIGA_ACKNOWLEDGE, sig_num))
1.1       root       79: 
                     80:        fprintf(stderr,"dossetsighandler failed %d\n", count);
                     81: }

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