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Annotation of os2sdk/demos/examples/share/shrchild.c, revision 1.1

1.1     ! root        1: /*
        !             2:  * This is the child process exec'd asynchronously from the child.c.
        !             3:  */
        !             4: 
        !             5: #include <doscalls.h>          /* necessary whenever doscalls are made */
        !             6: #include "share.h"             /* common shared memory declarations */
        !             7: 
        !             8: main()
        !             9: {
        !            10:        unsigned                Selector;
        !            11:        unsigned                rc;             /* return code */
        !            12:        unsigned                nBytes;
        !            13:        char                    c;
        !            14:        struct ShareRec         *SmemPtr;       /* shared memory pointer */
        !            15: 
        !            16:        /* get selector to the shared memory segment defined in parent */
        !            17: 
        !            18:        if (rc = DOSGETSHRSEG( (char *) SHRSEGNAME,
        !            19:                               (unsigned *) &Selector ))  {
        !            20:                DOSEXIT(1, 0);
        !            21:        }
        !            22: 
        !            23:        /* Get a far pointer from a 16 bit selector */
        !            24: 
        !            25:        SmemPtr = (struct ShareRec *) GETSEGPTR(Selector, 0);
        !            26:        
        !            27:        for (;;) {
        !            28: 
        !            29:            /* block if buffer empty */
        !            30:            DOSSEMWAIT((long)&(SmemPtr->emptysem), WAITFOREVER);
        !            31: 
        !            32:            /* mutual exclusion on buffer pointers */
        !            33:            DOSSEMREQUEST((long)&(SmemPtr->mutexsem), WAITFOREVER);
        !            34:            c = SmemPtr->CircBuffer[SmemPtr->tail];     /* get next char */
        !            35:            SmemPtr->tail++;                /* step pointer */
        !            36:            SmemPtr->tail %= CIRCBUFSIZE;   /* wrap at end  */
        !            37:            if (SmemPtr->tail == SmemPtr->head)
        !            38:                DOSSEMSET((long)&(SmemPtr->emptysem));
        !            39:            DOSSEMCLEAR((long)&(SmemPtr->mutexsem));
        !            40: 
        !            41:            DOSSEMCLEAR((long)&(SmemPtr->fullsem));
        !            42: 
        !            43:            DOSWRITE( 1, (char *) &c, 1, &nBytes );     /* display next char */
        !            44:            DOSSLEEP(1000L);    /* max 1 per sec to demo buffering & sems */
        !            45:        }
        !            46: }

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