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Annotation of xinu/sys/getstk.c, revision 1.1

1.1     ! root        1: /* getstk.c - getstk */
        !             2: 
        !             3: #include <conf.h>
        !             4: #include <kernel.h>
        !             5: #include <mem.h>
        !             6: 
        !             7: /*------------------------------------------------------------------------
        !             8:  * getstk  --  allocate stack memory, returning address of topmost int
        !             9:  *------------------------------------------------------------------------
        !            10:  */
        !            11: SYSCALL        *getstk(nbytes)
        !            12:        unsigned  int nbytes;
        !            13: {
        !            14:        PStype  ps;
        !            15:        struct  mblock  *p, *q; /* q follows p along memlist            */
        !            16:        struct  mblock  *fits, *fitsq;
        !            17:        unsigned len;
        !            18: 
        !            19:        disable(ps);
        !            20:        if (nbytes == 0) {
        !            21:                restore(ps);
        !            22:                return( (int *)SYSERR );
        !            23:        }
        !            24:        nbytes = (unsigned)roundew(nbytes);
        !            25:        fits = (struct mblock *)NULL;
        !            26:        q = &memlist;
        !            27:        for (p = q->mnext ; (char *)p != NULL ; q = p,p = p->mnext)
        !            28:                if ( p->mlen >= nbytes) {
        !            29:                        fitsq = q;
        !            30:                        fits = p;
        !            31:                }
        !            32:        if ((char *)fits == NULL) {
        !            33:                restore(ps);
        !            34:                return( (int *)SYSERR );
        !            35:        }
        !            36:        if (nbytes == (len = fits->mlen) ) {
        !            37:                fitsq->mnext = fits->mnext;
        !            38:        } else {
        !            39:                fits->mlen -= nbytes;
        !            40:        }
        !            41:        fits = (struct mblock *)((unsigned)fits + len - sizeof(int));
        !            42:        restore(ps);
        !            43:        return( (int *)fits );
        !            44: }

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