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Annotation of xinu/sys/getstk.c, revision 1.1.1.1

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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