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

1.1     ! root        1: /* getmem.c - getmem */
        !             2: 
        !             3: #include <conf.h>
        !             4: #include <kernel.h>
        !             5: #include <mem.h>
        !             6: 
        !             7: /*------------------------------------------------------------------------
        !             8:  * getmem  --  allocate heap storage, returning lowest integer address
        !             9:  *------------------------------------------------------------------------
        !            10:  */
        !            11: SYSCALL        *getmem(nbytes)
        !            12:        unsigned nbytes;
        !            13: {
        !            14:        PStype  ps;
        !            15:        struct  mblock  *p, *q, *leftover;
        !            16: 
        !            17:        disable(ps);
        !            18:        if (nbytes<=0 || (char *)memlist.mnext==NULL) {
        !            19:                restore(ps);
        !            20:                return( (int *)SYSERR);
        !            21:        }
        !            22:        nbytes = (unsigned) roundew(nbytes);
        !            23:        for (q= &memlist,p=memlist.mnext ; (char *)p!=NULL ; q=p,p=p->mnext)
        !            24:                if ( p->mlen == nbytes) {
        !            25:                        q->mnext = p->mnext;
        !            26:                        restore(ps);
        !            27:                        return( (int *)p );
        !            28:                } else if ( p->mlen > nbytes ) {
        !            29:                        leftover = (struct mblock *)( (unsigned)p + nbytes );
        !            30:                        q->mnext = leftover;
        !            31:                        leftover->mnext = p->mnext;
        !            32:                        leftover->mlen = p->mlen - nbytes;
        !            33:                        restore(ps);
        !            34:                        return( (int *)p );
        !            35:                }
        !            36:        restore(ps);
        !            37:        return( (int *)SYSERR );
        !            38: }

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