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

1.1       root        1: /* freemem.c - freemem */
                      2: 
                      3: #include <conf.h>
                      4: #include <kernel.h>
                      5: #include <mem.h>
                      6: 
                      7: /*------------------------------------------------------------------------
                      8:  *  freemem  --  free a memory block, returning it to memlist
                      9:  *------------------------------------------------------------------------
                     10:  */
                     11: SYSCALL        freemem(block, size)
                     12:        struct  mblock  *block;
                     13:        unsigned size;
                     14: {
                     15:        PStype  ps;
                     16:        struct  mblock  *p, *q;
                     17:        unsigned top;
                     18: 
                     19:        if (size==0 || (unsigned)block>(unsigned)maxaddr
                     20:                    || ((unsigned)block)<((unsigned)&end))
                     21:                return(SYSERR);
                     22:        size = (unsigned)roundew(size);
                     23:        disable(ps);
                     24:        for( p=memlist.mnext,q= &memlist ; (char *)p!=NULL && p<block ;
                     25:                    q=p,p=p->mnext )
                     26:                ;
                     27:        if ((top=q->mlen+(unsigned)q)>(unsigned)block && q!= &memlist ||
                     28:                    (char *)p!=NULL && (size+(unsigned)block) > (unsigned)p ) {
                     29:                restore(ps);
                     30:                return(SYSERR);
                     31:        }
                     32:        if ( q!= &memlist && top == (unsigned)block )
                     33:                q->mlen += size;
                     34:        else {
                     35:                block->mlen = size;
                     36:                block->mnext = p;
                     37:                q->mnext = block;
                     38:                q = block;
                     39:        }
                     40:        if ( (unsigned)( q->mlen + (unsigned)q ) == (unsigned)p) {
                     41:                q->mlen += p->mlen;
                     42:                q->mnext = p->mnext;
                     43:        }
                     44:        restore(ps);
                     45:        return(OK);
                     46: }

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