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Annotation of xinu/sys/freemem.c, revision 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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