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Annotation of 43BSD/contrib/icon/functions/pull.c, revision 1.1

1.1     ! root        1: #include "../h/rt.h"
        !             2: 
        !             3: /*
        !             4:  * pull(x) - pull an element from end of list x.
        !             5:  */
        !             6: 
        !             7: Xpull(nargs, arg1, arg0)
        !             8: int nargs;
        !             9: struct descrip arg1, arg0;
        !            10:    {
        !            11:    register int i;
        !            12:    register struct b_list *hp;
        !            13:    register struct b_lelem *bp;
        !            14:    extern struct b_lelem *alclstb();
        !            15: 
        !            16:    /*
        !            17:     * x must be a list.
        !            18:     */
        !            19:    DeRef(arg1)
        !            20:    if (QUAL(arg1) || TYPE(arg1) != T_LIST)
        !            21:       runerr(108, &arg1);
        !            22: 
        !            23:    /*
        !            24:     * Point at list header block and fail if the list is empty.
        !            25:     */
        !            26:    hp = (struct b_list *) BLKLOC(arg1);
        !            27:    if (hp->cursize <= 0)
        !            28:       fail();
        !            29:    /*
        !            30:     * Point bp at the last list element block.  If the last block has no
        !            31:     *  elements in use, point bp at the previous list element block.
        !            32:     */
        !            33:    bp = (struct b_lelem *) BLKLOC(hp->listtail);
        !            34:    if (bp->nused <= 0) {
        !            35:       bp = (struct b_lelem *) BLKLOC(bp->listprev);
        !            36:       BLKLOC(hp->listtail) = (union block *) bp;
        !            37:       bp->listnext = nulldesc;
        !            38:       }
        !            39:    /*
        !            40:     * Set i to position of last element and assign the element to
        !            41:     *  arg0 for return.  Decrement the usage count for the block
        !            42:     *  and the size of the list.
        !            43:     */
        !            44:    i = bp->first + bp->nused - 1;
        !            45:    if (i >= bp->nelem)
        !            46:       i -= bp->nelem;
        !            47:    arg0 = bp->lslots[i];
        !            48:    bp->nused--;
        !            49:    hp->cursize--;
        !            50:    }
        !            51: 
        !            52: Procblock(pull,1)

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