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

1.1     ! root        1: /* queue.c - dequeue, enqueue */
        !             2: 
        !             3: #include <conf.h>
        !             4: #include <kernel.h>
        !             5: #include <q.h>
        !             6: 
        !             7: /*------------------------------------------------------------------------
        !             8:  * enqueue  -- insert an item at the tail of a list
        !             9:  *------------------------------------------------------------------------
        !            10:  */
        !            11: int    enqueue(item, tail)
        !            12:        int     item;                   /* item to enqueue on a list    */
        !            13:        int     tail;                   /* index in q of list tail      */
        !            14: {
        !            15:        struct  qent    *tptr;          /* points to tail entry         */
        !            16:        struct  qent    *mptr;          /* points to item entry         */
        !            17: 
        !            18:        tptr = &q[tail];
        !            19:        mptr = &q[item];
        !            20:        mptr->qnext = tail;
        !            21:        mptr->qprev = tptr->qprev;
        !            22:        q[tptr->qprev].qnext = item;
        !            23:        tptr->qprev = item;
        !            24:        return(item);
        !            25: }
        !            26: 
        !            27: 
        !            28: /*------------------------------------------------------------------------
        !            29:  *  dequeue  --  remove an item from a list and return it
        !            30:  *------------------------------------------------------------------------
        !            31:  */
        !            32: int    dequeue(item)
        !            33:        int     item;
        !            34: {
        !            35:        struct  qent    *mptr;          /* pointer to q entry for item  */
        !            36: 
        !            37:        mptr = &q[item];
        !            38:        q[mptr->qprev].qnext = mptr->qnext;
        !            39:        q[mptr->qnext].qprev = mptr->qprev;
        !            40:        return(item);
        !            41: }

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