newqueue.c

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#include <xinu.h>

qid16 newqueue(void)
{
    static qid16 nextqid = NPROC; /* Next list in queuetab to use   */
    qid16 q;                      /* ID of allocated queue  */

    q = nextqid;
    if (q >= NQENT)
    { /* Check for table overflow   */
        return SYSERR;
    }

    nextqid += 2; /* Increment index for next call*/

    /* Initialize head and tail nodes to form an empty queue */

    queuetab[queuehead(q)].qnext = queuetail(q);
    queuetab[queuehead(q)].qprev = EMPTY;
    queuetab[queuehead(q)].qkey = MAXKEY;
    queuetab[queuetail(q)].qnext = EMPTY;
    queuetab[queuetail(q)].qprev = queuehead(q);
    queuetab[queuetail(q)].qkey = MINKEY;
    return q;
}