insertd.c

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/* insertd.c - insertd */

#include <xinu.h>

/*------------------------------------------------------------------------
 *  insertd  -  Insert a process in delta list using delay as the key
 *------------------------------------------------------------------------
 */
status  insertd(            /* Assumes interrupts disabled  */
      pid32     pid,        /* ID of process to insert  */
      qid16     q,      /* ID of queue to use       */
      int32     key     /* Delay from "now" (in ms.)    */
    )
{
    int32   next;           /* Runs through the delta list  */
    int32   prev;           /* Follows next through the list*/

    if (isbadqid(q) || isbadpid(pid)) {
        return SYSERR;
    }

    prev = queuehead(q);
    next = queuetab[queuehead(q)].qnext;
    while ((next != queuetail(q)) && (queuetab[next].qkey <= key)) {
        key -= queuetab[next].qkey;
        prev = next;
        next = queuetab[next].qnext;
    }

    /* Insert new node between prev and next nodes */

    queuetab[pid].qnext = next;
    queuetab[pid].qprev = prev;
    queuetab[pid].qkey = key;
    queuetab[prev].qnext = pid;
    queuetab[next].qprev = pid;
    if (next != queuetail(q)) {
        queuetab[next].qkey -= key;
    }

    return OK;
}