added Chris Provenzano's light-weight threading library.

[unix-history] / lib / libpthread / pthreads / queue.c

/* ==== queue.c ============================================================
* Copyright (c) 1993 by Chris Provenzano, proven@athena.mit.edu
*
* Description : Queue functions.
*
*  1.00 93/07/15 proven
*      -Started coding this file.
*/

#include <pthread/copyright.h>
#include <pthread.h>

/*
* All routines in this file assume that the queue has been appropriatly
* locked.
*/

/* ==========================================================================
* pthread_queue_init()
*/
void pthread_queue_init(struct pthread_queue *queue)
{
       queue->q_next = NULL;
       queue->q_last = NULL;
       queue->q_data = NULL;
}

/* ==========================================================================
* pthread_queue_enq()
*/
void pthread_queue_enq(struct pthread_queue *queue, struct pthread *thread)
{
       if (queue->q_last) {
               queue->q_last->next = thread;
       } else {
               queue->q_next = thread;
       }
       queue->q_last = thread;
       thread->queue = queue;
       thread->next = NULL;
       
}

/* ==========================================================================
* pthread_queue_get()
*/
struct pthread *pthread_queue_get(struct pthread_queue *queue)
{
       return(queue->q_next);
}

/* ==========================================================================
* pthread_queue_deq()
*/
struct pthread *pthread_queue_deq(struct pthread_queue *queue)
{
       struct pthread *thread = NULL;

       if (queue->q_next) {
               thread = queue->q_next;
               if (!(queue->q_next = queue->q_next->next)) {
                       queue->q_last = NULL;
               }
               thread->queue = NULL;
               thread->next = NULL;
       }
       return(thread);
}

/* ==========================================================================
* pthread_queue_remove()
*/
void pthread_queue_remove(struct pthread_queue *queue, struct pthread *thread)
{
       struct pthread **current = &(queue->q_next);
       struct pthread *prev = NULL;

       while (*current) {
               if (*current == thread) {
                       if ((*current)->next) {
                               *current = (*current)->next;
                       } else {
                               queue->q_last = prev;
                               *current = NULL;
                       }
               }
               prev = *current;
               current = &((*current)->next);
       }
       thread->queue = NULL;
       thread->next = NULL;
}