/* ==== prio_queue.c ==========================================================
 * Copyright (c) 1994 by Chris Provenzano, proven@mit.edu
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *  This product includes software developed by Chris Provenzano.
 * 4. The name of Chris Provenzano may not be used to endorse or promote 
 *	  products derived from this software without specific prior written
 *	  permission.
 *
 * THIS SOFTWARE IS PROVIDED BY CHRIS PROVENZANO ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL CHRIS PROVENZANO BE LIABLE FOR ANY 
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR 
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 
 * SUCH DAMAGE.
 *
 * Description : Priority Queue functions.
 *
 *  1.00 94/09/19 proven
 *      -Started coding this file.
 */

#ifndef lint
static const char rcsid[] = "$Id: prio_queue.c,v 1.2 1994/10/04 04:10:28 raeburn Exp $";
#endif

#include <pthread.h>

/* A thread when it becomes eligeble to run is placed on the run queue.
  This requires locking the kernel lock
*/

/* ==========================================================================
 * pthread_prio_queue_init()
 */
void pthread_prio_queue_init(struct pthread_prio_queue * queue)
{
	int i;

	for (i = 0; i < PTHREAD_MAX_PRIORITY; i++) {
		queue->level[i].first = NULL;
		queue->level[i].last = NULL;
	}
	queue->next = NULL;
	queue->data = NULL;
}

/* ==========================================================================
 * pthread_priority_enq()
 */
void pthread_prio_queue_enq(struct pthread_prio_queue * queue,
  struct pthread * pthread)
{
	int priority = pthread->pthread_priority;

	if (queue->next) {
		if (queue->level[priority].first) {
			pthread->next = (queue->level[priority].last)->next;
			(queue->level[priority].last)->next = pthread;
			queue->level[priority].last = pthread;
			return;
		} 
		if (priority != PTHREAD_MAX_PRIORITY) {
			int prev_priority;
			/* Find first higher priority thread queued on queue */
			for (prev_priority = priority + 1; prev_priority !=
			  PTHREAD_MAX_PRIORITY; prev_priority++) {
				if (queue->level[prev_priority].first) {
					pthread->next = (queue->level[prev_priority].last)->next;
					(queue->level[prev_priority].last)->next = pthread;
					queue->level[priority].first = pthread;
					queue->level[priority].last = pthread;
					return;
				}
			}
		}
	}
	queue->level[priority].first = pthread;
	queue->level[priority].last = pthread;
	pthread->next = queue->next;
	queue->next = pthread;
}

/* ==========================================================================
 * pthread_prio_queue_deq()
 */
struct pthread * pthread_prio_queue_deq(struct pthread_prio_queue * queue)
{
	struct pthread * pthread;
	int priority;

	if (pthread = queue->next) {
		priority = queue->next->pthread_priority;
		if (queue->level[priority].first == queue->level[priority].last) {
			queue->level[priority].first = NULL;
			queue->level[priority].last = NULL;
		} else {
			queue->level[priority].first = pthread->next;
		}
		queue->next = pthread->next;	
		pthread->next = NULL;
	}
	return(pthread);
}