/*

 * CDDL HEADER START

 *

 * The contents of this file are subject to the terms of the

 * Common Development and Distribution License (the "License").

 * You may not use this file except in compliance with the License.

 *

 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE

 * or http://www.opensolaris.org/os/licensing.

 * See the License for the specific language governing permissions

 * and limitations under the License.

 *

 * When distributing Covered Code, include this CDDL HEADER in each

 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.

 * If applicable, add the following below this CDDL HEADER, with the

 * fields enclosed by brackets "[]" replaced with your own identifying

 * information: Portions Copyright [yyyy] [name of copyright owner]

 *

 * CDDL HEADER END

 */

/*

 * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.

 * Use is subject to license terms.

 */

/*	Copyright (c) 1988 AT&T	*/

/*	  All Rights Reserved  	*/

#pragma ident	"%Z%%M%	%I%	%E% SMI"

/*

 * insque() and remque() insert or remove an element from a queue.

 * The queue is built from a doubly linked list whose elements are

 * defined by a structure where the first member of the structure

 * points to the next element in the queue and the second member

 * of the structure points to the previous element in the queue.

 */

#pragma weak _insque = insque

#pragma weak _remque = remque

#include "lint.h"

#include <sys/types.h>

#include <stdlib.h>

#include <search.h>

void

insque(void *elem, void *pred)

{

	if (pred == NULL) {    /* This is the first element being inserted. */

		((struct qelem *)elem)->q_forw = NULL;

		((struct qelem *)elem)->q_back = NULL;

	} else if (((struct qelem *)pred)->q_forw == NULL) {

					/* The element is inserted at */

					/* the end of the queue. */

		((struct qelem *)elem)->q_forw = NULL;

		((struct qelem *)elem)->q_back = pred;

		((struct qelem *)pred)->q_forw = elem;

	} else {		/* The element is inserted in the middle of */

				/* the queue. */

		((struct qelem *)elem)->q_forw = ((struct qelem *)pred)->q_forw;

		((struct qelem *)elem)->q_back = pred;

		((struct qelem *)pred)->q_forw->q_back = elem;

		((struct qelem *)pred)->q_forw = elem;

	}

}

void

remque(void *elem)

{

	if (((struct qelem *)elem)->q_back == NULL) {

					/* The first element is removed. */

		if (((struct qelem *)elem)->q_forw == NULL)

					/* The only element is removed. */

			return;

		((struct qelem *)elem)->q_forw->q_back = NULL;

	} else if (((struct qelem *)elem)->q_forw == NULL) {

					/* The last element is removed */

		((struct qelem *)elem)->q_back->q_forw = NULL;

	} else {	/* The middle element is removed. */

		((struct qelem *)elem)->q_back->q_forw =

		    ((struct qelem *)elem)->q_forw;

		((struct qelem *)elem)->q_forw->q_back =

		    ((struct qelem *)elem)->q_back;

	}

}