insque.c revision 7257d1b4d25bfac0c802847390e98a464fd787ac
/*
* 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;
}
}