queue.c revision 7c478bd95313f5f23a4c958a745db2134aa03244
/*
* CDDL HEADER START
*
* The contents of this file are subject to the terms of the
* Common Development and Distribution License, Version 1.0 only
* (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 (c) 1994, by Sun Microsytems, Inc.
*/
#pragma ident "%Z%%M% %I% %E% SMI"
/*
* Includes
*/
#include "queue.h"
#include "new.h"
/*
* queue_init() - initializes a queue_node to be unlinked.
*/
void
queue_init(queue_node_t * q)
{
q->next_p = q->prev_p = q;
} /* end queue_init */
/*
* queue_prepend() - prepends a queue_node to another in a list
*/
queue_node_t *
queue_prepend(queue_node_t * h, queue_node_t * q)
{
if (!h)
return ((q) ? q : NULL);
if (q) {
queue_node_t *qtail_p = q->prev_p;
queue_node_t *hnode_p = h->next_p;
hnode_p->prev_p = qtail_p;
h->next_p = q;
q->prev_p = h;
qtail_p->next_p = hnode_p;
}
return (h);
} /* end queue_prepend */
/*
* queue_append() - appends a queue_node to another in a list
*/
queue_node_t *
queue_append(queue_node_t * h, queue_node_t * q)
{
if (!h)
return ((q) ? q : NULL);
if (q) {
queue_node_t *htail_p = h->prev_p;
queue_node_t *qtail_p = q->prev_p;
h->prev_p = qtail_p;
htail_p->next_p = q;
q->prev_p = htail_p;
qtail_p->next_p = h;
}
return (h);
} /* end queue_append */
/*
* queue_remove() - removes a node from a list, returns a pointer to the next
* node in the list.
*/
queue_node_t *
queue_remove(queue_node_t * q)
{
queue_node_t *n;
n = q->next_p;
if (queue_isempty(q))
return (NULL);
q->next_p->prev_p = q->prev_p;
q->prev_p->next_p = q->next_p;
q->next_p = q->prev_p = q;
return (n);
} /* end queue_remove */
/*
* queue_isempty()
*/
boolean_t
queue_isempty(queue_node_t * q)
{
return ((q->next_p == q));
} /* queue_isempty */
/*
* queue_next() - returns the next element in a queue, or NULL if the
* supplied previous item was the last.
*/
queue_node_t *
queue_next(queue_node_t * h, queue_node_t * q)
{
if (!h)
return (NULL);
if (!q)
return (h);
if (q->next_p == h)
return (NULL);
return (q->next_p);
} /* end queue_next */