/*
 * 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 2003 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*
 * Simple doubly-linked list implementation.  This implementation assumes that
 * each list element contains an embedded dt_list_t (previous and next
 * pointers), which is typically the first member of the element struct.
 * An additional dt_list_t is used to store the head (dl_next) and tail
 * (dl_prev) pointers.  The current head and tail list elements have their
 * previous and next pointers set to NULL, respectively.
 */

#include <unistd.h>
#include <assert.h>
#include <dt_list.h>

void
dt_list_append(dt_list_t *dlp, void *new)
{
        dt_list_t *p = dlp->dl_prev;    /* p = tail list element */
        dt_list_t *q = new;             /* q = new list element */

        dlp->dl_prev = q;
        q->dl_prev = p;
        q->dl_next = NULL;

        if (p != NULL) {
                assert(p->dl_next == NULL);
                p->dl_next = q;
        } else {
                assert(dlp->dl_next == NULL);
                dlp->dl_next = q;
        }
}

void
dt_list_prepend(dt_list_t *dlp, void *new)
{
        dt_list_t *p = new;             /* p = new list element */
        dt_list_t *q = dlp->dl_next;    /* q = head list element */

        dlp->dl_next = p;
        p->dl_prev = NULL;
        p->dl_next = q;

        if (q != NULL) {
                assert(q->dl_prev == NULL);
                q->dl_prev = p;
        } else {
                assert(dlp->dl_prev == NULL);
                dlp->dl_prev = p;
        }
}

void
dt_list_insert(dt_list_t *dlp, void *after_me, void *new)
{
        dt_list_t *p = after_me;
        dt_list_t *q = new;

        if (p == NULL || p->dl_next == NULL) {
                dt_list_append(dlp, new);
                return;
        }

        q->dl_next = p->dl_next;
        q->dl_prev = p;
        p->dl_next = q;
        q->dl_next->dl_prev = q;
}

void
dt_list_delete(dt_list_t *dlp, void *existing)
{
        dt_list_t *p = existing;

        if (p->dl_prev != NULL)
                p->dl_prev->dl_next = p->dl_next;
        else
                dlp->dl_next = p->dl_next;

        if (p->dl_next != NULL)
                p->dl_next->dl_prev = p->dl_prev;
        else
                dlp->dl_prev = p->dl_prev;
}