1/*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License, Version 1.0 only
6 * (the "License").  You may not use this file except in compliance
7 * with the License.
8 *
9 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
10 * or http://www.opensolaris.org/os/licensing.
11 * See the License for the specific language governing permissions
12 * and limitations under the License.
13 *
14 * When distributing Covered Code, include this CDDL HEADER in each
15 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
16 * If applicable, add the following below this CDDL HEADER, with the
17 * fields enclosed by brackets "[]" replaced with your own identifying
18 * information: Portions Copyright [yyyy] [name of copyright owner]
19 *
20 * CDDL HEADER END
21 */
22/*
23 * Copyright 2003 Sun Microsystems, Inc.  All rights reserved.
24 * Use is subject to license terms.
25 */
26
27#pragma ident	"%Z%%M%	%I%	%E% SMI"
28
29/*
30 * Simple doubly-linked list implementation.  This implementation assumes that
31 * each list element contains an embedded dt_list_t (previous and next
32 * pointers), which is typically the first member of the element struct.
33 * An additional dt_list_t is used to store the head (dl_next) and tail
34 * (dl_prev) pointers.  The current head and tail list elements have their
35 * previous and next pointers set to NULL, respectively.
36 */
37
38#include <unistd.h>
39#include <assert.h>
40#include <dt_list.h>
41
42void
43dt_list_append(dt_list_t *dlp, void *new)
44{
45	dt_list_t *p = dlp->dl_prev;	/* p = tail list element */
46	dt_list_t *q = new;		/* q = new list element */
47
48	dlp->dl_prev = q;
49	q->dl_prev = p;
50	q->dl_next = NULL;
51
52	if (p != NULL) {
53		assert(p->dl_next == NULL);
54		p->dl_next = q;
55	} else {
56		assert(dlp->dl_next == NULL);
57		dlp->dl_next = q;
58	}
59}
60
61void
62dt_list_prepend(dt_list_t *dlp, void *new)
63{
64	dt_list_t *p = new;		/* p = new list element */
65	dt_list_t *q = dlp->dl_next;	/* q = head list element */
66
67	dlp->dl_next = p;
68	p->dl_prev = NULL;
69	p->dl_next = q;
70
71	if (q != NULL) {
72		assert(q->dl_prev == NULL);
73		q->dl_prev = p;
74	} else {
75		assert(dlp->dl_prev == NULL);
76		dlp->dl_prev = p;
77	}
78}
79
80void
81dt_list_insert(dt_list_t *dlp, void *after_me, void *new)
82{
83	dt_list_t *p = after_me;
84	dt_list_t *q = new;
85
86	if (p == NULL || p->dl_next == NULL) {
87		dt_list_append(dlp, new);
88		return;
89	}
90
91	q->dl_next = p->dl_next;
92	q->dl_prev = p;
93	p->dl_next = q;
94	q->dl_next->dl_prev = q;
95}
96
97void
98dt_list_delete(dt_list_t *dlp, void *existing)
99{
100	dt_list_t *p = existing;
101
102	if (p->dl_prev != NULL)
103		p->dl_prev->dl_next = p->dl_next;
104	else
105		dlp->dl_next = p->dl_next;
106
107	if (p->dl_next != NULL)
108		p->dl_next->dl_prev = p->dl_prev;
109	else
110		dlp->dl_prev = p->dl_prev;
111}
112