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 /*
28  * Simple doubly-linked list implementation.  This implementation assumes that
29  * each list element contains an embedded dt_list_t (previous and next
30  * pointers), which is typically the first member of the element struct.
31  * An additional dt_list_t is used to store the head (dl_next) and tail
32  * (dl_prev) pointers.  The current head and tail list elements have their
33  * previous and next pointers set to NULL, respectively.
34  */
35 
36 #include <unistd.h>
37 #include <assert.h>
38 #include <dt_list.h>
39 
40 void
dt_list_append(dt_list_t * dlp,void * new)41 dt_list_append(dt_list_t *dlp, void *new)
42 {
43 	dt_list_t *p = dlp->dl_prev;	/* p = tail list element */
44 	dt_list_t *q = new;		/* q = new list element */
45 
46 	dlp->dl_prev = q;
47 	q->dl_prev = p;
48 	q->dl_next = NULL;
49 
50 	if (p != NULL) {
51 		assert(p->dl_next == NULL);
52 		p->dl_next = q;
53 	} else {
54 		assert(dlp->dl_next == NULL);
55 		dlp->dl_next = q;
56 	}
57 }
58 
59 void
dt_list_prepend(dt_list_t * dlp,void * new)60 dt_list_prepend(dt_list_t *dlp, void *new)
61 {
62 	dt_list_t *p = new;		/* p = new list element */
63 	dt_list_t *q = dlp->dl_next;	/* q = head list element */
64 
65 	dlp->dl_next = p;
66 	p->dl_prev = NULL;
67 	p->dl_next = q;
68 
69 	if (q != NULL) {
70 		assert(q->dl_prev == NULL);
71 		q->dl_prev = p;
72 	} else {
73 		assert(dlp->dl_prev == NULL);
74 		dlp->dl_prev = p;
75 	}
76 }
77 
78 void
dt_list_insert(dt_list_t * dlp,void * after_me,void * new)79 dt_list_insert(dt_list_t *dlp, void *after_me, void *new)
80 {
81 	dt_list_t *p = after_me;
82 	dt_list_t *q = new;
83 
84 	if (p == NULL || p->dl_next == NULL) {
85 		dt_list_append(dlp, new);
86 		return;
87 	}
88 
89 	q->dl_next = p->dl_next;
90 	q->dl_prev = p;
91 	p->dl_next = q;
92 	q->dl_next->dl_prev = q;
93 }
94 
95 void
dt_list_delete(dt_list_t * dlp,void * existing)96 dt_list_delete(dt_list_t *dlp, void *existing)
97 {
98 	dt_list_t *p = existing;
99 
100 	if (p->dl_prev != NULL)
101 		p->dl_prev->dl_next = p->dl_next;
102 	else
103 		dlp->dl_next = p->dl_next;
104 
105 	if (p->dl_next != NULL)
106 		p->dl_next->dl_prev = p->dl_prev;
107 	else
108 		dlp->dl_prev = p->dl_prev;
109 }
110