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 2004 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  * Embedded Linked Lists
31  *
32  * Simple doubly-linked list implementation.  This implementation assumes that
33  * each list element contains an embedded cmd_list_t (previous and next
34  * pointers), which is typically the first member of the element struct.
35  * An additional cmd_list_t is used to store the head (l_next) and tail
36  * (l_prev) pointers.  The current head and tail list elements have their
37  * previous and next pointers set to NULL, respectively.
38  */
39 
40 #include <cmd_list.h>
41 #include <cmd.h>
42 
43 void
cmd_list_append(cmd_list_t * lp,void * new)44 cmd_list_append(cmd_list_t *lp, void *new)
45 {
46 	cmd_list_t *p = lp->l_prev;	/* p = tail list element */
47 	cmd_list_t *q = new;		/* q = new list element */
48 
49 	lp->l_prev = q;
50 	q->l_prev = p;
51 	q->l_next = NULL;
52 
53 	if (p != NULL)
54 		p->l_next = q;
55 	else
56 		lp->l_next = q;
57 }
58 
59 void
cmd_list_prepend(cmd_list_t * lp,void * new)60 cmd_list_prepend(cmd_list_t *lp, void *new)
61 {
62 	cmd_list_t *p = new;		/* p = new list element */
63 	cmd_list_t *q = lp->l_next;	/* q = head list element */
64 
65 	lp->l_next = p;
66 	p->l_prev = NULL;
67 	p->l_next = q;
68 
69 	if (q != NULL)
70 		q->l_prev = p;
71 	else
72 		lp->l_prev = p;
73 }
74 
75 void
cmd_list_insert_before(cmd_list_t * lp,void * before_me,void * new)76 cmd_list_insert_before(cmd_list_t *lp, void *before_me, void *new)
77 {
78 	cmd_list_t *p = before_me;
79 	cmd_list_t *q = new;
80 
81 	if (p == NULL || p->l_prev == NULL) {
82 		cmd_list_prepend(lp, new);
83 		return;
84 	}
85 
86 	q->l_prev = p->l_prev;
87 	q->l_next = p;
88 	p->l_prev = q;
89 	q->l_prev->l_next = q;
90 }
91 
92 void
cmd_list_insert_after(cmd_list_t * lp,void * after_me,void * new)93 cmd_list_insert_after(cmd_list_t *lp, void *after_me, void *new)
94 {
95 	cmd_list_t *p = after_me;
96 	cmd_list_t *q = new;
97 
98 	if (p == NULL || p->l_next == NULL) {
99 		cmd_list_append(lp, new);
100 		return;
101 	}
102 
103 	q->l_next = p->l_next;
104 	q->l_prev = p;
105 	p->l_next = q;
106 	q->l_next->l_prev = q;
107 }
108 
109 void
cmd_list_delete(cmd_list_t * lp,void * existing)110 cmd_list_delete(cmd_list_t *lp, void *existing)
111 {
112 	cmd_list_t *p = existing;
113 
114 	if (p->l_prev != NULL)
115 		p->l_prev->l_next = p->l_next;
116 	else
117 		lp->l_next = p->l_next;
118 
119 	if (p->l_next != NULL)
120 		p->l_next->l_prev = p->l_prev;
121 	else
122 		lp->l_prev = p->l_prev;
123 }
124