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 (c) 1994, by Sun Microsytems, Inc.
24 */
25
26 #pragma ident "%Z%%M% %I% %E% SMI"
27
28 /*
29 * Includes
30 */
31
32 #include "queue.h"
33 #include "new.h"
34
35
36 /*
37 * queue_init() - initializes a queue_node to be unlinked.
38 */
39
40 void
queue_init(queue_node_t * q)41 queue_init(queue_node_t * q)
42 {
43 q->next_p = q->prev_p = q;
44
45 } /* end queue_init */
46
47
48 /*
49 * queue_prepend() - prepends a queue_node to another in a list
50 */
51
52 queue_node_t *
queue_prepend(queue_node_t * h,queue_node_t * q)53 queue_prepend(queue_node_t * h, queue_node_t * q)
54 {
55 if (!h)
56 return ((q) ? q : NULL);
57
58 if (q) {
59 queue_node_t *qtail_p = q->prev_p;
60 queue_node_t *hnode_p = h->next_p;
61
62 hnode_p->prev_p = qtail_p;
63 h->next_p = q;
64
65 q->prev_p = h;
66 qtail_p->next_p = hnode_p;
67 }
68 return (h);
69
70 } /* end queue_prepend */
71
72
73 /*
74 * queue_append() - appends a queue_node to another in a list
75 */
76
77 queue_node_t *
queue_append(queue_node_t * h,queue_node_t * q)78 queue_append(queue_node_t * h, queue_node_t * q)
79 {
80 if (!h)
81 return ((q) ? q : NULL);
82
83 if (q) {
84 queue_node_t *htail_p = h->prev_p;
85 queue_node_t *qtail_p = q->prev_p;
86
87 h->prev_p = qtail_p;
88 htail_p->next_p = q;
89
90 q->prev_p = htail_p;
91 qtail_p->next_p = h;
92 }
93 return (h);
94
95 } /* end queue_append */
96
97
98 /*
99 * queue_remove() - removes a node from a list, returns a pointer to the next
100 * node in the list.
101 */
102
103 queue_node_t *
queue_remove(queue_node_t * q)104 queue_remove(queue_node_t * q)
105 {
106 queue_node_t *n;
107
108 n = q->next_p;
109
110 if (queue_isempty(q))
111 return (NULL);
112
113 q->next_p->prev_p = q->prev_p;
114 q->prev_p->next_p = q->next_p;
115
116 q->next_p = q->prev_p = q;
117
118 return (n);
119
120 } /* end queue_remove */
121
122
123 /*
124 * queue_isempty()
125 */
126
127 boolean_t
queue_isempty(queue_node_t * q)128 queue_isempty(queue_node_t * q)
129 {
130 return ((q->next_p == q));
131
132 } /* queue_isempty */
133
134
135 /*
136 * queue_next() - returns the next element in a queue, or NULL if the
137 * supplied previous item was the last.
138 */
139
140 queue_node_t *
queue_next(queue_node_t * h,queue_node_t * q)141 queue_next(queue_node_t * h, queue_node_t * q)
142 {
143 if (!h)
144 return (NULL);
145
146 if (!q)
147 return (h);
148
149 if (q->next_p == h)
150 return (NULL);
151
152 return (q->next_p);
153
154 } /* end queue_next */
155