Annotation of prex/sys/lib/queue.c, Revision 1.1.1.1
1.1 nbrk 1: /*-
2: * Copyright (c) 2005, Kohsuke Ohtani
3: * All rights reserved.
4: *
5: * Redistribution and use in source and binary forms, with or without
6: * modification, are permitted provided that the following conditions
7: * are met:
8: * 1. Redistributions of source code must retain the above copyright
9: * notice, this list of conditions and the following disclaimer.
10: * 2. Redistributions in binary form must reproduce the above copyright
11: * notice, this list of conditions and the following disclaimer in the
12: * documentation and/or other materials provided with the distribution.
13: * 3. Neither the name of the author nor the names of any co-contributors
14: * may be used to endorse or promote products derived from this software
15: * without specific prior written permission.
16: *
17: * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
18: * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19: * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20: * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
21: * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22: * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23: * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24: * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25: * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26: * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27: * SUCH DAMAGE.
28: */
29:
30: /*
31: * queue.c - generic queue management library
32: */
33:
34: #include <queue.h>
35:
36: /*
37: * Insert element at tail of queue
38: */
39: void
40: enqueue(queue_t head, queue_t item)
41: {
42: item->next = head;
43: item->prev = head->prev;
44: item->prev->next = item;
45: head->prev = item;
46: }
47:
48: /*
49: * Remove and return element of head of queue
50: */
51: queue_t
52: dequeue(queue_t head)
53: {
54: queue_t item;
55:
56: if (head->next == head)
57: return ((queue_t)0);
58: item = head->next;
59: item->next->prev = head;
60: head->next = item->next;
61: return item;
62: }
63:
64: /*
65: * Insert element after specified element
66: */
67: void
68: queue_insert(queue_t prev, queue_t item)
69: {
70: item->prev = prev;
71: item->next = prev->next;
72: prev->next->prev = item;
73: prev->next = item;
74: }
75:
76: /*
77: * Remove specified element from queue
78: */
79: void
80: queue_remove(queue_t item)
81: {
82: item->prev->next = item->next;
83: item->next->prev = item->prev;
84: }
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