2 * Copyright (c) 2010 Your File System Inc. All rights reserved.
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
13 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR `AS IS'' AND ANY EXPRESS OR
14 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
15 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
16 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
17 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
18 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
19 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
20 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
21 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
22 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 /* A better queue implementation.
27 * This differs from the original queue implementation in that that would
28 * only allow a structure to be threaded onto a single queue. This permits
29 * a given object to be on multiple queues, providing that each queue has
30 * a place in the structure definition.
33 #ifndef OPENAFS_OPR_QUEUE_H
34 #define OPENAFS_OPR_QUEUE_H 1
40 #define NULL (void *)0
45 struct opr_queue *next;
46 struct opr_queue *prev;
49 #define opr_queue_Scan(head, cursor) \
50 cursor = (head)->next; cursor != (head); cursor = cursor->next
52 #define opr_queue_ScanSafe(head, cursor, store) \
53 cursor = (head)->next, store = cursor->next; \
55 cursor = store, store = store->next
57 #define opr_queue_ScanBackwards(head, cursor) \
58 cursor = (head)->prev; cursor != (head); cursor = cursor->prev
60 #define opr_queue_ScanBackwardsSafe(head, cursor, store) \
61 cursor = (head)->prev, store = cursor->prev; \
63 cursor = store, store = store->prev
66 opr_queue_Zero(struct opr_queue *q) {
67 q->prev = q->next = NULL;
71 opr_queue_Init(struct opr_queue *q) {
72 q->prev = q->next = q;
76 opr_queue_add(struct opr_queue *element,
77 struct opr_queue *before, struct opr_queue *after) {
78 after->prev = element;
79 element->next = after;
80 element->prev = before;
81 before->next = element;
85 opr_queue_Append(struct opr_queue *queue, struct opr_queue *element) {
86 opr_queue_add(element, queue->prev, queue);
90 opr_queue_Prepend(struct opr_queue *queue, struct opr_queue *element) {
91 opr_queue_add(element, queue, queue->next);
95 opr_queue_InsertBefore(struct opr_queue *exist, struct opr_queue *adding) {
96 /* This may seem back to front, but take a list A, B, C where we want
97 * to add 1 before B. So, we're adding 1 with A the element before,
98 * and B the element after, hence the following: */
99 opr_queue_add(adding, exist->prev, exist);
103 opr_queue_InsertAfter(struct opr_queue *exist, struct opr_queue *adding) {
104 opr_queue_add(adding, exist, exist->next);
108 opr_queue_Remove(struct opr_queue *element) {
109 element->next->prev = element->prev;
110 element->prev->next = element->next;
111 element->prev = NULL;
112 element->next = NULL;
116 opr_queue_IsEmpty(struct opr_queue *q) {
117 return (q->prev == q);
121 opr_queue_IsOnQueue(struct opr_queue *q) {
122 return (q->prev != NULL);
126 opr_queue_IsEnd(struct opr_queue *q, struct opr_queue *cursor) {
127 return (cursor->next == q);
131 opr_queue_Count(struct opr_queue *q) {
132 struct opr_queue *cursor;
135 for (opr_queue_Scan(q, cursor)) {
141 /* Remove the members before pivot from Q1, and append them to Q2 */
144 opr_queue_SplitBeforeAppend(struct opr_queue *q1, struct opr_queue *q2,
145 struct opr_queue *pivot) {
147 if (q1 == pivot->prev)
149 /* Add ourselves to the end of list 2 */
150 q2->prev->next = q1->next; /* end of list 2, is now the start of list 1 */
151 q1->next->prev = q2->prev;
152 pivot->prev->next = q2; /* entry before the pivot is it at end of q2 */
153 q2->prev = pivot->prev;
155 /* Pull ourselves out of list q1. */
160 /* Remove the members after the pivot from Q1, and prepend them onto Q2 */
162 opr_queue_SplitAfterPrepend(struct opr_queue *q1, struct opr_queue *q2,
163 struct opr_queue *pivot) {
165 if (q1 == pivot->next)
168 /* start of q2 has last element of q1 before it */
169 q2->next->prev = q1->prev;
170 q1->prev->next = q2->next;
171 /* item that we're breaking at (pivot->next) is at start of q2 */
172 q2->next = pivot->next;
173 pivot->next->prev = q2;
175 /* Q1 now ends after pivot */
181 opr_queue_SpliceAppend(struct opr_queue *target, struct opr_queue *source)
184 if (source->next == source)
187 /* Stick the contents of source onto the end of target */
188 target->prev->next = source->next;
189 source->next->prev = target->prev;
190 source->prev->next = target;
191 target->prev = source->prev;
193 /* Reinitialise source */
194 source->next = source->prev = source;
198 opr_queue_SplicePrepend(struct opr_queue *target, struct opr_queue *source)
201 if (source->next == source)
204 /* Contents of source go onto the beginning of target */
205 target->next->prev = source->prev;
206 source->prev->next = target->next;
207 source->next->prev = target;
208 target->next = source->next;
210 /* Reinitialise source */
211 source->next = source->prev = source;
214 #define opr_queue_Entry(queue, structure, member) \
215 ((structure *)((char *)(queue)-(char *)(&((structure *)NULL)->member)))
217 #define opr_queue_First(queue, structure, member) \
218 opr_queue_Entry((queue)->next, structure, member)
220 #define opr_queue_Last(queue, structure, member) \
221 opr_queue_Entry((queue)->prev, structure, member)
223 #define opr_queue_Next(entry, structure, member) \
224 opr_queue_Entry((entry)->next, structure, member)
226 #define opr_queue_Prev(entry, structure, member) \
227 opr_queue_Entry((entry)->prev, structure, member)