1/* Copyright (c) 2013, Ben Noordhuis <info@bnoordhuis.nl>
2 *
3 * Permission to use, copy, modify, and/or distribute this software for any
4 * purpose with or without fee is hereby granted, provided that the above
5 * copyright notice and this permission notice appear in all copies.
6 *
7 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
8 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
9 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
10 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
11 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
12 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
13 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
14 */
15
16#ifndef QUEUE_H_
17#define QUEUE_H_
18
19#include <stddef.h>
20
21typedef void *QUEUE[2];
22
23/* Private macros. */
24#define QUEUE_NEXT(q) (*(QUEUE **) &((*(q))[0]))
25#define QUEUE_PREV(q) (*(QUEUE **) &((*(q))[1]))
26#define QUEUE_PREV_NEXT(q) (QUEUE_NEXT(QUEUE_PREV(q)))
27#define QUEUE_NEXT_PREV(q) (QUEUE_PREV(QUEUE_NEXT(q)))
28
29/* Public macros. */
30#define QUEUE_DATA(ptr, type, field) \
31 ((type *) ((char *) (ptr) - offsetof(type, field)))
32
33/* Important note: mutating the list while QUEUE_FOREACH is
34 * iterating over its elements results in undefined behavior.
35 */
36#define QUEUE_FOREACH(q, h) \
37 for ((q) = QUEUE_NEXT(h); (q) != (h); (q) = QUEUE_NEXT(q))
38
39#define QUEUE_EMPTY(q) \
40 ((const QUEUE *) (q) == (const QUEUE *) QUEUE_NEXT(q))
41
42#define QUEUE_HEAD(q) \
43 (QUEUE_NEXT(q))
44
45#define QUEUE_INIT(q) \
46 do { \
47 QUEUE_NEXT(q) = (q); \
48 QUEUE_PREV(q) = (q); \
49 } \
50 while (0)
51
52#define QUEUE_ADD(h, n) \
53 do { \
54 QUEUE_PREV_NEXT(h) = QUEUE_NEXT(n); \
55 QUEUE_NEXT_PREV(n) = QUEUE_PREV(h); \
56 QUEUE_PREV(h) = QUEUE_PREV(n); \
57 QUEUE_PREV_NEXT(h) = (h); \
58 } \
59 while (0)
60
61#define QUEUE_SPLIT(h, q, n) \
62 do { \
63 QUEUE_PREV(n) = QUEUE_PREV(h); \
64 QUEUE_PREV_NEXT(n) = (n); \
65 QUEUE_NEXT(n) = (q); \
66 QUEUE_PREV(h) = QUEUE_PREV(q); \
67 QUEUE_PREV_NEXT(h) = (h); \
68 QUEUE_PREV(q) = (n); \
69 } \
70 while (0)
71
72#define QUEUE_MOVE(h, n) \
73 do { \
74 if (QUEUE_EMPTY(h)) \
75 QUEUE_INIT(n); \
76 else { \
77 QUEUE* q = QUEUE_HEAD(h); \
78 QUEUE_SPLIT(h, q, n); \
79 } \
80 } \
81 while (0)
82
83#define QUEUE_INSERT_HEAD(h, q) \
84 do { \
85 QUEUE_NEXT(q) = QUEUE_NEXT(h); \
86 QUEUE_PREV(q) = (h); \
87 QUEUE_NEXT_PREV(q) = (q); \
88 QUEUE_NEXT(h) = (q); \
89 } \
90 while (0)
91
92#define QUEUE_INSERT_TAIL(h, q) \
93 do { \
94 QUEUE_NEXT(q) = (h); \
95 QUEUE_PREV(q) = QUEUE_PREV(h); \
96 QUEUE_PREV_NEXT(q) = (q); \
97 QUEUE_PREV(h) = (q); \
98 } \
99 while (0)
100
101#define QUEUE_REMOVE(q) \
102 do { \
103 QUEUE_PREV_NEXT(q) = QUEUE_NEXT(q); \
104 QUEUE_NEXT_PREV(q) = QUEUE_PREV(q); \
105 } \
106 while (0)
107
108#endif /* QUEUE_H_ */
109