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