c9761ceb2da4e9c438c5f9193d0f67caa667bc12
[dragonfly.git] / sys / sys / queue.h
1 /*
2  * Copyright (c) 1991, 1993
3  *      The Regents of the University of California.  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. All advertising materials mentioning features or use of this software
14  *    must display the following acknowledgement:
15  *      This product includes software developed by the University of
16  *      California, Berkeley and its contributors.
17  * 4. Neither the name of the University nor the names of its contributors
18  *    may be used to endorse or promote products derived from this software
19  *    without specific prior written permission.
20  *
21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31  * SUCH DAMAGE.
32  *
33  *      @(#)queue.h     8.5 (Berkeley) 8/20/94
34  * $FreeBSD: src/sys/sys/queue.h,v 1.32.2.7 2002/04/17 14:21:02 des Exp $
35  * $DragonFly: src/sys/sys/queue.h,v 1.11 2008/08/28 08:42:29 hasso Exp $
36  */
37
38 #ifndef _SYS_QUEUE_H_
39 #define _SYS_QUEUE_H_
40
41 #ifndef _MACHINE_STDINT_H_
42 #include <machine/stdint.h>     /* for __offsetof */
43 #endif
44
45 /*
46  * This file defines five types of data structures: singly-linked lists,
47  * singly-linked tail queues, lists, tail queues, and circular queues.
48  *
49  * A singly-linked list is headed by a single forward pointer. The elements
50  * are singly linked for minimum space and pointer manipulation overhead at
51  * the expense of O(n) removal for arbitrary elements. New elements can be
52  * added to the list after an existing element or at the head of the list.
53  * Elements being removed from the head of the list should use the explicit
54  * macro for this purpose for optimum efficiency. A singly-linked list may
55  * only be traversed in the forward direction.  Singly-linked lists are ideal
56  * for applications with large datasets and few or no removals or for
57  * implementing a LIFO queue.
58  *
59  * A singly-linked tail queue is headed by a pair of pointers, one to the
60  * head of the list and the other to the tail of the list. The elements are
61  * singly linked for minimum space and pointer manipulation overhead at the
62  * expense of O(n) removal for arbitrary elements. New elements can be added
63  * to the list after an existing element, at the head of the list, or at the
64  * end of the list. Elements being removed from the head of the tail queue
65  * should use the explicit macro for this purpose for optimum efficiency.
66  * A singly-linked tail queue may only be traversed in the forward direction.
67  * Singly-linked tail queues are ideal for applications with large datasets
68  * and few or no removals or for implementing a FIFO queue.
69  *
70  * A list is headed by a single forward pointer (or an array of forward
71  * pointers for a hash table header). The elements are doubly linked
72  * so that an arbitrary element can be removed without a need to
73  * traverse the list. New elements can be added to the list before
74  * or after an existing element or at the head of the list. A list
75  * may only be traversed in the forward direction.
76  *
77  * A tail queue is headed by a pair of pointers, one to the head of the
78  * list and the other to the tail of the list. The elements are doubly
79  * linked so that an arbitrary element can be removed without a need to
80  * traverse the list. New elements can be added to the list before or
81  * after an existing element, at the head of the list, or at the end of
82  * the list. A tail queue may be traversed in either direction.
83  *
84  * A circle queue is headed by a pair of pointers, one to the head of the
85  * list and the other to the tail of the list. The elements are doubly
86  * linked so that an arbitrary element can be removed without a need to
87  * traverse the list. New elements can be added to the list before or after
88  * an existing element, at the head of the list, or at the end of the list.
89  * A circle queue may be traversed in either direction, but has a more
90  * complex end of list detection.
91  *
92  * For details on the use of these macros, see the queue(3) manual page.
93  *
94  *
95  *                      SLIST   LIST    STAILQ  TAILQ   CIRCLEQ
96  * _HEAD                +       +       +       +       +
97  * _HEAD_INITIALIZER    +       +       +       +       +
98  * _ENTRY               +       +       +       +       +
99  * _INIT                +       +       +       +       +
100  * _EMPTY               +       +       +       +       +
101  * _FIRST               +       +       +       +       +
102  * _NEXT                +       +       +       +       +
103  * _PREV                -       -       -       +       +
104  * _LAST                -       -       +       +       +
105  * _FOREACH             +       +       +       +       +
106  * _FOREACH_MUTABLE     -       +       +       +       -
107  * _FOREACH_REVERSE     -       -       -       +       +
108  * _INSERT_HEAD         +       +       +       +       +
109  * _INSERT_BEFORE       -       +       -       +       +
110  * _INSERT_AFTER        +       +       +       +       +
111  * _INSERT_TAIL         -       -       +       +       +
112  * _CONCAT              -       -       +       +       -
113  * _REMOVE_HEAD         +       -       +       -       -
114  * _REMOVE              +       +       +       +       +
115  *
116  */
117
118 /*
119  * Singly-linked List declarations.
120  */
121 #define SLIST_HEAD(name, type)                                          \
122 struct name {                                                           \
123         struct type *slh_first; /* first element */                     \
124 }
125
126 #define SLIST_HEAD_INITIALIZER(head)                                    \
127         { NULL }
128  
129 #define SLIST_ENTRY(type)                                               \
130 struct {                                                                \
131         struct type *sle_next;  /* next element */                      \
132 }
133
134 #define SLIST_ENTRY_INITIALIZER { NULL }
135  
136 /*
137  * Singly-linked List functions.
138  */
139 #define SLIST_EMPTY(head)       ((head)->slh_first == NULL)
140
141 #define SLIST_FIRST(head)       ((head)->slh_first)
142
143 #define SLIST_FOREACH(var, head, field)                                 \
144         for ((var) = SLIST_FIRST((head));                               \
145             (var);                                                      \
146             (var) = SLIST_NEXT((var), field))
147
148 #define SLIST_INIT(head) do {                                           \
149         SLIST_FIRST((head)) = NULL;                                     \
150 } while (0)
151
152 #define SLIST_INSERT_AFTER(slistelm, elm, field) do {                   \
153         SLIST_NEXT((elm), field) = SLIST_NEXT((slistelm), field);       \
154         SLIST_NEXT((slistelm), field) = (elm);                          \
155 } while (0)
156
157 #define SLIST_INSERT_HEAD(head, elm, field) do {                        \
158         SLIST_NEXT((elm), field) = SLIST_FIRST((head));                 \
159         SLIST_FIRST((head)) = (elm);                                    \
160 } while (0)
161
162 #define SLIST_NEXT(elm, field)  ((elm)->field.sle_next)
163
164 #define SLIST_REMOVE(head, elm, type, field) do {                       \
165         if (SLIST_FIRST((head)) == (elm)) {                             \
166                 SLIST_REMOVE_HEAD((head), field);                       \
167         }                                                               \
168         else {                                                          \
169                 struct type *curelm = SLIST_FIRST((head));              \
170                 while (SLIST_NEXT(curelm, field) != (elm))              \
171                         curelm = SLIST_NEXT(curelm, field);             \
172                 SLIST_NEXT(curelm, field) =                             \
173                     SLIST_NEXT(SLIST_NEXT(curelm, field), field);       \
174         }                                                               \
175 } while (0)
176
177 #define SLIST_REMOVE_HEAD(head, field) do {                             \
178         SLIST_FIRST((head)) = SLIST_NEXT(SLIST_FIRST((head)), field);   \
179 } while (0)
180
181 /*
182  * Singly-linked Tail queue declarations.
183  */
184 #define STAILQ_HEAD(name, type)                                         \
185 struct name {                                                           \
186         struct type *stqh_first;/* first element */                     \
187         struct type **stqh_last;/* addr of last next element */         \
188 }
189
190 #define STAILQ_HEAD_INITIALIZER(head)                                   \
191         { NULL, &(head).stqh_first }
192
193 #define STAILQ_ENTRY(type)                                              \
194 struct {                                                                \
195         struct type *stqe_next; /* next element */                      \
196 }
197
198 /*
199  * Singly-linked Tail queue functions.
200  */
201 #define STAILQ_CONCAT(head1, head2) do {                                \
202         if (!STAILQ_EMPTY((head2))) {                                   \
203                 *(head1)->stqh_last = (head2)->stqh_first;              \
204                 (head1)->stqh_last = (head2)->stqh_last;                \
205                 STAILQ_INIT((head2));                                   \
206         }                                                               \
207 } while (0)
208
209 #define STAILQ_EMPTY(head)      ((head)->stqh_first == NULL)
210
211 #define STAILQ_FIRST(head)      ((head)->stqh_first)
212
213 #define STAILQ_FOREACH(var, head, field)                                \
214         for((var) = STAILQ_FIRST((head));                               \
215            (var);                                                       \
216            (var) = STAILQ_NEXT((var), field))
217
218 #define STAILQ_FOREACH_MUTABLE(var, head, field, tvar)                  \
219         for ((var) = STAILQ_FIRST((head));                              \
220             (var) && ((tvar) = STAILQ_NEXT((var), field), 1);           \
221             (var) = (tvar))
222
223 #define STAILQ_INIT(head) do {                                          \
224         STAILQ_FIRST((head)) = NULL;                                    \
225         (head)->stqh_last = &STAILQ_FIRST((head));                      \
226 } while (0)
227
228 #define STAILQ_INSERT_AFTER(head, tqelm, elm, field) do {               \
229         if ((STAILQ_NEXT((elm), field) = STAILQ_NEXT((tqelm), field)) == NULL)\
230                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
231         STAILQ_NEXT((tqelm), field) = (elm);                            \
232 } while (0)
233
234 #define STAILQ_INSERT_HEAD(head, elm, field) do {                       \
235         if ((STAILQ_NEXT((elm), field) = STAILQ_FIRST((head))) == NULL) \
236                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
237         STAILQ_FIRST((head)) = (elm);                                   \
238 } while (0)
239
240 #define STAILQ_INSERT_TAIL(head, elm, field) do {                       \
241         STAILQ_NEXT((elm), field) = NULL;                               \
242         *(head)->stqh_last = (elm);                                     \
243         (head)->stqh_last = &STAILQ_NEXT((elm), field);                 \
244 } while (0)
245
246 #define STAILQ_LAST(head, type, field)                                  \
247         (STAILQ_EMPTY(head) ?                                           \
248                 NULL :                                                  \
249                 ((struct type *)                                        \
250                 ((char *)((head)->stqh_last) - __offsetof(struct type, field))))
251
252 #define STAILQ_NEXT(elm, field) ((elm)->field.stqe_next)
253
254 #define STAILQ_REMOVE(head, elm, type, field) do {                      \
255         if (STAILQ_FIRST((head)) == (elm)) {                            \
256                 STAILQ_REMOVE_HEAD(head, field);                        \
257         }                                                               \
258         else {                                                          \
259                 struct type *curelm = STAILQ_FIRST((head));             \
260                 while (STAILQ_NEXT(curelm, field) != (elm))             \
261                         curelm = STAILQ_NEXT(curelm, field);            \
262                 if ((STAILQ_NEXT(curelm, field) =                       \
263                      STAILQ_NEXT(STAILQ_NEXT(curelm, field), field)) == NULL)\
264                         (head)->stqh_last = &STAILQ_NEXT((curelm), field);\
265         }                                                               \
266 } while (0)
267
268 #define STAILQ_REMOVE_HEAD(head, field) do {                            \
269         if ((STAILQ_FIRST((head)) =                                     \
270              STAILQ_NEXT(STAILQ_FIRST((head)), field)) == NULL)         \
271                 (head)->stqh_last = &STAILQ_FIRST((head));              \
272 } while (0)
273
274 #define STAILQ_REMOVE_HEAD_UNTIL(head, elm, field) do {                 \
275         if ((STAILQ_FIRST((head)) = STAILQ_NEXT((elm), field)) == NULL) \
276                 (head)->stqh_last = &STAILQ_FIRST((head));              \
277 } while (0)
278
279 /*
280  * List declarations.
281  */
282 #define LIST_HEAD(name, type)                                           \
283 struct name {                                                           \
284         struct type *lh_first;  /* first element */                     \
285 }
286
287 #define LIST_HEAD_INITIALIZER(head)                                     \
288         { NULL }
289
290 #define LIST_ENTRY(type)                                                \
291 struct {                                                                \
292         struct type *le_next;   /* next element */                      \
293         struct type **le_prev;  /* address of previous next element */  \
294 }
295
296 /*
297  * List functions.
298  */
299
300 #define LIST_EMPTY(head)        ((head)->lh_first == NULL)
301
302 #define LIST_FIRST(head)        ((head)->lh_first)
303
304 #define LIST_FOREACH(var, head, field)                                  \
305         for ((var) = LIST_FIRST((head));                                \
306             (var);                                                      \
307             (var) = LIST_NEXT((var), field))
308
309 #define LIST_FOREACH_MUTABLE(var, head, field, nvar)                    \
310         for ((var) = LIST_FIRST((head));                                \
311              (var) && ((nvar) = LIST_NEXT((var), field), 1);            \
312              (var) = (nvar))
313
314 #define LIST_INIT(head) do {                                            \
315         LIST_FIRST((head)) = NULL;                                      \
316 } while (0)
317
318 #define LIST_INSERT_AFTER(listelm, elm, field) do {                     \
319         if ((LIST_NEXT((elm), field) = LIST_NEXT((listelm), field)) != NULL)\
320                 LIST_NEXT((listelm), field)->field.le_prev =            \
321                     &LIST_NEXT((elm), field);                           \
322         LIST_NEXT((listelm), field) = (elm);                            \
323         (elm)->field.le_prev = &LIST_NEXT((listelm), field);            \
324 } while (0)
325
326 #define LIST_INSERT_BEFORE(listelm, elm, field) do {                    \
327         (elm)->field.le_prev = (listelm)->field.le_prev;                \
328         LIST_NEXT((elm), field) = (listelm);                            \
329         *(listelm)->field.le_prev = (elm);                              \
330         (listelm)->field.le_prev = &LIST_NEXT((elm), field);            \
331 } while (0)
332
333 #define LIST_INSERT_HEAD(head, elm, field) do {                         \
334         if ((LIST_NEXT((elm), field) = LIST_FIRST((head))) != NULL)     \
335                 LIST_FIRST((head))->field.le_prev = &LIST_NEXT((elm), field);\
336         LIST_FIRST((head)) = (elm);                                     \
337         (elm)->field.le_prev = &LIST_FIRST((head));                     \
338 } while (0)
339
340 #define LIST_NEXT(elm, field)   ((elm)->field.le_next)
341
342 #define LIST_REMOVE(elm, field) do {                                    \
343         if (LIST_NEXT((elm), field) != NULL)                            \
344                 LIST_NEXT((elm), field)->field.le_prev =                \
345                     (elm)->field.le_prev;                               \
346         *(elm)->field.le_prev = LIST_NEXT((elm), field);                \
347 } while (0)
348
349 /*
350  * Tail queue declarations.
351  */
352 #define TAILQ_HEAD(name, type)                                          \
353 struct name {                                                           \
354         struct type *tqh_first; /* first element */                     \
355         struct type **tqh_last; /* addr of last next element */         \
356 }
357
358 #define TAILQ_HEAD_INITIALIZER(head)                                    \
359         { NULL, &(head).tqh_first }
360
361 #define TAILQ_ENTRY(type)                                               \
362 struct {                                                                \
363         struct type *tqe_next;  /* next element */                      \
364         struct type **tqe_prev; /* address of previous next element */  \
365 }
366
367 /*
368  * Tail queue functions.
369  */
370 #define TAILQ_CONCAT(head1, head2, field) do {                          \
371         if (!TAILQ_EMPTY(head2)) {                                      \
372                 *(head1)->tqh_last = (head2)->tqh_first;                \
373                 (head2)->tqh_first->field.tqe_prev = (head1)->tqh_last; \
374                 (head1)->tqh_last = (head2)->tqh_last;                  \
375                 TAILQ_INIT((head2));                                    \
376         }                                                               \
377 } while (0)
378
379 #define TAILQ_EMPTY(head)       ((head)->tqh_first == NULL)
380
381 #define TAILQ_FIRST(head)       ((head)->tqh_first)
382
383 #define TAILQ_FOREACH(var, head, field)                                 \
384         for ((var) = TAILQ_FIRST((head));                               \
385             (var);                                                      \
386             (var) = TAILQ_NEXT((var), field))
387
388 #define TAILQ_FOREACH_SAFE(var, head, field, tvar)                      \
389         for ((var) = TAILQ_FIRST((head));                               \
390             (var) && ((tvar) = TAILQ_NEXT((var), field), 1);            \
391             (var) = (tvar))
392
393
394 #define TAILQ_FOREACH_REVERSE(var, head, headname, field)               \
395         for ((var) = TAILQ_LAST((head), headname);                      \
396             (var);                                                      \
397             (var) = TAILQ_PREV((var), headname, field))
398
399 #define TAILQ_FOREACH_MUTABLE(var, head, field, nvar)                   \
400         for ((var) = TAILQ_FIRST((head));                               \
401              (var) && ((nvar) = TAILQ_NEXT((var), field), (var));       \
402              (var) = (nvar))
403
404 #define TAILQ_INIT(head) do {                                           \
405         TAILQ_FIRST((head)) = NULL;                                     \
406         (head)->tqh_last = &TAILQ_FIRST((head));                        \
407 } while (0)
408
409 #define TAILQ_INSERT_AFTER(head, listelm, elm, field) do {              \
410         if ((TAILQ_NEXT((elm), field) = TAILQ_NEXT((listelm), field)) != NULL)\
411                 TAILQ_NEXT((elm), field)->field.tqe_prev =              \
412                     &TAILQ_NEXT((elm), field);                          \
413         else                                                            \
414                 (head)->tqh_last = &TAILQ_NEXT((elm), field);           \
415         TAILQ_NEXT((listelm), field) = (elm);                           \
416         (elm)->field.tqe_prev = &TAILQ_NEXT((listelm), field);          \
417 } while (0)
418
419 #define TAILQ_INSERT_BEFORE(listelm, elm, field) do {                   \
420         (elm)->field.tqe_prev = (listelm)->field.tqe_prev;              \
421         TAILQ_NEXT((elm), field) = (listelm);                           \
422         *(listelm)->field.tqe_prev = (elm);                             \
423         (listelm)->field.tqe_prev = &TAILQ_NEXT((elm), field);          \
424 } while (0)
425
426 #define TAILQ_INSERT_HEAD(head, elm, field) do {                        \
427         if ((TAILQ_NEXT((elm), field) = TAILQ_FIRST((head))) != NULL)   \
428                 TAILQ_FIRST((head))->field.tqe_prev =                   \
429                     &TAILQ_NEXT((elm), field);                          \
430         else                                                            \
431                 (head)->tqh_last = &TAILQ_NEXT((elm), field);           \
432         TAILQ_FIRST((head)) = (elm);                                    \
433         (elm)->field.tqe_prev = &TAILQ_FIRST((head));                   \
434 } while (0)
435
436 #define TAILQ_INSERT_TAIL(head, elm, field) do {                        \
437         TAILQ_NEXT((elm), field) = NULL;                                \
438         (elm)->field.tqe_prev = (head)->tqh_last;                       \
439         *(head)->tqh_last = (elm);                                      \
440         (head)->tqh_last = &TAILQ_NEXT((elm), field);                   \
441 } while (0)
442
443 #define TAILQ_LAST(head, headname)                                      \
444         (*(((struct headname *)((head)->tqh_last))->tqh_last))
445
446 #define TAILQ_NEXT(elm, field) ((elm)->field.tqe_next)
447
448 #define TAILQ_PREV(elm, headname, field)                                \
449         (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
450
451 #define TAILQ_REMOVE(head, elm, field) do {                             \
452         if ((TAILQ_NEXT((elm), field)) != NULL)                         \
453                 TAILQ_NEXT((elm), field)->field.tqe_prev =              \
454                     (elm)->field.tqe_prev;                              \
455         else                                                            \
456                 (head)->tqh_last = (elm)->field.tqe_prev;               \
457         *(elm)->field.tqe_prev = TAILQ_NEXT((elm), field);              \
458 } while (0)
459
460 /*
461  * Circular queue declarations.
462  */
463 #define CIRCLEQ_HEAD(name, type)                                        \
464 struct name {                                                           \
465         struct type *cqh_first;         /* first element */             \
466         struct type *cqh_last;          /* last element */              \
467 }
468
469 #define CIRCLEQ_HEAD_INITIALIZER(head)                                  \
470         { (void *)&(head), (void *)&(head) }
471
472 #define CIRCLEQ_ENTRY(type)                                             \
473 struct {                                                                \
474         struct type *cqe_next;          /* next element */              \
475         struct type *cqe_prev;          /* previous element */          \
476 }
477
478 /*
479  * Circular queue functions.
480  */
481 #define CIRCLEQ_EMPTY(head)     ((head)->cqh_first == (void *)(head))
482
483 #define CIRCLEQ_FIRST(head)     ((head)->cqh_first)
484
485 #define CIRCLEQ_FOREACH(var, head, field)                               \
486         for ((var) = CIRCLEQ_FIRST((head));                             \
487             (var) != (void *)(head) || ((var) = NULL);                  \
488             (var) = CIRCLEQ_NEXT((var), field))
489
490 #define CIRCLEQ_FOREACH_REVERSE(var, head, field)                       \
491         for ((var) = CIRCLEQ_LAST((head));                              \
492             (var) != (void *)(head) || ((var) = NULL);                  \
493             (var) = CIRCLEQ_PREV((var), field))
494
495 #define CIRCLEQ_INIT(head) do {                                         \
496         CIRCLEQ_FIRST((head)) = (void *)(head);                         \
497         CIRCLEQ_LAST((head)) = (void *)(head);                          \
498 } while (0)
499
500 #define CIRCLEQ_INSERT_AFTER(head, listelm, elm, field) do {            \
501         CIRCLEQ_NEXT((elm), field) = CIRCLEQ_NEXT((listelm), field);    \
502         CIRCLEQ_PREV((elm), field) = (listelm);                         \
503         if (CIRCLEQ_NEXT((listelm), field) == (void *)(head))           \
504                 CIRCLEQ_LAST((head)) = (elm);                           \
505         else                                                            \
506                 CIRCLEQ_PREV(CIRCLEQ_NEXT((listelm), field), field) = (elm);\
507         CIRCLEQ_NEXT((listelm), field) = (elm);                         \
508 } while (0)
509
510 #define CIRCLEQ_INSERT_BEFORE(head, listelm, elm, field) do {           \
511         CIRCLEQ_NEXT((elm), field) = (listelm);                         \
512         CIRCLEQ_PREV((elm), field) = CIRCLEQ_PREV((listelm), field);    \
513         if (CIRCLEQ_PREV((listelm), field) == (void *)(head))           \
514                 CIRCLEQ_FIRST((head)) = (elm);                          \
515         else                                                            \
516                 CIRCLEQ_NEXT(CIRCLEQ_PREV((listelm), field), field) = (elm);\
517         CIRCLEQ_PREV((listelm), field) = (elm);                         \
518 } while (0)
519
520 #define CIRCLEQ_INSERT_HEAD(head, elm, field) do {                      \
521         CIRCLEQ_NEXT((elm), field) = CIRCLEQ_FIRST((head));             \
522         CIRCLEQ_PREV((elm), field) = (void *)(head);                    \
523         if (CIRCLEQ_LAST((head)) == (void *)(head))                     \
524                 CIRCLEQ_LAST((head)) = (elm);                           \
525         else                                                            \
526                 CIRCLEQ_PREV(CIRCLEQ_FIRST((head)), field) = (elm);     \
527         CIRCLEQ_FIRST((head)) = (elm);                                  \
528 } while (0)
529
530 #define CIRCLEQ_INSERT_TAIL(head, elm, field) do {                      \
531         CIRCLEQ_NEXT((elm), field) = (void *)(head);                    \
532         CIRCLEQ_PREV((elm), field) = CIRCLEQ_LAST((head));              \
533         if (CIRCLEQ_FIRST((head)) == (void *)(head))                    \
534                 CIRCLEQ_FIRST((head)) = (elm);                          \
535         else                                                            \
536                 CIRCLEQ_NEXT(CIRCLEQ_LAST((head)), field) = (elm);      \
537         CIRCLEQ_LAST((head)) = (elm);                                   \
538 } while (0)
539
540 #define CIRCLEQ_LAST(head)      ((head)->cqh_last)
541
542 #define CIRCLEQ_NEXT(elm,field) ((elm)->field.cqe_next)
543
544 #define CIRCLEQ_PREV(elm,field) ((elm)->field.cqe_prev)
545
546 #define CIRCLEQ_REMOVE(head, elm, field) do {                           \
547         if (CIRCLEQ_NEXT((elm), field) == (void *)(head))               \
548                 CIRCLEQ_LAST((head)) = CIRCLEQ_PREV((elm), field);      \
549         else                                                            \
550                 CIRCLEQ_PREV(CIRCLEQ_NEXT((elm), field), field) =       \
551                     CIRCLEQ_PREV((elm), field);                         \
552         if (CIRCLEQ_PREV((elm), field) == (void *)(head))               \
553                 CIRCLEQ_FIRST((head)) = CIRCLEQ_NEXT((elm), field);     \
554         else                                                            \
555                 CIRCLEQ_NEXT(CIRCLEQ_PREV((elm), field), field) =       \
556                     CIRCLEQ_NEXT((elm), field);                         \
557 } while (0)
558
559 #ifdef _KERNEL
560
561 /*
562  * XXX insque() and remque() are an old way of handling certain queues.
563  * They bogusly assumes that all queue heads look alike.
564  */
565
566 struct quehead {
567         struct quehead *qh_link;
568         struct quehead *qh_rlink;
569 };
570
571 #ifdef  __GNUC__
572
573 static __inline void
574 insque(void *a, void *b)
575 {
576         struct quehead *element = (struct quehead *)a,
577                  *head = (struct quehead *)b;
578
579         element->qh_link = head->qh_link;
580         element->qh_rlink = head;
581         head->qh_link = element;
582         element->qh_link->qh_rlink = element;
583 }
584
585 static __inline void
586 remque(void *a)
587 {
588         struct quehead *element = (struct quehead *)a;
589
590         element->qh_link->qh_rlink = element->qh_rlink;
591         element->qh_rlink->qh_link = element->qh_link;
592         element->qh_rlink = 0;
593 }
594
595 #else /* !__GNUC__ */
596
597 void    insque (void *a, void *b);
598 void    remque (void *a);
599
600 #endif /* __GNUC__ */
601
602 #endif /* _KERNEL */
603
604 #endif /* !_SYS_QUEUE_H_ */