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	queue.h (22332B)
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	1 /* $OpenBSD: queue.h,v 1.38 2013/07/03 15:05:21 fgsch Exp $ …
	2 /* $NetBSD: queue.h,v 1.11 1996/05/16 05:17:14 mycroft Exp $ …
	3
	4 /*
	5 * Copyright (c) 1991, 1993
	6 * The Regents of the University of California. All rights reser…
	7 *
	8 * Redistribution and use in source and binary forms, with or without
	9 * modification, are permitted provided that the following conditions
	10 * are met:
	11 * 1. Redistributions of source code must retain the above copyright
	12 * notice, this list of conditions and the following disclaimer.
	13 * 2. Redistributions in binary form must reproduce the above copyright
	14 * notice, this list of conditions and the following disclaimer in the
	15 * documentation and/or other materials provided with the distributio…
	16 * 3. Neither the name of the University nor the names of its contributo…
	17 * may be used to endorse or promote products derived from this softw…
	18 * without specific prior written permission.
	19 *
	20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' A…
	21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PU…
	23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIA…
	24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUE…
	25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOO…
	26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, S…
	28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY…
	29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	30 * SUCH DAMAGE.
	31 *
	32 * @(#)queue.h 8.5 (Berkeley) 8/20/94
	33 */
	34
	35 #ifndef _SYS_QUEUE_H_
	36 #define _SYS_QUEUE_H_
	37
	38 /*
	39 * This file defines five types of data structures: singly-linked lists,
	40 * lists, simple queues, tail queues, and circular queues.
	41 *
	42 *
	43 * A singly-linked list is headed by a single forward pointer. The eleme…
	44 * are singly linked for minimum space and pointer manipulation overhead…
	45 * the expense of O(n) removal for arbitrary elements. New elements can …
	46 * added to the list after an existing element or at the head of the lis…
	47 * Elements being removed from the head of the list should use the expli…
	48 * macro for this purpose for optimum efficiency. A singly-linked list m…
	49 * only be traversed in the forward direction. Singly-linked lists are …
	50 * for applications with large datasets and few or no removals or for
	51 * implementing a LIFO queue.
	52 *
	53 * A list is headed by a single forward pointer (or an array of forward
	54 * pointers for a hash table header). The elements are doubly linked
	55 * so that an arbitrary element can be removed without a need to
	56 * traverse the list. New elements can be added to the list before
	57 * or after an existing element or at the head of the list. A list
	58 * may only be traversed in the forward direction.
	59 *
	60 * A simple queue is headed by a pair of pointers, one the head of the
	61 * list and the other to the tail of the list. The elements are singly
	62 * linked to save space, so elements can only be removed from the
	63 * head of the list. New elements can be added to the list before or aft…
	64 * an existing element, at the head of the list, or at the end of the
	65 * list. A simple queue may only be traversed in the forward direction.
	66 *
	67 * A tail queue is headed by a pair of pointers, one to the head of the
	68 * list and the other to the tail of the list. The elements are doubly
	69 * linked so that an arbitrary element can be removed without a need to
	70 * traverse the list. New elements can be added to the list before or
	71 * after an existing element, at the head of the list, or at the end of
	72 * the list. A tail queue may be traversed in either direction.
	73 *
	74 * A circle queue is headed by a pair of pointers, one to the head of the
	75 * list and the other to the tail of the list. The elements are doubly
	76 * linked so that an arbitrary element can be removed without a need to
	77 * traverse the list. New elements can be added to the list before or af…
	78 * an existing element, at the head of the list, or at the end of the li…
	79 * A circle queue may be traversed in either direction, but has a more
	80 * complex end of list detection.
	81 *
	82 * For details on the use of these macros, see the queue(3) manual page.
	83 */
	84
	85 #if defined(QUEUE_MACRO_DEBUG) \|\| (defined(_KERNEL) && defined(DIAGNOSTI…
	86 #define _Q_INVALIDATE(a) (a) = ((void *)-1)
	87 #else
	88 #define _Q_INVALIDATE(a)
	89 #endif
	90
	91 /*
	92 * Singly-linked List definitions.
	93 */
	94 #define SLIST_HEAD(name, type) …
	95 struct name { …
	96 struct type slh_first; / first element */ …
	97 }
	98
	99 #define SLIST_HEAD_INITIALIZER(head) …
	100 { NULL }
	101
	102 #define SLIST_ENTRY(type) …
	103 struct { \
	104 struct type sle_next; / next element */ …
	105 }
	106
	107 /*
	108 * Singly-linked List access methods.
	109 */
	110 #define SLIST_FIRST(head) ((head)->slh_first)
	111 #define SLIST_END(head) NULL
	112 #define SLIST_EMPTY(head) (SLIST_FIRST(head) == SLIST_END(…
	113 #define SLIST_NEXT(elm, field) ((elm)->field.sle_next)
	114
	115 #define SLIST_FOREACH(var, head, field) …
	116 for((var) = SLIST_FIRST(head); …
	117 (var) != SLIST_END(head); …
	118 (var) = SLIST_NEXT(var, field))
	119
	120 #define SLIST_FOREACH_SAFE(var, head, field, tvar) …
	121 for ((var) = SLIST_FIRST(head); \
	122 (var) && ((tvar) = SLIST_NEXT(var, field), 1); …
	123 (var) = (tvar))
	124
	125 /*
	126 * Singly-linked List functions.
	127 */
	128 #define SLIST_INIT(head) { …
	129 SLIST_FIRST(head) = SLIST_END(head); …
	130 }
	131
	132 #define SLIST_INSERT_AFTER(slistelm, elm, field) do { …
	133 (elm)->field.sle_next = (slistelm)->field.sle_next; …
	134 (slistelm)->field.sle_next = (elm); …
	135 } while (0)
	136
	137 #define SLIST_INSERT_HEAD(head, elm, field) do { …
	138 (elm)->field.sle_next = (head)->slh_first; …
	139 (head)->slh_first = (elm); …
	140 } while (0)
	141
	142 #define SLIST_REMOVE_AFTER(elm, field) do { …
	143 (elm)->field.sle_next = (elm)->field.sle_next->field.sle_next; …
	144 } while (0)
	145
	146 #define SLIST_REMOVE_HEAD(head, field) do { …
	147 (head)->slh_first = (head)->slh_first->field.sle_next; …
	148 } while (0)
	149
	150 #define SLIST_REMOVE(head, elm, type, field) do { …
	151 if ((head)->slh_first == (elm)) { …
	152 SLIST_REMOVE_HEAD((head), field); …
	153 } else { \
	154 struct type *curelm = (head)->slh_first; \
	155 \
	156 while (curelm->field.sle_next != (elm)) …
	157 curelm = curelm->field.sle_next; \
	158 curelm->field.sle_next = \
	159 curelm->field.sle_next->field.sle_next; …
	160 _Q_INVALIDATE((elm)->field.sle_next); …
	161 } …
	162 } while (0)
	163
	164 /*
	165 * List definitions.
	166 */
	167 #define LIST_HEAD(name, type) …
	168 struct name { …
	169 struct type lh_first; / first element */ …
	170 }
	171
	172 #define LIST_HEAD_INITIALIZER(head) …
	173 { NULL }
	174
	175 #define LIST_ENTRY(type) \
	176 struct { \
	177 struct type le_next; / next element */ …
	178 struct type *le_prev; / address of previous next elemen…
	179 }
	180
	181 /*
	182 * List access methods
	183 */
	184 #define LIST_FIRST(head) ((head)->lh_first)
	185 #define LIST_END(head) NULL
	186 #define LIST_EMPTY(head) (LIST_FIRST(head) == LIST…
	187 #define LIST_NEXT(elm, field) ((elm)->field.le_nex…
	188
	189 #define LIST_FOREACH(var, head, field) …
	190 for((var) = LIST_FIRST(head); …
	191 (var)!= LIST_END(head); …
	192 (var) = LIST_NEXT(var, field))
	193
	194 #define LIST_FOREACH_SAFE(var, head, field, tvar) …
	195 for ((var) = LIST_FIRST(head); \
	196 (var) && ((tvar) = LIST_NEXT(var, field), 1); …
	197 (var) = (tvar))
	198
	199 /*
	200 * List functions.
	201 */
	202 #define LIST_INIT(head) do { …
	203 LIST_FIRST(head) = LIST_END(head); …
	204 } while (0)
	205
	206 #define LIST_INSERT_AFTER(listelm, elm, field) do { …
	207 if (((elm)->field.le_next = (listelm)->field.le_next) != NULL) …
	208 (listelm)->field.le_next->field.le_prev = …
	209 &(elm)->field.le_next; …
	210 (listelm)->field.le_next = (elm); …
	211 (elm)->field.le_prev = &(listelm)->field.le_next; …
	212 } while (0)
	213
	214 #define LIST_INSERT_BEFORE(listelm, elm, field) do { …
	215 (elm)->field.le_prev = (listelm)->field.le_prev; \
	216 (elm)->field.le_next = (listelm); …
	217 *(listelm)->field.le_prev = (elm); …
	218 (listelm)->field.le_prev = &(elm)->field.le_next; …
	219 } while (0)
	220
	221 #define LIST_INSERT_HEAD(head, elm, field) do { …
	222 if (((elm)->field.le_next = (head)->lh_first) != NULL) …
	223 (head)->lh_first->field.le_prev = &(elm)->field.le_next;\
	224 (head)->lh_first = (elm); …
	225 (elm)->field.le_prev = &(head)->lh_first; …
	226 } while (0)
	227
	228 #define LIST_REMOVE(elm, field) do { …
	229 if ((elm)->field.le_next != NULL) …
	230 (elm)->field.le_next->field.le_prev = …
	231 (elm)->field.le_prev; …
	232 *(elm)->field.le_prev = (elm)->field.le_next; …
	233 _Q_INVALIDATE((elm)->field.le_prev); …
	234 _Q_INVALIDATE((elm)->field.le_next); …
	235 } while (0)
	236
	237 #define LIST_REPLACE(elm, elm2, field) do { …
	238 if (((elm2)->field.le_next = (elm)->field.le_next) != NULL) …
	239 (elm2)->field.le_next->field.le_prev = …
	240 &(elm2)->field.le_next; …
	241 (elm2)->field.le_prev = (elm)->field.le_prev; …
	242 *(elm2)->field.le_prev = (elm2); \
	243 _Q_INVALIDATE((elm)->field.le_prev); …
	244 _Q_INVALIDATE((elm)->field.le_next); …
	245 } while (0)
	246
	247 /*
	248 * Simple queue definitions.
	249 */
	250 #define SIMPLEQ_HEAD(name, type) \
	251 struct name { …
	252 struct type sqh_first; / first element */ …
	253 struct type *sqh_last; / addr of last next element */ …
	254 }
	255
	256 #define SIMPLEQ_HEAD_INITIALIZER(head) …
	257 { NULL, &(head).sqh_first }
	258
	259 #define SIMPLEQ_ENTRY(type) …
	260 struct { \
	261 struct type sqe_next; / next element */ …
	262 }
	263
	264 /*
	265 * Simple queue access methods.
	266 */
	267 #define SIMPLEQ_FIRST(head) ((head)->sqh_first)
	268 #define SIMPLEQ_END(head) NULL
	269 #define SIMPLEQ_EMPTY(head) (SIMPLEQ_FIRST(head) == SI…
	270 #define SIMPLEQ_NEXT(elm, field) ((elm)->field.sqe_next)
	271
	272 #define SIMPLEQ_FOREACH(var, head, field) …
	273 for((var) = SIMPLEQ_FIRST(head); \
	274 (var) != SIMPLEQ_END(head); …
	275 (var) = SIMPLEQ_NEXT(var, field))
	276
	277 #define SIMPLEQ_FOREACH_SAFE(var, head, field, tvar) …
	278 for ((var) = SIMPLEQ_FIRST(head); …
	279 (var) && ((tvar) = SIMPLEQ_NEXT(var, field), 1); …
	280 (var) = (tvar))
	281
	282 /*
	283 * Simple queue functions.
	284 */
	285 #define SIMPLEQ_INIT(head) do { …
	286 (head)->sqh_first = NULL; …
	287 (head)->sqh_last = &(head)->sqh_first; …
	288 } while (0)
	289
	290 #define SIMPLEQ_INSERT_HEAD(head, elm, field) do { …
	291 if (((elm)->field.sqe_next = (head)->sqh_first) == NULL) \
	292 (head)->sqh_last = &(elm)->field.sqe_next; …
	293 (head)->sqh_first = (elm); …
	294 } while (0)
	295
	296 #define SIMPLEQ_INSERT_TAIL(head, elm, field) do { …
	297 (elm)->field.sqe_next = NULL; …
	298 *(head)->sqh_last = (elm); …
	299 (head)->sqh_last = &(elm)->field.sqe_next; …
	300 } while (0)
	301
	302 #define SIMPLEQ_INSERT_AFTER(head, listelm, elm, field) do { …
	303 if (((elm)->field.sqe_next = (listelm)->field.sqe_next) == NULL)\
	304 (head)->sqh_last = &(elm)->field.sqe_next; …
	305 (listelm)->field.sqe_next = (elm); …
	306 } while (0)
	307
	308 #define SIMPLEQ_REMOVE_HEAD(head, field) do { \
	309 if (((head)->sqh_first = (head)->sqh_first->field.sqe_next) == N…
	310 (head)->sqh_last = &(head)->sqh_first; …
	311 } while (0)
	312
	313 #define SIMPLEQ_REMOVE_AFTER(head, elm, field) do { …
	314 if (((elm)->field.sqe_next = (elm)->field.sqe_next->field.sqe_ne…
	315 == NULL) …
	316 (head)->sqh_last = &(elm)->field.sqe_next; …
	317 } while (0)
	318
	319 /*
	320 * XOR Simple queue definitions.
	321 */
	322 #define XSIMPLEQ_HEAD(name, type) …
	323 struct name { …
	324 struct type sqx_first; / first element */ …
	325 struct type *sqx_last; / addr of last next element */ …
	326 unsigned long sqx_cookie; …
	327 }
	328
	329 #define XSIMPLEQ_ENTRY(type) …
	330 struct { \
	331 struct type sqx_next; / next element */ …
	332 }
	333
	334 /*
	335 * XOR Simple queue access methods.
	336 */
	337 #define XSIMPLEQ_XOR(head, ptr) ((__typeof(ptr))((head)->sqx_…
	338 (unsigned long)(ptr)))
	339 #define XSIMPLEQ_FIRST(head) XSIMPLEQ_XOR(head, ((head…
	340 #define XSIMPLEQ_END(head) NULL
	341 #define XSIMPLEQ_EMPTY(head) (XSIMPLEQ_FIRST(head) == …
	342 #define XSIMPLEQ_NEXT(head, elm, field) XSIMPLEQ_XOR(head, ((e…
	343
	344
	345 #define XSIMPLEQ_FOREACH(var, head, field) …
	346 for ((var) = XSIMPLEQ_FIRST(head); …
	347 (var) != XSIMPLEQ_END(head); \
	348 (var) = XSIMPLEQ_NEXT(head, var, field))
	349
	350 #define XSIMPLEQ_FOREACH_SAFE(var, head, field, tvar) …
	351 for ((var) = XSIMPLEQ_FIRST(head); …
	352 (var) && ((tvar) = XSIMPLEQ_NEXT(head, var, field), 1); …
	353 (var) = (tvar))
	354
	355 /*
	356 * XOR Simple queue functions.
	357 */
	358 #define XSIMPLEQ_INIT(head) do { …
	359 arc4random_buf(&(head)->sqx_cookie, sizeof((head)->sqx_cookie));…
	360 (head)->sqx_first = XSIMPLEQ_XOR(head, NULL); …
	361 (head)->sqx_last = XSIMPLEQ_XOR(head, &(head)->sqx_first); …
	362 } while (0)
	363
	364 #define XSIMPLEQ_INSERT_HEAD(head, elm, field) do { …
	365 if (((elm)->field.sqx_next = (head)->sqx_first) == …
	366 XSIMPLEQ_XOR(head, NULL)) …
	367 (head)->sqx_last = XSIMPLEQ_XOR(head, &(elm)->field.sqx_…
	368 (head)->sqx_first = XSIMPLEQ_XOR(head, (elm)); …
	369 } while (0)
	370
	371 #define XSIMPLEQ_INSERT_TAIL(head, elm, field) do { …
	372 (elm)->field.sqx_next = XSIMPLEQ_XOR(head, NULL); …
	373 *(XSIMPLEQ_XOR(head, (head)->sqx_last)) = XSIMPLEQ_XOR(head, (el…
	374 (head)->sqx_last = XSIMPLEQ_XOR(head, &(elm)->field.sqx_next); …
	375 } while (0)
	376
	377 #define XSIMPLEQ_INSERT_AFTER(head, listelm, elm, field) do { …
	378 if (((elm)->field.sqx_next = (listelm)->field.sqx_next) == …
	379 XSIMPLEQ_XOR(head, NULL)) …
	380 (head)->sqx_last = XSIMPLEQ_XOR(head, &(elm)->field.sqx_…
	381 (listelm)->field.sqx_next = XSIMPLEQ_XOR(head, (elm)); …
	382 } while (0)
	383
	384 #define XSIMPLEQ_REMOVE_HEAD(head, field) do { …
	385 if (((head)->sqx_first = XSIMPLEQ_XOR(head, …
	386 (head)->sqx_first)->field.sqx_next) == XSIMPLEQ_XOR(head, NU…
	387 (head)->sqx_last = XSIMPLEQ_XOR(head, &(head)->sqx_first…
	388 } while (0)
	389
	390 #define XSIMPLEQ_REMOVE_AFTER(head, elm, field) do { …
	391 if (((elm)->field.sqx_next = XSIMPLEQ_XOR(head, …
	392 (elm)->field.sqx_next)->field.sqx_next) …
	393 == XSIMPLEQ_XOR(head, NULL)) \
	394 (head)->sqx_last = …
	395 XSIMPLEQ_XOR(head, &(elm)->field.sqx_next); …
	396 } while (0)
	397
	398
	399 /*
	400 * Tail queue definitions.
	401 */
	402 #define TAILQ_HEAD(name, type) …
	403 struct name { …
	404 struct type tqh_first; / first element */ …
	405 struct type *tqh_last; / addr of last next element */ …
	406 }
	407
	408 #define TAILQ_HEAD_INITIALIZER(head) …
	409 { NULL, &(head).tqh_first }
	410
	411 #define TAILQ_ENTRY(type) …
	412 struct { \
	413 struct type tqe_next; / next element */ …
	414 struct type *tqe_prev; / address of previous next eleme…
	415 }
	416
	417 /*
	418 * tail queue access methods
	419 */
	420 #define TAILQ_FIRST(head) ((head)->tqh_first)
	421 #define TAILQ_END(head) NULL
	422 #define TAILQ_NEXT(elm, field) ((elm)->field.tqe_n…
	423 #define TAILQ_LAST(head, headname) …
	424 ((((struct headname )((head)->tqh_last))->tqh_last))
	425 /* XXX */
	426 #define TAILQ_PREV(elm, headname, field) \
	427 ((((struct headname )((elm)->field.tqe_prev))->tqh_last))
	428 #define TAILQ_EMPTY(head) …
	429 (TAILQ_FIRST(head) == TAILQ_END(head))
	430
	431 #define TAILQ_FOREACH(var, head, field) …
	432 for((var) = TAILQ_FIRST(head); …
	433 (var) != TAILQ_END(head); …
	434 (var) = TAILQ_NEXT(var, field))
	435
	436 #define TAILQ_FOREACH_SAFE(var, head, field, tvar) …
	437 for ((var) = TAILQ_FIRST(head); …
	438 (var) != TAILQ_END(head) && …
	439 ((tvar) = TAILQ_NEXT(var, field), 1); …
	440 (var) = (tvar))
	441
	442
	443 #define TAILQ_FOREACH_REVERSE(var, head, headname, field) …
	444 for((var) = TAILQ_LAST(head, headname); …
	445 (var) != TAILQ_END(head); …
	446 (var) = TAILQ_PREV(var, headname, field))
	447
	448 #define TAILQ_FOREACH_REVERSE_SAFE(var, head, headname, field, tv…
	449 for ((var) = TAILQ_LAST(head, headname); \
	450 (var) != TAILQ_END(head) && …
	451 ((tvar) = TAILQ_PREV(var, headname, field), 1); …
	452 (var) = (tvar))
	453
	454 /*
	455 * Tail queue functions.
	456 */
	457 #define TAILQ_INIT(head) do { …
	458 (head)->tqh_first = NULL; …
	459 (head)->tqh_last = &(head)->tqh_first; …
	460 } while (0)
	461
	462 #define TAILQ_INSERT_HEAD(head, elm, field) do { \
	463 if (((elm)->field.tqe_next = (head)->tqh_first) != NULL) \
	464 (head)->tqh_first->field.tqe_prev = …
	465 &(elm)->field.tqe_next; …
	466 else …
	467 (head)->tqh_last = &(elm)->field.tqe_next; …
	468 (head)->tqh_first = (elm); …
	469 (elm)->field.tqe_prev = &(head)->tqh_first; …
	470 } while (0)
	471
	472 #define TAILQ_INSERT_TAIL(head, elm, field) do { \
	473 (elm)->field.tqe_next = NULL; …
	474 (elm)->field.tqe_prev = (head)->tqh_last; …
	475 *(head)->tqh_last = (elm); …
	476 (head)->tqh_last = &(elm)->field.tqe_next; …
	477 } while (0)
	478
	479 #define TAILQ_INSERT_AFTER(head, listelm, elm, field) do { …
	480 if (((elm)->field.tqe_next = (listelm)->field.tqe_next) != NULL)\
	481 (elm)->field.tqe_next->field.tqe_prev = …
	482 &(elm)->field.tqe_next; …
	483 else …
	484 (head)->tqh_last = &(elm)->field.tqe_next; …
	485 (listelm)->field.tqe_next = (elm); …
	486 (elm)->field.tqe_prev = &(listelm)->field.tqe_next; …
	487 } while (0)
	488
	489 #define TAILQ_INSERT_BEFORE(listelm, elm, field) do { …
	490 (elm)->field.tqe_prev = (listelm)->field.tqe_prev; …
	491 (elm)->field.tqe_next = (listelm); …
	492 *(listelm)->field.tqe_prev = (elm); …
	493 (listelm)->field.tqe_prev = &(elm)->field.tqe_next; …
	494 } while (0)
	495
	496 #define TAILQ_REMOVE(head, elm, field) do { …
	497 if (((elm)->field.tqe_next) != NULL) …
	498 (elm)->field.tqe_next->field.tqe_prev = …
	499 (elm)->field.tqe_prev; …
	500 else …
	501 (head)->tqh_last = (elm)->field.tqe_prev; …
	502 *(elm)->field.tqe_prev = (elm)->field.tqe_next; …
	503 _Q_INVALIDATE((elm)->field.tqe_prev); …
	504 _Q_INVALIDATE((elm)->field.tqe_next); …
	505 } while (0)
	506
	507 #define TAILQ_REPLACE(head, elm, elm2, field) do { …
	508 if (((elm2)->field.tqe_next = (elm)->field.tqe_next) != NULL) …
	509 (elm2)->field.tqe_next->field.tqe_prev = \
	510 &(elm2)->field.tqe_next; …
	511 else …
	512 (head)->tqh_last = &(elm2)->field.tqe_next; …
	513 (elm2)->field.tqe_prev = (elm)->field.tqe_prev; …
	514 *(elm2)->field.tqe_prev = (elm2); …
	515 _Q_INVALIDATE((elm)->field.tqe_prev); …
	516 _Q_INVALIDATE((elm)->field.tqe_next); …
	517 } while (0)
	518
	519 /*
	520 * Circular queue definitions.
	521 */
	522 #define CIRCLEQ_HEAD(name, type) \
	523 struct name { …
	524 struct type cqh_first; / first element */ …
	525 struct type cqh_last; / last element */ …
	526 }
	527
	528 #define CIRCLEQ_HEAD_INITIALIZER(head) …
	529 { CIRCLEQ_END(&head), CIRCLEQ_END(&head) }
	530
	531 #define CIRCLEQ_ENTRY(type) …
	532 struct { \
	533 struct type cqe_next; / next element */ …
	534 struct type cqe_prev; / previous element */ …
	535 }
	536
	537 /*
	538 * Circular queue access methods
	539 */
	540 #define CIRCLEQ_FIRST(head) ((head)->cqh_first)
	541 #define CIRCLEQ_LAST(head) ((head)->cqh_last)
	542 #define CIRCLEQ_END(head) ((void *)(head))
	543 #define CIRCLEQ_NEXT(elm, field) ((elm)->field.cqe_next)
	544 #define CIRCLEQ_PREV(elm, field) ((elm)->field.cqe_prev)
	545 #define CIRCLEQ_EMPTY(head) …
	546 (CIRCLEQ_FIRST(head) == CIRCLEQ_END(head))
	547
	548 #define CIRCLEQ_FOREACH(var, head, field) …
	549 for((var) = CIRCLEQ_FIRST(head); \
	550 (var) != CIRCLEQ_END(head); …
	551 (var) = CIRCLEQ_NEXT(var, field))
	552
	553 #define CIRCLEQ_FOREACH_SAFE(var, head, field, tvar) …
	554 for ((var) = CIRCLEQ_FIRST(head); …
	555 (var) != CIRCLEQ_END(head) && …
	556 ((tvar) = CIRCLEQ_NEXT(var, field), 1); …
	557 (var) = (tvar))
	558
	559 #define CIRCLEQ_FOREACH_REVERSE(var, head, field) …
	560 for((var) = CIRCLEQ_LAST(head); …
	561 (var) != CIRCLEQ_END(head); …
	562 (var) = CIRCLEQ_PREV(var, field))
	563
	564 #define CIRCLEQ_FOREACH_REVERSE_SAFE(var, head, headname, field, …
	565 for ((var) = CIRCLEQ_LAST(head, headname); …
	566 (var) != CIRCLEQ_END(head) && …
	567 ((tvar) = CIRCLEQ_PREV(var, headname, field), 1); …
	568 (var) = (tvar))
	569
	570 /*
	571 * Circular queue functions.
	572 */
	573 #define CIRCLEQ_INIT(head) do { …
	574 (head)->cqh_first = CIRCLEQ_END(head); …
	575 (head)->cqh_last = CIRCLEQ_END(head); …
	576 } while (0)
	577
	578 #define CIRCLEQ_INSERT_AFTER(head, listelm, elm, field) do { …
	579 (elm)->field.cqe_next = (listelm)->field.cqe_next; …
	580 (elm)->field.cqe_prev = (listelm); …
	581 if ((listelm)->field.cqe_next == CIRCLEQ_END(head)) …
	582 (head)->cqh_last = (elm); …
	583 else …
	584 (listelm)->field.cqe_next->field.cqe_prev = (elm); …
	585 (listelm)->field.cqe_next = (elm); …
	586 } while (0)
	587
	588 #define CIRCLEQ_INSERT_BEFORE(head, listelm, elm, field) do { …
	589 (elm)->field.cqe_next = (listelm); …
	590 (elm)->field.cqe_prev = (listelm)->field.cqe_prev; …
	591 if ((listelm)->field.cqe_prev == CIRCLEQ_END(head)) …
	592 (head)->cqh_first = (elm); …
	593 else …
	594 (listelm)->field.cqe_prev->field.cqe_next = (elm); …
	595 (listelm)->field.cqe_prev = (elm); …
	596 } while (0)
	597
	598 #define CIRCLEQ_INSERT_HEAD(head, elm, field) do { …
	599 (elm)->field.cqe_next = (head)->cqh_first; …
	600 (elm)->field.cqe_prev = CIRCLEQ_END(head); …
	601 if ((head)->cqh_last == CIRCLEQ_END(head)) …
	602 (head)->cqh_last = (elm); …
	603 else …
	604 (head)->cqh_first->field.cqe_prev = (elm); …
	605 (head)->cqh_first = (elm); …
	606 } while (0)
	607
	608 #define CIRCLEQ_INSERT_TAIL(head, elm, field) do { …
	609 (elm)->field.cqe_next = CIRCLEQ_END(head); …
	610 (elm)->field.cqe_prev = (head)->cqh_last; …
	611 if ((head)->cqh_first == CIRCLEQ_END(head)) …
	612 (head)->cqh_first = (elm); …
	613 else …
	614 (head)->cqh_last->field.cqe_next = (elm); …
	615 (head)->cqh_last = (elm); …
	616 } while (0)
	617
	618 #define CIRCLEQ_REMOVE(head, elm, field) do { …
	619 if ((elm)->field.cqe_next == CIRCLEQ_END(head)) …
	620 (head)->cqh_last = (elm)->field.cqe_prev; …
	621 else …
	622 (elm)->field.cqe_next->field.cqe_prev = …
	623 (elm)->field.cqe_prev; …
	624 if ((elm)->field.cqe_prev == CIRCLEQ_END(head)) …
	625 (head)->cqh_first = (elm)->field.cqe_next; …
	626 else …
	627 (elm)->field.cqe_prev->field.cqe_next = …
	628 (elm)->field.cqe_next; …
	629 _Q_INVALIDATE((elm)->field.cqe_prev); …
	630 _Q_INVALIDATE((elm)->field.cqe_next); …
	631 } while (0)
	632
	633 #define CIRCLEQ_REPLACE(head, elm, elm2, field) do { …
	634 if (((elm2)->field.cqe_next = (elm)->field.cqe_next) == …
	635 CIRCLEQ_END(head)) …
	636 (head)->cqh_last = (elm2); …
	637 else …
	638 (elm2)->field.cqe_next->field.cqe_prev = (elm2); \
	639 if (((elm2)->field.cqe_prev = (elm)->field.cqe_prev) == …
	640 CIRCLEQ_END(head)) …
	641 (head)->cqh_first = (elm2); …
	642 else …
	643 (elm2)->field.cqe_prev->field.cqe_next = (elm2); \
	644 _Q_INVALIDATE((elm)->field.cqe_prev); …
	645 _Q_INVALIDATE((elm)->field.cqe_next); …
	646 } while (0)
	647
	648 #endif /* !_SYS_QUEUE_H_ */