recipes

packages recipes for the <noname> package manager
Log | Files | Refs

queue.h (18371B)


      1 /*	$OpenBSD: queue.h,v 1.45 2018/07/12 14:22:54 sashan 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 reserved.
      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 distribution.
     16  * 3. Neither the name of the University nor the names of its contributors
     17  *    may be used to endorse or promote products derived from this software
     18  *    without specific prior written permission.
     19  *
     20  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     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 #include <stddef.h>
     39 
     40 /*
     41  * This file defines five types of data structures: singly-linked lists,
     42  * lists, simple queues, tail queues and XOR simple queues.
     43  *
     44  *
     45  * A singly-linked list is headed by a single forward pointer. The elements
     46  * are singly linked for minimum space and pointer manipulation overhead at
     47  * the expense of O(n) removal for arbitrary elements. New elements can be
     48  * added to the list after an existing element or at the head of the list.
     49  * Elements being removed from the head of the list should use the explicit
     50  * macro for this purpose for optimum efficiency. A singly-linked list may
     51  * only be traversed in the forward direction.  Singly-linked lists are ideal
     52  * for applications with large datasets and few or no removals or for
     53  * implementing a LIFO queue.
     54  *
     55  * A list is headed by a single forward pointer (or an array of forward
     56  * pointers for a hash table header). The elements are doubly linked
     57  * so that an arbitrary element can be removed without a need to
     58  * traverse the list. New elements can be added to the list before
     59  * or after an existing element or at the head of the list. A list
     60  * may only be traversed in the forward direction.
     61  *
     62  * A simple queue is headed by a pair of pointers, one to the head of the
     63  * list and the other to the tail of the list. The elements are singly
     64  * linked to save space, so elements can only be removed from the
     65  * head of the list. New elements can be added to the list before or after
     66  * an existing element, at the head of the list, or at the end of the
     67  * list. A simple queue may only be traversed in the forward direction.
     68  *
     69  * A tail queue is headed by a pair of pointers, one to the head of the
     70  * list and the other to the tail of the list. The elements are doubly
     71  * linked so that an arbitrary element can be removed without a need to
     72  * traverse the list. New elements can be added to the list before or
     73  * after an existing element, at the head of the list, or at the end of
     74  * the list. A tail queue may be traversed in either direction.
     75  *
     76  * An XOR simple queue is used in the same way as a regular simple queue.
     77  * The difference is that the head structure also includes a "cookie" that
     78  * is XOR'd with the queue pointer (first, last or next) to generate the
     79  * real pointer value.
     80  *
     81  * For details on the use of these macros, see the queue(3) manual page.
     82  */
     83 
     84 #if defined(QUEUE_MACRO_DEBUG) || (defined(_KERNEL) && defined(DIAGNOSTIC))
     85 #define _Q_INVALID ((void *)-1)
     86 #define _Q_INVALIDATE(a) (a) = _Q_INVALID
     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(head))
    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 	}								\
    161 	_Q_INVALIDATE((elm)->field.sle_next);				\
    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 element */	\
    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_END(head))
    187 #define	LIST_NEXT(elm, field)		((elm)->field.le_next)
    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) == SIMPLEQ_END(head))
    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) == NULL) \
    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_next) \
    315 	    == NULL)							\
    316 		(head)->sqh_last = &(elm)->field.sqe_next;		\
    317 } while (0)
    318 
    319 #define SIMPLEQ_CONCAT(head1, head2) do {				\
    320 	if (!SIMPLEQ_EMPTY((head2))) {					\
    321 		*(head1)->sqh_last = (head2)->sqh_first;		\
    322 		(head1)->sqh_last = (head2)->sqh_last;			\
    323 		SIMPLEQ_INIT((head2));					\
    324 	}								\
    325 } while (0)
    326 
    327 /*
    328  * XOR Simple queue definitions.
    329  */
    330 #define XSIMPLEQ_HEAD(name, type)					\
    331 struct name {								\
    332 	struct type *sqx_first;	/* first element */			\
    333 	struct type **sqx_last;	/* addr of last next element */		\
    334 	unsigned long sqx_cookie;					\
    335 }
    336 
    337 #define XSIMPLEQ_ENTRY(type)						\
    338 struct {								\
    339 	struct type *sqx_next;	/* next element */			\
    340 }
    341 
    342 /*
    343  * XOR Simple queue access methods.
    344  */
    345 #define XSIMPLEQ_XOR(head, ptr)	    ((__typeof(ptr))((head)->sqx_cookie ^ \
    346 					(unsigned long)(ptr)))
    347 #define	XSIMPLEQ_FIRST(head)	    XSIMPLEQ_XOR(head, ((head)->sqx_first))
    348 #define	XSIMPLEQ_END(head)	    NULL
    349 #define	XSIMPLEQ_EMPTY(head)	    (XSIMPLEQ_FIRST(head) == XSIMPLEQ_END(head))
    350 #define	XSIMPLEQ_NEXT(head, elm, field)    XSIMPLEQ_XOR(head, ((elm)->field.sqx_next))
    351 
    352 
    353 #define XSIMPLEQ_FOREACH(var, head, field)				\
    354 	for ((var) = XSIMPLEQ_FIRST(head);				\
    355 	    (var) != XSIMPLEQ_END(head);				\
    356 	    (var) = XSIMPLEQ_NEXT(head, var, field))
    357 
    358 #define	XSIMPLEQ_FOREACH_SAFE(var, head, field, tvar)			\
    359 	for ((var) = XSIMPLEQ_FIRST(head);				\
    360 	    (var) && ((tvar) = XSIMPLEQ_NEXT(head, var, field), 1);	\
    361 	    (var) = (tvar))
    362 
    363 /*
    364  * XOR Simple queue functions.
    365  */
    366 #define	XSIMPLEQ_INIT(head) do {					\
    367 	arc4random_buf(&(head)->sqx_cookie, sizeof((head)->sqx_cookie)); \
    368 	(head)->sqx_first = XSIMPLEQ_XOR(head, NULL);			\
    369 	(head)->sqx_last = XSIMPLEQ_XOR(head, &(head)->sqx_first);	\
    370 } while (0)
    371 
    372 #define XSIMPLEQ_INSERT_HEAD(head, elm, field) do {			\
    373 	if (((elm)->field.sqx_next = (head)->sqx_first) ==		\
    374 	    XSIMPLEQ_XOR(head, NULL))					\
    375 		(head)->sqx_last = XSIMPLEQ_XOR(head, &(elm)->field.sqx_next); \
    376 	(head)->sqx_first = XSIMPLEQ_XOR(head, (elm));			\
    377 } while (0)
    378 
    379 #define XSIMPLEQ_INSERT_TAIL(head, elm, field) do {			\
    380 	(elm)->field.sqx_next = XSIMPLEQ_XOR(head, NULL);		\
    381 	*(XSIMPLEQ_XOR(head, (head)->sqx_last)) = XSIMPLEQ_XOR(head, (elm)); \
    382 	(head)->sqx_last = XSIMPLEQ_XOR(head, &(elm)->field.sqx_next);	\
    383 } while (0)
    384 
    385 #define XSIMPLEQ_INSERT_AFTER(head, listelm, elm, field) do {		\
    386 	if (((elm)->field.sqx_next = (listelm)->field.sqx_next) ==	\
    387 	    XSIMPLEQ_XOR(head, NULL))					\
    388 		(head)->sqx_last = XSIMPLEQ_XOR(head, &(elm)->field.sqx_next); \
    389 	(listelm)->field.sqx_next = XSIMPLEQ_XOR(head, (elm));		\
    390 } while (0)
    391 
    392 #define XSIMPLEQ_REMOVE_HEAD(head, field) do {				\
    393 	if (((head)->sqx_first = XSIMPLEQ_XOR(head,			\
    394 	    (head)->sqx_first)->field.sqx_next) == XSIMPLEQ_XOR(head, NULL)) \
    395 		(head)->sqx_last = XSIMPLEQ_XOR(head, &(head)->sqx_first); \
    396 } while (0)
    397 
    398 #define XSIMPLEQ_REMOVE_AFTER(head, elm, field) do {			\
    399 	if (((elm)->field.sqx_next = XSIMPLEQ_XOR(head,			\
    400 	    (elm)->field.sqx_next)->field.sqx_next)			\
    401 	    == XSIMPLEQ_XOR(head, NULL))				\
    402 		(head)->sqx_last = 					\
    403 		    XSIMPLEQ_XOR(head, &(elm)->field.sqx_next);		\
    404 } while (0)
    405 
    406 
    407 /*
    408  * Tail queue definitions.
    409  */
    410 #define TAILQ_HEAD(name, type)						\
    411 struct name {								\
    412 	struct type *tqh_first;	/* first element */			\
    413 	struct type **tqh_last;	/* addr of last next element */		\
    414 }
    415 
    416 #define TAILQ_HEAD_INITIALIZER(head)					\
    417 	{ NULL, &(head).tqh_first }
    418 
    419 #define TAILQ_ENTRY(type)						\
    420 struct {								\
    421 	struct type *tqe_next;	/* next element */			\
    422 	struct type **tqe_prev;	/* address of previous next element */	\
    423 }
    424 
    425 /*
    426  * Tail queue access methods.
    427  */
    428 #define	TAILQ_FIRST(head)		((head)->tqh_first)
    429 #define	TAILQ_END(head)			NULL
    430 #define	TAILQ_NEXT(elm, field)		((elm)->field.tqe_next)
    431 #define TAILQ_LAST(head, headname)					\
    432 	(*(((struct headname *)((head)->tqh_last))->tqh_last))
    433 /* XXX */
    434 #define TAILQ_PREV(elm, headname, field)				\
    435 	(*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
    436 #define	TAILQ_EMPTY(head)						\
    437 	(TAILQ_FIRST(head) == TAILQ_END(head))
    438 
    439 #define TAILQ_FOREACH(var, head, field)					\
    440 	for((var) = TAILQ_FIRST(head);					\
    441 	    (var) != TAILQ_END(head);					\
    442 	    (var) = TAILQ_NEXT(var, field))
    443 
    444 #define	TAILQ_FOREACH_SAFE(var, head, field, tvar)			\
    445 	for ((var) = TAILQ_FIRST(head);					\
    446 	    (var) != TAILQ_END(head) &&					\
    447 	    ((tvar) = TAILQ_NEXT(var, field), 1);			\
    448 	    (var) = (tvar))
    449 
    450 
    451 #define TAILQ_FOREACH_REVERSE(var, head, headname, field)		\
    452 	for((var) = TAILQ_LAST(head, headname);				\
    453 	    (var) != TAILQ_END(head);					\
    454 	    (var) = TAILQ_PREV(var, headname, field))
    455 
    456 #define	TAILQ_FOREACH_REVERSE_SAFE(var, head, headname, field, tvar)	\
    457 	for ((var) = TAILQ_LAST(head, headname);			\
    458 	    (var) != TAILQ_END(head) &&					\
    459 	    ((tvar) = TAILQ_PREV(var, headname, field), 1);		\
    460 	    (var) = (tvar))
    461 
    462 /*
    463  * Tail queue functions.
    464  */
    465 #define	TAILQ_INIT(head) do {						\
    466 	(head)->tqh_first = NULL;					\
    467 	(head)->tqh_last = &(head)->tqh_first;				\
    468 } while (0)
    469 
    470 #define TAILQ_INSERT_HEAD(head, elm, field) do {			\
    471 	if (((elm)->field.tqe_next = (head)->tqh_first) != NULL)	\
    472 		(head)->tqh_first->field.tqe_prev =			\
    473 		    &(elm)->field.tqe_next;				\
    474 	else								\
    475 		(head)->tqh_last = &(elm)->field.tqe_next;		\
    476 	(head)->tqh_first = (elm);					\
    477 	(elm)->field.tqe_prev = &(head)->tqh_first;			\
    478 } while (0)
    479 
    480 #define TAILQ_INSERT_TAIL(head, elm, field) do {			\
    481 	(elm)->field.tqe_next = NULL;					\
    482 	(elm)->field.tqe_prev = (head)->tqh_last;			\
    483 	*(head)->tqh_last = (elm);					\
    484 	(head)->tqh_last = &(elm)->field.tqe_next;			\
    485 } while (0)
    486 
    487 #define TAILQ_INSERT_AFTER(head, listelm, elm, field) do {		\
    488 	if (((elm)->field.tqe_next = (listelm)->field.tqe_next) != NULL)\
    489 		(elm)->field.tqe_next->field.tqe_prev =			\
    490 		    &(elm)->field.tqe_next;				\
    491 	else								\
    492 		(head)->tqh_last = &(elm)->field.tqe_next;		\
    493 	(listelm)->field.tqe_next = (elm);				\
    494 	(elm)->field.tqe_prev = &(listelm)->field.tqe_next;		\
    495 } while (0)
    496 
    497 #define	TAILQ_INSERT_BEFORE(listelm, elm, field) do {			\
    498 	(elm)->field.tqe_prev = (listelm)->field.tqe_prev;		\
    499 	(elm)->field.tqe_next = (listelm);				\
    500 	*(listelm)->field.tqe_prev = (elm);				\
    501 	(listelm)->field.tqe_prev = &(elm)->field.tqe_next;		\
    502 } while (0)
    503 
    504 #define TAILQ_REMOVE(head, elm, field) do {				\
    505 	if (((elm)->field.tqe_next) != NULL)				\
    506 		(elm)->field.tqe_next->field.tqe_prev =			\
    507 		    (elm)->field.tqe_prev;				\
    508 	else								\
    509 		(head)->tqh_last = (elm)->field.tqe_prev;		\
    510 	*(elm)->field.tqe_prev = (elm)->field.tqe_next;			\
    511 	_Q_INVALIDATE((elm)->field.tqe_prev);				\
    512 	_Q_INVALIDATE((elm)->field.tqe_next);				\
    513 } while (0)
    514 
    515 #define TAILQ_REPLACE(head, elm, elm2, field) do {			\
    516 	if (((elm2)->field.tqe_next = (elm)->field.tqe_next) != NULL)	\
    517 		(elm2)->field.tqe_next->field.tqe_prev =		\
    518 		    &(elm2)->field.tqe_next;				\
    519 	else								\
    520 		(head)->tqh_last = &(elm2)->field.tqe_next;		\
    521 	(elm2)->field.tqe_prev = (elm)->field.tqe_prev;			\
    522 	*(elm2)->field.tqe_prev = (elm2);				\
    523 	_Q_INVALIDATE((elm)->field.tqe_prev);				\
    524 	_Q_INVALIDATE((elm)->field.tqe_next);				\
    525 } while (0)
    526 
    527 #define TAILQ_CONCAT(head1, head2, field) do {				\
    528 	if (!TAILQ_EMPTY(head2)) {					\
    529 		*(head1)->tqh_last = (head2)->tqh_first;		\
    530 		(head2)->tqh_first->field.tqe_prev = (head1)->tqh_last;	\
    531 		(head1)->tqh_last = (head2)->tqh_last;			\
    532 		TAILQ_INIT((head2));					\
    533 	}								\
    534 } while (0)
    535 
    536 #endif	/* !_SYS_QUEUE_H_ */