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queue.h (22332B)


      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 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 /*
     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 elements
     44  * are singly linked for minimum space and pointer manipulation overhead at
     45  * the expense of O(n) removal for arbitrary elements. New elements can be
     46  * added to the list after an existing element or at the head of the list.
     47  * Elements being removed from the head of the list should use the explicit
     48  * macro for this purpose for optimum efficiency. A singly-linked list may
     49  * only be traversed in the forward direction.  Singly-linked lists are ideal
     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 after
     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 after
     78  * an existing element, at the head of the list, or at the end of the list.
     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(DIAGNOSTIC))
     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(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 		_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 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 /*
    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_cookie ^ \
    338 					(unsigned long)(ptr)))
    339 #define	XSIMPLEQ_FIRST(head)	    XSIMPLEQ_XOR(head, ((head)->sqx_first))
    340 #define	XSIMPLEQ_END(head)	    NULL
    341 #define	XSIMPLEQ_EMPTY(head)	    (XSIMPLEQ_FIRST(head) == XSIMPLEQ_END(head))
    342 #define	XSIMPLEQ_NEXT(head, elm, field)    XSIMPLEQ_XOR(head, ((elm)->field.sqx_next))
    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_next); \
    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, (elm)); \
    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_next); \
    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, NULL)) \
    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 element */	\
    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_next)
    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, tvar)	\
    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, tvar)	\
    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_ */