release/src/router/miniupnpd/bsdqueue.h

   1 /*      $OpenBSD: queue.h,v 1.31 2005/11/25 08:06:25 otto 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 #ifdef QUEUE_MACRO_DEBUG
  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 #ifdef SLIST_ENTRY
 103 #undef SLIST_ENTRY
 104 #endif
 105
 106 #define SLIST_ENTRY(type)                                               \
 107 struct {                                                                \
 108         struct type *sle_next;  /* next element */                      \
 109 }
 110
 111 /*
 112  * Singly-linked List access methods.
 113  */
 114 #define SLIST_FIRST(head)       ((head)->slh_first)
 115 #define SLIST_END(head)         NULL
 116 #define SLIST_EMPTY(head)       (SLIST_FIRST(head) == SLIST_END(head))
 117 #define SLIST_NEXT(elm, field)  ((elm)->field.sle_next)
 118
 119 #define SLIST_FOREACH(var, head, field)                                 \
 120         for((var) = SLIST_FIRST(head);                                  \
 121             (var) != SLIST_END(head);                                   \
 122             (var) = SLIST_NEXT(var, field))
 123
 124 #define SLIST_FOREACH_PREVPTR(var, varp, head, field)                   \
 125         for ((varp) = &SLIST_FIRST((head));                             \
 126             ((var) = *(varp)) != SLIST_END(head);                       \
 127             (varp) = &SLIST_NEXT((var), field))
 128
 129 /*
 130  * Singly-linked List functions.
 131  */
 132 #define SLIST_INIT(head) {                                              \
 133         SLIST_FIRST(head) = SLIST_END(head);                            \
 134 }
 135
 136 #define SLIST_INSERT_AFTER(slistelm, elm, field) do {                   \
 137         (elm)->field.sle_next = (slistelm)->field.sle_next;             \
 138         (slistelm)->field.sle_next = (elm);                             \
 139 } while (0)
 140
 141 #define SLIST_INSERT_HEAD(head, elm, field) do {                        \
 142         (elm)->field.sle_next = (head)->slh_first;                      \
 143         (head)->slh_first = (elm);                                      \
 144 } while (0)
 145
 146 #define SLIST_REMOVE_NEXT(head, elm, field) do {                        \
 147         (elm)->field.sle_next = (elm)->field.sle_next->field.sle_next;  \
 148 } while (0)
 149
 150 #define SLIST_REMOVE_HEAD(head, field) do {                             \
 151         (head)->slh_first = (head)->slh_first->field.sle_next;          \
 152 } while (0)
 153
 154 #define SLIST_REMOVE(head, elm, type, field) do {                       \
 155         if ((head)->slh_first == (elm)) {                               \
 156                 SLIST_REMOVE_HEAD((head), field);                       \
 157         } else {                                                        \
 158                 struct type *curelm = (head)->slh_first;                \
 159                                                                         \
 160                 while (curelm->field.sle_next != (elm))                 \
 161                         curelm = curelm->field.sle_next;                \
 162                 curelm->field.sle_next =                                \
 163                     curelm->field.sle_next->field.sle_next;             \
 164                 _Q_INVALIDATE((elm)->field.sle_next);                   \
 165         }                                                               \
 166 } while (0)
 167
 168 /*
 169  * List definitions.
 170  */
 171 #define LIST_HEAD(name, type)                                           \
 172 struct name {                                                           \
 173         struct type *lh_first;  /* first element */                     \
 174 }
 175
 176 #define LIST_HEAD_INITIALIZER(head)                                     \
 177         { NULL }
 178
 179 #define LIST_ENTRY(type)                                                \
 180 struct {                                                                \
 181         struct type *le_next;   /* next element */                      \
 182         struct type **le_prev;  /* address of previous next element */  \
 183 }
 184
 185 /*
 186  * List access methods
 187  */
 188 #define LIST_FIRST(head)                ((head)->lh_first)
 189 #define LIST_END(head)                  NULL
 190 #define LIST_EMPTY(head)                (LIST_FIRST(head) == LIST_END(head))
 191 #define LIST_NEXT(elm, field)           ((elm)->field.le_next)
 192
 193 #define LIST_FOREACH(var, head, field)                                  \
 194         for((var) = LIST_FIRST(head);                                   \
 195             (var)!= LIST_END(head);                                     \
 196             (var) = LIST_NEXT(var, field))
 197
 198 /*
 199  * List functions.
 200  */
 201 #define LIST_INIT(head) do {                                            \
 202         LIST_FIRST(head) = LIST_END(head);                              \
 203 } while (0)
 204
 205 #define LIST_INSERT_AFTER(listelm, elm, field) do {                     \
 206         if (((elm)->field.le_next = (listelm)->field.le_next) != NULL)  \
 207                 (listelm)->field.le_next->field.le_prev =               \
 208                     &(elm)->field.le_next;                              \
 209         (listelm)->field.le_next = (elm);                               \
 210         (elm)->field.le_prev = &(listelm)->field.le_next;               \
 211 } while (0)
 212
 213 #define LIST_INSERT_BEFORE(listelm, elm, field) do {                    \
 214         (elm)->field.le_prev = (listelm)->field.le_prev;                \
 215         (elm)->field.le_next = (listelm);                               \
 216         *(listelm)->field.le_prev = (elm);                              \
 217         (listelm)->field.le_prev = &(elm)->field.le_next;               \
 218 } while (0)
 219
 220 #define LIST_INSERT_HEAD(head, elm, field) do {                         \
 221         if (((elm)->field.le_next = (head)->lh_first) != NULL)          \
 222                 (head)->lh_first->field.le_prev = &(elm)->field.le_next;\
 223         (head)->lh_first = (elm);                                       \
 224         (elm)->field.le_prev = &(head)->lh_first;                       \
 225 } while (0)
 226
 227 #define LIST_REMOVE(elm, field) do {                                    \
 228         if ((elm)->field.le_next != NULL)                               \
 229                 (elm)->field.le_next->field.le_prev =                   \
 230                     (elm)->field.le_prev;                               \
 231         *(elm)->field.le_prev = (elm)->field.le_next;                   \
 232         _Q_INVALIDATE((elm)->field.le_prev);                            \
 233         _Q_INVALIDATE((elm)->field.le_next);                            \
 234 } while (0)
 235
 236 #define LIST_REPLACE(elm, elm2, field) do {                             \
 237         if (((elm2)->field.le_next = (elm)->field.le_next) != NULL)     \
 238                 (elm2)->field.le_next->field.le_prev =                  \
 239                     &(elm2)->field.le_next;                             \
 240         (elm2)->field.le_prev = (elm)->field.le_prev;                   \
 241         *(elm2)->field.le_prev = (elm2);                                \
 242         _Q_INVALIDATE((elm)->field.le_prev);                            \
 243         _Q_INVALIDATE((elm)->field.le_next);                            \
 244 } while (0)
 245
 246 /*
 247  * Simple queue definitions.
 248  */
 249 #define SIMPLEQ_HEAD(name, type)                                        \
 250 struct name {                                                           \
 251         struct type *sqh_first; /* first element */                     \
 252         struct type **sqh_last; /* addr of last next element */         \
 253 }
 254
 255 #define SIMPLEQ_HEAD_INITIALIZER(head)                                  \
 256         { NULL, &(head).sqh_first }
 257
 258 #define SIMPLEQ_ENTRY(type)                                             \
 259 struct {                                                                \
 260         struct type *sqe_next;  /* next element */                      \
 261 }
 262
 263 /*
 264  * Simple queue access methods.
 265  */
 266 #define SIMPLEQ_FIRST(head)         ((head)->sqh_first)
 267 #define SIMPLEQ_END(head)           NULL
 268 #define SIMPLEQ_EMPTY(head)         (SIMPLEQ_FIRST(head) == SIMPLEQ_END(head))
 269 #define SIMPLEQ_NEXT(elm, field)    ((elm)->field.sqe_next)
 270
 271 #define SIMPLEQ_FOREACH(var, head, field)                               \
 272         for((var) = SIMPLEQ_FIRST(head);                                \
 273             (var) != SIMPLEQ_END(head);                                 \
 274             (var) = SIMPLEQ_NEXT(var, field))
 275
 276 /*
 277  * Simple queue functions.
 278  */
 279 #define SIMPLEQ_INIT(head) do {                                         \
 280         (head)->sqh_first = NULL;                                       \
 281         (head)->sqh_last = &(head)->sqh_first;                          \
 282 } while (0)
 283
 284 #define SIMPLEQ_INSERT_HEAD(head, elm, field) do {                      \
 285         if (((elm)->field.sqe_next = (head)->sqh_first) == NULL)        \
 286                 (head)->sqh_last = &(elm)->field.sqe_next;              \
 287         (head)->sqh_first = (elm);                                      \
 288 } while (0)
 289
 290 #define SIMPLEQ_INSERT_TAIL(head, elm, field) do {                      \
 291         (elm)->field.sqe_next = NULL;                                   \
 292         *(head)->sqh_last = (elm);                                      \
 293         (head)->sqh_last = &(elm)->field.sqe_next;                      \
 294 } while (0)
 295
 296 #define SIMPLEQ_INSERT_AFTER(head, listelm, elm, field) do {            \
 297         if (((elm)->field.sqe_next = (listelm)->field.sqe_next) == NULL)\
 298                 (head)->sqh_last = &(elm)->field.sqe_next;              \
 299         (listelm)->field.sqe_next = (elm);                              \
 300 } while (0)
 301
 302 #define SIMPLEQ_REMOVE_HEAD(head, field) do {                   \
 303         if (((head)->sqh_first = (head)->sqh_first->field.sqe_next) == NULL) \
 304                 (head)->sqh_last = &(head)->sqh_first;                  \
 305 } while (0)
 306
 307 /*
 308  * Tail queue definitions.
 309  */
 310 #define TAILQ_HEAD(name, type)                                          \
 311 struct name {                                                           \
 312         struct type *tqh_first; /* first element */                     \
 313         struct type **tqh_last; /* addr of last next element */         \
 314 }
 315
 316 #define TAILQ_HEAD_INITIALIZER(head)                                    \
 317         { NULL, &(head).tqh_first }
 318
 319 #define TAILQ_ENTRY(type)                                               \
 320 struct {                                                                \
 321         struct type *tqe_next;  /* next element */                      \
 322         struct type **tqe_prev; /* address of previous next element */  \
 323 }
 324
 325 /*
 326  * tail queue access methods
 327  */
 328 #define TAILQ_FIRST(head)               ((head)->tqh_first)
 329 #define TAILQ_END(head)                 NULL
 330 #define TAILQ_NEXT(elm, field)          ((elm)->field.tqe_next)
 331 #define TAILQ_LAST(head, headname)                                      \
 332         (*(((struct headname *)((head)->tqh_last))->tqh_last))
 333 /* XXX */
 334 #define TAILQ_PREV(elm, headname, field)                                \
 335         (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
 336 #define TAILQ_EMPTY(head)                                               \
 337         (TAILQ_FIRST(head) == TAILQ_END(head))
 338
 339 #define TAILQ_FOREACH(var, head, field)                                 \
 340         for((var) = TAILQ_FIRST(head);                                  \
 341             (var) != TAILQ_END(head);                                   \
 342             (var) = TAILQ_NEXT(var, field))
 343
 344 #define TAILQ_FOREACH_REVERSE(var, head, headname, field)               \
 345         for((var) = TAILQ_LAST(head, headname);                         \
 346             (var) != TAILQ_END(head);                                   \
 347             (var) = TAILQ_PREV(var, headname, field))
 348
 349 /*
 350  * Tail queue functions.
 351  */
 352 #define TAILQ_INIT(head) do {                                           \
 353         (head)->tqh_first = NULL;                                       \
 354         (head)->tqh_last = &(head)->tqh_first;                          \
 355 } while (0)
 356
 357 #define TAILQ_INSERT_HEAD(head, elm, field) do {                        \
 358         if (((elm)->field.tqe_next = (head)->tqh_first) != NULL)        \
 359                 (head)->tqh_first->field.tqe_prev =                     \
 360                     &(elm)->field.tqe_next;                             \
 361         else                                                            \
 362                 (head)->tqh_last = &(elm)->field.tqe_next;              \
 363         (head)->tqh_first = (elm);                                      \
 364         (elm)->field.tqe_prev = &(head)->tqh_first;                     \
 365 } while (0)
 366
 367 #define TAILQ_INSERT_TAIL(head, elm, field) do {                        \
 368         (elm)->field.tqe_next = NULL;                                   \
 369         (elm)->field.tqe_prev = (head)->tqh_last;                       \
 370         *(head)->tqh_last = (elm);                                      \
 371         (head)->tqh_last = &(elm)->field.tqe_next;                      \
 372 } while (0)
 373
 374 #define TAILQ_INSERT_AFTER(head, listelm, elm, field) do {              \
 375         if (((elm)->field.tqe_next = (listelm)->field.tqe_next) != NULL)\
 376                 (elm)->field.tqe_next->field.tqe_prev =                 \
 377                     &(elm)->field.tqe_next;                             \
 378         else                                                            \
 379                 (head)->tqh_last = &(elm)->field.tqe_next;              \
 380         (listelm)->field.tqe_next = (elm);                              \
 381         (elm)->field.tqe_prev = &(listelm)->field.tqe_next;             \
 382 } while (0)
 383
 384 #define TAILQ_INSERT_BEFORE(listelm, elm, field) do {                   \
 385         (elm)->field.tqe_prev = (listelm)->field.tqe_prev;              \
 386         (elm)->field.tqe_next = (listelm);                              \
 387         *(listelm)->field.tqe_prev = (elm);                             \
 388         (listelm)->field.tqe_prev = &(elm)->field.tqe_next;             \
 389 } while (0)
 390
 391 #define TAILQ_REMOVE(head, elm, field) do {                             \
 392         if (((elm)->field.tqe_next) != NULL)                            \
 393                 (elm)->field.tqe_next->field.tqe_prev =                 \
 394                     (elm)->field.tqe_prev;                              \
 395         else                                                            \
 396                 (head)->tqh_last = (elm)->field.tqe_prev;               \
 397         *(elm)->field.tqe_prev = (elm)->field.tqe_next;                 \
 398         _Q_INVALIDATE((elm)->field.tqe_prev);                           \
 399         _Q_INVALIDATE((elm)->field.tqe_next);                           \
 400 } while (0)
 401
 402 #define TAILQ_REPLACE(head, elm, elm2, field) do {                      \
 403         if (((elm2)->field.tqe_next = (elm)->field.tqe_next) != NULL)   \
 404                 (elm2)->field.tqe_next->field.tqe_prev =                \
 405                     &(elm2)->field.tqe_next;                            \
 406         else                                                            \
 407                 (head)->tqh_last = &(elm2)->field.tqe_next;             \
 408         (elm2)->field.tqe_prev = (elm)->field.tqe_prev;                 \
 409         *(elm2)->field.tqe_prev = (elm2);                               \
 410         _Q_INVALIDATE((elm)->field.tqe_prev);                           \
 411         _Q_INVALIDATE((elm)->field.tqe_next);                           \
 412 } while (0)
 413
 414 /*
 415  * Circular queue definitions.
 416  */
 417 #define CIRCLEQ_HEAD(name, type)                                        \
 418 struct name {                                                           \
 419         struct type *cqh_first;         /* first element */             \
 420         struct type *cqh_last;          /* last element */              \
 421 }
 422
 423 #define CIRCLEQ_HEAD_INITIALIZER(head)                                  \
 424         { CIRCLEQ_END(&head), CIRCLEQ_END(&head) }
 425
 426 #define CIRCLEQ_ENTRY(type)                                             \
 427 struct {                                                                \
 428         struct type *cqe_next;          /* next element */              \
 429         struct type *cqe_prev;          /* previous element */          \
 430 }
 431
 432 /*
 433  * Circular queue access methods
 434  */
 435 #define CIRCLEQ_FIRST(head)             ((head)->cqh_first)
 436 #define CIRCLEQ_LAST(head)              ((head)->cqh_last)
 437 #define CIRCLEQ_END(head)               ((void *)(head))
 438 #define CIRCLEQ_NEXT(elm, field)        ((elm)->field.cqe_next)
 439 #define CIRCLEQ_PREV(elm, field)        ((elm)->field.cqe_prev)
 440 #define CIRCLEQ_EMPTY(head)                                             \
 441         (CIRCLEQ_FIRST(head) == CIRCLEQ_END(head))
 442
 443 #define CIRCLEQ_FOREACH(var, head, field)                               \
 444         for((var) = CIRCLEQ_FIRST(head);                                \
 445             (var) != CIRCLEQ_END(head);                                 \
 446             (var) = CIRCLEQ_NEXT(var, field))
 447
 448 #define CIRCLEQ_FOREACH_REVERSE(var, head, field)                       \
 449         for((var) = CIRCLEQ_LAST(head);                                 \
 450             (var) != CIRCLEQ_END(head);                                 \
 451             (var) = CIRCLEQ_PREV(var, field))
 452
 453 /*
 454  * Circular queue functions.
 455  */
 456 #define CIRCLEQ_INIT(head) do {                                         \
 457         (head)->cqh_first = CIRCLEQ_END(head);                          \
 458         (head)->cqh_last = CIRCLEQ_END(head);                           \
 459 } while (0)
 460
 461 #define CIRCLEQ_INSERT_AFTER(head, listelm, elm, field) do {            \
 462         (elm)->field.cqe_next = (listelm)->field.cqe_next;              \
 463         (elm)->field.cqe_prev = (listelm);                              \
 464         if ((listelm)->field.cqe_next == CIRCLEQ_END(head))             \
 465                 (head)->cqh_last = (elm);                               \
 466         else                                                            \
 467                 (listelm)->field.cqe_next->field.cqe_prev = (elm);      \
 468         (listelm)->field.cqe_next = (elm);                              \
 469 } while (0)
 470
 471 #define CIRCLEQ_INSERT_BEFORE(head, listelm, elm, field) do {           \
 472         (elm)->field.cqe_next = (listelm);                              \
 473         (elm)->field.cqe_prev = (listelm)->field.cqe_prev;              \
 474         if ((listelm)->field.cqe_prev == CIRCLEQ_END(head))             \
 475                 (head)->cqh_first = (elm);                              \
 476         else                                                            \
 477                 (listelm)->field.cqe_prev->field.cqe_next = (elm);      \
 478         (listelm)->field.cqe_prev = (elm);                              \
 479 } while (0)
 480
 481 #define CIRCLEQ_INSERT_HEAD(head, elm, field) do {                      \
 482         (elm)->field.cqe_next = (head)->cqh_first;                      \
 483         (elm)->field.cqe_prev = CIRCLEQ_END(head);                      \
 484         if ((head)->cqh_last == CIRCLEQ_END(head))                      \
 485                 (head)->cqh_last = (elm);                               \
 486         else                                                            \
 487                 (head)->cqh_first->field.cqe_prev = (elm);              \
 488         (head)->cqh_first = (elm);                                      \
 489 } while (0)
 490
 491 #define CIRCLEQ_INSERT_TAIL(head, elm, field) do {                      \
 492         (elm)->field.cqe_next = CIRCLEQ_END(head);                      \
 493         (elm)->field.cqe_prev = (head)->cqh_last;                       \
 494         if ((head)->cqh_first == CIRCLEQ_END(head))                     \
 495                 (head)->cqh_first = (elm);                              \
 496         else                                                            \
 497                 (head)->cqh_last->field.cqe_next = (elm);               \
 498         (head)->cqh_last = (elm);                                       \
 499 } while (0)
 500
 501 #define CIRCLEQ_REMOVE(head, elm, field) do {                           \
 502         if ((elm)->field.cqe_next == CIRCLEQ_END(head))                 \
 503                 (head)->cqh_last = (elm)->field.cqe_prev;               \
 504         else                                                            \
 505                 (elm)->field.cqe_next->field.cqe_prev =                 \
 506                     (elm)->field.cqe_prev;                              \
 507         if ((elm)->field.cqe_prev == CIRCLEQ_END(head))                 \
 508                 (head)->cqh_first = (elm)->field.cqe_next;              \
 509         else                                                            \
 510                 (elm)->field.cqe_prev->field.cqe_next =                 \
 511                     (elm)->field.cqe_next;                              \
 512         _Q_INVALIDATE((elm)->field.cqe_prev);                           \
 513         _Q_INVALIDATE((elm)->field.cqe_next);                           \
 514 } while (0)
 515
 516 #define CIRCLEQ_REPLACE(head, elm, elm2, field) do {                    \
 517         if (((elm2)->field.cqe_next = (elm)->field.cqe_next) ==         \
 518             CIRCLEQ_END(head))                                          \
 519                 (head).cqh_last = (elm2);                               \
 520         else                                                            \
 521                 (elm2)->field.cqe_next->field.cqe_prev = (elm2);        \
 522         if (((elm2)->field.cqe_prev = (elm)->field.cqe_prev) ==         \
 523             CIRCLEQ_END(head))                                          \
 524                 (head).cqh_first = (elm2);                              \
 525         else                                                            \
 526                 (elm2)->field.cqe_prev->field.cqe_next = (elm2);        \
 527         _Q_INVALIDATE((elm)->field.cqe_prev);                           \
 528         _Q_INVALIDATE((elm)->field.cqe_next);                           \
 529 } while (0)
 530
 531 #endif  /* !_SYS_QUEUE_H_ */