git.sur5r.net Git - i3/i3status/blob - queue.h

   1 /*      $OpenBSD: queue.h,v 1.1 2007/10/26 03:14:08 niallo 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_PREVPTR(var, varp, head, field)                   \
 121         for ((varp) = &SLIST_FIRST((head));                             \
 122             ((var) = *(varp)) != SLIST_END(head);                       \
 123             (varp) = &SLIST_NEXT((var), field))
 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_NEXT(head, 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 /*
 195  * List functions.
 196  */
 197 #define LIST_INIT(head) do {                                            \
 198         LIST_FIRST(head) = LIST_END(head);                              \
 199 } while (0)
 200
 201 #define LIST_INSERT_AFTER(listelm, elm, field) do {                     \
 202         if (((elm)->field.le_next = (listelm)->field.le_next) != NULL)  \
 203                 (listelm)->field.le_next->field.le_prev =               \
 204                     &(elm)->field.le_next;                              \
 205         (listelm)->field.le_next = (elm);                               \
 206         (elm)->field.le_prev = &(listelm)->field.le_next;               \
 207 } while (0)
 208
 209 #define LIST_INSERT_BEFORE(listelm, elm, field) do {                    \
 210         (elm)->field.le_prev = (listelm)->field.le_prev;                \
 211         (elm)->field.le_next = (listelm);                               \
 212         *(listelm)->field.le_prev = (elm);                              \
 213         (listelm)->field.le_prev = &(elm)->field.le_next;               \
 214 } while (0)
 215
 216 #define LIST_INSERT_HEAD(head, elm, field) do {                         \
 217         if (((elm)->field.le_next = (head)->lh_first) != NULL)          \
 218                 (head)->lh_first->field.le_prev = &(elm)->field.le_next;\
 219         (head)->lh_first = (elm);                                       \
 220         (elm)->field.le_prev = &(head)->lh_first;                       \
 221 } while (0)
 222
 223 #define LIST_REMOVE(elm, field) do {                                    \
 224         if ((elm)->field.le_next != NULL)                               \
 225                 (elm)->field.le_next->field.le_prev =                   \
 226                     (elm)->field.le_prev;                               \
 227         *(elm)->field.le_prev = (elm)->field.le_next;                   \
 228         _Q_INVALIDATE((elm)->field.le_prev);                            \
 229         _Q_INVALIDATE((elm)->field.le_next);                            \
 230 } while (0)
 231
 232 #define LIST_REPLACE(elm, elm2, field) do {                             \
 233         if (((elm2)->field.le_next = (elm)->field.le_next) != NULL)     \
 234                 (elm2)->field.le_next->field.le_prev =                  \
 235                     &(elm2)->field.le_next;                             \
 236         (elm2)->field.le_prev = (elm)->field.le_prev;                   \
 237         *(elm2)->field.le_prev = (elm2);                                \
 238         _Q_INVALIDATE((elm)->field.le_prev);                            \
 239         _Q_INVALIDATE((elm)->field.le_next);                            \
 240 } while (0)
 241
 242 /*
 243  * Simple queue definitions.
 244  */
 245 #define SIMPLEQ_HEAD(name, type)                                        \
 246 struct name {                                                           \
 247         struct type *sqh_first; /* first element */                     \
 248         struct type **sqh_last; /* addr of last next element */         \
 249 }
 250
 251 #define SIMPLEQ_HEAD_INITIALIZER(head)                                  \
 252         { NULL, &(head).sqh_first }
 253
 254 #define SIMPLEQ_ENTRY(type)                                             \
 255 struct {                                                                \
 256         struct type *sqe_next;  /* next element */                      \
 257 }
 258
 259 /*
 260  * Simple queue access methods.
 261  */
 262 #define SIMPLEQ_FIRST(head)         ((head)->sqh_first)
 263 #define SIMPLEQ_END(head)           NULL
 264 #define SIMPLEQ_EMPTY(head)         (SIMPLEQ_FIRST(head) == SIMPLEQ_END(head))
 265 #define SIMPLEQ_NEXT(elm, field)    ((elm)->field.sqe_next)
 266
 267 #define SIMPLEQ_FOREACH(var, head, field)                               \
 268         for((var) = SIMPLEQ_FIRST(head);                                \
 269             (var) != SIMPLEQ_END(head);                                 \
 270             (var) = SIMPLEQ_NEXT(var, field))
 271
 272 /*
 273  * Simple queue functions.
 274  */
 275 #define SIMPLEQ_INIT(head) do {                                         \
 276         (head)->sqh_first = NULL;                                       \
 277         (head)->sqh_last = &(head)->sqh_first;                          \
 278 } while (0)
 279
 280 #define SIMPLEQ_INSERT_HEAD(head, elm, field) do {                      \
 281         if (((elm)->field.sqe_next = (head)->sqh_first) == NULL)        \
 282                 (head)->sqh_last = &(elm)->field.sqe_next;              \
 283         (head)->sqh_first = (elm);                                      \
 284 } while (0)
 285
 286 #define SIMPLEQ_INSERT_TAIL(head, elm, field) do {                      \
 287         (elm)->field.sqe_next = NULL;                                   \
 288         *(head)->sqh_last = (elm);                                      \
 289         (head)->sqh_last = &(elm)->field.sqe_next;                      \
 290 } while (0)
 291
 292 #define SIMPLEQ_INSERT_AFTER(head, listelm, elm, field) do {            \
 293         if (((elm)->field.sqe_next = (listelm)->field.sqe_next) == NULL)\
 294                 (head)->sqh_last = &(elm)->field.sqe_next;              \
 295         (listelm)->field.sqe_next = (elm);                              \
 296 } while (0)
 297
 298 #define SIMPLEQ_REMOVE_HEAD(head, field) do {                   \
 299         if (((head)->sqh_first = (head)->sqh_first->field.sqe_next) == NULL) \
 300                 (head)->sqh_last = &(head)->sqh_first;                  \
 301 } while (0)
 302
 303 /*
 304  * Tail queue definitions.
 305  */
 306 #define TAILQ_HEAD(name, type)                                          \
 307 struct name {                                                           \
 308         struct type *tqh_first; /* first element */                     \
 309         struct type **tqh_last; /* addr of last next element */         \
 310 }
 311
 312 #define TAILQ_HEAD_INITIALIZER(head)                                    \
 313         { NULL, &(head).tqh_first }
 314
 315 #define TAILQ_ENTRY(type)                                               \
 316 struct {                                                                \
 317         struct type *tqe_next;  /* next element */                      \
 318         struct type **tqe_prev; /* address of previous next element */  \
 319 }
 320
 321 /*
 322  * tail queue access methods
 323  */
 324 #define TAILQ_FIRST(head)               ((head)->tqh_first)
 325 #define TAILQ_END(head)                 NULL
 326 #define TAILQ_NEXT(elm, field)          ((elm)->field.tqe_next)
 327 #define TAILQ_LAST(head, headname)                                      \
 328         (*(((struct headname *)((head)->tqh_last))->tqh_last))
 329 /* XXX */
 330 #define TAILQ_PREV(elm, headname, field)                                \
 331         (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
 332 #define TAILQ_EMPTY(head)                                               \
 333         (TAILQ_FIRST(head) == TAILQ_END(head))
 334
 335 #define TAILQ_FOREACH(var, head, field)                                 \
 336         for((var) = TAILQ_FIRST(head);                                  \
 337             (var) != TAILQ_END(head);                                   \
 338             (var) = TAILQ_NEXT(var, field))
 339
 340 #define TAILQ_FOREACH_REVERSE(var, head, headname, field)               \
 341         for((var) = TAILQ_LAST(head, headname);                         \
 342             (var) != TAILQ_END(head);                                   \
 343             (var) = TAILQ_PREV(var, headname, field))
 344
 345 /*
 346  * Tail queue functions.
 347  */
 348 #define TAILQ_INIT(head) do {                                           \
 349         (head)->tqh_first = NULL;                                       \
 350         (head)->tqh_last = &(head)->tqh_first;                          \
 351 } while (0)
 352
 353 #define TAILQ_INSERT_HEAD(head, elm, field) do {                        \
 354         if (((elm)->field.tqe_next = (head)->tqh_first) != NULL)        \
 355                 (head)->tqh_first->field.tqe_prev =                     \
 356                     &(elm)->field.tqe_next;                             \
 357         else                                                            \
 358                 (head)->tqh_last = &(elm)->field.tqe_next;              \
 359         (head)->tqh_first = (elm);                                      \
 360         (elm)->field.tqe_prev = &(head)->tqh_first;                     \
 361 } while (0)
 362
 363 #define TAILQ_INSERT_TAIL(head, elm, field) do {                        \
 364         (elm)->field.tqe_next = NULL;                                   \
 365         (elm)->field.tqe_prev = (head)->tqh_last;                       \
 366         *(head)->tqh_last = (elm);                                      \
 367         (head)->tqh_last = &(elm)->field.tqe_next;                      \
 368 } while (0)
 369
 370 #define TAILQ_INSERT_AFTER(head, listelm, elm, field) do {              \
 371         if (((elm)->field.tqe_next = (listelm)->field.tqe_next) != NULL)\
 372                 (elm)->field.tqe_next->field.tqe_prev =                 \
 373                     &(elm)->field.tqe_next;                             \
 374         else                                                            \
 375                 (head)->tqh_last = &(elm)->field.tqe_next;              \
 376         (listelm)->field.tqe_next = (elm);                              \
 377         (elm)->field.tqe_prev = &(listelm)->field.tqe_next;             \
 378 } while (0)
 379
 380 #define TAILQ_INSERT_BEFORE(listelm, elm, field) do {                   \
 381         (elm)->field.tqe_prev = (listelm)->field.tqe_prev;              \
 382         (elm)->field.tqe_next = (listelm);                              \
 383         *(listelm)->field.tqe_prev = (elm);                             \
 384         (listelm)->field.tqe_prev = &(elm)->field.tqe_next;             \
 385 } while (0)
 386
 387 #define TAILQ_REMOVE(head, elm, field) do {                             \
 388         if (((elm)->field.tqe_next) != NULL)                            \
 389                 (elm)->field.tqe_next->field.tqe_prev =                 \
 390                     (elm)->field.tqe_prev;                              \
 391         else                                                            \
 392                 (head)->tqh_last = (elm)->field.tqe_prev;               \
 393         *(elm)->field.tqe_prev = (elm)->field.tqe_next;                 \
 394         _Q_INVALIDATE((elm)->field.tqe_prev);                           \
 395         _Q_INVALIDATE((elm)->field.tqe_next);                           \
 396 } while (0)
 397
 398 #define TAILQ_REPLACE(head, elm, elm2, field) do {                      \
 399         if (((elm2)->field.tqe_next = (elm)->field.tqe_next) != NULL)   \
 400                 (elm2)->field.tqe_next->field.tqe_prev =                \
 401                     &(elm2)->field.tqe_next;                            \
 402         else                                                            \
 403                 (head)->tqh_last = &(elm2)->field.tqe_next;             \
 404         (elm2)->field.tqe_prev = (elm)->field.tqe_prev;                 \
 405         *(elm2)->field.tqe_prev = (elm2);                               \
 406         _Q_INVALIDATE((elm)->field.tqe_prev);                           \
 407         _Q_INVALIDATE((elm)->field.tqe_next);                           \
 408 } while (0)
 409
 410 /*
 411  * Circular queue definitions.
 412  */
 413 #define CIRCLEQ_HEAD(name, type)                                        \
 414 struct name {                                                           \
 415         struct type *cqh_first;         /* first element */             \
 416         struct type *cqh_last;          /* last element */              \
 417 }
 418
 419 #define CIRCLEQ_HEAD_INITIALIZER(head)                                  \
 420         { CIRCLEQ_END(&head), CIRCLEQ_END(&head) }
 421
 422 #define CIRCLEQ_ENTRY(type)                                             \
 423 struct {                                                                \
 424         struct type *cqe_next;          /* next element */              \
 425         struct type *cqe_prev;          /* previous element */          \
 426 }
 427
 428 /*
 429  * Circular queue access methods
 430  */
 431 #define CIRCLEQ_FIRST(head)             ((head)->cqh_first)
 432 #define CIRCLEQ_LAST(head)              ((head)->cqh_last)
 433 #define CIRCLEQ_END(head)               ((void *)(head))
 434 #define CIRCLEQ_NEXT(elm, field)        ((elm)->field.cqe_next)
 435 #define CIRCLEQ_PREV(elm, field)        ((elm)->field.cqe_prev)
 436 #define CIRCLEQ_EMPTY(head)                                             \
 437         (CIRCLEQ_FIRST(head) == CIRCLEQ_END(head))
 438
 439 #define CIRCLEQ_FOREACH(var, head, field)                               \
 440         for((var) = CIRCLEQ_FIRST(head);                                \
 441             (var) != CIRCLEQ_END(head);                                 \
 442             (var) = CIRCLEQ_NEXT(var, field))
 443
 444 #define CIRCLEQ_FOREACH_REVERSE(var, head, field)                       \
 445         for((var) = CIRCLEQ_LAST(head);                                 \
 446             (var) != CIRCLEQ_END(head);                                 \
 447             (var) = CIRCLEQ_PREV(var, field))
 448
 449 /*
 450  * Circular queue functions.
 451  */
 452 #define CIRCLEQ_INIT(head) do {                                         \
 453         (head)->cqh_first = CIRCLEQ_END(head);                          \
 454         (head)->cqh_last = CIRCLEQ_END(head);                           \
 455 } while (0)
 456
 457 #define CIRCLEQ_INSERT_AFTER(head, listelm, elm, field) do {            \
 458         (elm)->field.cqe_next = (listelm)->field.cqe_next;              \
 459         (elm)->field.cqe_prev = (listelm);                              \
 460         if ((listelm)->field.cqe_next == CIRCLEQ_END(head))             \
 461                 (head)->cqh_last = (elm);                               \
 462         else                                                            \
 463                 (listelm)->field.cqe_next->field.cqe_prev = (elm);      \
 464         (listelm)->field.cqe_next = (elm);                              \
 465 } while (0)
 466
 467 #define CIRCLEQ_INSERT_BEFORE(head, listelm, elm, field) do {           \
 468         (elm)->field.cqe_next = (listelm);                              \
 469         (elm)->field.cqe_prev = (listelm)->field.cqe_prev;              \
 470         if ((listelm)->field.cqe_prev == CIRCLEQ_END(head))             \
 471                 (head)->cqh_first = (elm);                              \
 472         else                                                            \
 473                 (listelm)->field.cqe_prev->field.cqe_next = (elm);      \
 474         (listelm)->field.cqe_prev = (elm);                              \
 475 } while (0)
 476
 477 #define CIRCLEQ_INSERT_HEAD(head, elm, field) do {                      \
 478         (elm)->field.cqe_next = (head)->cqh_first;                      \
 479         (elm)->field.cqe_prev = CIRCLEQ_END(head);                      \
 480         if ((head)->cqh_last == CIRCLEQ_END(head))                      \
 481                 (head)->cqh_last = (elm);                               \
 482         else                                                            \
 483                 (head)->cqh_first->field.cqe_prev = (elm);              \
 484         (head)->cqh_first = (elm);                                      \
 485 } while (0)
 486
 487 #define CIRCLEQ_INSERT_TAIL(head, elm, field) do {                      \
 488         (elm)->field.cqe_next = CIRCLEQ_END(head);                      \
 489         (elm)->field.cqe_prev = (head)->cqh_last;                       \
 490         if ((head)->cqh_first == CIRCLEQ_END(head))                     \
 491                 (head)->cqh_first = (elm);                              \
 492         else                                                            \
 493                 (head)->cqh_last->field.cqe_next = (elm);               \
 494         (head)->cqh_last = (elm);                                       \
 495 } while (0)
 496
 497 #define CIRCLEQ_REMOVE(head, elm, field) do {                           \
 498         if ((elm)->field.cqe_next == CIRCLEQ_END(head))                 \
 499                 (head)->cqh_last = (elm)->field.cqe_prev;               \
 500         else                                                            \
 501                 (elm)->field.cqe_next->field.cqe_prev =                 \
 502                     (elm)->field.cqe_prev;                              \
 503         if ((elm)->field.cqe_prev == CIRCLEQ_END(head))                 \
 504                 (head)->cqh_first = (elm)->field.cqe_next;              \
 505         else                                                            \
 506                 (elm)->field.cqe_prev->field.cqe_next =                 \
 507                     (elm)->field.cqe_next;                              \
 508         _Q_INVALIDATE((elm)->field.cqe_prev);                           \
 509         _Q_INVALIDATE((elm)->field.cqe_next);                           \
 510 } while (0)
 511
 512 #define CIRCLEQ_REPLACE(head, elm, elm2, field) do {                    \
 513         if (((elm2)->field.cqe_next = (elm)->field.cqe_next) ==         \
 514             CIRCLEQ_END(head))                                          \
 515                 (head)->cqh_last = (elm2);                              \
 516         else                                                            \
 517                 (elm2)->field.cqe_next->field.cqe_prev = (elm2);        \
 518         if (((elm2)->field.cqe_prev = (elm)->field.cqe_prev) ==         \
 519             CIRCLEQ_END(head))                                          \
 520                 (head)->cqh_first = (elm2);                             \
 521         else                                                            \
 522                 (elm2)->field.cqe_prev->field.cqe_next = (elm2);        \
 523         _Q_INVALIDATE((elm)->field.cqe_prev);                           \
 524         _Q_INVALIDATE((elm)->field.cqe_next);                           \
 525 } while (0)
 526
 527 #endif  /* !_SYS_QUEUE_H_ */