include/aversive/queue.h

   1 /*
   2  * Copyright (c) 1991, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. All advertising materials mentioning features or use of this software
  14  *    must display the following acknowledgement:
  15  *      This product includes software developed by the University of
  16  *      California, Berkeley and its contributors.
  17  * 4. Neither the name of the University nor the names of its contributors
  18  *    may be used to endorse or promote products derived from this software
  19  *    without specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31  * SUCH DAMAGE.
  32  *
  33  *      @(#)queue.h     8.5 (Berkeley) 8/20/94
  34  * $FreeBSD: src/sys/sys/queue.h,v 1.32.2.7 2002/04/17 14:21:02 des Exp $
  35  */
  36
  37 #ifndef _AVERSIVE_QUEUE_H_
  38 #define _AVERSIVE_QUEUE_H_
  39
  40 #ifndef __offsetof
  41 #define __offsetof(type, field)  ((size_t)(&(type *)0)->field))
  42 #endif
  43
  44 /*
  45  * This file defines five types of data structures: singly-linked lists,
  46  * singly-linked tail queues, lists, tail queues, and circular queues.
  47  *
  48  * A singly-linked list is headed by a single forward pointer. The elements
  49  * are singly linked for minimum space and pointer manipulation overhead at
  50  * the expense of O(n) removal for arbitrary elements. New elements can be
  51  * added to the list after an existing element or at the head of the list.
  52  * Elements being removed from the head of the list should use the explicit
  53  * macro for this purpose for optimum efficiency. A singly-linked list may
  54  * only be traversed in the forward direction.  Singly-linked lists are ideal
  55  * for applications with large datasets and few or no removals or for
  56  * implementing a LIFO queue.
  57  *
  58  * A singly-linked tail queue is headed by a pair of pointers, one to the
  59  * head of the list and the other to the tail of the list. The elements are
  60  * singly linked for minimum space and pointer manipulation overhead at the
  61  * expense of O(n) removal for arbitrary elements. New elements can be added
  62  * to the list after an existing element, at the head of the list, or at the
  63  * end of the list. Elements being removed from the head of the tail queue
  64  * should use the explicit macro for this purpose for optimum efficiency.
  65  * A singly-linked tail queue may only be traversed in the forward direction.
  66  * Singly-linked tail queues are ideal for applications with large datasets
  67  * and few or no removals or for implementing a FIFO queue.
  68  *
  69  * A list is headed by a single forward pointer (or an array of forward
  70  * pointers for a hash table header). The elements are doubly linked
  71  * 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
  73  * or after an existing element or at the head of the list. A list
  74  * may only be traversed in the forward direction.
  75  *
  76  * A tail queue is headed by a pair of pointers, one to the head of the
  77  * list and the other to the tail of the list. The elements are doubly
  78  * linked so that an arbitrary element can be removed without a need to
  79  * traverse the list. New elements can be added to the list before or
  80  * after an existing element, at the head of the list, or at the end of
  81  * the list. A tail queue may be traversed in either direction.
  82  *
  83  * A circle queue is headed by a pair of pointers, one to the head of the
  84  * list and the other to the tail of the list. The elements are doubly
  85  * linked so that an arbitrary element can be removed without a need to
  86  * traverse the list. New elements can be added to the list before or after
  87  * an existing element, at the head of the list, or at the end of the list.
  88  * A circle queue may be traversed in either direction, but has a more
  89  * complex end of list detection.
  90  *
  91  * For details on the use of these macros, see the queue(3) manual page.
  92  *
  93  *
  94  *                      SLIST   LIST    STAILQ  TAILQ   CIRCLEQ
  95  * _HEAD                +       +       +       +       +
  96  * _HEAD_INITIALIZER    +       +       +       +       +
  97  * _ENTRY               +       +       +       +       +
  98  * _INIT                +       +       +       +       +
  99  * _EMPTY               +       +       +       +       +
 100  * _FIRST               +       +       +       +       +
 101  * _NEXT                +       +       +       +       +
 102  * _PREV                -       -       -       +       +
 103  * _LAST                -       -       +       +       +
 104  * _FOREACH             +       +       +       +       +
 105  * _FOREACH_REVERSE     -       -       -       +       +
 106  * _INSERT_HEAD         +       +       +       +       +
 107  * _INSERT_BEFORE       -       +       -       +       +
 108  * _INSERT_AFTER        +       +       +       +       +
 109  * _INSERT_TAIL         -       -       +       +       +
 110  * _REMOVE_HEAD         +       -       +       -       -
 111  * _REMOVE              +       +       +       +       +
 112  *
 113  */
 114
 115 /*
 116  * Singly-linked List declarations.
 117  */
 118 #define SLIST_HEAD(name, type)                                          \
 119 struct name {                                                           \
 120         struct type *slh_first; /* first element */                     \
 121 }
 122
 123 #define SLIST_HEAD_INITIALIZER(head)                                    \
 124         { NULL }
 125
 126 #define SLIST_ENTRY(type)                                               \
 127 struct {                                                                \
 128         struct type *sle_next;  /* next element */                      \
 129 }
 130
 131 /*
 132  * Singly-linked List functions.
 133  */
 134 #define SLIST_EMPTY(head)       ((head)->slh_first == NULL)
 135
 136 #define SLIST_FIRST(head)       ((head)->slh_first)
 137
 138 #define SLIST_FOREACH(var, head, field)                                 \
 139         for ((var) = SLIST_FIRST((head));                               \
 140             (var);                                                      \
 141             (var) = SLIST_NEXT((var), field))
 142
 143 #define SLIST_INIT(head) do {                                           \
 144         SLIST_FIRST((head)) = NULL;                                     \
 145 } while (0)
 146
 147 #define SLIST_INSERT_AFTER(slistelm, elm, field) do {                   \
 148         SLIST_NEXT((elm), field) = SLIST_NEXT((slistelm), field);       \
 149         SLIST_NEXT((slistelm), field) = (elm);                          \
 150 } while (0)
 151
 152 #define SLIST_INSERT_HEAD(head, elm, field) do {                        \
 153         SLIST_NEXT((elm), field) = SLIST_FIRST((head));                 \
 154         SLIST_FIRST((head)) = (elm);                                    \
 155 } while (0)
 156
 157 #define SLIST_NEXT(elm, field)  ((elm)->field.sle_next)
 158
 159 #define SLIST_REMOVE(head, elm, type, field) do {                       \
 160         if (SLIST_FIRST((head)) == (elm)) {                             \
 161                 SLIST_REMOVE_HEAD((head), field);                       \
 162         }                                                               \
 163         else {                                                          \
 164                 struct type *curelm = SLIST_FIRST((head));              \
 165                 while (SLIST_NEXT(curelm, field) != (elm))              \
 166                         curelm = SLIST_NEXT(curelm, field);             \
 167                 SLIST_NEXT(curelm, field) =                             \
 168                     SLIST_NEXT(SLIST_NEXT(curelm, field), field);       \
 169         }                                                               \
 170 } while (0)
 171
 172 #define SLIST_REMOVE_HEAD(head, field) do {                             \
 173         SLIST_FIRST((head)) = SLIST_NEXT(SLIST_FIRST((head)), field);   \
 174 } while (0)
 175
 176 /*
 177  * Singly-linked Tail queue declarations.
 178  */
 179 #define STAILQ_HEAD(name, type)                                         \
 180 struct name {                                                           \
 181         struct type *stqh_first;/* first element */                     \
 182         struct type **stqh_last;/* addr of last next element */         \
 183 }
 184
 185 #define STAILQ_HEAD_INITIALIZER(head)                                   \
 186         { NULL, &(head).stqh_first }
 187
 188 #define STAILQ_ENTRY(type)                                              \
 189 struct {                                                                \
 190         struct type *stqe_next; /* next element */                      \
 191 }
 192
 193 /*
 194  * Singly-linked Tail queue functions.
 195  */
 196 #define STAILQ_EMPTY(head)      ((head)->stqh_first == NULL)
 197
 198 #define STAILQ_FIRST(head)      ((head)->stqh_first)
 199
 200 #define STAILQ_FOREACH(var, head, field)                                \
 201         for((var) = STAILQ_FIRST((head));                               \
 202            (var);                                                       \
 203            (var) = STAILQ_NEXT((var), field))
 204
 205 #define STAILQ_INIT(head) do {                                          \
 206         STAILQ_FIRST((head)) = NULL;                                    \
 207         (head)->stqh_last = &STAILQ_FIRST((head));                      \
 208 } while (0)
 209
 210 #define STAILQ_INSERT_AFTER(head, tqelm, elm, field) do {               \
 211         if ((STAILQ_NEXT((elm), field) = STAILQ_NEXT((tqelm), field)) == NULL)\
 212                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 213         STAILQ_NEXT((tqelm), field) = (elm);                            \
 214 } while (0)
 215
 216 #define STAILQ_INSERT_HEAD(head, elm, field) do {                       \
 217         if ((STAILQ_NEXT((elm), field) = STAILQ_FIRST((head))) == NULL) \
 218                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 219         STAILQ_FIRST((head)) = (elm);                                   \
 220 } while (0)
 221
 222 #define STAILQ_INSERT_TAIL(head, elm, field) do {                       \
 223         STAILQ_NEXT((elm), field) = NULL;                               \
 224         *(head)->stqh_last = (elm);                                     \
 225         (head)->stqh_last = &STAILQ_NEXT((elm), field);                 \
 226 } while (0)
 227
 228 #define STAILQ_LAST(head, type, field)                                  \
 229         (STAILQ_EMPTY(head) ?                                           \
 230                 NULL :                                                  \
 231                 ((struct type *)                                        \
 232                 ((char *)((head)->stqh_last) - __offsetof(struct type, field))))
 233
 234 #define STAILQ_NEXT(elm, field) ((elm)->field.stqe_next)
 235
 236 #define STAILQ_REMOVE(head, elm, type, field) do {                      \
 237         if (STAILQ_FIRST((head)) == (elm)) {                            \
 238                 STAILQ_REMOVE_HEAD(head, field);                        \
 239         }                                                               \
 240         else {                                                          \
 241                 struct type *curelm = STAILQ_FIRST((head));             \
 242                 while (STAILQ_NEXT(curelm, field) != (elm))             \
 243                         curelm = STAILQ_NEXT(curelm, field);            \
 244                 if ((STAILQ_NEXT(curelm, field) =                       \
 245                      STAILQ_NEXT(STAILQ_NEXT(curelm, field), field)) == NULL)\
 246                         (head)->stqh_last = &STAILQ_NEXT((curelm), field);\
 247         }                                                               \
 248 } while (0)
 249
 250 #define STAILQ_REMOVE_HEAD(head, field) do {                            \
 251         if ((STAILQ_FIRST((head)) =                                     \
 252              STAILQ_NEXT(STAILQ_FIRST((head)), field)) == NULL)         \
 253                 (head)->stqh_last = &STAILQ_FIRST((head));              \
 254 } while (0)
 255
 256 #define STAILQ_REMOVE_HEAD_UNTIL(head, elm, field) do {                 \
 257         if ((STAILQ_FIRST((head)) = STAILQ_NEXT((elm), field)) == NULL) \
 258                 (head)->stqh_last = &STAILQ_FIRST((head));              \
 259 } while (0)
 260
 261 /*
 262  * List declarations.
 263  */
 264 #define LIST_HEAD(name, type)                                           \
 265 struct name {                                                           \
 266         struct type *lh_first;  /* first element */                     \
 267 }
 268
 269 #define LIST_HEAD_INITIALIZER(head)                                     \
 270         { NULL }
 271
 272 #define LIST_ENTRY(type)                                                \
 273 struct {                                                                \
 274         struct type *le_next;   /* next element */                      \
 275         struct type **le_prev;  /* address of previous next element */  \
 276 }
 277
 278 /*
 279  * List functions.
 280  */
 281
 282 #define LIST_EMPTY(head)        ((head)->lh_first == NULL)
 283
 284 #define LIST_FIRST(head)        ((head)->lh_first)
 285
 286 #define LIST_FOREACH(var, head, field)                                  \
 287         for ((var) = LIST_FIRST((head));                                \
 288             (var);                                                      \
 289             (var) = LIST_NEXT((var), field))
 290
 291 #define LIST_INIT(head) do {                                            \
 292         LIST_FIRST((head)) = NULL;                                      \
 293 } while (0)
 294
 295 #define LIST_INSERT_AFTER(listelm, elm, field) do {                     \
 296         if ((LIST_NEXT((elm), field) = LIST_NEXT((listelm), field)) != NULL)\
 297                 LIST_NEXT((listelm), field)->field.le_prev =            \
 298                     &LIST_NEXT((elm), field);                           \
 299         LIST_NEXT((listelm), field) = (elm);                            \
 300         (elm)->field.le_prev = &LIST_NEXT((listelm), field);            \
 301 } while (0)
 302
 303 #define LIST_INSERT_BEFORE(listelm, elm, field) do {                    \
 304         (elm)->field.le_prev = (listelm)->field.le_prev;                \
 305         LIST_NEXT((elm), field) = (listelm);                            \
 306         *(listelm)->field.le_prev = (elm);                              \
 307         (listelm)->field.le_prev = &LIST_NEXT((elm), field);            \
 308 } while (0)
 309
 310 #define LIST_INSERT_HEAD(head, elm, field) do {                         \
 311         if ((LIST_NEXT((elm), field) = LIST_FIRST((head))) != NULL)     \
 312                 LIST_FIRST((head))->field.le_prev = &LIST_NEXT((elm), field);\
 313         LIST_FIRST((head)) = (elm);                                     \
 314         (elm)->field.le_prev = &LIST_FIRST((head));                     \
 315 } while (0)
 316
 317 #define LIST_NEXT(elm, field)   ((elm)->field.le_next)
 318
 319 #define LIST_REMOVE(elm, field) do {                                    \
 320         if (LIST_NEXT((elm), field) != NULL)                            \
 321                 LIST_NEXT((elm), field)->field.le_prev =                \
 322                     (elm)->field.le_prev;                               \
 323         *(elm)->field.le_prev = LIST_NEXT((elm), field);                \
 324 } while (0)
 325
 326 /*
 327  * Tail queue declarations.
 328  */
 329 #define TAILQ_HEAD(name, type)                                          \
 330 struct name {                                                           \
 331         struct type *tqh_first; /* first element */                     \
 332         struct type **tqh_last; /* addr of last next element */         \
 333 }
 334
 335 #define TAILQ_HEAD_INITIALIZER(head)                                    \
 336         { NULL, &(head).tqh_first }
 337
 338 #define TAILQ_ENTRY(type)                                               \
 339 struct {                                                                \
 340         struct type *tqe_next;  /* next element */                      \
 341         struct type **tqe_prev; /* address of previous next element */  \
 342 }
 343
 344 /*
 345  * Tail queue functions.
 346  */
 347 #define TAILQ_EMPTY(head)       ((head)->tqh_first == NULL)
 348
 349 #define TAILQ_FIRST(head)       ((head)->tqh_first)
 350
 351 #define TAILQ_FOREACH(var, head, field)                                 \
 352         for ((var) = TAILQ_FIRST((head));                               \
 353             (var);                                                      \
 354             (var) = TAILQ_NEXT((var), field))
 355
 356 #define TAILQ_FOREACH_REVERSE(var, head, headname, field)               \
 357         for ((var) = TAILQ_LAST((head), headname);                      \
 358             (var);                                                      \
 359             (var) = TAILQ_PREV((var), headname, field))
 360
 361 #define TAILQ_INIT(head) do {                                           \
 362         TAILQ_FIRST((head)) = NULL;                                     \
 363         (head)->tqh_last = &TAILQ_FIRST((head));                        \
 364 } while (0)
 365
 366 #define TAILQ_INSERT_AFTER(head, listelm, elm, field) do {              \
 367         if ((TAILQ_NEXT((elm), field) = TAILQ_NEXT((listelm), field)) != NULL)\
 368                 TAILQ_NEXT((elm), field)->field.tqe_prev =              \
 369                     &TAILQ_NEXT((elm), field);                          \
 370         else                                                            \
 371                 (head)->tqh_last = &TAILQ_NEXT((elm), field);           \
 372         TAILQ_NEXT((listelm), field) = (elm);                           \
 373         (elm)->field.tqe_prev = &TAILQ_NEXT((listelm), field);          \
 374 } while (0)
 375
 376 #define TAILQ_INSERT_BEFORE(listelm, elm, field) do {                   \
 377         (elm)->field.tqe_prev = (listelm)->field.tqe_prev;              \
 378         TAILQ_NEXT((elm), field) = (listelm);                           \
 379         *(listelm)->field.tqe_prev = (elm);                             \
 380         (listelm)->field.tqe_prev = &TAILQ_NEXT((elm), field);          \
 381 } while (0)
 382
 383 #define TAILQ_INSERT_HEAD(head, elm, field) do {                        \
 384         if ((TAILQ_NEXT((elm), field) = TAILQ_FIRST((head))) != NULL)   \
 385                 TAILQ_FIRST((head))->field.tqe_prev =                   \
 386                     &TAILQ_NEXT((elm), field);                          \
 387         else                                                            \
 388                 (head)->tqh_last = &TAILQ_NEXT((elm), field);           \
 389         TAILQ_FIRST((head)) = (elm);                                    \
 390         (elm)->field.tqe_prev = &TAILQ_FIRST((head));                   \
 391 } while (0)
 392
 393 #define TAILQ_INSERT_TAIL(head, elm, field) do {                        \
 394         TAILQ_NEXT((elm), field) = NULL;                                \
 395         (elm)->field.tqe_prev = (head)->tqh_last;                       \
 396         *(head)->tqh_last = (elm);                                      \
 397         (head)->tqh_last = &TAILQ_NEXT((elm), field);                   \
 398 } while (0)
 399
 400 #define TAILQ_LAST(head, headname)                                      \
 401         (*(((struct headname *)((head)->tqh_last))->tqh_last))
 402
 403 #define TAILQ_NEXT(elm, field) ((elm)->field.tqe_next)
 404
 405 #define TAILQ_PREV(elm, headname, field)                                \
 406         (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
 407
 408 #define TAILQ_REMOVE(head, elm, field) do {                             \
 409         if ((TAILQ_NEXT((elm), field)) != NULL)                         \
 410                 TAILQ_NEXT((elm), field)->field.tqe_prev =              \
 411                     (elm)->field.tqe_prev;                              \
 412         else                                                            \
 413                 (head)->tqh_last = (elm)->field.tqe_prev;               \
 414         *(elm)->field.tqe_prev = TAILQ_NEXT((elm), field);              \
 415 } while (0)
 416
 417 /*
 418  * Circular queue declarations.
 419  */
 420 #define CIRCLEQ_HEAD(name, type)                                        \
 421 struct name {                                                           \
 422         struct type *cqh_first;         /* first element */             \
 423         struct type *cqh_last;          /* last element */              \
 424 }
 425
 426 #define CIRCLEQ_HEAD_INITIALIZER(head)                                  \
 427         { (void *)&(head), (void *)&(head) }
 428
 429 #define CIRCLEQ_ENTRY(type)                                             \
 430 struct {                                                                \
 431         struct type *cqe_next;          /* next element */              \
 432         struct type *cqe_prev;          /* previous element */          \
 433 }
 434
 435 /*
 436  * Circular queue functions.
 437  */
 438 #define CIRCLEQ_EMPTY(head)     ((head)->cqh_first == (void *)(head))
 439
 440 #define CIRCLEQ_FIRST(head)     ((head)->cqh_first)
 441
 442 #define CIRCLEQ_FOREACH(var, head, field)                               \
 443         for ((var) = CIRCLEQ_FIRST((head));                             \
 444             (var) != (void *)(head) || ((var) = NULL);                  \
 445             (var) = CIRCLEQ_NEXT((var), field))
 446
 447 #define CIRCLEQ_FOREACH_REVERSE(var, head, field)                       \
 448         for ((var) = CIRCLEQ_LAST((head));                              \
 449             (var) != (void *)(head) || ((var) = NULL);                  \
 450             (var) = CIRCLEQ_PREV((var), field))
 451
 452 #define CIRCLEQ_INIT(head) do {                                         \
 453         CIRCLEQ_FIRST((head)) = (void *)(head);                         \
 454         CIRCLEQ_LAST((head)) = (void *)(head);                          \
 455 } while (0)
 456
 457 #define CIRCLEQ_INSERT_AFTER(head, listelm, elm, field) do {            \
 458         CIRCLEQ_NEXT((elm), field) = CIRCLEQ_NEXT((listelm), field);    \
 459         CIRCLEQ_PREV((elm), field) = (listelm);                         \
 460         if (CIRCLEQ_NEXT((listelm), field) == (void *)(head))           \
 461                 CIRCLEQ_LAST((head)) = (elm);                           \
 462         else                                                            \
 463                 CIRCLEQ_PREV(CIRCLEQ_NEXT((listelm), field), field) = (elm);\
 464         CIRCLEQ_NEXT((listelm), field) = (elm);                         \
 465 } while (0)
 466
 467 #define CIRCLEQ_INSERT_BEFORE(head, listelm, elm, field) do {           \
 468         CIRCLEQ_NEXT((elm), field) = (listelm);                         \
 469         CIRCLEQ_PREV((elm), field) = CIRCLEQ_PREV((listelm), field);    \
 470         if (CIRCLEQ_PREV((listelm), field) == (void *)(head))           \
 471                 CIRCLEQ_FIRST((head)) = (elm);                          \
 472         else                                                            \
 473                 CIRCLEQ_NEXT(CIRCLEQ_PREV((listelm), field), field) = (elm);\
 474         CIRCLEQ_PREV((listelm), field) = (elm);                         \
 475 } while (0)
 476
 477 #define CIRCLEQ_INSERT_HEAD(head, elm, field) do {                      \
 478         CIRCLEQ_NEXT((elm), field) = CIRCLEQ_FIRST((head));             \
 479         CIRCLEQ_PREV((elm), field) = (void *)(head);                    \
 480         if (CIRCLEQ_LAST((head)) == (void *)(head))                     \
 481                 CIRCLEQ_LAST((head)) = (elm);                           \
 482         else                                                            \
 483                 CIRCLEQ_PREV(CIRCLEQ_FIRST((head)), field) = (elm);     \
 484         CIRCLEQ_FIRST((head)) = (elm);                                  \
 485 } while (0)
 486
 487 #define CIRCLEQ_INSERT_TAIL(head, elm, field) do {                      \
 488         CIRCLEQ_NEXT((elm), field) = (void *)(head);                    \
 489         CIRCLEQ_PREV((elm), field) = CIRCLEQ_LAST((head));              \
 490         if (CIRCLEQ_FIRST((head)) == (void *)(head))                    \
 491                 CIRCLEQ_FIRST((head)) = (elm);                          \
 492         else                                                            \
 493                 CIRCLEQ_NEXT(CIRCLEQ_LAST((head)), field) = (elm);      \
 494         CIRCLEQ_LAST((head)) = (elm);                                   \
 495 } while (0)
 496
 497 #define CIRCLEQ_LAST(head)      ((head)->cqh_last)
 498
 499 #define CIRCLEQ_NEXT(elm,field) ((elm)->field.cqe_next)
 500
 501 #define CIRCLEQ_PREV(elm,field) ((elm)->field.cqe_prev)
 502
 503 #define CIRCLEQ_REMOVE(head, elm, field) do {                           \
 504         if (CIRCLEQ_NEXT((elm), field) == (void *)(head))               \
 505                 CIRCLEQ_LAST((head)) = CIRCLEQ_PREV((elm), field);      \
 506         else                                                            \
 507                 CIRCLEQ_PREV(CIRCLEQ_NEXT((elm), field), field) =       \
 508                     CIRCLEQ_PREV((elm), field);                         \
 509         if (CIRCLEQ_PREV((elm), field) == (void *)(head))               \
 510                 CIRCLEQ_FIRST((head)) = CIRCLEQ_NEXT((elm), field);     \
 511         else                                                            \
 512                 CIRCLEQ_NEXT(CIRCLEQ_PREV((elm), field), field) =       \
 513                     CIRCLEQ_NEXT((elm), field);                         \
 514 } while (0)
 515
 516
 517 #endif /* !_AVERSIVE_QUEUE_H_ */