sys/sys/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 _SYS_QUEUE_H_
  38 #define _SYS_QUEUE_H_
  39
  40 #include <machine/ansi.h>       /* for __offsetof */
  41
  42 /*
  43  * This file defines five types of data structures: singly-linked lists,
  44  * singly-linked tail queues, lists, tail queues, and circular queues.
  45  *
  46  * A singly-linked list is headed by a single forward pointer. The elements
  47  * are singly linked for minimum space and pointer manipulation overhead at
  48  * the expense of O(n) removal for arbitrary elements. New elements can be
  49  * added to the list after an existing element or at the head of the list.
  50  * Elements being removed from the head of the list should use the explicit
  51  * macro for this purpose for optimum efficiency. A singly-linked list may
  52  * only be traversed in the forward direction.  Singly-linked lists are ideal
  53  * for applications with large datasets and few or no removals or for
  54  * implementing a LIFO queue.
  55  *
  56  * A singly-linked tail queue is headed by a pair of pointers, one to the
  57  * head of the list and the other to the tail of the list. The elements are
  58  * singly linked for minimum space and pointer manipulation overhead at the
  59  * expense of O(n) removal for arbitrary elements. New elements can be added
  60  * to the list after an existing element, at the head of the list, or at the
  61  * end of the list. Elements being removed from the head of the tail queue
  62  * should use the explicit macro for this purpose for optimum efficiency.
  63  * A singly-linked tail queue may only be traversed in the forward direction.
  64  * Singly-linked tail queues are ideal for applications with large datasets
  65  * and few or no removals or for implementing a FIFO queue.
  66  *
  67  * A list is headed by a single forward pointer (or an array of forward
  68  * pointers for a hash table header). The elements are doubly linked
  69  * 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
  71  * or after an existing element or at the head of the list. A list
  72  * may only be traversed in the forward direction.
  73  *
  74  * A tail 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
  78  * after an existing element, at the head of the list, or at the end of
  79  * the list. A tail queue may be traversed in either direction.
  80  *
  81  * A circle queue is headed by a pair of pointers, one to the head of the
  82  * list and the other to the tail of the list. The elements are doubly
  83  * linked so that an arbitrary element can be removed without a need to
  84  * traverse the list. New elements can be added to the list before or after
  85  * an existing element, at the head of the list, or at the end of the list.
  86  * A circle queue may be traversed in either direction, but has a more
  87  * complex end of list detection.
  88  *
  89  * For details on the use of these macros, see the queue(3) manual page.
  90  *
  91  *
  92  *                      SLIST   LIST    STAILQ  TAILQ   CIRCLEQ
  93  * _HEAD                +       +       +       +       +
  94  * _HEAD_INITIALIZER    +       +       +       +       +
  95  * _ENTRY               +       +       +       +       +
  96  * _INIT                +       +       +       +       +
  97  * _EMPTY               +       +       +       +       +
  98  * _FIRST               +       +       +       +       +
  99  * _NEXT                +       +       +       +       +
 100  * _PREV                -       -       -       +       +
 101  * _LAST                -       -       +       +       +
 102  * _FOREACH             +       +       +       +       +
 103  * _FOREACH_REVERSE     -       -       -       +       +
 104  * _INSERT_HEAD         +       +       +       +       +
 105  * _INSERT_BEFORE       -       +       -       +       +
 106  * _INSERT_AFTER        +       +       +       +       +
 107  * _INSERT_TAIL         -       -       +       +       +
 108  * _REMOVE_HEAD         +       -       +       -       -
 109  * _REMOVE              +       +       +       +       +
 110  *
 111  */
 112
 113 /*
 114  * Singly-linked List declarations.
 115  */
 116 #define SLIST_HEAD(name, type)                                          \
 117 struct name {                                                           \
 118         struct type *slh_first; /* first element */                     \
 119 }
 120
 121 #define SLIST_HEAD_INITIALIZER(head)                                    \
 122         { NULL }
 123
 124 #define SLIST_ENTRY(type)                                               \
 125 struct {                                                                \
 126         struct type *sle_next;  /* next element */                      \
 127 }
 128
 129 /*
 130  * Singly-linked List functions.
 131  */
 132 #define SLIST_EMPTY(head)       ((head)->slh_first == NULL)
 133
 134 #define SLIST_FIRST(head)       ((head)->slh_first)
 135
 136 #define SLIST_FOREACH(var, head, field)                                 \
 137         for ((var) = SLIST_FIRST((head));                               \
 138             (var);                                                      \
 139             (var) = SLIST_NEXT((var), field))
 140
 141 #define SLIST_INIT(head) do {                                           \
 142         SLIST_FIRST((head)) = NULL;                                     \
 143 } while (0)
 144
 145 #define SLIST_INSERT_AFTER(slistelm, elm, field) do {                   \
 146         SLIST_NEXT((elm), field) = SLIST_NEXT((slistelm), field);       \
 147         SLIST_NEXT((slistelm), field) = (elm);                          \
 148 } while (0)
 149
 150 #define SLIST_INSERT_HEAD(head, elm, field) do {                        \
 151         SLIST_NEXT((elm), field) = SLIST_FIRST((head));                 \
 152         SLIST_FIRST((head)) = (elm);                                    \
 153 } while (0)
 154
 155 #define SLIST_NEXT(elm, field)  ((elm)->field.sle_next)
 156
 157 #define SLIST_REMOVE(head, elm, type, field) do {                       \
 158         if (SLIST_FIRST((head)) == (elm)) {                             \
 159                 SLIST_REMOVE_HEAD((head), field);                       \
 160         }                                                               \
 161         else {                                                          \
 162                 struct type *curelm = SLIST_FIRST((head));              \
 163                 while (SLIST_NEXT(curelm, field) != (elm))              \
 164                         curelm = SLIST_NEXT(curelm, field);             \
 165                 SLIST_NEXT(curelm, field) =                             \
 166                     SLIST_NEXT(SLIST_NEXT(curelm, field), field);       \
 167         }                                                               \
 168 } while (0)
 169
 170 #define SLIST_REMOVE_HEAD(head, field) do {                             \
 171         SLIST_FIRST((head)) = SLIST_NEXT(SLIST_FIRST((head)), field);   \
 172 } while (0)
 173
 174 /*
 175  * Singly-linked Tail queue declarations.
 176  */
 177 #define STAILQ_HEAD(name, type)                                         \
 178 struct name {                                                           \
 179         struct type *stqh_first;/* first element */                     \
 180         struct type **stqh_last;/* addr of last next element */         \
 181 }
 182
 183 #define STAILQ_HEAD_INITIALIZER(head)                                   \
 184         { NULL, &(head).stqh_first }
 185
 186 #define STAILQ_ENTRY(type)                                              \
 187 struct {                                                                \
 188         struct type *stqe_next; /* next element */                      \
 189 }
 190
 191 /*
 192  * Singly-linked Tail queue functions.
 193  */
 194 #define STAILQ_EMPTY(head)      ((head)->stqh_first == NULL)
 195
 196 #define STAILQ_FIRST(head)      ((head)->stqh_first)
 197
 198 #define STAILQ_FOREACH(var, head, field)                                \
 199         for((var) = STAILQ_FIRST((head));                               \
 200            (var);                                                       \
 201            (var) = STAILQ_NEXT((var), field))
 202
 203 #define STAILQ_INIT(head) do {                                          \
 204         STAILQ_FIRST((head)) = NULL;                                    \
 205         (head)->stqh_last = &STAILQ_FIRST((head));                      \
 206 } while (0)
 207
 208 #define STAILQ_INSERT_AFTER(head, tqelm, elm, field) do {               \
 209         if ((STAILQ_NEXT((elm), field) = STAILQ_NEXT((tqelm), field)) == NULL)\
 210                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 211         STAILQ_NEXT((tqelm), field) = (elm);                            \
 212 } while (0)
 213
 214 #define STAILQ_INSERT_HEAD(head, elm, field) do {                       \
 215         if ((STAILQ_NEXT((elm), field) = STAILQ_FIRST((head))) == NULL) \
 216                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 217         STAILQ_FIRST((head)) = (elm);                                   \
 218 } while (0)
 219
 220 #define STAILQ_INSERT_TAIL(head, elm, field) do {                       \
 221         STAILQ_NEXT((elm), field) = NULL;                               \
 222         *(head)->stqh_last = (elm);                                     \
 223         (head)->stqh_last = &STAILQ_NEXT((elm), field);                 \
 224 } while (0)
 225
 226 #define STAILQ_LAST(head, type, field)                                  \
 227         (STAILQ_EMPTY(head) ?                                           \
 228                 NULL :                                                  \
 229                 ((struct type *)                                        \
 230                 ((char *)((head)->stqh_last) - __offsetof(struct type, field))))
 231
 232 #define STAILQ_NEXT(elm, field) ((elm)->field.stqe_next)
 233
 234 #define STAILQ_REMOVE(head, elm, type, field) do {                      \
 235         if (STAILQ_FIRST((head)) == (elm)) {                            \
 236                 STAILQ_REMOVE_HEAD(head, field);                        \
 237         }                                                               \
 238         else {                                                          \
 239                 struct type *curelm = STAILQ_FIRST((head));             \
 240                 while (STAILQ_NEXT(curelm, field) != (elm))             \
 241                         curelm = STAILQ_NEXT(curelm, field);            \
 242                 if ((STAILQ_NEXT(curelm, field) =                       \
 243                      STAILQ_NEXT(STAILQ_NEXT(curelm, field), field)) == NULL)\
 244                         (head)->stqh_last = &STAILQ_NEXT((curelm), field);\
 245         }                                                               \
 246 } while (0)
 247
 248 #define STAILQ_REMOVE_HEAD(head, field) do {                            \
 249         if ((STAILQ_FIRST((head)) =                                     \
 250              STAILQ_NEXT(STAILQ_FIRST((head)), field)) == NULL)         \
 251                 (head)->stqh_last = &STAILQ_FIRST((head));              \
 252 } while (0)
 253
 254 #define STAILQ_REMOVE_HEAD_UNTIL(head, elm, field) do {                 \
 255         if ((STAILQ_FIRST((head)) = STAILQ_NEXT((elm), field)) == NULL) \
 256                 (head)->stqh_last = &STAILQ_FIRST((head));              \
 257 } while (0)
 258
 259 /*
 260  * List declarations.
 261  */
 262 #define LIST_HEAD(name, type)                                           \
 263 struct name {                                                           \
 264         struct type *lh_first;  /* first element */                     \
 265 }
 266
 267 #define LIST_HEAD_INITIALIZER(head)                                     \
 268         { NULL }
 269
 270 #define LIST_ENTRY(type)                                                \
 271 struct {                                                                \
 272         struct type *le_next;   /* next element */                      \
 273         struct type **le_prev;  /* address of previous next element */  \
 274 }
 275
 276 /*
 277  * List functions.
 278  */
 279
 280 #define LIST_EMPTY(head)        ((head)->lh_first == NULL)
 281
 282 #define LIST_FIRST(head)        ((head)->lh_first)
 283
 284 #define LIST_FOREACH(var, head, field)                                  \
 285         for ((var) = LIST_FIRST((head));                                \
 286             (var);                                                      \
 287             (var) = LIST_NEXT((var), field))
 288
 289 #define LIST_INIT(head) do {                                            \
 290         LIST_FIRST((head)) = NULL;                                      \
 291 } while (0)
 292
 293 #define LIST_INSERT_AFTER(listelm, elm, field) do {                     \
 294         if ((LIST_NEXT((elm), field) = LIST_NEXT((listelm), field)) != NULL)\
 295                 LIST_NEXT((listelm), field)->field.le_prev =            \
 296                     &LIST_NEXT((elm), field);                           \
 297         LIST_NEXT((listelm), field) = (elm);                            \
 298         (elm)->field.le_prev = &LIST_NEXT((listelm), field);            \
 299 } while (0)
 300
 301 #define LIST_INSERT_BEFORE(listelm, elm, field) do {                    \
 302         (elm)->field.le_prev = (listelm)->field.le_prev;                \
 303         LIST_NEXT((elm), field) = (listelm);                            \
 304         *(listelm)->field.le_prev = (elm);                              \
 305         (listelm)->field.le_prev = &LIST_NEXT((elm), field);            \
 306 } while (0)
 307
 308 #define LIST_INSERT_HEAD(head, elm, field) do {                         \
 309         if ((LIST_NEXT((elm), field) = LIST_FIRST((head))) != NULL)     \
 310                 LIST_FIRST((head))->field.le_prev = &LIST_NEXT((elm), field);\
 311         LIST_FIRST((head)) = (elm);                                     \
 312         (elm)->field.le_prev = &LIST_FIRST((head));                     \
 313 } while (0)
 314
 315 #define LIST_NEXT(elm, field)   ((elm)->field.le_next)
 316
 317 #define LIST_REMOVE(elm, field) do {                                    \
 318         if (LIST_NEXT((elm), field) != NULL)                            \
 319                 LIST_NEXT((elm), field)->field.le_prev =                \
 320                     (elm)->field.le_prev;                               \
 321         *(elm)->field.le_prev = LIST_NEXT((elm), field);                \
 322 } while (0)
 323
 324 /*
 325  * Tail queue declarations.
 326  */
 327 #define TAILQ_HEAD(name, type)                                          \
 328 struct name {                                                           \
 329         struct type *tqh_first; /* first element */                     \
 330         struct type **tqh_last; /* addr of last next element */         \
 331 }
 332
 333 #define TAILQ_HEAD_INITIALIZER(head)                                    \
 334         { NULL, &(head).tqh_first }
 335
 336 #define TAILQ_ENTRY(type)                                               \
 337 struct {                                                                \
 338         struct type *tqe_next;  /* next element */                      \
 339         struct type **tqe_prev; /* address of previous next element */  \
 340 }
 341
 342 /*
 343  * Tail queue functions.
 344  */
 345 #define TAILQ_EMPTY(head)       ((head)->tqh_first == NULL)
 346
 347 #define TAILQ_FIRST(head)       ((head)->tqh_first)
 348
 349 #define TAILQ_FOREACH(var, head, field)                                 \
 350         for ((var) = TAILQ_FIRST((head));                               \
 351             (var);                                                      \
 352             (var) = TAILQ_NEXT((var), field))
 353
 354 #define TAILQ_FOREACH_REVERSE(var, head, headname, field)               \
 355         for ((var) = TAILQ_LAST((head), headname);                      \
 356             (var);                                                      \
 357             (var) = TAILQ_PREV((var), headname, field))
 358
 359 #define TAILQ_INIT(head) do {                                           \
 360         TAILQ_FIRST((head)) = NULL;                                     \
 361         (head)->tqh_last = &TAILQ_FIRST((head));                        \
 362 } while (0)
 363
 364 #define TAILQ_INSERT_AFTER(head, listelm, elm, field) do {              \
 365         if ((TAILQ_NEXT((elm), field) = TAILQ_NEXT((listelm), field)) != NULL)\
 366                 TAILQ_NEXT((elm), field)->field.tqe_prev =              \
 367                     &TAILQ_NEXT((elm), field);                          \
 368         else                                                            \
 369                 (head)->tqh_last = &TAILQ_NEXT((elm), field);           \
 370         TAILQ_NEXT((listelm), field) = (elm);                           \
 371         (elm)->field.tqe_prev = &TAILQ_NEXT((listelm), field);          \
 372 } while (0)
 373
 374 #define TAILQ_INSERT_BEFORE(listelm, elm, field) do {                   \
 375         (elm)->field.tqe_prev = (listelm)->field.tqe_prev;              \
 376         TAILQ_NEXT((elm), field) = (listelm);                           \
 377         *(listelm)->field.tqe_prev = (elm);                             \
 378         (listelm)->field.tqe_prev = &TAILQ_NEXT((elm), field);          \
 379 } while (0)
 380
 381 #define TAILQ_INSERT_HEAD(head, elm, field) do {                        \
 382         if ((TAILQ_NEXT((elm), field) = TAILQ_FIRST((head))) != NULL)   \
 383                 TAILQ_FIRST((head))->field.tqe_prev =                   \
 384                     &TAILQ_NEXT((elm), field);                          \
 385         else                                                            \
 386                 (head)->tqh_last = &TAILQ_NEXT((elm), field);           \
 387         TAILQ_FIRST((head)) = (elm);                                    \
 388         (elm)->field.tqe_prev = &TAILQ_FIRST((head));                   \
 389 } while (0)
 390
 391 #define TAILQ_INSERT_TAIL(head, elm, field) do {                        \
 392         TAILQ_NEXT((elm), field) = NULL;                                \
 393         (elm)->field.tqe_prev = (head)->tqh_last;                       \
 394         *(head)->tqh_last = (elm);                                      \
 395         (head)->tqh_last = &TAILQ_NEXT((elm), field);                   \
 396 } while (0)
 397
 398 #define TAILQ_LAST(head, headname)                                      \
 399         (*(((struct headname *)((head)->tqh_last))->tqh_last))
 400
 401 #define TAILQ_NEXT(elm, field) ((elm)->field.tqe_next)
 402
 403 #define TAILQ_PREV(elm, headname, field)                                \
 404         (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
 405
 406 #define TAILQ_REMOVE(head, elm, field) do {                             \
 407         if ((TAILQ_NEXT((elm), field)) != NULL)                         \
 408                 TAILQ_NEXT((elm), field)->field.tqe_prev =              \
 409                     (elm)->field.tqe_prev;                              \
 410         else                                                            \
 411                 (head)->tqh_last = (elm)->field.tqe_prev;               \
 412         *(elm)->field.tqe_prev = TAILQ_NEXT((elm), field);              \
 413 } while (0)
 414
 415 /*
 416  * Circular queue declarations.
 417  */
 418 #define CIRCLEQ_HEAD(name, type)                                        \
 419 struct name {                                                           \
 420         struct type *cqh_first;         /* first element */             \
 421         struct type *cqh_last;          /* last element */              \
 422 }
 423
 424 #define CIRCLEQ_HEAD_INITIALIZER(head)                                  \
 425         { (void *)&(head), (void *)&(head) }
 426
 427 #define CIRCLEQ_ENTRY(type)                                             \
 428 struct {                                                                \
 429         struct type *cqe_next;          /* next element */              \
 430         struct type *cqe_prev;          /* previous element */          \
 431 }
 432
 433 /*
 434  * Circular queue functions.
 435  */
 436 #define CIRCLEQ_EMPTY(head)     ((head)->cqh_first == (void *)(head))
 437
 438 #define CIRCLEQ_FIRST(head)     ((head)->cqh_first)
 439
 440 #define CIRCLEQ_FOREACH(var, head, field)                               \
 441         for ((var) = CIRCLEQ_FIRST((head));                             \
 442             (var) != (void *)(head) || ((var) = NULL);                  \
 443             (var) = CIRCLEQ_NEXT((var), field))
 444
 445 #define CIRCLEQ_FOREACH_REVERSE(var, head, field)                       \
 446         for ((var) = CIRCLEQ_LAST((head));                              \
 447             (var) != (void *)(head) || ((var) = NULL);                  \
 448             (var) = CIRCLEQ_PREV((var), field))
 449
 450 #define CIRCLEQ_INIT(head) do {                                         \
 451         CIRCLEQ_FIRST((head)) = (void *)(head);                         \
 452         CIRCLEQ_LAST((head)) = (void *)(head);                          \
 453 } while (0)
 454
 455 #define CIRCLEQ_INSERT_AFTER(head, listelm, elm, field) do {            \
 456         CIRCLEQ_NEXT((elm), field) = CIRCLEQ_NEXT((listelm), field);    \
 457         CIRCLEQ_PREV((elm), field) = (listelm);                         \
 458         if (CIRCLEQ_NEXT((listelm), field) == (void *)(head))           \
 459                 CIRCLEQ_LAST((head)) = (elm);                           \
 460         else                                                            \
 461                 CIRCLEQ_PREV(CIRCLEQ_NEXT((listelm), field), field) = (elm);\
 462         CIRCLEQ_NEXT((listelm), field) = (elm);                         \
 463 } while (0)
 464
 465 #define CIRCLEQ_INSERT_BEFORE(head, listelm, elm, field) do {           \
 466         CIRCLEQ_NEXT((elm), field) = (listelm);                         \
 467         CIRCLEQ_PREV((elm), field) = CIRCLEQ_PREV((listelm), field);    \
 468         if (CIRCLEQ_PREV((listelm), field) == (void *)(head))           \
 469                 CIRCLEQ_FIRST((head)) = (elm);                          \
 470         else                                                            \
 471                 CIRCLEQ_NEXT(CIRCLEQ_PREV((listelm), field), field) = (elm);\
 472         CIRCLEQ_PREV((listelm), field) = (elm);                         \
 473 } while (0)
 474
 475 #define CIRCLEQ_INSERT_HEAD(head, elm, field) do {                      \
 476         CIRCLEQ_NEXT((elm), field) = CIRCLEQ_FIRST((head));             \
 477         CIRCLEQ_PREV((elm), field) = (void *)(head);                    \
 478         if (CIRCLEQ_LAST((head)) == (void *)(head))                     \
 479                 CIRCLEQ_LAST((head)) = (elm);                           \
 480         else                                                            \
 481                 CIRCLEQ_PREV(CIRCLEQ_FIRST((head)), field) = (elm);     \
 482         CIRCLEQ_FIRST((head)) = (elm);                                  \
 483 } while (0)
 484
 485 #define CIRCLEQ_INSERT_TAIL(head, elm, field) do {                      \
 486         CIRCLEQ_NEXT((elm), field) = (void *)(head);                    \
 487         CIRCLEQ_PREV((elm), field) = CIRCLEQ_LAST((head));              \
 488         if (CIRCLEQ_FIRST((head)) == (void *)(head))                    \
 489                 CIRCLEQ_FIRST((head)) = (elm);                          \
 490         else                                                            \
 491                 CIRCLEQ_NEXT(CIRCLEQ_LAST((head)), field) = (elm);      \
 492         CIRCLEQ_LAST((head)) = (elm);                                   \
 493 } while (0)
 494
 495 #define CIRCLEQ_LAST(head)      ((head)->cqh_last)
 496
 497 #define CIRCLEQ_NEXT(elm,field) ((elm)->field.cqe_next)
 498
 499 #define CIRCLEQ_PREV(elm,field) ((elm)->field.cqe_prev)
 500
 501 #define CIRCLEQ_REMOVE(head, elm, field) do {                           \
 502         if (CIRCLEQ_NEXT((elm), field) == (void *)(head))               \
 503                 CIRCLEQ_LAST((head)) = CIRCLEQ_PREV((elm), field);      \
 504         else                                                            \
 505                 CIRCLEQ_PREV(CIRCLEQ_NEXT((elm), field), field) =       \
 506                     CIRCLEQ_PREV((elm), field);                         \
 507         if (CIRCLEQ_PREV((elm), field) == (void *)(head))               \
 508                 CIRCLEQ_FIRST((head)) = CIRCLEQ_NEXT((elm), field);     \
 509         else                                                            \
 510                 CIRCLEQ_NEXT(CIRCLEQ_PREV((elm), field), field) =       \
 511                     CIRCLEQ_NEXT((elm), field);                         \
 512 } while (0)
 513
 514 #ifdef _KERNEL
 515
 516 /*
 517  * XXX insque() and remque() are an old way of handling certain queues.
 518  * They bogusly assumes that all queue heads look alike.
 519  */
 520
 521 struct quehead {
 522         struct quehead *qh_link;
 523         struct quehead *qh_rlink;
 524 };
 525
 526 #ifdef  __GNUC__
 527
 528 static __inline void
 529 insque(void *a, void *b)
 530 {
 531         struct quehead *element = (struct quehead *)a,
 532                  *head = (struct quehead *)b;
 533
 534         element->qh_link = head->qh_link;
 535         element->qh_rlink = head;
 536         head->qh_link = element;
 537         element->qh_link->qh_rlink = element;
 538 }
 539
 540 static __inline void
 541 remque(void *a)
 542 {
 543         struct quehead *element = (struct quehead *)a;
 544
 545         element->qh_link->qh_rlink = element->qh_rlink;
 546         element->qh_rlink->qh_link = element->qh_link;
 547         element->qh_rlink = 0;
 548 }
 549
 550 #else /* !__GNUC__ */
 551
 552 void    insque __P((void *a, void *b));
 553 void    remque __P((void *a));
 554
 555 #endif /* __GNUC__ */
 556
 557 #endif /* _KERNEL */
 558
 559 #endif /* !_SYS_QUEUE_H_ */