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  * $DragonFly: src/sys/sys/queue.h,v 1.5 2004/04/10 00:48:06 hsu Exp $
  36  */
  37
  38 #ifndef _SYS_QUEUE_H_
  39 #define _SYS_QUEUE_H_
  40
  41 #ifndef _MACHINE_STDINT_H_
  42 #include <machine/stdint.h>     /* for __offsetof */
  43 #endif
  44
  45 /*
  46  * This file defines five types of data structures: singly-linked lists,
  47  * singly-linked tail queues, lists, tail queues, and circular queues.
  48  *
  49  * A singly-linked list is headed by a single forward pointer. The elements
  50  * are singly linked for minimum space and pointer manipulation overhead at
  51  * the expense of O(n) removal for arbitrary elements. New elements can be
  52  * added to the list after an existing element or at the head of the list.
  53  * Elements being removed from the head of the list should use the explicit
  54  * macro for this purpose for optimum efficiency. A singly-linked list may
  55  * only be traversed in the forward direction.  Singly-linked lists are ideal
  56  * for applications with large datasets and few or no removals or for
  57  * implementing a LIFO queue.
  58  *
  59  * A singly-linked tail queue is headed by a pair of pointers, one to the
  60  * head of the list and the other to the tail of the list. The elements are
  61  * singly linked for minimum space and pointer manipulation overhead at the
  62  * expense of O(n) removal for arbitrary elements. New elements can be added
  63  * to the list after an existing element, at the head of the list, or at the
  64  * end of the list. Elements being removed from the head of the tail queue
  65  * should use the explicit macro for this purpose for optimum efficiency.
  66  * A singly-linked tail queue may only be traversed in the forward direction.
  67  * Singly-linked tail queues are ideal for applications with large datasets
  68  * and few or no removals or for implementing a FIFO queue.
  69  *
  70  * A list is headed by a single forward pointer (or an array of forward
  71  * pointers for a hash table header). The elements are doubly linked
  72  * so that an arbitrary element can be removed without a need to
  73  * traverse the list. New elements can be added to the list before
  74  * or after an existing element or at the head of the list. A list
  75  * may only be traversed in the forward direction.
  76  *
  77  * A tail queue is headed by a pair of pointers, one to the head of the
  78  * list and the other to the tail of the list. The elements are doubly
  79  * linked so that an arbitrary element can be removed without a need to
  80  * traverse the list. New elements can be added to the list before or
  81  * after an existing element, at the head of the list, or at the end of
  82  * the list. A tail queue may be traversed in either direction.
  83  *
  84  * A circle queue is headed by a pair of pointers, one to the head of the
  85  * list and the other to the tail of the list. The elements are doubly
  86  * linked so that an arbitrary element can be removed without a need to
  87  * traverse the list. New elements can be added to the list before or after
  88  * an existing element, at the head of the list, or at the end of the list.
  89  * A circle queue may be traversed in either direction, but has a more
  90  * complex end of list detection.
  91  *
  92  * For details on the use of these macros, see the queue(3) manual page.
  93  *
  94  *
  95  *                      SLIST   LIST    STAILQ  TAILQ   CIRCLEQ
  96  * _HEAD                +       +       +       +       +
  97  * _HEAD_INITIALIZER    +       +       +       +       +
  98  * _ENTRY               +       +       +       +       +
  99  * _INIT                +       +       +       +       +
 100  * _EMPTY               +       +       +       +       +
 101  * _FIRST               +       +       +       +       +
 102  * _NEXT                +       +       +       +       +
 103  * _PREV                -       -       -       +       +
 104  * _LAST                -       -       +       +       +
 105  * _FOREACH             +       +       +       +       +
 106  * _FOREACH_REVERSE     -       -       -       +       +
 107  * _INSERT_HEAD         +       +       +       +       +
 108  * _INSERT_BEFORE       -       +       -       +       +
 109  * _INSERT_AFTER        +       +       +       +       +
 110  * _INSERT_TAIL         -       -       +       +       +
 111  * _REMOVE_HEAD         +       -       +       -       -
 112  * _REMOVE              +       +       +       +       +
 113  *
 114  */
 115
 116 /*
 117  * Singly-linked List declarations.
 118  */
 119 #define SLIST_HEAD(name, type)                                          \
 120 struct name {                                                           \
 121         struct type *slh_first; /* first element */                     \
 122 }
 123
 124 #define SLIST_HEAD_INITIALIZER(head)                                    \
 125         { NULL }
 126
 127 #define SLIST_ENTRY(type)                                               \
 128 struct {                                                                \
 129         struct type *sle_next;  /* next element */                      \
 130 }
 131
 132 /*
 133  * Singly-linked List functions.
 134  */
 135 #define SLIST_EMPTY(head)       ((head)->slh_first == NULL)
 136
 137 #define SLIST_FIRST(head)       ((head)->slh_first)
 138
 139 #define SLIST_FOREACH(var, head, field)                                 \
 140         for ((var) = SLIST_FIRST((head));                               \
 141             (var);                                                      \
 142             (var) = SLIST_NEXT((var), field))
 143
 144 #define SLIST_INIT(head) do {                                           \
 145         SLIST_FIRST((head)) = NULL;                                     \
 146 } while (0)
 147
 148 #define SLIST_INSERT_AFTER(slistelm, elm, field) do {                   \
 149         SLIST_NEXT((elm), field) = SLIST_NEXT((slistelm), field);       \
 150         SLIST_NEXT((slistelm), field) = (elm);                          \
 151 } while (0)
 152
 153 #define SLIST_INSERT_HEAD(head, elm, field) do {                        \
 154         SLIST_NEXT((elm), field) = SLIST_FIRST((head));                 \
 155         SLIST_FIRST((head)) = (elm);                                    \
 156 } while (0)
 157
 158 #define SLIST_NEXT(elm, field)  ((elm)->field.sle_next)
 159
 160 #define SLIST_REMOVE(head, elm, type, field) do {                       \
 161         if (SLIST_FIRST((head)) == (elm)) {                             \
 162                 SLIST_REMOVE_HEAD((head), field);                       \
 163         }                                                               \
 164         else {                                                          \
 165                 struct type *curelm = SLIST_FIRST((head));              \
 166                 while (SLIST_NEXT(curelm, field) != (elm))              \
 167                         curelm = SLIST_NEXT(curelm, field);             \
 168                 SLIST_NEXT(curelm, field) =                             \
 169                     SLIST_NEXT(SLIST_NEXT(curelm, field), field);       \
 170         }                                                               \
 171 } while (0)
 172
 173 #define SLIST_REMOVE_HEAD(head, field) do {                             \
 174         SLIST_FIRST((head)) = SLIST_NEXT(SLIST_FIRST((head)), field);   \
 175 } while (0)
 176
 177 /*
 178  * Singly-linked Tail queue declarations.
 179  */
 180 #define STAILQ_HEAD(name, type)                                         \
 181 struct name {                                                           \
 182         struct type *stqh_first;/* first element */                     \
 183         struct type **stqh_last;/* addr of last next element */         \
 184 }
 185
 186 #define STAILQ_HEAD_INITIALIZER(head)                                   \
 187         { NULL, &(head).stqh_first }
 188
 189 #define STAILQ_ENTRY(type)                                              \
 190 struct {                                                                \
 191         struct type *stqe_next; /* next element */                      \
 192 }
 193
 194 /*
 195  * Singly-linked Tail queue functions.
 196  */
 197 #define STAILQ_EMPTY(head)      ((head)->stqh_first == NULL)
 198
 199 #define STAILQ_FIRST(head)      ((head)->stqh_first)
 200
 201 #define STAILQ_FOREACH(var, head, field)                                \
 202         for((var) = STAILQ_FIRST((head));                               \
 203            (var);                                                       \
 204            (var) = STAILQ_NEXT((var), field))
 205
 206 #define STAILQ_INIT(head) do {                                          \
 207         STAILQ_FIRST((head)) = NULL;                                    \
 208         (head)->stqh_last = &STAILQ_FIRST((head));                      \
 209 } while (0)
 210
 211 #define STAILQ_INSERT_AFTER(head, tqelm, elm, field) do {               \
 212         if ((STAILQ_NEXT((elm), field) = STAILQ_NEXT((tqelm), field)) == NULL)\
 213                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 214         STAILQ_NEXT((tqelm), field) = (elm);                            \
 215 } while (0)
 216
 217 #define STAILQ_INSERT_HEAD(head, elm, field) do {                       \
 218         if ((STAILQ_NEXT((elm), field) = STAILQ_FIRST((head))) == NULL) \
 219                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 220         STAILQ_FIRST((head)) = (elm);                                   \
 221 } while (0)
 222
 223 #define STAILQ_INSERT_TAIL(head, elm, field) do {                       \
 224         STAILQ_NEXT((elm), field) = NULL;                               \
 225         *(head)->stqh_last = (elm);                                     \
 226         (head)->stqh_last = &STAILQ_NEXT((elm), field);                 \
 227 } while (0)
 228
 229 #define STAILQ_LAST(head, type, field)                                  \
 230         (STAILQ_EMPTY(head) ?                                           \
 231                 NULL :                                                  \
 232                 ((struct type *)                                        \
 233                 ((char *)((head)->stqh_last) - __offsetof(struct type, field))))
 234
 235 #define STAILQ_NEXT(elm, field) ((elm)->field.stqe_next)
 236
 237 #define STAILQ_REMOVE(head, elm, type, field) do {                      \
 238         if (STAILQ_FIRST((head)) == (elm)) {                            \
 239                 STAILQ_REMOVE_HEAD(head, field);                        \
 240         }                                                               \
 241         else {                                                          \
 242                 struct type *curelm = STAILQ_FIRST((head));             \
 243                 while (STAILQ_NEXT(curelm, field) != (elm))             \
 244                         curelm = STAILQ_NEXT(curelm, field);            \
 245                 if ((STAILQ_NEXT(curelm, field) =                       \
 246                      STAILQ_NEXT(STAILQ_NEXT(curelm, field), field)) == NULL)\
 247                         (head)->stqh_last = &STAILQ_NEXT((curelm), field);\
 248         }                                                               \
 249 } while (0)
 250
 251 #define STAILQ_REMOVE_HEAD(head, field) do {                            \
 252         if ((STAILQ_FIRST((head)) =                                     \
 253              STAILQ_NEXT(STAILQ_FIRST((head)), field)) == NULL)         \
 254                 (head)->stqh_last = &STAILQ_FIRST((head));              \
 255 } while (0)
 256
 257 #define STAILQ_REMOVE_HEAD_UNTIL(head, elm, field) do {                 \
 258         if ((STAILQ_FIRST((head)) = STAILQ_NEXT((elm), field)) == NULL) \
 259                 (head)->stqh_last = &STAILQ_FIRST((head));              \
 260 } while (0)
 261
 262 /*
 263  * List declarations.
 264  */
 265 #define LIST_HEAD(name, type)                                           \
 266 struct name {                                                           \
 267         struct type *lh_first;  /* first element */                     \
 268 }
 269
 270 #define LIST_HEAD_INITIALIZER(head)                                     \
 271         { NULL }
 272
 273 #define LIST_ENTRY(type)                                                \
 274 struct {                                                                \
 275         struct type *le_next;   /* next element */                      \
 276         struct type **le_prev;  /* address of previous next element */  \
 277 }
 278
 279 /*
 280  * List functions.
 281  */
 282
 283 #define LIST_EMPTY(head)        ((head)->lh_first == NULL)
 284
 285 #define LIST_FIRST(head)        ((head)->lh_first)
 286
 287 #define LIST_FOREACH(var, head, field)                                  \
 288         for ((var) = LIST_FIRST((head));                                \
 289             (var);                                                      \
 290             (var) = LIST_NEXT((var), field))
 291
 292 #define LIST_INIT(head) do {                                            \
 293         LIST_FIRST((head)) = NULL;                                      \
 294 } while (0)
 295
 296 #define LIST_INSERT_AFTER(listelm, elm, field) do {                     \
 297         if ((LIST_NEXT((elm), field) = LIST_NEXT((listelm), field)) != NULL)\
 298                 LIST_NEXT((listelm), field)->field.le_prev =            \
 299                     &LIST_NEXT((elm), field);                           \
 300         LIST_NEXT((listelm), field) = (elm);                            \
 301         (elm)->field.le_prev = &LIST_NEXT((listelm), field);            \
 302 } while (0)
 303
 304 #define LIST_INSERT_BEFORE(listelm, elm, field) do {                    \
 305         (elm)->field.le_prev = (listelm)->field.le_prev;                \
 306         LIST_NEXT((elm), field) = (listelm);                            \
 307         *(listelm)->field.le_prev = (elm);                              \
 308         (listelm)->field.le_prev = &LIST_NEXT((elm), field);            \
 309 } while (0)
 310
 311 #define LIST_INSERT_HEAD(head, elm, field) do {                         \
 312         if ((LIST_NEXT((elm), field) = LIST_FIRST((head))) != NULL)     \
 313                 LIST_FIRST((head))->field.le_prev = &LIST_NEXT((elm), field);\
 314         LIST_FIRST((head)) = (elm);                                     \
 315         (elm)->field.le_prev = &LIST_FIRST((head));                     \
 316 } while (0)
 317
 318 #define LIST_NEXT(elm, field)   ((elm)->field.le_next)
 319
 320 #define LIST_REMOVE(elm, field) do {                                    \
 321         if (LIST_NEXT((elm), field) != NULL)                            \
 322                 LIST_NEXT((elm), field)->field.le_prev =                \
 323                     (elm)->field.le_prev;                               \
 324         *(elm)->field.le_prev = LIST_NEXT((elm), field);                \
 325 } while (0)
 326
 327 /*
 328  * Tail queue declarations.
 329  */
 330 #define TAILQ_HEAD(name, type)                                          \
 331 struct name {                                                           \
 332         struct type *tqh_first; /* first element */                     \
 333         struct type **tqh_last; /* addr of last next element */         \
 334 }
 335
 336 #define TAILQ_HEAD_INITIALIZER(head)                                    \
 337         { NULL, &(head).tqh_first }
 338
 339 #define TAILQ_ENTRY(type)                                               \
 340 struct {                                                                \
 341         struct type *tqe_next;  /* next element */                      \
 342         struct type **tqe_prev; /* address of previous next element */  \
 343 }
 344
 345 /*
 346  * Tail queue functions.
 347  */
 348 #define TAILQ_EMPTY(head)       ((head)->tqh_first == NULL)
 349
 350 #define TAILQ_FIRST(head)       ((head)->tqh_first)
 351
 352 #define TAILQ_FOREACH(var, head, field)                                 \
 353         for ((var) = TAILQ_FIRST((head));                               \
 354             (var);                                                      \
 355             (var) = TAILQ_NEXT((var), field))
 356
 357 #define TAILQ_FOREACH_REVERSE(var, head, headname, field)               \
 358         for ((var) = TAILQ_LAST((head), headname);                      \
 359             (var);                                                      \
 360             (var) = TAILQ_PREV((var), headname, field))
 361
 362 #define TAILQ_FOREACH_MUTABLE(var, head, field, nvar)                   \
 363         for ((var) = TAILQ_FIRST((head));                               \
 364              (var) && ((nvar) = TAILQ_NEXT((var), field), (var));       \
 365              (var) = (nvar))
 366
 367 #define TAILQ_INIT(head) do {                                           \
 368         TAILQ_FIRST((head)) = NULL;                                     \
 369         (head)->tqh_last = &TAILQ_FIRST((head));                        \
 370 } while (0)
 371
 372 #define TAILQ_INSERT_AFTER(head, listelm, elm, field) do {              \
 373         if ((TAILQ_NEXT((elm), field) = TAILQ_NEXT((listelm), field)) != NULL)\
 374                 TAILQ_NEXT((elm), field)->field.tqe_prev =              \
 375                     &TAILQ_NEXT((elm), field);                          \
 376         else                                                            \
 377                 (head)->tqh_last = &TAILQ_NEXT((elm), field);           \
 378         TAILQ_NEXT((listelm), field) = (elm);                           \
 379         (elm)->field.tqe_prev = &TAILQ_NEXT((listelm), field);          \
 380 } while (0)
 381
 382 #define TAILQ_INSERT_BEFORE(listelm, elm, field) do {                   \
 383         (elm)->field.tqe_prev = (listelm)->field.tqe_prev;              \
 384         TAILQ_NEXT((elm), field) = (listelm);                           \
 385         *(listelm)->field.tqe_prev = (elm);                             \
 386         (listelm)->field.tqe_prev = &TAILQ_NEXT((elm), field);          \
 387 } while (0)
 388
 389 #define TAILQ_INSERT_HEAD(head, elm, field) do {                        \
 390         if ((TAILQ_NEXT((elm), field) = TAILQ_FIRST((head))) != NULL)   \
 391                 TAILQ_FIRST((head))->field.tqe_prev =                   \
 392                     &TAILQ_NEXT((elm), field);                          \
 393         else                                                            \
 394                 (head)->tqh_last = &TAILQ_NEXT((elm), field);           \
 395         TAILQ_FIRST((head)) = (elm);                                    \
 396         (elm)->field.tqe_prev = &TAILQ_FIRST((head));                   \
 397 } while (0)
 398
 399 #define TAILQ_INSERT_TAIL(head, elm, field) do {                        \
 400         TAILQ_NEXT((elm), field) = NULL;                                \
 401         (elm)->field.tqe_prev = (head)->tqh_last;                       \
 402         *(head)->tqh_last = (elm);                                      \
 403         (head)->tqh_last = &TAILQ_NEXT((elm), field);                   \
 404 } while (0)
 405
 406 #define TAILQ_LAST(head, headname)                                      \
 407         (*(((struct headname *)((head)->tqh_last))->tqh_last))
 408
 409 #define TAILQ_NEXT(elm, field) ((elm)->field.tqe_next)
 410
 411 #define TAILQ_PREV(elm, headname, field)                                \
 412         (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
 413
 414 #define TAILQ_REMOVE(head, elm, field) do {                             \
 415         if ((TAILQ_NEXT((elm), field)) != NULL)                         \
 416                 TAILQ_NEXT((elm), field)->field.tqe_prev =              \
 417                     (elm)->field.tqe_prev;                              \
 418         else                                                            \
 419                 (head)->tqh_last = (elm)->field.tqe_prev;               \
 420         *(elm)->field.tqe_prev = TAILQ_NEXT((elm), field);              \
 421 } while (0)
 422
 423 /*
 424  * Circular queue declarations.
 425  */
 426 #define CIRCLEQ_HEAD(name, type)                                        \
 427 struct name {                                                           \
 428         struct type *cqh_first;         /* first element */             \
 429         struct type *cqh_last;          /* last element */              \
 430 }
 431
 432 #define CIRCLEQ_HEAD_INITIALIZER(head)                                  \
 433         { (void *)&(head), (void *)&(head) }
 434
 435 #define CIRCLEQ_ENTRY(type)                                             \
 436 struct {                                                                \
 437         struct type *cqe_next;          /* next element */              \
 438         struct type *cqe_prev;          /* previous element */          \
 439 }
 440
 441 /*
 442  * Circular queue functions.
 443  */
 444 #define CIRCLEQ_EMPTY(head)     ((head)->cqh_first == (void *)(head))
 445
 446 #define CIRCLEQ_FIRST(head)     ((head)->cqh_first)
 447
 448 #define CIRCLEQ_FOREACH(var, head, field)                               \
 449         for ((var) = CIRCLEQ_FIRST((head));                             \
 450             (var) != (void *)(head) || ((var) = NULL);                  \
 451             (var) = CIRCLEQ_NEXT((var), field))
 452
 453 #define CIRCLEQ_FOREACH_REVERSE(var, head, field)                       \
 454         for ((var) = CIRCLEQ_LAST((head));                              \
 455             (var) != (void *)(head) || ((var) = NULL);                  \
 456             (var) = CIRCLEQ_PREV((var), field))
 457
 458 #define CIRCLEQ_INIT(head) do {                                         \
 459         CIRCLEQ_FIRST((head)) = (void *)(head);                         \
 460         CIRCLEQ_LAST((head)) = (void *)(head);                          \
 461 } while (0)
 462
 463 #define CIRCLEQ_INSERT_AFTER(head, listelm, elm, field) do {            \
 464         CIRCLEQ_NEXT((elm), field) = CIRCLEQ_NEXT((listelm), field);    \
 465         CIRCLEQ_PREV((elm), field) = (listelm);                         \
 466         if (CIRCLEQ_NEXT((listelm), field) == (void *)(head))           \
 467                 CIRCLEQ_LAST((head)) = (elm);                           \
 468         else                                                            \
 469                 CIRCLEQ_PREV(CIRCLEQ_NEXT((listelm), field), field) = (elm);\
 470         CIRCLEQ_NEXT((listelm), field) = (elm);                         \
 471 } while (0)
 472
 473 #define CIRCLEQ_INSERT_BEFORE(head, listelm, elm, field) do {           \
 474         CIRCLEQ_NEXT((elm), field) = (listelm);                         \
 475         CIRCLEQ_PREV((elm), field) = CIRCLEQ_PREV((listelm), field);    \
 476         if (CIRCLEQ_PREV((listelm), field) == (void *)(head))           \
 477                 CIRCLEQ_FIRST((head)) = (elm);                          \
 478         else                                                            \
 479                 CIRCLEQ_NEXT(CIRCLEQ_PREV((listelm), field), field) = (elm);\
 480         CIRCLEQ_PREV((listelm), field) = (elm);                         \
 481 } while (0)
 482
 483 #define CIRCLEQ_INSERT_HEAD(head, elm, field) do {                      \
 484         CIRCLEQ_NEXT((elm), field) = CIRCLEQ_FIRST((head));             \
 485         CIRCLEQ_PREV((elm), field) = (void *)(head);                    \
 486         if (CIRCLEQ_LAST((head)) == (void *)(head))                     \
 487                 CIRCLEQ_LAST((head)) = (elm);                           \
 488         else                                                            \
 489                 CIRCLEQ_PREV(CIRCLEQ_FIRST((head)), field) = (elm);     \
 490         CIRCLEQ_FIRST((head)) = (elm);                                  \
 491 } while (0)
 492
 493 #define CIRCLEQ_INSERT_TAIL(head, elm, field) do {                      \
 494         CIRCLEQ_NEXT((elm), field) = (void *)(head);                    \
 495         CIRCLEQ_PREV((elm), field) = CIRCLEQ_LAST((head));              \
 496         if (CIRCLEQ_FIRST((head)) == (void *)(head))                    \
 497                 CIRCLEQ_FIRST((head)) = (elm);                          \
 498         else                                                            \
 499                 CIRCLEQ_NEXT(CIRCLEQ_LAST((head)), field) = (elm);      \
 500         CIRCLEQ_LAST((head)) = (elm);                                   \
 501 } while (0)
 502
 503 #define CIRCLEQ_LAST(head)      ((head)->cqh_last)
 504
 505 #define CIRCLEQ_NEXT(elm,field) ((elm)->field.cqe_next)
 506
 507 #define CIRCLEQ_PREV(elm,field) ((elm)->field.cqe_prev)
 508
 509 #define CIRCLEQ_REMOVE(head, elm, field) do {                           \
 510         if (CIRCLEQ_NEXT((elm), field) == (void *)(head))               \
 511                 CIRCLEQ_LAST((head)) = CIRCLEQ_PREV((elm), field);      \
 512         else                                                            \
 513                 CIRCLEQ_PREV(CIRCLEQ_NEXT((elm), field), field) =       \
 514                     CIRCLEQ_PREV((elm), field);                         \
 515         if (CIRCLEQ_PREV((elm), field) == (void *)(head))               \
 516                 CIRCLEQ_FIRST((head)) = CIRCLEQ_NEXT((elm), field);     \
 517         else                                                            \
 518                 CIRCLEQ_NEXT(CIRCLEQ_PREV((elm), field), field) =       \
 519                     CIRCLEQ_NEXT((elm), field);                         \
 520 } while (0)
 521
 522 #ifdef _KERNEL
 523
 524 /*
 525  * XXX insque() and remque() are an old way of handling certain queues.
 526  * They bogusly assumes that all queue heads look alike.
 527  */
 528
 529 struct quehead {
 530         struct quehead *qh_link;
 531         struct quehead *qh_rlink;
 532 };
 533
 534 #ifdef  __GNUC__
 535
 536 static __inline void
 537 insque(void *a, void *b)
 538 {
 539         struct quehead *element = (struct quehead *)a,
 540                  *head = (struct quehead *)b;
 541
 542         element->qh_link = head->qh_link;
 543         element->qh_rlink = head;
 544         head->qh_link = element;
 545         element->qh_link->qh_rlink = element;
 546 }
 547
 548 static __inline void
 549 remque(void *a)
 550 {
 551         struct quehead *element = (struct quehead *)a;
 552
 553         element->qh_link->qh_rlink = element->qh_rlink;
 554         element->qh_rlink->qh_link = element->qh_link;
 555         element->qh_rlink = 0;
 556 }
 557
 558 #else /* !__GNUC__ */
 559
 560 void    insque (void *a, void *b);
 561 void    remque (void *a);
 562
 563 #endif /* __GNUC__ */
 564
 565 #endif /* _KERNEL */
 566
 567 #endif /* !_SYS_QUEUE_H_ */