bsd/sys/queue.h

   1 /*
   2  * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * Copyright (c) 1999-2003 Apple Computer, Inc.  All Rights Reserved.
   7  *
   8  * This file contains Original Code and/or Modifications of Original Code
   9  * as defined in and that are subject to the Apple Public Source License
  10  * Version 2.0 (the 'License'). You may not use this file except in
  11  * compliance with the License. Please obtain a copy of the License at
  12  * http://www.opensource.apple.com/apsl/ and read it before using this
  13  * file.
  14  *
  15  * The Original Code and all software distributed under the License are
  16  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  17  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  18  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  20  * Please see the License for the specific language governing rights and
  21  * limitations under the License.
  22  *
  23  * @APPLE_LICENSE_HEADER_END@
  24  */
  25 /*
  26  * Copyright (c) 1991, 1993
  27  *      The Regents of the University of California.  All rights reserved.
  28  *
  29  * Redistribution and use in source and binary forms, with or without
  30  * modification, are permitted provided that the following conditions
  31  * are met:
  32  * 1. Redistributions of source code must retain the above copyright
  33  *    notice, this list of conditions and the following disclaimer.
  34  * 2. Redistributions in binary form must reproduce the above copyright
  35  *    notice, this list of conditions and the following disclaimer in the
  36  *    documentation and/or other materials provided with the distribution.
  37  * 3. All advertising materials mentioning features or use of this software
  38  *    must display the following acknowledgement:
  39  *      This product includes software developed by the University of
  40  *      California, Berkeley and its contributors.
  41  * 4. Neither the name of the University nor the names of its contributors
  42  *    may be used to endorse or promote products derived from this software
  43  *    without specific prior written permission.
  44  *
  45  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  46  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  47  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  48  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  49  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  50  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  51  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  52  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  53  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  54  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  55  * SUCH DAMAGE.
  56  *
  57  *      @(#)queue.h     8.5 (Berkeley) 8/20/94
  58  */
  59
  60 #ifndef _SYS_QUEUE_H_
  61 #define _SYS_QUEUE_H_
  62
  63 /*
  64  * This file defines five types of data structures: singly-linked lists,
  65  * slingly-linked tail queues, lists, tail queues, and circular queues.
  66  *
  67  * A singly-linked list is headed by a single forward pointer. The elements
  68  * are singly linked for minimum space and pointer manipulation overhead at
  69  * the expense of O(n) removal for arbitrary elements. New elements can be
  70  * added to the list after an existing element or at the head of the list.
  71  * Elements being removed from the head of the list should use the explicit
  72  * macro for this purpose for optimum efficiency. A singly-linked list may
  73  * only be traversed in the forward direction.  Singly-linked lists are ideal
  74  * for applications with large datasets and few or no removals or for
  75  * implementing a LIFO queue.
  76  *
  77  * A singly-linked tail queue is headed by a pair of pointers, one to the
  78  * head of the list and the other to the tail of the list. The elements are
  79  * singly linked for minimum space and pointer manipulation overhead at the
  80  * expense of O(n) removal for arbitrary elements. New elements can be added
  81  * to the list after an existing element, at the head of the list, or at the
  82  * end of the list. Elements being removed from the head of the tail queue
  83  * should use the explicit macro for this purpose for optimum efficiency.
  84  * A singly-linked tail queue may only be traversed in the forward direction.
  85  * Singly-linked tail queues are ideal for applications with large datasets
  86  * and few or no removals or for implementing a FIFO queue.
  87  *
  88  * A list is headed by a single forward pointer (or an array of forward
  89  * pointers for a hash table header). The elements are doubly linked
  90  * so that an arbitrary element can be removed without a need to
  91  * traverse the list. New elements can be added to the list before
  92  * or after an existing element or at the head of the list. A list
  93  * may only be traversed in the forward direction.
  94  *
  95  * A tail queue is headed by a pair of pointers, one to the head of the
  96  * list and the other to the tail of the list. The elements are doubly
  97  * linked so that an arbitrary element can be removed without a need to
  98  * traverse the list. New elements can be added to the list before or
  99  * after an existing element, at the head of the list, or at the end of
 100  * the list. A tail queue may only be traversed in the forward direction.
 101  *
 102  * A circle queue is headed by a pair of pointers, one to the head of the
 103  * list and the other to the tail of the list. The elements are doubly
 104  * linked so that an arbitrary element can be removed without a need to
 105  * traverse the list. New elements can be added to the list before or after
 106  * an existing element, at the head of the list, or at the end of the list.
 107  * A circle queue may be traversed in either direction, but has a more
 108  * complex end of list detection.
 109  *
 110  * For details on the use of these macros, see the queue(3) manual page.
 111  *
 112  *
 113  *                      SLIST   LIST    STAILQ  TAILQ   CIRCLEQ
 114  * _HEAD                +       +       +       +       +
 115  * _ENTRY               +       +       +       +       +
 116  * _INIT                +       +       +       +       +
 117  * _EMPTY               +       +       +       +       +
 118  * _FIRST               +       +       +       +       +
 119  * _NEXT                +       +       +       +       +
 120  * _PREV                -       -       -       +       +
 121  * _LAST                -       -       +       +       +
 122  * _FOREACH             +       +       -       +       +
 123  * _INSERT_HEAD         +       +       +       +       +
 124  * _INSERT_BEFORE       -       +       -       +       +
 125  * _INSERT_AFTER        +       +       +       +       +
 126  * _INSERT_TAIL         -       -       +       +       +
 127  * _REMOVE_HEAD         +       -       +       -       -
 128  * _REMOVE              +       +       +       +       +
 129  *
 130  */
 131
 132 /*
 133  * Singly-linked List definitions.
 134  */
 135 #define SLIST_HEAD(name, type)                                          \
 136 struct name {                                                           \
 137         struct type *slh_first; /* first element */                     \
 138 }
 139
 140 #define SLIST_ENTRY(type)                                               \
 141 struct {                                                                \
 142         struct type *sle_next;  /* next element */                      \
 143 }
 144
 145 /*
 146  * Singly-linked List functions.
 147  */
 148 #define SLIST_EMPTY(head)       ((head)->slh_first == NULL)
 149
 150 #define SLIST_FIRST(head)       ((head)->slh_first)
 151
 152 #define SLIST_FOREACH(var, head, field)                                 \
 153         for((var) = (head)->slh_first; (var); (var) = (var)->field.sle_next)
 154
 155 #define SLIST_INIT(head) {                                              \
 156         (head)->slh_first = NULL;                                       \
 157 }
 158
 159 #define SLIST_INSERT_AFTER(slistelm, elm, field) do {                   \
 160         (elm)->field.sle_next = (slistelm)->field.sle_next;             \
 161         (slistelm)->field.sle_next = (elm);                             \
 162 } while (0)
 163
 164 #define SLIST_INSERT_HEAD(head, elm, field) do {                        \
 165         (elm)->field.sle_next = (head)->slh_first;                      \
 166         (head)->slh_first = (elm);                                      \
 167 } while (0)
 168
 169 #define SLIST_NEXT(elm, field)  ((elm)->field.sle_next)
 170
 171 #define SLIST_REMOVE_HEAD(head, field) do {                             \
 172         (head)->slh_first = (head)->slh_first->field.sle_next;          \
 173 } while (0)
 174
 175 #define SLIST_REMOVE(head, elm, type, field) do {                       \
 176         if ((head)->slh_first == (elm)) {                               \
 177                 SLIST_REMOVE_HEAD((head), field);                       \
 178         }                                                               \
 179         else {                                                          \
 180                 struct type *curelm = (head)->slh_first;                \
 181                 while( curelm->field.sle_next != (elm) )                \
 182                         curelm = curelm->field.sle_next;                \
 183                 curelm->field.sle_next =                                \
 184                     curelm->field.sle_next->field.sle_next;             \
 185         }                                                               \
 186 } while (0)
 187
 188 /*
 189  * Singly-linked Tail queue definitions.
 190  */
 191 #define STAILQ_HEAD(name, type)                                         \
 192 struct name {                                                           \
 193         struct type *stqh_first;/* first element */                     \
 194         struct type **stqh_last;/* addr of last next element */         \
 195 }
 196
 197 #define STAILQ_HEAD_INITIALIZER(head)                                   \
 198         { NULL, &(head).stqh_first }
 199
 200 #define STAILQ_ENTRY(type)                                              \
 201 struct {                                                                \
 202         struct type *stqe_next; /* next element */                      \
 203 }
 204
 205 /*
 206  * Singly-linked Tail queue functions.
 207  */
 208 #define STAILQ_EMPTY(head) ((head)->stqh_first == NULL)
 209
 210 #define STAILQ_INIT(head) do {                                          \
 211         (head)->stqh_first = NULL;                                      \
 212         (head)->stqh_last = &(head)->stqh_first;                        \
 213 } while (0)
 214
 215 #define STAILQ_FIRST(head)      ((head)->stqh_first)
 216 #define STAILQ_LAST(head)       (*(head)->stqh_last)
 217
 218 #define STAILQ_INSERT_HEAD(head, elm, field) do {                       \
 219         if (((elm)->field.stqe_next = (head)->stqh_first) == NULL)      \
 220                 (head)->stqh_last = &(elm)->field.stqe_next;            \
 221         (head)->stqh_first = (elm);                                     \
 222 } while (0)
 223
 224 #define STAILQ_INSERT_TAIL(head, elm, field) do {                       \
 225         (elm)->field.stqe_next = NULL;                                  \
 226         *(head)->stqh_last = (elm);                                     \
 227         (head)->stqh_last = &(elm)->field.stqe_next;                    \
 228 } while (0)
 229
 230 #define STAILQ_INSERT_AFTER(head, tqelm, elm, field) do {               \
 231         if (((elm)->field.stqe_next = (tqelm)->field.stqe_next) == NULL)\
 232                 (head)->stqh_last = &(elm)->field.stqe_next;            \
 233         (tqelm)->field.stqe_next = (elm);                               \
 234 } while (0)
 235
 236 #define STAILQ_NEXT(elm, field) ((elm)->field.stqe_next)
 237
 238 #define STAILQ_REMOVE_HEAD(head, field) do {                            \
 239         if (((head)->stqh_first =                                       \
 240              (head)->stqh_first->field.stqe_next) == NULL)              \
 241                 (head)->stqh_last = &(head)->stqh_first;                \
 242 } while (0)
 243
 244 #define STAILQ_REMOVE_HEAD_UNTIL(head, elm, field) do {                 \
 245         if (((head)->stqh_first = (elm)->field.stqe_next) == NULL)      \
 246                 (head)->stqh_last = &(head)->stqh_first;                \
 247 } while (0)
 248
 249
 250 #define STAILQ_REMOVE(head, elm, type, field) do {                      \
 251         if ((head)->stqh_first == (elm)) {                              \
 252                 STAILQ_REMOVE_HEAD(head, field);                        \
 253         }                                                               \
 254         else {                                                          \
 255                 struct type *curelm = (head)->stqh_first;               \
 256                 while( curelm->field.stqe_next != (elm) )               \
 257                         curelm = curelm->field.stqe_next;               \
 258                 if((curelm->field.stqe_next =                           \
 259                     curelm->field.stqe_next->field.stqe_next) == NULL)  \
 260                         (head)->stqh_last = &(curelm)->field.stqe_next; \
 261         }                                                               \
 262 } while (0)
 263
 264 /*
 265  * List definitions.
 266  */
 267 #define LIST_HEAD(name, type)                                           \
 268 struct name {                                                           \
 269         struct type *lh_first;  /* first element */                     \
 270 }
 271
 272 #define LIST_HEAD_INITIALIZER(head)                                     \
 273         { NULL }
 274
 275 #define LIST_ENTRY(type)                                                \
 276 struct {                                                                \
 277         struct type *le_next;   /* next element */                      \
 278         struct type **le_prev;  /* address of previous next element */  \
 279 }
 280
 281 /*
 282  * List functions.
 283  */
 284
 285 #define LIST_EMPTY(head) ((head)->lh_first == NULL)
 286
 287 #define LIST_FIRST(head)        ((head)->lh_first)
 288
 289 #define LIST_FOREACH(var, head, field)                                  \
 290         for((var) = (head)->lh_first; (var); (var) = (var)->field.le_next)
 291
 292 #define LIST_INIT(head) do {                                            \
 293         (head)->lh_first = NULL;                                        \
 294 } while (0)
 295
 296 #define LIST_INSERT_AFTER(listelm, elm, field) do {                     \
 297         if (((elm)->field.le_next = (listelm)->field.le_next) != NULL)  \
 298                 (listelm)->field.le_next->field.le_prev =               \
 299                     &(elm)->field.le_next;                              \
 300         (listelm)->field.le_next = (elm);                               \
 301         (elm)->field.le_prev = &(listelm)->field.le_next;               \
 302 } while (0)
 303
 304 #define LIST_INSERT_BEFORE(listelm, elm, field) do {                    \
 305         (elm)->field.le_prev = (listelm)->field.le_prev;                \
 306         (elm)->field.le_next = (listelm);                               \
 307         *(listelm)->field.le_prev = (elm);                              \
 308         (listelm)->field.le_prev = &(elm)->field.le_next;               \
 309 } while (0)
 310
 311 #define LIST_INSERT_HEAD(head, elm, field) do {                         \
 312         if (((elm)->field.le_next = (head)->lh_first) != NULL)          \
 313                 (head)->lh_first->field.le_prev = &(elm)->field.le_next;\
 314         (head)->lh_first = (elm);                                       \
 315         (elm)->field.le_prev = &(head)->lh_first;                       \
 316 } while (0)
 317
 318 #define LIST_NEXT(elm, field)   ((elm)->field.le_next)
 319
 320 #define LIST_REMOVE(elm, field) do {                                    \
 321         if ((elm)->field.le_next != NULL)                               \
 322                 (elm)->field.le_next->field.le_prev =                   \
 323                     (elm)->field.le_prev;                               \
 324         *(elm)->field.le_prev = (elm)->field.le_next;                   \
 325 } while (0)
 326
 327 /*
 328  * Tail queue definitions.
 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_FOREACH(var, head, field)                                 \
 351         for (var = TAILQ_FIRST(head); var; var = TAILQ_NEXT(var, field))
 352
 353 #define TAILQ_FOREACH_REVERSE(var, head, field, headname)                                       \
 354         for (var = TAILQ_LAST(head, headname);                 \
 355                var; var = TAILQ_PREV(var, headname, field))
 356
 357 #define TAILQ_FIRST(head) ((head)->tqh_first)
 358
 359 #define TAILQ_LAST(head, headname) \
 360         (*(((struct headname *)((head)->tqh_last))->tqh_last))
 361
 362 #define TAILQ_NEXT(elm, field) ((elm)->field.tqe_next)
 363
 364 #define TAILQ_PREV(elm, headname, field) \
 365         (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
 366
 367 #define TAILQ_INIT(head) do {                                           \
 368         (head)->tqh_first = NULL;                                       \
 369         (head)->tqh_last = &(head)->tqh_first;                          \
 370 } while (0)
 371
 372 #define TAILQ_INSERT_HEAD(head, elm, field) do {                        \
 373         if (((elm)->field.tqe_next = (head)->tqh_first) != NULL)        \
 374                 (head)->tqh_first->field.tqe_prev =                     \
 375                     &(elm)->field.tqe_next;                             \
 376         else                                                            \
 377                 (head)->tqh_last = &(elm)->field.tqe_next;              \
 378         (head)->tqh_first = (elm);                                      \
 379         (elm)->field.tqe_prev = &(head)->tqh_first;                     \
 380 } while (0)
 381
 382 #define TAILQ_INSERT_TAIL(head, elm, field) do {                        \
 383         (elm)->field.tqe_next = NULL;                                   \
 384         (elm)->field.tqe_prev = (head)->tqh_last;                       \
 385         *(head)->tqh_last = (elm);                                      \
 386         (head)->tqh_last = &(elm)->field.tqe_next;                      \
 387 } while (0)
 388
 389 #define TAILQ_INSERT_AFTER(head, listelm, elm, field) do {              \
 390         if (((elm)->field.tqe_next = (listelm)->field.tqe_next) != NULL)\
 391                 (elm)->field.tqe_next->field.tqe_prev =                 \
 392                     &(elm)->field.tqe_next;                             \
 393         else                                                            \
 394                 (head)->tqh_last = &(elm)->field.tqe_next;              \
 395         (listelm)->field.tqe_next = (elm);                              \
 396         (elm)->field.tqe_prev = &(listelm)->field.tqe_next;             \
 397 } while (0)
 398
 399 #define TAILQ_INSERT_BEFORE(listelm, elm, field) do {                   \
 400         (elm)->field.tqe_prev = (listelm)->field.tqe_prev;              \
 401         (elm)->field.tqe_next = (listelm);                              \
 402         *(listelm)->field.tqe_prev = (elm);                             \
 403         (listelm)->field.tqe_prev = &(elm)->field.tqe_next;             \
 404 } while (0)
 405
 406 #define TAILQ_REMOVE(head, elm, field) do {                             \
 407         if (((elm)->field.tqe_next) != NULL)                            \
 408                 (elm)->field.tqe_next->field.tqe_prev =                 \
 409                     (elm)->field.tqe_prev;                              \
 410         else                                                            \
 411                 (head)->tqh_last = (elm)->field.tqe_prev;               \
 412         *(elm)->field.tqe_prev = (elm)->field.tqe_next;                 \
 413 } while (0)
 414
 415 /*
 416  * Circular queue definitions.
 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_ENTRY(type)                                             \
 425 struct {                                                                \
 426         struct type *cqe_next;          /* next element */              \
 427         struct type *cqe_prev;          /* previous element */          \
 428 }
 429
 430 /*
 431  * Circular queue functions.
 432  */
 433 #define CIRCLEQ_EMPTY(head) ((head)->cqh_first == (void *)(head))
 434
 435 #define CIRCLEQ_FIRST(head) ((head)->cqh_first)
 436
 437 #define CIRCLEQ_FOREACH(var, head, field)                               \
 438         for((var) = (head)->cqh_first;                                  \
 439             (var) != (void *)(head);                                    \
 440             (var) = (var)->field.cqe_next)
 441
 442 #define CIRCLEQ_INIT(head) do {                                         \
 443         (head)->cqh_first = (void *)(head);                             \
 444         (head)->cqh_last = (void *)(head);                              \
 445 } while (0)
 446
 447 #define CIRCLEQ_INSERT_AFTER(head, listelm, elm, field) do {            \
 448         (elm)->field.cqe_next = (listelm)->field.cqe_next;              \
 449         (elm)->field.cqe_prev = (listelm);                              \
 450         if ((listelm)->field.cqe_next == (void *)(head))                \
 451                 (head)->cqh_last = (elm);                               \
 452         else                                                            \
 453                 (listelm)->field.cqe_next->field.cqe_prev = (elm);      \
 454         (listelm)->field.cqe_next = (elm);                              \
 455 } while (0)
 456
 457 #define CIRCLEQ_INSERT_BEFORE(head, listelm, elm, field) do {           \
 458         (elm)->field.cqe_next = (listelm);                              \
 459         (elm)->field.cqe_prev = (listelm)->field.cqe_prev;              \
 460         if ((listelm)->field.cqe_prev == (void *)(head))                \
 461                 (head)->cqh_first = (elm);                              \
 462         else                                                            \
 463                 (listelm)->field.cqe_prev->field.cqe_next = (elm);      \
 464         (listelm)->field.cqe_prev = (elm);                              \
 465 } while (0)
 466
 467 #define CIRCLEQ_INSERT_HEAD(head, elm, field) do {                      \
 468         (elm)->field.cqe_next = (head)->cqh_first;                      \
 469         (elm)->field.cqe_prev = (void *)(head);                         \
 470         if ((head)->cqh_last == (void *)(head))                         \
 471                 (head)->cqh_last = (elm);                               \
 472         else                                                            \
 473                 (head)->cqh_first->field.cqe_prev = (elm);              \
 474         (head)->cqh_first = (elm);                                      \
 475 } while (0)
 476
 477 #define CIRCLEQ_INSERT_TAIL(head, elm, field) do {                      \
 478         (elm)->field.cqe_next = (void *)(head);                         \
 479         (elm)->field.cqe_prev = (head)->cqh_last;                       \
 480         if ((head)->cqh_first == (void *)(head))                        \
 481                 (head)->cqh_first = (elm);                              \
 482         else                                                            \
 483                 (head)->cqh_last->field.cqe_next = (elm);               \
 484         (head)->cqh_last = (elm);                                       \
 485 } while (0)
 486
 487 #define CIRCLEQ_LAST(head) ((head)->cqh_last)
 488
 489 #define CIRCLEQ_NEXT(elm,field) ((elm)->field.cqe_next)
 490
 491 #define CIRCLEQ_PREV(elm,field) ((elm)->field.cqe_prev)
 492
 493 #define CIRCLEQ_REMOVE(head, elm, field) do {                           \
 494         if ((elm)->field.cqe_next == (void *)(head))                    \
 495                 (head)->cqh_last = (elm)->field.cqe_prev;               \
 496         else                                                            \
 497                 (elm)->field.cqe_next->field.cqe_prev =                 \
 498                     (elm)->field.cqe_prev;                              \
 499         if ((elm)->field.cqe_prev == (void *)(head))                    \
 500                 (head)->cqh_first = (elm)->field.cqe_next;              \
 501         else                                                            \
 502                 (elm)->field.cqe_prev->field.cqe_next =                 \
 503                     (elm)->field.cqe_next;                              \
 504 } while (0)
 505
 506 #ifdef KERNEL
 507
 508 #if NOTFB31
 509
 510 /*
 511  * XXX insque() and remque() are an old way of handling certain queues.
 512  * They bogusly assumes that all queue heads look alike.
 513  */
 514
 515 struct quehead {
 516         struct quehead *qh_link;
 517         struct quehead *qh_rlink;
 518 };
 519
 520 #ifdef  __GNUC__
 521
 522 static __inline void
 523 insque(void *a, void *b)
 524 {
 525         struct quehead *element = a, *head = b;
 526
 527         element->qh_link = head->qh_link;
 528         element->qh_rlink = head;
 529         head->qh_link = element;
 530         element->qh_link->qh_rlink = element;
 531 }
 532
 533 static __inline void
 534 remque(void *a)
 535 {
 536         struct quehead *element = a;
 537
 538         element->qh_link->qh_rlink = element->qh_rlink;
 539         element->qh_rlink->qh_link = element->qh_link;
 540         element->qh_rlink = 0;
 541 }
 542
 543 #else /* !__GNUC__ */
 544
 545 void    insque __P((void *a, void *b));
 546 void    remque __P((void *a));
 547
 548 #endif /* __GNUC__ */
 549
 550 #endif
 551 #endif /* KERNEL */
 552
 553 #endif /* !_SYS_QUEUE_H_ */