bsd/sys/queue.h

   1 /*
   2  * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. The rights granted to you under the License
  10  * may not be used to create, or enable the creation or redistribution of,
  11  * unlawful or unlicensed copies of an Apple operating system, or to
  12  * circumvent, violate, or enable the circumvention or violation of, any
  13  * terms of an Apple operating system software license agreement.
  14  *
  15  * Please obtain a copy of the License at
  16  * http://www.opensource.apple.com/apsl/ and read it before using this file.
  17  *
  18  * The Original Code and all software distributed under the License are
  19  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  20  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  21  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  22  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  23  * Please see the License for the specific language governing rights and
  24  * limitations under the License.
  25  *
  26  * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  27  */
  28 /*-
  29  * Copyright (c) 1991, 1993
  30  *      The Regents of the University of California.  All rights reserved.
  31  *
  32  * Redistribution and use in source and binary forms, with or without
  33  * modification, are permitted provided that the following conditions
  34  * are met:
  35  * 1. Redistributions of source code must retain the above copyright
  36  *    notice, this list of conditions and the following disclaimer.
  37  * 2. Redistributions in binary form must reproduce the above copyright
  38  *    notice, this list of conditions and the following disclaimer in the
  39  *    documentation and/or other materials provided with the distribution.
  40  * 4. Neither the name of the University nor the names of its contributors
  41  *    may be used to endorse or promote products derived from this software
  42  *    without specific prior written permission.
  43  *
  44  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  45  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  46  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  47  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  48  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  49  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  50  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  51  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  52  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  53  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  54  * SUCH DAMAGE.
  55  *
  56  *      @(#)queue.h     8.5 (Berkeley) 8/20/94
  57  */
  58
  59 #ifndef _SYS_QUEUE_H_
  60 #define _SYS_QUEUE_H_
  61
  62 /*
  63  * This file defines five types of data structures: singly-linked lists,
  64  * singly-linked tail queues, lists, tail queues, and circular queues.
  65  *
  66  * A singly-linked list is headed by a single forward pointer. The elements
  67  * are singly linked for minimum space and pointer manipulation overhead at
  68  * the expense of O(n) removal for arbitrary elements. New elements can be
  69  * added to the list after an existing element or at the head of the list.
  70  * Elements being removed from the head of the list should use the explicit
  71  * macro for this purpose for optimum efficiency. A singly-linked list may
  72  * only be traversed in the forward direction.  Singly-linked lists are ideal
  73  * for applications with large datasets and few or no removals or for
  74  * implementing a LIFO queue.
  75  *
  76  * A singly-linked tail queue is headed by a pair of pointers, one to the
  77  * head of the list and the other to the tail of the list. The elements are
  78  * singly linked for minimum space and pointer manipulation overhead at the
  79  * expense of O(n) removal for arbitrary elements. New elements can be added
  80  * to the list after an existing element, at the head of the list, or at the
  81  * end of the list. Elements being removed from the head of the tail queue
  82  * should use the explicit macro for this purpose for optimum efficiency.
  83  * A singly-linked tail queue may only be traversed in the forward direction.
  84  * Singly-linked tail queues are ideal for applications with large datasets
  85  * and few or no removals or for implementing a FIFO queue.
  86  *
  87  * A list is headed by a single forward pointer (or an array of forward
  88  * pointers for a hash table header). The elements are doubly linked
  89  * so that an arbitrary element can be removed without a need to
  90  * traverse the list. New elements can be added to the list before
  91  * or after an existing element or at the head of the list. A list
  92  * may only be traversed in the forward direction.
  93  *
  94  * A tail queue is headed by a pair of pointers, one to the head of the
  95  * list and the other to the tail of the list. The elements are doubly
  96  * linked so that an arbitrary element can be removed without a need to
  97  * traverse the list. New elements can be added to the list before or
  98  * after an existing element, at the head of the list, or at the end of
  99  * the list. A tail queue may be traversed in either direction.
 100  *
 101  * A circle queue is headed by a pair of pointers, one to the head of the
 102  * list and the other to the tail of the list. The elements are doubly
 103  * linked so that an arbitrary element can be removed without a need to
 104  * traverse the list. New elements can be added to the list before or after
 105  * an existing element, at the head of the list, or at the end of the list.
 106  * A circle queue may be traversed in either direction, but has a more
 107  * complex end of list detection.
 108  * Note that circle queues are deprecated, because, as the removal log
 109  * in FreeBSD states, "CIRCLEQs are a disgrace to everything Knuth taught
 110  * us in Volume 1 Chapter 2. [...] Use TAILQ instead, it provides the same
 111  * functionality." Code using them will continue to compile, but they
 112  * are no longer documented on the man page.
 113  *
 114  * For details on the use of these macros, see the queue(3) manual page.
 115  *
 116  *
 117  *                              SLIST   LIST    STAILQ  TAILQ   CIRCLEQ
 118  * _HEAD                        +       +       +       +       +
 119  * _HEAD_INITIALIZER            +       +       +       +       -
 120  * _ENTRY                       +       +       +       +       +
 121  * _INIT                        +       +       +       +       +
 122  * _EMPTY                       +       +       +       +       +
 123  * _FIRST                       +       +       +       +       +
 124  * _NEXT                        +       +       +       +       +
 125  * _PREV                        -       -       -       +       +
 126  * _LAST                        -       -       +       +       +
 127  * _FOREACH                     +       +       +       +       +
 128  * _FOREACH_SAFE                +       +       +       +       -
 129  * _FOREACH_REVERSE             -       -       -       +       -
 130  * _FOREACH_REVERSE_SAFE        -       -       -       +       -
 131  * _INSERT_HEAD                 +       +       +       +       +
 132  * _INSERT_BEFORE               -       +       -       +       +
 133  * _INSERT_AFTER                +       +       +       +       +
 134  * _INSERT_TAIL                 -       -       +       +       +
 135  * _CONCAT                      -       -       +       +       -
 136  * _REMOVE_HEAD                 +       -       +       -       -
 137  * _REMOVE                      +       +       +       +       +
 138  *
 139  */
 140 #ifdef QUEUE_MACRO_DEBUG
 141 /* Store the last 2 places the queue element or head was altered */
 142 struct qm_trace {
 143         char * lastfile;
 144         int lastline;
 145         char * prevfile;
 146         int prevline;
 147 };
 148
 149 #define TRACEBUF        struct qm_trace trace;
 150 #define TRASHIT(x)      do {(x) = (void *)-1;} while (0)
 151
 152 #define QMD_TRACE_HEAD(head) do {                                       \
 153         (head)->trace.prevline = (head)->trace.lastline;                \
 154         (head)->trace.prevfile = (head)->trace.lastfile;                \
 155         (head)->trace.lastline = __LINE__;                              \
 156         (head)->trace.lastfile = __FILE__;                              \
 157 } while (0)
 158
 159 #define QMD_TRACE_ELEM(elem) do {                                       \
 160         (elem)->trace.prevline = (elem)->trace.lastline;                \
 161         (elem)->trace.prevfile = (elem)->trace.lastfile;                \
 162         (elem)->trace.lastline = __LINE__;                              \
 163         (elem)->trace.lastfile = __FILE__;                              \
 164 } while (0)
 165
 166 #else
 167 #define QMD_TRACE_ELEM(elem)
 168 #define QMD_TRACE_HEAD(head)
 169 #define TRACEBUF
 170 #define TRASHIT(x)
 171 #endif  /* QUEUE_MACRO_DEBUG */
 172
 173 /*
 174  * Singly-linked List declarations.
 175  */
 176 #define SLIST_HEAD(name, type)                                          \
 177 struct name {                                                           \
 178         struct type *slh_first; /* first element */                     \
 179 }
 180
 181 #define SLIST_HEAD_INITIALIZER(head)                                    \
 182         { NULL }
 183
 184 #define SLIST_ENTRY(type)                                               \
 185 struct {                                                                \
 186         struct type *sle_next;  /* next element */                      \
 187 }
 188
 189 /*
 190  * Singly-linked List functions.
 191  */
 192 #define SLIST_EMPTY(head)       ((head)->slh_first == NULL)
 193
 194 #define SLIST_FIRST(head)       ((head)->slh_first)
 195
 196 #define SLIST_FOREACH(var, head, field)                                 \
 197         for ((var) = SLIST_FIRST((head));                               \
 198             (var);                                                      \
 199             (var) = SLIST_NEXT((var), field))
 200
 201 #define SLIST_FOREACH_SAFE(var, head, field, tvar)                      \
 202         for ((var) = SLIST_FIRST((head));                               \
 203             (var) && ((tvar) = SLIST_NEXT((var), field), 1);            \
 204             (var) = (tvar))
 205
 206 #define SLIST_FOREACH_PREVPTR(var, varp, head, field)                   \
 207         for ((varp) = &SLIST_FIRST((head));                             \
 208             ((var) = *(varp)) != NULL;                                  \
 209             (varp) = &SLIST_NEXT((var), field))
 210
 211 #define SLIST_INIT(head) do {                                           \
 212         SLIST_FIRST((head)) = NULL;                                     \
 213 } while (0)
 214
 215 #define SLIST_INSERT_AFTER(slistelm, elm, field) do {                   \
 216         SLIST_NEXT((elm), field) = SLIST_NEXT((slistelm), field);       \
 217         SLIST_NEXT((slistelm), field) = (elm);                          \
 218 } while (0)
 219
 220 #define SLIST_INSERT_HEAD(head, elm, field) do {                        \
 221         SLIST_NEXT((elm), field) = SLIST_FIRST((head));                 \
 222         SLIST_FIRST((head)) = (elm);                                    \
 223 } while (0)
 224
 225 #define SLIST_NEXT(elm, field)  ((elm)->field.sle_next)
 226
 227 #define SLIST_REMOVE(head, elm, type, field) do {                       \
 228         if (SLIST_FIRST((head)) == (elm)) {                             \
 229                 SLIST_REMOVE_HEAD((head), field);                       \
 230         }                                                               \
 231         else {                                                          \
 232                 struct type *curelm = SLIST_FIRST((head));              \
 233                 while (SLIST_NEXT(curelm, field) != (elm))              \
 234                         curelm = SLIST_NEXT(curelm, field);             \
 235                 SLIST_NEXT(curelm, field) =                             \
 236                     SLIST_NEXT(SLIST_NEXT(curelm, field), field);       \
 237         }                                                               \
 238         TRASHIT((elm)->field.sle_next);                                 \
 239 } while (0)
 240
 241 #define SLIST_REMOVE_HEAD(head, field) do {                             \
 242         SLIST_FIRST((head)) = SLIST_NEXT(SLIST_FIRST((head)), field);   \
 243 } while (0)
 244
 245 /*
 246  * Singly-linked Tail queue declarations.
 247  */
 248 #define STAILQ_HEAD(name, type)                                         \
 249 struct name {                                                           \
 250         struct type *stqh_first;/* first element */                     \
 251         struct type **stqh_last;/* addr of last next element */         \
 252 }
 253
 254 #define STAILQ_HEAD_INITIALIZER(head)                                   \
 255         { NULL, &(head).stqh_first }
 256
 257 #define STAILQ_ENTRY(type)                                              \
 258 struct {                                                                \
 259         struct type *stqe_next; /* next element */                      \
 260 }
 261
 262 /*
 263  * Singly-linked Tail queue functions.
 264  */
 265 #define STAILQ_CONCAT(head1, head2) do {                                \
 266         if (!STAILQ_EMPTY((head2))) {                                   \
 267                 *(head1)->stqh_last = (head2)->stqh_first;              \
 268                 (head1)->stqh_last = (head2)->stqh_last;                \
 269                 STAILQ_INIT((head2));                                   \
 270         }                                                               \
 271 } while (0)
 272
 273 #define STAILQ_EMPTY(head)      ((head)->stqh_first == NULL)
 274
 275 #define STAILQ_FIRST(head)      ((head)->stqh_first)
 276
 277 #define STAILQ_FOREACH(var, head, field)                                \
 278         for((var) = STAILQ_FIRST((head));                               \
 279            (var);                                                       \
 280            (var) = STAILQ_NEXT((var), field))
 281
 282
 283 #define STAILQ_FOREACH_SAFE(var, head, field, tvar)                     \
 284         for ((var) = STAILQ_FIRST((head));                              \
 285             (var) && ((tvar) = STAILQ_NEXT((var), field), 1);           \
 286             (var) = (tvar))
 287
 288 #define STAILQ_INIT(head) do {                                          \
 289         STAILQ_FIRST((head)) = NULL;                                    \
 290         (head)->stqh_last = &STAILQ_FIRST((head));                      \
 291 } while (0)
 292
 293 #define STAILQ_INSERT_AFTER(head, tqelm, elm, field) do {               \
 294         if ((STAILQ_NEXT((elm), field) = STAILQ_NEXT((tqelm), field)) == NULL)\
 295                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 296         STAILQ_NEXT((tqelm), field) = (elm);                            \
 297 } while (0)
 298
 299 #define STAILQ_INSERT_HEAD(head, elm, field) do {                       \
 300         if ((STAILQ_NEXT((elm), field) = STAILQ_FIRST((head))) == NULL) \
 301                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 302         STAILQ_FIRST((head)) = (elm);                                   \
 303 } while (0)
 304
 305 #define STAILQ_INSERT_TAIL(head, elm, field) do {                       \
 306         STAILQ_NEXT((elm), field) = NULL;                               \
 307         *(head)->stqh_last = (elm);                                     \
 308         (head)->stqh_last = &STAILQ_NEXT((elm), field);                 \
 309 } while (0)
 310
 311 #define STAILQ_LAST(head, type, field)                                  \
 312         (STAILQ_EMPTY((head)) ?                                         \
 313                 NULL :                                                  \
 314                 ((struct type *)(void *)                                \
 315                 ((char *)((head)->stqh_last) - __offsetof(struct type, field))))
 316
 317 #define STAILQ_NEXT(elm, field) ((elm)->field.stqe_next)
 318
 319 #define STAILQ_REMOVE(head, elm, type, field) do {                      \
 320         if (STAILQ_FIRST((head)) == (elm)) {                            \
 321                 STAILQ_REMOVE_HEAD((head), field);                      \
 322         }                                                               \
 323         else {                                                          \
 324                 struct type *curelm = STAILQ_FIRST((head));             \
 325                 while (STAILQ_NEXT(curelm, field) != (elm))             \
 326                         curelm = STAILQ_NEXT(curelm, field);            \
 327                 if ((STAILQ_NEXT(curelm, field) =                       \
 328                      STAILQ_NEXT(STAILQ_NEXT(curelm, field), field)) == NULL)\
 329                         (head)->stqh_last = &STAILQ_NEXT((curelm), field);\
 330         }                                                               \
 331         TRASHIT((elm)->field.stqe_next);                                \
 332 } while (0)
 333
 334 #define STAILQ_REMOVE_HEAD(head, field) do {                            \
 335         if ((STAILQ_FIRST((head)) =                                     \
 336              STAILQ_NEXT(STAILQ_FIRST((head)), field)) == NULL)         \
 337                 (head)->stqh_last = &STAILQ_FIRST((head));              \
 338 } while (0)
 339
 340 #define STAILQ_REMOVE_HEAD_UNTIL(head, elm, field) do {                 \
 341         if ((STAILQ_FIRST((head)) = STAILQ_NEXT((elm), field)) == NULL) \
 342                 (head)->stqh_last = &STAILQ_FIRST((head));              \
 343 } while (0)
 344
 345 /*
 346  * List declarations.
 347  */
 348 #define LIST_HEAD(name, type)                                           \
 349 struct name {                                                           \
 350         struct type *lh_first;  /* first element */                     \
 351 }
 352
 353 #define LIST_HEAD_INITIALIZER(head)                                     \
 354         { NULL }
 355
 356 #define LIST_ENTRY(type)                                                \
 357 struct {                                                                \
 358         struct type *le_next;   /* next element */                      \
 359         struct type **le_prev;  /* address of previous next element */  \
 360 }
 361
 362 /*
 363  * List functions.
 364  */
 365
 366 #if (defined(_KERNEL) && defined(INVARIANTS)) || defined(QUEUE_MACRO_DEBUG)
 367 #define QMD_LIST_CHECK_HEAD(head, field) do {                           \
 368         if (LIST_FIRST((head)) != NULL &&                               \
 369             LIST_FIRST((head))->field.le_prev !=                        \
 370              &LIST_FIRST((head)))                                       \
 371                 panic("Bad list head %p first->prev != head", (head));  \
 372 } while (0)
 373
 374 #define QMD_LIST_CHECK_NEXT(elm, field) do {                            \
 375         if (LIST_NEXT((elm), field) != NULL &&                          \
 376             LIST_NEXT((elm), field)->field.le_prev !=                   \
 377              &((elm)->field.le_next))                                   \
 378                 panic("Bad link elm %p next->prev != elm", (elm));      \
 379 } while (0)
 380
 381 #define QMD_LIST_CHECK_PREV(elm, field) do {                            \
 382         if (*(elm)->field.le_prev != (elm))                             \
 383                 panic("Bad link elm %p prev->next != elm", (elm));      \
 384 } while (0)
 385 #else
 386 #define QMD_LIST_CHECK_HEAD(head, field)
 387 #define QMD_LIST_CHECK_NEXT(elm, field)
 388 #define QMD_LIST_CHECK_PREV(elm, field)
 389 #endif /* (_KERNEL && INVARIANTS) || QUEUE_MACRO_DEBUG */
 390
 391 #define LIST_EMPTY(head)        ((head)->lh_first == NULL)
 392
 393 #define LIST_FIRST(head)        ((head)->lh_first)
 394
 395 #define LIST_FOREACH(var, head, field)                                  \
 396         for ((var) = LIST_FIRST((head));                                \
 397             (var);                                                      \
 398             (var) = LIST_NEXT((var), field))
 399
 400 #define LIST_FOREACH_SAFE(var, head, field, tvar)                       \
 401         for ((var) = LIST_FIRST((head));                                \
 402             (var) && ((tvar) = LIST_NEXT((var), field), 1);             \
 403             (var) = (tvar))
 404
 405 #define LIST_INIT(head) do {                                            \
 406         LIST_FIRST((head)) = NULL;                                      \
 407 } while (0)
 408
 409 #define LIST_INSERT_AFTER(listelm, elm, field) do {                     \
 410         QMD_LIST_CHECK_NEXT(listelm, field);                            \
 411         if ((LIST_NEXT((elm), field) = LIST_NEXT((listelm), field)) != NULL)\
 412                 LIST_NEXT((listelm), field)->field.le_prev =            \
 413                     &LIST_NEXT((elm), field);                           \
 414         LIST_NEXT((listelm), field) = (elm);                            \
 415         (elm)->field.le_prev = &LIST_NEXT((listelm), field);            \
 416 } while (0)
 417
 418 #define LIST_INSERT_BEFORE(listelm, elm, field) do {                    \
 419         QMD_LIST_CHECK_PREV(listelm, field);                            \
 420         (elm)->field.le_prev = (listelm)->field.le_prev;                \
 421         LIST_NEXT((elm), field) = (listelm);                            \
 422         *(listelm)->field.le_prev = (elm);                              \
 423         (listelm)->field.le_prev = &LIST_NEXT((elm), field);            \
 424 } while (0)
 425
 426 #define LIST_INSERT_HEAD(head, elm, field) do {                         \
 427         QMD_LIST_CHECK_HEAD((head), field);                             \
 428         if ((LIST_NEXT((elm), field) = LIST_FIRST((head))) != NULL)     \
 429                 LIST_FIRST((head))->field.le_prev = &LIST_NEXT((elm), field);\
 430         LIST_FIRST((head)) = (elm);                                     \
 431         (elm)->field.le_prev = &LIST_FIRST((head));                     \
 432 } while (0)
 433
 434 #define LIST_NEXT(elm, field)   ((elm)->field.le_next)
 435
 436 #define LIST_REMOVE(elm, field) do {                                    \
 437         QMD_LIST_CHECK_NEXT(elm, field);                                \
 438         QMD_LIST_CHECK_PREV(elm, field);                                \
 439         if (LIST_NEXT((elm), field) != NULL)                            \
 440                 LIST_NEXT((elm), field)->field.le_prev =                \
 441                     (elm)->field.le_prev;                               \
 442         *(elm)->field.le_prev = LIST_NEXT((elm), field);                \
 443         TRASHIT((elm)->field.le_next);                                  \
 444         TRASHIT((elm)->field.le_prev);                                  \
 445 } while (0)
 446
 447 /*
 448  * Tail queue declarations.
 449  */
 450 #define TAILQ_HEAD(name, type)                                          \
 451 struct name {                                                           \
 452         struct type *tqh_first; /* first element */                     \
 453         struct type **tqh_last; /* addr of last next element */         \
 454         TRACEBUF                                                        \
 455 }
 456
 457 #define TAILQ_HEAD_INITIALIZER(head)                                    \
 458         { NULL, &(head).tqh_first }
 459
 460 #define TAILQ_ENTRY(type)                                               \
 461 struct {                                                                \
 462         struct type *tqe_next;  /* next element */                      \
 463         struct type **tqe_prev; /* address of previous next element */  \
 464         TRACEBUF                                                        \
 465 }
 466
 467 /*
 468  * Tail queue functions.
 469  */
 470 #define TAILQ_CONCAT(head1, head2, field) do {                          \
 471         if (!TAILQ_EMPTY(head2)) {                                      \
 472                 *(head1)->tqh_last = (head2)->tqh_first;                \
 473                 (head2)->tqh_first->field.tqe_prev = (head1)->tqh_last; \
 474                 (head1)->tqh_last = (head2)->tqh_last;                  \
 475                 TAILQ_INIT((head2));                                    \
 476                 QMD_TRACE_HEAD(head1);                                  \
 477                 QMD_TRACE_HEAD(head2);                                  \
 478         }                                                               \
 479 } while (0)
 480
 481 #define TAILQ_EMPTY(head)       ((head)->tqh_first == NULL)
 482
 483 #define TAILQ_FIRST(head)       ((head)->tqh_first)
 484
 485 #define TAILQ_FOREACH(var, head, field)                                 \
 486         for ((var) = TAILQ_FIRST((head));                               \
 487             (var);                                                      \
 488             (var) = TAILQ_NEXT((var), field))
 489
 490 #define TAILQ_FOREACH_SAFE(var, head, field, tvar)                      \
 491         for ((var) = TAILQ_FIRST((head));                               \
 492             (var) && ((tvar) = TAILQ_NEXT((var), field), 1);            \
 493             (var) = (tvar))
 494
 495 #define TAILQ_FOREACH_REVERSE(var, head, headname, field)               \
 496         for ((var) = TAILQ_LAST((head), headname);                      \
 497             (var);                                                      \
 498             (var) = TAILQ_PREV((var), headname, field))
 499
 500 #define TAILQ_FOREACH_REVERSE_SAFE(var, head, headname, field, tvar)    \
 501         for ((var) = TAILQ_LAST((head), headname);                      \
 502             (var) && ((tvar) = TAILQ_PREV((var), headname, field), 1);  \
 503             (var) = (tvar))
 504
 505 #define TAILQ_INIT(head) do {                                           \
 506         TAILQ_FIRST((head)) = NULL;                                     \
 507         (head)->tqh_last = &TAILQ_FIRST((head));                        \
 508         QMD_TRACE_HEAD(head);                                           \
 509 } while (0)
 510
 511 #define TAILQ_INSERT_AFTER(head, listelm, elm, field) do {              \
 512         if ((TAILQ_NEXT((elm), field) = TAILQ_NEXT((listelm), field)) != NULL)\
 513                 TAILQ_NEXT((elm), field)->field.tqe_prev =              \
 514                     &TAILQ_NEXT((elm), field);                          \
 515         else {                                                          \
 516                 (head)->tqh_last = &TAILQ_NEXT((elm), field);           \
 517                 QMD_TRACE_HEAD(head);                                   \
 518         }                                                               \
 519         TAILQ_NEXT((listelm), field) = (elm);                           \
 520         (elm)->field.tqe_prev = &TAILQ_NEXT((listelm), field);          \
 521         QMD_TRACE_ELEM(&(elm)->field);                                  \
 522         QMD_TRACE_ELEM(&listelm->field);                                \
 523 } while (0)
 524
 525 #define TAILQ_INSERT_BEFORE(listelm, elm, field) do {                   \
 526         (elm)->field.tqe_prev = (listelm)->field.tqe_prev;              \
 527         TAILQ_NEXT((elm), field) = (listelm);                           \
 528         *(listelm)->field.tqe_prev = (elm);                             \
 529         (listelm)->field.tqe_prev = &TAILQ_NEXT((elm), field);          \
 530         QMD_TRACE_ELEM(&(elm)->field);                                  \
 531         QMD_TRACE_ELEM(&listelm->field);                                \
 532 } while (0)
 533
 534 #define TAILQ_INSERT_HEAD(head, elm, field) do {                        \
 535         if ((TAILQ_NEXT((elm), field) = TAILQ_FIRST((head))) != NULL)   \
 536                 TAILQ_FIRST((head))->field.tqe_prev =                   \
 537                     &TAILQ_NEXT((elm), field);                          \
 538         else                                                            \
 539                 (head)->tqh_last = &TAILQ_NEXT((elm), field);           \
 540         TAILQ_FIRST((head)) = (elm);                                    \
 541         (elm)->field.tqe_prev = &TAILQ_FIRST((head));                   \
 542         QMD_TRACE_HEAD(head);                                           \
 543         QMD_TRACE_ELEM(&(elm)->field);                                  \
 544 } while (0)
 545
 546 #define TAILQ_INSERT_TAIL(head, elm, field) do {                        \
 547         TAILQ_NEXT((elm), field) = NULL;                                \
 548         (elm)->field.tqe_prev = (head)->tqh_last;                       \
 549         *(head)->tqh_last = (elm);                                      \
 550         (head)->tqh_last = &TAILQ_NEXT((elm), field);                   \
 551         QMD_TRACE_HEAD(head);                                           \
 552         QMD_TRACE_ELEM(&(elm)->field);                                  \
 553 } while (0)
 554
 555 #define TAILQ_LAST(head, headname)                                      \
 556         (*(((struct headname *)((head)->tqh_last))->tqh_last))
 557
 558 #define TAILQ_NEXT(elm, field) ((elm)->field.tqe_next)
 559
 560 #define TAILQ_PREV(elm, headname, field)                                \
 561         (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
 562
 563 #define TAILQ_REMOVE(head, elm, field) do {                             \
 564         if ((TAILQ_NEXT((elm), field)) != NULL)                         \
 565                 TAILQ_NEXT((elm), field)->field.tqe_prev =              \
 566                     (elm)->field.tqe_prev;                              \
 567         else {                                                          \
 568                 (head)->tqh_last = (elm)->field.tqe_prev;               \
 569                 QMD_TRACE_HEAD(head);                                   \
 570         }                                                               \
 571         *(elm)->field.tqe_prev = TAILQ_NEXT((elm), field);              \
 572         TRASHIT((elm)->field.tqe_next);                                 \
 573         TRASHIT((elm)->field.tqe_prev);                                 \
 574         QMD_TRACE_ELEM(&(elm)->field);                                  \
 575 } while (0)
 576
 577 /*
 578  * Circular queue definitions.
 579  */
 580 #define CIRCLEQ_HEAD(name, type)                                        \
 581 struct name {                                                           \
 582         struct type *cqh_first;         /* first element */             \
 583         struct type *cqh_last;          /* last element */              \
 584 }
 585
 586 #define CIRCLEQ_ENTRY(type)                                             \
 587 struct {                                                                \
 588         struct type *cqe_next;          /* next element */              \
 589         struct type *cqe_prev;          /* previous element */          \
 590 }
 591
 592 /*
 593  * Circular queue functions.
 594  */
 595 #define CIRCLEQ_EMPTY(head) ((head)->cqh_first == (void *)(head))
 596
 597 #define CIRCLEQ_FIRST(head) ((head)->cqh_first)
 598
 599 #define CIRCLEQ_FOREACH(var, head, field)                               \
 600         for((var) = (head)->cqh_first;                                  \
 601             (var) != (void *)(head);                                    \
 602             (var) = (var)->field.cqe_next)
 603
 604 #define CIRCLEQ_INIT(head) do {                                         \
 605         (head)->cqh_first = (void *)(head);                             \
 606         (head)->cqh_last = (void *)(head);                              \
 607 } while (0)
 608
 609 #define CIRCLEQ_INSERT_AFTER(head, listelm, elm, field) do {            \
 610         (elm)->field.cqe_next = (listelm)->field.cqe_next;              \
 611         (elm)->field.cqe_prev = (listelm);                              \
 612         if ((listelm)->field.cqe_next == (void *)(head))                \
 613                 (head)->cqh_last = (elm);                               \
 614         else                                                            \
 615                 (listelm)->field.cqe_next->field.cqe_prev = (elm);      \
 616         (listelm)->field.cqe_next = (elm);                              \
 617 } while (0)
 618
 619 #define CIRCLEQ_INSERT_BEFORE(head, listelm, elm, field) do {           \
 620         (elm)->field.cqe_next = (listelm);                              \
 621         (elm)->field.cqe_prev = (listelm)->field.cqe_prev;              \
 622         if ((listelm)->field.cqe_prev == (void *)(head))                \
 623                 (head)->cqh_first = (elm);                              \
 624         else                                                            \
 625                 (listelm)->field.cqe_prev->field.cqe_next = (elm);      \
 626         (listelm)->field.cqe_prev = (elm);                              \
 627 } while (0)
 628
 629 #define CIRCLEQ_INSERT_HEAD(head, elm, field) do {                      \
 630         (elm)->field.cqe_next = (head)->cqh_first;                      \
 631         (elm)->field.cqe_prev = (void *)(head);                         \
 632         if ((head)->cqh_last == (void *)(head))                         \
 633                 (head)->cqh_last = (elm);                               \
 634         else                                                            \
 635                 (head)->cqh_first->field.cqe_prev = (elm);              \
 636         (head)->cqh_first = (elm);                                      \
 637 } while (0)
 638
 639 #define CIRCLEQ_INSERT_TAIL(head, elm, field) do {                      \
 640         (elm)->field.cqe_next = (void *)(head);                         \
 641         (elm)->field.cqe_prev = (head)->cqh_last;                       \
 642         if ((head)->cqh_first == (void *)(head))                        \
 643                 (head)->cqh_first = (elm);                              \
 644         else                                                            \
 645                 (head)->cqh_last->field.cqe_next = (elm);               \
 646         (head)->cqh_last = (elm);                                       \
 647 } while (0)
 648
 649 #define CIRCLEQ_LAST(head) ((head)->cqh_last)
 650
 651 #define CIRCLEQ_NEXT(elm,field) ((elm)->field.cqe_next)
 652
 653 #define CIRCLEQ_PREV(elm,field) ((elm)->field.cqe_prev)
 654
 655 #define CIRCLEQ_REMOVE(head, elm, field) do {                           \
 656         if ((elm)->field.cqe_next == (void *)(head))                    \
 657                 (head)->cqh_last = (elm)->field.cqe_prev;               \
 658         else                                                            \
 659                 (elm)->field.cqe_next->field.cqe_prev =                 \
 660                     (elm)->field.cqe_prev;                              \
 661         if ((elm)->field.cqe_prev == (void *)(head))                    \
 662                 (head)->cqh_first = (elm)->field.cqe_next;              \
 663         else                                                            \
 664                 (elm)->field.cqe_prev->field.cqe_next =                 \
 665                     (elm)->field.cqe_next;                              \
 666 } while (0)
 667
 668 #ifdef _KERNEL
 669
 670 #if NOTFB31
 671
 672 /*
 673  * XXX insque() and remque() are an old way of handling certain queues.
 674  * They bogusly assumes that all queue heads look alike.
 675  */
 676
 677 struct quehead {
 678         struct quehead *qh_link;
 679         struct quehead *qh_rlink;
 680 };
 681
 682 #ifdef __GNUC__
 683
 684 static __inline void
 685 insque(void *a, void *b)
 686 {
 687         struct quehead *element = (struct quehead *)a,
 688                  *head = (struct quehead *)b;
 689
 690         element->qh_link = head->qh_link;
 691         element->qh_rlink = head;
 692         head->qh_link = element;
 693         element->qh_link->qh_rlink = element;
 694 }
 695
 696 static __inline void
 697 remque(void *a)
 698 {
 699         struct quehead *element = (struct quehead *)a;
 700
 701         element->qh_link->qh_rlink = element->qh_rlink;
 702         element->qh_rlink->qh_link = element->qh_link;
 703         element->qh_rlink = 0;
 704 }
 705
 706 #else /* !__GNUC__ */
 707
 708 void    insque(void *a, void *b);
 709 void    remque(void *a);
 710
 711 #endif /* __GNUC__ */
 712
 713 #endif
 714 #endif /* _KERNEL */
 715
 716 #endif /* !_SYS_QUEUE_H_ */