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  * 4. Neither the name of the University nor the names of its contributors
  14  *    may be used to endorse or promote products derived from this software
  15  *    without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  *
  29  *      @(#)queue.h     8.5 (Berkeley) 8/20/94
  30  * $FreeBSD$
  31  */
  32
  33 #ifndef _SYS_QUEUE_H_
  34 #define _SYS_QUEUE_H_
  35
  36 #include <sys/cdefs.h>
  37
  38 /*
  39  * This file defines four types of data structures: singly-linked lists,
  40  * singly-linked tail queues, lists and tail queues.
  41  *
  42  * A singly-linked list is headed by a single forward pointer. The elements
  43  * are singly linked for minimum space and pointer manipulation overhead at
  44  * the expense of O(n) removal for arbitrary elements. New elements can be
  45  * added to the list after an existing element or at the head of the list.
  46  * Elements being removed from the head of the list should use the explicit
  47  * macro for this purpose for optimum efficiency. A singly-linked list may
  48  * only be traversed in the forward direction.  Singly-linked lists are ideal
  49  * for applications with large datasets and few or no removals or for
  50  * implementing a LIFO queue.
  51  *
  52  * A singly-linked tail queue is headed by a pair of pointers, one to the
  53  * head of the list and the other to the tail of the list. The elements are
  54  * singly linked for minimum space and pointer manipulation overhead at the
  55  * expense of O(n) removal for arbitrary elements. New elements can be added
  56  * to the list after an existing element, at the head of the list, or at the
  57  * end of the list. Elements being removed from the head of the tail queue
  58  * should use the explicit macro for this purpose for optimum efficiency.
  59  * A singly-linked tail queue may only be traversed in the forward direction.
  60  * Singly-linked tail queues are ideal for applications with large datasets
  61  * and few or no removals or for implementing a FIFO queue.
  62  *
  63  * A list is headed by a single forward pointer (or an array of forward
  64  * pointers for a hash table header). The elements are doubly linked
  65  * so that an arbitrary element can be removed without a need to
  66  * traverse the list. New elements can be added to the list before
  67  * or after an existing element or at the head of the list. A list
  68  * may only be traversed in the forward direction.
  69  *
  70  * A tail queue is headed by a pair of pointers, one to the head of the
  71  * list and the other to the tail of the list. The elements are doubly
  72  * linked 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 or
  74  * after an existing element, at the head of the list, or at the end of
  75  * the list. A tail queue may be traversed in either direction.
  76  *
  77  * For details on the use of these macros, see the queue(3) manual page.
  78  *
  79  *
  80  *                              SLIST   LIST    STAILQ  TAILQ
  81  * _HEAD                        +       +       +       +
  82  * _HEAD_INITIALIZER            +       +       +       +
  83  * _ENTRY                       +       +       +       +
  84  * _INIT                        +       +       +       +
  85  * _EMPTY                       +       +       +       +
  86  * _FIRST                       +       +       +       +
  87  * _NEXT                        +       +       +       +
  88  * _PREV                        -       -       -       +
  89  * _LAST                        -       -       +       +
  90  * _FOREACH                     +       +       +       +
  91  * _FOREACH_SAFE                +       +       +       +
  92  * _FOREACH_REVERSE             -       -       -       +
  93  * _FOREACH_REVERSE_SAFE        -       -       -       +
  94  * _INSERT_HEAD                 +       +       +       +
  95  * _INSERT_BEFORE               -       +       -       +
  96  * _INSERT_AFTER                +       +       +       +
  97  * _INSERT_TAIL                 -       -       +       +
  98  * _CONCAT                      -       -       +       +
  99  * _REMOVE_AFTER                +       -       +       -
 100  * _REMOVE_HEAD                 +       -       +       -
 101  * _REMOVE                      +       +       +       +
 102  *
 103  */
 104 #ifdef QUEUE_MACRO_DEBUG
 105 /* Store the last 2 places the queue element or head was altered */
 106 struct qm_trace {
 107         char * lastfile;
 108         int lastline;
 109         char * prevfile;
 110         int prevline;
 111 };
 112
 113 #define TRACEBUF        struct qm_trace trace;
 114 #define TRASHIT(x)      do {(x) = (void *)-1;} while (0)
 115
 116 #define QMD_TRACE_HEAD(head) do {                                       \
 117         (head)->trace.prevline = (head)->trace.lastline;                \
 118         (head)->trace.prevfile = (head)->trace.lastfile;                \
 119         (head)->trace.lastline = __LINE__;                              \
 120         (head)->trace.lastfile = __FILE__;                              \
 121 } while (0)
 122
 123 #define QMD_TRACE_ELEM(elem) do {                                       \
 124         (elem)->trace.prevline = (elem)->trace.lastline;                \
 125         (elem)->trace.prevfile = (elem)->trace.lastfile;                \
 126         (elem)->trace.lastline = __LINE__;                              \
 127         (elem)->trace.lastfile = __FILE__;                              \
 128 } while (0)
 129
 130 #else
 131 #define QMD_TRACE_ELEM(elem)
 132 #define QMD_TRACE_HEAD(head)
 133 #define TRACEBUF
 134 #define TRASHIT(x)
 135 #endif  /* QUEUE_MACRO_DEBUG */
 136
 137 /*
 138  * Singly-linked List declarations.
 139  */
 140 #define SLIST_HEAD(name, type)                                          \
 141 struct name {                                                           \
 142         struct type *slh_first; /* first element */                     \
 143 }
 144
 145 #define SLIST_HEAD_INITIALIZER(head)                                    \
 146         { NULL }
 147
 148 #define SLIST_ENTRY(type)                                               \
 149 struct {                                                                \
 150         struct type *sle_next;  /* next element */                      \
 151 }
 152
 153 /*
 154  * Singly-linked List functions.
 155  */
 156 #define SLIST_EMPTY(head)       ((head)->slh_first == NULL)
 157
 158 #define SLIST_FIRST(head)       ((head)->slh_first)
 159
 160 #define SLIST_FOREACH(var, head, field)                                 \
 161         for ((var) = SLIST_FIRST((head));                               \
 162             (var);                                                      \
 163             (var) = SLIST_NEXT((var), field))
 164
 165 #define SLIST_FOREACH_SAFE(var, head, field, tvar)                      \
 166         for ((var) = SLIST_FIRST((head));                               \
 167             (var) && ((tvar) = SLIST_NEXT((var), field), 1);            \
 168             (var) = (tvar))
 169
 170 #define SLIST_FOREACH_PREVPTR(var, varp, head, field)                   \
 171         for ((varp) = &SLIST_FIRST((head));                             \
 172             ((var) = *(varp)) != NULL;                                  \
 173             (varp) = &SLIST_NEXT((var), field))
 174
 175 #define SLIST_INIT(head) do {                                           \
 176         SLIST_FIRST((head)) = NULL;                                     \
 177 } while (0)
 178
 179 #define SLIST_INSERT_AFTER(slistelm, elm, field) do {                   \
 180         SLIST_NEXT((elm), field) = SLIST_NEXT((slistelm), field);       \
 181         SLIST_NEXT((slistelm), field) = (elm);                          \
 182 } while (0)
 183
 184 #define SLIST_INSERT_HEAD(head, elm, field) do {                        \
 185         SLIST_NEXT((elm), field) = SLIST_FIRST((head));                 \
 186         SLIST_FIRST((head)) = (elm);                                    \
 187 } while (0)
 188
 189 #define SLIST_NEXT(elm, field)  ((elm)->field.sle_next)
 190
 191 #define SLIST_REMOVE(head, elm, type, field) do {                       \
 192         if (SLIST_FIRST((head)) == (elm)) {                             \
 193                 SLIST_REMOVE_HEAD((head), field);                       \
 194         }                                                               \
 195         else {                                                          \
 196                 struct type *curelm = SLIST_FIRST((head));              \
 197                 while (SLIST_NEXT(curelm, field) != (elm))              \
 198                         curelm = SLIST_NEXT(curelm, field);             \
 199                 SLIST_REMOVE_AFTER(curelm, field);                      \
 200         }                                                               \
 201         TRASHIT((elm)->field.sle_next);                                 \
 202 } while (0)
 203
 204 #define SLIST_REMOVE_AFTER(elm, field) do {                             \
 205         SLIST_NEXT(elm, field) =                                        \
 206             SLIST_NEXT(SLIST_NEXT(elm, field), field);                  \
 207 } while (0)
 208
 209 #define SLIST_REMOVE_HEAD(head, field) do {                             \
 210         SLIST_FIRST((head)) = SLIST_NEXT(SLIST_FIRST((head)), field);   \
 211 } while (0)
 212
 213 /*
 214  * Singly-linked Tail queue declarations.
 215  */
 216 #define STAILQ_HEAD(name, type)                                         \
 217 struct name {                                                           \
 218         struct type *stqh_first;/* first element */                     \
 219         struct type **stqh_last;/* addr of last next element */         \
 220 }
 221
 222 #define STAILQ_HEAD_INITIALIZER(head)                                   \
 223         { NULL, &(head).stqh_first }
 224
 225 #define STAILQ_ENTRY(type)                                              \
 226 struct {                                                                \
 227         struct type *stqe_next; /* next element */                      \
 228 }
 229
 230 /*
 231  * Singly-linked Tail queue functions.
 232  */
 233 #define STAILQ_CONCAT(head1, head2) do {                                \
 234         if (!STAILQ_EMPTY((head2))) {                                   \
 235                 *(head1)->stqh_last = (head2)->stqh_first;              \
 236                 (head1)->stqh_last = (head2)->stqh_last;                \
 237                 STAILQ_INIT((head2));                                   \
 238         }                                                               \
 239 } while (0)
 240
 241 #define STAILQ_EMPTY(head)      ((head)->stqh_first == NULL)
 242
 243 #define STAILQ_FIRST(head)      ((head)->stqh_first)
 244
 245 #define STAILQ_FOREACH(var, head, field)                                \
 246         for((var) = STAILQ_FIRST((head));                               \
 247            (var);                                                       \
 248            (var) = STAILQ_NEXT((var), field))
 249
 250
 251 #define STAILQ_FOREACH_SAFE(var, head, field, tvar)                     \
 252         for ((var) = STAILQ_FIRST((head));                              \
 253             (var) && ((tvar) = STAILQ_NEXT((var), field), 1);           \
 254             (var) = (tvar))
 255
 256 #define STAILQ_INIT(head) do {                                          \
 257         STAILQ_FIRST((head)) = NULL;                                    \
 258         (head)->stqh_last = &STAILQ_FIRST((head));                      \
 259 } while (0)
 260
 261 #define STAILQ_INSERT_AFTER(head, tqelm, elm, field) do {               \
 262         if ((STAILQ_NEXT((elm), field) = STAILQ_NEXT((tqelm), field)) == NULL)\
 263                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 264         STAILQ_NEXT((tqelm), field) = (elm);                            \
 265 } while (0)
 266
 267 #define STAILQ_INSERT_HEAD(head, elm, field) do {                       \
 268         if ((STAILQ_NEXT((elm), field) = STAILQ_FIRST((head))) == NULL) \
 269                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 270         STAILQ_FIRST((head)) = (elm);                                   \
 271 } while (0)
 272
 273 #define STAILQ_INSERT_TAIL(head, elm, field) do {                       \
 274         STAILQ_NEXT((elm), field) = NULL;                               \
 275         *(head)->stqh_last = (elm);                                     \
 276         (head)->stqh_last = &STAILQ_NEXT((elm), field);                 \
 277 } while (0)
 278
 279 #define STAILQ_LAST(head, type, field)                                  \
 280         (STAILQ_EMPTY((head)) ?                                         \
 281                 NULL :                                                  \
 282                 ((struct type *)(void *)                                \
 283                 ((char *)((head)->stqh_last) - __offsetof(struct type, field))))
 284
 285 #define STAILQ_NEXT(elm, field) ((elm)->field.stqe_next)
 286
 287 #define STAILQ_REMOVE(head, elm, type, field) do {                      \
 288         if (STAILQ_FIRST((head)) == (elm)) {                            \
 289                 STAILQ_REMOVE_HEAD((head), field);                      \
 290         }                                                               \
 291         else {                                                          \
 292                 struct type *curelm = STAILQ_FIRST((head));             \
 293                 while (STAILQ_NEXT(curelm, field) != (elm))             \
 294                         curelm = STAILQ_NEXT(curelm, field);            \
 295                 STAILQ_REMOVE_AFTER(head, curelm, field);               \
 296         }                                                               \
 297         TRASHIT((elm)->field.stqe_next);                                \
 298 } while (0)
 299
 300 #define STAILQ_REMOVE_HEAD(head, field) do {                            \
 301         if ((STAILQ_FIRST((head)) =                                     \
 302              STAILQ_NEXT(STAILQ_FIRST((head)), field)) == NULL)         \
 303                 (head)->stqh_last = &STAILQ_FIRST((head));              \
 304 } while (0)
 305
 306 #define STAILQ_REMOVE_AFTER(head, elm, field) do {                      \
 307         if ((STAILQ_NEXT(elm, field) =                                  \
 308              STAILQ_NEXT(STAILQ_NEXT(elm, field), field)) == NULL)      \
 309                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 310 } while (0)
 311
 312 #define STAILQ_SWAP(head1, head2, type) do {                            \
 313         struct type *swap_first = STAILQ_FIRST(head1);                  \
 314         struct type **swap_last = (head1)->stqh_last;                   \
 315         STAILQ_FIRST(head1) = STAILQ_FIRST(head2);                      \
 316         (head1)->stqh_last = (head2)->stqh_last;                        \
 317         STAILQ_FIRST(head2) = swap_first;                               \
 318         (head2)->stqh_last = swap_last;                                 \
 319         if (STAILQ_EMPTY(head1))                                        \
 320                 (head1)->stqh_last = &STAILQ_FIRST(head1);              \
 321         if (STAILQ_EMPTY(head2))                                        \
 322                 (head2)->stqh_last = &STAILQ_FIRST(head2);              \
 323 } while (0)
 324
 325
 326 /*
 327  * List declarations.
 328  */
 329 #define LIST_HEAD(name, type)                                           \
 330 struct name {                                                           \
 331         struct type *lh_first;  /* first element */                     \
 332 }
 333
 334 #define LIST_HEAD_INITIALIZER(head)                                     \
 335         { NULL }
 336
 337 #define LIST_ENTRY(type)                                                \
 338 struct {                                                                \
 339         struct type *le_next;   /* next element */                      \
 340         struct type **le_prev;  /* address of previous next element */  \
 341 }
 342
 343 /*
 344  * List functions.
 345  */
 346
 347 #if (defined(_KERNEL) && defined(INVARIANTS))
 348 #define QMD_LIST_CHECK_HEAD(head, field) do {                           \
 349         if (LIST_FIRST((head)) != NULL &&                               \
 350             LIST_FIRST((head))->field.le_prev !=                        \
 351              &LIST_FIRST((head)))                                       \
 352                 panic("Bad list head %p first->prev != head", (head));  \
 353 } while (0)
 354
 355 #define QMD_LIST_CHECK_NEXT(elm, field) do {                            \
 356         if (LIST_NEXT((elm), field) != NULL &&                          \
 357             LIST_NEXT((elm), field)->field.le_prev !=                   \
 358              &((elm)->field.le_next))                                   \
 359                 panic("Bad link elm %p next->prev != elm", (elm));      \
 360 } while (0)
 361
 362 #define QMD_LIST_CHECK_PREV(elm, field) do {                            \
 363         if (*(elm)->field.le_prev != (elm))                             \
 364                 panic("Bad link elm %p prev->next != elm", (elm));      \
 365 } while (0)
 366 #else
 367 #define QMD_LIST_CHECK_HEAD(head, field)
 368 #define QMD_LIST_CHECK_NEXT(elm, field)
 369 #define QMD_LIST_CHECK_PREV(elm, field)
 370 #endif /* (_KERNEL && INVARIANTS) */
 371
 372 #define LIST_EMPTY(head)        ((head)->lh_first == NULL)
 373
 374 #define LIST_FIRST(head)        ((head)->lh_first)
 375
 376 #define LIST_FOREACH(var, head, field)                                  \
 377         for ((var) = LIST_FIRST((head));                                \
 378             (var);                                                      \
 379             (var) = LIST_NEXT((var), field))
 380
 381 #define LIST_FOREACH_SAFE(var, head, field, tvar)                       \
 382         for ((var) = LIST_FIRST((head));                                \
 383             (var) && ((tvar) = LIST_NEXT((var), field), 1);             \
 384             (var) = (tvar))
 385
 386 #define LIST_INIT(head) do {                                            \
 387         LIST_FIRST((head)) = NULL;                                      \
 388 } while (0)
 389
 390 #define LIST_INSERT_AFTER(listelm, elm, field) do {                     \
 391         QMD_LIST_CHECK_NEXT(listelm, field);                            \
 392         if ((LIST_NEXT((elm), field) = LIST_NEXT((listelm), field)) != NULL)\
 393                 LIST_NEXT((listelm), field)->field.le_prev =            \
 394                     &LIST_NEXT((elm), field);                           \
 395         LIST_NEXT((listelm), field) = (elm);                            \
 396         (elm)->field.le_prev = &LIST_NEXT((listelm), field);            \
 397 } while (0)
 398
 399 #define LIST_INSERT_BEFORE(listelm, elm, field) do {                    \
 400         QMD_LIST_CHECK_PREV(listelm, field);                            \
 401         (elm)->field.le_prev = (listelm)->field.le_prev;                \
 402         LIST_NEXT((elm), field) = (listelm);                            \
 403         *(listelm)->field.le_prev = (elm);                              \
 404         (listelm)->field.le_prev = &LIST_NEXT((elm), field);            \
 405 } while (0)
 406
 407 #define LIST_INSERT_HEAD(head, elm, field) do {                         \
 408         QMD_LIST_CHECK_HEAD((head), field);                             \
 409         if ((LIST_NEXT((elm), field) = LIST_FIRST((head))) != NULL)     \
 410                 LIST_FIRST((head))->field.le_prev = &LIST_NEXT((elm), field);\
 411         LIST_FIRST((head)) = (elm);                                     \
 412         (elm)->field.le_prev = &LIST_FIRST((head));                     \
 413 } while (0)
 414
 415 #define LIST_NEXT(elm, field)   ((elm)->field.le_next)
 416
 417 #define LIST_REMOVE(elm, field) do {                                    \
 418         QMD_LIST_CHECK_NEXT(elm, field);                                \
 419         QMD_LIST_CHECK_PREV(elm, field);                                \
 420         if (LIST_NEXT((elm), field) != NULL)                            \
 421                 LIST_NEXT((elm), field)->field.le_prev =                \
 422                     (elm)->field.le_prev;                               \
 423         *(elm)->field.le_prev = LIST_NEXT((elm), field);                \
 424         TRASHIT((elm)->field.le_next);                                  \
 425         TRASHIT((elm)->field.le_prev);                                  \
 426 } while (0)
 427
 428 #define LIST_SWAP(head1, head2, type, field) do {                       \
 429         struct type *swap_tmp = LIST_FIRST((head1));                    \
 430         LIST_FIRST((head1)) = LIST_FIRST((head2));                      \
 431         LIST_FIRST((head2)) = swap_tmp;                                 \
 432         if ((swap_tmp = LIST_FIRST((head1))) != NULL)                   \
 433                 swap_tmp->field.le_prev = &LIST_FIRST((head1));         \
 434         if ((swap_tmp = LIST_FIRST((head2))) != NULL)                   \
 435                 swap_tmp->field.le_prev = &LIST_FIRST((head2));         \
 436 } while (0)
 437
 438 /*
 439  * Tail queue declarations.
 440  */
 441 #define TAILQ_HEAD(name, type)                                          \
 442 struct name {                                                           \
 443         struct type *tqh_first; /* first element */                     \
 444         struct type **tqh_last; /* addr of last next element */         \
 445         TRACEBUF                                                        \
 446 }
 447
 448 #define TAILQ_HEAD_INITIALIZER(head)                                    \
 449         { NULL, &(head).tqh_first }
 450
 451 #define TAILQ_ENTRY(type)                                               \
 452 struct {                                                                \
 453         struct type *tqe_next;  /* next element */                      \
 454         struct type **tqe_prev; /* address of previous next element */  \
 455         TRACEBUF                                                        \
 456 }
 457
 458 /*
 459  * Tail queue functions.
 460  */
 461 #if (defined(_KERNEL) && defined(INVARIANTS))
 462 #define QMD_TAILQ_CHECK_HEAD(head, field) do {                          \
 463         if (!TAILQ_EMPTY(head) &&                                       \
 464             TAILQ_FIRST((head))->field.tqe_prev !=                      \
 465              &TAILQ_FIRST((head)))                                      \
 466                 panic("Bad tailq head %p first->prev != head", (head)); \
 467 } while (0)
 468
 469 #define QMD_TAILQ_CHECK_TAIL(head, field) do {                          \
 470         if (*(head)->tqh_last != NULL)                                  \
 471                 panic("Bad tailq NEXT(%p->tqh_last) != NULL", (head));  \
 472 } while (0)
 473
 474 #define QMD_TAILQ_CHECK_NEXT(elm, field) do {                           \
 475         if (TAILQ_NEXT((elm), field) != NULL &&                         \
 476             TAILQ_NEXT((elm), field)->field.tqe_prev !=                 \
 477              &((elm)->field.tqe_next))                                  \
 478                 panic("Bad link elm %p next->prev != elm", (elm));      \
 479 } while (0)
 480
 481 #define QMD_TAILQ_CHECK_PREV(elm, field) do {                           \
 482         if (*(elm)->field.tqe_prev != (elm))                            \
 483                 panic("Bad link elm %p prev->next != elm", (elm));      \
 484 } while (0)
 485 #else
 486 #define QMD_TAILQ_CHECK_HEAD(head, field)
 487 #define QMD_TAILQ_CHECK_TAIL(head, headname)
 488 #define QMD_TAILQ_CHECK_NEXT(elm, field)
 489 #define QMD_TAILQ_CHECK_PREV(elm, field)
 490 #endif /* (_KERNEL && INVARIANTS) */
 491
 492 #define TAILQ_CONCAT(head1, head2, field) do {                          \
 493         if (!TAILQ_EMPTY(head2)) {                                      \
 494                 *(head1)->tqh_last = (head2)->tqh_first;                \
 495                 (head2)->tqh_first->field.tqe_prev = (head1)->tqh_last; \
 496                 (head1)->tqh_last = (head2)->tqh_last;                  \
 497                 TAILQ_INIT((head2));                                    \
 498                 QMD_TRACE_HEAD(head1);                                  \
 499                 QMD_TRACE_HEAD(head2);                                  \
 500         }                                                               \
 501 } while (0)
 502
 503 #define TAILQ_EMPTY(head)       ((head)->tqh_first == NULL)
 504
 505 #define TAILQ_FIRST(head)       ((head)->tqh_first)
 506
 507 #define TAILQ_FOREACH(var, head, field)                                 \
 508         for ((var) = TAILQ_FIRST((head));                               \
 509             (var);                                                      \
 510             (var) = TAILQ_NEXT((var), field))
 511
 512 #define TAILQ_FOREACH_SAFE(var, head, field, tvar)                      \
 513         for ((var) = TAILQ_FIRST((head));                               \
 514             (var) && ((tvar) = TAILQ_NEXT((var), field), 1);            \
 515             (var) = (tvar))
 516
 517 #define TAILQ_FOREACH_REVERSE(var, head, headname, field)               \
 518         for ((var) = TAILQ_LAST((head), headname);                      \
 519             (var);                                                      \
 520             (var) = TAILQ_PREV((var), headname, field))
 521
 522 #define TAILQ_FOREACH_REVERSE_SAFE(var, head, headname, field, tvar)    \
 523         for ((var) = TAILQ_LAST((head), headname);                      \
 524             (var) && ((tvar) = TAILQ_PREV((var), headname, field), 1);  \
 525             (var) = (tvar))
 526
 527 #define TAILQ_INIT(head) do {                                           \
 528         TAILQ_FIRST((head)) = NULL;                                     \
 529         (head)->tqh_last = &TAILQ_FIRST((head));                        \
 530         QMD_TRACE_HEAD(head);                                           \
 531 } while (0)
 532
 533 #define TAILQ_INSERT_AFTER(head, listelm, elm, field) do {              \
 534         QMD_TAILQ_CHECK_NEXT(listelm, field);                           \
 535         if ((TAILQ_NEXT((elm), field) = TAILQ_NEXT((listelm), field)) != NULL)\
 536                 TAILQ_NEXT((elm), field)->field.tqe_prev =              \
 537                     &TAILQ_NEXT((elm), field);                          \
 538         else {                                                          \
 539                 (head)->tqh_last = &TAILQ_NEXT((elm), field);           \
 540                 QMD_TRACE_HEAD(head);                                   \
 541         }                                                               \
 542         TAILQ_NEXT((listelm), field) = (elm);                           \
 543         (elm)->field.tqe_prev = &TAILQ_NEXT((listelm), field);          \
 544         QMD_TRACE_ELEM(&(elm)->field);                                  \
 545         QMD_TRACE_ELEM(&listelm->field);                                \
 546 } while (0)
 547
 548 #define TAILQ_INSERT_BEFORE(listelm, elm, field) do {                   \
 549         QMD_TAILQ_CHECK_PREV(listelm, field);                           \
 550         (elm)->field.tqe_prev = (listelm)->field.tqe_prev;              \
 551         TAILQ_NEXT((elm), field) = (listelm);                           \
 552         *(listelm)->field.tqe_prev = (elm);                             \
 553         (listelm)->field.tqe_prev = &TAILQ_NEXT((elm), field);          \
 554         QMD_TRACE_ELEM(&(elm)->field);                                  \
 555         QMD_TRACE_ELEM(&listelm->field);                                \
 556 } while (0)
 557
 558 #define TAILQ_INSERT_HEAD(head, elm, field) do {                        \
 559         QMD_TAILQ_CHECK_HEAD(head, field);                              \
 560         if ((TAILQ_NEXT((elm), field) = TAILQ_FIRST((head))) != NULL)   \
 561                 TAILQ_FIRST((head))->field.tqe_prev =                   \
 562                     &TAILQ_NEXT((elm), field);                          \
 563         else                                                            \
 564                 (head)->tqh_last = &TAILQ_NEXT((elm), field);           \
 565         TAILQ_FIRST((head)) = (elm);                                    \
 566         (elm)->field.tqe_prev = &TAILQ_FIRST((head));                   \
 567         QMD_TRACE_HEAD(head);                                           \
 568         QMD_TRACE_ELEM(&(elm)->field);                                  \
 569 } while (0)
 570
 571 #define TAILQ_INSERT_TAIL(head, elm, field) do {                        \
 572         QMD_TAILQ_CHECK_TAIL(head, field);                              \
 573         TAILQ_NEXT((elm), field) = NULL;                                \
 574         (elm)->field.tqe_prev = (head)->tqh_last;                       \
 575         *(head)->tqh_last = (elm);                                      \
 576         (head)->tqh_last = &TAILQ_NEXT((elm), field);                   \
 577         QMD_TRACE_HEAD(head);                                           \
 578         QMD_TRACE_ELEM(&(elm)->field);                                  \
 579 } while (0)
 580
 581 #define TAILQ_LAST(head, headname)                                      \
 582         (*(((struct headname *)((head)->tqh_last))->tqh_last))
 583
 584 #define TAILQ_NEXT(elm, field) ((elm)->field.tqe_next)
 585
 586 #define TAILQ_PREV(elm, headname, field)                                \
 587         (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
 588
 589 #define TAILQ_REMOVE(head, elm, field) do {                             \
 590         QMD_TAILQ_CHECK_NEXT(elm, field);                               \
 591         QMD_TAILQ_CHECK_PREV(elm, field);                               \
 592         if ((TAILQ_NEXT((elm), field)) != NULL)                         \
 593                 TAILQ_NEXT((elm), field)->field.tqe_prev =              \
 594                     (elm)->field.tqe_prev;                              \
 595         else {                                                          \
 596                 (head)->tqh_last = (elm)->field.tqe_prev;               \
 597                 QMD_TRACE_HEAD(head);                                   \
 598         }                                                               \
 599         *(elm)->field.tqe_prev = TAILQ_NEXT((elm), field);              \
 600         TRASHIT((elm)->field.tqe_next);                                 \
 601         TRASHIT((elm)->field.tqe_prev);                                 \
 602         QMD_TRACE_ELEM(&(elm)->field);                                  \
 603 } while (0)
 604
 605 #define TAILQ_SWAP(head1, head2, type, field) do {                      \
 606         struct type *swap_first = (head1)->tqh_first;                   \
 607         struct type **swap_last = (head1)->tqh_last;                    \
 608         (head1)->tqh_first = (head2)->tqh_first;                        \
 609         (head1)->tqh_last = (head2)->tqh_last;                          \
 610         (head2)->tqh_first = swap_first;                                \
 611         (head2)->tqh_last = swap_last;                                  \
 612         if ((swap_first = (head1)->tqh_first) != NULL)                  \
 613                 swap_first->field.tqe_prev = &(head1)->tqh_first;       \
 614         else                                                            \
 615                 (head1)->tqh_last = &(head1)->tqh_first;                \
 616         if ((swap_first = (head2)->tqh_first) != NULL)                  \
 617                 swap_first->field.tqe_prev = &(head2)->tqh_first;       \
 618         else                                                            \
 619                 (head2)->tqh_last = &(head2)->tqh_first;                \
 620 } while (0)
 621
 622 #endif /* !_SYS_QUEUE_H_ */