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 #define QMD_SAVELINK(name, link)        void **name = (void *)&(link)
 116
 117 #define QMD_TRACE_HEAD(head) do {                                       \
 118         (head)->trace.prevline = (head)->trace.lastline;                \
 119         (head)->trace.prevfile = (head)->trace.lastfile;                \
 120         (head)->trace.lastline = __LINE__;                              \
 121         (head)->trace.lastfile = __FILE__;                              \
 122 } while (0)
 123
 124 #define QMD_TRACE_ELEM(elem) do {                                       \
 125         (elem)->trace.prevline = (elem)->trace.lastline;                \
 126         (elem)->trace.prevfile = (elem)->trace.lastfile;                \
 127         (elem)->trace.lastline = __LINE__;                              \
 128         (elem)->trace.lastfile = __FILE__;                              \
 129 } while (0)
 130
 131 #else
 132 #define QMD_TRACE_ELEM(elem)
 133 #define QMD_TRACE_HEAD(head)
 134 #define QMD_SAVELINK(name, link)
 135 #define TRACEBUF
 136 #define TRASHIT(x)
 137 #endif  /* QUEUE_MACRO_DEBUG */
 138
 139 /*
 140  * Singly-linked List declarations.
 141  */
 142 #define SLIST_HEAD(name, type)                                          \
 143 struct name {                                                           \
 144         struct type *slh_first; /* first element */                     \
 145 }
 146
 147 #define SLIST_HEAD_INITIALIZER(head)                                    \
 148         { NULL }
 149
 150 #define SLIST_ENTRY(type)                                               \
 151 struct {                                                                \
 152         struct type *sle_next;  /* next element */                      \
 153 }
 154
 155 /*
 156  * Singly-linked List functions.
 157  */
 158 #define SLIST_EMPTY(head)       ((head)->slh_first == NULL)
 159
 160 #define SLIST_FIRST(head)       ((head)->slh_first)
 161
 162 #define SLIST_FOREACH(var, head, field)                                 \
 163         for ((var) = SLIST_FIRST((head));                               \
 164             (var);                                                      \
 165             (var) = SLIST_NEXT((var), field))
 166
 167 #define SLIST_FOREACH_SAFE(var, head, field, tvar)                      \
 168         for ((var) = SLIST_FIRST((head));                               \
 169             (var) && ((tvar) = SLIST_NEXT((var), field), 1);            \
 170             (var) = (tvar))
 171
 172 #define SLIST_FOREACH_PREVPTR(var, varp, head, field)                   \
 173         for ((varp) = &SLIST_FIRST((head));                             \
 174             ((var) = *(varp)) != NULL;                                  \
 175             (varp) = &SLIST_NEXT((var), field))
 176
 177 #define SLIST_INIT(head) do {                                           \
 178         SLIST_FIRST((head)) = NULL;                                     \
 179 } while (0)
 180
 181 #define SLIST_INSERT_AFTER(slistelm, elm, field) do {                   \
 182         SLIST_NEXT((elm), field) = SLIST_NEXT((slistelm), field);       \
 183         SLIST_NEXT((slistelm), field) = (elm);                          \
 184 } while (0)
 185
 186 #define SLIST_INSERT_HEAD(head, elm, field) do {                        \
 187         SLIST_NEXT((elm), field) = SLIST_FIRST((head));                 \
 188         SLIST_FIRST((head)) = (elm);                                    \
 189 } while (0)
 190
 191 #define SLIST_NEXT(elm, field)  ((elm)->field.sle_next)
 192
 193 #define SLIST_REMOVE(head, elm, type, field) do {                       \
 194         QMD_SAVELINK(oldnext, (elm)->field.sle_next);                   \
 195         if (SLIST_FIRST((head)) == (elm)) {                             \
 196                 SLIST_REMOVE_HEAD((head), field);                       \
 197         }                                                               \
 198         else {                                                          \
 199                 struct type *curelm = SLIST_FIRST((head));              \
 200                 while (SLIST_NEXT(curelm, field) != (elm))              \
 201                         curelm = SLIST_NEXT(curelm, field);             \
 202                 SLIST_REMOVE_AFTER(curelm, field);                      \
 203         }                                                               \
 204         TRASHIT(*oldnext);                                              \
 205 } while (0)
 206
 207 #define SLIST_REMOVE_AFTER(elm, field) do {                             \
 208         SLIST_NEXT(elm, field) =                                        \
 209             SLIST_NEXT(SLIST_NEXT(elm, field), field);                  \
 210 } while (0)
 211
 212 #define SLIST_REMOVE_HEAD(head, field) do {                             \
 213         SLIST_FIRST((head)) = SLIST_NEXT(SLIST_FIRST((head)), field);   \
 214 } while (0)
 215
 216 /*
 217  * Singly-linked Tail queue declarations.
 218  */
 219 #define STAILQ_HEAD(name, type)                                         \
 220 struct name {                                                           \
 221         struct type *stqh_first;/* first element */                     \
 222         struct type **stqh_last;/* addr of last next element */         \
 223 }
 224
 225 #define STAILQ_HEAD_INITIALIZER(head)                                   \
 226         { NULL, &(head).stqh_first }
 227
 228 #define STAILQ_ENTRY(type)                                              \
 229 struct {                                                                \
 230         struct type *stqe_next; /* next element */                      \
 231 }
 232
 233 /*
 234  * Singly-linked Tail queue functions.
 235  */
 236 #define STAILQ_CONCAT(head1, head2) do {                                \
 237         if (!STAILQ_EMPTY((head2))) {                                   \
 238                 *(head1)->stqh_last = (head2)->stqh_first;              \
 239                 (head1)->stqh_last = (head2)->stqh_last;                \
 240                 STAILQ_INIT((head2));                                   \
 241         }                                                               \
 242 } while (0)
 243
 244 #define STAILQ_EMPTY(head)      ((head)->stqh_first == NULL)
 245
 246 #define STAILQ_FIRST(head)      ((head)->stqh_first)
 247
 248 #define STAILQ_FOREACH(var, head, field)                                \
 249         for((var) = STAILQ_FIRST((head));                               \
 250            (var);                                                       \
 251            (var) = STAILQ_NEXT((var), field))
 252
 253
 254 #define STAILQ_FOREACH_SAFE(var, head, field, tvar)                     \
 255         for ((var) = STAILQ_FIRST((head));                              \
 256             (var) && ((tvar) = STAILQ_NEXT((var), field), 1);           \
 257             (var) = (tvar))
 258
 259 #define STAILQ_INIT(head) do {                                          \
 260         STAILQ_FIRST((head)) = NULL;                                    \
 261         (head)->stqh_last = &STAILQ_FIRST((head));                      \
 262 } while (0)
 263
 264 #define STAILQ_INSERT_AFTER(head, tqelm, elm, field) do {               \
 265         if ((STAILQ_NEXT((elm), field) = STAILQ_NEXT((tqelm), field)) == NULL)\
 266                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 267         STAILQ_NEXT((tqelm), field) = (elm);                            \
 268 } while (0)
 269
 270 #define STAILQ_INSERT_HEAD(head, elm, field) do {                       \
 271         if ((STAILQ_NEXT((elm), field) = STAILQ_FIRST((head))) == NULL) \
 272                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 273         STAILQ_FIRST((head)) = (elm);                                   \
 274 } while (0)
 275
 276 #define STAILQ_INSERT_TAIL(head, elm, field) do {                       \
 277         STAILQ_NEXT((elm), field) = NULL;                               \
 278         *(head)->stqh_last = (elm);                                     \
 279         (head)->stqh_last = &STAILQ_NEXT((elm), field);                 \
 280 } while (0)
 281
 282 #define STAILQ_LAST(head, type, field)                                  \
 283         (STAILQ_EMPTY((head)) ?                                         \
 284                 NULL :                                                  \
 285                 ((struct type *)(void *)                                \
 286                 ((char *)((head)->stqh_last) - __offsetof(struct type, field))))
 287
 288 #define STAILQ_NEXT(elm, field) ((elm)->field.stqe_next)
 289
 290 #define STAILQ_REMOVE(head, elm, type, field) do {                      \
 291         QMD_SAVELINK(oldnext, (elm)->field.stqe_next);                  \
 292         if (STAILQ_FIRST((head)) == (elm)) {                            \
 293                 STAILQ_REMOVE_HEAD((head), field);                      \
 294         }                                                               \
 295         else {                                                          \
 296                 struct type *curelm = STAILQ_FIRST((head));             \
 297                 while (STAILQ_NEXT(curelm, field) != (elm))             \
 298                         curelm = STAILQ_NEXT(curelm, field);            \
 299                 STAILQ_REMOVE_AFTER(head, curelm, field);               \
 300         }                                                               \
 301         TRASHIT(*oldnext);                                              \
 302 } while (0)
 303
 304 #define STAILQ_REMOVE_HEAD(head, field) do {                            \
 305         if ((STAILQ_FIRST((head)) =                                     \
 306              STAILQ_NEXT(STAILQ_FIRST((head)), field)) == NULL)         \
 307                 (head)->stqh_last = &STAILQ_FIRST((head));              \
 308 } while (0)
 309
 310 #define STAILQ_REMOVE_AFTER(head, elm, field) do {                      \
 311         if ((STAILQ_NEXT(elm, field) =                                  \
 312              STAILQ_NEXT(STAILQ_NEXT(elm, field), field)) == NULL)      \
 313                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 314 } while (0)
 315
 316 #define STAILQ_SWAP(head1, head2, type) do {                            \
 317         struct type *swap_first = STAILQ_FIRST(head1);                  \
 318         struct type **swap_last = (head1)->stqh_last;                   \
 319         STAILQ_FIRST(head1) = STAILQ_FIRST(head2);                      \
 320         (head1)->stqh_last = (head2)->stqh_last;                        \
 321         STAILQ_FIRST(head2) = swap_first;                               \
 322         (head2)->stqh_last = swap_last;                                 \
 323         if (STAILQ_EMPTY(head1))                                        \
 324                 (head1)->stqh_last = &STAILQ_FIRST(head1);              \
 325         if (STAILQ_EMPTY(head2))                                        \
 326                 (head2)->stqh_last = &STAILQ_FIRST(head2);              \
 327 } while (0)
 328
 329
 330 /*
 331  * List declarations.
 332  */
 333 #define LIST_HEAD(name, type)                                           \
 334 struct name {                                                           \
 335         struct type *lh_first;  /* first element */                     \
 336 }
 337
 338 #define LIST_HEAD_INITIALIZER(head)                                     \
 339         { NULL }
 340
 341 #define LIST_ENTRY(type)                                                \
 342 struct {                                                                \
 343         struct type *le_next;   /* next element */                      \
 344         struct type **le_prev;  /* address of previous next element */  \
 345 }
 346
 347 /*
 348  * List functions.
 349  */
 350
 351 #if (defined(_KERNEL) && defined(INVARIANTS))
 352 #define QMD_LIST_CHECK_HEAD(head, field) do {                           \
 353         if (LIST_FIRST((head)) != NULL &&                               \
 354             LIST_FIRST((head))->field.le_prev !=                        \
 355              &LIST_FIRST((head)))                                       \
 356                 panic("Bad list head %p first->prev != head", (head));  \
 357 } while (0)
 358
 359 #define QMD_LIST_CHECK_NEXT(elm, field) do {                            \
 360         if (LIST_NEXT((elm), field) != NULL &&                          \
 361             LIST_NEXT((elm), field)->field.le_prev !=                   \
 362              &((elm)->field.le_next))                                   \
 363                 panic("Bad link elm %p next->prev != elm", (elm));      \
 364 } while (0)
 365
 366 #define QMD_LIST_CHECK_PREV(elm, field) do {                            \
 367         if (*(elm)->field.le_prev != (elm))                             \
 368                 panic("Bad link elm %p prev->next != elm", (elm));      \
 369 } while (0)
 370 #else
 371 #define QMD_LIST_CHECK_HEAD(head, field)
 372 #define QMD_LIST_CHECK_NEXT(elm, field)
 373 #define QMD_LIST_CHECK_PREV(elm, field)
 374 #endif /* (_KERNEL && INVARIANTS) */
 375
 376 #define LIST_EMPTY(head)        ((head)->lh_first == NULL)
 377
 378 #define LIST_FIRST(head)        ((head)->lh_first)
 379
 380 #define LIST_FOREACH(var, head, field)                                  \
 381         for ((var) = LIST_FIRST((head));                                \
 382             (var);                                                      \
 383             (var) = LIST_NEXT((var), field))
 384
 385 #define LIST_FOREACH_SAFE(var, head, field, tvar)                       \
 386         for ((var) = LIST_FIRST((head));                                \
 387             (var) && ((tvar) = LIST_NEXT((var), field), 1);             \
 388             (var) = (tvar))
 389
 390 #define LIST_INIT(head) do {                                            \
 391         LIST_FIRST((head)) = NULL;                                      \
 392 } while (0)
 393
 394 #define LIST_INSERT_AFTER(listelm, elm, field) do {                     \
 395         QMD_LIST_CHECK_NEXT(listelm, field);                            \
 396         if ((LIST_NEXT((elm), field) = LIST_NEXT((listelm), field)) != NULL)\
 397                 LIST_NEXT((listelm), field)->field.le_prev =            \
 398                     &LIST_NEXT((elm), field);                           \
 399         LIST_NEXT((listelm), field) = (elm);                            \
 400         (elm)->field.le_prev = &LIST_NEXT((listelm), field);            \
 401 } while (0)
 402
 403 #define LIST_INSERT_BEFORE(listelm, elm, field) do {                    \
 404         QMD_LIST_CHECK_PREV(listelm, field);                            \
 405         (elm)->field.le_prev = (listelm)->field.le_prev;                \
 406         LIST_NEXT((elm), field) = (listelm);                            \
 407         *(listelm)->field.le_prev = (elm);                              \
 408         (listelm)->field.le_prev = &LIST_NEXT((elm), field);            \
 409 } while (0)
 410
 411 #define LIST_INSERT_HEAD(head, elm, field) do {                         \
 412         QMD_LIST_CHECK_HEAD((head), field);                             \
 413         if ((LIST_NEXT((elm), field) = LIST_FIRST((head))) != NULL)     \
 414                 LIST_FIRST((head))->field.le_prev = &LIST_NEXT((elm), field);\
 415         LIST_FIRST((head)) = (elm);                                     \
 416         (elm)->field.le_prev = &LIST_FIRST((head));                     \
 417 } while (0)
 418
 419 #define LIST_NEXT(elm, field)   ((elm)->field.le_next)
 420
 421 #define LIST_REMOVE(elm, field) do {                                    \
 422         QMD_SAVELINK(oldnext, (elm)->field.le_next);                    \
 423         QMD_SAVELINK(oldprev, (elm)->field.le_prev);                    \
 424         QMD_LIST_CHECK_NEXT(elm, field);                                \
 425         QMD_LIST_CHECK_PREV(elm, field);                                \
 426         if (LIST_NEXT((elm), field) != NULL)                            \
 427                 LIST_NEXT((elm), field)->field.le_prev =                \
 428                     (elm)->field.le_prev;                               \
 429         *(elm)->field.le_prev = LIST_NEXT((elm), field);                \
 430         TRASHIT(*oldnext);                                              \
 431         TRASHIT(*oldprev);                                              \
 432 } while (0)
 433
 434 #define LIST_SWAP(head1, head2, type, field) do {                       \
 435         struct type *swap_tmp = LIST_FIRST((head1));                    \
 436         LIST_FIRST((head1)) = LIST_FIRST((head2));                      \
 437         LIST_FIRST((head2)) = swap_tmp;                                 \
 438         if ((swap_tmp = LIST_FIRST((head1))) != NULL)                   \
 439                 swap_tmp->field.le_prev = &LIST_FIRST((head1));         \
 440         if ((swap_tmp = LIST_FIRST((head2))) != NULL)                   \
 441                 swap_tmp->field.le_prev = &LIST_FIRST((head2));         \
 442 } while (0)
 443
 444 /*
 445  * Tail queue declarations.
 446  */
 447 #define TAILQ_HEAD(name, type)                                          \
 448 struct name {                                                           \
 449         struct type *tqh_first; /* first element */                     \
 450         struct type **tqh_last; /* addr of last next element */         \
 451         TRACEBUF                                                        \
 452 }
 453
 454 #define TAILQ_HEAD_INITIALIZER(head)                                    \
 455         { NULL, &(head).tqh_first }
 456
 457 #define TAILQ_ENTRY(type)                                               \
 458 struct {                                                                \
 459         struct type *tqe_next;  /* next element */                      \
 460         struct type **tqe_prev; /* address of previous next element */  \
 461         TRACEBUF                                                        \
 462 }
 463
 464 /*
 465  * Tail queue functions.
 466  */
 467 #if (defined(_KERNEL) && defined(INVARIANTS))
 468 #define QMD_TAILQ_CHECK_HEAD(head, field) do {                          \
 469         if (!TAILQ_EMPTY(head) &&                                       \
 470             TAILQ_FIRST((head))->field.tqe_prev !=                      \
 471              &TAILQ_FIRST((head)))                                      \
 472                 panic("Bad tailq head %p first->prev != head", (head)); \
 473 } while (0)
 474
 475 #define QMD_TAILQ_CHECK_TAIL(head, field) do {                          \
 476         if (*(head)->tqh_last != NULL)                                  \
 477                 panic("Bad tailq NEXT(%p->tqh_last) != NULL", (head));  \
 478 } while (0)
 479
 480 #define QMD_TAILQ_CHECK_NEXT(elm, field) do {                           \
 481         if (TAILQ_NEXT((elm), field) != NULL &&                         \
 482             TAILQ_NEXT((elm), field)->field.tqe_prev !=                 \
 483              &((elm)->field.tqe_next))                                  \
 484                 panic("Bad link elm %p next->prev != elm", (elm));      \
 485 } while (0)
 486
 487 #define QMD_TAILQ_CHECK_PREV(elm, field) do {                           \
 488         if (*(elm)->field.tqe_prev != (elm))                            \
 489                 panic("Bad link elm %p prev->next != elm", (elm));      \
 490 } while (0)
 491 #else
 492 #define QMD_TAILQ_CHECK_HEAD(head, field)
 493 #define QMD_TAILQ_CHECK_TAIL(head, headname)
 494 #define QMD_TAILQ_CHECK_NEXT(elm, field)
 495 #define QMD_TAILQ_CHECK_PREV(elm, field)
 496 #endif /* (_KERNEL && INVARIANTS) */
 497
 498 #define TAILQ_CONCAT(head1, head2, field) do {                          \
 499         if (!TAILQ_EMPTY(head2)) {                                      \
 500                 *(head1)->tqh_last = (head2)->tqh_first;                \
 501                 (head2)->tqh_first->field.tqe_prev = (head1)->tqh_last; \
 502                 (head1)->tqh_last = (head2)->tqh_last;                  \
 503                 TAILQ_INIT((head2));                                    \
 504                 QMD_TRACE_HEAD(head1);                                  \
 505                 QMD_TRACE_HEAD(head2);                                  \
 506         }                                                               \
 507 } while (0)
 508
 509 #define TAILQ_EMPTY(head)       ((head)->tqh_first == NULL)
 510
 511 #define TAILQ_FIRST(head)       ((head)->tqh_first)
 512
 513 #define TAILQ_FOREACH(var, head, field)                                 \
 514         for ((var) = TAILQ_FIRST((head));                               \
 515             (var);                                                      \
 516             (var) = TAILQ_NEXT((var), field))
 517
 518 #define TAILQ_FOREACH_SAFE(var, head, field, tvar)                      \
 519         for ((var) = TAILQ_FIRST((head));                               \
 520             (var) && ((tvar) = TAILQ_NEXT((var), field), 1);            \
 521             (var) = (tvar))
 522
 523 #define TAILQ_FOREACH_REVERSE(var, head, headname, field)               \
 524         for ((var) = TAILQ_LAST((head), headname);                      \
 525             (var);                                                      \
 526             (var) = TAILQ_PREV((var), headname, field))
 527
 528 #define TAILQ_FOREACH_REVERSE_SAFE(var, head, headname, field, tvar)    \
 529         for ((var) = TAILQ_LAST((head), headname);                      \
 530             (var) && ((tvar) = TAILQ_PREV((var), headname, field), 1);  \
 531             (var) = (tvar))
 532
 533 #define TAILQ_INIT(head) do {                                           \
 534         TAILQ_FIRST((head)) = NULL;                                     \
 535         (head)->tqh_last = &TAILQ_FIRST((head));                        \
 536         QMD_TRACE_HEAD(head);                                           \
 537 } while (0)
 538
 539 #define TAILQ_INSERT_AFTER(head, listelm, elm, field) do {              \
 540         QMD_TAILQ_CHECK_NEXT(listelm, field);                           \
 541         if ((TAILQ_NEXT((elm), field) = TAILQ_NEXT((listelm), field)) != NULL)\
 542                 TAILQ_NEXT((elm), field)->field.tqe_prev =              \
 543                     &TAILQ_NEXT((elm), field);                          \
 544         else {                                                          \
 545                 (head)->tqh_last = &TAILQ_NEXT((elm), field);           \
 546                 QMD_TRACE_HEAD(head);                                   \
 547         }                                                               \
 548         TAILQ_NEXT((listelm), field) = (elm);                           \
 549         (elm)->field.tqe_prev = &TAILQ_NEXT((listelm), field);          \
 550         QMD_TRACE_ELEM(&(elm)->field);                                  \
 551         QMD_TRACE_ELEM(&listelm->field);                                \
 552 } while (0)
 553
 554 #define TAILQ_INSERT_BEFORE(listelm, elm, field) do {                   \
 555         QMD_TAILQ_CHECK_PREV(listelm, field);                           \
 556         (elm)->field.tqe_prev = (listelm)->field.tqe_prev;              \
 557         TAILQ_NEXT((elm), field) = (listelm);                           \
 558         *(listelm)->field.tqe_prev = (elm);                             \
 559         (listelm)->field.tqe_prev = &TAILQ_NEXT((elm), field);          \
 560         QMD_TRACE_ELEM(&(elm)->field);                                  \
 561         QMD_TRACE_ELEM(&listelm->field);                                \
 562 } while (0)
 563
 564 #define TAILQ_INSERT_HEAD(head, elm, field) do {                        \
 565         QMD_TAILQ_CHECK_HEAD(head, field);                              \
 566         if ((TAILQ_NEXT((elm), field) = TAILQ_FIRST((head))) != NULL)   \
 567                 TAILQ_FIRST((head))->field.tqe_prev =                   \
 568                     &TAILQ_NEXT((elm), field);                          \
 569         else                                                            \
 570                 (head)->tqh_last = &TAILQ_NEXT((elm), field);           \
 571         TAILQ_FIRST((head)) = (elm);                                    \
 572         (elm)->field.tqe_prev = &TAILQ_FIRST((head));                   \
 573         QMD_TRACE_HEAD(head);                                           \
 574         QMD_TRACE_ELEM(&(elm)->field);                                  \
 575 } while (0)
 576
 577 #define TAILQ_INSERT_TAIL(head, elm, field) do {                        \
 578         QMD_TAILQ_CHECK_TAIL(head, field);                              \
 579         TAILQ_NEXT((elm), field) = NULL;                                \
 580         (elm)->field.tqe_prev = (head)->tqh_last;                       \
 581         *(head)->tqh_last = (elm);                                      \
 582         (head)->tqh_last = &TAILQ_NEXT((elm), field);                   \
 583         QMD_TRACE_HEAD(head);                                           \
 584         QMD_TRACE_ELEM(&(elm)->field);                                  \
 585 } while (0)
 586
 587 #define TAILQ_LAST(head, headname)                                      \
 588         (*(((struct headname *)((head)->tqh_last))->tqh_last))
 589
 590 #define TAILQ_NEXT(elm, field) ((elm)->field.tqe_next)
 591
 592 #define TAILQ_PREV(elm, headname, field)                                \
 593         (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
 594
 595 #define TAILQ_REMOVE(head, elm, field) do {                             \
 596         QMD_SAVELINK(oldnext, (elm)->field.tqe_next);                   \
 597         QMD_SAVELINK(oldprev, (elm)->field.tqe_prev);                   \
 598         QMD_TAILQ_CHECK_NEXT(elm, field);                               \
 599         QMD_TAILQ_CHECK_PREV(elm, field);                               \
 600         if ((TAILQ_NEXT((elm), field)) != NULL)                         \
 601                 TAILQ_NEXT((elm), field)->field.tqe_prev =              \
 602                     (elm)->field.tqe_prev;                              \
 603         else {                                                          \
 604                 (head)->tqh_last = (elm)->field.tqe_prev;               \
 605                 QMD_TRACE_HEAD(head);                                   \
 606         }                                                               \
 607         *(elm)->field.tqe_prev = TAILQ_NEXT((elm), field);              \
 608         TRASHIT(*oldnext);                                              \
 609         TRASHIT(*oldprev);                                              \
 610         QMD_TRACE_ELEM(&(elm)->field);                                  \
 611 } while (0)
 612
 613 #define TAILQ_SWAP(head1, head2, type, field) do {                      \
 614         struct type *swap_first = (head1)->tqh_first;                   \
 615         struct type **swap_last = (head1)->tqh_last;                    \
 616         (head1)->tqh_first = (head2)->tqh_first;                        \
 617         (head1)->tqh_last = (head2)->tqh_last;                          \
 618         (head2)->tqh_first = swap_first;                                \
 619         (head2)->tqh_last = swap_last;                                  \
 620         if ((swap_first = (head1)->tqh_first) != NULL)                  \
 621                 swap_first->field.tqe_prev = &(head1)->tqh_first;       \
 622         else                                                            \
 623                 (head1)->tqh_last = &(head1)->tqh_first;                \
 624         if ((swap_first = (head2)->tqh_first) != NULL)                  \
 625                 swap_first->field.tqe_prev = &(head2)->tqh_first;       \
 626         else                                                            \
 627                 (head2)->tqh_last = &(head2)->tqh_first;                \
 628 } while (0)
 629
 630 #endif /* !_SYS_QUEUE_H_ */