lib/openbsd-queue.h

   1 /*      $OpenBSD: queue.h,v 1.43 2015/12/28 19:38:40 millert Exp $      */
   2 /*      $NetBSD: queue.h,v 1.11 1996/05/16 05:17:14 mycroft Exp $       */
   3
   4 /*
   5  * Copyright (c) 1991, 1993
   6  *      The Regents of the University of California.  All rights reserved.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  * 3. Neither the name of the University nor the names of its contributors
  17  *    may be used to endorse or promote products derived from this software
  18  *    without specific prior written permission.
  19  *
  20  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  *
  32  *      @(#)queue.h     8.5 (Berkeley) 8/20/94
  33  */
  34
  35 #ifndef _SYS_QUEUE_H_
  36 #define _SYS_QUEUE_H_
  37
  38 #ifdef __cplusplus
  39 extern "C" {
  40 #endif
  41
  42 /*
  43  * This file defines five types of data structures: singly-linked lists,
  44  * lists, simple queues, tail queues and XOR simple queues.
  45  *
  46  *
  47  * A singly-linked list is headed by a single forward pointer. The elements
  48  * are singly linked for minimum space and pointer manipulation overhead at
  49  * the expense of O(n) removal for arbitrary elements. New elements can be
  50  * added to the list after an existing element or at the head of the list.
  51  * Elements being removed from the head of the list should use the explicit
  52  * macro for this purpose for optimum efficiency. A singly-linked list may
  53  * only be traversed in the forward direction.  Singly-linked lists are ideal
  54  * for applications with large datasets and few or no removals or for
  55  * implementing a LIFO queue.
  56  *
  57  * A list is headed by a single forward pointer (or an array of forward
  58  * pointers for a hash table header). The elements are doubly linked
  59  * so that an arbitrary element can be removed without a need to
  60  * traverse the list. New elements can be added to the list before
  61  * or after an existing element or at the head of the list. A list
  62  * may only be traversed in the forward direction.
  63  *
  64  * A simple queue is headed by a pair of pointers, one to the head of the
  65  * list and the other to the tail of the list. The elements are singly
  66  * linked to save space, so elements can only be removed from the
  67  * head of the list. New elements can be added to the list before or after
  68  * an existing element, at the head of the list, or at the end of the
  69  * list. A simple queue may only be traversed in the forward direction.
  70  *
  71  * A tail queue is headed by a pair of pointers, one to the head of the
  72  * list and the other to the tail of the list. The elements are doubly
  73  * linked so that an arbitrary element can be removed without a need to
  74  * traverse the list. New elements can be added to the list before or
  75  * after an existing element, at the head of the list, or at the end of
  76  * the list. A tail queue may be traversed in either direction.
  77  *
  78  * An XOR simple queue is used in the same way as a regular simple queue.
  79  * The difference is that the head structure also includes a "cookie" that
  80  * is XOR'd with the queue pointer (first, last or next) to generate the
  81  * real pointer value.
  82  *
  83  * For details on the use of these macros, see the queue(3) manual page.
  84  */
  85
  86 #if defined(QUEUE_MACRO_DEBUG) || (defined(_KERNEL) && defined(DIAGNOSTIC))
  87 #define _Q_INVALIDATE(a) (a) = ((void *)-1)
  88 #else
  89 #define _Q_INVALIDATE(a)
  90 #endif
  91
  92 /*
  93  * Singly-linked List definitions.
  94  */
  95 #define SLIST_HEAD(name, type)                                                 \
  96         struct name {                                                          \
  97                 struct type *slh_first; /* first element */                    \
  98         }
  99
 100 #define SLIST_HEAD_INITIALIZER(head)                                           \
 101         {                                                                      \
 102                 NULL                                                           \
 103         }
 104
 105 #define SLIST_ENTRY(type)                                                      \
 106         struct {                                                               \
 107                 struct type *sle_next; /* next element */                      \
 108         }
 109
 110 /*
 111  * Singly-linked List access methods.
 112  */
 113 #define SLIST_FIRST(head)       ((head)->slh_first)
 114 #define SLIST_END(head)         NULL
 115 #define SLIST_EMPTY(head)       (SLIST_FIRST(head) == SLIST_END(head))
 116 #define SLIST_NEXT(elm, field)  ((elm)->field.sle_next)
 117
 118 #define SLIST_FOREACH(var, head, field)                                        \
 119         for ((var) = SLIST_FIRST(head); (var) != SLIST_END(head);              \
 120              (var) = SLIST_NEXT(var, field))
 121
 122 #define SLIST_FOREACH_SAFE(var, head, field, tvar)                             \
 123         for ((var) = SLIST_FIRST(head);                                        \
 124              (var) && ((tvar) = SLIST_NEXT(var, field), 1); (var) = (tvar))
 125
 126 /*
 127  * Singly-linked List functions.
 128  */
 129 #define SLIST_INIT(head)                                                       \
 130         {                                                                      \
 131                 SLIST_FIRST(head) = SLIST_END(head);                           \
 132         }
 133
 134 #define SLIST_INSERT_AFTER(slistelm, elm, field)                               \
 135         do {                                                                   \
 136                 (elm)->field.sle_next = (slistelm)->field.sle_next;            \
 137                 (slistelm)->field.sle_next = (elm);                            \
 138         } while (0)
 139
 140 #define SLIST_INSERT_HEAD(head, elm, field)                                    \
 141         do {                                                                   \
 142                 (elm)->field.sle_next = (head)->slh_first;                     \
 143                 (head)->slh_first = (elm);                                     \
 144         } while (0)
 145
 146 #define SLIST_REMOVE_AFTER(elm, field)                                         \
 147         do {                                                                   \
 148                 (elm)->field.sle_next = (elm)->field.sle_next->field.sle_next; \
 149         } while (0)
 150
 151 #define SLIST_REMOVE_HEAD(head, field)                                         \
 152         do {                                                                   \
 153                 (head)->slh_first = (head)->slh_first->field.sle_next;         \
 154         } while (0)
 155
 156 #define SLIST_REMOVE(head, elm, type, field)                                   \
 157         do {                                                                   \
 158                 if ((head)->slh_first == (elm)) {                              \
 159                         SLIST_REMOVE_HEAD((head), field);                      \
 160                 } else {                                                       \
 161                         struct type *curelm = (head)->slh_first;               \
 162                                                                                \
 163                         while (curelm->field.sle_next != (elm))                \
 164                                 curelm = curelm->field.sle_next;               \
 165                         curelm->field.sle_next =                               \
 166                                 curelm->field.sle_next->field.sle_next;        \
 167                 }                                                              \
 168                 _Q_INVALIDATE((elm)->field.sle_next);                          \
 169         } while (0)
 170
 171 /*
 172  * List definitions.
 173  */
 174 #define LIST_HEAD(name, type)                                                  \
 175         struct name {                                                          \
 176                 struct type *lh_first; /* first element */                     \
 177         }
 178
 179 #define LIST_HEAD_INITIALIZER(head)                                            \
 180         {                                                                      \
 181                 NULL                                                           \
 182         }
 183
 184 #define LIST_ENTRY(type)                                                       \
 185         struct {                                                               \
 186                 struct type *le_next;  /* next element */                      \
 187                 struct type **le_prev; /* address of previous next element */  \
 188         }
 189
 190 /*
 191  * List access methods.
 192  */
 193 #define LIST_FIRST(head)                ((head)->lh_first)
 194 #define LIST_END(head)                  NULL
 195 #define LIST_EMPTY(head)                (LIST_FIRST(head) == LIST_END(head))
 196 #define LIST_NEXT(elm, field)           ((elm)->field.le_next)
 197
 198 #define LIST_FOREACH(var, head, field)                                         \
 199         for ((var) = LIST_FIRST(head); (var) != LIST_END(head);                \
 200              (var) = LIST_NEXT(var, field))
 201
 202 #define LIST_FOREACH_SAFE(var, head, field, tvar)                              \
 203         for ((var) = LIST_FIRST(head);                                         \
 204              (var) && ((tvar) = LIST_NEXT(var, field), 1); (var) = (tvar))
 205
 206 /*
 207  * List functions.
 208  */
 209 #define LIST_INIT(head)                                                        \
 210         do {                                                                   \
 211                 LIST_FIRST(head) = LIST_END(head);                             \
 212         } while (0)
 213
 214 #define LIST_INSERT_AFTER(listelm, elm, field)                                 \
 215         do {                                                                   \
 216                 if (((elm)->field.le_next = (listelm)->field.le_next) != NULL) \
 217                         (listelm)->field.le_next->field.le_prev =              \
 218                                 &(elm)->field.le_next;                         \
 219                 (listelm)->field.le_next = (elm);                              \
 220                 (elm)->field.le_prev = &(listelm)->field.le_next;              \
 221         } while (0)
 222
 223 #define LIST_INSERT_BEFORE(listelm, elm, field)                                \
 224         do {                                                                   \
 225                 (elm)->field.le_prev = (listelm)->field.le_prev;               \
 226                 (elm)->field.le_next = (listelm);                              \
 227                 *(listelm)->field.le_prev = (elm);                             \
 228                 (listelm)->field.le_prev = &(elm)->field.le_next;              \
 229         } while (0)
 230
 231 #define LIST_INSERT_HEAD(head, elm, field)                                     \
 232         do {                                                                   \
 233                 if (((elm)->field.le_next = (head)->lh_first) != NULL)         \
 234                         (head)->lh_first->field.le_prev =                      \
 235                                 &(elm)->field.le_next;                         \
 236                 (head)->lh_first = (elm);                                      \
 237                 (elm)->field.le_prev = &(head)->lh_first;                      \
 238         } while (0)
 239
 240 #define LIST_REMOVE(elm, field)                                                \
 241         do {                                                                   \
 242                 if ((elm)->field.le_next != NULL)                              \
 243                         (elm)->field.le_next->field.le_prev =                  \
 244                                 (elm)->field.le_prev;                          \
 245                 *(elm)->field.le_prev = (elm)->field.le_next;                  \
 246                 _Q_INVALIDATE((elm)->field.le_prev);                           \
 247                 _Q_INVALIDATE((elm)->field.le_next);                           \
 248         } while (0)
 249
 250 #define LIST_REPLACE(elm, elm2, field)                                         \
 251         do {                                                                   \
 252                 if (((elm2)->field.le_next = (elm)->field.le_next) != NULL)    \
 253                         (elm2)->field.le_next->field.le_prev =                 \
 254                                 &(elm2)->field.le_next;                        \
 255                 (elm2)->field.le_prev = (elm)->field.le_prev;                  \
 256                 *(elm2)->field.le_prev = (elm2);                               \
 257                 _Q_INVALIDATE((elm)->field.le_prev);                           \
 258                 _Q_INVALIDATE((elm)->field.le_next);                           \
 259         } while (0)
 260
 261 /*
 262  * Simple queue definitions.
 263  */
 264 #define SIMPLEQ_HEAD(name, type)                                               \
 265         struct name {                                                          \
 266                 struct type *sqh_first; /* first element */                    \
 267                 struct type **sqh_last; /* addr of last next element */        \
 268         }
 269
 270 #define SIMPLEQ_HEAD_INITIALIZER(head)                                         \
 271         {                                                                      \
 272                 NULL, &(head).sqh_first                                        \
 273         }
 274
 275 #define SIMPLEQ_ENTRY(type)                                                    \
 276         struct {                                                               \
 277                 struct type *sqe_next; /* next element */                      \
 278         }
 279
 280 /*
 281  * Simple queue access methods.
 282  */
 283 #define SIMPLEQ_FIRST(head)         ((head)->sqh_first)
 284 #define SIMPLEQ_END(head)           NULL
 285 #define SIMPLEQ_EMPTY(head)         (SIMPLEQ_FIRST(head) == SIMPLEQ_END(head))
 286 #define SIMPLEQ_NEXT(elm, field)    ((elm)->field.sqe_next)
 287
 288 #define SIMPLEQ_FOREACH(var, head, field)                                      \
 289         for ((var) = SIMPLEQ_FIRST(head); (var) != SIMPLEQ_END(head);          \
 290              (var) = SIMPLEQ_NEXT(var, field))
 291
 292 #define SIMPLEQ_FOREACH_SAFE(var, head, field, tvar)                           \
 293         for ((var) = SIMPLEQ_FIRST(head);                                      \
 294              (var) && ((tvar) = SIMPLEQ_NEXT(var, field), 1); (var) = (tvar))
 295
 296 /*
 297  * Simple queue functions.
 298  */
 299 #define SIMPLEQ_INIT(head)                                                     \
 300         do {                                                                   \
 301                 (head)->sqh_first = NULL;                                      \
 302                 (head)->sqh_last = &(head)->sqh_first;                         \
 303         } while (0)
 304
 305 #define SIMPLEQ_INSERT_HEAD(head, elm, field)                                  \
 306         do {                                                                   \
 307                 if (((elm)->field.sqe_next = (head)->sqh_first) == NULL)       \
 308                         (head)->sqh_last = &(elm)->field.sqe_next;             \
 309                 (head)->sqh_first = (elm);                                     \
 310         } while (0)
 311
 312 #define SIMPLEQ_INSERT_TAIL(head, elm, field)                                  \
 313         do {                                                                   \
 314                 (elm)->field.sqe_next = NULL;                                  \
 315                 *(head)->sqh_last = (elm);                                     \
 316                 (head)->sqh_last = &(elm)->field.sqe_next;                     \
 317         } while (0)
 318
 319 #define SIMPLEQ_INSERT_AFTER(head, listelm, elm, field)                        \
 320         do {                                                                   \
 321                 if (((elm)->field.sqe_next = (listelm)->field.sqe_next)        \
 322                     == NULL)                                                   \
 323                         (head)->sqh_last = &(elm)->field.sqe_next;             \
 324                 (listelm)->field.sqe_next = (elm);                             \
 325         } while (0)
 326
 327 #define SIMPLEQ_REMOVE_HEAD(head, field)                                       \
 328         do {                                                                   \
 329                 if (((head)->sqh_first = (head)->sqh_first->field.sqe_next)    \
 330                     == NULL)                                                   \
 331                         (head)->sqh_last = &(head)->sqh_first;                 \
 332         } while (0)
 333
 334 #define SIMPLEQ_REMOVE_AFTER(head, elm, field)                                 \
 335         do {                                                                   \
 336                 if (((elm)->field.sqe_next =                                   \
 337                              (elm)->field.sqe_next->field.sqe_next)            \
 338                     == NULL)                                                   \
 339                         (head)->sqh_last = &(elm)->field.sqe_next;             \
 340         } while (0)
 341
 342 #define SIMPLEQ_CONCAT(head1, head2)                                           \
 343         do {                                                                   \
 344                 if (!SIMPLEQ_EMPTY((head2))) {                                 \
 345                         *(head1)->sqh_last = (head2)->sqh_first;               \
 346                         (head1)->sqh_last = (head2)->sqh_last;                 \
 347                         SIMPLEQ_INIT((head2));                                 \
 348                 }                                                              \
 349         } while (0)
 350
 351 /*
 352  * XOR Simple queue definitions.
 353  */
 354 #define XSIMPLEQ_HEAD(name, type)                                              \
 355         struct name {                                                          \
 356                 struct type *sqx_first; /* first element */                    \
 357                 struct type **sqx_last; /* addr of last next element */        \
 358                 unsigned long sqx_cookie;                                      \
 359         }
 360
 361 #define XSIMPLEQ_ENTRY(type)                                                   \
 362         struct {                                                               \
 363                 struct type *sqx_next; /* next element */                      \
 364         }
 365
 366 /*
 367  * XOR Simple queue access methods.
 368  */
 369 #define XSIMPLEQ_XOR(head, ptr)                                                \
 370         ((__typeof(ptr))((head)->sqx_cookie ^ (unsigned long)(ptr)))
 371 #define XSIMPLEQ_FIRST(head)        XSIMPLEQ_XOR(head, ((head)->sqx_first))
 372 #define XSIMPLEQ_END(head)          NULL
 373 #define XSIMPLEQ_EMPTY(head)        (XSIMPLEQ_FIRST(head) == XSIMPLEQ_END(head))
 374 #define XSIMPLEQ_NEXT(head, elm, field)    XSIMPLEQ_XOR(head, ((elm)->field.sqx_next))
 375
 376 #define XSIMPLEQ_FOREACH(var, head, field)                                     \
 377         for ((var) = XSIMPLEQ_FIRST(head); (var) != XSIMPLEQ_END(head);        \
 378              (var) = XSIMPLEQ_NEXT(head, var, field))
 379
 380 #define XSIMPLEQ_FOREACH_SAFE(var, head, field, tvar)                          \
 381         for ((var) = XSIMPLEQ_FIRST(head);                                     \
 382              (var) && ((tvar) = XSIMPLEQ_NEXT(head, var, field), 1);           \
 383              (var) = (tvar))
 384
 385 /*
 386  * XOR Simple queue functions.
 387  */
 388 #define XSIMPLEQ_INIT(head)                                                    \
 389         do {                                                                   \
 390                 arc4random_buf(&(head)->sqx_cookie,                            \
 391                                sizeof((head)->sqx_cookie));                    \
 392                 (head)->sqx_first = XSIMPLEQ_XOR(head, NULL);                  \
 393                 (head)->sqx_last = XSIMPLEQ_XOR(head, &(head)->sqx_first);     \
 394         } while (0)
 395
 396 #define XSIMPLEQ_INSERT_HEAD(head, elm, field)                                 \
 397         do {                                                                   \
 398                 if (((elm)->field.sqx_next = (head)->sqx_first)                \
 399                     == XSIMPLEQ_XOR(head, NULL))                               \
 400                         (head)->sqx_last =                                     \
 401                                 XSIMPLEQ_XOR(head, &(elm)->field.sqx_next);    \
 402                 (head)->sqx_first = XSIMPLEQ_XOR(head, (elm));                 \
 403         } while (0)
 404
 405 #define XSIMPLEQ_INSERT_TAIL(head, elm, field)                                 \
 406         do {                                                                   \
 407                 (elm)->field.sqx_next = XSIMPLEQ_XOR(head, NULL);              \
 408                 *(XSIMPLEQ_XOR(head, (head)->sqx_last)) =                      \
 409                         XSIMPLEQ_XOR(head, (elm));                             \
 410                 (head)->sqx_last = XSIMPLEQ_XOR(head, &(elm)->field.sqx_next); \
 411         } while (0)
 412
 413 #define XSIMPLEQ_INSERT_AFTER(head, listelm, elm, field)                       \
 414         do {                                                                   \
 415                 if (((elm)->field.sqx_next = (listelm)->field.sqx_next)        \
 416                     == XSIMPLEQ_XOR(head, NULL))                               \
 417                         (head)->sqx_last =                                     \
 418                                 XSIMPLEQ_XOR(head, &(elm)->field.sqx_next);    \
 419                 (listelm)->field.sqx_next = XSIMPLEQ_XOR(head, (elm));         \
 420         } while (0)
 421
 422 #define XSIMPLEQ_REMOVE_HEAD(head, field)                                      \
 423         do {                                                                   \
 424                 if (((head)->sqx_first = XSIMPLEQ_XOR(head, (head)->sqx_first) \
 425                                                  ->field.sqx_next)             \
 426                     == XSIMPLEQ_XOR(head, NULL))                               \
 427                         (head)->sqx_last =                                     \
 428                                 XSIMPLEQ_XOR(head, &(head)->sqx_first);        \
 429         } while (0)
 430
 431 #define XSIMPLEQ_REMOVE_AFTER(head, elm, field)                                \
 432         do {                                                                   \
 433                 if (((elm)->field.sqx_next =                                   \
 434                              XSIMPLEQ_XOR(head, (elm)->field.sqx_next)         \
 435                                      ->field.sqx_next)                         \
 436                     == XSIMPLEQ_XOR(head, NULL))                               \
 437                         (head)->sqx_last =                                     \
 438                                 XSIMPLEQ_XOR(head, &(elm)->field.sqx_next);    \
 439         } while (0)
 440
 441
 442 /*
 443  * Tail queue definitions.
 444  */
 445 #define TAILQ_HEAD(name, type)                                                 \
 446         struct name {                                                          \
 447                 struct type *tqh_first; /* first element */                    \
 448                 struct type **tqh_last; /* addr of last next element */        \
 449         }
 450
 451 #define TAILQ_HEAD_INITIALIZER(head)                                           \
 452         {                                                                      \
 453                 NULL, &(head).tqh_first                                        \
 454         }
 455
 456 #define TAILQ_ENTRY(type)                                                      \
 457         struct {                                                               \
 458                 struct type *tqe_next;  /* next element */                     \
 459                 struct type **tqe_prev; /* address of previous next element */ \
 460         }
 461
 462 /*
 463  * Tail queue access methods.
 464  */
 465 #define TAILQ_FIRST(head)               ((head)->tqh_first)
 466 #define TAILQ_END(head)                 NULL
 467 #define TAILQ_NEXT(elm, field)          ((elm)->field.tqe_next)
 468 #define TAILQ_LAST(head, headname)                                             \
 469         (*(((struct headname *)((head)->tqh_last))->tqh_last))
 470 /* XXX */
 471 #define TAILQ_PREV(elm, headname, field)                                       \
 472         (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
 473 #define TAILQ_EMPTY(head) (TAILQ_FIRST(head) == TAILQ_END(head))
 474
 475 #define TAILQ_FOREACH(var, head, field)                                        \
 476         for ((var) = TAILQ_FIRST(head); (var) != TAILQ_END(head);              \
 477              (var) = TAILQ_NEXT(var, field))
 478
 479 #define TAILQ_FOREACH_SAFE(var, head, field, tvar)                             \
 480         for ((var) = TAILQ_FIRST(head);                                        \
 481              (var) != TAILQ_END(head) && ((tvar) = TAILQ_NEXT(var, field), 1); \
 482              (var) = (tvar))
 483
 484
 485 #define TAILQ_FOREACH_REVERSE(var, head, headname, field)                      \
 486         for ((var) = TAILQ_LAST(head, headname); (var) != TAILQ_END(head);     \
 487              (var) = TAILQ_PREV(var, headname, field))
 488
 489 #define TAILQ_FOREACH_REVERSE_SAFE(var, head, headname, field, tvar)           \
 490         for ((var) = TAILQ_LAST(head, headname);                               \
 491              (var) != TAILQ_END(head)                                          \
 492              && ((tvar) = TAILQ_PREV(var, headname, field), 1);                \
 493              (var) = (tvar))
 494
 495 /*
 496  * Tail queue functions.
 497  */
 498 #define TAILQ_INIT(head)                                                       \
 499         do {                                                                   \
 500                 (head)->tqh_first = NULL;                                      \
 501                 (head)->tqh_last = &(head)->tqh_first;                         \
 502         } while (0)
 503
 504 #define TAILQ_INSERT_HEAD(head, elm, field)                                    \
 505         do {                                                                   \
 506                 if (((elm)->field.tqe_next = (head)->tqh_first) != NULL)       \
 507                         (head)->tqh_first->field.tqe_prev =                    \
 508                                 &(elm)->field.tqe_next;                        \
 509                 else                                                           \
 510                         (head)->tqh_last = &(elm)->field.tqe_next;             \
 511                 (head)->tqh_first = (elm);                                     \
 512                 (elm)->field.tqe_prev = &(head)->tqh_first;                    \
 513         } while (0)
 514
 515 #define TAILQ_INSERT_TAIL(head, elm, field)                                    \
 516         do {                                                                   \
 517                 (elm)->field.tqe_next = NULL;                                  \
 518                 (elm)->field.tqe_prev = (head)->tqh_last;                      \
 519                 *(head)->tqh_last = (elm);                                     \
 520                 (head)->tqh_last = &(elm)->field.tqe_next;                     \
 521         } while (0)
 522
 523 #define TAILQ_INSERT_AFTER(head, listelm, elm, field)                          \
 524         do {                                                                   \
 525                 if (((elm)->field.tqe_next = (listelm)->field.tqe_next)        \
 526                     != NULL)                                                   \
 527                         (elm)->field.tqe_next->field.tqe_prev =                \
 528                                 &(elm)->field.tqe_next;                        \
 529                 else                                                           \
 530                         (head)->tqh_last = &(elm)->field.tqe_next;             \
 531                 (listelm)->field.tqe_next = (elm);                             \
 532                 (elm)->field.tqe_prev = &(listelm)->field.tqe_next;            \
 533         } while (0)
 534
 535 #define TAILQ_INSERT_BEFORE(listelm, elm, field)                               \
 536         do {                                                                   \
 537                 (elm)->field.tqe_prev = (listelm)->field.tqe_prev;             \
 538                 (elm)->field.tqe_next = (listelm);                             \
 539                 *(listelm)->field.tqe_prev = (elm);                            \
 540                 (listelm)->field.tqe_prev = &(elm)->field.tqe_next;            \
 541         } while (0)
 542
 543 #define TAILQ_REMOVE(head, elm, field)                                         \
 544         do {                                                                   \
 545                 if (((elm)->field.tqe_next) != NULL)                           \
 546                         (elm)->field.tqe_next->field.tqe_prev =                \
 547                                 (elm)->field.tqe_prev;                         \
 548                 else                                                           \
 549                         (head)->tqh_last = (elm)->field.tqe_prev;              \
 550                 *(elm)->field.tqe_prev = (elm)->field.tqe_next;                \
 551                 _Q_INVALIDATE((elm)->field.tqe_prev);                          \
 552                 _Q_INVALIDATE((elm)->field.tqe_next);                          \
 553         } while (0)
 554
 555 #define TAILQ_REPLACE(head, elm, elm2, field)                                  \
 556         do {                                                                   \
 557                 if (((elm2)->field.tqe_next = (elm)->field.tqe_next) != NULL)  \
 558                         (elm2)->field.tqe_next->field.tqe_prev =               \
 559                                 &(elm2)->field.tqe_next;                       \
 560                 else                                                           \
 561                         (head)->tqh_last = &(elm2)->field.tqe_next;            \
 562                 (elm2)->field.tqe_prev = (elm)->field.tqe_prev;                \
 563                 *(elm2)->field.tqe_prev = (elm2);                              \
 564                 _Q_INVALIDATE((elm)->field.tqe_prev);                          \
 565                 _Q_INVALIDATE((elm)->field.tqe_next);                          \
 566         } while (0)
 567
 568 #define TAILQ_CONCAT(head1, head2, field)                                      \
 569         do {                                                                   \
 570                 if (!TAILQ_EMPTY(head2)) {                                     \
 571                         *(head1)->tqh_last = (head2)->tqh_first;               \
 572                         (head2)->tqh_first->field.tqe_prev =                   \
 573                                 (head1)->tqh_last;                             \
 574                         (head1)->tqh_last = (head2)->tqh_last;                 \
 575                         TAILQ_INIT((head2));                                   \
 576                 }                                                              \
 577         } while (0)
 578
 579 #ifdef __cplusplus
 580 }
 581 #endif
 582
 583 #endif /* !_SYS_QUEUE_H_ */