compat/queue.h

   1 /*      $OpenBSD: queue.h,v 1.44 2016/09/09 20:31:46 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 /*
  39  * This file defines five types of data structures: singly-linked lists,
  40  * lists, simple queues, tail queues and XOR simple queues.
  41  *
  42  *
  43  * A singly-linked list is headed by a single forward pointer. The elements
  44  * are singly linked for minimum space and pointer manipulation overhead at
  45  * the expense of O(n) removal for arbitrary elements. New elements can be
  46  * added to the list after an existing element or at the head of the list.
  47  * Elements being removed from the head of the list should use the explicit
  48  * macro for this purpose for optimum efficiency. A singly-linked list may
  49  * only be traversed in the forward direction.  Singly-linked lists are ideal
  50  * for applications with large datasets and few or no removals or for
  51  * implementing a LIFO queue.
  52  *
  53  * A list is headed by a single forward pointer (or an array of forward
  54  * pointers for a hash table header). The elements are doubly linked
  55  * so that an arbitrary element can be removed without a need to
  56  * traverse the list. New elements can be added to the list before
  57  * or after an existing element or at the head of the list. A list
  58  * may only be traversed in the forward direction.
  59  *
  60  * A simple queue is headed by a pair of pointers, one to the head of the
  61  * list and the other to the tail of the list. The elements are singly
  62  * linked to save space, so elements can only be removed from the
  63  * head of the list. New elements can be added to the list before or after
  64  * an existing element, at the head of the list, or at the end of the
  65  * list. A simple queue may only be traversed in the forward direction.
  66  *
  67  * A tail queue is headed by a pair of pointers, one to the head of the
  68  * list and the other to the tail of the list. The elements are doubly
  69  * linked so that an arbitrary element can be removed without a need to
  70  * traverse the list. New elements can be added to the list before or
  71  * after an existing element, at the head of the list, or at the end of
  72  * the list. A tail queue may be traversed in either direction.
  73  *
  74  * An XOR simple queue is used in the same way as a regular simple queue.
  75  * The difference is that the head structure also includes a "cookie" that
  76  * is XOR'd with the queue pointer (first, last or next) to generate the
  77  * real pointer value.
  78  *
  79  * For details on the use of these macros, see the queue(3) manual page.
  80  */
  81
  82 #if defined(QUEUE_MACRO_DEBUG) || (defined(_KERNEL) && defined(DIAGNOSTIC))
  83 #define _Q_INVALIDATE(a) (a) = ((void *)-1)
  84 #else
  85 #define _Q_INVALIDATE(a)
  86 #endif
  87
  88 /*
  89  * Singly-linked List definitions.
  90  */
  91 #define SLIST_HEAD(name, type)                                          \
  92 struct name {                                                           \
  93         struct type *slh_first; /* first element */                     \
  94 }
  95
  96 #define SLIST_HEAD_INITIALIZER(head)                                    \
  97         { NULL }
  98
  99 #define SLIST_ENTRY(type)                                               \
 100 struct {                                                                \
 101         struct type *sle_next;  /* next element */                      \
 102 }
 103
 104 /*
 105  * Singly-linked List access methods.
 106  */
 107 #define SLIST_FIRST(head)       ((head)->slh_first)
 108 #define SLIST_END(head)         NULL
 109 #define SLIST_EMPTY(head)       (SLIST_FIRST(head) == SLIST_END(head))
 110 #define SLIST_NEXT(elm, field)  ((elm)->field.sle_next)
 111
 112 #define SLIST_FOREACH(var, head, field)                                 \
 113         for((var) = SLIST_FIRST(head);                                  \
 114             (var) != SLIST_END(head);                                   \
 115             (var) = SLIST_NEXT(var, field))
 116
 117 #define SLIST_FOREACH_SAFE(var, head, field, tvar)                      \
 118         for ((var) = SLIST_FIRST(head);                         \
 119             (var) && ((tvar) = SLIST_NEXT(var, field), 1);              \
 120             (var) = (tvar))
 121
 122 /*
 123  * Singly-linked List functions.
 124  */
 125 #define SLIST_INIT(head) {                                              \
 126         SLIST_FIRST(head) = SLIST_END(head);                            \
 127 }
 128
 129 #define SLIST_INSERT_AFTER(slistelm, elm, field) do {                   \
 130         (elm)->field.sle_next = (slistelm)->field.sle_next;             \
 131         (slistelm)->field.sle_next = (elm);                             \
 132 } while (0)
 133
 134 #define SLIST_INSERT_HEAD(head, elm, field) do {                        \
 135         (elm)->field.sle_next = (head)->slh_first;                      \
 136         (head)->slh_first = (elm);                                      \
 137 } while (0)
 138
 139 #define SLIST_REMOVE_AFTER(elm, field) do {                             \
 140         (elm)->field.sle_next = (elm)->field.sle_next->field.sle_next;  \
 141 } while (0)
 142
 143 #define SLIST_REMOVE_HEAD(head, field) do {                             \
 144         (head)->slh_first = (head)->slh_first->field.sle_next;          \
 145 } while (0)
 146
 147 #define SLIST_REMOVE(head, elm, type, field) do {                       \
 148         if ((head)->slh_first == (elm)) {                               \
 149                 SLIST_REMOVE_HEAD((head), field);                       \
 150         } else {                                                        \
 151                 struct type *curelm = (head)->slh_first;                \
 152                                                                         \
 153                 while (curelm->field.sle_next != (elm))                 \
 154                         curelm = curelm->field.sle_next;                \
 155                 curelm->field.sle_next =                                \
 156                     curelm->field.sle_next->field.sle_next;             \
 157         }                                                               \
 158         _Q_INVALIDATE((elm)->field.sle_next);                           \
 159 } while (0)
 160
 161 /*
 162  * List definitions.
 163  */
 164 #define LIST_HEAD(name, type)                                           \
 165 struct name {                                                           \
 166         struct type *lh_first;  /* first element */                     \
 167 }
 168
 169 #define LIST_HEAD_INITIALIZER(head)                                     \
 170         { NULL }
 171
 172 #define LIST_ENTRY(type)                                                \
 173 struct {                                                                \
 174         struct type *le_next;   /* next element */                      \
 175         struct type **le_prev;  /* address of previous next element */  \
 176 }
 177
 178 /*
 179  * List access methods.
 180  */
 181 #define LIST_FIRST(head)                ((head)->lh_first)
 182 #define LIST_END(head)                  NULL
 183 #define LIST_EMPTY(head)                (LIST_FIRST(head) == LIST_END(head))
 184 #define LIST_NEXT(elm, field)           ((elm)->field.le_next)
 185
 186 #define LIST_FOREACH(var, head, field)                                  \
 187         for((var) = LIST_FIRST(head);                                   \
 188             (var)!= LIST_END(head);                                     \
 189             (var) = LIST_NEXT(var, field))
 190
 191 #define LIST_FOREACH_SAFE(var, head, field, tvar)                       \
 192         for ((var) = LIST_FIRST(head);                          \
 193             (var) && ((tvar) = LIST_NEXT(var, field), 1);               \
 194             (var) = (tvar))
 195
 196 /*
 197  * List functions.
 198  */
 199 #define LIST_INIT(head) do {                                            \
 200         LIST_FIRST(head) = LIST_END(head);                              \
 201 } while (0)
 202
 203 #define LIST_INSERT_AFTER(listelm, elm, field) do {                     \
 204         if (((elm)->field.le_next = (listelm)->field.le_next) != NULL)  \
 205                 (listelm)->field.le_next->field.le_prev =               \
 206                     &(elm)->field.le_next;                              \
 207         (listelm)->field.le_next = (elm);                               \
 208         (elm)->field.le_prev = &(listelm)->field.le_next;               \
 209 } while (0)
 210
 211 #define LIST_INSERT_BEFORE(listelm, elm, field) do {                    \
 212         (elm)->field.le_prev = (listelm)->field.le_prev;                \
 213         (elm)->field.le_next = (listelm);                               \
 214         *(listelm)->field.le_prev = (elm);                              \
 215         (listelm)->field.le_prev = &(elm)->field.le_next;               \
 216 } while (0)
 217
 218 #define LIST_INSERT_HEAD(head, elm, field) do {                         \
 219         if (((elm)->field.le_next = (head)->lh_first) != NULL)          \
 220                 (head)->lh_first->field.le_prev = &(elm)->field.le_next;\
 221         (head)->lh_first = (elm);                                       \
 222         (elm)->field.le_prev = &(head)->lh_first;                       \
 223 } while (0)
 224
 225 #define LIST_REMOVE(elm, field) do {                                    \
 226         if ((elm)->field.le_next != NULL)                               \
 227                 (elm)->field.le_next->field.le_prev =                   \
 228                     (elm)->field.le_prev;                               \
 229         *(elm)->field.le_prev = (elm)->field.le_next;                   \
 230         _Q_INVALIDATE((elm)->field.le_prev);                            \
 231         _Q_INVALIDATE((elm)->field.le_next);                            \
 232 } while (0)
 233
 234 #define LIST_REPLACE(elm, elm2, field) do {                             \
 235         if (((elm2)->field.le_next = (elm)->field.le_next) != NULL)     \
 236                 (elm2)->field.le_next->field.le_prev =                  \
 237                     &(elm2)->field.le_next;                             \
 238         (elm2)->field.le_prev = (elm)->field.le_prev;                   \
 239         *(elm2)->field.le_prev = (elm2);                                \
 240         _Q_INVALIDATE((elm)->field.le_prev);                            \
 241         _Q_INVALIDATE((elm)->field.le_next);                            \
 242 } while (0)
 243
 244 /*
 245  * Simple queue definitions.
 246  */
 247 #define SIMPLEQ_HEAD(name, type)                                        \
 248 struct name {                                                           \
 249         struct type *sqh_first; /* first element */                     \
 250         struct type **sqh_last; /* addr of last next element */         \
 251 }
 252
 253 #define SIMPLEQ_HEAD_INITIALIZER(head)                                  \
 254         { NULL, &(head).sqh_first }
 255
 256 #define SIMPLEQ_ENTRY(type)                                             \
 257 struct {                                                                \
 258         struct type *sqe_next;  /* next element */                      \
 259 }
 260
 261 /*
 262  * Simple queue access methods.
 263  */
 264 #define SIMPLEQ_FIRST(head)         ((head)->sqh_first)
 265 #define SIMPLEQ_END(head)           NULL
 266 #define SIMPLEQ_EMPTY(head)         (SIMPLEQ_FIRST(head) == SIMPLEQ_END(head))
 267 #define SIMPLEQ_NEXT(elm, field)    ((elm)->field.sqe_next)
 268
 269 #define SIMPLEQ_FOREACH(var, head, field)                               \
 270         for((var) = SIMPLEQ_FIRST(head);                                \
 271             (var) != SIMPLEQ_END(head);                                 \
 272             (var) = SIMPLEQ_NEXT(var, field))
 273
 274 #define SIMPLEQ_FOREACH_SAFE(var, head, field, tvar)                    \
 275         for ((var) = SIMPLEQ_FIRST(head);                               \
 276             (var) && ((tvar) = SIMPLEQ_NEXT(var, field), 1);            \
 277             (var) = (tvar))
 278
 279 /*
 280  * Simple queue functions.
 281  */
 282 #define SIMPLEQ_INIT(head) do {                                         \
 283         (head)->sqh_first = NULL;                                       \
 284         (head)->sqh_last = &(head)->sqh_first;                          \
 285 } while (0)
 286
 287 #define SIMPLEQ_INSERT_HEAD(head, elm, field) do {                      \
 288         if (((elm)->field.sqe_next = (head)->sqh_first) == NULL)        \
 289                 (head)->sqh_last = &(elm)->field.sqe_next;              \
 290         (head)->sqh_first = (elm);                                      \
 291 } while (0)
 292
 293 #define SIMPLEQ_INSERT_TAIL(head, elm, field) do {                      \
 294         (elm)->field.sqe_next = NULL;                                   \
 295         *(head)->sqh_last = (elm);                                      \
 296         (head)->sqh_last = &(elm)->field.sqe_next;                      \
 297 } while (0)
 298
 299 #define SIMPLEQ_INSERT_AFTER(head, listelm, elm, field) do {            \
 300         if (((elm)->field.sqe_next = (listelm)->field.sqe_next) == NULL)\
 301                 (head)->sqh_last = &(elm)->field.sqe_next;              \
 302         (listelm)->field.sqe_next = (elm);                              \
 303 } while (0)
 304
 305 #define SIMPLEQ_REMOVE_HEAD(head, field) do {                   \
 306         if (((head)->sqh_first = (head)->sqh_first->field.sqe_next) == NULL) \
 307                 (head)->sqh_last = &(head)->sqh_first;                  \
 308 } while (0)
 309
 310 #define SIMPLEQ_REMOVE_AFTER(head, elm, field) do {                     \
 311         if (((elm)->field.sqe_next = (elm)->field.sqe_next->field.sqe_next) \
 312             == NULL)                                                    \
 313                 (head)->sqh_last = &(elm)->field.sqe_next;              \
 314 } while (0)
 315
 316 #define SIMPLEQ_CONCAT(head1, head2) do {                               \
 317         if (!SIMPLEQ_EMPTY((head2))) {                                  \
 318                 *(head1)->sqh_last = (head2)->sqh_first;                \
 319                 (head1)->sqh_last = (head2)->sqh_last;                  \
 320                 SIMPLEQ_INIT((head2));                                  \
 321         }                                                               \
 322 } while (0)
 323
 324 /*
 325  * XOR Simple queue definitions.
 326  */
 327 #define XSIMPLEQ_HEAD(name, type)                                       \
 328 struct name {                                                           \
 329         struct type *sqx_first; /* first element */                     \
 330         struct type **sqx_last; /* addr of last next element */         \
 331         unsigned long sqx_cookie;                                       \
 332 }
 333
 334 #define XSIMPLEQ_ENTRY(type)                                            \
 335 struct {                                                                \
 336         struct type *sqx_next;  /* next element */                      \
 337 }
 338
 339 /*
 340  * XOR Simple queue access methods.
 341  */
 342 #define XSIMPLEQ_XOR(head, ptr)     ((__typeof(ptr))((head)->sqx_cookie ^ \
 343                                         (unsigned long)(ptr)))
 344 #define XSIMPLEQ_FIRST(head)        XSIMPLEQ_XOR(head, ((head)->sqx_first))
 345 #define XSIMPLEQ_END(head)          NULL
 346 #define XSIMPLEQ_EMPTY(head)        (XSIMPLEQ_FIRST(head) == XSIMPLEQ_END(head))
 347 #define XSIMPLEQ_NEXT(head, elm, field)    XSIMPLEQ_XOR(head, ((elm)->field.sqx_next))
 348
 349
 350 #define XSIMPLEQ_FOREACH(var, head, field)                              \
 351         for ((var) = XSIMPLEQ_FIRST(head);                              \
 352             (var) != XSIMPLEQ_END(head);                                \
 353             (var) = XSIMPLEQ_NEXT(head, var, field))
 354
 355 #define XSIMPLEQ_FOREACH_SAFE(var, head, field, tvar)                   \
 356         for ((var) = XSIMPLEQ_FIRST(head);                              \
 357             (var) && ((tvar) = XSIMPLEQ_NEXT(head, var, field), 1);     \
 358             (var) = (tvar))
 359
 360 /*
 361  * XOR Simple queue functions.
 362  */
 363 #define XSIMPLEQ_INIT(head) do {                                        \
 364         arc4random_buf(&(head)->sqx_cookie, sizeof((head)->sqx_cookie)); \
 365         (head)->sqx_first = XSIMPLEQ_XOR(head, NULL);                   \
 366         (head)->sqx_last = XSIMPLEQ_XOR(head, &(head)->sqx_first);      \
 367 } while (0)
 368
 369 #define XSIMPLEQ_INSERT_HEAD(head, elm, field) do {                     \
 370         if (((elm)->field.sqx_next = (head)->sqx_first) ==              \
 371             XSIMPLEQ_XOR(head, NULL))                                   \
 372                 (head)->sqx_last = XSIMPLEQ_XOR(head, &(elm)->field.sqx_next); \
 373         (head)->sqx_first = XSIMPLEQ_XOR(head, (elm));                  \
 374 } while (0)
 375
 376 #define XSIMPLEQ_INSERT_TAIL(head, elm, field) do {                     \
 377         (elm)->field.sqx_next = XSIMPLEQ_XOR(head, NULL);               \
 378         *(XSIMPLEQ_XOR(head, (head)->sqx_last)) = XSIMPLEQ_XOR(head, (elm)); \
 379         (head)->sqx_last = XSIMPLEQ_XOR(head, &(elm)->field.sqx_next);  \
 380 } while (0)
 381
 382 #define XSIMPLEQ_INSERT_AFTER(head, listelm, elm, field) do {           \
 383         if (((elm)->field.sqx_next = (listelm)->field.sqx_next) ==      \
 384             XSIMPLEQ_XOR(head, NULL))                                   \
 385                 (head)->sqx_last = XSIMPLEQ_XOR(head, &(elm)->field.sqx_next); \
 386         (listelm)->field.sqx_next = XSIMPLEQ_XOR(head, (elm));          \
 387 } while (0)
 388
 389 #define XSIMPLEQ_REMOVE_HEAD(head, field) do {                          \
 390         if (((head)->sqx_first = XSIMPLEQ_XOR(head,                     \
 391             (head)->sqx_first)->field.sqx_next) == XSIMPLEQ_XOR(head, NULL)) \
 392                 (head)->sqx_last = XSIMPLEQ_XOR(head, &(head)->sqx_first); \
 393 } while (0)
 394
 395 #define XSIMPLEQ_REMOVE_AFTER(head, elm, field) do {                    \
 396         if (((elm)->field.sqx_next = XSIMPLEQ_XOR(head,                 \
 397             (elm)->field.sqx_next)->field.sqx_next)                     \
 398             == XSIMPLEQ_XOR(head, NULL))                                \
 399                 (head)->sqx_last =                                      \
 400                     XSIMPLEQ_XOR(head, &(elm)->field.sqx_next);         \
 401 } while (0)
 402
 403
 404 /*
 405  * Tail queue definitions.
 406  */
 407 #define TAILQ_HEAD(name, type)                                          \
 408 struct name {                                                           \
 409         struct type *tqh_first; /* first element */                     \
 410         struct type **tqh_last; /* addr of last next element */         \
 411 }
 412
 413 #define TAILQ_HEAD_INITIALIZER(head)                                    \
 414         { NULL, &(head).tqh_first }
 415
 416 #define TAILQ_ENTRY(type)                                               \
 417 struct {                                                                \
 418         struct type *tqe_next;  /* next element */                      \
 419         struct type **tqe_prev; /* address of previous next element */  \
 420 }
 421
 422 /*
 423  * Tail queue access methods.
 424  */
 425 #define TAILQ_FIRST(head)               ((head)->tqh_first)
 426 #define TAILQ_END(head)                 NULL
 427 #define TAILQ_NEXT(elm, field)          ((elm)->field.tqe_next)
 428 #define TAILQ_LAST(head, headname)                                      \
 429         (*(((struct headname *)((head)->tqh_last))->tqh_last))
 430 /* XXX */
 431 #define TAILQ_PREV(elm, headname, field)                                \
 432         (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
 433 #define TAILQ_EMPTY(head)                                               \
 434         (TAILQ_FIRST(head) == TAILQ_END(head))
 435
 436 #define TAILQ_FOREACH(var, head, field)                                 \
 437         for((var) = TAILQ_FIRST(head);                                  \
 438             (var) != TAILQ_END(head);                                   \
 439             (var) = TAILQ_NEXT(var, field))
 440
 441 #define TAILQ_FOREACH_SAFE(var, head, field, tvar)                      \
 442         for ((var) = TAILQ_FIRST(head);                                 \
 443             (var) != TAILQ_END(head) &&                                 \
 444             ((tvar) = TAILQ_NEXT(var, field), 1);                       \
 445             (var) = (tvar))
 446
 447
 448 #define TAILQ_FOREACH_REVERSE(var, head, headname, field)               \
 449         for((var) = TAILQ_LAST(head, headname);                         \
 450             (var) != TAILQ_END(head);                                   \
 451             (var) = TAILQ_PREV(var, headname, field))
 452
 453 #define TAILQ_FOREACH_REVERSE_SAFE(var, head, headname, field, tvar)    \
 454         for ((var) = TAILQ_LAST(head, headname);                        \
 455             (var) != TAILQ_END(head) &&                                 \
 456             ((tvar) = TAILQ_PREV(var, headname, field), 1);             \
 457             (var) = (tvar))
 458
 459 /*
 460  * Tail queue functions.
 461  */
 462 #define TAILQ_INIT(head) do {                                           \
 463         (head)->tqh_first = NULL;                                       \
 464         (head)->tqh_last = &(head)->tqh_first;                          \
 465 } while (0)
 466
 467 #define TAILQ_INSERT_HEAD(head, elm, field) do {                        \
 468         if (((elm)->field.tqe_next = (head)->tqh_first) != NULL)        \
 469                 (head)->tqh_first->field.tqe_prev =                     \
 470                     &(elm)->field.tqe_next;                             \
 471         else                                                            \
 472                 (head)->tqh_last = &(elm)->field.tqe_next;              \
 473         (head)->tqh_first = (elm);                                      \
 474         (elm)->field.tqe_prev = &(head)->tqh_first;                     \
 475 } while (0)
 476
 477 #define TAILQ_INSERT_TAIL(head, elm, field) do {                        \
 478         (elm)->field.tqe_next = NULL;                                   \
 479         (elm)->field.tqe_prev = (head)->tqh_last;                       \
 480         *(head)->tqh_last = (elm);                                      \
 481         (head)->tqh_last = &(elm)->field.tqe_next;                      \
 482 } while (0)
 483
 484 #define TAILQ_INSERT_AFTER(head, listelm, elm, field) do {              \
 485         if (((elm)->field.tqe_next = (listelm)->field.tqe_next) != NULL)\
 486                 (elm)->field.tqe_next->field.tqe_prev =                 \
 487                     &(elm)->field.tqe_next;                             \
 488         else                                                            \
 489                 (head)->tqh_last = &(elm)->field.tqe_next;              \
 490         (listelm)->field.tqe_next = (elm);                              \
 491         (elm)->field.tqe_prev = &(listelm)->field.tqe_next;             \
 492 } while (0)
 493
 494 #define TAILQ_INSERT_BEFORE(listelm, elm, field) do {                   \
 495         (elm)->field.tqe_prev = (listelm)->field.tqe_prev;              \
 496         (elm)->field.tqe_next = (listelm);                              \
 497         *(listelm)->field.tqe_prev = (elm);                             \
 498         (listelm)->field.tqe_prev = &(elm)->field.tqe_next;             \
 499 } while (0)
 500
 501 #define TAILQ_REMOVE(head, elm, field) do {                             \
 502         if (((elm)->field.tqe_next) != NULL)                            \
 503                 (elm)->field.tqe_next->field.tqe_prev =                 \
 504                     (elm)->field.tqe_prev;                              \
 505         else                                                            \
 506                 (head)->tqh_last = (elm)->field.tqe_prev;               \
 507         *(elm)->field.tqe_prev = (elm)->field.tqe_next;                 \
 508         _Q_INVALIDATE((elm)->field.tqe_prev);                           \
 509         _Q_INVALIDATE((elm)->field.tqe_next);                           \
 510 } while (0)
 511
 512 #define TAILQ_REPLACE(head, elm, elm2, field) do {                      \
 513         if (((elm2)->field.tqe_next = (elm)->field.tqe_next) != NULL)   \
 514                 (elm2)->field.tqe_next->field.tqe_prev =                \
 515                     &(elm2)->field.tqe_next;                            \
 516         else                                                            \
 517                 (head)->tqh_last = &(elm2)->field.tqe_next;             \
 518         (elm2)->field.tqe_prev = (elm)->field.tqe_prev;                 \
 519         *(elm2)->field.tqe_prev = (elm2);                               \
 520         _Q_INVALIDATE((elm)->field.tqe_prev);                           \
 521         _Q_INVALIDATE((elm)->field.tqe_next);                           \
 522 } while (0)
 523
 524 #define TAILQ_CONCAT(head1, head2, field) do {                          \
 525         if (!TAILQ_EMPTY(head2)) {                                      \
 526                 *(head1)->tqh_last = (head2)->tqh_first;                \
 527                 (head2)->tqh_first->field.tqe_prev = (head1)->tqh_last; \
 528                 (head1)->tqh_last = (head2)->tqh_last;                  \
 529                 TAILQ_INIT((head2));                                    \
 530         }                                                               \
 531 } while (0)
 532
 533 #endif  /* !_SYS_QUEUE_H_ */