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   1 /*      $OpenBSD: queue.h,v 1.22 2001/06/23 04:39:35 angelos Exp $      */
   2 /*      $NetBSD: queue.h,v 1.11 1996/05/16 05:17:14 mycroft Exp $       */
   3
   4 /*
   5  *      University of California, Berkeley "advertising clause" removed as per
   6  *      authorisation given by William Hoskins, Director, Office of Technology
   7  *      Licensing, University of California, Berkeley, on the 22nd day of July
   8  *      1999.
   9  */
  10
  11 /*
  12  * Copyright (c) 1991, 1993
  13  *      The Regents of the University of California.  All rights reserved.
  14  *
  15  * Redistribution and use in source and binary forms, with or without
  16  * modification, are permitted provided that the following conditions
  17  * are met:
  18  * 1. Redistributions of source code must retain the above copyright
  19  *    notice, this list of conditions and the following disclaimer.
  20  * 2. Redistributions in binary form must reproduce the above copyright
  21  *    notice, this list of conditions and the following disclaimer in the
  22  *    documentation and/or other materials provided with the distribution.
  23  * 3. Neither the name of the University nor the names of its contributors
  24  *    may be used to endorse or promote products derived from this software
  25  *    without specific prior written permission.
  26  *
  27  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  28  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  29  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  30  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  31  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  32  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  33  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  34  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  35  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  36  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  37  * SUCH DAMAGE.
  38  *
  39  *      @(#)queue.h     8.5 (Berkeley) 8/20/94
  40  */
  41
  42 #ifndef _LOCAL_SYS_QUEUE_H_
  43 #define _LOCAL_SYS_QUEUE_H_
  44
  45 /*
  46  * This file defines five types of data structures: singly-linked lists,
  47  * lists, simple queues, tail queues, and circular queues.
  48  *
  49  *
  50  * A singly-linked list is headed by a single forward pointer. The elements
  51  * are singly linked for minimum space and pointer manipulation overhead at
  52  * the expense of O(n) removal for arbitrary elements. New elements can be
  53  * added to the list after an existing element or at the head of the list.
  54  * Elements being removed from the head of the list should use the explicit
  55  * macro for this purpose for optimum efficiency. A singly-linked list may
  56  * only be traversed in the forward direction.  Singly-linked lists are ideal
  57  * for applications with large datasets and few or no removals or for
  58  * implementing a LIFO queue.
  59  *
  60  * A list is headed by a single forward pointer (or an array of forward
  61  * pointers for a hash table header). The elements are doubly linked
  62  * so that an arbitrary element can be removed without a need to
  63  * traverse the list. New elements can be added to the list before
  64  * or after an existing element or at the head of the list. A list
  65  * may only be traversed in the forward direction.
  66  *
  67  * A simple queue is headed by a pair of pointers, one the head of the
  68  * list and the other to the tail of the list. The elements are singly
  69  * linked to save space, so elements can only be removed from the
  70  * head of the list. New elements can be added to the list before or after
  71  * an existing element, at the head of the list, or at the end of the
  72  * list. A simple queue may only be traversed in the forward direction.
  73  *
  74  * A tail queue is headed by a pair of pointers, one to the head of the
  75  * list and the other to the tail of the list. The elements are doubly
  76  * linked so that an arbitrary element can be removed without a need to
  77  * traverse the list. New elements can be added to the list before or
  78  * after an existing element, at the head of the list, or at the end of
  79  * the list. A tail queue may be traversed in either direction.
  80  *
  81  * A circle queue is headed by a pair of pointers, one to the head of the
  82  * list and the other to the tail of the list. The elements are doubly
  83  * linked so that an arbitrary element can be removed without a need to
  84  * traverse the list. New elements can be added to the list before or after
  85  * an existing element, at the head of the list, or at the end of the list.
  86  * A circle queue may be traversed in either direction, but has a more
  87  * complex end of list detection.
  88  *
  89  * For details on the use of these macros, see the queue(3) manual page.
  90  */
  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         { NULL }
 102
 103 #define SLIST_ENTRY(type)                                               \
 104 struct {                                                                \
 105         struct type *sle_next;  /* next element */                      \
 106 }
 107
 108 /*
 109  * Singly-linked List access methods.
 110  */
 111 #define SLIST_FIRST(head)       ((head)->slh_first)
 112 #define SLIST_END(head)         NULL
 113 #define SLIST_EMPTY(head)       (SLIST_FIRST(head) == SLIST_END(head))
 114 #define SLIST_NEXT(elm, field)  ((elm)->field.sle_next)
 115
 116 #define SLIST_FOREACH(var, head, field)                                 \
 117         for((var) = SLIST_FIRST(head);                                  \
 118             (var) != SLIST_END(head);                                   \
 119             (var) = SLIST_NEXT(var, field))
 120
 121 #define SLIST_FOREACH_SAFE(var, head, field, tvar)                      \
 122         for((var) = SLIST_FIRST(head);                                  \
 123             (var) != SLIST_END(head) &&                                 \
 124             ((tvar) = SLIST_NEXT(var, field), 1);                       \
 125             (var) = (tvar))
 126
 127 /*
 128  * Singly-linked List functions.
 129  */
 130 #define SLIST_INIT(head) {                                              \
 131         SLIST_FIRST(head) = SLIST_END(head);                            \
 132 }
 133
 134 #define SLIST_INSERT_AFTER(slistelm, elm, field) do {                   \
 135         (elm)->field.sle_next = (slistelm)->field.sle_next;             \
 136         (slistelm)->field.sle_next = (elm);                             \
 137 } while (0)
 138
 139 #define SLIST_INSERT_HEAD(head, elm, field) do {                        \
 140         (elm)->field.sle_next = (head)->slh_first;                      \
 141         (head)->slh_first = (elm);                                      \
 142 } while (0)
 143
 144 #define SLIST_REMOVE_HEAD(head, field) do {                             \
 145         (head)->slh_first = (head)->slh_first->field.sle_next;          \
 146 } while (0)
 147
 148 #define SLIST_REMOVE(head, elm, type, field) do {                       \
 149         if ((head)->slh_first == (elm)) {                               \
 150                 SLIST_REMOVE_HEAD((head), field);                       \
 151         }                                                               \
 152         else {                                                          \
 153                 struct type *curelm = (head)->slh_first;                \
 154                 while( curelm->field.sle_next != (elm) )                \
 155                         curelm = curelm->field.sle_next;                \
 156                 curelm->field.sle_next =                                \
 157                     curelm->field.sle_next->field.sle_next;             \
 158         }                                                               \
 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)!= LIST_END(head) &&                                   \
 194             ((tvar) = LIST_NEXT(var, field), 1);                        \
 195             (var) = (tvar))
 196
 197
 198 /*
 199  * List functions.
 200  */
 201 #define LIST_INIT(head) do {                                            \
 202         LIST_FIRST(head) = LIST_END(head);                              \
 203 } while (0)
 204
 205 #define LIST_INSERT_AFTER(listelm, elm, field) do {                     \
 206         if (((elm)->field.le_next = (listelm)->field.le_next) != NULL)  \
 207                 (listelm)->field.le_next->field.le_prev =               \
 208                     &(elm)->field.le_next;                              \
 209         (listelm)->field.le_next = (elm);                               \
 210         (elm)->field.le_prev = &(listelm)->field.le_next;               \
 211 } while (0)
 212
 213 #define LIST_INSERT_BEFORE(listelm, elm, field) do {                    \
 214         (elm)->field.le_prev = (listelm)->field.le_prev;                \
 215         (elm)->field.le_next = (listelm);                               \
 216         *(listelm)->field.le_prev = (elm);                              \
 217         (listelm)->field.le_prev = &(elm)->field.le_next;               \
 218 } while (0)
 219
 220 #define LIST_INSERT_HEAD(head, elm, field) do {                         \
 221         if (((elm)->field.le_next = (head)->lh_first) != NULL)          \
 222                 (head)->lh_first->field.le_prev = &(elm)->field.le_next;\
 223         (head)->lh_first = (elm);                                       \
 224         (elm)->field.le_prev = &(head)->lh_first;                       \
 225 } while (0)
 226
 227 #define LIST_REMOVE(elm, field) do {                                    \
 228         if ((elm)->field.le_next != NULL)                               \
 229                 (elm)->field.le_next->field.le_prev =                   \
 230                     (elm)->field.le_prev;                               \
 231         *(elm)->field.le_prev = (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 } while (0)
 241
 242 /*
 243  * Simple queue definitions.
 244  */
 245 #define SIMPLEQ_HEAD(name, type)                                        \
 246 struct name {                                                           \
 247         struct type *sqh_first; /* first element */                     \
 248         struct type **sqh_last; /* addr of last next element */         \
 249 }
 250
 251 #define SIMPLEQ_HEAD_INITIALIZER(head)                                  \
 252         { NULL, &(head).sqh_first }
 253
 254 #define SIMPLEQ_ENTRY(type)                                             \
 255 struct {                                                                \
 256         struct type *sqe_next;  /* next element */                      \
 257 }
 258
 259 /*
 260  * Simple queue access methods.
 261  */
 262 #define SIMPLEQ_FIRST(head)         ((head)->sqh_first)
 263 #define SIMPLEQ_END(head)           NULL
 264 #define SIMPLEQ_EMPTY(head)         (SIMPLEQ_FIRST(head) == SIMPLEQ_END(head))
 265 #define SIMPLEQ_NEXT(elm, field)    ((elm)->field.sqe_next)
 266
 267 #define SIMPLEQ_FOREACH(var, head, field)                               \
 268         for((var) = SIMPLEQ_FIRST(head);                                \
 269             (var) != SIMPLEQ_END(head);                                 \
 270             (var) = SIMPLEQ_NEXT(var, field))
 271
 272 #define SIMPLEQ_FOREACH_SAFE(var, head, field, tvar)                    \
 273         for((var) = SIMPLEQ_FIRST(head);                                \
 274             (var) != SIMPLEQ_END(head) &&                               \
 275             ((tvar) = SIMPLEQ_NEXT(var, field), 1);                     \
 276             (var) = (tvar))
 277
 278 /*
 279  * Simple queue functions.
 280  */
 281 #define SIMPLEQ_INIT(head) do {                                         \
 282         (head)->sqh_first = NULL;                                       \
 283         (head)->sqh_last = &(head)->sqh_first;                          \
 284 } while (0)
 285
 286 #define SIMPLEQ_INSERT_HEAD(head, elm, field) do {                      \
 287         if (((elm)->field.sqe_next = (head)->sqh_first) == NULL)        \
 288                 (head)->sqh_last = &(elm)->field.sqe_next;              \
 289         (head)->sqh_first = (elm);                                      \
 290 } while (0)
 291
 292 #define SIMPLEQ_INSERT_TAIL(head, elm, field) do {                      \
 293         (elm)->field.sqe_next = NULL;                                   \
 294         *(head)->sqh_last = (elm);                                      \
 295         (head)->sqh_last = &(elm)->field.sqe_next;                      \
 296 } while (0)
 297
 298 #define SIMPLEQ_INSERT_AFTER(head, listelm, elm, field) do {            \
 299         if (((elm)->field.sqe_next = (listelm)->field.sqe_next) == NULL)\
 300                 (head)->sqh_last = &(elm)->field.sqe_next;              \
 301         (listelm)->field.sqe_next = (elm);                              \
 302 } while (0)
 303
 304 #define SIMPLEQ_REMOVE_HEAD(head, elm, field) do {                      \
 305         if (((head)->sqh_first = (elm)->field.sqe_next) == NULL)        \
 306                 (head)->sqh_last = &(head)->sqh_first;                  \
 307 } while (0)
 308
 309 /*
 310  * Tail queue definitions.
 311  */
 312 #define TAILQ_HEAD(name, type)                                          \
 313 struct name {                                                           \
 314         struct type *tqh_first; /* first element */                     \
 315         struct type **tqh_last; /* addr of last next element */         \
 316 }
 317
 318 #define TAILQ_HEAD_INITIALIZER(head)                                    \
 319         { NULL, &(head).tqh_first }
 320
 321 #define TAILQ_ENTRY(type)                                               \
 322 struct {                                                                \
 323         struct type *tqe_next;  /* next element */                      \
 324         struct type **tqe_prev; /* address of previous next element */  \
 325 }
 326
 327 /*
 328  * tail queue access methods
 329  */
 330 #define TAILQ_FIRST(head)               ((head)->tqh_first)
 331 #define TAILQ_END(head)                 NULL
 332 #define TAILQ_NEXT(elm, field)          ((elm)->field.tqe_next)
 333 #define TAILQ_LAST(head, headname)                                      \
 334         (*(((struct headname *)((head)->tqh_last))->tqh_last))
 335 /* XXX */
 336 #define TAILQ_PREV(elm, headname, field)                                \
 337         (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
 338 #define TAILQ_EMPTY(head)                                               \
 339         (TAILQ_FIRST(head) == TAILQ_END(head))
 340
 341 #define TAILQ_FOREACH(var, head, field)                                 \
 342         for((var) = TAILQ_FIRST(head);                                  \
 343             (var) != TAILQ_END(head);                                   \
 344             (var) = TAILQ_NEXT(var, field))
 345
 346 #define TAILQ_FOREACH_SAFE(var, head, field, tvar)                      \
 347         for((var) = TAILQ_FIRST(head);                                  \
 348             (var) != TAILQ_END(head) &&                                 \
 349             ((tvar) = TAILQ_NEXT(var, field), 1);                       \
 350             (var) = (tvar))
 351
 352 #define TAILQ_FOREACH_REVERSE(var, head, field, headname)               \
 353         for((var) = TAILQ_LAST(head, headname);                         \
 354             (var) != TAILQ_END(head);                                   \
 355             (var) = TAILQ_PREV(var, headname, field))
 356
 357 #define TAILQ_FOREACH_REVERSE_SAFE(var, head, field, headname, tvar)    \
 358         for((var) = TAILQ_LAST(head, headname);                         \
 359             (var) != TAILQ_END(head) &&                                 \
 360             ((tvar) = TAILQ_PREV(var, headname, field), 1);             \
 361             (var) = (tvar))
 362
 363 /*
 364  * Tail queue functions.
 365  */
 366 #define TAILQ_INIT(head) do {                                           \
 367         (head)->tqh_first = NULL;                                       \
 368         (head)->tqh_last = &(head)->tqh_first;                          \
 369 } while (0)
 370
 371 #define TAILQ_INSERT_HEAD(head, elm, field) do {                        \
 372         if (((elm)->field.tqe_next = (head)->tqh_first) != NULL)        \
 373                 (head)->tqh_first->field.tqe_prev =                     \
 374                     &(elm)->field.tqe_next;                             \
 375         else                                                            \
 376                 (head)->tqh_last = &(elm)->field.tqe_next;              \
 377         (head)->tqh_first = (elm);                                      \
 378         (elm)->field.tqe_prev = &(head)->tqh_first;                     \
 379 } while (0)
 380
 381 #define TAILQ_INSERT_TAIL(head, elm, field) do {                        \
 382         (elm)->field.tqe_next = NULL;                                   \
 383         (elm)->field.tqe_prev = (head)->tqh_last;                       \
 384         *(head)->tqh_last = (elm);                                      \
 385         (head)->tqh_last = &(elm)->field.tqe_next;                      \
 386 } while (0)
 387
 388 #define TAILQ_INSERT_AFTER(head, listelm, elm, field) do {              \
 389         if (((elm)->field.tqe_next = (listelm)->field.tqe_next) != NULL)\
 390                 (elm)->field.tqe_next->field.tqe_prev =                 \
 391                     &(elm)->field.tqe_next;                             \
 392         else                                                            \
 393                 (head)->tqh_last = &(elm)->field.tqe_next;              \
 394         (listelm)->field.tqe_next = (elm);                              \
 395         (elm)->field.tqe_prev = &(listelm)->field.tqe_next;             \
 396 } while (0)
 397
 398 #define TAILQ_INSERT_BEFORE(listelm, elm, field) do {                   \
 399         (elm)->field.tqe_prev = (listelm)->field.tqe_prev;              \
 400         (elm)->field.tqe_next = (listelm);                              \
 401         *(listelm)->field.tqe_prev = (elm);                             \
 402         (listelm)->field.tqe_prev = &(elm)->field.tqe_next;             \
 403 } while (0)
 404
 405 #define TAILQ_REMOVE(head, elm, field) do {                             \
 406         if (((elm)->field.tqe_next) != NULL)                            \
 407                 (elm)->field.tqe_next->field.tqe_prev =                 \
 408                     (elm)->field.tqe_prev;                              \
 409         else                                                            \
 410                 (head)->tqh_last = (elm)->field.tqe_prev;               \
 411         *(elm)->field.tqe_prev = (elm)->field.tqe_next;                 \
 412 } while (0)
 413
 414 #define TAILQ_REPLACE(head, elm, elm2, field) do {                      \
 415         if (((elm2)->field.tqe_next = (elm)->field.tqe_next) != NULL)   \
 416                 (elm2)->field.tqe_next->field.tqe_prev =                \
 417                     &(elm2)->field.tqe_next;                            \
 418         else                                                            \
 419                 (head)->tqh_last = &(elm2)->field.tqe_next;             \
 420         (elm2)->field.tqe_prev = (elm)->field.tqe_prev;                 \
 421         *(elm2)->field.tqe_prev = (elm2);                               \
 422 } while (0)
 423
 424 /*
 425  * Circular queue definitions.
 426  */
 427 #define CIRCLEQ_HEAD(name, type)                                        \
 428 struct name {                                                           \
 429         struct type *cqh_first;         /* first element */             \
 430         struct type *cqh_last;          /* last element */              \
 431 }
 432
 433 #define CIRCLEQ_HEAD_INITIALIZER(head)                                  \
 434         { CIRCLEQ_END(&head), CIRCLEQ_END(&head) }
 435
 436 #define CIRCLEQ_ENTRY(type)                                             \
 437 struct {                                                                \
 438         struct type *cqe_next;          /* next element */              \
 439         struct type *cqe_prev;          /* previous element */          \
 440 }
 441
 442 /*
 443  * Circular queue access methods
 444  */
 445 #define CIRCLEQ_FIRST(head)             ((head)->cqh_first)
 446 #define CIRCLEQ_LAST(head)              ((head)->cqh_last)
 447 #define CIRCLEQ_END(head)               ((void *)(head))
 448 #define CIRCLEQ_NEXT(elm, field)        ((elm)->field.cqe_next)
 449 #define CIRCLEQ_PREV(elm, field)        ((elm)->field.cqe_prev)
 450 #define CIRCLEQ_EMPTY(head)                                             \
 451         (CIRCLEQ_FIRST(head) == CIRCLEQ_END(head))
 452
 453 #define CIRCLEQ_FOREACH(var, head, field)                               \
 454         for((var) = CIRCLEQ_FIRST(head);                                \
 455             (var) != CIRCLEQ_END(head);                                 \
 456             (var) = CIRCLEQ_NEXT(var, field))
 457
 458 #define CIRCLEQ_FOREACH_SAFE(var, head, field, tvar)                    \
 459         for((var) = CIRCLEQ_FIRST(head);                                \
 460             (var) != CIRCLEQ_END(head) &&                               \
 461             ((tvar) = CIRCLEQ_NEXT(var, field), 1);                     \
 462             (var) = (tvar))
 463
 464 #define CIRCLEQ_FOREACH_REVERSE(var, head, field)                       \
 465         for((var) = CIRCLEQ_LAST(head);                                 \
 466             (var) != CIRCLEQ_END(head);                                 \
 467             (var) = CIRCLEQ_PREV(var, field))
 468
 469 #define CIRCLEQ_FOREACH_REVERSE_SAFE(var, head, field, tvar)            \
 470         for((var) = CIRCLEQ_LAST(head);                                 \
 471             (var) != CIRCLEQ_END(head) &&                               \
 472             ((tvar) = CIRCLEQ_PREV(var, field), 1);                     \
 473             (var) = (tvar))
 474
 475 /*
 476  * Circular queue functions.
 477  */
 478 #define CIRCLEQ_INIT(head) do {                                         \
 479         (head)->cqh_first = CIRCLEQ_END(head);                          \
 480         (head)->cqh_last = CIRCLEQ_END(head);                           \
 481 } while (0)
 482
 483 #define CIRCLEQ_INSERT_AFTER(head, listelm, elm, field) do {            \
 484         (elm)->field.cqe_next = (listelm)->field.cqe_next;              \
 485         (elm)->field.cqe_prev = (listelm);                              \
 486         if ((listelm)->field.cqe_next == CIRCLEQ_END(head))             \
 487                 (head)->cqh_last = (elm);                               \
 488         else                                                            \
 489                 (listelm)->field.cqe_next->field.cqe_prev = (elm);      \
 490         (listelm)->field.cqe_next = (elm);                              \
 491 } while (0)
 492
 493 #define CIRCLEQ_INSERT_BEFORE(head, listelm, elm, field) do {           \
 494         (elm)->field.cqe_next = (listelm);                              \
 495         (elm)->field.cqe_prev = (listelm)->field.cqe_prev;              \
 496         if ((listelm)->field.cqe_prev == CIRCLEQ_END(head))             \
 497                 (head)->cqh_first = (elm);                              \
 498         else                                                            \
 499                 (listelm)->field.cqe_prev->field.cqe_next = (elm);      \
 500         (listelm)->field.cqe_prev = (elm);                              \
 501 } while (0)
 502
 503 #define CIRCLEQ_INSERT_HEAD(head, elm, field) do {                      \
 504         (elm)->field.cqe_next = (head)->cqh_first;                      \
 505         (elm)->field.cqe_prev = CIRCLEQ_END(head);                      \
 506         if ((head)->cqh_last == CIRCLEQ_END(head))                      \
 507                 (head)->cqh_last = (elm);                               \
 508         else                                                            \
 509                 (head)->cqh_first->field.cqe_prev = (elm);              \
 510         (head)->cqh_first = (elm);                                      \
 511 } while (0)
 512
 513 #define CIRCLEQ_INSERT_TAIL(head, elm, field) do {                      \
 514         (elm)->field.cqe_next = CIRCLEQ_END(head);                      \
 515         (elm)->field.cqe_prev = (head)->cqh_last;                       \
 516         if ((head)->cqh_first == CIRCLEQ_END(head))                     \
 517                 (head)->cqh_first = (elm);                              \
 518         else                                                            \
 519                 (head)->cqh_last->field.cqe_next = (elm);               \
 520         (head)->cqh_last = (elm);                                       \
 521 } while (0)
 522
 523 #define CIRCLEQ_REMOVE(head, elm, field) do {                           \
 524         if ((elm)->field.cqe_next == CIRCLEQ_END(head))                 \
 525                 (head)->cqh_last = (elm)->field.cqe_prev;               \
 526         else                                                            \
 527                 (elm)->field.cqe_next->field.cqe_prev =                 \
 528                     (elm)->field.cqe_prev;                              \
 529         if ((elm)->field.cqe_prev == CIRCLEQ_END(head))                 \
 530                 (head)->cqh_first = (elm)->field.cqe_next;              \
 531         else                                                            \
 532                 (elm)->field.cqe_prev->field.cqe_next =                 \
 533                     (elm)->field.cqe_next;                              \
 534 } while (0)
 535
 536 #define CIRCLEQ_REPLACE(head, elm, elm2, field) do {                    \
 537         if (((elm2)->field.cqe_next = (elm)->field.cqe_next) ==         \
 538             CIRCLEQ_END(head))                                          \
 539                 (head).cqh_last = (elm2);                               \
 540         else                                                            \
 541                 (elm2)->field.cqe_next->field.cqe_prev = (elm2);        \
 542         if (((elm2)->field.cqe_prev = (elm)->field.cqe_prev) ==         \
 543             CIRCLEQ_END(head))                                          \
 544                 (head).cqh_first = (elm2);                              \
 545         else                                                            \
 546                 (elm2)->field.cqe_prev->field.cqe_next = (elm2);        \
 547 } while (0)
 548
 549 #endif  /* !_LOCAL_SYS_QUEUE_H_ */