The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/sys/queue.h

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    1 /*      $NetBSD: queue.h,v 1.76 2021/01/16 23:51:51 chs Exp $   */
    2 
    3 /*
    4  * Copyright (c) 1991, 1993
    5  *      The Regents of the University of California.  All rights reserved.
    6  *
    7  * Redistribution and use in source and binary forms, with or without
    8  * modification, are permitted provided that the following conditions
    9  * are met:
   10  * 1. Redistributions of source code must retain the above copyright
   11  *    notice, this list of conditions and the following disclaimer.
   12  * 2. Redistributions in binary form must reproduce the above copyright
   13  *    notice, this list of conditions and the following disclaimer in the
   14  *    documentation and/or other materials provided with the distribution.
   15  * 3. Neither the name of the University nor the names of its contributors
   16  *    may be used to endorse or promote products derived from this software
   17  *    without specific prior written permission.
   18  *
   19  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   29  * SUCH DAMAGE.
   30  *
   31  *      @(#)queue.h     8.5 (Berkeley) 8/20/94
   32  */
   33 
   34 #ifndef _SYS_QUEUE_H_
   35 #define _SYS_QUEUE_H_
   36 
   37 /*
   38  * This file defines five types of data structures: singly-linked lists,
   39  * lists, simple queues, tail queues, and circular queues.
   40  *
   41  * A singly-linked list is headed by a single forward pointer. The
   42  * elements are singly linked for minimum space and pointer manipulation
   43  * overhead at the expense of O(n) removal for arbitrary elements. New
   44  * elements can be added to the list after an existing element or at the
   45  * head of the list.  Elements being removed from the head of the list
   46  * should use the explicit macro for this purpose for optimum
   47  * efficiency. A singly-linked list may only be traversed in the forward
   48  * direction.  Singly-linked lists are ideal for applications with large
   49  * datasets and few or no removals or for implementing a LIFO queue.
   50  *
   51  * A list is headed by a single forward pointer (or an array of forward
   52  * pointers for a hash table header). The elements are doubly linked
   53  * so that an arbitrary element can be removed without a need to
   54  * traverse the list. New elements can be added to the list before
   55  * or after an existing element or at the head of the list. A list
   56  * may only be traversed in the forward direction.
   57  *
   58  * A simple queue is headed by a pair of pointers, one the head of the
   59  * list and the other to the tail of the list. The elements are singly
   60  * linked to save space, so elements can only be removed from the
   61  * head of the list. New elements can be added to the list after
   62  * an existing element, at the head of the list, or at the end of the
   63  * list. A simple queue may only be traversed in the forward direction.
   64  *
   65  * A tail queue is headed by a pair of pointers, one to the head of the
   66  * list and the other to the tail of the list. The elements are doubly
   67  * linked so that an arbitrary element can be removed without a need to
   68  * traverse the list. New elements can be added to the list before or
   69  * after an existing element, at the head of the list, or at the end of
   70  * the list. A tail queue may be traversed in either direction.
   71  *
   72  * For details on the use of these macros, see the queue(3) manual page.
   73  */
   74 
   75 /*
   76  * Include the definition of NULL only on NetBSD because sys/null.h
   77  * is not available elsewhere.  This conditional makes the header
   78  * portable and it can simply be dropped verbatim into any system.
   79  * The caveat is that on other systems some other header
   80  * must provide NULL before the macros can be used.
   81  */
   82 #ifdef __NetBSD__
   83 #include <sys/null.h>
   84 #endif
   85 
   86 #if defined(_KERNEL) && defined(DIAGNOSTIC)
   87 #define QUEUEDEBUG      1
   88 #endif
   89 
   90 #if defined(QUEUEDEBUG)
   91 # if defined(_KERNEL)
   92 #  define QUEUEDEBUG_ABORT(...) panic(__VA_ARGS__)
   93 # else
   94 #  include <err.h>
   95 #  define QUEUEDEBUG_ABORT(...) err(1, __VA_ARGS__)
   96 # endif
   97 #endif
   98 
   99 /*
  100  * Singly-linked List definitions.
  101  */
  102 #define SLIST_HEAD(name, type)                                          \
  103 struct name {                                                           \
  104         struct type *slh_first; /* first element */                     \
  105 }
  106 
  107 #define SLIST_HEAD_INITIALIZER(head)                                    \
  108         { NULL }
  109 
  110 #define SLIST_ENTRY(type)                                               \
  111 struct {                                                                \
  112         struct type *sle_next;  /* next element */                      \
  113 }
  114 
  115 /*
  116  * Singly-linked List access methods.
  117  */
  118 #define SLIST_FIRST(head)       ((head)->slh_first)
  119 #define SLIST_END(head)         NULL
  120 #define SLIST_EMPTY(head)       ((head)->slh_first == NULL)
  121 #define SLIST_NEXT(elm, field)  ((elm)->field.sle_next)
  122 
  123 #define SLIST_FOREACH(var, head, field)                                 \
  124         for((var) = (head)->slh_first;                                  \
  125             (var) != SLIST_END(head);                                   \
  126             (var) = (var)->field.sle_next)
  127 
  128 #define SLIST_FOREACH_SAFE(var, head, field, tvar)                      \
  129         for ((var) = SLIST_FIRST((head));                               \
  130             (var) != SLIST_END(head) &&                                 \
  131             ((tvar) = SLIST_NEXT((var), field), 1);                     \
  132             (var) = (tvar))
  133 
  134 /*
  135  * Singly-linked List functions.
  136  */
  137 #define SLIST_INIT(head) do {                                           \
  138         (head)->slh_first = SLIST_END(head);                            \
  139 } while (/*CONSTCOND*/0)
  140 
  141 #define SLIST_INSERT_AFTER(slistelm, elm, field) do {                   \
  142         (elm)->field.sle_next = (slistelm)->field.sle_next;             \
  143         (slistelm)->field.sle_next = (elm);                             \
  144 } while (/*CONSTCOND*/0)
  145 
  146 #define SLIST_INSERT_HEAD(head, elm, field) do {                        \
  147         (elm)->field.sle_next = (head)->slh_first;                      \
  148         (head)->slh_first = (elm);                                      \
  149 } while (/*CONSTCOND*/0)
  150 
  151 #define SLIST_REMOVE_AFTER(slistelm, field) do {                        \
  152         (slistelm)->field.sle_next =                                    \
  153             SLIST_NEXT(SLIST_NEXT((slistelm), field), field);           \
  154 } while (/*CONSTCOND*/0)
  155 
  156 #define SLIST_REMOVE_HEAD(head, field) do {                             \
  157         (head)->slh_first = (head)->slh_first->field.sle_next;          \
  158 } while (/*CONSTCOND*/0)
  159 
  160 #define SLIST_REMOVE(head, elm, type, field) do {                       \
  161         if ((head)->slh_first == (elm)) {                               \
  162                 SLIST_REMOVE_HEAD((head), field);                       \
  163         }                                                               \
  164         else {                                                          \
  165                 struct type *curelm = (head)->slh_first;                \
  166                 while(curelm->field.sle_next != (elm))                  \
  167                         curelm = curelm->field.sle_next;                \
  168                 curelm->field.sle_next =                                \
  169                     curelm->field.sle_next->field.sle_next;             \
  170         }                                                               \
  171 } while (/*CONSTCOND*/0)
  172 
  173 
  174 /*
  175  * List definitions.
  176  */
  177 #define LIST_HEAD(name, type)                                           \
  178 struct name {                                                           \
  179         struct type *lh_first;  /* first element */                     \
  180 }
  181 
  182 #define LIST_HEAD_INITIALIZER(head)                                     \
  183         { NULL }
  184 
  185 #define LIST_ENTRY(type)                                                \
  186 struct {                                                                \
  187         struct type *le_next;   /* next element */                      \
  188         struct type **le_prev;  /* address of previous next element */  \
  189 }
  190 
  191 /*
  192  * List access methods.
  193  */
  194 #define LIST_FIRST(head)                ((head)->lh_first)
  195 #define LIST_END(head)                  NULL
  196 #define LIST_EMPTY(head)                ((head)->lh_first == LIST_END(head))
  197 #define LIST_NEXT(elm, field)           ((elm)->field.le_next)
  198 
  199 #define LIST_FOREACH(var, head, field)                                  \
  200         for ((var) = ((head)->lh_first);                                \
  201             (var) != LIST_END(head);                                    \
  202             (var) = ((var)->field.le_next))
  203 
  204 #define LIST_FOREACH_SAFE(var, head, field, tvar)                       \
  205         for ((var) = LIST_FIRST((head));                                \
  206             (var) != LIST_END(head) &&                                  \
  207             ((tvar) = LIST_NEXT((var), field), 1);                      \
  208             (var) = (tvar))
  209 
  210 #define LIST_MOVE(head1, head2, field) do {                             \
  211         LIST_INIT((head2));                                             \
  212         if (!LIST_EMPTY((head1))) {                                     \
  213                 (head2)->lh_first = (head1)->lh_first;                  \
  214                 (head2)->lh_first->field.le_prev = &(head2)->lh_first;  \
  215                 LIST_INIT((head1));                                     \
  216         }                                                               \
  217 } while (/*CONSTCOND*/0)
  218 
  219 /*
  220  * List functions.
  221  */
  222 #if defined(QUEUEDEBUG)
  223 #define QUEUEDEBUG_LIST_INSERT_HEAD(head, elm, field)                   \
  224         if ((head)->lh_first &&                                         \
  225             (head)->lh_first->field.le_prev != &(head)->lh_first)       \
  226                 QUEUEDEBUG_ABORT("LIST_INSERT_HEAD %p %s:%d", (head),   \
  227                     __FILE__, __LINE__);
  228 #define QUEUEDEBUG_LIST_OP(elm, field)                                  \
  229         if ((elm)->field.le_next &&                                     \
  230             (elm)->field.le_next->field.le_prev !=                      \
  231             &(elm)->field.le_next)                                      \
  232                 QUEUEDEBUG_ABORT("LIST_* forw %p %s:%d", (elm),         \
  233                     __FILE__, __LINE__);                                \
  234         if (*(elm)->field.le_prev != (elm))                             \
  235                 QUEUEDEBUG_ABORT("LIST_* back %p %s:%d", (elm),         \
  236                     __FILE__, __LINE__);
  237 #define QUEUEDEBUG_LIST_POSTREMOVE(elm, field)                          \
  238         (elm)->field.le_next = (void *)1L;                              \
  239         (elm)->field.le_prev = (void *)1L;
  240 #else
  241 #define QUEUEDEBUG_LIST_INSERT_HEAD(head, elm, field)
  242 #define QUEUEDEBUG_LIST_OP(elm, field)
  243 #define QUEUEDEBUG_LIST_POSTREMOVE(elm, field)
  244 #endif
  245 
  246 #define LIST_INIT(head) do {                                            \
  247         (head)->lh_first = LIST_END(head);                              \
  248 } while (/*CONSTCOND*/0)
  249 
  250 #define LIST_INSERT_AFTER(listelm, elm, field) do {                     \
  251         QUEUEDEBUG_LIST_OP((listelm), field)                            \
  252         if (((elm)->field.le_next = (listelm)->field.le_next) !=        \
  253             LIST_END(head))                                             \
  254                 (listelm)->field.le_next->field.le_prev =               \
  255                     &(elm)->field.le_next;                              \
  256         (listelm)->field.le_next = (elm);                               \
  257         (elm)->field.le_prev = &(listelm)->field.le_next;               \
  258 } while (/*CONSTCOND*/0)
  259 
  260 #define LIST_INSERT_BEFORE(listelm, elm, field) do {                    \
  261         QUEUEDEBUG_LIST_OP((listelm), field)                            \
  262         (elm)->field.le_prev = (listelm)->field.le_prev;                \
  263         (elm)->field.le_next = (listelm);                               \
  264         *(listelm)->field.le_prev = (elm);                              \
  265         (listelm)->field.le_prev = &(elm)->field.le_next;               \
  266 } while (/*CONSTCOND*/0)
  267 
  268 #define LIST_INSERT_HEAD(head, elm, field) do {                         \
  269         QUEUEDEBUG_LIST_INSERT_HEAD((head), (elm), field)               \
  270         if (((elm)->field.le_next = (head)->lh_first) != LIST_END(head))\
  271                 (head)->lh_first->field.le_prev = &(elm)->field.le_next;\
  272         (head)->lh_first = (elm);                                       \
  273         (elm)->field.le_prev = &(head)->lh_first;                       \
  274 } while (/*CONSTCOND*/0)
  275 
  276 #define LIST_REMOVE(elm, field) do {                                    \
  277         QUEUEDEBUG_LIST_OP((elm), field)                                \
  278         if ((elm)->field.le_next != NULL)                               \
  279                 (elm)->field.le_next->field.le_prev =                   \
  280                     (elm)->field.le_prev;                               \
  281         *(elm)->field.le_prev = (elm)->field.le_next;                   \
  282         QUEUEDEBUG_LIST_POSTREMOVE((elm), field)                        \
  283 } while (/*CONSTCOND*/0)
  284 
  285 #define LIST_REPLACE(elm, elm2, field) do {                             \
  286         if (((elm2)->field.le_next = (elm)->field.le_next) != NULL)     \
  287                 (elm2)->field.le_next->field.le_prev =                  \
  288                     &(elm2)->field.le_next;                             \
  289         (elm2)->field.le_prev = (elm)->field.le_prev;                   \
  290         *(elm2)->field.le_prev = (elm2);                                \
  291         QUEUEDEBUG_LIST_POSTREMOVE((elm), field)                        \
  292 } while (/*CONSTCOND*/0)
  293 
  294 /*
  295  * Simple queue definitions.
  296  */
  297 #define SIMPLEQ_HEAD(name, type)                                        \
  298 struct name {                                                           \
  299         struct type *sqh_first; /* first element */                     \
  300         struct type **sqh_last; /* addr of last next element */         \
  301 }
  302 
  303 #define SIMPLEQ_HEAD_INITIALIZER(head)                                  \
  304         { NULL, &(head).sqh_first }
  305 
  306 #define SIMPLEQ_ENTRY(type)                                             \
  307 struct {                                                                \
  308         struct type *sqe_next;  /* next element */                      \
  309 }
  310 
  311 /*
  312  * Simple queue access methods.
  313  */
  314 #define SIMPLEQ_FIRST(head)             ((head)->sqh_first)
  315 #define SIMPLEQ_END(head)               NULL
  316 #define SIMPLEQ_EMPTY(head)             ((head)->sqh_first == SIMPLEQ_END(head))
  317 #define SIMPLEQ_NEXT(elm, field)        ((elm)->field.sqe_next)
  318 
  319 #define SIMPLEQ_FOREACH(var, head, field)                               \
  320         for ((var) = ((head)->sqh_first);                               \
  321             (var) != SIMPLEQ_END(head);                                 \
  322             (var) = ((var)->field.sqe_next))
  323 
  324 #define SIMPLEQ_FOREACH_SAFE(var, head, field, next)                    \
  325         for ((var) = ((head)->sqh_first);                               \
  326             (var) != SIMPLEQ_END(head) &&                               \
  327             ((next = ((var)->field.sqe_next)), 1);                      \
  328             (var) = (next))
  329 
  330 /*
  331  * Simple queue functions.
  332  */
  333 #define SIMPLEQ_INIT(head) do {                                         \
  334         (head)->sqh_first = NULL;                                       \
  335         (head)->sqh_last = &(head)->sqh_first;                          \
  336 } while (/*CONSTCOND*/0)
  337 
  338 #define SIMPLEQ_INSERT_HEAD(head, elm, field) do {                      \
  339         if (((elm)->field.sqe_next = (head)->sqh_first) == NULL)        \
  340                 (head)->sqh_last = &(elm)->field.sqe_next;              \
  341         (head)->sqh_first = (elm);                                      \
  342 } while (/*CONSTCOND*/0)
  343 
  344 #define SIMPLEQ_INSERT_TAIL(head, elm, field) do {                      \
  345         (elm)->field.sqe_next = NULL;                                   \
  346         *(head)->sqh_last = (elm);                                      \
  347         (head)->sqh_last = &(elm)->field.sqe_next;                      \
  348 } while (/*CONSTCOND*/0)
  349 
  350 #define SIMPLEQ_INSERT_AFTER(head, listelm, elm, field) do {            \
  351         if (((elm)->field.sqe_next = (listelm)->field.sqe_next) == NULL)\
  352                 (head)->sqh_last = &(elm)->field.sqe_next;              \
  353         (listelm)->field.sqe_next = (elm);                              \
  354 } while (/*CONSTCOND*/0)
  355 
  356 #define SIMPLEQ_REMOVE_HEAD(head, field) do {                           \
  357         if (((head)->sqh_first = (head)->sqh_first->field.sqe_next) == NULL) \
  358                 (head)->sqh_last = &(head)->sqh_first;                  \
  359 } while (/*CONSTCOND*/0)
  360 
  361 #define SIMPLEQ_REMOVE_AFTER(head, elm, field) do {                     \
  362         if (((elm)->field.sqe_next = (elm)->field.sqe_next->field.sqe_next) \
  363             == NULL)                                                    \
  364                 (head)->sqh_last = &(elm)->field.sqe_next;              \
  365 } while (/*CONSTCOND*/0)
  366 
  367 #define SIMPLEQ_REMOVE(head, elm, type, field) do {                     \
  368         if ((head)->sqh_first == (elm)) {                               \
  369                 SIMPLEQ_REMOVE_HEAD((head), field);                     \
  370         } else {                                                        \
  371                 struct type *curelm = (head)->sqh_first;                \
  372                 while (curelm->field.sqe_next != (elm))                 \
  373                         curelm = curelm->field.sqe_next;                \
  374                 if ((curelm->field.sqe_next =                           \
  375                         curelm->field.sqe_next->field.sqe_next) == NULL) \
  376                             (head)->sqh_last = &(curelm)->field.sqe_next; \
  377         }                                                               \
  378 } while (/*CONSTCOND*/0)
  379 
  380 #define SIMPLEQ_CONCAT(head1, head2) do {                               \
  381         if (!SIMPLEQ_EMPTY((head2))) {                                  \
  382                 *(head1)->sqh_last = (head2)->sqh_first;                \
  383                 (head1)->sqh_last = (head2)->sqh_last;          \
  384                 SIMPLEQ_INIT((head2));                                  \
  385         }                                                               \
  386 } while (/*CONSTCOND*/0)
  387 
  388 #define SIMPLEQ_LAST(head, type, field)                                 \
  389         (SIMPLEQ_EMPTY((head)) ?                                                \
  390                 NULL :                                                  \
  391                 ((struct type *)(void *)                                \
  392                 ((char *)((head)->sqh_last) - offsetof(struct type, field))))
  393 
  394 /*
  395  * Tail queue definitions.
  396  */
  397 #define _TAILQ_HEAD(name, type, qual)                                   \
  398 struct name {                                                           \
  399         qual type *tqh_first;           /* first element */             \
  400         qual type *qual *tqh_last;      /* addr of last next element */ \
  401 }
  402 #define TAILQ_HEAD(name, type)  _TAILQ_HEAD(name, struct type,)
  403 
  404 #define TAILQ_HEAD_INITIALIZER(head)                                    \
  405         { TAILQ_END(head), &(head).tqh_first }
  406 
  407 #define _TAILQ_ENTRY(type, qual)                                        \
  408 struct {                                                                \
  409         qual type *tqe_next;            /* next element */              \
  410         qual type *qual *tqe_prev;      /* address of previous next element */\
  411 }
  412 #define TAILQ_ENTRY(type)       _TAILQ_ENTRY(struct type,)
  413 
  414 /*
  415  * Tail queue access methods.
  416  */
  417 #define TAILQ_FIRST(head)               ((head)->tqh_first)
  418 #define TAILQ_END(head)                 (NULL)
  419 #define TAILQ_NEXT(elm, field)          ((elm)->field.tqe_next)
  420 #define TAILQ_LAST(head, headname) \
  421         (*(((struct headname *)(void *)((head)->tqh_last))->tqh_last))
  422 #define TAILQ_PREV(elm, headname, field) \
  423         (*(((struct headname *)(void *)((elm)->field.tqe_prev))->tqh_last))
  424 #define TAILQ_EMPTY(head)               (TAILQ_FIRST(head) == TAILQ_END(head))
  425 
  426 
  427 #define TAILQ_FOREACH(var, head, field)                                 \
  428         for ((var) = ((head)->tqh_first);                               \
  429             (var) != TAILQ_END(head);                                   \
  430             (var) = ((var)->field.tqe_next))
  431 
  432 #define TAILQ_FOREACH_SAFE(var, head, field, next)                      \
  433         for ((var) = ((head)->tqh_first);                               \
  434             (var) != TAILQ_END(head) &&                                 \
  435             ((next) = TAILQ_NEXT(var, field), 1); (var) = (next))
  436 
  437 #define TAILQ_FOREACH_REVERSE(var, head, headname, field)               \
  438         for ((var) = TAILQ_LAST((head), headname);                      \
  439             (var) != TAILQ_END(head);                                   \
  440             (var) = TAILQ_PREV((var), headname, field))
  441 
  442 #define TAILQ_FOREACH_REVERSE_SAFE(var, head, headname, field, prev)    \
  443         for ((var) = TAILQ_LAST((head), headname);                      \
  444             (var) != TAILQ_END(head) &&                                 \
  445             ((prev) = TAILQ_PREV((var), headname, field), 1); (var) = (prev))
  446 
  447 /*
  448  * Tail queue functions.
  449  */
  450 #if defined(QUEUEDEBUG)
  451 #define QUEUEDEBUG_TAILQ_INSERT_HEAD(head, elm, field)                  \
  452         if ((head)->tqh_first &&                                        \
  453             (head)->tqh_first->field.tqe_prev != &(head)->tqh_first)    \
  454                 QUEUEDEBUG_ABORT("TAILQ_INSERT_HEAD %p %s:%d", (head),  \
  455                     __FILE__, __LINE__);
  456 #define QUEUEDEBUG_TAILQ_INSERT_TAIL(head, elm, field)                  \
  457         if (*(head)->tqh_last != NULL)                                  \
  458                 QUEUEDEBUG_ABORT("TAILQ_INSERT_TAIL %p %s:%d", (head),  \
  459                     __FILE__, __LINE__);
  460 #define QUEUEDEBUG_TAILQ_OP(elm, field)                                 \
  461         if ((elm)->field.tqe_next &&                                    \
  462             (elm)->field.tqe_next->field.tqe_prev !=                    \
  463             &(elm)->field.tqe_next)                                     \
  464                 QUEUEDEBUG_ABORT("TAILQ_* forw %p %s:%d", (elm),        \
  465                     __FILE__, __LINE__);                                \
  466         if (*(elm)->field.tqe_prev != (elm))                            \
  467                 QUEUEDEBUG_ABORT("TAILQ_* back %p %s:%d", (elm),        \
  468                     __FILE__, __LINE__);
  469 #define QUEUEDEBUG_TAILQ_PREREMOVE(head, elm, field)                    \
  470         if ((elm)->field.tqe_next == NULL &&                            \
  471             (head)->tqh_last != &(elm)->field.tqe_next)                 \
  472                 QUEUEDEBUG_ABORT("TAILQ_PREREMOVE head %p elm %p %s:%d",\
  473                     (head), (elm), __FILE__, __LINE__);
  474 #define QUEUEDEBUG_TAILQ_POSTREMOVE(elm, field)                         \
  475         (elm)->field.tqe_next = (void *)1L;                             \
  476         (elm)->field.tqe_prev = (void *)1L;
  477 #else
  478 #define QUEUEDEBUG_TAILQ_INSERT_HEAD(head, elm, field)
  479 #define QUEUEDEBUG_TAILQ_INSERT_TAIL(head, elm, field)
  480 #define QUEUEDEBUG_TAILQ_OP(elm, field)
  481 #define QUEUEDEBUG_TAILQ_PREREMOVE(head, elm, field)
  482 #define QUEUEDEBUG_TAILQ_POSTREMOVE(elm, field)
  483 #endif
  484 
  485 #define TAILQ_INIT(head) do {                                           \
  486         (head)->tqh_first = TAILQ_END(head);                            \
  487         (head)->tqh_last = &(head)->tqh_first;                          \
  488 } while (/*CONSTCOND*/0)
  489 
  490 #define TAILQ_INSERT_HEAD(head, elm, field) do {                        \
  491         QUEUEDEBUG_TAILQ_INSERT_HEAD((head), (elm), field)              \
  492         if (((elm)->field.tqe_next = (head)->tqh_first) != TAILQ_END(head))\
  493                 (head)->tqh_first->field.tqe_prev =                     \
  494                     &(elm)->field.tqe_next;                             \
  495         else                                                            \
  496                 (head)->tqh_last = &(elm)->field.tqe_next;              \
  497         (head)->tqh_first = (elm);                                      \
  498         (elm)->field.tqe_prev = &(head)->tqh_first;                     \
  499 } while (/*CONSTCOND*/0)
  500 
  501 #define TAILQ_INSERT_TAIL(head, elm, field) do {                        \
  502         QUEUEDEBUG_TAILQ_INSERT_TAIL((head), (elm), field)              \
  503         (elm)->field.tqe_next = TAILQ_END(head);                        \
  504         (elm)->field.tqe_prev = (head)->tqh_last;                       \
  505         *(head)->tqh_last = (elm);                                      \
  506         (head)->tqh_last = &(elm)->field.tqe_next;                      \
  507 } while (/*CONSTCOND*/0)
  508 
  509 #define TAILQ_INSERT_AFTER(head, listelm, elm, field) do {              \
  510         QUEUEDEBUG_TAILQ_OP((listelm), field)                           \
  511         if (((elm)->field.tqe_next = (listelm)->field.tqe_next) !=      \
  512             TAILQ_END(head))                                            \
  513                 (elm)->field.tqe_next->field.tqe_prev =                 \
  514                     &(elm)->field.tqe_next;                             \
  515         else                                                            \
  516                 (head)->tqh_last = &(elm)->field.tqe_next;              \
  517         (listelm)->field.tqe_next = (elm);                              \
  518         (elm)->field.tqe_prev = &(listelm)->field.tqe_next;             \
  519 } while (/*CONSTCOND*/0)
  520 
  521 #define TAILQ_INSERT_BEFORE(listelm, elm, field) do {                   \
  522         QUEUEDEBUG_TAILQ_OP((listelm), field)                           \
  523         (elm)->field.tqe_prev = (listelm)->field.tqe_prev;              \
  524         (elm)->field.tqe_next = (listelm);                              \
  525         *(listelm)->field.tqe_prev = (elm);                             \
  526         (listelm)->field.tqe_prev = &(elm)->field.tqe_next;             \
  527 } while (/*CONSTCOND*/0)
  528 
  529 #define TAILQ_REMOVE(head, elm, field) do {                             \
  530         QUEUEDEBUG_TAILQ_PREREMOVE((head), (elm), field)                \
  531         QUEUEDEBUG_TAILQ_OP((elm), field)                               \
  532         if (((elm)->field.tqe_next) != TAILQ_END(head))                 \
  533                 (elm)->field.tqe_next->field.tqe_prev =                 \
  534                     (elm)->field.tqe_prev;                              \
  535         else                                                            \
  536                 (head)->tqh_last = (elm)->field.tqe_prev;               \
  537         *(elm)->field.tqe_prev = (elm)->field.tqe_next;                 \
  538         QUEUEDEBUG_TAILQ_POSTREMOVE((elm), field);                      \
  539 } while (/*CONSTCOND*/0)
  540 
  541 #define TAILQ_REPLACE(head, elm, elm2, field) do {                      \
  542         if (((elm2)->field.tqe_next = (elm)->field.tqe_next) !=         \
  543             TAILQ_END(head))                                            \
  544                 (elm2)->field.tqe_next->field.tqe_prev =                \
  545                     &(elm2)->field.tqe_next;                            \
  546         else                                                            \
  547                 (head)->tqh_last = &(elm2)->field.tqe_next;             \
  548         (elm2)->field.tqe_prev = (elm)->field.tqe_prev;                 \
  549         *(elm2)->field.tqe_prev = (elm2);                               \
  550         QUEUEDEBUG_TAILQ_POSTREMOVE((elm), field);                      \
  551 } while (/*CONSTCOND*/0)
  552 
  553 #define TAILQ_CONCAT(head1, head2, field) do {                          \
  554         if (!TAILQ_EMPTY(head2)) {                                      \
  555                 *(head1)->tqh_last = (head2)->tqh_first;                \
  556                 (head2)->tqh_first->field.tqe_prev = (head1)->tqh_last; \
  557                 (head1)->tqh_last = (head2)->tqh_last;                  \
  558                 TAILQ_INIT((head2));                                    \
  559         }                                                               \
  560 } while (/*CONSTCOND*/0)
  561 
  562 /*
  563  * Singly-linked Tail queue declarations.
  564  */
  565 #define STAILQ_HEAD(name, type)                                         \
  566 struct name {                                                           \
  567         struct type *stqh_first;        /* first element */             \
  568         struct type **stqh_last;        /* addr of last next element */ \
  569 }
  570 
  571 #define STAILQ_HEAD_INITIALIZER(head)                                   \
  572         { NULL, &(head).stqh_first }
  573 
  574 #define STAILQ_ENTRY(type)                                              \
  575 struct {                                                                \
  576         struct type *stqe_next; /* next element */                      \
  577 }
  578 
  579 /*
  580  * Singly-linked Tail queue access methods.
  581  */
  582 #define STAILQ_FIRST(head)      ((head)->stqh_first)
  583 #define STAILQ_END(head)        NULL
  584 #define STAILQ_NEXT(elm, field) ((elm)->field.stqe_next)
  585 #define STAILQ_EMPTY(head)      (STAILQ_FIRST(head) == STAILQ_END(head))
  586 
  587 /*
  588  * Singly-linked Tail queue functions.
  589  */
  590 #define STAILQ_INIT(head) do {                                          \
  591         (head)->stqh_first = NULL;                                      \
  592         (head)->stqh_last = &(head)->stqh_first;                                \
  593 } while (/*CONSTCOND*/0)
  594 
  595 #define STAILQ_INSERT_HEAD(head, elm, field) do {                       \
  596         if (((elm)->field.stqe_next = (head)->stqh_first) == NULL)      \
  597                 (head)->stqh_last = &(elm)->field.stqe_next;            \
  598         (head)->stqh_first = (elm);                                     \
  599 } while (/*CONSTCOND*/0)
  600 
  601 #define STAILQ_INSERT_TAIL(head, elm, field) do {                       \
  602         (elm)->field.stqe_next = NULL;                                  \
  603         *(head)->stqh_last = (elm);                                     \
  604         (head)->stqh_last = &(elm)->field.stqe_next;                    \
  605 } while (/*CONSTCOND*/0)
  606 
  607 #define STAILQ_INSERT_AFTER(head, listelm, elm, field) do {             \
  608         if (((elm)->field.stqe_next = (listelm)->field.stqe_next) == NULL)\
  609                 (head)->stqh_last = &(elm)->field.stqe_next;            \
  610         (listelm)->field.stqe_next = (elm);                             \
  611 } while (/*CONSTCOND*/0)
  612 
  613 #define STAILQ_REMOVE_HEAD(head, field) do {                            \
  614         if (((head)->stqh_first = (head)->stqh_first->field.stqe_next) == NULL) \
  615                 (head)->stqh_last = &(head)->stqh_first;                        \
  616 } while (/*CONSTCOND*/0)
  617 
  618 #define STAILQ_REMOVE(head, elm, type, field) do {                      \
  619         if ((head)->stqh_first == (elm)) {                              \
  620                 STAILQ_REMOVE_HEAD((head), field);                      \
  621         } else {                                                        \
  622                 struct type *curelm = (head)->stqh_first;               \
  623                 while (curelm->field.stqe_next != (elm))                        \
  624                         curelm = curelm->field.stqe_next;               \
  625                 if ((curelm->field.stqe_next =                          \
  626                         curelm->field.stqe_next->field.stqe_next) == NULL) \
  627                             (head)->stqh_last = &(curelm)->field.stqe_next; \
  628         }                                                               \
  629 } while (/*CONSTCOND*/0)
  630 
  631 #define STAILQ_FOREACH(var, head, field)                                \
  632         for ((var) = ((head)->stqh_first);                              \
  633                 (var);                                                  \
  634                 (var) = ((var)->field.stqe_next))
  635 
  636 #define STAILQ_FOREACH_SAFE(var, head, field, tvar)                     \
  637         for ((var) = STAILQ_FIRST((head));                              \
  638             (var) && ((tvar) = STAILQ_NEXT((var), field), 1);           \
  639             (var) = (tvar))
  640 
  641 #define STAILQ_CONCAT(head1, head2) do {                                \
  642         if (!STAILQ_EMPTY((head2))) {                                   \
  643                 *(head1)->stqh_last = (head2)->stqh_first;              \
  644                 (head1)->stqh_last = (head2)->stqh_last;                \
  645                 STAILQ_INIT((head2));                                   \
  646         }                                                               \
  647 } while (/*CONSTCOND*/0)
  648 
  649 #define STAILQ_LAST(head, type, field)                                  \
  650         (STAILQ_EMPTY((head)) ?                                         \
  651                 NULL :                                                  \
  652                 ((struct type *)(void *)                                \
  653                 ((char *)((head)->stqh_last) - offsetof(struct type, field))))
  654 
  655 #endif  /* !_SYS_QUEUE_H_ */

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