bsdqueue.h

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00001 /*      $OpenBSD: queue.h,v 1.31 2005/11/25 08:06:25 otto Exp $ */
00002 /*      $NetBSD: queue.h,v 1.11 1996/05/16 05:17:14 mycroft Exp $       */
00003 
00004 /*
00005  * Copyright (c) 1991, 1993
00006  *      The Regents of the University of California.  All rights reserved.
00007  *
00008  * Redistribution and use in source and binary forms, with or without
00009  * modification, are permitted provided that the following conditions
00010  * are met:
00011  * 1. Redistributions of source code must retain the above copyright
00012  *    notice, this list of conditions and the following disclaimer.
00013  * 2. Redistributions in binary form must reproduce the above copyright
00014  *    notice, this list of conditions and the following disclaimer in the
00015  *    documentation and/or other materials provided with the distribution.
00016  * 3. Neither the name of the University nor the names of its contributors
00017  *    may be used to endorse or promote products derived from this software
00018  *    without specific prior written permission.
00019  *
00020  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
00021  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
00022  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
00023  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
00024  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
00025  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
00026  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
00027  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
00028  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
00029  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
00030  * SUCH DAMAGE.
00031  *
00032  *      @(#)queue.h     8.5 (Berkeley) 8/20/94
00033  */
00034 
00035 #ifndef _SYS_QUEUE_H_
00036 #define _SYS_QUEUE_H_
00037 
00038 /*
00039  * This file defines five types of data structures: singly-linked lists, 
00040  * lists, simple queues, tail queues, and circular queues.
00041  *
00042  *
00043  * A singly-linked list is headed by a single forward pointer. The elements
00044  * are singly linked for minimum space and pointer manipulation overhead at
00045  * the expense of O(n) removal for arbitrary elements. New elements can be
00046  * added to the list after an existing element or at the head of the list.
00047  * Elements being removed from the head of the list should use the explicit
00048  * macro for this purpose for optimum efficiency. A singly-linked list may
00049  * only be traversed in the forward direction.  Singly-linked lists are ideal
00050  * for applications with large datasets and few or no removals or for
00051  * implementing a LIFO queue.
00052  *
00053  * A list is headed by a single forward pointer (or an array of forward
00054  * pointers for a hash table header). The elements are doubly linked
00055  * so that an arbitrary element can be removed without a need to
00056  * traverse the list. New elements can be added to the list before
00057  * or after an existing element or at the head of the list. A list
00058  * may only be traversed in the forward direction.
00059  *
00060  * A simple queue is headed by a pair of pointers, one the head of the
00061  * list and the other to the tail of the list. The elements are singly
00062  * linked to save space, so elements can only be removed from the
00063  * head of the list. New elements can be added to the list before or after
00064  * an existing element, at the head of the list, or at the end of the
00065  * list. A simple queue may only be traversed in the forward direction.
00066  *
00067  * A tail queue is headed by a pair of pointers, one to the head of the
00068  * list and the other to the tail of the list. The elements are doubly
00069  * linked so that an arbitrary element can be removed without a need to
00070  * traverse the list. New elements can be added to the list before or
00071  * after an existing element, at the head of the list, or at the end of
00072  * the list. A tail queue may be traversed in either direction.
00073  *
00074  * A circle queue is headed by a pair of pointers, one to the head of the
00075  * list and the other to the tail of the list. The elements are doubly
00076  * linked so that an arbitrary element can be removed without a need to
00077  * traverse the list. New elements can be added to the list before or after
00078  * an existing element, at the head of the list, or at the end of the list.
00079  * A circle queue may be traversed in either direction, but has a more
00080  * complex end of list detection.
00081  *
00082  * For details on the use of these macros, see the queue(3) manual page.
00083  */
00084 
00085 #ifdef QUEUE_MACRO_DEBUG
00086 #define _Q_INVALIDATE(a) (a) = ((void *)-1)
00087 #else
00088 #define _Q_INVALIDATE(a)
00089 #endif
00090 
00091 /*
00092  * Singly-linked List definitions.
00093  */
00094 #define SLIST_HEAD(name, type)                                          \
00095 struct name {                                                           \
00096         struct type *slh_first; /* first element */                     \
00097 }
00098  
00099 #define SLIST_HEAD_INITIALIZER(head)                                    \
00100         { NULL }
00101 
00102 #ifdef SLIST_ENTRY
00103 #undef SLIST_ENTRY
00104 #endif
00105 
00106 #define SLIST_ENTRY(type)                                               \
00107 struct {                                                                \
00108         struct type *sle_next;  /* next element */                      \
00109 }
00110  
00111 /*
00112  * Singly-linked List access methods.
00113  */
00114 #define SLIST_FIRST(head)       ((head)->slh_first)
00115 #define SLIST_END(head)         NULL
00116 #define SLIST_EMPTY(head)       (SLIST_FIRST(head) == SLIST_END(head))
00117 #define SLIST_NEXT(elm, field)  ((elm)->field.sle_next)
00118 
00119 #define SLIST_FOREACH(var, head, field)                                 \
00120         for((var) = SLIST_FIRST(head);                                  \
00121             (var) != SLIST_END(head);                                   \
00122             (var) = SLIST_NEXT(var, field))
00123 
00124 #define SLIST_FOREACH_PREVPTR(var, varp, head, field)                   \
00125         for ((varp) = &SLIST_FIRST((head));                             \
00126             ((var) = *(varp)) != SLIST_END(head);                       \
00127             (varp) = &SLIST_NEXT((var), field))
00128 
00129 /*
00130  * Singly-linked List functions.
00131  */
00132 #define SLIST_INIT(head) {                                              \
00133         SLIST_FIRST(head) = SLIST_END(head);                            \
00134 }
00135 
00136 #define SLIST_INSERT_AFTER(slistelm, elm, field) do {                   \
00137         (elm)->field.sle_next = (slistelm)->field.sle_next;             \
00138         (slistelm)->field.sle_next = (elm);                             \
00139 } while (0)
00140 
00141 #define SLIST_INSERT_HEAD(head, elm, field) do {                        \
00142         (elm)->field.sle_next = (head)->slh_first;                      \
00143         (head)->slh_first = (elm);                                      \
00144 } while (0)
00145 
00146 #define SLIST_REMOVE_NEXT(head, elm, field) do {                        \
00147         (elm)->field.sle_next = (elm)->field.sle_next->field.sle_next;  \
00148 } while (0)
00149 
00150 #define SLIST_REMOVE_HEAD(head, field) do {                             \
00151         (head)->slh_first = (head)->slh_first->field.sle_next;          \
00152 } while (0)
00153 
00154 #define SLIST_REMOVE(head, elm, type, field) do {                       \
00155         if ((head)->slh_first == (elm)) {                               \
00156                 SLIST_REMOVE_HEAD((head), field);                       \
00157         } else {                                                        \
00158                 struct type *curelm = (head)->slh_first;                \
00159                                                                         \
00160                 while (curelm->field.sle_next != (elm))                 \
00161                         curelm = curelm->field.sle_next;                \
00162                 curelm->field.sle_next =                                \
00163                     curelm->field.sle_next->field.sle_next;             \
00164                 _Q_INVALIDATE((elm)->field.sle_next);                   \
00165         }                                                               \
00166 } while (0)
00167 
00168 /*
00169  * List definitions.
00170  */
00171 #define LIST_HEAD(name, type)                                           \
00172 struct name {                                                           \
00173         struct type *lh_first;  /* first element */                     \
00174 }
00175 
00176 #define LIST_HEAD_INITIALIZER(head)                                     \
00177         { NULL }
00178 
00179 #define LIST_ENTRY(type)                                                \
00180 struct {                                                                \
00181         struct type *le_next;   /* next element */                      \
00182         struct type **le_prev;  /* address of previous next element */  \
00183 }
00184 
00185 /*
00186  * List access methods
00187  */
00188 #define LIST_FIRST(head)                ((head)->lh_first)
00189 #define LIST_END(head)                  NULL
00190 #define LIST_EMPTY(head)                (LIST_FIRST(head) == LIST_END(head))
00191 #define LIST_NEXT(elm, field)           ((elm)->field.le_next)
00192 
00193 #define LIST_FOREACH(var, head, field)                                  \
00194         for((var) = LIST_FIRST(head);                                   \
00195             (var)!= LIST_END(head);                                     \
00196             (var) = LIST_NEXT(var, field))
00197 
00198 /*
00199  * List functions.
00200  */
00201 #define LIST_INIT(head) do {                                            \
00202         LIST_FIRST(head) = LIST_END(head);                              \
00203 } while (0)
00204 
00205 #define LIST_INSERT_AFTER(listelm, elm, field) do {                     \
00206         if (((elm)->field.le_next = (listelm)->field.le_next) != NULL)  \
00207                 (listelm)->field.le_next->field.le_prev =               \
00208                     &(elm)->field.le_next;                              \
00209         (listelm)->field.le_next = (elm);                               \
00210         (elm)->field.le_prev = &(listelm)->field.le_next;               \
00211 } while (0)
00212 
00213 #define LIST_INSERT_BEFORE(listelm, elm, field) do {                    \
00214         (elm)->field.le_prev = (listelm)->field.le_prev;                \
00215         (elm)->field.le_next = (listelm);                               \
00216         *(listelm)->field.le_prev = (elm);                              \
00217         (listelm)->field.le_prev = &(elm)->field.le_next;               \
00218 } while (0)
00219 
00220 #define LIST_INSERT_HEAD(head, elm, field) do {                         \
00221         if (((elm)->field.le_next = (head)->lh_first) != NULL)          \
00222                 (head)->lh_first->field.le_prev = &(elm)->field.le_next;\
00223         (head)->lh_first = (elm);                                       \
00224         (elm)->field.le_prev = &(head)->lh_first;                       \
00225 } while (0)
00226 
00227 #define LIST_REMOVE(elm, field) do {                                    \
00228         if ((elm)->field.le_next != NULL)                               \
00229                 (elm)->field.le_next->field.le_prev =                   \
00230                     (elm)->field.le_prev;                               \
00231         *(elm)->field.le_prev = (elm)->field.le_next;                   \
00232         _Q_INVALIDATE((elm)->field.le_prev);                            \
00233         _Q_INVALIDATE((elm)->field.le_next);                            \
00234 } while (0)
00235 
00236 #define LIST_REPLACE(elm, elm2, field) do {                             \
00237         if (((elm2)->field.le_next = (elm)->field.le_next) != NULL)     \
00238                 (elm2)->field.le_next->field.le_prev =                  \
00239                     &(elm2)->field.le_next;                             \
00240         (elm2)->field.le_prev = (elm)->field.le_prev;                   \
00241         *(elm2)->field.le_prev = (elm2);                                \
00242         _Q_INVALIDATE((elm)->field.le_prev);                            \
00243         _Q_INVALIDATE((elm)->field.le_next);                            \
00244 } while (0)
00245 
00246 /*
00247  * Simple queue definitions.
00248  */
00249 #define SIMPLEQ_HEAD(name, type)                                        \
00250 struct name {                                                           \
00251         struct type *sqh_first; /* first element */                     \
00252         struct type **sqh_last; /* addr of last next element */         \
00253 }
00254 
00255 #define SIMPLEQ_HEAD_INITIALIZER(head)                                  \
00256         { NULL, &(head).sqh_first }
00257 
00258 #define SIMPLEQ_ENTRY(type)                                             \
00259 struct {                                                                \
00260         struct type *sqe_next;  /* next element */                      \
00261 }
00262 
00263 /*
00264  * Simple queue access methods.
00265  */
00266 #define SIMPLEQ_FIRST(head)         ((head)->sqh_first)
00267 #define SIMPLEQ_END(head)           NULL
00268 #define SIMPLEQ_EMPTY(head)         (SIMPLEQ_FIRST(head) == SIMPLEQ_END(head))
00269 #define SIMPLEQ_NEXT(elm, field)    ((elm)->field.sqe_next)
00270 
00271 #define SIMPLEQ_FOREACH(var, head, field)                               \
00272         for((var) = SIMPLEQ_FIRST(head);                                \
00273             (var) != SIMPLEQ_END(head);                                 \
00274             (var) = SIMPLEQ_NEXT(var, field))
00275 
00276 /*
00277  * Simple queue functions.
00278  */
00279 #define SIMPLEQ_INIT(head) do {                                         \
00280         (head)->sqh_first = NULL;                                       \
00281         (head)->sqh_last = &(head)->sqh_first;                          \
00282 } while (0)
00283 
00284 #define SIMPLEQ_INSERT_HEAD(head, elm, field) do {                      \
00285         if (((elm)->field.sqe_next = (head)->sqh_first) == NULL)        \
00286                 (head)->sqh_last = &(elm)->field.sqe_next;              \
00287         (head)->sqh_first = (elm);                                      \
00288 } while (0)
00289 
00290 #define SIMPLEQ_INSERT_TAIL(head, elm, field) do {                      \
00291         (elm)->field.sqe_next = NULL;                                   \
00292         *(head)->sqh_last = (elm);                                      \
00293         (head)->sqh_last = &(elm)->field.sqe_next;                      \
00294 } while (0)
00295 
00296 #define SIMPLEQ_INSERT_AFTER(head, listelm, elm, field) do {            \
00297         if (((elm)->field.sqe_next = (listelm)->field.sqe_next) == NULL)\
00298                 (head)->sqh_last = &(elm)->field.sqe_next;              \
00299         (listelm)->field.sqe_next = (elm);                              \
00300 } while (0)
00301 
00302 #define SIMPLEQ_REMOVE_HEAD(head, field) do {                   \
00303         if (((head)->sqh_first = (head)->sqh_first->field.sqe_next) == NULL) \
00304                 (head)->sqh_last = &(head)->sqh_first;                  \
00305 } while (0)
00306 
00307 /*
00308  * Tail queue definitions.
00309  */
00310 #define TAILQ_HEAD(name, type)                                          \
00311 struct name {                                                           \
00312         struct type *tqh_first; /* first element */                     \
00313         struct type **tqh_last; /* addr of last next element */         \
00314 }
00315 
00316 #define TAILQ_HEAD_INITIALIZER(head)                                    \
00317         { NULL, &(head).tqh_first }
00318 
00319 #define TAILQ_ENTRY(type)                                               \
00320 struct {                                                                \
00321         struct type *tqe_next;  /* next element */                      \
00322         struct type **tqe_prev; /* address of previous next element */  \
00323 }
00324 
00325 /* 
00326  * tail queue access methods 
00327  */
00328 #define TAILQ_FIRST(head)               ((head)->tqh_first)
00329 #define TAILQ_END(head)                 NULL
00330 #define TAILQ_NEXT(elm, field)          ((elm)->field.tqe_next)
00331 #define TAILQ_LAST(head, headname)                                      \
00332         (*(((struct headname *)((head)->tqh_last))->tqh_last))
00333 /* XXX */
00334 #define TAILQ_PREV(elm, headname, field)                                \
00335         (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
00336 #define TAILQ_EMPTY(head)                                               \
00337         (TAILQ_FIRST(head) == TAILQ_END(head))
00338 
00339 #define TAILQ_FOREACH(var, head, field)                                 \
00340         for((var) = TAILQ_FIRST(head);                                  \
00341             (var) != TAILQ_END(head);                                   \
00342             (var) = TAILQ_NEXT(var, field))
00343 
00344 #define TAILQ_FOREACH_REVERSE(var, head, headname, field)               \
00345         for((var) = TAILQ_LAST(head, headname);                         \
00346             (var) != TAILQ_END(head);                                   \
00347             (var) = TAILQ_PREV(var, headname, field))
00348 
00349 /*
00350  * Tail queue functions.
00351  */
00352 #define TAILQ_INIT(head) do {                                           \
00353         (head)->tqh_first = NULL;                                       \
00354         (head)->tqh_last = &(head)->tqh_first;                          \
00355 } while (0)
00356 
00357 #define TAILQ_INSERT_HEAD(head, elm, field) do {                        \
00358         if (((elm)->field.tqe_next = (head)->tqh_first) != NULL)        \
00359                 (head)->tqh_first->field.tqe_prev =                     \
00360                     &(elm)->field.tqe_next;                             \
00361         else                                                            \
00362                 (head)->tqh_last = &(elm)->field.tqe_next;              \
00363         (head)->tqh_first = (elm);                                      \
00364         (elm)->field.tqe_prev = &(head)->tqh_first;                     \
00365 } while (0)
00366 
00367 #define TAILQ_INSERT_TAIL(head, elm, field) do {                        \
00368         (elm)->field.tqe_next = NULL;                                   \
00369         (elm)->field.tqe_prev = (head)->tqh_last;                       \
00370         *(head)->tqh_last = (elm);                                      \
00371         (head)->tqh_last = &(elm)->field.tqe_next;                      \
00372 } while (0)
00373 
00374 #define TAILQ_INSERT_AFTER(head, listelm, elm, field) do {              \
00375         if (((elm)->field.tqe_next = (listelm)->field.tqe_next) != NULL)\
00376                 (elm)->field.tqe_next->field.tqe_prev =                 \
00377                     &(elm)->field.tqe_next;                             \
00378         else                                                            \
00379                 (head)->tqh_last = &(elm)->field.tqe_next;              \
00380         (listelm)->field.tqe_next = (elm);                              \
00381         (elm)->field.tqe_prev = &(listelm)->field.tqe_next;             \
00382 } while (0)
00383 
00384 #define TAILQ_INSERT_BEFORE(listelm, elm, field) do {                   \
00385         (elm)->field.tqe_prev = (listelm)->field.tqe_prev;              \
00386         (elm)->field.tqe_next = (listelm);                              \
00387         *(listelm)->field.tqe_prev = (elm);                             \
00388         (listelm)->field.tqe_prev = &(elm)->field.tqe_next;             \
00389 } while (0)
00390 
00391 #define TAILQ_REMOVE(head, elm, field) do {                             \
00392         if (((elm)->field.tqe_next) != NULL)                            \
00393                 (elm)->field.tqe_next->field.tqe_prev =                 \
00394                     (elm)->field.tqe_prev;                              \
00395         else                                                            \
00396                 (head)->tqh_last = (elm)->field.tqe_prev;               \
00397         *(elm)->field.tqe_prev = (elm)->field.tqe_next;                 \
00398         _Q_INVALIDATE((elm)->field.tqe_prev);                           \
00399         _Q_INVALIDATE((elm)->field.tqe_next);                           \
00400 } while (0)
00401 
00402 #define TAILQ_REPLACE(head, elm, elm2, field) do {                      \
00403         if (((elm2)->field.tqe_next = (elm)->field.tqe_next) != NULL)   \
00404                 (elm2)->field.tqe_next->field.tqe_prev =                \
00405                     &(elm2)->field.tqe_next;                            \
00406         else                                                            \
00407                 (head)->tqh_last = &(elm2)->field.tqe_next;             \
00408         (elm2)->field.tqe_prev = (elm)->field.tqe_prev;                 \
00409         *(elm2)->field.tqe_prev = (elm2);                               \
00410         _Q_INVALIDATE((elm)->field.tqe_prev);                           \
00411         _Q_INVALIDATE((elm)->field.tqe_next);                           \
00412 } while (0)
00413 
00414 /*
00415  * Circular queue definitions.
00416  */
00417 #define CIRCLEQ_HEAD(name, type)                                        \
00418 struct name {                                                           \
00419         struct type *cqh_first;         /* first element */             \
00420         struct type *cqh_last;          /* last element */              \
00421 }
00422 
00423 #define CIRCLEQ_HEAD_INITIALIZER(head)                                  \
00424         { CIRCLEQ_END(&head), CIRCLEQ_END(&head) }
00425 
00426 #define CIRCLEQ_ENTRY(type)                                             \
00427 struct {                                                                \
00428         struct type *cqe_next;          /* next element */              \
00429         struct type *cqe_prev;          /* previous element */          \
00430 }
00431 
00432 /*
00433  * Circular queue access methods 
00434  */
00435 #define CIRCLEQ_FIRST(head)             ((head)->cqh_first)
00436 #define CIRCLEQ_LAST(head)              ((head)->cqh_last)
00437 #define CIRCLEQ_END(head)               ((void *)(head))
00438 #define CIRCLEQ_NEXT(elm, field)        ((elm)->field.cqe_next)
00439 #define CIRCLEQ_PREV(elm, field)        ((elm)->field.cqe_prev)
00440 #define CIRCLEQ_EMPTY(head)                                             \
00441         (CIRCLEQ_FIRST(head) == CIRCLEQ_END(head))
00442 
00443 #define CIRCLEQ_FOREACH(var, head, field)                               \
00444         for((var) = CIRCLEQ_FIRST(head);                                \
00445             (var) != CIRCLEQ_END(head);                                 \
00446             (var) = CIRCLEQ_NEXT(var, field))
00447 
00448 #define CIRCLEQ_FOREACH_REVERSE(var, head, field)                       \
00449         for((var) = CIRCLEQ_LAST(head);                                 \
00450             (var) != CIRCLEQ_END(head);                                 \
00451             (var) = CIRCLEQ_PREV(var, field))
00452 
00453 /*
00454  * Circular queue functions.
00455  */
00456 #define CIRCLEQ_INIT(head) do {                                         \
00457         (head)->cqh_first = CIRCLEQ_END(head);                          \
00458         (head)->cqh_last = CIRCLEQ_END(head);                           \
00459 } while (0)
00460 
00461 #define CIRCLEQ_INSERT_AFTER(head, listelm, elm, field) do {            \
00462         (elm)->field.cqe_next = (listelm)->field.cqe_next;              \
00463         (elm)->field.cqe_prev = (listelm);                              \
00464         if ((listelm)->field.cqe_next == CIRCLEQ_END(head))             \
00465                 (head)->cqh_last = (elm);                               \
00466         else                                                            \
00467                 (listelm)->field.cqe_next->field.cqe_prev = (elm);      \
00468         (listelm)->field.cqe_next = (elm);                              \
00469 } while (0)
00470 
00471 #define CIRCLEQ_INSERT_BEFORE(head, listelm, elm, field) do {           \
00472         (elm)->field.cqe_next = (listelm);                              \
00473         (elm)->field.cqe_prev = (listelm)->field.cqe_prev;              \
00474         if ((listelm)->field.cqe_prev == CIRCLEQ_END(head))             \
00475                 (head)->cqh_first = (elm);                              \
00476         else                                                            \
00477                 (listelm)->field.cqe_prev->field.cqe_next = (elm);      \
00478         (listelm)->field.cqe_prev = (elm);                              \
00479 } while (0)
00480 
00481 #define CIRCLEQ_INSERT_HEAD(head, elm, field) do {                      \
00482         (elm)->field.cqe_next = (head)->cqh_first;                      \
00483         (elm)->field.cqe_prev = CIRCLEQ_END(head);                      \
00484         if ((head)->cqh_last == CIRCLEQ_END(head))                      \
00485                 (head)->cqh_last = (elm);                               \
00486         else                                                            \
00487                 (head)->cqh_first->field.cqe_prev = (elm);              \
00488         (head)->cqh_first = (elm);                                      \
00489 } while (0)
00490 
00491 #define CIRCLEQ_INSERT_TAIL(head, elm, field) do {                      \
00492         (elm)->field.cqe_next = CIRCLEQ_END(head);                      \
00493         (elm)->field.cqe_prev = (head)->cqh_last;                       \
00494         if ((head)->cqh_first == CIRCLEQ_END(head))                     \
00495                 (head)->cqh_first = (elm);                              \
00496         else                                                            \
00497                 (head)->cqh_last->field.cqe_next = (elm);               \
00498         (head)->cqh_last = (elm);                                       \
00499 } while (0)
00500 
00501 #define CIRCLEQ_REMOVE(head, elm, field) do {                           \
00502         if ((elm)->field.cqe_next == CIRCLEQ_END(head))                 \
00503                 (head)->cqh_last = (elm)->field.cqe_prev;               \
00504         else                                                            \
00505                 (elm)->field.cqe_next->field.cqe_prev =                 \
00506                     (elm)->field.cqe_prev;                              \
00507         if ((elm)->field.cqe_prev == CIRCLEQ_END(head))                 \
00508                 (head)->cqh_first = (elm)->field.cqe_next;              \
00509         else                                                            \
00510                 (elm)->field.cqe_prev->field.cqe_next =                 \
00511                     (elm)->field.cqe_next;                              \
00512         _Q_INVALIDATE((elm)->field.cqe_prev);                           \
00513         _Q_INVALIDATE((elm)->field.cqe_next);                           \
00514 } while (0)
00515 
00516 #define CIRCLEQ_REPLACE(head, elm, elm2, field) do {                    \
00517         if (((elm2)->field.cqe_next = (elm)->field.cqe_next) ==         \
00518             CIRCLEQ_END(head))                                          \
00519                 (head).cqh_last = (elm2);                               \
00520         else                                                            \
00521                 (elm2)->field.cqe_next->field.cqe_prev = (elm2);        \
00522         if (((elm2)->field.cqe_prev = (elm)->field.cqe_prev) ==         \
00523             CIRCLEQ_END(head))                                          \
00524                 (head).cqh_first = (elm2);                              \
00525         else                                                            \
00526                 (elm2)->field.cqe_prev->field.cqe_next = (elm2);        \
00527         _Q_INVALIDATE((elm)->field.cqe_prev);                           \
00528         _Q_INVALIDATE((elm)->field.cqe_next);                           \
00529 } while (0)
00530 
00531 #endif  /* !_SYS_QUEUE_H_ */

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