git.sur5r.net Git - openldap/blob - include/ldap_queue.h

   1 /*
   2  * Copyright 2001 The OpenLDAP Foundation, Redwood City, California, USA
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted only as authorized by the OpenLDAP
   7  * Public License.  A copy of this license is available at
   8  * http://www.OpenLDAP.org/license.html or in file LICENSE in the
   9  * top-level directory of the distribution.
  10  */
  11 /* stolen from FreeBSD for use in OpenLDAP */
  12 /* $OpenLDAP$ */
  13 /*
  14  * Copyright (c) 1991, 1993
  15  *      The Regents of the University of California.  All rights reserved.
  16  *
  17  * Redistribution and use in source and binary forms, with or without
  18  * modification, are permitted provided that the following conditions
  19  * are met:
  20  * 1. Redistributions of source code must retain the above copyright
  21  *    notice, this list of conditions and the following disclaimer.
  22  * 2. Redistributions in binary form must reproduce the above copyright
  23  *    notice, this list of conditions and the following disclaimer in the
  24  *    documentation and/or other materials provided with the distribution.
  25  * 3. All advertising materials mentioning features or use of this software
  26  *    must display the following acknowledgement:
  27  *      This product includes software developed by the University of
  28  *      California, Berkeley and its contributors.
  29  * 4. Neither the name of the University nor the names of its contributors
  30  *    may be used to endorse or promote products derived from this software
  31  *    without specific prior written permission.
  32  *
  33  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  34  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  35  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  36  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  37  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  38  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  39  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  40  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  41  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  42  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  43  * SUCH DAMAGE.
  44  *
  45  *      @(#)queue.h     8.5 (Berkeley) 8/20/94
  46  * $FreeBSD: src/sys/sys/queue.h,v 1.32.2.5 2001/09/30 21:12:54 luigi Exp $
  47  */
  48
  49 #ifndef _LDAP_QUEUE_H_
  50 #define _LDAP_QUEUE_H_
  51
  52 /*
  53  * This file defines five types of data structures: singly-linked lists,
  54  * singly-linked tail queues, lists, tail queues, and circular queues.
  55  *
  56  * A singly-linked list is headed by a single forward pointer. The elements
  57  * are singly linked for minimum space and pointer manipulation overhead at
  58  * the expense of O(n) removal for arbitrary elements. New elements can be
  59  * added to the list after an existing element or at the head of the list.
  60  * Elements being removed from the head of the list should use the explicit
  61  * macro for this purpose for optimum efficiency. A singly-linked list may
  62  * only be traversed in the forward direction.  Singly-linked lists are ideal
  63  * for applications with large datasets and few or no removals or for
  64  * implementing a LIFO queue.
  65  *
  66  * A singly-linked tail queue is headed by a pair of pointers, one to the
  67  * head of the list and the other to the tail of the list. The elements are
  68  * singly linked for minimum space and pointer manipulation overhead at the
  69  * expense of O(n) removal for arbitrary elements. New elements can be added
  70  * to the list after an existing element, at the head of the list, or at the
  71  * end of the list. Elements being removed from the head of the tail queue
  72  * should use the explicit macro for this purpose for optimum efficiency.
  73  * A singly-linked tail queue may only be traversed in the forward direction.
  74  * Singly-linked tail queues are ideal for applications with large datasets
  75  * and few or no removals or for implementing a FIFO queue.
  76  *
  77  * A list is headed by a single forward pointer (or an array of forward
  78  * pointers for a hash table header). The elements are doubly linked
  79  * so that an arbitrary element can be removed without a need to
  80  * traverse the list. New elements can be added to the list before
  81  * or after an existing element or at the head of the list. A list
  82  * may only be traversed in the forward direction.
  83  *
  84  * A tail queue is headed by a pair of pointers, one to the head of the
  85  * list and the other to the tail of the list. The elements are doubly
  86  * linked so that an arbitrary element can be removed without a need to
  87  * traverse the list. New elements can be added to the list before or
  88  * after an existing element, at the head of the list, or at the end of
  89  * the list. A tail queue may be traversed in either direction.
  90  *
  91  * A circle queue is headed by a pair of pointers, one to the head of the
  92  * list and the other to the tail of the list. The elements are doubly
  93  * linked so that an arbitrary element can be removed without a need to
  94  * traverse the list. New elements can be added to the list before or after
  95  * an existing element, at the head of the list, or at the end of the list.
  96  * A circle queue may be traversed in either direction, but has a more
  97  * complex end of list detection.
  98  *
  99  * For details on the use of these macros, see the queue(3) manual page.
 100  *
 101  *
 102  *                      LDAP_SLIST      LIST    LDAP_STAILQ     TAILQ   LDAP_CIRCLEQ
 103  * _HEAD                +       +       +       +       +
 104  * _ENTRY               +       +       +       +       +
 105  * _INIT                +       +       +       +       +
 106  * _EMPTY               +       +       +       +       +
 107  * _FIRST               +       +       +       +       +
 108  * _NEXT                +       +       +       +       +
 109  * _PREV                -       -       -       +       +
 110  * _LAST                -       -       +       +       +
 111  * _FOREACH             +       +       +       +       +
 112  * _FOREACH_REVERSE     -       -       -       +       +
 113  * _INSERT_HEAD         +       +       +       +       +
 114  * _INSERT_BEFORE       -       +       -       +       +
 115  * _INSERT_AFTER        +       +       +       +       +
 116  * _INSERT_TAIL         -       -       +       +       +
 117  * _REMOVE_HEAD         +       -       +       -       -
 118  * _REMOVE              +       +       +       +       +
 119  *
 120  */
 121 /*
 122  * see queue(3) for instructions on how to use
 123  */
 124
 125 /*
 126  * Singly-linked List definitions.
 127  */
 128 #define LDAP_SLIST_HEAD(name, type)                                             \
 129 struct name {                                                           \
 130         struct type *slh_first; /* first element */                     \
 131 }
 132
 133 #define LDAP_SLIST_HEAD_INITIALIZER(head)                                       \
 134         { NULL }
 135
 136 #define LDAP_SLIST_ENTRY(type)                                          \
 137 struct {                                                                \
 138         struct type *sle_next;  /* next element */                      \
 139 }
 140
 141 /*
 142  * Singly-linked List functions.
 143  */
 144 #define LDAP_SLIST_EMPTY(head)  ((head)->slh_first == NULL)
 145
 146 #define LDAP_SLIST_FIRST(head)  ((head)->slh_first)
 147
 148 #define LDAP_SLIST_FOREACH(var, head, field)                                    \
 149         for((var) = (head)->slh_first; (var); (var) = (var)->field.sle_next)
 150
 151 #define LDAP_SLIST_INIT(head) {                                         \
 152         (head)->slh_first = NULL;                                       \
 153 }
 154
 155 #define LDAP_SLIST_INSERT_AFTER(slistelm, elm, field) do {                      \
 156         (elm)->field.sle_next = (slistelm)->field.sle_next;             \
 157         (slistelm)->field.sle_next = (elm);                             \
 158 } while (0)
 159
 160 #define LDAP_SLIST_INSERT_HEAD(head, elm, field) do {                   \
 161         (elm)->field.sle_next = (head)->slh_first;                      \
 162         (head)->slh_first = (elm);                                      \
 163 } while (0)
 164
 165 #define LDAP_SLIST_NEXT(elm, field)     ((elm)->field.sle_next)
 166
 167 #define LDAP_SLIST_REMOVE_HEAD(head, field) do {                                \
 168         (head)->slh_first = (head)->slh_first->field.sle_next;          \
 169 } while (0)
 170
 171 #define LDAP_SLIST_REMOVE(head, elm, type, field) do {                  \
 172         if ((head)->slh_first == (elm)) {                               \
 173                 LDAP_SLIST_REMOVE_HEAD((head), field);                  \
 174         }                                                               \
 175         else {                                                          \
 176                 struct type *curelm = (head)->slh_first;                \
 177                 while( curelm->field.sle_next != (elm) )                \
 178                         curelm = curelm->field.sle_next;                \
 179                 curelm->field.sle_next =                                \
 180                     curelm->field.sle_next->field.sle_next;             \
 181         }                                                               \
 182 } while (0)
 183
 184 /*
 185  * Singly-linked Tail queue definitions.
 186  */
 187 #define LDAP_STAILQ_HEAD(name, type)                                            \
 188 struct name {                                                           \
 189         struct type *stqh_first;/* first element */                     \
 190         struct type **stqh_last;/* addr of last next element */         \
 191 }
 192
 193 #define LDAP_STAILQ_HEAD_INITIALIZER(head)                                      \
 194         { NULL, &(head).stqh_first }
 195
 196 #define LDAP_STAILQ_ENTRY(type)                                         \
 197 struct {                                                                \
 198         struct type *stqe_next; /* next element */                      \
 199 }
 200
 201 /*
 202  * Singly-linked Tail queue functions.
 203  */
 204 #define LDAP_STAILQ_EMPTY(head) ((head)->stqh_first == NULL)
 205
 206 #define LDAP_STAILQ_INIT(head) do {                                             \
 207         (head)->stqh_first = NULL;                                      \
 208         (head)->stqh_last = &(head)->stqh_first;                        \
 209 } while (0)
 210
 211 #define LDAP_STAILQ_FIRST(head) ((head)->stqh_first)
 212
 213 #define LDAP_STAILQ_LAST(head, type, field)                                     \
 214         (LDAP_STAILQ_EMPTY(head) ?                                              \
 215                 NULL :                                                  \
 216                 ((struct type *)                                        \
 217                 ((char *)((head)->stqh_last) - offsetof(struct type, field))))
 218
 219 #define LDAP_STAILQ_FOREACH(var, head, field)                           \
 220         for((var) = (head)->stqh_first; (var); (var) = (var)->field.stqe_next)
 221
 222 #define LDAP_STAILQ_INSERT_HEAD(head, elm, field) do {                  \
 223         if (((elm)->field.stqe_next = (head)->stqh_first) == NULL)      \
 224                 (head)->stqh_last = &(elm)->field.stqe_next;            \
 225         (head)->stqh_first = (elm);                                     \
 226 } while (0)
 227
 228 #define LDAP_STAILQ_INSERT_TAIL(head, elm, field) do {                  \
 229         (elm)->field.stqe_next = NULL;                                  \
 230         *(head)->stqh_last = (elm);                                     \
 231         (head)->stqh_last = &(elm)->field.stqe_next;                    \
 232 } while (0)
 233
 234 #define LDAP_STAILQ_INSERT_AFTER(head, tqelm, elm, field) do {          \
 235         if (((elm)->field.stqe_next = (tqelm)->field.stqe_next) == NULL)\
 236                 (head)->stqh_last = &(elm)->field.stqe_next;            \
 237         (tqelm)->field.stqe_next = (elm);                               \
 238 } while (0)
 239
 240 #define LDAP_STAILQ_NEXT(elm, field)    ((elm)->field.stqe_next)
 241
 242 #define LDAP_STAILQ_REMOVE_HEAD(head, field) do {                               \
 243         if (((head)->stqh_first =                                       \
 244              (head)->stqh_first->field.stqe_next) == NULL)              \
 245                 (head)->stqh_last = &(head)->stqh_first;                \
 246 } while (0)
 247
 248 #define LDAP_STAILQ_REMOVE_HEAD_UNTIL(head, elm, field) do {                    \
 249         if (((head)->stqh_first = (elm)->field.stqe_next) == NULL)      \
 250                 (head)->stqh_last = &(head)->stqh_first;                \
 251 } while (0)
 252
 253 #define LDAP_STAILQ_REMOVE(head, elm, type, field) do {                 \
 254         if ((head)->stqh_first == (elm)) {                              \
 255                 LDAP_STAILQ_REMOVE_HEAD(head, field);                   \
 256         }                                                               \
 257         else {                                                          \
 258                 struct type *curelm = (head)->stqh_first;               \
 259                 while( curelm->field.stqe_next != (elm) )               \
 260                         curelm = curelm->field.stqe_next;               \
 261                 if((curelm->field.stqe_next =                           \
 262                     curelm->field.stqe_next->field.stqe_next) == NULL)  \
 263                         (head)->stqh_last = &(curelm)->field.stqe_next; \
 264         }                                                               \
 265 } while (0)
 266
 267 /*
 268  * List definitions.
 269  */
 270 #define LDAP_LIST_HEAD(name, type)                                              \
 271 struct name {                                                           \
 272         struct type *lh_first;  /* first element */                     \
 273 }
 274
 275 #define LDAP_LIST_HEAD_INITIALIZER(head)                                        \
 276         { NULL }
 277
 278 #define LDAP_LIST_ENTRY(type)                                           \
 279 struct {                                                                \
 280         struct type *le_next;   /* next element */                      \
 281         struct type **le_prev;  /* address of previous next element */  \
 282 }
 283
 284 /*
 285  * List functions.
 286  */
 287
 288 #define LDAP_LIST_EMPTY(head) ((head)->lh_first == NULL)
 289
 290 #define LDAP_LIST_FIRST(head)   ((head)->lh_first)
 291
 292 #define LDAP_LIST_FOREACH(var, head, field)                                     \
 293         for((var) = (head)->lh_first; (var); (var) = (var)->field.le_next)
 294
 295 #define LDAP_LIST_INIT(head) do {                                               \
 296         (head)->lh_first = NULL;                                        \
 297 } while (0)
 298
 299 #define LDAP_LIST_INSERT_AFTER(listelm, elm, field) do {                        \
 300         if (((elm)->field.le_next = (listelm)->field.le_next) != NULL)  \
 301                 (listelm)->field.le_next->field.le_prev =               \
 302                     &(elm)->field.le_next;                              \
 303         (listelm)->field.le_next = (elm);                               \
 304         (elm)->field.le_prev = &(listelm)->field.le_next;               \
 305 } while (0)
 306
 307 #define LDAP_LIST_INSERT_BEFORE(listelm, elm, field) do {                       \
 308         (elm)->field.le_prev = (listelm)->field.le_prev;                \
 309         (elm)->field.le_next = (listelm);                               \
 310         *(listelm)->field.le_prev = (elm);                              \
 311         (listelm)->field.le_prev = &(elm)->field.le_next;               \
 312 } while (0)
 313
 314 #define LDAP_LIST_INSERT_HEAD(head, elm, field) do {                            \
 315         if (((elm)->field.le_next = (head)->lh_first) != NULL)          \
 316                 (head)->lh_first->field.le_prev = &(elm)->field.le_next;\
 317         (head)->lh_first = (elm);                                       \
 318         (elm)->field.le_prev = &(head)->lh_first;                       \
 319 } while (0)
 320
 321 #define LDAP_LIST_NEXT(elm, field)      ((elm)->field.le_next)
 322
 323 #define LDAP_LIST_REMOVE(elm, field) do {                                       \
 324         if ((elm)->field.le_next != NULL)                               \
 325                 (elm)->field.le_next->field.le_prev =                   \
 326                     (elm)->field.le_prev;                               \
 327         *(elm)->field.le_prev = (elm)->field.le_next;                   \
 328 } while (0)
 329
 330 /*
 331  * Tail queue definitions.
 332  */
 333 #define LDAP_TAILQ_HEAD(name, type)                                             \
 334 struct name {                                                           \
 335         struct type *tqh_first; /* first element */                     \
 336         struct type **tqh_last; /* addr of last next element */         \
 337 }
 338
 339 #define LDAP_TAILQ_HEAD_INITIALIZER(head)                                       \
 340         { NULL, &(head).tqh_first }
 341
 342 #define LDAP_TAILQ_ENTRY(type)                                          \
 343 struct {                                                                \
 344         struct type *tqe_next;  /* next element */                      \
 345         struct type **tqe_prev; /* address of previous next element */  \
 346 }
 347
 348 /*
 349  * Tail queue functions.
 350  */
 351 #define LDAP_TAILQ_EMPTY(head) ((head)->tqh_first == NULL)
 352
 353 #define LDAP_TAILQ_FOREACH(var, head, field)                                    \
 354         for (var = LDAP_TAILQ_FIRST(head); var; var = TAILQ_NEXT(var, field))
 355
 356 #define LDAP_TAILQ_FOREACH_REVERSE(var, head, headname, field)          \
 357         for ((var) = LDAP_TAILQ_LAST((head), headname);                 \
 358              (var);                                                     \
 359              (var) = LDAP_TAILQ_PREV((var), headname, field))
 360
 361 #define LDAP_TAILQ_FIRST(head) ((head)->tqh_first)
 362
 363 #define LDAP_TAILQ_LAST(head, headname) \
 364         (*(((struct headname *)((head)->tqh_last))->tqh_last))
 365
 366 #define LDAP_TAILQ_NEXT(elm, field) ((elm)->field.tqe_next)
 367
 368 #define LDAP_TAILQ_PREV(elm, headname, field) \
 369         (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
 370
 371 #define LDAP_TAILQ_INIT(head) do {                                              \
 372         (head)->tqh_first = NULL;                                       \
 373         (head)->tqh_last = &(head)->tqh_first;                          \
 374 } while (0)
 375
 376 #define LDAP_TAILQ_INSERT_HEAD(head, elm, field) do {                   \
 377         if (((elm)->field.tqe_next = (head)->tqh_first) != NULL)        \
 378                 (head)->tqh_first->field.tqe_prev =                     \
 379                     &(elm)->field.tqe_next;                             \
 380         else                                                            \
 381                 (head)->tqh_last = &(elm)->field.tqe_next;              \
 382         (head)->tqh_first = (elm);                                      \
 383         (elm)->field.tqe_prev = &(head)->tqh_first;                     \
 384 } while (0)
 385
 386 #define LDAP_TAILQ_INSERT_TAIL(head, elm, field) do {                   \
 387         (elm)->field.tqe_next = NULL;                                   \
 388         (elm)->field.tqe_prev = (head)->tqh_last;                       \
 389         *(head)->tqh_last = (elm);                                      \
 390         (head)->tqh_last = &(elm)->field.tqe_next;                      \
 391 } while (0)
 392
 393 #define LDAP_TAILQ_INSERT_AFTER(head, listelm, elm, field) do {         \
 394         if (((elm)->field.tqe_next = (listelm)->field.tqe_next) != NULL)\
 395                 (elm)->field.tqe_next->field.tqe_prev =                 \
 396                     &(elm)->field.tqe_next;                             \
 397         else                                                            \
 398                 (head)->tqh_last = &(elm)->field.tqe_next;              \
 399         (listelm)->field.tqe_next = (elm);                              \
 400         (elm)->field.tqe_prev = &(listelm)->field.tqe_next;             \
 401 } while (0)
 402
 403 #define LDAP_TAILQ_INSERT_BEFORE(listelm, elm, field) do {                      \
 404         (elm)->field.tqe_prev = (listelm)->field.tqe_prev;              \
 405         (elm)->field.tqe_next = (listelm);                              \
 406         *(listelm)->field.tqe_prev = (elm);                             \
 407         (listelm)->field.tqe_prev = &(elm)->field.tqe_next;             \
 408 } while (0)
 409
 410 #define LDAP_TAILQ_REMOVE(head, elm, field) do {                                \
 411         if (((elm)->field.tqe_next) != NULL)                            \
 412                 (elm)->field.tqe_next->field.tqe_prev =                 \
 413                     (elm)->field.tqe_prev;                              \
 414         else                                                            \
 415                 (head)->tqh_last = (elm)->field.tqe_prev;               \
 416         *(elm)->field.tqe_prev = (elm)->field.tqe_next;                 \
 417 } while (0)
 418
 419 /*
 420  * Circular queue definitions.
 421  */
 422 #define LDAP_CIRCLEQ_HEAD(name, type)                                   \
 423 struct name {                                                           \
 424         struct type *cqh_first;         /* first element */             \
 425         struct type *cqh_last;          /* last element */              \
 426 }
 427
 428 #define LDAP_CIRCLEQ_ENTRY(type)                                                \
 429 struct {                                                                \
 430         struct type *cqe_next;          /* next element */              \
 431         struct type *cqe_prev;          /* previous element */          \
 432 }
 433
 434 /*
 435  * Circular queue functions.
 436  */
 437 #define LDAP_CIRCLEQ_EMPTY(head) ((head)->cqh_first == (void *)(head))
 438
 439 #define LDAP_CIRCLEQ_FIRST(head) ((head)->cqh_first)
 440
 441 #define LDAP_CIRCLEQ_FOREACH(var, head, field)                          \
 442         for((var) = (head)->cqh_first;                                  \
 443             (var) != (void *)(head);                                    \
 444             (var) = (var)->field.cqe_next)
 445
 446 #define LDAP_CIRCLEQ_FOREACH_REVERSE(var, head, field)                  \
 447         for((var) = (head)->cqh_last;                                   \
 448             (var) != (void *)(head);                                    \
 449             (var) = (var)->field.cqe_prev)
 450
 451 #define LDAP_CIRCLEQ_INIT(head) do {                                            \
 452         (head)->cqh_first = (void *)(head);                             \
 453         (head)->cqh_last = (void *)(head);                              \
 454 } while (0)
 455
 456 #define LDAP_CIRCLEQ_INSERT_AFTER(head, listelm, elm, field) do {               \
 457         (elm)->field.cqe_next = (listelm)->field.cqe_next;              \
 458         (elm)->field.cqe_prev = (listelm);                              \
 459         if ((listelm)->field.cqe_next == (void *)(head))                \
 460                 (head)->cqh_last = (elm);                               \
 461         else                                                            \
 462                 (listelm)->field.cqe_next->field.cqe_prev = (elm);      \
 463         (listelm)->field.cqe_next = (elm);                              \
 464 } while (0)
 465
 466 #define LDAP_CIRCLEQ_INSERT_BEFORE(head, listelm, elm, field) do {              \
 467         (elm)->field.cqe_next = (listelm);                              \
 468         (elm)->field.cqe_prev = (listelm)->field.cqe_prev;              \
 469         if ((listelm)->field.cqe_prev == (void *)(head))                \
 470                 (head)->cqh_first = (elm);                              \
 471         else                                                            \
 472                 (listelm)->field.cqe_prev->field.cqe_next = (elm);      \
 473         (listelm)->field.cqe_prev = (elm);                              \
 474 } while (0)
 475
 476 #define LDAP_CIRCLEQ_INSERT_HEAD(head, elm, field) do {                 \
 477         (elm)->field.cqe_next = (head)->cqh_first;                      \
 478         (elm)->field.cqe_prev = (void *)(head);                         \
 479         if ((head)->cqh_last == (void *)(head))                         \
 480                 (head)->cqh_last = (elm);                               \
 481         else                                                            \
 482                 (head)->cqh_first->field.cqe_prev = (elm);              \
 483         (head)->cqh_first = (elm);                                      \
 484 } while (0)
 485
 486 #define LDAP_CIRCLEQ_INSERT_TAIL(head, elm, field) do {                 \
 487         (elm)->field.cqe_next = (void *)(head);                         \
 488         (elm)->field.cqe_prev = (head)->cqh_last;                       \
 489         if ((head)->cqh_first == (void *)(head))                        \
 490                 (head)->cqh_first = (elm);                              \
 491         else                                                            \
 492                 (head)->cqh_last->field.cqe_next = (elm);               \
 493         (head)->cqh_last = (elm);                                       \
 494 } while (0)
 495
 496 #define LDAP_CIRCLEQ_LAST(head) ((head)->cqh_last)
 497
 498 #define LDAP_CIRCLEQ_NEXT(elm,field) ((elm)->field.cqe_next)
 499
 500 #define LDAP_CIRCLEQ_PREV(elm,field) ((elm)->field.cqe_prev)
 501
 502 #define LDAP_CIRCLEQ_REMOVE(head, elm, field) do {                              \
 503         if ((elm)->field.cqe_next == (void *)(head))                    \
 504                 (head)->cqh_last = (elm)->field.cqe_prev;               \
 505         else                                                            \
 506                 (elm)->field.cqe_next->field.cqe_prev =                 \
 507                     (elm)->field.cqe_prev;                              \
 508         if ((elm)->field.cqe_prev == (void *)(head))                    \
 509                 (head)->cqh_first = (elm)->field.cqe_next;              \
 510         else                                                            \
 511                 (elm)->field.cqe_prev->field.cqe_next =                 \
 512                     (elm)->field.cqe_next;                              \
 513 } while (0)
 514
 515 #endif /* !_LDAP_QUEUE_H_ */