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

   1 /*
   2  * Copyright 2001-2003 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  * All macros are prefixed with LDAP_.
 101  *
 102  *                      SLIST_  LIST_   STAILQ_ TAILQ_  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 /*
 123  * Singly-linked List definitions.
 124  */
 125 #define LDAP_SLIST_HEAD(name, type)                                     \
 126 struct name {                                                           \
 127         struct type *slh_first; /* first element */                     \
 128 }
 129
 130 #define LDAP_SLIST_HEAD_INITIALIZER(head)                               \
 131         { NULL }
 132
 133 #define LDAP_SLIST_ENTRY(type)                                          \
 134 struct {                                                                \
 135         struct type *sle_next;  /* next element */                      \
 136 }
 137
 138 #define LDAP_SLIST_ENTRY_INITIALIZER(entry)                             \
 139         { NULL }
 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 #define LDAP_STAILQ_ENTRY_INITIALIZER(entry)                            \
 202         { NULL }
 203
 204 /*
 205  * Singly-linked Tail queue functions.
 206  */
 207 #define LDAP_STAILQ_EMPTY(head) ((head)->stqh_first == NULL)
 208
 209 #define LDAP_STAILQ_INIT(head) do {                                     \
 210         (head)->stqh_first = NULL;                                      \
 211         (head)->stqh_last = &(head)->stqh_first;                        \
 212 } while (0)
 213
 214 #define LDAP_STAILQ_FIRST(head) ((head)->stqh_first)
 215
 216 #define LDAP_STAILQ_LAST(head, type, field)                             \
 217         (LDAP_STAILQ_EMPTY(head) ?                                      \
 218                 NULL :                                                  \
 219                 ((struct type *)                                        \
 220                 ((char *)((head)->stqh_last) - offsetof(struct type, field))))
 221
 222 #define LDAP_STAILQ_FOREACH(var, head, field)                           \
 223         for((var) = (head)->stqh_first; (var); (var) = (var)->field.stqe_next)
 224
 225 #define LDAP_STAILQ_INSERT_HEAD(head, elm, field) do {                  \
 226         if (((elm)->field.stqe_next = (head)->stqh_first) == NULL)      \
 227                 (head)->stqh_last = &(elm)->field.stqe_next;            \
 228         (head)->stqh_first = (elm);                                     \
 229 } while (0)
 230
 231 #define LDAP_STAILQ_INSERT_TAIL(head, elm, field) do {                  \
 232         (elm)->field.stqe_next = NULL;                                  \
 233         *(head)->stqh_last = (elm);                                     \
 234         (head)->stqh_last = &(elm)->field.stqe_next;                    \
 235 } while (0)
 236
 237 #define LDAP_STAILQ_INSERT_AFTER(head, tqelm, elm, field) do {          \
 238         if (((elm)->field.stqe_next = (tqelm)->field.stqe_next) == NULL)\
 239                 (head)->stqh_last = &(elm)->field.stqe_next;            \
 240         (tqelm)->field.stqe_next = (elm);                               \
 241 } while (0)
 242
 243 #define LDAP_STAILQ_NEXT(elm, field)    ((elm)->field.stqe_next)
 244
 245 #define LDAP_STAILQ_REMOVE_HEAD(head, field) do {                       \
 246         if (((head)->stqh_first =                                       \
 247              (head)->stqh_first->field.stqe_next) == NULL)              \
 248                 (head)->stqh_last = &(head)->stqh_first;                \
 249 } while (0)
 250
 251 #define LDAP_STAILQ_REMOVE_HEAD_UNTIL(head, elm, field) do {            \
 252         if (((head)->stqh_first = (elm)->field.stqe_next) == NULL)      \
 253                 (head)->stqh_last = &(head)->stqh_first;                \
 254 } while (0)
 255
 256 #define LDAP_STAILQ_REMOVE(head, elm, type, field) do {                 \
 257         if ((head)->stqh_first == (elm)) {                              \
 258                 LDAP_STAILQ_REMOVE_HEAD(head, field);                   \
 259         }                                                               \
 260         else {                                                          \
 261                 struct type *curelm = (head)->stqh_first;               \
 262                 while( curelm->field.stqe_next != (elm) )               \
 263                         curelm = curelm->field.stqe_next;               \
 264                 if((curelm->field.stqe_next =                           \
 265                     curelm->field.stqe_next->field.stqe_next) == NULL)  \
 266                         (head)->stqh_last = &(curelm)->field.stqe_next; \
 267         }                                                               \
 268 } while (0)
 269
 270 /*
 271  * List definitions.
 272  */
 273 #define LDAP_LIST_HEAD(name, type)                                      \
 274 struct name {                                                           \
 275         struct type *lh_first;  /* first element */                     \
 276 }
 277
 278 #define LDAP_LIST_HEAD_INITIALIZER(head)                                \
 279         { NULL }
 280
 281 #define LDAP_LIST_ENTRY(type)                                           \
 282 struct {                                                                \
 283         struct type *le_next;   /* next element */                      \
 284         struct type **le_prev;  /* address of previous next element */  \
 285 }
 286
 287 #define LDAP_LIST_ENTRY_INITIALIZER(entry)                      \
 288         { NULL, NULL }
 289
 290 /*
 291  * List functions.
 292  */
 293
 294 #define LDAP_LIST_EMPTY(head) ((head)->lh_first == NULL)
 295
 296 #define LDAP_LIST_FIRST(head)   ((head)->lh_first)
 297
 298 #define LDAP_LIST_FOREACH(var, head, field)                             \
 299         for((var) = (head)->lh_first; (var); (var) = (var)->field.le_next)
 300
 301 #define LDAP_LIST_INIT(head) do {                                       \
 302         (head)->lh_first = NULL;                                        \
 303 } while (0)
 304
 305 #define LDAP_LIST_INSERT_AFTER(listelm, elm, field) do {                \
 306         if (((elm)->field.le_next = (listelm)->field.le_next) != NULL)  \
 307                 (listelm)->field.le_next->field.le_prev =               \
 308                     &(elm)->field.le_next;                              \
 309         (listelm)->field.le_next = (elm);                               \
 310         (elm)->field.le_prev = &(listelm)->field.le_next;               \
 311 } while (0)
 312
 313 #define LDAP_LIST_INSERT_BEFORE(listelm, elm, field) do {               \
 314         (elm)->field.le_prev = (listelm)->field.le_prev;                \
 315         (elm)->field.le_next = (listelm);                               \
 316         *(listelm)->field.le_prev = (elm);                              \
 317         (listelm)->field.le_prev = &(elm)->field.le_next;               \
 318 } while (0)
 319
 320 #define LDAP_LIST_INSERT_HEAD(head, elm, field) do {                    \
 321         if (((elm)->field.le_next = (head)->lh_first) != NULL)          \
 322                 (head)->lh_first->field.le_prev = &(elm)->field.le_next;\
 323         (head)->lh_first = (elm);                                       \
 324         (elm)->field.le_prev = &(head)->lh_first;                       \
 325 } while (0)
 326
 327 #define LDAP_LIST_NEXT(elm, field)      ((elm)->field.le_next)
 328
 329 #define LDAP_LIST_REMOVE(elm, field) do {                               \
 330         if ((elm)->field.le_next != NULL)                               \
 331                 (elm)->field.le_next->field.le_prev =                   \
 332                     (elm)->field.le_prev;                               \
 333         *(elm)->field.le_prev = (elm)->field.le_next;                   \
 334 } while (0)
 335
 336 /*
 337  * Tail queue definitions.
 338  */
 339 #define LDAP_TAILQ_HEAD(name, type)                                     \
 340 struct name {                                                           \
 341         struct type *tqh_first; /* first element */                     \
 342         struct type **tqh_last; /* addr of last next element */         \
 343 }
 344
 345 #define LDAP_TAILQ_HEAD_INITIALIZER(head)                               \
 346         { NULL, &(head).tqh_first }
 347
 348 #define LDAP_TAILQ_ENTRY(type)                                          \
 349 struct {                                                                \
 350         struct type *tqe_next;  /* next element */                      \
 351         struct type **tqe_prev; /* address of previous next element */  \
 352 }
 353
 354 #define LDAP_TAILQ_ENTRY_INITIALIZER(entry)                             \
 355         { NULL, NULL }
 356
 357 /*
 358  * Tail queue functions.
 359  */
 360 #define LDAP_TAILQ_EMPTY(head) ((head)->tqh_first == NULL)
 361
 362 #define LDAP_TAILQ_FOREACH(var, head, field)                            \
 363         for (var = LDAP_TAILQ_FIRST(head); var; var = TAILQ_NEXT(var, field))
 364
 365 #define LDAP_TAILQ_FOREACH_REVERSE(var, head, type, field)              \
 366         for ((var) = LDAP_TAILQ_LAST((head), type, field);              \
 367              (var);                                                     \
 368              (var) = LDAP_TAILQ_PREV((var), head, type, field))
 369
 370 #define LDAP_TAILQ_FIRST(head) ((head)->tqh_first)
 371
 372 #define LDAP_TAILQ_LAST(head, type, field)                              \
 373         (LDAP_TAILQ_EMPTY(head) ?                                       \
 374                 NULL :                                                  \
 375                 ((struct type *)                                        \
 376                 ((char *)((head)->tqh_last) - offsetof(struct type, field))))
 377
 378 #define LDAP_TAILQ_NEXT(elm, field) ((elm)->field.tqe_next)
 379
 380 #define LDAP_TAILQ_PREV(elm, head, type, field)                         \
 381         ((struct type *)((elm)->field.tqe_prev) == LDAP_TAILQ_FIRST(head) ? \
 382         NULL :                                                          \
 383         ((struct type *)                                                \
 384         ((char *)((elm)->field.tqe_prev) - offsetof(struct type, field))))
 385
 386 #define LDAP_TAILQ_INIT(head) do {                                      \
 387         (head)->tqh_first = NULL;                                       \
 388         (head)->tqh_last = &(head)->tqh_first;                          \
 389 } while (0)
 390
 391 #define LDAP_TAILQ_INSERT_HEAD(head, elm, field) do {                   \
 392         if (((elm)->field.tqe_next = (head)->tqh_first) != NULL)        \
 393                 (head)->tqh_first->field.tqe_prev =                     \
 394                     &(elm)->field.tqe_next;                             \
 395         else                                                            \
 396                 (head)->tqh_last = &(elm)->field.tqe_next;              \
 397         (head)->tqh_first = (elm);                                      \
 398         (elm)->field.tqe_prev = &(head)->tqh_first;                     \
 399 } while (0)
 400
 401 #define LDAP_TAILQ_INSERT_TAIL(head, elm, field) do {                   \
 402         (elm)->field.tqe_next = NULL;                                   \
 403         (elm)->field.tqe_prev = (head)->tqh_last;                       \
 404         *(head)->tqh_last = (elm);                                      \
 405         (head)->tqh_last = &(elm)->field.tqe_next;                      \
 406 } while (0)
 407
 408 #define LDAP_TAILQ_INSERT_AFTER(head, listelm, elm, field) do {         \
 409         if (((elm)->field.tqe_next = (listelm)->field.tqe_next) != NULL)\
 410                 (elm)->field.tqe_next->field.tqe_prev =                 \
 411                     &(elm)->field.tqe_next;                             \
 412         else                                                            \
 413                 (head)->tqh_last = &(elm)->field.tqe_next;              \
 414         (listelm)->field.tqe_next = (elm);                              \
 415         (elm)->field.tqe_prev = &(listelm)->field.tqe_next;             \
 416 } while (0)
 417
 418 #define LDAP_TAILQ_INSERT_BEFORE(listelm, elm, field) do {              \
 419         (elm)->field.tqe_prev = (listelm)->field.tqe_prev;              \
 420         (elm)->field.tqe_next = (listelm);                              \
 421         *(listelm)->field.tqe_prev = (elm);                             \
 422         (listelm)->field.tqe_prev = &(elm)->field.tqe_next;             \
 423 } while (0)
 424
 425 #define LDAP_TAILQ_REMOVE(head, elm, field) do {                        \
 426         if (((elm)->field.tqe_next) != NULL)                            \
 427                 (elm)->field.tqe_next->field.tqe_prev =                 \
 428                     (elm)->field.tqe_prev;                              \
 429         else                                                            \
 430                 (head)->tqh_last = (elm)->field.tqe_prev;               \
 431         *(elm)->field.tqe_prev = (elm)->field.tqe_next;                 \
 432 } while (0)
 433
 434 /*
 435  * Circular queue definitions.
 436  */
 437 #define LDAP_CIRCLEQ_HEAD(name, type)                                   \
 438 struct name {                                                           \
 439         struct type *cqh_first;         /* first element */             \
 440         struct type *cqh_last;          /* last element */              \
 441 }
 442
 443 #define LDAP_CIRCLEQ_ENTRY(type)                                        \
 444 struct {                                                                \
 445         struct type *cqe_next;          /* next element */              \
 446         struct type *cqe_prev;          /* previous element */          \
 447 }
 448
 449 /*
 450  * Circular queue functions.
 451  */
 452 #define LDAP_CIRCLEQ_EMPTY(head) ((head)->cqh_first == (void *)(head))
 453
 454 #define LDAP_CIRCLEQ_FIRST(head) ((head)->cqh_first)
 455
 456 #define LDAP_CIRCLEQ_FOREACH(var, head, field)                          \
 457         for((var) = (head)->cqh_first;                                  \
 458             (var) != (void *)(head);                                    \
 459             (var) = (var)->field.cqe_next)
 460
 461 #define LDAP_CIRCLEQ_FOREACH_REVERSE(var, head, field)                  \
 462         for((var) = (head)->cqh_last;                                   \
 463             (var) != (void *)(head);                                    \
 464             (var) = (var)->field.cqe_prev)
 465
 466 #define LDAP_CIRCLEQ_INIT(head) do {                                    \
 467         (head)->cqh_first = (void *)(head);                             \
 468         (head)->cqh_last = (void *)(head);                              \
 469 } while (0)
 470
 471 #define LDAP_CIRCLEQ_INSERT_AFTER(head, listelm, elm, field) do {       \
 472         (elm)->field.cqe_next = (listelm)->field.cqe_next;              \
 473         (elm)->field.cqe_prev = (listelm);                              \
 474         if ((listelm)->field.cqe_next == (void *)(head))                \
 475                 (head)->cqh_last = (elm);                               \
 476         else                                                            \
 477                 (listelm)->field.cqe_next->field.cqe_prev = (elm);      \
 478         (listelm)->field.cqe_next = (elm);                              \
 479 } while (0)
 480
 481 #define LDAP_CIRCLEQ_INSERT_BEFORE(head, listelm, elm, field) do {      \
 482         (elm)->field.cqe_next = (listelm);                              \
 483         (elm)->field.cqe_prev = (listelm)->field.cqe_prev;              \
 484         if ((listelm)->field.cqe_prev == (void *)(head))                \
 485                 (head)->cqh_first = (elm);                              \
 486         else                                                            \
 487                 (listelm)->field.cqe_prev->field.cqe_next = (elm);      \
 488         (listelm)->field.cqe_prev = (elm);                              \
 489 } while (0)
 490
 491 #define LDAP_CIRCLEQ_INSERT_HEAD(head, elm, field) do {                 \
 492         (elm)->field.cqe_next = (head)->cqh_first;                      \
 493         (elm)->field.cqe_prev = (void *)(head);                         \
 494         if ((head)->cqh_last == (void *)(head))                         \
 495                 (head)->cqh_last = (elm);                               \
 496         else                                                            \
 497                 (head)->cqh_first->field.cqe_prev = (elm);              \
 498         (head)->cqh_first = (elm);                                      \
 499 } while (0)
 500
 501 #define LDAP_CIRCLEQ_INSERT_TAIL(head, elm, field) do {                 \
 502         (elm)->field.cqe_next = (void *)(head);                         \
 503         (elm)->field.cqe_prev = (head)->cqh_last;                       \
 504         if ((head)->cqh_first == (void *)(head))                        \
 505                 (head)->cqh_first = (elm);                              \
 506         else                                                            \
 507                 (head)->cqh_last->field.cqe_next = (elm);               \
 508         (head)->cqh_last = (elm);                                       \
 509 } while (0)
 510
 511 #define LDAP_CIRCLEQ_LAST(head) ((head)->cqh_last)
 512
 513 #define LDAP_CIRCLEQ_NEXT(elm,field) ((elm)->field.cqe_next)
 514
 515 #define LDAP_CIRCLEQ_PREV(elm,field) ((elm)->field.cqe_prev)
 516
 517 #define LDAP_CIRCLEQ_REMOVE(head, elm, field) do {                      \
 518         if ((elm)->field.cqe_next == (void *)(head))                    \
 519                 (head)->cqh_last = (elm)->field.cqe_prev;               \
 520         else                                                            \
 521                 (elm)->field.cqe_next->field.cqe_prev =                 \
 522                     (elm)->field.cqe_prev;                              \
 523         if ((elm)->field.cqe_prev == (void *)(head))                    \
 524                 (head)->cqh_first = (elm)->field.cqe_next;              \
 525         else                                                            \
 526                 (elm)->field.cqe_prev->field.cqe_next =                 \
 527                     (elm)->field.cqe_next;                              \
 528 } while (0)
 529
 530 #endif /* !_LDAP_QUEUE_H_ */