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

   1 /* ldap_queue.h -- queue macros */
   2 /* $OpenLDAP$ */
   3 /* This work is part of OpenLDAP Software <http://www.openldap.org/>.
   4  *
   5  * Copyright 2001-2005 The OpenLDAP Foundation.
   6  * All rights reserved.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted only as authorized by the OpenLDAP
  10  * Public License.
  11  *
  12  * A copy of this license is available in file LICENSE in the
  13  * top-level directory of the distribution or, alternatively, at
  14  * <http://www.OpenLDAP.org/license.html>.
  15  */
  16 /* Copyright (c) 1991, 1993
  17  *      The Regents of the University of California.  All rights reserved.
  18  *
  19  * Redistribution and use in source and binary forms, with or without
  20  * modification, are permitted provided that the following conditions
  21  * are met:
  22  * 1. Redistributions of source code must retain the above copyright
  23  *    notice, this list of conditions and the following disclaimer.
  24  * 2. Redistributions in binary form must reproduce the above copyright
  25  *    notice, this list of conditions and the following disclaimer in the
  26  *    documentation and/or other materials provided with the distribution.
  27  * 3. All advertising materials mentioning features or use of this software
  28  *    must display the following acknowledgement:
  29  *      This product includes software developed by the University of
  30  *      California, Berkeley and its contributors.
  31  * 4. Neither the name of the University nor the names of its contributors
  32  *    may be used to endorse or promote products derived from this software
  33  *    without specific prior written permission.
  34  *
  35  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  36  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  37  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  38  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  39  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  40  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  41  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  42  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  43  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  44  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  45  * SUCH DAMAGE.
  46  *
  47  *      @(#)queue.h     8.5 (Berkeley) 8/20/94
  48  * $FreeBSD: src/sys/sys/queue.h,v 1.32.2.5 2001/09/30 21:12:54 luigi Exp $
  49  *
  50  * See also: ftp://ftp.cs.berkeley.edu/pub/4bsd/README.Impt.License.Change
  51  */
  52 /* ACKNOWLEDGEMENTS:
  53  * This work is derived from FreeBSD queue.h work.  Adapted for use in
  54  * OpenLDAP Software by Kurt D. Zeilenga.
  55  */
  56
  57 #ifndef _LDAP_QUEUE_H_
  58 #define _LDAP_QUEUE_H_
  59
  60 /*
  61  * This file defines five types of data structures: singly-linked lists,
  62  * singly-linked tail queues, lists, tail queues, and circular queues.
  63  *
  64  * A singly-linked list is headed by a single forward pointer. The elements
  65  * are singly linked for minimum space and pointer manipulation overhead at
  66  * the expense of O(n) removal for arbitrary elements. New elements can be
  67  * added to the list after an existing element or at the head of the list.
  68  * Elements being removed from the head of the list should use the explicit
  69  * macro for this purpose for optimum efficiency. A singly-linked list may
  70  * only be traversed in the forward direction.  Singly-linked lists are ideal
  71  * for applications with large datasets and few or no removals or for
  72  * implementing a LIFO queue.
  73  *
  74  * A singly-linked tail queue is headed by a pair of pointers, one to the
  75  * head of the list and the other to the tail of the list. The elements are
  76  * singly linked for minimum space and pointer manipulation overhead at the
  77  * expense of O(n) removal for arbitrary elements. New elements can be added
  78  * to the list after an existing element, at the head of the list, or at the
  79  * end of the list. Elements being removed from the head of the tail queue
  80  * should use the explicit macro for this purpose for optimum efficiency.
  81  * A singly-linked tail queue may only be traversed in the forward direction.
  82  * Singly-linked tail queues are ideal for applications with large datasets
  83  * and few or no removals or for implementing a FIFO queue.
  84  *
  85  * A list is headed by a single forward pointer (or an array of forward
  86  * pointers for a hash table header). The elements are doubly linked
  87  * so that an arbitrary element can be removed without a need to
  88  * traverse the list. New elements can be added to the list before
  89  * or after an existing element or at the head of the list. A list
  90  * may only be traversed in the forward direction.
  91  *
  92  * A tail queue is headed by a pair of pointers, one to the head of the
  93  * list and the other to the tail of the list. The elements are doubly
  94  * linked so that an arbitrary element can be removed without a need to
  95  * traverse the list. New elements can be added to the list before or
  96  * after an existing element, at the head of the list, or at the end of
  97  * the list. A tail queue may be traversed in either direction.
  98  *
  99  * A circle queue is headed by a pair of pointers, one to the head of the
 100  * list and the other to the tail of the list. The elements are doubly
 101  * linked so that an arbitrary element can be removed without a need to
 102  * traverse the list. New elements can be added to the list before or after
 103  * an existing element, at the head of the list, or at the end of the list.
 104  * A circle queue may be traversed in either direction, but has a more
 105  * complex end of list detection.
 106  *
 107  * For details on the use of these macros, see the queue(3) manual page.
 108  * All macros are prefixed with LDAP_.
 109  *
 110  *                      SLIST_  LIST_   STAILQ_ TAILQ_  CIRCLEQ_
 111  * _HEAD                +       +       +       +       +
 112  * _ENTRY               +       +       +       +       +
 113  * _INIT                +       +       +       +       +
 114  * _EMPTY               +       +       +       +       +
 115  * _FIRST               +       +       +       +       +
 116  * _NEXT                +       +       +       +       +
 117  * _PREV                -       -       -       +       +
 118  * _LAST                -       -       +       +       +
 119  * _FOREACH             +       +       +       +       +
 120  * _FOREACH_REVERSE     -       -       -       +       +
 121  * _INSERT_HEAD         +       +       +       +       +
 122  * _INSERT_BEFORE       -       +       -       +       +
 123  * _INSERT_AFTER        +       +       +       +       +
 124  * _INSERT_TAIL         -       -       +       +       +
 125  * _REMOVE_HEAD         +       -       +       -       -
 126  * _REMOVE              +       +       +       +       +
 127  *
 128  */
 129
 130 /*
 131  * Singly-linked List definitions.
 132  */
 133 #define LDAP_SLIST_HEAD(name, type)                                     \
 134 struct name {                                                           \
 135         struct type *slh_first; /* first element */                     \
 136 }
 137
 138 #define LDAP_SLIST_HEAD_INITIALIZER(head)                               \
 139         { NULL }
 140
 141 #define LDAP_SLIST_ENTRY(type)                                          \
 142 struct {                                                                \
 143         struct type *sle_next;  /* next element */                      \
 144 }
 145
 146 #define LDAP_SLIST_ENTRY_INITIALIZER(entry)                             \
 147         { NULL }
 148
 149 /*
 150  * Singly-linked List functions.
 151  */
 152 #define LDAP_SLIST_EMPTY(head)  ((head)->slh_first == NULL)
 153
 154 #define LDAP_SLIST_FIRST(head)  ((head)->slh_first)
 155
 156 #define LDAP_SLIST_FOREACH(var, head, field)                            \
 157         for((var) = (head)->slh_first; (var); (var) = (var)->field.sle_next)
 158
 159 #define LDAP_SLIST_INIT(head) {                                         \
 160         (head)->slh_first = NULL;                                       \
 161 }
 162
 163 #define LDAP_SLIST_INSERT_AFTER(slistelm, elm, field) do {              \
 164         (elm)->field.sle_next = (slistelm)->field.sle_next;             \
 165         (slistelm)->field.sle_next = (elm);                             \
 166 } while (0)
 167
 168 #define LDAP_SLIST_INSERT_HEAD(head, elm, field) do {                   \
 169         (elm)->field.sle_next = (head)->slh_first;                      \
 170         (head)->slh_first = (elm);                                      \
 171 } while (0)
 172
 173 #define LDAP_SLIST_NEXT(elm, field)     ((elm)->field.sle_next)
 174
 175 #define LDAP_SLIST_REMOVE_HEAD(head, field) do {                        \
 176         (head)->slh_first = (head)->slh_first->field.sle_next;          \
 177 } while (0)
 178
 179 #define LDAP_SLIST_REMOVE(head, elm, type, field) do {                  \
 180         if ((head)->slh_first == (elm)) {                               \
 181                 LDAP_SLIST_REMOVE_HEAD((head), field);                  \
 182         }                                                               \
 183         else {                                                          \
 184                 struct type *curelm = (head)->slh_first;                \
 185                 while( curelm->field.sle_next != (elm) )                \
 186                         curelm = curelm->field.sle_next;                \
 187                 curelm->field.sle_next =                                \
 188                     curelm->field.sle_next->field.sle_next;             \
 189         }                                                               \
 190 } while (0)
 191
 192 /*
 193  * Singly-linked Tail queue definitions.
 194  */
 195 #define LDAP_STAILQ_HEAD(name, type)                                    \
 196 struct name {                                                           \
 197         struct type *stqh_first;/* first element */                     \
 198         struct type **stqh_last;/* addr of last next element */         \
 199 }
 200
 201 #define LDAP_STAILQ_HEAD_INITIALIZER(head)                              \
 202         { NULL, &(head).stqh_first }
 203
 204 #define LDAP_STAILQ_ENTRY(type)                                         \
 205 struct {                                                                \
 206         struct type *stqe_next; /* next element */                      \
 207 }
 208
 209 #define LDAP_STAILQ_ENTRY_INITIALIZER(entry)                            \
 210         { NULL }
 211
 212 /*
 213  * Singly-linked Tail queue functions.
 214  */
 215 #define LDAP_STAILQ_EMPTY(head) ((head)->stqh_first == NULL)
 216
 217 #define LDAP_STAILQ_INIT(head) do {                                     \
 218         (head)->stqh_first = NULL;                                      \
 219         (head)->stqh_last = &(head)->stqh_first;                        \
 220 } while (0)
 221
 222 #define LDAP_STAILQ_FIRST(head) ((head)->stqh_first)
 223
 224 #define LDAP_STAILQ_LAST(head, type, field)                             \
 225         (LDAP_STAILQ_EMPTY(head) ?                                      \
 226                 NULL :                                                  \
 227                 ((struct type *)                                        \
 228                 ((char *)((head)->stqh_last) - offsetof(struct type, field))))
 229
 230 #define LDAP_STAILQ_FOREACH(var, head, field)                           \
 231         for((var) = (head)->stqh_first; (var); (var) = (var)->field.stqe_next)
 232
 233 #define LDAP_STAILQ_INSERT_HEAD(head, elm, field) do {                  \
 234         if (((elm)->field.stqe_next = (head)->stqh_first) == NULL)      \
 235                 (head)->stqh_last = &(elm)->field.stqe_next;            \
 236         (head)->stqh_first = (elm);                                     \
 237 } while (0)
 238
 239 #define LDAP_STAILQ_INSERT_TAIL(head, elm, field) do {                  \
 240         (elm)->field.stqe_next = NULL;                                  \
 241         *(head)->stqh_last = (elm);                                     \
 242         (head)->stqh_last = &(elm)->field.stqe_next;                    \
 243 } while (0)
 244
 245 #define LDAP_STAILQ_INSERT_AFTER(head, tqelm, elm, field) do {          \
 246         if (((elm)->field.stqe_next = (tqelm)->field.stqe_next) == NULL)\
 247                 (head)->stqh_last = &(elm)->field.stqe_next;            \
 248         (tqelm)->field.stqe_next = (elm);                               \
 249 } while (0)
 250
 251 #define LDAP_STAILQ_NEXT(elm, field)    ((elm)->field.stqe_next)
 252
 253 #define LDAP_STAILQ_REMOVE_HEAD(head, field) do {                       \
 254         if (((head)->stqh_first =                                       \
 255              (head)->stqh_first->field.stqe_next) == NULL)              \
 256                 (head)->stqh_last = &(head)->stqh_first;                \
 257 } while (0)
 258
 259 #define LDAP_STAILQ_REMOVE_HEAD_UNTIL(head, elm, field) do {            \
 260         if (((head)->stqh_first = (elm)->field.stqe_next) == NULL)      \
 261                 (head)->stqh_last = &(head)->stqh_first;                \
 262 } while (0)
 263
 264 #define LDAP_STAILQ_REMOVE(head, elm, type, field) do {                 \
 265         if ((head)->stqh_first == (elm)) {                              \
 266                 LDAP_STAILQ_REMOVE_HEAD(head, field);                   \
 267         }                                                               \
 268         else {                                                          \
 269                 struct type *curelm = (head)->stqh_first;               \
 270                 while( curelm->field.stqe_next != (elm) )               \
 271                         curelm = curelm->field.stqe_next;               \
 272                 if((curelm->field.stqe_next =                           \
 273                     curelm->field.stqe_next->field.stqe_next) == NULL)  \
 274                         (head)->stqh_last = &(curelm)->field.stqe_next; \
 275         }                                                               \
 276 } while (0)
 277
 278 /*
 279  * List definitions.
 280  */
 281 #define LDAP_LIST_HEAD(name, type)                                      \
 282 struct name {                                                           \
 283         struct type *lh_first;  /* first element */                     \
 284 }
 285
 286 #define LDAP_LIST_HEAD_INITIALIZER(head)                                \
 287         { NULL }
 288
 289 #define LDAP_LIST_ENTRY(type)                                           \
 290 struct {                                                                \
 291         struct type *le_next;   /* next element */                      \
 292         struct type **le_prev;  /* address of previous next element */  \
 293 }
 294
 295 #define LDAP_LIST_ENTRY_INITIALIZER(entry)                      \
 296         { NULL, NULL }
 297
 298 /*
 299  * List functions.
 300  */
 301
 302 #define LDAP_LIST_EMPTY(head) ((head)->lh_first == NULL)
 303
 304 #define LDAP_LIST_FIRST(head)   ((head)->lh_first)
 305
 306 #define LDAP_LIST_FOREACH(var, head, field)                             \
 307         for((var) = (head)->lh_first; (var); (var) = (var)->field.le_next)
 308
 309 #define LDAP_LIST_INIT(head) do {                                       \
 310         (head)->lh_first = NULL;                                        \
 311 } while (0)
 312
 313 #define LDAP_LIST_INSERT_AFTER(listelm, elm, field) do {                \
 314         if (((elm)->field.le_next = (listelm)->field.le_next) != NULL)  \
 315                 (listelm)->field.le_next->field.le_prev =               \
 316                     &(elm)->field.le_next;                              \
 317         (listelm)->field.le_next = (elm);                               \
 318         (elm)->field.le_prev = &(listelm)->field.le_next;               \
 319 } while (0)
 320
 321 #define LDAP_LIST_INSERT_BEFORE(listelm, elm, field) do {               \
 322         (elm)->field.le_prev = (listelm)->field.le_prev;                \
 323         (elm)->field.le_next = (listelm);                               \
 324         *(listelm)->field.le_prev = (elm);                              \
 325         (listelm)->field.le_prev = &(elm)->field.le_next;               \
 326 } while (0)
 327
 328 #define LDAP_LIST_INSERT_HEAD(head, elm, field) do {                    \
 329         if (((elm)->field.le_next = (head)->lh_first) != NULL)          \
 330                 (head)->lh_first->field.le_prev = &(elm)->field.le_next;\
 331         (head)->lh_first = (elm);                                       \
 332         (elm)->field.le_prev = &(head)->lh_first;                       \
 333 } while (0)
 334
 335 #define LDAP_LIST_NEXT(elm, field)      ((elm)->field.le_next)
 336
 337 #define LDAP_LIST_REMOVE(elm, field) do {                               \
 338         if ((elm)->field.le_next != NULL)                               \
 339                 (elm)->field.le_next->field.le_prev =                   \
 340                     (elm)->field.le_prev;                               \
 341         *(elm)->field.le_prev = (elm)->field.le_next;                   \
 342 } while (0)
 343
 344 /*
 345  * Tail queue definitions.
 346  */
 347 #define LDAP_TAILQ_HEAD(name, type)                                     \
 348 struct name {                                                           \
 349         struct type *tqh_first; /* first element */                     \
 350         struct type **tqh_last; /* addr of last next element */         \
 351 }
 352
 353 #define LDAP_TAILQ_HEAD_INITIALIZER(head)                               \
 354         { NULL, &(head).tqh_first }
 355
 356 #define LDAP_TAILQ_ENTRY(type)                                          \
 357 struct {                                                                \
 358         struct type *tqe_next;  /* next element */                      \
 359         struct type **tqe_prev; /* address of previous next element */  \
 360 }
 361
 362 #define LDAP_TAILQ_ENTRY_INITIALIZER(entry)                             \
 363         { NULL, NULL }
 364
 365 /*
 366  * Tail queue functions.
 367  */
 368 #define LDAP_TAILQ_EMPTY(head) ((head)->tqh_first == NULL)
 369
 370 #define LDAP_TAILQ_FOREACH(var, head, field)                            \
 371         for (var = LDAP_TAILQ_FIRST(head); var; var = LDAP_TAILQ_NEXT(var, field))
 372
 373 #define LDAP_TAILQ_FOREACH_REVERSE(var, head, type, field)              \
 374         for ((var) = LDAP_TAILQ_LAST((head), type, field);              \
 375              (var);                                                     \
 376              (var) = LDAP_TAILQ_PREV((var), head, type, field))
 377
 378 #define LDAP_TAILQ_FIRST(head) ((head)->tqh_first)
 379
 380 #define LDAP_TAILQ_LAST(head, type, field)                              \
 381         (LDAP_TAILQ_EMPTY(head) ?                                       \
 382                 NULL :                                                  \
 383                 ((struct type *)                                        \
 384                 ((char *)((head)->tqh_last) - offsetof(struct type, field))))
 385
 386 #define LDAP_TAILQ_NEXT(elm, field) ((elm)->field.tqe_next)
 387
 388 #define LDAP_TAILQ_PREV(elm, head, type, field)                         \
 389         ((struct type *)((elm)->field.tqe_prev) == LDAP_TAILQ_FIRST(head) ? \
 390         NULL :                                                          \
 391         ((struct type *)                                                \
 392         ((char *)((elm)->field.tqe_prev) - offsetof(struct type, field))))
 393
 394 #define LDAP_TAILQ_INIT(head) do {                                      \
 395         (head)->tqh_first = NULL;                                       \
 396         (head)->tqh_last = &(head)->tqh_first;                          \
 397 } while (0)
 398
 399 #define LDAP_TAILQ_INSERT_HEAD(head, elm, field) do {                   \
 400         if (((elm)->field.tqe_next = (head)->tqh_first) != NULL)        \
 401                 (head)->tqh_first->field.tqe_prev =                     \
 402                     &(elm)->field.tqe_next;                             \
 403         else                                                            \
 404                 (head)->tqh_last = &(elm)->field.tqe_next;              \
 405         (head)->tqh_first = (elm);                                      \
 406         (elm)->field.tqe_prev = &(head)->tqh_first;                     \
 407 } while (0)
 408
 409 #define LDAP_TAILQ_INSERT_TAIL(head, elm, field) do {                   \
 410         (elm)->field.tqe_next = NULL;                                   \
 411         (elm)->field.tqe_prev = (head)->tqh_last;                       \
 412         *(head)->tqh_last = (elm);                                      \
 413         (head)->tqh_last = &(elm)->field.tqe_next;                      \
 414 } while (0)
 415
 416 #define LDAP_TAILQ_INSERT_AFTER(head, listelm, elm, field) do {         \
 417         if (((elm)->field.tqe_next = (listelm)->field.tqe_next) != NULL)\
 418                 (elm)->field.tqe_next->field.tqe_prev =                 \
 419                     &(elm)->field.tqe_next;                             \
 420         else                                                            \
 421                 (head)->tqh_last = &(elm)->field.tqe_next;              \
 422         (listelm)->field.tqe_next = (elm);                              \
 423         (elm)->field.tqe_prev = &(listelm)->field.tqe_next;             \
 424 } while (0)
 425
 426 #define LDAP_TAILQ_INSERT_BEFORE(listelm, elm, field) do {              \
 427         (elm)->field.tqe_prev = (listelm)->field.tqe_prev;              \
 428         (elm)->field.tqe_next = (listelm);                              \
 429         *(listelm)->field.tqe_prev = (elm);                             \
 430         (listelm)->field.tqe_prev = &(elm)->field.tqe_next;             \
 431 } while (0)
 432
 433 #define LDAP_TAILQ_REMOVE(head, elm, field) do {                        \
 434         if (((elm)->field.tqe_next) != NULL)                            \
 435                 (elm)->field.tqe_next->field.tqe_prev =                 \
 436                     (elm)->field.tqe_prev;                              \
 437         else                                                            \
 438                 (head)->tqh_last = (elm)->field.tqe_prev;               \
 439         *(elm)->field.tqe_prev = (elm)->field.tqe_next;                 \
 440 } while (0)
 441
 442 /*
 443  * Circular queue definitions.
 444  */
 445 #define LDAP_CIRCLEQ_HEAD(name, type)                                   \
 446 struct name {                                                           \
 447         struct type *cqh_first;         /* first element */             \
 448         struct type *cqh_last;          /* last element */              \
 449 }
 450
 451 #define LDAP_CIRCLEQ_ENTRY(type)                                        \
 452 struct {                                                                \
 453         struct type *cqe_next;          /* next element */              \
 454         struct type *cqe_prev;          /* previous element */          \
 455 }
 456
 457 /*
 458  * Circular queue functions.
 459  */
 460 #define LDAP_CIRCLEQ_EMPTY(head) ((head)->cqh_first == (void *)(head))
 461
 462 #define LDAP_CIRCLEQ_FIRST(head) ((head)->cqh_first)
 463
 464 #define LDAP_CIRCLEQ_FOREACH(var, head, field)                          \
 465         for((var) = (head)->cqh_first;                                  \
 466             (var) != (void *)(head);                                    \
 467             (var) = (var)->field.cqe_next)
 468
 469 #define LDAP_CIRCLEQ_FOREACH_REVERSE(var, head, field)                  \
 470         for((var) = (head)->cqh_last;                                   \
 471             (var) != (void *)(head);                                    \
 472             (var) = (var)->field.cqe_prev)
 473
 474 #define LDAP_CIRCLEQ_INIT(head) do {                                    \
 475         (head)->cqh_first = (void *)(head);                             \
 476         (head)->cqh_last = (void *)(head);                              \
 477 } while (0)
 478
 479 #define LDAP_CIRCLEQ_INSERT_AFTER(head, listelm, elm, field) do {       \
 480         (elm)->field.cqe_next = (listelm)->field.cqe_next;              \
 481         (elm)->field.cqe_prev = (listelm);                              \
 482         if ((listelm)->field.cqe_next == (void *)(head))                \
 483                 (head)->cqh_last = (elm);                               \
 484         else                                                            \
 485                 (listelm)->field.cqe_next->field.cqe_prev = (elm);      \
 486         (listelm)->field.cqe_next = (elm);                              \
 487 } while (0)
 488
 489 #define LDAP_CIRCLEQ_INSERT_BEFORE(head, listelm, elm, field) do {      \
 490         (elm)->field.cqe_next = (listelm);                              \
 491         (elm)->field.cqe_prev = (listelm)->field.cqe_prev;              \
 492         if ((listelm)->field.cqe_prev == (void *)(head))                \
 493                 (head)->cqh_first = (elm);                              \
 494         else                                                            \
 495                 (listelm)->field.cqe_prev->field.cqe_next = (elm);      \
 496         (listelm)->field.cqe_prev = (elm);                              \
 497 } while (0)
 498
 499 #define LDAP_CIRCLEQ_INSERT_HEAD(head, elm, field) do {                 \
 500         (elm)->field.cqe_next = (head)->cqh_first;                      \
 501         (elm)->field.cqe_prev = (void *)(head);                         \
 502         if ((head)->cqh_last == (void *)(head))                         \
 503                 (head)->cqh_last = (elm);                               \
 504         else                                                            \
 505                 (head)->cqh_first->field.cqe_prev = (elm);              \
 506         (head)->cqh_first = (elm);                                      \
 507 } while (0)
 508
 509 #define LDAP_CIRCLEQ_INSERT_TAIL(head, elm, field) do {                 \
 510         (elm)->field.cqe_next = (void *)(head);                         \
 511         (elm)->field.cqe_prev = (head)->cqh_last;                       \
 512         if ((head)->cqh_first == (void *)(head))                        \
 513                 (head)->cqh_first = (elm);                              \
 514         else                                                            \
 515                 (head)->cqh_last->field.cqe_next = (elm);               \
 516         (head)->cqh_last = (elm);                                       \
 517 } while (0)
 518
 519 #define LDAP_CIRCLEQ_LAST(head) ((head)->cqh_last)
 520
 521 #define LDAP_CIRCLEQ_NEXT(elm,field) ((elm)->field.cqe_next)
 522
 523 #define LDAP_CIRCLEQ_PREV(elm,field) ((elm)->field.cqe_prev)
 524
 525 #define LDAP_CIRCLEQ_REMOVE(head, elm, field) do {                      \
 526         if ((elm)->field.cqe_next == (void *)(head))                    \
 527                 (head)->cqh_last = (elm)->field.cqe_prev;               \
 528         else                                                            \
 529                 (elm)->field.cqe_next->field.cqe_prev =                 \
 530                     (elm)->field.cqe_prev;                              \
 531         if ((elm)->field.cqe_prev == (void *)(head))                    \
 532                 (head)->cqh_first = (elm)->field.cqe_next;              \
 533         else                                                            \
 534                 (elm)->field.cqe_prev->field.cqe_next =                 \
 535                     (elm)->field.cqe_next;                              \
 536 } while (0)
 537
 538 #endif /* !_LDAP_QUEUE_H_ */