1 /* ldap_queue.h -- queue macros */ 2 /* $OpenLDAP$ */ 3 /* This work is part of OpenLDAP Software <http://www.openldap.org/>. 4 * 5 * Copyright 2001-2021 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 * _ENTRY_INIT + + + + + 115 * _EMPTY + + + + + 116 * _FIRST + + + + + 117 * _NEXT + + + + + 118 * _PREV - - - + + 119 * _LAST - - + + + 120 * _FOREACH + + + + + 121 * _FOREACH_REVERSE - - - + + 122 * _INSERT_HEAD + + + + + 123 * _INSERT_BEFORE - + - + + 124 * _INSERT_AFTER + + + + + 125 * _INSERT_TAIL - - + + + 126 * _REMOVE_HEAD + - + - - 127 * _REMOVE + + + + + 128 * 129 */ 130 131 /* 132 * Singly-linked List definitions. 133 */ 134 #define LDAP_SLIST_HEAD(name, type) \ 135 struct name { \ 136 struct type *slh_first; /* first element */ \ 137 } 138 139 #define LDAP_SLIST_HEAD_INITIALIZER(head) \ 140 { NULL } 141 142 #define LDAP_SLIST_ENTRY(type) \ 143 struct { \ 144 struct type *sle_next; /* next element */ \ 145 } 146 147 #define LDAP_SLIST_ENTRY_INITIALIZER(entry) \ 148 { NULL } 149 150 /* 151 * Singly-linked List functions. 152 */ 153 #define LDAP_SLIST_EMPTY(head) ((head)->slh_first == NULL) 154 155 #define LDAP_SLIST_FIRST(head) ((head)->slh_first) 156 157 #define LDAP_SLIST_FOREACH(var, head, field) \ 158 for((var) = (head)->slh_first; (var); (var) = (var)->field.sle_next) 159 160 #define LDAP_SLIST_INIT(head) { \ 161 (head)->slh_first = NULL; \ 162 } 163 164 #define LDAP_SLIST_ENTRY_INIT(var, field) { \ 165 (var)->field.sle_next = NULL; \ 166 } 167 168 #define LDAP_SLIST_INSERT_AFTER(slistelm, elm, field) do { \ 169 (elm)->field.sle_next = (slistelm)->field.sle_next; \ 170 (slistelm)->field.sle_next = (elm); \ 171 } while (0) 172 173 #define LDAP_SLIST_INSERT_HEAD(head, elm, field) do { \ 174 (elm)->field.sle_next = (head)->slh_first; \ 175 (head)->slh_first = (elm); \ 176 } while (0) 177 178 #define LDAP_SLIST_NEXT(elm, field) ((elm)->field.sle_next) 179 180 #define LDAP_SLIST_REMOVE_HEAD(head, field) do { \ 181 (head)->slh_first = (head)->slh_first->field.sle_next; \ 182 } while (0) 183 184 #define LDAP_SLIST_REMOVE(head, elm, type, field) do { \ 185 if ((head)->slh_first == (elm)) { \ 186 LDAP_SLIST_REMOVE_HEAD((head), field); \ 187 } \ 188 else { \ 189 struct type *curelm = (head)->slh_first; \ 190 while( curelm->field.sle_next != (elm) ) \ 191 curelm = curelm->field.sle_next; \ 192 curelm->field.sle_next = \ 193 curelm->field.sle_next->field.sle_next; \ 194 } \ 195 } while (0) 196 197 /* 198 * Singly-linked Tail queue definitions. 199 */ 200 #define LDAP_STAILQ_HEAD(name, type) \ 201 struct name { \ 202 struct type *stqh_first;/* first element */ \ 203 struct type **stqh_last;/* addr of last next element */ \ 204 } 205 206 #define LDAP_STAILQ_HEAD_INITIALIZER(head) \ 207 { NULL, &(head).stqh_first } 208 209 #define LDAP_STAILQ_ENTRY(type) \ 210 struct { \ 211 struct type *stqe_next; /* next element */ \ 212 } 213 214 #define LDAP_STAILQ_ENTRY_INITIALIZER(entry) \ 215 { NULL } 216 217 /* 218 * Singly-linked Tail queue functions. 219 */ 220 #define LDAP_STAILQ_EMPTY(head) ((head)->stqh_first == NULL) 221 222 #define LDAP_STAILQ_INIT(head) do { \ 223 (head)->stqh_first = NULL; \ 224 (head)->stqh_last = &(head)->stqh_first; \ 225 } while (0) 226 227 #define LDAP_STAILQ_ENTRY_INIT(var, field) { \ 228 (var)->field.stqe_next = NULL; \ 229 } 230 231 #define LDAP_STAILQ_FIRST(head) ((head)->stqh_first) 232 233 #define LDAP_STAILQ_LAST(head, type, field) \ 234 (LDAP_STAILQ_EMPTY(head) ? \ 235 NULL : \ 236 ((struct type *) \ 237 ((char *)((head)->stqh_last) - offsetof(struct type, field)))) 238 239 #define LDAP_STAILQ_FOREACH(var, head, field) \ 240 for((var) = (head)->stqh_first; (var); (var) = (var)->field.stqe_next) 241 242 #define LDAP_STAILQ_INSERT_HEAD(head, elm, field) do { \ 243 if (((elm)->field.stqe_next = (head)->stqh_first) == NULL) \ 244 (head)->stqh_last = &(elm)->field.stqe_next; \ 245 (head)->stqh_first = (elm); \ 246 } while (0) 247 248 #define LDAP_STAILQ_INSERT_TAIL(head, elm, field) do { \ 249 (elm)->field.stqe_next = NULL; \ 250 *(head)->stqh_last = (elm); \ 251 (head)->stqh_last = &(elm)->field.stqe_next; \ 252 } while (0) 253 254 #define LDAP_STAILQ_INSERT_AFTER(head, tqelm, elm, field) do { \ 255 if (((elm)->field.stqe_next = (tqelm)->field.stqe_next) == NULL)\ 256 (head)->stqh_last = &(elm)->field.stqe_next; \ 257 (tqelm)->field.stqe_next = (elm); \ 258 } while (0) 259 260 #define LDAP_STAILQ_NEXT(elm, field) ((elm)->field.stqe_next) 261 262 #define LDAP_STAILQ_REMOVE_HEAD(head, field) do { \ 263 if (((head)->stqh_first = \ 264 (head)->stqh_first->field.stqe_next) == NULL) \ 265 (head)->stqh_last = &(head)->stqh_first; \ 266 } while (0) 267 268 #define LDAP_STAILQ_REMOVE_HEAD_UNTIL(head, elm, field) do { \ 269 if (((head)->stqh_first = (elm)->field.stqe_next) == NULL) \ 270 (head)->stqh_last = &(head)->stqh_first; \ 271 } while (0) 272 273 #define LDAP_STAILQ_REMOVE(head, elm, type, field) do { \ 274 if ((head)->stqh_first == (elm)) { \ 275 LDAP_STAILQ_REMOVE_HEAD(head, field); \ 276 } \ 277 else { \ 278 struct type *curelm = (head)->stqh_first; \ 279 while( curelm->field.stqe_next != (elm) ) \ 280 curelm = curelm->field.stqe_next; \ 281 if((curelm->field.stqe_next = \ 282 curelm->field.stqe_next->field.stqe_next) == NULL) \ 283 (head)->stqh_last = &(curelm)->field.stqe_next; \ 284 } \ 285 } while (0) 286 287 /* 288 * List definitions. 289 */ 290 #define LDAP_LIST_HEAD(name, type) \ 291 struct name { \ 292 struct type *lh_first; /* first element */ \ 293 } 294 295 #define LDAP_LIST_HEAD_INITIALIZER(head) \ 296 { NULL } 297 298 #define LDAP_LIST_ENTRY(type) \ 299 struct { \ 300 struct type *le_next; /* next element */ \ 301 struct type **le_prev; /* address of previous next element */ \ 302 } 303 304 #define LDAP_LIST_ENTRY_INITIALIZER(entry) \ 305 { NULL, NULL } 306 307 /* 308 * List functions. 309 */ 310 311 #define LDAP_LIST_EMPTY(head) ((head)->lh_first == NULL) 312 313 #define LDAP_LIST_FIRST(head) ((head)->lh_first) 314 315 #define LDAP_LIST_FOREACH(var, head, field) \ 316 for((var) = (head)->lh_first; (var); (var) = (var)->field.le_next) 317 318 #define LDAP_LIST_INIT(head) do { \ 319 (head)->lh_first = NULL; \ 320 } while (0) 321 322 #define LDAP_LIST_ENTRY_INIT(var, field) do { \ 323 (var)->field.le_next = NULL; \ 324 (var)->field.le_prev = NULL; \ 325 } while (0) 326 327 #define LDAP_LIST_INSERT_AFTER(listelm, elm, field) do { \ 328 if (((elm)->field.le_next = (listelm)->field.le_next) != NULL) \ 329 (listelm)->field.le_next->field.le_prev = \ 330 &(elm)->field.le_next; \ 331 (listelm)->field.le_next = (elm); \ 332 (elm)->field.le_prev = &(listelm)->field.le_next; \ 333 } while (0) 334 335 #define LDAP_LIST_INSERT_BEFORE(listelm, elm, field) do { \ 336 (elm)->field.le_prev = (listelm)->field.le_prev; \ 337 (elm)->field.le_next = (listelm); \ 338 *(listelm)->field.le_prev = (elm); \ 339 (listelm)->field.le_prev = &(elm)->field.le_next; \ 340 } while (0) 341 342 #define LDAP_LIST_INSERT_HEAD(head, elm, field) do { \ 343 if (((elm)->field.le_next = (head)->lh_first) != NULL) \ 344 (head)->lh_first->field.le_prev = &(elm)->field.le_next;\ 345 (head)->lh_first = (elm); \ 346 (elm)->field.le_prev = &(head)->lh_first; \ 347 } while (0) 348 349 #define LDAP_LIST_NEXT(elm, field) ((elm)->field.le_next) 350 351 #define LDAP_LIST_REMOVE(elm, field) do { \ 352 if ((elm)->field.le_next != NULL) \ 353 (elm)->field.le_next->field.le_prev = \ 354 (elm)->field.le_prev; \ 355 *(elm)->field.le_prev = (elm)->field.le_next; \ 356 } while (0) 357 358 /* 359 * Tail queue definitions. 360 */ 361 #define LDAP_TAILQ_HEAD(name, type) \ 362 struct name { \ 363 struct type *tqh_first; /* first element */ \ 364 struct type **tqh_last; /* addr of last next element */ \ 365 } 366 367 #define LDAP_TAILQ_HEAD_INITIALIZER(head) \ 368 { NULL, &(head).tqh_first } 369 370 #define LDAP_TAILQ_ENTRY(type) \ 371 struct { \ 372 struct type *tqe_next; /* next element */ \ 373 struct type **tqe_prev; /* address of previous next element */ \ 374 } 375 376 #define LDAP_TAILQ_ENTRY_INITIALIZER(entry) \ 377 { NULL, NULL } 378 379 /* 380 * Tail queue functions. 381 */ 382 #define LDAP_TAILQ_EMPTY(head) ((head)->tqh_first == NULL) 383 384 #define LDAP_TAILQ_FOREACH(var, head, field) \ 385 for (var = LDAP_TAILQ_FIRST(head); var; var = LDAP_TAILQ_NEXT(var, field)) 386 387 #define LDAP_TAILQ_FOREACH_REVERSE(var, head, headname, field) \ 388 for ((var) = LDAP_TAILQ_LAST((head), headname); \ 389 (var); \ 390 (var) = LDAP_TAILQ_PREV((var), headname, field)) 391 392 #define LDAP_TAILQ_FIRST(head) ((head)->tqh_first) 393 394 #define LDAP_TAILQ_LAST(head, headname) \ 395 (*(((struct headname *)((head)->tqh_last))->tqh_last)) 396 397 #define LDAP_TAILQ_NEXT(elm, field) ((elm)->field.tqe_next) 398 399 #define LDAP_TAILQ_PREV(elm, headname, field) \ 400 (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last)) 401 402 #define LDAP_TAILQ_INIT(head) do { \ 403 (head)->tqh_first = NULL; \ 404 (head)->tqh_last = &(head)->tqh_first; \ 405 } while (0) 406 407 #define LDAP_TAILQ_ENTRY_INIT(var, field) do { \ 408 (var)->field.tqe_next = NULL; \ 409 (var)->field.tqe_prev = NULL; \ 410 } while (0) 411 412 #define LDAP_TAILQ_INSERT_HEAD(head, elm, field) do { \ 413 if (((elm)->field.tqe_next = (head)->tqh_first) != NULL) \ 414 (head)->tqh_first->field.tqe_prev = \ 415 &(elm)->field.tqe_next; \ 416 else \ 417 (head)->tqh_last = &(elm)->field.tqe_next; \ 418 (head)->tqh_first = (elm); \ 419 (elm)->field.tqe_prev = &(head)->tqh_first; \ 420 } while (0) 421 422 #define LDAP_TAILQ_INSERT_TAIL(head, elm, field) do { \ 423 (elm)->field.tqe_next = NULL; \ 424 (elm)->field.tqe_prev = (head)->tqh_last; \ 425 *(head)->tqh_last = (elm); \ 426 (head)->tqh_last = &(elm)->field.tqe_next; \ 427 } while (0) 428 429 #define LDAP_TAILQ_INSERT_AFTER(head, listelm, elm, field) do { \ 430 if (((elm)->field.tqe_next = (listelm)->field.tqe_next) != NULL)\ 431 (elm)->field.tqe_next->field.tqe_prev = \ 432 &(elm)->field.tqe_next; \ 433 else \ 434 (head)->tqh_last = &(elm)->field.tqe_next; \ 435 (listelm)->field.tqe_next = (elm); \ 436 (elm)->field.tqe_prev = &(listelm)->field.tqe_next; \ 437 } while (0) 438 439 #define LDAP_TAILQ_INSERT_BEFORE(listelm, elm, field) do { \ 440 (elm)->field.tqe_prev = (listelm)->field.tqe_prev; \ 441 (elm)->field.tqe_next = (listelm); \ 442 *(listelm)->field.tqe_prev = (elm); \ 443 (listelm)->field.tqe_prev = &(elm)->field.tqe_next; \ 444 } while (0) 445 446 #define LDAP_TAILQ_REMOVE(head, elm, field) do { \ 447 if (((elm)->field.tqe_next) != NULL) \ 448 (elm)->field.tqe_next->field.tqe_prev = \ 449 (elm)->field.tqe_prev; \ 450 else \ 451 (head)->tqh_last = (elm)->field.tqe_prev; \ 452 *(elm)->field.tqe_prev = (elm)->field.tqe_next; \ 453 } while (0) 454 455 /* 456 * Circular queue definitions. 457 */ 458 #define LDAP_CIRCLEQ_HEAD(name, type) \ 459 struct name { \ 460 struct type *cqh_first; /* first element */ \ 461 struct type *cqh_last; /* last element */ \ 462 } 463 464 #define LDAP_CIRCLEQ_ENTRY(type) \ 465 struct { \ 466 struct type *cqe_next; /* next element */ \ 467 struct type *cqe_prev; /* previous element */ \ 468 } 469 470 /* 471 * Circular queue functions. 472 */ 473 #define LDAP_CIRCLEQ_EMPTY(head) ((head)->cqh_first == (void *)(head)) 474 475 #define LDAP_CIRCLEQ_FIRST(head) ((head)->cqh_first) 476 477 #define LDAP_CIRCLEQ_FOREACH(var, head, field) \ 478 for((var) = (head)->cqh_first; \ 479 (var) != (void *)(head); \ 480 (var) = (var)->field.cqe_next) 481 482 #define LDAP_CIRCLEQ_FOREACH_REVERSE(var, head, field) \ 483 for((var) = (head)->cqh_last; \ 484 (var) != (void *)(head); \ 485 (var) = (var)->field.cqe_prev) 486 487 #define LDAP_CIRCLEQ_INIT(head) do { \ 488 (head)->cqh_first = (void *)(head); \ 489 (head)->cqh_last = (void *)(head); \ 490 } while (0) 491 492 #define LDAP_CIRCLEQ_ENTRY_INIT(var, field) do { \ 493 (var)->field.cqe_next = NULL; \ 494 (var)->field.cqe_prev = NULL; \ 495 } while (0) 496 497 #define LDAP_CIRCLEQ_INSERT_AFTER(head, listelm, elm, field) do { \ 498 (elm)->field.cqe_next = (listelm)->field.cqe_next; \ 499 (elm)->field.cqe_prev = (listelm); \ 500 if ((listelm)->field.cqe_next == (void *)(head)) \ 501 (head)->cqh_last = (elm); \ 502 else \ 503 (listelm)->field.cqe_next->field.cqe_prev = (elm); \ 504 (listelm)->field.cqe_next = (elm); \ 505 } while (0) 506 507 #define LDAP_CIRCLEQ_INSERT_BEFORE(head, listelm, elm, field) do { \ 508 (elm)->field.cqe_next = (listelm); \ 509 (elm)->field.cqe_prev = (listelm)->field.cqe_prev; \ 510 if ((listelm)->field.cqe_prev == (void *)(head)) \ 511 (head)->cqh_first = (elm); \ 512 else \ 513 (listelm)->field.cqe_prev->field.cqe_next = (elm); \ 514 (listelm)->field.cqe_prev = (elm); \ 515 } while (0) 516 517 #define LDAP_CIRCLEQ_INSERT_HEAD(head, elm, field) do { \ 518 (elm)->field.cqe_next = (head)->cqh_first; \ 519 (elm)->field.cqe_prev = (void *)(head); \ 520 if ((head)->cqh_last == (void *)(head)) \ 521 (head)->cqh_last = (elm); \ 522 else \ 523 (head)->cqh_first->field.cqe_prev = (elm); \ 524 (head)->cqh_first = (elm); \ 525 } while (0) 526 527 #define LDAP_CIRCLEQ_INSERT_TAIL(head, elm, field) do { \ 528 (elm)->field.cqe_next = (void *)(head); \ 529 (elm)->field.cqe_prev = (head)->cqh_last; \ 530 if ((head)->cqh_first == (void *)(head)) \ 531 (head)->cqh_first = (elm); \ 532 else \ 533 (head)->cqh_last->field.cqe_next = (elm); \ 534 (head)->cqh_last = (elm); \ 535 } while (0) 536 537 #define LDAP_CIRCLEQ_LAST(head) ((head)->cqh_last) 538 539 #define LDAP_CIRCLEQ_NEXT(elm,field) ((elm)->field.cqe_next) 540 541 #define LDAP_CIRCLEQ_PREV(elm,field) ((elm)->field.cqe_prev) 542 543 #define LDAP_CIRCLEQ_REMOVE(head, elm, field) do { \ 544 if ((elm)->field.cqe_next == (void *)(head)) \ 545 (head)->cqh_last = (elm)->field.cqe_prev; \ 546 else \ 547 (elm)->field.cqe_next->field.cqe_prev = \ 548 (elm)->field.cqe_prev; \ 549 if ((elm)->field.cqe_prev == (void *)(head)) \ 550 (head)->cqh_first = (elm)->field.cqe_next; \ 551 else \ 552 (elm)->field.cqe_prev->field.cqe_next = \ 553 (elm)->field.cqe_next; \ 554 } while (0) 555 556 #endif /* !_LDAP_QUEUE_H_ */ 557