1/* 2 * Copyright (c) 1991, 1993 3 * The Regents of the University of California. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 3. Neither the name of the University nor the names of its contributors 14 * may be used to endorse or promote products derived from this software 15 * without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 * 29 * @(#)queue.h 8.5 (Berkeley) 8/20/94 30 */ 31 32#ifndef _SYS_QUEUE_H_ 33#define _SYS_QUEUE_H_ 34 35/* 36 * This file defines five types of data structures: singly-linked lists, 37 * lists, simple queues, tail queues, and circular queues. 38 * 39 * A singly-linked list is headed by a single forward pointer. The 40 * elements are singly linked for minimum space and pointer manipulation 41 * overhead at the expense of O(n) removal for arbitrary elements. New 42 * elements can be added to the list after an existing element or at the 43 * head of the list. Elements being removed from the head of the list 44 * should use the explicit macro for this purpose for optimum 45 * efficiency. A singly-linked list may only be traversed in the forward 46 * direction. Singly-linked lists are ideal for applications with large 47 * datasets and few or no removals or for implementing a LIFO queue. 48 * 49 * A list is headed by a single forward pointer (or an array of forward 50 * pointers for a hash table header). The elements are doubly linked 51 * so that an arbitrary element can be removed without a need to 52 * traverse the list. New elements can be added to the list before 53 * or after an existing element or at the head of the list. A list 54 * may only be traversed in the forward direction. 55 * 56 * A simple queue is headed by a pair of pointers, one the head of the 57 * list and the other to the tail of the list. The elements are singly 58 * linked to save space, so elements can only be removed from the 59 * head of the list. New elements can be added to the list after 60 * an existing element, at the head of the list, or at the end of the 61 * list. A simple queue may only be traversed in the forward direction. 62 * 63 * A tail queue is headed by a pair of pointers, one to the head of the 64 * list and the other to the tail of the list. The elements are doubly 65 * linked so that an arbitrary element can be removed without a need to 66 * traverse the list. New elements can be added to the list before or 67 * after an existing element, at the head of the list, or at the end of 68 * the list. A tail queue may be traversed in either direction. 69 * 70 * A circle queue is headed by a pair of pointers, one to the head of the 71 * list and the other to the tail of the list. The elements are doubly 72 * linked so that an arbitrary element can be removed without a need to 73 * traverse the list. New elements can be added to the list before or after 74 * an existing element, at the head of the list, or at the end of the list. 75 * A circle queue may be traversed in either direction, but has a more 76 * complex end of list detection. 77 * 78 * For details on the use of these macros, see the queue(3) manual page. 79 */ 80 81/* 82 * List definitions. 83 */ 84#define LIST_HEAD(name, type) \ 85struct name { \ 86 struct type *lh_first; /* first element */ \ 87} 88 89#define LIST_HEAD_INITIALIZER(head) \ 90 { NULL } 91 92#define LIST_ENTRY(type) \ 93struct { \ 94 struct type *le_next; /* next element */ \ 95 struct type **le_prev; /* address of previous next element */ \ 96} 97 98/* 99 * List functions. 100 */ 101#define LIST_INIT(head) do { \ 102 (head)->lh_first = NULL; \ 103} while (/*CONSTCOND*/0) 104 105#define LIST_INSERT_AFTER(listelm, elm, field) do { \ 106 if (((elm)->field.le_next = (listelm)->field.le_next) != NULL) \ 107 (listelm)->field.le_next->field.le_prev = \ 108 &(elm)->field.le_next; \ 109 (listelm)->field.le_next = (elm); \ 110 (elm)->field.le_prev = &(listelm)->field.le_next; \ 111} while (/*CONSTCOND*/0) 112 113#define LIST_INSERT_BEFORE(listelm, elm, field) do { \ 114 (elm)->field.le_prev = (listelm)->field.le_prev; \ 115 (elm)->field.le_next = (listelm); \ 116 *(listelm)->field.le_prev = (elm); \ 117 (listelm)->field.le_prev = &(elm)->field.le_next; \ 118} while (/*CONSTCOND*/0) 119 120#define LIST_INSERT_HEAD(head, elm, field) do { \ 121 if (((elm)->field.le_next = (head)->lh_first) != NULL) \ 122 (head)->lh_first->field.le_prev = &(elm)->field.le_next;\ 123 (head)->lh_first = (elm); \ 124 (elm)->field.le_prev = &(head)->lh_first; \ 125} while (/*CONSTCOND*/0) 126 127#define LIST_REMOVE(elm, field) do { \ 128 if ((elm)->field.le_next != NULL) \ 129 (elm)->field.le_next->field.le_prev = \ 130 (elm)->field.le_prev; \ 131 *(elm)->field.le_prev = (elm)->field.le_next; \ 132} while (/*CONSTCOND*/0) 133 134#define LIST_FOREACH(var, head, field) \ 135 for ((var) = ((head)->lh_first); \ 136 (var); \ 137 (var) = ((var)->field.le_next)) 138 139/* 140 * List access methods. 141 */ 142#define LIST_EMPTY(head) ((head)->lh_first == NULL) 143#define LIST_FIRST(head) ((head)->lh_first) 144#define LIST_NEXT(elm, field) ((elm)->field.le_next) 145 146 147/* 148 * Singly-linked List definitions. 149 */ 150#define SLIST_HEAD(name, type) \ 151struct name { \ 152 struct type *slh_first; /* first element */ \ 153} 154 155#define SLIST_HEAD_INITIALIZER(head) \ 156 { NULL } 157 158#define SLIST_ENTRY(type) \ 159struct { \ 160 struct type *sle_next; /* next element */ \ 161} 162 163/* 164 * Singly-linked List functions. 165 */ 166#define SLIST_INIT(head) do { \ 167 (head)->slh_first = NULL; \ 168} while (/*CONSTCOND*/0) 169 170#define SLIST_INSERT_AFTER(slistelm, elm, field) do { \ 171 (elm)->field.sle_next = (slistelm)->field.sle_next; \ 172 (slistelm)->field.sle_next = (elm); \ 173} while (/*CONSTCOND*/0) 174 175#define SLIST_INSERT_HEAD(head, elm, field) do { \ 176 (elm)->field.sle_next = (head)->slh_first; \ 177 (head)->slh_first = (elm); \ 178} while (/*CONSTCOND*/0) 179 180#define SLIST_REMOVE_HEAD(head, field) do { \ 181 (head)->slh_first = (head)->slh_first->field.sle_next; \ 182} while (/*CONSTCOND*/0) 183 184#define SLIST_REMOVE(head, elm, type, field) do { \ 185 if ((head)->slh_first == (elm)) { \ 186 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 (/*CONSTCOND*/0) 196 197#define SLIST_FOREACH(var, head, field) \ 198 for((var) = (head)->slh_first; (var); (var) = (var)->field.sle_next) 199 200/* 201 * Singly-linked List access methods. 202 */ 203#define SLIST_EMPTY(head) ((head)->slh_first == NULL) 204#define SLIST_FIRST(head) ((head)->slh_first) 205#define SLIST_NEXT(elm, field) ((elm)->field.sle_next) 206 207 208/* 209 * Singly-linked Tail queue declarations. 210 */ 211#define STAILQ_HEAD(name, type) \ 212struct name { \ 213 struct type *stqh_first; /* first element */ \ 214 struct type **stqh_last; /* addr of last next element */ \ 215} 216 217#define STAILQ_HEAD_INITIALIZER(head) \ 218 { NULL, &(head).stqh_first } 219 220#define STAILQ_ENTRY(type) \ 221struct { \ 222 struct type *stqe_next; /* next element */ \ 223} 224 225/* 226 * Singly-linked Tail queue functions. 227 */ 228#define STAILQ_INIT(head) do { \ 229 (head)->stqh_first = NULL; \ 230 (head)->stqh_last = &(head)->stqh_first; \ 231} while (/*CONSTCOND*/0) 232 233#define 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 (/*CONSTCOND*/0) 238 239#define 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 (/*CONSTCOND*/0) 244 245#define STAILQ_INSERT_AFTER(head, listelm, elm, field) do { \ 246 if (((elm)->field.stqe_next = (listelm)->field.stqe_next) == NULL)\ 247 (head)->stqh_last = &(elm)->field.stqe_next; \ 248 (listelm)->field.stqe_next = (elm); \ 249} while (/*CONSTCOND*/0) 250 251#define STAILQ_REMOVE_HEAD(head, field) do { \ 252 if (((head)->stqh_first = (head)->stqh_first->field.stqe_next) == NULL) \ 253 (head)->stqh_last = &(head)->stqh_first; \ 254} while (/*CONSTCOND*/0) 255 256#define STAILQ_REMOVE(head, elm, type, field) do { \ 257 if ((head)->stqh_first == (elm)) { \ 258 STAILQ_REMOVE_HEAD((head), field); \ 259 } else { \ 260 struct type *curelm = (head)->stqh_first; \ 261 while (curelm->field.stqe_next != (elm)) \ 262 curelm = curelm->field.stqe_next; \ 263 if ((curelm->field.stqe_next = \ 264 curelm->field.stqe_next->field.stqe_next) == NULL) \ 265 (head)->stqh_last = &(curelm)->field.stqe_next; \ 266 } \ 267} while (/*CONSTCOND*/0) 268 269#define STAILQ_FOREACH(var, head, field) \ 270 for ((var) = ((head)->stqh_first); \ 271 (var); \ 272 (var) = ((var)->field.stqe_next)) 273 274#define STAILQ_CONCAT(head1, head2) do { \ 275 if (!STAILQ_EMPTY((head2))) { \ 276 *(head1)->stqh_last = (head2)->stqh_first; \ 277 (head1)->stqh_last = (head2)->stqh_last; \ 278 STAILQ_INIT((head2)); \ 279 } \ 280} while (/*CONSTCOND*/0) 281 282/* 283 * Singly-linked Tail queue access methods. 284 */ 285#define STAILQ_EMPTY(head) ((head)->stqh_first == NULL) 286#define STAILQ_FIRST(head) ((head)->stqh_first) 287#define STAILQ_NEXT(elm, field) ((elm)->field.stqe_next) 288 289 290/* 291 * Simple queue definitions. 292 */ 293#define SIMPLEQ_HEAD(name, type) \ 294struct name { \ 295 struct type *sqh_first; /* first element */ \ 296 struct type **sqh_last; /* addr of last next element */ \ 297} 298 299#define SIMPLEQ_HEAD_INITIALIZER(head) \ 300 { NULL, &(head).sqh_first } 301 302#define SIMPLEQ_ENTRY(type) \ 303struct { \ 304 struct type *sqe_next; /* next element */ \ 305} 306 307/* 308 * Simple queue functions. 309 */ 310#define SIMPLEQ_INIT(head) do { \ 311 (head)->sqh_first = NULL; \ 312 (head)->sqh_last = &(head)->sqh_first; \ 313} while (/*CONSTCOND*/0) 314 315#define SIMPLEQ_INSERT_HEAD(head, elm, field) do { \ 316 if (((elm)->field.sqe_next = (head)->sqh_first) == NULL) \ 317 (head)->sqh_last = &(elm)->field.sqe_next; \ 318 (head)->sqh_first = (elm); \ 319} while (/*CONSTCOND*/0) 320 321#define SIMPLEQ_INSERT_TAIL(head, elm, field) do { \ 322 (elm)->field.sqe_next = NULL; \ 323 *(head)->sqh_last = (elm); \ 324 (head)->sqh_last = &(elm)->field.sqe_next; \ 325} while (/*CONSTCOND*/0) 326 327#define SIMPLEQ_INSERT_AFTER(head, listelm, elm, field) do { \ 328 if (((elm)->field.sqe_next = (listelm)->field.sqe_next) == NULL)\ 329 (head)->sqh_last = &(elm)->field.sqe_next; \ 330 (listelm)->field.sqe_next = (elm); \ 331} while (/*CONSTCOND*/0) 332 333#define SIMPLEQ_REMOVE_HEAD(head, field) do { \ 334 if (((head)->sqh_first = (head)->sqh_first->field.sqe_next) == NULL) \ 335 (head)->sqh_last = &(head)->sqh_first; \ 336} while (/*CONSTCOND*/0) 337 338#define SIMPLEQ_REMOVE(head, elm, type, field) do { \ 339 if ((head)->sqh_first == (elm)) { \ 340 SIMPLEQ_REMOVE_HEAD((head), field); \ 341 } else { \ 342 struct type *curelm = (head)->sqh_first; \ 343 while (curelm->field.sqe_next != (elm)) \ 344 curelm = curelm->field.sqe_next; \ 345 if ((curelm->field.sqe_next = \ 346 curelm->field.sqe_next->field.sqe_next) == NULL) \ 347 (head)->sqh_last = &(curelm)->field.sqe_next; \ 348 } \ 349} while (/*CONSTCOND*/0) 350 351#define SIMPLEQ_FOREACH(var, head, field) \ 352 for ((var) = ((head)->sqh_first); \ 353 (var); \ 354 (var) = ((var)->field.sqe_next)) 355 356/* 357 * Simple queue access methods. 358 */ 359#define SIMPLEQ_EMPTY(head) ((head)->sqh_first == NULL) 360#define SIMPLEQ_FIRST(head) ((head)->sqh_first) 361#define SIMPLEQ_NEXT(elm, field) ((elm)->field.sqe_next) 362 363 364/* 365 * Tail queue definitions. 366 */ 367#define _TAILQ_HEAD(name, type, qual) \ 368struct name { \ 369 qual type *tqh_first; /* first element */ \ 370 qual type *qual *tqh_last; /* addr of last next element */ \ 371} 372#define TAILQ_HEAD(name, type) _TAILQ_HEAD(name, struct type,) 373 374#define TAILQ_HEAD_INITIALIZER(head) \ 375 { NULL, &(head).tqh_first } 376 377#define _TAILQ_ENTRY(type, qual) \ 378struct { \ 379 qual type *tqe_next; /* next element */ \ 380 qual type *qual *tqe_prev; /* address of previous next element */\ 381} 382#define TAILQ_ENTRY(type) _TAILQ_ENTRY(struct type,) 383 384/* 385 * Tail queue functions. 386 */ 387#define TAILQ_INIT(head) do { \ 388 (head)->tqh_first = NULL; \ 389 (head)->tqh_last = &(head)->tqh_first; \ 390} while (/*CONSTCOND*/0) 391 392#define TAILQ_INSERT_HEAD(head, elm, field) do { \ 393 if (((elm)->field.tqe_next = (head)->tqh_first) != NULL) \ 394 (head)->tqh_first->field.tqe_prev = \ 395 &(elm)->field.tqe_next; \ 396 else \ 397 (head)->tqh_last = &(elm)->field.tqe_next; \ 398 (head)->tqh_first = (elm); \ 399 (elm)->field.tqe_prev = &(head)->tqh_first; \ 400} while (/*CONSTCOND*/0) 401 402#define TAILQ_INSERT_TAIL(head, elm, field) do { \ 403 (elm)->field.tqe_next = NULL; \ 404 (elm)->field.tqe_prev = (head)->tqh_last; \ 405 *(head)->tqh_last = (elm); \ 406 (head)->tqh_last = &(elm)->field.tqe_next; \ 407} while (/*CONSTCOND*/0) 408 409#define TAILQ_INSERT_AFTER(head, listelm, elm, field) do { \ 410 if (((elm)->field.tqe_next = (listelm)->field.tqe_next) != NULL)\ 411 (elm)->field.tqe_next->field.tqe_prev = \ 412 &(elm)->field.tqe_next; \ 413 else \ 414 (head)->tqh_last = &(elm)->field.tqe_next; \ 415 (listelm)->field.tqe_next = (elm); \ 416 (elm)->field.tqe_prev = &(listelm)->field.tqe_next; \ 417} while (/*CONSTCOND*/0) 418 419#define TAILQ_INSERT_BEFORE(listelm, elm, field) do { \ 420 (elm)->field.tqe_prev = (listelm)->field.tqe_prev; \ 421 (elm)->field.tqe_next = (listelm); \ 422 *(listelm)->field.tqe_prev = (elm); \ 423 (listelm)->field.tqe_prev = &(elm)->field.tqe_next; \ 424} while (/*CONSTCOND*/0) 425 426#define TAILQ_REMOVE(head, elm, field) do { \ 427 if (((elm)->field.tqe_next) != NULL) \ 428 (elm)->field.tqe_next->field.tqe_prev = \ 429 (elm)->field.tqe_prev; \ 430 else \ 431 (head)->tqh_last = (elm)->field.tqe_prev; \ 432 *(elm)->field.tqe_prev = (elm)->field.tqe_next; \ 433} while (/*CONSTCOND*/0) 434 435#define TAILQ_FOREACH(var, head, field) \ 436 for ((var) = ((head)->tqh_first); \ 437 (var); \ 438 (var) = ((var)->field.tqe_next)) 439 440#define TAILQ_FOREACH_REVERSE(var, head, headname, field) \ 441 for ((var) = (*(((struct headname *)((head)->tqh_last))->tqh_last)); \ 442 (var); \ 443 (var) = (*(((struct headname *)((var)->field.tqe_prev))->tqh_last))) 444 445#define TAILQ_CONCAT(head1, head2, field) do { \ 446 if (!TAILQ_EMPTY(head2)) { \ 447 *(head1)->tqh_last = (head2)->tqh_first; \ 448 (head2)->tqh_first->field.tqe_prev = (head1)->tqh_last; \ 449 (head1)->tqh_last = (head2)->tqh_last; \ 450 TAILQ_INIT((head2)); \ 451 } \ 452} while (/*CONSTCOND*/0) 453 454/* 455 * Tail queue access methods. 456 */ 457#define TAILQ_EMPTY(head) ((head)->tqh_first == NULL) 458#define TAILQ_FIRST(head) ((head)->tqh_first) 459#define TAILQ_NEXT(elm, field) ((elm)->field.tqe_next) 460 461#define TAILQ_LAST(head, headname) \ 462 (*(((struct headname *)((head)->tqh_last))->tqh_last)) 463#define TAILQ_PREV(elm, headname, field) \ 464 (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last)) 465 466 467/* 468 * Circular queue definitions. 469 */ 470#define CIRCLEQ_HEAD(name, type) \ 471struct name { \ 472 struct type *cqh_first; /* first element */ \ 473 struct type *cqh_last; /* last element */ \ 474} 475 476#define CIRCLEQ_HEAD_INITIALIZER(head) \ 477 { (void *)&head, (void *)&head } 478 479#define CIRCLEQ_ENTRY(type) \ 480struct { \ 481 struct type *cqe_next; /* next element */ \ 482 struct type *cqe_prev; /* previous element */ \ 483} 484 485/* 486 * Circular queue functions. 487 */ 488#define CIRCLEQ_INIT(head) do { \ 489 (head)->cqh_first = (void *)(head); \ 490 (head)->cqh_last = (void *)(head); \ 491} while (/*CONSTCOND*/0) 492 493#define CIRCLEQ_INSERT_AFTER(head, listelm, elm, field) do { \ 494 (elm)->field.cqe_next = (listelm)->field.cqe_next; \ 495 (elm)->field.cqe_prev = (listelm); \ 496 if ((listelm)->field.cqe_next == (void *)(head)) \ 497 (head)->cqh_last = (elm); \ 498 else \ 499 (listelm)->field.cqe_next->field.cqe_prev = (elm); \ 500 (listelm)->field.cqe_next = (elm); \ 501} while (/*CONSTCOND*/0) 502 503#define CIRCLEQ_INSERT_BEFORE(head, listelm, elm, field) do { \ 504 (elm)->field.cqe_next = (listelm); \ 505 (elm)->field.cqe_prev = (listelm)->field.cqe_prev; \ 506 if ((listelm)->field.cqe_prev == (void *)(head)) \ 507 (head)->cqh_first = (elm); \ 508 else \ 509 (listelm)->field.cqe_prev->field.cqe_next = (elm); \ 510 (listelm)->field.cqe_prev = (elm); \ 511} while (/*CONSTCOND*/0) 512 513#define CIRCLEQ_INSERT_HEAD(head, elm, field) do { \ 514 (elm)->field.cqe_next = (head)->cqh_first; \ 515 (elm)->field.cqe_prev = (void *)(head); \ 516 if ((head)->cqh_last == (void *)(head)) \ 517 (head)->cqh_last = (elm); \ 518 else \ 519 (head)->cqh_first->field.cqe_prev = (elm); \ 520 (head)->cqh_first = (elm); \ 521} while (/*CONSTCOND*/0) 522 523#define CIRCLEQ_INSERT_TAIL(head, elm, field) do { \ 524 (elm)->field.cqe_next = (void *)(head); \ 525 (elm)->field.cqe_prev = (head)->cqh_last; \ 526 if ((head)->cqh_first == (void *)(head)) \ 527 (head)->cqh_first = (elm); \ 528 else \ 529 (head)->cqh_last->field.cqe_next = (elm); \ 530 (head)->cqh_last = (elm); \ 531} while (/*CONSTCOND*/0) 532 533#define CIRCLEQ_REMOVE(head, elm, field) do { \ 534 if ((elm)->field.cqe_next == (void *)(head)) \ 535 (head)->cqh_last = (elm)->field.cqe_prev; \ 536 else \ 537 (elm)->field.cqe_next->field.cqe_prev = \ 538 (elm)->field.cqe_prev; \ 539 if ((elm)->field.cqe_prev == (void *)(head)) \ 540 (head)->cqh_first = (elm)->field.cqe_next; \ 541 else \ 542 (elm)->field.cqe_prev->field.cqe_next = \ 543 (elm)->field.cqe_next; \ 544} while (/*CONSTCOND*/0) 545 546#define CIRCLEQ_FOREACH(var, head, field) \ 547 for ((var) = ((head)->cqh_first); \ 548 (var) != (const void *)(head); \ 549 (var) = ((var)->field.cqe_next)) 550 551#define CIRCLEQ_FOREACH_REVERSE(var, head, field) \ 552 for ((var) = ((head)->cqh_last); \ 553 (var) != (const void *)(head); \ 554 (var) = ((var)->field.cqe_prev)) 555 556/* 557 * Circular queue access methods. 558 */ 559#define CIRCLEQ_EMPTY(head) ((head)->cqh_first == (void *)(head)) 560#define CIRCLEQ_FIRST(head) ((head)->cqh_first) 561#define CIRCLEQ_LAST(head) ((head)->cqh_last) 562#define CIRCLEQ_NEXT(elm, field) ((elm)->field.cqe_next) 563#define CIRCLEQ_PREV(elm, field) ((elm)->field.cqe_prev) 564 565#define CIRCLEQ_LOOP_NEXT(head, elm, field) \ 566 (((elm)->field.cqe_next == (void *)(head)) \ 567 ? ((head)->cqh_first) \ 568 : (elm->field.cqe_next)) 569#define CIRCLEQ_LOOP_PREV(head, elm, field) \ 570 (((elm)->field.cqe_prev == (void *)(head)) \ 571 ? ((head)->cqh_last) \ 572 : (elm->field.cqe_prev)) 573 574#endif /* sys/queue.h */ 575