1/* $NetBSD: queue.h,v 1.31 2002/06/01 23:51:05 lukem Exp $ */ 2 3/* 4 * Copyright (c) 1991, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 3. All advertising materials mentioning features or use of this software 16 * must display the following acknowledgement: 17 * This product includes software developed by the University of 18 * California, Berkeley and its contributors. 19 * 4. Neither the name of the University nor the names of its contributors 20 * may be used to endorse or promote products derived from this software 21 * without specific prior written permission. 22 * 23 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33 * SUCH DAMAGE. 34 * 35 * @(#)queue.h 8.5 (Berkeley) 8/20/94 36 */ 37 38#ifndef _SYS_QUEUE_H_ 39#define _SYS_QUEUE_H_ 40 41/* 42 * This file defines five types of data structures: singly-linked lists, 43 * lists, simple queues, tail queues, and circular queues. 44 * 45 * A singly-linked list is headed by a single forward pointer. The 46 * elements are singly linked for minimum space and pointer manipulation 47 * overhead at the expense of O(n) removal for arbitrary elements. New 48 * elements can be added to the list after an existing element or at the 49 * head of the list. Elements being removed from the head of the list 50 * should use the explicit macro for this purpose for optimum 51 * efficiency. A singly-linked list may only be traversed in the forward 52 * direction. Singly-linked lists are ideal for applications with large 53 * datasets and few or no removals or for implementing a LIFO queue. 54 * 55 * A list is headed by a single forward pointer (or an array of forward 56 * pointers for a hash table header). The elements are doubly linked 57 * so that an arbitrary element can be removed without a need to 58 * traverse the list. New elements can be added to the list before 59 * or after an existing element or at the head of the list. A list 60 * may only be traversed in the forward direction. 61 * 62 * A simple queue is headed by a pair of pointers, one the head of the 63 * list and the other to the tail of the list. The elements are singly 64 * linked to save space, so only elements can only be removed from the 65 * head of the list. New elements can be added to the list after 66 * an existing element, at the head of the list, or at the end of the 67 * list. A simple queue may only be traversed in the forward direction. 68 * 69 * A tail queue is headed by a pair of pointers, one to the head of the 70 * list and the other to the tail of the list. The elements are doubly 71 * linked so that an arbitrary element can be removed without a need to 72 * traverse the list. New elements can be added to the list before or 73 * after an existing element, at the head of the list, or at the end of 74 * the list. A tail queue may be traversed in either direction. 75 * 76 * A circle queue is headed by a pair of pointers, one to the head of the 77 * list and the other to the tail of the list. The elements are doubly 78 * linked so that an arbitrary element can be removed without a need to 79 * traverse the list. New elements can be added to the list before or after 80 * an existing element, at the head of the list, or at the end of the list. 81 * A circle queue may be traversed in either direction, but has a more 82 * complex end of list detection. 83 * 84 * For details on the use of these macros, see the queue(3) manual page. 85 */ 86 87/* 88 * List definitions. 89 */ 90#define LIST_HEAD(name, type) \ 91struct name { \ 92 struct type *lh_first; /* first element */ \ 93} 94 95#define LIST_HEAD_INITIALIZER(head) \ 96 { NULL } 97 98#define LIST_ENTRY(type) \ 99struct { \ 100 struct type *le_next; /* next element */ \ 101 struct type **le_prev; /* address of previous next element */ \ 102} 103 104/* 105 * List functions. 106 */ 107#if defined(_KERNEL) && defined(QUEUEDEBUG) 108#define QUEUEDEBUG_LIST_INSERT_HEAD(head, elm, field) \ 109 if ((head)->lh_first && \ 110 (head)->lh_first->field.le_prev != &(head)->lh_first) \ 111 panic("LIST_INSERT_HEAD %p %s:%d", (head), __FILE__, __LINE__); 112#define QUEUEDEBUG_LIST_OP(elm, field) \ 113 if ((elm)->field.le_next && \ 114 (elm)->field.le_next->field.le_prev != \ 115 &(elm)->field.le_next) \ 116 panic("LIST_* forw %p %s:%d", (elm), __FILE__, __LINE__);\ 117 if (*(elm)->field.le_prev != (elm)) \ 118 panic("LIST_* back %p %s:%d", (elm), __FILE__, __LINE__); 119#define QUEUEDEBUG_LIST_POSTREMOVE(elm, field) \ 120 (elm)->field.le_next = (void *)1L; \ 121 (elm)->field.le_prev = (void *)1L; 122#else 123#define QUEUEDEBUG_LIST_INSERT_HEAD(head, elm, field) 124#define QUEUEDEBUG_LIST_OP(elm, field) 125#define QUEUEDEBUG_LIST_POSTREMOVE(elm, field) 126#endif 127 128#define LIST_INIT(head) do { \ 129 (head)->lh_first = NULL; \ 130} while (/*CONSTCOND*/0) 131 132#define LIST_INSERT_AFTER(listelm, elm, field) do { \ 133 QUEUEDEBUG_LIST_OP((listelm), field) \ 134 if (((elm)->field.le_next = (listelm)->field.le_next) != NULL) \ 135 (listelm)->field.le_next->field.le_prev = \ 136 &(elm)->field.le_next; \ 137 (listelm)->field.le_next = (elm); \ 138 (elm)->field.le_prev = &(listelm)->field.le_next; \ 139} while (/*CONSTCOND*/0) 140 141#define LIST_INSERT_BEFORE(listelm, elm, field) do { \ 142 QUEUEDEBUG_LIST_OP((listelm), field) \ 143 (elm)->field.le_prev = (listelm)->field.le_prev; \ 144 (elm)->field.le_next = (listelm); \ 145 *(listelm)->field.le_prev = (elm); \ 146 (listelm)->field.le_prev = &(elm)->field.le_next; \ 147} while (/*CONSTCOND*/0) 148 149#define LIST_INSERT_HEAD(head, elm, field) do { \ 150 QUEUEDEBUG_LIST_INSERT_HEAD((head), (elm), field) \ 151 if (((elm)->field.le_next = (head)->lh_first) != NULL) \ 152 (head)->lh_first->field.le_prev = &(elm)->field.le_next;\ 153 (head)->lh_first = (elm); \ 154 (elm)->field.le_prev = &(head)->lh_first; \ 155} while (/*CONSTCOND*/0) 156 157#define LIST_REMOVE(elm, field) do { \ 158 QUEUEDEBUG_LIST_OP((elm), field) \ 159 if ((elm)->field.le_next != NULL) \ 160 (elm)->field.le_next->field.le_prev = \ 161 (elm)->field.le_prev; \ 162 *(elm)->field.le_prev = (elm)->field.le_next; \ 163 QUEUEDEBUG_LIST_POSTREMOVE((elm), field) \ 164} while (/*CONSTCOND*/0) 165 166#define LIST_FOREACH(var, head, field) \ 167 for ((var) = ((head)->lh_first); \ 168 (var); \ 169 (var) = ((var)->field.le_next)) 170 171/* 172 * List access methods. 173 */ 174#define LIST_EMPTY(head) ((head)->lh_first == NULL) 175#define LIST_FIRST(head) ((head)->lh_first) 176#define LIST_NEXT(elm, field) ((elm)->field.le_next) 177 178/* 179 * Singly-linked List definitions. 180 */ 181#define SLIST_HEAD(name, type) \ 182struct name { \ 183 struct type *slh_first; /* first element */ \ 184} 185 186#define SLIST_HEAD_INITIALIZER(head) \ 187 { NULL } 188 189#define SLIST_ENTRY(type) \ 190struct { \ 191 struct type *sle_next; /* next element */ \ 192} 193 194/* 195 * Singly-linked List functions. 196 */ 197#define SLIST_EMPTY(head) ((head)->slh_first == NULL) 198#define SLIST_FIRST(head) ((head)->slh_first) 199#define SLIST_NEXT(elm, field) ((elm)->field.sle_next) 200 201#define SLIST_FOREACH(var, head, field) \ 202 for((var) = (head)->slh_first; (var); (var) = (var)->field.sle_next) 203 204#define SLIST_INIT(head) do { \ 205 (head)->slh_first = NULL; \ 206} while (/*CONSTCOND*/0) 207 208#define SLIST_INSERT_AFTER(slistelm, elm, field) do { \ 209 (elm)->field.sle_next = (slistelm)->field.sle_next; \ 210 (slistelm)->field.sle_next = (elm); \ 211} while (/*CONSTCOND*/0) 212 213#define SLIST_INSERT_HEAD(head, elm, field) do { \ 214 (elm)->field.sle_next = (head)->slh_first; \ 215 (head)->slh_first = (elm); \ 216} while (/*CONSTCOND*/0) 217 218#define SLIST_NEXT(elm, field) ((elm)->field.sle_next) 219 220#define SLIST_REMOVE_HEAD(head, field) do { \ 221 (head)->slh_first = (head)->slh_first->field.sle_next; \ 222} while (/*CONSTCOND*/0) 223 224#define SLIST_REMOVE(head, elm, type, field) do { \ 225 if ((head)->slh_first == (elm)) { \ 226 SLIST_REMOVE_HEAD((head), field); \ 227 } \ 228 else { \ 229 struct type *curelm = (head)->slh_first; \ 230 while(curelm->field.sle_next != (elm)) \ 231 curelm = curelm->field.sle_next; \ 232 curelm->field.sle_next = \ 233 curelm->field.sle_next->field.sle_next; \ 234 } \ 235} while (/*CONSTCOND*/0) 236 237/* 238 * Simple queue definitions. 239 */ 240#define SIMPLEQ_HEAD(name, type) \ 241struct name { \ 242 struct type *sqh_first; /* first element */ \ 243 struct type **sqh_last; /* addr of last next element */ \ 244} 245 246#define SIMPLEQ_HEAD_INITIALIZER(head) \ 247 { NULL, &(head).sqh_first } 248 249#define SIMPLEQ_ENTRY(type) \ 250struct { \ 251 struct type *sqe_next; /* next element */ \ 252} 253 254/* 255 * Simple queue functions. 256 */ 257#define SIMPLEQ_INIT(head) do { \ 258 (head)->sqh_first = NULL; \ 259 (head)->sqh_last = &(head)->sqh_first; \ 260} while (/*CONSTCOND*/0) 261 262#define SIMPLEQ_INSERT_HEAD(head, elm, field) do { \ 263 if (((elm)->field.sqe_next = (head)->sqh_first) == NULL) \ 264 (head)->sqh_last = &(elm)->field.sqe_next; \ 265 (head)->sqh_first = (elm); \ 266} while (/*CONSTCOND*/0) 267 268#define SIMPLEQ_INSERT_TAIL(head, elm, field) do { \ 269 (elm)->field.sqe_next = NULL; \ 270 *(head)->sqh_last = (elm); \ 271 (head)->sqh_last = &(elm)->field.sqe_next; \ 272} while (/*CONSTCOND*/0) 273 274#define SIMPLEQ_INSERT_AFTER(head, listelm, elm, field) do { \ 275 if (((elm)->field.sqe_next = (listelm)->field.sqe_next) == NULL)\ 276 (head)->sqh_last = &(elm)->field.sqe_next; \ 277 (listelm)->field.sqe_next = (elm); \ 278} while (/*CONSTCOND*/0) 279 280#define SIMPLEQ_REMOVE_HEAD(head, field) do { \ 281 if (((head)->sqh_first = (head)->sqh_first->field.sqe_next) == NULL) \ 282 (head)->sqh_last = &(head)->sqh_first; \ 283} while (/*CONSTCOND*/0) 284 285#define SIMPLEQ_REMOVE(head, elm, type, field) do { \ 286 if ((head)->sqh_first == (elm)) { \ 287 SIMPLEQ_REMOVE_HEAD((head), field); \ 288 } else { \ 289 struct type *curelm = (head)->sqh_first; \ 290 while (curelm->field.sqe_next != (elm)) \ 291 curelm = curelm->field.sqe_next; \ 292 if ((curelm->field.sqe_next = \ 293 curelm->field.sqe_next->field.sqe_next) == NULL) \ 294 (head)->sqh_last = &(curelm)->field.sqe_next; \ 295 } \ 296} while (/*CONSTCOND*/0) 297 298#define SIMPLEQ_FOREACH(var, head, field) \ 299 for ((var) = ((head)->sqh_first); \ 300 (var); \ 301 (var) = ((var)->field.sqe_next)) 302 303/* 304 * Simple queue access methods. 305 */ 306#define SIMPLEQ_EMPTY(head) ((head)->sqh_first == NULL) 307#define SIMPLEQ_FIRST(head) ((head)->sqh_first) 308#define SIMPLEQ_NEXT(elm, field) ((elm)->field.sqe_next) 309 310/* 311 * Tail queue definitions. 312 */ 313#define TAILQ_HEAD(name, type) \ 314struct name { \ 315 struct type *tqh_first; /* first element */ \ 316 struct type **tqh_last; /* addr of last next element */ \ 317} 318 319#define TAILQ_HEAD_INITIALIZER(head) \ 320 { NULL, &(head).tqh_first } 321 322#define TAILQ_ENTRY(type) \ 323struct { \ 324 struct type *tqe_next; /* next element */ \ 325 struct type **tqe_prev; /* address of previous next element */ \ 326} 327 328/* 329 * Tail queue functions. 330 */ 331#if defined(_KERNEL) && defined(QUEUEDEBUG) 332#define QUEUEDEBUG_TAILQ_INSERT_HEAD(head, elm, field) \ 333 if ((head)->tqh_first && \ 334 (head)->tqh_first->field.tqe_prev != &(head)->tqh_first) \ 335 panic("TAILQ_INSERT_HEAD %p %s:%d", (head), __FILE__, __LINE__); 336#define QUEUEDEBUG_TAILQ_INSERT_TAIL(head, elm, field) \ 337 if (*(head)->tqh_last != NULL) \ 338 panic("TAILQ_INSERT_TAIL %p %s:%d", (head), __FILE__, __LINE__); 339#define QUEUEDEBUG_TAILQ_OP(elm, field) \ 340 if ((elm)->field.tqe_next && \ 341 (elm)->field.tqe_next->field.tqe_prev != \ 342 &(elm)->field.tqe_next) \ 343 panic("TAILQ_* forw %p %s:%d", (elm), __FILE__, __LINE__);\ 344 if (*(elm)->field.tqe_prev != (elm)) \ 345 panic("TAILQ_* back %p %s:%d", (elm), __FILE__, __LINE__); 346#define QUEUEDEBUG_TAILQ_POSTREMOVE(elm, field) \ 347 (elm)->field.tqe_next = (void *)1L; \ 348 (elm)->field.tqe_prev = (void *)1L; 349#else 350#define QUEUEDEBUG_TAILQ_INSERT_HEAD(head, elm, field) 351#define QUEUEDEBUG_TAILQ_INSERT_TAIL(head, elm, field) 352#define QUEUEDEBUG_TAILQ_OP(elm, field) 353#define QUEUEDEBUG_TAILQ_POSTREMOVE(elm, field) 354#endif 355 356#define TAILQ_INIT(head) do { \ 357 (head)->tqh_first = NULL; \ 358 (head)->tqh_last = &(head)->tqh_first; \ 359} while (/*CONSTCOND*/0) 360 361#define TAILQ_INSERT_HEAD(head, elm, field) do { \ 362 QUEUEDEBUG_TAILQ_INSERT_HEAD((head), (elm), field) \ 363 if (((elm)->field.tqe_next = (head)->tqh_first) != NULL) \ 364 (head)->tqh_first->field.tqe_prev = \ 365 &(elm)->field.tqe_next; \ 366 else \ 367 (head)->tqh_last = &(elm)->field.tqe_next; \ 368 (head)->tqh_first = (elm); \ 369 (elm)->field.tqe_prev = &(head)->tqh_first; \ 370} while (/*CONSTCOND*/0) 371 372#define TAILQ_INSERT_TAIL(head, elm, field) do { \ 373 QUEUEDEBUG_TAILQ_INSERT_TAIL((head), (elm), field) \ 374 (elm)->field.tqe_next = NULL; \ 375 (elm)->field.tqe_prev = (head)->tqh_last; \ 376 *(head)->tqh_last = (elm); \ 377 (head)->tqh_last = &(elm)->field.tqe_next; \ 378} while (/*CONSTCOND*/0) 379 380#define TAILQ_INSERT_AFTER(head, listelm, elm, field) do { \ 381 QUEUEDEBUG_TAILQ_OP((listelm), field) \ 382 if (((elm)->field.tqe_next = (listelm)->field.tqe_next) != NULL)\ 383 (elm)->field.tqe_next->field.tqe_prev = \ 384 &(elm)->field.tqe_next; \ 385 else \ 386 (head)->tqh_last = &(elm)->field.tqe_next; \ 387 (listelm)->field.tqe_next = (elm); \ 388 (elm)->field.tqe_prev = &(listelm)->field.tqe_next; \ 389} while (/*CONSTCOND*/0) 390 391#define TAILQ_INSERT_BEFORE(listelm, elm, field) do { \ 392 QUEUEDEBUG_TAILQ_OP((listelm), field) \ 393 (elm)->field.tqe_prev = (listelm)->field.tqe_prev; \ 394 (elm)->field.tqe_next = (listelm); \ 395 *(listelm)->field.tqe_prev = (elm); \ 396 (listelm)->field.tqe_prev = &(elm)->field.tqe_next; \ 397} while (/*CONSTCOND*/0) 398 399#define TAILQ_REMOVE(head, elm, field) do { \ 400 QUEUEDEBUG_TAILQ_OP((elm), field) \ 401 if (((elm)->field.tqe_next) != NULL) \ 402 (elm)->field.tqe_next->field.tqe_prev = \ 403 (elm)->field.tqe_prev; \ 404 else \ 405 (head)->tqh_last = (elm)->field.tqe_prev; \ 406 *(elm)->field.tqe_prev = (elm)->field.tqe_next; \ 407 QUEUEDEBUG_TAILQ_POSTREMOVE((elm), field); \ 408} while (/*CONSTCOND*/0) 409 410/* 411 * Tail queue access methods. 412 */ 413#define TAILQ_EMPTY(head) ((head)->tqh_first == NULL) 414#define TAILQ_FIRST(head) ((head)->tqh_first) 415#define TAILQ_NEXT(elm, field) ((elm)->field.tqe_next) 416 417#define TAILQ_LAST(head, headname) \ 418 (*(((struct headname *)((head)->tqh_last))->tqh_last)) 419#define TAILQ_PREV(elm, headname, field) \ 420 (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last)) 421 422#define TAILQ_FOREACH(var, head, field) \ 423 for ((var) = ((head)->tqh_first); \ 424 (var); \ 425 (var) = ((var)->field.tqe_next)) 426 427#define TAILQ_FOREACH_REVERSE(var, head, headname, field) \ 428 for ((var) = (*(((struct headname *)((head)->tqh_last))->tqh_last)); \ 429 (var); \ 430 (var) = (*(((struct headname *)((var)->field.tqe_prev))->tqh_last))) 431 432/* 433 * Circular queue definitions. 434 */ 435#define CIRCLEQ_HEAD(name, type) \ 436struct name { \ 437 struct type *cqh_first; /* first element */ \ 438 struct type *cqh_last; /* last element */ \ 439} 440 441#define CIRCLEQ_HEAD_INITIALIZER(head) \ 442 { (void *)&head, (void *)&head } 443 444#define CIRCLEQ_ENTRY(type) \ 445struct { \ 446 struct type *cqe_next; /* next element */ \ 447 struct type *cqe_prev; /* previous element */ \ 448} 449 450/* 451 * Circular queue functions. 452 */ 453#define CIRCLEQ_INIT(head) do { \ 454 (head)->cqh_first = (void *)(head); \ 455 (head)->cqh_last = (void *)(head); \ 456} while (/*CONSTCOND*/0) 457 458#define CIRCLEQ_INSERT_AFTER(head, listelm, elm, field) do { \ 459 (elm)->field.cqe_next = (listelm)->field.cqe_next; \ 460 (elm)->field.cqe_prev = (listelm); \ 461 if ((listelm)->field.cqe_next == (void *)(head)) \ 462 (head)->cqh_last = (elm); \ 463 else \ 464 (listelm)->field.cqe_next->field.cqe_prev = (elm); \ 465 (listelm)->field.cqe_next = (elm); \ 466} while (/*CONSTCOND*/0) 467 468#define CIRCLEQ_INSERT_BEFORE(head, listelm, elm, field) do { \ 469 (elm)->field.cqe_next = (listelm); \ 470 (elm)->field.cqe_prev = (listelm)->field.cqe_prev; \ 471 if ((listelm)->field.cqe_prev == (void *)(head)) \ 472 (head)->cqh_first = (elm); \ 473 else \ 474 (listelm)->field.cqe_prev->field.cqe_next = (elm); \ 475 (listelm)->field.cqe_prev = (elm); \ 476} while (/*CONSTCOND*/0) 477 478#define CIRCLEQ_INSERT_HEAD(head, elm, field) do { \ 479 (elm)->field.cqe_next = (head)->cqh_first; \ 480 (elm)->field.cqe_prev = (void *)(head); \ 481 if ((head)->cqh_last == (void *)(head)) \ 482 (head)->cqh_last = (elm); \ 483 else \ 484 (head)->cqh_first->field.cqe_prev = (elm); \ 485 (head)->cqh_first = (elm); \ 486} while (/*CONSTCOND*/0) 487 488#define CIRCLEQ_INSERT_TAIL(head, elm, field) do { \ 489 (elm)->field.cqe_next = (void *)(head); \ 490 (elm)->field.cqe_prev = (head)->cqh_last; \ 491 if ((head)->cqh_first == (void *)(head)) \ 492 (head)->cqh_first = (elm); \ 493 else \ 494 (head)->cqh_last->field.cqe_next = (elm); \ 495 (head)->cqh_last = (elm); \ 496} while (/*CONSTCOND*/0) 497 498#define CIRCLEQ_REMOVE(head, elm, field) do { \ 499 if ((elm)->field.cqe_next == (void *)(head)) \ 500 (head)->cqh_last = (elm)->field.cqe_prev; \ 501 else \ 502 (elm)->field.cqe_next->field.cqe_prev = \ 503 (elm)->field.cqe_prev; \ 504 if ((elm)->field.cqe_prev == (void *)(head)) \ 505 (head)->cqh_first = (elm)->field.cqe_next; \ 506 else \ 507 (elm)->field.cqe_prev->field.cqe_next = \ 508 (elm)->field.cqe_next; \ 509} while (/*CONSTCOND*/0) 510 511#define CIRCLEQ_FOREACH(var, head, field) \ 512 for ((var) = ((head)->cqh_first); \ 513 (var) != (void *)(head); \ 514 (var) = ((var)->field.cqe_next)) 515 516#define CIRCLEQ_FOREACH_REVERSE(var, head, field) \ 517 for ((var) = ((head)->cqh_last); \ 518 (var) != (void *)(head); \ 519 (var) = ((var)->field.cqe_prev)) 520 521/* 522 * Circular queue access methods. 523 */ 524#define CIRCLEQ_EMPTY(head) ((head)->cqh_first == (void *)(head)) 525#define CIRCLEQ_FIRST(head) ((head)->cqh_first) 526#define CIRCLEQ_LAST(head) ((head)->cqh_last) 527#define CIRCLEQ_NEXT(elm, field) ((elm)->field.cqe_next) 528#define CIRCLEQ_PREV(elm, field) ((elm)->field.cqe_prev) 529#endif /* !_SYS_QUEUE_H_ */ 530