Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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FreeBSD/Linux Kernel Cross Reference
sys/sys/queue.h
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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. All advertising materials mentioning features or use of this software 14 * must display the following acknowledgement: 15 * This product includes software developed by the University of 16 * California, Berkeley and its contributors. 17 * 4. Neither the name of the University nor the names of its contributors 18 * may be used to endorse or promote products derived from this software 19 * without specific prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 * 33 * @(#)queue.h 8.5 (Berkeley) 8/20/94 34 * $FreeBSD: releng/5.0/sys/sys/queue.h 101351 2002-08-05 05:18:43Z alfred $ 35 */ 36 37 #ifndef _SYS_QUEUE_H_ 38 #define _SYS_QUEUE_H_ 39 40 #include <sys/cdefs.h> 41 42 /* 43 * This file defines four types of data structures: singly-linked lists, 44 * singly-linked tail queues, lists and tail queues. 45 * 46 * A singly-linked list is headed by a single forward pointer. The elements 47 * are singly linked for minimum space and pointer manipulation overhead at 48 * the expense of O(n) removal for arbitrary elements. New elements can be 49 * added to the list after an existing element or at the head of the list. 50 * Elements being removed from the head of the list should use the explicit 51 * macro for this purpose for optimum efficiency. A singly-linked list may 52 * only be traversed in the forward direction. Singly-linked lists are ideal 53 * for applications with large datasets and few or no removals or for 54 * implementing a LIFO queue. 55 * 56 * A singly-linked tail queue is headed by a pair of pointers, one to the 57 * head of the list and the other to the tail of the list. The elements are 58 * singly linked for minimum space and pointer manipulation overhead at the 59 * expense of O(n) removal for arbitrary elements. New elements can be added 60 * to the list after an existing element, at the head of the list, or at the 61 * end of the list. Elements being removed from the head of the tail queue 62 * should use the explicit macro for this purpose for optimum efficiency. 63 * A singly-linked tail queue may only be traversed in the forward direction. 64 * Singly-linked tail queues are ideal for applications with large datasets 65 * and few or no removals or for implementing a FIFO queue. 66 * 67 * A list is headed by a single forward pointer (or an array of forward 68 * pointers for a hash table header). The elements are doubly linked 69 * so that an arbitrary element can be removed without a need to 70 * traverse the list. New elements can be added to the list before 71 * or after an existing element or at the head of the list. A list 72 * may only be traversed in the forward direction. 73 * 74 * A tail queue is headed by a pair of pointers, one to the head of the 75 * list and the other to the tail of the list. The elements are doubly 76 * linked so that an arbitrary element can be removed without a need to 77 * traverse the list. New elements can be added to the list before or 78 * after an existing element, at the head of the list, or at the end of 79 * the list. A tail queue may be traversed in either direction. 80 * 81 * For details on the use of these macros, see the queue(3) manual page. 82 * 83 * 84 * SLIST LIST STAILQ TAILQ 85 * _HEAD + + + + 86 * _HEAD_INITIALIZER + + + + 87 * _ENTRY + + + + 88 * _INIT + + + + 89 * _EMPTY + + + + 90 * _FIRST + + + + 91 * _NEXT + + + + 92 * _PREV - - - + 93 * _LAST - - + + 94 * _FOREACH + + + + 95 * _FOREACH_REVERSE - - - + 96 * _INSERT_HEAD + + + + 97 * _INSERT_BEFORE - + - + 98 * _INSERT_AFTER + + + + 99 * _INSERT_TAIL - - + + 100 * _CONCAT - - + + 101 * _REMOVE_HEAD + - + - 102 * _REMOVE + + + + 103 * 104 */ 105 #define QUEUE_MACRO_DEBUG 0 106 #if QUEUE_MACRO_DEBUG 107 /* Store the last 2 places the queue element or head was altered */ 108 struct qm_trace { 109 char * lastfile; 110 int lastline; 111 char * prevfile; 112 int prevline; 113 }; 114 115 #define TRACEBUF struct qm_trace trace; 116 #define TRASHIT(x) do {(x) = (void *)-1;} while (0) 117 118 #define QMD_TRACE_HEAD(head) do { \ 119 (head)->trace.prevline = (head)->trace.lastline; \ 120 (head)->trace.prevfile = (head)->trace.lastfile; \ 121 (head)->trace.lastline = __LINE__; \ 122 (head)->trace.lastfile = __FILE__; \ 123 } while (0) 124 125 #define QMD_TRACE_ELEM(elem) do { \ 126 (elem)->trace.prevline = (elem)->trace.lastline; \ 127 (elem)->trace.prevfile = (elem)->trace.lastfile; \ 128 (elem)->trace.lastline = __LINE__; \ 129 (elem)->trace.lastfile = __FILE__; \ 130 } while (0) 131 132 #else 133 #define QMD_TRACE_ELEM(elem) 134 #define QMD_TRACE_HEAD(head) 135 #define TRACEBUF 136 #define TRASHIT(x) 137 #endif /* QUEUE_MACRO_DEBUG */ 138 139 /* 140 * Singly-linked List declarations. 141 */ 142 #define SLIST_HEAD(name, type) \ 143 struct name { \ 144 struct type *slh_first; /* first element */ \ 145 } 146 147 #define SLIST_HEAD_INITIALIZER(head) \ 148 { NULL } 149 150 #define SLIST_ENTRY(type) \ 151 struct { \ 152 struct type *sle_next; /* next element */ \ 153 } 154 155 /* 156 * Singly-linked List functions. 157 */ 158 #define SLIST_EMPTY(head) ((head)->slh_first == NULL) 159 160 #define SLIST_FIRST(head) ((head)->slh_first) 161 162 #define SLIST_FOREACH(var, head, field) \ 163 for ((var) = SLIST_FIRST((head)); \ 164 (var); \ 165 (var) = SLIST_NEXT((var), field)) 166 167 #define SLIST_FOREACH_PREVPTR(var, varp, head, field) \ 168 for ((varp) = &SLIST_FIRST((head)); \ 169 ((var) = *(varp)) != NULL; \ 170 (varp) = &SLIST_NEXT((var), field)) 171 172 #define SLIST_INIT(head) do { \ 173 SLIST_FIRST((head)) = NULL; \ 174 } while (0) 175 176 #define SLIST_INSERT_AFTER(slistelm, elm, field) do { \ 177 SLIST_NEXT((elm), field) = SLIST_NEXT((slistelm), field); \ 178 SLIST_NEXT((slistelm), field) = (elm); \ 179 } while (0) 180 181 #define SLIST_INSERT_HEAD(head, elm, field) do { \ 182 SLIST_NEXT((elm), field) = SLIST_FIRST((head)); \ 183 SLIST_FIRST((head)) = (elm); \ 184 } while (0) 185 186 #define SLIST_NEXT(elm, field) ((elm)->field.sle_next) 187 188 #define SLIST_REMOVE(head, elm, type, field) do { \ 189 if (SLIST_FIRST((head)) == (elm)) { \ 190 SLIST_REMOVE_HEAD((head), field); \ 191 } \ 192 else { \ 193 struct type *curelm = SLIST_FIRST((head)); \ 194 while (SLIST_NEXT(curelm, field) != (elm)) \ 195 curelm = SLIST_NEXT(curelm, field); \ 196 SLIST_NEXT(curelm, field) = \ 197 SLIST_NEXT(SLIST_NEXT(curelm, field), field); \ 198 } \ 199 } while (0) 200 201 #define SLIST_REMOVE_HEAD(head, field) do { \ 202 SLIST_FIRST((head)) = SLIST_NEXT(SLIST_FIRST((head)), field); \ 203 } while (0) 204 205 /* 206 * Singly-linked Tail queue declarations. 207 */ 208 #define STAILQ_HEAD(name, type) \ 209 struct name { \ 210 struct type *stqh_first;/* first element */ \ 211 struct type **stqh_last;/* addr of last next element */ \ 212 } 213 214 #define STAILQ_HEAD_INITIALIZER(head) \ 215 { NULL, &(head).stqh_first } 216 217 #define STAILQ_ENTRY(type) \ 218 struct { \ 219 struct type *stqe_next; /* next element */ \ 220 } 221 222 /* 223 * Singly-linked Tail queue functions. 224 */ 225 #define STAILQ_CONCAT(head1, head2) do { \ 226 if (!STAILQ_EMPTY((head2))) { \ 227 *(head1)->stqh_last = (head2)->stqh_first; \ 228 (head1)->stqh_last = (head2)->stqh_last; \ 229 STAILQ_INIT((head2)); \ 230 } \ 231 } while (0) 232 233 #define STAILQ_EMPTY(head) ((head)->stqh_first == NULL) 234 235 #define STAILQ_FIRST(head) ((head)->stqh_first) 236 237 #define STAILQ_FOREACH(var, head, field) \ 238 for((var) = STAILQ_FIRST((head)); \ 239 (var); \ 240 (var) = STAILQ_NEXT((var), field)) 241 242 #define STAILQ_INIT(head) do { \ 243 STAILQ_FIRST((head)) = NULL; \ 244 (head)->stqh_last = &STAILQ_FIRST((head)); \ 245 } while (0) 246 247 #define STAILQ_INSERT_AFTER(head, tqelm, elm, field) do { \ 248 if ((STAILQ_NEXT((elm), field) = STAILQ_NEXT((tqelm), field)) == NULL)\ 249 (head)->stqh_last = &STAILQ_NEXT((elm), field); \ 250 STAILQ_NEXT((tqelm), field) = (elm); \ 251 } while (0) 252 253 #define STAILQ_INSERT_HEAD(head, elm, field) do { \ 254 if ((STAILQ_NEXT((elm), field) = STAILQ_FIRST((head))) == NULL) \ 255 (head)->stqh_last = &STAILQ_NEXT((elm), field); \ 256 STAILQ_FIRST((head)) = (elm); \ 257 } while (0) 258 259 #define STAILQ_INSERT_TAIL(head, elm, field) do { \ 260 STAILQ_NEXT((elm), field) = NULL; \ 261 *(head)->stqh_last = (elm); \ 262 (head)->stqh_last = &STAILQ_NEXT((elm), field); \ 263 } while (0) 264 265 #define STAILQ_LAST(head, type, field) \ 266 (STAILQ_EMPTY((head)) ? \ 267 NULL : \ 268 ((struct type *) \ 269 ((char *)((head)->stqh_last) - __offsetof(struct type, field)))) 270 271 #define STAILQ_NEXT(elm, field) ((elm)->field.stqe_next) 272 273 #define STAILQ_REMOVE(head, elm, type, field) do { \ 274 if (STAILQ_FIRST((head)) == (elm)) { \ 275 STAILQ_REMOVE_HEAD((head), field); \ 276 } \ 277 else { \ 278 struct type *curelm = STAILQ_FIRST((head)); \ 279 while (STAILQ_NEXT(curelm, field) != (elm)) \ 280 curelm = STAILQ_NEXT(curelm, field); \ 281 if ((STAILQ_NEXT(curelm, field) = \ 282 STAILQ_NEXT(STAILQ_NEXT(curelm, field), field)) == NULL)\ 283 (head)->stqh_last = &STAILQ_NEXT((curelm), field);\ 284 } \ 285 } while (0) 286 287 #define STAILQ_REMOVE_HEAD(head, field) do { \ 288 if ((STAILQ_FIRST((head)) = \ 289 STAILQ_NEXT(STAILQ_FIRST((head)), field)) == NULL) \ 290 (head)->stqh_last = &STAILQ_FIRST((head)); \ 291 } while (0) 292 293 #define STAILQ_REMOVE_HEAD_UNTIL(head, elm, field) do { \ 294 if ((STAILQ_FIRST((head)) = STAILQ_NEXT((elm), field)) == NULL) \ 295 (head)->stqh_last = &STAILQ_FIRST((head)); \ 296 } while (0) 297 298 /* 299 * List declarations. 300 */ 301 #define LIST_HEAD(name, type) \ 302 struct name { \ 303 struct type *lh_first; /* first element */ \ 304 } 305 306 #define LIST_HEAD_INITIALIZER(head) \ 307 { NULL } 308 309 #define LIST_ENTRY(type) \ 310 struct { \ 311 struct type *le_next; /* next element */ \ 312 struct type **le_prev; /* address of previous next element */ \ 313 } 314 315 /* 316 * List functions. 317 */ 318 319 #define LIST_EMPTY(head) ((head)->lh_first == NULL) 320 321 #define LIST_FIRST(head) ((head)->lh_first) 322 323 #define LIST_FOREACH(var, head, field) \ 324 for ((var) = LIST_FIRST((head)); \ 325 (var); \ 326 (var) = LIST_NEXT((var), field)) 327 328 #define LIST_INIT(head) do { \ 329 LIST_FIRST((head)) = NULL; \ 330 } while (0) 331 332 #define LIST_INSERT_AFTER(listelm, elm, field) do { \ 333 if ((LIST_NEXT((elm), field) = LIST_NEXT((listelm), field)) != NULL)\ 334 LIST_NEXT((listelm), field)->field.le_prev = \ 335 &LIST_NEXT((elm), field); \ 336 LIST_NEXT((listelm), field) = (elm); \ 337 (elm)->field.le_prev = &LIST_NEXT((listelm), field); \ 338 } while (0) 339 340 #define LIST_INSERT_BEFORE(listelm, elm, field) do { \ 341 (elm)->field.le_prev = (listelm)->field.le_prev; \ 342 LIST_NEXT((elm), field) = (listelm); \ 343 *(listelm)->field.le_prev = (elm); \ 344 (listelm)->field.le_prev = &LIST_NEXT((elm), field); \ 345 } while (0) 346 347 #define LIST_INSERT_HEAD(head, elm, field) do { \ 348 if ((LIST_NEXT((elm), field) = LIST_FIRST((head))) != NULL) \ 349 LIST_FIRST((head))->field.le_prev = &LIST_NEXT((elm), field);\ 350 LIST_FIRST((head)) = (elm); \ 351 (elm)->field.le_prev = &LIST_FIRST((head)); \ 352 } while (0) 353 354 #define LIST_NEXT(elm, field) ((elm)->field.le_next) 355 356 #define LIST_REMOVE(elm, field) do { \ 357 if (LIST_NEXT((elm), field) != NULL) \ 358 LIST_NEXT((elm), field)->field.le_prev = \ 359 (elm)->field.le_prev; \ 360 *(elm)->field.le_prev = LIST_NEXT((elm), field); \ 361 } while (0) 362 363 /* 364 * Tail queue declarations. 365 */ 366 #define TAILQ_HEAD(name, type) \ 367 struct name { \ 368 struct type *tqh_first; /* first element */ \ 369 struct type **tqh_last; /* addr of last next element */ \ 370 TRACEBUF \ 371 } 372 373 #define TAILQ_HEAD_INITIALIZER(head) \ 374 { NULL, &(head).tqh_first } 375 376 #define TAILQ_ENTRY(type) \ 377 struct { \ 378 struct type *tqe_next; /* next element */ \ 379 struct type **tqe_prev; /* address of previous next element */ \ 380 TRACEBUF \ 381 } 382 383 /* 384 * Tail queue functions. 385 */ 386 #define TAILQ_CONCAT(head1, head2, field) do { \ 387 if (!TAILQ_EMPTY(head2)) { \ 388 *(head1)->tqh_last = (head2)->tqh_first; \ 389 (head2)->tqh_first->field.tqe_prev = (head1)->tqh_last; \ 390 (head1)->tqh_last = (head2)->tqh_last; \ 391 TAILQ_INIT((head2)); \ 392 QMD_TRACE_HEAD(head); \ 393 QMD_TRACE_HEAD(head2); \ 394 } \ 395 } while (0) 396 397 #define TAILQ_EMPTY(head) ((head)->tqh_first == NULL) 398 399 #define TAILQ_FIRST(head) ((head)->tqh_first) 400 401 #define TAILQ_FOREACH(var, head, field) \ 402 for ((var) = TAILQ_FIRST((head)); \ 403 (var); \ 404 (var) = TAILQ_NEXT((var), field)) 405 406 #define TAILQ_FOREACH_REVERSE(var, head, headname, field) \ 407 for ((var) = TAILQ_LAST((head), headname); \ 408 (var); \ 409 (var) = TAILQ_PREV((var), headname, field)) 410 411 #define TAILQ_INIT(head) do { \ 412 TAILQ_FIRST((head)) = NULL; \ 413 (head)->tqh_last = &TAILQ_FIRST((head)); \ 414 QMD_TRACE_HEAD(head); \ 415 } while (0) 416 417 #define TAILQ_INSERT_AFTER(head, listelm, elm, field) do { \ 418 if ((TAILQ_NEXT((elm), field) = TAILQ_NEXT((listelm), field)) != NULL)\ 419 TAILQ_NEXT((elm), field)->field.tqe_prev = \ 420 &TAILQ_NEXT((elm), field); \ 421 else { \ 422 (head)->tqh_last = &TAILQ_NEXT((elm), field); \ 423 QMD_TRACE_HEAD(head); \ 424 } \ 425 TAILQ_NEXT((listelm), field) = (elm); \ 426 (elm)->field.tqe_prev = &TAILQ_NEXT((listelm), field); \ 427 QMD_TRACE_ELEM(&(elm)->field); \ 428 QMD_TRACE_ELEM(&listelm->field); \ 429 } while (0) 430 431 #define TAILQ_INSERT_BEFORE(listelm, elm, field) do { \ 432 (elm)->field.tqe_prev = (listelm)->field.tqe_prev; \ 433 TAILQ_NEXT((elm), field) = (listelm); \ 434 *(listelm)->field.tqe_prev = (elm); \ 435 (listelm)->field.tqe_prev = &TAILQ_NEXT((elm), field); \ 436 QMD_TRACE_ELEM(&(elm)->field); \ 437 QMD_TRACE_ELEM(&listelm->field); \ 438 } while (0) 439 440 #define TAILQ_INSERT_HEAD(head, elm, field) do { \ 441 if ((TAILQ_NEXT((elm), field) = TAILQ_FIRST((head))) != NULL) \ 442 TAILQ_FIRST((head))->field.tqe_prev = \ 443 &TAILQ_NEXT((elm), field); \ 444 else \ 445 (head)->tqh_last = &TAILQ_NEXT((elm), field); \ 446 TAILQ_FIRST((head)) = (elm); \ 447 (elm)->field.tqe_prev = &TAILQ_FIRST((head)); \ 448 QMD_TRACE_HEAD(head); \ 449 QMD_TRACE_ELEM(&(elm)->field); \ 450 } while (0) 451 452 #define TAILQ_INSERT_TAIL(head, elm, field) do { \ 453 TAILQ_NEXT((elm), field) = NULL; \ 454 (elm)->field.tqe_prev = (head)->tqh_last; \ 455 *(head)->tqh_last = (elm); \ 456 (head)->tqh_last = &TAILQ_NEXT((elm), field); \ 457 QMD_TRACE_HEAD(head); \ 458 QMD_TRACE_ELEM(&(elm)->field); \ 459 } while (0) 460 461 #define TAILQ_LAST(head, headname) \ 462 (*(((struct headname *)((head)->tqh_last))->tqh_last)) 463 464 #define TAILQ_NEXT(elm, field) ((elm)->field.tqe_next) 465 466 #define TAILQ_PREV(elm, headname, field) \ 467 (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last)) 468 469 #define TAILQ_REMOVE(head, elm, field) do { \ 470 if ((TAILQ_NEXT((elm), field)) != NULL) \ 471 TAILQ_NEXT((elm), field)->field.tqe_prev = \ 472 (elm)->field.tqe_prev; \ 473 else { \ 474 (head)->tqh_last = (elm)->field.tqe_prev; \ 475 QMD_TRACE_HEAD(head); \ 476 } \ 477 *(elm)->field.tqe_prev = TAILQ_NEXT((elm), field); \ 478 TRASHIT((elm)->field.tqe_next); \ 479 TRASHIT((elm)->field.tqe_prev); \ 480 QMD_TRACE_ELEM(&(elm)->field); \ 481 } while (0) 482 483 484 #ifdef _KERNEL 485 486 /* 487 * XXX insque() and remque() are an old way of handling certain queues. 488 * They bogusly assumes that all queue heads look alike. 489 */ 490 491 struct quehead { 492 struct quehead *qh_link; 493 struct quehead *qh_rlink; 494 }; 495 496 #ifdef __GNUC__ 497 498 static __inline void 499 insque(void *a, void *b) 500 { 501 struct quehead *element = (struct quehead *)a, 502 *head = (struct quehead *)b; 503 504 element->qh_link = head->qh_link; 505 element->qh_rlink = head; 506 head->qh_link = element; 507 element->qh_link->qh_rlink = element; 508 } 509 510 static __inline void 511 remque(void *a) 512 { 513 struct quehead *element = (struct quehead *)a; 514 515 element->qh_link->qh_rlink = element->qh_rlink; 516 element->qh_rlink->qh_link = element->qh_link; 517 element->qh_rlink = 0; 518 } 519 520 #else /* !__GNUC__ */ 521 522 void insque(void *a, void *b); 523 void remque(void *a); 524 525 #endif /* __GNUC__ */ 526 527 #endif /* _KERNEL */ 528 529 #endif /* !_SYS_QUEUE_H_ */
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