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 * Derived from FreeBSD src/sys/sys/queue.h:1.63. 32 */ 33 34 #ifndef _COMPAT_QUEUE_H_ 35 #define _COMPAT_QUEUE_H_ 36 37 #include <sys/cdefs.h> 38 39 /* 40 * This file defines four types of data structures: singly-linked lists, 41 * singly-linked tail queues, lists and tail queues. 42 * 43 * A singly-linked list is headed by a single forward pointer. The elements 44 * are singly linked for minimum space and pointer manipulation overhead at 45 * the expense of O(n) removal for arbitrary elements. New elements can be 46 * added to the list after an existing element or at the head of the list. 47 * Elements being removed from the head of the list should use the explicit 48 * macro for this purpose for optimum efficiency. A singly-linked list may 49 * only be traversed in the forward direction. Singly-linked lists are ideal 50 * for applications with large datasets and few or no removals or for 51 * implementing a LIFO queue. 52 * 53 * A singly-linked tail queue is headed by a pair of pointers, one to the 54 * head of the list and the other to the tail of the list. The elements are 55 * singly linked for minimum space and pointer manipulation overhead at the 56 * expense of O(n) removal for arbitrary elements. New elements can be added 57 * to the list after an existing element, at the head of the list, or at the 58 * end of the list. Elements being removed from the head of the tail queue 59 * should use the explicit macro for this purpose for optimum efficiency. 60 * A singly-linked tail queue may only be traversed in the forward direction. 61 * Singly-linked tail queues are ideal for applications with large datasets 62 * and few or no removals or for implementing a FIFO queue. 63 * 64 * A list is headed by a single forward pointer (or an array of forward 65 * pointers for a hash table header). The elements are doubly linked 66 * so that an arbitrary element can be removed without a need to 67 * traverse the list. New elements can be added to the list before 68 * or after an existing element or at the head of the list. A list 69 * may only be traversed in the forward direction. 70 * 71 * A tail queue is headed by a pair of pointers, one to the head of the 72 * list and the other to the tail of the list. The elements are doubly 73 * linked so that an arbitrary element can be removed without a need to 74 * traverse the list. New elements can be added to the list before or 75 * after an existing element, at the head of the list, or at the end of 76 * the list. A tail queue may be traversed in either direction. 77 * 78 * For details on the use of these macros, see the queue(3) manual page. 79 * 80 * 81 * SLIST LIST STAILQ TAILQ 82 * _HEAD + + + + 83 * _HEAD_INITIALIZER + + + + 84 * _ENTRY + + + + 85 * _INIT + + + + 86 * _EMPTY + + + + 87 * _FIRST + + + + 88 * _NEXT + + + + 89 * _PREV - - - + 90 * _LAST - - + + 91 * _FOREACH + + + + 92 * _FOREACH_SAFE + + + + 93 * _FOREACH_REVERSE - - - + 94 * _FOREACH_REVERSE_SAFE - - - + 95 * _INSERT_HEAD + + + + 96 * _INSERT_BEFORE - + - + 97 * _INSERT_AFTER + + + + 98 * _INSERT_TAIL - - + + 99 * _CONCAT - - + + 100 * _REMOVE_HEAD + - + - 101 * _REMOVE + + + + 102 * 103 */ 104 #ifdef QUEUE_MACRO_DEBUG 105 /* Store the last 2 places the queue element or head was altered */ 106 struct qm_trace { 107 char * lastfile; 108 int lastline; 109 char * prevfile; 110 int prevline; 111 }; 112 113 #define TRACEBUF struct qm_trace trace; 114 #define TRASHIT(x) do {(x) = (void *)-1;} while (0) 115 116 #define QMD_TRACE_HEAD(head) do { \ 117 (head)->trace.prevline = (head)->trace.lastline; \ 118 (head)->trace.prevfile = (head)->trace.lastfile; \ 119 (head)->trace.lastline = __LINE__; \ 120 (head)->trace.lastfile = __FILE__; \ 121 } while (0) 122 123 #define QMD_TRACE_ELEM(elem) do { \ 124 (elem)->trace.prevline = (elem)->trace.lastline; \ 125 (elem)->trace.prevfile = (elem)->trace.lastfile; \ 126 (elem)->trace.lastline = __LINE__; \ 127 (elem)->trace.lastfile = __FILE__; \ 128 } while (0) 129 130 #else 131 #define QMD_TRACE_ELEM(elem) 132 #define QMD_TRACE_HEAD(head) 133 #define TRACEBUF 134 #define TRASHIT(x) 135 #endif /* QUEUE_MACRO_DEBUG */ 136 137 /* 138 * Singly-linked List declarations. 139 */ 140 #define SLIST_HEAD(name, type) \ 141 struct name { \ 142 struct type *slh_first; /* first element */ \ 143 } 144 145 #define SLIST_HEAD_INITIALIZER(head) \ 146 { NULL } 147 148 #define SLIST_ENTRY(type) \ 149 struct { \ 150 struct type *sle_next; /* next element */ \ 151 } 152 153 /* 154 * Singly-linked List functions. 155 */ 156 #define SLIST_EMPTY(head) ((head)->slh_first == NULL) 157 158 #define SLIST_FIRST(head) ((head)->slh_first) 159 160 #define SLIST_FOREACH(var, head, field) \ 161 for ((var) = SLIST_FIRST((head)); \ 162 (var); \ 163 (var) = SLIST_NEXT((var), field)) 164 165 #define SLIST_FOREACH_SAFE(var, head, field, tvar) \ 166 for ((var) = SLIST_FIRST((head)); \ 167 (var) && ((tvar) = SLIST_NEXT((var), field), 1); \ 168 (var) = (tvar)) 169 170 #define SLIST_FOREACH_PREVPTR(var, varp, head, field) \ 171 for ((varp) = &SLIST_FIRST((head)); \ 172 ((var) = *(varp)) != NULL; \ 173 (varp) = &SLIST_NEXT((var), field)) 174 175 #define SLIST_INIT(head) do { \ 176 SLIST_FIRST((head)) = NULL; \ 177 } while (0) 178 179 #define SLIST_INSERT_AFTER(slistelm, elm, field) do { \ 180 SLIST_NEXT((elm), field) = SLIST_NEXT((slistelm), field); \ 181 SLIST_NEXT((slistelm), field) = (elm); \ 182 } while (0) 183 184 #define SLIST_INSERT_HEAD(head, elm, field) do { \ 185 SLIST_NEXT((elm), field) = SLIST_FIRST((head)); \ 186 SLIST_FIRST((head)) = (elm); \ 187 } while (0) 188 189 #define SLIST_NEXT(elm, field) ((elm)->field.sle_next) 190 191 #define SLIST_REMOVE(head, elm, type, field) do { \ 192 if (SLIST_FIRST((head)) == (elm)) { \ 193 SLIST_REMOVE_HEAD((head), field); \ 194 } \ 195 else { \ 196 struct type *curelm = SLIST_FIRST((head)); \ 197 while (SLIST_NEXT(curelm, field) != (elm)) \ 198 curelm = SLIST_NEXT(curelm, field); \ 199 SLIST_NEXT(curelm, field) = \ 200 SLIST_NEXT(SLIST_NEXT(curelm, field), field); \ 201 } \ 202 TRASHIT((elm)->field.sle_next); \ 203 } while (0) 204 205 #define SLIST_REMOVE_HEAD(head, field) do { \ 206 SLIST_FIRST((head)) = SLIST_NEXT(SLIST_FIRST((head)), field); \ 207 } while (0) 208 209 /* 210 * Singly-linked Tail queue declarations. 211 */ 212 #define STAILQ_HEAD(name, type) \ 213 struct name { \ 214 struct type *stqh_first;/* first element */ \ 215 struct type **stqh_last;/* addr of last next element */ \ 216 } 217 218 #define STAILQ_HEAD_INITIALIZER(head) \ 219 { NULL, &(head).stqh_first } 220 221 #define STAILQ_ENTRY(type) \ 222 struct { \ 223 struct type *stqe_next; /* next element */ \ 224 } 225 226 /* 227 * Singly-linked Tail queue functions. 228 */ 229 #define STAILQ_CONCAT(head1, head2) do { \ 230 if (!STAILQ_EMPTY((head2))) { \ 231 *(head1)->stqh_last = (head2)->stqh_first; \ 232 (head1)->stqh_last = (head2)->stqh_last; \ 233 STAILQ_INIT((head2)); \ 234 } \ 235 } while (0) 236 237 #define STAILQ_EMPTY(head) ((head)->stqh_first == NULL) 238 239 #define STAILQ_FIRST(head) ((head)->stqh_first) 240 241 #define STAILQ_FOREACH(var, head, field) \ 242 for((var) = STAILQ_FIRST((head)); \ 243 (var); \ 244 (var) = STAILQ_NEXT((var), field)) 245 246 247 #define STAILQ_FOREACH_SAFE(var, head, field, tvar) \ 248 for ((var) = STAILQ_FIRST((head)); \ 249 (var) && ((tvar) = STAILQ_NEXT((var), field), 1); \ 250 (var) = (tvar)) 251 252 #define STAILQ_INIT(head) do { \ 253 STAILQ_FIRST((head)) = NULL; \ 254 (head)->stqh_last = &STAILQ_FIRST((head)); \ 255 } while (0) 256 257 #define STAILQ_INSERT_AFTER(head, tqelm, elm, field) do { \ 258 if ((STAILQ_NEXT((elm), field) = STAILQ_NEXT((tqelm), field)) == NULL)\ 259 (head)->stqh_last = &STAILQ_NEXT((elm), field); \ 260 STAILQ_NEXT((tqelm), field) = (elm); \ 261 } while (0) 262 263 #define STAILQ_INSERT_HEAD(head, elm, field) do { \ 264 if ((STAILQ_NEXT((elm), field) = STAILQ_FIRST((head))) == NULL) \ 265 (head)->stqh_last = &STAILQ_NEXT((elm), field); \ 266 STAILQ_FIRST((head)) = (elm); \ 267 } while (0) 268 269 #define STAILQ_INSERT_TAIL(head, elm, field) do { \ 270 STAILQ_NEXT((elm), field) = NULL; \ 271 *(head)->stqh_last = (elm); \ 272 (head)->stqh_last = &STAILQ_NEXT((elm), field); \ 273 } while (0) 274 275 #define STAILQ_LAST(head, type, field) \ 276 (STAILQ_EMPTY((head)) ? \ 277 NULL : \ 278 ((struct type *) \ 279 ((char *)((head)->stqh_last) - __offsetof(struct type, field)))) 280 281 #define STAILQ_NEXT(elm, field) ((elm)->field.stqe_next) 282 283 #define STAILQ_REMOVE(head, elm, type, field) do { \ 284 if (STAILQ_FIRST((head)) == (elm)) { \ 285 STAILQ_REMOVE_HEAD((head), field); \ 286 } \ 287 else { \ 288 struct type *curelm = STAILQ_FIRST((head)); \ 289 while (STAILQ_NEXT(curelm, field) != (elm)) \ 290 curelm = STAILQ_NEXT(curelm, field); \ 291 if ((STAILQ_NEXT(curelm, field) = \ 292 STAILQ_NEXT(STAILQ_NEXT(curelm, field), field)) == NULL)\ 293 (head)->stqh_last = &STAILQ_NEXT((curelm), field);\ 294 } \ 295 TRASHIT((elm)->field.stqe_next); \ 296 } while (0) 297 298 #define STAILQ_REMOVE_HEAD(head, field) do { \ 299 if ((STAILQ_FIRST((head)) = \ 300 STAILQ_NEXT(STAILQ_FIRST((head)), field)) == NULL) \ 301 (head)->stqh_last = &STAILQ_FIRST((head)); \ 302 } while (0) 303 304 #define STAILQ_REMOVE_HEAD_UNTIL(head, elm, field) do { \ 305 if ((STAILQ_FIRST((head)) = STAILQ_NEXT((elm), field)) == NULL) \ 306 (head)->stqh_last = &STAILQ_FIRST((head)); \ 307 } while (0) 308 309 /* 310 * List declarations. 311 */ 312 #define LIST_HEAD(name, type) \ 313 struct name { \ 314 struct type *lh_first; /* first element */ \ 315 } 316 317 #define LIST_HEAD_INITIALIZER(head) \ 318 { NULL } 319 320 #define LIST_ENTRY(type) \ 321 struct { \ 322 struct type *le_next; /* next element */ \ 323 struct type **le_prev; /* address of previous next element */ \ 324 } 325 326 /* 327 * List functions. 328 */ 329 330 #if (defined(_KERNEL) && defined(INVARIANTS)) || defined(QUEUE_MACRO_DEBUG) 331 #define QMD_LIST_CHECK_HEAD(head, field) do { \ 332 if (LIST_FIRST((head)) != NULL && \ 333 LIST_FIRST((head))->field.le_prev != \ 334 &LIST_FIRST((head))) \ 335 panic("Bad list head %p first->prev != head", (head)); \ 336 } while (0) 337 338 #define QMD_LIST_CHECK_NEXT(elm, field) do { \ 339 if (LIST_NEXT((elm), field) != NULL && \ 340 LIST_NEXT((elm), field)->field.le_prev != \ 341 &((elm)->field.le_next)) \ 342 panic("Bad link elm %p next->prev != elm", (elm)); \ 343 } while (0) 344 345 #define QMD_LIST_CHECK_PREV(elm, field) do { \ 346 if (*(elm)->field.le_prev != (elm)) \ 347 panic("Bad link elm %p prev->next != elm", (elm)); \ 348 } while (0) 349 #else 350 #define QMD_LIST_CHECK_HEAD(head, field) 351 #define QMD_LIST_CHECK_NEXT(elm, field) 352 #define QMD_LIST_CHECK_PREV(elm, field) 353 #endif /* (_KERNEL && INVARIANTS) || QUEUE_MACRO_DEBUG */ 354 355 #define LIST_EMPTY(head) ((head)->lh_first == NULL) 356 357 #define LIST_FIRST(head) ((head)->lh_first) 358 359 #define LIST_FOREACH(var, head, field) \ 360 for ((var) = LIST_FIRST((head)); \ 361 (var); \ 362 (var) = LIST_NEXT((var), field)) 363 364 #define LIST_FOREACH_SAFE(var, head, field, tvar) \ 365 for ((var) = LIST_FIRST((head)); \ 366 (var) && ((tvar) = LIST_NEXT((var), field), 1); \ 367 (var) = (tvar)) 368 369 #define LIST_INIT(head) do { \ 370 LIST_FIRST((head)) = NULL; \ 371 } while (0) 372 373 #define LIST_INSERT_AFTER(listelm, elm, field) do { \ 374 QMD_LIST_CHECK_NEXT(listelm, field); \ 375 if ((LIST_NEXT((elm), field) = LIST_NEXT((listelm), field)) != NULL)\ 376 LIST_NEXT((listelm), field)->field.le_prev = \ 377 &LIST_NEXT((elm), field); \ 378 LIST_NEXT((listelm), field) = (elm); \ 379 (elm)->field.le_prev = &LIST_NEXT((listelm), field); \ 380 } while (0) 381 382 #define LIST_INSERT_BEFORE(listelm, elm, field) do { \ 383 QMD_LIST_CHECK_PREV(listelm, field); \ 384 (elm)->field.le_prev = (listelm)->field.le_prev; \ 385 LIST_NEXT((elm), field) = (listelm); \ 386 *(listelm)->field.le_prev = (elm); \ 387 (listelm)->field.le_prev = &LIST_NEXT((elm), field); \ 388 } while (0) 389 390 #define LIST_INSERT_HEAD(head, elm, field) do { \ 391 QMD_LIST_CHECK_HEAD((head), field); \ 392 if ((LIST_NEXT((elm), field) = LIST_FIRST((head))) != NULL) \ 393 LIST_FIRST((head))->field.le_prev = &LIST_NEXT((elm), field);\ 394 LIST_FIRST((head)) = (elm); \ 395 (elm)->field.le_prev = &LIST_FIRST((head)); \ 396 } while (0) 397 398 #define LIST_NEXT(elm, field) ((elm)->field.le_next) 399 400 #define LIST_REMOVE(elm, field) do { \ 401 QMD_LIST_CHECK_NEXT(elm, field); \ 402 QMD_LIST_CHECK_PREV(elm, field); \ 403 if (LIST_NEXT((elm), field) != NULL) \ 404 LIST_NEXT((elm), field)->field.le_prev = \ 405 (elm)->field.le_prev; \ 406 *(elm)->field.le_prev = LIST_NEXT((elm), field); \ 407 TRASHIT((elm)->field.le_next); \ 408 TRASHIT((elm)->field.le_prev); \ 409 } while (0) 410 411 /* 412 * Tail queue declarations. 413 */ 414 #define TAILQ_HEAD(name, type) \ 415 struct name { \ 416 struct type *tqh_first; /* first element */ \ 417 struct type **tqh_last; /* addr of last next element */ \ 418 TRACEBUF \ 419 } 420 421 #define TAILQ_HEAD_INITIALIZER(head) \ 422 { NULL, &(head).tqh_first } 423 424 #define TAILQ_ENTRY(type) \ 425 struct { \ 426 struct type *tqe_next; /* next element */ \ 427 struct type **tqe_prev; /* address of previous next element */ \ 428 TRACEBUF \ 429 } 430 431 /* 432 * Tail queue functions. 433 */ 434 #define TAILQ_CONCAT(head1, head2, field) do { \ 435 if (!TAILQ_EMPTY(head2)) { \ 436 *(head1)->tqh_last = (head2)->tqh_first; \ 437 (head2)->tqh_first->field.tqe_prev = (head1)->tqh_last; \ 438 (head1)->tqh_last = (head2)->tqh_last; \ 439 TAILQ_INIT((head2)); \ 440 QMD_TRACE_HEAD(head1); \ 441 QMD_TRACE_HEAD(head2); \ 442 } \ 443 } while (0) 444 445 #define TAILQ_EMPTY(head) ((head)->tqh_first == NULL) 446 447 #define TAILQ_FIRST(head) ((head)->tqh_first) 448 449 #define TAILQ_FOREACH(var, head, field) \ 450 for ((var) = TAILQ_FIRST((head)); \ 451 (var); \ 452 (var) = TAILQ_NEXT((var), field)) 453 454 #define TAILQ_FOREACH_SAFE(var, head, field, tvar) \ 455 for ((var) = TAILQ_FIRST((head)); \ 456 (var) && ((tvar) = TAILQ_NEXT((var), field), 1); \ 457 (var) = (tvar)) 458 459 #define TAILQ_FOREACH_REVERSE(var, head, headname, field) \ 460 for ((var) = TAILQ_LAST((head), headname); \ 461 (var); \ 462 (var) = TAILQ_PREV((var), headname, field)) 463 464 #define TAILQ_FOREACH_REVERSE_SAFE(var, head, headname, field, tvar) \ 465 for ((var) = TAILQ_LAST((head), headname); \ 466 (var) && ((tvar) = TAILQ_PREV((var), headname, field), 1); \ 467 (var) = (tvar)) 468 469 #define TAILQ_INIT(head) do { \ 470 TAILQ_FIRST((head)) = NULL; \ 471 (head)->tqh_last = &TAILQ_FIRST((head)); \ 472 QMD_TRACE_HEAD(head); \ 473 } while (0) 474 475 #define TAILQ_INSERT_AFTER(head, listelm, elm, field) do { \ 476 if ((TAILQ_NEXT((elm), field) = TAILQ_NEXT((listelm), field)) != NULL)\ 477 TAILQ_NEXT((elm), field)->field.tqe_prev = \ 478 &TAILQ_NEXT((elm), field); \ 479 else { \ 480 (head)->tqh_last = &TAILQ_NEXT((elm), field); \ 481 QMD_TRACE_HEAD(head); \ 482 } \ 483 TAILQ_NEXT((listelm), field) = (elm); \ 484 (elm)->field.tqe_prev = &TAILQ_NEXT((listelm), field); \ 485 QMD_TRACE_ELEM(&(elm)->field); \ 486 QMD_TRACE_ELEM(&listelm->field); \ 487 } while (0) 488 489 #define TAILQ_INSERT_BEFORE(listelm, elm, field) do { \ 490 (elm)->field.tqe_prev = (listelm)->field.tqe_prev; \ 491 TAILQ_NEXT((elm), field) = (listelm); \ 492 *(listelm)->field.tqe_prev = (elm); \ 493 (listelm)->field.tqe_prev = &TAILQ_NEXT((elm), field); \ 494 QMD_TRACE_ELEM(&(elm)->field); \ 495 QMD_TRACE_ELEM(&listelm->field); \ 496 } while (0) 497 498 #define TAILQ_INSERT_HEAD(head, elm, field) do { \ 499 if ((TAILQ_NEXT((elm), field) = TAILQ_FIRST((head))) != NULL) \ 500 TAILQ_FIRST((head))->field.tqe_prev = \ 501 &TAILQ_NEXT((elm), field); \ 502 else \ 503 (head)->tqh_last = &TAILQ_NEXT((elm), field); \ 504 TAILQ_FIRST((head)) = (elm); \ 505 (elm)->field.tqe_prev = &TAILQ_FIRST((head)); \ 506 QMD_TRACE_HEAD(head); \ 507 QMD_TRACE_ELEM(&(elm)->field); \ 508 } while (0) 509 510 #define TAILQ_INSERT_TAIL(head, elm, field) do { \ 511 TAILQ_NEXT((elm), field) = NULL; \ 512 (elm)->field.tqe_prev = (head)->tqh_last; \ 513 *(head)->tqh_last = (elm); \ 514 (head)->tqh_last = &TAILQ_NEXT((elm), field); \ 515 QMD_TRACE_HEAD(head); \ 516 QMD_TRACE_ELEM(&(elm)->field); \ 517 } while (0) 518 519 #define TAILQ_LAST(head, headname) \ 520 (*(((struct headname *)((head)->tqh_last))->tqh_last)) 521 522 #define TAILQ_NEXT(elm, field) ((elm)->field.tqe_next) 523 524 #define TAILQ_PREV(elm, headname, field) \ 525 (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last)) 526 527 #define TAILQ_REMOVE(head, elm, field) do { \ 528 if ((TAILQ_NEXT((elm), field)) != NULL) \ 529 TAILQ_NEXT((elm), field)->field.tqe_prev = \ 530 (elm)->field.tqe_prev; \ 531 else { \ 532 (head)->tqh_last = (elm)->field.tqe_prev; \ 533 QMD_TRACE_HEAD(head); \ 534 } \ 535 *(elm)->field.tqe_prev = TAILQ_NEXT((elm), field); \ 536 TRASHIT((elm)->field.tqe_next); \ 537 TRASHIT((elm)->field.tqe_prev); \ 538 QMD_TRACE_ELEM(&(elm)->field); \ 539 } while (0) 540 541 #endif /* !_COMPAT_QUEUE_H_ */ 542