queue.h (18544B)
1 /* $OpenBSD: queue.h,v 1.42 2015/11/19 21:03:36 millert Exp $ */ 2 /* $NetBSD: queue.h,v 1.11 1996/05/16 05:17:14 mycroft Exp $ */ 3 4 /* 5 * Copyright (c) 1991, 1993 6 * The Regents of the University of California. All rights reserved. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. Neither the name of the University nor the names of its contributors 17 * may be used to endorse or promote products derived from this software 18 * without specific prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30 * SUCH DAMAGE. 31 * 32 * @(#)queue.h 8.5 (Berkeley) 8/20/94 33 */ 34 35 #ifndef _SYS_QUEUE_H_ 36 #define _SYS_QUEUE_H_ 37 38 /* 39 * This file defines five types of data structures: singly-linked lists, 40 * lists, simple queues, tail queues, and circular queues. 41 * 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 list is headed by a single forward pointer (or an array of forward 54 * pointers for a hash table header). The elements are doubly linked 55 * so that an arbitrary element can be removed without a need to 56 * traverse the list. New elements can be added to the list before 57 * or after an existing element or at the head of the list. A list 58 * may only be traversed in the forward direction. 59 * 60 * A simple queue is headed by a pair of pointers, one the head of the 61 * list and the other to the tail of the list. The elements are singly 62 * linked to save space, so elements can only be removed from the 63 * head of the list. New elements can be added to the list before or after 64 * an existing element, at the head of the list, or at the end of the 65 * list. A simple queue may only be traversed in the forward direction. 66 * 67 * A tail queue is headed by a pair of pointers, one to the head of the 68 * list and the other to the tail of the list. The elements are doubly 69 * linked 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 or 71 * after an existing element, at the head of the list, or at the end of 72 * the list. A tail queue may be traversed in either direction. 73 * 74 * A circle 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 after 78 * an existing element, at the head of the list, or at the end of the list. 79 * A circle queue may be traversed in either direction, but has a more 80 * complex end of list detection. 81 * 82 * For details on the use of these macros, see the queue(3) manual page. 83 */ 84 85 #if defined(QUEUE_MACRO_DEBUG) || (defined(_KERNEL) && defined(DIAGNOSTIC)) 86 #define _Q_INVALIDATE(a) (a) = ((void *)-1) 87 #else 88 #define _Q_INVALIDATE(a) 89 #endif 90 91 /* 92 * Singly-linked List definitions. 93 */ 94 #define SLIST_HEAD(name, type) \ 95 struct name { \ 96 struct type *slh_first; /* first element */ \ 97 } 98 99 #define SLIST_HEAD_INITIALIZER(head) \ 100 { NULL } 101 102 #define SLIST_ENTRY(type) \ 103 struct { \ 104 struct type *sle_next; /* next element */ \ 105 } 106 107 /* 108 * Singly-linked List access methods. 109 */ 110 #define SLIST_FIRST(head) ((head)->slh_first) 111 #define SLIST_END(head) NULL 112 #define SLIST_EMPTY(head) (SLIST_FIRST(head) == SLIST_END(head)) 113 #define SLIST_NEXT(elm, field) ((elm)->field.sle_next) 114 115 #define SLIST_FOREACH(var, head, field) \ 116 for((var) = SLIST_FIRST(head); \ 117 (var) != SLIST_END(head); \ 118 (var) = SLIST_NEXT(var, field)) 119 120 #define SLIST_FOREACH_SAFE(var, head, field, tvar) \ 121 for ((var) = SLIST_FIRST(head); \ 122 (var) && ((tvar) = SLIST_NEXT(var, field), 1); \ 123 (var) = (tvar)) 124 125 /* 126 * Singly-linked List functions. 127 */ 128 #define SLIST_INIT(head) { \ 129 SLIST_FIRST(head) = SLIST_END(head); \ 130 } 131 132 #define SLIST_INSERT_AFTER(slistelm, elm, field) do { \ 133 (elm)->field.sle_next = (slistelm)->field.sle_next; \ 134 (slistelm)->field.sle_next = (elm); \ 135 } while (0) 136 137 #define SLIST_INSERT_HEAD(head, elm, field) do { \ 138 (elm)->field.sle_next = (head)->slh_first; \ 139 (head)->slh_first = (elm); \ 140 } while (0) 141 142 #define SLIST_REMOVE_AFTER(elm, field) do { \ 143 (elm)->field.sle_next = (elm)->field.sle_next->field.sle_next; \ 144 } while (0) 145 146 #define SLIST_REMOVE_HEAD(head, field) do { \ 147 (head)->slh_first = (head)->slh_first->field.sle_next; \ 148 } while (0) 149 150 #define SLIST_REMOVE(head, elm, type, field) do { \ 151 if ((head)->slh_first == (elm)) { \ 152 SLIST_REMOVE_HEAD((head), field); \ 153 } else { \ 154 struct type *curelm = (head)->slh_first; \ 155 \ 156 while (curelm->field.sle_next != (elm)) \ 157 curelm = curelm->field.sle_next; \ 158 curelm->field.sle_next = \ 159 curelm->field.sle_next->field.sle_next; \ 160 } \ 161 _Q_INVALIDATE((elm)->field.sle_next); \ 162 } while (0) 163 164 /* 165 * List definitions. 166 */ 167 #define LIST_HEAD(name, type) \ 168 struct name { \ 169 struct type *lh_first; /* first element */ \ 170 } 171 172 #define LIST_HEAD_INITIALIZER(head) \ 173 { NULL } 174 175 #define LIST_ENTRY(type) \ 176 struct { \ 177 struct type *le_next; /* next element */ \ 178 struct type **le_prev; /* address of previous next element */ \ 179 } 180 181 /* 182 * List access methods 183 */ 184 #define LIST_FIRST(head) ((head)->lh_first) 185 #define LIST_END(head) NULL 186 #define LIST_EMPTY(head) (LIST_FIRST(head) == LIST_END(head)) 187 #define LIST_NEXT(elm, field) ((elm)->field.le_next) 188 189 #define LIST_FOREACH(var, head, field) \ 190 for((var) = LIST_FIRST(head); \ 191 (var)!= LIST_END(head); \ 192 (var) = LIST_NEXT(var, field)) 193 194 #define LIST_FOREACH_SAFE(var, head, field, tvar) \ 195 for ((var) = LIST_FIRST(head); \ 196 (var) && ((tvar) = LIST_NEXT(var, field), 1); \ 197 (var) = (tvar)) 198 199 /* 200 * List functions. 201 */ 202 #define LIST_INIT(head) do { \ 203 LIST_FIRST(head) = LIST_END(head); \ 204 } while (0) 205 206 #define LIST_INSERT_AFTER(listelm, elm, field) do { \ 207 if (((elm)->field.le_next = (listelm)->field.le_next) != NULL) \ 208 (listelm)->field.le_next->field.le_prev = \ 209 &(elm)->field.le_next; \ 210 (listelm)->field.le_next = (elm); \ 211 (elm)->field.le_prev = &(listelm)->field.le_next; \ 212 } while (0) 213 214 #define LIST_INSERT_BEFORE(listelm, elm, field) do { \ 215 (elm)->field.le_prev = (listelm)->field.le_prev; \ 216 (elm)->field.le_next = (listelm); \ 217 *(listelm)->field.le_prev = (elm); \ 218 (listelm)->field.le_prev = &(elm)->field.le_next; \ 219 } while (0) 220 221 #define LIST_INSERT_HEAD(head, elm, field) do { \ 222 if (((elm)->field.le_next = (head)->lh_first) != NULL) \ 223 (head)->lh_first->field.le_prev = &(elm)->field.le_next;\ 224 (head)->lh_first = (elm); \ 225 (elm)->field.le_prev = &(head)->lh_first; \ 226 } while (0) 227 228 #define LIST_REMOVE(elm, field) do { \ 229 if ((elm)->field.le_next != NULL) \ 230 (elm)->field.le_next->field.le_prev = \ 231 (elm)->field.le_prev; \ 232 *(elm)->field.le_prev = (elm)->field.le_next; \ 233 _Q_INVALIDATE((elm)->field.le_prev); \ 234 _Q_INVALIDATE((elm)->field.le_next); \ 235 } while (0) 236 237 #define LIST_REPLACE(elm, elm2, field) do { \ 238 if (((elm2)->field.le_next = (elm)->field.le_next) != NULL) \ 239 (elm2)->field.le_next->field.le_prev = \ 240 &(elm2)->field.le_next; \ 241 (elm2)->field.le_prev = (elm)->field.le_prev; \ 242 *(elm2)->field.le_prev = (elm2); \ 243 _Q_INVALIDATE((elm)->field.le_prev); \ 244 _Q_INVALIDATE((elm)->field.le_next); \ 245 } while (0) 246 247 /* 248 * Simple queue definitions. 249 */ 250 #define SIMPLEQ_HEAD(name, type) \ 251 struct name { \ 252 struct type *sqh_first; /* first element */ \ 253 struct type **sqh_last; /* addr of last next element */ \ 254 } 255 256 #define SIMPLEQ_HEAD_INITIALIZER(head) \ 257 { NULL, &(head).sqh_first } 258 259 #define SIMPLEQ_ENTRY(type) \ 260 struct { \ 261 struct type *sqe_next; /* next element */ \ 262 } 263 264 /* 265 * Simple queue access methods. 266 */ 267 #define SIMPLEQ_FIRST(head) ((head)->sqh_first) 268 #define SIMPLEQ_END(head) NULL 269 #define SIMPLEQ_EMPTY(head) (SIMPLEQ_FIRST(head) == SIMPLEQ_END(head)) 270 #define SIMPLEQ_NEXT(elm, field) ((elm)->field.sqe_next) 271 272 #define SIMPLEQ_FOREACH(var, head, field) \ 273 for((var) = SIMPLEQ_FIRST(head); \ 274 (var) != SIMPLEQ_END(head); \ 275 (var) = SIMPLEQ_NEXT(var, field)) 276 277 #define SIMPLEQ_FOREACH_SAFE(var, head, field, tvar) \ 278 for ((var) = SIMPLEQ_FIRST(head); \ 279 (var) && ((tvar) = SIMPLEQ_NEXT(var, field), 1); \ 280 (var) = (tvar)) 281 282 /* 283 * Simple queue functions. 284 */ 285 #define SIMPLEQ_INIT(head) do { \ 286 (head)->sqh_first = NULL; \ 287 (head)->sqh_last = &(head)->sqh_first; \ 288 } while (0) 289 290 #define SIMPLEQ_INSERT_HEAD(head, elm, field) do { \ 291 if (((elm)->field.sqe_next = (head)->sqh_first) == NULL) \ 292 (head)->sqh_last = &(elm)->field.sqe_next; \ 293 (head)->sqh_first = (elm); \ 294 } while (0) 295 296 #define SIMPLEQ_INSERT_TAIL(head, elm, field) do { \ 297 (elm)->field.sqe_next = NULL; \ 298 *(head)->sqh_last = (elm); \ 299 (head)->sqh_last = &(elm)->field.sqe_next; \ 300 } while (0) 301 302 #define SIMPLEQ_INSERT_AFTER(head, listelm, elm, field) do { \ 303 if (((elm)->field.sqe_next = (listelm)->field.sqe_next) == NULL)\ 304 (head)->sqh_last = &(elm)->field.sqe_next; \ 305 (listelm)->field.sqe_next = (elm); \ 306 } while (0) 307 308 #define SIMPLEQ_REMOVE_HEAD(head, field) do { \ 309 if (((head)->sqh_first = (head)->sqh_first->field.sqe_next) == NULL) \ 310 (head)->sqh_last = &(head)->sqh_first; \ 311 } while (0) 312 313 #define SIMPLEQ_REMOVE_AFTER(head, elm, field) do { \ 314 if (((elm)->field.sqe_next = (elm)->field.sqe_next->field.sqe_next) \ 315 == NULL) \ 316 (head)->sqh_last = &(elm)->field.sqe_next; \ 317 } while (0) 318 319 #define SIMPLEQ_CONCAT(head1, head2) do { \ 320 if (!SIMPLEQ_EMPTY((head2))) { \ 321 *(head1)->sqh_last = (head2)->sqh_first; \ 322 (head1)->sqh_last = (head2)->sqh_last; \ 323 SIMPLEQ_INIT((head2)); \ 324 } \ 325 } while (0) 326 327 /* 328 * XOR Simple queue definitions. 329 */ 330 #define XSIMPLEQ_HEAD(name, type) \ 331 struct name { \ 332 struct type *sqx_first; /* first element */ \ 333 struct type **sqx_last; /* addr of last next element */ \ 334 unsigned long sqx_cookie; \ 335 } 336 337 #define XSIMPLEQ_ENTRY(type) \ 338 struct { \ 339 struct type *sqx_next; /* next element */ \ 340 } 341 342 /* 343 * XOR Simple queue access methods. 344 */ 345 #define XSIMPLEQ_XOR(head, ptr) ((__typeof(ptr))((head)->sqx_cookie ^ \ 346 (unsigned long)(ptr))) 347 #define XSIMPLEQ_FIRST(head) XSIMPLEQ_XOR(head, ((head)->sqx_first)) 348 #define XSIMPLEQ_END(head) NULL 349 #define XSIMPLEQ_EMPTY(head) (XSIMPLEQ_FIRST(head) == XSIMPLEQ_END(head)) 350 #define XSIMPLEQ_NEXT(head, elm, field) XSIMPLEQ_XOR(head, ((elm)->field.sqx_next)) 351 352 353 #define XSIMPLEQ_FOREACH(var, head, field) \ 354 for ((var) = XSIMPLEQ_FIRST(head); \ 355 (var) != XSIMPLEQ_END(head); \ 356 (var) = XSIMPLEQ_NEXT(head, var, field)) 357 358 #define XSIMPLEQ_FOREACH_SAFE(var, head, field, tvar) \ 359 for ((var) = XSIMPLEQ_FIRST(head); \ 360 (var) && ((tvar) = XSIMPLEQ_NEXT(head, var, field), 1); \ 361 (var) = (tvar)) 362 363 /* 364 * XOR Simple queue functions. 365 */ 366 #define XSIMPLEQ_INIT(head) do { \ 367 arc4random_buf(&(head)->sqx_cookie, sizeof((head)->sqx_cookie)); \ 368 (head)->sqx_first = XSIMPLEQ_XOR(head, NULL); \ 369 (head)->sqx_last = XSIMPLEQ_XOR(head, &(head)->sqx_first); \ 370 } while (0) 371 372 #define XSIMPLEQ_INSERT_HEAD(head, elm, field) do { \ 373 if (((elm)->field.sqx_next = (head)->sqx_first) == \ 374 XSIMPLEQ_XOR(head, NULL)) \ 375 (head)->sqx_last = XSIMPLEQ_XOR(head, &(elm)->field.sqx_next); \ 376 (head)->sqx_first = XSIMPLEQ_XOR(head, (elm)); \ 377 } while (0) 378 379 #define XSIMPLEQ_INSERT_TAIL(head, elm, field) do { \ 380 (elm)->field.sqx_next = XSIMPLEQ_XOR(head, NULL); \ 381 *(XSIMPLEQ_XOR(head, (head)->sqx_last)) = XSIMPLEQ_XOR(head, (elm)); \ 382 (head)->sqx_last = XSIMPLEQ_XOR(head, &(elm)->field.sqx_next); \ 383 } while (0) 384 385 #define XSIMPLEQ_INSERT_AFTER(head, listelm, elm, field) do { \ 386 if (((elm)->field.sqx_next = (listelm)->field.sqx_next) == \ 387 XSIMPLEQ_XOR(head, NULL)) \ 388 (head)->sqx_last = XSIMPLEQ_XOR(head, &(elm)->field.sqx_next); \ 389 (listelm)->field.sqx_next = XSIMPLEQ_XOR(head, (elm)); \ 390 } while (0) 391 392 #define XSIMPLEQ_REMOVE_HEAD(head, field) do { \ 393 if (((head)->sqx_first = XSIMPLEQ_XOR(head, \ 394 (head)->sqx_first)->field.sqx_next) == XSIMPLEQ_XOR(head, NULL)) \ 395 (head)->sqx_last = XSIMPLEQ_XOR(head, &(head)->sqx_first); \ 396 } while (0) 397 398 #define XSIMPLEQ_REMOVE_AFTER(head, elm, field) do { \ 399 if (((elm)->field.sqx_next = XSIMPLEQ_XOR(head, \ 400 (elm)->field.sqx_next)->field.sqx_next) \ 401 == XSIMPLEQ_XOR(head, NULL)) \ 402 (head)->sqx_last = \ 403 XSIMPLEQ_XOR(head, &(elm)->field.sqx_next); \ 404 } while (0) 405 406 407 /* 408 * Tail queue definitions. 409 */ 410 #define TAILQ_HEAD(name, type) \ 411 struct name { \ 412 struct type *tqh_first; /* first element */ \ 413 struct type **tqh_last; /* addr of last next element */ \ 414 } 415 416 #define TAILQ_HEAD_INITIALIZER(head) \ 417 { NULL, &(head).tqh_first } 418 419 #define TAILQ_ENTRY(type) \ 420 struct { \ 421 struct type *tqe_next; /* next element */ \ 422 struct type **tqe_prev; /* address of previous next element */ \ 423 } 424 425 /* 426 * tail queue access methods 427 */ 428 #define TAILQ_FIRST(head) ((head)->tqh_first) 429 #define TAILQ_END(head) NULL 430 #define TAILQ_NEXT(elm, field) ((elm)->field.tqe_next) 431 #define TAILQ_LAST(head, headname) \ 432 (*(((struct headname *)((head)->tqh_last))->tqh_last)) 433 /* XXX */ 434 #define TAILQ_PREV(elm, headname, field) \ 435 (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last)) 436 #define TAILQ_EMPTY(head) \ 437 (TAILQ_FIRST(head) == TAILQ_END(head)) 438 439 #define TAILQ_FOREACH(var, head, field) \ 440 for((var) = TAILQ_FIRST(head); \ 441 (var) != TAILQ_END(head); \ 442 (var) = TAILQ_NEXT(var, field)) 443 444 #define TAILQ_FOREACH_SAFE(var, head, field, tvar) \ 445 for ((var) = TAILQ_FIRST(head); \ 446 (var) != TAILQ_END(head) && \ 447 ((tvar) = TAILQ_NEXT(var, field), 1); \ 448 (var) = (tvar)) 449 450 451 #define TAILQ_FOREACH_REVERSE(var, head, headname, field) \ 452 for((var) = TAILQ_LAST(head, headname); \ 453 (var) != TAILQ_END(head); \ 454 (var) = TAILQ_PREV(var, headname, field)) 455 456 #define TAILQ_FOREACH_REVERSE_SAFE(var, head, headname, field, tvar) \ 457 for ((var) = TAILQ_LAST(head, headname); \ 458 (var) != TAILQ_END(head) && \ 459 ((tvar) = TAILQ_PREV(var, headname, field), 1); \ 460 (var) = (tvar)) 461 462 /* 463 * Tail queue functions. 464 */ 465 #define TAILQ_INIT(head) do { \ 466 (head)->tqh_first = NULL; \ 467 (head)->tqh_last = &(head)->tqh_first; \ 468 } while (0) 469 470 #define TAILQ_INSERT_HEAD(head, elm, field) do { \ 471 if (((elm)->field.tqe_next = (head)->tqh_first) != NULL) \ 472 (head)->tqh_first->field.tqe_prev = \ 473 &(elm)->field.tqe_next; \ 474 else \ 475 (head)->tqh_last = &(elm)->field.tqe_next; \ 476 (head)->tqh_first = (elm); \ 477 (elm)->field.tqe_prev = &(head)->tqh_first; \ 478 } while (0) 479 480 #define TAILQ_INSERT_TAIL(head, elm, field) do { \ 481 (elm)->field.tqe_next = NULL; \ 482 (elm)->field.tqe_prev = (head)->tqh_last; \ 483 *(head)->tqh_last = (elm); \ 484 (head)->tqh_last = &(elm)->field.tqe_next; \ 485 } while (0) 486 487 #define TAILQ_INSERT_AFTER(head, listelm, elm, field) do { \ 488 if (((elm)->field.tqe_next = (listelm)->field.tqe_next) != NULL)\ 489 (elm)->field.tqe_next->field.tqe_prev = \ 490 &(elm)->field.tqe_next; \ 491 else \ 492 (head)->tqh_last = &(elm)->field.tqe_next; \ 493 (listelm)->field.tqe_next = (elm); \ 494 (elm)->field.tqe_prev = &(listelm)->field.tqe_next; \ 495 } while (0) 496 497 #define TAILQ_INSERT_BEFORE(listelm, elm, field) do { \ 498 (elm)->field.tqe_prev = (listelm)->field.tqe_prev; \ 499 (elm)->field.tqe_next = (listelm); \ 500 *(listelm)->field.tqe_prev = (elm); \ 501 (listelm)->field.tqe_prev = &(elm)->field.tqe_next; \ 502 } while (0) 503 504 #define TAILQ_REMOVE(head, elm, field) do { \ 505 if (((elm)->field.tqe_next) != NULL) \ 506 (elm)->field.tqe_next->field.tqe_prev = \ 507 (elm)->field.tqe_prev; \ 508 else \ 509 (head)->tqh_last = (elm)->field.tqe_prev; \ 510 *(elm)->field.tqe_prev = (elm)->field.tqe_next; \ 511 _Q_INVALIDATE((elm)->field.tqe_prev); \ 512 _Q_INVALIDATE((elm)->field.tqe_next); \ 513 } while (0) 514 515 #define TAILQ_REPLACE(head, elm, elm2, field) do { \ 516 if (((elm2)->field.tqe_next = (elm)->field.tqe_next) != NULL) \ 517 (elm2)->field.tqe_next->field.tqe_prev = \ 518 &(elm2)->field.tqe_next; \ 519 else \ 520 (head)->tqh_last = &(elm2)->field.tqe_next; \ 521 (elm2)->field.tqe_prev = (elm)->field.tqe_prev; \ 522 *(elm2)->field.tqe_prev = (elm2); \ 523 _Q_INVALIDATE((elm)->field.tqe_prev); \ 524 _Q_INVALIDATE((elm)->field.tqe_next); \ 525 } while (0) 526 527 #define TAILQ_CONCAT(head1, head2, field) do { \ 528 if (!TAILQ_EMPTY(head2)) { \ 529 *(head1)->tqh_last = (head2)->tqh_first; \ 530 (head2)->tqh_first->field.tqe_prev = (head1)->tqh_last; \ 531 (head1)->tqh_last = (head2)->tqh_last; \ 532 TAILQ_INIT((head2)); \ 533 } \ 534 } while (0) 535 536 #endif /* !_SYS_QUEUE_H_ */