1 /* $OpenBSD: queue.h,v 1.45 2018/07/12 14:22:54 sashan 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 XOR simple 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 to 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 * An XOR simple queue is used in the same way as a regular simple queue. 75 * The difference is that the head structure also includes a "cookie" that 76 * is XOR'd with the queue pointer (first, last or next) to generate the 77 * real pointer value. 78 * 79 * For details on the use of these macros, see the queue(3) manual page. 80 */ 81 82 #if defined(QUEUE_MACRO_DEBUG) || (defined(_KERNEL) && defined(DIAGNOSTIC)) 83 #define _Q_INVALID ((void *)-1) 84 #define _Q_INVALIDATE(a) (a) = _Q_INVALID 85 #else 86 #define _Q_INVALIDATE(a) 87 #endif 88 89 /* 90 * Singly-linked List definitions. 91 */ 92 #define SLIST_HEAD(name, type) \ 93 struct name { \ 94 struct type *slh_first; /* first element */ \ 95 } 96 97 #define SLIST_HEAD_INITIALIZER(head) \ 98 { NULL } 99 100 #define SLIST_ENTRY(type) \ 101 struct { \ 102 struct type *sle_next; /* next element */ \ 103 } 104 105 /* 106 * Singly-linked List access methods. 107 */ 108 #define SLIST_FIRST(head) ((head)->slh_first) 109 #define SLIST_END(head) NULL 110 #define SLIST_EMPTY(head) (SLIST_FIRST(head) == SLIST_END(head)) 111 #define SLIST_NEXT(elm, field) ((elm)->field.sle_next) 112 113 #define SLIST_FOREACH(var, head, field) \ 114 for((var) = SLIST_FIRST(head); \ 115 (var) != SLIST_END(head); \ 116 (var) = SLIST_NEXT(var, field)) 117 118 #define SLIST_FOREACH_SAFE(var, head, field, tvar) \ 119 for ((var) = SLIST_FIRST(head); \ 120 (var) && ((tvar) = SLIST_NEXT(var, field), 1); \ 121 (var) = (tvar)) 122 123 /* 124 * Singly-linked List functions. 125 */ 126 #define SLIST_INIT(head) { \ 127 SLIST_FIRST(head) = SLIST_END(head); \ 128 } 129 130 #define SLIST_INSERT_AFTER(slistelm, elm, field) do { \ 131 (elm)->field.sle_next = (slistelm)->field.sle_next; \ 132 (slistelm)->field.sle_next = (elm); \ 133 } while (0) 134 135 #define SLIST_INSERT_HEAD(head, elm, field) do { \ 136 (elm)->field.sle_next = (head)->slh_first; \ 137 (head)->slh_first = (elm); \ 138 } while (0) 139 140 #define SLIST_REMOVE_AFTER(elm, field) do { \ 141 (elm)->field.sle_next = (elm)->field.sle_next->field.sle_next; \ 142 } while (0) 143 144 #define SLIST_REMOVE_HEAD(head, field) do { \ 145 (head)->slh_first = (head)->slh_first->field.sle_next; \ 146 } while (0) 147 148 #define SLIST_REMOVE(head, elm, type, field) do { \ 149 if ((head)->slh_first == (elm)) { \ 150 SLIST_REMOVE_HEAD((head), field); \ 151 } else { \ 152 struct type *curelm = (head)->slh_first; \ 153 \ 154 while (curelm->field.sle_next != (elm)) \ 155 curelm = curelm->field.sle_next; \ 156 curelm->field.sle_next = \ 157 curelm->field.sle_next->field.sle_next; \ 158 } \ 159 _Q_INVALIDATE((elm)->field.sle_next); \ 160 } while (0) 161 162 /* 163 * List definitions. 164 */ 165 #define LIST_HEAD(name, type) \ 166 struct name { \ 167 struct type *lh_first; /* first element */ \ 168 } 169 170 #define LIST_HEAD_INITIALIZER(head) \ 171 { NULL } 172 173 #define LIST_ENTRY(type) \ 174 struct { \ 175 struct type *le_next; /* next element */ \ 176 struct type **le_prev; /* address of previous next element */ \ 177 } 178 179 /* 180 * List access methods. 181 */ 182 #define LIST_FIRST(head) ((head)->lh_first) 183 #define LIST_END(head) NULL 184 #define LIST_EMPTY(head) (LIST_FIRST(head) == LIST_END(head)) 185 #define LIST_NEXT(elm, field) ((elm)->field.le_next) 186 187 #define LIST_FOREACH(var, head, field) \ 188 for((var) = LIST_FIRST(head); \ 189 (var)!= LIST_END(head); \ 190 (var) = LIST_NEXT(var, field)) 191 192 #define LIST_FOREACH_SAFE(var, head, field, tvar) \ 193 for ((var) = LIST_FIRST(head); \ 194 (var) && ((tvar) = LIST_NEXT(var, field), 1); \ 195 (var) = (tvar)) 196 197 /* 198 * List functions. 199 */ 200 #define LIST_INIT(head) do { \ 201 LIST_FIRST(head) = LIST_END(head); \ 202 } while (0) 203 204 #define LIST_INSERT_AFTER(listelm, elm, field) do { \ 205 if (((elm)->field.le_next = (listelm)->field.le_next) != NULL) \ 206 (listelm)->field.le_next->field.le_prev = \ 207 &(elm)->field.le_next; \ 208 (listelm)->field.le_next = (elm); \ 209 (elm)->field.le_prev = &(listelm)->field.le_next; \ 210 } while (0) 211 212 #define LIST_INSERT_BEFORE(listelm, elm, field) do { \ 213 (elm)->field.le_prev = (listelm)->field.le_prev; \ 214 (elm)->field.le_next = (listelm); \ 215 *(listelm)->field.le_prev = (elm); \ 216 (listelm)->field.le_prev = &(elm)->field.le_next; \ 217 } while (0) 218 219 #define LIST_INSERT_HEAD(head, elm, field) do { \ 220 if (((elm)->field.le_next = (head)->lh_first) != NULL) \ 221 (head)->lh_first->field.le_prev = &(elm)->field.le_next;\ 222 (head)->lh_first = (elm); \ 223 (elm)->field.le_prev = &(head)->lh_first; \ 224 } while (0) 225 226 #define LIST_REMOVE(elm, field) do { \ 227 if ((elm)->field.le_next != NULL) \ 228 (elm)->field.le_next->field.le_prev = \ 229 (elm)->field.le_prev; \ 230 *(elm)->field.le_prev = (elm)->field.le_next; \ 231 _Q_INVALIDATE((elm)->field.le_prev); \ 232 _Q_INVALIDATE((elm)->field.le_next); \ 233 } while (0) 234 235 #define LIST_REPLACE(elm, elm2, field) do { \ 236 if (((elm2)->field.le_next = (elm)->field.le_next) != NULL) \ 237 (elm2)->field.le_next->field.le_prev = \ 238 &(elm2)->field.le_next; \ 239 (elm2)->field.le_prev = (elm)->field.le_prev; \ 240 *(elm2)->field.le_prev = (elm2); \ 241 _Q_INVALIDATE((elm)->field.le_prev); \ 242 _Q_INVALIDATE((elm)->field.le_next); \ 243 } while (0) 244 245 /* 246 * Simple queue definitions. 247 */ 248 #define SIMPLEQ_HEAD(name, type) \ 249 struct name { \ 250 struct type *sqh_first; /* first element */ \ 251 struct type **sqh_last; /* addr of last next element */ \ 252 } 253 254 #define SIMPLEQ_HEAD_INITIALIZER(head) \ 255 { NULL, &(head).sqh_first } 256 257 #define SIMPLEQ_ENTRY(type) \ 258 struct { \ 259 struct type *sqe_next; /* next element */ \ 260 } 261 262 /* 263 * Simple queue access methods. 264 */ 265 #define SIMPLEQ_FIRST(head) ((head)->sqh_first) 266 #define SIMPLEQ_END(head) NULL 267 #define SIMPLEQ_EMPTY(head) (SIMPLEQ_FIRST(head) == SIMPLEQ_END(head)) 268 #define SIMPLEQ_NEXT(elm, field) ((elm)->field.sqe_next) 269 270 #define SIMPLEQ_FOREACH(var, head, field) \ 271 for((var) = SIMPLEQ_FIRST(head); \ 272 (var) != SIMPLEQ_END(head); \ 273 (var) = SIMPLEQ_NEXT(var, field)) 274 275 #define SIMPLEQ_FOREACH_SAFE(var, head, field, tvar) \ 276 for ((var) = SIMPLEQ_FIRST(head); \ 277 (var) && ((tvar) = SIMPLEQ_NEXT(var, field), 1); \ 278 (var) = (tvar)) 279 280 /* 281 * Simple queue functions. 282 */ 283 #define SIMPLEQ_INIT(head) do { \ 284 (head)->sqh_first = NULL; \ 285 (head)->sqh_last = &(head)->sqh_first; \ 286 } while (0) 287 288 #define SIMPLEQ_INSERT_HEAD(head, elm, field) do { \ 289 if (((elm)->field.sqe_next = (head)->sqh_first) == NULL) \ 290 (head)->sqh_last = &(elm)->field.sqe_next; \ 291 (head)->sqh_first = (elm); \ 292 } while (0) 293 294 #define SIMPLEQ_INSERT_TAIL(head, elm, field) do { \ 295 (elm)->field.sqe_next = NULL; \ 296 *(head)->sqh_last = (elm); \ 297 (head)->sqh_last = &(elm)->field.sqe_next; \ 298 } while (0) 299 300 #define SIMPLEQ_INSERT_AFTER(head, listelm, elm, field) do { \ 301 if (((elm)->field.sqe_next = (listelm)->field.sqe_next) == NULL)\ 302 (head)->sqh_last = &(elm)->field.sqe_next; \ 303 (listelm)->field.sqe_next = (elm); \ 304 } while (0) 305 306 #define SIMPLEQ_REMOVE_HEAD(head, field) do { \ 307 if (((head)->sqh_first = (head)->sqh_first->field.sqe_next) == NULL) \ 308 (head)->sqh_last = &(head)->sqh_first; \ 309 } while (0) 310 311 #define SIMPLEQ_REMOVE_AFTER(head, elm, field) do { \ 312 if (((elm)->field.sqe_next = (elm)->field.sqe_next->field.sqe_next) \ 313 == NULL) \ 314 (head)->sqh_last = &(elm)->field.sqe_next; \ 315 } while (0) 316 317 #define SIMPLEQ_CONCAT(head1, head2) do { \ 318 if (!SIMPLEQ_EMPTY((head2))) { \ 319 *(head1)->sqh_last = (head2)->sqh_first; \ 320 (head1)->sqh_last = (head2)->sqh_last; \ 321 SIMPLEQ_INIT((head2)); \ 322 } \ 323 } while (0) 324 325 /* 326 * XOR Simple queue definitions. 327 */ 328 #define XSIMPLEQ_HEAD(name, type) \ 329 struct name { \ 330 struct type *sqx_first; /* first element */ \ 331 struct type **sqx_last; /* addr of last next element */ \ 332 unsigned long sqx_cookie; \ 333 } 334 335 #define XSIMPLEQ_ENTRY(type) \ 336 struct { \ 337 struct type *sqx_next; /* next element */ \ 338 } 339 340 /* 341 * XOR Simple queue access methods. 342 */ 343 #define XSIMPLEQ_XOR(head, ptr) ((__typeof(ptr))((head)->sqx_cookie ^ \ 344 (unsigned long)(ptr))) 345 #define XSIMPLEQ_FIRST(head) XSIMPLEQ_XOR(head, ((head)->sqx_first)) 346 #define XSIMPLEQ_END(head) NULL 347 #define XSIMPLEQ_EMPTY(head) (XSIMPLEQ_FIRST(head) == XSIMPLEQ_END(head)) 348 #define XSIMPLEQ_NEXT(head, elm, field) XSIMPLEQ_XOR(head, ((elm)->field.sqx_next)) 349 350 351 #define XSIMPLEQ_FOREACH(var, head, field) \ 352 for ((var) = XSIMPLEQ_FIRST(head); \ 353 (var) != XSIMPLEQ_END(head); \ 354 (var) = XSIMPLEQ_NEXT(head, var, field)) 355 356 #define XSIMPLEQ_FOREACH_SAFE(var, head, field, tvar) \ 357 for ((var) = XSIMPLEQ_FIRST(head); \ 358 (var) && ((tvar) = XSIMPLEQ_NEXT(head, var, field), 1); \ 359 (var) = (tvar)) 360 361 /* 362 * XOR Simple queue functions. 363 */ 364 #define XSIMPLEQ_INIT(head) do { \ 365 arc4random_buf(&(head)->sqx_cookie, sizeof((head)->sqx_cookie)); \ 366 (head)->sqx_first = XSIMPLEQ_XOR(head, NULL); \ 367 (head)->sqx_last = XSIMPLEQ_XOR(head, &(head)->sqx_first); \ 368 } while (0) 369 370 #define XSIMPLEQ_INSERT_HEAD(head, elm, field) do { \ 371 if (((elm)->field.sqx_next = (head)->sqx_first) == \ 372 XSIMPLEQ_XOR(head, NULL)) \ 373 (head)->sqx_last = XSIMPLEQ_XOR(head, &(elm)->field.sqx_next); \ 374 (head)->sqx_first = XSIMPLEQ_XOR(head, (elm)); \ 375 } while (0) 376 377 #define XSIMPLEQ_INSERT_TAIL(head, elm, field) do { \ 378 (elm)->field.sqx_next = XSIMPLEQ_XOR(head, NULL); \ 379 *(XSIMPLEQ_XOR(head, (head)->sqx_last)) = XSIMPLEQ_XOR(head, (elm)); \ 380 (head)->sqx_last = XSIMPLEQ_XOR(head, &(elm)->field.sqx_next); \ 381 } while (0) 382 383 #define XSIMPLEQ_INSERT_AFTER(head, listelm, elm, field) do { \ 384 if (((elm)->field.sqx_next = (listelm)->field.sqx_next) == \ 385 XSIMPLEQ_XOR(head, NULL)) \ 386 (head)->sqx_last = XSIMPLEQ_XOR(head, &(elm)->field.sqx_next); \ 387 (listelm)->field.sqx_next = XSIMPLEQ_XOR(head, (elm)); \ 388 } while (0) 389 390 #define XSIMPLEQ_REMOVE_HEAD(head, field) do { \ 391 if (((head)->sqx_first = XSIMPLEQ_XOR(head, \ 392 (head)->sqx_first)->field.sqx_next) == XSIMPLEQ_XOR(head, NULL)) \ 393 (head)->sqx_last = XSIMPLEQ_XOR(head, &(head)->sqx_first); \ 394 } while (0) 395 396 #define XSIMPLEQ_REMOVE_AFTER(head, elm, field) do { \ 397 if (((elm)->field.sqx_next = XSIMPLEQ_XOR(head, \ 398 (elm)->field.sqx_next)->field.sqx_next) \ 399 == XSIMPLEQ_XOR(head, NULL)) \ 400 (head)->sqx_last = \ 401 XSIMPLEQ_XOR(head, &(elm)->field.sqx_next); \ 402 } while (0) 403 404 405 /* 406 * Tail queue definitions. 407 */ 408 #define TAILQ_HEAD(name, type) \ 409 struct name { \ 410 struct type *tqh_first; /* first element */ \ 411 struct type **tqh_last; /* addr of last next element */ \ 412 } 413 414 #define TAILQ_HEAD_INITIALIZER(head) \ 415 { NULL, &(head).tqh_first } 416 417 #define TAILQ_ENTRY(type) \ 418 struct { \ 419 struct type *tqe_next; /* next element */ \ 420 struct type **tqe_prev; /* address of previous next element */ \ 421 } 422 423 /* 424 * Tail queue access methods. 425 */ 426 #define TAILQ_FIRST(head) ((head)->tqh_first) 427 #define TAILQ_END(head) NULL 428 #define TAILQ_NEXT(elm, field) ((elm)->field.tqe_next) 429 #define TAILQ_LAST(head, headname) \ 430 (*(((struct headname *)((head)->tqh_last))->tqh_last)) 431 /* XXX */ 432 #define TAILQ_PREV(elm, headname, field) \ 433 (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last)) 434 #define TAILQ_EMPTY(head) \ 435 (TAILQ_FIRST(head) == TAILQ_END(head)) 436 437 #define TAILQ_FOREACH(var, head, field) \ 438 for((var) = TAILQ_FIRST(head); \ 439 (var) != TAILQ_END(head); \ 440 (var) = TAILQ_NEXT(var, field)) 441 442 #define TAILQ_FOREACH_SAFE(var, head, field, tvar) \ 443 for ((var) = TAILQ_FIRST(head); \ 444 (var) != TAILQ_END(head) && \ 445 ((tvar) = TAILQ_NEXT(var, field), 1); \ 446 (var) = (tvar)) 447 448 449 #define TAILQ_FOREACH_REVERSE(var, head, headname, field) \ 450 for((var) = TAILQ_LAST(head, headname); \ 451 (var) != TAILQ_END(head); \ 452 (var) = TAILQ_PREV(var, headname, field)) 453 454 #define TAILQ_FOREACH_REVERSE_SAFE(var, head, headname, field, tvar) \ 455 for ((var) = TAILQ_LAST(head, headname); \ 456 (var) != TAILQ_END(head) && \ 457 ((tvar) = TAILQ_PREV(var, headname, field), 1); \ 458 (var) = (tvar)) 459 460 /* 461 * Tail queue functions. 462 */ 463 #define TAILQ_INIT(head) do { \ 464 (head)->tqh_first = NULL; \ 465 (head)->tqh_last = &(head)->tqh_first; \ 466 } while (0) 467 468 #define TAILQ_INSERT_HEAD(head, elm, field) do { \ 469 if (((elm)->field.tqe_next = (head)->tqh_first) != NULL) \ 470 (head)->tqh_first->field.tqe_prev = \ 471 &(elm)->field.tqe_next; \ 472 else \ 473 (head)->tqh_last = &(elm)->field.tqe_next; \ 474 (head)->tqh_first = (elm); \ 475 (elm)->field.tqe_prev = &(head)->tqh_first; \ 476 } while (0) 477 478 #define TAILQ_INSERT_TAIL(head, elm, field) do { \ 479 (elm)->field.tqe_next = NULL; \ 480 (elm)->field.tqe_prev = (head)->tqh_last; \ 481 *(head)->tqh_last = (elm); \ 482 (head)->tqh_last = &(elm)->field.tqe_next; \ 483 } while (0) 484 485 #define TAILQ_INSERT_AFTER(head, listelm, elm, field) do { \ 486 if (((elm)->field.tqe_next = (listelm)->field.tqe_next) != NULL)\ 487 (elm)->field.tqe_next->field.tqe_prev = \ 488 &(elm)->field.tqe_next; \ 489 else \ 490 (head)->tqh_last = &(elm)->field.tqe_next; \ 491 (listelm)->field.tqe_next = (elm); \ 492 (elm)->field.tqe_prev = &(listelm)->field.tqe_next; \ 493 } while (0) 494 495 #define TAILQ_INSERT_BEFORE(listelm, elm, field) do { \ 496 (elm)->field.tqe_prev = (listelm)->field.tqe_prev; \ 497 (elm)->field.tqe_next = (listelm); \ 498 *(listelm)->field.tqe_prev = (elm); \ 499 (listelm)->field.tqe_prev = &(elm)->field.tqe_next; \ 500 } while (0) 501 502 #define TAILQ_REMOVE(head, elm, field) do { \ 503 if (((elm)->field.tqe_next) != NULL) \ 504 (elm)->field.tqe_next->field.tqe_prev = \ 505 (elm)->field.tqe_prev; \ 506 else \ 507 (head)->tqh_last = (elm)->field.tqe_prev; \ 508 *(elm)->field.tqe_prev = (elm)->field.tqe_next; \ 509 _Q_INVALIDATE((elm)->field.tqe_prev); \ 510 _Q_INVALIDATE((elm)->field.tqe_next); \ 511 } while (0) 512 513 #define TAILQ_REPLACE(head, elm, elm2, field) do { \ 514 if (((elm2)->field.tqe_next = (elm)->field.tqe_next) != NULL) \ 515 (elm2)->field.tqe_next->field.tqe_prev = \ 516 &(elm2)->field.tqe_next; \ 517 else \ 518 (head)->tqh_last = &(elm2)->field.tqe_next; \ 519 (elm2)->field.tqe_prev = (elm)->field.tqe_prev; \ 520 *(elm2)->field.tqe_prev = (elm2); \ 521 _Q_INVALIDATE((elm)->field.tqe_prev); \ 522 _Q_INVALIDATE((elm)->field.tqe_next); \ 523 } while (0) 524 525 #define TAILQ_CONCAT(head1, head2, field) do { \ 526 if (!TAILQ_EMPTY(head2)) { \ 527 *(head1)->tqh_last = (head2)->tqh_first; \ 528 (head2)->tqh_first->field.tqe_prev = (head1)->tqh_last; \ 529 (head1)->tqh_last = (head2)->tqh_last; \ 530 TAILQ_INIT((head2)); \ 531 } \ 532 } while (0) 533 534 #endif /* !_SYS_QUEUE_H_ */ 535