]>
git.proxmox.com Git - mirror_frr.git/blob - lib/freebsd-queue.h
2 * Copyright (c) 1991, 1993
3 * The Regents of the University of California. All rights reserved.
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
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 * 4. 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.
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
29 * @(#)queue.h 8.5 (Berkeley) 8/20/94
37 * This file defines four types of data structures: singly-linked lists,
38 * singly-linked tail queues, lists and tail queues.
40 * A singly-linked list is headed by a single forward pointer. The elements
41 * are singly linked for minimum space and pointer manipulation overhead at
42 * the expense of O(n) removal for arbitrary elements. New elements can be
43 * added to the list after an existing element or at the head of the list.
44 * Elements being removed from the head of the list should use the explicit
45 * macro for this purpose for optimum efficiency. A singly-linked list may
46 * only be traversed in the forward direction. Singly-linked lists are ideal
47 * for applications with large datasets and few or no removals or for
48 * implementing a LIFO queue.
50 * A singly-linked tail queue is headed by a pair of pointers, one to the
51 * head of the list and the other to the tail of the list. The elements are
52 * singly linked for minimum space and pointer manipulation overhead at the
53 * expense of O(n) removal for arbitrary elements. New elements can be added
54 * to the list after an existing element, at the head of the list, or at the
55 * end of the list. Elements being removed from the head of the tail queue
56 * should use the explicit macro for this purpose for optimum efficiency.
57 * A singly-linked tail queue may only be traversed in the forward direction.
58 * Singly-linked tail queues are ideal for applications with large datasets
59 * and few or no removals or for implementing a FIFO queue.
61 * A list is headed by a single forward pointer (or an array of forward
62 * pointers for a hash table header). The elements are doubly linked
63 * so that an arbitrary element can be removed without a need to
64 * traverse the list. New elements can be added to the list before
65 * or after an existing element or at the head of the list. A list
66 * may only be traversed in the forward direction.
68 * A tail queue is headed by a pair of pointers, one to the head of the
69 * list and the other to the tail of the list. The elements are doubly
70 * linked so that an arbitrary element can be removed without a need to
71 * traverse the list. New elements can be added to the list before or
72 * after an existing element, at the head of the list, or at the end of
73 * the list. A tail queue may be traversed in either direction.
75 * For details on the use of these macros, see the queue(3) manual page.
78 * SLIST LIST STAILQ TAILQ
80 * _HEAD_INITIALIZER + + + +
89 * _FOREACH_SAFE + + + +
90 * _FOREACH_REVERSE - - - +
91 * _FOREACH_REVERSE_SAFE - - - +
92 * _INSERT_HEAD + + + +
93 * _INSERT_BEFORE - + - +
94 * _INSERT_AFTER + + + +
95 * _INSERT_TAIL - - + +
97 * _REMOVE_AFTER + - + -
98 * _REMOVE_HEAD + - + -
103 #ifdef QUEUE_MACRO_DEBUG
104 /* Store the last 2 places the queue element or head was altered */
112 #define TRACEBUF struct qm_trace trace;
113 #define TRASHIT(x) do {(x) = (void *)-1;} while (0)
114 #define QMD_SAVELINK(name, link) void **name = (void *)&(link)
116 #define QMD_TRACE_HEAD(head) \
118 (head)->trace.prevline = (head)->trace.lastline; \
119 (head)->trace.prevfile = (head)->trace.lastfile; \
120 (head)->trace.lastline = __LINE__; \
121 (head)->trace.lastfile = __FILE__; \
124 #define QMD_TRACE_ELEM(elem) \
126 (elem)->trace.prevline = (elem)->trace.lastline; \
127 (elem)->trace.prevfile = (elem)->trace.lastfile; \
128 (elem)->trace.lastline = __LINE__; \
129 (elem)->trace.lastfile = __FILE__; \
133 #define QMD_TRACE_ELEM(elem)
134 #define QMD_TRACE_HEAD(head)
135 #define QMD_SAVELINK(name, link)
138 #endif /* QUEUE_MACRO_DEBUG */
141 * Singly-linked List declarations.
143 #define SLIST_HEAD(name, type) \
145 struct type *slh_first; /* first element */ \
148 #define SLIST_HEAD_INITIALIZER(head) \
153 #define SLIST_ENTRY(type) \
155 struct type *sle_next; /* next element */ \
159 * Singly-linked List functions.
161 #define SLIST_EMPTY(head) ((head)->slh_first == NULL)
163 #define SLIST_FIRST(head) ((head)->slh_first)
165 #define SLIST_FOREACH(var, head, field) \
166 for ((var) = SLIST_FIRST((head)); (var); \
167 (var) = SLIST_NEXT((var), field))
169 #define SLIST_FOREACH_SAFE(var, head, field, tvar) \
170 for ((var) = SLIST_FIRST((head)); \
171 (var) && ((tvar) = SLIST_NEXT((var), field), 1); (var) = (tvar))
173 #define SLIST_FOREACH_PREVPTR(var, varp, head, field) \
174 for ((varp) = &SLIST_FIRST((head)); ((var) = *(varp)) != NULL; \
175 (varp) = &SLIST_NEXT((var), field))
177 #define SLIST_INIT(head) \
179 SLIST_FIRST((head)) = NULL; \
182 #define SLIST_INSERT_AFTER(slistelm, elm, field) \
184 SLIST_NEXT((elm), field) = SLIST_NEXT((slistelm), field); \
185 SLIST_NEXT((slistelm), field) = (elm); \
188 #define SLIST_INSERT_HEAD(head, elm, field) \
190 SLIST_NEXT((elm), field) = SLIST_FIRST((head)); \
191 SLIST_FIRST((head)) = (elm); \
194 #define SLIST_NEXT(elm, field) ((elm)->field.sle_next)
196 #define SLIST_REMOVE(head, elm, type, field) \
198 QMD_SAVELINK(oldnext, (elm)->field.sle_next); \
199 if (SLIST_FIRST((head)) == (elm)) { \
200 SLIST_REMOVE_HEAD((head), field); \
202 struct type *curelm = SLIST_FIRST((head)); \
203 while (SLIST_NEXT(curelm, field) != (elm)) \
204 curelm = SLIST_NEXT(curelm, field); \
205 SLIST_REMOVE_AFTER(curelm, field); \
210 #define SLIST_REMOVE_AFTER(elm, field) \
212 SLIST_NEXT(elm, field) = \
213 SLIST_NEXT(SLIST_NEXT(elm, field), field); \
216 #define SLIST_REMOVE_HEAD(head, field) \
218 SLIST_FIRST((head)) = SLIST_NEXT(SLIST_FIRST((head)), field); \
221 #define SLIST_SWAP(head1, head2, type) \
223 struct type *swap_first = SLIST_FIRST(head1); \
224 SLIST_FIRST(head1) = SLIST_FIRST(head2); \
225 SLIST_FIRST(head2) = swap_first; \
229 * Singly-linked Tail queue declarations.
231 #define STAILQ_HEAD(name, type) \
233 struct type *stqh_first; /* first element */ \
234 struct type **stqh_last; /* addr of last next element */ \
237 #define STAILQ_HEAD_INITIALIZER(head) \
239 NULL, &(head).stqh_first \
242 #define STAILQ_ENTRY(type) \
244 struct type *stqe_next; /* next element */ \
248 * Singly-linked Tail queue functions.
250 #define STAILQ_CONCAT(head1, head2) \
252 if (!STAILQ_EMPTY((head2))) { \
253 *(head1)->stqh_last = (head2)->stqh_first; \
254 (head1)->stqh_last = (head2)->stqh_last; \
255 STAILQ_INIT((head2)); \
259 #define STAILQ_EMPTY(head) ((head)->stqh_first == NULL)
261 #define STAILQ_FIRST(head) ((head)->stqh_first)
263 #define STAILQ_FOREACH(var, head, field) \
264 for ((var) = STAILQ_FIRST((head)); (var); \
265 (var) = STAILQ_NEXT((var), field))
268 #define STAILQ_FOREACH_SAFE(var, head, field, tvar) \
269 for ((var) = STAILQ_FIRST((head)); \
270 (var) && ((tvar) = STAILQ_NEXT((var), field), 1); (var) = (tvar))
272 #define STAILQ_INIT(head) \
274 STAILQ_FIRST((head)) = NULL; \
275 (head)->stqh_last = &STAILQ_FIRST((head)); \
278 #define STAILQ_INSERT_AFTER(head, tqelm, elm, field) \
280 if ((STAILQ_NEXT((elm), field) = STAILQ_NEXT((tqelm), field)) \
282 (head)->stqh_last = &STAILQ_NEXT((elm), field); \
283 STAILQ_NEXT((tqelm), field) = (elm); \
286 #define STAILQ_INSERT_HEAD(head, elm, field) \
288 if ((STAILQ_NEXT((elm), field) = STAILQ_FIRST((head))) \
290 (head)->stqh_last = &STAILQ_NEXT((elm), field); \
291 STAILQ_FIRST((head)) = (elm); \
294 #define STAILQ_INSERT_TAIL(head, elm, field) \
296 STAILQ_NEXT((elm), field) = NULL; \
297 *(head)->stqh_last = (elm); \
298 (head)->stqh_last = &STAILQ_NEXT((elm), field); \
301 #define STAILQ_LAST(head, type, field) \
302 (STAILQ_EMPTY((head)) \
304 : ((struct type *)(void *)((char *)((head)->stqh_last) \
305 - offsetof(struct type, field))))
307 #define STAILQ_NEXT(elm, field) ((elm)->field.stqe_next)
309 #define STAILQ_REMOVE(head, elm, type, field) \
311 QMD_SAVELINK(oldnext, (elm)->field.stqe_next); \
312 if (STAILQ_FIRST((head)) == (elm)) { \
313 STAILQ_REMOVE_HEAD((head), field); \
315 struct type *curelm = STAILQ_FIRST((head)); \
316 while (STAILQ_NEXT(curelm, field) != (elm)) \
317 curelm = STAILQ_NEXT(curelm, field); \
318 STAILQ_REMOVE_AFTER(head, curelm, field); \
323 #define STAILQ_REMOVE_AFTER(head, elm, field) \
325 if ((STAILQ_NEXT(elm, field) = \
326 STAILQ_NEXT(STAILQ_NEXT(elm, field), field)) \
328 (head)->stqh_last = &STAILQ_NEXT((elm), field); \
331 #define STAILQ_REMOVE_HEAD(head, field) \
333 if ((STAILQ_FIRST((head)) = \
334 STAILQ_NEXT(STAILQ_FIRST((head)), field)) \
336 (head)->stqh_last = &STAILQ_FIRST((head)); \
339 #define STAILQ_SWAP(head1, head2, type) \
341 struct type *swap_first = STAILQ_FIRST(head1); \
342 struct type **swap_last = (head1)->stqh_last; \
343 STAILQ_FIRST(head1) = STAILQ_FIRST(head2); \
344 (head1)->stqh_last = (head2)->stqh_last; \
345 STAILQ_FIRST(head2) = swap_first; \
346 (head2)->stqh_last = swap_last; \
347 if (STAILQ_EMPTY(head1)) \
348 (head1)->stqh_last = &STAILQ_FIRST(head1); \
349 if (STAILQ_EMPTY(head2)) \
350 (head2)->stqh_last = &STAILQ_FIRST(head2); \
357 #define LIST_HEAD(name, type) \
359 struct type *lh_first; /* first element */ \
362 #define LIST_HEAD_INITIALIZER(head) \
367 #define LIST_ENTRY(type) \
369 struct type *le_next; /* next element */ \
370 struct type **le_prev; /* address of previous next element */ \
377 #if (defined(_KERNEL) && defined(INVARIANTS))
378 #define QMD_LIST_CHECK_HEAD(head, field) \
380 if (LIST_FIRST((head)) != NULL \
381 && LIST_FIRST((head))->field.le_prev \
382 != &LIST_FIRST((head))) \
383 panic("Bad list head %p first->prev != head", (head)); \
386 #define QMD_LIST_CHECK_NEXT(elm, field) \
388 if (LIST_NEXT((elm), field) != NULL \
389 && LIST_NEXT((elm), field)->field.le_prev \
390 != &((elm)->field.le_next)) \
391 panic("Bad link elm %p next->prev != elm", (elm)); \
394 #define QMD_LIST_CHECK_PREV(elm, field) \
396 if (*(elm)->field.le_prev != (elm)) \
397 panic("Bad link elm %p prev->next != elm", (elm)); \
400 #define QMD_LIST_CHECK_HEAD(head, field)
401 #define QMD_LIST_CHECK_NEXT(elm, field)
402 #define QMD_LIST_CHECK_PREV(elm, field)
403 #endif /* (_KERNEL && INVARIANTS) */
405 #define LIST_EMPTY(head) ((head)->lh_first == NULL)
407 #define LIST_FIRST(head) ((head)->lh_first)
409 #define LIST_FOREACH(var, head, field) \
410 for ((var) = LIST_FIRST((head)); (var); (var) = LIST_NEXT((var), field))
412 #define LIST_FOREACH_SAFE(var, head, field, tvar) \
413 for ((var) = LIST_FIRST((head)); \
414 (var) && ((tvar) = LIST_NEXT((var), field), 1); (var) = (tvar))
416 #define LIST_INIT(head) \
418 LIST_FIRST((head)) = NULL; \
421 #define LIST_INSERT_AFTER(listelm, elm, field) \
423 QMD_LIST_CHECK_NEXT(listelm, field); \
424 if ((LIST_NEXT((elm), field) = LIST_NEXT((listelm), field)) \
426 LIST_NEXT((listelm), field)->field.le_prev = \
427 &LIST_NEXT((elm), field); \
428 LIST_NEXT((listelm), field) = (elm); \
429 (elm)->field.le_prev = &LIST_NEXT((listelm), field); \
432 #define LIST_INSERT_BEFORE(listelm, elm, field) \
434 QMD_LIST_CHECK_PREV(listelm, field); \
435 (elm)->field.le_prev = (listelm)->field.le_prev; \
436 LIST_NEXT((elm), field) = (listelm); \
437 *(listelm)->field.le_prev = (elm); \
438 (listelm)->field.le_prev = &LIST_NEXT((elm), field); \
441 #define LIST_INSERT_HEAD(head, elm, field) \
443 QMD_LIST_CHECK_HEAD((head), field); \
444 if ((LIST_NEXT((elm), field) = LIST_FIRST((head))) != NULL) \
445 LIST_FIRST((head))->field.le_prev = \
446 &LIST_NEXT((elm), field); \
447 LIST_FIRST((head)) = (elm); \
448 (elm)->field.le_prev = &LIST_FIRST((head)); \
451 #define LIST_NEXT(elm, field) ((elm)->field.le_next)
453 #define LIST_REMOVE(elm, field) \
455 QMD_SAVELINK(oldnext, (elm)->field.le_next); \
456 QMD_SAVELINK(oldprev, (elm)->field.le_prev); \
457 QMD_LIST_CHECK_NEXT(elm, field); \
458 QMD_LIST_CHECK_PREV(elm, field); \
459 if (LIST_NEXT((elm), field) != NULL) \
460 LIST_NEXT((elm), field)->field.le_prev = \
461 (elm)->field.le_prev; \
462 *(elm)->field.le_prev = LIST_NEXT((elm), field); \
467 #define LIST_SWAP(head1, head2, type, field) \
469 struct type *swap_tmp = LIST_FIRST((head1)); \
470 LIST_FIRST((head1)) = LIST_FIRST((head2)); \
471 LIST_FIRST((head2)) = swap_tmp; \
472 if ((swap_tmp = LIST_FIRST((head1))) != NULL) \
473 swap_tmp->field.le_prev = &LIST_FIRST((head1)); \
474 if ((swap_tmp = LIST_FIRST((head2))) != NULL) \
475 swap_tmp->field.le_prev = &LIST_FIRST((head2)); \
479 * Tail queue declarations.
481 #define TAILQ_HEAD(name, type) \
483 struct type *tqh_first; /* first element */ \
484 struct type **tqh_last; /* addr of last next element */ \
488 #define TAILQ_HEAD_INITIALIZER(head) \
490 NULL, &(head).tqh_first \
493 #define TAILQ_ENTRY(type) \
495 struct type *tqe_next; /* next element */ \
496 struct type **tqe_prev; /* address of previous next element */ \
501 * Tail queue functions.
503 #if (defined(_KERNEL) && defined(INVARIANTS))
504 #define QMD_TAILQ_CHECK_HEAD(head, field) \
506 if (!TAILQ_EMPTY(head) \
507 && TAILQ_FIRST((head))->field.tqe_prev \
508 != &TAILQ_FIRST((head))) \
509 panic("Bad tailq head %p first->prev != head", \
513 #define QMD_TAILQ_CHECK_TAIL(head, field) \
515 if (*(head)->tqh_last != NULL) \
516 panic("Bad tailq NEXT(%p->tqh_last) != NULL", (head)); \
519 #define QMD_TAILQ_CHECK_NEXT(elm, field) \
521 if (TAILQ_NEXT((elm), field) != NULL \
522 && TAILQ_NEXT((elm), field)->field.tqe_prev \
523 != &((elm)->field.tqe_next)) \
524 panic("Bad link elm %p next->prev != elm", (elm)); \
527 #define QMD_TAILQ_CHECK_PREV(elm, field) \
529 if (*(elm)->field.tqe_prev != (elm)) \
530 panic("Bad link elm %p prev->next != elm", (elm)); \
533 #define QMD_TAILQ_CHECK_HEAD(head, field)
534 #define QMD_TAILQ_CHECK_TAIL(head, headname)
535 #define QMD_TAILQ_CHECK_NEXT(elm, field)
536 #define QMD_TAILQ_CHECK_PREV(elm, field)
537 #endif /* (_KERNEL && INVARIANTS) */
539 #define TAILQ_CONCAT(head1, head2, field) \
541 if (!TAILQ_EMPTY(head2)) { \
542 *(head1)->tqh_last = (head2)->tqh_first; \
543 (head2)->tqh_first->field.tqe_prev = \
545 (head1)->tqh_last = (head2)->tqh_last; \
546 TAILQ_INIT((head2)); \
547 QMD_TRACE_HEAD(head1); \
548 QMD_TRACE_HEAD(head2); \
552 #define TAILQ_EMPTY(head) ((head)->tqh_first == NULL)
554 #define TAILQ_FIRST(head) ((head)->tqh_first)
556 #define TAILQ_FOREACH(var, head, field) \
557 for ((var) = TAILQ_FIRST((head)); (var); \
558 (var) = TAILQ_NEXT((var), field))
560 #define TAILQ_FOREACH_SAFE(var, head, field, tvar) \
561 for ((var) = TAILQ_FIRST((head)); \
562 (var) && ((tvar) = TAILQ_NEXT((var), field), 1); (var) = (tvar))
564 #define TAILQ_FOREACH_REVERSE(var, head, headname, field) \
565 for ((var) = TAILQ_LAST((head), headname); (var); \
566 (var) = TAILQ_PREV((var), headname, field))
568 #define TAILQ_FOREACH_REVERSE_SAFE(var, head, headname, field, tvar) \
569 for ((var) = TAILQ_LAST((head), headname); \
570 (var) && ((tvar) = TAILQ_PREV((var), headname, field), 1); \
573 #define TAILQ_INIT(head) \
575 TAILQ_FIRST((head)) = NULL; \
576 (head)->tqh_last = &TAILQ_FIRST((head)); \
577 QMD_TRACE_HEAD(head); \
580 #define TAILQ_INSERT_AFTER(head, listelm, elm, field) \
582 QMD_TAILQ_CHECK_NEXT(listelm, field); \
583 if ((TAILQ_NEXT((elm), field) = TAILQ_NEXT((listelm), field)) \
585 TAILQ_NEXT((elm), field)->field.tqe_prev = \
586 &TAILQ_NEXT((elm), field); \
588 (head)->tqh_last = &TAILQ_NEXT((elm), field); \
589 QMD_TRACE_HEAD(head); \
591 TAILQ_NEXT((listelm), field) = (elm); \
592 (elm)->field.tqe_prev = &TAILQ_NEXT((listelm), field); \
593 QMD_TRACE_ELEM(&(elm)->field); \
594 QMD_TRACE_ELEM(&listelm->field); \
597 #define TAILQ_INSERT_BEFORE(listelm, elm, field) \
599 QMD_TAILQ_CHECK_PREV(listelm, field); \
600 (elm)->field.tqe_prev = (listelm)->field.tqe_prev; \
601 TAILQ_NEXT((elm), field) = (listelm); \
602 *(listelm)->field.tqe_prev = (elm); \
603 (listelm)->field.tqe_prev = &TAILQ_NEXT((elm), field); \
604 QMD_TRACE_ELEM(&(elm)->field); \
605 QMD_TRACE_ELEM(&listelm->field); \
608 #define TAILQ_INSERT_HEAD(head, elm, field) \
610 QMD_TAILQ_CHECK_HEAD(head, field); \
611 if ((TAILQ_NEXT((elm), field) = TAILQ_FIRST((head))) != NULL) \
612 TAILQ_FIRST((head))->field.tqe_prev = \
613 &TAILQ_NEXT((elm), field); \
615 (head)->tqh_last = &TAILQ_NEXT((elm), field); \
616 TAILQ_FIRST((head)) = (elm); \
617 (elm)->field.tqe_prev = &TAILQ_FIRST((head)); \
618 QMD_TRACE_HEAD(head); \
619 QMD_TRACE_ELEM(&(elm)->field); \
622 #define TAILQ_INSERT_TAIL(head, elm, field) \
624 QMD_TAILQ_CHECK_TAIL(head, field); \
625 TAILQ_NEXT((elm), field) = NULL; \
626 (elm)->field.tqe_prev = (head)->tqh_last; \
627 *(head)->tqh_last = (elm); \
628 (head)->tqh_last = &TAILQ_NEXT((elm), field); \
629 QMD_TRACE_HEAD(head); \
630 QMD_TRACE_ELEM(&(elm)->field); \
633 #define TAILQ_LAST(head, headname) \
634 (*(((struct headname *)((head)->tqh_last))->tqh_last))
636 #define TAILQ_NEXT(elm, field) ((elm)->field.tqe_next)
638 #define TAILQ_PREV(elm, headname, field) \
639 (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
641 #define TAILQ_REMOVE(head, elm, field) \
643 QMD_SAVELINK(oldnext, (elm)->field.tqe_next); \
644 QMD_SAVELINK(oldprev, (elm)->field.tqe_prev); \
645 QMD_TAILQ_CHECK_NEXT(elm, field); \
646 QMD_TAILQ_CHECK_PREV(elm, field); \
647 if ((TAILQ_NEXT((elm), field)) != NULL) \
648 TAILQ_NEXT((elm), field)->field.tqe_prev = \
649 (elm)->field.tqe_prev; \
651 (head)->tqh_last = (elm)->field.tqe_prev; \
652 QMD_TRACE_HEAD(head); \
654 *(elm)->field.tqe_prev = TAILQ_NEXT((elm), field); \
657 QMD_TRACE_ELEM(&(elm)->field); \
660 #define TAILQ_SWAP(head1, head2, type, field) \
662 struct type *swap_first = (head1)->tqh_first; \
663 struct type **swap_last = (head1)->tqh_last; \
664 (head1)->tqh_first = (head2)->tqh_first; \
665 (head1)->tqh_last = (head2)->tqh_last; \
666 (head2)->tqh_first = swap_first; \
667 (head2)->tqh_last = swap_last; \
668 if ((swap_first = (head1)->tqh_first) != NULL) \
669 swap_first->field.tqe_prev = &(head1)->tqh_first; \
671 (head1)->tqh_last = &(head1)->tqh_first; \
672 if ((swap_first = (head2)->tqh_first) != NULL) \
673 swap_first->field.tqe_prev = &(head2)->tqh_first; \
675 (head2)->tqh_last = &(head2)->tqh_first; \
678 #endif /* !_SYS_QUEUE_H_ */