2 * Copyright (c) 1991, 1993
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6 * modification, are permitted provided that the following conditions
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29 * @(#)queue.h 8.5 (Berkeley) 8/20/94
36 #include <sys/cdefs.h>
39 * This file defines four types of data structures: singly-linked lists,
40 * singly-linked tail queues, lists and tail queues.
42 * A singly-linked list is headed by a single forward pointer. The elements
43 * are singly linked for minimum space and pointer manipulation overhead at
44 * the expense of O(n) removal for arbitrary elements. New elements can be
45 * added to the list after an existing element or at the head of the list.
46 * Elements being removed from the head of the list should use the explicit
47 * macro for this purpose for optimum efficiency. A singly-linked list may
48 * only be traversed in the forward direction. Singly-linked lists are ideal
49 * for applications with large datasets and few or no removals or for
50 * implementing a LIFO queue.
52 * A singly-linked tail queue is headed by a pair of pointers, one to the
53 * head of the list and the other to the tail of the list. The elements are
54 * singly linked for minimum space and pointer manipulation overhead at the
55 * expense of O(n) removal for arbitrary elements. New elements can be added
56 * to the list after an existing element, at the head of the list, or at the
57 * end of the list. Elements being removed from the head of the tail queue
58 * should use the explicit macro for this purpose for optimum efficiency.
59 * A singly-linked tail queue may only be traversed in the forward direction.
60 * Singly-linked tail queues are ideal for applications with large datasets
61 * and few or no removals or for implementing a FIFO queue.
63 * A list is headed by a single forward pointer (or an array of forward
64 * pointers for a hash table header). The elements are doubly linked
65 * so that an arbitrary element can be removed without a need to
66 * traverse the list. New elements can be added to the list before
67 * or after an existing element or at the head of the list. A list
68 * may only be traversed in the forward direction.
70 * A tail queue is headed by a pair of pointers, one to the head of the
71 * list and the other to the tail of the list. The elements are doubly
72 * linked so that an arbitrary element can be removed without a need to
73 * traverse the list. New elements can be added to the list before or
74 * after an existing element, at the head of the list, or at the end of
75 * the list. A tail queue may be traversed in either direction.
77 * For details on the use of these macros, see the queue(3) manual page.
80 * SLIST LIST STAILQ TAILQ
82 * _HEAD_INITIALIZER + + + +
91 * _FOREACH_FROM + + + +
92 * _FOREACH_SAFE + + + +
93 * _FOREACH_FROM_SAFE + + + +
94 * _FOREACH_REVERSE - - - +
95 * _FOREACH_REVERSE_FROM - - - +
96 * _FOREACH_REVERSE_SAFE - - - +
97 * _FOREACH_REVERSE_FROM_SAFE - - - +
98 * _INSERT_HEAD + + + +
99 * _INSERT_BEFORE - + - +
100 * _INSERT_AFTER + + + +
101 * _INSERT_TAIL - - + +
103 * _REMOVE_AFTER + - + -
104 * _REMOVE_HEAD + - + -
109 #ifdef QUEUE_MACRO_DEBUG
110 /* Store the last 2 places the queue element or head was altered */
118 #define TRACEBUF struct qm_trace trace;
119 #define TRASHIT(x) do {(x) = (void *)-1;} while (0)
120 #define QMD_SAVELINK(name, link) void **name = (void *)&(link)
122 #define QMD_TRACE_HEAD(head) do { \
123 (head)->trace.prevline = (head)->trace.lastline; \
124 (head)->trace.prevfile = (head)->trace.lastfile; \
125 (head)->trace.lastline = __LINE__; \
126 (head)->trace.lastfile = __FILE__; \
129 #define QMD_TRACE_ELEM(elem) do { \
130 (elem)->trace.prevline = (elem)->trace.lastline; \
131 (elem)->trace.prevfile = (elem)->trace.lastfile; \
132 (elem)->trace.lastline = __LINE__; \
133 (elem)->trace.lastfile = __FILE__; \
137 #define QMD_TRACE_ELEM(elem)
138 #define QMD_TRACE_HEAD(head)
139 #define QMD_SAVELINK(name, link)
142 #endif /* QUEUE_MACRO_DEBUG */
145 * Singly-linked List declarations.
147 #define SLIST_HEAD(name, type) \
149 struct type *slh_first; /* first element */ \
152 #define SLIST_HEAD_INITIALIZER(head) \
155 #define SLIST_ENTRY(type) \
157 struct type *sle_next; /* next element */ \
161 * Singly-linked List functions.
163 #define SLIST_EMPTY(head) ((head)->slh_first == NULL)
165 #define SLIST_FIRST(head) ((head)->slh_first)
167 #define SLIST_FOREACH(var, head, field) \
168 for ((var) = SLIST_FIRST((head)); \
170 (var) = SLIST_NEXT((var), field))
172 #define SLIST_FOREACH_FROM(var, head, field) \
173 for ((var) = ((var) ? (var) : SLIST_FIRST((head))); \
175 (var) = SLIST_NEXT((var), field))
177 #define SLIST_FOREACH_SAFE(var, head, field, tvar) \
178 for ((var) = SLIST_FIRST((head)); \
179 (var) && ((tvar) = SLIST_NEXT((var), field), 1); \
182 #define SLIST_FOREACH_FROM_SAFE(var, head, field, tvar) \
183 for ((var) = ((var) ? (var) : SLIST_FIRST((head))); \
184 (var) && ((tvar) = SLIST_NEXT((var), field), 1); \
187 #define SLIST_FOREACH_PREVPTR(var, varp, head, field) \
188 for ((varp) = &SLIST_FIRST((head)); \
189 ((var) = *(varp)) != NULL; \
190 (varp) = &SLIST_NEXT((var), field))
192 #define SLIST_INIT(head) do { \
193 SLIST_FIRST((head)) = NULL; \
196 #define SLIST_INSERT_AFTER(slistelm, elm, field) do { \
197 SLIST_NEXT((elm), field) = SLIST_NEXT((slistelm), field); \
198 SLIST_NEXT((slistelm), field) = (elm); \
201 #define SLIST_INSERT_HEAD(head, elm, field) do { \
202 SLIST_NEXT((elm), field) = SLIST_FIRST((head)); \
203 SLIST_FIRST((head)) = (elm); \
206 #define SLIST_NEXT(elm, field) ((elm)->field.sle_next)
208 #define SLIST_REMOVE(head, elm, type, field) do { \
209 QMD_SAVELINK(oldnext, (elm)->field.sle_next); \
210 if (SLIST_FIRST((head)) == (elm)) { \
211 SLIST_REMOVE_HEAD((head), field); \
214 struct type *curelm = SLIST_FIRST((head)); \
215 while (SLIST_NEXT(curelm, field) != (elm)) \
216 curelm = SLIST_NEXT(curelm, field); \
217 SLIST_REMOVE_AFTER(curelm, field); \
222 #define SLIST_REMOVE_AFTER(elm, field) do { \
223 SLIST_NEXT(elm, field) = \
224 SLIST_NEXT(SLIST_NEXT(elm, field), field); \
227 #define SLIST_REMOVE_HEAD(head, field) do { \
228 SLIST_FIRST((head)) = SLIST_NEXT(SLIST_FIRST((head)), field); \
231 #define SLIST_SWAP(head1, head2, type) do { \
232 struct type *swap_first = SLIST_FIRST(head1); \
233 SLIST_FIRST(head1) = SLIST_FIRST(head2); \
234 SLIST_FIRST(head2) = swap_first; \
238 * Singly-linked Tail queue declarations.
240 #define STAILQ_HEAD(name, type) \
242 struct type *stqh_first;/* first element */ \
243 struct type **stqh_last;/* addr of last next element */ \
246 #define STAILQ_HEAD_INITIALIZER(head) \
247 { NULL, &(head).stqh_first }
249 #define STAILQ_ENTRY(type) \
251 struct type *stqe_next; /* next element */ \
255 * Singly-linked Tail queue functions.
257 #define STAILQ_CONCAT(head1, head2) do { \
258 if (!STAILQ_EMPTY((head2))) { \
259 *(head1)->stqh_last = (head2)->stqh_first; \
260 (head1)->stqh_last = (head2)->stqh_last; \
261 STAILQ_INIT((head2)); \
265 #define STAILQ_EMPTY(head) ((head)->stqh_first == NULL)
267 #define STAILQ_FIRST(head) ((head)->stqh_first)
269 #define STAILQ_FOREACH(var, head, field) \
270 for((var) = STAILQ_FIRST((head)); \
272 (var) = STAILQ_NEXT((var), field))
274 #define STAILQ_FOREACH_FROM(var, head, field) \
275 for ((var) = ((var) ? (var) : STAILQ_FIRST((head))); \
277 (var) = STAILQ_NEXT((var), field))
279 #define STAILQ_FOREACH_SAFE(var, head, field, tvar) \
280 for ((var) = STAILQ_FIRST((head)); \
281 (var) && ((tvar) = STAILQ_NEXT((var), field), 1); \
284 #define STAILQ_FOREACH_FROM_SAFE(var, head, field, tvar) \
285 for ((var) = ((var) ? (var) : STAILQ_FIRST((head))); \
286 (var) && ((tvar) = STAILQ_NEXT((var), field), 1); \
289 #define STAILQ_INIT(head) do { \
290 STAILQ_FIRST((head)) = NULL; \
291 (head)->stqh_last = &STAILQ_FIRST((head)); \
294 #define STAILQ_INSERT_AFTER(head, tqelm, elm, field) do { \
295 if ((STAILQ_NEXT((elm), field) = STAILQ_NEXT((tqelm), field)) == NULL)\
296 (head)->stqh_last = &STAILQ_NEXT((elm), field); \
297 STAILQ_NEXT((tqelm), field) = (elm); \
300 #define STAILQ_INSERT_HEAD(head, elm, field) do { \
301 if ((STAILQ_NEXT((elm), field) = STAILQ_FIRST((head))) == NULL) \
302 (head)->stqh_last = &STAILQ_NEXT((elm), field); \
303 STAILQ_FIRST((head)) = (elm); \
306 #define STAILQ_INSERT_TAIL(head, elm, field) do { \
307 STAILQ_NEXT((elm), field) = NULL; \
308 *(head)->stqh_last = (elm); \
309 (head)->stqh_last = &STAILQ_NEXT((elm), field); \
312 #define STAILQ_LAST(head, type, field) \
313 (STAILQ_EMPTY((head)) ? \
315 ((struct type *)(void *) \
316 ((char *)((head)->stqh_last) - __offsetof(struct type, field))))
318 #define STAILQ_NEXT(elm, field) ((elm)->field.stqe_next)
320 #define STAILQ_REMOVE(head, elm, type, field) do { \
321 QMD_SAVELINK(oldnext, (elm)->field.stqe_next); \
322 if (STAILQ_FIRST((head)) == (elm)) { \
323 STAILQ_REMOVE_HEAD((head), field); \
326 struct type *curelm = STAILQ_FIRST((head)); \
327 while (STAILQ_NEXT(curelm, field) != (elm)) \
328 curelm = STAILQ_NEXT(curelm, field); \
329 STAILQ_REMOVE_AFTER(head, curelm, field); \
334 #define STAILQ_REMOVE_AFTER(head, elm, field) do { \
335 if ((STAILQ_NEXT(elm, field) = \
336 STAILQ_NEXT(STAILQ_NEXT(elm, field), field)) == NULL) \
337 (head)->stqh_last = &STAILQ_NEXT((elm), field); \
340 #define STAILQ_REMOVE_HEAD(head, field) do { \
341 if ((STAILQ_FIRST((head)) = \
342 STAILQ_NEXT(STAILQ_FIRST((head)), field)) == NULL) \
343 (head)->stqh_last = &STAILQ_FIRST((head)); \
346 #define STAILQ_SWAP(head1, head2, type) do { \
347 struct type *swap_first = STAILQ_FIRST(head1); \
348 struct type **swap_last = (head1)->stqh_last; \
349 STAILQ_FIRST(head1) = STAILQ_FIRST(head2); \
350 (head1)->stqh_last = (head2)->stqh_last; \
351 STAILQ_FIRST(head2) = swap_first; \
352 (head2)->stqh_last = swap_last; \
353 if (STAILQ_EMPTY(head1)) \
354 (head1)->stqh_last = &STAILQ_FIRST(head1); \
355 if (STAILQ_EMPTY(head2)) \
356 (head2)->stqh_last = &STAILQ_FIRST(head2); \
363 #define LIST_HEAD(name, type) \
365 struct type *lh_first; /* first element */ \
368 #define LIST_HEAD_INITIALIZER(head) \
371 #define LIST_ENTRY(type) \
373 struct type *le_next; /* next element */ \
374 struct type **le_prev; /* address of previous next element */ \
381 #if (defined(_KERNEL) && defined(INVARIANTS))
382 #define QMD_LIST_CHECK_HEAD(head, field) do { \
383 if (LIST_FIRST((head)) != NULL && \
384 LIST_FIRST((head))->field.le_prev != \
385 &LIST_FIRST((head))) \
386 panic("Bad list head %p first->prev != head", (head)); \
389 #define QMD_LIST_CHECK_NEXT(elm, field) do { \
390 if (LIST_NEXT((elm), field) != NULL && \
391 LIST_NEXT((elm), field)->field.le_prev != \
392 &((elm)->field.le_next)) \
393 panic("Bad link elm %p next->prev != elm", (elm)); \
396 #define QMD_LIST_CHECK_PREV(elm, field) do { \
397 if (*(elm)->field.le_prev != (elm)) \
398 panic("Bad link elm %p prev->next != elm", (elm)); \
401 #define QMD_LIST_CHECK_HEAD(head, field)
402 #define QMD_LIST_CHECK_NEXT(elm, field)
403 #define QMD_LIST_CHECK_PREV(elm, field)
404 #endif /* (_KERNEL && INVARIANTS) */
406 #define LIST_EMPTY(head) ((head)->lh_first == NULL)
408 #define LIST_FIRST(head) ((head)->lh_first)
410 #define LIST_FOREACH(var, head, field) \
411 for ((var) = LIST_FIRST((head)); \
413 (var) = LIST_NEXT((var), field))
415 #define LIST_FOREACH_FROM(var, head, field) \
416 for ((var) = ((var) ? (var) : LIST_FIRST((head))); \
418 (var) = LIST_NEXT((var), field))
420 #define LIST_FOREACH_SAFE(var, head, field, tvar) \
421 for ((var) = LIST_FIRST((head)); \
422 (var) && ((tvar) = LIST_NEXT((var), field), 1); \
425 #define LIST_FOREACH_FROM_SAFE(var, head, field, tvar) \
426 for ((var) = ((var) ? (var) : LIST_FIRST((head))); \
427 (var) && ((tvar) = LIST_NEXT((var), field), 1); \
430 #define LIST_INIT(head) do { \
431 LIST_FIRST((head)) = NULL; \
434 #define LIST_INSERT_AFTER(listelm, elm, field) do { \
435 QMD_LIST_CHECK_NEXT(listelm, field); \
436 if ((LIST_NEXT((elm), field) = LIST_NEXT((listelm), field)) != NULL)\
437 LIST_NEXT((listelm), field)->field.le_prev = \
438 &LIST_NEXT((elm), field); \
439 LIST_NEXT((listelm), field) = (elm); \
440 (elm)->field.le_prev = &LIST_NEXT((listelm), field); \
443 #define LIST_INSERT_BEFORE(listelm, elm, field) do { \
444 QMD_LIST_CHECK_PREV(listelm, field); \
445 (elm)->field.le_prev = (listelm)->field.le_prev; \
446 LIST_NEXT((elm), field) = (listelm); \
447 *(listelm)->field.le_prev = (elm); \
448 (listelm)->field.le_prev = &LIST_NEXT((elm), field); \
451 #define LIST_INSERT_HEAD(head, elm, field) do { \
452 QMD_LIST_CHECK_HEAD((head), field); \
453 if ((LIST_NEXT((elm), field) = LIST_FIRST((head))) != NULL) \
454 LIST_FIRST((head))->field.le_prev = &LIST_NEXT((elm), field);\
455 LIST_FIRST((head)) = (elm); \
456 (elm)->field.le_prev = &LIST_FIRST((head)); \
459 #define LIST_NEXT(elm, field) ((elm)->field.le_next)
461 #define LIST_REMOVE(elm, field) do { \
462 QMD_SAVELINK(oldnext, (elm)->field.le_next); \
463 QMD_SAVELINK(oldprev, (elm)->field.le_prev); \
464 QMD_LIST_CHECK_NEXT(elm, field); \
465 QMD_LIST_CHECK_PREV(elm, field); \
466 if (LIST_NEXT((elm), field) != NULL) \
467 LIST_NEXT((elm), field)->field.le_prev = \
468 (elm)->field.le_prev; \
469 *(elm)->field.le_prev = LIST_NEXT((elm), field); \
474 #define LIST_SWAP(head1, head2, type, field) do { \
475 struct type *swap_tmp = LIST_FIRST((head1)); \
476 LIST_FIRST((head1)) = LIST_FIRST((head2)); \
477 LIST_FIRST((head2)) = swap_tmp; \
478 if ((swap_tmp = LIST_FIRST((head1))) != NULL) \
479 swap_tmp->field.le_prev = &LIST_FIRST((head1)); \
480 if ((swap_tmp = LIST_FIRST((head2))) != NULL) \
481 swap_tmp->field.le_prev = &LIST_FIRST((head2)); \
485 * Tail queue declarations.
487 #define TAILQ_HEAD(name, type) \
489 struct type *tqh_first; /* first element */ \
490 struct type **tqh_last; /* addr of last next element */ \
494 #define TAILQ_HEAD_INITIALIZER(head) \
495 { NULL, &(head).tqh_first }
497 #define TAILQ_ENTRY(type) \
499 struct type *tqe_next; /* next element */ \
500 struct type **tqe_prev; /* address of previous next element */ \
505 * Tail queue functions.
507 #if (defined(_KERNEL) && defined(INVARIANTS))
508 #define QMD_TAILQ_CHECK_HEAD(head, field) do { \
509 if (!TAILQ_EMPTY(head) && \
510 TAILQ_FIRST((head))->field.tqe_prev != \
511 &TAILQ_FIRST((head))) \
512 panic("Bad tailq head %p first->prev != head", (head)); \
515 #define QMD_TAILQ_CHECK_TAIL(head, field) do { \
516 if (*(head)->tqh_last != NULL) \
517 panic("Bad tailq NEXT(%p->tqh_last) != NULL", (head)); \
520 #define QMD_TAILQ_CHECK_NEXT(elm, field) do { \
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) do { \
528 if (*(elm)->field.tqe_prev != (elm)) \
529 panic("Bad link elm %p prev->next != elm", (elm)); \
532 #define QMD_TAILQ_CHECK_HEAD(head, field)
533 #define QMD_TAILQ_CHECK_TAIL(head, headname)
534 #define QMD_TAILQ_CHECK_NEXT(elm, field)
535 #define QMD_TAILQ_CHECK_PREV(elm, field)
536 #endif /* (_KERNEL && INVARIANTS) */
538 #define TAILQ_CONCAT(head1, head2, field) do { \
539 if (!TAILQ_EMPTY(head2)) { \
540 *(head1)->tqh_last = (head2)->tqh_first; \
541 (head2)->tqh_first->field.tqe_prev = (head1)->tqh_last; \
542 (head1)->tqh_last = (head2)->tqh_last; \
543 TAILQ_INIT((head2)); \
544 QMD_TRACE_HEAD(head1); \
545 QMD_TRACE_HEAD(head2); \
549 #define TAILQ_EMPTY(head) ((head)->tqh_first == NULL)
551 #define TAILQ_FIRST(head) ((head)->tqh_first)
553 #define TAILQ_FOREACH(var, head, field) \
554 for ((var) = TAILQ_FIRST((head)); \
556 (var) = TAILQ_NEXT((var), field))
558 #define TAILQ_FOREACH_FROM(var, head, field) \
559 for ((var) = ((var) ? (var) : TAILQ_FIRST((head))); \
561 (var) = TAILQ_NEXT((var), field))
563 #define TAILQ_FOREACH_SAFE(var, head, field, tvar) \
564 for ((var) = TAILQ_FIRST((head)); \
565 (var) && ((tvar) = TAILQ_NEXT((var), field), 1); \
568 #define TAILQ_FOREACH_FROM_SAFE(var, head, field, tvar) \
569 for ((var) = ((var) ? (var) : TAILQ_FIRST((head))); \
570 (var) && ((tvar) = TAILQ_NEXT((var), field), 1); \
573 #define TAILQ_FOREACH_REVERSE(var, head, headname, field) \
574 for ((var) = TAILQ_LAST((head), headname); \
576 (var) = TAILQ_PREV((var), headname, field))
578 #define TAILQ_FOREACH_REVERSE_FROM(var, head, headname, field) \
579 for ((var) = ((var) ? (var) : TAILQ_LAST((head), headname)); \
581 (var) = TAILQ_PREV((var), headname, field))
583 #define TAILQ_FOREACH_REVERSE_SAFE(var, head, headname, field, tvar) \
584 for ((var) = TAILQ_LAST((head), headname); \
585 (var) && ((tvar) = TAILQ_PREV((var), headname, field), 1); \
588 #define TAILQ_FOREACH_REVERSE_FROM_SAFE(var, head, headname, field, tvar) \
589 for ((var) = ((var) ? (var) : TAILQ_LAST((head), headname)); \
590 (var) && ((tvar) = TAILQ_PREV((var), headname, field), 1); \
593 #define TAILQ_INIT(head) do { \
594 TAILQ_FIRST((head)) = NULL; \
595 (head)->tqh_last = &TAILQ_FIRST((head)); \
596 QMD_TRACE_HEAD(head); \
599 #define TAILQ_INSERT_AFTER(head, listelm, elm, field) do { \
600 QMD_TAILQ_CHECK_NEXT(listelm, field); \
601 if ((TAILQ_NEXT((elm), field) = TAILQ_NEXT((listelm), field)) != NULL)\
602 TAILQ_NEXT((elm), field)->field.tqe_prev = \
603 &TAILQ_NEXT((elm), field); \
605 (head)->tqh_last = &TAILQ_NEXT((elm), field); \
606 QMD_TRACE_HEAD(head); \
608 TAILQ_NEXT((listelm), field) = (elm); \
609 (elm)->field.tqe_prev = &TAILQ_NEXT((listelm), field); \
610 QMD_TRACE_ELEM(&(elm)->field); \
611 QMD_TRACE_ELEM(&listelm->field); \
614 #define TAILQ_INSERT_BEFORE(listelm, elm, field) do { \
615 QMD_TAILQ_CHECK_PREV(listelm, field); \
616 (elm)->field.tqe_prev = (listelm)->field.tqe_prev; \
617 TAILQ_NEXT((elm), field) = (listelm); \
618 *(listelm)->field.tqe_prev = (elm); \
619 (listelm)->field.tqe_prev = &TAILQ_NEXT((elm), field); \
620 QMD_TRACE_ELEM(&(elm)->field); \
621 QMD_TRACE_ELEM(&listelm->field); \
624 #define TAILQ_INSERT_HEAD(head, elm, field) do { \
625 QMD_TAILQ_CHECK_HEAD(head, field); \
626 if ((TAILQ_NEXT((elm), field) = TAILQ_FIRST((head))) != NULL) \
627 TAILQ_FIRST((head))->field.tqe_prev = \
628 &TAILQ_NEXT((elm), field); \
630 (head)->tqh_last = &TAILQ_NEXT((elm), field); \
631 TAILQ_FIRST((head)) = (elm); \
632 (elm)->field.tqe_prev = &TAILQ_FIRST((head)); \
633 QMD_TRACE_HEAD(head); \
634 QMD_TRACE_ELEM(&(elm)->field); \
637 #define TAILQ_INSERT_TAIL(head, elm, field) do { \
638 QMD_TAILQ_CHECK_TAIL(head, field); \
639 TAILQ_NEXT((elm), field) = NULL; \
640 (elm)->field.tqe_prev = (head)->tqh_last; \
641 *(head)->tqh_last = (elm); \
642 (head)->tqh_last = &TAILQ_NEXT((elm), field); \
643 QMD_TRACE_HEAD(head); \
644 QMD_TRACE_ELEM(&(elm)->field); \
647 #define TAILQ_LAST(head, headname) \
648 (*(((struct headname *)((head)->tqh_last))->tqh_last))
650 #define TAILQ_NEXT(elm, field) ((elm)->field.tqe_next)
652 #define TAILQ_PREV(elm, headname, field) \
653 (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
655 #define TAILQ_REMOVE(head, elm, field) do { \
656 QMD_SAVELINK(oldnext, (elm)->field.tqe_next); \
657 QMD_SAVELINK(oldprev, (elm)->field.tqe_prev); \
658 QMD_TAILQ_CHECK_NEXT(elm, field); \
659 QMD_TAILQ_CHECK_PREV(elm, field); \
660 if ((TAILQ_NEXT((elm), field)) != NULL) \
661 TAILQ_NEXT((elm), field)->field.tqe_prev = \
662 (elm)->field.tqe_prev; \
664 (head)->tqh_last = (elm)->field.tqe_prev; \
665 QMD_TRACE_HEAD(head); \
667 *(elm)->field.tqe_prev = TAILQ_NEXT((elm), field); \
670 QMD_TRACE_ELEM(&(elm)->field); \
673 #define TAILQ_SWAP(head1, head2, type, field) do { \
674 struct type *swap_first = (head1)->tqh_first; \
675 struct type **swap_last = (head1)->tqh_last; \
676 (head1)->tqh_first = (head2)->tqh_first; \
677 (head1)->tqh_last = (head2)->tqh_last; \
678 (head2)->tqh_first = swap_first; \
679 (head2)->tqh_last = swap_last; \
680 if ((swap_first = (head1)->tqh_first) != NULL) \
681 swap_first->field.tqe_prev = &(head1)->tqh_first; \
683 (head1)->tqh_last = &(head1)->tqh_first; \
684 if ((swap_first = (head2)->tqh_first) != NULL) \
685 swap_first->field.tqe_prev = &(head2)->tqh_first; \
687 (head2)->tqh_last = &(head2)->tqh_first; \
690 #endif /* !_SYS_QUEUE_H_ */