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 be traversed in either 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)) ? NULL : \
314 __containerof((head)->stqh_last, struct type, field.stqe_next))
316 #define STAILQ_NEXT(elm, field) ((elm)->field.stqe_next)
318 #define STAILQ_REMOVE(head, elm, type, field) do { \
319 QMD_SAVELINK(oldnext, (elm)->field.stqe_next); \
320 if (STAILQ_FIRST((head)) == (elm)) { \
321 STAILQ_REMOVE_HEAD((head), field); \
324 struct type *curelm = STAILQ_FIRST((head)); \
325 while (STAILQ_NEXT(curelm, field) != (elm)) \
326 curelm = STAILQ_NEXT(curelm, field); \
327 STAILQ_REMOVE_AFTER(head, curelm, field); \
332 #define STAILQ_REMOVE_AFTER(head, elm, field) do { \
333 if ((STAILQ_NEXT(elm, field) = \
334 STAILQ_NEXT(STAILQ_NEXT(elm, field), field)) == NULL) \
335 (head)->stqh_last = &STAILQ_NEXT((elm), field); \
338 #define STAILQ_REMOVE_HEAD(head, field) do { \
339 if ((STAILQ_FIRST((head)) = \
340 STAILQ_NEXT(STAILQ_FIRST((head)), field)) == NULL) \
341 (head)->stqh_last = &STAILQ_FIRST((head)); \
344 #define STAILQ_SWAP(head1, head2, type) do { \
345 struct type *swap_first = STAILQ_FIRST(head1); \
346 struct type **swap_last = (head1)->stqh_last; \
347 STAILQ_FIRST(head1) = STAILQ_FIRST(head2); \
348 (head1)->stqh_last = (head2)->stqh_last; \
349 STAILQ_FIRST(head2) = swap_first; \
350 (head2)->stqh_last = swap_last; \
351 if (STAILQ_EMPTY(head1)) \
352 (head1)->stqh_last = &STAILQ_FIRST(head1); \
353 if (STAILQ_EMPTY(head2)) \
354 (head2)->stqh_last = &STAILQ_FIRST(head2); \
361 #define LIST_HEAD(name, type) \
363 struct type *lh_first; /* first element */ \
366 #define LIST_HEAD_INITIALIZER(head) \
369 #define LIST_ENTRY(type) \
371 struct type *le_next; /* next element */ \
372 struct type **le_prev; /* address of previous next element */ \
379 #if (defined(_KERNEL) && defined(INVARIANTS))
380 #define QMD_LIST_CHECK_HEAD(head, field) do { \
381 if (LIST_FIRST((head)) != NULL && \
382 LIST_FIRST((head))->field.le_prev != \
383 &LIST_FIRST((head))) \
384 panic("Bad list head %p first->prev != head", (head)); \
387 #define QMD_LIST_CHECK_NEXT(elm, field) do { \
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) do { \
395 if (*(elm)->field.le_prev != (elm)) \
396 panic("Bad link elm %p prev->next != elm", (elm)); \
399 #define QMD_LIST_CHECK_HEAD(head, field)
400 #define QMD_LIST_CHECK_NEXT(elm, field)
401 #define QMD_LIST_CHECK_PREV(elm, field)
402 #endif /* (_KERNEL && INVARIANTS) */
404 #define LIST_EMPTY(head) ((head)->lh_first == NULL)
406 #define LIST_FIRST(head) ((head)->lh_first)
408 #define LIST_FOREACH(var, head, field) \
409 for ((var) = LIST_FIRST((head)); \
411 (var) = LIST_NEXT((var), field))
413 #define LIST_FOREACH_FROM(var, head, field) \
414 for ((var) = ((var) ? (var) : LIST_FIRST((head))); \
416 (var) = LIST_NEXT((var), field))
418 #define LIST_FOREACH_SAFE(var, head, field, tvar) \
419 for ((var) = LIST_FIRST((head)); \
420 (var) && ((tvar) = LIST_NEXT((var), field), 1); \
423 #define LIST_FOREACH_FROM_SAFE(var, head, field, tvar) \
424 for ((var) = ((var) ? (var) : LIST_FIRST((head))); \
425 (var) && ((tvar) = LIST_NEXT((var), field), 1); \
428 #define LIST_INIT(head) do { \
429 LIST_FIRST((head)) = NULL; \
432 #define LIST_INSERT_AFTER(listelm, elm, field) do { \
433 QMD_LIST_CHECK_NEXT(listelm, field); \
434 if ((LIST_NEXT((elm), field) = LIST_NEXT((listelm), field)) != NULL)\
435 LIST_NEXT((listelm), field)->field.le_prev = \
436 &LIST_NEXT((elm), field); \
437 LIST_NEXT((listelm), field) = (elm); \
438 (elm)->field.le_prev = &LIST_NEXT((listelm), field); \
441 #define LIST_INSERT_BEFORE(listelm, elm, field) do { \
442 QMD_LIST_CHECK_PREV(listelm, field); \
443 (elm)->field.le_prev = (listelm)->field.le_prev; \
444 LIST_NEXT((elm), field) = (listelm); \
445 *(listelm)->field.le_prev = (elm); \
446 (listelm)->field.le_prev = &LIST_NEXT((elm), field); \
449 #define LIST_INSERT_HEAD(head, elm, field) do { \
450 QMD_LIST_CHECK_HEAD((head), field); \
451 if ((LIST_NEXT((elm), field) = LIST_FIRST((head))) != NULL) \
452 LIST_FIRST((head))->field.le_prev = &LIST_NEXT((elm), field);\
453 LIST_FIRST((head)) = (elm); \
454 (elm)->field.le_prev = &LIST_FIRST((head)); \
457 #define LIST_NEXT(elm, field) ((elm)->field.le_next)
459 #define LIST_PREV(elm, head, type, field) \
460 ((elm)->field.le_prev == &LIST_FIRST((head)) ? NULL : \
461 __containerof((elm)->field.le_prev, struct type, field.le_next))
463 #define LIST_REMOVE(elm, field) do { \
464 QMD_SAVELINK(oldnext, (elm)->field.le_next); \
465 QMD_SAVELINK(oldprev, (elm)->field.le_prev); \
466 QMD_LIST_CHECK_NEXT(elm, field); \
467 QMD_LIST_CHECK_PREV(elm, field); \
468 if (LIST_NEXT((elm), field) != NULL) \
469 LIST_NEXT((elm), field)->field.le_prev = \
470 (elm)->field.le_prev; \
471 *(elm)->field.le_prev = LIST_NEXT((elm), field); \
476 #define LIST_SWAP(head1, head2, type, field) do { \
477 struct type *swap_tmp = LIST_FIRST((head1)); \
478 LIST_FIRST((head1)) = LIST_FIRST((head2)); \
479 LIST_FIRST((head2)) = swap_tmp; \
480 if ((swap_tmp = LIST_FIRST((head1))) != NULL) \
481 swap_tmp->field.le_prev = &LIST_FIRST((head1)); \
482 if ((swap_tmp = LIST_FIRST((head2))) != NULL) \
483 swap_tmp->field.le_prev = &LIST_FIRST((head2)); \
487 * Tail queue declarations.
489 #define TAILQ_HEAD(name, type) \
491 struct type *tqh_first; /* first element */ \
492 struct type **tqh_last; /* addr of last next element */ \
496 #define TAILQ_HEAD_INITIALIZER(head) \
497 { NULL, &(head).tqh_first }
499 #define TAILQ_ENTRY(type) \
501 struct type *tqe_next; /* next element */ \
502 struct type **tqe_prev; /* address of previous next element */ \
507 * Tail queue functions.
509 #if (defined(_KERNEL) && defined(INVARIANTS))
510 #define QMD_TAILQ_CHECK_HEAD(head, field) do { \
511 if (!TAILQ_EMPTY(head) && \
512 TAILQ_FIRST((head))->field.tqe_prev != \
513 &TAILQ_FIRST((head))) \
514 panic("Bad tailq head %p first->prev != head", (head)); \
517 #define QMD_TAILQ_CHECK_TAIL(head, field) do { \
518 if (*(head)->tqh_last != NULL) \
519 panic("Bad tailq NEXT(%p->tqh_last) != NULL", (head)); \
522 #define QMD_TAILQ_CHECK_NEXT(elm, field) do { \
523 if (TAILQ_NEXT((elm), field) != NULL && \
524 TAILQ_NEXT((elm), field)->field.tqe_prev != \
525 &((elm)->field.tqe_next)) \
526 panic("Bad link elm %p next->prev != elm", (elm)); \
529 #define QMD_TAILQ_CHECK_PREV(elm, field) do { \
530 if (*(elm)->field.tqe_prev != (elm)) \
531 panic("Bad link elm %p prev->next != elm", (elm)); \
534 #define QMD_TAILQ_CHECK_HEAD(head, field)
535 #define QMD_TAILQ_CHECK_TAIL(head, headname)
536 #define QMD_TAILQ_CHECK_NEXT(elm, field)
537 #define QMD_TAILQ_CHECK_PREV(elm, field)
538 #endif /* (_KERNEL && INVARIANTS) */
540 #define TAILQ_CONCAT(head1, head2, field) do { \
541 if (!TAILQ_EMPTY(head2)) { \
542 *(head1)->tqh_last = (head2)->tqh_first; \
543 (head2)->tqh_first->field.tqe_prev = (head1)->tqh_last; \
544 (head1)->tqh_last = (head2)->tqh_last; \
545 TAILQ_INIT((head2)); \
546 QMD_TRACE_HEAD(head1); \
547 QMD_TRACE_HEAD(head2); \
551 #define TAILQ_EMPTY(head) ((head)->tqh_first == NULL)
553 #define TAILQ_FIRST(head) ((head)->tqh_first)
555 #define TAILQ_FOREACH(var, head, field) \
556 for ((var) = TAILQ_FIRST((head)); \
558 (var) = TAILQ_NEXT((var), field))
560 #define TAILQ_FOREACH_FROM(var, head, field) \
561 for ((var) = ((var) ? (var) : TAILQ_FIRST((head))); \
563 (var) = TAILQ_NEXT((var), field))
565 #define TAILQ_FOREACH_SAFE(var, head, field, tvar) \
566 for ((var) = TAILQ_FIRST((head)); \
567 (var) && ((tvar) = TAILQ_NEXT((var), field), 1); \
570 #define TAILQ_FOREACH_FROM_SAFE(var, head, field, tvar) \
571 for ((var) = ((var) ? (var) : TAILQ_FIRST((head))); \
572 (var) && ((tvar) = TAILQ_NEXT((var), field), 1); \
575 #define TAILQ_FOREACH_REVERSE(var, head, headname, field) \
576 for ((var) = TAILQ_LAST((head), headname); \
578 (var) = TAILQ_PREV((var), headname, field))
580 #define TAILQ_FOREACH_REVERSE_FROM(var, head, headname, field) \
581 for ((var) = ((var) ? (var) : TAILQ_LAST((head), headname)); \
583 (var) = TAILQ_PREV((var), headname, field))
585 #define TAILQ_FOREACH_REVERSE_SAFE(var, head, headname, field, tvar) \
586 for ((var) = TAILQ_LAST((head), headname); \
587 (var) && ((tvar) = TAILQ_PREV((var), headname, field), 1); \
590 #define TAILQ_FOREACH_REVERSE_FROM_SAFE(var, head, headname, field, tvar) \
591 for ((var) = ((var) ? (var) : TAILQ_LAST((head), headname)); \
592 (var) && ((tvar) = TAILQ_PREV((var), headname, field), 1); \
595 #define TAILQ_INIT(head) do { \
596 TAILQ_FIRST((head)) = NULL; \
597 (head)->tqh_last = &TAILQ_FIRST((head)); \
598 QMD_TRACE_HEAD(head); \
601 #define TAILQ_INSERT_AFTER(head, listelm, elm, field) do { \
602 QMD_TAILQ_CHECK_NEXT(listelm, field); \
603 if ((TAILQ_NEXT((elm), field) = TAILQ_NEXT((listelm), field)) != NULL)\
604 TAILQ_NEXT((elm), field)->field.tqe_prev = \
605 &TAILQ_NEXT((elm), field); \
607 (head)->tqh_last = &TAILQ_NEXT((elm), field); \
608 QMD_TRACE_HEAD(head); \
610 TAILQ_NEXT((listelm), field) = (elm); \
611 (elm)->field.tqe_prev = &TAILQ_NEXT((listelm), field); \
612 QMD_TRACE_ELEM(&(elm)->field); \
613 QMD_TRACE_ELEM(&listelm->field); \
616 #define TAILQ_INSERT_BEFORE(listelm, elm, field) do { \
617 QMD_TAILQ_CHECK_PREV(listelm, field); \
618 (elm)->field.tqe_prev = (listelm)->field.tqe_prev; \
619 TAILQ_NEXT((elm), field) = (listelm); \
620 *(listelm)->field.tqe_prev = (elm); \
621 (listelm)->field.tqe_prev = &TAILQ_NEXT((elm), field); \
622 QMD_TRACE_ELEM(&(elm)->field); \
623 QMD_TRACE_ELEM(&listelm->field); \
626 #define TAILQ_INSERT_HEAD(head, elm, field) do { \
627 QMD_TAILQ_CHECK_HEAD(head, field); \
628 if ((TAILQ_NEXT((elm), field) = TAILQ_FIRST((head))) != NULL) \
629 TAILQ_FIRST((head))->field.tqe_prev = \
630 &TAILQ_NEXT((elm), field); \
632 (head)->tqh_last = &TAILQ_NEXT((elm), field); \
633 TAILQ_FIRST((head)) = (elm); \
634 (elm)->field.tqe_prev = &TAILQ_FIRST((head)); \
635 QMD_TRACE_HEAD(head); \
636 QMD_TRACE_ELEM(&(elm)->field); \
639 #define TAILQ_INSERT_TAIL(head, elm, field) do { \
640 QMD_TAILQ_CHECK_TAIL(head, field); \
641 TAILQ_NEXT((elm), field) = NULL; \
642 (elm)->field.tqe_prev = (head)->tqh_last; \
643 *(head)->tqh_last = (elm); \
644 (head)->tqh_last = &TAILQ_NEXT((elm), field); \
645 QMD_TRACE_HEAD(head); \
646 QMD_TRACE_ELEM(&(elm)->field); \
649 #define TAILQ_LAST(head, headname) \
650 (*(((struct headname *)((head)->tqh_last))->tqh_last))
652 #define TAILQ_NEXT(elm, field) ((elm)->field.tqe_next)
654 #define TAILQ_PREV(elm, headname, field) \
655 (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
657 #define TAILQ_REMOVE(head, elm, field) do { \
658 QMD_SAVELINK(oldnext, (elm)->field.tqe_next); \
659 QMD_SAVELINK(oldprev, (elm)->field.tqe_prev); \
660 QMD_TAILQ_CHECK_NEXT(elm, field); \
661 QMD_TAILQ_CHECK_PREV(elm, field); \
662 if ((TAILQ_NEXT((elm), field)) != NULL) \
663 TAILQ_NEXT((elm), field)->field.tqe_prev = \
664 (elm)->field.tqe_prev; \
666 (head)->tqh_last = (elm)->field.tqe_prev; \
667 QMD_TRACE_HEAD(head); \
669 *(elm)->field.tqe_prev = TAILQ_NEXT((elm), field); \
672 QMD_TRACE_ELEM(&(elm)->field); \
675 #define TAILQ_SWAP(head1, head2, type, field) do { \
676 struct type *swap_first = (head1)->tqh_first; \
677 struct type **swap_last = (head1)->tqh_last; \
678 (head1)->tqh_first = (head2)->tqh_first; \
679 (head1)->tqh_last = (head2)->tqh_last; \
680 (head2)->tqh_first = swap_first; \
681 (head2)->tqh_last = swap_last; \
682 if ((swap_first = (head1)->tqh_first) != NULL) \
683 swap_first->field.tqe_prev = &(head1)->tqh_first; \
685 (head1)->tqh_last = &(head1)->tqh_first; \
686 if ((swap_first = (head2)->tqh_first) != NULL) \
687 swap_first->field.tqe_prev = &(head2)->tqh_first; \
689 (head2)->tqh_last = &(head2)->tqh_first; \
692 #endif /* !_SYS_QUEUE_H_ */