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2 * Copyright (c) 1991, 1993
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29 * @(#)queue.h 8.5 (Berkeley) 8/20/94
41 * This file defines four types of data structures: singly-linked lists,
42 * singly-linked tail queues, lists and tail queues.
44 * A singly-linked list is headed by a single forward pointer. The elements
45 * are singly linked for minimum space and pointer manipulation overhead at
46 * the expense of O(n) removal for arbitrary elements. New elements can be
47 * added to the list after an existing element or at the head of the list.
48 * Elements being removed from the head of the list should use the explicit
49 * macro for this purpose for optimum efficiency. A singly-linked list may
50 * only be traversed in the forward direction. Singly-linked lists are ideal
51 * for applications with large datasets and few or no removals or for
52 * implementing a LIFO queue.
54 * A singly-linked tail queue is headed by a pair of pointers, one to the
55 * head of the list and the other to the tail of the list. The elements are
56 * singly linked for minimum space and pointer manipulation overhead at the
57 * expense of O(n) removal for arbitrary elements. New elements can be added
58 * to the list after an existing element, at the head of the list, or at the
59 * end of the list. Elements being removed from the head of the tail queue
60 * should use the explicit macro for this purpose for optimum efficiency.
61 * A singly-linked tail queue may only be traversed in the forward direction.
62 * Singly-linked tail queues are ideal for applications with large datasets
63 * and few or no removals or for implementing a FIFO queue.
65 * A list is headed by a single forward pointer (or an array of forward
66 * pointers for a hash table header). The elements are doubly linked
67 * so that an arbitrary element can be removed without a need to
68 * traverse the list. New elements can be added to the list before
69 * or after an existing element or at the head of the list. A list
70 * may only be traversed in the forward direction.
72 * A tail queue is headed by a pair of pointers, one to the head of the
73 * list and the other to the tail of the list. The elements are doubly
74 * linked so that an arbitrary element can be removed without a need to
75 * traverse the list. New elements can be added to the list before or
76 * after an existing element, at the head of the list, or at the end of
77 * the list. A tail queue may be traversed in either direction.
79 * For details on the use of these macros, see the queue(3) manual page.
82 * SLIST LIST STAILQ TAILQ
84 * _HEAD_INITIALIZER + + + +
93 * _FOREACH_SAFE + + + +
94 * _FOREACH_REVERSE - - - +
95 * _FOREACH_REVERSE_SAFE - - - +
96 * _INSERT_HEAD + + + +
97 * _INSERT_BEFORE - + - +
98 * _INSERT_AFTER + + + +
99 * _INSERT_TAIL - - + +
101 * _REMOVE_AFTER + - + -
102 * _REMOVE_HEAD + - + -
107 #ifdef QUEUE_MACRO_DEBUG
108 /* Store the last 2 places the queue element or head was altered */
116 #define TRACEBUF struct qm_trace trace;
117 #define TRASHIT(x) do {(x) = (void *)-1;} while (0)
118 #define QMD_SAVELINK(name, link) void **name = (void *)&(link)
120 #define QMD_TRACE_HEAD(head) \
122 (head)->trace.prevline = (head)->trace.lastline; \
123 (head)->trace.prevfile = (head)->trace.lastfile; \
124 (head)->trace.lastline = __LINE__; \
125 (head)->trace.lastfile = __FILE__; \
128 #define QMD_TRACE_ELEM(elem) \
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) \
157 #define SLIST_ENTRY(type) \
159 struct type *sle_next; /* next element */ \
163 * Singly-linked List functions.
165 #define SLIST_EMPTY(head) ((head)->slh_first == NULL)
167 #define SLIST_FIRST(head) ((head)->slh_first)
169 #define SLIST_FOREACH(var, head, field) \
170 for ((var) = SLIST_FIRST((head)); (var); \
171 (var) = SLIST_NEXT((var), field))
173 #define SLIST_FOREACH_SAFE(var, head, field, tvar) \
174 for ((var) = SLIST_FIRST((head)); \
175 (var) && ((tvar) = SLIST_NEXT((var), field), 1); (var) = (tvar))
177 #define SLIST_FOREACH_PREVPTR(var, varp, head, field) \
178 for ((varp) = &SLIST_FIRST((head)); ((var) = *(varp)) != NULL; \
179 (varp) = &SLIST_NEXT((var), field))
181 #define SLIST_INIT(head) \
183 SLIST_FIRST((head)) = NULL; \
186 #define SLIST_INSERT_AFTER(slistelm, elm, field) \
188 SLIST_NEXT((elm), field) = SLIST_NEXT((slistelm), field); \
189 SLIST_NEXT((slistelm), field) = (elm); \
192 #define SLIST_INSERT_HEAD(head, elm, field) \
194 SLIST_NEXT((elm), field) = SLIST_FIRST((head)); \
195 SLIST_FIRST((head)) = (elm); \
198 #define SLIST_NEXT(elm, field) ((elm)->field.sle_next)
200 #define SLIST_REMOVE(head, elm, type, field) \
202 QMD_SAVELINK(oldnext, (elm)->field.sle_next); \
203 if (SLIST_FIRST((head)) == (elm)) { \
204 SLIST_REMOVE_HEAD((head), field); \
206 struct type *curelm = SLIST_FIRST((head)); \
207 while (SLIST_NEXT(curelm, field) != (elm)) \
208 curelm = SLIST_NEXT(curelm, field); \
209 SLIST_REMOVE_AFTER(curelm, field); \
214 #define SLIST_REMOVE_AFTER(elm, field) \
216 SLIST_NEXT(elm, field) = \
217 SLIST_NEXT(SLIST_NEXT(elm, field), field); \
220 #define SLIST_REMOVE_HEAD(head, field) \
222 SLIST_FIRST((head)) = SLIST_NEXT(SLIST_FIRST((head)), field); \
225 #define SLIST_SWAP(head1, head2, type) \
227 struct type *swap_first = SLIST_FIRST(head1); \
228 SLIST_FIRST(head1) = SLIST_FIRST(head2); \
229 SLIST_FIRST(head2) = swap_first; \
233 * Singly-linked Tail queue declarations.
235 #define STAILQ_HEAD(name, type) \
237 struct type *stqh_first; /* first element */ \
238 struct type **stqh_last; /* addr of last next element */ \
241 #define STAILQ_HEAD_INITIALIZER(head) \
243 NULL, &(head).stqh_first \
246 #define STAILQ_ENTRY(type) \
248 struct type *stqe_next; /* next element */ \
252 * Singly-linked Tail queue functions.
254 #define STAILQ_CONCAT(head1, head2) \
256 if (!STAILQ_EMPTY((head2))) { \
257 *(head1)->stqh_last = (head2)->stqh_first; \
258 (head1)->stqh_last = (head2)->stqh_last; \
259 STAILQ_INIT((head2)); \
263 #define STAILQ_EMPTY(head) ((head)->stqh_first == NULL)
265 #define STAILQ_FIRST(head) ((head)->stqh_first)
267 #define STAILQ_FOREACH(var, head, field) \
268 for ((var) = STAILQ_FIRST((head)); (var); \
269 (var) = STAILQ_NEXT((var), field))
272 #define STAILQ_FOREACH_SAFE(var, head, field, tvar) \
273 for ((var) = STAILQ_FIRST((head)); \
274 (var) && ((tvar) = STAILQ_NEXT((var), field), 1); (var) = (tvar))
276 #define STAILQ_INIT(head) \
278 STAILQ_FIRST((head)) = NULL; \
279 (head)->stqh_last = &STAILQ_FIRST((head)); \
282 #define STAILQ_INSERT_AFTER(head, tqelm, elm, field) \
284 if ((STAILQ_NEXT((elm), field) = STAILQ_NEXT((tqelm), field)) \
286 (head)->stqh_last = &STAILQ_NEXT((elm), field); \
287 STAILQ_NEXT((tqelm), field) = (elm); \
290 #define STAILQ_INSERT_HEAD(head, elm, field) \
292 if ((STAILQ_NEXT((elm), field) = STAILQ_FIRST((head))) \
294 (head)->stqh_last = &STAILQ_NEXT((elm), field); \
295 STAILQ_FIRST((head)) = (elm); \
298 #define STAILQ_INSERT_TAIL(head, elm, field) \
300 STAILQ_NEXT((elm), field) = NULL; \
301 *(head)->stqh_last = (elm); \
302 (head)->stqh_last = &STAILQ_NEXT((elm), field); \
305 #define STAILQ_LAST(head, type, field) \
306 (STAILQ_EMPTY((head)) \
308 : ((struct type *)(void *)((char *)((head)->stqh_last) \
309 - offsetof(struct type, field))))
311 #define STAILQ_NEXT(elm, field) ((elm)->field.stqe_next)
313 #define STAILQ_REMOVE(head, elm, type, field) \
315 QMD_SAVELINK(oldnext, (elm)->field.stqe_next); \
316 if (STAILQ_FIRST((head)) == (elm)) { \
317 STAILQ_REMOVE_HEAD((head), field); \
319 struct type *curelm = STAILQ_FIRST((head)); \
320 while (STAILQ_NEXT(curelm, field) != (elm)) \
321 curelm = STAILQ_NEXT(curelm, field); \
322 STAILQ_REMOVE_AFTER(head, curelm, field); \
327 #define STAILQ_REMOVE_AFTER(head, elm, field) \
329 if ((STAILQ_NEXT(elm, field) = \
330 STAILQ_NEXT(STAILQ_NEXT(elm, field), field)) \
332 (head)->stqh_last = &STAILQ_NEXT((elm), field); \
335 #define STAILQ_REMOVE_HEAD(head, field) \
337 if ((STAILQ_FIRST((head)) = \
338 STAILQ_NEXT(STAILQ_FIRST((head)), field)) \
340 (head)->stqh_last = &STAILQ_FIRST((head)); \
343 #define STAILQ_SWAP(head1, head2, type) \
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) \
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) \
384 if (LIST_FIRST((head)) != NULL \
385 && LIST_FIRST((head))->field.le_prev \
386 != &LIST_FIRST((head))) \
387 panic("Bad list head %p first->prev != head", (head)); \
390 #define QMD_LIST_CHECK_NEXT(elm, field) \
392 if (LIST_NEXT((elm), field) != NULL \
393 && LIST_NEXT((elm), field)->field.le_prev \
394 != &((elm)->field.le_next)) \
395 panic("Bad link elm %p next->prev != elm", (elm)); \
398 #define QMD_LIST_CHECK_PREV(elm, field) \
400 if (*(elm)->field.le_prev != (elm)) \
401 panic("Bad link elm %p prev->next != elm", (elm)); \
404 #define QMD_LIST_CHECK_HEAD(head, field)
405 #define QMD_LIST_CHECK_NEXT(elm, field)
406 #define QMD_LIST_CHECK_PREV(elm, field)
407 #endif /* (_KERNEL && INVARIANTS) */
409 #define LIST_EMPTY(head) ((head)->lh_first == NULL)
411 #define LIST_FIRST(head) ((head)->lh_first)
413 #define LIST_FOREACH(var, head, field) \
414 for ((var) = LIST_FIRST((head)); (var); (var) = LIST_NEXT((var), field))
416 #define LIST_FOREACH_SAFE(var, head, field, tvar) \
417 for ((var) = LIST_FIRST((head)); \
418 (var) && ((tvar) = LIST_NEXT((var), field), 1); (var) = (tvar))
420 #define LIST_INIT(head) \
422 LIST_FIRST((head)) = NULL; \
425 #define LIST_INSERT_AFTER(listelm, elm, field) \
427 QMD_LIST_CHECK_NEXT(listelm, field); \
428 if ((LIST_NEXT((elm), field) = LIST_NEXT((listelm), field)) \
430 LIST_NEXT((listelm), field)->field.le_prev = \
431 &LIST_NEXT((elm), field); \
432 LIST_NEXT((listelm), field) = (elm); \
433 (elm)->field.le_prev = &LIST_NEXT((listelm), field); \
436 #define LIST_INSERT_BEFORE(listelm, elm, field) \
438 QMD_LIST_CHECK_PREV(listelm, field); \
439 (elm)->field.le_prev = (listelm)->field.le_prev; \
440 LIST_NEXT((elm), field) = (listelm); \
441 *(listelm)->field.le_prev = (elm); \
442 (listelm)->field.le_prev = &LIST_NEXT((elm), field); \
445 #define LIST_INSERT_HEAD(head, elm, field) \
447 QMD_LIST_CHECK_HEAD((head), field); \
448 if ((LIST_NEXT((elm), field) = LIST_FIRST((head))) != NULL) \
449 LIST_FIRST((head))->field.le_prev = \
450 &LIST_NEXT((elm), field); \
451 LIST_FIRST((head)) = (elm); \
452 (elm)->field.le_prev = &LIST_FIRST((head)); \
455 #define LIST_NEXT(elm, field) ((elm)->field.le_next)
457 #define LIST_REMOVE(elm, field) \
459 QMD_SAVELINK(oldnext, (elm)->field.le_next); \
460 QMD_SAVELINK(oldprev, (elm)->field.le_prev); \
461 QMD_LIST_CHECK_NEXT(elm, field); \
462 QMD_LIST_CHECK_PREV(elm, field); \
463 if (LIST_NEXT((elm), field) != NULL) \
464 LIST_NEXT((elm), field)->field.le_prev = \
465 (elm)->field.le_prev; \
466 *(elm)->field.le_prev = LIST_NEXT((elm), field); \
471 #define LIST_SWAP(head1, head2, type, field) \
473 struct type *swap_tmp = LIST_FIRST((head1)); \
474 LIST_FIRST((head1)) = LIST_FIRST((head2)); \
475 LIST_FIRST((head2)) = swap_tmp; \
476 if ((swap_tmp = LIST_FIRST((head1))) != NULL) \
477 swap_tmp->field.le_prev = &LIST_FIRST((head1)); \
478 if ((swap_tmp = LIST_FIRST((head2))) != NULL) \
479 swap_tmp->field.le_prev = &LIST_FIRST((head2)); \
483 * Tail queue declarations.
485 #define TAILQ_HEAD(name, type) \
487 struct type *tqh_first; /* first element */ \
488 struct type **tqh_last; /* addr of last next element */ \
492 #define TAILQ_HEAD_INITIALIZER(head) \
494 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) \
510 if (!TAILQ_EMPTY(head) \
511 && TAILQ_FIRST((head))->field.tqe_prev \
512 != &TAILQ_FIRST((head))) \
513 panic("Bad tailq head %p first->prev != head", \
517 #define QMD_TAILQ_CHECK_TAIL(head, field) \
519 if (*(head)->tqh_last != NULL) \
520 panic("Bad tailq NEXT(%p->tqh_last) != NULL", (head)); \
523 #define QMD_TAILQ_CHECK_NEXT(elm, field) \
525 if (TAILQ_NEXT((elm), field) != NULL \
526 && TAILQ_NEXT((elm), field)->field.tqe_prev \
527 != &((elm)->field.tqe_next)) \
528 panic("Bad link elm %p next->prev != elm", (elm)); \
531 #define QMD_TAILQ_CHECK_PREV(elm, field) \
533 if (*(elm)->field.tqe_prev != (elm)) \
534 panic("Bad link elm %p prev->next != elm", (elm)); \
537 #define QMD_TAILQ_CHECK_HEAD(head, field)
538 #define QMD_TAILQ_CHECK_TAIL(head, headname)
539 #define QMD_TAILQ_CHECK_NEXT(elm, field)
540 #define QMD_TAILQ_CHECK_PREV(elm, field)
541 #endif /* (_KERNEL && INVARIANTS) */
543 #define TAILQ_CONCAT(head1, head2, field) \
545 if (!TAILQ_EMPTY(head2)) { \
546 *(head1)->tqh_last = (head2)->tqh_first; \
547 (head2)->tqh_first->field.tqe_prev = \
549 (head1)->tqh_last = (head2)->tqh_last; \
550 TAILQ_INIT((head2)); \
551 QMD_TRACE_HEAD(head1); \
552 QMD_TRACE_HEAD(head2); \
556 #define TAILQ_EMPTY(head) ((head)->tqh_first == NULL)
558 #define TAILQ_FIRST(head) ((head)->tqh_first)
560 #define TAILQ_FOREACH(var, head, field) \
561 for ((var) = TAILQ_FIRST((head)); (var); \
562 (var) = TAILQ_NEXT((var), field))
564 #define TAILQ_FOREACH_SAFE(var, head, field, tvar) \
565 for ((var) = TAILQ_FIRST((head)); \
566 (var) && ((tvar) = TAILQ_NEXT((var), field), 1); (var) = (tvar))
568 #define TAILQ_FOREACH_REVERSE(var, head, headname, field) \
569 for ((var) = TAILQ_LAST((head), headname); (var); \
570 (var) = TAILQ_PREV((var), headname, field))
572 #define TAILQ_FOREACH_REVERSE_SAFE(var, head, headname, field, tvar) \
573 for ((var) = TAILQ_LAST((head), headname); \
574 (var) && ((tvar) = TAILQ_PREV((var), headname, field), 1); \
577 #define TAILQ_INIT(head) \
579 TAILQ_FIRST((head)) = NULL; \
580 (head)->tqh_last = &TAILQ_FIRST((head)); \
581 QMD_TRACE_HEAD(head); \
584 #define TAILQ_INSERT_AFTER(head, listelm, elm, field) \
586 QMD_TAILQ_CHECK_NEXT(listelm, field); \
587 if ((TAILQ_NEXT((elm), field) = TAILQ_NEXT((listelm), field)) \
589 TAILQ_NEXT((elm), field)->field.tqe_prev = \
590 &TAILQ_NEXT((elm), field); \
592 (head)->tqh_last = &TAILQ_NEXT((elm), field); \
593 QMD_TRACE_HEAD(head); \
595 TAILQ_NEXT((listelm), field) = (elm); \
596 (elm)->field.tqe_prev = &TAILQ_NEXT((listelm), field); \
597 QMD_TRACE_ELEM(&(elm)->field); \
598 QMD_TRACE_ELEM(&listelm->field); \
601 #define TAILQ_INSERT_BEFORE(listelm, elm, field) \
603 QMD_TAILQ_CHECK_PREV(listelm, field); \
604 (elm)->field.tqe_prev = (listelm)->field.tqe_prev; \
605 TAILQ_NEXT((elm), field) = (listelm); \
606 *(listelm)->field.tqe_prev = (elm); \
607 (listelm)->field.tqe_prev = &TAILQ_NEXT((elm), field); \
608 QMD_TRACE_ELEM(&(elm)->field); \
609 QMD_TRACE_ELEM(&listelm->field); \
612 #define TAILQ_INSERT_HEAD(head, elm, field) \
614 QMD_TAILQ_CHECK_HEAD(head, field); \
615 if ((TAILQ_NEXT((elm), field) = TAILQ_FIRST((head))) != NULL) \
616 TAILQ_FIRST((head))->field.tqe_prev = \
617 &TAILQ_NEXT((elm), field); \
619 (head)->tqh_last = &TAILQ_NEXT((elm), field); \
620 TAILQ_FIRST((head)) = (elm); \
621 (elm)->field.tqe_prev = &TAILQ_FIRST((head)); \
622 QMD_TRACE_HEAD(head); \
623 QMD_TRACE_ELEM(&(elm)->field); \
626 #define TAILQ_INSERT_TAIL(head, elm, field) \
628 QMD_TAILQ_CHECK_TAIL(head, field); \
629 TAILQ_NEXT((elm), field) = NULL; \
630 (elm)->field.tqe_prev = (head)->tqh_last; \
631 *(head)->tqh_last = (elm); \
632 (head)->tqh_last = &TAILQ_NEXT((elm), field); \
633 QMD_TRACE_HEAD(head); \
634 QMD_TRACE_ELEM(&(elm)->field); \
637 #define TAILQ_LAST(head, headname) \
638 (*(((struct headname *)((head)->tqh_last))->tqh_last))
640 #define TAILQ_NEXT(elm, field) ((elm)->field.tqe_next)
642 #define TAILQ_PREV(elm, headname, field) \
643 (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
645 #define TAILQ_REMOVE(head, elm, field) \
647 QMD_SAVELINK(oldnext, (elm)->field.tqe_next); \
648 QMD_SAVELINK(oldprev, (elm)->field.tqe_prev); \
649 QMD_TAILQ_CHECK_NEXT(elm, field); \
650 QMD_TAILQ_CHECK_PREV(elm, field); \
651 if ((TAILQ_NEXT((elm), field)) != NULL) \
652 TAILQ_NEXT((elm), field)->field.tqe_prev = \
653 (elm)->field.tqe_prev; \
655 (head)->tqh_last = (elm)->field.tqe_prev; \
656 QMD_TRACE_HEAD(head); \
658 *(elm)->field.tqe_prev = TAILQ_NEXT((elm), field); \
661 QMD_TRACE_ELEM(&(elm)->field); \
664 #define TAILQ_SWAP(head1, head2, type, field) \
666 struct type *swap_first = (head1)->tqh_first; \
667 struct type **swap_last = (head1)->tqh_last; \
668 (head1)->tqh_first = (head2)->tqh_first; \
669 (head1)->tqh_last = (head2)->tqh_last; \
670 (head2)->tqh_first = swap_first; \
671 (head2)->tqh_last = swap_last; \
672 if ((swap_first = (head1)->tqh_first) != NULL) \
673 swap_first->field.tqe_prev = &(head1)->tqh_first; \
675 (head1)->tqh_last = &(head1)->tqh_first; \
676 if ((swap_first = (head2)->tqh_first) != NULL) \
677 swap_first->field.tqe_prev = &(head2)->tqh_first; \
679 (head2)->tqh_last = &(head2)->tqh_first; \
686 #endif /* !_SYS_QUEUE_H_ */