2 * Copyright (c) 1991, 1993
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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_SAFE + + + +
92 * _FOREACH_REVERSE - - - +
93 * _FOREACH_REVERSE_SAFE - - - +
94 * _INSERT_HEAD + + + +
95 * _INSERT_BEFORE - + - +
96 * _INSERT_AFTER + + + +
97 * _INSERT_TAIL - - + +
99 * _REMOVE_AFTER + - + -
100 * _REMOVE_HEAD + - + -
104 #ifdef QUEUE_MACRO_DEBUG
105 /* Store the last 2 places the queue element or head was altered */
113 #define TRACEBUF struct qm_trace trace;
114 #define TRASHIT(x) do {(x) = (void *)-1;} while (0)
115 #define QMD_SAVELINK(name, link) void **name = (void *)&(link)
117 #define QMD_TRACE_HEAD(head) do { \
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) do { \
125 (elem)->trace.prevline = (elem)->trace.lastline; \
126 (elem)->trace.prevfile = (elem)->trace.lastfile; \
127 (elem)->trace.lastline = __LINE__; \
128 (elem)->trace.lastfile = __FILE__; \
132 #define QMD_TRACE_ELEM(elem)
133 #define QMD_TRACE_HEAD(head)
134 #define QMD_SAVELINK(name, link)
137 #endif /* QUEUE_MACRO_DEBUG */
140 * Singly-linked List declarations.
142 #define SLIST_HEAD(name, type) \
144 struct type *slh_first; /* first element */ \
147 #define SLIST_HEAD_INITIALIZER(head) \
150 #define SLIST_ENTRY(type) \
152 struct type *sle_next; /* next element */ \
156 * Singly-linked List functions.
158 #define SLIST_EMPTY(head) ((head)->slh_first == NULL)
160 #define SLIST_FIRST(head) ((head)->slh_first)
162 #define SLIST_FOREACH(var, head, field) \
163 for ((var) = SLIST_FIRST((head)); \
165 (var) = SLIST_NEXT((var), field))
167 #define SLIST_FOREACH_SAFE(var, head, field, tvar) \
168 for ((var) = SLIST_FIRST((head)); \
169 (var) && ((tvar) = SLIST_NEXT((var), field), 1); \
172 #define SLIST_FOREACH_PREVPTR(var, varp, head, field) \
173 for ((varp) = &SLIST_FIRST((head)); \
174 ((var) = *(varp)) != NULL; \
175 (varp) = &SLIST_NEXT((var), field))
177 #define SLIST_INIT(head) do { \
178 SLIST_FIRST((head)) = NULL; \
181 #define SLIST_INSERT_AFTER(slistelm, elm, field) do { \
182 SLIST_NEXT((elm), field) = SLIST_NEXT((slistelm), field); \
183 SLIST_NEXT((slistelm), field) = (elm); \
186 #define SLIST_INSERT_HEAD(head, elm, field) do { \
187 SLIST_NEXT((elm), field) = SLIST_FIRST((head)); \
188 SLIST_FIRST((head)) = (elm); \
191 #define SLIST_NEXT(elm, field) ((elm)->field.sle_next)
193 #define SLIST_REMOVE(head, elm, type, field) do { \
194 QMD_SAVELINK(oldnext, (elm)->field.sle_next); \
195 if (SLIST_FIRST((head)) == (elm)) { \
196 SLIST_REMOVE_HEAD((head), field); \
199 struct type *curelm = SLIST_FIRST((head)); \
200 while (SLIST_NEXT(curelm, field) != (elm)) \
201 curelm = SLIST_NEXT(curelm, field); \
202 SLIST_REMOVE_AFTER(curelm, field); \
207 #define SLIST_REMOVE_AFTER(elm, field) do { \
208 SLIST_NEXT(elm, field) = \
209 SLIST_NEXT(SLIST_NEXT(elm, field), field); \
212 #define SLIST_REMOVE_HEAD(head, field) do { \
213 SLIST_FIRST((head)) = SLIST_NEXT(SLIST_FIRST((head)), field); \
217 * Singly-linked Tail queue declarations.
219 #define STAILQ_HEAD(name, type) \
221 struct type *stqh_first;/* first element */ \
222 struct type **stqh_last;/* addr of last next element */ \
225 #define STAILQ_HEAD_INITIALIZER(head) \
226 { NULL, &(head).stqh_first }
228 #define STAILQ_ENTRY(type) \
230 struct type *stqe_next; /* next element */ \
234 * Singly-linked Tail queue functions.
236 #define STAILQ_CONCAT(head1, head2) do { \
237 if (!STAILQ_EMPTY((head2))) { \
238 *(head1)->stqh_last = (head2)->stqh_first; \
239 (head1)->stqh_last = (head2)->stqh_last; \
240 STAILQ_INIT((head2)); \
244 #define STAILQ_EMPTY(head) ((head)->stqh_first == NULL)
246 #define STAILQ_FIRST(head) ((head)->stqh_first)
248 #define STAILQ_FOREACH(var, head, field) \
249 for((var) = STAILQ_FIRST((head)); \
251 (var) = STAILQ_NEXT((var), field))
254 #define STAILQ_FOREACH_SAFE(var, head, field, tvar) \
255 for ((var) = STAILQ_FIRST((head)); \
256 (var) && ((tvar) = STAILQ_NEXT((var), field), 1); \
259 #define STAILQ_INIT(head) do { \
260 STAILQ_FIRST((head)) = NULL; \
261 (head)->stqh_last = &STAILQ_FIRST((head)); \
264 #define STAILQ_INSERT_AFTER(head, tqelm, elm, field) do { \
265 if ((STAILQ_NEXT((elm), field) = STAILQ_NEXT((tqelm), field)) == NULL)\
266 (head)->stqh_last = &STAILQ_NEXT((elm), field); \
267 STAILQ_NEXT((tqelm), field) = (elm); \
270 #define STAILQ_INSERT_HEAD(head, elm, field) do { \
271 if ((STAILQ_NEXT((elm), field) = STAILQ_FIRST((head))) == NULL) \
272 (head)->stqh_last = &STAILQ_NEXT((elm), field); \
273 STAILQ_FIRST((head)) = (elm); \
276 #define STAILQ_INSERT_TAIL(head, elm, field) do { \
277 STAILQ_NEXT((elm), field) = NULL; \
278 *(head)->stqh_last = (elm); \
279 (head)->stqh_last = &STAILQ_NEXT((elm), field); \
282 #define STAILQ_LAST(head, type, field) \
283 (STAILQ_EMPTY((head)) ? \
285 ((struct type *)(void *) \
286 ((char *)((head)->stqh_last) - __offsetof(struct type, field))))
288 #define STAILQ_NEXT(elm, field) ((elm)->field.stqe_next)
290 #define STAILQ_REMOVE(head, elm, type, field) do { \
291 QMD_SAVELINK(oldnext, (elm)->field.stqe_next); \
292 if (STAILQ_FIRST((head)) == (elm)) { \
293 STAILQ_REMOVE_HEAD((head), field); \
296 struct type *curelm = STAILQ_FIRST((head)); \
297 while (STAILQ_NEXT(curelm, field) != (elm)) \
298 curelm = STAILQ_NEXT(curelm, field); \
299 STAILQ_REMOVE_AFTER(head, curelm, field); \
304 #define STAILQ_REMOVE_HEAD(head, field) do { \
305 if ((STAILQ_FIRST((head)) = \
306 STAILQ_NEXT(STAILQ_FIRST((head)), field)) == NULL) \
307 (head)->stqh_last = &STAILQ_FIRST((head)); \
310 #define STAILQ_REMOVE_AFTER(head, elm, field) do { \
311 if ((STAILQ_NEXT(elm, field) = \
312 STAILQ_NEXT(STAILQ_NEXT(elm, field), field)) == NULL) \
313 (head)->stqh_last = &STAILQ_NEXT((elm), field); \
316 #define STAILQ_SWAP(head1, head2, type) do { \
317 struct type *swap_first = STAILQ_FIRST(head1); \
318 struct type **swap_last = (head1)->stqh_last; \
319 STAILQ_FIRST(head1) = STAILQ_FIRST(head2); \
320 (head1)->stqh_last = (head2)->stqh_last; \
321 STAILQ_FIRST(head2) = swap_first; \
322 (head2)->stqh_last = swap_last; \
323 if (STAILQ_EMPTY(head1)) \
324 (head1)->stqh_last = &STAILQ_FIRST(head1); \
325 if (STAILQ_EMPTY(head2)) \
326 (head2)->stqh_last = &STAILQ_FIRST(head2); \
333 #define LIST_HEAD(name, type) \
335 struct type *lh_first; /* first element */ \
338 #define LIST_HEAD_INITIALIZER(head) \
341 #define LIST_ENTRY(type) \
343 struct type *le_next; /* next element */ \
344 struct type **le_prev; /* address of previous next element */ \
351 #if (defined(_KERNEL) && defined(INVARIANTS))
352 #define QMD_LIST_CHECK_HEAD(head, field) do { \
353 if (LIST_FIRST((head)) != NULL && \
354 LIST_FIRST((head))->field.le_prev != \
355 &LIST_FIRST((head))) \
356 panic("Bad list head %p first->prev != head", (head)); \
359 #define QMD_LIST_CHECK_NEXT(elm, field) do { \
360 if (LIST_NEXT((elm), field) != NULL && \
361 LIST_NEXT((elm), field)->field.le_prev != \
362 &((elm)->field.le_next)) \
363 panic("Bad link elm %p next->prev != elm", (elm)); \
366 #define QMD_LIST_CHECK_PREV(elm, field) do { \
367 if (*(elm)->field.le_prev != (elm)) \
368 panic("Bad link elm %p prev->next != elm", (elm)); \
371 #define QMD_LIST_CHECK_HEAD(head, field)
372 #define QMD_LIST_CHECK_NEXT(elm, field)
373 #define QMD_LIST_CHECK_PREV(elm, field)
374 #endif /* (_KERNEL && INVARIANTS) */
376 #define LIST_EMPTY(head) ((head)->lh_first == NULL)
378 #define LIST_FIRST(head) ((head)->lh_first)
380 #define LIST_FOREACH(var, head, field) \
381 for ((var) = LIST_FIRST((head)); \
383 (var) = LIST_NEXT((var), field))
385 #define LIST_FOREACH_SAFE(var, head, field, tvar) \
386 for ((var) = LIST_FIRST((head)); \
387 (var) && ((tvar) = LIST_NEXT((var), field), 1); \
390 #define LIST_INIT(head) do { \
391 LIST_FIRST((head)) = NULL; \
394 #define LIST_INSERT_AFTER(listelm, elm, field) do { \
395 QMD_LIST_CHECK_NEXT(listelm, field); \
396 if ((LIST_NEXT((elm), field) = LIST_NEXT((listelm), field)) != NULL)\
397 LIST_NEXT((listelm), field)->field.le_prev = \
398 &LIST_NEXT((elm), field); \
399 LIST_NEXT((listelm), field) = (elm); \
400 (elm)->field.le_prev = &LIST_NEXT((listelm), field); \
403 #define LIST_INSERT_BEFORE(listelm, elm, field) do { \
404 QMD_LIST_CHECK_PREV(listelm, field); \
405 (elm)->field.le_prev = (listelm)->field.le_prev; \
406 LIST_NEXT((elm), field) = (listelm); \
407 *(listelm)->field.le_prev = (elm); \
408 (listelm)->field.le_prev = &LIST_NEXT((elm), field); \
411 #define LIST_INSERT_HEAD(head, elm, field) do { \
412 QMD_LIST_CHECK_HEAD((head), field); \
413 if ((LIST_NEXT((elm), field) = LIST_FIRST((head))) != NULL) \
414 LIST_FIRST((head))->field.le_prev = &LIST_NEXT((elm), field);\
415 LIST_FIRST((head)) = (elm); \
416 (elm)->field.le_prev = &LIST_FIRST((head)); \
419 #define LIST_NEXT(elm, field) ((elm)->field.le_next)
421 #define LIST_REMOVE(elm, field) do { \
422 QMD_SAVELINK(oldnext, (elm)->field.le_next); \
423 QMD_SAVELINK(oldprev, (elm)->field.le_prev); \
424 QMD_LIST_CHECK_NEXT(elm, field); \
425 QMD_LIST_CHECK_PREV(elm, field); \
426 if (LIST_NEXT((elm), field) != NULL) \
427 LIST_NEXT((elm), field)->field.le_prev = \
428 (elm)->field.le_prev; \
429 *(elm)->field.le_prev = LIST_NEXT((elm), field); \
434 #define LIST_SWAP(head1, head2, type, field) do { \
435 struct type *swap_tmp = LIST_FIRST((head1)); \
436 LIST_FIRST((head1)) = LIST_FIRST((head2)); \
437 LIST_FIRST((head2)) = swap_tmp; \
438 if ((swap_tmp = LIST_FIRST((head1))) != NULL) \
439 swap_tmp->field.le_prev = &LIST_FIRST((head1)); \
440 if ((swap_tmp = LIST_FIRST((head2))) != NULL) \
441 swap_tmp->field.le_prev = &LIST_FIRST((head2)); \
445 * Tail queue declarations.
447 #define TAILQ_HEAD(name, type) \
449 struct type *tqh_first; /* first element */ \
450 struct type **tqh_last; /* addr of last next element */ \
454 #define TAILQ_HEAD_INITIALIZER(head) \
455 { NULL, &(head).tqh_first }
457 #define TAILQ_ENTRY(type) \
459 struct type *tqe_next; /* next element */ \
460 struct type **tqe_prev; /* address of previous next element */ \
465 * Tail queue functions.
467 #if (defined(_KERNEL) && defined(INVARIANTS))
468 #define QMD_TAILQ_CHECK_HEAD(head, field) do { \
469 if (!TAILQ_EMPTY(head) && \
470 TAILQ_FIRST((head))->field.tqe_prev != \
471 &TAILQ_FIRST((head))) \
472 panic("Bad tailq head %p first->prev != head", (head)); \
475 #define QMD_TAILQ_CHECK_TAIL(head, field) do { \
476 if (*(head)->tqh_last != NULL) \
477 panic("Bad tailq NEXT(%p->tqh_last) != NULL", (head)); \
480 #define QMD_TAILQ_CHECK_NEXT(elm, field) do { \
481 if (TAILQ_NEXT((elm), field) != NULL && \
482 TAILQ_NEXT((elm), field)->field.tqe_prev != \
483 &((elm)->field.tqe_next)) \
484 panic("Bad link elm %p next->prev != elm", (elm)); \
487 #define QMD_TAILQ_CHECK_PREV(elm, field) do { \
488 if (*(elm)->field.tqe_prev != (elm)) \
489 panic("Bad link elm %p prev->next != elm", (elm)); \
492 #define QMD_TAILQ_CHECK_HEAD(head, field)
493 #define QMD_TAILQ_CHECK_TAIL(head, headname)
494 #define QMD_TAILQ_CHECK_NEXT(elm, field)
495 #define QMD_TAILQ_CHECK_PREV(elm, field)
496 #endif /* (_KERNEL && INVARIANTS) */
498 #define TAILQ_CONCAT(head1, head2, field) do { \
499 if (!TAILQ_EMPTY(head2)) { \
500 *(head1)->tqh_last = (head2)->tqh_first; \
501 (head2)->tqh_first->field.tqe_prev = (head1)->tqh_last; \
502 (head1)->tqh_last = (head2)->tqh_last; \
503 TAILQ_INIT((head2)); \
504 QMD_TRACE_HEAD(head1); \
505 QMD_TRACE_HEAD(head2); \
509 #define TAILQ_EMPTY(head) ((head)->tqh_first == NULL)
511 #define TAILQ_FIRST(head) ((head)->tqh_first)
513 #define TAILQ_FOREACH(var, head, field) \
514 for ((var) = TAILQ_FIRST((head)); \
516 (var) = TAILQ_NEXT((var), field))
518 #define TAILQ_FOREACH_SAFE(var, head, field, tvar) \
519 for ((var) = TAILQ_FIRST((head)); \
520 (var) && ((tvar) = TAILQ_NEXT((var), field), 1); \
523 #define TAILQ_FOREACH_REVERSE(var, head, headname, field) \
524 for ((var) = TAILQ_LAST((head), headname); \
526 (var) = TAILQ_PREV((var), headname, field))
528 #define TAILQ_FOREACH_REVERSE_SAFE(var, head, headname, field, tvar) \
529 for ((var) = TAILQ_LAST((head), headname); \
530 (var) && ((tvar) = TAILQ_PREV((var), headname, field), 1); \
533 #define TAILQ_INIT(head) do { \
534 TAILQ_FIRST((head)) = NULL; \
535 (head)->tqh_last = &TAILQ_FIRST((head)); \
536 QMD_TRACE_HEAD(head); \
539 #define TAILQ_INSERT_AFTER(head, listelm, elm, field) do { \
540 QMD_TAILQ_CHECK_NEXT(listelm, field); \
541 if ((TAILQ_NEXT((elm), field) = TAILQ_NEXT((listelm), field)) != NULL)\
542 TAILQ_NEXT((elm), field)->field.tqe_prev = \
543 &TAILQ_NEXT((elm), field); \
545 (head)->tqh_last = &TAILQ_NEXT((elm), field); \
546 QMD_TRACE_HEAD(head); \
548 TAILQ_NEXT((listelm), field) = (elm); \
549 (elm)->field.tqe_prev = &TAILQ_NEXT((listelm), field); \
550 QMD_TRACE_ELEM(&(elm)->field); \
551 QMD_TRACE_ELEM(&listelm->field); \
554 #define TAILQ_INSERT_BEFORE(listelm, elm, field) do { \
555 QMD_TAILQ_CHECK_PREV(listelm, field); \
556 (elm)->field.tqe_prev = (listelm)->field.tqe_prev; \
557 TAILQ_NEXT((elm), field) = (listelm); \
558 *(listelm)->field.tqe_prev = (elm); \
559 (listelm)->field.tqe_prev = &TAILQ_NEXT((elm), field); \
560 QMD_TRACE_ELEM(&(elm)->field); \
561 QMD_TRACE_ELEM(&listelm->field); \
564 #define TAILQ_INSERT_HEAD(head, elm, field) do { \
565 QMD_TAILQ_CHECK_HEAD(head, field); \
566 if ((TAILQ_NEXT((elm), field) = TAILQ_FIRST((head))) != NULL) \
567 TAILQ_FIRST((head))->field.tqe_prev = \
568 &TAILQ_NEXT((elm), field); \
570 (head)->tqh_last = &TAILQ_NEXT((elm), field); \
571 TAILQ_FIRST((head)) = (elm); \
572 (elm)->field.tqe_prev = &TAILQ_FIRST((head)); \
573 QMD_TRACE_HEAD(head); \
574 QMD_TRACE_ELEM(&(elm)->field); \
577 #define TAILQ_INSERT_TAIL(head, elm, field) do { \
578 QMD_TAILQ_CHECK_TAIL(head, field); \
579 TAILQ_NEXT((elm), field) = NULL; \
580 (elm)->field.tqe_prev = (head)->tqh_last; \
581 *(head)->tqh_last = (elm); \
582 (head)->tqh_last = &TAILQ_NEXT((elm), field); \
583 QMD_TRACE_HEAD(head); \
584 QMD_TRACE_ELEM(&(elm)->field); \
587 #define TAILQ_LAST(head, headname) \
588 (*(((struct headname *)((head)->tqh_last))->tqh_last))
590 #define TAILQ_NEXT(elm, field) ((elm)->field.tqe_next)
592 #define TAILQ_PREV(elm, headname, field) \
593 (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
595 #define TAILQ_REMOVE(head, elm, field) do { \
596 QMD_SAVELINK(oldnext, (elm)->field.tqe_next); \
597 QMD_SAVELINK(oldprev, (elm)->field.tqe_prev); \
598 QMD_TAILQ_CHECK_NEXT(elm, field); \
599 QMD_TAILQ_CHECK_PREV(elm, field); \
600 if ((TAILQ_NEXT((elm), field)) != NULL) \
601 TAILQ_NEXT((elm), field)->field.tqe_prev = \
602 (elm)->field.tqe_prev; \
604 (head)->tqh_last = (elm)->field.tqe_prev; \
605 QMD_TRACE_HEAD(head); \
607 *(elm)->field.tqe_prev = TAILQ_NEXT((elm), field); \
610 QMD_TRACE_ELEM(&(elm)->field); \
613 #define TAILQ_SWAP(head1, head2, type, field) do { \
614 struct type *swap_first = (head1)->tqh_first; \
615 struct type **swap_last = (head1)->tqh_last; \
616 (head1)->tqh_first = (head2)->tqh_first; \
617 (head1)->tqh_last = (head2)->tqh_last; \
618 (head2)->tqh_first = swap_first; \
619 (head2)->tqh_last = swap_last; \
620 if ((swap_first = (head1)->tqh_first) != NULL) \
621 swap_first->field.tqe_prev = &(head1)->tqh_first; \
623 (head1)->tqh_last = &(head1)->tqh_first; \
624 if ((swap_first = (head2)->tqh_first) != NULL) \
625 swap_first->field.tqe_prev = &(head2)->tqh_first; \
627 (head2)->tqh_last = &(head2)->tqh_first; \
630 #endif /* !_SYS_QUEUE_H_ */