1/*
2 * Copyright (c) 1991, 1993
3 *	The Regents of the University of California.  All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
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 *
14 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 *
26 *	@(#)queue.h	8.5 (Berkeley) 8/20/94
27 * $FreeBSD: src/sys/sys/queue.h,v 1.38 2000/05/26 02:06:56 jake Exp $
28 */
29
30#ifndef _SYS_QUEUE_H_
31#define	_SYS_QUEUE_H_
32
33/*
34 * This file defines five types of data structures: singly-linked lists,
35 * singly-linked tail queues, lists, tail queues, and circular queues.
36 *
37 * A singly-linked list is headed by a single forward pointer. The elements
38 * are singly linked for minimum space and pointer manipulation overhead at
39 * the expense of O(n) removal for arbitrary elements. New elements can be
40 * added to the list after an existing element or at the head of the list.
41 * Elements being removed from the head of the list should use the explicit
42 * macro for this purpose for optimum efficiency. A singly-linked list may
43 * only be traversed in the forward direction.  Singly-linked lists are ideal
44 * for applications with large datasets and few or no removals or for
45 * implementing a LIFO queue.
46 *
47 * A singly-linked tail queue is headed by a pair of pointers, one to the
48 * head of the list and the other to the tail of the list. The elements are
49 * singly linked for minimum space and pointer manipulation overhead at the
50 * expense of O(n) removal for arbitrary elements. New elements can be added
51 * to the list after an existing element, at the head of the list, or at the
52 * end of the list. Elements being removed from the head of the tail queue
53 * should use the explicit macro for this purpose for optimum efficiency.
54 * A singly-linked tail queue may only be traversed in the forward direction.
55 * Singly-linked tail queues are ideal for applications with large datasets
56 * and few or no removals or for implementing a FIFO queue.
57 *
58 * A list is headed by a single forward pointer (or an array of forward
59 * pointers for a hash table header). The elements are doubly linked
60 * so that an arbitrary element can be removed without a need to
61 * traverse the list. New elements can be added to the list before
62 * or after an existing element or at the head of the list. A list
63 * may only be traversed in the forward direction.
64 *
65 * A tail queue is headed by a pair of pointers, one to the head of the
66 * list and the other to the tail of the list. The elements are doubly
67 * linked 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 or
69 * after an existing element, at the head of the list, or at the end of
70 * the list. A tail queue may be traversed in either direction.
71 *
72 * A circle 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 after
76 * an existing element, at the head of the list, or at the end of the list.
77 * A circle queue may be traversed in either direction, but has a more
78 * complex end of list detection.
79 *
80 * For details on the use of these macros, see the queue(3) manual page.
81 *
82 *
83 *			SLIST	LIST	STAILQ	TAILQ	CIRCLEQ
84 * _HEAD		+	+	+	+	+
85 * _HEAD_INITIALIZER	+	+	+	+	+
86 * _ENTRY		+	+	+	+	+
87 * _INIT		+	+	+	+	+
88 * _EMPTY		+	+	+	+	+
89 * _FIRST		+	+	+	+	+
90 * _NEXT		+	+	+	+	+
91 * _PREV		-	-	-	+	+
92 * _LAST		-	-	+	+	+
93 * _FOREACH		+	+	+	+	+
94 * _FOREACH_REVERSE	-	-	-	+	+
95 * _INSERT_HEAD		+	+	+	+	+
96 * _INSERT_BEFORE	-	+	-	+	+
97 * _INSERT_AFTER	+	+	+	+	+
98 * _INSERT_TAIL		-	-	+	+	+
99 * _REMOVE_HEAD		+	-	+	-	-
100 * _REMOVE		+	+	+	+	+
101 *
102 */
103
104/*
105 * Singly-linked List declarations.
106 */
107#define	SLIST_HEAD(name, type)						\
108struct name {								\
109	struct type *slh_first;	/* first element */			\
110}
111
112#define	SLIST_HEAD_INITIALIZER(head)					\
113	{ NULL }
114
115#define	SLIST_ENTRY(type)						\
116struct {								\
117	struct type *sle_next;	/* next element */			\
118}
119
120/*
121 * Singly-linked List functions.
122 */
123#define	SLIST_EMPTY(head)	((head)->slh_first == NULL)
124
125#define	SLIST_FIRST(head)	((head)->slh_first)
126
127#define	SLIST_FOREACH(var, head, field)					\
128	for ((var) = SLIST_FIRST((head));				\
129	    (var);							\
130	    (var) = SLIST_NEXT((var), field))
131
132#define	SLIST_INIT(head) do {						\
133	SLIST_FIRST((head)) = NULL;					\
134} while (0)
135
136#define	SLIST_INSERT_AFTER(slistelm, elm, field) do {			\
137	SLIST_NEXT((elm), field) = SLIST_NEXT((slistelm), field);	\
138	SLIST_NEXT((slistelm), field) = (elm);				\
139} while (0)
140
141#define	SLIST_INSERT_HEAD(head, elm, field) do {			\
142	SLIST_NEXT((elm), field) = SLIST_FIRST((head));			\
143	SLIST_FIRST((head)) = (elm);					\
144} while (0)
145
146#define	SLIST_NEXT(elm, field)	((elm)->field.sle_next)
147
148#define	SLIST_REMOVE(head, elm, type, field) do {			\
149	if (SLIST_FIRST((head)) == (elm)) {				\
150		SLIST_REMOVE_HEAD((head), field);			\
151	}								\
152	else {								\
153		struct type *curelm = SLIST_FIRST((head));		\
154		while (SLIST_NEXT(curelm, field) != (elm))		\
155			curelm = SLIST_NEXT(curelm, field);		\
156		SLIST_NEXT(curelm, field) =				\
157		    SLIST_NEXT(SLIST_NEXT(curelm, field), field);	\
158	}								\
159} while (0)
160
161#define	SLIST_REMOVE_HEAD(head, field) do {				\
162	SLIST_FIRST((head)) = SLIST_NEXT(SLIST_FIRST((head)), field);	\
163} while (0)
164
165/*
166 * Singly-linked Tail queue declarations.
167 */
168#define	STAILQ_HEAD(name, type)						\
169struct name {								\
170	struct type *stqh_first;/* first element */			\
171	struct type **stqh_last;/* addr of last next element */		\
172}
173
174#define	STAILQ_HEAD_INITIALIZER(head)					\
175	{ NULL, &(head).stqh_first }
176
177#define	STAILQ_ENTRY(type)						\
178struct {								\
179	struct type *stqe_next;	/* next element */			\
180}
181
182/*
183 * Singly-linked Tail queue functions.
184 */
185#define	STAILQ_EMPTY(head)	((head)->stqh_first == NULL)
186
187#define	STAILQ_FIRST(head)	((head)->stqh_first)
188
189#define	STAILQ_FOREACH(var, head, field)				\
190	for((var) = STAILQ_FIRST((head));				\
191	   (var);							\
192	   (var) = STAILQ_NEXT((var), field))
193
194#define	STAILQ_INIT(head) do {						\
195	STAILQ_FIRST((head)) = NULL;					\
196	(head)->stqh_last = &STAILQ_FIRST((head));			\
197} while (0)
198
199#define	STAILQ_INSERT_AFTER(head, tqelm, elm, field) do {		\
200	if ((STAILQ_NEXT((elm), field) = STAILQ_NEXT((tqelm), field)) == NULL)\
201		(head)->stqh_last = &STAILQ_NEXT((elm), field);		\
202	STAILQ_NEXT((tqelm), field) = (elm);				\
203} while (0)
204
205#define	STAILQ_INSERT_HEAD(head, elm, field) do {			\
206	if ((STAILQ_NEXT((elm), field) = STAILQ_FIRST((head))) == NULL)	\
207		(head)->stqh_last = &STAILQ_NEXT((elm), field);		\
208	STAILQ_FIRST((head)) = (elm);					\
209} while (0)
210
211#define	STAILQ_INSERT_TAIL(head, elm, field) do {			\
212	STAILQ_NEXT((elm), field) = NULL;				\
213	STAILQ_LAST((head)) = (elm);					\
214	(head)->stqh_last = &STAILQ_NEXT((elm), field);			\
215} while (0)
216
217#define	STAILQ_LAST(head)	(*(head)->stqh_last)
218
219#define	STAILQ_NEXT(elm, field)	((elm)->field.stqe_next)
220
221#define	STAILQ_REMOVE(head, elm, type, field) do {			\
222	if (STAILQ_FIRST((head)) == (elm)) {				\
223		STAILQ_REMOVE_HEAD(head, field);			\
224	}								\
225	else {								\
226		struct type *curelm = STAILQ_FIRST((head));		\
227		while (STAILQ_NEXT(curelm, field) != (elm))		\
228			curelm = STAILQ_NEXT(curelm, field);		\
229		if ((STAILQ_NEXT(curelm, field) =			\
230		     STAILQ_NEXT(STAILQ_NEXT(curelm, field), field)) == NULL)\
231			(head)->stqh_last = &STAILQ_NEXT((curelm), field);\
232	}								\
233} while (0)
234
235#define	STAILQ_REMOVE_HEAD(head, field) do {				\
236	if ((STAILQ_FIRST((head)) =					\
237	     STAILQ_NEXT(STAILQ_FIRST((head)), field)) == NULL)		\
238		(head)->stqh_last = &STAILQ_FIRST((head));		\
239} while (0)
240
241#define	STAILQ_REMOVE_HEAD_UNTIL(head, elm, field) do {			\
242	if ((STAILQ_FIRST((head)) = STAILQ_NEXT((elm), field)) == NULL)	\
243		(head)->stqh_last = &STAILQ_FIRST((head));		\
244} while (0)
245
246/*
247 * List declarations.
248 */
249#define	LIST_HEAD(name, type)						\
250struct name {								\
251	struct type *lh_first;	/* first element */			\
252}
253
254#define	LIST_HEAD_INITIALIZER(head)					\
255	{ NULL }
256
257#define	LIST_ENTRY(type)						\
258struct {								\
259	struct type *le_next;	/* next element */			\
260	struct type **le_prev;	/* address of previous next element */	\
261}
262
263/*
264 * List functions.
265 */
266
267#define	LIST_EMPTY(head)	((head)->lh_first == NULL)
268
269#define	LIST_FIRST(head)	((head)->lh_first)
270
271#define	LIST_FOREACH(var, head, field)					\
272	for ((var) = LIST_FIRST((head));				\
273	    (var);							\
274	    (var) = LIST_NEXT((var), field))
275
276#define	LIST_INIT(head) do {						\
277	LIST_FIRST((head)) = NULL;					\
278} while (0)
279
280#define	LIST_INSERT_AFTER(listelm, elm, field) do {			\
281	if ((LIST_NEXT((elm), field) = LIST_NEXT((listelm), field)) != NULL)\
282		LIST_NEXT((listelm), field)->field.le_prev =		\
283		    &LIST_NEXT((elm), field);				\
284	LIST_NEXT((listelm), field) = (elm);				\
285	(elm)->field.le_prev = &LIST_NEXT((listelm), field);		\
286} while (0)
287
288#define	LIST_INSERT_BEFORE(listelm, elm, field) do {			\
289	(elm)->field.le_prev = (listelm)->field.le_prev;		\
290	LIST_NEXT((elm), field) = (listelm);				\
291	*(listelm)->field.le_prev = (elm);				\
292	(listelm)->field.le_prev = &LIST_NEXT((elm), field);		\
293} while (0)
294
295#define	LIST_INSERT_HEAD(head, elm, field) do {				\
296	if ((LIST_NEXT((elm), field) = LIST_FIRST((head))) != NULL)	\
297		LIST_FIRST((head))->field.le_prev = &LIST_NEXT((elm), field);\
298	LIST_FIRST((head)) = (elm);					\
299	(elm)->field.le_prev = &LIST_FIRST((head));			\
300} while (0)
301
302#define	LIST_NEXT(elm, field)	((elm)->field.le_next)
303
304#define	LIST_REMOVE(elm, field) do {					\
305	if (LIST_NEXT((elm), field) != NULL)				\
306		LIST_NEXT((elm), field)->field.le_prev = 		\
307		    (elm)->field.le_prev;				\
308	*(elm)->field.le_prev = LIST_NEXT((elm), field);		\
309} while (0)
310
311/*
312 * Tail queue declarations.
313 */
314#define	TAILQ_HEAD(name, type)						\
315struct name {								\
316	struct type *tqh_first;	/* first element */			\
317	struct type **tqh_last;	/* addr of last next element */		\
318}
319
320#define	TAILQ_HEAD_INITIALIZER(head)					\
321	{ NULL, &(head).tqh_first }
322
323#define	TAILQ_ENTRY(type)						\
324struct {								\
325	struct type *tqe_next;	/* next element */			\
326	struct type **tqe_prev;	/* address of previous next element */	\
327}
328
329/*
330 * Tail queue functions.
331 */
332#define	TAILQ_EMPTY(head)	((head)->tqh_first == NULL)
333
334#define	TAILQ_FIRST(head)	((head)->tqh_first)
335
336#define	TAILQ_FOREACH(var, head, field)					\
337	for ((var) = TAILQ_FIRST((head));				\
338	    (var);							\
339	    (var) = TAILQ_NEXT((var), field))
340
341#define	TAILQ_FOREACH_REVERSE(var, head, headname, field)		\
342	for ((var) = TAILQ_LAST((head), headname);			\
343	    (var);							\
344	    (var) = TAILQ_PREV((var), headname, field))
345
346#define	TAILQ_INIT(head) do {						\
347	TAILQ_FIRST((head)) = NULL;					\
348	(head)->tqh_last = &TAILQ_FIRST((head));			\
349} while (0)
350
351#define	TAILQ_INSERT_AFTER(head, listelm, elm, field) do {		\
352	if ((TAILQ_NEXT((elm), field) = TAILQ_NEXT((listelm), field)) != NULL)\
353		TAILQ_NEXT((elm), field)->field.tqe_prev = 		\
354		    &TAILQ_NEXT((elm), field);				\
355	else								\
356		(head)->tqh_last = &TAILQ_NEXT((elm), field);		\
357	TAILQ_NEXT((listelm), field) = (elm);				\
358	(elm)->field.tqe_prev = &TAILQ_NEXT((listelm), field);		\
359} while (0)
360
361#define	TAILQ_INSERT_BEFORE(listelm, elm, field) do {			\
362	(elm)->field.tqe_prev = (listelm)->field.tqe_prev;		\
363	TAILQ_NEXT((elm), field) = (listelm);				\
364	*(listelm)->field.tqe_prev = (elm);				\
365	(listelm)->field.tqe_prev = &TAILQ_NEXT((elm), field);		\
366} while (0)
367
368#define	TAILQ_INSERT_HEAD(head, elm, field) do {			\
369	if ((TAILQ_NEXT((elm), field) = TAILQ_FIRST((head))) != NULL)	\
370		TAILQ_FIRST((head))->field.tqe_prev =			\
371		    &TAILQ_NEXT((elm), field);				\
372	else								\
373		(head)->tqh_last = &TAILQ_NEXT((elm), field);		\
374	TAILQ_FIRST((head)) = (elm);					\
375	(elm)->field.tqe_prev = &TAILQ_FIRST((head));			\
376} while (0)
377
378#define	TAILQ_INSERT_TAIL(head, elm, field) do {			\
379	TAILQ_NEXT((elm), field) = NULL;				\
380	(elm)->field.tqe_prev = (head)->tqh_last;			\
381	*(head)->tqh_last = (elm);					\
382	(head)->tqh_last = &TAILQ_NEXT((elm), field);			\
383} while (0)
384
385#define	TAILQ_LAST(head, headname)					\
386	(*(((struct headname *)((head)->tqh_last))->tqh_last))
387
388#define	TAILQ_NEXT(elm, field) ((elm)->field.tqe_next)
389
390#define	TAILQ_PREV(elm, headname, field)				\
391	(*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
392
393#define	TAILQ_REMOVE(head, elm, field) do {				\
394	if ((TAILQ_NEXT((elm), field)) != NULL)				\
395		TAILQ_NEXT((elm), field)->field.tqe_prev = 		\
396		    (elm)->field.tqe_prev;				\
397	else								\
398		(head)->tqh_last = (elm)->field.tqe_prev;		\
399	*(elm)->field.tqe_prev = TAILQ_NEXT((elm), field);		\
400} while (0)
401
402/*
403 * Circular queue declarations.
404 */
405#define	CIRCLEQ_HEAD(name, type)					\
406struct name {								\
407	struct type *cqh_first;		/* first element */		\
408	struct type *cqh_last;		/* last element */		\
409}
410
411#define	CIRCLEQ_HEAD_INITIALIZER(head)					\
412	{ (void *)&(head), (void *)&(head) }
413
414#define	CIRCLEQ_ENTRY(type)						\
415struct {								\
416	struct type *cqe_next;		/* next element */		\
417	struct type *cqe_prev;		/* previous element */		\
418}
419
420/*
421 * Circular queue functions.
422 */
423#define	CIRCLEQ_EMPTY(head)	((head)->cqh_first == (void *)(head))
424
425#define	CIRCLEQ_FIRST(head)	((head)->cqh_first)
426
427#define	CIRCLEQ_FOREACH(var, head, field)				\
428	for ((var) = CIRCLEQ_FIRST((head));				\
429	    (var) != (void *)(head);					\
430	    (var) = CIRCLEQ_NEXT((var), field))
431
432#define	CIRCLEQ_FOREACH_REVERSE(var, head, field)			\
433	for ((var) = CIRCLEQ_LAST((head));				\
434	    (var) != (void *)(head);					\
435	    (var) = CIRCLEQ_PREV((var), field))
436
437#define	CIRCLEQ_INIT(head) do {						\
438	CIRCLEQ_FIRST((head)) = (void *)(head);				\
439	CIRCLEQ_LAST((head)) = (void *)(head);				\
440} while (0)
441
442#define	CIRCLEQ_INSERT_AFTER(head, listelm, elm, field) do {		\
443	CIRCLEQ_NEXT((elm), field) = CIRCLEQ_NEXT((listelm), field);	\
444	CIRCLEQ_PREV((elm), field) = (listelm);				\
445	if (CIRCLEQ_NEXT((listelm), field) == (void *)(head))		\
446		CIRCLEQ_LAST((head)) = (elm);				\
447	else								\
448		CIRCLEQ_PREV(CIRCLEQ_NEXT((listelm), field), field) = (elm);\
449	CIRCLEQ_NEXT((listelm), field) = (elm);				\
450} while (0)
451
452#define	CIRCLEQ_INSERT_BEFORE(head, listelm, elm, field) do {		\
453	CIRCLEQ_NEXT((elm), field) = (listelm);				\
454	CIRCLEQ_PREV((elm), field) = CIRCLEQ_PREV((listelm), field);	\
455	if (CIRCLEQ_PREV((listelm), field) == (void *)(head))		\
456		CIRCLEQ_FIRST((head)) = (elm);				\
457	else								\
458		CIRCLEQ_NEXT(CIRCLEQ_PREV((listelm), field), field) = (elm);\
459	CIRCLEQ_PREV((listelm), field) = (elm);				\
460} while (0)
461
462#define	CIRCLEQ_INSERT_HEAD(head, elm, field) do {			\
463	CIRCLEQ_NEXT((elm), field) = CIRCLEQ_FIRST((head));		\
464	CIRCLEQ_PREV((elm), field) = (void *)(head);			\
465	if (CIRCLEQ_LAST((head)) == (void *)(head))			\
466		CIRCLEQ_LAST((head)) = (elm);				\
467	else								\
468		CIRCLEQ_PREV(CIRCLEQ_FIRST((head)), field) = (elm);	\
469	CIRCLEQ_FIRST((head)) = (elm);					\
470} while (0)
471
472#define	CIRCLEQ_INSERT_TAIL(head, elm, field) do {			\
473	CIRCLEQ_NEXT((elm), field) = (void *)(head);			\
474	CIRCLEQ_PREV((elm), field) = CIRCLEQ_LAST((head));		\
475	if (CIRCLEQ_FIRST((head)) == (void *)(head))			\
476		CIRCLEQ_FIRST((head)) = (elm);				\
477	else								\
478		CIRCLEQ_NEXT(CIRCLEQ_LAST((head)), field) = (elm);	\
479	CIRCLEQ_LAST((head)) = (elm);					\
480} while (0)
481
482#define	CIRCLEQ_LAST(head)	((head)->cqh_last)
483
484#define	CIRCLEQ_NEXT(elm,field)	((elm)->field.cqe_next)
485
486#define	CIRCLEQ_PREV(elm,field)	((elm)->field.cqe_prev)
487
488#define	CIRCLEQ_REMOVE(head, elm, field) do {				\
489	if (CIRCLEQ_NEXT((elm), field) == (void *)(head))		\
490		CIRCLEQ_LAST((head)) = CIRCLEQ_PREV((elm), field);	\
491	else								\
492		CIRCLEQ_PREV(CIRCLEQ_NEXT((elm), field), field) =	\
493		    CIRCLEQ_PREV((elm), field);				\
494	if (CIRCLEQ_PREV((elm), field) == (void *)(head))		\
495		CIRCLEQ_FIRST((head)) = CIRCLEQ_NEXT((elm), field);	\
496	else								\
497		CIRCLEQ_NEXT(CIRCLEQ_PREV((elm), field), field) =	\
498		    CIRCLEQ_NEXT((elm), field);				\
499} while (0)
500
501#endif /* !_SYS_QUEUE_H_ */
502