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/*

 * Copyright (c) 1991, 1993

 *	The Regents of the University of California.  All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 * 1. Redistributions of source code must retain the above copyright

 *    notice, this list of conditions and the following disclaimer.

 * 2. Redistributions in binary form must reproduce the above copyright

 *    notice, this list of conditions and the following disclaimer in the

 *    documentation and/or other materials provided with the distribution.

 * 3. All advertising materials mentioning features or use of this software

 *    must display the following acknowledgement:

 *	This product includes software developed by the University of

 *	California, Berkeley and its contributors.

 * 4. Neither the name of the University nor the names of its contributors

 *    may be used to endorse or promote products derived from this software

 *    without specific prior written permission.

 *

 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND

 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE

 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL

 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS

 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)

 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT

 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY

 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF

 * SUCH DAMAGE.

 *

 *	@(#)queue.h	8.5 (Berkeley) 8/20/94

 * $FreeBSD: src/sys/sys/queue.h,v 1.48 2002/04/17 14:00:37 tmm Exp $

 */

#ifndef _SYS_QUEUE_H_

#define	_SYS_QUEUE_H_

#include 	/* for __offsetof */

/*

 * This file defines four types of data structures: singly-linked lists,

 * singly-linked tail queues, lists and tail queues.

 *

 * A singly-linked list is headed by a single forward pointer. The elements

 * are singly linked for minimum space and pointer manipulation overhead at

 * the expense of O(n) removal for arbitrary elements. New elements can be

 * added to the list after an existing element or at the head of the list.

 * Elements being removed from the head of the list should use the explicit

 * macro for this purpose for optimum efficiency. A singly-linked list may

 * only be traversed in the forward direction.  Singly-linked lists are ideal

 * for applications with large datasets and few or no removals or for

 * implementing a LIFO queue.

 *

 * A singly-linked tail queue is headed by a pair of pointers, one to the

 * head of the list and the other to the tail of the list. The elements are

 * singly linked for minimum space and pointer manipulation overhead at the

 * expense of O(n) removal for arbitrary elements. New elements can be added

 * to the list after an existing element, at the head of the list, or at the

 * end of the list. Elements being removed from the head of the tail queue

 * should use the explicit macro for this purpose for optimum efficiency.

 * A singly-linked tail queue may only be traversed in the forward direction.

 * Singly-linked tail queues are ideal for applications with large datasets

 * and few or no removals or for implementing a FIFO queue.

 *

 * A list is headed by a single forward pointer (or an array of forward

 * pointers for a hash table header). The elements are doubly linked

 * so that an arbitrary element can be removed without a need to

 * traverse the list. New elements can be added to the list before

 * or after an existing element or at the head of the list. A list

 * may only be traversed in the forward direction.

 *

 * A tail queue is headed by a pair of pointers, one to the head of the

 * list and the other to the tail of the list. The elements are doubly

 * linked so that an arbitrary element can be removed without a need to

 * traverse the list. New elements can be added to the list before or

 * after an existing element, at the head of the list, or at the end of

 * the list. A tail queue may be traversed in either direction.

 *

 * For details on the use of these macros, see the queue(3) manual page.

 *

 *

 *			SLIST	LIST	STAILQ	TAILQ

 * _HEAD		+	+	+	+

 * _HEAD_INITIALIZER	+	+	+	+

 * _ENTRY		+	+	+	+

 * _INIT		+	+	+	+

 * _EMPTY		+	+	+	+

 * _FIRST		+	+	+	+

 * _NEXT		+	+	+	+

 * _PREV		-	-	-	+

 * _LAST		-	-	+	+

 * _FOREACH		+	+	+	+

 * _FOREACH_REVERSE	-	-	-	+

 * _INSERT_HEAD		+	+	+	+

 * _INSERT_BEFORE	-	+	-	+

 * _INSERT_AFTER	+	+	+	+

 * _INSERT_TAIL		-	-	+	+

 * _CONCAT		-	-	+	+

 * _REMOVE_HEAD		+	-	+	-

 * _REMOVE		+	+	+	+

 *

 */

/*

 * Singly-linked List declarations.

 */

#define	SLIST_HEAD(name, type)						\

struct name {								\

	struct type *slh_first;	/* first element */			\

}

#define	SLIST_HEAD_INITIALIZER(head)					\

	{ NULL }

#define	SLIST_ENTRY(type)						\

struct {								\

	struct type *sle_next;	/* next element */			\

}

/*

 * Singly-linked List functions.

 */

#define	SLIST_EMPTY(head)	((head)->slh_first == NULL)

#define	SLIST_FIRST(head)	((head)->slh_first)

#define	SLIST_FOREACH(var, head, field)					\

	for ((var) = SLIST_FIRST((head));				\

	    (var);							\

	    (var) = SLIST_NEXT((var), field))

#define	SLIST_INIT(head) do {						\

	SLIST_FIRST((head)) = NULL;					\

} while (0)

#define	SLIST_INSERT_AFTER(slistelm, elm, field) do {			\

	SLIST_NEXT((elm), field) = SLIST_NEXT((slistelm), field);	\

	SLIST_NEXT((slistelm), field) = (elm);				\

} while (0)

#define	SLIST_INSERT_HEAD(head, elm, field) do {			\

	SLIST_NEXT((elm), field) = SLIST_FIRST((head));			\

	SLIST_FIRST((head)) = (elm);					\

} while (0)

#define	SLIST_NEXT(elm, field)	((elm)->field.sle_next)

#define	SLIST_REMOVE(head, elm, type, field) do {			\

	if (SLIST_FIRST((head)) == (elm)) {				\

		SLIST_REMOVE_HEAD((head), field);			\

	}								\

	else {								\

		struct type *curelm = SLIST_FIRST((head));		\

		while (SLIST_NEXT(curelm, field) != (elm))		\

			curelm = SLIST_NEXT(curelm, field);		\

		SLIST_NEXT(curelm, field) =				\

		    SLIST_NEXT(SLIST_NEXT(curelm, field), field);	\

	}								\

} while (0)

#define	SLIST_REMOVE_HEAD(head, field) do {				\

	SLIST_FIRST((head)) = SLIST_NEXT(SLIST_FIRST((head)), field);	\

} while (0)

/*

 * Singly-linked Tail queue declarations.

 */

#define	STAILQ_HEAD(name, type)						\

struct name {								\

	struct type *stqh_first;/* first element */			\

	struct type **stqh_last;/* addr of last next element */		\

}

#define	STAILQ_HEAD_INITIALIZER(head)					\

	{ NULL, &(head).stqh_first }

#define	STAILQ_ENTRY(type)						\

struct {								\

	struct type *stqe_next;	/* next element */			\

}

/*

 * Singly-linked Tail queue functions.

 */

#define	STAILQ_CONCAT(head1, head2) do {				\

	if (!STAILQ_EMPTY((head2))) {					\

		*(head1)->stqh_last = (head2)->stqh_first;		\

		(head1)->stqh_last = (head2)->stqh_last;		\

		STAILQ_INIT((head2));					\

	}								\

} while (0)

#define	STAILQ_EMPTY(head)	((head)->stqh_first == NULL)

#define	STAILQ_FIRST(head)	((head)->stqh_first)

#define	STAILQ_FOREACH(var, head, field)				\

	for((var) = STAILQ_FIRST((head));				\

	   (var);							\

	   (var) = STAILQ_NEXT((var), field))

#define	STAILQ_INIT(head) do {						\

	STAILQ_FIRST((head)) = NULL;					\

	(head)->stqh_last = &STAILQ_FIRST((head));			\

} while (0)

#define	STAILQ_INSERT_AFTER(head, tqelm, elm, field) do {		\

	if ((STAILQ_NEXT((elm), field) = STAILQ_NEXT((tqelm), field)) == NULL)\

		(head)->stqh_last = &STAILQ_NEXT((elm), field);		\

	STAILQ_NEXT((tqelm), field) = (elm);				\

} while (0)

#define	STAILQ_INSERT_HEAD(head, elm, field) do {			\

	if ((STAILQ_NEXT((elm), field) = STAILQ_FIRST((head))) == NULL)	\

		(head)->stqh_last = &STAILQ_NEXT((elm), field);		\

	STAILQ_FIRST((head)) = (elm);					\

} while (0)

#define	STAILQ_INSERT_TAIL(head, elm, field) do {			\

	STAILQ_NEXT((elm), field) = NULL;				\

	*(head)->stqh_last = (elm);					\

	(head)->stqh_last = &STAILQ_NEXT((elm), field);			\

} while (0)

#define	STAILQ_LAST(head, type, field)					\

	(STAILQ_EMPTY((head)) ?						\

		NULL :							\

	        ((struct type *)					\

		((char *)((head)->stqh_last) - __offsetof(struct type, field))))

#define	STAILQ_NEXT(elm, field)	((elm)->field.stqe_next)

#define	STAILQ_REMOVE(head, elm, type, field) do {			\

	if (STAILQ_FIRST((head)) == (elm)) {				\

		STAILQ_REMOVE_HEAD((head), field);			\

	}								\

	else {								\

		struct type *curelm = STAILQ_FIRST((head));		\

		while (STAILQ_NEXT(curelm, field) != (elm))		\

			curelm = STAILQ_NEXT(curelm, field);		\

		if ((STAILQ_NEXT(curelm, field) =			\

		     STAILQ_NEXT(STAILQ_NEXT(curelm, field), field)) == NULL)\

			(head)->stqh_last = &STAILQ_NEXT((curelm), field);\

	}								\

} while (0)

#define	STAILQ_REMOVE_HEAD(head, field) do {				\

	if ((STAILQ_FIRST((head)) =					\

	     STAILQ_NEXT(STAILQ_FIRST((head)), field)) == NULL)		\

		(head)->stqh_last = &STAILQ_FIRST((head));		\

} while (0)

#define	STAILQ_REMOVE_HEAD_UNTIL(head, elm, field) do {			\

	if ((STAILQ_FIRST((head)) = STAILQ_NEXT((elm), field)) == NULL)	\

		(head)->stqh_last = &STAILQ_FIRST((head));		\

} while (0)

/*

 * List declarations.

 */

#define	LIST_HEAD(name, type)						\

struct name {								\

	struct type *lh_first;	/* first element */			\

}

#define	LIST_HEAD_INITIALIZER(head)					\

	{ NULL }

#define	LIST_ENTRY(type)						\

struct {								\

	struct type *le_next;	/* next element */			\

	struct type **le_prev;	/* address of previous next element */	\

}

/*

 * List functions.

 */

#define	LIST_EMPTY(head)	((head)->lh_first == NULL)

#define	LIST_FIRST(head)	((head)->lh_first)

#define	LIST_FOREACH(var, head, field)					\

	for ((var) = LIST_FIRST((head));				\

	    (var);							\

	    (var) = LIST_NEXT((var), field))

#define	LIST_INIT(head) do {						\

	LIST_FIRST((head)) = NULL;					\

} while (0)

#define	LIST_INSERT_AFTER(listelm, elm, field) do {			\

	if ((LIST_NEXT((elm), field) = LIST_NEXT((listelm), field)) != NULL)\

		LIST_NEXT((listelm), field)->field.le_prev =		\

		    &LIST_NEXT((elm), field);				\

	LIST_NEXT((listelm), field) = (elm);				\

	(elm)->field.le_prev = &LIST_NEXT((listelm), field);		\

} while (0)

#define	LIST_INSERT_BEFORE(listelm, elm, field) do {			\

	(elm)->field.le_prev = (listelm)->field.le_prev;		\

	LIST_NEXT((elm), field) = (listelm);				\

	*(listelm)->field.le_prev = (elm);				\

	(listelm)->field.le_prev = &LIST_NEXT((elm), field);		\

} while (0)

#define	LIST_INSERT_HEAD(head, elm, field) do {				\

	if ((LIST_NEXT((elm), field) = LIST_FIRST((head))) != NULL)	\

		LIST_FIRST((head))->field.le_prev = &LIST_NEXT((elm), field);\

	LIST_FIRST((head)) = (elm);					\

	(elm)->field.le_prev = &LIST_FIRST((head));			\

} while (0)

#define	LIST_NEXT(elm, field)	((elm)->field.le_next)

#define	LIST_REMOVE(elm, field) do {					\

	if (LIST_NEXT((elm), field) != NULL)				\

		LIST_NEXT((elm), field)->field.le_prev = 		\

		    (elm)->field.le_prev;				\

	*(elm)->field.le_prev = LIST_NEXT((elm), field);		\

} while (0)

/*

 * Tail queue declarations.

 */

#define	TAILQ_HEAD(name, type)						\

struct name {								\

	struct type *tqh_first;	/* first element */			\

	struct type **tqh_last;	/* addr of last next element */		\

}

#define	TAILQ_HEAD_INITIALIZER(head)					\

	{ NULL, &(head).tqh_first }

#define	TAILQ_ENTRY(type)						\

struct {								\

	struct type *tqe_next;	/* next element */			\

	struct type **tqe_prev;	/* address of previous next element */	\

}

/*

 * Tail queue functions.

 */

#define	TAILQ_CONCAT(head1, head2, field) do {				\

	if (!TAILQ_EMPTY(head2)) {					\

		*(head1)->tqh_last = (head2)->tqh_first;		\

		(head2)->tqh_first->field.tqe_prev = (head1)->tqh_last;	\

		(head1)->tqh_last = (head2)->tqh_last;			\

		TAILQ_INIT((head2));					\

	}								\

} while (0)

#define	TAILQ_EMPTY(head)	((head)->tqh_first == NULL)

#define	TAILQ_FIRST(head)	((head)->tqh_first)

#define	TAILQ_FOREACH(var, head, field)					\

	for ((var) = TAILQ_FIRST((head));				\

	    (var);							\

	    (var) = TAILQ_NEXT((var), field))

#define	TAILQ_FOREACH_REVERSE(var, head, headname, field)		\

	for ((var) = TAILQ_LAST((head), headname);			\

	    (var);							\

	    (var) = TAILQ_PREV((var), headname, field))

#define	TAILQ_INIT(head) do {						\

	TAILQ_FIRST((head)) = NULL;					\

	(head)->tqh_last = &TAILQ_FIRST((head));			\

} while (0)

#define	TAILQ_INSERT_AFTER(head, listelm, elm, field) do {		\

	if ((TAILQ_NEXT((elm), field) = TAILQ_NEXT((listelm), field)) != NULL)\

		TAILQ_NEXT((elm), field)->field.tqe_prev = 		\

		    &TAILQ_NEXT((elm), field);				\

	else								\

		(head)->tqh_last = &TAILQ_NEXT((elm), field);		\

	TAILQ_NEXT((listelm), field) = (elm);				\

	(elm)->field.tqe_prev = &TAILQ_NEXT((listelm), field);		\

} while (0)

#define	TAILQ_INSERT_BEFORE(listelm, elm, field) do {			\

	(elm)->field.tqe_prev = (listelm)->field.tqe_prev;		\

	TAILQ_NEXT((elm), field) = (listelm);				\

	*(listelm)->field.tqe_prev = (elm);				\

	(listelm)->field.tqe_prev = &TAILQ_NEXT((elm), field);		\

} while (0)

#define	TAILQ_INSERT_HEAD(head, elm, field) do {			\

	if ((TAILQ_NEXT((elm), field) = TAILQ_FIRST((head))) != NULL)	\

		TAILQ_FIRST((head))->field.tqe_prev =			\

		    &TAILQ_NEXT((elm), field);				\

	else								\

		(head)->tqh_last = &TAILQ_NEXT((elm), field);		\

	TAILQ_FIRST((head)) = (elm);					\

	(elm)->field.tqe_prev = &TAILQ_FIRST((head));			\

} while (0)

#define	TAILQ_INSERT_TAIL(head, elm, field) do {			\

	TAILQ_NEXT((elm), field) = NULL;				\

	(elm)->field.tqe_prev = (head)->tqh_last;			\

	*(head)->tqh_last = (elm);					\

	(head)->tqh_last = &TAILQ_NEXT((elm), field);			\

} while (0)

#define	TAILQ_LAST(head, headname)					\

	(*(((struct headname *)((head)->tqh_last))->tqh_last))

#define	TAILQ_NEXT(elm, field) ((elm)->field.tqe_next)

#define	TAILQ_PREV(elm, headname, field)				\

	(*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))

#define	TAILQ_REMOVE(head, elm, field) do {				\

	if ((TAILQ_NEXT((elm), field)) != NULL)				\

		TAILQ_NEXT((elm), field)->field.tqe_prev = 		\

		    (elm)->field.tqe_prev;				\

	else								\

		(head)->tqh_last = (elm)->field.tqe_prev;		\

	*(elm)->field.tqe_prev = TAILQ_NEXT((elm), field);		\

} while (0)

#ifdef _KERNEL

/*

 * XXX insque() and remque() are an old way of handling certain queues.

 * They bogusly assumes that all queue heads look alike.

 */

struct quehead {

	struct quehead *qh_link;

	struct quehead *qh_rlink;

};

#ifdef	__GNUC__

static __inline void

insque(void *a, void *b)

{

	struct quehead *element = (struct quehead *)a,

		 *head = (struct quehead *)b;

	element->qh_link = head->qh_link;

	element->qh_rlink = head;

	head->qh_link = element;

	element->qh_link->qh_rlink = element;

}

static __inline void

remque(void *a)

{

	struct quehead *element = (struct quehead *)a;

	element->qh_link->qh_rlink = element->qh_rlink;

	element->qh_rlink->qh_link = element->qh_link;

	element->qh_rlink = 0;

}

#else /* !__GNUC__ */

void	insque(void *a, void *b);

void	remque(void *a);

#endif /* __GNUC__ */

#endif /* _KERNEL */

#endif /* !_SYS_QUEUE_H_ */