/*	$NetBSD: queue.h,v 1.37 2004/03/23 10:50:31 he Exp $	*/
/*	$Id: queue.h 373 2005-09-27 22:53:15Z orange $ */

/*
 * 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. 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
 */

#ifndef _SYS_QUEUE_H_
#define _SYS_QUEUE_H_

/*
 * This file defines seven types of data structures:
 * singly-linked lists, lists, simple queues, tail queues, singly-linked
 * tail queues, circular queues, and simple priority 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 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 simple queue is headed by a pair of pointers, one the head of the
 * list and the other to the tail of the list. The elements are singly
 * linked to save space, so only elements can only be removed from the
 * head of the list. 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. A simple queue 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.
 *
 * A circle 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 circle queue may be traversed in either direction, but has a more
 * complex end of list detection.
 *
 * For details on the use of these macros, see the queue(3) manual page.
 *
 *			SLIST	LIST	STAILQ	TAILQ	CIRCLEQ SIMPLEQ SPRIOQ
 * _HEAD		+	+	+	+	+	+	+
 * _HEAD_INITIALIZER	+	+	+	+	+	+	+
 * _ENTRY		+	+	+	+	+	+	+
 * _INIT		+	+	+	+	+	+	+
 * _EMPTY		+	+	+	+	+	+	+
 * _FIRST		+	+	+	+	+	+	+
 * _NEXT		+	+	+	+	+	+	+
 * _PREV		-	-	-	+	+	-	-
 * _LAST		-	-	+	+	+	-	-
 * _FOREACH		+	+	+	+	+	+	+
 * _FOREACH_REVERSE	-	-	-	+	+	-	-
 * _INSERT		-	-	-	-	-	-	+
 * _INSERT_HEAD		+	+	+	+	+	+	-
 * _INSERT_BEFORE	-	+	-	+	+	-	-
 * _INSERT_AFTER	+	+	+	+	+	+	-
 * _INSERT_TAIL		-	-	+	+	+	+	-
 * _REMOVE_HEAD		+	-	+	-	-	+	+
 * _REMOVE		+	+	+	+	+	+	+
 * _VALUE		-	-	-	-	-	-	+
 *
 */

/*
 * List definitions.
 */
#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.
 */
#if defined(_KERNEL) && defined(QUEUEDEBUG)
#define QUEUEDEBUG_LIST_INSERT_HEAD(head, elm, field)			\
	if ((head)->lh_first &&						\
	    (head)->lh_first->field.le_prev != &(head)->lh_first)	\
		panic("LIST_INSERT_HEAD %p %s:%d", (head), __FILE__, __LINE__);
#define QUEUEDEBUG_LIST_OP(elm, field)					\
	if ((elm)->field.le_next &&					\
	    (elm)->field.le_next->field.le_prev !=			\
	    &(elm)->field.le_next)					\
		panic("LIST_* forw %p %s:%d", (elm), __FILE__, __LINE__);\
	if (*(elm)->field.le_prev != (elm))				\
		panic("LIST_* back %p %s:%d", (elm), __FILE__, __LINE__);
#define QUEUEDEBUG_LIST_POSTREMOVE(elm, field)				\
	(elm)->field.le_next = (void *)1L;				\
	(elm)->field.le_prev = (void *)1L;
#else
#define QUEUEDEBUG_LIST_INSERT_HEAD(head, elm, field)
#define QUEUEDEBUG_LIST_OP(elm, field)
#define QUEUEDEBUG_LIST_POSTREMOVE(elm, field)
#endif

#define LIST_INIT(head) do {						\
	(head)->lh_first = NULL;					\
} while (/*CONSTCOND*/0)

#define LIST_INSERT_AFTER(listelm, elm, field) do {			\
	QUEUEDEBUG_LIST_OP((listelm), field)				\
	if (((elm)->field.le_next = (listelm)->field.le_next) != NULL)	\
		(listelm)->field.le_next->field.le_prev =		\
		    &(elm)->field.le_next;				\
	(listelm)->field.le_next = (elm);				\
	(elm)->field.le_prev = &(listelm)->field.le_next;		\
} while (/*CONSTCOND*/0)

#define LIST_INSERT_BEFORE(listelm, elm, field) do {			\
	QUEUEDEBUG_LIST_OP((listelm), field)				\
	(elm)->field.le_prev = (listelm)->field.le_prev;		\
	(elm)->field.le_next = (listelm);				\
	*(listelm)->field.le_prev = (elm);				\
	(listelm)->field.le_prev = &(elm)->field.le_next;		\
} while (/*CONSTCOND*/0)

#define LIST_INSERT_HEAD(head, elm, field) do {				\
	QUEUEDEBUG_LIST_INSERT_HEAD((head), (elm), field)		\
	if (((elm)->field.le_next = (head)->lh_first) != NULL)		\
		(head)->lh_first->field.le_prev = &(elm)->field.le_next;\
	(head)->lh_first = (elm);					\
	(elm)->field.le_prev = &(head)->lh_first;			\
} while (/*CONSTCOND*/0)

#define LIST_REMOVE(elm, field) do {					\
	QUEUEDEBUG_LIST_OP((elm), field)				\
	if ((elm)->field.le_next != NULL)				\
		(elm)->field.le_next->field.le_prev =			\
		    (elm)->field.le_prev;				\
	*(elm)->field.le_prev = (elm)->field.le_next;			\
	QUEUEDEBUG_LIST_POSTREMOVE((elm), field)			\
} while (/*CONSTCOND*/0)

#define LIST_FOREACH(var, head, field)					\
	for ((var) = ((head)->lh_first);				\
		(var);							\
		(var) = ((var)->field.le_next))

/*
 * List access methods.
 */
#define LIST_EMPTY(head)		((head)->lh_first == NULL)
#define LIST_FIRST(head)		((head)->lh_first)
#define LIST_NEXT(elm, field)		((elm)->field.le_next)

/*
 * Singly-linked List definitions.
 */
#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_NEXT(elm, field)	((elm)->field.sle_next)

#define SLIST_FOREACH(var, head, field)					\
	for((var) = (head)->slh_first; (var); (var) = (var)->field.sle_next)

#define SLIST_INIT(head) do {						\
	(head)->slh_first = NULL;					\
} while (/*CONSTCOND*/0)

#define SLIST_INSERT_AFTER(slistelm, elm, field) do {			\
	(elm)->field.sle_next = (slistelm)->field.sle_next;		\
	(slistelm)->field.sle_next = (elm);				\
} while (/*CONSTCOND*/0)

#define SLIST_INSERT_HEAD(head, elm, field) do {			\
	(elm)->field.sle_next = (head)->slh_first;			\
	(head)->slh_first = (elm);					\
} while (/*CONSTCOND*/0)

#define SLIST_REMOVE_HEAD(head, field) do {				\
	(head)->slh_first = (head)->slh_first->field.sle_next;		\
} while (/*CONSTCOND*/0)

#define SLIST_REMOVE(head, elm, type, field) do {			\
	if ((head)->slh_first == (elm)) {				\
		SLIST_REMOVE_HEAD((head), field);			\
	}								\
	else {								\
		struct type *curelm = (head)->slh_first;		\
		while(curelm->field.sle_next != (elm))			\
			curelm = curelm->field.sle_next;		\
		curelm->field.sle_next =				\
		    curelm->field.sle_next->field.sle_next;		\
	}								\
} while (/*CONSTCOND*/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_INIT(head) do {						\
	(head)->stqh_first = NULL;					\
	(head)->stqh_last = &(head)->stqh_first;				\
} while (/*CONSTCOND*/0)

#define STAILQ_INSERT_HEAD(head, elm, field) do {			\
	if (((elm)->field.stqe_next = (head)->stqh_first) == NULL)	\
		(head)->stqh_last = &(elm)->field.stqe_next;		\
	(head)->stqh_first = (elm);					\
} while (/*CONSTCOND*/0)

#define STAILQ_INSERT_TAIL(head, elm, field) do {			\
	(elm)->field.stqe_next = NULL;					\
	*(head)->stqh_last = (elm);					\
	(head)->stqh_last = &(elm)->field.stqe_next;			\
} while (/*CONSTCOND*/0)

#define STAILQ_INSERT_AFTER(head, listelm, elm, field) do {		\
	if (((elm)->field.stqe_next = (listelm)->field.stqe_next) == NULL)\
		(head)->stqh_last = &(elm)->field.stqe_next;		\
	(listelm)->field.stqe_next = (elm);				\
} while (/*CONSTCOND*/0)

#define STAILQ_REMOVE_HEAD(head, field) do {				\
	if (((head)->stqh_first = (head)->stqh_first->field.stqe_next) == NULL) \
		(head)->stqh_last = &(head)->stqh_first;			\
} while (/*CONSTCOND*/0)

#define STAILQ_REMOVE(head, elm, type, field) do {			\
	if ((head)->stqh_first == (elm)) {				\
		STAILQ_REMOVE_HEAD((head), field);			\
	} else {							\
		struct type *curelm = (head)->stqh_first;		\
		while (curelm->field.stqe_next != (elm))			\
			curelm = curelm->field.stqe_next;		\
		if ((curelm->field.stqe_next =				\
			curelm->field.stqe_next->field.stqe_next) == NULL) \
			    (head)->stqh_last = &(curelm)->field.stqe_next; \
	}								\
} while (/*CONSTCOND*/0)

#define STAILQ_FOREACH(var, head, field)				\
	for ((var) = ((head)->stqh_first);				\
		(var);							\
		(var) = ((var)->field.stqe_next))

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

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

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

/*
 * Simple queue definitions.
 */
#define SIMPLEQ_HEAD(name, type)					\
struct name {								\
	struct type *sqh_first; /* first element */			\
	struct type **sqh_last; /* addr of last next element */		\
}

#define SIMPLEQ_HEAD_INITIALIZER(head)					\
	{ NULL, &(head).sqh_first }

#define SIMPLEQ_ENTRY(type)						\
struct {								\
	struct type *sqe_next;	/* next element */			\
}

/*
 * Simple queue functions.
 */
#define SIMPLEQ_INIT(head) do {						\
	(head)->sqh_first = NULL;					\
	(head)->sqh_last = &(head)->sqh_first;				\
} while (/*CONSTCOND*/0)

#define SIMPLEQ_INSERT_HEAD(head, elm, field) do {			\
	if (((elm)->field.sqe_next = (head)->sqh_first) == NULL)	\
		(head)->sqh_last = &(elm)->field.sqe_next;		\
	(head)->sqh_first = (elm);					\
} while (/*CONSTCOND*/0)

#define SIMPLEQ_INSERT_TAIL(head, elm, field) do {			\
	(elm)->field.sqe_next = NULL;					\
	*(head)->sqh_last = (elm);					\
	(head)->sqh_last = &(elm)->field.sqe_next;			\
} while (/*CONSTCOND*/0)

#define SIMPLEQ_INSERT_AFTER(head, listelm, elm, field) do {		\
	if (((elm)->field.sqe_next = (listelm)->field.sqe_next) == NULL)\
		(head)->sqh_last = &(elm)->field.sqe_next;		\
	(listelm)->field.sqe_next = (elm);				\
} while (/*CONSTCOND*/0)

#define SIMPLEQ_REMOVE_HEAD(head, field) do {				\
	if (((head)->sqh_first = (head)->sqh_first->field.sqe_next) == NULL) \
		(head)->sqh_last = &(head)->sqh_first;			\
} while (/*CONSTCOND*/0)

#define SIMPLEQ_REMOVE(head, elm, type, field) do {			\
	if ((head)->sqh_first == (elm)) {				\
		SIMPLEQ_REMOVE_HEAD((head), field);			\
	} else {							\
		struct type *curelm = (head)->sqh_first;		\
		while (curelm->field.sqe_next != (elm))			\
			curelm = curelm->field.sqe_next;		\
		if ((curelm->field.sqe_next =				\
			curelm->field.sqe_next->field.sqe_next) == NULL) \
			    (head)->sqh_last = &(curelm)->field.sqe_next; \
	}								\
} while (/*CONSTCOND*/0)

#define SIMPLEQ_FOREACH(var, head, field)				\
	for ((var) = ((head)->sqh_first);				\
		(var);							\
		(var) = ((var)->field.sqe_next))

/*
 * Simple queue access methods.
 */
#define SIMPLEQ_EMPTY(head)		((head)->sqh_first == NULL)
#define SIMPLEQ_FIRST(head)		((head)->sqh_first)
#define SIMPLEQ_NEXT(elm, field)	((elm)->field.sqe_next)

/*
 * Tail queue definitions.
 */
#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.
 */
#if defined(_KERNEL) && defined(QUEUEDEBUG)
#define QUEUEDEBUG_TAILQ_INSERT_HEAD(head, elm, field)			\
	if ((head)->tqh_first &&					\
	    (head)->tqh_first->field.tqe_prev != &(head)->tqh_first)	\
		panic("TAILQ_INSERT_HEAD %p %s:%d", (head), __FILE__, __LINE__);
#define QUEUEDEBUG_TAILQ_INSERT_TAIL(head, elm, field)			\
	if (*(head)->tqh_last != NULL)					\
		panic("TAILQ_INSERT_TAIL %p %s:%d", (head), __FILE__, __LINE__);
#define QUEUEDEBUG_TAILQ_OP(elm, field)					\
	if ((elm)->field.tqe_next &&					\
	    (elm)->field.tqe_next->field.tqe_prev !=			\
	    &(elm)->field.tqe_next)					\
		panic("TAILQ_* forw %p %s:%d", (elm), __FILE__, __LINE__);\
	if (*(elm)->field.tqe_prev != (elm))				\
		panic("TAILQ_* back %p %s:%d", (elm), __FILE__, __LINE__);
#define QUEUEDEBUG_TAILQ_PREREMOVE(head, elm, field)			\
	if ((elm)->field.tqe_next == NULL &&				\
	    (head)->tqh_last != &(elm)->field.tqe_next)			\
		panic("TAILQ_PREREMOVE head %p elm %p %s:%d",		\
		      (head), (elm), __FILE__, __LINE__);
#define QUEUEDEBUG_TAILQ_POSTREMOVE(elm, field)				\
	(elm)->field.tqe_next = (void *)1L;				\
	(elm)->field.tqe_prev = (void *)1L;
#else
#define QUEUEDEBUG_TAILQ_INSERT_HEAD(head, elm, field)
#define QUEUEDEBUG_TAILQ_INSERT_TAIL(head, elm, field)
#define QUEUEDEBUG_TAILQ_OP(elm, field)
#define QUEUEDEBUG_TAILQ_PREREMOVE(head, elm, field)
#define QUEUEDEBUG_TAILQ_POSTREMOVE(elm, field)
#endif

#define TAILQ_INIT(head) do {						\
	(head)->tqh_first = NULL;					\
	(head)->tqh_last = &(head)->tqh_first;				\
} while (/*CONSTCOND*/0)

#define TAILQ_INSERT_HEAD(head, elm, field) do {			\
	QUEUEDEBUG_TAILQ_INSERT_HEAD((head), (elm), field)		\
	if (((elm)->field.tqe_next = (head)->tqh_first) != NULL)	\
		(head)->tqh_first->field.tqe_prev =			\
		    &(elm)->field.tqe_next;				\
	else								\
		(head)->tqh_last = &(elm)->field.tqe_next;		\
	(head)->tqh_first = (elm);					\
	(elm)->field.tqe_prev = &(head)->tqh_first;			\
} while (/*CONSTCOND*/0)

#define TAILQ_INSERT_TAIL(head, elm, field) do {			\
	QUEUEDEBUG_TAILQ_INSERT_TAIL((head), (elm), field)		\
	(elm)->field.tqe_next = NULL;					\
	(elm)->field.tqe_prev = (head)->tqh_last;			\
	*(head)->tqh_last = (elm);					\
	(head)->tqh_last = &(elm)->field.tqe_next;			\
} while (/*CONSTCOND*/0)

#define TAILQ_INSERT_AFTER(head, listelm, elm, field) do {		\
	QUEUEDEBUG_TAILQ_OP((listelm), field)				\
	if (((elm)->field.tqe_next = (listelm)->field.tqe_next) != NULL)\
		(elm)->field.tqe_next->field.tqe_prev =			\
		    &(elm)->field.tqe_next;				\
	else								\
		(head)->tqh_last = &(elm)->field.tqe_next;		\
	(listelm)->field.tqe_next = (elm);				\
	(elm)->field.tqe_prev = &(listelm)->field.tqe_next;		\
} while (/*CONSTCOND*/0)

#define TAILQ_INSERT_BEFORE(listelm, elm, field) do {			\
	QUEUEDEBUG_TAILQ_OP((listelm), field)				\
	(elm)->field.tqe_prev = (listelm)->field.tqe_prev;		\
	(elm)->field.tqe_next = (listelm);				\
	*(listelm)->field.tqe_prev = (elm);				\
	(listelm)->field.tqe_prev = &(elm)->field.tqe_next;		\
} while (/*CONSTCOND*/0)

#define TAILQ_REMOVE(head, elm, field) do {				\
	QUEUEDEBUG_TAILQ_PREREMOVE((head), (elm), field)		\
	QUEUEDEBUG_TAILQ_OP((elm), field)				\
	if (((elm)->field.tqe_next) != NULL)				\
		(elm)->field.tqe_next->field.tqe_prev =			\
		    (elm)->field.tqe_prev;				\
	else								\
		(head)->tqh_last = (elm)->field.tqe_prev;		\
	*(elm)->field.tqe_prev = (elm)->field.tqe_next;			\
	QUEUEDEBUG_TAILQ_POSTREMOVE((elm), field);			\
} while (/*CONSTCOND*/0)

/*
 * Tail queue access methods.
 */
#define TAILQ_EMPTY(head)		((head)->tqh_first == NULL)
#define TAILQ_FIRST(head)		((head)->tqh_first)
#define TAILQ_NEXT(elm, field)		((elm)->field.tqe_next)

#define TAILQ_LAST(head, headname) \
	(*(((struct headname *)((head)->tqh_last))->tqh_last))
#define TAILQ_PREV(elm, headname, field) \
	(*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))

#define TAILQ_FOREACH(var, head, field)					\
	for ((var) = ((head)->tqh_first);				\
		(var);							\
		(var) = ((var)->field.tqe_next))

#define TAILQ_FOREACH_REVERSE(var, head, headname, field)		\
	for ((var) = (*(((struct headname *)((head)->tqh_last))->tqh_last));	\
		(var);							\
		(var) = (*(((struct headname *)((var)->field.tqe_prev))->tqh_last)))

/*
 * Circular queue definitions.
 */
#define CIRCLEQ_HEAD(name, type)					\
struct name {								\
	struct type *cqh_first;		/* first element */		\
	struct type *cqh_last;		/* last element */		\
}

#define CIRCLEQ_HEAD_INITIALIZER(head)					\
	{ (void *)&head, (void *)&head }

#define CIRCLEQ_ENTRY(type)						\
struct {								\
	struct type *cqe_next;		/* next element */		\
	struct type *cqe_prev;		/* previous element */		\
}

/*
 * Circular queue functions.
 */
#define CIRCLEQ_INIT(head) do {						\
	(head)->cqh_first = (void *)(head);				\
	(head)->cqh_last = (void *)(head);				\
} while (/*CONSTCOND*/0)

#define CIRCLEQ_INSERT_AFTER(head, listelm, elm, field) do {		\
	(elm)->field.cqe_next = (listelm)->field.cqe_next;		\
	(elm)->field.cqe_prev = (listelm);				\
	if ((listelm)->field.cqe_next == (void *)(head))		\
		(head)->cqh_last = (elm);				\
	else								\
		(listelm)->field.cqe_next->field.cqe_prev = (elm);	\
	(listelm)->field.cqe_next = (elm);				\
} while (/*CONSTCOND*/0)

#define CIRCLEQ_INSERT_BEFORE(head, listelm, elm, field) do {		\
	(elm)->field.cqe_next = (listelm);				\
	(elm)->field.cqe_prev = (listelm)->field.cqe_prev;		\
	if ((listelm)->field.cqe_prev == (void *)(head))		\
		(head)->cqh_first = (elm);				\
	else								\
		(listelm)->field.cqe_prev->field.cqe_next = (elm);	\
	(listelm)->field.cqe_prev = (elm);				\
} while (/*CONSTCOND*/0)

#define CIRCLEQ_INSERT_HEAD(head, elm, field) do {			\
	(elm)->field.cqe_next = (head)->cqh_first;			\
	(elm)->field.cqe_prev = (void *)(head);				\
	if ((head)->cqh_last == (void *)(head))				\
		(head)->cqh_last = (elm);				\
	else								\
		(head)->cqh_first->field.cqe_prev = (elm);		\
	(head)->cqh_first = (elm);					\
} while (/*CONSTCOND*/0)

#define CIRCLEQ_INSERT_TAIL(head, elm, field) do {			\
	(elm)->field.cqe_next = (void *)(head);				\
	(elm)->field.cqe_prev = (head)->cqh_last;			\
	if ((head)->cqh_first == (void *)(head))			\
		(head)->cqh_first = (elm);				\
	else								\
		(head)->cqh_last->field.cqe_next = (elm);		\
	(head)->cqh_last = (elm);					\
} while (/*CONSTCOND*/0)

#define CIRCLEQ_REMOVE(head, elm, field) do {				\
	if ((elm)->field.cqe_next == (void *)(head))			\
		(head)->cqh_last = (elm)->field.cqe_prev;		\
	else								\
		(elm)->field.cqe_next->field.cqe_prev =			\
		    (elm)->field.cqe_prev;				\
	if ((elm)->field.cqe_prev == (void *)(head))			\
		(head)->cqh_first = (elm)->field.cqe_next;		\
	else								\
		(elm)->field.cqe_prev->field.cqe_next =			\
		    (elm)->field.cqe_next;				\
} while (/*CONSTCOND*/0)

#define CIRCLEQ_FOREACH(var, head, field)				\
	for ((var) = ((head)->cqh_first);				\
		(var) != (void *)(head);				\
		(var) = ((var)->field.cqe_next))

#define CIRCLEQ_FOREACH_REVERSE(var, head, field)			\
	for ((var) = ((head)->cqh_last);				\
		(var) != (void *)(head);				\
		(var) = ((var)->field.cqe_prev))

/*
 * Circular queue access methods.
 */
#define CIRCLEQ_EMPTY(head)		((head)->cqh_first == (void *)(head))
#define CIRCLEQ_FIRST(head)		((head)->cqh_first)
#define CIRCLEQ_LAST(head)		((head)->cqh_last)
#define CIRCLEQ_NEXT(elm, field)	((elm)->field.cqe_next)
#define CIRCLEQ_PREV(elm, field)	((elm)->field.cqe_prev)

/*
 * Simple priority queue definitions.
 */
#define SPRIOQ_HEAD(name, type)						\
struct name {								\
	struct type *sph_first;						\
}

#define SPRIOQ_HEAD_INITIALIZER(head)					\
	{ NULL }
#define SPRIOQ_ENTRY(type, valuetype)					\
struct {								\
	struct type *spe_next;						\
	valuetype spe_value;						\
}

/*
 * Simple priority queue functions.
 */
#define SPRIOQ_INSERT(head, elm, type, field, compar) do {		\
	struct type **curelm;						\
	for(curelm=&(head)->sph_first; 					\
			*curelm; 					\
			curelm=&(*curelm)->field.spe_next) {		\
		if( (compar)((elm), *curelm) < 0 ) {			\
			break;						\
		}							\
	}								\
	(elm)->field.spe_next=*curelm;					\
	*curelm=(elm);							\
} while (/*CONSTCOND*/0)

#define SPRIOQ_REMOVE_HEAD(head, field) do {				\
	(head)->sph_first = (head)->sph_first->field.spe_next;		\
} while (/*CONSTCOND*/0)

#define SPRIOQ_REMOVE(head, elm, type, field) do {			\
	if ((head)->sph_first == (elm)) {				\
		SPRIOQ_REMOVE_HEAD((head), field);			\
	}								\
	else {								\
		struct type *curelm = (head)->sph_first;		\
		while(curelm->field.spe_next != (elm))			\
			curelm = curelm->field.spe_next;		\
		curelm->field.spe_next =				\
		    curelm->field.spe_next->field.spe_next;		\
	}								\
} while (/*CONSTCOND*/0)

#define SPRIOQ_FOREACH(var, head, field)				\
	for((var) = (head)->sph_first; (var); (var) = (var)->field.spe_next)

/*
 * Simple priority queue access methods.
 */
#define SPRIOQ_EMPTY(head)		((head)->sph_first == NULL)
#define SPRIOQ_FIRST(head)		((head)->sph_first)
#define SPRIOQ_NEXT(elm, field)		((elm)->field.spe_next)
#define SPRIOQ_VALUE(elm, field)	((elm)->field.spe_value)

#endif	/* !_SYS_QUEUE_H_ */