/*	$NetBSD: queue.h,v 1.68 2014/11/19 08:10:01 uebayasi Exp $	*/

/*

 * 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 five types of data structures: singly-linked lists,

 * lists, simple queues, tail queues, and circular 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 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.

 */

/*

 * Include the definition of NULL only on NetBSD because sys/null.h

 * is not available elsewhere.  This conditional makes the header

 * portable and it can simply be dropped verbatim into any system.

 * The caveat is that on other systems some other header

 * must provide NULL before the macros can be used.

 */

#ifdef __NetBSD__

#include <sys/null.h>

#endif

#if defined(QUEUEDEBUG)

# if defined(_KERNEL)

#  define QUEUEDEBUG_ABORT(...) panic(__VA_ARGS__)

# else

#  include <err.h>

#  define QUEUEDEBUG_ABORT(...) err(1, __VA_ARGS__)

# endif

#endif

/*

 * 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 access methods.

 */

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

#define	SLIST_END(head)		NULL

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

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

#define	SLIST_FOREACH(var, head, field)					\

	for((var) = (head)->slh_first;					\

	    (var) != SLIST_END(head);					\

	    (var) = (var)->field.sle_next)

#define	SLIST_FOREACH_SAFE(var, head, field, tvar)			\

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

	    (var) != SLIST_END(head) &&					\

	    ((tvar) = SLIST_NEXT((var), field), 1);			\

	    (var) = (tvar))

/*

 * Singly-linked List functions.

 */

#define	SLIST_INIT(head) do {						\

	(head)->slh_first = SLIST_END(head);				\

} 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_AFTER(slistelm, field) do {			\

	(slistelm)->field.sle_next =					\

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

} 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)

/*

 * 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 access methods.

 */

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

#define	LIST_END(head)			NULL

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

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

#define	LIST_FOREACH(var, head, field)					\

	for ((var) = ((head)->lh_first);				\

	    (var) != LIST_END(head);					\

	    (var) = ((var)->field.le_next))

#define	LIST_FOREACH_SAFE(var, head, field, tvar)			\

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

	    (var) != LIST_END(head) &&					\

	    ((tvar) = LIST_NEXT((var), field), 1);			\

	    (var) = (tvar))

#define	LIST_MOVE(head1, head2) do {					\

	LIST_INIT((head2));						\

	if (!LIST_EMPTY((head1))) {					\

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

		LIST_INIT((head1));					\

	}								\

} while (/*CONSTCOND*/0)

/*

 * List functions.

 */

#if defined(QUEUEDEBUG)

#define	QUEUEDEBUG_LIST_INSERT_HEAD(head, elm, field)			\

	if ((head)->lh_first &&						\

	    (head)->lh_first->field.le_prev != &(head)->lh_first)	\

		QUEUEDEBUG_ABORT("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)					\

		QUEUEDEBUG_ABORT("LIST_* forw %p %s:%d", (elm),		\

		    __FILE__, __LINE__);				\

	if (*(elm)->field.le_prev != (elm))				\

		QUEUEDEBUG_ABORT("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 = LIST_END(head);				\

} 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) != 	\

	    LIST_END(head))						\

		(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) != LIST_END(head))\

		(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_REPLACE(elm, elm2, field) do {				\

	if (((elm2)->field.le_next = (elm)->field.le_next) != NULL)	\

		(elm2)->field.le_next->field.le_prev =			\

		    &(elm2)->field.le_next;				\

	(elm2)->field.le_prev = (elm)->field.le_prev;			\

	*(elm2)->field.le_prev = (elm2);				\

	QUEUEDEBUG_LIST_POSTREMOVE((elm), field)			\

} while (/*CONSTCOND*/0)

/*

 * 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 access methods.

 */

#define	SIMPLEQ_FIRST(head)		((head)->sqh_first)

#define	SIMPLEQ_END(head)		NULL

#define	SIMPLEQ_EMPTY(head)		((head)->sqh_first == SIMPLEQ_END(head))

#define	SIMPLEQ_NEXT(elm, field)	((elm)->field.sqe_next)

#define	SIMPLEQ_FOREACH(var, head, field)				\

	for ((var) = ((head)->sqh_first);				\

	    (var) != SIMPLEQ_END(head);					\

	    (var) = ((var)->field.sqe_next))

#define	SIMPLEQ_FOREACH_SAFE(var, head, field, next)			\

	for ((var) = ((head)->sqh_first);				\

	    (var) != SIMPLEQ_END(head) &&				\

	    ((next = ((var)->field.sqe_next)), 1);			\

	    (var) = (next))

/*

 * 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_AFTER(head, elm, field) do {			\

	if (((elm)->field.sqe_next = (elm)->field.sqe_next->field.sqe_next) \

	    == NULL)							\

		(head)->sqh_last = &(elm)->field.sqe_next;		\

} 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_CONCAT(head1, head2) do {				\

	if (!SIMPLEQ_EMPTY((head2))) {					\

		*(head1)->sqh_last = (head2)->sqh_first;		\

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

		SIMPLEQ_INIT((head2));					\

	}								\

} while (/*CONSTCOND*/0)

#define	SIMPLEQ_LAST(head, type, field)					\

	(SIMPLEQ_EMPTY((head)) ?						\

		NULL :							\

	        ((struct type *)(void *)				\

		((char *)((head)->sqh_last) - offsetof(struct type, field))))

/*

 * Tail queue definitions.

 */

#define	_TAILQ_HEAD(name, type, qual)					\

struct name {								\

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

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

}

#define TAILQ_HEAD(name, type)	_TAILQ_HEAD(name, struct type,)

#define	TAILQ_HEAD_INITIALIZER(head)					\

	{ TAILQ_END(head), &(head).tqh_first }

#define	_TAILQ_ENTRY(type, qual)					\

struct {								\

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

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

}

#define TAILQ_ENTRY(type)	_TAILQ_ENTRY(struct type,)

/*

 * Tail queue access methods.

 */

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

#define	TAILQ_END(head)			(NULL)

#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_EMPTY(head)		(TAILQ_FIRST(head) == TAILQ_END(head))

#define	TAILQ_FOREACH(var, head, field)					\

	for ((var) = ((head)->tqh_first);				\

	    (var) != TAILQ_END(head);					\

	    (var) = ((var)->field.tqe_next))

#define	TAILQ_FOREACH_SAFE(var, head, field, next)			\

	for ((var) = ((head)->tqh_first);				\

	    (var) != TAILQ_END(head) &&					\

	    ((next) = TAILQ_NEXT(var, field), 1); (var) = (next))

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

	for ((var) = (*(((struct headname *)((head)->tqh_last))->tqh_last));\

	    (var) != TAILQ_END(head);					\

	    (var) = (*(((struct headname *)((var)->field.tqe_prev))->tqh_last)))

#define	TAILQ_FOREACH_REVERSE_SAFE(var, head, headname, field, prev)	\

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

	    (var) != TAILQ_END(head) && 				\

	    ((prev) = TAILQ_PREV((var), headname, field), 1); (var) = (prev))

/*

 * Tail queue functions.

 */

#if defined(QUEUEDEBUG)

#define	QUEUEDEBUG_TAILQ_INSERT_HEAD(head, elm, field)			\

	if ((head)->tqh_first &&					\

	    (head)->tqh_first->field.tqe_prev != &(head)->tqh_first)	\

		QUEUEDEBUG_ABORT("TAILQ_INSERT_HEAD %p %s:%d", (head),	\

		    __FILE__, __LINE__);

#define	QUEUEDEBUG_TAILQ_INSERT_TAIL(head, elm, field)			\

	if (*(head)->tqh_last != NULL)					\

		QUEUEDEBUG_ABORT("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)					\

		QUEUEDEBUG_ABORT("TAILQ_* forw %p %s:%d", (elm),	\

		    __FILE__, __LINE__);				\

	if (*(elm)->field.tqe_prev != (elm))				\

		QUEUEDEBUG_ABORT("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)			\

		QUEUEDEBUG_ABORT("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 = TAILQ_END(head);				\

	(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) != TAILQ_END(head))\

		(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 = TAILQ_END(head);			\

	(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) != 	\

	    TAILQ_END(head))						\

		(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) != TAILQ_END(head))			\

		(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)

#define TAILQ_REPLACE(head, elm, elm2, field) do {			\

        if (((elm2)->field.tqe_next = (elm)->field.tqe_next) != 	\

	    TAILQ_END(head))   						\

                (elm2)->field.tqe_next->field.tqe_prev =		\

                    &(elm2)->field.tqe_next;				\

        else								\

                (head)->tqh_last = &(elm2)->field.tqe_next;		\

        (elm2)->field.tqe_prev = (elm)->field.tqe_prev;			\

        *(elm2)->field.tqe_prev = (elm2);				\

	QUEUEDEBUG_TAILQ_POSTREMOVE((elm), field);			\

} while (/*CONSTCOND*/0)

#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 (/*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 access methods.

 */

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

#define	STAILQ_END(head)	NULL

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

#define	STAILQ_EMPTY(head)	(STAILQ_FIRST(head) == STAILQ_END(head))

/*

 * 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_FOREACH_SAFE(var, head, field, tvar)			\

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

	    (var) && ((tvar) = STAILQ_NEXT((var), field), 1);		\

	    (var) = (tvar))

#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 (/*CONSTCOND*/0)

#define	STAILQ_LAST(head, type, field)					\

	(STAILQ_EMPTY((head)) ?						\

		NULL :							\

	        ((struct type *)(void *)				\

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

#ifndef _KERNEL

/*

 * Circular queue definitions. Do not use. We still keep the macros

 * for compatibility but because of pointer aliasing issues their use

 * is discouraged!

 */

/*

 * __launder_type():  We use this ugly hack to work around the the compiler

 * noticing that two types may not alias each other and elide tests in code.

 * We hit this in the CIRCLEQ macros when comparing 'struct name *' and

 * 'struct type *' (see CIRCLEQ_HEAD()).  Modern compilers (such as GCC

 * 4.8) declare these comparisons as always false, causing the code to

 * not run as designed.

 *

 * This hack is only to be used for comparisons and thus can be fully const.

 * Do not use for assignment.

 *

 * If we ever choose to change the ABI of the CIRCLEQ macros, we could fix

 * this by changing the head/tail sentinal values, but see the note above

 * this one.

 */

static __inline const void * __launder_type(const void *);

static __inline const void *

__launder_type(const void *__x)

{

	__asm __volatile("" : "+r" (__x));

	return __x;

}

#if defined(QUEUEDEBUG)

#define QUEUEDEBUG_CIRCLEQ_HEAD(head, field)				\

	if ((head)->cqh_first != CIRCLEQ_ENDC(head) &&			\

	    (head)->cqh_first->field.cqe_prev != CIRCLEQ_ENDC(head))	\

		QUEUEDEBUG_ABORT("CIRCLEQ head forw %p %s:%d", (head),	\

		      __FILE__, __LINE__);				\

	if ((head)->cqh_last != CIRCLEQ_ENDC(head) &&			\

	    (head)->cqh_last->field.cqe_next != CIRCLEQ_ENDC(head))	\

		QUEUEDEBUG_ABORT("CIRCLEQ head back %p %s:%d", (head),	\

		      __FILE__, __LINE__);

#define QUEUEDEBUG_CIRCLEQ_ELM(head, elm, field)			\

	if ((elm)->field.cqe_next == CIRCLEQ_ENDC(head)) {		\

		if ((head)->cqh_last != (elm))				\

			QUEUEDEBUG_ABORT("CIRCLEQ elm last %p %s:%d",	\

			    (elm), __FILE__, __LINE__);			\

	} else {							\

		if ((elm)->field.cqe_next->field.cqe_prev != (elm))	\

			QUEUEDEBUG_ABORT("CIRCLEQ elm forw %p %s:%d",	\

			    (elm), __FILE__, __LINE__);			\

	}								\

	if ((elm)->field.cqe_prev == CIRCLEQ_ENDC(head)) {		\

		if ((head)->cqh_first != (elm))				\

			QUEUEDEBUG_ABORT("CIRCLEQ elm first %p %s:%d",	\

			    (elm), __FILE__, __LINE__);			\

	} else {							\

		if ((elm)->field.cqe_prev->field.cqe_next != (elm))	\

			QUEUEDEBUG_ABORT("CIRCLEQ elm prev %p %s:%d",	\

			    (elm), __FILE__, __LINE__);			\

	}

#define QUEUEDEBUG_CIRCLEQ_POSTREMOVE(elm, field)			\

	(elm)->field.cqe_next = (void *)1L;				\

	(elm)->field.cqe_prev = (void *)1L;

#else

#define QUEUEDEBUG_CIRCLEQ_HEAD(head, field)

#define QUEUEDEBUG_CIRCLEQ_ELM(head, elm, field)

#define QUEUEDEBUG_CIRCLEQ_POSTREMOVE(elm, field)

#endif

#define	CIRCLEQ_HEAD(name, type)					\

struct name {								\

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

	struct type *cqh_last;		/* last element */		\

}

#define	CIRCLEQ_HEAD_INITIALIZER(head)					\

	{ CIRCLEQ_END(&head), CIRCLEQ_END(&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 = CIRCLEQ_END(head);				\

	(head)->cqh_last = CIRCLEQ_END(head);				\

} while (/*CONSTCOND*/0)

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

	QUEUEDEBUG_CIRCLEQ_HEAD((head), field)				\

	QUEUEDEBUG_CIRCLEQ_ELM((head), (listelm), field)		\

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

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

	if ((listelm)->field.cqe_next == CIRCLEQ_ENDC(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 {		\

	QUEUEDEBUG_CIRCLEQ_HEAD((head), field)				\

	QUEUEDEBUG_CIRCLEQ_ELM((head), (listelm), field)		\

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

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

	if ((listelm)->field.cqe_prev == CIRCLEQ_ENDC(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 {			\

	QUEUEDEBUG_CIRCLEQ_HEAD((head), field)				\

	(elm)->field.cqe_next = (head)->cqh_first;			\

	(elm)->field.cqe_prev = CIRCLEQ_END(head);			\

	if ((head)->cqh_last == CIRCLEQ_ENDC(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 {			\

	QUEUEDEBUG_CIRCLEQ_HEAD((head), field)				\

	(elm)->field.cqe_next = CIRCLEQ_END(head);			\

	(elm)->field.cqe_prev = (head)->cqh_last;			\

	if ((head)->cqh_first == CIRCLEQ_ENDC(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 {				\

	QUEUEDEBUG_CIRCLEQ_HEAD((head), field)				\

	QUEUEDEBUG_CIRCLEQ_ELM((head), (elm), field)			\

	if ((elm)->field.cqe_next == CIRCLEQ_ENDC(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 == CIRCLEQ_ENDC(head))		\

		(head)->cqh_first = (elm)->field.cqe_next;		\

	else								\

		(elm)->field.cqe_prev->field.cqe_next =			\

		    (elm)->field.cqe_next;				\

	QUEUEDEBUG_CIRCLEQ_POSTREMOVE((elm), field)			\

} while (/*CONSTCOND*/0)

#define	CIRCLEQ_FOREACH(var, head, field)				\

	for ((var) = ((head)->cqh_first);				\

		(var) != CIRCLEQ_ENDC(head);				\

		(var) = ((var)->field.cqe_next))

#define	CIRCLEQ_FOREACH_REVERSE(var, head, field)			\

	for ((var) = ((head)->cqh_last);				\

		(var) != CIRCLEQ_ENDC(head);				\

		(var) = ((var)->field.cqe_prev))

/*

 * Circular queue access methods.

 */

#define	CIRCLEQ_FIRST(head)		((head)->cqh_first)

#define	CIRCLEQ_LAST(head)		((head)->cqh_last)

/* For comparisons */

#define	CIRCLEQ_ENDC(head)		(__launder_type(head))

/* For assignments */

#define	CIRCLEQ_END(head)		((void *)(head))

#define	CIRCLEQ_NEXT(elm, field)	((elm)->field.cqe_next)

#define	CIRCLEQ_PREV(elm, field)	((elm)->field.cqe_prev)

#define	CIRCLEQ_EMPTY(head)						\

    (CIRCLEQ_FIRST(head) == CIRCLEQ_ENDC(head))

#define CIRCLEQ_LOOP_NEXT(head, elm, field)				\

	(((elm)->field.cqe_next == CIRCLEQ_ENDC(head))			\

	    ? ((head)->cqh_first)					\

	    : (elm->field.cqe_next))

#define CIRCLEQ_LOOP_PREV(head, elm, field)				\

	(((elm)->field.cqe_prev == CIRCLEQ_ENDC(head))			\

	    ? ((head)->cqh_last)					\

	    : (elm->field.cqe_prev))

#endif /* !_KERNEL */

#endif	/* !_SYS_QUEUE_H_ */