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version 4.0

/*************************************************************************
* (C) 2015 AITNET ltd - Sofia/Bulgaria - <misho@aitnet.org>
*  by Michael Pounov <misho@elwix.org>
*
* $Author: misho $
* $Id: aqueue.h,v 1.2 2016/05/18 12:47:42 misho Exp $
*
**************************************************************************
The ELWIX and AITNET software is distributed under the following
terms:

All of the documentation and software included in the ELWIX and AITNET
Releases is copyrighted by ELWIX - Sofia/Bulgaria <info@elwix.org>

Copyright 2004 - 2015
	by Michael Pounov <misho@elwix.org>.  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 Michael Pounov <misho@elwix.org>
ELWIX - Embedded LightWeight unIX and its contributors.
4. Neither the name of AITNET 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 AITNET 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.
*/
/*-
 * 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.
 * 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: head/sys/sys/queue.h 279242 2015-02-24 17:36:44Z hselasky $
 */

#ifndef _SYS_QUEUE_H_
#define	_SYS_QUEUE_H_

//#include <sys/cdefs.h>

/*
 * 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 be traversed in either 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_FROM		+	+	+	+
 * _FOREACH_SAFE		+	+	+	+
 * _FOREACH_FROM_SAFE		+	+	+	+
 * _FOREACH_REVERSE		-	-	-	+
 * _FOREACH_REVERSE_FROM	-	-	-	+
 * _FOREACH_REVERSE_SAFE	-	-	-	+
 * _FOREACH_REVERSE_FROM_SAFE	-	-	-	+
 * _INSERT_HEAD			+	+	+	+
 * _INSERT_BEFORE		-	+	-	+
 * _INSERT_AFTER		+	+	+	+
 * _INSERT_TAIL			-	-	+	+
 * _CONCAT			-	-	+	+
 * _REMOVE_AFTER		+	-	+	-
 * _REMOVE_HEAD			+	-	+	-
 * _REMOVE			+	+	+	+
 * _SWAP			+	+	+	+
 *
 */
#ifdef QUEUE_MACRO_DEBUG
/* Store the last 2 places the queue element or head was altered */
struct qm_trace {
	unsigned long	 lastline;
	unsigned long	 prevline;
	const char	*lastfile;
	const char	*prevfile;
};

#define	TRACEBUF	struct qm_trace trace;
#define	TRACEBUF_INITIALIZER	{ __LINE__, 0, __FILE__, NULL } ,
#define	TRASHIT(x)	do {(x) = (void *)-1;} while (0)
#define	QMD_SAVELINK(name, link)	void **name = (void *)&(link)

#define	QMD_TRACE_HEAD(head) do {					\
	(head)->trace.prevline = (head)->trace.lastline;		\
	(head)->trace.prevfile = (head)->trace.lastfile;		\
	(head)->trace.lastline = __LINE__;				\
	(head)->trace.lastfile = __FILE__;				\
} while (0)

#define	QMD_TRACE_ELEM(elem) do {					\
	(elem)->trace.prevline = (elem)->trace.lastline;		\
	(elem)->trace.prevfile = (elem)->trace.lastfile;		\
	(elem)->trace.lastline = __LINE__;				\
	(elem)->trace.lastfile = __FILE__;				\
} while (0)

#else
#define	QMD_TRACE_ELEM(elem)
#define	QMD_TRACE_HEAD(head)
#define	QMD_SAVELINK(name, link)
#define	TRACEBUF
#define	TRACEBUF_INITIALIZER
#define	TRASHIT(x)
#endif	/* QUEUE_MACRO_DEBUG */

/*
 * 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_FOREACH_FROM(var, head, field)				\
	for ((var) = ((var) ? (var) : SLIST_FIRST((head)));		\
	    (var);							\
	    (var) = SLIST_NEXT((var), field))

#define	SLIST_FOREACH_SAFE(var, head, field, tvar)			\
	for ((var) = SLIST_FIRST((head));				\
	    (var) && ((tvar) = SLIST_NEXT((var), field), 1);		\
	    (var) = (tvar))

#define	SLIST_FOREACH_FROM_SAFE(var, head, field, tvar)			\
	for ((var) = ((var) ? (var) : SLIST_FIRST((head)));		\
	    (var) && ((tvar) = SLIST_NEXT((var), field), 1);		\
	    (var) = (tvar))

#define	SLIST_FOREACH_PREVPTR(var, varp, head, field)			\
	for ((varp) = &SLIST_FIRST((head));				\
	    ((var) = *(varp)) != NULL;					\
	    (varp) = &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 {			\
	QMD_SAVELINK(oldnext, (elm)->field.sle_next);			\
	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_REMOVE_AFTER(curelm, field);			\
	}								\
	TRASHIT(*oldnext);						\
} while (0)

#define SLIST_REMOVE_AFTER(elm, field) do {				\
	SLIST_NEXT(elm, field) =					\
	    SLIST_NEXT(SLIST_NEXT(elm, field), field);			\
} while (0)

#define	SLIST_REMOVE_HEAD(head, field) do {				\
	SLIST_FIRST((head)) = SLIST_NEXT(SLIST_FIRST((head)), field);	\
} while (0)

#define SLIST_SWAP(head1, head2, type) do {				\
	struct type *swap_first = SLIST_FIRST(head1);			\
	SLIST_FIRST(head1) = SLIST_FIRST(head2);			\
	SLIST_FIRST(head2) = swap_first;				\
} 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_FOREACH_FROM(var, head, field)				\
	for ((var) = ((var) ? (var) : STAILQ_FIRST((head)));		\
	   (var);							\
	   (var) = STAILQ_NEXT((var), field))

#define	STAILQ_FOREACH_SAFE(var, head, field, tvar)			\
	for ((var) = STAILQ_FIRST((head));				\
	    (var) && ((tvar) = STAILQ_NEXT((var), field), 1);		\
	    (var) = (tvar))

#define	STAILQ_FOREACH_FROM_SAFE(var, head, field, tvar)		\
	for ((var) = ((var) ? (var) : STAILQ_FIRST((head)));		\
	    (var) && ((tvar) = STAILQ_NEXT((var), field), 1);		\
	    (var) = (tvar))

#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 :					\
	    __containerof((head)->stqh_last, struct type, field.stqe_next))

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

#define	STAILQ_REMOVE(head, elm, type, field) do {			\
	QMD_SAVELINK(oldnext, (elm)->field.stqe_next);			\
	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);		\
		STAILQ_REMOVE_AFTER(head, curelm, field);		\
	}								\
	TRASHIT(*oldnext);						\
} while (0)

#define STAILQ_REMOVE_AFTER(head, elm, field) do {			\
	if ((STAILQ_NEXT(elm, field) =					\
	     STAILQ_NEXT(STAILQ_NEXT(elm, field), field)) == NULL)	\
		(head)->stqh_last = &STAILQ_NEXT((elm), 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_SWAP(head1, head2, type) do {				\
	struct type *swap_first = STAILQ_FIRST(head1);			\
	struct type **swap_last = (head1)->stqh_last;			\
	STAILQ_FIRST(head1) = STAILQ_FIRST(head2);			\
	(head1)->stqh_last = (head2)->stqh_last;			\
	STAILQ_FIRST(head2) = swap_first;				\
	(head2)->stqh_last = swap_last;					\
	if (STAILQ_EMPTY(head1))					\
		(head1)->stqh_last = &STAILQ_FIRST(head1);		\
	if (STAILQ_EMPTY(head2))					\
		(head2)->stqh_last = &STAILQ_FIRST(head2);		\
} 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.
 */

#if (defined(_KERNEL) && defined(INVARIANTS))
#define	QMD_LIST_CHECK_HEAD(head, field) do {				\
	if (LIST_FIRST((head)) != NULL &&				\
	    LIST_FIRST((head))->field.le_prev !=			\
	     &LIST_FIRST((head)))					\
		panic("Bad list head %p first->prev != head", (head));	\
} while (0)

#define	QMD_LIST_CHECK_NEXT(elm, field) do {				\
	if (LIST_NEXT((elm), field) != NULL &&				\
	    LIST_NEXT((elm), field)->field.le_prev !=			\
	     &((elm)->field.le_next))					\
	     	panic("Bad link elm %p next->prev != elm", (elm));	\
} while (0)

#define	QMD_LIST_CHECK_PREV(elm, field) do {				\
	if (*(elm)->field.le_prev != (elm))				\
		panic("Bad link elm %p prev->next != elm", (elm));	\
} while (0)
#else
#define	QMD_LIST_CHECK_HEAD(head, field)
#define	QMD_LIST_CHECK_NEXT(elm, field)
#define	QMD_LIST_CHECK_PREV(elm, field)
#endif /* (_KERNEL && INVARIANTS) */

#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_FOREACH_FROM(var, head, field)				\
	for ((var) = ((var) ? (var) : LIST_FIRST((head)));		\
	    (var);							\
	    (var) = LIST_NEXT((var), field))

#define	LIST_FOREACH_SAFE(var, head, field, tvar)			\
	for ((var) = LIST_FIRST((head));				\
	    (var) && ((tvar) = LIST_NEXT((var), field), 1);		\
	    (var) = (tvar))

#define	LIST_FOREACH_FROM_SAFE(var, head, field, tvar)			\
	for ((var) = ((var) ? (var) : LIST_FIRST((head)));		\
	    (var) && ((tvar) = LIST_NEXT((var), field), 1);		\
	    (var) = (tvar))

#define	LIST_INIT(head) do {						\
	LIST_FIRST((head)) = NULL;					\
} while (0)

#define	LIST_INSERT_AFTER(listelm, elm, field) do {			\
	QMD_LIST_CHECK_NEXT(listelm, field);				\
	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 {			\
	QMD_LIST_CHECK_PREV(listelm, field);				\
	(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 {				\
	QMD_LIST_CHECK_HEAD((head), field);				\
	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_PREV(elm, head, type, field)				\
	((elm)->field.le_prev == &LIST_FIRST((head)) ? NULL :		\
	    __containerof((elm)->field.le_prev, struct type, field.le_next))

#define	LIST_REMOVE(elm, field) do {					\
	QMD_SAVELINK(oldnext, (elm)->field.le_next);			\
	QMD_SAVELINK(oldprev, (elm)->field.le_prev);			\
	QMD_LIST_CHECK_NEXT(elm, field);				\
	QMD_LIST_CHECK_PREV(elm, field);				\
	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);		\
	TRASHIT(*oldnext);						\
	TRASHIT(*oldprev);						\
} while (0)

#define LIST_SWAP(head1, head2, type, field) do {			\
	struct type *swap_tmp = LIST_FIRST((head1));			\
	LIST_FIRST((head1)) = LIST_FIRST((head2));			\
	LIST_FIRST((head2)) = swap_tmp;					\
	if ((swap_tmp = LIST_FIRST((head1))) != NULL)			\
		swap_tmp->field.le_prev = &LIST_FIRST((head1));		\
	if ((swap_tmp = LIST_FIRST((head2))) != NULL)			\
		swap_tmp->field.le_prev = &LIST_FIRST((head2));		\
} 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 */		\
	TRACEBUF							\
}

#define	TAILQ_HEAD_INITIALIZER(head)					\
	{ NULL, &(head).tqh_first, TRACEBUF_INITIALIZER }

#define	TAILQ_ENTRY(type)						\
struct {								\
	struct type *tqe_next;	/* next element */			\
	struct type **tqe_prev;	/* address of previous next element */	\
	TRACEBUF							\
}

/*
 * Tail queue functions.
 */
#if (defined(_KERNEL) && defined(INVARIANTS))
#define	QMD_TAILQ_CHECK_HEAD(head, field) do {				\
	if (!TAILQ_EMPTY(head) &&					\
	    TAILQ_FIRST((head))->field.tqe_prev !=			\
	     &TAILQ_FIRST((head)))					\
		panic("Bad tailq head %p first->prev != head", (head));	\
} while (0)

#define	QMD_TAILQ_CHECK_TAIL(head, field) do {				\
	if (*(head)->tqh_last != NULL)					\
	    	panic("Bad tailq NEXT(%p->tqh_last) != NULL", (head)); 	\
} while (0)

#define	QMD_TAILQ_CHECK_NEXT(elm, field) do {				\
	if (TAILQ_NEXT((elm), field) != NULL &&				\
	    TAILQ_NEXT((elm), field)->field.tqe_prev !=			\
	     &((elm)->field.tqe_next))					\
		panic("Bad link elm %p next->prev != elm", (elm));	\
} while (0)

#define	QMD_TAILQ_CHECK_PREV(elm, field) do {				\
	if (*(elm)->field.tqe_prev != (elm))				\
		panic("Bad link elm %p prev->next != elm", (elm));	\
} while (0)
#else
#define	QMD_TAILQ_CHECK_HEAD(head, field)
#define	QMD_TAILQ_CHECK_TAIL(head, headname)
#define	QMD_TAILQ_CHECK_NEXT(elm, field)
#define	QMD_TAILQ_CHECK_PREV(elm, field)
#endif /* (_KERNEL && INVARIANTS) */

#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));					\
		QMD_TRACE_HEAD(head1);					\
		QMD_TRACE_HEAD(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_FROM(var, head, field)				\
	for ((var) = ((var) ? (var) : TAILQ_FIRST((head)));		\
	    (var);							\
	    (var) = TAILQ_NEXT((var), field))

#define	TAILQ_FOREACH_SAFE(var, head, field, tvar)			\
	for ((var) = TAILQ_FIRST((head));				\
	    (var) && ((tvar) = TAILQ_NEXT((var), field), 1);		\
	    (var) = (tvar))

#define	TAILQ_FOREACH_FROM_SAFE(var, head, field, tvar)			\
	for ((var) = ((var) ? (var) : TAILQ_FIRST((head)));		\
	    (var) && ((tvar) = TAILQ_NEXT((var), field), 1);		\
	    (var) = (tvar))

#define	TAILQ_FOREACH_REVERSE(var, head, headname, field)		\
	for ((var) = TAILQ_LAST((head), headname);			\
	    (var);							\
	    (var) = TAILQ_PREV((var), headname, field))

#define	TAILQ_FOREACH_REVERSE_FROM(var, head, headname, field)		\
	for ((var) = ((var) ? (var) : TAILQ_LAST((head), headname));	\
	    (var);							\
	    (var) = TAILQ_PREV((var), headname, field))

#define	TAILQ_FOREACH_REVERSE_SAFE(var, head, headname, field, tvar)	\
	for ((var) = TAILQ_LAST((head), headname);			\
	    (var) && ((tvar) = TAILQ_PREV((var), headname, field), 1);	\
	    (var) = (tvar))

#define	TAILQ_FOREACH_REVERSE_FROM_SAFE(var, head, headname, field, tvar) \
	for ((var) = ((var) ? (var) : TAILQ_LAST((head), headname));	\
	    (var) && ((tvar) = TAILQ_PREV((var), headname, field), 1);	\
	    (var) = (tvar))

#define	TAILQ_INIT(head) do {						\
	TAILQ_FIRST((head)) = NULL;					\
	(head)->tqh_last = &TAILQ_FIRST((head));			\
	QMD_TRACE_HEAD(head);						\
} while (0)

#define	TAILQ_INSERT_AFTER(head, listelm, elm, field) do {		\
	QMD_TAILQ_CHECK_NEXT(listelm, field);				\
	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);		\
		QMD_TRACE_HEAD(head);					\
	}								\
	TAILQ_NEXT((listelm), field) = (elm);				\
	(elm)->field.tqe_prev = &TAILQ_NEXT((listelm), field);		\
	QMD_TRACE_ELEM(&(elm)->field);					\
	QMD_TRACE_ELEM(&(listelm)->field);				\
} while (0)

#define	TAILQ_INSERT_BEFORE(listelm, elm, field) do {			\
	QMD_TAILQ_CHECK_PREV(listelm, field);				\
	(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);		\
	QMD_TRACE_ELEM(&(elm)->field);					\
	QMD_TRACE_ELEM(&(listelm)->field);				\
} while (0)

#define	TAILQ_INSERT_HEAD(head, elm, field) do {			\
	QMD_TAILQ_CHECK_HEAD(head, field);				\
	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));			\
	QMD_TRACE_HEAD(head);						\
	QMD_TRACE_ELEM(&(elm)->field);					\
} while (0)

#define	TAILQ_INSERT_TAIL(head, elm, field) do {			\
	QMD_TAILQ_CHECK_TAIL(head, field);				\
	TAILQ_NEXT((elm), field) = NULL;				\
	(elm)->field.tqe_prev = (head)->tqh_last;			\
	*(head)->tqh_last = (elm);					\
	(head)->tqh_last = &TAILQ_NEXT((elm), field);			\
	QMD_TRACE_HEAD(head);						\
	QMD_TRACE_ELEM(&(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 {				\
	QMD_SAVELINK(oldnext, (elm)->field.tqe_next);			\
	QMD_SAVELINK(oldprev, (elm)->field.tqe_prev);			\
	QMD_TAILQ_CHECK_NEXT(elm, field);				\
	QMD_TAILQ_CHECK_PREV(elm, field);				\
	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;		\
		QMD_TRACE_HEAD(head);					\
	}								\
	*(elm)->field.tqe_prev = TAILQ_NEXT((elm), field);		\
	TRASHIT(*oldnext);						\
	TRASHIT(*oldprev);						\
	QMD_TRACE_ELEM(&(elm)->field);					\
} while (0)

#define TAILQ_SWAP(head1, head2, type, field) do {			\
	struct type *swap_first = (head1)->tqh_first;			\
	struct type **swap_last = (head1)->tqh_last;			\
	(head1)->tqh_first = (head2)->tqh_first;			\
	(head1)->tqh_last = (head2)->tqh_last;				\
	(head2)->tqh_first = swap_first;				\
	(head2)->tqh_last = swap_last;					\
	if ((swap_first = (head1)->tqh_first) != NULL)			\
		swap_first->field.tqe_prev = &(head1)->tqh_first;	\
	else								\
		(head1)->tqh_last = &(head1)->tqh_first;		\
	if ((swap_first = (head2)->tqh_first) != NULL)			\
		swap_first->field.tqe_prev = &(head2)->tqh_first;	\
	else								\
		(head2)->tqh_last = &(head2)->tqh_first;		\
} while (0)

#endif /* !_SYS_QUEUE_H_ */