//==========================================================================
//
//      include/sys/queue.h
//
//==========================================================================
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//
// -------------------------------------------
//
// Portions of this software may have been derived from OpenBSD, 
// FreeBSD or other sources, and are covered by the appropriate
// copyright disclaimers included herein.
//
// Portions created by Red Hat are
// Copyright (C) 2002 Red Hat, Inc. All Rights Reserved.
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//####BSDCOPYRIGHTEND####
//==========================================================================

/*
 * 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 1.32.2.4 2001/03/31 03:33:39 hsu Exp $
 */

#ifndef _SYS_QUEUE_H_
#define	_SYS_QUEUE_H_

/*
 * This file defines five types of data structures: singly-linked lists,
 * singly-linked tail queues, lists, 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 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.
 *
 * 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
 * _HEAD		+	+	+	+	+
 * _ENTRY		+	+	+	+	+
 * _INIT		+	+	+	+	+
 * _EMPTY		+	+	+	+	+
 * _FIRST		+	+	+	+	+
 * _NEXT		+	+	+	+	+
 * _PREV		-	-	-	+	+
 * _LAST		-	-	+	+	+
 * _FOREACH		+	+	+	+	+
 * _FOREACH_REVERSE	-	-	-	+	+
 * _INSERT_HEAD		+	+	+	+	+
 * _INSERT_BEFORE	-	+	-	+	+
 * _INSERT_AFTER	+	+	+	+	+
 * _INSERT_TAIL		-	-	+	+	+
 * _REMOVE_HEAD		+	-	+	-	-
 * _REMOVE		+	+	+	+	+
 *
 */

/*
 * 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_FOREACH(var, head, field)					\
	for((var) = (head)->slh_first; (var); (var) = (var)->field.sle_next)

#define SLIST_INIT(head) {						\
	(head)->slh_first = NULL;					\
}

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

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

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

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

/*
 * Singly-linked Tail queue definitions.
 */
#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_EMPTY(head) ((head)->stqh_first == NULL)

#define	STAILQ_INIT(head) do {						\
	(head)->stqh_first = NULL;					\
	(head)->stqh_last = &(head)->stqh_first;			\
} while (0)

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

#define	STAILQ_LAST(head, type, field)					\
	(STAILQ_EMPTY(head) ?						\
		NULL :							\
	        ((struct type *)					\
		((char *)((head)->stqh_last) - __offsetof(struct type, field))))

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

#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 (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 (0)

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

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

#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 (0)

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

/*
 * List definitions.
 */
#define LIST_HEAD(name, type)						\
struct name {								\
	struct type *lh_first;	/* first element */			\
}

#define LIST_HEAD_INITIALIZER(head)					\
	{ NULL }