openbsd-compat/fake-queue.h - security/openssh-library - Rivoreo Source Code Repositories

 /*	$OpenBSD: queue.h,v 1.22 2001/06/23 04:39:35 angelos Exp $	*/
 /*	$NetBSD: queue.h,v 1.11 1996/05/16 05:17:14 mycroft 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. 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
  */

 #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 before or 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.
  */

 /*
  * 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)	(SLIST_FIRST(head) == SLIST_END(head))
 #define	SLIST_NEXT(elm, field)	((elm)->field.sle_next)

 #define	SLIST_FOREACH(var, head, field)					\
 	for((var) = SLIST_FIRST(head);					\
 	    (var) != SLIST_END(head);					\
 	    (var) = SLIST_NEXT(var, field))

 /*
  * Singly-linked List functions.
  */
 #define	SLIST_INIT(head) {						\
 	SLIST_FIRST(head) = SLIST_END(head);				\
 }

 #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_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)

 /*
  * 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)		(LIST_FIRST(head) == LIST_END(head))
 #define	LIST_NEXT(elm, field)		((elm)->field.le_next)

 #define LIST_FOREACH(var, head, field)					\
 	for((var) = LIST_FIRST(head);					\
 	    (var)!= LIST_END(head);					\
 	    (var) = LIST_NEXT(var, field))

 /*
  * List functions.
  */
 #define	LIST_INIT(head) do {						\
 	LIST_FIRST(head) = LIST_END(head);				\
 } while (0)

 #define LIST_INSERT_AFTER(listelm, elm, field) do {			\
 	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 (0)

 #define	LIST_INSERT_BEFORE(listelm, elm, field) do {			\
 	(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 (0)

 #define LIST_INSERT_HEAD(head, elm, field) do {				\
 	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 (0)

 #define LIST_REMOVE(elm, field) do {					\
 	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;			\
 } while (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);				\
 } while (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)	    (SIMPLEQ_FIRST(head) == SIMPLEQ_END(head))
 #define	SIMPLEQ_NEXT(elm, field)    ((elm)->field.sqe_next)

 #define SIMPLEQ_FOREACH(var, head, field)				\
 	for((var) = SIMPLEQ_FIRST(head);				\
 	    (var) != SIMPLEQ_END(head);					\
 	    (var) = SIMPLEQ_NEXT(var, field))

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

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

 /*
  * 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 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))
 /* XXX */
 #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) = TAILQ_FIRST(head);					\
 	    (var) != TAILQ_END(head);					\
 	    (var) = TAILQ_NEXT(var, field))

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

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

 #define TAILQ_INSERT_HEAD(head, elm, field) do {			\
 	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 (0)

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

 #define TAILQ_INSERT_AFTER(head, listelm, elm, field) do {		\
 	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 (0)

 #define	TAILQ_INSERT_BEFORE(listelm, elm, field) do {			\
 	(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 (0)

 #define TAILQ_REMOVE(head, elm, field) do {				\
 	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;			\
 } while (0)

 #define TAILQ_REPLACE(head, elm, elm2, field) do {			\
 	if (((elm2)->field.tqe_next = (elm)->field.tqe_next) != NULL)	\
 		(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);				\
 } while (0)

 /*
  * 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)					\
 	{ 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 access methods
  */
 #define	CIRCLEQ_FIRST(head)		((head)->cqh_first)
 #define	CIRCLEQ_LAST(head)		((head)->cqh_last)
 #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_END(head))

 #define CIRCLEQ_FOREACH(var, head, field)				\
 	for((var) = CIRCLEQ_FIRST(head);				\
 	    (var) != CIRCLEQ_END(head);					\
 	    (var) = CIRCLEQ_NEXT(var, field))

 #define CIRCLEQ_FOREACH_REVERSE(var, head, field)			\
 	for((var) = CIRCLEQ_LAST(head);					\
 	    (var) != CIRCLEQ_END(head);					\
 	    (var) = CIRCLEQ_PREV(var, field))

 /*
  * Circular queue functions.
  */
 #define	CIRCLEQ_INIT(head) do {						\
 	(head)->cqh_first = CIRCLEQ_END(head);				\
 	(head)->cqh_last = CIRCLEQ_END(head);				\
 } while (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 == CIRCLEQ_END(head))		\
 		(head)->cqh_last = (elm);				\
 	else								\
 		(listelm)->field.cqe_next->field.cqe_prev = (elm);	\
 	(listelm)->field.cqe_next = (elm);				\
 } while (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 == CIRCLEQ_END(head))		\
 		(head)->cqh_first = (elm);				\
 	else								\
 		(listelm)->field.cqe_prev->field.cqe_next = (elm);	\
 	(listelm)->field.cqe_prev = (elm);				\
 } while (0)

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

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

 #define	CIRCLEQ_REMOVE(head, elm, field) do {				\
 	if ((elm)->field.cqe_next == CIRCLEQ_END(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_END(head))			\
 		(head)->cqh_first = (elm)->field.cqe_next;		\
 	else								\
 		(elm)->field.cqe_prev->field.cqe_next =			\
 		    (elm)->field.cqe_next;				\
 } while (0)

 #define CIRCLEQ_REPLACE(head, elm, elm2, field) do {			\
 	if (((elm2)->field.cqe_next = (elm)->field.cqe_next) ==		\
 	    CIRCLEQ_END(head))						\
 		(head).cqh_last = (elm2);				\
 	else								\
 		(elm2)->field.cqe_next->field.cqe_prev = (elm2);	\
 	if (((elm2)->field.cqe_prev = (elm)->field.cqe_prev) ==		\
 	    CIRCLEQ_END(head))						\
 		(head).cqh_first = (elm2);				\
 	else								\
 		(elm2)->field.cqe_prev->field.cqe_next = (elm2);	\
 } while (0)

 #endif	/* !_SYS_QUEUE_H_ */
	/* $OpenBSD: queue.h,v 1.22 2001/06/23 04:39:35 angelos Exp $ */
	/* $NetBSD: queue.h,v 1.11 1996/05/16 05:17:14 mycroft 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. 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
	*/

	#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 before or 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.
	*/

	/*
	* 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) (SLIST_FIRST(head) == SLIST_END(head))
	#define SLIST_NEXT(elm, field) ((elm)->field.sle_next)

	#define SLIST_FOREACH(var, head, field) \
	for((var) = SLIST_FIRST(head); \
	(var) != SLIST_END(head); \
	(var) = SLIST_NEXT(var, field))

	/*
	* Singly-linked List functions.
	*/
	#define SLIST_INIT(head) { \
	SLIST_FIRST(head) = SLIST_END(head); \
	}

	#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_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)

	/*
	* 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) (LIST_FIRST(head) == LIST_END(head))
	#define LIST_NEXT(elm, field) ((elm)->field.le_next)

	#define LIST_FOREACH(var, head, field) \
	for((var) = LIST_FIRST(head); \
	(var)!= LIST_END(head); \
	(var) = LIST_NEXT(var, field))

	/*
	* List functions.
	*/
	#define LIST_INIT(head) do { \
	LIST_FIRST(head) = LIST_END(head); \
	} while (0)

	#define LIST_INSERT_AFTER(listelm, elm, field) do { \
	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 (0)

	#define LIST_INSERT_BEFORE(listelm, elm, field) do { \
	(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 (0)

	#define LIST_INSERT_HEAD(head, elm, field) do { \
	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 (0)

	#define LIST_REMOVE(elm, field) do { \
	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; \
	} while (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); \
	} while (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) (SIMPLEQ_FIRST(head) == SIMPLEQ_END(head))
	#define SIMPLEQ_NEXT(elm, field) ((elm)->field.sqe_next)

	#define SIMPLEQ_FOREACH(var, head, field) \
	for((var) = SIMPLEQ_FIRST(head); \
	(var) != SIMPLEQ_END(head); \
	(var) = SIMPLEQ_NEXT(var, field))

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

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

	/*
	* 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 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))
	/* XXX */
	#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) = TAILQ_FIRST(head); \
	(var) != TAILQ_END(head); \
	(var) = TAILQ_NEXT(var, field))

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

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

	#define TAILQ_INSERT_HEAD(head, elm, field) do { \
	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 (0)

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

	#define TAILQ_INSERT_AFTER(head, listelm, elm, field) do { \
	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 (0)

	#define TAILQ_INSERT_BEFORE(listelm, elm, field) do { \
	(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 (0)

	#define TAILQ_REMOVE(head, elm, field) do { \
	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; \
	} while (0)

	#define TAILQ_REPLACE(head, elm, elm2, field) do { \
	if (((elm2)->field.tqe_next = (elm)->field.tqe_next) != NULL) \
	(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); \
	} while (0)

	/*
	* 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) \
	{ 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 access methods
	*/
	#define CIRCLEQ_FIRST(head) ((head)->cqh_first)
	#define CIRCLEQ_LAST(head) ((head)->cqh_last)
	#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_END(head))

	#define CIRCLEQ_FOREACH(var, head, field) \
	for((var) = CIRCLEQ_FIRST(head); \
	(var) != CIRCLEQ_END(head); \
	(var) = CIRCLEQ_NEXT(var, field))

	#define CIRCLEQ_FOREACH_REVERSE(var, head, field) \
	for((var) = CIRCLEQ_LAST(head); \
	(var) != CIRCLEQ_END(head); \
	(var) = CIRCLEQ_PREV(var, field))

	/*
	* Circular queue functions.
	*/
	#define CIRCLEQ_INIT(head) do { \
	(head)->cqh_first = CIRCLEQ_END(head); \
	(head)->cqh_last = CIRCLEQ_END(head); \
	} while (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 == CIRCLEQ_END(head)) \
	(head)->cqh_last = (elm); \
	else \
	(listelm)->field.cqe_next->field.cqe_prev = (elm); \
	(listelm)->field.cqe_next = (elm); \
	} while (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 == CIRCLEQ_END(head)) \
	(head)->cqh_first = (elm); \
	else \
	(listelm)->field.cqe_prev->field.cqe_next = (elm); \
	(listelm)->field.cqe_prev = (elm); \
	} while (0)

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

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

	#define CIRCLEQ_REMOVE(head, elm, field) do { \
	if ((elm)->field.cqe_next == CIRCLEQ_END(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_END(head)) \
	(head)->cqh_first = (elm)->field.cqe_next; \
	else \
	(elm)->field.cqe_prev->field.cqe_next = \
	(elm)->field.cqe_next; \
	} while (0)

	#define CIRCLEQ_REPLACE(head, elm, elm2, field) do { \
	if (((elm2)->field.cqe_next = (elm)->field.cqe_next) == \
	CIRCLEQ_END(head)) \
	(head).cqh_last = (elm2); \
	else \
	(elm2)->field.cqe_next->field.cqe_prev = (elm2); \
	if (((elm2)->field.cqe_prev = (elm)->field.cqe_prev) == \
	CIRCLEQ_END(head)) \
	(head).cqh_first = (elm2); \
	else \
	(elm2)->field.cqe_prev->field.cqe_next = (elm2); \
	} while (0)

	#endif /* !_SYS_QUEUE_H_ */