/*-

  * 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.

  * © Portions copyright (c) 2007 Symbian Software Ltd. All rights reserved.

  *	@(#)queue.h	8.5 (Berkeley) 8/20/94

  * $FreeBSD: src/sys/sys/queue.h,v 1.60.2.1 2005/08/16 22:41:39 phk Exp $

  */

 #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 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.

  *

  * 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_SAFE		+	+	+	+

  * _FOREACH_REVERSE		-	-	-	+

  * _FOREACH_REVERSE_SAFE	-	-	-	+

  * _INSERT_HEAD			+	+	+	+

  * _INSERT_BEFORE		-	+	-	+

  * _INSERT_AFTER		+	+	+	+

  * _INSERT_TAIL			-	-	+	+

  * _CONCAT			-	-	+	+

  * _REMOVE_HEAD			+	-	+	-

  * _REMOVE			+	+	+	+

  *

  */

 #define	QUEUE_MACRO_DEBUG 0

 #if QUEUE_MACRO_DEBUG

 /* Store the last 2 places the queue element or head was altered */

 struct qm_trace {

 	char * lastfile;

 	int lastline;

 	char * prevfile;

 	int prevline;

 };

 #define	TRACEBUF	struct qm_trace trace;

 #define	TRASHIT(x)	do {(x) = (void *)-1;} while (0)

 #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	TRACEBUF

 #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_SAFE(var, head, field, tvar)			\

 	for ((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 {			\

 	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_NEXT(curelm, field) =				\

 		    SLIST_NEXT(SLIST_NEXT(curelm, field), field);	\

 	}								\

 } while (0)

 #define	SLIST_REMOVE_HEAD(head, field) do {				\

 	SLIST_FIRST((head)) = SLIST_NEXT(SLIST_FIRST((head)), field);	\

 } 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_SAFE(var, head, field, tvar)			\

 	for ((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 :							\

 	        ((struct type *)					\

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

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

 #define	STAILQ_REMOVE(head, elm, type, field) do {			\

 	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);		\

 		if ((STAILQ_NEXT(curelm, field) =			\

 		     STAILQ_NEXT(STAILQ_NEXT(curelm, field), field)) == NULL)\

 			(head)->stqh_last = &STAILQ_NEXT((curelm), 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_REMOVE_HEAD_UNTIL(head, elm, field) do {			\

 	if ((STAILQ_FIRST((head)) = STAILQ_NEXT((elm), field)) == NULL)	\

 		(head)->stqh_last = &STAILQ_FIRST((head));		\

 } 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.

  */

 #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_SAFE(var, head, field, tvar)			\

 	for ((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 {			\

 	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 {			\

 	(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 {				\

 	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_REMOVE(elm, field) do {					\

 	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);		\

 } 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 }

 #define	TAILQ_ENTRY(type)						\

 struct {								\

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

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

 	TRACEBUF							\

 }

 /*

  * Tail queue functions.

  */

 #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_SAFE(var, head, field, tvar)			\

 	for ((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_SAFE(var, head, headname, field, tvar)	\

 	for ((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 {		\

 	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 {			\

 	(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 {			\

 	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 {			\

 	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 {				\

 	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((elm)->field.tqe_next);					\

 	TRASHIT((elm)->field.tqe_prev);					\

 	QMD_TRACE_ELEM(&(elm)->field);					\

 } while (0)

 #ifdef _KERNEL

 /*

  * XXX insque() and remque() are an old way of handling certain queues.

  * They bogusly assumes that all queue heads look alike.

  */

 struct quehead {

 	struct quehead *qh_link;

 	struct quehead *qh_rlink;

 };

 #ifdef __CC_SUPPORTS___INLINE

 static __inline void

 insque(void *a, void *b)

 {

 	struct quehead *element = (struct quehead *)a,

 		 *head = (struct quehead *)b;

 	element->qh_link = head->qh_link;

 	element->qh_rlink = head;

 	head->qh_link = element;

 	element->qh_link->qh_rlink = element;

 }

 static __inline void

 remque(void *a)

 {

 	struct quehead *element = (struct quehead *)a;

 	element->qh_link->qh_rlink = element->qh_rlink;

 	element->qh_rlink->qh_link = element->qh_link;

 	element->qh_rlink = 0;

 }

 #endif /* __CC_SUPPORTS___INLINE */

 #endif /* _KERNEL */

 #endif /* !_SYS_QUEUE_H_ */