queue.h 8.5 (Berkeley) 8/20/94

how_to_use_LIST_of_queue.c

#include <stdio.h>
#include <stdlib.h>

#include "queue.h"

// Be careful! LIST_* are MACROS, NOT functions. No formal parameters!

typedef struct List {
    int data;
    LIST_ENTRY ( List ) linker;
} List;

typedef LIST_HEAD ( ListHead, List ) ListHead; 

typedef int ( *remove_fn ) ( List *node );

static int if_node_remove ( List *node )
{
    return node->data & 0x1 ? 1 : 0;
}

void display_list ( ListHead *headp )
{
    List *node = NULL;
    LIST_FOREACH ( node, headp, linker ) {
        printf ( "%d\n", node->data );
    }
}

void initialise_list ( ListHead *headp, const unsigned number ) 
{
    for ( int i = number; i > 0; --i ) {
        List *node = ( List * ) calloc ( 1, sizeof ( List ) );
        node->data = i * 1;
        node->linker.le_next = NULL;
        node->linker.le_prev = NULL;
        LIST_INSERT_HEAD ( headp, node, linker );
    }

}

void remove_node ( ListHead *headp, const unsigned id )
{
    List *node = LIST_FIRST ( headp );
    for ( int i = 1; i < id; ++i, node = LIST_NEXT ( node, linker ) ) 
        ;
    LIST_REMOVE ( node, linker );
    free ( node );
}

void insert_node_before ( ListHead *headp, const unsigned id ) 
{
    List *node = LIST_FIRST ( headp );
    for ( int i = 1; i < id; ++i, node = LIST_NEXT ( node, linker ) ) 
        ;
    List *new_node = (List *) calloc ( 1, sizeof ( List ) );
    new_node->data = id * 100;
    new_node->linker.le_next = NULL;
    new_node->linker.le_prev = NULL;
    LIST_INSERT_BEFORE ( node, new_node, linker );
}

void remove_node_if ( ListHead *headp, remove_fn rm )
{
    List *node = NULL, *tmp_node = NULL;
    LIST_FOREACH_SAFE ( node, headp, linker, tmp_node ) {
        if ( rm ( node ) ) {
            LIST_REMOVE ( node, linker );
            free ( node );
        }
    }
}

void replace_node ( ListHead *headp, const unsigned id ) 
{
    List *node = LIST_FIRST ( headp );
    for ( int i = 1; i < id; ++i, node = LIST_NEXT ( node, linker ) ) 
        ;
    List *new_node = (List *) calloc ( 1, sizeof ( List ) );
    new_node->data = id * 1000;
    new_node->linker.le_next = NULL;
    new_node->linker.le_prev = NULL;
    LIST_REPLACE ( node, new_node, linker );
}

void release_list ( ListHead *headp )
{
    List *node = NULL, *tmp_node = NULL;
    LIST_FOREACH_SAFE ( node, headp, linker, tmp_node ) {
        LIST_REMOVE ( node, linker );
        free ( node );
    }
}

int main(int argc, char const* argv[])
{

    ListHead head = LIST_HEAD_INITIALIZER ( head );
    ListHead *headp = &head;

    LIST_INIT ( headp );

    initialise_list( headp, 13 );
    remove_node ( headp, 3 ); 
    insert_node_before ( headp, 3 );
    replace_node ( headp, 3 );
    remove_node_if ( headp, if_node_remove );

    display_list ( headp );

    release_list ( headp );
    /* printf ( "after release list ... \n " ); */
    /* display_list ( headp ); */

    LIST_INIT ( headp );

    return 0;
}

new_list_based_on_queue&gdsl.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>

#include "queue.h"

typedef struct Node {
    void *element;
    LIST_ENTRY ( Node ) linker;
} Node;
typedef LIST_HEAD ( Head, Node ) Head;

typedef  Node* ( *Alloc_func ) ( void *data );
typedef  void  ( *Free_func ) ( Node *node );
typedef struct List {
    Head *head;
    char *name;
    unsigned card;
    Alloc_func malloc_node_func;
    Free_func free_node_func;
} List;

typedef enum BOOL {
    NO  = 0,
    YES = 1
} BOOL;
typedef BOOL ( *is_remove_func ) ( Node *node );

extern List* malloc_list ( const char *name, 
        Alloc_func malloc_node_func, Free_func free_node_func )
{
    List *list = (List*) calloc ( 1, sizeof ( List ) );
    if ( list == NULL ) {
        return NULL;
    }

    list->head = (Head*) calloc ( 1, sizeof ( Head ) );
    if ( list->head == NULL ) {
        free ( list );
        return NULL;
    }
    LIST_INIT ( list->head );

    list->name = 
        (char*) calloc ( 1, ( 1 + strlen ( name ) ) * sizeof ( char ) );
    if ( list->name == NULL ) {
        free ( list->head );
        free ( list );
        return NULL;
    }
    strcpy ( list->name, name );

    if ( malloc_node_func == NULL || free_node_func == NULL ) {
        free ( list->name );
        free ( list->head );
        free ( list );
        return NULL;
    }
    list->malloc_node_func = malloc_node_func;
    list->free_node_func = free_node_func;

    return list;
}

extern void free_list ( List *list )
{
    assert ( list != NULL );

    if ( list->head != NULL ) {
        free ( list->head );
    }
    if ( list->name != NULL ) {
        free ( list->name );
    }

    free ( list );
}

extern Node* insert_head ( List *list, void *data ) {
    assert ( data != NULL );

    Node *node = list->malloc_node_func ( data );
    if ( node == NULL ) {
        return NULL;
    }

    LIST_INSERT_HEAD ( list->head, node, linker );
    list->card++;

    return node;
}

extern void remove_node ( List *list, Node *node )
{
    assert ( node != NULL );

    LIST_REMOVE ( node, linker );
    list->card--;
    list->free_node_func ( node );
}

extern void remove_node_if ( List *list, is_remove_func rm )
{
    assert ( rm != NULL );

    Node *node, *tmp_node;
    LIST_FOREACH_SAFE ( node, list->head, linker, tmp_node ) {
        if ( rm ( node ) ) {
            remove_node ( list, node );
        }
    }
}

extern void remove_head ( List *list )
{
    Node *node = LIST_FIRST ( list->head );
    assert ( node != NULL );

    remove_node ( list, node );
}

extern void remove_all_nodes ( List *list )
{
    while ( LIST_FIRST(list->head) != NULL ) {
        remove_head ( list );
    }

    /* Node *node = NULL, *tmp_node = NULL; */
    /* LIST_FOREACH_SAFE ( node, list->head, linker, tmp_node ) { */
    /* LIST_REMOVE ( node, linker ); */
    /* list->free_node_func ( node ); */
    /* } */
}

////////////////////////////////////

typedef struct Car {
    unsigned id;
} Car;

static Node* malloc_node ( void *data )
{   
    Node *node = (Node*) calloc ( 1, sizeof ( Node ) );
    if ( node == NULL ) {
        return NULL;
    }

    Car *car = (Car*) calloc ( 1, sizeof ( Car ) );
    if ( car == NULL ) {
        return NULL;
    }

    car->id = *(unsigned *)data;
    node->element = car;

    return node;
}

static void free_node ( Node *node )
{
    assert ( node != NULL );

    free ( node->element );
    free ( node );
}

static void display_list ( List *list )
{
    Node *node = NULL;
    printf ( "%s (%d): \n", list->name, list->card );
    LIST_FOREACH ( node, list->head, linker ) {
        printf ( "%d\n", ( (Car*) node->element )->id );
    }
}

static List* initialize_list () 
{   
    List *list = malloc_list ( "Car list", malloc_node, free_node );
    for ( int i = 10; i > 0; --i ) {
        insert_head ( list, &i );
    }
    return list;
}

static BOOL is_car_remove ( Node *node )
{
    return ( (Car*) node->element )->id & 0x1 ? YES : NO; 
}

int main(int argc, char const* argv[])
{
    List *list = initialize_list ();
    remove_head ( list );
    display_list ( list );
    remove_node_if ( list, is_car_remove );
    display_list ( list );
    remove_all_nodes ( list );
    display_list ( list );
    return 0;
}

queue.h

/*	$OpenBSD: queue.h,v 1.36 2012/04/11 13:29:14 naddy 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. 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.
 */

#if defined(QUEUE_MACRO_DEBUG) || (defined(_KERNEL) && defined(DIAGNOSTIC))
#define _Q_INVALIDATE(a) (a) = ((void *)-1)
#else
#define _Q_INVALIDATE(a)
#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)	(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))

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

/*
 * 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_AFTER(elm, field) do {				\
	(elm)->field.sle_next = (elm)->field.sle_next->field.sle_next;	\
} 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;		\
		_Q_INVALIDATE((elm)->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))

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

/*
 * 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;			\
	_Q_INVALIDATE((elm)->field.le_prev);				\
	_Q_INVALIDATE((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);				\
	_Q_INVALIDATE((elm)->field.le_prev);				\
	_Q_INVALIDATE((elm)->field.le_next);				\
} 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))

#define	SIMPLEQ_FOREACH_SAFE(var, head, field, tvar)			\
	for ((var) = SIMPLEQ_FIRST(head);				\
	    (var) && ((tvar) = SIMPLEQ_NEXT(var, field), 1);		\
	    (var) = (tvar))

/*
 * 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, field) do {			\
	if (((head)->sqh_first = (head)->sqh_first->field.sqe_next) == NULL) \
		(head)->sqh_last = &(head)->sqh_first;			\
} while (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 (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_SAFE(var, head, field, tvar)			\
	for ((var) = TAILQ_FIRST(head);					\
	    (var) != TAILQ_END(head) &&					\
	    ((tvar) = TAILQ_NEXT(var, field), 1);			\
	    (var) = (tvar))


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

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

/*
 * 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;			\
	_Q_INVALIDATE((elm)->field.tqe_prev);				\
	_Q_INVALIDATE((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);				\
	_Q_INVALIDATE((elm)->field.tqe_prev);				\
	_Q_INVALIDATE((elm)->field.tqe_next);				\
} 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_SAFE(var, head, field, tvar)			\
	for ((var) = CIRCLEQ_FIRST(head);				\
	    (var) != CIRCLEQ_END(head) &&				\
	    ((tvar) = CIRCLEQ_NEXT(var, field), 1);			\
	    (var) = (tvar))

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

#define	CIRCLEQ_FOREACH_REVERSE_SAFE(var, head, headname, field, tvar)	\
	for ((var) = CIRCLEQ_LAST(head, headname);			\
	    (var) != CIRCLEQ_END(head) && 				\
	    ((tvar) = CIRCLEQ_PREV(var, headname, field), 1);		\
	    (var) = (tvar))

/*
 * 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;				\
	_Q_INVALIDATE((elm)->field.cqe_prev);				\
	_Q_INVALIDATE((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);	\
	_Q_INVALIDATE((elm)->field.cqe_prev);				\
	_Q_INVALIDATE((elm)->field.cqe_next);				\
} while (0)

#endif	/* !_SYS_QUEUE_H_ */