978 lines
25 KiB
Groff
978 lines
25 KiB
Groff
.\" Copyright (c) 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)queue.3 8.2 (Berkeley) 1/24/94
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.\" $FreeBSD$
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.\"
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.Dd January 24, 1994
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.Dt QUEUE 3
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.Os
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.Sh NAME
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.Nm SLIST_EMPTY ,
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.Nm SLIST_ENTRY ,
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.Nm SLIST_FIRST ,
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.Nm SLIST_FOREACH ,
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.Nm SLIST_FOREACH_SAFE ,
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.Nm SLIST_HEAD ,
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.Nm SLIST_HEAD_INITIALIZER ,
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.Nm SLIST_INIT ,
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.Nm SLIST_INSERT_AFTER ,
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.Nm SLIST_INSERT_HEAD ,
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.Nm SLIST_NEXT ,
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.Nm SLIST_REMOVE_HEAD ,
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.Nm SLIST_REMOVE ,
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.Nm STAILQ_CONCAT ,
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.Nm STAILQ_EMPTY ,
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.Nm STAILQ_ENTRY ,
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.Nm STAILQ_FIRST ,
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.Nm STAILQ_FOREACH ,
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.Nm STAILQ_FOREACH_SAFE ,
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.Nm STAILQ_HEAD ,
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.Nm STAILQ_HEAD_INITIALIZER ,
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.Nm STAILQ_INIT ,
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.Nm STAILQ_INSERT_AFTER ,
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.Nm STAILQ_INSERT_HEAD ,
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.Nm STAILQ_INSERT_TAIL ,
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.Nm STAILQ_LAST ,
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.Nm STAILQ_NEXT ,
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.Nm STAILQ_REMOVE_HEAD ,
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.Nm STAILQ_REMOVE ,
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.Nm LIST_EMPTY ,
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.Nm LIST_ENTRY ,
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.Nm LIST_FIRST ,
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.Nm LIST_FOREACH ,
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.Nm LIST_FOREACH_SAFE ,
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.Nm LIST_HEAD ,
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.Nm LIST_HEAD_INITIALIZER ,
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.Nm LIST_INIT ,
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.Nm LIST_INSERT_AFTER ,
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.Nm LIST_INSERT_BEFORE ,
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.Nm LIST_INSERT_HEAD ,
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.Nm LIST_NEXT ,
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.Nm LIST_REMOVE ,
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.Nm TAILQ_CONCAT ,
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.Nm TAILQ_EMPTY ,
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.Nm TAILQ_ENTRY ,
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.Nm TAILQ_FIRST ,
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.Nm TAILQ_FOREACH ,
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.Nm TAILQ_FOREACH_SAFE ,
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.Nm TAILQ_FOREACH_REVERSE ,
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.Nm TAILQ_FOREACH_REVERSE_SAFE ,
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.Nm TAILQ_HEAD ,
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.Nm TAILQ_HEAD_INITIALIZER ,
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.Nm TAILQ_INIT ,
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.Nm TAILQ_INSERT_AFTER ,
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.Nm TAILQ_INSERT_BEFORE ,
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.Nm TAILQ_INSERT_HEAD ,
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.Nm TAILQ_INSERT_TAIL ,
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.Nm TAILQ_LAST ,
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.Nm TAILQ_NEXT ,
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.Nm TAILQ_PREV ,
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.Nm TAILQ_REMOVE
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.Nd implementations of singly-linked lists, singly-linked tail queues,
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lists and tail queues
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.Sh SYNOPSIS
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.In sys/queue.h
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.\"
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.Fn SLIST_EMPTY "SLIST_HEAD *head"
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.Fn SLIST_ENTRY "TYPE"
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.Fn SLIST_FIRST "SLIST_HEAD *head"
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.Fn SLIST_FOREACH "TYPE *var" "SLIST_HEAD *head" "SLIST_ENTRY NAME"
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.Fn SLIST_FOREACH_SAFE "TYPE *var" "SLIST_HEAD *head" "SLIST_ENTRY NAME" "TYPE *temp_var"
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.Fn SLIST_HEAD "HEADNAME" "TYPE"
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.Fn SLIST_HEAD_INITIALIZER "SLIST_HEAD head"
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.Fn SLIST_INIT "SLIST_HEAD *head"
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.Fn SLIST_INSERT_AFTER "TYPE *listelm" "TYPE *elm" "SLIST_ENTRY NAME"
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.Fn SLIST_INSERT_HEAD "SLIST_HEAD *head" "TYPE *elm" "SLIST_ENTRY NAME"
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.Fn SLIST_NEXT "TYPE *elm" "SLIST_ENTRY NAME"
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.Fn SLIST_REMOVE_HEAD "SLIST_HEAD *head" "SLIST_ENTRY NAME"
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.Fn SLIST_REMOVE "SLIST_HEAD *head" "TYPE *elm" "TYPE" "SLIST_ENTRY NAME"
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.\"
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.Fn STAILQ_CONCAT "STAILQ_HEAD *head1" "STAILQ_HEAD *head2"
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.Fn STAILQ_EMPTY "STAILQ_HEAD *head"
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.Fn STAILQ_ENTRY "TYPE"
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.Fn STAILQ_FIRST "STAILQ_HEAD *head"
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.Fn STAILQ_FOREACH "TYPE *var" "STAILQ_HEAD *head" "STAILQ_ENTRY NAME"
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.Fn STAILQ_FOREACH_SAFE "TYPE *var" "STAILQ_HEAD *head" "STAILQ_ENTRY NAME" "TYPE *temp_var"
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.Fn STAILQ_HEAD "HEADNAME" "TYPE"
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.Fn STAILQ_HEAD_INITIALIZER "STAILQ_HEAD head"
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.Fn STAILQ_INIT "STAILQ_HEAD *head"
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.Fn STAILQ_INSERT_AFTER "STAILQ_HEAD *head" "TYPE *listelm" "TYPE *elm" "STAILQ_ENTRY NAME"
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.Fn STAILQ_INSERT_HEAD "STAILQ_HEAD *head" "TYPE *elm" "STAILQ_ENTRY NAME"
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.Fn STAILQ_INSERT_TAIL "STAILQ_HEAD *head" "TYPE *elm" "STAILQ_ENTRY NAME"
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.Fn STAILQ_LAST "STAILQ_HEAD *head" "TYPE" "STAILQ_ENTRY NAME"
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.Fn STAILQ_NEXT "TYPE *elm" "STAILQ_ENTRY NAME"
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.Fn STAILQ_REMOVE_HEAD "STAILQ_HEAD *head" "STAILQ_ENTRY NAME"
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.Fn STAILQ_REMOVE "STAILQ_HEAD *head" "TYPE *elm" "TYPE" "STAILQ_ENTRY NAME"
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.\"
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.Fn LIST_EMPTY "LIST_HEAD *head"
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.Fn LIST_ENTRY "TYPE"
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.Fn LIST_FIRST "LIST_HEAD *head"
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.Fn LIST_FOREACH "TYPE *var" "LIST_HEAD *head" "LIST_ENTRY NAME"
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.Fn LIST_FOREACH_SAFE "TYPE *var" "LIST_HEAD *head" "LIST_ENTRY NAME" "TYPE *temp_var"
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.Fn LIST_HEAD "HEADNAME" "TYPE"
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.Fn LIST_HEAD_INITIALIZER "LIST_HEAD head"
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.Fn LIST_INIT "LIST_HEAD *head"
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.Fn LIST_INSERT_AFTER "TYPE *listelm" "TYPE *elm" "LIST_ENTRY NAME"
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.Fn LIST_INSERT_BEFORE "TYPE *listelm" "TYPE *elm" "LIST_ENTRY NAME"
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.Fn LIST_INSERT_HEAD "LIST_HEAD *head" "TYPE *elm" "LIST_ENTRY NAME"
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.Fn LIST_NEXT "TYPE *elm" "LIST_ENTRY NAME"
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.Fn LIST_REMOVE "TYPE *elm" "LIST_ENTRY NAME"
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.\"
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.Fn TAILQ_CONCAT "TAILQ_HEAD *head1" "TAILQ_HEAD *head2" "TAILQ_ENTRY NAME"
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.Fn TAILQ_EMPTY "TAILQ_HEAD *head"
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.Fn TAILQ_ENTRY "TYPE"
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.Fn TAILQ_FIRST "TAILQ_HEAD *head"
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.Fn TAILQ_FOREACH "TYPE *var" "TAILQ_HEAD *head" "TAILQ_ENTRY NAME"
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.Fn TAILQ_FOREACH_SAFE "TYPE *var" "TAILQ_HEAD *head" "TAILQ_ENTRY NAME" "TYPE *temp_var"
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.Fn TAILQ_FOREACH_REVERSE "TYPE *var" "TAILQ_HEAD *head" "HEADNAME" "TAILQ_ENTRY NAME"
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.Fn TAILQ_FOREACH_REVERSE_SAFE "TYPE *var" "TAILQ_HEAD *head" "HEADNAME" "TAILQ_ENTRY NAME" "TYPE *temp_var"
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.Fn TAILQ_HEAD "HEADNAME" "TYPE"
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.Fn TAILQ_HEAD_INITIALIZER "TAILQ_HEAD head"
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.Fn TAILQ_INIT "TAILQ_HEAD *head"
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.Fn TAILQ_INSERT_AFTER "TAILQ_HEAD *head" "TYPE *listelm" "TYPE *elm" "TAILQ_ENTRY NAME"
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.Fn TAILQ_INSERT_BEFORE "TYPE *listelm" "TYPE *elm" "TAILQ_ENTRY NAME"
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.Fn TAILQ_INSERT_HEAD "TAILQ_HEAD *head" "TYPE *elm" "TAILQ_ENTRY NAME"
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.Fn TAILQ_INSERT_TAIL "TAILQ_HEAD *head" "TYPE *elm" "TAILQ_ENTRY NAME"
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.Fn TAILQ_LAST "TAILQ_HEAD *head" "HEADNAME"
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.Fn TAILQ_NEXT "TYPE *elm" "TAILQ_ENTRY NAME"
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.Fn TAILQ_PREV "TYPE *elm" "HEADNAME" "TAILQ_ENTRY NAME"
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.Fn TAILQ_REMOVE "TAILQ_HEAD *head" "TYPE *elm" "TAILQ_ENTRY NAME"
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.\"
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.Sh DESCRIPTION
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These macros define and operate on four types of data structures:
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singly-linked lists, singly-linked tail queues, lists, and tail queues.
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All four structures support the following functionality:
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.Bl -enum -compact -offset indent
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.It
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Insertion of a new entry at the head of the list.
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.It
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Insertion of a new entry after any element in the list.
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.It
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O(1) removal of an entry from the head of the list.
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.It
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O(n) removal of any entry in the list.
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.It
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Forward traversal through the list.
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.El
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.Pp
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Singly-linked lists are the simplest of the five data structures
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and support only the above functionality.
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Singly-linked lists are ideal for applications with large datasets
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and few or no removals,
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or for implementing a LIFO queue.
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.Pp
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Singly-linked tail queues add the following functionality:
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.Bl -enum -compact -offset indent
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.It
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Entries can be added at the end of a list.
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.It
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They may be concatenated.
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.El
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However:
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.Bl -enum -compact -offset indent
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.It
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All list insertions must specify the head of the list.
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.It
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Each head entry requires two pointers rather than one.
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.It
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Code size is about 15% greater and operations run about 20% slower
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than singly-linked lists.
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.El
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.Pp
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Singly-linked tailqs are ideal for applications with large datasets and
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few or no removals,
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or for implementing a FIFO queue.
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.Pp
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All doubly linked types of data structures (lists and tail queues)
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additionally allow:
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.Bl -enum -compact -offset indent
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.It
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Insertion of a new entry before any element in the list.
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.It
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O(1) removal of any entry in the list.
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.El
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However:
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.Bl -enum -compact -offset indent
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.It
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Each elements requires two pointers rather than one.
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.It
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Code size and execution time of operations (except for removal) is about
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twice that of the singly-linked data-structures.
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.El
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.Pp
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Linked lists are the simplest of the doubly linked data structures and support
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only the above functionality over singly-linked lists.
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.Pp
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Tail queues add the following functionality:
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.Bl -enum -compact -offset indent
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.It
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Entries can be added at the end of a list.
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.It
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They may be traversed backwards, from tail to head.
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.It
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They may be concatenated.
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.El
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However:
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.Bl -enum -compact -offset indent
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.It
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All list insertions and removals must specify the head of the list.
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.It
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Each head entry requires two pointers rather than one.
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.It
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Code size is about 15% greater and operations run about 20% slower
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than singly-linked lists.
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.El
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.Pp
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In the macro definitions,
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.Fa TYPE
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is the name of a user defined structure,
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that must contain a field of type
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.Li SLIST_ENTRY ,
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.Li STAILQ_ENTRY ,
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.Li LIST_ENTRY ,
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or
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.Li TAILQ_ENTRY ,
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named
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.Fa NAME .
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The argument
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.Fa HEADNAME
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is the name of a user defined structure that must be declared
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using the macros
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.Li SLIST_HEAD ,
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.Li STAILQ_HEAD ,
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.Li LIST_HEAD ,
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or
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.Li TAILQ_HEAD .
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See the examples below for further explanation of how these
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macros are used.
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.Sh SINGLY-LINKED LISTS
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A singly-linked list is headed by a structure defined by the
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.Nm SLIST_HEAD
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macro.
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This structure contains a single pointer to the first element
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on the list.
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The elements are singly linked for minimum space and pointer manipulation
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overhead at the expense of O(n) removal for arbitrary elements.
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New elements can be added to the list after an existing element or
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at the head of the list.
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An
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.Fa SLIST_HEAD
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structure is declared as follows:
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.Bd -literal -offset indent
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SLIST_HEAD(HEADNAME, TYPE) head;
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.Ed
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.Pp
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where
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.Fa HEADNAME
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is the name of the structure to be defined, and
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.Fa TYPE
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is the type of the elements to be linked into the list.
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A pointer to the head of the list can later be declared as:
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.Bd -literal -offset indent
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struct HEADNAME *headp;
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.Ed
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.Pp
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(The names
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.Li head
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and
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.Li headp
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are user selectable.)
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.Pp
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The macro
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.Nm SLIST_HEAD_INITIALIZER
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evaluates to an initializer for the list
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.Fa head .
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.Pp
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The macro
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.Nm SLIST_EMPTY
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evaluates to true if there are no elements in the list.
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.Pp
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The macro
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.Nm SLIST_ENTRY
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declares a structure that connects the elements in
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the list.
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.Pp
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The macro
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.Nm SLIST_FIRST
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returns the first element in the list or NULL if the list is empty.
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.Pp
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The macro
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.Nm SLIST_FOREACH
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traverses the list referenced by
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.Fa head
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in the forward direction, assigning each element in
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turn to
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.Fa var .
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.Pp
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The macro
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.Nm SLIST_FOREACH_SAFE
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traverses the list referenced by
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.Fa head
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in the forward direction, assigning each element in
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turn to
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.Fa var .
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However, unlike
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.Fn SLIST_FOREACH
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here it is permitted to both remove
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.Fa var
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as well as free it from within the loop safely without interfering with the
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traversal.
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.Pp
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The macro
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.Nm SLIST_INIT
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initializes the list referenced by
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.Fa head .
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.Pp
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The macro
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.Nm SLIST_INSERT_HEAD
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inserts the new element
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.Fa elm
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at the head of the list.
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.Pp
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The macro
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.Nm SLIST_INSERT_AFTER
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inserts the new element
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.Fa elm
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after the element
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.Fa listelm .
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.Pp
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The macro
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.Nm SLIST_NEXT
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returns the next element in the list.
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.Pp
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The macro
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.Nm SLIST_REMOVE_HEAD
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removes the element
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.Fa elm
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from the head of the list.
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For optimum efficiency,
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elements being removed from the head of the list should explicitly use
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this macro instead of the generic
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.Fa SLIST_REMOVE
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macro.
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.Pp
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The macro
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.Nm SLIST_REMOVE
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removes the element
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.Fa elm
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from the list.
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.Sh SINGLY-LINKED LIST EXAMPLE
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.Bd -literal
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SLIST_HEAD(slisthead, entry) head =
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SLIST_HEAD_INITIALIZER(head);
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struct slisthead *headp; /* Singly-linked List head. */
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struct entry {
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...
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SLIST_ENTRY(entry) entries; /* Singly-linked List. */
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...
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} *n1, *n2, *n3, *np;
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SLIST_INIT(&head); /* Initialize the list. */
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n1 = malloc(sizeof(struct entry)); /* Insert at the head. */
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SLIST_INSERT_HEAD(&head, n1, entries);
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n2 = malloc(sizeof(struct entry)); /* Insert after. */
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SLIST_INSERT_AFTER(n1, n2, entries);
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SLIST_REMOVE(&head, n2, entry, entries);/* Deletion. */
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free(n2);
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n3 = SLIST_FIRST(&head);
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SLIST_REMOVE_HEAD(&head, entries); /* Deletion from the head. */
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free(n3);
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/* Forward traversal. */
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SLIST_FOREACH(np, &head, entries)
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np-> ...
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/* Safe forward traversal. */
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SLIST_FOREACH_SAFE(np, &head, entries, np_temp) {
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np->do_stuff();
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...
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SLIST_REMOVE(&head, np, entry, entries);
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free(np);
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}
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while (!SLIST_EMPTY(&head)) { /* List Deletion. */
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n1 = SLIST_FIRST(&head);
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SLIST_REMOVE_HEAD(&head, entries);
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free(n1);
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}
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.Ed
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.Sh SINGLY-LINKED TAIL QUEUES
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A singly-linked tail queue is headed by a structure defined by the
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.Nm STAILQ_HEAD
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macro.
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This structure contains a pair of pointers,
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one to the first element in the tail queue and the other to
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the last element in the tail queue.
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The elements are singly linked for minimum space and pointer
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manipulation overhead at the expense of O(n) removal for arbitrary
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elements.
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New elements can be added to the tail queue after an existing element,
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at the head of the tail queue, or at the end of the tail queue.
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A
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.Fa STAILQ_HEAD
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structure is declared as follows:
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.Bd -literal -offset indent
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STAILQ_HEAD(HEADNAME, TYPE) head;
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.Ed
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.Pp
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where
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.Li HEADNAME
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is the name of the structure to be defined, and
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.Li TYPE
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is the type of the elements to be linked into the tail queue.
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A pointer to the head of the tail queue can later be declared as:
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.Bd -literal -offset indent
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struct HEADNAME *headp;
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.Ed
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.Pp
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(The names
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.Li head
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and
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.Li headp
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are user selectable.)
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.Pp
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The macro
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|
.Nm STAILQ_HEAD_INITIALIZER
|
|
evaluates to an initializer for the tail queue
|
|
.Fa head .
|
|
.Pp
|
|
The macro
|
|
.Nm STAILQ_CONCAT
|
|
concatenates the tail queue headed by
|
|
.Fa head2
|
|
onto the end of the one headed by
|
|
.Fa head1
|
|
removing all entries from the former.
|
|
.Pp
|
|
The macro
|
|
.Nm STAILQ_EMPTY
|
|
evaluates to true if there are no items on the tail queue.
|
|
.Pp
|
|
The macro
|
|
.Nm STAILQ_ENTRY
|
|
declares a structure that connects the elements in
|
|
the tail queue.
|
|
.Pp
|
|
The macro
|
|
.Nm STAILQ_FIRST
|
|
returns the first item on the tail queue or NULL if the tail queue
|
|
is empty.
|
|
.Pp
|
|
The macro
|
|
.Nm STAILQ_FOREACH
|
|
traverses the tail queue referenced by
|
|
.Fa head
|
|
in the forward direction, assigning each element
|
|
in turn to
|
|
.Fa var .
|
|
.Pp
|
|
The macro
|
|
.Nm STAILQ_FOREACH_SAFE
|
|
traverses the tail queue referenced by
|
|
.Fa head
|
|
in the forward direction, assigning each element
|
|
in turn to
|
|
.Fa var .
|
|
However, unlike
|
|
.Fn STAILQ_FOREACH
|
|
here it is permitted to both remove
|
|
.Fa var
|
|
as well as free it from within the loop safely without interfering with the
|
|
traversal.
|
|
.Pp
|
|
The macro
|
|
.Nm STAILQ_INIT
|
|
initializes the tail queue referenced by
|
|
.Fa head .
|
|
.Pp
|
|
The macro
|
|
.Nm STAILQ_INSERT_HEAD
|
|
inserts the new element
|
|
.Fa elm
|
|
at the head of the tail queue.
|
|
.Pp
|
|
The macro
|
|
.Nm STAILQ_INSERT_TAIL
|
|
inserts the new element
|
|
.Fa elm
|
|
at the end of the tail queue.
|
|
.Pp
|
|
The macro
|
|
.Nm STAILQ_INSERT_AFTER
|
|
inserts the new element
|
|
.Fa elm
|
|
after the element
|
|
.Fa listelm .
|
|
.Pp
|
|
The macro
|
|
.Nm STAILQ_LAST
|
|
returns the last item on the tail queue.
|
|
If the tail queue is empty the return value is undefined.
|
|
.Pp
|
|
The macro
|
|
.Nm STAILQ_NEXT
|
|
returns the next item on the tail queue, or NULL this item is the last.
|
|
.Pp
|
|
The macro
|
|
.Nm STAILQ_REMOVE_HEAD
|
|
removes the element at the head of the tail queue.
|
|
For optimum efficiency,
|
|
elements being removed from the head of the tail queue should
|
|
use this macro explicitly rather than the generic
|
|
.Fa STAILQ_REMOVE
|
|
macro.
|
|
.Pp
|
|
The macro
|
|
.Nm STAILQ_REMOVE
|
|
removes the element
|
|
.Fa elm
|
|
from the tail queue.
|
|
.Sh SINGLY-LINKED TAIL QUEUE EXAMPLE
|
|
.Bd -literal
|
|
STAILQ_HEAD(stailhead, entry) head =
|
|
STAILQ_HEAD_INITIALIZER(head);
|
|
struct stailhead *headp; /* Singly-linked tail queue head. */
|
|
struct entry {
|
|
...
|
|
STAILQ_ENTRY(entry) entries; /* Tail queue. */
|
|
...
|
|
} *n1, *n2, *n3, *np;
|
|
|
|
STAILQ_INIT(&head); /* Initialize the queue. */
|
|
|
|
n1 = malloc(sizeof(struct entry)); /* Insert at the head. */
|
|
STAILQ_INSERT_HEAD(&head, n1, entries);
|
|
|
|
n1 = malloc(sizeof(struct entry)); /* Insert at the tail. */
|
|
STAILQ_INSERT_TAIL(&head, n1, entries);
|
|
|
|
n2 = malloc(sizeof(struct entry)); /* Insert after. */
|
|
STAILQ_INSERT_AFTER(&head, n1, n2, entries);
|
|
/* Deletion. */
|
|
STAILQ_REMOVE(&head, n2, entry, entries);
|
|
free(n2);
|
|
/* Deletion from the head. */
|
|
n3 = STAILQ_FIRST(&head);
|
|
STAILQ_REMOVE_HEAD(&head, entries);
|
|
free(n3);
|
|
/* Forward traversal. */
|
|
STAILQ_FOREACH(np, &head, entries)
|
|
np-> ...
|
|
/* Safe forward traversal. */
|
|
STAILQ_FOREACH_SAFE(np, &head, entries, np_temp) {
|
|
np->do_stuff();
|
|
...
|
|
STAILQ_REMOVE(&head, np, entry, entries);
|
|
free(np);
|
|
}
|
|
/* TailQ Deletion. */
|
|
while (!STAILQ_EMPTY(&head)) {
|
|
n1 = STAILQ_FIRST(&head);
|
|
STAILQ_REMOVE_HEAD(&head, entries);
|
|
free(n1);
|
|
}
|
|
/* Faster TailQ Deletion. */
|
|
n1 = STAILQ_FIRST(&head);
|
|
while (n1 != NULL) {
|
|
n2 = STAILQ_NEXT(n1, entries);
|
|
free(n1);
|
|
n1 = n2;
|
|
}
|
|
STAILQ_INIT(&head);
|
|
.Ed
|
|
.Sh LISTS
|
|
A list is headed by a structure defined by the
|
|
.Nm LIST_HEAD
|
|
macro.
|
|
This structure contains a single pointer to the first element
|
|
on the list.
|
|
The elements are doubly linked so that an arbitrary element can be
|
|
removed without traversing the list.
|
|
New elements can be added to the list after an existing element,
|
|
before an existing element, or at the head of the list.
|
|
A
|
|
.Fa LIST_HEAD
|
|
structure is declared as follows:
|
|
.Bd -literal -offset indent
|
|
LIST_HEAD(HEADNAME, TYPE) head;
|
|
.Ed
|
|
.Pp
|
|
where
|
|
.Fa HEADNAME
|
|
is the name of the structure to be defined, and
|
|
.Fa TYPE
|
|
is the type of the elements to be linked into the list.
|
|
A pointer to the head of the list can later be declared as:
|
|
.Bd -literal -offset indent
|
|
struct HEADNAME *headp;
|
|
.Ed
|
|
.Pp
|
|
(The names
|
|
.Li head
|
|
and
|
|
.Li headp
|
|
are user selectable.)
|
|
.Pp
|
|
The macro
|
|
.Nm LIST_HEAD_INITIALIZER
|
|
evaluates to an initializer for the list
|
|
.Fa head .
|
|
.Pp
|
|
The macro
|
|
.Nm LIST_EMPTY
|
|
evaluates to true if there are no elements in the list.
|
|
.Pp
|
|
The macro
|
|
.Nm LIST_ENTRY
|
|
declares a structure that connects the elements in
|
|
the list.
|
|
.Pp
|
|
The macro
|
|
.Nm LIST_FIRST
|
|
returns the first element in the list or NULL if the list
|
|
is empty.
|
|
.Pp
|
|
The macro
|
|
.Nm LIST_FOREACH
|
|
traverses the list referenced by
|
|
.Fa head
|
|
in the forward direction, assigning each element in turn to
|
|
.Fa var .
|
|
.Pp
|
|
The macro
|
|
.Nm LIST_FOREACH_SAFE
|
|
traverses the list referenced by
|
|
.Fa head
|
|
in the forward direction, assigning each element in turn to
|
|
.Fa var .
|
|
However, unlike
|
|
.Fn LIST_FOREACH
|
|
here it is permitted to both remove
|
|
.Fa var
|
|
as well as free it from within the loop safely without interfering with the
|
|
traversal.
|
|
.Pp
|
|
The macro
|
|
.Nm LIST_INIT
|
|
initializes the list referenced by
|
|
.Fa head .
|
|
.Pp
|
|
The macro
|
|
.Nm LIST_INSERT_HEAD
|
|
inserts the new element
|
|
.Fa elm
|
|
at the head of the list.
|
|
.Pp
|
|
The macro
|
|
.Nm LIST_INSERT_AFTER
|
|
inserts the new element
|
|
.Fa elm
|
|
after the element
|
|
.Fa listelm .
|
|
.Pp
|
|
The macro
|
|
.Nm LIST_INSERT_BEFORE
|
|
inserts the new element
|
|
.Fa elm
|
|
before the element
|
|
.Fa listelm .
|
|
.Pp
|
|
The macro
|
|
.Nm LIST_NEXT
|
|
returns the next element in the list, or NULL if this is the last.
|
|
.Pp
|
|
The macro
|
|
.Nm LIST_REMOVE
|
|
removes the element
|
|
.Fa elm
|
|
from the list.
|
|
.Sh LIST EXAMPLE
|
|
.Bd -literal
|
|
LIST_HEAD(listhead, entry) head =
|
|
LIST_HEAD_INITIALIZER(head);
|
|
struct listhead *headp; /* List head. */
|
|
struct entry {
|
|
...
|
|
LIST_ENTRY(entry) entries; /* List. */
|
|
...
|
|
} *n1, *n2, *n3, *np, *np_temp;
|
|
|
|
LIST_INIT(&head); /* Initialize the list. */
|
|
|
|
n1 = malloc(sizeof(struct entry)); /* Insert at the head. */
|
|
LIST_INSERT_HEAD(&head, n1, entries);
|
|
|
|
n2 = malloc(sizeof(struct entry)); /* Insert after. */
|
|
LIST_INSERT_AFTER(n1, n2, entries);
|
|
|
|
n3 = malloc(sizeof(struct entry)); /* Insert before. */
|
|
LIST_INSERT_BEFORE(n2, n3, entries);
|
|
|
|
LIST_REMOVE(n2, entries); /* Deletion. */
|
|
free(n2);
|
|
/* Forward traversal. */
|
|
LIST_FOREACH(np, &head, entries)
|
|
np-> ...
|
|
|
|
/* Safe forward traversal. */
|
|
LIST_FOREACH_SAFE(np, &head, entries, np_temp) {
|
|
np->do_stuff();
|
|
...
|
|
LIST_REMOVE(np, entries);
|
|
free(np);
|
|
}
|
|
|
|
while (!LIST_EMPTY(&head)) { /* List Deletion. */
|
|
n1 = LIST_FIRST(&head);
|
|
LIST_REMOVE(n1, entries);
|
|
free(n1);
|
|
}
|
|
|
|
n1 = LIST_FIRST(&head); /* Faster List Deletion. */
|
|
while (n1 != NULL) {
|
|
n2 = LIST_NEXT(n1, entries);
|
|
free(n1);
|
|
n1 = n2;
|
|
}
|
|
LIST_INIT(&head);
|
|
.Ed
|
|
.Sh TAIL QUEUES
|
|
A tail queue is headed by a structure defined by the
|
|
.Nm TAILQ_HEAD
|
|
macro.
|
|
This structure contains a pair of pointers,
|
|
one to the first element in the tail queue and the other to
|
|
the last element in the tail queue.
|
|
The elements are doubly linked so that an arbitrary element can be
|
|
removed without traversing the tail queue.
|
|
New elements can be added to the tail queue after an existing element,
|
|
before an existing element, at the head of the tail queue,
|
|
or at the end of the tail queue.
|
|
A
|
|
.Fa TAILQ_HEAD
|
|
structure is declared as follows:
|
|
.Bd -literal -offset indent
|
|
TAILQ_HEAD(HEADNAME, TYPE) head;
|
|
.Ed
|
|
.Pp
|
|
where
|
|
.Li HEADNAME
|
|
is the name of the structure to be defined, and
|
|
.Li TYPE
|
|
is the type of the elements to be linked into the tail queue.
|
|
A pointer to the head of the tail queue can later be declared as:
|
|
.Bd -literal -offset indent
|
|
struct HEADNAME *headp;
|
|
.Ed
|
|
.Pp
|
|
(The names
|
|
.Li head
|
|
and
|
|
.Li headp
|
|
are user selectable.)
|
|
.Pp
|
|
The macro
|
|
.Nm TAILQ_HEAD_INITIALIZER
|
|
evaluates to an initializer for the tail queue
|
|
.Fa head .
|
|
.Pp
|
|
The macro
|
|
.Nm TAILQ_CONCAT
|
|
concatenates the tail queue headed by
|
|
.Fa head2
|
|
onto the end of the one headed by
|
|
.Fa head1
|
|
removing all entries from the former.
|
|
.Pp
|
|
The macro
|
|
.Nm TAILQ_EMPTY
|
|
evaluates to true if there are no items on the tail queue.
|
|
.Pp
|
|
The macro
|
|
.Nm TAILQ_ENTRY
|
|
declares a structure that connects the elements in
|
|
the tail queue.
|
|
.Pp
|
|
The macro
|
|
.Nm TAILQ_FIRST
|
|
returns the first item on the tail queue or NULL if the tail queue
|
|
is empty.
|
|
.Pp
|
|
The macro
|
|
.Nm TAILQ_FOREACH
|
|
traverses the tail queue referenced by
|
|
.Fa head
|
|
in the forward direction, assigning each element in turn to
|
|
.Fa var .
|
|
.Fa var
|
|
is set to
|
|
.Dv NULL
|
|
if the loop completes normally, or if there were no elements.
|
|
.Pp
|
|
The macro
|
|
.Nm TAILQ_FOREACH_REVERSE
|
|
traverses the tail queue referenced by
|
|
.Fa head
|
|
in the reverse direction, assigning each element in turn to
|
|
.Fa var .
|
|
.Pp
|
|
The macros
|
|
.Nm TAILQ_FOREACH_SAFE
|
|
and
|
|
.Nm TAILQ_FOREACH_REVERSE_SAFE
|
|
traverse the list referenced by
|
|
.Fa head
|
|
in the forward or reverse direction respectively,
|
|
assigning each element in turn to
|
|
.Fa var .
|
|
However, unlike their unsafe counterparts,
|
|
.Nm TAILQ_FOREACH
|
|
and
|
|
.Nm TAILQ_FOREACH_REVERSE
|
|
permit to both remove
|
|
.Fa var
|
|
as well as free it from within the loop safely without interfering with the
|
|
traversal.
|
|
.Pp
|
|
The macro
|
|
.Nm TAILQ_INIT
|
|
initializes the tail queue referenced by
|
|
.Fa head .
|
|
.Pp
|
|
The macro
|
|
.Nm TAILQ_INSERT_HEAD
|
|
inserts the new element
|
|
.Fa elm
|
|
at the head of the tail queue.
|
|
.Pp
|
|
The macro
|
|
.Nm TAILQ_INSERT_TAIL
|
|
inserts the new element
|
|
.Fa elm
|
|
at the end of the tail queue.
|
|
.Pp
|
|
The macro
|
|
.Nm TAILQ_INSERT_AFTER
|
|
inserts the new element
|
|
.Fa elm
|
|
after the element
|
|
.Fa listelm .
|
|
.Pp
|
|
The macro
|
|
.Nm TAILQ_INSERT_BEFORE
|
|
inserts the new element
|
|
.Fa elm
|
|
before the element
|
|
.Fa listelm .
|
|
.Pp
|
|
The macro
|
|
.Nm TAILQ_LAST
|
|
returns the last item on the tail queue.
|
|
If the tail queue is empty the return value is undefined.
|
|
.Pp
|
|
The macro
|
|
.Nm TAILQ_NEXT
|
|
returns the next item on the tail queue, or NULL if this item is the last.
|
|
.Pp
|
|
The macro
|
|
.Nm TAILQ_PREV
|
|
returns the previous item on the tail queue, or NULL if this item
|
|
is the first.
|
|
.Pp
|
|
The macro
|
|
.Nm TAILQ_REMOVE
|
|
removes the element
|
|
.Fa elm
|
|
from the tail queue.
|
|
.Sh TAIL QUEUE EXAMPLE
|
|
.Bd -literal
|
|
TAILQ_HEAD(tailhead, entry) head =
|
|
TAILQ_HEAD_INITIALIZER(head);
|
|
struct tailhead *headp; /* Tail queue head. */
|
|
struct entry {
|
|
...
|
|
TAILQ_ENTRY(entry) entries; /* Tail queue. */
|
|
...
|
|
} *n1, *n2, *n3, *np;
|
|
|
|
TAILQ_INIT(&head); /* Initialize the queue. */
|
|
|
|
n1 = malloc(sizeof(struct entry)); /* Insert at the head. */
|
|
TAILQ_INSERT_HEAD(&head, n1, entries);
|
|
|
|
n1 = malloc(sizeof(struct entry)); /* Insert at the tail. */
|
|
TAILQ_INSERT_TAIL(&head, n1, entries);
|
|
|
|
n2 = malloc(sizeof(struct entry)); /* Insert after. */
|
|
TAILQ_INSERT_AFTER(&head, n1, n2, entries);
|
|
|
|
n3 = malloc(sizeof(struct entry)); /* Insert before. */
|
|
TAILQ_INSERT_BEFORE(n2, n3, entries);
|
|
|
|
TAILQ_REMOVE(&head, n2, entries); /* Deletion. */
|
|
free(n2);
|
|
/* Forward traversal. */
|
|
TAILQ_FOREACH(np, &head, entries)
|
|
np-> ...
|
|
/* Safe forward traversal. */
|
|
TAILQ_FOREACH_SAFE(np, &head, entries, np_temp) {
|
|
np->do_stuff();
|
|
...
|
|
TAILQ_REMOVE(&head, np, entries);
|
|
free(np);
|
|
}
|
|
/* Reverse traversal. */
|
|
TAILQ_FOREACH_REVERSE(np, &head, tailhead, entries)
|
|
np-> ...
|
|
/* TailQ Deletion. */
|
|
while (!TAILQ_EMPTY(&head)) {
|
|
n1 = TAILQ_FIRST(&head);
|
|
TAILQ_REMOVE(&head, n1, entries);
|
|
free(n1);
|
|
}
|
|
/* Faster TailQ Deletion. */
|
|
n1 = TAILQ_FIRST(&head);
|
|
while (n1 != NULL) {
|
|
n2 = TAILQ_NEXT(n1, entries);
|
|
free(n1);
|
|
n1 = n2;
|
|
}
|
|
TAILQ_INIT(&head);
|
|
.Ed
|
|
.Sh HISTORY
|
|
The
|
|
.Nm queue
|
|
functions first appeared in
|
|
.Bx 4.4 .
|