2020-10-25 09:36:43 +00:00
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.\" Copyright (c) 1993
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.\" The Regents of the University of California. All rights reserved.
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.\" and Copyright (c) 2020 by Alejandro Colomar <colomar.6.4.3@gmail.com>
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.\"
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.\" %%%LICENSE_START(BSD_3_CLAUSE_UCB)
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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. 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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.\" 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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.\" SUCH DAMAGE.
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.\" %%%LICENSE_END
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.\"
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.\"
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.TH TAILQ 3 2020-10-21 "GNU" "Linux Programmer's Manual"
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.SH NAME
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2020-10-25 09:36:44 +00:00
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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_FROM ,
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.\" .Nm TAILQ_FOREACH_FROM_SAFE ,
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.Nm TAILQ_FOREACH_REVERSE ,
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.\" .Nm TAILQ_FOREACH_REVERSE_FROM ,
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.\" .Nm TAILQ_FOREACH_REVERSE_FROM_SAFE ,
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.\" .Nm TAILQ_FOREACH_REVERSE_SAFE ,
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.\" .Nm TAILQ_FOREACH_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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.\" .Nm TAILQ_SWAP
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2020-10-25 09:36:43 +00:00
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.SH SYNOPSIS
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2020-10-25 09:36:45 +00:00
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.In sys/queue.h
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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_FROM "TYPE *var" "TAILQ_HEAD *head" "TAILQ_ENTRY NAME"
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.\" .Fn TAILQ_FOREACH_FROM_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_FROM "TYPE *var" "TAILQ_HEAD *head" "HEADNAME" "TAILQ_ENTRY NAME"
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.\" .Fn TAILQ_FOREACH_REVERSE_FROM_SAFE "TYPE *var" "TAILQ_HEAD *head" "HEADNAME" "TAILQ_ENTRY NAME" "TYPE *temp_var"
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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_FOREACH_SAFE "TYPE *var" "TAILQ_HEAD *head" "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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.\" .Fn TAILQ_SWAP "TAILQ_HEAD *head1" "TAILQ_HEAD *head2" "TYPE" "TAILQ_ENTRY NAME"
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.\"
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2020-10-25 09:36:43 +00:00
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.SH DESCRIPTION
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2020-10-25 09:36:46 +00:00
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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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.Li TAILQ_ENTRY ,
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or
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.Li CIRCLEQ_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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.Li TAILQ_HEAD ,
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or
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.Li CIRCLEQ_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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.Ss Tail queues
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A tail queue is headed by a structure defined by the
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.Nm TAILQ_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 doubly linked so that an arbitrary element can be
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removed without traversing the tail queue.
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New elements can be added to the tail queue after an existing element,
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before an existing element, at the head of the tail queue,
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or at the end of the tail queue.
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A
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.Fa TAILQ_HEAD
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structure is declared as follows:
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.Bd -literal -offset indent
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TAILQ_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 TAILQ_HEAD_INITIALIZER
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evaluates to an initializer for the tail queue
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.Fa head .
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.Pp
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The macro
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.Nm TAILQ_CONCAT
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concatenates the tail queue headed by
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.Fa head2
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onto the end of the one headed by
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.Fa head1
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removing all entries from the former.
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.Pp
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The macro
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.Nm TAILQ_EMPTY
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evaluates to true if there are no items on the tail queue.
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.Pp
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The macro
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.Nm TAILQ_ENTRY
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declares a structure that connects the elements in
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the tail queue.
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.Pp
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The macro
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.Nm TAILQ_FIRST
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returns the first item on the tail queue or NULL if the tail queue
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is empty.
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.Pp
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The macro
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.Nm TAILQ_FOREACH
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traverses the tail queue referenced by
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.Fa head
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in the forward direction, assigning each element in turn to
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.Fa var .
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.Fa var
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is set to
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.Dv NULL
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if the loop completes normally, or if there were no elements.
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.\" .Pp
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.\" The macro
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.\" .Nm TAILQ_FOREACH_FROM
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.\" behaves identically to
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.\" .Nm TAILQ_FOREACH
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.\" when
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.\" .Fa var
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.\" is NULL, else it treats
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.\" .Fa var
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.\" as a previously found TAILQ element and begins the loop at
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.\" .Fa var
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.\" instead of the first element in the TAILQ referenced by
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.\" .Fa head .
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.Pp
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The macro
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.Nm TAILQ_FOREACH_REVERSE
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traverses the tail queue referenced by
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.Fa head
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in the reverse direction, assigning each element in turn to
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.Fa var .
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.\" .Pp
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.\" The macro
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.\" .Nm TAILQ_FOREACH_REVERSE_FROM
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.\" behaves identically to
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.\" .Nm TAILQ_FOREACH_REVERSE
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.\" when
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.\" .Fa var
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.\" is NULL, else it treats
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.\" .Fa var
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.\" as a previously found TAILQ element and begins the reverse loop at
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.\" .Fa var
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.\" instead of the last element in the TAILQ referenced by
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.\" .Fa head .
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.\" .Pp
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.\" The macros
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.\" .Nm TAILQ_FOREACH_SAFE
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.\" and
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.\" .Nm TAILQ_FOREACH_REVERSE_SAFE
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.\" traverse the list referenced by
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.\" .Fa head
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.\" in the forward or reverse direction respectively,
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.\" assigning each element in turn to
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.\" .Fa var .
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.\" However, unlike their unsafe counterparts,
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.\" .Nm TAILQ_FOREACH
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.\" and
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.\" .Nm TAILQ_FOREACH_REVERSE
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.\" permit 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 TAILQ_FOREACH_FROM_SAFE
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.\" behaves identically to
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.\" .Nm TAILQ_FOREACH_SAFE
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.\" when
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.\" .Fa var
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.\" is NULL, else it treats
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.\" .Fa var
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.\" as a previously found TAILQ element and begins the loop at
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.\" .Fa var
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.\" instead of the first element in the TAILQ referenced by
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.\" .Fa head .
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.\" .Pp
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.\" The macro
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.\" .Nm TAILQ_FOREACH_REVERSE_FROM_SAFE
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.\" behaves identically to
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.\" .Nm TAILQ_FOREACH_REVERSE_SAFE
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.\" when
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.\" .Fa var
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.\" is NULL, else it treats
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.\" .Fa var
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.\" as a previously found TAILQ element and begins the reverse loop at
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.\" .Fa var
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.\" instead of the last element in the TAILQ referenced by
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.\" .Fa head .
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.Pp
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The macro
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.Nm TAILQ_INIT
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initializes the tail queue referenced by
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.Fa head .
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.Pp
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The macro
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.Nm TAILQ_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 tail queue.
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.Pp
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The macro
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.Nm TAILQ_INSERT_TAIL
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inserts the new element
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.Fa elm
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at the end of the tail queue.
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.Pp
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The macro
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.Nm TAILQ_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 TAILQ_INSERT_BEFORE
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inserts the new element
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.Fa elm
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before the element
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.Fa listelm .
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.Pp
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The macro
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.Nm TAILQ_LAST
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returns the last item on the tail queue.
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If the tail queue is empty the return value is
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.Dv NULL .
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.Pp
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The macro
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.Nm TAILQ_NEXT
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returns the next item on the tail queue, or NULL if this item is the last.
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.Pp
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The macro
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.Nm TAILQ_PREV
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returns the previous item on the tail queue, or NULL if this item
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is the first.
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.Pp
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The macro
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.Nm TAILQ_REMOVE
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removes the element
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.Fa elm
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from the tail queue.
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.\" .Pp
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.\" The macro
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.\" .Nm TAILQ_SWAP
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.\" swaps the contents of
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.\" .Fa head1
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.\" and
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.\" .Fa head2 .
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.Pp
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See the EXAMPLES section below for an example program using a tail queue.
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2020-10-25 09:36:43 +00:00
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.SH RETURN VALUE
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.SH CONFORMING TO
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.SH BUGS
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.SH EXAMPLES
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2020-10-25 09:36:47 +00:00
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.Ss Tail queue example
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.Bd -literal
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#include <stddef.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <sys/queue.h>
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struct entry {
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int data;
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TAILQ_ENTRY(entry) entries; /* Tail queue. */
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};
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TAILQ_HEAD(tailhead, entry);
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int
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main(void)
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{
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struct entry *n1, *n2, *n3, *np;
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struct tailhead head; /* Tail queue head. */
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int i;
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TAILQ_INIT(&head); /* Initialize the queue. */
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n1 = malloc(sizeof(struct entry)); /* Insert at the head. */
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TAILQ_INSERT_HEAD(&head, n1, entries);
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n1 = malloc(sizeof(struct entry)); /* Insert at the tail. */
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TAILQ_INSERT_TAIL(&head, n1, entries);
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n2 = malloc(sizeof(struct entry)); /* Insert after. */
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|
TAILQ_INSERT_AFTER(&head, n1, n2, entries);
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|
n3 = malloc(sizeof(struct entry)); /* Insert before. */
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|
TAILQ_INSERT_BEFORE(n2, n3, entries);
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|
TAILQ_REMOVE(&head, n2, entries); /* Deletion. */
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|
free(n2);
|
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|
/* Forward traversal. */
|
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|
|
i = 0;
|
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|
|
TAILQ_FOREACH(np, &head, entries)
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|
np->data = i++;
|
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|
/* Reverse traversal. */
|
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|
TAILQ_FOREACH_REVERSE(np, &head, tailhead, entries)
|
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|
|
printf("%i\en", np->data);
|
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|
|
/* TailQ Deletion. */
|
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|
|
n1 = TAILQ_FIRST(&head);
|
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|
|
while (n1 != NULL) {
|
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|
|
n2 = TAILQ_NEXT(n1, entries);
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|
|
free(n1);
|
|
|
|
n1 = n2;
|
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|
|
}
|
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|
|
TAILQ_INIT(&head);
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|
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|
|
exit(EXIT_SUCCESS);
|
|
|
|
}
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.Ed
|
2020-10-25 09:36:43 +00:00
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.SH SEE ALSO
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