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.\" $OpenBSD: insque.3,v 1.11 2020/04/26 13:59:56 jmc Exp $
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.\" Copyright (c) 1993 John Brezak
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.\" 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. The name of the author may be used to endorse or promote products
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.\" derived from this software without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR `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 AUTHOR 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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.\"
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.Dd $Mdocdate: April 26 2020 $
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.Dt INSQUE 3
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.Os
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.Sh NAME
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.Nm insque ,
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.Nm remque
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.Nd insert/remove element from a queue
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.Sh SYNOPSIS
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.In search.h
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.Ft void
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.Fn insque "void *elem" "void *pred"
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.Ft void
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.Fn remque "void *elem"
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.Sh DESCRIPTION
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.Bf -symbolic
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These interfaces have been superseded by the
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.Xr queue 3
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macros and are provided for compatibility with legacy code.
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.Ef
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.Pp
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.Fn insque
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and
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.Fn remque
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manipulate queues built from doubly linked lists.
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The queue can be either circular or linear.
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Each element in the queue must be of the following form:
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.Bd -literal -offset indent
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struct qelem {
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struct qelem *q_forw;
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struct qelem *q_back;
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char q_data[];
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};
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.Ed
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.Pp
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The first two elements in the struct must be pointers of the
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same type that point to the next and previous elements in
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the queue respectively.
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Any subsequent data in the struct is application-dependent.
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.Pp
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The
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.Fn insque
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function inserts
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.Fa elem
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into a queue immediately after
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.Fa pred .
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.Pp
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The
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.Fn remque
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function removes
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.Fa elem
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from the queue.
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.Pp
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These functions are not atomic unless that machine architecture allows it.
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.Sh SEE ALSO
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.Xr queue 3
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.Sh STANDARDS
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The
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.Fn insque
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and
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.Fn remque
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functions conform to the X/Open System Interfaces option of the
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.St -p1003.1-2008
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specification.
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.Sh HISTORY
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The
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.Fn insque
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and
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.Fn remque
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functions are derived from the
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.Li insque
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and
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.Li remque
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instructions on the VAX.
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They first appeared in
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.Bx 4.2 .
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