.\"	$OpenBSD: insque.3,v 1.7 2007/05/31 19:19:31 jmc Exp $
.\" Copyright (c) 1993 John Brezak
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.Dd $Mdocdate: May 31 2007 $
.Dt INSQUE 3
.Os
.Sh NAME
.Nm insque ,
.Nm remque
.Nd insert/remove element from a queue
.Sh SYNOPSIS
.Fd #include <search.h>
.Ft void
.Fn insque "void *elem" "void *pred"
.Ft void
.Fn remque "void *elem"
.Sh DESCRIPTION
.Bf -symbolic
These interfaces have been superceded by the
.Xr queue 3
macros and are provided for compatibility with legacy code.
.Ef
.Pp
.Fn insque
and
.Fn remque
manipulate queues built from doubly linked lists.
The queue can be either circular or linear.
Each element in the queue must be of the following form:
.Bd -literal -offset indent
struct qelem {
	struct qelem   *q_forw;
	struct qelem   *q_back;
	char            q_data[];
};
.Ed
.Pp
The first two elements in the struct must be pointers of the
same type that point to the previous and next elements in
the queue respectively.
Any subsequent data in the struct is application-dependent.
.Pp
The
.Fn insque
function inserts
.Fa elem
into a queue immediately after
.Fa pred .
.Pp
The
.Fn remque
function removes
.Fa elem
from the queue.
.Pp
These functions are not atomic unless that machine architecture allows it.
.Sh SEE ALSO
.Xr queue 3
.Sh STANDARDS
The
.Fn insque
and
.Fn remque
functions conform to the
.St -p1003.1-2001
and
.St -xpg4.3
specifications.
.Sh HISTORY
The
.Fn insque
and
.Fn remque
functions are derived from the
.Li insque
and
.Li remque
instructions on the
.Tn VAX .
They first appeared in
.Bx 4.2 .