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.Dd $Mdocdate: April 26 2020 $
.Dt INSQUE 3
.Os
.Sh NAME
.Nm insque ,
.Nm remque
.Nd legacy doubly linked lists
.Sh SYNOPSIS
.In search.h
.Ft void
.Fn insque "void *elem" "void *pred"
.Ft void
.Fn remque "void *elem"
.Sh DESCRIPTION
.Bf -symbolic
These interfaces have been superseded by the
.Xr queue 3
macros and are provided for compatibility with legacy code.
.Ef
.Pp
.Fn insque
and
.Fn remque
manipulate a legacy variety of intrusive doubly linked lists.
A list can be either circular or linear.
Each element in the list 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 members of the struct must be pointers of the
same type that point to the next and previous elements in
the list, respectively.
Any subsequent data in the struct is application-dependent.
.Pp
The
.Fn insque
function inserts
.Fa elem
into a list immediately after
.Fa pred .
.Pp
The
.Fn remque
function removes
.Fa elem
from the list.
.Pp
These functions are not atomic.
.Sh SEE ALSO
.Xr queue 3
.Sh STANDARDS
The
.Fn insque
and
.Fn remque
functions conform to the X/Open System Interfaces option of the
.St -p1003.1-2008
specification.
.Sh HISTORY
The
.Fn insque
and
.Fn remque
functions are derived from the
.Li insque
and
.Li remque
instructions on the VAX.
They first appeared in
.Bx 4.2 .