More robust yacc/bison failure output handling.

[p5sagit/p5-mst-13.2.git] / lib / SelectSaver.pm

package SelectSaver;

=head1 NAME

SelectSaver - save and restore selected file handle

=head1 SYNOPSIS

    use SelectSaver;

    {
       my $saver = new SelectSaver(FILEHANDLE);
       # FILEHANDLE is selected
    }
    # previous handle is selected

    {
       my $saver = new SelectSaver;
       # new handle may be selected, or not
    }
    # previous handle is selected

=head1 DESCRIPTION

A C<SelectSaver> object contains a reference to the file handle that
was selected when it was created.  If its C<new> method gets an extra
parameter, then that parameter is selected; otherwise, the selected
file handle remains unchanged.

When a C<SelectSaver> is destroyed, it re-selects the file handle
that was selected when it was created.

=cut

require 5.000;
use Carp;
use Symbol;

sub new {
    @_ >= 1 && @_ <= 2 or croak 'usage: new SelectSaver [FILEHANDLE]';
    my $fh = select;
    my $self = bless [$fh], $_[0];
    select qualify($_[1], caller) if @_ > 1;
    $self;
}

sub DESTROY {
    my $this = $_[0];
    select $$this[0];
}

1;