sub getTopicNames {
    my $this = shift;
    my $dh;
    opendir( $dh, "$Foswiki::cfg{DataDir}/$this->{web}" )
      or return ();

    # the name filter is used to ensure we don't return filenames
    # that contain illegal characters as topic names.
    { use locale;
    	my @topicList =
      		map { /^(.*)\.txt$/; $1; }
      		sort
      		grep { !/$Foswiki::cfg{NameFilter}/ && /\.txt$/ } readdir($dh);
    }
    closedir($dh);
    return @topicList;
}