private function getAvailableArchiveFileName()
    {
        $returnValue = (string) '';

        
    	$filebase = basename($this->filename);
    	$dotpos = strrpos($filebase, ".");
    	if ($dotpos === false) {
    		$dotpos = strlen($filebase);
    	}
    	$prefix = $this->directory.DIRECTORY_SEPARATOR.substr($filebase, 0, $dotpos)."_".date('Y-m-d');
    	$sufix = substr($filebase, $dotpos).($this->compression === self::COMPRESSION_ZIP ? '.zip' : '');
    	$count_string = "";
    	$count = 0;
    	while (file_exists($prefix.$count_string.$sufix)) {
    		$count_string = "_".++$count;
    	}
        $returnValue = $prefix.$count_string.$sufix;
        

        return (string) $returnValue;
    }