protected function lockFileName($file, array $options = array()) {
        $lockDir = $this->getOption('lock_dir', $options, $this->getCachePath() . 'locks' . DIRECTORY_SEPARATOR);
        return $lockDir . preg_replace('/\W/', '_', $file) . $this->getOption(xPDO::OPT_LOCKFILE_EXTENSION, $options, '.lock');
    }