public function setDirLevel($dirLevel)
    {
        $dirLevel = (int)$dirLevel;
        if ($dirLevel < 0 || $dirLevel > 16) {
            throw new Exception\InvalidArgumentException(
                "Directory level '{$dirLevel}' must be between 0 and 16"
            );
        }
        $this->dirLevel = $dirLevel;

        return $this;
    }