public function getParent()
    {
        // that's a lastIndexOf
        $index = ((($res = strrpos($this->path, self::$separator)) === false) ? -1 : $res);
        if ($index < $this->prefixLength) {
            if (($this->prefixLength > 0) && (strlen($this->path) > $this->prefixLength)) {
                return substr($this->path, 0, $this->prefixLength);
            }

            return null;
        }

        return substr($this->path, 0, $index);
    }