Ensures the root directory exists and has correct permissions.
protected function ensureDirectory() {
if (!file_exists($this->directory)) {
mkdir($this->directory, 0700, TRUE);
}
chmod($this->directory, 0700);
$htaccess_path = $this->directory . '/.htaccess';
if (!file_exists($htaccess_path) && file_put_contents($htaccess_path, self::HTACCESS)) {
@chmod($htaccess_path, 0444);
}
}