public function save(string $namespace, string $hash, string $content): void
    {
        $fileName = $this->getFileName($namespace, $hash);
        $this->ensureDirectory(dirname($fileName));

        $success = false;
        if (!file_exists($fileName) || is_writable($fileName)) {
            $success = file_put_contents($fileName, $content);
        }
        if ($success === false) {
            throw new ExportDataException('Unable to write file ' . $fileName);
        }
    }