public function stream_flush()
    {
        // If the stream wasn't opened for writing, just return false
        if (!$this->_writeBuffer) {
            return false;
        }
        $ret = $this->_oss->putObject(AliyunOSS::getBucket(), $this->_objectName, $this->_objectBuffer);
        $this->_objectBuffer = null;

        return $ret;
    }