[boost] Will the boost::asio::streambuf keep in sequency order when ostream write to boost::asio::streambuf multiple time?

Hi, Are there any problems in following statements? The receiver works a few minutes, then got wrong number in header field. std::shared_ptr<boost::asio::streambuf> buffer = std::make_shared<boost::asio::streambuf>(); std::ostream os(buffer.get()); os.write((char *) &sendHeader, sizeof(sendHeader)); os.write((char *) sb.data(), sb.size()); boost::asio::async_write(socket_, *buffer.get(), .....); Thank you. - JHH