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POReading messages from a serial port with Boost Asio
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copied!<p>I would like to use <a href="http://en.wikipedia.org/wiki/Asio_C++_library" rel="nofollow">Boost Asio</a> to read variable length messages from the serial port. I would like to read and wait long enough to be sure that the line is idle, but I do not want to block completely.</p> <p>The following code is what I have so far, and I am in the process of testing it:</p> <pre><code>long readData(void *_pData, unsigned long _uSize, size_t millis) { size_t n = 0; // n will return the message size. if (millis > 0) // millis is the acceptable idle time, 0 is invalid in my case. { size_t uBytesTransferred = 0; boost::asio::deadline_timer timeout(m_ioService); ReadCallback readCallback(uBytesTransferred, timeout); WaitCallback waitCallback(m_port); while (_uSize - (unsigned long)n > 0) { // Setup asynchronous read with timeout m_ioService.reset(); m_port.async_read_some(boost::asio::buffer((char*)_pData + n, _uSize - (unsigned long)n), readCallback); timeout.expires_from_now(boost::posix_time::milliseconds(millis)); timeout.async_wait(waitCallback); // Block until asynchronous callbacks are finished m_ioService.run(); // Continue if any bytes were received, stop otherwise if (uBytesTransferred > 0) { n += uBytesTransferred; m_uBytesReceived += uBytesTransferred; } else { break; } } } return n; } </code></pre> <p>I would like to know if this is the correct way of doing this (that is, reading until the line is idle) with Boost Asio?</p> <p>Here are my callback handlers:</p> <pre><code>struct ReadCallback { ReadCallback(std::size_t &_uBytesTransferred, boost::asio::deadline_timer &_timeout) :m_uBytesTransferred(_uBytesTransferred), m_timeout(_timeout) {} void operator()(const boost::system::error_code &_error, std::size_t _uBytesTransferred) { m_uBytesTransferred = _uBytesTransferred; if (!_error && (_uBytesTransferred > 0) ) { m_timeout.cancel(); } } std::size_t &m_uBytesTransferred; boost::asio::deadline_timer &m_timeout; private: ReadCallback(); ReadCallback &operator=(const ReadCallback&); }; struct WaitCallback { WaitCallback(boost::asio::serial_port &_port) :m_port(_port) {} void operator()(const boost::system::error_code &_error) { if (!_error) { m_port.cancel(); } } boost::asio::serial_port &m_port; private: WaitCallback(); WaitCallback &operator=(const WaitCallback&); }; </code></pre>

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