异步读取串行端口 [英] Reading a Serial Port Asynchronously Boost

问题描述

我尝试从串行端口异步读取几个字节。目前我使用的代码（来源是如何执行非阻塞读取使用asio？），只允许我读取1个字节，然后退出。如何获得它，使代码保持读取，直到没有更多的输入数据在串行端口？感谢：）

I am trying to read several bytes asynchronously from a serial port. Currently the code I am using (source is How do I perform a nonblocking read using asio?), only allows me to read 1 byte and then it exits. How do I get it so that the code keeps reading until there is no more incoming data in the serial port? Thanks :)

    void foo()
{
    boost::asio::io_service io_svc;
    boost::asio::serial_port ser_port(io_svc, "/dev/ttyS0");
    boost::asio::deadline_timer timeout(io_svc);
    unsigned char my_buffer[2];
    bool data_available = false;

    ser_port.async_read_some(boost::asio::buffer(my_buffer),
            boost::bind(&read_callback, boost::ref(data_available),
                    boost::ref(timeout),boost::asio::placeholders::error(),
                    boost::asio::placeholders::bytes_transferred()));
    timeout.expires_from_now(boost::posix_time::seconds(30));
    timeout.async_wait(boost::bind(&wait_callback, boost::ref(ser_port),boost::asio::placeholders::error()));

    io_svc.run();

    io_svc.

    if(!data_available)
    {
        ser_port.close();
        cout << "ser_port was closed";
    }

}

void read_callback(bool& data_available, boost::asio::deadline_timer& timeout, const boost::system::error_code& error, std::size_t bytes_transferred)
{
    if (error || !bytes_transferred)
    {
        // No data was read!
        data_available = false;
        return;
    }

    timeout.cancel();
    data_available = true;
}

void wait_callback(boost::asio::serial_port& ser_port, const boost::system::error_code& error)
{
    if (error)
    {
        // Data was read and this timeout was cancelled

        return;
    }

    ser_port.cancel();
}

推荐答案

c> read_callback 你取消你的计时器，不要开始新的读。

那么你期望ASIO做什么。

In your read_callback you cancel your timer and do not start a new read.
So what do you expect ASIO to do. You just canceled all handlers and like the documentation states, the run method will return when no handlers are left.

因此，如果你想有更多的数据，而不仅仅是一个字节你收到你可以做两件事情：

首先，再次调用asio以从端口读取更多。

So if you want to have more data than just the one byte you receive you can do two things:
First just issue another call to asio to read more from the port.

void read_callback(bool& data_available, boost::asio::deadline_timer& timeout, const  boost::system::error_code& error, std::size_t bytes_transferred)
{
    if (error || !bytes_transferred)
    {
        // No data was read!
        data_available = false;
        return;
    }
    // do something with the data you just read
    ser_port.async_read_some(boost::asio::buffer(my_buffer),
        boost::bind(&read_callback, boost::ref(data_available),
                boost::ref(timeout),boost::asio::placeholders::error(),
                boost::asio::placeholders::bytes_transferred()));
    //restart your timer
    data_available = true;
}

或者您可以使用 transfer_at_least 至少获得所需的数据量。

or you can add use transfer_at_least to get at least the amount of data you need.

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