c++ - 与设备文件的异步读写

Question

我正在将一些二进制数据写入/dev/itun 之类的设备文件。

void ahaConnector::asyncWriteData(vector<uint8_t> packedMessage) {

    cout<<"\n async write data packed message";
    deviceStreamDescriptor.assign(device);
    boost::asio::write (
                       deviceStreamDescriptor,
                       boost::asio::buffer(packedMessage)
                       );


    readbuffer.resize(1024);
    deviceStreamDescriptor.async_read_some(boost::asio::buffer(readbuffer),
                                boost::bind(&ahaConnector::readHeader, this,
                                boost::asio::placeholders::error(),
                                boost::asio::placeholders::bytes_transferred()
                                ));
    io_service.run();

}

void ahaConnector::readHeader(const boost::system::error_code &ec, std::size_t bytes_transferred) {


    if(!ec) {

        std::cout<<"\n Bytes transfereed :"<<bytes_transferred<<" "<<readbuffer.size();


        deviceStreamDescriptor.async_read_some(boost::asio::buffer(readbuffer),
                                        boost::bind(&ahaConnector::readHeader, this,
                                        boost::asio::placeholders::error(),
                                        boost::asio::placeholders::bytes_transferred()
                                        ));

        Callbacks callbacks;
        callbacks.OnReceivingPackedMessage();
        io_service.run();

    }
    else {

        cout<<"\n System Error Code "<<ec;
    }

}

回调函数 readhandler 已成功执行，但我无法将控制从我的回调函数转移到另一个类。

从设计的角度来看是有问题的。我需要处理从回调函数收到的消息以获得进一步的逻辑。我应该在这里使用另一个线程吗？

Answer 1

查看此代码，您可能只想替换 read(device,...)通过 boost Asio 对 Posix 流的支持:

#include <boost/asio.hpp>
#include <boost/asio/posix/stream_descriptor.hpp>
#include <boost/function.hpp>
#include <iostream>

static int device = 0;

using namespace boost;

int main() {
    boost::asio::io_service io_svc;
    boost::asio::posix::stream_descriptor iodevice(io_svc, device);

    char buffer[1024];
    function<void(system::error_code const&, size_t)> callback;
    callback = [&](boost::system::error_code const& ec, size_t bytes_transferred) {
            if (ec)
            {
                std::cout << "Error '" << ec.message() << "' during asynchronous operation\n";
            }
            else
            {
                std::cout << "Read exactly " << bytes_transferred << " bytes\n";
                std::cout << "Data: '"; 
                std::cout.write(buffer, bytes_transferred);  
                std::cout << "'\n";

                iodevice.async_read_some(asio::buffer(buffer), callback);
            }
        };

    iodevice.async_read_some(asio::buffer(buffer), callback);

    io_svc.run();
}

查看 Live On Coliru 。

遗憾的是，在 Coliru 上它无法工作，因为输入是从非流重定向的。但是，如果您以交互方式运行它，它将起作用并打印输入的前 10 个字符。