c++ boost asio串行通信在basic_serial_port.hpp中“不能访问私有成员”

Question

我正在编写一个C++程序，通过COM端口与多个设备-- Arduino Pro Mini w/ATmega328 328和带有全球定位系统屏蔽的Arduino Uno --同时通信，我使用的是boost::asio包。我不是C++大师，所以我偶尔会弄糊涂，试图找出什么地方/什么时候传递引用或值；我认为这就是其中之一。

下面是设置串行通信端口的代码

std::string IMU_COM_PORT = "COM5"; // or whatever... it varies
int IMU_BAUD_RATE = 57600;
std::string ARDUINO_COM_PORT = "COM3"; // also varies
int ARDUINO_BAUD_RATE = 115200;

int main() {
    std::vector<boost::thread *> sensorThreads;
    int sensorThreadCount = 0;

    using namespace::boost::asio;

    // get the COM port handle for the IMU sensor
    boost::asio::io_service IMU_io;
    boost::asio::serial_port IMU_port(IMU_io);
    IMU_port.open(IMU_COM_PORT);
    if (!IMU_port.is_open()) {
        cerr << "Failed to connect to IMU." << endl;
    }
    else {
        IMU_port.set_option(boost::asio::serial_port_base::baud_rate(IMU_BAUD_RATE));
        // the IMU has to be put into triggered output mode with a specific command: #o0
        // to put it back into continuous output mode we can use this command: #o1
        std::string IMU_init_cmd = "#o0";
        boost::asio::write(IMU_port, boost::asio::buffer(IMU_init_cmd.c_str(), IMU_init_cmd.size()));
        // now the IMU should be ready

        sensorThreads.push_back(new boost::thread(testIMUThread, IMU_port));
        sensorThreadCount++;
    }

    // get the COM port handle for the ARDUINO board with GPS sensor
    boost::asio::io_service ARDUINO_io;
    boost::asio::serial_port ARDUINO_port(ARDUINO_io);
    ARDUINO_port.open(ARDUINO_COM_PORT);
    if (!ARDUINO_port.is_open()) {
        cerr << "Failed to connect to ARDUINO." << endl;
    }
    else {
        ARDUINO_port.set_option(boost::asio::serial_port_base::baud_rate(ARDUINO_BAUD_RATE));
        // now the ARDUINO w/GPS sensor should be ready

        sensorThreads.push_back(new boost::thread(testGPSThread, ARDUINO_port));
        sensorThreadCount++;
    }

    for (int i = 0; i < sensorThreadCount; i++) {
        sensorThreads[i]->join();
        delete sensorThreads[i];
    }
}

我的两个测试线程函数基本上是相同的，唯一的区别是它们发送给设备的字节(S)表示有什么东西(我的计算机)正在等待从它们读取数据。

void testIMUThread(boost::asio::serial_port *port) {
    while(true) { cout << readCOMLine(port, "#f") << endl; }
}
void testGPSThread(boost::asio::serial_port *port) {
    while(true) { cout << readCOMLine(port, "r") << endl; }
}

这两个测试线程都使用了一个执行串行读写的函数。

std::string readCOMLine(boost::asio::serial_port *port, std::string requestDataCmd) {
    char c;
    std::string s;
    boost::asio::write(port, boost::asio::buffer(requestDataCmd.c_str(), requestDataCmd.size()));
    while(true) {
        boost::asio::read(port, boost::asio::buffer(&c,1));
        switch(c) {
            case '\r': break;
            case '\n': return s;
            default: s += c;
        }
    }
}

上面的代码不编译，而是生成以下内容(在MSVC2010中)：Error 11 error C2248: 'boost::asio::basic_io_object<IoObjectService>::basic_io_object' : cannot access private member declared in class 'boost::asio::basic_io_object<IoObjectService>' C:\boost_1_51_0\boost\asio\basic_serial_port.hpp

这条错误信息对我没有帮助--至少对我来说--因为我还没有找到根本原因。我在这里错过了什么？

谢谢你的帮助。

编辑:解决方案(感谢山姆·米勒)

使用按引用传递(即boost::ref())

sensorThreads.push_back(new boost::thread(testIMUThread, IMU_port));
sensorThreads.push_back(new boost::thread(testIMUThread, ARDUINO_port));

在main()变成

sensorThreads.push_back(new boost::thread(testIMUThread, boost::ref(IMU_port)));
sensorThreads.push_back(new boost::thread(testIMUThread, boost::ref(ARDUINO_port)));

然后将工作马和线程函数按如下方式修改

std::string readCOMLine(boost::asio::serial_port &port, std::string requestDataCmd) {
    char c;
    std::string s;
    boost::asio::write(port, boost::asio::buffer(requestDataCmd.c_str(), requestDataCmd.size()));
    while(true) {
        boost::asio::read(port, boost::asio::buffer(&c,1));
        switch(c) {
            case '\r': break;
            case '\n': return s;
            default: s += c;
        }
    }
}
void testIMUThread(boost::asio::serial_port &port) {
    while(true) { cout << readCOMLine(port, "#f") << endl; }
}
void testGPSThread(boost::asio::serial_port &port) {
    while(true) { cout << readCOMLine(port, "r") << endl; }
}

另一方面，如果使用按指针传递，则main()中的线程初始化如下所示

sensorThreads.push_back(new boost::thread(testIMUThread, &IMU_port));
sensorThreads.push_back(new boost::thread(testIMUThread, &ARDUINO_port));

线程的功能如下

void testIMUThread(boost::asio::serial_port *port) {
    while(true) { cout << readCOMLine(port, "#f") << endl; }
}
void testGPSThread(boost::asio::serial_port *port) {
    while(true) { cout << readCOMLine(port, "r") << endl; }
}

但是，我必须对完成所有工作的函数(即读/写调用)进行一些额外的更改(在修改输入参数的基础上)。

std::string readCOMLine(boost::asio::serial_port *port, std::string requestDataCmd) {
    char c;
    std::string s;
    port->write_some(boost::asio::buffer(requestDataCmd.c_str(), requestDataCmd.size())); // this line
    while(true) {
        port->read_some(boost::asio::buffer(&c,1)); // and this line
        switch(c) {
            case '\r': break;
            case '\n': return s;
            default: s += c;
        }
    }
}

这两种解决方案都是编译的，而且似乎都符合我的目的。

谢谢!

Answer 1

boost::asio::serial_port对象不可复制

你应该传递一个引用

sensorThreads.push_back(new boost::thread(testIMUThread, boost::ref(IMU_port)));

或者一个指针

sensorThreads.push_back(new boost::thread(testIMUThread, &IMU_port));

这里有一个柯尔鲁，显示了这两种方法。