C++11——多线程编程1

翻译来自：https://thispointer.com//c-11-multithreading-part-1-three-different-ways-to-create-threads/

我们可以使用std::thread对象附加一个回调，当这个新线程启动时，它将被执行。 这些回调可以是，
1、函数指针
2、函数对象
3、Lambda函数

 

新线程将在创建新对象后立即开始，并且将与已启动的线程并行执行传递的回调。
此外，任何线程可以通过在该线程的对象上调用join()函数来等待另一个线程退出。

看一个主线程创建单独线程的例子，创建完新的线程后，主线程将打印一些信息并等待新创建的线程退出。

函数指针

#include <iostream>
#include <thread>

void thread_function() {
    for (int i = 0; i < 100; i++)
        std::cout << "thread function excuting" << std::endl;
}

int main() {
    std::thread threadObj(thread_function);
    for (int i = 0; i < 100; i++)
        std::cout << "Display from MainThread" << std::endl;
    threadObj.join();
    std::cout << "Exit of Main function" << std::endl;
    return 0;
}

 

函数对象

函数对象创建线程:
#include <iostream>
#include <thread>

class DisplayThread {
public:
    void operator ()() {
        for (int i = 0; i < 100; i++)
            std::cout << "Display Thread Excecuting" << std::endl;
    }
};


int main() {
    std::thread threadObj((DisplayThread()));
    for (int i = 0; i < 100; i++)
        std::cout << "Display From Main Thread " << std::endl;
    std::cout << "Waiting For Thread to complete" << std::endl;
    threadObj.join();
    std::cout << "Exiting from Main Thread" << std::endl;

    return 0;
}

 

线程间的区分

每个std::thread对象都有一个相关联的id，可以获取到
std::thread::get_id() ：成员函数中给出对应线程对象的id
std::this_thread::get_id() ： 给出当前线程的id
如果std::thread对象没有关联的线程，get_id()将返回默认构造的std::thread::id对象：“not any thread”
std::thread::id也可以表示id

 

#include <iostream>
#include <thread>

void thread_function() {
    std::cout << "inside thread :: ID = " << std::this_thread::get_id() << std::endl;
}

int main() {
    std::thread threadObj1(thread_function);
    std::thread threadObj2(thread_function);

    if (threadObj1.get_id() != threadObj2.get_id()) {
        std::cout << "Both Threads have different IDs" << std::endl;
    }
    std::cout << "From Main Thread :: ID of Thread 1 = " << threadObj1.get_id() << std::endl;
    std::cout << "From Main Thread :: ID of Thread 2 = " << threadObj2.get_id() << std::endl;

    threadObj1.join();
    threadObj2.join();
    std::cout << "From Main Thread :: ID of Main" << std::this_thread::get_id();
    return 0;
}