std::condition_variable(3)复习

#include <iostream>                // std::cout
#include <thread>                // std::thread
#include <mutex>                // std::mutex, std::unique_lock
#include <condition_variable>    // std::condition_variable

std::mutex mtx;
std::condition_variable cv;

int cargo = 0; // shared value by producers and consumers

void consumer()
{
    std::unique_lock < std::mutex > lck(mtx);
    while (cargo == 0)
        cv.wait(lck);
    std::cout << cargo << '
';
    cargo = 0;
}

void producer(int id)
{
    std::unique_lock < std::mutex > lck(mtx);
    cargo = id;
    cv.notify_one();//如果存在多个等待唤醒的线程则唤醒的线程时不确定的
}

int main()
{
    std::thread consumers[10], producers[10];
　　//多个生产者，多个消费者，只要加锁还是安全的
    // spawn 10 consumers and 10 producers:
    for (int i = 0; i < 10; ++i) {
        consumers[i] = std::thread(consumer);//消费者线程
        producers[i] = std::thread(producer, i + 1);//生产者线程
    }

    // join them back:
    for (int i = 0; i < 10; ++i) {
        producers[i].join();
        consumers[i].join();
    }
    getchar();
    return 0;
}

 通常std::condition_variable使用std::unique_lock锁住线程，如果使用其的可以用std::condition_variable_any