c++怎么使用条件变量condition_variable_c++条件变量同步机制详解

#include <iostream>
#include <thread>
#include <queue>
#include <mutex>
#include <condition_variable>

std::queue<int> data_queue;
std::mutex mtx;
std::condition_variable cv;
bool finished = false;

void producer() {
    for (int i = 0; i < 5; ++i) {
        std::lock_guard<std::mutex> lock(mtx);
        data_queue.push(i);
        std::cout << "生产: " << i << "\n";
        cv.notify_one(); // 通知消费者
    }
    {
        std::lock_guard<std::mutex> lock(mtx);
        finished = true;
        cv.notify_all(); // 通知所有消费者结束
    }
}

void consumer() {
    while (true) {
        std::unique_lock<std::mutex> lock(mtx);
        // 等待队列非空或生产结束
        cv.wait(lock, [] { 
            return !data_queue.empty() || finished; 
        });

        if (!data_queue.empty()) {
            int value = data_queue.front();
            data_queue.pop();
            std::cout << "消费: " << value << "\n";
        }

        if (data_queue.empty() && finished) {
            break; // 结束消费
        }
        lock.unlock();
        cv.notify_one(); // 通知生产者可以继续生产（如果需要）
    }
}

int main() {
    std::thread p(producer);
    std::thread c1(consumer);
    std::thread c2(consumer);

    p.join();
    c1.join();
    c2.join();

    return 0;
}