c++怎么使用条件变量std::condition_variable_c++多线程条件变量用法

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

std::mutex mtx;
std::condition_variable cv;
bool ready = false;

void worker_thread() {
    std::unique_lock<std::mutex> lock(mtx);
    // 等待直到 ready 为 true
    cv.wait(lock, []{ return ready; });
    std::cout << "工作线程开始执行任务\n";
}

void main_thread() {
    std::this_thread::sleep_for(std::chrono::seconds(1));
    {
        std::lock_guard<std::mutex> lock(mtx);
        ready = true;
    }
    cv.notify_one(); // 唤醒一个等待的线程
}

int main() {
    std::thread t1(worker_thread);
    std::thread t2(main_thread);

    t1.join();
    t2.join();
    return 0;
}

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

std::queue<int> tasks;
std::mutex task_mutex;
std::condition_variable task_cv;
bool finished = false;

void consumer() {
    while (true) {
        std::unique_lock<std::mutex> lock(task_mutex);
        // 等待任务或结束信号
        task_cv.wait(lock, []{ return !tasks.empty() || finished; });

        if (finished && tasks.empty()) {
            lock.unlock();
            break;
        }

        int task = tasks.front();
        tasks.pop();
        lock.unlock();

        std::cout << "处理任务: " << task << "\n";
        std::this_thread::sleep_for(std::chrono::milliseconds(100));
    }
}

void producer() {
    for (int i = 1; i <= 5; ++i) {
        {
            std::lock_guard<std::mutex> lock(task_mutex);
            tasks.push(i);
        }
        task_cv.notify_one();
        std::this_thread::sleep_for(std::chrono::milliseconds(50));
    }

    {
        std::lock_guard<std::mutex> lock(task_mutex);
        finished = true;
    }
    task_cv.notify_all(); // 唤醒所有消费者结束
}

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

    p.join();
    c.join();
    return 0;
}