c++ 怎么使用条件变量std::condition_variable_c++线程等待与条件同步实现

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

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";
}

int main() {
    std::thread worker(worker_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

    worker.join();
    return 0;
}

while (!predicate()) {
    wait(lock);
}

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

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

void producer() {
    for (int i = 0; i < 5; ++i) {
        std::this_thread::sleep_for(std::chrono::milliseconds(100));
        std::lock_guard<std::mutex> lock(task_mutex);
        tasks.push(i);
        std::cout << "生产任务: " << i << "\n";
        task_cv.notify_one();
    }
    {
        std::lock_guard<std::mutex> lock(task_mutex);
        finished = true;
    }
    task_cv.notify_all();  // 通知消费者结束
}

void consumer() {
    while (true) {
        std::unique_lock<std::mutex> lock(task_mutex);
        task_cv.wait(lock, []{ return !tasks.empty() || finished; });

        if (finished && tasks.empty()) break;

        int task = tasks.front();
        tasks.pop();
        lock.unlock();  // 处理任务时不持有锁
        std::cout << "消费任务: " << task << "\n";
        std::this_thread::sleep_for(std::chrono::milliseconds(50));
    }
}