C++20 协程实现线程同步示例

class Event
{
public:Event() = default;Event(const Event&) = delete;Event(Event&&) = delete;Event& operator=(const Event&) = delete;Event& operator=(Event&&) = delete;class Awaiter;Awaiter operator co_await() const noexcept;void notify() noexcept;private:friend class Awaiter;mutable std::atomic<void*> suspendedWaiter{nullptr};mutable std::atomic<bool> notified{false};
};class Event::Awaiter
{
public:Awaiter(const Event& eve): event(eve){}bool await_ready() const;bool await_suspend(std::coroutine_handle<> corHandle) noexcept;void await_resume() noexcept{}private:friend class Event;const Event& event;std::coroutine_handle<> coroutineHandle;
};bool Event::Awaiter::await_ready() const
{if (event.suspendedWaiter.load() != nullptr){throw std::runtime_error("无效");}return event.notified;
}bool Event::Awaiter::await_suspend(std::coroutine_handle<> corHandle) noexcept
{coroutineHandle = corHandle;if (event.notified) return false;event.suspendedWaiter.store(this);return true;
}void Event::notify() noexcept
{notified = true;auto* waiter = static_cast<Awaiter*>(suspendedWaiter.load());if (waiter != nullptr){waiter->coroutineHandle.resume();}
}Event::Awaiter Event::operator co_await() const noexcept
{return Awaiter{*this};
}struct Task
{struct promise_type{Task get_return_object() { return {}; }std::suspend_never initial_suspend() { return {}; }std::suspend_always final_suspend() noexcept { return {}; }void return_void(){}void unhandled_exception(){}};
};Task receiver(Event& event)
{auto start = std::chrono::high_resolution_clock::now();co_await event;std::cout << "获取通知" << std::endl;auto end = std::chrono::high_resolution_clock::now();std::chrono::duration<double> elapsed = end - start;std::cout << std::format("等待 {} 秒\n", elapsed.count());
}using namespace std::chrono_literals;int main()
{std::cout << '\n';std::cout << "等待前通知" << '\n';Event event1{};auto senderThread1 = std::thread([&event1] { event1.notify(); }); // 通知auto receiverThread1 = std::thread(receiver, std::ref(event1));receiverThread1.join();senderThread1.join();std::cout << '\n';std::cout << "等待两秒后通知" << '\n';Event event2{};auto receiverThread2 = std::thread(receiver, std::ref(event2));auto senderThread2 = std::thread([&event2]{std::this_thread::sleep_for(2s);event2.notify(); // Notification});receiverThread2.join();senderThread2.join();std::cout << '\n';
}