promise.hpp

#pragma once
 
#ifdef __cpp_lib_coroutine
 
#include <coroutine>
 
#include "task.hpp"
 
namespace dispatch_queue {
 
namespace detail {
 
template<typename T>
class promise {
public:
    auto get_return_object() { return future; }
    std::suspend_never initial_suspend() noexcept { return {}; }
    std::suspend_always final_suspend() noexcept { return {}; }
    void return_value(T&& value) {
        future->set_value(std::move(value));
    }
    void unhandled_exception() {
        future->set_exception(std::current_exception());
    }
 
private:
    std::shared_ptr<detail::task_future<T>> future = detail::task_future<T>::create_pending();
};
 
 
template<>
class promise<void> {
public:
    auto get_return_object() { return future; }
    std::suspend_never initial_suspend() noexcept { return {}; }
    std::suspend_always final_suspend() noexcept { return {}; }
    void return_void() {
        future->set_value();
    }
    void unhandled_exception() {
        future->set_exception(std::current_exception());
    }
 
private:
    std::shared_ptr<detail::task_future<void>> future = detail::task_future<void>::create_pending();
};
 
} // end namespace detail
 
} // end namespace dispatch_queue
 
template<typename T, typename... Args>
struct std::coroutine_traits<dispatch_queue::task<T>, Args...> {
    using promise_type = dispatch_queue::detail::promise<T>;
};
 
#endif