resumable.cpp

#ifndef RESUMABLE_BY_DUGI
#define RESUMABLE_BY_DUGI
#include <coroutine>
#include <stdexcept>

struct CallToFinsihedCoroutine : public std::logic_error {
    using std::logic_error::logic_error;
};

template <typename T>
class Resumable {
public:
	struct promise_type {
		T _returned;
		auto get_return_object() {
			return handle_type::from_promise(*this);
		}
		auto initial_suspend() {
			return std::suspend_always();
		}
		auto final_suspend() {
			return std::suspend_always();
		}
		void unhandled_exception() {
			throw std::current_exception();
		}
		auto yield_value(const T& value){
			_returned = value;
			return std::suspend_always();
		}
		void return_value(const T& value) {
			_returned = value;
		}
	};
	using handle_type = std::coroutine_handle<promise_type>;
	Resumable(handle_type handle) : _handle(handle) { }
	Resumable(const Resumable&) = delete;
	T operator()() {
		if (_handle.done())
			throw CallToFinsihedCoroutine("Call to finished coroutine");
		_handle.resume();
		return _handle.promise()._returned;
	}
	explicit operator bool() {
		return !_handle.done();	
	}
	~Resumable() {
		_handle.destroy();
	}
private:
	handle_type _handle;
};
#endif // RESUMABLE_BY_DUGI