simple_async_tasks.cpp

// The MIT License (MIT)
//
// Copyright (c) 2021 Mateusz Pusz
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.
 
#include <mp-coro/sync_await.h>
#include <mp-coro/task.h>
#include <chrono>
#include <iostream>
#include <thread>
 
mp_coro::task<int> async_foo() {
    struct awaitable {
        int result;
        static bool await_ready() noexcept {
            TRACE_FUNC();
            return false;
        }
        void await_suspend(std::coroutine_handle<> handle) {
            auto work = [&, handle] {
                using namespace std::chrono_literals;
                std::this_thread::sleep_for(200ms);
                result = 42;
                handle.resume();
            };
            TRACE_FUNC();
            std::jthread(work).detach(); // TODO: Fix that (replace with a thread pool)
        }
        int await_resume() noexcept {
            TRACE_FUNC();
            return result;
        }
    };
    co_return co_await awaitable {};
}
 
mp_coro::task<long> bar() {
    const auto task = async_foo();
    const long i = co_await task;
    co_return i + 23;
}
 
int main() {
    try {
        std::cout << sync_await(bar()) << "\n";
    } catch (const std::exception &ex) {
        std::cout << "Unhandled exception caught: " << ex.what() << "\n";
    }
}