【C++20】协程(Coroutine)体验

使用GCC10.1的g++编译器。GCC10.1构建方法参看【C++20】GCC10.1构建经验

$ g++10 -o out co_vs_callback.cpp -fcoroutines -lpthread

/*
 * co_vs_callback.cpp
 *
 *  Created on: Mar 13, 2019
 *      Author: frank
 */
#include <iostream>
#include <thread>
//#include <experimental/coroutine>
#include <coroutine>
#include <chrono>
#include <functional>

// $ clang++ -std=c++2a -fcoroutines-ts -lstdc++ co_vs_callback.cpp
// $ g++11.1 -g -std=c++20 -fcoroutines -o test main.cpp -lpthread

using call_back = std::function<void(int)>;
void Add100ByCallback(int init, call_back f) // 异步调用
{
    std::thread t([init, f]()
                  {
                      std::this_thread::sleep_for(std::chrono::seconds(5));
                      f(init + 100);
                  });
    t.detach();
}

struct Add100AWaitable
{
    Add100AWaitable(int init) : init_(init) {}
    bool await_ready() const { return false; }
    int await_resume() { return result_; }
    void await_suspend(std::coroutine_handle<> handle) // handle，协程控制句柄
    {
        auto f = [handle, this](int value) mutable
        {
            result_ = value;
            handle.resume();
        };
        Add100ByCallback(init_, f); // 调用原来的异步调用
    }
    int init_;
    int result_;
};

struct Task
{
    struct promise_type
    {
        auto get_return_object() { return Task{}; }
        auto initial_suspend() { return std::suspend_never{}; }
        auto final_suspend() noexcept { return std::suspend_never{}; }
        void unhandled_exception() { std::terminate(); }
        void return_void() {}
    };
};

Task Add100ByCoroutine(int init, call_back f)
{
    int ret = co_await Add100AWaitable(init); // await_resume() 函数返回值
    ret = co_await Add100AWaitable(ret);
    ret = co_await Add100AWaitable(ret);
    f(ret);
}

int main()
{
    Add100ByCallback(5, [](int value)
                     { std::cout << "get result: " << value << "\n"; });
    Add100ByCoroutine(10, [](int value)
                      { std::cout << "get result from coroutine1: " << value << "\n"; });
    Add100ByCoroutine(20, [](int value)
                      { std::cout << "get result from coroutine2: " << value << "\n"; });
    Add100ByCoroutine(30, [](int value)
                      { std::cout << "get result from coroutine3: " << value << "\n"; });
    Add100ByCoroutine(40, [](int value)
                      { std::cout << "get result from coroutine4: " << value << "\n"; });
    getchar();
}

效果1： 

稍微修改下: