用lambda函数改写std::asio的例子程序

#include "stdafx.h"

#define ASIO_STANDALONE

#include <iostream>
#include <asio.hpp>

void do_callback(asio::steady_timer& timer, int& count)
{
    timer.async_wait(
        [&](const asio::error_code& ec){
            if (count < 5){
                std::cout << count << std::endl;
                ++(count);

                timer.expires_at(timer.expiry() + asio::chrono::seconds(1));
                do_callback(timer, count);
            }else{
                std::cout << "Final count is " << count << std::endl;
            }
        }
    );
}

class Callback
{
public:
    Callback(asio::io_context& io)
        : timer_(io, asio::chrono::seconds(1)),
        count_(0)
    {
        do_callback();
    }

    ~Callback()
    {
        std::cout << "Final count is " << count_ << std::endl;
    }

    void do_callback()
    {
        timer_.async_wait(
            [this](const asio::error_code& ec){
                if (count_ < 5){
                    std::cout << count_ << std::endl;
                    ++(count_);

                    timer_.expires_at(timer_.expiry() + asio::chrono::seconds(1));
                    do_callback();
                }
            }
        );
    }
private:
    asio::steady_timer timer_;
    int count_;
};

class StrandCallback
{
public:
    StrandCallback(asio::io_context& io)
        : strand_(io),
        timer1_(io, asio::chrono::seconds(1)),
        timer2_(io, asio::chrono::seconds(1)),
        count_(0)
    {
        do_callback1();
        do_callback2();
    }

    ~StrandCallback()
    {
        std::cout << "Final count is " << count_ << std::endl;
    }

    void do_callback1()
    {
        timer1_.async_wait(
        asio::bind_executor(strand_,
            [this](const asio::error_code& ec){
                if (count_ < 10){
                    std::cout << "Timer 1: " << count_ << std::endl;
                    ++count_;

                    timer1_.expires_at(timer1_.expiry() + asio::chrono::seconds(3));

                    do_callback1();
                }
            })
        );
    }

    void do_callback2()
    {
        timer2_.async_wait(
        asio::bind_executor(strand_,
            [this](const asio::error_code& ec){
                if (count_ < 10){
                    std::cout << "Timer 2: " << count_ << std::endl;
                    ++count_;

                    timer2_.expires_at(timer2_.expiry() + asio::chrono::seconds(2));

                    do_callback2();
                }
            })
        );
    }


private:
    asio::io_context::strand strand_;
    asio::steady_timer timer1_;
    asio::steady_timer timer2_;
    int count_;
};

int _tmain(int argc, _TCHAR* argv[])
{
    asio::io_context io;

    // 场景1
    //int count = 0;
    //asio::steady_timer t(io, asio::chrono::seconds(1));
    //do_callback(t, count);

    // 场景2
    //Callback c(io);

    // 场景3
    StrandCallback sc(io);

    io.run();

    return 0;
}