C++ Boost.asio学习笔记(一)，定时器

#include <iostream>
#include <boost/asio.hpp>
#include <boost/date_time/posix_time/posix_time.hpp>

using namespace std;

//asio同步定时器
int main()
{
	//所有使用asio的程序都要创建一个io_service对象，这个对象提供io功能支持
	boost::asio::io_service io_service;
	
    //定义一个定时器对象，超时时间设置为5秒
	boost::asio::deadline_timer timer(io_service, boost::posix_time::seconds(5));
	//这是在定时器上阻塞等待的简单范例.调用deadline_timer::wait()会在定时器到期(5秒钟)后才返回.
	timer.wait();
	//定时器5秒到期后执行下面的语句
	cout<<"timeout!"<<endl;
	system("pause");
	return 0;
}

#include <iostream>
#include <boost/asio.hpp>
#include <boost/date_time/posix_time/posix_time.hpp>

using namespace std;

//异步等待调用的回调函数，等待时间到期后调用
void sync_wait_handle(const boost::system::error_code &error_code)
{
	cout<<"async_wait() callback"<<endl;
	cout<<"error_code : "<<error_code<<endl;
}

//asio异步定时器
int main()
{

	boost::asio::io_service io_service;
	boost::asio::deadline_timer timer(io_service, boost::posix_time::seconds(5));
	timer.async_wait(&sync_wait_handle);
	//最后,必须在io_service对象上调用io_service::run()成员函数.
	//Asio库保证回调函数在调用了io_service::run()的线程上执行.
	//因此只有调用了io_service::run()函数,异步等待完成的回调函数才能被调用.
	//Io_service::run()将会一直在运行,因为其还有工作要做.
	//本例中,这个工作是异步等待定时器,因此直到定时器过期而且回调函数执行完毕,才会退出.
	//在调用io_service::run()前为其指定工作是很重要的.
	//例如,如果上例中忘记调用deadline_timer::async_wait(),io_service无事可做,
	//则io_service::run()调用会立即返回.
	io_service.run();

	system("pause");
	return 0;
}

#include <iostream>
#include <boost/asio.hpp>
#include <boost/date_time/posix_time/posix_time.hpp>
#include <boost/bind.hpp>

using namespace std;

void print_handle(const boost::system::error_code &error_code,
	              boost::asio::deadline_timer *timer, int *count)
{
	if (*count < 5)
	{
		cout<<*count<<endl;
		++(*count);
		//将过期时间从前一个过期时间向后延迟一秒.在原来基础上定义新的过期时间,
		//可以确保定时器标记的秒数不会由于处理函数执行而延时
		timer->expires_at(timer->expires_at() + boost::posix_time::seconds(1));
		timer->async_wait(boost::bind(print_handle, boost::asio::placeholders::error, timer, count));
	}
}

//asio向处理函数传递参数
int main()
{
	boost::asio::io_service io_service;
	int count = 0;
	boost::asio::deadline_timer timer(io_service, boost::posix_time::seconds(5));
	//向回调函数传递参数
	timer.async_wait(boost::bind(print_handle, boost::asio::placeholders::error, &timer, &count));
	io_service.run();

	cout<<"final count is "<<count<<endl;
	system("pause");
	return 0;
}

#include <iostream>
#include <boost/asio.hpp>
#include <boost/date_time/posix_time/posix_time.hpp>
#include <boost/bind.hpp>

using namespace std;

class Printer
{
public:
	Printer(boost::asio::io_service &io_service)
		   :timer_(io_service, boost::posix_time::seconds(3)), count_(0)
	{
		timer_.async_wait(boost::bind(&Printer::print, this));
	}

	~Printer()
	{
		cout<<"destroy printer, final count_ is "<<count_<<endl;
	}

	void print()
	{
		if (count_ < 5)
		{
			cout<<count_<<endl;
			++count_;
			timer_.expires_at(timer_.expires_at() + boost::posix_time::seconds(1));
			timer_.async_wait(boost::bind(&Printer::print, this));
		}
	}

private:
	boost::asio::deadline_timer timer_;
	int count_;
};

//asio将类的成员函数作为回调处理函数
int main()
{

	boost::asio::io_service io_service;
	Printer printer(io_service);
	io_service.run();

	system("pause");
	return 0;
}