Boost_Asio(4) strand

最新推荐文章于 2025-06-14 14:43:55 发布

Lasuerte

最新推荐文章于 2025-06-14 14:43:55 发布

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分类专栏： Boost_Asio

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本文通过示例代码展示了如何利用Boost.Asio库中的Strand特性来确保多线程环境下任务按预期顺序执行。对比直接使用io_service的post方法时任务执行顺序的不确定性，使用Strand能够有效保证任务的顺序执行。

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// asio_strand.cpp : 定义控制台应用程序的入口点。
//

#include "stdafx.h"

/*
	代码中开启了两个线程运行io_service的run函数
	未使用strand来post任务时候 显示是不确定的
	而使用了strand后 显示是按照输入的次序依次显示
*/
#include <boost/asio.hpp>
#include <boost/shared_ptr.hpp>
#include <boost/thread.hpp>
#include <boost/thread/mutex.hpp>
#include <boost/bind.hpp>
#include <iostream>

boost::mutex global_stream_lock;

void WorkerThread(boost::shared_ptr< boost::asio::io_service > io_service)
{
	global_stream_lock.lock();
	std::cout << "[" << boost::this_thread::get_id()
		<< "] Thread Start" << std::endl;
	global_stream_lock.unlock();

	io_service->run();

	global_stream_lock.lock();
	std::cout << "[" << boost::this_thread::get_id()
		<< "] Thread Finish" << std::endl;
	global_stream_lock.unlock();
}

void PrintNum(int x)
{
	std::cout << "[" << boost::this_thread::get_id()
		<< "] x: " << x << std::endl;
}

int main(int argc, char * argv[])
{
	boost::shared_ptr< boost::asio::io_service > io_service(
		new boost::asio::io_service
		);
	boost::shared_ptr< boost::asio::io_service::work > work(
		new boost::asio::io_service::work(*io_service)
		);
	boost::asio::io_service::strand strand(*io_service);

	global_stream_lock.lock();
	std::cout << "[" << boost::this_thread::get_id()
		<< "] The program will exit when all work has finished." << std::endl;
	global_stream_lock.unlock();

	boost::thread_group worker_threads;
	for (int x = 0; x < 2; ++x)
	{
		worker_threads.create_thread(boost::bind(&WorkerThread, io_service));
	}

	boost::this_thread::sleep(boost::posix_time::milliseconds(1000));
	
	strand.post( boost::bind( &PrintNum, 1 ) );
	strand.post( boost::bind( &PrintNum, 2 ) );
	strand.post( boost::bind( &PrintNum, 3 ) );
	strand.post( boost::bind( &PrintNum, 4 ) );
	strand.post( boost::bind( &PrintNum, 5 ) );
	

// 	io_service->post(boost::bind(&PrintNum, 1));
// 	io_service->post(boost::bind(&PrintNum, 2));
// 	io_service->post(boost::bind(&PrintNum, 3));
// 	io_service->post(boost::bind(&PrintNum, 4));
// 	io_service->post(boost::bind(&PrintNum, 5));
	work.reset();

	worker_threads.join_all();

	system("pause");
	return 0;
}