boost asio 学习(四)使用strand将任务排序

http://www.gamedev.net/blog/950/entry-2249317-a-guide-to-getting-started-with-boostasio?pg=5

4. Serializing our workload with strand
使用strand将任务排序
即使在多线程情况下，我们也希望任务能按照post的次序执行

// 1111.cpp : 定义控制台应用程序的入口点。
//
#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();

return 0;
}
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、

// deleteMe.cpp : 定义控制台应用程序的入口点。
//

#include "stdafx.h"
#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 < 4; ++x)
    {
        worker_threads.create_thread(boost::bind(&WorkerThread, io_service));
    }

    boost::this_thread::sleep(boost::posix_time::milliseconds(100));
    io_service->post(strand.wrap(boost::bind(&PrintNum, 1)));
    io_service->post(strand.wrap(boost::bind(&PrintNum, 2)));

    boost::this_thread::sleep(boost::posix_time::milliseconds(100));
    io_service->post(strand.wrap(boost::bind(&PrintNum, 3)));
    io_service->post(strand.wrap(boost::bind(&PrintNum, 4)));

    boost::this_thread::sleep(boost::posix_time::milliseconds(100));
    io_service->post(strand.wrap(boost::bind(&PrintNum, 5)));
    io_service->post(strand.wrap(boost::bind(&PrintNum, 6)));

    work.reset();

    worker_threads.join_all();

    return 0;
}