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、

 1 // deleteMe.cpp : 定义控制台应用程序的入口点。
 2 //
 3 
 4 #include "stdafx.h"
 5 #include <boost/asio.hpp>
 6 #include <boost/shared_ptr.hpp>
 7 #include <boost/thread.hpp>
 8 #include <boost/thread/mutex.hpp>
 9 #include <boost/bind.hpp>
10 #include <iostream>
11 
12 
13 boost::mutex global_stream_lock;
14 
15 void WorkerThread(boost::shared_ptr< boost::asio::io_service > io_service)
16 {
17     global_stream_lock.lock();
18     std::cout << "[" << boost::this_thread::get_id() << "] Thread Start" << std::endl;
19     global_stream_lock.unlock();
20 
21     io_service->run();
22 
23     global_stream_lock.lock();
24     std::cout << "[" << boost::this_thread::get_id()
25         << "] Thread Finish" << std::endl;
26     global_stream_lock.unlock();
27 }
28 
29 void PrintNum(int x)
30 {
31     std::cout << "[" << boost::this_thread::get_id()
32         << "] x: " << x << std::endl;
33 }
34 
35 int main(int argc, char * argv[])
36 {
37     boost::shared_ptr< boost::asio::io_service > io_service(
38         new boost::asio::io_service
39     );
40     boost::shared_ptr< boost::asio::io_service::work > work(
41         new boost::asio::io_service::work(*io_service)
42     );
43     boost::asio::io_service::strand strand(*io_service);
44 
45     global_stream_lock.lock();
46     std::cout << "[" << boost::this_thread::get_id()
47         << "] The program will exit when all  work has finished." << std::endl;
48     global_stream_lock.unlock();
49 
50     boost::thread_group worker_threads;
51     for (int x = 0; x < 4; ++x)
52     {
53         worker_threads.create_thread(boost::bind(&WorkerThread, io_service));
54     }
55 
56     boost::this_thread::sleep(boost::posix_time::milliseconds(100));
57     io_service->post(strand.wrap(boost::bind(&PrintNum, 1)));
58     io_service->post(strand.wrap(boost::bind(&PrintNum, 2)));
59 
60     boost::this_thread::sleep(boost::posix_time::milliseconds(100));
61     io_service->post(strand.wrap(boost::bind(&PrintNum, 3)));
62     io_service->post(strand.wrap(boost::bind(&PrintNum, 4)));
63 
64     boost::this_thread::sleep(boost::posix_time::milliseconds(100));
65     io_service->post(strand.wrap(boost::bind(&PrintNum, 5)));
66     io_service->post(strand.wrap(boost::bind(&PrintNum, 6)));
67 
68     work.reset();
69 
70     worker_threads.join_all();
71 
72     return 0;
73 }

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