如何使用Boost庫創建TimerHandler

Question

我正在使用C++進行項目工作。

我想被稱爲指定時間後TimerHandler，但在同一時間，我不希望阻止在下面的代碼當前線程或io.run之後的任何代碼（）：

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

class TimerTest 
{ 
public: 
    static void PrintOutTimerHandler(const boost::system::error_code&, const std::string& message) 
    { 
     std::cout << "PrintOutTimerHandler called: " << ", message: " << message << std::endl; 
    } 

    void run() 
    { 
     boost::asio::io_service io; 
     boost::asio::deadline_timer dt(io, boost::posix_time::seconds(5)); 

     std::cout << "Start:\t" << std::endl; 

     dt.async_wait(boost::bind(PrintOutTimerHandler, boost::asio::placeholders::error, std::string("here is the message"))); 

     // Do some job here 
     for (int i = 0; i < 1000000; ++i) 
      ++i, --i; 

     std::cout << "End:\t" << std::endl; 

     io.run(); 

     std::cout << "When to reach here 1: " << std::endl; 
    } 
}; 

int main() 
{ 
    TimerTest tt; 
    tt.run(); 

    std::cout << "When to reach here 2: " << std::endl; 

    return 0; 
} 

/* Current output: 
Start: 
End: 
PrintOutTimerHandler called: , message: here is the message 
When to reach here 1: 
When to reach here 2: 
*/ 

/* Expected output: 
Start: 
End: 
When to reach here 1: 
When to reach here 2: 
PrintOutTimerHandler called: , message: here is the message 
*/ 

我想我已經說清楚了。我的問題是：

• 如果可以不 引入一個新的線程，諸如Flex 的ActionScript來解決，這是最好的，但 我想不會（我猜的ActionScript是 使用隱藏線）;
• 如果我們必須 引入一個額外的線程做 工作，你會介意爲我寫下 僞代碼嗎？

謝謝。

Peter

Answer 1

這裏是一個例子。在一個單獨的線程

asio::io_service io_service; 
asio::thread t(boost::bind(&asio::io_service::run, &io_service)); 

運行io_service對象或線程組

boost::thread_group threads; 
for (std::size_t i = 0; i < my_thread_count; ++i) 
    threads.create_thread(boost::bind(&asio::io_service::run, &io_service)); 

在運行它記住，你的主線程應始終運行，因爲當它的存在也催生了將退出所有線程。

我希望這會有所幫助。

Answer 2

我誤解了OrcunC說的，但實際上他是正確的。以下是修改後的版本供您參考：

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

class TimerTest 
{ 
public: 
    static void PrintOutTimerHandler(const boost::system::error_code&, const std::string& message) 
    { 
     std::cout << "PrintOutTimerHandler called: " << ", message: " << message << std::endl; 
    } 

    TimerTest(unsigned int timeout) 
     : dt(io, boost::posix_time::milliseconds(timeout)) 
    { 
    } 

    void run() 
    { 
     std::cout << "Start:\t" << std::endl; 

     dt.async_wait(boost::bind(PrintOutTimerHandler, boost::asio::placeholders::error, std::string("here is the message"))); 

     boost::thread thrd(boost::bind(&boost::asio::io_service::run, &io)); 

     // Do some job here 
     for (int i = 0; i < 1000000; ++i) 
      ++i, --i; 

     std::cout << "End:\t" << std::endl; 

     std::cout << "When to reach here 1: " << std::endl; 
    } 

    boost::asio::io_service  io; 
    boost::asio::deadline_timer dt; 
}; 

int main() 
{ 
    TimerTest tt(5000); 
    tt.run(); 

    std::cout << "When to reach here 2: " << std::endl; 

    // Keep the main thread active for testing purpose. Otherwise, 
    // once the TimerTest object is destroyed when exiting the main() function, 
    // the sub thread spawed in tt.run() will also exit; 
    Sleep(10000); 
} 

/* Current output and Expected output: 
Start: 
End: 
When to reach here 1: 
When to reach here 2: 
PrintOutTimerHandler called: , message: here is the message 
*/