Question

I’m working on a project using C++.

I want a TimerHandler to be called after a specified time, but at the same time I don’t want to block the current thread or any code after io.run() in the following code:

#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
 */

I think I made myself clear. My questions are:

• If this can be solved without
  introducing a new thread, like Flex
  ActionScript, that’s is the best, but
  I guess not (I guess ActionScript is
  using a hidden thread);
• If we have to
  introduce an extra thread to do the
  job, would you mind writing down the
  pseudo code for me?

Thanks.

Peter

Answer 1

Here is an example . Run the io_service in a separate thread

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

or run it in a thread group

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));

Remember that your main thread should always run because when it exists all threads spawned will also exit.

I hope this helps.