Boost logo

Boost Users :

From: Jerry Swan (jeremiah.s_at_[hidden])
Date: 2004-03-16 09:44:07


This works perfectly, thanks.

Jerry.

----- Original Message -----
From: "Ben Hutchings" <ben.hutchings_at_[hidden]>
To: <boost-users_at_[hidden]>
Sent: Thursday, March 11, 2004 7:02 PM
Subject: RE: [Boost-users] boost::thread and std::system

> Jerry Swan <jeremiah.s_at_[hidden]> wrote:
> > I'd like to be able to issue a call to std::system that will time-out
> > after a specified period. Is it possible to achieve this using the
> > boost::threads library?
>
> You can stop waiting for it to complete, but you can't terminate the
> external program.
>
> > If so could someone kindly sketch how this might be achieved?
>
> You need to have the calling thread create a synchronised flag
> (bool with condition, protected by mutex) and a child thread that
> calls system() and then sets the flag when that returns. The
> original thread then performs a timed wait for the flag to be set.
>
> Here's my solution. The synchronised flag can be encapsulated as an
> "event" like this:
>
> struct one_time_event
> {
> public:
> one_time_event()
> : flag(false)
> {
> }
> void trigger()
> {
> boost::mutex::scoped_lock lock(mutex);
> flag = true;
> cond.notify_all();
> }
> void wait()
> {
> boost::mutex::scoped_lock lock(mutex);
> while (!flag)
> cond.wait(lock);
> }
> bool timed_wait(boost::xtime & time)
> {
> boost::mutex::scoped_lock lock(mutex);
> while (!flag)
> if (!cond.timed_wait(lock, time))
> return false;
> return true;
> }
>
> private:
> boost::mutex mutex;
> boost::condition cond;
> bool flag;
> };
>
> (This is a basic event that you use once and then throw away. More
> complex event classes are possible but harder to use correctly.)
>
> Using this class it's really very easy:
>
> void call_system(const char * command, one_time_event & event)
> {
> std::system(command);
> event.trigger();
> }
>
> bool system_with_time_limit(const char * command, boost::xtime &
> time)
> {
> one_time_event event;
> boost::thread thread(
> boost::bind(call_system, command, boost::ref(event)));
> return event.timed_wait(time);
> }
>
> Ben.
>
> _______________________________________________
> Boost-users mailing list
> Boost-users_at_[hidden]
> http://lists.boost.org/mailman/listinfo.cgi/boost-users


Boost-users list run by williamkempf at hotmail.com, kalb at libertysoft.com, bjorn.karlsson at readsoft.com, gregod at cs.rpi.edu, wekempf at cox.net