me22 wrote:
On 16/06/07, Meryl Silverburgh <silverburgh.meryl@gmail.com> wrote:
Can you please tell me if i can do this with boost::thread library? 1. create a timer (say 5 seconds) which execute a function in a different thread when it expires. 2. the creator can cancel the timer before it expires.
It's not premade, but you could do it easily enough. Start a thread which will wait (until an xtime), then call a function (stored in a boost::function<void()> perhaps), so long as a flag isn't set (you could make that in a shared_ptr<bool> to avoid lifetime worries).
That works. However, it's nicer to use a 'condition' instead of a global flag and a 'timed_wait' on that condition to put the thread asleep. This way the condition will wake up the thread so it can be reused. I'll attach a simple "interval timer" that uses a condition variable to terminate the thread. Changing it to the "stop watch timer" described in the OP should be a matter of just adding some more conditions. Regards, Tobias #include <string> #include <iostream> #include <boost/bind.hpp> #include <boost/thread.hpp> #include <boost/noncopyable.hpp> class timer : boost::noncopyable { boost::xtime wait_time, next_time; boost::mutex monitor; boost::condition aborted; boost::thread thread; public: explicit timer(boost::xtime const & interval) : wait_time(interval) , thread( boost::bind(& timer::thread_body, this) ) { } ~timer() { aborted.notify_one(); thread.join(); } private: void calc_next_time() { boost::xtime_get(& next_time, boost::TIME_UTC); next_time.sec += wait_time.sec; next_time.nsec += wait_time.nsec; next_time.sec += next_time.nsec / 1000000000; next_time.nsec %= 1000000000; } void thread_body() { boost::mutex::scoped_lock lock(monitor); for (;;) { calc_next_time(); if (aborted.timed_wait(lock, next_time)) break; std::cout << "event" << std::endl; } } }; int main() { boost::xtime interval = { 0, 200000000 }; timer t(interval); std::string s; std::getline(std::cin, s); return 0; }