Ticket #8768: wait_until-example.cpp

#include <boost/chrono.hpp>
#include <boost/thread.hpp>
#include <boost/optional.hpp>

template <class Clock>
class fixed_point_clock
{
public:
        typedef typename Clock::duration duration;
        typedef typename duration::rep rep;
        typedef typename duration::period period;
        typedef boost::chrono::time_point<fixed_point_clock> time_point;

        static time_point now()
        {
                if (!fixedPoint.is_initialized())
                        fixedPoint = boost::in_place(Clock::now().time_since_epoch());
                return *fixedPoint;
        }
private:
        static boost::optional<time_point> fixedPoint;
};
template <class Clock>
boost::optional<typename fixed_point_clock<Clock>::time_point>
        fixed_point_clock<Clock>::fixedPoint = boost::none;

int main()
{
        using namespace std;
        //any clock can be used, important that we get:   t - Clock::t == -1 milliseconds
        //it easier to achieve with fixed_point_clock
        //typedef boost::chrono::system_clock clock;
        typedef fixed_point_clock<boost::chrono::system_clock> clock;

        boost::condition_variable var;
        boost::mutex mut;
        boost::mutex::scoped_lock lk(mut);

        auto until = clock::now() - boost::chrono::milliseconds(1);

        //in wait_until:   " do_wait(lock, ceil<milliseconds>(t-Clock::now()).count()) "
        //if ceil<milliseconds>(t-Clock::now()).count() == -1 then boost::detail::timeout::milliseconds == 0xf...f,
        //witch is a special value - is_sentinel(), it is checked in win32/thread.cpp: this_thread::interruptible_wait

        var.wait_until(lk, until); //infinite wait

        cout << "done" << endl;
        return EXIT_SUCCESS;
}