std::chrono::time_point_cast (3) - Linux Manuals

std::chrono::time_point_cast: std::chrono::time_point_cast

NAME

std::chrono::time_point_cast - std::chrono::time_point_cast

Synopsis

template <class ToDuration, class Clock, class Duration> (since C++11)
time_point<Clock, ToDuration> time_point_cast( (until C++14)
const time_point<Clock, Duration> &t);
template <class ToDuration, class Clock, class Duration>
constexpr time_point<Clock, ToDuration> time_point_cast( (since C++14)
const time_point<Clock, Duration> &t);

Converts a std::chrono::time_point from one duration to another.

Parameters

t - time_point to convert from

Return value

std::chrono::time_point<Clock, ToDuration>(std::chrono::duration_cast<ToDuration>(t.time_since_epoch()))

Notes

time_point_cast will only participate in overload resolution if ToDuration is an instantiation of duration.

Example

// Run this code

  #include <iostream>
  #include <chrono>

  using Clock = std::chrono::high_resolution_clock;
  using Ms = std::chrono::milliseconds;
  using Sec = std::chrono::seconds;

  template<class Duration>
  using TimePoint = std::chrono::time_point<Clock, Duration>;

  inline void print_ms(const TimePoint<Ms>& time_point)
  {
      std::cout << time_point.time_since_epoch().count() << " ms\n";
  }

  int main()
  {
      TimePoint<Sec> time_point_sec(Sec(4));

      // implicit cast, no precision loss
      TimePoint<Ms> time_point_ms(time_point_sec);
      print_ms(time_point_ms); // 4000 ms

      time_point_ms = TimePoint<Ms>(Ms(5756));

      // explicit cast, need when precision loss may happens
      // 5756 truncated to 5000
      time_point_sec = std::chrono::time_point_cast<Sec>(time_point_ms);
      print_ms(time_point_sec); // 5000 ms
  }

Output:

  4000 ms
  5000 ms