Std::chrono::time_point_cast (3) Linux Manual Page

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

std::chrono::time_point_cast (3) Linux Manual Page