std::chrono::time_point_cast

 

C++

Language

Standard library headers

Concepts

Utilities library

Strings library

Containers library

Algorithms library

Iterators library

Numerics library

Input/output library

Localizations library

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Filesystem library (C++17)

Technical Specifications

 

Utilities library

Type support (basic types, RTTI, type traits)

Dynamic memory management

Error handling

Program utilities

Variadic functions

Date and time

Function objects

initializer_list (C++11)

bitset

hash (C++11)

Relational operators

rel_ops::operator!=rel_ops::operator>rel_ops::operator<=rel_ops::operator>=

Optional and any

optional (C++17)

any (C++17)

Pairs and tuples

pair

tuple (C++11)

apply (C++17)

piecewise_construct_t (C++11)

piecewise_construct (C++11)

integer_sequence (C++14)

Swap, forward and move

swap

exchange (C++14)

forward (C++11)

move (C++11)

move_if_noexcept (C++11)

Type operations

declval (C++11)

as_const (C++17)

 

Date and time utilities

time_point (C++11)

duration (C++11)

system_clock (C++11)

steady_clock (C++11)

high_resolution_clock (C++11)

C-style date and time

 

std::chrono::time_point

Member functions

time_point::time_point

time_point::time_since_epoch

time_point::operator+time_point::operator-

time_point::min

time_point::max

Non-member functions

common_type

operator+operator-

operator==operator!=operator<operator<=operator>operator>=

time_point_cast

floor (C++17)

ceil (C++17)

round (C++17)

 

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

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