Defined in header <chrono> | ||
|---|---|---|
template<
class Rep,
class Period = std::ratio<1>
> class duration;
| (since C++11) |
Class template std::chrono::duration represents a time interval.
It consists of a count of ticks of type Rep and a tick period, where the tick period is a compile-time rational fraction representing the time in seconds from one tick to the next.
The only data stored in a duration is a tick count of type Rep. If Rep is floating point, then the duration can represent fractions of ticks. Period is included as part of the duration's type, and is only used when converting between different durations.
| Member type | Definition |
|---|---|
rep | Rep, an arithmetic type representing the number of ticks |
period | Period (until C++17)typename Period::type (since C++17), a std::ratio representing the tick period (i.e. the number of second's fractions per tick) |
| constructs new duration (public member function) |
|
| assigns the contents (public member function) |
|
| returns the count of ticks (public member function) |
|
|
[static] | returns the special duration value zero (public static member function) |
|
[static] | returns the special duration value min (public static member function) |
|
[static] | returns the special duration value max (public static member function) |
| implements unary + and unary - (public member function) |
|
| increments or decrements the tick count (public member function) |
|
| implements compound assignment between two durations (public member function) |
|
(C++11) | implements arithmetic operations with durations as arguments (function template) |
|
(C++11)(C++11)(removed in C++20)(C++11)(C++11)(C++11)(C++11)(C++20) | compares two durations (function template) |
|
(C++11) | converts a duration to another, with a different tick interval (function template) |
|
(C++17) | converts a duration to another, rounding down (function template) |
|
(C++17) | converts a duration to another, rounding up (function template) |
|
(C++17) | converts a duration to another, rounding to nearest, ties to even (function template) |
|
(C++17) | obtains the absolute value of the duration (function template) |
|
(C++20) | performs stream output on a duration (function template) |
|
(C++20) | parses a duration from a stream according to the provided format (function template) |
| Type | Definition |
|---|---|
std::chrono::nanoseconds | duration</*signed integer type of at least 64 bits*/, std::nano> |
std::chrono::microseconds | duration</*signed integer type of at least 55 bits*/, std::micro> |
std::chrono::milliseconds | duration</*signed integer type of at least 45 bits*/, std::milli> |
std::chrono::seconds | duration</*signed integer type of at least 35 bits*/> |
std::chrono::minutes | duration</*signed integer type of at least 29 bits*/, std::ratio<60>> |
std::chrono::hours | duration</*signed integer type of at least 23 bits*/, std::ratio<3600>> |
std::chrono::days (since C++20) | duration</*signed integer type of at least 25 bits*/, std::ratio<86400>> |
std::chrono::weeks (since C++20) | duration</*signed integer type of at least 22 bits*/, std::ratio<604800>> |
std::chrono::months (since C++20) | duration</*signed integer type of at least 20 bits*/, std::ratio<2629746>> |
std::chrono::years (since C++20) | duration</*signed integer type of at least 17 bits*/, std::ratio<31556952>> |
Note: each of the predefined duration types up to hours covers a range of at least ±292 years.
| Each of the predefined duration types | (since C++20) |
|
(C++11) | specializes the std::common_type trait (class template specialization) |
|
(C++11) | indicates that a duration is convertible to duration with different tick period (class template) |
|
(C++11) | constructs zero, min, and max values of a tick count of given type (class template) |
|
(C++20) | formatting support for duration (class template specialization) |
Defined in inline namespace std::literals::chrono_literals |
|
|---|---|
|
(C++14) | a std::chrono::duration literal representing hours (function) |
|
(C++14) | a std::chrono::duration literal representing minutes (function) |
|
(C++14) | a std::chrono::duration literal representing seconds (function) |
|
(C++14) | a std::chrono::duration literal representing milliseconds (function) |
|
(C++14) | a std::chrono::duration literal representing microseconds (function) |
|
(C++14) | a std::chrono::duration literal representing nanoseconds (function) |
| Note: the literal suffixes | (since C++20) |
| Feature-test macro | Value | Std | Comment |
|---|---|---|---|
__cpp_lib_chrono_udls | 201304L | (C++14) | User-defined literals for time types |
The actual time interval (in seconds) that is held by a duration object d is roughly equal to d.count() * D::period::num / D::period::den, where D is of type chrono::duration<> and d is an object of such type.
This example shows how to define several custom duration types and convert between types:
#include <chrono>
#include <iostream>
using namespace std::chrono_literals;
template<typename T1, typename T2>
using mul = std::ratio_multiply<T1, T2>;
int main()
{
using shakes = std::chrono::duration<int, mul<std::deca, std::nano>>;
using jiffies = std::chrono::duration<int, std::centi>;
using microfortnights = std::chrono::duration<float,
mul<mul<std::ratio<2>, std::chrono::weeks::period>, std::micro>>;
using nanocenturies = std::chrono::duration<float,
mul<mul<std::hecto, std::chrono::years::period>, std::nano>>;
using fps_24 = std::chrono::duration<double, std::ratio<1,24>>;
std::cout << "1 second is:\n";
// integer scale conversion with no precision loss: no cast
std::cout << std::chrono::microseconds(1s).count() << " microseconds\n"
<< shakes(1s).count() << " shakes\n"
<< jiffies(1s).count() << " jiffies\n";
// integer scale conversion with precision loss: requires a cast
std::cout << std::chrono::duration_cast<std::chrono::minutes>(1s).count()
<< " minutes\n";
// floating-point scale conversion: no cast
std::cout << microfortnights(1s).count() << " microfortnights\n"
<< nanocenturies(1s).count() << " nanocenturies\n"
<< fps_24(1s).count() << " frames at 24fps\n";
}Output:
1 second is: 1000000 microseconds 100000000 shakes 100 jiffies 0 minutes 0.82672 microfortnights 0.316887 nanocenturies 24 frames at 24fps
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