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

std::chrono::duration: std::chrono::duration

NAME

std::chrono::duration - std::chrono::duration

Synopsis

Defined in header <chrono>
template<
class Rep, (since C++11)
class Period = std::ratio<1>
> class duration;

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 constant representing the number of 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 types

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 seconds per tick)

Member functions

                constructs new duration
constructor (public member function)
                assigns the contents
operator= (public member function)
                returns the count of ticks
count (public member function)

zero returns the special duration value zero
                (public static member function)
[static]

min returns the special duration value min
                (public static member function)
[static]

max returns the special duration value max
                (public static member function)
[static]
                implements unary + and unary -
operator+ (public member function)
operator-

operator++ increments or decrements the tick count
operator++(int) (public member function)
operator--
operator--(int)

operator+=
operator-= implements compound assignment between two durations
operator*= (public member function)
operator/=
operator%=

Non-member functions

                                        specializes the std::common_type trait
std::common_type<std::chrono::duration> (class template specialization)

operator+
operator- implements arithmetic operations with durations as arguments
operator* (function template)
operator/
operator%

operator==
operator!= compares two durations
operator< (function template)
operator<=
operator>
operator>=
                                        converts a duration to another, with a different tick interval
duration_cast (function template)

floor(std::chrono::duration) converts a duration to another, rounding down
                                        (function template)
(C++17)

ceil(std::chrono::duration) converts a duration to another, rounding up
                                        (function template)
(C++17)

round(std::chrono::duration) converts a duration to another, rounding to nearest, ties to even
                                        (function template)
(C++17)

abs(std::chrono::duration) obtains the absolute value of the duration
                                        (function template)
(C++17)

operator<< performs stream output on a duration
                                        (function template)
(C++20)

to_stream outputs a duration into a stream according to the provided format
                                        (function template)
(C++20)

from_stream parses a duration from a stream according to the provided format
                                        (function template)
(C++20)

Helper types

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 days, weeks, months and years covers a range of at least ±40000 years. years is equal to 365.2425 days (the average length of a Gregorian year). months is equal to 30.436875 days (exactly 1/12 of years).(since C++20)

Helper classes

                        indicates that a duration is convertible to duration with different tick period
treat_as_floating_point (class template)
                        constructs zero, min, and max values of a tick count of given type
duration_values (class template)

Literals

Defined in inline namespace std::literals::chrono_literals

operator""h A std::chrono::duration literal representing hours
              (function)
(C++14)

operator""min A std::chrono::duration literal representing minutes
              (function)
(C++14)

operator""s A std::chrono::duration literal representing seconds
              (function)
(C++14)

operator""ms A std::chrono::duration literal representing milliseconds
              (function)
(C++14)

operator""us A std::chrono::duration literal representing microseconds
              (function)
(C++14)

operator""ns A std::chrono::duration literal representing nanoseconds
              (function)
(C++14)

Note: the literal suffixes d and y do not refer to days and years but to day and year, respectively. (since C++20)

Example

This example shows how to define several custom duration types and convert between types:
// Run this code

  #include <iostream>
  #include <chrono>

  constexpr auto year = 31556952ll; // seconds in average Gregorian year

  int main()
  {
      using shakes = std::chrono::duration<int, std::ratio<1, 100000000>>;
      using jiffies = std::chrono::duration<int, std::centi>;
      using microfortnights = std::chrono::duration<float, std::ratio<14*24*60*60, 1000000>>;
      using nanocenturies = std::chrono::duration<float, std::ratio<100*year, 1000000000>>;

      std::chrono::seconds sec(1);

      std::cout << "1 second is:\n";

      // integer scale conversion with no precision loss: no cast
      std::cout << std::chrono::microseconds(sec).count() << " microseconds\n"
                << shakes(sec).count() << " shakes\n"
                << jiffies(sec).count() << " jiffies\n";

      // integer scale conversion with precision loss: requires a cast
      std::cout << std::chrono::duration_cast<std::chrono::minutes>(sec).count()
                << " minutes\n";

      // floating-point scale conversion: no cast
      std::cout << microfortnights(sec).count() << " microfortnights\n"
                << nanocenturies(sec).count() << " nanocenturies\n";
  }

Output:

  1 second is:
  1000000 microseconds
  100000000 shakes
  100 jiffies
  0 minutes
  0.82672 microfortnights
  0.316887 nanocenturies