Duration

表示一个实践段，由时刻（tick)和时刻数组成

	std::chrono::duration<int,std::ratio<3600>> hours(1);
	std::chrono::duration<int,std::ratio<60>> minutes(14);
	std::cout<<std::chrono::duration_cast<std::chrono::seconds>(hours+minutes).count()<<'\n';

4440
//1h14min=4440s

提供了一些通俗易懂的成员函数

operator=
 
assigns the contents
(public member function)
count
 
returns the count of ticks
(public member function)
zero
  
[static]
 
returns the special duration value zero
(public static member function)
min
  
[static]
 
returns the special duration value min
(public static member function)
max
  
[static]
 
returns the special duration value max
(public static member function)
operator+
operator-
 
implements unary + and unary -
(public member function)
operator++
operator++(int)
operator--
operator--(int)
 
increments or decrements the tick count
(public member function)
operator+=
operator-=
operator*=
operator/=
operator%=
 
implements compound assignment between two durations
(public member function)

提供了比较


operator+
operator-
operator*
operator/
operator%
  
(C++11)
 
implements arithmetic operations with durations as arguments
(function template)
operator==
operator!=
operator<
operator<=
operator>
operator>=
operator<=>
  
(C++11)
(C++11)(removed in C++20)
(C++11)
(C++11)
(C++11)
(C++11)
(C++20)
 
compares two durations
(function template)

提供了简单的数学运算

duration_cast
  
(C++11)
 
converts a duration to another, with a different tick interval
(function template)
floor(std::chrono::duration)
  
(C++17)
 
converts a duration to another, rounding down
(function template)
ceil(std::chrono::duration)
  
(C++17)
 
converts a duration to another, rounding up
(function template)
round(std::chrono::duration)
  
(C++17)
 
converts a duration to another, rounding to nearest, ties to even
(function template)
abs(std::chrono::duration)
  
(C++17)
 
obtains the absolute value of the duration
(function template)

提供了流转换

operator<<
  
(C++20)
 
performs stream output on a duration
(function template)
from_stream
  
(C++20)
 
parses a duration from a stream according to the provided format
(function template)

这些目前编译器支持性还不是很好

Clocks

clocks由一个时间点(epoch)和一个tick组成

    auto now=std::chrono::system_clock::now();
    std::time_t t_c=std::chrono::system_clock::to_time_t(now);
    std::cout<<std::ctime(&t_c)<<'\n';
    std::this_thread::sleep_for(std::chrono::seconds(2l));

    now=std::chrono::system_clock::now();
    t_c=std::chrono::system_clock::to_time_t(now);
    std::cout<<std::ctime(&t_c)<<'\n';

Thu Dec 05 13:39:39 2024

Thu Dec 05 13:39:41 2024

主要提供了以下：

system_clock (C++11)	wall clock time from the system-wide realtime clock (class)
steady_clock (C++11)	monotonic clock that will never be adjusted (class)
high_resolution_clock (C++11)	the clock with the shortest tick period available (class)
is_clockis_clock_v (C++20)	determines if a type is a Clock (class template) (variable template)
utc_clock (C++20)	Clock for Coordinated Universal Time (UTC) (class)
tai_clock (C++20)	Clock for International Atomic Time (TAI) (class)
gps_clock (C++20)	Clock for GPS time (class)
file_clock (C++20)	Clock used for file time (typedef)
local_t (C++20)	pseudo-clock representing local time (class)

Time Point

代表一个时间点，是通过记录一个距离时钟开始时间的Duration实现的

auto base=std::chrono::steady_clock::now();
    std::this_thread::sleep_for(std::chrono::milliseconds(1145l));
    auto now=std::chrono::steady_clock::now();
    std::chrono::duration<double> diff=now-base;
    std::cout<<diff.count()<<'\n';
    std::cout<<base.time_since_epoch().count()<<'\n';
    std::cout<<now.time_since_epoch().count()<<'\n';
    std::cout<<now.time_since_epoch().count()-base.time_since_epoch().count()<<'\n';

1.1506
909922889200
911073490400
1150601200

提供了time_since_epoch()方法返回记录的Duration

提供了合乎常理的运算符重载和数学运算

operator+=operator-=	modifies the time point by the given duration (public member function)
operator++operator++(int)operator--operator--(int) (C++20)	increments or decrements the duration (public member function)
min [static]	returns the time point corresponding to the smallest duration (public static member function)
max [static]	returns the time point corresponding to the largest duration (public static member function)

operator+operator- (C++11)	performs add and subtract operations involving a time point (function template)
operator==operator!=operator<operator<=operator>operator>=operator<=> (C++11)(C++11)(removed in C++20)(C++11)(C++11)(C++11)(C++11)(C++20)	compares two time points (function template)
time_point_cast (C++11)	converts a time point to another time point on the same clock, with a different duration (function template)
floor(std::chrono::time_point) (C++17)	converts a time_point to another, rounding down (function template)
ceil(std::chrono::time_point) (C++17)	converts a time_point to another, rounding up (function template)
round(std::chrono::time_point) (C++17)	converts a time_point to another, rounding to nearest, ties to even (function template)