std::chrono::clock_time_conversion
Defined in header <chrono> |
||
---|---|---|
template<class Dest, class Source> struct clock_time_conversion { }; |
(since C++20) |
std::chrono::clock_time_conversion
is a trait that specifies how to convert a std::chrono::time_point
of the Source
clock to that of the Dest
clock. It does so by providing an const-callable operator()
that accepts an argument of type std::chrono::time_point<Source, Duration>
and returns a std::chrono::time_point<Dest, OtherDuration>
that represents an equivalent point in time. The duration of the returned time point is computed from the source duration in a manner that varies for each specialization. clock_time_conversion
is normally only used indirectly, via std::chrono::clock_cast
.
A program may specialize clock_time_conversion
if at least one of the template parameters is a user-defined clock type.
The primary template is an empty struct. The standard defines the following specializations:
template<class Clock> struct clock_time_conversion<Clock, Clock>; |
(1) | (since C++20) |
template<> struct clock_time_conversion<std::chrono::system_clock, std::chrono::system_clock>; |
(2) | (since C++20) |
template<> struct clock_time_conversion<std::chrono::utc_clock, std::chrono::utc_clock>; |
(3) | (since C++20) |
template<> struct clock_time_conversion<std::chrono::system_clock, std::chrono::utc_clock>; |
(4) | (since C++20) |
template<> struct clock_time_conversion<std::chrono::utc_clock, std::chrono::system_clock>; |
(5) | (since C++20) |
template<class Clock> struct clock_time_conversion<Clock, std::chrono::system_clock>; |
(6) | (since C++20) |
template<class Clock> struct clock_time_conversion<std::chrono::system_clock, Clock>; |
(7) | (since C++20) |
template<class Clock> struct clock_time_conversion<Clock, std::chrono::utc_clock>; |
(8) | (since C++20) |
template<class Clock> struct clock_time_conversion<std::chrono::utc_clock, Clock>; |
(9) | (since C++20) |
operator()
returns a copy of the argument.
std::chrono::sys_time
and
std::chrono::utc_time
:
operator()
calls
std::chrono::utc_clock::to_sys
and
std::chrono::utc_clock::from_sys
, respectively.
std::chrono::sys_time
when
Clock
supports
from_sys
and
to_sys
:
operator()
calls
Clock::to_sys
and
Clock::from_sys
, respectively.
std::chrono::utc_time
when
Clock
supports
from_utc
and
to_utc
:
operator()
calls
Clock::to_utc
and
Clock::from_utc
, respectively.
Member functions
Each specialization has an implicitly-declared default constructor, copy constructor, move constructor, copy assignment operator, move assignment operator, and destructor.
std::chrono::clock_time_conversion::operator()
template <class Duration> std::chrono::time_point<Clock, Duration> operator()(const std::chrono::time_point<Clock, Duration>& t) const; |
(1) | (member of specialization (1)) |
template <class Duration> std::chrono::sys_time<Duration> operator()(const std::chrono::sys_time<Duration> & t) const; |
(2) | (member of specialization (2)) |
template <class Duration> std::chrono::utc_time<Duration> operator()(const std::chrono::utc_time<Duration>& t) const; |
(3) | (member of specialization (3)) |
template <class Duration> std::chrono::sys_time<Duration> operator()(const std::chrono::utc_time<Duration>& t) const; |
(4) | (member of specialization (4)) |
template <class Duration> std::chrono::utc_time<Duration> operator()(const std::chrono::sys_time<Duration>& t) const; |
(5) | (member of specialization (5)) |
template <class Duration> auto operator()(const std::chrono::sys_time<Duration>& t) const -> decltype(Clock::from_sys(t)); |
(6) | (member of specialization (6)) |
template <class Duration> auto operator()(const std::chrono::time_point<SourceClock, Duration>& t) const -> decltype(Clock::to_sys(t)); |
(7) | (member of specialization (7)) |
template <class Duration> auto operator()(const std::chrono::utc_time<Duration>& t) const -> decltype(Clock::from_utc(t)); |
(8) | (member of specialization (8)) |
template <class Duration> auto operator()(const std::chrono::time_point<Clock, Duration>& t) const -> decltype(Clock::to_utc(t)); |
(9) | (member of specialization (9)) |
Converts the argument std::chrono::time_point
to the destination clock.
t
unchanged.
std::chrono::utc_clock::to_sys(t)
.
std::chrono::utc_clock::from_sys(t)
.
Clock::from_sys(t)
. This overload participates in overload resolution only if the expression
Clock::from_sys(t)
is well-formed. The program is ill-formed if
Clock::from_sys(t)
does not return
std::chrono::time_point<Clock, Duration>
where
Duration
is some valid specialization of
std::chrono::duration
.
Clock::to_sys(t)
. This overload participates in overload resolution only if the expression
Clock::to_sys(t)
is well-formed. The program is ill-formed if
Clock::to_sys(t)
does not return
std::chrono::sys_time<Duration>
where
Duration
is some valid specialization of
std::chrono::duration
.
Clock::from_utc(t)
. This overload participates in overload resolution only if the expression
Clock::from_utc(t)
is well-formed. The program is ill-formed if
Clock::from_utc(t)
does not return
std::chrono::time_point<Clock, Duration>
where
Duration
is some valid specialization of
std::chrono::duration
.
Clock::to_utc(t)
. This overload participates in overload resolution only if the expression
Clock::to_utc(t)
is well-formed. The program is ill-formed if
Clock::to_utc(t)
does not return
std::chrono::utc_time<Duration>
where
Duration
is some valid specialization of
std::chrono::duration
.
Parameters
t | - | time point to convert |
Return value
The result of the conversion as described above:
t
.
Clock::from_sys(t)
.
Clock::to_sys(t)
.
Clock::from_utc(t)
.
Clock::to_utc(t)
.
See also
(C++20)
|
convert time points of one clock to another (function template) |
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