[#absl-Clock]
= xref:absl.adoc[absl]::Clock
:relfileprefix: ../
:mrdocs:

An abstract interface representing a Clock, which is an object that can tell you the current time, sleep, and wait for a condition variable.

== Synopsis

Declared in `<absl/time/clock_interface.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
class Clock;
----

== Description

This interface allows decoupling code that uses time from the code that creates a point in time. You can use this to your advantage by injecting Clocks into interfaces rather than having implementations call absl::Now() directly.

Implementations of this interface must be thread‐safe.

The Clock::GetRealClock() function returns a reference to the global realtime clock.

Example:

bool IsWeekend(Clock& clock) { absl::Time now = clock.TimeNow(); // ... code to check if 'now' is a weekend. }

// Production code. IsWeekend(Clock::GetRealClock());

// Test code: MyTestClock test_clock(SATURDAY); IsWeekend(test_clock);

== Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:absl/Clock/2destructor.adoc[`~Clock`] [.small]#[destructor]# [.small]#[virtual]#
| Destroys the clock.
| xref:absl/Clock/AwaitWithDeadline.adoc[`AwaitWithDeadline`]  [.small]#[virtual]#
| Returns when cond is true or the deadline has passed. Returns true iff cond holds when returning.
| xref:absl/Clock/Sleep.adoc[`Sleep`]  [.small]#[virtual]#
| Sleeps for the specified duration.
| xref:absl/Clock/SleepUntil.adoc[`SleepUntil`]  [.small]#[virtual]#
| Sleeps until the specified time.
| xref:absl/Clock/TimeNow.adoc[`TimeNow`]  [.small]#[virtual]#
| Returns the current time.
|===


== Static Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:absl/Clock/GetRealClock.adoc[`GetRealClock`] 
| Returns a reference to the global realtime clock. The returned clock is thread‐safe.
|===


== Derived Classes

[cols="1,4"]
|===
| Name| Description
| xref:absl/SimulatedClock.adoc[`SimulatedClock`] 
| A simulated clock is a concrete Clock implementation that does not "tick" on its own. Time is advanced by explicit calls to the AdvanceTime() or SetTime() functions.
|===


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