72 lines
2.7 KiB
ReStructuredText
72 lines
2.7 KiB
ReStructuredText
NSPR defines a platform-dependent type, :ref:`PRIntervalTime`, for timing
|
|
intervals of fewer than approximately 6 hours. This chapter describes
|
|
:ref:`PRIntervalTime` and the functions that allow you to use it for timing
|
|
purposes:
|
|
|
|
- `Interval Time Type and
|
|
Constants <#Interval_Time_Type_and_Constants>`__
|
|
- `Interval Functions <#Interval_Functions>`__
|
|
|
|
.. _Interval_Time_Type_and_Constants:
|
|
|
|
Interval Time Type and Constants
|
|
--------------------------------
|
|
|
|
All timed functions in NSPR require a parameter that depicts the amount
|
|
of time allowed to elapse before the operation is declared failed. The
|
|
type of such arguments is :ref:`PRIntervalTime`. Such parameters are common
|
|
in NSPR functions such as those used for I/O operations and operations
|
|
on condition variables.
|
|
|
|
NSPR 2.0 provides interval times that are efficient in terms of
|
|
performance and storage requirements. Conceptually, they are based on
|
|
free-running counters that increment at a fixed rate without possibility
|
|
of outside influence (as might be observed if one was using a
|
|
time-of-day clock that gets reset due to some administrative action).
|
|
The counters have no fixed epoch and have a finite period. To make use
|
|
of these counters, the application must declare a point in time, the
|
|
epoch, and an amount of time elapsed since that **epoch**, the
|
|
**interval**. In almost all cases the epoch is defined as the value of
|
|
the interval timer at the time it was sampled.
|
|
|
|
- :ref:`PRIntervalTime`
|
|
|
|
.. _Interval_Functions:
|
|
|
|
Interval Functions
|
|
------------------
|
|
|
|
Interval timing functions are divided into three groups:
|
|
|
|
- `Getting the Current Interval and Ticks Per
|
|
Second <#Getting_the_Current_Interval_and_Ticks_Per_Second>`__
|
|
- `Converting Standard Clock Units to Platform-Dependent
|
|
Intervals <#Converting_Standard_Clock_Units_to_Platform-Dependent_Intervals>`__
|
|
- `Converting Platform-Dependent Intervals to Standard Clock
|
|
Units <#Converting_Platform-Dependent_Intervals_to_Standard_Clock_Units>`__
|
|
|
|
.. _Getting_the_Current_Interval_and_Ticks_Per_Second:
|
|
|
|
Getting the Current Interval and Ticks Per Second
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
- :ref:`PR_IntervalNow`
|
|
- :ref:`PR_TicksPerSecond`
|
|
|
|
.. _Converting_Standard_Clock_Units_to_Platform-Dependent_Intervals:
|
|
|
|
Converting Standard Clock Units to Platform-Dependent Intervals
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
- :ref:`PR_SecondsToInterval`
|
|
- :ref:`PR_MillisecondsToInterval`
|
|
- :ref:`PR_MicrosecondsToInterval`
|
|
|
|
.. _Converting_Platform-Dependent_Intervals_to_Standard_Clock_Units:
|
|
|
|
Converting Platform-Dependent Intervals to Standard Clock Units
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
- :ref:`PR_IntervalToSeconds`
|
|
- :ref:`PR_IntervalToMilliseconds`
|
|
- :ref:`PR_IntervalToMicroseconds`
|