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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`
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