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Depends on D137611 Differential Revision: https://phabricator.services.mozilla.com/D137612
72 lines
2.7 KiB
ReStructuredText
72 lines
2.7 KiB
ReStructuredText
NSPR defines a platform-dependent type, :ref:`PRIntervalTime`, for timing
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intervals of fewer than approximately 6 hours. This chapter describes
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:ref:`PRIntervalTime` and the functions that allow you to use it for timing
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purposes:
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- `Interval Time Type and
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Constants <#Interval_Time_Type_and_Constants>`__
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- `Interval Functions <#Interval_Functions>`__
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.. _Interval_Time_Type_and_Constants:
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Interval Time Type and Constants
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--------------------------------
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All timed functions in NSPR require a parameter that depicts the amount
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of time allowed to elapse before the operation is declared failed. The
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type of such arguments is :ref:`PRIntervalTime`. Such parameters are common
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in NSPR functions such as those used for I/O operations and operations
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on condition variables.
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NSPR 2.0 provides interval times that are efficient in terms of
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performance and storage requirements. Conceptually, they are based on
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free-running counters that increment at a fixed rate without possibility
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of outside influence (as might be observed if one was using a
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time-of-day clock that gets reset due to some administrative action).
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The counters have no fixed epoch and have a finite period. To make use
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of these counters, the application must declare a point in time, the
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epoch, and an amount of time elapsed since that **epoch**, the
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**interval**. In almost all cases the epoch is defined as the value of
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the interval timer at the time it was sampled.
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- :ref:`PRIntervalTime`
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.. _Interval_Functions:
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Interval Functions
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------------------
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Interval timing functions are divided into three groups:
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- `Getting the Current Interval and Ticks Per
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Second <#Getting_the_Current_Interval_and_Ticks_Per_Second>`__
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- `Converting Standard Clock Units to Platform-Dependent
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Intervals <#Converting_Standard_Clock_Units_to_Platform-Dependent_Intervals>`__
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- `Converting Platform-Dependent Intervals to Standard Clock
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Units <#Converting_Platform-Dependent_Intervals_to_Standard_Clock_Units>`__
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.. _Getting_the_Current_Interval_and_Ticks_Per_Second:
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Getting the Current Interval and Ticks Per Second
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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- :ref:`PR_IntervalNow`
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- :ref:`PR_TicksPerSecond`
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.. _Converting_Standard_Clock_Units_to_Platform-Dependent_Intervals:
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Converting Standard Clock Units to Platform-Dependent Intervals
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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- :ref:`PR_SecondsToInterval`
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- :ref:`PR_MillisecondsToInterval`
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- :ref:`PR_MicrosecondsToInterval`
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.. _Converting_Platform-Dependent_Intervals_to_Standard_Clock_Units:
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Converting Platform-Dependent Intervals to Standard Clock Units
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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- :ref:`PR_IntervalToSeconds`
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- :ref:`PR_IntervalToMilliseconds`
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- :ref:`PR_IntervalToMicroseconds`
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