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diff --git a/docs/nspr/reference/interval_timing.rst b/docs/nspr/reference/interval_timing.rst new file mode 100644 index 0000000000..2d19d6004b --- /dev/null +++ b/docs/nspr/reference/interval_timing.rst @@ -0,0 +1,72 @@ +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` |