How to: Use the High-Resolution Timer
[This documentation is for preview only, and is subject to change in later releases. Blank topics are included as placeholders.]
Some devices support a high-resolution timer. This timer, when present, provides more precise measurements than you can obtain by using the TickCount property, which has a 1-millisecond resolution. In applications where precise time measurements are important, the high-resolution timer provides the best results. For example, some Direct3D applications display more smoothly when the animation is based on the high-resolution timer. You can also use this timer in an application to determine how much time a method or a section of code requires to execute.
This code example provides a class that makes it easier to use the high-resolution timer in managed code on Windows CE. The example has the following features:
Platform invoke declarations for the native methods in Windows CE.
A property that is used to get the frequency of the high-resolution counter.
A property that is used to get the value of the high-resolution counter.
An implementation that supports the TickCount property as a fallback if the QueryPerformanceCounter function is not supported or is emulated.
An example of how the high-resolution counter can be used to time an operation.
Public Class HiResTimer Private isPerfCounterSupported As Boolean = False Private timerFrequency As Int64 = 0 ' Windows CE native library with QueryPerformanceCounter(). Private Const [lib] As String = "coredll.dll" Public Declare Function QueryPerformanceCounter Lib "Coredll.dll" _ (ByRef count As Int64) As Integer Public Declare Function QueryPerformanceFrequency Lib "Coredll.dll" _ (ByRef timerFrequency As Int64) As Integer Public Sub New() ' Query the high-resolution timer only if it is supported. ' A returned frequency of 1000 typically indicates that it is not ' supported and is emulated by the OS using the same value that is ' returned by Environment.TickCount. ' A return value of 0 indicates that the performance counter is ' not supported. Dim returnVal As Integer = QueryPerformanceFrequency(timerFrequency) If returnVal <> 0 AndAlso timerFrequency <> 1000 Then ' The performance counter is supported. isPerfCounterSupported = True Else ' The performance counter is not supported. Use ' Environment.TickCount instead. timerFrequency = 1000 End If End Sub Public ReadOnly Property Frequency() As Int64 Get Return timerFrequency End Get End Property Public ReadOnly Property Value() As Int64 Get Dim tickCount As Int64 = 0 If isPerfCounterSupported Then ' Get the value here if the counter is supported. QueryPerformanceCounter(tickCount) Return tickCount Else ' Otherwise, use Environment.TickCount Return CType(Environment.TickCount, Int64) End If End Get End Property Shared Sub Main() Dim timer As New HiResTimer() ' This example shows how to use the high-resolution counter to ' time an operation. ' Get counter value before the operation starts. Dim counterAtStart As Int64 = timer.Value ' Perform an operation that takes a measureable amount of time. Dim count As Integer For count = 0 To 9999 count += 1 count -= 1 Next count ' Get counter value after the operation ends. Dim counterAtEnd As Int64 = timer.Value ' Get time elapsed in tenths of milliseconds Dim timeElapsedInTicks As Int64 = counterAtEnd - counterAtStart Dim timeElapseInTenthsOfMilliseconds As Int64 = timeElapsedInTicks * 10000 / timer.Frequency MessageBox.Show("Time Spent in operation (tenths of ms) " + timeElapseInTenthsOfMilliseconds.ToString + vbLf + "Counter Value At Start: " + counterAtStart.ToString + vbLf + "Counter Value At End : " + counterAtEnd.ToString + vbLf + "Counter Frequency : " + timer.Frequency.ToString) End Sub End Class