High Precision Timer

[dday9]

Below is a high precision timer that uses the QueryPerformance API's. I tried to structure it just like a normal timer would be so that it makes it easier to use.

My might you want to use this timer over normal timer? Well, in my case I needed a game loop that will be consistently executed. With the normal timer, any intervals around 15 - 20 milliseconds are no longer accurate and for a game loop you want an interval of 16.6 milliseconds(60 FPS).

Here is the code:

Option Strict On
Option Explicit On
<System.ComponentModel.DefaultEvent("Tick")> _
Public Class PrecisionTimer
    Inherits System.ComponentModel.Component

    Private frequency As Long
    Private waitThread As Threading.Thread

#Region "Api"

    Private Declare Function QueryPerformanceCounter Lib "kernel32" (ByRef lpPerformanceCount As Long) As Integer
    Private Declare Function QueryPerformanceFrequency Lib "kernel32" (ByRef lpFrequency As Long) As Integer

#End Region

#Region "Events"

    Public Event Tick(ByVal sender As Object, ByVal e As EventArgs)

#End Region

#Region "Methods"

    Private Sub CheckCompatibility()
        Dim test As Long
        If Not CBool(QueryPerformanceCounter(test)) Then
            Throw New Exception("High-resolution counter is not supported for this computer.")
        End If
    End Sub

    Public Sub Start()
        Me.Enabled = True
        waitThread = New Threading.Thread(AddressOf Wait)
        waitThread.IsBackground = True
        waitThread.Start()
    End Sub

    Public Sub [Stop]()
        Me.Enabled = False
    End Sub

    Private Sub Wait()
        Dim counter1, counter2 As Long
        QueryPerformanceCounter(counter1)

        If Me.LowerCpuUsage Then

            Do
                QueryPerformanceCounter(counter2)
                Threading.Thread.Sleep(2)
            Loop Until (counter2 - counter1) / (frequency / 1000) >= Me.Interval

        Else

            Do
                QueryPerformanceCounter(counter2)
            Loop Until (counter2 - counter1) / (frequency / 1000) >= Me.Interval

        End If

        Console.WriteLine((counter2 - counter1) / (frequency / 1000))

        RaiseEvent Tick(Me, EventArgs.Empty)

        If Me.AutoReset Then
            Me.Enabled = False
        ElseIf Me.Enabled Then
            waitThread = New Threading.Thread(AddressOf Wait)
            waitThread.Start()
        End If

    End Sub

#End Region

#Region "New Constructor"

    Sub New()
        Call CheckCompatibility()
        QueryPerformanceFrequency(frequency)
        Me.Interval = 100
    End Sub

    Sub New(ByVal interval As Double)
        Call CheckCompatibility()
        QueryPerformanceFrequency(frequency)
        Me.Interval = interval
    End Sub

#End Region

#Region "Properties"

    Public Property AutoReset As Boolean
    Private pEnabled As Boolean
    Public Property Enabled() As Boolean
        Get
            Return pEnabled
        End Get
        Set(ByVal value As Boolean)
            If pEnabled <> value Then
                pEnabled = value
                If pEnabled Then RaiseEvent Tick(Me, EventArgs.Empty)
            End If
        End Set
    End Property
    Public Property Interval As Double
    Public Property LowerCpuUsage As Boolean

#End Region

End Class

I'd like to thank Jacob Roman for introducing me to the QueryPerformance API's.