Visual Basic

Public Class CRC32<br />
<br />
' This is v2 of the VB CRC32 algorithm provided by Paul<br />
<br />
' (wpsjr1@succeed.net) - much quicker than the nasty<br />
<br />
' original version I posted. Excellent work!<br />
<br />
Private crc32Table() As Integer<br />
<br />
Private Const BUFFER_SIZE As Integer = 1024<br />
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Public Function GetCrc32(ByRef stream As System.IO.Stream) As Integer<br />
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Dim crc32Result As Integer<br />
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crc32Result = &HFFFFFFFF<br />
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Dim buffer(BUFFER_SIZE) As Byte<br />
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Dim readSize As Integer = BUFFER_SIZE<br />
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Dim count As Integer = stream.Read(buffer, 0, readSize)<br />
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Dim i As Integer<br />
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Dim iLookup As Integer<br />
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Dim tot As Integer = 0<br />
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Do While (count > 0)<br />
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For i = 0 To count - 1<br />
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iLookup = (crc32Result And &HFF) Xor buffer(i)<br />
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crc32Result = ((crc32Result And &HFFFFFF00) \ &H100) And &HFFFFFF ' nasty shr 8 with vb :/<br />
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crc32Result = crc32Result Xor crc32Table(iLookup)<br />
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Next i<br />
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count = stream.Read(buffer, 0, readSize)<br />
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Loop<br />
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GetCrc32 = Not (crc32Result)<br />
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End Function<br />
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Public Sub New()<br />
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' This is the official polynomial used by CRC32 in PKZip.<br />
<br />
' Often the polynomial is shown reversed (04C11DB7).<br />
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Dim dwPolynomial As Integer = &HEDB88320<br />
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Dim i As Integer, j As Integer<br />
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ReDim crc32Table(256)<br />
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Dim dwCrc As Integer<br />
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For i = 0 To 255<br />
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dwCrc = i<br />
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For j = 8 To 1 Step -1<br />
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If (dwCrc And 1) Then<br />
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dwCrc = ((dwCrc And &HFFFFFFFE) \ 2&) And &H7FFFFFFF<br />
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dwCrc = dwCrc Xor dwPolynomial<br />
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Else<br />
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dwCrc = ((dwCrc And &HFFFFFFFE) \ 2&) And &H7FFFFFFF<br />
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End If<br />
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Next j<br />
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crc32Table(i) = dwCrc<br />
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Next i<br />
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End Sub<br />
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End Class<br />
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Public Class GetCRC32OF<br />
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Public Sub CRC32File()<br />
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End Sub<br />
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End Class

<Browsable(False)> _
Public Property MyProperty() As Integer
    ...
End Property

Public Property SomeProperty As Integer
    Get
        If Me.DesignMode Then
            ' The control is being used on a design surface...
        Else
            ' The control is NOT being used a design surface...
        End If
    End Get
    ...
End Property