>(1)> Is that Polynomal PKZip CRC complaint BTW?
>
>I don't know whether it's pkzip compliant. Should be tested. But a CRC is a CRC, so I expect both use the same algorithm
>
>(2) > If yes, with that, they never get negative values.
>It's just a matter of interpreting the 32 bits. It's a hex value. Is 0xFFFFFFFF in decimal 4,294,967,295 or -1
>
>
>(3) If you leave your class as is, add a method crc32vfp() or crc32Unsigned()
>Use your existing method which returns Integer, convert Integer to UInteger and return that

This works.

Here is the equivalent for a VFP equivalent CRC32 class:

Public Class CRC32VFP

    Public cMessage As String = ""
    Public cFileName As String = ""
    Public lLogError As Boolean = True
    Public nCRC32 As UInteger = 0
    Public oApp As Framework.Framework.App
    Private cFileDoesNotExist As String = ""
    Private nBufferSize As Integer = 1024
    Private nCRC32Table() As UInteger
    Private nLanguage As Integer = 0
    Private oProcess As Framework.Framework.LXProcess

    ' This is when we access the data provider in desktop and Web service mode
    Sub New(ByVal toApplication As Framework.Framework.App)
        oApp = toApplication
        nLanguage = oApp.nLanguage
        Init()
        Initialize()
    End Sub

    ' This is when we access the data provider in a Web mode
    Public Sub New(ByVal toProcess As Framework.Framework.LXProcess)
        oProcess = toProcess
        oApp = oProcess.oApp
        nLanguage = oProcess.nLanguage
        Init()
        Initialize()
    End Sub

    Private Function Init() As Boolean

        ' Based on the language
        Select Case nLanguage

            ' English
            Case 1
                cFileDoesNotExist = "The file ##File## does not exist."

                ' French
            Case 2
                cFileDoesNotExist = "Le fichier ##File## n'existe pas."

                ' Spanish
            Case 3
                cFileDoesNotExist = "The file ##File## does not exist."

                ' Portuguese
            Case 4
                cFileDoesNotExist = "The file ##File## does not exist."

        End Select

        Return True
    End Function

    ' This is the official polynomial used by CRC32 in PKZip.
    ' Often the polynomial is shown reversed (04C11DB7).
    ' Initialize
    Private Function Initialize() As Boolean
        Dim lnDWPolynomial As UInteger = &HEDB88320UI
        Dim lnCounter As Integer = 0
        Dim lnCounter2 As Integer = 0
        ReDim nCRC32Table(256)
        Dim lnDWCRC As UInteger

        For lnCounter = 0 To 255
            lnDWCRC = lnCounter

            For lnCounter2 = 8 To 1 Step -1

                If (lnDWCRC And 1) Then
                    lnDWCRC = ((lnDWCRC And &HFFFFFFFE) \ 2&) And &H7FFFFFFF
                    lnDWCRC = lnDWCRC Xor lnDWPolynomial
                Else
                    lnDWCRC = ((lnDWCRC And &HFFFFFFFE) \ 2&) And &H7FFFFFFF
                End If

            Next

            nCRC32Table(lnCounter) = lnDWCRC
        Next

        Return True
    End Function

    ' This is the main method to call
    Public Function GetCRC() As Boolean
        Dim lcMessage As String = ""
        Dim lnCounter As Integer = 0
        Dim lnDelay As Integer = 250
        Dim lnRetry As Integer = 8
        Dim loStream As Stream = Nothing

        ' Reset the values
        cMessage = ""
        nCRC32 = 0

        For lnCounter = 1 To lnRetry

            Try

                ' If the file exists
                If oApp.FileExist(cFileName) Then
                    loStream = New FileStream(cFileName, FileMode.Open, FileAccess.Read, FileShare.Read, 8192)
                Else
                    lcMessage = oApp.StrTran(cFileDoesNotExist, "##File##", cFileName)

                    ' If we log the error
                    If lLogError Then

                        ' Get the proper definition as per the current scope
                        If oProcess Is Nothing Then
                            oApp.ErrorSetup(, "CRC32: " + lcMessage)
                        Else
                            oProcess.ErrorSetup(, "CRC32: " + lcMessage)
                        End If

                    Else
                        Return False
                    End If

                End If

                Exit For

            Catch loError As Exception

                ' If we have not reached the maximum tries of 8, we retry
                If lnCounter < 8 Then

                    ' Wait for a timeout before retrying
                    System.Threading.Thread.Sleep(lnDelay)

                    Continue For
                End If

                ' If we log the error
                If lLogError Then

                    ' Get the proper definition as per the current scope
                    If oProcess Is Nothing Then
                        oApp.ErrorSetup(loError)
                    Else
                        oProcess.ErrorSetup(loError)
                    End If

                Else
                    cMessage = loError.Message
                End If

            End Try

        Next

        nCRC32 = GetCrc32(loStream)
        loStream.Close()
        Return True
    End Function

    Private Function GetCrc32(ByRef toStream As System.IO.Stream) As UInteger
        Dim lnCRC32Result As UInteger = &HFFFFFFFFUI
        Dim loBuffer(nBufferSize) As Byte
        Dim lnReadSize As Integer = nBufferSize
        Dim lnCount As Integer = 0
        Dim lnCounter As Integer = 0
        Dim lnLookup As Integer = 0

        lnCount = toStream.Read(loBuffer, 0, lnReadSize)

        Do While lnCount > 0

            For lnCounter = 0 To lnCount - 1
                lnLookup = (lnCRC32Result And &HFF) Xor loBuffer(lnCounter)

                ' Nasty shr 8 with vb :/
                lnCRC32Result = ((lnCRC32Result And &HFFFFFF00) \ &H100) And 16777215

                lnCRC32Result = lnCRC32Result Xor nCRC32Table(lnLookup)
            Next

            lnCount = toStream.Read(loBuffer, 0, lnReadSize)
        Loop

        Return Not lnCRC32Result
    End Function

End Class