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Compare two file version numbers

Compare two file version numbers

When installing application, dlls, OCX's etc, it is useful to determine which file version is the latest. The version numbers normally take the form "1.201.30", with the numbers given in descending order of importance. The following code parses the version number strings of two files and returns the file number which has the latest version number. Note, use this code in conjuction with the article which demonstrated how to return file version numbers:


Code:

Option Explicit

'Purpose   :    Check two file version numbers
'Inputs    :    sFile1. The first file to check the version number of.
'               sFile1. The second file to check the version number of.
'Outputs   :    Returns 1 if the first file has the lastest version number.
'               Returns 2 if the second file has the lastest version number.
'               Returns -1 if error occurs.
'Notes     :    If the files contains a different length version parts eg.
'               File1 = "1.1.03" and File2 = "1.1.4"
'               Then File2's version number will be consider to be File2 = "1.1.40"

Function FileVersionCompare(sFile1 As String, sFile2 As String) As Long
    Dim lFile1Ver As Long, lPos1 As Long, lOldPos1 As Long, lLen1 As Long
    Dim lFile2Ver As Long, lPos2 As Long, lOldPos2 As Long, lLen2 As Long
    Dim lVerLen As Long
    
    On Error GoTo ErrFailed
    lLen1 = Len(sFile1)
    lLen2 = Len(sFile2)
    lPos1 = 1
    lPos2 = 1

    Do
        'Find the position of the file 1's  decimal seperator
        lPos1 = InStr(lPos1, sFile1, ".")
        If lPos1 = 0 Then
            lPos1 = lLen1 + 1
        End If
        'Find the position of the file 2's  decimal seperator
        lPos2 = InStr(lPos2, sFile2, ".")
        If lPos2 = 0 Then
            lPos2 = lLen2 + 1
        End If
        
        'Determine the length of the version part
        If lPos1 - lOldPos1 > lPos2 - lOldPos2 Then
            lVerLen = lPos1 - lOldPos1 - 1
        Else
            lVerLen = lPos2 - lOldPos2 - 1
        End If
        
        'Determine the value of the version part
        lFile1Ver = CLng(Mid$(sFile1, lOldPos1 + 1, lPos1 - lOldPos1 - 1)) * 10 ^ (lVerLen - (lPos1 - lOldPos1 - 1) + 1) / 10
        lFile2Ver = CLng(Mid$(sFile2, lOldPos2 + 1, lPos2 - lOldPos2 - 1)) * 10 ^ (lVerLen - (lPos2 - lOldPos2 - 1) + 1) / 10
        
        If lFile1Ver > lFile2Ver Then
            'File1 is the latest
            FileVersionCompare = 1
            Exit Do
        ElseIf lFile1Ver < lFile2Ver Then
            'File2 is the latest
            FileVersionCompare = 2
            Exit Do
        End If
        
        If lPos1 >= lLen1 Or lPos2 >= lLen2 Then
            'Finished checking version parts
            Exit Do
        End If
        'Store the position of the last decimal seperator
        lOldPos1 = lPos1
        lOldPos2 = lPos2
        'Look at the next version part
        lPos1 = lPos1 + 1
        lPos2 = lPos2 + 1
    Loop
    Exit Function
ErrFailed:
    FileVersionCompare = -1
    On Error GoTo 0
End Function

'Demonstration routine
Sub Test()
    Dim lRetVal As Long
    lRetVal = FileVersionCompare("1.2.03", "1.2.04")
    Select Case lRetVal
    Case 1
        MsgBox "File 1 is the latest"
    Case 2
        MsgBox "File 2 is the latest"
    Case -1
        MsgBox "Error occured"
    End Select
End Sub