Sunday, November 25, 2012

Compare Two Files in VB6

This function will allow you to compare one file to another. It will do either a lax check (compare file lengths only) or a stringent check (a byte by byte comparison).

Pretty straightforward demonstration of string handling for Visual Basic 6, posted by request.

Public Function AreTheyTheSame(ByVal File1 As String, _
ByVal File2 As String, Optional StringentCheck As _
Boolean = False) As Boolean

On Error GoTo ErrorHandler

If Dir(File1) = "" Then Exit Function
If Dir(File2) = "" Then Exit Function

Dim lLen1 As Long, lLen2 As Long
Dim iFileNum1 As Integer
Dim iFileNum2 As Integer
Dim bytArr1() As Byte, bytArr2() As Byte
Dim lCtr As Long, lStart As Long
Dim bAns As Boolean

lLen1 = FileLen(File1)
lLen2 = FileLen(File2)
If lLen1 <> lLen2 Then
Exit Function
ElseIf StringentCheck = False Then
AreTheyTheSame = True
Exit Function
iFileNum1 = FreeFile
Open File1 For Binary Access Read As #iFileNum1
iFileNum2 = FreeFile
Open File2 For Binary Access Read As #iFileNum2

'put contents of both into byte Array
bytArr1() = InputB(LOF(iFileNum1), #iFileNum1)
bytArr2() = InputB(LOF(iFileNum2), #iFileNum2)
lLen1 = UBound(bytArr1)
lStart = LBound(bytArr1)

bAns = True
For lCtr = lStart To lLen1
If bytArr1(lCtr) <> bytArr2(lCtr) Then
bAns = False
Exit For
End If

AreTheyTheSame = bAns

End If

If iFileNum1 > 0 Then Close #iFileNum1
If iFileNum2 > 0 Then Close #iFileNum2
End Function

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