modFuzzyPercent.bas

Function FuzzyPercent(ByVal String1 As String, _
                      ByVal String2 As String, _
                      Optional Algorithm As Integer = 3, _
                      Optional Normalised As Boolean = False) As Single
'*************************************
'** Return a % match on two strings **
'*************************************
Dim intLen1 As Integer, intLen2 As Integer
Dim intCurLen As Integer
Dim intTo As Integer
Dim intPos As Integer
Dim intPtr As Integer
Dim intScore As Integer
Dim intTotScore As Integer
Dim intStartPos As Integer
Dim strWork As String

'-------------------------------------------------------
'-- If strings havent been normalised, normalise them --
'-------------------------------------------------------
If Normalised = False Then
    String1 = LCase$(Application.Trim(String1))
    String2 = LCase$(Application.Trim(String2))
End If

'----------------------------------------------
'-- Give 100% match if strings exactly equal --
'----------------------------------------------
If String1 = String2 Then
    FuzzyPercent = 1
    Exit Function
End If

intLen1 = Len(String1)
intLen2 = Len(String2)

'----------------------------------------
'-- Give 0% match if string length< 2 --
'----------------------------------------
If intLen1< 2 Then
    FuzzyPercent = 0
    Exit Function
End If

intTotScore = 0                   'initialise total possible score
intScore = 0                      'initialise current score

'--------------------------------------------------------
'-- If Algorithm = 1 or 3, Search for single characters --
'--------------------------------------------------------
If (Algorithm And 1)<> 0 Then
    FuzzyAlg1 String1, String2, intScore, intTotScore
    If intLen1< intLen2 Then FuzzyAlg1 String2, String1, intScore, intTotScore
End If

'-----------------------------------------------------------
'-- If Algorithm = 2 or 3, Search for pairs, triplets etc. --
'-----------------------------------------------------------
If (Algorithm And 2)<> 0 Then
    FuzzyAlg2 String1, String2, intScore, intTotScore
    If intLen1< intLen2 Then FuzzyAlg2 String2, String1, intScore, intTotScore
End If

FuzzyPercent = intScore / intTotScore

End Function
Private Sub FuzzyAlg1(ByVal String1 As String, _
                      ByVal String2 As String, _
                      ByRef Score As Integer, _
                      ByRef TotScore As Integer)
Dim intLen1 As Integer, intPos As Integer, intPtr As Integer, intStartPos As Integer

intLen1 = Len(String1)
TotScore = TotScore + intLen1              'update total possible score
intPos = 0
For intPtr = 1 To intLen1
    intStartPos = intPos + 1
    intPos = InStr(intStartPos, String2, Mid$(String1, intPtr, 1))
    If intPos > 0 Then
        If intPos > intStartPos + 3 Then     'No match if char is > 3 bytes away
            intPos = intStartPos
        Else
            Score = Score + 1          'Update current score
        End If
    Else
        intPos = intStartPos
    End If
Next intPtr
End Sub
Private Sub FuzzyAlg2(ByVal String1 As String, _
                        ByVal String2 As String, _
                        ByRef Score As Integer, _
                        ByRef TotScore As Integer)
Dim intCurLen As Integer, intLen1 As Integer, intTo As Integer, intPtr As Integer, intPos As Integer
Dim strWork As String

intLen1 = Len(String1)
For intCurLen = 2 To intLen1
    strWork = String2                          'Get a copy of String2
    intTo = intLen1 - intCurLen + 1
    TotScore = TotScore + Int(intLen1 / intCurLen)  'Update total possible score
    For intPtr = 1 To intTo Step intCurLen
        intPos = InStr(strWork, Mid$(String1, intPtr, intCurLen))
        If intPos > 0 Then
            Mid$(strWork, intPos, intCurLen) = String$(intCurLen, &H0) 'corrupt found string
            Score = Score + 1     'Update current score
        End If
    Next intPtr
Next intCurLen

End Sub