VB6 Code - Class Untuk Mengetahui Crc32 Dari Sebuah File

Di bawah ini merupakan class VB6 untuk mengetahui CRC32 dari sebuah file. Untuk keperluan ini copy dan pastekan kode di bawah ini ke dalam class, kemudian ganti nama kelasnya menjadi clsCRC.

Option Explicit

Private crcTable(0 To 255) As Long 'crc32

Private Function CRC32(ByRef bArrayIn() As Byte, ByVal lLen As Long, Optional ByVal lcrc As Long = 0) As Long
  
  Dim lCurPos As Long
  Dim lTemp As Long
  
  If lLen = 0 Then Exit Function 'In case of empty file
  lTemp = lcrc Xor &HFFFFFFFF 'lcrc is for current value from partial check on the partial array
  
  For lCurPos = 0 To lLen
    lTemp = (((lTemp And &HFFFFFF00) \ &H100) And &HFFFFFF) Xor (crcTable((lTemp And 255) Xor bArrayIn(lCurPos)))
  Next lCurPos
  
  CRC32 = lTemp Xor &HFFFFFFFF

End Function

Private Function BuildTable() As Boolean

  Dim I As Long, x As Long, crc As Long
  Const Limit = &HEDB88320 'usally its shown backward, cant  remember what it was.

  For I = 0 To 255
    crc = I
    For x = 0 To 7
      If crc And 1 Then
        crc = (((crc And &HFFFFFFFE) \ 2) And &H7FFFFFFF) Xor Limit
      Else
        crc = ((crc And &HFFFFFFFE) \ 2) And &H7FFFFFFF
      End If
    Next x
    crcTable(I) = crc
  Next I

End Function

Private Sub Class_Initialize()
  BuildTable
End Sub

Public Function CekCRC32(FileName As String) As String

    Dim lngCrc As Long
    Dim sCrc As Long
    
    On Error GoTo ErrHandler
    
    Open FileName For Binary Access Read As #1
        ReDim tmp(LOF(1)) As Byte
        Get #1, , tmp()
    Close #1

    lngCrc = UBound(tmp)
    lngCrc = CRC32(tmp, lngCrc)
    CekCRC32 = Hex(lngCrc)
    
    Exit Function

ErrHandler:

    MsgBox Err.Description, vbCritical, "Error"

 End Function

Contoh penggunaan Class CRC32

Option  Explicit

Private Sub Form_Load()
    Dim crc As New clsCRC
    MsgBox crc.CekCRC32("C:\boot.ini")
End Sub