Attribute VB_Name = "basCRC32File"
Option Explicit
Option Base 0

' basCRC32File: Calculates CRC-32 checksum for a file.
' Calls crc32 function in basCRC32.
' Version 1. Published 23 October 2006.
'************************* COPYRIGHT NOTICE*************************
' This code was originally written in Visual Basic by David Ireland
' and is copyright (c) 2006 D.I. Management Services Pty Limited,
' all rights reserved.

' You are free to use this code as part of your own applications
' provided you keep this copyright notice intact and acknowledge
' its authorship with the words:

'   "Contains security software by David Ireland of
'   DI Management Services Pty Ltd <www.di-mgt.com.au>."

' This code may only be used as part of an application. It may
' not be reproduced or distributed separately by any means without
' the express written permission of the author.

' David Ireland and DI Management Services Pty Limited make no
' representations concerning either the merchantability of this
' software or the suitability of this software for any particular
' purpose. It is provided "as is" without express or implied
' warranty of any kind.

' Please forward comments or bug reports to www.di-mgt.com.au.
' The latest version of this source code can be downloaded from
' www.di-mgt.com.au/crypto.html.
'****************** END OF COPYRIGHT NOTICE*************************

Public Function CRC32Sum(sFileName As String) As String
' Computes the CRC-32 checksum for a file
    Dim sContents As String
    Dim lCRC As Long
    Dim sPad As String
    
    sContents = ReadFileIntoString(sFileName)
    If Len(sContents) = 0 Then
        Exit Function
    End If
    
    lCRC = crc32(sContents)
    CRC32Sum = Hex(lCRC)
    
    ' Pad to exactly 8 hex digits
    If Len(CRC32Sum) <> 8 Then
        sPad = String(8 - Len(CRC32Sum), "0")
        CRC32Sum = sPad & CRC32Sum
    End If
    
End Function

Private Function ReadFileIntoString(sFilePath As String) As String
' Reads file (if it exists) into a string.
    Dim strIn As String
    Dim hFile As Integer
    
    ' Check if file exists
    If Len(Dir(sFilePath)) = 0 Then
        Exit Function
    End If
    hFile = FreeFile
    Open sFilePath For Binary Access Read As #hFile
    strIn = Input(LOF(hFile), #hFile)
    Close #hFile
    ReadFileIntoString = strIn
    
End Function