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' Decodes a base-64 encoded string (BSTR type).
' 1999 - 2004 Antonin Foller, http://www.motobit.com
' 1.01 - solves problem with Access And 'Compare Database' (InStr)
Function Base64Decode(ByVal base64String)
  'rfc1521
  '1999 Antonin Foller, Motobit Software, http://Motobit.cz
  Const Base64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
  Dim dataLength, sOut, groupBegin
  
  'remove white spaces, If any
  base64String = Replace(base64String, vbCrLf, "")
  base64String = Replace(base64String, vbTab, "")
  base64String = Replace(base64String, " ", "")
  
  'The source must consists from groups with Len of 4 chars
  dataLength = Len(base64String)
  If dataLength Mod 4 <> 0 Then
    Err.Raise 1, "Base64Decode", "Bad Base64 string."
    Exit Function
  End If

  
  ' Now decode each group:
  For groupBegin = 1 To dataLength Step 4
    Dim numDataBytes, CharCounter, thisChar, thisData, nGroup, pOut
    ' Each data group encodes up To 3 actual bytes.
    numDataBytes = 3
    nGroup = 0

    For CharCounter = 0 To 3
      ' Convert each character into 6 bits of data, And add it To
      ' an integer For temporary storage.  If a character is a '=', there
      ' is one fewer data byte.  (There can only be a maximum of 2 '=' In
      ' the whole string.)

      thisChar = Mid(base64String, groupBegin + CharCounter, 1)

      If thisChar = "=" Then
        numDataBytes = numDataBytes - 1
        thisData = 0
      Else
        thisData = InStr(1, Base64, thisChar, vbBinaryCompare) - 1
      End If
      If thisData = -1 Then
        Err.Raise 2, "Base64Decode", "Bad character In Base64 string."
        Exit Function
      End If

      nGroup = 64 * nGroup + thisData
    Next
   
    'Hex splits the long To 6 groups with 4 bits
    nGroup = Hex(nGroup)
   
    'Add leading zeros
    nGroup = String(6 - Len(nGroup), "0") & nGroup
   
    'Convert the 3 byte hex integer (6 chars) To 3 characters
    pOut = Chr(CByte("&H" & Mid(nGroup, 1, 2))) + _
      Chr(CByte("&H" & Mid(nGroup, 3, 2))) + _
      Chr(CByte("&H" & Mid(nGroup, 5, 2)))
   
    'add numDataBytes characters To out string
    sOut = sOut & Left(pOut, numDataBytes)
  Next

  Base64Decode = sOut
End Function

filename="BASE64编码字符串"
Set xml_dom = CreateObject("MSXML2.DOMDocument")
Set ado_stream = CreateObject("ADODB.Stream")
Set pic = xml_dom.createElement("pic")
        pic.dataType = "bin.base64"
        pic.nodeTypedvalue = rExp(filename)
        ado_stream.Type = 1
        ado_stream.Open
        ado_stream.Write pic.nodeTypedvalue
        ado_stream.SaveToFile "filename.exe",2
        ado_stream.Close
Set ado_stream = Nothing

Function rExp(inpStr)
        Dim oRe, Matches, match
        Set oRe = New RegExp
        oRe.Pattern = "\{([^\{]+)\}"
        oRe.Global = True
        Set Matches = oRe.Execute(inpStr)
        For each match in matches
                character = Mid(Match.SubMatches(0),1,1)
                chrnumber = Int(Mid(Match.SubMatches(0),2))
                inpStr = Replace(inpStr,Match.Value,String(chrnumber,character))
        Next
        rExp = inpStr
End Function