Base64 Encode String in VBScript

This answer improves on Patrick Cuff's great answer in that it adds support for UTF-8 and UTF-16 LE encodings ("Unicode"). (Additionally, the code is streamlined).

Examples:

' Base64-encode: from UTF-8-encoded bytes.
Base64Encode("Motörhead", False) ' "TW90w7ZyaGVhZA=="

' Base64-encode: from UTF-16 LE-encoded bytes.
Base64Encode("Motörhead", True) ' "TQBvAHQA9gByAGgAZQBhAGQA"


' Base64-decode: back to a VBScript string via UTF-8.
Base64Decode("TW90w7ZyaGVhZA==", False) ' "Motörhead"

' Base64-decode: back to a VBScript string via UTF-16 LE.
Base64Decode("TQBvAHQA9gByAGgAZQBhAGQA", True) ' "Motörhead"

Important:

• If you want to be able to represent all Unicode characters (e.g., €) as literals in your .vbs file, save it as UTF-16LE ("Unicode").

• If your script is run as a console application, via cscript.exe, not all Unicode characters may render correctly in direct-to-display output (due to font limitations, but you can copy & paste them) and, more importantly, if you try to capture or redirect the output, any non-ASCII-range characters that aren't part of the console's OEM code page are effectively lost (replaced with literal ? characters).

---

' Base64-encodes the specified string.
' Parameter fAsUtf16LE determines how the input text is encoded at the
' byte level before Base64 encoding is applied.
' * Pass False to use UTF-8 encoding.
' * Pass True to use UTF-16 LE encoding.
Function Base64Encode(ByVal sText, ByVal fAsUtf16LE)

    ' Use an aux. XML document with a Base64-encoded element.
    ' Assigning the byte stream (array) returned by StrToBytes() to .NodeTypedValue
    ' automatically performs Base64-encoding, whose result can then be accessed
    ' as the element's text.
    With CreateObject("Msxml2.DOMDocument").CreateElement("aux")
        .DataType = "bin.base64"
        if fAsUtf16LE then
            .NodeTypedValue = StrToBytes(sText, "utf-16le", 2)
        else
            .NodeTypedValue = StrToBytes(sText, "utf-8", 3)
        end if
        Base64Encode = .Text
    End With

End Function


' Decodes the specified Base64-encoded string. 
' If the decoded string's original encoding was:
' * UTF-8, pass False for fIsUtf16LE.
' * UTF-16 LE, pass True for fIsUtf16LE.
Function Base64Decode(ByVal sBase64EncodedText, ByVal fIsUtf16LE)

    Dim sTextEncoding
    if fIsUtf16LE Then sTextEncoding = "utf-16le" Else sTextEncoding = "utf-8"

    ' Use an aux. XML document with a Base64-encoded element.
    ' Assigning the encoded text to .Text makes the decoded byte array
    ' available via .nodeTypedValue, which we can pass to BytesToStr()
    With CreateObject("Msxml2.DOMDocument").CreateElement("aux")
        .DataType = "bin.base64"
        .Text = sBase64EncodedText
        Base64Decode = BytesToStr(.NodeTypedValue, sTextEncoding)
    End With

End Function


' Returns a binary representation (byte array) of the specified string in
' the specified text encoding, such as "utf-8" or "utf-16le".
' Pass the number of bytes that the encoding's BOM uses as iBomByteCount;
' pass 0 to include the BOM in the output.
function StrToBytes(ByVal sText, ByVal sTextEncoding, ByVal iBomByteCount)

    ' Create a text string with the specified encoding and then
    ' get its binary (byte array) representation.
    With CreateObject("ADODB.Stream")
        ' Create a stream with the specified text encoding...
        .Type = 2  ' adTypeText
        .Charset = sTextEncoding
        .Open
        .WriteText sText
        ' ... and convert it to a binary stream to get a byte-array 
        ' representation.
        .Position = 0 
        .Type = 1  ' adTypeBinary
        .Position = iBomByteCount ' skip the BOM
        StrToBytes = .Read
        .Close
    End With 

end function

' Returns a string that corresponds to the specified byte array, interpreted
' with the specified text encoding, such as "utf-8" or "utf-16le".
function BytesToStr(ByVal byteArray, ByVal sTextEncoding)

    If LCase(sTextEncoding) = "utf-16le" then
        ' UTF-16 LE happens to be VBScript's internal encoding, so we can
        ' take a shortcut and use CStr() to directly convert the byte array
        ' to a string.
        BytesToStr = CStr(byteArray)
    Else ' Convert the specified text encoding to a VBScript string.
        ' Create a binary stream and copy the input byte array to it.
        With CreateObject("ADODB.Stream")
            .Type = 1 ' adTypeBinary
            .Open
            .Write byteArray
            ' Now change the type to text, set the encoding, and output the 
            ' result as text.
            .Position = 0
            .Type = 2 ' adTypeText
            .CharSet = sTextEncoding
            BytesToStr = .ReadText
            .Close
        End With
    End If

end function

I was originally using some VBScript code from Antonin Foller: Base64 Encode VBS Function and Base64 Decode VBS Function.

Searching Antonin's site, I saw he had some code for quoted printable encoding, using the CDO.Message object, so I tried that.

Finally, I ported the code mentioned in Mark's answer to VBScript (also used some code from this SO question), and used the Stream___StringToBinary and Stream_BinaryToString functions from Antonin's site to get functions that used MSXML encoding.

I ran a quick test to measure the encoding time for a 1,500 character message (the average message size I need to send to my web service) across all four methods:

• Native VBScript (VBScript)
• Quoted Printable, using CDO.Message (QP)
• Quoted Printable Binary, using CDO.Message (QP Binary)
• MSXML/ADODB.Stream (MSXML)

Here are the results:

Iterations   : 10,000
Message Size :  1,500

+-------------+-----------+
+ Method      | Time (ms) + 
+-------------+-----------+
| VBScript    |   301,391 |
+-------------+-----------+
| QP          |    12,922 |
+-------------+-----------+
| QP (Binary) |    13,953 |
+-------------+-----------+
| MSXML       |     3,312 |
+-------------+-----------+

I also monitored the memory utilization (Mem Usage for the cscript.exe process in the Windows Task Manager) while the test was running. I don't have any raw numbers, but the memory utilization for both the quoted printable and MSXML solutions were below the VBScript solution (7,000K for the former, around 16,000K for VBScript).

I decided to go with the MSXML solution for my driver. For those interested, here's the code I'm using:

base64.vbs
Function Base64Encode(sText)
    Dim oXML, oNode

    Set oXML = CreateObject("Msxml2.DOMDocument.3.0")
    Set oNode = oXML.CreateElement("base64")
    oNode.dataType = "bin.base64"
    oNode.nodeTypedValue =Stream_StringToBinary(sText)
    Base64Encode = oNode.text
    Set oNode = Nothing
    Set oXML = Nothing
End Function

Function Base64Decode(ByVal vCode)
    Dim oXML, oNode

    Set oXML = CreateObject("Msxml2.DOMDocument.3.0")
    Set oNode = oXML.CreateElement("base64")
    oNode.dataType = "bin.base64"
    oNode.text = vCode
    Base64Decode = Stream_BinaryToString(oNode.nodeTypedValue)
    Set oNode = Nothing
    Set oXML = Nothing
End Function

'Stream_StringToBinary Function
'2003 Antonin Foller, http://www.motobit.com
'Text - string parameter To convert To binary data
Function Stream_StringToBinary(Text)
  Const adTypeText = 2
  Const adTypeBinary = 1

  'Create Stream object
  Dim BinaryStream 'As New Stream
  Set BinaryStream = CreateObject("ADODB.Stream")

  'Specify stream type - we want To save text/string data.
  BinaryStream.Type = adTypeText

  'Specify charset For the source text (unicode) data.
  BinaryStream.CharSet = "us-ascii"

  'Open the stream And write text/string data To the object
  BinaryStream.Open
  BinaryStream.WriteText Text

  'Change stream type To binary
  BinaryStream.Position = 0
  BinaryStream.Type = adTypeBinary

  'Ignore first two bytes - sign of
  BinaryStream.Position = 0

  'Open the stream And get binary data from the object
  Stream_StringToBinary = BinaryStream.Read

  Set BinaryStream = Nothing
End Function

'Stream_BinaryToString Function
'2003 Antonin Foller, http://www.motobit.com
'Binary - VT_UI1 | VT_ARRAY data To convert To a string 
Function Stream_BinaryToString(Binary)
  Const adTypeText = 2
  Const adTypeBinary = 1

  'Create Stream object
  Dim BinaryStream 'As New Stream
  Set BinaryStream = CreateObject("ADODB.Stream")

  'Specify stream type - we want To save binary data.
  BinaryStream.Type = adTypeBinary

  'Open the stream And write binary data To the object
  BinaryStream.Open
  BinaryStream.Write Binary

  'Change stream type To text/string
  BinaryStream.Position = 0
  BinaryStream.Type = adTypeText

  'Specify charset For the output text (unicode) data.
  BinaryStream.CharSet = "us-ascii"

  'Open the stream And get text/string data from the object
  Stream_BinaryToString = BinaryStream.ReadText
  Set BinaryStream = Nothing
End Function