Base64 Encode String in VBScript

I have a web service load driver that's a Windows Script File (WSF), that includes some VBScript and JavaScript files. My web service requires that the incoming message is base64 encoded. I currently have a VBScript function that does this, but it's very inefficient (memory intensive, mostly due to VBScripts awful string concatenation)

[Aside; Yes, I've seen Jeff's latest blog post. The concatenation is happening in a loop across messages that are 1,000's to 10,000's bytes in size.]

I've tried using some custom string concatenation routines; one using an array and one using ADODB.Stream. These help, a little, but I think it would help more if I had some other way of encoding the message rather than via my own VBS function.

Is there some other way of encoding my message, preferebly using native Windows methods?

Solution

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