Base64 Encode String in VBScript

base64encodingvbscriptwsh

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?

Best Answer

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