Base64 Encode String in VBScript

Question

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 1

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

Solution 2

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

Solution 3

It's possible to encode base64 in pure vbscript without ADODB.Stream and MSXml2.DOMDocument.

for example:

Function btoa(sourceStr)
    Dim i, j, n, carr, rarr(), a, b, c
    carr = Array("A", "B", "C", "D", "E", "F", "G", "H", _
            "I", "J", "K", "L", "M", "N", "O" ,"P", _
            "Q", "R", "S", "T", "U", "V", "W", "X", _
            "Y", "Z", "a", "b", "c", "d", "e", "f", _
            "g", "h", "i", "j", "k", "l", "m", "n", _
            "o", "p", "q", "r", "s", "t", "u", "v", _
            "w", "x", "y", "z", "0", "1", "2", "3", _
            "4", "5", "6", "7", "8", "9", "+", "/")
    n = Len(sourceStr)-1
    ReDim rarr(n\3)
    For i=0 To n Step 3
        a = AscW(Mid(sourceStr,i+1,1))
        If i < n Then
            b = AscW(Mid(sourceStr,i+2,1))
        Else
            b = 0
        End If
        If i < n-1 Then
            c = AscW(Mid(sourceStr,i+3,1))
        Else
            c = 0
        End If
        rarr(i\3) = carr(a\4) & carr((a And 3) * 16 + b\16) & carr((b And 15) * 4 + c\64) & carr(c And 63)
    Next
    i = UBound(rarr)
    If n Mod 3 = 0 Then
        rarr(i) = Left(rarr(i),2) & "=="
    ElseIf n Mod 3 = 1 Then
        rarr(i) = Left(rarr(i),3) & "="
    End If
    btoa = Join(rarr,"")
End Function


Function char_to_utf8(sChar)
    Dim c, b1, b2, b3
    c = AscW(sChar)
    If c < 0 Then
        c = c + &H10000
    End If
    If c < &H80 Then
        char_to_utf8 = sChar
    ElseIf c < &H800 Then
        b1 = c Mod 64
        b2 = (c - b1) / 64
        char_to_utf8 = ChrW(&HC0 + b2) & ChrW(&H80 + b1)
    ElseIf c < &H10000 Then
        b1 = c Mod 64
        b2 = ((c - b1) / 64) Mod 64
        b3 = (c - b1 - (64 * b2)) / 4096
        char_to_utf8 = ChrW(&HE0 + b3) & ChrW(&H80 + b2) & ChrW(&H80 + b1)
    Else
    End If
End Function

Function str_to_utf8(sSource)
    Dim i, n, rarr()
    n = Len(sSource)
    ReDim rarr(n - 1)
    For i=0 To n-1
        rarr(i) = char_to_utf8(Mid(sSource,i+1,1))
    Next
    str_to_utf8 = Join(rarr,"")
End Function

Function str_to_base64(sSource)
    str_to_base64 = btoa(str_to_utf8(sSource))
End Function

'test

msgbox btoa("Hello")   'SGVsbG8=
msgbox btoa("Hell")    'SGVsbA==

msgbox str_to_base64("中文한국어")  '5Lit5paH7ZWc6rWt7Ja0

If there are wide characters (AscW(c) > 255 or < 0) in your string, you can convert it to utf-8 before call btoa.

utf-8 convertion also can be written in pure vbscript.

Solution 4

So I have some other full example of encoder and decoder:

Encoder:

' This script reads jpg picture named SuperPicture.jpg, converts it to base64
' code using encoding abilities of MSXml2.DOMDocument object and saves
' the resulting data to encoded.txt file

Option Explicit

Const fsDoOverwrite     = true  ' Overwrite file with base64 code
Const fsAsASCII         = false ' Create base64 code file as ASCII file
Const adTypeBinary      = 1     ' Binary file is encoded

' Variables for writing base64 code to file
Dim objFSO
Dim objFileOut

' Variables for encoding
Dim objXML
Dim objDocElem

' Variable for reading binary picture
Dim objStream

' Open data stream from picture
Set objStream = CreateObject("ADODB.Stream")
objStream.Type = adTypeBinary
objStream.Open()
objStream.LoadFromFile("SuperPicture.jpg")

' Create XML Document object and root node
' that will contain the data
Set objXML = CreateObject("MSXml2.DOMDocument")
Set objDocElem = objXML.createElement("Base64Data")
objDocElem.dataType = "bin.base64"

' Set binary value
objDocElem.nodeTypedValue = objStream.Read()

' Open data stream to base64 code file
Set objFSO = CreateObject("Scripting.FileSystemObject")
Set objFileOut = objFSO.CreateTextFile("encoded.txt", fsDoOverwrite, fsAsASCII)

' Get base64 value and write to file
objFileOut.Write objDocElem.text
objFileOut.Close()

' Clean all
Set objFSO = Nothing
Set objFileOut = Nothing
Set objXML = Nothing
Set objDocElem = Nothing
Set objStream = Nothing

Decoder:

' This script reads base64 encoded picture from file named encoded.txt,
' converts it in to back to binary reprisentation using encoding abilities
' of MSXml2.DOMDocument object and saves data to SuperPicture.jpg file

Option Explicit

Const foForReading          = 1 ' Open base 64 code file for reading
Const foAsASCII             = 0 ' Open base 64 code file as ASCII file
Const adSaveCreateOverWrite = 2 ' Mode for ADODB.Stream
Const adTypeBinary          = 1 ' Binary file is encoded

' Variables for reading base64 code from file
Dim objFSO
Dim objFileIn
Dim objStreamIn

' Variables for decoding
Dim objXML
Dim objDocElem

' Variable for write binary picture
Dim objStream

' Open data stream from base64 code filr
Set objFSO = CreateObject("Scripting.FileSystemObject")
Set objFileIn   = objFSO.GetFile("encoded.txt")
Set objStreamIn = objFileIn.OpenAsTextStream(foForReading, foAsASCII)

' Create XML Document object and root node
' that will contain the data
Set objXML = CreateObject("MSXml2.DOMDocument")
Set objDocElem = objXML.createElement("Base64Data")
objDocElem.DataType = "bin.base64"

' Set text value
objDocElem.text = objStreamIn.ReadAll()

' Open data stream to picture file
Set objStream = CreateObject("ADODB.Stream")
objStream.Type = adTypeBinary
objStream.Open()

' Get binary value and write to file
objStream.Write objDocElem.NodeTypedValue
objStream.SaveToFile "SuperPicture.jpg", adSaveCreateOverWrite

' Clean all
Set objFSO = Nothing
Set objFileIn = Nothing
Set objStreamIn = Nothing
Set objXML = Nothing
Set objDocElem = Nothing
Set objStream = Nothing

Solution 5

This is a decode example that does not use the ADODB object.

option explicit
dim inobj,outobj,infile,myname,state,rec,outfile,content,table(256),bits,c,x,outword
state = 0
const r64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
myname = wscript.scriptfullname
set inobj = createobject("Scripting.FileSystemObject")
set outobj = createobject("Scripting.FileSystemObject")
set infile = inobj.opentextfile(myname,1)
set outfile = outobj.createtextfile("q.png")
for x = 1 to 256 step 1
    table(x) = -1
next
for x = 1 to 64 step 1
    table(1+asc(mid(r64,x,1))) = x - 1
next
bits = 0
do until(infile.atendofstream)
    dim size
    rec = infile.readline
    if (state = 1) then 
        content = mid(rec,2)
        size = len(content)
        for x = 1 to size step 1
            c = table(1+asc(mid(content,x,1)))
            if (c <> -1) then
                if (bits = 0) then
                    outword = c*4
                    bits = 6
                elseif (bits = 2) then
                    outword = c+outword
                    outfile.write(chr(clng("&H" & hex(outword mod 256))))
                    bits = 0
                elseif (bits = 4) then
                    outword = outword + int(c/4)
                    outfile.write(chr(clng("&H" & hex(outword mod 256))))
                    outword = c*64
                    bits = 2
                else
                    outword = outword + int(c/16)
                    outfile.write(chr(clng("&H" & hex(outword mod 256))))
                    outword = c*16
                    bits = 4
                end if
            end if
        next
    end if
    if (rec = "'PAYLOAD") then
        state = 1
    end if
loop
infile.close
outfile.close
wscript.echo "q.png created"
wscript.quit
'PAYLOAD
'iVBORw0KGgoAAAANSUhEUgAAAD4AAAA+CAIAAAD8oz8TAAABoklEQVRo3u2awQrDMAxDl7H/
'/+Xu0EsgSDw7hRF7vWywpO0UW5acjOu6Xmde79ex1+f+GGPACfcqzePXdVvvts7iv6rx56Ou
'8FNYkgyZx9xzZ3TVHfg7VEHdR+o6ZsWV54O/yDvUQj2KzYyH5wof5f14fR97xdPrmjy1ArVQ
'55yteMYzEqma5B2qoM5VBK+OuXUrHutjJ8c59l4z/vV6Vv15PbOjiFRunB/rOcYgIz1jEPek
'nnh+rBPsiYbOaRu/DipzKrqkqNOJdgEIF3mNVLGa7jM9YSReg+t6U/UvFTYqmn13gGeUr9C1
'ul85rlCVgVTHnGeo2xGIdnT3PRR3vbUYhjAJqXxRHxTtslfsrxOe8aziWdlnAukRVPGmuX9P
'KnG0y9Wjv+71IPf8JEMIZxeP9ZHDkvO0z6XoXmlF1APTMIpR38R5qd8ZAa7gc76JaMl+ZwR4
'N0vdn6hRf89+ZwRIXZy/e473bks9sd9uterERvmbKP4end6cVlFRHt2n9mxTN9b3PTzfIco5
'4Ip9mGd1ud8bUriS3Oh6RuC318GofwHqKhl/Nn0DHQAAAABJRU5ErkJggg==

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