Read file to string in VBA - vba

Question

I'm working on a sub that will use an HTTP post to upload a file to a server. I've already worked out all of the code to actually sent the post request, but I can't figure out how to get the file into the appropriate format. The server is expecting the file's bytes as a string, but no matter what approach I take to creating the string the values don't match up with what's expected.
Here is the code I currently have:
Sub Test()
Dim FileNum As Integer
Dim TestString As String
Dim TestBytes() As Byte
Dim TestByte As Variant
FileNum = FreeFile
Open ActiveDocument.Path & "\" & ActiveDocument.name For Binary Access Read As #FileNum 'Open document to write to string
ReDim TestBytes(LOF(FileNum) - 1)
Get FileNum, , TestBytes
Close FileNum
For Each TestByte In TestBytes
TestString = TestString & Hex(TestByte)
Next TestByte
Debug.Print TestString
End Sub
The output looks something like this (truncated, as the full string is obviously quite long):
504B3414060800021076DD8E8C9D130825B436F6E74656E745F54797065735D2E786D6C20...
The problem is, the example output I have says it should look like this:
UEsDBBQABgAIAAAAIQCuTjGvewEAAAIGAAATAAgCW0NvbnRlbnRfVHlwZXNdLnhtbCCiBAIooAACA...
I assumed the problem was that my test code is trying to encode the bytes as hex values, whereas the example is obviously not in hex, but when I just try to output the file's bytes directly as a string I get a lot of invalid characters. Here's the code:
Sub Test()
Dim FileNum As Integer
Dim TestString As String
Dim TestBytes() As Byte
Dim TestByte As Variant
FileNum = FreeFile
Open ActiveDocument.Path & "\" & ActiveDocument.name For Binary Access Read As #FileNum 'Open document to write to string
TestString = String$(LOF(FileNum), Chr(32)) 'Fill string with blank space to set string length
Get FileNum, , TestString 'Write binary data from file to string
Debug.Print TestString
End Sub
And here's the output:
PK ! vÝŽŒ p  ...
Is there something I'm missing as to how I can encode the bytes to get output that's encoded the same as the example output? When performing a similar operation in another language (e.g. Java using readFileToString), how is the string encoded?

Answer 1

Using Alex K.'s advice in the comments above, and the Base64 encoding function found here, I came to this solution:
Sub Test()
Dim FileNum As Integer
Dim TestString As String
Dim TestBytes() As Byte
Dim TestByte As Variant
FileNum = FreeFile
Open ActiveDocument.Path & "\" & ActiveDocument.name For Binary Access Read As #FileNum 'Open document to write to string
TestString = String$(LOF(FileNum), Chr(32)) 'Fill string with blank space to set string length
Get FileNum, , TestString 'Write binary data from file to string
TestString = EncodeBase64(TestString)
Debug.Print TestString
End Sub
Function EncodeBase64(text As String) As String
Dim arrData() As Byte
arrData = StrConv(text, vbFromUnicode)
Dim objXML As MSXML2.DOMDocument
Dim objNode As MSXML2.IXMLDOMElement
Set objXML = New MSXML2.DOMDocument
Set objNode = objXML.createElement("b64")
objNode.DataType = "bin.base64"
objNode.nodeTypedValue = arrData
EncodeBase64 = objNode.text
Set objNode = Nothing
Set objXML = Nothing
End Function
Which outputs the correct string:
UEsDBBQABgAIAAAAIQCuTjGvewEAAAIGAAATAAgCW0NvbnRlbnRfVHlwZXNdLnhtbCCiBAIooAACA...