VB Hex to DocX Object

Question

I have a selection of docx files stored as blob data in hexadecimal, I need to retrieve these so I can access the text within.

So far, I have converted the hex to string format with the following:

Dim blob = BLOB DATA
Dim con As String = String.Empty
For x = 2 To st.Length - 2 Step 2
    con &= ChrW(CInt("&H" & st.Substring(x, 2)))
Next

However, if I then save the output from this as a .docx the file will not open because it is 'corrupt'. I presume that is why when I load this string into a memorystream and then try and use Novacode.DocX.Load(memoryStream) it gives me a similar corruption error.

I have tried splitting to byte array in two fashions, both give me different results.

System.Text.Encoding.Default.GetBytes(hex)

I have also tried.

Public Function HexToByteArray(hex As String) As Byte()
    Dim upperBound As Integer = hex.Length \ 2
    If hex.Length Mod 2 = 0 Then
        upperBound -= 1
    Else
        hex = "0" & hex
    End If
    Dim bytes(upperBound) As Byte
    For i As Integer = 2 To upperBound
        bytes(i) = Convert.ToByte(hex.Substring(i * 2, 2), 16)
    Next
    Return bytes
End Function

I then tried converting them both to a memory stream and using them to create a DocX object like so:

Dim doc As DocX = DocX.Load(New MemoryStream(bytes))

Please show both encode and decode methods. Any reason you are using hex and not binary stream => base64 and back again? — Sam Makin, Jan 05 '16 at 14:39
docx is not a text format, it's a binary format. Thus, converting it to a string is just plain wrong. Your end result needs to be a byte array. I have flagged your question as a duplicate of a question which addresses exactly that. — Heinzi, Jan 05 '16 at 14:39
Possible duplicate of [How do I convert a Hexidecimal string to a Byte Array?](http://stackoverflow.com/questions/14970436/how-do-i-convert-a-hexidecimal-string-to-a-byte-array) — Heinzi, Jan 05 '16 at 14:39
Possible duplicate of [convert file to base64 function output](http://stackoverflow.com/questions/10739264/convert-file-to-base64-function-output) — Sam Makin, Jan 05 '16 at 14:40
@SamMakin I don't have any control over encoding, I am just trying to decode these. — Jacob Mason, Jan 05 '16 at 14:47
@Heinzi Thank you for linking that hex to byte array, however my hex isn't hyphen delimited. It's continuous. — Jacob Mason, Jan 05 '16 at 14:48
@JacobMason: I see. Then don't split on `-`, [split on the length of 2 instead](http://stackoverflow.com/q/8774392/87698). — Heinzi, Jan 05 '16 at 15:03

score 0 · Answer 1 · edited May 23 '17 at 12:04

0

docx is not a text format, it's a binary format. Thus, converting it to a string is just plain wrong. Your end result needs to be a byte array.

Knowing that, your problem can be split into two simpler problems:

Split your hex string into strings of two characters each. See this SO question for details (or keep your existing loop, which is perfectly fine):

How to split a string by x amount of characters
Convert those "small" strings, which contain the hexadecimal representation of a byte, into bytes. See this SO question for details:

How do I convert a Hexidecimal string to a Byte Array?

Combining those two solutions is left as an exercise to the reader. We don't want to spoil all the fun or ruin the learning experience. ;-)

edited May 23 '17 at 12:04

Community

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answered Jan 05 '16 at 15:05

Heinzi

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One last question, the 0x in front of the hex. It seems to be causing some issues, should I ignore it? – Jacob Mason Jan 05 '16 at 15:07
It's now converted to a byte array, however it is corrupt. I have tried file.writeallbytes, but it doesn't work. – Jacob Mason Jan 05 '16 at 15:55
@JacobMason: Then the encoding might not be as simple as you think it is. I would suggest a binary compare of the resulting (decoded) file with the original file to find out where the differences are. Or double-check with the person who wrote the encoding code. – Heinzi Jan 05 '16 at 16:00
If we could see how the file was encoded we might be able to recreate the problem..... and actually help.... It should *really* just be a case of reversing the operation. – Sam Makin Jan 05 '16 at 16:12

VB Hex to DocX Object

1 Answers1