VB .NET Convert string to array of bytes without converting the characters

Question

I'm trying to split a string of 32 numerical characters into a 16 length Array of Byte and each value has to stay numerical

from "70033023311330000000004195081460" to array {&H_70, &H_03, &H_30, &H_23, ..}

I've tried multiple stuff but each time either it's the conversion that's wrong or I can't find the appropriate combination of functions to implement it.

'it splits but per 1 character only instead of two
str.Select(Function(n) Convert.ToByte(n, 10)).ToArray

'I also tried looping but then the leading zero disappears and the output is a string converted to HEX which is also not what I want.
Function ConvertStringToHexBinary(str As String) As Byte()
        Dim arr(15) As Byte
        Dim k = 0
        For i As Integer = 0 To str.Length - 1
            arr(k) = str(i) & str(i + 1)
            k += 1
            i += 1
        Next
        Return arr
    End Function

Anyone got any suggestion what to do?

Convert.ToByte(str(i) & str(i+1), 16). 16 is the important part. — Hans Passant
– Hans Passant, Commented Aug 6, 2020 at 10:29

Caius Jard · Accepted Answer · 2020-08-06 17:21:03Z

1

G3nt_M3caj's use of LINQ might be.. er.. appealing to the LINQ lovers but it's horrifically inefficient. LINQ is a hammer; not everything is a nail.

This one is about 3 times faster than the LINQ version:

Dim str As String = "70033023311330000000004195081460"
Dim byt(str.Length/2) as Byte
For i = 0 to str.Length - 1 Step 2
  byt(i/2) = Convert.ToByte(str.Substring(i, 2))
Next i

And this one, which does it all with math and doesn't do any new stringing at all is just under 3 times faster than the above (making it around 9 times faster than the LINQ version):

Dim str As String = "70033023311330000000004195081460"
Dim byt(str.Length / 2) As Byte
For i = 0 To str.Length - 1
    If i Mod 2 = 0 Then
        byt(i / 2) = (Convert.ToByte(str(i)) - &H30) * &HA
    Else
        byt(i / 2) += Convert.ToByte(str(i)) - &H30
    End If
Next i

Of the two, I prefer the stringy version because it's easier to read and work out what's going on - another advantage loops approaches often have over a LINQ approach

edited Aug 6, 2020 at 17:21

answered Aug 6, 2020 at 16:49

Caius Jard

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1 Comment

G3nt_M3caj Over a year ago

Caius Jard, let me give an advice, to you and other as you with ‘k’ appas. Doesn’t reference on your answers G3nt_M3caj as I doesn’t reference anyone in my answers to show my methods is better than others. If you have advices about LINQ, RegEx or whatever (and maybe we are agree in some points) is better you give that advice directly to OP not to me. That’s the correct modus operandi.

G3nt_M3caj · Accepted Answer · 2020-08-06 10:54:44Z

0

Do you need something like this?

 Dim str As String = "70033023311330000000004195081460"
 Dim mBytes() As Byte = str.
        Select(Function(x, n) New With {x, n}).
        GroupBy(Function(x) x.n \ 2, Function(x) x.x).
        Select(Function(y) Convert.ToByte(New String(y.ToArray()), 10)).ToArray

edited Aug 6, 2020 at 10:54

answered Aug 6, 2020 at 10:22

G3nt_M3caj

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2 Comments

iThomas Over a year ago

this is exactly what I needed thanks for your help! Although I made an error in my example it had to be Convert.ToByte(n, 16) and not 10 and now it works perfectly :)

G3nt_M3caj Over a year ago

I have simplified further. :)

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