Converting a base64 string to a Hex string

  • Thread starter Thread starter Jeremy Kitchen
  • Start date Start date
J

Jeremy Kitchen

Are there any library functions that can help me to do this? If
necessary I can convert the string to a byte array. I don't want to
have to write my own Hex conversion if it isn't necessary.

Thanks for any help
Jeremy Kitchen
 
Are there any library functions that can help me to do this? If
necessary I can convert the string to a byte array. I don't want to
have to write my own Hex conversion if it isn't necessary.

Thanks for any help
Jeremy Kitchen
Click to expand...

Forgive me if I'm way off, but do you want to take a string such as
"1234ABCDEFG" and end up with "3132333441424344"?

You can use the ASCII object in System.Text.AsciiEncoding to get the
bytes of the string, then convert each byte to a Hex string with the
ToString overload that accepts a format.

Dim sBase As String = "1234ABCD"
Dim bBase() As Byte
Dim sHex As String = String.Empty
Dim sHexByte As String

bBase = System.Text.ASCIIEncoding.ASCII.GetBytes(sBase)

For i As Integer = 0 To bBase.Length - 1
sHexByte = bBase(i).ToString("x")
If sHexByte.Length = 0 Then
sHexByte = "0" & sHexByte
End If
sHex &= sHexByte
Next

Console.WriteLine(sHex)
Console.ReadLine()
 
jayeldee said:
Dim sBase As String = "1234ABCD"
Dim bBase() As Byte
Dim sHex As String = String.Empty
Dim sHexByte As String

bBase = System.Text.ASCIIEncoding.ASCII.GetBytes(sBase)

For i As Integer = 0 To bBase.Length - 1
sHexByte = bBase(i).ToString("x")
If sHexByte.Length = 0 Then
sHexByte = "0" & sHexByte
End If
sHex &= sHexByte
Next

Console.WriteLine(sHex)
Console.ReadLine()
Click to expand...

Just a few suggestions, hope you don't mind...

You don't need to keep track of the byte index (the For i As
Integer... loop). Instead you may want to use a For Each loop -- just
a question of preference, though, but the loop may become more
"readable":

For Each B As Byte In Sytem.Text.Encoding. _
ASCII.GetBytes(Base64Text)
...
Next

Also, you'll be glad to know that the ToString("x") method of the
integer data types (Byte, Integer, Long, UInteger, etc) allows a
"length" parameter, so you don't have to manually padd the returned
string:

For Each B As Byte In Sytem.Text.Encoding. _
ASCII.GetBytes(Base64Text)
'HexChar will be zero-padded up to two digits
Dim HexChar As String = B.ToString("x2")
...
Next

Finally, just remember that base64 encoded strings are *usually* used
to encode a large amount of data. Concatenating strings in a loop
using the "&" operator is not a real problem if the number of
iterations is small -- but, how many is "small"? Don't ask me.
Personally, I'll resort to a StringBuilder whenever I see a loop. Of
course, there's no rule in stone, here. But since we may consider that
the typical content of a base64 encoded string can be quite large, the
use of a StringBuilder may be advised:

Dim S As New System.Text.StringBuilder
For Each B As Byte In Sytem.Text.Encoding. _
ASCII.GetBytes(Base64Text)
S.Append(B.ToString("x2"))
Next
HexText = S.ToString


Just for the fun of it (and if the OP doesn't mind writing VB code
that threads on the limits of readability), we could also have:

Public Function CharToHex(Value As Char) As String
Return Convert.ToByte(Value).ToString("x2")
End Function

'...
HexText = String.Join(Nothing, _
System.Array.ConvertAll(Of Char, String)( _
Base64Text.ToCharArray, AddressOf CharToHex))


:-))

Regards,

Branco.
 
jayeldee wrote:
Just a few suggestions, hope you don't mind...
Click to expand...

Awesome suggestions. I just made it quick, dirty, and readable. I
forgot about the padding of the string and probably should've used a
StringBuilder (I almost always do in any examples I toss together.)
 
Jeremy said:
Are there any library functions that can help me to do this? If
necessary I can convert the string to a byte array. I don't want to
have to write my own Hex conversion if it isn't necessary.
Click to expand...

Is this what you want?

\\\
Dim ret As String
'b64 is a string containing base-64 encoded data
Dim b64 As String = "VXNlcm5hbWU6"
'Decode the base64 data to a byte array
Dim b64bytes() As Byte = System.Convert.FromBase64String(b64)

'Loop through each byte, adding the hex value for each byte to our
return string
For Each b As Byte In b64bytes
ret &= Hex(b).PadLeft(2, "0"c)
Next

'Display the finished string
MsgBox(ret)
///
 
Is this what you want?

\\\
Dim ret As String
'b64 is a string containing base-64 encoded data
Dim b64 As String = "VXNlcm5hbWU6"
'Decode the base64 data to a byte array
Dim b64bytes() As Byte = System.Convert.FromBase64String(b64)

'Loop through each byte, adding the hex value for each byte to our
return string
For Each b As Byte In b64bytes
ret &= Hex(b).PadLeft(2, "0"c)
Next

'Display the finished string
MsgBox(ret)
///
Click to expand...


Thanks everyone.
 
Thanks everyone.
Click to expand...


Ack, I am having trouble getting it to convert back to base64

Imports System.Text
Module Module1

Sub Main()
Dim baseStr As String = "4WUC/38ff+GAm2GGOeR5Up7fi5Q0RU
+h8Zf5vKsOtXE="
Console.WriteLine(baseStr)
Console.WriteLine(Base64ToHex(baseStr))
Console.WriteLine()

Console.WriteLine(baseStr)
Console.WriteLine(HexToBase64(Base64ToHex(baseStr)))
Console.ReadLine()
End Sub

Function Base64ToHex(ByVal sBase As String) As String
Dim bBase() As Byte = Convert.FromBase64String(sBase)
Dim Hex As New StringBuilder

For Each HexByte As Byte In bBase
Console.Write(HexByte & " ")
Hex.Append(HexByte.ToString("x2"))
Next
Console.WriteLine()
Return Hex.ToString.ToUpper
End Function
Private Function HexToBase64(ByVal HexText As String) As String
Dim result(HexText.Length) As Byte

Dim i As Integer = 0
While i < HexText.Length
result(i) = Convert.ToByte(HexText.Substring(i, 2), 16)
Console.Write(result(i) & " ")
i += 2
End While
Console.WriteLine()

Return Convert.ToBase64String(result)
End Function
End Module

It is returning a much different string than I started with
 
Jeremy said:
Ack, I am having trouble getting it to convert back to base64
Click to expand...

It's because you're not accounting for each byte taking two characters
within the string.

Try replacing your HexToBase64 function with the following:

\\\
Private Function HexToBase64(ByVal HexText As String) As String
Dim result(HexText.Length \ 2) As Byte

Dim i As Integer = 0
While i < HexText.Length \ 2
result(i) = Convert.ToByte(HexText.Substring(i * 2, 2), 16)
Console.Write(result(i) & " ")
i += 1
End While
Console.WriteLine()

Return Convert.ToBase64String(result)
End Function
///

HTH,
 
It's because you're not accounting for each byte taking two characters
within the string.

Try replacing your HexToBase64 function with the following:

\\\
Private Function HexToBase64(ByVal HexText As String) As String
Dim result(HexText.Length \ 2) As Byte

Dim i As Integer = 0
While i < HexText.Length \ 2
result(i) = Convert.ToByte(HexText.Substring(i * 2, 2), 16)
Console.Write(result(i) & " ")
i += 1
End While
Console.WriteLine()

Return Convert.ToBase64String(result)
End Function
///

HTH,
Click to expand...

I eventually realized said fact...and fixed it. Thanks for the help
though
 
Jeremy Kitchen wrote:
Ack, I am having trouble getting it to convert back to base64
Click to expand...
Private Function HexToBase64(ByVal HexText As String) As String
Dim result(HexText.Length) As Byte

Dim i As Integer = 0
While i < HexText.Length
result(i) = Convert.ToByte(HexText.Substring(i, 2), 16)
Console.Write(result(i) & " ")
i += 2
End While
Console.WriteLine()

Return Convert.ToBase64String(result)
End Function
Click to expand...
<snip>

The size of Result must be half of the hex-string size; also, its
index is independent of the index that traverses the hex-string.

<code>
Private Function HexToBase64(ByVal HexText As String) As String
Dim Size As Integer = HexText.Length
Dim Result(0 To (Size >> 1) - 1) As Byte
Dim Pos As Integer
For Index As Integer = 0 To Size - 1 Step 2
Result(Pos) = Convert.ToByte(HexText.Substring(Index, 2), 16)
Pos += 1
Next
Return Convert.ToBase64String(Result)
End Function
</code>

HTH.

Regards,

Branco.
 
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