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Encoding.Unicode.GetBytes

Posted on 2006-10-27
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Last Modified: 2010-05-18
Easy 500 to someone who understands....

Consider the following and tell me why inputBytes does not always equal outputBytes? I think it has something to do with the size of inputBytes but what can I do to coerce input bytes to always be 'convertable' to and from a unicode string?

 byte[] inputBytes;
.
.
// inputBytes is created from 'somewhere'
.
.
byte[] outputBytes = Encoding.Unicode.GetBytes(Encoding.GetString(inputBytes));
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Question by:Solveweb
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8 Comments
 
LVL 22

Expert Comment

by:_TAD_
ID: 17820479

That's because the Input bytes are probably encoded with a default encoding that is not Unicode.

I would guess ASCII, UTF-8 or Latin1 encoding is the default

In any case, you will want to convert the encoding

Here's a site that may help
http://msdn2.microsoft.com/en-us/library/kdcak6ye.aspx


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LVL 22

Expert Comment

by:_TAD_
ID: 17820480

That's because the Input bytes are probably encoded with a default encoding that is not Unicode.

I would guess ASCII, UTF-8 or Latin1 encoding is the default

In any case, you will want to convert the encoding

Here's a site that may help
http://msdn2.microsoft.com/en-us/library/kdcak6ye.aspx


0
 
LVL 22

Expert Comment

by:_TAD_
ID: 17820481

That's because the Input bytes are probably encoded with a default encoding that is not Unicode.

I would guess ASCII, UTF-8 or Latin1 encoding is the default

In any case, you will want to convert the encoding

Here's a site that may help
http://msdn2.microsoft.com/en-us/library/kdcak6ye.aspx


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Author Comment

by:Solveweb
ID: 17820513
Actually the inputBytes isnt encoded from a string at all - Its created using a custom authentication routine, so I cant exactly 'convert' the Encoding from anything. at all...
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LVL 22

Expert Comment

by:_TAD_
ID: 17820629


Sure it is... You show it being encoded right here:

byte[] outputBytes = Encoding.Unicode.GetBytes(Encoding.GetString(inputBytes));


First you take the input bytes and encode them into ASCII (or whatever your default encoding is) {Encoding.GetString(inputBytes)}, and then you decode them with Unicode {Encoding.Unicode.GetBytes()}.


since you are not using "byte[] outputBytes = inputBytes"  It is clear that the input bytes are in a format other than Unicode.  You have to do a transformation if the bytes aren't in the right format.

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Author Comment

by:Solveweb
ID: 17820764
Sorry --- The code example was wrong --- Should have been as follows which clearly converts to and from the same code page --- I have also added a code snippet that demonstrated the same issue when xk gets to [0, 216] ....

byte[] inputBytes;
// inputBytes is created from 'somewhere'
byte[] outputBytes = Encoding.Unicode.GetBytes(Encoding.Unicode.GetString(inputBytes));

//problem can also be demonstrated with the following snippet....
for (byte xi = 0; xi < 255; xi++)
            {
                for (byte xj = 0; xj < 255; xj++)
                {
                    byte[] xk = new byte[2] { xi, xj };
                    string xs = Encoding.Default.GetString(xk);
                    if (xs==string.Empty)
                        string badCodeThatDoesntEncode = "yes";
                }

            }
0
 
LVL 4

Accepted Solution

by:
ostdp earned 500 total points
ID: 17821665
You may have a case of invalid characters occuring during the conversion. In multibyte character sets not all two byte sequences are valid sequences, hence if you are creating the inputBytes in a non unicode compatible fashion (you said authentication, so I assume a hash function), the default behavior of the encoders is to _discard_ invalid sequences, hence the discrepancy between inputBytes and outputBytes.

Btw. the default string encoding in .Net is unicode.
0
 

Author Comment

by:Solveweb
ID: 17822736
Rats! It would be nice if there was a way of doing this - Simply to squash down a byte array to as small as possible string representation (single byte string conversion not good enough). Now I know - Unicode doesnt mean quite mean two byte encoding in the way I thought it might. Hmm.. back to the drawing board

Thanks
0

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