Re: [cp-patches] FYI: Patch: character encoder/decoder cleanup/fixes

[Archie Cobbs]

Jeroen Frijters wrote:
> The string isn't valid Unicode so the UTF-8 encoder is within its rights
> to encode the surrogate as an invalid character.

Correct.. (unfortunately :-)

> > Yes, which is how I came across this bug. There are classes 
> > in Classpath that store arbitrary binary data within String
> > objects.
> 
> Class files don't use UTF-8 to encode strings, they use the format used
> by DataOutputStream.writeUTF (what Sun calls "modified UTF").

Right.. though it would be nice if there were an encoder
for "modified UTF" as well.

> So maybe all we need to do is make sure that
> DataOutputStream.writeUTF/DataInputStream.readUTF can roundtrip *any*
> string (even if it has invalid Unicode characters).

Definitely .. here's a test case (this one works):

    import java.io.*;
    import java.util.*;
    public class xx {
        public static void main(String[] args) throws Exception {
            String s = "\ud8aa";
            ByteArrayOutputStream bas = new ByteArrayOutputStream();
            DataOutputStream das = new DataOutputStream(bas);
            das.writeUTF(s);
            das.close();
            DataInputStream dis = new DataInputStream(
              new ByteArrayInputStream(bas.toByteArray()));
            String t = dis.readUTF();
            System.out.println(s.equals(t));
        }
    }

My error was assuming that "UTF-8" encoding and Java's "modified UTF"
were the same thing when in fact they are different.

-Archie

__________________________________________________________________________
Archie Cobbs      *        CTO, Awarix        *      http://www.awarix.com


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