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From "Nathan Beyer" <nbe...@kc.rr.com>
Subject RE: [bug-to-bug] UTF-8: interpreting non-shortest forms
Date Sat, 25 Mar 2006 05:23:55 GMT
I've seen similar differences between other VMs around the handling of UTF-8
encoded data, especially between Sun and IBM VMs.  For example, if you read
a file with a UTF-8 encoding that contains an invalid byte(s), the IBM VM
will throw an IOException, but the Sun VM will convert the invalid byte(s)
into the Unicode unknown character (diamond-backed-question-mark).

Personally, I prefer VMs that explicitly stick to Unicode and the various
encodings and indicate error conditions.

-Nathan

> -----Original Message-----
> From: Stepan Mishura [mailto:stepan.mishura@gmail.com]
> Sent: Friday, March 24, 2006 12:57 AM
> To: harmony-dev
> Subject: [bug-to-bug] UTF-8: interpreting non-shortest forms
> 
> According to Unicode standart 4.0 (since 3.0) interpretation of non-
> shortest
> forms is forbidden for UTF-8. So if a byte sequence is not in table of
> well-formed UTF-8 byte sequences then it is considered as ill-formed and
> treated as error. Harmony follows Unicode spec. but RI doesn't. I didn't
> find in the spec. explanation but I assume it is caused by backward
> compatibility.
> 
> The following example demonstrates the difference. For example, code point
> '1071' should be represented by the next UTF-8 byte sequence <D0 AF>. But
> it
> may be represented as 3 bytes sequence: <E0 90 AF> that is its non-
> shortest
> form. So the following code prints "ERROR" on Harmony implementation and
> "Ok
> with non-shortest forms" on RI
> 
>         String s1 = new String(new byte[]{(byte) 0xE0, (byte) 0x90, (byte)
> 0xAF}, "UTF-8");
>         String s2 = new String(new char[]{1071});
> 
>         if(s1.equals(s2)){
>             System.out.println("Ok with non-shortest forms");
>         } else {
>             System.out.println("ERROR");
>         }
> 
> We should decide whether we going to be compatible with RI or Unicode
> spec.
> 
> Thanks,
> Stepan Mishura
> Intel Middleware Products Division


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