UTF-8

Richard Emberson emberson at faslab.com
Sat Oct 17 00:50:29 BST 1998


Does the UTF-8 encoding require that the minimum byte count
be used when a character is encoded.
Recall that the form of a UTF-8 encoding is:

 0xxxxxxx
 110xxxxx 10xxxxxx
 1110xxxx 10xxxxxx 10xxxxxx
 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
 111110xx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
 1111110x 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx


So one could, for example, claim that:

 00111111

and

 11000000 10111111

represent the same character, #x3F, or

 11110001 10111111 10111111 10111111

and

 11111000 10000001 10111111 10111111 10111111

represent #x7FFFF (note: x10000 < x7FFFF < x10FFFF as so is legal).

The reason I ask is whether an XML parser has to worry about 
5 and 6 byte UTF-8 encodings or can it *allways* assume that the
values represented by such encoding are not legal unicode characters.

Thanks.

Richard Emberson

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