Re: coding tags and utf-16

[Kenichi Handa <handa@m17n.org>]

In article <m3hd6et0de.fsf@seneca.benny.turtle-trading.net>, Benjamin Riefenstahl <b.riefenstahl@turtle-trading.net> writes:

> Kenichi Handa writes:
>>> ("\\`\xEF\xBB\xBF" . utf-8)
>> 
>> As far as I know, UTF-8 should not start with this sequence unless
>> the text really starts with ZWNBSP (very unlikely).

> UTF-8 can start with a BOM.  See
> <http://www.unicode.org/faq/utf_bom.html#29>.

That's why I wrote "unless ..." part.  For decoding UTF-8,
we should not delete that BOM but treat it as the content of
the text.  For UTF-16, Unicode explicitly says that "The BOM
is not considered part of the content of the text", but for
UTF-8, it doesn't say such a thing.

Anyway, as Unicode doesn't recommend but doesn't inhibit BOM
in UTF-8 either, if people agree, I'll add it too.

>>> ("\\`\xFE\xFF" . utf-16-be)
>>> ("\\`\xFF\xFE" . utf-16-le)
>> 
>> Although it's not clear how safe they are, if no one objects,
>> I'll add them in auto-coding-regexp-alist.

> Shouldn't those be utf-16-[bl]e-with-signature?  Or has the naming
> convention changed?

Actually utf-16-be is an alias of utf-16be-with-signature
(more precisely, an alias of mule-utf-16be-with-signature)
and is different from utf-16be (and we don't have
utf-16-be-with-signature).  I have a responsibility for this
confusing naming.  I long ago mistakenly accepted and
committed those names (utf-16-[bl]e), and now keeping them
for backward compatibility.  Anyway I agree that using
utf-16[bl]e-with-signature here is better.

---
Kenichi Handa
handa@m17n.org