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UTF-16 without BOM is exiled

From: Kornél Pál <kornelpal@gmail.com>
Date: Thu, 07 May 2009 00:38:23 +0200
Message-ID: <4A02115F.3090407@gmail.com>
To: public-html-comments@w3.org
Hi,

After having a look at HTML5 editor's draft I believe that 8.2.2.3 
incorrectly instructs changing UTF-16 to UTF-8.

UTF-16 without BOM cannot be detected using the sniffing algorithm 
because is incompatible with ASCII. But the browser may guess (step 6.) 
that it's UTF-16 but it will only be tentative.

After the parser may find and encoding specified in the UTF-16 text.

If the encoding found is UTF-16 then that is instructed by step 1. of 
8.2.2.3 to be changed to UTF-8 that is definitely wrong.

Another problem is that if you were able to find an encoding name other 
than UTF-16 in a valid HTML code decoded as if it were UTF-16 you 
shouldn't restart parsing because if it isn't UTF-16 then the encoding 
found is not accurate either.

4.2.5.5 also states:

If an HTML document does not start with a BOM, and if its encoding is 
not explicitly given by Content-Type metadata, then the character 
encoding used must be an ASCII-compatible character encoding

and

If an HTML document contains a meta element with a charset attribute or 
a meta element in the Encoding declaration state, then the character 
encoding used must be an ASCII-compatible character encoding.

These together are equivalent to saying that UTF-16 without BOM is not 
allowed but I believe that this was not the intent. If it really is I 
would prefer to have an explicit note about this.

Encoding found by parsing using UTF-16 should be UTF-16 and any other 
values should be treated as a parse error.

Permitting UTF-16 without BOM makes sense because encoding autodetection 
is permitted as well and ASCII compatible encodings having encoding 
specified using <meta> will not reach the autodetection stage.

Best regards,
Kornél Pál
Received on Thursday, 7 May 2009 08:00:02 GMT

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