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Re: coding tags and utf-16
From: |
Kenichi Handa |
Subject: |
Re: coding tags and utf-16 |
Date: |
Tue, 28 Feb 2006 10:08:36 +0900 |
User-agent: |
SEMI/1.14.3 (Ushinoya) FLIM/1.14.2 (Yagi-Nishiguchi) APEL/10.2 Emacs/22.0.50 (i686-pc-linux-gnu) MULE/5.0 (SAKAKI) |
Sorry for the late responce.
In article <address@hidden>, Kevin Rodgers <address@hidden> writes:
>> I thought we had discussed this already. The BOM-encodings should
>> have priority since the likelihood of a misdetection is negligible
>> (the character pair does not make sense at the start of a text in
>> latin-1 in any language): the only thing that can reasonably be
>> expected to happen is that a binary file is detected as utf-16. Not
>> much of an issue, I'd say.
I've just digged out old mails we exchanged on this topic
(about a year ago). To my understanding, there was no
clear conclusion. Here are the extracts:
------------------------------------------------------------
I wrote:
> I think BOM is not that safe because there are many charsets
> who have normal letters at 0xFE and 0xFF.
Jason wrote:
> But what are those characters, and are they likely to appear as a pair
> at the beginning of the file, and nowhere else?
I wrote:
> Sorry, I don't know.
Dave wrote:
>> Exactly what Windows does for what? Recognizing a utf-16 registry
>> file when opened in the registry editor?
> Auto-detecting utf-16 generally. Although I don't think it would give
> false positives on iso-8859 text, I don't know if it could with other
> charsets.
>
> I could believe that Windows doesn't just go by byte-order-mark in
> some locales where there might be a problem. If so, it could be
> useful to do the same thing.
------------------------------------------------------------
For instance, I've just googled the two character sequence
of 0xFE 0xFF of koi8 and found several occurrences.
> Exactly. So why haven't these entries been added to
> auto-coding-regexp-alist?
> ("\\`\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).
> ("\\`\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.
> ("\\`\x00\x00\xFE\xFF" . utf-32-be)
> ("\\`\xFF\xFE\x00\x00" . utf-32-le)
Emacs doesn't support those encoding for the momemnt.
---
Kenichi Handa
address@hidden