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Re: Subsets of Unicode and coding systems
From: |
Kenichi Handa |
Subject: |
Re: Subsets of Unicode and coding systems |
Date: |
Thu, 08 Dec 2011 13:16:26 +0900 |
> Date: Tue, 6 Dec 2011 12:38:57 +0100
> From: Ulrich Mueller <address@hidden>
>
> Sometimes I want to check if a file saved in UTF-8 encoding contains
> only characters from a certain subset of the Unicode character
> repertoire, like the MES-* [1] or WGL4 [2] subsets. (For example, for
> things published on the WWW one might rather avoid exotic characters
> for better compatibility.)
>
> My idea was now to define a coding system e.g. for MES-2 and set the
> buffer-file-coding-system accordingly, so that Emacs would check it
> upon saving the file.
>
> Now I have the following questions:
> 1. Is using coding systems for this purpose a reasonable approach
> at all, or is there a better way to achieve this?
> 2. Where can I find documentation how to define a coding system?
I agree with Eli, defining proper categories provides more
flexible usage, but FYI, something like this defines the
coding system utf-8-mes-2.
(let ((repertory '((0 . #x017f) #x018f #x0192 #x01b4
(#x01de . #x01ef) (#x01fa . #x01ff)
;;; add more here
))
list)
(dolist (elm repertory)
(if (consp elm)
(let ((from (car elm))
(to (cdr elm)))
(while (<= from to)
(setq list (cons from (cons from list)))
(setq from (1+ from))))
(setq list (cons elm (cons elm list)))))
(define-charset 'unicode-mes-2 "MES-2 subset of Unicode"
:code-space [0 255 0 255]
:ascii-compatible-p t
:map (apply 'vector (nreverse list)))
(define-coding-system 'utf-8-mes-2 "UTF-8 for MES-2 subset"
:mnemonic ?M
:coding-type 'utf-8
:charset-list '(unicode-mes-2)
:mime-charset 'utf-8))
See the docstring of define-charset and define-coding-system
to understand the code.
---
Kenichi Handa
address@hidden