Message-ID: <3F4F03C2.D9D1F88@acm.org>
From: Eric Sosman <esosman AT acm DOT org>
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Subject: Re: wide character functions
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Date: Fri, 29 Aug 2003 12:39:48 GMT
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Eli Zaretskii wrote:
> 
> Wide characters is one representation of non-ASCII characters.
> Another representation, which should also be supported by the library,
> is the multibyte representation, whereby every characters is
> represented as a series of 8-bit bytes.  (Many libraries choose UTF-8
> as their multibyte representation.)  The is* macros should support the
> multibyte representation in a manner equivalent to what the isw*
> macros do with the wide characters.  That is, if you pass a wide
> representation of a character CH to iswprint and the multibyte
> representation of the same character to isprint, you should get ther
> same result (I think).

    No; is*() and to*() work only with "plain"
one-`char'-is-one-character
data.  (And with the special value EOF, of course.)  In fact, since the
argument to any of these is the value of a single character, there's no
way they could see the second and subsequent characters of a multibyte
encoding.

    The point remains, though, that introducing wide character and
multibyte support involves more than merely implementing the functions
with `w' in their names.  For example, the *printf() family must be
made aware of multibyte encodings (searching the format string for the
single character '%' does *not* suffice), and in C99 a FILE* stream
can have either wide- or narrow-character orientation.

-- 
Eric Sosman
esosman AT acm DOT org