Re: [Boost-users] [regex] Working with wchar_t on older UNIXplatforms

From: Andrei Tarassov (andrei.tarassov_at_[hidden])
Date: 2006-03-21 13:23:15

John,

Thanks for help! I've managed to create my own traits classes and even
made the whole stuff compile, but I found that it would not work :-)

Right now I am doing intermediate encoding/decoding between wchar_t and
the local encoding (which is determined by the locale). However, I do
not like that approach much.

I am intrigued with what you said about converting data from UTF-8 to
UTF-32 on the fly. It is absolutely not a problem to convert my Unicode
strings to UTF-8 encoded strings. Where could I read about those on the
fly conversions and what limitations do they have (e.g. how locale
settings are handled)?

Thanks,
Andrei

-----Original Message-----
From: boost-users-bounces_at_[hidden]
[mailto:boost-users-bounces_at_[hidden]] On Behalf Of John Maddock
Sent: Tuesday, March 21, 2006 12:36
To: boost-users_at_[hidden]
Subject: Re: [Boost-users] [regex] Working with wchar_t on older
UNIXplatforms

> Now I tried to integrate wregex in the software, but it just would
> not compile complaining about missing wstring (and defined
> BOOST_NO_WREGEX). I tried to make up my own regex character traits
> class, but this does not seem to help, because some other
> classes/types (such as sub_match) make use of basic_string<charT>.
>
> Is there any way to bypass the problem?

OK all the following comments apply to 1.33.1.

There are two easy options and one harder option:

Easy option #1, use STLport if it supports wstring.
Easy option #2, use the ICU/Unicode support in 1.33.1 to search your
data 
directly (as long as it's in UTF-8, UTF-16 or UTF-32 format).  You'll
get 
back iterators into your data (whatever encoding it's in), so there's no

problems determining offsets etc.

The slightly harder option, as you've guessed already: write your own
traits 
class, from 1.33 onwards you can use vector<charT> in place of 
basic_string<charT> in the traits class.  If you take a look at the
traits 
class used by the Unicode/ICU support code it should give you the
general 
idea, and there are docs here: 
http://www.boost.org/libs/regex/doc/concepts.html#traits

And finally... if you data is in MBCS format you might get some ideas
from 
the unicode suuport code in 1.33.x: basically in order to handle
multibyte 
encodings it converts from UTF-8 or UTF-16 to UTF-32 code points on the
fly. 
Of course this requires that the on-the-fly conversions are
bidirectional, 
this works OK for Unicode, but I'm not sure about how far you would get
with 
other encodings.

HTH, John. 

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