Re: [boost] Unicode and codecvt facets

Subject: Re: [boost] Unicode and codecvt facets
From: Bo Persson (bop_at_[hidden])
Date: 2010-07-06 13:09:19

Mathias Gaunard wrote:
> Le 05/07/2010 18:48, Bo Persson wrote:
>
>> You can, but you should specialize on the third parameter, if you
>> want to treat chars differently than default.
>>
>> A codecvt<char, char, my_state_t>  could easily do any kind of
>> conversions you need.
>
> I don't particularly need state, what I would like is to be able to
> use the right character types rather than wide characters, which are
> implementation-specific.

You mean the implementation doesn't provide the right character types? 
:-)

The third parameter is there so you can specialize the use of chars, 
other that the default implementation's. The codecvt<char, char, 
mbstate_t> does what is "standard" on the platform. If you want 
something else, you need a codecvt<char, char, non_std_state_t>, even 
if you don't use the state variable passed to your codecvt<>. The 
standard codecvt<> doesn't use it either.

>
> Also it doesn't seem states other than mbstate_t can be used by
> filebufs.

It should work, but perhaps not the most tested part on a standard 
library.

The filebuf (basic_filebuf, that is) is templated on char and 
std::char_traits<char>. Again, if you want something other that 
default, you need basic_filebuf<char, non_std_char_traits<char>>.

With the current standard you only have char and wchar_t. You could 
perhaps use some other int types as characters, but will then run into 
problems like having no string literals available.

Bo Persson