[boost] narrow_wide_string class

From: Blake Madden (madden_blake_at_[hidden])
Date: 2004-01-16 16:37:58

I am working on a string class that can represent a string constant, but can 
be used with both char and wchar_t values.  For example:

//assigned with unicode "A HREF"
const narrow_wide_string<> A_HREF = L"A HREF";

//ahref will be ANSI "A HREF"
std::string ahref = A_HREF;
//wahref will be unicode "A HREF"
std::wstring wahref = A_HREF;
//returns 6
size_t size = strlen(A_HREF);
//returns 6
size_t wsize = wcslen(A_HREF);

Essentially, this solves the problem of needing to embed string literals 
inside of templatized string functions that are meant to work with both char 
and wchar_t types.  Currently, if you have to use string literals, then you 
to overload your string functions: one version that takes char, the other 
wchar_t.  With this class, you can just make one templatized function and 
use this class to string your constant.

It also can be initialized with individual unicode values and will convert 
the internal char string using a customizable codecvt paramter.  This means 
that you could do this:

//"unicode_to_shiftjis" is a user-defined codecvt class that converts 
Japanese unicode
//text to the corresonding Shift JIS values.
narrow_wide_string<unicode_to_shiftjis<wchar_t, char, mbstate_t> >
   japanese_text(3, 0x30A0, 0x30B4, 0);
//similar to saying
wchar_t japanese_text[3] = { 0x30A0, 0x30B4, 0; }

The benefit is that if you have ANSI (char) and unicode strings in your 
code, you do not have to maintain both a unicode string literal and an ANSI 
literal for the same string.  Also, the class handles the conversion to char 
format for you, so you never have to hard code encoded char literals (e.g., 
Shift JIS).  Simply provide the (immutable) unicode value, and if you need 
to use a different ANSI encoding then simply plug in a differetn codecvt 
functor.

Would there be any interest in a class such as this for possible boost 
consideration?  I shall add this to Boost Yahoo files if anyone is 
interested.

Blake Madden

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