Re: stl, iostream and wchar_t

From:

Alberto Ganesh Barbati <AlbertoBarbati@libero.it>

Newsgroups:

comp.lang.c++.moderated

Date:

Thu, 10 Jul 2008 19:38:05 CST

Message-ID:

<kKwdk.24724$Ca.15195@twister2.libero.it>

kmmx ha scritto:

Can anyone tell me what the proper method to write a unicode string to
a file is, using streams?

some quick sample code:
typedef std::basic_ofstream<TCHAR, std::char_traits<TCHAR> >
_tofstream;

_tofstream s(_T("filename.txt"));
wchar_t* msg = _T("FOOBAR");
s << msg;

This works fine as long as I only write ANSI characters. As soon as I
write unicode:

wchar_t* msg = _T("??");

There are no such thing as "ANSI characters". There are ASCII characters
and the code page usually called "ANSI" was invented by Microsoft and
has never been standardized by ANSI.

we run into problems. See
http://www.codeproject.com/KB/stl/upgradingstlappstounicode.aspx

Okay, so I can use this giant hack mentioned in the article to write a
unicode string. But that just seems "wrong."

In fact it's sort of wrong. What you need is a codecvt facet that
provide the encode you need. For example, have a look here:

http://www.boost.org/doc/libs/1_35_0/libs/serialization/doc/codecvt.html

I tried opening the file in binary mode as well and writing that way.
But then it seems any time I try to write a wchar_t, the streams
badbit gets set.

Of course you always need to open these files as binary as an
UTF-encoded file is *not* a text file according to the meaning of "text"
used by the C library.

Ganesh

--
[ See http://www.gotw.ca/resources/clcm.htm for info about ]
[ comp.lang.c++.moderated. First time posters: Do this! ]