Re: [boost] Making Boost.Filesystem work with GENERAL filenames with g++ in Windows (a solution)

Subject: Re: [boost] Making Boost.Filesystem work with GENERAL filenames with g++ in Windows (a solution)
From: Artyom Beilis (artyomtnk_at_[hidden])
Date: 2011-10-26 05:47:39

----- Original Message -----
> From: Alf P. Steinbach <alf.p.steinbach+usenet_at_[hidden]>
>
> First, apologies if I'm posting to the wrong group/list; if so then please 
> redirect me.
> 
> IMHO access to files is a crucial part of Boost.Filesystem. However, with Boost 
> 1.47, and using g++ 4.4.1 in Windows 7, boost::filesystem::ifstream etc. fail to 
> open or create files with non-ANSI characters. It works fine with Visual C++; it 
> FAILS with g++ 4.4.1, which is the one bundled with the Code::Blocks IDE.
> 
> The failure probably has nothing to do with the g++ version: it's due to g++ 
> not offering the Visual C++ wchar_t oriented extensions to the standard 
> iostreams (Boost.Filesystem uses these Visual C++ extensions).
> 
> I stumbled onto this while I was writing about using Unicode in C++ programming 
> in Windows.
> 

Why just not to implement boost::filesystem::fstream over _wfopen and custom
streambuf implementation?

It is relatively simple. 

I have implemented such thing under booster namespace as part of cppcms project

http://cppcms.svn.sourceforge.net/viewvc/cppcms/framework/trunk/booster/booster/nowide/
http://cppcms.svn.sourceforge.net/viewvc/cppcms/framework/trunk/booster/lib/nowide/src/

http://cppcms.svn.sourceforge.net/viewvc/cppcms/framework/trunk/booster/booster/nowide/fstream.h?revision=1967&view=markup


> I wrote up a technical solution in section 5, starting on page 16, of that 
> work-in-progress document, available on Google Docs at:
> 
> 
> https://docs.google.com/viewer?a=v&pid=explorer&chrome=true&srcid=0B2oiI2reHOh4ZjdkNmUyNDctNzI1Yi00NmJjLThiMzgtYmI3OGE0ZmE5MDg2&hl=en
> 
> Essentially, the fix I ended up with, full source code given in the above doc, 
> uses Windows short file names if (1) there is no wide character support and if 
> furthermore (2) the filename can't be perfectly translated to ANSI. The C++ 
> implementation's support for wide chars is automatically detected using 
> C++98-compatible code.
> 
> I do not know what to do with this.
> 

That is what very good about stream buffers... You can implement anything
you need.

Using short file names is no go for two reasons:

1. It works only when file exists (can't create new file)
2. It is quite deprecated


> But considering that Boost.Filesystem is slated for later inclusion in the C++ 
> standard library (or at least into TR2), I think it would be nice if it is able 
> to give access to all accessible files in Windows, also with g++,

This is a problem that can be fixed easily in Boost.Filesystem.

> so that we 
> don't end up with a file handling part of the standard library that 
> can't handle files in general;

This is a "bug" in Windows operating system... but this is other story.

> hence this posting and plea for advice  --  
> what more should I do, if anything?
> 

Write a patch that implements stream buffer over stdio and _wfopen?

> Cheers,
> 
> - Alf
> 



Artyom Beilis
--------------
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