[Insight-developers] Unicode filenames, VS6 and fdstream (was:Unicode filenames and borland issue)

[Tom Vercauteren]

Hi Bill,

I just finished implementing your suggestion. I created some stream
classes that inherits from (i/o)fstream on all systems except for
mingw and borland where
1) they inherit from (i/o)stream
2) they implement some functions that are only in (i/o)fstream to get
a uniform API
3) use the c-style open and code from fdstream to allow unicode filenames

On MSVC, the new implementation takes advantage of the MSVC-specific
wide string constructor of (i/o)fstream [1]. This could thus be easier
for VS6.

The file is here:
http://www.itk.org/Bug/file_download.php?file_id=2646&type=bug

I tested it on windows xp with
* visual c++ 2008 express
* mingw with gcc 3.4
* borland 5.5
* cygwin 1.7 with gcc 4.3

Could you give it a try on VS6?

Thanks,
Tom

[1] This constructor is not available on both borland and mingw which
implies that stdio_filebuf is not sufficient and we need a more
portable solution such as fdstream.

On Tue, Nov 10, 2009 at 22:25, Bill Lorensen <bill.lorensen at gmail.com> wrote:
> fdstream is the problem on vs6 I think. We might be able to modify the
> fdstream header with ifdef's for VS6. Really make fdstream look like
> (i/o)stream. Maybe with (uggh!) #defines to redefine fd(i/o)stream to
> be (i/o)stream only on VS6 (and maybe VS7).
>
> On Tue, Nov 10, 2009 at 4:11 PM, Tom Vercauteren
> <tom.vercauteren at m4x.org> wrote:
>> Hi Bill,
>>
>> Thanks for taking a look at this!
>>
>> Are the problems you found related to the use of _wfopen and _wopen or
>> to the use of fdstream? This is an important distinction for the
>> unicode filename porting because the plan I had in mind relies on
>> fdstream being used in all cases (ITK_USE_REVIEW_UTF8_STRINGS on or
>> off).
>>
>> Indeed here is what I found (VS6 not taken into account here):
>>
>> 1) c-style file IO can be ported relatively easily to utf8 on windows
>> (msvc, borland, mingw). Just replace fopen by _wfopen and open by
>> _wopen together with some string conversion
>>
>> 2) c++-style IO is more involved. There is a wide string version of
>> ofstream.open() and ifstream.open() on msvc but not on mingw (did not
>> try with on borland).
>>
>> Since the fstreams cannot be opened with a unicode filename on mingw,
>> the workaround is to open the file using c-style functions and then
>> create a stream from the result of the c-style open.
>>
>> A gcc specific extension exists for that (stdio_filebuf) but it is
>> obviously non-portable. fdstream does the same thing but appeared to
>> be portable.
>>
>> So to get unicode filename enabled streams, we need to replace code like
>>
>> A)
>> std::ifstream readstream(filename, std::ios::binary | std::ios::in)
>>
>> by code like
>>
>> B)
>> int fd = _wopen(filename, _O_RDONLY);
>> boost::fdistream readstream(fd);
>> [...]
>> close(fd)
>>
>> We might of course pepper the code with ifdefs each time a stream is
>> used (as is already done to workaround a sgi bug in metaImage.cxx
>> http://public.kitware.com/cgi-bin/viewcvs.cgi/Utilities/MetaIO/metaImage.cxx?root=Insight&view=markup
>> ) but I wanted to avoid that by restricting these ifdefs to live in a
>> specified file/module. Hence my plan to wrap only the c-style (f)open
>> functions and use fdstreams everywhere.
>>
>> Note that since we need to close the file descriptor and because
>> fd(i/o)streams do not inherit from (i/o)fstream but only from
>> (i/o)stream, it is not obvious to have a function that uses either the
>> A mode or B mode above.
>>
>> Sorry for this long email,
>> Tom
>>
>> P.S.: some information is also available on the bug tracker:
>> http://public.kitware.com/Bug/view.php?id=9623
>>
>> On Tue, Nov 10, 2009 at 21:11, Bill Lorensen <bill.lorensen at gmail.com> wrote:
>>> My first try with VS6 is not encouraging. I suggest that we instrument
>>> the code so that VS6 ITK cannot use Unicode.
>>
>