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

[Bill Lorensen]

VS6 does not have a wide string constructor for (i/o)fstream. I'm not
sure in what VS version they added thw wide string constructor.

Bill


On Tue, Nov 10, 2009 at 8:41 PM, Tom Vercauteren
<tom.vercauteren at m4x.org> wrote:
> 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.
>>>
>>
>