C++ equivalent for tmpfile()

[Catfish3]

http://cplusplus.com/reference/cstdio/tmpfile/

Searching the Reference, I couldn't find a C++ stream equivalent for the above.

[MiiNiPaa]

Well, I didn't find one. You can always write tempfile class yourself and use it in all future projects.
Here what can be used to create it in Windows:
http://msdn.microsoft.com/en-us/library/windows/desktop/aa364992%28v=vs.85%29.aspx
http://msdn.microsoft.com/en-us/library/windows/desktop/aa364991%28v=vs.85%29.aspx

[Cubbi]

As far as I know, std::tmpfile is the only way to get both atomic unique name generation / file opening and auto-deletion.

I would write a streambuf wrapper, it's a very legitimate case for one. Or, to write less code, you could use fileno() (on a POSIX system) or whatever Windows has to get a HANDLE from FILE*, and then construct a boost.iostreams file_descriptor stream.

[Catfish3]

I would write a streambuf wrapper, it's a very legitimate case for one.

Please give more detail, because I don't understand how and why.

Do you suggest coding a class that uses a FILE internally, and can be used in place of a std::streambuf?

[Cubbi]

Yes: a class derived from streambuf with a FILE* data member, obtained in its constructor by calling std::tmpfile. That's just how you add new stream types to the streams library. As for detail, JLBorges likes to link to this tutorial: http://www.mr-edd.co.uk/blog/beginners_guide_streambuf , I like boost.iostreams: http://www.boost.org/doc/libs/release/libs/iostreams/doc/tutorial/writing_devices.html for simple cases like this.

[Catfish3]

Thanks for the links and help, but I'm giving up.

I had begun writing a TmpFileSb class, but I stopped shortly after, because of the overwhelming feeling that I was doing someone else's work.

[Duthomhas]

Google around "stdiostream" and "stdiobuf" to find the things other people have already done. At one time, I think there was one in Boost...

Here's mine:
http://www.cplusplus.com/forum/articles/22316/
(It is unfinished, alas... you'll need to pay attention to the two bugs in there.)

From a thread about the same thing (using FILE* the C++ way):
http://www.cplusplus.com/forum/beginner/22230/#msg116635 (without FILE*)
http://www.cplusplus.com/forum/beginner/22230/#msg116842 (using my stdiostream)

Hope this helps.

[edit] If I ever get time I'd like to fix those two bugs and put this in an actual code article... If you fix it I'll put your name in the header.

[Catfish3]

Thanks Duoas. I'll need a good tmpfile() component when/if I attempt the Burrows-Wheeler Transform, a topic for another article.

[Catfish3]

Duoas, I'm trying to fix the bugs, but so far I failed.

You rely on std::basic_iostream to delete the stream buffer pointer you feed it. But it doesn't? This is why your destructor isn't called. I think.

http://cplusplus.com/reference/istream/basic_iostream/~basic_iostream/

[JLBorges]

libstdc++ specific (AFAIK, works only for char and wchar_t):

#include <cstdio>
#include <iostream>
#include <string>
#include <ext/stdio_filebuf.h> // libstdc++ specific

int main()
{
    __gnu_cxx::stdio_filebuf<char> tmpfile_buf( std::tmpfile(),
                            std::ios::in|std::ios::out|std::ios::binary ) ;
    std::iostream temp_fstream( &tmpfile_buf ) ;

    // use temp_fstream
    temp_fstream << 12345 << ' ' << 67.89 << "Hello World\n" ;

    temp_fstream.seekg(0) ;
    int i = 0 ; temp_fstream >> i ;
    double d = 0 ; temp_fstream >> d ;
    std::string str ; std::getline( temp_fstream, str ) ;
    std::cout << i << '\n' << d << '\n' << str << '\n' ;
}

Portable: boost::iostreams::file_descriptor with fileno() (POSIX) or _fileno() (Windows)