El Diumenge, 24 de març de 2013, a les 06:32:46, Thomas Freitag va escriure: > Am 23.03.2013 20:08, schrieb Albert Astals Cid: > > El Dissabte, 23 de març de 2013, a les 20:01:58, Thomas Freitag va escriure: > >> Am 23.03.2013 18:59, schrieb Ihar `Philips` Filipau: > >>> On 3/23/13, Ihar `Philips` Filipau <[email protected]> wrote: > >>>>> (i tried to find a way to duplicate a FILE* but failed) > >>>> > >>>> How did you duplicate FILE*? > >>>> > >>>> How did the `fdopen( fileno(oldfile), mode )` failed? > >>> > >>> Nope. This is the right way: > >>> > >>> int new_fd = dup( fileno(oldfile) ); > >>> FILE *new_file = fdopen( new_fd, mode ); > >> > >> Duplicating the FILE pointer in that way is not a solution: I tried it > >> that way when I began to implement thread safe feature: At least under > >> Ubuntu and gcc the duplicated file pointer uses the same underlying > >> buffer, and that corrupts the thread safe feature. > > > > Exactly, it is the documented behaviour > > > > "They refer to the same open file description and thus share file offset" > > > >> That's why I used the > >> fileName to create a complete new file pointer. > >> Of course we can do it in that way if we detect that the file is deleted > >> (and only then!), but a program which use threads to render different > >> pages the same time will then render garbage :-( > > > > No. We either write the file back to a temporary location as i suggested > > in my initial mail, or use the only fd with locking. I think i'm favoring > > the second use case since writing the file back might not even work if we > > run out of free space. > > I think, You're second solution is quite easy to implement (I mean > really only easy to implement, it will take some time to change every > code snippet and deeply test the changed code): since FileStream already > use it's own buffer, there is no really need of the underlying system > file buffer. So implementing something like a sharable GooFile (or > extend gfile) which can be locked and remember the next read position in > FileStream and then do something like gfile->read(readposition, buf, > buflength) wouldn't really reduce the speed. But then I would prefer use > the low level file handles instead of the file pointer. And it's even > better than to write platform specific code and rely on Windows that the > open file is not deletable and search for a Mac solution. > Then the UniqueFileStream mechanism and the streamOwner instance > variable can be removed, too. > On the other hand: who deletes a just opened file and expects stability > of the application which just opens the file? Is it really worth the effort?
It is a fairly typical use case. Open a file you just downloaded temporarily with firefox or your mail client and then close firefox/mail client, the "correct" behaviour is the firefox/mail client to clean up the temporary files they created, but i still want okular to work on that file. Cheers, Albert > > Cheers, > Thomas > > > Cheers, > > > > Albert > >> > >> Cheers, > >> Thomas > >> > >>> It is OK to use *NIX function here - the dup() - since deleting open > >>> file can happen only on the *NIX-like OS, Mac OS X included. Windows > >>> doesn't allow that. Correct me if I'm wrong. Tested on Linux, HP-UX > >>> and Solaris for the safety sake: the fclose() would close the dup()ed > >>> file descriptor. > >>> > >>> Though I'm not sure how to integrate that with the rest of the portable > >>> code. :) > >>> > >>> FYI. > >>> _______________________________________________ > >>> poppler mailing list > >>> [email protected] > >>> http://lists.freedesktop.org/mailman/listinfo/poppler > >>> > >>> . > >> > >> _______________________________________________ > >> poppler mailing list > >> [email protected] > >> http://lists.freedesktop.org/mailman/listinfo/poppler > > > > _______________________________________________ > > poppler mailing list > > [email protected] > > http://lists.freedesktop.org/mailman/listinfo/poppler > > > > . > > _______________________________________________ > poppler mailing list > [email protected] > http://lists.freedesktop.org/mailman/listinfo/poppler _______________________________________________ poppler mailing list [email protected] http://lists.freedesktop.org/mailman/listinfo/poppler
