[MPlayer-dev-eng] [PATCH] Use unrar for open vobsubs if available

[Ulion]

2007/12/8, Reimar Döffinger <Reimar.Doeffinger at stud.uni-karlsruhe.de>:
> Hello,
> On Sat, Dec 08, 2007 at 12:43:36AM +0800, Ulion wrote:
> > 2007/12/8, Reimar Doeffinger <Reimar.Doeffinger at stud.uni-karlsruhe.de>:
> [...]
> > > > How about:
> > > >
> > > >         fd = open("/dev/null", O_WRONLY);
> > > >         if(fd == -1)
> > > >             _exit(EXIT_FAILURE);
> > > >         if (fd != 2) {
> > > >             dup2(fd, 2);
> > > >             close(fd);
> > > >         }
> > >
> > > What is the point of the != 2 check then? Either you assume that
> > > stdin, stdout and stderr are correctly set at the beginning,
> > > then fd _can_ not be 2 (because you did not close it before).
> > > Or if you don't assume that and you should check for that case (which,
> > > due to "open" being required to return the smallest non-open
> > > descriptor, my < 3 test does, though I admit it is not ideal
> > > in clearness).
> >
> > I assume stdout is correctly set, does not assume whether stdin and
> > stderr are correctly set.
> > So my last code will works fine with the assume -- stdout is correctly set.
> > That's enough for current implement since it only care the stdout.
>
> Except that if you only assume stdout is opened, the first file opened
> by the unrar binary would become its stdin.
> The same applies to stderr if this dup2 fails.
> A truly proper solution would also try to close all other open file
> descriptors that are not needed, but that is quite ugly (I think OpenBSD
> has an extra syscall for that, I must say that really is a very
> advisable thing).
> I think code like this would make sense (note you'll have to replace
> that pipefd by the right variable, I forgot the name):
> > // close MPlayer's stdin, stdout and stderr so the unrar binary
> > // can not mess them up
> > // TODO: close all other files except the pipe
> > close(0); close(1); close(2);
> > // assign new stdin, stdout and stderr and check they actually got the
> > // right descriptors
> > if (open("/dev/null", O_RDONLY) != 0 || dup(pipefd) != 1 || open("/dev/null", O_WRONLY) != 2)
> >   _exit(EXIT_FAILURE);

This one is really good, updated.

-- 
Ulion
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