On Tue, Jan 20, 2004 at 05:27:22PM +0000 Nick Ing-Simmons wrote:
> Tassilo Parseval <[EMAIL PROTECTED]> writes:
> >
> >My concern was with PerIO_fdopen(). I didn't know whether perl would
> >reuse the fd (and simply sort of wrap it in a PerlIO) or duplicate it.
>
> There is a pod which tells you.
I missed the entry on PerlIO_fdopen (it is bundled with PerlIO_open). I
should have used '/' in perldoc.
> >In case of duping, ignoring O_NONBLOCK would be bad.
>
> AFAIK a dup()ed fd inherits the non-blocking-ness along with
> all the other kernel level attributes like file position.
As I've read in the PODs now, PerlIO_fdopen() will not dup the handle
(since fdopen wont do it) and so I can't use it. perlapio.pod mentions
"dup" only once (in PerlIO_reopen) and that doesn't help:
Perl prefers to "dup" the new low-level descriptor to the descrip-
tor used by the existing PerlIO. This may become the behaviour of
this function in the future.
I've come to the conclusion that I will use the "<&$fd" trick and use
do_openn() because thus I can pass 'Nullfp' as the PerlIO* argument.
> >The problem with fd-versus-FILE IO is eventually what bothers me.
>
> For Perl5.8+ you can avoid the buffering issues of that problem
> by just using :unix layer.
This is good to know. I haven't yet looked much into the layers stuff
though.
> >> > #define sv_to_file(sv) (PerlIO_exportFILE(IoIFP(sv_2io(sv)), NULL))
> >> >
> >> That is "okay" anywhere with perl5.8+ - but please read the PODs.
> >> In perl5.8+ there isn't necessarily a FILE * in normal perl IO.
> >> So the above may have to
> >>
> >> FILE *stdio = fdopen(PerlIO_fileno(pio),mode))
> >
> >Sigh, so not even my non-Win32 path is necessarily right.
>
> Why do you need a FILE *?
> Won't a PerlIO * do? - you always have one of those.
>
> IMHO you only need a FILE * for passing external C libraries
> that expect such a thing.
This was my situation. The library was able to deal with either a
filename or a FILE* handle. It was therefore natural to allow the same
thing from Perl.
> >Anyway, Nick, thanks for your patient attempts to explain this book
> >with 7^7 seals to me. I think I'm now able to find a way through this
> >muddle somehow.
>
> I will try and remember to add the essence of these discussions
> to the PODs.
That would be really nice. I simply cannot imagine that I am the only
one having such a hard time with perlio.
Tassilo
--
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