Date: Mon, 10 Nov 2003 12:41:09 -0500 From: marius aamodt eriksen <marius@monkey.org> To: hackers@openbsd.org, tech-kern@netbsd.org, freebsd-hackers@freebsd.org Cc: Niels Provos <provos@monkey.org> Subject: kqueue, NOTE_EOF Message-ID: <20031110174109.GA13852@monkey.org>
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hi -
in order to be able to preserve consistent semantics across poll,
select, and kqueue (EVFILT_READ), i propose the following change: on
EVFILT_READ, add an fflag NOTE_EOF which will return when the file
pointer *is* at the end of the file (effectively always returning on
EVFILT_READ, but setting the NOTE_EOF flag when it is at the end).
specifically, this allows libevent[1] to behave consistently across
underlying polling infrastructures (this has become a practical
issue).
in openbsd, this was a trivial change in filt_ufsread():
kn->kn_data = ip->i_ffs_size - kn->kn_fp->f_offset;
+if (kn->kn_data == 0 && kn->kn_sfflags & NOTE_EOF) {
+ kn->kn_fflags |= NOTE_EOF;
+ return (1);
+}
+
return (kn->kn_data != 0);
(and adding NOTE_EOF to event.h, of course)
what do you think about this? can it be integrated into netbsd and
freebsd as well? i have discussed this with provos@, and we seem to
agree this is a viable solution.
thanks,
marius.
[1] http://monkey.org/~provos/libevent
--
> marius@monkey.org > http://monkey.org/~marius
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