[ViewVC] Diff of: cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.175 by root, Mon Sep 8 16:36:14 2008 UTC vs.
Revision 1.179 by root, Sat Sep 13 19:14:21 2008 UTC

 writing a server, you should C<accept ()> in a loop to accept as many
 connections as possible during one iteration. You might also want to have
 a look at C<ev_set_io_collect_interval ()> to increase the amount of
 readiness notifications you get per iteration.
+This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
+C<writefds> set (and to work around Microsoft Windows bugs, also onto the
+C<exceptfds> set on that platform).
 =item C<EVBACKEND_POLL>    (value 2, poll backend, available everywhere except on windows)
 And this is your standard poll(2) backend. It's more complicated
 than select, but handles sparse fds better and has no artificial
 limit on the number of fds you can use (except it will slow down
 considerably with a lot of inactive fds). It scales similarly to select,
 i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
 performance tips.
+This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
+C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
 =item C<EVBACKEND_EPOLL>   (value 4, Linux)
 For few fds, this backend is a bit little slower than poll and select,
 but it scales phenomenally better. While poll and select usually scale
 keep at least one watcher active per fd at all times.
 While nominally embeddable in other event loops, this feature is broken in
 all kernel versions tested so far.
+This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
+C<EVBACKEND_POLL>.
 =item C<EVBACKEND_KQUEUE>  (value 8, most BSD clones)
 Kqueue deserves special mention, as at the time of this writing, it
 was broken on all BSDs except NetBSD (usually it doesn't work reliably
 with anything but sockets and pipes, except on Darwin, where of course
 almost everywhere, you should only use it when you have a lot of sockets
 (for which it usually works), by embedding it into another event loop
 (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for
 sockets.
+This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
+C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
+C<NOTE_EOF>.
 =item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
 This is not implemented yet (and might never be, unless you send me an
 implementation). According to reports, C</dev/poll> only supports sockets
 and is not embeddable, which would limit the usefulness of this backend
 might perform better.
 On the positive side, ignoring the spurious readiness notifications, this
 backend actually performed to specification in all tests and is fully
 embeddable, which is a rare feat among the OS-specific backends.
+This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
+C<EVBACKEND_POLL>.
 =item C<EVBACKEND_ALL>
 Try all backends (even potentially broken ones that wouldn't be tried
 with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
 Returns the current "event loop time", which is the time the event loop
 received events and started processing them. This timestamp does not
 change as long as callbacks are being processed, and this is also the base
 time used for relative timers. You can treat it as the timestamp of the
 event occurring (or more correctly, libev finding out about it).
+=item ev_now_update (loop)
+Establishes the current time by querying the kernel, updating the time
+returned by C<ev_now ()> in the progress. This is a costly operation and
+is usually done automatically within C<ev_loop ()>.
+This function is rarely useful, but when some event callback runs for a
+very long time without entering the event loop, updating libev's idea of
+the current time is a good idea.
+See also "The special problem of time updates" in the C<ev_timer> section.
 =item ev_loop (loop, int flags)
 Finally, this is it, the event handler. This function usually is called
 after you initialised all your watchers and you want to start handling
    {
      struct ev_io io;
      int otherfd;
      void *somedata;
      struct whatever *mostinteresting;
-   }
+   };
+   ...
+   struct my_io w;
+   ev_io_init (&w.io, my_cb, fd, EV_READ);
 And since your callback will be called with a pointer to the watcher, you
 can cast it back to your own type:
    static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
    }
 More interesting and less C-conformant ways of casting your callback type
 instead have been omitted.
-Another common scenario is having some data structure with multiple
+Another common scenario is to use some data structure with multiple
-watchers:
+embedded watchers:
    struct my_biggy
    {
      int some_data;
      ev_timer t1;
      ev_timer t2;
    }
-In this case getting the pointer to C<my_biggy> is a bit more complicated,
+In this case getting the pointer to C<my_biggy> is a bit more
-you need to use C<offsetof>:
+complicated: Either you store the address of your C<my_biggy> struct
+in the C<data> member of the watcher, or you need to use some pointer
+arithmetic using C<offsetof> inside your watchers:
    #include <stddef.h>
    static void
    t1_cb (EV_P_ struct ev_timer *w, int revents)
 but if multiple timers become ready during the same loop iteration then
 order of execution is undefined.
 =head3 The special problem of time updates
-Requesting the current time is a costly operation (it usually takes at
+Establishing the current time is a costly operation (it usually takes at
-least two syscalls): EV therefore updates it's idea of the current time
+least two system calls): EV therefore updates its idea of the current
-only before and after C<ev_loop> polls for new events, which causes the
+time only before and after C<ev_loop> polls for new events, which causes
-difference between C<ev_now ()> and C<ev_time ()>.
+a growing difference between C<ev_now ()> and C<ev_time ()> when handling
+lots of events.
 The relative timeouts are calculated relative to the C<ev_now ()>
 time. This is usually the right thing as this timestamp refers to the time
 of the event triggering whatever timeout you are modifying/starting. If
 you suspect event processing to be delayed and you I<need> to base the
 timeout on the current time, use something like this to adjust for this:
    ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
+If the event loop is suspended for a long time, you can also force an
+update of the time returned by C<ev_now ()> by calling C<ev_now_update
+()>.
 =head3 Watcher-Specific Functions and Data Members
 =over 4

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Comparing libev/ev.pod (file contents): Revision 1.175 by root, Mon Sep 8 16:36:14 2008 UTC vs. Revision 1.179 by root, Sat Sep 13 19:14:21 2008 UTC

Diff Legend

Comparing libev/ev.pod (file contents):
Revision 1.175 by root, Mon Sep 8 16:36:14 2008 UTC vs.
Revision 1.179 by root, Sat Sep 13 19:14:21 2008 UTC