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

Comparing libev/ev.pod (file contents):
Revision 1.191 by root, Tue Sep 30 19:45:23 2008 UTC vs.
Revision 1.204 by root, Mon Oct 27 11:08:29 2008 UTC

    // a single header file is required
    #include <ev.h>
    // every watcher type has its own typedef'd struct
-   // with the name ev_<type>
+   // with the name ev_TYPE
    ev_io stdin_watcher;
    ev_timer timeout_watcher;
    // all watcher callbacks have a similar signature
    // this callback is called when data is readable on stdin
    static void
-   stdin_cb (EV_P_ struct ev_io *w, int revents)
+   stdin_cb (EV_P_ ev_io *w, int revents)
    {
      puts ("stdin ready");
      // for one-shot events, one must manually stop the watcher
      // with its corresponding stop function.
      ev_io_stop (EV_A_ w);
      ev_unloop (EV_A_ EVUNLOOP_ALL);
    }
    // another callback, this time for a time-out
    static void
-   timeout_cb (EV_P_ struct ev_timer *w, int revents)
+   timeout_cb (EV_P_ ev_timer *w, int revents)
    {
      puts ("timeout");
      // this causes the innermost ev_loop to stop iterating
      ev_unloop (EV_A_ EVUNLOOP_ONE);
    }
    int
    main (void)
    {
      // use the default event loop unless you have special needs
-     struct ev_loop *loop = ev_default_loop (0);
+     ev_loop *loop = ev_default_loop (0);
      // initialise an io watcher, then start it
      // this one will watch for stdin to become readable
      ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
      ev_io_start (loop, &stdin_watcher);
 Libev is very configurable. In this manual the default (and most common)
 configuration will be described, which supports multiple event loops. For
 more info about various configuration options please have a look at
 B<EMBED> section in this manual. If libev was configured without support
 for multiple event loops, then all functions taking an initial argument of
-name C<loop> (which is always of type C<struct ev_loop *>) will not have
+name C<loop> (which is always of type C<ev_loop *>) will not have
 this argument.
 =head2 TIME REPRESENTATION
 Libev represents time as a single floating point number, representing the
 =back
 =head1 FUNCTIONS CONTROLLING THE EVENT LOOP
-An event loop is described by a C<struct ev_loop *>. The library knows two
+An event loop is described by a C<struct ev_loop *> (the C<struct>
-types of such loops, the I<default> loop, which supports signals and child
+is I<not> optional in this case, as there is also an C<ev_loop>
-events, and dynamically created loops which do not.
+I<function>).
+The library knows two types of such loops, the I<default> loop, which
+supports signals and child events, and dynamically created loops which do
+not.
 =over 4
 =item struct ev_loop *ev_default_loop (unsigned int flags)
 epoll scales either O(1) or O(active_fds). The epoll design has a number
 of shortcomings, such as silently dropping events in some hard-to-detect
 cases and requiring a system call per fd change, no fork support and bad
 support for dup.
+Epoll is also notoriously buggy - embedding epoll fds should work, but
+of course doesn't, and epoll just loves to report events for totally
+I<different> file descriptors (even already closed ones) than registered
+in the set (especially on SMP systems). Libev tries to counter these
+spurious notifications by employing an additional generation counter and
+comparing that against the events to filter out spurious ones.
 While stopping, setting and starting an I/O watcher in the same iteration
 will result in some caching, there is still a system call per such incident
 (because the fd could point to a different file description now), so its
 best to avoid that. Also, C<dup ()>'ed file descriptors might not work
 very well if you register events for both fds.
-Please note that epoll sometimes generates spurious notifications, so you
-need to use non-blocking I/O or other means to avoid blocking when no data
-(or space) is available.
 Best performance from this backend is achieved by not unregistering all
 watchers for a file descriptor until it has been closed, if possible,
 i.e. keep at least one watcher active per fd at all times. Stopping and
 starting a watcher (without re-setting it) also usually doesn't cause
 responsibility to either stop all watchers cleanly yourself I<before>
 calling this function, or cope with the fact afterwards (which is usually
 the easiest thing, you can just ignore the watchers and/or C<free ()> them
 for example).
-Note that certain global state, such as signal state, will not be freed by
+Note that certain global state, such as signal state (and installed signal
-this function, and related watchers (such as signal and child watchers)
+handlers), will not be freed by this function, and related watchers (such
-would need to be stopped manually.
+as signal and child watchers) would need to be stopped manually.
 In general it is not advisable to call this function except in the
 rare occasion where you really need to free e.g. the signal handling
 pipe fds. If you need dynamically allocated loops it is better to use
 C<ev_loop_new> and C<ev_loop_destroy>).
 C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
 C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
 This "unloop state" will be cleared when entering C<ev_loop> again.
+It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
 =item ev_ref (loop)
 =item ev_unref (loop)
 Ref/unref can be used to add or remove a reference count on the event
 respectively).
 Example: Create a signal watcher, but keep it from keeping C<ev_loop>
 running when nothing else is active.
-   struct ev_signal exitsig;
+   ev_signal exitsig;
    ev_signal_init (&exitsig, sig_cb, SIGINT);
    ev_signal_start (loop, &exitsig);
    evf_unref (loop);
 Example: For some weird reason, unregister the above signal handler again.
 they fire on, say, one-second boundaries only.
 =item ev_loop_verify (loop)
 This function only does something when C<EV_VERIFY> support has been
-compiled in. which is the default for non-minimal builds. It tries to go
+compiled in, which is the default for non-minimal builds. It tries to go
 through all internal structures and checks them for validity. If anything
 is found to be inconsistent, it will print an error message to standard
 error and call C<abort ()>.
 This can be used to catch bugs inside libev itself: under normal
 =back
 =head1 ANATOMY OF A WATCHER
+In the following description, uppercase C<TYPE> in names stands for the
+watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
+watchers and C<ev_io_start> for I/O watchers.
 A watcher is a structure that you create and register to record your
 interest in some event. For instance, if you want to wait for STDIN to
 become readable, you would create an C<ev_io> watcher for that:
-   static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
+   static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
    {
      ev_io_stop (w);
      ev_unloop (loop, EVUNLOOP_ALL);
    }
    struct ev_loop *loop = ev_default_loop (0);
-   struct ev_io stdin_watcher;
+   ev_io stdin_watcher;
    ev_init (&stdin_watcher, my_cb);
    ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
    ev_io_start (loop, &stdin_watcher);
    ev_loop (loop, 0);
 As you can see, you are responsible for allocating the memory for your
-watcher structures (and it is usually a bad idea to do this on the stack,
+watcher structures (and it is I<usually> a bad idea to do this on the
-although this can sometimes be quite valid).
+stack).
+Each watcher has an associated watcher structure (called C<struct ev_TYPE>
+or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
 Each watcher structure must be initialised by a call to C<ev_init
 (watcher *, callback)>, which expects a callback to be provided. This
 callback gets invoked each time the event occurs (or, in the case of I/O
 watchers, each time the event loop detects that the file descriptor given
 is readable and/or writable).
-Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro
+Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
-with arguments specific to this watcher type. There is also a macro
+macro to configure it, with arguments specific to the watcher type. There
-to combine initialisation and setting in one call: C<< ev_<type>_init
+is also a macro to combine initialisation and setting in one call: C<<
-(watcher *, callback, ...) >>.
+ev_TYPE_init (watcher *, callback, ...) >>.
 To make the watcher actually watch out for events, you have to start it
-with a watcher-specific start function (C<< ev_<type>_start (loop, watcher
+with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
 *) >>), and you can stop watching for events at any time by calling the
-corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.
+corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
 As long as your watcher is active (has been started but not stopped) you
 must not touch the values stored in it. Most specifically you must never
-reinitialise it or call its C<set> macro.
+reinitialise it or call its C<ev_TYPE_set> macro.
 Each and every callback receives the event loop pointer as first, the
 registered watcher structure as second, and a bitset of received events as
 third argument.
 =item C<EV_ERROR>
 An unspecified error has occurred, the watcher has been stopped. This might
 happen because the watcher could not be properly started because libev
 ran out of memory, a file descriptor was found to be closed or any other
+problem. Libev considers these application bugs.
-problem. You best act on it by reporting the problem and somehow coping
+You best act on it by reporting the problem and somehow coping with the
-with the watcher being stopped.
+watcher being stopped. Note that well-written programs should not receive
+an error ever, so when your watcher receives it, this usually indicates a
+bug in your program.
 Libev will usually signal a few "dummy" events together with an error, for
 example it might indicate that a fd is readable or writable, and if your
 callbacks is well-written it can just attempt the operation and cope with
 the error from read() or write(). This will not work in multi-threaded
 =back
 =head2 GENERIC WATCHER FUNCTIONS
-In the following description, C<TYPE> stands for the watcher type,
-e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
 =over 4
 =item C<ev_init> (ev_TYPE *watcher, callback)
 This macro initialises the generic portion of a watcher. The contents
 which rolls both calls into one.
 You can reinitialise a watcher at any time as long as it has been stopped
 (or never started) and there are no pending events outstanding.
-The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
+The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
 int revents)>.
 Example: Initialise an C<ev_io> watcher in two steps.
    ev_io w;
    ev_io_start (EV_DEFAULT_UC, &w);
 =item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
-Stops the given watcher again (if active) and clears the pending
+Stops the given watcher if active, and clears the pending status (whether
+the watcher was active or not).
-status. It is possible that stopped watchers are pending (for example,
+It is possible that stopped watchers are pending - for example,
-non-repeating timers are being stopped when they become pending), but
+non-repeating timers are being stopped when they become pending - but
-C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If
+calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
-you want to free or reuse the memory used by the watcher it is therefore a
+pending. If you want to free or reuse the memory used by the watcher it is
-good idea to always call its C<ev_TYPE_stop> function.
+therefore a good idea to always call its C<ev_TYPE_stop> function.
 =item bool ev_is_active (ev_TYPE *watcher)
 Returns a true value iff the watcher is active (i.e. it has been started
 and not yet been stopped). As long as a watcher is active you must not modify
 The default priority used by watchers when no priority has been set is
 always C<0>, which is supposed to not be too high and not be too low :).
 Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
 fine, as long as you do not mind that the priority value you query might
-or might not have been adjusted to be within valid range.
+or might not have been clamped to the valid range.
 =item ev_invoke (loop, ev_TYPE *watcher, int revents)
 Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
 C<loop> nor C<revents> need to be valid as long as the watcher callback
 member, you can also "subclass" the watcher type and provide your own
 data:
    struct my_io
    {
-     struct ev_io io;
+     ev_io io;
      int otherfd;
      void *somedata;
      struct whatever *mostinteresting;
    };
    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)
+   static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
    {
      struct my_io *w = (struct my_io *)w_;
      ...
    }
 programmers):
    #include <stddef.h>
    static void
-   t1_cb (EV_P_ struct ev_timer *w, int revents)
+   t1_cb (EV_P_ ev_timer *w, int revents)
    {
      struct my_biggy big = (struct my_biggy *
        (((char *)w) - offsetof (struct my_biggy, t1));
    }
    static void
-   t2_cb (EV_P_ struct ev_timer *w, int revents)
+   t2_cb (EV_P_ ev_timer *w, int revents)
    {
      struct my_biggy big = (struct my_biggy *
        (((char *)w) - offsetof (struct my_biggy, t2));
    }
 Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
 readable, but only once. Since it is likely line-buffered, you could
 attempt to read a whole line in the callback.
    static void
-   stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
+   stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
    {
       ev_io_stop (loop, w);
      .. read from stdin here (or from w->fd) and handle any I/O errors
    }
    ...
    struct ev_loop *loop = ev_default_init (0);
-   struct ev_io stdin_readable;
+   ev_io stdin_readable;
    ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
    ev_io_start (loop, &stdin_readable);
    ev_loop (loop, 0);
 The callback is guaranteed to be invoked only I<after> its timeout has
 passed, but if multiple timers become ready during the same loop iteration
 then order of execution is undefined.
+=head3 Be smart about timeouts
+Many real-world problems involve some kind of timeout, usually for error
+recovery. A typical example is an HTTP request - if the other side hangs,
+you want to raise some error after a while.
+What follows are some ways to handle this problem, from obvious and
+inefficient to smart and efficient.
+In the following, a 60 second activity timeout is assumed - a timeout that
+gets reset to 60 seconds each time there is activity (e.g. each time some
+data or other life sign was received).
+=over 4
+=item 1. Use a timer and stop, reinitialise and start it on activity.
+This is the most obvious, but not the most simple way: In the beginning,
+start the watcher:
+   ev_timer_init (timer, callback, 60., 0.);
+   ev_timer_start (loop, timer);
+Then, each time there is some activity, C<ev_timer_stop> it, initialise it
+and start it again:
+   ev_timer_stop (loop, timer);
+   ev_timer_set (timer, 60., 0.);
+   ev_timer_start (loop, timer);
+This is relatively simple to implement, but means that each time there is
+some activity, libev will first have to remove the timer from its internal
+data structure and then add it again. Libev tries to be fast, but it's
+still not a constant-time operation.
+=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
+This is the easiest way, and involves using C<ev_timer_again> instead of
+C<ev_timer_start>.
+To implement this, configure an C<ev_timer> with a C<repeat> value
+of C<60> and then call C<ev_timer_again> at start and each time you
+successfully read or write some data. If you go into an idle state where
+you do not expect data to travel on the socket, you can C<ev_timer_stop>
+the timer, and C<ev_timer_again> will automatically restart it if need be.
+That means you can ignore both the C<ev_timer_start> function and the
+C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
+member and C<ev_timer_again>.
+At start:
+   ev_timer_init (timer, callback);
+   timer->repeat = 60.;
+   ev_timer_again (loop, timer);
+Each time there is some activity:
+   ev_timer_again (loop, timer);
+It is even possible to change the time-out on the fly, regardless of
+whether the watcher is active or not:
+   timer->repeat = 30.;
+   ev_timer_again (loop, timer);
+This is slightly more efficient then stopping/starting the timer each time
+you want to modify its timeout value, as libev does not have to completely
+remove and re-insert the timer from/into its internal data structure.
+It is, however, even simpler than the "obvious" way to do it.
+=item 3. Let the timer time out, but then re-arm it as required.
+This method is more tricky, but usually most efficient: Most timeouts are
+relatively long compared to the intervals between other activity - in
+our example, within 60 seconds, there are usually many I/O events with
+associated activity resets.
+In this case, it would be more efficient to leave the C<ev_timer> alone,
+but remember the time of last activity, and check for a real timeout only
+within the callback:
+   ev_tstamp last_activity; // time of last activity
+   static void
+   callback (EV_P_ ev_timer *w, int revents)
+   {
+     ev_tstamp now     = ev_now (EV_A);
+     ev_tstamp timeout = last_activity + 60.;
+     // if last_activity + 60. is older than now, we did time out
+     if (timeout < now)
+       {
+         // timeout occured, take action
+       }
+     else
+       {
+         // callback was invoked, but there was some activity, re-arm
+         // the watcher to fire in last_activity + 60, which is
+         // guaranteed to be in the future, so "again" is positive:
+         w->again = timeout - now;
+         ev_timer_again (EV_A_ w);
+       }
+   }
+To summarise the callback: first calculate the real timeout (defined
+as "60 seconds after the last activity"), then check if that time has
+been reached, which means something I<did>, in fact, time out. Otherwise
+the callback was invoked too early (C<timeout> is in the future), so
+re-schedule the timer to fire at that future time, to see if maybe we have
+a timeout then.
+Note how C<ev_timer_again> is used, taking advantage of the
+C<ev_timer_again> optimisation when the timer is already running.
+This scheme causes more callback invocations (about one every 60 seconds
+minus half the average time between activity), but virtually no calls to
+libev to change the timeout.
+To start the timer, simply initialise the watcher and set C<last_activity>
+to the current time (meaning we just have some activity :), then call the
+callback, which will "do the right thing" and start the timer:
+   ev_timer_init (timer, callback);
+   last_activity = ev_now (loop);
+   callback (loop, timer, EV_TIMEOUT);
+And when there is some activity, simply store the current time in
+C<last_activity>, no libev calls at all:
+   last_actiivty = ev_now (loop);
+This technique is slightly more complex, but in most cases where the
+time-out is unlikely to be triggered, much more efficient.
+Changing the timeout is trivial as well (if it isn't hard-coded in the
+callback :) - just change the timeout and invoke the callback, which will
+fix things for you.
+=item 4. Wee, just use a double-linked list for your timeouts.
+If there is not one request, but many thousands (millions...), all
+employing some kind of timeout with the same timeout value, then one can
+do even better:
+When starting the timeout, calculate the timeout value and put the timeout
+at the I<end> of the list.
+Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
+the list is expected to fire (for example, using the technique #3).
+When there is some activity, remove the timer from the list, recalculate
+the timeout, append it to the end of the list again, and make sure to
+update the C<ev_timer> if it was taken from the beginning of the list.
+This way, one can manage an unlimited number of timeouts in O(1) time for
+starting, stopping and updating the timers, at the expense of a major
+complication, and having to use a constant timeout. The constant timeout
+ensures that the list stays sorted.
+=back
+So which method the best?
+Method #2 is a simple no-brain-required solution that is adequate in most
+situations. Method #3 requires a bit more thinking, but handles many cases
+better, and isn't very complicated either. In most case, choosing either
+one is fine, with #3 being better in typical situations.
+Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
+rather complicated, but extremely efficient, something that really pays
+off after the first million or so of active timers, i.e. it's usually
+overkill :)
 =head3 The special problem of time updates
 Establishing the current time is a costly operation (it usually takes at
 least two system calls): EV therefore updates its idea of the current
 time only before and after C<ev_loop> collects new events, which causes a
 If the timer is started but non-repeating, stop it (as if it timed out).
 If the timer is repeating, either start it if necessary (with the
 C<repeat> value), or reset the running timer to the C<repeat> value.
-This sounds a bit complicated, but here is a useful and typical
+This sounds a bit complicated, see "Be smart about timeouts", above, for a
-example: Imagine you have a TCP connection and you want a so-called idle
+usage example.
-timeout, that is, you want to be called when there have been, say, 60
-seconds of inactivity on the socket. The easiest way to do this is to
-configure an C<ev_timer> with a C<repeat> value of C<60> and then call
-C<ev_timer_again> each time you successfully read or write some data. If
-you go into an idle state where you do not expect data to travel on the
-socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
-automatically restart it if need be.
-That means you can ignore the C<after> value and C<ev_timer_start>
-altogether and only ever use the C<repeat> value and C<ev_timer_again>:
-   ev_timer_init (timer, callback, 0., 5.);
-   ev_timer_again (loop, timer);
-   ...
-   timer->again = 17.;
-   ev_timer_again (loop, timer);
-   ...
-   timer->again = 10.;
-   ev_timer_again (loop, timer);
-This is more slightly efficient then stopping/starting the timer each time
-you want to modify its timeout value.
-Note, however, that it is often even more efficient to remember the
-time of the last activity and let the timer time-out naturally. In the
-callback, you then check whether the time-out is real, or, if there was
-some activity, you reschedule the watcher to time-out in "last_activity +
-timeout - ev_now ()" seconds.
 =item ev_tstamp repeat [read-write]
 The current C<repeat> value. Will be used each time the watcher times out
 or C<ev_timer_again> is called, and determines the next timeout (if any),
 =head3 Examples
 Example: Create a timer that fires after 60 seconds.
    static void
-   one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
+   one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
    {
      .. one minute over, w is actually stopped right here
    }
-   struct ev_timer mytimer;
+   ev_timer mytimer;
    ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
    ev_timer_start (loop, &mytimer);
 Example: Create a timeout timer that times out after 10 seconds of
 inactivity.
    static void
-   timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
+   timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
    {
      .. ten seconds without any activity
    }
-   struct ev_timer mytimer;
+   ev_timer mytimer;
    ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
    ev_timer_again (&mytimer); /* start timer */
    ev_loop (loop, 0);
    // and in some piece of code that gets executed on any "activity":
 If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
 it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
 only event loop modification you are allowed to do).
-The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic
+The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
 *w, ev_tstamp now)>, e.g.:
+   static ev_tstamp
-   static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
+   my_rescheduler (ev_periodic *w, ev_tstamp now)
    {
      return now + 60.;
    }
 It must return the next time to trigger, based on the passed time value
 The current interval value. Can be modified any time, but changes only
 take effect when the periodic timer fires or C<ev_periodic_again> is being
 called.
-=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]
+=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
 The current reschedule callback, or C<0>, if this functionality is
 switched off. Can be changed any time, but changes only take effect when
 the periodic timer fires or C<ev_periodic_again> is being called.
 Example: Call a callback every hour, or, more precisely, whenever the
 system time is divisible by 3600. The callback invocation times have
 potentially a lot of jitter, but good long-term stability.
    static void
-   clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
+   clock_cb (struct ev_loop *loop, ev_io *w, int revents)
    {
      ... its now a full hour (UTC, or TAI or whatever your clock follows)
    }
-   struct ev_periodic hourly_tick;
+   ev_periodic hourly_tick;
    ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
    ev_periodic_start (loop, &hourly_tick);
 Example: The same as above, but use a reschedule callback to do it:
    #include <math.h>
    static ev_tstamp
-   my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
+   my_scheduler_cb (ev_periodic *w, ev_tstamp now)
    {
      return now + (3600. - fmod (now, 3600.));
    }
    ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
 Example: Call a callback every hour, starting now:
-   struct ev_periodic hourly_tick;
+   ev_periodic hourly_tick;
    ev_periodic_init (&hourly_tick, clock_cb,
                      fmod (ev_now (loop), 3600.), 3600., 0);
    ev_periodic_start (loop, &hourly_tick);
 =head3 Examples
 Example: Try to exit cleanly on SIGINT.
    static void
-   sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
+   sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
    {
      ev_unloop (loop, EVUNLOOP_ALL);
    }
-   struct ev_signal signal_watcher;
+   ev_signal signal_watcher;
    ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
    ev_signal_start (loop, &signal_watcher);
 =head2 C<ev_child> - watch out for process status changes
 its completion.
    ev_child cw;
    static void
-   child_cb (EV_P_ struct ev_child *w, int revents)
+   child_cb (EV_P_ ev_child *w, int revents)
    {
      ev_child_stop (EV_A_ w);
      printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
    }
 to exchange stat structures with application programs compiled using the
 default compilation environment.
 =head3 Inotify and Kqueue
-When C<inotify (7)> support has been compiled into libev (generally only
+When C<inotify (7)> support has been compiled into libev (generally
+only available with Linux 2.6.25 or above due to bugs in earlier
-available with Linux) and present at runtime, it will be used to speed up
+implementations) and present at runtime, it will be used to speed up
-change detection where possible. The inotify descriptor will be created lazily
+change detection where possible. The inotify descriptor will be created
-when the first C<ev_stat> watcher is being started.
+lazily when the first C<ev_stat> watcher is being started.
 Inotify presence does not change the semantics of C<ev_stat> watchers
 except that changes might be detected earlier, and in some cases, to avoid
 making regular C<stat> calls. Even in the presence of inotify support
 there are many cases where libev has to resort to regular C<stat> polling,
 Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
 callback, free it. Also, use no error checking, as usual.
    static void
-   idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
+   idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
    {
      free (w);
      // now do something you wanted to do when the program has
      // no longer anything immediate to do.
    }
-   struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
+   ev_idle *idle_watcher = malloc (sizeof (ev_idle));
    ev_idle_init (idle_watcher, idle_cb);
    ev_idle_start (loop, idle_cb);
 =head2 C<ev_prepare> and C<ev_check> - customise your event loop!
    static ev_io iow [nfd];
    static ev_timer tw;
    static void
-   io_cb (ev_loop *loop, ev_io *w, int revents)
+   io_cb (struct ev_loop *loop, ev_io *w, int revents)
    {
    }
    // create io watchers for each fd and a timer before blocking
    static void
-   adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
+   adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
    {
      int timeout = 3600000;
      struct pollfd fds [nfd];
      // actual code will need to loop here and realloc etc.
      adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
        }
    }
    // stop all watchers after blocking
    static void
-   adns_check_cb (ev_loop *loop, ev_check *w, int revents)
+   adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
    {
      ev_timer_stop (loop, &tw);
      for (int i = 0; i < nfd; ++i)
        {
 C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
 used).
    struct ev_loop *loop_hi = ev_default_init (0);
    struct ev_loop *loop_lo = 0;
-   struct ev_embed embed;
+   ev_embed embed;
    // see if there is a chance of getting one that works
    // (remember that a flags value of 0 means autodetection)
    loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
      ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
 kqueue implementation). Store the kqueue/socket-only event loop in
 C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
    struct ev_loop *loop = ev_default_init (0);
    struct ev_loop *loop_socket = 0;
-   struct ev_embed embed;
+   ev_embed embed;
    if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
      if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
        {
          ev_embed_init (&embed, 0, loop_socket);
 =over 4
 =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
 This function combines a simple timer and an I/O watcher, calls your
-callback on whichever event happens first and automatically stop both
+callback on whichever event happens first and automatically stops both
 watchers. This is useful if you want to wait for a single event on an fd
 or timeout without having to allocate/configure/start/stop/free one or
 more watchers yourself.
-If C<fd> is less than 0, then no I/O watcher will be started and events
+If C<fd> is less than 0, then no I/O watcher will be started and the
-is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
+C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
-C<events> set will be created and started.
+the given C<fd> and C<events> set will be created and started.
 If C<timeout> is less than 0, then no timeout watcher will be
 started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
-repeat = 0) will be started. While C<0> is a valid timeout, it is of
+repeat = 0) will be started. C<0> is a valid timeout.
-dubious value.
 The callback has the type C<void (*cb)(int revents, void *arg)> and gets
 passed an C<revents> set like normal event callbacks (a combination of
 C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
-value passed to C<ev_once>:
+value passed to C<ev_once>. Note that it is possible to receive I<both>
+a timeout and an io event at the same time - you probably should give io
+events precedence.
+Example: wait up to ten seconds for data to appear on STDIN_FILENO.
    static void stdin_ready (int revents, void *arg)
    {
+     if (revents & EV_READ)
+       /* stdin might have data for us, joy! */;
-     if (revents & EV_TIMEOUT)
+     else if (revents & EV_TIMEOUT)
        /* doh, nothing entered */;
-     else if (revents & EV_READ)
-       /* stdin might have data for us, joy! */;
    }
    ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
-=item ev_feed_event (ev_loop *, watcher *, int revents)
+=item ev_feed_event (struct ev_loop *, watcher *, int revents)
 Feeds the given event set into the event loop, as if the specified event
 had happened for the specified watcher (which must be a pointer to an
 initialised but not necessarily started event watcher).
-=item ev_feed_fd_event (ev_loop *, int fd, int revents)
+=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
 Feed an event on the given fd, as if a file descriptor backend detected
 the given events it.
-=item ev_feed_signal_event (ev_loop *loop, int signum)
+=item ev_feed_signal_event (struct ev_loop *loop, int signum)
 Feed an event as if the given signal occurred (C<loop> must be the default
 loop!).
 =back
 =item D
 Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
 be found at L<http://proj.llucax.com.ar/wiki/evd>.
+=item Ocaml
+Erkki Seppala has written Ocaml bindings for libev, to be found at
+L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
 =back
 =head1 MACRO MAGIC

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Comparing libev/ev.pod (file contents): Revision 1.191 by root, Tue Sep 30 19:45:23 2008 UTC vs. Revision 1.204 by root, Mon Oct 27 11:08:29 2008 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.191 by root, Tue Sep 30 19:45:23 2008 UTC vs.
Revision 1.204 by root, Mon Oct 27 11:08:29 2008 UTC