symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
version of the library your program was compiled against.
-Usually, its a good idea to terminate if the major versions mismatch,
+Usually, it's a good idea to terminate if the major versions mismatch,
as this indicates an incompatible change. Minor versions are usually
compatible to older versions, so a larger minor version alone is usually
not a problem.
create, you also create another event loop. Libev itself does no locking
whatsoever, so if you mix calls to the same event loop in different
threads, make sure you lock (this is usually a bad idea, though, even if
-done correctly, because its hideous and inefficient).
+done correctly, because it's hideous and inefficient).
=over 4
=over 4
-=item EVFLAG_AUTO
+=item C<EVFLAG_AUTO>
-The default flags value. Use this if you have no clue (its the right
+The default flags value. Use this if you have no clue (it's the right
thing, believe me).
-=item EVFLAG_NOENV
+=item C<EVFLAG_NOENV>
If this flag bit is ored into the flag value (or the program runs setuid
or setgid) then libev will I<not> look at the environment variable
useful to try out specific backends to test their performance, or to work
around bugs.
-=item EVMETHOD_SELECT portable select backend
+=item C<EVMETHOD_SELECT> (portable select backend)
-=item EVMETHOD_POLL poll backend (everywhere except windows)
+=item C<EVMETHOD_POLL> (poll backend, available everywhere except on windows)
-=item EVMETHOD_EPOLL linux only
+=item C<EVMETHOD_EPOLL> (linux only)
-=item EVMETHOD_KQUEUE some bsds only
+=item C<EVMETHOD_KQUEUE> (some bsds only)
-=item EVMETHOD_DEVPOLL solaris 8 only
+=item C<EVMETHOD_DEVPOLL> (solaris 8 only)
-=item EVMETHOD_PORT solaris 10 only
+=item C<EVMETHOD_PORT> (solaris 10 only)
If one or more of these are ored into the flags value, then only these
backends will be tried (in the reverse order as given here). If one are
Destroys the default loop again (frees all memory and kernel state
etc.). This stops all registered event watchers (by not touching them in
-any way whatsoever, although you cnanot rely on this :).
+any way whatsoever, although you cannot rely on this :).
=item ev_loop_destroy (loop)
use the event library in both processes. If you just fork+exec, you don't
have to call it.
-The function itself is quite fast and its usually not a problem to call
+The function itself is quite fast and it's usually not a problem to call
it just in case after a fork. To make this easy, the function will fit in
quite nicely into a call to C<pthread_atfork>:
Returns one of the C<EVMETHOD_*> flags indicating the event backend in
use.
-=item ev_tstamp = ev_now (loop)
+=item ev_tstamp ev_now (loop)
Returns the current "event loop time", which is the time the event loop
got events and started processing them. This timestamp does not change
A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
those events and any outstanding ones, but will not block your process in
-case there are no events.
+case there are no events and will return after one iteration of the loop.
A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
neccessary) and will handle those and any outstanding ones. It will block
-your process until at least one new event arrives.
+your process until at least one new event arrives, and will return after
+one iteration of the loop.
This flags value could be used to implement alternative looping
constructs, but the C<prepare> and C<check> watchers provide a better and
=item ev_unloop (loop, how)
-Can be used to make a call to C<ev_loop> return early. The C<how> argument
-must be either C<EVUNLOOP_ONCE>, which will make the innermost C<ev_loop>
-call return, or C<EVUNLOOP_ALL>, which will make all nested C<ev_loop>
-calls return.
+Can be used to make a call to C<ev_loop> return early (but only after it
+has processed all outstanding events). The C<how> argument must be either
+C<EVUNLOOP_ONCE>, which will make the innermost C<ev_loop> call return, or
+C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
=item ev_ref (loop)
=item ev_unref (loop)
-Ref/unref can be used to add or remove a refcount on the event loop: Every
-watcher keeps one reference. If you have a long-runing watcher you never
-unregister that should not keep ev_loop from running, ev_unref() after
-starting, and ev_ref() before stopping it. Libev itself uses this for
-example for its internal signal pipe: It is not visible to you as a user
-and should not keep C<ev_loop> from exiting if the work is done. It is
-also an excellent way to do this for generic recurring timers or from
-within third-party libraries. Just remember to unref after start and ref
-before stop.
+Ref/unref can be used to add or remove a reference count on the event
+loop: Every watcher keeps one reference, and as long as the reference
+count is nonzero, C<ev_loop> will not return on its own. If you have
+a watcher you never unregister that should not keep C<ev_loop> from
+returning, ev_unref() after starting, and ev_ref() before stopping it. For
+example, libev itself uses this for its internal signal pipe: It is not
+visible to the libev user and should not keep C<ev_loop> from exiting if
+no event watchers registered by it are active. It is also an excellent
+way to do this for generic recurring timers or from within third-party
+libraries. Just remember to I<unref after start> and I<ref before stop>.
=back
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 ev_io watcher for that:
+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)
{
=over 4
-=item EV_READ
+=item C<EV_READ>
-=item EV_WRITE
+=item C<EV_WRITE>
-The file descriptor in the ev_io watcher has become readable and/or
+The file descriptor in the C<ev_io> watcher has become readable and/or
writable.
-=item EV_TIMEOUT
+=item C<EV_TIMEOUT>
-The ev_timer watcher has timed out.
+The C<ev_timer> watcher has timed out.
-=item EV_PERIODIC
+=item C<EV_PERIODIC>
-The ev_periodic watcher has timed out.
+The C<ev_periodic> watcher has timed out.
-=item EV_SIGNAL
+=item C<EV_SIGNAL>
-The signal specified in the ev_signal watcher has been received by a thread.
+The signal specified in the C<ev_signal> watcher has been received by a thread.
-=item EV_CHILD
+=item C<EV_CHILD>
-The pid specified in the ev_child watcher has received a status change.
+The pid specified in the C<ev_child> watcher has received a status change.
-=item EV_IDLE
+=item C<EV_IDLE>
-The ev_idle watcher has determined that you have nothing better to do.
+The C<ev_idle> watcher has determined that you have nothing better to do.
-=item EV_PREPARE
+=item C<EV_PREPARE>
-=item EV_CHECK
+=item C<EV_CHECK>
-All ev_prepare watchers are invoked just I<before> C<ev_loop> starts
-to gather new events, and all ev_check watchers are invoked just after
+All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts
+to gather new events, and all C<ev_check> watchers are invoked just after
C<ev_loop> has gathered them, but before it invokes any callbacks for any
received events. Callbacks of both watcher types can start and stop as
many watchers as they want, and all of them will be taken into account
-(for example, a ev_prepare watcher might start an idle watcher to keep
+(for example, a C<ev_prepare> watcher might start an idle watcher to keep
C<ev_loop> from blocking).
-=item EV_ERROR
+=item C<EV_ERROR>
An unspecified error has occured, the watcher has been stopped. This might
happen because the watcher could not be properly started because libev
This section describes each watcher in detail, but will not repeat
information given in the last section.
-=head2 struct ev_io - is my file descriptor readable or writable
+=head2 C<ev_io> - is this file descriptor readable or writable
I/O watchers check whether a file descriptor is readable or writable
in each iteration of the event loop (This behaviour is called
=item ev_io_set (ev_io *, int fd, int events)
-Configures an ev_io watcher. The fd is the file descriptor to rceeive
+Configures an C<ev_io> watcher. The fd is the file descriptor to rceeive
events for and events is either C<EV_READ>, C<EV_WRITE> or C<EV_READ |
EV_WRITE> to receive the given events.
=back
-=head2 struct ev_timer - relative and optionally recurring timeouts
+=head2 C<ev_timer> - relative and optionally recurring timeouts
Timer watchers are simple relative timers that generate an event after a
given time, and optionally repeating in regular intervals after that.
detecting time jumps is hard, and soem inaccuracies are unavoidable (the
monotonic clock option helps a lot here).
+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 *need* to base the timeout
+ion the current time, use something like this to adjust for this:
+
+ ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
+
=over 4
=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
example: Imagine you have a tcp connection and you want a so-called idle
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 ev_timer with after=repeat=60 and calling ev_timer_again each
+configure an C<ev_timer> with after=repeat=60 and calling 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 stop
the timer, and again will automatically restart it if need be.
=back
-=head2 ev_periodic - to cron or not to cron it
+=head2 C<ev_periodic> - to cron or not to cron it
Periodic watchers are also timers of a kind, but they are very versatile
(and unfortunately a bit complex).
-Unlike ev_timer's, they are not based on real time (or relative time)
+Unlike C<ev_timer>'s, they are not based on real time (or relative time)
but on wallclock time (absolute time). You can tell a periodic watcher
to trigger "at" some specific point in time. For example, if you tell a
periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now ()
+ 10.>) and then reset your system clock to the last year, then it will
-take a year to trigger the event (unlike an ev_timer, which would trigger
+take a year to trigger the event (unlike an C<ev_timer>, which would trigger
roughly 10 seconds later and of course not if you reset your system time
again).
This doesn't mean there will always be 3600 seconds in between triggers,
but only that the the callback will be called when the system time shows a
-full hour (UTC), or more correct, when the system time is evenly divisible
+full hour (UTC), or more correctly, when the system time is evenly divisible
by 3600.
Another way to think about it (for the mathematically inclined) is that
-ev_periodic will try to run the callback in this mode at the next possible
+C<ev_periodic> will try to run the callback in this mode at the next possible
time where C<time = at (mod interval)>, regardless of any time jumps.
=item * manual reschedule mode (reschedule_cb = callback)
current time as second argument.
NOTE: I<This callback MUST NOT stop or destroy the periodic or any other
-periodic watcher, ever, or make any event loop modificstions>. If you need
-to stop it, return 1e30 (or so, fudge fudge) and stop it afterwards.
+periodic watcher, ever, or make any event loop modifications>. If you need
+to stop it, return C<now + 1e30> (or so, fudge fudge) and stop it afterwards.
+
+Also, I<<this callback must always return a time that is later than the
+passed C<now> value >>. Not even C<now> itself will be ok.
Its prototype is c<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
ev_tstamp now)>, e.g.:
=back
-=head2 ev_signal - signal me when a signal gets signalled
+=head2 C<ev_signal> - signal me when a signal gets signalled
Signal watchers will trigger an event when the process receives a specific
signal one or more times. Even though signals are very asynchronous, libev
-will try its best to deliver signals synchronously, i.e. as part of the
+will try it's best to deliver signals synchronously, i.e. as part of the
normal event processing, like any other event.
You cna configure as many watchers as you like per signal. Only when the
=back
-=head2 ev_child - wait for pid status changes
+=head2 C<ev_child> - wait for pid status changes
Child watchers trigger when your process receives a SIGCHLD in response to
some child status changes (most typically when a child of yours dies).
=back
-=head2 ev_idle - when you've got nothing better to do
+=head2 C<ev_idle> - when you've got nothing better to do
Idle watchers trigger events when there are no other I/O or timer (or
periodic) events pending. That is, as long as your process is busy
watchers, integrate net-snmp or a coroutine library and lots more.
This is done by examining in each prepare call which file descriptors need
-to be watched by the other library, registering ev_io watchers for them
-and starting an ev_timer watcher for any timeouts (many libraries provide
+to be watched by the other library, registering C<ev_io> watchers for them
+and starting an C<ev_timer> watcher for any timeouts (many libraries provide
just this functionality). Then, in the check watcher you check for any
events that occured (by making your callbacks set soem flags for example)
and call back into the library.
more watchers yourself.
If C<fd> is less than 0, then no I/O watcher will be started and events is
-ignored. Otherwise, an ev_io watcher for the given C<fd> and C<events> set
+ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and C<events> set
will be craeted and started.
If C<timeout> is less than 0, then no timeout watcher will be
-started. Otherwise an ev_timer watcher with after = C<timeout> (and repeat
+started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and repeat
= 0) will be started.
The callback has the type C<void (*cb)(int revents, void *arg)> and
-gets passed an events set (normally a combination of EV_ERROR, EV_READ,
-
EV_WRITE or EV_TIMEOUT) and the C<arg> value passed to C<ev_once>:
+gets passed an events set (normally 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>:
static void stdin_ready (int revents, void *arg)
{
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