(fractional) number of seconds since the (POSIX) epoch (somewhere near
the beginning of 1970, details are complicated, don't ask). This type is
called C<ev_tstamp>, which is what you should use too. It usually aliases
-to the double type in C.
+to the C<double> type in C, and when you need to do any calculations on
+it, you should treat it as such.
+
=head1 GLOBAL FUNCTIONS
=item ev_tstamp ev_time ()
-Returns the current time as libev would use it.
+Returns the current time as libev would use it. Please note that the
+C<ev_now> function is usually faster and also often returns the timestamp
+you actually want to know.
=item int ev_version_major ()
compatible to older versions, so a larger minor version alone is usually
not a problem.
+Example: make sure we haven't accidentally been linked against the wrong
+version:
+
+ assert (("libev version mismatch",
+ ev_version_major () == EV_VERSION_MAJOR
+ && ev_version_minor () >= EV_VERSION_MINOR));
+
+=item unsigned int ev_supported_backends ()
+
+Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
+value) compiled into this binary of libev (independent of their
+availability on the system you are running on). See C<ev_default_loop> for
+a description of the set values.
+
+Example: make sure we have the epoll method, because yeah this is cool and
+a must have and can we have a torrent of it please!!!11
+
+ assert (("sorry, no epoll, no sex",
+ ev_supported_backends () & EVBACKEND_EPOLL));
+
+=item unsigned int ev_recommended_backends ()
+
+Return the set of all backends compiled into this binary of libev and also
+recommended for this platform. This set is often smaller than the one
+returned by C<ev_supported_backends>, as for example kqueue is broken on
+most BSDs and will not be autodetected unless you explicitly request it
+(assuming you know what you are doing). This is the set of backends that
+libev will probe for if you specify no backends explicitly.
+
+=item unsigned int ev_embeddable_backends ()
+
+Returns the set of backends that are embeddable in other event loops. This
+is the theoretical, all-platform, value. To find which backends
+might be supported on the current system, you would need to look at
+C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
+recommended ones.
+
+See the description of C<ev_embed> watchers for more info.
+
=item ev_set_allocator (void *(*cb)(void *ptr, long size))
Sets the allocation function to use (the prototype is similar to the
free some memory if it cannot allocate memory, to use a special allocator,
or even to sleep a while and retry until some memory is available.
+Example: replace the libev allocator with one that waits a bit and then
+retries: better than mine).
+
+ static void *
+ persistent_realloc (void *ptr, long size)
+ {
+ for (;;)
+ {
+ void *newptr = realloc (ptr, size);
+
+ if (newptr)
+ return newptr;
+
+ sleep (60);
+ }
+ }
+
+ ...
+ ev_set_allocator (persistent_realloc);
+
=item ev_set_syserr_cb (void (*cb)(const char *msg));
Set the callback function to call on a retryable syscall error (such
requested operation, or, if the condition doesn't go away, do bad stuff
(such as abort).
+Example: do the same thing as libev does internally:
+
+ static void
+ fatal_error (const char *msg)
+ {
+ perror (msg);
+ abort ();
+ }
+
+ ...
+ ev_set_syserr_cb (fatal_error);
+
=back
=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
This will initialise the default event loop if it hasn't been initialised
yet and return it. If the default loop could not be initialised, returns
false. If it already was initialised it simply returns it (and ignores the
-flags).
+flags. If that is troubling you, check C<ev_backend ()> afterwards).
If you don't know what event loop to use, use the one returned from this
function.
The flags argument can be used to specify special behaviour or specific
-backends to use, and is usually specified as 0 (or EVFLAG_AUTO).
+backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
-It supports the following flags:
+The following flags are supported:
=over 4
useful to try out specific backends to test their performance, or to work
around bugs.
-=item C<EVMETHOD_SELECT> (portable select backend)
+=item C<EVBACKEND_SELECT> (value 1, portable select backend)
-=item C<EVMETHOD_POLL> (poll backend, available everywhere except on windows)
+This is your standard select(2) backend. Not I<completely> standard, as
+libev tries to roll its own fd_set with no limits on the number of fds,
+but if that fails, expect a fairly low limit on the number of fds when
+using this backend. It doesn't scale too well (O(highest_fd)), but its usually
+the fastest backend for a low number of fds.
-=item C<EVMETHOD_EPOLL> (linux only)
+=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
-=item C<EVMETHOD_KQUEUE> (some bsds only)
+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).
-=item C<EVMETHOD_DEVPOLL> (solaris 8 only)
+=item C<EVBACKEND_EPOLL> (value 4, Linux)
-=item C<EVMETHOD_PORT> (solaris 10 only)
+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 like
+O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
+either O(1) or O(active_fds).
-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
-specified, any backend will do.
+While stopping and starting an I/O watcher in the same iteration will
+result in some caching, there is still a syscall per such incident
+(because the fd could point to a different file description now), so its
+best to avoid that. Also, 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.
+
+=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 with
+anything but sockets and pipes, except on Darwin, where of course its
+completely useless). For this reason its not being "autodetected"
+unless you explicitly specify it explicitly in the flags (i.e. using
+C<EVBACKEND_KQUEUE>).
+
+It scales in the same way as the epoll backend, but the interface to the
+kernel is more efficient (which says nothing about its actual speed, of
+course). While starting and stopping an I/O watcher does not cause an
+extra syscall as with epoll, it still adds up to four event changes per
+incident, so its best to avoid that.
+
+=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
+
+This is not implemented yet (and might never be).
+
+=item C<EVBACKEND_PORT> (value 32, Solaris 10)
+
+This uses the Solaris 10 port mechanism. As with everything on Solaris,
+it's really slow, but it still scales very well (O(active_fds)).
+
+Please note that solaris ports can result in a lot of spurious
+notifications, so you need to use non-blocking I/O or other means to avoid
+blocking when no data (or space) is available.
+
+=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
+C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
=back
+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 none are
+specified, most compiled-in backend will be tried, usually in reverse
+order of their flag values :)
+
+The most typical usage is like this:
+
+ if (!ev_default_loop (0))
+ fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
+
+Restrict libev to the select and poll backends, and do not allow
+environment settings to be taken into account:
+
+ ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
+
+Use whatever libev has to offer, but make sure that kqueue is used if
+available (warning, breaks stuff, best use only with your own private
+event loop and only if you know the OS supports your types of fds):
+
+ ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
+
=item struct ev_loop *ev_loop_new (unsigned int flags)
Similar to C<ev_default_loop>, but always creates a new event loop that is
handle signal and child watchers, and attempts to do so will be greeted by
undefined behaviour (or a failed assertion if assertions are enabled).
+Example: try to create a event loop that uses epoll and nothing else.
+
+ struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
+ if (!epoller)
+ fatal ("no epoll found here, maybe it hides under your chair");
+
=item ev_default_destroy ()
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 cannot rely on this :).
+etc.). None of the active event watchers will be stopped in the normal
+sense, so e.g. C<ev_is_active> might still return true. It is your
+responsibility to either stop all watchers cleanly yoursef I<before>
+calling this function, or cope with the fact afterwards (which is usually
+the easiest thing, youc na just ignore the watchers and/or C<free ()> them
+for example).
=item ev_loop_destroy (loop)
after forking, in either the parent or child process (or both, but that
again makes little sense).
-You I<must> call this function after forking if and only if you want to
-use the event library in both processes. If you just fork+exec, you don't
-have to call it.
+You I<must> call this function in the child process after forking if and
+only if you want to 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 it's usually not a problem to call
it just in case after a fork. To make this easy, the function will fit in
pthread_atfork (0, 0, ev_default_fork);
+At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
+without calling this function, so if you force one of those backends you
+do not need to care.
+
=item ev_loop_fork (loop)
Like C<ev_default_fork>, but acts on an event loop created by
C<ev_loop_new>. Yes, you have to call this on every allocated event loop
after fork, and how you do this is entirely your own problem.
-=item unsigned int ev_method (loop)
+=item unsigned int ev_backend (loop)
-Returns one of the C<EVMETHOD_*> flags indicating the event backend in
+Returns one of the C<EVBACKEND_*> flags indicating the event backend in
use.
=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
-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
-occuring (or more correctly, the mainloop finding out about it).
+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 occuring (or more correctly, libev finding out about it).
=item ev_loop (loop, int flags)
after you initialised all your watchers and you want to start handling
events.
-If the flags argument is specified as 0, it will not return until either
-no event watchers are active anymore or C<ev_unloop> was called.
+If the flags argument is specified as C<0>, it will not return until
+either no event watchers are active anymore or C<ev_unloop> was called.
+
+Please note that an explicit C<ev_unloop> is usually better than
+relying on all watchers to be stopped when deciding when a program has
+finished (especially in interactive programs), but having a program that
+automatically loops as long as it has to and no longer by virtue of
+relying on its watchers stopping correctly is a thing of beauty.
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
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, 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
-more generic mechanism.
+one iteration of the loop. This is useful if you are waiting for some
+external event in conjunction with something not expressible using other
+libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
+usually a better approach for this kind of thing.
+
+Here are the gory details of what C<ev_loop> does:
+
+ * If there are no active watchers (reference count is zero), return.
+ - Queue prepare watchers and then call all outstanding watchers.
+ - If we have been forked, recreate the kernel state.
+ - Update the kernel state with all outstanding changes.
+ - Update the "event loop time".
+ - Calculate for how long to block.
+ - Block the process, waiting for any events.
+ - Queue all outstanding I/O (fd) events.
+ - Update the "event loop time" and do time jump handling.
+ - Queue all outstanding timers.
+ - Queue all outstanding periodics.
+ - If no events are pending now, queue all idle watchers.
+ - Queue all check watchers.
+ - Call all queued watchers in reverse order (i.e. check watchers first).
+ Signals and child watchers are implemented as I/O watchers, and will
+ be handled here by queueing them when their watcher gets executed.
+ - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
+ were used, return, otherwise continue with step *.
+
+Example: queue some jobs and then loop until no events are outsanding
+anymore.
+
+ ... queue jobs here, make sure they register event watchers as long
+ ... as they still have work to do (even an idle watcher will do..)
+ ev_loop (my_loop, 0);
+ ... jobs done. yeah!
=item ev_unloop (loop, how)
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_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.
=item ev_ref (loop)
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>.
+Example: create a signal watcher, but keep it from keeping C<ev_loop>
+running when nothing else is active.
+
+ struct dv_signal exitsig;
+ ev_signal_init (&exitsig, sig_cb, SIGINT);
+ ev_signal_start (myloop, &exitsig);
+ evf_unref (myloop);
+
+Example: for some weird reason, unregister the above signal handler again.
+
+ ev_ref (myloop);
+ ev_signal_stop (myloop, &exitsig);
+
=back
=head1 ANATOMY OF A 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 set method.
-
-You can check whether an event is active by calling the C<ev_is_active
-(watcher *)> macro. To see whether an event is outstanding (but the
-callback for it has not been called yet) you can use the C<ev_is_pending
-(watcher *)> macro.
+reinitialise it or call its C<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
=back
+=head2 SUMMARY OF 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
+of the watcher object can be arbitrary (so C<malloc> will do). Only
+the generic parts of the watcher are initialised, you I<need> to call
+the type-specific C<ev_TYPE_set> macro afterwards to initialise the
+type-specific parts. For each type there is also a C<ev_TYPE_init> macro
+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 callbakc is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
+int revents)>.
+
+=item C<ev_TYPE_set> (ev_TYPE *, [args])
+
+This macro initialises the type-specific parts of a watcher. You need to
+call C<ev_init> at least once before you call this macro, but you can
+call C<ev_TYPE_set> any number of times. You must not, however, call this
+macro on a watcher that is active (it can be pending, however, which is a
+difference to the C<ev_init> macro).
+
+Although some watcher types do not have type-specific arguments
+(e.g. C<ev_prepare>) you still need to call its C<set> macro.
+
+=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
+
+This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
+calls into a single call. This is the most convinient method to initialise
+a watcher. The same limitations apply, of course.
+
+=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
+
+Starts (activates) the given watcher. Only active watchers will receive
+events. If the watcher is already active nothing will happen.
+
+=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
+
+Stops the given watcher again (if active) and clears the pending
+status. It is possible that stopped watchers are pending (for example,
+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
+you want to free or reuse the memory used by the watcher it is 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
+it.
+
+=item bool ev_is_pending (ev_TYPE *watcher)
+
+Returns a true value iff the watcher is pending, (i.e. it has outstanding
+events but its callback has not yet been invoked). As long as a watcher
+is pending (but not active) you must not call an init function on it (but
+C<ev_TYPE_set> is safe) and you must make sure the watcher is available to
+libev (e.g. you cnanot C<free ()> it).
+
+=item callback = ev_cb (ev_TYPE *watcher)
+
+Returns the callback currently set on the watcher.
+
+=item ev_cb_set (ev_TYPE *watcher, callback)
+
+Change the callback. You can change the callback at virtually any time
+(modulo threads).
+
+=back
+
+
=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
Each watcher has, by default, a member C<void *data> that you can change
This section describes each watcher in detail, but will not repeat
information given in the last section.
+
=head2 C<ev_io> - is this file descriptor readable or writable
I/O watchers check whether a file descriptor is readable or writable
condition persists. Remember you can stop the watcher if you don't want to
act on the event and neither want to receive future events).
-In general you can register as many read and/or write event watchers oer
+In general you can register as many read and/or write event watchers per
fd as you want (as long as you don't confuse yourself). Setting all file
descriptors to non-blocking mode is also usually a good idea (but not
required if you know what you are doing).
You have to be careful with dup'ed file descriptors, though. Some backends
(the linux epoll backend is a notable example) cannot handle dup'ed file
descriptors correctly if you register interest in two or more fds pointing
-to the same file/socket etc. description.
+to the same underlying file/socket etc. description (that is, they share
+the same underlying "file open").
If you must do this, then force the use of a known-to-be-good backend
-(at the time of this writing, this includes only EVMETHOD_SELECT and
-EVMETHOD_POLL).
+(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
+C<EVBACKEND_POLL>).
=over 4
events for and events is either C<EV_READ>, C<EV_WRITE> or C<EV_READ |
EV_WRITE> to receive the given events.
+Please note that most of the more scalable backend mechanisms (for example
+epoll and solaris ports) can result in spurious readyness notifications
+for file descriptors, so you practically need to use non-blocking I/O (and
+treat callback invocation as hint only), or retest separately with a safe
+interface before doing I/O (XLib can do this), or force the use of either
+C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>, which don't suffer from this
+problem. Also note that it is quite easy to have your callback invoked
+when the readyness condition is no longer valid even when employing
+typical ways of handling events, so its a good idea to use non-blocking
+I/O unconditionally.
+
=back
+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)
+ {
+ ev_io_stop (loop, w);
+ .. read from stdin here (or from w->fd) and haqndle any I/O errors
+ }
+
+ ...
+ struct ev_loop *loop = ev_default_init (0);
+ struct 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);
+
+
=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.
The timers are based on real time, that is, if you register an event that
-times out after an hour and youreset your system clock to last years
+times out after an hour and you reset your system clock to last years
time, it will still time out after (roughly) and hour. "Roughly" because
-detecting time jumps is hard, and soem inaccuracies are unavoidable (the
+detecting time jumps is hard, and some 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:
+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.);
+The callback is guarenteed to be invoked only when its timeout has passed,
+but if multiple timers become ready during the same loop iteration then
+order of execution is undefined.
+
=over 4
=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
The timer itself will do a best-effort at avoiding drift, that is, if you
configure a timer to trigger every 10 seconds, then it will trigger at
exactly 10 second intervals. If, however, your program cannot keep up with
-the timer (ecause it takes longer than those 10 seconds to do stuff) the
+the timer (because it takes longer than those 10 seconds to do stuff) the
timer will not fire more than once per event loop iteration.
=item ev_timer_again (loop)
=back
+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 over, w is actually stopped right here
+ }
+
+ struct 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)
+ {
+ .. ten seconds without any activity
+ }
+
+ struct 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":
+ // reset the timeout to start ticking again at 10 seconds
+ ev_timer_again (&mytimer);
+
+
=head2 C<ev_periodic> - to cron or not to cron
Periodic watchers are also timers of a kind, but they are very versatile
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 ()
+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 C<ev_timer>, which would trigger
roughly 10 seconds later and of course not if you reset your system time
They can also be used to implement vastly more complex timers, such as
triggering an event on eahc midnight, local time.
+As with timers, the callback is guarenteed to be invoked only when the
+time (C<at>) has been passed, but if multiple periodic timers become ready
+during the same loop iteration then order of execution is undefined.
+
=over 4
=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
Lots of arguments, lets sort it out... There are basically three modes of
operation, and we will explain them from simplest to complex:
-
=over 4
=item * absolute timer (interval = reschedule_cb = 0)
=back
+Example: call a callback every hour, or, more precisely, whenever the
+system clock is divisible by 3600. The callback invocation times have
+potentially a lot of jittering, but good long-term stability.
+
+ static void
+ clock_cb (struct ev_loop *loop, struct 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_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)
+ {
+ return fmod (now, 3600.) + 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_init (&hourly_tick, clock_cb,
+ fmod (ev_now (loop), 3600.), 3600., 0);
+ ev_periodic_start (loop, &hourly_tick);
+
+
=head2 C<ev_signal> - signal me when a signal gets signalled
Signal watchers will trigger an event when the process receives a specific
=back
+
=head2 C<ev_child> - wait for pid status changes
Child watchers trigger when your process receives a SIGCHLD in response to
=back
+Example: try to exit cleanly on SIGINT and SIGTERM.
+
+ static void
+ sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
+ {
+ ev_unloop (loop, EVUNLOOP_ALL);
+ }
+
+ struct ev_signal signal_watcher;
+ ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
+ ev_signal_start (loop, &sigint_cb);
+
+
=head2 C<ev_idle> - when you've got nothing better to do
Idle watchers trigger events when there are no other events are pending
=back
+Example: dynamically allocate an C<ev_idle>, start it, and in the
+callback, free it. Alos, use no error checking, as usual.
+
+ static void
+ idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
+ {
+ free (w);
+ // now do something you wanted to do when the program has
+ // no longer asnything immediate to do.
+ }
+
+ struct ev_idle *idle_watcher = malloc (sizeof (struct 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
Prepare and check watchers are usually (but not always) used in tandem:
prepare watchers get invoked before the process blocks and check watchers
afterwards.
-Their main purpose is to integrate other event mechanisms into libev. This
-could be used, for example, to track variable changes, implement your own
-watchers, integrate net-snmp or a coroutine library and lots more.
+Their main purpose is to integrate other event mechanisms into libev and
+their use is somewhat advanced. This could be used, for example, to track
+variable changes, implement your own 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 C<ev_io> watchers for
=back
+Example: *TODO*.
+
+
+=head2 C<ev_embed> - when one backend isn't enough
+
+This is a rather advanced watcher type that lets you embed one event loop
+into another (currently only C<ev_io> events are supported in the embedded
+loop, other types of watchers might be handled in a delayed or incorrect
+fashion and must not be used).
+
+There are primarily two reasons you would want that: work around bugs and
+prioritise I/O.
+
+As an example for a bug workaround, the kqueue backend might only support
+sockets on some platform, so it is unusable as generic backend, but you
+still want to make use of it because you have many sockets and it scales
+so nicely. In this case, you would create a kqueue-based loop and embed it
+into your default loop (which might use e.g. poll). Overall operation will
+be a bit slower because first libev has to poll and then call kevent, but
+at least you can use both at what they are best.
+
+As for prioritising I/O: rarely you have the case where some fds have
+to be watched and handled very quickly (with low latency), and even
+priorities and idle watchers might have too much overhead. In this case
+you would put all the high priority stuff in one loop and all the rest in
+a second one, and embed the second one in the first.
+
+As long as the watcher is active, the callback will be invoked every time
+there might be events pending in the embedded loop. The callback must then
+call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
+their callbacks (you could also start an idle watcher to give the embedded
+loop strictly lower priority for example). You can also set the callback
+to C<0>, in which case the embed watcher will automatically execute the
+embedded loop sweep.
+
+As long as the watcher is started it will automatically handle events. The
+callback will be invoked whenever some events have been handled. You can
+set the callback to C<0> to avoid having to specify one if you are not
+interested in that.
+
+Also, there have not currently been made special provisions for forking:
+when you fork, you not only have to call C<ev_loop_fork> on both loops,
+but you will also have to stop and restart any C<ev_embed> watchers
+yourself.
+
+Unfortunately, not all backends are embeddable, only the ones returned by
+C<ev_embeddable_backends> are, which, unfortunately, does not include any
+portable one.
+
+So when you want to use this feature you will always have to be prepared
+that you cannot get an embeddable loop. The recommended way to get around
+this is to have a separate variables for your embeddable loop, try to
+create it, and if that fails, use the normal loop for everything:
+
+ struct ev_loop *loop_hi = ev_default_init (0);
+ struct ev_loop *loop_lo = 0;
+ struct 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 ())
+ : 0;
+
+ // if we got one, then embed it, otherwise default to loop_hi
+ if (loop_lo)
+ {
+ ev_embed_init (&embed, 0, loop_lo);
+ ev_embed_start (loop_hi, &embed);
+ }
+ else
+ loop_lo = loop_hi;
+
+=over 4
+
+=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
+
+=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
+
+Configures the watcher to embed the given loop, which must be
+embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
+invoked automatically, otherwise it is the responsibility of the callback
+to invoke it (it will continue to be called until the sweep has been done,
+if you do not want thta, you need to temporarily stop the embed watcher).
+
+=item ev_embed_sweep (loop, ev_embed *)
+
+Make a single, non-blocking sweep over the embedded loop. This works
+similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
+apropriate way for embedded loops.
+
+=back
+
+
=head1 OTHER FUNCTIONS
There are some other functions of possible interest. Described. Here. Now.
This function combines a simple timer and an I/O watcher, calls your
callback on whichever event happens first and automatically stop both
watchers. This is useful if you want to wait for a single event on an fd
-or timeout without havign to allocate/configure/start/stop/free one or
+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
dubious value.
The callback has the type C<void (*cb)(int revents, void *arg)> and gets
-passed an events set like normal event callbacks (with a combination of
+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>:
ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
-=item ev_feed_event (loop, watcher, int events)
+=item ev_feed_event (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 (loop, int fd, int revents)
+=item ev_feed_fd_event (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 (loop, int signum)
+=item ev_feed_signal_event (ev_loop *loop, int signum)
-Feed an event as if the given signal occured (loop must be the default loop!).
+Feed an event as if the given signal occured (C<loop> must be the default
+loop!).
=back
+
=head1 LIBEVENT EMULATION
-TBD.
+Libev offers a compatibility emulation layer for libevent. It cannot
+emulate the internals of libevent, so here are some usage hints:
+
+=over 4
+
+=item * Use it by including <event.h>, as usual.
+
+=item * The following members are fully supported: ev_base, ev_callback,
+ev_arg, ev_fd, ev_res, ev_events.
+
+=item * Avoid using ev_flags and the EVLIST_*-macros, while it is
+maintained by libev, it does not work exactly the same way as in libevent (consider
+it a private API).
+
+=item * Priorities are not currently supported. Initialising priorities
+will fail and all watchers will have the same priority, even though there
+is an ev_pri field.
+
+=item * Other members are not supported.
+
+=item * The libev emulation is I<not> ABI compatible to libevent, you need
+to use the libev header file and library.
+
+=back
=head1 C++ SUPPORT
-TBD.
+Libev comes with some simplistic wrapper classes for C++ that mainly allow
+you to use some convinience methods to start/stop watchers and also change
+the callback model to a model using method callbacks on objects.
+
+To use it,
+
+ #include <ev++.h>
+
+(it is not installed by default). This automatically includes F<ev.h>
+and puts all of its definitions (many of them macros) into the global
+namespace. All C++ specific things are put into the C<ev> namespace.
+
+It should support all the same embedding options as F<ev.h>, most notably
+C<EV_MULTIPLICITY>.
+
+Here is a list of things available in the C<ev> namespace:
+
+=over 4
+
+=item C<ev::READ>, C<ev::WRITE> etc.
+
+These are just enum values with the same values as the C<EV_READ> etc.
+macros from F<ev.h>.
+
+=item C<ev::tstamp>, C<ev::now>
+
+Aliases to the same types/functions as with the C<ev_> prefix.
+
+=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
+
+For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
+the same name in the C<ev> namespace, with the exception of C<ev_signal>
+which is called C<ev::sig> to avoid clashes with the C<signal> macro
+defines by many implementations.
+
+All of those classes have these methods:
+
+=over 4
+
+=item ev::TYPE::TYPE (object *, object::method *)
+
+=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)
+
+=item ev::TYPE::~TYPE
+
+The constructor takes a pointer to an object and a method pointer to
+the event handler callback to call in this class. The constructor calls
+C<ev_init> for you, which means you have to call the C<set> method
+before starting it. If you do not specify a loop then the constructor
+automatically associates the default loop with this watcher.
+
+The destructor automatically stops the watcher if it is active.
+
+=item w->set (struct ev_loop *)
+
+Associates a different C<struct ev_loop> with this watcher. You can only
+do this when the watcher is inactive (and not pending either).
+
+=item w->set ([args])
+
+Basically the same as C<ev_TYPE_set>, with the same args. Must be
+called at least once. Unlike the C counterpart, an active watcher gets
+automatically stopped and restarted.
+
+=item w->start ()
+
+Starts the watcher. Note that there is no C<loop> argument as the
+constructor already takes the loop.
+
+=item w->stop ()
+
+Stops the watcher if it is active. Again, no C<loop> argument.
+
+=item w->again () C<ev::timer>, C<ev::periodic> only
+
+For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
+C<ev_TYPE_again> function.
+
+=item w->sweep () C<ev::embed> only
+
+Invokes C<ev_embed_sweep>.
+
+=back
+
+=back
+
+Example: Define a class with an IO and idle watcher, start one of them in
+the constructor.
+
+ class myclass
+ {
+ ev_io io; void io_cb (ev::io &w, int revents);
+ ev_idle idle void idle_cb (ev::idle &w, int revents);
+
+ myclass ();
+ }
+
+ myclass::myclass (int fd)
+ : io (this, &myclass::io_cb),
+ idle (this, &myclass::idle_cb)
+ {
+ io.start (fd, ev::READ);
+ }
+
+=head1 EMBEDDING
+
+Libev can (and often is) directly embedded into host
+applications. Examples of applications that embed it include the Deliantra
+Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
+and rxvt-unicode.
+
+The goal is to enable you to just copy the neecssary files into your
+source directory without having to change even a single line in them, so
+you can easily upgrade by simply copying (or having a checked-out copy of
+libev somewhere in your source tree).
+
+=head2 FILESETS
+
+Depending on what features you need you need to include one or more sets of files
+in your app.
+
+=head3 CORE EVENT LOOP
+
+To include only the libev core (all the C<ev_*> functions), with manual
+configuration (no autoconf):
+
+ #define EV_STANDALONE 1
+ #include "ev.c"
+
+This will automatically include F<ev.h>, too, and should be done in a
+single C source file only to provide the function implementations. To use
+it, do the same for F<ev.h> in all files wishing to use this API (best
+done by writing a wrapper around F<ev.h> that you can include instead and
+where you can put other configuration options):
+
+ #define EV_STANDALONE 1
+ #include "ev.h"
+
+Both header files and implementation files can be compiled with a C++
+compiler (at least, thats a stated goal, and breakage will be treated
+as a bug).
+
+You need the following files in your source tree, or in a directory
+in your include path (e.g. in libev/ when using -Ilibev):
+
+ ev.h
+ ev.c
+ ev_vars.h
+ ev_wrap.h
+
+ ev_win32.c required on win32 platforms only
+
+ ev_select.c only when select backend is enabled (which is is by default)
+ ev_poll.c only when poll backend is enabled (disabled by default)
+ ev_epoll.c only when the epoll backend is enabled (disabled by default)
+ ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
+ ev_port.c only when the solaris port backend is enabled (disabled by default)
+
+F<ev.c> includes the backend files directly when enabled, so you only need
+to compile a single file.
+
+=head3 LIBEVENT COMPATIBILITY API
+
+To include the libevent compatibility API, also include:
+
+ #include "event.c"
+
+in the file including F<ev.c>, and:
+
+ #include "event.h"
+
+in the files that want to use the libevent API. This also includes F<ev.h>.
+
+You need the following additional files for this:
+
+ event.h
+ event.c
+
+=head3 AUTOCONF SUPPORT
+
+Instead of using C<EV_STANDALONE=1> and providing your config in
+whatever way you want, you can also C<m4_include([libev.m4])> in your
+F<configure.ac> and leave C<EV_STANDALONE> off. F<ev.c> will then include
+F<config.h> and configure itself accordingly.
+
+For this of course you need the m4 file:
+
+ libev.m4
+
+=head2 PREPROCESSOR SYMBOLS/MACROS
+
+Libev can be configured via a variety of preprocessor symbols you have to define
+before including any of its files. The default is not to build for multiplicity
+and only include the select backend.
+
+=over 4
+
+=item EV_STANDALONE
+
+Must always be C<1> if you do not use autoconf configuration, which
+keeps libev from including F<config.h>, and it also defines dummy
+implementations for some libevent functions (such as logging, which is not
+supported). It will also not define any of the structs usually found in
+F<event.h> that are not directly supported by the libev core alone.
+
+=item EV_USE_MONOTONIC
+
+If defined to be C<1>, libev will try to detect the availability of the
+monotonic clock option at both compiletime and runtime. Otherwise no use
+of the monotonic clock option will be attempted. If you enable this, you
+usually have to link against librt or something similar. Enabling it when
+the functionality isn't available is safe, though, althoguh you have
+to make sure you link against any libraries where the C<clock_gettime>
+function is hiding in (often F<-lrt>).
+
+=item EV_USE_REALTIME
+
+If defined to be C<1>, libev will try to detect the availability of the
+realtime clock option at compiletime (and assume its availability at
+runtime if successful). Otherwise no use of the realtime clock option will
+be attempted. This effectively replaces C<gettimeofday> by C<clock_get
+(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries
+in the description of C<EV_USE_MONOTONIC>, though.
+
+=item EV_USE_SELECT
+
+If undefined or defined to be C<1>, libev will compile in support for the
+C<select>(2) backend. No attempt at autodetection will be done: if no
+other method takes over, select will be it. Otherwise the select backend
+will not be compiled in.
+
+=item EV_SELECT_USE_FD_SET
+
+If defined to C<1>, then the select backend will use the system C<fd_set>
+structure. This is useful if libev doesn't compile due to a missing
+C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on
+exotic systems. This usually limits the range of file descriptors to some
+low limit such as 1024 or might have other limitations (winsocket only
+allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
+influence the size of the C<fd_set> used.
+
+=item EV_SELECT_IS_WINSOCKET
+
+When defined to C<1>, the select backend will assume that
+select/socket/connect etc. don't understand file descriptors but
+wants osf handles on win32 (this is the case when the select to
+be used is the winsock select). This means that it will call
+C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
+it is assumed that all these functions actually work on fds, even
+on win32. Should not be defined on non-win32 platforms.
+
+=item EV_USE_POLL
+
+If defined to be C<1>, libev will compile in support for the C<poll>(2)
+backend. Otherwise it will be enabled on non-win32 platforms. It
+takes precedence over select.
+
+=item EV_USE_EPOLL
+
+If defined to be C<1>, libev will compile in support for the Linux
+C<epoll>(7) backend. Its availability will be detected at runtime,
+otherwise another method will be used as fallback. This is the
+preferred backend for GNU/Linux systems.
+
+=item EV_USE_KQUEUE
+
+If defined to be C<1>, libev will compile in support for the BSD style
+C<kqueue>(2) backend. Its actual availability will be detected at runtime,
+otherwise another method will be used as fallback. This is the preferred
+backend for BSD and BSD-like systems, although on most BSDs kqueue only
+supports some types of fds correctly (the only platform we found that
+supports ptys for example was NetBSD), so kqueue might be compiled in, but
+not be used unless explicitly requested. The best way to use it is to find
+out whether kqueue supports your type of fd properly and use an embedded
+kqueue loop.
+
+=item EV_USE_PORT
+
+If defined to be C<1>, libev will compile in support for the Solaris
+10 port style backend. Its availability will be detected at runtime,
+otherwise another method will be used as fallback. This is the preferred
+backend for Solaris 10 systems.
+
+=item EV_USE_DEVPOLL
+
+reserved for future expansion, works like the USE symbols above.
+
+=item EV_H
+
+The name of the F<ev.h> header file used to include it. The default if
+undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This
+can be used to virtually rename the F<ev.h> header file in case of conflicts.
+
+=item EV_CONFIG_H
+
+If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
+F<ev.c>'s idea of where to find the F<config.h> file, similarly to
+C<EV_H>, above.
+
+=item EV_EVENT_H
+
+Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
+of how the F<event.h> header can be found.
+
+=item EV_PROTOTYPES
+
+If defined to be C<0>, then F<ev.h> will not define any function
+prototypes, but still define all the structs and other symbols. This is
+occasionally useful if you want to provide your own wrapper functions
+around libev functions.
+
+=item EV_MULTIPLICITY
+
+If undefined or defined to C<1>, then all event-loop-specific functions
+will have the C<struct ev_loop *> as first argument, and you can create
+additional independent event loops. Otherwise there will be no support
+for multiple event loops and there is no first event loop pointer
+argument. Instead, all functions act on the single default loop.
+
+=item EV_PERIODICS
+
+If undefined or defined to be C<1>, then periodic timers are supported,
+otherwise not. This saves a few kb of code.
+
+=item EV_COMMON
+
+By default, all watchers have a C<void *data> member. By redefining
+this macro to a something else you can include more and other types of
+members. You have to define it each time you include one of the files,
+though, and it must be identical each time.
+
+For example, the perl EV module uses something like this:
+
+ #define EV_COMMON \
+ SV *self; /* contains this struct */ \
+ SV *cb_sv, *fh /* note no trailing ";" */
+
+=item EV_CB_DECLARE(type)
+
+=item EV_CB_INVOKE(watcher,revents)
+
+=item ev_set_cb(ev,cb)
+
+Can be used to change the callback member declaration in each watcher,
+and the way callbacks are invoked and set. Must expand to a struct member
+definition and a statement, respectively. See the F<ev.v> header file for
+their default definitions. One possible use for overriding these is to
+avoid the ev_loop pointer as first argument in all cases, or to use method
+calls instead of plain function calls in C++.
+
+=head2 EXAMPLES
+
+For a real-world example of a program the includes libev
+verbatim, you can have a look at the EV perl module
+(L<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
+the F<libev/> subdirectory and includes them in the F<EV/EVAPI.h> (public
+interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
+will be compiled. It is pretty complex because it provides its own header
+file.
+
+The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
+that everybody includes and which overrides some autoconf choices:
+
+ #define EV_USE_POLL 0
+ #define EV_MULTIPLICITY 0
+ #define EV_PERIODICS 0
+ #define EV_CONFIG_H <config.h>
+
+ #include "ev++.h"
+
+And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
+
+ #include "ev_cpp.h"
+ #include "ev.c"
=head1 AUTHOR
projects / software / libev.git / blobdiff