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

Comparing libev/ev.pod (file contents):
Revision 1.32 by root, Fri Nov 23 08:36:35 2007 UTC vs.
Revision 1.35 by root, Fri Nov 23 19:35:09 2007 UTC

…		…
45		45
46	Libev represents time as a single floating point number, representing the	46	Libev represents time as a single floating point number, representing the
47	(fractional) number of seconds since the (POSIX) epoch (somewhere near	47	(fractional) number of seconds since the (POSIX) epoch (somewhere near
48	the beginning of 1970, details are complicated, don't ask). This type is	48	the beginning of 1970, details are complicated, don't ask). This type is
49	called C<ev_tstamp>, which is what you should use too. It usually aliases	49	called C<ev_tstamp>, which is what you should use too. It usually aliases
50	to the double type in C.	50	to the C<double> type in C, and when you need to do any calculations on
		51	it, you should treat it as such.
		52
51		53
52	=head1 GLOBAL FUNCTIONS	54	=head1 GLOBAL FUNCTIONS
53		55
54	These functions can be called anytime, even before initialising the	56	These functions can be called anytime, even before initialising the
55	library in any way.	57	library in any way.
…		…
75	Usually, it's a good idea to terminate if the major versions mismatch,	77	Usually, it's a good idea to terminate if the major versions mismatch,
76	as this indicates an incompatible change. Minor versions are usually	78	as this indicates an incompatible change. Minor versions are usually
77	compatible to older versions, so a larger minor version alone is usually	79	compatible to older versions, so a larger minor version alone is usually
78	not a problem.	80	not a problem.
79		81
		82	Example: make sure we haven't accidentally been linked against the wrong
		83	version:
		84
		85	assert (("libev version mismatch",
		86	ev_version_major () == EV_VERSION_MAJOR
		87	&& ev_version_minor () >= EV_VERSION_MINOR));
		88
80	=item unsigned int ev_supported_backends ()	89	=item unsigned int ev_supported_backends ()
81		90
82	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>	91	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
83	value) compiled into this binary of libev (independent of their	92	value) compiled into this binary of libev (independent of their
84	availability on the system you are running on). See C<ev_default_loop> for	93	availability on the system you are running on). See C<ev_default_loop> for
85	a description of the set values.	94	a description of the set values.
		95
		96	Example: make sure we have the epoll method, because yeah this is cool and
		97	a must have and can we have a torrent of it please!!!11
		98
		99	assert (("sorry, no epoll, no sex",
		100	ev_supported_backends () & EVBACKEND_EPOLL));
86		101
87	=item unsigned int ev_recommended_backends ()	102	=item unsigned int ev_recommended_backends ()
88		103
89	Return the set of all backends compiled into this binary of libev and also	104	Return the set of all backends compiled into this binary of libev and also
90	recommended for this platform. This set is often smaller than the one	105	recommended for this platform. This set is often smaller than the one
91	returned by C<ev_supported_backends>, as for example kqueue is broken on	106	returned by C<ev_supported_backends>, as for example kqueue is broken on
92	most BSDs and will not be autodetected unless you explicitly request it	107	most BSDs and will not be autodetected unless you explicitly request it
93	(assuming you know what you are doing). This is the set of backends that	108	(assuming you know what you are doing). This is the set of backends that
94	C<EVFLAG_AUTO> will probe for.	109	libev will probe for if you specify no backends explicitly.
		110
		111	=item unsigned int ev_embeddable_backends ()
		112
		113	Returns the set of backends that are embeddable in other event loops. This
		114	is the theoretical, all-platform, value. To find which backends
		115	might be supported on the current system, you would need to look at
		116	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
		117	recommended ones.
		118
		119	See the description of C<ev_embed> watchers for more info.
95		120
96	=item ev_set_allocator (void (cb)(void *ptr, long size))	121	=item ev_set_allocator (void (cb)(void *ptr, long size))
97		122
98	Sets the allocation function to use (the prototype is similar to the	123	Sets the allocation function to use (the prototype is similar to the
99	realloc C function, the semantics are identical). It is used to allocate	124	realloc C function, the semantics are identical). It is used to allocate
…		…
102	destructive action. The default is your system realloc function.	127	destructive action. The default is your system realloc function.
103		128
104	You could override this function in high-availability programs to, say,	129	You could override this function in high-availability programs to, say,
105	free some memory if it cannot allocate memory, to use a special allocator,	130	free some memory if it cannot allocate memory, to use a special allocator,
106	or even to sleep a while and retry until some memory is available.	131	or even to sleep a while and retry until some memory is available.
		132
		133	Example: replace the libev allocator with one that waits a bit and then
		134	retries: better than mine).
		135
		136	static void *
		137	persistent_realloc (void *ptr, long size)
		138	{
		139	for (;;)
		140	{
		141	void *newptr = realloc (ptr, size);
		142
		143	if (newptr)
		144	return newptr;
		145
		146	sleep (60);
		147	}
		148	}
		149
		150	...
		151	ev_set_allocator (persistent_realloc);
107		152
108	=item ev_set_syserr_cb (void (cb)(const char msg));	153	=item ev_set_syserr_cb (void (cb)(const char msg));
109		154
110	Set the callback function to call on a retryable syscall error (such	155	Set the callback function to call on a retryable syscall error (such
111	as failed select, poll, epoll_wait). The message is a printable string	156	as failed select, poll, epoll_wait). The message is a printable string
…		…
113	callback is set, then libev will expect it to remedy the sitution, no	158	callback is set, then libev will expect it to remedy the sitution, no
114	matter what, when it returns. That is, libev will generally retry the	159	matter what, when it returns. That is, libev will generally retry the
115	requested operation, or, if the condition doesn't go away, do bad stuff	160	requested operation, or, if the condition doesn't go away, do bad stuff
116	(such as abort).	161	(such as abort).
117		162
		163	Example: do the same thing as libev does internally:
		164
		165	static void
		166	fatal_error (const char *msg)
		167	{
		168	perror (msg);
		169	abort ();
		170	}
		171
		172	...
		173	ev_set_syserr_cb (fatal_error);
		174
118	=back	175	=back
119		176
120	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	177	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
121		178
122	An event loop is described by a C<struct ev_loop *>. The library knows two	179	An event loop is described by a C<struct ev_loop *>. The library knows two
…		…
141		198
142	If you don't know what event loop to use, use the one returned from this	199	If you don't know what event loop to use, use the one returned from this
143	function.	200	function.
144		201
145	The flags argument can be used to specify special behaviour or specific	202	The flags argument can be used to specify special behaviour or specific
146	backends to use, and is usually specified as C<0> (or EVFLAG_AUTO).	203	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
147		204
148	It supports the following flags:	205	The following flags are supported:
149		206
150	=over 4	207	=over 4
151		208
152	=item C<EVFLAG_AUTO>	209	=item C<EVFLAG_AUTO>
153		210
…		…
198	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	255	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
199		256
200	Kqueue deserves special mention, as at the time of this writing, it	257	Kqueue deserves special mention, as at the time of this writing, it
201	was broken on all BSDs except NetBSD (usually it doesn't work with	258	was broken on all BSDs except NetBSD (usually it doesn't work with
202	anything but sockets and pipes, except on Darwin, where of course its	259	anything but sockets and pipes, except on Darwin, where of course its
203	completely useless). For this reason its not being "autodetected" unless	260	completely useless). For this reason its not being "autodetected"
204	you explicitly specify the flags (i.e. you don't use EVFLAG_AUTO).	261	unless you explicitly specify it explicitly in the flags (i.e. using
		262	C<EVBACKEND_KQUEUE>).
205		263
206	It scales in the same way as the epoll backend, but the interface to the	264	It scales in the same way as the epoll backend, but the interface to the
207	kernel is more efficient (which says nothing about its actual speed, of	265	kernel is more efficient (which says nothing about its actual speed, of
208	course). While starting and stopping an I/O watcher does not cause an	266	course). While starting and stopping an I/O watcher does not cause an
209	extra syscall as with epoll, it still adds up to four event changes per	267	extra syscall as with epoll, it still adds up to four event changes per
…		…
233	If one or more of these are ored into the flags value, then only these	291	If one or more of these are ored into the flags value, then only these
234	backends will be tried (in the reverse order as given here). If none are	292	backends will be tried (in the reverse order as given here). If none are
235	specified, most compiled-in backend will be tried, usually in reverse	293	specified, most compiled-in backend will be tried, usually in reverse
236	order of their flag values :)	294	order of their flag values :)
237		295
		296	The most typical usage is like this:
		297
		298	if (!ev_default_loop (0))
		299	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		300
		301	Restrict libev to the select and poll backends, and do not allow
		302	environment settings to be taken into account:
		303
		304	ev_default_loop (EVBACKEND_POLL \| EVBACKEND_SELECT \| EVFLAG_NOENV);
		305
		306	Use whatever libev has to offer, but make sure that kqueue is used if
		307	available (warning, breaks stuff, best use only with your own private
		308	event loop and only if you know the OS supports your types of fds):
		309
		310	ev_default_loop (ev_recommended_backends () \| EVBACKEND_KQUEUE);
		311
238	=item struct ev_loop *ev_loop_new (unsigned int flags)	312	=item struct ev_loop *ev_loop_new (unsigned int flags)
239		313
240	Similar to C<ev_default_loop>, but always creates a new event loop that is	314	Similar to C<ev_default_loop>, but always creates a new event loop that is
241	always distinct from the default loop. Unlike the default loop, it cannot	315	always distinct from the default loop. Unlike the default loop, it cannot
242	handle signal and child watchers, and attempts to do so will be greeted by	316	handle signal and child watchers, and attempts to do so will be greeted by
243	undefined behaviour (or a failed assertion if assertions are enabled).	317	undefined behaviour (or a failed assertion if assertions are enabled).
244		318
		319	Example: try to create a event loop that uses epoll and nothing else.
		320
		321	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);
		322	if (!epoller)
		323	fatal ("no epoll found here, maybe it hides under your chair");
		324
245	=item ev_default_destroy ()	325	=item ev_default_destroy ()
246		326
247	Destroys the default loop again (frees all memory and kernel state	327	Destroys the default loop again (frees all memory and kernel state
248	etc.). This stops all registered event watchers (by not touching them in	328	etc.). This stops all registered event watchers (by not touching them in
249	any way whatsoever, although you cannot rely on this :).	329	any way whatsoever, although you cannot rely on this :).
…		…
286	use.	366	use.
287		367
288	=item ev_tstamp ev_now (loop)	368	=item ev_tstamp ev_now (loop)
289		369
290	Returns the current "event loop time", which is the time the event loop	370	Returns the current "event loop time", which is the time the event loop
291	got events and started processing them. This timestamp does not change	371	received events and started processing them. This timestamp does not
292	as long as callbacks are being processed, and this is also the base time	372	change as long as callbacks are being processed, and this is also the base
293	used for relative timers. You can treat it as the timestamp of the event	373	time used for relative timers. You can treat it as the timestamp of the
294	occuring (or more correctly, the mainloop finding out about it).	374	event occuring (or more correctly, libev finding out about it).
295		375
296	=item ev_loop (loop, int flags)	376	=item ev_loop (loop, int flags)
297		377
298	Finally, this is it, the event handler. This function usually is called	378	Finally, this is it, the event handler. This function usually is called
299	after you initialised all your watchers and you want to start handling	379	after you initialised all your watchers and you want to start handling
300	events.	380	events.
301		381
302	If the flags argument is specified as 0, it will not return until either	382	If the flags argument is specified as C<0>, it will not return until
303	no event watchers are active anymore or C<ev_unloop> was called.	383	either no event watchers are active anymore or C<ev_unloop> was called.
		384
		385	Please note that an explicit C<ev_unloop> is usually better than
		386	relying on all watchers to be stopped when deciding when a program has
		387	finished (especially in interactive programs), but having a program that
		388	automatically loops as long as it has to and no longer by virtue of
		389	relying on its watchers stopping correctly is a thing of beauty.
304		390
305	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	391	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
306	those events and any outstanding ones, but will not block your process in	392	those events and any outstanding ones, but will not block your process in
307	case there are no events and will return after one iteration of the loop.	393	case there are no events and will return after one iteration of the loop.
308		394
309	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	395	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
310	neccessary) and will handle those and any outstanding ones. It will block	396	neccessary) and will handle those and any outstanding ones. It will block
311	your process until at least one new event arrives, and will return after	397	your process until at least one new event arrives, and will return after
312	one iteration of the loop.	398	one iteration of the loop. This is useful if you are waiting for some
		399	external event in conjunction with something not expressible using other
		400	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
		401	usually a better approach for this kind of thing.
313		402
314	This flags value could be used to implement alternative looping
315	constructs, but the C<prepare> and C<check> watchers provide a better and
316	more generic mechanism.
317
318	Here are the gory details of what ev_loop does:	403	Here are the gory details of what C<ev_loop> does:
319		404
320	1. If there are no active watchers (reference count is zero), return.	405	* If there are no active watchers (reference count is zero), return.
321	2. Queue and immediately call all prepare watchers.	406	- Queue prepare watchers and then call all outstanding watchers.
322	3. If we have been forked, recreate the kernel state.	407	- If we have been forked, recreate the kernel state.
323	4. Update the kernel state with all outstanding changes.	408	- Update the kernel state with all outstanding changes.
324	5. Update the "event loop time".	409	- Update the "event loop time".
325	6. Calculate for how long to block.	410	- Calculate for how long to block.
326	7. Block the process, waiting for events.	411	- Block the process, waiting for any events.
		412	- Queue all outstanding I/O (fd) events.
327	8. Update the "event loop time" and do time jump handling.	413	- Update the "event loop time" and do time jump handling.
328	9. Queue all outstanding timers.	414	- Queue all outstanding timers.
329	10. Queue all outstanding periodics.	415	- Queue all outstanding periodics.
330	11. If no events are pending now, queue all idle watchers.	416	- If no events are pending now, queue all idle watchers.
331	12. Queue all check watchers.	417	- Queue all check watchers.
332	13. Call all queued watchers in reverse order (i.e. check watchers first).	418	- Call all queued watchers in reverse order (i.e. check watchers first).
		419	Signals and child watchers are implemented as I/O watchers, and will
		420	be handled here by queueing them when their watcher gets executed.
333	14. If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	421	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
334	was used, return, otherwise continue with step #1.	422	were used, return, otherwise continue with step *.
		423
		424	Example: queue some jobs and then loop until no events are outsanding
		425	anymore.
		426
		427	... queue jobs here, make sure they register event watchers as long
		428	... as they still have work to do (even an idle watcher will do..)
		429	ev_loop (my_loop, 0);
		430	... jobs done. yeah!
335		431
336	=item ev_unloop (loop, how)	432	=item ev_unloop (loop, how)
337		433
338	Can be used to make a call to C<ev_loop> return early (but only after it	434	Can be used to make a call to C<ev_loop> return early (but only after it
339	has processed all outstanding events). The C<how> argument must be either	435	has processed all outstanding events). The C<how> argument must be either
…		…
353	visible to the libev user and should not keep C<ev_loop> from exiting if	449	visible to the libev user and should not keep C<ev_loop> from exiting if
354	no event watchers registered by it are active. It is also an excellent	450	no event watchers registered by it are active. It is also an excellent
355	way to do this for generic recurring timers or from within third-party	451	way to do this for generic recurring timers or from within third-party
356	libraries. Just remember to I<unref after start> and I<ref before stop>.	452	libraries. Just remember to I<unref after start> and I<ref before stop>.
357		453
		454	Example: create a signal watcher, but keep it from keeping C<ev_loop>
		455	running when nothing else is active.
		456
		457	struct dv_signal exitsig;
		458	ev_signal_init (&exitsig, sig_cb, SIGINT);
		459	ev_signal_start (myloop, &exitsig);
		460	evf_unref (myloop);
		461
		462	Example: for some weird reason, unregister the above signal handler again.
		463
		464	ev_ref (myloop);
		465	ev_signal_stop (myloop, &exitsig);
		466
358	=back	467	=back
359		468
360	=head1 ANATOMY OF A WATCHER	469	=head1 ANATOMY OF A WATCHER
361		470
362	A watcher is a structure that you create and register to record your	471	A watcher is a structure that you create and register to record your
…		…
502		611
503	=head1 WATCHER TYPES	612	=head1 WATCHER TYPES
504		613
505	This section describes each watcher in detail, but will not repeat	614	This section describes each watcher in detail, but will not repeat
506	information given in the last section.	615	information given in the last section.
		616
507		617
508	=head2 C<ev_io> - is this file descriptor readable or writable	618	=head2 C<ev_io> - is this file descriptor readable or writable
509		619
510	I/O watchers check whether a file descriptor is readable or writable	620	I/O watchers check whether a file descriptor is readable or writable
511	in each iteration of the event loop (This behaviour is called	621	in each iteration of the event loop (This behaviour is called
…		…
549	typical ways of handling events, so its a good idea to use non-blocking	659	typical ways of handling events, so its a good idea to use non-blocking
550	I/O unconditionally.	660	I/O unconditionally.
551		661
552	=back	662	=back
553		663
		664	Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well
		665	readable, but only once. Since it is likely line-buffered, you could
		666	attempt to read a whole line in the callback:
		667
		668	static void
		669	stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)
		670	{
		671	ev_io_stop (loop, w);
		672	.. read from stdin here (or from w->fd) and haqndle any I/O errors
		673	}
		674
		675	...
		676	struct ev_loop *loop = ev_default_init (0);
		677	struct ev_io stdin_readable;
		678	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
		679	ev_io_start (loop, &stdin_readable);
		680	ev_loop (loop, 0);
		681
		682
554	=head2 C<ev_timer> - relative and optionally recurring timeouts	683	=head2 C<ev_timer> - relative and optionally recurring timeouts
555		684
556	Timer watchers are simple relative timers that generate an event after a	685	Timer watchers are simple relative timers that generate an event after a
557	given time, and optionally repeating in regular intervals after that.	686	given time, and optionally repeating in regular intervals after that.
558		687
…		…
610	state where you do not expect data to travel on the socket, you can stop	739	state where you do not expect data to travel on the socket, you can stop
611	the timer, and again will automatically restart it if need be.	740	the timer, and again will automatically restart it if need be.
612		741
613	=back	742	=back
614		743
		744	Example: create a timer that fires after 60 seconds.
		745
		746	static void
		747	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)
		748	{
		749	.. one minute over, w is actually stopped right here
		750	}
		751
		752	struct ev_timer mytimer;
		753	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
		754	ev_timer_start (loop, &mytimer);
		755
		756	Example: create a timeout timer that times out after 10 seconds of
		757	inactivity.
		758
		759	static void
		760	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)
		761	{
		762	.. ten seconds without any activity
		763	}
		764
		765	struct ev_timer mytimer;
		766	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
		767	ev_timer_again (&mytimer); /* start timer */
		768	ev_loop (loop, 0);
		769
		770	// and in some piece of code that gets executed on any "activity":
		771	// reset the timeout to start ticking again at 10 seconds
		772	ev_timer_again (&mytimer);
		773
		774
615	=head2 C<ev_periodic> - to cron or not to cron	775	=head2 C<ev_periodic> - to cron or not to cron
616		776
617	Periodic watchers are also timers of a kind, but they are very versatile	777	Periodic watchers are also timers of a kind, but they are very versatile
618	(and unfortunately a bit complex).	778	(and unfortunately a bit complex).
619		779
…		…
714	a different time than the last time it was called (e.g. in a crond like	874	a different time than the last time it was called (e.g. in a crond like
715	program when the crontabs have changed).	875	program when the crontabs have changed).
716		876
717	=back	877	=back
718		878
		879	Example: call a callback every hour, or, more precisely, whenever the
		880	system clock is divisible by 3600. The callback invocation times have
		881	potentially a lot of jittering, but good long-term stability.
		882
		883	static void
		884	clock_cb (struct ev_loop loop, struct ev_io w, int revents)
		885	{
		886	... its now a full hour (UTC, or TAI or whatever your clock follows)
		887	}
		888
		889	struct ev_periodic hourly_tick;
		890	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
		891	ev_periodic_start (loop, &hourly_tick);
		892
		893	Example: the same as above, but use a reschedule callback to do it:
		894
		895	#include <math.h>
		896
		897	static ev_tstamp
		898	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
		899	{
		900	return fmod (now, 3600.) + 3600.;
		901	}
		902
		903	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
		904
		905	Example: call a callback every hour, starting now:
		906
		907	struct ev_periodic hourly_tick;
		908	ev_periodic_init (&hourly_tick, clock_cb,
		909	fmod (ev_now (loop), 3600.), 3600., 0);
		910	ev_periodic_start (loop, &hourly_tick);
		911
		912
719	=head2 C<ev_signal> - signal me when a signal gets signalled	913	=head2 C<ev_signal> - signal me when a signal gets signalled
720		914
721	Signal watchers will trigger an event when the process receives a specific	915	Signal watchers will trigger an event when the process receives a specific
722	signal one or more times. Even though signals are very asynchronous, libev	916	signal one or more times. Even though signals are very asynchronous, libev
723	will try it's best to deliver signals synchronously, i.e. as part of the	917	will try it's best to deliver signals synchronously, i.e. as part of the
…		…
739	Configures the watcher to trigger on the given signal number (usually one	933	Configures the watcher to trigger on the given signal number (usually one
740	of the C<SIGxxx> constants).	934	of the C<SIGxxx> constants).
741		935
742	=back	936	=back
743		937
		938
744	=head2 C<ev_child> - wait for pid status changes	939	=head2 C<ev_child> - wait for pid status changes
745		940
746	Child watchers trigger when your process receives a SIGCHLD in response to	941	Child watchers trigger when your process receives a SIGCHLD in response to
747	some child status changes (most typically when a child of yours dies).	942	some child status changes (most typically when a child of yours dies).
748		943
…		…
758	the status word (use the macros from C<sys/wait.h> and see your systems	953	the status word (use the macros from C<sys/wait.h> and see your systems
759	C<waitpid> documentation). The C<rpid> member contains the pid of the	954	C<waitpid> documentation). The C<rpid> member contains the pid of the
760	process causing the status change.	955	process causing the status change.
761		956
762	=back	957	=back
		958
		959	Example: try to exit cleanly on SIGINT and SIGTERM.
		960
		961	static void
		962	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)
		963	{
		964	ev_unloop (loop, EVUNLOOP_ALL);
		965	}
		966
		967	struct ev_signal signal_watcher;
		968	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		969	ev_signal_start (loop, &sigint_cb);
		970
763		971
764	=head2 C<ev_idle> - when you've got nothing better to do	972	=head2 C<ev_idle> - when you've got nothing better to do
765		973
766	Idle watchers trigger events when there are no other events are pending	974	Idle watchers trigger events when there are no other events are pending
767	(prepare, check and other idle watchers do not count). That is, as long	975	(prepare, check and other idle watchers do not count). That is, as long
…		…
787	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	995	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
788	believe me.	996	believe me.
789		997
790	=back	998	=back
791		999
		1000	Example: dynamically allocate an C<ev_idle>, start it, and in the
		1001	callback, free it. Alos, use no error checking, as usual.
		1002
		1003	static void
		1004	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)
		1005	{
		1006	free (w);
		1007	// now do something you wanted to do when the program has
		1008	// no longer asnything immediate to do.
		1009	}
		1010
		1011	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
		1012	ev_idle_init (idle_watcher, idle_cb);
		1013	ev_idle_start (loop, idle_cb);
		1014
		1015
792	=head2 C<ev_prepare> and C<ev_check> - customise your event loop	1016	=head2 C<ev_prepare> and C<ev_check> - customise your event loop
793		1017
794	Prepare and check watchers are usually (but not always) used in tandem:	1018	Prepare and check watchers are usually (but not always) used in tandem:
795	prepare watchers get invoked before the process blocks and check watchers	1019	prepare watchers get invoked before the process blocks and check watchers
796	afterwards.	1020	afterwards.
797		1021
798	Their main purpose is to integrate other event mechanisms into libev. This	1022	Their main purpose is to integrate other event mechanisms into libev and
799	could be used, for example, to track variable changes, implement your own	1023	their use is somewhat advanced. This could be used, for example, to track
800	watchers, integrate net-snmp or a coroutine library and lots more.	1024	variable changes, implement your own watchers, integrate net-snmp or a
		1025	coroutine library and lots more.
801		1026
802	This is done by examining in each prepare call which file descriptors need	1027	This is done by examining in each prepare call which file descriptors need
803	to be watched by the other library, registering C<ev_io> watchers for	1028	to be watched by the other library, registering C<ev_io> watchers for
804	them and starting an C<ev_timer> watcher for any timeouts (many libraries	1029	them and starting an C<ev_timer> watcher for any timeouts (many libraries
805	provide just this functionality). Then, in the check watcher you check for	1030	provide just this functionality). Then, in the check watcher you check for
…		…
827	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1052	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
828	macros, but using them is utterly, utterly and completely pointless.	1053	macros, but using them is utterly, utterly and completely pointless.
829		1054
830	=back	1055	=back
831		1056
		1057	Example: TODO.
		1058
		1059
		1060	=head2 C<ev_embed> - when one backend isn't enough
		1061
		1062	This is a rather advanced watcher type that lets you embed one event loop
		1063	into another.
		1064
		1065	There are primarily two reasons you would want that: work around bugs and
		1066	prioritise I/O.
		1067
		1068	As an example for a bug workaround, the kqueue backend might only support
		1069	sockets on some platform, so it is unusable as generic backend, but you
		1070	still want to make use of it because you have many sockets and it scales
		1071	so nicely. In this case, you would create a kqueue-based loop and embed it
		1072	into your default loop (which might use e.g. poll). Overall operation will
		1073	be a bit slower because first libev has to poll and then call kevent, but
		1074	at least you can use both at what they are best.
		1075
		1076	As for prioritising I/O: rarely you have the case where some fds have
		1077	to be watched and handled very quickly (with low latency), and even
		1078	priorities and idle watchers might have too much overhead. In this case
		1079	you would put all the high priority stuff in one loop and all the rest in
		1080	a second one, and embed the second one in the first.
		1081
		1082	As long as the watcher is started it will automatically handle events. The
		1083	callback will be invoked whenever some events have been handled. You can
		1084	set the callback to C<0> to avoid having to specify one if you are not
		1085	interested in that.
		1086
		1087	Also, there have not currently been made special provisions for forking:
		1088	when you fork, you not only have to call C<ev_loop_fork> on both loops,
		1089	but you will also have to stop and restart any C<ev_embed> watchers
		1090	yourself.
		1091
		1092	Unfortunately, not all backends are embeddable, only the ones returned by
		1093	C<ev_embeddable_backends> are, which, unfortunately, does not include any
		1094	portable one.
		1095
		1096	So when you want to use this feature you will always have to be prepared
		1097	that you cannot get an embeddable loop. The recommended way to get around
		1098	this is to have a separate variables for your embeddable loop, try to
		1099	create it, and if that fails, use the normal loop for everything:
		1100
		1101	struct ev_loop *loop_hi = ev_default_init (0);
		1102	struct ev_loop *loop_lo = 0;
		1103	struct ev_embed embed;
		1104
		1105	// see if there is a chance of getting one that works
		1106	// (remember that a flags value of 0 means autodetection)
		1107	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		1108	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		1109	: 0;
		1110
		1111	// if we got one, then embed it, otherwise default to loop_hi
		1112	if (loop_lo)
		1113	{
		1114	ev_embed_init (&embed, 0, loop_lo);
		1115	ev_embed_start (loop_hi, &embed);
		1116	}
		1117	else
		1118	loop_lo = loop_hi;
		1119
		1120	=over 4
		1121
		1122	=item ev_embed_init (ev_embed , callback, struct ev_loop loop)
		1123
		1124	=item ev_embed_set (ev_embed , callback, struct ev_loop loop)
		1125
		1126	Configures the watcher to embed the given loop, which must be embeddable.
		1127
		1128	=back
		1129
		1130
832	=head1 OTHER FUNCTIONS	1131	=head1 OTHER FUNCTIONS
833		1132
834	There are some other functions of possible interest. Described. Here. Now.	1133	There are some other functions of possible interest. Described. Here. Now.
835		1134
836	=over 4	1135	=over 4
…		…
882		1181
883	Feed an event as if the given signal occured (loop must be the default loop!).	1182	Feed an event as if the given signal occured (loop must be the default loop!).
884		1183
885	=back	1184	=back
886		1185
		1186
887	=head1 LIBEVENT EMULATION	1187	=head1 LIBEVENT EMULATION
888		1188
889	Libev offers a compatibility emulation layer for libevent. It cannot	1189	Libev offers a compatibility emulation layer for libevent. It cannot
890	emulate the internals of libevent, so here are some usage hints:	1190	emulate the internals of libevent, so here are some usage hints:
891		1191

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Comparing libev/ev.pod (file contents): Revision 1.32 by root, Fri Nov 23 08:36:35 2007 UTC vs. Revision 1.35 by root, Fri Nov 23 19:35:09 2007 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.32 by root, Fri Nov 23 08:36:35 2007 UTC vs.
Revision 1.35 by root, Fri Nov 23 19:35:09 2007 UTC