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

Comparing libev/ev.pod (file contents):
Revision 1.13 by root, Mon Nov 12 08:35:36 2007 UTC vs.
Revision 1.32 by root, Fri Nov 23 08:36:35 2007 UTC

…		…
39	F<README.embed> in the libev distribution. If libev was configured without	39	F<README.embed> in the libev distribution. If libev was configured without
40	support for multiple event loops, then all functions taking an initial	40	support for multiple event loops, then all functions taking an initial
41	argument of name C<loop> (which is always of type C<struct ev_loop *>)	41	argument of name C<loop> (which is always of type C<struct ev_loop *>)
42	will not have this argument.	42	will not have this argument.
43		43
44	=head1 TIME AND OTHER GLOBAL FUNCTIONS	44	=head1 TIME REPRESENTATION
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 double type in C.
51		51
		52	=head1 GLOBAL FUNCTIONS
		53
		54	These functions can be called anytime, even before initialising the
		55	library in any way.
		56
52	=over 4	57	=over 4
53		58
54	=item ev_tstamp ev_time ()	59	=item ev_tstamp ev_time ()
55		60
56	Returns the current time as libev would use it.	61	Returns the current time as libev would use it. Please note that the
		62	C<ev_now> function is usually faster and also often returns the timestamp
		63	you actually want to know.
57		64
58	=item int ev_version_major ()	65	=item int ev_version_major ()
59		66
60	=item int ev_version_minor ()	67	=item int ev_version_minor ()
61		68
…		…
67		74
68	Usually, it's a good idea to terminate if the major versions mismatch,	75	Usually, it's a good idea to terminate if the major versions mismatch,
69	as this indicates an incompatible change. Minor versions are usually	76	as this indicates an incompatible change. Minor versions are usually
70	compatible to older versions, so a larger minor version alone is usually	77	compatible to older versions, so a larger minor version alone is usually
71	not a problem.	78	not a problem.
		79
		80	=item unsigned int ev_supported_backends ()
		81
		82	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
		83	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
		85	a description of the set values.
		86
		87	=item unsigned int ev_recommended_backends ()
		88
		89	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
		91	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
		93	(assuming you know what you are doing). This is the set of backends that
		94	C<EVFLAG_AUTO> will probe for.
72		95
73	=item ev_set_allocator (void (cb)(void *ptr, long size))	96	=item ev_set_allocator (void (cb)(void *ptr, long size))
74		97
75	Sets the allocation function to use (the prototype is similar to the	98	Sets the allocation function to use (the prototype is similar to the
76	realloc C function, the semantics are identical). It is used to allocate	99	realloc C function, the semantics are identical). It is used to allocate
…		…
99	An event loop is described by a C<struct ev_loop *>. The library knows two	122	An event loop is described by a C<struct ev_loop *>. The library knows two
100	types of such loops, the I<default> loop, which supports signals and child	123	types of such loops, the I<default> loop, which supports signals and child
101	events, and dynamically created loops which do not.	124	events, and dynamically created loops which do not.
102		125
103	If you use threads, a common model is to run the default event loop	126	If you use threads, a common model is to run the default event loop
104	in your main thread (or in a separate thrad) and for each thread you	127	in your main thread (or in a separate thread) and for each thread you
105	create, you also create another event loop. Libev itself does no locking	128	create, you also create another event loop. Libev itself does no locking
106	whatsoever, so if you mix calls to the same event loop in different	129	whatsoever, so if you mix calls to the same event loop in different
107	threads, make sure you lock (this is usually a bad idea, though, even if	130	threads, make sure you lock (this is usually a bad idea, though, even if
108	done correctly, because it's hideous and inefficient).	131	done correctly, because it's hideous and inefficient).
109		132
…		…
112	=item struct ev_loop *ev_default_loop (unsigned int flags)	135	=item struct ev_loop *ev_default_loop (unsigned int flags)
113		136
114	This will initialise the default event loop if it hasn't been initialised	137	This will initialise the default event loop if it hasn't been initialised
115	yet and return it. If the default loop could not be initialised, returns	138	yet and return it. If the default loop could not be initialised, returns
116	false. If it already was initialised it simply returns it (and ignores the	139	false. If it already was initialised it simply returns it (and ignores the
117	flags).	140	flags. If that is troubling you, check C<ev_backend ()> afterwards).
118		141
119	If you don't know what event loop to use, use the one returned from this	142	If you don't know what event loop to use, use the one returned from this
120	function.	143	function.
121		144
122	The flags argument can be used to specify special behaviour or specific	145	The flags argument can be used to specify special behaviour or specific
123	backends to use, and is usually specified as 0 (or EVFLAG_AUTO).	146	backends to use, and is usually specified as C<0> (or EVFLAG_AUTO).
124		147
125	It supports the following flags:	148	It supports the following flags:
126		149
127	=over 4	150	=over 4
128		151
…		…
138	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	161	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
139	override the flags completely if it is found in the environment. This is	162	override the flags completely if it is found in the environment. This is
140	useful to try out specific backends to test their performance, or to work	163	useful to try out specific backends to test their performance, or to work
141	around bugs.	164	around bugs.
142		165
143	=item C<EVMETHOD_SELECT> (portable select backend)	166	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
144		167
		168	This is your standard select(2) backend. Not I<completely> standard, as
		169	libev tries to roll its own fd_set with no limits on the number of fds,
		170	but if that fails, expect a fairly low limit on the number of fds when
		171	using this backend. It doesn't scale too well (O(highest_fd)), but its usually
		172	the fastest backend for a low number of fds.
		173
145	=item C<EVMETHOD_POLL> (poll backend, available everywhere except on windows)	174	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
146		175
147	=item C<EVMETHOD_EPOLL> (linux only)	176	And this is your standard poll(2) backend. It's more complicated than
		177	select, but handles sparse fds better and has no artificial limit on the
		178	number of fds you can use (except it will slow down considerably with a
		179	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).
148		180
149	=item C<EVMETHOD_KQUEUE> (some bsds only)	181	=item C<EVBACKEND_EPOLL> (value 4, Linux)
150		182
151	=item C<EVMETHOD_DEVPOLL> (solaris 8 only)	183	For few fds, this backend is a bit little slower than poll and select,
		184	but it scales phenomenally better. While poll and select usually scale like
		185	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
		186	either O(1) or O(active_fds).
152		187
153	=item C<EVMETHOD_PORT> (solaris 10 only)	188	While stopping and starting an I/O watcher in the same iteration will
		189	result in some caching, there is still a syscall per such incident
		190	(because the fd could point to a different file description now), so its
		191	best to avoid that. Also, dup()ed file descriptors might not work very
		192	well if you register events for both fds.
		193
		194	Please note that epoll sometimes generates spurious notifications, so you
		195	need to use non-blocking I/O or other means to avoid blocking when no data
		196	(or space) is available.
		197
		198	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
		199
		200	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
		202	anything but sockets and pipes, except on Darwin, where of course its
		203	completely useless). For this reason its not being "autodetected" unless
		204	you explicitly specify the flags (i.e. you don't use EVFLAG_AUTO).
		205
		206	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
		208	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
		210	incident, so its best to avoid that.
		211
		212	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
		213
		214	This is not implemented yet (and might never be).
		215
		216	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
		217
		218	This uses the Solaris 10 port mechanism. As with everything on Solaris,
		219	it's really slow, but it still scales very well (O(active_fds)).
		220
		221	Please note that solaris ports can result in a lot of spurious
		222	notifications, so you need to use non-blocking I/O or other means to avoid
		223	blocking when no data (or space) is available.
		224
		225	=item C<EVBACKEND_ALL>
		226
		227	Try all backends (even potentially broken ones that wouldn't be tried
		228	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
		229	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
		230
		231	=back
154		232
155	If one or more of these are ored into the flags value, then only these	233	If one or more of these are ored into the flags value, then only these
156	backends will be tried (in the reverse order as given here). If one are	234	backends will be tried (in the reverse order as given here). If none are
157	specified, any backend will do.	235	specified, most compiled-in backend will be tried, usually in reverse
158		236	order of their flag values :)
159	=back
160		237
161	=item struct ev_loop *ev_loop_new (unsigned int flags)	238	=item struct ev_loop *ev_loop_new (unsigned int flags)
162		239
163	Similar to C<ev_default_loop>, but always creates a new event loop that is	240	Similar to C<ev_default_loop>, but always creates a new event loop that is
164	always distinct from the default loop. Unlike the default loop, it cannot	241	always distinct from the default loop. Unlike the default loop, it cannot
…		…
181	This function reinitialises the kernel state for backends that have	258	This function reinitialises the kernel state for backends that have
182	one. Despite the name, you can call it anytime, but it makes most sense	259	one. Despite the name, you can call it anytime, but it makes most sense
183	after forking, in either the parent or child process (or both, but that	260	after forking, in either the parent or child process (or both, but that
184	again makes little sense).	261	again makes little sense).
185		262
186	You I<must> call this function after forking if and only if you want to	263	You I<must> call this function in the child process after forking if and
187	use the event library in both processes. If you just fork+exec, you don't	264	only if you want to use the event library in both processes. If you just
188	have to call it.	265	fork+exec, you don't have to call it.
189		266
190	The function itself is quite fast and it's usually not a problem to call	267	The function itself is quite fast and it's usually not a problem to call
191	it just in case after a fork. To make this easy, the function will fit in	268	it just in case after a fork. To make this easy, the function will fit in
192	quite nicely into a call to C<pthread_atfork>:	269	quite nicely into a call to C<pthread_atfork>:
193		270
194	pthread_atfork (0, 0, ev_default_fork);	271	pthread_atfork (0, 0, ev_default_fork);
195		272
		273	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
		274	without calling this function, so if you force one of those backends you
		275	do not need to care.
		276
196	=item ev_loop_fork (loop)	277	=item ev_loop_fork (loop)
197		278
198	Like C<ev_default_fork>, but acts on an event loop created by	279	Like C<ev_default_fork>, but acts on an event loop created by
199	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	280	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
200	after fork, and how you do this is entirely your own problem.	281	after fork, and how you do this is entirely your own problem.
201		282
202	=item unsigned int ev_method (loop)	283	=item unsigned int ev_backend (loop)
203		284
204	Returns one of the C<EVMETHOD_*> flags indicating the event backend in	285	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
205	use.	286	use.
206		287
207	=item ev_tstamp ev_now (loop)	288	=item ev_tstamp ev_now (loop)
208		289
209	Returns the current "event loop time", which is the time the event loop	290	Returns the current "event loop time", which is the time the event loop
…		…
232		313
233	This flags value could be used to implement alternative looping	314	This flags value could be used to implement alternative looping
234	constructs, but the C<prepare> and C<check> watchers provide a better and	315	constructs, but the C<prepare> and C<check> watchers provide a better and
235	more generic mechanism.	316	more generic mechanism.
236		317
		318	Here are the gory details of what ev_loop does:
		319
		320	1. If there are no active watchers (reference count is zero), return.
		321	2. Queue and immediately call all prepare watchers.
		322	3. If we have been forked, recreate the kernel state.
		323	4. Update the kernel state with all outstanding changes.
		324	5. Update the "event loop time".
		325	6. Calculate for how long to block.
		326	7. Block the process, waiting for events.
		327	8. Update the "event loop time" and do time jump handling.
		328	9. Queue all outstanding timers.
		329	10. Queue all outstanding periodics.
		330	11. If no events are pending now, queue all idle watchers.
		331	12. Queue all check watchers.
		332	13. Call all queued watchers in reverse order (i.e. check watchers first).
		333	14. If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
		334	was used, return, otherwise continue with step #1.
		335
237	=item ev_unloop (loop, how)	336	=item ev_unloop (loop, how)
238		337
239	Can be used to make a call to C<ev_loop> return early (but only after it	338	Can be used to make a call to C<ev_loop> return early (but only after it
240	has processed all outstanding events). The C<how> argument must be either	339	has processed all outstanding events). The C<how> argument must be either
241	C<EVUNLOOP_ONCE>, which will make the innermost C<ev_loop> call return, or	340	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
242	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	341	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
243		342
244	=item ev_ref (loop)	343	=item ev_ref (loop)
245		344
246	=item ev_unref (loop)	345	=item ev_unref (loop)
…		…
297	*) >>), and you can stop watching for events at any time by calling the	396	*) >>), and you can stop watching for events at any time by calling the
298	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	397	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.
299		398
300	As long as your watcher is active (has been started but not stopped) you	399	As long as your watcher is active (has been started but not stopped) you
301	must not touch the values stored in it. Most specifically you must never	400	must not touch the values stored in it. Most specifically you must never
302	reinitialise it or call its set method.	401	reinitialise it or call its set macro.
303		402
304	You cna check whether an event is active by calling the C<ev_is_active	403	You can check whether an event is active by calling the C<ev_is_active
305	(watcher *)> macro. To see whether an event is outstanding (but the	404	(watcher *)> macro. To see whether an event is outstanding (but the
306	callback for it has not been called yet) you cna use the C<ev_is_pending	405	callback for it has not been called yet) you can use the C<ev_is_pending
307	(watcher *)> macro.	406	(watcher *)> macro.
308		407
309	Each and every callback receives the event loop pointer as first, the	408	Each and every callback receives the event loop pointer as first, the
310	registered watcher structure as second, and a bitset of received events as	409	registered watcher structure as second, and a bitset of received events as
311	third argument.	410	third argument.
312		411
313	The rceeived events usually include a single bit per event type received	412	The received events usually include a single bit per event type received
314	(you can receive multiple events at the same time). The possible bit masks	413	(you can receive multiple events at the same time). The possible bit masks
315	are:	414	are:
316		415
317	=over 4	416	=over 4
318		417
…		…
372	=back	471	=back
373		472
374	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	473	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
375		474
376	Each watcher has, by default, a member C<void *data> that you can change	475	Each watcher has, by default, a member C<void *data> that you can change
377	and read at any time, libev will completely ignore it. This cna be used	476	and read at any time, libev will completely ignore it. This can be used
378	to associate arbitrary data with your watcher. If you need more data and	477	to associate arbitrary data with your watcher. If you need more data and
379	don't want to allocate memory and store a pointer to it in that data	478	don't want to allocate memory and store a pointer to it in that data
380	member, you can also "subclass" the watcher type and provide your own	479	member, you can also "subclass" the watcher type and provide your own
381	data:	480	data:
382		481
…		…
409	=head2 C<ev_io> - is this file descriptor readable or writable	508	=head2 C<ev_io> - is this file descriptor readable or writable
410		509
411	I/O watchers check whether a file descriptor is readable or writable	510	I/O watchers check whether a file descriptor is readable or writable
412	in each iteration of the event loop (This behaviour is called	511	in each iteration of the event loop (This behaviour is called
413	level-triggering because you keep receiving events as long as the	512	level-triggering because you keep receiving events as long as the
414	condition persists. Remember you cna stop the watcher if you don't want to	513	condition persists. Remember you can stop the watcher if you don't want to
415	act on the event and neither want to receive future events).	514	act on the event and neither want to receive future events).
416		515
417	In general you can register as many read and/or write event watchers oer	516	In general you can register as many read and/or write event watchers per
418	fd as you want (as long as you don't confuse yourself). Setting all file	517	fd as you want (as long as you don't confuse yourself). Setting all file
419	descriptors to non-blocking mode is also usually a good idea (but not	518	descriptors to non-blocking mode is also usually a good idea (but not
420	required if you know what you are doing).	519	required if you know what you are doing).
421		520
422	You have to be careful with dup'ed file descriptors, though. Some backends	521	You have to be careful with dup'ed file descriptors, though. Some backends
423	(the linux epoll backend is a notable example) cannot handle dup'ed file	522	(the linux epoll backend is a notable example) cannot handle dup'ed file
424	descriptors correctly if you register interest in two or more fds pointing	523	descriptors correctly if you register interest in two or more fds pointing
425	to the same file/socket etc. description.	524	to the same underlying file/socket etc. description (that is, they share
		525	the same underlying "file open").
426		526
427	If you must do this, then force the use of a known-to-be-good backend	527	If you must do this, then force the use of a known-to-be-good backend
428	(at the time of this writing, this includes only EVMETHOD_SELECT and	528	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
429	EVMETHOD_POLL).	529	C<EVBACKEND_POLL>).
430		530
431	=over 4	531	=over 4
432		532
433	=item ev_io_init (ev_io *, callback, int fd, int events)	533	=item ev_io_init (ev_io *, callback, int fd, int events)
434		534
…		…
436		536
437	Configures an C<ev_io> watcher. The fd is the file descriptor to rceeive	537	Configures an C<ev_io> watcher. The fd is the file descriptor to rceeive
438	events for and events is either C<EV_READ>, C<EV_WRITE> or C<EV_READ \|	538	events for and events is either C<EV_READ>, C<EV_WRITE> or C<EV_READ \|
439	EV_WRITE> to receive the given events.	539	EV_WRITE> to receive the given events.
440		540
		541	Please note that most of the more scalable backend mechanisms (for example
		542	epoll and solaris ports) can result in spurious readyness notifications
		543	for file descriptors, so you practically need to use non-blocking I/O (and
		544	treat callback invocation as hint only), or retest separately with a safe
		545	interface before doing I/O (XLib can do this), or force the use of either
		546	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>, which don't suffer from this
		547	problem. Also note that it is quite easy to have your callback invoked
		548	when the readyness condition is no longer valid even when employing
		549	typical ways of handling events, so its a good idea to use non-blocking
		550	I/O unconditionally.
		551
441	=back	552	=back
442		553
443	=head2 C<ev_timer> - relative and optionally recurring timeouts	554	=head2 C<ev_timer> - relative and optionally recurring timeouts
444		555
445	Timer watchers are simple relative timers that generate an event after a	556	Timer watchers are simple relative timers that generate an event after a
446	given time, and optionally repeating in regular intervals after that.	557	given time, and optionally repeating in regular intervals after that.
447		558
448	The timers are based on real time, that is, if you register an event that	559	The timers are based on real time, that is, if you register an event that
449	times out after an hour and youreset your system clock to last years	560	times out after an hour and you reset your system clock to last years
450	time, it will still time out after (roughly) and hour. "Roughly" because	561	time, it will still time out after (roughly) and hour. "Roughly" because
451	detecting time jumps is hard, and soem inaccuracies are unavoidable (the	562	detecting time jumps is hard, and some inaccuracies are unavoidable (the
452	monotonic clock option helps a lot here).	563	monotonic clock option helps a lot here).
453		564
454	The relative timeouts are calculated relative to the C<ev_now ()>	565	The relative timeouts are calculated relative to the C<ev_now ()>
455	time. This is usually the right thing as this timestamp refers to the time	566	time. This is usually the right thing as this timestamp refers to the time
456	of the event triggering whatever timeout you are modifying/starting. If	567	of the event triggering whatever timeout you are modifying/starting. If
457	you suspect event processing to be delayed and you need to base the timeout	568	you suspect event processing to be delayed and you I<need> to base the timeout
458	ion the current time, use something like this to adjust for this:	569	on the current time, use something like this to adjust for this:
459		570
460	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	571	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
		572
		573	The callback is guarenteed to be invoked only when its timeout has passed,
		574	but if multiple timers become ready during the same loop iteration then
		575	order of execution is undefined.
461		576
462	=over 4	577	=over 4
463		578
464	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	579	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
465		580
…		…
471	later, again, and again, until stopped manually.	586	later, again, and again, until stopped manually.
472		587
473	The timer itself will do a best-effort at avoiding drift, that is, if you	588	The timer itself will do a best-effort at avoiding drift, that is, if you
474	configure a timer to trigger every 10 seconds, then it will trigger at	589	configure a timer to trigger every 10 seconds, then it will trigger at
475	exactly 10 second intervals. If, however, your program cannot keep up with	590	exactly 10 second intervals. If, however, your program cannot keep up with
476	the timer (ecause it takes longer than those 10 seconds to do stuff) the	591	the timer (because it takes longer than those 10 seconds to do stuff) the
477	timer will not fire more than once per event loop iteration.	592	timer will not fire more than once per event loop iteration.
478		593
479	=item ev_timer_again (loop)	594	=item ev_timer_again (loop)
480		595
481	This will act as if the timer timed out and restart it again if it is	596	This will act as if the timer timed out and restart it again if it is
…		…
495	state where you do not expect data to travel on the socket, you can stop	610	state where you do not expect data to travel on the socket, you can stop
496	the timer, and again will automatically restart it if need be.	611	the timer, and again will automatically restart it if need be.
497		612
498	=back	613	=back
499		614
500	=head2 C<ev_periodic> - to cron or not to cron it	615	=head2 C<ev_periodic> - to cron or not to cron
501		616
502	Periodic watchers are also timers of a kind, but they are very versatile	617	Periodic watchers are also timers of a kind, but they are very versatile
503	(and unfortunately a bit complex).	618	(and unfortunately a bit complex).
504		619
505	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	620	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
…		…
512	again).	627	again).
513		628
514	They can also be used to implement vastly more complex timers, such as	629	They can also be used to implement vastly more complex timers, such as
515	triggering an event on eahc midnight, local time.	630	triggering an event on eahc midnight, local time.
516		631
		632	As with timers, the callback is guarenteed to be invoked only when the
		633	time (C<at>) has been passed, but if multiple periodic timers become ready
		634	during the same loop iteration then order of execution is undefined.
		635
517	=over 4	636	=over 4
518		637
519	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	638	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
520		639
521	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	640	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
522		641
523	Lots of arguments, lets sort it out... There are basically three modes of	642	Lots of arguments, lets sort it out... There are basically three modes of
524	operation, and we will explain them from simplest to complex:	643	operation, and we will explain them from simplest to complex:
525
526		644
527	=over 4	645	=over 4
528		646
529	=item * absolute timer (interval = reschedule_cb = 0)	647	=item * absolute timer (interval = reschedule_cb = 0)
530		648
…		…
558	In this mode the values for C<interval> and C<at> are both being	676	In this mode the values for C<interval> and C<at> are both being
559	ignored. Instead, each time the periodic watcher gets scheduled, the	677	ignored. Instead, each time the periodic watcher gets scheduled, the
560	reschedule callback will be called with the watcher as first, and the	678	reschedule callback will be called with the watcher as first, and the
561	current time as second argument.	679	current time as second argument.
562		680
563	NOTE: I<This callback MUST NOT stop or destroy the periodic or any other	681	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
564	periodic watcher, ever, or make any event loop modifications>. If you need	682	ever, or make any event loop modifications>. If you need to stop it,
565	to stop it, return C<now + 1e30> (or so, fudge fudge) and stop it afterwards.	683	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
566		684	starting a prepare watcher).
567	Also, I<< this callback must always return a time that is later than the
568	passed C<now> value >>. Not even C<now> itself will be ok.
569		685
570	Its prototype is C<ev_tstamp (reschedule_cb)(struct ev_periodic w,	686	Its prototype is C<ev_tstamp (reschedule_cb)(struct ev_periodic w,
571	ev_tstamp now)>, e.g.:	687	ev_tstamp now)>, e.g.:
572		688
573	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	689	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
…		…
578	It must return the next time to trigger, based on the passed time value	694	It must return the next time to trigger, based on the passed time value
579	(that is, the lowest time value larger than to the second argument). It	695	(that is, the lowest time value larger than to the second argument). It
580	will usually be called just before the callback will be triggered, but	696	will usually be called just before the callback will be triggered, but
581	might be called at other times, too.	697	might be called at other times, too.
582		698
		699	NOTE: I<< This callback must always return a time that is later than the
		700	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.
		701
583	This can be used to create very complex timers, such as a timer that	702	This can be used to create very complex timers, such as a timer that
584	triggers on each midnight, local time. To do this, you would calculate the	703	triggers on each midnight, local time. To do this, you would calculate the
585	next midnight after C<now> and return the timestamp value for this. How you do this	704	next midnight after C<now> and return the timestamp value for this. How
586	is, again, up to you (but it is not trivial).	705	you do this is, again, up to you (but it is not trivial, which is the main
		706	reason I omitted it as an example).
587		707
588	=back	708	=back
589		709
590	=item ev_periodic_again (loop, ev_periodic *)	710	=item ev_periodic_again (loop, ev_periodic *)
591		711
…		…
601	Signal watchers will trigger an event when the process receives a specific	721	Signal watchers will trigger an event when the process receives a specific
602	signal one or more times. Even though signals are very asynchronous, libev	722	signal one or more times. Even though signals are very asynchronous, libev
603	will try it's best to deliver signals synchronously, i.e. as part of the	723	will try it's best to deliver signals synchronously, i.e. as part of the
604	normal event processing, like any other event.	724	normal event processing, like any other event.
605		725
606	You cna configure as many watchers as you like per signal. Only when the	726	You can configure as many watchers as you like per signal. Only when the
607	first watcher gets started will libev actually register a signal watcher	727	first watcher gets started will libev actually register a signal watcher
608	with the kernel (thus it coexists with your own signal handlers as long	728	with the kernel (thus it coexists with your own signal handlers as long
609	as you don't register any with libev). Similarly, when the last signal	729	as you don't register any with libev). Similarly, when the last signal
610	watcher for a signal is stopped libev will reset the signal handler to	730	watcher for a signal is stopped libev will reset the signal handler to
611	SIG_DFL (regardless of what it was set to before).	731	SIG_DFL (regardless of what it was set to before).
…		…
633	=item ev_child_set (ev_child *, int pid)	753	=item ev_child_set (ev_child *, int pid)
634		754
635	Configures the watcher to wait for status changes of process C<pid> (or	755	Configures the watcher to wait for status changes of process C<pid> (or
636	I<any> process if C<pid> is specified as C<0>). The callback can look	756	I<any> process if C<pid> is specified as C<0>). The callback can look
637	at the C<rstatus> member of the C<ev_child> watcher structure to see	757	at the C<rstatus> member of the C<ev_child> watcher structure to see
638	the status word (use the macros from C<sys/wait.h>). The C<rpid> member	758	the status word (use the macros from C<sys/wait.h> and see your systems
639	contains the pid of the process causing the status change.	759	C<waitpid> documentation). The C<rpid> member contains the pid of the
		760	process causing the status change.
640		761
641	=back	762	=back
642		763
643	=head2 C<ev_idle> - when you've got nothing better to do	764	=head2 C<ev_idle> - when you've got nothing better to do
644		765
645	Idle watchers trigger events when there are no other I/O or timer (or	766	Idle watchers trigger events when there are no other events are pending
646	periodic) events pending. That is, as long as your process is busy	767	(prepare, check and other idle watchers do not count). That is, as long
647	handling sockets or timeouts it will not be called. But when your process	768	as your process is busy handling sockets or timeouts (or even signals,
648	is idle all idle watchers are being called again and again - until	769	imagine) it will not be triggered. But when your process is idle all idle
		770	watchers are being called again and again, once per event loop iteration -
649	stopped, that is, or your process receives more events.	771	until stopped, that is, or your process receives more events and becomes
		772	busy.
650		773
651	The most noteworthy effect is that as long as any idle watchers are	774	The most noteworthy effect is that as long as any idle watchers are
652	active, the process will not block when waiting for new events.	775	active, the process will not block when waiting for new events.
653		776
654	Apart from keeping your process non-blocking (which is a useful	777	Apart from keeping your process non-blocking (which is a useful
…		…
664	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	787	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
665	believe me.	788	believe me.
666		789
667	=back	790	=back
668		791
669	=head2 prepare and check - your hooks into the event loop	792	=head2 C<ev_prepare> and C<ev_check> - customise your event loop
670		793
671	Prepare and check watchers usually (but not always) are used in	794	Prepare and check watchers are usually (but not always) used in tandem:
672	tandom. Prepare watchers get invoked before the process blocks and check	795	prepare watchers get invoked before the process blocks and check watchers
673	watchers afterwards.	796	afterwards.
674		797
675	Their main purpose is to integrate other event mechanisms into libev. This	798	Their main purpose is to integrate other event mechanisms into libev. This
676	could be used, for example, to track variable changes, implement your own	799	could be used, for example, to track variable changes, implement your own
677	watchers, integrate net-snmp or a coroutine library and lots more.	800	watchers, integrate net-snmp or a coroutine library and lots more.
678		801
679	This is done by examining in each prepare call which file descriptors need	802	This is done by examining in each prepare call which file descriptors need
680	to be watched by the other library, registering C<ev_io> watchers for them	803	to be watched by the other library, registering C<ev_io> watchers for
681	and starting an C<ev_timer> watcher for any timeouts (many libraries provide	804	them and starting an C<ev_timer> watcher for any timeouts (many libraries
682	just this functionality). Then, in the check watcher you check for any	805	provide just this functionality). Then, in the check watcher you check for
683	events that occured (by making your callbacks set soem flags for example)	806	any events that occured (by checking the pending status of all watchers
684	and call back into the library.	807	and stopping them) and call back into the library. The I/O and timer
		808	callbacks will never actually be called (but must be valid nevertheless,
		809	because you never know, you know?).
685		810
686	As another example, the perl Coro module uses these hooks to integrate	811	As another example, the Perl Coro module uses these hooks to integrate
687	coroutines into libev programs, by yielding to other active coroutines	812	coroutines into libev programs, by yielding to other active coroutines
688	during each prepare and only letting the process block if no coroutines	813	during each prepare and only letting the process block if no coroutines
689	are ready to run.	814	are ready to run (it's actually more complicated: it only runs coroutines
		815	with priority higher than or equal to the event loop and one coroutine
		816	of lower priority, but only once, using idle watchers to keep the event
		817	loop from blocking if lower-priority coroutines are active, thus mapping
		818	low-priority coroutines to idle/background tasks).
690		819
691	=over 4	820	=over 4
692		821
693	=item ev_prepare_init (ev_prepare *, callback)	822	=item ev_prepare_init (ev_prepare *, callback)
694		823
695	=item ev_check_init (ev_check *, callback)	824	=item ev_check_init (ev_check *, callback)
696		825
697	Initialises and configures the prepare or check watcher - they have no	826	Initialises and configures the prepare or check watcher - they have no
698	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	827	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
699	macros, but using them is utterly, utterly pointless.	828	macros, but using them is utterly, utterly and completely pointless.
700		829
701	=back	830	=back
702		831
703	=head1 OTHER FUNCTIONS	832	=head1 OTHER FUNCTIONS
704		833
705	There are some other fucntions of possible interest. Described. Here. Now.	834	There are some other functions of possible interest. Described. Here. Now.
706		835
707	=over 4	836	=over 4
708		837
709	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	838	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
710		839
711	This function combines a simple timer and an I/O watcher, calls your	840	This function combines a simple timer and an I/O watcher, calls your
712	callback on whichever event happens first and automatically stop both	841	callback on whichever event happens first and automatically stop both
713	watchers. This is useful if you want to wait for a single event on an fd	842	watchers. This is useful if you want to wait for a single event on an fd
714	or timeout without havign to allocate/configure/start/stop/free one or	843	or timeout without having to allocate/configure/start/stop/free one or
715	more watchers yourself.	844	more watchers yourself.
716		845
717	If C<fd> is less than 0, then no I/O watcher will be started and events is	846	If C<fd> is less than 0, then no I/O watcher will be started and events
718	ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and C<events> set	847	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
719	will be craeted and started.	848	C<events> set will be craeted and started.
720		849
721	If C<timeout> is less than 0, then no timeout watcher will be	850	If C<timeout> is less than 0, then no timeout watcher will be
722	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and repeat	851	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
723	= 0) will be started.	852	repeat = 0) will be started. While C<0> is a valid timeout, it is of
		853	dubious value.
724		854
725	The callback has the type C<void (cb)(int revents, void arg)> and	855	The callback has the type C<void (cb)(int revents, void arg)> and gets
726	gets passed an events set (normally a combination of C<EV_ERROR>, C<EV_READ>,	856	passed an C<revents> set like normal event callbacks (a combination of
727	C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> value passed to C<ev_once>:	857	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
		858	value passed to C<ev_once>:
728		859
729	static void stdin_ready (int revents, void *arg)	860	static void stdin_ready (int revents, void *arg)
730	{	861	{
731	if (revents & EV_TIMEOUT)	862	if (revents & EV_TIMEOUT)
732	/* doh, nothing entered */	863	/* doh, nothing entered */;
733	else if (revents & EV_READ)	864	else if (revents & EV_READ)
734	/* stdin might have data for us, joy! */	865	/* stdin might have data for us, joy! */;
735	}	866	}
736		867
737	ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0);	868	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
738		869
739	=item ev_feed_event (loop, watcher, int events)	870	=item ev_feed_event (loop, watcher, int events)
740		871
741	Feeds the given event set into the event loop, as if the specified event	872	Feeds the given event set into the event loop, as if the specified event
742	has happened for the specified watcher (which must be a pointer to an	873	had happened for the specified watcher (which must be a pointer to an
743	initialised but not necessarily active event watcher).	874	initialised but not necessarily started event watcher).
744		875
745	=item ev_feed_fd_event (loop, int fd, int revents)	876	=item ev_feed_fd_event (loop, int fd, int revents)
746		877
747	Feed an event on the given fd, as if a file descriptor backend detected it.	878	Feed an event on the given fd, as if a file descriptor backend detected
		879	the given events it.
748		880
749	=item ev_feed_signal_event (loop, int signum)	881	=item ev_feed_signal_event (loop, int signum)
750		882
751	Feed an event as if the given signal occured (loop must be the default loop!).	883	Feed an event as if the given signal occured (loop must be the default loop!).
752		884
753	=back	885	=back
754		886
		887	=head1 LIBEVENT EMULATION
		888
		889	Libev offers a compatibility emulation layer for libevent. It cannot
		890	emulate the internals of libevent, so here are some usage hints:
		891
		892	=over 4
		893
		894	=item * Use it by including <event.h>, as usual.
		895
		896	=item * The following members are fully supported: ev_base, ev_callback,
		897	ev_arg, ev_fd, ev_res, ev_events.
		898
		899	=item * Avoid using ev_flags and the EVLIST_*-macros, while it is
		900	maintained by libev, it does not work exactly the same way as in libevent (consider
		901	it a private API).
		902
		903	=item * Priorities are not currently supported. Initialising priorities
		904	will fail and all watchers will have the same priority, even though there
		905	is an ev_pri field.
		906
		907	=item * Other members are not supported.
		908
		909	=item * The libev emulation is I<not> ABI compatible to libevent, you need
		910	to use the libev header file and library.
		911
		912	=back
		913
		914	=head1 C++ SUPPORT
		915
		916	TBD.
		917
755	=head1 AUTHOR	918	=head1 AUTHOR
756		919
757	Marc Lehmann <libev@schmorp.de>.	920	Marc Lehmann <libev@schmorp.de>.
758		921

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Revision 1.32 by root, Fri Nov 23 08:36:35 2007 UTC