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

Comparing libev/ev.pod (file contents):
Revision 1.16 by root, Mon Nov 12 08:47:14 2007 UTC vs.
Revision 1.33 by root, Fri Nov 23 15:26:08 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	libev will probe for if you specify no backends explicitly.
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 C<EVFLAG_AUTO>).
124		147
125	It supports the following flags:	148	The following flags are supported:
126		149
127	=over 4	150	=over 4
128		151
129	=item C<EVFLAG_AUTO>	152	=item C<EVFLAG_AUTO>
130		153
…		…
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"
		204	unless you explicitly specify it explicitly in the flags (i.e. using
		205	C<EVBACKEND_KQUEUE>).
		206
		207	It scales in the same way as the epoll backend, but the interface to the
		208	kernel is more efficient (which says nothing about its actual speed, of
		209	course). While starting and stopping an I/O watcher does not cause an
		210	extra syscall as with epoll, it still adds up to four event changes per
		211	incident, so its best to avoid that.
		212
		213	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
		214
		215	This is not implemented yet (and might never be).
		216
		217	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
		218
		219	This uses the Solaris 10 port mechanism. As with everything on Solaris,
		220	it's really slow, but it still scales very well (O(active_fds)).
		221
		222	Please note that solaris ports can result in a lot of spurious
		223	notifications, so you need to use non-blocking I/O or other means to avoid
		224	blocking when no data (or space) is available.
		225
		226	=item C<EVBACKEND_ALL>
		227
		228	Try all backends (even potentially broken ones that wouldn't be tried
		229	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
		230	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
		231
		232	=back
154		233
155	If one or more of these are ored into the flags value, then only these	234	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	235	backends will be tried (in the reverse order as given here). If none are
157	specified, any backend will do.	236	specified, most compiled-in backend will be tried, usually in reverse
		237	order of their flag values :)
158		238
159	=back	239	The most typical usage is like this:
		240
		241	if (!ev_default_loop (0))
		242	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		243
		244	Restrict libev to the select and poll backends, and do not allow
		245	environment settings to be taken into account:
		246
		247	ev_default_loop (EVBACKEND_POLL \| EVBACKEND_SELECT \| EVFLAG_NOENV);
		248
		249	Use whatever libev has to offer, but make sure that kqueue is used if
		250	available (warning, breaks stuff, best use only with your own private
		251	event loop and only if you know the OS supports your types of fds):
		252
		253	ev_default_loop (ev_recommended_backends () \| EVBACKEND_KQUEUE);
160		254
161	=item struct ev_loop *ev_loop_new (unsigned int flags)	255	=item struct ev_loop *ev_loop_new (unsigned int flags)
162		256
163	Similar to C<ev_default_loop>, but always creates a new event loop that is	257	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	258	always distinct from the default loop. Unlike the default loop, it cannot
…		…
181	This function reinitialises the kernel state for backends that have	275	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	276	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	277	after forking, in either the parent or child process (or both, but that
184	again makes little sense).	278	again makes little sense).
185		279
186	You I<must> call this function after forking if and only if you want to	280	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	281	only if you want to use the event library in both processes. If you just
188	have to call it.	282	fork+exec, you don't have to call it.
189		283
190	The function itself is quite fast and it's usually not a problem to call	284	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	285	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>:	286	quite nicely into a call to C<pthread_atfork>:
193		287
194	pthread_atfork (0, 0, ev_default_fork);	288	pthread_atfork (0, 0, ev_default_fork);
195		289
		290	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
		291	without calling this function, so if you force one of those backends you
		292	do not need to care.
		293
196	=item ev_loop_fork (loop)	294	=item ev_loop_fork (loop)
197		295
198	Like C<ev_default_fork>, but acts on an event loop created by	296	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	297	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.	298	after fork, and how you do this is entirely your own problem.
201		299
202	=item unsigned int ev_method (loop)	300	=item unsigned int ev_backend (loop)
203		301
204	Returns one of the C<EVMETHOD_*> flags indicating the event backend in	302	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
205	use.	303	use.
206		304
207	=item ev_tstamp ev_now (loop)	305	=item ev_tstamp ev_now (loop)
208		306
209	Returns the current "event loop time", which is the time the event loop	307	Returns the current "event loop time", which is the time the event loop
…		…
216		314
217	Finally, this is it, the event handler. This function usually is called	315	Finally, this is it, the event handler. This function usually is called
218	after you initialised all your watchers and you want to start handling	316	after you initialised all your watchers and you want to start handling
219	events.	317	events.
220		318
221	If the flags argument is specified as 0, it will not return until either	319	If the flags argument is specified as C<0>, it will not return until
222	no event watchers are active anymore or C<ev_unloop> was called.	320	either no event watchers are active anymore or C<ev_unloop> was called.
223		321
224	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	322	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
225	those events and any outstanding ones, but will not block your process in	323	those events and any outstanding ones, but will not block your process in
226	case there are no events and will return after one iteration of the loop.	324	case there are no events and will return after one iteration of the loop.
227		325
228	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	326	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
229	neccessary) and will handle those and any outstanding ones. It will block	327	neccessary) and will handle those and any outstanding ones. It will block
230	your process until at least one new event arrives, and will return after	328	your process until at least one new event arrives, and will return after
231	one iteration of the loop.	329	one iteration of the loop. This is useful if you are waiting for some
		330	external event in conjunction with something not expressible using other
		331	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
		332	usually a better approach for this kind of thing.
232		333
233	This flags value could be used to implement alternative looping	334	Here are the gory details of what C<ev_loop> does:
234	constructs, but the C<prepare> and C<check> watchers provide a better and	335
235	more generic mechanism.	336	* If there are no active watchers (reference count is zero), return.
		337	- Queue prepare watchers and then call all outstanding watchers.
		338	- If we have been forked, recreate the kernel state.
		339	- Update the kernel state with all outstanding changes.
		340	- Update the "event loop time".
		341	- Calculate for how long to block.
		342	- Block the process, waiting for any events.
		343	- Queue all outstanding I/O (fd) events.
		344	- Update the "event loop time" and do time jump handling.
		345	- Queue all outstanding timers.
		346	- Queue all outstanding periodics.
		347	- If no events are pending now, queue all idle watchers.
		348	- Queue all check watchers.
		349	- Call all queued watchers in reverse order (i.e. check watchers first).
		350	Signals and child watchers are implemented as I/O watchers, and will
		351	be handled here by queueing them when their watcher gets executed.
		352	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
		353	were used, return, otherwise continue with step *.
236		354
237	=item ev_unloop (loop, how)	355	=item ev_unloop (loop, how)
238		356
239	Can be used to make a call to C<ev_loop> return early (but only after it	357	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	358	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	359	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.	360	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
243		361
244	=item ev_ref (loop)	362	=item ev_ref (loop)
245		363
246	=item ev_unref (loop)	364	=item ev_unref (loop)
…		…
297	*) >>), and you can stop watching for events at any time by calling the	415	*) >>), and you can stop watching for events at any time by calling the
298	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	416	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.
299		417
300	As long as your watcher is active (has been started but not stopped) you	418	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	419	must not touch the values stored in it. Most specifically you must never
302	reinitialise it or call its set method.	420	reinitialise it or call its set macro.
303		421
304	You can check whether an event is active by calling the C<ev_is_active	422	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	423	(watcher *)> macro. To see whether an event is outstanding (but the
306	callback for it has not been called yet) you can use the C<ev_is_pending	424	callback for it has not been called yet) you can use the C<ev_is_pending
307	(watcher *)> macro.	425	(watcher *)> macro.
…		…
412	in each iteration of the event loop (This behaviour is called	530	in each iteration of the event loop (This behaviour is called
413	level-triggering because you keep receiving events as long as the	531	level-triggering because you keep receiving events as long as the
414	condition persists. Remember you can stop the watcher if you don't want to	532	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).	533	act on the event and neither want to receive future events).
416		534
417	In general you can register as many read and/or write event watchers oer	535	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	536	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	537	descriptors to non-blocking mode is also usually a good idea (but not
420	required if you know what you are doing).	538	required if you know what you are doing).
421		539
422	You have to be careful with dup'ed file descriptors, though. Some backends	540	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	541	(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	542	descriptors correctly if you register interest in two or more fds pointing
425	to the same file/socket etc. description.	543	to the same underlying file/socket etc. description (that is, they share
		544	the same underlying "file open").
426		545
427	If you must do this, then force the use of a known-to-be-good backend	546	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	547	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
429	EVMETHOD_POLL).	548	C<EVBACKEND_POLL>).
430		549
431	=over 4	550	=over 4
432		551
433	=item ev_io_init (ev_io *, callback, int fd, int events)	552	=item ev_io_init (ev_io *, callback, int fd, int events)
434		553
…		…
436		555
437	Configures an C<ev_io> watcher. The fd is the file descriptor to rceeive	556	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 \|	557	events for and events is either C<EV_READ>, C<EV_WRITE> or C<EV_READ \|
439	EV_WRITE> to receive the given events.	558	EV_WRITE> to receive the given events.
440		559
		560	Please note that most of the more scalable backend mechanisms (for example
		561	epoll and solaris ports) can result in spurious readyness notifications
		562	for file descriptors, so you practically need to use non-blocking I/O (and
		563	treat callback invocation as hint only), or retest separately with a safe
		564	interface before doing I/O (XLib can do this), or force the use of either
		565	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>, which don't suffer from this
		566	problem. Also note that it is quite easy to have your callback invoked
		567	when the readyness condition is no longer valid even when employing
		568	typical ways of handling events, so its a good idea to use non-blocking
		569	I/O unconditionally.
		570
441	=back	571	=back
442		572
443	=head2 C<ev_timer> - relative and optionally recurring timeouts	573	=head2 C<ev_timer> - relative and optionally recurring timeouts
444		574
445	Timer watchers are simple relative timers that generate an event after a	575	Timer watchers are simple relative timers that generate an event after a
446	given time, and optionally repeating in regular intervals after that.	576	given time, and optionally repeating in regular intervals after that.
447		577
448	The timers are based on real time, that is, if you register an event that	578	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	579	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	580	time, it will still time out after (roughly) and hour. "Roughly" because
451	detecting time jumps is hard, and soem inaccuracies are unavoidable (the	581	detecting time jumps is hard, and some inaccuracies are unavoidable (the
452	monotonic clock option helps a lot here).	582	monotonic clock option helps a lot here).
453		583
454	The relative timeouts are calculated relative to the C<ev_now ()>	584	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	585	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	586	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	587	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:	588	on the current time, use something like this to adjust for this:
459		589
460	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	590	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
		591
		592	The callback is guarenteed to be invoked only when its timeout has passed,
		593	but if multiple timers become ready during the same loop iteration then
		594	order of execution is undefined.
461		595
462	=over 4	596	=over 4
463		597
464	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	598	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
465		599
…		…
471	later, again, and again, until stopped manually.	605	later, again, and again, until stopped manually.
472		606
473	The timer itself will do a best-effort at avoiding drift, that is, if you	607	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	608	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	609	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	610	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.	611	timer will not fire more than once per event loop iteration.
478		612
479	=item ev_timer_again (loop)	613	=item ev_timer_again (loop)
480		614
481	This will act as if the timer timed out and restart it again if it is	615	This will act as if the timer timed out and restart it again if it is
…		…
512	again).	646	again).
513		647
514	They can also be used to implement vastly more complex timers, such as	648	They can also be used to implement vastly more complex timers, such as
515	triggering an event on eahc midnight, local time.	649	triggering an event on eahc midnight, local time.
516		650
		651	As with timers, the callback is guarenteed to be invoked only when the
		652	time (C<at>) has been passed, but if multiple periodic timers become ready
		653	during the same loop iteration then order of execution is undefined.
		654
517	=over 4	655	=over 4
518		656
519	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	657	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
520		658
521	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	659	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
522		660
523	Lots of arguments, lets sort it out... There are basically three modes of	661	Lots of arguments, lets sort it out... There are basically three modes of
524	operation, and we will explain them from simplest to complex:	662	operation, and we will explain them from simplest to complex:
525
526		663
527	=over 4	664	=over 4
528		665
529	=item * absolute timer (interval = reschedule_cb = 0)	666	=item * absolute timer (interval = reschedule_cb = 0)
530		667
…		…
558	In this mode the values for C<interval> and C<at> are both being	695	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	696	ignored. Instead, each time the periodic watcher gets scheduled, the
560	reschedule callback will be called with the watcher as first, and the	697	reschedule callback will be called with the watcher as first, and the
561	current time as second argument.	698	current time as second argument.
562		699
563	NOTE: I<This callback MUST NOT stop or destroy the periodic or any other	700	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	701	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.	702	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
566		703	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		704
570	Its prototype is C<ev_tstamp (reschedule_cb)(struct ev_periodic w,	705	Its prototype is C<ev_tstamp (reschedule_cb)(struct ev_periodic w,
571	ev_tstamp now)>, e.g.:	706	ev_tstamp now)>, e.g.:
572		707
573	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	708	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	713	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	714	(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	715	will usually be called just before the callback will be triggered, but
581	might be called at other times, too.	716	might be called at other times, too.
582		717
		718	NOTE: I<< This callback must always return a time that is later than the
		719	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.
		720
583	This can be used to create very complex timers, such as a timer that	721	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	722	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	723	next midnight after C<now> and return the timestamp value for this. How
586	is, again, up to you (but it is not trivial).	724	you do this is, again, up to you (but it is not trivial, which is the main
		725	reason I omitted it as an example).
587		726
588	=back	727	=back
589		728
590	=item ev_periodic_again (loop, ev_periodic *)	729	=item ev_periodic_again (loop, ev_periodic *)
591		730
…		…
670	=back	809	=back
671		810
672	=head2 C<ev_prepare> and C<ev_check> - customise your event loop	811	=head2 C<ev_prepare> and C<ev_check> - customise your event loop
673		812
674	Prepare and check watchers are usually (but not always) used in tandem:	813	Prepare and check watchers are usually (but not always) used in tandem:
675	Prepare watchers get invoked before the process blocks and check watchers	814	prepare watchers get invoked before the process blocks and check watchers
676	afterwards.	815	afterwards.
677		816
678	Their main purpose is to integrate other event mechanisms into libev. This	817	Their main purpose is to integrate other event mechanisms into libev. This
679	could be used, for example, to track variable changes, implement your own	818	could be used, for example, to track variable changes, implement your own
680	watchers, integrate net-snmp or a coroutine library and lots more.	819	watchers, integrate net-snmp or a coroutine library and lots more.
…		…
683	to be watched by the other library, registering C<ev_io> watchers for	822	to be watched by the other library, registering C<ev_io> watchers for
684	them and starting an C<ev_timer> watcher for any timeouts (many libraries	823	them and starting an C<ev_timer> watcher for any timeouts (many libraries
685	provide just this functionality). Then, in the check watcher you check for	824	provide just this functionality). Then, in the check watcher you check for
686	any events that occured (by checking the pending status of all watchers	825	any events that occured (by checking the pending status of all watchers
687	and stopping them) and call back into the library. The I/O and timer	826	and stopping them) and call back into the library. The I/O and timer
688	callbacks will never actually be called (but must be valid neverthelles,	827	callbacks will never actually be called (but must be valid nevertheless,
689	because you never know, you know?).	828	because you never know, you know?).
690		829
691	As another example, the Perl Coro module uses these hooks to integrate	830	As another example, the Perl Coro module uses these hooks to integrate
692	coroutines into libev programs, by yielding to other active coroutines	831	coroutines into libev programs, by yielding to other active coroutines
693	during each prepare and only letting the process block if no coroutines	832	during each prepare and only letting the process block if no coroutines
694	are ready to run (its actually more complicated, it only runs coroutines	833	are ready to run (it's actually more complicated: it only runs coroutines
695	with priority higher than the event loop and one lower priority once,	834	with priority higher than or equal to the event loop and one coroutine
696	using idle watchers to keep the event loop from blocking if lower-priority	835	of lower priority, but only once, using idle watchers to keep the event
697	coroutines exist, thus mapping low-priority coroutines to idle/background	836	loop from blocking if lower-priority coroutines are active, thus mapping
698	tasks).	837	low-priority coroutines to idle/background tasks).
699		838
700	=over 4	839	=over 4
701		840
702	=item ev_prepare_init (ev_prepare *, callback)	841	=item ev_prepare_init (ev_prepare *, callback)
703		842
…		…
718	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	857	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
719		858
720	This function combines a simple timer and an I/O watcher, calls your	859	This function combines a simple timer and an I/O watcher, calls your
721	callback on whichever event happens first and automatically stop both	860	callback on whichever event happens first and automatically stop both
722	watchers. This is useful if you want to wait for a single event on an fd	861	watchers. This is useful if you want to wait for a single event on an fd
723	or timeout without havign to allocate/configure/start/stop/free one or	862	or timeout without having to allocate/configure/start/stop/free one or
724	more watchers yourself.	863	more watchers yourself.
725		864
726	If C<fd> is less than 0, then no I/O watcher will be started and events	865	If C<fd> is less than 0, then no I/O watcher will be started and events
727	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	866	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
728	C<events> set will be craeted and started.	867	C<events> set will be craeted and started.
…		…
731	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	870	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
732	repeat = 0) will be started. While C<0> is a valid timeout, it is of	871	repeat = 0) will be started. While C<0> is a valid timeout, it is of
733	dubious value.	872	dubious value.
734		873
735	The callback has the type C<void (cb)(int revents, void arg)> and gets	874	The callback has the type C<void (cb)(int revents, void arg)> and gets
736	passed an events set like normal event callbacks (with a combination of	875	passed an C<revents> set like normal event callbacks (a combination of
737	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	876	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
738	value passed to C<ev_once>:	877	value passed to C<ev_once>:
739		878
740	static void stdin_ready (int revents, void *arg)	879	static void stdin_ready (int revents, void *arg)
741	{	880	{
…		…
762		901
763	Feed an event as if the given signal occured (loop must be the default loop!).	902	Feed an event as if the given signal occured (loop must be the default loop!).
764		903
765	=back	904	=back
766		905
		906	=head1 LIBEVENT EMULATION
		907
		908	Libev offers a compatibility emulation layer for libevent. It cannot
		909	emulate the internals of libevent, so here are some usage hints:
		910
		911	=over 4
		912
		913	=item * Use it by including <event.h>, as usual.
		914
		915	=item * The following members are fully supported: ev_base, ev_callback,
		916	ev_arg, ev_fd, ev_res, ev_events.
		917
		918	=item * Avoid using ev_flags and the EVLIST_*-macros, while it is
		919	maintained by libev, it does not work exactly the same way as in libevent (consider
		920	it a private API).
		921
		922	=item * Priorities are not currently supported. Initialising priorities
		923	will fail and all watchers will have the same priority, even though there
		924	is an ev_pri field.
		925
		926	=item * Other members are not supported.
		927
		928	=item * The libev emulation is I<not> ABI compatible to libevent, you need
		929	to use the libev header file and library.
		930
		931	=back
		932
		933	=head1 C++ SUPPORT
		934
		935	TBD.
		936
767	=head1 AUTHOR	937	=head1 AUTHOR
768		938
769	Marc Lehmann <libev@schmorp.de>.	939	Marc Lehmann <libev@schmorp.de>.
770		940

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Comparing libev/ev.pod (file contents): Revision 1.16 by root, Mon Nov 12 08:47:14 2007 UTC vs. Revision 1.33 by root, Fri Nov 23 15:26:08 2007 UTC

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Revision 1.16 by root, Mon Nov 12 08:47:14 2007 UTC vs.
Revision 1.33 by root, Fri Nov 23 15:26:08 2007 UTC