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

Comparing libev/ev.pod (file contents):
Revision 1.18 by root, Mon Nov 12 09:01:12 2007 UTC vs.
Revision 1.33 by root, Fri Nov 23 15:26:08 2007 UTC

…		…
56		56
57	=over 4	57	=over 4
58		58
59	=item ev_tstamp ev_time ()	59	=item ev_tstamp ev_time ()
60		60
61	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.
62		64
63	=item int ev_version_major ()	65	=item int ev_version_major ()
64		66
65	=item int ev_version_minor ()	67	=item int ev_version_minor ()
66		68
…		…
72		74
73	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,
74	as this indicates an incompatible change. Minor versions are usually	76	as this indicates an incompatible change. Minor versions are usually
75	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
76	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.
77		95
78	=item ev_set_allocator (void (cb)(void *ptr, long size))	96	=item ev_set_allocator (void (cb)(void *ptr, long size))
79		97
80	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
81	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
…		…
117	=item struct ev_loop *ev_default_loop (unsigned int flags)	135	=item struct ev_loop *ev_default_loop (unsigned int flags)
118		136
119	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
120	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
121	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
122	flags).	140	flags. If that is troubling you, check C<ev_backend ()> afterwards).
123		141
124	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
125	function.	143	function.
126		144
127	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
128	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>).
129		147
130	It supports the following flags:	148	The following flags are supported:
131		149
132	=over 4	150	=over 4
133		151
134	=item C<EVFLAG_AUTO>	152	=item C<EVFLAG_AUTO>
135		153
…		…
143	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	161	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
144	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
145	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
146	around bugs.	164	around bugs.
147		165
148	=item C<EVMETHOD_SELECT> (portable select backend)	166	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
149		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
150	=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)
151		175
152	=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).
153		180
154	=item C<EVMETHOD_KQUEUE> (some bsds only)	181	=item C<EVBACKEND_EPOLL> (value 4, Linux)
155		182
156	=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).
157		187
158	=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
159		233
160	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
161	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
162	specified, any backend will do.	236	specified, most compiled-in backend will be tried, usually in reverse
		237	order of their flag values :)
163		238
164	=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);
165		254
166	=item struct ev_loop *ev_loop_new (unsigned int flags)	255	=item struct ev_loop *ev_loop_new (unsigned int flags)
167		256
168	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
169	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
…		…
186	This function reinitialises the kernel state for backends that have	275	This function reinitialises the kernel state for backends that have
187	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
188	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
189	again makes little sense).	278	again makes little sense).
190		279
191	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
192	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
193	have to call it.	282	fork+exec, you don't have to call it.
194		283
195	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
196	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
197	quite nicely into a call to C<pthread_atfork>:	286	quite nicely into a call to C<pthread_atfork>:
198		287
199	pthread_atfork (0, 0, ev_default_fork);	288	pthread_atfork (0, 0, ev_default_fork);
200		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
201	=item ev_loop_fork (loop)	294	=item ev_loop_fork (loop)
202		295
203	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
204	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
205	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.
206		299
207	=item unsigned int ev_method (loop)	300	=item unsigned int ev_backend (loop)
208		301
209	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
210	use.	303	use.
211		304
212	=item ev_tstamp ev_now (loop)	305	=item ev_tstamp ev_now (loop)
213		306
214	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
…		…
221		314
222	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
223	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
224	events.	317	events.
225		318
226	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
227	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.
228		321
229	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
230	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
231	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.
232		325
233	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
234	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
235	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
236	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.
237		333
238	This flags value could be used to implement alternative looping	334	Here are the gory details of what C<ev_loop> does:
239	constructs, but the C<prepare> and C<check> watchers provide a better and	335
240	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 *.
241		354
242	=item ev_unloop (loop, how)	355	=item ev_unloop (loop, how)
243		356
244	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
245	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
246	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
247	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.
248		361
249	=item ev_ref (loop)	362	=item ev_ref (loop)
250		363
251	=item ev_unref (loop)	364	=item ev_unref (loop)
…		…
302	*) >>), 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
303	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	416	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.
304		417
305	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
306	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
307	reinitialise it or call its set method.	420	reinitialise it or call its set macro.
308		421
309	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
310	(watcher *)> macro. To see whether an event is outstanding (but the	423	(watcher *)> macro. To see whether an event is outstanding (but the
311	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
312	(watcher *)> macro.	425	(watcher *)> macro.
…		…
417	in each iteration of the event loop (This behaviour is called	530	in each iteration of the event loop (This behaviour is called
418	level-triggering because you keep receiving events as long as the	531	level-triggering because you keep receiving events as long as the
419	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
420	act on the event and neither want to receive future events).	533	act on the event and neither want to receive future events).
421		534
422	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
423	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
424	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
425	required if you know what you are doing).	538	required if you know what you are doing).
426		539
427	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
428	(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
429	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
430	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").
431		545
432	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
433	(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
434	EVMETHOD_POLL).	548	C<EVBACKEND_POLL>).
435		549
436	=over 4	550	=over 4
437		551
438	=item ev_io_init (ev_io *, callback, int fd, int events)	552	=item ev_io_init (ev_io *, callback, int fd, int events)
439		553
…		…
441		555
442	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
443	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 \|
444	EV_WRITE> to receive the given events.	558	EV_WRITE> to receive the given events.
445		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
446	=back	571	=back
447		572
448	=head2 C<ev_timer> - relative and optionally recurring timeouts	573	=head2 C<ev_timer> - relative and optionally recurring timeouts
449		574
450	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
451	given time, and optionally repeating in regular intervals after that.	576	given time, and optionally repeating in regular intervals after that.
452		577
453	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
454	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
455	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
456	detecting time jumps is hard, and soem inaccuracies are unavoidable (the	581	detecting time jumps is hard, and some inaccuracies are unavoidable (the
457	monotonic clock option helps a lot here).	582	monotonic clock option helps a lot here).
458		583
459	The relative timeouts are calculated relative to the C<ev_now ()>	584	The relative timeouts are calculated relative to the C<ev_now ()>
460	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
461	of the event triggering whatever timeout you are modifying/starting. If	586	of the event triggering whatever timeout you are modifying/starting. If
462	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
463	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:
464		589
465	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.
466		595
467	=over 4	596	=over 4
468		597
469	=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)
470		599
…		…
476	later, again, and again, until stopped manually.	605	later, again, and again, until stopped manually.
477		606
478	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
479	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
480	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
481	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
482	timer will not fire more than once per event loop iteration.	611	timer will not fire more than once per event loop iteration.
483		612
484	=item ev_timer_again (loop)	613	=item ev_timer_again (loop)
485		614
486	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
…		…
517	again).	646	again).
518		647
519	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
520	triggering an event on eahc midnight, local time.	649	triggering an event on eahc midnight, local time.
521		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
522	=over 4	655	=over 4
523		656
524	=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)
525		658
526	=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)
527		660
528	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
529	operation, and we will explain them from simplest to complex:	662	operation, and we will explain them from simplest to complex:
530
531		663
532	=over 4	664	=over 4
533		665
534	=item * absolute timer (interval = reschedule_cb = 0)	666	=item * absolute timer (interval = reschedule_cb = 0)
535		667
…		…
582	(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
583	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
584	might be called at other times, too.	716	might be called at other times, too.
585		717
586	NOTE: I<< This callback must always return a time that is later than the	718	NOTE: I<< This callback must always return a time that is later than the
587	passed C<now> value >>. Not even C<now> itself will do, it must be larger.	719	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.
588		720
589	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
590	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
591	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
592	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).
593		726
594	=back	727	=back
595		728
596	=item ev_periodic_again (loop, ev_periodic *)	729	=item ev_periodic_again (loop, ev_periodic *)
597		730
…		…
676	=back	809	=back
677		810
678	=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
679		812
680	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:
681	Prepare watchers get invoked before the process blocks and check watchers	814	prepare watchers get invoked before the process blocks and check watchers
682	afterwards.	815	afterwards.
683		816
684	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
685	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
686	watchers, integrate net-snmp or a coroutine library and lots more.	819	watchers, integrate net-snmp or a coroutine library and lots more.
…		…
689	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
690	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
691	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
692	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
693	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
694	callbacks will never actually be called (but must be valid neverthelles,	827	callbacks will never actually be called (but must be valid nevertheless,
695	because you never know, you know?).	828	because you never know, you know?).
696		829
697	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
698	coroutines into libev programs, by yielding to other active coroutines	831	coroutines into libev programs, by yielding to other active coroutines
699	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
700	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
701	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
702	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
703	coroutines exist, thus mapping low-priority coroutines to idle/background	836	loop from blocking if lower-priority coroutines are active, thus mapping
704	tasks).	837	low-priority coroutines to idle/background tasks).
705		838
706	=over 4	839	=over 4
707		840
708	=item ev_prepare_init (ev_prepare *, callback)	841	=item ev_prepare_init (ev_prepare *, callback)
709		842
…		…
724	=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)
725		858
726	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
727	callback on whichever event happens first and automatically stop both	860	callback on whichever event happens first and automatically stop both
728	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
729	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
730	more watchers yourself.	863	more watchers yourself.
731		864
732	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
733	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
734	C<events> set will be craeted and started.	867	C<events> set will be craeted and started.
…		…
737	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
738	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
739	dubious value.	872	dubious value.
740		873
741	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
742	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
743	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>
744	value passed to C<ev_once>:	877	value passed to C<ev_once>:
745		878
746	static void stdin_ready (int revents, void *arg)	879	static void stdin_ready (int revents, void *arg)
747	{	880	{
…		…
768		901
769	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!).
770		903
771	=back	904	=back
772		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
773	=head1 AUTHOR	937	=head1 AUTHOR
774		938
775	Marc Lehmann <libev@schmorp.de>.	939	Marc Lehmann <libev@schmorp.de>.
776		940

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Comparing libev/ev.pod (file contents): Revision 1.18 by root, Mon Nov 12 09:01:12 2007 UTC vs. Revision 1.33 by root, Fri Nov 23 15:26:08 2007 UTC

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Revision 1.18 by root, Mon Nov 12 09:01:12 2007 UTC vs.
Revision 1.33 by root, Fri Nov 23 15:26:08 2007 UTC