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

Comparing libev/ev.pod (file contents):
Revision 1.11 by root, Mon Nov 12 08:32:52 2007 UTC vs.
Revision 1.30 by root, Fri Nov 23 04:36:03 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
…		…
99	An event loop is described by a C<struct ev_loop *>. The library knows two	106	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	107	types of such loops, the I<default> loop, which supports signals and child
101	events, and dynamically created loops which do not.	108	events, and dynamically created loops which do not.
102		109
103	If you use threads, a common model is to run the default event loop	110	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	111	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	112	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	113	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	114	threads, make sure you lock (this is usually a bad idea, though, even if
108	done correctly, because it's hideous and inefficient).	115	done correctly, because it's hideous and inefficient).
109		116
…		…
138	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	145	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
139	override the flags completely if it is found in the environment. This is	146	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	147	useful to try out specific backends to test their performance, or to work
141	around bugs.	148	around bugs.
142		149
143	=item C<EVMETHOD_SELECT> (portable select backend)	150	=item C<EVMETHOD_SELECT> (value 1, portable select backend)
144		151
		152	This is your standard select(2) backend. Not I<completely> standard, as
		153	libev tries to roll its own fd_set with no limits on the number of fds,
		154	but if that fails, expect a fairly low limit on the number of fds when
		155	using this backend. It doesn't scale too well (O(highest_fd)), but its usually
		156	the fastest backend for a low number of fds.
		157
145	=item C<EVMETHOD_POLL> (poll backend, available everywhere except on windows)	158	=item C<EVMETHOD_POLL> (value 2, poll backend, available everywhere except on windows)
146		159
		160	And this is your standard poll(2) backend. It's more complicated than
		161	select, but handles sparse fds better and has no artificial limit on the
		162	number of fds you can use (except it will slow down considerably with a
		163	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).
		164
147	=item C<EVMETHOD_EPOLL> (linux only)	165	=item C<EVMETHOD_EPOLL> (value 4, Linux)
148		166
149	=item C<EVMETHOD_KQUEUE> (some bsds only)	167	For few fds, this backend is a bit little slower than poll and select,
		168	but it scales phenomenally better. While poll and select usually scale like
		169	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
		170	either O(1) or O(active_fds).
150		171
		172	While stopping and starting an I/O watcher in the same iteration will
		173	result in some caching, there is still a syscall per such incident
		174	(because the fd could point to a different file description now), so its
		175	best to avoid that. Also, dup()ed file descriptors might not work very
		176	well if you register events for both fds.
		177
		178	=item C<EVMETHOD_KQUEUE> (value 8, most BSD clones)
		179
		180	Kqueue deserves special mention, as at the time of this writing, it
		181	was broken on all BSDs except NetBSD (usually it doesn't work with
		182	anything but sockets and pipes, except on Darwin, where of course its
		183	completely useless). For this reason its not being "autodetected" unless
		184	you explicitly specify the flags (i.e. you don't use EVFLAG_AUTO).
		185
		186	It scales in the same way as the epoll backend, but the interface to the
		187	kernel is more efficient (which says nothing about its actual speed, of
		188	course). While starting and stopping an I/O watcher does not cause an
		189	extra syscall as with epoll, it still adds up to four event changes per
		190	incident, so its best to avoid that.
		191
151	=item C<EVMETHOD_DEVPOLL> (solaris 8 only)	192	=item C<EVMETHOD_DEVPOLL> (value 16, Solaris 8)
152		193
		194	This is not implemented yet (and might never be).
		195
153	=item C<EVMETHOD_PORT> (solaris 10 only)	196	=item C<EVMETHOD_PORT> (value 32, Solaris 10)
		197
		198	This uses the Solaris 10 port mechanism. As with everything on Solaris,
		199	it's really slow, but it still scales very well (O(active_fds)).
		200
		201	=item C<EVMETHOD_ALL>
		202
		203	Try all backends (even potentially broken ones that wouldn't be tried
		204	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
		205	C<EVMETHOD_ALL & ~EVMETHOD_KQUEUE>.
		206
		207	=back
154		208
155	If one or more of these are ored into the flags value, then only these	209	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	210	backends will be tried (in the reverse order as given here). If none are
157	specified, any backend will do.	211	specified, most compiled-in backend will be tried, usually in reverse
158		212	order of their flag values :)
159	=back
160		213
161	=item struct ev_loop *ev_loop_new (unsigned int flags)	214	=item struct ev_loop *ev_loop_new (unsigned int flags)
162		215
163	Similar to C<ev_default_loop>, but always creates a new event loop that is	216	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	217	always distinct from the default loop. Unlike the default loop, it cannot
…		…
181	This function reinitialises the kernel state for backends that have	234	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	235	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	236	after forking, in either the parent or child process (or both, but that
184	again makes little sense).	237	again makes little sense).
185		238
186	You I<must> call this function after forking if and only if you want to	239	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	240	only if you want to use the event library in both processes. If you just
188	have to call it.	241	fork+exec, you don't have to call it.
189		242
190	The function itself is quite fast and it's usually not a problem to call	243	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	244	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>:	245	quite nicely into a call to C<pthread_atfork>:
193		246
…		…
232		285
233	This flags value could be used to implement alternative looping	286	This flags value could be used to implement alternative looping
234	constructs, but the C<prepare> and C<check> watchers provide a better and	287	constructs, but the C<prepare> and C<check> watchers provide a better and
235	more generic mechanism.	288	more generic mechanism.
236		289
		290	Here are the gory details of what ev_loop does:
		291
		292	1. If there are no active watchers (reference count is zero), return.
		293	2. Queue and immediately call all prepare watchers.
		294	3. If we have been forked, recreate the kernel state.
		295	4. Update the kernel state with all outstanding changes.
		296	5. Update the "event loop time".
		297	6. Calculate for how long to block.
		298	7. Block the process, waiting for events.
		299	8. Update the "event loop time" and do time jump handling.
		300	9. Queue all outstanding timers.
		301	10. Queue all outstanding periodics.
		302	11. If no events are pending now, queue all idle watchers.
		303	12. Queue all check watchers.
		304	13. Call all queued watchers in reverse order (i.e. check watchers first).
		305	14. If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
		306	was used, return, otherwise continue with step #1.
		307
237	=item ev_unloop (loop, how)	308	=item ev_unloop (loop, how)
238		309
239	Can be used to make a call to C<ev_loop> return early (but only after it	310	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	311	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	312	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.	313	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
243		314
244	=item ev_ref (loop)	315	=item ev_ref (loop)
245		316
246	=item ev_unref (loop)	317	=item ev_unref (loop)
…		…
299		370
300	As long as your watcher is active (has been started but not stopped) you	371	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	372	must not touch the values stored in it. Most specifically you must never
302	reinitialise it or call its set method.	373	reinitialise it or call its set method.
303		374
304	You cna check whether an event is active by calling the C<ev_is_active	375	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	376	(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	377	callback for it has not been called yet) you can use the C<ev_is_pending
307	(watcher *)> macro.	378	(watcher *)> macro.
308		379
309	Each and every callback receives the event loop pointer as first, the	380	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	381	registered watcher structure as second, and a bitset of received events as
311	third argument.	382	third argument.
312		383
313	The rceeived events usually include a single bit per event type received	384	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	385	(you can receive multiple events at the same time). The possible bit masks
315	are:	386	are:
316		387
317	=over 4	388	=over 4
318		389
…		…
372	=back	443	=back
373		444
374	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	445	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
375		446
376	Each watcher has, by default, a member C<void *data> that you can change	447	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	448	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	449	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	450	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	451	member, you can also "subclass" the watcher type and provide your own
381	data:	452	data:
382		453
…		…
409	=head2 C<ev_io> - is this file descriptor readable or writable	480	=head2 C<ev_io> - is this file descriptor readable or writable
410		481
411	I/O watchers check whether a file descriptor is readable or writable	482	I/O watchers check whether a file descriptor is readable or writable
412	in each iteration of the event loop (This behaviour is called	483	in each iteration of the event loop (This behaviour is called
413	level-triggering because you keep receiving events as long as the	484	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	485	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).	486	act on the event and neither want to receive future events).
416		487
417	In general you can register as many read and/or write event watchers oer	488	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	489	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	490	descriptors to non-blocking mode is also usually a good idea (but not
420	required if you know what you are doing).	491	required if you know what you are doing).
421		492
422	You have to be careful with dup'ed file descriptors, though. Some backends	493	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	494	(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	495	descriptors correctly if you register interest in two or more fds pointing
425	to the same file/socket etc. description.	496	to the same underlying file/socket etc. description (that is, they share
		497	the same underlying "file open").
426		498
427	If you must do this, then force the use of a known-to-be-good backend	499	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	500	(at the time of this writing, this includes only EVMETHOD_SELECT and
429	EVMETHOD_POLL).	501	EVMETHOD_POLL).
430		502
…		…
444		516
445	Timer watchers are simple relative timers that generate an event after a	517	Timer watchers are simple relative timers that generate an event after a
446	given time, and optionally repeating in regular intervals after that.	518	given time, and optionally repeating in regular intervals after that.
447		519
448	The timers are based on real time, that is, if you register an event that	520	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	521	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	522	time, it will still time out after (roughly) and hour. "Roughly" because
451	detecting time jumps is hard, and soem inaccuracies are unavoidable (the	523	detecting time jumps is hard, and some inaccuracies are unavoidable (the
452	monotonic clock option helps a lot here).	524	monotonic clock option helps a lot here).
453		525
454	The relative timeouts are calculated relative to the C<ev_now ()>	526	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	527	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	528	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	529	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:	530	on the current time, use something like this to adjust for this:
459		531
460	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	532	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
		533
		534	The callback is guarenteed to be invoked only when its timeout has passed,
		535	but if multiple timers become ready during the same loop iteration then
		536	order of execution is undefined.
461		537
462	=over 4	538	=over 4
463		539
464	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	540	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
465		541
…		…
471	later, again, and again, until stopped manually.	547	later, again, and again, until stopped manually.
472		548
473	The timer itself will do a best-effort at avoiding drift, that is, if you	549	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	550	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	551	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	552	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.	553	timer will not fire more than once per event loop iteration.
478		554
479	=item ev_timer_again (loop)	555	=item ev_timer_again (loop)
480		556
481	This will act as if the timer timed out and restart it again if it is	557	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	571	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.	572	the timer, and again will automatically restart it if need be.
497		573
498	=back	574	=back
499		575
500	=head2 C<ev_periodic> - to cron or not to cron it	576	=head2 C<ev_periodic> - to cron or not to cron
501		577
502	Periodic watchers are also timers of a kind, but they are very versatile	578	Periodic watchers are also timers of a kind, but they are very versatile
503	(and unfortunately a bit complex).	579	(and unfortunately a bit complex).
504		580
505	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	581	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
…		…
512	again).	588	again).
513		589
514	They can also be used to implement vastly more complex timers, such as	590	They can also be used to implement vastly more complex timers, such as
515	triggering an event on eahc midnight, local time.	591	triggering an event on eahc midnight, local time.
516		592
		593	As with timers, the callback is guarenteed to be invoked only when the
		594	time (C<at>) has been passed, but if multiple periodic timers become ready
		595	during the same loop iteration then order of execution is undefined.
		596
517	=over 4	597	=over 4
518		598
519	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	599	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
520		600
521	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	601	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
522		602
523	Lots of arguments, lets sort it out... There are basically three modes of	603	Lots of arguments, lets sort it out... There are basically three modes of
524	operation, and we will explain them from simplest to complex:	604	operation, and we will explain them from simplest to complex:
525
526		605
527	=over 4	606	=over 4
528		607
529	=item * absolute timer (interval = reschedule_cb = 0)	608	=item * absolute timer (interval = reschedule_cb = 0)
530		609
…		…
544		623
545	ev_periodic_set (&periodic, 0., 3600., 0);	624	ev_periodic_set (&periodic, 0., 3600., 0);
546		625
547	This doesn't mean there will always be 3600 seconds in between triggers,	626	This doesn't mean there will always be 3600 seconds in between triggers,
548	but only that the the callback will be called when the system time shows a	627	but only that the the callback will be called when the system time shows a
549	full hour (UTC), or more correct, when the system time is evenly divisible	628	full hour (UTC), or more correctly, when the system time is evenly divisible
550	by 3600.	629	by 3600.
551		630
552	Another way to think about it (for the mathematically inclined) is that	631	Another way to think about it (for the mathematically inclined) is that
553	C<ev_periodic> will try to run the callback in this mode at the next possible	632	C<ev_periodic> will try to run the callback in this mode at the next possible
554	time where C<time = at (mod interval)>, regardless of any time jumps.	633	time where C<time = at (mod interval)>, regardless of any time jumps.
…		…
558	In this mode the values for C<interval> and C<at> are both being	637	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	638	ignored. Instead, each time the periodic watcher gets scheduled, the
560	reschedule callback will be called with the watcher as first, and the	639	reschedule callback will be called with the watcher as first, and the
561	current time as second argument.	640	current time as second argument.
562		641
563	NOTE: I<This callback MUST NOT stop or destroy the periodic or any other	642	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
564	periodic watcher, ever, or make any event loop modificstions>. If you need	643	ever, or make any event loop modifications>. If you need to stop it,
565	to stop it, return 1e30 (or so, fudge fudge) and stop it afterwards.	644	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
		645	starting a prepare watcher).
566		646
567	Its prototype is c<ev_tstamp (reschedule_cb)(struct ev_periodic w,	647	Its prototype is C<ev_tstamp (reschedule_cb)(struct ev_periodic w,
568	ev_tstamp now)>, e.g.:	648	ev_tstamp now)>, e.g.:
569		649
570	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	650	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
571	{	651	{
572	return now + 60.;	652	return now + 60.;
…		…
575	It must return the next time to trigger, based on the passed time value	655	It must return the next time to trigger, based on the passed time value
576	(that is, the lowest time value larger than to the second argument). It	656	(that is, the lowest time value larger than to the second argument). It
577	will usually be called just before the callback will be triggered, but	657	will usually be called just before the callback will be triggered, but
578	might be called at other times, too.	658	might be called at other times, too.
579		659
		660	NOTE: I<< This callback must always return a time that is later than the
		661	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.
		662
580	This can be used to create very complex timers, such as a timer that	663	This can be used to create very complex timers, such as a timer that
581	triggers on each midnight, local time. To do this, you would calculate the	664	triggers on each midnight, local time. To do this, you would calculate the
582	next midnight after C<now> and return the timestamp value for this. How you do this	665	next midnight after C<now> and return the timestamp value for this. How
583	is, again, up to you (but it is not trivial).	666	you do this is, again, up to you (but it is not trivial, which is the main
		667	reason I omitted it as an example).
584		668
585	=back	669	=back
586		670
587	=item ev_periodic_again (loop, ev_periodic *)	671	=item ev_periodic_again (loop, ev_periodic *)
588		672
…		…
598	Signal watchers will trigger an event when the process receives a specific	682	Signal watchers will trigger an event when the process receives a specific
599	signal one or more times. Even though signals are very asynchronous, libev	683	signal one or more times. Even though signals are very asynchronous, libev
600	will try it's best to deliver signals synchronously, i.e. as part of the	684	will try it's best to deliver signals synchronously, i.e. as part of the
601	normal event processing, like any other event.	685	normal event processing, like any other event.
602		686
603	You cna configure as many watchers as you like per signal. Only when the	687	You can configure as many watchers as you like per signal. Only when the
604	first watcher gets started will libev actually register a signal watcher	688	first watcher gets started will libev actually register a signal watcher
605	with the kernel (thus it coexists with your own signal handlers as long	689	with the kernel (thus it coexists with your own signal handlers as long
606	as you don't register any with libev). Similarly, when the last signal	690	as you don't register any with libev). Similarly, when the last signal
607	watcher for a signal is stopped libev will reset the signal handler to	691	watcher for a signal is stopped libev will reset the signal handler to
608	SIG_DFL (regardless of what it was set to before).	692	SIG_DFL (regardless of what it was set to before).
…		…
630	=item ev_child_set (ev_child *, int pid)	714	=item ev_child_set (ev_child *, int pid)
631		715
632	Configures the watcher to wait for status changes of process C<pid> (or	716	Configures the watcher to wait for status changes of process C<pid> (or
633	I<any> process if C<pid> is specified as C<0>). The callback can look	717	I<any> process if C<pid> is specified as C<0>). The callback can look
634	at the C<rstatus> member of the C<ev_child> watcher structure to see	718	at the C<rstatus> member of the C<ev_child> watcher structure to see
635	the status word (use the macros from C<sys/wait.h>). The C<rpid> member	719	the status word (use the macros from C<sys/wait.h> and see your systems
636	contains the pid of the process causing the status change.	720	C<waitpid> documentation). The C<rpid> member contains the pid of the
		721	process causing the status change.
637		722
638	=back	723	=back
639		724
640	=head2 C<ev_idle> - when you've got nothing better to do	725	=head2 C<ev_idle> - when you've got nothing better to do
641		726
642	Idle watchers trigger events when there are no other I/O or timer (or	727	Idle watchers trigger events when there are no other events are pending
643	periodic) events pending. That is, as long as your process is busy	728	(prepare, check and other idle watchers do not count). That is, as long
644	handling sockets or timeouts it will not be called. But when your process	729	as your process is busy handling sockets or timeouts (or even signals,
645	is idle all idle watchers are being called again and again - until	730	imagine) it will not be triggered. But when your process is idle all idle
		731	watchers are being called again and again, once per event loop iteration -
646	stopped, that is, or your process receives more events.	732	until stopped, that is, or your process receives more events and becomes
		733	busy.
647		734
648	The most noteworthy effect is that as long as any idle watchers are	735	The most noteworthy effect is that as long as any idle watchers are
649	active, the process will not block when waiting for new events.	736	active, the process will not block when waiting for new events.
650		737
651	Apart from keeping your process non-blocking (which is a useful	738	Apart from keeping your process non-blocking (which is a useful
…		…
661	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	748	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
662	believe me.	749	believe me.
663		750
664	=back	751	=back
665		752
666	=head2 prepare and check - your hooks into the event loop	753	=head2 C<ev_prepare> and C<ev_check> - customise your event loop
667		754
668	Prepare and check watchers usually (but not always) are used in	755	Prepare and check watchers are usually (but not always) used in tandem:
669	tandom. Prepare watchers get invoked before the process blocks and check	756	prepare watchers get invoked before the process blocks and check watchers
670	watchers afterwards.	757	afterwards.
671		758
672	Their main purpose is to integrate other event mechanisms into libev. This	759	Their main purpose is to integrate other event mechanisms into libev. This
673	could be used, for example, to track variable changes, implement your own	760	could be used, for example, to track variable changes, implement your own
674	watchers, integrate net-snmp or a coroutine library and lots more.	761	watchers, integrate net-snmp or a coroutine library and lots more.
675		762
676	This is done by examining in each prepare call which file descriptors need	763	This is done by examining in each prepare call which file descriptors need
677	to be watched by the other library, registering C<ev_io> watchers for them	764	to be watched by the other library, registering C<ev_io> watchers for
678	and starting an C<ev_timer> watcher for any timeouts (many libraries provide	765	them and starting an C<ev_timer> watcher for any timeouts (many libraries
679	just this functionality). Then, in the check watcher you check for any	766	provide just this functionality). Then, in the check watcher you check for
680	events that occured (by making your callbacks set soem flags for example)	767	any events that occured (by checking the pending status of all watchers
681	and call back into the library.	768	and stopping them) and call back into the library. The I/O and timer
		769	callbacks will never actually be called (but must be valid nevertheless,
		770	because you never know, you know?).
682		771
683	As another example, the perl Coro module uses these hooks to integrate	772	As another example, the Perl Coro module uses these hooks to integrate
684	coroutines into libev programs, by yielding to other active coroutines	773	coroutines into libev programs, by yielding to other active coroutines
685	during each prepare and only letting the process block if no coroutines	774	during each prepare and only letting the process block if no coroutines
686	are ready to run.	775	are ready to run (it's actually more complicated: it only runs coroutines
		776	with priority higher than or equal to the event loop and one coroutine
		777	of lower priority, but only once, using idle watchers to keep the event
		778	loop from blocking if lower-priority coroutines are active, thus mapping
		779	low-priority coroutines to idle/background tasks).
687		780
688	=over 4	781	=over 4
689		782
690	=item ev_prepare_init (ev_prepare *, callback)	783	=item ev_prepare_init (ev_prepare *, callback)
691		784
692	=item ev_check_init (ev_check *, callback)	785	=item ev_check_init (ev_check *, callback)
693		786
694	Initialises and configures the prepare or check watcher - they have no	787	Initialises and configures the prepare or check watcher - they have no
695	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	788	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
696	macros, but using them is utterly, utterly pointless.	789	macros, but using them is utterly, utterly and completely pointless.
697		790
698	=back	791	=back
699		792
700	=head1 OTHER FUNCTIONS	793	=head1 OTHER FUNCTIONS
701		794
702	There are some other fucntions of possible interest. Described. Here. Now.	795	There are some other functions of possible interest. Described. Here. Now.
703		796
704	=over 4	797	=over 4
705		798
706	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	799	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
707		800
708	This function combines a simple timer and an I/O watcher, calls your	801	This function combines a simple timer and an I/O watcher, calls your
709	callback on whichever event happens first and automatically stop both	802	callback on whichever event happens first and automatically stop both
710	watchers. This is useful if you want to wait for a single event on an fd	803	watchers. This is useful if you want to wait for a single event on an fd
711	or timeout without havign to allocate/configure/start/stop/free one or	804	or timeout without having to allocate/configure/start/stop/free one or
712	more watchers yourself.	805	more watchers yourself.
713		806
714	If C<fd> is less than 0, then no I/O watcher will be started and events is	807	If C<fd> is less than 0, then no I/O watcher will be started and events
715	ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and C<events> set	808	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
716	will be craeted and started.	809	C<events> set will be craeted and started.
717		810
718	If C<timeout> is less than 0, then no timeout watcher will be	811	If C<timeout> is less than 0, then no timeout watcher will be
719	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and repeat	812	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
720	= 0) will be started.	813	repeat = 0) will be started. While C<0> is a valid timeout, it is of
		814	dubious value.
721		815
722	The callback has the type C<void (cb)(int revents, void arg)> and	816	The callback has the type C<void (cb)(int revents, void arg)> and gets
723	gets passed an events set (normally a combination of C<EV_ERROR>, C<EV_READ>,	817	passed an C<revents> set like normal event callbacks (a combination of
724	C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> value passed to C<ev_once>:	818	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
		819	value passed to C<ev_once>:
725		820
726	static void stdin_ready (int revents, void *arg)	821	static void stdin_ready (int revents, void *arg)
727	{	822	{
728	if (revents & EV_TIMEOUT)	823	if (revents & EV_TIMEOUT)
729	/* doh, nothing entered */	824	/* doh, nothing entered */;
730	else if (revents & EV_READ)	825	else if (revents & EV_READ)
731	/* stdin might have data for us, joy! */	826	/* stdin might have data for us, joy! */;
732	}	827	}
733		828
734	ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0);	829	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
735		830
736	=item ev_feed_event (loop, watcher, int events)	831	=item ev_feed_event (loop, watcher, int events)
737		832
738	Feeds the given event set into the event loop, as if the specified event	833	Feeds the given event set into the event loop, as if the specified event
739	has happened for the specified watcher (which must be a pointer to an	834	had happened for the specified watcher (which must be a pointer to an
740	initialised but not necessarily active event watcher).	835	initialised but not necessarily started event watcher).
741		836
742	=item ev_feed_fd_event (loop, int fd, int revents)	837	=item ev_feed_fd_event (loop, int fd, int revents)
743		838
744	Feed an event on the given fd, as if a file descriptor backend detected it.	839	Feed an event on the given fd, as if a file descriptor backend detected
		840	the given events it.
745		841
746	=item ev_feed_signal_event (loop, int signum)	842	=item ev_feed_signal_event (loop, int signum)
747		843
748	Feed an event as if the given signal occured (loop must be the default loop!).	844	Feed an event as if the given signal occured (loop must be the default loop!).
749		845
750	=back	846	=back
751		847
		848	=head1 LIBEVENT EMULATION
		849
		850	Libev offers a compatibility emulation layer for libevent. It cannot
		851	emulate the internals of libevent, so here are some usage hints:
		852
		853	=over 4
		854
		855	=item * Use it by including <event.h>, as usual.
		856
		857	=item * The following members are fully supported: ev_base, ev_callback,
		858	ev_arg, ev_fd, ev_res, ev_events.
		859
		860	=item * Avoid using ev_flags and the EVLIST_*-macros, while it is
		861	maintained by libev, it does not work exactly the same way as in libevent (consider
		862	it a private API).
		863
		864	=item * Priorities are not currently supported. Initialising priorities
		865	will fail and all watchers will have the same priority, even though there
		866	is an ev_pri field.
		867
		868	=item * Other members are not supported.
		869
		870	=item * The libev emulation is I<not> ABI compatible to libevent, you need
		871	to use the libev header file and library.
		872
		873	=back
		874
		875	=head1 C++ SUPPORT
		876
		877	TBD.
		878
752	=head1 AUTHOR	879	=head1 AUTHOR
753		880
754	Marc Lehmann <libev@schmorp.de>.	881	Marc Lehmann <libev@schmorp.de>.
755		882

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Revision 1.11 by root, Mon Nov 12 08:32:52 2007 UTC vs.
Revision 1.30 by root, Fri Nov 23 04:36:03 2007 UTC