[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 1.31 by root, Fri Nov 23 05:00:45 2007 UTC

…		…
39	F<README.embed> in the libev distribution. If libev was configured without	39	F<README.embed> in the libev distribution. If libev was configured without
40	support for multiple event loops, then all functions taking an initial	40	support for multiple event loops, then all functions taking an initial
41	argument of name C<loop> (which is always of type C<struct ev_loop *>)	41	argument of name C<loop> (which is always of type C<struct ev_loop *>)
42	will not have this argument.	42	will not have this argument.
43		43
44	=head1 TIME AND OTHER GLOBAL FUNCTIONS	44	=head1 TIME REPRESENTATION
45		45
46	Libev represents time as a single floating point number, representing the	46	Libev represents time as a single floating point number, representing the
47	(fractional) number of seconds since the (POSIX) epoch (somewhere near	47	(fractional) number of seconds since the (POSIX) epoch (somewhere near
48	the beginning of 1970, details are complicated, don't ask). This type is	48	the beginning of 1970, details are complicated, don't ask). This type is
49	called C<ev_tstamp>, which is what you should use too. It usually aliases	49	called C<ev_tstamp>, which is what you should use too. It usually aliases
50	to the double type in C.	50	to the double type in C.
51		51
		52	=head1 GLOBAL FUNCTIONS
		53
		54	These functions can be called anytime, even before initialising the
		55	library in any way.
		56
52	=over 4	57	=over 4
53		58
54	=item ev_tstamp ev_time ()	59	=item ev_tstamp ev_time ()
55		60
56	Returns the current time as libev would use it.	61	Returns the current time as libev would use it. Please note that the
		62	C<ev_now> function is usually faster and also often returns the timestamp
		63	you actually want to know.
57		64
58	=item int ev_version_major ()	65	=item int ev_version_major ()
59		66
60	=item int ev_version_minor ()	67	=item int ev_version_minor ()
61		68
…		…
67		74
68	Usually, it's a good idea to terminate if the major versions mismatch,	75	Usually, it's a good idea to terminate if the major versions mismatch,
69	as this indicates an incompatible change. Minor versions are usually	76	as this indicates an incompatible change. Minor versions are usually
70	compatible to older versions, so a larger minor version alone is usually	77	compatible to older versions, so a larger minor version alone is usually
71	not a problem.	78	not a problem.
		79
		80	=item unsigned int ev_supported_backends ()
		81
		82	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
		83	value) compiled into this binary of libev (independent of their
		84	availability on the system you are running on). See C<ev_default_loop> for
		85	a description of the set values.
		86
		87	=item unsigned int ev_recommended_backends ()
		88
		89	Return the set of all backends compiled into this binary of libev and also
		90	recommended for this platform. This set is often smaller than the one
		91	returned by C<ev_supported_backends>, as for example kqueue is broken on
		92	most BSDs and will not be autodetected unless you explicitly request it
		93	(assuming you know what you are doing). This is the set of backends that
		94	C<EVFLAG_AUTO> will probe for.
72		95
73	=item ev_set_allocator (void (cb)(void *ptr, long size))	96	=item ev_set_allocator (void (cb)(void *ptr, long size))
74		97
75	Sets the allocation function to use (the prototype is similar to the	98	Sets the allocation function to use (the prototype is similar to the
76	realloc C function, the semantics are identical). It is used to allocate	99	realloc C function, the semantics are identical). It is used to allocate
…		…
99	An event loop is described by a C<struct ev_loop *>. The library knows two	122	An event loop is described by a C<struct ev_loop *>. The library knows two
100	types of such loops, the I<default> loop, which supports signals and child	123	types of such loops, the I<default> loop, which supports signals and child
101	events, and dynamically created loops which do not.	124	events, and dynamically created loops which do not.
102		125
103	If you use threads, a common model is to run the default event loop	126	If you use threads, a common model is to run the default event loop
104	in your main thread (or in a separate thrad) and for each thread you	127	in your main thread (or in a separate thread) and for each thread you
105	create, you also create another event loop. Libev itself does no locking	128	create, you also create another event loop. Libev itself does no locking
106	whatsoever, so if you mix calls to the same event loop in different	129	whatsoever, so if you mix calls to the same event loop in different
107	threads, make sure you lock (this is usually a bad idea, though, even if	130	threads, make sure you lock (this is usually a bad idea, though, even if
108	done correctly, because it's hideous and inefficient).	131	done correctly, because it's hideous and inefficient).
109		132
…		…
112	=item struct ev_loop *ev_default_loop (unsigned int flags)	135	=item struct ev_loop *ev_default_loop (unsigned int flags)
113		136
114	This will initialise the default event loop if it hasn't been initialised	137	This will initialise the default event loop if it hasn't been initialised
115	yet and return it. If the default loop could not be initialised, returns	138	yet and return it. If the default loop could not be initialised, returns
116	false. If it already was initialised it simply returns it (and ignores the	139	false. If it already was initialised it simply returns it (and ignores the
117	flags).	140	flags. If that is troubling you, check C<ev_backend ()> afterwards).
118		141
119	If you don't know what event loop to use, use the one returned from this	142	If you don't know what event loop to use, use the one returned from this
120	function.	143	function.
121		144
122	The flags argument can be used to specify special behaviour or specific	145	The flags argument can be used to specify special behaviour or specific
123	backends to use, and is usually specified as 0 (or EVFLAG_AUTO).	146	backends to use, and is usually specified as C<0> (or EVFLAG_AUTO).
124		147
125	It supports the following flags:	148	It supports the following flags:
126		149
127	=over 4	150	=over 4
128		151
…		…
138	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	161	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
139	override the flags completely if it is found in the environment. This is	162	override the flags completely if it is found in the environment. This is
140	useful to try out specific backends to test their performance, or to work	163	useful to try out specific backends to test their performance, or to work
141	around bugs.	164	around bugs.
142		165
143	=item C<EVMETHOD_SELECT> (portable select backend)	166	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
144		167
		168	This is your standard select(2) backend. Not I<completely> standard, as
		169	libev tries to roll its own fd_set with no limits on the number of fds,
		170	but if that fails, expect a fairly low limit on the number of fds when
		171	using this backend. It doesn't scale too well (O(highest_fd)), but its usually
		172	the fastest backend for a low number of fds.
		173
145	=item C<EVMETHOD_POLL> (poll backend, available everywhere except on windows)	174	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
146		175
147	=item C<EVMETHOD_EPOLL> (linux only)	176	And this is your standard poll(2) backend. It's more complicated than
		177	select, but handles sparse fds better and has no artificial limit on the
		178	number of fds you can use (except it will slow down considerably with a
		179	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).
148		180
149	=item C<EVMETHOD_KQUEUE> (some bsds only)	181	=item C<EVBACKEND_EPOLL> (value 4, Linux)
150		182
151	=item C<EVMETHOD_DEVPOLL> (solaris 8 only)	183	For few fds, this backend is a bit little slower than poll and select,
		184	but it scales phenomenally better. While poll and select usually scale like
		185	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
		186	either O(1) or O(active_fds).
152		187
153	=item C<EVMETHOD_PORT> (solaris 10 only)	188	While stopping and starting an I/O watcher in the same iteration will
		189	result in some caching, there is still a syscall per such incident
		190	(because the fd could point to a different file description now), so its
		191	best to avoid that. Also, dup()ed file descriptors might not work very
		192	well if you register events for both fds.
		193
		194	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
		195
		196	Kqueue deserves special mention, as at the time of this writing, it
		197	was broken on all BSDs except NetBSD (usually it doesn't work with
		198	anything but sockets and pipes, except on Darwin, where of course its
		199	completely useless). For this reason its not being "autodetected" unless
		200	you explicitly specify the flags (i.e. you don't use EVFLAG_AUTO).
		201
		202	It scales in the same way as the epoll backend, but the interface to the
		203	kernel is more efficient (which says nothing about its actual speed, of
		204	course). While starting and stopping an I/O watcher does not cause an
		205	extra syscall as with epoll, it still adds up to four event changes per
		206	incident, so its best to avoid that.
		207
		208	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
		209
		210	This is not implemented yet (and might never be).
		211
		212	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
		213
		214	This uses the Solaris 10 port mechanism. As with everything on Solaris,
		215	it's really slow, but it still scales very well (O(active_fds)).
		216
		217	=item C<EVBACKEND_ALL>
		218
		219	Try all backends (even potentially broken ones that wouldn't be tried
		220	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
		221	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
		222
		223	=back
154		224
155	If one or more of these are ored into the flags value, then only these	225	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	226	backends will be tried (in the reverse order as given here). If none are
157	specified, any backend will do.	227	specified, most compiled-in backend will be tried, usually in reverse
158		228	order of their flag values :)
159	=back
160		229
161	=item struct ev_loop *ev_loop_new (unsigned int flags)	230	=item struct ev_loop *ev_loop_new (unsigned int flags)
162		231
163	Similar to C<ev_default_loop>, but always creates a new event loop that is	232	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	233	always distinct from the default loop. Unlike the default loop, it cannot
…		…
181	This function reinitialises the kernel state for backends that have	250	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	251	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	252	after forking, in either the parent or child process (or both, but that
184	again makes little sense).	253	again makes little sense).
185		254
186	You I<must> call this function after forking if and only if you want to	255	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	256	only if you want to use the event library in both processes. If you just
188	have to call it.	257	fork+exec, you don't have to call it.
189		258
190	The function itself is quite fast and it's usually not a problem to call	259	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	260	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>:	261	quite nicely into a call to C<pthread_atfork>:
193		262
194	pthread_atfork (0, 0, ev_default_fork);	263	pthread_atfork (0, 0, ev_default_fork);
195		264
		265	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
		266	without calling this function, so if you force one of those backends you
		267	do not need to care.
		268
196	=item ev_loop_fork (loop)	269	=item ev_loop_fork (loop)
197		270
198	Like C<ev_default_fork>, but acts on an event loop created by	271	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	272	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.	273	after fork, and how you do this is entirely your own problem.
201		274
202	=item unsigned int ev_method (loop)	275	=item unsigned int ev_backend (loop)
203		276
204	Returns one of the C<EVMETHOD_*> flags indicating the event backend in	277	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
205	use.	278	use.
206		279
207	=item ev_tstamp ev_now (loop)	280	=item ev_tstamp ev_now (loop)
208		281
209	Returns the current "event loop time", which is the time the event loop	282	Returns the current "event loop time", which is the time the event loop
…		…
232		305
233	This flags value could be used to implement alternative looping	306	This flags value could be used to implement alternative looping
234	constructs, but the C<prepare> and C<check> watchers provide a better and	307	constructs, but the C<prepare> and C<check> watchers provide a better and
235	more generic mechanism.	308	more generic mechanism.
236		309
		310	Here are the gory details of what ev_loop does:
		311
		312	1. If there are no active watchers (reference count is zero), return.
		313	2. Queue and immediately call all prepare watchers.
		314	3. If we have been forked, recreate the kernel state.
		315	4. Update the kernel state with all outstanding changes.
		316	5. Update the "event loop time".
		317	6. Calculate for how long to block.
		318	7. Block the process, waiting for events.
		319	8. Update the "event loop time" and do time jump handling.
		320	9. Queue all outstanding timers.
		321	10. Queue all outstanding periodics.
		322	11. If no events are pending now, queue all idle watchers.
		323	12. Queue all check watchers.
		324	13. Call all queued watchers in reverse order (i.e. check watchers first).
		325	14. If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
		326	was used, return, otherwise continue with step #1.
		327
237	=item ev_unloop (loop, how)	328	=item ev_unloop (loop, how)
238		329
239	Can be used to make a call to C<ev_loop> return early (but only after it	330	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	331	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	332	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.	333	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
243		334
244	=item ev_ref (loop)	335	=item ev_ref (loop)
245		336
246	=item ev_unref (loop)	337	=item ev_unref (loop)
…		…
297	*) >>), and you can stop watching for events at any time by calling the	388	*) >>), and you can stop watching for events at any time by calling the
298	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	389	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.
299		390
300	As long as your watcher is active (has been started but not stopped) you	391	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	392	must not touch the values stored in it. Most specifically you must never
302	reinitialise it or call its set method.	393	reinitialise it or call its set macro.
303		394
304	You cna check whether an event is active by calling the C<ev_is_active	395	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	396	(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	397	callback for it has not been called yet) you can use the C<ev_is_pending
307	(watcher *)> macro.	398	(watcher *)> macro.
308		399
309	Each and every callback receives the event loop pointer as first, the	400	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	401	registered watcher structure as second, and a bitset of received events as
311	third argument.	402	third argument.
312		403
313	The rceeived events usually include a single bit per event type received	404	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	405	(you can receive multiple events at the same time). The possible bit masks
315	are:	406	are:
316		407
317	=over 4	408	=over 4
318		409
…		…
372	=back	463	=back
373		464
374	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	465	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
375		466
376	Each watcher has, by default, a member C<void *data> that you can change	467	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	468	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	469	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	470	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	471	member, you can also "subclass" the watcher type and provide your own
381	data:	472	data:
382		473
…		…
409	=head2 C<ev_io> - is this file descriptor readable or writable	500	=head2 C<ev_io> - is this file descriptor readable or writable
410		501
411	I/O watchers check whether a file descriptor is readable or writable	502	I/O watchers check whether a file descriptor is readable or writable
412	in each iteration of the event loop (This behaviour is called	503	in each iteration of the event loop (This behaviour is called
413	level-triggering because you keep receiving events as long as the	504	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	505	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).	506	act on the event and neither want to receive future events).
416		507
417	In general you can register as many read and/or write event watchers oer	508	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	509	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	510	descriptors to non-blocking mode is also usually a good idea (but not
420	required if you know what you are doing).	511	required if you know what you are doing).
421		512
422	You have to be careful with dup'ed file descriptors, though. Some backends	513	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	514	(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	515	descriptors correctly if you register interest in two or more fds pointing
425	to the same file/socket etc. description.	516	to the same underlying file/socket etc. description (that is, they share
		517	the same underlying "file open").
426		518
427	If you must do this, then force the use of a known-to-be-good backend	519	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	520	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
429	EVMETHOD_POLL).	521	C<EVBACKEND_POLL>).
430		522
431	=over 4	523	=over 4
432		524
433	=item ev_io_init (ev_io *, callback, int fd, int events)	525	=item ev_io_init (ev_io *, callback, int fd, int events)
434		526
…		…
444		536
445	Timer watchers are simple relative timers that generate an event after a	537	Timer watchers are simple relative timers that generate an event after a
446	given time, and optionally repeating in regular intervals after that.	538	given time, and optionally repeating in regular intervals after that.
447		539
448	The timers are based on real time, that is, if you register an event that	540	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	541	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	542	time, it will still time out after (roughly) and hour. "Roughly" because
451	detecting time jumps is hard, and soem inaccuracies are unavoidable (the	543	detecting time jumps is hard, and some inaccuracies are unavoidable (the
452	monotonic clock option helps a lot here).	544	monotonic clock option helps a lot here).
453		545
454	The relative timeouts are calculated relative to the C<ev_now ()>	546	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	547	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	548	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	549	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:	550	on the current time, use something like this to adjust for this:
459		551
460	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	552	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
		553
		554	The callback is guarenteed to be invoked only when its timeout has passed,
		555	but if multiple timers become ready during the same loop iteration then
		556	order of execution is undefined.
461		557
462	=over 4	558	=over 4
463		559
464	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	560	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
465		561
…		…
471	later, again, and again, until stopped manually.	567	later, again, and again, until stopped manually.
472		568
473	The timer itself will do a best-effort at avoiding drift, that is, if you	569	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	570	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	571	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	572	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.	573	timer will not fire more than once per event loop iteration.
478		574
479	=item ev_timer_again (loop)	575	=item ev_timer_again (loop)
480		576
481	This will act as if the timer timed out and restart it again if it is	577	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	591	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.	592	the timer, and again will automatically restart it if need be.
497		593
498	=back	594	=back
499		595
500	=head2 C<ev_periodic> - to cron or not to cron it	596	=head2 C<ev_periodic> - to cron or not to cron
501		597
502	Periodic watchers are also timers of a kind, but they are very versatile	598	Periodic watchers are also timers of a kind, but they are very versatile
503	(and unfortunately a bit complex).	599	(and unfortunately a bit complex).
504		600
505	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	601	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
…		…
512	again).	608	again).
513		609
514	They can also be used to implement vastly more complex timers, such as	610	They can also be used to implement vastly more complex timers, such as
515	triggering an event on eahc midnight, local time.	611	triggering an event on eahc midnight, local time.
516		612
		613	As with timers, the callback is guarenteed to be invoked only when the
		614	time (C<at>) has been passed, but if multiple periodic timers become ready
		615	during the same loop iteration then order of execution is undefined.
		616
517	=over 4	617	=over 4
518		618
519	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	619	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
520		620
521	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	621	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
522		622
523	Lots of arguments, lets sort it out... There are basically three modes of	623	Lots of arguments, lets sort it out... There are basically three modes of
524	operation, and we will explain them from simplest to complex:	624	operation, and we will explain them from simplest to complex:
525
526		625
527	=over 4	626	=over 4
528		627
529	=item * absolute timer (interval = reschedule_cb = 0)	628	=item * absolute timer (interval = reschedule_cb = 0)
530		629
…		…
544		643
545	ev_periodic_set (&periodic, 0., 3600., 0);	644	ev_periodic_set (&periodic, 0., 3600., 0);
546		645
547	This doesn't mean there will always be 3600 seconds in between triggers,	646	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	647	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	648	full hour (UTC), or more correctly, when the system time is evenly divisible
550	by 3600.	649	by 3600.
551		650
552	Another way to think about it (for the mathematically inclined) is that	651	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	652	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.	653	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	657	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	658	ignored. Instead, each time the periodic watcher gets scheduled, the
560	reschedule callback will be called with the watcher as first, and the	659	reschedule callback will be called with the watcher as first, and the
561	current time as second argument.	660	current time as second argument.
562		661
563	NOTE: I<This callback MUST NOT stop or destroy the periodic or any other	662	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	663	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.	664	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
		665	starting a prepare watcher).
566		666
567	Its prototype is c<ev_tstamp (reschedule_cb)(struct ev_periodic w,	667	Its prototype is C<ev_tstamp (reschedule_cb)(struct ev_periodic w,
568	ev_tstamp now)>, e.g.:	668	ev_tstamp now)>, e.g.:
569		669
570	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	670	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
571	{	671	{
572	return now + 60.;	672	return now + 60.;
…		…
575	It must return the next time to trigger, based on the passed time value	675	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	676	(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	677	will usually be called just before the callback will be triggered, but
578	might be called at other times, too.	678	might be called at other times, too.
579		679
		680	NOTE: I<< This callback must always return a time that is later than the
		681	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.
		682
580	This can be used to create very complex timers, such as a timer that	683	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	684	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	685	next midnight after C<now> and return the timestamp value for this. How
583	is, again, up to you (but it is not trivial).	686	you do this is, again, up to you (but it is not trivial, which is the main
		687	reason I omitted it as an example).
584		688
585	=back	689	=back
586		690
587	=item ev_periodic_again (loop, ev_periodic *)	691	=item ev_periodic_again (loop, ev_periodic *)
588		692
…		…
598	Signal watchers will trigger an event when the process receives a specific	702	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	703	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	704	will try it's best to deliver signals synchronously, i.e. as part of the
601	normal event processing, like any other event.	705	normal event processing, like any other event.
602		706
603	You cna configure as many watchers as you like per signal. Only when the	707	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	708	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	709	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	710	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	711	watcher for a signal is stopped libev will reset the signal handler to
608	SIG_DFL (regardless of what it was set to before).	712	SIG_DFL (regardless of what it was set to before).
…		…
630	=item ev_child_set (ev_child *, int pid)	734	=item ev_child_set (ev_child *, int pid)
631		735
632	Configures the watcher to wait for status changes of process C<pid> (or	736	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	737	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	738	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	739	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.	740	C<waitpid> documentation). The C<rpid> member contains the pid of the
		741	process causing the status change.
637		742
638	=back	743	=back
639		744
640	=head2 C<ev_idle> - when you've got nothing better to do	745	=head2 C<ev_idle> - when you've got nothing better to do
641		746
642	Idle watchers trigger events when there are no other I/O or timer (or	747	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	748	(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	749	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	750	imagine) it will not be triggered. But when your process is idle all idle
		751	watchers are being called again and again, once per event loop iteration -
646	stopped, that is, or your process receives more events.	752	until stopped, that is, or your process receives more events and becomes
		753	busy.
647		754
648	The most noteworthy effect is that as long as any idle watchers are	755	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.	756	active, the process will not block when waiting for new events.
650		757
651	Apart from keeping your process non-blocking (which is a useful	758	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,	768	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
662	believe me.	769	believe me.
663		770
664	=back	771	=back
665		772
666	=head2 prepare and check - your hooks into the event loop	773	=head2 C<ev_prepare> and C<ev_check> - customise your event loop
667		774
668	Prepare and check watchers usually (but not always) are used in	775	Prepare and check watchers are usually (but not always) used in tandem:
669	tandom. Prepare watchers get invoked before the process blocks and check	776	prepare watchers get invoked before the process blocks and check watchers
670	watchers afterwards.	777	afterwards.
671		778
672	Their main purpose is to integrate other event mechanisms into libev. This	779	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	780	could be used, for example, to track variable changes, implement your own
674	watchers, integrate net-snmp or a coroutine library and lots more.	781	watchers, integrate net-snmp or a coroutine library and lots more.
675		782
676	This is done by examining in each prepare call which file descriptors need	783	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	784	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	785	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	786	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)	787	any events that occured (by checking the pending status of all watchers
681	and call back into the library.	788	and stopping them) and call back into the library. The I/O and timer
		789	callbacks will never actually be called (but must be valid nevertheless,
		790	because you never know, you know?).
682		791
683	As another example, the perl Coro module uses these hooks to integrate	792	As another example, the Perl Coro module uses these hooks to integrate
684	coroutines into libev programs, by yielding to other active coroutines	793	coroutines into libev programs, by yielding to other active coroutines
685	during each prepare and only letting the process block if no coroutines	794	during each prepare and only letting the process block if no coroutines
686	are ready to run.	795	are ready to run (it's actually more complicated: it only runs coroutines
		796	with priority higher than or equal to the event loop and one coroutine
		797	of lower priority, but only once, using idle watchers to keep the event
		798	loop from blocking if lower-priority coroutines are active, thus mapping
		799	low-priority coroutines to idle/background tasks).
687		800
688	=over 4	801	=over 4
689		802
690	=item ev_prepare_init (ev_prepare *, callback)	803	=item ev_prepare_init (ev_prepare *, callback)
691		804
692	=item ev_check_init (ev_check *, callback)	805	=item ev_check_init (ev_check *, callback)
693		806
694	Initialises and configures the prepare or check watcher - they have no	807	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>	808	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
696	macros, but using them is utterly, utterly pointless.	809	macros, but using them is utterly, utterly and completely pointless.
697		810
698	=back	811	=back
699		812
700	=head1 OTHER FUNCTIONS	813	=head1 OTHER FUNCTIONS
701		814
702	There are some other fucntions of possible interest. Described. Here. Now.	815	There are some other functions of possible interest. Described. Here. Now.
703		816
704	=over 4	817	=over 4
705		818
706	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	819	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
707		820
708	This function combines a simple timer and an I/O watcher, calls your	821	This function combines a simple timer and an I/O watcher, calls your
709	callback on whichever event happens first and automatically stop both	822	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	823	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	824	or timeout without having to allocate/configure/start/stop/free one or
712	more watchers yourself.	825	more watchers yourself.
713		826
714	If C<fd> is less than 0, then no I/O watcher will be started and events is	827	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	828	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
716	will be craeted and started.	829	C<events> set will be craeted and started.
717		830
718	If C<timeout> is less than 0, then no timeout watcher will be	831	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	832	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
720	= 0) will be started.	833	repeat = 0) will be started. While C<0> is a valid timeout, it is of
		834	dubious value.
721		835
722	The callback has the type C<void (cb)(int revents, void arg)> and	836	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>,	837	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>:	838	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
		839	value passed to C<ev_once>:
725		840
726	static void stdin_ready (int revents, void *arg)	841	static void stdin_ready (int revents, void *arg)
727	{	842	{
728	if (revents & EV_TIMEOUT)	843	if (revents & EV_TIMEOUT)
729	/* doh, nothing entered */	844	/* doh, nothing entered */;
730	else if (revents & EV_READ)	845	else if (revents & EV_READ)
731	/* stdin might have data for us, joy! */	846	/* stdin might have data for us, joy! */;
732	}	847	}
733		848
734	ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0);	849	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
735		850
736	=item ev_feed_event (loop, watcher, int events)	851	=item ev_feed_event (loop, watcher, int events)
737		852
738	Feeds the given event set into the event loop, as if the specified event	853	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	854	had happened for the specified watcher (which must be a pointer to an
740	initialised but not necessarily active event watcher).	855	initialised but not necessarily started event watcher).
741		856
742	=item ev_feed_fd_event (loop, int fd, int revents)	857	=item ev_feed_fd_event (loop, int fd, int revents)
743		858
744	Feed an event on the given fd, as if a file descriptor backend detected it.	859	Feed an event on the given fd, as if a file descriptor backend detected
		860	the given events it.
745		861
746	=item ev_feed_signal_event (loop, int signum)	862	=item ev_feed_signal_event (loop, int signum)
747		863
748	Feed an event as if the given signal occured (loop must be the default loop!).	864	Feed an event as if the given signal occured (loop must be the default loop!).
749		865
750	=back	866	=back
751		867
		868	=head1 LIBEVENT EMULATION
		869
		870	Libev offers a compatibility emulation layer for libevent. It cannot
		871	emulate the internals of libevent, so here are some usage hints:
		872
		873	=over 4
		874
		875	=item * Use it by including <event.h>, as usual.
		876
		877	=item * The following members are fully supported: ev_base, ev_callback,
		878	ev_arg, ev_fd, ev_res, ev_events.
		879
		880	=item * Avoid using ev_flags and the EVLIST_*-macros, while it is
		881	maintained by libev, it does not work exactly the same way as in libevent (consider
		882	it a private API).
		883
		884	=item * Priorities are not currently supported. Initialising priorities
		885	will fail and all watchers will have the same priority, even though there
		886	is an ev_pri field.
		887
		888	=item * Other members are not supported.
		889
		890	=item * The libev emulation is I<not> ABI compatible to libevent, you need
		891	to use the libev header file and library.
		892
		893	=back
		894
		895	=head1 C++ SUPPORT
		896
		897	TBD.
		898
752	=head1 AUTHOR	899	=head1 AUTHOR
753		900
754	Marc Lehmann <libev@schmorp.de>.	901	Marc Lehmann <libev@schmorp.de>.
755		902

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Revision 1.31 by root, Fri Nov 23 05:00:45 2007 UTC