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…		…
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
		14	#include <stdio.h> // for puts
		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
18		20
19	// all watcher callbacks have a similar signature	21	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	22	// this callback is called when data is readable on stdin
21	static void	23	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	25	{
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
28		30
29	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_run's to stop iterating
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_break (EV_A_ EVBREAK_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_run to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_break (EV_A_ EVBREAK_ONE);
40	}	42	}
41		43
42	int	44	int
43	main (void)	45	main (void)
44	{	46	{
…		…
54	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
57		59
58	// now wait for events to arrive	60	// now wait for events to arrive
59	ev_loop (loop, 0);	61	ev_run (loop, 0);
60		62
61	// unloop was called, so exit	63	// unloop was called, so exit
62	return 0;	64	return 0;
63	}	65	}
64		66
65	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
66		70
67	The newest version of this document is also available as an html-formatted	71	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	72	web page you might find easier to navigate when reading it for the first
69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.	73	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		74
		75	While this document tries to be as complete as possible in documenting
		76	libev, its usage and the rationale behind its design, it is not a tutorial
		77	on event-based programming, nor will it introduce event-based programming
		78	with libev.
		79
		80	Familiarity with event based programming techniques in general is assumed
		81	throughout this document.
		82
		83	=head1 ABOUT LIBEV
70		84
71	Libev is an event loop: you register interest in certain events (such as a	85	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	86	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	87	these event sources and provide your program with events.
74		88
…		…
84	=head2 FEATURES	98	=head2 FEATURES
85		99
86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	100	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	101	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	102	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	103	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
90	with customised rescheduling (C<ev_periodic>), synchronous signals	104	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
91	(C<ev_signal>), process status change events (C<ev_child>), and event	105	timers (C<ev_timer>), absolute timers with customised rescheduling
92	watchers dealing with the event loop mechanism itself (C<ev_idle>,	106	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
93	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	107	change events (C<ev_child>), and event watchers dealing with the event
94	file watchers (C<ev_stat>) and even limited support for fork events	108	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
95	(C<ev_fork>).	109	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		110	limited support for fork events (C<ev_fork>).
96		111
97	It also is quite fast (see this	112	It also is quite fast (see this
98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	113	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
99	for example).	114	for example).
100		115
…		…
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	123	name C<loop> (which is always of type C<struct ev_loop *>) will not have
109	this argument.	124	this argument.
110		125
111	=head2 TIME REPRESENTATION	126	=head2 TIME REPRESENTATION
112		127
113	Libev represents time as a single floating point number, representing the	128	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	129	the (fractional) number of seconds since the (POSIX) epoch (in practice
115	the beginning of 1970, details are complicated, don't ask). This type is	130	somewhere near the beginning of 1970, details are complicated, don't
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	131	ask). This type is called C<ev_tstamp>, which is what you should use
117	to the C<double> type in C, and when you need to do any calculations on	132	too. It usually aliases to the C<double> type in C. When you need to do
118	it, you should treat it as some floating point value. Unlike the name	133	any calculations on it, you should treat it as some floating point value.
		134
119	component C<stamp> might indicate, it is also used for time differences	135	Unlike the name component C<stamp> might indicate, it is also used for
120	throughout libev.	136	time differences (e.g. delays) throughout libev.
121		137
122	=head1 ERROR HANDLING	138	=head1 ERROR HANDLING
123		139
124	Libev knows three classes of errors: operating system errors, usage errors	140	Libev knows three classes of errors: operating system errors, usage errors
125	and internal errors (bugs).	141	and internal errors (bugs).
…		…
149		165
150	=item ev_tstamp ev_time ()	166	=item ev_tstamp ev_time ()
151		167
152	Returns the current time as libev would use it. Please note that the	168	Returns the current time as libev would use it. Please note that the
153	C<ev_now> function is usually faster and also often returns the timestamp	169	C<ev_now> function is usually faster and also often returns the timestamp
154	you actually want to know.	170	you actually want to know. Also interesting is the combination of
		171	C<ev_update_now> and C<ev_now>.
155		172
156	=item ev_sleep (ev_tstamp interval)	173	=item ev_sleep (ev_tstamp interval)
157		174
158	Sleep for the given interval: The current thread will be blocked until	175	Sleep for the given interval: The current thread will be blocked until
159	either it is interrupted or the given time interval has passed. Basically	176	either it is interrupted or the given time interval has passed. Basically
…		…
176	as this indicates an incompatible change. Minor versions are usually	193	as this indicates an incompatible change. Minor versions are usually
177	compatible to older versions, so a larger minor version alone is usually	194	compatible to older versions, so a larger minor version alone is usually
178	not a problem.	195	not a problem.
179		196
180	Example: Make sure we haven't accidentally been linked against the wrong	197	Example: Make sure we haven't accidentally been linked against the wrong
181	version.	198	version (note, however, that this will not detect other ABI mismatches,
		199	such as LFS or reentrancy).
182		200
183	assert (("libev version mismatch",	201	assert (("libev version mismatch",
184	ev_version_major () == EV_VERSION_MAJOR	202	ev_version_major () == EV_VERSION_MAJOR
185	&& ev_version_minor () >= EV_VERSION_MINOR));	203	&& ev_version_minor () >= EV_VERSION_MINOR));
186		204
…		…
197	assert (("sorry, no epoll, no sex",	215	assert (("sorry, no epoll, no sex",
198	ev_supported_backends () & EVBACKEND_EPOLL));	216	ev_supported_backends () & EVBACKEND_EPOLL));
199		217
200	=item unsigned int ev_recommended_backends ()	218	=item unsigned int ev_recommended_backends ()
201		219
202	Return the set of all backends compiled into this binary of libev and also	220	Return the set of all backends compiled into this binary of libev and
203	recommended for this platform. This set is often smaller than the one	221	also recommended for this platform, meaning it will work for most file
		222	descriptor types. This set is often smaller than the one returned by
204	returned by C<ev_supported_backends>, as for example kqueue is broken on	223	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
205	most BSDs and will not be auto-detected unless you explicitly request it	224	and will not be auto-detected unless you explicitly request it (assuming
206	(assuming you know what you are doing). This is the set of backends that	225	you know what you are doing). This is the set of backends that libev will
207	libev will probe for if you specify no backends explicitly.	226	probe for if you specify no backends explicitly.
208		227
209	=item unsigned int ev_embeddable_backends ()	228	=item unsigned int ev_embeddable_backends ()
210		229
211	Returns the set of backends that are embeddable in other event loops. This	230	Returns the set of backends that are embeddable in other event loops. This
212	is the theoretical, all-platform, value. To find which backends	231	value is platform-specific but can include backends not available on the
213	might be supported on the current system, you would need to look at	232	current system. To find which embeddable backends might be supported on
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	233	the current system, you would need to look at C<ev_embeddable_backends ()
215	recommended ones.	234	& ev_supported_backends ()>, likewise for recommended ones.
216		235
217	See the description of C<ev_embed> watchers for more info.	236	See the description of C<ev_embed> watchers for more info.
218		237
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	238	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
220		239
221	Sets the allocation function to use (the prototype is similar - the	240	Sets the allocation function to use (the prototype is similar - the
222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	241	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
223	used to allocate and free memory (no surprises here). If it returns zero	242	used to allocate and free memory (no surprises here). If it returns zero
224	when memory needs to be allocated (C<size != 0>), the library might abort	243	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	269	}
251		270
252	...	271	...
253	ev_set_allocator (persistent_realloc);	272	ev_set_allocator (persistent_realloc);
254		273
255	=item ev_set_syserr_cb (void (*cb)(const char *msg));	274	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
256		275
257	Set the callback function to call on a retryable system call error (such	276	Set the callback function to call on a retryable system call error (such
258	as failed select, poll, epoll_wait). The message is a printable string	277	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	278	indicating the system call or subsystem causing the problem. If this
260	callback is set, then libev will expect it to remedy the situation, no	279	callback is set, then libev will expect it to remedy the situation, no
…		…
276		295
277	=back	296	=back
278		297
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	298	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
280		299
281	An event loop is described by a C<struct ev_loop *>. The library knows two	300	An event loop is described by a C<struct ev_loop *> (the C<struct> is
282	types of such loops, the I<default> loop, which supports signals and child	301	I<not> optional in this case unless libev 3 compatibility is disabled, as
283	events, and dynamically created loops which do not.	302	libev 3 had an C<ev_loop> function colliding with the struct name).
		303
		304	The library knows two types of such loops, the I<default> loop, which
		305	supports signals and child events, and dynamically created event loops
		306	which do not.
284		307
285	=over 4	308	=over 4
286		309
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	310	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		311
…		…
294	If you don't know what event loop to use, use the one returned from this	317	If you don't know what event loop to use, use the one returned from this
295	function.	318	function.
296		319
297	Note that this function is I<not> thread-safe, so if you want to use it	320	Note that this function is I<not> thread-safe, so if you want to use it
298	from multiple threads, you have to lock (note also that this is unlikely,	321	from multiple threads, you have to lock (note also that this is unlikely,
299	as loops cannot bes hared easily between threads anyway).	322	as loops cannot be shared easily between threads anyway).
300		323
301	The default loop is the only loop that can handle C<ev_signal> and	324	The default loop is the only loop that can handle C<ev_signal> and
302	C<ev_child> watchers, and to do this, it always registers a handler	325	C<ev_child> watchers, and to do this, it always registers a handler
303	for C<SIGCHLD>. If this is a problem for your application you can either	326	for C<SIGCHLD>. If this is a problem for your application you can either
304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	327	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
…		…
326	useful to try out specific backends to test their performance, or to work	349	useful to try out specific backends to test their performance, or to work
327	around bugs.	350	around bugs.
328		351
329	=item C<EVFLAG_FORKCHECK>	352	=item C<EVFLAG_FORKCHECK>
330		353
331	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	354	Instead of calling C<ev_loop_fork> manually after a fork, you can also
332	a fork, you can also make libev check for a fork in each iteration by	355	make libev check for a fork in each iteration by enabling this flag.
333	enabling this flag.
334		356
335	This works by calling C<getpid ()> on every iteration of the loop,	357	This works by calling C<getpid ()> on every iteration of the loop,
336	and thus this might slow down your event loop if you do a lot of loop	358	and thus this might slow down your event loop if you do a lot of loop
337	iterations and little real work, but is usually not noticeable (on my	359	iterations and little real work, but is usually not noticeable (on my
338	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	360	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
…		…
344	flag.	366	flag.
345		367
346	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	368	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
347	environment variable.	369	environment variable.
348		370
		371	=item C<EVFLAG_NOINOTIFY>
		372
		373	When this flag is specified, then libev will not attempt to use the
		374	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and
		375	testing, this flag can be useful to conserve inotify file descriptors, as
		376	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		377
		378	=item C<EVFLAG_SIGNALFD>
		379
		380	When this flag is specified, then libev will attempt to use the
		381	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API
		382	delivers signals synchronously, which makes it both faster and might make
		383	it possible to get the queued signal data. It can also simplify signal
		384	handling with threads, as long as you properly block signals in your
		385	threads that are not interested in handling them.
		386
		387	Signalfd will not be used by default as this changes your signal mask, and
		388	there are a lot of shoddy libraries and programs (glib's threadpool for
		389	example) that can't properly initialise their signal masks.
		390
349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	391	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
350		392
351	This is your standard select(2) backend. Not I<completely> standard, as	393	This is your standard select(2) backend. Not I<completely> standard, as
352	libev tries to roll its own fd_set with no limits on the number of fds,	394	libev tries to roll its own fd_set with no limits on the number of fds,
353	but if that fails, expect a fairly low limit on the number of fds when	395	but if that fails, expect a fairly low limit on the number of fds when
…		…
377	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and	419	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
378	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	420	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
379		421
380	=item C<EVBACKEND_EPOLL> (value 4, Linux)	422	=item C<EVBACKEND_EPOLL> (value 4, Linux)
381		423
		424	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		425	kernels).
		426
382	For few fds, this backend is a bit little slower than poll and select,	427	For few fds, this backend is a bit little slower than poll and select,
383	but it scales phenomenally better. While poll and select usually scale	428	but it scales phenomenally better. While poll and select usually scale
384	like O(total_fds) where n is the total number of fds (or the highest fd),	429	like O(total_fds) where n is the total number of fds (or the highest fd),
385	epoll scales either O(1) or O(active_fds). The epoll design has a number	430	epoll scales either O(1) or O(active_fds).
386	of shortcomings, such as silently dropping events in some hard-to-detect	431
387	cases and requiring a system call per fd change, no fork support and bad	432	The epoll mechanism deserves honorable mention as the most misdesigned
388	support for dup.	433	of the more advanced event mechanisms: mere annoyances include silently
		434	dropping file descriptors, requiring a system call per change per file
		435	descriptor (and unnecessary guessing of parameters), problems with dup and
		436	so on. The biggest issue is fork races, however - if a program forks then
		437	I<both> parent and child process have to recreate the epoll set, which can
		438	take considerable time (one syscall per file descriptor) and is of course
		439	hard to detect.
		440
		441	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		442	of course I<doesn't>, and epoll just loves to report events for totally
		443	I<different> file descriptors (even already closed ones, so one cannot
		444	even remove them from the set) than registered in the set (especially
		445	on SMP systems). Libev tries to counter these spurious notifications by
		446	employing an additional generation counter and comparing that against the
		447	events to filter out spurious ones, recreating the set when required. Last
		448	not least, it also refuses to work with some file descriptors which work
		449	perfectly fine with C<select> (files, many character devices...).
389		450
390	While stopping, setting and starting an I/O watcher in the same iteration	451	While stopping, setting and starting an I/O watcher in the same iteration
391	will result in some caching, there is still a system call per such incident	452	will result in some caching, there is still a system call per such
392	(because the fd could point to a different file description now), so its	453	incident (because the same I<file descriptor> could point to a different
393	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	454	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
394	very well if you register events for both fds.	455	file descriptors might not work very well if you register events for both
395		456	file descriptors.
396	Please note that epoll sometimes generates spurious notifications, so you
397	need to use non-blocking I/O or other means to avoid blocking when no data
398	(or space) is available.
399		457
400	Best performance from this backend is achieved by not unregistering all	458	Best performance from this backend is achieved by not unregistering all
401	watchers for a file descriptor until it has been closed, if possible, i.e.	459	watchers for a file descriptor until it has been closed, if possible,
402	keep at least one watcher active per fd at all times.	460	i.e. keep at least one watcher active per fd at all times. Stopping and
		461	starting a watcher (without re-setting it) also usually doesn't cause
		462	extra overhead. A fork can both result in spurious notifications as well
		463	as in libev having to destroy and recreate the epoll object, which can
		464	take considerable time and thus should be avoided.
		465
		466	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		467	faster than epoll for maybe up to a hundred file descriptors, depending on
		468	the usage. So sad.
403		469
404	While nominally embeddable in other event loops, this feature is broken in	470	While nominally embeddable in other event loops, this feature is broken in
405	all kernel versions tested so far.	471	all kernel versions tested so far.
406		472
407	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	473	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
…		…
410	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	476	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
411		477
412	Kqueue deserves special mention, as at the time of this writing, it	478	Kqueue deserves special mention, as at the time of this writing, it
413	was broken on all BSDs except NetBSD (usually it doesn't work reliably	479	was broken on all BSDs except NetBSD (usually it doesn't work reliably
414	with anything but sockets and pipes, except on Darwin, where of course	480	with anything but sockets and pipes, except on Darwin, where of course
415	it's completely useless). For this reason it's not being "auto-detected"	481	it's completely useless). Unlike epoll, however, whose brokenness
		482	is by design, these kqueue bugs can (and eventually will) be fixed
		483	without API changes to existing programs. For this reason it's not being
416	unless you explicitly specify it explicitly in the flags (i.e. using	484	"auto-detected" unless you explicitly specify it in the flags (i.e. using
417	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	485	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
418	system like NetBSD.	486	system like NetBSD.
419		487
420	You still can embed kqueue into a normal poll or select backend and use it	488	You still can embed kqueue into a normal poll or select backend and use it
421	only for sockets (after having made sure that sockets work with kqueue on	489	only for sockets (after having made sure that sockets work with kqueue on
…		…
423		491
424	It scales in the same way as the epoll backend, but the interface to the	492	It scales in the same way as the epoll backend, but the interface to the
425	kernel is more efficient (which says nothing about its actual speed, of	493	kernel is more efficient (which says nothing about its actual speed, of
426	course). While stopping, setting and starting an I/O watcher does never	494	course). While stopping, setting and starting an I/O watcher does never
427	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	495	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
428	two event changes per incident, support for C<fork ()> is very bad and it	496	two event changes per incident. Support for C<fork ()> is very bad (but
429	drops fds silently in similarly hard-to-detect cases.	497	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		498	cases
430		499
431	This backend usually performs well under most conditions.	500	This backend usually performs well under most conditions.
432		501
433	While nominally embeddable in other event loops, this doesn't work	502	While nominally embeddable in other event loops, this doesn't work
434	everywhere, so you might need to test for this. And since it is broken	503	everywhere, so you might need to test for this. And since it is broken
435	almost everywhere, you should only use it when you have a lot of sockets	504	almost everywhere, you should only use it when you have a lot of sockets
436	(for which it usually works), by embedding it into another event loop	505	(for which it usually works), by embedding it into another event loop
437	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	506	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
438	sockets.	507	also broken on OS X)) and, did I mention it, using it only for sockets.
439		508
440	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	509	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
441	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with	510	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
442	C<NOTE_EOF>.	511	C<NOTE_EOF>.
443		512
…		…
460	While this backend scales well, it requires one system call per active	529	While this backend scales well, it requires one system call per active
461	file descriptor per loop iteration. For small and medium numbers of file	530	file descriptor per loop iteration. For small and medium numbers of file
462	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	531	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
463	might perform better.	532	might perform better.
464		533
465	On the positive side, ignoring the spurious readiness notifications, this	534	On the positive side, with the exception of the spurious readiness
466	backend actually performed to specification in all tests and is fully	535	notifications, this backend actually performed fully to specification
467	embeddable, which is a rare feat among the OS-specific backends.	536	in all tests and is fully embeddable, which is a rare feat among the
		537	OS-specific backends (I vastly prefer correctness over speed hacks).
468		538
469	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	539	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
470	C<EVBACKEND_POLL>.	540	C<EVBACKEND_POLL>.
471		541
472	=item C<EVBACKEND_ALL>	542	=item C<EVBACKEND_ALL>
…		…
477		547
478	It is definitely not recommended to use this flag.	548	It is definitely not recommended to use this flag.
479		549
480	=back	550	=back
481		551
482	If one or more of these are or'ed into the flags value, then only these	552	If one or more of the backend flags are or'ed into the flags value,
483	backends will be tried (in the reverse order as listed here). If none are	553	then only these backends will be tried (in the reverse order as listed
484	specified, all backends in C<ev_recommended_backends ()> will be tried.	554	here). If none are specified, all backends in C<ev_recommended_backends
		555	()> will be tried.
485		556
486	The most typical usage is like this:	557	Example: This is the most typical usage.
487		558
488	if (!ev_default_loop (0))	559	if (!ev_default_loop (0))
489	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	560	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
490		561
491	Restrict libev to the select and poll backends, and do not allow	562	Example: Restrict libev to the select and poll backends, and do not allow
492	environment settings to be taken into account:	563	environment settings to be taken into account:
493		564
494	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	565	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
495		566
496	Use whatever libev has to offer, but make sure that kqueue is used if	567	Example: Use whatever libev has to offer, but make sure that kqueue is
497	available (warning, breaks stuff, best use only with your own private	568	used if available (warning, breaks stuff, best use only with your own
498	event loop and only if you know the OS supports your types of fds):	569	private event loop and only if you know the OS supports your types of
		570	fds):
499		571
500	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	572	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
501		573
502	=item struct ev_loop *ev_loop_new (unsigned int flags)	574	=item struct ev_loop *ev_loop_new (unsigned int flags)
503		575
504	Similar to C<ev_default_loop>, but always creates a new event loop that is	576	Similar to C<ev_default_loop>, but always creates a new event loop that is
505	always distinct from the default loop. Unlike the default loop, it cannot	577	always distinct from the default loop.
506	handle signal and child watchers, and attempts to do so will be greeted by
507	undefined behaviour (or a failed assertion if assertions are enabled).
508		578
509	Note that this function I<is> thread-safe, and the recommended way to use	579	Note that this function I<is> thread-safe, and one common way to use
510	libev with threads is indeed to create one loop per thread, and using the	580	libev with threads is indeed to create one loop per thread, and using the
511	default loop in the "main" or "initial" thread.	581	default loop in the "main" or "initial" thread.
512		582
513	Example: Try to create a event loop that uses epoll and nothing else.	583	Example: Try to create a event loop that uses epoll and nothing else.
514		584
…		…
516	if (!epoller)	586	if (!epoller)
517	fatal ("no epoll found here, maybe it hides under your chair");	587	fatal ("no epoll found here, maybe it hides under your chair");
518		588
519	=item ev_default_destroy ()	589	=item ev_default_destroy ()
520		590
521	Destroys the default loop again (frees all memory and kernel state	591	Destroys the default loop (frees all memory and kernel state etc.). None
522	etc.). None of the active event watchers will be stopped in the normal	592	of the active event watchers will be stopped in the normal sense, so
523	sense, so e.g. C<ev_is_active> might still return true. It is your	593	e.g. C<ev_is_active> might still return true. It is your responsibility to
524	responsibility to either stop all watchers cleanly yourself I<before>	594	either stop all watchers cleanly yourself I<before> calling this function,
525	calling this function, or cope with the fact afterwards (which is usually	595	or cope with the fact afterwards (which is usually the easiest thing, you
526	the easiest thing, you can just ignore the watchers and/or C<free ()> them	596	can just ignore the watchers and/or C<free ()> them for example).
527	for example).
528		597
529	Note that certain global state, such as signal state, will not be freed by	598	Note that certain global state, such as signal state (and installed signal
530	this function, and related watchers (such as signal and child watchers)	599	handlers), will not be freed by this function, and related watchers (such
531	would need to be stopped manually.	600	as signal and child watchers) would need to be stopped manually.
532		601
533	In general it is not advisable to call this function except in the	602	In general it is not advisable to call this function except in the
534	rare occasion where you really need to free e.g. the signal handling	603	rare occasion where you really need to free e.g. the signal handling
535	pipe fds. If you need dynamically allocated loops it is better to use	604	pipe fds. If you need dynamically allocated loops it is better to use
536	C<ev_loop_new> and C<ev_loop_destroy>).	605	C<ev_loop_new> and C<ev_loop_destroy>.
537		606
538	=item ev_loop_destroy (loop)	607	=item ev_loop_destroy (loop)
539		608
540	Like C<ev_default_destroy>, but destroys an event loop created by an	609	Like C<ev_default_destroy>, but destroys an event loop created by an
541	earlier call to C<ev_loop_new>.	610	earlier call to C<ev_loop_new>.
542		611
543	=item ev_default_fork ()	612	=item ev_default_fork ()
544		613
545	This function sets a flag that causes subsequent C<ev_loop> iterations	614	This function sets a flag that causes subsequent C<ev_run> iterations
546	to reinitialise the kernel state for backends that have one. Despite the	615	to reinitialise the kernel state for backends that have one. Despite the
547	name, you can call it anytime, but it makes most sense after forking, in	616	name, you can call it anytime, but it makes most sense after forking, in
548	the child process (or both child and parent, but that again makes little	617	the child process (or both child and parent, but that again makes little
549	sense). You I<must> call it in the child before using any of the libev	618	sense). You I<must> call it in the child before using any of the libev
550	functions, and it will only take effect at the next C<ev_loop> iteration.	619	functions, and it will only take effect at the next C<ev_run> iteration.
		620
		621	Again, you I<have> to call it on I<any> loop that you want to re-use after
		622	a fork, I<even if you do not plan to use the loop in the parent>. This is
		623	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		624	during fork.
551		625
552	On the other hand, you only need to call this function in the child	626	On the other hand, you only need to call this function in the child
553	process if and only if you want to use the event library in the child. If	627	process if and only if you want to use the event loop in the child. If
554	you just fork+exec, you don't have to call it at all.	628	you just fork+exec or create a new loop in the child, you don't have to
		629	call it at all (in fact, C<epoll> is so badly broken that it makes a
		630	difference, but libev will usually detect this case on its own and do a
		631	costly reset of the backend).
555		632
556	The function itself is quite fast and it's usually not a problem to call	633	The function itself is quite fast and it's usually not a problem to call
557	it just in case after a fork. To make this easy, the function will fit in	634	it just in case after a fork. To make this easy, the function will fit in
558	quite nicely into a call to C<pthread_atfork>:	635	quite nicely into a call to C<pthread_atfork>:
559		636
…		…
561		638
562	=item ev_loop_fork (loop)	639	=item ev_loop_fork (loop)
563		640
564	Like C<ev_default_fork>, but acts on an event loop created by	641	Like C<ev_default_fork>, but acts on an event loop created by
565	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	642	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
566	after fork, and how you do this is entirely your own problem.	643	after fork that you want to re-use in the child, and how you keep track of
		644	them is entirely your own problem.
567		645
568	=item int ev_is_default_loop (loop)	646	=item int ev_is_default_loop (loop)
569		647
570	Returns true when the given loop actually is the default loop, false otherwise.	648	Returns true when the given loop is, in fact, the default loop, and false
		649	otherwise.
571		650
572	=item unsigned int ev_loop_count (loop)	651	=item unsigned int ev_iteration (loop)
573		652
574	Returns the count of loop iterations for the loop, which is identical to	653	Returns the current iteration count for the event loop, which is identical
575	the number of times libev did poll for new events. It starts at C<0> and	654	to the number of times libev did poll for new events. It starts at C<0>
576	happily wraps around with enough iterations.	655	and happily wraps around with enough iterations.
577		656
578	This value can sometimes be useful as a generation counter of sorts (it	657	This value can sometimes be useful as a generation counter of sorts (it
579	"ticks" the number of loop iterations), as it roughly corresponds with	658	"ticks" the number of loop iterations), as it roughly corresponds with
580	C<ev_prepare> and C<ev_check> calls.	659	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		660	prepare and check phases.
		661
		662	=item unsigned int ev_depth (loop)
		663
		664	Returns the number of times C<ev_run> was entered minus the number of
		665	times C<ev_run> was exited, in other words, the recursion depth.
		666
		667	Outside C<ev_run>, this number is zero. In a callback, this number is
		668	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		669	in which case it is higher.
		670
		671	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread
		672	etc.), doesn't count as "exit" - consider this as a hint to avoid such
		673	ungentleman-like behaviour unless it's really convenient.
581		674
582	=item unsigned int ev_backend (loop)	675	=item unsigned int ev_backend (loop)
583		676
584	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	677	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
585	use.	678	use.
…		…
594		687
595	=item ev_now_update (loop)	688	=item ev_now_update (loop)
596		689
597	Establishes the current time by querying the kernel, updating the time	690	Establishes the current time by querying the kernel, updating the time
598	returned by C<ev_now ()> in the progress. This is a costly operation and	691	returned by C<ev_now ()> in the progress. This is a costly operation and
599	is usually done automatically within C<ev_loop ()>.	692	is usually done automatically within C<ev_run ()>.
600		693
601	This function is rarely useful, but when some event callback runs for a	694	This function is rarely useful, but when some event callback runs for a
602	very long time without entering the event loop, updating libev's idea of	695	very long time without entering the event loop, updating libev's idea of
603	the current time is a good idea.	696	the current time is a good idea.
604		697
605	See also "The special problem of time updates" in the C<ev_timer> section.	698	See also L<The special problem of time updates> in the C<ev_timer> section.
606		699
		700	=item ev_suspend (loop)
		701
		702	=item ev_resume (loop)
		703
		704	These two functions suspend and resume an event loop, for use when the
		705	loop is not used for a while and timeouts should not be processed.
		706
		707	A typical use case would be an interactive program such as a game: When
		708	the user presses C<^Z> to suspend the game and resumes it an hour later it
		709	would be best to handle timeouts as if no time had actually passed while
		710	the program was suspended. This can be achieved by calling C<ev_suspend>
		711	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		712	C<ev_resume> directly afterwards to resume timer processing.
		713
		714	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		715	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		716	will be rescheduled (that is, they will lose any events that would have
		717	occurred while suspended).
		718
		719	After calling C<ev_suspend> you B<must not> call I<any> function on the
		720	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		721	without a previous call to C<ev_suspend>.
		722
		723	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		724	event loop time (see C<ev_now_update>).
		725
607	=item ev_loop (loop, int flags)	726	=item ev_run (loop, int flags)
608		727
609	Finally, this is it, the event handler. This function usually is called	728	Finally, this is it, the event handler. This function usually is called
610	after you initialised all your watchers and you want to start handling	729	after you have initialised all your watchers and you want to start
611	events.	730	handling events. It will ask the operating system for any new events, call
		731	the watcher callbacks, an then repeat the whole process indefinitely: This
		732	is why event loops are called I<loops>.
612		733
613	If the flags argument is specified as C<0>, it will not return until	734	If the flags argument is specified as C<0>, it will keep handling events
614	either no event watchers are active anymore or C<ev_unloop> was called.	735	until either no event watchers are active anymore or C<ev_break> was
		736	called.
615		737
616	Please note that an explicit C<ev_unloop> is usually better than	738	Please note that an explicit C<ev_break> is usually better than
617	relying on all watchers to be stopped when deciding when a program has	739	relying on all watchers to be stopped when deciding when a program has
618	finished (especially in interactive programs), but having a program that	740	finished (especially in interactive programs), but having a program
619	automatically loops as long as it has to and no longer by virtue of	741	that automatically loops as long as it has to and no longer by virtue
620	relying on its watchers stopping correctly is a thing of beauty.	742	of relying on its watchers stopping correctly, that is truly a thing of
		743	beauty.
621		744
622	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	745	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
623	those events and any outstanding ones, but will not block your process in	746	those events and any already outstanding ones, but will not wait and
624	case there are no events and will return after one iteration of the loop.	747	block your process in case there are no events and will return after one
		748	iteration of the loop. This is sometimes useful to poll and handle new
		749	events while doing lengthy calculations, to keep the program responsive.
625		750
626	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	751	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
627	necessary) and will handle those and any outstanding ones. It will block	752	necessary) and will handle those and any already outstanding ones. It
628	your process until at least one new event arrives, and will return after	753	will block your process until at least one new event arrives (which could
629	one iteration of the loop. This is useful if you are waiting for some	754	be an event internal to libev itself, so there is no guarantee that a
630	external event in conjunction with something not expressible using other	755	user-registered callback will be called), and will return after one
		756	iteration of the loop.
		757
		758	This is useful if you are waiting for some external event in conjunction
		759	with something not expressible using other libev watchers (i.e. "roll your
631	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	760	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
632	usually a better approach for this kind of thing.	761	usually a better approach for this kind of thing.
633		762
634	Here are the gory details of what C<ev_loop> does:	763	Here are the gory details of what C<ev_run> does:
635		764
		765	- Increment loop depth.
		766	- Reset the ev_break status.
636	- Before the first iteration, call any pending watchers.	767	- Before the first iteration, call any pending watchers.
		768	LOOP:
637	* If EVFLAG_FORKCHECK was used, check for a fork.	769	- If EVFLAG_FORKCHECK was used, check for a fork.
638	- If a fork was detected (by any means), queue and call all fork watchers.	770	- If a fork was detected (by any means), queue and call all fork watchers.
639	- Queue and call all prepare watchers.	771	- Queue and call all prepare watchers.
		772	- If ev_break was called, goto FINISH.
640	- If we have been forked, detach and recreate the kernel state	773	- If we have been forked, detach and recreate the kernel state
641	as to not disturb the other process.	774	as to not disturb the other process.
642	- Update the kernel state with all outstanding changes.	775	- Update the kernel state with all outstanding changes.
643	- Update the "event loop time" (ev_now ()).	776	- Update the "event loop time" (ev_now ()).
644	- Calculate for how long to sleep or block, if at all	777	- Calculate for how long to sleep or block, if at all
645	(active idle watchers, EVLOOP_NONBLOCK or not having	778	(active idle watchers, EVRUN_NOWAIT or not having
646	any active watchers at all will result in not sleeping).	779	any active watchers at all will result in not sleeping).
647	- Sleep if the I/O and timer collect interval say so.	780	- Sleep if the I/O and timer collect interval say so.
		781	- Increment loop iteration counter.
648	- Block the process, waiting for any events.	782	- Block the process, waiting for any events.
649	- Queue all outstanding I/O (fd) events.	783	- Queue all outstanding I/O (fd) events.
650	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	784	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
651	- Queue all outstanding timers.	785	- Queue all expired timers.
652	- Queue all outstanding periodics.	786	- Queue all expired periodics.
653	- Unless any events are pending now, queue all idle watchers.	787	- Queue all idle watchers with priority higher than that of pending events.
654	- Queue all check watchers.	788	- Queue all check watchers.
655	- Call all queued watchers in reverse order (i.e. check watchers first).	789	- Call all queued watchers in reverse order (i.e. check watchers first).
656	Signals and child watchers are implemented as I/O watchers, and will	790	Signals and child watchers are implemented as I/O watchers, and will
657	be handled here by queueing them when their watcher gets executed.	791	be handled here by queueing them when their watcher gets executed.
658	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	792	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
659	were used, or there are no active watchers, return, otherwise	793	were used, or there are no active watchers, goto FINISH, otherwise
660	continue with step *.	794	continue with step LOOP.
		795	FINISH:
		796	- Reset the ev_break status iff it was EVBREAK_ONE.
		797	- Decrement the loop depth.
		798	- Return.
661		799
662	Example: Queue some jobs and then loop until no events are outstanding	800	Example: Queue some jobs and then loop until no events are outstanding
663	anymore.	801	anymore.
664		802
665	... queue jobs here, make sure they register event watchers as long	803	... queue jobs here, make sure they register event watchers as long
666	... as they still have work to do (even an idle watcher will do..)	804	... as they still have work to do (even an idle watcher will do..)
667	ev_loop (my_loop, 0);	805	ev_run (my_loop, 0);
668	... jobs done or somebody called unloop. yeah!	806	... jobs done or somebody called unloop. yeah!
669		807
670	=item ev_unloop (loop, how)	808	=item ev_break (loop, how)
671		809
672	Can be used to make a call to C<ev_loop> return early (but only after it	810	Can be used to make a call to C<ev_run> return early (but only after it
673	has processed all outstanding events). The C<how> argument must be either	811	has processed all outstanding events). The C<how> argument must be either
674	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	812	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
675	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	813	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
676		814
677	This "unloop state" will be cleared when entering C<ev_loop> again.	815	This "unloop state" will be cleared when entering C<ev_run> again.
		816
		817	It is safe to call C<ev_break> from outside any C<ev_run> calls. ##TODO##
678		818
679	=item ev_ref (loop)	819	=item ev_ref (loop)
680		820
681	=item ev_unref (loop)	821	=item ev_unref (loop)
682		822
683	Ref/unref can be used to add or remove a reference count on the event	823	Ref/unref can be used to add or remove a reference count on the event
684	loop: Every watcher keeps one reference, and as long as the reference	824	loop: Every watcher keeps one reference, and as long as the reference
685	count is nonzero, C<ev_loop> will not return on its own. If you have	825	count is nonzero, C<ev_run> will not return on its own.
686	a watcher you never unregister that should not keep C<ev_loop> from	826
687	returning, ev_unref() after starting, and ev_ref() before stopping it. For	827	This is useful when you have a watcher that you never intend to
		828	unregister, but that nevertheless should not keep C<ev_run> from
		829	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
		830	before stopping it.
		831
688	example, libev itself uses this for its internal signal pipe: It is not	832	As an example, libev itself uses this for its internal signal pipe: It
689	visible to the libev user and should not keep C<ev_loop> from exiting if	833	is not visible to the libev user and should not keep C<ev_run> from
690	no event watchers registered by it are active. It is also an excellent	834	exiting if no event watchers registered by it are active. It is also an
691	way to do this for generic recurring timers or from within third-party	835	excellent way to do this for generic recurring timers or from within
692	libraries. Just remember to I<unref after start> and I<ref before stop>	836	third-party libraries. Just remember to I<unref after start> and I<ref
693	(but only if the watcher wasn't active before, or was active before,	837	before stop> (but only if the watcher wasn't active before, or was active
694	respectively).	838	before, respectively. Note also that libev might stop watchers itself
		839	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		840	in the callback).
695		841
696	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	842	Example: Create a signal watcher, but keep it from keeping C<ev_run>
697	running when nothing else is active.	843	running when nothing else is active.
698		844
699	struct ev_signal exitsig;	845	ev_signal exitsig;
700	ev_signal_init (&exitsig, sig_cb, SIGINT);	846	ev_signal_init (&exitsig, sig_cb, SIGINT);
701	ev_signal_start (loop, &exitsig);	847	ev_signal_start (loop, &exitsig);
702	evf_unref (loop);	848	evf_unref (loop);
703		849
704	Example: For some weird reason, unregister the above signal handler again.	850	Example: For some weird reason, unregister the above signal handler again.
…		…
718	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	864	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
719	allows libev to delay invocation of I/O and timer/periodic callbacks	865	allows libev to delay invocation of I/O and timer/periodic callbacks
720	to increase efficiency of loop iterations (or to increase power-saving	866	to increase efficiency of loop iterations (or to increase power-saving
721	opportunities).	867	opportunities).
722		868
723	The background is that sometimes your program runs just fast enough to	869	The idea is that sometimes your program runs just fast enough to handle
724	handle one (or very few) event(s) per loop iteration. While this makes	870	one (or very few) event(s) per loop iteration. While this makes the
725	the program responsive, it also wastes a lot of CPU time to poll for new	871	program responsive, it also wastes a lot of CPU time to poll for new
726	events, especially with backends like C<select ()> which have a high	872	events, especially with backends like C<select ()> which have a high
727	overhead for the actual polling but can deliver many events at once.	873	overhead for the actual polling but can deliver many events at once.
728		874
729	By setting a higher I<io collect interval> you allow libev to spend more	875	By setting a higher I<io collect interval> you allow libev to spend more
730	time collecting I/O events, so you can handle more events per iteration,	876	time collecting I/O events, so you can handle more events per iteration,
731	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	877	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
732	C<ev_timer>) will be not affected. Setting this to a non-null value will	878	C<ev_timer>) will be not affected. Setting this to a non-null value will
733	introduce an additional C<ev_sleep ()> call into most loop iterations.	879	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		880	sleep time ensures that libev will not poll for I/O events more often then
		881	once per this interval, on average.
734		882
735	Likewise, by setting a higher I<timeout collect interval> you allow libev	883	Likewise, by setting a higher I<timeout collect interval> you allow libev
736	to spend more time collecting timeouts, at the expense of increased	884	to spend more time collecting timeouts, at the expense of increased
737	latency (the watcher callback will be called later). C<ev_io> watchers	885	latency/jitter/inexactness (the watcher callback will be called
738	will not be affected. Setting this to a non-null value will not introduce	886	later). C<ev_io> watchers will not be affected. Setting this to a non-null
739	any overhead in libev.	887	value will not introduce any overhead in libev.
740		888
741	Many (busy) programs can usually benefit by setting the I/O collect	889	Many (busy) programs can usually benefit by setting the I/O collect
742	interval to a value near C<0.1> or so, which is often enough for	890	interval to a value near C<0.1> or so, which is often enough for
743	interactive servers (of course not for games), likewise for timeouts. It	891	interactive servers (of course not for games), likewise for timeouts. It
744	usually doesn't make much sense to set it to a lower value than C<0.01>,	892	usually doesn't make much sense to set it to a lower value than C<0.01>,
745	as this approaches the timing granularity of most systems.	893	as this approaches the timing granularity of most systems. Note that if
		894	you do transactions with the outside world and you can't increase the
		895	parallelity, then this setting will limit your transaction rate (if you
		896	need to poll once per transaction and the I/O collect interval is 0.01,
		897	then you can't do more than 100 transactions per second).
746		898
747	Setting the I<timeout collect interval> can improve the opportunity for	899	Setting the I<timeout collect interval> can improve the opportunity for
748	saving power, as the program will "bundle" timer callback invocations that	900	saving power, as the program will "bundle" timer callback invocations that
749	are "near" in time together, by delaying some, thus reducing the number of	901	are "near" in time together, by delaying some, thus reducing the number of
750	times the process sleeps and wakes up again. Another useful technique to	902	times the process sleeps and wakes up again. Another useful technique to
751	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	903	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
752	they fire on, say, one-second boundaries only.	904	they fire on, say, one-second boundaries only.
753		905
		906	Example: we only need 0.1s timeout granularity, and we wish not to poll
		907	more often than 100 times per second:
		908
		909	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		910	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		911
		912	=item ev_invoke_pending (loop)
		913
		914	This call will simply invoke all pending watchers while resetting their
		915	pending state. Normally, C<ev_run> does this automatically when required,
		916	but when overriding the invoke callback this call comes handy. This
		917	function can be invoked from a watcher - this can be useful for example
		918	when you want to do some lengthy calculation and want to pass further
		919	event handling to another thread (you still have to make sure only one
		920	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		921
		922	=item int ev_pending_count (loop)
		923
		924	Returns the number of pending watchers - zero indicates that no watchers
		925	are pending.
		926
		927	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		928
		929	This overrides the invoke pending functionality of the loop: Instead of
		930	invoking all pending watchers when there are any, C<ev_run> will call
		931	this callback instead. This is useful, for example, when you want to
		932	invoke the actual watchers inside another context (another thread etc.).
		933
		934	If you want to reset the callback, use C<ev_invoke_pending> as new
		935	callback.
		936
		937	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		938
		939	Sometimes you want to share the same loop between multiple threads. This
		940	can be done relatively simply by putting mutex_lock/unlock calls around
		941	each call to a libev function.
		942
		943	However, C<ev_run> can run an indefinite time, so it is not feasible
		944	to wait for it to return. One way around this is to wake up the event
		945	loop via C<ev_break> and C<av_async_send>, another way is to set these
		946	I<release> and I<acquire> callbacks on the loop.
		947
		948	When set, then C<release> will be called just before the thread is
		949	suspended waiting for new events, and C<acquire> is called just
		950	afterwards.
		951
		952	Ideally, C<release> will just call your mutex_unlock function, and
		953	C<acquire> will just call the mutex_lock function again.
		954
		955	While event loop modifications are allowed between invocations of
		956	C<release> and C<acquire> (that's their only purpose after all), no
		957	modifications done will affect the event loop, i.e. adding watchers will
		958	have no effect on the set of file descriptors being watched, or the time
		959	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		960	to take note of any changes you made.
		961
		962	In theory, threads executing C<ev_run> will be async-cancel safe between
		963	invocations of C<release> and C<acquire>.
		964
		965	See also the locking example in the C<THREADS> section later in this
		966	document.
		967
		968	=item ev_set_userdata (loop, void *data)
		969
		970	=item ev_userdata (loop)
		971
		972	Set and retrieve a single C<void *> associated with a loop. When
		973	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		974	C<0.>
		975
		976	These two functions can be used to associate arbitrary data with a loop,
		977	and are intended solely for the C<invoke_pending_cb>, C<release> and
		978	C<acquire> callbacks described above, but of course can be (ab-)used for
		979	any other purpose as well.
		980
754	=item ev_loop_verify (loop)	981	=item ev_verify (loop)
755		982
756	This function only does something when C<EV_VERIFY> support has been	983	This function only does something when C<EV_VERIFY> support has been
757	compiled in. It tries to go through all internal structures and checks	984	compiled in, which is the default for non-minimal builds. It tries to go
758	them for validity. If anything is found to be inconsistent, it will print	985	through all internal structures and checks them for validity. If anything
759	an error message to standard error and call C<abort ()>.	986	is found to be inconsistent, it will print an error message to standard
		987	error and call C<abort ()>.
760		988
761	This can be used to catch bugs inside libev itself: under normal	989	This can be used to catch bugs inside libev itself: under normal
762	circumstances, this function will never abort as of course libev keeps its	990	circumstances, this function will never abort as of course libev keeps its
763	data structures consistent.	991	data structures consistent.
764		992
765	=back	993	=back
766		994
767		995
768	=head1 ANATOMY OF A WATCHER	996	=head1 ANATOMY OF A WATCHER
769		997
		998	In the following description, uppercase C<TYPE> in names stands for the
		999	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		1000	watchers and C<ev_io_start> for I/O watchers.
		1001
770	A watcher is a structure that you create and register to record your	1002	A watcher is an opaque structure that you allocate and register to record
771	interest in some event. For instance, if you want to wait for STDIN to	1003	your interest in some event. To make a concrete example, imagine you want
772	become readable, you would create an C<ev_io> watcher for that:	1004	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1005	for that:
773		1006
774	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1007	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
775	{	1008	{
776	ev_io_stop (w);	1009	ev_io_stop (w);
777	ev_unloop (loop, EVUNLOOP_ALL);	1010	ev_break (loop, EVBREAK_ALL);
778	}	1011	}
779		1012
780	struct ev_loop *loop = ev_default_loop (0);	1013	struct ev_loop *loop = ev_default_loop (0);
		1014
781	struct ev_io stdin_watcher;	1015	ev_io stdin_watcher;
		1016
782	ev_init (&stdin_watcher, my_cb);	1017	ev_init (&stdin_watcher, my_cb);
783	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1018	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
784	ev_io_start (loop, &stdin_watcher);	1019	ev_io_start (loop, &stdin_watcher);
		1020
785	ev_loop (loop, 0);	1021	ev_run (loop, 0);
786		1022
787	As you can see, you are responsible for allocating the memory for your	1023	As you can see, you are responsible for allocating the memory for your
788	watcher structures (and it is usually a bad idea to do this on the stack,	1024	watcher structures (and it is I<usually> a bad idea to do this on the
789	although this can sometimes be quite valid).	1025	stack).
790		1026
		1027	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		1028	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
		1029
791	Each watcher structure must be initialised by a call to C<ev_init	1030	Each watcher structure must be initialised by a call to C<ev_init (watcher
792	(watcher *, callback)>, which expects a callback to be provided. This	1031	*, callback)>, which expects a callback to be provided. This callback is
793	callback gets invoked each time the event occurs (or, in the case of I/O	1032	invoked each time the event occurs (or, in the case of I/O watchers, each
794	watchers, each time the event loop detects that the file descriptor given	1033	time the event loop detects that the file descriptor given is readable
795	is readable and/or writable).	1034	and/or writable).
796		1035
797	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1036	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
798	with arguments specific to this watcher type. There is also a macro	1037	macro to configure it, with arguments specific to the watcher type. There
799	to combine initialisation and setting in one call: C<< ev_<type>_init	1038	is also a macro to combine initialisation and setting in one call: C<<
800	(watcher *, callback, ...) >>.	1039	ev_TYPE_init (watcher *, callback, ...) >>.
801		1040
802	To make the watcher actually watch out for events, you have to start it	1041	To make the watcher actually watch out for events, you have to start it
803	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	1042	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
804	*) >>), and you can stop watching for events at any time by calling the	1043	*) >>), and you can stop watching for events at any time by calling the
805	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1044	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
806		1045
807	As long as your watcher is active (has been started but not stopped) you	1046	As long as your watcher is active (has been started but not stopped) you
808	must not touch the values stored in it. Most specifically you must never	1047	must not touch the values stored in it. Most specifically you must never
809	reinitialise it or call its C<set> macro.	1048	reinitialise it or call its C<ev_TYPE_set> macro.
810		1049
811	Each and every callback receives the event loop pointer as first, the	1050	Each and every callback receives the event loop pointer as first, the
812	registered watcher structure as second, and a bitset of received events as	1051	registered watcher structure as second, and a bitset of received events as
813	third argument.	1052	third argument.
814		1053
…		…
823	=item C<EV_WRITE>	1062	=item C<EV_WRITE>
824		1063
825	The file descriptor in the C<ev_io> watcher has become readable and/or	1064	The file descriptor in the C<ev_io> watcher has become readable and/or
826	writable.	1065	writable.
827		1066
828	=item C<EV_TIMEOUT>	1067	=item C<EV_TIMER>
829		1068
830	The C<ev_timer> watcher has timed out.	1069	The C<ev_timer> watcher has timed out.
831		1070
832	=item C<EV_PERIODIC>	1071	=item C<EV_PERIODIC>
833		1072
…		…
851		1090
852	=item C<EV_PREPARE>	1091	=item C<EV_PREPARE>
853		1092
854	=item C<EV_CHECK>	1093	=item C<EV_CHECK>
855		1094
856	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1095	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
857	to gather new events, and all C<ev_check> watchers are invoked just after	1096	to gather new events, and all C<ev_check> watchers are invoked just after
858	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1097	C<ev_run> has gathered them, but before it invokes any callbacks for any
859	received events. Callbacks of both watcher types can start and stop as	1098	received events. Callbacks of both watcher types can start and stop as
860	many watchers as they want, and all of them will be taken into account	1099	many watchers as they want, and all of them will be taken into account
861	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1100	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
862	C<ev_loop> from blocking).	1101	C<ev_run> from blocking).
863		1102
864	=item C<EV_EMBED>	1103	=item C<EV_EMBED>
865		1104
866	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1105	The embedded event loop specified in the C<ev_embed> watcher needs attention.
867		1106
…		…
871	C<ev_fork>).	1110	C<ev_fork>).
872		1111
873	=item C<EV_ASYNC>	1112	=item C<EV_ASYNC>
874		1113
875	The given async watcher has been asynchronously notified (see C<ev_async>).	1114	The given async watcher has been asynchronously notified (see C<ev_async>).
		1115
		1116	=item C<EV_CUSTOM>
		1117
		1118	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1119	by libev users to signal watchers (e.g. via C<ev_feed_event>).
876		1120
877	=item C<EV_ERROR>	1121	=item C<EV_ERROR>
878		1122
879	An unspecified error has occurred, the watcher has been stopped. This might	1123	An unspecified error has occurred, the watcher has been stopped. This might
880	happen because the watcher could not be properly started because libev	1124	happen because the watcher could not be properly started because libev
881	ran out of memory, a file descriptor was found to be closed or any other	1125	ran out of memory, a file descriptor was found to be closed or any other
		1126	problem. Libev considers these application bugs.
		1127
882	problem. You best act on it by reporting the problem and somehow coping	1128	You best act on it by reporting the problem and somehow coping with the
883	with the watcher being stopped.	1129	watcher being stopped. Note that well-written programs should not receive
		1130	an error ever, so when your watcher receives it, this usually indicates a
		1131	bug in your program.
884		1132
885	Libev will usually signal a few "dummy" events together with an error,	1133	Libev will usually signal a few "dummy" events together with an error, for
886	for example it might indicate that a fd is readable or writable, and if	1134	example it might indicate that a fd is readable or writable, and if your
887	your callbacks is well-written it can just attempt the operation and cope	1135	callbacks is well-written it can just attempt the operation and cope with
888	with the error from read() or write(). This will not work in multi-threaded	1136	the error from read() or write(). This will not work in multi-threaded
889	programs, though, so beware.	1137	programs, though, as the fd could already be closed and reused for another
		1138	thing, so beware.
890		1139
891	=back	1140	=back
892		1141
		1142	=head2 WATCHER STATES
		1143
		1144	There are various watcher states mentioned throughout this manual -
		1145	active, pending and so on. In this section these states and the rules to
		1146	transition between them will be described in more detail - and while these
		1147	rules might look complicated, they usually do "the right thing".
		1148
		1149	=over 4
		1150
		1151	=item initialiased
		1152
		1153	Before a watcher can be registered with the event looop it has to be
		1154	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1155	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1156
		1157	In this state it is simply some block of memory that is suitable for use
		1158	in an event loop. It can be moved around, freed, reused etc. at will.
		1159
		1160	=item started/running/active
		1161
		1162	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1163	property of the event loop, and is actively waiting for events. While in
		1164	this state it cannot be accessed (except in a few documented ways), moved,
		1165	freed or anything else - the only legal thing is to keep a pointer to it,
		1166	and call libev functions on it that are documented to work on active watchers.
		1167
		1168	=item pending
		1169
		1170	If a watcher is active and libev determines that an event it is interested
		1171	in has occurred (such as a timer expiring), it will become pending. It will
		1172	stay in this pending state until either it is stopped or its callback is
		1173	about to be invoked, so it is not normally pending inside the watcher
		1174	callback.
		1175
		1176	The watcher might or might not be active while it is pending (for example,
		1177	an expired non-repeating timer can be pending but no longer active). If it
		1178	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1179	but it is still property of the event loop at this time, so cannot be
		1180	moved, freed or reused. And if it is active the rules described in the
		1181	previous item still apply.
		1182
		1183	It is also possible to feed an event on a watcher that is not active (e.g.
		1184	via C<ev_feed_event>), in which case it becomes pending without being
		1185	active.
		1186
		1187	=item stopped
		1188
		1189	A watcher can be stopped implicitly by libev (in which case it might still
		1190	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1191	latter will clear any pending state the watcher might be in, regardless
		1192	of whether it was active or not, so stopping a watcher explicitly before
		1193	freeing it is often a good idea.
		1194
		1195	While stopped (and not pending) the watcher is essentially in the
		1196	initialised state, that is it can be reused, moved, modified in any way
		1197	you wish.
		1198
		1199	=back
		1200
893	=head2 GENERIC WATCHER FUNCTIONS	1201	=head2 GENERIC WATCHER FUNCTIONS
894
895	In the following description, C<TYPE> stands for the watcher type,
896	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
897		1202
898	=over 4	1203	=over 4
899		1204
900	=item C<ev_init> (ev_TYPE *watcher, callback)	1205	=item C<ev_init> (ev_TYPE *watcher, callback)
901		1206
…		…
907	which rolls both calls into one.	1212	which rolls both calls into one.
908		1213
909	You can reinitialise a watcher at any time as long as it has been stopped	1214	You can reinitialise a watcher at any time as long as it has been stopped
910	(or never started) and there are no pending events outstanding.	1215	(or never started) and there are no pending events outstanding.
911		1216
912	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1217	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
913	int revents)>.	1218	int revents)>.
914		1219
		1220	Example: Initialise an C<ev_io> watcher in two steps.
		1221
		1222	ev_io w;
		1223	ev_init (&w, my_cb);
		1224	ev_io_set (&w, STDIN_FILENO, EV_READ);
		1225
915	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1226	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
916		1227
917	This macro initialises the type-specific parts of a watcher. You need to	1228	This macro initialises the type-specific parts of a watcher. You need to
918	call C<ev_init> at least once before you call this macro, but you can	1229	call C<ev_init> at least once before you call this macro, but you can
919	call C<ev_TYPE_set> any number of times. You must not, however, call this	1230	call C<ev_TYPE_set> any number of times. You must not, however, call this
920	macro on a watcher that is active (it can be pending, however, which is a	1231	macro on a watcher that is active (it can be pending, however, which is a
921	difference to the C<ev_init> macro).	1232	difference to the C<ev_init> macro).
922		1233
923	Although some watcher types do not have type-specific arguments	1234	Although some watcher types do not have type-specific arguments
924	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	1235	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
925		1236
		1237	See C<ev_init>, above, for an example.
		1238
926	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1239	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
927		1240
928	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1241	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
929	calls into a single call. This is the most convenient method to initialise	1242	calls into a single call. This is the most convenient method to initialise
930	a watcher. The same limitations apply, of course.	1243	a watcher. The same limitations apply, of course.
931		1244
		1245	Example: Initialise and set an C<ev_io> watcher in one step.
		1246
		1247	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1248
932	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1249	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
933		1250
934	Starts (activates) the given watcher. Only active watchers will receive	1251	Starts (activates) the given watcher. Only active watchers will receive
935	events. If the watcher is already active nothing will happen.	1252	events. If the watcher is already active nothing will happen.
936		1253
		1254	Example: Start the C<ev_io> watcher that is being abused as example in this
		1255	whole section.
		1256
		1257	ev_io_start (EV_DEFAULT_UC, &w);
		1258
937	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1259	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
938		1260
939	Stops the given watcher again (if active) and clears the pending	1261	Stops the given watcher if active, and clears the pending status (whether
		1262	the watcher was active or not).
		1263
940	status. It is possible that stopped watchers are pending (for example,	1264	It is possible that stopped watchers are pending - for example,
941	non-repeating timers are being stopped when they become pending), but	1265	non-repeating timers are being stopped when they become pending - but
942	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1266	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
943	you want to free or reuse the memory used by the watcher it is therefore a	1267	pending. If you want to free or reuse the memory used by the watcher it is
944	good idea to always call its C<ev_TYPE_stop> function.	1268	therefore a good idea to always call its C<ev_TYPE_stop> function.
945		1269
946	=item bool ev_is_active (ev_TYPE *watcher)	1270	=item bool ev_is_active (ev_TYPE *watcher)
947		1271
948	Returns a true value iff the watcher is active (i.e. it has been started	1272	Returns a true value iff the watcher is active (i.e. it has been started
949	and not yet been stopped). As long as a watcher is active you must not modify	1273	and not yet been stopped). As long as a watcher is active you must not modify
…		…
965	=item ev_cb_set (ev_TYPE *watcher, callback)	1289	=item ev_cb_set (ev_TYPE *watcher, callback)
966		1290
967	Change the callback. You can change the callback at virtually any time	1291	Change the callback. You can change the callback at virtually any time
968	(modulo threads).	1292	(modulo threads).
969		1293
970	=item ev_set_priority (ev_TYPE *watcher, priority)	1294	=item ev_set_priority (ev_TYPE *watcher, int priority)
971		1295
972	=item int ev_priority (ev_TYPE *watcher)	1296	=item int ev_priority (ev_TYPE *watcher)
973		1297
974	Set and query the priority of the watcher. The priority is a small	1298	Set and query the priority of the watcher. The priority is a small
975	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1299	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
976	(default: C<-2>). Pending watchers with higher priority will be invoked	1300	(default: C<-2>). Pending watchers with higher priority will be invoked
977	before watchers with lower priority, but priority will not keep watchers	1301	before watchers with lower priority, but priority will not keep watchers
978	from being executed (except for C<ev_idle> watchers).	1302	from being executed (except for C<ev_idle> watchers).
979		1303
980	This means that priorities are I<only> used for ordering callback
981	invocation after new events have been received. This is useful, for
982	example, to reduce latency after idling, or more often, to bind two
983	watchers on the same event and make sure one is called first.
984
985	If you need to suppress invocation when higher priority events are pending	1304	If you need to suppress invocation when higher priority events are pending
986	you need to look at C<ev_idle> watchers, which provide this functionality.	1305	you need to look at C<ev_idle> watchers, which provide this functionality.
987		1306
988	You I<must not> change the priority of a watcher as long as it is active or	1307	You I<must not> change the priority of a watcher as long as it is active or
989	pending.	1308	pending.
990		1309
		1310	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1311	fine, as long as you do not mind that the priority value you query might
		1312	or might not have been clamped to the valid range.
		1313
991	The default priority used by watchers when no priority has been set is	1314	The default priority used by watchers when no priority has been set is
992	always C<0>, which is supposed to not be too high and not be too low :).	1315	always C<0>, which is supposed to not be too high and not be too low :).
993		1316
994	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1317	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
995	fine, as long as you do not mind that the priority value you query might	1318	priorities.
996	or might not have been adjusted to be within valid range.
997		1319
998	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1320	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
999		1321
1000	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1322	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1001	C<loop> nor C<revents> need to be valid as long as the watcher callback	1323	C<loop> nor C<revents> need to be valid as long as the watcher callback
1002	can deal with that fact.	1324	can deal with that fact, as both are simply passed through to the
		1325	callback.
1003		1326
1004	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1327	=item int ev_clear_pending (loop, ev_TYPE *watcher)
1005		1328
1006	If the watcher is pending, this function returns clears its pending status	1329	If the watcher is pending, this function clears its pending status and
1007	and returns its C<revents> bitset (as if its callback was invoked). If the	1330	returns its C<revents> bitset (as if its callback was invoked). If the
1008	watcher isn't pending it does nothing and returns C<0>.	1331	watcher isn't pending it does nothing and returns C<0>.
1009		1332
		1333	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1334	callback to be invoked, which can be accomplished with this function.
		1335
		1336	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1337
		1338	Feeds the given event set into the event loop, as if the specified event
		1339	had happened for the specified watcher (which must be a pointer to an
		1340	initialised but not necessarily started event watcher). Obviously you must
		1341	not free the watcher as long as it has pending events.
		1342
		1343	Stopping the watcher, letting libev invoke it, or calling
		1344	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1345	not started in the first place.
		1346
		1347	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1348	functions that do not need a watcher.
		1349
1010	=back	1350	=back
1011		1351
1012		1352
1013	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1353	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1014		1354
1015	Each watcher has, by default, a member C<void *data> that you can change	1355	Each watcher has, by default, a member C<void *data> that you can change
1016	and read at any time, libev will completely ignore it. This can be used	1356	and read at any time: libev will completely ignore it. This can be used
1017	to associate arbitrary data with your watcher. If you need more data and	1357	to associate arbitrary data with your watcher. If you need more data and
1018	don't want to allocate memory and store a pointer to it in that data	1358	don't want to allocate memory and store a pointer to it in that data
1019	member, you can also "subclass" the watcher type and provide your own	1359	member, you can also "subclass" the watcher type and provide your own
1020	data:	1360	data:
1021		1361
1022	struct my_io	1362	struct my_io
1023	{	1363	{
1024	struct ev_io io;	1364	ev_io io;
1025	int otherfd;	1365	int otherfd;
1026	void *somedata;	1366	void *somedata;
1027	struct whatever *mostinteresting;	1367	struct whatever *mostinteresting;
1028	};	1368	};
1029		1369
…		…
1032	ev_io_init (&w.io, my_cb, fd, EV_READ);	1372	ev_io_init (&w.io, my_cb, fd, EV_READ);
1033		1373
1034	And since your callback will be called with a pointer to the watcher, you	1374	And since your callback will be called with a pointer to the watcher, you
1035	can cast it back to your own type:	1375	can cast it back to your own type:
1036		1376
1037	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1377	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1038	{	1378	{
1039	struct my_io *w = (struct my_io *)w_;	1379	struct my_io *w = (struct my_io *)w_;
1040	...	1380	...
1041	}	1381	}
1042		1382
…		…
1053	ev_timer t2;	1393	ev_timer t2;
1054	}	1394	}
1055		1395
1056	In this case getting the pointer to C<my_biggy> is a bit more	1396	In this case getting the pointer to C<my_biggy> is a bit more
1057	complicated: Either you store the address of your C<my_biggy> struct	1397	complicated: Either you store the address of your C<my_biggy> struct
1058	in the C<data> member of the watcher, or you need to use some pointer	1398	in the C<data> member of the watcher (for woozies), or you need to use
1059	arithmetic using C<offsetof> inside your watchers:	1399	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1400	programmers):
1060		1401
1061	#include <stddef.h>	1402	#include <stddef.h>
1062		1403
1063	static void	1404	static void
1064	t1_cb (EV_P_ struct ev_timer *w, int revents)	1405	t1_cb (EV_P_ ev_timer *w, int revents)
1065	{	1406	{
1066	struct my_biggy big = (struct my_biggy *	1407	struct my_biggy big = (struct my_biggy *)
1067	(((char *)w) - offsetof (struct my_biggy, t1));	1408	(((char *)w) - offsetof (struct my_biggy, t1));
1068	}	1409	}
1069		1410
1070	static void	1411	static void
1071	t2_cb (EV_P_ struct ev_timer *w, int revents)	1412	t2_cb (EV_P_ ev_timer *w, int revents)
1072	{	1413	{
1073	struct my_biggy big = (struct my_biggy *	1414	struct my_biggy big = (struct my_biggy *)
1074	(((char *)w) - offsetof (struct my_biggy, t2));	1415	(((char *)w) - offsetof (struct my_biggy, t2));
1075	}	1416	}
		1417
		1418	=head2 WATCHER PRIORITY MODELS
		1419
		1420	Many event loops support I<watcher priorities>, which are usually small
		1421	integers that influence the ordering of event callback invocation
		1422	between watchers in some way, all else being equal.
		1423
		1424	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1425	description for the more technical details such as the actual priority
		1426	range.
		1427
		1428	There are two common ways how these these priorities are being interpreted
		1429	by event loops:
		1430
		1431	In the more common lock-out model, higher priorities "lock out" invocation
		1432	of lower priority watchers, which means as long as higher priority
		1433	watchers receive events, lower priority watchers are not being invoked.
		1434
		1435	The less common only-for-ordering model uses priorities solely to order
		1436	callback invocation within a single event loop iteration: Higher priority
		1437	watchers are invoked before lower priority ones, but they all get invoked
		1438	before polling for new events.
		1439
		1440	Libev uses the second (only-for-ordering) model for all its watchers
		1441	except for idle watchers (which use the lock-out model).
		1442
		1443	The rationale behind this is that implementing the lock-out model for
		1444	watchers is not well supported by most kernel interfaces, and most event
		1445	libraries will just poll for the same events again and again as long as
		1446	their callbacks have not been executed, which is very inefficient in the
		1447	common case of one high-priority watcher locking out a mass of lower
		1448	priority ones.
		1449
		1450	Static (ordering) priorities are most useful when you have two or more
		1451	watchers handling the same resource: a typical usage example is having an
		1452	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1453	timeouts. Under load, data might be received while the program handles
		1454	other jobs, but since timers normally get invoked first, the timeout
		1455	handler will be executed before checking for data. In that case, giving
		1456	the timer a lower priority than the I/O watcher ensures that I/O will be
		1457	handled first even under adverse conditions (which is usually, but not
		1458	always, what you want).
		1459
		1460	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1461	will only be executed when no same or higher priority watchers have
		1462	received events, they can be used to implement the "lock-out" model when
		1463	required.
		1464
		1465	For example, to emulate how many other event libraries handle priorities,
		1466	you can associate an C<ev_idle> watcher to each such watcher, and in
		1467	the normal watcher callback, you just start the idle watcher. The real
		1468	processing is done in the idle watcher callback. This causes libev to
		1469	continuously poll and process kernel event data for the watcher, but when
		1470	the lock-out case is known to be rare (which in turn is rare :), this is
		1471	workable.
		1472
		1473	Usually, however, the lock-out model implemented that way will perform
		1474	miserably under the type of load it was designed to handle. In that case,
		1475	it might be preferable to stop the real watcher before starting the
		1476	idle watcher, so the kernel will not have to process the event in case
		1477	the actual processing will be delayed for considerable time.
		1478
		1479	Here is an example of an I/O watcher that should run at a strictly lower
		1480	priority than the default, and which should only process data when no
		1481	other events are pending:
		1482
		1483	ev_idle idle; // actual processing watcher
		1484	ev_io io; // actual event watcher
		1485
		1486	static void
		1487	io_cb (EV_P_ ev_io *w, int revents)
		1488	{
		1489	// stop the I/O watcher, we received the event, but
		1490	// are not yet ready to handle it.
		1491	ev_io_stop (EV_A_ w);
		1492
		1493	// start the idle watcher to handle the actual event.
		1494	// it will not be executed as long as other watchers
		1495	// with the default priority are receiving events.
		1496	ev_idle_start (EV_A_ &idle);
		1497	}
		1498
		1499	static void
		1500	idle_cb (EV_P_ ev_idle *w, int revents)
		1501	{
		1502	// actual processing
		1503	read (STDIN_FILENO, ...);
		1504
		1505	// have to start the I/O watcher again, as
		1506	// we have handled the event
		1507	ev_io_start (EV_P_ &io);
		1508	}
		1509
		1510	// initialisation
		1511	ev_idle_init (&idle, idle_cb);
		1512	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1513	ev_io_start (EV_DEFAULT_ &io);
		1514
		1515	In the "real" world, it might also be beneficial to start a timer, so that
		1516	low-priority connections can not be locked out forever under load. This
		1517	enables your program to keep a lower latency for important connections
		1518	during short periods of high load, while not completely locking out less
		1519	important ones.
1076		1520
1077		1521
1078	=head1 WATCHER TYPES	1522	=head1 WATCHER TYPES
1079		1523
1080	This section describes each watcher in detail, but will not repeat	1524	This section describes each watcher in detail, but will not repeat
…		…
1104	In general you can register as many read and/or write event watchers per	1548	In general you can register as many read and/or write event watchers per
1105	fd as you want (as long as you don't confuse yourself). Setting all file	1549	fd as you want (as long as you don't confuse yourself). Setting all file
1106	descriptors to non-blocking mode is also usually a good idea (but not	1550	descriptors to non-blocking mode is also usually a good idea (but not
1107	required if you know what you are doing).	1551	required if you know what you are doing).
1108		1552
1109	If you must do this, then force the use of a known-to-be-good backend	1553	If you cannot use non-blocking mode, then force the use of a
1110	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1554	known-to-be-good backend (at the time of this writing, this includes only
1111	C<EVBACKEND_POLL>).	1555	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1556	descriptors for which non-blocking operation makes no sense (such as
		1557	files) - libev doesn't guarantee any specific behaviour in that case.
1112		1558
1113	Another thing you have to watch out for is that it is quite easy to	1559	Another thing you have to watch out for is that it is quite easy to
1114	receive "spurious" readiness notifications, that is your callback might	1560	receive "spurious" readiness notifications, that is your callback might
1115	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1561	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1116	because there is no data. Not only are some backends known to create a	1562	because there is no data. Not only are some backends known to create a
1117	lot of those (for example Solaris ports), it is very easy to get into	1563	lot of those (for example Solaris ports), it is very easy to get into
1118	this situation even with a relatively standard program structure. Thus	1564	this situation even with a relatively standard program structure. Thus
1119	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1565	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1120	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1566	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1121		1567
1122	If you cannot run the fd in non-blocking mode (for example you should not	1568	If you cannot run the fd in non-blocking mode (for example you should
1123	play around with an Xlib connection), then you have to separately re-test	1569	not play around with an Xlib connection), then you have to separately
1124	whether a file descriptor is really ready with a known-to-be good interface	1570	re-test whether a file descriptor is really ready with a known-to-be good
1125	such as poll (fortunately in our Xlib example, Xlib already does this on	1571	interface such as poll (fortunately in our Xlib example, Xlib already
1126	its own, so its quite safe to use).	1572	does this on its own, so its quite safe to use). Some people additionally
		1573	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1574	indefinitely.
		1575
		1576	But really, best use non-blocking mode.
1127		1577
1128	=head3 The special problem of disappearing file descriptors	1578	=head3 The special problem of disappearing file descriptors
1129		1579
1130	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1580	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1131	descriptor (either by calling C<close> explicitly or by any other means,	1581	descriptor (either due to calling C<close> explicitly or any other means,
1132	such as C<dup>). The reason is that you register interest in some file	1582	such as C<dup2>). The reason is that you register interest in some file
1133	descriptor, but when it goes away, the operating system will silently drop	1583	descriptor, but when it goes away, the operating system will silently drop
1134	this interest. If another file descriptor with the same number then is	1584	this interest. If another file descriptor with the same number then is
1135	registered with libev, there is no efficient way to see that this is, in	1585	registered with libev, there is no efficient way to see that this is, in
1136	fact, a different file descriptor.	1586	fact, a different file descriptor.
1137		1587
…		…
1168	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1618	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1169	C<EVBACKEND_POLL>.	1619	C<EVBACKEND_POLL>.
1170		1620
1171	=head3 The special problem of SIGPIPE	1621	=head3 The special problem of SIGPIPE
1172		1622
1173	While not really specific to libev, it is easy to forget about SIGPIPE:	1623	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1174	when writing to a pipe whose other end has been closed, your program gets	1624	when writing to a pipe whose other end has been closed, your program gets
1175	send a SIGPIPE, which, by default, aborts your program. For most programs	1625	sent a SIGPIPE, which, by default, aborts your program. For most programs
1176	this is sensible behaviour, for daemons, this is usually undesirable.	1626	this is sensible behaviour, for daemons, this is usually undesirable.
1177		1627
1178	So when you encounter spurious, unexplained daemon exits, make sure you	1628	So when you encounter spurious, unexplained daemon exits, make sure you
1179	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1629	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1180	somewhere, as that would have given you a big clue).	1630	somewhere, as that would have given you a big clue).
1181		1631
		1632	=head3 The special problem of accept()ing when you can't
		1633
		1634	Many implementations of the POSIX C<accept> function (for example,
		1635	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1636	connection from the pending queue in all error cases.
		1637
		1638	For example, larger servers often run out of file descriptors (because
		1639	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1640	rejecting the connection, leading to libev signalling readiness on
		1641	the next iteration again (the connection still exists after all), and
		1642	typically causing the program to loop at 100% CPU usage.
		1643
		1644	Unfortunately, the set of errors that cause this issue differs between
		1645	operating systems, there is usually little the app can do to remedy the
		1646	situation, and no known thread-safe method of removing the connection to
		1647	cope with overload is known (to me).
		1648
		1649	One of the easiest ways to handle this situation is to just ignore it
		1650	- when the program encounters an overload, it will just loop until the
		1651	situation is over. While this is a form of busy waiting, no OS offers an
		1652	event-based way to handle this situation, so it's the best one can do.
		1653
		1654	A better way to handle the situation is to log any errors other than
		1655	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1656	messages, and continue as usual, which at least gives the user an idea of
		1657	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1658	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1659	usage.
		1660
		1661	If your program is single-threaded, then you could also keep a dummy file
		1662	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1663	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1664	close that fd, and create a new dummy fd. This will gracefully refuse
		1665	clients under typical overload conditions.
		1666
		1667	The last way to handle it is to simply log the error and C<exit>, as
		1668	is often done with C<malloc> failures, but this results in an easy
		1669	opportunity for a DoS attack.
1182		1670
1183	=head3 Watcher-Specific Functions	1671	=head3 Watcher-Specific Functions
1184		1672
1185	=over 4	1673	=over 4
1186		1674
1187	=item ev_io_init (ev_io *, callback, int fd, int events)	1675	=item ev_io_init (ev_io *, callback, int fd, int events)
1188		1676
1189	=item ev_io_set (ev_io *, int fd, int events)	1677	=item ev_io_set (ev_io *, int fd, int events)
1190		1678
1191	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1679	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1192	receive events for and events is either C<EV_READ>, C<EV_WRITE> or	1680	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1193	C<EV_READ | EV_WRITE> to receive the given events.	1681	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1194		1682
1195	=item int fd [read-only]	1683	=item int fd [read-only]
1196		1684
1197	The file descriptor being watched.	1685	The file descriptor being watched.
1198		1686
…		…
1207	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1695	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1208	readable, but only once. Since it is likely line-buffered, you could	1696	readable, but only once. Since it is likely line-buffered, you could
1209	attempt to read a whole line in the callback.	1697	attempt to read a whole line in the callback.
1210		1698
1211	static void	1699	static void
1212	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1700	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1213	{	1701	{
1214	ev_io_stop (loop, w);	1702	ev_io_stop (loop, w);
1215	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1703	.. read from stdin here (or from w->fd) and handle any I/O errors
1216	}	1704	}
1217		1705
1218	...	1706	...
1219	struct ev_loop *loop = ev_default_init (0);	1707	struct ev_loop *loop = ev_default_init (0);
1220	struct ev_io stdin_readable;	1708	ev_io stdin_readable;
1221	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1709	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1222	ev_io_start (loop, &stdin_readable);	1710	ev_io_start (loop, &stdin_readable);
1223	ev_loop (loop, 0);	1711	ev_run (loop, 0);
1224		1712
1225		1713
1226	=head2 C<ev_timer> - relative and optionally repeating timeouts	1714	=head2 C<ev_timer> - relative and optionally repeating timeouts
1227		1715
1228	Timer watchers are simple relative timers that generate an event after a	1716	Timer watchers are simple relative timers that generate an event after a
1229	given time, and optionally repeating in regular intervals after that.	1717	given time, and optionally repeating in regular intervals after that.
1230		1718
1231	The timers are based on real time, that is, if you register an event that	1719	The timers are based on real time, that is, if you register an event that
1232	times out after an hour and you reset your system clock to January last	1720	times out after an hour and you reset your system clock to January last
1233	year, it will still time out after (roughly) and hour. "Roughly" because	1721	year, it will still time out after (roughly) one hour. "Roughly" because
1234	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1722	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1235	monotonic clock option helps a lot here).	1723	monotonic clock option helps a lot here).
1236		1724
1237	The callback is guaranteed to be invoked only after its timeout has passed,	1725	The callback is guaranteed to be invoked only I<after> its timeout has
1238	but if multiple timers become ready during the same loop iteration then	1726	passed (not I<at>, so on systems with very low-resolution clocks this
1239	order of execution is undefined.	1727	might introduce a small delay). If multiple timers become ready during the
		1728	same loop iteration then the ones with earlier time-out values are invoked
		1729	before ones of the same priority with later time-out values (but this is
		1730	no longer true when a callback calls C<ev_run> recursively).
		1731
		1732	=head3 Be smart about timeouts
		1733
		1734	Many real-world problems involve some kind of timeout, usually for error
		1735	recovery. A typical example is an HTTP request - if the other side hangs,
		1736	you want to raise some error after a while.
		1737
		1738	What follows are some ways to handle this problem, from obvious and
		1739	inefficient to smart and efficient.
		1740
		1741	In the following, a 60 second activity timeout is assumed - a timeout that
		1742	gets reset to 60 seconds each time there is activity (e.g. each time some
		1743	data or other life sign was received).
		1744
		1745	=over 4
		1746
		1747	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1748
		1749	This is the most obvious, but not the most simple way: In the beginning,
		1750	start the watcher:
		1751
		1752	ev_timer_init (timer, callback, 60., 0.);
		1753	ev_timer_start (loop, timer);
		1754
		1755	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1756	and start it again:
		1757
		1758	ev_timer_stop (loop, timer);
		1759	ev_timer_set (timer, 60., 0.);
		1760	ev_timer_start (loop, timer);
		1761
		1762	This is relatively simple to implement, but means that each time there is
		1763	some activity, libev will first have to remove the timer from its internal
		1764	data structure and then add it again. Libev tries to be fast, but it's
		1765	still not a constant-time operation.
		1766
		1767	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1768
		1769	This is the easiest way, and involves using C<ev_timer_again> instead of
		1770	C<ev_timer_start>.
		1771
		1772	To implement this, configure an C<ev_timer> with a C<repeat> value
		1773	of C<60> and then call C<ev_timer_again> at start and each time you
		1774	successfully read or write some data. If you go into an idle state where
		1775	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1776	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1777
		1778	That means you can ignore both the C<ev_timer_start> function and the
		1779	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1780	member and C<ev_timer_again>.
		1781
		1782	At start:
		1783
		1784	ev_init (timer, callback);
		1785	timer->repeat = 60.;
		1786	ev_timer_again (loop, timer);
		1787
		1788	Each time there is some activity:
		1789
		1790	ev_timer_again (loop, timer);
		1791
		1792	It is even possible to change the time-out on the fly, regardless of
		1793	whether the watcher is active or not:
		1794
		1795	timer->repeat = 30.;
		1796	ev_timer_again (loop, timer);
		1797
		1798	This is slightly more efficient then stopping/starting the timer each time
		1799	you want to modify its timeout value, as libev does not have to completely
		1800	remove and re-insert the timer from/into its internal data structure.
		1801
		1802	It is, however, even simpler than the "obvious" way to do it.
		1803
		1804	=item 3. Let the timer time out, but then re-arm it as required.
		1805
		1806	This method is more tricky, but usually most efficient: Most timeouts are
		1807	relatively long compared to the intervals between other activity - in
		1808	our example, within 60 seconds, there are usually many I/O events with
		1809	associated activity resets.
		1810
		1811	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1812	but remember the time of last activity, and check for a real timeout only
		1813	within the callback:
		1814
		1815	ev_tstamp last_activity; // time of last activity
		1816
		1817	static void
		1818	callback (EV_P_ ev_timer *w, int revents)
		1819	{
		1820	ev_tstamp now = ev_now (EV_A);
		1821	ev_tstamp timeout = last_activity + 60.;
		1822
		1823	// if last_activity + 60. is older than now, we did time out
		1824	if (timeout < now)
		1825	{
		1826	// timeout occurred, take action
		1827	}
		1828	else
		1829	{
		1830	// callback was invoked, but there was some activity, re-arm
		1831	// the watcher to fire in last_activity + 60, which is
		1832	// guaranteed to be in the future, so "again" is positive:
		1833	w->repeat = timeout - now;
		1834	ev_timer_again (EV_A_ w);
		1835	}
		1836	}
		1837
		1838	To summarise the callback: first calculate the real timeout (defined
		1839	as "60 seconds after the last activity"), then check if that time has
		1840	been reached, which means something I<did>, in fact, time out. Otherwise
		1841	the callback was invoked too early (C<timeout> is in the future), so
		1842	re-schedule the timer to fire at that future time, to see if maybe we have
		1843	a timeout then.
		1844
		1845	Note how C<ev_timer_again> is used, taking advantage of the
		1846	C<ev_timer_again> optimisation when the timer is already running.
		1847
		1848	This scheme causes more callback invocations (about one every 60 seconds
		1849	minus half the average time between activity), but virtually no calls to
		1850	libev to change the timeout.
		1851
		1852	To start the timer, simply initialise the watcher and set C<last_activity>
		1853	to the current time (meaning we just have some activity :), then call the
		1854	callback, which will "do the right thing" and start the timer:
		1855
		1856	ev_init (timer, callback);
		1857	last_activity = ev_now (loop);
		1858	callback (loop, timer, EV_TIMER);
		1859
		1860	And when there is some activity, simply store the current time in
		1861	C<last_activity>, no libev calls at all:
		1862
		1863	last_activity = ev_now (loop);
		1864
		1865	This technique is slightly more complex, but in most cases where the
		1866	time-out is unlikely to be triggered, much more efficient.
		1867
		1868	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1869	callback :) - just change the timeout and invoke the callback, which will
		1870	fix things for you.
		1871
		1872	=item 4. Wee, just use a double-linked list for your timeouts.
		1873
		1874	If there is not one request, but many thousands (millions...), all
		1875	employing some kind of timeout with the same timeout value, then one can
		1876	do even better:
		1877
		1878	When starting the timeout, calculate the timeout value and put the timeout
		1879	at the I<end> of the list.
		1880
		1881	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1882	the list is expected to fire (for example, using the technique #3).
		1883
		1884	When there is some activity, remove the timer from the list, recalculate
		1885	the timeout, append it to the end of the list again, and make sure to
		1886	update the C<ev_timer> if it was taken from the beginning of the list.
		1887
		1888	This way, one can manage an unlimited number of timeouts in O(1) time for
		1889	starting, stopping and updating the timers, at the expense of a major
		1890	complication, and having to use a constant timeout. The constant timeout
		1891	ensures that the list stays sorted.
		1892
		1893	=back
		1894
		1895	So which method the best?
		1896
		1897	Method #2 is a simple no-brain-required solution that is adequate in most
		1898	situations. Method #3 requires a bit more thinking, but handles many cases
		1899	better, and isn't very complicated either. In most case, choosing either
		1900	one is fine, with #3 being better in typical situations.
		1901
		1902	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1903	rather complicated, but extremely efficient, something that really pays
		1904	off after the first million or so of active timers, i.e. it's usually
		1905	overkill :)
1240		1906
1241	=head3 The special problem of time updates	1907	=head3 The special problem of time updates
1242		1908
1243	Establishing the current time is a costly operation (it usually takes at	1909	Establishing the current time is a costly operation (it usually takes at
1244	least two system calls): EV therefore updates its idea of the current	1910	least two system calls): EV therefore updates its idea of the current
1245	time only before and after C<ev_loop> polls for new events, which causes	1911	time only before and after C<ev_run> collects new events, which causes a
1246	a growing difference between C<ev_now ()> and C<ev_time ()> when handling	1912	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1247	lots of events.	1913	lots of events in one iteration.
1248		1914
1249	The relative timeouts are calculated relative to the C<ev_now ()>	1915	The relative timeouts are calculated relative to the C<ev_now ()>
1250	time. This is usually the right thing as this timestamp refers to the time	1916	time. This is usually the right thing as this timestamp refers to the time
1251	of the event triggering whatever timeout you are modifying/starting. If	1917	of the event triggering whatever timeout you are modifying/starting. If
1252	you suspect event processing to be delayed and you I<need> to base the	1918	you suspect event processing to be delayed and you I<need> to base the
…		…
1256		1922
1257	If the event loop is suspended for a long time, you can also force an	1923	If the event loop is suspended for a long time, you can also force an
1258	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1924	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1259	()>.	1925	()>.
1260		1926
		1927	=head3 The special problems of suspended animation
		1928
		1929	When you leave the server world it is quite customary to hit machines that
		1930	can suspend/hibernate - what happens to the clocks during such a suspend?
		1931
		1932	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1933	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1934	to run until the system is suspended, but they will not advance while the
		1935	system is suspended. That means, on resume, it will be as if the program
		1936	was frozen for a few seconds, but the suspend time will not be counted
		1937	towards C<ev_timer> when a monotonic clock source is used. The real time
		1938	clock advanced as expected, but if it is used as sole clocksource, then a
		1939	long suspend would be detected as a time jump by libev, and timers would
		1940	be adjusted accordingly.
		1941
		1942	I would not be surprised to see different behaviour in different between
		1943	operating systems, OS versions or even different hardware.
		1944
		1945	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1946	time jump in the monotonic clocks and the realtime clock. If the program
		1947	is suspended for a very long time, and monotonic clock sources are in use,
		1948	then you can expect C<ev_timer>s to expire as the full suspension time
		1949	will be counted towards the timers. When no monotonic clock source is in
		1950	use, then libev will again assume a timejump and adjust accordingly.
		1951
		1952	It might be beneficial for this latter case to call C<ev_suspend>
		1953	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1954	deterministic behaviour in this case (you can do nothing against
		1955	C<SIGSTOP>).
		1956
1261	=head3 Watcher-Specific Functions and Data Members	1957	=head3 Watcher-Specific Functions and Data Members
1262		1958
1263	=over 4	1959	=over 4
1264		1960
1265	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1961	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1288	If the timer is started but non-repeating, stop it (as if it timed out).	1984	If the timer is started but non-repeating, stop it (as if it timed out).
1289		1985
1290	If the timer is repeating, either start it if necessary (with the	1986	If the timer is repeating, either start it if necessary (with the
1291	C<repeat> value), or reset the running timer to the C<repeat> value.	1987	C<repeat> value), or reset the running timer to the C<repeat> value.
1292		1988
1293	This sounds a bit complicated, but here is a useful and typical	1989	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1294	example: Imagine you have a TCP connection and you want a so-called idle	1990	usage example.
1295	timeout, that is, you want to be called when there have been, say, 60
1296	seconds of inactivity on the socket. The easiest way to do this is to
1297	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1298	C<ev_timer_again> each time you successfully read or write some data. If
1299	you go into an idle state where you do not expect data to travel on the
1300	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1301	automatically restart it if need be.
1302		1991
1303	That means you can ignore the C<after> value and C<ev_timer_start>	1992	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1304	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1305		1993
1306	ev_timer_init (timer, callback, 0., 5.);	1994	Returns the remaining time until a timer fires. If the timer is active,
1307	ev_timer_again (loop, timer);	1995	then this time is relative to the current event loop time, otherwise it's
1308	...	1996	the timeout value currently configured.
1309	timer->again = 17.;
1310	ev_timer_again (loop, timer);
1311	...
1312	timer->again = 10.;
1313	ev_timer_again (loop, timer);
1314		1997
1315	This is more slightly efficient then stopping/starting the timer each time	1998	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1316	you want to modify its timeout value.	1999	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2000	will return C<4>. When the timer expires and is restarted, it will return
		2001	roughly C<7> (likely slightly less as callback invocation takes some time,
		2002	too), and so on.
1317		2003
1318	=item ev_tstamp repeat [read-write]	2004	=item ev_tstamp repeat [read-write]
1319		2005
1320	The current C<repeat> value. Will be used each time the watcher times out	2006	The current C<repeat> value. Will be used each time the watcher times out
1321	or C<ev_timer_again> is called and determines the next timeout (if any),	2007	or C<ev_timer_again> is called, and determines the next timeout (if any),
1322	which is also when any modifications are taken into account.	2008	which is also when any modifications are taken into account.
1323		2009
1324	=back	2010	=back
1325		2011
1326	=head3 Examples	2012	=head3 Examples
1327		2013
1328	Example: Create a timer that fires after 60 seconds.	2014	Example: Create a timer that fires after 60 seconds.
1329		2015
1330	static void	2016	static void
1331	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2017	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1332	{	2018	{
1333	.. one minute over, w is actually stopped right here	2019	.. one minute over, w is actually stopped right here
1334	}	2020	}
1335		2021
1336	struct ev_timer mytimer;	2022	ev_timer mytimer;
1337	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	2023	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1338	ev_timer_start (loop, &mytimer);	2024	ev_timer_start (loop, &mytimer);
1339		2025
1340	Example: Create a timeout timer that times out after 10 seconds of	2026	Example: Create a timeout timer that times out after 10 seconds of
1341	inactivity.	2027	inactivity.
1342		2028
1343	static void	2029	static void
1344	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2030	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1345	{	2031	{
1346	.. ten seconds without any activity	2032	.. ten seconds without any activity
1347	}	2033	}
1348		2034
1349	struct ev_timer mytimer;	2035	ev_timer mytimer;
1350	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2036	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1351	ev_timer_again (&mytimer); /* start timer */	2037	ev_timer_again (&mytimer); /* start timer */
1352	ev_loop (loop, 0);	2038	ev_run (loop, 0);
1353		2039
1354	// and in some piece of code that gets executed on any "activity":	2040	// and in some piece of code that gets executed on any "activity":
1355	// reset the timeout to start ticking again at 10 seconds	2041	// reset the timeout to start ticking again at 10 seconds
1356	ev_timer_again (&mytimer);	2042	ev_timer_again (&mytimer);
1357		2043
…		…
1359	=head2 C<ev_periodic> - to cron or not to cron?	2045	=head2 C<ev_periodic> - to cron or not to cron?
1360		2046
1361	Periodic watchers are also timers of a kind, but they are very versatile	2047	Periodic watchers are also timers of a kind, but they are very versatile
1362	(and unfortunately a bit complex).	2048	(and unfortunately a bit complex).
1363		2049
1364	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2050	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1365	but on wall clock time (absolute time). You can tell a periodic watcher	2051	relative time, the physical time that passes) but on wall clock time
1366	to trigger after some specific point in time. For example, if you tell a	2052	(absolute time, the thing you can read on your calender or clock). The
1367	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	2053	difference is that wall clock time can run faster or slower than real
1368	+ 10.>, that is, an absolute time not a delay) and then reset your system	2054	time, and time jumps are not uncommon (e.g. when you adjust your
1369	clock to January of the previous year, then it will take more than year	2055	wrist-watch).
1370	to trigger the event (unlike an C<ev_timer>, which would still trigger
1371	roughly 10 seconds later as it uses a relative timeout).
1372		2056
		2057	You can tell a periodic watcher to trigger after some specific point
		2058	in time: for example, if you tell a periodic watcher to trigger "in 10
		2059	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2060	not a delay) and then reset your system clock to January of the previous
		2061	year, then it will take a year or more to trigger the event (unlike an
		2062	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2063	it, as it uses a relative timeout).
		2064
1373	C<ev_periodic>s can also be used to implement vastly more complex timers,	2065	C<ev_periodic> watchers can also be used to implement vastly more complex
1374	such as triggering an event on each "midnight, local time", or other	2066	timers, such as triggering an event on each "midnight, local time", or
1375	complicated, rules.	2067	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2068	those cannot react to time jumps.
1376		2069
1377	As with timers, the callback is guaranteed to be invoked only when the	2070	As with timers, the callback is guaranteed to be invoked only when the
1378	time (C<at>) has passed, but if multiple periodic timers become ready	2071	point in time where it is supposed to trigger has passed. If multiple
1379	during the same loop iteration then order of execution is undefined.	2072	timers become ready during the same loop iteration then the ones with
		2073	earlier time-out values are invoked before ones with later time-out values
		2074	(but this is no longer true when a callback calls C<ev_run> recursively).
1380		2075
1381	=head3 Watcher-Specific Functions and Data Members	2076	=head3 Watcher-Specific Functions and Data Members
1382		2077
1383	=over 4	2078	=over 4
1384		2079
1385	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2080	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1386		2081
1387	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2082	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1388		2083
1389	Lots of arguments, lets sort it out... There are basically three modes of	2084	Lots of arguments, let's sort it out... There are basically three modes of
1390	operation, and we will explain them from simplest to complex:	2085	operation, and we will explain them from simplest to most complex:
1391		2086
1392	=over 4	2087	=over 4
1393		2088
1394	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2089	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1395		2090
1396	In this configuration the watcher triggers an event after the wall clock	2091	In this configuration the watcher triggers an event after the wall clock
1397	time C<at> has passed and doesn't repeat. It will not adjust when a time	2092	time C<offset> has passed. It will not repeat and will not adjust when a
1398	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2093	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1399	run when the system time reaches or surpasses this time.	2094	will be stopped and invoked when the system clock reaches or surpasses
		2095	this point in time.
1400		2096
1401	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2097	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1402		2098
1403	In this mode the watcher will always be scheduled to time out at the next	2099	In this mode the watcher will always be scheduled to time out at the next
1404	C<at + N * interval> time (for some integer N, which can also be negative)	2100	C<offset + N * interval> time (for some integer N, which can also be
1405	and then repeat, regardless of any time jumps.	2101	negative) and then repeat, regardless of any time jumps. The C<offset>
		2102	argument is merely an offset into the C<interval> periods.
1406		2103
1407	This can be used to create timers that do not drift with respect to system	2104	This can be used to create timers that do not drift with respect to the
1408	time, for example, here is a C<ev_periodic> that triggers each hour, on	2105	system clock, for example, here is an C<ev_periodic> that triggers each
1409	the hour:	2106	hour, on the hour (with respect to UTC):
1410		2107
1411	ev_periodic_set (&periodic, 0., 3600., 0);	2108	ev_periodic_set (&periodic, 0., 3600., 0);
1412		2109
1413	This doesn't mean there will always be 3600 seconds in between triggers,	2110	This doesn't mean there will always be 3600 seconds in between triggers,
1414	but only that the callback will be called when the system time shows a	2111	but only that the callback will be called when the system time shows a
1415	full hour (UTC), or more correctly, when the system time is evenly divisible	2112	full hour (UTC), or more correctly, when the system time is evenly divisible
1416	by 3600.	2113	by 3600.
1417		2114
1418	Another way to think about it (for the mathematically inclined) is that	2115	Another way to think about it (for the mathematically inclined) is that
1419	C<ev_periodic> will try to run the callback in this mode at the next possible	2116	C<ev_periodic> will try to run the callback in this mode at the next possible
1420	time where C<time = at (mod interval)>, regardless of any time jumps.	2117	time where C<time = offset (mod interval)>, regardless of any time jumps.
1421		2118
1422	For numerical stability it is preferable that the C<at> value is near	2119	For numerical stability it is preferable that the C<offset> value is near
1423	C<ev_now ()> (the current time), but there is no range requirement for	2120	C<ev_now ()> (the current time), but there is no range requirement for
1424	this value, and in fact is often specified as zero.	2121	this value, and in fact is often specified as zero.
1425		2122
1426	Note also that there is an upper limit to how often a timer can fire (CPU	2123	Note also that there is an upper limit to how often a timer can fire (CPU
1427	speed for example), so if C<interval> is very small then timing stability	2124	speed for example), so if C<interval> is very small then timing stability
1428	will of course deteriorate. Libev itself tries to be exact to be about one	2125	will of course deteriorate. Libev itself tries to be exact to be about one
1429	millisecond (if the OS supports it and the machine is fast enough).	2126	millisecond (if the OS supports it and the machine is fast enough).
1430		2127
1431	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2128	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1432		2129
1433	In this mode the values for C<interval> and C<at> are both being	2130	In this mode the values for C<interval> and C<offset> are both being
1434	ignored. Instead, each time the periodic watcher gets scheduled, the	2131	ignored. Instead, each time the periodic watcher gets scheduled, the
1435	reschedule callback will be called with the watcher as first, and the	2132	reschedule callback will be called with the watcher as first, and the
1436	current time as second argument.	2133	current time as second argument.
1437		2134
1438	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2135	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1439	ever, or make ANY event loop modifications whatsoever>.	2136	or make ANY other event loop modifications whatsoever, unless explicitly
		2137	allowed by documentation here>.
1440		2138
1441	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2139	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1442	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2140	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1443	only event loop modification you are allowed to do).	2141	only event loop modification you are allowed to do).
1444		2142
1445	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	2143	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1446	*w, ev_tstamp now)>, e.g.:	2144	*w, ev_tstamp now)>, e.g.:
1447		2145
		2146	static ev_tstamp
1448	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	2147	my_rescheduler (ev_periodic *w, ev_tstamp now)
1449	{	2148	{
1450	return now + 60.;	2149	return now + 60.;
1451	}	2150	}
1452		2151
1453	It must return the next time to trigger, based on the passed time value	2152	It must return the next time to trigger, based on the passed time value
…		…
1473	a different time than the last time it was called (e.g. in a crond like	2172	a different time than the last time it was called (e.g. in a crond like
1474	program when the crontabs have changed).	2173	program when the crontabs have changed).
1475		2174
1476	=item ev_tstamp ev_periodic_at (ev_periodic *)	2175	=item ev_tstamp ev_periodic_at (ev_periodic *)
1477		2176
1478	When active, returns the absolute time that the watcher is supposed to	2177	When active, returns the absolute time that the watcher is supposed
1479	trigger next.	2178	to trigger next. This is not the same as the C<offset> argument to
		2179	C<ev_periodic_set>, but indeed works even in interval and manual
		2180	rescheduling modes.
1480		2181
1481	=item ev_tstamp offset [read-write]	2182	=item ev_tstamp offset [read-write]
1482		2183
1483	When repeating, this contains the offset value, otherwise this is the	2184	When repeating, this contains the offset value, otherwise this is the
1484	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2185	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2186	although libev might modify this value for better numerical stability).
1485		2187
1486	Can be modified any time, but changes only take effect when the periodic	2188	Can be modified any time, but changes only take effect when the periodic
1487	timer fires or C<ev_periodic_again> is being called.	2189	timer fires or C<ev_periodic_again> is being called.
1488		2190
1489	=item ev_tstamp interval [read-write]	2191	=item ev_tstamp interval [read-write]
1490		2192
1491	The current interval value. Can be modified any time, but changes only	2193	The current interval value. Can be modified any time, but changes only
1492	take effect when the periodic timer fires or C<ev_periodic_again> is being	2194	take effect when the periodic timer fires or C<ev_periodic_again> is being
1493	called.	2195	called.
1494		2196
1495	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2197	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1496		2198
1497	The current reschedule callback, or C<0>, if this functionality is	2199	The current reschedule callback, or C<0>, if this functionality is
1498	switched off. Can be changed any time, but changes only take effect when	2200	switched off. Can be changed any time, but changes only take effect when
1499	the periodic timer fires or C<ev_periodic_again> is being called.	2201	the periodic timer fires or C<ev_periodic_again> is being called.
1500		2202
1501	=back	2203	=back
1502		2204
1503	=head3 Examples	2205	=head3 Examples
1504		2206
1505	Example: Call a callback every hour, or, more precisely, whenever the	2207	Example: Call a callback every hour, or, more precisely, whenever the
1506	system clock is divisible by 3600. The callback invocation times have	2208	system time is divisible by 3600. The callback invocation times have
1507	potentially a lot of jitter, but good long-term stability.	2209	potentially a lot of jitter, but good long-term stability.
1508		2210
1509	static void	2211	static void
1510	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2212	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1511	{	2213	{
1512	... its now a full hour (UTC, or TAI or whatever your clock follows)	2214	... its now a full hour (UTC, or TAI or whatever your clock follows)
1513	}	2215	}
1514		2216
1515	struct ev_periodic hourly_tick;	2217	ev_periodic hourly_tick;
1516	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2218	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1517	ev_periodic_start (loop, &hourly_tick);	2219	ev_periodic_start (loop, &hourly_tick);
1518		2220
1519	Example: The same as above, but use a reschedule callback to do it:	2221	Example: The same as above, but use a reschedule callback to do it:
1520		2222
1521	#include <math.h>	2223	#include <math.h>
1522		2224
1523	static ev_tstamp	2225	static ev_tstamp
1524	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2226	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1525	{	2227	{
1526	return fmod (now, 3600.) + 3600.;	2228	return now + (3600. - fmod (now, 3600.));
1527	}	2229	}
1528		2230
1529	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2231	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1530		2232
1531	Example: Call a callback every hour, starting now:	2233	Example: Call a callback every hour, starting now:
1532		2234
1533	struct ev_periodic hourly_tick;	2235	ev_periodic hourly_tick;
1534	ev_periodic_init (&hourly_tick, clock_cb,	2236	ev_periodic_init (&hourly_tick, clock_cb,
1535	fmod (ev_now (loop), 3600.), 3600., 0);	2237	fmod (ev_now (loop), 3600.), 3600., 0);
1536	ev_periodic_start (loop, &hourly_tick);	2238	ev_periodic_start (loop, &hourly_tick);
1537		2239
1538		2240
…		…
1541	Signal watchers will trigger an event when the process receives a specific	2243	Signal watchers will trigger an event when the process receives a specific
1542	signal one or more times. Even though signals are very asynchronous, libev	2244	signal one or more times. Even though signals are very asynchronous, libev
1543	will try it's best to deliver signals synchronously, i.e. as part of the	2245	will try it's best to deliver signals synchronously, i.e. as part of the
1544	normal event processing, like any other event.	2246	normal event processing, like any other event.
1545		2247
		2248	If you want signals to be delivered truly asynchronously, just use
		2249	C<sigaction> as you would do without libev and forget about sharing
		2250	the signal. You can even use C<ev_async> from a signal handler to
		2251	synchronously wake up an event loop.
		2252
1546	You can configure as many watchers as you like per signal. Only when the	2253	You can configure as many watchers as you like for the same signal, but
		2254	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2255	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2256	C<SIGINT> in both the default loop and another loop at the same time. At
		2257	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2258
1547	first watcher gets started will libev actually register a signal watcher	2259	When the first watcher gets started will libev actually register something
1548	with the kernel (thus it coexists with your own signal handlers as long	2260	with the kernel (thus it coexists with your own signal handlers as long as
1549	as you don't register any with libev). Similarly, when the last signal	2261	you don't register any with libev for the same signal).
1550	watcher for a signal is stopped libev will reset the signal handler to
1551	SIG_DFL (regardless of what it was set to before).
1552		2262
1553	If possible and supported, libev will install its handlers with	2263	If possible and supported, libev will install its handlers with
1554	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2264	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1555	interrupted. If you have a problem with system calls getting interrupted by	2265	not be unduly interrupted. If you have a problem with system calls getting
1556	signals you can block all signals in an C<ev_check> watcher and unblock	2266	interrupted by signals you can block all signals in an C<ev_check> watcher
1557	them in an C<ev_prepare> watcher.	2267	and unblock them in an C<ev_prepare> watcher.
		2268
		2269	=head3 The special problem of inheritance over fork/execve/pthread_create
		2270
		2271	Both the signal mask (C<sigprocmask>) and the signal disposition
		2272	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2273	stopping it again), that is, libev might or might not block the signal,
		2274	and might or might not set or restore the installed signal handler.
		2275
		2276	While this does not matter for the signal disposition (libev never
		2277	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2278	C<execve>), this matters for the signal mask: many programs do not expect
		2279	certain signals to be blocked.
		2280
		2281	This means that before calling C<exec> (from the child) you should reset
		2282	the signal mask to whatever "default" you expect (all clear is a good
		2283	choice usually).
		2284
		2285	The simplest way to ensure that the signal mask is reset in the child is
		2286	to install a fork handler with C<pthread_atfork> that resets it. That will
		2287	catch fork calls done by libraries (such as the libc) as well.
		2288
		2289	In current versions of libev, the signal will not be blocked indefinitely
		2290	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2291	the window of opportunity for problems, it will not go away, as libev
		2292	I<has> to modify the signal mask, at least temporarily.
		2293
		2294	So I can't stress this enough: I<If you do not reset your signal mask when
		2295	you expect it to be empty, you have a race condition in your code>. This
		2296	is not a libev-specific thing, this is true for most event libraries.
1558		2297
1559	=head3 Watcher-Specific Functions and Data Members	2298	=head3 Watcher-Specific Functions and Data Members
1560		2299
1561	=over 4	2300	=over 4
1562		2301
…		…
1573		2312
1574	=back	2313	=back
1575		2314
1576	=head3 Examples	2315	=head3 Examples
1577		2316
1578	Example: Try to exit cleanly on SIGINT and SIGTERM.	2317	Example: Try to exit cleanly on SIGINT.
1579		2318
1580	static void	2319	static void
1581	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2320	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1582	{	2321	{
1583	ev_unloop (loop, EVUNLOOP_ALL);	2322	ev_break (loop, EVBREAK_ALL);
1584	}	2323	}
1585		2324
1586	struct ev_signal signal_watcher;	2325	ev_signal signal_watcher;
1587	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2326	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1588	ev_signal_start (loop, &sigint_cb);	2327	ev_signal_start (loop, &signal_watcher);
1589		2328
1590		2329
1591	=head2 C<ev_child> - watch out for process status changes	2330	=head2 C<ev_child> - watch out for process status changes
1592		2331
1593	Child watchers trigger when your process receives a SIGCHLD in response to	2332	Child watchers trigger when your process receives a SIGCHLD in response to
1594	some child status changes (most typically when a child of yours dies). It	2333	some child status changes (most typically when a child of yours dies or
1595	is permissible to install a child watcher I<after> the child has been	2334	exits). It is permissible to install a child watcher I<after> the child
1596	forked (which implies it might have already exited), as long as the event	2335	has been forked (which implies it might have already exited), as long
1597	loop isn't entered (or is continued from a watcher).	2336	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2337	forking and then immediately registering a watcher for the child is fine,
		2338	but forking and registering a watcher a few event loop iterations later or
		2339	in the next callback invocation is not.
1598		2340
1599	Only the default event loop is capable of handling signals, and therefore	2341	Only the default event loop is capable of handling signals, and therefore
1600	you can only register child watchers in the default event loop.	2342	you can only register child watchers in the default event loop.
1601		2343
		2344	Due to some design glitches inside libev, child watchers will always be
		2345	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2346	libev)
		2347
1602	=head3 Process Interaction	2348	=head3 Process Interaction
1603		2349
1604	Libev grabs C<SIGCHLD> as soon as the default event loop is	2350	Libev grabs C<SIGCHLD> as soon as the default event loop is
1605	initialised. This is necessary to guarantee proper behaviour even if	2351	initialised. This is necessary to guarantee proper behaviour even if the
1606	the first child watcher is started after the child exits. The occurrence	2352	first child watcher is started after the child exits. The occurrence
1607	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2353	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1608	synchronously as part of the event loop processing. Libev always reaps all	2354	synchronously as part of the event loop processing. Libev always reaps all
1609	children, even ones not watched.	2355	children, even ones not watched.
1610		2356
1611	=head3 Overriding the Built-In Processing	2357	=head3 Overriding the Built-In Processing
…		…
1621	=head3 Stopping the Child Watcher	2367	=head3 Stopping the Child Watcher
1622		2368
1623	Currently, the child watcher never gets stopped, even when the	2369	Currently, the child watcher never gets stopped, even when the
1624	child terminates, so normally one needs to stop the watcher in the	2370	child terminates, so normally one needs to stop the watcher in the
1625	callback. Future versions of libev might stop the watcher automatically	2371	callback. Future versions of libev might stop the watcher automatically
1626	when a child exit is detected.	2372	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2373	problem).
1627		2374
1628	=head3 Watcher-Specific Functions and Data Members	2375	=head3 Watcher-Specific Functions and Data Members
1629		2376
1630	=over 4	2377	=over 4
1631		2378
…		…
1663	its completion.	2410	its completion.
1664		2411
1665	ev_child cw;	2412	ev_child cw;
1666		2413
1667	static void	2414	static void
1668	child_cb (EV_P_ struct ev_child *w, int revents)	2415	child_cb (EV_P_ ev_child *w, int revents)
1669	{	2416	{
1670	ev_child_stop (EV_A_ w);	2417	ev_child_stop (EV_A_ w);
1671	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2418	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1672	}	2419	}
1673		2420
…		…
1688		2435
1689		2436
1690	=head2 C<ev_stat> - did the file attributes just change?	2437	=head2 C<ev_stat> - did the file attributes just change?
1691		2438
1692	This watches a file system path for attribute changes. That is, it calls	2439	This watches a file system path for attribute changes. That is, it calls
1693	C<stat> regularly (or when the OS says it changed) and sees if it changed	2440	C<stat> on that path in regular intervals (or when the OS says it changed)
1694	compared to the last time, invoking the callback if it did.	2441	and sees if it changed compared to the last time, invoking the callback if
		2442	it did.
1695		2443
1696	The path does not need to exist: changing from "path exists" to "path does	2444	The path does not need to exist: changing from "path exists" to "path does
1697	not exist" is a status change like any other. The condition "path does	2445	not exist" is a status change like any other. The condition "path does not
1698	not exist" is signified by the C<st_nlink> field being zero (which is	2446	exist" (or more correctly "path cannot be stat'ed") is signified by the
1699	otherwise always forced to be at least one) and all the other fields of	2447	C<st_nlink> field being zero (which is otherwise always forced to be at
1700	the stat buffer having unspecified contents.	2448	least one) and all the other fields of the stat buffer having unspecified
		2449	contents.
1701		2450
1702	The path I<should> be absolute and I<must not> end in a slash. If it is	2451	The path I<must not> end in a slash or contain special components such as
		2452	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1703	relative and your working directory changes, the behaviour is undefined.	2453	your working directory changes, then the behaviour is undefined.
1704		2454
1705	Since there is no standard to do this, the portable implementation simply	2455	Since there is no portable change notification interface available, the
1706	calls C<stat (2)> regularly on the path to see if it changed somehow. You	2456	portable implementation simply calls C<stat(2)> regularly on the path
1707	can specify a recommended polling interval for this case. If you specify	2457	to see if it changed somehow. You can specify a recommended polling
1708	a polling interval of C<0> (highly recommended!) then a I<suitable,	2458	interval for this case. If you specify a polling interval of C<0> (highly
1709	unspecified default> value will be used (which you can expect to be around	2459	recommended!) then a I<suitable, unspecified default> value will be used
1710	five seconds, although this might change dynamically). Libev will also	2460	(which you can expect to be around five seconds, although this might
1711	impose a minimum interval which is currently around C<0.1>, but thats	2461	change dynamically). Libev will also impose a minimum interval which is
1712	usually overkill.	2462	currently around C<0.1>, but that's usually overkill.
1713		2463
1714	This watcher type is not meant for massive numbers of stat watchers,	2464	This watcher type is not meant for massive numbers of stat watchers,
1715	as even with OS-supported change notifications, this can be	2465	as even with OS-supported change notifications, this can be
1716	resource-intensive.	2466	resource-intensive.
1717		2467
1718	At the time of this writing, only the Linux inotify interface is	2468	At the time of this writing, the only OS-specific interface implemented
1719	implemented (implementing kqueue support is left as an exercise for the	2469	is the Linux inotify interface (implementing kqueue support is left as an
1720	reader, note, however, that the author sees no way of implementing ev_stat	2470	exercise for the reader. Note, however, that the author sees no way of
1721	semantics with kqueue). Inotify will be used to give hints only and should	2471	implementing C<ev_stat> semantics with kqueue, except as a hint).
1722	not change the semantics of C<ev_stat> watchers, which means that libev
1723	sometimes needs to fall back to regular polling again even with inotify,
1724	but changes are usually detected immediately, and if the file exists there
1725	will be no polling.
1726		2472
1727	=head3 ABI Issues (Largefile Support)	2473	=head3 ABI Issues (Largefile Support)
1728		2474
1729	Libev by default (unless the user overrides this) uses the default	2475	Libev by default (unless the user overrides this) uses the default
1730	compilation environment, which means that on systems with large file	2476	compilation environment, which means that on systems with large file
1731	support disabled by default, you get the 32 bit version of the stat	2477	support disabled by default, you get the 32 bit version of the stat
1732	structure. When using the library from programs that change the ABI to	2478	structure. When using the library from programs that change the ABI to
1733	use 64 bit file offsets the programs will fail. In that case you have to	2479	use 64 bit file offsets the programs will fail. In that case you have to
1734	compile libev with the same flags to get binary compatibility. This is	2480	compile libev with the same flags to get binary compatibility. This is
1735	obviously the case with any flags that change the ABI, but the problem is	2481	obviously the case with any flags that change the ABI, but the problem is
1736	most noticeably disabled with ev_stat and large file support.	2482	most noticeably displayed with ev_stat and large file support.
1737		2483
1738	The solution for this is to lobby your distribution maker to make large	2484	The solution for this is to lobby your distribution maker to make large
1739	file interfaces available by default (as e.g. FreeBSD does) and not	2485	file interfaces available by default (as e.g. FreeBSD does) and not
1740	optional. Libev cannot simply switch on large file support because it has	2486	optional. Libev cannot simply switch on large file support because it has
1741	to exchange stat structures with application programs compiled using the	2487	to exchange stat structures with application programs compiled using the
1742	default compilation environment.	2488	default compilation environment.
1743		2489
1744	=head3 Inotify	2490	=head3 Inotify and Kqueue
1745		2491
1746	When C<inotify (7)> support has been compiled into libev (generally only	2492	When C<inotify (7)> support has been compiled into libev and present at
1747	available on Linux) and present at runtime, it will be used to speed up	2493	runtime, it will be used to speed up change detection where possible. The
1748	change detection where possible. The inotify descriptor will be created lazily	2494	inotify descriptor will be created lazily when the first C<ev_stat>
1749	when the first C<ev_stat> watcher is being started.	2495	watcher is being started.
1750		2496
1751	Inotify presence does not change the semantics of C<ev_stat> watchers	2497	Inotify presence does not change the semantics of C<ev_stat> watchers
1752	except that changes might be detected earlier, and in some cases, to avoid	2498	except that changes might be detected earlier, and in some cases, to avoid
1753	making regular C<stat> calls. Even in the presence of inotify support	2499	making regular C<stat> calls. Even in the presence of inotify support
1754	there are many cases where libev has to resort to regular C<stat> polling.	2500	there are many cases where libev has to resort to regular C<stat> polling,
		2501	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2502	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2503	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2504	xfs are fully working) libev usually gets away without polling.
1755		2505
1756	(There is no support for kqueue, as apparently it cannot be used to	2506	There is no support for kqueue, as apparently it cannot be used to
1757	implement this functionality, due to the requirement of having a file	2507	implement this functionality, due to the requirement of having a file
1758	descriptor open on the object at all times).	2508	descriptor open on the object at all times, and detecting renames, unlinks
		2509	etc. is difficult.
		2510
		2511	=head3 C<stat ()> is a synchronous operation
		2512
		2513	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2514	the process. The exception are C<ev_stat> watchers - those call C<stat
		2515	()>, which is a synchronous operation.
		2516
		2517	For local paths, this usually doesn't matter: unless the system is very
		2518	busy or the intervals between stat's are large, a stat call will be fast,
		2519	as the path data is usually in memory already (except when starting the
		2520	watcher).
		2521
		2522	For networked file systems, calling C<stat ()> can block an indefinite
		2523	time due to network issues, and even under good conditions, a stat call
		2524	often takes multiple milliseconds.
		2525
		2526	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2527	paths, although this is fully supported by libev.
1759		2528
1760	=head3 The special problem of stat time resolution	2529	=head3 The special problem of stat time resolution
1761		2530
1762	The C<stat ()> system call only supports full-second resolution portably, and	2531	The C<stat ()> system call only supports full-second resolution portably,
1763	even on systems where the resolution is higher, many file systems still	2532	and even on systems where the resolution is higher, most file systems
1764	only support whole seconds.	2533	still only support whole seconds.
1765		2534
1766	That means that, if the time is the only thing that changes, you can	2535	That means that, if the time is the only thing that changes, you can
1767	easily miss updates: on the first update, C<ev_stat> detects a change and	2536	easily miss updates: on the first update, C<ev_stat> detects a change and
1768	calls your callback, which does something. When there is another update	2537	calls your callback, which does something. When there is another update
1769	within the same second, C<ev_stat> will be unable to detect it as the stat	2538	within the same second, C<ev_stat> will be unable to detect unless the
1770	data does not change.	2539	stat data does change in other ways (e.g. file size).
1771		2540
1772	The solution to this is to delay acting on a change for slightly more	2541	The solution to this is to delay acting on a change for slightly more
1773	than a second (or till slightly after the next full second boundary), using	2542	than a second (or till slightly after the next full second boundary), using
1774	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2543	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1775	ev_timer_again (loop, w)>).	2544	ev_timer_again (loop, w)>).
…		…
1795	C<path>. The C<interval> is a hint on how quickly a change is expected to	2564	C<path>. The C<interval> is a hint on how quickly a change is expected to
1796	be detected and should normally be specified as C<0> to let libev choose	2565	be detected and should normally be specified as C<0> to let libev choose
1797	a suitable value. The memory pointed to by C<path> must point to the same	2566	a suitable value. The memory pointed to by C<path> must point to the same
1798	path for as long as the watcher is active.	2567	path for as long as the watcher is active.
1799		2568
1800	The callback will receive C<EV_STAT> when a change was detected, relative	2569	The callback will receive an C<EV_STAT> event when a change was detected,
1801	to the attributes at the time the watcher was started (or the last change	2570	relative to the attributes at the time the watcher was started (or the
1802	was detected).	2571	last change was detected).
1803		2572
1804	=item ev_stat_stat (loop, ev_stat *)	2573	=item ev_stat_stat (loop, ev_stat *)
1805		2574
1806	Updates the stat buffer immediately with new values. If you change the	2575	Updates the stat buffer immediately with new values. If you change the
1807	watched path in your callback, you could call this function to avoid	2576	watched path in your callback, you could call this function to avoid
…		…
1890		2659
1891		2660
1892	=head2 C<ev_idle> - when you've got nothing better to do...	2661	=head2 C<ev_idle> - when you've got nothing better to do...
1893		2662
1894	Idle watchers trigger events when no other events of the same or higher	2663	Idle watchers trigger events when no other events of the same or higher
1895	priority are pending (prepare, check and other idle watchers do not	2664	priority are pending (prepare, check and other idle watchers do not count
1896	count).	2665	as receiving "events").
1897		2666
1898	That is, as long as your process is busy handling sockets or timeouts	2667	That is, as long as your process is busy handling sockets or timeouts
1899	(or even signals, imagine) of the same or higher priority it will not be	2668	(or even signals, imagine) of the same or higher priority it will not be
1900	triggered. But when your process is idle (or only lower-priority watchers	2669	triggered. But when your process is idle (or only lower-priority watchers
1901	are pending), the idle watchers are being called once per event loop	2670	are pending), the idle watchers are being called once per event loop
…		…
1912		2681
1913	=head3 Watcher-Specific Functions and Data Members	2682	=head3 Watcher-Specific Functions and Data Members
1914		2683
1915	=over 4	2684	=over 4
1916		2685
1917	=item ev_idle_init (ev_signal *, callback)	2686	=item ev_idle_init (ev_idle *, callback)
1918		2687
1919	Initialises and configures the idle watcher - it has no parameters of any	2688	Initialises and configures the idle watcher - it has no parameters of any
1920	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2689	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1921	believe me.	2690	believe me.
1922		2691
…		…
1926		2695
1927	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2696	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1928	callback, free it. Also, use no error checking, as usual.	2697	callback, free it. Also, use no error checking, as usual.
1929		2698
1930	static void	2699	static void
1931	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2700	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1932	{	2701	{
1933	free (w);	2702	free (w);
1934	// now do something you wanted to do when the program has	2703	// now do something you wanted to do when the program has
1935	// no longer anything immediate to do.	2704	// no longer anything immediate to do.
1936	}	2705	}
1937		2706
1938	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2707	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1939	ev_idle_init (idle_watcher, idle_cb);	2708	ev_idle_init (idle_watcher, idle_cb);
1940	ev_idle_start (loop, idle_cb);	2709	ev_idle_start (loop, idle_watcher);
1941		2710
1942		2711
1943	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2712	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1944		2713
1945	Prepare and check watchers are usually (but not always) used in tandem:	2714	Prepare and check watchers are usually (but not always) used in pairs:
1946	prepare watchers get invoked before the process blocks and check watchers	2715	prepare watchers get invoked before the process blocks and check watchers
1947	afterwards.	2716	afterwards.
1948		2717
1949	You I<must not> call C<ev_loop> or similar functions that enter	2718	You I<must not> call C<ev_run> or similar functions that enter
1950	the current event loop from either C<ev_prepare> or C<ev_check>	2719	the current event loop from either C<ev_prepare> or C<ev_check>
1951	watchers. Other loops than the current one are fine, however. The	2720	watchers. Other loops than the current one are fine, however. The
1952	rationale behind this is that you do not need to check for recursion in	2721	rationale behind this is that you do not need to check for recursion in
1953	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2722	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1954	C<ev_check> so if you have one watcher of each kind they will always be	2723	C<ev_check> so if you have one watcher of each kind they will always be
1955	called in pairs bracketing the blocking call.	2724	called in pairs bracketing the blocking call.
1956		2725
1957	Their main purpose is to integrate other event mechanisms into libev and	2726	Their main purpose is to integrate other event mechanisms into libev and
1958	their use is somewhat advanced. This could be used, for example, to track	2727	their use is somewhat advanced. They could be used, for example, to track
1959	variable changes, implement your own watchers, integrate net-snmp or a	2728	variable changes, implement your own watchers, integrate net-snmp or a
1960	coroutine library and lots more. They are also occasionally useful if	2729	coroutine library and lots more. They are also occasionally useful if
1961	you cache some data and want to flush it before blocking (for example,	2730	you cache some data and want to flush it before blocking (for example,
1962	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2731	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1963	watcher).	2732	watcher).
1964		2733
1965	This is done by examining in each prepare call which file descriptors need	2734	This is done by examining in each prepare call which file descriptors
1966	to be watched by the other library, registering C<ev_io> watchers for	2735	need to be watched by the other library, registering C<ev_io> watchers
1967	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2736	for them and starting an C<ev_timer> watcher for any timeouts (many
1968	provide just this functionality). Then, in the check watcher you check for	2737	libraries provide exactly this functionality). Then, in the check watcher,
1969	any events that occurred (by checking the pending status of all watchers	2738	you check for any events that occurred (by checking the pending status
1970	and stopping them) and call back into the library. The I/O and timer	2739	of all watchers and stopping them) and call back into the library. The
1971	callbacks will never actually be called (but must be valid nevertheless,	2740	I/O and timer callbacks will never actually be called (but must be valid
1972	because you never know, you know?).	2741	nevertheless, because you never know, you know?).
1973		2742
1974	As another example, the Perl Coro module uses these hooks to integrate	2743	As another example, the Perl Coro module uses these hooks to integrate
1975	coroutines into libev programs, by yielding to other active coroutines	2744	coroutines into libev programs, by yielding to other active coroutines
1976	during each prepare and only letting the process block if no coroutines	2745	during each prepare and only letting the process block if no coroutines
1977	are ready to run (it's actually more complicated: it only runs coroutines	2746	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1980	loop from blocking if lower-priority coroutines are active, thus mapping	2749	loop from blocking if lower-priority coroutines are active, thus mapping
1981	low-priority coroutines to idle/background tasks).	2750	low-priority coroutines to idle/background tasks).
1982		2751
1983	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2752	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1984	priority, to ensure that they are being run before any other watchers	2753	priority, to ensure that they are being run before any other watchers
		2754	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2755
1985	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2756	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1986	too) should not activate ("feed") events into libev. While libev fully	2757	activate ("feed") events into libev. While libev fully supports this, they
1987	supports this, they might get executed before other C<ev_check> watchers	2758	might get executed before other C<ev_check> watchers did their job. As
1988	did their job. As C<ev_check> watchers are often used to embed other	2759	C<ev_check> watchers are often used to embed other (non-libev) event
1989	(non-libev) event loops those other event loops might be in an unusable	2760	loops those other event loops might be in an unusable state until their
1990	state until their C<ev_check> watcher ran (always remind yourself to	2761	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1991	coexist peacefully with others).	2762	others).
1992		2763
1993	=head3 Watcher-Specific Functions and Data Members	2764	=head3 Watcher-Specific Functions and Data Members
1994		2765
1995	=over 4	2766	=over 4
1996		2767
…		…
1998		2769
1999	=item ev_check_init (ev_check *, callback)	2770	=item ev_check_init (ev_check *, callback)
2000		2771
2001	Initialises and configures the prepare or check watcher - they have no	2772	Initialises and configures the prepare or check watcher - they have no
2002	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2773	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
2003	macros, but using them is utterly, utterly and completely pointless.	2774	macros, but using them is utterly, utterly, utterly and completely
		2775	pointless.
2004		2776
2005	=back	2777	=back
2006		2778
2007	=head3 Examples	2779	=head3 Examples
2008		2780
…		…
2021		2793
2022	static ev_io iow [nfd];	2794	static ev_io iow [nfd];
2023	static ev_timer tw;	2795	static ev_timer tw;
2024		2796
2025	static void	2797	static void
2026	io_cb (ev_loop *loop, ev_io *w, int revents)	2798	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2027	{	2799	{
2028	}	2800	}
2029		2801
2030	// create io watchers for each fd and a timer before blocking	2802	// create io watchers for each fd and a timer before blocking
2031	static void	2803	static void
2032	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2804	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2033	{	2805	{
2034	int timeout = 3600000;	2806	int timeout = 3600000;
2035	struct pollfd fds [nfd];	2807	struct pollfd fds [nfd];
2036	// actual code will need to loop here and realloc etc.	2808	// actual code will need to loop here and realloc etc.
2037	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2809	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2038		2810
2039	/* the callback is illegal, but won't be called as we stop during check */	2811	/* the callback is illegal, but won't be called as we stop during check */
2040	ev_timer_init (&tw, 0, timeout * 1e-3);	2812	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2041	ev_timer_start (loop, &tw);	2813	ev_timer_start (loop, &tw);
2042		2814
2043	// create one ev_io per pollfd	2815	// create one ev_io per pollfd
2044	for (int i = 0; i < nfd; ++i)	2816	for (int i = 0; i < nfd; ++i)
2045	{	2817	{
…		…
2052	}	2824	}
2053	}	2825	}
2054		2826
2055	// stop all watchers after blocking	2827	// stop all watchers after blocking
2056	static void	2828	static void
2057	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2829	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2058	{	2830	{
2059	ev_timer_stop (loop, &tw);	2831	ev_timer_stop (loop, &tw);
2060		2832
2061	for (int i = 0; i < nfd; ++i)	2833	for (int i = 0; i < nfd; ++i)
2062	{	2834	{
…		…
2101	}	2873	}
2102		2874
2103	// do not ever call adns_afterpoll	2875	// do not ever call adns_afterpoll
2104		2876
2105	Method 4: Do not use a prepare or check watcher because the module you	2877	Method 4: Do not use a prepare or check watcher because the module you
2106	want to embed is too inflexible to support it. Instead, you can override	2878	want to embed is not flexible enough to support it. Instead, you can
2107	their poll function. The drawback with this solution is that the main	2879	override their poll function. The drawback with this solution is that the
2108	loop is now no longer controllable by EV. The C<Glib::EV> module does	2880	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2109	this.	2881	this approach, effectively embedding EV as a client into the horrible
		2882	libglib event loop.
2110		2883
2111	static gint	2884	static gint
2112	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2885	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2113	{	2886	{
2114	int got_events = 0;	2887	int got_events = 0;
…		…
2118		2891
2119	if (timeout >= 0)	2892	if (timeout >= 0)
2120	// create/start timer	2893	// create/start timer
2121		2894
2122	// poll	2895	// poll
2123	ev_loop (EV_A_ 0);	2896	ev_run (EV_A_ 0);
2124		2897
2125	// stop timer again	2898	// stop timer again
2126	if (timeout >= 0)	2899	if (timeout >= 0)
2127	ev_timer_stop (EV_A_ &to);	2900	ev_timer_stop (EV_A_ &to);
2128		2901
…		…
2145	prioritise I/O.	2918	prioritise I/O.
2146		2919
2147	As an example for a bug workaround, the kqueue backend might only support	2920	As an example for a bug workaround, the kqueue backend might only support
2148	sockets on some platform, so it is unusable as generic backend, but you	2921	sockets on some platform, so it is unusable as generic backend, but you
2149	still want to make use of it because you have many sockets and it scales	2922	still want to make use of it because you have many sockets and it scales
2150	so nicely. In this case, you would create a kqueue-based loop and embed it	2923	so nicely. In this case, you would create a kqueue-based loop and embed
2151	into your default loop (which might use e.g. poll). Overall operation will	2924	it into your default loop (which might use e.g. poll). Overall operation
2152	be a bit slower because first libev has to poll and then call kevent, but	2925	will be a bit slower because first libev has to call C<poll> and then
2153	at least you can use both at what they are best.	2926	C<kevent>, but at least you can use both mechanisms for what they are
		2927	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2154		2928
2155	As for prioritising I/O: rarely you have the case where some fds have	2929	As for prioritising I/O: under rare circumstances you have the case where
2156	to be watched and handled very quickly (with low latency), and even	2930	some fds have to be watched and handled very quickly (with low latency),
2157	priorities and idle watchers might have too much overhead. In this case	2931	and even priorities and idle watchers might have too much overhead. In
2158	you would put all the high priority stuff in one loop and all the rest in	2932	this case you would put all the high priority stuff in one loop and all
2159	a second one, and embed the second one in the first.	2933	the rest in a second one, and embed the second one in the first.
2160		2934
2161	As long as the watcher is active, the callback will be invoked every time	2935	As long as the watcher is active, the callback will be invoked every
2162	there might be events pending in the embedded loop. The callback must then	2936	time there might be events pending in the embedded loop. The callback
2163	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2937	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2164	their callbacks (you could also start an idle watcher to give the embedded	2938	sweep and invoke their callbacks (the callback doesn't need to invoke the
2165	loop strictly lower priority for example). You can also set the callback	2939	C<ev_embed_sweep> function directly, it could also start an idle watcher
2166	to C<0>, in which case the embed watcher will automatically execute the	2940	to give the embedded loop strictly lower priority for example).
2167	embedded loop sweep.
2168		2941
2169	As long as the watcher is started it will automatically handle events. The	2942	You can also set the callback to C<0>, in which case the embed watcher
2170	callback will be invoked whenever some events have been handled. You can	2943	will automatically execute the embedded loop sweep whenever necessary.
2171	set the callback to C<0> to avoid having to specify one if you are not
2172	interested in that.
2173		2944
2174	Also, there have not currently been made special provisions for forking:	2945	Fork detection will be handled transparently while the C<ev_embed> watcher
2175	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2946	is active, i.e., the embedded loop will automatically be forked when the
2176	but you will also have to stop and restart any C<ev_embed> watchers	2947	embedding loop forks. In other cases, the user is responsible for calling
2177	yourself.	2948	C<ev_loop_fork> on the embedded loop.
2178		2949
2179	Unfortunately, not all backends are embeddable, only the ones returned by	2950	Unfortunately, not all backends are embeddable: only the ones returned by
2180	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2951	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2181	portable one.	2952	portable one.
2182		2953
2183	So when you want to use this feature you will always have to be prepared	2954	So when you want to use this feature you will always have to be prepared
2184	that you cannot get an embeddable loop. The recommended way to get around	2955	that you cannot get an embeddable loop. The recommended way to get around
2185	this is to have a separate variables for your embeddable loop, try to	2956	this is to have a separate variables for your embeddable loop, try to
2186	create it, and if that fails, use the normal loop for everything.	2957	create it, and if that fails, use the normal loop for everything.
		2958
		2959	=head3 C<ev_embed> and fork
		2960
		2961	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2962	automatically be applied to the embedded loop as well, so no special
		2963	fork handling is required in that case. When the watcher is not running,
		2964	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2965	as applicable.
2187		2966
2188	=head3 Watcher-Specific Functions and Data Members	2967	=head3 Watcher-Specific Functions and Data Members
2189		2968
2190	=over 4	2969	=over 4
2191		2970
…		…
2200	if you do not want that, you need to temporarily stop the embed watcher).	2979	if you do not want that, you need to temporarily stop the embed watcher).
2201		2980
2202	=item ev_embed_sweep (loop, ev_embed *)	2981	=item ev_embed_sweep (loop, ev_embed *)
2203		2982
2204	Make a single, non-blocking sweep over the embedded loop. This works	2983	Make a single, non-blocking sweep over the embedded loop. This works
2205	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2984	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2206	appropriate way for embedded loops.	2985	appropriate way for embedded loops.
2207		2986
2208	=item struct ev_loop *other [read-only]	2987	=item struct ev_loop *other [read-only]
2209		2988
2210	The embedded event loop.	2989	The embedded event loop.
…		…
2219	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2998	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2220	used).	2999	used).
2221		3000
2222	struct ev_loop *loop_hi = ev_default_init (0);	3001	struct ev_loop *loop_hi = ev_default_init (0);
2223	struct ev_loop *loop_lo = 0;	3002	struct ev_loop *loop_lo = 0;
2224	struct ev_embed embed;	3003	ev_embed embed;
2225		3004
2226	// see if there is a chance of getting one that works	3005	// see if there is a chance of getting one that works
2227	// (remember that a flags value of 0 means autodetection)	3006	// (remember that a flags value of 0 means autodetection)
2228	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3007	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2229	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3008	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2243	kqueue implementation). Store the kqueue/socket-only event loop in	3022	kqueue implementation). Store the kqueue/socket-only event loop in
2244	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3023	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2245		3024
2246	struct ev_loop *loop = ev_default_init (0);	3025	struct ev_loop *loop = ev_default_init (0);
2247	struct ev_loop *loop_socket = 0;	3026	struct ev_loop *loop_socket = 0;
2248	struct ev_embed embed;	3027	ev_embed embed;
2249		3028
2250	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3029	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2251	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3030	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2252	{	3031	{
2253	ev_embed_init (&embed, 0, loop_socket);	3032	ev_embed_init (&embed, 0, loop_socket);
…		…
2268	event loop blocks next and before C<ev_check> watchers are being called,	3047	event loop blocks next and before C<ev_check> watchers are being called,
2269	and only in the child after the fork. If whoever good citizen calling	3048	and only in the child after the fork. If whoever good citizen calling
2270	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3049	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2271	handlers will be invoked, too, of course.	3050	handlers will be invoked, too, of course.
2272		3051
		3052	=head3 The special problem of life after fork - how is it possible?
		3053
		3054	Most uses of C<fork()> consist of forking, then some simple calls to set
		3055	up/change the process environment, followed by a call to C<exec()>. This
		3056	sequence should be handled by libev without any problems.
		3057
		3058	This changes when the application actually wants to do event handling
		3059	in the child, or both parent in child, in effect "continuing" after the
		3060	fork.
		3061
		3062	The default mode of operation (for libev, with application help to detect
		3063	forks) is to duplicate all the state in the child, as would be expected
		3064	when I<either> the parent I<or> the child process continues.
		3065
		3066	When both processes want to continue using libev, then this is usually the
		3067	wrong result. In that case, usually one process (typically the parent) is
		3068	supposed to continue with all watchers in place as before, while the other
		3069	process typically wants to start fresh, i.e. without any active watchers.
		3070
		3071	The cleanest and most efficient way to achieve that with libev is to
		3072	simply create a new event loop, which of course will be "empty", and
		3073	use that for new watchers. This has the advantage of not touching more
		3074	memory than necessary, and thus avoiding the copy-on-write, and the
		3075	disadvantage of having to use multiple event loops (which do not support
		3076	signal watchers).
		3077
		3078	When this is not possible, or you want to use the default loop for
		3079	other reasons, then in the process that wants to start "fresh", call
		3080	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		3081	the default loop will "orphan" (not stop) all registered watchers, so you
		3082	have to be careful not to execute code that modifies those watchers. Note
		3083	also that in that case, you have to re-register any signal watchers.
		3084
2273	=head3 Watcher-Specific Functions and Data Members	3085	=head3 Watcher-Specific Functions and Data Members
2274		3086
2275	=over 4	3087	=over 4
2276		3088
2277	=item ev_fork_init (ev_signal *, callback)	3089	=item ev_fork_init (ev_signal *, callback)
…		…
2281	believe me.	3093	believe me.
2282		3094
2283	=back	3095	=back
2284		3096
2285		3097
2286	=head2 C<ev_async> - how to wake up another event loop	3098	=head2 C<ev_async> - how to wake up an event loop
2287		3099
2288	In general, you cannot use an C<ev_loop> from multiple threads or other	3100	In general, you cannot use an C<ev_run> from multiple threads or other
2289	asynchronous sources such as signal handlers (as opposed to multiple event	3101	asynchronous sources such as signal handlers (as opposed to multiple event
2290	loops - those are of course safe to use in different threads).	3102	loops - those are of course safe to use in different threads).
2291		3103
2292	Sometimes, however, you need to wake up another event loop you do not	3104	Sometimes, however, you need to wake up an event loop you do not control,
2293	control, for example because it belongs to another thread. This is what	3105	for example because it belongs to another thread. This is what C<ev_async>
2294	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3106	watchers do: as long as the C<ev_async> watcher is active, you can signal
2295	can signal it by calling C<ev_async_send>, which is thread- and signal	3107	it by calling C<ev_async_send>, which is thread- and signal safe.
2296	safe.
2297		3108
2298	This functionality is very similar to C<ev_signal> watchers, as signals,	3109	This functionality is very similar to C<ev_signal> watchers, as signals,
2299	too, are asynchronous in nature, and signals, too, will be compressed	3110	too, are asynchronous in nature, and signals, too, will be compressed
2300	(i.e. the number of callback invocations may be less than the number of	3111	(i.e. the number of callback invocations may be less than the number of
2301	C<ev_async_sent> calls).	3112	C<ev_async_sent> calls).
…		…
2306	=head3 Queueing	3117	=head3 Queueing
2307		3118
2308	C<ev_async> does not support queueing of data in any way. The reason	3119	C<ev_async> does not support queueing of data in any way. The reason
2309	is that the author does not know of a simple (or any) algorithm for a	3120	is that the author does not know of a simple (or any) algorithm for a
2310	multiple-writer-single-reader queue that works in all cases and doesn't	3121	multiple-writer-single-reader queue that works in all cases and doesn't
2311	need elaborate support such as pthreads.	3122	need elaborate support such as pthreads or unportable memory access
		3123	semantics.
2312		3124
2313	That means that if you want to queue data, you have to provide your own	3125	That means that if you want to queue data, you have to provide your own
2314	queue. But at least I can tell you would implement locking around your	3126	queue. But at least I can tell you how to implement locking around your
2315	queue:	3127	queue:
2316		3128
2317	=over 4	3129	=over 4
2318		3130
2319	=item queueing from a signal handler context	3131	=item queueing from a signal handler context
2320		3132
2321	To implement race-free queueing, you simply add to the queue in the signal	3133	To implement race-free queueing, you simply add to the queue in the signal
2322	handler but you block the signal handler in the watcher callback. Here is an example that does that for	3134	handler but you block the signal handler in the watcher callback. Here is
2323	some fictitious SIGUSR1 handler:	3135	an example that does that for some fictitious SIGUSR1 handler:
2324		3136
2325	static ev_async mysig;	3137	static ev_async mysig;
2326		3138
2327	static void	3139	static void
2328	sigusr1_handler (void)	3140	sigusr1_handler (void)
…		…
2394	=over 4	3206	=over 4
2395		3207
2396	=item ev_async_init (ev_async *, callback)	3208	=item ev_async_init (ev_async *, callback)
2397		3209
2398	Initialises and configures the async watcher - it has no parameters of any	3210	Initialises and configures the async watcher - it has no parameters of any
2399	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3211	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2400	believe me.	3212	trust me.
2401		3213
2402	=item ev_async_send (loop, ev_async *)	3214	=item ev_async_send (loop, ev_async *)
2403		3215
2404	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3216	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2405	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3217	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2406	C<ev_feed_event>, this call is safe to do in other threads, signal or	3218	C<ev_feed_event>, this call is safe to do from other threads, signal or
2407	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3219	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2408	section below on what exactly this means).	3220	section below on what exactly this means).
2409		3221
		3222	Note that, as with other watchers in libev, multiple events might get
		3223	compressed into a single callback invocation (another way to look at this
		3224	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3225	reset when the event loop detects that).
		3226
2410	This call incurs the overhead of a system call only once per loop iteration,	3227	This call incurs the overhead of a system call only once per event loop
2411	so while the overhead might be noticeable, it doesn't apply to repeated	3228	iteration, so while the overhead might be noticeable, it doesn't apply to
2412	calls to C<ev_async_send>.	3229	repeated calls to C<ev_async_send> for the same event loop.
2413		3230
2414	=item bool = ev_async_pending (ev_async *)	3231	=item bool = ev_async_pending (ev_async *)
2415		3232
2416	Returns a non-zero value when C<ev_async_send> has been called on the	3233	Returns a non-zero value when C<ev_async_send> has been called on the
2417	watcher but the event has not yet been processed (or even noted) by the	3234	watcher but the event has not yet been processed (or even noted) by the
…		…
2420	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3237	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2421	the loop iterates next and checks for the watcher to have become active,	3238	the loop iterates next and checks for the watcher to have become active,
2422	it will reset the flag again. C<ev_async_pending> can be used to very	3239	it will reset the flag again. C<ev_async_pending> can be used to very
2423	quickly check whether invoking the loop might be a good idea.	3240	quickly check whether invoking the loop might be a good idea.
2424		3241
2425	Not that this does I<not> check whether the watcher itself is pending, only	3242	Not that this does I<not> check whether the watcher itself is pending,
2426	whether it has been requested to make this watcher pending.	3243	only whether it has been requested to make this watcher pending: there
		3244	is a time window between the event loop checking and resetting the async
		3245	notification, and the callback being invoked.
2427		3246
2428	=back	3247	=back
2429		3248
2430		3249
2431	=head1 OTHER FUNCTIONS	3250	=head1 OTHER FUNCTIONS
…		…
2435	=over 4	3254	=over 4
2436		3255
2437	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3256	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2438		3257
2439	This function combines a simple timer and an I/O watcher, calls your	3258	This function combines a simple timer and an I/O watcher, calls your
2440	callback on whichever event happens first and automatically stop both	3259	callback on whichever event happens first and automatically stops both
2441	watchers. This is useful if you want to wait for a single event on an fd	3260	watchers. This is useful if you want to wait for a single event on an fd
2442	or timeout without having to allocate/configure/start/stop/free one or	3261	or timeout without having to allocate/configure/start/stop/free one or
2443	more watchers yourself.	3262	more watchers yourself.
2444		3263
2445	If C<fd> is less than 0, then no I/O watcher will be started and events	3264	If C<fd> is less than 0, then no I/O watcher will be started and the
2446	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	3265	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2447	C<events> set will be created and started.	3266	the given C<fd> and C<events> set will be created and started.
2448		3267
2449	If C<timeout> is less than 0, then no timeout watcher will be	3268	If C<timeout> is less than 0, then no timeout watcher will be
2450	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3269	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2451	repeat = 0) will be started. While C<0> is a valid timeout, it is of	3270	repeat = 0) will be started. C<0> is a valid timeout.
2452	dubious value.
2453		3271
2454	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3272	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2455	passed an C<revents> set like normal event callbacks (a combination of	3273	passed an C<revents> set like normal event callbacks (a combination of
2456	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3274	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2457	value passed to C<ev_once>:	3275	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3276	a timeout and an io event at the same time - you probably should give io
		3277	events precedence.
		3278
		3279	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2458		3280
2459	static void stdin_ready (int revents, void *arg)	3281	static void stdin_ready (int revents, void *arg)
2460	{	3282	{
		3283	if (revents & EV_READ)
		3284	/* stdin might have data for us, joy! */;
2461	if (revents & EV_TIMEOUT)	3285	else if (revents & EV_TIMER)
2462	/* doh, nothing entered */;	3286	/* doh, nothing entered */;
2463	else if (revents & EV_READ)
2464	/* stdin might have data for us, joy! */;
2465	}	3287	}
2466		3288
2467	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3289	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2468		3290
2469	=item ev_feed_event (ev_loop *, watcher *, int revents)
2470
2471	Feeds the given event set into the event loop, as if the specified event
2472	had happened for the specified watcher (which must be a pointer to an
2473	initialised but not necessarily started event watcher).
2474
2475	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3291	=item ev_feed_fd_event (loop, int fd, int revents)
2476		3292
2477	Feed an event on the given fd, as if a file descriptor backend detected	3293	Feed an event on the given fd, as if a file descriptor backend detected
2478	the given events it.	3294	the given events it.
2479		3295
2480	=item ev_feed_signal_event (ev_loop *loop, int signum)	3296	=item ev_feed_signal_event (loop, int signum)
2481		3297
2482	Feed an event as if the given signal occurred (C<loop> must be the default	3298	Feed an event as if the given signal occurred (C<loop> must be the default
2483	loop!).	3299	loop!).
2484		3300
2485	=back	3301	=back
…		…
2565		3381
2566	=over 4	3382	=over 4
2567		3383
2568	=item ev::TYPE::TYPE ()	3384	=item ev::TYPE::TYPE ()
2569		3385
2570	=item ev::TYPE::TYPE (struct ev_loop *)	3386	=item ev::TYPE::TYPE (loop)
2571		3387
2572	=item ev::TYPE::~TYPE	3388	=item ev::TYPE::~TYPE
2573		3389
2574	The constructor (optionally) takes an event loop to associate the watcher	3390	The constructor (optionally) takes an event loop to associate the watcher
2575	with. If it is omitted, it will use C<EV_DEFAULT>.	3391	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2607		3423
2608	myclass obj;	3424	myclass obj;
2609	ev::io iow;	3425	ev::io iow;
2610	iow.set <myclass, &myclass::io_cb> (&obj);	3426	iow.set <myclass, &myclass::io_cb> (&obj);
2611		3427
		3428	=item w->set (object *)
		3429
		3430	This is a variation of a method callback - leaving out the method to call
		3431	will default the method to C<operator ()>, which makes it possible to use
		3432	functor objects without having to manually specify the C<operator ()> all
		3433	the time. Incidentally, you can then also leave out the template argument
		3434	list.
		3435
		3436	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3437	int revents)>.
		3438
		3439	See the method-C<set> above for more details.
		3440
		3441	Example: use a functor object as callback.
		3442
		3443	struct myfunctor
		3444	{
		3445	void operator() (ev::io &w, int revents)
		3446	{
		3447	...
		3448	}
		3449	}
		3450
		3451	myfunctor f;
		3452
		3453	ev::io w;
		3454	w.set (&f);
		3455
2612	=item w->set<function> (void *data = 0)	3456	=item w->set<function> (void *data = 0)
2613		3457
2614	Also sets a callback, but uses a static method or plain function as	3458	Also sets a callback, but uses a static method or plain function as
2615	callback. The optional C<data> argument will be stored in the watcher's	3459	callback. The optional C<data> argument will be stored in the watcher's
2616	C<data> member and is free for you to use.	3460	C<data> member and is free for you to use.
2617		3461
2618	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3462	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2619		3463
2620	See the method-C<set> above for more details.	3464	See the method-C<set> above for more details.
2621		3465
2622	Example:	3466	Example: Use a plain function as callback.
2623		3467
2624	static void io_cb (ev::io &w, int revents) { }	3468	static void io_cb (ev::io &w, int revents) { }
2625	iow.set <io_cb> ();	3469	iow.set <io_cb> ();
2626		3470
2627	=item w->set (struct ev_loop *)	3471	=item w->set (loop)
2628		3472
2629	Associates a different C<struct ev_loop> with this watcher. You can only	3473	Associates a different C<struct ev_loop> with this watcher. You can only
2630	do this when the watcher is inactive (and not pending either).	3474	do this when the watcher is inactive (and not pending either).
2631		3475
2632	=item w->set ([arguments])	3476	=item w->set ([arguments])
2633		3477
2634	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3478	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
2635	called at least once. Unlike the C counterpart, an active watcher gets	3479	method or a suitable start method must be called at least once. Unlike the
2636	automatically stopped and restarted when reconfiguring it with this	3480	C counterpart, an active watcher gets automatically stopped and restarted
2637	method.	3481	when reconfiguring it with this method.
2638		3482
2639	=item w->start ()	3483	=item w->start ()
2640		3484
2641	Starts the watcher. Note that there is no C<loop> argument, as the	3485	Starts the watcher. Note that there is no C<loop> argument, as the
2642	constructor already stores the event loop.	3486	constructor already stores the event loop.
2643		3487
		3488	=item w->start ([arguments])
		3489
		3490	Instead of calling C<set> and C<start> methods separately, it is often
		3491	convenient to wrap them in one call. Uses the same type of arguments as
		3492	the configure C<set> method of the watcher.
		3493
2644	=item w->stop ()	3494	=item w->stop ()
2645		3495
2646	Stops the watcher if it is active. Again, no C<loop> argument.	3496	Stops the watcher if it is active. Again, no C<loop> argument.
2647		3497
2648	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3498	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2660		3510
2661	=back	3511	=back
2662		3512
2663	=back	3513	=back
2664		3514
2665	Example: Define a class with an IO and idle watcher, start one of them in	3515	Example: Define a class with two I/O and idle watchers, start the I/O
2666	the constructor.	3516	watchers in the constructor.
2667		3517
2668	class myclass	3518	class myclass
2669	{	3519	{
2670	ev::io io; void io_cb (ev::io &w, int revents);	3520	ev::io io ; void io_cb (ev::io &w, int revents);
		3521	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
2671	ev:idle idle void idle_cb (ev::idle &w, int revents);	3522	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2672		3523
2673	myclass (int fd)	3524	myclass (int fd)
2674	{	3525	{
2675	io .set <myclass, &myclass::io_cb > (this);	3526	io .set <myclass, &myclass::io_cb > (this);
		3527	io2 .set <myclass, &myclass::io2_cb > (this);
2676	idle.set <myclass, &myclass::idle_cb> (this);	3528	idle.set <myclass, &myclass::idle_cb> (this);
2677		3529
2678	io.start (fd, ev::READ);	3530	io.set (fd, ev::WRITE); // configure the watcher
		3531	io.start (); // start it whenever convenient
		3532
		3533	io2.start (fd, ev::READ); // set + start in one call
2679	}	3534	}
2680	};	3535	};
2681		3536
2682		3537
2683	=head1 OTHER LANGUAGE BINDINGS	3538	=head1 OTHER LANGUAGE BINDINGS
…		…
2692	=item Perl	3547	=item Perl
2693		3548
2694	The EV module implements the full libev API and is actually used to test	3549	The EV module implements the full libev API and is actually used to test
2695	libev. EV is developed together with libev. Apart from the EV core module,	3550	libev. EV is developed together with libev. Apart from the EV core module,
2696	there are additional modules that implement libev-compatible interfaces	3551	there are additional modules that implement libev-compatible interfaces
2697	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3552	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2698	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3553	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3554	and C<EV::Glib>).
2699		3555
2700	It can be found and installed via CPAN, its homepage is at	3556	It can be found and installed via CPAN, its homepage is at
2701	L<http://software.schmorp.de/pkg/EV>.	3557	L<http://software.schmorp.de/pkg/EV>.
2702		3558
2703	=item Python	3559	=item Python
2704		3560
2705	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3561	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2706	seems to be quite complete and well-documented. Note, however, that the	3562	seems to be quite complete and well-documented.
2707	patch they require for libev is outright dangerous as it breaks the ABI
2708	for everybody else, and therefore, should never be applied in an installed
2709	libev (if python requires an incompatible ABI then it needs to embed
2710	libev).
2711		3563
2712	=item Ruby	3564	=item Ruby
2713		3565
2714	Tony Arcieri has written a ruby extension that offers access to a subset	3566	Tony Arcieri has written a ruby extension that offers access to a subset
2715	of the libev API and adds file handle abstractions, asynchronous DNS and	3567	of the libev API and adds file handle abstractions, asynchronous DNS and
2716	more on top of it. It can be found via gem servers. Its homepage is at	3568	more on top of it. It can be found via gem servers. Its homepage is at
2717	L<http://rev.rubyforge.org/>.	3569	L<http://rev.rubyforge.org/>.
2718		3570
		3571	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3572	makes rev work even on mingw.
		3573
		3574	=item Haskell
		3575
		3576	A haskell binding to libev is available at
		3577	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3578
2719	=item D	3579	=item D
2720		3580
2721	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3581	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2722	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3582	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3583
		3584	=item Ocaml
		3585
		3586	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3587	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3588
		3589	=item Lua
		3590
		3591	Brian Maher has written a partial interface to libev for lua (at the
		3592	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3593	L<http://github.com/brimworks/lua-ev>.
2723		3594
2724	=back	3595	=back
2725		3596
2726		3597
2727	=head1 MACRO MAGIC	3598	=head1 MACRO MAGIC
…		…
2741	loop argument"). The C<EV_A> form is used when this is the sole argument,	3612	loop argument"). The C<EV_A> form is used when this is the sole argument,
2742	C<EV_A_> is used when other arguments are following. Example:	3613	C<EV_A_> is used when other arguments are following. Example:
2743		3614
2744	ev_unref (EV_A);	3615	ev_unref (EV_A);
2745	ev_timer_add (EV_A_ watcher);	3616	ev_timer_add (EV_A_ watcher);
2746	ev_loop (EV_A_ 0);	3617	ev_run (EV_A_ 0);
2747		3618
2748	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3619	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2749	which is often provided by the following macro.	3620	which is often provided by the following macro.
2750		3621
2751	=item C<EV_P>, C<EV_P_>	3622	=item C<EV_P>, C<EV_P_>
…		…
2791	}	3662	}
2792		3663
2793	ev_check check;	3664	ev_check check;
2794	ev_check_init (&check, check_cb);	3665	ev_check_init (&check, check_cb);
2795	ev_check_start (EV_DEFAULT_ &check);	3666	ev_check_start (EV_DEFAULT_ &check);
2796	ev_loop (EV_DEFAULT_ 0);	3667	ev_run (EV_DEFAULT_ 0);
2797		3668
2798	=head1 EMBEDDING	3669	=head1 EMBEDDING
2799		3670
2800	Libev can (and often is) directly embedded into host	3671	Libev can (and often is) directly embedded into host
2801	applications. Examples of applications that embed it include the Deliantra	3672	applications. Examples of applications that embed it include the Deliantra
…		…
2828		3699
2829	#define EV_STANDALONE 1	3700	#define EV_STANDALONE 1
2830	#include "ev.h"	3701	#include "ev.h"
2831		3702
2832	Both header files and implementation files can be compiled with a C++	3703	Both header files and implementation files can be compiled with a C++
2833	compiler (at least, thats a stated goal, and breakage will be treated	3704	compiler (at least, that's a stated goal, and breakage will be treated
2834	as a bug).	3705	as a bug).
2835		3706
2836	You need the following files in your source tree, or in a directory	3707	You need the following files in your source tree, or in a directory
2837	in your include path (e.g. in libev/ when using -Ilibev):	3708	in your include path (e.g. in libev/ when using -Ilibev):
2838		3709
…		…
2881	libev.m4	3752	libev.m4
2882		3753
2883	=head2 PREPROCESSOR SYMBOLS/MACROS	3754	=head2 PREPROCESSOR SYMBOLS/MACROS
2884		3755
2885	Libev can be configured via a variety of preprocessor symbols you have to	3756	Libev can be configured via a variety of preprocessor symbols you have to
2886	define before including any of its files. The default in the absence of	3757	define before including (or compiling) any of its files. The default in
2887	autoconf is noted for every option.	3758	the absence of autoconf is documented for every option.
		3759
		3760	Symbols marked with "(h)" do not change the ABI, and can have different
		3761	values when compiling libev vs. including F<ev.h>, so it is permissible
		3762	to redefine them before including F<ev.h> without breaking compatibility
		3763	to a compiled library. All other symbols change the ABI, which means all
		3764	users of libev and the libev code itself must be compiled with compatible
		3765	settings.
2888		3766
2889	=over 4	3767	=over 4
2890		3768
		3769	=item EV_COMPAT3 (h)
		3770
		3771	Backwards compatibility is a major concern for libev. This is why this
		3772	release of libev comes with wrappers for the functions and symbols that
		3773	have been renamed between libev version 3 and 4.
		3774
		3775	You can disable these wrappers (to test compatibility with future
		3776	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		3777	sources. This has the additional advantage that you can drop the C<struct>
		3778	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		3779	typedef in that case.
		3780
		3781	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		3782	and in some even more future version the compatibility code will be
		3783	removed completely.
		3784
2891	=item EV_STANDALONE	3785	=item EV_STANDALONE (h)
2892		3786
2893	Must always be C<1> if you do not use autoconf configuration, which	3787	Must always be C<1> if you do not use autoconf configuration, which
2894	keeps libev from including F<config.h>, and it also defines dummy	3788	keeps libev from including F<config.h>, and it also defines dummy
2895	implementations for some libevent functions (such as logging, which is not	3789	implementations for some libevent functions (such as logging, which is not
2896	supported). It will also not define any of the structs usually found in	3790	supported). It will also not define any of the structs usually found in
2897	F<event.h> that are not directly supported by the libev core alone.	3791	F<event.h> that are not directly supported by the libev core alone.
2898		3792
		3793	In standalone mode, libev will still try to automatically deduce the
		3794	configuration, but has to be more conservative.
		3795
2899	=item EV_USE_MONOTONIC	3796	=item EV_USE_MONOTONIC
2900		3797
2901	If defined to be C<1>, libev will try to detect the availability of the	3798	If defined to be C<1>, libev will try to detect the availability of the
2902	monotonic clock option at both compile time and runtime. Otherwise no use	3799	monotonic clock option at both compile time and runtime. Otherwise no
2903	of the monotonic clock option will be attempted. If you enable this, you	3800	use of the monotonic clock option will be attempted. If you enable this,
2904	usually have to link against librt or something similar. Enabling it when	3801	you usually have to link against librt or something similar. Enabling it
2905	the functionality isn't available is safe, though, although you have	3802	when the functionality isn't available is safe, though, although you have
2906	to make sure you link against any libraries where the C<clock_gettime>	3803	to make sure you link against any libraries where the C<clock_gettime>
2907	function is hiding in (often F<-lrt>).	3804	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2908		3805
2909	=item EV_USE_REALTIME	3806	=item EV_USE_REALTIME
2910		3807
2911	If defined to be C<1>, libev will try to detect the availability of the	3808	If defined to be C<1>, libev will try to detect the availability of the
2912	real-time clock option at compile time (and assume its availability at	3809	real-time clock option at compile time (and assume its availability
2913	runtime if successful). Otherwise no use of the real-time clock option will	3810	at runtime if successful). Otherwise no use of the real-time clock
2914	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3811	option will be attempted. This effectively replaces C<gettimeofday>
2915	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3812	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2916	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3813	correctness. See the note about libraries in the description of
		3814	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3815	C<EV_USE_CLOCK_SYSCALL>.
		3816
		3817	=item EV_USE_CLOCK_SYSCALL
		3818
		3819	If defined to be C<1>, libev will try to use a direct syscall instead
		3820	of calling the system-provided C<clock_gettime> function. This option
		3821	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3822	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3823	programs needlessly. Using a direct syscall is slightly slower (in
		3824	theory), because no optimised vdso implementation can be used, but avoids
		3825	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3826	higher, as it simplifies linking (no need for C<-lrt>).
2917		3827
2918	=item EV_USE_NANOSLEEP	3828	=item EV_USE_NANOSLEEP
2919		3829
2920	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3830	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2921	and will use it for delays. Otherwise it will use C<select ()>.	3831	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2937		3847
2938	=item EV_SELECT_USE_FD_SET	3848	=item EV_SELECT_USE_FD_SET
2939		3849
2940	If defined to C<1>, then the select backend will use the system C<fd_set>	3850	If defined to C<1>, then the select backend will use the system C<fd_set>
2941	structure. This is useful if libev doesn't compile due to a missing	3851	structure. This is useful if libev doesn't compile due to a missing
2942	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3852	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2943	exotic systems. This usually limits the range of file descriptors to some	3853	on exotic systems. This usually limits the range of file descriptors to
2944	low limit such as 1024 or might have other limitations (winsocket only	3854	some low limit such as 1024 or might have other limitations (winsocket
2945	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3855	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2946	influence the size of the C<fd_set> used.	3856	configures the maximum size of the C<fd_set>.
2947		3857
2948	=item EV_SELECT_IS_WINSOCKET	3858	=item EV_SELECT_IS_WINSOCKET
2949		3859
2950	When defined to C<1>, the select backend will assume that	3860	When defined to C<1>, the select backend will assume that
2951	select/socket/connect etc. don't understand file descriptors but	3861	select/socket/connect etc. don't understand file descriptors but
…		…
2953	be used is the winsock select). This means that it will call	3863	be used is the winsock select). This means that it will call
2954	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3864	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2955	it is assumed that all these functions actually work on fds, even	3865	it is assumed that all these functions actually work on fds, even
2956	on win32. Should not be defined on non-win32 platforms.	3866	on win32. Should not be defined on non-win32 platforms.
2957		3867
2958	=item EV_FD_TO_WIN32_HANDLE	3868	=item EV_FD_TO_WIN32_HANDLE(fd)
2959		3869
2960	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3870	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
2961	file descriptors to socket handles. When not defining this symbol (the	3871	file descriptors to socket handles. When not defining this symbol (the
2962	default), then libev will call C<_get_osfhandle>, which is usually	3872	default), then libev will call C<_get_osfhandle>, which is usually
2963	correct. In some cases, programs use their own file descriptor management,	3873	correct. In some cases, programs use their own file descriptor management,
2964	in which case they can provide this function to map fds to socket handles.	3874	in which case they can provide this function to map fds to socket handles.
		3875
		3876	=item EV_WIN32_HANDLE_TO_FD(handle)
		3877
		3878	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3879	using the standard C<_open_osfhandle> function. For programs implementing
		3880	their own fd to handle mapping, overwriting this function makes it easier
		3881	to do so. This can be done by defining this macro to an appropriate value.
		3882
		3883	=item EV_WIN32_CLOSE_FD(fd)
		3884
		3885	If programs implement their own fd to handle mapping on win32, then this
		3886	macro can be used to override the C<close> function, useful to unregister
		3887	file descriptors again. Note that the replacement function has to close
		3888	the underlying OS handle.
2965		3889
2966	=item EV_USE_POLL	3890	=item EV_USE_POLL
2967		3891
2968	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3892	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2969	backend. Otherwise it will be enabled on non-win32 platforms. It	3893	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3016	as well as for signal and thread safety in C<ev_async> watchers.	3940	as well as for signal and thread safety in C<ev_async> watchers.
3017		3941
3018	In the absence of this define, libev will use C<sig_atomic_t volatile>	3942	In the absence of this define, libev will use C<sig_atomic_t volatile>
3019	(from F<signal.h>), which is usually good enough on most platforms.	3943	(from F<signal.h>), which is usually good enough on most platforms.
3020		3944
3021	=item EV_H	3945	=item EV_H (h)
3022		3946
3023	The name of the F<ev.h> header file used to include it. The default if	3947	The name of the F<ev.h> header file used to include it. The default if
3024	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	3948	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3025	used to virtually rename the F<ev.h> header file in case of conflicts.	3949	used to virtually rename the F<ev.h> header file in case of conflicts.
3026		3950
3027	=item EV_CONFIG_H	3951	=item EV_CONFIG_H (h)
3028		3952
3029	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	3953	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3030	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	3954	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3031	C<EV_H>, above.	3955	C<EV_H>, above.
3032		3956
3033	=item EV_EVENT_H	3957	=item EV_EVENT_H (h)
3034		3958
3035	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	3959	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3036	of how the F<event.h> header can be found, the default is C<"event.h">.	3960	of how the F<event.h> header can be found, the default is C<"event.h">.
3037		3961
3038	=item EV_PROTOTYPES	3962	=item EV_PROTOTYPES (h)
3039		3963
3040	If defined to be C<0>, then F<ev.h> will not define any function	3964	If defined to be C<0>, then F<ev.h> will not define any function
3041	prototypes, but still define all the structs and other symbols. This is	3965	prototypes, but still define all the structs and other symbols. This is
3042	occasionally useful if you want to provide your own wrapper functions	3966	occasionally useful if you want to provide your own wrapper functions
3043	around libev functions.	3967	around libev functions.
…		…
3062	When doing priority-based operations, libev usually has to linearly search	3986	When doing priority-based operations, libev usually has to linearly search
3063	all the priorities, so having many of them (hundreds) uses a lot of space	3987	all the priorities, so having many of them (hundreds) uses a lot of space
3064	and time, so using the defaults of five priorities (-2 .. +2) is usually	3988	and time, so using the defaults of five priorities (-2 .. +2) is usually
3065	fine.	3989	fine.
3066		3990
3067	If your embedding application does not need any priorities, defining these both to	3991	If your embedding application does not need any priorities, defining these
3068	C<0> will save some memory and CPU.	3992	both to C<0> will save some memory and CPU.
3069		3993
3070	=item EV_PERIODIC_ENABLE	3994	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		3995	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		3996	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3071		3997
3072	If undefined or defined to be C<1>, then periodic timers are supported. If	3998	If undefined or defined to be C<1> (and the platform supports it), then
3073	defined to be C<0>, then they are not. Disabling them saves a few kB of	3999	the respective watcher type is supported. If defined to be C<0>, then it
3074	code.	4000	is not. Disabling watcher types mainly saves code size.
3075		4001
3076	=item EV_IDLE_ENABLE	4002	=item EV_FEATURES
3077
3078	If undefined or defined to be C<1>, then idle watchers are supported. If
3079	defined to be C<0>, then they are not. Disabling them saves a few kB of
3080	code.
3081
3082	=item EV_EMBED_ENABLE
3083
3084	If undefined or defined to be C<1>, then embed watchers are supported. If
3085	defined to be C<0>, then they are not.
3086
3087	=item EV_STAT_ENABLE
3088
3089	If undefined or defined to be C<1>, then stat watchers are supported. If
3090	defined to be C<0>, then they are not.
3091
3092	=item EV_FORK_ENABLE
3093
3094	If undefined or defined to be C<1>, then fork watchers are supported. If
3095	defined to be C<0>, then they are not.
3096
3097	=item EV_ASYNC_ENABLE
3098
3099	If undefined or defined to be C<1>, then async watchers are supported. If
3100	defined to be C<0>, then they are not.
3101
3102	=item EV_MINIMAL
3103		4003
3104	If you need to shave off some kilobytes of code at the expense of some	4004	If you need to shave off some kilobytes of code at the expense of some
3105	speed, define this symbol to C<1>. Currently this is used to override some	4005	speed (but with the full API), you can define this symbol to request
3106	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4006	certain subsets of functionality. The default is to enable all features
3107	much smaller 2-heap for timer management over the default 4-heap.	4007	that can be enabled on the platform.
		4008
		4009	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4010	with some broad features you want) and then selectively re-enable
		4011	additional parts you want, for example if you want everything minimal,
		4012	but multiple event loop support, async and child watchers and the poll
		4013	backend, use this:
		4014
		4015	#define EV_FEATURES 0
		4016	#define EV_MULTIPLICITY 1
		4017	#define EV_USE_POLL 1
		4018	#define EV_CHILD_ENABLE 1
		4019	#define EV_ASYNC_ENABLE 1
		4020
		4021	The actual value is a bitset, it can be a combination of the following
		4022	values:
		4023
		4024	=over 4
		4025
		4026	=item C<1> - faster/larger code
		4027
		4028	Use larger code to speed up some operations.
		4029
		4030	Currently this is used to override some inlining decisions (enlarging the
		4031	code size by roughly 30% on amd64).
		4032
		4033	When optimising for size, use of compiler flags such as C<-Os> with
		4034	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4035	assertions.
		4036
		4037	=item C<2> - faster/larger data structures
		4038
		4039	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4040	hash table sizes and so on. This will usually further increase code size
		4041	and can additionally have an effect on the size of data structures at
		4042	runtime.
		4043
		4044	=item C<4> - full API configuration
		4045
		4046	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4047	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4048
		4049	=item C<8> - full API
		4050
		4051	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4052	details on which parts of the API are still available without this
		4053	feature, and do not complain if this subset changes over time.
		4054
		4055	=item C<16> - enable all optional watcher types
		4056
		4057	Enables all optional watcher types. If you want to selectively enable
		4058	only some watcher types other than I/O and timers (e.g. prepare,
		4059	embed, async, child...) you can enable them manually by defining
		4060	C<EV_watchertype_ENABLE> to C<1> instead.
		4061
		4062	=item C<32> - enable all backends
		4063
		4064	This enables all backends - without this feature, you need to enable at
		4065	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4066
		4067	=item C<64> - enable OS-specific "helper" APIs
		4068
		4069	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4070	default.
		4071
		4072	=back
		4073
		4074	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4075	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4076	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4077	watchers, timers and monotonic clock support.
		4078
		4079	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4080	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4081	your program might be left out as well - a binary starting a timer and an
		4082	I/O watcher then might come out at only 5Kb.
		4083
		4084	=item EV_AVOID_STDIO
		4085
		4086	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4087	functions (printf, scanf, perror etc.). This will increase the code size
		4088	somewhat, but if your program doesn't otherwise depend on stdio and your
		4089	libc allows it, this avoids linking in the stdio library which is quite
		4090	big.
		4091
		4092	Note that error messages might become less precise when this option is
		4093	enabled.
		4094
		4095	=item EV_NSIG
		4096
		4097	The highest supported signal number, +1 (or, the number of
		4098	signals): Normally, libev tries to deduce the maximum number of signals
		4099	automatically, but sometimes this fails, in which case it can be
		4100	specified. Also, using a lower number than detected (C<32> should be
		4101	good for about any system in existence) can save some memory, as libev
		4102	statically allocates some 12-24 bytes per signal number.
3108		4103
3109	=item EV_PID_HASHSIZE	4104	=item EV_PID_HASHSIZE
3110		4105
3111	C<ev_child> watchers use a small hash table to distribute workload by	4106	C<ev_child> watchers use a small hash table to distribute workload by
3112	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4107	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3113	than enough. If you need to manage thousands of children you might want to	4108	usually more than enough. If you need to manage thousands of children you
3114	increase this value (I<must> be a power of two).	4109	might want to increase this value (I<must> be a power of two).
3115		4110
3116	=item EV_INOTIFY_HASHSIZE	4111	=item EV_INOTIFY_HASHSIZE
3117		4112
3118	C<ev_stat> watchers use a small hash table to distribute workload by	4113	C<ev_stat> watchers use a small hash table to distribute workload by
3119	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4114	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3120	usually more than enough. If you need to manage thousands of C<ev_stat>	4115	disabled), usually more than enough. If you need to manage thousands of
3121	watchers you might want to increase this value (I<must> be a power of	4116	C<ev_stat> watchers you might want to increase this value (I<must> be a
3122	two).	4117	power of two).
3123		4118
3124	=item EV_USE_4HEAP	4119	=item EV_USE_4HEAP
3125		4120
3126	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4121	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3127	timer and periodics heap, libev uses a 4-heap when this symbol is defined	4122	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3128	to C<1>. The 4-heap uses more complicated (longer) code but has	4123	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3129	noticeably faster performance with many (thousands) of watchers.	4124	faster performance with many (thousands) of watchers.
3130		4125
3131	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4126	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3132	(disabled).	4127	will be C<0>.
3133		4128
3134	=item EV_HEAP_CACHE_AT	4129	=item EV_HEAP_CACHE_AT
3135		4130
3136	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4131	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3137	timer and periodics heap, libev can cache the timestamp (I<at>) within	4132	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3138	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4133	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3139	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4134	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3140	but avoids random read accesses on heap changes. This improves performance	4135	but avoids random read accesses on heap changes. This improves performance
3141	noticeably with with many (hundreds) of watchers.	4136	noticeably with many (hundreds) of watchers.
3142		4137
3143	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4138	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3144	(disabled).	4139	will be C<0>.
3145		4140
3146	=item EV_VERIFY	4141	=item EV_VERIFY
3147		4142
3148	Controls how much internal verification (see C<ev_loop_verify ()>) will	4143	Controls how much internal verification (see C<ev_verify ()>) will
3149	be done: If set to C<0>, no internal verification code will be compiled	4144	be done: If set to C<0>, no internal verification code will be compiled
3150	in. If set to C<1>, then verification code will be compiled in, but not	4145	in. If set to C<1>, then verification code will be compiled in, but not
3151	called. If set to C<2>, then the internal verification code will be	4146	called. If set to C<2>, then the internal verification code will be
3152	called once per loop, which can slow down libev. If set to C<3>, then the	4147	called once per loop, which can slow down libev. If set to C<3>, then the
3153	verification code will be called very frequently, which will slow down	4148	verification code will be called very frequently, which will slow down
3154	libev considerably.	4149	libev considerably.
3155		4150
3156	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4151	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3157	C<0.>	4152	will be C<0>.
3158		4153
3159	=item EV_COMMON	4154	=item EV_COMMON
3160		4155
3161	By default, all watchers have a C<void *data> member. By redefining	4156	By default, all watchers have a C<void *data> member. By redefining
3162	this macro to a something else you can include more and other types of	4157	this macro to something else you can include more and other types of
3163	members. You have to define it each time you include one of the files,	4158	members. You have to define it each time you include one of the files,
3164	though, and it must be identical each time.	4159	though, and it must be identical each time.
3165		4160
3166	For example, the perl EV module uses something like this:	4161	For example, the perl EV module uses something like this:
3167		4162
…		…
3179	and the way callbacks are invoked and set. Must expand to a struct member	4174	and the way callbacks are invoked and set. Must expand to a struct member
3180	definition and a statement, respectively. See the F<ev.h> header file for	4175	definition and a statement, respectively. See the F<ev.h> header file for
3181	their default definitions. One possible use for overriding these is to	4176	their default definitions. One possible use for overriding these is to
3182	avoid the C<struct ev_loop *> as first argument in all cases, or to use	4177	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3183	method calls instead of plain function calls in C++.	4178	method calls instead of plain function calls in C++.
		4179
		4180	=back
3184		4181
3185	=head2 EXPORTED API SYMBOLS	4182	=head2 EXPORTED API SYMBOLS
3186		4183
3187	If you need to re-export the API (e.g. via a DLL) and you need a list of	4184	If you need to re-export the API (e.g. via a DLL) and you need a list of
3188	exported symbols, you can use the provided F<Symbol.*> files which list	4185	exported symbols, you can use the provided F<Symbol.*> files which list
…		…
3218	file.	4215	file.
3219		4216
3220	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4217	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3221	that everybody includes and which overrides some configure choices:	4218	that everybody includes and which overrides some configure choices:
3222		4219
3223	#define EV_MINIMAL 1	4220	#define EV_FEATURES 8
3224	#define EV_USE_POLL 0	4221	#define EV_USE_SELECT 1
3225	#define EV_MULTIPLICITY 0
3226	#define EV_PERIODIC_ENABLE 0	4222	#define EV_PREPARE_ENABLE 1
		4223	#define EV_IDLE_ENABLE 1
3227	#define EV_STAT_ENABLE 0	4224	#define EV_SIGNAL_ENABLE 1
3228	#define EV_FORK_ENABLE 0	4225	#define EV_CHILD_ENABLE 1
		4226	#define EV_USE_STDEXCEPT 0
3229	#define EV_CONFIG_H <config.h>	4227	#define EV_CONFIG_H <config.h>
3230	#define EV_MINPRI 0
3231	#define EV_MAXPRI 0
3232		4228
3233	#include "ev++.h"	4229	#include "ev++.h"
3234		4230
3235	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4231	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3236		4232
3237	#include "ev_cpp.h"	4233	#include "ev_cpp.h"
3238	#include "ev.c"	4234	#include "ev.c"
3239		4235
		4236	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3240		4237
3241	=head1 THREADS AND COROUTINES	4238	=head2 THREADS AND COROUTINES
3242		4239
3243	=head2 THREADS	4240	=head3 THREADS
3244		4241
3245	Libev itself is completely thread-safe, but it uses no locking. This	4242	All libev functions are reentrant and thread-safe unless explicitly
		4243	documented otherwise, but libev implements no locking itself. This means
3246	means that you can use as many loops as you want in parallel, as long as	4244	that you can use as many loops as you want in parallel, as long as there
3247	only one thread ever calls into one libev function with the same loop	4245	are no concurrent calls into any libev function with the same loop
3248	parameter.	4246	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		4247	of course): libev guarantees that different event loops share no data
		4248	structures that need any locking.
3249		4249
3250	Or put differently: calls with different loop parameters can be done in	4250	Or to put it differently: calls with different loop parameters can be done
3251	parallel from multiple threads, calls with the same loop parameter must be	4251	concurrently from multiple threads, calls with the same loop parameter
3252	done serially (but can be done from different threads, as long as only one	4252	must be done serially (but can be done from different threads, as long as
3253	thread ever is inside a call at any point in time, e.g. by using a mutex	4253	only one thread ever is inside a call at any point in time, e.g. by using
3254	per loop).	4254	a mutex per loop).
		4255
		4256	Specifically to support threads (and signal handlers), libev implements
		4257	so-called C<ev_async> watchers, which allow some limited form of
		4258	concurrency on the same event loop, namely waking it up "from the
		4259	outside".
3255		4260
3256	If you want to know which design (one loop, locking, or multiple loops	4261	If you want to know which design (one loop, locking, or multiple loops
3257	without or something else still) is best for your problem, then I cannot	4262	without or something else still) is best for your problem, then I cannot
3258	help you. I can give some generic advice however:	4263	help you, but here is some generic advice:
3259		4264
3260	=over 4	4265	=over 4
3261		4266
3262	=item * most applications have a main thread: use the default libev loop	4267	=item * most applications have a main thread: use the default libev loop
3263	in that thread, or create a separate thread running only the default loop.	4268	in that thread, or create a separate thread running only the default loop.
…		…
3275		4280
3276	Choosing a model is hard - look around, learn, know that usually you can do	4281	Choosing a model is hard - look around, learn, know that usually you can do
3277	better than you currently do :-)	4282	better than you currently do :-)
3278		4283
3279	=item * often you need to talk to some other thread which blocks in the	4284	=item * often you need to talk to some other thread which blocks in the
		4285	event loop.
		4286
3280	event loop - C<ev_async> watchers can be used to wake them up from other	4287	C<ev_async> watchers can be used to wake them up from other threads safely
3281	threads safely (or from signal contexts...).	4288	(or from signal contexts...).
		4289
		4290	An example use would be to communicate signals or other events that only
		4291	work in the default loop by registering the signal watcher with the
		4292	default loop and triggering an C<ev_async> watcher from the default loop
		4293	watcher callback into the event loop interested in the signal.
3282		4294
3283	=back	4295	=back
3284		4296
		4297	=head4 THREAD LOCKING EXAMPLE
		4298
		4299	Here is a fictitious example of how to run an event loop in a different
		4300	thread than where callbacks are being invoked and watchers are
		4301	created/added/removed.
		4302
		4303	For a real-world example, see the C<EV::Loop::Async> perl module,
		4304	which uses exactly this technique (which is suited for many high-level
		4305	languages).
		4306
		4307	The example uses a pthread mutex to protect the loop data, a condition
		4308	variable to wait for callback invocations, an async watcher to notify the
		4309	event loop thread and an unspecified mechanism to wake up the main thread.
		4310
		4311	First, you need to associate some data with the event loop:
		4312
		4313	typedef struct {
		4314	mutex_t lock; /* global loop lock */
		4315	ev_async async_w;
		4316	thread_t tid;
		4317	cond_t invoke_cv;
		4318	} userdata;
		4319
		4320	void prepare_loop (EV_P)
		4321	{
		4322	// for simplicity, we use a static userdata struct.
		4323	static userdata u;
		4324
		4325	ev_async_init (&u->async_w, async_cb);
		4326	ev_async_start (EV_A_ &u->async_w);
		4327
		4328	pthread_mutex_init (&u->lock, 0);
		4329	pthread_cond_init (&u->invoke_cv, 0);
		4330
		4331	// now associate this with the loop
		4332	ev_set_userdata (EV_A_ u);
		4333	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4334	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4335
		4336	// then create the thread running ev_loop
		4337	pthread_create (&u->tid, 0, l_run, EV_A);
		4338	}
		4339
		4340	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4341	solely to wake up the event loop so it takes notice of any new watchers
		4342	that might have been added:
		4343
		4344	static void
		4345	async_cb (EV_P_ ev_async *w, int revents)
		4346	{
		4347	// just used for the side effects
		4348	}
		4349
		4350	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4351	protecting the loop data, respectively.
		4352
		4353	static void
		4354	l_release (EV_P)
		4355	{
		4356	userdata *u = ev_userdata (EV_A);
		4357	pthread_mutex_unlock (&u->lock);
		4358	}
		4359
		4360	static void
		4361	l_acquire (EV_P)
		4362	{
		4363	userdata *u = ev_userdata (EV_A);
		4364	pthread_mutex_lock (&u->lock);
		4365	}
		4366
		4367	The event loop thread first acquires the mutex, and then jumps straight
		4368	into C<ev_run>:
		4369
		4370	void *
		4371	l_run (void *thr_arg)
		4372	{
		4373	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4374
		4375	l_acquire (EV_A);
		4376	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4377	ev_run (EV_A_ 0);
		4378	l_release (EV_A);
		4379
		4380	return 0;
		4381	}
		4382
		4383	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4384	signal the main thread via some unspecified mechanism (signals? pipe
		4385	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4386	have been called (in a while loop because a) spurious wakeups are possible
		4387	and b) skipping inter-thread-communication when there are no pending
		4388	watchers is very beneficial):
		4389
		4390	static void
		4391	l_invoke (EV_P)
		4392	{
		4393	userdata *u = ev_userdata (EV_A);
		4394
		4395	while (ev_pending_count (EV_A))
		4396	{
		4397	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4398	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4399	}
		4400	}
		4401
		4402	Now, whenever the main thread gets told to invoke pending watchers, it
		4403	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4404	thread to continue:
		4405
		4406	static void
		4407	real_invoke_pending (EV_P)
		4408	{
		4409	userdata *u = ev_userdata (EV_A);
		4410
		4411	pthread_mutex_lock (&u->lock);
		4412	ev_invoke_pending (EV_A);
		4413	pthread_cond_signal (&u->invoke_cv);
		4414	pthread_mutex_unlock (&u->lock);
		4415	}
		4416
		4417	Whenever you want to start/stop a watcher or do other modifications to an
		4418	event loop, you will now have to lock:
		4419
		4420	ev_timer timeout_watcher;
		4421	userdata *u = ev_userdata (EV_A);
		4422
		4423	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4424
		4425	pthread_mutex_lock (&u->lock);
		4426	ev_timer_start (EV_A_ &timeout_watcher);
		4427	ev_async_send (EV_A_ &u->async_w);
		4428	pthread_mutex_unlock (&u->lock);
		4429
		4430	Note that sending the C<ev_async> watcher is required because otherwise
		4431	an event loop currently blocking in the kernel will have no knowledge
		4432	about the newly added timer. By waking up the loop it will pick up any new
		4433	watchers in the next event loop iteration.
		4434
3285	=head2 COROUTINES	4435	=head3 COROUTINES
3286		4436
3287	Libev is much more accommodating to coroutines ("cooperative threads"):	4437	Libev is very accommodating to coroutines ("cooperative threads"):
3288	libev fully supports nesting calls to it's functions from different	4438	libev fully supports nesting calls to its functions from different
3289	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4439	coroutines (e.g. you can call C<ev_run> on the same loop from two
3290	different coroutines and switch freely between both coroutines running the	4440	different coroutines, and switch freely between both coroutines running
3291	loop, as long as you don't confuse yourself). The only exception is that	4441	the loop, as long as you don't confuse yourself). The only exception is
3292	you must not do this from C<ev_periodic> reschedule callbacks.	4442	that you must not do this from C<ev_periodic> reschedule callbacks.
3293		4443
3294	Care has been invested into making sure that libev does not keep local	4444	Care has been taken to ensure that libev does not keep local state inside
3295	state inside C<ev_loop>, and other calls do not usually allow coroutine	4445	C<ev_run>, and other calls do not usually allow for coroutine switches as
3296	switches.	4446	they do not call any callbacks.
3297		4447
		4448	=head2 COMPILER WARNINGS
3298		4449
3299	=head1 COMPLEXITIES	4450	Depending on your compiler and compiler settings, you might get no or a
		4451	lot of warnings when compiling libev code. Some people are apparently
		4452	scared by this.
3300		4453
3301	In this section the complexities of (many of) the algorithms used inside	4454	However, these are unavoidable for many reasons. For one, each compiler
3302	libev will be explained. For complexity discussions about backends see the	4455	has different warnings, and each user has different tastes regarding
3303	documentation for C<ev_default_init>.	4456	warning options. "Warn-free" code therefore cannot be a goal except when
		4457	targeting a specific compiler and compiler-version.
3304		4458
3305	All of the following are about amortised time: If an array needs to be	4459	Another reason is that some compiler warnings require elaborate
3306	extended, libev needs to realloc and move the whole array, but this	4460	workarounds, or other changes to the code that make it less clear and less
3307	happens asymptotically never with higher number of elements, so O(1) might	4461	maintainable.
3308	mean it might do a lengthy realloc operation in rare cases, but on average
3309	it is much faster and asymptotically approaches constant time.
3310		4462
3311	=over 4	4463	And of course, some compiler warnings are just plain stupid, or simply
		4464	wrong (because they don't actually warn about the condition their message
		4465	seems to warn about). For example, certain older gcc versions had some
		4466	warnings that resulted in an extreme number of false positives. These have
		4467	been fixed, but some people still insist on making code warn-free with
		4468	such buggy versions.
3312		4469
3313	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	4470	While libev is written to generate as few warnings as possible,
		4471	"warn-free" code is not a goal, and it is recommended not to build libev
		4472	with any compiler warnings enabled unless you are prepared to cope with
		4473	them (e.g. by ignoring them). Remember that warnings are just that:
		4474	warnings, not errors, or proof of bugs.
3314		4475
3315	This means that, when you have a watcher that triggers in one hour and
3316	there are 100 watchers that would trigger before that then inserting will
3317	have to skip roughly seven (C<ld 100>) of these watchers.
3318		4476
3319	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	4477	=head2 VALGRIND
3320		4478
3321	That means that changing a timer costs less than removing/adding them	4479	Valgrind has a special section here because it is a popular tool that is
3322	as only the relative motion in the event queue has to be paid for.	4480	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3323		4481
3324	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	4482	If you think you found a bug (memory leak, uninitialised data access etc.)
		4483	in libev, then check twice: If valgrind reports something like:
3325		4484
3326	These just add the watcher into an array or at the head of a list.	4485	==2274== definitely lost: 0 bytes in 0 blocks.
		4486	==2274== possibly lost: 0 bytes in 0 blocks.
		4487	==2274== still reachable: 256 bytes in 1 blocks.
3327		4488
3328	=item Stopping check/prepare/idle/fork/async watchers: O(1)	4489	Then there is no memory leak, just as memory accounted to global variables
		4490	is not a memleak - the memory is still being referenced, and didn't leak.
3329		4491
3330	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	4492	Similarly, under some circumstances, valgrind might report kernel bugs
		4493	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		4494	although an acceptable workaround has been found here), or it might be
		4495	confused.
3331		4496
3332	These watchers are stored in lists then need to be walked to find the	4497	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3333	correct watcher to remove. The lists are usually short (you don't usually	4498	make it into some kind of religion.
3334	have many watchers waiting for the same fd or signal).
3335		4499
3336	=item Finding the next timer in each loop iteration: O(1)	4500	If you are unsure about something, feel free to contact the mailing list
		4501	with the full valgrind report and an explanation on why you think this
		4502	is a bug in libev (best check the archives, too :). However, don't be
		4503	annoyed when you get a brisk "this is no bug" answer and take the chance
		4504	of learning how to interpret valgrind properly.
3337		4505
3338	By virtue of using a binary or 4-heap, the next timer is always found at a	4506	If you need, for some reason, empty reports from valgrind for your project
3339	fixed position in the storage array.	4507	I suggest using suppression lists.
3340		4508
3341	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3342		4509
3343	A change means an I/O watcher gets started or stopped, which requires	4510	=head1 PORTABILITY NOTES
3344	libev to recalculate its status (and possibly tell the kernel, depending
3345	on backend and whether C<ev_io_set> was used).
3346		4511
3347	=item Activating one watcher (putting it into the pending state): O(1)	4512	=head2 GNU/LINUX 32 BIT LIMITATIONS
3348		4513
3349	=item Priority handling: O(number_of_priorities)	4514	GNU/Linux is the only common platform that supports 64 bit file/large file
		4515	interfaces but I<disables> them by default.
3350		4516
3351	Priorities are implemented by allocating some space for each	4517	That means that libev compiled in the default environment doesn't support
3352	priority. When doing priority-based operations, libev usually has to	4518	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
3353	linearly search all the priorities, but starting/stopping and activating
3354	watchers becomes O(1) w.r.t. priority handling.
3355		4519
3356	=item Sending an ev_async: O(1)	4520	Unfortunately, many programs try to work around this GNU/Linux issue
		4521	by enabling the large file API, which makes them incompatible with the
		4522	standard libev compiled for their system.
3357		4523
3358	=item Processing ev_async_send: O(number_of_async_watchers)	4524	Likewise, libev cannot enable the large file API itself as this would
		4525	suddenly make it incompatible to the default compile time environment,
		4526	i.e. all programs not using special compile switches.
3359		4527
3360	=item Processing signals: O(max_signal_number)	4528	=head2 OS/X AND DARWIN BUGS
3361		4529
3362	Sending involves a system call I<iff> there were no other C<ev_async_send>	4530	The whole thing is a bug if you ask me - basically any system interface
3363	calls in the current loop iteration. Checking for async and signal events	4531	you touch is broken, whether it is locales, poll, kqueue or even the
3364	involves iterating over all running async watchers or all signal numbers.	4532	OpenGL drivers.
3365		4533
3366	=back	4534	=head3 C<kqueue> is buggy
3367		4535
		4536	The kqueue syscall is broken in all known versions - most versions support
		4537	only sockets, many support pipes.
3368		4538
		4539	Libev tries to work around this by not using C<kqueue> by default on this
		4540	rotten platform, but of course you can still ask for it when creating a
		4541	loop - embedding a socket-only kqueue loop into a select-based one is
		4542	probably going to work well.
		4543
		4544	=head3 C<poll> is buggy
		4545
		4546	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4547	implementation by something calling C<kqueue> internally around the 10.5.6
		4548	release, so now C<kqueue> I<and> C<poll> are broken.
		4549
		4550	Libev tries to work around this by not using C<poll> by default on
		4551	this rotten platform, but of course you can still ask for it when creating
		4552	a loop.
		4553
		4554	=head3 C<select> is buggy
		4555
		4556	All that's left is C<select>, and of course Apple found a way to fuck this
		4557	one up as well: On OS/X, C<select> actively limits the number of file
		4558	descriptors you can pass in to 1024 - your program suddenly crashes when
		4559	you use more.
		4560
		4561	There is an undocumented "workaround" for this - defining
		4562	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4563	work on OS/X.
		4564
		4565	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4566
		4567	=head3 C<errno> reentrancy
		4568
		4569	The default compile environment on Solaris is unfortunately so
		4570	thread-unsafe that you can't even use components/libraries compiled
		4571	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4572	defined by default. A valid, if stupid, implementation choice.
		4573
		4574	If you want to use libev in threaded environments you have to make sure
		4575	it's compiled with C<_REENTRANT> defined.
		4576
		4577	=head3 Event port backend
		4578
		4579	The scalable event interface for Solaris is called "event
		4580	ports". Unfortunately, this mechanism is very buggy in all major
		4581	releases. If you run into high CPU usage, your program freezes or you get
		4582	a large number of spurious wakeups, make sure you have all the relevant
		4583	and latest kernel patches applied. No, I don't know which ones, but there
		4584	are multiple ones to apply, and afterwards, event ports actually work
		4585	great.
		4586
		4587	If you can't get it to work, you can try running the program by setting
		4588	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4589	C<select> backends.
		4590
		4591	=head2 AIX POLL BUG
		4592
		4593	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4594	this by trying to avoid the poll backend altogether (i.e. it's not even
		4595	compiled in), which normally isn't a big problem as C<select> works fine
		4596	with large bitsets on AIX, and AIX is dead anyway.
		4597
3369	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4598	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4599
		4600	=head3 General issues
3370		4601
3371	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4602	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3372	requires, and its I/O model is fundamentally incompatible with the POSIX	4603	requires, and its I/O model is fundamentally incompatible with the POSIX
3373	model. Libev still offers limited functionality on this platform in	4604	model. Libev still offers limited functionality on this platform in
3374	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4605	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3375	descriptors. This only applies when using Win32 natively, not when using	4606	descriptors. This only applies when using Win32 natively, not when using
3376	e.g. cygwin.	4607	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4608	as every compielr comes with a slightly differently broken/incompatible
		4609	environment.
3377		4610
3378	Lifting these limitations would basically require the full	4611	Lifting these limitations would basically require the full
3379	re-implementation of the I/O system. If you are into these kinds of	4612	re-implementation of the I/O system. If you are into this kind of thing,
3380	things, then note that glib does exactly that for you in a very portable	4613	then note that glib does exactly that for you in a very portable way (note
3381	way (note also that glib is the slowest event library known to man).	4614	also that glib is the slowest event library known to man).
3382		4615
3383	There is no supported compilation method available on windows except	4616	There is no supported compilation method available on windows except
3384	embedding it into other applications.	4617	embedding it into other applications.
		4618
		4619	Sensible signal handling is officially unsupported by Microsoft - libev
		4620	tries its best, but under most conditions, signals will simply not work.
3385		4621
3386	Not a libev limitation but worth mentioning: windows apparently doesn't	4622	Not a libev limitation but worth mentioning: windows apparently doesn't
3387	accept large writes: instead of resulting in a partial write, windows will	4623	accept large writes: instead of resulting in a partial write, windows will
3388	either accept everything or return C<ENOBUFS> if the buffer is too large,	4624	either accept everything or return C<ENOBUFS> if the buffer is too large,
3389	so make sure you only write small amounts into your sockets (less than a	4625	so make sure you only write small amounts into your sockets (less than a
3390	megabyte seems safe, but thsi apparently depends on the amount of memory	4626	megabyte seems safe, but this apparently depends on the amount of memory
3391	available).	4627	available).
3392		4628
3393	Due to the many, low, and arbitrary limits on the win32 platform and	4629	Due to the many, low, and arbitrary limits on the win32 platform and
3394	the abysmal performance of winsockets, using a large number of sockets	4630	the abysmal performance of winsockets, using a large number of sockets
3395	is not recommended (and not reasonable). If your program needs to use	4631	is not recommended (and not reasonable). If your program needs to use
3396	more than a hundred or so sockets, then likely it needs to use a totally	4632	more than a hundred or so sockets, then likely it needs to use a totally
3397	different implementation for windows, as libev offers the POSIX readiness	4633	different implementation for windows, as libev offers the POSIX readiness
3398	notification model, which cannot be implemented efficiently on windows	4634	notification model, which cannot be implemented efficiently on windows
3399	(Microsoft monopoly games).	4635	(due to Microsoft monopoly games).
3400		4636
3401	A typical way to use libev under windows is to embed it (see the embedding	4637	A typical way to use libev under windows is to embed it (see the embedding
3402	section for details) and use the following F<evwrap.h> header file instead	4638	section for details) and use the following F<evwrap.h> header file instead
3403	of F<ev.h>:	4639	of F<ev.h>:
3404		4640
…		…
3406	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	4642	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3407		4643
3408	#include "ev.h"	4644	#include "ev.h"
3409		4645
3410	And compile the following F<evwrap.c> file into your project (make sure	4646	And compile the following F<evwrap.c> file into your project (make sure
3411	you do I<not> compile the F<ev.c> or any other embedded soruce files!):	4647	you do I<not> compile the F<ev.c> or any other embedded source files!):
3412		4648
3413	#include "evwrap.h"	4649	#include "evwrap.h"
3414	#include "ev.c"	4650	#include "ev.c"
3415		4651
3416	=over 4
3417
3418	=item The winsocket select function	4652	=head3 The winsocket C<select> function
3419		4653
3420	The winsocket C<select> function doesn't follow POSIX in that it	4654	The winsocket C<select> function doesn't follow POSIX in that it
3421	requires socket I<handles> and not socket I<file descriptors> (it is	4655	requires socket I<handles> and not socket I<file descriptors> (it is
3422	also extremely buggy). This makes select very inefficient, and also	4656	also extremely buggy). This makes select very inefficient, and also
3423	requires a mapping from file descriptors to socket handles (the Microsoft	4657	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3432	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4666	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3433		4667
3434	Note that winsockets handling of fd sets is O(n), so you can easily get a	4668	Note that winsockets handling of fd sets is O(n), so you can easily get a
3435	complexity in the O(n²) range when using win32.	4669	complexity in the O(n²) range when using win32.
3436		4670
3437	=item Limited number of file descriptors	4671	=head3 Limited number of file descriptors
3438		4672
3439	Windows has numerous arbitrary (and low) limits on things.	4673	Windows has numerous arbitrary (and low) limits on things.
3440		4674
3441	Early versions of winsocket's select only supported waiting for a maximum	4675	Early versions of winsocket's select only supported waiting for a maximum
3442	of C<64> handles (probably owning to the fact that all windows kernels	4676	of C<64> handles (probably owning to the fact that all windows kernels
3443	can only wait for C<64> things at the same time internally; Microsoft	4677	can only wait for C<64> things at the same time internally; Microsoft
3444	recommends spawning a chain of threads and wait for 63 handles and the	4678	recommends spawning a chain of threads and wait for 63 handles and the
3445	previous thread in each. Great).	4679	previous thread in each. Sounds great!).
3446		4680
3447	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4681	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3448	to some high number (e.g. C<2048>) before compiling the winsocket select	4682	to some high number (e.g. C<2048>) before compiling the winsocket select
3449	call (which might be in libev or elsewhere, for example, perl does its own	4683	call (which might be in libev or elsewhere, for example, perl and many
3450	select emulation on windows).	4684	other interpreters do their own select emulation on windows).
3451		4685
3452	Another limit is the number of file descriptors in the Microsoft runtime	4686	Another limit is the number of file descriptors in the Microsoft runtime
3453	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4687	libraries, which by default is C<64> (there must be a hidden I<64>
3454	or something like this inside Microsoft). You can increase this by calling	4688	fetish or something like this inside Microsoft). You can increase this
3455	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4689	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3456	arbitrary limit), but is broken in many versions of the Microsoft runtime	4690	(another arbitrary limit), but is broken in many versions of the Microsoft
3457	libraries.
3458
3459	This might get you to about C<512> or C<2048> sockets (depending on	4691	runtime libraries. This might get you to about C<512> or C<2048> sockets
3460	windows version and/or the phase of the moon). To get more, you need to	4692	(depending on windows version and/or the phase of the moon). To get more,
3461	wrap all I/O functions and provide your own fd management, but the cost of	4693	you need to wrap all I/O functions and provide your own fd management, but
3462	calling select (O(n²)) will likely make this unworkable.	4694	the cost of calling select (O(n²)) will likely make this unworkable.
3463		4695
3464	=back
3465
3466
3467	=head1 PORTABILITY REQUIREMENTS	4696	=head2 PORTABILITY REQUIREMENTS
3468		4697
3469	In addition to a working ISO-C implementation, libev relies on a few	4698	In addition to a working ISO-C implementation and of course the
3470	additional extensions:	4699	backend-specific APIs, libev relies on a few additional extensions:
3471		4700
3472	=over 4	4701	=over 4
3473		4702
3474	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	4703	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3475	calling conventions regardless of C<ev_watcher_type *>.	4704	calling conventions regardless of C<ev_watcher_type *>.
…		…
3481	calls them using an C<ev_watcher *> internally.	4710	calls them using an C<ev_watcher *> internally.
3482		4711
3483	=item C<sig_atomic_t volatile> must be thread-atomic as well	4712	=item C<sig_atomic_t volatile> must be thread-atomic as well
3484		4713
3485	The type C<sig_atomic_t volatile> (or whatever is defined as	4714	The type C<sig_atomic_t volatile> (or whatever is defined as
3486	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	4715	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3487	threads. This is not part of the specification for C<sig_atomic_t>, but is	4716	threads. This is not part of the specification for C<sig_atomic_t>, but is
3488	believed to be sufficiently portable.	4717	believed to be sufficiently portable.
3489		4718
3490	=item C<sigprocmask> must work in a threaded environment	4719	=item C<sigprocmask> must work in a threaded environment
3491		4720
…		…
3500	except the initial one, and run the default loop in the initial thread as	4729	except the initial one, and run the default loop in the initial thread as
3501	well.	4730	well.
3502		4731
3503	=item C<long> must be large enough for common memory allocation sizes	4732	=item C<long> must be large enough for common memory allocation sizes
3504		4733
3505	To improve portability and simplify using libev, libev uses C<long>	4734	To improve portability and simplify its API, libev uses C<long> internally
3506	internally instead of C<size_t> when allocating its data structures. On	4735	instead of C<size_t> when allocating its data structures. On non-POSIX
3507	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4736	systems (Microsoft...) this might be unexpectedly low, but is still at
3508	is still at least 31 bits everywhere, which is enough for hundreds of	4737	least 31 bits everywhere, which is enough for hundreds of millions of
3509	millions of watchers.	4738	watchers.
3510		4739
3511	=item C<double> must hold a time value in seconds with enough accuracy	4740	=item C<double> must hold a time value in seconds with enough accuracy
3512		4741
3513	The type C<double> is used to represent timestamps. It is required to	4742	The type C<double> is used to represent timestamps. It is required to
3514	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4743	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3515	enough for at least into the year 4000. This requirement is fulfilled by	4744	good enough for at least into the year 4000 with millisecond accuracy
		4745	(the design goal for libev). This requirement is overfulfilled by
3516	implementations implementing IEEE 754 (basically all existing ones).	4746	implementations using IEEE 754, which is basically all existing ones. With
		4747	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
3517		4748
3518	=back	4749	=back
3519		4750
3520	If you know of other additional requirements drop me a note.	4751	If you know of other additional requirements drop me a note.
3521		4752
3522		4753
3523	=head1 COMPILER WARNINGS	4754	=head1 ALGORITHMIC COMPLEXITIES
3524		4755
3525	Depending on your compiler and compiler settings, you might get no or a	4756	In this section the complexities of (many of) the algorithms used inside
3526	lot of warnings when compiling libev code. Some people are apparently	4757	libev will be documented. For complexity discussions about backends see
3527	scared by this.	4758	the documentation for C<ev_default_init>.
3528		4759
3529	However, these are unavoidable for many reasons. For one, each compiler	4760	All of the following are about amortised time: If an array needs to be
3530	has different warnings, and each user has different tastes regarding	4761	extended, libev needs to realloc and move the whole array, but this
3531	warning options. "Warn-free" code therefore cannot be a goal except when	4762	happens asymptotically rarer with higher number of elements, so O(1) might
3532	targeting a specific compiler and compiler-version.	4763	mean that libev does a lengthy realloc operation in rare cases, but on
		4764	average it is much faster and asymptotically approaches constant time.
3533		4765
3534	Another reason is that some compiler warnings require elaborate	4766	=over 4
3535	workarounds, or other changes to the code that make it less clear and less
3536	maintainable.
3537		4767
3538	And of course, some compiler warnings are just plain stupid, or simply	4768	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3539	wrong (because they don't actually warn about the condition their message
3540	seems to warn about).
3541		4769
3542	While libev is written to generate as few warnings as possible,	4770	This means that, when you have a watcher that triggers in one hour and
3543	"warn-free" code is not a goal, and it is recommended not to build libev	4771	there are 100 watchers that would trigger before that, then inserting will
3544	with any compiler warnings enabled unless you are prepared to cope with	4772	have to skip roughly seven (C<ld 100>) of these watchers.
3545	them (e.g. by ignoring them). Remember that warnings are just that:
3546	warnings, not errors, or proof of bugs.
3547		4773
		4774	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3548		4775
3549	=head1 VALGRIND	4776	That means that changing a timer costs less than removing/adding them,
		4777	as only the relative motion in the event queue has to be paid for.
3550		4778
3551	Valgrind has a special section here because it is a popular tool that is	4779	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3552	highly useful, but valgrind reports are very hard to interpret.
3553		4780
3554	If you think you found a bug (memory leak, uninitialised data access etc.)	4781	These just add the watcher into an array or at the head of a list.
3555	in libev, then check twice: If valgrind reports something like:
3556		4782
3557	==2274== definitely lost: 0 bytes in 0 blocks.	4783	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3558	==2274== possibly lost: 0 bytes in 0 blocks.
3559	==2274== still reachable: 256 bytes in 1 blocks.
3560		4784
3561	Then there is no memory leak. Similarly, under some circumstances,	4785	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3562	valgrind might report kernel bugs as if it were a bug in libev, or it
3563	might be confused (it is a very good tool, but only a tool).
3564		4786
3565	If you are unsure about something, feel free to contact the mailing list	4787	These watchers are stored in lists, so they need to be walked to find the
3566	with the full valgrind report and an explanation on why you think this is	4788	correct watcher to remove. The lists are usually short (you don't usually
3567	a bug in libev. However, don't be annoyed when you get a brisk "this is	4789	have many watchers waiting for the same fd or signal: one is typical, two
3568	no bug" answer and take the chance of learning how to interpret valgrind	4790	is rare).
3569	properly.
3570		4791
3571	If you need, for some reason, empty reports from valgrind for your project	4792	=item Finding the next timer in each loop iteration: O(1)
3572	I suggest using suppression lists.
3573		4793
		4794	By virtue of using a binary or 4-heap, the next timer is always found at a
		4795	fixed position in the storage array.
		4796
		4797	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4798
		4799	A change means an I/O watcher gets started or stopped, which requires
		4800	libev to recalculate its status (and possibly tell the kernel, depending
		4801	on backend and whether C<ev_io_set> was used).
		4802
		4803	=item Activating one watcher (putting it into the pending state): O(1)
		4804
		4805	=item Priority handling: O(number_of_priorities)
		4806
		4807	Priorities are implemented by allocating some space for each
		4808	priority. When doing priority-based operations, libev usually has to
		4809	linearly search all the priorities, but starting/stopping and activating
		4810	watchers becomes O(1) with respect to priority handling.
		4811
		4812	=item Sending an ev_async: O(1)
		4813
		4814	=item Processing ev_async_send: O(number_of_async_watchers)
		4815
		4816	=item Processing signals: O(max_signal_number)
		4817
		4818	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4819	calls in the current loop iteration. Checking for async and signal events
		4820	involves iterating over all running async watchers or all signal numbers.
		4821
		4822	=back
		4823
		4824
		4825	=head1 PORTING FROM LIBEV 3.X TO 4.X
		4826
		4827	The major version 4 introduced some minor incompatible changes to the API.
		4828
		4829	At the moment, the C<ev.h> header file tries to implement superficial
		4830	compatibility, so most programs should still compile. Those might be
		4831	removed in later versions of libev, so better update early than late.
		4832
		4833	=over 4
		4834
		4835	=item function/symbol renames
		4836
		4837	A number of functions and symbols have been renamed:
		4838
		4839	ev_loop => ev_run
		4840	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		4841	EVLOOP_ONESHOT => EVRUN_ONCE
		4842
		4843	ev_unloop => ev_break
		4844	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		4845	EVUNLOOP_ONE => EVBREAK_ONE
		4846	EVUNLOOP_ALL => EVBREAK_ALL
		4847
		4848	EV_TIMEOUT => EV_TIMER
		4849
		4850	ev_loop_count => ev_iteration
		4851	ev_loop_depth => ev_depth
		4852	ev_loop_verify => ev_verify
		4853
		4854	Most functions working on C<struct ev_loop> objects don't have an
		4855	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		4856	associated constants have been renamed to not collide with the C<struct
		4857	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		4858	as all other watcher types. Note that C<ev_loop_fork> is still called
		4859	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		4860	typedef.
		4861
		4862	=item C<EV_COMPAT3> backwards compatibility mechanism
		4863
		4864	The backward compatibility mechanism can be controlled by
		4865	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		4866	section.
		4867
		4868	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		4869
		4870	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		4871	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		4872	and work, but the library code will of course be larger.
		4873
		4874	=back
		4875
		4876
		4877	=head1 GLOSSARY
		4878
		4879	=over 4
		4880
		4881	=item active
		4882
		4883	A watcher is active as long as it has been started and not yet stopped.
		4884	See L<WATCHER STATES> for details.
		4885
		4886	=item application
		4887
		4888	In this document, an application is whatever is using libev.
		4889
		4890	=item backend
		4891
		4892	The part of the code dealing with the operating system interfaces.
		4893
		4894	=item callback
		4895
		4896	The address of a function that is called when some event has been
		4897	detected. Callbacks are being passed the event loop, the watcher that
		4898	received the event, and the actual event bitset.
		4899
		4900	=item callback/watcher invocation
		4901
		4902	The act of calling the callback associated with a watcher.
		4903
		4904	=item event
		4905
		4906	A change of state of some external event, such as data now being available
		4907	for reading on a file descriptor, time having passed or simply not having
		4908	any other events happening anymore.
		4909
		4910	In libev, events are represented as single bits (such as C<EV_READ> or
		4911	C<EV_TIMER>).
		4912
		4913	=item event library
		4914
		4915	A software package implementing an event model and loop.
		4916
		4917	=item event loop
		4918
		4919	An entity that handles and processes external events and converts them
		4920	into callback invocations.
		4921
		4922	=item event model
		4923
		4924	The model used to describe how an event loop handles and processes
		4925	watchers and events.
		4926
		4927	=item pending
		4928
		4929	A watcher is pending as soon as the corresponding event has been
		4930	detected. See L<WATCHER STATES> for details.
		4931
		4932	=item real time
		4933
		4934	The physical time that is observed. It is apparently strictly monotonic :)
		4935
		4936	=item wall-clock time
		4937
		4938	The time and date as shown on clocks. Unlike real time, it can actually
		4939	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4940	clock.
		4941
		4942	=item watcher
		4943
		4944	A data structure that describes interest in certain events. Watchers need
		4945	to be started (attached to an event loop) before they can receive events.
		4946
		4947	=back
3574		4948
3575	=head1 AUTHOR	4949	=head1 AUTHOR
3576		4950
3577	Marc Lehmann <libev@schmorp.de>.	4951	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3578		4952

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