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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 interetsing 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
…		…
359	writing a server, you should C<accept ()> in a loop to accept as many	401	writing a server, you should C<accept ()> in a loop to accept as many
360	connections as possible during one iteration. You might also want to have	402	connections as possible during one iteration. You might also want to have
361	a look at C<ev_set_io_collect_interval ()> to increase the amount of	403	a look at C<ev_set_io_collect_interval ()> to increase the amount of
362	readiness notifications you get per iteration.	404	readiness notifications you get per iteration.
363		405
		406	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		407	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		408	C<exceptfds> set on that platform).
		409
364	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	410	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
365		411
366	And this is your standard poll(2) backend. It's more complicated	412	And this is your standard poll(2) backend. It's more complicated
367	than select, but handles sparse fds better and has no artificial	413	than select, but handles sparse fds better and has no artificial
368	limit on the number of fds you can use (except it will slow down	414	limit on the number of fds you can use (except it will slow down
369	considerably with a lot of inactive fds). It scales similarly to select,	415	considerably with a lot of inactive fds). It scales similarly to select,
370	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for	416	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
371	performance tips.	417	performance tips.
372		418
		419	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		420	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		421
373	=item C<EVBACKEND_EPOLL> (value 4, Linux)	422	=item C<EVBACKEND_EPOLL> (value 4, Linux)
		423
		424	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		425	kernels).
374		426
375	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,
376	but it scales phenomenally better. While poll and select usually scale	428	but it scales phenomenally better. While poll and select usually scale
377	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),
378	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).
379	of shortcomings, such as silently dropping events in some hard-to-detect	431
380	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
381	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...).
382		450
383	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
384	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
385	(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
386	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
387	very well if you register events for both fds.	455	file descriptors might not work very well if you register events for both
388		456	file descriptors.
389	Please note that epoll sometimes generates spurious notifications, so you
390	need to use non-blocking I/O or other means to avoid blocking when no data
391	(or space) is available.
392		457
393	Best performance from this backend is achieved by not unregistering all	458	Best performance from this backend is achieved by not unregistering all
394	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,
395	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.
396		469
397	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
398	all kernel versions tested so far.	471	all kernel versions tested so far.
		472
		473	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		474	C<EVBACKEND_POLL>.
399		475
400	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	476	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
401		477
402	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
403	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
404	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
405	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
406	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
407	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)
408	system like NetBSD.	486	system like NetBSD.
409		487
410	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
411	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
…		…
413		491
414	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
415	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
416	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
417	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
418	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
419	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
420		499
421	This backend usually performs well under most conditions.	500	This backend usually performs well under most conditions.
422		501
423	While nominally embeddable in other event loops, this doesn't work	502	While nominally embeddable in other event loops, this doesn't work
424	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
425	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
426	(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
427	(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
428	sockets.	507	also broken on OS X)) and, did I mention it, using it only for sockets.
		508
		509	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		510	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		511	C<NOTE_EOF>.
429		512
430	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	513	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
431		514
432	This is not implemented yet (and might never be, unless you send me an	515	This is not implemented yet (and might never be, unless you send me an
433	implementation). According to reports, C</dev/poll> only supports sockets	516	implementation). According to reports, C</dev/poll> only supports sockets
…		…
446	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
447	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
448	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	531	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
449	might perform better.	532	might perform better.
450		533
451	On the positive side, ignoring the spurious readiness notifications, this	534	On the positive side, with the exception of the spurious readiness
452	backend actually performed to specification in all tests and is fully	535	notifications, this backend actually performed fully to specification
453	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).
		538
		539	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		540	C<EVBACKEND_POLL>.
454		541
455	=item C<EVBACKEND_ALL>	542	=item C<EVBACKEND_ALL>
456		543
457	Try all backends (even potentially broken ones that wouldn't be tried	544	Try all backends (even potentially broken ones that wouldn't be tried
458	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	545	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
460		547
461	It is definitely not recommended to use this flag.	548	It is definitely not recommended to use this flag.
462		549
463	=back	550	=back
464		551
465	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,
466	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
467	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.
468		556
469	The most typical usage is like this:	557	Example: This is the most typical usage.
470		558
471	if (!ev_default_loop (0))	559	if (!ev_default_loop (0))
472	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	560	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
473		561
474	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
475	environment settings to be taken into account:	563	environment settings to be taken into account:
476		564
477	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	565	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
478		566
479	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
480	available (warning, breaks stuff, best use only with your own private	568	used if available (warning, breaks stuff, best use only with your own
481	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):
482		571
483	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	572	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
484		573
485	=item struct ev_loop *ev_loop_new (unsigned int flags)	574	=item struct ev_loop *ev_loop_new (unsigned int flags)
486		575
487	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
488	always distinct from the default loop. Unlike the default loop, it cannot	577	always distinct from the default loop.
489	handle signal and child watchers, and attempts to do so will be greeted by
490	undefined behaviour (or a failed assertion if assertions are enabled).
491		578
492	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
493	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
494	default loop in the "main" or "initial" thread.	581	default loop in the "main" or "initial" thread.
495		582
496	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.
497		584
…		…
499	if (!epoller)	586	if (!epoller)
500	fatal ("no epoll found here, maybe it hides under your chair");	587	fatal ("no epoll found here, maybe it hides under your chair");
501		588
502	=item ev_default_destroy ()	589	=item ev_default_destroy ()
503		590
504	Destroys the default loop again (frees all memory and kernel state	591	Destroys the default loop (frees all memory and kernel state etc.). None
505	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
506	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
507	responsibility to either stop all watchers cleanly yourself I<before>	594	either stop all watchers cleanly yourself I<before> calling this function,
508	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
509	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).
510	for example).
511		597
512	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
513	this function, and related watchers (such as signal and child watchers)	599	handlers), will not be freed by this function, and related watchers (such
514	would need to be stopped manually.	600	as signal and child watchers) would need to be stopped manually.
515		601
516	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
517	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
518	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
519	C<ev_loop_new> and C<ev_loop_destroy>).	605	C<ev_loop_new> and C<ev_loop_destroy>.
520		606
521	=item ev_loop_destroy (loop)	607	=item ev_loop_destroy (loop)
522		608
523	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
524	earlier call to C<ev_loop_new>.	610	earlier call to C<ev_loop_new>.
525		611
526	=item ev_default_fork ()	612	=item ev_default_fork ()
527		613
528	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
529	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
530	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
531	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
532	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
533	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.
534		625
535	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
536	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
537	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).
538		632
539	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
540	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
541	quite nicely into a call to C<pthread_atfork>:	635	quite nicely into a call to C<pthread_atfork>:
542		636
…		…
544		638
545	=item ev_loop_fork (loop)	639	=item ev_loop_fork (loop)
546		640
547	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
548	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
549	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.
550		645
551	=item int ev_is_default_loop (loop)	646	=item int ev_is_default_loop (loop)
552		647
553	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.
554		650
555	=item unsigned int ev_loop_count (loop)	651	=item unsigned int ev_iteration (loop)
556		652
557	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
558	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>
559	happily wraps around with enough iterations.	655	and happily wraps around with enough iterations.
560		656
561	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
562	"ticks" the number of loop iterations), as it roughly corresponds with	658	"ticks" the number of loop iterations), as it roughly corresponds with
563	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.
564		674
565	=item unsigned int ev_backend (loop)	675	=item unsigned int ev_backend (loop)
566		676
567	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
568	use.	678	use.
…		…
577		687
578	=item ev_now_update (loop)	688	=item ev_now_update (loop)
579		689
580	Establishes the current time by querying the kernel, updating the time	690	Establishes the current time by querying the kernel, updating the time
581	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
582	is usually done automatically within C<ev_loop ()>.	692	is usually done automatically within C<ev_run ()>.
583		693
584	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
585	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
586	the current time is a good idea.	696	the current time is a good idea.
587		697
588	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.
589		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
590	=item ev_loop (loop, int flags)	726	=item ev_run (loop, int flags)
591		727
592	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
593	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
594	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>.
595		733
596	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
597	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.
598		737
599	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
600	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
601	finished (especially in interactive programs), but having a program that	740	finished (especially in interactive programs), but having a program
602	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
603	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.
604		744
605	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
606	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
607	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.
608		750
609	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
610	necessary) and will handle those and any outstanding ones. It will block	752	necessary) and will handle those and any already outstanding ones. It
611	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
612	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
613	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
614	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
615	usually a better approach for this kind of thing.	761	usually a better approach for this kind of thing.
616		762
617	Here are the gory details of what C<ev_loop> does:	763	Here are the gory details of what C<ev_run> does:
618		764
		765	- Increment loop depth.
		766	- Reset the ev_break status.
619	- Before the first iteration, call any pending watchers.	767	- Before the first iteration, call any pending watchers.
		768	LOOP:
620	* If EVFLAG_FORKCHECK was used, check for a fork.	769	- If EVFLAG_FORKCHECK was used, check for a fork.
621	- 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.
622	- Queue and call all prepare watchers.	771	- Queue and call all prepare watchers.
		772	- If ev_break was called, goto FINISH.
623	- If we have been forked, detach and recreate the kernel state	773	- If we have been forked, detach and recreate the kernel state
624	as to not disturb the other process.	774	as to not disturb the other process.
625	- Update the kernel state with all outstanding changes.	775	- Update the kernel state with all outstanding changes.
626	- Update the "event loop time" (ev_now ()).	776	- Update the "event loop time" (ev_now ()).
627	- Calculate for how long to sleep or block, if at all	777	- Calculate for how long to sleep or block, if at all
628	(active idle watchers, EVLOOP_NONBLOCK or not having	778	(active idle watchers, EVRUN_NOWAIT or not having
629	any active watchers at all will result in not sleeping).	779	any active watchers at all will result in not sleeping).
630	- 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.
631	- Block the process, waiting for any events.	782	- Block the process, waiting for any events.
632	- Queue all outstanding I/O (fd) events.	783	- Queue all outstanding I/O (fd) events.
633	- 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.
634	- Queue all outstanding timers.	785	- Queue all expired timers.
635	- Queue all outstanding periodics.	786	- Queue all expired periodics.
636	- Unless any events are pending now, queue all idle watchers.	787	- Queue all idle watchers with priority higher than that of pending events.
637	- Queue all check watchers.	788	- Queue all check watchers.
638	- 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).
639	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
640	be handled here by queueing them when their watcher gets executed.	791	be handled here by queueing them when their watcher gets executed.
641	- 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
642	were used, or there are no active watchers, return, otherwise	793	were used, or there are no active watchers, goto FINISH, otherwise
643	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.
644		799
645	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
646	anymore.	801	anymore.
647		802
648	... queue jobs here, make sure they register event watchers as long	803	... queue jobs here, make sure they register event watchers as long
649	... 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..)
650	ev_loop (my_loop, 0);	805	ev_run (my_loop, 0);
651	... jobs done or somebody called unloop. yeah!	806	... jobs done or somebody called unloop. yeah!
652		807
653	=item ev_unloop (loop, how)	808	=item ev_break (loop, how)
654		809
655	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
656	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
657	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
658	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.
659		814
660	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##
661		818
662	=item ev_ref (loop)	819	=item ev_ref (loop)
663		820
664	=item ev_unref (loop)	821	=item ev_unref (loop)
665		822
666	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
667	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
668	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.
669	a watcher you never unregister that should not keep C<ev_loop> from	826
670	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
671	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
672	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
673	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
674	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
675	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
676	(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
677	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).
678		841
679	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>
680	running when nothing else is active.	843	running when nothing else is active.
681		844
682	struct ev_signal exitsig;	845	ev_signal exitsig;
683	ev_signal_init (&exitsig, sig_cb, SIGINT);	846	ev_signal_init (&exitsig, sig_cb, SIGINT);
684	ev_signal_start (loop, &exitsig);	847	ev_signal_start (loop, &exitsig);
685	evf_unref (loop);	848	evf_unref (loop);
686		849
687	Example: For some weird reason, unregister the above signal handler again.	850	Example: For some weird reason, unregister the above signal handler again.
…		…
701	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>)
702	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
703	to increase efficiency of loop iterations (or to increase power-saving	866	to increase efficiency of loop iterations (or to increase power-saving
704	opportunities).	867	opportunities).
705		868
706	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
707	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
708	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
709	events, especially with backends like C<select ()> which have a high	872	events, especially with backends like C<select ()> which have a high
710	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.
711		874
712	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
713	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,
714	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
715	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
716	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.
717		882
718	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
719	to spend more time collecting timeouts, at the expense of increased	884	to spend more time collecting timeouts, at the expense of increased
720	latency (the watcher callback will be called later). C<ev_io> watchers	885	latency/jitter/inexactness (the watcher callback will be called
721	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
722	any overhead in libev.	887	value will not introduce any overhead in libev.
723		888
724	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
725	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
726	interactive servers (of course not for games), likewise for timeouts. It	891	interactive servers (of course not for games), likewise for timeouts. It
727	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>,
728	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).
729		898
730	Setting the I<timeout collect interval> can improve the opportunity for	899	Setting the I<timeout collect interval> can improve the opportunity for
731	saving power, as the program will "bundle" timer callback invocations that	900	saving power, as the program will "bundle" timer callback invocations that
732	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
733	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
734	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
735	they fire on, say, one-second boundaries only.	904	they fire on, say, one-second boundaries only.
736		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
737	=item ev_loop_verify (loop)	981	=item ev_verify (loop)
738		982
739	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
740	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
741	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
742	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 ()>.
743		988
744	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
745	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
746	data structures consistent.	991	data structures consistent.
747		992
748	=back	993	=back
749		994
750		995
751	=head1 ANATOMY OF A WATCHER	996	=head1 ANATOMY OF A WATCHER
752		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
753	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
754	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
755	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:
756		1006
757	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)
758	{	1008	{
759	ev_io_stop (w);	1009	ev_io_stop (w);
760	ev_unloop (loop, EVUNLOOP_ALL);	1010	ev_break (loop, EVBREAK_ALL);
761	}	1011	}
762		1012
763	struct ev_loop *loop = ev_default_loop (0);	1013	struct ev_loop *loop = ev_default_loop (0);
		1014
764	struct ev_io stdin_watcher;	1015	ev_io stdin_watcher;
		1016
765	ev_init (&stdin_watcher, my_cb);	1017	ev_init (&stdin_watcher, my_cb);
766	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1018	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
767	ev_io_start (loop, &stdin_watcher);	1019	ev_io_start (loop, &stdin_watcher);
		1020
768	ev_loop (loop, 0);	1021	ev_run (loop, 0);
769		1022
770	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
771	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
772	although this can sometimes be quite valid).	1025	stack).
773		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
774	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
775	(watcher *, callback)>, which expects a callback to be provided. This	1031	*, callback)>, which expects a callback to be provided. This callback is
776	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
777	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
778	is readable and/or writable).	1034	and/or writable).
779		1035
780	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 *, ...) >>
781	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
782	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<<
783	(watcher *, callback, ...) >>.	1039	ev_TYPE_init (watcher *, callback, ...) >>.
784		1040
785	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
786	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
787	*) >>), 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
788	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1044	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
789		1045
790	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
791	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
792	reinitialise it or call its C<set> macro.	1048	reinitialise it or call its C<ev_TYPE_set> macro.
793		1049
794	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
795	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
796	third argument.	1052	third argument.
797		1053
…		…
806	=item C<EV_WRITE>	1062	=item C<EV_WRITE>
807		1063
808	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
809	writable.	1065	writable.
810		1066
811	=item C<EV_TIMEOUT>	1067	=item C<EV_TIMER>
812		1068
813	The C<ev_timer> watcher has timed out.	1069	The C<ev_timer> watcher has timed out.
814		1070
815	=item C<EV_PERIODIC>	1071	=item C<EV_PERIODIC>
816		1072
…		…
834		1090
835	=item C<EV_PREPARE>	1091	=item C<EV_PREPARE>
836		1092
837	=item C<EV_CHECK>	1093	=item C<EV_CHECK>
838		1094
839	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
840	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
841	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
842	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
843	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
844	(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
845	C<ev_loop> from blocking).	1101	C<ev_run> from blocking).
846		1102
847	=item C<EV_EMBED>	1103	=item C<EV_EMBED>
848		1104
849	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.
850		1106
…		…
854	C<ev_fork>).	1110	C<ev_fork>).
855		1111
856	=item C<EV_ASYNC>	1112	=item C<EV_ASYNC>
857		1113
858	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>).
859		1120
860	=item C<EV_ERROR>	1121	=item C<EV_ERROR>
861		1122
862	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
863	happen because the watcher could not be properly started because libev	1124	happen because the watcher could not be properly started because libev
864	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
865	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
866	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.
867		1132
868	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
869	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
870	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
871	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
872	programs, though, so beware.	1137	programs, though, as the fd could already be closed and reused for another
		1138	thing, so beware.
873		1139
874	=back	1140	=back
875		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
876	=head2 GENERIC WATCHER FUNCTIONS	1201	=head2 GENERIC WATCHER FUNCTIONS
877
878	In the following description, C<TYPE> stands for the watcher type,
879	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
880		1202
881	=over 4	1203	=over 4
882		1204
883	=item C<ev_init> (ev_TYPE *watcher, callback)	1205	=item C<ev_init> (ev_TYPE *watcher, callback)
884		1206
…		…
890	which rolls both calls into one.	1212	which rolls both calls into one.
891		1213
892	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
893	(or never started) and there are no pending events outstanding.	1215	(or never started) and there are no pending events outstanding.
894		1216
895	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,
896	int revents)>.	1218	int revents)>.
897		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
898	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1226	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
899		1227
900	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
901	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
902	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
903	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
904	difference to the C<ev_init> macro).	1232	difference to the C<ev_init> macro).
905		1233
906	Although some watcher types do not have type-specific arguments	1234	Although some watcher types do not have type-specific arguments
907	(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.
908		1236
		1237	See C<ev_init>, above, for an example.
		1238
909	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1239	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
910		1240
911	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
912	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
913	a watcher. The same limitations apply, of course.	1243	a watcher. The same limitations apply, of course.
914		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
915	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1249	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
916		1250
917	Starts (activates) the given watcher. Only active watchers will receive	1251	Starts (activates) the given watcher. Only active watchers will receive
918	events. If the watcher is already active nothing will happen.	1252	events. If the watcher is already active nothing will happen.
919		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
920	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1259	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
921		1260
922	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
923	status. It is possible that stopped watchers are pending (for example,	1264	It is possible that stopped watchers are pending - for example,
924	non-repeating timers are being stopped when they become pending), but	1265	non-repeating timers are being stopped when they become pending - but
925	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
926	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
927	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.
928		1269
929	=item bool ev_is_active (ev_TYPE *watcher)	1270	=item bool ev_is_active (ev_TYPE *watcher)
930		1271
931	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
932	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
…		…
948	=item ev_cb_set (ev_TYPE *watcher, callback)	1289	=item ev_cb_set (ev_TYPE *watcher, callback)
949		1290
950	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
951	(modulo threads).	1292	(modulo threads).
952		1293
953	=item ev_set_priority (ev_TYPE *watcher, priority)	1294	=item ev_set_priority (ev_TYPE *watcher, int priority)
954		1295
955	=item int ev_priority (ev_TYPE *watcher)	1296	=item int ev_priority (ev_TYPE *watcher)
956		1297
957	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
958	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>
959	(default: C<-2>). Pending watchers with higher priority will be invoked	1300	(default: C<-2>). Pending watchers with higher priority will be invoked
960	before watchers with lower priority, but priority will not keep watchers	1301	before watchers with lower priority, but priority will not keep watchers
961	from being executed (except for C<ev_idle> watchers).	1302	from being executed (except for C<ev_idle> watchers).
962		1303
963	This means that priorities are I<only> used for ordering callback
964	invocation after new events have been received. This is useful, for
965	example, to reduce latency after idling, or more often, to bind two
966	watchers on the same event and make sure one is called first.
967
968	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
969	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.
970		1306
971	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
972	pending.	1308	pending.
973		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
974	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
975	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 :).
976		1316
977	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
978	fine, as long as you do not mind that the priority value you query might	1318	priorities.
979	or might not have been adjusted to be within valid range.
980		1319
981	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1320	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
982		1321
983	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
984	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
985	can deal with that fact.	1324	can deal with that fact, as both are simply passed through to the
		1325	callback.
986		1326
987	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1327	=item int ev_clear_pending (loop, ev_TYPE *watcher)
988		1328
989	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
990	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
991	watcher isn't pending it does nothing and returns C<0>.	1331	watcher isn't pending it does nothing and returns C<0>.
992		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
993	=back	1350	=back
994		1351
995		1352
996	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1353	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
997		1354
998	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
999	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
1000	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
1001	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
1002	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
1003	data:	1360	data:
1004		1361
1005	struct my_io	1362	struct my_io
1006	{	1363	{
1007	struct ev_io io;	1364	ev_io io;
1008	int otherfd;	1365	int otherfd;
1009	void *somedata;	1366	void *somedata;
1010	struct whatever *mostinteresting;	1367	struct whatever *mostinteresting;
1011	};	1368	};
1012		1369
…		…
1015	ev_io_init (&w.io, my_cb, fd, EV_READ);	1372	ev_io_init (&w.io, my_cb, fd, EV_READ);
1016		1373
1017	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
1018	can cast it back to your own type:	1375	can cast it back to your own type:
1019		1376
1020	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)
1021	{	1378	{
1022	struct my_io *w = (struct my_io *)w_;	1379	struct my_io *w = (struct my_io *)w_;
1023	...	1380	...
1024	}	1381	}
1025		1382
…		…
1036	ev_timer t2;	1393	ev_timer t2;
1037	}	1394	}
1038		1395
1039	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
1040	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
1041	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
1042	arithmetic using C<offsetof> inside your watchers:	1399	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1400	programmers):
1043		1401
1044	#include <stddef.h>	1402	#include <stddef.h>
1045		1403
1046	static void	1404	static void
1047	t1_cb (EV_P_ struct ev_timer *w, int revents)	1405	t1_cb (EV_P_ ev_timer *w, int revents)
1048	{	1406	{
1049	struct my_biggy big = (struct my_biggy *	1407	struct my_biggy big = (struct my_biggy *)
1050	(((char *)w) - offsetof (struct my_biggy, t1));	1408	(((char *)w) - offsetof (struct my_biggy, t1));
1051	}	1409	}
1052		1410
1053	static void	1411	static void
1054	t2_cb (EV_P_ struct ev_timer *w, int revents)	1412	t2_cb (EV_P_ ev_timer *w, int revents)
1055	{	1413	{
1056	struct my_biggy big = (struct my_biggy *	1414	struct my_biggy big = (struct my_biggy *)
1057	(((char *)w) - offsetof (struct my_biggy, t2));	1415	(((char *)w) - offsetof (struct my_biggy, t2));
1058	}	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.
1059		1520
1060		1521
1061	=head1 WATCHER TYPES	1522	=head1 WATCHER TYPES
1062		1523
1063	This section describes each watcher in detail, but will not repeat	1524	This section describes each watcher in detail, but will not repeat
…		…
1087	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
1088	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
1089	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
1090	required if you know what you are doing).	1551	required if you know what you are doing).
1091		1552
1092	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
1093	(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
1094	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.
1095		1558
1096	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
1097	receive "spurious" readiness notifications, that is your callback might	1560	receive "spurious" readiness notifications, that is your callback might
1098	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
1099	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
1100	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
1101	this situation even with a relatively standard program structure. Thus	1564	this situation even with a relatively standard program structure. Thus
1102	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
1103	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.
1104		1567
1105	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
1106	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
1107	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
1108	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
1109	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.
1110		1577
1111	=head3 The special problem of disappearing file descriptors	1578	=head3 The special problem of disappearing file descriptors
1112		1579
1113	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
1114	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,
1115	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
1116	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
1117	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
1118	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
1119	fact, a different file descriptor.	1586	fact, a different file descriptor.
1120		1587
…		…
1151	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1618	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1152	C<EVBACKEND_POLL>.	1619	C<EVBACKEND_POLL>.
1153		1620
1154	=head3 The special problem of SIGPIPE	1621	=head3 The special problem of SIGPIPE
1155		1622
1156	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>:
1157	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
1158	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
1159	this is sensible behaviour, for daemons, this is usually undesirable.	1626	this is sensible behaviour, for daemons, this is usually undesirable.
1160		1627
1161	So when you encounter spurious, unexplained daemon exits, make sure you	1628	So when you encounter spurious, unexplained daemon exits, make sure you
1162	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
1163	somewhere, as that would have given you a big clue).	1630	somewhere, as that would have given you a big clue).
1164		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.
1165		1670
1166	=head3 Watcher-Specific Functions	1671	=head3 Watcher-Specific Functions
1167		1672
1168	=over 4	1673	=over 4
1169		1674
1170	=item ev_io_init (ev_io *, callback, int fd, int events)	1675	=item ev_io_init (ev_io *, callback, int fd, int events)
1171		1676
1172	=item ev_io_set (ev_io *, int fd, int events)	1677	=item ev_io_set (ev_io *, int fd, int events)
1173		1678
1174	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
1175	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
1176	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.
1177		1682
1178	=item int fd [read-only]	1683	=item int fd [read-only]
1179		1684
1180	The file descriptor being watched.	1685	The file descriptor being watched.
1181		1686
…		…
1190	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
1191	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
1192	attempt to read a whole line in the callback.	1697	attempt to read a whole line in the callback.
1193		1698
1194	static void	1699	static void
1195	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)
1196	{	1701	{
1197	ev_io_stop (loop, w);	1702	ev_io_stop (loop, w);
1198	.. 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
1199	}	1704	}
1200		1705
1201	...	1706	...
1202	struct ev_loop *loop = ev_default_init (0);	1707	struct ev_loop *loop = ev_default_init (0);
1203	struct ev_io stdin_readable;	1708	ev_io stdin_readable;
1204	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);
1205	ev_io_start (loop, &stdin_readable);	1710	ev_io_start (loop, &stdin_readable);
1206	ev_loop (loop, 0);	1711	ev_run (loop, 0);
1207		1712
1208		1713
1209	=head2 C<ev_timer> - relative and optionally repeating timeouts	1714	=head2 C<ev_timer> - relative and optionally repeating timeouts
1210		1715
1211	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
1212	given time, and optionally repeating in regular intervals after that.	1717	given time, and optionally repeating in regular intervals after that.
1213		1718
1214	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
1215	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
1216	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
1217	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1722	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1218	monotonic clock option helps a lot here).	1723	monotonic clock option helps a lot here).
1219		1724
1220	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
1221	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
1222	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 :)
1223		1906
1224	=head3 The special problem of time updates	1907	=head3 The special problem of time updates
1225		1908
1226	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
1227	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
1228	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
1229	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
1230	lots of events.	1913	lots of events in one iteration.
1231		1914
1232	The relative timeouts are calculated relative to the C<ev_now ()>	1915	The relative timeouts are calculated relative to the C<ev_now ()>
1233	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
1234	of the event triggering whatever timeout you are modifying/starting. If	1917	of the event triggering whatever timeout you are modifying/starting. If
1235	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
…		…
1239		1922
1240	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
1241	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
1242	()>.	1925	()>.
1243		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
1244	=head3 Watcher-Specific Functions and Data Members	1957	=head3 Watcher-Specific Functions and Data Members
1245		1958
1246	=over 4	1959	=over 4
1247		1960
1248	=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)
…		…
1271	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).
1272		1985
1273	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
1274	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.
1275		1988
1276	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
1277	example: Imagine you have a TCP connection and you want a so-called idle	1990	usage example.
1278	timeout, that is, you want to be called when there have been, say, 60
1279	seconds of inactivity on the socket. The easiest way to do this is to
1280	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1281	C<ev_timer_again> each time you successfully read or write some data. If
1282	you go into an idle state where you do not expect data to travel on the
1283	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1284	automatically restart it if need be.
1285		1991
1286	That means you can ignore the C<after> value and C<ev_timer_start>	1992	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1287	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1288		1993
1289	ev_timer_init (timer, callback, 0., 5.);	1994	Returns the remaining time until a timer fires. If the timer is active,
1290	ev_timer_again (loop, timer);	1995	then this time is relative to the current event loop time, otherwise it's
1291	...	1996	the timeout value currently configured.
1292	timer->again = 17.;
1293	ev_timer_again (loop, timer);
1294	...
1295	timer->again = 10.;
1296	ev_timer_again (loop, timer);
1297		1997
1298	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
1299	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.
1300		2003
1301	=item ev_tstamp repeat [read-write]	2004	=item ev_tstamp repeat [read-write]
1302		2005
1303	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
1304	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),
1305	which is also when any modifications are taken into account.	2008	which is also when any modifications are taken into account.
1306		2009
1307	=back	2010	=back
1308		2011
1309	=head3 Examples	2012	=head3 Examples
1310		2013
1311	Example: Create a timer that fires after 60 seconds.	2014	Example: Create a timer that fires after 60 seconds.
1312		2015
1313	static void	2016	static void
1314	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)
1315	{	2018	{
1316	.. one minute over, w is actually stopped right here	2019	.. one minute over, w is actually stopped right here
1317	}	2020	}
1318		2021
1319	struct ev_timer mytimer;	2022	ev_timer mytimer;
1320	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	2023	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1321	ev_timer_start (loop, &mytimer);	2024	ev_timer_start (loop, &mytimer);
1322		2025
1323	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
1324	inactivity.	2027	inactivity.
1325		2028
1326	static void	2029	static void
1327	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2030	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1328	{	2031	{
1329	.. ten seconds without any activity	2032	.. ten seconds without any activity
1330	}	2033	}
1331		2034
1332	struct ev_timer mytimer;	2035	ev_timer mytimer;
1333	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 */
1334	ev_timer_again (&mytimer); /* start timer */	2037	ev_timer_again (&mytimer); /* start timer */
1335	ev_loop (loop, 0);	2038	ev_run (loop, 0);
1336		2039
1337	// 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":
1338	// reset the timeout to start ticking again at 10 seconds	2041	// reset the timeout to start ticking again at 10 seconds
1339	ev_timer_again (&mytimer);	2042	ev_timer_again (&mytimer);
1340		2043
…		…
1342	=head2 C<ev_periodic> - to cron or not to cron?	2045	=head2 C<ev_periodic> - to cron or not to cron?
1343		2046
1344	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
1345	(and unfortunately a bit complex).	2048	(and unfortunately a bit complex).
1346		2049
1347	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
1348	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
1349	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
1350	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
1351	+ 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
1352	clock to January of the previous year, then it will take more than year	2055	wrist-watch).
1353	to trigger the event (unlike an C<ev_timer>, which would still trigger
1354	roughly 10 seconds later as it uses a relative timeout).
1355		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
1356	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
1357	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
1358	complicated, rules.	2067	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2068	those cannot react to time jumps.
1359		2069
1360	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
1361	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
1362	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).
1363		2075
1364	=head3 Watcher-Specific Functions and Data Members	2076	=head3 Watcher-Specific Functions and Data Members
1365		2077
1366	=over 4	2078	=over 4
1367		2079
1368	=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)
1369		2081
1370	=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)
1371		2083
1372	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
1373	operation, and we will explain them from simplest to complex:	2085	operation, and we will explain them from simplest to most complex:
1374		2086
1375	=over 4	2087	=over 4
1376		2088
1377	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2089	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1378		2090
1379	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
1380	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
1381	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
1382	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.
1383		2096
1384	=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)
1385		2098
1386	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
1387	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
1388	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.
1389		2103
1390	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
1391	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
1392	the hour:	2106	hour, on the hour (with respect to UTC):
1393		2107
1394	ev_periodic_set (&periodic, 0., 3600., 0);	2108	ev_periodic_set (&periodic, 0., 3600., 0);
1395		2109
1396	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,
1397	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
1398	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
1399	by 3600.	2113	by 3600.
1400		2114
1401	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
1402	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
1403	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.
1404		2118
1405	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
1406	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
1407	this value, and in fact is often specified as zero.	2121	this value, and in fact is often specified as zero.
1408		2122
1409	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
1410	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
1411	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
1412	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).
1413		2127
1414	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2128	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1415		2129
1416	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
1417	ignored. Instead, each time the periodic watcher gets scheduled, the	2131	ignored. Instead, each time the periodic watcher gets scheduled, the
1418	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
1419	current time as second argument.	2133	current time as second argument.
1420		2134
1421	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,
1422	ever, or make ANY event loop modifications whatsoever>.	2136	or make ANY other event loop modifications whatsoever, unless explicitly
		2137	allowed by documentation here>.
1423		2138
1424	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
1425	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
1426	only event loop modification you are allowed to do).	2141	only event loop modification you are allowed to do).
1427		2142
1428	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	2143	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1429	*w, ev_tstamp now)>, e.g.:	2144	*w, ev_tstamp now)>, e.g.:
1430		2145
		2146	static ev_tstamp
1431	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	2147	my_rescheduler (ev_periodic *w, ev_tstamp now)
1432	{	2148	{
1433	return now + 60.;	2149	return now + 60.;
1434	}	2150	}
1435		2151
1436	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
…		…
1456	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
1457	program when the crontabs have changed).	2173	program when the crontabs have changed).
1458		2174
1459	=item ev_tstamp ev_periodic_at (ev_periodic *)	2175	=item ev_tstamp ev_periodic_at (ev_periodic *)
1460		2176
1461	When active, returns the absolute time that the watcher is supposed to	2177	When active, returns the absolute time that the watcher is supposed
1462	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.
1463		2181
1464	=item ev_tstamp offset [read-write]	2182	=item ev_tstamp offset [read-write]
1465		2183
1466	When repeating, this contains the offset value, otherwise this is the	2184	When repeating, this contains the offset value, otherwise this is the
1467	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).
1468		2187
1469	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
1470	timer fires or C<ev_periodic_again> is being called.	2189	timer fires or C<ev_periodic_again> is being called.
1471		2190
1472	=item ev_tstamp interval [read-write]	2191	=item ev_tstamp interval [read-write]
1473		2192
1474	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
1475	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
1476	called.	2195	called.
1477		2196
1478	=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]
1479		2198
1480	The current reschedule callback, or C<0>, if this functionality is	2199	The current reschedule callback, or C<0>, if this functionality is
1481	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
1482	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.
1483		2202
1484	=back	2203	=back
1485		2204
1486	=head3 Examples	2205	=head3 Examples
1487		2206
1488	Example: Call a callback every hour, or, more precisely, whenever the	2207	Example: Call a callback every hour, or, more precisely, whenever the
1489	system clock is divisible by 3600. The callback invocation times have	2208	system time is divisible by 3600. The callback invocation times have
1490	potentially a lot of jitter, but good long-term stability.	2209	potentially a lot of jitter, but good long-term stability.
1491		2210
1492	static void	2211	static void
1493	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2212	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1494	{	2213	{
1495	... 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)
1496	}	2215	}
1497		2216
1498	struct ev_periodic hourly_tick;	2217	ev_periodic hourly_tick;
1499	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2218	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1500	ev_periodic_start (loop, &hourly_tick);	2219	ev_periodic_start (loop, &hourly_tick);
1501		2220
1502	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:
1503		2222
1504	#include <math.h>	2223	#include <math.h>
1505		2224
1506	static ev_tstamp	2225	static ev_tstamp
1507	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2226	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1508	{	2227	{
1509	return fmod (now, 3600.) + 3600.;	2228	return now + (3600. - fmod (now, 3600.));
1510	}	2229	}
1511		2230
1512	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);
1513		2232
1514	Example: Call a callback every hour, starting now:	2233	Example: Call a callback every hour, starting now:
1515		2234
1516	struct ev_periodic hourly_tick;	2235	ev_periodic hourly_tick;
1517	ev_periodic_init (&hourly_tick, clock_cb,	2236	ev_periodic_init (&hourly_tick, clock_cb,
1518	fmod (ev_now (loop), 3600.), 3600., 0);	2237	fmod (ev_now (loop), 3600.), 3600., 0);
1519	ev_periodic_start (loop, &hourly_tick);	2238	ev_periodic_start (loop, &hourly_tick);
1520		2239
1521		2240
…		…
1524	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
1525	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
1526	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
1527	normal event processing, like any other event.	2246	normal event processing, like any other event.
1528		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
1529	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
1530	first watcher gets started will libev actually register a signal watcher	2259	When the first watcher gets started will libev actually register something
1531	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
1532	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).
1533	watcher for a signal is stopped libev will reset the signal handler to
1534	SIG_DFL (regardless of what it was set to before).
1535		2262
1536	If possible and supported, libev will install its handlers with	2263	If possible and supported, libev will install its handlers with
1537	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2264	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1538	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
1539	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
1540	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.
1541		2297
1542	=head3 Watcher-Specific Functions and Data Members	2298	=head3 Watcher-Specific Functions and Data Members
1543		2299
1544	=over 4	2300	=over 4
1545		2301
…		…
1556		2312
1557	=back	2313	=back
1558		2314
1559	=head3 Examples	2315	=head3 Examples
1560		2316
1561	Example: Try to exit cleanly on SIGINT and SIGTERM.	2317	Example: Try to exit cleanly on SIGINT.
1562		2318
1563	static void	2319	static void
1564	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2320	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1565	{	2321	{
1566	ev_unloop (loop, EVUNLOOP_ALL);	2322	ev_break (loop, EVBREAK_ALL);
1567	}	2323	}
1568		2324
1569	struct ev_signal signal_watcher;	2325	ev_signal signal_watcher;
1570	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2326	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1571	ev_signal_start (loop, &sigint_cb);	2327	ev_signal_start (loop, &signal_watcher);
1572		2328
1573		2329
1574	=head2 C<ev_child> - watch out for process status changes	2330	=head2 C<ev_child> - watch out for process status changes
1575		2331
1576	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
1577	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
1578	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
1579	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
1580	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.
1581		2340
1582	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
1583	you can only register child watchers in the default event loop.	2342	you can only register child watchers in the default event loop.
1584		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
1585	=head3 Process Interaction	2348	=head3 Process Interaction
1586		2349
1587	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
1588	initialised. This is necessary to guarantee proper behaviour even if	2351	initialised. This is necessary to guarantee proper behaviour even if the
1589	the first child watcher is started after the child exits. The occurrence	2352	first child watcher is started after the child exits. The occurrence
1590	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2353	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1591	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
1592	children, even ones not watched.	2355	children, even ones not watched.
1593		2356
1594	=head3 Overriding the Built-In Processing	2357	=head3 Overriding the Built-In Processing
…		…
1604	=head3 Stopping the Child Watcher	2367	=head3 Stopping the Child Watcher
1605		2368
1606	Currently, the child watcher never gets stopped, even when the	2369	Currently, the child watcher never gets stopped, even when the
1607	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
1608	callback. Future versions of libev might stop the watcher automatically	2371	callback. Future versions of libev might stop the watcher automatically
1609	when a child exit is detected.	2372	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2373	problem).
1610		2374
1611	=head3 Watcher-Specific Functions and Data Members	2375	=head3 Watcher-Specific Functions and Data Members
1612		2376
1613	=over 4	2377	=over 4
1614		2378
…		…
1646	its completion.	2410	its completion.
1647		2411
1648	ev_child cw;	2412	ev_child cw;
1649		2413
1650	static void	2414	static void
1651	child_cb (EV_P_ struct ev_child *w, int revents)	2415	child_cb (EV_P_ ev_child *w, int revents)
1652	{	2416	{
1653	ev_child_stop (EV_A_ w);	2417	ev_child_stop (EV_A_ w);
1654	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);
1655	}	2419	}
1656		2420
…		…
1671		2435
1672		2436
1673	=head2 C<ev_stat> - did the file attributes just change?	2437	=head2 C<ev_stat> - did the file attributes just change?
1674		2438
1675	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
1676	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)
1677	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.
1678		2443
1679	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
1680	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
1681	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
1682	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
1683	the stat buffer having unspecified contents.	2448	least one) and all the other fields of the stat buffer having unspecified
		2449	contents.
1684		2450
1685	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
1686	relative and your working directory changes, the behaviour is undefined.	2453	your working directory changes, then the behaviour is undefined.
1687		2454
1688	Since there is no standard to do this, the portable implementation simply	2455	Since there is no portable change notification interface available, the
1689	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
1690	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
1691	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
1692	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
1693	five seconds, although this might change dynamically). Libev will also	2460	(which you can expect to be around five seconds, although this might
1694	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
1695	usually overkill.	2462	currently around C<0.1>, but that's usually overkill.
1696		2463
1697	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,
1698	as even with OS-supported change notifications, this can be	2465	as even with OS-supported change notifications, this can be
1699	resource-intensive.	2466	resource-intensive.
1700		2467
1701	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
1702	implemented (implementing kqueue support is left as an exercise for the	2469	is the Linux inotify interface (implementing kqueue support is left as an
1703	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
1704	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).
1705	not change the semantics of C<ev_stat> watchers, which means that libev
1706	sometimes needs to fall back to regular polling again even with inotify,
1707	but changes are usually detected immediately, and if the file exists there
1708	will be no polling.
1709		2472
1710	=head3 ABI Issues (Largefile Support)	2473	=head3 ABI Issues (Largefile Support)
1711		2474
1712	Libev by default (unless the user overrides this) uses the default	2475	Libev by default (unless the user overrides this) uses the default
1713	compilation environment, which means that on systems with large file	2476	compilation environment, which means that on systems with large file
1714	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
1715	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
1716	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
1717	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
1718	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
1719	most noticeably disabled with ev_stat and large file support.	2482	most noticeably displayed with ev_stat and large file support.
1720		2483
1721	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
1722	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
1723	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
1724	to exchange stat structures with application programs compiled using the	2487	to exchange stat structures with application programs compiled using the
1725	default compilation environment.	2488	default compilation environment.
1726		2489
1727	=head3 Inotify	2490	=head3 Inotify and Kqueue
1728		2491
1729	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
1730	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
1731	change detection where possible. The inotify descriptor will be created lazily	2494	inotify descriptor will be created lazily when the first C<ev_stat>
1732	when the first C<ev_stat> watcher is being started.	2495	watcher is being started.
1733		2496
1734	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
1735	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
1736	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
1737	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.
1738		2505
1739	(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
1740	implement this functionality, due to the requirement of having a file	2507	implement this functionality, due to the requirement of having a file
1741	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.
1742		2528
1743	=head3 The special problem of stat time resolution	2529	=head3 The special problem of stat time resolution
1744		2530
1745	The C<stat ()> system call only supports full-second resolution portably, and	2531	The C<stat ()> system call only supports full-second resolution portably,
1746	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
1747	only support whole seconds.	2533	still only support whole seconds.
1748		2534
1749	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
1750	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
1751	calls your callback, which does something. When there is another update	2537	calls your callback, which does something. When there is another update
1752	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
1753	data does not change.	2539	stat data does change in other ways (e.g. file size).
1754		2540
1755	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
1756	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
1757	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);
1758	ev_timer_again (loop, w)>).	2544	ev_timer_again (loop, w)>).
…		…
1778	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
1779	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
1780	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
1781	path for as long as the watcher is active.	2567	path for as long as the watcher is active.
1782		2568
1783	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,
1784	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
1785	was detected).	2571	last change was detected).
1786		2572
1787	=item ev_stat_stat (loop, ev_stat *)	2573	=item ev_stat_stat (loop, ev_stat *)
1788		2574
1789	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
1790	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
…		…
1873		2659
1874		2660
1875	=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...
1876		2662
1877	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
1878	priority are pending (prepare, check and other idle watchers do not	2664	priority are pending (prepare, check and other idle watchers do not count
1879	count).	2665	as receiving "events").
1880		2666
1881	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
1882	(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
1883	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
1884	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
…		…
1895		2681
1896	=head3 Watcher-Specific Functions and Data Members	2682	=head3 Watcher-Specific Functions and Data Members
1897		2683
1898	=over 4	2684	=over 4
1899		2685
1900	=item ev_idle_init (ev_signal *, callback)	2686	=item ev_idle_init (ev_idle *, callback)
1901		2687
1902	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
1903	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,
1904	believe me.	2690	believe me.
1905		2691
…		…
1909		2695
1910	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
1911	callback, free it. Also, use no error checking, as usual.	2697	callback, free it. Also, use no error checking, as usual.
1912		2698
1913	static void	2699	static void
1914	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2700	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1915	{	2701	{
1916	free (w);	2702	free (w);
1917	// now do something you wanted to do when the program has	2703	// now do something you wanted to do when the program has
1918	// no longer anything immediate to do.	2704	// no longer anything immediate to do.
1919	}	2705	}
1920		2706
1921	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2707	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1922	ev_idle_init (idle_watcher, idle_cb);	2708	ev_idle_init (idle_watcher, idle_cb);
1923	ev_idle_start (loop, idle_cb);	2709	ev_idle_start (loop, idle_watcher);
1924		2710
1925		2711
1926	=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!
1927		2713
1928	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:
1929	prepare watchers get invoked before the process blocks and check watchers	2715	prepare watchers get invoked before the process blocks and check watchers
1930	afterwards.	2716	afterwards.
1931		2717
1932	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
1933	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>
1934	watchers. Other loops than the current one are fine, however. The	2720	watchers. Other loops than the current one are fine, however. The
1935	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
1936	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,
1937	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
1938	called in pairs bracketing the blocking call.	2724	called in pairs bracketing the blocking call.
1939		2725
1940	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
1941	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
1942	variable changes, implement your own watchers, integrate net-snmp or a	2728	variable changes, implement your own watchers, integrate net-snmp or a
1943	coroutine library and lots more. They are also occasionally useful if	2729	coroutine library and lots more. They are also occasionally useful if
1944	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,
1945	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>
1946	watcher).	2732	watcher).
1947		2733
1948	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
1949	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
1950	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
1951	provide just this functionality). Then, in the check watcher you check for	2737	libraries provide exactly this functionality). Then, in the check watcher,
1952	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
1953	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
1954	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
1955	because you never know, you know?).	2741	nevertheless, because you never know, you know?).
1956		2742
1957	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
1958	coroutines into libev programs, by yielding to other active coroutines	2744	coroutines into libev programs, by yielding to other active coroutines
1959	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
1960	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
…		…
1963	loop from blocking if lower-priority coroutines are active, thus mapping	2749	loop from blocking if lower-priority coroutines are active, thus mapping
1964	low-priority coroutines to idle/background tasks).	2750	low-priority coroutines to idle/background tasks).
1965		2751
1966	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>)
1967	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
1968	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
1969	too) should not activate ("feed") events into libev. While libev fully	2757	activate ("feed") events into libev. While libev fully supports this, they
1970	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
1971	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
1972	(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
1973	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
1974	coexist peacefully with others).	2762	others).
1975		2763
1976	=head3 Watcher-Specific Functions and Data Members	2764	=head3 Watcher-Specific Functions and Data Members
1977		2765
1978	=over 4	2766	=over 4
1979		2767
…		…
1981		2769
1982	=item ev_check_init (ev_check *, callback)	2770	=item ev_check_init (ev_check *, callback)
1983		2771
1984	Initialises and configures the prepare or check watcher - they have no	2772	Initialises and configures the prepare or check watcher - they have no
1985	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>
1986	macros, but using them is utterly, utterly and completely pointless.	2774	macros, but using them is utterly, utterly, utterly and completely
		2775	pointless.
1987		2776
1988	=back	2777	=back
1989		2778
1990	=head3 Examples	2779	=head3 Examples
1991		2780
…		…
2004		2793
2005	static ev_io iow [nfd];	2794	static ev_io iow [nfd];
2006	static ev_timer tw;	2795	static ev_timer tw;
2007		2796
2008	static void	2797	static void
2009	io_cb (ev_loop *loop, ev_io *w, int revents)	2798	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2010	{	2799	{
2011	}	2800	}
2012		2801
2013	// create io watchers for each fd and a timer before blocking	2802	// create io watchers for each fd and a timer before blocking
2014	static void	2803	static void
2015	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2804	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2016	{	2805	{
2017	int timeout = 3600000;	2806	int timeout = 3600000;
2018	struct pollfd fds [nfd];	2807	struct pollfd fds [nfd];
2019	// actual code will need to loop here and realloc etc.	2808	// actual code will need to loop here and realloc etc.
2020	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2809	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2021		2810
2022	/* 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 */
2023	ev_timer_init (&tw, 0, timeout * 1e-3);	2812	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2024	ev_timer_start (loop, &tw);	2813	ev_timer_start (loop, &tw);
2025		2814
2026	// create one ev_io per pollfd	2815	// create one ev_io per pollfd
2027	for (int i = 0; i < nfd; ++i)	2816	for (int i = 0; i < nfd; ++i)
2028	{	2817	{
…		…
2035	}	2824	}
2036	}	2825	}
2037		2826
2038	// stop all watchers after blocking	2827	// stop all watchers after blocking
2039	static void	2828	static void
2040	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2829	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2041	{	2830	{
2042	ev_timer_stop (loop, &tw);	2831	ev_timer_stop (loop, &tw);
2043		2832
2044	for (int i = 0; i < nfd; ++i)	2833	for (int i = 0; i < nfd; ++i)
2045	{	2834	{
…		…
2084	}	2873	}
2085		2874
2086	// do not ever call adns_afterpoll	2875	// do not ever call adns_afterpoll
2087		2876
2088	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
2089	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
2090	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
2091	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
2092	this.	2881	this approach, effectively embedding EV as a client into the horrible
		2882	libglib event loop.
2093		2883
2094	static gint	2884	static gint
2095	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2885	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2096	{	2886	{
2097	int got_events = 0;	2887	int got_events = 0;
…		…
2101		2891
2102	if (timeout >= 0)	2892	if (timeout >= 0)
2103	// create/start timer	2893	// create/start timer
2104		2894
2105	// poll	2895	// poll
2106	ev_loop (EV_A_ 0);	2896	ev_run (EV_A_ 0);
2107		2897
2108	// stop timer again	2898	// stop timer again
2109	if (timeout >= 0)	2899	if (timeout >= 0)
2110	ev_timer_stop (EV_A_ &to);	2900	ev_timer_stop (EV_A_ &to);
2111		2901
…		…
2128	prioritise I/O.	2918	prioritise I/O.
2129		2919
2130	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
2131	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
2132	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
2133	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
2134	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
2135	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
2136	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 :)
2137		2928
2138	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
2139	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),
2140	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
2141	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
2142	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.
2143		2934
2144	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
2145	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
2146	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
2147	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
2148	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
2149	to C<0>, in which case the embed watcher will automatically execute the	2940	to give the embedded loop strictly lower priority for example).
2150	embedded loop sweep.
2151		2941
2152	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
2153	callback will be invoked whenever some events have been handled. You can	2943	will automatically execute the embedded loop sweep whenever necessary.
2154	set the callback to C<0> to avoid having to specify one if you are not
2155	interested in that.
2156		2944
2157	Also, there have not currently been made special provisions for forking:	2945	Fork detection will be handled transparently while the C<ev_embed> watcher
2158	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
2159	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
2160	yourself.	2948	C<ev_loop_fork> on the embedded loop.
2161		2949
2162	Unfortunately, not all backends are embeddable, only the ones returned by	2950	Unfortunately, not all backends are embeddable: only the ones returned by
2163	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2951	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2164	portable one.	2952	portable one.
2165		2953
2166	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
2167	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
2168	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
2169	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.
2170		2966
2171	=head3 Watcher-Specific Functions and Data Members	2967	=head3 Watcher-Specific Functions and Data Members
2172		2968
2173	=over 4	2969	=over 4
2174		2970
…		…
2183	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).
2184		2980
2185	=item ev_embed_sweep (loop, ev_embed *)	2981	=item ev_embed_sweep (loop, ev_embed *)
2186		2982
2187	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
2188	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
2189	appropriate way for embedded loops.	2985	appropriate way for embedded loops.
2190		2986
2191	=item struct ev_loop *other [read-only]	2987	=item struct ev_loop *other [read-only]
2192		2988
2193	The embedded event loop.	2989	The embedded event loop.
…		…
2202	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
2203	used).	2999	used).
2204		3000
2205	struct ev_loop *loop_hi = ev_default_init (0);	3001	struct ev_loop *loop_hi = ev_default_init (0);
2206	struct ev_loop *loop_lo = 0;	3002	struct ev_loop *loop_lo = 0;
2207	struct ev_embed embed;	3003	ev_embed embed;
2208		3004
2209	// see if there is a chance of getting one that works	3005	// see if there is a chance of getting one that works
2210	// (remember that a flags value of 0 means autodetection)	3006	// (remember that a flags value of 0 means autodetection)
2211	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3007	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2212	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3008	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2226	kqueue implementation). Store the kqueue/socket-only event loop in	3022	kqueue implementation). Store the kqueue/socket-only event loop in
2227	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3023	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2228		3024
2229	struct ev_loop *loop = ev_default_init (0);	3025	struct ev_loop *loop = ev_default_init (0);
2230	struct ev_loop *loop_socket = 0;	3026	struct ev_loop *loop_socket = 0;
2231	struct ev_embed embed;	3027	ev_embed embed;
2232		3028
2233	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3029	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2234	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3030	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2235	{	3031	{
2236	ev_embed_init (&embed, 0, loop_socket);	3032	ev_embed_init (&embed, 0, loop_socket);
…		…
2251	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,
2252	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
2253	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
2254	handlers will be invoked, too, of course.	3050	handlers will be invoked, too, of course.
2255		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
2256	=head3 Watcher-Specific Functions and Data Members	3085	=head3 Watcher-Specific Functions and Data Members
2257		3086
2258	=over 4	3087	=over 4
2259		3088
2260	=item ev_fork_init (ev_signal *, callback)	3089	=item ev_fork_init (ev_signal *, callback)
…		…
2264	believe me.	3093	believe me.
2265		3094
2266	=back	3095	=back
2267		3096
2268		3097
2269	=head2 C<ev_async> - how to wake up another event loop	3098	=head2 C<ev_async> - how to wake up an event loop
2270		3099
2271	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
2272	asynchronous sources such as signal handlers (as opposed to multiple event	3101	asynchronous sources such as signal handlers (as opposed to multiple event
2273	loops - those are of course safe to use in different threads).	3102	loops - those are of course safe to use in different threads).
2274		3103
2275	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,
2276	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>
2277	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
2278	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.
2279	safe.
2280		3108
2281	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,
2282	too, are asynchronous in nature, and signals, too, will be compressed	3110	too, are asynchronous in nature, and signals, too, will be compressed
2283	(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
2284	C<ev_async_sent> calls).	3112	C<ev_async_sent> calls).
…		…
2289	=head3 Queueing	3117	=head3 Queueing
2290		3118
2291	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
2292	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
2293	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
2294	need elaborate support such as pthreads.	3122	need elaborate support such as pthreads or unportable memory access
		3123	semantics.
2295		3124
2296	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
2297	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
2298	queue:	3127	queue:
2299		3128
2300	=over 4	3129	=over 4
2301		3130
2302	=item queueing from a signal handler context	3131	=item queueing from a signal handler context
2303		3132
2304	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
2305	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
2306	some fictitious SIGUSR1 handler:	3135	an example that does that for some fictitious SIGUSR1 handler:
2307		3136
2308	static ev_async mysig;	3137	static ev_async mysig;
2309		3138
2310	static void	3139	static void
2311	sigusr1_handler (void)	3140	sigusr1_handler (void)
…		…
2377	=over 4	3206	=over 4
2378		3207
2379	=item ev_async_init (ev_async *, callback)	3208	=item ev_async_init (ev_async *, callback)
2380		3209
2381	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
2382	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,
2383	believe me.	3212	trust me.
2384		3213
2385	=item ev_async_send (loop, ev_async *)	3214	=item ev_async_send (loop, ev_async *)
2386		3215
2387	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
2388	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
2389	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
2390	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
2391	section below on what exactly this means).	3220	section below on what exactly this means).
2392		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
2393	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
2394	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
2395	calls to C<ev_async_send>.	3229	repeated calls to C<ev_async_send> for the same event loop.
2396		3230
2397	=item bool = ev_async_pending (ev_async *)	3231	=item bool = ev_async_pending (ev_async *)
2398		3232
2399	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
2400	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
…		…
2403	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
2404	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,
2405	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
2406	quickly check whether invoking the loop might be a good idea.	3240	quickly check whether invoking the loop might be a good idea.
2407		3241
2408	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,
2409	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.
2410		3246
2411	=back	3247	=back
2412		3248
2413		3249
2414	=head1 OTHER FUNCTIONS	3250	=head1 OTHER FUNCTIONS
…		…
2418	=over 4	3254	=over 4
2419		3255
2420	=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)
2421		3257
2422	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
2423	callback on whichever event happens first and automatically stop both	3259	callback on whichever event happens first and automatically stops both
2424	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
2425	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
2426	more watchers yourself.	3262	more watchers yourself.
2427		3263
2428	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
2429	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
2430	C<events> set will be created and started.	3266	the given C<fd> and C<events> set will be created and started.
2431		3267
2432	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
2433	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
2434	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.
2435	dubious value.
2436		3271
2437	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
2438	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
2439	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>
2440	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.
2441		3280
2442	static void stdin_ready (int revents, void *arg)	3281	static void stdin_ready (int revents, void *arg)
2443	{	3282	{
		3283	if (revents & EV_READ)
		3284	/* stdin might have data for us, joy! */;
2444	if (revents & EV_TIMEOUT)	3285	else if (revents & EV_TIMER)
2445	/* doh, nothing entered */;	3286	/* doh, nothing entered */;
2446	else if (revents & EV_READ)
2447	/* stdin might have data for us, joy! */;
2448	}	3287	}
2449		3288
2450	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3289	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2451		3290
2452	=item ev_feed_event (ev_loop *, watcher *, int revents)
2453
2454	Feeds the given event set into the event loop, as if the specified event
2455	had happened for the specified watcher (which must be a pointer to an
2456	initialised but not necessarily started event watcher).
2457
2458	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3291	=item ev_feed_fd_event (loop, int fd, int revents)
2459		3292
2460	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
2461	the given events it.	3294	the given events it.
2462		3295
2463	=item ev_feed_signal_event (ev_loop *loop, int signum)	3296	=item ev_feed_signal_event (loop, int signum)
2464		3297
2465	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
2466	loop!).	3299	loop!).
2467		3300
2468	=back	3301	=back
…		…
2548		3381
2549	=over 4	3382	=over 4
2550		3383
2551	=item ev::TYPE::TYPE ()	3384	=item ev::TYPE::TYPE ()
2552		3385
2553	=item ev::TYPE::TYPE (struct ev_loop *)	3386	=item ev::TYPE::TYPE (loop)
2554		3387
2555	=item ev::TYPE::~TYPE	3388	=item ev::TYPE::~TYPE
2556		3389
2557	The constructor (optionally) takes an event loop to associate the watcher	3390	The constructor (optionally) takes an event loop to associate the watcher
2558	with. If it is omitted, it will use C<EV_DEFAULT>.	3391	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2590		3423
2591	myclass obj;	3424	myclass obj;
2592	ev::io iow;	3425	ev::io iow;
2593	iow.set <myclass, &myclass::io_cb> (&obj);	3426	iow.set <myclass, &myclass::io_cb> (&obj);
2594		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
2595	=item w->set<function> (void *data = 0)	3456	=item w->set<function> (void *data = 0)
2596		3457
2597	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
2598	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
2599	C<data> member and is free for you to use.	3460	C<data> member and is free for you to use.
2600		3461
2601	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)>.
2602		3463
2603	See the method-C<set> above for more details.	3464	See the method-C<set> above for more details.
2604		3465
2605	Example:	3466	Example: Use a plain function as callback.
2606		3467
2607	static void io_cb (ev::io &w, int revents) { }	3468	static void io_cb (ev::io &w, int revents) { }
2608	iow.set <io_cb> ();	3469	iow.set <io_cb> ();
2609		3470
2610	=item w->set (struct ev_loop *)	3471	=item w->set (loop)
2611		3472
2612	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
2613	do this when the watcher is inactive (and not pending either).	3474	do this when the watcher is inactive (and not pending either).
2614		3475
2615	=item w->set ([arguments])	3476	=item w->set ([arguments])
2616		3477
2617	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
2618	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
2619	automatically stopped and restarted when reconfiguring it with this	3480	C counterpart, an active watcher gets automatically stopped and restarted
2620	method.	3481	when reconfiguring it with this method.
2621		3482
2622	=item w->start ()	3483	=item w->start ()
2623		3484
2624	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
2625	constructor already stores the event loop.	3486	constructor already stores the event loop.
2626		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
2627	=item w->stop ()	3494	=item w->stop ()
2628		3495
2629	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.
2630		3497
2631	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3498	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2643		3510
2644	=back	3511	=back
2645		3512
2646	=back	3513	=back
2647		3514
2648	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
2649	the constructor.	3516	watchers in the constructor.
2650		3517
2651	class myclass	3518	class myclass
2652	{	3519	{
2653	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);
2654	ev:idle idle void idle_cb (ev::idle &w, int revents);	3522	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2655		3523
2656	myclass (int fd)	3524	myclass (int fd)
2657	{	3525	{
2658	io .set <myclass, &myclass::io_cb > (this);	3526	io .set <myclass, &myclass::io_cb > (this);
		3527	io2 .set <myclass, &myclass::io2_cb > (this);
2659	idle.set <myclass, &myclass::idle_cb> (this);	3528	idle.set <myclass, &myclass::idle_cb> (this);
2660		3529
2661	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
2662	}	3534	}
2663	};	3535	};
2664		3536
2665		3537
2666	=head1 OTHER LANGUAGE BINDINGS	3538	=head1 OTHER LANGUAGE BINDINGS
…		…
2675	=item Perl	3547	=item Perl
2676		3548
2677	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
2678	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,
2679	there are additional modules that implement libev-compatible interfaces	3551	there are additional modules that implement libev-compatible interfaces
2680	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),
2681	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>).
2682		3555
2683	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
2684	L<http://software.schmorp.de/pkg/EV>.	3557	L<http://software.schmorp.de/pkg/EV>.
2685		3558
2686	=item Python	3559	=item Python
2687		3560
2688	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
2689	seems to be quite complete and well-documented. Note, however, that the	3562	seems to be quite complete and well-documented.
2690	patch they require for libev is outright dangerous as it breaks the ABI
2691	for everybody else, and therefore, should never be applied in an installed
2692	libev (if python requires an incompatible ABI then it needs to embed
2693	libev).
2694		3563
2695	=item Ruby	3564	=item Ruby
2696		3565
2697	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
2698	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
2699	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
2700	L<http://rev.rubyforge.org/>.	3569	L<http://rev.rubyforge.org/>.
2701		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
2702	=item D	3579	=item D
2703		3580
2704	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
2705	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>.
2706		3594
2707	=back	3595	=back
2708		3596
2709		3597
2710	=head1 MACRO MAGIC	3598	=head1 MACRO MAGIC
…		…
2724	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,
2725	C<EV_A_> is used when other arguments are following. Example:	3613	C<EV_A_> is used when other arguments are following. Example:
2726		3614
2727	ev_unref (EV_A);	3615	ev_unref (EV_A);
2728	ev_timer_add (EV_A_ watcher);	3616	ev_timer_add (EV_A_ watcher);
2729	ev_loop (EV_A_ 0);	3617	ev_run (EV_A_ 0);
2730		3618
2731	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,
2732	which is often provided by the following macro.	3620	which is often provided by the following macro.
2733		3621
2734	=item C<EV_P>, C<EV_P_>	3622	=item C<EV_P>, C<EV_P_>
…		…
2774	}	3662	}
2775		3663
2776	ev_check check;	3664	ev_check check;
2777	ev_check_init (&check, check_cb);	3665	ev_check_init (&check, check_cb);
2778	ev_check_start (EV_DEFAULT_ &check);	3666	ev_check_start (EV_DEFAULT_ &check);
2779	ev_loop (EV_DEFAULT_ 0);	3667	ev_run (EV_DEFAULT_ 0);
2780		3668
2781	=head1 EMBEDDING	3669	=head1 EMBEDDING
2782		3670
2783	Libev can (and often is) directly embedded into host	3671	Libev can (and often is) directly embedded into host
2784	applications. Examples of applications that embed it include the Deliantra	3672	applications. Examples of applications that embed it include the Deliantra
…		…
2811		3699
2812	#define EV_STANDALONE 1	3700	#define EV_STANDALONE 1
2813	#include "ev.h"	3701	#include "ev.h"
2814		3702
2815	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++
2816	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
2817	as a bug).	3705	as a bug).
2818		3706
2819	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
2820	in your include path (e.g. in libev/ when using -Ilibev):	3708	in your include path (e.g. in libev/ when using -Ilibev):
2821		3709
…		…
2864	libev.m4	3752	libev.m4
2865		3753
2866	=head2 PREPROCESSOR SYMBOLS/MACROS	3754	=head2 PREPROCESSOR SYMBOLS/MACROS
2867		3755
2868	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
2869	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
2870	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.
2871		3766
2872	=over 4	3767	=over 4
2873		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
2874	=item EV_STANDALONE	3785	=item EV_STANDALONE (h)
2875		3786
2876	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
2877	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
2878	implementations for some libevent functions (such as logging, which is not	3789	implementations for some libevent functions (such as logging, which is not
2879	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
2880	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.
2881		3792
		3793	In standalone mode, libev will still try to automatically deduce the
		3794	configuration, but has to be more conservative.
		3795
2882	=item EV_USE_MONOTONIC	3796	=item EV_USE_MONOTONIC
2883		3797
2884	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
2885	monotonic clock option at both compile time and runtime. Otherwise no use	3799	monotonic clock option at both compile time and runtime. Otherwise no
2886	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,
2887	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
2888	the functionality isn't available is safe, though, although you have	3802	when the functionality isn't available is safe, though, although you have
2889	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>
2890	function is hiding in (often F<-lrt>).	3804	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2891		3805
2892	=item EV_USE_REALTIME	3806	=item EV_USE_REALTIME
2893		3807
2894	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
2895	real-time clock option at compile time (and assume its availability at	3809	real-time clock option at compile time (and assume its availability
2896	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
2897	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3811	option will be attempted. This effectively replaces C<gettimeofday>
2898	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3812	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2899	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>).
2900		3827
2901	=item EV_USE_NANOSLEEP	3828	=item EV_USE_NANOSLEEP
2902		3829
2903	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
2904	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 ()>.
…		…
2920		3847
2921	=item EV_SELECT_USE_FD_SET	3848	=item EV_SELECT_USE_FD_SET
2922		3849
2923	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>
2924	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
2925	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
2926	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
2927	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
2928	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,
2929	influence the size of the C<fd_set> used.	3856	configures the maximum size of the C<fd_set>.
2930		3857
2931	=item EV_SELECT_IS_WINSOCKET	3858	=item EV_SELECT_IS_WINSOCKET
2932		3859
2933	When defined to C<1>, the select backend will assume that	3860	When defined to C<1>, the select backend will assume that
2934	select/socket/connect etc. don't understand file descriptors but	3861	select/socket/connect etc. don't understand file descriptors but
…		…
2936	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
2937	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,
2938	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
2939	on win32. Should not be defined on non-win32 platforms.	3866	on win32. Should not be defined on non-win32 platforms.
2940		3867
2941	=item EV_FD_TO_WIN32_HANDLE	3868	=item EV_FD_TO_WIN32_HANDLE(fd)
2942		3869
2943	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
2944	file descriptors to socket handles. When not defining this symbol (the	3871	file descriptors to socket handles. When not defining this symbol (the
2945	default), then libev will call C<_get_osfhandle>, which is usually	3872	default), then libev will call C<_get_osfhandle>, which is usually
2946	correct. In some cases, programs use their own file descriptor management,	3873	correct. In some cases, programs use their own file descriptor management,
2947	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.
2948		3889
2949	=item EV_USE_POLL	3890	=item EV_USE_POLL
2950		3891
2951	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)
2952	backend. Otherwise it will be enabled on non-win32 platforms. It	3893	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
2999	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.
3000		3941
3001	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>
3002	(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.
3003		3944
3004	=item EV_H	3945	=item EV_H (h)
3005		3946
3006	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
3007	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
3008	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.
3009		3950
3010	=item EV_CONFIG_H	3951	=item EV_CONFIG_H (h)
3011		3952
3012	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
3013	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
3014	C<EV_H>, above.	3955	C<EV_H>, above.
3015		3956
3016	=item EV_EVENT_H	3957	=item EV_EVENT_H (h)
3017		3958
3018	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
3019	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">.
3020		3961
3021	=item EV_PROTOTYPES	3962	=item EV_PROTOTYPES (h)
3022		3963
3023	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
3024	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
3025	occasionally useful if you want to provide your own wrapper functions	3966	occasionally useful if you want to provide your own wrapper functions
3026	around libev functions.	3967	around libev functions.
…		…
3045	When doing priority-based operations, libev usually has to linearly search	3986	When doing priority-based operations, libev usually has to linearly search
3046	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
3047	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
3048	fine.	3989	fine.
3049		3990
3050	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
3051	C<0> will save some memory and CPU.	3992	both to C<0> will save some memory and CPU.
3052		3993
3053	=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.
3054		3997
3055	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
3056	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
3057	code.	4000	is not. Disabling watcher types mainly saves code size.
3058		4001
3059	=item EV_IDLE_ENABLE	4002	=item EV_FEATURES
3060
3061	If undefined or defined to be C<1>, then idle watchers are supported. If
3062	defined to be C<0>, then they are not. Disabling them saves a few kB of
3063	code.
3064
3065	=item EV_EMBED_ENABLE
3066
3067	If undefined or defined to be C<1>, then embed watchers are supported. If
3068	defined to be C<0>, then they are not.
3069
3070	=item EV_STAT_ENABLE
3071
3072	If undefined or defined to be C<1>, then stat watchers are supported. If
3073	defined to be C<0>, then they are not.
3074
3075	=item EV_FORK_ENABLE
3076
3077	If undefined or defined to be C<1>, then fork watchers are supported. If
3078	defined to be C<0>, then they are not.
3079
3080	=item EV_ASYNC_ENABLE
3081
3082	If undefined or defined to be C<1>, then async watchers are supported. If
3083	defined to be C<0>, then they are not.
3084
3085	=item EV_MINIMAL
3086		4003
3087	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
3088	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
3089	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
3090	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.
3091		4103
3092	=item EV_PID_HASHSIZE	4104	=item EV_PID_HASHSIZE
3093		4105
3094	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
3095	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),
3096	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
3097	increase this value (I<must> be a power of two).	4109	might want to increase this value (I<must> be a power of two).
3098		4110
3099	=item EV_INOTIFY_HASHSIZE	4111	=item EV_INOTIFY_HASHSIZE
3100		4112
3101	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
3102	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>
3103	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
3104	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
3105	two).	4117	power of two).
3106		4118
3107	=item EV_USE_4HEAP	4119	=item EV_USE_4HEAP
3108		4120
3109	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
3110	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
3111	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
3112	noticeably faster performance with many (thousands) of watchers.	4124	faster performance with many (thousands) of watchers.
3113		4125
3114	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
3115	(disabled).	4127	will be C<0>.
3116		4128
3117	=item EV_HEAP_CACHE_AT	4129	=item EV_HEAP_CACHE_AT
3118		4130
3119	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
3120	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
3121	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>),
3122	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,
3123	but avoids random read accesses on heap changes. This improves performance	4135	but avoids random read accesses on heap changes. This improves performance
3124	noticeably with with many (hundreds) of watchers.	4136	noticeably with many (hundreds) of watchers.
3125		4137
3126	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
3127	(disabled).	4139	will be C<0>.
3128		4140
3129	=item EV_VERIFY	4141	=item EV_VERIFY
3130		4142
3131	Controls how much internal verification (see C<ev_loop_verify ()>) will	4143	Controls how much internal verification (see C<ev_verify ()>) will
3132	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
3133	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
3134	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
3135	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
3136	verification code will be called very frequently, which will slow down	4148	verification code will be called very frequently, which will slow down
3137	libev considerably.	4149	libev considerably.
3138		4150
3139	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
3140	C<0.>	4152	will be C<0>.
3141		4153
3142	=item EV_COMMON	4154	=item EV_COMMON
3143		4155
3144	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
3145	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
3146	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,
3147	though, and it must be identical each time.	4159	though, and it must be identical each time.
3148		4160
3149	For example, the perl EV module uses something like this:	4161	For example, the perl EV module uses something like this:
3150		4162
…		…
3162	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
3163	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
3164	their default definitions. One possible use for overriding these is to	4176	their default definitions. One possible use for overriding these is to
3165	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
3166	method calls instead of plain function calls in C++.	4178	method calls instead of plain function calls in C++.
		4179
		4180	=back
3167		4181
3168	=head2 EXPORTED API SYMBOLS	4182	=head2 EXPORTED API SYMBOLS
3169		4183
3170	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
3171	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
…		…
3201	file.	4215	file.
3202		4216
3203	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
3204	that everybody includes and which overrides some configure choices:	4218	that everybody includes and which overrides some configure choices:
3205		4219
3206	#define EV_MINIMAL 1	4220	#define EV_FEATURES 8
3207	#define EV_USE_POLL 0	4221	#define EV_USE_SELECT 1
3208	#define EV_MULTIPLICITY 0
3209	#define EV_PERIODIC_ENABLE 0	4222	#define EV_PREPARE_ENABLE 1
		4223	#define EV_IDLE_ENABLE 1
3210	#define EV_STAT_ENABLE 0	4224	#define EV_SIGNAL_ENABLE 1
3211	#define EV_FORK_ENABLE 0	4225	#define EV_CHILD_ENABLE 1
		4226	#define EV_USE_STDEXCEPT 0
3212	#define EV_CONFIG_H <config.h>	4227	#define EV_CONFIG_H <config.h>
3213	#define EV_MINPRI 0
3214	#define EV_MAXPRI 0
3215		4228
3216	#include "ev++.h"	4229	#include "ev++.h"
3217		4230
3218	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:
3219		4232
3220	#include "ev_cpp.h"	4233	#include "ev_cpp.h"
3221	#include "ev.c"	4234	#include "ev.c"
3222		4235
		4236	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3223		4237
3224	=head1 THREADS AND COROUTINES	4238	=head2 THREADS AND COROUTINES
3225		4239
3226	=head2 THREADS	4240	=head3 THREADS
3227		4241
3228	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
3229	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
3230	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
3231	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.
3232		4249
3233	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
3234	parallel from multiple threads, calls with the same loop parameter must be	4251	concurrently from multiple threads, calls with the same loop parameter
3235	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
3236	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
3237	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".
3238		4260
3239	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
3240	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
3241	help you. I can give some generic advice however:	4263	help you, but here is some generic advice:
3242		4264
3243	=over 4	4265	=over 4
3244		4266
3245	=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
3246	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.
…		…
3258		4280
3259	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
3260	better than you currently do :-)	4282	better than you currently do :-)
3261		4283
3262	=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
3263	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
3264	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.
3265		4294
3266	=back	4295	=back
3267		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
3268	=head2 COROUTINES	4435	=head3 COROUTINES
3269		4436
3270	Libev is much more accommodating to coroutines ("cooperative threads"):	4437	Libev is very accommodating to coroutines ("cooperative threads"):
3271	libev fully supports nesting calls to it's functions from different	4438	libev fully supports nesting calls to its functions from different
3272	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
3273	different coroutines and switch freely between both coroutines running the	4440	different coroutines, and switch freely between both coroutines running
3274	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
3275	you must not do this from C<ev_periodic> reschedule callbacks.	4442	that you must not do this from C<ev_periodic> reschedule callbacks.
3276		4443
3277	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
3278	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
3279	switches.	4446	they do not call any callbacks.
3280		4447
		4448	=head2 COMPILER WARNINGS
3281		4449
3282	=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.
3283		4453
3284	In this section the complexities of (many of) the algorithms used inside	4454	However, these are unavoidable for many reasons. For one, each compiler
3285	libev will be explained. For complexity discussions about backends see the	4455	has different warnings, and each user has different tastes regarding
3286	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.
3287		4458
3288	All of the following are about amortised time: If an array needs to be	4459	Another reason is that some compiler warnings require elaborate
3289	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
3290	happens asymptotically never with higher number of elements, so O(1) might	4461	maintainable.
3291	mean it might do a lengthy realloc operation in rare cases, but on average
3292	it is much faster and asymptotically approaches constant time.
3293		4462
3294	=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.
3295		4469
3296	=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.
3297		4475
3298	This means that, when you have a watcher that triggers in one hour and
3299	there are 100 watchers that would trigger before that then inserting will
3300	have to skip roughly seven (C<ld 100>) of these watchers.
3301		4476
3302	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	4477	=head2 VALGRIND
3303		4478
3304	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
3305	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.
3306		4481
3307	=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:
3308		4484
3309	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.
3310		4488
3311	=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.
3312		4491
3313	=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.
3314		4496
3315	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
3316	correct watcher to remove. The lists are usually short (you don't usually	4498	make it into some kind of religion.
3317	have many watchers waiting for the same fd or signal).
3318		4499
3319	=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.
3320		4505
3321	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
3322	fixed position in the storage array.	4507	I suggest using suppression lists.
3323		4508
3324	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3325		4509
3326	A change means an I/O watcher gets started or stopped, which requires	4510	=head1 PORTABILITY NOTES
3327	libev to recalculate its status (and possibly tell the kernel, depending
3328	on backend and whether C<ev_io_set> was used).
3329		4511
3330	=item Activating one watcher (putting it into the pending state): O(1)	4512	=head2 GNU/LINUX 32 BIT LIMITATIONS
3331		4513
3332	=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.
3333		4516
3334	Priorities are implemented by allocating some space for each	4517	That means that libev compiled in the default environment doesn't support
3335	priority. When doing priority-based operations, libev usually has to	4518	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
3336	linearly search all the priorities, but starting/stopping and activating
3337	watchers becomes O(1) w.r.t. priority handling.
3338		4519
3339	=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.
3340		4523
3341	=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.
3342		4527
3343	=item Processing signals: O(max_signal_number)	4528	=head2 OS/X AND DARWIN BUGS
3344		4529
3345	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
3346	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
3347	involves iterating over all running async watchers or all signal numbers.	4532	OpenGL drivers.
3348		4533
3349	=back	4534	=head3 C<kqueue> is buggy
3350		4535
		4536	The kqueue syscall is broken in all known versions - most versions support
		4537	only sockets, many support pipes.
3351		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
3352	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4598	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4599
		4600	=head3 General issues
3353		4601
3354	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
3355	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
3356	model. Libev still offers limited functionality on this platform in	4604	model. Libev still offers limited functionality on this platform in
3357	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
3358	descriptors. This only applies when using Win32 natively, not when using	4606	descriptors. This only applies when using Win32 natively, not when using
3359	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.
3360		4610
3361	Lifting these limitations would basically require the full	4611	Lifting these limitations would basically require the full
3362	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,
3363	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
3364	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).
3365		4615
3366	There is no supported compilation method available on windows except	4616	There is no supported compilation method available on windows except
3367	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.
3368		4621
3369	Not a libev limitation but worth mentioning: windows apparently doesn't	4622	Not a libev limitation but worth mentioning: windows apparently doesn't
3370	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
3371	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,
3372	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
3373	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
3374	available).	4627	available).
3375		4628
3376	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
3377	the abysmal performance of winsockets, using a large number of sockets	4630	the abysmal performance of winsockets, using a large number of sockets
3378	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
3379	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
3380	different implementation for windows, as libev offers the POSIX readiness	4633	different implementation for windows, as libev offers the POSIX readiness
3381	notification model, which cannot be implemented efficiently on windows	4634	notification model, which cannot be implemented efficiently on windows
3382	(Microsoft monopoly games).	4635	(due to Microsoft monopoly games).
3383		4636
3384	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
3385	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
3386	of F<ev.h>:	4639	of F<ev.h>:
3387		4640
…		…
3389	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	4642	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3390		4643
3391	#include "ev.h"	4644	#include "ev.h"
3392		4645
3393	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
3394	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!):
3395		4648
3396	#include "evwrap.h"	4649	#include "evwrap.h"
3397	#include "ev.c"	4650	#include "ev.c"
3398		4651
3399	=over 4
3400
3401	=item The winsocket select function	4652	=head3 The winsocket C<select> function
3402		4653
3403	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
3404	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
3405	also extremely buggy). This makes select very inefficient, and also	4656	also extremely buggy). This makes select very inefficient, and also
3406	requires a mapping from file descriptors to socket handles (the Microsoft	4657	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3415	#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 */
3416		4667
3417	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
3418	complexity in the O(n²) range when using win32.	4669	complexity in the O(n²) range when using win32.
3419		4670
3420	=item Limited number of file descriptors	4671	=head3 Limited number of file descriptors
3421		4672
3422	Windows has numerous arbitrary (and low) limits on things.	4673	Windows has numerous arbitrary (and low) limits on things.
3423		4674
3424	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
3425	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
3426	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
3427	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
3428	previous thread in each. Great).	4679	previous thread in each. Sounds great!).
3429		4680
3430	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>
3431	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
3432	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
3433	select emulation on windows).	4684	other interpreters do their own select emulation on windows).
3434		4685
3435	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
3436	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>
3437	or something like this inside Microsoft). You can increase this by calling	4688	fetish or something like this inside Microsoft). You can increase this
3438	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4689	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3439	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
3440	libraries.
3441
3442	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
3443	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,
3444	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
3445	calling select (O(n²)) will likely make this unworkable.	4694	the cost of calling select (O(n²)) will likely make this unworkable.
3446		4695
3447	=back
3448
3449
3450	=head1 PORTABILITY REQUIREMENTS	4696	=head2 PORTABILITY REQUIREMENTS
3451		4697
3452	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
3453	additional extensions:	4699	backend-specific APIs, libev relies on a few additional extensions:
3454		4700
3455	=over 4	4701	=over 4
3456		4702
3457	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	4703	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3458	calling conventions regardless of C<ev_watcher_type *>.	4704	calling conventions regardless of C<ev_watcher_type *>.
…		…
3464	calls them using an C<ev_watcher *> internally.	4710	calls them using an C<ev_watcher *> internally.
3465		4711
3466	=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
3467		4713
3468	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
3469	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
3470	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
3471	believed to be sufficiently portable.	4717	believed to be sufficiently portable.
3472		4718
3473	=item C<sigprocmask> must work in a threaded environment	4719	=item C<sigprocmask> must work in a threaded environment
3474		4720
…		…
3483	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
3484	well.	4730	well.
3485		4731
3486	=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
3487		4733
3488	To improve portability and simplify using libev, libev uses C<long>	4734	To improve portability and simplify its API, libev uses C<long> internally
3489	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
3490	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4736	systems (Microsoft...) this might be unexpectedly low, but is still at
3491	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
3492	millions of watchers.	4738	watchers.
3493		4739
3494	=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
3495		4741
3496	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
3497	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
3498	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
3499	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.
3500		4748
3501	=back	4749	=back
3502		4750
3503	If you know of other additional requirements drop me a note.	4751	If you know of other additional requirements drop me a note.
3504		4752
3505		4753
3506	=head1 COMPILER WARNINGS	4754	=head1 ALGORITHMIC COMPLEXITIES
3507		4755
3508	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
3509	lot of warnings when compiling libev code. Some people are apparently	4757	libev will be documented. For complexity discussions about backends see
3510	scared by this.	4758	the documentation for C<ev_default_init>.
3511		4759
3512	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
3513	has different warnings, and each user has different tastes regarding	4761	extended, libev needs to realloc and move the whole array, but this
3514	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
3515	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.
3516		4765
3517	Another reason is that some compiler warnings require elaborate	4766	=over 4
3518	workarounds, or other changes to the code that make it less clear and less
3519	maintainable.
3520		4767
3521	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)
3522	wrong (because they don't actually warn about the condition their message
3523	seems to warn about).
3524		4769
3525	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
3526	"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
3527	with any compiler warnings enabled unless you are prepared to cope with	4772	have to skip roughly seven (C<ld 100>) of these watchers.
3528	them (e.g. by ignoring them). Remember that warnings are just that:
3529	warnings, not errors, or proof of bugs.
3530		4773
		4774	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3531		4775
3532	=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.
3533		4778
3534	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)
3535	highly useful, but valgrind reports are very hard to interpret.
3536		4780
3537	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.
3538	in libev, then check twice: If valgrind reports something like:
3539		4782
3540	==2274== definitely lost: 0 bytes in 0 blocks.	4783	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3541	==2274== possibly lost: 0 bytes in 0 blocks.
3542	==2274== still reachable: 256 bytes in 1 blocks.
3543		4784
3544	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))
3545	valgrind might report kernel bugs as if it were a bug in libev, or it
3546	might be confused (it is a very good tool, but only a tool).
3547		4786
3548	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
3549	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
3550	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
3551	no bug" answer and take the chance of learning how to interpret valgrind	4790	is rare).
3552	properly.
3553		4791
3554	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)
3555	I suggest using suppression lists.
3556		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
3557		4948
3558	=head1 AUTHOR	4949	=head1 AUTHOR
3559		4950
3560	Marc Lehmann <libev@schmorp.de>.	4951	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3561		4952

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