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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 practise
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).
…		…
176	as this indicates an incompatible change. Minor versions are usually	192	as this indicates an incompatible change. Minor versions are usually
177	compatible to older versions, so a larger minor version alone is usually	193	compatible to older versions, so a larger minor version alone is usually
178	not a problem.	194	not a problem.
179		195
180	Example: Make sure we haven't accidentally been linked against the wrong	196	Example: Make sure we haven't accidentally been linked against the wrong
181	version.	197	version (note, however, that this will not detect ABI mismatches :).
182		198
183	assert (("libev version mismatch",	199	assert (("libev version mismatch",
184	ev_version_major () == EV_VERSION_MAJOR	200	ev_version_major () == EV_VERSION_MAJOR
185	&& ev_version_minor () >= EV_VERSION_MINOR));	201	&& ev_version_minor () >= EV_VERSION_MINOR));
186		202
…		…
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	230	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
215	recommended ones.	231	recommended ones.
216		232
217	See the description of C<ev_embed> watchers for more info.	233	See the description of C<ev_embed> watchers for more info.
218		234
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	235	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
220		236
221	Sets the allocation function to use (the prototype is similar - the	237	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	238	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	239	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	240	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	266	}
251		267
252	...	268	...
253	ev_set_allocator (persistent_realloc);	269	ev_set_allocator (persistent_realloc);
254		270
255	=item ev_set_syserr_cb (void (*cb)(const char *msg));	271	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
256		272
257	Set the callback function to call on a retryable system call error (such	273	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	274	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	275	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	276	callback is set, then libev will expect it to remedy the situation, no
…		…
276		292
277	=back	293	=back
278		294
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	295	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
280		296
281	An event loop is described by a C<struct ev_loop *>. The library knows two	297	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	298	I<not> optional in case unless libev 3 compatibility is disabled, as libev
283	events, and dynamically created loops which do not.	299	3 had an C<ev_loop> function colliding with the struct name).
		300
		301	The library knows two types of such loops, the I<default> loop, which
		302	supports signals and child events, and dynamically created event loops
		303	which do not.
284		304
285	=over 4	305	=over 4
286		306
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	307	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		308
…		…
294	If you don't know what event loop to use, use the one returned from this	314	If you don't know what event loop to use, use the one returned from this
295	function.	315	function.
296		316
297	Note that this function is I<not> thread-safe, so if you want to use it	317	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,	318	from multiple threads, you have to lock (note also that this is unlikely,
299	as loops cannot bes hared easily between threads anyway).	319	as loops cannot be shared easily between threads anyway).
300		320
301	The default loop is the only loop that can handle C<ev_signal> and	321	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	322	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	323	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	324	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	346	useful to try out specific backends to test their performance, or to work
327	around bugs.	347	around bugs.
328		348
329	=item C<EVFLAG_FORKCHECK>	349	=item C<EVFLAG_FORKCHECK>
330		350
331	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	351	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	352	make libev check for a fork in each iteration by enabling this flag.
333	enabling this flag.
334		353
335	This works by calling C<getpid ()> on every iteration of the loop,	354	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	355	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	356	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	357	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
…		…
344	flag.	363	flag.
345		364
346	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	365	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
347	environment variable.	366	environment variable.
348		367
		368	=item C<EVFLAG_NOINOTIFY>
		369
		370	When this flag is specified, then libev will not attempt to use the
		371	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and
		372	testing, this flag can be useful to conserve inotify file descriptors, as
		373	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		374
		375	=item C<EVFLAG_SIGNALFD>
		376
		377	When this flag is specified, then libev will attempt to use the
		378	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API
		379	delivers signals synchronously, which makes it both faster and might make
		380	it possible to get the queued signal data. It can also simplify signal
		381	handling with threads, as long as you properly block signals in your
		382	threads that are not interested in handling them.
		383
		384	Signalfd will not be used by default as this changes your signal mask, and
		385	there are a lot of shoddy libraries and programs (glib's threadpool for
		386	example) that can't properly initialise their signal masks.
		387
349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	388	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
350		389
351	This is your standard select(2) backend. Not I<completely> standard, as	390	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,	391	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	392	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	398	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	399	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	400	a look at C<ev_set_io_collect_interval ()> to increase the amount of
362	readiness notifications you get per iteration.	401	readiness notifications you get per iteration.
363		402
		403	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		404	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		405	C<exceptfds> set on that platform).
		406
364	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	407	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
365		408
366	And this is your standard poll(2) backend. It's more complicated	409	And this is your standard poll(2) backend. It's more complicated
367	than select, but handles sparse fds better and has no artificial	410	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	411	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,	412	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	413	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
371	performance tips.	414	performance tips.
372		415
		416	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		417	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		418
373	=item C<EVBACKEND_EPOLL> (value 4, Linux)	419	=item C<EVBACKEND_EPOLL> (value 4, Linux)
		420
		421	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		422	kernels).
374		423
375	For few fds, this backend is a bit little slower than poll and select,	424	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	425	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),	426	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	427	epoll scales either O(1) or O(active_fds).
379	of shortcomings, such as silently dropping events in some hard-to-detect	428
380	cases and requiring a system call per fd change, no fork support and bad	429	The epoll mechanism deserves honorable mention as the most misdesigned
381	support for dup.	430	of the more advanced event mechanisms: mere annoyances include silently
		431	dropping file descriptors, requiring a system call per change per file
		432	descriptor (and unnecessary guessing of parameters), problems with dup and
		433	so on. The biggest issue is fork races, however - if a program forks then
		434	I<both> parent and child process have to recreate the epoll set, which can
		435	take considerable time (one syscall per file descriptor) and is of course
		436	hard to detect.
		437
		438	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		439	of course I<doesn't>, and epoll just loves to report events for totally
		440	I<different> file descriptors (even already closed ones, so one cannot
		441	even remove them from the set) than registered in the set (especially
		442	on SMP systems). Libev tries to counter these spurious notifications by
		443	employing an additional generation counter and comparing that against the
		444	events to filter out spurious ones, recreating the set when required. Last
		445	not least, it also refuses to work with some file descriptors which work
		446	perfectly fine with C<select> (files, many character devices...).
382		447
383	While stopping, setting and starting an I/O watcher in the same iteration	448	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	449	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	450	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	451	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
387	very well if you register events for both fds.	452	file descriptors might not work very well if you register events for both
388		453	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		454
393	Best performance from this backend is achieved by not unregistering all	455	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.	456	watchers for a file descriptor until it has been closed, if possible,
395	keep at least one watcher active per fd at all times.	457	i.e. keep at least one watcher active per fd at all times. Stopping and
		458	starting a watcher (without re-setting it) also usually doesn't cause
		459	extra overhead. A fork can both result in spurious notifications as well
		460	as in libev having to destroy and recreate the epoll object, which can
		461	take considerable time and thus should be avoided.
		462
		463	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		464	faster than epoll for maybe up to a hundred file descriptors, depending on
		465	the usage. So sad.
396		466
397	While nominally embeddable in other event loops, this feature is broken in	467	While nominally embeddable in other event loops, this feature is broken in
398	all kernel versions tested so far.	468	all kernel versions tested so far.
		469
		470	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		471	C<EVBACKEND_POLL>.
399		472
400	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	473	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
401		474
402	Kqueue deserves special mention, as at the time of this writing, it	475	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	476	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	477	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"	478	it's completely useless). Unlike epoll, however, whose brokenness
		479	is by design, these kqueue bugs can (and eventually will) be fixed
		480	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	481	"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)	482	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
408	system like NetBSD.	483	system like NetBSD.
409		484
410	You still can embed kqueue into a normal poll or select backend and use it	485	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	486	only for sockets (after having made sure that sockets work with kqueue on
…		…
413		488
414	It scales in the same way as the epoll backend, but the interface to the	489	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	490	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	491	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	492	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	493	two event changes per incident. Support for C<fork ()> is very bad (but
419	drops fds silently in similarly hard-to-detect cases.	494	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		495	cases
420		496
421	This backend usually performs well under most conditions.	497	This backend usually performs well under most conditions.
422		498
423	While nominally embeddable in other event loops, this doesn't work	499	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	500	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	501	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	502	(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	503	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
428	sockets.	504	also broken on OS X)) and, did I mention it, using it only for sockets.
		505
		506	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		507	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		508	C<NOTE_EOF>.
429		509
430	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	510	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
431		511
432	This is not implemented yet (and might never be, unless you send me an	512	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	513	implementation). According to reports, C</dev/poll> only supports sockets
…		…
446	While this backend scales well, it requires one system call per active	526	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	527	file descriptor per loop iteration. For small and medium numbers of file
448	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	528	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
449	might perform better.	529	might perform better.
450		530
451	On the positive side, ignoring the spurious readiness notifications, this	531	On the positive side, with the exception of the spurious readiness
452	backend actually performed to specification in all tests and is fully	532	notifications, this backend actually performed fully to specification
453	embeddable, which is a rare feat among the OS-specific backends.	533	in all tests and is fully embeddable, which is a rare feat among the
		534	OS-specific backends (I vastly prefer correctness over speed hacks).
		535
		536	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		537	C<EVBACKEND_POLL>.
454		538
455	=item C<EVBACKEND_ALL>	539	=item C<EVBACKEND_ALL>
456		540
457	Try all backends (even potentially broken ones that wouldn't be tried	541	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	542	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
460		544
461	It is definitely not recommended to use this flag.	545	It is definitely not recommended to use this flag.
462		546
463	=back	547	=back
464		548
465	If one or more of these are or'ed into the flags value, then only these	549	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	550	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.	551	here). If none are specified, all backends in C<ev_recommended_backends
		552	()> will be tried.
468		553
469	The most typical usage is like this:	554	Example: This is the most typical usage.
470		555
471	if (!ev_default_loop (0))	556	if (!ev_default_loop (0))
472	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	557	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
473		558
474	Restrict libev to the select and poll backends, and do not allow	559	Example: Restrict libev to the select and poll backends, and do not allow
475	environment settings to be taken into account:	560	environment settings to be taken into account:
476		561
477	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	562	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
478		563
479	Use whatever libev has to offer, but make sure that kqueue is used if	564	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	565	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):	566	private event loop and only if you know the OS supports your types of
		567	fds):
482		568
483	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	569	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
484		570
485	=item struct ev_loop *ev_loop_new (unsigned int flags)	571	=item struct ev_loop *ev_loop_new (unsigned int flags)
486		572
487	Similar to C<ev_default_loop>, but always creates a new event loop that is	573	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	574	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		575
492	Note that this function I<is> thread-safe, and the recommended way to use	576	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	577	libev with threads is indeed to create one loop per thread, and using the
494	default loop in the "main" or "initial" thread.	578	default loop in the "main" or "initial" thread.
495		579
496	Example: Try to create a event loop that uses epoll and nothing else.	580	Example: Try to create a event loop that uses epoll and nothing else.
497		581
…		…
499	if (!epoller)	583	if (!epoller)
500	fatal ("no epoll found here, maybe it hides under your chair");	584	fatal ("no epoll found here, maybe it hides under your chair");
501		585
502	=item ev_default_destroy ()	586	=item ev_default_destroy ()
503		587
504	Destroys the default loop again (frees all memory and kernel state	588	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	589	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	590	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>	591	either stop all watchers cleanly yourself I<before> calling this function,
508	calling this function, or cope with the fact afterwards (which is usually	592	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	593	can just ignore the watchers and/or C<free ()> them for example).
510	for example).
511		594
512	Note that certain global state, such as signal state, will not be freed by	595	Note that certain global state, such as signal state (and installed signal
513	this function, and related watchers (such as signal and child watchers)	596	handlers), will not be freed by this function, and related watchers (such
514	would need to be stopped manually.	597	as signal and child watchers) would need to be stopped manually.
515		598
516	In general it is not advisable to call this function except in the	599	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	600	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	601	pipe fds. If you need dynamically allocated loops it is better to use
519	C<ev_loop_new> and C<ev_loop_destroy>).	602	C<ev_loop_new> and C<ev_loop_destroy>.
520		603
521	=item ev_loop_destroy (loop)	604	=item ev_loop_destroy (loop)
522		605
523	Like C<ev_default_destroy>, but destroys an event loop created by an	606	Like C<ev_default_destroy>, but destroys an event loop created by an
524	earlier call to C<ev_loop_new>.	607	earlier call to C<ev_loop_new>.
525		608
526	=item ev_default_fork ()	609	=item ev_default_fork ()
527		610
528	This function sets a flag that causes subsequent C<ev_loop> iterations	611	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	612	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	613	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	614	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	615	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.	616	functions, and it will only take effect at the next C<ev_run> iteration.
		617
		618	Again, you I<have> to call it on I<any> loop that you want to re-use after
		619	a fork, I<even if you do not plan to use the loop in the parent>. This is
		620	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		621	during fork.
534		622
535	On the other hand, you only need to call this function in the child	623	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	624	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.	625	you just fork+exec or create a new loop in the child, you don't have to
		626	call it at all (in fact, C<epoll> is so badly broken that it makes a
		627	difference, but libev will usually detect this case on its own and do a
		628	costly reset of the backend).
538		629
539	The function itself is quite fast and it's usually not a problem to call	630	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	631	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>:	632	quite nicely into a call to C<pthread_atfork>:
542		633
…		…
544		635
545	=item ev_loop_fork (loop)	636	=item ev_loop_fork (loop)
546		637
547	Like C<ev_default_fork>, but acts on an event loop created by	638	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	639	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.	640	after fork that you want to re-use in the child, and how you keep track of
		641	them is entirely your own problem.
550		642
551	=item int ev_is_default_loop (loop)	643	=item int ev_is_default_loop (loop)
552		644
553	Returns true when the given loop actually is the default loop, false otherwise.	645	Returns true when the given loop is, in fact, the default loop, and false
		646	otherwise.
554		647
555	=item unsigned int ev_loop_count (loop)	648	=item unsigned int ev_iteration (loop)
556		649
557	Returns the count of loop iterations for the loop, which is identical to	650	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	651	to the number of times libev did poll for new events. It starts at C<0>
559	happily wraps around with enough iterations.	652	and happily wraps around with enough iterations.
560		653
561	This value can sometimes be useful as a generation counter of sorts (it	654	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	655	"ticks" the number of loop iterations), as it roughly corresponds with
563	C<ev_prepare> and C<ev_check> calls.	656	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		657	prepare and check phases.
		658
		659	=item unsigned int ev_depth (loop)
		660
		661	Returns the number of times C<ev_run> was entered minus the number of
		662	times C<ev_run> was exited, in other words, the recursion depth.
		663
		664	Outside C<ev_run>, this number is zero. In a callback, this number is
		665	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		666	in which case it is higher.
		667
		668	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread
		669	etc.), doesn't count as "exit" - consider this as a hint to avoid such
		670	ungentleman-like behaviour unless it's really convenient.
564		671
565	=item unsigned int ev_backend (loop)	672	=item unsigned int ev_backend (loop)
566		673
567	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	674	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
568	use.	675	use.
…		…
573	received events and started processing them. This timestamp does not	680	received events and started processing them. This timestamp does not
574	change as long as callbacks are being processed, and this is also the base	681	change as long as callbacks are being processed, and this is also the base
575	time used for relative timers. You can treat it as the timestamp of the	682	time used for relative timers. You can treat it as the timestamp of the
576	event occurring (or more correctly, libev finding out about it).	683	event occurring (or more correctly, libev finding out about it).
577		684
		685	=item ev_now_update (loop)
		686
		687	Establishes the current time by querying the kernel, updating the time
		688	returned by C<ev_now ()> in the progress. This is a costly operation and
		689	is usually done automatically within C<ev_run ()>.
		690
		691	This function is rarely useful, but when some event callback runs for a
		692	very long time without entering the event loop, updating libev's idea of
		693	the current time is a good idea.
		694
		695	See also L<The special problem of time updates> in the C<ev_timer> section.
		696
		697	=item ev_suspend (loop)
		698
		699	=item ev_resume (loop)
		700
		701	These two functions suspend and resume an event loop, for use when the
		702	loop is not used for a while and timeouts should not be processed.
		703
		704	A typical use case would be an interactive program such as a game: When
		705	the user presses C<^Z> to suspend the game and resumes it an hour later it
		706	would be best to handle timeouts as if no time had actually passed while
		707	the program was suspended. This can be achieved by calling C<ev_suspend>
		708	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		709	C<ev_resume> directly afterwards to resume timer processing.
		710
		711	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		712	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		713	will be rescheduled (that is, they will lose any events that would have
		714	occurred while suspended).
		715
		716	After calling C<ev_suspend> you B<must not> call I<any> function on the
		717	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		718	without a previous call to C<ev_suspend>.
		719
		720	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		721	event loop time (see C<ev_now_update>).
		722
578	=item ev_loop (loop, int flags)	723	=item ev_run (loop, int flags)
579		724
580	Finally, this is it, the event handler. This function usually is called	725	Finally, this is it, the event handler. This function usually is called
581	after you initialised all your watchers and you want to start handling	726	after you have initialised all your watchers and you want to start
582	events.	727	handling events. It will ask the operating system for any new events, call
		728	the watcher callbacks, an then repeat the whole process indefinitely: This
		729	is why event loops are called I<loops>.
583		730
584	If the flags argument is specified as C<0>, it will not return until	731	If the flags argument is specified as C<0>, it will keep handling events
585	either no event watchers are active anymore or C<ev_unloop> was called.	732	until either no event watchers are active anymore or C<ev_break> was
		733	called.
586		734
587	Please note that an explicit C<ev_unloop> is usually better than	735	Please note that an explicit C<ev_break> is usually better than
588	relying on all watchers to be stopped when deciding when a program has	736	relying on all watchers to be stopped when deciding when a program has
589	finished (especially in interactive programs), but having a program that	737	finished (especially in interactive programs), but having a program
590	automatically loops as long as it has to and no longer by virtue of	738	that automatically loops as long as it has to and no longer by virtue
591	relying on its watchers stopping correctly is a thing of beauty.	739	of relying on its watchers stopping correctly, that is truly a thing of
		740	beauty.
592		741
593	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	742	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
594	those events and any outstanding ones, but will not block your process in	743	those events and any already outstanding ones, but will not wait and
595	case there are no events and will return after one iteration of the loop.	744	block your process in case there are no events and will return after one
		745	iteration of the loop. This is sometimes useful to poll and handle new
		746	events while doing lengthy calculations, to keep the program responsive.
596		747
597	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	748	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
598	necessary) and will handle those and any outstanding ones. It will block	749	necessary) and will handle those and any already outstanding ones. It
599	your process until at least one new event arrives, and will return after	750	will block your process until at least one new event arrives (which could
600	one iteration of the loop. This is useful if you are waiting for some	751	be an event internal to libev itself, so there is no guarantee that a
601	external event in conjunction with something not expressible using other	752	user-registered callback will be called), and will return after one
		753	iteration of the loop.
		754
		755	This is useful if you are waiting for some external event in conjunction
		756	with something not expressible using other libev watchers (i.e. "roll your
602	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	757	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
603	usually a better approach for this kind of thing.	758	usually a better approach for this kind of thing.
604		759
605	Here are the gory details of what C<ev_loop> does:	760	Here are the gory details of what C<ev_run> does:
606		761
		762	- Increment loop depth.
		763	- Reset the ev_break status.
607	- Before the first iteration, call any pending watchers.	764	- Before the first iteration, call any pending watchers.
		765	LOOP:
608	* If EVFLAG_FORKCHECK was used, check for a fork.	766	- If EVFLAG_FORKCHECK was used, check for a fork.
609	- If a fork was detected, queue and call all fork watchers.	767	- If a fork was detected (by any means), queue and call all fork watchers.
610	- Queue and call all prepare watchers.	768	- Queue and call all prepare watchers.
		769	- If ev_break was called, goto FINISH.
611	- If we have been forked, recreate the kernel state.	770	- If we have been forked, detach and recreate the kernel state
		771	as to not disturb the other process.
612	- Update the kernel state with all outstanding changes.	772	- Update the kernel state with all outstanding changes.
613	- Update the "event loop time".	773	- Update the "event loop time" (ev_now ()).
614	- Calculate for how long to sleep or block, if at all	774	- Calculate for how long to sleep or block, if at all
615	(active idle watchers, EVLOOP_NONBLOCK or not having	775	(active idle watchers, EVRUN_NOWAIT or not having
616	any active watchers at all will result in not sleeping).	776	any active watchers at all will result in not sleeping).
617	- Sleep if the I/O and timer collect interval say so.	777	- Sleep if the I/O and timer collect interval say so.
		778	- Increment loop iteration counter.
618	- Block the process, waiting for any events.	779	- Block the process, waiting for any events.
619	- Queue all outstanding I/O (fd) events.	780	- Queue all outstanding I/O (fd) events.
620	- Update the "event loop time" and do time jump handling.	781	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
621	- Queue all outstanding timers.	782	- Queue all expired timers.
622	- Queue all outstanding periodics.	783	- Queue all expired periodics.
623	- If no events are pending now, queue all idle watchers.	784	- Queue all idle watchers with priority higher than that of pending events.
624	- Queue all check watchers.	785	- Queue all check watchers.
625	- Call all queued watchers in reverse order (i.e. check watchers first).	786	- Call all queued watchers in reverse order (i.e. check watchers first).
626	Signals and child watchers are implemented as I/O watchers, and will	787	Signals and child watchers are implemented as I/O watchers, and will
627	be handled here by queueing them when their watcher gets executed.	788	be handled here by queueing them when their watcher gets executed.
628	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	789	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
629	were used, or there are no active watchers, return, otherwise	790	were used, or there are no active watchers, goto FINISH, otherwise
630	continue with step *.	791	continue with step LOOP.
		792	FINISH:
		793	- Reset the ev_break status iff it was EVBREAK_ONE.
		794	- Decrement the loop depth.
		795	- Return.
631		796
632	Example: Queue some jobs and then loop until no events are outstanding	797	Example: Queue some jobs and then loop until no events are outstanding
633	anymore.	798	anymore.
634		799
635	... queue jobs here, make sure they register event watchers as long	800	... queue jobs here, make sure they register event watchers as long
636	... as they still have work to do (even an idle watcher will do..)	801	... as they still have work to do (even an idle watcher will do..)
637	ev_loop (my_loop, 0);	802	ev_run (my_loop, 0);
638	... jobs done. yeah!	803	... jobs done or somebody called unloop. yeah!
639		804
640	=item ev_unloop (loop, how)	805	=item ev_break (loop, how)
641		806
642	Can be used to make a call to C<ev_loop> return early (but only after it	807	Can be used to make a call to C<ev_run> return early (but only after it
643	has processed all outstanding events). The C<how> argument must be either	808	has processed all outstanding events). The C<how> argument must be either
644	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	809	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
645	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	810	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
646		811
647	This "unloop state" will be cleared when entering C<ev_loop> again.	812	This "unloop state" will be cleared when entering C<ev_run> again.
		813
		814	It is safe to call C<ev_break> from outside any C<ev_run> calls. ##TODO##
648		815
649	=item ev_ref (loop)	816	=item ev_ref (loop)
650		817
651	=item ev_unref (loop)	818	=item ev_unref (loop)
652		819
653	Ref/unref can be used to add or remove a reference count on the event	820	Ref/unref can be used to add or remove a reference count on the event
654	loop: Every watcher keeps one reference, and as long as the reference	821	loop: Every watcher keeps one reference, and as long as the reference
655	count is nonzero, C<ev_loop> will not return on its own. If you have	822	count is nonzero, C<ev_run> will not return on its own.
656	a watcher you never unregister that should not keep C<ev_loop> from	823
657	returning, ev_unref() after starting, and ev_ref() before stopping it. For	824	This is useful when you have a watcher that you never intend to
		825	unregister, but that nevertheless should not keep C<ev_run> from
		826	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
		827	before stopping it.
		828
658	example, libev itself uses this for its internal signal pipe: It is not	829	As an example, libev itself uses this for its internal signal pipe: It
659	visible to the libev user and should not keep C<ev_loop> from exiting if	830	is not visible to the libev user and should not keep C<ev_run> from
660	no event watchers registered by it are active. It is also an excellent	831	exiting if no event watchers registered by it are active. It is also an
661	way to do this for generic recurring timers or from within third-party	832	excellent way to do this for generic recurring timers or from within
662	libraries. Just remember to I<unref after start> and I<ref before stop>	833	third-party libraries. Just remember to I<unref after start> and I<ref
663	(but only if the watcher wasn't active before, or was active before,	834	before stop> (but only if the watcher wasn't active before, or was active
664	respectively).	835	before, respectively. Note also that libev might stop watchers itself
		836	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		837	in the callback).
665		838
666	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	839	Example: Create a signal watcher, but keep it from keeping C<ev_run>
667	running when nothing else is active.	840	running when nothing else is active.
668		841
669	struct ev_signal exitsig;	842	ev_signal exitsig;
670	ev_signal_init (&exitsig, sig_cb, SIGINT);	843	ev_signal_init (&exitsig, sig_cb, SIGINT);
671	ev_signal_start (loop, &exitsig);	844	ev_signal_start (loop, &exitsig);
672	evf_unref (loop);	845	evf_unref (loop);
673		846
674	Example: For some weird reason, unregister the above signal handler again.	847	Example: For some weird reason, unregister the above signal handler again.
…		…
679	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	852	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
680		853
681	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	854	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
682		855
683	These advanced functions influence the time that libev will spend waiting	856	These advanced functions influence the time that libev will spend waiting
684	for events. Both are by default C<0>, meaning that libev will try to	857	for events. Both time intervals are by default C<0>, meaning that libev
685	invoke timer/periodic callbacks and I/O callbacks with minimum latency.	858	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		859	latency.
686		860
687	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	861	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
688	allows libev to delay invocation of I/O and timer/periodic callbacks to	862	allows libev to delay invocation of I/O and timer/periodic callbacks
689	increase efficiency of loop iterations.	863	to increase efficiency of loop iterations (or to increase power-saving
		864	opportunities).
690		865
691	The background is that sometimes your program runs just fast enough to	866	The idea is that sometimes your program runs just fast enough to handle
692	handle one (or very few) event(s) per loop iteration. While this makes	867	one (or very few) event(s) per loop iteration. While this makes the
693	the program responsive, it also wastes a lot of CPU time to poll for new	868	program responsive, it also wastes a lot of CPU time to poll for new
694	events, especially with backends like C<select ()> which have a high	869	events, especially with backends like C<select ()> which have a high
695	overhead for the actual polling but can deliver many events at once.	870	overhead for the actual polling but can deliver many events at once.
696		871
697	By setting a higher I<io collect interval> you allow libev to spend more	872	By setting a higher I<io collect interval> you allow libev to spend more
698	time collecting I/O events, so you can handle more events per iteration,	873	time collecting I/O events, so you can handle more events per iteration,
699	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	874	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
700	C<ev_timer>) will be not affected. Setting this to a non-null value will	875	C<ev_timer>) will be not affected. Setting this to a non-null value will
701	introduce an additional C<ev_sleep ()> call into most loop iterations.	876	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		877	sleep time ensures that libev will not poll for I/O events more often then
		878	once per this interval, on average.
702		879
703	Likewise, by setting a higher I<timeout collect interval> you allow libev	880	Likewise, by setting a higher I<timeout collect interval> you allow libev
704	to spend more time collecting timeouts, at the expense of increased	881	to spend more time collecting timeouts, at the expense of increased
705	latency (the watcher callback will be called later). C<ev_io> watchers	882	latency/jitter/inexactness (the watcher callback will be called
706	will not be affected. Setting this to a non-null value will not introduce	883	later). C<ev_io> watchers will not be affected. Setting this to a non-null
707	any overhead in libev.	884	value will not introduce any overhead in libev.
708		885
709	Many (busy) programs can usually benefit by setting the I/O collect	886	Many (busy) programs can usually benefit by setting the I/O collect
710	interval to a value near C<0.1> or so, which is often enough for	887	interval to a value near C<0.1> or so, which is often enough for
711	interactive servers (of course not for games), likewise for timeouts. It	888	interactive servers (of course not for games), likewise for timeouts. It
712	usually doesn't make much sense to set it to a lower value than C<0.01>,	889	usually doesn't make much sense to set it to a lower value than C<0.01>,
713	as this approaches the timing granularity of most systems.	890	as this approaches the timing granularity of most systems. Note that if
		891	you do transactions with the outside world and you can't increase the
		892	parallelity, then this setting will limit your transaction rate (if you
		893	need to poll once per transaction and the I/O collect interval is 0.01,
		894	then you can't do more than 100 transactions per second).
714		895
		896	Setting the I<timeout collect interval> can improve the opportunity for
		897	saving power, as the program will "bundle" timer callback invocations that
		898	are "near" in time together, by delaying some, thus reducing the number of
		899	times the process sleeps and wakes up again. Another useful technique to
		900	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		901	they fire on, say, one-second boundaries only.
		902
		903	Example: we only need 0.1s timeout granularity, and we wish not to poll
		904	more often than 100 times per second:
		905
		906	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		907	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		908
		909	=item ev_invoke_pending (loop)
		910
		911	This call will simply invoke all pending watchers while resetting their
		912	pending state. Normally, C<ev_run> does this automatically when required,
		913	but when overriding the invoke callback this call comes handy.
		914
		915	=item int ev_pending_count (loop)
		916
		917	Returns the number of pending watchers - zero indicates that no watchers
		918	are pending.
		919
		920	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		921
		922	This overrides the invoke pending functionality of the loop: Instead of
		923	invoking all pending watchers when there are any, C<ev_run> will call
		924	this callback instead. This is useful, for example, when you want to
		925	invoke the actual watchers inside another context (another thread etc.).
		926
		927	If you want to reset the callback, use C<ev_invoke_pending> as new
		928	callback.
		929
		930	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		931
		932	Sometimes you want to share the same loop between multiple threads. This
		933	can be done relatively simply by putting mutex_lock/unlock calls around
		934	each call to a libev function.
		935
		936	However, C<ev_run> can run an indefinite time, so it is not feasible
		937	to wait for it to return. One way around this is to wake up the event
		938	loop via C<ev_break> and C<av_async_send>, another way is to set these
		939	I<release> and I<acquire> callbacks on the loop.
		940
		941	When set, then C<release> will be called just before the thread is
		942	suspended waiting for new events, and C<acquire> is called just
		943	afterwards.
		944
		945	Ideally, C<release> will just call your mutex_unlock function, and
		946	C<acquire> will just call the mutex_lock function again.
		947
		948	While event loop modifications are allowed between invocations of
		949	C<release> and C<acquire> (that's their only purpose after all), no
		950	modifications done will affect the event loop, i.e. adding watchers will
		951	have no effect on the set of file descriptors being watched, or the time
		952	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		953	to take note of any changes you made.
		954
		955	In theory, threads executing C<ev_run> will be async-cancel safe between
		956	invocations of C<release> and C<acquire>.
		957
		958	See also the locking example in the C<THREADS> section later in this
		959	document.
		960
		961	=item ev_set_userdata (loop, void *data)
		962
		963	=item ev_userdata (loop)
		964
		965	Set and retrieve a single C<void *> associated with a loop. When
		966	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		967	C<0.>
		968
		969	These two functions can be used to associate arbitrary data with a loop,
		970	and are intended solely for the C<invoke_pending_cb>, C<release> and
		971	C<acquire> callbacks described above, but of course can be (ab-)used for
		972	any other purpose as well.
		973
715	=item ev_loop_verify (loop)	974	=item ev_verify (loop)
716		975
717	This function only does something when C<EV_VERIFY> support has been	976	This function only does something when C<EV_VERIFY> support has been
718	compiled in. It tries to go through all internal structures and checks	977	compiled in, which is the default for non-minimal builds. It tries to go
719	them for validity. If anything is found to be inconsistent, it will print	978	through all internal structures and checks them for validity. If anything
720	an error message to standard error and call C<abort ()>.	979	is found to be inconsistent, it will print an error message to standard
		980	error and call C<abort ()>.
721		981
722	This can be used to catch bugs inside libev itself: under normal	982	This can be used to catch bugs inside libev itself: under normal
723	circumstances, this function will never abort as of course libev keeps its	983	circumstances, this function will never abort as of course libev keeps its
724	data structures consistent.	984	data structures consistent.
725		985
726	=back	986	=back
727		987
728		988
729	=head1 ANATOMY OF A WATCHER	989	=head1 ANATOMY OF A WATCHER
730		990
		991	In the following description, uppercase C<TYPE> in names stands for the
		992	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		993	watchers and C<ev_io_start> for I/O watchers.
		994
731	A watcher is a structure that you create and register to record your	995	A watcher is a structure that you create and register to record your
732	interest in some event. For instance, if you want to wait for STDIN to	996	interest in some event. For instance, if you want to wait for STDIN to
733	become readable, you would create an C<ev_io> watcher for that:	997	become readable, you would create an C<ev_io> watcher for that:
734		998
735	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	999	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
736	{	1000	{
737	ev_io_stop (w);	1001	ev_io_stop (w);
738	ev_unloop (loop, EVUNLOOP_ALL);	1002	ev_break (loop, EVBREAK_ALL);
739	}	1003	}
740		1004
741	struct ev_loop *loop = ev_default_loop (0);	1005	struct ev_loop *loop = ev_default_loop (0);
		1006
742	struct ev_io stdin_watcher;	1007	ev_io stdin_watcher;
		1008
743	ev_init (&stdin_watcher, my_cb);	1009	ev_init (&stdin_watcher, my_cb);
744	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1010	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
745	ev_io_start (loop, &stdin_watcher);	1011	ev_io_start (loop, &stdin_watcher);
		1012
746	ev_loop (loop, 0);	1013	ev_run (loop, 0);
747		1014
748	As you can see, you are responsible for allocating the memory for your	1015	As you can see, you are responsible for allocating the memory for your
749	watcher structures (and it is usually a bad idea to do this on the stack,	1016	watcher structures (and it is I<usually> a bad idea to do this on the
750	although this can sometimes be quite valid).	1017	stack).
		1018
		1019	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		1020	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
751		1021
752	Each watcher structure must be initialised by a call to C<ev_init	1022	Each watcher structure must be initialised by a call to C<ev_init
753	(watcher *, callback)>, which expects a callback to be provided. This	1023	(watcher *, callback)>, which expects a callback to be provided. This
754	callback gets invoked each time the event occurs (or, in the case of I/O	1024	callback gets invoked each time the event occurs (or, in the case of I/O
755	watchers, each time the event loop detects that the file descriptor given	1025	watchers, each time the event loop detects that the file descriptor given
756	is readable and/or writable).	1026	is readable and/or writable).
757		1027
758	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1028	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
759	with arguments specific to this watcher type. There is also a macro	1029	macro to configure it, with arguments specific to the watcher type. There
760	to combine initialisation and setting in one call: C<< ev_<type>_init	1030	is also a macro to combine initialisation and setting in one call: C<<
761	(watcher *, callback, ...) >>.	1031	ev_TYPE_init (watcher *, callback, ...) >>.
762		1032
763	To make the watcher actually watch out for events, you have to start it	1033	To make the watcher actually watch out for events, you have to start it
764	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	1034	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
765	*) >>), and you can stop watching for events at any time by calling the	1035	*) >>), and you can stop watching for events at any time by calling the
766	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1036	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
767		1037
768	As long as your watcher is active (has been started but not stopped) you	1038	As long as your watcher is active (has been started but not stopped) you
769	must not touch the values stored in it. Most specifically you must never	1039	must not touch the values stored in it. Most specifically you must never
770	reinitialise it or call its C<set> macro.	1040	reinitialise it or call its C<ev_TYPE_set> macro.
771		1041
772	Each and every callback receives the event loop pointer as first, the	1042	Each and every callback receives the event loop pointer as first, the
773	registered watcher structure as second, and a bitset of received events as	1043	registered watcher structure as second, and a bitset of received events as
774	third argument.	1044	third argument.
775		1045
…		…
784	=item C<EV_WRITE>	1054	=item C<EV_WRITE>
785		1055
786	The file descriptor in the C<ev_io> watcher has become readable and/or	1056	The file descriptor in the C<ev_io> watcher has become readable and/or
787	writable.	1057	writable.
788		1058
789	=item C<EV_TIMEOUT>	1059	=item C<EV_TIMER>
790		1060
791	The C<ev_timer> watcher has timed out.	1061	The C<ev_timer> watcher has timed out.
792		1062
793	=item C<EV_PERIODIC>	1063	=item C<EV_PERIODIC>
794		1064
…		…
812		1082
813	=item C<EV_PREPARE>	1083	=item C<EV_PREPARE>
814		1084
815	=item C<EV_CHECK>	1085	=item C<EV_CHECK>
816		1086
817	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1087	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
818	to gather new events, and all C<ev_check> watchers are invoked just after	1088	to gather new events, and all C<ev_check> watchers are invoked just after
819	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1089	C<ev_run> has gathered them, but before it invokes any callbacks for any
820	received events. Callbacks of both watcher types can start and stop as	1090	received events. Callbacks of both watcher types can start and stop as
821	many watchers as they want, and all of them will be taken into account	1091	many watchers as they want, and all of them will be taken into account
822	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1092	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
823	C<ev_loop> from blocking).	1093	C<ev_run> from blocking).
824		1094
825	=item C<EV_EMBED>	1095	=item C<EV_EMBED>
826		1096
827	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1097	The embedded event loop specified in the C<ev_embed> watcher needs attention.
828		1098
…		…
832	C<ev_fork>).	1102	C<ev_fork>).
833		1103
834	=item C<EV_ASYNC>	1104	=item C<EV_ASYNC>
835		1105
836	The given async watcher has been asynchronously notified (see C<ev_async>).	1106	The given async watcher has been asynchronously notified (see C<ev_async>).
		1107
		1108	=item C<EV_CUSTOM>
		1109
		1110	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1111	by libev users to signal watchers (e.g. via C<ev_feed_event>).
837		1112
838	=item C<EV_ERROR>	1113	=item C<EV_ERROR>
839		1114
840	An unspecified error has occurred, the watcher has been stopped. This might	1115	An unspecified error has occurred, the watcher has been stopped. This might
841	happen because the watcher could not be properly started because libev	1116	happen because the watcher could not be properly started because libev
842	ran out of memory, a file descriptor was found to be closed or any other	1117	ran out of memory, a file descriptor was found to be closed or any other
		1118	problem. Libev considers these application bugs.
		1119
843	problem. You best act on it by reporting the problem and somehow coping	1120	You best act on it by reporting the problem and somehow coping with the
844	with the watcher being stopped.	1121	watcher being stopped. Note that well-written programs should not receive
		1122	an error ever, so when your watcher receives it, this usually indicates a
		1123	bug in your program.
845		1124
846	Libev will usually signal a few "dummy" events together with an error,	1125	Libev will usually signal a few "dummy" events together with an error, for
847	for example it might indicate that a fd is readable or writable, and if	1126	example it might indicate that a fd is readable or writable, and if your
848	your callbacks is well-written it can just attempt the operation and cope	1127	callbacks is well-written it can just attempt the operation and cope with
849	with the error from read() or write(). This will not work in multi-threaded	1128	the error from read() or write(). This will not work in multi-threaded
850	programs, though, so beware.	1129	programs, though, as the fd could already be closed and reused for another
		1130	thing, so beware.
851		1131
852	=back	1132	=back
853		1133
854	=head2 GENERIC WATCHER FUNCTIONS	1134	=head2 GENERIC WATCHER FUNCTIONS
855
856	In the following description, C<TYPE> stands for the watcher type,
857	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
858		1135
859	=over 4	1136	=over 4
860		1137
861	=item C<ev_init> (ev_TYPE *watcher, callback)	1138	=item C<ev_init> (ev_TYPE *watcher, callback)
862		1139
…		…
868	which rolls both calls into one.	1145	which rolls both calls into one.
869		1146
870	You can reinitialise a watcher at any time as long as it has been stopped	1147	You can reinitialise a watcher at any time as long as it has been stopped
871	(or never started) and there are no pending events outstanding.	1148	(or never started) and there are no pending events outstanding.
872		1149
873	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1150	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
874	int revents)>.	1151	int revents)>.
875		1152
		1153	Example: Initialise an C<ev_io> watcher in two steps.
		1154
		1155	ev_io w;
		1156	ev_init (&w, my_cb);
		1157	ev_io_set (&w, STDIN_FILENO, EV_READ);
		1158
876	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1159	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
877		1160
878	This macro initialises the type-specific parts of a watcher. You need to	1161	This macro initialises the type-specific parts of a watcher. You need to
879	call C<ev_init> at least once before you call this macro, but you can	1162	call C<ev_init> at least once before you call this macro, but you can
880	call C<ev_TYPE_set> any number of times. You must not, however, call this	1163	call C<ev_TYPE_set> any number of times. You must not, however, call this
881	macro on a watcher that is active (it can be pending, however, which is a	1164	macro on a watcher that is active (it can be pending, however, which is a
882	difference to the C<ev_init> macro).	1165	difference to the C<ev_init> macro).
883		1166
884	Although some watcher types do not have type-specific arguments	1167	Although some watcher types do not have type-specific arguments
885	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	1168	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
886		1169
		1170	See C<ev_init>, above, for an example.
		1171
887	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1172	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
888		1173
889	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1174	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
890	calls into a single call. This is the most convenient method to initialise	1175	calls into a single call. This is the most convenient method to initialise
891	a watcher. The same limitations apply, of course.	1176	a watcher. The same limitations apply, of course.
892		1177
		1178	Example: Initialise and set an C<ev_io> watcher in one step.
		1179
		1180	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1181
893	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1182	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
894		1183
895	Starts (activates) the given watcher. Only active watchers will receive	1184	Starts (activates) the given watcher. Only active watchers will receive
896	events. If the watcher is already active nothing will happen.	1185	events. If the watcher is already active nothing will happen.
897		1186
		1187	Example: Start the C<ev_io> watcher that is being abused as example in this
		1188	whole section.
		1189
		1190	ev_io_start (EV_DEFAULT_UC, &w);
		1191
898	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1192	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
899		1193
900	Stops the given watcher again (if active) and clears the pending	1194	Stops the given watcher if active, and clears the pending status (whether
		1195	the watcher was active or not).
		1196
901	status. It is possible that stopped watchers are pending (for example,	1197	It is possible that stopped watchers are pending - for example,
902	non-repeating timers are being stopped when they become pending), but	1198	non-repeating timers are being stopped when they become pending - but
903	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1199	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
904	you want to free or reuse the memory used by the watcher it is therefore a	1200	pending. If you want to free or reuse the memory used by the watcher it is
905	good idea to always call its C<ev_TYPE_stop> function.	1201	therefore a good idea to always call its C<ev_TYPE_stop> function.
906		1202
907	=item bool ev_is_active (ev_TYPE *watcher)	1203	=item bool ev_is_active (ev_TYPE *watcher)
908		1204
909	Returns a true value iff the watcher is active (i.e. it has been started	1205	Returns a true value iff the watcher is active (i.e. it has been started
910	and not yet been stopped). As long as a watcher is active you must not modify	1206	and not yet been stopped). As long as a watcher is active you must not modify
…		…
926	=item ev_cb_set (ev_TYPE *watcher, callback)	1222	=item ev_cb_set (ev_TYPE *watcher, callback)
927		1223
928	Change the callback. You can change the callback at virtually any time	1224	Change the callback. You can change the callback at virtually any time
929	(modulo threads).	1225	(modulo threads).
930		1226
931	=item ev_set_priority (ev_TYPE *watcher, priority)	1227	=item ev_set_priority (ev_TYPE *watcher, int priority)
932		1228
933	=item int ev_priority (ev_TYPE *watcher)	1229	=item int ev_priority (ev_TYPE *watcher)
934		1230
935	Set and query the priority of the watcher. The priority is a small	1231	Set and query the priority of the watcher. The priority is a small
936	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1232	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
937	(default: C<-2>). Pending watchers with higher priority will be invoked	1233	(default: C<-2>). Pending watchers with higher priority will be invoked
938	before watchers with lower priority, but priority will not keep watchers	1234	before watchers with lower priority, but priority will not keep watchers
939	from being executed (except for C<ev_idle> watchers).	1235	from being executed (except for C<ev_idle> watchers).
940		1236
941	This means that priorities are I<only> used for ordering callback
942	invocation after new events have been received. This is useful, for
943	example, to reduce latency after idling, or more often, to bind two
944	watchers on the same event and make sure one is called first.
945
946	If you need to suppress invocation when higher priority events are pending	1237	If you need to suppress invocation when higher priority events are pending
947	you need to look at C<ev_idle> watchers, which provide this functionality.	1238	you need to look at C<ev_idle> watchers, which provide this functionality.
948		1239
949	You I<must not> change the priority of a watcher as long as it is active or	1240	You I<must not> change the priority of a watcher as long as it is active or
950	pending.	1241	pending.
951		1242
		1243	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1244	fine, as long as you do not mind that the priority value you query might
		1245	or might not have been clamped to the valid range.
		1246
952	The default priority used by watchers when no priority has been set is	1247	The default priority used by watchers when no priority has been set is
953	always C<0>, which is supposed to not be too high and not be too low :).	1248	always C<0>, which is supposed to not be too high and not be too low :).
954		1249
955	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1250	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
956	fine, as long as you do not mind that the priority value you query might	1251	priorities.
957	or might not have been adjusted to be within valid range.
958		1252
959	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1253	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
960		1254
961	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1255	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
962	C<loop> nor C<revents> need to be valid as long as the watcher callback	1256	C<loop> nor C<revents> need to be valid as long as the watcher callback
963	can deal with that fact.	1257	can deal with that fact, as both are simply passed through to the
		1258	callback.
964		1259
965	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1260	=item int ev_clear_pending (loop, ev_TYPE *watcher)
966		1261
967	If the watcher is pending, this function returns clears its pending status	1262	If the watcher is pending, this function clears its pending status and
968	and returns its C<revents> bitset (as if its callback was invoked). If the	1263	returns its C<revents> bitset (as if its callback was invoked). If the
969	watcher isn't pending it does nothing and returns C<0>.	1264	watcher isn't pending it does nothing and returns C<0>.
970		1265
		1266	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1267	callback to be invoked, which can be accomplished with this function.
		1268
		1269	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1270
		1271	Feeds the given event set into the event loop, as if the specified event
		1272	had happened for the specified watcher (which must be a pointer to an
		1273	initialised but not necessarily started event watcher). Obviously you must
		1274	not free the watcher as long as it has pending events.
		1275
		1276	Stopping the watcher, letting libev invoke it, or calling
		1277	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1278	not started in the first place.
		1279
		1280	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1281	functions that do not need a watcher.
		1282
971	=back	1283	=back
972		1284
973		1285
974	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1286	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
975		1287
976	Each watcher has, by default, a member C<void *data> that you can change	1288	Each watcher has, by default, a member C<void *data> that you can change
977	and read at any time, libev will completely ignore it. This can be used	1289	and read at any time: libev will completely ignore it. This can be used
978	to associate arbitrary data with your watcher. If you need more data and	1290	to associate arbitrary data with your watcher. If you need more data and
979	don't want to allocate memory and store a pointer to it in that data	1291	don't want to allocate memory and store a pointer to it in that data
980	member, you can also "subclass" the watcher type and provide your own	1292	member, you can also "subclass" the watcher type and provide your own
981	data:	1293	data:
982		1294
983	struct my_io	1295	struct my_io
984	{	1296	{
985	struct ev_io io;	1297	ev_io io;
986	int otherfd;	1298	int otherfd;
987	void *somedata;	1299	void *somedata;
988	struct whatever *mostinteresting;	1300	struct whatever *mostinteresting;
989	}	1301	};
		1302
		1303	...
		1304	struct my_io w;
		1305	ev_io_init (&w.io, my_cb, fd, EV_READ);
990		1306
991	And since your callback will be called with a pointer to the watcher, you	1307	And since your callback will be called with a pointer to the watcher, you
992	can cast it back to your own type:	1308	can cast it back to your own type:
993		1309
994	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1310	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
995	{	1311	{
996	struct my_io *w = (struct my_io *)w_;	1312	struct my_io *w = (struct my_io *)w_;
997	...	1313	...
998	}	1314	}
999		1315
1000	More interesting and less C-conformant ways of casting your callback type	1316	More interesting and less C-conformant ways of casting your callback type
1001	instead have been omitted.	1317	instead have been omitted.
1002		1318
1003	Another common scenario is having some data structure with multiple	1319	Another common scenario is to use some data structure with multiple
1004	watchers:	1320	embedded watchers:
1005		1321
1006	struct my_biggy	1322	struct my_biggy
1007	{	1323	{
1008	int some_data;	1324	int some_data;
1009	ev_timer t1;	1325	ev_timer t1;
1010	ev_timer t2;	1326	ev_timer t2;
1011	}	1327	}
1012		1328
1013	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1329	In this case getting the pointer to C<my_biggy> is a bit more
1014	you need to use C<offsetof>:	1330	complicated: Either you store the address of your C<my_biggy> struct
		1331	in the C<data> member of the watcher (for woozies), or you need to use
		1332	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1333	programmers):
1015		1334
1016	#include <stddef.h>	1335	#include <stddef.h>
1017		1336
1018	static void	1337	static void
1019	t1_cb (EV_P_ struct ev_timer *w, int revents)	1338	t1_cb (EV_P_ ev_timer *w, int revents)
1020	{	1339	{
1021	struct my_biggy big = (struct my_biggy *	1340	struct my_biggy big = (struct my_biggy *)
1022	(((char *)w) - offsetof (struct my_biggy, t1));	1341	(((char *)w) - offsetof (struct my_biggy, t1));
1023	}	1342	}
1024		1343
1025	static void	1344	static void
1026	t2_cb (EV_P_ struct ev_timer *w, int revents)	1345	t2_cb (EV_P_ ev_timer *w, int revents)
1027	{	1346	{
1028	struct my_biggy big = (struct my_biggy *	1347	struct my_biggy big = (struct my_biggy *)
1029	(((char *)w) - offsetof (struct my_biggy, t2));	1348	(((char *)w) - offsetof (struct my_biggy, t2));
1030	}	1349	}
		1350
		1351	=head2 WATCHER PRIORITY MODELS
		1352
		1353	Many event loops support I<watcher priorities>, which are usually small
		1354	integers that influence the ordering of event callback invocation
		1355	between watchers in some way, all else being equal.
		1356
		1357	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1358	description for the more technical details such as the actual priority
		1359	range.
		1360
		1361	There are two common ways how these these priorities are being interpreted
		1362	by event loops:
		1363
		1364	In the more common lock-out model, higher priorities "lock out" invocation
		1365	of lower priority watchers, which means as long as higher priority
		1366	watchers receive events, lower priority watchers are not being invoked.
		1367
		1368	The less common only-for-ordering model uses priorities solely to order
		1369	callback invocation within a single event loop iteration: Higher priority
		1370	watchers are invoked before lower priority ones, but they all get invoked
		1371	before polling for new events.
		1372
		1373	Libev uses the second (only-for-ordering) model for all its watchers
		1374	except for idle watchers (which use the lock-out model).
		1375
		1376	The rationale behind this is that implementing the lock-out model for
		1377	watchers is not well supported by most kernel interfaces, and most event
		1378	libraries will just poll for the same events again and again as long as
		1379	their callbacks have not been executed, which is very inefficient in the
		1380	common case of one high-priority watcher locking out a mass of lower
		1381	priority ones.
		1382
		1383	Static (ordering) priorities are most useful when you have two or more
		1384	watchers handling the same resource: a typical usage example is having an
		1385	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1386	timeouts. Under load, data might be received while the program handles
		1387	other jobs, but since timers normally get invoked first, the timeout
		1388	handler will be executed before checking for data. In that case, giving
		1389	the timer a lower priority than the I/O watcher ensures that I/O will be
		1390	handled first even under adverse conditions (which is usually, but not
		1391	always, what you want).
		1392
		1393	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1394	will only be executed when no same or higher priority watchers have
		1395	received events, they can be used to implement the "lock-out" model when
		1396	required.
		1397
		1398	For example, to emulate how many other event libraries handle priorities,
		1399	you can associate an C<ev_idle> watcher to each such watcher, and in
		1400	the normal watcher callback, you just start the idle watcher. The real
		1401	processing is done in the idle watcher callback. This causes libev to
		1402	continuously poll and process kernel event data for the watcher, but when
		1403	the lock-out case is known to be rare (which in turn is rare :), this is
		1404	workable.
		1405
		1406	Usually, however, the lock-out model implemented that way will perform
		1407	miserably under the type of load it was designed to handle. In that case,
		1408	it might be preferable to stop the real watcher before starting the
		1409	idle watcher, so the kernel will not have to process the event in case
		1410	the actual processing will be delayed for considerable time.
		1411
		1412	Here is an example of an I/O watcher that should run at a strictly lower
		1413	priority than the default, and which should only process data when no
		1414	other events are pending:
		1415
		1416	ev_idle idle; // actual processing watcher
		1417	ev_io io; // actual event watcher
		1418
		1419	static void
		1420	io_cb (EV_P_ ev_io *w, int revents)
		1421	{
		1422	// stop the I/O watcher, we received the event, but
		1423	// are not yet ready to handle it.
		1424	ev_io_stop (EV_A_ w);
		1425
		1426	// start the idle watcher to handle the actual event.
		1427	// it will not be executed as long as other watchers
		1428	// with the default priority are receiving events.
		1429	ev_idle_start (EV_A_ &idle);
		1430	}
		1431
		1432	static void
		1433	idle_cb (EV_P_ ev_idle *w, int revents)
		1434	{
		1435	// actual processing
		1436	read (STDIN_FILENO, ...);
		1437
		1438	// have to start the I/O watcher again, as
		1439	// we have handled the event
		1440	ev_io_start (EV_P_ &io);
		1441	}
		1442
		1443	// initialisation
		1444	ev_idle_init (&idle, idle_cb);
		1445	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1446	ev_io_start (EV_DEFAULT_ &io);
		1447
		1448	In the "real" world, it might also be beneficial to start a timer, so that
		1449	low-priority connections can not be locked out forever under load. This
		1450	enables your program to keep a lower latency for important connections
		1451	during short periods of high load, while not completely locking out less
		1452	important ones.
1031		1453
1032		1454
1033	=head1 WATCHER TYPES	1455	=head1 WATCHER TYPES
1034		1456
1035	This section describes each watcher in detail, but will not repeat	1457	This section describes each watcher in detail, but will not repeat
…		…
1059	In general you can register as many read and/or write event watchers per	1481	In general you can register as many read and/or write event watchers per
1060	fd as you want (as long as you don't confuse yourself). Setting all file	1482	fd as you want (as long as you don't confuse yourself). Setting all file
1061	descriptors to non-blocking mode is also usually a good idea (but not	1483	descriptors to non-blocking mode is also usually a good idea (but not
1062	required if you know what you are doing).	1484	required if you know what you are doing).
1063		1485
1064	If you must do this, then force the use of a known-to-be-good backend	1486	If you cannot use non-blocking mode, then force the use of a
1065	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1487	known-to-be-good backend (at the time of this writing, this includes only
1066	C<EVBACKEND_POLL>).	1488	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1489	descriptors for which non-blocking operation makes no sense (such as
		1490	files) - libev doesn't guarantee any specific behaviour in that case.
1067		1491
1068	Another thing you have to watch out for is that it is quite easy to	1492	Another thing you have to watch out for is that it is quite easy to
1069	receive "spurious" readiness notifications, that is your callback might	1493	receive "spurious" readiness notifications, that is your callback might
1070	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1494	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1071	because there is no data. Not only are some backends known to create a	1495	because there is no data. Not only are some backends known to create a
1072	lot of those (for example Solaris ports), it is very easy to get into	1496	lot of those (for example Solaris ports), it is very easy to get into
1073	this situation even with a relatively standard program structure. Thus	1497	this situation even with a relatively standard program structure. Thus
1074	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1498	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1075	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1499	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1076		1500
1077	If you cannot run the fd in non-blocking mode (for example you should not	1501	If you cannot run the fd in non-blocking mode (for example you should
1078	play around with an Xlib connection), then you have to separately re-test	1502	not play around with an Xlib connection), then you have to separately
1079	whether a file descriptor is really ready with a known-to-be good interface	1503	re-test whether a file descriptor is really ready with a known-to-be good
1080	such as poll (fortunately in our Xlib example, Xlib already does this on	1504	interface such as poll (fortunately in our Xlib example, Xlib already
1081	its own, so its quite safe to use).	1505	does this on its own, so its quite safe to use). Some people additionally
		1506	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1507	indefinitely.
		1508
		1509	But really, best use non-blocking mode.
1082		1510
1083	=head3 The special problem of disappearing file descriptors	1511	=head3 The special problem of disappearing file descriptors
1084		1512
1085	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1513	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1086	descriptor (either by calling C<close> explicitly or by any other means,	1514	descriptor (either due to calling C<close> explicitly or any other means,
1087	such as C<dup>). The reason is that you register interest in some file	1515	such as C<dup2>). The reason is that you register interest in some file
1088	descriptor, but when it goes away, the operating system will silently drop	1516	descriptor, but when it goes away, the operating system will silently drop
1089	this interest. If another file descriptor with the same number then is	1517	this interest. If another file descriptor with the same number then is
1090	registered with libev, there is no efficient way to see that this is, in	1518	registered with libev, there is no efficient way to see that this is, in
1091	fact, a different file descriptor.	1519	fact, a different file descriptor.
1092		1520
…		…
1123	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1551	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1124	C<EVBACKEND_POLL>.	1552	C<EVBACKEND_POLL>.
1125		1553
1126	=head3 The special problem of SIGPIPE	1554	=head3 The special problem of SIGPIPE
1127		1555
1128	While not really specific to libev, it is easy to forget about SIGPIPE:	1556	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1129	when reading from a pipe whose other end has been closed, your program	1557	when writing to a pipe whose other end has been closed, your program gets
1130	gets send a SIGPIPE, which, by default, aborts your program. For most	1558	sent a SIGPIPE, which, by default, aborts your program. For most programs
1131	programs this is sensible behaviour, for daemons, this is usually	1559	this is sensible behaviour, for daemons, this is usually undesirable.
1132	undesirable.
1133		1560
1134	So when you encounter spurious, unexplained daemon exits, make sure you	1561	So when you encounter spurious, unexplained daemon exits, make sure you
1135	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1562	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1136	somewhere, as that would have given you a big clue).	1563	somewhere, as that would have given you a big clue).
1137		1564
		1565	=head3 The special problem of accept()ing when you can't
		1566
		1567	Many implementations of the POSIX C<accept> function (for example,
		1568	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1569	connection from the pending queue in all error cases.
		1570
		1571	For example, larger servers often run out of file descriptors (because
		1572	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1573	rejecting the connection, leading to libev signalling readiness on
		1574	the next iteration again (the connection still exists after all), and
		1575	typically causing the program to loop at 100% CPU usage.
		1576
		1577	Unfortunately, the set of errors that cause this issue differs between
		1578	operating systems, there is usually little the app can do to remedy the
		1579	situation, and no known thread-safe method of removing the connection to
		1580	cope with overload is known (to me).
		1581
		1582	One of the easiest ways to handle this situation is to just ignore it
		1583	- when the program encounters an overload, it will just loop until the
		1584	situation is over. While this is a form of busy waiting, no OS offers an
		1585	event-based way to handle this situation, so it's the best one can do.
		1586
		1587	A better way to handle the situation is to log any errors other than
		1588	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1589	messages, and continue as usual, which at least gives the user an idea of
		1590	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1591	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1592	usage.
		1593
		1594	If your program is single-threaded, then you could also keep a dummy file
		1595	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1596	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1597	close that fd, and create a new dummy fd. This will gracefully refuse
		1598	clients under typical overload conditions.
		1599
		1600	The last way to handle it is to simply log the error and C<exit>, as
		1601	is often done with C<malloc> failures, but this results in an easy
		1602	opportunity for a DoS attack.
1138		1603
1139	=head3 Watcher-Specific Functions	1604	=head3 Watcher-Specific Functions
1140		1605
1141	=over 4	1606	=over 4
1142		1607
1143	=item ev_io_init (ev_io *, callback, int fd, int events)	1608	=item ev_io_init (ev_io *, callback, int fd, int events)
1144		1609
1145	=item ev_io_set (ev_io *, int fd, int events)	1610	=item ev_io_set (ev_io *, int fd, int events)
1146		1611
1147	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1612	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1148	receive events for and events is either C<EV_READ>, C<EV_WRITE> or	1613	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1149	C<EV_READ | EV_WRITE> to receive the given events.	1614	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1150		1615
1151	=item int fd [read-only]	1616	=item int fd [read-only]
1152		1617
1153	The file descriptor being watched.	1618	The file descriptor being watched.
1154		1619
…		…
1163	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1628	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1164	readable, but only once. Since it is likely line-buffered, you could	1629	readable, but only once. Since it is likely line-buffered, you could
1165	attempt to read a whole line in the callback.	1630	attempt to read a whole line in the callback.
1166		1631
1167	static void	1632	static void
1168	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1633	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1169	{	1634	{
1170	ev_io_stop (loop, w);	1635	ev_io_stop (loop, w);
1171	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1636	.. read from stdin here (or from w->fd) and handle any I/O errors
1172	}	1637	}
1173		1638
1174	...	1639	...
1175	struct ev_loop *loop = ev_default_init (0);	1640	struct ev_loop *loop = ev_default_init (0);
1176	struct ev_io stdin_readable;	1641	ev_io stdin_readable;
1177	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1642	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1178	ev_io_start (loop, &stdin_readable);	1643	ev_io_start (loop, &stdin_readable);
1179	ev_loop (loop, 0);	1644	ev_run (loop, 0);
1180		1645
1181		1646
1182	=head2 C<ev_timer> - relative and optionally repeating timeouts	1647	=head2 C<ev_timer> - relative and optionally repeating timeouts
1183		1648
1184	Timer watchers are simple relative timers that generate an event after a	1649	Timer watchers are simple relative timers that generate an event after a
1185	given time, and optionally repeating in regular intervals after that.	1650	given time, and optionally repeating in regular intervals after that.
1186		1651
1187	The timers are based on real time, that is, if you register an event that	1652	The timers are based on real time, that is, if you register an event that
1188	times out after an hour and you reset your system clock to January last	1653	times out after an hour and you reset your system clock to January last
1189	year, it will still time out after (roughly) and hour. "Roughly" because	1654	year, it will still time out after (roughly) one hour. "Roughly" because
1190	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1655	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1191	monotonic clock option helps a lot here).	1656	monotonic clock option helps a lot here).
		1657
		1658	The callback is guaranteed to be invoked only I<after> its timeout has
		1659	passed (not I<at>, so on systems with very low-resolution clocks this
		1660	might introduce a small delay). If multiple timers become ready during the
		1661	same loop iteration then the ones with earlier time-out values are invoked
		1662	before ones of the same priority with later time-out values (but this is
		1663	no longer true when a callback calls C<ev_run> recursively).
		1664
		1665	=head3 Be smart about timeouts
		1666
		1667	Many real-world problems involve some kind of timeout, usually for error
		1668	recovery. A typical example is an HTTP request - if the other side hangs,
		1669	you want to raise some error after a while.
		1670
		1671	What follows are some ways to handle this problem, from obvious and
		1672	inefficient to smart and efficient.
		1673
		1674	In the following, a 60 second activity timeout is assumed - a timeout that
		1675	gets reset to 60 seconds each time there is activity (e.g. each time some
		1676	data or other life sign was received).
		1677
		1678	=over 4
		1679
		1680	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1681
		1682	This is the most obvious, but not the most simple way: In the beginning,
		1683	start the watcher:
		1684
		1685	ev_timer_init (timer, callback, 60., 0.);
		1686	ev_timer_start (loop, timer);
		1687
		1688	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1689	and start it again:
		1690
		1691	ev_timer_stop (loop, timer);
		1692	ev_timer_set (timer, 60., 0.);
		1693	ev_timer_start (loop, timer);
		1694
		1695	This is relatively simple to implement, but means that each time there is
		1696	some activity, libev will first have to remove the timer from its internal
		1697	data structure and then add it again. Libev tries to be fast, but it's
		1698	still not a constant-time operation.
		1699
		1700	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1701
		1702	This is the easiest way, and involves using C<ev_timer_again> instead of
		1703	C<ev_timer_start>.
		1704
		1705	To implement this, configure an C<ev_timer> with a C<repeat> value
		1706	of C<60> and then call C<ev_timer_again> at start and each time you
		1707	successfully read or write some data. If you go into an idle state where
		1708	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1709	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1710
		1711	That means you can ignore both the C<ev_timer_start> function and the
		1712	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1713	member and C<ev_timer_again>.
		1714
		1715	At start:
		1716
		1717	ev_init (timer, callback);
		1718	timer->repeat = 60.;
		1719	ev_timer_again (loop, timer);
		1720
		1721	Each time there is some activity:
		1722
		1723	ev_timer_again (loop, timer);
		1724
		1725	It is even possible to change the time-out on the fly, regardless of
		1726	whether the watcher is active or not:
		1727
		1728	timer->repeat = 30.;
		1729	ev_timer_again (loop, timer);
		1730
		1731	This is slightly more efficient then stopping/starting the timer each time
		1732	you want to modify its timeout value, as libev does not have to completely
		1733	remove and re-insert the timer from/into its internal data structure.
		1734
		1735	It is, however, even simpler than the "obvious" way to do it.
		1736
		1737	=item 3. Let the timer time out, but then re-arm it as required.
		1738
		1739	This method is more tricky, but usually most efficient: Most timeouts are
		1740	relatively long compared to the intervals between other activity - in
		1741	our example, within 60 seconds, there are usually many I/O events with
		1742	associated activity resets.
		1743
		1744	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1745	but remember the time of last activity, and check for a real timeout only
		1746	within the callback:
		1747
		1748	ev_tstamp last_activity; // time of last activity
		1749
		1750	static void
		1751	callback (EV_P_ ev_timer *w, int revents)
		1752	{
		1753	ev_tstamp now = ev_now (EV_A);
		1754	ev_tstamp timeout = last_activity + 60.;
		1755
		1756	// if last_activity + 60. is older than now, we did time out
		1757	if (timeout < now)
		1758	{
		1759	// timeout occurred, take action
		1760	}
		1761	else
		1762	{
		1763	// callback was invoked, but there was some activity, re-arm
		1764	// the watcher to fire in last_activity + 60, which is
		1765	// guaranteed to be in the future, so "again" is positive:
		1766	w->repeat = timeout - now;
		1767	ev_timer_again (EV_A_ w);
		1768	}
		1769	}
		1770
		1771	To summarise the callback: first calculate the real timeout (defined
		1772	as "60 seconds after the last activity"), then check if that time has
		1773	been reached, which means something I<did>, in fact, time out. Otherwise
		1774	the callback was invoked too early (C<timeout> is in the future), so
		1775	re-schedule the timer to fire at that future time, to see if maybe we have
		1776	a timeout then.
		1777
		1778	Note how C<ev_timer_again> is used, taking advantage of the
		1779	C<ev_timer_again> optimisation when the timer is already running.
		1780
		1781	This scheme causes more callback invocations (about one every 60 seconds
		1782	minus half the average time between activity), but virtually no calls to
		1783	libev to change the timeout.
		1784
		1785	To start the timer, simply initialise the watcher and set C<last_activity>
		1786	to the current time (meaning we just have some activity :), then call the
		1787	callback, which will "do the right thing" and start the timer:
		1788
		1789	ev_init (timer, callback);
		1790	last_activity = ev_now (loop);
		1791	callback (loop, timer, EV_TIMER);
		1792
		1793	And when there is some activity, simply store the current time in
		1794	C<last_activity>, no libev calls at all:
		1795
		1796	last_activity = ev_now (loop);
		1797
		1798	This technique is slightly more complex, but in most cases where the
		1799	time-out is unlikely to be triggered, much more efficient.
		1800
		1801	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1802	callback :) - just change the timeout and invoke the callback, which will
		1803	fix things for you.
		1804
		1805	=item 4. Wee, just use a double-linked list for your timeouts.
		1806
		1807	If there is not one request, but many thousands (millions...), all
		1808	employing some kind of timeout with the same timeout value, then one can
		1809	do even better:
		1810
		1811	When starting the timeout, calculate the timeout value and put the timeout
		1812	at the I<end> of the list.
		1813
		1814	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1815	the list is expected to fire (for example, using the technique #3).
		1816
		1817	When there is some activity, remove the timer from the list, recalculate
		1818	the timeout, append it to the end of the list again, and make sure to
		1819	update the C<ev_timer> if it was taken from the beginning of the list.
		1820
		1821	This way, one can manage an unlimited number of timeouts in O(1) time for
		1822	starting, stopping and updating the timers, at the expense of a major
		1823	complication, and having to use a constant timeout. The constant timeout
		1824	ensures that the list stays sorted.
		1825
		1826	=back
		1827
		1828	So which method the best?
		1829
		1830	Method #2 is a simple no-brain-required solution that is adequate in most
		1831	situations. Method #3 requires a bit more thinking, but handles many cases
		1832	better, and isn't very complicated either. In most case, choosing either
		1833	one is fine, with #3 being better in typical situations.
		1834
		1835	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1836	rather complicated, but extremely efficient, something that really pays
		1837	off after the first million or so of active timers, i.e. it's usually
		1838	overkill :)
		1839
		1840	=head3 The special problem of time updates
		1841
		1842	Establishing the current time is a costly operation (it usually takes at
		1843	least two system calls): EV therefore updates its idea of the current
		1844	time only before and after C<ev_run> collects new events, which causes a
		1845	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1846	lots of events in one iteration.
1192		1847
1193	The relative timeouts are calculated relative to the C<ev_now ()>	1848	The relative timeouts are calculated relative to the C<ev_now ()>
1194	time. This is usually the right thing as this timestamp refers to the time	1849	time. This is usually the right thing as this timestamp refers to the time
1195	of the event triggering whatever timeout you are modifying/starting. If	1850	of the event triggering whatever timeout you are modifying/starting. If
1196	you suspect event processing to be delayed and you I<need> to base the timeout	1851	you suspect event processing to be delayed and you I<need> to base the
1197	on the current time, use something like this to adjust for this:	1852	timeout on the current time, use something like this to adjust for this:
1198		1853
1199	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1854	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1200		1855
1201	The callback is guaranteed to be invoked only after its timeout has passed,	1856	If the event loop is suspended for a long time, you can also force an
1202	but if multiple timers become ready during the same loop iteration then	1857	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1203	order of execution is undefined.	1858	()>.
		1859
		1860	=head3 The special problems of suspended animation
		1861
		1862	When you leave the server world it is quite customary to hit machines that
		1863	can suspend/hibernate - what happens to the clocks during such a suspend?
		1864
		1865	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1866	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1867	to run until the system is suspended, but they will not advance while the
		1868	system is suspended. That means, on resume, it will be as if the program
		1869	was frozen for a few seconds, but the suspend time will not be counted
		1870	towards C<ev_timer> when a monotonic clock source is used. The real time
		1871	clock advanced as expected, but if it is used as sole clocksource, then a
		1872	long suspend would be detected as a time jump by libev, and timers would
		1873	be adjusted accordingly.
		1874
		1875	I would not be surprised to see different behaviour in different between
		1876	operating systems, OS versions or even different hardware.
		1877
		1878	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1879	time jump in the monotonic clocks and the realtime clock. If the program
		1880	is suspended for a very long time, and monotonic clock sources are in use,
		1881	then you can expect C<ev_timer>s to expire as the full suspension time
		1882	will be counted towards the timers. When no monotonic clock source is in
		1883	use, then libev will again assume a timejump and adjust accordingly.
		1884
		1885	It might be beneficial for this latter case to call C<ev_suspend>
		1886	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1887	deterministic behaviour in this case (you can do nothing against
		1888	C<SIGSTOP>).
1204		1889
1205	=head3 Watcher-Specific Functions and Data Members	1890	=head3 Watcher-Specific Functions and Data Members
1206		1891
1207	=over 4	1892	=over 4
1208		1893
…		…
1232	If the timer is started but non-repeating, stop it (as if it timed out).	1917	If the timer is started but non-repeating, stop it (as if it timed out).
1233		1918
1234	If the timer is repeating, either start it if necessary (with the	1919	If the timer is repeating, either start it if necessary (with the
1235	C<repeat> value), or reset the running timer to the C<repeat> value.	1920	C<repeat> value), or reset the running timer to the C<repeat> value.
1236		1921
1237	This sounds a bit complicated, but here is a useful and typical	1922	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1238	example: Imagine you have a TCP connection and you want a so-called idle	1923	usage example.
1239	timeout, that is, you want to be called when there have been, say, 60
1240	seconds of inactivity on the socket. The easiest way to do this is to
1241	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1242	C<ev_timer_again> each time you successfully read or write some data. If
1243	you go into an idle state where you do not expect data to travel on the
1244	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1245	automatically restart it if need be.
1246		1924
1247	That means you can ignore the C<after> value and C<ev_timer_start>	1925	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1248	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1249		1926
1250	ev_timer_init (timer, callback, 0., 5.);	1927	Returns the remaining time until a timer fires. If the timer is active,
1251	ev_timer_again (loop, timer);	1928	then this time is relative to the current event loop time, otherwise it's
1252	...	1929	the timeout value currently configured.
1253	timer->again = 17.;
1254	ev_timer_again (loop, timer);
1255	...
1256	timer->again = 10.;
1257	ev_timer_again (loop, timer);
1258		1930
1259	This is more slightly efficient then stopping/starting the timer each time	1931	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1260	you want to modify its timeout value.	1932	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		1933	will return C<4>. When the timer expires and is restarted, it will return
		1934	roughly C<7> (likely slightly less as callback invocation takes some time,
		1935	too), and so on.
1261		1936
1262	=item ev_tstamp repeat [read-write]	1937	=item ev_tstamp repeat [read-write]
1263		1938
1264	The current C<repeat> value. Will be used each time the watcher times out	1939	The current C<repeat> value. Will be used each time the watcher times out
1265	or C<ev_timer_again> is called and determines the next timeout (if any),	1940	or C<ev_timer_again> is called, and determines the next timeout (if any),
1266	which is also when any modifications are taken into account.	1941	which is also when any modifications are taken into account.
1267		1942
1268	=back	1943	=back
1269		1944
1270	=head3 Examples	1945	=head3 Examples
1271		1946
1272	Example: Create a timer that fires after 60 seconds.	1947	Example: Create a timer that fires after 60 seconds.
1273		1948
1274	static void	1949	static void
1275	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1950	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1276	{	1951	{
1277	.. one minute over, w is actually stopped right here	1952	.. one minute over, w is actually stopped right here
1278	}	1953	}
1279		1954
1280	struct ev_timer mytimer;	1955	ev_timer mytimer;
1281	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1956	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1282	ev_timer_start (loop, &mytimer);	1957	ev_timer_start (loop, &mytimer);
1283		1958
1284	Example: Create a timeout timer that times out after 10 seconds of	1959	Example: Create a timeout timer that times out after 10 seconds of
1285	inactivity.	1960	inactivity.
1286		1961
1287	static void	1962	static void
1288	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1963	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1289	{	1964	{
1290	.. ten seconds without any activity	1965	.. ten seconds without any activity
1291	}	1966	}
1292		1967
1293	struct ev_timer mytimer;	1968	ev_timer mytimer;
1294	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1969	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1295	ev_timer_again (&mytimer); /* start timer */	1970	ev_timer_again (&mytimer); /* start timer */
1296	ev_loop (loop, 0);	1971	ev_run (loop, 0);
1297		1972
1298	// and in some piece of code that gets executed on any "activity":	1973	// and in some piece of code that gets executed on any "activity":
1299	// reset the timeout to start ticking again at 10 seconds	1974	// reset the timeout to start ticking again at 10 seconds
1300	ev_timer_again (&mytimer);	1975	ev_timer_again (&mytimer);
1301		1976
…		…
1303	=head2 C<ev_periodic> - to cron or not to cron?	1978	=head2 C<ev_periodic> - to cron or not to cron?
1304		1979
1305	Periodic watchers are also timers of a kind, but they are very versatile	1980	Periodic watchers are also timers of a kind, but they are very versatile
1306	(and unfortunately a bit complex).	1981	(and unfortunately a bit complex).
1307		1982
1308	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1983	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1309	but on wall clock time (absolute time). You can tell a periodic watcher	1984	relative time, the physical time that passes) but on wall clock time
1310	to trigger after some specific point in time. For example, if you tell a	1985	(absolute time, the thing you can read on your calender or clock). The
1311	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	1986	difference is that wall clock time can run faster or slower than real
1312	+ 10.>, that is, an absolute time not a delay) and then reset your system	1987	time, and time jumps are not uncommon (e.g. when you adjust your
1313	clock to January of the previous year, then it will take more than year	1988	wrist-watch).
1314	to trigger the event (unlike an C<ev_timer>, which would still trigger
1315	roughly 10 seconds later as it uses a relative timeout).
1316		1989
		1990	You can tell a periodic watcher to trigger after some specific point
		1991	in time: for example, if you tell a periodic watcher to trigger "in 10
		1992	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1993	not a delay) and then reset your system clock to January of the previous
		1994	year, then it will take a year or more to trigger the event (unlike an
		1995	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1996	it, as it uses a relative timeout).
		1997
1317	C<ev_periodic>s can also be used to implement vastly more complex timers,	1998	C<ev_periodic> watchers can also be used to implement vastly more complex
1318	such as triggering an event on each "midnight, local time", or other	1999	timers, such as triggering an event on each "midnight, local time", or
1319	complicated, rules.	2000	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2001	those cannot react to time jumps.
1320		2002
1321	As with timers, the callback is guaranteed to be invoked only when the	2003	As with timers, the callback is guaranteed to be invoked only when the
1322	time (C<at>) has passed, but if multiple periodic timers become ready	2004	point in time where it is supposed to trigger has passed. If multiple
1323	during the same loop iteration then order of execution is undefined.	2005	timers become ready during the same loop iteration then the ones with
		2006	earlier time-out values are invoked before ones with later time-out values
		2007	(but this is no longer true when a callback calls C<ev_run> recursively).
1324		2008
1325	=head3 Watcher-Specific Functions and Data Members	2009	=head3 Watcher-Specific Functions and Data Members
1326		2010
1327	=over 4	2011	=over 4
1328		2012
1329	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2013	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1330		2014
1331	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2015	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1332		2016
1333	Lots of arguments, lets sort it out... There are basically three modes of	2017	Lots of arguments, let's sort it out... There are basically three modes of
1334	operation, and we will explain them from simplest to complex:	2018	operation, and we will explain them from simplest to most complex:
1335		2019
1336	=over 4	2020	=over 4
1337		2021
1338	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2022	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1339		2023
1340	In this configuration the watcher triggers an event after the wall clock	2024	In this configuration the watcher triggers an event after the wall clock
1341	time C<at> has passed and doesn't repeat. It will not adjust when a time	2025	time C<offset> has passed. It will not repeat and will not adjust when a
1342	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2026	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1343	run when the system time reaches or surpasses this time.	2027	will be stopped and invoked when the system clock reaches or surpasses
		2028	this point in time.
1344		2029
1345	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2030	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1346		2031
1347	In this mode the watcher will always be scheduled to time out at the next	2032	In this mode the watcher will always be scheduled to time out at the next
1348	C<at + N * interval> time (for some integer N, which can also be negative)	2033	C<offset + N * interval> time (for some integer N, which can also be
1349	and then repeat, regardless of any time jumps.	2034	negative) and then repeat, regardless of any time jumps. The C<offset>
		2035	argument is merely an offset into the C<interval> periods.
1350		2036
1351	This can be used to create timers that do not drift with respect to system	2037	This can be used to create timers that do not drift with respect to the
1352	time, for example, here is a C<ev_periodic> that triggers each hour, on	2038	system clock, for example, here is an C<ev_periodic> that triggers each
1353	the hour:	2039	hour, on the hour (with respect to UTC):
1354		2040
1355	ev_periodic_set (&periodic, 0., 3600., 0);	2041	ev_periodic_set (&periodic, 0., 3600., 0);
1356		2042
1357	This doesn't mean there will always be 3600 seconds in between triggers,	2043	This doesn't mean there will always be 3600 seconds in between triggers,
1358	but only that the callback will be called when the system time shows a	2044	but only that the callback will be called when the system time shows a
1359	full hour (UTC), or more correctly, when the system time is evenly divisible	2045	full hour (UTC), or more correctly, when the system time is evenly divisible
1360	by 3600.	2046	by 3600.
1361		2047
1362	Another way to think about it (for the mathematically inclined) is that	2048	Another way to think about it (for the mathematically inclined) is that
1363	C<ev_periodic> will try to run the callback in this mode at the next possible	2049	C<ev_periodic> will try to run the callback in this mode at the next possible
1364	time where C<time = at (mod interval)>, regardless of any time jumps.	2050	time where C<time = offset (mod interval)>, regardless of any time jumps.
1365		2051
1366	For numerical stability it is preferable that the C<at> value is near	2052	For numerical stability it is preferable that the C<offset> value is near
1367	C<ev_now ()> (the current time), but there is no range requirement for	2053	C<ev_now ()> (the current time), but there is no range requirement for
1368	this value, and in fact is often specified as zero.	2054	this value, and in fact is often specified as zero.
1369		2055
1370	Note also that there is an upper limit to how often a timer can fire (CPU	2056	Note also that there is an upper limit to how often a timer can fire (CPU
1371	speed for example), so if C<interval> is very small then timing stability	2057	speed for example), so if C<interval> is very small then timing stability
1372	will of course deteriorate. Libev itself tries to be exact to be about one	2058	will of course deteriorate. Libev itself tries to be exact to be about one
1373	millisecond (if the OS supports it and the machine is fast enough).	2059	millisecond (if the OS supports it and the machine is fast enough).
1374		2060
1375	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2061	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1376		2062
1377	In this mode the values for C<interval> and C<at> are both being	2063	In this mode the values for C<interval> and C<offset> are both being
1378	ignored. Instead, each time the periodic watcher gets scheduled, the	2064	ignored. Instead, each time the periodic watcher gets scheduled, the
1379	reschedule callback will be called with the watcher as first, and the	2065	reschedule callback will be called with the watcher as first, and the
1380	current time as second argument.	2066	current time as second argument.
1381		2067
1382	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2068	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1383	ever, or make ANY event loop modifications whatsoever>.	2069	or make ANY other event loop modifications whatsoever, unless explicitly
		2070	allowed by documentation here>.
1384		2071
1385	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2072	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1386	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2073	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1387	only event loop modification you are allowed to do).	2074	only event loop modification you are allowed to do).
1388		2075
1389	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	2076	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1390	*w, ev_tstamp now)>, e.g.:	2077	*w, ev_tstamp now)>, e.g.:
1391		2078
		2079	static ev_tstamp
1392	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	2080	my_rescheduler (ev_periodic *w, ev_tstamp now)
1393	{	2081	{
1394	return now + 60.;	2082	return now + 60.;
1395	}	2083	}
1396		2084
1397	It must return the next time to trigger, based on the passed time value	2085	It must return the next time to trigger, based on the passed time value
…		…
1417	a different time than the last time it was called (e.g. in a crond like	2105	a different time than the last time it was called (e.g. in a crond like
1418	program when the crontabs have changed).	2106	program when the crontabs have changed).
1419		2107
1420	=item ev_tstamp ev_periodic_at (ev_periodic *)	2108	=item ev_tstamp ev_periodic_at (ev_periodic *)
1421		2109
1422	When active, returns the absolute time that the watcher is supposed to	2110	When active, returns the absolute time that the watcher is supposed
1423	trigger next.	2111	to trigger next. This is not the same as the C<offset> argument to
		2112	C<ev_periodic_set>, but indeed works even in interval and manual
		2113	rescheduling modes.
1424		2114
1425	=item ev_tstamp offset [read-write]	2115	=item ev_tstamp offset [read-write]
1426		2116
1427	When repeating, this contains the offset value, otherwise this is the	2117	When repeating, this contains the offset value, otherwise this is the
1428	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2118	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2119	although libev might modify this value for better numerical stability).
1429		2120
1430	Can be modified any time, but changes only take effect when the periodic	2121	Can be modified any time, but changes only take effect when the periodic
1431	timer fires or C<ev_periodic_again> is being called.	2122	timer fires or C<ev_periodic_again> is being called.
1432		2123
1433	=item ev_tstamp interval [read-write]	2124	=item ev_tstamp interval [read-write]
1434		2125
1435	The current interval value. Can be modified any time, but changes only	2126	The current interval value. Can be modified any time, but changes only
1436	take effect when the periodic timer fires or C<ev_periodic_again> is being	2127	take effect when the periodic timer fires or C<ev_periodic_again> is being
1437	called.	2128	called.
1438		2129
1439	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2130	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1440		2131
1441	The current reschedule callback, or C<0>, if this functionality is	2132	The current reschedule callback, or C<0>, if this functionality is
1442	switched off. Can be changed any time, but changes only take effect when	2133	switched off. Can be changed any time, but changes only take effect when
1443	the periodic timer fires or C<ev_periodic_again> is being called.	2134	the periodic timer fires or C<ev_periodic_again> is being called.
1444		2135
1445	=back	2136	=back
1446		2137
1447	=head3 Examples	2138	=head3 Examples
1448		2139
1449	Example: Call a callback every hour, or, more precisely, whenever the	2140	Example: Call a callback every hour, or, more precisely, whenever the
1450	system clock is divisible by 3600. The callback invocation times have	2141	system time is divisible by 3600. The callback invocation times have
1451	potentially a lot of jitter, but good long-term stability.	2142	potentially a lot of jitter, but good long-term stability.
1452		2143
1453	static void	2144	static void
1454	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2145	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1455	{	2146	{
1456	... its now a full hour (UTC, or TAI or whatever your clock follows)	2147	... its now a full hour (UTC, or TAI or whatever your clock follows)
1457	}	2148	}
1458		2149
1459	struct ev_periodic hourly_tick;	2150	ev_periodic hourly_tick;
1460	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2151	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1461	ev_periodic_start (loop, &hourly_tick);	2152	ev_periodic_start (loop, &hourly_tick);
1462		2153
1463	Example: The same as above, but use a reschedule callback to do it:	2154	Example: The same as above, but use a reschedule callback to do it:
1464		2155
1465	#include <math.h>	2156	#include <math.h>
1466		2157
1467	static ev_tstamp	2158	static ev_tstamp
1468	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2159	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1469	{	2160	{
1470	return fmod (now, 3600.) + 3600.;	2161	return now + (3600. - fmod (now, 3600.));
1471	}	2162	}
1472		2163
1473	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2164	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1474		2165
1475	Example: Call a callback every hour, starting now:	2166	Example: Call a callback every hour, starting now:
1476		2167
1477	struct ev_periodic hourly_tick;	2168	ev_periodic hourly_tick;
1478	ev_periodic_init (&hourly_tick, clock_cb,	2169	ev_periodic_init (&hourly_tick, clock_cb,
1479	fmod (ev_now (loop), 3600.), 3600., 0);	2170	fmod (ev_now (loop), 3600.), 3600., 0);
1480	ev_periodic_start (loop, &hourly_tick);	2171	ev_periodic_start (loop, &hourly_tick);
1481		2172
1482		2173
…		…
1485	Signal watchers will trigger an event when the process receives a specific	2176	Signal watchers will trigger an event when the process receives a specific
1486	signal one or more times. Even though signals are very asynchronous, libev	2177	signal one or more times. Even though signals are very asynchronous, libev
1487	will try it's best to deliver signals synchronously, i.e. as part of the	2178	will try it's best to deliver signals synchronously, i.e. as part of the
1488	normal event processing, like any other event.	2179	normal event processing, like any other event.
1489		2180
		2181	If you want signals to be delivered truly asynchronously, just use
		2182	C<sigaction> as you would do without libev and forget about sharing
		2183	the signal. You can even use C<ev_async> from a signal handler to
		2184	synchronously wake up an event loop.
		2185
1490	You can configure as many watchers as you like per signal. Only when the	2186	You can configure as many watchers as you like for the same signal, but
		2187	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2188	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2189	C<SIGINT> in both the default loop and another loop at the same time. At
		2190	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2191
1491	first watcher gets started will libev actually register a signal watcher	2192	When the first watcher gets started will libev actually register something
1492	with the kernel (thus it coexists with your own signal handlers as long	2193	with the kernel (thus it coexists with your own signal handlers as long as
1493	as you don't register any with libev). Similarly, when the last signal	2194	you don't register any with libev for the same signal).
1494	watcher for a signal is stopped libev will reset the signal handler to
1495	SIG_DFL (regardless of what it was set to before).
1496		2195
1497	If possible and supported, libev will install its handlers with	2196	If possible and supported, libev will install its handlers with
1498	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2197	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1499	interrupted. If you have a problem with system calls getting interrupted by	2198	not be unduly interrupted. If you have a problem with system calls getting
1500	signals you can block all signals in an C<ev_check> watcher and unblock	2199	interrupted by signals you can block all signals in an C<ev_check> watcher
1501	them in an C<ev_prepare> watcher.	2200	and unblock them in an C<ev_prepare> watcher.
		2201
		2202	=head3 The special problem of inheritance over fork/execve/pthread_create
		2203
		2204	Both the signal mask (C<sigprocmask>) and the signal disposition
		2205	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2206	stopping it again), that is, libev might or might not block the signal,
		2207	and might or might not set or restore the installed signal handler.
		2208
		2209	While this does not matter for the signal disposition (libev never
		2210	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2211	C<execve>), this matters for the signal mask: many programs do not expect
		2212	certain signals to be blocked.
		2213
		2214	This means that before calling C<exec> (from the child) you should reset
		2215	the signal mask to whatever "default" you expect (all clear is a good
		2216	choice usually).
		2217
		2218	The simplest way to ensure that the signal mask is reset in the child is
		2219	to install a fork handler with C<pthread_atfork> that resets it. That will
		2220	catch fork calls done by libraries (such as the libc) as well.
		2221
		2222	In current versions of libev, the signal will not be blocked indefinitely
		2223	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2224	the window of opportunity for problems, it will not go away, as libev
		2225	I<has> to modify the signal mask, at least temporarily.
		2226
		2227	So I can't stress this enough: I<If you do not reset your signal mask when
		2228	you expect it to be empty, you have a race condition in your code>. This
		2229	is not a libev-specific thing, this is true for most event libraries.
1502		2230
1503	=head3 Watcher-Specific Functions and Data Members	2231	=head3 Watcher-Specific Functions and Data Members
1504		2232
1505	=over 4	2233	=over 4
1506		2234
…		…
1517		2245
1518	=back	2246	=back
1519		2247
1520	=head3 Examples	2248	=head3 Examples
1521		2249
1522	Example: Try to exit cleanly on SIGINT and SIGTERM.	2250	Example: Try to exit cleanly on SIGINT.
1523		2251
1524	static void	2252	static void
1525	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2253	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1526	{	2254	{
1527	ev_unloop (loop, EVUNLOOP_ALL);	2255	ev_break (loop, EVBREAK_ALL);
1528	}	2256	}
1529		2257
1530	struct ev_signal signal_watcher;	2258	ev_signal signal_watcher;
1531	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2259	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1532	ev_signal_start (loop, &sigint_cb);	2260	ev_signal_start (loop, &signal_watcher);
1533		2261
1534		2262
1535	=head2 C<ev_child> - watch out for process status changes	2263	=head2 C<ev_child> - watch out for process status changes
1536		2264
1537	Child watchers trigger when your process receives a SIGCHLD in response to	2265	Child watchers trigger when your process receives a SIGCHLD in response to
1538	some child status changes (most typically when a child of yours dies). It	2266	some child status changes (most typically when a child of yours dies or
1539	is permissible to install a child watcher I<after> the child has been	2267	exits). It is permissible to install a child watcher I<after> the child
1540	forked (which implies it might have already exited), as long as the event	2268	has been forked (which implies it might have already exited), as long
1541	loop isn't entered (or is continued from a watcher).	2269	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2270	forking and then immediately registering a watcher for the child is fine,
		2271	but forking and registering a watcher a few event loop iterations later or
		2272	in the next callback invocation is not.
1542		2273
1543	Only the default event loop is capable of handling signals, and therefore	2274	Only the default event loop is capable of handling signals, and therefore
1544	you can only register child watchers in the default event loop.	2275	you can only register child watchers in the default event loop.
1545		2276
		2277	Due to some design glitches inside libev, child watchers will always be
		2278	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2279	libev)
		2280
1546	=head3 Process Interaction	2281	=head3 Process Interaction
1547		2282
1548	Libev grabs C<SIGCHLD> as soon as the default event loop is	2283	Libev grabs C<SIGCHLD> as soon as the default event loop is
1549	initialised. This is necessary to guarantee proper behaviour even if	2284	initialised. This is necessary to guarantee proper behaviour even if the
1550	the first child watcher is started after the child exits. The occurrence	2285	first child watcher is started after the child exits. The occurrence
1551	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2286	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1552	synchronously as part of the event loop processing. Libev always reaps all	2287	synchronously as part of the event loop processing. Libev always reaps all
1553	children, even ones not watched.	2288	children, even ones not watched.
1554		2289
1555	=head3 Overriding the Built-In Processing	2290	=head3 Overriding the Built-In Processing
…		…
1559	handler, you can override it easily by installing your own handler for	2294	handler, you can override it easily by installing your own handler for
1560	C<SIGCHLD> after initialising the default loop, and making sure the	2295	C<SIGCHLD> after initialising the default loop, and making sure the
1561	default loop never gets destroyed. You are encouraged, however, to use an	2296	default loop never gets destroyed. You are encouraged, however, to use an
1562	event-based approach to child reaping and thus use libev's support for	2297	event-based approach to child reaping and thus use libev's support for
1563	that, so other libev users can use C<ev_child> watchers freely.	2298	that, so other libev users can use C<ev_child> watchers freely.
		2299
		2300	=head3 Stopping the Child Watcher
		2301
		2302	Currently, the child watcher never gets stopped, even when the
		2303	child terminates, so normally one needs to stop the watcher in the
		2304	callback. Future versions of libev might stop the watcher automatically
		2305	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2306	problem).
1564		2307
1565	=head3 Watcher-Specific Functions and Data Members	2308	=head3 Watcher-Specific Functions and Data Members
1566		2309
1567	=over 4	2310	=over 4
1568		2311
…		…
1600	its completion.	2343	its completion.
1601		2344
1602	ev_child cw;	2345	ev_child cw;
1603		2346
1604	static void	2347	static void
1605	child_cb (EV_P_ struct ev_child *w, int revents)	2348	child_cb (EV_P_ ev_child *w, int revents)
1606	{	2349	{
1607	ev_child_stop (EV_A_ w);	2350	ev_child_stop (EV_A_ w);
1608	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2351	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1609	}	2352	}
1610		2353
…		…
1625		2368
1626		2369
1627	=head2 C<ev_stat> - did the file attributes just change?	2370	=head2 C<ev_stat> - did the file attributes just change?
1628		2371
1629	This watches a file system path for attribute changes. That is, it calls	2372	This watches a file system path for attribute changes. That is, it calls
1630	C<stat> regularly (or when the OS says it changed) and sees if it changed	2373	C<stat> on that path in regular intervals (or when the OS says it changed)
1631	compared to the last time, invoking the callback if it did.	2374	and sees if it changed compared to the last time, invoking the callback if
		2375	it did.
1632		2376
1633	The path does not need to exist: changing from "path exists" to "path does	2377	The path does not need to exist: changing from "path exists" to "path does
1634	not exist" is a status change like any other. The condition "path does	2378	not exist" is a status change like any other. The condition "path does not
1635	not exist" is signified by the C<st_nlink> field being zero (which is	2379	exist" (or more correctly "path cannot be stat'ed") is signified by the
1636	otherwise always forced to be at least one) and all the other fields of	2380	C<st_nlink> field being zero (which is otherwise always forced to be at
1637	the stat buffer having unspecified contents.	2381	least one) and all the other fields of the stat buffer having unspecified
		2382	contents.
1638		2383
1639	The path I<should> be absolute and I<must not> end in a slash. If it is	2384	The path I<must not> end in a slash or contain special components such as
		2385	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1640	relative and your working directory changes, the behaviour is undefined.	2386	your working directory changes, then the behaviour is undefined.
1641		2387
1642	Since there is no standard to do this, the portable implementation simply	2388	Since there is no portable change notification interface available, the
1643	calls C<stat (2)> regularly on the path to see if it changed somehow. You	2389	portable implementation simply calls C<stat(2)> regularly on the path
1644	can specify a recommended polling interval for this case. If you specify	2390	to see if it changed somehow. You can specify a recommended polling
1645	a polling interval of C<0> (highly recommended!) then a I<suitable,	2391	interval for this case. If you specify a polling interval of C<0> (highly
1646	unspecified default> value will be used (which you can expect to be around	2392	recommended!) then a I<suitable, unspecified default> value will be used
1647	five seconds, although this might change dynamically). Libev will also	2393	(which you can expect to be around five seconds, although this might
1648	impose a minimum interval which is currently around C<0.1>, but thats	2394	change dynamically). Libev will also impose a minimum interval which is
1649	usually overkill.	2395	currently around C<0.1>, but that's usually overkill.
1650		2396
1651	This watcher type is not meant for massive numbers of stat watchers,	2397	This watcher type is not meant for massive numbers of stat watchers,
1652	as even with OS-supported change notifications, this can be	2398	as even with OS-supported change notifications, this can be
1653	resource-intensive.	2399	resource-intensive.
1654		2400
1655	At the time of this writing, only the Linux inotify interface is	2401	At the time of this writing, the only OS-specific interface implemented
1656	implemented (implementing kqueue support is left as an exercise for the	2402	is the Linux inotify interface (implementing kqueue support is left as an
1657	reader, note, however, that the author sees no way of implementing ev_stat	2403	exercise for the reader. Note, however, that the author sees no way of
1658	semantics with kqueue). Inotify will be used to give hints only and should	2404	implementing C<ev_stat> semantics with kqueue, except as a hint).
1659	not change the semantics of C<ev_stat> watchers, which means that libev
1660	sometimes needs to fall back to regular polling again even with inotify,
1661	but changes are usually detected immediately, and if the file exists there
1662	will be no polling.
1663		2405
1664	=head3 ABI Issues (Largefile Support)	2406	=head3 ABI Issues (Largefile Support)
1665		2407
1666	Libev by default (unless the user overrides this) uses the default	2408	Libev by default (unless the user overrides this) uses the default
1667	compilation environment, which means that on systems with optionally	2409	compilation environment, which means that on systems with large file
1668	disabled large file support, you get the 32 bit version of the stat	2410	support disabled by default, you get the 32 bit version of the stat
1669	structure. When using the library from programs that change the ABI to	2411	structure. When using the library from programs that change the ABI to
1670	use 64 bit file offsets the programs will fail. In that case you have to	2412	use 64 bit file offsets the programs will fail. In that case you have to
1671	compile libev with the same flags to get binary compatibility. This is	2413	compile libev with the same flags to get binary compatibility. This is
1672	obviously the case with any flags that change the ABI, but the problem is	2414	obviously the case with any flags that change the ABI, but the problem is
1673	most noticeably with ev_stat and large file support.	2415	most noticeably displayed with ev_stat and large file support.
1674		2416
1675	=head3 Inotify	2417	The solution for this is to lobby your distribution maker to make large
		2418	file interfaces available by default (as e.g. FreeBSD does) and not
		2419	optional. Libev cannot simply switch on large file support because it has
		2420	to exchange stat structures with application programs compiled using the
		2421	default compilation environment.
1676		2422
		2423	=head3 Inotify and Kqueue
		2424
1677	When C<inotify (7)> support has been compiled into libev (generally only	2425	When C<inotify (7)> support has been compiled into libev and present at
1678	available on Linux) and present at runtime, it will be used to speed up	2426	runtime, it will be used to speed up change detection where possible. The
1679	change detection where possible. The inotify descriptor will be created lazily	2427	inotify descriptor will be created lazily when the first C<ev_stat>
1680	when the first C<ev_stat> watcher is being started.	2428	watcher is being started.
1681		2429
1682	Inotify presence does not change the semantics of C<ev_stat> watchers	2430	Inotify presence does not change the semantics of C<ev_stat> watchers
1683	except that changes might be detected earlier, and in some cases, to avoid	2431	except that changes might be detected earlier, and in some cases, to avoid
1684	making regular C<stat> calls. Even in the presence of inotify support	2432	making regular C<stat> calls. Even in the presence of inotify support
1685	there are many cases where libev has to resort to regular C<stat> polling.	2433	there are many cases where libev has to resort to regular C<stat> polling,
		2434	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2435	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2436	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2437	xfs are fully working) libev usually gets away without polling.
1686		2438
1687	(There is no support for kqueue, as apparently it cannot be used to	2439	There is no support for kqueue, as apparently it cannot be used to
1688	implement this functionality, due to the requirement of having a file	2440	implement this functionality, due to the requirement of having a file
1689	descriptor open on the object at all times).	2441	descriptor open on the object at all times, and detecting renames, unlinks
		2442	etc. is difficult.
		2443
		2444	=head3 C<stat ()> is a synchronous operation
		2445
		2446	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2447	the process. The exception are C<ev_stat> watchers - those call C<stat
		2448	()>, which is a synchronous operation.
		2449
		2450	For local paths, this usually doesn't matter: unless the system is very
		2451	busy or the intervals between stat's are large, a stat call will be fast,
		2452	as the path data is usually in memory already (except when starting the
		2453	watcher).
		2454
		2455	For networked file systems, calling C<stat ()> can block an indefinite
		2456	time due to network issues, and even under good conditions, a stat call
		2457	often takes multiple milliseconds.
		2458
		2459	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2460	paths, although this is fully supported by libev.
1690		2461
1691	=head3 The special problem of stat time resolution	2462	=head3 The special problem of stat time resolution
1692		2463
1693	The C<stat ()> system call only supports full-second resolution portably, and	2464	The C<stat ()> system call only supports full-second resolution portably,
1694	even on systems where the resolution is higher, many file systems still	2465	and even on systems where the resolution is higher, most file systems
1695	only support whole seconds.	2466	still only support whole seconds.
1696		2467
1697	That means that, if the time is the only thing that changes, you can	2468	That means that, if the time is the only thing that changes, you can
1698	easily miss updates: on the first update, C<ev_stat> detects a change and	2469	easily miss updates: on the first update, C<ev_stat> detects a change and
1699	calls your callback, which does something. When there is another update	2470	calls your callback, which does something. When there is another update
1700	within the same second, C<ev_stat> will be unable to detect it as the stat	2471	within the same second, C<ev_stat> will be unable to detect unless the
1701	data does not change.	2472	stat data does change in other ways (e.g. file size).
1702		2473
1703	The solution to this is to delay acting on a change for slightly more	2474	The solution to this is to delay acting on a change for slightly more
1704	than a second (or till slightly after the next full second boundary), using	2475	than a second (or till slightly after the next full second boundary), using
1705	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2476	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1706	ev_timer_again (loop, w)>).	2477	ev_timer_again (loop, w)>).
…		…
1726	C<path>. The C<interval> is a hint on how quickly a change is expected to	2497	C<path>. The C<interval> is a hint on how quickly a change is expected to
1727	be detected and should normally be specified as C<0> to let libev choose	2498	be detected and should normally be specified as C<0> to let libev choose
1728	a suitable value. The memory pointed to by C<path> must point to the same	2499	a suitable value. The memory pointed to by C<path> must point to the same
1729	path for as long as the watcher is active.	2500	path for as long as the watcher is active.
1730		2501
1731	The callback will receive C<EV_STAT> when a change was detected, relative	2502	The callback will receive an C<EV_STAT> event when a change was detected,
1732	to the attributes at the time the watcher was started (or the last change	2503	relative to the attributes at the time the watcher was started (or the
1733	was detected).	2504	last change was detected).
1734		2505
1735	=item ev_stat_stat (loop, ev_stat *)	2506	=item ev_stat_stat (loop, ev_stat *)
1736		2507
1737	Updates the stat buffer immediately with new values. If you change the	2508	Updates the stat buffer immediately with new values. If you change the
1738	watched path in your callback, you could call this function to avoid	2509	watched path in your callback, you could call this function to avoid
…		…
1821		2592
1822		2593
1823	=head2 C<ev_idle> - when you've got nothing better to do...	2594	=head2 C<ev_idle> - when you've got nothing better to do...
1824		2595
1825	Idle watchers trigger events when no other events of the same or higher	2596	Idle watchers trigger events when no other events of the same or higher
1826	priority are pending (prepare, check and other idle watchers do not	2597	priority are pending (prepare, check and other idle watchers do not count
1827	count).	2598	as receiving "events").
1828		2599
1829	That is, as long as your process is busy handling sockets or timeouts	2600	That is, as long as your process is busy handling sockets or timeouts
1830	(or even signals, imagine) of the same or higher priority it will not be	2601	(or even signals, imagine) of the same or higher priority it will not be
1831	triggered. But when your process is idle (or only lower-priority watchers	2602	triggered. But when your process is idle (or only lower-priority watchers
1832	are pending), the idle watchers are being called once per event loop	2603	are pending), the idle watchers are being called once per event loop
…		…
1843		2614
1844	=head3 Watcher-Specific Functions and Data Members	2615	=head3 Watcher-Specific Functions and Data Members
1845		2616
1846	=over 4	2617	=over 4
1847		2618
1848	=item ev_idle_init (ev_signal *, callback)	2619	=item ev_idle_init (ev_idle *, callback)
1849		2620
1850	Initialises and configures the idle watcher - it has no parameters of any	2621	Initialises and configures the idle watcher - it has no parameters of any
1851	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2622	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1852	believe me.	2623	believe me.
1853		2624
…		…
1857		2628
1858	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2629	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1859	callback, free it. Also, use no error checking, as usual.	2630	callback, free it. Also, use no error checking, as usual.
1860		2631
1861	static void	2632	static void
1862	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2633	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1863	{	2634	{
1864	free (w);	2635	free (w);
1865	// now do something you wanted to do when the program has	2636	// now do something you wanted to do when the program has
1866	// no longer anything immediate to do.	2637	// no longer anything immediate to do.
1867	}	2638	}
1868		2639
1869	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2640	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1870	ev_idle_init (idle_watcher, idle_cb);	2641	ev_idle_init (idle_watcher, idle_cb);
1871	ev_idle_start (loop, idle_cb);	2642	ev_idle_start (loop, idle_watcher);
1872		2643
1873		2644
1874	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2645	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1875		2646
1876	Prepare and check watchers are usually (but not always) used in tandem:	2647	Prepare and check watchers are usually (but not always) used in pairs:
1877	prepare watchers get invoked before the process blocks and check watchers	2648	prepare watchers get invoked before the process blocks and check watchers
1878	afterwards.	2649	afterwards.
1879		2650
1880	You I<must not> call C<ev_loop> or similar functions that enter	2651	You I<must not> call C<ev_run> or similar functions that enter
1881	the current event loop from either C<ev_prepare> or C<ev_check>	2652	the current event loop from either C<ev_prepare> or C<ev_check>
1882	watchers. Other loops than the current one are fine, however. The	2653	watchers. Other loops than the current one are fine, however. The
1883	rationale behind this is that you do not need to check for recursion in	2654	rationale behind this is that you do not need to check for recursion in
1884	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2655	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1885	C<ev_check> so if you have one watcher of each kind they will always be	2656	C<ev_check> so if you have one watcher of each kind they will always be
1886	called in pairs bracketing the blocking call.	2657	called in pairs bracketing the blocking call.
1887		2658
1888	Their main purpose is to integrate other event mechanisms into libev and	2659	Their main purpose is to integrate other event mechanisms into libev and
1889	their use is somewhat advanced. This could be used, for example, to track	2660	their use is somewhat advanced. They could be used, for example, to track
1890	variable changes, implement your own watchers, integrate net-snmp or a	2661	variable changes, implement your own watchers, integrate net-snmp or a
1891	coroutine library and lots more. They are also occasionally useful if	2662	coroutine library and lots more. They are also occasionally useful if
1892	you cache some data and want to flush it before blocking (for example,	2663	you cache some data and want to flush it before blocking (for example,
1893	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2664	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1894	watcher).	2665	watcher).
1895		2666
1896	This is done by examining in each prepare call which file descriptors need	2667	This is done by examining in each prepare call which file descriptors
1897	to be watched by the other library, registering C<ev_io> watchers for	2668	need to be watched by the other library, registering C<ev_io> watchers
1898	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2669	for them and starting an C<ev_timer> watcher for any timeouts (many
1899	provide just this functionality). Then, in the check watcher you check for	2670	libraries provide exactly this functionality). Then, in the check watcher,
1900	any events that occurred (by checking the pending status of all watchers	2671	you check for any events that occurred (by checking the pending status
1901	and stopping them) and call back into the library. The I/O and timer	2672	of all watchers and stopping them) and call back into the library. The
1902	callbacks will never actually be called (but must be valid nevertheless,	2673	I/O and timer callbacks will never actually be called (but must be valid
1903	because you never know, you know?).	2674	nevertheless, because you never know, you know?).
1904		2675
1905	As another example, the Perl Coro module uses these hooks to integrate	2676	As another example, the Perl Coro module uses these hooks to integrate
1906	coroutines into libev programs, by yielding to other active coroutines	2677	coroutines into libev programs, by yielding to other active coroutines
1907	during each prepare and only letting the process block if no coroutines	2678	during each prepare and only letting the process block if no coroutines
1908	are ready to run (it's actually more complicated: it only runs coroutines	2679	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1911	loop from blocking if lower-priority coroutines are active, thus mapping	2682	loop from blocking if lower-priority coroutines are active, thus mapping
1912	low-priority coroutines to idle/background tasks).	2683	low-priority coroutines to idle/background tasks).
1913		2684
1914	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2685	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1915	priority, to ensure that they are being run before any other watchers	2686	priority, to ensure that they are being run before any other watchers
		2687	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2688
1916	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2689	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1917	too) should not activate ("feed") events into libev. While libev fully	2690	activate ("feed") events into libev. While libev fully supports this, they
1918	supports this, they might get executed before other C<ev_check> watchers	2691	might get executed before other C<ev_check> watchers did their job. As
1919	did their job. As C<ev_check> watchers are often used to embed other	2692	C<ev_check> watchers are often used to embed other (non-libev) event
1920	(non-libev) event loops those other event loops might be in an unusable	2693	loops those other event loops might be in an unusable state until their
1921	state until their C<ev_check> watcher ran (always remind yourself to	2694	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1922	coexist peacefully with others).	2695	others).
1923		2696
1924	=head3 Watcher-Specific Functions and Data Members	2697	=head3 Watcher-Specific Functions and Data Members
1925		2698
1926	=over 4	2699	=over 4
1927		2700
…		…
1929		2702
1930	=item ev_check_init (ev_check *, callback)	2703	=item ev_check_init (ev_check *, callback)
1931		2704
1932	Initialises and configures the prepare or check watcher - they have no	2705	Initialises and configures the prepare or check watcher - they have no
1933	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2706	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1934	macros, but using them is utterly, utterly and completely pointless.	2707	macros, but using them is utterly, utterly, utterly and completely
		2708	pointless.
1935		2709
1936	=back	2710	=back
1937		2711
1938	=head3 Examples	2712	=head3 Examples
1939		2713
…		…
1952		2726
1953	static ev_io iow [nfd];	2727	static ev_io iow [nfd];
1954	static ev_timer tw;	2728	static ev_timer tw;
1955		2729
1956	static void	2730	static void
1957	io_cb (ev_loop *loop, ev_io *w, int revents)	2731	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1958	{	2732	{
1959	}	2733	}
1960		2734
1961	// create io watchers for each fd and a timer before blocking	2735	// create io watchers for each fd and a timer before blocking
1962	static void	2736	static void
1963	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2737	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1964	{	2738	{
1965	int timeout = 3600000;	2739	int timeout = 3600000;
1966	struct pollfd fds [nfd];	2740	struct pollfd fds [nfd];
1967	// actual code will need to loop here and realloc etc.	2741	// actual code will need to loop here and realloc etc.
1968	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2742	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1969		2743
1970	/* the callback is illegal, but won't be called as we stop during check */	2744	/* the callback is illegal, but won't be called as we stop during check */
1971	ev_timer_init (&tw, 0, timeout * 1e-3);	2745	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
1972	ev_timer_start (loop, &tw);	2746	ev_timer_start (loop, &tw);
1973		2747
1974	// create one ev_io per pollfd	2748	// create one ev_io per pollfd
1975	for (int i = 0; i < nfd; ++i)	2749	for (int i = 0; i < nfd; ++i)
1976	{	2750	{
…		…
1983	}	2757	}
1984	}	2758	}
1985		2759
1986	// stop all watchers after blocking	2760	// stop all watchers after blocking
1987	static void	2761	static void
1988	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2762	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1989	{	2763	{
1990	ev_timer_stop (loop, &tw);	2764	ev_timer_stop (loop, &tw);
1991		2765
1992	for (int i = 0; i < nfd; ++i)	2766	for (int i = 0; i < nfd; ++i)
1993	{	2767	{
…		…
2032	}	2806	}
2033		2807
2034	// do not ever call adns_afterpoll	2808	// do not ever call adns_afterpoll
2035		2809
2036	Method 4: Do not use a prepare or check watcher because the module you	2810	Method 4: Do not use a prepare or check watcher because the module you
2037	want to embed is too inflexible to support it. Instead, you can override	2811	want to embed is not flexible enough to support it. Instead, you can
2038	their poll function. The drawback with this solution is that the main	2812	override their poll function. The drawback with this solution is that the
2039	loop is now no longer controllable by EV. The C<Glib::EV> module does	2813	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2040	this.	2814	this approach, effectively embedding EV as a client into the horrible
		2815	libglib event loop.
2041		2816
2042	static gint	2817	static gint
2043	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2818	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2044	{	2819	{
2045	int got_events = 0;	2820	int got_events = 0;
…		…
2049		2824
2050	if (timeout >= 0)	2825	if (timeout >= 0)
2051	// create/start timer	2826	// create/start timer
2052		2827
2053	// poll	2828	// poll
2054	ev_loop (EV_A_ 0);	2829	ev_run (EV_A_ 0);
2055		2830
2056	// stop timer again	2831	// stop timer again
2057	if (timeout >= 0)	2832	if (timeout >= 0)
2058	ev_timer_stop (EV_A_ &to);	2833	ev_timer_stop (EV_A_ &to);
2059		2834
…		…
2076	prioritise I/O.	2851	prioritise I/O.
2077		2852
2078	As an example for a bug workaround, the kqueue backend might only support	2853	As an example for a bug workaround, the kqueue backend might only support
2079	sockets on some platform, so it is unusable as generic backend, but you	2854	sockets on some platform, so it is unusable as generic backend, but you
2080	still want to make use of it because you have many sockets and it scales	2855	still want to make use of it because you have many sockets and it scales
2081	so nicely. In this case, you would create a kqueue-based loop and embed it	2856	so nicely. In this case, you would create a kqueue-based loop and embed
2082	into your default loop (which might use e.g. poll). Overall operation will	2857	it into your default loop (which might use e.g. poll). Overall operation
2083	be a bit slower because first libev has to poll and then call kevent, but	2858	will be a bit slower because first libev has to call C<poll> and then
2084	at least you can use both at what they are best.	2859	C<kevent>, but at least you can use both mechanisms for what they are
		2860	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2085		2861
2086	As for prioritising I/O: rarely you have the case where some fds have	2862	As for prioritising I/O: under rare circumstances you have the case where
2087	to be watched and handled very quickly (with low latency), and even	2863	some fds have to be watched and handled very quickly (with low latency),
2088	priorities and idle watchers might have too much overhead. In this case	2864	and even priorities and idle watchers might have too much overhead. In
2089	you would put all the high priority stuff in one loop and all the rest in	2865	this case you would put all the high priority stuff in one loop and all
2090	a second one, and embed the second one in the first.	2866	the rest in a second one, and embed the second one in the first.
2091		2867
2092	As long as the watcher is active, the callback will be invoked every time	2868	As long as the watcher is active, the callback will be invoked every
2093	there might be events pending in the embedded loop. The callback must then	2869	time there might be events pending in the embedded loop. The callback
2094	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2870	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2095	their callbacks (you could also start an idle watcher to give the embedded	2871	sweep and invoke their callbacks (the callback doesn't need to invoke the
2096	loop strictly lower priority for example). You can also set the callback	2872	C<ev_embed_sweep> function directly, it could also start an idle watcher
2097	to C<0>, in which case the embed watcher will automatically execute the	2873	to give the embedded loop strictly lower priority for example).
2098	embedded loop sweep.
2099		2874
2100	As long as the watcher is started it will automatically handle events. The	2875	You can also set the callback to C<0>, in which case the embed watcher
2101	callback will be invoked whenever some events have been handled. You can	2876	will automatically execute the embedded loop sweep whenever necessary.
2102	set the callback to C<0> to avoid having to specify one if you are not
2103	interested in that.
2104		2877
2105	Also, there have not currently been made special provisions for forking:	2878	Fork detection will be handled transparently while the C<ev_embed> watcher
2106	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2879	is active, i.e., the embedded loop will automatically be forked when the
2107	but you will also have to stop and restart any C<ev_embed> watchers	2880	embedding loop forks. In other cases, the user is responsible for calling
2108	yourself.	2881	C<ev_loop_fork> on the embedded loop.
2109		2882
2110	Unfortunately, not all backends are embeddable, only the ones returned by	2883	Unfortunately, not all backends are embeddable: only the ones returned by
2111	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2884	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2112	portable one.	2885	portable one.
2113		2886
2114	So when you want to use this feature you will always have to be prepared	2887	So when you want to use this feature you will always have to be prepared
2115	that you cannot get an embeddable loop. The recommended way to get around	2888	that you cannot get an embeddable loop. The recommended way to get around
2116	this is to have a separate variables for your embeddable loop, try to	2889	this is to have a separate variables for your embeddable loop, try to
2117	create it, and if that fails, use the normal loop for everything.	2890	create it, and if that fails, use the normal loop for everything.
		2891
		2892	=head3 C<ev_embed> and fork
		2893
		2894	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2895	automatically be applied to the embedded loop as well, so no special
		2896	fork handling is required in that case. When the watcher is not running,
		2897	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2898	as applicable.
2118		2899
2119	=head3 Watcher-Specific Functions and Data Members	2900	=head3 Watcher-Specific Functions and Data Members
2120		2901
2121	=over 4	2902	=over 4
2122		2903
…		…
2131	if you do not want that, you need to temporarily stop the embed watcher).	2912	if you do not want that, you need to temporarily stop the embed watcher).
2132		2913
2133	=item ev_embed_sweep (loop, ev_embed *)	2914	=item ev_embed_sweep (loop, ev_embed *)
2134		2915
2135	Make a single, non-blocking sweep over the embedded loop. This works	2916	Make a single, non-blocking sweep over the embedded loop. This works
2136	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2917	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2137	appropriate way for embedded loops.	2918	appropriate way for embedded loops.
2138		2919
2139	=item struct ev_loop *other [read-only]	2920	=item struct ev_loop *other [read-only]
2140		2921
2141	The embedded event loop.	2922	The embedded event loop.
…		…
2150	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2931	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2151	used).	2932	used).
2152		2933
2153	struct ev_loop *loop_hi = ev_default_init (0);	2934	struct ev_loop *loop_hi = ev_default_init (0);
2154	struct ev_loop *loop_lo = 0;	2935	struct ev_loop *loop_lo = 0;
2155	struct ev_embed embed;	2936	ev_embed embed;
2156		2937
2157	// see if there is a chance of getting one that works	2938	// see if there is a chance of getting one that works
2158	// (remember that a flags value of 0 means autodetection)	2939	// (remember that a flags value of 0 means autodetection)
2159	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2940	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2160	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2941	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2174	kqueue implementation). Store the kqueue/socket-only event loop in	2955	kqueue implementation). Store the kqueue/socket-only event loop in
2175	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2956	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2176		2957
2177	struct ev_loop *loop = ev_default_init (0);	2958	struct ev_loop *loop = ev_default_init (0);
2178	struct ev_loop *loop_socket = 0;	2959	struct ev_loop *loop_socket = 0;
2179	struct ev_embed embed;	2960	ev_embed embed;
2180		2961
2181	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2962	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2182	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2963	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2183	{	2964	{
2184	ev_embed_init (&embed, 0, loop_socket);	2965	ev_embed_init (&embed, 0, loop_socket);
…		…
2199	event loop blocks next and before C<ev_check> watchers are being called,	2980	event loop blocks next and before C<ev_check> watchers are being called,
2200	and only in the child after the fork. If whoever good citizen calling	2981	and only in the child after the fork. If whoever good citizen calling
2201	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2982	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2202	handlers will be invoked, too, of course.	2983	handlers will be invoked, too, of course.
2203		2984
		2985	=head3 The special problem of life after fork - how is it possible?
		2986
		2987	Most uses of C<fork()> consist of forking, then some simple calls to set
		2988	up/change the process environment, followed by a call to C<exec()>. This
		2989	sequence should be handled by libev without any problems.
		2990
		2991	This changes when the application actually wants to do event handling
		2992	in the child, or both parent in child, in effect "continuing" after the
		2993	fork.
		2994
		2995	The default mode of operation (for libev, with application help to detect
		2996	forks) is to duplicate all the state in the child, as would be expected
		2997	when I<either> the parent I<or> the child process continues.
		2998
		2999	When both processes want to continue using libev, then this is usually the
		3000	wrong result. In that case, usually one process (typically the parent) is
		3001	supposed to continue with all watchers in place as before, while the other
		3002	process typically wants to start fresh, i.e. without any active watchers.
		3003
		3004	The cleanest and most efficient way to achieve that with libev is to
		3005	simply create a new event loop, which of course will be "empty", and
		3006	use that for new watchers. This has the advantage of not touching more
		3007	memory than necessary, and thus avoiding the copy-on-write, and the
		3008	disadvantage of having to use multiple event loops (which do not support
		3009	signal watchers).
		3010
		3011	When this is not possible, or you want to use the default loop for
		3012	other reasons, then in the process that wants to start "fresh", call
		3013	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		3014	the default loop will "orphan" (not stop) all registered watchers, so you
		3015	have to be careful not to execute code that modifies those watchers. Note
		3016	also that in that case, you have to re-register any signal watchers.
		3017
2204	=head3 Watcher-Specific Functions and Data Members	3018	=head3 Watcher-Specific Functions and Data Members
2205		3019
2206	=over 4	3020	=over 4
2207		3021
2208	=item ev_fork_init (ev_signal *, callback)	3022	=item ev_fork_init (ev_signal *, callback)
…		…
2212	believe me.	3026	believe me.
2213		3027
2214	=back	3028	=back
2215		3029
2216		3030
2217	=head2 C<ev_async> - how to wake up another event loop	3031	=head2 C<ev_async> - how to wake up an event loop
2218		3032
2219	In general, you cannot use an C<ev_loop> from multiple threads or other	3033	In general, you cannot use an C<ev_run> from multiple threads or other
2220	asynchronous sources such as signal handlers (as opposed to multiple event	3034	asynchronous sources such as signal handlers (as opposed to multiple event
2221	loops - those are of course safe to use in different threads).	3035	loops - those are of course safe to use in different threads).
2222		3036
2223	Sometimes, however, you need to wake up another event loop you do not	3037	Sometimes, however, you need to wake up an event loop you do not control,
2224	control, for example because it belongs to another thread. This is what	3038	for example because it belongs to another thread. This is what C<ev_async>
2225	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3039	watchers do: as long as the C<ev_async> watcher is active, you can signal
2226	can signal it by calling C<ev_async_send>, which is thread- and signal	3040	it by calling C<ev_async_send>, which is thread- and signal safe.
2227	safe.
2228		3041
2229	This functionality is very similar to C<ev_signal> watchers, as signals,	3042	This functionality is very similar to C<ev_signal> watchers, as signals,
2230	too, are asynchronous in nature, and signals, too, will be compressed	3043	too, are asynchronous in nature, and signals, too, will be compressed
2231	(i.e. the number of callback invocations may be less than the number of	3044	(i.e. the number of callback invocations may be less than the number of
2232	C<ev_async_sent> calls).	3045	C<ev_async_sent> calls).
…		…
2237	=head3 Queueing	3050	=head3 Queueing
2238		3051
2239	C<ev_async> does not support queueing of data in any way. The reason	3052	C<ev_async> does not support queueing of data in any way. The reason
2240	is that the author does not know of a simple (or any) algorithm for a	3053	is that the author does not know of a simple (or any) algorithm for a
2241	multiple-writer-single-reader queue that works in all cases and doesn't	3054	multiple-writer-single-reader queue that works in all cases and doesn't
2242	need elaborate support such as pthreads.	3055	need elaborate support such as pthreads or unportable memory access
		3056	semantics.
2243		3057
2244	That means that if you want to queue data, you have to provide your own	3058	That means that if you want to queue data, you have to provide your own
2245	queue. But at least I can tell you would implement locking around your	3059	queue. But at least I can tell you how to implement locking around your
2246	queue:	3060	queue:
2247		3061
2248	=over 4	3062	=over 4
2249		3063
2250	=item queueing from a signal handler context	3064	=item queueing from a signal handler context
2251		3065
2252	To implement race-free queueing, you simply add to the queue in the signal	3066	To implement race-free queueing, you simply add to the queue in the signal
2253	handler but you block the signal handler in the watcher callback. Here is an example that does that for	3067	handler but you block the signal handler in the watcher callback. Here is
2254	some fictitious SIGUSR1 handler:	3068	an example that does that for some fictitious SIGUSR1 handler:
2255		3069
2256	static ev_async mysig;	3070	static ev_async mysig;
2257		3071
2258	static void	3072	static void
2259	sigusr1_handler (void)	3073	sigusr1_handler (void)
…		…
2325	=over 4	3139	=over 4
2326		3140
2327	=item ev_async_init (ev_async *, callback)	3141	=item ev_async_init (ev_async *, callback)
2328		3142
2329	Initialises and configures the async watcher - it has no parameters of any	3143	Initialises and configures the async watcher - it has no parameters of any
2330	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3144	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2331	believe me.	3145	trust me.
2332		3146
2333	=item ev_async_send (loop, ev_async *)	3147	=item ev_async_send (loop, ev_async *)
2334		3148
2335	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3149	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2336	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3150	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2337	C<ev_feed_event>, this call is safe to do in other threads, signal or	3151	C<ev_feed_event>, this call is safe to do from other threads, signal or
2338	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3152	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2339	section below on what exactly this means).	3153	section below on what exactly this means).
2340		3154
		3155	Note that, as with other watchers in libev, multiple events might get
		3156	compressed into a single callback invocation (another way to look at this
		3157	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3158	reset when the event loop detects that).
		3159
2341	This call incurs the overhead of a system call only once per loop iteration,	3160	This call incurs the overhead of a system call only once per event loop
2342	so while the overhead might be noticeable, it doesn't apply to repeated	3161	iteration, so while the overhead might be noticeable, it doesn't apply to
2343	calls to C<ev_async_send>.	3162	repeated calls to C<ev_async_send> for the same event loop.
2344		3163
2345	=item bool = ev_async_pending (ev_async *)	3164	=item bool = ev_async_pending (ev_async *)
2346		3165
2347	Returns a non-zero value when C<ev_async_send> has been called on the	3166	Returns a non-zero value when C<ev_async_send> has been called on the
2348	watcher but the event has not yet been processed (or even noted) by the	3167	watcher but the event has not yet been processed (or even noted) by the
…		…
2351	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3170	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2352	the loop iterates next and checks for the watcher to have become active,	3171	the loop iterates next and checks for the watcher to have become active,
2353	it will reset the flag again. C<ev_async_pending> can be used to very	3172	it will reset the flag again. C<ev_async_pending> can be used to very
2354	quickly check whether invoking the loop might be a good idea.	3173	quickly check whether invoking the loop might be a good idea.
2355		3174
2356	Not that this does I<not> check whether the watcher itself is pending, only	3175	Not that this does I<not> check whether the watcher itself is pending,
2357	whether it has been requested to make this watcher pending.	3176	only whether it has been requested to make this watcher pending: there
		3177	is a time window between the event loop checking and resetting the async
		3178	notification, and the callback being invoked.
2358		3179
2359	=back	3180	=back
2360		3181
2361		3182
2362	=head1 OTHER FUNCTIONS	3183	=head1 OTHER FUNCTIONS
…		…
2366	=over 4	3187	=over 4
2367		3188
2368	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3189	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2369		3190
2370	This function combines a simple timer and an I/O watcher, calls your	3191	This function combines a simple timer and an I/O watcher, calls your
2371	callback on whichever event happens first and automatically stop both	3192	callback on whichever event happens first and automatically stops both
2372	watchers. This is useful if you want to wait for a single event on an fd	3193	watchers. This is useful if you want to wait for a single event on an fd
2373	or timeout without having to allocate/configure/start/stop/free one or	3194	or timeout without having to allocate/configure/start/stop/free one or
2374	more watchers yourself.	3195	more watchers yourself.
2375		3196
2376	If C<fd> is less than 0, then no I/O watcher will be started and events	3197	If C<fd> is less than 0, then no I/O watcher will be started and the
2377	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	3198	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2378	C<events> set will be created and started.	3199	the given C<fd> and C<events> set will be created and started.
2379		3200
2380	If C<timeout> is less than 0, then no timeout watcher will be	3201	If C<timeout> is less than 0, then no timeout watcher will be
2381	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3202	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2382	repeat = 0) will be started. While C<0> is a valid timeout, it is of	3203	repeat = 0) will be started. C<0> is a valid timeout.
2383	dubious value.
2384		3204
2385	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3205	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2386	passed an C<revents> set like normal event callbacks (a combination of	3206	passed an C<revents> set like normal event callbacks (a combination of
2387	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3207	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2388	value passed to C<ev_once>:	3208	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3209	a timeout and an io event at the same time - you probably should give io
		3210	events precedence.
		3211
		3212	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2389		3213
2390	static void stdin_ready (int revents, void *arg)	3214	static void stdin_ready (int revents, void *arg)
2391	{	3215	{
		3216	if (revents & EV_READ)
		3217	/* stdin might have data for us, joy! */;
2392	if (revents & EV_TIMEOUT)	3218	else if (revents & EV_TIMER)
2393	/* doh, nothing entered */;	3219	/* doh, nothing entered */;
2394	else if (revents & EV_READ)
2395	/* stdin might have data for us, joy! */;
2396	}	3220	}
2397		3221
2398	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3222	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2399		3223
2400	=item ev_feed_event (ev_loop *, watcher *, int revents)
2401
2402	Feeds the given event set into the event loop, as if the specified event
2403	had happened for the specified watcher (which must be a pointer to an
2404	initialised but not necessarily started event watcher).
2405
2406	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3224	=item ev_feed_fd_event (loop, int fd, int revents)
2407		3225
2408	Feed an event on the given fd, as if a file descriptor backend detected	3226	Feed an event on the given fd, as if a file descriptor backend detected
2409	the given events it.	3227	the given events it.
2410		3228
2411	=item ev_feed_signal_event (ev_loop *loop, int signum)	3229	=item ev_feed_signal_event (loop, int signum)
2412		3230
2413	Feed an event as if the given signal occurred (C<loop> must be the default	3231	Feed an event as if the given signal occurred (C<loop> must be the default
2414	loop!).	3232	loop!).
2415		3233
2416	=back	3234	=back
…		…
2496		3314
2497	=over 4	3315	=over 4
2498		3316
2499	=item ev::TYPE::TYPE ()	3317	=item ev::TYPE::TYPE ()
2500		3318
2501	=item ev::TYPE::TYPE (struct ev_loop *)	3319	=item ev::TYPE::TYPE (loop)
2502		3320
2503	=item ev::TYPE::~TYPE	3321	=item ev::TYPE::~TYPE
2504		3322
2505	The constructor (optionally) takes an event loop to associate the watcher	3323	The constructor (optionally) takes an event loop to associate the watcher
2506	with. If it is omitted, it will use C<EV_DEFAULT>.	3324	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2538		3356
2539	myclass obj;	3357	myclass obj;
2540	ev::io iow;	3358	ev::io iow;
2541	iow.set <myclass, &myclass::io_cb> (&obj);	3359	iow.set <myclass, &myclass::io_cb> (&obj);
2542		3360
		3361	=item w->set (object *)
		3362
		3363	This is a variation of a method callback - leaving out the method to call
		3364	will default the method to C<operator ()>, which makes it possible to use
		3365	functor objects without having to manually specify the C<operator ()> all
		3366	the time. Incidentally, you can then also leave out the template argument
		3367	list.
		3368
		3369	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3370	int revents)>.
		3371
		3372	See the method-C<set> above for more details.
		3373
		3374	Example: use a functor object as callback.
		3375
		3376	struct myfunctor
		3377	{
		3378	void operator() (ev::io &w, int revents)
		3379	{
		3380	...
		3381	}
		3382	}
		3383
		3384	myfunctor f;
		3385
		3386	ev::io w;
		3387	w.set (&f);
		3388
2543	=item w->set<function> (void *data = 0)	3389	=item w->set<function> (void *data = 0)
2544		3390
2545	Also sets a callback, but uses a static method or plain function as	3391	Also sets a callback, but uses a static method or plain function as
2546	callback. The optional C<data> argument will be stored in the watcher's	3392	callback. The optional C<data> argument will be stored in the watcher's
2547	C<data> member and is free for you to use.	3393	C<data> member and is free for you to use.
2548		3394
2549	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3395	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2550		3396
2551	See the method-C<set> above for more details.	3397	See the method-C<set> above for more details.
2552		3398
2553	Example:	3399	Example: Use a plain function as callback.
2554		3400
2555	static void io_cb (ev::io &w, int revents) { }	3401	static void io_cb (ev::io &w, int revents) { }
2556	iow.set <io_cb> ();	3402	iow.set <io_cb> ();
2557		3403
2558	=item w->set (struct ev_loop *)	3404	=item w->set (loop)
2559		3405
2560	Associates a different C<struct ev_loop> with this watcher. You can only	3406	Associates a different C<struct ev_loop> with this watcher. You can only
2561	do this when the watcher is inactive (and not pending either).	3407	do this when the watcher is inactive (and not pending either).
2562		3408
2563	=item w->set ([arguments])	3409	=item w->set ([arguments])
2564		3410
2565	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3411	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
2566	called at least once. Unlike the C counterpart, an active watcher gets	3412	method or a suitable start method must be called at least once. Unlike the
2567	automatically stopped and restarted when reconfiguring it with this	3413	C counterpart, an active watcher gets automatically stopped and restarted
2568	method.	3414	when reconfiguring it with this method.
2569		3415
2570	=item w->start ()	3416	=item w->start ()
2571		3417
2572	Starts the watcher. Note that there is no C<loop> argument, as the	3418	Starts the watcher. Note that there is no C<loop> argument, as the
2573	constructor already stores the event loop.	3419	constructor already stores the event loop.
2574		3420
		3421	=item w->start ([arguments])
		3422
		3423	Instead of calling C<set> and C<start> methods separately, it is often
		3424	convenient to wrap them in one call. Uses the same type of arguments as
		3425	the configure C<set> method of the watcher.
		3426
2575	=item w->stop ()	3427	=item w->stop ()
2576		3428
2577	Stops the watcher if it is active. Again, no C<loop> argument.	3429	Stops the watcher if it is active. Again, no C<loop> argument.
2578		3430
2579	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3431	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2591		3443
2592	=back	3444	=back
2593		3445
2594	=back	3446	=back
2595		3447
2596	Example: Define a class with an IO and idle watcher, start one of them in	3448	Example: Define a class with two I/O and idle watchers, start the I/O
2597	the constructor.	3449	watchers in the constructor.
2598		3450
2599	class myclass	3451	class myclass
2600	{	3452	{
2601	ev::io io; void io_cb (ev::io &w, int revents);	3453	ev::io io ; void io_cb (ev::io &w, int revents);
		3454	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
2602	ev:idle idle void idle_cb (ev::idle &w, int revents);	3455	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2603		3456
2604	myclass (int fd)	3457	myclass (int fd)
2605	{	3458	{
2606	io .set <myclass, &myclass::io_cb > (this);	3459	io .set <myclass, &myclass::io_cb > (this);
		3460	io2 .set <myclass, &myclass::io2_cb > (this);
2607	idle.set <myclass, &myclass::idle_cb> (this);	3461	idle.set <myclass, &myclass::idle_cb> (this);
2608		3462
2609	io.start (fd, ev::READ);	3463	io.set (fd, ev::WRITE); // configure the watcher
		3464	io.start (); // start it whenever convenient
		3465
		3466	io2.start (fd, ev::READ); // set + start in one call
2610	}	3467	}
2611	};	3468	};
2612		3469
2613		3470
2614	=head1 OTHER LANGUAGE BINDINGS	3471	=head1 OTHER LANGUAGE BINDINGS
…		…
2623	=item Perl	3480	=item Perl
2624		3481
2625	The EV module implements the full libev API and is actually used to test	3482	The EV module implements the full libev API and is actually used to test
2626	libev. EV is developed together with libev. Apart from the EV core module,	3483	libev. EV is developed together with libev. Apart from the EV core module,
2627	there are additional modules that implement libev-compatible interfaces	3484	there are additional modules that implement libev-compatible interfaces
2628	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3485	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2629	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3486	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3487	and C<EV::Glib>).
2630		3488
2631	It can be found and installed via CPAN, its homepage is at	3489	It can be found and installed via CPAN, its homepage is at
2632	L<http://software.schmorp.de/pkg/EV>.	3490	L<http://software.schmorp.de/pkg/EV>.
2633		3491
2634	=item Python	3492	=item Python
2635		3493
2636	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3494	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2637	seems to be quite complete and well-documented. Note, however, that the	3495	seems to be quite complete and well-documented.
2638	patch they require for libev is outright dangerous as it breaks the ABI
2639	for everybody else, and therefore, should never be applied in an installed
2640	libev (if python requires an incompatible ABI then it needs to embed
2641	libev).
2642		3496
2643	=item Ruby	3497	=item Ruby
2644		3498
2645	Tony Arcieri has written a ruby extension that offers access to a subset	3499	Tony Arcieri has written a ruby extension that offers access to a subset
2646	of the libev API and adds file handle abstractions, asynchronous DNS and	3500	of the libev API and adds file handle abstractions, asynchronous DNS and
2647	more on top of it. It can be found via gem servers. Its homepage is at	3501	more on top of it. It can be found via gem servers. Its homepage is at
2648	L<http://rev.rubyforge.org/>.	3502	L<http://rev.rubyforge.org/>.
2649		3503
		3504	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3505	makes rev work even on mingw.
		3506
		3507	=item Haskell
		3508
		3509	A haskell binding to libev is available at
		3510	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3511
2650	=item D	3512	=item D
2651		3513
2652	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3514	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2653	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	3515	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3516
		3517	=item Ocaml
		3518
		3519	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3520	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3521
		3522	=item Lua
		3523
		3524	Brian Maher has written a partial interface to libev for lua (at the
		3525	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3526	L<http://github.com/brimworks/lua-ev>.
2654		3527
2655	=back	3528	=back
2656		3529
2657		3530
2658	=head1 MACRO MAGIC	3531	=head1 MACRO MAGIC
…		…
2672	loop argument"). The C<EV_A> form is used when this is the sole argument,	3545	loop argument"). The C<EV_A> form is used when this is the sole argument,
2673	C<EV_A_> is used when other arguments are following. Example:	3546	C<EV_A_> is used when other arguments are following. Example:
2674		3547
2675	ev_unref (EV_A);	3548	ev_unref (EV_A);
2676	ev_timer_add (EV_A_ watcher);	3549	ev_timer_add (EV_A_ watcher);
2677	ev_loop (EV_A_ 0);	3550	ev_run (EV_A_ 0);
2678		3551
2679	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3552	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2680	which is often provided by the following macro.	3553	which is often provided by the following macro.
2681		3554
2682	=item C<EV_P>, C<EV_P_>	3555	=item C<EV_P>, C<EV_P_>
…		…
2722	}	3595	}
2723		3596
2724	ev_check check;	3597	ev_check check;
2725	ev_check_init (&check, check_cb);	3598	ev_check_init (&check, check_cb);
2726	ev_check_start (EV_DEFAULT_ &check);	3599	ev_check_start (EV_DEFAULT_ &check);
2727	ev_loop (EV_DEFAULT_ 0);	3600	ev_run (EV_DEFAULT_ 0);
2728		3601
2729	=head1 EMBEDDING	3602	=head1 EMBEDDING
2730		3603
2731	Libev can (and often is) directly embedded into host	3604	Libev can (and often is) directly embedded into host
2732	applications. Examples of applications that embed it include the Deliantra	3605	applications. Examples of applications that embed it include the Deliantra
…		…
2759		3632
2760	#define EV_STANDALONE 1	3633	#define EV_STANDALONE 1
2761	#include "ev.h"	3634	#include "ev.h"
2762		3635
2763	Both header files and implementation files can be compiled with a C++	3636	Both header files and implementation files can be compiled with a C++
2764	compiler (at least, thats a stated goal, and breakage will be treated	3637	compiler (at least, that's a stated goal, and breakage will be treated
2765	as a bug).	3638	as a bug).
2766		3639
2767	You need the following files in your source tree, or in a directory	3640	You need the following files in your source tree, or in a directory
2768	in your include path (e.g. in libev/ when using -Ilibev):	3641	in your include path (e.g. in libev/ when using -Ilibev):
2769		3642
…		…
2812	libev.m4	3685	libev.m4
2813		3686
2814	=head2 PREPROCESSOR SYMBOLS/MACROS	3687	=head2 PREPROCESSOR SYMBOLS/MACROS
2815		3688
2816	Libev can be configured via a variety of preprocessor symbols you have to	3689	Libev can be configured via a variety of preprocessor symbols you have to
2817	define before including any of its files. The default in the absence of	3690	define before including (or compiling) any of its files. The default in
2818	autoconf is noted for every option.	3691	the absence of autoconf is documented for every option.
		3692
		3693	Symbols marked with "(h)" do not change the ABI, and can have different
		3694	values when compiling libev vs. including F<ev.h>, so it is permissible
		3695	to redefine them before including F<ev.h> without breaking compatibility
		3696	to a compiled library. All other symbols change the ABI, which means all
		3697	users of libev and the libev code itself must be compiled with compatible
		3698	settings.
2819		3699
2820	=over 4	3700	=over 4
2821		3701
		3702	=item EV_COMPAT3 (h)
		3703
		3704	Backwards compatibility is a major concern for libev. This is why this
		3705	release of libev comes with wrappers for the functions and symbols that
		3706	have been renamed between libev version 3 and 4.
		3707
		3708	You can disable these wrappers (to test compatibility with future
		3709	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		3710	sources. This has the additional advantage that you can drop the C<struct>
		3711	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		3712	typedef in that case.
		3713
		3714	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		3715	and in some even more future version the compatibility code will be
		3716	removed completely.
		3717
2822	=item EV_STANDALONE	3718	=item EV_STANDALONE (h)
2823		3719
2824	Must always be C<1> if you do not use autoconf configuration, which	3720	Must always be C<1> if you do not use autoconf configuration, which
2825	keeps libev from including F<config.h>, and it also defines dummy	3721	keeps libev from including F<config.h>, and it also defines dummy
2826	implementations for some libevent functions (such as logging, which is not	3722	implementations for some libevent functions (such as logging, which is not
2827	supported). It will also not define any of the structs usually found in	3723	supported). It will also not define any of the structs usually found in
2828	F<event.h> that are not directly supported by the libev core alone.	3724	F<event.h> that are not directly supported by the libev core alone.
2829		3725
		3726	In standalone mode, libev will still try to automatically deduce the
		3727	configuration, but has to be more conservative.
		3728
2830	=item EV_USE_MONOTONIC	3729	=item EV_USE_MONOTONIC
2831		3730
2832	If defined to be C<1>, libev will try to detect the availability of the	3731	If defined to be C<1>, libev will try to detect the availability of the
2833	monotonic clock option at both compile time and runtime. Otherwise no use	3732	monotonic clock option at both compile time and runtime. Otherwise no
2834	of the monotonic clock option will be attempted. If you enable this, you	3733	use of the monotonic clock option will be attempted. If you enable this,
2835	usually have to link against librt or something similar. Enabling it when	3734	you usually have to link against librt or something similar. Enabling it
2836	the functionality isn't available is safe, though, although you have	3735	when the functionality isn't available is safe, though, although you have
2837	to make sure you link against any libraries where the C<clock_gettime>	3736	to make sure you link against any libraries where the C<clock_gettime>
2838	function is hiding in (often F<-lrt>).	3737	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2839		3738
2840	=item EV_USE_REALTIME	3739	=item EV_USE_REALTIME
2841		3740
2842	If defined to be C<1>, libev will try to detect the availability of the	3741	If defined to be C<1>, libev will try to detect the availability of the
2843	real-time clock option at compile time (and assume its availability at	3742	real-time clock option at compile time (and assume its availability
2844	runtime if successful). Otherwise no use of the real-time clock option will	3743	at runtime if successful). Otherwise no use of the real-time clock
2845	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3744	option will be attempted. This effectively replaces C<gettimeofday>
2846	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3745	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2847	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3746	correctness. See the note about libraries in the description of
		3747	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3748	C<EV_USE_CLOCK_SYSCALL>.
		3749
		3750	=item EV_USE_CLOCK_SYSCALL
		3751
		3752	If defined to be C<1>, libev will try to use a direct syscall instead
		3753	of calling the system-provided C<clock_gettime> function. This option
		3754	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3755	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3756	programs needlessly. Using a direct syscall is slightly slower (in
		3757	theory), because no optimised vdso implementation can be used, but avoids
		3758	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3759	higher, as it simplifies linking (no need for C<-lrt>).
2848		3760
2849	=item EV_USE_NANOSLEEP	3761	=item EV_USE_NANOSLEEP
2850		3762
2851	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3763	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2852	and will use it for delays. Otherwise it will use C<select ()>.	3764	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2868		3780
2869	=item EV_SELECT_USE_FD_SET	3781	=item EV_SELECT_USE_FD_SET
2870		3782
2871	If defined to C<1>, then the select backend will use the system C<fd_set>	3783	If defined to C<1>, then the select backend will use the system C<fd_set>
2872	structure. This is useful if libev doesn't compile due to a missing	3784	structure. This is useful if libev doesn't compile due to a missing
2873	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3785	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2874	exotic systems. This usually limits the range of file descriptors to some	3786	on exotic systems. This usually limits the range of file descriptors to
2875	low limit such as 1024 or might have other limitations (winsocket only	3787	some low limit such as 1024 or might have other limitations (winsocket
2876	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3788	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2877	influence the size of the C<fd_set> used.	3789	configures the maximum size of the C<fd_set>.
2878		3790
2879	=item EV_SELECT_IS_WINSOCKET	3791	=item EV_SELECT_IS_WINSOCKET
2880		3792
2881	When defined to C<1>, the select backend will assume that	3793	When defined to C<1>, the select backend will assume that
2882	select/socket/connect etc. don't understand file descriptors but	3794	select/socket/connect etc. don't understand file descriptors but
…		…
2884	be used is the winsock select). This means that it will call	3796	be used is the winsock select). This means that it will call
2885	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3797	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2886	it is assumed that all these functions actually work on fds, even	3798	it is assumed that all these functions actually work on fds, even
2887	on win32. Should not be defined on non-win32 platforms.	3799	on win32. Should not be defined on non-win32 platforms.
2888		3800
2889	=item EV_FD_TO_WIN32_HANDLE	3801	=item EV_FD_TO_WIN32_HANDLE(fd)
2890		3802
2891	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3803	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
2892	file descriptors to socket handles. When not defining this symbol (the	3804	file descriptors to socket handles. When not defining this symbol (the
2893	default), then libev will call C<_get_osfhandle>, which is usually	3805	default), then libev will call C<_get_osfhandle>, which is usually
2894	correct. In some cases, programs use their own file descriptor management,	3806	correct. In some cases, programs use their own file descriptor management,
2895	in which case they can provide this function to map fds to socket handles.	3807	in which case they can provide this function to map fds to socket handles.
		3808
		3809	=item EV_WIN32_HANDLE_TO_FD(handle)
		3810
		3811	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3812	using the standard C<_open_osfhandle> function. For programs implementing
		3813	their own fd to handle mapping, overwriting this function makes it easier
		3814	to do so. This can be done by defining this macro to an appropriate value.
		3815
		3816	=item EV_WIN32_CLOSE_FD(fd)
		3817
		3818	If programs implement their own fd to handle mapping on win32, then this
		3819	macro can be used to override the C<close> function, useful to unregister
		3820	file descriptors again. Note that the replacement function has to close
		3821	the underlying OS handle.
2896		3822
2897	=item EV_USE_POLL	3823	=item EV_USE_POLL
2898		3824
2899	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3825	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2900	backend. Otherwise it will be enabled on non-win32 platforms. It	3826	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
2947	as well as for signal and thread safety in C<ev_async> watchers.	3873	as well as for signal and thread safety in C<ev_async> watchers.
2948		3874
2949	In the absence of this define, libev will use C<sig_atomic_t volatile>	3875	In the absence of this define, libev will use C<sig_atomic_t volatile>
2950	(from F<signal.h>), which is usually good enough on most platforms.	3876	(from F<signal.h>), which is usually good enough on most platforms.
2951		3877
2952	=item EV_H	3878	=item EV_H (h)
2953		3879
2954	The name of the F<ev.h> header file used to include it. The default if	3880	The name of the F<ev.h> header file used to include it. The default if
2955	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	3881	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2956	used to virtually rename the F<ev.h> header file in case of conflicts.	3882	used to virtually rename the F<ev.h> header file in case of conflicts.
2957		3883
2958	=item EV_CONFIG_H	3884	=item EV_CONFIG_H (h)
2959		3885
2960	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	3886	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2961	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	3887	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2962	C<EV_H>, above.	3888	C<EV_H>, above.
2963		3889
2964	=item EV_EVENT_H	3890	=item EV_EVENT_H (h)
2965		3891
2966	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	3892	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2967	of how the F<event.h> header can be found, the default is C<"event.h">.	3893	of how the F<event.h> header can be found, the default is C<"event.h">.
2968		3894
2969	=item EV_PROTOTYPES	3895	=item EV_PROTOTYPES (h)
2970		3896
2971	If defined to be C<0>, then F<ev.h> will not define any function	3897	If defined to be C<0>, then F<ev.h> will not define any function
2972	prototypes, but still define all the structs and other symbols. This is	3898	prototypes, but still define all the structs and other symbols. This is
2973	occasionally useful if you want to provide your own wrapper functions	3899	occasionally useful if you want to provide your own wrapper functions
2974	around libev functions.	3900	around libev functions.
…		…
2993	When doing priority-based operations, libev usually has to linearly search	3919	When doing priority-based operations, libev usually has to linearly search
2994	all the priorities, so having many of them (hundreds) uses a lot of space	3920	all the priorities, so having many of them (hundreds) uses a lot of space
2995	and time, so using the defaults of five priorities (-2 .. +2) is usually	3921	and time, so using the defaults of five priorities (-2 .. +2) is usually
2996	fine.	3922	fine.
2997		3923
2998	If your embedding application does not need any priorities, defining these both to	3924	If your embedding application does not need any priorities, defining these
2999	C<0> will save some memory and CPU.	3925	both to C<0> will save some memory and CPU.
3000		3926
3001	=item EV_PERIODIC_ENABLE	3927	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		3928	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		3929	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3002		3930
3003	If undefined or defined to be C<1>, then periodic timers are supported. If	3931	If undefined or defined to be C<1> (and the platform supports it), then
3004	defined to be C<0>, then they are not. Disabling them saves a few kB of	3932	the respective watcher type is supported. If defined to be C<0>, then it
3005	code.	3933	is not. Disabling watcher types mainly saves code size.
3006		3934
3007	=item EV_IDLE_ENABLE	3935	=item EV_FEATURES
3008
3009	If undefined or defined to be C<1>, then idle watchers are supported. If
3010	defined to be C<0>, then they are not. Disabling them saves a few kB of
3011	code.
3012
3013	=item EV_EMBED_ENABLE
3014
3015	If undefined or defined to be C<1>, then embed watchers are supported. If
3016	defined to be C<0>, then they are not.
3017
3018	=item EV_STAT_ENABLE
3019
3020	If undefined or defined to be C<1>, then stat watchers are supported. If
3021	defined to be C<0>, then they are not.
3022
3023	=item EV_FORK_ENABLE
3024
3025	If undefined or defined to be C<1>, then fork watchers are supported. If
3026	defined to be C<0>, then they are not.
3027
3028	=item EV_ASYNC_ENABLE
3029
3030	If undefined or defined to be C<1>, then async watchers are supported. If
3031	defined to be C<0>, then they are not.
3032
3033	=item EV_MINIMAL
3034		3936
3035	If you need to shave off some kilobytes of code at the expense of some	3937	If you need to shave off some kilobytes of code at the expense of some
3036	speed, define this symbol to C<1>. Currently this is used to override some	3938	speed (but with the full API), you can define this symbol to request
3037	inlining decisions, saves roughly 30% code size on amd64. It also selects a	3939	certain subsets of functionality. The default is to enable all features
3038	much smaller 2-heap for timer management over the default 4-heap.	3940	that can be enabled on the platform.
		3941
		3942	A typical way to use this symbol is to define it to C<0> (or to a bitset
		3943	with some broad features you want) and then selectively re-enable
		3944	additional parts you want, for example if you want everything minimal,
		3945	but multiple event loop support, async and child watchers and the poll
		3946	backend, use this:
		3947
		3948	#define EV_FEATURES 0
		3949	#define EV_MULTIPLICITY 1
		3950	#define EV_USE_POLL 1
		3951	#define EV_CHILD_ENABLE 1
		3952	#define EV_ASYNC_ENABLE 1
		3953
		3954	The actual value is a bitset, it can be a combination of the following
		3955	values:
		3956
		3957	=over 4
		3958
		3959	=item C<1> - faster/larger code
		3960
		3961	Use larger code to speed up some operations.
		3962
		3963	Currently this is used to override some inlining decisions (enlarging the
		3964	code size by roughly 30% on amd64).
		3965
		3966	When optimising for size, use of compiler flags such as C<-Os> with
		3967	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		3968	assertions.
		3969
		3970	=item C<2> - faster/larger data structures
		3971
		3972	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		3973	hash table sizes and so on. This will usually further increase code size
		3974	and can additionally have an effect on the size of data structures at
		3975	runtime.
		3976
		3977	=item C<4> - full API configuration
		3978
		3979	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		3980	enables multiplicity (C<EV_MULTIPLICITY>=1).
		3981
		3982	=item C<8> - full API
		3983
		3984	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		3985	details on which parts of the API are still available without this
		3986	feature, and do not complain if this subset changes over time.
		3987
		3988	=item C<16> - enable all optional watcher types
		3989
		3990	Enables all optional watcher types. If you want to selectively enable
		3991	only some watcher types other than I/O and timers (e.g. prepare,
		3992	embed, async, child...) you can enable them manually by defining
		3993	C<EV_watchertype_ENABLE> to C<1> instead.
		3994
		3995	=item C<32> - enable all backends
		3996
		3997	This enables all backends - without this feature, you need to enable at
		3998	least one backend manually (C<EV_USE_SELECT> is a good choice).
		3999
		4000	=item C<64> - enable OS-specific "helper" APIs
		4001
		4002	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4003	default.
		4004
		4005	=back
		4006
		4007	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4008	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4009	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4010	watchers, timers and monotonic clock support.
		4011
		4012	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4013	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4014	your program might be left out as well - a binary starting a timer and an
		4015	I/O watcher then might come out at only 5Kb.
		4016
		4017	=item EV_AVOID_STDIO
		4018
		4019	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4020	functions (printf, scanf, perror etc.). This will increase the code size
		4021	somewhat, but if your program doesn't otherwise depend on stdio and your
		4022	libc allows it, this avoids linking in the stdio library which is quite
		4023	big.
		4024
		4025	Note that error messages might become less precise when this option is
		4026	enabled.
		4027
		4028	=item EV_NSIG
		4029
		4030	The highest supported signal number, +1 (or, the number of
		4031	signals): Normally, libev tries to deduce the maximum number of signals
		4032	automatically, but sometimes this fails, in which case it can be
		4033	specified. Also, using a lower number than detected (C<32> should be
		4034	good for about any system in existence) can save some memory, as libev
		4035	statically allocates some 12-24 bytes per signal number.
3039		4036
3040	=item EV_PID_HASHSIZE	4037	=item EV_PID_HASHSIZE
3041		4038
3042	C<ev_child> watchers use a small hash table to distribute workload by	4039	C<ev_child> watchers use a small hash table to distribute workload by
3043	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4040	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3044	than enough. If you need to manage thousands of children you might want to	4041	usually more than enough. If you need to manage thousands of children you
3045	increase this value (I<must> be a power of two).	4042	might want to increase this value (I<must> be a power of two).
3046		4043
3047	=item EV_INOTIFY_HASHSIZE	4044	=item EV_INOTIFY_HASHSIZE
3048		4045
3049	C<ev_stat> watchers use a small hash table to distribute workload by	4046	C<ev_stat> watchers use a small hash table to distribute workload by
3050	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4047	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3051	usually more than enough. If you need to manage thousands of C<ev_stat>	4048	disabled), usually more than enough. If you need to manage thousands of
3052	watchers you might want to increase this value (I<must> be a power of	4049	C<ev_stat> watchers you might want to increase this value (I<must> be a
3053	two).	4050	power of two).
3054		4051
3055	=item EV_USE_4HEAP	4052	=item EV_USE_4HEAP
3056		4053
3057	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4054	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3058	timer and periodics heap, libev uses a 4-heap when this symbol is defined	4055	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3059	to C<1>. The 4-heap uses more complicated (longer) code but has	4056	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3060	noticeably faster performance with many (thousands) of watchers.	4057	faster performance with many (thousands) of watchers.
3061		4058
3062	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4059	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3063	(disabled).	4060	will be C<0>.
3064		4061
3065	=item EV_HEAP_CACHE_AT	4062	=item EV_HEAP_CACHE_AT
3066		4063
3067	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4064	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3068	timer and periodics heap, libev can cache the timestamp (I<at>) within	4065	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3069	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4066	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3070	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4067	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3071	but avoids random read accesses on heap changes. This improves performance	4068	but avoids random read accesses on heap changes. This improves performance
3072	noticeably with with many (hundreds) of watchers.	4069	noticeably with many (hundreds) of watchers.
3073		4070
3074	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4071	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3075	(disabled).	4072	will be C<0>.
3076		4073
3077	=item EV_VERIFY	4074	=item EV_VERIFY
3078		4075
3079	Controls how much internal verification (see C<ev_loop_verify ()>) will	4076	Controls how much internal verification (see C<ev_verify ()>) will
3080	be done: If set to C<0>, no internal verification code will be compiled	4077	be done: If set to C<0>, no internal verification code will be compiled
3081	in. If set to C<1>, then verification code will be compiled in, but not	4078	in. If set to C<1>, then verification code will be compiled in, but not
3082	called. If set to C<2>, then the internal verification code will be	4079	called. If set to C<2>, then the internal verification code will be
3083	called once per loop, which can slow down libev. If set to C<3>, then the	4080	called once per loop, which can slow down libev. If set to C<3>, then the
3084	verification code will be called very frequently, which will slow down	4081	verification code will be called very frequently, which will slow down
3085	libev considerably.	4082	libev considerably.
3086		4083
3087	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4084	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3088	C<0.>	4085	will be C<0>.
3089		4086
3090	=item EV_COMMON	4087	=item EV_COMMON
3091		4088
3092	By default, all watchers have a C<void *data> member. By redefining	4089	By default, all watchers have a C<void *data> member. By redefining
3093	this macro to a something else you can include more and other types of	4090	this macro to something else you can include more and other types of
3094	members. You have to define it each time you include one of the files,	4091	members. You have to define it each time you include one of the files,
3095	though, and it must be identical each time.	4092	though, and it must be identical each time.
3096		4093
3097	For example, the perl EV module uses something like this:	4094	For example, the perl EV module uses something like this:
3098		4095
…		…
3110	and the way callbacks are invoked and set. Must expand to a struct member	4107	and the way callbacks are invoked and set. Must expand to a struct member
3111	definition and a statement, respectively. See the F<ev.h> header file for	4108	definition and a statement, respectively. See the F<ev.h> header file for
3112	their default definitions. One possible use for overriding these is to	4109	their default definitions. One possible use for overriding these is to
3113	avoid the C<struct ev_loop *> as first argument in all cases, or to use	4110	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3114	method calls instead of plain function calls in C++.	4111	method calls instead of plain function calls in C++.
		4112
		4113	=back
3115		4114
3116	=head2 EXPORTED API SYMBOLS	4115	=head2 EXPORTED API SYMBOLS
3117		4116
3118	If you need to re-export the API (e.g. via a DLL) and you need a list of	4117	If you need to re-export the API (e.g. via a DLL) and you need a list of
3119	exported symbols, you can use the provided F<Symbol.*> files which list	4118	exported symbols, you can use the provided F<Symbol.*> files which list
…		…
3149	file.	4148	file.
3150		4149
3151	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4150	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3152	that everybody includes and which overrides some configure choices:	4151	that everybody includes and which overrides some configure choices:
3153		4152
3154	#define EV_MINIMAL 1	4153	#define EV_FEATURES 8
3155	#define EV_USE_POLL 0	4154	#define EV_USE_SELECT 1
3156	#define EV_MULTIPLICITY 0
3157	#define EV_PERIODIC_ENABLE 0	4155	#define EV_PREPARE_ENABLE 1
		4156	#define EV_IDLE_ENABLE 1
3158	#define EV_STAT_ENABLE 0	4157	#define EV_SIGNAL_ENABLE 1
3159	#define EV_FORK_ENABLE 0	4158	#define EV_CHILD_ENABLE 1
		4159	#define EV_USE_STDEXCEPT 0
3160	#define EV_CONFIG_H <config.h>	4160	#define EV_CONFIG_H <config.h>
3161	#define EV_MINPRI 0
3162	#define EV_MAXPRI 0
3163		4161
3164	#include "ev++.h"	4162	#include "ev++.h"
3165		4163
3166	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4164	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3167		4165
3168	#include "ev_cpp.h"	4166	#include "ev_cpp.h"
3169	#include "ev.c"	4167	#include "ev.c"
3170		4168
		4169	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3171		4170
3172	=head1 THREADS AND COROUTINES	4171	=head2 THREADS AND COROUTINES
3173		4172
3174	=head2 THREADS	4173	=head3 THREADS
3175		4174
3176	Libev itself is completely thread-safe, but it uses no locking. This	4175	All libev functions are reentrant and thread-safe unless explicitly
		4176	documented otherwise, but libev implements no locking itself. This means
3177	means that you can use as many loops as you want in parallel, as long as	4177	that you can use as many loops as you want in parallel, as long as there
3178	only one thread ever calls into one libev function with the same loop	4178	are no concurrent calls into any libev function with the same loop
3179	parameter.	4179	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		4180	of course): libev guarantees that different event loops share no data
		4181	structures that need any locking.
3180		4182
3181	Or put differently: calls with different loop parameters can be done in	4183	Or to put it differently: calls with different loop parameters can be done
3182	parallel from multiple threads, calls with the same loop parameter must be	4184	concurrently from multiple threads, calls with the same loop parameter
3183	done serially (but can be done from different threads, as long as only one	4185	must be done serially (but can be done from different threads, as long as
3184	thread ever is inside a call at any point in time, e.g. by using a mutex	4186	only one thread ever is inside a call at any point in time, e.g. by using
3185	per loop).	4187	a mutex per loop).
3186		4188
3187	If you want to know which design is best for your problem, then I cannot	4189	Specifically to support threads (and signal handlers), libev implements
		4190	so-called C<ev_async> watchers, which allow some limited form of
		4191	concurrency on the same event loop, namely waking it up "from the
		4192	outside".
		4193
		4194	If you want to know which design (one loop, locking, or multiple loops
		4195	without or something else still) is best for your problem, then I cannot
3188	help you but by giving some generic advice:	4196	help you, but here is some generic advice:
3189		4197
3190	=over 4	4198	=over 4
3191		4199
3192	=item * most applications have a main thread: use the default libev loop	4200	=item * most applications have a main thread: use the default libev loop
3193	in that thread, or create a separate thread running only the default loop.	4201	in that thread, or create a separate thread running only the default loop.
…		…
3205		4213
3206	Choosing a model is hard - look around, learn, know that usually you can do	4214	Choosing a model is hard - look around, learn, know that usually you can do
3207	better than you currently do :-)	4215	better than you currently do :-)
3208		4216
3209	=item * often you need to talk to some other thread which blocks in the	4217	=item * often you need to talk to some other thread which blocks in the
		4218	event loop.
		4219
3210	event loop - C<ev_async> watchers can be used to wake them up from other	4220	C<ev_async> watchers can be used to wake them up from other threads safely
3211	threads safely (or from signal contexts...).	4221	(or from signal contexts...).
		4222
		4223	An example use would be to communicate signals or other events that only
		4224	work in the default loop by registering the signal watcher with the
		4225	default loop and triggering an C<ev_async> watcher from the default loop
		4226	watcher callback into the event loop interested in the signal.
3212		4227
3213	=back	4228	=back
3214		4229
		4230	=head4 THREAD LOCKING EXAMPLE
		4231
		4232	Here is a fictitious example of how to run an event loop in a different
		4233	thread than where callbacks are being invoked and watchers are
		4234	created/added/removed.
		4235
		4236	For a real-world example, see the C<EV::Loop::Async> perl module,
		4237	which uses exactly this technique (which is suited for many high-level
		4238	languages).
		4239
		4240	The example uses a pthread mutex to protect the loop data, a condition
		4241	variable to wait for callback invocations, an async watcher to notify the
		4242	event loop thread and an unspecified mechanism to wake up the main thread.
		4243
		4244	First, you need to associate some data with the event loop:
		4245
		4246	typedef struct {
		4247	mutex_t lock; /* global loop lock */
		4248	ev_async async_w;
		4249	thread_t tid;
		4250	cond_t invoke_cv;
		4251	} userdata;
		4252
		4253	void prepare_loop (EV_P)
		4254	{
		4255	// for simplicity, we use a static userdata struct.
		4256	static userdata u;
		4257
		4258	ev_async_init (&u->async_w, async_cb);
		4259	ev_async_start (EV_A_ &u->async_w);
		4260
		4261	pthread_mutex_init (&u->lock, 0);
		4262	pthread_cond_init (&u->invoke_cv, 0);
		4263
		4264	// now associate this with the loop
		4265	ev_set_userdata (EV_A_ u);
		4266	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4267	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4268
		4269	// then create the thread running ev_loop
		4270	pthread_create (&u->tid, 0, l_run, EV_A);
		4271	}
		4272
		4273	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4274	solely to wake up the event loop so it takes notice of any new watchers
		4275	that might have been added:
		4276
		4277	static void
		4278	async_cb (EV_P_ ev_async *w, int revents)
		4279	{
		4280	// just used for the side effects
		4281	}
		4282
		4283	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4284	protecting the loop data, respectively.
		4285
		4286	static void
		4287	l_release (EV_P)
		4288	{
		4289	userdata *u = ev_userdata (EV_A);
		4290	pthread_mutex_unlock (&u->lock);
		4291	}
		4292
		4293	static void
		4294	l_acquire (EV_P)
		4295	{
		4296	userdata *u = ev_userdata (EV_A);
		4297	pthread_mutex_lock (&u->lock);
		4298	}
		4299
		4300	The event loop thread first acquires the mutex, and then jumps straight
		4301	into C<ev_run>:
		4302
		4303	void *
		4304	l_run (void *thr_arg)
		4305	{
		4306	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4307
		4308	l_acquire (EV_A);
		4309	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4310	ev_run (EV_A_ 0);
		4311	l_release (EV_A);
		4312
		4313	return 0;
		4314	}
		4315
		4316	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4317	signal the main thread via some unspecified mechanism (signals? pipe
		4318	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4319	have been called (in a while loop because a) spurious wakeups are possible
		4320	and b) skipping inter-thread-communication when there are no pending
		4321	watchers is very beneficial):
		4322
		4323	static void
		4324	l_invoke (EV_P)
		4325	{
		4326	userdata *u = ev_userdata (EV_A);
		4327
		4328	while (ev_pending_count (EV_A))
		4329	{
		4330	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4331	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4332	}
		4333	}
		4334
		4335	Now, whenever the main thread gets told to invoke pending watchers, it
		4336	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4337	thread to continue:
		4338
		4339	static void
		4340	real_invoke_pending (EV_P)
		4341	{
		4342	userdata *u = ev_userdata (EV_A);
		4343
		4344	pthread_mutex_lock (&u->lock);
		4345	ev_invoke_pending (EV_A);
		4346	pthread_cond_signal (&u->invoke_cv);
		4347	pthread_mutex_unlock (&u->lock);
		4348	}
		4349
		4350	Whenever you want to start/stop a watcher or do other modifications to an
		4351	event loop, you will now have to lock:
		4352
		4353	ev_timer timeout_watcher;
		4354	userdata *u = ev_userdata (EV_A);
		4355
		4356	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4357
		4358	pthread_mutex_lock (&u->lock);
		4359	ev_timer_start (EV_A_ &timeout_watcher);
		4360	ev_async_send (EV_A_ &u->async_w);
		4361	pthread_mutex_unlock (&u->lock);
		4362
		4363	Note that sending the C<ev_async> watcher is required because otherwise
		4364	an event loop currently blocking in the kernel will have no knowledge
		4365	about the newly added timer. By waking up the loop it will pick up any new
		4366	watchers in the next event loop iteration.
		4367
3215	=head2 COROUTINES	4368	=head3 COROUTINES
3216		4369
3217	Libev is much more accommodating to coroutines ("cooperative threads"):	4370	Libev is very accommodating to coroutines ("cooperative threads"):
3218	libev fully supports nesting calls to it's functions from different	4371	libev fully supports nesting calls to its functions from different
3219	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4372	coroutines (e.g. you can call C<ev_run> on the same loop from two
3220	different coroutines and switch freely between both coroutines running the	4373	different coroutines, and switch freely between both coroutines running
3221	loop, as long as you don't confuse yourself). The only exception is that	4374	the loop, as long as you don't confuse yourself). The only exception is
3222	you must not do this from C<ev_periodic> reschedule callbacks.	4375	that you must not do this from C<ev_periodic> reschedule callbacks.
3223		4376
3224	Care has been invested into making sure that libev does not keep local	4377	Care has been taken to ensure that libev does not keep local state inside
3225	state inside C<ev_loop>, and other calls do not usually allow coroutine	4378	C<ev_run>, and other calls do not usually allow for coroutine switches as
3226	switches.	4379	they do not call any callbacks.
3227		4380
		4381	=head2 COMPILER WARNINGS
3228		4382
3229	=head1 COMPLEXITIES	4383	Depending on your compiler and compiler settings, you might get no or a
		4384	lot of warnings when compiling libev code. Some people are apparently
		4385	scared by this.
3230		4386
3231	In this section the complexities of (many of) the algorithms used inside	4387	However, these are unavoidable for many reasons. For one, each compiler
3232	libev will be explained. For complexity discussions about backends see the	4388	has different warnings, and each user has different tastes regarding
3233	documentation for C<ev_default_init>.	4389	warning options. "Warn-free" code therefore cannot be a goal except when
		4390	targeting a specific compiler and compiler-version.
3234		4391
3235	All of the following are about amortised time: If an array needs to be	4392	Another reason is that some compiler warnings require elaborate
3236	extended, libev needs to realloc and move the whole array, but this	4393	workarounds, or other changes to the code that make it less clear and less
3237	happens asymptotically never with higher number of elements, so O(1) might	4394	maintainable.
3238	mean it might do a lengthy realloc operation in rare cases, but on average
3239	it is much faster and asymptotically approaches constant time.
3240		4395
3241	=over 4	4396	And of course, some compiler warnings are just plain stupid, or simply
		4397	wrong (because they don't actually warn about the condition their message
		4398	seems to warn about). For example, certain older gcc versions had some
		4399	warnings that resulted in an extreme number of false positives. These have
		4400	been fixed, but some people still insist on making code warn-free with
		4401	such buggy versions.
3242		4402
3243	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	4403	While libev is written to generate as few warnings as possible,
		4404	"warn-free" code is not a goal, and it is recommended not to build libev
		4405	with any compiler warnings enabled unless you are prepared to cope with
		4406	them (e.g. by ignoring them). Remember that warnings are just that:
		4407	warnings, not errors, or proof of bugs.
3244		4408
3245	This means that, when you have a watcher that triggers in one hour and
3246	there are 100 watchers that would trigger before that then inserting will
3247	have to skip roughly seven (C<ld 100>) of these watchers.
3248		4409
3249	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	4410	=head2 VALGRIND
3250		4411
3251	That means that changing a timer costs less than removing/adding them	4412	Valgrind has a special section here because it is a popular tool that is
3252	as only the relative motion in the event queue has to be paid for.	4413	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3253		4414
3254	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	4415	If you think you found a bug (memory leak, uninitialised data access etc.)
		4416	in libev, then check twice: If valgrind reports something like:
3255		4417
3256	These just add the watcher into an array or at the head of a list.	4418	==2274== definitely lost: 0 bytes in 0 blocks.
		4419	==2274== possibly lost: 0 bytes in 0 blocks.
		4420	==2274== still reachable: 256 bytes in 1 blocks.
3257		4421
3258	=item Stopping check/prepare/idle/fork/async watchers: O(1)	4422	Then there is no memory leak, just as memory accounted to global variables
		4423	is not a memleak - the memory is still being referenced, and didn't leak.
3259		4424
3260	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	4425	Similarly, under some circumstances, valgrind might report kernel bugs
		4426	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		4427	although an acceptable workaround has been found here), or it might be
		4428	confused.
3261		4429
3262	These watchers are stored in lists then need to be walked to find the	4430	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3263	correct watcher to remove. The lists are usually short (you don't usually	4431	make it into some kind of religion.
3264	have many watchers waiting for the same fd or signal).
3265		4432
3266	=item Finding the next timer in each loop iteration: O(1)	4433	If you are unsure about something, feel free to contact the mailing list
		4434	with the full valgrind report and an explanation on why you think this
		4435	is a bug in libev (best check the archives, too :). However, don't be
		4436	annoyed when you get a brisk "this is no bug" answer and take the chance
		4437	of learning how to interpret valgrind properly.
3267		4438
3268	By virtue of using a binary or 4-heap, the next timer is always found at a	4439	If you need, for some reason, empty reports from valgrind for your project
3269	fixed position in the storage array.	4440	I suggest using suppression lists.
3270		4441
3271	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3272		4442
3273	A change means an I/O watcher gets started or stopped, which requires	4443	=head1 PORTABILITY NOTES
3274	libev to recalculate its status (and possibly tell the kernel, depending
3275	on backend and whether C<ev_io_set> was used).
3276		4444
3277	=item Activating one watcher (putting it into the pending state): O(1)	4445	=head2 GNU/LINUX 32 BIT LIMITATIONS
3278		4446
3279	=item Priority handling: O(number_of_priorities)	4447	GNU/Linux is the only common platform that supports 64 bit file/large file
		4448	interfaces but I<disables> them by default.
3280		4449
3281	Priorities are implemented by allocating some space for each	4450	That means that libev compiled in the default environment doesn't support
3282	priority. When doing priority-based operations, libev usually has to	4451	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
3283	linearly search all the priorities, but starting/stopping and activating
3284	watchers becomes O(1) w.r.t. priority handling.
3285		4452
3286	=item Sending an ev_async: O(1)	4453	Unfortunately, many programs try to work around this GNU/Linux issue
		4454	by enabling the large file API, which makes them incompatible with the
		4455	standard libev compiled for their system.
3287		4456
3288	=item Processing ev_async_send: O(number_of_async_watchers)	4457	Likewise, libev cannot enable the large file API itself as this would
		4458	suddenly make it incompatible to the default compile time environment,
		4459	i.e. all programs not using special compile switches.
3289		4460
3290	=item Processing signals: O(max_signal_number)	4461	=head2 OS/X AND DARWIN BUGS
3291		4462
3292	Sending involves a system call I<iff> there were no other C<ev_async_send>	4463	The whole thing is a bug if you ask me - basically any system interface
3293	calls in the current loop iteration. Checking for async and signal events	4464	you touch is broken, whether it is locales, poll, kqueue or even the
3294	involves iterating over all running async watchers or all signal numbers.	4465	OpenGL drivers.
3295		4466
3296	=back	4467	=head3 C<kqueue> is buggy
3297		4468
		4469	The kqueue syscall is broken in all known versions - most versions support
		4470	only sockets, many support pipes.
3298		4471
		4472	Libev tries to work around this by not using C<kqueue> by default on
		4473	this rotten platform, but of course you can still ask for it when creating
		4474	a loop.
		4475
		4476	=head3 C<poll> is buggy
		4477
		4478	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4479	implementation by something calling C<kqueue> internally around the 10.5.6
		4480	release, so now C<kqueue> I<and> C<poll> are broken.
		4481
		4482	Libev tries to work around this by not using C<poll> by default on
		4483	this rotten platform, but of course you can still ask for it when creating
		4484	a loop.
		4485
		4486	=head3 C<select> is buggy
		4487
		4488	All that's left is C<select>, and of course Apple found a way to fuck this
		4489	one up as well: On OS/X, C<select> actively limits the number of file
		4490	descriptors you can pass in to 1024 - your program suddenly crashes when
		4491	you use more.
		4492
		4493	There is an undocumented "workaround" for this - defining
		4494	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4495	work on OS/X.
		4496
		4497	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4498
		4499	=head3 C<errno> reentrancy
		4500
		4501	The default compile environment on Solaris is unfortunately so
		4502	thread-unsafe that you can't even use components/libraries compiled
		4503	without C<-D_REENTRANT> (as long as they use C<errno>), which, of course,
		4504	isn't defined by default.
		4505
		4506	If you want to use libev in threaded environments you have to make sure
		4507	it's compiled with C<_REENTRANT> defined.
		4508
		4509	=head3 Event port backend
		4510
		4511	The scalable event interface for Solaris is called "event ports". Unfortunately,
		4512	this mechanism is very buggy. If you run into high CPU usage, your program
		4513	freezes or you get a large number of spurious wakeups, make sure you have
		4514	all the relevant and latest kernel patches applied. No, I don't know which
		4515	ones, but there are multiple ones.
		4516
		4517	If you can't get it to work, you can try running the program by setting
		4518	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4519	C<select> backends.
		4520
		4521	=head2 AIX POLL BUG
		4522
		4523	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4524	this by trying to avoid the poll backend altogether (i.e. it's not even
		4525	compiled in), which normally isn't a big problem as C<select> works fine
		4526	with large bitsets, and AIX is dead anyway.
		4527
3299	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4528	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4529
		4530	=head3 General issues
3300		4531
3301	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4532	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3302	requires, and its I/O model is fundamentally incompatible with the POSIX	4533	requires, and its I/O model is fundamentally incompatible with the POSIX
3303	model. Libev still offers limited functionality on this platform in	4534	model. Libev still offers limited functionality on this platform in
3304	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4535	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3305	descriptors. This only applies when using Win32 natively, not when using	4536	descriptors. This only applies when using Win32 natively, not when using
3306	e.g. cygwin.	4537	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4538	as every compielr comes with a slightly differently broken/incompatible
		4539	environment.
3307		4540
3308	Lifting these limitations would basically require the full	4541	Lifting these limitations would basically require the full
3309	re-implementation of the I/O system. If you are into these kinds of	4542	re-implementation of the I/O system. If you are into this kind of thing,
3310	things, then note that glib does exactly that for you in a very portable	4543	then note that glib does exactly that for you in a very portable way (note
3311	way (note also that glib is the slowest event library known to man).	4544	also that glib is the slowest event library known to man).
3312		4545
3313	There is no supported compilation method available on windows except	4546	There is no supported compilation method available on windows except
3314	embedding it into other applications.	4547	embedding it into other applications.
		4548
		4549	Sensible signal handling is officially unsupported by Microsoft - libev
		4550	tries its best, but under most conditions, signals will simply not work.
3315		4551
3316	Not a libev limitation but worth mentioning: windows apparently doesn't	4552	Not a libev limitation but worth mentioning: windows apparently doesn't
3317	accept large writes: instead of resulting in a partial write, windows will	4553	accept large writes: instead of resulting in a partial write, windows will
3318	either accept everything or return C<ENOBUFS> if the buffer is too large,	4554	either accept everything or return C<ENOBUFS> if the buffer is too large,
3319	so make sure you only write small amounts into your sockets (less than a	4555	so make sure you only write small amounts into your sockets (less than a
3320	megabyte seems safe, but thsi apparently depends on the amount of memory	4556	megabyte seems safe, but this apparently depends on the amount of memory
3321	available).	4557	available).
3322		4558
3323	Due to the many, low, and arbitrary limits on the win32 platform and	4559	Due to the many, low, and arbitrary limits on the win32 platform and
3324	the abysmal performance of winsockets, using a large number of sockets	4560	the abysmal performance of winsockets, using a large number of sockets
3325	is not recommended (and not reasonable). If your program needs to use	4561	is not recommended (and not reasonable). If your program needs to use
3326	more than a hundred or so sockets, then likely it needs to use a totally	4562	more than a hundred or so sockets, then likely it needs to use a totally
3327	different implementation for windows, as libev offers the POSIX readiness	4563	different implementation for windows, as libev offers the POSIX readiness
3328	notification model, which cannot be implemented efficiently on windows	4564	notification model, which cannot be implemented efficiently on windows
3329	(Microsoft monopoly games).	4565	(due to Microsoft monopoly games).
3330		4566
3331	A typical way to use libev under windows is to embed it (see the embedding	4567	A typical way to use libev under windows is to embed it (see the embedding
3332	section for details) and use the following F<evwrap.h> header file instead	4568	section for details) and use the following F<evwrap.h> header file instead
3333	of F<ev.h>:	4569	of F<ev.h>:
3334		4570
…		…
3336	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	4572	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3337		4573
3338	#include "ev.h"	4574	#include "ev.h"
3339		4575
3340	And compile the following F<evwrap.c> file into your project (make sure	4576	And compile the following F<evwrap.c> file into your project (make sure
3341	you do I<not> compile the F<ev.c> or any other embedded soruce files!):	4577	you do I<not> compile the F<ev.c> or any other embedded source files!):
3342		4578
3343	#include "evwrap.h"	4579	#include "evwrap.h"
3344	#include "ev.c"	4580	#include "ev.c"
3345		4581
3346	=over 4
3347
3348	=item The winsocket select function	4582	=head3 The winsocket C<select> function
3349		4583
3350	The winsocket C<select> function doesn't follow POSIX in that it	4584	The winsocket C<select> function doesn't follow POSIX in that it
3351	requires socket I<handles> and not socket I<file descriptors> (it is	4585	requires socket I<handles> and not socket I<file descriptors> (it is
3352	also extremely buggy). This makes select very inefficient, and also	4586	also extremely buggy). This makes select very inefficient, and also
3353	requires a mapping from file descriptors to socket handles (the Microsoft	4587	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3362	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4596	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3363		4597
3364	Note that winsockets handling of fd sets is O(n), so you can easily get a	4598	Note that winsockets handling of fd sets is O(n), so you can easily get a
3365	complexity in the O(n²) range when using win32.	4599	complexity in the O(n²) range when using win32.
3366		4600
3367	=item Limited number of file descriptors	4601	=head3 Limited number of file descriptors
3368		4602
3369	Windows has numerous arbitrary (and low) limits on things.	4603	Windows has numerous arbitrary (and low) limits on things.
3370		4604
3371	Early versions of winsocket's select only supported waiting for a maximum	4605	Early versions of winsocket's select only supported waiting for a maximum
3372	of C<64> handles (probably owning to the fact that all windows kernels	4606	of C<64> handles (probably owning to the fact that all windows kernels
3373	can only wait for C<64> things at the same time internally; Microsoft	4607	can only wait for C<64> things at the same time internally; Microsoft
3374	recommends spawning a chain of threads and wait for 63 handles and the	4608	recommends spawning a chain of threads and wait for 63 handles and the
3375	previous thread in each. Great).	4609	previous thread in each. Sounds great!).
3376		4610
3377	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4611	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3378	to some high number (e.g. C<2048>) before compiling the winsocket select	4612	to some high number (e.g. C<2048>) before compiling the winsocket select
3379	call (which might be in libev or elsewhere, for example, perl does its own	4613	call (which might be in libev or elsewhere, for example, perl and many
3380	select emulation on windows).	4614	other interpreters do their own select emulation on windows).
3381		4615
3382	Another limit is the number of file descriptors in the Microsoft runtime	4616	Another limit is the number of file descriptors in the Microsoft runtime
3383	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4617	libraries, which by default is C<64> (there must be a hidden I<64>
3384	or something like this inside Microsoft). You can increase this by calling	4618	fetish or something like this inside Microsoft). You can increase this
3385	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4619	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3386	arbitrary limit), but is broken in many versions of the Microsoft runtime	4620	(another arbitrary limit), but is broken in many versions of the Microsoft
3387	libraries.
3388
3389	This might get you to about C<512> or C<2048> sockets (depending on	4621	runtime libraries. This might get you to about C<512> or C<2048> sockets
3390	windows version and/or the phase of the moon). To get more, you need to	4622	(depending on windows version and/or the phase of the moon). To get more,
3391	wrap all I/O functions and provide your own fd management, but the cost of	4623	you need to wrap all I/O functions and provide your own fd management, but
3392	calling select (O(n²)) will likely make this unworkable.	4624	the cost of calling select (O(n²)) will likely make this unworkable.
3393		4625
3394	=back
3395
3396
3397	=head1 PORTABILITY REQUIREMENTS	4626	=head2 PORTABILITY REQUIREMENTS
3398		4627
3399	In addition to a working ISO-C implementation, libev relies on a few	4628	In addition to a working ISO-C implementation and of course the
3400	additional extensions:	4629	backend-specific APIs, libev relies on a few additional extensions:
3401		4630
3402	=over 4	4631	=over 4
3403		4632
3404	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	4633	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3405	calling conventions regardless of C<ev_watcher_type *>.	4634	calling conventions regardless of C<ev_watcher_type *>.
…		…
3411	calls them using an C<ev_watcher *> internally.	4640	calls them using an C<ev_watcher *> internally.
3412		4641
3413	=item C<sig_atomic_t volatile> must be thread-atomic as well	4642	=item C<sig_atomic_t volatile> must be thread-atomic as well
3414		4643
3415	The type C<sig_atomic_t volatile> (or whatever is defined as	4644	The type C<sig_atomic_t volatile> (or whatever is defined as
3416	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	4645	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3417	threads. This is not part of the specification for C<sig_atomic_t>, but is	4646	threads. This is not part of the specification for C<sig_atomic_t>, but is
3418	believed to be sufficiently portable.	4647	believed to be sufficiently portable.
3419		4648
3420	=item C<sigprocmask> must work in a threaded environment	4649	=item C<sigprocmask> must work in a threaded environment
3421		4650
…		…
3430	except the initial one, and run the default loop in the initial thread as	4659	except the initial one, and run the default loop in the initial thread as
3431	well.	4660	well.
3432		4661
3433	=item C<long> must be large enough for common memory allocation sizes	4662	=item C<long> must be large enough for common memory allocation sizes
3434		4663
3435	To improve portability and simplify using libev, libev uses C<long>	4664	To improve portability and simplify its API, libev uses C<long> internally
3436	internally instead of C<size_t> when allocating its data structures. On	4665	instead of C<size_t> when allocating its data structures. On non-POSIX
3437	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4666	systems (Microsoft...) this might be unexpectedly low, but is still at
3438	is still at least 31 bits everywhere, which is enough for hundreds of	4667	least 31 bits everywhere, which is enough for hundreds of millions of
3439	millions of watchers.	4668	watchers.
3440		4669
3441	=item C<double> must hold a time value in seconds with enough accuracy	4670	=item C<double> must hold a time value in seconds with enough accuracy
3442		4671
3443	The type C<double> is used to represent timestamps. It is required to	4672	The type C<double> is used to represent timestamps. It is required to
3444	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4673	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3445	enough for at least into the year 4000. This requirement is fulfilled by	4674	good enough for at least into the year 4000 with millisecond accuracy
		4675	(the design goal for libev). This requirement is overfulfilled by
3446	implementations implementing IEEE 754 (basically all existing ones).	4676	implementations using IEEE 754, which is basically all existing ones. With
		4677	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
3447		4678
3448	=back	4679	=back
3449		4680
3450	If you know of other additional requirements drop me a note.	4681	If you know of other additional requirements drop me a note.
3451		4682
3452		4683
3453	=head1 COMPILER WARNINGS	4684	=head1 ALGORITHMIC COMPLEXITIES
3454		4685
3455	Depending on your compiler and compiler settings, you might get no or a	4686	In this section the complexities of (many of) the algorithms used inside
3456	lot of warnings when compiling libev code. Some people are apparently	4687	libev will be documented. For complexity discussions about backends see
3457	scared by this.	4688	the documentation for C<ev_default_init>.
3458		4689
3459	However, these are unavoidable for many reasons. For one, each compiler	4690	All of the following are about amortised time: If an array needs to be
3460	has different warnings, and each user has different tastes regarding	4691	extended, libev needs to realloc and move the whole array, but this
3461	warning options. "Warn-free" code therefore cannot be a goal except when	4692	happens asymptotically rarer with higher number of elements, so O(1) might
3462	targeting a specific compiler and compiler-version.	4693	mean that libev does a lengthy realloc operation in rare cases, but on
		4694	average it is much faster and asymptotically approaches constant time.
3463		4695
3464	Another reason is that some compiler warnings require elaborate	4696	=over 4
3465	workarounds, or other changes to the code that make it less clear and less
3466	maintainable.
3467		4697
3468	And of course, some compiler warnings are just plain stupid, or simply	4698	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3469	wrong (because they don't actually warn about the condition their message
3470	seems to warn about).
3471		4699
3472	While libev is written to generate as few warnings as possible,	4700	This means that, when you have a watcher that triggers in one hour and
3473	"warn-free" code is not a goal, and it is recommended not to build libev	4701	there are 100 watchers that would trigger before that, then inserting will
3474	with any compiler warnings enabled unless you are prepared to cope with	4702	have to skip roughly seven (C<ld 100>) of these watchers.
3475	them (e.g. by ignoring them). Remember that warnings are just that:
3476	warnings, not errors, or proof of bugs.
3477		4703
		4704	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3478		4705
3479	=head1 VALGRIND	4706	That means that changing a timer costs less than removing/adding them,
		4707	as only the relative motion in the event queue has to be paid for.
3480		4708
3481	Valgrind has a special section here because it is a popular tool that is	4709	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3482	highly useful, but valgrind reports are very hard to interpret.
3483		4710
3484	If you think you found a bug (memory leak, uninitialised data access etc.)	4711	These just add the watcher into an array or at the head of a list.
3485	in libev, then check twice: If valgrind reports something like:
3486		4712
3487	==2274== definitely lost: 0 bytes in 0 blocks.	4713	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3488	==2274== possibly lost: 0 bytes in 0 blocks.
3489	==2274== still reachable: 256 bytes in 1 blocks.
3490		4714
3491	Then there is no memory leak. Similarly, under some circumstances,	4715	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3492	valgrind might report kernel bugs as if it were a bug in libev, or it
3493	might be confused (it is a very good tool, but only a tool).
3494		4716
3495	If you are unsure about something, feel free to contact the mailing list	4717	These watchers are stored in lists, so they need to be walked to find the
3496	with the full valgrind report and an explanation on why you think this is	4718	correct watcher to remove. The lists are usually short (you don't usually
3497	a bug in libev. However, don't be annoyed when you get a brisk "this is	4719	have many watchers waiting for the same fd or signal: one is typical, two
3498	no bug" answer and take the chance of learning how to interpret valgrind	4720	is rare).
3499	properly.
3500		4721
3501	If you need, for some reason, empty reports from valgrind for your project	4722	=item Finding the next timer in each loop iteration: O(1)
3502	I suggest using suppression lists.
3503		4723
		4724	By virtue of using a binary or 4-heap, the next timer is always found at a
		4725	fixed position in the storage array.
		4726
		4727	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4728
		4729	A change means an I/O watcher gets started or stopped, which requires
		4730	libev to recalculate its status (and possibly tell the kernel, depending
		4731	on backend and whether C<ev_io_set> was used).
		4732
		4733	=item Activating one watcher (putting it into the pending state): O(1)
		4734
		4735	=item Priority handling: O(number_of_priorities)
		4736
		4737	Priorities are implemented by allocating some space for each
		4738	priority. When doing priority-based operations, libev usually has to
		4739	linearly search all the priorities, but starting/stopping and activating
		4740	watchers becomes O(1) with respect to priority handling.
		4741
		4742	=item Sending an ev_async: O(1)
		4743
		4744	=item Processing ev_async_send: O(number_of_async_watchers)
		4745
		4746	=item Processing signals: O(max_signal_number)
		4747
		4748	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4749	calls in the current loop iteration. Checking for async and signal events
		4750	involves iterating over all running async watchers or all signal numbers.
		4751
		4752	=back
		4753
		4754
		4755	=head1 PORTING FROM LIBEV 3.X TO 4.X
		4756
		4757	The major version 4 introduced some minor incompatible changes to the API.
		4758
		4759	At the moment, the C<ev.h> header file tries to implement superficial
		4760	compatibility, so most programs should still compile. Those might be
		4761	removed in later versions of libev, so better update early than late.
		4762
		4763	=over 4
		4764
		4765	=item function/symbol renames
		4766
		4767	A number of functions and symbols have been renamed:
		4768
		4769	ev_loop => ev_run
		4770	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		4771	EVLOOP_ONESHOT => EVRUN_ONCE
		4772
		4773	ev_unloop => ev_break
		4774	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		4775	EVUNLOOP_ONE => EVBREAK_ONE
		4776	EVUNLOOP_ALL => EVBREAK_ALL
		4777
		4778	EV_TIMEOUT => EV_TIMER
		4779
		4780	ev_loop_count => ev_iteration
		4781	ev_loop_depth => ev_depth
		4782	ev_loop_verify => ev_verify
		4783
		4784	Most functions working on C<struct ev_loop> objects don't have an
		4785	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		4786	associated constants have been renamed to not collide with the C<struct
		4787	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		4788	as all other watcher types. Note that C<ev_loop_fork> is still called
		4789	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		4790	typedef.
		4791
		4792	=item C<EV_COMPAT3> backwards compatibility mechanism
		4793
		4794	The backward compatibility mechanism can be controlled by
		4795	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		4796	section.
		4797
		4798	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		4799
		4800	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		4801	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		4802	and work, but the library code will of course be larger.
		4803
		4804	=back
		4805
		4806
		4807	=head1 GLOSSARY
		4808
		4809	=over 4
		4810
		4811	=item active
		4812
		4813	A watcher is active as long as it has been started (has been attached to
		4814	an event loop) but not yet stopped (disassociated from the event loop).
		4815
		4816	=item application
		4817
		4818	In this document, an application is whatever is using libev.
		4819
		4820	=item callback
		4821
		4822	The address of a function that is called when some event has been
		4823	detected. Callbacks are being passed the event loop, the watcher that
		4824	received the event, and the actual event bitset.
		4825
		4826	=item callback invocation
		4827
		4828	The act of calling the callback associated with a watcher.
		4829
		4830	=item event
		4831
		4832	A change of state of some external event, such as data now being available
		4833	for reading on a file descriptor, time having passed or simply not having
		4834	any other events happening anymore.
		4835
		4836	In libev, events are represented as single bits (such as C<EV_READ> or
		4837	C<EV_TIMER>).
		4838
		4839	=item event library
		4840
		4841	A software package implementing an event model and loop.
		4842
		4843	=item event loop
		4844
		4845	An entity that handles and processes external events and converts them
		4846	into callback invocations.
		4847
		4848	=item event model
		4849
		4850	The model used to describe how an event loop handles and processes
		4851	watchers and events.
		4852
		4853	=item pending
		4854
		4855	A watcher is pending as soon as the corresponding event has been detected,
		4856	and stops being pending as soon as the watcher will be invoked or its
		4857	pending status is explicitly cleared by the application.
		4858
		4859	A watcher can be pending, but not active. Stopping a watcher also clears
		4860	its pending status.
		4861
		4862	=item real time
		4863
		4864	The physical time that is observed. It is apparently strictly monotonic :)
		4865
		4866	=item wall-clock time
		4867
		4868	The time and date as shown on clocks. Unlike real time, it can actually
		4869	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4870	clock.
		4871
		4872	=item watcher
		4873
		4874	A data structure that describes interest in certain events. Watchers need
		4875	to be started (attached to an event loop) before they can receive events.
		4876
		4877	=item watcher invocation
		4878
		4879	The act of calling the callback associated with a watcher.
		4880
		4881	=back
3504		4882
3505	=head1 AUTHOR	4883	=head1 AUTHOR
3506		4884
3507	Marc Lehmann <libev@schmorp.de>.	4885	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3508		4886

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