ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.178 by root, Sat Sep 13 18:25:50 2008 UTC vs.
Revision 1.311 by root, Thu Oct 21 14:40:07 2010 UTC

…		…
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 this case unless libev 3 compatibility is disabled, as
283	events, and dynamically created loops which do not.	299	libev 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.
…		…
577		684
578	=item ev_now_update (loop)	685	=item ev_now_update (loop)
579		686
580	Establishes the current time by querying the kernel, updating the time	687	Establishes the current time by querying the kernel, updating the time
581	returned by C<ev_now ()> in the progress. This is a costly operation and	688	returned by C<ev_now ()> in the progress. This is a costly operation and
582	is usually done automatically within C<ev_loop ()>.	689	is usually done automatically within C<ev_run ()>.
583		690
584	This function is rarely useful, but when some event callback runs for a	691	This function is rarely useful, but when some event callback runs for a
585	very long time without entering the event loop, updating libev's idea of	692	very long time without entering the event loop, updating libev's idea of
586	the current time is a good idea.	693	the current time is a good idea.
587		694
588	See also "The special problem of time updates" in the C<ev_timer> section.	695	See also L<The special problem of time updates> in the C<ev_timer> section.
589		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
590	=item ev_loop (loop, int flags)	723	=item ev_run (loop, int flags)
591		724
592	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
593	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
594	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>.
595		730
596	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
597	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.
598		734
599	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
600	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
601	finished (especially in interactive programs), but having a program that	737	finished (especially in interactive programs), but having a program
602	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
603	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.
604		741
605	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
606	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
607	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.
608		747
609	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
610	necessary) and will handle those and any outstanding ones. It will block	749	necessary) and will handle those and any already outstanding ones. It
611	your process until at least one new event arrives, and will return after	750	will block your process until at least one new event arrives (which could
612	one iteration of the loop. This is useful if you are waiting for some	751	be an event internal to libev itself, so there is no guarantee that a
613	external event in conjunction with something not expressible using other	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
614	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
615	usually a better approach for this kind of thing.	758	usually a better approach for this kind of thing.
616		759
617	Here are the gory details of what C<ev_loop> does:	760	Here are the gory details of what C<ev_run> does:
618		761
		762	- Increment loop depth.
		763	- Reset the ev_break status.
619	- Before the first iteration, call any pending watchers.	764	- Before the first iteration, call any pending watchers.
		765	LOOP:
620	* If EVFLAG_FORKCHECK was used, check for a fork.	766	- If EVFLAG_FORKCHECK was used, check for a fork.
621	- If a fork was detected (by any means), queue and call all fork watchers.	767	- If a fork was detected (by any means), queue and call all fork watchers.
622	- Queue and call all prepare watchers.	768	- Queue and call all prepare watchers.
		769	- If ev_break was called, goto FINISH.
623	- If we have been forked, detach and recreate the kernel state	770	- If we have been forked, detach and recreate the kernel state
624	as to not disturb the other process.	771	as to not disturb the other process.
625	- Update the kernel state with all outstanding changes.	772	- Update the kernel state with all outstanding changes.
626	- Update the "event loop time" (ev_now ()).	773	- Update the "event loop time" (ev_now ()).
627	- Calculate for how long to sleep or block, if at all	774	- Calculate for how long to sleep or block, if at all
628	(active idle watchers, EVLOOP_NONBLOCK or not having	775	(active idle watchers, EVRUN_NOWAIT or not having
629	any active watchers at all will result in not sleeping).	776	any active watchers at all will result in not sleeping).
630	- 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.
631	- Block the process, waiting for any events.	779	- Block the process, waiting for any events.
632	- Queue all outstanding I/O (fd) events.	780	- Queue all outstanding I/O (fd) events.
633	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	781	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
634	- Queue all outstanding timers.	782	- Queue all expired timers.
635	- Queue all outstanding periodics.	783	- Queue all expired periodics.
636	- Unless any events are pending now, queue all idle watchers.	784	- Queue all idle watchers with priority higher than that of pending events.
637	- Queue all check watchers.	785	- Queue all check watchers.
638	- 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).
639	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
640	be handled here by queueing them when their watcher gets executed.	788	be handled here by queueing them when their watcher gets executed.
641	- 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
642	were used, or there are no active watchers, return, otherwise	790	were used, or there are no active watchers, goto FINISH, otherwise
643	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.
644		796
645	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
646	anymore.	798	anymore.
647		799
648	... queue jobs here, make sure they register event watchers as long	800	... queue jobs here, make sure they register event watchers as long
649	... as they still have work to do (even an idle watcher will do..)	801	... as they still have work to do (even an idle watcher will do..)
650	ev_loop (my_loop, 0);	802	ev_run (my_loop, 0);
651	... jobs done or somebody called unloop. yeah!	803	... jobs done or somebody called unloop. yeah!
652		804
653	=item ev_unloop (loop, how)	805	=item ev_break (loop, how)
654		806
655	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
656	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
657	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
658	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.
659		811
660	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##
661		815
662	=item ev_ref (loop)	816	=item ev_ref (loop)
663		817
664	=item ev_unref (loop)	818	=item ev_unref (loop)
665		819
666	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
667	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
668	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.
669	a watcher you never unregister that should not keep C<ev_loop> from	823
670	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
671	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
672	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
673	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
674	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
675	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
676	(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
677	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).
678		838
679	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>
680	running when nothing else is active.	840	running when nothing else is active.
681		841
682	struct ev_signal exitsig;	842	ev_signal exitsig;
683	ev_signal_init (&exitsig, sig_cb, SIGINT);	843	ev_signal_init (&exitsig, sig_cb, SIGINT);
684	ev_signal_start (loop, &exitsig);	844	ev_signal_start (loop, &exitsig);
685	evf_unref (loop);	845	evf_unref (loop);
686		846
687	Example: For some weird reason, unregister the above signal handler again.	847	Example: For some weird reason, unregister the above signal handler again.
…		…
701	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	861	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
702	allows libev to delay invocation of I/O and timer/periodic callbacks	862	allows libev to delay invocation of I/O and timer/periodic callbacks
703	to increase efficiency of loop iterations (or to increase power-saving	863	to increase efficiency of loop iterations (or to increase power-saving
704	opportunities).	864	opportunities).
705		865
706	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
707	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
708	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
709	events, especially with backends like C<select ()> which have a high	869	events, especially with backends like C<select ()> which have a high
710	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.
711		871
712	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
713	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,
714	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
715	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
716	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.
717		879
718	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
719	to spend more time collecting timeouts, at the expense of increased	881	to spend more time collecting timeouts, at the expense of increased
720	latency (the watcher callback will be called later). C<ev_io> watchers	882	latency/jitter/inexactness (the watcher callback will be called
721	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
722	any overhead in libev.	884	value will not introduce any overhead in libev.
723		885
724	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
725	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
726	interactive servers (of course not for games), likewise for timeouts. It	888	interactive servers (of course not for games), likewise for timeouts. It
727	usually doesn't make much sense to set it to a lower value than C<0.01>,	889	usually doesn't make much sense to set it to a lower value than C<0.01>,
728	as this approaches the timing granularity of most systems.	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).
729		895
730	Setting the I<timeout collect interval> can improve the opportunity for	896	Setting the I<timeout collect interval> can improve the opportunity for
731	saving power, as the program will "bundle" timer callback invocations that	897	saving power, as the program will "bundle" timer callback invocations that
732	are "near" in time together, by delaying some, thus reducing the number of	898	are "near" in time together, by delaying some, thus reducing the number of
733	times the process sleeps and wakes up again. Another useful technique to	899	times the process sleeps and wakes up again. Another useful technique to
734	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	900	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
735	they fire on, say, one-second boundaries only.	901	they fire on, say, one-second boundaries only.
736		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
737	=item ev_loop_verify (loop)	974	=item ev_verify (loop)
738		975
739	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
740	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
741	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
742	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 ()>.
743		981
744	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
745	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
746	data structures consistent.	984	data structures consistent.
747		985
748	=back	986	=back
749		987
750		988
751	=head1 ANATOMY OF A WATCHER	989	=head1 ANATOMY OF A WATCHER
752		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
753	A watcher is a structure that you create and register to record your	995	A watcher is an opaque structure that you allocate and register to record
754	interest in some event. For instance, if you want to wait for STDIN to	996	your interest in some event. To make a concrete example, imagine you want
755	become readable, you would create an C<ev_io> watcher for that:	997	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		998	for that:
756		999
757	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1000	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
758	{	1001	{
759	ev_io_stop (w);	1002	ev_io_stop (w);
760	ev_unloop (loop, EVUNLOOP_ALL);	1003	ev_break (loop, EVBREAK_ALL);
761	}	1004	}
762		1005
763	struct ev_loop *loop = ev_default_loop (0);	1006	struct ev_loop *loop = ev_default_loop (0);
		1007
764	struct ev_io stdin_watcher;	1008	ev_io stdin_watcher;
		1009
765	ev_init (&stdin_watcher, my_cb);	1010	ev_init (&stdin_watcher, my_cb);
766	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1011	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
767	ev_io_start (loop, &stdin_watcher);	1012	ev_io_start (loop, &stdin_watcher);
		1013
768	ev_loop (loop, 0);	1014	ev_run (loop, 0);
769		1015
770	As you can see, you are responsible for allocating the memory for your	1016	As you can see, you are responsible for allocating the memory for your
771	watcher structures (and it is usually a bad idea to do this on the stack,	1017	watcher structures (and it is I<usually> a bad idea to do this on the
772	although this can sometimes be quite valid).	1018	stack).
773		1019
		1020	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		1021	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
		1022
774	Each watcher structure must be initialised by a call to C<ev_init	1023	Each watcher structure must be initialised by a call to C<ev_init (watcher
775	(watcher *, callback)>, which expects a callback to be provided. This	1024	*, callback)>, which expects a callback to be provided. This callback is
776	callback gets invoked each time the event occurs (or, in the case of I/O	1025	invoked each time the event occurs (or, in the case of I/O watchers, each
777	watchers, each time the event loop detects that the file descriptor given	1026	time the event loop detects that the file descriptor given is readable
778	is readable and/or writable).	1027	and/or writable).
779		1028
780	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1029	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
781	with arguments specific to this watcher type. There is also a macro	1030	macro to configure it, with arguments specific to the watcher type. There
782	to combine initialisation and setting in one call: C<< ev_<type>_init	1031	is also a macro to combine initialisation and setting in one call: C<<
783	(watcher *, callback, ...) >>.	1032	ev_TYPE_init (watcher *, callback, ...) >>.
784		1033
785	To make the watcher actually watch out for events, you have to start it	1034	To make the watcher actually watch out for events, you have to start it
786	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	1035	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
787	*) >>), and you can stop watching for events at any time by calling the	1036	*) >>), and you can stop watching for events at any time by calling the
788	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1037	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
789		1038
790	As long as your watcher is active (has been started but not stopped) you	1039	As long as your watcher is active (has been started but not stopped) you
791	must not touch the values stored in it. Most specifically you must never	1040	must not touch the values stored in it. Most specifically you must never
792	reinitialise it or call its C<set> macro.	1041	reinitialise it or call its C<ev_TYPE_set> macro.
793		1042
794	Each and every callback receives the event loop pointer as first, the	1043	Each and every callback receives the event loop pointer as first, the
795	registered watcher structure as second, and a bitset of received events as	1044	registered watcher structure as second, and a bitset of received events as
796	third argument.	1045	third argument.
797		1046
…		…
806	=item C<EV_WRITE>	1055	=item C<EV_WRITE>
807		1056
808	The file descriptor in the C<ev_io> watcher has become readable and/or	1057	The file descriptor in the C<ev_io> watcher has become readable and/or
809	writable.	1058	writable.
810		1059
811	=item C<EV_TIMEOUT>	1060	=item C<EV_TIMER>
812		1061
813	The C<ev_timer> watcher has timed out.	1062	The C<ev_timer> watcher has timed out.
814		1063
815	=item C<EV_PERIODIC>	1064	=item C<EV_PERIODIC>
816		1065
…		…
834		1083
835	=item C<EV_PREPARE>	1084	=item C<EV_PREPARE>
836		1085
837	=item C<EV_CHECK>	1086	=item C<EV_CHECK>
838		1087
839	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1088	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
840	to gather new events, and all C<ev_check> watchers are invoked just after	1089	to gather new events, and all C<ev_check> watchers are invoked just after
841	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1090	C<ev_run> has gathered them, but before it invokes any callbacks for any
842	received events. Callbacks of both watcher types can start and stop as	1091	received events. Callbacks of both watcher types can start and stop as
843	many watchers as they want, and all of them will be taken into account	1092	many watchers as they want, and all of them will be taken into account
844	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1093	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
845	C<ev_loop> from blocking).	1094	C<ev_run> from blocking).
846		1095
847	=item C<EV_EMBED>	1096	=item C<EV_EMBED>
848		1097
849	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1098	The embedded event loop specified in the C<ev_embed> watcher needs attention.
850		1099
…		…
854	C<ev_fork>).	1103	C<ev_fork>).
855		1104
856	=item C<EV_ASYNC>	1105	=item C<EV_ASYNC>
857		1106
858	The given async watcher has been asynchronously notified (see C<ev_async>).	1107	The given async watcher has been asynchronously notified (see C<ev_async>).
		1108
		1109	=item C<EV_CUSTOM>
		1110
		1111	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1112	by libev users to signal watchers (e.g. via C<ev_feed_event>).
859		1113
860	=item C<EV_ERROR>	1114	=item C<EV_ERROR>
861		1115
862	An unspecified error has occurred, the watcher has been stopped. This might	1116	An unspecified error has occurred, the watcher has been stopped. This might
863	happen because the watcher could not be properly started because libev	1117	happen because the watcher could not be properly started because libev
864	ran out of memory, a file descriptor was found to be closed or any other	1118	ran out of memory, a file descriptor was found to be closed or any other
		1119	problem. Libev considers these application bugs.
		1120
865	problem. You best act on it by reporting the problem and somehow coping	1121	You best act on it by reporting the problem and somehow coping with the
866	with the watcher being stopped.	1122	watcher being stopped. Note that well-written programs should not receive
		1123	an error ever, so when your watcher receives it, this usually indicates a
		1124	bug in your program.
867		1125
868	Libev will usually signal a few "dummy" events together with an error,	1126	Libev will usually signal a few "dummy" events together with an error, for
869	for example it might indicate that a fd is readable or writable, and if	1127	example it might indicate that a fd is readable or writable, and if your
870	your callbacks is well-written it can just attempt the operation and cope	1128	callbacks is well-written it can just attempt the operation and cope with
871	with the error from read() or write(). This will not work in multi-threaded	1129	the error from read() or write(). This will not work in multi-threaded
872	programs, though, so beware.	1130	programs, though, as the fd could already be closed and reused for another
		1131	thing, so beware.
873		1132
874	=back	1133	=back
875		1134
		1135	=head2 WATCHER STATES
		1136
		1137	There are various watcher states mentioned throughout this manual -
		1138	active, pending and so on. In this section these states and the rules to
		1139	transition between them will be described in more detail - and while these
		1140	rules might look complicated, they usually do "the right thing".
		1141
		1142	=over 4
		1143
		1144	=item initialiased
		1145
		1146	Before a watcher can be registered with the event looop it has to be
		1147	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1148	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1149
		1150	In this state it is simply some block of memory that is suitable for use
		1151	in an event loop. It can be moved around, freed, reused etc. at will.
		1152
		1153	=item started/running/active
		1154
		1155	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1156	property of the event loop, and is actively waiting for events. While in
		1157	this state it cannot be accessed (except in a few documented ways), moved,
		1158	freed or anything else - the only legal thing is to keep a pointer to it,
		1159	and call libev functions on it that are documented to work on active watchers.
		1160
		1161	=item pending
		1162
		1163	If a watcher is active and libev determines that an event it is interested
		1164	in has occured (such as a timer expiring), it will become pending. It will
		1165	stay in this pending state until either it is stopped or its callback is
		1166	about to be invoked, so it is not normally pending inside the watcher
		1167	callback.
		1168
		1169	The watcher might or might not be active while it is pending (for example,
		1170	an expired non-repeating timer can be pending but no longer active). If it
		1171	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1172	but it is still property of the event loop at this time, so cannot be
		1173	moved, freed or reused. And if it is active the rules described in the
		1174	previous item still apply.
		1175
		1176	It is also possible to feed an event on a watcher that is not active (e.g.
		1177	via C<ev_feed_event>), in which case it becomes pending without being
		1178	active.
		1179
		1180	=item stopped
		1181
		1182	A watcher can be stopped implicitly by libev (in which case it might still
		1183	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1184	latter will clear any pending state the watcher might be in, regardless
		1185	of whether it was active or not, so stopping a watcher explicitly before
		1186	freeing it is often a good idea.
		1187
		1188	While stopped (and not pending) the watcher is essentially in the
		1189	initialised state, that is it can be reused, moved, modified in any way
		1190	you wish.
		1191
		1192	=back
		1193
876	=head2 GENERIC WATCHER FUNCTIONS	1194	=head2 GENERIC WATCHER FUNCTIONS
877
878	In the following description, C<TYPE> stands for the watcher type,
879	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
880		1195
881	=over 4	1196	=over 4
882		1197
883	=item C<ev_init> (ev_TYPE *watcher, callback)	1198	=item C<ev_init> (ev_TYPE *watcher, callback)
884		1199
…		…
890	which rolls both calls into one.	1205	which rolls both calls into one.
891		1206
892	You can reinitialise a watcher at any time as long as it has been stopped	1207	You can reinitialise a watcher at any time as long as it has been stopped
893	(or never started) and there are no pending events outstanding.	1208	(or never started) and there are no pending events outstanding.
894		1209
895	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1210	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
896	int revents)>.	1211	int revents)>.
897		1212
		1213	Example: Initialise an C<ev_io> watcher in two steps.
		1214
		1215	ev_io w;
		1216	ev_init (&w, my_cb);
		1217	ev_io_set (&w, STDIN_FILENO, EV_READ);
		1218
898	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1219	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
899		1220
900	This macro initialises the type-specific parts of a watcher. You need to	1221	This macro initialises the type-specific parts of a watcher. You need to
901	call C<ev_init> at least once before you call this macro, but you can	1222	call C<ev_init> at least once before you call this macro, but you can
902	call C<ev_TYPE_set> any number of times. You must not, however, call this	1223	call C<ev_TYPE_set> any number of times. You must not, however, call this
903	macro on a watcher that is active (it can be pending, however, which is a	1224	macro on a watcher that is active (it can be pending, however, which is a
904	difference to the C<ev_init> macro).	1225	difference to the C<ev_init> macro).
905		1226
906	Although some watcher types do not have type-specific arguments	1227	Although some watcher types do not have type-specific arguments
907	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	1228	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
908		1229
		1230	See C<ev_init>, above, for an example.
		1231
909	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1232	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
910		1233
911	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1234	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
912	calls into a single call. This is the most convenient method to initialise	1235	calls into a single call. This is the most convenient method to initialise
913	a watcher. The same limitations apply, of course.	1236	a watcher. The same limitations apply, of course.
914		1237
		1238	Example: Initialise and set an C<ev_io> watcher in one step.
		1239
		1240	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1241
915	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1242	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
916		1243
917	Starts (activates) the given watcher. Only active watchers will receive	1244	Starts (activates) the given watcher. Only active watchers will receive
918	events. If the watcher is already active nothing will happen.	1245	events. If the watcher is already active nothing will happen.
919		1246
		1247	Example: Start the C<ev_io> watcher that is being abused as example in this
		1248	whole section.
		1249
		1250	ev_io_start (EV_DEFAULT_UC, &w);
		1251
920	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1252	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
921		1253
922	Stops the given watcher again (if active) and clears the pending	1254	Stops the given watcher if active, and clears the pending status (whether
		1255	the watcher was active or not).
		1256
923	status. It is possible that stopped watchers are pending (for example,	1257	It is possible that stopped watchers are pending - for example,
924	non-repeating timers are being stopped when they become pending), but	1258	non-repeating timers are being stopped when they become pending - but
925	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1259	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
926	you want to free or reuse the memory used by the watcher it is therefore a	1260	pending. If you want to free or reuse the memory used by the watcher it is
927	good idea to always call its C<ev_TYPE_stop> function.	1261	therefore a good idea to always call its C<ev_TYPE_stop> function.
928		1262
929	=item bool ev_is_active (ev_TYPE *watcher)	1263	=item bool ev_is_active (ev_TYPE *watcher)
930		1264
931	Returns a true value iff the watcher is active (i.e. it has been started	1265	Returns a true value iff the watcher is active (i.e. it has been started
932	and not yet been stopped). As long as a watcher is active you must not modify	1266	and not yet been stopped). As long as a watcher is active you must not modify
…		…
948	=item ev_cb_set (ev_TYPE *watcher, callback)	1282	=item ev_cb_set (ev_TYPE *watcher, callback)
949		1283
950	Change the callback. You can change the callback at virtually any time	1284	Change the callback. You can change the callback at virtually any time
951	(modulo threads).	1285	(modulo threads).
952		1286
953	=item ev_set_priority (ev_TYPE *watcher, priority)	1287	=item ev_set_priority (ev_TYPE *watcher, int priority)
954		1288
955	=item int ev_priority (ev_TYPE *watcher)	1289	=item int ev_priority (ev_TYPE *watcher)
956		1290
957	Set and query the priority of the watcher. The priority is a small	1291	Set and query the priority of the watcher. The priority is a small
958	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1292	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
959	(default: C<-2>). Pending watchers with higher priority will be invoked	1293	(default: C<-2>). Pending watchers with higher priority will be invoked
960	before watchers with lower priority, but priority will not keep watchers	1294	before watchers with lower priority, but priority will not keep watchers
961	from being executed (except for C<ev_idle> watchers).	1295	from being executed (except for C<ev_idle> watchers).
962		1296
963	This means that priorities are I<only> used for ordering callback
964	invocation after new events have been received. This is useful, for
965	example, to reduce latency after idling, or more often, to bind two
966	watchers on the same event and make sure one is called first.
967
968	If you need to suppress invocation when higher priority events are pending	1297	If you need to suppress invocation when higher priority events are pending
969	you need to look at C<ev_idle> watchers, which provide this functionality.	1298	you need to look at C<ev_idle> watchers, which provide this functionality.
970		1299
971	You I<must not> change the priority of a watcher as long as it is active or	1300	You I<must not> change the priority of a watcher as long as it is active or
972	pending.	1301	pending.
973		1302
		1303	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1304	fine, as long as you do not mind that the priority value you query might
		1305	or might not have been clamped to the valid range.
		1306
974	The default priority used by watchers when no priority has been set is	1307	The default priority used by watchers when no priority has been set is
975	always C<0>, which is supposed to not be too high and not be too low :).	1308	always C<0>, which is supposed to not be too high and not be too low :).
976		1309
977	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1310	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
978	fine, as long as you do not mind that the priority value you query might	1311	priorities.
979	or might not have been adjusted to be within valid range.
980		1312
981	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1313	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
982		1314
983	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1315	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
984	C<loop> nor C<revents> need to be valid as long as the watcher callback	1316	C<loop> nor C<revents> need to be valid as long as the watcher callback
985	can deal with that fact.	1317	can deal with that fact, as both are simply passed through to the
		1318	callback.
986		1319
987	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1320	=item int ev_clear_pending (loop, ev_TYPE *watcher)
988		1321
989	If the watcher is pending, this function returns clears its pending status	1322	If the watcher is pending, this function clears its pending status and
990	and returns its C<revents> bitset (as if its callback was invoked). If the	1323	returns its C<revents> bitset (as if its callback was invoked). If the
991	watcher isn't pending it does nothing and returns C<0>.	1324	watcher isn't pending it does nothing and returns C<0>.
992		1325
		1326	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1327	callback to be invoked, which can be accomplished with this function.
		1328
		1329	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1330
		1331	Feeds the given event set into the event loop, as if the specified event
		1332	had happened for the specified watcher (which must be a pointer to an
		1333	initialised but not necessarily started event watcher). Obviously you must
		1334	not free the watcher as long as it has pending events.
		1335
		1336	Stopping the watcher, letting libev invoke it, or calling
		1337	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1338	not started in the first place.
		1339
		1340	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1341	functions that do not need a watcher.
		1342
993	=back	1343	=back
994		1344
995		1345
996	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1346	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
997		1347
998	Each watcher has, by default, a member C<void *data> that you can change	1348	Each watcher has, by default, a member C<void *data> that you can change
999	and read at any time, libev will completely ignore it. This can be used	1349	and read at any time: libev will completely ignore it. This can be used
1000	to associate arbitrary data with your watcher. If you need more data and	1350	to associate arbitrary data with your watcher. If you need more data and
1001	don't want to allocate memory and store a pointer to it in that data	1351	don't want to allocate memory and store a pointer to it in that data
1002	member, you can also "subclass" the watcher type and provide your own	1352	member, you can also "subclass" the watcher type and provide your own
1003	data:	1353	data:
1004		1354
1005	struct my_io	1355	struct my_io
1006	{	1356	{
1007	struct ev_io io;	1357	ev_io io;
1008	int otherfd;	1358	int otherfd;
1009	void *somedata;	1359	void *somedata;
1010	struct whatever *mostinteresting;	1360	struct whatever *mostinteresting;
1011	};	1361	};
1012		1362
…		…
1015	ev_io_init (&w.io, my_cb, fd, EV_READ);	1365	ev_io_init (&w.io, my_cb, fd, EV_READ);
1016		1366
1017	And since your callback will be called with a pointer to the watcher, you	1367	And since your callback will be called with a pointer to the watcher, you
1018	can cast it back to your own type:	1368	can cast it back to your own type:
1019		1369
1020	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1370	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1021	{	1371	{
1022	struct my_io *w = (struct my_io *)w_;	1372	struct my_io *w = (struct my_io *)w_;
1023	...	1373	...
1024	}	1374	}
1025		1375
…		…
1036	ev_timer t2;	1386	ev_timer t2;
1037	}	1387	}
1038		1388
1039	In this case getting the pointer to C<my_biggy> is a bit more	1389	In this case getting the pointer to C<my_biggy> is a bit more
1040	complicated: Either you store the address of your C<my_biggy> struct	1390	complicated: Either you store the address of your C<my_biggy> struct
1041	in the C<data> member of the watcher, or you need to use some pointer	1391	in the C<data> member of the watcher (for woozies), or you need to use
1042	arithmetic using C<offsetof> inside your watchers:	1392	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1393	programmers):
1043		1394
1044	#include <stddef.h>	1395	#include <stddef.h>
1045		1396
1046	static void	1397	static void
1047	t1_cb (EV_P_ struct ev_timer *w, int revents)	1398	t1_cb (EV_P_ ev_timer *w, int revents)
1048	{	1399	{
1049	struct my_biggy big = (struct my_biggy *	1400	struct my_biggy big = (struct my_biggy *)
1050	(((char *)w) - offsetof (struct my_biggy, t1));	1401	(((char *)w) - offsetof (struct my_biggy, t1));
1051	}	1402	}
1052		1403
1053	static void	1404	static void
1054	t2_cb (EV_P_ struct ev_timer *w, int revents)	1405	t2_cb (EV_P_ ev_timer *w, int revents)
1055	{	1406	{
1056	struct my_biggy big = (struct my_biggy *	1407	struct my_biggy big = (struct my_biggy *)
1057	(((char *)w) - offsetof (struct my_biggy, t2));	1408	(((char *)w) - offsetof (struct my_biggy, t2));
1058	}	1409	}
		1410
		1411	=head2 WATCHER PRIORITY MODELS
		1412
		1413	Many event loops support I<watcher priorities>, which are usually small
		1414	integers that influence the ordering of event callback invocation
		1415	between watchers in some way, all else being equal.
		1416
		1417	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1418	description for the more technical details such as the actual priority
		1419	range.
		1420
		1421	There are two common ways how these these priorities are being interpreted
		1422	by event loops:
		1423
		1424	In the more common lock-out model, higher priorities "lock out" invocation
		1425	of lower priority watchers, which means as long as higher priority
		1426	watchers receive events, lower priority watchers are not being invoked.
		1427
		1428	The less common only-for-ordering model uses priorities solely to order
		1429	callback invocation within a single event loop iteration: Higher priority
		1430	watchers are invoked before lower priority ones, but they all get invoked
		1431	before polling for new events.
		1432
		1433	Libev uses the second (only-for-ordering) model for all its watchers
		1434	except for idle watchers (which use the lock-out model).
		1435
		1436	The rationale behind this is that implementing the lock-out model for
		1437	watchers is not well supported by most kernel interfaces, and most event
		1438	libraries will just poll for the same events again and again as long as
		1439	their callbacks have not been executed, which is very inefficient in the
		1440	common case of one high-priority watcher locking out a mass of lower
		1441	priority ones.
		1442
		1443	Static (ordering) priorities are most useful when you have two or more
		1444	watchers handling the same resource: a typical usage example is having an
		1445	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1446	timeouts. Under load, data might be received while the program handles
		1447	other jobs, but since timers normally get invoked first, the timeout
		1448	handler will be executed before checking for data. In that case, giving
		1449	the timer a lower priority than the I/O watcher ensures that I/O will be
		1450	handled first even under adverse conditions (which is usually, but not
		1451	always, what you want).
		1452
		1453	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1454	will only be executed when no same or higher priority watchers have
		1455	received events, they can be used to implement the "lock-out" model when
		1456	required.
		1457
		1458	For example, to emulate how many other event libraries handle priorities,
		1459	you can associate an C<ev_idle> watcher to each such watcher, and in
		1460	the normal watcher callback, you just start the idle watcher. The real
		1461	processing is done in the idle watcher callback. This causes libev to
		1462	continuously poll and process kernel event data for the watcher, but when
		1463	the lock-out case is known to be rare (which in turn is rare :), this is
		1464	workable.
		1465
		1466	Usually, however, the lock-out model implemented that way will perform
		1467	miserably under the type of load it was designed to handle. In that case,
		1468	it might be preferable to stop the real watcher before starting the
		1469	idle watcher, so the kernel will not have to process the event in case
		1470	the actual processing will be delayed for considerable time.
		1471
		1472	Here is an example of an I/O watcher that should run at a strictly lower
		1473	priority than the default, and which should only process data when no
		1474	other events are pending:
		1475
		1476	ev_idle idle; // actual processing watcher
		1477	ev_io io; // actual event watcher
		1478
		1479	static void
		1480	io_cb (EV_P_ ev_io *w, int revents)
		1481	{
		1482	// stop the I/O watcher, we received the event, but
		1483	// are not yet ready to handle it.
		1484	ev_io_stop (EV_A_ w);
		1485
		1486	// start the idle watcher to handle the actual event.
		1487	// it will not be executed as long as other watchers
		1488	// with the default priority are receiving events.
		1489	ev_idle_start (EV_A_ &idle);
		1490	}
		1491
		1492	static void
		1493	idle_cb (EV_P_ ev_idle *w, int revents)
		1494	{
		1495	// actual processing
		1496	read (STDIN_FILENO, ...);
		1497
		1498	// have to start the I/O watcher again, as
		1499	// we have handled the event
		1500	ev_io_start (EV_P_ &io);
		1501	}
		1502
		1503	// initialisation
		1504	ev_idle_init (&idle, idle_cb);
		1505	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1506	ev_io_start (EV_DEFAULT_ &io);
		1507
		1508	In the "real" world, it might also be beneficial to start a timer, so that
		1509	low-priority connections can not be locked out forever under load. This
		1510	enables your program to keep a lower latency for important connections
		1511	during short periods of high load, while not completely locking out less
		1512	important ones.
1059		1513
1060		1514
1061	=head1 WATCHER TYPES	1515	=head1 WATCHER TYPES
1062		1516
1063	This section describes each watcher in detail, but will not repeat	1517	This section describes each watcher in detail, but will not repeat
…		…
1087	In general you can register as many read and/or write event watchers per	1541	In general you can register as many read and/or write event watchers per
1088	fd as you want (as long as you don't confuse yourself). Setting all file	1542	fd as you want (as long as you don't confuse yourself). Setting all file
1089	descriptors to non-blocking mode is also usually a good idea (but not	1543	descriptors to non-blocking mode is also usually a good idea (but not
1090	required if you know what you are doing).	1544	required if you know what you are doing).
1091		1545
1092	If you must do this, then force the use of a known-to-be-good backend	1546	If you cannot use non-blocking mode, then force the use of a
1093	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1547	known-to-be-good backend (at the time of this writing, this includes only
1094	C<EVBACKEND_POLL>).	1548	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1549	descriptors for which non-blocking operation makes no sense (such as
		1550	files) - libev doesn't guarantee any specific behaviour in that case.
1095		1551
1096	Another thing you have to watch out for is that it is quite easy to	1552	Another thing you have to watch out for is that it is quite easy to
1097	receive "spurious" readiness notifications, that is your callback might	1553	receive "spurious" readiness notifications, that is your callback might
1098	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1554	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1099	because there is no data. Not only are some backends known to create a	1555	because there is no data. Not only are some backends known to create a
1100	lot of those (for example Solaris ports), it is very easy to get into	1556	lot of those (for example Solaris ports), it is very easy to get into
1101	this situation even with a relatively standard program structure. Thus	1557	this situation even with a relatively standard program structure. Thus
1102	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1558	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1103	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1559	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1104		1560
1105	If you cannot run the fd in non-blocking mode (for example you should not	1561	If you cannot run the fd in non-blocking mode (for example you should
1106	play around with an Xlib connection), then you have to separately re-test	1562	not play around with an Xlib connection), then you have to separately
1107	whether a file descriptor is really ready with a known-to-be good interface	1563	re-test whether a file descriptor is really ready with a known-to-be good
1108	such as poll (fortunately in our Xlib example, Xlib already does this on	1564	interface such as poll (fortunately in our Xlib example, Xlib already
1109	its own, so its quite safe to use).	1565	does this on its own, so its quite safe to use). Some people additionally
		1566	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1567	indefinitely.
		1568
		1569	But really, best use non-blocking mode.
1110		1570
1111	=head3 The special problem of disappearing file descriptors	1571	=head3 The special problem of disappearing file descriptors
1112		1572
1113	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1573	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1114	descriptor (either by calling C<close> explicitly or by any other means,	1574	descriptor (either due to calling C<close> explicitly or any other means,
1115	such as C<dup>). The reason is that you register interest in some file	1575	such as C<dup2>). The reason is that you register interest in some file
1116	descriptor, but when it goes away, the operating system will silently drop	1576	descriptor, but when it goes away, the operating system will silently drop
1117	this interest. If another file descriptor with the same number then is	1577	this interest. If another file descriptor with the same number then is
1118	registered with libev, there is no efficient way to see that this is, in	1578	registered with libev, there is no efficient way to see that this is, in
1119	fact, a different file descriptor.	1579	fact, a different file descriptor.
1120		1580
…		…
1151	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1611	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1152	C<EVBACKEND_POLL>.	1612	C<EVBACKEND_POLL>.
1153		1613
1154	=head3 The special problem of SIGPIPE	1614	=head3 The special problem of SIGPIPE
1155		1615
1156	While not really specific to libev, it is easy to forget about SIGPIPE:	1616	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1157	when writing to a pipe whose other end has been closed, your program gets	1617	when writing to a pipe whose other end has been closed, your program gets
1158	send a SIGPIPE, which, by default, aborts your program. For most programs	1618	sent a SIGPIPE, which, by default, aborts your program. For most programs
1159	this is sensible behaviour, for daemons, this is usually undesirable.	1619	this is sensible behaviour, for daemons, this is usually undesirable.
1160		1620
1161	So when you encounter spurious, unexplained daemon exits, make sure you	1621	So when you encounter spurious, unexplained daemon exits, make sure you
1162	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1622	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1163	somewhere, as that would have given you a big clue).	1623	somewhere, as that would have given you a big clue).
1164		1624
		1625	=head3 The special problem of accept()ing when you can't
		1626
		1627	Many implementations of the POSIX C<accept> function (for example,
		1628	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1629	connection from the pending queue in all error cases.
		1630
		1631	For example, larger servers often run out of file descriptors (because
		1632	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1633	rejecting the connection, leading to libev signalling readiness on
		1634	the next iteration again (the connection still exists after all), and
		1635	typically causing the program to loop at 100% CPU usage.
		1636
		1637	Unfortunately, the set of errors that cause this issue differs between
		1638	operating systems, there is usually little the app can do to remedy the
		1639	situation, and no known thread-safe method of removing the connection to
		1640	cope with overload is known (to me).
		1641
		1642	One of the easiest ways to handle this situation is to just ignore it
		1643	- when the program encounters an overload, it will just loop until the
		1644	situation is over. While this is a form of busy waiting, no OS offers an
		1645	event-based way to handle this situation, so it's the best one can do.
		1646
		1647	A better way to handle the situation is to log any errors other than
		1648	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1649	messages, and continue as usual, which at least gives the user an idea of
		1650	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1651	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1652	usage.
		1653
		1654	If your program is single-threaded, then you could also keep a dummy file
		1655	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1656	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1657	close that fd, and create a new dummy fd. This will gracefully refuse
		1658	clients under typical overload conditions.
		1659
		1660	The last way to handle it is to simply log the error and C<exit>, as
		1661	is often done with C<malloc> failures, but this results in an easy
		1662	opportunity for a DoS attack.
1165		1663
1166	=head3 Watcher-Specific Functions	1664	=head3 Watcher-Specific Functions
1167		1665
1168	=over 4	1666	=over 4
1169		1667
1170	=item ev_io_init (ev_io *, callback, int fd, int events)	1668	=item ev_io_init (ev_io *, callback, int fd, int events)
1171		1669
1172	=item ev_io_set (ev_io *, int fd, int events)	1670	=item ev_io_set (ev_io *, int fd, int events)
1173		1671
1174	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1672	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1175	receive events for and events is either C<EV_READ>, C<EV_WRITE> or	1673	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1176	C<EV_READ | EV_WRITE> to receive the given events.	1674	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1177		1675
1178	=item int fd [read-only]	1676	=item int fd [read-only]
1179		1677
1180	The file descriptor being watched.	1678	The file descriptor being watched.
1181		1679
…		…
1190	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1688	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1191	readable, but only once. Since it is likely line-buffered, you could	1689	readable, but only once. Since it is likely line-buffered, you could
1192	attempt to read a whole line in the callback.	1690	attempt to read a whole line in the callback.
1193		1691
1194	static void	1692	static void
1195	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1693	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1196	{	1694	{
1197	ev_io_stop (loop, w);	1695	ev_io_stop (loop, w);
1198	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1696	.. read from stdin here (or from w->fd) and handle any I/O errors
1199	}	1697	}
1200		1698
1201	...	1699	...
1202	struct ev_loop *loop = ev_default_init (0);	1700	struct ev_loop *loop = ev_default_init (0);
1203	struct ev_io stdin_readable;	1701	ev_io stdin_readable;
1204	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1702	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1205	ev_io_start (loop, &stdin_readable);	1703	ev_io_start (loop, &stdin_readable);
1206	ev_loop (loop, 0);	1704	ev_run (loop, 0);
1207		1705
1208		1706
1209	=head2 C<ev_timer> - relative and optionally repeating timeouts	1707	=head2 C<ev_timer> - relative and optionally repeating timeouts
1210		1708
1211	Timer watchers are simple relative timers that generate an event after a	1709	Timer watchers are simple relative timers that generate an event after a
1212	given time, and optionally repeating in regular intervals after that.	1710	given time, and optionally repeating in regular intervals after that.
1213		1711
1214	The timers are based on real time, that is, if you register an event that	1712	The timers are based on real time, that is, if you register an event that
1215	times out after an hour and you reset your system clock to January last	1713	times out after an hour and you reset your system clock to January last
1216	year, it will still time out after (roughly) and hour. "Roughly" because	1714	year, it will still time out after (roughly) one hour. "Roughly" because
1217	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1715	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1218	monotonic clock option helps a lot here).	1716	monotonic clock option helps a lot here).
1219		1717
1220	The callback is guaranteed to be invoked only after its timeout has passed,	1718	The callback is guaranteed to be invoked only I<after> its timeout has
1221	but if multiple timers become ready during the same loop iteration then	1719	passed (not I<at>, so on systems with very low-resolution clocks this
1222	order of execution is undefined.	1720	might introduce a small delay). If multiple timers become ready during the
		1721	same loop iteration then the ones with earlier time-out values are invoked
		1722	before ones of the same priority with later time-out values (but this is
		1723	no longer true when a callback calls C<ev_run> recursively).
		1724
		1725	=head3 Be smart about timeouts
		1726
		1727	Many real-world problems involve some kind of timeout, usually for error
		1728	recovery. A typical example is an HTTP request - if the other side hangs,
		1729	you want to raise some error after a while.
		1730
		1731	What follows are some ways to handle this problem, from obvious and
		1732	inefficient to smart and efficient.
		1733
		1734	In the following, a 60 second activity timeout is assumed - a timeout that
		1735	gets reset to 60 seconds each time there is activity (e.g. each time some
		1736	data or other life sign was received).
		1737
		1738	=over 4
		1739
		1740	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1741
		1742	This is the most obvious, but not the most simple way: In the beginning,
		1743	start the watcher:
		1744
		1745	ev_timer_init (timer, callback, 60., 0.);
		1746	ev_timer_start (loop, timer);
		1747
		1748	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1749	and start it again:
		1750
		1751	ev_timer_stop (loop, timer);
		1752	ev_timer_set (timer, 60., 0.);
		1753	ev_timer_start (loop, timer);
		1754
		1755	This is relatively simple to implement, but means that each time there is
		1756	some activity, libev will first have to remove the timer from its internal
		1757	data structure and then add it again. Libev tries to be fast, but it's
		1758	still not a constant-time operation.
		1759
		1760	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1761
		1762	This is the easiest way, and involves using C<ev_timer_again> instead of
		1763	C<ev_timer_start>.
		1764
		1765	To implement this, configure an C<ev_timer> with a C<repeat> value
		1766	of C<60> and then call C<ev_timer_again> at start and each time you
		1767	successfully read or write some data. If you go into an idle state where
		1768	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1769	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1770
		1771	That means you can ignore both the C<ev_timer_start> function and the
		1772	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1773	member and C<ev_timer_again>.
		1774
		1775	At start:
		1776
		1777	ev_init (timer, callback);
		1778	timer->repeat = 60.;
		1779	ev_timer_again (loop, timer);
		1780
		1781	Each time there is some activity:
		1782
		1783	ev_timer_again (loop, timer);
		1784
		1785	It is even possible to change the time-out on the fly, regardless of
		1786	whether the watcher is active or not:
		1787
		1788	timer->repeat = 30.;
		1789	ev_timer_again (loop, timer);
		1790
		1791	This is slightly more efficient then stopping/starting the timer each time
		1792	you want to modify its timeout value, as libev does not have to completely
		1793	remove and re-insert the timer from/into its internal data structure.
		1794
		1795	It is, however, even simpler than the "obvious" way to do it.
		1796
		1797	=item 3. Let the timer time out, but then re-arm it as required.
		1798
		1799	This method is more tricky, but usually most efficient: Most timeouts are
		1800	relatively long compared to the intervals between other activity - in
		1801	our example, within 60 seconds, there are usually many I/O events with
		1802	associated activity resets.
		1803
		1804	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1805	but remember the time of last activity, and check for a real timeout only
		1806	within the callback:
		1807
		1808	ev_tstamp last_activity; // time of last activity
		1809
		1810	static void
		1811	callback (EV_P_ ev_timer *w, int revents)
		1812	{
		1813	ev_tstamp now = ev_now (EV_A);
		1814	ev_tstamp timeout = last_activity + 60.;
		1815
		1816	// if last_activity + 60. is older than now, we did time out
		1817	if (timeout < now)
		1818	{
		1819	// timeout occurred, take action
		1820	}
		1821	else
		1822	{
		1823	// callback was invoked, but there was some activity, re-arm
		1824	// the watcher to fire in last_activity + 60, which is
		1825	// guaranteed to be in the future, so "again" is positive:
		1826	w->repeat = timeout - now;
		1827	ev_timer_again (EV_A_ w);
		1828	}
		1829	}
		1830
		1831	To summarise the callback: first calculate the real timeout (defined
		1832	as "60 seconds after the last activity"), then check if that time has
		1833	been reached, which means something I<did>, in fact, time out. Otherwise
		1834	the callback was invoked too early (C<timeout> is in the future), so
		1835	re-schedule the timer to fire at that future time, to see if maybe we have
		1836	a timeout then.
		1837
		1838	Note how C<ev_timer_again> is used, taking advantage of the
		1839	C<ev_timer_again> optimisation when the timer is already running.
		1840
		1841	This scheme causes more callback invocations (about one every 60 seconds
		1842	minus half the average time between activity), but virtually no calls to
		1843	libev to change the timeout.
		1844
		1845	To start the timer, simply initialise the watcher and set C<last_activity>
		1846	to the current time (meaning we just have some activity :), then call the
		1847	callback, which will "do the right thing" and start the timer:
		1848
		1849	ev_init (timer, callback);
		1850	last_activity = ev_now (loop);
		1851	callback (loop, timer, EV_TIMER);
		1852
		1853	And when there is some activity, simply store the current time in
		1854	C<last_activity>, no libev calls at all:
		1855
		1856	last_activity = ev_now (loop);
		1857
		1858	This technique is slightly more complex, but in most cases where the
		1859	time-out is unlikely to be triggered, much more efficient.
		1860
		1861	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1862	callback :) - just change the timeout and invoke the callback, which will
		1863	fix things for you.
		1864
		1865	=item 4. Wee, just use a double-linked list for your timeouts.
		1866
		1867	If there is not one request, but many thousands (millions...), all
		1868	employing some kind of timeout with the same timeout value, then one can
		1869	do even better:
		1870
		1871	When starting the timeout, calculate the timeout value and put the timeout
		1872	at the I<end> of the list.
		1873
		1874	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1875	the list is expected to fire (for example, using the technique #3).
		1876
		1877	When there is some activity, remove the timer from the list, recalculate
		1878	the timeout, append it to the end of the list again, and make sure to
		1879	update the C<ev_timer> if it was taken from the beginning of the list.
		1880
		1881	This way, one can manage an unlimited number of timeouts in O(1) time for
		1882	starting, stopping and updating the timers, at the expense of a major
		1883	complication, and having to use a constant timeout. The constant timeout
		1884	ensures that the list stays sorted.
		1885
		1886	=back
		1887
		1888	So which method the best?
		1889
		1890	Method #2 is a simple no-brain-required solution that is adequate in most
		1891	situations. Method #3 requires a bit more thinking, but handles many cases
		1892	better, and isn't very complicated either. In most case, choosing either
		1893	one is fine, with #3 being better in typical situations.
		1894
		1895	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1896	rather complicated, but extremely efficient, something that really pays
		1897	off after the first million or so of active timers, i.e. it's usually
		1898	overkill :)
1223		1899
1224	=head3 The special problem of time updates	1900	=head3 The special problem of time updates
1225		1901
1226	Establishing the current time is a costly operation (it usually takes at	1902	Establishing the current time is a costly operation (it usually takes at
1227	least two system calls): EV therefore updates its idea of the current	1903	least two system calls): EV therefore updates its idea of the current
1228	time only before and after C<ev_loop> polls for new events, which causes	1904	time only before and after C<ev_run> collects new events, which causes a
1229	a growing difference between C<ev_now ()> and C<ev_time ()> when handling	1905	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1230	lots of events.	1906	lots of events in one iteration.
1231		1907
1232	The relative timeouts are calculated relative to the C<ev_now ()>	1908	The relative timeouts are calculated relative to the C<ev_now ()>
1233	time. This is usually the right thing as this timestamp refers to the time	1909	time. This is usually the right thing as this timestamp refers to the time
1234	of the event triggering whatever timeout you are modifying/starting. If	1910	of the event triggering whatever timeout you are modifying/starting. If
1235	you suspect event processing to be delayed and you I<need> to base the	1911	you suspect event processing to be delayed and you I<need> to base the
…		…
1239		1915
1240	If the event loop is suspended for a long time, you can also force an	1916	If the event loop is suspended for a long time, you can also force an
1241	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1917	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1242	()>.	1918	()>.
1243		1919
		1920	=head3 The special problems of suspended animation
		1921
		1922	When you leave the server world it is quite customary to hit machines that
		1923	can suspend/hibernate - what happens to the clocks during such a suspend?
		1924
		1925	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1926	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1927	to run until the system is suspended, but they will not advance while the
		1928	system is suspended. That means, on resume, it will be as if the program
		1929	was frozen for a few seconds, but the suspend time will not be counted
		1930	towards C<ev_timer> when a monotonic clock source is used. The real time
		1931	clock advanced as expected, but if it is used as sole clocksource, then a
		1932	long suspend would be detected as a time jump by libev, and timers would
		1933	be adjusted accordingly.
		1934
		1935	I would not be surprised to see different behaviour in different between
		1936	operating systems, OS versions or even different hardware.
		1937
		1938	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1939	time jump in the monotonic clocks and the realtime clock. If the program
		1940	is suspended for a very long time, and monotonic clock sources are in use,
		1941	then you can expect C<ev_timer>s to expire as the full suspension time
		1942	will be counted towards the timers. When no monotonic clock source is in
		1943	use, then libev will again assume a timejump and adjust accordingly.
		1944
		1945	It might be beneficial for this latter case to call C<ev_suspend>
		1946	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1947	deterministic behaviour in this case (you can do nothing against
		1948	C<SIGSTOP>).
		1949
1244	=head3 Watcher-Specific Functions and Data Members	1950	=head3 Watcher-Specific Functions and Data Members
1245		1951
1246	=over 4	1952	=over 4
1247		1953
1248	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1954	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1271	If the timer is started but non-repeating, stop it (as if it timed out).	1977	If the timer is started but non-repeating, stop it (as if it timed out).
1272		1978
1273	If the timer is repeating, either start it if necessary (with the	1979	If the timer is repeating, either start it if necessary (with the
1274	C<repeat> value), or reset the running timer to the C<repeat> value.	1980	C<repeat> value), or reset the running timer to the C<repeat> value.
1275		1981
1276	This sounds a bit complicated, but here is a useful and typical	1982	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1277	example: Imagine you have a TCP connection and you want a so-called idle	1983	usage example.
1278	timeout, that is, you want to be called when there have been, say, 60
1279	seconds of inactivity on the socket. The easiest way to do this is to
1280	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1281	C<ev_timer_again> each time you successfully read or write some data. If
1282	you go into an idle state where you do not expect data to travel on the
1283	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1284	automatically restart it if need be.
1285		1984
1286	That means you can ignore the C<after> value and C<ev_timer_start>	1985	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1287	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1288		1986
1289	ev_timer_init (timer, callback, 0., 5.);	1987	Returns the remaining time until a timer fires. If the timer is active,
1290	ev_timer_again (loop, timer);	1988	then this time is relative to the current event loop time, otherwise it's
1291	...	1989	the timeout value currently configured.
1292	timer->again = 17.;
1293	ev_timer_again (loop, timer);
1294	...
1295	timer->again = 10.;
1296	ev_timer_again (loop, timer);
1297		1990
1298	This is more slightly efficient then stopping/starting the timer each time	1991	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1299	you want to modify its timeout value.	1992	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		1993	will return C<4>. When the timer expires and is restarted, it will return
		1994	roughly C<7> (likely slightly less as callback invocation takes some time,
		1995	too), and so on.
1300		1996
1301	=item ev_tstamp repeat [read-write]	1997	=item ev_tstamp repeat [read-write]
1302		1998
1303	The current C<repeat> value. Will be used each time the watcher times out	1999	The current C<repeat> value. Will be used each time the watcher times out
1304	or C<ev_timer_again> is called and determines the next timeout (if any),	2000	or C<ev_timer_again> is called, and determines the next timeout (if any),
1305	which is also when any modifications are taken into account.	2001	which is also when any modifications are taken into account.
1306		2002
1307	=back	2003	=back
1308		2004
1309	=head3 Examples	2005	=head3 Examples
1310		2006
1311	Example: Create a timer that fires after 60 seconds.	2007	Example: Create a timer that fires after 60 seconds.
1312		2008
1313	static void	2009	static void
1314	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2010	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1315	{	2011	{
1316	.. one minute over, w is actually stopped right here	2012	.. one minute over, w is actually stopped right here
1317	}	2013	}
1318		2014
1319	struct ev_timer mytimer;	2015	ev_timer mytimer;
1320	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	2016	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1321	ev_timer_start (loop, &mytimer);	2017	ev_timer_start (loop, &mytimer);
1322		2018
1323	Example: Create a timeout timer that times out after 10 seconds of	2019	Example: Create a timeout timer that times out after 10 seconds of
1324	inactivity.	2020	inactivity.
1325		2021
1326	static void	2022	static void
1327	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2023	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1328	{	2024	{
1329	.. ten seconds without any activity	2025	.. ten seconds without any activity
1330	}	2026	}
1331		2027
1332	struct ev_timer mytimer;	2028	ev_timer mytimer;
1333	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2029	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1334	ev_timer_again (&mytimer); /* start timer */	2030	ev_timer_again (&mytimer); /* start timer */
1335	ev_loop (loop, 0);	2031	ev_run (loop, 0);
1336		2032
1337	// and in some piece of code that gets executed on any "activity":	2033	// and in some piece of code that gets executed on any "activity":
1338	// reset the timeout to start ticking again at 10 seconds	2034	// reset the timeout to start ticking again at 10 seconds
1339	ev_timer_again (&mytimer);	2035	ev_timer_again (&mytimer);
1340		2036
…		…
1342	=head2 C<ev_periodic> - to cron or not to cron?	2038	=head2 C<ev_periodic> - to cron or not to cron?
1343		2039
1344	Periodic watchers are also timers of a kind, but they are very versatile	2040	Periodic watchers are also timers of a kind, but they are very versatile
1345	(and unfortunately a bit complex).	2041	(and unfortunately a bit complex).
1346		2042
1347	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2043	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1348	but on wall clock time (absolute time). You can tell a periodic watcher	2044	relative time, the physical time that passes) but on wall clock time
1349	to trigger after some specific point in time. For example, if you tell a	2045	(absolute time, the thing you can read on your calender or clock). The
1350	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	2046	difference is that wall clock time can run faster or slower than real
1351	+ 10.>, that is, an absolute time not a delay) and then reset your system	2047	time, and time jumps are not uncommon (e.g. when you adjust your
1352	clock to January of the previous year, then it will take more than year	2048	wrist-watch).
1353	to trigger the event (unlike an C<ev_timer>, which would still trigger
1354	roughly 10 seconds later as it uses a relative timeout).
1355		2049
		2050	You can tell a periodic watcher to trigger after some specific point
		2051	in time: for example, if you tell a periodic watcher to trigger "in 10
		2052	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2053	not a delay) and then reset your system clock to January of the previous
		2054	year, then it will take a year or more to trigger the event (unlike an
		2055	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2056	it, as it uses a relative timeout).
		2057
1356	C<ev_periodic>s can also be used to implement vastly more complex timers,	2058	C<ev_periodic> watchers can also be used to implement vastly more complex
1357	such as triggering an event on each "midnight, local time", or other	2059	timers, such as triggering an event on each "midnight, local time", or
1358	complicated, rules.	2060	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2061	those cannot react to time jumps.
1359		2062
1360	As with timers, the callback is guaranteed to be invoked only when the	2063	As with timers, the callback is guaranteed to be invoked only when the
1361	time (C<at>) has passed, but if multiple periodic timers become ready	2064	point in time where it is supposed to trigger has passed. If multiple
1362	during the same loop iteration then order of execution is undefined.	2065	timers become ready during the same loop iteration then the ones with
		2066	earlier time-out values are invoked before ones with later time-out values
		2067	(but this is no longer true when a callback calls C<ev_run> recursively).
1363		2068
1364	=head3 Watcher-Specific Functions and Data Members	2069	=head3 Watcher-Specific Functions and Data Members
1365		2070
1366	=over 4	2071	=over 4
1367		2072
1368	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2073	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1369		2074
1370	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2075	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1371		2076
1372	Lots of arguments, lets sort it out... There are basically three modes of	2077	Lots of arguments, let's sort it out... There are basically three modes of
1373	operation, and we will explain them from simplest to complex:	2078	operation, and we will explain them from simplest to most complex:
1374		2079
1375	=over 4	2080	=over 4
1376		2081
1377	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2082	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1378		2083
1379	In this configuration the watcher triggers an event after the wall clock	2084	In this configuration the watcher triggers an event after the wall clock
1380	time C<at> has passed and doesn't repeat. It will not adjust when a time	2085	time C<offset> has passed. It will not repeat and will not adjust when a
1381	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2086	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1382	run when the system time reaches or surpasses this time.	2087	will be stopped and invoked when the system clock reaches or surpasses
		2088	this point in time.
1383		2089
1384	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2090	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1385		2091
1386	In this mode the watcher will always be scheduled to time out at the next	2092	In this mode the watcher will always be scheduled to time out at the next
1387	C<at + N * interval> time (for some integer N, which can also be negative)	2093	C<offset + N * interval> time (for some integer N, which can also be
1388	and then repeat, regardless of any time jumps.	2094	negative) and then repeat, regardless of any time jumps. The C<offset>
		2095	argument is merely an offset into the C<interval> periods.
1389		2096
1390	This can be used to create timers that do not drift with respect to system	2097	This can be used to create timers that do not drift with respect to the
1391	time, for example, here is a C<ev_periodic> that triggers each hour, on	2098	system clock, for example, here is an C<ev_periodic> that triggers each
1392	the hour:	2099	hour, on the hour (with respect to UTC):
1393		2100
1394	ev_periodic_set (&periodic, 0., 3600., 0);	2101	ev_periodic_set (&periodic, 0., 3600., 0);
1395		2102
1396	This doesn't mean there will always be 3600 seconds in between triggers,	2103	This doesn't mean there will always be 3600 seconds in between triggers,
1397	but only that the callback will be called when the system time shows a	2104	but only that the callback will be called when the system time shows a
1398	full hour (UTC), or more correctly, when the system time is evenly divisible	2105	full hour (UTC), or more correctly, when the system time is evenly divisible
1399	by 3600.	2106	by 3600.
1400		2107
1401	Another way to think about it (for the mathematically inclined) is that	2108	Another way to think about it (for the mathematically inclined) is that
1402	C<ev_periodic> will try to run the callback in this mode at the next possible	2109	C<ev_periodic> will try to run the callback in this mode at the next possible
1403	time where C<time = at (mod interval)>, regardless of any time jumps.	2110	time where C<time = offset (mod interval)>, regardless of any time jumps.
1404		2111
1405	For numerical stability it is preferable that the C<at> value is near	2112	For numerical stability it is preferable that the C<offset> value is near
1406	C<ev_now ()> (the current time), but there is no range requirement for	2113	C<ev_now ()> (the current time), but there is no range requirement for
1407	this value, and in fact is often specified as zero.	2114	this value, and in fact is often specified as zero.
1408		2115
1409	Note also that there is an upper limit to how often a timer can fire (CPU	2116	Note also that there is an upper limit to how often a timer can fire (CPU
1410	speed for example), so if C<interval> is very small then timing stability	2117	speed for example), so if C<interval> is very small then timing stability
1411	will of course deteriorate. Libev itself tries to be exact to be about one	2118	will of course deteriorate. Libev itself tries to be exact to be about one
1412	millisecond (if the OS supports it and the machine is fast enough).	2119	millisecond (if the OS supports it and the machine is fast enough).
1413		2120
1414	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2121	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1415		2122
1416	In this mode the values for C<interval> and C<at> are both being	2123	In this mode the values for C<interval> and C<offset> are both being
1417	ignored. Instead, each time the periodic watcher gets scheduled, the	2124	ignored. Instead, each time the periodic watcher gets scheduled, the
1418	reschedule callback will be called with the watcher as first, and the	2125	reschedule callback will be called with the watcher as first, and the
1419	current time as second argument.	2126	current time as second argument.
1420		2127
1421	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2128	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1422	ever, or make ANY event loop modifications whatsoever>.	2129	or make ANY other event loop modifications whatsoever, unless explicitly
		2130	allowed by documentation here>.
1423		2131
1424	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2132	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1425	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2133	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1426	only event loop modification you are allowed to do).	2134	only event loop modification you are allowed to do).
1427		2135
1428	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	2136	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1429	*w, ev_tstamp now)>, e.g.:	2137	*w, ev_tstamp now)>, e.g.:
1430		2138
		2139	static ev_tstamp
1431	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	2140	my_rescheduler (ev_periodic *w, ev_tstamp now)
1432	{	2141	{
1433	return now + 60.;	2142	return now + 60.;
1434	}	2143	}
1435		2144
1436	It must return the next time to trigger, based on the passed time value	2145	It must return the next time to trigger, based on the passed time value
…		…
1456	a different time than the last time it was called (e.g. in a crond like	2165	a different time than the last time it was called (e.g. in a crond like
1457	program when the crontabs have changed).	2166	program when the crontabs have changed).
1458		2167
1459	=item ev_tstamp ev_periodic_at (ev_periodic *)	2168	=item ev_tstamp ev_periodic_at (ev_periodic *)
1460		2169
1461	When active, returns the absolute time that the watcher is supposed to	2170	When active, returns the absolute time that the watcher is supposed
1462	trigger next.	2171	to trigger next. This is not the same as the C<offset> argument to
		2172	C<ev_periodic_set>, but indeed works even in interval and manual
		2173	rescheduling modes.
1463		2174
1464	=item ev_tstamp offset [read-write]	2175	=item ev_tstamp offset [read-write]
1465		2176
1466	When repeating, this contains the offset value, otherwise this is the	2177	When repeating, this contains the offset value, otherwise this is the
1467	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2178	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2179	although libev might modify this value for better numerical stability).
1468		2180
1469	Can be modified any time, but changes only take effect when the periodic	2181	Can be modified any time, but changes only take effect when the periodic
1470	timer fires or C<ev_periodic_again> is being called.	2182	timer fires or C<ev_periodic_again> is being called.
1471		2183
1472	=item ev_tstamp interval [read-write]	2184	=item ev_tstamp interval [read-write]
1473		2185
1474	The current interval value. Can be modified any time, but changes only	2186	The current interval value. Can be modified any time, but changes only
1475	take effect when the periodic timer fires or C<ev_periodic_again> is being	2187	take effect when the periodic timer fires or C<ev_periodic_again> is being
1476	called.	2188	called.
1477		2189
1478	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2190	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1479		2191
1480	The current reschedule callback, or C<0>, if this functionality is	2192	The current reschedule callback, or C<0>, if this functionality is
1481	switched off. Can be changed any time, but changes only take effect when	2193	switched off. Can be changed any time, but changes only take effect when
1482	the periodic timer fires or C<ev_periodic_again> is being called.	2194	the periodic timer fires or C<ev_periodic_again> is being called.
1483		2195
1484	=back	2196	=back
1485		2197
1486	=head3 Examples	2198	=head3 Examples
1487		2199
1488	Example: Call a callback every hour, or, more precisely, whenever the	2200	Example: Call a callback every hour, or, more precisely, whenever the
1489	system clock is divisible by 3600. The callback invocation times have	2201	system time is divisible by 3600. The callback invocation times have
1490	potentially a lot of jitter, but good long-term stability.	2202	potentially a lot of jitter, but good long-term stability.
1491		2203
1492	static void	2204	static void
1493	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2205	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1494	{	2206	{
1495	... its now a full hour (UTC, or TAI or whatever your clock follows)	2207	... its now a full hour (UTC, or TAI or whatever your clock follows)
1496	}	2208	}
1497		2209
1498	struct ev_periodic hourly_tick;	2210	ev_periodic hourly_tick;
1499	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2211	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1500	ev_periodic_start (loop, &hourly_tick);	2212	ev_periodic_start (loop, &hourly_tick);
1501		2213
1502	Example: The same as above, but use a reschedule callback to do it:	2214	Example: The same as above, but use a reschedule callback to do it:
1503		2215
1504	#include <math.h>	2216	#include <math.h>
1505		2217
1506	static ev_tstamp	2218	static ev_tstamp
1507	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2219	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1508	{	2220	{
1509	return fmod (now, 3600.) + 3600.;	2221	return now + (3600. - fmod (now, 3600.));
1510	}	2222	}
1511		2223
1512	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2224	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1513		2225
1514	Example: Call a callback every hour, starting now:	2226	Example: Call a callback every hour, starting now:
1515		2227
1516	struct ev_periodic hourly_tick;	2228	ev_periodic hourly_tick;
1517	ev_periodic_init (&hourly_tick, clock_cb,	2229	ev_periodic_init (&hourly_tick, clock_cb,
1518	fmod (ev_now (loop), 3600.), 3600., 0);	2230	fmod (ev_now (loop), 3600.), 3600., 0);
1519	ev_periodic_start (loop, &hourly_tick);	2231	ev_periodic_start (loop, &hourly_tick);
1520		2232
1521		2233
…		…
1524	Signal watchers will trigger an event when the process receives a specific	2236	Signal watchers will trigger an event when the process receives a specific
1525	signal one or more times. Even though signals are very asynchronous, libev	2237	signal one or more times. Even though signals are very asynchronous, libev
1526	will try it's best to deliver signals synchronously, i.e. as part of the	2238	will try it's best to deliver signals synchronously, i.e. as part of the
1527	normal event processing, like any other event.	2239	normal event processing, like any other event.
1528		2240
		2241	If you want signals to be delivered truly asynchronously, just use
		2242	C<sigaction> as you would do without libev and forget about sharing
		2243	the signal. You can even use C<ev_async> from a signal handler to
		2244	synchronously wake up an event loop.
		2245
1529	You can configure as many watchers as you like per signal. Only when the	2246	You can configure as many watchers as you like for the same signal, but
		2247	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2248	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2249	C<SIGINT> in both the default loop and another loop at the same time. At
		2250	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2251
1530	first watcher gets started will libev actually register a signal watcher	2252	When the first watcher gets started will libev actually register something
1531	with the kernel (thus it coexists with your own signal handlers as long	2253	with the kernel (thus it coexists with your own signal handlers as long as
1532	as you don't register any with libev). Similarly, when the last signal	2254	you don't register any with libev for the same signal).
1533	watcher for a signal is stopped libev will reset the signal handler to
1534	SIG_DFL (regardless of what it was set to before).
1535		2255
1536	If possible and supported, libev will install its handlers with	2256	If possible and supported, libev will install its handlers with
1537	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2257	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1538	interrupted. If you have a problem with system calls getting interrupted by	2258	not be unduly interrupted. If you have a problem with system calls getting
1539	signals you can block all signals in an C<ev_check> watcher and unblock	2259	interrupted by signals you can block all signals in an C<ev_check> watcher
1540	them in an C<ev_prepare> watcher.	2260	and unblock them in an C<ev_prepare> watcher.
		2261
		2262	=head3 The special problem of inheritance over fork/execve/pthread_create
		2263
		2264	Both the signal mask (C<sigprocmask>) and the signal disposition
		2265	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2266	stopping it again), that is, libev might or might not block the signal,
		2267	and might or might not set or restore the installed signal handler.
		2268
		2269	While this does not matter for the signal disposition (libev never
		2270	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2271	C<execve>), this matters for the signal mask: many programs do not expect
		2272	certain signals to be blocked.
		2273
		2274	This means that before calling C<exec> (from the child) you should reset
		2275	the signal mask to whatever "default" you expect (all clear is a good
		2276	choice usually).
		2277
		2278	The simplest way to ensure that the signal mask is reset in the child is
		2279	to install a fork handler with C<pthread_atfork> that resets it. That will
		2280	catch fork calls done by libraries (such as the libc) as well.
		2281
		2282	In current versions of libev, the signal will not be blocked indefinitely
		2283	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2284	the window of opportunity for problems, it will not go away, as libev
		2285	I<has> to modify the signal mask, at least temporarily.
		2286
		2287	So I can't stress this enough: I<If you do not reset your signal mask when
		2288	you expect it to be empty, you have a race condition in your code>. This
		2289	is not a libev-specific thing, this is true for most event libraries.
1541		2290
1542	=head3 Watcher-Specific Functions and Data Members	2291	=head3 Watcher-Specific Functions and Data Members
1543		2292
1544	=over 4	2293	=over 4
1545		2294
…		…
1556		2305
1557	=back	2306	=back
1558		2307
1559	=head3 Examples	2308	=head3 Examples
1560		2309
1561	Example: Try to exit cleanly on SIGINT and SIGTERM.	2310	Example: Try to exit cleanly on SIGINT.
1562		2311
1563	static void	2312	static void
1564	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2313	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1565	{	2314	{
1566	ev_unloop (loop, EVUNLOOP_ALL);	2315	ev_break (loop, EVBREAK_ALL);
1567	}	2316	}
1568		2317
1569	struct ev_signal signal_watcher;	2318	ev_signal signal_watcher;
1570	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2319	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1571	ev_signal_start (loop, &sigint_cb);	2320	ev_signal_start (loop, &signal_watcher);
1572		2321
1573		2322
1574	=head2 C<ev_child> - watch out for process status changes	2323	=head2 C<ev_child> - watch out for process status changes
1575		2324
1576	Child watchers trigger when your process receives a SIGCHLD in response to	2325	Child watchers trigger when your process receives a SIGCHLD in response to
1577	some child status changes (most typically when a child of yours dies). It	2326	some child status changes (most typically when a child of yours dies or
1578	is permissible to install a child watcher I<after> the child has been	2327	exits). It is permissible to install a child watcher I<after> the child
1579	forked (which implies it might have already exited), as long as the event	2328	has been forked (which implies it might have already exited), as long
1580	loop isn't entered (or is continued from a watcher).	2329	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2330	forking and then immediately registering a watcher for the child is fine,
		2331	but forking and registering a watcher a few event loop iterations later or
		2332	in the next callback invocation is not.
1581		2333
1582	Only the default event loop is capable of handling signals, and therefore	2334	Only the default event loop is capable of handling signals, and therefore
1583	you can only register child watchers in the default event loop.	2335	you can only register child watchers in the default event loop.
1584		2336
		2337	Due to some design glitches inside libev, child watchers will always be
		2338	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2339	libev)
		2340
1585	=head3 Process Interaction	2341	=head3 Process Interaction
1586		2342
1587	Libev grabs C<SIGCHLD> as soon as the default event loop is	2343	Libev grabs C<SIGCHLD> as soon as the default event loop is
1588	initialised. This is necessary to guarantee proper behaviour even if	2344	initialised. This is necessary to guarantee proper behaviour even if the
1589	the first child watcher is started after the child exits. The occurrence	2345	first child watcher is started after the child exits. The occurrence
1590	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2346	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1591	synchronously as part of the event loop processing. Libev always reaps all	2347	synchronously as part of the event loop processing. Libev always reaps all
1592	children, even ones not watched.	2348	children, even ones not watched.
1593		2349
1594	=head3 Overriding the Built-In Processing	2350	=head3 Overriding the Built-In Processing
…		…
1604	=head3 Stopping the Child Watcher	2360	=head3 Stopping the Child Watcher
1605		2361
1606	Currently, the child watcher never gets stopped, even when the	2362	Currently, the child watcher never gets stopped, even when the
1607	child terminates, so normally one needs to stop the watcher in the	2363	child terminates, so normally one needs to stop the watcher in the
1608	callback. Future versions of libev might stop the watcher automatically	2364	callback. Future versions of libev might stop the watcher automatically
1609	when a child exit is detected.	2365	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2366	problem).
1610		2367
1611	=head3 Watcher-Specific Functions and Data Members	2368	=head3 Watcher-Specific Functions and Data Members
1612		2369
1613	=over 4	2370	=over 4
1614		2371
…		…
1646	its completion.	2403	its completion.
1647		2404
1648	ev_child cw;	2405	ev_child cw;
1649		2406
1650	static void	2407	static void
1651	child_cb (EV_P_ struct ev_child *w, int revents)	2408	child_cb (EV_P_ ev_child *w, int revents)
1652	{	2409	{
1653	ev_child_stop (EV_A_ w);	2410	ev_child_stop (EV_A_ w);
1654	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2411	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1655	}	2412	}
1656		2413
…		…
1671		2428
1672		2429
1673	=head2 C<ev_stat> - did the file attributes just change?	2430	=head2 C<ev_stat> - did the file attributes just change?
1674		2431
1675	This watches a file system path for attribute changes. That is, it calls	2432	This watches a file system path for attribute changes. That is, it calls
1676	C<stat> regularly (or when the OS says it changed) and sees if it changed	2433	C<stat> on that path in regular intervals (or when the OS says it changed)
1677	compared to the last time, invoking the callback if it did.	2434	and sees if it changed compared to the last time, invoking the callback if
		2435	it did.
1678		2436
1679	The path does not need to exist: changing from "path exists" to "path does	2437	The path does not need to exist: changing from "path exists" to "path does
1680	not exist" is a status change like any other. The condition "path does	2438	not exist" is a status change like any other. The condition "path does not
1681	not exist" is signified by the C<st_nlink> field being zero (which is	2439	exist" (or more correctly "path cannot be stat'ed") is signified by the
1682	otherwise always forced to be at least one) and all the other fields of	2440	C<st_nlink> field being zero (which is otherwise always forced to be at
1683	the stat buffer having unspecified contents.	2441	least one) and all the other fields of the stat buffer having unspecified
		2442	contents.
1684		2443
1685	The path I<should> be absolute and I<must not> end in a slash. If it is	2444	The path I<must not> end in a slash or contain special components such as
		2445	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1686	relative and your working directory changes, the behaviour is undefined.	2446	your working directory changes, then the behaviour is undefined.
1687		2447
1688	Since there is no standard to do this, the portable implementation simply	2448	Since there is no portable change notification interface available, the
1689	calls C<stat (2)> regularly on the path to see if it changed somehow. You	2449	portable implementation simply calls C<stat(2)> regularly on the path
1690	can specify a recommended polling interval for this case. If you specify	2450	to see if it changed somehow. You can specify a recommended polling
1691	a polling interval of C<0> (highly recommended!) then a I<suitable,	2451	interval for this case. If you specify a polling interval of C<0> (highly
1692	unspecified default> value will be used (which you can expect to be around	2452	recommended!) then a I<suitable, unspecified default> value will be used
1693	five seconds, although this might change dynamically). Libev will also	2453	(which you can expect to be around five seconds, although this might
1694	impose a minimum interval which is currently around C<0.1>, but thats	2454	change dynamically). Libev will also impose a minimum interval which is
1695	usually overkill.	2455	currently around C<0.1>, but that's usually overkill.
1696		2456
1697	This watcher type is not meant for massive numbers of stat watchers,	2457	This watcher type is not meant for massive numbers of stat watchers,
1698	as even with OS-supported change notifications, this can be	2458	as even with OS-supported change notifications, this can be
1699	resource-intensive.	2459	resource-intensive.
1700		2460
1701	At the time of this writing, only the Linux inotify interface is	2461	At the time of this writing, the only OS-specific interface implemented
1702	implemented (implementing kqueue support is left as an exercise for the	2462	is the Linux inotify interface (implementing kqueue support is left as an
1703	reader, note, however, that the author sees no way of implementing ev_stat	2463	exercise for the reader. Note, however, that the author sees no way of
1704	semantics with kqueue). Inotify will be used to give hints only and should	2464	implementing C<ev_stat> semantics with kqueue, except as a hint).
1705	not change the semantics of C<ev_stat> watchers, which means that libev
1706	sometimes needs to fall back to regular polling again even with inotify,
1707	but changes are usually detected immediately, and if the file exists there
1708	will be no polling.
1709		2465
1710	=head3 ABI Issues (Largefile Support)	2466	=head3 ABI Issues (Largefile Support)
1711		2467
1712	Libev by default (unless the user overrides this) uses the default	2468	Libev by default (unless the user overrides this) uses the default
1713	compilation environment, which means that on systems with large file	2469	compilation environment, which means that on systems with large file
1714	support disabled by default, you get the 32 bit version of the stat	2470	support disabled by default, you get the 32 bit version of the stat
1715	structure. When using the library from programs that change the ABI to	2471	structure. When using the library from programs that change the ABI to
1716	use 64 bit file offsets the programs will fail. In that case you have to	2472	use 64 bit file offsets the programs will fail. In that case you have to
1717	compile libev with the same flags to get binary compatibility. This is	2473	compile libev with the same flags to get binary compatibility. This is
1718	obviously the case with any flags that change the ABI, but the problem is	2474	obviously the case with any flags that change the ABI, but the problem is
1719	most noticeably disabled with ev_stat and large file support.	2475	most noticeably displayed with ev_stat and large file support.
1720		2476
1721	The solution for this is to lobby your distribution maker to make large	2477	The solution for this is to lobby your distribution maker to make large
1722	file interfaces available by default (as e.g. FreeBSD does) and not	2478	file interfaces available by default (as e.g. FreeBSD does) and not
1723	optional. Libev cannot simply switch on large file support because it has	2479	optional. Libev cannot simply switch on large file support because it has
1724	to exchange stat structures with application programs compiled using the	2480	to exchange stat structures with application programs compiled using the
1725	default compilation environment.	2481	default compilation environment.
1726		2482
1727	=head3 Inotify	2483	=head3 Inotify and Kqueue
1728		2484
1729	When C<inotify (7)> support has been compiled into libev (generally only	2485	When C<inotify (7)> support has been compiled into libev and present at
1730	available on Linux) and present at runtime, it will be used to speed up	2486	runtime, it will be used to speed up change detection where possible. The
1731	change detection where possible. The inotify descriptor will be created lazily	2487	inotify descriptor will be created lazily when the first C<ev_stat>
1732	when the first C<ev_stat> watcher is being started.	2488	watcher is being started.
1733		2489
1734	Inotify presence does not change the semantics of C<ev_stat> watchers	2490	Inotify presence does not change the semantics of C<ev_stat> watchers
1735	except that changes might be detected earlier, and in some cases, to avoid	2491	except that changes might be detected earlier, and in some cases, to avoid
1736	making regular C<stat> calls. Even in the presence of inotify support	2492	making regular C<stat> calls. Even in the presence of inotify support
1737	there are many cases where libev has to resort to regular C<stat> polling.	2493	there are many cases where libev has to resort to regular C<stat> polling,
		2494	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2495	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2496	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2497	xfs are fully working) libev usually gets away without polling.
1738		2498
1739	(There is no support for kqueue, as apparently it cannot be used to	2499	There is no support for kqueue, as apparently it cannot be used to
1740	implement this functionality, due to the requirement of having a file	2500	implement this functionality, due to the requirement of having a file
1741	descriptor open on the object at all times).	2501	descriptor open on the object at all times, and detecting renames, unlinks
		2502	etc. is difficult.
		2503
		2504	=head3 C<stat ()> is a synchronous operation
		2505
		2506	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2507	the process. The exception are C<ev_stat> watchers - those call C<stat
		2508	()>, which is a synchronous operation.
		2509
		2510	For local paths, this usually doesn't matter: unless the system is very
		2511	busy or the intervals between stat's are large, a stat call will be fast,
		2512	as the path data is usually in memory already (except when starting the
		2513	watcher).
		2514
		2515	For networked file systems, calling C<stat ()> can block an indefinite
		2516	time due to network issues, and even under good conditions, a stat call
		2517	often takes multiple milliseconds.
		2518
		2519	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2520	paths, although this is fully supported by libev.
1742		2521
1743	=head3 The special problem of stat time resolution	2522	=head3 The special problem of stat time resolution
1744		2523
1745	The C<stat ()> system call only supports full-second resolution portably, and	2524	The C<stat ()> system call only supports full-second resolution portably,
1746	even on systems where the resolution is higher, many file systems still	2525	and even on systems where the resolution is higher, most file systems
1747	only support whole seconds.	2526	still only support whole seconds.
1748		2527
1749	That means that, if the time is the only thing that changes, you can	2528	That means that, if the time is the only thing that changes, you can
1750	easily miss updates: on the first update, C<ev_stat> detects a change and	2529	easily miss updates: on the first update, C<ev_stat> detects a change and
1751	calls your callback, which does something. When there is another update	2530	calls your callback, which does something. When there is another update
1752	within the same second, C<ev_stat> will be unable to detect it as the stat	2531	within the same second, C<ev_stat> will be unable to detect unless the
1753	data does not change.	2532	stat data does change in other ways (e.g. file size).
1754		2533
1755	The solution to this is to delay acting on a change for slightly more	2534	The solution to this is to delay acting on a change for slightly more
1756	than a second (or till slightly after the next full second boundary), using	2535	than a second (or till slightly after the next full second boundary), using
1757	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2536	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1758	ev_timer_again (loop, w)>).	2537	ev_timer_again (loop, w)>).
…		…
1778	C<path>. The C<interval> is a hint on how quickly a change is expected to	2557	C<path>. The C<interval> is a hint on how quickly a change is expected to
1779	be detected and should normally be specified as C<0> to let libev choose	2558	be detected and should normally be specified as C<0> to let libev choose
1780	a suitable value. The memory pointed to by C<path> must point to the same	2559	a suitable value. The memory pointed to by C<path> must point to the same
1781	path for as long as the watcher is active.	2560	path for as long as the watcher is active.
1782		2561
1783	The callback will receive C<EV_STAT> when a change was detected, relative	2562	The callback will receive an C<EV_STAT> event when a change was detected,
1784	to the attributes at the time the watcher was started (or the last change	2563	relative to the attributes at the time the watcher was started (or the
1785	was detected).	2564	last change was detected).
1786		2565
1787	=item ev_stat_stat (loop, ev_stat *)	2566	=item ev_stat_stat (loop, ev_stat *)
1788		2567
1789	Updates the stat buffer immediately with new values. If you change the	2568	Updates the stat buffer immediately with new values. If you change the
1790	watched path in your callback, you could call this function to avoid	2569	watched path in your callback, you could call this function to avoid
…		…
1873		2652
1874		2653
1875	=head2 C<ev_idle> - when you've got nothing better to do...	2654	=head2 C<ev_idle> - when you've got nothing better to do...
1876		2655
1877	Idle watchers trigger events when no other events of the same or higher	2656	Idle watchers trigger events when no other events of the same or higher
1878	priority are pending (prepare, check and other idle watchers do not	2657	priority are pending (prepare, check and other idle watchers do not count
1879	count).	2658	as receiving "events").
1880		2659
1881	That is, as long as your process is busy handling sockets or timeouts	2660	That is, as long as your process is busy handling sockets or timeouts
1882	(or even signals, imagine) of the same or higher priority it will not be	2661	(or even signals, imagine) of the same or higher priority it will not be
1883	triggered. But when your process is idle (or only lower-priority watchers	2662	triggered. But when your process is idle (or only lower-priority watchers
1884	are pending), the idle watchers are being called once per event loop	2663	are pending), the idle watchers are being called once per event loop
…		…
1895		2674
1896	=head3 Watcher-Specific Functions and Data Members	2675	=head3 Watcher-Specific Functions and Data Members
1897		2676
1898	=over 4	2677	=over 4
1899		2678
1900	=item ev_idle_init (ev_signal *, callback)	2679	=item ev_idle_init (ev_idle *, callback)
1901		2680
1902	Initialises and configures the idle watcher - it has no parameters of any	2681	Initialises and configures the idle watcher - it has no parameters of any
1903	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2682	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1904	believe me.	2683	believe me.
1905		2684
…		…
1909		2688
1910	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2689	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1911	callback, free it. Also, use no error checking, as usual.	2690	callback, free it. Also, use no error checking, as usual.
1912		2691
1913	static void	2692	static void
1914	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2693	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1915	{	2694	{
1916	free (w);	2695	free (w);
1917	// now do something you wanted to do when the program has	2696	// now do something you wanted to do when the program has
1918	// no longer anything immediate to do.	2697	// no longer anything immediate to do.
1919	}	2698	}
1920		2699
1921	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2700	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1922	ev_idle_init (idle_watcher, idle_cb);	2701	ev_idle_init (idle_watcher, idle_cb);
1923	ev_idle_start (loop, idle_cb);	2702	ev_idle_start (loop, idle_watcher);
1924		2703
1925		2704
1926	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2705	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1927		2706
1928	Prepare and check watchers are usually (but not always) used in tandem:	2707	Prepare and check watchers are usually (but not always) used in pairs:
1929	prepare watchers get invoked before the process blocks and check watchers	2708	prepare watchers get invoked before the process blocks and check watchers
1930	afterwards.	2709	afterwards.
1931		2710
1932	You I<must not> call C<ev_loop> or similar functions that enter	2711	You I<must not> call C<ev_run> or similar functions that enter
1933	the current event loop from either C<ev_prepare> or C<ev_check>	2712	the current event loop from either C<ev_prepare> or C<ev_check>
1934	watchers. Other loops than the current one are fine, however. The	2713	watchers. Other loops than the current one are fine, however. The
1935	rationale behind this is that you do not need to check for recursion in	2714	rationale behind this is that you do not need to check for recursion in
1936	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2715	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1937	C<ev_check> so if you have one watcher of each kind they will always be	2716	C<ev_check> so if you have one watcher of each kind they will always be
1938	called in pairs bracketing the blocking call.	2717	called in pairs bracketing the blocking call.
1939		2718
1940	Their main purpose is to integrate other event mechanisms into libev and	2719	Their main purpose is to integrate other event mechanisms into libev and
1941	their use is somewhat advanced. This could be used, for example, to track	2720	their use is somewhat advanced. They could be used, for example, to track
1942	variable changes, implement your own watchers, integrate net-snmp or a	2721	variable changes, implement your own watchers, integrate net-snmp or a
1943	coroutine library and lots more. They are also occasionally useful if	2722	coroutine library and lots more. They are also occasionally useful if
1944	you cache some data and want to flush it before blocking (for example,	2723	you cache some data and want to flush it before blocking (for example,
1945	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2724	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1946	watcher).	2725	watcher).
1947		2726
1948	This is done by examining in each prepare call which file descriptors need	2727	This is done by examining in each prepare call which file descriptors
1949	to be watched by the other library, registering C<ev_io> watchers for	2728	need to be watched by the other library, registering C<ev_io> watchers
1950	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2729	for them and starting an C<ev_timer> watcher for any timeouts (many
1951	provide just this functionality). Then, in the check watcher you check for	2730	libraries provide exactly this functionality). Then, in the check watcher,
1952	any events that occurred (by checking the pending status of all watchers	2731	you check for any events that occurred (by checking the pending status
1953	and stopping them) and call back into the library. The I/O and timer	2732	of all watchers and stopping them) and call back into the library. The
1954	callbacks will never actually be called (but must be valid nevertheless,	2733	I/O and timer callbacks will never actually be called (but must be valid
1955	because you never know, you know?).	2734	nevertheless, because you never know, you know?).
1956		2735
1957	As another example, the Perl Coro module uses these hooks to integrate	2736	As another example, the Perl Coro module uses these hooks to integrate
1958	coroutines into libev programs, by yielding to other active coroutines	2737	coroutines into libev programs, by yielding to other active coroutines
1959	during each prepare and only letting the process block if no coroutines	2738	during each prepare and only letting the process block if no coroutines
1960	are ready to run (it's actually more complicated: it only runs coroutines	2739	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1963	loop from blocking if lower-priority coroutines are active, thus mapping	2742	loop from blocking if lower-priority coroutines are active, thus mapping
1964	low-priority coroutines to idle/background tasks).	2743	low-priority coroutines to idle/background tasks).
1965		2744
1966	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2745	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1967	priority, to ensure that they are being run before any other watchers	2746	priority, to ensure that they are being run before any other watchers
		2747	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2748
1968	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2749	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1969	too) should not activate ("feed") events into libev. While libev fully	2750	activate ("feed") events into libev. While libev fully supports this, they
1970	supports this, they might get executed before other C<ev_check> watchers	2751	might get executed before other C<ev_check> watchers did their job. As
1971	did their job. As C<ev_check> watchers are often used to embed other	2752	C<ev_check> watchers are often used to embed other (non-libev) event
1972	(non-libev) event loops those other event loops might be in an unusable	2753	loops those other event loops might be in an unusable state until their
1973	state until their C<ev_check> watcher ran (always remind yourself to	2754	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1974	coexist peacefully with others).	2755	others).
1975		2756
1976	=head3 Watcher-Specific Functions and Data Members	2757	=head3 Watcher-Specific Functions and Data Members
1977		2758
1978	=over 4	2759	=over 4
1979		2760
…		…
1981		2762
1982	=item ev_check_init (ev_check *, callback)	2763	=item ev_check_init (ev_check *, callback)
1983		2764
1984	Initialises and configures the prepare or check watcher - they have no	2765	Initialises and configures the prepare or check watcher - they have no
1985	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2766	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1986	macros, but using them is utterly, utterly and completely pointless.	2767	macros, but using them is utterly, utterly, utterly and completely
		2768	pointless.
1987		2769
1988	=back	2770	=back
1989		2771
1990	=head3 Examples	2772	=head3 Examples
1991		2773
…		…
2004		2786
2005	static ev_io iow [nfd];	2787	static ev_io iow [nfd];
2006	static ev_timer tw;	2788	static ev_timer tw;
2007		2789
2008	static void	2790	static void
2009	io_cb (ev_loop *loop, ev_io *w, int revents)	2791	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2010	{	2792	{
2011	}	2793	}
2012		2794
2013	// create io watchers for each fd and a timer before blocking	2795	// create io watchers for each fd and a timer before blocking
2014	static void	2796	static void
2015	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2797	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2016	{	2798	{
2017	int timeout = 3600000;	2799	int timeout = 3600000;
2018	struct pollfd fds [nfd];	2800	struct pollfd fds [nfd];
2019	// actual code will need to loop here and realloc etc.	2801	// actual code will need to loop here and realloc etc.
2020	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2802	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2021		2803
2022	/* the callback is illegal, but won't be called as we stop during check */	2804	/* the callback is illegal, but won't be called as we stop during check */
2023	ev_timer_init (&tw, 0, timeout * 1e-3);	2805	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2024	ev_timer_start (loop, &tw);	2806	ev_timer_start (loop, &tw);
2025		2807
2026	// create one ev_io per pollfd	2808	// create one ev_io per pollfd
2027	for (int i = 0; i < nfd; ++i)	2809	for (int i = 0; i < nfd; ++i)
2028	{	2810	{
…		…
2035	}	2817	}
2036	}	2818	}
2037		2819
2038	// stop all watchers after blocking	2820	// stop all watchers after blocking
2039	static void	2821	static void
2040	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2822	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2041	{	2823	{
2042	ev_timer_stop (loop, &tw);	2824	ev_timer_stop (loop, &tw);
2043		2825
2044	for (int i = 0; i < nfd; ++i)	2826	for (int i = 0; i < nfd; ++i)
2045	{	2827	{
…		…
2084	}	2866	}
2085		2867
2086	// do not ever call adns_afterpoll	2868	// do not ever call adns_afterpoll
2087		2869
2088	Method 4: Do not use a prepare or check watcher because the module you	2870	Method 4: Do not use a prepare or check watcher because the module you
2089	want to embed is too inflexible to support it. Instead, you can override	2871	want to embed is not flexible enough to support it. Instead, you can
2090	their poll function. The drawback with this solution is that the main	2872	override their poll function. The drawback with this solution is that the
2091	loop is now no longer controllable by EV. The C<Glib::EV> module does	2873	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2092	this.	2874	this approach, effectively embedding EV as a client into the horrible
		2875	libglib event loop.
2093		2876
2094	static gint	2877	static gint
2095	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2878	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2096	{	2879	{
2097	int got_events = 0;	2880	int got_events = 0;
…		…
2101		2884
2102	if (timeout >= 0)	2885	if (timeout >= 0)
2103	// create/start timer	2886	// create/start timer
2104		2887
2105	// poll	2888	// poll
2106	ev_loop (EV_A_ 0);	2889	ev_run (EV_A_ 0);
2107		2890
2108	// stop timer again	2891	// stop timer again
2109	if (timeout >= 0)	2892	if (timeout >= 0)
2110	ev_timer_stop (EV_A_ &to);	2893	ev_timer_stop (EV_A_ &to);
2111		2894
…		…
2128	prioritise I/O.	2911	prioritise I/O.
2129		2912
2130	As an example for a bug workaround, the kqueue backend might only support	2913	As an example for a bug workaround, the kqueue backend might only support
2131	sockets on some platform, so it is unusable as generic backend, but you	2914	sockets on some platform, so it is unusable as generic backend, but you
2132	still want to make use of it because you have many sockets and it scales	2915	still want to make use of it because you have many sockets and it scales
2133	so nicely. In this case, you would create a kqueue-based loop and embed it	2916	so nicely. In this case, you would create a kqueue-based loop and embed
2134	into your default loop (which might use e.g. poll). Overall operation will	2917	it into your default loop (which might use e.g. poll). Overall operation
2135	be a bit slower because first libev has to poll and then call kevent, but	2918	will be a bit slower because first libev has to call C<poll> and then
2136	at least you can use both at what they are best.	2919	C<kevent>, but at least you can use both mechanisms for what they are
		2920	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2137		2921
2138	As for prioritising I/O: rarely you have the case where some fds have	2922	As for prioritising I/O: under rare circumstances you have the case where
2139	to be watched and handled very quickly (with low latency), and even	2923	some fds have to be watched and handled very quickly (with low latency),
2140	priorities and idle watchers might have too much overhead. In this case	2924	and even priorities and idle watchers might have too much overhead. In
2141	you would put all the high priority stuff in one loop and all the rest in	2925	this case you would put all the high priority stuff in one loop and all
2142	a second one, and embed the second one in the first.	2926	the rest in a second one, and embed the second one in the first.
2143		2927
2144	As long as the watcher is active, the callback will be invoked every time	2928	As long as the watcher is active, the callback will be invoked every
2145	there might be events pending in the embedded loop. The callback must then	2929	time there might be events pending in the embedded loop. The callback
2146	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2930	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2147	their callbacks (you could also start an idle watcher to give the embedded	2931	sweep and invoke their callbacks (the callback doesn't need to invoke the
2148	loop strictly lower priority for example). You can also set the callback	2932	C<ev_embed_sweep> function directly, it could also start an idle watcher
2149	to C<0>, in which case the embed watcher will automatically execute the	2933	to give the embedded loop strictly lower priority for example).
2150	embedded loop sweep.
2151		2934
2152	As long as the watcher is started it will automatically handle events. The	2935	You can also set the callback to C<0>, in which case the embed watcher
2153	callback will be invoked whenever some events have been handled. You can	2936	will automatically execute the embedded loop sweep whenever necessary.
2154	set the callback to C<0> to avoid having to specify one if you are not
2155	interested in that.
2156		2937
2157	Also, there have not currently been made special provisions for forking:	2938	Fork detection will be handled transparently while the C<ev_embed> watcher
2158	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2939	is active, i.e., the embedded loop will automatically be forked when the
2159	but you will also have to stop and restart any C<ev_embed> watchers	2940	embedding loop forks. In other cases, the user is responsible for calling
2160	yourself.	2941	C<ev_loop_fork> on the embedded loop.
2161		2942
2162	Unfortunately, not all backends are embeddable, only the ones returned by	2943	Unfortunately, not all backends are embeddable: only the ones returned by
2163	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2944	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2164	portable one.	2945	portable one.
2165		2946
2166	So when you want to use this feature you will always have to be prepared	2947	So when you want to use this feature you will always have to be prepared
2167	that you cannot get an embeddable loop. The recommended way to get around	2948	that you cannot get an embeddable loop. The recommended way to get around
2168	this is to have a separate variables for your embeddable loop, try to	2949	this is to have a separate variables for your embeddable loop, try to
2169	create it, and if that fails, use the normal loop for everything.	2950	create it, and if that fails, use the normal loop for everything.
		2951
		2952	=head3 C<ev_embed> and fork
		2953
		2954	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2955	automatically be applied to the embedded loop as well, so no special
		2956	fork handling is required in that case. When the watcher is not running,
		2957	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2958	as applicable.
2170		2959
2171	=head3 Watcher-Specific Functions and Data Members	2960	=head3 Watcher-Specific Functions and Data Members
2172		2961
2173	=over 4	2962	=over 4
2174		2963
…		…
2183	if you do not want that, you need to temporarily stop the embed watcher).	2972	if you do not want that, you need to temporarily stop the embed watcher).
2184		2973
2185	=item ev_embed_sweep (loop, ev_embed *)	2974	=item ev_embed_sweep (loop, ev_embed *)
2186		2975
2187	Make a single, non-blocking sweep over the embedded loop. This works	2976	Make a single, non-blocking sweep over the embedded loop. This works
2188	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2977	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2189	appropriate way for embedded loops.	2978	appropriate way for embedded loops.
2190		2979
2191	=item struct ev_loop *other [read-only]	2980	=item struct ev_loop *other [read-only]
2192		2981
2193	The embedded event loop.	2982	The embedded event loop.
…		…
2202	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2991	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2203	used).	2992	used).
2204		2993
2205	struct ev_loop *loop_hi = ev_default_init (0);	2994	struct ev_loop *loop_hi = ev_default_init (0);
2206	struct ev_loop *loop_lo = 0;	2995	struct ev_loop *loop_lo = 0;
2207	struct ev_embed embed;	2996	ev_embed embed;
2208		2997
2209	// see if there is a chance of getting one that works	2998	// see if there is a chance of getting one that works
2210	// (remember that a flags value of 0 means autodetection)	2999	// (remember that a flags value of 0 means autodetection)
2211	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3000	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2212	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3001	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2226	kqueue implementation). Store the kqueue/socket-only event loop in	3015	kqueue implementation). Store the kqueue/socket-only event loop in
2227	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3016	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2228		3017
2229	struct ev_loop *loop = ev_default_init (0);	3018	struct ev_loop *loop = ev_default_init (0);
2230	struct ev_loop *loop_socket = 0;	3019	struct ev_loop *loop_socket = 0;
2231	struct ev_embed embed;	3020	ev_embed embed;
2232		3021
2233	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3022	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2234	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3023	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2235	{	3024	{
2236	ev_embed_init (&embed, 0, loop_socket);	3025	ev_embed_init (&embed, 0, loop_socket);
…		…
2251	event loop blocks next and before C<ev_check> watchers are being called,	3040	event loop blocks next and before C<ev_check> watchers are being called,
2252	and only in the child after the fork. If whoever good citizen calling	3041	and only in the child after the fork. If whoever good citizen calling
2253	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3042	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2254	handlers will be invoked, too, of course.	3043	handlers will be invoked, too, of course.
2255		3044
		3045	=head3 The special problem of life after fork - how is it possible?
		3046
		3047	Most uses of C<fork()> consist of forking, then some simple calls to set
		3048	up/change the process environment, followed by a call to C<exec()>. This
		3049	sequence should be handled by libev without any problems.
		3050
		3051	This changes when the application actually wants to do event handling
		3052	in the child, or both parent in child, in effect "continuing" after the
		3053	fork.
		3054
		3055	The default mode of operation (for libev, with application help to detect
		3056	forks) is to duplicate all the state in the child, as would be expected
		3057	when I<either> the parent I<or> the child process continues.
		3058
		3059	When both processes want to continue using libev, then this is usually the
		3060	wrong result. In that case, usually one process (typically the parent) is
		3061	supposed to continue with all watchers in place as before, while the other
		3062	process typically wants to start fresh, i.e. without any active watchers.
		3063
		3064	The cleanest and most efficient way to achieve that with libev is to
		3065	simply create a new event loop, which of course will be "empty", and
		3066	use that for new watchers. This has the advantage of not touching more
		3067	memory than necessary, and thus avoiding the copy-on-write, and the
		3068	disadvantage of having to use multiple event loops (which do not support
		3069	signal watchers).
		3070
		3071	When this is not possible, or you want to use the default loop for
		3072	other reasons, then in the process that wants to start "fresh", call
		3073	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		3074	the default loop will "orphan" (not stop) all registered watchers, so you
		3075	have to be careful not to execute code that modifies those watchers. Note
		3076	also that in that case, you have to re-register any signal watchers.
		3077
2256	=head3 Watcher-Specific Functions and Data Members	3078	=head3 Watcher-Specific Functions and Data Members
2257		3079
2258	=over 4	3080	=over 4
2259		3081
2260	=item ev_fork_init (ev_signal *, callback)	3082	=item ev_fork_init (ev_signal *, callback)
…		…
2264	believe me.	3086	believe me.
2265		3087
2266	=back	3088	=back
2267		3089
2268		3090
2269	=head2 C<ev_async> - how to wake up another event loop	3091	=head2 C<ev_async> - how to wake up an event loop
2270		3092
2271	In general, you cannot use an C<ev_loop> from multiple threads or other	3093	In general, you cannot use an C<ev_run> from multiple threads or other
2272	asynchronous sources such as signal handlers (as opposed to multiple event	3094	asynchronous sources such as signal handlers (as opposed to multiple event
2273	loops - those are of course safe to use in different threads).	3095	loops - those are of course safe to use in different threads).
2274		3096
2275	Sometimes, however, you need to wake up another event loop you do not	3097	Sometimes, however, you need to wake up an event loop you do not control,
2276	control, for example because it belongs to another thread. This is what	3098	for example because it belongs to another thread. This is what C<ev_async>
2277	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3099	watchers do: as long as the C<ev_async> watcher is active, you can signal
2278	can signal it by calling C<ev_async_send>, which is thread- and signal	3100	it by calling C<ev_async_send>, which is thread- and signal safe.
2279	safe.
2280		3101
2281	This functionality is very similar to C<ev_signal> watchers, as signals,	3102	This functionality is very similar to C<ev_signal> watchers, as signals,
2282	too, are asynchronous in nature, and signals, too, will be compressed	3103	too, are asynchronous in nature, and signals, too, will be compressed
2283	(i.e. the number of callback invocations may be less than the number of	3104	(i.e. the number of callback invocations may be less than the number of
2284	C<ev_async_sent> calls).	3105	C<ev_async_sent> calls).
…		…
2289	=head3 Queueing	3110	=head3 Queueing
2290		3111
2291	C<ev_async> does not support queueing of data in any way. The reason	3112	C<ev_async> does not support queueing of data in any way. The reason
2292	is that the author does not know of a simple (or any) algorithm for a	3113	is that the author does not know of a simple (or any) algorithm for a
2293	multiple-writer-single-reader queue that works in all cases and doesn't	3114	multiple-writer-single-reader queue that works in all cases and doesn't
2294	need elaborate support such as pthreads.	3115	need elaborate support such as pthreads or unportable memory access
		3116	semantics.
2295		3117
2296	That means that if you want to queue data, you have to provide your own	3118	That means that if you want to queue data, you have to provide your own
2297	queue. But at least I can tell you would implement locking around your	3119	queue. But at least I can tell you how to implement locking around your
2298	queue:	3120	queue:
2299		3121
2300	=over 4	3122	=over 4
2301		3123
2302	=item queueing from a signal handler context	3124	=item queueing from a signal handler context
2303		3125
2304	To implement race-free queueing, you simply add to the queue in the signal	3126	To implement race-free queueing, you simply add to the queue in the signal
2305	handler but you block the signal handler in the watcher callback. Here is an example that does that for	3127	handler but you block the signal handler in the watcher callback. Here is
2306	some fictitious SIGUSR1 handler:	3128	an example that does that for some fictitious SIGUSR1 handler:
2307		3129
2308	static ev_async mysig;	3130	static ev_async mysig;
2309		3131
2310	static void	3132	static void
2311	sigusr1_handler (void)	3133	sigusr1_handler (void)
…		…
2377	=over 4	3199	=over 4
2378		3200
2379	=item ev_async_init (ev_async *, callback)	3201	=item ev_async_init (ev_async *, callback)
2380		3202
2381	Initialises and configures the async watcher - it has no parameters of any	3203	Initialises and configures the async watcher - it has no parameters of any
2382	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3204	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2383	believe me.	3205	trust me.
2384		3206
2385	=item ev_async_send (loop, ev_async *)	3207	=item ev_async_send (loop, ev_async *)
2386		3208
2387	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3209	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2388	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3210	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2389	C<ev_feed_event>, this call is safe to do in other threads, signal or	3211	C<ev_feed_event>, this call is safe to do from other threads, signal or
2390	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3212	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2391	section below on what exactly this means).	3213	section below on what exactly this means).
2392		3214
		3215	Note that, as with other watchers in libev, multiple events might get
		3216	compressed into a single callback invocation (another way to look at this
		3217	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3218	reset when the event loop detects that).
		3219
2393	This call incurs the overhead of a system call only once per loop iteration,	3220	This call incurs the overhead of a system call only once per event loop
2394	so while the overhead might be noticeable, it doesn't apply to repeated	3221	iteration, so while the overhead might be noticeable, it doesn't apply to
2395	calls to C<ev_async_send>.	3222	repeated calls to C<ev_async_send> for the same event loop.
2396		3223
2397	=item bool = ev_async_pending (ev_async *)	3224	=item bool = ev_async_pending (ev_async *)
2398		3225
2399	Returns a non-zero value when C<ev_async_send> has been called on the	3226	Returns a non-zero value when C<ev_async_send> has been called on the
2400	watcher but the event has not yet been processed (or even noted) by the	3227	watcher but the event has not yet been processed (or even noted) by the
…		…
2403	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3230	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2404	the loop iterates next and checks for the watcher to have become active,	3231	the loop iterates next and checks for the watcher to have become active,
2405	it will reset the flag again. C<ev_async_pending> can be used to very	3232	it will reset the flag again. C<ev_async_pending> can be used to very
2406	quickly check whether invoking the loop might be a good idea.	3233	quickly check whether invoking the loop might be a good idea.
2407		3234
2408	Not that this does I<not> check whether the watcher itself is pending, only	3235	Not that this does I<not> check whether the watcher itself is pending,
2409	whether it has been requested to make this watcher pending.	3236	only whether it has been requested to make this watcher pending: there
		3237	is a time window between the event loop checking and resetting the async
		3238	notification, and the callback being invoked.
2410		3239
2411	=back	3240	=back
2412		3241
2413		3242
2414	=head1 OTHER FUNCTIONS	3243	=head1 OTHER FUNCTIONS
…		…
2418	=over 4	3247	=over 4
2419		3248
2420	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3249	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2421		3250
2422	This function combines a simple timer and an I/O watcher, calls your	3251	This function combines a simple timer and an I/O watcher, calls your
2423	callback on whichever event happens first and automatically stop both	3252	callback on whichever event happens first and automatically stops both
2424	watchers. This is useful if you want to wait for a single event on an fd	3253	watchers. This is useful if you want to wait for a single event on an fd
2425	or timeout without having to allocate/configure/start/stop/free one or	3254	or timeout without having to allocate/configure/start/stop/free one or
2426	more watchers yourself.	3255	more watchers yourself.
2427		3256
2428	If C<fd> is less than 0, then no I/O watcher will be started and events	3257	If C<fd> is less than 0, then no I/O watcher will be started and the
2429	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	3258	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2430	C<events> set will be created and started.	3259	the given C<fd> and C<events> set will be created and started.
2431		3260
2432	If C<timeout> is less than 0, then no timeout watcher will be	3261	If C<timeout> is less than 0, then no timeout watcher will be
2433	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3262	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2434	repeat = 0) will be started. While C<0> is a valid timeout, it is of	3263	repeat = 0) will be started. C<0> is a valid timeout.
2435	dubious value.
2436		3264
2437	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3265	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2438	passed an C<revents> set like normal event callbacks (a combination of	3266	passed an C<revents> set like normal event callbacks (a combination of
2439	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3267	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2440	value passed to C<ev_once>:	3268	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3269	a timeout and an io event at the same time - you probably should give io
		3270	events precedence.
		3271
		3272	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2441		3273
2442	static void stdin_ready (int revents, void *arg)	3274	static void stdin_ready (int revents, void *arg)
2443	{	3275	{
		3276	if (revents & EV_READ)
		3277	/* stdin might have data for us, joy! */;
2444	if (revents & EV_TIMEOUT)	3278	else if (revents & EV_TIMER)
2445	/* doh, nothing entered */;	3279	/* doh, nothing entered */;
2446	else if (revents & EV_READ)
2447	/* stdin might have data for us, joy! */;
2448	}	3280	}
2449		3281
2450	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3282	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2451		3283
2452	=item ev_feed_event (ev_loop *, watcher *, int revents)
2453
2454	Feeds the given event set into the event loop, as if the specified event
2455	had happened for the specified watcher (which must be a pointer to an
2456	initialised but not necessarily started event watcher).
2457
2458	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3284	=item ev_feed_fd_event (loop, int fd, int revents)
2459		3285
2460	Feed an event on the given fd, as if a file descriptor backend detected	3286	Feed an event on the given fd, as if a file descriptor backend detected
2461	the given events it.	3287	the given events it.
2462		3288
2463	=item ev_feed_signal_event (ev_loop *loop, int signum)	3289	=item ev_feed_signal_event (loop, int signum)
2464		3290
2465	Feed an event as if the given signal occurred (C<loop> must be the default	3291	Feed an event as if the given signal occurred (C<loop> must be the default
2466	loop!).	3292	loop!).
2467		3293
2468	=back	3294	=back
…		…
2548		3374
2549	=over 4	3375	=over 4
2550		3376
2551	=item ev::TYPE::TYPE ()	3377	=item ev::TYPE::TYPE ()
2552		3378
2553	=item ev::TYPE::TYPE (struct ev_loop *)	3379	=item ev::TYPE::TYPE (loop)
2554		3380
2555	=item ev::TYPE::~TYPE	3381	=item ev::TYPE::~TYPE
2556		3382
2557	The constructor (optionally) takes an event loop to associate the watcher	3383	The constructor (optionally) takes an event loop to associate the watcher
2558	with. If it is omitted, it will use C<EV_DEFAULT>.	3384	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2590		3416
2591	myclass obj;	3417	myclass obj;
2592	ev::io iow;	3418	ev::io iow;
2593	iow.set <myclass, &myclass::io_cb> (&obj);	3419	iow.set <myclass, &myclass::io_cb> (&obj);
2594		3420
		3421	=item w->set (object *)
		3422
		3423	This is a variation of a method callback - leaving out the method to call
		3424	will default the method to C<operator ()>, which makes it possible to use
		3425	functor objects without having to manually specify the C<operator ()> all
		3426	the time. Incidentally, you can then also leave out the template argument
		3427	list.
		3428
		3429	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3430	int revents)>.
		3431
		3432	See the method-C<set> above for more details.
		3433
		3434	Example: use a functor object as callback.
		3435
		3436	struct myfunctor
		3437	{
		3438	void operator() (ev::io &w, int revents)
		3439	{
		3440	...
		3441	}
		3442	}
		3443
		3444	myfunctor f;
		3445
		3446	ev::io w;
		3447	w.set (&f);
		3448
2595	=item w->set<function> (void *data = 0)	3449	=item w->set<function> (void *data = 0)
2596		3450
2597	Also sets a callback, but uses a static method or plain function as	3451	Also sets a callback, but uses a static method or plain function as
2598	callback. The optional C<data> argument will be stored in the watcher's	3452	callback. The optional C<data> argument will be stored in the watcher's
2599	C<data> member and is free for you to use.	3453	C<data> member and is free for you to use.
2600		3454
2601	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3455	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2602		3456
2603	See the method-C<set> above for more details.	3457	See the method-C<set> above for more details.
2604		3458
2605	Example:	3459	Example: Use a plain function as callback.
2606		3460
2607	static void io_cb (ev::io &w, int revents) { }	3461	static void io_cb (ev::io &w, int revents) { }
2608	iow.set <io_cb> ();	3462	iow.set <io_cb> ();
2609		3463
2610	=item w->set (struct ev_loop *)	3464	=item w->set (loop)
2611		3465
2612	Associates a different C<struct ev_loop> with this watcher. You can only	3466	Associates a different C<struct ev_loop> with this watcher. You can only
2613	do this when the watcher is inactive (and not pending either).	3467	do this when the watcher is inactive (and not pending either).
2614		3468
2615	=item w->set ([arguments])	3469	=item w->set ([arguments])
2616		3470
2617	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3471	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
2618	called at least once. Unlike the C counterpart, an active watcher gets	3472	method or a suitable start method must be called at least once. Unlike the
2619	automatically stopped and restarted when reconfiguring it with this	3473	C counterpart, an active watcher gets automatically stopped and restarted
2620	method.	3474	when reconfiguring it with this method.
2621		3475
2622	=item w->start ()	3476	=item w->start ()
2623		3477
2624	Starts the watcher. Note that there is no C<loop> argument, as the	3478	Starts the watcher. Note that there is no C<loop> argument, as the
2625	constructor already stores the event loop.	3479	constructor already stores the event loop.
2626		3480
		3481	=item w->start ([arguments])
		3482
		3483	Instead of calling C<set> and C<start> methods separately, it is often
		3484	convenient to wrap them in one call. Uses the same type of arguments as
		3485	the configure C<set> method of the watcher.
		3486
2627	=item w->stop ()	3487	=item w->stop ()
2628		3488
2629	Stops the watcher if it is active. Again, no C<loop> argument.	3489	Stops the watcher if it is active. Again, no C<loop> argument.
2630		3490
2631	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3491	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2643		3503
2644	=back	3504	=back
2645		3505
2646	=back	3506	=back
2647		3507
2648	Example: Define a class with an IO and idle watcher, start one of them in	3508	Example: Define a class with two I/O and idle watchers, start the I/O
2649	the constructor.	3509	watchers in the constructor.
2650		3510
2651	class myclass	3511	class myclass
2652	{	3512	{
2653	ev::io io; void io_cb (ev::io &w, int revents);	3513	ev::io io ; void io_cb (ev::io &w, int revents);
		3514	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
2654	ev:idle idle void idle_cb (ev::idle &w, int revents);	3515	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2655		3516
2656	myclass (int fd)	3517	myclass (int fd)
2657	{	3518	{
2658	io .set <myclass, &myclass::io_cb > (this);	3519	io .set <myclass, &myclass::io_cb > (this);
		3520	io2 .set <myclass, &myclass::io2_cb > (this);
2659	idle.set <myclass, &myclass::idle_cb> (this);	3521	idle.set <myclass, &myclass::idle_cb> (this);
2660		3522
2661	io.start (fd, ev::READ);	3523	io.set (fd, ev::WRITE); // configure the watcher
		3524	io.start (); // start it whenever convenient
		3525
		3526	io2.start (fd, ev::READ); // set + start in one call
2662	}	3527	}
2663	};	3528	};
2664		3529
2665		3530
2666	=head1 OTHER LANGUAGE BINDINGS	3531	=head1 OTHER LANGUAGE BINDINGS
…		…
2675	=item Perl	3540	=item Perl
2676		3541
2677	The EV module implements the full libev API and is actually used to test	3542	The EV module implements the full libev API and is actually used to test
2678	libev. EV is developed together with libev. Apart from the EV core module,	3543	libev. EV is developed together with libev. Apart from the EV core module,
2679	there are additional modules that implement libev-compatible interfaces	3544	there are additional modules that implement libev-compatible interfaces
2680	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3545	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2681	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3546	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3547	and C<EV::Glib>).
2682		3548
2683	It can be found and installed via CPAN, its homepage is at	3549	It can be found and installed via CPAN, its homepage is at
2684	L<http://software.schmorp.de/pkg/EV>.	3550	L<http://software.schmorp.de/pkg/EV>.
2685		3551
2686	=item Python	3552	=item Python
2687		3553
2688	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3554	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2689	seems to be quite complete and well-documented. Note, however, that the	3555	seems to be quite complete and well-documented.
2690	patch they require for libev is outright dangerous as it breaks the ABI
2691	for everybody else, and therefore, should never be applied in an installed
2692	libev (if python requires an incompatible ABI then it needs to embed
2693	libev).
2694		3556
2695	=item Ruby	3557	=item Ruby
2696		3558
2697	Tony Arcieri has written a ruby extension that offers access to a subset	3559	Tony Arcieri has written a ruby extension that offers access to a subset
2698	of the libev API and adds file handle abstractions, asynchronous DNS and	3560	of the libev API and adds file handle abstractions, asynchronous DNS and
2699	more on top of it. It can be found via gem servers. Its homepage is at	3561	more on top of it. It can be found via gem servers. Its homepage is at
2700	L<http://rev.rubyforge.org/>.	3562	L<http://rev.rubyforge.org/>.
2701		3563
		3564	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3565	makes rev work even on mingw.
		3566
		3567	=item Haskell
		3568
		3569	A haskell binding to libev is available at
		3570	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3571
2702	=item D	3572	=item D
2703		3573
2704	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3574	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2705	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3575	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3576
		3577	=item Ocaml
		3578
		3579	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3580	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3581
		3582	=item Lua
		3583
		3584	Brian Maher has written a partial interface to libev for lua (at the
		3585	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3586	L<http://github.com/brimworks/lua-ev>.
2706		3587
2707	=back	3588	=back
2708		3589
2709		3590
2710	=head1 MACRO MAGIC	3591	=head1 MACRO MAGIC
…		…
2724	loop argument"). The C<EV_A> form is used when this is the sole argument,	3605	loop argument"). The C<EV_A> form is used when this is the sole argument,
2725	C<EV_A_> is used when other arguments are following. Example:	3606	C<EV_A_> is used when other arguments are following. Example:
2726		3607
2727	ev_unref (EV_A);	3608	ev_unref (EV_A);
2728	ev_timer_add (EV_A_ watcher);	3609	ev_timer_add (EV_A_ watcher);
2729	ev_loop (EV_A_ 0);	3610	ev_run (EV_A_ 0);
2730		3611
2731	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3612	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2732	which is often provided by the following macro.	3613	which is often provided by the following macro.
2733		3614
2734	=item C<EV_P>, C<EV_P_>	3615	=item C<EV_P>, C<EV_P_>
…		…
2774	}	3655	}
2775		3656
2776	ev_check check;	3657	ev_check check;
2777	ev_check_init (&check, check_cb);	3658	ev_check_init (&check, check_cb);
2778	ev_check_start (EV_DEFAULT_ &check);	3659	ev_check_start (EV_DEFAULT_ &check);
2779	ev_loop (EV_DEFAULT_ 0);	3660	ev_run (EV_DEFAULT_ 0);
2780		3661
2781	=head1 EMBEDDING	3662	=head1 EMBEDDING
2782		3663
2783	Libev can (and often is) directly embedded into host	3664	Libev can (and often is) directly embedded into host
2784	applications. Examples of applications that embed it include the Deliantra	3665	applications. Examples of applications that embed it include the Deliantra
…		…
2811		3692
2812	#define EV_STANDALONE 1	3693	#define EV_STANDALONE 1
2813	#include "ev.h"	3694	#include "ev.h"
2814		3695
2815	Both header files and implementation files can be compiled with a C++	3696	Both header files and implementation files can be compiled with a C++
2816	compiler (at least, thats a stated goal, and breakage will be treated	3697	compiler (at least, that's a stated goal, and breakage will be treated
2817	as a bug).	3698	as a bug).
2818		3699
2819	You need the following files in your source tree, or in a directory	3700	You need the following files in your source tree, or in a directory
2820	in your include path (e.g. in libev/ when using -Ilibev):	3701	in your include path (e.g. in libev/ when using -Ilibev):
2821		3702
…		…
2864	libev.m4	3745	libev.m4
2865		3746
2866	=head2 PREPROCESSOR SYMBOLS/MACROS	3747	=head2 PREPROCESSOR SYMBOLS/MACROS
2867		3748
2868	Libev can be configured via a variety of preprocessor symbols you have to	3749	Libev can be configured via a variety of preprocessor symbols you have to
2869	define before including any of its files. The default in the absence of	3750	define before including (or compiling) any of its files. The default in
2870	autoconf is noted for every option.	3751	the absence of autoconf is documented for every option.
		3752
		3753	Symbols marked with "(h)" do not change the ABI, and can have different
		3754	values when compiling libev vs. including F<ev.h>, so it is permissible
		3755	to redefine them before including F<ev.h> without breaking compatibility
		3756	to a compiled library. All other symbols change the ABI, which means all
		3757	users of libev and the libev code itself must be compiled with compatible
		3758	settings.
2871		3759
2872	=over 4	3760	=over 4
2873		3761
		3762	=item EV_COMPAT3 (h)
		3763
		3764	Backwards compatibility is a major concern for libev. This is why this
		3765	release of libev comes with wrappers for the functions and symbols that
		3766	have been renamed between libev version 3 and 4.
		3767
		3768	You can disable these wrappers (to test compatibility with future
		3769	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		3770	sources. This has the additional advantage that you can drop the C<struct>
		3771	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		3772	typedef in that case.
		3773
		3774	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		3775	and in some even more future version the compatibility code will be
		3776	removed completely.
		3777
2874	=item EV_STANDALONE	3778	=item EV_STANDALONE (h)
2875		3779
2876	Must always be C<1> if you do not use autoconf configuration, which	3780	Must always be C<1> if you do not use autoconf configuration, which
2877	keeps libev from including F<config.h>, and it also defines dummy	3781	keeps libev from including F<config.h>, and it also defines dummy
2878	implementations for some libevent functions (such as logging, which is not	3782	implementations for some libevent functions (such as logging, which is not
2879	supported). It will also not define any of the structs usually found in	3783	supported). It will also not define any of the structs usually found in
2880	F<event.h> that are not directly supported by the libev core alone.	3784	F<event.h> that are not directly supported by the libev core alone.
2881		3785
		3786	In standalone mode, libev will still try to automatically deduce the
		3787	configuration, but has to be more conservative.
		3788
2882	=item EV_USE_MONOTONIC	3789	=item EV_USE_MONOTONIC
2883		3790
2884	If defined to be C<1>, libev will try to detect the availability of the	3791	If defined to be C<1>, libev will try to detect the availability of the
2885	monotonic clock option at both compile time and runtime. Otherwise no use	3792	monotonic clock option at both compile time and runtime. Otherwise no
2886	of the monotonic clock option will be attempted. If you enable this, you	3793	use of the monotonic clock option will be attempted. If you enable this,
2887	usually have to link against librt or something similar. Enabling it when	3794	you usually have to link against librt or something similar. Enabling it
2888	the functionality isn't available is safe, though, although you have	3795	when the functionality isn't available is safe, though, although you have
2889	to make sure you link against any libraries where the C<clock_gettime>	3796	to make sure you link against any libraries where the C<clock_gettime>
2890	function is hiding in (often F<-lrt>).	3797	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2891		3798
2892	=item EV_USE_REALTIME	3799	=item EV_USE_REALTIME
2893		3800
2894	If defined to be C<1>, libev will try to detect the availability of the	3801	If defined to be C<1>, libev will try to detect the availability of the
2895	real-time clock option at compile time (and assume its availability at	3802	real-time clock option at compile time (and assume its availability
2896	runtime if successful). Otherwise no use of the real-time clock option will	3803	at runtime if successful). Otherwise no use of the real-time clock
2897	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3804	option will be attempted. This effectively replaces C<gettimeofday>
2898	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3805	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2899	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3806	correctness. See the note about libraries in the description of
		3807	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3808	C<EV_USE_CLOCK_SYSCALL>.
		3809
		3810	=item EV_USE_CLOCK_SYSCALL
		3811
		3812	If defined to be C<1>, libev will try to use a direct syscall instead
		3813	of calling the system-provided C<clock_gettime> function. This option
		3814	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3815	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3816	programs needlessly. Using a direct syscall is slightly slower (in
		3817	theory), because no optimised vdso implementation can be used, but avoids
		3818	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3819	higher, as it simplifies linking (no need for C<-lrt>).
2900		3820
2901	=item EV_USE_NANOSLEEP	3821	=item EV_USE_NANOSLEEP
2902		3822
2903	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3823	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2904	and will use it for delays. Otherwise it will use C<select ()>.	3824	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2920		3840
2921	=item EV_SELECT_USE_FD_SET	3841	=item EV_SELECT_USE_FD_SET
2922		3842
2923	If defined to C<1>, then the select backend will use the system C<fd_set>	3843	If defined to C<1>, then the select backend will use the system C<fd_set>
2924	structure. This is useful if libev doesn't compile due to a missing	3844	structure. This is useful if libev doesn't compile due to a missing
2925	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3845	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2926	exotic systems. This usually limits the range of file descriptors to some	3846	on exotic systems. This usually limits the range of file descriptors to
2927	low limit such as 1024 or might have other limitations (winsocket only	3847	some low limit such as 1024 or might have other limitations (winsocket
2928	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3848	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2929	influence the size of the C<fd_set> used.	3849	configures the maximum size of the C<fd_set>.
2930		3850
2931	=item EV_SELECT_IS_WINSOCKET	3851	=item EV_SELECT_IS_WINSOCKET
2932		3852
2933	When defined to C<1>, the select backend will assume that	3853	When defined to C<1>, the select backend will assume that
2934	select/socket/connect etc. don't understand file descriptors but	3854	select/socket/connect etc. don't understand file descriptors but
…		…
2936	be used is the winsock select). This means that it will call	3856	be used is the winsock select). This means that it will call
2937	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3857	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2938	it is assumed that all these functions actually work on fds, even	3858	it is assumed that all these functions actually work on fds, even
2939	on win32. Should not be defined on non-win32 platforms.	3859	on win32. Should not be defined on non-win32 platforms.
2940		3860
2941	=item EV_FD_TO_WIN32_HANDLE	3861	=item EV_FD_TO_WIN32_HANDLE(fd)
2942		3862
2943	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3863	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
2944	file descriptors to socket handles. When not defining this symbol (the	3864	file descriptors to socket handles. When not defining this symbol (the
2945	default), then libev will call C<_get_osfhandle>, which is usually	3865	default), then libev will call C<_get_osfhandle>, which is usually
2946	correct. In some cases, programs use their own file descriptor management,	3866	correct. In some cases, programs use their own file descriptor management,
2947	in which case they can provide this function to map fds to socket handles.	3867	in which case they can provide this function to map fds to socket handles.
		3868
		3869	=item EV_WIN32_HANDLE_TO_FD(handle)
		3870
		3871	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3872	using the standard C<_open_osfhandle> function. For programs implementing
		3873	their own fd to handle mapping, overwriting this function makes it easier
		3874	to do so. This can be done by defining this macro to an appropriate value.
		3875
		3876	=item EV_WIN32_CLOSE_FD(fd)
		3877
		3878	If programs implement their own fd to handle mapping on win32, then this
		3879	macro can be used to override the C<close> function, useful to unregister
		3880	file descriptors again. Note that the replacement function has to close
		3881	the underlying OS handle.
2948		3882
2949	=item EV_USE_POLL	3883	=item EV_USE_POLL
2950		3884
2951	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3885	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2952	backend. Otherwise it will be enabled on non-win32 platforms. It	3886	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
2999	as well as for signal and thread safety in C<ev_async> watchers.	3933	as well as for signal and thread safety in C<ev_async> watchers.
3000		3934
3001	In the absence of this define, libev will use C<sig_atomic_t volatile>	3935	In the absence of this define, libev will use C<sig_atomic_t volatile>
3002	(from F<signal.h>), which is usually good enough on most platforms.	3936	(from F<signal.h>), which is usually good enough on most platforms.
3003		3937
3004	=item EV_H	3938	=item EV_H (h)
3005		3939
3006	The name of the F<ev.h> header file used to include it. The default if	3940	The name of the F<ev.h> header file used to include it. The default if
3007	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	3941	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3008	used to virtually rename the F<ev.h> header file in case of conflicts.	3942	used to virtually rename the F<ev.h> header file in case of conflicts.
3009		3943
3010	=item EV_CONFIG_H	3944	=item EV_CONFIG_H (h)
3011		3945
3012	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	3946	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3013	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	3947	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3014	C<EV_H>, above.	3948	C<EV_H>, above.
3015		3949
3016	=item EV_EVENT_H	3950	=item EV_EVENT_H (h)
3017		3951
3018	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	3952	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3019	of how the F<event.h> header can be found, the default is C<"event.h">.	3953	of how the F<event.h> header can be found, the default is C<"event.h">.
3020		3954
3021	=item EV_PROTOTYPES	3955	=item EV_PROTOTYPES (h)
3022		3956
3023	If defined to be C<0>, then F<ev.h> will not define any function	3957	If defined to be C<0>, then F<ev.h> will not define any function
3024	prototypes, but still define all the structs and other symbols. This is	3958	prototypes, but still define all the structs and other symbols. This is
3025	occasionally useful if you want to provide your own wrapper functions	3959	occasionally useful if you want to provide your own wrapper functions
3026	around libev functions.	3960	around libev functions.
…		…
3045	When doing priority-based operations, libev usually has to linearly search	3979	When doing priority-based operations, libev usually has to linearly search
3046	all the priorities, so having many of them (hundreds) uses a lot of space	3980	all the priorities, so having many of them (hundreds) uses a lot of space
3047	and time, so using the defaults of five priorities (-2 .. +2) is usually	3981	and time, so using the defaults of five priorities (-2 .. +2) is usually
3048	fine.	3982	fine.
3049		3983
3050	If your embedding application does not need any priorities, defining these both to	3984	If your embedding application does not need any priorities, defining these
3051	C<0> will save some memory and CPU.	3985	both to C<0> will save some memory and CPU.
3052		3986
3053	=item EV_PERIODIC_ENABLE	3987	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		3988	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		3989	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3054		3990
3055	If undefined or defined to be C<1>, then periodic timers are supported. If	3991	If undefined or defined to be C<1> (and the platform supports it), then
3056	defined to be C<0>, then they are not. Disabling them saves a few kB of	3992	the respective watcher type is supported. If defined to be C<0>, then it
3057	code.	3993	is not. Disabling watcher types mainly saves code size.
3058		3994
3059	=item EV_IDLE_ENABLE	3995	=item EV_FEATURES
3060
3061	If undefined or defined to be C<1>, then idle watchers are supported. If
3062	defined to be C<0>, then they are not. Disabling them saves a few kB of
3063	code.
3064
3065	=item EV_EMBED_ENABLE
3066
3067	If undefined or defined to be C<1>, then embed watchers are supported. If
3068	defined to be C<0>, then they are not.
3069
3070	=item EV_STAT_ENABLE
3071
3072	If undefined or defined to be C<1>, then stat watchers are supported. If
3073	defined to be C<0>, then they are not.
3074
3075	=item EV_FORK_ENABLE
3076
3077	If undefined or defined to be C<1>, then fork watchers are supported. If
3078	defined to be C<0>, then they are not.
3079
3080	=item EV_ASYNC_ENABLE
3081
3082	If undefined or defined to be C<1>, then async watchers are supported. If
3083	defined to be C<0>, then they are not.
3084
3085	=item EV_MINIMAL
3086		3996
3087	If you need to shave off some kilobytes of code at the expense of some	3997	If you need to shave off some kilobytes of code at the expense of some
3088	speed, define this symbol to C<1>. Currently this is used to override some	3998	speed (but with the full API), you can define this symbol to request
3089	inlining decisions, saves roughly 30% code size on amd64. It also selects a	3999	certain subsets of functionality. The default is to enable all features
3090	much smaller 2-heap for timer management over the default 4-heap.	4000	that can be enabled on the platform.
		4001
		4002	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4003	with some broad features you want) and then selectively re-enable
		4004	additional parts you want, for example if you want everything minimal,
		4005	but multiple event loop support, async and child watchers and the poll
		4006	backend, use this:
		4007
		4008	#define EV_FEATURES 0
		4009	#define EV_MULTIPLICITY 1
		4010	#define EV_USE_POLL 1
		4011	#define EV_CHILD_ENABLE 1
		4012	#define EV_ASYNC_ENABLE 1
		4013
		4014	The actual value is a bitset, it can be a combination of the following
		4015	values:
		4016
		4017	=over 4
		4018
		4019	=item C<1> - faster/larger code
		4020
		4021	Use larger code to speed up some operations.
		4022
		4023	Currently this is used to override some inlining decisions (enlarging the
		4024	code size by roughly 30% on amd64).
		4025
		4026	When optimising for size, use of compiler flags such as C<-Os> with
		4027	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4028	assertions.
		4029
		4030	=item C<2> - faster/larger data structures
		4031
		4032	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4033	hash table sizes and so on. This will usually further increase code size
		4034	and can additionally have an effect on the size of data structures at
		4035	runtime.
		4036
		4037	=item C<4> - full API configuration
		4038
		4039	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4040	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4041
		4042	=item C<8> - full API
		4043
		4044	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4045	details on which parts of the API are still available without this
		4046	feature, and do not complain if this subset changes over time.
		4047
		4048	=item C<16> - enable all optional watcher types
		4049
		4050	Enables all optional watcher types. If you want to selectively enable
		4051	only some watcher types other than I/O and timers (e.g. prepare,
		4052	embed, async, child...) you can enable them manually by defining
		4053	C<EV_watchertype_ENABLE> to C<1> instead.
		4054
		4055	=item C<32> - enable all backends
		4056
		4057	This enables all backends - without this feature, you need to enable at
		4058	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4059
		4060	=item C<64> - enable OS-specific "helper" APIs
		4061
		4062	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4063	default.
		4064
		4065	=back
		4066
		4067	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4068	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4069	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4070	watchers, timers and monotonic clock support.
		4071
		4072	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4073	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4074	your program might be left out as well - a binary starting a timer and an
		4075	I/O watcher then might come out at only 5Kb.
		4076
		4077	=item EV_AVOID_STDIO
		4078
		4079	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4080	functions (printf, scanf, perror etc.). This will increase the code size
		4081	somewhat, but if your program doesn't otherwise depend on stdio and your
		4082	libc allows it, this avoids linking in the stdio library which is quite
		4083	big.
		4084
		4085	Note that error messages might become less precise when this option is
		4086	enabled.
		4087
		4088	=item EV_NSIG
		4089
		4090	The highest supported signal number, +1 (or, the number of
		4091	signals): Normally, libev tries to deduce the maximum number of signals
		4092	automatically, but sometimes this fails, in which case it can be
		4093	specified. Also, using a lower number than detected (C<32> should be
		4094	good for about any system in existence) can save some memory, as libev
		4095	statically allocates some 12-24 bytes per signal number.
3091		4096
3092	=item EV_PID_HASHSIZE	4097	=item EV_PID_HASHSIZE
3093		4098
3094	C<ev_child> watchers use a small hash table to distribute workload by	4099	C<ev_child> watchers use a small hash table to distribute workload by
3095	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4100	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3096	than enough. If you need to manage thousands of children you might want to	4101	usually more than enough. If you need to manage thousands of children you
3097	increase this value (I<must> be a power of two).	4102	might want to increase this value (I<must> be a power of two).
3098		4103
3099	=item EV_INOTIFY_HASHSIZE	4104	=item EV_INOTIFY_HASHSIZE
3100		4105
3101	C<ev_stat> watchers use a small hash table to distribute workload by	4106	C<ev_stat> watchers use a small hash table to distribute workload by
3102	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4107	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3103	usually more than enough. If you need to manage thousands of C<ev_stat>	4108	disabled), usually more than enough. If you need to manage thousands of
3104	watchers you might want to increase this value (I<must> be a power of	4109	C<ev_stat> watchers you might want to increase this value (I<must> be a
3105	two).	4110	power of two).
3106		4111
3107	=item EV_USE_4HEAP	4112	=item EV_USE_4HEAP
3108		4113
3109	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4114	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3110	timer and periodics heap, libev uses a 4-heap when this symbol is defined	4115	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3111	to C<1>. The 4-heap uses more complicated (longer) code but has	4116	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3112	noticeably faster performance with many (thousands) of watchers.	4117	faster performance with many (thousands) of watchers.
3113		4118
3114	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4119	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3115	(disabled).	4120	will be C<0>.
3116		4121
3117	=item EV_HEAP_CACHE_AT	4122	=item EV_HEAP_CACHE_AT
3118		4123
3119	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4124	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3120	timer and periodics heap, libev can cache the timestamp (I<at>) within	4125	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3121	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4126	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3122	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4127	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3123	but avoids random read accesses on heap changes. This improves performance	4128	but avoids random read accesses on heap changes. This improves performance
3124	noticeably with with many (hundreds) of watchers.	4129	noticeably with many (hundreds) of watchers.
3125		4130
3126	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4131	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3127	(disabled).	4132	will be C<0>.
3128		4133
3129	=item EV_VERIFY	4134	=item EV_VERIFY
3130		4135
3131	Controls how much internal verification (see C<ev_loop_verify ()>) will	4136	Controls how much internal verification (see C<ev_verify ()>) will
3132	be done: If set to C<0>, no internal verification code will be compiled	4137	be done: If set to C<0>, no internal verification code will be compiled
3133	in. If set to C<1>, then verification code will be compiled in, but not	4138	in. If set to C<1>, then verification code will be compiled in, but not
3134	called. If set to C<2>, then the internal verification code will be	4139	called. If set to C<2>, then the internal verification code will be
3135	called once per loop, which can slow down libev. If set to C<3>, then the	4140	called once per loop, which can slow down libev. If set to C<3>, then the
3136	verification code will be called very frequently, which will slow down	4141	verification code will be called very frequently, which will slow down
3137	libev considerably.	4142	libev considerably.
3138		4143
3139	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4144	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3140	C<0.>	4145	will be C<0>.
3141		4146
3142	=item EV_COMMON	4147	=item EV_COMMON
3143		4148
3144	By default, all watchers have a C<void *data> member. By redefining	4149	By default, all watchers have a C<void *data> member. By redefining
3145	this macro to a something else you can include more and other types of	4150	this macro to something else you can include more and other types of
3146	members. You have to define it each time you include one of the files,	4151	members. You have to define it each time you include one of the files,
3147	though, and it must be identical each time.	4152	though, and it must be identical each time.
3148		4153
3149	For example, the perl EV module uses something like this:	4154	For example, the perl EV module uses something like this:
3150		4155
…		…
3162	and the way callbacks are invoked and set. Must expand to a struct member	4167	and the way callbacks are invoked and set. Must expand to a struct member
3163	definition and a statement, respectively. See the F<ev.h> header file for	4168	definition and a statement, respectively. See the F<ev.h> header file for
3164	their default definitions. One possible use for overriding these is to	4169	their default definitions. One possible use for overriding these is to
3165	avoid the C<struct ev_loop *> as first argument in all cases, or to use	4170	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3166	method calls instead of plain function calls in C++.	4171	method calls instead of plain function calls in C++.
		4172
		4173	=back
3167		4174
3168	=head2 EXPORTED API SYMBOLS	4175	=head2 EXPORTED API SYMBOLS
3169		4176
3170	If you need to re-export the API (e.g. via a DLL) and you need a list of	4177	If you need to re-export the API (e.g. via a DLL) and you need a list of
3171	exported symbols, you can use the provided F<Symbol.*> files which list	4178	exported symbols, you can use the provided F<Symbol.*> files which list
…		…
3201	file.	4208	file.
3202		4209
3203	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4210	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3204	that everybody includes and which overrides some configure choices:	4211	that everybody includes and which overrides some configure choices:
3205		4212
3206	#define EV_MINIMAL 1	4213	#define EV_FEATURES 8
3207	#define EV_USE_POLL 0	4214	#define EV_USE_SELECT 1
3208	#define EV_MULTIPLICITY 0
3209	#define EV_PERIODIC_ENABLE 0	4215	#define EV_PREPARE_ENABLE 1
		4216	#define EV_IDLE_ENABLE 1
3210	#define EV_STAT_ENABLE 0	4217	#define EV_SIGNAL_ENABLE 1
3211	#define EV_FORK_ENABLE 0	4218	#define EV_CHILD_ENABLE 1
		4219	#define EV_USE_STDEXCEPT 0
3212	#define EV_CONFIG_H <config.h>	4220	#define EV_CONFIG_H <config.h>
3213	#define EV_MINPRI 0
3214	#define EV_MAXPRI 0
3215		4221
3216	#include "ev++.h"	4222	#include "ev++.h"
3217		4223
3218	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4224	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3219		4225
3220	#include "ev_cpp.h"	4226	#include "ev_cpp.h"
3221	#include "ev.c"	4227	#include "ev.c"
3222		4228
		4229	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3223		4230
3224	=head1 THREADS AND COROUTINES	4231	=head2 THREADS AND COROUTINES
3225		4232
3226	=head2 THREADS	4233	=head3 THREADS
3227		4234
3228	Libev itself is completely thread-safe, but it uses no locking. This	4235	All libev functions are reentrant and thread-safe unless explicitly
		4236	documented otherwise, but libev implements no locking itself. This means
3229	means that you can use as many loops as you want in parallel, as long as	4237	that you can use as many loops as you want in parallel, as long as there
3230	only one thread ever calls into one libev function with the same loop	4238	are no concurrent calls into any libev function with the same loop
3231	parameter.	4239	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		4240	of course): libev guarantees that different event loops share no data
		4241	structures that need any locking.
3232		4242
3233	Or put differently: calls with different loop parameters can be done in	4243	Or to put it differently: calls with different loop parameters can be done
3234	parallel from multiple threads, calls with the same loop parameter must be	4244	concurrently from multiple threads, calls with the same loop parameter
3235	done serially (but can be done from different threads, as long as only one	4245	must be done serially (but can be done from different threads, as long as
3236	thread ever is inside a call at any point in time, e.g. by using a mutex	4246	only one thread ever is inside a call at any point in time, e.g. by using
3237	per loop).	4247	a mutex per loop).
		4248
		4249	Specifically to support threads (and signal handlers), libev implements
		4250	so-called C<ev_async> watchers, which allow some limited form of
		4251	concurrency on the same event loop, namely waking it up "from the
		4252	outside".
3238		4253
3239	If you want to know which design (one loop, locking, or multiple loops	4254	If you want to know which design (one loop, locking, or multiple loops
3240	without or something else still) is best for your problem, then I cannot	4255	without or something else still) is best for your problem, then I cannot
3241	help you. I can give some generic advice however:	4256	help you, but here is some generic advice:
3242		4257
3243	=over 4	4258	=over 4
3244		4259
3245	=item * most applications have a main thread: use the default libev loop	4260	=item * most applications have a main thread: use the default libev loop
3246	in that thread, or create a separate thread running only the default loop.	4261	in that thread, or create a separate thread running only the default loop.
…		…
3258		4273
3259	Choosing a model is hard - look around, learn, know that usually you can do	4274	Choosing a model is hard - look around, learn, know that usually you can do
3260	better than you currently do :-)	4275	better than you currently do :-)
3261		4276
3262	=item * often you need to talk to some other thread which blocks in the	4277	=item * often you need to talk to some other thread which blocks in the
		4278	event loop.
		4279
3263	event loop - C<ev_async> watchers can be used to wake them up from other	4280	C<ev_async> watchers can be used to wake them up from other threads safely
3264	threads safely (or from signal contexts...).	4281	(or from signal contexts...).
		4282
		4283	An example use would be to communicate signals or other events that only
		4284	work in the default loop by registering the signal watcher with the
		4285	default loop and triggering an C<ev_async> watcher from the default loop
		4286	watcher callback into the event loop interested in the signal.
3265		4287
3266	=back	4288	=back
3267		4289
		4290	=head4 THREAD LOCKING EXAMPLE
		4291
		4292	Here is a fictitious example of how to run an event loop in a different
		4293	thread than where callbacks are being invoked and watchers are
		4294	created/added/removed.
		4295
		4296	For a real-world example, see the C<EV::Loop::Async> perl module,
		4297	which uses exactly this technique (which is suited for many high-level
		4298	languages).
		4299
		4300	The example uses a pthread mutex to protect the loop data, a condition
		4301	variable to wait for callback invocations, an async watcher to notify the
		4302	event loop thread and an unspecified mechanism to wake up the main thread.
		4303
		4304	First, you need to associate some data with the event loop:
		4305
		4306	typedef struct {
		4307	mutex_t lock; /* global loop lock */
		4308	ev_async async_w;
		4309	thread_t tid;
		4310	cond_t invoke_cv;
		4311	} userdata;
		4312
		4313	void prepare_loop (EV_P)
		4314	{
		4315	// for simplicity, we use a static userdata struct.
		4316	static userdata u;
		4317
		4318	ev_async_init (&u->async_w, async_cb);
		4319	ev_async_start (EV_A_ &u->async_w);
		4320
		4321	pthread_mutex_init (&u->lock, 0);
		4322	pthread_cond_init (&u->invoke_cv, 0);
		4323
		4324	// now associate this with the loop
		4325	ev_set_userdata (EV_A_ u);
		4326	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4327	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4328
		4329	// then create the thread running ev_loop
		4330	pthread_create (&u->tid, 0, l_run, EV_A);
		4331	}
		4332
		4333	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4334	solely to wake up the event loop so it takes notice of any new watchers
		4335	that might have been added:
		4336
		4337	static void
		4338	async_cb (EV_P_ ev_async *w, int revents)
		4339	{
		4340	// just used for the side effects
		4341	}
		4342
		4343	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4344	protecting the loop data, respectively.
		4345
		4346	static void
		4347	l_release (EV_P)
		4348	{
		4349	userdata *u = ev_userdata (EV_A);
		4350	pthread_mutex_unlock (&u->lock);
		4351	}
		4352
		4353	static void
		4354	l_acquire (EV_P)
		4355	{
		4356	userdata *u = ev_userdata (EV_A);
		4357	pthread_mutex_lock (&u->lock);
		4358	}
		4359
		4360	The event loop thread first acquires the mutex, and then jumps straight
		4361	into C<ev_run>:
		4362
		4363	void *
		4364	l_run (void *thr_arg)
		4365	{
		4366	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4367
		4368	l_acquire (EV_A);
		4369	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4370	ev_run (EV_A_ 0);
		4371	l_release (EV_A);
		4372
		4373	return 0;
		4374	}
		4375
		4376	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4377	signal the main thread via some unspecified mechanism (signals? pipe
		4378	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4379	have been called (in a while loop because a) spurious wakeups are possible
		4380	and b) skipping inter-thread-communication when there are no pending
		4381	watchers is very beneficial):
		4382
		4383	static void
		4384	l_invoke (EV_P)
		4385	{
		4386	userdata *u = ev_userdata (EV_A);
		4387
		4388	while (ev_pending_count (EV_A))
		4389	{
		4390	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4391	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4392	}
		4393	}
		4394
		4395	Now, whenever the main thread gets told to invoke pending watchers, it
		4396	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4397	thread to continue:
		4398
		4399	static void
		4400	real_invoke_pending (EV_P)
		4401	{
		4402	userdata *u = ev_userdata (EV_A);
		4403
		4404	pthread_mutex_lock (&u->lock);
		4405	ev_invoke_pending (EV_A);
		4406	pthread_cond_signal (&u->invoke_cv);
		4407	pthread_mutex_unlock (&u->lock);
		4408	}
		4409
		4410	Whenever you want to start/stop a watcher or do other modifications to an
		4411	event loop, you will now have to lock:
		4412
		4413	ev_timer timeout_watcher;
		4414	userdata *u = ev_userdata (EV_A);
		4415
		4416	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4417
		4418	pthread_mutex_lock (&u->lock);
		4419	ev_timer_start (EV_A_ &timeout_watcher);
		4420	ev_async_send (EV_A_ &u->async_w);
		4421	pthread_mutex_unlock (&u->lock);
		4422
		4423	Note that sending the C<ev_async> watcher is required because otherwise
		4424	an event loop currently blocking in the kernel will have no knowledge
		4425	about the newly added timer. By waking up the loop it will pick up any new
		4426	watchers in the next event loop iteration.
		4427
3268	=head2 COROUTINES	4428	=head3 COROUTINES
3269		4429
3270	Libev is much more accommodating to coroutines ("cooperative threads"):	4430	Libev is very accommodating to coroutines ("cooperative threads"):
3271	libev fully supports nesting calls to it's functions from different	4431	libev fully supports nesting calls to its functions from different
3272	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4432	coroutines (e.g. you can call C<ev_run> on the same loop from two
3273	different coroutines and switch freely between both coroutines running the	4433	different coroutines, and switch freely between both coroutines running
3274	loop, as long as you don't confuse yourself). The only exception is that	4434	the loop, as long as you don't confuse yourself). The only exception is
3275	you must not do this from C<ev_periodic> reschedule callbacks.	4435	that you must not do this from C<ev_periodic> reschedule callbacks.
3276		4436
3277	Care has been invested into making sure that libev does not keep local	4437	Care has been taken to ensure that libev does not keep local state inside
3278	state inside C<ev_loop>, and other calls do not usually allow coroutine	4438	C<ev_run>, and other calls do not usually allow for coroutine switches as
3279	switches.	4439	they do not call any callbacks.
3280		4440
		4441	=head2 COMPILER WARNINGS
3281		4442
3282	=head1 COMPLEXITIES	4443	Depending on your compiler and compiler settings, you might get no or a
		4444	lot of warnings when compiling libev code. Some people are apparently
		4445	scared by this.
3283		4446
3284	In this section the complexities of (many of) the algorithms used inside	4447	However, these are unavoidable for many reasons. For one, each compiler
3285	libev will be explained. For complexity discussions about backends see the	4448	has different warnings, and each user has different tastes regarding
3286	documentation for C<ev_default_init>.	4449	warning options. "Warn-free" code therefore cannot be a goal except when
		4450	targeting a specific compiler and compiler-version.
3287		4451
3288	All of the following are about amortised time: If an array needs to be	4452	Another reason is that some compiler warnings require elaborate
3289	extended, libev needs to realloc and move the whole array, but this	4453	workarounds, or other changes to the code that make it less clear and less
3290	happens asymptotically never with higher number of elements, so O(1) might	4454	maintainable.
3291	mean it might do a lengthy realloc operation in rare cases, but on average
3292	it is much faster and asymptotically approaches constant time.
3293		4455
3294	=over 4	4456	And of course, some compiler warnings are just plain stupid, or simply
		4457	wrong (because they don't actually warn about the condition their message
		4458	seems to warn about). For example, certain older gcc versions had some
		4459	warnings that resulted in an extreme number of false positives. These have
		4460	been fixed, but some people still insist on making code warn-free with
		4461	such buggy versions.
3295		4462
3296	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	4463	While libev is written to generate as few warnings as possible,
		4464	"warn-free" code is not a goal, and it is recommended not to build libev
		4465	with any compiler warnings enabled unless you are prepared to cope with
		4466	them (e.g. by ignoring them). Remember that warnings are just that:
		4467	warnings, not errors, or proof of bugs.
3297		4468
3298	This means that, when you have a watcher that triggers in one hour and
3299	there are 100 watchers that would trigger before that then inserting will
3300	have to skip roughly seven (C<ld 100>) of these watchers.
3301		4469
3302	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	4470	=head2 VALGRIND
3303		4471
3304	That means that changing a timer costs less than removing/adding them	4472	Valgrind has a special section here because it is a popular tool that is
3305	as only the relative motion in the event queue has to be paid for.	4473	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3306		4474
3307	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	4475	If you think you found a bug (memory leak, uninitialised data access etc.)
		4476	in libev, then check twice: If valgrind reports something like:
3308		4477
3309	These just add the watcher into an array or at the head of a list.	4478	==2274== definitely lost: 0 bytes in 0 blocks.
		4479	==2274== possibly lost: 0 bytes in 0 blocks.
		4480	==2274== still reachable: 256 bytes in 1 blocks.
3310		4481
3311	=item Stopping check/prepare/idle/fork/async watchers: O(1)	4482	Then there is no memory leak, just as memory accounted to global variables
		4483	is not a memleak - the memory is still being referenced, and didn't leak.
3312		4484
3313	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	4485	Similarly, under some circumstances, valgrind might report kernel bugs
		4486	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		4487	although an acceptable workaround has been found here), or it might be
		4488	confused.
3314		4489
3315	These watchers are stored in lists then need to be walked to find the	4490	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3316	correct watcher to remove. The lists are usually short (you don't usually	4491	make it into some kind of religion.
3317	have many watchers waiting for the same fd or signal).
3318		4492
3319	=item Finding the next timer in each loop iteration: O(1)	4493	If you are unsure about something, feel free to contact the mailing list
		4494	with the full valgrind report and an explanation on why you think this
		4495	is a bug in libev (best check the archives, too :). However, don't be
		4496	annoyed when you get a brisk "this is no bug" answer and take the chance
		4497	of learning how to interpret valgrind properly.
3320		4498
3321	By virtue of using a binary or 4-heap, the next timer is always found at a	4499	If you need, for some reason, empty reports from valgrind for your project
3322	fixed position in the storage array.	4500	I suggest using suppression lists.
3323		4501
3324	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3325		4502
3326	A change means an I/O watcher gets started or stopped, which requires	4503	=head1 PORTABILITY NOTES
3327	libev to recalculate its status (and possibly tell the kernel, depending
3328	on backend and whether C<ev_io_set> was used).
3329		4504
3330	=item Activating one watcher (putting it into the pending state): O(1)	4505	=head2 GNU/LINUX 32 BIT LIMITATIONS
3331		4506
3332	=item Priority handling: O(number_of_priorities)	4507	GNU/Linux is the only common platform that supports 64 bit file/large file
		4508	interfaces but I<disables> them by default.
3333		4509
3334	Priorities are implemented by allocating some space for each	4510	That means that libev compiled in the default environment doesn't support
3335	priority. When doing priority-based operations, libev usually has to	4511	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
3336	linearly search all the priorities, but starting/stopping and activating
3337	watchers becomes O(1) w.r.t. priority handling.
3338		4512
3339	=item Sending an ev_async: O(1)	4513	Unfortunately, many programs try to work around this GNU/Linux issue
		4514	by enabling the large file API, which makes them incompatible with the
		4515	standard libev compiled for their system.
3340		4516
3341	=item Processing ev_async_send: O(number_of_async_watchers)	4517	Likewise, libev cannot enable the large file API itself as this would
		4518	suddenly make it incompatible to the default compile time environment,
		4519	i.e. all programs not using special compile switches.
3342		4520
3343	=item Processing signals: O(max_signal_number)	4521	=head2 OS/X AND DARWIN BUGS
3344		4522
3345	Sending involves a system call I<iff> there were no other C<ev_async_send>	4523	The whole thing is a bug if you ask me - basically any system interface
3346	calls in the current loop iteration. Checking for async and signal events	4524	you touch is broken, whether it is locales, poll, kqueue or even the
3347	involves iterating over all running async watchers or all signal numbers.	4525	OpenGL drivers.
3348		4526
3349	=back	4527	=head3 C<kqueue> is buggy
3350		4528
		4529	The kqueue syscall is broken in all known versions - most versions support
		4530	only sockets, many support pipes.
3351		4531
		4532	Libev tries to work around this by not using C<kqueue> by default on
		4533	this rotten platform, but of course you can still ask for it when creating
		4534	a loop.
		4535
		4536	=head3 C<poll> is buggy
		4537
		4538	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4539	implementation by something calling C<kqueue> internally around the 10.5.6
		4540	release, so now C<kqueue> I<and> C<poll> are broken.
		4541
		4542	Libev tries to work around this by not using C<poll> by default on
		4543	this rotten platform, but of course you can still ask for it when creating
		4544	a loop.
		4545
		4546	=head3 C<select> is buggy
		4547
		4548	All that's left is C<select>, and of course Apple found a way to fuck this
		4549	one up as well: On OS/X, C<select> actively limits the number of file
		4550	descriptors you can pass in to 1024 - your program suddenly crashes when
		4551	you use more.
		4552
		4553	There is an undocumented "workaround" for this - defining
		4554	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4555	work on OS/X.
		4556
		4557	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4558
		4559	=head3 C<errno> reentrancy
		4560
		4561	The default compile environment on Solaris is unfortunately so
		4562	thread-unsafe that you can't even use components/libraries compiled
		4563	without C<-D_REENTRANT> (as long as they use C<errno>), which, of course,
		4564	isn't defined by default.
		4565
		4566	If you want to use libev in threaded environments you have to make sure
		4567	it's compiled with C<_REENTRANT> defined.
		4568
		4569	=head3 Event port backend
		4570
		4571	The scalable event interface for Solaris is called "event ports". Unfortunately,
		4572	this mechanism is very buggy. If you run into high CPU usage, your program
		4573	freezes or you get a large number of spurious wakeups, make sure you have
		4574	all the relevant and latest kernel patches applied. No, I don't know which
		4575	ones, but there are multiple ones.
		4576
		4577	If you can't get it to work, you can try running the program by setting
		4578	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4579	C<select> backends.
		4580
		4581	=head2 AIX POLL BUG
		4582
		4583	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4584	this by trying to avoid the poll backend altogether (i.e. it's not even
		4585	compiled in), which normally isn't a big problem as C<select> works fine
		4586	with large bitsets, and AIX is dead anyway.
		4587
3352	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4588	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4589
		4590	=head3 General issues
3353		4591
3354	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4592	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3355	requires, and its I/O model is fundamentally incompatible with the POSIX	4593	requires, and its I/O model is fundamentally incompatible with the POSIX
3356	model. Libev still offers limited functionality on this platform in	4594	model. Libev still offers limited functionality on this platform in
3357	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4595	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3358	descriptors. This only applies when using Win32 natively, not when using	4596	descriptors. This only applies when using Win32 natively, not when using
3359	e.g. cygwin.	4597	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4598	as every compielr comes with a slightly differently broken/incompatible
		4599	environment.
3360		4600
3361	Lifting these limitations would basically require the full	4601	Lifting these limitations would basically require the full
3362	re-implementation of the I/O system. If you are into these kinds of	4602	re-implementation of the I/O system. If you are into this kind of thing,
3363	things, then note that glib does exactly that for you in a very portable	4603	then note that glib does exactly that for you in a very portable way (note
3364	way (note also that glib is the slowest event library known to man).	4604	also that glib is the slowest event library known to man).
3365		4605
3366	There is no supported compilation method available on windows except	4606	There is no supported compilation method available on windows except
3367	embedding it into other applications.	4607	embedding it into other applications.
		4608
		4609	Sensible signal handling is officially unsupported by Microsoft - libev
		4610	tries its best, but under most conditions, signals will simply not work.
3368		4611
3369	Not a libev limitation but worth mentioning: windows apparently doesn't	4612	Not a libev limitation but worth mentioning: windows apparently doesn't
3370	accept large writes: instead of resulting in a partial write, windows will	4613	accept large writes: instead of resulting in a partial write, windows will
3371	either accept everything or return C<ENOBUFS> if the buffer is too large,	4614	either accept everything or return C<ENOBUFS> if the buffer is too large,
3372	so make sure you only write small amounts into your sockets (less than a	4615	so make sure you only write small amounts into your sockets (less than a
3373	megabyte seems safe, but thsi apparently depends on the amount of memory	4616	megabyte seems safe, but this apparently depends on the amount of memory
3374	available).	4617	available).
3375		4618
3376	Due to the many, low, and arbitrary limits on the win32 platform and	4619	Due to the many, low, and arbitrary limits on the win32 platform and
3377	the abysmal performance of winsockets, using a large number of sockets	4620	the abysmal performance of winsockets, using a large number of sockets
3378	is not recommended (and not reasonable). If your program needs to use	4621	is not recommended (and not reasonable). If your program needs to use
3379	more than a hundred or so sockets, then likely it needs to use a totally	4622	more than a hundred or so sockets, then likely it needs to use a totally
3380	different implementation for windows, as libev offers the POSIX readiness	4623	different implementation for windows, as libev offers the POSIX readiness
3381	notification model, which cannot be implemented efficiently on windows	4624	notification model, which cannot be implemented efficiently on windows
3382	(Microsoft monopoly games).	4625	(due to Microsoft monopoly games).
3383		4626
3384	A typical way to use libev under windows is to embed it (see the embedding	4627	A typical way to use libev under windows is to embed it (see the embedding
3385	section for details) and use the following F<evwrap.h> header file instead	4628	section for details) and use the following F<evwrap.h> header file instead
3386	of F<ev.h>:	4629	of F<ev.h>:
3387		4630
…		…
3389	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	4632	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3390		4633
3391	#include "ev.h"	4634	#include "ev.h"
3392		4635
3393	And compile the following F<evwrap.c> file into your project (make sure	4636	And compile the following F<evwrap.c> file into your project (make sure
3394	you do I<not> compile the F<ev.c> or any other embedded soruce files!):	4637	you do I<not> compile the F<ev.c> or any other embedded source files!):
3395		4638
3396	#include "evwrap.h"	4639	#include "evwrap.h"
3397	#include "ev.c"	4640	#include "ev.c"
3398		4641
3399	=over 4
3400
3401	=item The winsocket select function	4642	=head3 The winsocket C<select> function
3402		4643
3403	The winsocket C<select> function doesn't follow POSIX in that it	4644	The winsocket C<select> function doesn't follow POSIX in that it
3404	requires socket I<handles> and not socket I<file descriptors> (it is	4645	requires socket I<handles> and not socket I<file descriptors> (it is
3405	also extremely buggy). This makes select very inefficient, and also	4646	also extremely buggy). This makes select very inefficient, and also
3406	requires a mapping from file descriptors to socket handles (the Microsoft	4647	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3415	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4656	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3416		4657
3417	Note that winsockets handling of fd sets is O(n), so you can easily get a	4658	Note that winsockets handling of fd sets is O(n), so you can easily get a
3418	complexity in the O(n²) range when using win32.	4659	complexity in the O(n²) range when using win32.
3419		4660
3420	=item Limited number of file descriptors	4661	=head3 Limited number of file descriptors
3421		4662
3422	Windows has numerous arbitrary (and low) limits on things.	4663	Windows has numerous arbitrary (and low) limits on things.
3423		4664
3424	Early versions of winsocket's select only supported waiting for a maximum	4665	Early versions of winsocket's select only supported waiting for a maximum
3425	of C<64> handles (probably owning to the fact that all windows kernels	4666	of C<64> handles (probably owning to the fact that all windows kernels
3426	can only wait for C<64> things at the same time internally; Microsoft	4667	can only wait for C<64> things at the same time internally; Microsoft
3427	recommends spawning a chain of threads and wait for 63 handles and the	4668	recommends spawning a chain of threads and wait for 63 handles and the
3428	previous thread in each. Great).	4669	previous thread in each. Sounds great!).
3429		4670
3430	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4671	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3431	to some high number (e.g. C<2048>) before compiling the winsocket select	4672	to some high number (e.g. C<2048>) before compiling the winsocket select
3432	call (which might be in libev or elsewhere, for example, perl does its own	4673	call (which might be in libev or elsewhere, for example, perl and many
3433	select emulation on windows).	4674	other interpreters do their own select emulation on windows).
3434		4675
3435	Another limit is the number of file descriptors in the Microsoft runtime	4676	Another limit is the number of file descriptors in the Microsoft runtime
3436	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4677	libraries, which by default is C<64> (there must be a hidden I<64>
3437	or something like this inside Microsoft). You can increase this by calling	4678	fetish or something like this inside Microsoft). You can increase this
3438	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4679	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3439	arbitrary limit), but is broken in many versions of the Microsoft runtime	4680	(another arbitrary limit), but is broken in many versions of the Microsoft
3440	libraries.
3441
3442	This might get you to about C<512> or C<2048> sockets (depending on	4681	runtime libraries. This might get you to about C<512> or C<2048> sockets
3443	windows version and/or the phase of the moon). To get more, you need to	4682	(depending on windows version and/or the phase of the moon). To get more,
3444	wrap all I/O functions and provide your own fd management, but the cost of	4683	you need to wrap all I/O functions and provide your own fd management, but
3445	calling select (O(n²)) will likely make this unworkable.	4684	the cost of calling select (O(n²)) will likely make this unworkable.
3446		4685
3447	=back
3448
3449
3450	=head1 PORTABILITY REQUIREMENTS	4686	=head2 PORTABILITY REQUIREMENTS
3451		4687
3452	In addition to a working ISO-C implementation, libev relies on a few	4688	In addition to a working ISO-C implementation and of course the
3453	additional extensions:	4689	backend-specific APIs, libev relies on a few additional extensions:
3454		4690
3455	=over 4	4691	=over 4
3456		4692
3457	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	4693	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3458	calling conventions regardless of C<ev_watcher_type *>.	4694	calling conventions regardless of C<ev_watcher_type *>.
…		…
3464	calls them using an C<ev_watcher *> internally.	4700	calls them using an C<ev_watcher *> internally.
3465		4701
3466	=item C<sig_atomic_t volatile> must be thread-atomic as well	4702	=item C<sig_atomic_t volatile> must be thread-atomic as well
3467		4703
3468	The type C<sig_atomic_t volatile> (or whatever is defined as	4704	The type C<sig_atomic_t volatile> (or whatever is defined as
3469	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	4705	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3470	threads. This is not part of the specification for C<sig_atomic_t>, but is	4706	threads. This is not part of the specification for C<sig_atomic_t>, but is
3471	believed to be sufficiently portable.	4707	believed to be sufficiently portable.
3472		4708
3473	=item C<sigprocmask> must work in a threaded environment	4709	=item C<sigprocmask> must work in a threaded environment
3474		4710
…		…
3483	except the initial one, and run the default loop in the initial thread as	4719	except the initial one, and run the default loop in the initial thread as
3484	well.	4720	well.
3485		4721
3486	=item C<long> must be large enough for common memory allocation sizes	4722	=item C<long> must be large enough for common memory allocation sizes
3487		4723
3488	To improve portability and simplify using libev, libev uses C<long>	4724	To improve portability and simplify its API, libev uses C<long> internally
3489	internally instead of C<size_t> when allocating its data structures. On	4725	instead of C<size_t> when allocating its data structures. On non-POSIX
3490	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4726	systems (Microsoft...) this might be unexpectedly low, but is still at
3491	is still at least 31 bits everywhere, which is enough for hundreds of	4727	least 31 bits everywhere, which is enough for hundreds of millions of
3492	millions of watchers.	4728	watchers.
3493		4729
3494	=item C<double> must hold a time value in seconds with enough accuracy	4730	=item C<double> must hold a time value in seconds with enough accuracy
3495		4731
3496	The type C<double> is used to represent timestamps. It is required to	4732	The type C<double> is used to represent timestamps. It is required to
3497	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4733	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3498	enough for at least into the year 4000. This requirement is fulfilled by	4734	good enough for at least into the year 4000 with millisecond accuracy
		4735	(the design goal for libev). This requirement is overfulfilled by
3499	implementations implementing IEEE 754 (basically all existing ones).	4736	implementations using IEEE 754, which is basically all existing ones. With
		4737	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
3500		4738
3501	=back	4739	=back
3502		4740
3503	If you know of other additional requirements drop me a note.	4741	If you know of other additional requirements drop me a note.
3504		4742
3505		4743
3506	=head1 COMPILER WARNINGS	4744	=head1 ALGORITHMIC COMPLEXITIES
3507		4745
3508	Depending on your compiler and compiler settings, you might get no or a	4746	In this section the complexities of (many of) the algorithms used inside
3509	lot of warnings when compiling libev code. Some people are apparently	4747	libev will be documented. For complexity discussions about backends see
3510	scared by this.	4748	the documentation for C<ev_default_init>.
3511		4749
3512	However, these are unavoidable for many reasons. For one, each compiler	4750	All of the following are about amortised time: If an array needs to be
3513	has different warnings, and each user has different tastes regarding	4751	extended, libev needs to realloc and move the whole array, but this
3514	warning options. "Warn-free" code therefore cannot be a goal except when	4752	happens asymptotically rarer with higher number of elements, so O(1) might
3515	targeting a specific compiler and compiler-version.	4753	mean that libev does a lengthy realloc operation in rare cases, but on
		4754	average it is much faster and asymptotically approaches constant time.
3516		4755
3517	Another reason is that some compiler warnings require elaborate	4756	=over 4
3518	workarounds, or other changes to the code that make it less clear and less
3519	maintainable.
3520		4757
3521	And of course, some compiler warnings are just plain stupid, or simply	4758	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3522	wrong (because they don't actually warn about the condition their message
3523	seems to warn about).
3524		4759
3525	While libev is written to generate as few warnings as possible,	4760	This means that, when you have a watcher that triggers in one hour and
3526	"warn-free" code is not a goal, and it is recommended not to build libev	4761	there are 100 watchers that would trigger before that, then inserting will
3527	with any compiler warnings enabled unless you are prepared to cope with	4762	have to skip roughly seven (C<ld 100>) of these watchers.
3528	them (e.g. by ignoring them). Remember that warnings are just that:
3529	warnings, not errors, or proof of bugs.
3530		4763
		4764	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3531		4765
3532	=head1 VALGRIND	4766	That means that changing a timer costs less than removing/adding them,
		4767	as only the relative motion in the event queue has to be paid for.
3533		4768
3534	Valgrind has a special section here because it is a popular tool that is	4769	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3535	highly useful, but valgrind reports are very hard to interpret.
3536		4770
3537	If you think you found a bug (memory leak, uninitialised data access etc.)	4771	These just add the watcher into an array or at the head of a list.
3538	in libev, then check twice: If valgrind reports something like:
3539		4772
3540	==2274== definitely lost: 0 bytes in 0 blocks.	4773	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3541	==2274== possibly lost: 0 bytes in 0 blocks.
3542	==2274== still reachable: 256 bytes in 1 blocks.
3543		4774
3544	Then there is no memory leak. Similarly, under some circumstances,	4775	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3545	valgrind might report kernel bugs as if it were a bug in libev, or it
3546	might be confused (it is a very good tool, but only a tool).
3547		4776
3548	If you are unsure about something, feel free to contact the mailing list	4777	These watchers are stored in lists, so they need to be walked to find the
3549	with the full valgrind report and an explanation on why you think this is	4778	correct watcher to remove. The lists are usually short (you don't usually
3550	a bug in libev. However, don't be annoyed when you get a brisk "this is	4779	have many watchers waiting for the same fd or signal: one is typical, two
3551	no bug" answer and take the chance of learning how to interpret valgrind	4780	is rare).
3552	properly.
3553		4781
3554	If you need, for some reason, empty reports from valgrind for your project	4782	=item Finding the next timer in each loop iteration: O(1)
3555	I suggest using suppression lists.
3556		4783
		4784	By virtue of using a binary or 4-heap, the next timer is always found at a
		4785	fixed position in the storage array.
		4786
		4787	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4788
		4789	A change means an I/O watcher gets started or stopped, which requires
		4790	libev to recalculate its status (and possibly tell the kernel, depending
		4791	on backend and whether C<ev_io_set> was used).
		4792
		4793	=item Activating one watcher (putting it into the pending state): O(1)
		4794
		4795	=item Priority handling: O(number_of_priorities)
		4796
		4797	Priorities are implemented by allocating some space for each
		4798	priority. When doing priority-based operations, libev usually has to
		4799	linearly search all the priorities, but starting/stopping and activating
		4800	watchers becomes O(1) with respect to priority handling.
		4801
		4802	=item Sending an ev_async: O(1)
		4803
		4804	=item Processing ev_async_send: O(number_of_async_watchers)
		4805
		4806	=item Processing signals: O(max_signal_number)
		4807
		4808	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4809	calls in the current loop iteration. Checking for async and signal events
		4810	involves iterating over all running async watchers or all signal numbers.
		4811
		4812	=back
		4813
		4814
		4815	=head1 PORTING FROM LIBEV 3.X TO 4.X
		4816
		4817	The major version 4 introduced some minor incompatible changes to the API.
		4818
		4819	At the moment, the C<ev.h> header file tries to implement superficial
		4820	compatibility, so most programs should still compile. Those might be
		4821	removed in later versions of libev, so better update early than late.
		4822
		4823	=over 4
		4824
		4825	=item function/symbol renames
		4826
		4827	A number of functions and symbols have been renamed:
		4828
		4829	ev_loop => ev_run
		4830	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		4831	EVLOOP_ONESHOT => EVRUN_ONCE
		4832
		4833	ev_unloop => ev_break
		4834	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		4835	EVUNLOOP_ONE => EVBREAK_ONE
		4836	EVUNLOOP_ALL => EVBREAK_ALL
		4837
		4838	EV_TIMEOUT => EV_TIMER
		4839
		4840	ev_loop_count => ev_iteration
		4841	ev_loop_depth => ev_depth
		4842	ev_loop_verify => ev_verify
		4843
		4844	Most functions working on C<struct ev_loop> objects don't have an
		4845	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		4846	associated constants have been renamed to not collide with the C<struct
		4847	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		4848	as all other watcher types. Note that C<ev_loop_fork> is still called
		4849	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		4850	typedef.
		4851
		4852	=item C<EV_COMPAT3> backwards compatibility mechanism
		4853
		4854	The backward compatibility mechanism can be controlled by
		4855	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		4856	section.
		4857
		4858	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		4859
		4860	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		4861	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		4862	and work, but the library code will of course be larger.
		4863
		4864	=back
		4865
		4866
		4867	=head1 GLOSSARY
		4868
		4869	=over 4
		4870
		4871	=item active
		4872
		4873	A watcher is active as long as it has been started (has been attached to
		4874	an event loop) but not yet stopped (disassociated from the event loop).
		4875
		4876	=item application
		4877
		4878	In this document, an application is whatever is using libev.
		4879
		4880	=item callback
		4881
		4882	The address of a function that is called when some event has been
		4883	detected. Callbacks are being passed the event loop, the watcher that
		4884	received the event, and the actual event bitset.
		4885
		4886	=item callback invocation
		4887
		4888	The act of calling the callback associated with a watcher.
		4889
		4890	=item event
		4891
		4892	A change of state of some external event, such as data now being available
		4893	for reading on a file descriptor, time having passed or simply not having
		4894	any other events happening anymore.
		4895
		4896	In libev, events are represented as single bits (such as C<EV_READ> or
		4897	C<EV_TIMER>).
		4898
		4899	=item event library
		4900
		4901	A software package implementing an event model and loop.
		4902
		4903	=item event loop
		4904
		4905	An entity that handles and processes external events and converts them
		4906	into callback invocations.
		4907
		4908	=item event model
		4909
		4910	The model used to describe how an event loop handles and processes
		4911	watchers and events.
		4912
		4913	=item pending
		4914
		4915	A watcher is pending as soon as the corresponding event has been detected,
		4916	and stops being pending as soon as the watcher will be invoked or its
		4917	pending status is explicitly cleared by the application.
		4918
		4919	A watcher can be pending, but not active. Stopping a watcher also clears
		4920	its pending status.
		4921
		4922	=item real time
		4923
		4924	The physical time that is observed. It is apparently strictly monotonic :)
		4925
		4926	=item wall-clock time
		4927
		4928	The time and date as shown on clocks. Unlike real time, it can actually
		4929	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4930	clock.
		4931
		4932	=item watcher
		4933
		4934	A data structure that describes interest in certain events. Watchers need
		4935	to be started (attached to an event loop) before they can receive events.
		4936
		4937	=item watcher invocation
		4938
		4939	The act of calling the callback associated with a watcher.
		4940
		4941	=back
3557		4942
3558	=head1 AUTHOR	4943	=head1 AUTHOR
3559		4944
3560	Marc Lehmann <libev@schmorp.de>.	4945	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3561		4946

Diff Legend

–	Removed lines
+	Added lines
<	Changed lines
>	Changed lines