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…		…
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
		14	#include <stdio.h> // for puts
		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
18		20
19	// all watcher callbacks have a similar signature	21	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	22	// this callback is called when data is readable on stdin
21	static void	23	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	25	{
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
…		…
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_unloop (EV_A_ EVUNLOOP_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_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	42	}
…		…
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
…		…
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>
282	types of such loops, the I<default> loop, which supports signals and child	298	is I<not> optional in this case, as there is also an C<ev_loop>
283	events, and dynamically created loops which do not.	299	I<function>).
		300
		301	The library knows two types of such loops, the I<default> loop, which
		302	supports signals and child events, and dynamically created loops which do
		303	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
…		…
377	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and	416	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
378	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	417	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
379		418
380	=item C<EVBACKEND_EPOLL> (value 4, Linux)	419	=item C<EVBACKEND_EPOLL> (value 4, Linux)
381		420
		421	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		422	kernels).
		423
382	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,
383	but it scales phenomenally better. While poll and select usually scale	425	but it scales phenomenally better. While poll and select usually scale
384	like O(total_fds) where n is the total number of fds (or the highest fd),	426	like O(total_fds) where n is the total number of fds (or the highest fd),
385	epoll scales either O(1) or O(active_fds). The epoll design has a number	427	epoll scales either O(1) or O(active_fds).
386	of shortcomings, such as silently dropping events in some hard-to-detect	428
387	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
388	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.
389		445
390	While stopping, setting and starting an I/O watcher in the same iteration	446	While stopping, setting and starting an I/O watcher in the same iteration
391	will result in some caching, there is still a system call per such incident	447	will result in some caching, there is still a system call per such
392	(because the fd could point to a different file description now), so its	448	incident (because the same I<file descriptor> could point to a different
393	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	449	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
394	very well if you register events for both fds.	450	file descriptors might not work very well if you register events for both
395		451	file descriptors.
396	Please note that epoll sometimes generates spurious notifications, so you
397	need to use non-blocking I/O or other means to avoid blocking when no data
398	(or space) is available.
399		452
400	Best performance from this backend is achieved by not unregistering all	453	Best performance from this backend is achieved by not unregistering all
401	watchers for a file descriptor until it has been closed, if possible,	454	watchers for a file descriptor until it has been closed, if possible,
402	i.e. keep at least one watcher active per fd at all times. Stopping and	455	i.e. keep at least one watcher active per fd at all times. Stopping and
403	starting a watcher (without re-setting it) also usually doesn't cause	456	starting a watcher (without re-setting it) also usually doesn't cause
404	extra overhead.	457	extra overhead. A fork can both result in spurious notifications as well
		458	as in libev having to destroy and recreate the epoll object, which can
		459	take considerable time and thus should be avoided.
		460
		461	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		462	faster than epoll for maybe up to a hundred file descriptors, depending on
		463	the usage. So sad.
405		464
406	While nominally embeddable in other event loops, this feature is broken in	465	While nominally embeddable in other event loops, this feature is broken in
407	all kernel versions tested so far.	466	all kernel versions tested so far.
408		467
409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	468	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
410	C<EVBACKEND_POLL>.	469	C<EVBACKEND_POLL>.
411		470
412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	471	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
413		472
414	Kqueue deserves special mention, as at the time of this writing, it was	473	Kqueue deserves special mention, as at the time of this writing, it
415	broken on all BSDs except NetBSD (usually it doesn't work reliably with	474	was broken on all BSDs except NetBSD (usually it doesn't work reliably
416	anything but sockets and pipes, except on Darwin, where of course it's	475	with anything but sockets and pipes, except on Darwin, where of course
417	completely useless). For this reason it's not being "auto-detected" unless	476	it's completely useless). Unlike epoll, however, whose brokenness
418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or	477	is by design, these kqueue bugs can (and eventually will) be fixed
419	libev was compiled on a known-to-be-good (-enough) system like NetBSD.	478	without API changes to existing programs. For this reason it's not being
		479	"auto-detected" unless you explicitly specify it in the flags (i.e. using
		480	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		481	system like NetBSD.
420		482
421	You still can embed kqueue into a normal poll or select backend and use it	483	You still can embed kqueue into a normal poll or select backend and use it
422	only for sockets (after having made sure that sockets work with kqueue on	484	only for sockets (after having made sure that sockets work with kqueue on
423	the target platform). See C<ev_embed> watchers for more info.	485	the target platform). See C<ev_embed> watchers for more info.
424		486
425	It scales in the same way as the epoll backend, but the interface to the	487	It scales in the same way as the epoll backend, but the interface to the
426	kernel is more efficient (which says nothing about its actual speed, of	488	kernel is more efficient (which says nothing about its actual speed, of
427	course). While stopping, setting and starting an I/O watcher does never	489	course). While stopping, setting and starting an I/O watcher does never
428	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	490	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
429	two event changes per incident. Support for C<fork ()> is very bad and it	491	two event changes per incident. Support for C<fork ()> is very bad (but
430	drops fds silently in similarly hard-to-detect cases.	492	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		493	cases
431		494
432	This backend usually performs well under most conditions.	495	This backend usually performs well under most conditions.
433		496
434	While nominally embeddable in other event loops, this doesn't work	497	While nominally embeddable in other event loops, this doesn't work
435	everywhere, so you might need to test for this. And since it is broken	498	everywhere, so you might need to test for this. And since it is broken
436	almost everywhere, you should only use it when you have a lot of sockets	499	almost everywhere, you should only use it when you have a lot of sockets
437	(for which it usually works), by embedding it into another event loop	500	(for which it usually works), by embedding it into another event loop
438	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,	501	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
439	using it only for sockets.	502	also broken on OS X)) and, did I mention it, using it only for sockets.
440		503
441	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	504	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
442	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with	505	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
443	C<NOTE_EOF>.	506	C<NOTE_EOF>.
444		507
…		…
464	might perform better.	527	might perform better.
465		528
466	On the positive side, with the exception of the spurious readiness	529	On the positive side, with the exception of the spurious readiness
467	notifications, this backend actually performed fully to specification	530	notifications, this backend actually performed fully to specification
468	in all tests and is fully embeddable, which is a rare feat among the	531	in all tests and is fully embeddable, which is a rare feat among the
469	OS-specific backends.	532	OS-specific backends (I vastly prefer correctness over speed hacks).
470		533
471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	534	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
472	C<EVBACKEND_POLL>.	535	C<EVBACKEND_POLL>.
473		536
474	=item C<EVBACKEND_ALL>	537	=item C<EVBACKEND_ALL>
…		…
479		542
480	It is definitely not recommended to use this flag.	543	It is definitely not recommended to use this flag.
481		544
482	=back	545	=back
483		546
484	If one or more of these are or'ed into the flags value, then only these	547	If one or more of the backend flags are or'ed into the flags value,
485	backends will be tried (in the reverse order as listed here). If none are	548	then only these backends will be tried (in the reverse order as listed
486	specified, all backends in C<ev_recommended_backends ()> will be tried.	549	here). If none are specified, all backends in C<ev_recommended_backends
		550	()> will be tried.
487		551
488	Example: This is the most typical usage.	552	Example: This is the most typical usage.
489		553
490	if (!ev_default_loop (0))	554	if (!ev_default_loop (0))
491	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	555	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
503	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	567	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
504		568
505	=item struct ev_loop *ev_loop_new (unsigned int flags)	569	=item struct ev_loop *ev_loop_new (unsigned int flags)
506		570
507	Similar to C<ev_default_loop>, but always creates a new event loop that is	571	Similar to C<ev_default_loop>, but always creates a new event loop that is
508	always distinct from the default loop. Unlike the default loop, it cannot	572	always distinct from the default loop.
509	handle signal and child watchers, and attempts to do so will be greeted by
510	undefined behaviour (or a failed assertion if assertions are enabled).
511		573
512	Note that this function I<is> thread-safe, and the recommended way to use	574	Note that this function I<is> thread-safe, and one common way to use
513	libev with threads is indeed to create one loop per thread, and using the	575	libev with threads is indeed to create one loop per thread, and using the
514	default loop in the "main" or "initial" thread.	576	default loop in the "main" or "initial" thread.
515		577
516	Example: Try to create a event loop that uses epoll and nothing else.	578	Example: Try to create a event loop that uses epoll and nothing else.
517		579
…		…
519	if (!epoller)	581	if (!epoller)
520	fatal ("no epoll found here, maybe it hides under your chair");	582	fatal ("no epoll found here, maybe it hides under your chair");
521		583
522	=item ev_default_destroy ()	584	=item ev_default_destroy ()
523		585
524	Destroys the default loop again (frees all memory and kernel state	586	Destroys the default loop (frees all memory and kernel state etc.). None
525	etc.). None of the active event watchers will be stopped in the normal	587	of the active event watchers will be stopped in the normal sense, so
526	sense, so e.g. C<ev_is_active> might still return true. It is your	588	e.g. C<ev_is_active> might still return true. It is your responsibility to
527	responsibility to either stop all watchers cleanly yourself I<before>	589	either stop all watchers cleanly yourself I<before> calling this function,
528	calling this function, or cope with the fact afterwards (which is usually	590	or cope with the fact afterwards (which is usually the easiest thing, you
529	the easiest thing, you can just ignore the watchers and/or C<free ()> them	591	can just ignore the watchers and/or C<free ()> them for example).
530	for example).
531		592
532	Note that certain global state, such as signal state, will not be freed by	593	Note that certain global state, such as signal state (and installed signal
533	this function, and related watchers (such as signal and child watchers)	594	handlers), will not be freed by this function, and related watchers (such
534	would need to be stopped manually.	595	as signal and child watchers) would need to be stopped manually.
535		596
536	In general it is not advisable to call this function except in the	597	In general it is not advisable to call this function except in the
537	rare occasion where you really need to free e.g. the signal handling	598	rare occasion where you really need to free e.g. the signal handling
538	pipe fds. If you need dynamically allocated loops it is better to use	599	pipe fds. If you need dynamically allocated loops it is better to use
539	C<ev_loop_new> and C<ev_loop_destroy>).	600	C<ev_loop_new> and C<ev_loop_destroy>.
540		601
541	=item ev_loop_destroy (loop)	602	=item ev_loop_destroy (loop)
542		603
543	Like C<ev_default_destroy>, but destroys an event loop created by an	604	Like C<ev_default_destroy>, but destroys an event loop created by an
544	earlier call to C<ev_loop_new>.	605	earlier call to C<ev_loop_new>.
…		…
550	name, you can call it anytime, but it makes most sense after forking, in	611	name, you can call it anytime, but it makes most sense after forking, in
551	the child process (or both child and parent, but that again makes little	612	the child process (or both child and parent, but that again makes little
552	sense). You I<must> call it in the child before using any of the libev	613	sense). You I<must> call it in the child before using any of the libev
553	functions, and it will only take effect at the next C<ev_loop> iteration.	614	functions, and it will only take effect at the next C<ev_loop> iteration.
554		615
		616	Again, you I<have> to call it on I<any> loop that you want to re-use after
		617	a fork, I<even if you do not plan to use the loop in the parent>. This is
		618	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		619	during fork.
		620
555	On the other hand, you only need to call this function in the child	621	On the other hand, you only need to call this function in the child
556	process if and only if you want to use the event library in the child. If	622	process if and only if you want to use the event loop in the child. If you
557	you just fork+exec, you don't have to call it at all.	623	just fork+exec or create a new loop in the child, you don't have to call
		624	it at all.
558		625
559	The function itself is quite fast and it's usually not a problem to call	626	The function itself is quite fast and it's usually not a problem to call
560	it just in case after a fork. To make this easy, the function will fit in	627	it just in case after a fork. To make this easy, the function will fit in
561	quite nicely into a call to C<pthread_atfork>:	628	quite nicely into a call to C<pthread_atfork>:
562		629
…		…
564		631
565	=item ev_loop_fork (loop)	632	=item ev_loop_fork (loop)
566		633
567	Like C<ev_default_fork>, but acts on an event loop created by	634	Like C<ev_default_fork>, but acts on an event loop created by
568	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	635	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
569	after fork that you want to re-use in the child, and how you do this is	636	after fork that you want to re-use in the child, and how you keep track of
570	entirely your own problem.	637	them is entirely your own problem.
571		638
572	=item int ev_is_default_loop (loop)	639	=item int ev_is_default_loop (loop)
573		640
574	Returns true when the given loop is, in fact, the default loop, and false	641	Returns true when the given loop is, in fact, the default loop, and false
575	otherwise.	642	otherwise.
576		643
577	=item unsigned int ev_loop_count (loop)	644	=item unsigned int ev_iteration (loop)
578		645
579	Returns the count of loop iterations for the loop, which is identical to	646	Returns the current iteration count for the loop, which is identical to
580	the number of times libev did poll for new events. It starts at C<0> and	647	the number of times libev did poll for new events. It starts at C<0> and
581	happily wraps around with enough iterations.	648	happily wraps around with enough iterations.
582		649
583	This value can sometimes be useful as a generation counter of sorts (it	650	This value can sometimes be useful as a generation counter of sorts (it
584	"ticks" the number of loop iterations), as it roughly corresponds with	651	"ticks" the number of loop iterations), as it roughly corresponds with
585	C<ev_prepare> and C<ev_check> calls.	652	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		653	prepare and check phases.
		654
		655	=item unsigned int ev_depth (loop)
		656
		657	Returns the number of times C<ev_loop> was entered minus the number of
		658	times C<ev_loop> was exited, in other words, the recursion depth.
		659
		660	Outside C<ev_loop>, this number is zero. In a callback, this number is
		661	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),
		662	in which case it is higher.
		663
		664	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread
		665	etc.), doesn't count as "exit" - consider this as a hint to avoid such
		666	ungentleman behaviour unless it's really convenient.
586		667
587	=item unsigned int ev_backend (loop)	668	=item unsigned int ev_backend (loop)
588		669
589	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	670	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
590	use.	671	use.
…		…
605		686
606	This function is rarely useful, but when some event callback runs for a	687	This function is rarely useful, but when some event callback runs for a
607	very long time without entering the event loop, updating libev's idea of	688	very long time without entering the event loop, updating libev's idea of
608	the current time is a good idea.	689	the current time is a good idea.
609		690
610	See also "The special problem of time updates" in the C<ev_timer> section.	691	See also L<The special problem of time updates> in the C<ev_timer> section.
		692
		693	=item ev_suspend (loop)
		694
		695	=item ev_resume (loop)
		696
		697	These two functions suspend and resume a loop, for use when the loop is
		698	not used for a while and timeouts should not be processed.
		699
		700	A typical use case would be an interactive program such as a game: When
		701	the user presses C<^Z> to suspend the game and resumes it an hour later it
		702	would be best to handle timeouts as if no time had actually passed while
		703	the program was suspended. This can be achieved by calling C<ev_suspend>
		704	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		705	C<ev_resume> directly afterwards to resume timer processing.
		706
		707	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		708	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		709	will be rescheduled (that is, they will lose any events that would have
		710	occurred while suspended).
		711
		712	After calling C<ev_suspend> you B<must not> call I<any> function on the
		713	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		714	without a previous call to C<ev_suspend>.
		715
		716	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		717	event loop time (see C<ev_now_update>).
611		718
612	=item ev_loop (loop, int flags)	719	=item ev_loop (loop, int flags)
613		720
614	Finally, this is it, the event handler. This function usually is called	721	Finally, this is it, the event handler. This function usually is called
615	after you initialised all your watchers and you want to start handling	722	after you have initialised all your watchers and you want to start
616	events.	723	handling events.
617		724
618	If the flags argument is specified as C<0>, it will not return until	725	If the flags argument is specified as C<0>, it will not return until
619	either no event watchers are active anymore or C<ev_unloop> was called.	726	either no event watchers are active anymore or C<ev_unloop> was called.
620		727
621	Please note that an explicit C<ev_unloop> is usually better than	728	Please note that an explicit C<ev_unloop> is usually better than
…		…
631	the loop.	738	the loop.
632		739
633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	740	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
634	necessary) and will handle those and any already outstanding ones. It	741	necessary) and will handle those and any already outstanding ones. It
635	will block your process until at least one new event arrives (which could	742	will block your process until at least one new event arrives (which could
636	be an event internal to libev itself, so there is no guarentee that a	743	be an event internal to libev itself, so there is no guarantee that a
637	user-registered callback will be called), and will return after one	744	user-registered callback will be called), and will return after one
638	iteration of the loop.	745	iteration of the loop.
639		746
640	This is useful if you are waiting for some external event in conjunction	747	This is useful if you are waiting for some external event in conjunction
641	with something not expressible using other libev watchers (i.e. "roll your	748	with something not expressible using other libev watchers (i.e. "roll your
…		…
685	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	792	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
686	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	793	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
687		794
688	This "unloop state" will be cleared when entering C<ev_loop> again.	795	This "unloop state" will be cleared when entering C<ev_loop> again.
689		796
		797	It is safe to call C<ev_unloop> from outside any C<ev_loop> calls.
		798
690	=item ev_ref (loop)	799	=item ev_ref (loop)
691		800
692	=item ev_unref (loop)	801	=item ev_unref (loop)
693		802
694	Ref/unref can be used to add or remove a reference count on the event	803	Ref/unref can be used to add or remove a reference count on the event
695	loop: Every watcher keeps one reference, and as long as the reference	804	loop: Every watcher keeps one reference, and as long as the reference
696	count is nonzero, C<ev_loop> will not return on its own.	805	count is nonzero, C<ev_loop> will not return on its own.
697		806
698	If you have a watcher you never unregister that should not keep C<ev_loop>	807	This is useful when you have a watcher that you never intend to
699	from returning, call ev_unref() after starting, and ev_ref() before	808	unregister, but that nevertheless should not keep C<ev_loop> from
		809	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
700	stopping it.	810	before stopping it.
701		811
702	As an example, libev itself uses this for its internal signal pipe: It is	812	As an example, libev itself uses this for its internal signal pipe: It
703	not visible to the libev user and should not keep C<ev_loop> from exiting	813	is not visible to the libev user and should not keep C<ev_loop> from
704	if no event watchers registered by it are active. It is also an excellent	814	exiting if no event watchers registered by it are active. It is also an
705	way to do this for generic recurring timers or from within third-party	815	excellent way to do this for generic recurring timers or from within
706	libraries. Just remember to I<unref after start> and I<ref before stop>	816	third-party libraries. Just remember to I<unref after start> and I<ref
707	(but only if the watcher wasn't active before, or was active before,	817	before stop> (but only if the watcher wasn't active before, or was active
708	respectively).	818	before, respectively. Note also that libev might stop watchers itself
		819	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		820	in the callback).
709		821
710	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	822	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
711	running when nothing else is active.	823	running when nothing else is active.
712		824
713	struct ev_signal exitsig;	825	ev_signal exitsig;
714	ev_signal_init (&exitsig, sig_cb, SIGINT);	826	ev_signal_init (&exitsig, sig_cb, SIGINT);
715	ev_signal_start (loop, &exitsig);	827	ev_signal_start (loop, &exitsig);
716	evf_unref (loop);	828	evf_unref (loop);
717		829
718	Example: For some weird reason, unregister the above signal handler again.	830	Example: For some weird reason, unregister the above signal handler again.
…		…
742		854
743	By setting a higher I<io collect interval> you allow libev to spend more	855	By setting a higher I<io collect interval> you allow libev to spend more
744	time collecting I/O events, so you can handle more events per iteration,	856	time collecting I/O events, so you can handle more events per iteration,
745	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	857	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
746	C<ev_timer>) will be not affected. Setting this to a non-null value will	858	C<ev_timer>) will be not affected. Setting this to a non-null value will
747	introduce an additional C<ev_sleep ()> call into most loop iterations.	859	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		860	sleep time ensures that libev will not poll for I/O events more often then
		861	once per this interval, on average.
748		862
749	Likewise, by setting a higher I<timeout collect interval> you allow libev	863	Likewise, by setting a higher I<timeout collect interval> you allow libev
750	to spend more time collecting timeouts, at the expense of increased	864	to spend more time collecting timeouts, at the expense of increased
751	latency/jitter/inexactness (the watcher callback will be called	865	latency/jitter/inexactness (the watcher callback will be called
752	later). C<ev_io> watchers will not be affected. Setting this to a non-null	866	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
754		868
755	Many (busy) programs can usually benefit by setting the I/O collect	869	Many (busy) programs can usually benefit by setting the I/O collect
756	interval to a value near C<0.1> or so, which is often enough for	870	interval to a value near C<0.1> or so, which is often enough for
757	interactive servers (of course not for games), likewise for timeouts. It	871	interactive servers (of course not for games), likewise for timeouts. It
758	usually doesn't make much sense to set it to a lower value than C<0.01>,	872	usually doesn't make much sense to set it to a lower value than C<0.01>,
759	as this approaches the timing granularity of most systems.	873	as this approaches the timing granularity of most systems. Note that if
		874	you do transactions with the outside world and you can't increase the
		875	parallelity, then this setting will limit your transaction rate (if you
		876	need to poll once per transaction and the I/O collect interval is 0.01,
		877	then you can't do more than 100 transactions per second).
760		878
761	Setting the I<timeout collect interval> can improve the opportunity for	879	Setting the I<timeout collect interval> can improve the opportunity for
762	saving power, as the program will "bundle" timer callback invocations that	880	saving power, as the program will "bundle" timer callback invocations that
763	are "near" in time together, by delaying some, thus reducing the number of	881	are "near" in time together, by delaying some, thus reducing the number of
764	times the process sleeps and wakes up again. Another useful technique to	882	times the process sleeps and wakes up again. Another useful technique to
765	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	883	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
766	they fire on, say, one-second boundaries only.	884	they fire on, say, one-second boundaries only.
767		885
		886	Example: we only need 0.1s timeout granularity, and we wish not to poll
		887	more often than 100 times per second:
		888
		889	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		890	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		891
		892	=item ev_invoke_pending (loop)
		893
		894	This call will simply invoke all pending watchers while resetting their
		895	pending state. Normally, C<ev_loop> does this automatically when required,
		896	but when overriding the invoke callback this call comes handy.
		897
		898	=item int ev_pending_count (loop)
		899
		900	Returns the number of pending watchers - zero indicates that no watchers
		901	are pending.
		902
		903	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		904
		905	This overrides the invoke pending functionality of the loop: Instead of
		906	invoking all pending watchers when there are any, C<ev_loop> will call
		907	this callback instead. This is useful, for example, when you want to
		908	invoke the actual watchers inside another context (another thread etc.).
		909
		910	If you want to reset the callback, use C<ev_invoke_pending> as new
		911	callback.
		912
		913	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		914
		915	Sometimes you want to share the same loop between multiple threads. This
		916	can be done relatively simply by putting mutex_lock/unlock calls around
		917	each call to a libev function.
		918
		919	However, C<ev_loop> can run an indefinite time, so it is not feasible to
		920	wait for it to return. One way around this is to wake up the loop via
		921	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>
		922	and I<acquire> callbacks on the loop.
		923
		924	When set, then C<release> will be called just before the thread is
		925	suspended waiting for new events, and C<acquire> is called just
		926	afterwards.
		927
		928	Ideally, C<release> will just call your mutex_unlock function, and
		929	C<acquire> will just call the mutex_lock function again.
		930
		931	While event loop modifications are allowed between invocations of
		932	C<release> and C<acquire> (that's their only purpose after all), no
		933	modifications done will affect the event loop, i.e. adding watchers will
		934	have no effect on the set of file descriptors being watched, or the time
		935	waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it
		936	to take note of any changes you made.
		937
		938	In theory, threads executing C<ev_loop> will be async-cancel safe between
		939	invocations of C<release> and C<acquire>.
		940
		941	See also the locking example in the C<THREADS> section later in this
		942	document.
		943
		944	=item ev_set_userdata (loop, void *data)
		945
		946	=item ev_userdata (loop)
		947
		948	Set and retrieve a single C<void *> associated with a loop. When
		949	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		950	C<0.>
		951
		952	These two functions can be used to associate arbitrary data with a loop,
		953	and are intended solely for the C<invoke_pending_cb>, C<release> and
		954	C<acquire> callbacks described above, but of course can be (ab-)used for
		955	any other purpose as well.
		956
768	=item ev_loop_verify (loop)	957	=item ev_loop_verify (loop)
769		958
770	This function only does something when C<EV_VERIFY> support has been	959	This function only does something when C<EV_VERIFY> support has been
771	compiled in. which is the default for non-minimal builds. It tries to go	960	compiled in, which is the default for non-minimal builds. It tries to go
772	through all internal structures and checks them for validity. If anything	961	through all internal structures and checks them for validity. If anything
773	is found to be inconsistent, it will print an error message to standard	962	is found to be inconsistent, it will print an error message to standard
774	error and call C<abort ()>.	963	error and call C<abort ()>.
775		964
776	This can be used to catch bugs inside libev itself: under normal	965	This can be used to catch bugs inside libev itself: under normal
…		…
780	=back	969	=back
781		970
782		971
783	=head1 ANATOMY OF A WATCHER	972	=head1 ANATOMY OF A WATCHER
784		973
		974	In the following description, uppercase C<TYPE> in names stands for the
		975	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		976	watchers and C<ev_io_start> for I/O watchers.
		977
785	A watcher is a structure that you create and register to record your	978	A watcher is a structure that you create and register to record your
786	interest in some event. For instance, if you want to wait for STDIN to	979	interest in some event. For instance, if you want to wait for STDIN to
787	become readable, you would create an C<ev_io> watcher for that:	980	become readable, you would create an C<ev_io> watcher for that:
788		981
789	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	982	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
790	{	983	{
791	ev_io_stop (w);	984	ev_io_stop (w);
792	ev_unloop (loop, EVUNLOOP_ALL);	985	ev_unloop (loop, EVUNLOOP_ALL);
793	}	986	}
794		987
795	struct ev_loop *loop = ev_default_loop (0);	988	struct ev_loop *loop = ev_default_loop (0);
		989
796	struct ev_io stdin_watcher;	990	ev_io stdin_watcher;
		991
797	ev_init (&stdin_watcher, my_cb);	992	ev_init (&stdin_watcher, my_cb);
798	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	993	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
799	ev_io_start (loop, &stdin_watcher);	994	ev_io_start (loop, &stdin_watcher);
		995
800	ev_loop (loop, 0);	996	ev_loop (loop, 0);
801		997
802	As you can see, you are responsible for allocating the memory for your	998	As you can see, you are responsible for allocating the memory for your
803	watcher structures (and it is usually a bad idea to do this on the stack,	999	watcher structures (and it is I<usually> a bad idea to do this on the
804	although this can sometimes be quite valid).	1000	stack).
		1001
		1002	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		1003	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
805		1004
806	Each watcher structure must be initialised by a call to C<ev_init	1005	Each watcher structure must be initialised by a call to C<ev_init
807	(watcher *, callback)>, which expects a callback to be provided. This	1006	(watcher *, callback)>, which expects a callback to be provided. This
808	callback gets invoked each time the event occurs (or, in the case of I/O	1007	callback gets invoked each time the event occurs (or, in the case of I/O
809	watchers, each time the event loop detects that the file descriptor given	1008	watchers, each time the event loop detects that the file descriptor given
810	is readable and/or writable).	1009	is readable and/or writable).
811		1010
812	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1011	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
813	with arguments specific to this watcher type. There is also a macro	1012	macro to configure it, with arguments specific to the watcher type. There
814	to combine initialisation and setting in one call: C<< ev_<type>_init	1013	is also a macro to combine initialisation and setting in one call: C<<
815	(watcher *, callback, ...) >>.	1014	ev_TYPE_init (watcher *, callback, ...) >>.
816		1015
817	To make the watcher actually watch out for events, you have to start it	1016	To make the watcher actually watch out for events, you have to start it
818	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	1017	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
819	*) >>), and you can stop watching for events at any time by calling the	1018	*) >>), and you can stop watching for events at any time by calling the
820	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1019	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
821		1020
822	As long as your watcher is active (has been started but not stopped) you	1021	As long as your watcher is active (has been started but not stopped) you
823	must not touch the values stored in it. Most specifically you must never	1022	must not touch the values stored in it. Most specifically you must never
824	reinitialise it or call its C<set> macro.	1023	reinitialise it or call its C<ev_TYPE_set> macro.
825		1024
826	Each and every callback receives the event loop pointer as first, the	1025	Each and every callback receives the event loop pointer as first, the
827	registered watcher structure as second, and a bitset of received events as	1026	registered watcher structure as second, and a bitset of received events as
828	third argument.	1027	third argument.
829		1028
…		…
838	=item C<EV_WRITE>	1037	=item C<EV_WRITE>
839		1038
840	The file descriptor in the C<ev_io> watcher has become readable and/or	1039	The file descriptor in the C<ev_io> watcher has become readable and/or
841	writable.	1040	writable.
842		1041
843	=item C<EV_TIMEOUT>	1042	=item C<EV_TIMER>
844		1043
845	The C<ev_timer> watcher has timed out.	1044	The C<ev_timer> watcher has timed out.
846		1045
847	=item C<EV_PERIODIC>	1046	=item C<EV_PERIODIC>
848		1047
…		…
887		1086
888	=item C<EV_ASYNC>	1087	=item C<EV_ASYNC>
889		1088
890	The given async watcher has been asynchronously notified (see C<ev_async>).	1089	The given async watcher has been asynchronously notified (see C<ev_async>).
891		1090
		1091	=item C<EV_CUSTOM>
		1092
		1093	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1094	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		1095
892	=item C<EV_ERROR>	1096	=item C<EV_ERROR>
893		1097
894	An unspecified error has occurred, the watcher has been stopped. This might	1098	An unspecified error has occurred, the watcher has been stopped. This might
895	happen because the watcher could not be properly started because libev	1099	happen because the watcher could not be properly started because libev
896	ran out of memory, a file descriptor was found to be closed or any other	1100	ran out of memory, a file descriptor was found to be closed or any other
		1101	problem. Libev considers these application bugs.
		1102
897	problem. You best act on it by reporting the problem and somehow coping	1103	You best act on it by reporting the problem and somehow coping with the
898	with the watcher being stopped.	1104	watcher being stopped. Note that well-written programs should not receive
		1105	an error ever, so when your watcher receives it, this usually indicates a
		1106	bug in your program.
899		1107
900	Libev will usually signal a few "dummy" events together with an error, for	1108	Libev will usually signal a few "dummy" events together with an error, for
901	example it might indicate that a fd is readable or writable, and if your	1109	example it might indicate that a fd is readable or writable, and if your
902	callbacks is well-written it can just attempt the operation and cope with	1110	callbacks is well-written it can just attempt the operation and cope with
903	the error from read() or write(). This will not work in multi-threaded	1111	the error from read() or write(). This will not work in multi-threaded
…		…
906		1114
907	=back	1115	=back
908		1116
909	=head2 GENERIC WATCHER FUNCTIONS	1117	=head2 GENERIC WATCHER FUNCTIONS
910		1118
911	In the following description, C<TYPE> stands for the watcher type,
912	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
913
914	=over 4	1119	=over 4
915		1120
916	=item C<ev_init> (ev_TYPE *watcher, callback)	1121	=item C<ev_init> (ev_TYPE *watcher, callback)
917		1122
918	This macro initialises the generic portion of a watcher. The contents	1123	This macro initialises the generic portion of a watcher. The contents
…		…
923	which rolls both calls into one.	1128	which rolls both calls into one.
924		1129
925	You can reinitialise a watcher at any time as long as it has been stopped	1130	You can reinitialise a watcher at any time as long as it has been stopped
926	(or never started) and there are no pending events outstanding.	1131	(or never started) and there are no pending events outstanding.
927		1132
928	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1133	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
929	int revents)>.	1134	int revents)>.
930		1135
931	Example: Initialise an C<ev_io> watcher in two steps.	1136	Example: Initialise an C<ev_io> watcher in two steps.
932		1137
933	ev_io w;	1138	ev_io w;
934	ev_init (&w, my_cb);	1139	ev_init (&w, my_cb);
935	ev_io_set (&w, STDIN_FILENO, EV_READ);	1140	ev_io_set (&w, STDIN_FILENO, EV_READ);
936		1141
937	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1142	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
938		1143
939	This macro initialises the type-specific parts of a watcher. You need to	1144	This macro initialises the type-specific parts of a watcher. You need to
940	call C<ev_init> at least once before you call this macro, but you can	1145	call C<ev_init> at least once before you call this macro, but you can
941	call C<ev_TYPE_set> any number of times. You must not, however, call this	1146	call C<ev_TYPE_set> any number of times. You must not, however, call this
942	macro on a watcher that is active (it can be pending, however, which is a	1147	macro on a watcher that is active (it can be pending, however, which is a
…		…
955		1160
956	Example: Initialise and set an C<ev_io> watcher in one step.	1161	Example: Initialise and set an C<ev_io> watcher in one step.
957		1162
958	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1163	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
959		1164
960	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1165	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
961		1166
962	Starts (activates) the given watcher. Only active watchers will receive	1167	Starts (activates) the given watcher. Only active watchers will receive
963	events. If the watcher is already active nothing will happen.	1168	events. If the watcher is already active nothing will happen.
964		1169
965	Example: Start the C<ev_io> watcher that is being abused as example in this	1170	Example: Start the C<ev_io> watcher that is being abused as example in this
966	whole section.	1171	whole section.
967		1172
968	ev_io_start (EV_DEFAULT_UC, &w);	1173	ev_io_start (EV_DEFAULT_UC, &w);
969		1174
970	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1175	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
971		1176
972	Stops the given watcher again (if active) and clears the pending	1177	Stops the given watcher if active, and clears the pending status (whether
		1178	the watcher was active or not).
		1179
973	status. It is possible that stopped watchers are pending (for example,	1180	It is possible that stopped watchers are pending - for example,
974	non-repeating timers are being stopped when they become pending), but	1181	non-repeating timers are being stopped when they become pending - but
975	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1182	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
976	you want to free or reuse the memory used by the watcher it is therefore a	1183	pending. If you want to free or reuse the memory used by the watcher it is
977	good idea to always call its C<ev_TYPE_stop> function.	1184	therefore a good idea to always call its C<ev_TYPE_stop> function.
978		1185
979	=item bool ev_is_active (ev_TYPE *watcher)	1186	=item bool ev_is_active (ev_TYPE *watcher)
980		1187
981	Returns a true value iff the watcher is active (i.e. it has been started	1188	Returns a true value iff the watcher is active (i.e. it has been started
982	and not yet been stopped). As long as a watcher is active you must not modify	1189	and not yet been stopped). As long as a watcher is active you must not modify
…		…
998	=item ev_cb_set (ev_TYPE *watcher, callback)	1205	=item ev_cb_set (ev_TYPE *watcher, callback)
999		1206
1000	Change the callback. You can change the callback at virtually any time	1207	Change the callback. You can change the callback at virtually any time
1001	(modulo threads).	1208	(modulo threads).
1002		1209
1003	=item ev_set_priority (ev_TYPE *watcher, priority)	1210	=item ev_set_priority (ev_TYPE *watcher, int priority)
1004		1211
1005	=item int ev_priority (ev_TYPE *watcher)	1212	=item int ev_priority (ev_TYPE *watcher)
1006		1213
1007	Set and query the priority of the watcher. The priority is a small	1214	Set and query the priority of the watcher. The priority is a small
1008	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1215	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1009	(default: C<-2>). Pending watchers with higher priority will be invoked	1216	(default: C<-2>). Pending watchers with higher priority will be invoked
1010	before watchers with lower priority, but priority will not keep watchers	1217	before watchers with lower priority, but priority will not keep watchers
1011	from being executed (except for C<ev_idle> watchers).	1218	from being executed (except for C<ev_idle> watchers).
1012		1219
1013	This means that priorities are I<only> used for ordering callback
1014	invocation after new events have been received. This is useful, for
1015	example, to reduce latency after idling, or more often, to bind two
1016	watchers on the same event and make sure one is called first.
1017
1018	If you need to suppress invocation when higher priority events are pending	1220	If you need to suppress invocation when higher priority events are pending
1019	you need to look at C<ev_idle> watchers, which provide this functionality.	1221	you need to look at C<ev_idle> watchers, which provide this functionality.
1020		1222
1021	You I<must not> change the priority of a watcher as long as it is active or	1223	You I<must not> change the priority of a watcher as long as it is active or
1022	pending.	1224	pending.
1023		1225
		1226	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1227	fine, as long as you do not mind that the priority value you query might
		1228	or might not have been clamped to the valid range.
		1229
1024	The default priority used by watchers when no priority has been set is	1230	The default priority used by watchers when no priority has been set is
1025	always C<0>, which is supposed to not be too high and not be too low :).	1231	always C<0>, which is supposed to not be too high and not be too low :).
1026		1232
1027	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1233	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1028	fine, as long as you do not mind that the priority value you query might	1234	priorities.
1029	or might not have been adjusted to be within valid range.
1030		1235
1031	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1236	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1032		1237
1033	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1238	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1034	C<loop> nor C<revents> need to be valid as long as the watcher callback	1239	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1041	returns its C<revents> bitset (as if its callback was invoked). If the	1246	returns its C<revents> bitset (as if its callback was invoked). If the
1042	watcher isn't pending it does nothing and returns C<0>.	1247	watcher isn't pending it does nothing and returns C<0>.
1043		1248
1044	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1249	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1045	callback to be invoked, which can be accomplished with this function.	1250	callback to be invoked, which can be accomplished with this function.
		1251
		1252	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1253
		1254	Feeds the given event set into the event loop, as if the specified event
		1255	had happened for the specified watcher (which must be a pointer to an
		1256	initialised but not necessarily started event watcher). Obviously you must
		1257	not free the watcher as long as it has pending events.
		1258
		1259	Stopping the watcher, letting libev invoke it, or calling
		1260	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1261	not started in the first place.
		1262
		1263	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1264	functions that do not need a watcher.
1046		1265
1047	=back	1266	=back
1048		1267
1049		1268
1050	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1269	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
1056	member, you can also "subclass" the watcher type and provide your own	1275	member, you can also "subclass" the watcher type and provide your own
1057	data:	1276	data:
1058		1277
1059	struct my_io	1278	struct my_io
1060	{	1279	{
1061	struct ev_io io;	1280	ev_io io;
1062	int otherfd;	1281	int otherfd;
1063	void *somedata;	1282	void *somedata;
1064	struct whatever *mostinteresting;	1283	struct whatever *mostinteresting;
1065	};	1284	};
1066		1285
…		…
1069	ev_io_init (&w.io, my_cb, fd, EV_READ);	1288	ev_io_init (&w.io, my_cb, fd, EV_READ);
1070		1289
1071	And since your callback will be called with a pointer to the watcher, you	1290	And since your callback will be called with a pointer to the watcher, you
1072	can cast it back to your own type:	1291	can cast it back to your own type:
1073		1292
1074	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1293	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1075	{	1294	{
1076	struct my_io *w = (struct my_io *)w_;	1295	struct my_io *w = (struct my_io *)w_;
1077	...	1296	...
1078	}	1297	}
1079		1298
…		…
1097	programmers):	1316	programmers):
1098		1317
1099	#include <stddef.h>	1318	#include <stddef.h>
1100		1319
1101	static void	1320	static void
1102	t1_cb (EV_P_ struct ev_timer *w, int revents)	1321	t1_cb (EV_P_ ev_timer *w, int revents)
1103	{	1322	{
1104	struct my_biggy big = (struct my_biggy *	1323	struct my_biggy big = (struct my_biggy *)
1105	(((char *)w) - offsetof (struct my_biggy, t1));	1324	(((char *)w) - offsetof (struct my_biggy, t1));
1106	}	1325	}
1107		1326
1108	static void	1327	static void
1109	t2_cb (EV_P_ struct ev_timer *w, int revents)	1328	t2_cb (EV_P_ ev_timer *w, int revents)
1110	{	1329	{
1111	struct my_biggy big = (struct my_biggy *	1330	struct my_biggy big = (struct my_biggy *)
1112	(((char *)w) - offsetof (struct my_biggy, t2));	1331	(((char *)w) - offsetof (struct my_biggy, t2));
1113	}	1332	}
		1333
		1334	=head2 WATCHER PRIORITY MODELS
		1335
		1336	Many event loops support I<watcher priorities>, which are usually small
		1337	integers that influence the ordering of event callback invocation
		1338	between watchers in some way, all else being equal.
		1339
		1340	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1341	description for the more technical details such as the actual priority
		1342	range.
		1343
		1344	There are two common ways how these these priorities are being interpreted
		1345	by event loops:
		1346
		1347	In the more common lock-out model, higher priorities "lock out" invocation
		1348	of lower priority watchers, which means as long as higher priority
		1349	watchers receive events, lower priority watchers are not being invoked.
		1350
		1351	The less common only-for-ordering model uses priorities solely to order
		1352	callback invocation within a single event loop iteration: Higher priority
		1353	watchers are invoked before lower priority ones, but they all get invoked
		1354	before polling for new events.
		1355
		1356	Libev uses the second (only-for-ordering) model for all its watchers
		1357	except for idle watchers (which use the lock-out model).
		1358
		1359	The rationale behind this is that implementing the lock-out model for
		1360	watchers is not well supported by most kernel interfaces, and most event
		1361	libraries will just poll for the same events again and again as long as
		1362	their callbacks have not been executed, which is very inefficient in the
		1363	common case of one high-priority watcher locking out a mass of lower
		1364	priority ones.
		1365
		1366	Static (ordering) priorities are most useful when you have two or more
		1367	watchers handling the same resource: a typical usage example is having an
		1368	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1369	timeouts. Under load, data might be received while the program handles
		1370	other jobs, but since timers normally get invoked first, the timeout
		1371	handler will be executed before checking for data. In that case, giving
		1372	the timer a lower priority than the I/O watcher ensures that I/O will be
		1373	handled first even under adverse conditions (which is usually, but not
		1374	always, what you want).
		1375
		1376	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1377	will only be executed when no same or higher priority watchers have
		1378	received events, they can be used to implement the "lock-out" model when
		1379	required.
		1380
		1381	For example, to emulate how many other event libraries handle priorities,
		1382	you can associate an C<ev_idle> watcher to each such watcher, and in
		1383	the normal watcher callback, you just start the idle watcher. The real
		1384	processing is done in the idle watcher callback. This causes libev to
		1385	continuously poll and process kernel event data for the watcher, but when
		1386	the lock-out case is known to be rare (which in turn is rare :), this is
		1387	workable.
		1388
		1389	Usually, however, the lock-out model implemented that way will perform
		1390	miserably under the type of load it was designed to handle. In that case,
		1391	it might be preferable to stop the real watcher before starting the
		1392	idle watcher, so the kernel will not have to process the event in case
		1393	the actual processing will be delayed for considerable time.
		1394
		1395	Here is an example of an I/O watcher that should run at a strictly lower
		1396	priority than the default, and which should only process data when no
		1397	other events are pending:
		1398
		1399	ev_idle idle; // actual processing watcher
		1400	ev_io io; // actual event watcher
		1401
		1402	static void
		1403	io_cb (EV_P_ ev_io *w, int revents)
		1404	{
		1405	// stop the I/O watcher, we received the event, but
		1406	// are not yet ready to handle it.
		1407	ev_io_stop (EV_A_ w);
		1408
		1409	// start the idle watcher to handle the actual event.
		1410	// it will not be executed as long as other watchers
		1411	// with the default priority are receiving events.
		1412	ev_idle_start (EV_A_ &idle);
		1413	}
		1414
		1415	static void
		1416	idle_cb (EV_P_ ev_idle *w, int revents)
		1417	{
		1418	// actual processing
		1419	read (STDIN_FILENO, ...);
		1420
		1421	// have to start the I/O watcher again, as
		1422	// we have handled the event
		1423	ev_io_start (EV_P_ &io);
		1424	}
		1425
		1426	// initialisation
		1427	ev_idle_init (&idle, idle_cb);
		1428	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1429	ev_io_start (EV_DEFAULT_ &io);
		1430
		1431	In the "real" world, it might also be beneficial to start a timer, so that
		1432	low-priority connections can not be locked out forever under load. This
		1433	enables your program to keep a lower latency for important connections
		1434	during short periods of high load, while not completely locking out less
		1435	important ones.
1114		1436
1115		1437
1116	=head1 WATCHER TYPES	1438	=head1 WATCHER TYPES
1117		1439
1118	This section describes each watcher in detail, but will not repeat	1440	This section describes each watcher in detail, but will not repeat
…		…
1144	descriptors to non-blocking mode is also usually a good idea (but not	1466	descriptors to non-blocking mode is also usually a good idea (but not
1145	required if you know what you are doing).	1467	required if you know what you are doing).
1146		1468
1147	If you cannot use non-blocking mode, then force the use of a	1469	If you cannot use non-blocking mode, then force the use of a
1148	known-to-be-good backend (at the time of this writing, this includes only	1470	known-to-be-good backend (at the time of this writing, this includes only
1149	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).	1471	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1472	descriptors for which non-blocking operation makes no sense (such as
		1473	files) - libev doesn't guarantee any specific behaviour in that case.
1150		1474
1151	Another thing you have to watch out for is that it is quite easy to	1475	Another thing you have to watch out for is that it is quite easy to
1152	receive "spurious" readiness notifications, that is your callback might	1476	receive "spurious" readiness notifications, that is your callback might
1153	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1477	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1154	because there is no data. Not only are some backends known to create a	1478	because there is no data. Not only are some backends known to create a
…		…
1219		1543
1220	So when you encounter spurious, unexplained daemon exits, make sure you	1544	So when you encounter spurious, unexplained daemon exits, make sure you
1221	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1545	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1222	somewhere, as that would have given you a big clue).	1546	somewhere, as that would have given you a big clue).
1223		1547
		1548	=head3 The special problem of accept()ing when you can't
		1549
		1550	Many implementations of the POSIX C<accept> function (for example,
		1551	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1552	connection from the pending queue in all error cases.
		1553
		1554	For example, larger servers often run out of file descriptors (because
		1555	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1556	rejecting the connection, leading to libev signalling readiness on
		1557	the next iteration again (the connection still exists after all), and
		1558	typically causing the program to loop at 100% CPU usage.
		1559
		1560	Unfortunately, the set of errors that cause this issue differs between
		1561	operating systems, there is usually little the app can do to remedy the
		1562	situation, and no known thread-safe method of removing the connection to
		1563	cope with overload is known (to me).
		1564
		1565	One of the easiest ways to handle this situation is to just ignore it
		1566	- when the program encounters an overload, it will just loop until the
		1567	situation is over. While this is a form of busy waiting, no OS offers an
		1568	event-based way to handle this situation, so it's the best one can do.
		1569
		1570	A better way to handle the situation is to log any errors other than
		1571	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1572	messages, and continue as usual, which at least gives the user an idea of
		1573	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1574	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1575	usage.
		1576
		1577	If your program is single-threaded, then you could also keep a dummy file
		1578	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1579	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1580	close that fd, and create a new dummy fd. This will gracefully refuse
		1581	clients under typical overload conditions.
		1582
		1583	The last way to handle it is to simply log the error and C<exit>, as
		1584	is often done with C<malloc> failures, but this results in an easy
		1585	opportunity for a DoS attack.
1224		1586
1225	=head3 Watcher-Specific Functions	1587	=head3 Watcher-Specific Functions
1226		1588
1227	=over 4	1589	=over 4
1228		1590
…		…
1249	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1611	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1250	readable, but only once. Since it is likely line-buffered, you could	1612	readable, but only once. Since it is likely line-buffered, you could
1251	attempt to read a whole line in the callback.	1613	attempt to read a whole line in the callback.
1252		1614
1253	static void	1615	static void
1254	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1616	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1255	{	1617	{
1256	ev_io_stop (loop, w);	1618	ev_io_stop (loop, w);
1257	.. read from stdin here (or from w->fd) and handle any I/O errors	1619	.. read from stdin here (or from w->fd) and handle any I/O errors
1258	}	1620	}
1259		1621
1260	...	1622	...
1261	struct ev_loop *loop = ev_default_init (0);	1623	struct ev_loop *loop = ev_default_init (0);
1262	struct ev_io stdin_readable;	1624	ev_io stdin_readable;
1263	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1625	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1264	ev_io_start (loop, &stdin_readable);	1626	ev_io_start (loop, &stdin_readable);
1265	ev_loop (loop, 0);	1627	ev_loop (loop, 0);
1266		1628
1267		1629
…		…
1275	year, it will still time out after (roughly) one hour. "Roughly" because	1637	year, it will still time out after (roughly) one hour. "Roughly" because
1276	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1638	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1277	monotonic clock option helps a lot here).	1639	monotonic clock option helps a lot here).
1278		1640
1279	The callback is guaranteed to be invoked only I<after> its timeout has	1641	The callback is guaranteed to be invoked only I<after> its timeout has
1280	passed, but if multiple timers become ready during the same loop iteration	1642	passed (not I<at>, so on systems with very low-resolution clocks this
1281	then order of execution is undefined.	1643	might introduce a small delay). If multiple timers become ready during the
		1644	same loop iteration then the ones with earlier time-out values are invoked
		1645	before ones of the same priority with later time-out values (but this is
		1646	no longer true when a callback calls C<ev_loop> recursively).
		1647
		1648	=head3 Be smart about timeouts
		1649
		1650	Many real-world problems involve some kind of timeout, usually for error
		1651	recovery. A typical example is an HTTP request - if the other side hangs,
		1652	you want to raise some error after a while.
		1653
		1654	What follows are some ways to handle this problem, from obvious and
		1655	inefficient to smart and efficient.
		1656
		1657	In the following, a 60 second activity timeout is assumed - a timeout that
		1658	gets reset to 60 seconds each time there is activity (e.g. each time some
		1659	data or other life sign was received).
		1660
		1661	=over 4
		1662
		1663	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1664
		1665	This is the most obvious, but not the most simple way: In the beginning,
		1666	start the watcher:
		1667
		1668	ev_timer_init (timer, callback, 60., 0.);
		1669	ev_timer_start (loop, timer);
		1670
		1671	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1672	and start it again:
		1673
		1674	ev_timer_stop (loop, timer);
		1675	ev_timer_set (timer, 60., 0.);
		1676	ev_timer_start (loop, timer);
		1677
		1678	This is relatively simple to implement, but means that each time there is
		1679	some activity, libev will first have to remove the timer from its internal
		1680	data structure and then add it again. Libev tries to be fast, but it's
		1681	still not a constant-time operation.
		1682
		1683	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1684
		1685	This is the easiest way, and involves using C<ev_timer_again> instead of
		1686	C<ev_timer_start>.
		1687
		1688	To implement this, configure an C<ev_timer> with a C<repeat> value
		1689	of C<60> and then call C<ev_timer_again> at start and each time you
		1690	successfully read or write some data. If you go into an idle state where
		1691	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1692	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1693
		1694	That means you can ignore both the C<ev_timer_start> function and the
		1695	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1696	member and C<ev_timer_again>.
		1697
		1698	At start:
		1699
		1700	ev_init (timer, callback);
		1701	timer->repeat = 60.;
		1702	ev_timer_again (loop, timer);
		1703
		1704	Each time there is some activity:
		1705
		1706	ev_timer_again (loop, timer);
		1707
		1708	It is even possible to change the time-out on the fly, regardless of
		1709	whether the watcher is active or not:
		1710
		1711	timer->repeat = 30.;
		1712	ev_timer_again (loop, timer);
		1713
		1714	This is slightly more efficient then stopping/starting the timer each time
		1715	you want to modify its timeout value, as libev does not have to completely
		1716	remove and re-insert the timer from/into its internal data structure.
		1717
		1718	It is, however, even simpler than the "obvious" way to do it.
		1719
		1720	=item 3. Let the timer time out, but then re-arm it as required.
		1721
		1722	This method is more tricky, but usually most efficient: Most timeouts are
		1723	relatively long compared to the intervals between other activity - in
		1724	our example, within 60 seconds, there are usually many I/O events with
		1725	associated activity resets.
		1726
		1727	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1728	but remember the time of last activity, and check for a real timeout only
		1729	within the callback:
		1730
		1731	ev_tstamp last_activity; // time of last activity
		1732
		1733	static void
		1734	callback (EV_P_ ev_timer *w, int revents)
		1735	{
		1736	ev_tstamp now = ev_now (EV_A);
		1737	ev_tstamp timeout = last_activity + 60.;
		1738
		1739	// if last_activity + 60. is older than now, we did time out
		1740	if (timeout < now)
		1741	{
		1742	// timeout occurred, take action
		1743	}
		1744	else
		1745	{
		1746	// callback was invoked, but there was some activity, re-arm
		1747	// the watcher to fire in last_activity + 60, which is
		1748	// guaranteed to be in the future, so "again" is positive:
		1749	w->repeat = timeout - now;
		1750	ev_timer_again (EV_A_ w);
		1751	}
		1752	}
		1753
		1754	To summarise the callback: first calculate the real timeout (defined
		1755	as "60 seconds after the last activity"), then check if that time has
		1756	been reached, which means something I<did>, in fact, time out. Otherwise
		1757	the callback was invoked too early (C<timeout> is in the future), so
		1758	re-schedule the timer to fire at that future time, to see if maybe we have
		1759	a timeout then.
		1760
		1761	Note how C<ev_timer_again> is used, taking advantage of the
		1762	C<ev_timer_again> optimisation when the timer is already running.
		1763
		1764	This scheme causes more callback invocations (about one every 60 seconds
		1765	minus half the average time between activity), but virtually no calls to
		1766	libev to change the timeout.
		1767
		1768	To start the timer, simply initialise the watcher and set C<last_activity>
		1769	to the current time (meaning we just have some activity :), then call the
		1770	callback, which will "do the right thing" and start the timer:
		1771
		1772	ev_init (timer, callback);
		1773	last_activity = ev_now (loop);
		1774	callback (loop, timer, EV_TIMER);
		1775
		1776	And when there is some activity, simply store the current time in
		1777	C<last_activity>, no libev calls at all:
		1778
		1779	last_activity = ev_now (loop);
		1780
		1781	This technique is slightly more complex, but in most cases where the
		1782	time-out is unlikely to be triggered, much more efficient.
		1783
		1784	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1785	callback :) - just change the timeout and invoke the callback, which will
		1786	fix things for you.
		1787
		1788	=item 4. Wee, just use a double-linked list for your timeouts.
		1789
		1790	If there is not one request, but many thousands (millions...), all
		1791	employing some kind of timeout with the same timeout value, then one can
		1792	do even better:
		1793
		1794	When starting the timeout, calculate the timeout value and put the timeout
		1795	at the I<end> of the list.
		1796
		1797	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1798	the list is expected to fire (for example, using the technique #3).
		1799
		1800	When there is some activity, remove the timer from the list, recalculate
		1801	the timeout, append it to the end of the list again, and make sure to
		1802	update the C<ev_timer> if it was taken from the beginning of the list.
		1803
		1804	This way, one can manage an unlimited number of timeouts in O(1) time for
		1805	starting, stopping and updating the timers, at the expense of a major
		1806	complication, and having to use a constant timeout. The constant timeout
		1807	ensures that the list stays sorted.
		1808
		1809	=back
		1810
		1811	So which method the best?
		1812
		1813	Method #2 is a simple no-brain-required solution that is adequate in most
		1814	situations. Method #3 requires a bit more thinking, but handles many cases
		1815	better, and isn't very complicated either. In most case, choosing either
		1816	one is fine, with #3 being better in typical situations.
		1817
		1818	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1819	rather complicated, but extremely efficient, something that really pays
		1820	off after the first million or so of active timers, i.e. it's usually
		1821	overkill :)
1282		1822
1283	=head3 The special problem of time updates	1823	=head3 The special problem of time updates
1284		1824
1285	Establishing the current time is a costly operation (it usually takes at	1825	Establishing the current time is a costly operation (it usually takes at
1286	least two system calls): EV therefore updates its idea of the current	1826	least two system calls): EV therefore updates its idea of the current
…		…
1298		1838
1299	If the event loop is suspended for a long time, you can also force an	1839	If the event loop is suspended for a long time, you can also force an
1300	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1840	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1301	()>.	1841	()>.
1302		1842
		1843	=head3 The special problems of suspended animation
		1844
		1845	When you leave the server world it is quite customary to hit machines that
		1846	can suspend/hibernate - what happens to the clocks during such a suspend?
		1847
		1848	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1849	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1850	to run until the system is suspended, but they will not advance while the
		1851	system is suspended. That means, on resume, it will be as if the program
		1852	was frozen for a few seconds, but the suspend time will not be counted
		1853	towards C<ev_timer> when a monotonic clock source is used. The real time
		1854	clock advanced as expected, but if it is used as sole clocksource, then a
		1855	long suspend would be detected as a time jump by libev, and timers would
		1856	be adjusted accordingly.
		1857
		1858	I would not be surprised to see different behaviour in different between
		1859	operating systems, OS versions or even different hardware.
		1860
		1861	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1862	time jump in the monotonic clocks and the realtime clock. If the program
		1863	is suspended for a very long time, and monotonic clock sources are in use,
		1864	then you can expect C<ev_timer>s to expire as the full suspension time
		1865	will be counted towards the timers. When no monotonic clock source is in
		1866	use, then libev will again assume a timejump and adjust accordingly.
		1867
		1868	It might be beneficial for this latter case to call C<ev_suspend>
		1869	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1870	deterministic behaviour in this case (you can do nothing against
		1871	C<SIGSTOP>).
		1872
1303	=head3 Watcher-Specific Functions and Data Members	1873	=head3 Watcher-Specific Functions and Data Members
1304		1874
1305	=over 4	1875	=over 4
1306		1876
1307	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1877	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1330	If the timer is started but non-repeating, stop it (as if it timed out).	1900	If the timer is started but non-repeating, stop it (as if it timed out).
1331		1901
1332	If the timer is repeating, either start it if necessary (with the	1902	If the timer is repeating, either start it if necessary (with the
1333	C<repeat> value), or reset the running timer to the C<repeat> value.	1903	C<repeat> value), or reset the running timer to the C<repeat> value.
1334		1904
1335	This sounds a bit complicated, but here is a useful and typical	1905	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1336	example: Imagine you have a TCP connection and you want a so-called idle	1906	usage example.
1337	timeout, that is, you want to be called when there have been, say, 60
1338	seconds of inactivity on the socket. The easiest way to do this is to
1339	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1340	C<ev_timer_again> each time you successfully read or write some data. If
1341	you go into an idle state where you do not expect data to travel on the
1342	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1343	automatically restart it if need be.
1344		1907
1345	That means you can ignore the C<after> value and C<ev_timer_start>	1908	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1346	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1347		1909
1348	ev_timer_init (timer, callback, 0., 5.);	1910	Returns the remaining time until a timer fires. If the timer is active,
1349	ev_timer_again (loop, timer);	1911	then this time is relative to the current event loop time, otherwise it's
1350	...	1912	the timeout value currently configured.
1351	timer->again = 17.;
1352	ev_timer_again (loop, timer);
1353	...
1354	timer->again = 10.;
1355	ev_timer_again (loop, timer);
1356		1913
1357	This is more slightly efficient then stopping/starting the timer each time	1914	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1358	you want to modify its timeout value.	1915	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
1359		1916	will return C<4>. When the timer expires and is restarted, it will return
1360	Note, however, that it is often even more efficient to remember the	1917	roughly C<7> (likely slightly less as callback invocation takes some time,
1361	time of the last activity and let the timer time-out naturally. In the	1918	too), and so on.
1362	callback, you then check whether the time-out is real, or, if there was
1363	some activity, you reschedule the watcher to time-out in "last_activity +
1364	timeout - ev_now ()" seconds.
1365		1919
1366	=item ev_tstamp repeat [read-write]	1920	=item ev_tstamp repeat [read-write]
1367		1921
1368	The current C<repeat> value. Will be used each time the watcher times out	1922	The current C<repeat> value. Will be used each time the watcher times out
1369	or C<ev_timer_again> is called, and determines the next timeout (if any),	1923	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1374	=head3 Examples	1928	=head3 Examples
1375		1929
1376	Example: Create a timer that fires after 60 seconds.	1930	Example: Create a timer that fires after 60 seconds.
1377		1931
1378	static void	1932	static void
1379	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1933	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1380	{	1934	{
1381	.. one minute over, w is actually stopped right here	1935	.. one minute over, w is actually stopped right here
1382	}	1936	}
1383		1937
1384	struct ev_timer mytimer;	1938	ev_timer mytimer;
1385	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1939	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1386	ev_timer_start (loop, &mytimer);	1940	ev_timer_start (loop, &mytimer);
1387		1941
1388	Example: Create a timeout timer that times out after 10 seconds of	1942	Example: Create a timeout timer that times out after 10 seconds of
1389	inactivity.	1943	inactivity.
1390		1944
1391	static void	1945	static void
1392	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1946	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1393	{	1947	{
1394	.. ten seconds without any activity	1948	.. ten seconds without any activity
1395	}	1949	}
1396		1950
1397	struct ev_timer mytimer;	1951	ev_timer mytimer;
1398	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1952	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1399	ev_timer_again (&mytimer); /* start timer */	1953	ev_timer_again (&mytimer); /* start timer */
1400	ev_loop (loop, 0);	1954	ev_loop (loop, 0);
1401		1955
1402	// and in some piece of code that gets executed on any "activity":	1956	// and in some piece of code that gets executed on any "activity":
…		…
1407	=head2 C<ev_periodic> - to cron or not to cron?	1961	=head2 C<ev_periodic> - to cron or not to cron?
1408		1962
1409	Periodic watchers are also timers of a kind, but they are very versatile	1963	Periodic watchers are also timers of a kind, but they are very versatile
1410	(and unfortunately a bit complex).	1964	(and unfortunately a bit complex).
1411		1965
1412	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1966	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1413	but on wall clock time (absolute time). You can tell a periodic watcher	1967	relative time, the physical time that passes) but on wall clock time
1414	to trigger after some specific point in time. For example, if you tell a	1968	(absolute time, the thing you can read on your calender or clock). The
1415	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	1969	difference is that wall clock time can run faster or slower than real
1416	+ 10.>, that is, an absolute time not a delay) and then reset your system	1970	time, and time jumps are not uncommon (e.g. when you adjust your
1417	clock to January of the previous year, then it will take more than year	1971	wrist-watch).
1418	to trigger the event (unlike an C<ev_timer>, which would still trigger
1419	roughly 10 seconds later as it uses a relative timeout).
1420		1972
		1973	You can tell a periodic watcher to trigger after some specific point
		1974	in time: for example, if you tell a periodic watcher to trigger "in 10
		1975	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1976	not a delay) and then reset your system clock to January of the previous
		1977	year, then it will take a year or more to trigger the event (unlike an
		1978	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1979	it, as it uses a relative timeout).
		1980
1421	C<ev_periodic>s can also be used to implement vastly more complex timers,	1981	C<ev_periodic> watchers can also be used to implement vastly more complex
1422	such as triggering an event on each "midnight, local time", or other	1982	timers, such as triggering an event on each "midnight, local time", or
1423	complicated rules.	1983	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1984	those cannot react to time jumps.
1424		1985
1425	As with timers, the callback is guaranteed to be invoked only when the	1986	As with timers, the callback is guaranteed to be invoked only when the
1426	time (C<at>) has passed, but if multiple periodic timers become ready	1987	point in time where it is supposed to trigger has passed. If multiple
1427	during the same loop iteration, then order of execution is undefined.	1988	timers become ready during the same loop iteration then the ones with
		1989	earlier time-out values are invoked before ones with later time-out values
		1990	(but this is no longer true when a callback calls C<ev_loop> recursively).
1428		1991
1429	=head3 Watcher-Specific Functions and Data Members	1992	=head3 Watcher-Specific Functions and Data Members
1430		1993
1431	=over 4	1994	=over 4
1432		1995
1433	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1996	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1434		1997
1435	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1998	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1436		1999
1437	Lots of arguments, lets sort it out... There are basically three modes of	2000	Lots of arguments, let's sort it out... There are basically three modes of
1438	operation, and we will explain them from simplest to most complex:	2001	operation, and we will explain them from simplest to most complex:
1439		2002
1440	=over 4	2003	=over 4
1441		2004
1442	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2005	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1443		2006
1444	In this configuration the watcher triggers an event after the wall clock	2007	In this configuration the watcher triggers an event after the wall clock
1445	time C<at> has passed. It will not repeat and will not adjust when a time	2008	time C<offset> has passed. It will not repeat and will not adjust when a
1446	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2009	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1447	only run when the system clock reaches or surpasses this time.	2010	will be stopped and invoked when the system clock reaches or surpasses
		2011	this point in time.
1448		2012
1449	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2013	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1450		2014
1451	In this mode the watcher will always be scheduled to time out at the next	2015	In this mode the watcher will always be scheduled to time out at the next
1452	C<at + N * interval> time (for some integer N, which can also be negative)	2016	C<offset + N * interval> time (for some integer N, which can also be
1453	and then repeat, regardless of any time jumps.	2017	negative) and then repeat, regardless of any time jumps. The C<offset>
		2018	argument is merely an offset into the C<interval> periods.
1454		2019
1455	This can be used to create timers that do not drift with respect to the	2020	This can be used to create timers that do not drift with respect to the
1456	system clock, for example, here is a C<ev_periodic> that triggers each	2021	system clock, for example, here is an C<ev_periodic> that triggers each
1457	hour, on the hour:	2022	hour, on the hour (with respect to UTC):
1458		2023
1459	ev_periodic_set (&periodic, 0., 3600., 0);	2024	ev_periodic_set (&periodic, 0., 3600., 0);
1460		2025
1461	This doesn't mean there will always be 3600 seconds in between triggers,	2026	This doesn't mean there will always be 3600 seconds in between triggers,
1462	but only that the callback will be called when the system time shows a	2027	but only that the callback will be called when the system time shows a
1463	full hour (UTC), or more correctly, when the system time is evenly divisible	2028	full hour (UTC), or more correctly, when the system time is evenly divisible
1464	by 3600.	2029	by 3600.
1465		2030
1466	Another way to think about it (for the mathematically inclined) is that	2031	Another way to think about it (for the mathematically inclined) is that
1467	C<ev_periodic> will try to run the callback in this mode at the next possible	2032	C<ev_periodic> will try to run the callback in this mode at the next possible
1468	time where C<time = at (mod interval)>, regardless of any time jumps.	2033	time where C<time = offset (mod interval)>, regardless of any time jumps.
1469		2034
1470	For numerical stability it is preferable that the C<at> value is near	2035	For numerical stability it is preferable that the C<offset> value is near
1471	C<ev_now ()> (the current time), but there is no range requirement for	2036	C<ev_now ()> (the current time), but there is no range requirement for
1472	this value, and in fact is often specified as zero.	2037	this value, and in fact is often specified as zero.
1473		2038
1474	Note also that there is an upper limit to how often a timer can fire (CPU	2039	Note also that there is an upper limit to how often a timer can fire (CPU
1475	speed for example), so if C<interval> is very small then timing stability	2040	speed for example), so if C<interval> is very small then timing stability
1476	will of course deteriorate. Libev itself tries to be exact to be about one	2041	will of course deteriorate. Libev itself tries to be exact to be about one
1477	millisecond (if the OS supports it and the machine is fast enough).	2042	millisecond (if the OS supports it and the machine is fast enough).
1478		2043
1479	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2044	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1480		2045
1481	In this mode the values for C<interval> and C<at> are both being	2046	In this mode the values for C<interval> and C<offset> are both being
1482	ignored. Instead, each time the periodic watcher gets scheduled, the	2047	ignored. Instead, each time the periodic watcher gets scheduled, the
1483	reschedule callback will be called with the watcher as first, and the	2048	reschedule callback will be called with the watcher as first, and the
1484	current time as second argument.	2049	current time as second argument.
1485		2050
1486	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2051	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1487	ever, or make ANY event loop modifications whatsoever>.	2052	or make ANY other event loop modifications whatsoever, unless explicitly
		2053	allowed by documentation here>.
1488		2054
1489	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2055	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1490	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2056	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1491	only event loop modification you are allowed to do).	2057	only event loop modification you are allowed to do).
1492		2058
1493	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	2059	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1494	*w, ev_tstamp now)>, e.g.:	2060	*w, ev_tstamp now)>, e.g.:
1495		2061
		2062	static ev_tstamp
1496	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	2063	my_rescheduler (ev_periodic *w, ev_tstamp now)
1497	{	2064	{
1498	return now + 60.;	2065	return now + 60.;
1499	}	2066	}
1500		2067
1501	It must return the next time to trigger, based on the passed time value	2068	It must return the next time to trigger, based on the passed time value
…		…
1521	a different time than the last time it was called (e.g. in a crond like	2088	a different time than the last time it was called (e.g. in a crond like
1522	program when the crontabs have changed).	2089	program when the crontabs have changed).
1523		2090
1524	=item ev_tstamp ev_periodic_at (ev_periodic *)	2091	=item ev_tstamp ev_periodic_at (ev_periodic *)
1525		2092
1526	When active, returns the absolute time that the watcher is supposed to	2093	When active, returns the absolute time that the watcher is supposed
1527	trigger next.	2094	to trigger next. This is not the same as the C<offset> argument to
		2095	C<ev_periodic_set>, but indeed works even in interval and manual
		2096	rescheduling modes.
1528		2097
1529	=item ev_tstamp offset [read-write]	2098	=item ev_tstamp offset [read-write]
1530		2099
1531	When repeating, this contains the offset value, otherwise this is the	2100	When repeating, this contains the offset value, otherwise this is the
1532	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2101	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2102	although libev might modify this value for better numerical stability).
1533		2103
1534	Can be modified any time, but changes only take effect when the periodic	2104	Can be modified any time, but changes only take effect when the periodic
1535	timer fires or C<ev_periodic_again> is being called.	2105	timer fires or C<ev_periodic_again> is being called.
1536		2106
1537	=item ev_tstamp interval [read-write]	2107	=item ev_tstamp interval [read-write]
1538		2108
1539	The current interval value. Can be modified any time, but changes only	2109	The current interval value. Can be modified any time, but changes only
1540	take effect when the periodic timer fires or C<ev_periodic_again> is being	2110	take effect when the periodic timer fires or C<ev_periodic_again> is being
1541	called.	2111	called.
1542		2112
1543	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2113	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1544		2114
1545	The current reschedule callback, or C<0>, if this functionality is	2115	The current reschedule callback, or C<0>, if this functionality is
1546	switched off. Can be changed any time, but changes only take effect when	2116	switched off. Can be changed any time, but changes only take effect when
1547	the periodic timer fires or C<ev_periodic_again> is being called.	2117	the periodic timer fires or C<ev_periodic_again> is being called.
1548		2118
…		…
1553	Example: Call a callback every hour, or, more precisely, whenever the	2123	Example: Call a callback every hour, or, more precisely, whenever the
1554	system time is divisible by 3600. The callback invocation times have	2124	system time is divisible by 3600. The callback invocation times have
1555	potentially a lot of jitter, but good long-term stability.	2125	potentially a lot of jitter, but good long-term stability.
1556		2126
1557	static void	2127	static void
1558	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2128	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1559	{	2129	{
1560	... its now a full hour (UTC, or TAI or whatever your clock follows)	2130	... its now a full hour (UTC, or TAI or whatever your clock follows)
1561	}	2131	}
1562		2132
1563	struct ev_periodic hourly_tick;	2133	ev_periodic hourly_tick;
1564	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2134	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1565	ev_periodic_start (loop, &hourly_tick);	2135	ev_periodic_start (loop, &hourly_tick);
1566		2136
1567	Example: The same as above, but use a reschedule callback to do it:	2137	Example: The same as above, but use a reschedule callback to do it:
1568		2138
1569	#include <math.h>	2139	#include <math.h>
1570		2140
1571	static ev_tstamp	2141	static ev_tstamp
1572	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2142	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1573	{	2143	{
1574	return now + (3600. - fmod (now, 3600.));	2144	return now + (3600. - fmod (now, 3600.));
1575	}	2145	}
1576		2146
1577	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2147	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1578		2148
1579	Example: Call a callback every hour, starting now:	2149	Example: Call a callback every hour, starting now:
1580		2150
1581	struct ev_periodic hourly_tick;	2151	ev_periodic hourly_tick;
1582	ev_periodic_init (&hourly_tick, clock_cb,	2152	ev_periodic_init (&hourly_tick, clock_cb,
1583	fmod (ev_now (loop), 3600.), 3600., 0);	2153	fmod (ev_now (loop), 3600.), 3600., 0);
1584	ev_periodic_start (loop, &hourly_tick);	2154	ev_periodic_start (loop, &hourly_tick);
1585		2155
1586		2156
…		…
1589	Signal watchers will trigger an event when the process receives a specific	2159	Signal watchers will trigger an event when the process receives a specific
1590	signal one or more times. Even though signals are very asynchronous, libev	2160	signal one or more times. Even though signals are very asynchronous, libev
1591	will try it's best to deliver signals synchronously, i.e. as part of the	2161	will try it's best to deliver signals synchronously, i.e. as part of the
1592	normal event processing, like any other event.	2162	normal event processing, like any other event.
1593		2163
1594	If you want signals asynchronously, just use C<sigaction> as you would	2164	If you want signals to be delivered truly asynchronously, just use
1595	do without libev and forget about sharing the signal. You can even use	2165	C<sigaction> as you would do without libev and forget about sharing
1596	C<ev_async> from a signal handler to synchronously wake up an event loop.	2166	the signal. You can even use C<ev_async> from a signal handler to
		2167	synchronously wake up an event loop.
1597		2168
1598	You can configure as many watchers as you like per signal. Only when the	2169	You can configure as many watchers as you like for the same signal, but
		2170	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2171	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2172	C<SIGINT> in both the default loop and another loop at the same time. At
		2173	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2174
1599	first watcher gets started will libev actually register a signal handler	2175	When the first watcher gets started will libev actually register something
1600	with the kernel (thus it coexists with your own signal handlers as long as	2176	with the kernel (thus it coexists with your own signal handlers as long as
1601	you don't register any with libev for the same signal). Similarly, when	2177	you don't register any with libev for the same signal).
1602	the last signal watcher for a signal is stopped, libev will reset the
1603	signal handler to SIG_DFL (regardless of what it was set to before).
1604		2178
1605	If possible and supported, libev will install its handlers with	2179	If possible and supported, libev will install its handlers with
1606	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2180	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1607	interrupted. If you have a problem with system calls getting interrupted by	2181	not be unduly interrupted. If you have a problem with system calls getting
1608	signals you can block all signals in an C<ev_check> watcher and unblock	2182	interrupted by signals you can block all signals in an C<ev_check> watcher
1609	them in an C<ev_prepare> watcher.	2183	and unblock them in an C<ev_prepare> watcher.
		2184
		2185	=head3 The special problem of inheritance over fork/execve/pthread_create
		2186
		2187	Both the signal mask (C<sigprocmask>) and the signal disposition
		2188	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2189	stopping it again), that is, libev might or might not block the signal,
		2190	and might or might not set or restore the installed signal handler.
		2191
		2192	While this does not matter for the signal disposition (libev never
		2193	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2194	C<execve>), this matters for the signal mask: many programs do not expect
		2195	certain signals to be blocked.
		2196
		2197	This means that before calling C<exec> (from the child) you should reset
		2198	the signal mask to whatever "default" you expect (all clear is a good
		2199	choice usually).
		2200
		2201	The simplest way to ensure that the signal mask is reset in the child is
		2202	to install a fork handler with C<pthread_atfork> that resets it. That will
		2203	catch fork calls done by libraries (such as the libc) as well.
		2204
		2205	In current versions of libev, the signal will not be blocked indefinitely
		2206	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2207	the window of opportunity for problems, it will not go away, as libev
		2208	I<has> to modify the signal mask, at least temporarily.
		2209
		2210	So I can't stress this enough: I<If you do not reset your signal mask when
		2211	you expect it to be empty, you have a race condition in your code>. This
		2212	is not a libev-specific thing, this is true for most event libraries.
1610		2213
1611	=head3 Watcher-Specific Functions and Data Members	2214	=head3 Watcher-Specific Functions and Data Members
1612		2215
1613	=over 4	2216	=over 4
1614		2217
…		…
1628	=head3 Examples	2231	=head3 Examples
1629		2232
1630	Example: Try to exit cleanly on SIGINT.	2233	Example: Try to exit cleanly on SIGINT.
1631		2234
1632	static void	2235	static void
1633	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2236	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1634	{	2237	{
1635	ev_unloop (loop, EVUNLOOP_ALL);	2238	ev_unloop (loop, EVUNLOOP_ALL);
1636	}	2239	}
1637		2240
1638	struct ev_signal signal_watcher;	2241	ev_signal signal_watcher;
1639	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2242	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1640	ev_signal_start (loop, &signal_watcher);	2243	ev_signal_start (loop, &signal_watcher);
1641		2244
1642		2245
1643	=head2 C<ev_child> - watch out for process status changes	2246	=head2 C<ev_child> - watch out for process status changes
…		…
1646	some child status changes (most typically when a child of yours dies or	2249	some child status changes (most typically when a child of yours dies or
1647	exits). It is permissible to install a child watcher I<after> the child	2250	exits). It is permissible to install a child watcher I<after> the child
1648	has been forked (which implies it might have already exited), as long	2251	has been forked (which implies it might have already exited), as long
1649	as the event loop isn't entered (or is continued from a watcher), i.e.,	2252	as the event loop isn't entered (or is continued from a watcher), i.e.,
1650	forking and then immediately registering a watcher for the child is fine,	2253	forking and then immediately registering a watcher for the child is fine,
1651	but forking and registering a watcher a few event loop iterations later is	2254	but forking and registering a watcher a few event loop iterations later or
1652	not.	2255	in the next callback invocation is not.
1653		2256
1654	Only the default event loop is capable of handling signals, and therefore	2257	Only the default event loop is capable of handling signals, and therefore
1655	you can only register child watchers in the default event loop.	2258	you can only register child watchers in the default event loop.
1656		2259
		2260	Due to some design glitches inside libev, child watchers will always be
		2261	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2262	libev)
		2263
1657	=head3 Process Interaction	2264	=head3 Process Interaction
1658		2265
1659	Libev grabs C<SIGCHLD> as soon as the default event loop is	2266	Libev grabs C<SIGCHLD> as soon as the default event loop is
1660	initialised. This is necessary to guarantee proper behaviour even if	2267	initialised. This is necessary to guarantee proper behaviour even if the
1661	the first child watcher is started after the child exits. The occurrence	2268	first child watcher is started after the child exits. The occurrence
1662	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2269	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1663	synchronously as part of the event loop processing. Libev always reaps all	2270	synchronously as part of the event loop processing. Libev always reaps all
1664	children, even ones not watched.	2271	children, even ones not watched.
1665		2272
1666	=head3 Overriding the Built-In Processing	2273	=head3 Overriding the Built-In Processing
…		…
1676	=head3 Stopping the Child Watcher	2283	=head3 Stopping the Child Watcher
1677		2284
1678	Currently, the child watcher never gets stopped, even when the	2285	Currently, the child watcher never gets stopped, even when the
1679	child terminates, so normally one needs to stop the watcher in the	2286	child terminates, so normally one needs to stop the watcher in the
1680	callback. Future versions of libev might stop the watcher automatically	2287	callback. Future versions of libev might stop the watcher automatically
1681	when a child exit is detected.	2288	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2289	problem).
1682		2290
1683	=head3 Watcher-Specific Functions and Data Members	2291	=head3 Watcher-Specific Functions and Data Members
1684		2292
1685	=over 4	2293	=over 4
1686		2294
…		…
1718	its completion.	2326	its completion.
1719		2327
1720	ev_child cw;	2328	ev_child cw;
1721		2329
1722	static void	2330	static void
1723	child_cb (EV_P_ struct ev_child *w, int revents)	2331	child_cb (EV_P_ ev_child *w, int revents)
1724	{	2332	{
1725	ev_child_stop (EV_A_ w);	2333	ev_child_stop (EV_A_ w);
1726	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2334	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1727	}	2335	}
1728		2336
…		…
1743		2351
1744		2352
1745	=head2 C<ev_stat> - did the file attributes just change?	2353	=head2 C<ev_stat> - did the file attributes just change?
1746		2354
1747	This watches a file system path for attribute changes. That is, it calls	2355	This watches a file system path for attribute changes. That is, it calls
1748	C<stat> regularly (or when the OS says it changed) and sees if it changed	2356	C<stat> on that path in regular intervals (or when the OS says it changed)
1749	compared to the last time, invoking the callback if it did.	2357	and sees if it changed compared to the last time, invoking the callback if
		2358	it did.
1750		2359
1751	The path does not need to exist: changing from "path exists" to "path does	2360	The path does not need to exist: changing from "path exists" to "path does
1752	not exist" is a status change like any other. The condition "path does	2361	not exist" is a status change like any other. The condition "path does not
1753	not exist" is signified by the C<st_nlink> field being zero (which is	2362	exist" (or more correctly "path cannot be stat'ed") is signified by the
1754	otherwise always forced to be at least one) and all the other fields of	2363	C<st_nlink> field being zero (which is otherwise always forced to be at
1755	the stat buffer having unspecified contents.	2364	least one) and all the other fields of the stat buffer having unspecified
		2365	contents.
1756		2366
1757	The path I<should> be absolute and I<must not> end in a slash. If it is	2367	The path I<must not> end in a slash or contain special components such as
		2368	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1758	relative and your working directory changes, the behaviour is undefined.	2369	your working directory changes, then the behaviour is undefined.
1759		2370
1760	Since there is no standard kernel interface to do this, the portable	2371	Since there is no portable change notification interface available, the
1761	implementation simply calls C<stat (2)> regularly on the path to see if	2372	portable implementation simply calls C<stat(2)> regularly on the path
1762	it changed somehow. You can specify a recommended polling interval for	2373	to see if it changed somehow. You can specify a recommended polling
1763	this case. If you specify a polling interval of C<0> (highly recommended!)	2374	interval for this case. If you specify a polling interval of C<0> (highly
1764	then a I<suitable, unspecified default> value will be used (which	2375	recommended!) then a I<suitable, unspecified default> value will be used
1765	you can expect to be around five seconds, although this might change	2376	(which you can expect to be around five seconds, although this might
1766	dynamically). Libev will also impose a minimum interval which is currently	2377	change dynamically). Libev will also impose a minimum interval which is
1767	around C<0.1>, but thats usually overkill.	2378	currently around C<0.1>, but that's usually overkill.
1768		2379
1769	This watcher type is not meant for massive numbers of stat watchers,	2380	This watcher type is not meant for massive numbers of stat watchers,
1770	as even with OS-supported change notifications, this can be	2381	as even with OS-supported change notifications, this can be
1771	resource-intensive.	2382	resource-intensive.
1772		2383
1773	At the time of this writing, the only OS-specific interface implemented	2384	At the time of this writing, the only OS-specific interface implemented
1774	is the Linux inotify interface (implementing kqueue support is left as	2385	is the Linux inotify interface (implementing kqueue support is left as an
1775	an exercise for the reader. Note, however, that the author sees no way	2386	exercise for the reader. Note, however, that the author sees no way of
1776	of implementing C<ev_stat> semantics with kqueue).	2387	implementing C<ev_stat> semantics with kqueue, except as a hint).
1777		2388
1778	=head3 ABI Issues (Largefile Support)	2389	=head3 ABI Issues (Largefile Support)
1779		2390
1780	Libev by default (unless the user overrides this) uses the default	2391	Libev by default (unless the user overrides this) uses the default
1781	compilation environment, which means that on systems with large file	2392	compilation environment, which means that on systems with large file
1782	support disabled by default, you get the 32 bit version of the stat	2393	support disabled by default, you get the 32 bit version of the stat
1783	structure. When using the library from programs that change the ABI to	2394	structure. When using the library from programs that change the ABI to
1784	use 64 bit file offsets the programs will fail. In that case you have to	2395	use 64 bit file offsets the programs will fail. In that case you have to
1785	compile libev with the same flags to get binary compatibility. This is	2396	compile libev with the same flags to get binary compatibility. This is
1786	obviously the case with any flags that change the ABI, but the problem is	2397	obviously the case with any flags that change the ABI, but the problem is
1787	most noticeably disabled with ev_stat and large file support.	2398	most noticeably displayed with ev_stat and large file support.
1788		2399
1789	The solution for this is to lobby your distribution maker to make large	2400	The solution for this is to lobby your distribution maker to make large
1790	file interfaces available by default (as e.g. FreeBSD does) and not	2401	file interfaces available by default (as e.g. FreeBSD does) and not
1791	optional. Libev cannot simply switch on large file support because it has	2402	optional. Libev cannot simply switch on large file support because it has
1792	to exchange stat structures with application programs compiled using the	2403	to exchange stat structures with application programs compiled using the
1793	default compilation environment.	2404	default compilation environment.
1794		2405
1795	=head3 Inotify and Kqueue	2406	=head3 Inotify and Kqueue
1796		2407
1797	When C<inotify (7)> support has been compiled into libev (generally only	2408	When C<inotify (7)> support has been compiled into libev and present at
1798	available with Linux) and present at runtime, it will be used to speed up	2409	runtime, it will be used to speed up change detection where possible. The
1799	change detection where possible. The inotify descriptor will be created lazily	2410	inotify descriptor will be created lazily when the first C<ev_stat>
1800	when the first C<ev_stat> watcher is being started.	2411	watcher is being started.
1801		2412
1802	Inotify presence does not change the semantics of C<ev_stat> watchers	2413	Inotify presence does not change the semantics of C<ev_stat> watchers
1803	except that changes might be detected earlier, and in some cases, to avoid	2414	except that changes might be detected earlier, and in some cases, to avoid
1804	making regular C<stat> calls. Even in the presence of inotify support	2415	making regular C<stat> calls. Even in the presence of inotify support
1805	there are many cases where libev has to resort to regular C<stat> polling,	2416	there are many cases where libev has to resort to regular C<stat> polling,
1806	but as long as the path exists, libev usually gets away without polling.	2417	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2418	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2419	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2420	xfs are fully working) libev usually gets away without polling.
1807		2421
1808	There is no support for kqueue, as apparently it cannot be used to	2422	There is no support for kqueue, as apparently it cannot be used to
1809	implement this functionality, due to the requirement of having a file	2423	implement this functionality, due to the requirement of having a file
1810	descriptor open on the object at all times, and detecting renames, unlinks	2424	descriptor open on the object at all times, and detecting renames, unlinks
1811	etc. is difficult.	2425	etc. is difficult.
1812		2426
		2427	=head3 C<stat ()> is a synchronous operation
		2428
		2429	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2430	the process. The exception are C<ev_stat> watchers - those call C<stat
		2431	()>, which is a synchronous operation.
		2432
		2433	For local paths, this usually doesn't matter: unless the system is very
		2434	busy or the intervals between stat's are large, a stat call will be fast,
		2435	as the path data is usually in memory already (except when starting the
		2436	watcher).
		2437
		2438	For networked file systems, calling C<stat ()> can block an indefinite
		2439	time due to network issues, and even under good conditions, a stat call
		2440	often takes multiple milliseconds.
		2441
		2442	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2443	paths, although this is fully supported by libev.
		2444
1813	=head3 The special problem of stat time resolution	2445	=head3 The special problem of stat time resolution
1814		2446
1815	The C<stat ()> system call only supports full-second resolution portably, and	2447	The C<stat ()> system call only supports full-second resolution portably,
1816	even on systems where the resolution is higher, most file systems still	2448	and even on systems where the resolution is higher, most file systems
1817	only support whole seconds.	2449	still only support whole seconds.
1818		2450
1819	That means that, if the time is the only thing that changes, you can	2451	That means that, if the time is the only thing that changes, you can
1820	easily miss updates: on the first update, C<ev_stat> detects a change and	2452	easily miss updates: on the first update, C<ev_stat> detects a change and
1821	calls your callback, which does something. When there is another update	2453	calls your callback, which does something. When there is another update
1822	within the same second, C<ev_stat> will be unable to detect unless the	2454	within the same second, C<ev_stat> will be unable to detect unless the
…		…
1965		2597
1966	=head3 Watcher-Specific Functions and Data Members	2598	=head3 Watcher-Specific Functions and Data Members
1967		2599
1968	=over 4	2600	=over 4
1969		2601
1970	=item ev_idle_init (ev_signal *, callback)	2602	=item ev_idle_init (ev_idle *, callback)
1971		2603
1972	Initialises and configures the idle watcher - it has no parameters of any	2604	Initialises and configures the idle watcher - it has no parameters of any
1973	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2605	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1974	believe me.	2606	believe me.
1975		2607
…		…
1979		2611
1980	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2612	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1981	callback, free it. Also, use no error checking, as usual.	2613	callback, free it. Also, use no error checking, as usual.
1982		2614
1983	static void	2615	static void
1984	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2616	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1985	{	2617	{
1986	free (w);	2618	free (w);
1987	// now do something you wanted to do when the program has	2619	// now do something you wanted to do when the program has
1988	// no longer anything immediate to do.	2620	// no longer anything immediate to do.
1989	}	2621	}
1990		2622
1991	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2623	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1992	ev_idle_init (idle_watcher, idle_cb);	2624	ev_idle_init (idle_watcher, idle_cb);
1993	ev_idle_start (loop, idle_cb);	2625	ev_idle_start (loop, idle_watcher);
1994		2626
1995		2627
1996	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2628	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1997		2629
1998	Prepare and check watchers are usually (but not always) used in pairs:	2630	Prepare and check watchers are usually (but not always) used in pairs:
…		…
2077		2709
2078	static ev_io iow [nfd];	2710	static ev_io iow [nfd];
2079	static ev_timer tw;	2711	static ev_timer tw;
2080		2712
2081	static void	2713	static void
2082	io_cb (ev_loop *loop, ev_io *w, int revents)	2714	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2083	{	2715	{
2084	}	2716	}
2085		2717
2086	// create io watchers for each fd and a timer before blocking	2718	// create io watchers for each fd and a timer before blocking
2087	static void	2719	static void
2088	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2720	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2089	{	2721	{
2090	int timeout = 3600000;	2722	int timeout = 3600000;
2091	struct pollfd fds [nfd];	2723	struct pollfd fds [nfd];
2092	// actual code will need to loop here and realloc etc.	2724	// actual code will need to loop here and realloc etc.
2093	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2725	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2094		2726
2095	/* the callback is illegal, but won't be called as we stop during check */	2727	/* the callback is illegal, but won't be called as we stop during check */
2096	ev_timer_init (&tw, 0, timeout * 1e-3);	2728	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2097	ev_timer_start (loop, &tw);	2729	ev_timer_start (loop, &tw);
2098		2730
2099	// create one ev_io per pollfd	2731	// create one ev_io per pollfd
2100	for (int i = 0; i < nfd; ++i)	2732	for (int i = 0; i < nfd; ++i)
2101	{	2733	{
…		…
2108	}	2740	}
2109	}	2741	}
2110		2742
2111	// stop all watchers after blocking	2743	// stop all watchers after blocking
2112	static void	2744	static void
2113	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2745	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2114	{	2746	{
2115	ev_timer_stop (loop, &tw);	2747	ev_timer_stop (loop, &tw);
2116		2748
2117	for (int i = 0; i < nfd; ++i)	2749	for (int i = 0; i < nfd; ++i)
2118	{	2750	{
…		…
2214	some fds have to be watched and handled very quickly (with low latency),	2846	some fds have to be watched and handled very quickly (with low latency),
2215	and even priorities and idle watchers might have too much overhead. In	2847	and even priorities and idle watchers might have too much overhead. In
2216	this case you would put all the high priority stuff in one loop and all	2848	this case you would put all the high priority stuff in one loop and all
2217	the rest in a second one, and embed the second one in the first.	2849	the rest in a second one, and embed the second one in the first.
2218		2850
2219	As long as the watcher is active, the callback will be invoked every time	2851	As long as the watcher is active, the callback will be invoked every
2220	there might be events pending in the embedded loop. The callback must then	2852	time there might be events pending in the embedded loop. The callback
2221	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2853	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2222	their callbacks (you could also start an idle watcher to give the embedded	2854	sweep and invoke their callbacks (the callback doesn't need to invoke the
2223	loop strictly lower priority for example). You can also set the callback	2855	C<ev_embed_sweep> function directly, it could also start an idle watcher
2224	to C<0>, in which case the embed watcher will automatically execute the	2856	to give the embedded loop strictly lower priority for example).
2225	embedded loop sweep.
2226		2857
2227	As long as the watcher is started it will automatically handle events. The	2858	You can also set the callback to C<0>, in which case the embed watcher
2228	callback will be invoked whenever some events have been handled. You can	2859	will automatically execute the embedded loop sweep whenever necessary.
2229	set the callback to C<0> to avoid having to specify one if you are not
2230	interested in that.
2231		2860
2232	Also, there have not currently been made special provisions for forking:	2861	Fork detection will be handled transparently while the C<ev_embed> watcher
2233	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2862	is active, i.e., the embedded loop will automatically be forked when the
2234	but you will also have to stop and restart any C<ev_embed> watchers	2863	embedding loop forks. In other cases, the user is responsible for calling
2235	yourself - but you can use a fork watcher to handle this automatically,	2864	C<ev_loop_fork> on the embedded loop.
2236	and future versions of libev might do just that.
2237		2865
2238	Unfortunately, not all backends are embeddable: only the ones returned by	2866	Unfortunately, not all backends are embeddable: only the ones returned by
2239	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2867	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2240	portable one.	2868	portable one.
2241		2869
…		…
2286	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2914	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2287	used).	2915	used).
2288		2916
2289	struct ev_loop *loop_hi = ev_default_init (0);	2917	struct ev_loop *loop_hi = ev_default_init (0);
2290	struct ev_loop *loop_lo = 0;	2918	struct ev_loop *loop_lo = 0;
2291	struct ev_embed embed;	2919	ev_embed embed;
2292		2920
2293	// see if there is a chance of getting one that works	2921	// see if there is a chance of getting one that works
2294	// (remember that a flags value of 0 means autodetection)	2922	// (remember that a flags value of 0 means autodetection)
2295	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2923	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2296	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2924	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2310	kqueue implementation). Store the kqueue/socket-only event loop in	2938	kqueue implementation). Store the kqueue/socket-only event loop in
2311	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2939	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2312		2940
2313	struct ev_loop *loop = ev_default_init (0);	2941	struct ev_loop *loop = ev_default_init (0);
2314	struct ev_loop *loop_socket = 0;	2942	struct ev_loop *loop_socket = 0;
2315	struct ev_embed embed;	2943	ev_embed embed;
2316		2944
2317	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2945	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2318	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2946	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2319	{	2947	{
2320	ev_embed_init (&embed, 0, loop_socket);	2948	ev_embed_init (&embed, 0, loop_socket);
…		…
2335	event loop blocks next and before C<ev_check> watchers are being called,	2963	event loop blocks next and before C<ev_check> watchers are being called,
2336	and only in the child after the fork. If whoever good citizen calling	2964	and only in the child after the fork. If whoever good citizen calling
2337	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2965	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2338	handlers will be invoked, too, of course.	2966	handlers will be invoked, too, of course.
2339		2967
		2968	=head3 The special problem of life after fork - how is it possible?
		2969
		2970	Most uses of C<fork()> consist of forking, then some simple calls to set
		2971	up/change the process environment, followed by a call to C<exec()>. This
		2972	sequence should be handled by libev without any problems.
		2973
		2974	This changes when the application actually wants to do event handling
		2975	in the child, or both parent in child, in effect "continuing" after the
		2976	fork.
		2977
		2978	The default mode of operation (for libev, with application help to detect
		2979	forks) is to duplicate all the state in the child, as would be expected
		2980	when I<either> the parent I<or> the child process continues.
		2981
		2982	When both processes want to continue using libev, then this is usually the
		2983	wrong result. In that case, usually one process (typically the parent) is
		2984	supposed to continue with all watchers in place as before, while the other
		2985	process typically wants to start fresh, i.e. without any active watchers.
		2986
		2987	The cleanest and most efficient way to achieve that with libev is to
		2988	simply create a new event loop, which of course will be "empty", and
		2989	use that for new watchers. This has the advantage of not touching more
		2990	memory than necessary, and thus avoiding the copy-on-write, and the
		2991	disadvantage of having to use multiple event loops (which do not support
		2992	signal watchers).
		2993
		2994	When this is not possible, or you want to use the default loop for
		2995	other reasons, then in the process that wants to start "fresh", call
		2996	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2997	the default loop will "orphan" (not stop) all registered watchers, so you
		2998	have to be careful not to execute code that modifies those watchers. Note
		2999	also that in that case, you have to re-register any signal watchers.
		3000
2340	=head3 Watcher-Specific Functions and Data Members	3001	=head3 Watcher-Specific Functions and Data Members
2341		3002
2342	=over 4	3003	=over 4
2343		3004
2344	=item ev_fork_init (ev_signal *, callback)	3005	=item ev_fork_init (ev_signal *, callback)
…		…
2348	believe me.	3009	believe me.
2349		3010
2350	=back	3011	=back
2351		3012
2352		3013
2353	=head2 C<ev_async> - how to wake up another event loop	3014	=head2 C<ev_async> - how to wake up an event loop
2354		3015
2355	In general, you cannot use an C<ev_loop> from multiple threads or other	3016	In general, you cannot use an C<ev_loop> from multiple threads or other
2356	asynchronous sources such as signal handlers (as opposed to multiple event	3017	asynchronous sources such as signal handlers (as opposed to multiple event
2357	loops - those are of course safe to use in different threads).	3018	loops - those are of course safe to use in different threads).
2358		3019
2359	Sometimes, however, you need to wake up another event loop you do not	3020	Sometimes, however, you need to wake up an event loop you do not control,
2360	control, for example because it belongs to another thread. This is what	3021	for example because it belongs to another thread. This is what C<ev_async>
2361	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3022	watchers do: as long as the C<ev_async> watcher is active, you can signal
2362	can signal it by calling C<ev_async_send>, which is thread- and signal	3023	it by calling C<ev_async_send>, which is thread- and signal safe.
2363	safe.
2364		3024
2365	This functionality is very similar to C<ev_signal> watchers, as signals,	3025	This functionality is very similar to C<ev_signal> watchers, as signals,
2366	too, are asynchronous in nature, and signals, too, will be compressed	3026	too, are asynchronous in nature, and signals, too, will be compressed
2367	(i.e. the number of callback invocations may be less than the number of	3027	(i.e. the number of callback invocations may be less than the number of
2368	C<ev_async_sent> calls).	3028	C<ev_async_sent> calls).
…		…
2373	=head3 Queueing	3033	=head3 Queueing
2374		3034
2375	C<ev_async> does not support queueing of data in any way. The reason	3035	C<ev_async> does not support queueing of data in any way. The reason
2376	is that the author does not know of a simple (or any) algorithm for a	3036	is that the author does not know of a simple (or any) algorithm for a
2377	multiple-writer-single-reader queue that works in all cases and doesn't	3037	multiple-writer-single-reader queue that works in all cases and doesn't
2378	need elaborate support such as pthreads.	3038	need elaborate support such as pthreads or unportable memory access
		3039	semantics.
2379		3040
2380	That means that if you want to queue data, you have to provide your own	3041	That means that if you want to queue data, you have to provide your own
2381	queue. But at least I can tell you how to implement locking around your	3042	queue. But at least I can tell you how to implement locking around your
2382	queue:	3043	queue:
2383		3044
…		…
2461	=over 4	3122	=over 4
2462		3123
2463	=item ev_async_init (ev_async *, callback)	3124	=item ev_async_init (ev_async *, callback)
2464		3125
2465	Initialises and configures the async watcher - it has no parameters of any	3126	Initialises and configures the async watcher - it has no parameters of any
2466	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3127	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2467	trust me.	3128	trust me.
2468		3129
2469	=item ev_async_send (loop, ev_async *)	3130	=item ev_async_send (loop, ev_async *)
2470		3131
2471	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3132	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2472	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3133	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2473	C<ev_feed_event>, this call is safe to do from other threads, signal or	3134	C<ev_feed_event>, this call is safe to do from other threads, signal or
2474	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3135	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2475	section below on what exactly this means).	3136	section below on what exactly this means).
2476		3137
		3138	Note that, as with other watchers in libev, multiple events might get
		3139	compressed into a single callback invocation (another way to look at this
		3140	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3141	reset when the event loop detects that).
		3142
2477	This call incurs the overhead of a system call only once per loop iteration,	3143	This call incurs the overhead of a system call only once per event loop
2478	so while the overhead might be noticeable, it doesn't apply to repeated	3144	iteration, so while the overhead might be noticeable, it doesn't apply to
2479	calls to C<ev_async_send>.	3145	repeated calls to C<ev_async_send> for the same event loop.
2480		3146
2481	=item bool = ev_async_pending (ev_async *)	3147	=item bool = ev_async_pending (ev_async *)
2482		3148
2483	Returns a non-zero value when C<ev_async_send> has been called on the	3149	Returns a non-zero value when C<ev_async_send> has been called on the
2484	watcher but the event has not yet been processed (or even noted) by the	3150	watcher but the event has not yet been processed (or even noted) by the
…		…
2487	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3153	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2488	the loop iterates next and checks for the watcher to have become active,	3154	the loop iterates next and checks for the watcher to have become active,
2489	it will reset the flag again. C<ev_async_pending> can be used to very	3155	it will reset the flag again. C<ev_async_pending> can be used to very
2490	quickly check whether invoking the loop might be a good idea.	3156	quickly check whether invoking the loop might be a good idea.
2491		3157
2492	Not that this does I<not> check whether the watcher itself is pending, only	3158	Not that this does I<not> check whether the watcher itself is pending,
2493	whether it has been requested to make this watcher pending.	3159	only whether it has been requested to make this watcher pending: there
		3160	is a time window between the event loop checking and resetting the async
		3161	notification, and the callback being invoked.
2494		3162
2495	=back	3163	=back
2496		3164
2497		3165
2498	=head1 OTHER FUNCTIONS	3166	=head1 OTHER FUNCTIONS
…		…
2513	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for	3181	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2514	the given C<fd> and C<events> set will be created and started.	3182	the given C<fd> and C<events> set will be created and started.
2515		3183
2516	If C<timeout> is less than 0, then no timeout watcher will be	3184	If C<timeout> is less than 0, then no timeout watcher will be
2517	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3185	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2518	repeat = 0) will be started. While C<0> is a valid timeout, it is of	3186	repeat = 0) will be started. C<0> is a valid timeout.
2519	dubious value.
2520		3187
2521	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3188	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2522	passed an C<revents> set like normal event callbacks (a combination of	3189	passed an C<revents> set like normal event callbacks (a combination of
2523	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3190	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2524	value passed to C<ev_once>:	3191	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3192	a timeout and an io event at the same time - you probably should give io
		3193	events precedence.
		3194
		3195	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2525		3196
2526	static void stdin_ready (int revents, void *arg)	3197	static void stdin_ready (int revents, void *arg)
2527	{	3198	{
		3199	if (revents & EV_READ)
		3200	/* stdin might have data for us, joy! */;
2528	if (revents & EV_TIMEOUT)	3201	else if (revents & EV_TIMER)
2529	/* doh, nothing entered */;	3202	/* doh, nothing entered */;
2530	else if (revents & EV_READ)
2531	/* stdin might have data for us, joy! */;
2532	}	3203	}
2533		3204
2534	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3205	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2535		3206
2536	=item ev_feed_event (ev_loop *, watcher *, int revents)
2537
2538	Feeds the given event set into the event loop, as if the specified event
2539	had happened for the specified watcher (which must be a pointer to an
2540	initialised but not necessarily started event watcher).
2541
2542	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3207	=item ev_feed_fd_event (loop, int fd, int revents)
2543		3208
2544	Feed an event on the given fd, as if a file descriptor backend detected	3209	Feed an event on the given fd, as if a file descriptor backend detected
2545	the given events it.	3210	the given events it.
2546		3211
2547	=item ev_feed_signal_event (ev_loop *loop, int signum)	3212	=item ev_feed_signal_event (loop, int signum)
2548		3213
2549	Feed an event as if the given signal occurred (C<loop> must be the default	3214	Feed an event as if the given signal occurred (C<loop> must be the default
2550	loop!).	3215	loop!).
2551		3216
2552	=back	3217	=back
…		…
2632		3297
2633	=over 4	3298	=over 4
2634		3299
2635	=item ev::TYPE::TYPE ()	3300	=item ev::TYPE::TYPE ()
2636		3301
2637	=item ev::TYPE::TYPE (struct ev_loop *)	3302	=item ev::TYPE::TYPE (loop)
2638		3303
2639	=item ev::TYPE::~TYPE	3304	=item ev::TYPE::~TYPE
2640		3305
2641	The constructor (optionally) takes an event loop to associate the watcher	3306	The constructor (optionally) takes an event loop to associate the watcher
2642	with. If it is omitted, it will use C<EV_DEFAULT>.	3307	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2674		3339
2675	myclass obj;	3340	myclass obj;
2676	ev::io iow;	3341	ev::io iow;
2677	iow.set <myclass, &myclass::io_cb> (&obj);	3342	iow.set <myclass, &myclass::io_cb> (&obj);
2678		3343
		3344	=item w->set (object *)
		3345
		3346	This is a variation of a method callback - leaving out the method to call
		3347	will default the method to C<operator ()>, which makes it possible to use
		3348	functor objects without having to manually specify the C<operator ()> all
		3349	the time. Incidentally, you can then also leave out the template argument
		3350	list.
		3351
		3352	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3353	int revents)>.
		3354
		3355	See the method-C<set> above for more details.
		3356
		3357	Example: use a functor object as callback.
		3358
		3359	struct myfunctor
		3360	{
		3361	void operator() (ev::io &w, int revents)
		3362	{
		3363	...
		3364	}
		3365	}
		3366
		3367	myfunctor f;
		3368
		3369	ev::io w;
		3370	w.set (&f);
		3371
2679	=item w->set<function> (void *data = 0)	3372	=item w->set<function> (void *data = 0)
2680		3373
2681	Also sets a callback, but uses a static method or plain function as	3374	Also sets a callback, but uses a static method or plain function as
2682	callback. The optional C<data> argument will be stored in the watcher's	3375	callback. The optional C<data> argument will be stored in the watcher's
2683	C<data> member and is free for you to use.	3376	C<data> member and is free for you to use.
…		…
2689	Example: Use a plain function as callback.	3382	Example: Use a plain function as callback.
2690		3383
2691	static void io_cb (ev::io &w, int revents) { }	3384	static void io_cb (ev::io &w, int revents) { }
2692	iow.set <io_cb> ();	3385	iow.set <io_cb> ();
2693		3386
2694	=item w->set (struct ev_loop *)	3387	=item w->set (loop)
2695		3388
2696	Associates a different C<struct ev_loop> with this watcher. You can only	3389	Associates a different C<struct ev_loop> with this watcher. You can only
2697	do this when the watcher is inactive (and not pending either).	3390	do this when the watcher is inactive (and not pending either).
2698		3391
2699	=item w->set ([arguments])	3392	=item w->set ([arguments])
…		…
2769	L<http://software.schmorp.de/pkg/EV>.	3462	L<http://software.schmorp.de/pkg/EV>.
2770		3463
2771	=item Python	3464	=item Python
2772		3465
2773	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3466	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2774	seems to be quite complete and well-documented. Note, however, that the	3467	seems to be quite complete and well-documented.
2775	patch they require for libev is outright dangerous as it breaks the ABI
2776	for everybody else, and therefore, should never be applied in an installed
2777	libev (if python requires an incompatible ABI then it needs to embed
2778	libev).
2779		3468
2780	=item Ruby	3469	=item Ruby
2781		3470
2782	Tony Arcieri has written a ruby extension that offers access to a subset	3471	Tony Arcieri has written a ruby extension that offers access to a subset
2783	of the libev API and adds file handle abstractions, asynchronous DNS and	3472	of the libev API and adds file handle abstractions, asynchronous DNS and
2784	more on top of it. It can be found via gem servers. Its homepage is at	3473	more on top of it. It can be found via gem servers. Its homepage is at
2785	L<http://rev.rubyforge.org/>.	3474	L<http://rev.rubyforge.org/>.
2786		3475
		3476	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3477	makes rev work even on mingw.
		3478
		3479	=item Haskell
		3480
		3481	A haskell binding to libev is available at
		3482	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3483
2787	=item D	3484	=item D
2788		3485
2789	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3486	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2790	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3487	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3488
		3489	=item Ocaml
		3490
		3491	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3492	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3493
		3494	=item Lua
		3495
		3496	Brian Maher has written a partial interface to libev for lua (at the
		3497	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3498	L<http://github.com/brimworks/lua-ev>.
2791		3499
2792	=back	3500	=back
2793		3501
2794		3502
2795	=head1 MACRO MAGIC	3503	=head1 MACRO MAGIC
…		…
2896		3604
2897	#define EV_STANDALONE 1	3605	#define EV_STANDALONE 1
2898	#include "ev.h"	3606	#include "ev.h"
2899		3607
2900	Both header files and implementation files can be compiled with a C++	3608	Both header files and implementation files can be compiled with a C++
2901	compiler (at least, thats a stated goal, and breakage will be treated	3609	compiler (at least, that's a stated goal, and breakage will be treated
2902	as a bug).	3610	as a bug).
2903		3611
2904	You need the following files in your source tree, or in a directory	3612	You need the following files in your source tree, or in a directory
2905	in your include path (e.g. in libev/ when using -Ilibev):	3613	in your include path (e.g. in libev/ when using -Ilibev):
2906		3614
…		…
2949	libev.m4	3657	libev.m4
2950		3658
2951	=head2 PREPROCESSOR SYMBOLS/MACROS	3659	=head2 PREPROCESSOR SYMBOLS/MACROS
2952		3660
2953	Libev can be configured via a variety of preprocessor symbols you have to	3661	Libev can be configured via a variety of preprocessor symbols you have to
2954	define before including any of its files. The default in the absence of	3662	define before including (or compiling) any of its files. The default in
2955	autoconf is documented for every option.	3663	the absence of autoconf is documented for every option.
		3664
		3665	Symbols marked with "(h)" do not change the ABI, and can have different
		3666	values when compiling libev vs. including F<ev.h>, so it is permissible
		3667	to redefine them before including F<ev.h> without breaking compatibility
		3668	to a compiled library. All other symbols change the ABI, which means all
		3669	users of libev and the libev code itself must be compiled with compatible
		3670	settings.
2956		3671
2957	=over 4	3672	=over 4
2958		3673
2959	=item EV_STANDALONE	3674	=item EV_STANDALONE (h)
2960		3675
2961	Must always be C<1> if you do not use autoconf configuration, which	3676	Must always be C<1> if you do not use autoconf configuration, which
2962	keeps libev from including F<config.h>, and it also defines dummy	3677	keeps libev from including F<config.h>, and it also defines dummy
2963	implementations for some libevent functions (such as logging, which is not	3678	implementations for some libevent functions (such as logging, which is not
2964	supported). It will also not define any of the structs usually found in	3679	supported). It will also not define any of the structs usually found in
2965	F<event.h> that are not directly supported by the libev core alone.	3680	F<event.h> that are not directly supported by the libev core alone.
2966		3681
		3682	In standalone mode, libev will still try to automatically deduce the
		3683	configuration, but has to be more conservative.
		3684
2967	=item EV_USE_MONOTONIC	3685	=item EV_USE_MONOTONIC
2968		3686
2969	If defined to be C<1>, libev will try to detect the availability of the	3687	If defined to be C<1>, libev will try to detect the availability of the
2970	monotonic clock option at both compile time and runtime. Otherwise no use	3688	monotonic clock option at both compile time and runtime. Otherwise no
2971	of the monotonic clock option will be attempted. If you enable this, you	3689	use of the monotonic clock option will be attempted. If you enable this,
2972	usually have to link against librt or something similar. Enabling it when	3690	you usually have to link against librt or something similar. Enabling it
2973	the functionality isn't available is safe, though, although you have	3691	when the functionality isn't available is safe, though, although you have
2974	to make sure you link against any libraries where the C<clock_gettime>	3692	to make sure you link against any libraries where the C<clock_gettime>
2975	function is hiding in (often F<-lrt>).	3693	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2976		3694
2977	=item EV_USE_REALTIME	3695	=item EV_USE_REALTIME
2978		3696
2979	If defined to be C<1>, libev will try to detect the availability of the	3697	If defined to be C<1>, libev will try to detect the availability of the
2980	real-time clock option at compile time (and assume its availability at	3698	real-time clock option at compile time (and assume its availability
2981	runtime if successful). Otherwise no use of the real-time clock option will	3699	at runtime if successful). Otherwise no use of the real-time clock
2982	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3700	option will be attempted. This effectively replaces C<gettimeofday>
2983	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3701	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2984	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3702	correctness. See the note about libraries in the description of
		3703	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3704	C<EV_USE_CLOCK_SYSCALL>.
		3705
		3706	=item EV_USE_CLOCK_SYSCALL
		3707
		3708	If defined to be C<1>, libev will try to use a direct syscall instead
		3709	of calling the system-provided C<clock_gettime> function. This option
		3710	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3711	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3712	programs needlessly. Using a direct syscall is slightly slower (in
		3713	theory), because no optimised vdso implementation can be used, but avoids
		3714	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3715	higher, as it simplifies linking (no need for C<-lrt>).
2985		3716
2986	=item EV_USE_NANOSLEEP	3717	=item EV_USE_NANOSLEEP
2987		3718
2988	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3719	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2989	and will use it for delays. Otherwise it will use C<select ()>.	3720	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3005		3736
3006	=item EV_SELECT_USE_FD_SET	3737	=item EV_SELECT_USE_FD_SET
3007		3738
3008	If defined to C<1>, then the select backend will use the system C<fd_set>	3739	If defined to C<1>, then the select backend will use the system C<fd_set>
3009	structure. This is useful if libev doesn't compile due to a missing	3740	structure. This is useful if libev doesn't compile due to a missing
3010	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3741	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3011	exotic systems. This usually limits the range of file descriptors to some	3742	on exotic systems. This usually limits the range of file descriptors to
3012	low limit such as 1024 or might have other limitations (winsocket only	3743	some low limit such as 1024 or might have other limitations (winsocket
3013	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3744	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3014	influence the size of the C<fd_set> used.	3745	configures the maximum size of the C<fd_set>.
3015		3746
3016	=item EV_SELECT_IS_WINSOCKET	3747	=item EV_SELECT_IS_WINSOCKET
3017		3748
3018	When defined to C<1>, the select backend will assume that	3749	When defined to C<1>, the select backend will assume that
3019	select/socket/connect etc. don't understand file descriptors but	3750	select/socket/connect etc. don't understand file descriptors but
…		…
3021	be used is the winsock select). This means that it will call	3752	be used is the winsock select). This means that it will call
3022	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3753	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3023	it is assumed that all these functions actually work on fds, even	3754	it is assumed that all these functions actually work on fds, even
3024	on win32. Should not be defined on non-win32 platforms.	3755	on win32. Should not be defined on non-win32 platforms.
3025		3756
3026	=item EV_FD_TO_WIN32_HANDLE	3757	=item EV_FD_TO_WIN32_HANDLE(fd)
3027		3758
3028	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3759	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3029	file descriptors to socket handles. When not defining this symbol (the	3760	file descriptors to socket handles. When not defining this symbol (the
3030	default), then libev will call C<_get_osfhandle>, which is usually	3761	default), then libev will call C<_get_osfhandle>, which is usually
3031	correct. In some cases, programs use their own file descriptor management,	3762	correct. In some cases, programs use their own file descriptor management,
3032	in which case they can provide this function to map fds to socket handles.	3763	in which case they can provide this function to map fds to socket handles.
		3764
		3765	=item EV_WIN32_HANDLE_TO_FD(handle)
		3766
		3767	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3768	using the standard C<_open_osfhandle> function. For programs implementing
		3769	their own fd to handle mapping, overwriting this function makes it easier
		3770	to do so. This can be done by defining this macro to an appropriate value.
		3771
		3772	=item EV_WIN32_CLOSE_FD(fd)
		3773
		3774	If programs implement their own fd to handle mapping on win32, then this
		3775	macro can be used to override the C<close> function, useful to unregister
		3776	file descriptors again. Note that the replacement function has to close
		3777	the underlying OS handle.
3033		3778
3034	=item EV_USE_POLL	3779	=item EV_USE_POLL
3035		3780
3036	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3781	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3037	backend. Otherwise it will be enabled on non-win32 platforms. It	3782	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3084	as well as for signal and thread safety in C<ev_async> watchers.	3829	as well as for signal and thread safety in C<ev_async> watchers.
3085		3830
3086	In the absence of this define, libev will use C<sig_atomic_t volatile>	3831	In the absence of this define, libev will use C<sig_atomic_t volatile>
3087	(from F<signal.h>), which is usually good enough on most platforms.	3832	(from F<signal.h>), which is usually good enough on most platforms.
3088		3833
3089	=item EV_H	3834	=item EV_H (h)
3090		3835
3091	The name of the F<ev.h> header file used to include it. The default if	3836	The name of the F<ev.h> header file used to include it. The default if
3092	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	3837	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3093	used to virtually rename the F<ev.h> header file in case of conflicts.	3838	used to virtually rename the F<ev.h> header file in case of conflicts.
3094		3839
3095	=item EV_CONFIG_H	3840	=item EV_CONFIG_H (h)
3096		3841
3097	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	3842	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3098	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	3843	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3099	C<EV_H>, above.	3844	C<EV_H>, above.
3100		3845
3101	=item EV_EVENT_H	3846	=item EV_EVENT_H (h)
3102		3847
3103	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	3848	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3104	of how the F<event.h> header can be found, the default is C<"event.h">.	3849	of how the F<event.h> header can be found, the default is C<"event.h">.
3105		3850
3106	=item EV_PROTOTYPES	3851	=item EV_PROTOTYPES (h)
3107		3852
3108	If defined to be C<0>, then F<ev.h> will not define any function	3853	If defined to be C<0>, then F<ev.h> will not define any function
3109	prototypes, but still define all the structs and other symbols. This is	3854	prototypes, but still define all the structs and other symbols. This is
3110	occasionally useful if you want to provide your own wrapper functions	3855	occasionally useful if you want to provide your own wrapper functions
3111	around libev functions.	3856	around libev functions.
…		…
3133	fine.	3878	fine.
3134		3879
3135	If your embedding application does not need any priorities, defining these	3880	If your embedding application does not need any priorities, defining these
3136	both to C<0> will save some memory and CPU.	3881	both to C<0> will save some memory and CPU.
3137		3882
3138	=item EV_PERIODIC_ENABLE	3883	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		3884	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		3885	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3139		3886
3140	If undefined or defined to be C<1>, then periodic timers are supported. If	3887	If undefined or defined to be C<1> (and the platform supports it), then
3141	defined to be C<0>, then they are not. Disabling them saves a few kB of	3888	the respective watcher type is supported. If defined to be C<0>, then it
3142	code.	3889	is not. Disabling watcher types mainly saves code size.
3143		3890
3144	=item EV_IDLE_ENABLE	3891	=item EV_FEATURES
3145
3146	If undefined or defined to be C<1>, then idle watchers are supported. If
3147	defined to be C<0>, then they are not. Disabling them saves a few kB of
3148	code.
3149
3150	=item EV_EMBED_ENABLE
3151
3152	If undefined or defined to be C<1>, then embed watchers are supported. If
3153	defined to be C<0>, then they are not. Embed watchers rely on most other
3154	watcher types, which therefore must not be disabled.
3155
3156	=item EV_STAT_ENABLE
3157
3158	If undefined or defined to be C<1>, then stat watchers are supported. If
3159	defined to be C<0>, then they are not.
3160
3161	=item EV_FORK_ENABLE
3162
3163	If undefined or defined to be C<1>, then fork watchers are supported. If
3164	defined to be C<0>, then they are not.
3165
3166	=item EV_ASYNC_ENABLE
3167
3168	If undefined or defined to be C<1>, then async watchers are supported. If
3169	defined to be C<0>, then they are not.
3170
3171	=item EV_MINIMAL
3172		3892
3173	If you need to shave off some kilobytes of code at the expense of some	3893	If you need to shave off some kilobytes of code at the expense of some
3174	speed, define this symbol to C<1>. Currently this is used to override some	3894	speed (but with the full API), you can define this symbol to request
3175	inlining decisions, saves roughly 30% code size on amd64. It also selects a	3895	certain subsets of functionality. The default is to enable all features
3176	much smaller 2-heap for timer management over the default 4-heap.	3896	that can be enabled on the platform.
		3897
		3898	A typical way to use this symbol is to define it to C<0> (or to a bitset
		3899	with some broad features you want) and then selectively re-enable
		3900	additional parts you want, for example if you want everything minimal,
		3901	but multiple event loop support, async and child watchers and the poll
		3902	backend, use this:
		3903
		3904	#define EV_FEATURES 0
		3905	#define EV_MULTIPLICITY 1
		3906	#define EV_USE_POLL 1
		3907	#define EV_CHILD_ENABLE 1
		3908	#define EV_ASYNC_ENABLE 1
		3909
		3910	The actual value is a bitset, it can be a combination of the following
		3911	values:
		3912
		3913	=over 4
		3914
		3915	=item C<1> - faster/larger code
		3916
		3917	Use larger code to speed up some operations.
		3918
		3919	Currently this is used to override some inlining decisions (enlarging the
		3920	code size by roughly 30% on amd64).
		3921
		3922	When optimising for size, use of compiler flags such as C<-Os> with
		3923	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		3924	assertions.
		3925
		3926	=item C<2> - faster/larger data structures
		3927
		3928	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		3929	hash table sizes and so on. This will usually further increase code size
		3930	and can additionally have an effect on the size of data structures at
		3931	runtime.
		3932
		3933	=item C<4> - full API configuration
		3934
		3935	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		3936	enables multiplicity (C<EV_MULTIPLICITY>=1).
		3937
		3938	=item C<8> - full API
		3939
		3940	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		3941	details on which parts of the API are still available without this
		3942	feature, and do not complain if this subset changes over time.
		3943
		3944	=item C<16> - enable all optional watcher types
		3945
		3946	Enables all optional watcher types. If you want to selectively enable
		3947	only some watcher types other than I/O and timers (e.g. prepare,
		3948	embed, async, child...) you can enable them manually by defining
		3949	C<EV_watchertype_ENABLE> to C<1> instead.
		3950
		3951	=item C<32> - enable all backends
		3952
		3953	This enables all backends - without this feature, you need to enable at
		3954	least one backend manually (C<EV_USE_SELECT> is a good choice).
		3955
		3956	=item C<64> - enable OS-specific "helper" APIs
		3957
		3958	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		3959	default.
		3960
		3961	=back
		3962
		3963	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		3964	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		3965	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		3966	watchers, timers and monotonic clock support.
		3967
		3968	With an intelligent-enough linker (gcc+binutils are intelligent enough
		3969	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		3970	your program might be left out as well - a binary starting a timer and an
		3971	I/O watcher then might come out at only 5Kb.
		3972
		3973	=item EV_AVOID_STDIO
		3974
		3975	If this is set to C<1> at compiletime, then libev will avoid using stdio
		3976	functions (printf, scanf, perror etc.). This will increase the code size
		3977	somewhat, but if your program doesn't otherwise depend on stdio and your
		3978	libc allows it, this avoids linking in the stdio library which is quite
		3979	big.
		3980
		3981	Note that error messages might become less precise when this option is
		3982	enabled.
		3983
		3984	=item EV_NSIG
		3985
		3986	The highest supported signal number, +1 (or, the number of
		3987	signals): Normally, libev tries to deduce the maximum number of signals
		3988	automatically, but sometimes this fails, in which case it can be
		3989	specified. Also, using a lower number than detected (C<32> should be
		3990	good for about any system in existence) can save some memory, as libev
		3991	statically allocates some 12-24 bytes per signal number.
3177		3992
3178	=item EV_PID_HASHSIZE	3993	=item EV_PID_HASHSIZE
3179		3994
3180	C<ev_child> watchers use a small hash table to distribute workload by	3995	C<ev_child> watchers use a small hash table to distribute workload by
3181	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3996	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3182	than enough. If you need to manage thousands of children you might want to	3997	usually more than enough. If you need to manage thousands of children you
3183	increase this value (I<must> be a power of two).	3998	might want to increase this value (I<must> be a power of two).
3184		3999
3185	=item EV_INOTIFY_HASHSIZE	4000	=item EV_INOTIFY_HASHSIZE
3186		4001
3187	C<ev_stat> watchers use a small hash table to distribute workload by	4002	C<ev_stat> watchers use a small hash table to distribute workload by
3188	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4003	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3189	usually more than enough. If you need to manage thousands of C<ev_stat>	4004	disabled), usually more than enough. If you need to manage thousands of
3190	watchers you might want to increase this value (I<must> be a power of	4005	C<ev_stat> watchers you might want to increase this value (I<must> be a
3191	two).	4006	power of two).
3192		4007
3193	=item EV_USE_4HEAP	4008	=item EV_USE_4HEAP
3194		4009
3195	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4010	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3196	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4011	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3197	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4012	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3198	faster performance with many (thousands) of watchers.	4013	faster performance with many (thousands) of watchers.
3199		4014
3200	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4015	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3201	(disabled).	4016	will be C<0>.
3202		4017
3203	=item EV_HEAP_CACHE_AT	4018	=item EV_HEAP_CACHE_AT
3204		4019
3205	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4020	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3206	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4021	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3207	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4022	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3208	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4023	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3209	but avoids random read accesses on heap changes. This improves performance	4024	but avoids random read accesses on heap changes. This improves performance
3210	noticeably with many (hundreds) of watchers.	4025	noticeably with many (hundreds) of watchers.
3211		4026
3212	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4027	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3213	(disabled).	4028	will be C<0>.
3214		4029
3215	=item EV_VERIFY	4030	=item EV_VERIFY
3216		4031
3217	Controls how much internal verification (see C<ev_loop_verify ()>) will	4032	Controls how much internal verification (see C<ev_loop_verify ()>) will
3218	be done: If set to C<0>, no internal verification code will be compiled	4033	be done: If set to C<0>, no internal verification code will be compiled
…		…
3220	called. If set to C<2>, then the internal verification code will be	4035	called. If set to C<2>, then the internal verification code will be
3221	called once per loop, which can slow down libev. If set to C<3>, then the	4036	called once per loop, which can slow down libev. If set to C<3>, then the
3222	verification code will be called very frequently, which will slow down	4037	verification code will be called very frequently, which will slow down
3223	libev considerably.	4038	libev considerably.
3224		4039
3225	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4040	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3226	C<0>.	4041	will be C<0>.
3227		4042
3228	=item EV_COMMON	4043	=item EV_COMMON
3229		4044
3230	By default, all watchers have a C<void *data> member. By redefining	4045	By default, all watchers have a C<void *data> member. By redefining
3231	this macro to a something else you can include more and other types of	4046	this macro to something else you can include more and other types of
3232	members. You have to define it each time you include one of the files,	4047	members. You have to define it each time you include one of the files,
3233	though, and it must be identical each time.	4048	though, and it must be identical each time.
3234		4049
3235	For example, the perl EV module uses something like this:	4050	For example, the perl EV module uses something like this:
3236		4051
…		…
3289	file.	4104	file.
3290		4105
3291	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4106	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3292	that everybody includes and which overrides some configure choices:	4107	that everybody includes and which overrides some configure choices:
3293		4108
3294	#define EV_MINIMAL 1	4109	#define EV_FEATURES 8
3295	#define EV_USE_POLL 0	4110	#define EV_USE_SELECT 1
3296	#define EV_MULTIPLICITY 0
3297	#define EV_PERIODIC_ENABLE 0	4111	#define EV_PREPARE_ENABLE 1
		4112	#define EV_IDLE_ENABLE 1
3298	#define EV_STAT_ENABLE 0	4113	#define EV_SIGNAL_ENABLE 1
3299	#define EV_FORK_ENABLE 0	4114	#define EV_CHILD_ENABLE 1
		4115	#define EV_USE_STDEXCEPT 0
3300	#define EV_CONFIG_H <config.h>	4116	#define EV_CONFIG_H <config.h>
3301	#define EV_MINPRI 0
3302	#define EV_MAXPRI 0
3303		4117
3304	#include "ev++.h"	4118	#include "ev++.h"
3305		4119
3306	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4120	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3307		4121
…		…
3367	default loop and triggering an C<ev_async> watcher from the default loop	4181	default loop and triggering an C<ev_async> watcher from the default loop
3368	watcher callback into the event loop interested in the signal.	4182	watcher callback into the event loop interested in the signal.
3369		4183
3370	=back	4184	=back
3371		4185
		4186	=head4 THREAD LOCKING EXAMPLE
		4187
		4188	Here is a fictitious example of how to run an event loop in a different
		4189	thread than where callbacks are being invoked and watchers are
		4190	created/added/removed.
		4191
		4192	For a real-world example, see the C<EV::Loop::Async> perl module,
		4193	which uses exactly this technique (which is suited for many high-level
		4194	languages).
		4195
		4196	The example uses a pthread mutex to protect the loop data, a condition
		4197	variable to wait for callback invocations, an async watcher to notify the
		4198	event loop thread and an unspecified mechanism to wake up the main thread.
		4199
		4200	First, you need to associate some data with the event loop:
		4201
		4202	typedef struct {
		4203	mutex_t lock; /* global loop lock */
		4204	ev_async async_w;
		4205	thread_t tid;
		4206	cond_t invoke_cv;
		4207	} userdata;
		4208
		4209	void prepare_loop (EV_P)
		4210	{
		4211	// for simplicity, we use a static userdata struct.
		4212	static userdata u;
		4213
		4214	ev_async_init (&u->async_w, async_cb);
		4215	ev_async_start (EV_A_ &u->async_w);
		4216
		4217	pthread_mutex_init (&u->lock, 0);
		4218	pthread_cond_init (&u->invoke_cv, 0);
		4219
		4220	// now associate this with the loop
		4221	ev_set_userdata (EV_A_ u);
		4222	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4223	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4224
		4225	// then create the thread running ev_loop
		4226	pthread_create (&u->tid, 0, l_run, EV_A);
		4227	}
		4228
		4229	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4230	solely to wake up the event loop so it takes notice of any new watchers
		4231	that might have been added:
		4232
		4233	static void
		4234	async_cb (EV_P_ ev_async *w, int revents)
		4235	{
		4236	// just used for the side effects
		4237	}
		4238
		4239	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4240	protecting the loop data, respectively.
		4241
		4242	static void
		4243	l_release (EV_P)
		4244	{
		4245	userdata *u = ev_userdata (EV_A);
		4246	pthread_mutex_unlock (&u->lock);
		4247	}
		4248
		4249	static void
		4250	l_acquire (EV_P)
		4251	{
		4252	userdata *u = ev_userdata (EV_A);
		4253	pthread_mutex_lock (&u->lock);
		4254	}
		4255
		4256	The event loop thread first acquires the mutex, and then jumps straight
		4257	into C<ev_loop>:
		4258
		4259	void *
		4260	l_run (void *thr_arg)
		4261	{
		4262	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4263
		4264	l_acquire (EV_A);
		4265	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4266	ev_loop (EV_A_ 0);
		4267	l_release (EV_A);
		4268
		4269	return 0;
		4270	}
		4271
		4272	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4273	signal the main thread via some unspecified mechanism (signals? pipe
		4274	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4275	have been called (in a while loop because a) spurious wakeups are possible
		4276	and b) skipping inter-thread-communication when there are no pending
		4277	watchers is very beneficial):
		4278
		4279	static void
		4280	l_invoke (EV_P)
		4281	{
		4282	userdata *u = ev_userdata (EV_A);
		4283
		4284	while (ev_pending_count (EV_A))
		4285	{
		4286	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4287	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4288	}
		4289	}
		4290
		4291	Now, whenever the main thread gets told to invoke pending watchers, it
		4292	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4293	thread to continue:
		4294
		4295	static void
		4296	real_invoke_pending (EV_P)
		4297	{
		4298	userdata *u = ev_userdata (EV_A);
		4299
		4300	pthread_mutex_lock (&u->lock);
		4301	ev_invoke_pending (EV_A);
		4302	pthread_cond_signal (&u->invoke_cv);
		4303	pthread_mutex_unlock (&u->lock);
		4304	}
		4305
		4306	Whenever you want to start/stop a watcher or do other modifications to an
		4307	event loop, you will now have to lock:
		4308
		4309	ev_timer timeout_watcher;
		4310	userdata *u = ev_userdata (EV_A);
		4311
		4312	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4313
		4314	pthread_mutex_lock (&u->lock);
		4315	ev_timer_start (EV_A_ &timeout_watcher);
		4316	ev_async_send (EV_A_ &u->async_w);
		4317	pthread_mutex_unlock (&u->lock);
		4318
		4319	Note that sending the C<ev_async> watcher is required because otherwise
		4320	an event loop currently blocking in the kernel will have no knowledge
		4321	about the newly added timer. By waking up the loop it will pick up any new
		4322	watchers in the next event loop iteration.
		4323
3372	=head3 COROUTINES	4324	=head3 COROUTINES
3373		4325
3374	Libev is very accommodating to coroutines ("cooperative threads"):	4326	Libev is very accommodating to coroutines ("cooperative threads"):
3375	libev fully supports nesting calls to its functions from different	4327	libev fully supports nesting calls to its functions from different
3376	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4328	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3377	different coroutines, and switch freely between both coroutines running the	4329	different coroutines, and switch freely between both coroutines running
3378	loop, as long as you don't confuse yourself). The only exception is that	4330	the loop, as long as you don't confuse yourself). The only exception is
3379	you must not do this from C<ev_periodic> reschedule callbacks.	4331	that you must not do this from C<ev_periodic> reschedule callbacks.
3380		4332
3381	Care has been taken to ensure that libev does not keep local state inside	4333	Care has been taken to ensure that libev does not keep local state inside
3382	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4334	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3383	they do not clal any callbacks.	4335	they do not call any callbacks.
3384		4336
3385	=head2 COMPILER WARNINGS	4337	=head2 COMPILER WARNINGS
3386		4338
3387	Depending on your compiler and compiler settings, you might get no or a	4339	Depending on your compiler and compiler settings, you might get no or a
3388	lot of warnings when compiling libev code. Some people are apparently	4340	lot of warnings when compiling libev code. Some people are apparently
…		…
3398	maintainable.	4350	maintainable.
3399		4351
3400	And of course, some compiler warnings are just plain stupid, or simply	4352	And of course, some compiler warnings are just plain stupid, or simply
3401	wrong (because they don't actually warn about the condition their message	4353	wrong (because they don't actually warn about the condition their message
3402	seems to warn about). For example, certain older gcc versions had some	4354	seems to warn about). For example, certain older gcc versions had some
3403	warnings that resulted an extreme number of false positives. These have	4355	warnings that resulted in an extreme number of false positives. These have
3404	been fixed, but some people still insist on making code warn-free with	4356	been fixed, but some people still insist on making code warn-free with
3405	such buggy versions.	4357	such buggy versions.
3406		4358
3407	While libev is written to generate as few warnings as possible,	4359	While libev is written to generate as few warnings as possible,
3408	"warn-free" code is not a goal, and it is recommended not to build libev	4360	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3422	==2274== definitely lost: 0 bytes in 0 blocks.	4374	==2274== definitely lost: 0 bytes in 0 blocks.
3423	==2274== possibly lost: 0 bytes in 0 blocks.	4375	==2274== possibly lost: 0 bytes in 0 blocks.
3424	==2274== still reachable: 256 bytes in 1 blocks.	4376	==2274== still reachable: 256 bytes in 1 blocks.
3425		4377
3426	Then there is no memory leak, just as memory accounted to global variables	4378	Then there is no memory leak, just as memory accounted to global variables
3427	is not a memleak - the memory is still being refernced, and didn't leak.	4379	is not a memleak - the memory is still being referenced, and didn't leak.
3428		4380
3429	Similarly, under some circumstances, valgrind might report kernel bugs	4381	Similarly, under some circumstances, valgrind might report kernel bugs
3430	as if it were a bug in libev (e.g. in realloc or in the poll backend,	4382	as if it were a bug in libev (e.g. in realloc or in the poll backend,
3431	although an acceptable workaround has been found here), or it might be	4383	although an acceptable workaround has been found here), or it might be
3432	confused.	4384	confused.
…		…
3444	I suggest using suppression lists.	4396	I suggest using suppression lists.
3445		4397
3446		4398
3447	=head1 PORTABILITY NOTES	4399	=head1 PORTABILITY NOTES
3448		4400
		4401	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4402
		4403	GNU/Linux is the only common platform that supports 64 bit file/large file
		4404	interfaces but I<disables> them by default.
		4405
		4406	That means that libev compiled in the default environment doesn't support
		4407	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4408
		4409	Unfortunately, many programs try to work around this GNU/Linux issue
		4410	by enabling the large file API, which makes them incompatible with the
		4411	standard libev compiled for their system.
		4412
		4413	Likewise, libev cannot enable the large file API itself as this would
		4414	suddenly make it incompatible to the default compile time environment,
		4415	i.e. all programs not using special compile switches.
		4416
		4417	=head2 OS/X AND DARWIN BUGS
		4418
		4419	The whole thing is a bug if you ask me - basically any system interface
		4420	you touch is broken, whether it is locales, poll, kqueue or even the
		4421	OpenGL drivers.
		4422
		4423	=head3 C<kqueue> is buggy
		4424
		4425	The kqueue syscall is broken in all known versions - most versions support
		4426	only sockets, many support pipes.
		4427
		4428	Libev tries to work around this by not using C<kqueue> by default on
		4429	this rotten platform, but of course you can still ask for it when creating
		4430	a loop.
		4431
		4432	=head3 C<poll> is buggy
		4433
		4434	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4435	implementation by something calling C<kqueue> internally around the 10.5.6
		4436	release, so now C<kqueue> I<and> C<poll> are broken.
		4437
		4438	Libev tries to work around this by not using C<poll> by default on
		4439	this rotten platform, but of course you can still ask for it when creating
		4440	a loop.
		4441
		4442	=head3 C<select> is buggy
		4443
		4444	All that's left is C<select>, and of course Apple found a way to fuck this
		4445	one up as well: On OS/X, C<select> actively limits the number of file
		4446	descriptors you can pass in to 1024 - your program suddenly crashes when
		4447	you use more.
		4448
		4449	There is an undocumented "workaround" for this - defining
		4450	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4451	work on OS/X.
		4452
		4453	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4454
		4455	=head3 C<errno> reentrancy
		4456
		4457	The default compile environment on Solaris is unfortunately so
		4458	thread-unsafe that you can't even use components/libraries compiled
		4459	without C<-D_REENTRANT> (as long as they use C<errno>), which, of course,
		4460	isn't defined by default.
		4461
		4462	If you want to use libev in threaded environments you have to make sure
		4463	it's compiled with C<_REENTRANT> defined.
		4464
		4465	=head3 Event port backend
		4466
		4467	The scalable event interface for Solaris is called "event ports". Unfortunately,
		4468	this mechanism is very buggy. If you run into high CPU usage, your program
		4469	freezes or you get a large number of spurious wakeups, make sure you have
		4470	all the relevant and latest kernel patches applied. No, I don't know which
		4471	ones, but there are multiple ones.
		4472
		4473	If you can't get it to work, you can try running the program by setting
		4474	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4475	C<select> backends.
		4476
		4477	=head2 AIX POLL BUG
		4478
		4479	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4480	this by trying to avoid the poll backend altogether (i.e. it's not even
		4481	compiled in), which normally isn't a big problem as C<select> works fine
		4482	with large bitsets, and AIX is dead anyway.
		4483
3449	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4484	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4485
		4486	=head3 General issues
3450		4487
3451	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4488	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3452	requires, and its I/O model is fundamentally incompatible with the POSIX	4489	requires, and its I/O model is fundamentally incompatible with the POSIX
3453	model. Libev still offers limited functionality on this platform in	4490	model. Libev still offers limited functionality on this platform in
3454	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4491	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3455	descriptors. This only applies when using Win32 natively, not when using	4492	descriptors. This only applies when using Win32 natively, not when using
3456	e.g. cygwin.	4493	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4494	as every compielr comes with a slightly differently broken/incompatible
		4495	environment.
3457		4496
3458	Lifting these limitations would basically require the full	4497	Lifting these limitations would basically require the full
3459	re-implementation of the I/O system. If you are into these kinds of	4498	re-implementation of the I/O system. If you are into this kind of thing,
3460	things, then note that glib does exactly that for you in a very portable	4499	then note that glib does exactly that for you in a very portable way (note
3461	way (note also that glib is the slowest event library known to man).	4500	also that glib is the slowest event library known to man).
3462		4501
3463	There is no supported compilation method available on windows except	4502	There is no supported compilation method available on windows except
3464	embedding it into other applications.	4503	embedding it into other applications.
		4504
		4505	Sensible signal handling is officially unsupported by Microsoft - libev
		4506	tries its best, but under most conditions, signals will simply not work.
3465		4507
3466	Not a libev limitation but worth mentioning: windows apparently doesn't	4508	Not a libev limitation but worth mentioning: windows apparently doesn't
3467	accept large writes: instead of resulting in a partial write, windows will	4509	accept large writes: instead of resulting in a partial write, windows will
3468	either accept everything or return C<ENOBUFS> if the buffer is too large,	4510	either accept everything or return C<ENOBUFS> if the buffer is too large,
3469	so make sure you only write small amounts into your sockets (less than a	4511	so make sure you only write small amounts into your sockets (less than a
…		…
3474	the abysmal performance of winsockets, using a large number of sockets	4516	the abysmal performance of winsockets, using a large number of sockets
3475	is not recommended (and not reasonable). If your program needs to use	4517	is not recommended (and not reasonable). If your program needs to use
3476	more than a hundred or so sockets, then likely it needs to use a totally	4518	more than a hundred or so sockets, then likely it needs to use a totally
3477	different implementation for windows, as libev offers the POSIX readiness	4519	different implementation for windows, as libev offers the POSIX readiness
3478	notification model, which cannot be implemented efficiently on windows	4520	notification model, which cannot be implemented efficiently on windows
3479	(Microsoft monopoly games).	4521	(due to Microsoft monopoly games).
3480		4522
3481	A typical way to use libev under windows is to embed it (see the embedding	4523	A typical way to use libev under windows is to embed it (see the embedding
3482	section for details) and use the following F<evwrap.h> header file instead	4524	section for details) and use the following F<evwrap.h> header file instead
3483	of F<ev.h>:	4525	of F<ev.h>:
3484		4526
…		…
3491	you do I<not> compile the F<ev.c> or any other embedded source files!):	4533	you do I<not> compile the F<ev.c> or any other embedded source files!):
3492		4534
3493	#include "evwrap.h"	4535	#include "evwrap.h"
3494	#include "ev.c"	4536	#include "ev.c"
3495		4537
3496	=over 4
3497
3498	=item The winsocket select function	4538	=head3 The winsocket C<select> function
3499		4539
3500	The winsocket C<select> function doesn't follow POSIX in that it	4540	The winsocket C<select> function doesn't follow POSIX in that it
3501	requires socket I<handles> and not socket I<file descriptors> (it is	4541	requires socket I<handles> and not socket I<file descriptors> (it is
3502	also extremely buggy). This makes select very inefficient, and also	4542	also extremely buggy). This makes select very inefficient, and also
3503	requires a mapping from file descriptors to socket handles (the Microsoft	4543	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3512	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4552	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3513		4553
3514	Note that winsockets handling of fd sets is O(n), so you can easily get a	4554	Note that winsockets handling of fd sets is O(n), so you can easily get a
3515	complexity in the O(n²) range when using win32.	4555	complexity in the O(n²) range when using win32.
3516		4556
3517	=item Limited number of file descriptors	4557	=head3 Limited number of file descriptors
3518		4558
3519	Windows has numerous arbitrary (and low) limits on things.	4559	Windows has numerous arbitrary (and low) limits on things.
3520		4560
3521	Early versions of winsocket's select only supported waiting for a maximum	4561	Early versions of winsocket's select only supported waiting for a maximum
3522	of C<64> handles (probably owning to the fact that all windows kernels	4562	of C<64> handles (probably owning to the fact that all windows kernels
3523	can only wait for C<64> things at the same time internally; Microsoft	4563	can only wait for C<64> things at the same time internally; Microsoft
3524	recommends spawning a chain of threads and wait for 63 handles and the	4564	recommends spawning a chain of threads and wait for 63 handles and the
3525	previous thread in each. Great).	4565	previous thread in each. Sounds great!).
3526		4566
3527	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4567	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3528	to some high number (e.g. C<2048>) before compiling the winsocket select	4568	to some high number (e.g. C<2048>) before compiling the winsocket select
3529	call (which might be in libev or elsewhere, for example, perl does its own	4569	call (which might be in libev or elsewhere, for example, perl and many
3530	select emulation on windows).	4570	other interpreters do their own select emulation on windows).
3531		4571
3532	Another limit is the number of file descriptors in the Microsoft runtime	4572	Another limit is the number of file descriptors in the Microsoft runtime
3533	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4573	libraries, which by default is C<64> (there must be a hidden I<64>
3534	or something like this inside Microsoft). You can increase this by calling	4574	fetish or something like this inside Microsoft). You can increase this
3535	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4575	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3536	arbitrary limit), but is broken in many versions of the Microsoft runtime	4576	(another arbitrary limit), but is broken in many versions of the Microsoft
3537	libraries.
3538
3539	This might get you to about C<512> or C<2048> sockets (depending on	4577	runtime libraries. This might get you to about C<512> or C<2048> sockets
3540	windows version and/or the phase of the moon). To get more, you need to	4578	(depending on windows version and/or the phase of the moon). To get more,
3541	wrap all I/O functions and provide your own fd management, but the cost of	4579	you need to wrap all I/O functions and provide your own fd management, but
3542	calling select (O(n²)) will likely make this unworkable.	4580	the cost of calling select (O(n²)) will likely make this unworkable.
3543
3544	=back
3545		4581
3546	=head2 PORTABILITY REQUIREMENTS	4582	=head2 PORTABILITY REQUIREMENTS
3547		4583
3548	In addition to a working ISO-C implementation and of course the	4584	In addition to a working ISO-C implementation and of course the
3549	backend-specific APIs, libev relies on a few additional extensions:	4585	backend-specific APIs, libev relies on a few additional extensions:
…		…
3590	=item C<double> must hold a time value in seconds with enough accuracy	4626	=item C<double> must hold a time value in seconds with enough accuracy
3591		4627
3592	The type C<double> is used to represent timestamps. It is required to	4628	The type C<double> is used to represent timestamps. It is required to
3593	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4629	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
3594	enough for at least into the year 4000. This requirement is fulfilled by	4630	enough for at least into the year 4000. This requirement is fulfilled by
3595	implementations implementing IEEE 754 (basically all existing ones).	4631	implementations implementing IEEE 754, which is basically all existing
		4632	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4633	2200.
3596		4634
3597	=back	4635	=back
3598		4636
3599	If you know of other additional requirements drop me a note.	4637	If you know of other additional requirements drop me a note.
3600		4638
…		…
3668	involves iterating over all running async watchers or all signal numbers.	4706	involves iterating over all running async watchers or all signal numbers.
3669		4707
3670	=back	4708	=back
3671		4709
3672		4710
		4711	=head1 PORTING FROM LIBEV 3.X TO 4.X
		4712
		4713	The major version 4 introduced some minor incompatible changes to the API.
		4714
		4715	At the moment, the C<ev.h> header file tries to implement superficial
		4716	compatibility, so most programs should still compile. Those might be
		4717	removed in later versions of libev, so better update early than late.
		4718
		4719	=over 4
		4720
		4721	=item C<ev_loop_count> renamed to C<ev_iteration>
		4722
		4723	=item C<ev_loop_depth> renamed to C<ev_depth>
		4724
		4725	=item C<ev_loop_verify> renamed to C<ev_verify>
		4726
		4727	Most functions working on C<struct ev_loop> objects don't have an
		4728	C<ev_loop_> prefix, so it was removed. Note that C<ev_loop_fork> is
		4729	still called C<ev_loop_fork> because it would otherwise clash with the
		4730	C<ev_fork> typedef.
		4731
		4732	=item C<EV_TIMEOUT> renamed to C<EV_TIMER> in C<revents>
		4733
		4734	This is a simple rename - all other watcher types use their name
		4735	as revents flag, and now C<ev_timer> does, too.
		4736
		4737	Both C<EV_TIMER> and C<EV_TIMEOUT> symbols were present in 3.x versions
		4738	and continue to be present for the foreseeable future, so this is mostly a
		4739	documentation change.
		4740
		4741	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		4742
		4743	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		4744	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		4745	and work, but the library code will of course be larger.
		4746
		4747	=back
		4748
		4749
		4750	=head1 GLOSSARY
		4751
		4752	=over 4
		4753
		4754	=item active
		4755
		4756	A watcher is active as long as it has been started (has been attached to
		4757	an event loop) but not yet stopped (disassociated from the event loop).
		4758
		4759	=item application
		4760
		4761	In this document, an application is whatever is using libev.
		4762
		4763	=item callback
		4764
		4765	The address of a function that is called when some event has been
		4766	detected. Callbacks are being passed the event loop, the watcher that
		4767	received the event, and the actual event bitset.
		4768
		4769	=item callback invocation
		4770
		4771	The act of calling the callback associated with a watcher.
		4772
		4773	=item event
		4774
		4775	A change of state of some external event, such as data now being available
		4776	for reading on a file descriptor, time having passed or simply not having
		4777	any other events happening anymore.
		4778
		4779	In libev, events are represented as single bits (such as C<EV_READ> or
		4780	C<EV_TIMER>).
		4781
		4782	=item event library
		4783
		4784	A software package implementing an event model and loop.
		4785
		4786	=item event loop
		4787
		4788	An entity that handles and processes external events and converts them
		4789	into callback invocations.
		4790
		4791	=item event model
		4792
		4793	The model used to describe how an event loop handles and processes
		4794	watchers and events.
		4795
		4796	=item pending
		4797
		4798	A watcher is pending as soon as the corresponding event has been detected,
		4799	and stops being pending as soon as the watcher will be invoked or its
		4800	pending status is explicitly cleared by the application.
		4801
		4802	A watcher can be pending, but not active. Stopping a watcher also clears
		4803	its pending status.
		4804
		4805	=item real time
		4806
		4807	The physical time that is observed. It is apparently strictly monotonic :)
		4808
		4809	=item wall-clock time
		4810
		4811	The time and date as shown on clocks. Unlike real time, it can actually
		4812	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4813	clock.
		4814
		4815	=item watcher
		4816
		4817	A data structure that describes interest in certain events. Watchers need
		4818	to be started (attached to an event loop) before they can receive events.
		4819
		4820	=item watcher invocation
		4821
		4822	The act of calling the callback associated with a watcher.
		4823
		4824	=back
		4825
3673	=head1 AUTHOR	4826	=head1 AUTHOR
3674		4827
3675	Marc Lehmann <libev@schmorp.de>.	4828	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3676		4829

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