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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	Familarity 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 (somewhere
115	the beginning of 1970, details are complicated, don't ask). This type is	130	near the beginning of 1970, details are complicated, don't ask). This
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	131	type is called C<ev_tstamp>, which is what you should use too. It usually
117	to the C<double> type in C, and when you need to do any calculations on	132	aliases to the C<double> type in C. When you need to do any calculations
118	it, you should treat it as some floating point value. Unlike the name	133	on it, you should treat it as some floating point value. Unlike the name
119	component C<stamp> might indicate, it is also used for time differences	134	component C<stamp> might indicate, it is also used for time differences
120	throughout libev.	135	throughout libev.
121		136
122	=head1 ERROR HANDLING	137	=head1 ERROR HANDLING
123		138
…		…
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	229	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
215	recommended ones.	230	recommended ones.
216		231
217	See the description of C<ev_embed> watchers for more info.	232	See the description of C<ev_embed> watchers for more info.
218		233
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	234	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
220		235
221	Sets the allocation function to use (the prototype is similar - the	236	Sets the allocation function to use (the prototype is similar - the
222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	237	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
223	used to allocate and free memory (no surprises here). If it returns zero	238	used to allocate and free memory (no surprises here). If it returns zero
224	when memory needs to be allocated (C<size != 0>), the library might abort	239	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	265	}
251		266
252	...	267	...
253	ev_set_allocator (persistent_realloc);	268	ev_set_allocator (persistent_realloc);
254		269
255	=item ev_set_syserr_cb (void (*cb)(const char *msg));	270	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
256		271
257	Set the callback function to call on a retryable system call error (such	272	Set the callback function to call on a retryable system call error (such
258	as failed select, poll, epoll_wait). The message is a printable string	273	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	274	indicating the system call or subsystem causing the problem. If this
260	callback is set, then libev will expect it to remedy the situation, no	275	callback is set, then libev will expect it to remedy the situation, no
…		…
276		291
277	=back	292	=back
278		293
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	294	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
280		295
281	An event loop is described by a C<struct ev_loop *>. The library knows two	296	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	297	is I<not> optional in this case, as there is also an C<ev_loop>
283	events, and dynamically created loops which do not.	298	I<function>).
		299
		300	The library knows two types of such loops, the I<default> loop, which
		301	supports signals and child events, and dynamically created loops which do
		302	not.
284		303
285	=over 4	304	=over 4
286		305
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	306	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		307
…		…
294	If you don't know what event loop to use, use the one returned from this	313	If you don't know what event loop to use, use the one returned from this
295	function.	314	function.
296		315
297	Note that this function is I<not> thread-safe, so if you want to use it	316	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,	317	from multiple threads, you have to lock (note also that this is unlikely,
299	as loops cannot bes hared easily between threads anyway).	318	as loops cannot be shared easily between threads anyway).
300		319
301	The default loop is the only loop that can handle C<ev_signal> and	320	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	321	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	322	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	323	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
…		…
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>.
…		…
582		643
583	This value can sometimes be useful as a generation counter of sorts (it	644	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	645	"ticks" the number of loop iterations), as it roughly corresponds with
585	C<ev_prepare> and C<ev_check> calls.	646	C<ev_prepare> and C<ev_check> calls.
586		647
		648	=item unsigned int ev_loop_depth (loop)
		649
		650	Returns the number of times C<ev_loop> was entered minus the number of
		651	times C<ev_loop> was exited, in other words, the recursion depth.
		652
		653	Outside C<ev_loop>, this number is zero. In a callback, this number is
		654	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),
		655	in which case it is higher.
		656
		657	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread
		658	etc.), doesn't count as exit.
		659
587	=item unsigned int ev_backend (loop)	660	=item unsigned int ev_backend (loop)
588		661
589	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	662	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
590	use.	663	use.
591		664
…		…
605		678
606	This function is rarely useful, but when some event callback runs for a	679	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	680	very long time without entering the event loop, updating libev's idea of
608	the current time is a good idea.	681	the current time is a good idea.
609		682
610	See also "The special problem of time updates" in the C<ev_timer> section.	683	See also L<The special problem of time updates> in the C<ev_timer> section.
		684
		685	=item ev_suspend (loop)
		686
		687	=item ev_resume (loop)
		688
		689	These two functions suspend and resume a loop, for use when the loop is
		690	not used for a while and timeouts should not be processed.
		691
		692	A typical use case would be an interactive program such as a game: When
		693	the user presses C<^Z> to suspend the game and resumes it an hour later it
		694	would be best to handle timeouts as if no time had actually passed while
		695	the program was suspended. This can be achieved by calling C<ev_suspend>
		696	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		697	C<ev_resume> directly afterwards to resume timer processing.
		698
		699	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		700	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		701	will be rescheduled (that is, they will lose any events that would have
		702	occured while suspended).
		703
		704	After calling C<ev_suspend> you B<must not> call I<any> function on the
		705	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		706	without a previous call to C<ev_suspend>.
		707
		708	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		709	event loop time (see C<ev_now_update>).
611		710
612	=item ev_loop (loop, int flags)	711	=item ev_loop (loop, int flags)
613		712
614	Finally, this is it, the event handler. This function usually is called	713	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	714	after you have initialised all your watchers and you want to start
616	events.	715	handling events.
617		716
618	If the flags argument is specified as C<0>, it will not return until	717	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.	718	either no event watchers are active anymore or C<ev_unloop> was called.
620		719
621	Please note that an explicit C<ev_unloop> is usually better than	720	Please note that an explicit C<ev_unloop> is usually better than
…		…
631	the loop.	730	the loop.
632		731
633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	732	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	733	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	734	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	735	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	736	user-registered callback will be called), and will return after one
638	iteration of the loop.	737	iteration of the loop.
639		738
640	This is useful if you are waiting for some external event in conjunction	739	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	740	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	784	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.	785	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
687		786
688	This "unloop state" will be cleared when entering C<ev_loop> again.	787	This "unloop state" will be cleared when entering C<ev_loop> again.
689		788
		789	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		790
690	=item ev_ref (loop)	791	=item ev_ref (loop)
691		792
692	=item ev_unref (loop)	793	=item ev_unref (loop)
693		794
694	Ref/unref can be used to add or remove a reference count on the event	795	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	796	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.	797	count is nonzero, C<ev_loop> will not return on its own.
697		798
698	If you have a watcher you never unregister that should not keep C<ev_loop>	799	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	800	unregister, but that nevertheless should not keep C<ev_loop> from
		801	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
700	stopping it.	802	before stopping it.
701		803
702	As an example, libev itself uses this for its internal signal pipe: It is	804	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	805	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	806	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	807	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>	808	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,	809	before stop> (but only if the watcher wasn't active before, or was active
708	respectively).	810	before, respectively. Note also that libev might stop watchers itself
		811	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		812	in the callback).
709		813
710	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	814	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
711	running when nothing else is active.	815	running when nothing else is active.
712		816
713	struct ev_signal exitsig;	817	ev_signal exitsig;
714	ev_signal_init (&exitsig, sig_cb, SIGINT);	818	ev_signal_init (&exitsig, sig_cb, SIGINT);
715	ev_signal_start (loop, &exitsig);	819	ev_signal_start (loop, &exitsig);
716	evf_unref (loop);	820	evf_unref (loop);
717		821
718	Example: For some weird reason, unregister the above signal handler again.	822	Example: For some weird reason, unregister the above signal handler again.
…		…
742		846
743	By setting a higher I<io collect interval> you allow libev to spend more	847	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,	848	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	849	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	850	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.	851	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		852	sleep time ensures that libev will not poll for I/O events more often then
		853	once per this interval, on average.
748		854
749	Likewise, by setting a higher I<timeout collect interval> you allow libev	855	Likewise, by setting a higher I<timeout collect interval> you allow libev
750	to spend more time collecting timeouts, at the expense of increased	856	to spend more time collecting timeouts, at the expense of increased
751	latency/jitter/inexactness (the watcher callback will be called	857	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	858	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
754		860
755	Many (busy) programs can usually benefit by setting the I/O collect	861	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	862	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	863	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>,	864	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.	865	as this approaches the timing granularity of most systems. Note that if
		866	you do transactions with the outside world and you can't increase the
		867	parallelity, then this setting will limit your transaction rate (if you
		868	need to poll once per transaction and the I/O collect interval is 0.01,
		869	then you can't do more than 100 transations per second).
760		870
761	Setting the I<timeout collect interval> can improve the opportunity for	871	Setting the I<timeout collect interval> can improve the opportunity for
762	saving power, as the program will "bundle" timer callback invocations that	872	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	873	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	874	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	875	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
766	they fire on, say, one-second boundaries only.	876	they fire on, say, one-second boundaries only.
767		877
		878	Example: we only need 0.1s timeout granularity, and we wish not to poll
		879	more often than 100 times per second:
		880
		881	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		882	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		883
		884	=item ev_invoke_pending (loop)
		885
		886	This call will simply invoke all pending watchers while resetting their
		887	pending state. Normally, C<ev_loop> does this automatically when required,
		888	but when overriding the invoke callback this call comes handy.
		889
		890	=item int ev_pending_count (loop)
		891
		892	Returns the number of pending watchers - zero indicates that no watchers
		893	are pending.
		894
		895	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		896
		897	This overrides the invoke pending functionality of the loop: Instead of
		898	invoking all pending watchers when there are any, C<ev_loop> will call
		899	this callback instead. This is useful, for example, when you want to
		900	invoke the actual watchers inside another context (another thread etc.).
		901
		902	If you want to reset the callback, use C<ev_invoke_pending> as new
		903	callback.
		904
		905	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		906
		907	Sometimes you want to share the same loop between multiple threads. This
		908	can be done relatively simply by putting mutex_lock/unlock calls around
		909	each call to a libev function.
		910
		911	However, C<ev_loop> can run an indefinite time, so it is not feasible to
		912	wait for it to return. One way around this is to wake up the loop via
		913	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>
		914	and I<acquire> callbacks on the loop.
		915
		916	When set, then C<release> will be called just before the thread is
		917	suspended waiting for new events, and C<acquire> is called just
		918	afterwards.
		919
		920	Ideally, C<release> will just call your mutex_unlock function, and
		921	C<acquire> will just call the mutex_lock function again.
		922
		923	While event loop modifications are allowed between invocations of
		924	C<release> and C<acquire> (that's their only purpose after all), no
		925	modifications done will affect the event loop, i.e. adding watchers will
		926	have no effect on the set of file descriptors being watched, or the time
		927	waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it
		928	to take note of any changes you made.
		929
		930	In theory, threads executing C<ev_loop> will be async-cancel safe between
		931	invocations of C<release> and C<acquire>.
		932
		933	See also the locking example in the C<THREADS> section later in this
		934	document.
		935
		936	=item ev_set_userdata (loop, void *data)
		937
		938	=item ev_userdata (loop)
		939
		940	Set and retrieve a single C<void *> associated with a loop. When
		941	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		942	C<0.>
		943
		944	These two functions can be used to associate arbitrary data with a loop,
		945	and are intended solely for the C<invoke_pending_cb>, C<release> and
		946	C<acquire> callbacks described above, but of course can be (ab-)used for
		947	any other purpose as well.
		948
768	=item ev_loop_verify (loop)	949	=item ev_loop_verify (loop)
769		950
770	This function only does something when C<EV_VERIFY> support has been	951	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	952	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	953	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	954	is found to be inconsistent, it will print an error message to standard
774	error and call C<abort ()>.	955	error and call C<abort ()>.
775		956
776	This can be used to catch bugs inside libev itself: under normal	957	This can be used to catch bugs inside libev itself: under normal
…		…
780	=back	961	=back
781		962
782		963
783	=head1 ANATOMY OF A WATCHER	964	=head1 ANATOMY OF A WATCHER
784		965
		966	In the following description, uppercase C<TYPE> in names stands for the
		967	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		968	watchers and C<ev_io_start> for I/O watchers.
		969
785	A watcher is a structure that you create and register to record your	970	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	971	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:	972	become readable, you would create an C<ev_io> watcher for that:
788		973
789	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	974	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
790	{	975	{
791	ev_io_stop (w);	976	ev_io_stop (w);
792	ev_unloop (loop, EVUNLOOP_ALL);	977	ev_unloop (loop, EVUNLOOP_ALL);
793	}	978	}
794		979
795	struct ev_loop *loop = ev_default_loop (0);	980	struct ev_loop *loop = ev_default_loop (0);
		981
796	struct ev_io stdin_watcher;	982	ev_io stdin_watcher;
		983
797	ev_init (&stdin_watcher, my_cb);	984	ev_init (&stdin_watcher, my_cb);
798	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	985	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
799	ev_io_start (loop, &stdin_watcher);	986	ev_io_start (loop, &stdin_watcher);
		987
800	ev_loop (loop, 0);	988	ev_loop (loop, 0);
801		989
802	As you can see, you are responsible for allocating the memory for your	990	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,	991	watcher structures (and it is I<usually> a bad idea to do this on the
804	although this can sometimes be quite valid).	992	stack).
		993
		994	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		995	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
805		996
806	Each watcher structure must be initialised by a call to C<ev_init	997	Each watcher structure must be initialised by a call to C<ev_init
807	(watcher *, callback)>, which expects a callback to be provided. This	998	(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	999	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	1000	watchers, each time the event loop detects that the file descriptor given
810	is readable and/or writable).	1001	is readable and/or writable).
811		1002
812	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1003	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	1004	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	1005	is also a macro to combine initialisation and setting in one call: C<<
815	(watcher *, callback, ...) >>.	1006	ev_TYPE_init (watcher *, callback, ...) >>.
816		1007
817	To make the watcher actually watch out for events, you have to start it	1008	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	1009	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	1010	*) >>), and you can stop watching for events at any time by calling the
820	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1011	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
821		1012
822	As long as your watcher is active (has been started but not stopped) you	1013	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	1014	must not touch the values stored in it. Most specifically you must never
824	reinitialise it or call its C<set> macro.	1015	reinitialise it or call its C<ev_TYPE_set> macro.
825		1016
826	Each and every callback receives the event loop pointer as first, the	1017	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	1018	registered watcher structure as second, and a bitset of received events as
828	third argument.	1019	third argument.
829		1020
…		…
838	=item C<EV_WRITE>	1029	=item C<EV_WRITE>
839		1030
840	The file descriptor in the C<ev_io> watcher has become readable and/or	1031	The file descriptor in the C<ev_io> watcher has become readable and/or
841	writable.	1032	writable.
842		1033
843	=item C<EV_TIMEOUT>	1034	=item C<EV_TIMER>
844		1035
845	The C<ev_timer> watcher has timed out.	1036	The C<ev_timer> watcher has timed out.
846		1037
847	=item C<EV_PERIODIC>	1038	=item C<EV_PERIODIC>
848		1039
…		…
887		1078
888	=item C<EV_ASYNC>	1079	=item C<EV_ASYNC>
889		1080
890	The given async watcher has been asynchronously notified (see C<ev_async>).	1081	The given async watcher has been asynchronously notified (see C<ev_async>).
891		1082
		1083	=item C<EV_CUSTOM>
		1084
		1085	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1086	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		1087
892	=item C<EV_ERROR>	1088	=item C<EV_ERROR>
893		1089
894	An unspecified error has occurred, the watcher has been stopped. This might	1090	An unspecified error has occurred, the watcher has been stopped. This might
895	happen because the watcher could not be properly started because libev	1091	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	1092	ran out of memory, a file descriptor was found to be closed or any other
		1093	problem. Libev considers these application bugs.
		1094
897	problem. You best act on it by reporting the problem and somehow coping	1095	You best act on it by reporting the problem and somehow coping with the
898	with the watcher being stopped.	1096	watcher being stopped. Note that well-written programs should not receive
		1097	an error ever, so when your watcher receives it, this usually indicates a
		1098	bug in your program.
899		1099
900	Libev will usually signal a few "dummy" events together with an error, for	1100	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	1101	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	1102	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	1103	the error from read() or write(). This will not work in multi-threaded
…		…
906		1106
907	=back	1107	=back
908		1108
909	=head2 GENERIC WATCHER FUNCTIONS	1109	=head2 GENERIC WATCHER FUNCTIONS
910		1110
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	1111	=over 4
915		1112
916	=item C<ev_init> (ev_TYPE *watcher, callback)	1113	=item C<ev_init> (ev_TYPE *watcher, callback)
917		1114
918	This macro initialises the generic portion of a watcher. The contents	1115	This macro initialises the generic portion of a watcher. The contents
…		…
923	which rolls both calls into one.	1120	which rolls both calls into one.
924		1121
925	You can reinitialise a watcher at any time as long as it has been stopped	1122	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.	1123	(or never started) and there are no pending events outstanding.
927		1124
928	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1125	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
929	int revents)>.	1126	int revents)>.
930		1127
931	Example: Initialise an C<ev_io> watcher in two steps.	1128	Example: Initialise an C<ev_io> watcher in two steps.
932		1129
933	ev_io w;	1130	ev_io w;
934	ev_init (&w, my_cb);	1131	ev_init (&w, my_cb);
935	ev_io_set (&w, STDIN_FILENO, EV_READ);	1132	ev_io_set (&w, STDIN_FILENO, EV_READ);
936		1133
937	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1134	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
938		1135
939	This macro initialises the type-specific parts of a watcher. You need to	1136	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	1137	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	1138	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	1139	macro on a watcher that is active (it can be pending, however, which is a
…		…
955		1152
956	Example: Initialise and set an C<ev_io> watcher in one step.	1153	Example: Initialise and set an C<ev_io> watcher in one step.
957		1154
958	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1155	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
959		1156
960	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1157	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
961		1158
962	Starts (activates) the given watcher. Only active watchers will receive	1159	Starts (activates) the given watcher. Only active watchers will receive
963	events. If the watcher is already active nothing will happen.	1160	events. If the watcher is already active nothing will happen.
964		1161
965	Example: Start the C<ev_io> watcher that is being abused as example in this	1162	Example: Start the C<ev_io> watcher that is being abused as example in this
966	whole section.	1163	whole section.
967		1164
968	ev_io_start (EV_DEFAULT_UC, &w);	1165	ev_io_start (EV_DEFAULT_UC, &w);
969		1166
970	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1167	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
971		1168
972	Stops the given watcher again (if active) and clears the pending	1169	Stops the given watcher if active, and clears the pending status (whether
		1170	the watcher was active or not).
		1171
973	status. It is possible that stopped watchers are pending (for example,	1172	It is possible that stopped watchers are pending - for example,
974	non-repeating timers are being stopped when they become pending), but	1173	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	1174	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	1175	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.	1176	therefore a good idea to always call its C<ev_TYPE_stop> function.
978		1177
979	=item bool ev_is_active (ev_TYPE *watcher)	1178	=item bool ev_is_active (ev_TYPE *watcher)
980		1179
981	Returns a true value iff the watcher is active (i.e. it has been started	1180	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	1181	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)	1197	=item ev_cb_set (ev_TYPE *watcher, callback)
999		1198
1000	Change the callback. You can change the callback at virtually any time	1199	Change the callback. You can change the callback at virtually any time
1001	(modulo threads).	1200	(modulo threads).
1002		1201
1003	=item ev_set_priority (ev_TYPE *watcher, priority)	1202	=item ev_set_priority (ev_TYPE *watcher, int priority)
1004		1203
1005	=item int ev_priority (ev_TYPE *watcher)	1204	=item int ev_priority (ev_TYPE *watcher)
1006		1205
1007	Set and query the priority of the watcher. The priority is a small	1206	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>	1207	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1009	(default: C<-2>). Pending watchers with higher priority will be invoked	1208	(default: C<-2>). Pending watchers with higher priority will be invoked
1010	before watchers with lower priority, but priority will not keep watchers	1209	before watchers with lower priority, but priority will not keep watchers
1011	from being executed (except for C<ev_idle> watchers).	1210	from being executed (except for C<ev_idle> watchers).
1012		1211
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	1212	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.	1213	you need to look at C<ev_idle> watchers, which provide this functionality.
1020		1214
1021	You I<must not> change the priority of a watcher as long as it is active or	1215	You I<must not> change the priority of a watcher as long as it is active or
1022	pending.	1216	pending.
1023		1217
		1218	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1219	fine, as long as you do not mind that the priority value you query might
		1220	or might not have been clamped to the valid range.
		1221
1024	The default priority used by watchers when no priority has been set is	1222	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 :).	1223	always C<0>, which is supposed to not be too high and not be too low :).
1026		1224
1027	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1225	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	1226	priorities.
1029	or might not have been adjusted to be within valid range.
1030		1227
1031	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1228	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1032		1229
1033	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1230	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	1231	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	1238	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>.	1239	watcher isn't pending it does nothing and returns C<0>.
1043		1240
1044	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1241	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.	1242	callback to be invoked, which can be accomplished with this function.
		1243
		1244	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1245
		1246	Feeds the given event set into the event loop, as if the specified event
		1247	had happened for the specified watcher (which must be a pointer to an
		1248	initialised but not necessarily started event watcher). Obviously you must
		1249	not free the watcher as long as it has pending events.
		1250
		1251	Stopping the watcher, letting libev invoke it, or calling
		1252	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1253	not started in the first place.
		1254
		1255	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1256	functions that do not need a watcher.
1046		1257
1047	=back	1258	=back
1048		1259
1049		1260
1050	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1261	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
1056	member, you can also "subclass" the watcher type and provide your own	1267	member, you can also "subclass" the watcher type and provide your own
1057	data:	1268	data:
1058		1269
1059	struct my_io	1270	struct my_io
1060	{	1271	{
1061	struct ev_io io;	1272	ev_io io;
1062	int otherfd;	1273	int otherfd;
1063	void *somedata;	1274	void *somedata;
1064	struct whatever *mostinteresting;	1275	struct whatever *mostinteresting;
1065	};	1276	};
1066		1277
…		…
1069	ev_io_init (&w.io, my_cb, fd, EV_READ);	1280	ev_io_init (&w.io, my_cb, fd, EV_READ);
1070		1281
1071	And since your callback will be called with a pointer to the watcher, you	1282	And since your callback will be called with a pointer to the watcher, you
1072	can cast it back to your own type:	1283	can cast it back to your own type:
1073		1284
1074	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1285	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1075	{	1286	{
1076	struct my_io *w = (struct my_io *)w_;	1287	struct my_io *w = (struct my_io *)w_;
1077	...	1288	...
1078	}	1289	}
1079		1290
…		…
1097	programmers):	1308	programmers):
1098		1309
1099	#include <stddef.h>	1310	#include <stddef.h>
1100		1311
1101	static void	1312	static void
1102	t1_cb (EV_P_ struct ev_timer *w, int revents)	1313	t1_cb (EV_P_ ev_timer *w, int revents)
1103	{	1314	{
1104	struct my_biggy big = (struct my_biggy *	1315	struct my_biggy big = (struct my_biggy *)
1105	(((char *)w) - offsetof (struct my_biggy, t1));	1316	(((char *)w) - offsetof (struct my_biggy, t1));
1106	}	1317	}
1107		1318
1108	static void	1319	static void
1109	t2_cb (EV_P_ struct ev_timer *w, int revents)	1320	t2_cb (EV_P_ ev_timer *w, int revents)
1110	{	1321	{
1111	struct my_biggy big = (struct my_biggy *	1322	struct my_biggy big = (struct my_biggy *)
1112	(((char *)w) - offsetof (struct my_biggy, t2));	1323	(((char *)w) - offsetof (struct my_biggy, t2));
1113	}	1324	}
		1325
		1326	=head2 WATCHER PRIORITY MODELS
		1327
		1328	Many event loops support I<watcher priorities>, which are usually small
		1329	integers that influence the ordering of event callback invocation
		1330	between watchers in some way, all else being equal.
		1331
		1332	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1333	description for the more technical details such as the actual priority
		1334	range.
		1335
		1336	There are two common ways how these these priorities are being interpreted
		1337	by event loops:
		1338
		1339	In the more common lock-out model, higher priorities "lock out" invocation
		1340	of lower priority watchers, which means as long as higher priority
		1341	watchers receive events, lower priority watchers are not being invoked.
		1342
		1343	The less common only-for-ordering model uses priorities solely to order
		1344	callback invocation within a single event loop iteration: Higher priority
		1345	watchers are invoked before lower priority ones, but they all get invoked
		1346	before polling for new events.
		1347
		1348	Libev uses the second (only-for-ordering) model for all its watchers
		1349	except for idle watchers (which use the lock-out model).
		1350
		1351	The rationale behind this is that implementing the lock-out model for
		1352	watchers is not well supported by most kernel interfaces, and most event
		1353	libraries will just poll for the same events again and again as long as
		1354	their callbacks have not been executed, which is very inefficient in the
		1355	common case of one high-priority watcher locking out a mass of lower
		1356	priority ones.
		1357
		1358	Static (ordering) priorities are most useful when you have two or more
		1359	watchers handling the same resource: a typical usage example is having an
		1360	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1361	timeouts. Under load, data might be received while the program handles
		1362	other jobs, but since timers normally get invoked first, the timeout
		1363	handler will be executed before checking for data. In that case, giving
		1364	the timer a lower priority than the I/O watcher ensures that I/O will be
		1365	handled first even under adverse conditions (which is usually, but not
		1366	always, what you want).
		1367
		1368	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1369	will only be executed when no same or higher priority watchers have
		1370	received events, they can be used to implement the "lock-out" model when
		1371	required.
		1372
		1373	For example, to emulate how many other event libraries handle priorities,
		1374	you can associate an C<ev_idle> watcher to each such watcher, and in
		1375	the normal watcher callback, you just start the idle watcher. The real
		1376	processing is done in the idle watcher callback. This causes libev to
		1377	continously poll and process kernel event data for the watcher, but when
		1378	the lock-out case is known to be rare (which in turn is rare :), this is
		1379	workable.
		1380
		1381	Usually, however, the lock-out model implemented that way will perform
		1382	miserably under the type of load it was designed to handle. In that case,
		1383	it might be preferable to stop the real watcher before starting the
		1384	idle watcher, so the kernel will not have to process the event in case
		1385	the actual processing will be delayed for considerable time.
		1386
		1387	Here is an example of an I/O watcher that should run at a strictly lower
		1388	priority than the default, and which should only process data when no
		1389	other events are pending:
		1390
		1391	ev_idle idle; // actual processing watcher
		1392	ev_io io; // actual event watcher
		1393
		1394	static void
		1395	io_cb (EV_P_ ev_io *w, int revents)
		1396	{
		1397	// stop the I/O watcher, we received the event, but
		1398	// are not yet ready to handle it.
		1399	ev_io_stop (EV_A_ w);
		1400
		1401	// start the idle watcher to ahndle the actual event.
		1402	// it will not be executed as long as other watchers
		1403	// with the default priority are receiving events.
		1404	ev_idle_start (EV_A_ &idle);
		1405	}
		1406
		1407	static void
		1408	idle_cb (EV_P_ ev_idle *w, int revents)
		1409	{
		1410	// actual processing
		1411	read (STDIN_FILENO, ...);
		1412
		1413	// have to start the I/O watcher again, as
		1414	// we have handled the event
		1415	ev_io_start (EV_P_ &io);
		1416	}
		1417
		1418	// initialisation
		1419	ev_idle_init (&idle, idle_cb);
		1420	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1421	ev_io_start (EV_DEFAULT_ &io);
		1422
		1423	In the "real" world, it might also be beneficial to start a timer, so that
		1424	low-priority connections can not be locked out forever under load. This
		1425	enables your program to keep a lower latency for important connections
		1426	during short periods of high load, while not completely locking out less
		1427	important ones.
1114		1428
1115		1429
1116	=head1 WATCHER TYPES	1430	=head1 WATCHER TYPES
1117		1431
1118	This section describes each watcher in detail, but will not repeat	1432	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	1458	descriptors to non-blocking mode is also usually a good idea (but not
1145	required if you know what you are doing).	1459	required if you know what you are doing).
1146		1460
1147	If you cannot use non-blocking mode, then force the use of a	1461	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	1462	known-to-be-good backend (at the time of this writing, this includes only
1149	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).	1463	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1464	descriptors for which non-blocking operation makes no sense (such as
		1465	files) - libev doesn't guarentee any specific behaviour in that case.
1150		1466
1151	Another thing you have to watch out for is that it is quite easy to	1467	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	1468	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	1469	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	1470	because there is no data. Not only are some backends known to create a
…		…
1219		1535
1220	So when you encounter spurious, unexplained daemon exits, make sure you	1536	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	1537	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).	1538	somewhere, as that would have given you a big clue).
1223		1539
		1540	=head3 The special problem of accept()ing when you can't
		1541
		1542	Many implementations of the POSIX C<accept> function (for example,
		1543	found in port-2004 Linux) have the peculiar behaviour of not removing a
		1544	connection from the pending queue in all error cases.
		1545
		1546	For example, larger servers often run out of file descriptors (because
		1547	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1548	rejecting the connection, leading to libev signalling readiness on
		1549	the next iteration again (the connection still exists after all), and
		1550	typically causing the program to loop at 100% CPU usage.
		1551
		1552	Unfortunately, the set of errors that cause this issue differs between
		1553	operating systems, there is usually little the app can do to remedy the
		1554	situation, and no known thread-safe method of removing the connection to
		1555	cope with overload is known (to me).
		1556
		1557	One of the easiest ways to handle this situation is to just ignore it
		1558	- when the program encounters an overload, it will just loop until the
		1559	situation is over. While this is a form of busy waiting, no OS offers an
		1560	event-based way to handle this situation, so it's the best one can do.
		1561
		1562	A better way to handle the situation is to log any errors other than
		1563	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1564	messages, and continue as usual, which at least gives the user an idea of
		1565	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1566	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1567	usage.
		1568
		1569	If your program is single-threaded, then you could also keep a dummy file
		1570	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1571	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1572	close that fd, and create a new dummy fd. This will gracefully refuse
		1573	clients under typical overload conditions.
		1574
		1575	The last way to handle it is to simply log the error and C<exit>, as
		1576	is often done with C<malloc> failures, but this results in an easy
		1577	opportunity for a DoS attack.
1224		1578
1225	=head3 Watcher-Specific Functions	1579	=head3 Watcher-Specific Functions
1226		1580
1227	=over 4	1581	=over 4
1228		1582
…		…
1249	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1603	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	1604	readable, but only once. Since it is likely line-buffered, you could
1251	attempt to read a whole line in the callback.	1605	attempt to read a whole line in the callback.
1252		1606
1253	static void	1607	static void
1254	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1608	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1255	{	1609	{
1256	ev_io_stop (loop, w);	1610	ev_io_stop (loop, w);
1257	.. read from stdin here (or from w->fd) and handle any I/O errors	1611	.. read from stdin here (or from w->fd) and handle any I/O errors
1258	}	1612	}
1259		1613
1260	...	1614	...
1261	struct ev_loop *loop = ev_default_init (0);	1615	struct ev_loop *loop = ev_default_init (0);
1262	struct ev_io stdin_readable;	1616	ev_io stdin_readable;
1263	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1617	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1264	ev_io_start (loop, &stdin_readable);	1618	ev_io_start (loop, &stdin_readable);
1265	ev_loop (loop, 0);	1619	ev_loop (loop, 0);
1266		1620
1267		1621
…		…
1275	year, it will still time out after (roughly) one hour. "Roughly" because	1629	year, it will still time out after (roughly) one hour. "Roughly" because
1276	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1630	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1277	monotonic clock option helps a lot here).	1631	monotonic clock option helps a lot here).
1278		1632
1279	The callback is guaranteed to be invoked only I<after> its timeout has	1633	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	1634	passed (not I<at>, so on systems with very low-resolution clocks this
1281	then order of execution is undefined.	1635	might introduce a small delay). If multiple timers become ready during the
		1636	same loop iteration then the ones with earlier time-out values are invoked
		1637	before ones of the same priority with later time-out values (but this is
		1638	no longer true when a callback calls C<ev_loop> recursively).
		1639
		1640	=head3 Be smart about timeouts
		1641
		1642	Many real-world problems involve some kind of timeout, usually for error
		1643	recovery. A typical example is an HTTP request - if the other side hangs,
		1644	you want to raise some error after a while.
		1645
		1646	What follows are some ways to handle this problem, from obvious and
		1647	inefficient to smart and efficient.
		1648
		1649	In the following, a 60 second activity timeout is assumed - a timeout that
		1650	gets reset to 60 seconds each time there is activity (e.g. each time some
		1651	data or other life sign was received).
		1652
		1653	=over 4
		1654
		1655	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1656
		1657	This is the most obvious, but not the most simple way: In the beginning,
		1658	start the watcher:
		1659
		1660	ev_timer_init (timer, callback, 60., 0.);
		1661	ev_timer_start (loop, timer);
		1662
		1663	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1664	and start it again:
		1665
		1666	ev_timer_stop (loop, timer);
		1667	ev_timer_set (timer, 60., 0.);
		1668	ev_timer_start (loop, timer);
		1669
		1670	This is relatively simple to implement, but means that each time there is
		1671	some activity, libev will first have to remove the timer from its internal
		1672	data structure and then add it again. Libev tries to be fast, but it's
		1673	still not a constant-time operation.
		1674
		1675	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1676
		1677	This is the easiest way, and involves using C<ev_timer_again> instead of
		1678	C<ev_timer_start>.
		1679
		1680	To implement this, configure an C<ev_timer> with a C<repeat> value
		1681	of C<60> and then call C<ev_timer_again> at start and each time you
		1682	successfully read or write some data. If you go into an idle state where
		1683	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1684	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1685
		1686	That means you can ignore both the C<ev_timer_start> function and the
		1687	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1688	member and C<ev_timer_again>.
		1689
		1690	At start:
		1691
		1692	ev_init (timer, callback);
		1693	timer->repeat = 60.;
		1694	ev_timer_again (loop, timer);
		1695
		1696	Each time there is some activity:
		1697
		1698	ev_timer_again (loop, timer);
		1699
		1700	It is even possible to change the time-out on the fly, regardless of
		1701	whether the watcher is active or not:
		1702
		1703	timer->repeat = 30.;
		1704	ev_timer_again (loop, timer);
		1705
		1706	This is slightly more efficient then stopping/starting the timer each time
		1707	you want to modify its timeout value, as libev does not have to completely
		1708	remove and re-insert the timer from/into its internal data structure.
		1709
		1710	It is, however, even simpler than the "obvious" way to do it.
		1711
		1712	=item 3. Let the timer time out, but then re-arm it as required.
		1713
		1714	This method is more tricky, but usually most efficient: Most timeouts are
		1715	relatively long compared to the intervals between other activity - in
		1716	our example, within 60 seconds, there are usually many I/O events with
		1717	associated activity resets.
		1718
		1719	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1720	but remember the time of last activity, and check for a real timeout only
		1721	within the callback:
		1722
		1723	ev_tstamp last_activity; // time of last activity
		1724
		1725	static void
		1726	callback (EV_P_ ev_timer *w, int revents)
		1727	{
		1728	ev_tstamp now = ev_now (EV_A);
		1729	ev_tstamp timeout = last_activity + 60.;
		1730
		1731	// if last_activity + 60. is older than now, we did time out
		1732	if (timeout < now)
		1733	{
		1734	// timeout occured, take action
		1735	}
		1736	else
		1737	{
		1738	// callback was invoked, but there was some activity, re-arm
		1739	// the watcher to fire in last_activity + 60, which is
		1740	// guaranteed to be in the future, so "again" is positive:
		1741	w->repeat = timeout - now;
		1742	ev_timer_again (EV_A_ w);
		1743	}
		1744	}
		1745
		1746	To summarise the callback: first calculate the real timeout (defined
		1747	as "60 seconds after the last activity"), then check if that time has
		1748	been reached, which means something I<did>, in fact, time out. Otherwise
		1749	the callback was invoked too early (C<timeout> is in the future), so
		1750	re-schedule the timer to fire at that future time, to see if maybe we have
		1751	a timeout then.
		1752
		1753	Note how C<ev_timer_again> is used, taking advantage of the
		1754	C<ev_timer_again> optimisation when the timer is already running.
		1755
		1756	This scheme causes more callback invocations (about one every 60 seconds
		1757	minus half the average time between activity), but virtually no calls to
		1758	libev to change the timeout.
		1759
		1760	To start the timer, simply initialise the watcher and set C<last_activity>
		1761	to the current time (meaning we just have some activity :), then call the
		1762	callback, which will "do the right thing" and start the timer:
		1763
		1764	ev_init (timer, callback);
		1765	last_activity = ev_now (loop);
		1766	callback (loop, timer, EV_TIMER);
		1767
		1768	And when there is some activity, simply store the current time in
		1769	C<last_activity>, no libev calls at all:
		1770
		1771	last_actiivty = ev_now (loop);
		1772
		1773	This technique is slightly more complex, but in most cases where the
		1774	time-out is unlikely to be triggered, much more efficient.
		1775
		1776	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1777	callback :) - just change the timeout and invoke the callback, which will
		1778	fix things for you.
		1779
		1780	=item 4. Wee, just use a double-linked list for your timeouts.
		1781
		1782	If there is not one request, but many thousands (millions...), all
		1783	employing some kind of timeout with the same timeout value, then one can
		1784	do even better:
		1785
		1786	When starting the timeout, calculate the timeout value and put the timeout
		1787	at the I<end> of the list.
		1788
		1789	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1790	the list is expected to fire (for example, using the technique #3).
		1791
		1792	When there is some activity, remove the timer from the list, recalculate
		1793	the timeout, append it to the end of the list again, and make sure to
		1794	update the C<ev_timer> if it was taken from the beginning of the list.
		1795
		1796	This way, one can manage an unlimited number of timeouts in O(1) time for
		1797	starting, stopping and updating the timers, at the expense of a major
		1798	complication, and having to use a constant timeout. The constant timeout
		1799	ensures that the list stays sorted.
		1800
		1801	=back
		1802
		1803	So which method the best?
		1804
		1805	Method #2 is a simple no-brain-required solution that is adequate in most
		1806	situations. Method #3 requires a bit more thinking, but handles many cases
		1807	better, and isn't very complicated either. In most case, choosing either
		1808	one is fine, with #3 being better in typical situations.
		1809
		1810	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1811	rather complicated, but extremely efficient, something that really pays
		1812	off after the first million or so of active timers, i.e. it's usually
		1813	overkill :)
1282		1814
1283	=head3 The special problem of time updates	1815	=head3 The special problem of time updates
1284		1816
1285	Establishing the current time is a costly operation (it usually takes at	1817	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	1818	least two system calls): EV therefore updates its idea of the current
…		…
1298		1830
1299	If the event loop is suspended for a long time, you can also force an	1831	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	1832	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1301	()>.	1833	()>.
1302		1834
		1835	=head3 The special problems of suspended animation
		1836
		1837	When you leave the server world it is quite customary to hit machines that
		1838	can suspend/hibernate - what happens to the clocks during such a suspend?
		1839
		1840	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1841	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1842	to run until the system is suspended, but they will not advance while the
		1843	system is suspended. That means, on resume, it will be as if the program
		1844	was frozen for a few seconds, but the suspend time will not be counted
		1845	towards C<ev_timer> when a monotonic clock source is used. The real time
		1846	clock advanced as expected, but if it is used as sole clocksource, then a
		1847	long suspend would be detected as a time jump by libev, and timers would
		1848	be adjusted accordingly.
		1849
		1850	I would not be surprised to see different behaviour in different between
		1851	operating systems, OS versions or even different hardware.
		1852
		1853	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1854	time jump in the monotonic clocks and the realtime clock. If the program
		1855	is suspended for a very long time, and monotonic clock sources are in use,
		1856	then you can expect C<ev_timer>s to expire as the full suspension time
		1857	will be counted towards the timers. When no monotonic clock source is in
		1858	use, then libev will again assume a timejump and adjust accordingly.
		1859
		1860	It might be beneficial for this latter case to call C<ev_suspend>
		1861	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1862	deterministic behaviour in this case (you can do nothing against
		1863	C<SIGSTOP>).
		1864
1303	=head3 Watcher-Specific Functions and Data Members	1865	=head3 Watcher-Specific Functions and Data Members
1304		1866
1305	=over 4	1867	=over 4
1306		1868
1307	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1869	=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).	1892	If the timer is started but non-repeating, stop it (as if it timed out).
1331		1893
1332	If the timer is repeating, either start it if necessary (with the	1894	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.	1895	C<repeat> value), or reset the running timer to the C<repeat> value.
1334		1896
1335	This sounds a bit complicated, but here is a useful and typical	1897	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	1898	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		1899
1345	That means you can ignore the C<after> value and C<ev_timer_start>	1900	=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		1901
1348	ev_timer_init (timer, callback, 0., 5.);	1902	Returns the remaining time until a timer fires. If the timer is active,
1349	ev_timer_again (loop, timer);	1903	then this time is relative to the current event loop time, otherwise it's
1350	...	1904	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		1905
1357	This is more slightly efficient then stopping/starting the timer each time	1906	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1358	you want to modify its timeout value.	1907	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
1359		1908	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	1909	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	1910	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		1911
1366	=item ev_tstamp repeat [read-write]	1912	=item ev_tstamp repeat [read-write]
1367		1913
1368	The current C<repeat> value. Will be used each time the watcher times out	1914	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),	1915	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1374	=head3 Examples	1920	=head3 Examples
1375		1921
1376	Example: Create a timer that fires after 60 seconds.	1922	Example: Create a timer that fires after 60 seconds.
1377		1923
1378	static void	1924	static void
1379	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1925	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1380	{	1926	{
1381	.. one minute over, w is actually stopped right here	1927	.. one minute over, w is actually stopped right here
1382	}	1928	}
1383		1929
1384	struct ev_timer mytimer;	1930	ev_timer mytimer;
1385	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1931	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1386	ev_timer_start (loop, &mytimer);	1932	ev_timer_start (loop, &mytimer);
1387		1933
1388	Example: Create a timeout timer that times out after 10 seconds of	1934	Example: Create a timeout timer that times out after 10 seconds of
1389	inactivity.	1935	inactivity.
1390		1936
1391	static void	1937	static void
1392	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1938	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1393	{	1939	{
1394	.. ten seconds without any activity	1940	.. ten seconds without any activity
1395	}	1941	}
1396		1942
1397	struct ev_timer mytimer;	1943	ev_timer mytimer;
1398	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1944	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1399	ev_timer_again (&mytimer); /* start timer */	1945	ev_timer_again (&mytimer); /* start timer */
1400	ev_loop (loop, 0);	1946	ev_loop (loop, 0);
1401		1947
1402	// and in some piece of code that gets executed on any "activity":	1948	// and in some piece of code that gets executed on any "activity":
…		…
1407	=head2 C<ev_periodic> - to cron or not to cron?	1953	=head2 C<ev_periodic> - to cron or not to cron?
1408		1954
1409	Periodic watchers are also timers of a kind, but they are very versatile	1955	Periodic watchers are also timers of a kind, but they are very versatile
1410	(and unfortunately a bit complex).	1956	(and unfortunately a bit complex).
1411		1957
1412	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1958	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	1959	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	1960	(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 ()	1961	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	1962	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	1963	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		1964
		1965	You can tell a periodic watcher to trigger after some specific point
		1966	in time: for example, if you tell a periodic watcher to trigger "in 10
		1967	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1968	not a delay) and then reset your system clock to January of the previous
		1969	year, then it will take a year or more to trigger the event (unlike an
		1970	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1971	it, as it uses a relative timeout).
		1972
1421	C<ev_periodic>s can also be used to implement vastly more complex timers,	1973	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	1974	timers, such as triggering an event on each "midnight, local time", or
1423	complicated rules.	1975	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1976	those cannot react to time jumps.
1424		1977
1425	As with timers, the callback is guaranteed to be invoked only when the	1978	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	1979	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.	1980	timers become ready during the same loop iteration then the ones with
		1981	earlier time-out values are invoked before ones with later time-out values
		1982	(but this is no longer true when a callback calls C<ev_loop> recursively).
1428		1983
1429	=head3 Watcher-Specific Functions and Data Members	1984	=head3 Watcher-Specific Functions and Data Members
1430		1985
1431	=over 4	1986	=over 4
1432		1987
1433	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1988	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1434		1989
1435	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1990	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1436		1991
1437	Lots of arguments, lets sort it out... There are basically three modes of	1992	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:	1993	operation, and we will explain them from simplest to most complex:
1439		1994
1440	=over 4	1995	=over 4
1441		1996
1442	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1997	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1443		1998
1444	In this configuration the watcher triggers an event after the wall clock	1999	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	2000	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	2001	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.	2002	will be stopped and invoked when the system clock reaches or surpasses
		2003	this point in time.
1448		2004
1449	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2005	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1450		2006
1451	In this mode the watcher will always be scheduled to time out at the next	2007	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)	2008	C<offset + N * interval> time (for some integer N, which can also be
1453	and then repeat, regardless of any time jumps.	2009	negative) and then repeat, regardless of any time jumps. The C<offset>
		2010	argument is merely an offset into the C<interval> periods.
1454		2011
1455	This can be used to create timers that do not drift with respect to the	2012	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	2013	system clock, for example, here is an C<ev_periodic> that triggers each
1457	hour, on the hour:	2014	hour, on the hour (with respect to UTC):
1458		2015
1459	ev_periodic_set (&periodic, 0., 3600., 0);	2016	ev_periodic_set (&periodic, 0., 3600., 0);
1460		2017
1461	This doesn't mean there will always be 3600 seconds in between triggers,	2018	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	2019	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	2020	full hour (UTC), or more correctly, when the system time is evenly divisible
1464	by 3600.	2021	by 3600.
1465		2022
1466	Another way to think about it (for the mathematically inclined) is that	2023	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	2024	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.	2025	time where C<time = offset (mod interval)>, regardless of any time jumps.
1469		2026
1470	For numerical stability it is preferable that the C<at> value is near	2027	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	2028	C<ev_now ()> (the current time), but there is no range requirement for
1472	this value, and in fact is often specified as zero.	2029	this value, and in fact is often specified as zero.
1473		2030
1474	Note also that there is an upper limit to how often a timer can fire (CPU	2031	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	2032	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	2033	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).	2034	millisecond (if the OS supports it and the machine is fast enough).
1478		2035
1479	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2036	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1480		2037
1481	In this mode the values for C<interval> and C<at> are both being	2038	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	2039	ignored. Instead, each time the periodic watcher gets scheduled, the
1483	reschedule callback will be called with the watcher as first, and the	2040	reschedule callback will be called with the watcher as first, and the
1484	current time as second argument.	2041	current time as second argument.
1485		2042
1486	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2043	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1487	ever, or make ANY event loop modifications whatsoever>.	2044	or make ANY other event loop modifications whatsoever, unless explicitly
		2045	allowed by documentation here>.
1488		2046
1489	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2047	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	2048	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1491	only event loop modification you are allowed to do).	2049	only event loop modification you are allowed to do).
1492		2050
1493	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	2051	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1494	*w, ev_tstamp now)>, e.g.:	2052	*w, ev_tstamp now)>, e.g.:
1495		2053
		2054	static ev_tstamp
1496	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	2055	my_rescheduler (ev_periodic *w, ev_tstamp now)
1497	{	2056	{
1498	return now + 60.;	2057	return now + 60.;
1499	}	2058	}
1500		2059
1501	It must return the next time to trigger, based on the passed time value	2060	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	2080	a different time than the last time it was called (e.g. in a crond like
1522	program when the crontabs have changed).	2081	program when the crontabs have changed).
1523		2082
1524	=item ev_tstamp ev_periodic_at (ev_periodic *)	2083	=item ev_tstamp ev_periodic_at (ev_periodic *)
1525		2084
1526	When active, returns the absolute time that the watcher is supposed to	2085	When active, returns the absolute time that the watcher is supposed
1527	trigger next.	2086	to trigger next. This is not the same as the C<offset> argument to
		2087	C<ev_periodic_set>, but indeed works even in interval and manual
		2088	rescheduling modes.
1528		2089
1529	=item ev_tstamp offset [read-write]	2090	=item ev_tstamp offset [read-write]
1530		2091
1531	When repeating, this contains the offset value, otherwise this is the	2092	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>).	2093	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2094	although libev might modify this value for better numerical stability).
1533		2095
1534	Can be modified any time, but changes only take effect when the periodic	2096	Can be modified any time, but changes only take effect when the periodic
1535	timer fires or C<ev_periodic_again> is being called.	2097	timer fires or C<ev_periodic_again> is being called.
1536		2098
1537	=item ev_tstamp interval [read-write]	2099	=item ev_tstamp interval [read-write]
1538		2100
1539	The current interval value. Can be modified any time, but changes only	2101	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	2102	take effect when the periodic timer fires or C<ev_periodic_again> is being
1541	called.	2103	called.
1542		2104
1543	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2105	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1544		2106
1545	The current reschedule callback, or C<0>, if this functionality is	2107	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	2108	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.	2109	the periodic timer fires or C<ev_periodic_again> is being called.
1548		2110
…		…
1553	Example: Call a callback every hour, or, more precisely, whenever the	2115	Example: Call a callback every hour, or, more precisely, whenever the
1554	system time is divisible by 3600. The callback invocation times have	2116	system time is divisible by 3600. The callback invocation times have
1555	potentially a lot of jitter, but good long-term stability.	2117	potentially a lot of jitter, but good long-term stability.
1556		2118
1557	static void	2119	static void
1558	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2120	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1559	{	2121	{
1560	... its now a full hour (UTC, or TAI or whatever your clock follows)	2122	... its now a full hour (UTC, or TAI or whatever your clock follows)
1561	}	2123	}
1562		2124
1563	struct ev_periodic hourly_tick;	2125	ev_periodic hourly_tick;
1564	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2126	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1565	ev_periodic_start (loop, &hourly_tick);	2127	ev_periodic_start (loop, &hourly_tick);
1566		2128
1567	Example: The same as above, but use a reschedule callback to do it:	2129	Example: The same as above, but use a reschedule callback to do it:
1568		2130
1569	#include <math.h>	2131	#include <math.h>
1570		2132
1571	static ev_tstamp	2133	static ev_tstamp
1572	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2134	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1573	{	2135	{
1574	return now + (3600. - fmod (now, 3600.));	2136	return now + (3600. - fmod (now, 3600.));
1575	}	2137	}
1576		2138
1577	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2139	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1578		2140
1579	Example: Call a callback every hour, starting now:	2141	Example: Call a callback every hour, starting now:
1580		2142
1581	struct ev_periodic hourly_tick;	2143	ev_periodic hourly_tick;
1582	ev_periodic_init (&hourly_tick, clock_cb,	2144	ev_periodic_init (&hourly_tick, clock_cb,
1583	fmod (ev_now (loop), 3600.), 3600., 0);	2145	fmod (ev_now (loop), 3600.), 3600., 0);
1584	ev_periodic_start (loop, &hourly_tick);	2146	ev_periodic_start (loop, &hourly_tick);
1585		2147
1586		2148
…		…
1589	Signal watchers will trigger an event when the process receives a specific	2151	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	2152	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	2153	will try it's best to deliver signals synchronously, i.e. as part of the
1592	normal event processing, like any other event.	2154	normal event processing, like any other event.
1593		2155
1594	If you want signals asynchronously, just use C<sigaction> as you would	2156	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	2157	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.	2158	the signal. You can even use C<ev_async> from a signal handler to
		2159	synchronously wake up an event loop.
1597		2160
1598	You can configure as many watchers as you like per signal. Only when the	2161	You can configure as many watchers as you like for the same signal, but
		2162	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2163	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2164	C<SIGINT> in both the default loop and another loop at the same time. At
		2165	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2166
1599	first watcher gets started will libev actually register a signal handler	2167	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	2168	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	2169	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		2170
1605	If possible and supported, libev will install its handlers with	2171	If possible and supported, libev will install its handlers with
1606	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2172	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1607	interrupted. If you have a problem with system calls getting interrupted by	2173	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	2174	interrupted by signals you can block all signals in an C<ev_check> watcher
1609	them in an C<ev_prepare> watcher.	2175	and unblock them in an C<ev_prepare> watcher.
		2176
		2177	=head3 The special problem of inheritance over fork/execve/pthread_create
		2178
		2179	Both the signal mask (C<sigprocmask>) and the signal disposition
		2180	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2181	stopping it again), that is, libev might or might not block the signal,
		2182	and might or might not set or restore the installed signal handler.
		2183
		2184	While this does not matter for the signal disposition (libev never
		2185	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2186	C<execve>), this matters for the signal mask: many programs do not expect
		2187	certain signals to be blocked.
		2188
		2189	This means that before calling C<exec> (from the child) you should reset
		2190	the signal mask to whatever "default" you expect (all clear is a good
		2191	choice usually).
		2192
		2193	The simplest way to ensure that the signal mask is reset in the child is
		2194	to install a fork handler with C<pthread_atfork> that resets it. That will
		2195	catch fork calls done by libraries (such as the libc) as well.
		2196
		2197	In current versions of libev, the signal will not be blocked indefinitely
		2198	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2199	the window of opportunity for problems, it will not go away, as libev
		2200	I<has> to modify the signal mask, at least temporarily.
		2201
		2202	So I can't stress this enough: I<If you do not reset your signal mask when
		2203	you expect it to be empty, you have a race condition in your code>. This
		2204	is not a libev-specific thing, this is true for most event libraries.
1610		2205
1611	=head3 Watcher-Specific Functions and Data Members	2206	=head3 Watcher-Specific Functions and Data Members
1612		2207
1613	=over 4	2208	=over 4
1614		2209
…		…
1625		2220
1626	=back	2221	=back
1627		2222
1628	=head3 Examples	2223	=head3 Examples
1629		2224
1630	Example: Try to exit cleanly on SIGINT and SIGTERM.	2225	Example: Try to exit cleanly on SIGINT.
1631		2226
1632	static void	2227	static void
1633	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2228	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1634	{	2229	{
1635	ev_unloop (loop, EVUNLOOP_ALL);	2230	ev_unloop (loop, EVUNLOOP_ALL);
1636	}	2231	}
1637		2232
1638	struct ev_signal signal_watcher;	2233	ev_signal signal_watcher;
1639	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2234	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1640	ev_signal_start (loop, &sigint_cb);	2235	ev_signal_start (loop, &signal_watcher);
1641		2236
1642		2237
1643	=head2 C<ev_child> - watch out for process status changes	2238	=head2 C<ev_child> - watch out for process status changes
1644		2239
1645	Child watchers trigger when your process receives a SIGCHLD in response to	2240	Child watchers trigger when your process receives a SIGCHLD in response to
1646	some child status changes (most typically when a child of yours dies or	2241	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	2242	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	2243	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.,	2244	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,	2245	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	2246	but forking and registering a watcher a few event loop iterations later or
1652	not.	2247	in the next callback invocation is not.
1653		2248
1654	Only the default event loop is capable of handling signals, and therefore	2249	Only the default event loop is capable of handling signals, and therefore
1655	you can only register child watchers in the default event loop.	2250	you can only register child watchers in the default event loop.
1656		2251
		2252	Due to some design glitches inside libev, child watchers will always be
		2253	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2254	libev)
		2255
1657	=head3 Process Interaction	2256	=head3 Process Interaction
1658		2257
1659	Libev grabs C<SIGCHLD> as soon as the default event loop is	2258	Libev grabs C<SIGCHLD> as soon as the default event loop is
1660	initialised. This is necessary to guarantee proper behaviour even if	2259	initialised. This is necessary to guarantee proper behaviour even if the
1661	the first child watcher is started after the child exits. The occurrence	2260	first child watcher is started after the child exits. The occurrence
1662	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2261	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1663	synchronously as part of the event loop processing. Libev always reaps all	2262	synchronously as part of the event loop processing. Libev always reaps all
1664	children, even ones not watched.	2263	children, even ones not watched.
1665		2264
1666	=head3 Overriding the Built-In Processing	2265	=head3 Overriding the Built-In Processing
…		…
1676	=head3 Stopping the Child Watcher	2275	=head3 Stopping the Child Watcher
1677		2276
1678	Currently, the child watcher never gets stopped, even when the	2277	Currently, the child watcher never gets stopped, even when the
1679	child terminates, so normally one needs to stop the watcher in the	2278	child terminates, so normally one needs to stop the watcher in the
1680	callback. Future versions of libev might stop the watcher automatically	2279	callback. Future versions of libev might stop the watcher automatically
1681	when a child exit is detected.	2280	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2281	problem).
1682		2282
1683	=head3 Watcher-Specific Functions and Data Members	2283	=head3 Watcher-Specific Functions and Data Members
1684		2284
1685	=over 4	2285	=over 4
1686		2286
…		…
1718	its completion.	2318	its completion.
1719		2319
1720	ev_child cw;	2320	ev_child cw;
1721		2321
1722	static void	2322	static void
1723	child_cb (EV_P_ struct ev_child *w, int revents)	2323	child_cb (EV_P_ ev_child *w, int revents)
1724	{	2324	{
1725	ev_child_stop (EV_A_ w);	2325	ev_child_stop (EV_A_ w);
1726	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2326	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1727	}	2327	}
1728		2328
…		…
1743		2343
1744		2344
1745	=head2 C<ev_stat> - did the file attributes just change?	2345	=head2 C<ev_stat> - did the file attributes just change?
1746		2346
1747	This watches a file system path for attribute changes. That is, it calls	2347	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	2348	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.	2349	and sees if it changed compared to the last time, invoking the callback if
		2350	it did.
1750		2351
1751	The path does not need to exist: changing from "path exists" to "path does	2352	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	2353	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	2354	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	2355	C<st_nlink> field being zero (which is otherwise always forced to be at
1755	the stat buffer having unspecified contents.	2356	least one) and all the other fields of the stat buffer having unspecified
		2357	contents.
1756		2358
1757	The path I<should> be absolute and I<must not> end in a slash. If it is	2359	The path I<must not> end in a slash or contain special components such as
		2360	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.	2361	your working directory changes, then the behaviour is undefined.
1759		2362
1760	Since there is no standard kernel interface to do this, the portable	2363	Since there is no portable change notification interface available, the
1761	implementation simply calls C<stat (2)> regularly on the path to see if	2364	portable implementation simply calls C<stat(2)> regularly on the path
1762	it changed somehow. You can specify a recommended polling interval for	2365	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!)	2366	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	2367	recommended!) then a I<suitable, unspecified default> value will be used
1765	you can expect to be around five seconds, although this might change	2368	(which you can expect to be around five seconds, although this might
1766	dynamically). Libev will also impose a minimum interval which is currently	2369	change dynamically). Libev will also impose a minimum interval which is
1767	around C<0.1>, but thats usually overkill.	2370	currently around C<0.1>, but that's usually overkill.
1768		2371
1769	This watcher type is not meant for massive numbers of stat watchers,	2372	This watcher type is not meant for massive numbers of stat watchers,
1770	as even with OS-supported change notifications, this can be	2373	as even with OS-supported change notifications, this can be
1771	resource-intensive.	2374	resource-intensive.
1772		2375
1773	At the time of this writing, the only OS-specific interface implemented	2376	At the time of this writing, the only OS-specific interface implemented
1774	is the Linux inotify interface (implementing kqueue support is left as	2377	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	2378	exercise for the reader. Note, however, that the author sees no way of
1776	of implementing C<ev_stat> semantics with kqueue).	2379	implementing C<ev_stat> semantics with kqueue, except as a hint).
1777		2380
1778	=head3 ABI Issues (Largefile Support)	2381	=head3 ABI Issues (Largefile Support)
1779		2382
1780	Libev by default (unless the user overrides this) uses the default	2383	Libev by default (unless the user overrides this) uses the default
1781	compilation environment, which means that on systems with large file	2384	compilation environment, which means that on systems with large file
1782	support disabled by default, you get the 32 bit version of the stat	2385	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	2386	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	2387	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	2388	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	2389	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.	2390	most noticeably displayed with ev_stat and large file support.
1788		2391
1789	The solution for this is to lobby your distribution maker to make large	2392	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	2393	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	2394	optional. Libev cannot simply switch on large file support because it has
1792	to exchange stat structures with application programs compiled using the	2395	to exchange stat structures with application programs compiled using the
1793	default compilation environment.	2396	default compilation environment.
1794		2397
1795	=head3 Inotify and Kqueue	2398	=head3 Inotify and Kqueue
1796		2399
1797	When C<inotify (7)> support has been compiled into libev (generally only	2400	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	2401	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	2402	inotify descriptor will be created lazily when the first C<ev_stat>
1800	when the first C<ev_stat> watcher is being started.	2403	watcher is being started.
1801		2404
1802	Inotify presence does not change the semantics of C<ev_stat> watchers	2405	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	2406	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	2407	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,	2408	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.	2409	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2410	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2411	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2412	xfs are fully working) libev usually gets away without polling.
1807		2413
1808	There is no support for kqueue, as apparently it cannot be used to	2414	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	2415	implement this functionality, due to the requirement of having a file
1810	descriptor open on the object at all times, and detecting renames, unlinks	2416	descriptor open on the object at all times, and detecting renames, unlinks
1811	etc. is difficult.	2417	etc. is difficult.
1812		2418
		2419	=head3 C<stat ()> is a synchronous operation
		2420
		2421	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2422	the process. The exception are C<ev_stat> watchers - those call C<stat
		2423	()>, which is a synchronous operation.
		2424
		2425	For local paths, this usually doesn't matter: unless the system is very
		2426	busy or the intervals between stat's are large, a stat call will be fast,
		2427	as the path data is usually in memory already (except when starting the
		2428	watcher).
		2429
		2430	For networked file systems, calling C<stat ()> can block an indefinite
		2431	time due to network issues, and even under good conditions, a stat call
		2432	often takes multiple milliseconds.
		2433
		2434	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2435	paths, although this is fully supported by libev.
		2436
1813	=head3 The special problem of stat time resolution	2437	=head3 The special problem of stat time resolution
1814		2438
1815	The C<stat ()> system call only supports full-second resolution portably, and	2439	The C<stat ()> system call only supports full-second resolution portably,
1816	even on systems where the resolution is higher, most file systems still	2440	and even on systems where the resolution is higher, most file systems
1817	only support whole seconds.	2441	still only support whole seconds.
1818		2442
1819	That means that, if the time is the only thing that changes, you can	2443	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	2444	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	2445	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	2446	within the same second, C<ev_stat> will be unable to detect unless the
…		…
1965		2589
1966	=head3 Watcher-Specific Functions and Data Members	2590	=head3 Watcher-Specific Functions and Data Members
1967		2591
1968	=over 4	2592	=over 4
1969		2593
1970	=item ev_idle_init (ev_signal *, callback)	2594	=item ev_idle_init (ev_idle *, callback)
1971		2595
1972	Initialises and configures the idle watcher - it has no parameters of any	2596	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,	2597	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1974	believe me.	2598	believe me.
1975		2599
…		…
1979		2603
1980	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2604	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1981	callback, free it. Also, use no error checking, as usual.	2605	callback, free it. Also, use no error checking, as usual.
1982		2606
1983	static void	2607	static void
1984	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2608	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1985	{	2609	{
1986	free (w);	2610	free (w);
1987	// now do something you wanted to do when the program has	2611	// now do something you wanted to do when the program has
1988	// no longer anything immediate to do.	2612	// no longer anything immediate to do.
1989	}	2613	}
1990		2614
1991	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2615	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1992	ev_idle_init (idle_watcher, idle_cb);	2616	ev_idle_init (idle_watcher, idle_cb);
1993	ev_idle_start (loop, idle_cb);	2617	ev_idle_start (loop, idle_watcher);
1994		2618
1995		2619
1996	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2620	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1997		2621
1998	Prepare and check watchers are usually (but not always) used in pairs:	2622	Prepare and check watchers are usually (but not always) used in pairs:
…		…
2077		2701
2078	static ev_io iow [nfd];	2702	static ev_io iow [nfd];
2079	static ev_timer tw;	2703	static ev_timer tw;
2080		2704
2081	static void	2705	static void
2082	io_cb (ev_loop *loop, ev_io *w, int revents)	2706	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2083	{	2707	{
2084	}	2708	}
2085		2709
2086	// create io watchers for each fd and a timer before blocking	2710	// create io watchers for each fd and a timer before blocking
2087	static void	2711	static void
2088	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2712	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2089	{	2713	{
2090	int timeout = 3600000;	2714	int timeout = 3600000;
2091	struct pollfd fds [nfd];	2715	struct pollfd fds [nfd];
2092	// actual code will need to loop here and realloc etc.	2716	// actual code will need to loop here and realloc etc.
2093	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2717	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2094		2718
2095	/* the callback is illegal, but won't be called as we stop during check */	2719	/* the callback is illegal, but won't be called as we stop during check */
2096	ev_timer_init (&tw, 0, timeout * 1e-3);	2720	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2097	ev_timer_start (loop, &tw);	2721	ev_timer_start (loop, &tw);
2098		2722
2099	// create one ev_io per pollfd	2723	// create one ev_io per pollfd
2100	for (int i = 0; i < nfd; ++i)	2724	for (int i = 0; i < nfd; ++i)
2101	{	2725	{
…		…
2108	}	2732	}
2109	}	2733	}
2110		2734
2111	// stop all watchers after blocking	2735	// stop all watchers after blocking
2112	static void	2736	static void
2113	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2737	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2114	{	2738	{
2115	ev_timer_stop (loop, &tw);	2739	ev_timer_stop (loop, &tw);
2116		2740
2117	for (int i = 0; i < nfd; ++i)	2741	for (int i = 0; i < nfd; ++i)
2118	{	2742	{
…		…
2214	some fds have to be watched and handled very quickly (with low latency),	2838	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	2839	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	2840	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.	2841	the rest in a second one, and embed the second one in the first.
2218		2842
2219	As long as the watcher is active, the callback will be invoked every time	2843	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	2844	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	2845	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	2846	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	2847	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	2848	to give the embedded loop strictly lower priority for example).
2225	embedded loop sweep.
2226		2849
2227	As long as the watcher is started it will automatically handle events. The	2850	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	2851	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		2852
2232	Also, there have not currently been made special provisions for forking:	2853	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,	2854	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	2855	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,	2856	C<ev_loop_fork> on the embedded loop.
2236	and future versions of libev might do just that.
2237		2857
2238	Unfortunately, not all backends are embeddable: only the ones returned by	2858	Unfortunately, not all backends are embeddable: only the ones returned by
2239	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2859	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2240	portable one.	2860	portable one.
2241		2861
2242	So when you want to use this feature you will always have to be prepared	2862	So when you want to use this feature you will always have to be prepared
2243	that you cannot get an embeddable loop. The recommended way to get around	2863	that you cannot get an embeddable loop. The recommended way to get around
2244	this is to have a separate variables for your embeddable loop, try to	2864	this is to have a separate variables for your embeddable loop, try to
2245	create it, and if that fails, use the normal loop for everything.	2865	create it, and if that fails, use the normal loop for everything.
		2866
		2867	=head3 C<ev_embed> and fork
		2868
		2869	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2870	automatically be applied to the embedded loop as well, so no special
		2871	fork handling is required in that case. When the watcher is not running,
		2872	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2873	as applicable.
2246		2874
2247	=head3 Watcher-Specific Functions and Data Members	2875	=head3 Watcher-Specific Functions and Data Members
2248		2876
2249	=over 4	2877	=over 4
2250		2878
…		…
2278	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2906	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2279	used).	2907	used).
2280		2908
2281	struct ev_loop *loop_hi = ev_default_init (0);	2909	struct ev_loop *loop_hi = ev_default_init (0);
2282	struct ev_loop *loop_lo = 0;	2910	struct ev_loop *loop_lo = 0;
2283	struct ev_embed embed;	2911	ev_embed embed;
2284		2912
2285	// see if there is a chance of getting one that works	2913	// see if there is a chance of getting one that works
2286	// (remember that a flags value of 0 means autodetection)	2914	// (remember that a flags value of 0 means autodetection)
2287	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2915	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2288	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2916	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2302	kqueue implementation). Store the kqueue/socket-only event loop in	2930	kqueue implementation). Store the kqueue/socket-only event loop in
2303	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2931	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2304		2932
2305	struct ev_loop *loop = ev_default_init (0);	2933	struct ev_loop *loop = ev_default_init (0);
2306	struct ev_loop *loop_socket = 0;	2934	struct ev_loop *loop_socket = 0;
2307	struct ev_embed embed;	2935	ev_embed embed;
2308		2936
2309	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2937	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2310	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2938	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2311	{	2939	{
2312	ev_embed_init (&embed, 0, loop_socket);	2940	ev_embed_init (&embed, 0, loop_socket);
…		…
2327	event loop blocks next and before C<ev_check> watchers are being called,	2955	event loop blocks next and before C<ev_check> watchers are being called,
2328	and only in the child after the fork. If whoever good citizen calling	2956	and only in the child after the fork. If whoever good citizen calling
2329	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2957	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2330	handlers will be invoked, too, of course.	2958	handlers will be invoked, too, of course.
2331		2959
		2960	=head3 The special problem of life after fork - how is it possible?
		2961
		2962	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2963	up/change the process environment, followed by a call to C<exec()>. This
		2964	sequence should be handled by libev without any problems.
		2965
		2966	This changes when the application actually wants to do event handling
		2967	in the child, or both parent in child, in effect "continuing" after the
		2968	fork.
		2969
		2970	The default mode of operation (for libev, with application help to detect
		2971	forks) is to duplicate all the state in the child, as would be expected
		2972	when I<either> the parent I<or> the child process continues.
		2973
		2974	When both processes want to continue using libev, then this is usually the
		2975	wrong result. In that case, usually one process (typically the parent) is
		2976	supposed to continue with all watchers in place as before, while the other
		2977	process typically wants to start fresh, i.e. without any active watchers.
		2978
		2979	The cleanest and most efficient way to achieve that with libev is to
		2980	simply create a new event loop, which of course will be "empty", and
		2981	use that for new watchers. This has the advantage of not touching more
		2982	memory than necessary, and thus avoiding the copy-on-write, and the
		2983	disadvantage of having to use multiple event loops (which do not support
		2984	signal watchers).
		2985
		2986	When this is not possible, or you want to use the default loop for
		2987	other reasons, then in the process that wants to start "fresh", call
		2988	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2989	the default loop will "orphan" (not stop) all registered watchers, so you
		2990	have to be careful not to execute code that modifies those watchers. Note
		2991	also that in that case, you have to re-register any signal watchers.
		2992
2332	=head3 Watcher-Specific Functions and Data Members	2993	=head3 Watcher-Specific Functions and Data Members
2333		2994
2334	=over 4	2995	=over 4
2335		2996
2336	=item ev_fork_init (ev_signal *, callback)	2997	=item ev_fork_init (ev_signal *, callback)
…		…
2365	=head3 Queueing	3026	=head3 Queueing
2366		3027
2367	C<ev_async> does not support queueing of data in any way. The reason	3028	C<ev_async> does not support queueing of data in any way. The reason
2368	is that the author does not know of a simple (or any) algorithm for a	3029	is that the author does not know of a simple (or any) algorithm for a
2369	multiple-writer-single-reader queue that works in all cases and doesn't	3030	multiple-writer-single-reader queue that works in all cases and doesn't
2370	need elaborate support such as pthreads.	3031	need elaborate support such as pthreads or unportable memory access
		3032	semantics.
2371		3033
2372	That means that if you want to queue data, you have to provide your own	3034	That means that if you want to queue data, you have to provide your own
2373	queue. But at least I can tell you how to implement locking around your	3035	queue. But at least I can tell you how to implement locking around your
2374	queue:	3036	queue:
2375		3037
2376	=over 4	3038	=over 4
2377		3039
2378	=item queueing from a signal handler context	3040	=item queueing from a signal handler context
2379		3041
2380	To implement race-free queueing, you simply add to the queue in the signal	3042	To implement race-free queueing, you simply add to the queue in the signal
2381	handler but you block the signal handler in the watcher callback. Here is an example that does that for	3043	handler but you block the signal handler in the watcher callback. Here is
2382	some fictitious SIGUSR1 handler:	3044	an example that does that for some fictitious SIGUSR1 handler:
2383		3045
2384	static ev_async mysig;	3046	static ev_async mysig;
2385		3047
2386	static void	3048	static void
2387	sigusr1_handler (void)	3049	sigusr1_handler (void)
…		…
2453	=over 4	3115	=over 4
2454		3116
2455	=item ev_async_init (ev_async *, callback)	3117	=item ev_async_init (ev_async *, callback)
2456		3118
2457	Initialises and configures the async watcher - it has no parameters of any	3119	Initialises and configures the async watcher - it has no parameters of any
2458	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3120	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2459	trust me.	3121	trust me.
2460		3122
2461	=item ev_async_send (loop, ev_async *)	3123	=item ev_async_send (loop, ev_async *)
2462		3124
2463	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3125	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2464	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3126	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2465	C<ev_feed_event>, this call is safe to do from other threads, signal or	3127	C<ev_feed_event>, this call is safe to do from other threads, signal or
2466	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3128	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2467	section below on what exactly this means).	3129	section below on what exactly this means).
2468		3130
		3131	Note that, as with other watchers in libev, multiple events might get
		3132	compressed into a single callback invocation (another way to look at this
		3133	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3134	reset when the event loop detects that).
		3135
2469	This call incurs the overhead of a system call only once per loop iteration,	3136	This call incurs the overhead of a system call only once per event loop
2470	so while the overhead might be noticeable, it doesn't apply to repeated	3137	iteration, so while the overhead might be noticeable, it doesn't apply to
2471	calls to C<ev_async_send>.	3138	repeated calls to C<ev_async_send> for the same event loop.
2472		3139
2473	=item bool = ev_async_pending (ev_async *)	3140	=item bool = ev_async_pending (ev_async *)
2474		3141
2475	Returns a non-zero value when C<ev_async_send> has been called on the	3142	Returns a non-zero value when C<ev_async_send> has been called on the
2476	watcher but the event has not yet been processed (or even noted) by the	3143	watcher but the event has not yet been processed (or even noted) by the
…		…
2479	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3146	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2480	the loop iterates next and checks for the watcher to have become active,	3147	the loop iterates next and checks for the watcher to have become active,
2481	it will reset the flag again. C<ev_async_pending> can be used to very	3148	it will reset the flag again. C<ev_async_pending> can be used to very
2482	quickly check whether invoking the loop might be a good idea.	3149	quickly check whether invoking the loop might be a good idea.
2483		3150
2484	Not that this does I<not> check whether the watcher itself is pending, only	3151	Not that this does I<not> check whether the watcher itself is pending,
2485	whether it has been requested to make this watcher pending.	3152	only whether it has been requested to make this watcher pending: there
		3153	is a time window between the event loop checking and resetting the async
		3154	notification, and the callback being invoked.
2486		3155
2487	=back	3156	=back
2488		3157
2489		3158
2490	=head1 OTHER FUNCTIONS	3159	=head1 OTHER FUNCTIONS
…		…
2494	=over 4	3163	=over 4
2495		3164
2496	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3165	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2497		3166
2498	This function combines a simple timer and an I/O watcher, calls your	3167	This function combines a simple timer and an I/O watcher, calls your
2499	callback on whichever event happens first and automatically stop both	3168	callback on whichever event happens first and automatically stops both
2500	watchers. This is useful if you want to wait for a single event on an fd	3169	watchers. This is useful if you want to wait for a single event on an fd
2501	or timeout without having to allocate/configure/start/stop/free one or	3170	or timeout without having to allocate/configure/start/stop/free one or
2502	more watchers yourself.	3171	more watchers yourself.
2503		3172
2504	If C<fd> is less than 0, then no I/O watcher will be started and events	3173	If C<fd> is less than 0, then no I/O watcher will be started and the
2505	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	3174	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2506	C<events> set will be created and started.	3175	the given C<fd> and C<events> set will be created and started.
2507		3176
2508	If C<timeout> is less than 0, then no timeout watcher will be	3177	If C<timeout> is less than 0, then no timeout watcher will be
2509	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3178	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2510	repeat = 0) will be started. While C<0> is a valid timeout, it is of	3179	repeat = 0) will be started. C<0> is a valid timeout.
2511	dubious value.
2512		3180
2513	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3181	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2514	passed an C<revents> set like normal event callbacks (a combination of	3182	passed an C<revents> set like normal event callbacks (a combination of
2515	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3183	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2516	value passed to C<ev_once>:	3184	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3185	a timeout and an io event at the same time - you probably should give io
		3186	events precedence.
		3187
		3188	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2517		3189
2518	static void stdin_ready (int revents, void *arg)	3190	static void stdin_ready (int revents, void *arg)
2519	{	3191	{
		3192	if (revents & EV_READ)
		3193	/* stdin might have data for us, joy! */;
2520	if (revents & EV_TIMEOUT)	3194	else if (revents & EV_TIMER)
2521	/* doh, nothing entered */;	3195	/* doh, nothing entered */;
2522	else if (revents & EV_READ)
2523	/* stdin might have data for us, joy! */;
2524	}	3196	}
2525		3197
2526	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3198	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2527		3199
2528	=item ev_feed_event (ev_loop *, watcher *, int revents)
2529
2530	Feeds the given event set into the event loop, as if the specified event
2531	had happened for the specified watcher (which must be a pointer to an
2532	initialised but not necessarily started event watcher).
2533
2534	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3200	=item ev_feed_fd_event (loop, int fd, int revents)
2535		3201
2536	Feed an event on the given fd, as if a file descriptor backend detected	3202	Feed an event on the given fd, as if a file descriptor backend detected
2537	the given events it.	3203	the given events it.
2538		3204
2539	=item ev_feed_signal_event (ev_loop *loop, int signum)	3205	=item ev_feed_signal_event (loop, int signum)
2540		3206
2541	Feed an event as if the given signal occurred (C<loop> must be the default	3207	Feed an event as if the given signal occurred (C<loop> must be the default
2542	loop!).	3208	loop!).
2543		3209
2544	=back	3210	=back
…		…
2624		3290
2625	=over 4	3291	=over 4
2626		3292
2627	=item ev::TYPE::TYPE ()	3293	=item ev::TYPE::TYPE ()
2628		3294
2629	=item ev::TYPE::TYPE (struct ev_loop *)	3295	=item ev::TYPE::TYPE (loop)
2630		3296
2631	=item ev::TYPE::~TYPE	3297	=item ev::TYPE::~TYPE
2632		3298
2633	The constructor (optionally) takes an event loop to associate the watcher	3299	The constructor (optionally) takes an event loop to associate the watcher
2634	with. If it is omitted, it will use C<EV_DEFAULT>.	3300	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2666		3332
2667	myclass obj;	3333	myclass obj;
2668	ev::io iow;	3334	ev::io iow;
2669	iow.set <myclass, &myclass::io_cb> (&obj);	3335	iow.set <myclass, &myclass::io_cb> (&obj);
2670		3336
		3337	=item w->set (object *)
		3338
		3339	This is an B<experimental> feature that might go away in a future version.
		3340
		3341	This is a variation of a method callback - leaving out the method to call
		3342	will default the method to C<operator ()>, which makes it possible to use
		3343	functor objects without having to manually specify the C<operator ()> all
		3344	the time. Incidentally, you can then also leave out the template argument
		3345	list.
		3346
		3347	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3348	int revents)>.
		3349
		3350	See the method-C<set> above for more details.
		3351
		3352	Example: use a functor object as callback.
		3353
		3354	struct myfunctor
		3355	{
		3356	void operator() (ev::io &w, int revents)
		3357	{
		3358	...
		3359	}
		3360	}
		3361
		3362	myfunctor f;
		3363
		3364	ev::io w;
		3365	w.set (&f);
		3366
2671	=item w->set<function> (void *data = 0)	3367	=item w->set<function> (void *data = 0)
2672		3368
2673	Also sets a callback, but uses a static method or plain function as	3369	Also sets a callback, but uses a static method or plain function as
2674	callback. The optional C<data> argument will be stored in the watcher's	3370	callback. The optional C<data> argument will be stored in the watcher's
2675	C<data> member and is free for you to use.	3371	C<data> member and is free for you to use.
…		…
2681	Example: Use a plain function as callback.	3377	Example: Use a plain function as callback.
2682		3378
2683	static void io_cb (ev::io &w, int revents) { }	3379	static void io_cb (ev::io &w, int revents) { }
2684	iow.set <io_cb> ();	3380	iow.set <io_cb> ();
2685		3381
2686	=item w->set (struct ev_loop *)	3382	=item w->set (loop)
2687		3383
2688	Associates a different C<struct ev_loop> with this watcher. You can only	3384	Associates a different C<struct ev_loop> with this watcher. You can only
2689	do this when the watcher is inactive (and not pending either).	3385	do this when the watcher is inactive (and not pending either).
2690		3386
2691	=item w->set ([arguments])	3387	=item w->set ([arguments])
…		…
2761	L<http://software.schmorp.de/pkg/EV>.	3457	L<http://software.schmorp.de/pkg/EV>.
2762		3458
2763	=item Python	3459	=item Python
2764		3460
2765	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3461	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2766	seems to be quite complete and well-documented. Note, however, that the	3462	seems to be quite complete and well-documented.
2767	patch they require for libev is outright dangerous as it breaks the ABI
2768	for everybody else, and therefore, should never be applied in an installed
2769	libev (if python requires an incompatible ABI then it needs to embed
2770	libev).
2771		3463
2772	=item Ruby	3464	=item Ruby
2773		3465
2774	Tony Arcieri has written a ruby extension that offers access to a subset	3466	Tony Arcieri has written a ruby extension that offers access to a subset
2775	of the libev API and adds file handle abstractions, asynchronous DNS and	3467	of the libev API and adds file handle abstractions, asynchronous DNS and
2776	more on top of it. It can be found via gem servers. Its homepage is at	3468	more on top of it. It can be found via gem servers. Its homepage is at
2777	L<http://rev.rubyforge.org/>.	3469	L<http://rev.rubyforge.org/>.
2778		3470
		3471	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3472	makes rev work even on mingw.
		3473
		3474	=item Haskell
		3475
		3476	A haskell binding to libev is available at
		3477	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3478
2779	=item D	3479	=item D
2780		3480
2781	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3481	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2782	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3482	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3483
		3484	=item Ocaml
		3485
		3486	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3487	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3488
		3489	=item Lua
		3490
		3491	Brian Maher has written a partial interface to libev for lua (at the
		3492	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3493	L<http://github.com/brimworks/lua-ev>.
2783		3494
2784	=back	3495	=back
2785		3496
2786		3497
2787	=head1 MACRO MAGIC	3498	=head1 MACRO MAGIC
…		…
2888		3599
2889	#define EV_STANDALONE 1	3600	#define EV_STANDALONE 1
2890	#include "ev.h"	3601	#include "ev.h"
2891		3602
2892	Both header files and implementation files can be compiled with a C++	3603	Both header files and implementation files can be compiled with a C++
2893	compiler (at least, thats a stated goal, and breakage will be treated	3604	compiler (at least, that's a stated goal, and breakage will be treated
2894	as a bug).	3605	as a bug).
2895		3606
2896	You need the following files in your source tree, or in a directory	3607	You need the following files in your source tree, or in a directory
2897	in your include path (e.g. in libev/ when using -Ilibev):	3608	in your include path (e.g. in libev/ when using -Ilibev):
2898		3609
…		…
2941	libev.m4	3652	libev.m4
2942		3653
2943	=head2 PREPROCESSOR SYMBOLS/MACROS	3654	=head2 PREPROCESSOR SYMBOLS/MACROS
2944		3655
2945	Libev can be configured via a variety of preprocessor symbols you have to	3656	Libev can be configured via a variety of preprocessor symbols you have to
2946	define before including any of its files. The default in the absence of	3657	define before including (or compiling) any of its files. The default in
2947	autoconf is documented for every option.	3658	the absence of autoconf is documented for every option.
		3659
		3660	Symbols marked with "(h)" do not change the ABI, and can have different
		3661	values when compiling libev vs. including F<ev.h>, so it is permissible
		3662	to redefine them before including F<ev.h> without breakign compatibility
		3663	to a compiled library. All other symbols change the ABI, which means all
		3664	users of libev and the libev code itself must be compiled with compatible
		3665	settings.
2948		3666
2949	=over 4	3667	=over 4
2950		3668
2951	=item EV_STANDALONE	3669	=item EV_STANDALONE (h)
2952		3670
2953	Must always be C<1> if you do not use autoconf configuration, which	3671	Must always be C<1> if you do not use autoconf configuration, which
2954	keeps libev from including F<config.h>, and it also defines dummy	3672	keeps libev from including F<config.h>, and it also defines dummy
2955	implementations for some libevent functions (such as logging, which is not	3673	implementations for some libevent functions (such as logging, which is not
2956	supported). It will also not define any of the structs usually found in	3674	supported). It will also not define any of the structs usually found in
2957	F<event.h> that are not directly supported by the libev core alone.	3675	F<event.h> that are not directly supported by the libev core alone.
2958		3676
		3677	In standalone mode, libev will still try to automatically deduce the
		3678	configuration, but has to be more conservative.
		3679
2959	=item EV_USE_MONOTONIC	3680	=item EV_USE_MONOTONIC
2960		3681
2961	If defined to be C<1>, libev will try to detect the availability of the	3682	If defined to be C<1>, libev will try to detect the availability of the
2962	monotonic clock option at both compile time and runtime. Otherwise no use	3683	monotonic clock option at both compile time and runtime. Otherwise no
2963	of the monotonic clock option will be attempted. If you enable this, you	3684	use of the monotonic clock option will be attempted. If you enable this,
2964	usually have to link against librt or something similar. Enabling it when	3685	you usually have to link against librt or something similar. Enabling it
2965	the functionality isn't available is safe, though, although you have	3686	when the functionality isn't available is safe, though, although you have
2966	to make sure you link against any libraries where the C<clock_gettime>	3687	to make sure you link against any libraries where the C<clock_gettime>
2967	function is hiding in (often F<-lrt>).	3688	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2968		3689
2969	=item EV_USE_REALTIME	3690	=item EV_USE_REALTIME
2970		3691
2971	If defined to be C<1>, libev will try to detect the availability of the	3692	If defined to be C<1>, libev will try to detect the availability of the
2972	real-time clock option at compile time (and assume its availability at	3693	real-time clock option at compile time (and assume its availability
2973	runtime if successful). Otherwise no use of the real-time clock option will	3694	at runtime if successful). Otherwise no use of the real-time clock
2974	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3695	option will be attempted. This effectively replaces C<gettimeofday>
2975	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3696	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2976	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3697	correctness. See the note about libraries in the description of
		3698	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3699	C<EV_USE_CLOCK_SYSCALL>.
		3700
		3701	=item EV_USE_CLOCK_SYSCALL
		3702
		3703	If defined to be C<1>, libev will try to use a direct syscall instead
		3704	of calling the system-provided C<clock_gettime> function. This option
		3705	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3706	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3707	programs needlessly. Using a direct syscall is slightly slower (in
		3708	theory), because no optimised vdso implementation can be used, but avoids
		3709	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3710	higher, as it simplifies linking (no need for C<-lrt>).
2977		3711
2978	=item EV_USE_NANOSLEEP	3712	=item EV_USE_NANOSLEEP
2979		3713
2980	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3714	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2981	and will use it for delays. Otherwise it will use C<select ()>.	3715	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2997		3731
2998	=item EV_SELECT_USE_FD_SET	3732	=item EV_SELECT_USE_FD_SET
2999		3733
3000	If defined to C<1>, then the select backend will use the system C<fd_set>	3734	If defined to C<1>, then the select backend will use the system C<fd_set>
3001	structure. This is useful if libev doesn't compile due to a missing	3735	structure. This is useful if libev doesn't compile due to a missing
3002	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3736	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3003	exotic systems. This usually limits the range of file descriptors to some	3737	on exotic systems. This usually limits the range of file descriptors to
3004	low limit such as 1024 or might have other limitations (winsocket only	3738	some low limit such as 1024 or might have other limitations (winsocket
3005	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3739	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3006	influence the size of the C<fd_set> used.	3740	configures the maximum size of the C<fd_set>.
3007		3741
3008	=item EV_SELECT_IS_WINSOCKET	3742	=item EV_SELECT_IS_WINSOCKET
3009		3743
3010	When defined to C<1>, the select backend will assume that	3744	When defined to C<1>, the select backend will assume that
3011	select/socket/connect etc. don't understand file descriptors but	3745	select/socket/connect etc. don't understand file descriptors but
…		…
3013	be used is the winsock select). This means that it will call	3747	be used is the winsock select). This means that it will call
3014	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3748	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3015	it is assumed that all these functions actually work on fds, even	3749	it is assumed that all these functions actually work on fds, even
3016	on win32. Should not be defined on non-win32 platforms.	3750	on win32. Should not be defined on non-win32 platforms.
3017		3751
3018	=item EV_FD_TO_WIN32_HANDLE	3752	=item EV_FD_TO_WIN32_HANDLE(fd)
3019		3753
3020	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3754	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3021	file descriptors to socket handles. When not defining this symbol (the	3755	file descriptors to socket handles. When not defining this symbol (the
3022	default), then libev will call C<_get_osfhandle>, which is usually	3756	default), then libev will call C<_get_osfhandle>, which is usually
3023	correct. In some cases, programs use their own file descriptor management,	3757	correct. In some cases, programs use their own file descriptor management,
3024	in which case they can provide this function to map fds to socket handles.	3758	in which case they can provide this function to map fds to socket handles.
		3759
		3760	=item EV_WIN32_HANDLE_TO_FD(handle)
		3761
		3762	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3763	using the standard C<_open_osfhandle> function. For programs implementing
		3764	their own fd to handle mapping, overwriting this function makes it easier
		3765	to do so. This can be done by defining this macro to an appropriate value.
		3766
		3767	=item EV_WIN32_CLOSE_FD(fd)
		3768
		3769	If programs implement their own fd to handle mapping on win32, then this
		3770	macro can be used to override the C<close> function, useful to unregister
		3771	file descriptors again. Note that the replacement function has to close
		3772	the underlying OS handle.
3025		3773
3026	=item EV_USE_POLL	3774	=item EV_USE_POLL
3027		3775
3028	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3776	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3029	backend. Otherwise it will be enabled on non-win32 platforms. It	3777	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3076	as well as for signal and thread safety in C<ev_async> watchers.	3824	as well as for signal and thread safety in C<ev_async> watchers.
3077		3825
3078	In the absence of this define, libev will use C<sig_atomic_t volatile>	3826	In the absence of this define, libev will use C<sig_atomic_t volatile>
3079	(from F<signal.h>), which is usually good enough on most platforms.	3827	(from F<signal.h>), which is usually good enough on most platforms.
3080		3828
3081	=item EV_H	3829	=item EV_H (h)
3082		3830
3083	The name of the F<ev.h> header file used to include it. The default if	3831	The name of the F<ev.h> header file used to include it. The default if
3084	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	3832	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3085	used to virtually rename the F<ev.h> header file in case of conflicts.	3833	used to virtually rename the F<ev.h> header file in case of conflicts.
3086		3834
3087	=item EV_CONFIG_H	3835	=item EV_CONFIG_H (h)
3088		3836
3089	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	3837	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3090	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	3838	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3091	C<EV_H>, above.	3839	C<EV_H>, above.
3092		3840
3093	=item EV_EVENT_H	3841	=item EV_EVENT_H (h)
3094		3842
3095	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	3843	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3096	of how the F<event.h> header can be found, the default is C<"event.h">.	3844	of how the F<event.h> header can be found, the default is C<"event.h">.
3097		3845
3098	=item EV_PROTOTYPES	3846	=item EV_PROTOTYPES (h)
3099		3847
3100	If defined to be C<0>, then F<ev.h> will not define any function	3848	If defined to be C<0>, then F<ev.h> will not define any function
3101	prototypes, but still define all the structs and other symbols. This is	3849	prototypes, but still define all the structs and other symbols. This is
3102	occasionally useful if you want to provide your own wrapper functions	3850	occasionally useful if you want to provide your own wrapper functions
3103	around libev functions.	3851	around libev functions.
…		…
3125	fine.	3873	fine.
3126		3874
3127	If your embedding application does not need any priorities, defining these	3875	If your embedding application does not need any priorities, defining these
3128	both to C<0> will save some memory and CPU.	3876	both to C<0> will save some memory and CPU.
3129		3877
3130	=item EV_PERIODIC_ENABLE	3878	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		3879	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		3880	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3131		3881
3132	If undefined or defined to be C<1>, then periodic timers are supported. If	3882	If undefined or defined to be C<1> (and the platform supports it), then
3133	defined to be C<0>, then they are not. Disabling them saves a few kB of	3883	the respective watcher type is supported. If defined to be C<0>, then it
3134	code.	3884	is not. Disabling watcher types mainly saves codesize.
3135		3885
3136	=item EV_IDLE_ENABLE	3886	=item EV_FEATURES
3137
3138	If undefined or defined to be C<1>, then idle watchers are supported. If
3139	defined to be C<0>, then they are not. Disabling them saves a few kB of
3140	code.
3141
3142	=item EV_EMBED_ENABLE
3143
3144	If undefined or defined to be C<1>, then embed watchers are supported. If
3145	defined to be C<0>, then they are not. Embed watchers rely on most other
3146	watcher types, which therefore must not be disabled.
3147
3148	=item EV_STAT_ENABLE
3149
3150	If undefined or defined to be C<1>, then stat watchers are supported. If
3151	defined to be C<0>, then they are not.
3152
3153	=item EV_FORK_ENABLE
3154
3155	If undefined or defined to be C<1>, then fork watchers are supported. If
3156	defined to be C<0>, then they are not.
3157
3158	=item EV_ASYNC_ENABLE
3159
3160	If undefined or defined to be C<1>, then async watchers are supported. If
3161	defined to be C<0>, then they are not.
3162
3163	=item EV_MINIMAL
3164		3887
3165	If you need to shave off some kilobytes of code at the expense of some	3888	If you need to shave off some kilobytes of code at the expense of some
3166	speed, define this symbol to C<1>. Currently this is used to override some	3889	speed (but with the full API), you can define this symbol to request
3167	inlining decisions, saves roughly 30% code size on amd64. It also selects a	3890	certain subsets of functionality. The default is to enable all features
3168	much smaller 2-heap for timer management over the default 4-heap.	3891	that can be enabled on the platform.
		3892
		3893	A typical way to use this symbol is to define it to C<0> (or to a bitset
		3894	with some broad features you want) and then selectively re-enable
		3895	additional parts you want, for example if you want everything minimal,
		3896	but multiple event loop support, async and child watchers and the poll
		3897	backend, use this:
		3898
		3899	#define EV_FEATURES 0
		3900	#define EV_MULTIPLICITY 1
		3901	#define EV_USE_POLL 1
		3902	#define EV_CHILD_ENABLE 1
		3903	#define EV_ASYNC_ENABLE 1
		3904
		3905	The actual value is a bitset, it can be a combination of the following
		3906	values:
		3907
		3908	=over 4
		3909
		3910	=item C<1> - faster/larger code
		3911
		3912	Use larger code to speed up some operations.
		3913
		3914	Currently this is used to override some inlining decisions (enlarging the roughly
		3915	30% code size on amd64.
		3916
		3917	When optimising for size, use of compiler flags such as C<-Os> with
		3918	gcc recommended, as well as C<-DNDEBUG>, as libev contains a number of
		3919	assertions.
		3920
		3921	=item C<2> - faster/larger data structures
		3922
		3923	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		3924	hash table sizes and so on. This will usually further increase codesize
		3925	and can additionally have an effect on the size of data structures at
		3926	runtime.
		3927
		3928	=item C<4> - full API configuration
		3929
		3930	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		3931	enables multiplicity (C<EV_MULTIPLICITY>=1).
		3932
		3933	=item C<8> - full API
		3934
		3935	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		3936	details on which parts of the API are still available without this
		3937	feature, and do not complain if this subset changes over time.
		3938
		3939	=item C<16> - enable all optional watcher types
		3940
		3941	Enables all optional watcher types. If you want to selectively enable
		3942	only some watcher types other than I/O and timers (e.g. prepare,
		3943	embed, async, child...) you can enable them manually by defining
		3944	C<EV_watchertype_ENABLE> to C<1> instead.
		3945
		3946	=item C<32> - enable all backends
		3947
		3948	This enables all backends - without this feature, you need to enable at
		3949	least one backend manually (C<EV_USE_SELECT> is a good choice).
		3950
		3951	=item C<64> - enable OS-specific "helper" APIs
		3952
		3953	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		3954	default.
		3955
		3956	=back
		3957
		3958	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		3959	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		3960	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		3961	watchers, timers and monotonic clock support.
		3962
		3963	With an intelligent-enough linker (gcc+binutils are intelligent enough
		3964	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		3965	your program might be left out as well - a binary starting a timer and an
		3966	I/O watcher then might come out at only 5Kb.
		3967
		3968	=item EV_AVOID_STDIO
		3969
		3970	If this is set to C<1> at compiletime, then libev will avoid using stdio
		3971	functions (printf, scanf, perror etc.). This will increase the codesize
		3972	somewhat, but if your program doesn't otherwise depend on stdio and your
		3973	libc allows it, this avoids linking in the stdio library which is quite
		3974	big.
		3975
		3976	Note that error messages might become less precise when this option is
		3977	enabled.
		3978
		3979	=item EV_NSIG
		3980
		3981	The highest supported signal number, +1 (or, the number of
		3982	signals): Normally, libev tries to deduce the maximum number of signals
		3983	automatically, but sometimes this fails, in which case it can be
		3984	specified. Also, using a lower number than detected (C<32> should be
		3985	good for about any system in existance) can save some memory, as libev
		3986	statically allocates some 12-24 bytes per signal number.
3169		3987
3170	=item EV_PID_HASHSIZE	3988	=item EV_PID_HASHSIZE
3171		3989
3172	C<ev_child> watchers use a small hash table to distribute workload by	3990	C<ev_child> watchers use a small hash table to distribute workload by
3173	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3991	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3174	than enough. If you need to manage thousands of children you might want to	3992	usually more than enough. If you need to manage thousands of children you
3175	increase this value (I<must> be a power of two).	3993	might want to increase this value (I<must> be a power of two).
3176		3994
3177	=item EV_INOTIFY_HASHSIZE	3995	=item EV_INOTIFY_HASHSIZE
3178		3996
3179	C<ev_stat> watchers use a small hash table to distribute workload by	3997	C<ev_stat> watchers use a small hash table to distribute workload by
3180	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3998	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3181	usually more than enough. If you need to manage thousands of C<ev_stat>	3999	disabled), usually more than enough. If you need to manage thousands of
3182	watchers you might want to increase this value (I<must> be a power of	4000	C<ev_stat> watchers you might want to increase this value (I<must> be a
3183	two).	4001	power of two).
3184		4002
3185	=item EV_USE_4HEAP	4003	=item EV_USE_4HEAP
3186		4004
3187	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4005	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3188	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4006	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3189	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4007	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3190	faster performance with many (thousands) of watchers.	4008	faster performance with many (thousands) of watchers.
3191		4009
3192	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4010	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3193	(disabled).	4011	will be C<0>.
3194		4012
3195	=item EV_HEAP_CACHE_AT	4013	=item EV_HEAP_CACHE_AT
3196		4014
3197	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4015	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3198	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4016	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3199	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4017	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3200	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4018	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3201	but avoids random read accesses on heap changes. This improves performance	4019	but avoids random read accesses on heap changes. This improves performance
3202	noticeably with many (hundreds) of watchers.	4020	noticeably with many (hundreds) of watchers.
3203		4021
3204	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4022	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3205	(disabled).	4023	will be C<0>.
3206		4024
3207	=item EV_VERIFY	4025	=item EV_VERIFY
3208		4026
3209	Controls how much internal verification (see C<ev_loop_verify ()>) will	4027	Controls how much internal verification (see C<ev_loop_verify ()>) will
3210	be done: If set to C<0>, no internal verification code will be compiled	4028	be done: If set to C<0>, no internal verification code will be compiled
…		…
3212	called. If set to C<2>, then the internal verification code will be	4030	called. If set to C<2>, then the internal verification code will be
3213	called once per loop, which can slow down libev. If set to C<3>, then the	4031	called once per loop, which can slow down libev. If set to C<3>, then the
3214	verification code will be called very frequently, which will slow down	4032	verification code will be called very frequently, which will slow down
3215	libev considerably.	4033	libev considerably.
3216		4034
3217	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4035	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3218	C<0>.	4036	will be C<0>.
3219		4037
3220	=item EV_COMMON	4038	=item EV_COMMON
3221		4039
3222	By default, all watchers have a C<void *data> member. By redefining	4040	By default, all watchers have a C<void *data> member. By redefining
3223	this macro to a something else you can include more and other types of	4041	this macro to a something else you can include more and other types of
…		…
3240	and the way callbacks are invoked and set. Must expand to a struct member	4058	and the way callbacks are invoked and set. Must expand to a struct member
3241	definition and a statement, respectively. See the F<ev.h> header file for	4059	definition and a statement, respectively. See the F<ev.h> header file for
3242	their default definitions. One possible use for overriding these is to	4060	their default definitions. One possible use for overriding these is to
3243	avoid the C<struct ev_loop *> as first argument in all cases, or to use	4061	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3244	method calls instead of plain function calls in C++.	4062	method calls instead of plain function calls in C++.
		4063
		4064	=back
3245		4065
3246	=head2 EXPORTED API SYMBOLS	4066	=head2 EXPORTED API SYMBOLS
3247		4067
3248	If you need to re-export the API (e.g. via a DLL) and you need a list of	4068	If you need to re-export the API (e.g. via a DLL) and you need a list of
3249	exported symbols, you can use the provided F<Symbol.*> files which list	4069	exported symbols, you can use the provided F<Symbol.*> files which list
…		…
3279	file.	4099	file.
3280		4100
3281	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4101	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3282	that everybody includes and which overrides some configure choices:	4102	that everybody includes and which overrides some configure choices:
3283		4103
3284	#define EV_MINIMAL 1	4104	#define EV_FEATURES 8
3285	#define EV_USE_POLL 0	4105	#define EV_USE_SELECT 1
3286	#define EV_MULTIPLICITY 0
3287	#define EV_PERIODIC_ENABLE 0	4106	#define EV_PREPARE_ENABLE 1
		4107	#define EV_IDLE_ENABLE 1
3288	#define EV_STAT_ENABLE 0	4108	#define EV_SIGNAL_ENABLE 1
3289	#define EV_FORK_ENABLE 0	4109	#define EV_CHILD_ENABLE 1
		4110	#define EV_USE_STDEXCEPT 0
3290	#define EV_CONFIG_H <config.h>	4111	#define EV_CONFIG_H <config.h>
3291	#define EV_MINPRI 0
3292	#define EV_MAXPRI 0
3293		4112
3294	#include "ev++.h"	4113	#include "ev++.h"
3295		4114
3296	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4115	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3297		4116
3298	#include "ev_cpp.h"	4117	#include "ev_cpp.h"
3299	#include "ev.c"	4118	#include "ev.c"
3300		4119
		4120	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3301		4121
3302	=head1 THREADS AND COROUTINES	4122	=head2 THREADS AND COROUTINES
3303		4123
3304	=head2 THREADS	4124	=head3 THREADS
3305		4125
3306	Libev itself is thread-safe (unless the opposite is specifically	4126	All libev functions are reentrant and thread-safe unless explicitly
3307	documented for a function), but it uses no locking itself. This means that	4127	documented otherwise, but libev implements no locking itself. This means
3308	you can use as many loops as you want in parallel, as long as only one	4128	that you can use as many loops as you want in parallel, as long as there
3309	thread ever calls into one libev function with the same loop parameter:	4129	are no concurrent calls into any libev function with the same loop
		4130	parameter (C<ev_default_*> calls have an implicit default loop parameter,
3310	libev guarantees that different event loops share no data structures that	4131	of course): libev guarantees that different event loops share no data
3311	need locking.	4132	structures that need any locking.
3312		4133
3313	Or to put it differently: calls with different loop parameters can be done	4134	Or to put it differently: calls with different loop parameters can be done
3314	concurrently from multiple threads, calls with the same loop parameter	4135	concurrently from multiple threads, calls with the same loop parameter
3315	must be done serially (but can be done from different threads, as long as	4136	must be done serially (but can be done from different threads, as long as
3316	only one thread ever is inside a call at any point in time, e.g. by using	4137	only one thread ever is inside a call at any point in time, e.g. by using
3317	a mutex per loop).	4138	a mutex per loop).
3318		4139
3319	Specifically to support threads (and signal handlers), libev implements	4140	Specifically to support threads (and signal handlers), libev implements
3320	so-called C<ev_async> watchers, which allow some limited form of	4141	so-called C<ev_async> watchers, which allow some limited form of
3321	concurrency on the same event loop.	4142	concurrency on the same event loop, namely waking it up "from the
		4143	outside".
3322		4144
3323	If you want to know which design (one loop, locking, or multiple loops	4145	If you want to know which design (one loop, locking, or multiple loops
3324	without or something else still) is best for your problem, then I cannot	4146	without or something else still) is best for your problem, then I cannot
3325	help you. I can give some generic advice however:	4147	help you, but here is some generic advice:
3326		4148
3327	=over 4	4149	=over 4
3328		4150
3329	=item * most applications have a main thread: use the default libev loop	4151	=item * most applications have a main thread: use the default libev loop
3330	in that thread, or create a separate thread running only the default loop.	4152	in that thread, or create a separate thread running only the default loop.
…		…
3354	default loop and triggering an C<ev_async> watcher from the default loop	4176	default loop and triggering an C<ev_async> watcher from the default loop
3355	watcher callback into the event loop interested in the signal.	4177	watcher callback into the event loop interested in the signal.
3356		4178
3357	=back	4179	=back
3358		4180
		4181	=head4 THREAD LOCKING EXAMPLE
		4182
		4183	Here is a fictitious example of how to run an event loop in a different
		4184	thread than where callbacks are being invoked and watchers are
		4185	created/added/removed.
		4186
		4187	For a real-world example, see the C<EV::Loop::Async> perl module,
		4188	which uses exactly this technique (which is suited for many high-level
		4189	languages).
		4190
		4191	The example uses a pthread mutex to protect the loop data, a condition
		4192	variable to wait for callback invocations, an async watcher to notify the
		4193	event loop thread and an unspecified mechanism to wake up the main thread.
		4194
		4195	First, you need to associate some data with the event loop:
		4196
		4197	typedef struct {
		4198	mutex_t lock; /* global loop lock */
		4199	ev_async async_w;
		4200	thread_t tid;
		4201	cond_t invoke_cv;
		4202	} userdata;
		4203
		4204	void prepare_loop (EV_P)
		4205	{
		4206	// for simplicity, we use a static userdata struct.
		4207	static userdata u;
		4208
		4209	ev_async_init (&u->async_w, async_cb);
		4210	ev_async_start (EV_A_ &u->async_w);
		4211
		4212	pthread_mutex_init (&u->lock, 0);
		4213	pthread_cond_init (&u->invoke_cv, 0);
		4214
		4215	// now associate this with the loop
		4216	ev_set_userdata (EV_A_ u);
		4217	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4218	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4219
		4220	// then create the thread running ev_loop
		4221	pthread_create (&u->tid, 0, l_run, EV_A);
		4222	}
		4223
		4224	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4225	solely to wake up the event loop so it takes notice of any new watchers
		4226	that might have been added:
		4227
		4228	static void
		4229	async_cb (EV_P_ ev_async *w, int revents)
		4230	{
		4231	// just used for the side effects
		4232	}
		4233
		4234	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4235	protecting the loop data, respectively.
		4236
		4237	static void
		4238	l_release (EV_P)
		4239	{
		4240	userdata *u = ev_userdata (EV_A);
		4241	pthread_mutex_unlock (&u->lock);
		4242	}
		4243
		4244	static void
		4245	l_acquire (EV_P)
		4246	{
		4247	userdata *u = ev_userdata (EV_A);
		4248	pthread_mutex_lock (&u->lock);
		4249	}
		4250
		4251	The event loop thread first acquires the mutex, and then jumps straight
		4252	into C<ev_loop>:
		4253
		4254	void *
		4255	l_run (void *thr_arg)
		4256	{
		4257	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4258
		4259	l_acquire (EV_A);
		4260	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4261	ev_loop (EV_A_ 0);
		4262	l_release (EV_A);
		4263
		4264	return 0;
		4265	}
		4266
		4267	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4268	signal the main thread via some unspecified mechanism (signals? pipe
		4269	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4270	have been called (in a while loop because a) spurious wakeups are possible
		4271	and b) skipping inter-thread-communication when there are no pending
		4272	watchers is very beneficial):
		4273
		4274	static void
		4275	l_invoke (EV_P)
		4276	{
		4277	userdata *u = ev_userdata (EV_A);
		4278
		4279	while (ev_pending_count (EV_A))
		4280	{
		4281	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4282	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4283	}
		4284	}
		4285
		4286	Now, whenever the main thread gets told to invoke pending watchers, it
		4287	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4288	thread to continue:
		4289
		4290	static void
		4291	real_invoke_pending (EV_P)
		4292	{
		4293	userdata *u = ev_userdata (EV_A);
		4294
		4295	pthread_mutex_lock (&u->lock);
		4296	ev_invoke_pending (EV_A);
		4297	pthread_cond_signal (&u->invoke_cv);
		4298	pthread_mutex_unlock (&u->lock);
		4299	}
		4300
		4301	Whenever you want to start/stop a watcher or do other modifications to an
		4302	event loop, you will now have to lock:
		4303
		4304	ev_timer timeout_watcher;
		4305	userdata *u = ev_userdata (EV_A);
		4306
		4307	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4308
		4309	pthread_mutex_lock (&u->lock);
		4310	ev_timer_start (EV_A_ &timeout_watcher);
		4311	ev_async_send (EV_A_ &u->async_w);
		4312	pthread_mutex_unlock (&u->lock);
		4313
		4314	Note that sending the C<ev_async> watcher is required because otherwise
		4315	an event loop currently blocking in the kernel will have no knowledge
		4316	about the newly added timer. By waking up the loop it will pick up any new
		4317	watchers in the next event loop iteration.
		4318
3359	=head2 COROUTINES	4319	=head3 COROUTINES
3360		4320
3361	Libev is much more accommodating to coroutines ("cooperative threads"):	4321	Libev is very accommodating to coroutines ("cooperative threads"):
3362	libev fully supports nesting calls to it's functions from different	4322	libev fully supports nesting calls to its functions from different
3363	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4323	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3364	different coroutines and switch freely between both coroutines running the	4324	different coroutines, and switch freely between both coroutines running
3365	loop, as long as you don't confuse yourself). The only exception is that	4325	the loop, as long as you don't confuse yourself). The only exception is
3366	you must not do this from C<ev_periodic> reschedule callbacks.	4326	that you must not do this from C<ev_periodic> reschedule callbacks.
3367		4327
3368	Care has been taken to ensure that libev does not keep local state inside	4328	Care has been taken to ensure that libev does not keep local state inside
3369	C<ev_loop>, and other calls do not usually allow coroutine switches.	4329	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		4330	they do not call any callbacks.
3370		4331
		4332	=head2 COMPILER WARNINGS
3371		4333
3372	=head1 COMPLEXITIES	4334	Depending on your compiler and compiler settings, you might get no or a
		4335	lot of warnings when compiling libev code. Some people are apparently
		4336	scared by this.
3373		4337
3374	In this section the complexities of (many of) the algorithms used inside	4338	However, these are unavoidable for many reasons. For one, each compiler
3375	libev will be explained. For complexity discussions about backends see the	4339	has different warnings, and each user has different tastes regarding
3376	documentation for C<ev_default_init>.	4340	warning options. "Warn-free" code therefore cannot be a goal except when
		4341	targeting a specific compiler and compiler-version.
3377		4342
3378	All of the following are about amortised time: If an array needs to be	4343	Another reason is that some compiler warnings require elaborate
3379	extended, libev needs to realloc and move the whole array, but this	4344	workarounds, or other changes to the code that make it less clear and less
3380	happens asymptotically never with higher number of elements, so O(1) might	4345	maintainable.
3381	mean it might do a lengthy realloc operation in rare cases, but on average
3382	it is much faster and asymptotically approaches constant time.
3383		4346
3384	=over 4	4347	And of course, some compiler warnings are just plain stupid, or simply
		4348	wrong (because they don't actually warn about the condition their message
		4349	seems to warn about). For example, certain older gcc versions had some
		4350	warnings that resulted an extreme number of false positives. These have
		4351	been fixed, but some people still insist on making code warn-free with
		4352	such buggy versions.
3385		4353
3386	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	4354	While libev is written to generate as few warnings as possible,
		4355	"warn-free" code is not a goal, and it is recommended not to build libev
		4356	with any compiler warnings enabled unless you are prepared to cope with
		4357	them (e.g. by ignoring them). Remember that warnings are just that:
		4358	warnings, not errors, or proof of bugs.
3387		4359
3388	This means that, when you have a watcher that triggers in one hour and
3389	there are 100 watchers that would trigger before that then inserting will
3390	have to skip roughly seven (C<ld 100>) of these watchers.
3391		4360
3392	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	4361	=head2 VALGRIND
3393		4362
3394	That means that changing a timer costs less than removing/adding them	4363	Valgrind has a special section here because it is a popular tool that is
3395	as only the relative motion in the event queue has to be paid for.	4364	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3396		4365
3397	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	4366	If you think you found a bug (memory leak, uninitialised data access etc.)
		4367	in libev, then check twice: If valgrind reports something like:
3398		4368
3399	These just add the watcher into an array or at the head of a list.	4369	==2274== definitely lost: 0 bytes in 0 blocks.
		4370	==2274== possibly lost: 0 bytes in 0 blocks.
		4371	==2274== still reachable: 256 bytes in 1 blocks.
3400		4372
3401	=item Stopping check/prepare/idle/fork/async watchers: O(1)	4373	Then there is no memory leak, just as memory accounted to global variables
		4374	is not a memleak - the memory is still being referenced, and didn't leak.
3402		4375
3403	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	4376	Similarly, under some circumstances, valgrind might report kernel bugs
		4377	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		4378	although an acceptable workaround has been found here), or it might be
		4379	confused.
3404		4380
3405	These watchers are stored in lists then need to be walked to find the	4381	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3406	correct watcher to remove. The lists are usually short (you don't usually	4382	make it into some kind of religion.
3407	have many watchers waiting for the same fd or signal).
3408		4383
3409	=item Finding the next timer in each loop iteration: O(1)	4384	If you are unsure about something, feel free to contact the mailing list
		4385	with the full valgrind report and an explanation on why you think this
		4386	is a bug in libev (best check the archives, too :). However, don't be
		4387	annoyed when you get a brisk "this is no bug" answer and take the chance
		4388	of learning how to interpret valgrind properly.
3410		4389
3411	By virtue of using a binary or 4-heap, the next timer is always found at a	4390	If you need, for some reason, empty reports from valgrind for your project
3412	fixed position in the storage array.	4391	I suggest using suppression lists.
3413		4392
3414	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3415		4393
3416	A change means an I/O watcher gets started or stopped, which requires	4394	=head1 PORTABILITY NOTES
3417	libev to recalculate its status (and possibly tell the kernel, depending
3418	on backend and whether C<ev_io_set> was used).
3419		4395
3420	=item Activating one watcher (putting it into the pending state): O(1)
3421
3422	=item Priority handling: O(number_of_priorities)
3423
3424	Priorities are implemented by allocating some space for each
3425	priority. When doing priority-based operations, libev usually has to
3426	linearly search all the priorities, but starting/stopping and activating
3427	watchers becomes O(1) with respect to priority handling.
3428
3429	=item Sending an ev_async: O(1)
3430
3431	=item Processing ev_async_send: O(number_of_async_watchers)
3432
3433	=item Processing signals: O(max_signal_number)
3434
3435	Sending involves a system call I<iff> there were no other C<ev_async_send>
3436	calls in the current loop iteration. Checking for async and signal events
3437	involves iterating over all running async watchers or all signal numbers.
3438
3439	=back
3440
3441
3442	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4396	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3443		4397
3444	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4398	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3445	requires, and its I/O model is fundamentally incompatible with the POSIX	4399	requires, and its I/O model is fundamentally incompatible with the POSIX
3446	model. Libev still offers limited functionality on this platform in	4400	model. Libev still offers limited functionality on this platform in
3447	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4401	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3454	way (note also that glib is the slowest event library known to man).	4408	way (note also that glib is the slowest event library known to man).
3455		4409
3456	There is no supported compilation method available on windows except	4410	There is no supported compilation method available on windows except
3457	embedding it into other applications.	4411	embedding it into other applications.
3458		4412
		4413	Sensible signal handling is officially unsupported by Microsoft - libev
		4414	tries its best, but under most conditions, signals will simply not work.
		4415
3459	Not a libev limitation but worth mentioning: windows apparently doesn't	4416	Not a libev limitation but worth mentioning: windows apparently doesn't
3460	accept large writes: instead of resulting in a partial write, windows will	4417	accept large writes: instead of resulting in a partial write, windows will
3461	either accept everything or return C<ENOBUFS> if the buffer is too large,	4418	either accept everything or return C<ENOBUFS> if the buffer is too large,
3462	so make sure you only write small amounts into your sockets (less than a	4419	so make sure you only write small amounts into your sockets (less than a
3463	megabyte seems safe, but this apparently depends on the amount of memory	4420	megabyte seems safe, but this apparently depends on the amount of memory
…		…
3467	the abysmal performance of winsockets, using a large number of sockets	4424	the abysmal performance of winsockets, using a large number of sockets
3468	is not recommended (and not reasonable). If your program needs to use	4425	is not recommended (and not reasonable). If your program needs to use
3469	more than a hundred or so sockets, then likely it needs to use a totally	4426	more than a hundred or so sockets, then likely it needs to use a totally
3470	different implementation for windows, as libev offers the POSIX readiness	4427	different implementation for windows, as libev offers the POSIX readiness
3471	notification model, which cannot be implemented efficiently on windows	4428	notification model, which cannot be implemented efficiently on windows
3472	(Microsoft monopoly games).	4429	(due to Microsoft monopoly games).
3473		4430
3474	A typical way to use libev under windows is to embed it (see the embedding	4431	A typical way to use libev under windows is to embed it (see the embedding
3475	section for details) and use the following F<evwrap.h> header file instead	4432	section for details) and use the following F<evwrap.h> header file instead
3476	of F<ev.h>:	4433	of F<ev.h>:
3477		4434
…		…
3513		4470
3514	Early versions of winsocket's select only supported waiting for a maximum	4471	Early versions of winsocket's select only supported waiting for a maximum
3515	of C<64> handles (probably owning to the fact that all windows kernels	4472	of C<64> handles (probably owning to the fact that all windows kernels
3516	can only wait for C<64> things at the same time internally; Microsoft	4473	can only wait for C<64> things at the same time internally; Microsoft
3517	recommends spawning a chain of threads and wait for 63 handles and the	4474	recommends spawning a chain of threads and wait for 63 handles and the
3518	previous thread in each. Great).	4475	previous thread in each. Sounds great!).
3519		4476
3520	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4477	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3521	to some high number (e.g. C<2048>) before compiling the winsocket select	4478	to some high number (e.g. C<2048>) before compiling the winsocket select
3522	call (which might be in libev or elsewhere, for example, perl does its own	4479	call (which might be in libev or elsewhere, for example, perl and many
3523	select emulation on windows).	4480	other interpreters do their own select emulation on windows).
3524		4481
3525	Another limit is the number of file descriptors in the Microsoft runtime	4482	Another limit is the number of file descriptors in the Microsoft runtime
3526	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4483	libraries, which by default is C<64> (there must be a hidden I<64>
3527	or something like this inside Microsoft). You can increase this by calling	4484	fetish or something like this inside Microsoft). You can increase this
3528	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4485	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3529	arbitrary limit), but is broken in many versions of the Microsoft runtime	4486	(another arbitrary limit), but is broken in many versions of the Microsoft
3530	libraries.
3531
3532	This might get you to about C<512> or C<2048> sockets (depending on	4487	runtime libraries. This might get you to about C<512> or C<2048> sockets
3533	windows version and/or the phase of the moon). To get more, you need to	4488	(depending on windows version and/or the phase of the moon). To get more,
3534	wrap all I/O functions and provide your own fd management, but the cost of	4489	you need to wrap all I/O functions and provide your own fd management, but
3535	calling select (O(n²)) will likely make this unworkable.	4490	the cost of calling select (O(n²)) will likely make this unworkable.
3536		4491
3537	=back	4492	=back
3538		4493
3539
3540	=head1 PORTABILITY REQUIREMENTS	4494	=head2 PORTABILITY REQUIREMENTS
3541		4495
3542	In addition to a working ISO-C implementation, libev relies on a few	4496	In addition to a working ISO-C implementation and of course the
3543	additional extensions:	4497	backend-specific APIs, libev relies on a few additional extensions:
3544		4498
3545	=over 4	4499	=over 4
3546		4500
3547	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	4501	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3548	calling conventions regardless of C<ev_watcher_type *>.	4502	calling conventions regardless of C<ev_watcher_type *>.
…		…
3573	except the initial one, and run the default loop in the initial thread as	4527	except the initial one, and run the default loop in the initial thread as
3574	well.	4528	well.
3575		4529
3576	=item C<long> must be large enough for common memory allocation sizes	4530	=item C<long> must be large enough for common memory allocation sizes
3577		4531
3578	To improve portability and simplify using libev, libev uses C<long>	4532	To improve portability and simplify its API, libev uses C<long> internally
3579	internally instead of C<size_t> when allocating its data structures. On	4533	instead of C<size_t> when allocating its data structures. On non-POSIX
3580	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4534	systems (Microsoft...) this might be unexpectedly low, but is still at
3581	is still at least 31 bits everywhere, which is enough for hundreds of	4535	least 31 bits everywhere, which is enough for hundreds of millions of
3582	millions of watchers.	4536	watchers.
3583		4537
3584	=item C<double> must hold a time value in seconds with enough accuracy	4538	=item C<double> must hold a time value in seconds with enough accuracy
3585		4539
3586	The type C<double> is used to represent timestamps. It is required to	4540	The type C<double> is used to represent timestamps. It is required to
3587	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4541	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
3588	enough for at least into the year 4000. This requirement is fulfilled by	4542	enough for at least into the year 4000. This requirement is fulfilled by
3589	implementations implementing IEEE 754 (basically all existing ones).	4543	implementations implementing IEEE 754, which is basically all existing
		4544	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4545	2200.
3590		4546
3591	=back	4547	=back
3592		4548
3593	If you know of other additional requirements drop me a note.	4549	If you know of other additional requirements drop me a note.
3594		4550
3595		4551
3596	=head1 COMPILER WARNINGS	4552	=head1 ALGORITHMIC COMPLEXITIES
3597		4553
3598	Depending on your compiler and compiler settings, you might get no or a	4554	In this section the complexities of (many of) the algorithms used inside
3599	lot of warnings when compiling libev code. Some people are apparently	4555	libev will be documented. For complexity discussions about backends see
3600	scared by this.	4556	the documentation for C<ev_default_init>.
3601		4557
3602	However, these are unavoidable for many reasons. For one, each compiler	4558	All of the following are about amortised time: If an array needs to be
3603	has different warnings, and each user has different tastes regarding	4559	extended, libev needs to realloc and move the whole array, but this
3604	warning options. "Warn-free" code therefore cannot be a goal except when	4560	happens asymptotically rarer with higher number of elements, so O(1) might
3605	targeting a specific compiler and compiler-version.	4561	mean that libev does a lengthy realloc operation in rare cases, but on
		4562	average it is much faster and asymptotically approaches constant time.
3606		4563
3607	Another reason is that some compiler warnings require elaborate	4564	=over 4
3608	workarounds, or other changes to the code that make it less clear and less
3609	maintainable.
3610		4565
3611	And of course, some compiler warnings are just plain stupid, or simply	4566	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3612	wrong (because they don't actually warn about the condition their message
3613	seems to warn about).
3614		4567
3615	While libev is written to generate as few warnings as possible,	4568	This means that, when you have a watcher that triggers in one hour and
3616	"warn-free" code is not a goal, and it is recommended not to build libev	4569	there are 100 watchers that would trigger before that, then inserting will
3617	with any compiler warnings enabled unless you are prepared to cope with	4570	have to skip roughly seven (C<ld 100>) of these watchers.
3618	them (e.g. by ignoring them). Remember that warnings are just that:
3619	warnings, not errors, or proof of bugs.
3620		4571
		4572	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3621		4573
3622	=head1 VALGRIND	4574	That means that changing a timer costs less than removing/adding them,
		4575	as only the relative motion in the event queue has to be paid for.
3623		4576
3624	Valgrind has a special section here because it is a popular tool that is	4577	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3625	highly useful, but valgrind reports are very hard to interpret.
3626		4578
3627	If you think you found a bug (memory leak, uninitialised data access etc.)	4579	These just add the watcher into an array or at the head of a list.
3628	in libev, then check twice: If valgrind reports something like:
3629		4580
3630	==2274== definitely lost: 0 bytes in 0 blocks.	4581	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3631	==2274== possibly lost: 0 bytes in 0 blocks.
3632	==2274== still reachable: 256 bytes in 1 blocks.
3633		4582
3634	Then there is no memory leak. Similarly, under some circumstances,	4583	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3635	valgrind might report kernel bugs as if it were a bug in libev, or it
3636	might be confused (it is a very good tool, but only a tool).
3637		4584
3638	If you are unsure about something, feel free to contact the mailing list	4585	These watchers are stored in lists, so they need to be walked to find the
3639	with the full valgrind report and an explanation on why you think this is	4586	correct watcher to remove. The lists are usually short (you don't usually
3640	a bug in libev. However, don't be annoyed when you get a brisk "this is	4587	have many watchers waiting for the same fd or signal: one is typical, two
3641	no bug" answer and take the chance of learning how to interpret valgrind	4588	is rare).
3642	properly.
3643		4589
3644	If you need, for some reason, empty reports from valgrind for your project	4590	=item Finding the next timer in each loop iteration: O(1)
3645	I suggest using suppression lists.
3646		4591
		4592	By virtue of using a binary or 4-heap, the next timer is always found at a
		4593	fixed position in the storage array.
		4594
		4595	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4596
		4597	A change means an I/O watcher gets started or stopped, which requires
		4598	libev to recalculate its status (and possibly tell the kernel, depending
		4599	on backend and whether C<ev_io_set> was used).
		4600
		4601	=item Activating one watcher (putting it into the pending state): O(1)
		4602
		4603	=item Priority handling: O(number_of_priorities)
		4604
		4605	Priorities are implemented by allocating some space for each
		4606	priority. When doing priority-based operations, libev usually has to
		4607	linearly search all the priorities, but starting/stopping and activating
		4608	watchers becomes O(1) with respect to priority handling.
		4609
		4610	=item Sending an ev_async: O(1)
		4611
		4612	=item Processing ev_async_send: O(number_of_async_watchers)
		4613
		4614	=item Processing signals: O(max_signal_number)
		4615
		4616	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4617	calls in the current loop iteration. Checking for async and signal events
		4618	involves iterating over all running async watchers or all signal numbers.
		4619
		4620	=back
		4621
		4622
		4623	=head1 PORTING FROM 3.X TO 4.X
		4624
		4625	The major version 4 introduced some minor incompatible changes to the API.
		4626
		4627	=over 4
		4628
		4629	=item C<EV_TIMEOUT> replaced by C<EV_TIMER> in C<revents>
		4630
		4631	This is a simple rename - all other watcher types use their name
		4632	as revents flag, and now C<ev_timer> does, too.
		4633
		4634	Both C<EV_TIMER> and C<EV_TIMEOUT> symbols were present in 3.x versions
		4635	and continue to be present for the forseeable future, so this is mostly a
		4636	documentation change.
		4637
		4638	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		4639
		4640	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		4641	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		4642	and work, but the library code will of course be larger.
		4643
		4644	=back
		4645
		4646
		4647	=head1 GLOSSARY
		4648
		4649	=over 4
		4650
		4651	=item active
		4652
		4653	A watcher is active as long as it has been started (has been attached to
		4654	an event loop) but not yet stopped (disassociated from the event loop).
		4655
		4656	=item application
		4657
		4658	In this document, an application is whatever is using libev.
		4659
		4660	=item callback
		4661
		4662	The address of a function that is called when some event has been
		4663	detected. Callbacks are being passed the event loop, the watcher that
		4664	received the event, and the actual event bitset.
		4665
		4666	=item callback invocation
		4667
		4668	The act of calling the callback associated with a watcher.
		4669
		4670	=item event
		4671
		4672	A change of state of some external event, such as data now being available
		4673	for reading on a file descriptor, time having passed or simply not having
		4674	any other events happening anymore.
		4675
		4676	In libev, events are represented as single bits (such as C<EV_READ> or
		4677	C<EV_TIMER>).
		4678
		4679	=item event library
		4680
		4681	A software package implementing an event model and loop.
		4682
		4683	=item event loop
		4684
		4685	An entity that handles and processes external events and converts them
		4686	into callback invocations.
		4687
		4688	=item event model
		4689
		4690	The model used to describe how an event loop handles and processes
		4691	watchers and events.
		4692
		4693	=item pending
		4694
		4695	A watcher is pending as soon as the corresponding event has been detected,
		4696	and stops being pending as soon as the watcher will be invoked or its
		4697	pending status is explicitly cleared by the application.
		4698
		4699	A watcher can be pending, but not active. Stopping a watcher also clears
		4700	its pending status.
		4701
		4702	=item real time
		4703
		4704	The physical time that is observed. It is apparently strictly monotonic :)
		4705
		4706	=item wall-clock time
		4707
		4708	The time and date as shown on clocks. Unlike real time, it can actually
		4709	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4710	clock.
		4711
		4712	=item watcher
		4713
		4714	A data structure that describes interest in certain events. Watchers need
		4715	to be started (attached to an event loop) before they can receive events.
		4716
		4717	=item watcher invocation
		4718
		4719	The act of calling the callback associated with a watcher.
		4720
		4721	=back
3647		4722
3648	=head1 AUTHOR	4723	=head1 AUTHOR
3649		4724
3650	Marc Lehmann <libev@schmorp.de>.	4725	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3651		4726

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