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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
…		…
103	Libev is very configurable. In this manual the default (and most common)	117	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	118	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	119	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	120	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	121	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	122	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	123	this argument.
110		124
111	=head2 TIME REPRESENTATION	125	=head2 TIME REPRESENTATION
112		126
113	Libev represents time as a single floating point number, representing the	127	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	128	the (fractional) number of seconds since the (POSIX) epoch (somewhere
115	the beginning of 1970, details are complicated, don't ask). This type is	129	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	130	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	131	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	132	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	133	component C<stamp> might indicate, it is also used for time differences
120	throughout libev.	134	throughout libev.
121		135
122	=head1 ERROR HANDLING	136	=head1 ERROR HANDLING
123		137
…		…
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	228	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
215	recommended ones.	229	recommended ones.
216		230
217	See the description of C<ev_embed> watchers for more info.	231	See the description of C<ev_embed> watchers for more info.
218		232
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	233	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
220		234
221	Sets the allocation function to use (the prototype is similar - the	235	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	236	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	237	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	238	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	264	}
251		265
252	...	266	...
253	ev_set_allocator (persistent_realloc);	267	ev_set_allocator (persistent_realloc);
254		268
255	=item ev_set_syserr_cb (void (*cb)(const char *msg));	269	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
256		270
257	Set the callback function to call on a retryable system call error (such	271	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	272	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	273	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	274	callback is set, then libev will expect it to remedy the situation, no
…		…
276		290
277	=back	291	=back
278		292
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	293	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
280		294
281	An event loop is described by a C<struct ev_loop *>. The library knows two	295	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	296	is I<not> optional in this case, as there is also an C<ev_loop>
283	events, and dynamically created loops which do not.	297	I<function>).
		298
		299	The library knows two types of such loops, the I<default> loop, which
		300	supports signals and child events, and dynamically created loops which do
		301	not.
284		302
285	=over 4	303	=over 4
286		304
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	305	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		306
…		…
294	If you don't know what event loop to use, use the one returned from this	312	If you don't know what event loop to use, use the one returned from this
295	function.	313	function.
296		314
297	Note that this function is I<not> thread-safe, so if you want to use it	315	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,	316	from multiple threads, you have to lock (note also that this is unlikely,
299	as loops cannot bes hared easily between threads anyway).	317	as loops cannot be shared easily between threads anyway).
300		318
301	The default loop is the only loop that can handle C<ev_signal> and	319	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	320	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	321	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	322	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
…		…
359	writing a server, you should C<accept ()> in a loop to accept as many	377	writing a server, you should C<accept ()> in a loop to accept as many
360	connections as possible during one iteration. You might also want to have	378	connections as possible during one iteration. You might also want to have
361	a look at C<ev_set_io_collect_interval ()> to increase the amount of	379	a look at C<ev_set_io_collect_interval ()> to increase the amount of
362	readiness notifications you get per iteration.	380	readiness notifications you get per iteration.
363		381
		382	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		383	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		384	C<exceptfds> set on that platform).
		385
364	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	386	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
365		387
366	And this is your standard poll(2) backend. It's more complicated	388	And this is your standard poll(2) backend. It's more complicated
367	than select, but handles sparse fds better and has no artificial	389	than select, but handles sparse fds better and has no artificial
368	limit on the number of fds you can use (except it will slow down	390	limit on the number of fds you can use (except it will slow down
369	considerably with a lot of inactive fds). It scales similarly to select,	391	considerably with a lot of inactive fds). It scales similarly to select,
370	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for	392	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
371	performance tips.	393	performance tips.
372		394
		395	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		396	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		397
373	=item C<EVBACKEND_EPOLL> (value 4, Linux)	398	=item C<EVBACKEND_EPOLL> (value 4, Linux)
374		399
375	For few fds, this backend is a bit little slower than poll and select,	400	For few fds, this backend is a bit little slower than poll and select,
376	but it scales phenomenally better. While poll and select usually scale	401	but it scales phenomenally better. While poll and select usually scale
377	like O(total_fds) where n is the total number of fds (or the highest fd),	402	like O(total_fds) where n is the total number of fds (or the highest fd),
378	epoll scales either O(1) or O(active_fds). The epoll design has a number	403	epoll scales either O(1) or O(active_fds).
379	of shortcomings, such as silently dropping events in some hard-to-detect	404
380	cases and requiring a system call per fd change, no fork support and bad	405	The epoll mechanism deserves honorable mention as the most misdesigned
381	support for dup.	406	of the more advanced event mechanisms: mere annoyances include silently
		407	dropping file descriptors, requiring a system call per change per file
		408	descriptor (and unnecessary guessing of parameters), problems with dup and
		409	so on. The biggest issue is fork races, however - if a program forks then
		410	I<both> parent and child process have to recreate the epoll set, which can
		411	take considerable time (one syscall per file descriptor) and is of course
		412	hard to detect.
		413
		414	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		415	of course I<doesn't>, and epoll just loves to report events for totally
		416	I<different> file descriptors (even already closed ones, so one cannot
		417	even remove them from the set) than registered in the set (especially
		418	on SMP systems). Libev tries to counter these spurious notifications by
		419	employing an additional generation counter and comparing that against the
		420	events to filter out spurious ones, recreating the set when required.
382		421
383	While stopping, setting and starting an I/O watcher in the same iteration	422	While stopping, setting and starting an I/O watcher in the same iteration
384	will result in some caching, there is still a system call per such incident	423	will result in some caching, there is still a system call per such
385	(because the fd could point to a different file description now), so its	424	incident (because the same I<file descriptor> could point to a different
386	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	425	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
387	very well if you register events for both fds.	426	file descriptors might not work very well if you register events for both
388		427	file descriptors.
389	Please note that epoll sometimes generates spurious notifications, so you
390	need to use non-blocking I/O or other means to avoid blocking when no data
391	(or space) is available.
392		428
393	Best performance from this backend is achieved by not unregistering all	429	Best performance from this backend is achieved by not unregistering all
394	watchers for a file descriptor until it has been closed, if possible, i.e.	430	watchers for a file descriptor until it has been closed, if possible,
395	keep at least one watcher active per fd at all times.	431	i.e. keep at least one watcher active per fd at all times. Stopping and
		432	starting a watcher (without re-setting it) also usually doesn't cause
		433	extra overhead. A fork can both result in spurious notifications as well
		434	as in libev having to destroy and recreate the epoll object, which can
		435	take considerable time and thus should be avoided.
		436
		437	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		438	faster than epoll for maybe up to a hundred file descriptors, depending on
		439	the usage. So sad.
396		440
397	While nominally embeddable in other event loops, this feature is broken in	441	While nominally embeddable in other event loops, this feature is broken in
398	all kernel versions tested so far.	442	all kernel versions tested so far.
		443
		444	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		445	C<EVBACKEND_POLL>.
399		446
400	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	447	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
401		448
402	Kqueue deserves special mention, as at the time of this writing, it	449	Kqueue deserves special mention, as at the time of this writing, it
403	was broken on all BSDs except NetBSD (usually it doesn't work reliably	450	was broken on all BSDs except NetBSD (usually it doesn't work reliably
404	with anything but sockets and pipes, except on Darwin, where of course	451	with anything but sockets and pipes, except on Darwin, where of course
405	it's completely useless). For this reason it's not being "auto-detected"	452	it's completely useless). Unlike epoll, however, whose brokenness
		453	is by design, these kqueue bugs can (and eventually will) be fixed
		454	without API changes to existing programs. For this reason it's not being
406	unless you explicitly specify it explicitly in the flags (i.e. using	455	"auto-detected" unless you explicitly specify it in the flags (i.e. using
407	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	456	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
408	system like NetBSD.	457	system like NetBSD.
409		458
410	You still can embed kqueue into a normal poll or select backend and use it	459	You still can embed kqueue into a normal poll or select backend and use it
411	only for sockets (after having made sure that sockets work with kqueue on	460	only for sockets (after having made sure that sockets work with kqueue on
…		…
413		462
414	It scales in the same way as the epoll backend, but the interface to the	463	It scales in the same way as the epoll backend, but the interface to the
415	kernel is more efficient (which says nothing about its actual speed, of	464	kernel is more efficient (which says nothing about its actual speed, of
416	course). While stopping, setting and starting an I/O watcher does never	465	course). While stopping, setting and starting an I/O watcher does never
417	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	466	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
418	two event changes per incident, support for C<fork ()> is very bad and it	467	two event changes per incident. Support for C<fork ()> is very bad (but
419	drops fds silently in similarly hard-to-detect cases.	468	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		469	cases
420		470
421	This backend usually performs well under most conditions.	471	This backend usually performs well under most conditions.
422		472
423	While nominally embeddable in other event loops, this doesn't work	473	While nominally embeddable in other event loops, this doesn't work
424	everywhere, so you might need to test for this. And since it is broken	474	everywhere, so you might need to test for this. And since it is broken
425	almost everywhere, you should only use it when you have a lot of sockets	475	almost everywhere, you should only use it when you have a lot of sockets
426	(for which it usually works), by embedding it into another event loop	476	(for which it usually works), by embedding it into another event loop
427	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	477	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
428	sockets.	478	also broken on OS X)) and, did I mention it, using it only for sockets.
		479
		480	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		481	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		482	C<NOTE_EOF>.
429		483
430	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	484	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
431		485
432	This is not implemented yet (and might never be, unless you send me an	486	This is not implemented yet (and might never be, unless you send me an
433	implementation). According to reports, C</dev/poll> only supports sockets	487	implementation). According to reports, C</dev/poll> only supports sockets
…		…
446	While this backend scales well, it requires one system call per active	500	While this backend scales well, it requires one system call per active
447	file descriptor per loop iteration. For small and medium numbers of file	501	file descriptor per loop iteration. For small and medium numbers of file
448	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	502	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
449	might perform better.	503	might perform better.
450		504
451	On the positive side, ignoring the spurious readiness notifications, this	505	On the positive side, with the exception of the spurious readiness
452	backend actually performed to specification in all tests and is fully	506	notifications, this backend actually performed fully to specification
453	embeddable, which is a rare feat among the OS-specific backends.	507	in all tests and is fully embeddable, which is a rare feat among the
		508	OS-specific backends (I vastly prefer correctness over speed hacks).
		509
		510	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		511	C<EVBACKEND_POLL>.
454		512
455	=item C<EVBACKEND_ALL>	513	=item C<EVBACKEND_ALL>
456		514
457	Try all backends (even potentially broken ones that wouldn't be tried	515	Try all backends (even potentially broken ones that wouldn't be tried
458	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	516	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
464		522
465	If one or more of these are or'ed into the flags value, then only these	523	If one or more of these are or'ed into the flags value, then only these
466	backends will be tried (in the reverse order as listed here). If none are	524	backends will be tried (in the reverse order as listed here). If none are
467	specified, all backends in C<ev_recommended_backends ()> will be tried.	525	specified, all backends in C<ev_recommended_backends ()> will be tried.
468		526
469	The most typical usage is like this:	527	Example: This is the most typical usage.
470		528
471	if (!ev_default_loop (0))	529	if (!ev_default_loop (0))
472	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	530	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
473		531
474	Restrict libev to the select and poll backends, and do not allow	532	Example: Restrict libev to the select and poll backends, and do not allow
475	environment settings to be taken into account:	533	environment settings to be taken into account:
476		534
477	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	535	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
478		536
479	Use whatever libev has to offer, but make sure that kqueue is used if	537	Example: Use whatever libev has to offer, but make sure that kqueue is
480	available (warning, breaks stuff, best use only with your own private	538	used if available (warning, breaks stuff, best use only with your own
481	event loop and only if you know the OS supports your types of fds):	539	private event loop and only if you know the OS supports your types of
		540	fds):
482		541
483	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	542	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
484		543
485	=item struct ev_loop *ev_loop_new (unsigned int flags)	544	=item struct ev_loop *ev_loop_new (unsigned int flags)
486		545
…		…
507	responsibility to either stop all watchers cleanly yourself I<before>	566	responsibility to either stop all watchers cleanly yourself I<before>
508	calling this function, or cope with the fact afterwards (which is usually	567	calling this function, or cope with the fact afterwards (which is usually
509	the easiest thing, you can just ignore the watchers and/or C<free ()> them	568	the easiest thing, you can just ignore the watchers and/or C<free ()> them
510	for example).	569	for example).
511		570
512	Note that certain global state, such as signal state, will not be freed by	571	Note that certain global state, such as signal state (and installed signal
513	this function, and related watchers (such as signal and child watchers)	572	handlers), will not be freed by this function, and related watchers (such
514	would need to be stopped manually.	573	as signal and child watchers) would need to be stopped manually.
515		574
516	In general it is not advisable to call this function except in the	575	In general it is not advisable to call this function except in the
517	rare occasion where you really need to free e.g. the signal handling	576	rare occasion where you really need to free e.g. the signal handling
518	pipe fds. If you need dynamically allocated loops it is better to use	577	pipe fds. If you need dynamically allocated loops it is better to use
519	C<ev_loop_new> and C<ev_loop_destroy>).	578	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
544		603
545	=item ev_loop_fork (loop)	604	=item ev_loop_fork (loop)
546		605
547	Like C<ev_default_fork>, but acts on an event loop created by	606	Like C<ev_default_fork>, but acts on an event loop created by
548	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	607	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
549	after fork, and how you do this is entirely your own problem.	608	after fork that you want to re-use in the child, and how you do this is
		609	entirely your own problem.
550		610
551	=item int ev_is_default_loop (loop)	611	=item int ev_is_default_loop (loop)
552		612
553	Returns true when the given loop actually is the default loop, false otherwise.	613	Returns true when the given loop is, in fact, the default loop, and false
		614	otherwise.
554		615
555	=item unsigned int ev_loop_count (loop)	616	=item unsigned int ev_loop_count (loop)
556		617
557	Returns the count of loop iterations for the loop, which is identical to	618	Returns the count of loop iterations for the loop, which is identical to
558	the number of times libev did poll for new events. It starts at C<0> and	619	the number of times libev did poll for new events. It starts at C<0> and
559	happily wraps around with enough iterations.	620	happily wraps around with enough iterations.
560		621
561	This value can sometimes be useful as a generation counter of sorts (it	622	This value can sometimes be useful as a generation counter of sorts (it
562	"ticks" the number of loop iterations), as it roughly corresponds with	623	"ticks" the number of loop iterations), as it roughly corresponds with
563	C<ev_prepare> and C<ev_check> calls.	624	C<ev_prepare> and C<ev_check> calls.
		625
		626	=item unsigned int ev_loop_depth (loop)
		627
		628	Returns the number of times C<ev_loop> was entered minus the number of
		629	times C<ev_loop> was exited, in other words, the recursion depth.
		630
		631	Outside C<ev_loop>, this number is zero. In a callback, this number is
		632	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),
		633	in which case it is higher.
		634
		635	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread
		636	etc.), doesn't count as exit.
564		637
565	=item unsigned int ev_backend (loop)	638	=item unsigned int ev_backend (loop)
566		639
567	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	640	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
568	use.	641	use.
…		…
573	received events and started processing them. This timestamp does not	646	received events and started processing them. This timestamp does not
574	change as long as callbacks are being processed, and this is also the base	647	change as long as callbacks are being processed, and this is also the base
575	time used for relative timers. You can treat it as the timestamp of the	648	time used for relative timers. You can treat it as the timestamp of the
576	event occurring (or more correctly, libev finding out about it).	649	event occurring (or more correctly, libev finding out about it).
577		650
		651	=item ev_now_update (loop)
		652
		653	Establishes the current time by querying the kernel, updating the time
		654	returned by C<ev_now ()> in the progress. This is a costly operation and
		655	is usually done automatically within C<ev_loop ()>.
		656
		657	This function is rarely useful, but when some event callback runs for a
		658	very long time without entering the event loop, updating libev's idea of
		659	the current time is a good idea.
		660
		661	See also L<The special problem of time updates> in the C<ev_timer> section.
		662
		663	=item ev_suspend (loop)
		664
		665	=item ev_resume (loop)
		666
		667	These two functions suspend and resume a loop, for use when the loop is
		668	not used for a while and timeouts should not be processed.
		669
		670	A typical use case would be an interactive program such as a game: When
		671	the user presses C<^Z> to suspend the game and resumes it an hour later it
		672	would be best to handle timeouts as if no time had actually passed while
		673	the program was suspended. This can be achieved by calling C<ev_suspend>
		674	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		675	C<ev_resume> directly afterwards to resume timer processing.
		676
		677	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		678	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		679	will be rescheduled (that is, they will lose any events that would have
		680	occured while suspended).
		681
		682	After calling C<ev_suspend> you B<must not> call I<any> function on the
		683	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		684	without a previous call to C<ev_suspend>.
		685
		686	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		687	event loop time (see C<ev_now_update>).
		688
578	=item ev_loop (loop, int flags)	689	=item ev_loop (loop, int flags)
579		690
580	Finally, this is it, the event handler. This function usually is called	691	Finally, this is it, the event handler. This function usually is called
581	after you initialised all your watchers and you want to start handling	692	after you initialised all your watchers and you want to start handling
582	events.	693	events.
…		…
584	If the flags argument is specified as C<0>, it will not return until	695	If the flags argument is specified as C<0>, it will not return until
585	either no event watchers are active anymore or C<ev_unloop> was called.	696	either no event watchers are active anymore or C<ev_unloop> was called.
586		697
587	Please note that an explicit C<ev_unloop> is usually better than	698	Please note that an explicit C<ev_unloop> is usually better than
588	relying on all watchers to be stopped when deciding when a program has	699	relying on all watchers to be stopped when deciding when a program has
589	finished (especially in interactive programs), but having a program that	700	finished (especially in interactive programs), but having a program
590	automatically loops as long as it has to and no longer by virtue of	701	that automatically loops as long as it has to and no longer by virtue
591	relying on its watchers stopping correctly is a thing of beauty.	702	of relying on its watchers stopping correctly, that is truly a thing of
		703	beauty.
592		704
593	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	705	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
594	those events and any outstanding ones, but will not block your process in	706	those events and any already outstanding ones, but will not block your
595	case there are no events and will return after one iteration of the loop.	707	process in case there are no events and will return after one iteration of
		708	the loop.
596		709
597	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	710	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
598	necessary) and will handle those and any outstanding ones. It will block	711	necessary) and will handle those and any already outstanding ones. It
599	your process until at least one new event arrives, and will return after	712	will block your process until at least one new event arrives (which could
600	one iteration of the loop. This is useful if you are waiting for some	713	be an event internal to libev itself, so there is no guarantee that a
601	external event in conjunction with something not expressible using other	714	user-registered callback will be called), and will return after one
		715	iteration of the loop.
		716
		717	This is useful if you are waiting for some external event in conjunction
		718	with something not expressible using other libev watchers (i.e. "roll your
602	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	719	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
603	usually a better approach for this kind of thing.	720	usually a better approach for this kind of thing.
604		721
605	Here are the gory details of what C<ev_loop> does:	722	Here are the gory details of what C<ev_loop> does:
606		723
607	- Before the first iteration, call any pending watchers.	724	- Before the first iteration, call any pending watchers.
…		…
617	any active watchers at all will result in not sleeping).	734	any active watchers at all will result in not sleeping).
618	- Sleep if the I/O and timer collect interval say so.	735	- Sleep if the I/O and timer collect interval say so.
619	- Block the process, waiting for any events.	736	- Block the process, waiting for any events.
620	- Queue all outstanding I/O (fd) events.	737	- Queue all outstanding I/O (fd) events.
621	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	738	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
622	- Queue all outstanding timers.	739	- Queue all expired timers.
623	- Queue all outstanding periodics.	740	- Queue all expired periodics.
624	- Unless any events are pending now, queue all idle watchers.	741	- Unless any events are pending now, queue all idle watchers.
625	- Queue all check watchers.	742	- Queue all check watchers.
626	- Call all queued watchers in reverse order (i.e. check watchers first).	743	- Call all queued watchers in reverse order (i.e. check watchers first).
627	Signals and child watchers are implemented as I/O watchers, and will	744	Signals and child watchers are implemented as I/O watchers, and will
628	be handled here by queueing them when their watcher gets executed.	745	be handled here by queueing them when their watcher gets executed.
…		…
645	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	762	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
646	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	763	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
647		764
648	This "unloop state" will be cleared when entering C<ev_loop> again.	765	This "unloop state" will be cleared when entering C<ev_loop> again.
649		766
		767	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		768
650	=item ev_ref (loop)	769	=item ev_ref (loop)
651		770
652	=item ev_unref (loop)	771	=item ev_unref (loop)
653		772
654	Ref/unref can be used to add or remove a reference count on the event	773	Ref/unref can be used to add or remove a reference count on the event
655	loop: Every watcher keeps one reference, and as long as the reference	774	loop: Every watcher keeps one reference, and as long as the reference
656	count is nonzero, C<ev_loop> will not return on its own. If you have	775	count is nonzero, C<ev_loop> will not return on its own.
		776
657	a watcher you never unregister that should not keep C<ev_loop> from	777	If you have a watcher you never unregister that should not keep C<ev_loop>
658	returning, ev_unref() after starting, and ev_ref() before stopping it. For	778	from returning, call ev_unref() after starting, and ev_ref() before
		779	stopping it.
		780
659	example, libev itself uses this for its internal signal pipe: It is not	781	As an example, libev itself uses this for its internal signal pipe: It
660	visible to the libev user and should not keep C<ev_loop> from exiting if	782	is not visible to the libev user and should not keep C<ev_loop> from
661	no event watchers registered by it are active. It is also an excellent	783	exiting if no event watchers registered by it are active. It is also an
662	way to do this for generic recurring timers or from within third-party	784	excellent way to do this for generic recurring timers or from within
663	libraries. Just remember to I<unref after start> and I<ref before stop>	785	third-party libraries. Just remember to I<unref after start> and I<ref
664	(but only if the watcher wasn't active before, or was active before,	786	before stop> (but only if the watcher wasn't active before, or was active
665	respectively).	787	before, respectively. Note also that libev might stop watchers itself
		788	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		789	in the callback).
666		790
667	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	791	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
668	running when nothing else is active.	792	running when nothing else is active.
669		793
670	struct ev_signal exitsig;	794	ev_signal exitsig;
671	ev_signal_init (&exitsig, sig_cb, SIGINT);	795	ev_signal_init (&exitsig, sig_cb, SIGINT);
672	ev_signal_start (loop, &exitsig);	796	ev_signal_start (loop, &exitsig);
673	evf_unref (loop);	797	evf_unref (loop);
674		798
675	Example: For some weird reason, unregister the above signal handler again.	799	Example: For some weird reason, unregister the above signal handler again.
…		…
689	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	813	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
690	allows libev to delay invocation of I/O and timer/periodic callbacks	814	allows libev to delay invocation of I/O and timer/periodic callbacks
691	to increase efficiency of loop iterations (or to increase power-saving	815	to increase efficiency of loop iterations (or to increase power-saving
692	opportunities).	816	opportunities).
693		817
694	The background is that sometimes your program runs just fast enough to	818	The idea is that sometimes your program runs just fast enough to handle
695	handle one (or very few) event(s) per loop iteration. While this makes	819	one (or very few) event(s) per loop iteration. While this makes the
696	the program responsive, it also wastes a lot of CPU time to poll for new	820	program responsive, it also wastes a lot of CPU time to poll for new
697	events, especially with backends like C<select ()> which have a high	821	events, especially with backends like C<select ()> which have a high
698	overhead for the actual polling but can deliver many events at once.	822	overhead for the actual polling but can deliver many events at once.
699		823
700	By setting a higher I<io collect interval> you allow libev to spend more	824	By setting a higher I<io collect interval> you allow libev to spend more
701	time collecting I/O events, so you can handle more events per iteration,	825	time collecting I/O events, so you can handle more events per iteration,
702	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	826	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
703	C<ev_timer>) will be not affected. Setting this to a non-null value will	827	C<ev_timer>) will be not affected. Setting this to a non-null value will
704	introduce an additional C<ev_sleep ()> call into most loop iterations.	828	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		829	sleep time ensures that libev will not poll for I/O events more often then
		830	once per this interval, on average.
705		831
706	Likewise, by setting a higher I<timeout collect interval> you allow libev	832	Likewise, by setting a higher I<timeout collect interval> you allow libev
707	to spend more time collecting timeouts, at the expense of increased	833	to spend more time collecting timeouts, at the expense of increased
708	latency (the watcher callback will be called later). C<ev_io> watchers	834	latency/jitter/inexactness (the watcher callback will be called
709	will not be affected. Setting this to a non-null value will not introduce	835	later). C<ev_io> watchers will not be affected. Setting this to a non-null
710	any overhead in libev.	836	value will not introduce any overhead in libev.
711		837
712	Many (busy) programs can usually benefit by setting the I/O collect	838	Many (busy) programs can usually benefit by setting the I/O collect
713	interval to a value near C<0.1> or so, which is often enough for	839	interval to a value near C<0.1> or so, which is often enough for
714	interactive servers (of course not for games), likewise for timeouts. It	840	interactive servers (of course not for games), likewise for timeouts. It
715	usually doesn't make much sense to set it to a lower value than C<0.01>,	841	usually doesn't make much sense to set it to a lower value than C<0.01>,
716	as this approaches the timing granularity of most systems.	842	as this approaches the timing granularity of most systems. Note that if
		843	you do transactions with the outside world and you can't increase the
		844	parallelity, then this setting will limit your transaction rate (if you
		845	need to poll once per transaction and the I/O collect interval is 0.01,
		846	then you can't do more than 100 transations per second).
717		847
718	Setting the I<timeout collect interval> can improve the opportunity for	848	Setting the I<timeout collect interval> can improve the opportunity for
719	saving power, as the program will "bundle" timer callback invocations that	849	saving power, as the program will "bundle" timer callback invocations that
720	are "near" in time together, by delaying some, thus reducing the number of	850	are "near" in time together, by delaying some, thus reducing the number of
721	times the process sleeps and wakes up again. Another useful technique to	851	times the process sleeps and wakes up again. Another useful technique to
722	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	852	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
723	they fire on, say, one-second boundaries only.	853	they fire on, say, one-second boundaries only.
724		854
		855	Example: we only need 0.1s timeout granularity, and we wish not to poll
		856	more often than 100 times per second:
		857
		858	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		859	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		860
		861	=item ev_invoke_pending (loop)
		862
		863	This call will simply invoke all pending watchers while resetting their
		864	pending state. Normally, C<ev_loop> does this automatically when required,
		865	but when overriding the invoke callback this call comes handy.
		866
		867	=item int ev_pending_count (loop)
		868
		869	Returns the number of pending watchers - zero indicates that no watchers
		870	are pending.
		871
		872	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		873
		874	This overrides the invoke pending functionality of the loop: Instead of
		875	invoking all pending watchers when there are any, C<ev_loop> will call
		876	this callback instead. This is useful, for example, when you want to
		877	invoke the actual watchers inside another context (another thread etc.).
		878
		879	If you want to reset the callback, use C<ev_invoke_pending> as new
		880	callback.
		881
		882	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		883
		884	Sometimes you want to share the same loop between multiple threads. This
		885	can be done relatively simply by putting mutex_lock/unlock calls around
		886	each call to a libev function.
		887
		888	However, C<ev_loop> can run an indefinite time, so it is not feasible to
		889	wait for it to return. One way around this is to wake up the loop via
		890	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>
		891	and I<acquire> callbacks on the loop.
		892
		893	When set, then C<release> will be called just before the thread is
		894	suspended waiting for new events, and C<acquire> is called just
		895	afterwards.
		896
		897	Ideally, C<release> will just call your mutex_unlock function, and
		898	C<acquire> will just call the mutex_lock function again.
		899
		900	While event loop modifications are allowed between invocations of
		901	C<release> and C<acquire> (that's their only purpose after all), no
		902	modifications done will affect the event loop, i.e. adding watchers will
		903	have no effect on the set of file descriptors being watched, or the time
		904	waited. USe an C<ev_async> watcher to wake up C<ev_loop> when you want it
		905	to take note of any changes you made.
		906
		907	In theory, threads executing C<ev_loop> will be async-cancel safe between
		908	invocations of C<release> and C<acquire>.
		909
		910	See also the locking example in the C<THREADS> section later in this
		911	document.
		912
		913	=item ev_set_userdata (loop, void *data)
		914
		915	=item ev_userdata (loop)
		916
		917	Set and retrieve a single C<void *> associated with a loop. When
		918	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		919	C<0.>
		920
		921	These two functions can be used to associate arbitrary data with a loop,
		922	and are intended solely for the C<invoke_pending_cb>, C<release> and
		923	C<acquire> callbacks described above, but of course can be (ab-)used for
		924	any other purpose as well.
		925
725	=item ev_loop_verify (loop)	926	=item ev_loop_verify (loop)
726		927
727	This function only does something when C<EV_VERIFY> support has been	928	This function only does something when C<EV_VERIFY> support has been
728	compiled in. It tries to go through all internal structures and checks	929	compiled in, which is the default for non-minimal builds. It tries to go
729	them for validity. If anything is found to be inconsistent, it will print	930	through all internal structures and checks them for validity. If anything
730	an error message to standard error and call C<abort ()>.	931	is found to be inconsistent, it will print an error message to standard
		932	error and call C<abort ()>.
731		933
732	This can be used to catch bugs inside libev itself: under normal	934	This can be used to catch bugs inside libev itself: under normal
733	circumstances, this function will never abort as of course libev keeps its	935	circumstances, this function will never abort as of course libev keeps its
734	data structures consistent.	936	data structures consistent.
735		937
736	=back	938	=back
737		939
738		940
739	=head1 ANATOMY OF A WATCHER	941	=head1 ANATOMY OF A WATCHER
740		942
		943	In the following description, uppercase C<TYPE> in names stands for the
		944	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		945	watchers and C<ev_io_start> for I/O watchers.
		946
741	A watcher is a structure that you create and register to record your	947	A watcher is a structure that you create and register to record your
742	interest in some event. For instance, if you want to wait for STDIN to	948	interest in some event. For instance, if you want to wait for STDIN to
743	become readable, you would create an C<ev_io> watcher for that:	949	become readable, you would create an C<ev_io> watcher for that:
744		950
745	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	951	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
746	{	952	{
747	ev_io_stop (w);	953	ev_io_stop (w);
748	ev_unloop (loop, EVUNLOOP_ALL);	954	ev_unloop (loop, EVUNLOOP_ALL);
749	}	955	}
750		956
751	struct ev_loop *loop = ev_default_loop (0);	957	struct ev_loop *loop = ev_default_loop (0);
		958
752	struct ev_io stdin_watcher;	959	ev_io stdin_watcher;
		960
753	ev_init (&stdin_watcher, my_cb);	961	ev_init (&stdin_watcher, my_cb);
754	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	962	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
755	ev_io_start (loop, &stdin_watcher);	963	ev_io_start (loop, &stdin_watcher);
		964
756	ev_loop (loop, 0);	965	ev_loop (loop, 0);
757		966
758	As you can see, you are responsible for allocating the memory for your	967	As you can see, you are responsible for allocating the memory for your
759	watcher structures (and it is usually a bad idea to do this on the stack,	968	watcher structures (and it is I<usually> a bad idea to do this on the
760	although this can sometimes be quite valid).	969	stack).
		970
		971	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		972	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
761		973
762	Each watcher structure must be initialised by a call to C<ev_init	974	Each watcher structure must be initialised by a call to C<ev_init
763	(watcher *, callback)>, which expects a callback to be provided. This	975	(watcher *, callback)>, which expects a callback to be provided. This
764	callback gets invoked each time the event occurs (or, in the case of I/O	976	callback gets invoked each time the event occurs (or, in the case of I/O
765	watchers, each time the event loop detects that the file descriptor given	977	watchers, each time the event loop detects that the file descriptor given
766	is readable and/or writable).	978	is readable and/or writable).
767		979
768	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	980	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
769	with arguments specific to this watcher type. There is also a macro	981	macro to configure it, with arguments specific to the watcher type. There
770	to combine initialisation and setting in one call: C<< ev_<type>_init	982	is also a macro to combine initialisation and setting in one call: C<<
771	(watcher *, callback, ...) >>.	983	ev_TYPE_init (watcher *, callback, ...) >>.
772		984
773	To make the watcher actually watch out for events, you have to start it	985	To make the watcher actually watch out for events, you have to start it
774	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	986	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
775	*) >>), and you can stop watching for events at any time by calling the	987	*) >>), and you can stop watching for events at any time by calling the
776	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	988	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
777		989
778	As long as your watcher is active (has been started but not stopped) you	990	As long as your watcher is active (has been started but not stopped) you
779	must not touch the values stored in it. Most specifically you must never	991	must not touch the values stored in it. Most specifically you must never
780	reinitialise it or call its C<set> macro.	992	reinitialise it or call its C<ev_TYPE_set> macro.
781		993
782	Each and every callback receives the event loop pointer as first, the	994	Each and every callback receives the event loop pointer as first, the
783	registered watcher structure as second, and a bitset of received events as	995	registered watcher structure as second, and a bitset of received events as
784	third argument.	996	third argument.
785		997
…		…
843		1055
844	=item C<EV_ASYNC>	1056	=item C<EV_ASYNC>
845		1057
846	The given async watcher has been asynchronously notified (see C<ev_async>).	1058	The given async watcher has been asynchronously notified (see C<ev_async>).
847		1059
		1060	=item C<EV_CUSTOM>
		1061
		1062	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1063	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		1064
848	=item C<EV_ERROR>	1065	=item C<EV_ERROR>
849		1066
850	An unspecified error has occurred, the watcher has been stopped. This might	1067	An unspecified error has occurred, the watcher has been stopped. This might
851	happen because the watcher could not be properly started because libev	1068	happen because the watcher could not be properly started because libev
852	ran out of memory, a file descriptor was found to be closed or any other	1069	ran out of memory, a file descriptor was found to be closed or any other
		1070	problem. Libev considers these application bugs.
		1071
853	problem. You best act on it by reporting the problem and somehow coping	1072	You best act on it by reporting the problem and somehow coping with the
854	with the watcher being stopped.	1073	watcher being stopped. Note that well-written programs should not receive
		1074	an error ever, so when your watcher receives it, this usually indicates a
		1075	bug in your program.
855		1076
856	Libev will usually signal a few "dummy" events together with an error,	1077	Libev will usually signal a few "dummy" events together with an error, for
857	for example it might indicate that a fd is readable or writable, and if	1078	example it might indicate that a fd is readable or writable, and if your
858	your callbacks is well-written it can just attempt the operation and cope	1079	callbacks is well-written it can just attempt the operation and cope with
859	with the error from read() or write(). This will not work in multi-threaded	1080	the error from read() or write(). This will not work in multi-threaded
860	programs, though, so beware.	1081	programs, though, as the fd could already be closed and reused for another
		1082	thing, so beware.
861		1083
862	=back	1084	=back
863		1085
864	=head2 GENERIC WATCHER FUNCTIONS	1086	=head2 GENERIC WATCHER FUNCTIONS
865
866	In the following description, C<TYPE> stands for the watcher type,
867	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
868		1087
869	=over 4	1088	=over 4
870		1089
871	=item C<ev_init> (ev_TYPE *watcher, callback)	1090	=item C<ev_init> (ev_TYPE *watcher, callback)
872		1091
…		…
878	which rolls both calls into one.	1097	which rolls both calls into one.
879		1098
880	You can reinitialise a watcher at any time as long as it has been stopped	1099	You can reinitialise a watcher at any time as long as it has been stopped
881	(or never started) and there are no pending events outstanding.	1100	(or never started) and there are no pending events outstanding.
882		1101
883	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1102	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
884	int revents)>.	1103	int revents)>.
		1104
		1105	Example: Initialise an C<ev_io> watcher in two steps.
		1106
		1107	ev_io w;
		1108	ev_init (&w, my_cb);
		1109	ev_io_set (&w, STDIN_FILENO, EV_READ);
885		1110
886	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1111	=item C<ev_TYPE_set> (ev_TYPE *, [args])
887		1112
888	This macro initialises the type-specific parts of a watcher. You need to	1113	This macro initialises the type-specific parts of a watcher. You need to
889	call C<ev_init> at least once before you call this macro, but you can	1114	call C<ev_init> at least once before you call this macro, but you can
…		…
892	difference to the C<ev_init> macro).	1117	difference to the C<ev_init> macro).
893		1118
894	Although some watcher types do not have type-specific arguments	1119	Although some watcher types do not have type-specific arguments
895	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	1120	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
896		1121
		1122	See C<ev_init>, above, for an example.
		1123
897	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1124	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
898		1125
899	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1126	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
900	calls into a single call. This is the most convenient method to initialise	1127	calls into a single call. This is the most convenient method to initialise
901	a watcher. The same limitations apply, of course.	1128	a watcher. The same limitations apply, of course.
902		1129
		1130	Example: Initialise and set an C<ev_io> watcher in one step.
		1131
		1132	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1133
903	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1134	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
904		1135
905	Starts (activates) the given watcher. Only active watchers will receive	1136	Starts (activates) the given watcher. Only active watchers will receive
906	events. If the watcher is already active nothing will happen.	1137	events. If the watcher is already active nothing will happen.
907		1138
		1139	Example: Start the C<ev_io> watcher that is being abused as example in this
		1140	whole section.
		1141
		1142	ev_io_start (EV_DEFAULT_UC, &w);
		1143
908	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1144	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
909		1145
910	Stops the given watcher again (if active) and clears the pending	1146	Stops the given watcher if active, and clears the pending status (whether
		1147	the watcher was active or not).
		1148
911	status. It is possible that stopped watchers are pending (for example,	1149	It is possible that stopped watchers are pending - for example,
912	non-repeating timers are being stopped when they become pending), but	1150	non-repeating timers are being stopped when they become pending - but
913	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1151	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
914	you want to free or reuse the memory used by the watcher it is therefore a	1152	pending. If you want to free or reuse the memory used by the watcher it is
915	good idea to always call its C<ev_TYPE_stop> function.	1153	therefore a good idea to always call its C<ev_TYPE_stop> function.
916		1154
917	=item bool ev_is_active (ev_TYPE *watcher)	1155	=item bool ev_is_active (ev_TYPE *watcher)
918		1156
919	Returns a true value iff the watcher is active (i.e. it has been started	1157	Returns a true value iff the watcher is active (i.e. it has been started
920	and not yet been stopped). As long as a watcher is active you must not modify	1158	and not yet been stopped). As long as a watcher is active you must not modify
…		…
946	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1184	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
947	(default: C<-2>). Pending watchers with higher priority will be invoked	1185	(default: C<-2>). Pending watchers with higher priority will be invoked
948	before watchers with lower priority, but priority will not keep watchers	1186	before watchers with lower priority, but priority will not keep watchers
949	from being executed (except for C<ev_idle> watchers).	1187	from being executed (except for C<ev_idle> watchers).
950		1188
951	This means that priorities are I<only> used for ordering callback
952	invocation after new events have been received. This is useful, for
953	example, to reduce latency after idling, or more often, to bind two
954	watchers on the same event and make sure one is called first.
955
956	If you need to suppress invocation when higher priority events are pending	1189	If you need to suppress invocation when higher priority events are pending
957	you need to look at C<ev_idle> watchers, which provide this functionality.	1190	you need to look at C<ev_idle> watchers, which provide this functionality.
958		1191
959	You I<must not> change the priority of a watcher as long as it is active or	1192	You I<must not> change the priority of a watcher as long as it is active or
960	pending.	1193	pending.
961		1194
		1195	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1196	fine, as long as you do not mind that the priority value you query might
		1197	or might not have been clamped to the valid range.
		1198
962	The default priority used by watchers when no priority has been set is	1199	The default priority used by watchers when no priority has been set is
963	always C<0>, which is supposed to not be too high and not be too low :).	1200	always C<0>, which is supposed to not be too high and not be too low :).
964		1201
965	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1202	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
966	fine, as long as you do not mind that the priority value you query might	1203	priorities.
967	or might not have been adjusted to be within valid range.
968		1204
969	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1205	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
970		1206
971	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1207	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
972	C<loop> nor C<revents> need to be valid as long as the watcher callback	1208	C<loop> nor C<revents> need to be valid as long as the watcher callback
973	can deal with that fact.	1209	can deal with that fact, as both are simply passed through to the
		1210	callback.
974		1211
975	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1212	=item int ev_clear_pending (loop, ev_TYPE *watcher)
976		1213
977	If the watcher is pending, this function returns clears its pending status	1214	If the watcher is pending, this function clears its pending status and
978	and returns its C<revents> bitset (as if its callback was invoked). If the	1215	returns its C<revents> bitset (as if its callback was invoked). If the
979	watcher isn't pending it does nothing and returns C<0>.	1216	watcher isn't pending it does nothing and returns C<0>.
980		1217
		1218	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1219	callback to be invoked, which can be accomplished with this function.
		1220
981	=back	1221	=back
982		1222
983		1223
984	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1224	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
985		1225
986	Each watcher has, by default, a member C<void *data> that you can change	1226	Each watcher has, by default, a member C<void *data> that you can change
987	and read at any time, libev will completely ignore it. This can be used	1227	and read at any time: libev will completely ignore it. This can be used
988	to associate arbitrary data with your watcher. If you need more data and	1228	to associate arbitrary data with your watcher. If you need more data and
989	don't want to allocate memory and store a pointer to it in that data	1229	don't want to allocate memory and store a pointer to it in that data
990	member, you can also "subclass" the watcher type and provide your own	1230	member, you can also "subclass" the watcher type and provide your own
991	data:	1231	data:
992		1232
993	struct my_io	1233	struct my_io
994	{	1234	{
995	struct ev_io io;	1235	ev_io io;
996	int otherfd;	1236	int otherfd;
997	void *somedata;	1237	void *somedata;
998	struct whatever *mostinteresting;	1238	struct whatever *mostinteresting;
999	}	1239	};
		1240
		1241	...
		1242	struct my_io w;
		1243	ev_io_init (&w.io, my_cb, fd, EV_READ);
1000		1244
1001	And since your callback will be called with a pointer to the watcher, you	1245	And since your callback will be called with a pointer to the watcher, you
1002	can cast it back to your own type:	1246	can cast it back to your own type:
1003		1247
1004	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1248	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1005	{	1249	{
1006	struct my_io *w = (struct my_io *)w_;	1250	struct my_io *w = (struct my_io *)w_;
1007	...	1251	...
1008	}	1252	}
1009		1253
1010	More interesting and less C-conformant ways of casting your callback type	1254	More interesting and less C-conformant ways of casting your callback type
1011	instead have been omitted.	1255	instead have been omitted.
1012		1256
1013	Another common scenario is having some data structure with multiple	1257	Another common scenario is to use some data structure with multiple
1014	watchers:	1258	embedded watchers:
1015		1259
1016	struct my_biggy	1260	struct my_biggy
1017	{	1261	{
1018	int some_data;	1262	int some_data;
1019	ev_timer t1;	1263	ev_timer t1;
1020	ev_timer t2;	1264	ev_timer t2;
1021	}	1265	}
1022		1266
1023	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1267	In this case getting the pointer to C<my_biggy> is a bit more
1024	you need to use C<offsetof>:	1268	complicated: Either you store the address of your C<my_biggy> struct
		1269	in the C<data> member of the watcher (for woozies), or you need to use
		1270	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1271	programmers):
1025		1272
1026	#include <stddef.h>	1273	#include <stddef.h>
1027		1274
1028	static void	1275	static void
1029	t1_cb (EV_P_ struct ev_timer *w, int revents)	1276	t1_cb (EV_P_ ev_timer *w, int revents)
1030	{	1277	{
1031	struct my_biggy big = (struct my_biggy *	1278	struct my_biggy big = (struct my_biggy *)
1032	(((char *)w) - offsetof (struct my_biggy, t1));	1279	(((char *)w) - offsetof (struct my_biggy, t1));
1033	}	1280	}
1034		1281
1035	static void	1282	static void
1036	t2_cb (EV_P_ struct ev_timer *w, int revents)	1283	t2_cb (EV_P_ ev_timer *w, int revents)
1037	{	1284	{
1038	struct my_biggy big = (struct my_biggy *	1285	struct my_biggy big = (struct my_biggy *)
1039	(((char *)w) - offsetof (struct my_biggy, t2));	1286	(((char *)w) - offsetof (struct my_biggy, t2));
1040	}	1287	}
		1288
		1289	=head2 WATCHER PRIORITY MODELS
		1290
		1291	Many event loops support I<watcher priorities>, which are usually small
		1292	integers that influence the ordering of event callback invocation
		1293	between watchers in some way, all else being equal.
		1294
		1295	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1296	description for the more technical details such as the actual priority
		1297	range.
		1298
		1299	There are two common ways how these these priorities are being interpreted
		1300	by event loops:
		1301
		1302	In the more common lock-out model, higher priorities "lock out" invocation
		1303	of lower priority watchers, which means as long as higher priority
		1304	watchers receive events, lower priority watchers are not being invoked.
		1305
		1306	The less common only-for-ordering model uses priorities solely to order
		1307	callback invocation within a single event loop iteration: Higher priority
		1308	watchers are invoked before lower priority ones, but they all get invoked
		1309	before polling for new events.
		1310
		1311	Libev uses the second (only-for-ordering) model for all its watchers
		1312	except for idle watchers (which use the lock-out model).
		1313
		1314	The rationale behind this is that implementing the lock-out model for
		1315	watchers is not well supported by most kernel interfaces, and most event
		1316	libraries will just poll for the same events again and again as long as
		1317	their callbacks have not been executed, which is very inefficient in the
		1318	common case of one high-priority watcher locking out a mass of lower
		1319	priority ones.
		1320
		1321	Static (ordering) priorities are most useful when you have two or more
		1322	watchers handling the same resource: a typical usage example is having an
		1323	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1324	timeouts. Under load, data might be received while the program handles
		1325	other jobs, but since timers normally get invoked first, the timeout
		1326	handler will be executed before checking for data. In that case, giving
		1327	the timer a lower priority than the I/O watcher ensures that I/O will be
		1328	handled first even under adverse conditions (which is usually, but not
		1329	always, what you want).
		1330
		1331	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1332	will only be executed when no same or higher priority watchers have
		1333	received events, they can be used to implement the "lock-out" model when
		1334	required.
		1335
		1336	For example, to emulate how many other event libraries handle priorities,
		1337	you can associate an C<ev_idle> watcher to each such watcher, and in
		1338	the normal watcher callback, you just start the idle watcher. The real
		1339	processing is done in the idle watcher callback. This causes libev to
		1340	continously poll and process kernel event data for the watcher, but when
		1341	the lock-out case is known to be rare (which in turn is rare :), this is
		1342	workable.
		1343
		1344	Usually, however, the lock-out model implemented that way will perform
		1345	miserably under the type of load it was designed to handle. In that case,
		1346	it might be preferable to stop the real watcher before starting the
		1347	idle watcher, so the kernel will not have to process the event in case
		1348	the actual processing will be delayed for considerable time.
		1349
		1350	Here is an example of an I/O watcher that should run at a strictly lower
		1351	priority than the default, and which should only process data when no
		1352	other events are pending:
		1353
		1354	ev_idle idle; // actual processing watcher
		1355	ev_io io; // actual event watcher
		1356
		1357	static void
		1358	io_cb (EV_P_ ev_io *w, int revents)
		1359	{
		1360	// stop the I/O watcher, we received the event, but
		1361	// are not yet ready to handle it.
		1362	ev_io_stop (EV_A_ w);
		1363
		1364	// start the idle watcher to ahndle the actual event.
		1365	// it will not be executed as long as other watchers
		1366	// with the default priority are receiving events.
		1367	ev_idle_start (EV_A_ &idle);
		1368	}
		1369
		1370	static void
		1371	idle_cb (EV_P_ ev_idle *w, int revents)
		1372	{
		1373	// actual processing
		1374	read (STDIN_FILENO, ...);
		1375
		1376	// have to start the I/O watcher again, as
		1377	// we have handled the event
		1378	ev_io_start (EV_P_ &io);
		1379	}
		1380
		1381	// initialisation
		1382	ev_idle_init (&idle, idle_cb);
		1383	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1384	ev_io_start (EV_DEFAULT_ &io);
		1385
		1386	In the "real" world, it might also be beneficial to start a timer, so that
		1387	low-priority connections can not be locked out forever under load. This
		1388	enables your program to keep a lower latency for important connections
		1389	during short periods of high load, while not completely locking out less
		1390	important ones.
1041		1391
1042		1392
1043	=head1 WATCHER TYPES	1393	=head1 WATCHER TYPES
1044		1394
1045	This section describes each watcher in detail, but will not repeat	1395	This section describes each watcher in detail, but will not repeat
…		…
1069	In general you can register as many read and/or write event watchers per	1419	In general you can register as many read and/or write event watchers per
1070	fd as you want (as long as you don't confuse yourself). Setting all file	1420	fd as you want (as long as you don't confuse yourself). Setting all file
1071	descriptors to non-blocking mode is also usually a good idea (but not	1421	descriptors to non-blocking mode is also usually a good idea (but not
1072	required if you know what you are doing).	1422	required if you know what you are doing).
1073		1423
1074	If you must do this, then force the use of a known-to-be-good backend	1424	If you cannot use non-blocking mode, then force the use of a
1075	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1425	known-to-be-good backend (at the time of this writing, this includes only
1076	C<EVBACKEND_POLL>).	1426	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1427	descriptors for which non-blocking operation makes no sense (such as
		1428	files) - libev doesn't guarentee any specific behaviour in that case.
1077		1429
1078	Another thing you have to watch out for is that it is quite easy to	1430	Another thing you have to watch out for is that it is quite easy to
1079	receive "spurious" readiness notifications, that is your callback might	1431	receive "spurious" readiness notifications, that is your callback might
1080	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1432	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1081	because there is no data. Not only are some backends known to create a	1433	because there is no data. Not only are some backends known to create a
1082	lot of those (for example Solaris ports), it is very easy to get into	1434	lot of those (for example Solaris ports), it is very easy to get into
1083	this situation even with a relatively standard program structure. Thus	1435	this situation even with a relatively standard program structure. Thus
1084	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1436	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1085	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1437	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1086		1438
1087	If you cannot run the fd in non-blocking mode (for example you should not	1439	If you cannot run the fd in non-blocking mode (for example you should
1088	play around with an Xlib connection), then you have to separately re-test	1440	not play around with an Xlib connection), then you have to separately
1089	whether a file descriptor is really ready with a known-to-be good interface	1441	re-test whether a file descriptor is really ready with a known-to-be good
1090	such as poll (fortunately in our Xlib example, Xlib already does this on	1442	interface such as poll (fortunately in our Xlib example, Xlib already
1091	its own, so its quite safe to use).	1443	does this on its own, so its quite safe to use). Some people additionally
		1444	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1445	indefinitely.
		1446
		1447	But really, best use non-blocking mode.
1092		1448
1093	=head3 The special problem of disappearing file descriptors	1449	=head3 The special problem of disappearing file descriptors
1094		1450
1095	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1451	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1096	descriptor (either by calling C<close> explicitly or by any other means,	1452	descriptor (either due to calling C<close> explicitly or any other means,
1097	such as C<dup>). The reason is that you register interest in some file	1453	such as C<dup2>). The reason is that you register interest in some file
1098	descriptor, but when it goes away, the operating system will silently drop	1454	descriptor, but when it goes away, the operating system will silently drop
1099	this interest. If another file descriptor with the same number then is	1455	this interest. If another file descriptor with the same number then is
1100	registered with libev, there is no efficient way to see that this is, in	1456	registered with libev, there is no efficient way to see that this is, in
1101	fact, a different file descriptor.	1457	fact, a different file descriptor.
1102		1458
…		…
1133	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1489	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1134	C<EVBACKEND_POLL>.	1490	C<EVBACKEND_POLL>.
1135		1491
1136	=head3 The special problem of SIGPIPE	1492	=head3 The special problem of SIGPIPE
1137		1493
1138	While not really specific to libev, it is easy to forget about SIGPIPE:	1494	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1139	when reading from a pipe whose other end has been closed, your program	1495	when writing to a pipe whose other end has been closed, your program gets
1140	gets send a SIGPIPE, which, by default, aborts your program. For most	1496	sent a SIGPIPE, which, by default, aborts your program. For most programs
1141	programs this is sensible behaviour, for daemons, this is usually	1497	this is sensible behaviour, for daemons, this is usually undesirable.
1142	undesirable.
1143		1498
1144	So when you encounter spurious, unexplained daemon exits, make sure you	1499	So when you encounter spurious, unexplained daemon exits, make sure you
1145	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1500	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1146	somewhere, as that would have given you a big clue).	1501	somewhere, as that would have given you a big clue).
1147		1502
…		…
1153	=item ev_io_init (ev_io *, callback, int fd, int events)	1508	=item ev_io_init (ev_io *, callback, int fd, int events)
1154		1509
1155	=item ev_io_set (ev_io *, int fd, int events)	1510	=item ev_io_set (ev_io *, int fd, int events)
1156		1511
1157	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1512	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1158	receive events for and events is either C<EV_READ>, C<EV_WRITE> or	1513	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1159	C<EV_READ | EV_WRITE> to receive the given events.	1514	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1160		1515
1161	=item int fd [read-only]	1516	=item int fd [read-only]
1162		1517
1163	The file descriptor being watched.	1518	The file descriptor being watched.
1164		1519
…		…
1173	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1528	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1174	readable, but only once. Since it is likely line-buffered, you could	1529	readable, but only once. Since it is likely line-buffered, you could
1175	attempt to read a whole line in the callback.	1530	attempt to read a whole line in the callback.
1176		1531
1177	static void	1532	static void
1178	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1533	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1179	{	1534	{
1180	ev_io_stop (loop, w);	1535	ev_io_stop (loop, w);
1181	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1536	.. read from stdin here (or from w->fd) and handle any I/O errors
1182	}	1537	}
1183		1538
1184	...	1539	...
1185	struct ev_loop *loop = ev_default_init (0);	1540	struct ev_loop *loop = ev_default_init (0);
1186	struct ev_io stdin_readable;	1541	ev_io stdin_readable;
1187	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1542	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1188	ev_io_start (loop, &stdin_readable);	1543	ev_io_start (loop, &stdin_readable);
1189	ev_loop (loop, 0);	1544	ev_loop (loop, 0);
1190		1545
1191		1546
…		…
1194	Timer watchers are simple relative timers that generate an event after a	1549	Timer watchers are simple relative timers that generate an event after a
1195	given time, and optionally repeating in regular intervals after that.	1550	given time, and optionally repeating in regular intervals after that.
1196		1551
1197	The timers are based on real time, that is, if you register an event that	1552	The timers are based on real time, that is, if you register an event that
1198	times out after an hour and you reset your system clock to January last	1553	times out after an hour and you reset your system clock to January last
1199	year, it will still time out after (roughly) and hour. "Roughly" because	1554	year, it will still time out after (roughly) one hour. "Roughly" because
1200	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1555	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1201	monotonic clock option helps a lot here).	1556	monotonic clock option helps a lot here).
		1557
		1558	The callback is guaranteed to be invoked only I<after> its timeout has
		1559	passed (not I<at>, so on systems with very low-resolution clocks this
		1560	might introduce a small delay). If multiple timers become ready during the
		1561	same loop iteration then the ones with earlier time-out values are invoked
		1562	before ones of the same priority with later time-out values (but this is
		1563	no longer true when a callback calls C<ev_loop> recursively).
		1564
		1565	=head3 Be smart about timeouts
		1566
		1567	Many real-world problems involve some kind of timeout, usually for error
		1568	recovery. A typical example is an HTTP request - if the other side hangs,
		1569	you want to raise some error after a while.
		1570
		1571	What follows are some ways to handle this problem, from obvious and
		1572	inefficient to smart and efficient.
		1573
		1574	In the following, a 60 second activity timeout is assumed - a timeout that
		1575	gets reset to 60 seconds each time there is activity (e.g. each time some
		1576	data or other life sign was received).
		1577
		1578	=over 4
		1579
		1580	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1581
		1582	This is the most obvious, but not the most simple way: In the beginning,
		1583	start the watcher:
		1584
		1585	ev_timer_init (timer, callback, 60., 0.);
		1586	ev_timer_start (loop, timer);
		1587
		1588	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1589	and start it again:
		1590
		1591	ev_timer_stop (loop, timer);
		1592	ev_timer_set (timer, 60., 0.);
		1593	ev_timer_start (loop, timer);
		1594
		1595	This is relatively simple to implement, but means that each time there is
		1596	some activity, libev will first have to remove the timer from its internal
		1597	data structure and then add it again. Libev tries to be fast, but it's
		1598	still not a constant-time operation.
		1599
		1600	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1601
		1602	This is the easiest way, and involves using C<ev_timer_again> instead of
		1603	C<ev_timer_start>.
		1604
		1605	To implement this, configure an C<ev_timer> with a C<repeat> value
		1606	of C<60> and then call C<ev_timer_again> at start and each time you
		1607	successfully read or write some data. If you go into an idle state where
		1608	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1609	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1610
		1611	That means you can ignore both the C<ev_timer_start> function and the
		1612	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1613	member and C<ev_timer_again>.
		1614
		1615	At start:
		1616
		1617	ev_init (timer, callback);
		1618	timer->repeat = 60.;
		1619	ev_timer_again (loop, timer);
		1620
		1621	Each time there is some activity:
		1622
		1623	ev_timer_again (loop, timer);
		1624
		1625	It is even possible to change the time-out on the fly, regardless of
		1626	whether the watcher is active or not:
		1627
		1628	timer->repeat = 30.;
		1629	ev_timer_again (loop, timer);
		1630
		1631	This is slightly more efficient then stopping/starting the timer each time
		1632	you want to modify its timeout value, as libev does not have to completely
		1633	remove and re-insert the timer from/into its internal data structure.
		1634
		1635	It is, however, even simpler than the "obvious" way to do it.
		1636
		1637	=item 3. Let the timer time out, but then re-arm it as required.
		1638
		1639	This method is more tricky, but usually most efficient: Most timeouts are
		1640	relatively long compared to the intervals between other activity - in
		1641	our example, within 60 seconds, there are usually many I/O events with
		1642	associated activity resets.
		1643
		1644	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1645	but remember the time of last activity, and check for a real timeout only
		1646	within the callback:
		1647
		1648	ev_tstamp last_activity; // time of last activity
		1649
		1650	static void
		1651	callback (EV_P_ ev_timer *w, int revents)
		1652	{
		1653	ev_tstamp now = ev_now (EV_A);
		1654	ev_tstamp timeout = last_activity + 60.;
		1655
		1656	// if last_activity + 60. is older than now, we did time out
		1657	if (timeout < now)
		1658	{
		1659	// timeout occured, take action
		1660	}
		1661	else
		1662	{
		1663	// callback was invoked, but there was some activity, re-arm
		1664	// the watcher to fire in last_activity + 60, which is
		1665	// guaranteed to be in the future, so "again" is positive:
		1666	w->repeat = timeout - now;
		1667	ev_timer_again (EV_A_ w);
		1668	}
		1669	}
		1670
		1671	To summarise the callback: first calculate the real timeout (defined
		1672	as "60 seconds after the last activity"), then check if that time has
		1673	been reached, which means something I<did>, in fact, time out. Otherwise
		1674	the callback was invoked too early (C<timeout> is in the future), so
		1675	re-schedule the timer to fire at that future time, to see if maybe we have
		1676	a timeout then.
		1677
		1678	Note how C<ev_timer_again> is used, taking advantage of the
		1679	C<ev_timer_again> optimisation when the timer is already running.
		1680
		1681	This scheme causes more callback invocations (about one every 60 seconds
		1682	minus half the average time between activity), but virtually no calls to
		1683	libev to change the timeout.
		1684
		1685	To start the timer, simply initialise the watcher and set C<last_activity>
		1686	to the current time (meaning we just have some activity :), then call the
		1687	callback, which will "do the right thing" and start the timer:
		1688
		1689	ev_init (timer, callback);
		1690	last_activity = ev_now (loop);
		1691	callback (loop, timer, EV_TIMEOUT);
		1692
		1693	And when there is some activity, simply store the current time in
		1694	C<last_activity>, no libev calls at all:
		1695
		1696	last_actiivty = ev_now (loop);
		1697
		1698	This technique is slightly more complex, but in most cases where the
		1699	time-out is unlikely to be triggered, much more efficient.
		1700
		1701	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1702	callback :) - just change the timeout and invoke the callback, which will
		1703	fix things for you.
		1704
		1705	=item 4. Wee, just use a double-linked list for your timeouts.
		1706
		1707	If there is not one request, but many thousands (millions...), all
		1708	employing some kind of timeout with the same timeout value, then one can
		1709	do even better:
		1710
		1711	When starting the timeout, calculate the timeout value and put the timeout
		1712	at the I<end> of the list.
		1713
		1714	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1715	the list is expected to fire (for example, using the technique #3).
		1716
		1717	When there is some activity, remove the timer from the list, recalculate
		1718	the timeout, append it to the end of the list again, and make sure to
		1719	update the C<ev_timer> if it was taken from the beginning of the list.
		1720
		1721	This way, one can manage an unlimited number of timeouts in O(1) time for
		1722	starting, stopping and updating the timers, at the expense of a major
		1723	complication, and having to use a constant timeout. The constant timeout
		1724	ensures that the list stays sorted.
		1725
		1726	=back
		1727
		1728	So which method the best?
		1729
		1730	Method #2 is a simple no-brain-required solution that is adequate in most
		1731	situations. Method #3 requires a bit more thinking, but handles many cases
		1732	better, and isn't very complicated either. In most case, choosing either
		1733	one is fine, with #3 being better in typical situations.
		1734
		1735	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1736	rather complicated, but extremely efficient, something that really pays
		1737	off after the first million or so of active timers, i.e. it's usually
		1738	overkill :)
		1739
		1740	=head3 The special problem of time updates
		1741
		1742	Establishing the current time is a costly operation (it usually takes at
		1743	least two system calls): EV therefore updates its idea of the current
		1744	time only before and after C<ev_loop> collects new events, which causes a
		1745	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1746	lots of events in one iteration.
1202		1747
1203	The relative timeouts are calculated relative to the C<ev_now ()>	1748	The relative timeouts are calculated relative to the C<ev_now ()>
1204	time. This is usually the right thing as this timestamp refers to the time	1749	time. This is usually the right thing as this timestamp refers to the time
1205	of the event triggering whatever timeout you are modifying/starting. If	1750	of the event triggering whatever timeout you are modifying/starting. If
1206	you suspect event processing to be delayed and you I<need> to base the timeout	1751	you suspect event processing to be delayed and you I<need> to base the
1207	on the current time, use something like this to adjust for this:	1752	timeout on the current time, use something like this to adjust for this:
1208		1753
1209	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1754	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1210		1755
1211	The callback is guaranteed to be invoked only after its timeout has passed,	1756	If the event loop is suspended for a long time, you can also force an
1212	but if multiple timers become ready during the same loop iteration then	1757	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1213	order of execution is undefined.	1758	()>.
1214		1759
1215	=head3 Watcher-Specific Functions and Data Members	1760	=head3 Watcher-Specific Functions and Data Members
1216		1761
1217	=over 4	1762	=over 4
1218		1763
…		…
1242	If the timer is started but non-repeating, stop it (as if it timed out).	1787	If the timer is started but non-repeating, stop it (as if it timed out).
1243		1788
1244	If the timer is repeating, either start it if necessary (with the	1789	If the timer is repeating, either start it if necessary (with the
1245	C<repeat> value), or reset the running timer to the C<repeat> value.	1790	C<repeat> value), or reset the running timer to the C<repeat> value.
1246		1791
1247	This sounds a bit complicated, but here is a useful and typical	1792	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1248	example: Imagine you have a TCP connection and you want a so-called idle	1793	usage example.
1249	timeout, that is, you want to be called when there have been, say, 60
1250	seconds of inactivity on the socket. The easiest way to do this is to
1251	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1252	C<ev_timer_again> each time you successfully read or write some data. If
1253	you go into an idle state where you do not expect data to travel on the
1254	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1255	automatically restart it if need be.
1256
1257	That means you can ignore the C<after> value and C<ev_timer_start>
1258	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1259
1260	ev_timer_init (timer, callback, 0., 5.);
1261	ev_timer_again (loop, timer);
1262	...
1263	timer->again = 17.;
1264	ev_timer_again (loop, timer);
1265	...
1266	timer->again = 10.;
1267	ev_timer_again (loop, timer);
1268
1269	This is more slightly efficient then stopping/starting the timer each time
1270	you want to modify its timeout value.
1271		1794
1272	=item ev_tstamp repeat [read-write]	1795	=item ev_tstamp repeat [read-write]
1273		1796
1274	The current C<repeat> value. Will be used each time the watcher times out	1797	The current C<repeat> value. Will be used each time the watcher times out
1275	or C<ev_timer_again> is called and determines the next timeout (if any),	1798	or C<ev_timer_again> is called, and determines the next timeout (if any),
1276	which is also when any modifications are taken into account.	1799	which is also when any modifications are taken into account.
1277		1800
1278	=back	1801	=back
1279		1802
1280	=head3 Examples	1803	=head3 Examples
1281		1804
1282	Example: Create a timer that fires after 60 seconds.	1805	Example: Create a timer that fires after 60 seconds.
1283		1806
1284	static void	1807	static void
1285	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1808	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1286	{	1809	{
1287	.. one minute over, w is actually stopped right here	1810	.. one minute over, w is actually stopped right here
1288	}	1811	}
1289		1812
1290	struct ev_timer mytimer;	1813	ev_timer mytimer;
1291	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1814	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1292	ev_timer_start (loop, &mytimer);	1815	ev_timer_start (loop, &mytimer);
1293		1816
1294	Example: Create a timeout timer that times out after 10 seconds of	1817	Example: Create a timeout timer that times out after 10 seconds of
1295	inactivity.	1818	inactivity.
1296		1819
1297	static void	1820	static void
1298	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1821	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1299	{	1822	{
1300	.. ten seconds without any activity	1823	.. ten seconds without any activity
1301	}	1824	}
1302		1825
1303	struct ev_timer mytimer;	1826	ev_timer mytimer;
1304	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1827	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1305	ev_timer_again (&mytimer); /* start timer */	1828	ev_timer_again (&mytimer); /* start timer */
1306	ev_loop (loop, 0);	1829	ev_loop (loop, 0);
1307		1830
1308	// and in some piece of code that gets executed on any "activity":	1831	// and in some piece of code that gets executed on any "activity":
…		…
1313	=head2 C<ev_periodic> - to cron or not to cron?	1836	=head2 C<ev_periodic> - to cron or not to cron?
1314		1837
1315	Periodic watchers are also timers of a kind, but they are very versatile	1838	Periodic watchers are also timers of a kind, but they are very versatile
1316	(and unfortunately a bit complex).	1839	(and unfortunately a bit complex).
1317		1840
1318	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1841	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1319	but on wall clock time (absolute time). You can tell a periodic watcher	1842	relative time, the physical time that passes) but on wall clock time
1320	to trigger after some specific point in time. For example, if you tell a	1843	(absolute time, the thing you can read on your calender or clock). The
1321	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	1844	difference is that wall clock time can run faster or slower than real
1322	+ 10.>, that is, an absolute time not a delay) and then reset your system	1845	time, and time jumps are not uncommon (e.g. when you adjust your
1323	clock to January of the previous year, then it will take more than year	1846	wrist-watch).
1324	to trigger the event (unlike an C<ev_timer>, which would still trigger
1325	roughly 10 seconds later as it uses a relative timeout).
1326		1847
		1848	You can tell a periodic watcher to trigger after some specific point
		1849	in time: for example, if you tell a periodic watcher to trigger "in 10
		1850	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1851	not a delay) and then reset your system clock to January of the previous
		1852	year, then it will take a year or more to trigger the event (unlike an
		1853	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1854	it, as it uses a relative timeout).
		1855
1327	C<ev_periodic>s can also be used to implement vastly more complex timers,	1856	C<ev_periodic> watchers can also be used to implement vastly more complex
1328	such as triggering an event on each "midnight, local time", or other	1857	timers, such as triggering an event on each "midnight, local time", or
1329	complicated, rules.	1858	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1859	those cannot react to time jumps.
1330		1860
1331	As with timers, the callback is guaranteed to be invoked only when the	1861	As with timers, the callback is guaranteed to be invoked only when the
1332	time (C<at>) has passed, but if multiple periodic timers become ready	1862	point in time where it is supposed to trigger has passed. If multiple
1333	during the same loop iteration then order of execution is undefined.	1863	timers become ready during the same loop iteration then the ones with
		1864	earlier time-out values are invoked before ones with later time-out values
		1865	(but this is no longer true when a callback calls C<ev_loop> recursively).
1334		1866
1335	=head3 Watcher-Specific Functions and Data Members	1867	=head3 Watcher-Specific Functions and Data Members
1336		1868
1337	=over 4	1869	=over 4
1338		1870
1339	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1871	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1340		1872
1341	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1873	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1342		1874
1343	Lots of arguments, lets sort it out... There are basically three modes of	1875	Lots of arguments, let's sort it out... There are basically three modes of
1344	operation, and we will explain them from simplest to complex:	1876	operation, and we will explain them from simplest to most complex:
1345		1877
1346	=over 4	1878	=over 4
1347		1879
1348	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1880	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1349		1881
1350	In this configuration the watcher triggers an event after the wall clock	1882	In this configuration the watcher triggers an event after the wall clock
1351	time C<at> has passed and doesn't repeat. It will not adjust when a time	1883	time C<offset> has passed. It will not repeat and will not adjust when a
1352	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1884	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1353	run when the system time reaches or surpasses this time.	1885	will be stopped and invoked when the system clock reaches or surpasses
		1886	this point in time.
1354		1887
1355	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1888	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1356		1889
1357	In this mode the watcher will always be scheduled to time out at the next	1890	In this mode the watcher will always be scheduled to time out at the next
1358	C<at + N * interval> time (for some integer N, which can also be negative)	1891	C<offset + N * interval> time (for some integer N, which can also be
1359	and then repeat, regardless of any time jumps.	1892	negative) and then repeat, regardless of any time jumps. The C<offset>
		1893	argument is merely an offset into the C<interval> periods.
1360		1894
1361	This can be used to create timers that do not drift with respect to system	1895	This can be used to create timers that do not drift with respect to the
1362	time, for example, here is a C<ev_periodic> that triggers each hour, on	1896	system clock, for example, here is an C<ev_periodic> that triggers each
1363	the hour:	1897	hour, on the hour (with respect to UTC):
1364		1898
1365	ev_periodic_set (&periodic, 0., 3600., 0);	1899	ev_periodic_set (&periodic, 0., 3600., 0);
1366		1900
1367	This doesn't mean there will always be 3600 seconds in between triggers,	1901	This doesn't mean there will always be 3600 seconds in between triggers,
1368	but only that the callback will be called when the system time shows a	1902	but only that the callback will be called when the system time shows a
1369	full hour (UTC), or more correctly, when the system time is evenly divisible	1903	full hour (UTC), or more correctly, when the system time is evenly divisible
1370	by 3600.	1904	by 3600.
1371		1905
1372	Another way to think about it (for the mathematically inclined) is that	1906	Another way to think about it (for the mathematically inclined) is that
1373	C<ev_periodic> will try to run the callback in this mode at the next possible	1907	C<ev_periodic> will try to run the callback in this mode at the next possible
1374	time where C<time = at (mod interval)>, regardless of any time jumps.	1908	time where C<time = offset (mod interval)>, regardless of any time jumps.
1375		1909
1376	For numerical stability it is preferable that the C<at> value is near	1910	For numerical stability it is preferable that the C<offset> value is near
1377	C<ev_now ()> (the current time), but there is no range requirement for	1911	C<ev_now ()> (the current time), but there is no range requirement for
1378	this value, and in fact is often specified as zero.	1912	this value, and in fact is often specified as zero.
1379		1913
1380	Note also that there is an upper limit to how often a timer can fire (CPU	1914	Note also that there is an upper limit to how often a timer can fire (CPU
1381	speed for example), so if C<interval> is very small then timing stability	1915	speed for example), so if C<interval> is very small then timing stability
1382	will of course deteriorate. Libev itself tries to be exact to be about one	1916	will of course deteriorate. Libev itself tries to be exact to be about one
1383	millisecond (if the OS supports it and the machine is fast enough).	1917	millisecond (if the OS supports it and the machine is fast enough).
1384		1918
1385	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1919	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1386		1920
1387	In this mode the values for C<interval> and C<at> are both being	1921	In this mode the values for C<interval> and C<offset> are both being
1388	ignored. Instead, each time the periodic watcher gets scheduled, the	1922	ignored. Instead, each time the periodic watcher gets scheduled, the
1389	reschedule callback will be called with the watcher as first, and the	1923	reschedule callback will be called with the watcher as first, and the
1390	current time as second argument.	1924	current time as second argument.
1391		1925
1392	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1926	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1393	ever, or make ANY event loop modifications whatsoever>.	1927	or make ANY other event loop modifications whatsoever, unless explicitly
		1928	allowed by documentation here>.
1394		1929
1395	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1930	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1396	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	1931	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1397	only event loop modification you are allowed to do).	1932	only event loop modification you are allowed to do).
1398		1933
1399	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1934	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1400	*w, ev_tstamp now)>, e.g.:	1935	*w, ev_tstamp now)>, e.g.:
1401		1936
		1937	static ev_tstamp
1402	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1938	my_rescheduler (ev_periodic *w, ev_tstamp now)
1403	{	1939	{
1404	return now + 60.;	1940	return now + 60.;
1405	}	1941	}
1406		1942
1407	It must return the next time to trigger, based on the passed time value	1943	It must return the next time to trigger, based on the passed time value
…		…
1427	a different time than the last time it was called (e.g. in a crond like	1963	a different time than the last time it was called (e.g. in a crond like
1428	program when the crontabs have changed).	1964	program when the crontabs have changed).
1429		1965
1430	=item ev_tstamp ev_periodic_at (ev_periodic *)	1966	=item ev_tstamp ev_periodic_at (ev_periodic *)
1431		1967
1432	When active, returns the absolute time that the watcher is supposed to	1968	When active, returns the absolute time that the watcher is supposed
1433	trigger next.	1969	to trigger next. This is not the same as the C<offset> argument to
		1970	C<ev_periodic_set>, but indeed works even in interval and manual
		1971	rescheduling modes.
1434		1972
1435	=item ev_tstamp offset [read-write]	1973	=item ev_tstamp offset [read-write]
1436		1974
1437	When repeating, this contains the offset value, otherwise this is the	1975	When repeating, this contains the offset value, otherwise this is the
1438	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1976	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		1977	although libev might modify this value for better numerical stability).
1439		1978
1440	Can be modified any time, but changes only take effect when the periodic	1979	Can be modified any time, but changes only take effect when the periodic
1441	timer fires or C<ev_periodic_again> is being called.	1980	timer fires or C<ev_periodic_again> is being called.
1442		1981
1443	=item ev_tstamp interval [read-write]	1982	=item ev_tstamp interval [read-write]
1444		1983
1445	The current interval value. Can be modified any time, but changes only	1984	The current interval value. Can be modified any time, but changes only
1446	take effect when the periodic timer fires or C<ev_periodic_again> is being	1985	take effect when the periodic timer fires or C<ev_periodic_again> is being
1447	called.	1986	called.
1448		1987
1449	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1988	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1450		1989
1451	The current reschedule callback, or C<0>, if this functionality is	1990	The current reschedule callback, or C<0>, if this functionality is
1452	switched off. Can be changed any time, but changes only take effect when	1991	switched off. Can be changed any time, but changes only take effect when
1453	the periodic timer fires or C<ev_periodic_again> is being called.	1992	the periodic timer fires or C<ev_periodic_again> is being called.
1454		1993
1455	=back	1994	=back
1456		1995
1457	=head3 Examples	1996	=head3 Examples
1458		1997
1459	Example: Call a callback every hour, or, more precisely, whenever the	1998	Example: Call a callback every hour, or, more precisely, whenever the
1460	system clock is divisible by 3600. The callback invocation times have	1999	system time is divisible by 3600. The callback invocation times have
1461	potentially a lot of jitter, but good long-term stability.	2000	potentially a lot of jitter, but good long-term stability.
1462		2001
1463	static void	2002	static void
1464	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2003	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1465	{	2004	{
1466	... its now a full hour (UTC, or TAI or whatever your clock follows)	2005	... its now a full hour (UTC, or TAI or whatever your clock follows)
1467	}	2006	}
1468		2007
1469	struct ev_periodic hourly_tick;	2008	ev_periodic hourly_tick;
1470	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2009	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1471	ev_periodic_start (loop, &hourly_tick);	2010	ev_periodic_start (loop, &hourly_tick);
1472		2011
1473	Example: The same as above, but use a reschedule callback to do it:	2012	Example: The same as above, but use a reschedule callback to do it:
1474		2013
1475	#include <math.h>	2014	#include <math.h>
1476		2015
1477	static ev_tstamp	2016	static ev_tstamp
1478	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2017	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1479	{	2018	{
1480	return fmod (now, 3600.) + 3600.;	2019	return now + (3600. - fmod (now, 3600.));
1481	}	2020	}
1482		2021
1483	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2022	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1484		2023
1485	Example: Call a callback every hour, starting now:	2024	Example: Call a callback every hour, starting now:
1486		2025
1487	struct ev_periodic hourly_tick;	2026	ev_periodic hourly_tick;
1488	ev_periodic_init (&hourly_tick, clock_cb,	2027	ev_periodic_init (&hourly_tick, clock_cb,
1489	fmod (ev_now (loop), 3600.), 3600., 0);	2028	fmod (ev_now (loop), 3600.), 3600., 0);
1490	ev_periodic_start (loop, &hourly_tick);	2029	ev_periodic_start (loop, &hourly_tick);
1491		2030
1492		2031
…		…
1495	Signal watchers will trigger an event when the process receives a specific	2034	Signal watchers will trigger an event when the process receives a specific
1496	signal one or more times. Even though signals are very asynchronous, libev	2035	signal one or more times. Even though signals are very asynchronous, libev
1497	will try it's best to deliver signals synchronously, i.e. as part of the	2036	will try it's best to deliver signals synchronously, i.e. as part of the
1498	normal event processing, like any other event.	2037	normal event processing, like any other event.
1499		2038
		2039	If you want signals asynchronously, just use C<sigaction> as you would
		2040	do without libev and forget about sharing the signal. You can even use
		2041	C<ev_async> from a signal handler to synchronously wake up an event loop.
		2042
1500	You can configure as many watchers as you like per signal. Only when the	2043	You can configure as many watchers as you like per signal. Only when the
1501	first watcher gets started will libev actually register a signal watcher	2044	first watcher gets started will libev actually register a signal handler
1502	with the kernel (thus it coexists with your own signal handlers as long	2045	with the kernel (thus it coexists with your own signal handlers as long as
1503	as you don't register any with libev). Similarly, when the last signal	2046	you don't register any with libev for the same signal). Similarly, when
1504	watcher for a signal is stopped libev will reset the signal handler to	2047	the last signal watcher for a signal is stopped, libev will reset the
1505	SIG_DFL (regardless of what it was set to before).	2048	signal handler to SIG_DFL (regardless of what it was set to before).
1506		2049
1507	If possible and supported, libev will install its handlers with	2050	If possible and supported, libev will install its handlers with
1508	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2051	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1509	interrupted. If you have a problem with system calls getting interrupted by	2052	interrupted. If you have a problem with system calls getting interrupted by
1510	signals you can block all signals in an C<ev_check> watcher and unblock	2053	signals you can block all signals in an C<ev_check> watcher and unblock
…		…
1527		2070
1528	=back	2071	=back
1529		2072
1530	=head3 Examples	2073	=head3 Examples
1531		2074
1532	Example: Try to exit cleanly on SIGINT and SIGTERM.	2075	Example: Try to exit cleanly on SIGINT.
1533		2076
1534	static void	2077	static void
1535	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2078	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1536	{	2079	{
1537	ev_unloop (loop, EVUNLOOP_ALL);	2080	ev_unloop (loop, EVUNLOOP_ALL);
1538	}	2081	}
1539		2082
1540	struct ev_signal signal_watcher;	2083	ev_signal signal_watcher;
1541	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2084	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1542	ev_signal_start (loop, &sigint_cb);	2085	ev_signal_start (loop, &signal_watcher);
1543		2086
1544		2087
1545	=head2 C<ev_child> - watch out for process status changes	2088	=head2 C<ev_child> - watch out for process status changes
1546		2089
1547	Child watchers trigger when your process receives a SIGCHLD in response to	2090	Child watchers trigger when your process receives a SIGCHLD in response to
1548	some child status changes (most typically when a child of yours dies). It	2091	some child status changes (most typically when a child of yours dies or
1549	is permissible to install a child watcher I<after> the child has been	2092	exits). It is permissible to install a child watcher I<after> the child
1550	forked (which implies it might have already exited), as long as the event	2093	has been forked (which implies it might have already exited), as long
1551	loop isn't entered (or is continued from a watcher).	2094	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2095	forking and then immediately registering a watcher for the child is fine,
		2096	but forking and registering a watcher a few event loop iterations later or
		2097	in the next callback invocation is not.
1552		2098
1553	Only the default event loop is capable of handling signals, and therefore	2099	Only the default event loop is capable of handling signals, and therefore
1554	you can only register child watchers in the default event loop.	2100	you can only register child watchers in the default event loop.
		2101
		2102	Due to some design glitches inside libev, child watchers will always be
		2103	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2104	libev)
1555		2105
1556	=head3 Process Interaction	2106	=head3 Process Interaction
1557		2107
1558	Libev grabs C<SIGCHLD> as soon as the default event loop is	2108	Libev grabs C<SIGCHLD> as soon as the default event loop is
1559	initialised. This is necessary to guarantee proper behaviour even if	2109	initialised. This is necessary to guarantee proper behaviour even if
…		…
1569	handler, you can override it easily by installing your own handler for	2119	handler, you can override it easily by installing your own handler for
1570	C<SIGCHLD> after initialising the default loop, and making sure the	2120	C<SIGCHLD> after initialising the default loop, and making sure the
1571	default loop never gets destroyed. You are encouraged, however, to use an	2121	default loop never gets destroyed. You are encouraged, however, to use an
1572	event-based approach to child reaping and thus use libev's support for	2122	event-based approach to child reaping and thus use libev's support for
1573	that, so other libev users can use C<ev_child> watchers freely.	2123	that, so other libev users can use C<ev_child> watchers freely.
		2124
		2125	=head3 Stopping the Child Watcher
		2126
		2127	Currently, the child watcher never gets stopped, even when the
		2128	child terminates, so normally one needs to stop the watcher in the
		2129	callback. Future versions of libev might stop the watcher automatically
		2130	when a child exit is detected.
1574		2131
1575	=head3 Watcher-Specific Functions and Data Members	2132	=head3 Watcher-Specific Functions and Data Members
1576		2133
1577	=over 4	2134	=over 4
1578		2135
…		…
1610	its completion.	2167	its completion.
1611		2168
1612	ev_child cw;	2169	ev_child cw;
1613		2170
1614	static void	2171	static void
1615	child_cb (EV_P_ struct ev_child *w, int revents)	2172	child_cb (EV_P_ ev_child *w, int revents)
1616	{	2173	{
1617	ev_child_stop (EV_A_ w);	2174	ev_child_stop (EV_A_ w);
1618	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2175	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1619	}	2176	}
1620		2177
…		…
1635		2192
1636		2193
1637	=head2 C<ev_stat> - did the file attributes just change?	2194	=head2 C<ev_stat> - did the file attributes just change?
1638		2195
1639	This watches a file system path for attribute changes. That is, it calls	2196	This watches a file system path for attribute changes. That is, it calls
1640	C<stat> regularly (or when the OS says it changed) and sees if it changed	2197	C<stat> on that path in regular intervals (or when the OS says it changed)
1641	compared to the last time, invoking the callback if it did.	2198	and sees if it changed compared to the last time, invoking the callback if
		2199	it did.
1642		2200
1643	The path does not need to exist: changing from "path exists" to "path does	2201	The path does not need to exist: changing from "path exists" to "path does
1644	not exist" is a status change like any other. The condition "path does	2202	not exist" is a status change like any other. The condition "path does not
1645	not exist" is signified by the C<st_nlink> field being zero (which is	2203	exist" (or more correctly "path cannot be stat'ed") is signified by the
1646	otherwise always forced to be at least one) and all the other fields of	2204	C<st_nlink> field being zero (which is otherwise always forced to be at
1647	the stat buffer having unspecified contents.	2205	least one) and all the other fields of the stat buffer having unspecified
		2206	contents.
1648		2207
1649	The path I<should> be absolute and I<must not> end in a slash. If it is	2208	The path I<must not> end in a slash or contain special components such as
		2209	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1650	relative and your working directory changes, the behaviour is undefined.	2210	your working directory changes, then the behaviour is undefined.
1651		2211
1652	Since there is no standard to do this, the portable implementation simply	2212	Since there is no portable change notification interface available, the
1653	calls C<stat (2)> regularly on the path to see if it changed somehow. You	2213	portable implementation simply calls C<stat(2)> regularly on the path
1654	can specify a recommended polling interval for this case. If you specify	2214	to see if it changed somehow. You can specify a recommended polling
1655	a polling interval of C<0> (highly recommended!) then a I<suitable,	2215	interval for this case. If you specify a polling interval of C<0> (highly
1656	unspecified default> value will be used (which you can expect to be around	2216	recommended!) then a I<suitable, unspecified default> value will be used
1657	five seconds, although this might change dynamically). Libev will also	2217	(which you can expect to be around five seconds, although this might
1658	impose a minimum interval which is currently around C<0.1>, but thats	2218	change dynamically). Libev will also impose a minimum interval which is
1659	usually overkill.	2219	currently around C<0.1>, but that's usually overkill.
1660		2220
1661	This watcher type is not meant for massive numbers of stat watchers,	2221	This watcher type is not meant for massive numbers of stat watchers,
1662	as even with OS-supported change notifications, this can be	2222	as even with OS-supported change notifications, this can be
1663	resource-intensive.	2223	resource-intensive.
1664		2224
1665	At the time of this writing, only the Linux inotify interface is	2225	At the time of this writing, the only OS-specific interface implemented
1666	implemented (implementing kqueue support is left as an exercise for the	2226	is the Linux inotify interface (implementing kqueue support is left as an
1667	reader, note, however, that the author sees no way of implementing ev_stat	2227	exercise for the reader. Note, however, that the author sees no way of
1668	semantics with kqueue). Inotify will be used to give hints only and should	2228	implementing C<ev_stat> semantics with kqueue, except as a hint).
1669	not change the semantics of C<ev_stat> watchers, which means that libev
1670	sometimes needs to fall back to regular polling again even with inotify,
1671	but changes are usually detected immediately, and if the file exists there
1672	will be no polling.
1673		2229
1674	=head3 ABI Issues (Largefile Support)	2230	=head3 ABI Issues (Largefile Support)
1675		2231
1676	Libev by default (unless the user overrides this) uses the default	2232	Libev by default (unless the user overrides this) uses the default
1677	compilation environment, which means that on systems with large file	2233	compilation environment, which means that on systems with large file
1678	support disabled by default, you get the 32 bit version of the stat	2234	support disabled by default, you get the 32 bit version of the stat
1679	structure. When using the library from programs that change the ABI to	2235	structure. When using the library from programs that change the ABI to
1680	use 64 bit file offsets the programs will fail. In that case you have to	2236	use 64 bit file offsets the programs will fail. In that case you have to
1681	compile libev with the same flags to get binary compatibility. This is	2237	compile libev with the same flags to get binary compatibility. This is
1682	obviously the case with any flags that change the ABI, but the problem is	2238	obviously the case with any flags that change the ABI, but the problem is
1683	most noticeably disabled with ev_stat and large file support.	2239	most noticeably displayed with ev_stat and large file support.
1684		2240
1685	The solution for this is to lobby your distribution maker to make large	2241	The solution for this is to lobby your distribution maker to make large
1686	file interfaces available by default (as e.g. FreeBSD does) and not	2242	file interfaces available by default (as e.g. FreeBSD does) and not
1687	optional. Libev cannot simply switch on large file support because it has	2243	optional. Libev cannot simply switch on large file support because it has
1688	to exchange stat structures with application programs compiled using the	2244	to exchange stat structures with application programs compiled using the
1689	default compilation environment.	2245	default compilation environment.
1690		2246
1691	=head3 Inotify	2247	=head3 Inotify and Kqueue
1692		2248
1693	When C<inotify (7)> support has been compiled into libev (generally only	2249	When C<inotify (7)> support has been compiled into libev and present at
1694	available on Linux) and present at runtime, it will be used to speed up	2250	runtime, it will be used to speed up change detection where possible. The
1695	change detection where possible. The inotify descriptor will be created lazily	2251	inotify descriptor will be created lazily when the first C<ev_stat>
1696	when the first C<ev_stat> watcher is being started.	2252	watcher is being started.
1697		2253
1698	Inotify presence does not change the semantics of C<ev_stat> watchers	2254	Inotify presence does not change the semantics of C<ev_stat> watchers
1699	except that changes might be detected earlier, and in some cases, to avoid	2255	except that changes might be detected earlier, and in some cases, to avoid
1700	making regular C<stat> calls. Even in the presence of inotify support	2256	making regular C<stat> calls. Even in the presence of inotify support
1701	there are many cases where libev has to resort to regular C<stat> polling.	2257	there are many cases where libev has to resort to regular C<stat> polling,
		2258	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2259	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2260	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2261	xfs are fully working) libev usually gets away without polling.
1702		2262
1703	(There is no support for kqueue, as apparently it cannot be used to	2263	There is no support for kqueue, as apparently it cannot be used to
1704	implement this functionality, due to the requirement of having a file	2264	implement this functionality, due to the requirement of having a file
1705	descriptor open on the object at all times).	2265	descriptor open on the object at all times, and detecting renames, unlinks
		2266	etc. is difficult.
		2267
		2268	=head3 C<stat ()> is a synchronous operation
		2269
		2270	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2271	the process. The exception are C<ev_stat> watchers - those call C<stat
		2272	()>, which is a synchronous operation.
		2273
		2274	For local paths, this usually doesn't matter: unless the system is very
		2275	busy or the intervals between stat's are large, a stat call will be fast,
		2276	as the path data is usually in memory already (except when starting the
		2277	watcher).
		2278
		2279	For networked file systems, calling C<stat ()> can block an indefinite
		2280	time due to network issues, and even under good conditions, a stat call
		2281	often takes multiple milliseconds.
		2282
		2283	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2284	paths, although this is fully supported by libev.
1706		2285
1707	=head3 The special problem of stat time resolution	2286	=head3 The special problem of stat time resolution
1708		2287
1709	The C<stat ()> system call only supports full-second resolution portably, and	2288	The C<stat ()> system call only supports full-second resolution portably,
1710	even on systems where the resolution is higher, many file systems still	2289	and even on systems where the resolution is higher, most file systems
1711	only support whole seconds.	2290	still only support whole seconds.
1712		2291
1713	That means that, if the time is the only thing that changes, you can	2292	That means that, if the time is the only thing that changes, you can
1714	easily miss updates: on the first update, C<ev_stat> detects a change and	2293	easily miss updates: on the first update, C<ev_stat> detects a change and
1715	calls your callback, which does something. When there is another update	2294	calls your callback, which does something. When there is another update
1716	within the same second, C<ev_stat> will be unable to detect it as the stat	2295	within the same second, C<ev_stat> will be unable to detect unless the
1717	data does not change.	2296	stat data does change in other ways (e.g. file size).
1718		2297
1719	The solution to this is to delay acting on a change for slightly more	2298	The solution to this is to delay acting on a change for slightly more
1720	than a second (or till slightly after the next full second boundary), using	2299	than a second (or till slightly after the next full second boundary), using
1721	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2300	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1722	ev_timer_again (loop, w)>).	2301	ev_timer_again (loop, w)>).
…		…
1742	C<path>. The C<interval> is a hint on how quickly a change is expected to	2321	C<path>. The C<interval> is a hint on how quickly a change is expected to
1743	be detected and should normally be specified as C<0> to let libev choose	2322	be detected and should normally be specified as C<0> to let libev choose
1744	a suitable value. The memory pointed to by C<path> must point to the same	2323	a suitable value. The memory pointed to by C<path> must point to the same
1745	path for as long as the watcher is active.	2324	path for as long as the watcher is active.
1746		2325
1747	The callback will receive C<EV_STAT> when a change was detected, relative	2326	The callback will receive an C<EV_STAT> event when a change was detected,
1748	to the attributes at the time the watcher was started (or the last change	2327	relative to the attributes at the time the watcher was started (or the
1749	was detected).	2328	last change was detected).
1750		2329
1751	=item ev_stat_stat (loop, ev_stat *)	2330	=item ev_stat_stat (loop, ev_stat *)
1752		2331
1753	Updates the stat buffer immediately with new values. If you change the	2332	Updates the stat buffer immediately with new values. If you change the
1754	watched path in your callback, you could call this function to avoid	2333	watched path in your callback, you could call this function to avoid
…		…
1837		2416
1838		2417
1839	=head2 C<ev_idle> - when you've got nothing better to do...	2418	=head2 C<ev_idle> - when you've got nothing better to do...
1840		2419
1841	Idle watchers trigger events when no other events of the same or higher	2420	Idle watchers trigger events when no other events of the same or higher
1842	priority are pending (prepare, check and other idle watchers do not	2421	priority are pending (prepare, check and other idle watchers do not count
1843	count).	2422	as receiving "events").
1844		2423
1845	That is, as long as your process is busy handling sockets or timeouts	2424	That is, as long as your process is busy handling sockets or timeouts
1846	(or even signals, imagine) of the same or higher priority it will not be	2425	(or even signals, imagine) of the same or higher priority it will not be
1847	triggered. But when your process is idle (or only lower-priority watchers	2426	triggered. But when your process is idle (or only lower-priority watchers
1848	are pending), the idle watchers are being called once per event loop	2427	are pending), the idle watchers are being called once per event loop
…		…
1859		2438
1860	=head3 Watcher-Specific Functions and Data Members	2439	=head3 Watcher-Specific Functions and Data Members
1861		2440
1862	=over 4	2441	=over 4
1863		2442
1864	=item ev_idle_init (ev_signal *, callback)	2443	=item ev_idle_init (ev_idle *, callback)
1865		2444
1866	Initialises and configures the idle watcher - it has no parameters of any	2445	Initialises and configures the idle watcher - it has no parameters of any
1867	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2446	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1868	believe me.	2447	believe me.
1869		2448
…		…
1873		2452
1874	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2453	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1875	callback, free it. Also, use no error checking, as usual.	2454	callback, free it. Also, use no error checking, as usual.
1876		2455
1877	static void	2456	static void
1878	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2457	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1879	{	2458	{
1880	free (w);	2459	free (w);
1881	// now do something you wanted to do when the program has	2460	// now do something you wanted to do when the program has
1882	// no longer anything immediate to do.	2461	// no longer anything immediate to do.
1883	}	2462	}
1884		2463
1885	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2464	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1886	ev_idle_init (idle_watcher, idle_cb);	2465	ev_idle_init (idle_watcher, idle_cb);
1887	ev_idle_start (loop, idle_cb);	2466	ev_idle_start (loop, idle_watcher);
1888		2467
1889		2468
1890	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2469	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1891		2470
1892	Prepare and check watchers are usually (but not always) used in tandem:	2471	Prepare and check watchers are usually (but not always) used in pairs:
1893	prepare watchers get invoked before the process blocks and check watchers	2472	prepare watchers get invoked before the process blocks and check watchers
1894	afterwards.	2473	afterwards.
1895		2474
1896	You I<must not> call C<ev_loop> or similar functions that enter	2475	You I<must not> call C<ev_loop> or similar functions that enter
1897	the current event loop from either C<ev_prepare> or C<ev_check>	2476	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1900	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2479	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1901	C<ev_check> so if you have one watcher of each kind they will always be	2480	C<ev_check> so if you have one watcher of each kind they will always be
1902	called in pairs bracketing the blocking call.	2481	called in pairs bracketing the blocking call.
1903		2482
1904	Their main purpose is to integrate other event mechanisms into libev and	2483	Their main purpose is to integrate other event mechanisms into libev and
1905	their use is somewhat advanced. This could be used, for example, to track	2484	their use is somewhat advanced. They could be used, for example, to track
1906	variable changes, implement your own watchers, integrate net-snmp or a	2485	variable changes, implement your own watchers, integrate net-snmp or a
1907	coroutine library and lots more. They are also occasionally useful if	2486	coroutine library and lots more. They are also occasionally useful if
1908	you cache some data and want to flush it before blocking (for example,	2487	you cache some data and want to flush it before blocking (for example,
1909	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2488	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1910	watcher).	2489	watcher).
1911		2490
1912	This is done by examining in each prepare call which file descriptors need	2491	This is done by examining in each prepare call which file descriptors
1913	to be watched by the other library, registering C<ev_io> watchers for	2492	need to be watched by the other library, registering C<ev_io> watchers
1914	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2493	for them and starting an C<ev_timer> watcher for any timeouts (many
1915	provide just this functionality). Then, in the check watcher you check for	2494	libraries provide exactly this functionality). Then, in the check watcher,
1916	any events that occurred (by checking the pending status of all watchers	2495	you check for any events that occurred (by checking the pending status
1917	and stopping them) and call back into the library. The I/O and timer	2496	of all watchers and stopping them) and call back into the library. The
1918	callbacks will never actually be called (but must be valid nevertheless,	2497	I/O and timer callbacks will never actually be called (but must be valid
1919	because you never know, you know?).	2498	nevertheless, because you never know, you know?).
1920		2499
1921	As another example, the Perl Coro module uses these hooks to integrate	2500	As another example, the Perl Coro module uses these hooks to integrate
1922	coroutines into libev programs, by yielding to other active coroutines	2501	coroutines into libev programs, by yielding to other active coroutines
1923	during each prepare and only letting the process block if no coroutines	2502	during each prepare and only letting the process block if no coroutines
1924	are ready to run (it's actually more complicated: it only runs coroutines	2503	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1927	loop from blocking if lower-priority coroutines are active, thus mapping	2506	loop from blocking if lower-priority coroutines are active, thus mapping
1928	low-priority coroutines to idle/background tasks).	2507	low-priority coroutines to idle/background tasks).
1929		2508
1930	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2509	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1931	priority, to ensure that they are being run before any other watchers	2510	priority, to ensure that they are being run before any other watchers
		2511	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2512
1932	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2513	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1933	too) should not activate ("feed") events into libev. While libev fully	2514	activate ("feed") events into libev. While libev fully supports this, they
1934	supports this, they might get executed before other C<ev_check> watchers	2515	might get executed before other C<ev_check> watchers did their job. As
1935	did their job. As C<ev_check> watchers are often used to embed other	2516	C<ev_check> watchers are often used to embed other (non-libev) event
1936	(non-libev) event loops those other event loops might be in an unusable	2517	loops those other event loops might be in an unusable state until their
1937	state until their C<ev_check> watcher ran (always remind yourself to	2518	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1938	coexist peacefully with others).	2519	others).
1939		2520
1940	=head3 Watcher-Specific Functions and Data Members	2521	=head3 Watcher-Specific Functions and Data Members
1941		2522
1942	=over 4	2523	=over 4
1943		2524
…		…
1945		2526
1946	=item ev_check_init (ev_check *, callback)	2527	=item ev_check_init (ev_check *, callback)
1947		2528
1948	Initialises and configures the prepare or check watcher - they have no	2529	Initialises and configures the prepare or check watcher - they have no
1949	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2530	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1950	macros, but using them is utterly, utterly and completely pointless.	2531	macros, but using them is utterly, utterly, utterly and completely
		2532	pointless.
1951		2533
1952	=back	2534	=back
1953		2535
1954	=head3 Examples	2536	=head3 Examples
1955		2537
…		…
1968		2550
1969	static ev_io iow [nfd];	2551	static ev_io iow [nfd];
1970	static ev_timer tw;	2552	static ev_timer tw;
1971		2553
1972	static void	2554	static void
1973	io_cb (ev_loop *loop, ev_io *w, int revents)	2555	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1974	{	2556	{
1975	}	2557	}
1976		2558
1977	// create io watchers for each fd and a timer before blocking	2559	// create io watchers for each fd and a timer before blocking
1978	static void	2560	static void
1979	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2561	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1980	{	2562	{
1981	int timeout = 3600000;	2563	int timeout = 3600000;
1982	struct pollfd fds [nfd];	2564	struct pollfd fds [nfd];
1983	// actual code will need to loop here and realloc etc.	2565	// actual code will need to loop here and realloc etc.
1984	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2566	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1985		2567
1986	/* the callback is illegal, but won't be called as we stop during check */	2568	/* the callback is illegal, but won't be called as we stop during check */
1987	ev_timer_init (&tw, 0, timeout * 1e-3);	2569	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
1988	ev_timer_start (loop, &tw);	2570	ev_timer_start (loop, &tw);
1989		2571
1990	// create one ev_io per pollfd	2572	// create one ev_io per pollfd
1991	for (int i = 0; i < nfd; ++i)	2573	for (int i = 0; i < nfd; ++i)
1992	{	2574	{
…		…
1999	}	2581	}
2000	}	2582	}
2001		2583
2002	// stop all watchers after blocking	2584	// stop all watchers after blocking
2003	static void	2585	static void
2004	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2586	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2005	{	2587	{
2006	ev_timer_stop (loop, &tw);	2588	ev_timer_stop (loop, &tw);
2007		2589
2008	for (int i = 0; i < nfd; ++i)	2590	for (int i = 0; i < nfd; ++i)
2009	{	2591	{
…		…
2048	}	2630	}
2049		2631
2050	// do not ever call adns_afterpoll	2632	// do not ever call adns_afterpoll
2051		2633
2052	Method 4: Do not use a prepare or check watcher because the module you	2634	Method 4: Do not use a prepare or check watcher because the module you
2053	want to embed is too inflexible to support it. Instead, you can override	2635	want to embed is not flexible enough to support it. Instead, you can
2054	their poll function. The drawback with this solution is that the main	2636	override their poll function. The drawback with this solution is that the
2055	loop is now no longer controllable by EV. The C<Glib::EV> module does	2637	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2056	this.	2638	this approach, effectively embedding EV as a client into the horrible
		2639	libglib event loop.
2057		2640
2058	static gint	2641	static gint
2059	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2642	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2060	{	2643	{
2061	int got_events = 0;	2644	int got_events = 0;
…		…
2092	prioritise I/O.	2675	prioritise I/O.
2093		2676
2094	As an example for a bug workaround, the kqueue backend might only support	2677	As an example for a bug workaround, the kqueue backend might only support
2095	sockets on some platform, so it is unusable as generic backend, but you	2678	sockets on some platform, so it is unusable as generic backend, but you
2096	still want to make use of it because you have many sockets and it scales	2679	still want to make use of it because you have many sockets and it scales
2097	so nicely. In this case, you would create a kqueue-based loop and embed it	2680	so nicely. In this case, you would create a kqueue-based loop and embed
2098	into your default loop (which might use e.g. poll). Overall operation will	2681	it into your default loop (which might use e.g. poll). Overall operation
2099	be a bit slower because first libev has to poll and then call kevent, but	2682	will be a bit slower because first libev has to call C<poll> and then
2100	at least you can use both at what they are best.	2683	C<kevent>, but at least you can use both mechanisms for what they are
		2684	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2101		2685
2102	As for prioritising I/O: rarely you have the case where some fds have	2686	As for prioritising I/O: under rare circumstances you have the case where
2103	to be watched and handled very quickly (with low latency), and even	2687	some fds have to be watched and handled very quickly (with low latency),
2104	priorities and idle watchers might have too much overhead. In this case	2688	and even priorities and idle watchers might have too much overhead. In
2105	you would put all the high priority stuff in one loop and all the rest in	2689	this case you would put all the high priority stuff in one loop and all
2106	a second one, and embed the second one in the first.	2690	the rest in a second one, and embed the second one in the first.
2107		2691
2108	As long as the watcher is active, the callback will be invoked every time	2692	As long as the watcher is active, the callback will be invoked every
2109	there might be events pending in the embedded loop. The callback must then	2693	time there might be events pending in the embedded loop. The callback
2110	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2694	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2111	their callbacks (you could also start an idle watcher to give the embedded	2695	sweep and invoke their callbacks (the callback doesn't need to invoke the
2112	loop strictly lower priority for example). You can also set the callback	2696	C<ev_embed_sweep> function directly, it could also start an idle watcher
2113	to C<0>, in which case the embed watcher will automatically execute the	2697	to give the embedded loop strictly lower priority for example).
2114	embedded loop sweep.
2115		2698
2116	As long as the watcher is started it will automatically handle events. The	2699	You can also set the callback to C<0>, in which case the embed watcher
2117	callback will be invoked whenever some events have been handled. You can	2700	will automatically execute the embedded loop sweep whenever necessary.
2118	set the callback to C<0> to avoid having to specify one if you are not
2119	interested in that.
2120		2701
2121	Also, there have not currently been made special provisions for forking:	2702	Fork detection will be handled transparently while the C<ev_embed> watcher
2122	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2703	is active, i.e., the embedded loop will automatically be forked when the
2123	but you will also have to stop and restart any C<ev_embed> watchers	2704	embedding loop forks. In other cases, the user is responsible for calling
2124	yourself.	2705	C<ev_loop_fork> on the embedded loop.
2125		2706
2126	Unfortunately, not all backends are embeddable, only the ones returned by	2707	Unfortunately, not all backends are embeddable: only the ones returned by
2127	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2708	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2128	portable one.	2709	portable one.
2129		2710
2130	So when you want to use this feature you will always have to be prepared	2711	So when you want to use this feature you will always have to be prepared
2131	that you cannot get an embeddable loop. The recommended way to get around	2712	that you cannot get an embeddable loop. The recommended way to get around
2132	this is to have a separate variables for your embeddable loop, try to	2713	this is to have a separate variables for your embeddable loop, try to
2133	create it, and if that fails, use the normal loop for everything.	2714	create it, and if that fails, use the normal loop for everything.
		2715
		2716	=head3 C<ev_embed> and fork
		2717
		2718	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2719	automatically be applied to the embedded loop as well, so no special
		2720	fork handling is required in that case. When the watcher is not running,
		2721	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2722	as applicable.
2134		2723
2135	=head3 Watcher-Specific Functions and Data Members	2724	=head3 Watcher-Specific Functions and Data Members
2136		2725
2137	=over 4	2726	=over 4
2138		2727
…		…
2166	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2755	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2167	used).	2756	used).
2168		2757
2169	struct ev_loop *loop_hi = ev_default_init (0);	2758	struct ev_loop *loop_hi = ev_default_init (0);
2170	struct ev_loop *loop_lo = 0;	2759	struct ev_loop *loop_lo = 0;
2171	struct ev_embed embed;	2760	ev_embed embed;
2172		2761
2173	// see if there is a chance of getting one that works	2762	// see if there is a chance of getting one that works
2174	// (remember that a flags value of 0 means autodetection)	2763	// (remember that a flags value of 0 means autodetection)
2175	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2764	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2176	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2765	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2190	kqueue implementation). Store the kqueue/socket-only event loop in	2779	kqueue implementation). Store the kqueue/socket-only event loop in
2191	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2780	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2192		2781
2193	struct ev_loop *loop = ev_default_init (0);	2782	struct ev_loop *loop = ev_default_init (0);
2194	struct ev_loop *loop_socket = 0;	2783	struct ev_loop *loop_socket = 0;
2195	struct ev_embed embed;	2784	ev_embed embed;
2196		2785
2197	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2786	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2198	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2787	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2199	{	2788	{
2200	ev_embed_init (&embed, 0, loop_socket);	2789	ev_embed_init (&embed, 0, loop_socket);
…		…
2215	event loop blocks next and before C<ev_check> watchers are being called,	2804	event loop blocks next and before C<ev_check> watchers are being called,
2216	and only in the child after the fork. If whoever good citizen calling	2805	and only in the child after the fork. If whoever good citizen calling
2217	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2806	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2218	handlers will be invoked, too, of course.	2807	handlers will be invoked, too, of course.
2219		2808
		2809	=head3 The special problem of life after fork - how is it possible?
		2810
		2811	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2812	up/change the process environment, followed by a call to C<exec()>. This
		2813	sequence should be handled by libev without any problems.
		2814
		2815	This changes when the application actually wants to do event handling
		2816	in the child, or both parent in child, in effect "continuing" after the
		2817	fork.
		2818
		2819	The default mode of operation (for libev, with application help to detect
		2820	forks) is to duplicate all the state in the child, as would be expected
		2821	when I<either> the parent I<or> the child process continues.
		2822
		2823	When both processes want to continue using libev, then this is usually the
		2824	wrong result. In that case, usually one process (typically the parent) is
		2825	supposed to continue with all watchers in place as before, while the other
		2826	process typically wants to start fresh, i.e. without any active watchers.
		2827
		2828	The cleanest and most efficient way to achieve that with libev is to
		2829	simply create a new event loop, which of course will be "empty", and
		2830	use that for new watchers. This has the advantage of not touching more
		2831	memory than necessary, and thus avoiding the copy-on-write, and the
		2832	disadvantage of having to use multiple event loops (which do not support
		2833	signal watchers).
		2834
		2835	When this is not possible, or you want to use the default loop for
		2836	other reasons, then in the process that wants to start "fresh", call
		2837	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2838	the default loop will "orphan" (not stop) all registered watchers, so you
		2839	have to be careful not to execute code that modifies those watchers. Note
		2840	also that in that case, you have to re-register any signal watchers.
		2841
2220	=head3 Watcher-Specific Functions and Data Members	2842	=head3 Watcher-Specific Functions and Data Members
2221		2843
2222	=over 4	2844	=over 4
2223		2845
2224	=item ev_fork_init (ev_signal *, callback)	2846	=item ev_fork_init (ev_signal *, callback)
…		…
2256	is that the author does not know of a simple (or any) algorithm for a	2878	is that the author does not know of a simple (or any) algorithm for a
2257	multiple-writer-single-reader queue that works in all cases and doesn't	2879	multiple-writer-single-reader queue that works in all cases and doesn't
2258	need elaborate support such as pthreads.	2880	need elaborate support such as pthreads.
2259		2881
2260	That means that if you want to queue data, you have to provide your own	2882	That means that if you want to queue data, you have to provide your own
2261	queue. But at least I can tell you would implement locking around your	2883	queue. But at least I can tell you how to implement locking around your
2262	queue:	2884	queue:
2263		2885
2264	=over 4	2886	=over 4
2265		2887
2266	=item queueing from a signal handler context	2888	=item queueing from a signal handler context
2267		2889
2268	To implement race-free queueing, you simply add to the queue in the signal	2890	To implement race-free queueing, you simply add to the queue in the signal
2269	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2891	handler but you block the signal handler in the watcher callback. Here is
2270	some fictitious SIGUSR1 handler:	2892	an example that does that for some fictitious SIGUSR1 handler:
2271		2893
2272	static ev_async mysig;	2894	static ev_async mysig;
2273		2895
2274	static void	2896	static void
2275	sigusr1_handler (void)	2897	sigusr1_handler (void)
…		…
2341	=over 4	2963	=over 4
2342		2964
2343	=item ev_async_init (ev_async *, callback)	2965	=item ev_async_init (ev_async *, callback)
2344		2966
2345	Initialises and configures the async watcher - it has no parameters of any	2967	Initialises and configures the async watcher - it has no parameters of any
2346	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2968	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2347	believe me.	2969	trust me.
2348		2970
2349	=item ev_async_send (loop, ev_async *)	2971	=item ev_async_send (loop, ev_async *)
2350		2972
2351	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2973	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2352	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2974	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2353	C<ev_feed_event>, this call is safe to do in other threads, signal or	2975	C<ev_feed_event>, this call is safe to do from other threads, signal or
2354	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	2976	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2355	section below on what exactly this means).	2977	section below on what exactly this means).
2356		2978
		2979	Note that, as with other watchers in libev, multiple events might get
		2980	compressed into a single callback invocation (another way to look at this
		2981	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		2982	reset when the event loop detects that).
		2983
2357	This call incurs the overhead of a system call only once per loop iteration,	2984	This call incurs the overhead of a system call only once per event loop
2358	so while the overhead might be noticeable, it doesn't apply to repeated	2985	iteration, so while the overhead might be noticeable, it doesn't apply to
2359	calls to C<ev_async_send>.	2986	repeated calls to C<ev_async_send> for the same event loop.
2360		2987
2361	=item bool = ev_async_pending (ev_async *)	2988	=item bool = ev_async_pending (ev_async *)
2362		2989
2363	Returns a non-zero value when C<ev_async_send> has been called on the	2990	Returns a non-zero value when C<ev_async_send> has been called on the
2364	watcher but the event has not yet been processed (or even noted) by the	2991	watcher but the event has not yet been processed (or even noted) by the
…		…
2367	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	2994	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2368	the loop iterates next and checks for the watcher to have become active,	2995	the loop iterates next and checks for the watcher to have become active,
2369	it will reset the flag again. C<ev_async_pending> can be used to very	2996	it will reset the flag again. C<ev_async_pending> can be used to very
2370	quickly check whether invoking the loop might be a good idea.	2997	quickly check whether invoking the loop might be a good idea.
2371		2998
2372	Not that this does I<not> check whether the watcher itself is pending, only	2999	Not that this does I<not> check whether the watcher itself is pending,
2373	whether it has been requested to make this watcher pending.	3000	only whether it has been requested to make this watcher pending: there
		3001	is a time window between the event loop checking and resetting the async
		3002	notification, and the callback being invoked.
2374		3003
2375	=back	3004	=back
2376		3005
2377		3006
2378	=head1 OTHER FUNCTIONS	3007	=head1 OTHER FUNCTIONS
…		…
2382	=over 4	3011	=over 4
2383		3012
2384	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3013	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2385		3014
2386	This function combines a simple timer and an I/O watcher, calls your	3015	This function combines a simple timer and an I/O watcher, calls your
2387	callback on whichever event happens first and automatically stop both	3016	callback on whichever event happens first and automatically stops both
2388	watchers. This is useful if you want to wait for a single event on an fd	3017	watchers. This is useful if you want to wait for a single event on an fd
2389	or timeout without having to allocate/configure/start/stop/free one or	3018	or timeout without having to allocate/configure/start/stop/free one or
2390	more watchers yourself.	3019	more watchers yourself.
2391		3020
2392	If C<fd> is less than 0, then no I/O watcher will be started and events	3021	If C<fd> is less than 0, then no I/O watcher will be started and the
2393	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	3022	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2394	C<events> set will be created and started.	3023	the given C<fd> and C<events> set will be created and started.
2395		3024
2396	If C<timeout> is less than 0, then no timeout watcher will be	3025	If C<timeout> is less than 0, then no timeout watcher will be
2397	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3026	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2398	repeat = 0) will be started. While C<0> is a valid timeout, it is of	3027	repeat = 0) will be started. C<0> is a valid timeout.
2399	dubious value.
2400		3028
2401	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3029	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2402	passed an C<revents> set like normal event callbacks (a combination of	3030	passed an C<revents> set like normal event callbacks (a combination of
2403	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3031	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2404	value passed to C<ev_once>:	3032	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3033	a timeout and an io event at the same time - you probably should give io
		3034	events precedence.
		3035
		3036	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2405		3037
2406	static void stdin_ready (int revents, void *arg)	3038	static void stdin_ready (int revents, void *arg)
2407	{	3039	{
		3040	if (revents & EV_READ)
		3041	/* stdin might have data for us, joy! */;
2408	if (revents & EV_TIMEOUT)	3042	else if (revents & EV_TIMEOUT)
2409	/* doh, nothing entered */;	3043	/* doh, nothing entered */;
2410	else if (revents & EV_READ)
2411	/* stdin might have data for us, joy! */;
2412	}	3044	}
2413		3045
2414	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3046	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2415		3047
2416	=item ev_feed_event (ev_loop *, watcher *, int revents)	3048	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2417		3049
2418	Feeds the given event set into the event loop, as if the specified event	3050	Feeds the given event set into the event loop, as if the specified event
2419	had happened for the specified watcher (which must be a pointer to an	3051	had happened for the specified watcher (which must be a pointer to an
2420	initialised but not necessarily started event watcher).	3052	initialised but not necessarily started event watcher).
2421		3053
2422	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3054	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2423		3055
2424	Feed an event on the given fd, as if a file descriptor backend detected	3056	Feed an event on the given fd, as if a file descriptor backend detected
2425	the given events it.	3057	the given events it.
2426		3058
2427	=item ev_feed_signal_event (ev_loop *loop, int signum)	3059	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2428		3060
2429	Feed an event as if the given signal occurred (C<loop> must be the default	3061	Feed an event as if the given signal occurred (C<loop> must be the default
2430	loop!).	3062	loop!).
2431		3063
2432	=back	3064	=back
…		…
2554		3186
2555	myclass obj;	3187	myclass obj;
2556	ev::io iow;	3188	ev::io iow;
2557	iow.set <myclass, &myclass::io_cb> (&obj);	3189	iow.set <myclass, &myclass::io_cb> (&obj);
2558		3190
		3191	=item w->set (object *)
		3192
		3193	This is an B<experimental> feature that might go away in a future version.
		3194
		3195	This is a variation of a method callback - leaving out the method to call
		3196	will default the method to C<operator ()>, which makes it possible to use
		3197	functor objects without having to manually specify the C<operator ()> all
		3198	the time. Incidentally, you can then also leave out the template argument
		3199	list.
		3200
		3201	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3202	int revents)>.
		3203
		3204	See the method-C<set> above for more details.
		3205
		3206	Example: use a functor object as callback.
		3207
		3208	struct myfunctor
		3209	{
		3210	void operator() (ev::io &w, int revents)
		3211	{
		3212	...
		3213	}
		3214	}
		3215
		3216	myfunctor f;
		3217
		3218	ev::io w;
		3219	w.set (&f);
		3220
2559	=item w->set<function> (void *data = 0)	3221	=item w->set<function> (void *data = 0)
2560		3222
2561	Also sets a callback, but uses a static method or plain function as	3223	Also sets a callback, but uses a static method or plain function as
2562	callback. The optional C<data> argument will be stored in the watcher's	3224	callback. The optional C<data> argument will be stored in the watcher's
2563	C<data> member and is free for you to use.	3225	C<data> member and is free for you to use.
2564		3226
2565	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3227	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2566		3228
2567	See the method-C<set> above for more details.	3229	See the method-C<set> above for more details.
2568		3230
2569	Example:	3231	Example: Use a plain function as callback.
2570		3232
2571	static void io_cb (ev::io &w, int revents) { }	3233	static void io_cb (ev::io &w, int revents) { }
2572	iow.set <io_cb> ();	3234	iow.set <io_cb> ();
2573		3235
2574	=item w->set (struct ev_loop *)	3236	=item w->set (struct ev_loop *)
…		…
2612	Example: Define a class with an IO and idle watcher, start one of them in	3274	Example: Define a class with an IO and idle watcher, start one of them in
2613	the constructor.	3275	the constructor.
2614		3276
2615	class myclass	3277	class myclass
2616	{	3278	{
2617	ev::io io; void io_cb (ev::io &w, int revents);	3279	ev::io io ; void io_cb (ev::io &w, int revents);
2618	ev:idle idle void idle_cb (ev::idle &w, int revents);	3280	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2619		3281
2620	myclass (int fd)	3282	myclass (int fd)
2621	{	3283	{
2622	io .set <myclass, &myclass::io_cb > (this);	3284	io .set <myclass, &myclass::io_cb > (this);
2623	idle.set <myclass, &myclass::idle_cb> (this);	3285	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2639	=item Perl	3301	=item Perl
2640		3302
2641	The EV module implements the full libev API and is actually used to test	3303	The EV module implements the full libev API and is actually used to test
2642	libev. EV is developed together with libev. Apart from the EV core module,	3304	libev. EV is developed together with libev. Apart from the EV core module,
2643	there are additional modules that implement libev-compatible interfaces	3305	there are additional modules that implement libev-compatible interfaces
2644	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3306	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2645	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3307	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3308	and C<EV::Glib>).
2646		3309
2647	It can be found and installed via CPAN, its homepage is at	3310	It can be found and installed via CPAN, its homepage is at
2648	L<http://software.schmorp.de/pkg/EV>.	3311	L<http://software.schmorp.de/pkg/EV>.
2649		3312
2650	=item Python	3313	=item Python
2651		3314
2652	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3315	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2653	seems to be quite complete and well-documented. Note, however, that the	3316	seems to be quite complete and well-documented.
2654	patch they require for libev is outright dangerous as it breaks the ABI
2655	for everybody else, and therefore, should never be applied in an installed
2656	libev (if python requires an incompatible ABI then it needs to embed
2657	libev).
2658		3317
2659	=item Ruby	3318	=item Ruby
2660		3319
2661	Tony Arcieri has written a ruby extension that offers access to a subset	3320	Tony Arcieri has written a ruby extension that offers access to a subset
2662	of the libev API and adds file handle abstractions, asynchronous DNS and	3321	of the libev API and adds file handle abstractions, asynchronous DNS and
2663	more on top of it. It can be found via gem servers. Its homepage is at	3322	more on top of it. It can be found via gem servers. Its homepage is at
2664	L<http://rev.rubyforge.org/>.	3323	L<http://rev.rubyforge.org/>.
2665		3324
		3325	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3326	makes rev work even on mingw.
		3327
		3328	=item Haskell
		3329
		3330	A haskell binding to libev is available at
		3331	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3332
2666	=item D	3333	=item D
2667		3334
2668	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3335	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2669	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	3336	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3337
		3338	=item Ocaml
		3339
		3340	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3341	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2670		3342
2671	=back	3343	=back
2672		3344
2673		3345
2674	=head1 MACRO MAGIC	3346	=head1 MACRO MAGIC
…		…
2775		3447
2776	#define EV_STANDALONE 1	3448	#define EV_STANDALONE 1
2777	#include "ev.h"	3449	#include "ev.h"
2778		3450
2779	Both header files and implementation files can be compiled with a C++	3451	Both header files and implementation files can be compiled with a C++
2780	compiler (at least, thats a stated goal, and breakage will be treated	3452	compiler (at least, that's a stated goal, and breakage will be treated
2781	as a bug).	3453	as a bug).
2782		3454
2783	You need the following files in your source tree, or in a directory	3455	You need the following files in your source tree, or in a directory
2784	in your include path (e.g. in libev/ when using -Ilibev):	3456	in your include path (e.g. in libev/ when using -Ilibev):
2785		3457
…		…
2829		3501
2830	=head2 PREPROCESSOR SYMBOLS/MACROS	3502	=head2 PREPROCESSOR SYMBOLS/MACROS
2831		3503
2832	Libev can be configured via a variety of preprocessor symbols you have to	3504	Libev can be configured via a variety of preprocessor symbols you have to
2833	define before including any of its files. The default in the absence of	3505	define before including any of its files. The default in the absence of
2834	autoconf is noted for every option.	3506	autoconf is documented for every option.
2835		3507
2836	=over 4	3508	=over 4
2837		3509
2838	=item EV_STANDALONE	3510	=item EV_STANDALONE
2839		3511
…		…
2841	keeps libev from including F<config.h>, and it also defines dummy	3513	keeps libev from including F<config.h>, and it also defines dummy
2842	implementations for some libevent functions (such as logging, which is not	3514	implementations for some libevent functions (such as logging, which is not
2843	supported). It will also not define any of the structs usually found in	3515	supported). It will also not define any of the structs usually found in
2844	F<event.h> that are not directly supported by the libev core alone.	3516	F<event.h> that are not directly supported by the libev core alone.
2845		3517
		3518	In stanbdalone mode, libev will still try to automatically deduce the
		3519	configuration, but has to be more conservative.
		3520
2846	=item EV_USE_MONOTONIC	3521	=item EV_USE_MONOTONIC
2847		3522
2848	If defined to be C<1>, libev will try to detect the availability of the	3523	If defined to be C<1>, libev will try to detect the availability of the
2849	monotonic clock option at both compile time and runtime. Otherwise no use	3524	monotonic clock option at both compile time and runtime. Otherwise no
2850	of the monotonic clock option will be attempted. If you enable this, you	3525	use of the monotonic clock option will be attempted. If you enable this,
2851	usually have to link against librt or something similar. Enabling it when	3526	you usually have to link against librt or something similar. Enabling it
2852	the functionality isn't available is safe, though, although you have	3527	when the functionality isn't available is safe, though, although you have
2853	to make sure you link against any libraries where the C<clock_gettime>	3528	to make sure you link against any libraries where the C<clock_gettime>
2854	function is hiding in (often F<-lrt>).	3529	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2855		3530
2856	=item EV_USE_REALTIME	3531	=item EV_USE_REALTIME
2857		3532
2858	If defined to be C<1>, libev will try to detect the availability of the	3533	If defined to be C<1>, libev will try to detect the availability of the
2859	real-time clock option at compile time (and assume its availability at	3534	real-time clock option at compile time (and assume its availability
2860	runtime if successful). Otherwise no use of the real-time clock option will	3535	at runtime if successful). Otherwise no use of the real-time clock
2861	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3536	option will be attempted. This effectively replaces C<gettimeofday>
2862	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3537	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2863	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3538	correctness. See the note about libraries in the description of
		3539	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3540	C<EV_USE_CLOCK_SYSCALL>.
		3541
		3542	=item EV_USE_CLOCK_SYSCALL
		3543
		3544	If defined to be C<1>, libev will try to use a direct syscall instead
		3545	of calling the system-provided C<clock_gettime> function. This option
		3546	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3547	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3548	programs needlessly. Using a direct syscall is slightly slower (in
		3549	theory), because no optimised vdso implementation can be used, but avoids
		3550	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3551	higher, as it simplifies linking (no need for C<-lrt>).
2864		3552
2865	=item EV_USE_NANOSLEEP	3553	=item EV_USE_NANOSLEEP
2866		3554
2867	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3555	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2868	and will use it for delays. Otherwise it will use C<select ()>.	3556	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2884		3572
2885	=item EV_SELECT_USE_FD_SET	3573	=item EV_SELECT_USE_FD_SET
2886		3574
2887	If defined to C<1>, then the select backend will use the system C<fd_set>	3575	If defined to C<1>, then the select backend will use the system C<fd_set>
2888	structure. This is useful if libev doesn't compile due to a missing	3576	structure. This is useful if libev doesn't compile due to a missing
2889	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3577	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2890	exotic systems. This usually limits the range of file descriptors to some	3578	on exotic systems. This usually limits the range of file descriptors to
2891	low limit such as 1024 or might have other limitations (winsocket only	3579	some low limit such as 1024 or might have other limitations (winsocket
2892	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3580	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2893	influence the size of the C<fd_set> used.	3581	configures the maximum size of the C<fd_set>.
2894		3582
2895	=item EV_SELECT_IS_WINSOCKET	3583	=item EV_SELECT_IS_WINSOCKET
2896		3584
2897	When defined to C<1>, the select backend will assume that	3585	When defined to C<1>, the select backend will assume that
2898	select/socket/connect etc. don't understand file descriptors but	3586	select/socket/connect etc. don't understand file descriptors but
…		…
3009	When doing priority-based operations, libev usually has to linearly search	3697	When doing priority-based operations, libev usually has to linearly search
3010	all the priorities, so having many of them (hundreds) uses a lot of space	3698	all the priorities, so having many of them (hundreds) uses a lot of space
3011	and time, so using the defaults of five priorities (-2 .. +2) is usually	3699	and time, so using the defaults of five priorities (-2 .. +2) is usually
3012	fine.	3700	fine.
3013		3701
3014	If your embedding application does not need any priorities, defining these both to	3702	If your embedding application does not need any priorities, defining these
3015	C<0> will save some memory and CPU.	3703	both to C<0> will save some memory and CPU.
3016		3704
3017	=item EV_PERIODIC_ENABLE	3705	=item EV_PERIODIC_ENABLE
3018		3706
3019	If undefined or defined to be C<1>, then periodic timers are supported. If	3707	If undefined or defined to be C<1>, then periodic timers are supported. If
3020	defined to be C<0>, then they are not. Disabling them saves a few kB of	3708	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3027	code.	3715	code.
3028		3716
3029	=item EV_EMBED_ENABLE	3717	=item EV_EMBED_ENABLE
3030		3718
3031	If undefined or defined to be C<1>, then embed watchers are supported. If	3719	If undefined or defined to be C<1>, then embed watchers are supported. If
3032	defined to be C<0>, then they are not.	3720	defined to be C<0>, then they are not. Embed watchers rely on most other
		3721	watcher types, which therefore must not be disabled.
3033		3722
3034	=item EV_STAT_ENABLE	3723	=item EV_STAT_ENABLE
3035		3724
3036	If undefined or defined to be C<1>, then stat watchers are supported. If	3725	If undefined or defined to be C<1>, then stat watchers are supported. If
3037	defined to be C<0>, then they are not.	3726	defined to be C<0>, then they are not.
…		…
3047	defined to be C<0>, then they are not.	3736	defined to be C<0>, then they are not.
3048		3737
3049	=item EV_MINIMAL	3738	=item EV_MINIMAL
3050		3739
3051	If you need to shave off some kilobytes of code at the expense of some	3740	If you need to shave off some kilobytes of code at the expense of some
3052	speed, define this symbol to C<1>. Currently this is used to override some	3741	speed (but with the full API), define this symbol to C<1>. Currently this
3053	inlining decisions, saves roughly 30% code size on amd64. It also selects a	3742	is used to override some inlining decisions, saves roughly 30% code size
3054	much smaller 2-heap for timer management over the default 4-heap.	3743	on amd64. It also selects a much smaller 2-heap for timer management over
		3744	the default 4-heap.
		3745
		3746	You can save even more by disabling watcher types you do not need
		3747	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>
		3748	(C<-DNDEBUG>) will usually reduce code size a lot.
		3749
		3750	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to
		3751	provide a bare-bones event library. See C<ev.h> for details on what parts
		3752	of the API are still available, and do not complain if this subset changes
		3753	over time.
3055		3754
3056	=item EV_PID_HASHSIZE	3755	=item EV_PID_HASHSIZE
3057		3756
3058	C<ev_child> watchers use a small hash table to distribute workload by	3757	C<ev_child> watchers use a small hash table to distribute workload by
3059	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3758	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
3069	two).	3768	two).
3070		3769
3071	=item EV_USE_4HEAP	3770	=item EV_USE_4HEAP
3072		3771
3073	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3772	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3074	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3773	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3075	to C<1>. The 4-heap uses more complicated (longer) code but has	3774	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3076	noticeably faster performance with many (thousands) of watchers.	3775	faster performance with many (thousands) of watchers.
3077		3776
3078	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3777	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3079	(disabled).	3778	(disabled).
3080		3779
3081	=item EV_HEAP_CACHE_AT	3780	=item EV_HEAP_CACHE_AT
3082		3781
3083	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3782	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3084	timer and periodics heap, libev can cache the timestamp (I<at>) within	3783	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3085	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3784	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3086	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3785	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3087	but avoids random read accesses on heap changes. This improves performance	3786	but avoids random read accesses on heap changes. This improves performance
3088	noticeably with with many (hundreds) of watchers.	3787	noticeably with many (hundreds) of watchers.
3089		3788
3090	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3789	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3091	(disabled).	3790	(disabled).
3092		3791
3093	=item EV_VERIFY	3792	=item EV_VERIFY
…		…
3099	called once per loop, which can slow down libev. If set to C<3>, then the	3798	called once per loop, which can slow down libev. If set to C<3>, then the
3100	verification code will be called very frequently, which will slow down	3799	verification code will be called very frequently, which will slow down
3101	libev considerably.	3800	libev considerably.
3102		3801
3103	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3802	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3104	C<0.>	3803	C<0>.
3105		3804
3106	=item EV_COMMON	3805	=item EV_COMMON
3107		3806
3108	By default, all watchers have a C<void *data> member. By redefining	3807	By default, all watchers have a C<void *data> member. By redefining
3109	this macro to a something else you can include more and other types of	3808	this macro to a something else you can include more and other types of
…		…
3126	and the way callbacks are invoked and set. Must expand to a struct member	3825	and the way callbacks are invoked and set. Must expand to a struct member
3127	definition and a statement, respectively. See the F<ev.h> header file for	3826	definition and a statement, respectively. See the F<ev.h> header file for
3128	their default definitions. One possible use for overriding these is to	3827	their default definitions. One possible use for overriding these is to
3129	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3828	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3130	method calls instead of plain function calls in C++.	3829	method calls instead of plain function calls in C++.
		3830
		3831	=back
3131		3832
3132	=head2 EXPORTED API SYMBOLS	3833	=head2 EXPORTED API SYMBOLS
3133		3834
3134	If you need to re-export the API (e.g. via a DLL) and you need a list of	3835	If you need to re-export the API (e.g. via a DLL) and you need a list of
3135	exported symbols, you can use the provided F<Symbol.*> files which list	3836	exported symbols, you can use the provided F<Symbol.*> files which list
…		…
3182	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3883	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3183		3884
3184	#include "ev_cpp.h"	3885	#include "ev_cpp.h"
3185	#include "ev.c"	3886	#include "ev.c"
3186		3887
		3888	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3187		3889
3188	=head1 THREADS AND COROUTINES	3890	=head2 THREADS AND COROUTINES
3189		3891
3190	=head2 THREADS	3892	=head3 THREADS
3191		3893
3192	Libev itself is completely thread-safe, but it uses no locking. This	3894	All libev functions are reentrant and thread-safe unless explicitly
		3895	documented otherwise, but libev implements no locking itself. This means
3193	means that you can use as many loops as you want in parallel, as long as	3896	that you can use as many loops as you want in parallel, as long as there
3194	only one thread ever calls into one libev function with the same loop	3897	are no concurrent calls into any libev function with the same loop
3195	parameter.	3898	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3899	of course): libev guarantees that different event loops share no data
		3900	structures that need any locking.
3196		3901
3197	Or put differently: calls with different loop parameters can be done in	3902	Or to put it differently: calls with different loop parameters can be done
3198	parallel from multiple threads, calls with the same loop parameter must be	3903	concurrently from multiple threads, calls with the same loop parameter
3199	done serially (but can be done from different threads, as long as only one	3904	must be done serially (but can be done from different threads, as long as
3200	thread ever is inside a call at any point in time, e.g. by using a mutex	3905	only one thread ever is inside a call at any point in time, e.g. by using
3201	per loop).	3906	a mutex per loop).
		3907
		3908	Specifically to support threads (and signal handlers), libev implements
		3909	so-called C<ev_async> watchers, which allow some limited form of
		3910	concurrency on the same event loop, namely waking it up "from the
		3911	outside".
3202		3912
3203	If you want to know which design (one loop, locking, or multiple loops	3913	If you want to know which design (one loop, locking, or multiple loops
3204	without or something else still) is best for your problem, then I cannot	3914	without or something else still) is best for your problem, then I cannot
3205	help you. I can give some generic advice however:	3915	help you, but here is some generic advice:
3206		3916
3207	=over 4	3917	=over 4
3208		3918
3209	=item * most applications have a main thread: use the default libev loop	3919	=item * most applications have a main thread: use the default libev loop
3210	in that thread, or create a separate thread running only the default loop.	3920	in that thread, or create a separate thread running only the default loop.
…		…
3222		3932
3223	Choosing a model is hard - look around, learn, know that usually you can do	3933	Choosing a model is hard - look around, learn, know that usually you can do
3224	better than you currently do :-)	3934	better than you currently do :-)
3225		3935
3226	=item * often you need to talk to some other thread which blocks in the	3936	=item * often you need to talk to some other thread which blocks in the
		3937	event loop.
		3938
3227	event loop - C<ev_async> watchers can be used to wake them up from other	3939	C<ev_async> watchers can be used to wake them up from other threads safely
3228	threads safely (or from signal contexts...).	3940	(or from signal contexts...).
		3941
		3942	An example use would be to communicate signals or other events that only
		3943	work in the default loop by registering the signal watcher with the
		3944	default loop and triggering an C<ev_async> watcher from the default loop
		3945	watcher callback into the event loop interested in the signal.
3229		3946
3230	=back	3947	=back
3231		3948
		3949	=head4 THREAD LOCKING EXAMPLE
		3950
		3951	Here is a fictitious example of how to run an event loop in a different
		3952	thread than where callbacks are being invoked and watchers are
		3953	created/added/removed.
		3954
		3955	For a real-world example, see the C<EV::Loop::Async> perl module,
		3956	which uses exactly this technique (which is suited for many high-level
		3957	languages).
		3958
		3959	The example uses a pthread mutex to protect the loop data, a condition
		3960	variable to wait for callback invocations, an async watcher to notify the
		3961	event loop thread and an unspecified mechanism to wake up the main thread.
		3962
		3963	First, you need to associate some data with the event loop:
		3964
		3965	typedef struct {
		3966	mutex_t lock; /* global loop lock */
		3967	ev_async async_w;
		3968	thread_t tid;
		3969	cond_t invoke_cv;
		3970	} userdata;
		3971
		3972	void prepare_loop (EV_P)
		3973	{
		3974	// for simplicity, we use a static userdata struct.
		3975	static userdata u;
		3976
		3977	ev_async_init (&u->async_w, async_cb);
		3978	ev_async_start (EV_A_ &u->async_w);
		3979
		3980	pthread_mutex_init (&u->lock, 0);
		3981	pthread_cond_init (&u->invoke_cv, 0);
		3982
		3983	// now associate this with the loop
		3984	ev_set_userdata (EV_A_ u);
		3985	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3986	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3987
		3988	// then create the thread running ev_loop
		3989	pthread_create (&u->tid, 0, l_run, EV_A);
		3990	}
		3991
		3992	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3993	solely to wake up the event loop so it takes notice of any new watchers
		3994	that might have been added:
		3995
		3996	static void
		3997	async_cb (EV_P_ ev_async *w, int revents)
		3998	{
		3999	// just used for the side effects
		4000	}
		4001
		4002	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4003	protecting the loop data, respectively.
		4004
		4005	static void
		4006	l_release (EV_P)
		4007	{
		4008	userdata *u = ev_userdata (EV_A);
		4009	pthread_mutex_unlock (&u->lock);
		4010	}
		4011
		4012	static void
		4013	l_acquire (EV_P)
		4014	{
		4015	userdata *u = ev_userdata (EV_A);
		4016	pthread_mutex_lock (&u->lock);
		4017	}
		4018
		4019	The event loop thread first acquires the mutex, and then jumps straight
		4020	into C<ev_loop>:
		4021
		4022	void *
		4023	l_run (void *thr_arg)
		4024	{
		4025	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4026
		4027	l_acquire (EV_A);
		4028	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4029	ev_loop (EV_A_ 0);
		4030	l_release (EV_A);
		4031
		4032	return 0;
		4033	}
		4034
		4035	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4036	signal the main thread via some unspecified mechanism (signals? pipe
		4037	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4038	have been called (in a while loop because a) spurious wakeups are possible
		4039	and b) skipping inter-thread-communication when there are no pending
		4040	watchers is very beneficial):
		4041
		4042	static void
		4043	l_invoke (EV_P)
		4044	{
		4045	userdata *u = ev_userdata (EV_A);
		4046
		4047	while (ev_pending_count (EV_A))
		4048	{
		4049	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4050	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4051	}
		4052	}
		4053
		4054	Now, whenever the main thread gets told to invoke pending watchers, it
		4055	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4056	thread to continue:
		4057
		4058	static void
		4059	real_invoke_pending (EV_P)
		4060	{
		4061	userdata *u = ev_userdata (EV_A);
		4062
		4063	pthread_mutex_lock (&u->lock);
		4064	ev_invoke_pending (EV_A);
		4065	pthread_cond_signal (&u->invoke_cv);
		4066	pthread_mutex_unlock (&u->lock);
		4067	}
		4068
		4069	Whenever you want to start/stop a watcher or do other modifications to an
		4070	event loop, you will now have to lock:
		4071
		4072	ev_timer timeout_watcher;
		4073	userdata *u = ev_userdata (EV_A);
		4074
		4075	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4076
		4077	pthread_mutex_lock (&u->lock);
		4078	ev_timer_start (EV_A_ &timeout_watcher);
		4079	ev_async_send (EV_A_ &u->async_w);
		4080	pthread_mutex_unlock (&u->lock);
		4081
		4082	Note that sending the C<ev_async> watcher is required because otherwise
		4083	an event loop currently blocking in the kernel will have no knowledge
		4084	about the newly added timer. By waking up the loop it will pick up any new
		4085	watchers in the next event loop iteration.
		4086
3232	=head2 COROUTINES	4087	=head3 COROUTINES
3233		4088
3234	Libev is much more accommodating to coroutines ("cooperative threads"):	4089	Libev is very accommodating to coroutines ("cooperative threads"):
3235	libev fully supports nesting calls to it's functions from different	4090	libev fully supports nesting calls to its functions from different
3236	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4091	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3237	different coroutines and switch freely between both coroutines running the	4092	different coroutines, and switch freely between both coroutines running
3238	loop, as long as you don't confuse yourself). The only exception is that	4093	the loop, as long as you don't confuse yourself). The only exception is
3239	you must not do this from C<ev_periodic> reschedule callbacks.	4094	that you must not do this from C<ev_periodic> reschedule callbacks.
3240		4095
3241	Care has been invested into making sure that libev does not keep local	4096	Care has been taken to ensure that libev does not keep local state inside
3242	state inside C<ev_loop>, and other calls do not usually allow coroutine	4097	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3243	switches.	4098	they do not call any callbacks.
3244		4099
		4100	=head2 COMPILER WARNINGS
3245		4101
3246	=head1 COMPLEXITIES	4102	Depending on your compiler and compiler settings, you might get no or a
		4103	lot of warnings when compiling libev code. Some people are apparently
		4104	scared by this.
3247		4105
3248	In this section the complexities of (many of) the algorithms used inside	4106	However, these are unavoidable for many reasons. For one, each compiler
3249	libev will be explained. For complexity discussions about backends see the	4107	has different warnings, and each user has different tastes regarding
3250	documentation for C<ev_default_init>.	4108	warning options. "Warn-free" code therefore cannot be a goal except when
		4109	targeting a specific compiler and compiler-version.
3251		4110
3252	All of the following are about amortised time: If an array needs to be	4111	Another reason is that some compiler warnings require elaborate
3253	extended, libev needs to realloc and move the whole array, but this	4112	workarounds, or other changes to the code that make it less clear and less
3254	happens asymptotically never with higher number of elements, so O(1) might	4113	maintainable.
3255	mean it might do a lengthy realloc operation in rare cases, but on average
3256	it is much faster and asymptotically approaches constant time.
3257		4114
3258	=over 4	4115	And of course, some compiler warnings are just plain stupid, or simply
		4116	wrong (because they don't actually warn about the condition their message
		4117	seems to warn about). For example, certain older gcc versions had some
		4118	warnings that resulted an extreme number of false positives. These have
		4119	been fixed, but some people still insist on making code warn-free with
		4120	such buggy versions.
3259		4121
3260	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	4122	While libev is written to generate as few warnings as possible,
		4123	"warn-free" code is not a goal, and it is recommended not to build libev
		4124	with any compiler warnings enabled unless you are prepared to cope with
		4125	them (e.g. by ignoring them). Remember that warnings are just that:
		4126	warnings, not errors, or proof of bugs.
3261		4127
3262	This means that, when you have a watcher that triggers in one hour and
3263	there are 100 watchers that would trigger before that then inserting will
3264	have to skip roughly seven (C<ld 100>) of these watchers.
3265		4128
3266	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	4129	=head2 VALGRIND
3267		4130
3268	That means that changing a timer costs less than removing/adding them	4131	Valgrind has a special section here because it is a popular tool that is
3269	as only the relative motion in the event queue has to be paid for.	4132	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3270		4133
3271	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	4134	If you think you found a bug (memory leak, uninitialised data access etc.)
		4135	in libev, then check twice: If valgrind reports something like:
3272		4136
3273	These just add the watcher into an array or at the head of a list.	4137	==2274== definitely lost: 0 bytes in 0 blocks.
		4138	==2274== possibly lost: 0 bytes in 0 blocks.
		4139	==2274== still reachable: 256 bytes in 1 blocks.
3274		4140
3275	=item Stopping check/prepare/idle/fork/async watchers: O(1)	4141	Then there is no memory leak, just as memory accounted to global variables
		4142	is not a memleak - the memory is still being referenced, and didn't leak.
3276		4143
3277	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	4144	Similarly, under some circumstances, valgrind might report kernel bugs
		4145	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		4146	although an acceptable workaround has been found here), or it might be
		4147	confused.
3278		4148
3279	These watchers are stored in lists then need to be walked to find the	4149	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3280	correct watcher to remove. The lists are usually short (you don't usually	4150	make it into some kind of religion.
3281	have many watchers waiting for the same fd or signal).
3282		4151
3283	=item Finding the next timer in each loop iteration: O(1)	4152	If you are unsure about something, feel free to contact the mailing list
		4153	with the full valgrind report and an explanation on why you think this
		4154	is a bug in libev (best check the archives, too :). However, don't be
		4155	annoyed when you get a brisk "this is no bug" answer and take the chance
		4156	of learning how to interpret valgrind properly.
3284		4157
3285	By virtue of using a binary or 4-heap, the next timer is always found at a	4158	If you need, for some reason, empty reports from valgrind for your project
3286	fixed position in the storage array.	4159	I suggest using suppression lists.
3287		4160
3288	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3289		4161
3290	A change means an I/O watcher gets started or stopped, which requires	4162	=head1 PORTABILITY NOTES
3291	libev to recalculate its status (and possibly tell the kernel, depending
3292	on backend and whether C<ev_io_set> was used).
3293		4163
3294	=item Activating one watcher (putting it into the pending state): O(1)
3295
3296	=item Priority handling: O(number_of_priorities)
3297
3298	Priorities are implemented by allocating some space for each
3299	priority. When doing priority-based operations, libev usually has to
3300	linearly search all the priorities, but starting/stopping and activating
3301	watchers becomes O(1) w.r.t. priority handling.
3302
3303	=item Sending an ev_async: O(1)
3304
3305	=item Processing ev_async_send: O(number_of_async_watchers)
3306
3307	=item Processing signals: O(max_signal_number)
3308
3309	Sending involves a system call I<iff> there were no other C<ev_async_send>
3310	calls in the current loop iteration. Checking for async and signal events
3311	involves iterating over all running async watchers or all signal numbers.
3312
3313	=back
3314
3315
3316	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4164	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3317		4165
3318	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4166	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3319	requires, and its I/O model is fundamentally incompatible with the POSIX	4167	requires, and its I/O model is fundamentally incompatible with the POSIX
3320	model. Libev still offers limited functionality on this platform in	4168	model. Libev still offers limited functionality on this platform in
3321	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4169	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3328	way (note also that glib is the slowest event library known to man).	4176	way (note also that glib is the slowest event library known to man).
3329		4177
3330	There is no supported compilation method available on windows except	4178	There is no supported compilation method available on windows except
3331	embedding it into other applications.	4179	embedding it into other applications.
3332		4180
		4181	Sensible signal handling is officially unsupported by Microsoft - libev
		4182	tries its best, but under most conditions, signals will simply not work.
		4183
3333	Not a libev limitation but worth mentioning: windows apparently doesn't	4184	Not a libev limitation but worth mentioning: windows apparently doesn't
3334	accept large writes: instead of resulting in a partial write, windows will	4185	accept large writes: instead of resulting in a partial write, windows will
3335	either accept everything or return C<ENOBUFS> if the buffer is too large,	4186	either accept everything or return C<ENOBUFS> if the buffer is too large,
3336	so make sure you only write small amounts into your sockets (less than a	4187	so make sure you only write small amounts into your sockets (less than a
3337	megabyte seems safe, but thsi apparently depends on the amount of memory	4188	megabyte seems safe, but this apparently depends on the amount of memory
3338	available).	4189	available).
3339		4190
3340	Due to the many, low, and arbitrary limits on the win32 platform and	4191	Due to the many, low, and arbitrary limits on the win32 platform and
3341	the abysmal performance of winsockets, using a large number of sockets	4192	the abysmal performance of winsockets, using a large number of sockets
3342	is not recommended (and not reasonable). If your program needs to use	4193	is not recommended (and not reasonable). If your program needs to use
3343	more than a hundred or so sockets, then likely it needs to use a totally	4194	more than a hundred or so sockets, then likely it needs to use a totally
3344	different implementation for windows, as libev offers the POSIX readiness	4195	different implementation for windows, as libev offers the POSIX readiness
3345	notification model, which cannot be implemented efficiently on windows	4196	notification model, which cannot be implemented efficiently on windows
3346	(Microsoft monopoly games).	4197	(due to Microsoft monopoly games).
3347		4198
3348	A typical way to use libev under windows is to embed it (see the embedding	4199	A typical way to use libev under windows is to embed it (see the embedding
3349	section for details) and use the following F<evwrap.h> header file instead	4200	section for details) and use the following F<evwrap.h> header file instead
3350	of F<ev.h>:	4201	of F<ev.h>:
3351		4202
…		…
3353	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	4204	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3354		4205
3355	#include "ev.h"	4206	#include "ev.h"
3356		4207
3357	And compile the following F<evwrap.c> file into your project (make sure	4208	And compile the following F<evwrap.c> file into your project (make sure
3358	you do I<not> compile the F<ev.c> or any other embedded soruce files!):	4209	you do I<not> compile the F<ev.c> or any other embedded source files!):
3359		4210
3360	#include "evwrap.h"	4211	#include "evwrap.h"
3361	#include "ev.c"	4212	#include "ev.c"
3362		4213
3363	=over 4	4214	=over 4
…		…
3387		4238
3388	Early versions of winsocket's select only supported waiting for a maximum	4239	Early versions of winsocket's select only supported waiting for a maximum
3389	of C<64> handles (probably owning to the fact that all windows kernels	4240	of C<64> handles (probably owning to the fact that all windows kernels
3390	can only wait for C<64> things at the same time internally; Microsoft	4241	can only wait for C<64> things at the same time internally; Microsoft
3391	recommends spawning a chain of threads and wait for 63 handles and the	4242	recommends spawning a chain of threads and wait for 63 handles and the
3392	previous thread in each. Great).	4243	previous thread in each. Sounds great!).
3393		4244
3394	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4245	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3395	to some high number (e.g. C<2048>) before compiling the winsocket select	4246	to some high number (e.g. C<2048>) before compiling the winsocket select
3396	call (which might be in libev or elsewhere, for example, perl does its own	4247	call (which might be in libev or elsewhere, for example, perl and many
3397	select emulation on windows).	4248	other interpreters do their own select emulation on windows).
3398		4249
3399	Another limit is the number of file descriptors in the Microsoft runtime	4250	Another limit is the number of file descriptors in the Microsoft runtime
3400	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4251	libraries, which by default is C<64> (there must be a hidden I<64>
3401	or something like this inside Microsoft). You can increase this by calling	4252	fetish or something like this inside Microsoft). You can increase this
3402	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4253	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3403	arbitrary limit), but is broken in many versions of the Microsoft runtime	4254	(another arbitrary limit), but is broken in many versions of the Microsoft
3404	libraries.
3405
3406	This might get you to about C<512> or C<2048> sockets (depending on	4255	runtime libraries. This might get you to about C<512> or C<2048> sockets
3407	windows version and/or the phase of the moon). To get more, you need to	4256	(depending on windows version and/or the phase of the moon). To get more,
3408	wrap all I/O functions and provide your own fd management, but the cost of	4257	you need to wrap all I/O functions and provide your own fd management, but
3409	calling select (O(n²)) will likely make this unworkable.	4258	the cost of calling select (O(n²)) will likely make this unworkable.
3410		4259
3411	=back	4260	=back
3412		4261
3413
3414	=head1 PORTABILITY REQUIREMENTS	4262	=head2 PORTABILITY REQUIREMENTS
3415		4263
3416	In addition to a working ISO-C implementation, libev relies on a few	4264	In addition to a working ISO-C implementation and of course the
3417	additional extensions:	4265	backend-specific APIs, libev relies on a few additional extensions:
3418		4266
3419	=over 4	4267	=over 4
3420		4268
3421	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	4269	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3422	calling conventions regardless of C<ev_watcher_type *>.	4270	calling conventions regardless of C<ev_watcher_type *>.
…		…
3428	calls them using an C<ev_watcher *> internally.	4276	calls them using an C<ev_watcher *> internally.
3429		4277
3430	=item C<sig_atomic_t volatile> must be thread-atomic as well	4278	=item C<sig_atomic_t volatile> must be thread-atomic as well
3431		4279
3432	The type C<sig_atomic_t volatile> (or whatever is defined as	4280	The type C<sig_atomic_t volatile> (or whatever is defined as
3433	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	4281	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3434	threads. This is not part of the specification for C<sig_atomic_t>, but is	4282	threads. This is not part of the specification for C<sig_atomic_t>, but is
3435	believed to be sufficiently portable.	4283	believed to be sufficiently portable.
3436		4284
3437	=item C<sigprocmask> must work in a threaded environment	4285	=item C<sigprocmask> must work in a threaded environment
3438		4286
…		…
3447	except the initial one, and run the default loop in the initial thread as	4295	except the initial one, and run the default loop in the initial thread as
3448	well.	4296	well.
3449		4297
3450	=item C<long> must be large enough for common memory allocation sizes	4298	=item C<long> must be large enough for common memory allocation sizes
3451		4299
3452	To improve portability and simplify using libev, libev uses C<long>	4300	To improve portability and simplify its API, libev uses C<long> internally
3453	internally instead of C<size_t> when allocating its data structures. On	4301	instead of C<size_t> when allocating its data structures. On non-POSIX
3454	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4302	systems (Microsoft...) this might be unexpectedly low, but is still at
3455	is still at least 31 bits everywhere, which is enough for hundreds of	4303	least 31 bits everywhere, which is enough for hundreds of millions of
3456	millions of watchers.	4304	watchers.
3457		4305
3458	=item C<double> must hold a time value in seconds with enough accuracy	4306	=item C<double> must hold a time value in seconds with enough accuracy
3459		4307
3460	The type C<double> is used to represent timestamps. It is required to	4308	The type C<double> is used to represent timestamps. It is required to
3461	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4309	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
3462	enough for at least into the year 4000. This requirement is fulfilled by	4310	enough for at least into the year 4000. This requirement is fulfilled by
3463	implementations implementing IEEE 754 (basically all existing ones).	4311	implementations implementing IEEE 754, which is basically all existing
		4312	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4313	2200.
3464		4314
3465	=back	4315	=back
3466		4316
3467	If you know of other additional requirements drop me a note.	4317	If you know of other additional requirements drop me a note.
3468		4318
3469		4319
3470	=head1 COMPILER WARNINGS	4320	=head1 ALGORITHMIC COMPLEXITIES
3471		4321
3472	Depending on your compiler and compiler settings, you might get no or a	4322	In this section the complexities of (many of) the algorithms used inside
3473	lot of warnings when compiling libev code. Some people are apparently	4323	libev will be documented. For complexity discussions about backends see
3474	scared by this.	4324	the documentation for C<ev_default_init>.
3475		4325
3476	However, these are unavoidable for many reasons. For one, each compiler	4326	All of the following are about amortised time: If an array needs to be
3477	has different warnings, and each user has different tastes regarding	4327	extended, libev needs to realloc and move the whole array, but this
3478	warning options. "Warn-free" code therefore cannot be a goal except when	4328	happens asymptotically rarer with higher number of elements, so O(1) might
3479	targeting a specific compiler and compiler-version.	4329	mean that libev does a lengthy realloc operation in rare cases, but on
		4330	average it is much faster and asymptotically approaches constant time.
3480		4331
3481	Another reason is that some compiler warnings require elaborate	4332	=over 4
3482	workarounds, or other changes to the code that make it less clear and less
3483	maintainable.
3484		4333
3485	And of course, some compiler warnings are just plain stupid, or simply	4334	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3486	wrong (because they don't actually warn about the condition their message
3487	seems to warn about).
3488		4335
3489	While libev is written to generate as few warnings as possible,	4336	This means that, when you have a watcher that triggers in one hour and
3490	"warn-free" code is not a goal, and it is recommended not to build libev	4337	there are 100 watchers that would trigger before that, then inserting will
3491	with any compiler warnings enabled unless you are prepared to cope with	4338	have to skip roughly seven (C<ld 100>) of these watchers.
3492	them (e.g. by ignoring them). Remember that warnings are just that:
3493	warnings, not errors, or proof of bugs.
3494		4339
		4340	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3495		4341
3496	=head1 VALGRIND	4342	That means that changing a timer costs less than removing/adding them,
		4343	as only the relative motion in the event queue has to be paid for.
3497		4344
3498	Valgrind has a special section here because it is a popular tool that is	4345	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3499	highly useful, but valgrind reports are very hard to interpret.
3500		4346
3501	If you think you found a bug (memory leak, uninitialised data access etc.)	4347	These just add the watcher into an array or at the head of a list.
3502	in libev, then check twice: If valgrind reports something like:
3503		4348
3504	==2274== definitely lost: 0 bytes in 0 blocks.	4349	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3505	==2274== possibly lost: 0 bytes in 0 blocks.
3506	==2274== still reachable: 256 bytes in 1 blocks.
3507		4350
3508	Then there is no memory leak. Similarly, under some circumstances,	4351	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3509	valgrind might report kernel bugs as if it were a bug in libev, or it
3510	might be confused (it is a very good tool, but only a tool).
3511		4352
3512	If you are unsure about something, feel free to contact the mailing list	4353	These watchers are stored in lists, so they need to be walked to find the
3513	with the full valgrind report and an explanation on why you think this is	4354	correct watcher to remove. The lists are usually short (you don't usually
3514	a bug in libev. However, don't be annoyed when you get a brisk "this is	4355	have many watchers waiting for the same fd or signal: one is typical, two
3515	no bug" answer and take the chance of learning how to interpret valgrind	4356	is rare).
3516	properly.
3517		4357
3518	If you need, for some reason, empty reports from valgrind for your project	4358	=item Finding the next timer in each loop iteration: O(1)
3519	I suggest using suppression lists.
3520		4359
		4360	By virtue of using a binary or 4-heap, the next timer is always found at a
		4361	fixed position in the storage array.
		4362
		4363	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4364
		4365	A change means an I/O watcher gets started or stopped, which requires
		4366	libev to recalculate its status (and possibly tell the kernel, depending
		4367	on backend and whether C<ev_io_set> was used).
		4368
		4369	=item Activating one watcher (putting it into the pending state): O(1)
		4370
		4371	=item Priority handling: O(number_of_priorities)
		4372
		4373	Priorities are implemented by allocating some space for each
		4374	priority. When doing priority-based operations, libev usually has to
		4375	linearly search all the priorities, but starting/stopping and activating
		4376	watchers becomes O(1) with respect to priority handling.
		4377
		4378	=item Sending an ev_async: O(1)
		4379
		4380	=item Processing ev_async_send: O(number_of_async_watchers)
		4381
		4382	=item Processing signals: O(max_signal_number)
		4383
		4384	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4385	calls in the current loop iteration. Checking for async and signal events
		4386	involves iterating over all running async watchers or all signal numbers.
		4387
		4388	=back
		4389
		4390
		4391	=head1 GLOSSARY
		4392
		4393	=over 4
		4394
		4395	=item active
		4396
		4397	A watcher is active as long as it has been started (has been attached to
		4398	an event loop) but not yet stopped (disassociated from the event loop).
		4399
		4400	=item application
		4401
		4402	In this document, an application is whatever is using libev.
		4403
		4404	=item callback
		4405
		4406	The address of a function that is called when some event has been
		4407	detected. Callbacks are being passed the event loop, the watcher that
		4408	received the event, and the actual event bitset.
		4409
		4410	=item callback invocation
		4411
		4412	The act of calling the callback associated with a watcher.
		4413
		4414	=item event
		4415
		4416	A change of state of some external event, such as data now being available
		4417	for reading on a file descriptor, time having passed or simply not having
		4418	any other events happening anymore.
		4419
		4420	In libev, events are represented as single bits (such as C<EV_READ> or
		4421	C<EV_TIMEOUT>).
		4422
		4423	=item event library
		4424
		4425	A software package implementing an event model and loop.
		4426
		4427	=item event loop
		4428
		4429	An entity that handles and processes external events and converts them
		4430	into callback invocations.
		4431
		4432	=item event model
		4433
		4434	The model used to describe how an event loop handles and processes
		4435	watchers and events.
		4436
		4437	=item pending
		4438
		4439	A watcher is pending as soon as the corresponding event has been detected,
		4440	and stops being pending as soon as the watcher will be invoked or its
		4441	pending status is explicitly cleared by the application.
		4442
		4443	A watcher can be pending, but not active. Stopping a watcher also clears
		4444	its pending status.
		4445
		4446	=item real time
		4447
		4448	The physical time that is observed. It is apparently strictly monotonic :)
		4449
		4450	=item wall-clock time
		4451
		4452	The time and date as shown on clocks. Unlike real time, it can actually
		4453	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4454	clock.
		4455
		4456	=item watcher
		4457
		4458	A data structure that describes interest in certain events. Watchers need
		4459	to be started (attached to an event loop) before they can receive events.
		4460
		4461	=item watcher invocation
		4462
		4463	The act of calling the callback associated with a watcher.
		4464
		4465	=back
3521		4466
3522	=head1 AUTHOR	4467	=head1 AUTHOR
3523		4468
3524	Marc Lehmann <libev@schmorp.de>.	4469	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3525		4470

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