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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.
608	* If EVFLAG_FORKCHECK was used, check for a fork.	725	* If EVFLAG_FORKCHECK was used, check for a fork.
609	- If a fork was detected, queue and call all fork watchers.	726	- If a fork was detected (by any means), queue and call all fork watchers.
610	- Queue and call all prepare watchers.	727	- Queue and call all prepare watchers.
611	- If we have been forked, recreate the kernel state.	728	- If we have been forked, detach and recreate the kernel state
		729	as to not disturb the other process.
612	- Update the kernel state with all outstanding changes.	730	- Update the kernel state with all outstanding changes.
613	- Update the "event loop time".	731	- Update the "event loop time" (ev_now ()).
614	- Calculate for how long to sleep or block, if at all	732	- Calculate for how long to sleep or block, if at all
615	(active idle watchers, EVLOOP_NONBLOCK or not having	733	(active idle watchers, EVLOOP_NONBLOCK or not having
616	any active watchers at all will result in not sleeping).	734	any active watchers at all will result in not sleeping).
617	- Sleep if the I/O and timer collect interval say so.	735	- Sleep if the I/O and timer collect interval say so.
618	- Block the process, waiting for any events.	736	- Block the process, waiting for any events.
619	- Queue all outstanding I/O (fd) events.	737	- Queue all outstanding I/O (fd) events.
620	- Update the "event loop time" and do time jump handling.	738	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
621	- Queue all outstanding timers.	739	- Queue all expired timers.
622	- Queue all outstanding periodics.	740	- Queue all expired periodics.
623	- If no events are pending now, queue all idle watchers.	741	- Unless any events are pending now, queue all idle watchers.
624	- Queue all check watchers.	742	- Queue all check watchers.
625	- 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).
626	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
627	be handled here by queueing them when their watcher gets executed.	745	be handled here by queueing them when their watcher gets executed.
628	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	746	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
633	anymore.	751	anymore.
634		752
635	... queue jobs here, make sure they register event watchers as long	753	... queue jobs here, make sure they register event watchers as long
636	... as they still have work to do (even an idle watcher will do..)	754	... as they still have work to do (even an idle watcher will do..)
637	ev_loop (my_loop, 0);	755	ev_loop (my_loop, 0);
638	... jobs done. yeah!	756	... jobs done or somebody called unloop. yeah!
639		757
640	=item ev_unloop (loop, how)	758	=item ev_unloop (loop, how)
641		759
642	Can be used to make a call to C<ev_loop> return early (but only after it	760	Can be used to make a call to C<ev_loop> return early (but only after it
643	has processed all outstanding events). The C<how> argument must be either	761	has processed all outstanding events). The C<how> argument must be either
644	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	762	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
645	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.
646		764
647	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.
648		766
		767	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		768
649	=item ev_ref (loop)	769	=item ev_ref (loop)
650		770
651	=item ev_unref (loop)	771	=item ev_unref (loop)
652		772
653	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
654	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
655	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
656	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>
657	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
658	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
659	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
660	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
661	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
662	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
663	(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
664	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).
665		790
666	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>
667	running when nothing else is active.	792	running when nothing else is active.
668		793
669	struct ev_signal exitsig;	794	ev_signal exitsig;
670	ev_signal_init (&exitsig, sig_cb, SIGINT);	795	ev_signal_init (&exitsig, sig_cb, SIGINT);
671	ev_signal_start (loop, &exitsig);	796	ev_signal_start (loop, &exitsig);
672	evf_unref (loop);	797	evf_unref (loop);
673		798
674	Example: For some weird reason, unregister the above signal handler again.	799	Example: For some weird reason, unregister the above signal handler again.
…		…
679	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	804	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
680		805
681	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	806	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
682		807
683	These advanced functions influence the time that libev will spend waiting	808	These advanced functions influence the time that libev will spend waiting
684	for events. Both are by default C<0>, meaning that libev will try to	809	for events. Both time intervals are by default C<0>, meaning that libev
685	invoke timer/periodic callbacks and I/O callbacks with minimum latency.	810	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		811	latency.
686		812
687	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>)
688	allows libev to delay invocation of I/O and timer/periodic callbacks to	814	allows libev to delay invocation of I/O and timer/periodic callbacks
689	increase efficiency of loop iterations.	815	to increase efficiency of loop iterations (or to increase power-saving
		816	opportunities).
690		817
691	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
692	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
693	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
694	events, especially with backends like C<select ()> which have a high	821	events, especially with backends like C<select ()> which have a high
695	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.
696		823
697	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
698	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,
699	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
700	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
701	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.
702		831
703	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
704	to spend more time collecting timeouts, at the expense of increased	833	to spend more time collecting timeouts, at the expense of increased
705	latency (the watcher callback will be called later). C<ev_io> watchers	834	latency/jitter/inexactness (the watcher callback will be called
706	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
707	any overhead in libev.	836	value will not introduce any overhead in libev.
708		837
709	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
710	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
711	interactive servers (of course not for games), likewise for timeouts. It	840	interactive servers (of course not for games), likewise for timeouts. It
712	usually doesn't make much sense to set it to a lower value than C<0.01>,	841	usually doesn't make much sense to set it to a lower value than C<0.01>,
713	as this approaches the timing granularity of most systems.	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).
		847
		848	Setting the I<timeout collect interval> can improve the opportunity for
		849	saving power, as the program will "bundle" timer callback invocations that
		850	are "near" in time together, by delaying some, thus reducing the number of
		851	times the process sleeps and wakes up again. Another useful technique to
		852	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		853	they fire on, say, one-second boundaries only.
		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 ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		868
		869	This overrides the invoke pending functionality of the loop: Instead of
		870	invoking all pending watchers when there are any, C<ev_loop> will call
		871	this callback instead. This is useful, for example, when you want to
		872	invoke the actual watchers inside another context (another thread etc.).
		873
		874	If you want to reset the callback, use C<ev_invoke_pending> as new
		875	callback.
		876
		877	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		878
		879	Sometimes you want to share the same loop between multiple threads. This
		880	can be done relatively simply by putting mutex_lock/unlock calls around
		881	each call to a libev function.
		882
		883	However, C<ev_loop> can run an indefinite time, so it is not feasible to
		884	wait for it to return. One way around this is to wake up the loop via
		885	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>
		886	and I<acquire> callbacks on the loop.
		887
		888	When set, then C<release> will be called just before the thread is
		889	suspended waiting for new events, and C<acquire> is called just
		890	afterwards.
		891
		892	Ideally, C<release> will just call your mutex_unlock function, and
		893	C<acquire> will just call the mutex_lock function again.
		894
		895	While event loop modifications are allowed between invocations of
		896	C<release> and C<acquire> (that's their only purpose after all), no
		897	modifications done will affect the event loop, i.e. adding watchers will
		898	have no effect on the set of file descriptors being watched, or the time
		899	waited. USe an C<ev_async> watcher to wake up C<ev_loop> when you want it
		900	to take note of any changes you made.
		901
		902	In theory, threads executing C<ev_loop> will be async-cancel safe between
		903	invocations of C<release> and C<acquire>.
		904
		905	See also the locking example in the C<THREADS> section later in this
		906	document.
		907
		908	=item ev_set_userdata (loop, void *data)
		909
		910	=item ev_userdata (loop)
		911
		912	Set and retrieve a single C<void *> associated with a loop. When
		913	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		914	C<0.>
		915
		916	These two functions can be used to associate arbitrary data with a loop,
		917	and are intended solely for the C<invoke_pending_cb>, C<release> and
		918	C<acquire> callbacks described above, but of course can be (ab-)used for
		919	any other purpose as well.
714		920
715	=item ev_loop_verify (loop)	921	=item ev_loop_verify (loop)
716		922
717	This function only does something when C<EV_VERIFY> support has been	923	This function only does something when C<EV_VERIFY> support has been
718	compiled in. It tries to go through all internal structures and checks	924	compiled in, which is the default for non-minimal builds. It tries to go
719	them for validity. If anything is found to be inconsistent, it will print	925	through all internal structures and checks them for validity. If anything
720	an error message to standard error and call C<abort ()>.	926	is found to be inconsistent, it will print an error message to standard
		927	error and call C<abort ()>.
721		928
722	This can be used to catch bugs inside libev itself: under normal	929	This can be used to catch bugs inside libev itself: under normal
723	circumstances, this function will never abort as of course libev keeps its	930	circumstances, this function will never abort as of course libev keeps its
724	data structures consistent.	931	data structures consistent.
725		932
726	=back	933	=back
727		934
728		935
729	=head1 ANATOMY OF A WATCHER	936	=head1 ANATOMY OF A WATCHER
730		937
		938	In the following description, uppercase C<TYPE> in names stands for the
		939	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		940	watchers and C<ev_io_start> for I/O watchers.
		941
731	A watcher is a structure that you create and register to record your	942	A watcher is a structure that you create and register to record your
732	interest in some event. For instance, if you want to wait for STDIN to	943	interest in some event. For instance, if you want to wait for STDIN to
733	become readable, you would create an C<ev_io> watcher for that:	944	become readable, you would create an C<ev_io> watcher for that:
734		945
735	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	946	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
736	{	947	{
737	ev_io_stop (w);	948	ev_io_stop (w);
738	ev_unloop (loop, EVUNLOOP_ALL);	949	ev_unloop (loop, EVUNLOOP_ALL);
739	}	950	}
740		951
741	struct ev_loop *loop = ev_default_loop (0);	952	struct ev_loop *loop = ev_default_loop (0);
		953
742	struct ev_io stdin_watcher;	954	ev_io stdin_watcher;
		955
743	ev_init (&stdin_watcher, my_cb);	956	ev_init (&stdin_watcher, my_cb);
744	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	957	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
745	ev_io_start (loop, &stdin_watcher);	958	ev_io_start (loop, &stdin_watcher);
		959
746	ev_loop (loop, 0);	960	ev_loop (loop, 0);
747		961
748	As you can see, you are responsible for allocating the memory for your	962	As you can see, you are responsible for allocating the memory for your
749	watcher structures (and it is usually a bad idea to do this on the stack,	963	watcher structures (and it is I<usually> a bad idea to do this on the
750	although this can sometimes be quite valid).	964	stack).
		965
		966	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		967	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
751		968
752	Each watcher structure must be initialised by a call to C<ev_init	969	Each watcher structure must be initialised by a call to C<ev_init
753	(watcher *, callback)>, which expects a callback to be provided. This	970	(watcher *, callback)>, which expects a callback to be provided. This
754	callback gets invoked each time the event occurs (or, in the case of I/O	971	callback gets invoked each time the event occurs (or, in the case of I/O
755	watchers, each time the event loop detects that the file descriptor given	972	watchers, each time the event loop detects that the file descriptor given
756	is readable and/or writable).	973	is readable and/or writable).
757		974
758	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	975	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
759	with arguments specific to this watcher type. There is also a macro	976	macro to configure it, with arguments specific to the watcher type. There
760	to combine initialisation and setting in one call: C<< ev_<type>_init	977	is also a macro to combine initialisation and setting in one call: C<<
761	(watcher *, callback, ...) >>.	978	ev_TYPE_init (watcher *, callback, ...) >>.
762		979
763	To make the watcher actually watch out for events, you have to start it	980	To make the watcher actually watch out for events, you have to start it
764	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	981	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
765	*) >>), and you can stop watching for events at any time by calling the	982	*) >>), and you can stop watching for events at any time by calling the
766	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	983	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
767		984
768	As long as your watcher is active (has been started but not stopped) you	985	As long as your watcher is active (has been started but not stopped) you
769	must not touch the values stored in it. Most specifically you must never	986	must not touch the values stored in it. Most specifically you must never
770	reinitialise it or call its C<set> macro.	987	reinitialise it or call its C<ev_TYPE_set> macro.
771		988
772	Each and every callback receives the event loop pointer as first, the	989	Each and every callback receives the event loop pointer as first, the
773	registered watcher structure as second, and a bitset of received events as	990	registered watcher structure as second, and a bitset of received events as
774	third argument.	991	third argument.
775		992
…		…
833		1050
834	=item C<EV_ASYNC>	1051	=item C<EV_ASYNC>
835		1052
836	The given async watcher has been asynchronously notified (see C<ev_async>).	1053	The given async watcher has been asynchronously notified (see C<ev_async>).
837		1054
		1055	=item C<EV_CUSTOM>
		1056
		1057	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1058	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		1059
838	=item C<EV_ERROR>	1060	=item C<EV_ERROR>
839		1061
840	An unspecified error has occurred, the watcher has been stopped. This might	1062	An unspecified error has occurred, the watcher has been stopped. This might
841	happen because the watcher could not be properly started because libev	1063	happen because the watcher could not be properly started because libev
842	ran out of memory, a file descriptor was found to be closed or any other	1064	ran out of memory, a file descriptor was found to be closed or any other
		1065	problem. Libev considers these application bugs.
		1066
843	problem. You best act on it by reporting the problem and somehow coping	1067	You best act on it by reporting the problem and somehow coping with the
844	with the watcher being stopped.	1068	watcher being stopped. Note that well-written programs should not receive
		1069	an error ever, so when your watcher receives it, this usually indicates a
		1070	bug in your program.
845		1071
846	Libev will usually signal a few "dummy" events together with an error,	1072	Libev will usually signal a few "dummy" events together with an error, for
847	for example it might indicate that a fd is readable or writable, and if	1073	example it might indicate that a fd is readable or writable, and if your
848	your callbacks is well-written it can just attempt the operation and cope	1074	callbacks is well-written it can just attempt the operation and cope with
849	with the error from read() or write(). This will not work in multi-threaded	1075	the error from read() or write(). This will not work in multi-threaded
850	programs, though, so beware.	1076	programs, though, as the fd could already be closed and reused for another
		1077	thing, so beware.
851		1078
852	=back	1079	=back
853		1080
854	=head2 GENERIC WATCHER FUNCTIONS	1081	=head2 GENERIC WATCHER FUNCTIONS
855
856	In the following description, C<TYPE> stands for the watcher type,
857	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
858		1082
859	=over 4	1083	=over 4
860		1084
861	=item C<ev_init> (ev_TYPE *watcher, callback)	1085	=item C<ev_init> (ev_TYPE *watcher, callback)
862		1086
…		…
868	which rolls both calls into one.	1092	which rolls both calls into one.
869		1093
870	You can reinitialise a watcher at any time as long as it has been stopped	1094	You can reinitialise a watcher at any time as long as it has been stopped
871	(or never started) and there are no pending events outstanding.	1095	(or never started) and there are no pending events outstanding.
872		1096
873	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1097	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
874	int revents)>.	1098	int revents)>.
		1099
		1100	Example: Initialise an C<ev_io> watcher in two steps.
		1101
		1102	ev_io w;
		1103	ev_init (&w, my_cb);
		1104	ev_io_set (&w, STDIN_FILENO, EV_READ);
875		1105
876	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1106	=item C<ev_TYPE_set> (ev_TYPE *, [args])
877		1107
878	This macro initialises the type-specific parts of a watcher. You need to	1108	This macro initialises the type-specific parts of a watcher. You need to
879	call C<ev_init> at least once before you call this macro, but you can	1109	call C<ev_init> at least once before you call this macro, but you can
…		…
882	difference to the C<ev_init> macro).	1112	difference to the C<ev_init> macro).
883		1113
884	Although some watcher types do not have type-specific arguments	1114	Although some watcher types do not have type-specific arguments
885	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	1115	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
886		1116
		1117	See C<ev_init>, above, for an example.
		1118
887	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1119	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
888		1120
889	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1121	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
890	calls into a single call. This is the most convenient method to initialise	1122	calls into a single call. This is the most convenient method to initialise
891	a watcher. The same limitations apply, of course.	1123	a watcher. The same limitations apply, of course.
892		1124
		1125	Example: Initialise and set an C<ev_io> watcher in one step.
		1126
		1127	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1128
893	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1129	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
894		1130
895	Starts (activates) the given watcher. Only active watchers will receive	1131	Starts (activates) the given watcher. Only active watchers will receive
896	events. If the watcher is already active nothing will happen.	1132	events. If the watcher is already active nothing will happen.
897		1133
		1134	Example: Start the C<ev_io> watcher that is being abused as example in this
		1135	whole section.
		1136
		1137	ev_io_start (EV_DEFAULT_UC, &w);
		1138
898	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1139	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
899		1140
900	Stops the given watcher again (if active) and clears the pending	1141	Stops the given watcher if active, and clears the pending status (whether
		1142	the watcher was active or not).
		1143
901	status. It is possible that stopped watchers are pending (for example,	1144	It is possible that stopped watchers are pending - for example,
902	non-repeating timers are being stopped when they become pending), but	1145	non-repeating timers are being stopped when they become pending - but
903	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1146	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
904	you want to free or reuse the memory used by the watcher it is therefore a	1147	pending. If you want to free or reuse the memory used by the watcher it is
905	good idea to always call its C<ev_TYPE_stop> function.	1148	therefore a good idea to always call its C<ev_TYPE_stop> function.
906		1149
907	=item bool ev_is_active (ev_TYPE *watcher)	1150	=item bool ev_is_active (ev_TYPE *watcher)
908		1151
909	Returns a true value iff the watcher is active (i.e. it has been started	1152	Returns a true value iff the watcher is active (i.e. it has been started
910	and not yet been stopped). As long as a watcher is active you must not modify	1153	and not yet been stopped). As long as a watcher is active you must not modify
…		…
936	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1179	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
937	(default: C<-2>). Pending watchers with higher priority will be invoked	1180	(default: C<-2>). Pending watchers with higher priority will be invoked
938	before watchers with lower priority, but priority will not keep watchers	1181	before watchers with lower priority, but priority will not keep watchers
939	from being executed (except for C<ev_idle> watchers).	1182	from being executed (except for C<ev_idle> watchers).
940		1183
941	This means that priorities are I<only> used for ordering callback
942	invocation after new events have been received. This is useful, for
943	example, to reduce latency after idling, or more often, to bind two
944	watchers on the same event and make sure one is called first.
945
946	If you need to suppress invocation when higher priority events are pending	1184	If you need to suppress invocation when higher priority events are pending
947	you need to look at C<ev_idle> watchers, which provide this functionality.	1185	you need to look at C<ev_idle> watchers, which provide this functionality.
948		1186
949	You I<must not> change the priority of a watcher as long as it is active or	1187	You I<must not> change the priority of a watcher as long as it is active or
950	pending.	1188	pending.
951		1189
		1190	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1191	fine, as long as you do not mind that the priority value you query might
		1192	or might not have been clamped to the valid range.
		1193
952	The default priority used by watchers when no priority has been set is	1194	The default priority used by watchers when no priority has been set is
953	always C<0>, which is supposed to not be too high and not be too low :).	1195	always C<0>, which is supposed to not be too high and not be too low :).
954		1196
955	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1197	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
956	fine, as long as you do not mind that the priority value you query might	1198	priorities.
957	or might not have been adjusted to be within valid range.
958		1199
959	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1200	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
960		1201
961	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1202	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
962	C<loop> nor C<revents> need to be valid as long as the watcher callback	1203	C<loop> nor C<revents> need to be valid as long as the watcher callback
963	can deal with that fact.	1204	can deal with that fact, as both are simply passed through to the
		1205	callback.
964		1206
965	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1207	=item int ev_clear_pending (loop, ev_TYPE *watcher)
966		1208
967	If the watcher is pending, this function returns clears its pending status	1209	If the watcher is pending, this function clears its pending status and
968	and returns its C<revents> bitset (as if its callback was invoked). If the	1210	returns its C<revents> bitset (as if its callback was invoked). If the
969	watcher isn't pending it does nothing and returns C<0>.	1211	watcher isn't pending it does nothing and returns C<0>.
970		1212
		1213	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1214	callback to be invoked, which can be accomplished with this function.
		1215
971	=back	1216	=back
972		1217
973		1218
974	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1219	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
975		1220
976	Each watcher has, by default, a member C<void *data> that you can change	1221	Each watcher has, by default, a member C<void *data> that you can change
977	and read at any time, libev will completely ignore it. This can be used	1222	and read at any time: libev will completely ignore it. This can be used
978	to associate arbitrary data with your watcher. If you need more data and	1223	to associate arbitrary data with your watcher. If you need more data and
979	don't want to allocate memory and store a pointer to it in that data	1224	don't want to allocate memory and store a pointer to it in that data
980	member, you can also "subclass" the watcher type and provide your own	1225	member, you can also "subclass" the watcher type and provide your own
981	data:	1226	data:
982		1227
983	struct my_io	1228	struct my_io
984	{	1229	{
985	struct ev_io io;	1230	ev_io io;
986	int otherfd;	1231	int otherfd;
987	void *somedata;	1232	void *somedata;
988	struct whatever *mostinteresting;	1233	struct whatever *mostinteresting;
989	}	1234	};
		1235
		1236	...
		1237	struct my_io w;
		1238	ev_io_init (&w.io, my_cb, fd, EV_READ);
990		1239
991	And since your callback will be called with a pointer to the watcher, you	1240	And since your callback will be called with a pointer to the watcher, you
992	can cast it back to your own type:	1241	can cast it back to your own type:
993		1242
994	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1243	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
995	{	1244	{
996	struct my_io *w = (struct my_io *)w_;	1245	struct my_io *w = (struct my_io *)w_;
997	...	1246	...
998	}	1247	}
999		1248
1000	More interesting and less C-conformant ways of casting your callback type	1249	More interesting and less C-conformant ways of casting your callback type
1001	instead have been omitted.	1250	instead have been omitted.
1002		1251
1003	Another common scenario is having some data structure with multiple	1252	Another common scenario is to use some data structure with multiple
1004	watchers:	1253	embedded watchers:
1005		1254
1006	struct my_biggy	1255	struct my_biggy
1007	{	1256	{
1008	int some_data;	1257	int some_data;
1009	ev_timer t1;	1258	ev_timer t1;
1010	ev_timer t2;	1259	ev_timer t2;
1011	}	1260	}
1012		1261
1013	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1262	In this case getting the pointer to C<my_biggy> is a bit more
1014	you need to use C<offsetof>:	1263	complicated: Either you store the address of your C<my_biggy> struct
		1264	in the C<data> member of the watcher (for woozies), or you need to use
		1265	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1266	programmers):
1015		1267
1016	#include <stddef.h>	1268	#include <stddef.h>
1017		1269
1018	static void	1270	static void
1019	t1_cb (EV_P_ struct ev_timer *w, int revents)	1271	t1_cb (EV_P_ ev_timer *w, int revents)
1020	{	1272	{
1021	struct my_biggy big = (struct my_biggy *	1273	struct my_biggy big = (struct my_biggy *)
1022	(((char *)w) - offsetof (struct my_biggy, t1));	1274	(((char *)w) - offsetof (struct my_biggy, t1));
1023	}	1275	}
1024		1276
1025	static void	1277	static void
1026	t2_cb (EV_P_ struct ev_timer *w, int revents)	1278	t2_cb (EV_P_ ev_timer *w, int revents)
1027	{	1279	{
1028	struct my_biggy big = (struct my_biggy *	1280	struct my_biggy big = (struct my_biggy *)
1029	(((char *)w) - offsetof (struct my_biggy, t2));	1281	(((char *)w) - offsetof (struct my_biggy, t2));
1030	}	1282	}
		1283
		1284	=head2 WATCHER PRIORITY MODELS
		1285
		1286	Many event loops support I<watcher priorities>, which are usually small
		1287	integers that influence the ordering of event callback invocation
		1288	between watchers in some way, all else being equal.
		1289
		1290	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1291	description for the more technical details such as the actual priority
		1292	range.
		1293
		1294	There are two common ways how these these priorities are being interpreted
		1295	by event loops:
		1296
		1297	In the more common lock-out model, higher priorities "lock out" invocation
		1298	of lower priority watchers, which means as long as higher priority
		1299	watchers receive events, lower priority watchers are not being invoked.
		1300
		1301	The less common only-for-ordering model uses priorities solely to order
		1302	callback invocation within a single event loop iteration: Higher priority
		1303	watchers are invoked before lower priority ones, but they all get invoked
		1304	before polling for new events.
		1305
		1306	Libev uses the second (only-for-ordering) model for all its watchers
		1307	except for idle watchers (which use the lock-out model).
		1308
		1309	The rationale behind this is that implementing the lock-out model for
		1310	watchers is not well supported by most kernel interfaces, and most event
		1311	libraries will just poll for the same events again and again as long as
		1312	their callbacks have not been executed, which is very inefficient in the
		1313	common case of one high-priority watcher locking out a mass of lower
		1314	priority ones.
		1315
		1316	Static (ordering) priorities are most useful when you have two or more
		1317	watchers handling the same resource: a typical usage example is having an
		1318	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1319	timeouts. Under load, data might be received while the program handles
		1320	other jobs, but since timers normally get invoked first, the timeout
		1321	handler will be executed before checking for data. In that case, giving
		1322	the timer a lower priority than the I/O watcher ensures that I/O will be
		1323	handled first even under adverse conditions (which is usually, but not
		1324	always, what you want).
		1325
		1326	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1327	will only be executed when no same or higher priority watchers have
		1328	received events, they can be used to implement the "lock-out" model when
		1329	required.
		1330
		1331	For example, to emulate how many other event libraries handle priorities,
		1332	you can associate an C<ev_idle> watcher to each such watcher, and in
		1333	the normal watcher callback, you just start the idle watcher. The real
		1334	processing is done in the idle watcher callback. This causes libev to
		1335	continously poll and process kernel event data for the watcher, but when
		1336	the lock-out case is known to be rare (which in turn is rare :), this is
		1337	workable.
		1338
		1339	Usually, however, the lock-out model implemented that way will perform
		1340	miserably under the type of load it was designed to handle. In that case,
		1341	it might be preferable to stop the real watcher before starting the
		1342	idle watcher, so the kernel will not have to process the event in case
		1343	the actual processing will be delayed for considerable time.
		1344
		1345	Here is an example of an I/O watcher that should run at a strictly lower
		1346	priority than the default, and which should only process data when no
		1347	other events are pending:
		1348
		1349	ev_idle idle; // actual processing watcher
		1350	ev_io io; // actual event watcher
		1351
		1352	static void
		1353	io_cb (EV_P_ ev_io *w, int revents)
		1354	{
		1355	// stop the I/O watcher, we received the event, but
		1356	// are not yet ready to handle it.
		1357	ev_io_stop (EV_A_ w);
		1358
		1359	// start the idle watcher to ahndle the actual event.
		1360	// it will not be executed as long as other watchers
		1361	// with the default priority are receiving events.
		1362	ev_idle_start (EV_A_ &idle);
		1363	}
		1364
		1365	static void
		1366	idle_cb (EV_P_ ev_idle *w, int revents)
		1367	{
		1368	// actual processing
		1369	read (STDIN_FILENO, ...);
		1370
		1371	// have to start the I/O watcher again, as
		1372	// we have handled the event
		1373	ev_io_start (EV_P_ &io);
		1374	}
		1375
		1376	// initialisation
		1377	ev_idle_init (&idle, idle_cb);
		1378	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1379	ev_io_start (EV_DEFAULT_ &io);
		1380
		1381	In the "real" world, it might also be beneficial to start a timer, so that
		1382	low-priority connections can not be locked out forever under load. This
		1383	enables your program to keep a lower latency for important connections
		1384	during short periods of high load, while not completely locking out less
		1385	important ones.
1031		1386
1032		1387
1033	=head1 WATCHER TYPES	1388	=head1 WATCHER TYPES
1034		1389
1035	This section describes each watcher in detail, but will not repeat	1390	This section describes each watcher in detail, but will not repeat
…		…
1059	In general you can register as many read and/or write event watchers per	1414	In general you can register as many read and/or write event watchers per
1060	fd as you want (as long as you don't confuse yourself). Setting all file	1415	fd as you want (as long as you don't confuse yourself). Setting all file
1061	descriptors to non-blocking mode is also usually a good idea (but not	1416	descriptors to non-blocking mode is also usually a good idea (but not
1062	required if you know what you are doing).	1417	required if you know what you are doing).
1063		1418
1064	If you must do this, then force the use of a known-to-be-good backend	1419	If you cannot use non-blocking mode, then force the use of a
1065	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1420	known-to-be-good backend (at the time of this writing, this includes only
1066	C<EVBACKEND_POLL>).	1421	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1422	descriptors for which non-blocking operation makes no sense (such as
		1423	files) - libev doesn't guarentee any specific behaviour in that case.
1067		1424
1068	Another thing you have to watch out for is that it is quite easy to	1425	Another thing you have to watch out for is that it is quite easy to
1069	receive "spurious" readiness notifications, that is your callback might	1426	receive "spurious" readiness notifications, that is your callback might
1070	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1427	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1071	because there is no data. Not only are some backends known to create a	1428	because there is no data. Not only are some backends known to create a
1072	lot of those (for example Solaris ports), it is very easy to get into	1429	lot of those (for example Solaris ports), it is very easy to get into
1073	this situation even with a relatively standard program structure. Thus	1430	this situation even with a relatively standard program structure. Thus
1074	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1431	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1075	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1432	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1076		1433
1077	If you cannot run the fd in non-blocking mode (for example you should not	1434	If you cannot run the fd in non-blocking mode (for example you should
1078	play around with an Xlib connection), then you have to separately re-test	1435	not play around with an Xlib connection), then you have to separately
1079	whether a file descriptor is really ready with a known-to-be good interface	1436	re-test whether a file descriptor is really ready with a known-to-be good
1080	such as poll (fortunately in our Xlib example, Xlib already does this on	1437	interface such as poll (fortunately in our Xlib example, Xlib already
1081	its own, so its quite safe to use).	1438	does this on its own, so its quite safe to use). Some people additionally
		1439	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1440	indefinitely.
		1441
		1442	But really, best use non-blocking mode.
1082		1443
1083	=head3 The special problem of disappearing file descriptors	1444	=head3 The special problem of disappearing file descriptors
1084		1445
1085	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1446	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1086	descriptor (either by calling C<close> explicitly or by any other means,	1447	descriptor (either due to calling C<close> explicitly or any other means,
1087	such as C<dup>). The reason is that you register interest in some file	1448	such as C<dup2>). The reason is that you register interest in some file
1088	descriptor, but when it goes away, the operating system will silently drop	1449	descriptor, but when it goes away, the operating system will silently drop
1089	this interest. If another file descriptor with the same number then is	1450	this interest. If another file descriptor with the same number then is
1090	registered with libev, there is no efficient way to see that this is, in	1451	registered with libev, there is no efficient way to see that this is, in
1091	fact, a different file descriptor.	1452	fact, a different file descriptor.
1092		1453
…		…
1123	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1484	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1124	C<EVBACKEND_POLL>.	1485	C<EVBACKEND_POLL>.
1125		1486
1126	=head3 The special problem of SIGPIPE	1487	=head3 The special problem of SIGPIPE
1127		1488
1128	While not really specific to libev, it is easy to forget about SIGPIPE:	1489	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1129	when reading from a pipe whose other end has been closed, your program	1490	when writing to a pipe whose other end has been closed, your program gets
1130	gets send a SIGPIPE, which, by default, aborts your program. For most	1491	sent a SIGPIPE, which, by default, aborts your program. For most programs
1131	programs this is sensible behaviour, for daemons, this is usually	1492	this is sensible behaviour, for daemons, this is usually undesirable.
1132	undesirable.
1133		1493
1134	So when you encounter spurious, unexplained daemon exits, make sure you	1494	So when you encounter spurious, unexplained daemon exits, make sure you
1135	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1495	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1136	somewhere, as that would have given you a big clue).	1496	somewhere, as that would have given you a big clue).
1137		1497
…		…
1143	=item ev_io_init (ev_io *, callback, int fd, int events)	1503	=item ev_io_init (ev_io *, callback, int fd, int events)
1144		1504
1145	=item ev_io_set (ev_io *, int fd, int events)	1505	=item ev_io_set (ev_io *, int fd, int events)
1146		1506
1147	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1507	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1148	receive events for and events is either C<EV_READ>, C<EV_WRITE> or	1508	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1149	C<EV_READ | EV_WRITE> to receive the given events.	1509	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1150		1510
1151	=item int fd [read-only]	1511	=item int fd [read-only]
1152		1512
1153	The file descriptor being watched.	1513	The file descriptor being watched.
1154		1514
…		…
1163	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1523	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1164	readable, but only once. Since it is likely line-buffered, you could	1524	readable, but only once. Since it is likely line-buffered, you could
1165	attempt to read a whole line in the callback.	1525	attempt to read a whole line in the callback.
1166		1526
1167	static void	1527	static void
1168	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1528	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1169	{	1529	{
1170	ev_io_stop (loop, w);	1530	ev_io_stop (loop, w);
1171	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1531	.. read from stdin here (or from w->fd) and handle any I/O errors
1172	}	1532	}
1173		1533
1174	...	1534	...
1175	struct ev_loop *loop = ev_default_init (0);	1535	struct ev_loop *loop = ev_default_init (0);
1176	struct ev_io stdin_readable;	1536	ev_io stdin_readable;
1177	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1537	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1178	ev_io_start (loop, &stdin_readable);	1538	ev_io_start (loop, &stdin_readable);
1179	ev_loop (loop, 0);	1539	ev_loop (loop, 0);
1180		1540
1181		1541
…		…
1184	Timer watchers are simple relative timers that generate an event after a	1544	Timer watchers are simple relative timers that generate an event after a
1185	given time, and optionally repeating in regular intervals after that.	1545	given time, and optionally repeating in regular intervals after that.
1186		1546
1187	The timers are based on real time, that is, if you register an event that	1547	The timers are based on real time, that is, if you register an event that
1188	times out after an hour and you reset your system clock to January last	1548	times out after an hour and you reset your system clock to January last
1189	year, it will still time out after (roughly) and hour. "Roughly" because	1549	year, it will still time out after (roughly) one hour. "Roughly" because
1190	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1550	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1191	monotonic clock option helps a lot here).	1551	monotonic clock option helps a lot here).
		1552
		1553	The callback is guaranteed to be invoked only I<after> its timeout has
		1554	passed (not I<at>, so on systems with very low-resolution clocks this
		1555	might introduce a small delay). If multiple timers become ready during the
		1556	same loop iteration then the ones with earlier time-out values are invoked
		1557	before ones of the same priority with later time-out values (but this is
		1558	no longer true when a callback calls C<ev_loop> recursively).
		1559
		1560	=head3 Be smart about timeouts
		1561
		1562	Many real-world problems involve some kind of timeout, usually for error
		1563	recovery. A typical example is an HTTP request - if the other side hangs,
		1564	you want to raise some error after a while.
		1565
		1566	What follows are some ways to handle this problem, from obvious and
		1567	inefficient to smart and efficient.
		1568
		1569	In the following, a 60 second activity timeout is assumed - a timeout that
		1570	gets reset to 60 seconds each time there is activity (e.g. each time some
		1571	data or other life sign was received).
		1572
		1573	=over 4
		1574
		1575	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1576
		1577	This is the most obvious, but not the most simple way: In the beginning,
		1578	start the watcher:
		1579
		1580	ev_timer_init (timer, callback, 60., 0.);
		1581	ev_timer_start (loop, timer);
		1582
		1583	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1584	and start it again:
		1585
		1586	ev_timer_stop (loop, timer);
		1587	ev_timer_set (timer, 60., 0.);
		1588	ev_timer_start (loop, timer);
		1589
		1590	This is relatively simple to implement, but means that each time there is
		1591	some activity, libev will first have to remove the timer from its internal
		1592	data structure and then add it again. Libev tries to be fast, but it's
		1593	still not a constant-time operation.
		1594
		1595	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1596
		1597	This is the easiest way, and involves using C<ev_timer_again> instead of
		1598	C<ev_timer_start>.
		1599
		1600	To implement this, configure an C<ev_timer> with a C<repeat> value
		1601	of C<60> and then call C<ev_timer_again> at start and each time you
		1602	successfully read or write some data. If you go into an idle state where
		1603	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1604	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1605
		1606	That means you can ignore both the C<ev_timer_start> function and the
		1607	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1608	member and C<ev_timer_again>.
		1609
		1610	At start:
		1611
		1612	ev_init (timer, callback);
		1613	timer->repeat = 60.;
		1614	ev_timer_again (loop, timer);
		1615
		1616	Each time there is some activity:
		1617
		1618	ev_timer_again (loop, timer);
		1619
		1620	It is even possible to change the time-out on the fly, regardless of
		1621	whether the watcher is active or not:
		1622
		1623	timer->repeat = 30.;
		1624	ev_timer_again (loop, timer);
		1625
		1626	This is slightly more efficient then stopping/starting the timer each time
		1627	you want to modify its timeout value, as libev does not have to completely
		1628	remove and re-insert the timer from/into its internal data structure.
		1629
		1630	It is, however, even simpler than the "obvious" way to do it.
		1631
		1632	=item 3. Let the timer time out, but then re-arm it as required.
		1633
		1634	This method is more tricky, but usually most efficient: Most timeouts are
		1635	relatively long compared to the intervals between other activity - in
		1636	our example, within 60 seconds, there are usually many I/O events with
		1637	associated activity resets.
		1638
		1639	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1640	but remember the time of last activity, and check for a real timeout only
		1641	within the callback:
		1642
		1643	ev_tstamp last_activity; // time of last activity
		1644
		1645	static void
		1646	callback (EV_P_ ev_timer *w, int revents)
		1647	{
		1648	ev_tstamp now = ev_now (EV_A);
		1649	ev_tstamp timeout = last_activity + 60.;
		1650
		1651	// if last_activity + 60. is older than now, we did time out
		1652	if (timeout < now)
		1653	{
		1654	// timeout occured, take action
		1655	}
		1656	else
		1657	{
		1658	// callback was invoked, but there was some activity, re-arm
		1659	// the watcher to fire in last_activity + 60, which is
		1660	// guaranteed to be in the future, so "again" is positive:
		1661	w->repeat = timeout - now;
		1662	ev_timer_again (EV_A_ w);
		1663	}
		1664	}
		1665
		1666	To summarise the callback: first calculate the real timeout (defined
		1667	as "60 seconds after the last activity"), then check if that time has
		1668	been reached, which means something I<did>, in fact, time out. Otherwise
		1669	the callback was invoked too early (C<timeout> is in the future), so
		1670	re-schedule the timer to fire at that future time, to see if maybe we have
		1671	a timeout then.
		1672
		1673	Note how C<ev_timer_again> is used, taking advantage of the
		1674	C<ev_timer_again> optimisation when the timer is already running.
		1675
		1676	This scheme causes more callback invocations (about one every 60 seconds
		1677	minus half the average time between activity), but virtually no calls to
		1678	libev to change the timeout.
		1679
		1680	To start the timer, simply initialise the watcher and set C<last_activity>
		1681	to the current time (meaning we just have some activity :), then call the
		1682	callback, which will "do the right thing" and start the timer:
		1683
		1684	ev_init (timer, callback);
		1685	last_activity = ev_now (loop);
		1686	callback (loop, timer, EV_TIMEOUT);
		1687
		1688	And when there is some activity, simply store the current time in
		1689	C<last_activity>, no libev calls at all:
		1690
		1691	last_actiivty = ev_now (loop);
		1692
		1693	This technique is slightly more complex, but in most cases where the
		1694	time-out is unlikely to be triggered, much more efficient.
		1695
		1696	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1697	callback :) - just change the timeout and invoke the callback, which will
		1698	fix things for you.
		1699
		1700	=item 4. Wee, just use a double-linked list for your timeouts.
		1701
		1702	If there is not one request, but many thousands (millions...), all
		1703	employing some kind of timeout with the same timeout value, then one can
		1704	do even better:
		1705
		1706	When starting the timeout, calculate the timeout value and put the timeout
		1707	at the I<end> of the list.
		1708
		1709	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1710	the list is expected to fire (for example, using the technique #3).
		1711
		1712	When there is some activity, remove the timer from the list, recalculate
		1713	the timeout, append it to the end of the list again, and make sure to
		1714	update the C<ev_timer> if it was taken from the beginning of the list.
		1715
		1716	This way, one can manage an unlimited number of timeouts in O(1) time for
		1717	starting, stopping and updating the timers, at the expense of a major
		1718	complication, and having to use a constant timeout. The constant timeout
		1719	ensures that the list stays sorted.
		1720
		1721	=back
		1722
		1723	So which method the best?
		1724
		1725	Method #2 is a simple no-brain-required solution that is adequate in most
		1726	situations. Method #3 requires a bit more thinking, but handles many cases
		1727	better, and isn't very complicated either. In most case, choosing either
		1728	one is fine, with #3 being better in typical situations.
		1729
		1730	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1731	rather complicated, but extremely efficient, something that really pays
		1732	off after the first million or so of active timers, i.e. it's usually
		1733	overkill :)
		1734
		1735	=head3 The special problem of time updates
		1736
		1737	Establishing the current time is a costly operation (it usually takes at
		1738	least two system calls): EV therefore updates its idea of the current
		1739	time only before and after C<ev_loop> collects new events, which causes a
		1740	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1741	lots of events in one iteration.
1192		1742
1193	The relative timeouts are calculated relative to the C<ev_now ()>	1743	The relative timeouts are calculated relative to the C<ev_now ()>
1194	time. This is usually the right thing as this timestamp refers to the time	1744	time. This is usually the right thing as this timestamp refers to the time
1195	of the event triggering whatever timeout you are modifying/starting. If	1745	of the event triggering whatever timeout you are modifying/starting. If
1196	you suspect event processing to be delayed and you I<need> to base the timeout	1746	you suspect event processing to be delayed and you I<need> to base the
1197	on the current time, use something like this to adjust for this:	1747	timeout on the current time, use something like this to adjust for this:
1198		1748
1199	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1749	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1200		1750
1201	The callback is guaranteed to be invoked only after its timeout has passed,	1751	If the event loop is suspended for a long time, you can also force an
1202	but if multiple timers become ready during the same loop iteration then	1752	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1203	order of execution is undefined.	1753	()>.
1204		1754
1205	=head3 Watcher-Specific Functions and Data Members	1755	=head3 Watcher-Specific Functions and Data Members
1206		1756
1207	=over 4	1757	=over 4
1208		1758
…		…
1232	If the timer is started but non-repeating, stop it (as if it timed out).	1782	If the timer is started but non-repeating, stop it (as if it timed out).
1233		1783
1234	If the timer is repeating, either start it if necessary (with the	1784	If the timer is repeating, either start it if necessary (with the
1235	C<repeat> value), or reset the running timer to the C<repeat> value.	1785	C<repeat> value), or reset the running timer to the C<repeat> value.
1236		1786
1237	This sounds a bit complicated, but here is a useful and typical	1787	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1238	example: Imagine you have a TCP connection and you want a so-called idle	1788	usage example.
1239	timeout, that is, you want to be called when there have been, say, 60
1240	seconds of inactivity on the socket. The easiest way to do this is to
1241	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1242	C<ev_timer_again> each time you successfully read or write some data. If
1243	you go into an idle state where you do not expect data to travel on the
1244	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1245	automatically restart it if need be.
1246
1247	That means you can ignore the C<after> value and C<ev_timer_start>
1248	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1249
1250	ev_timer_init (timer, callback, 0., 5.);
1251	ev_timer_again (loop, timer);
1252	...
1253	timer->again = 17.;
1254	ev_timer_again (loop, timer);
1255	...
1256	timer->again = 10.;
1257	ev_timer_again (loop, timer);
1258
1259	This is more slightly efficient then stopping/starting the timer each time
1260	you want to modify its timeout value.
1261		1789
1262	=item ev_tstamp repeat [read-write]	1790	=item ev_tstamp repeat [read-write]
1263		1791
1264	The current C<repeat> value. Will be used each time the watcher times out	1792	The current C<repeat> value. Will be used each time the watcher times out
1265	or C<ev_timer_again> is called and determines the next timeout (if any),	1793	or C<ev_timer_again> is called, and determines the next timeout (if any),
1266	which is also when any modifications are taken into account.	1794	which is also when any modifications are taken into account.
1267		1795
1268	=back	1796	=back
1269		1797
1270	=head3 Examples	1798	=head3 Examples
1271		1799
1272	Example: Create a timer that fires after 60 seconds.	1800	Example: Create a timer that fires after 60 seconds.
1273		1801
1274	static void	1802	static void
1275	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1803	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1276	{	1804	{
1277	.. one minute over, w is actually stopped right here	1805	.. one minute over, w is actually stopped right here
1278	}	1806	}
1279		1807
1280	struct ev_timer mytimer;	1808	ev_timer mytimer;
1281	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1809	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1282	ev_timer_start (loop, &mytimer);	1810	ev_timer_start (loop, &mytimer);
1283		1811
1284	Example: Create a timeout timer that times out after 10 seconds of	1812	Example: Create a timeout timer that times out after 10 seconds of
1285	inactivity.	1813	inactivity.
1286		1814
1287	static void	1815	static void
1288	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1816	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1289	{	1817	{
1290	.. ten seconds without any activity	1818	.. ten seconds without any activity
1291	}	1819	}
1292		1820
1293	struct ev_timer mytimer;	1821	ev_timer mytimer;
1294	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1822	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1295	ev_timer_again (&mytimer); /* start timer */	1823	ev_timer_again (&mytimer); /* start timer */
1296	ev_loop (loop, 0);	1824	ev_loop (loop, 0);
1297		1825
1298	// and in some piece of code that gets executed on any "activity":	1826	// and in some piece of code that gets executed on any "activity":
…		…
1303	=head2 C<ev_periodic> - to cron or not to cron?	1831	=head2 C<ev_periodic> - to cron or not to cron?
1304		1832
1305	Periodic watchers are also timers of a kind, but they are very versatile	1833	Periodic watchers are also timers of a kind, but they are very versatile
1306	(and unfortunately a bit complex).	1834	(and unfortunately a bit complex).
1307		1835
1308	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1836	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1309	but on wall clock time (absolute time). You can tell a periodic watcher	1837	relative time, the physical time that passes) but on wall clock time
1310	to trigger after some specific point in time. For example, if you tell a	1838	(absolute time, the thing you can read on your calender or clock). The
1311	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	1839	difference is that wall clock time can run faster or slower than real
1312	+ 10.>, that is, an absolute time not a delay) and then reset your system	1840	time, and time jumps are not uncommon (e.g. when you adjust your
1313	clock to January of the previous year, then it will take more than year	1841	wrist-watch).
1314	to trigger the event (unlike an C<ev_timer>, which would still trigger
1315	roughly 10 seconds later as it uses a relative timeout).
1316		1842
		1843	You can tell a periodic watcher to trigger after some specific point
		1844	in time: for example, if you tell a periodic watcher to trigger "in 10
		1845	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1846	not a delay) and then reset your system clock to January of the previous
		1847	year, then it will take a year or more to trigger the event (unlike an
		1848	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1849	it, as it uses a relative timeout).
		1850
1317	C<ev_periodic>s can also be used to implement vastly more complex timers,	1851	C<ev_periodic> watchers can also be used to implement vastly more complex
1318	such as triggering an event on each "midnight, local time", or other	1852	timers, such as triggering an event on each "midnight, local time", or
1319	complicated, rules.	1853	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1854	those cannot react to time jumps.
1320		1855
1321	As with timers, the callback is guaranteed to be invoked only when the	1856	As with timers, the callback is guaranteed to be invoked only when the
1322	time (C<at>) has passed, but if multiple periodic timers become ready	1857	point in time where it is supposed to trigger has passed. If multiple
1323	during the same loop iteration then order of execution is undefined.	1858	timers become ready during the same loop iteration then the ones with
		1859	earlier time-out values are invoked before ones with later time-out values
		1860	(but this is no longer true when a callback calls C<ev_loop> recursively).
1324		1861
1325	=head3 Watcher-Specific Functions and Data Members	1862	=head3 Watcher-Specific Functions and Data Members
1326		1863
1327	=over 4	1864	=over 4
1328		1865
1329	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1866	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1330		1867
1331	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1868	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1332		1869
1333	Lots of arguments, lets sort it out... There are basically three modes of	1870	Lots of arguments, let's sort it out... There are basically three modes of
1334	operation, and we will explain them from simplest to complex:	1871	operation, and we will explain them from simplest to most complex:
1335		1872
1336	=over 4	1873	=over 4
1337		1874
1338	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1875	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1339		1876
1340	In this configuration the watcher triggers an event after the wall clock	1877	In this configuration the watcher triggers an event after the wall clock
1341	time C<at> has passed and doesn't repeat. It will not adjust when a time	1878	time C<offset> has passed. It will not repeat and will not adjust when a
1342	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1879	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1343	run when the system time reaches or surpasses this time.	1880	will be stopped and invoked when the system clock reaches or surpasses
		1881	this point in time.
1344		1882
1345	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1883	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1346		1884
1347	In this mode the watcher will always be scheduled to time out at the next	1885	In this mode the watcher will always be scheduled to time out at the next
1348	C<at + N * interval> time (for some integer N, which can also be negative)	1886	C<offset + N * interval> time (for some integer N, which can also be
1349	and then repeat, regardless of any time jumps.	1887	negative) and then repeat, regardless of any time jumps. The C<offset>
		1888	argument is merely an offset into the C<interval> periods.
1350		1889
1351	This can be used to create timers that do not drift with respect to system	1890	This can be used to create timers that do not drift with respect to the
1352	time, for example, here is a C<ev_periodic> that triggers each hour, on	1891	system clock, for example, here is an C<ev_periodic> that triggers each
1353	the hour:	1892	hour, on the hour (with respect to UTC):
1354		1893
1355	ev_periodic_set (&periodic, 0., 3600., 0);	1894	ev_periodic_set (&periodic, 0., 3600., 0);
1356		1895
1357	This doesn't mean there will always be 3600 seconds in between triggers,	1896	This doesn't mean there will always be 3600 seconds in between triggers,
1358	but only that the callback will be called when the system time shows a	1897	but only that the callback will be called when the system time shows a
1359	full hour (UTC), or more correctly, when the system time is evenly divisible	1898	full hour (UTC), or more correctly, when the system time is evenly divisible
1360	by 3600.	1899	by 3600.
1361		1900
1362	Another way to think about it (for the mathematically inclined) is that	1901	Another way to think about it (for the mathematically inclined) is that
1363	C<ev_periodic> will try to run the callback in this mode at the next possible	1902	C<ev_periodic> will try to run the callback in this mode at the next possible
1364	time where C<time = at (mod interval)>, regardless of any time jumps.	1903	time where C<time = offset (mod interval)>, regardless of any time jumps.
1365		1904
1366	For numerical stability it is preferable that the C<at> value is near	1905	For numerical stability it is preferable that the C<offset> value is near
1367	C<ev_now ()> (the current time), but there is no range requirement for	1906	C<ev_now ()> (the current time), but there is no range requirement for
1368	this value, and in fact is often specified as zero.	1907	this value, and in fact is often specified as zero.
1369		1908
1370	Note also that there is an upper limit to how often a timer can fire (CPU	1909	Note also that there is an upper limit to how often a timer can fire (CPU
1371	speed for example), so if C<interval> is very small then timing stability	1910	speed for example), so if C<interval> is very small then timing stability
1372	will of course deteriorate. Libev itself tries to be exact to be about one	1911	will of course deteriorate. Libev itself tries to be exact to be about one
1373	millisecond (if the OS supports it and the machine is fast enough).	1912	millisecond (if the OS supports it and the machine is fast enough).
1374		1913
1375	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1914	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1376		1915
1377	In this mode the values for C<interval> and C<at> are both being	1916	In this mode the values for C<interval> and C<offset> are both being
1378	ignored. Instead, each time the periodic watcher gets scheduled, the	1917	ignored. Instead, each time the periodic watcher gets scheduled, the
1379	reschedule callback will be called with the watcher as first, and the	1918	reschedule callback will be called with the watcher as first, and the
1380	current time as second argument.	1919	current time as second argument.
1381		1920
1382	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1921	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1383	ever, or make ANY event loop modifications whatsoever>.	1922	or make ANY other event loop modifications whatsoever, unless explicitly
		1923	allowed by documentation here>.
1384		1924
1385	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1925	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1386	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	1926	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1387	only event loop modification you are allowed to do).	1927	only event loop modification you are allowed to do).
1388		1928
1389	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1929	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1390	*w, ev_tstamp now)>, e.g.:	1930	*w, ev_tstamp now)>, e.g.:
1391		1931
		1932	static ev_tstamp
1392	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1933	my_rescheduler (ev_periodic *w, ev_tstamp now)
1393	{	1934	{
1394	return now + 60.;	1935	return now + 60.;
1395	}	1936	}
1396		1937
1397	It must return the next time to trigger, based on the passed time value	1938	It must return the next time to trigger, based on the passed time value
…		…
1417	a different time than the last time it was called (e.g. in a crond like	1958	a different time than the last time it was called (e.g. in a crond like
1418	program when the crontabs have changed).	1959	program when the crontabs have changed).
1419		1960
1420	=item ev_tstamp ev_periodic_at (ev_periodic *)	1961	=item ev_tstamp ev_periodic_at (ev_periodic *)
1421		1962
1422	When active, returns the absolute time that the watcher is supposed to	1963	When active, returns the absolute time that the watcher is supposed
1423	trigger next.	1964	to trigger next. This is not the same as the C<offset> argument to
		1965	C<ev_periodic_set>, but indeed works even in interval and manual
		1966	rescheduling modes.
1424		1967
1425	=item ev_tstamp offset [read-write]	1968	=item ev_tstamp offset [read-write]
1426		1969
1427	When repeating, this contains the offset value, otherwise this is the	1970	When repeating, this contains the offset value, otherwise this is the
1428	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1971	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		1972	although libev might modify this value for better numerical stability).
1429		1973
1430	Can be modified any time, but changes only take effect when the periodic	1974	Can be modified any time, but changes only take effect when the periodic
1431	timer fires or C<ev_periodic_again> is being called.	1975	timer fires or C<ev_periodic_again> is being called.
1432		1976
1433	=item ev_tstamp interval [read-write]	1977	=item ev_tstamp interval [read-write]
1434		1978
1435	The current interval value. Can be modified any time, but changes only	1979	The current interval value. Can be modified any time, but changes only
1436	take effect when the periodic timer fires or C<ev_periodic_again> is being	1980	take effect when the periodic timer fires or C<ev_periodic_again> is being
1437	called.	1981	called.
1438		1982
1439	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1983	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1440		1984
1441	The current reschedule callback, or C<0>, if this functionality is	1985	The current reschedule callback, or C<0>, if this functionality is
1442	switched off. Can be changed any time, but changes only take effect when	1986	switched off. Can be changed any time, but changes only take effect when
1443	the periodic timer fires or C<ev_periodic_again> is being called.	1987	the periodic timer fires or C<ev_periodic_again> is being called.
1444		1988
1445	=back	1989	=back
1446		1990
1447	=head3 Examples	1991	=head3 Examples
1448		1992
1449	Example: Call a callback every hour, or, more precisely, whenever the	1993	Example: Call a callback every hour, or, more precisely, whenever the
1450	system clock is divisible by 3600. The callback invocation times have	1994	system time is divisible by 3600. The callback invocation times have
1451	potentially a lot of jitter, but good long-term stability.	1995	potentially a lot of jitter, but good long-term stability.
1452		1996
1453	static void	1997	static void
1454	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1998	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1455	{	1999	{
1456	... its now a full hour (UTC, or TAI or whatever your clock follows)	2000	... its now a full hour (UTC, or TAI or whatever your clock follows)
1457	}	2001	}
1458		2002
1459	struct ev_periodic hourly_tick;	2003	ev_periodic hourly_tick;
1460	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2004	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1461	ev_periodic_start (loop, &hourly_tick);	2005	ev_periodic_start (loop, &hourly_tick);
1462		2006
1463	Example: The same as above, but use a reschedule callback to do it:	2007	Example: The same as above, but use a reschedule callback to do it:
1464		2008
1465	#include <math.h>	2009	#include <math.h>
1466		2010
1467	static ev_tstamp	2011	static ev_tstamp
1468	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2012	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1469	{	2013	{
1470	return fmod (now, 3600.) + 3600.;	2014	return now + (3600. - fmod (now, 3600.));
1471	}	2015	}
1472		2016
1473	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2017	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1474		2018
1475	Example: Call a callback every hour, starting now:	2019	Example: Call a callback every hour, starting now:
1476		2020
1477	struct ev_periodic hourly_tick;	2021	ev_periodic hourly_tick;
1478	ev_periodic_init (&hourly_tick, clock_cb,	2022	ev_periodic_init (&hourly_tick, clock_cb,
1479	fmod (ev_now (loop), 3600.), 3600., 0);	2023	fmod (ev_now (loop), 3600.), 3600., 0);
1480	ev_periodic_start (loop, &hourly_tick);	2024	ev_periodic_start (loop, &hourly_tick);
1481		2025
1482		2026
…		…
1485	Signal watchers will trigger an event when the process receives a specific	2029	Signal watchers will trigger an event when the process receives a specific
1486	signal one or more times. Even though signals are very asynchronous, libev	2030	signal one or more times. Even though signals are very asynchronous, libev
1487	will try it's best to deliver signals synchronously, i.e. as part of the	2031	will try it's best to deliver signals synchronously, i.e. as part of the
1488	normal event processing, like any other event.	2032	normal event processing, like any other event.
1489		2033
		2034	If you want signals asynchronously, just use C<sigaction> as you would
		2035	do without libev and forget about sharing the signal. You can even use
		2036	C<ev_async> from a signal handler to synchronously wake up an event loop.
		2037
1490	You can configure as many watchers as you like per signal. Only when the	2038	You can configure as many watchers as you like per signal. Only when the
1491	first watcher gets started will libev actually register a signal watcher	2039	first watcher gets started will libev actually register a signal handler
1492	with the kernel (thus it coexists with your own signal handlers as long	2040	with the kernel (thus it coexists with your own signal handlers as long as
1493	as you don't register any with libev). Similarly, when the last signal	2041	you don't register any with libev for the same signal). Similarly, when
1494	watcher for a signal is stopped libev will reset the signal handler to	2042	the last signal watcher for a signal is stopped, libev will reset the
1495	SIG_DFL (regardless of what it was set to before).	2043	signal handler to SIG_DFL (regardless of what it was set to before).
1496		2044
1497	If possible and supported, libev will install its handlers with	2045	If possible and supported, libev will install its handlers with
1498	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2046	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1499	interrupted. If you have a problem with system calls getting interrupted by	2047	interrupted. If you have a problem with system calls getting interrupted by
1500	signals you can block all signals in an C<ev_check> watcher and unblock	2048	signals you can block all signals in an C<ev_check> watcher and unblock
…		…
1517		2065
1518	=back	2066	=back
1519		2067
1520	=head3 Examples	2068	=head3 Examples
1521		2069
1522	Example: Try to exit cleanly on SIGINT and SIGTERM.	2070	Example: Try to exit cleanly on SIGINT.
1523		2071
1524	static void	2072	static void
1525	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2073	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1526	{	2074	{
1527	ev_unloop (loop, EVUNLOOP_ALL);	2075	ev_unloop (loop, EVUNLOOP_ALL);
1528	}	2076	}
1529		2077
1530	struct ev_signal signal_watcher;	2078	ev_signal signal_watcher;
1531	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2079	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1532	ev_signal_start (loop, &sigint_cb);	2080	ev_signal_start (loop, &signal_watcher);
1533		2081
1534		2082
1535	=head2 C<ev_child> - watch out for process status changes	2083	=head2 C<ev_child> - watch out for process status changes
1536		2084
1537	Child watchers trigger when your process receives a SIGCHLD in response to	2085	Child watchers trigger when your process receives a SIGCHLD in response to
1538	some child status changes (most typically when a child of yours dies). It	2086	some child status changes (most typically when a child of yours dies or
1539	is permissible to install a child watcher I<after> the child has been	2087	exits). It is permissible to install a child watcher I<after> the child
1540	forked (which implies it might have already exited), as long as the event	2088	has been forked (which implies it might have already exited), as long
1541	loop isn't entered (or is continued from a watcher).	2089	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2090	forking and then immediately registering a watcher for the child is fine,
		2091	but forking and registering a watcher a few event loop iterations later or
		2092	in the next callback invocation is not.
1542		2093
1543	Only the default event loop is capable of handling signals, and therefore	2094	Only the default event loop is capable of handling signals, and therefore
1544	you can only register child watchers in the default event loop.	2095	you can only register child watchers in the default event loop.
		2096
		2097	Due to some design glitches inside libev, child watchers will always be
		2098	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2099	libev)
1545		2100
1546	=head3 Process Interaction	2101	=head3 Process Interaction
1547		2102
1548	Libev grabs C<SIGCHLD> as soon as the default event loop is	2103	Libev grabs C<SIGCHLD> as soon as the default event loop is
1549	initialised. This is necessary to guarantee proper behaviour even if	2104	initialised. This is necessary to guarantee proper behaviour even if
…		…
1559	handler, you can override it easily by installing your own handler for	2114	handler, you can override it easily by installing your own handler for
1560	C<SIGCHLD> after initialising the default loop, and making sure the	2115	C<SIGCHLD> after initialising the default loop, and making sure the
1561	default loop never gets destroyed. You are encouraged, however, to use an	2116	default loop never gets destroyed. You are encouraged, however, to use an
1562	event-based approach to child reaping and thus use libev's support for	2117	event-based approach to child reaping and thus use libev's support for
1563	that, so other libev users can use C<ev_child> watchers freely.	2118	that, so other libev users can use C<ev_child> watchers freely.
		2119
		2120	=head3 Stopping the Child Watcher
		2121
		2122	Currently, the child watcher never gets stopped, even when the
		2123	child terminates, so normally one needs to stop the watcher in the
		2124	callback. Future versions of libev might stop the watcher automatically
		2125	when a child exit is detected.
1564		2126
1565	=head3 Watcher-Specific Functions and Data Members	2127	=head3 Watcher-Specific Functions and Data Members
1566		2128
1567	=over 4	2129	=over 4
1568		2130
…		…
1600	its completion.	2162	its completion.
1601		2163
1602	ev_child cw;	2164	ev_child cw;
1603		2165
1604	static void	2166	static void
1605	child_cb (EV_P_ struct ev_child *w, int revents)	2167	child_cb (EV_P_ ev_child *w, int revents)
1606	{	2168	{
1607	ev_child_stop (EV_A_ w);	2169	ev_child_stop (EV_A_ w);
1608	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2170	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1609	}	2171	}
1610		2172
…		…
1625		2187
1626		2188
1627	=head2 C<ev_stat> - did the file attributes just change?	2189	=head2 C<ev_stat> - did the file attributes just change?
1628		2190
1629	This watches a file system path for attribute changes. That is, it calls	2191	This watches a file system path for attribute changes. That is, it calls
1630	C<stat> regularly (or when the OS says it changed) and sees if it changed	2192	C<stat> on that path in regular intervals (or when the OS says it changed)
1631	compared to the last time, invoking the callback if it did.	2193	and sees if it changed compared to the last time, invoking the callback if
		2194	it did.
1632		2195
1633	The path does not need to exist: changing from "path exists" to "path does	2196	The path does not need to exist: changing from "path exists" to "path does
1634	not exist" is a status change like any other. The condition "path does	2197	not exist" is a status change like any other. The condition "path does not
1635	not exist" is signified by the C<st_nlink> field being zero (which is	2198	exist" (or more correctly "path cannot be stat'ed") is signified by the
1636	otherwise always forced to be at least one) and all the other fields of	2199	C<st_nlink> field being zero (which is otherwise always forced to be at
1637	the stat buffer having unspecified contents.	2200	least one) and all the other fields of the stat buffer having unspecified
		2201	contents.
1638		2202
1639	The path I<should> be absolute and I<must not> end in a slash. If it is	2203	The path I<must not> end in a slash or contain special components such as
		2204	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1640	relative and your working directory changes, the behaviour is undefined.	2205	your working directory changes, then the behaviour is undefined.
1641		2206
1642	Since there is no standard to do this, the portable implementation simply	2207	Since there is no portable change notification interface available, the
1643	calls C<stat (2)> regularly on the path to see if it changed somehow. You	2208	portable implementation simply calls C<stat(2)> regularly on the path
1644	can specify a recommended polling interval for this case. If you specify	2209	to see if it changed somehow. You can specify a recommended polling
1645	a polling interval of C<0> (highly recommended!) then a I<suitable,	2210	interval for this case. If you specify a polling interval of C<0> (highly
1646	unspecified default> value will be used (which you can expect to be around	2211	recommended!) then a I<suitable, unspecified default> value will be used
1647	five seconds, although this might change dynamically). Libev will also	2212	(which you can expect to be around five seconds, although this might
1648	impose a minimum interval which is currently around C<0.1>, but thats	2213	change dynamically). Libev will also impose a minimum interval which is
1649	usually overkill.	2214	currently around C<0.1>, but that's usually overkill.
1650		2215
1651	This watcher type is not meant for massive numbers of stat watchers,	2216	This watcher type is not meant for massive numbers of stat watchers,
1652	as even with OS-supported change notifications, this can be	2217	as even with OS-supported change notifications, this can be
1653	resource-intensive.	2218	resource-intensive.
1654		2219
1655	At the time of this writing, only the Linux inotify interface is	2220	At the time of this writing, the only OS-specific interface implemented
1656	implemented (implementing kqueue support is left as an exercise for the	2221	is the Linux inotify interface (implementing kqueue support is left as an
1657	reader, note, however, that the author sees no way of implementing ev_stat	2222	exercise for the reader. Note, however, that the author sees no way of
1658	semantics with kqueue). Inotify will be used to give hints only and should	2223	implementing C<ev_stat> semantics with kqueue, except as a hint).
1659	not change the semantics of C<ev_stat> watchers, which means that libev
1660	sometimes needs to fall back to regular polling again even with inotify,
1661	but changes are usually detected immediately, and if the file exists there
1662	will be no polling.
1663		2224
1664	=head3 ABI Issues (Largefile Support)	2225	=head3 ABI Issues (Largefile Support)
1665		2226
1666	Libev by default (unless the user overrides this) uses the default	2227	Libev by default (unless the user overrides this) uses the default
1667	compilation environment, which means that on systems with optionally	2228	compilation environment, which means that on systems with large file
1668	disabled large file support, you get the 32 bit version of the stat	2229	support disabled by default, you get the 32 bit version of the stat
1669	structure. When using the library from programs that change the ABI to	2230	structure. When using the library from programs that change the ABI to
1670	use 64 bit file offsets the programs will fail. In that case you have to	2231	use 64 bit file offsets the programs will fail. In that case you have to
1671	compile libev with the same flags to get binary compatibility. This is	2232	compile libev with the same flags to get binary compatibility. This is
1672	obviously the case with any flags that change the ABI, but the problem is	2233	obviously the case with any flags that change the ABI, but the problem is
1673	most noticeably with ev_stat and large file support.	2234	most noticeably displayed with ev_stat and large file support.
1674		2235
1675	=head3 Inotify	2236	The solution for this is to lobby your distribution maker to make large
		2237	file interfaces available by default (as e.g. FreeBSD does) and not
		2238	optional. Libev cannot simply switch on large file support because it has
		2239	to exchange stat structures with application programs compiled using the
		2240	default compilation environment.
1676		2241
		2242	=head3 Inotify and Kqueue
		2243
1677	When C<inotify (7)> support has been compiled into libev (generally only	2244	When C<inotify (7)> support has been compiled into libev and present at
1678	available on Linux) and present at runtime, it will be used to speed up	2245	runtime, it will be used to speed up change detection where possible. The
1679	change detection where possible. The inotify descriptor will be created lazily	2246	inotify descriptor will be created lazily when the first C<ev_stat>
1680	when the first C<ev_stat> watcher is being started.	2247	watcher is being started.
1681		2248
1682	Inotify presence does not change the semantics of C<ev_stat> watchers	2249	Inotify presence does not change the semantics of C<ev_stat> watchers
1683	except that changes might be detected earlier, and in some cases, to avoid	2250	except that changes might be detected earlier, and in some cases, to avoid
1684	making regular C<stat> calls. Even in the presence of inotify support	2251	making regular C<stat> calls. Even in the presence of inotify support
1685	there are many cases where libev has to resort to regular C<stat> polling.	2252	there are many cases where libev has to resort to regular C<stat> polling,
		2253	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2254	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2255	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2256	xfs are fully working) libev usually gets away without polling.
1686		2257
1687	(There is no support for kqueue, as apparently it cannot be used to	2258	There is no support for kqueue, as apparently it cannot be used to
1688	implement this functionality, due to the requirement of having a file	2259	implement this functionality, due to the requirement of having a file
1689	descriptor open on the object at all times).	2260	descriptor open on the object at all times, and detecting renames, unlinks
		2261	etc. is difficult.
		2262
		2263	=head3 C<stat ()> is a synchronous operation
		2264
		2265	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2266	the process. The exception are C<ev_stat> watchers - those call C<stat
		2267	()>, which is a synchronous operation.
		2268
		2269	For local paths, this usually doesn't matter: unless the system is very
		2270	busy or the intervals between stat's are large, a stat call will be fast,
		2271	as the path data is usually in memory already (except when starting the
		2272	watcher).
		2273
		2274	For networked file systems, calling C<stat ()> can block an indefinite
		2275	time due to network issues, and even under good conditions, a stat call
		2276	often takes multiple milliseconds.
		2277
		2278	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2279	paths, although this is fully supported by libev.
1690		2280
1691	=head3 The special problem of stat time resolution	2281	=head3 The special problem of stat time resolution
1692		2282
1693	The C<stat ()> system call only supports full-second resolution portably, and	2283	The C<stat ()> system call only supports full-second resolution portably,
1694	even on systems where the resolution is higher, many file systems still	2284	and even on systems where the resolution is higher, most file systems
1695	only support whole seconds.	2285	still only support whole seconds.
1696		2286
1697	That means that, if the time is the only thing that changes, you can	2287	That means that, if the time is the only thing that changes, you can
1698	easily miss updates: on the first update, C<ev_stat> detects a change and	2288	easily miss updates: on the first update, C<ev_stat> detects a change and
1699	calls your callback, which does something. When there is another update	2289	calls your callback, which does something. When there is another update
1700	within the same second, C<ev_stat> will be unable to detect it as the stat	2290	within the same second, C<ev_stat> will be unable to detect unless the
1701	data does not change.	2291	stat data does change in other ways (e.g. file size).
1702		2292
1703	The solution to this is to delay acting on a change for slightly more	2293	The solution to this is to delay acting on a change for slightly more
1704	than a second (or till slightly after the next full second boundary), using	2294	than a second (or till slightly after the next full second boundary), using
1705	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2295	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1706	ev_timer_again (loop, w)>).	2296	ev_timer_again (loop, w)>).
…		…
1726	C<path>. The C<interval> is a hint on how quickly a change is expected to	2316	C<path>. The C<interval> is a hint on how quickly a change is expected to
1727	be detected and should normally be specified as C<0> to let libev choose	2317	be detected and should normally be specified as C<0> to let libev choose
1728	a suitable value. The memory pointed to by C<path> must point to the same	2318	a suitable value. The memory pointed to by C<path> must point to the same
1729	path for as long as the watcher is active.	2319	path for as long as the watcher is active.
1730		2320
1731	The callback will receive C<EV_STAT> when a change was detected, relative	2321	The callback will receive an C<EV_STAT> event when a change was detected,
1732	to the attributes at the time the watcher was started (or the last change	2322	relative to the attributes at the time the watcher was started (or the
1733	was detected).	2323	last change was detected).
1734		2324
1735	=item ev_stat_stat (loop, ev_stat *)	2325	=item ev_stat_stat (loop, ev_stat *)
1736		2326
1737	Updates the stat buffer immediately with new values. If you change the	2327	Updates the stat buffer immediately with new values. If you change the
1738	watched path in your callback, you could call this function to avoid	2328	watched path in your callback, you could call this function to avoid
…		…
1821		2411
1822		2412
1823	=head2 C<ev_idle> - when you've got nothing better to do...	2413	=head2 C<ev_idle> - when you've got nothing better to do...
1824		2414
1825	Idle watchers trigger events when no other events of the same or higher	2415	Idle watchers trigger events when no other events of the same or higher
1826	priority are pending (prepare, check and other idle watchers do not	2416	priority are pending (prepare, check and other idle watchers do not count
1827	count).	2417	as receiving "events").
1828		2418
1829	That is, as long as your process is busy handling sockets or timeouts	2419	That is, as long as your process is busy handling sockets or timeouts
1830	(or even signals, imagine) of the same or higher priority it will not be	2420	(or even signals, imagine) of the same or higher priority it will not be
1831	triggered. But when your process is idle (or only lower-priority watchers	2421	triggered. But when your process is idle (or only lower-priority watchers
1832	are pending), the idle watchers are being called once per event loop	2422	are pending), the idle watchers are being called once per event loop
…		…
1843		2433
1844	=head3 Watcher-Specific Functions and Data Members	2434	=head3 Watcher-Specific Functions and Data Members
1845		2435
1846	=over 4	2436	=over 4
1847		2437
1848	=item ev_idle_init (ev_signal *, callback)	2438	=item ev_idle_init (ev_idle *, callback)
1849		2439
1850	Initialises and configures the idle watcher - it has no parameters of any	2440	Initialises and configures the idle watcher - it has no parameters of any
1851	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2441	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1852	believe me.	2442	believe me.
1853		2443
…		…
1857		2447
1858	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2448	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1859	callback, free it. Also, use no error checking, as usual.	2449	callback, free it. Also, use no error checking, as usual.
1860		2450
1861	static void	2451	static void
1862	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2452	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1863	{	2453	{
1864	free (w);	2454	free (w);
1865	// now do something you wanted to do when the program has	2455	// now do something you wanted to do when the program has
1866	// no longer anything immediate to do.	2456	// no longer anything immediate to do.
1867	}	2457	}
1868		2458
1869	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2459	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1870	ev_idle_init (idle_watcher, idle_cb);	2460	ev_idle_init (idle_watcher, idle_cb);
1871	ev_idle_start (loop, idle_cb);	2461	ev_idle_start (loop, idle_watcher);
1872		2462
1873		2463
1874	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2464	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1875		2465
1876	Prepare and check watchers are usually (but not always) used in tandem:	2466	Prepare and check watchers are usually (but not always) used in pairs:
1877	prepare watchers get invoked before the process blocks and check watchers	2467	prepare watchers get invoked before the process blocks and check watchers
1878	afterwards.	2468	afterwards.
1879		2469
1880	You I<must not> call C<ev_loop> or similar functions that enter	2470	You I<must not> call C<ev_loop> or similar functions that enter
1881	the current event loop from either C<ev_prepare> or C<ev_check>	2471	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1884	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2474	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1885	C<ev_check> so if you have one watcher of each kind they will always be	2475	C<ev_check> so if you have one watcher of each kind they will always be
1886	called in pairs bracketing the blocking call.	2476	called in pairs bracketing the blocking call.
1887		2477
1888	Their main purpose is to integrate other event mechanisms into libev and	2478	Their main purpose is to integrate other event mechanisms into libev and
1889	their use is somewhat advanced. This could be used, for example, to track	2479	their use is somewhat advanced. They could be used, for example, to track
1890	variable changes, implement your own watchers, integrate net-snmp or a	2480	variable changes, implement your own watchers, integrate net-snmp or a
1891	coroutine library and lots more. They are also occasionally useful if	2481	coroutine library and lots more. They are also occasionally useful if
1892	you cache some data and want to flush it before blocking (for example,	2482	you cache some data and want to flush it before blocking (for example,
1893	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2483	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1894	watcher).	2484	watcher).
1895		2485
1896	This is done by examining in each prepare call which file descriptors need	2486	This is done by examining in each prepare call which file descriptors
1897	to be watched by the other library, registering C<ev_io> watchers for	2487	need to be watched by the other library, registering C<ev_io> watchers
1898	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2488	for them and starting an C<ev_timer> watcher for any timeouts (many
1899	provide just this functionality). Then, in the check watcher you check for	2489	libraries provide exactly this functionality). Then, in the check watcher,
1900	any events that occurred (by checking the pending status of all watchers	2490	you check for any events that occurred (by checking the pending status
1901	and stopping them) and call back into the library. The I/O and timer	2491	of all watchers and stopping them) and call back into the library. The
1902	callbacks will never actually be called (but must be valid nevertheless,	2492	I/O and timer callbacks will never actually be called (but must be valid
1903	because you never know, you know?).	2493	nevertheless, because you never know, you know?).
1904		2494
1905	As another example, the Perl Coro module uses these hooks to integrate	2495	As another example, the Perl Coro module uses these hooks to integrate
1906	coroutines into libev programs, by yielding to other active coroutines	2496	coroutines into libev programs, by yielding to other active coroutines
1907	during each prepare and only letting the process block if no coroutines	2497	during each prepare and only letting the process block if no coroutines
1908	are ready to run (it's actually more complicated: it only runs coroutines	2498	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1911	loop from blocking if lower-priority coroutines are active, thus mapping	2501	loop from blocking if lower-priority coroutines are active, thus mapping
1912	low-priority coroutines to idle/background tasks).	2502	low-priority coroutines to idle/background tasks).
1913		2503
1914	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2504	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1915	priority, to ensure that they are being run before any other watchers	2505	priority, to ensure that they are being run before any other watchers
		2506	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2507
1916	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2508	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1917	too) should not activate ("feed") events into libev. While libev fully	2509	activate ("feed") events into libev. While libev fully supports this, they
1918	supports this, they might get executed before other C<ev_check> watchers	2510	might get executed before other C<ev_check> watchers did their job. As
1919	did their job. As C<ev_check> watchers are often used to embed other	2511	C<ev_check> watchers are often used to embed other (non-libev) event
1920	(non-libev) event loops those other event loops might be in an unusable	2512	loops those other event loops might be in an unusable state until their
1921	state until their C<ev_check> watcher ran (always remind yourself to	2513	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1922	coexist peacefully with others).	2514	others).
1923		2515
1924	=head3 Watcher-Specific Functions and Data Members	2516	=head3 Watcher-Specific Functions and Data Members
1925		2517
1926	=over 4	2518	=over 4
1927		2519
…		…
1929		2521
1930	=item ev_check_init (ev_check *, callback)	2522	=item ev_check_init (ev_check *, callback)
1931		2523
1932	Initialises and configures the prepare or check watcher - they have no	2524	Initialises and configures the prepare or check watcher - they have no
1933	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2525	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1934	macros, but using them is utterly, utterly and completely pointless.	2526	macros, but using them is utterly, utterly, utterly and completely
		2527	pointless.
1935		2528
1936	=back	2529	=back
1937		2530
1938	=head3 Examples	2531	=head3 Examples
1939		2532
…		…
1952		2545
1953	static ev_io iow [nfd];	2546	static ev_io iow [nfd];
1954	static ev_timer tw;	2547	static ev_timer tw;
1955		2548
1956	static void	2549	static void
1957	io_cb (ev_loop *loop, ev_io *w, int revents)	2550	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1958	{	2551	{
1959	}	2552	}
1960		2553
1961	// create io watchers for each fd and a timer before blocking	2554	// create io watchers for each fd and a timer before blocking
1962	static void	2555	static void
1963	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2556	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1964	{	2557	{
1965	int timeout = 3600000;	2558	int timeout = 3600000;
1966	struct pollfd fds [nfd];	2559	struct pollfd fds [nfd];
1967	// actual code will need to loop here and realloc etc.	2560	// actual code will need to loop here and realloc etc.
1968	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2561	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1969		2562
1970	/* the callback is illegal, but won't be called as we stop during check */	2563	/* the callback is illegal, but won't be called as we stop during check */
1971	ev_timer_init (&tw, 0, timeout * 1e-3);	2564	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
1972	ev_timer_start (loop, &tw);	2565	ev_timer_start (loop, &tw);
1973		2566
1974	// create one ev_io per pollfd	2567	// create one ev_io per pollfd
1975	for (int i = 0; i < nfd; ++i)	2568	for (int i = 0; i < nfd; ++i)
1976	{	2569	{
…		…
1983	}	2576	}
1984	}	2577	}
1985		2578
1986	// stop all watchers after blocking	2579	// stop all watchers after blocking
1987	static void	2580	static void
1988	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2581	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1989	{	2582	{
1990	ev_timer_stop (loop, &tw);	2583	ev_timer_stop (loop, &tw);
1991		2584
1992	for (int i = 0; i < nfd; ++i)	2585	for (int i = 0; i < nfd; ++i)
1993	{	2586	{
…		…
2032	}	2625	}
2033		2626
2034	// do not ever call adns_afterpoll	2627	// do not ever call adns_afterpoll
2035		2628
2036	Method 4: Do not use a prepare or check watcher because the module you	2629	Method 4: Do not use a prepare or check watcher because the module you
2037	want to embed is too inflexible to support it. Instead, you can override	2630	want to embed is not flexible enough to support it. Instead, you can
2038	their poll function. The drawback with this solution is that the main	2631	override their poll function. The drawback with this solution is that the
2039	loop is now no longer controllable by EV. The C<Glib::EV> module does	2632	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2040	this.	2633	this approach, effectively embedding EV as a client into the horrible
		2634	libglib event loop.
2041		2635
2042	static gint	2636	static gint
2043	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2637	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2044	{	2638	{
2045	int got_events = 0;	2639	int got_events = 0;
…		…
2076	prioritise I/O.	2670	prioritise I/O.
2077		2671
2078	As an example for a bug workaround, the kqueue backend might only support	2672	As an example for a bug workaround, the kqueue backend might only support
2079	sockets on some platform, so it is unusable as generic backend, but you	2673	sockets on some platform, so it is unusable as generic backend, but you
2080	still want to make use of it because you have many sockets and it scales	2674	still want to make use of it because you have many sockets and it scales
2081	so nicely. In this case, you would create a kqueue-based loop and embed it	2675	so nicely. In this case, you would create a kqueue-based loop and embed
2082	into your default loop (which might use e.g. poll). Overall operation will	2676	it into your default loop (which might use e.g. poll). Overall operation
2083	be a bit slower because first libev has to poll and then call kevent, but	2677	will be a bit slower because first libev has to call C<poll> and then
2084	at least you can use both at what they are best.	2678	C<kevent>, but at least you can use both mechanisms for what they are
		2679	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2085		2680
2086	As for prioritising I/O: rarely you have the case where some fds have	2681	As for prioritising I/O: under rare circumstances you have the case where
2087	to be watched and handled very quickly (with low latency), and even	2682	some fds have to be watched and handled very quickly (with low latency),
2088	priorities and idle watchers might have too much overhead. In this case	2683	and even priorities and idle watchers might have too much overhead. In
2089	you would put all the high priority stuff in one loop and all the rest in	2684	this case you would put all the high priority stuff in one loop and all
2090	a second one, and embed the second one in the first.	2685	the rest in a second one, and embed the second one in the first.
2091		2686
2092	As long as the watcher is active, the callback will be invoked every time	2687	As long as the watcher is active, the callback will be invoked every
2093	there might be events pending in the embedded loop. The callback must then	2688	time there might be events pending in the embedded loop. The callback
2094	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2689	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2095	their callbacks (you could also start an idle watcher to give the embedded	2690	sweep and invoke their callbacks (the callback doesn't need to invoke the
2096	loop strictly lower priority for example). You can also set the callback	2691	C<ev_embed_sweep> function directly, it could also start an idle watcher
2097	to C<0>, in which case the embed watcher will automatically execute the	2692	to give the embedded loop strictly lower priority for example).
2098	embedded loop sweep.
2099		2693
2100	As long as the watcher is started it will automatically handle events. The	2694	You can also set the callback to C<0>, in which case the embed watcher
2101	callback will be invoked whenever some events have been handled. You can	2695	will automatically execute the embedded loop sweep whenever necessary.
2102	set the callback to C<0> to avoid having to specify one if you are not
2103	interested in that.
2104		2696
2105	Also, there have not currently been made special provisions for forking:	2697	Fork detection will be handled transparently while the C<ev_embed> watcher
2106	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2698	is active, i.e., the embedded loop will automatically be forked when the
2107	but you will also have to stop and restart any C<ev_embed> watchers	2699	embedding loop forks. In other cases, the user is responsible for calling
2108	yourself.	2700	C<ev_loop_fork> on the embedded loop.
2109		2701
2110	Unfortunately, not all backends are embeddable, only the ones returned by	2702	Unfortunately, not all backends are embeddable: only the ones returned by
2111	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2703	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2112	portable one.	2704	portable one.
2113		2705
2114	So when you want to use this feature you will always have to be prepared	2706	So when you want to use this feature you will always have to be prepared
2115	that you cannot get an embeddable loop. The recommended way to get around	2707	that you cannot get an embeddable loop. The recommended way to get around
2116	this is to have a separate variables for your embeddable loop, try to	2708	this is to have a separate variables for your embeddable loop, try to
2117	create it, and if that fails, use the normal loop for everything.	2709	create it, and if that fails, use the normal loop for everything.
		2710
		2711	=head3 C<ev_embed> and fork
		2712
		2713	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2714	automatically be applied to the embedded loop as well, so no special
		2715	fork handling is required in that case. When the watcher is not running,
		2716	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2717	as applicable.
2118		2718
2119	=head3 Watcher-Specific Functions and Data Members	2719	=head3 Watcher-Specific Functions and Data Members
2120		2720
2121	=over 4	2721	=over 4
2122		2722
…		…
2150	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2750	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2151	used).	2751	used).
2152		2752
2153	struct ev_loop *loop_hi = ev_default_init (0);	2753	struct ev_loop *loop_hi = ev_default_init (0);
2154	struct ev_loop *loop_lo = 0;	2754	struct ev_loop *loop_lo = 0;
2155	struct ev_embed embed;	2755	ev_embed embed;
2156		2756
2157	// see if there is a chance of getting one that works	2757	// see if there is a chance of getting one that works
2158	// (remember that a flags value of 0 means autodetection)	2758	// (remember that a flags value of 0 means autodetection)
2159	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2759	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2160	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2760	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2174	kqueue implementation). Store the kqueue/socket-only event loop in	2774	kqueue implementation). Store the kqueue/socket-only event loop in
2175	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2775	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2176		2776
2177	struct ev_loop *loop = ev_default_init (0);	2777	struct ev_loop *loop = ev_default_init (0);
2178	struct ev_loop *loop_socket = 0;	2778	struct ev_loop *loop_socket = 0;
2179	struct ev_embed embed;	2779	ev_embed embed;
2180		2780
2181	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2781	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2182	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2782	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2183	{	2783	{
2184	ev_embed_init (&embed, 0, loop_socket);	2784	ev_embed_init (&embed, 0, loop_socket);
…		…
2199	event loop blocks next and before C<ev_check> watchers are being called,	2799	event loop blocks next and before C<ev_check> watchers are being called,
2200	and only in the child after the fork. If whoever good citizen calling	2800	and only in the child after the fork. If whoever good citizen calling
2201	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2801	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2202	handlers will be invoked, too, of course.	2802	handlers will be invoked, too, of course.
2203		2803
		2804	=head3 The special problem of life after fork - how is it possible?
		2805
		2806	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2807	up/change the process environment, followed by a call to C<exec()>. This
		2808	sequence should be handled by libev without any problems.
		2809
		2810	This changes when the application actually wants to do event handling
		2811	in the child, or both parent in child, in effect "continuing" after the
		2812	fork.
		2813
		2814	The default mode of operation (for libev, with application help to detect
		2815	forks) is to duplicate all the state in the child, as would be expected
		2816	when I<either> the parent I<or> the child process continues.
		2817
		2818	When both processes want to continue using libev, then this is usually the
		2819	wrong result. In that case, usually one process (typically the parent) is
		2820	supposed to continue with all watchers in place as before, while the other
		2821	process typically wants to start fresh, i.e. without any active watchers.
		2822
		2823	The cleanest and most efficient way to achieve that with libev is to
		2824	simply create a new event loop, which of course will be "empty", and
		2825	use that for new watchers. This has the advantage of not touching more
		2826	memory than necessary, and thus avoiding the copy-on-write, and the
		2827	disadvantage of having to use multiple event loops (which do not support
		2828	signal watchers).
		2829
		2830	When this is not possible, or you want to use the default loop for
		2831	other reasons, then in the process that wants to start "fresh", call
		2832	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2833	the default loop will "orphan" (not stop) all registered watchers, so you
		2834	have to be careful not to execute code that modifies those watchers. Note
		2835	also that in that case, you have to re-register any signal watchers.
		2836
2204	=head3 Watcher-Specific Functions and Data Members	2837	=head3 Watcher-Specific Functions and Data Members
2205		2838
2206	=over 4	2839	=over 4
2207		2840
2208	=item ev_fork_init (ev_signal *, callback)	2841	=item ev_fork_init (ev_signal *, callback)
…		…
2240	is that the author does not know of a simple (or any) algorithm for a	2873	is that the author does not know of a simple (or any) algorithm for a
2241	multiple-writer-single-reader queue that works in all cases and doesn't	2874	multiple-writer-single-reader queue that works in all cases and doesn't
2242	need elaborate support such as pthreads.	2875	need elaborate support such as pthreads.
2243		2876
2244	That means that if you want to queue data, you have to provide your own	2877	That means that if you want to queue data, you have to provide your own
2245	queue. But at least I can tell you would implement locking around your	2878	queue. But at least I can tell you how to implement locking around your
2246	queue:	2879	queue:
2247		2880
2248	=over 4	2881	=over 4
2249		2882
2250	=item queueing from a signal handler context	2883	=item queueing from a signal handler context
2251		2884
2252	To implement race-free queueing, you simply add to the queue in the signal	2885	To implement race-free queueing, you simply add to the queue in the signal
2253	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2886	handler but you block the signal handler in the watcher callback. Here is
2254	some fictitious SIGUSR1 handler:	2887	an example that does that for some fictitious SIGUSR1 handler:
2255		2888
2256	static ev_async mysig;	2889	static ev_async mysig;
2257		2890
2258	static void	2891	static void
2259	sigusr1_handler (void)	2892	sigusr1_handler (void)
…		…
2325	=over 4	2958	=over 4
2326		2959
2327	=item ev_async_init (ev_async *, callback)	2960	=item ev_async_init (ev_async *, callback)
2328		2961
2329	Initialises and configures the async watcher - it has no parameters of any	2962	Initialises and configures the async watcher - it has no parameters of any
2330	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2963	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2331	believe me.	2964	trust me.
2332		2965
2333	=item ev_async_send (loop, ev_async *)	2966	=item ev_async_send (loop, ev_async *)
2334		2967
2335	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2968	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2336	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2969	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2337	C<ev_feed_event>, this call is safe to do in other threads, signal or	2970	C<ev_feed_event>, this call is safe to do from other threads, signal or
2338	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	2971	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2339	section below on what exactly this means).	2972	section below on what exactly this means).
2340		2973
		2974	Note that, as with other watchers in libev, multiple events might get
		2975	compressed into a single callback invocation (another way to look at this
		2976	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		2977	reset when the event loop detects that).
		2978
2341	This call incurs the overhead of a system call only once per loop iteration,	2979	This call incurs the overhead of a system call only once per event loop
2342	so while the overhead might be noticeable, it doesn't apply to repeated	2980	iteration, so while the overhead might be noticeable, it doesn't apply to
2343	calls to C<ev_async_send>.	2981	repeated calls to C<ev_async_send> for the same event loop.
2344		2982
2345	=item bool = ev_async_pending (ev_async *)	2983	=item bool = ev_async_pending (ev_async *)
2346		2984
2347	Returns a non-zero value when C<ev_async_send> has been called on the	2985	Returns a non-zero value when C<ev_async_send> has been called on the
2348	watcher but the event has not yet been processed (or even noted) by the	2986	watcher but the event has not yet been processed (or even noted) by the
…		…
2351	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	2989	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2352	the loop iterates next and checks for the watcher to have become active,	2990	the loop iterates next and checks for the watcher to have become active,
2353	it will reset the flag again. C<ev_async_pending> can be used to very	2991	it will reset the flag again. C<ev_async_pending> can be used to very
2354	quickly check whether invoking the loop might be a good idea.	2992	quickly check whether invoking the loop might be a good idea.
2355		2993
2356	Not that this does I<not> check whether the watcher itself is pending, only	2994	Not that this does I<not> check whether the watcher itself is pending,
2357	whether it has been requested to make this watcher pending.	2995	only whether it has been requested to make this watcher pending: there
		2996	is a time window between the event loop checking and resetting the async
		2997	notification, and the callback being invoked.
2358		2998
2359	=back	2999	=back
2360		3000
2361		3001
2362	=head1 OTHER FUNCTIONS	3002	=head1 OTHER FUNCTIONS
…		…
2366	=over 4	3006	=over 4
2367		3007
2368	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3008	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2369		3009
2370	This function combines a simple timer and an I/O watcher, calls your	3010	This function combines a simple timer and an I/O watcher, calls your
2371	callback on whichever event happens first and automatically stop both	3011	callback on whichever event happens first and automatically stops both
2372	watchers. This is useful if you want to wait for a single event on an fd	3012	watchers. This is useful if you want to wait for a single event on an fd
2373	or timeout without having to allocate/configure/start/stop/free one or	3013	or timeout without having to allocate/configure/start/stop/free one or
2374	more watchers yourself.	3014	more watchers yourself.
2375		3015
2376	If C<fd> is less than 0, then no I/O watcher will be started and events	3016	If C<fd> is less than 0, then no I/O watcher will be started and the
2377	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	3017	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2378	C<events> set will be created and started.	3018	the given C<fd> and C<events> set will be created and started.
2379		3019
2380	If C<timeout> is less than 0, then no timeout watcher will be	3020	If C<timeout> is less than 0, then no timeout watcher will be
2381	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3021	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2382	repeat = 0) will be started. While C<0> is a valid timeout, it is of	3022	repeat = 0) will be started. C<0> is a valid timeout.
2383	dubious value.
2384		3023
2385	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3024	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2386	passed an C<revents> set like normal event callbacks (a combination of	3025	passed an C<revents> set like normal event callbacks (a combination of
2387	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3026	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2388	value passed to C<ev_once>:	3027	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3028	a timeout and an io event at the same time - you probably should give io
		3029	events precedence.
		3030
		3031	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2389		3032
2390	static void stdin_ready (int revents, void *arg)	3033	static void stdin_ready (int revents, void *arg)
2391	{	3034	{
		3035	if (revents & EV_READ)
		3036	/* stdin might have data for us, joy! */;
2392	if (revents & EV_TIMEOUT)	3037	else if (revents & EV_TIMEOUT)
2393	/* doh, nothing entered */;	3038	/* doh, nothing entered */;
2394	else if (revents & EV_READ)
2395	/* stdin might have data for us, joy! */;
2396	}	3039	}
2397		3040
2398	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3041	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2399		3042
2400	=item ev_feed_event (ev_loop *, watcher *, int revents)	3043	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2401		3044
2402	Feeds the given event set into the event loop, as if the specified event	3045	Feeds the given event set into the event loop, as if the specified event
2403	had happened for the specified watcher (which must be a pointer to an	3046	had happened for the specified watcher (which must be a pointer to an
2404	initialised but not necessarily started event watcher).	3047	initialised but not necessarily started event watcher).
2405		3048
2406	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3049	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2407		3050
2408	Feed an event on the given fd, as if a file descriptor backend detected	3051	Feed an event on the given fd, as if a file descriptor backend detected
2409	the given events it.	3052	the given events it.
2410		3053
2411	=item ev_feed_signal_event (ev_loop *loop, int signum)	3054	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2412		3055
2413	Feed an event as if the given signal occurred (C<loop> must be the default	3056	Feed an event as if the given signal occurred (C<loop> must be the default
2414	loop!).	3057	loop!).
2415		3058
2416	=back	3059	=back
…		…
2538		3181
2539	myclass obj;	3182	myclass obj;
2540	ev::io iow;	3183	ev::io iow;
2541	iow.set <myclass, &myclass::io_cb> (&obj);	3184	iow.set <myclass, &myclass::io_cb> (&obj);
2542		3185
		3186	=item w->set (object *)
		3187
		3188	This is an B<experimental> feature that might go away in a future version.
		3189
		3190	This is a variation of a method callback - leaving out the method to call
		3191	will default the method to C<operator ()>, which makes it possible to use
		3192	functor objects without having to manually specify the C<operator ()> all
		3193	the time. Incidentally, you can then also leave out the template argument
		3194	list.
		3195
		3196	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3197	int revents)>.
		3198
		3199	See the method-C<set> above for more details.
		3200
		3201	Example: use a functor object as callback.
		3202
		3203	struct myfunctor
		3204	{
		3205	void operator() (ev::io &w, int revents)
		3206	{
		3207	...
		3208	}
		3209	}
		3210
		3211	myfunctor f;
		3212
		3213	ev::io w;
		3214	w.set (&f);
		3215
2543	=item w->set<function> (void *data = 0)	3216	=item w->set<function> (void *data = 0)
2544		3217
2545	Also sets a callback, but uses a static method or plain function as	3218	Also sets a callback, but uses a static method or plain function as
2546	callback. The optional C<data> argument will be stored in the watcher's	3219	callback. The optional C<data> argument will be stored in the watcher's
2547	C<data> member and is free for you to use.	3220	C<data> member and is free for you to use.
2548		3221
2549	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3222	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2550		3223
2551	See the method-C<set> above for more details.	3224	See the method-C<set> above for more details.
2552		3225
2553	Example:	3226	Example: Use a plain function as callback.
2554		3227
2555	static void io_cb (ev::io &w, int revents) { }	3228	static void io_cb (ev::io &w, int revents) { }
2556	iow.set <io_cb> ();	3229	iow.set <io_cb> ();
2557		3230
2558	=item w->set (struct ev_loop *)	3231	=item w->set (struct ev_loop *)
…		…
2596	Example: Define a class with an IO and idle watcher, start one of them in	3269	Example: Define a class with an IO and idle watcher, start one of them in
2597	the constructor.	3270	the constructor.
2598		3271
2599	class myclass	3272	class myclass
2600	{	3273	{
2601	ev::io io; void io_cb (ev::io &w, int revents);	3274	ev::io io ; void io_cb (ev::io &w, int revents);
2602	ev:idle idle void idle_cb (ev::idle &w, int revents);	3275	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2603		3276
2604	myclass (int fd)	3277	myclass (int fd)
2605	{	3278	{
2606	io .set <myclass, &myclass::io_cb > (this);	3279	io .set <myclass, &myclass::io_cb > (this);
2607	idle.set <myclass, &myclass::idle_cb> (this);	3280	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2623	=item Perl	3296	=item Perl
2624		3297
2625	The EV module implements the full libev API and is actually used to test	3298	The EV module implements the full libev API and is actually used to test
2626	libev. EV is developed together with libev. Apart from the EV core module,	3299	libev. EV is developed together with libev. Apart from the EV core module,
2627	there are additional modules that implement libev-compatible interfaces	3300	there are additional modules that implement libev-compatible interfaces
2628	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3301	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2629	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3302	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3303	and C<EV::Glib>).
2630		3304
2631	It can be found and installed via CPAN, its homepage is at	3305	It can be found and installed via CPAN, its homepage is at
2632	L<http://software.schmorp.de/pkg/EV>.	3306	L<http://software.schmorp.de/pkg/EV>.
2633		3307
2634	=item Python	3308	=item Python
2635		3309
2636	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3310	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2637	seems to be quite complete and well-documented. Note, however, that the	3311	seems to be quite complete and well-documented.
2638	patch they require for libev is outright dangerous as it breaks the ABI
2639	for everybody else, and therefore, should never be applied in an installed
2640	libev (if python requires an incompatible ABI then it needs to embed
2641	libev).
2642		3312
2643	=item Ruby	3313	=item Ruby
2644		3314
2645	Tony Arcieri has written a ruby extension that offers access to a subset	3315	Tony Arcieri has written a ruby extension that offers access to a subset
2646	of the libev API and adds file handle abstractions, asynchronous DNS and	3316	of the libev API and adds file handle abstractions, asynchronous DNS and
2647	more on top of it. It can be found via gem servers. Its homepage is at	3317	more on top of it. It can be found via gem servers. Its homepage is at
2648	L<http://rev.rubyforge.org/>.	3318	L<http://rev.rubyforge.org/>.
2649		3319
		3320	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3321	makes rev work even on mingw.
		3322
		3323	=item Haskell
		3324
		3325	A haskell binding to libev is available at
		3326	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3327
2650	=item D	3328	=item D
2651		3329
2652	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3330	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2653	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	3331	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3332
		3333	=item Ocaml
		3334
		3335	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3336	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2654		3337
2655	=back	3338	=back
2656		3339
2657		3340
2658	=head1 MACRO MAGIC	3341	=head1 MACRO MAGIC
…		…
2759		3442
2760	#define EV_STANDALONE 1	3443	#define EV_STANDALONE 1
2761	#include "ev.h"	3444	#include "ev.h"
2762		3445
2763	Both header files and implementation files can be compiled with a C++	3446	Both header files and implementation files can be compiled with a C++
2764	compiler (at least, thats a stated goal, and breakage will be treated	3447	compiler (at least, that's a stated goal, and breakage will be treated
2765	as a bug).	3448	as a bug).
2766		3449
2767	You need the following files in your source tree, or in a directory	3450	You need the following files in your source tree, or in a directory
2768	in your include path (e.g. in libev/ when using -Ilibev):	3451	in your include path (e.g. in libev/ when using -Ilibev):
2769		3452
…		…
2813		3496
2814	=head2 PREPROCESSOR SYMBOLS/MACROS	3497	=head2 PREPROCESSOR SYMBOLS/MACROS
2815		3498
2816	Libev can be configured via a variety of preprocessor symbols you have to	3499	Libev can be configured via a variety of preprocessor symbols you have to
2817	define before including any of its files. The default in the absence of	3500	define before including any of its files. The default in the absence of
2818	autoconf is noted for every option.	3501	autoconf is documented for every option.
2819		3502
2820	=over 4	3503	=over 4
2821		3504
2822	=item EV_STANDALONE	3505	=item EV_STANDALONE
2823		3506
…		…
2825	keeps libev from including F<config.h>, and it also defines dummy	3508	keeps libev from including F<config.h>, and it also defines dummy
2826	implementations for some libevent functions (such as logging, which is not	3509	implementations for some libevent functions (such as logging, which is not
2827	supported). It will also not define any of the structs usually found in	3510	supported). It will also not define any of the structs usually found in
2828	F<event.h> that are not directly supported by the libev core alone.	3511	F<event.h> that are not directly supported by the libev core alone.
2829		3512
		3513	In stanbdalone mode, libev will still try to automatically deduce the
		3514	configuration, but has to be more conservative.
		3515
2830	=item EV_USE_MONOTONIC	3516	=item EV_USE_MONOTONIC
2831		3517
2832	If defined to be C<1>, libev will try to detect the availability of the	3518	If defined to be C<1>, libev will try to detect the availability of the
2833	monotonic clock option at both compile time and runtime. Otherwise no use	3519	monotonic clock option at both compile time and runtime. Otherwise no
2834	of the monotonic clock option will be attempted. If you enable this, you	3520	use of the monotonic clock option will be attempted. If you enable this,
2835	usually have to link against librt or something similar. Enabling it when	3521	you usually have to link against librt or something similar. Enabling it
2836	the functionality isn't available is safe, though, although you have	3522	when the functionality isn't available is safe, though, although you have
2837	to make sure you link against any libraries where the C<clock_gettime>	3523	to make sure you link against any libraries where the C<clock_gettime>
2838	function is hiding in (often F<-lrt>).	3524	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2839		3525
2840	=item EV_USE_REALTIME	3526	=item EV_USE_REALTIME
2841		3527
2842	If defined to be C<1>, libev will try to detect the availability of the	3528	If defined to be C<1>, libev will try to detect the availability of the
2843	real-time clock option at compile time (and assume its availability at	3529	real-time clock option at compile time (and assume its availability
2844	runtime if successful). Otherwise no use of the real-time clock option will	3530	at runtime if successful). Otherwise no use of the real-time clock
2845	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3531	option will be attempted. This effectively replaces C<gettimeofday>
2846	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3532	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2847	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3533	correctness. See the note about libraries in the description of
		3534	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3535	C<EV_USE_CLOCK_SYSCALL>.
		3536
		3537	=item EV_USE_CLOCK_SYSCALL
		3538
		3539	If defined to be C<1>, libev will try to use a direct syscall instead
		3540	of calling the system-provided C<clock_gettime> function. This option
		3541	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3542	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3543	programs needlessly. Using a direct syscall is slightly slower (in
		3544	theory), because no optimised vdso implementation can be used, but avoids
		3545	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3546	higher, as it simplifies linking (no need for C<-lrt>).
2848		3547
2849	=item EV_USE_NANOSLEEP	3548	=item EV_USE_NANOSLEEP
2850		3549
2851	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3550	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2852	and will use it for delays. Otherwise it will use C<select ()>.	3551	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2868		3567
2869	=item EV_SELECT_USE_FD_SET	3568	=item EV_SELECT_USE_FD_SET
2870		3569
2871	If defined to C<1>, then the select backend will use the system C<fd_set>	3570	If defined to C<1>, then the select backend will use the system C<fd_set>
2872	structure. This is useful if libev doesn't compile due to a missing	3571	structure. This is useful if libev doesn't compile due to a missing
2873	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3572	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2874	exotic systems. This usually limits the range of file descriptors to some	3573	on exotic systems. This usually limits the range of file descriptors to
2875	low limit such as 1024 or might have other limitations (winsocket only	3574	some low limit such as 1024 or might have other limitations (winsocket
2876	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3575	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2877	influence the size of the C<fd_set> used.	3576	configures the maximum size of the C<fd_set>.
2878		3577
2879	=item EV_SELECT_IS_WINSOCKET	3578	=item EV_SELECT_IS_WINSOCKET
2880		3579
2881	When defined to C<1>, the select backend will assume that	3580	When defined to C<1>, the select backend will assume that
2882	select/socket/connect etc. don't understand file descriptors but	3581	select/socket/connect etc. don't understand file descriptors but
…		…
2993	When doing priority-based operations, libev usually has to linearly search	3692	When doing priority-based operations, libev usually has to linearly search
2994	all the priorities, so having many of them (hundreds) uses a lot of space	3693	all the priorities, so having many of them (hundreds) uses a lot of space
2995	and time, so using the defaults of five priorities (-2 .. +2) is usually	3694	and time, so using the defaults of five priorities (-2 .. +2) is usually
2996	fine.	3695	fine.
2997		3696
2998	If your embedding application does not need any priorities, defining these both to	3697	If your embedding application does not need any priorities, defining these
2999	C<0> will save some memory and CPU.	3698	both to C<0> will save some memory and CPU.
3000		3699
3001	=item EV_PERIODIC_ENABLE	3700	=item EV_PERIODIC_ENABLE
3002		3701
3003	If undefined or defined to be C<1>, then periodic timers are supported. If	3702	If undefined or defined to be C<1>, then periodic timers are supported. If
3004	defined to be C<0>, then they are not. Disabling them saves a few kB of	3703	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3011	code.	3710	code.
3012		3711
3013	=item EV_EMBED_ENABLE	3712	=item EV_EMBED_ENABLE
3014		3713
3015	If undefined or defined to be C<1>, then embed watchers are supported. If	3714	If undefined or defined to be C<1>, then embed watchers are supported. If
3016	defined to be C<0>, then they are not.	3715	defined to be C<0>, then they are not. Embed watchers rely on most other
		3716	watcher types, which therefore must not be disabled.
3017		3717
3018	=item EV_STAT_ENABLE	3718	=item EV_STAT_ENABLE
3019		3719
3020	If undefined or defined to be C<1>, then stat watchers are supported. If	3720	If undefined or defined to be C<1>, then stat watchers are supported. If
3021	defined to be C<0>, then they are not.	3721	defined to be C<0>, then they are not.
…		…
3031	defined to be C<0>, then they are not.	3731	defined to be C<0>, then they are not.
3032		3732
3033	=item EV_MINIMAL	3733	=item EV_MINIMAL
3034		3734
3035	If you need to shave off some kilobytes of code at the expense of some	3735	If you need to shave off some kilobytes of code at the expense of some
3036	speed, define this symbol to C<1>. Currently this is used to override some	3736	speed (but with the full API), define this symbol to C<1>. Currently this
3037	inlining decisions, saves roughly 30% code size on amd64. It also selects a	3737	is used to override some inlining decisions, saves roughly 30% code size
3038	much smaller 2-heap for timer management over the default 4-heap.	3738	on amd64. It also selects a much smaller 2-heap for timer management over
		3739	the default 4-heap.
		3740
		3741	You can save even more by disabling watcher types you do not need
		3742	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>
		3743	(C<-DNDEBUG>) will usually reduce code size a lot.
		3744
		3745	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to
		3746	provide a bare-bones event library. See C<ev.h> for details on what parts
		3747	of the API are still available, and do not complain if this subset changes
		3748	over time.
3039		3749
3040	=item EV_PID_HASHSIZE	3750	=item EV_PID_HASHSIZE
3041		3751
3042	C<ev_child> watchers use a small hash table to distribute workload by	3752	C<ev_child> watchers use a small hash table to distribute workload by
3043	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3753	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
3053	two).	3763	two).
3054		3764
3055	=item EV_USE_4HEAP	3765	=item EV_USE_4HEAP
3056		3766
3057	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3767	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3058	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3768	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3059	to C<1>. The 4-heap uses more complicated (longer) code but has	3769	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3060	noticeably faster performance with many (thousands) of watchers.	3770	faster performance with many (thousands) of watchers.
3061		3771
3062	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3772	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3063	(disabled).	3773	(disabled).
3064		3774
3065	=item EV_HEAP_CACHE_AT	3775	=item EV_HEAP_CACHE_AT
3066		3776
3067	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3777	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3068	timer and periodics heap, libev can cache the timestamp (I<at>) within	3778	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3069	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3779	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3070	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3780	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3071	but avoids random read accesses on heap changes. This improves performance	3781	but avoids random read accesses on heap changes. This improves performance
3072	noticeably with with many (hundreds) of watchers.	3782	noticeably with many (hundreds) of watchers.
3073		3783
3074	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3784	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3075	(disabled).	3785	(disabled).
3076		3786
3077	=item EV_VERIFY	3787	=item EV_VERIFY
…		…
3083	called once per loop, which can slow down libev. If set to C<3>, then the	3793	called once per loop, which can slow down libev. If set to C<3>, then the
3084	verification code will be called very frequently, which will slow down	3794	verification code will be called very frequently, which will slow down
3085	libev considerably.	3795	libev considerably.
3086		3796
3087	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3797	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3088	C<0.>	3798	C<0>.
3089		3799
3090	=item EV_COMMON	3800	=item EV_COMMON
3091		3801
3092	By default, all watchers have a C<void *data> member. By redefining	3802	By default, all watchers have a C<void *data> member. By redefining
3093	this macro to a something else you can include more and other types of	3803	this macro to a something else you can include more and other types of
…		…
3110	and the way callbacks are invoked and set. Must expand to a struct member	3820	and the way callbacks are invoked and set. Must expand to a struct member
3111	definition and a statement, respectively. See the F<ev.h> header file for	3821	definition and a statement, respectively. See the F<ev.h> header file for
3112	their default definitions. One possible use for overriding these is to	3822	their default definitions. One possible use for overriding these is to
3113	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3823	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3114	method calls instead of plain function calls in C++.	3824	method calls instead of plain function calls in C++.
		3825
		3826	=back
3115		3827
3116	=head2 EXPORTED API SYMBOLS	3828	=head2 EXPORTED API SYMBOLS
3117		3829
3118	If you need to re-export the API (e.g. via a DLL) and you need a list of	3830	If you need to re-export the API (e.g. via a DLL) and you need a list of
3119	exported symbols, you can use the provided F<Symbol.*> files which list	3831	exported symbols, you can use the provided F<Symbol.*> files which list
…		…
3166	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3878	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3167		3879
3168	#include "ev_cpp.h"	3880	#include "ev_cpp.h"
3169	#include "ev.c"	3881	#include "ev.c"
3170		3882
		3883	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3171		3884
3172	=head1 THREADS AND COROUTINES	3885	=head2 THREADS AND COROUTINES
3173		3886
3174	=head2 THREADS	3887	=head3 THREADS
3175		3888
3176	Libev itself is completely thread-safe, but it uses no locking. This	3889	All libev functions are reentrant and thread-safe unless explicitly
		3890	documented otherwise, but libev implements no locking itself. This means
3177	means that you can use as many loops as you want in parallel, as long as	3891	that you can use as many loops as you want in parallel, as long as there
3178	only one thread ever calls into one libev function with the same loop	3892	are no concurrent calls into any libev function with the same loop
3179	parameter.	3893	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3894	of course): libev guarantees that different event loops share no data
		3895	structures that need any locking.
3180		3896
3181	Or put differently: calls with different loop parameters can be done in	3897	Or to put it differently: calls with different loop parameters can be done
3182	parallel from multiple threads, calls with the same loop parameter must be	3898	concurrently from multiple threads, calls with the same loop parameter
3183	done serially (but can be done from different threads, as long as only one	3899	must be done serially (but can be done from different threads, as long as
3184	thread ever is inside a call at any point in time, e.g. by using a mutex	3900	only one thread ever is inside a call at any point in time, e.g. by using
3185	per loop).	3901	a mutex per loop).
3186		3902
3187	If you want to know which design is best for your problem, then I cannot	3903	Specifically to support threads (and signal handlers), libev implements
		3904	so-called C<ev_async> watchers, which allow some limited form of
		3905	concurrency on the same event loop, namely waking it up "from the
		3906	outside".
		3907
		3908	If you want to know which design (one loop, locking, or multiple loops
		3909	without or something else still) is best for your problem, then I cannot
3188	help you but by giving some generic advice:	3910	help you, but here is some generic advice:
3189		3911
3190	=over 4	3912	=over 4
3191		3913
3192	=item * most applications have a main thread: use the default libev loop	3914	=item * most applications have a main thread: use the default libev loop
3193	in that thread, or create a separate thread running only the default loop.	3915	in that thread, or create a separate thread running only the default loop.
…		…
3205		3927
3206	Choosing a model is hard - look around, learn, know that usually you can do	3928	Choosing a model is hard - look around, learn, know that usually you can do
3207	better than you currently do :-)	3929	better than you currently do :-)
3208		3930
3209	=item * often you need to talk to some other thread which blocks in the	3931	=item * often you need to talk to some other thread which blocks in the
		3932	event loop.
		3933
3210	event loop - C<ev_async> watchers can be used to wake them up from other	3934	C<ev_async> watchers can be used to wake them up from other threads safely
3211	threads safely (or from signal contexts...).	3935	(or from signal contexts...).
		3936
		3937	An example use would be to communicate signals or other events that only
		3938	work in the default loop by registering the signal watcher with the
		3939	default loop and triggering an C<ev_async> watcher from the default loop
		3940	watcher callback into the event loop interested in the signal.
3212		3941
3213	=back	3942	=back
3214		3943
		3944	=head4 THREAD LOCKING EXAMPLE
		3945
		3946	Here is a fictitious example of how to run an event loop in a different
		3947	thread than where callbacks are being invoked and watchers are
		3948	created/added/removed.
		3949
		3950	For a real-world example, see the C<EV::Loop::Async> perl module,
		3951	which uses exactly this technique (which is suited for many high-level
		3952	languages).
		3953
		3954	The example uses a pthread mutex to protect the loop data, a condition
		3955	variable to wait for callback invocations, an async watcher to notify the
		3956	event loop thread and an unspecified mechanism to wake up the main thread.
		3957
		3958	First, you need to associate some data with the event loop:
		3959
		3960	typedef struct {
		3961	mutex_t lock; /* global loop lock */
		3962	ev_async async_w;
		3963	thread_t tid;
		3964	cond_t invoke_cv;
		3965	} userdata;
		3966
		3967	void prepare_loop (EV_P)
		3968	{
		3969	// for simplicity, we use a static userdata struct.
		3970	static userdata u;
		3971
		3972	ev_async_init (&u->async_w, async_cb);
		3973	ev_async_start (EV_A_ &u->async_w);
		3974
		3975	pthread_mutex_init (&u->lock, 0);
		3976	pthread_cond_init (&u->invoke_cv, 0);
		3977
		3978	// now associate this with the loop
		3979	ev_set_userdata (EV_A_ u);
		3980	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3981	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3982
		3983	// then create the thread running ev_loop
		3984	pthread_create (&u->tid, 0, l_run, EV_A);
		3985	}
		3986
		3987	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3988	solely to wake up the event loop so it takes notice of any new watchers
		3989	that might have been added:
		3990
		3991	static void
		3992	async_cb (EV_P_ ev_async *w, int revents)
		3993	{
		3994	// just used for the side effects
		3995	}
		3996
		3997	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3998	protecting the loop data, respectively.
		3999
		4000	static void
		4001	l_release (EV_P)
		4002	{
		4003	udat *u = ev_userdata (EV_A);
		4004	pthread_mutex_unlock (&u->lock);
		4005	}
		4006
		4007	static void
		4008	l_acquire (EV_P)
		4009	{
		4010	udat *u = ev_userdata (EV_A);
		4011	pthread_mutex_lock (&u->lock);
		4012	}
		4013
		4014	The event loop thread first acquires the mutex, and then jumps straight
		4015	into C<ev_loop>:
		4016
		4017	void *
		4018	l_run (void *thr_arg)
		4019	{
		4020	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4021
		4022	l_acquire (EV_A);
		4023	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4024	ev_loop (EV_A_ 0);
		4025	l_release (EV_A);
		4026
		4027	return 0;
		4028	}
		4029
		4030	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4031	signal the main thread via some unspecified mechanism (signals? pipe
		4032	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4033	have been called:
		4034
		4035	static void
		4036	l_invoke (EV_P)
		4037	{
		4038	udat *u = ev_userdata (EV_A);
		4039
		4040	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4041
		4042	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4043	}
		4044
		4045	Now, whenever the main thread gets told to invoke pending watchers, it
		4046	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4047	thread to continue:
		4048
		4049	static void
		4050	real_invoke_pending (EV_P)
		4051	{
		4052	udat *u = ev_userdata (EV_A);
		4053
		4054	pthread_mutex_lock (&u->lock);
		4055	ev_invoke_pending (EV_A);
		4056	pthread_cond_signal (&u->invoke_cv);
		4057	pthread_mutex_unlock (&u->lock);
		4058	}
		4059
		4060	Whenever you want to start/stop a watcher or do other modifications to an
		4061	event loop, you will now have to lock:
		4062
		4063	ev_timer timeout_watcher;
		4064	udat *u = ev_userdata (EV_A);
		4065
		4066	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4067
		4068	pthread_mutex_lock (&u->lock);
		4069	ev_timer_start (EV_A_ &timeout_watcher);
		4070	ev_async_send (EV_A_ &u->async_w);
		4071	pthread_mutex_unlock (&u->lock);
		4072
		4073	Note that sending the C<ev_async> watcher is required because otherwise
		4074	an event loop currently blocking in the kernel will have no knowledge
		4075	about the newly added timer. By waking up the loop it will pick up any new
		4076	watchers in the next event loop iteration.
		4077
3215	=head2 COROUTINES	4078	=head3 COROUTINES
3216		4079
3217	Libev is much more accommodating to coroutines ("cooperative threads"):	4080	Libev is very accommodating to coroutines ("cooperative threads"):
3218	libev fully supports nesting calls to it's functions from different	4081	libev fully supports nesting calls to its functions from different
3219	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4082	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3220	different coroutines and switch freely between both coroutines running the	4083	different coroutines, and switch freely between both coroutines running the
3221	loop, as long as you don't confuse yourself). The only exception is that	4084	loop, as long as you don't confuse yourself). The only exception is that
3222	you must not do this from C<ev_periodic> reschedule callbacks.	4085	you must not do this from C<ev_periodic> reschedule callbacks.
3223		4086
3224	Care has been invested into making sure that libev does not keep local	4087	Care has been taken to ensure that libev does not keep local state inside
3225	state inside C<ev_loop>, and other calls do not usually allow coroutine	4088	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3226	switches.	4089	they do not call any callbacks.
3227		4090
		4091	=head2 COMPILER WARNINGS
3228		4092
3229	=head1 COMPLEXITIES	4093	Depending on your compiler and compiler settings, you might get no or a
		4094	lot of warnings when compiling libev code. Some people are apparently
		4095	scared by this.
3230		4096
3231	In this section the complexities of (many of) the algorithms used inside	4097	However, these are unavoidable for many reasons. For one, each compiler
3232	libev will be explained. For complexity discussions about backends see the	4098	has different warnings, and each user has different tastes regarding
3233	documentation for C<ev_default_init>.	4099	warning options. "Warn-free" code therefore cannot be a goal except when
		4100	targeting a specific compiler and compiler-version.
3234		4101
3235	All of the following are about amortised time: If an array needs to be	4102	Another reason is that some compiler warnings require elaborate
3236	extended, libev needs to realloc and move the whole array, but this	4103	workarounds, or other changes to the code that make it less clear and less
3237	happens asymptotically never with higher number of elements, so O(1) might	4104	maintainable.
3238	mean it might do a lengthy realloc operation in rare cases, but on average
3239	it is much faster and asymptotically approaches constant time.
3240		4105
3241	=over 4	4106	And of course, some compiler warnings are just plain stupid, or simply
		4107	wrong (because they don't actually warn about the condition their message
		4108	seems to warn about). For example, certain older gcc versions had some
		4109	warnings that resulted an extreme number of false positives. These have
		4110	been fixed, but some people still insist on making code warn-free with
		4111	such buggy versions.
3242		4112
3243	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	4113	While libev is written to generate as few warnings as possible,
		4114	"warn-free" code is not a goal, and it is recommended not to build libev
		4115	with any compiler warnings enabled unless you are prepared to cope with
		4116	them (e.g. by ignoring them). Remember that warnings are just that:
		4117	warnings, not errors, or proof of bugs.
3244		4118
3245	This means that, when you have a watcher that triggers in one hour and
3246	there are 100 watchers that would trigger before that then inserting will
3247	have to skip roughly seven (C<ld 100>) of these watchers.
3248		4119
3249	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	4120	=head2 VALGRIND
3250		4121
3251	That means that changing a timer costs less than removing/adding them	4122	Valgrind has a special section here because it is a popular tool that is
3252	as only the relative motion in the event queue has to be paid for.	4123	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3253		4124
3254	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	4125	If you think you found a bug (memory leak, uninitialised data access etc.)
		4126	in libev, then check twice: If valgrind reports something like:
3255		4127
3256	These just add the watcher into an array or at the head of a list.	4128	==2274== definitely lost: 0 bytes in 0 blocks.
		4129	==2274== possibly lost: 0 bytes in 0 blocks.
		4130	==2274== still reachable: 256 bytes in 1 blocks.
3257		4131
3258	=item Stopping check/prepare/idle/fork/async watchers: O(1)	4132	Then there is no memory leak, just as memory accounted to global variables
		4133	is not a memleak - the memory is still being referenced, and didn't leak.
3259		4134
3260	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	4135	Similarly, under some circumstances, valgrind might report kernel bugs
		4136	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		4137	although an acceptable workaround has been found here), or it might be
		4138	confused.
3261		4139
3262	These watchers are stored in lists then need to be walked to find the	4140	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3263	correct watcher to remove. The lists are usually short (you don't usually	4141	make it into some kind of religion.
3264	have many watchers waiting for the same fd or signal).
3265		4142
3266	=item Finding the next timer in each loop iteration: O(1)	4143	If you are unsure about something, feel free to contact the mailing list
		4144	with the full valgrind report and an explanation on why you think this
		4145	is a bug in libev (best check the archives, too :). However, don't be
		4146	annoyed when you get a brisk "this is no bug" answer and take the chance
		4147	of learning how to interpret valgrind properly.
3267		4148
3268	By virtue of using a binary or 4-heap, the next timer is always found at a	4149	If you need, for some reason, empty reports from valgrind for your project
3269	fixed position in the storage array.	4150	I suggest using suppression lists.
3270		4151
3271	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3272		4152
3273	A change means an I/O watcher gets started or stopped, which requires	4153	=head1 PORTABILITY NOTES
3274	libev to recalculate its status (and possibly tell the kernel, depending
3275	on backend and whether C<ev_io_set> was used).
3276		4154
3277	=item Activating one watcher (putting it into the pending state): O(1)
3278
3279	=item Priority handling: O(number_of_priorities)
3280
3281	Priorities are implemented by allocating some space for each
3282	priority. When doing priority-based operations, libev usually has to
3283	linearly search all the priorities, but starting/stopping and activating
3284	watchers becomes O(1) w.r.t. priority handling.
3285
3286	=item Sending an ev_async: O(1)
3287
3288	=item Processing ev_async_send: O(number_of_async_watchers)
3289
3290	=item Processing signals: O(max_signal_number)
3291
3292	Sending involves a system call I<iff> there were no other C<ev_async_send>
3293	calls in the current loop iteration. Checking for async and signal events
3294	involves iterating over all running async watchers or all signal numbers.
3295
3296	=back
3297
3298
3299	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4155	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3300		4156
3301	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4157	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3302	requires, and its I/O model is fundamentally incompatible with the POSIX	4158	requires, and its I/O model is fundamentally incompatible with the POSIX
3303	model. Libev still offers limited functionality on this platform in	4159	model. Libev still offers limited functionality on this platform in
3304	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4160	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3311	way (note also that glib is the slowest event library known to man).	4167	way (note also that glib is the slowest event library known to man).
3312		4168
3313	There is no supported compilation method available on windows except	4169	There is no supported compilation method available on windows except
3314	embedding it into other applications.	4170	embedding it into other applications.
3315		4171
		4172	Sensible signal handling is officially unsupported by Microsoft - libev
		4173	tries its best, but under most conditions, signals will simply not work.
		4174
3316	Not a libev limitation but worth mentioning: windows apparently doesn't	4175	Not a libev limitation but worth mentioning: windows apparently doesn't
3317	accept large writes: instead of resulting in a partial write, windows will	4176	accept large writes: instead of resulting in a partial write, windows will
3318	either accept everything or return C<ENOBUFS> if the buffer is too large,	4177	either accept everything or return C<ENOBUFS> if the buffer is too large,
3319	so make sure you only write small amounts into your sockets (less than a	4178	so make sure you only write small amounts into your sockets (less than a
3320	megabyte seems safe, but thsi apparently depends on the amount of memory	4179	megabyte seems safe, but this apparently depends on the amount of memory
3321	available).	4180	available).
3322		4181
3323	Due to the many, low, and arbitrary limits on the win32 platform and	4182	Due to the many, low, and arbitrary limits on the win32 platform and
3324	the abysmal performance of winsockets, using a large number of sockets	4183	the abysmal performance of winsockets, using a large number of sockets
3325	is not recommended (and not reasonable). If your program needs to use	4184	is not recommended (and not reasonable). If your program needs to use
3326	more than a hundred or so sockets, then likely it needs to use a totally	4185	more than a hundred or so sockets, then likely it needs to use a totally
3327	different implementation for windows, as libev offers the POSIX readiness	4186	different implementation for windows, as libev offers the POSIX readiness
3328	notification model, which cannot be implemented efficiently on windows	4187	notification model, which cannot be implemented efficiently on windows
3329	(Microsoft monopoly games).	4188	(due to Microsoft monopoly games).
3330		4189
3331	A typical way to use libev under windows is to embed it (see the embedding	4190	A typical way to use libev under windows is to embed it (see the embedding
3332	section for details) and use the following F<evwrap.h> header file instead	4191	section for details) and use the following F<evwrap.h> header file instead
3333	of F<ev.h>:	4192	of F<ev.h>:
3334		4193
…		…
3336	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	4195	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3337		4196
3338	#include "ev.h"	4197	#include "ev.h"
3339		4198
3340	And compile the following F<evwrap.c> file into your project (make sure	4199	And compile the following F<evwrap.c> file into your project (make sure
3341	you do I<not> compile the F<ev.c> or any other embedded soruce files!):	4200	you do I<not> compile the F<ev.c> or any other embedded source files!):
3342		4201
3343	#include "evwrap.h"	4202	#include "evwrap.h"
3344	#include "ev.c"	4203	#include "ev.c"
3345		4204
3346	=over 4	4205	=over 4
…		…
3370		4229
3371	Early versions of winsocket's select only supported waiting for a maximum	4230	Early versions of winsocket's select only supported waiting for a maximum
3372	of C<64> handles (probably owning to the fact that all windows kernels	4231	of C<64> handles (probably owning to the fact that all windows kernels
3373	can only wait for C<64> things at the same time internally; Microsoft	4232	can only wait for C<64> things at the same time internally; Microsoft
3374	recommends spawning a chain of threads and wait for 63 handles and the	4233	recommends spawning a chain of threads and wait for 63 handles and the
3375	previous thread in each. Great).	4234	previous thread in each. Sounds great!).
3376		4235
3377	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4236	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3378	to some high number (e.g. C<2048>) before compiling the winsocket select	4237	to some high number (e.g. C<2048>) before compiling the winsocket select
3379	call (which might be in libev or elsewhere, for example, perl does its own	4238	call (which might be in libev or elsewhere, for example, perl and many
3380	select emulation on windows).	4239	other interpreters do their own select emulation on windows).
3381		4240
3382	Another limit is the number of file descriptors in the Microsoft runtime	4241	Another limit is the number of file descriptors in the Microsoft runtime
3383	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4242	libraries, which by default is C<64> (there must be a hidden I<64>
3384	or something like this inside Microsoft). You can increase this by calling	4243	fetish or something like this inside Microsoft). You can increase this
3385	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4244	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3386	arbitrary limit), but is broken in many versions of the Microsoft runtime	4245	(another arbitrary limit), but is broken in many versions of the Microsoft
3387	libraries.
3388
3389	This might get you to about C<512> or C<2048> sockets (depending on	4246	runtime libraries. This might get you to about C<512> or C<2048> sockets
3390	windows version and/or the phase of the moon). To get more, you need to	4247	(depending on windows version and/or the phase of the moon). To get more,
3391	wrap all I/O functions and provide your own fd management, but the cost of	4248	you need to wrap all I/O functions and provide your own fd management, but
3392	calling select (O(n²)) will likely make this unworkable.	4249	the cost of calling select (O(n²)) will likely make this unworkable.
3393		4250
3394	=back	4251	=back
3395		4252
3396
3397	=head1 PORTABILITY REQUIREMENTS	4253	=head2 PORTABILITY REQUIREMENTS
3398		4254
3399	In addition to a working ISO-C implementation, libev relies on a few	4255	In addition to a working ISO-C implementation and of course the
3400	additional extensions:	4256	backend-specific APIs, libev relies on a few additional extensions:
3401		4257
3402	=over 4	4258	=over 4
3403		4259
3404	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	4260	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3405	calling conventions regardless of C<ev_watcher_type *>.	4261	calling conventions regardless of C<ev_watcher_type *>.
…		…
3411	calls them using an C<ev_watcher *> internally.	4267	calls them using an C<ev_watcher *> internally.
3412		4268
3413	=item C<sig_atomic_t volatile> must be thread-atomic as well	4269	=item C<sig_atomic_t volatile> must be thread-atomic as well
3414		4270
3415	The type C<sig_atomic_t volatile> (or whatever is defined as	4271	The type C<sig_atomic_t volatile> (or whatever is defined as
3416	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	4272	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3417	threads. This is not part of the specification for C<sig_atomic_t>, but is	4273	threads. This is not part of the specification for C<sig_atomic_t>, but is
3418	believed to be sufficiently portable.	4274	believed to be sufficiently portable.
3419		4275
3420	=item C<sigprocmask> must work in a threaded environment	4276	=item C<sigprocmask> must work in a threaded environment
3421		4277
…		…
3430	except the initial one, and run the default loop in the initial thread as	4286	except the initial one, and run the default loop in the initial thread as
3431	well.	4287	well.
3432		4288
3433	=item C<long> must be large enough for common memory allocation sizes	4289	=item C<long> must be large enough for common memory allocation sizes
3434		4290
3435	To improve portability and simplify using libev, libev uses C<long>	4291	To improve portability and simplify its API, libev uses C<long> internally
3436	internally instead of C<size_t> when allocating its data structures. On	4292	instead of C<size_t> when allocating its data structures. On non-POSIX
3437	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4293	systems (Microsoft...) this might be unexpectedly low, but is still at
3438	is still at least 31 bits everywhere, which is enough for hundreds of	4294	least 31 bits everywhere, which is enough for hundreds of millions of
3439	millions of watchers.	4295	watchers.
3440		4296
3441	=item C<double> must hold a time value in seconds with enough accuracy	4297	=item C<double> must hold a time value in seconds with enough accuracy
3442		4298
3443	The type C<double> is used to represent timestamps. It is required to	4299	The type C<double> is used to represent timestamps. It is required to
3444	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4300	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
3445	enough for at least into the year 4000. This requirement is fulfilled by	4301	enough for at least into the year 4000. This requirement is fulfilled by
3446	implementations implementing IEEE 754 (basically all existing ones).	4302	implementations implementing IEEE 754, which is basically all existing
		4303	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4304	2200.
3447		4305
3448	=back	4306	=back
3449		4307
3450	If you know of other additional requirements drop me a note.	4308	If you know of other additional requirements drop me a note.
3451		4309
3452		4310
3453	=head1 COMPILER WARNINGS	4311	=head1 ALGORITHMIC COMPLEXITIES
3454		4312
3455	Depending on your compiler and compiler settings, you might get no or a	4313	In this section the complexities of (many of) the algorithms used inside
3456	lot of warnings when compiling libev code. Some people are apparently	4314	libev will be documented. For complexity discussions about backends see
3457	scared by this.	4315	the documentation for C<ev_default_init>.
3458		4316
3459	However, these are unavoidable for many reasons. For one, each compiler	4317	All of the following are about amortised time: If an array needs to be
3460	has different warnings, and each user has different tastes regarding	4318	extended, libev needs to realloc and move the whole array, but this
3461	warning options. "Warn-free" code therefore cannot be a goal except when	4319	happens asymptotically rarer with higher number of elements, so O(1) might
3462	targeting a specific compiler and compiler-version.	4320	mean that libev does a lengthy realloc operation in rare cases, but on
		4321	average it is much faster and asymptotically approaches constant time.
3463		4322
3464	Another reason is that some compiler warnings require elaborate	4323	=over 4
3465	workarounds, or other changes to the code that make it less clear and less
3466	maintainable.
3467		4324
3468	And of course, some compiler warnings are just plain stupid, or simply	4325	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3469	wrong (because they don't actually warn about the condition their message
3470	seems to warn about).
3471		4326
3472	While libev is written to generate as few warnings as possible,	4327	This means that, when you have a watcher that triggers in one hour and
3473	"warn-free" code is not a goal, and it is recommended not to build libev	4328	there are 100 watchers that would trigger before that, then inserting will
3474	with any compiler warnings enabled unless you are prepared to cope with	4329	have to skip roughly seven (C<ld 100>) of these watchers.
3475	them (e.g. by ignoring them). Remember that warnings are just that:
3476	warnings, not errors, or proof of bugs.
3477		4330
		4331	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3478		4332
3479	=head1 VALGRIND	4333	That means that changing a timer costs less than removing/adding them,
		4334	as only the relative motion in the event queue has to be paid for.
3480		4335
3481	Valgrind has a special section here because it is a popular tool that is	4336	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3482	highly useful, but valgrind reports are very hard to interpret.
3483		4337
3484	If you think you found a bug (memory leak, uninitialised data access etc.)	4338	These just add the watcher into an array or at the head of a list.
3485	in libev, then check twice: If valgrind reports something like:
3486		4339
3487	==2274== definitely lost: 0 bytes in 0 blocks.	4340	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3488	==2274== possibly lost: 0 bytes in 0 blocks.
3489	==2274== still reachable: 256 bytes in 1 blocks.
3490		4341
3491	Then there is no memory leak. Similarly, under some circumstances,	4342	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3492	valgrind might report kernel bugs as if it were a bug in libev, or it
3493	might be confused (it is a very good tool, but only a tool).
3494		4343
3495	If you are unsure about something, feel free to contact the mailing list	4344	These watchers are stored in lists, so they need to be walked to find the
3496	with the full valgrind report and an explanation on why you think this is	4345	correct watcher to remove. The lists are usually short (you don't usually
3497	a bug in libev. However, don't be annoyed when you get a brisk "this is	4346	have many watchers waiting for the same fd or signal: one is typical, two
3498	no bug" answer and take the chance of learning how to interpret valgrind	4347	is rare).
3499	properly.
3500		4348
3501	If you need, for some reason, empty reports from valgrind for your project	4349	=item Finding the next timer in each loop iteration: O(1)
3502	I suggest using suppression lists.
3503		4350
		4351	By virtue of using a binary or 4-heap, the next timer is always found at a
		4352	fixed position in the storage array.
		4353
		4354	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4355
		4356	A change means an I/O watcher gets started or stopped, which requires
		4357	libev to recalculate its status (and possibly tell the kernel, depending
		4358	on backend and whether C<ev_io_set> was used).
		4359
		4360	=item Activating one watcher (putting it into the pending state): O(1)
		4361
		4362	=item Priority handling: O(number_of_priorities)
		4363
		4364	Priorities are implemented by allocating some space for each
		4365	priority. When doing priority-based operations, libev usually has to
		4366	linearly search all the priorities, but starting/stopping and activating
		4367	watchers becomes O(1) with respect to priority handling.
		4368
		4369	=item Sending an ev_async: O(1)
		4370
		4371	=item Processing ev_async_send: O(number_of_async_watchers)
		4372
		4373	=item Processing signals: O(max_signal_number)
		4374
		4375	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4376	calls in the current loop iteration. Checking for async and signal events
		4377	involves iterating over all running async watchers or all signal numbers.
		4378
		4379	=back
		4380
		4381
		4382	=head1 GLOSSARY
		4383
		4384	=over 4
		4385
		4386	=item active
		4387
		4388	A watcher is active as long as it has been started (has been attached to
		4389	an event loop) but not yet stopped (disassociated from the event loop).
		4390
		4391	=item application
		4392
		4393	In this document, an application is whatever is using libev.
		4394
		4395	=item callback
		4396
		4397	The address of a function that is called when some event has been
		4398	detected. Callbacks are being passed the event loop, the watcher that
		4399	received the event, and the actual event bitset.
		4400
		4401	=item callback invocation
		4402
		4403	The act of calling the callback associated with a watcher.
		4404
		4405	=item event
		4406
		4407	A change of state of some external event, such as data now being available
		4408	for reading on a file descriptor, time having passed or simply not having
		4409	any other events happening anymore.
		4410
		4411	In libev, events are represented as single bits (such as C<EV_READ> or
		4412	C<EV_TIMEOUT>).
		4413
		4414	=item event library
		4415
		4416	A software package implementing an event model and loop.
		4417
		4418	=item event loop
		4419
		4420	An entity that handles and processes external events and converts them
		4421	into callback invocations.
		4422
		4423	=item event model
		4424
		4425	The model used to describe how an event loop handles and processes
		4426	watchers and events.
		4427
		4428	=item pending
		4429
		4430	A watcher is pending as soon as the corresponding event has been detected,
		4431	and stops being pending as soon as the watcher will be invoked or its
		4432	pending status is explicitly cleared by the application.
		4433
		4434	A watcher can be pending, but not active. Stopping a watcher also clears
		4435	its pending status.
		4436
		4437	=item real time
		4438
		4439	The physical time that is observed. It is apparently strictly monotonic :)
		4440
		4441	=item wall-clock time
		4442
		4443	The time and date as shown on clocks. Unlike real time, it can actually
		4444	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4445	clock.
		4446
		4447	=item watcher
		4448
		4449	A data structure that describes interest in certain events. Watchers need
		4450	to be started (attached to an event loop) before they can receive events.
		4451
		4452	=item watcher invocation
		4453
		4454	The act of calling the callback associated with a watcher.
		4455
		4456	=back
3504		4457
3505	=head1 AUTHOR	4458	=head1 AUTHOR
3506		4459
3507	Marc Lehmann <libev@schmorp.de>.	4460	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3508		4461

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