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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.
…		…
583		656
584	This function is rarely useful, but when some event callback runs for a	657	This function is rarely useful, but when some event callback runs for a
585	very long time without entering the event loop, updating libev's idea of	658	very long time without entering the event loop, updating libev's idea of
586	the current time is a good idea.	659	the current time is a good idea.
587		660
588	See also "The special problem of time updates" in the C<ev_timer> section.	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>).
589		688
590	=item ev_loop (loop, int flags)	689	=item ev_loop (loop, int flags)
591		690
592	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
593	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
…		…
596	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
597	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.
598		697
599	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
600	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
601	finished (especially in interactive programs), but having a program that	700	finished (especially in interactive programs), but having a program
602	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
603	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.
604		704
605	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
606	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
607	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.
608		709
609	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
610	necessary) and will handle those and any outstanding ones. It will block	711	necessary) and will handle those and any already outstanding ones. It
611	your process until at least one new event arrives, and will return after	712	will block your process until at least one new event arrives (which could
612	one iteration of the loop. This is useful if you are waiting for some	713	be an event internal to libev itself, so there is no guarantee that a
613	external event in conjunction with something not expressible using other	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
614	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
615	usually a better approach for this kind of thing.	720	usually a better approach for this kind of thing.
616		721
617	Here are the gory details of what C<ev_loop> does:	722	Here are the gory details of what C<ev_loop> does:
618		723
619	- Before the first iteration, call any pending watchers.	724	- Before the first iteration, call any pending watchers.
…		…
629	any active watchers at all will result in not sleeping).	734	any active watchers at all will result in not sleeping).
630	- Sleep if the I/O and timer collect interval say so.	735	- Sleep if the I/O and timer collect interval say so.
631	- Block the process, waiting for any events.	736	- Block the process, waiting for any events.
632	- Queue all outstanding I/O (fd) events.	737	- Queue all outstanding I/O (fd) events.
633	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	738	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
634	- Queue all outstanding timers.	739	- Queue all expired timers.
635	- Queue all outstanding periodics.	740	- Queue all expired periodics.
636	- Unless any events are pending now, queue all idle watchers.	741	- Unless any events are pending now, queue all idle watchers.
637	- Queue all check watchers.	742	- Queue all check watchers.
638	- 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).
639	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
640	be handled here by queueing them when their watcher gets executed.	745	be handled here by queueing them when their watcher gets executed.
…		…
657	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
658	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.
659		764
660	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.
661		766
		767	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		768
662	=item ev_ref (loop)	769	=item ev_ref (loop)
663		770
664	=item ev_unref (loop)	771	=item ev_unref (loop)
665		772
666	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
667	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
668	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
669	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>
670	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
671	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
672	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
673	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
674	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
675	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
676	(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
677	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).
678		790
679	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>
680	running when nothing else is active.	792	running when nothing else is active.
681		793
682	struct ev_signal exitsig;	794	ev_signal exitsig;
683	ev_signal_init (&exitsig, sig_cb, SIGINT);	795	ev_signal_init (&exitsig, sig_cb, SIGINT);
684	ev_signal_start (loop, &exitsig);	796	ev_signal_start (loop, &exitsig);
685	evf_unref (loop);	797	evf_unref (loop);
686		798
687	Example: For some weird reason, unregister the above signal handler again.	799	Example: For some weird reason, unregister the above signal handler again.
…		…
701	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	813	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
702	allows libev to delay invocation of I/O and timer/periodic callbacks	814	allows libev to delay invocation of I/O and timer/periodic callbacks
703	to increase efficiency of loop iterations (or to increase power-saving	815	to increase efficiency of loop iterations (or to increase power-saving
704	opportunities).	816	opportunities).
705		817
706	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
707	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
708	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
709	events, especially with backends like C<select ()> which have a high	821	events, especially with backends like C<select ()> which have a high
710	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.
711		823
712	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
713	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,
714	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
715	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
716	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.
717		831
718	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
719	to spend more time collecting timeouts, at the expense of increased	833	to spend more time collecting timeouts, at the expense of increased
720	latency (the watcher callback will be called later). C<ev_io> watchers	834	latency/jitter/inexactness (the watcher callback will be called
721	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
722	any overhead in libev.	836	value will not introduce any overhead in libev.
723		837
724	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
725	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
726	interactive servers (of course not for games), likewise for timeouts. It	840	interactive servers (of course not for games), likewise for timeouts. It
727	usually doesn't make much sense to set it to a lower value than C<0.01>,	841	usually doesn't make much sense to set it to a lower value than C<0.01>,
728	as this approaches the timing granularity of most systems.	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).
729		847
730	Setting the I<timeout collect interval> can improve the opportunity for	848	Setting the I<timeout collect interval> can improve the opportunity for
731	saving power, as the program will "bundle" timer callback invocations that	849	saving power, as the program will "bundle" timer callback invocations that
732	are "near" in time together, by delaying some, thus reducing the number of	850	are "near" in time together, by delaying some, thus reducing the number of
733	times the process sleeps and wakes up again. Another useful technique to	851	times the process sleeps and wakes up again. Another useful technique to
734	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	852	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
735	they fire on, say, one-second boundaries only.	853	they fire on, say, one-second boundaries only.
736		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	=item ev_set_userdata (loop, void *data)
		896
		897	=item ev_userdata (loop)
		898
		899	Set and retrieve a single C<void *> associated with a loop. When
		900	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		901	C<0.>
		902
		903	These two functions can be used to associate arbitrary data with a loop,
		904	and are intended solely for the C<invoke_pending_cb>, C<release> and
		905	C<acquire> callbacks described above, but of course can be (ab-)used for
		906	any other purpose as well.
		907
737	=item ev_loop_verify (loop)	908	=item ev_loop_verify (loop)
738		909
739	This function only does something when C<EV_VERIFY> support has been	910	This function only does something when C<EV_VERIFY> support has been
740	compiled in. It tries to go through all internal structures and checks	911	compiled in, which is the default for non-minimal builds. It tries to go
741	them for validity. If anything is found to be inconsistent, it will print	912	through all internal structures and checks them for validity. If anything
742	an error message to standard error and call C<abort ()>.	913	is found to be inconsistent, it will print an error message to standard
		914	error and call C<abort ()>.
743		915
744	This can be used to catch bugs inside libev itself: under normal	916	This can be used to catch bugs inside libev itself: under normal
745	circumstances, this function will never abort as of course libev keeps its	917	circumstances, this function will never abort as of course libev keeps its
746	data structures consistent.	918	data structures consistent.
747		919
748	=back	920	=back
749		921
750		922
751	=head1 ANATOMY OF A WATCHER	923	=head1 ANATOMY OF A WATCHER
752		924
		925	In the following description, uppercase C<TYPE> in names stands for the
		926	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		927	watchers and C<ev_io_start> for I/O watchers.
		928
753	A watcher is a structure that you create and register to record your	929	A watcher is a structure that you create and register to record your
754	interest in some event. For instance, if you want to wait for STDIN to	930	interest in some event. For instance, if you want to wait for STDIN to
755	become readable, you would create an C<ev_io> watcher for that:	931	become readable, you would create an C<ev_io> watcher for that:
756		932
757	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	933	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
758	{	934	{
759	ev_io_stop (w);	935	ev_io_stop (w);
760	ev_unloop (loop, EVUNLOOP_ALL);	936	ev_unloop (loop, EVUNLOOP_ALL);
761	}	937	}
762		938
763	struct ev_loop *loop = ev_default_loop (0);	939	struct ev_loop *loop = ev_default_loop (0);
		940
764	struct ev_io stdin_watcher;	941	ev_io stdin_watcher;
		942
765	ev_init (&stdin_watcher, my_cb);	943	ev_init (&stdin_watcher, my_cb);
766	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	944	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
767	ev_io_start (loop, &stdin_watcher);	945	ev_io_start (loop, &stdin_watcher);
		946
768	ev_loop (loop, 0);	947	ev_loop (loop, 0);
769		948
770	As you can see, you are responsible for allocating the memory for your	949	As you can see, you are responsible for allocating the memory for your
771	watcher structures (and it is usually a bad idea to do this on the stack,	950	watcher structures (and it is I<usually> a bad idea to do this on the
772	although this can sometimes be quite valid).	951	stack).
		952
		953	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		954	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
773		955
774	Each watcher structure must be initialised by a call to C<ev_init	956	Each watcher structure must be initialised by a call to C<ev_init
775	(watcher *, callback)>, which expects a callback to be provided. This	957	(watcher *, callback)>, which expects a callback to be provided. This
776	callback gets invoked each time the event occurs (or, in the case of I/O	958	callback gets invoked each time the event occurs (or, in the case of I/O
777	watchers, each time the event loop detects that the file descriptor given	959	watchers, each time the event loop detects that the file descriptor given
778	is readable and/or writable).	960	is readable and/or writable).
779		961
780	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	962	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
781	with arguments specific to this watcher type. There is also a macro	963	macro to configure it, with arguments specific to the watcher type. There
782	to combine initialisation and setting in one call: C<< ev_<type>_init	964	is also a macro to combine initialisation and setting in one call: C<<
783	(watcher *, callback, ...) >>.	965	ev_TYPE_init (watcher *, callback, ...) >>.
784		966
785	To make the watcher actually watch out for events, you have to start it	967	To make the watcher actually watch out for events, you have to start it
786	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	968	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
787	*) >>), and you can stop watching for events at any time by calling the	969	*) >>), and you can stop watching for events at any time by calling the
788	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	970	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
789		971
790	As long as your watcher is active (has been started but not stopped) you	972	As long as your watcher is active (has been started but not stopped) you
791	must not touch the values stored in it. Most specifically you must never	973	must not touch the values stored in it. Most specifically you must never
792	reinitialise it or call its C<set> macro.	974	reinitialise it or call its C<ev_TYPE_set> macro.
793		975
794	Each and every callback receives the event loop pointer as first, the	976	Each and every callback receives the event loop pointer as first, the
795	registered watcher structure as second, and a bitset of received events as	977	registered watcher structure as second, and a bitset of received events as
796	third argument.	978	third argument.
797		979
…		…
855		1037
856	=item C<EV_ASYNC>	1038	=item C<EV_ASYNC>
857		1039
858	The given async watcher has been asynchronously notified (see C<ev_async>).	1040	The given async watcher has been asynchronously notified (see C<ev_async>).
859		1041
		1042	=item C<EV_CUSTOM>
		1043
		1044	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1045	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		1046
860	=item C<EV_ERROR>	1047	=item C<EV_ERROR>
861		1048
862	An unspecified error has occurred, the watcher has been stopped. This might	1049	An unspecified error has occurred, the watcher has been stopped. This might
863	happen because the watcher could not be properly started because libev	1050	happen because the watcher could not be properly started because libev
864	ran out of memory, a file descriptor was found to be closed or any other	1051	ran out of memory, a file descriptor was found to be closed or any other
		1052	problem. Libev considers these application bugs.
		1053
865	problem. You best act on it by reporting the problem and somehow coping	1054	You best act on it by reporting the problem and somehow coping with the
866	with the watcher being stopped.	1055	watcher being stopped. Note that well-written programs should not receive
		1056	an error ever, so when your watcher receives it, this usually indicates a
		1057	bug in your program.
867		1058
868	Libev will usually signal a few "dummy" events together with an error,	1059	Libev will usually signal a few "dummy" events together with an error, for
869	for example it might indicate that a fd is readable or writable, and if	1060	example it might indicate that a fd is readable or writable, and if your
870	your callbacks is well-written it can just attempt the operation and cope	1061	callbacks is well-written it can just attempt the operation and cope with
871	with the error from read() or write(). This will not work in multi-threaded	1062	the error from read() or write(). This will not work in multi-threaded
872	programs, though, so beware.	1063	programs, though, as the fd could already be closed and reused for another
		1064	thing, so beware.
873		1065
874	=back	1066	=back
875		1067
876	=head2 GENERIC WATCHER FUNCTIONS	1068	=head2 GENERIC WATCHER FUNCTIONS
877
878	In the following description, C<TYPE> stands for the watcher type,
879	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
880		1069
881	=over 4	1070	=over 4
882		1071
883	=item C<ev_init> (ev_TYPE *watcher, callback)	1072	=item C<ev_init> (ev_TYPE *watcher, callback)
884		1073
…		…
890	which rolls both calls into one.	1079	which rolls both calls into one.
891		1080
892	You can reinitialise a watcher at any time as long as it has been stopped	1081	You can reinitialise a watcher at any time as long as it has been stopped
893	(or never started) and there are no pending events outstanding.	1082	(or never started) and there are no pending events outstanding.
894		1083
895	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1084	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
896	int revents)>.	1085	int revents)>.
		1086
		1087	Example: Initialise an C<ev_io> watcher in two steps.
		1088
		1089	ev_io w;
		1090	ev_init (&w, my_cb);
		1091	ev_io_set (&w, STDIN_FILENO, EV_READ);
897		1092
898	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1093	=item C<ev_TYPE_set> (ev_TYPE *, [args])
899		1094
900	This macro initialises the type-specific parts of a watcher. You need to	1095	This macro initialises the type-specific parts of a watcher. You need to
901	call C<ev_init> at least once before you call this macro, but you can	1096	call C<ev_init> at least once before you call this macro, but you can
…		…
904	difference to the C<ev_init> macro).	1099	difference to the C<ev_init> macro).
905		1100
906	Although some watcher types do not have type-specific arguments	1101	Although some watcher types do not have type-specific arguments
907	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	1102	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
908		1103
		1104	See C<ev_init>, above, for an example.
		1105
909	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1106	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
910		1107
911	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1108	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
912	calls into a single call. This is the most convenient method to initialise	1109	calls into a single call. This is the most convenient method to initialise
913	a watcher. The same limitations apply, of course.	1110	a watcher. The same limitations apply, of course.
914		1111
		1112	Example: Initialise and set an C<ev_io> watcher in one step.
		1113
		1114	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1115
915	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1116	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
916		1117
917	Starts (activates) the given watcher. Only active watchers will receive	1118	Starts (activates) the given watcher. Only active watchers will receive
918	events. If the watcher is already active nothing will happen.	1119	events. If the watcher is already active nothing will happen.
919		1120
		1121	Example: Start the C<ev_io> watcher that is being abused as example in this
		1122	whole section.
		1123
		1124	ev_io_start (EV_DEFAULT_UC, &w);
		1125
920	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1126	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
921		1127
922	Stops the given watcher again (if active) and clears the pending	1128	Stops the given watcher if active, and clears the pending status (whether
		1129	the watcher was active or not).
		1130
923	status. It is possible that stopped watchers are pending (for example,	1131	It is possible that stopped watchers are pending - for example,
924	non-repeating timers are being stopped when they become pending), but	1132	non-repeating timers are being stopped when they become pending - but
925	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1133	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
926	you want to free or reuse the memory used by the watcher it is therefore a	1134	pending. If you want to free or reuse the memory used by the watcher it is
927	good idea to always call its C<ev_TYPE_stop> function.	1135	therefore a good idea to always call its C<ev_TYPE_stop> function.
928		1136
929	=item bool ev_is_active (ev_TYPE *watcher)	1137	=item bool ev_is_active (ev_TYPE *watcher)
930		1138
931	Returns a true value iff the watcher is active (i.e. it has been started	1139	Returns a true value iff the watcher is active (i.e. it has been started
932	and not yet been stopped). As long as a watcher is active you must not modify	1140	and not yet been stopped). As long as a watcher is active you must not modify
…		…
958	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1166	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
959	(default: C<-2>). Pending watchers with higher priority will be invoked	1167	(default: C<-2>). Pending watchers with higher priority will be invoked
960	before watchers with lower priority, but priority will not keep watchers	1168	before watchers with lower priority, but priority will not keep watchers
961	from being executed (except for C<ev_idle> watchers).	1169	from being executed (except for C<ev_idle> watchers).
962		1170
963	This means that priorities are I<only> used for ordering callback
964	invocation after new events have been received. This is useful, for
965	example, to reduce latency after idling, or more often, to bind two
966	watchers on the same event and make sure one is called first.
967
968	If you need to suppress invocation when higher priority events are pending	1171	If you need to suppress invocation when higher priority events are pending
969	you need to look at C<ev_idle> watchers, which provide this functionality.	1172	you need to look at C<ev_idle> watchers, which provide this functionality.
970		1173
971	You I<must not> change the priority of a watcher as long as it is active or	1174	You I<must not> change the priority of a watcher as long as it is active or
972	pending.	1175	pending.
973		1176
		1177	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1178	fine, as long as you do not mind that the priority value you query might
		1179	or might not have been clamped to the valid range.
		1180
974	The default priority used by watchers when no priority has been set is	1181	The default priority used by watchers when no priority has been set is
975	always C<0>, which is supposed to not be too high and not be too low :).	1182	always C<0>, which is supposed to not be too high and not be too low :).
976		1183
977	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1184	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
978	fine, as long as you do not mind that the priority value you query might	1185	priorities.
979	or might not have been adjusted to be within valid range.
980		1186
981	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1187	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
982		1188
983	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1189	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
984	C<loop> nor C<revents> need to be valid as long as the watcher callback	1190	C<loop> nor C<revents> need to be valid as long as the watcher callback
985	can deal with that fact.	1191	can deal with that fact, as both are simply passed through to the
		1192	callback.
986		1193
987	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1194	=item int ev_clear_pending (loop, ev_TYPE *watcher)
988		1195
989	If the watcher is pending, this function returns clears its pending status	1196	If the watcher is pending, this function clears its pending status and
990	and returns its C<revents> bitset (as if its callback was invoked). If the	1197	returns its C<revents> bitset (as if its callback was invoked). If the
991	watcher isn't pending it does nothing and returns C<0>.	1198	watcher isn't pending it does nothing and returns C<0>.
992		1199
		1200	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1201	callback to be invoked, which can be accomplished with this function.
		1202
993	=back	1203	=back
994		1204
995		1205
996	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1206	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
997		1207
998	Each watcher has, by default, a member C<void *data> that you can change	1208	Each watcher has, by default, a member C<void *data> that you can change
999	and read at any time, libev will completely ignore it. This can be used	1209	and read at any time: libev will completely ignore it. This can be used
1000	to associate arbitrary data with your watcher. If you need more data and	1210	to associate arbitrary data with your watcher. If you need more data and
1001	don't want to allocate memory and store a pointer to it in that data	1211	don't want to allocate memory and store a pointer to it in that data
1002	member, you can also "subclass" the watcher type and provide your own	1212	member, you can also "subclass" the watcher type and provide your own
1003	data:	1213	data:
1004		1214
1005	struct my_io	1215	struct my_io
1006	{	1216	{
1007	struct ev_io io;	1217	ev_io io;
1008	int otherfd;	1218	int otherfd;
1009	void *somedata;	1219	void *somedata;
1010	struct whatever *mostinteresting;	1220	struct whatever *mostinteresting;
1011	}	1221	};
		1222
		1223	...
		1224	struct my_io w;
		1225	ev_io_init (&w.io, my_cb, fd, EV_READ);
1012		1226
1013	And since your callback will be called with a pointer to the watcher, you	1227	And since your callback will be called with a pointer to the watcher, you
1014	can cast it back to your own type:	1228	can cast it back to your own type:
1015		1229
1016	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1230	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1017	{	1231	{
1018	struct my_io *w = (struct my_io *)w_;	1232	struct my_io *w = (struct my_io *)w_;
1019	...	1233	...
1020	}	1234	}
1021		1235
1022	More interesting and less C-conformant ways of casting your callback type	1236	More interesting and less C-conformant ways of casting your callback type
1023	instead have been omitted.	1237	instead have been omitted.
1024		1238
1025	Another common scenario is having some data structure with multiple	1239	Another common scenario is to use some data structure with multiple
1026	watchers:	1240	embedded watchers:
1027		1241
1028	struct my_biggy	1242	struct my_biggy
1029	{	1243	{
1030	int some_data;	1244	int some_data;
1031	ev_timer t1;	1245	ev_timer t1;
1032	ev_timer t2;	1246	ev_timer t2;
1033	}	1247	}
1034		1248
1035	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1249	In this case getting the pointer to C<my_biggy> is a bit more
1036	you need to use C<offsetof>:	1250	complicated: Either you store the address of your C<my_biggy> struct
		1251	in the C<data> member of the watcher (for woozies), or you need to use
		1252	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1253	programmers):
1037		1254
1038	#include <stddef.h>	1255	#include <stddef.h>
1039		1256
1040	static void	1257	static void
1041	t1_cb (EV_P_ struct ev_timer *w, int revents)	1258	t1_cb (EV_P_ ev_timer *w, int revents)
1042	{	1259	{
1043	struct my_biggy big = (struct my_biggy *	1260	struct my_biggy big = (struct my_biggy *)
1044	(((char *)w) - offsetof (struct my_biggy, t1));	1261	(((char *)w) - offsetof (struct my_biggy, t1));
1045	}	1262	}
1046		1263
1047	static void	1264	static void
1048	t2_cb (EV_P_ struct ev_timer *w, int revents)	1265	t2_cb (EV_P_ ev_timer *w, int revents)
1049	{	1266	{
1050	struct my_biggy big = (struct my_biggy *	1267	struct my_biggy big = (struct my_biggy *)
1051	(((char *)w) - offsetof (struct my_biggy, t2));	1268	(((char *)w) - offsetof (struct my_biggy, t2));
1052	}	1269	}
		1270
		1271	=head2 WATCHER PRIORITY MODELS
		1272
		1273	Many event loops support I<watcher priorities>, which are usually small
		1274	integers that influence the ordering of event callback invocation
		1275	between watchers in some way, all else being equal.
		1276
		1277	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1278	description for the more technical details such as the actual priority
		1279	range.
		1280
		1281	There are two common ways how these these priorities are being interpreted
		1282	by event loops:
		1283
		1284	In the more common lock-out model, higher priorities "lock out" invocation
		1285	of lower priority watchers, which means as long as higher priority
		1286	watchers receive events, lower priority watchers are not being invoked.
		1287
		1288	The less common only-for-ordering model uses priorities solely to order
		1289	callback invocation within a single event loop iteration: Higher priority
		1290	watchers are invoked before lower priority ones, but they all get invoked
		1291	before polling for new events.
		1292
		1293	Libev uses the second (only-for-ordering) model for all its watchers
		1294	except for idle watchers (which use the lock-out model).
		1295
		1296	The rationale behind this is that implementing the lock-out model for
		1297	watchers is not well supported by most kernel interfaces, and most event
		1298	libraries will just poll for the same events again and again as long as
		1299	their callbacks have not been executed, which is very inefficient in the
		1300	common case of one high-priority watcher locking out a mass of lower
		1301	priority ones.
		1302
		1303	Static (ordering) priorities are most useful when you have two or more
		1304	watchers handling the same resource: a typical usage example is having an
		1305	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1306	timeouts. Under load, data might be received while the program handles
		1307	other jobs, but since timers normally get invoked first, the timeout
		1308	handler will be executed before checking for data. In that case, giving
		1309	the timer a lower priority than the I/O watcher ensures that I/O will be
		1310	handled first even under adverse conditions (which is usually, but not
		1311	always, what you want).
		1312
		1313	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1314	will only be executed when no same or higher priority watchers have
		1315	received events, they can be used to implement the "lock-out" model when
		1316	required.
		1317
		1318	For example, to emulate how many other event libraries handle priorities,
		1319	you can associate an C<ev_idle> watcher to each such watcher, and in
		1320	the normal watcher callback, you just start the idle watcher. The real
		1321	processing is done in the idle watcher callback. This causes libev to
		1322	continously poll and process kernel event data for the watcher, but when
		1323	the lock-out case is known to be rare (which in turn is rare :), this is
		1324	workable.
		1325
		1326	Usually, however, the lock-out model implemented that way will perform
		1327	miserably under the type of load it was designed to handle. In that case,
		1328	it might be preferable to stop the real watcher before starting the
		1329	idle watcher, so the kernel will not have to process the event in case
		1330	the actual processing will be delayed for considerable time.
		1331
		1332	Here is an example of an I/O watcher that should run at a strictly lower
		1333	priority than the default, and which should only process data when no
		1334	other events are pending:
		1335
		1336	ev_idle idle; // actual processing watcher
		1337	ev_io io; // actual event watcher
		1338
		1339	static void
		1340	io_cb (EV_P_ ev_io *w, int revents)
		1341	{
		1342	// stop the I/O watcher, we received the event, but
		1343	// are not yet ready to handle it.
		1344	ev_io_stop (EV_A_ w);
		1345
		1346	// start the idle watcher to ahndle the actual event.
		1347	// it will not be executed as long as other watchers
		1348	// with the default priority are receiving events.
		1349	ev_idle_start (EV_A_ &idle);
		1350	}
		1351
		1352	static void
		1353	idle_cb (EV_P_ ev_idle *w, int revents)
		1354	{
		1355	// actual processing
		1356	read (STDIN_FILENO, ...);
		1357
		1358	// have to start the I/O watcher again, as
		1359	// we have handled the event
		1360	ev_io_start (EV_P_ &io);
		1361	}
		1362
		1363	// initialisation
		1364	ev_idle_init (&idle, idle_cb);
		1365	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1366	ev_io_start (EV_DEFAULT_ &io);
		1367
		1368	In the "real" world, it might also be beneficial to start a timer, so that
		1369	low-priority connections can not be locked out forever under load. This
		1370	enables your program to keep a lower latency for important connections
		1371	during short periods of high load, while not completely locking out less
		1372	important ones.
1053		1373
1054		1374
1055	=head1 WATCHER TYPES	1375	=head1 WATCHER TYPES
1056		1376
1057	This section describes each watcher in detail, but will not repeat	1377	This section describes each watcher in detail, but will not repeat
…		…
1081	In general you can register as many read and/or write event watchers per	1401	In general you can register as many read and/or write event watchers per
1082	fd as you want (as long as you don't confuse yourself). Setting all file	1402	fd as you want (as long as you don't confuse yourself). Setting all file
1083	descriptors to non-blocking mode is also usually a good idea (but not	1403	descriptors to non-blocking mode is also usually a good idea (but not
1084	required if you know what you are doing).	1404	required if you know what you are doing).
1085		1405
1086	If you must do this, then force the use of a known-to-be-good backend	1406	If you cannot use non-blocking mode, then force the use of a
1087	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1407	known-to-be-good backend (at the time of this writing, this includes only
1088	C<EVBACKEND_POLL>).	1408	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1409	descriptors for which non-blocking operation makes no sense (such as
		1410	files) - libev doesn't guarentee any specific behaviour in that case.
1089		1411
1090	Another thing you have to watch out for is that it is quite easy to	1412	Another thing you have to watch out for is that it is quite easy to
1091	receive "spurious" readiness notifications, that is your callback might	1413	receive "spurious" readiness notifications, that is your callback might
1092	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1414	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1093	because there is no data. Not only are some backends known to create a	1415	because there is no data. Not only are some backends known to create a
1094	lot of those (for example Solaris ports), it is very easy to get into	1416	lot of those (for example Solaris ports), it is very easy to get into
1095	this situation even with a relatively standard program structure. Thus	1417	this situation even with a relatively standard program structure. Thus
1096	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1418	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1097	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1419	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1098		1420
1099	If you cannot run the fd in non-blocking mode (for example you should not	1421	If you cannot run the fd in non-blocking mode (for example you should
1100	play around with an Xlib connection), then you have to separately re-test	1422	not play around with an Xlib connection), then you have to separately
1101	whether a file descriptor is really ready with a known-to-be good interface	1423	re-test whether a file descriptor is really ready with a known-to-be good
1102	such as poll (fortunately in our Xlib example, Xlib already does this on	1424	interface such as poll (fortunately in our Xlib example, Xlib already
1103	its own, so its quite safe to use).	1425	does this on its own, so its quite safe to use). Some people additionally
		1426	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1427	indefinitely.
		1428
		1429	But really, best use non-blocking mode.
1104		1430
1105	=head3 The special problem of disappearing file descriptors	1431	=head3 The special problem of disappearing file descriptors
1106		1432
1107	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1433	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1108	descriptor (either by calling C<close> explicitly or by any other means,	1434	descriptor (either due to calling C<close> explicitly or any other means,
1109	such as C<dup>). The reason is that you register interest in some file	1435	such as C<dup2>). The reason is that you register interest in some file
1110	descriptor, but when it goes away, the operating system will silently drop	1436	descriptor, but when it goes away, the operating system will silently drop
1111	this interest. If another file descriptor with the same number then is	1437	this interest. If another file descriptor with the same number then is
1112	registered with libev, there is no efficient way to see that this is, in	1438	registered with libev, there is no efficient way to see that this is, in
1113	fact, a different file descriptor.	1439	fact, a different file descriptor.
1114		1440
…		…
1145	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1471	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1146	C<EVBACKEND_POLL>.	1472	C<EVBACKEND_POLL>.
1147		1473
1148	=head3 The special problem of SIGPIPE	1474	=head3 The special problem of SIGPIPE
1149		1475
1150	While not really specific to libev, it is easy to forget about SIGPIPE:	1476	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1151	when writing to a pipe whose other end has been closed, your program gets	1477	when writing to a pipe whose other end has been closed, your program gets
1152	send a SIGPIPE, which, by default, aborts your program. For most programs	1478	sent a SIGPIPE, which, by default, aborts your program. For most programs
1153	this is sensible behaviour, for daemons, this is usually undesirable.	1479	this is sensible behaviour, for daemons, this is usually undesirable.
1154		1480
1155	So when you encounter spurious, unexplained daemon exits, make sure you	1481	So when you encounter spurious, unexplained daemon exits, make sure you
1156	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1482	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1157	somewhere, as that would have given you a big clue).	1483	somewhere, as that would have given you a big clue).
…		…
1164	=item ev_io_init (ev_io *, callback, int fd, int events)	1490	=item ev_io_init (ev_io *, callback, int fd, int events)
1165		1491
1166	=item ev_io_set (ev_io *, int fd, int events)	1492	=item ev_io_set (ev_io *, int fd, int events)
1167		1493
1168	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1494	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1169	receive events for and events is either C<EV_READ>, C<EV_WRITE> or	1495	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1170	C<EV_READ | EV_WRITE> to receive the given events.	1496	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1171		1497
1172	=item int fd [read-only]	1498	=item int fd [read-only]
1173		1499
1174	The file descriptor being watched.	1500	The file descriptor being watched.
1175		1501
…		…
1184	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1510	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1185	readable, but only once. Since it is likely line-buffered, you could	1511	readable, but only once. Since it is likely line-buffered, you could
1186	attempt to read a whole line in the callback.	1512	attempt to read a whole line in the callback.
1187		1513
1188	static void	1514	static void
1189	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1515	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1190	{	1516	{
1191	ev_io_stop (loop, w);	1517	ev_io_stop (loop, w);
1192	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1518	.. read from stdin here (or from w->fd) and handle any I/O errors
1193	}	1519	}
1194		1520
1195	...	1521	...
1196	struct ev_loop *loop = ev_default_init (0);	1522	struct ev_loop *loop = ev_default_init (0);
1197	struct ev_io stdin_readable;	1523	ev_io stdin_readable;
1198	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1524	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1199	ev_io_start (loop, &stdin_readable);	1525	ev_io_start (loop, &stdin_readable);
1200	ev_loop (loop, 0);	1526	ev_loop (loop, 0);
1201		1527
1202		1528
…		…
1205	Timer watchers are simple relative timers that generate an event after a	1531	Timer watchers are simple relative timers that generate an event after a
1206	given time, and optionally repeating in regular intervals after that.	1532	given time, and optionally repeating in regular intervals after that.
1207		1533
1208	The timers are based on real time, that is, if you register an event that	1534	The timers are based on real time, that is, if you register an event that
1209	times out after an hour and you reset your system clock to January last	1535	times out after an hour and you reset your system clock to January last
1210	year, it will still time out after (roughly) and hour. "Roughly" because	1536	year, it will still time out after (roughly) one hour. "Roughly" because
1211	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1537	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1212	monotonic clock option helps a lot here).	1538	monotonic clock option helps a lot here).
1213		1539
1214	The callback is guaranteed to be invoked only after its timeout has passed,	1540	The callback is guaranteed to be invoked only I<after> its timeout has
1215	but if multiple timers become ready during the same loop iteration then	1541	passed (not I<at>, so on systems with very low-resolution clocks this
1216	order of execution is undefined.	1542	might introduce a small delay). If multiple timers become ready during the
		1543	same loop iteration then the ones with earlier time-out values are invoked
		1544	before ones of the same priority with later time-out values (but this is
		1545	no longer true when a callback calls C<ev_loop> recursively).
		1546
		1547	=head3 Be smart about timeouts
		1548
		1549	Many real-world problems involve some kind of timeout, usually for error
		1550	recovery. A typical example is an HTTP request - if the other side hangs,
		1551	you want to raise some error after a while.
		1552
		1553	What follows are some ways to handle this problem, from obvious and
		1554	inefficient to smart and efficient.
		1555
		1556	In the following, a 60 second activity timeout is assumed - a timeout that
		1557	gets reset to 60 seconds each time there is activity (e.g. each time some
		1558	data or other life sign was received).
		1559
		1560	=over 4
		1561
		1562	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1563
		1564	This is the most obvious, but not the most simple way: In the beginning,
		1565	start the watcher:
		1566
		1567	ev_timer_init (timer, callback, 60., 0.);
		1568	ev_timer_start (loop, timer);
		1569
		1570	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1571	and start it again:
		1572
		1573	ev_timer_stop (loop, timer);
		1574	ev_timer_set (timer, 60., 0.);
		1575	ev_timer_start (loop, timer);
		1576
		1577	This is relatively simple to implement, but means that each time there is
		1578	some activity, libev will first have to remove the timer from its internal
		1579	data structure and then add it again. Libev tries to be fast, but it's
		1580	still not a constant-time operation.
		1581
		1582	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1583
		1584	This is the easiest way, and involves using C<ev_timer_again> instead of
		1585	C<ev_timer_start>.
		1586
		1587	To implement this, configure an C<ev_timer> with a C<repeat> value
		1588	of C<60> and then call C<ev_timer_again> at start and each time you
		1589	successfully read or write some data. If you go into an idle state where
		1590	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1591	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1592
		1593	That means you can ignore both the C<ev_timer_start> function and the
		1594	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1595	member and C<ev_timer_again>.
		1596
		1597	At start:
		1598
		1599	ev_init (timer, callback);
		1600	timer->repeat = 60.;
		1601	ev_timer_again (loop, timer);
		1602
		1603	Each time there is some activity:
		1604
		1605	ev_timer_again (loop, timer);
		1606
		1607	It is even possible to change the time-out on the fly, regardless of
		1608	whether the watcher is active or not:
		1609
		1610	timer->repeat = 30.;
		1611	ev_timer_again (loop, timer);
		1612
		1613	This is slightly more efficient then stopping/starting the timer each time
		1614	you want to modify its timeout value, as libev does not have to completely
		1615	remove and re-insert the timer from/into its internal data structure.
		1616
		1617	It is, however, even simpler than the "obvious" way to do it.
		1618
		1619	=item 3. Let the timer time out, but then re-arm it as required.
		1620
		1621	This method is more tricky, but usually most efficient: Most timeouts are
		1622	relatively long compared to the intervals between other activity - in
		1623	our example, within 60 seconds, there are usually many I/O events with
		1624	associated activity resets.
		1625
		1626	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1627	but remember the time of last activity, and check for a real timeout only
		1628	within the callback:
		1629
		1630	ev_tstamp last_activity; // time of last activity
		1631
		1632	static void
		1633	callback (EV_P_ ev_timer *w, int revents)
		1634	{
		1635	ev_tstamp now = ev_now (EV_A);
		1636	ev_tstamp timeout = last_activity + 60.;
		1637
		1638	// if last_activity + 60. is older than now, we did time out
		1639	if (timeout < now)
		1640	{
		1641	// timeout occured, take action
		1642	}
		1643	else
		1644	{
		1645	// callback was invoked, but there was some activity, re-arm
		1646	// the watcher to fire in last_activity + 60, which is
		1647	// guaranteed to be in the future, so "again" is positive:
		1648	w->repeat = timeout - now;
		1649	ev_timer_again (EV_A_ w);
		1650	}
		1651	}
		1652
		1653	To summarise the callback: first calculate the real timeout (defined
		1654	as "60 seconds after the last activity"), then check if that time has
		1655	been reached, which means something I<did>, in fact, time out. Otherwise
		1656	the callback was invoked too early (C<timeout> is in the future), so
		1657	re-schedule the timer to fire at that future time, to see if maybe we have
		1658	a timeout then.
		1659
		1660	Note how C<ev_timer_again> is used, taking advantage of the
		1661	C<ev_timer_again> optimisation when the timer is already running.
		1662
		1663	This scheme causes more callback invocations (about one every 60 seconds
		1664	minus half the average time between activity), but virtually no calls to
		1665	libev to change the timeout.
		1666
		1667	To start the timer, simply initialise the watcher and set C<last_activity>
		1668	to the current time (meaning we just have some activity :), then call the
		1669	callback, which will "do the right thing" and start the timer:
		1670
		1671	ev_init (timer, callback);
		1672	last_activity = ev_now (loop);
		1673	callback (loop, timer, EV_TIMEOUT);
		1674
		1675	And when there is some activity, simply store the current time in
		1676	C<last_activity>, no libev calls at all:
		1677
		1678	last_actiivty = ev_now (loop);
		1679
		1680	This technique is slightly more complex, but in most cases where the
		1681	time-out is unlikely to be triggered, much more efficient.
		1682
		1683	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1684	callback :) - just change the timeout and invoke the callback, which will
		1685	fix things for you.
		1686
		1687	=item 4. Wee, just use a double-linked list for your timeouts.
		1688
		1689	If there is not one request, but many thousands (millions...), all
		1690	employing some kind of timeout with the same timeout value, then one can
		1691	do even better:
		1692
		1693	When starting the timeout, calculate the timeout value and put the timeout
		1694	at the I<end> of the list.
		1695
		1696	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1697	the list is expected to fire (for example, using the technique #3).
		1698
		1699	When there is some activity, remove the timer from the list, recalculate
		1700	the timeout, append it to the end of the list again, and make sure to
		1701	update the C<ev_timer> if it was taken from the beginning of the list.
		1702
		1703	This way, one can manage an unlimited number of timeouts in O(1) time for
		1704	starting, stopping and updating the timers, at the expense of a major
		1705	complication, and having to use a constant timeout. The constant timeout
		1706	ensures that the list stays sorted.
		1707
		1708	=back
		1709
		1710	So which method the best?
		1711
		1712	Method #2 is a simple no-brain-required solution that is adequate in most
		1713	situations. Method #3 requires a bit more thinking, but handles many cases
		1714	better, and isn't very complicated either. In most case, choosing either
		1715	one is fine, with #3 being better in typical situations.
		1716
		1717	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1718	rather complicated, but extremely efficient, something that really pays
		1719	off after the first million or so of active timers, i.e. it's usually
		1720	overkill :)
1217		1721
1218	=head3 The special problem of time updates	1722	=head3 The special problem of time updates
1219		1723
1220	Establishing the current time is a costly operation (it usually takes at	1724	Establishing the current time is a costly operation (it usually takes at
1221	least two system calls): EV therefore updates its idea of the current	1725	least two system calls): EV therefore updates its idea of the current
1222	time only before and after C<ev_loop> polls for new events, which causes	1726	time only before and after C<ev_loop> collects new events, which causes a
1223	a growing difference between C<ev_now ()> and C<ev_time ()> when handling	1727	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1224	lots of events.	1728	lots of events in one iteration.
1225		1729
1226	The relative timeouts are calculated relative to the C<ev_now ()>	1730	The relative timeouts are calculated relative to the C<ev_now ()>
1227	time. This is usually the right thing as this timestamp refers to the time	1731	time. This is usually the right thing as this timestamp refers to the time
1228	of the event triggering whatever timeout you are modifying/starting. If	1732	of the event triggering whatever timeout you are modifying/starting. If
1229	you suspect event processing to be delayed and you I<need> to base the	1733	you suspect event processing to be delayed and you I<need> to base the
1230	timeout on the current time, use something like this to adjust for this:	1734	timeout on the current time, use something like this to adjust for this:
1231		1735
1232	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1736	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1233		1737
1234	If the event loop is suspended for a long time, one can also force an	1738	If the event loop is suspended for a long time, you can also force an
1235	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1739	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1236	()>.	1740	()>.
1237		1741
1238	=head3 Watcher-Specific Functions and Data Members	1742	=head3 Watcher-Specific Functions and Data Members
1239		1743
…		…
1265	If the timer is started but non-repeating, stop it (as if it timed out).	1769	If the timer is started but non-repeating, stop it (as if it timed out).
1266		1770
1267	If the timer is repeating, either start it if necessary (with the	1771	If the timer is repeating, either start it if necessary (with the
1268	C<repeat> value), or reset the running timer to the C<repeat> value.	1772	C<repeat> value), or reset the running timer to the C<repeat> value.
1269		1773
1270	This sounds a bit complicated, but here is a useful and typical	1774	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1271	example: Imagine you have a TCP connection and you want a so-called idle	1775	usage example.
1272	timeout, that is, you want to be called when there have been, say, 60
1273	seconds of inactivity on the socket. The easiest way to do this is to
1274	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1275	C<ev_timer_again> each time you successfully read or write some data. If
1276	you go into an idle state where you do not expect data to travel on the
1277	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1278	automatically restart it if need be.
1279
1280	That means you can ignore the C<after> value and C<ev_timer_start>
1281	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1282
1283	ev_timer_init (timer, callback, 0., 5.);
1284	ev_timer_again (loop, timer);
1285	...
1286	timer->again = 17.;
1287	ev_timer_again (loop, timer);
1288	...
1289	timer->again = 10.;
1290	ev_timer_again (loop, timer);
1291
1292	This is more slightly efficient then stopping/starting the timer each time
1293	you want to modify its timeout value.
1294		1776
1295	=item ev_tstamp repeat [read-write]	1777	=item ev_tstamp repeat [read-write]
1296		1778
1297	The current C<repeat> value. Will be used each time the watcher times out	1779	The current C<repeat> value. Will be used each time the watcher times out
1298	or C<ev_timer_again> is called and determines the next timeout (if any),	1780	or C<ev_timer_again> is called, and determines the next timeout (if any),
1299	which is also when any modifications are taken into account.	1781	which is also when any modifications are taken into account.
1300		1782
1301	=back	1783	=back
1302		1784
1303	=head3 Examples	1785	=head3 Examples
1304		1786
1305	Example: Create a timer that fires after 60 seconds.	1787	Example: Create a timer that fires after 60 seconds.
1306		1788
1307	static void	1789	static void
1308	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1790	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1309	{	1791	{
1310	.. one minute over, w is actually stopped right here	1792	.. one minute over, w is actually stopped right here
1311	}	1793	}
1312		1794
1313	struct ev_timer mytimer;	1795	ev_timer mytimer;
1314	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1796	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1315	ev_timer_start (loop, &mytimer);	1797	ev_timer_start (loop, &mytimer);
1316		1798
1317	Example: Create a timeout timer that times out after 10 seconds of	1799	Example: Create a timeout timer that times out after 10 seconds of
1318	inactivity.	1800	inactivity.
1319		1801
1320	static void	1802	static void
1321	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1803	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1322	{	1804	{
1323	.. ten seconds without any activity	1805	.. ten seconds without any activity
1324	}	1806	}
1325		1807
1326	struct ev_timer mytimer;	1808	ev_timer mytimer;
1327	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1809	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1328	ev_timer_again (&mytimer); /* start timer */	1810	ev_timer_again (&mytimer); /* start timer */
1329	ev_loop (loop, 0);	1811	ev_loop (loop, 0);
1330		1812
1331	// and in some piece of code that gets executed on any "activity":	1813	// and in some piece of code that gets executed on any "activity":
…		…
1336	=head2 C<ev_periodic> - to cron or not to cron?	1818	=head2 C<ev_periodic> - to cron or not to cron?
1337		1819
1338	Periodic watchers are also timers of a kind, but they are very versatile	1820	Periodic watchers are also timers of a kind, but they are very versatile
1339	(and unfortunately a bit complex).	1821	(and unfortunately a bit complex).
1340		1822
1341	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1823	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1342	but on wall clock time (absolute time). You can tell a periodic watcher	1824	relative time, the physical time that passes) but on wall clock time
1343	to trigger after some specific point in time. For example, if you tell a	1825	(absolute time, the thing you can read on your calender or clock). The
1344	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	1826	difference is that wall clock time can run faster or slower than real
1345	+ 10.>, that is, an absolute time not a delay) and then reset your system	1827	time, and time jumps are not uncommon (e.g. when you adjust your
1346	clock to January of the previous year, then it will take more than year	1828	wrist-watch).
1347	to trigger the event (unlike an C<ev_timer>, which would still trigger
1348	roughly 10 seconds later as it uses a relative timeout).
1349		1829
		1830	You can tell a periodic watcher to trigger after some specific point
		1831	in time: for example, if you tell a periodic watcher to trigger "in 10
		1832	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1833	not a delay) and then reset your system clock to January of the previous
		1834	year, then it will take a year or more to trigger the event (unlike an
		1835	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1836	it, as it uses a relative timeout).
		1837
1350	C<ev_periodic>s can also be used to implement vastly more complex timers,	1838	C<ev_periodic> watchers can also be used to implement vastly more complex
1351	such as triggering an event on each "midnight, local time", or other	1839	timers, such as triggering an event on each "midnight, local time", or
1352	complicated, rules.	1840	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1841	those cannot react to time jumps.
1353		1842
1354	As with timers, the callback is guaranteed to be invoked only when the	1843	As with timers, the callback is guaranteed to be invoked only when the
1355	time (C<at>) has passed, but if multiple periodic timers become ready	1844	point in time where it is supposed to trigger has passed. If multiple
1356	during the same loop iteration then order of execution is undefined.	1845	timers become ready during the same loop iteration then the ones with
		1846	earlier time-out values are invoked before ones with later time-out values
		1847	(but this is no longer true when a callback calls C<ev_loop> recursively).
1357		1848
1358	=head3 Watcher-Specific Functions and Data Members	1849	=head3 Watcher-Specific Functions and Data Members
1359		1850
1360	=over 4	1851	=over 4
1361		1852
1362	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1853	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1363		1854
1364	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1855	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1365		1856
1366	Lots of arguments, lets sort it out... There are basically three modes of	1857	Lots of arguments, let's sort it out... There are basically three modes of
1367	operation, and we will explain them from simplest to complex:	1858	operation, and we will explain them from simplest to most complex:
1368		1859
1369	=over 4	1860	=over 4
1370		1861
1371	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1862	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1372		1863
1373	In this configuration the watcher triggers an event after the wall clock	1864	In this configuration the watcher triggers an event after the wall clock
1374	time C<at> has passed and doesn't repeat. It will not adjust when a time	1865	time C<offset> has passed. It will not repeat and will not adjust when a
1375	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1866	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1376	run when the system time reaches or surpasses this time.	1867	will be stopped and invoked when the system clock reaches or surpasses
		1868	this point in time.
1377		1869
1378	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1870	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1379		1871
1380	In this mode the watcher will always be scheduled to time out at the next	1872	In this mode the watcher will always be scheduled to time out at the next
1381	C<at + N * interval> time (for some integer N, which can also be negative)	1873	C<offset + N * interval> time (for some integer N, which can also be
1382	and then repeat, regardless of any time jumps.	1874	negative) and then repeat, regardless of any time jumps. The C<offset>
		1875	argument is merely an offset into the C<interval> periods.
1383		1876
1384	This can be used to create timers that do not drift with respect to system	1877	This can be used to create timers that do not drift with respect to the
1385	time, for example, here is a C<ev_periodic> that triggers each hour, on	1878	system clock, for example, here is an C<ev_periodic> that triggers each
1386	the hour:	1879	hour, on the hour (with respect to UTC):
1387		1880
1388	ev_periodic_set (&periodic, 0., 3600., 0);	1881	ev_periodic_set (&periodic, 0., 3600., 0);
1389		1882
1390	This doesn't mean there will always be 3600 seconds in between triggers,	1883	This doesn't mean there will always be 3600 seconds in between triggers,
1391	but only that the callback will be called when the system time shows a	1884	but only that the callback will be called when the system time shows a
1392	full hour (UTC), or more correctly, when the system time is evenly divisible	1885	full hour (UTC), or more correctly, when the system time is evenly divisible
1393	by 3600.	1886	by 3600.
1394		1887
1395	Another way to think about it (for the mathematically inclined) is that	1888	Another way to think about it (for the mathematically inclined) is that
1396	C<ev_periodic> will try to run the callback in this mode at the next possible	1889	C<ev_periodic> will try to run the callback in this mode at the next possible
1397	time where C<time = at (mod interval)>, regardless of any time jumps.	1890	time where C<time = offset (mod interval)>, regardless of any time jumps.
1398		1891
1399	For numerical stability it is preferable that the C<at> value is near	1892	For numerical stability it is preferable that the C<offset> value is near
1400	C<ev_now ()> (the current time), but there is no range requirement for	1893	C<ev_now ()> (the current time), but there is no range requirement for
1401	this value, and in fact is often specified as zero.	1894	this value, and in fact is often specified as zero.
1402		1895
1403	Note also that there is an upper limit to how often a timer can fire (CPU	1896	Note also that there is an upper limit to how often a timer can fire (CPU
1404	speed for example), so if C<interval> is very small then timing stability	1897	speed for example), so if C<interval> is very small then timing stability
1405	will of course deteriorate. Libev itself tries to be exact to be about one	1898	will of course deteriorate. Libev itself tries to be exact to be about one
1406	millisecond (if the OS supports it and the machine is fast enough).	1899	millisecond (if the OS supports it and the machine is fast enough).
1407		1900
1408	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1901	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1409		1902
1410	In this mode the values for C<interval> and C<at> are both being	1903	In this mode the values for C<interval> and C<offset> are both being
1411	ignored. Instead, each time the periodic watcher gets scheduled, the	1904	ignored. Instead, each time the periodic watcher gets scheduled, the
1412	reschedule callback will be called with the watcher as first, and the	1905	reschedule callback will be called with the watcher as first, and the
1413	current time as second argument.	1906	current time as second argument.
1414		1907
1415	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1908	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1416	ever, or make ANY event loop modifications whatsoever>.	1909	or make ANY other event loop modifications whatsoever, unless explicitly
		1910	allowed by documentation here>.
1417		1911
1418	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1912	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1419	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	1913	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1420	only event loop modification you are allowed to do).	1914	only event loop modification you are allowed to do).
1421		1915
1422	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1916	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1423	*w, ev_tstamp now)>, e.g.:	1917	*w, ev_tstamp now)>, e.g.:
1424		1918
		1919	static ev_tstamp
1425	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1920	my_rescheduler (ev_periodic *w, ev_tstamp now)
1426	{	1921	{
1427	return now + 60.;	1922	return now + 60.;
1428	}	1923	}
1429		1924
1430	It must return the next time to trigger, based on the passed time value	1925	It must return the next time to trigger, based on the passed time value
…		…
1450	a different time than the last time it was called (e.g. in a crond like	1945	a different time than the last time it was called (e.g. in a crond like
1451	program when the crontabs have changed).	1946	program when the crontabs have changed).
1452		1947
1453	=item ev_tstamp ev_periodic_at (ev_periodic *)	1948	=item ev_tstamp ev_periodic_at (ev_periodic *)
1454		1949
1455	When active, returns the absolute time that the watcher is supposed to	1950	When active, returns the absolute time that the watcher is supposed
1456	trigger next.	1951	to trigger next. This is not the same as the C<offset> argument to
		1952	C<ev_periodic_set>, but indeed works even in interval and manual
		1953	rescheduling modes.
1457		1954
1458	=item ev_tstamp offset [read-write]	1955	=item ev_tstamp offset [read-write]
1459		1956
1460	When repeating, this contains the offset value, otherwise this is the	1957	When repeating, this contains the offset value, otherwise this is the
1461	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1958	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		1959	although libev might modify this value for better numerical stability).
1462		1960
1463	Can be modified any time, but changes only take effect when the periodic	1961	Can be modified any time, but changes only take effect when the periodic
1464	timer fires or C<ev_periodic_again> is being called.	1962	timer fires or C<ev_periodic_again> is being called.
1465		1963
1466	=item ev_tstamp interval [read-write]	1964	=item ev_tstamp interval [read-write]
1467		1965
1468	The current interval value. Can be modified any time, but changes only	1966	The current interval value. Can be modified any time, but changes only
1469	take effect when the periodic timer fires or C<ev_periodic_again> is being	1967	take effect when the periodic timer fires or C<ev_periodic_again> is being
1470	called.	1968	called.
1471		1969
1472	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1970	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1473		1971
1474	The current reschedule callback, or C<0>, if this functionality is	1972	The current reschedule callback, or C<0>, if this functionality is
1475	switched off. Can be changed any time, but changes only take effect when	1973	switched off. Can be changed any time, but changes only take effect when
1476	the periodic timer fires or C<ev_periodic_again> is being called.	1974	the periodic timer fires or C<ev_periodic_again> is being called.
1477		1975
1478	=back	1976	=back
1479		1977
1480	=head3 Examples	1978	=head3 Examples
1481		1979
1482	Example: Call a callback every hour, or, more precisely, whenever the	1980	Example: Call a callback every hour, or, more precisely, whenever the
1483	system clock is divisible by 3600. The callback invocation times have	1981	system time is divisible by 3600. The callback invocation times have
1484	potentially a lot of jitter, but good long-term stability.	1982	potentially a lot of jitter, but good long-term stability.
1485		1983
1486	static void	1984	static void
1487	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1985	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1488	{	1986	{
1489	... its now a full hour (UTC, or TAI or whatever your clock follows)	1987	... its now a full hour (UTC, or TAI or whatever your clock follows)
1490	}	1988	}
1491		1989
1492	struct ev_periodic hourly_tick;	1990	ev_periodic hourly_tick;
1493	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1991	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1494	ev_periodic_start (loop, &hourly_tick);	1992	ev_periodic_start (loop, &hourly_tick);
1495		1993
1496	Example: The same as above, but use a reschedule callback to do it:	1994	Example: The same as above, but use a reschedule callback to do it:
1497		1995
1498	#include <math.h>	1996	#include <math.h>
1499		1997
1500	static ev_tstamp	1998	static ev_tstamp
1501	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1999	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1502	{	2000	{
1503	return fmod (now, 3600.) + 3600.;	2001	return now + (3600. - fmod (now, 3600.));
1504	}	2002	}
1505		2003
1506	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2004	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1507		2005
1508	Example: Call a callback every hour, starting now:	2006	Example: Call a callback every hour, starting now:
1509		2007
1510	struct ev_periodic hourly_tick;	2008	ev_periodic hourly_tick;
1511	ev_periodic_init (&hourly_tick, clock_cb,	2009	ev_periodic_init (&hourly_tick, clock_cb,
1512	fmod (ev_now (loop), 3600.), 3600., 0);	2010	fmod (ev_now (loop), 3600.), 3600., 0);
1513	ev_periodic_start (loop, &hourly_tick);	2011	ev_periodic_start (loop, &hourly_tick);
1514		2012
1515		2013
…		…
1518	Signal watchers will trigger an event when the process receives a specific	2016	Signal watchers will trigger an event when the process receives a specific
1519	signal one or more times. Even though signals are very asynchronous, libev	2017	signal one or more times. Even though signals are very asynchronous, libev
1520	will try it's best to deliver signals synchronously, i.e. as part of the	2018	will try it's best to deliver signals synchronously, i.e. as part of the
1521	normal event processing, like any other event.	2019	normal event processing, like any other event.
1522		2020
		2021	If you want signals asynchronously, just use C<sigaction> as you would
		2022	do without libev and forget about sharing the signal. You can even use
		2023	C<ev_async> from a signal handler to synchronously wake up an event loop.
		2024
1523	You can configure as many watchers as you like per signal. Only when the	2025	You can configure as many watchers as you like per signal. Only when the
1524	first watcher gets started will libev actually register a signal watcher	2026	first watcher gets started will libev actually register a signal handler
1525	with the kernel (thus it coexists with your own signal handlers as long	2027	with the kernel (thus it coexists with your own signal handlers as long as
1526	as you don't register any with libev). Similarly, when the last signal	2028	you don't register any with libev for the same signal). Similarly, when
1527	watcher for a signal is stopped libev will reset the signal handler to	2029	the last signal watcher for a signal is stopped, libev will reset the
1528	SIG_DFL (regardless of what it was set to before).	2030	signal handler to SIG_DFL (regardless of what it was set to before).
1529		2031
1530	If possible and supported, libev will install its handlers with	2032	If possible and supported, libev will install its handlers with
1531	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2033	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1532	interrupted. If you have a problem with system calls getting interrupted by	2034	interrupted. If you have a problem with system calls getting interrupted by
1533	signals you can block all signals in an C<ev_check> watcher and unblock	2035	signals you can block all signals in an C<ev_check> watcher and unblock
…		…
1550		2052
1551	=back	2053	=back
1552		2054
1553	=head3 Examples	2055	=head3 Examples
1554		2056
1555	Example: Try to exit cleanly on SIGINT and SIGTERM.	2057	Example: Try to exit cleanly on SIGINT.
1556		2058
1557	static void	2059	static void
1558	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2060	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1559	{	2061	{
1560	ev_unloop (loop, EVUNLOOP_ALL);	2062	ev_unloop (loop, EVUNLOOP_ALL);
1561	}	2063	}
1562		2064
1563	struct ev_signal signal_watcher;	2065	ev_signal signal_watcher;
1564	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2066	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1565	ev_signal_start (loop, &sigint_cb);	2067	ev_signal_start (loop, &signal_watcher);
1566		2068
1567		2069
1568	=head2 C<ev_child> - watch out for process status changes	2070	=head2 C<ev_child> - watch out for process status changes
1569		2071
1570	Child watchers trigger when your process receives a SIGCHLD in response to	2072	Child watchers trigger when your process receives a SIGCHLD in response to
1571	some child status changes (most typically when a child of yours dies). It	2073	some child status changes (most typically when a child of yours dies or
1572	is permissible to install a child watcher I<after> the child has been	2074	exits). It is permissible to install a child watcher I<after> the child
1573	forked (which implies it might have already exited), as long as the event	2075	has been forked (which implies it might have already exited), as long
1574	loop isn't entered (or is continued from a watcher).	2076	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2077	forking and then immediately registering a watcher for the child is fine,
		2078	but forking and registering a watcher a few event loop iterations later or
		2079	in the next callback invocation is not.
1575		2080
1576	Only the default event loop is capable of handling signals, and therefore	2081	Only the default event loop is capable of handling signals, and therefore
1577	you can only register child watchers in the default event loop.	2082	you can only register child watchers in the default event loop.
		2083
		2084	Due to some design glitches inside libev, child watchers will always be
		2085	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2086	libev)
1578		2087
1579	=head3 Process Interaction	2088	=head3 Process Interaction
1580		2089
1581	Libev grabs C<SIGCHLD> as soon as the default event loop is	2090	Libev grabs C<SIGCHLD> as soon as the default event loop is
1582	initialised. This is necessary to guarantee proper behaviour even if	2091	initialised. This is necessary to guarantee proper behaviour even if
…		…
1640	its completion.	2149	its completion.
1641		2150
1642	ev_child cw;	2151	ev_child cw;
1643		2152
1644	static void	2153	static void
1645	child_cb (EV_P_ struct ev_child *w, int revents)	2154	child_cb (EV_P_ ev_child *w, int revents)
1646	{	2155	{
1647	ev_child_stop (EV_A_ w);	2156	ev_child_stop (EV_A_ w);
1648	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2157	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1649	}	2158	}
1650		2159
…		…
1665		2174
1666		2175
1667	=head2 C<ev_stat> - did the file attributes just change?	2176	=head2 C<ev_stat> - did the file attributes just change?
1668		2177
1669	This watches a file system path for attribute changes. That is, it calls	2178	This watches a file system path for attribute changes. That is, it calls
1670	C<stat> regularly (or when the OS says it changed) and sees if it changed	2179	C<stat> on that path in regular intervals (or when the OS says it changed)
1671	compared to the last time, invoking the callback if it did.	2180	and sees if it changed compared to the last time, invoking the callback if
		2181	it did.
1672		2182
1673	The path does not need to exist: changing from "path exists" to "path does	2183	The path does not need to exist: changing from "path exists" to "path does
1674	not exist" is a status change like any other. The condition "path does	2184	not exist" is a status change like any other. The condition "path does not
1675	not exist" is signified by the C<st_nlink> field being zero (which is	2185	exist" (or more correctly "path cannot be stat'ed") is signified by the
1676	otherwise always forced to be at least one) and all the other fields of	2186	C<st_nlink> field being zero (which is otherwise always forced to be at
1677	the stat buffer having unspecified contents.	2187	least one) and all the other fields of the stat buffer having unspecified
		2188	contents.
1678		2189
1679	The path I<should> be absolute and I<must not> end in a slash. If it is	2190	The path I<must not> end in a slash or contain special components such as
		2191	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1680	relative and your working directory changes, the behaviour is undefined.	2192	your working directory changes, then the behaviour is undefined.
1681		2193
1682	Since there is no standard to do this, the portable implementation simply	2194	Since there is no portable change notification interface available, the
1683	calls C<stat (2)> regularly on the path to see if it changed somehow. You	2195	portable implementation simply calls C<stat(2)> regularly on the path
1684	can specify a recommended polling interval for this case. If you specify	2196	to see if it changed somehow. You can specify a recommended polling
1685	a polling interval of C<0> (highly recommended!) then a I<suitable,	2197	interval for this case. If you specify a polling interval of C<0> (highly
1686	unspecified default> value will be used (which you can expect to be around	2198	recommended!) then a I<suitable, unspecified default> value will be used
1687	five seconds, although this might change dynamically). Libev will also	2199	(which you can expect to be around five seconds, although this might
1688	impose a minimum interval which is currently around C<0.1>, but thats	2200	change dynamically). Libev will also impose a minimum interval which is
1689	usually overkill.	2201	currently around C<0.1>, but that's usually overkill.
1690		2202
1691	This watcher type is not meant for massive numbers of stat watchers,	2203	This watcher type is not meant for massive numbers of stat watchers,
1692	as even with OS-supported change notifications, this can be	2204	as even with OS-supported change notifications, this can be
1693	resource-intensive.	2205	resource-intensive.
1694		2206
1695	At the time of this writing, only the Linux inotify interface is	2207	At the time of this writing, the only OS-specific interface implemented
1696	implemented (implementing kqueue support is left as an exercise for the	2208	is the Linux inotify interface (implementing kqueue support is left as an
1697	reader, note, however, that the author sees no way of implementing ev_stat	2209	exercise for the reader. Note, however, that the author sees no way of
1698	semantics with kqueue). Inotify will be used to give hints only and should	2210	implementing C<ev_stat> semantics with kqueue, except as a hint).
1699	not change the semantics of C<ev_stat> watchers, which means that libev
1700	sometimes needs to fall back to regular polling again even with inotify,
1701	but changes are usually detected immediately, and if the file exists there
1702	will be no polling.
1703		2211
1704	=head3 ABI Issues (Largefile Support)	2212	=head3 ABI Issues (Largefile Support)
1705		2213
1706	Libev by default (unless the user overrides this) uses the default	2214	Libev by default (unless the user overrides this) uses the default
1707	compilation environment, which means that on systems with large file	2215	compilation environment, which means that on systems with large file
1708	support disabled by default, you get the 32 bit version of the stat	2216	support disabled by default, you get the 32 bit version of the stat
1709	structure. When using the library from programs that change the ABI to	2217	structure. When using the library from programs that change the ABI to
1710	use 64 bit file offsets the programs will fail. In that case you have to	2218	use 64 bit file offsets the programs will fail. In that case you have to
1711	compile libev with the same flags to get binary compatibility. This is	2219	compile libev with the same flags to get binary compatibility. This is
1712	obviously the case with any flags that change the ABI, but the problem is	2220	obviously the case with any flags that change the ABI, but the problem is
1713	most noticeably disabled with ev_stat and large file support.	2221	most noticeably displayed with ev_stat and large file support.
1714		2222
1715	The solution for this is to lobby your distribution maker to make large	2223	The solution for this is to lobby your distribution maker to make large
1716	file interfaces available by default (as e.g. FreeBSD does) and not	2224	file interfaces available by default (as e.g. FreeBSD does) and not
1717	optional. Libev cannot simply switch on large file support because it has	2225	optional. Libev cannot simply switch on large file support because it has
1718	to exchange stat structures with application programs compiled using the	2226	to exchange stat structures with application programs compiled using the
1719	default compilation environment.	2227	default compilation environment.
1720		2228
1721	=head3 Inotify	2229	=head3 Inotify and Kqueue
1722		2230
1723	When C<inotify (7)> support has been compiled into libev (generally only	2231	When C<inotify (7)> support has been compiled into libev and present at
1724	available on Linux) and present at runtime, it will be used to speed up	2232	runtime, it will be used to speed up change detection where possible. The
1725	change detection where possible. The inotify descriptor will be created lazily	2233	inotify descriptor will be created lazily when the first C<ev_stat>
1726	when the first C<ev_stat> watcher is being started.	2234	watcher is being started.
1727		2235
1728	Inotify presence does not change the semantics of C<ev_stat> watchers	2236	Inotify presence does not change the semantics of C<ev_stat> watchers
1729	except that changes might be detected earlier, and in some cases, to avoid	2237	except that changes might be detected earlier, and in some cases, to avoid
1730	making regular C<stat> calls. Even in the presence of inotify support	2238	making regular C<stat> calls. Even in the presence of inotify support
1731	there are many cases where libev has to resort to regular C<stat> polling.	2239	there are many cases where libev has to resort to regular C<stat> polling,
		2240	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2241	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2242	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2243	xfs are fully working) libev usually gets away without polling.
1732		2244
1733	(There is no support for kqueue, as apparently it cannot be used to	2245	There is no support for kqueue, as apparently it cannot be used to
1734	implement this functionality, due to the requirement of having a file	2246	implement this functionality, due to the requirement of having a file
1735	descriptor open on the object at all times).	2247	descriptor open on the object at all times, and detecting renames, unlinks
		2248	etc. is difficult.
		2249
		2250	=head3 C<stat ()> is a synchronous operation
		2251
		2252	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2253	the process. The exception are C<ev_stat> watchers - those call C<stat
		2254	()>, which is a synchronous operation.
		2255
		2256	For local paths, this usually doesn't matter: unless the system is very
		2257	busy or the intervals between stat's are large, a stat call will be fast,
		2258	as the path data is usually in memory already (except when starting the
		2259	watcher).
		2260
		2261	For networked file systems, calling C<stat ()> can block an indefinite
		2262	time due to network issues, and even under good conditions, a stat call
		2263	often takes multiple milliseconds.
		2264
		2265	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2266	paths, although this is fully supported by libev.
1736		2267
1737	=head3 The special problem of stat time resolution	2268	=head3 The special problem of stat time resolution
1738		2269
1739	The C<stat ()> system call only supports full-second resolution portably, and	2270	The C<stat ()> system call only supports full-second resolution portably,
1740	even on systems where the resolution is higher, many file systems still	2271	and even on systems where the resolution is higher, most file systems
1741	only support whole seconds.	2272	still only support whole seconds.
1742		2273
1743	That means that, if the time is the only thing that changes, you can	2274	That means that, if the time is the only thing that changes, you can
1744	easily miss updates: on the first update, C<ev_stat> detects a change and	2275	easily miss updates: on the first update, C<ev_stat> detects a change and
1745	calls your callback, which does something. When there is another update	2276	calls your callback, which does something. When there is another update
1746	within the same second, C<ev_stat> will be unable to detect it as the stat	2277	within the same second, C<ev_stat> will be unable to detect unless the
1747	data does not change.	2278	stat data does change in other ways (e.g. file size).
1748		2279
1749	The solution to this is to delay acting on a change for slightly more	2280	The solution to this is to delay acting on a change for slightly more
1750	than a second (or till slightly after the next full second boundary), using	2281	than a second (or till slightly after the next full second boundary), using
1751	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2282	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1752	ev_timer_again (loop, w)>).	2283	ev_timer_again (loop, w)>).
…		…
1772	C<path>. The C<interval> is a hint on how quickly a change is expected to	2303	C<path>. The C<interval> is a hint on how quickly a change is expected to
1773	be detected and should normally be specified as C<0> to let libev choose	2304	be detected and should normally be specified as C<0> to let libev choose
1774	a suitable value. The memory pointed to by C<path> must point to the same	2305	a suitable value. The memory pointed to by C<path> must point to the same
1775	path for as long as the watcher is active.	2306	path for as long as the watcher is active.
1776		2307
1777	The callback will receive C<EV_STAT> when a change was detected, relative	2308	The callback will receive an C<EV_STAT> event when a change was detected,
1778	to the attributes at the time the watcher was started (or the last change	2309	relative to the attributes at the time the watcher was started (or the
1779	was detected).	2310	last change was detected).
1780		2311
1781	=item ev_stat_stat (loop, ev_stat *)	2312	=item ev_stat_stat (loop, ev_stat *)
1782		2313
1783	Updates the stat buffer immediately with new values. If you change the	2314	Updates the stat buffer immediately with new values. If you change the
1784	watched path in your callback, you could call this function to avoid	2315	watched path in your callback, you could call this function to avoid
…		…
1867		2398
1868		2399
1869	=head2 C<ev_idle> - when you've got nothing better to do...	2400	=head2 C<ev_idle> - when you've got nothing better to do...
1870		2401
1871	Idle watchers trigger events when no other events of the same or higher	2402	Idle watchers trigger events when no other events of the same or higher
1872	priority are pending (prepare, check and other idle watchers do not	2403	priority are pending (prepare, check and other idle watchers do not count
1873	count).	2404	as receiving "events").
1874		2405
1875	That is, as long as your process is busy handling sockets or timeouts	2406	That is, as long as your process is busy handling sockets or timeouts
1876	(or even signals, imagine) of the same or higher priority it will not be	2407	(or even signals, imagine) of the same or higher priority it will not be
1877	triggered. But when your process is idle (or only lower-priority watchers	2408	triggered. But when your process is idle (or only lower-priority watchers
1878	are pending), the idle watchers are being called once per event loop	2409	are pending), the idle watchers are being called once per event loop
…		…
1889		2420
1890	=head3 Watcher-Specific Functions and Data Members	2421	=head3 Watcher-Specific Functions and Data Members
1891		2422
1892	=over 4	2423	=over 4
1893		2424
1894	=item ev_idle_init (ev_signal *, callback)	2425	=item ev_idle_init (ev_idle *, callback)
1895		2426
1896	Initialises and configures the idle watcher - it has no parameters of any	2427	Initialises and configures the idle watcher - it has no parameters of any
1897	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2428	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1898	believe me.	2429	believe me.
1899		2430
…		…
1903		2434
1904	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2435	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1905	callback, free it. Also, use no error checking, as usual.	2436	callback, free it. Also, use no error checking, as usual.
1906		2437
1907	static void	2438	static void
1908	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2439	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1909	{	2440	{
1910	free (w);	2441	free (w);
1911	// now do something you wanted to do when the program has	2442	// now do something you wanted to do when the program has
1912	// no longer anything immediate to do.	2443	// no longer anything immediate to do.
1913	}	2444	}
1914		2445
1915	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2446	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1916	ev_idle_init (idle_watcher, idle_cb);	2447	ev_idle_init (idle_watcher, idle_cb);
1917	ev_idle_start (loop, idle_cb);	2448	ev_idle_start (loop, idle_watcher);
1918		2449
1919		2450
1920	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2451	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1921		2452
1922	Prepare and check watchers are usually (but not always) used in tandem:	2453	Prepare and check watchers are usually (but not always) used in pairs:
1923	prepare watchers get invoked before the process blocks and check watchers	2454	prepare watchers get invoked before the process blocks and check watchers
1924	afterwards.	2455	afterwards.
1925		2456
1926	You I<must not> call C<ev_loop> or similar functions that enter	2457	You I<must not> call C<ev_loop> or similar functions that enter
1927	the current event loop from either C<ev_prepare> or C<ev_check>	2458	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1930	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2461	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1931	C<ev_check> so if you have one watcher of each kind they will always be	2462	C<ev_check> so if you have one watcher of each kind they will always be
1932	called in pairs bracketing the blocking call.	2463	called in pairs bracketing the blocking call.
1933		2464
1934	Their main purpose is to integrate other event mechanisms into libev and	2465	Their main purpose is to integrate other event mechanisms into libev and
1935	their use is somewhat advanced. This could be used, for example, to track	2466	their use is somewhat advanced. They could be used, for example, to track
1936	variable changes, implement your own watchers, integrate net-snmp or a	2467	variable changes, implement your own watchers, integrate net-snmp or a
1937	coroutine library and lots more. They are also occasionally useful if	2468	coroutine library and lots more. They are also occasionally useful if
1938	you cache some data and want to flush it before blocking (for example,	2469	you cache some data and want to flush it before blocking (for example,
1939	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2470	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1940	watcher).	2471	watcher).
1941		2472
1942	This is done by examining in each prepare call which file descriptors need	2473	This is done by examining in each prepare call which file descriptors
1943	to be watched by the other library, registering C<ev_io> watchers for	2474	need to be watched by the other library, registering C<ev_io> watchers
1944	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2475	for them and starting an C<ev_timer> watcher for any timeouts (many
1945	provide just this functionality). Then, in the check watcher you check for	2476	libraries provide exactly this functionality). Then, in the check watcher,
1946	any events that occurred (by checking the pending status of all watchers	2477	you check for any events that occurred (by checking the pending status
1947	and stopping them) and call back into the library. The I/O and timer	2478	of all watchers and stopping them) and call back into the library. The
1948	callbacks will never actually be called (but must be valid nevertheless,	2479	I/O and timer callbacks will never actually be called (but must be valid
1949	because you never know, you know?).	2480	nevertheless, because you never know, you know?).
1950		2481
1951	As another example, the Perl Coro module uses these hooks to integrate	2482	As another example, the Perl Coro module uses these hooks to integrate
1952	coroutines into libev programs, by yielding to other active coroutines	2483	coroutines into libev programs, by yielding to other active coroutines
1953	during each prepare and only letting the process block if no coroutines	2484	during each prepare and only letting the process block if no coroutines
1954	are ready to run (it's actually more complicated: it only runs coroutines	2485	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1957	loop from blocking if lower-priority coroutines are active, thus mapping	2488	loop from blocking if lower-priority coroutines are active, thus mapping
1958	low-priority coroutines to idle/background tasks).	2489	low-priority coroutines to idle/background tasks).
1959		2490
1960	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2491	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1961	priority, to ensure that they are being run before any other watchers	2492	priority, to ensure that they are being run before any other watchers
		2493	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2494
1962	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2495	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1963	too) should not activate ("feed") events into libev. While libev fully	2496	activate ("feed") events into libev. While libev fully supports this, they
1964	supports this, they might get executed before other C<ev_check> watchers	2497	might get executed before other C<ev_check> watchers did their job. As
1965	did their job. As C<ev_check> watchers are often used to embed other	2498	C<ev_check> watchers are often used to embed other (non-libev) event
1966	(non-libev) event loops those other event loops might be in an unusable	2499	loops those other event loops might be in an unusable state until their
1967	state until their C<ev_check> watcher ran (always remind yourself to	2500	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1968	coexist peacefully with others).	2501	others).
1969		2502
1970	=head3 Watcher-Specific Functions and Data Members	2503	=head3 Watcher-Specific Functions and Data Members
1971		2504
1972	=over 4	2505	=over 4
1973		2506
…		…
1975		2508
1976	=item ev_check_init (ev_check *, callback)	2509	=item ev_check_init (ev_check *, callback)
1977		2510
1978	Initialises and configures the prepare or check watcher - they have no	2511	Initialises and configures the prepare or check watcher - they have no
1979	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2512	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1980	macros, but using them is utterly, utterly and completely pointless.	2513	macros, but using them is utterly, utterly, utterly and completely
		2514	pointless.
1981		2515
1982	=back	2516	=back
1983		2517
1984	=head3 Examples	2518	=head3 Examples
1985		2519
…		…
1998		2532
1999	static ev_io iow [nfd];	2533	static ev_io iow [nfd];
2000	static ev_timer tw;	2534	static ev_timer tw;
2001		2535
2002	static void	2536	static void
2003	io_cb (ev_loop *loop, ev_io *w, int revents)	2537	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2004	{	2538	{
2005	}	2539	}
2006		2540
2007	// create io watchers for each fd and a timer before blocking	2541	// create io watchers for each fd and a timer before blocking
2008	static void	2542	static void
2009	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2543	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2010	{	2544	{
2011	int timeout = 3600000;	2545	int timeout = 3600000;
2012	struct pollfd fds [nfd];	2546	struct pollfd fds [nfd];
2013	// actual code will need to loop here and realloc etc.	2547	// actual code will need to loop here and realloc etc.
2014	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2548	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2015		2549
2016	/* the callback is illegal, but won't be called as we stop during check */	2550	/* the callback is illegal, but won't be called as we stop during check */
2017	ev_timer_init (&tw, 0, timeout * 1e-3);	2551	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2018	ev_timer_start (loop, &tw);	2552	ev_timer_start (loop, &tw);
2019		2553
2020	// create one ev_io per pollfd	2554	// create one ev_io per pollfd
2021	for (int i = 0; i < nfd; ++i)	2555	for (int i = 0; i < nfd; ++i)
2022	{	2556	{
…		…
2029	}	2563	}
2030	}	2564	}
2031		2565
2032	// stop all watchers after blocking	2566	// stop all watchers after blocking
2033	static void	2567	static void
2034	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2568	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2035	{	2569	{
2036	ev_timer_stop (loop, &tw);	2570	ev_timer_stop (loop, &tw);
2037		2571
2038	for (int i = 0; i < nfd; ++i)	2572	for (int i = 0; i < nfd; ++i)
2039	{	2573	{
…		…
2078	}	2612	}
2079		2613
2080	// do not ever call adns_afterpoll	2614	// do not ever call adns_afterpoll
2081		2615
2082	Method 4: Do not use a prepare or check watcher because the module you	2616	Method 4: Do not use a prepare or check watcher because the module you
2083	want to embed is too inflexible to support it. Instead, you can override	2617	want to embed is not flexible enough to support it. Instead, you can
2084	their poll function. The drawback with this solution is that the main	2618	override their poll function. The drawback with this solution is that the
2085	loop is now no longer controllable by EV. The C<Glib::EV> module does	2619	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2086	this.	2620	this approach, effectively embedding EV as a client into the horrible
		2621	libglib event loop.
2087		2622
2088	static gint	2623	static gint
2089	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2624	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2090	{	2625	{
2091	int got_events = 0;	2626	int got_events = 0;
…		…
2122	prioritise I/O.	2657	prioritise I/O.
2123		2658
2124	As an example for a bug workaround, the kqueue backend might only support	2659	As an example for a bug workaround, the kqueue backend might only support
2125	sockets on some platform, so it is unusable as generic backend, but you	2660	sockets on some platform, so it is unusable as generic backend, but you
2126	still want to make use of it because you have many sockets and it scales	2661	still want to make use of it because you have many sockets and it scales
2127	so nicely. In this case, you would create a kqueue-based loop and embed it	2662	so nicely. In this case, you would create a kqueue-based loop and embed
2128	into your default loop (which might use e.g. poll). Overall operation will	2663	it into your default loop (which might use e.g. poll). Overall operation
2129	be a bit slower because first libev has to poll and then call kevent, but	2664	will be a bit slower because first libev has to call C<poll> and then
2130	at least you can use both at what they are best.	2665	C<kevent>, but at least you can use both mechanisms for what they are
		2666	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2131		2667
2132	As for prioritising I/O: rarely you have the case where some fds have	2668	As for prioritising I/O: under rare circumstances you have the case where
2133	to be watched and handled very quickly (with low latency), and even	2669	some fds have to be watched and handled very quickly (with low latency),
2134	priorities and idle watchers might have too much overhead. In this case	2670	and even priorities and idle watchers might have too much overhead. In
2135	you would put all the high priority stuff in one loop and all the rest in	2671	this case you would put all the high priority stuff in one loop and all
2136	a second one, and embed the second one in the first.	2672	the rest in a second one, and embed the second one in the first.
2137		2673
2138	As long as the watcher is active, the callback will be invoked every time	2674	As long as the watcher is active, the callback will be invoked every
2139	there might be events pending in the embedded loop. The callback must then	2675	time there might be events pending in the embedded loop. The callback
2140	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2676	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2141	their callbacks (you could also start an idle watcher to give the embedded	2677	sweep and invoke their callbacks (the callback doesn't need to invoke the
2142	loop strictly lower priority for example). You can also set the callback	2678	C<ev_embed_sweep> function directly, it could also start an idle watcher
2143	to C<0>, in which case the embed watcher will automatically execute the	2679	to give the embedded loop strictly lower priority for example).
2144	embedded loop sweep.
2145		2680
2146	As long as the watcher is started it will automatically handle events. The	2681	You can also set the callback to C<0>, in which case the embed watcher
2147	callback will be invoked whenever some events have been handled. You can	2682	will automatically execute the embedded loop sweep whenever necessary.
2148	set the callback to C<0> to avoid having to specify one if you are not
2149	interested in that.
2150		2683
2151	Also, there have not currently been made special provisions for forking:	2684	Fork detection will be handled transparently while the C<ev_embed> watcher
2152	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2685	is active, i.e., the embedded loop will automatically be forked when the
2153	but you will also have to stop and restart any C<ev_embed> watchers	2686	embedding loop forks. In other cases, the user is responsible for calling
2154	yourself.	2687	C<ev_loop_fork> on the embedded loop.
2155		2688
2156	Unfortunately, not all backends are embeddable, only the ones returned by	2689	Unfortunately, not all backends are embeddable: only the ones returned by
2157	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2690	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2158	portable one.	2691	portable one.
2159		2692
2160	So when you want to use this feature you will always have to be prepared	2693	So when you want to use this feature you will always have to be prepared
2161	that you cannot get an embeddable loop. The recommended way to get around	2694	that you cannot get an embeddable loop. The recommended way to get around
2162	this is to have a separate variables for your embeddable loop, try to	2695	this is to have a separate variables for your embeddable loop, try to
2163	create it, and if that fails, use the normal loop for everything.	2696	create it, and if that fails, use the normal loop for everything.
		2697
		2698	=head3 C<ev_embed> and fork
		2699
		2700	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2701	automatically be applied to the embedded loop as well, so no special
		2702	fork handling is required in that case. When the watcher is not running,
		2703	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2704	as applicable.
2164		2705
2165	=head3 Watcher-Specific Functions and Data Members	2706	=head3 Watcher-Specific Functions and Data Members
2166		2707
2167	=over 4	2708	=over 4
2168		2709
…		…
2196	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2737	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2197	used).	2738	used).
2198		2739
2199	struct ev_loop *loop_hi = ev_default_init (0);	2740	struct ev_loop *loop_hi = ev_default_init (0);
2200	struct ev_loop *loop_lo = 0;	2741	struct ev_loop *loop_lo = 0;
2201	struct ev_embed embed;	2742	ev_embed embed;
2202		2743
2203	// see if there is a chance of getting one that works	2744	// see if there is a chance of getting one that works
2204	// (remember that a flags value of 0 means autodetection)	2745	// (remember that a flags value of 0 means autodetection)
2205	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2746	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2206	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2747	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2220	kqueue implementation). Store the kqueue/socket-only event loop in	2761	kqueue implementation). Store the kqueue/socket-only event loop in
2221	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2762	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2222		2763
2223	struct ev_loop *loop = ev_default_init (0);	2764	struct ev_loop *loop = ev_default_init (0);
2224	struct ev_loop *loop_socket = 0;	2765	struct ev_loop *loop_socket = 0;
2225	struct ev_embed embed;	2766	ev_embed embed;
2226		2767
2227	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2768	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2228	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2769	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2229	{	2770	{
2230	ev_embed_init (&embed, 0, loop_socket);	2771	ev_embed_init (&embed, 0, loop_socket);
…		…
2245	event loop blocks next and before C<ev_check> watchers are being called,	2786	event loop blocks next and before C<ev_check> watchers are being called,
2246	and only in the child after the fork. If whoever good citizen calling	2787	and only in the child after the fork. If whoever good citizen calling
2247	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2788	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2248	handlers will be invoked, too, of course.	2789	handlers will be invoked, too, of course.
2249		2790
		2791	=head3 The special problem of life after fork - how is it possible?
		2792
		2793	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2794	up/change the process environment, followed by a call to C<exec()>. This
		2795	sequence should be handled by libev without any problems.
		2796
		2797	This changes when the application actually wants to do event handling
		2798	in the child, or both parent in child, in effect "continuing" after the
		2799	fork.
		2800
		2801	The default mode of operation (for libev, with application help to detect
		2802	forks) is to duplicate all the state in the child, as would be expected
		2803	when I<either> the parent I<or> the child process continues.
		2804
		2805	When both processes want to continue using libev, then this is usually the
		2806	wrong result. In that case, usually one process (typically the parent) is
		2807	supposed to continue with all watchers in place as before, while the other
		2808	process typically wants to start fresh, i.e. without any active watchers.
		2809
		2810	The cleanest and most efficient way to achieve that with libev is to
		2811	simply create a new event loop, which of course will be "empty", and
		2812	use that for new watchers. This has the advantage of not touching more
		2813	memory than necessary, and thus avoiding the copy-on-write, and the
		2814	disadvantage of having to use multiple event loops (which do not support
		2815	signal watchers).
		2816
		2817	When this is not possible, or you want to use the default loop for
		2818	other reasons, then in the process that wants to start "fresh", call
		2819	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2820	the default loop will "orphan" (not stop) all registered watchers, so you
		2821	have to be careful not to execute code that modifies those watchers. Note
		2822	also that in that case, you have to re-register any signal watchers.
		2823
2250	=head3 Watcher-Specific Functions and Data Members	2824	=head3 Watcher-Specific Functions and Data Members
2251		2825
2252	=over 4	2826	=over 4
2253		2827
2254	=item ev_fork_init (ev_signal *, callback)	2828	=item ev_fork_init (ev_signal *, callback)
…		…
2286	is that the author does not know of a simple (or any) algorithm for a	2860	is that the author does not know of a simple (or any) algorithm for a
2287	multiple-writer-single-reader queue that works in all cases and doesn't	2861	multiple-writer-single-reader queue that works in all cases and doesn't
2288	need elaborate support such as pthreads.	2862	need elaborate support such as pthreads.
2289		2863
2290	That means that if you want to queue data, you have to provide your own	2864	That means that if you want to queue data, you have to provide your own
2291	queue. But at least I can tell you would implement locking around your	2865	queue. But at least I can tell you how to implement locking around your
2292	queue:	2866	queue:
2293		2867
2294	=over 4	2868	=over 4
2295		2869
2296	=item queueing from a signal handler context	2870	=item queueing from a signal handler context
2297		2871
2298	To implement race-free queueing, you simply add to the queue in the signal	2872	To implement race-free queueing, you simply add to the queue in the signal
2299	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2873	handler but you block the signal handler in the watcher callback. Here is
2300	some fictitious SIGUSR1 handler:	2874	an example that does that for some fictitious SIGUSR1 handler:
2301		2875
2302	static ev_async mysig;	2876	static ev_async mysig;
2303		2877
2304	static void	2878	static void
2305	sigusr1_handler (void)	2879	sigusr1_handler (void)
…		…
2371	=over 4	2945	=over 4
2372		2946
2373	=item ev_async_init (ev_async *, callback)	2947	=item ev_async_init (ev_async *, callback)
2374		2948
2375	Initialises and configures the async watcher - it has no parameters of any	2949	Initialises and configures the async watcher - it has no parameters of any
2376	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2950	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2377	believe me.	2951	trust me.
2378		2952
2379	=item ev_async_send (loop, ev_async *)	2953	=item ev_async_send (loop, ev_async *)
2380		2954
2381	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2955	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2382	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2956	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2383	C<ev_feed_event>, this call is safe to do in other threads, signal or	2957	C<ev_feed_event>, this call is safe to do from other threads, signal or
2384	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	2958	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2385	section below on what exactly this means).	2959	section below on what exactly this means).
2386		2960
		2961	Note that, as with other watchers in libev, multiple events might get
		2962	compressed into a single callback invocation (another way to look at this
		2963	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		2964	reset when the event loop detects that).
		2965
2387	This call incurs the overhead of a system call only once per loop iteration,	2966	This call incurs the overhead of a system call only once per event loop
2388	so while the overhead might be noticeable, it doesn't apply to repeated	2967	iteration, so while the overhead might be noticeable, it doesn't apply to
2389	calls to C<ev_async_send>.	2968	repeated calls to C<ev_async_send> for the same event loop.
2390		2969
2391	=item bool = ev_async_pending (ev_async *)	2970	=item bool = ev_async_pending (ev_async *)
2392		2971
2393	Returns a non-zero value when C<ev_async_send> has been called on the	2972	Returns a non-zero value when C<ev_async_send> has been called on the
2394	watcher but the event has not yet been processed (or even noted) by the	2973	watcher but the event has not yet been processed (or even noted) by the
…		…
2397	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	2976	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2398	the loop iterates next and checks for the watcher to have become active,	2977	the loop iterates next and checks for the watcher to have become active,
2399	it will reset the flag again. C<ev_async_pending> can be used to very	2978	it will reset the flag again. C<ev_async_pending> can be used to very
2400	quickly check whether invoking the loop might be a good idea.	2979	quickly check whether invoking the loop might be a good idea.
2401		2980
2402	Not that this does I<not> check whether the watcher itself is pending, only	2981	Not that this does I<not> check whether the watcher itself is pending,
2403	whether it has been requested to make this watcher pending.	2982	only whether it has been requested to make this watcher pending: there
		2983	is a time window between the event loop checking and resetting the async
		2984	notification, and the callback being invoked.
2404		2985
2405	=back	2986	=back
2406		2987
2407		2988
2408	=head1 OTHER FUNCTIONS	2989	=head1 OTHER FUNCTIONS
…		…
2412	=over 4	2993	=over 4
2413		2994
2414	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2995	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2415		2996
2416	This function combines a simple timer and an I/O watcher, calls your	2997	This function combines a simple timer and an I/O watcher, calls your
2417	callback on whichever event happens first and automatically stop both	2998	callback on whichever event happens first and automatically stops both
2418	watchers. This is useful if you want to wait for a single event on an fd	2999	watchers. This is useful if you want to wait for a single event on an fd
2419	or timeout without having to allocate/configure/start/stop/free one or	3000	or timeout without having to allocate/configure/start/stop/free one or
2420	more watchers yourself.	3001	more watchers yourself.
2421		3002
2422	If C<fd> is less than 0, then no I/O watcher will be started and events	3003	If C<fd> is less than 0, then no I/O watcher will be started and the
2423	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	3004	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2424	C<events> set will be created and started.	3005	the given C<fd> and C<events> set will be created and started.
2425		3006
2426	If C<timeout> is less than 0, then no timeout watcher will be	3007	If C<timeout> is less than 0, then no timeout watcher will be
2427	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3008	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2428	repeat = 0) will be started. While C<0> is a valid timeout, it is of	3009	repeat = 0) will be started. C<0> is a valid timeout.
2429	dubious value.
2430		3010
2431	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3011	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2432	passed an C<revents> set like normal event callbacks (a combination of	3012	passed an C<revents> set like normal event callbacks (a combination of
2433	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3013	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2434	value passed to C<ev_once>:	3014	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3015	a timeout and an io event at the same time - you probably should give io
		3016	events precedence.
		3017
		3018	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2435		3019
2436	static void stdin_ready (int revents, void *arg)	3020	static void stdin_ready (int revents, void *arg)
2437	{	3021	{
		3022	if (revents & EV_READ)
		3023	/* stdin might have data for us, joy! */;
2438	if (revents & EV_TIMEOUT)	3024	else if (revents & EV_TIMEOUT)
2439	/* doh, nothing entered */;	3025	/* doh, nothing entered */;
2440	else if (revents & EV_READ)
2441	/* stdin might have data for us, joy! */;
2442	}	3026	}
2443		3027
2444	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3028	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2445		3029
2446	=item ev_feed_event (ev_loop *, watcher *, int revents)	3030	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2447		3031
2448	Feeds the given event set into the event loop, as if the specified event	3032	Feeds the given event set into the event loop, as if the specified event
2449	had happened for the specified watcher (which must be a pointer to an	3033	had happened for the specified watcher (which must be a pointer to an
2450	initialised but not necessarily started event watcher).	3034	initialised but not necessarily started event watcher).
2451		3035
2452	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3036	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2453		3037
2454	Feed an event on the given fd, as if a file descriptor backend detected	3038	Feed an event on the given fd, as if a file descriptor backend detected
2455	the given events it.	3039	the given events it.
2456		3040
2457	=item ev_feed_signal_event (ev_loop *loop, int signum)	3041	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2458		3042
2459	Feed an event as if the given signal occurred (C<loop> must be the default	3043	Feed an event as if the given signal occurred (C<loop> must be the default
2460	loop!).	3044	loop!).
2461		3045
2462	=back	3046	=back
…		…
2584		3168
2585	myclass obj;	3169	myclass obj;
2586	ev::io iow;	3170	ev::io iow;
2587	iow.set <myclass, &myclass::io_cb> (&obj);	3171	iow.set <myclass, &myclass::io_cb> (&obj);
2588		3172
		3173	=item w->set (object *)
		3174
		3175	This is an B<experimental> feature that might go away in a future version.
		3176
		3177	This is a variation of a method callback - leaving out the method to call
		3178	will default the method to C<operator ()>, which makes it possible to use
		3179	functor objects without having to manually specify the C<operator ()> all
		3180	the time. Incidentally, you can then also leave out the template argument
		3181	list.
		3182
		3183	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3184	int revents)>.
		3185
		3186	See the method-C<set> above for more details.
		3187
		3188	Example: use a functor object as callback.
		3189
		3190	struct myfunctor
		3191	{
		3192	void operator() (ev::io &w, int revents)
		3193	{
		3194	...
		3195	}
		3196	}
		3197
		3198	myfunctor f;
		3199
		3200	ev::io w;
		3201	w.set (&f);
		3202
2589	=item w->set<function> (void *data = 0)	3203	=item w->set<function> (void *data = 0)
2590		3204
2591	Also sets a callback, but uses a static method or plain function as	3205	Also sets a callback, but uses a static method or plain function as
2592	callback. The optional C<data> argument will be stored in the watcher's	3206	callback. The optional C<data> argument will be stored in the watcher's
2593	C<data> member and is free for you to use.	3207	C<data> member and is free for you to use.
2594		3208
2595	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3209	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2596		3210
2597	See the method-C<set> above for more details.	3211	See the method-C<set> above for more details.
2598		3212
2599	Example:	3213	Example: Use a plain function as callback.
2600		3214
2601	static void io_cb (ev::io &w, int revents) { }	3215	static void io_cb (ev::io &w, int revents) { }
2602	iow.set <io_cb> ();	3216	iow.set <io_cb> ();
2603		3217
2604	=item w->set (struct ev_loop *)	3218	=item w->set (struct ev_loop *)
…		…
2642	Example: Define a class with an IO and idle watcher, start one of them in	3256	Example: Define a class with an IO and idle watcher, start one of them in
2643	the constructor.	3257	the constructor.
2644		3258
2645	class myclass	3259	class myclass
2646	{	3260	{
2647	ev::io io; void io_cb (ev::io &w, int revents);	3261	ev::io io ; void io_cb (ev::io &w, int revents);
2648	ev:idle idle void idle_cb (ev::idle &w, int revents);	3262	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2649		3263
2650	myclass (int fd)	3264	myclass (int fd)
2651	{	3265	{
2652	io .set <myclass, &myclass::io_cb > (this);	3266	io .set <myclass, &myclass::io_cb > (this);
2653	idle.set <myclass, &myclass::idle_cb> (this);	3267	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2669	=item Perl	3283	=item Perl
2670		3284
2671	The EV module implements the full libev API and is actually used to test	3285	The EV module implements the full libev API and is actually used to test
2672	libev. EV is developed together with libev. Apart from the EV core module,	3286	libev. EV is developed together with libev. Apart from the EV core module,
2673	there are additional modules that implement libev-compatible interfaces	3287	there are additional modules that implement libev-compatible interfaces
2674	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3288	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2675	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3289	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3290	and C<EV::Glib>).
2676		3291
2677	It can be found and installed via CPAN, its homepage is at	3292	It can be found and installed via CPAN, its homepage is at
2678	L<http://software.schmorp.de/pkg/EV>.	3293	L<http://software.schmorp.de/pkg/EV>.
2679		3294
2680	=item Python	3295	=item Python
2681		3296
2682	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3297	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2683	seems to be quite complete and well-documented. Note, however, that the	3298	seems to be quite complete and well-documented.
2684	patch they require for libev is outright dangerous as it breaks the ABI
2685	for everybody else, and therefore, should never be applied in an installed
2686	libev (if python requires an incompatible ABI then it needs to embed
2687	libev).
2688		3299
2689	=item Ruby	3300	=item Ruby
2690		3301
2691	Tony Arcieri has written a ruby extension that offers access to a subset	3302	Tony Arcieri has written a ruby extension that offers access to a subset
2692	of the libev API and adds file handle abstractions, asynchronous DNS and	3303	of the libev API and adds file handle abstractions, asynchronous DNS and
2693	more on top of it. It can be found via gem servers. Its homepage is at	3304	more on top of it. It can be found via gem servers. Its homepage is at
2694	L<http://rev.rubyforge.org/>.	3305	L<http://rev.rubyforge.org/>.
2695		3306
		3307	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3308	makes rev work even on mingw.
		3309
		3310	=item Haskell
		3311
		3312	A haskell binding to libev is available at
		3313	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3314
2696	=item D	3315	=item D
2697		3316
2698	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3317	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2699	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3318	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3319
		3320	=item Ocaml
		3321
		3322	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3323	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2700		3324
2701	=back	3325	=back
2702		3326
2703		3327
2704	=head1 MACRO MAGIC	3328	=head1 MACRO MAGIC
…		…
2805		3429
2806	#define EV_STANDALONE 1	3430	#define EV_STANDALONE 1
2807	#include "ev.h"	3431	#include "ev.h"
2808		3432
2809	Both header files and implementation files can be compiled with a C++	3433	Both header files and implementation files can be compiled with a C++
2810	compiler (at least, thats a stated goal, and breakage will be treated	3434	compiler (at least, that's a stated goal, and breakage will be treated
2811	as a bug).	3435	as a bug).
2812		3436
2813	You need the following files in your source tree, or in a directory	3437	You need the following files in your source tree, or in a directory
2814	in your include path (e.g. in libev/ when using -Ilibev):	3438	in your include path (e.g. in libev/ when using -Ilibev):
2815		3439
…		…
2859		3483
2860	=head2 PREPROCESSOR SYMBOLS/MACROS	3484	=head2 PREPROCESSOR SYMBOLS/MACROS
2861		3485
2862	Libev can be configured via a variety of preprocessor symbols you have to	3486	Libev can be configured via a variety of preprocessor symbols you have to
2863	define before including any of its files. The default in the absence of	3487	define before including any of its files. The default in the absence of
2864	autoconf is noted for every option.	3488	autoconf is documented for every option.
2865		3489
2866	=over 4	3490	=over 4
2867		3491
2868	=item EV_STANDALONE	3492	=item EV_STANDALONE
2869		3493
…		…
2871	keeps libev from including F<config.h>, and it also defines dummy	3495	keeps libev from including F<config.h>, and it also defines dummy
2872	implementations for some libevent functions (such as logging, which is not	3496	implementations for some libevent functions (such as logging, which is not
2873	supported). It will also not define any of the structs usually found in	3497	supported). It will also not define any of the structs usually found in
2874	F<event.h> that are not directly supported by the libev core alone.	3498	F<event.h> that are not directly supported by the libev core alone.
2875		3499
		3500	In stanbdalone mode, libev will still try to automatically deduce the
		3501	configuration, but has to be more conservative.
		3502
2876	=item EV_USE_MONOTONIC	3503	=item EV_USE_MONOTONIC
2877		3504
2878	If defined to be C<1>, libev will try to detect the availability of the	3505	If defined to be C<1>, libev will try to detect the availability of the
2879	monotonic clock option at both compile time and runtime. Otherwise no use	3506	monotonic clock option at both compile time and runtime. Otherwise no
2880	of the monotonic clock option will be attempted. If you enable this, you	3507	use of the monotonic clock option will be attempted. If you enable this,
2881	usually have to link against librt or something similar. Enabling it when	3508	you usually have to link against librt or something similar. Enabling it
2882	the functionality isn't available is safe, though, although you have	3509	when the functionality isn't available is safe, though, although you have
2883	to make sure you link against any libraries where the C<clock_gettime>	3510	to make sure you link against any libraries where the C<clock_gettime>
2884	function is hiding in (often F<-lrt>).	3511	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2885		3512
2886	=item EV_USE_REALTIME	3513	=item EV_USE_REALTIME
2887		3514
2888	If defined to be C<1>, libev will try to detect the availability of the	3515	If defined to be C<1>, libev will try to detect the availability of the
2889	real-time clock option at compile time (and assume its availability at	3516	real-time clock option at compile time (and assume its availability
2890	runtime if successful). Otherwise no use of the real-time clock option will	3517	at runtime if successful). Otherwise no use of the real-time clock
2891	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3518	option will be attempted. This effectively replaces C<gettimeofday>
2892	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3519	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2893	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3520	correctness. See the note about libraries in the description of
		3521	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3522	C<EV_USE_CLOCK_SYSCALL>.
		3523
		3524	=item EV_USE_CLOCK_SYSCALL
		3525
		3526	If defined to be C<1>, libev will try to use a direct syscall instead
		3527	of calling the system-provided C<clock_gettime> function. This option
		3528	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3529	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3530	programs needlessly. Using a direct syscall is slightly slower (in
		3531	theory), because no optimised vdso implementation can be used, but avoids
		3532	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3533	higher, as it simplifies linking (no need for C<-lrt>).
2894		3534
2895	=item EV_USE_NANOSLEEP	3535	=item EV_USE_NANOSLEEP
2896		3536
2897	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3537	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2898	and will use it for delays. Otherwise it will use C<select ()>.	3538	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2914		3554
2915	=item EV_SELECT_USE_FD_SET	3555	=item EV_SELECT_USE_FD_SET
2916		3556
2917	If defined to C<1>, then the select backend will use the system C<fd_set>	3557	If defined to C<1>, then the select backend will use the system C<fd_set>
2918	structure. This is useful if libev doesn't compile due to a missing	3558	structure. This is useful if libev doesn't compile due to a missing
2919	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3559	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2920	exotic systems. This usually limits the range of file descriptors to some	3560	on exotic systems. This usually limits the range of file descriptors to
2921	low limit such as 1024 or might have other limitations (winsocket only	3561	some low limit such as 1024 or might have other limitations (winsocket
2922	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3562	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2923	influence the size of the C<fd_set> used.	3563	configures the maximum size of the C<fd_set>.
2924		3564
2925	=item EV_SELECT_IS_WINSOCKET	3565	=item EV_SELECT_IS_WINSOCKET
2926		3566
2927	When defined to C<1>, the select backend will assume that	3567	When defined to C<1>, the select backend will assume that
2928	select/socket/connect etc. don't understand file descriptors but	3568	select/socket/connect etc. don't understand file descriptors but
…		…
3039	When doing priority-based operations, libev usually has to linearly search	3679	When doing priority-based operations, libev usually has to linearly search
3040	all the priorities, so having many of them (hundreds) uses a lot of space	3680	all the priorities, so having many of them (hundreds) uses a lot of space
3041	and time, so using the defaults of five priorities (-2 .. +2) is usually	3681	and time, so using the defaults of five priorities (-2 .. +2) is usually
3042	fine.	3682	fine.
3043		3683
3044	If your embedding application does not need any priorities, defining these both to	3684	If your embedding application does not need any priorities, defining these
3045	C<0> will save some memory and CPU.	3685	both to C<0> will save some memory and CPU.
3046		3686
3047	=item EV_PERIODIC_ENABLE	3687	=item EV_PERIODIC_ENABLE
3048		3688
3049	If undefined or defined to be C<1>, then periodic timers are supported. If	3689	If undefined or defined to be C<1>, then periodic timers are supported. If
3050	defined to be C<0>, then they are not. Disabling them saves a few kB of	3690	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3057	code.	3697	code.
3058		3698
3059	=item EV_EMBED_ENABLE	3699	=item EV_EMBED_ENABLE
3060		3700
3061	If undefined or defined to be C<1>, then embed watchers are supported. If	3701	If undefined or defined to be C<1>, then embed watchers are supported. If
3062	defined to be C<0>, then they are not.	3702	defined to be C<0>, then they are not. Embed watchers rely on most other
		3703	watcher types, which therefore must not be disabled.
3063		3704
3064	=item EV_STAT_ENABLE	3705	=item EV_STAT_ENABLE
3065		3706
3066	If undefined or defined to be C<1>, then stat watchers are supported. If	3707	If undefined or defined to be C<1>, then stat watchers are supported. If
3067	defined to be C<0>, then they are not.	3708	defined to be C<0>, then they are not.
…		…
3077	defined to be C<0>, then they are not.	3718	defined to be C<0>, then they are not.
3078		3719
3079	=item EV_MINIMAL	3720	=item EV_MINIMAL
3080		3721
3081	If you need to shave off some kilobytes of code at the expense of some	3722	If you need to shave off some kilobytes of code at the expense of some
3082	speed, define this symbol to C<1>. Currently this is used to override some	3723	speed (but with the full API), define this symbol to C<1>. Currently this
3083	inlining decisions, saves roughly 30% code size on amd64. It also selects a	3724	is used to override some inlining decisions, saves roughly 30% code size
3084	much smaller 2-heap for timer management over the default 4-heap.	3725	on amd64. It also selects a much smaller 2-heap for timer management over
		3726	the default 4-heap.
		3727
		3728	You can save even more by disabling watcher types you do not need
		3729	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>
		3730	(C<-DNDEBUG>) will usually reduce code size a lot.
		3731
		3732	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to
		3733	provide a bare-bones event library. See C<ev.h> for details on what parts
		3734	of the API are still available, and do not complain if this subset changes
		3735	over time.
3085		3736
3086	=item EV_PID_HASHSIZE	3737	=item EV_PID_HASHSIZE
3087		3738
3088	C<ev_child> watchers use a small hash table to distribute workload by	3739	C<ev_child> watchers use a small hash table to distribute workload by
3089	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3740	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
3099	two).	3750	two).
3100		3751
3101	=item EV_USE_4HEAP	3752	=item EV_USE_4HEAP
3102		3753
3103	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3754	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3104	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3755	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3105	to C<1>. The 4-heap uses more complicated (longer) code but has	3756	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3106	noticeably faster performance with many (thousands) of watchers.	3757	faster performance with many (thousands) of watchers.
3107		3758
3108	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3759	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3109	(disabled).	3760	(disabled).
3110		3761
3111	=item EV_HEAP_CACHE_AT	3762	=item EV_HEAP_CACHE_AT
3112		3763
3113	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3764	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3114	timer and periodics heap, libev can cache the timestamp (I<at>) within	3765	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3115	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3766	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3116	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3767	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3117	but avoids random read accesses on heap changes. This improves performance	3768	but avoids random read accesses on heap changes. This improves performance
3118	noticeably with with many (hundreds) of watchers.	3769	noticeably with many (hundreds) of watchers.
3119		3770
3120	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3771	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3121	(disabled).	3772	(disabled).
3122		3773
3123	=item EV_VERIFY	3774	=item EV_VERIFY
…		…
3129	called once per loop, which can slow down libev. If set to C<3>, then the	3780	called once per loop, which can slow down libev. If set to C<3>, then the
3130	verification code will be called very frequently, which will slow down	3781	verification code will be called very frequently, which will slow down
3131	libev considerably.	3782	libev considerably.
3132		3783
3133	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3784	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3134	C<0.>	3785	C<0>.
3135		3786
3136	=item EV_COMMON	3787	=item EV_COMMON
3137		3788
3138	By default, all watchers have a C<void *data> member. By redefining	3789	By default, all watchers have a C<void *data> member. By redefining
3139	this macro to a something else you can include more and other types of	3790	this macro to a something else you can include more and other types of
…		…
3156	and the way callbacks are invoked and set. Must expand to a struct member	3807	and the way callbacks are invoked and set. Must expand to a struct member
3157	definition and a statement, respectively. See the F<ev.h> header file for	3808	definition and a statement, respectively. See the F<ev.h> header file for
3158	their default definitions. One possible use for overriding these is to	3809	their default definitions. One possible use for overriding these is to
3159	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3810	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3160	method calls instead of plain function calls in C++.	3811	method calls instead of plain function calls in C++.
		3812
		3813	=back
3161		3814
3162	=head2 EXPORTED API SYMBOLS	3815	=head2 EXPORTED API SYMBOLS
3163		3816
3164	If you need to re-export the API (e.g. via a DLL) and you need a list of	3817	If you need to re-export the API (e.g. via a DLL) and you need a list of
3165	exported symbols, you can use the provided F<Symbol.*> files which list	3818	exported symbols, you can use the provided F<Symbol.*> files which list
…		…
3212	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3865	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3213		3866
3214	#include "ev_cpp.h"	3867	#include "ev_cpp.h"
3215	#include "ev.c"	3868	#include "ev.c"
3216		3869
		3870	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3217		3871
3218	=head1 THREADS AND COROUTINES	3872	=head2 THREADS AND COROUTINES
3219		3873
3220	=head2 THREADS	3874	=head3 THREADS
3221		3875
3222	Libev itself is completely thread-safe, but it uses no locking. This	3876	All libev functions are reentrant and thread-safe unless explicitly
		3877	documented otherwise, but libev implements no locking itself. This means
3223	means that you can use as many loops as you want in parallel, as long as	3878	that you can use as many loops as you want in parallel, as long as there
3224	only one thread ever calls into one libev function with the same loop	3879	are no concurrent calls into any libev function with the same loop
3225	parameter.	3880	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3881	of course): libev guarantees that different event loops share no data
		3882	structures that need any locking.
3226		3883
3227	Or put differently: calls with different loop parameters can be done in	3884	Or to put it differently: calls with different loop parameters can be done
3228	parallel from multiple threads, calls with the same loop parameter must be	3885	concurrently from multiple threads, calls with the same loop parameter
3229	done serially (but can be done from different threads, as long as only one	3886	must be done serially (but can be done from different threads, as long as
3230	thread ever is inside a call at any point in time, e.g. by using a mutex	3887	only one thread ever is inside a call at any point in time, e.g. by using
3231	per loop).	3888	a mutex per loop).
		3889
		3890	Specifically to support threads (and signal handlers), libev implements
		3891	so-called C<ev_async> watchers, which allow some limited form of
		3892	concurrency on the same event loop, namely waking it up "from the
		3893	outside".
3232		3894
3233	If you want to know which design (one loop, locking, or multiple loops	3895	If you want to know which design (one loop, locking, or multiple loops
3234	without or something else still) is best for your problem, then I cannot	3896	without or something else still) is best for your problem, then I cannot
3235	help you. I can give some generic advice however:	3897	help you, but here is some generic advice:
3236		3898
3237	=over 4	3899	=over 4
3238		3900
3239	=item * most applications have a main thread: use the default libev loop	3901	=item * most applications have a main thread: use the default libev loop
3240	in that thread, or create a separate thread running only the default loop.	3902	in that thread, or create a separate thread running only the default loop.
…		…
3252		3914
3253	Choosing a model is hard - look around, learn, know that usually you can do	3915	Choosing a model is hard - look around, learn, know that usually you can do
3254	better than you currently do :-)	3916	better than you currently do :-)
3255		3917
3256	=item * often you need to talk to some other thread which blocks in the	3918	=item * often you need to talk to some other thread which blocks in the
		3919	event loop.
		3920
3257	event loop - C<ev_async> watchers can be used to wake them up from other	3921	C<ev_async> watchers can be used to wake them up from other threads safely
3258	threads safely (or from signal contexts...).	3922	(or from signal contexts...).
		3923
		3924	An example use would be to communicate signals or other events that only
		3925	work in the default loop by registering the signal watcher with the
		3926	default loop and triggering an C<ev_async> watcher from the default loop
		3927	watcher callback into the event loop interested in the signal.
3259		3928
3260	=back	3929	=back
3261		3930
		3931	=head4 THREAD LOCKING EXAMPLE
		3932
3262	=head2 COROUTINES	3933	=head3 COROUTINES
3263		3934
3264	Libev is much more accommodating to coroutines ("cooperative threads"):	3935	Libev is very accommodating to coroutines ("cooperative threads"):
3265	libev fully supports nesting calls to it's functions from different	3936	libev fully supports nesting calls to its functions from different
3266	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3937	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3267	different coroutines and switch freely between both coroutines running the	3938	different coroutines, and switch freely between both coroutines running the
3268	loop, as long as you don't confuse yourself). The only exception is that	3939	loop, as long as you don't confuse yourself). The only exception is that
3269	you must not do this from C<ev_periodic> reschedule callbacks.	3940	you must not do this from C<ev_periodic> reschedule callbacks.
3270		3941
3271	Care has been invested into making sure that libev does not keep local	3942	Care has been taken to ensure that libev does not keep local state inside
3272	state inside C<ev_loop>, and other calls do not usually allow coroutine	3943	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3273	switches.	3944	they do not call any callbacks.
3274		3945
		3946	=head2 COMPILER WARNINGS
3275		3947
3276	=head1 COMPLEXITIES	3948	Depending on your compiler and compiler settings, you might get no or a
		3949	lot of warnings when compiling libev code. Some people are apparently
		3950	scared by this.
3277		3951
3278	In this section the complexities of (many of) the algorithms used inside	3952	However, these are unavoidable for many reasons. For one, each compiler
3279	libev will be explained. For complexity discussions about backends see the	3953	has different warnings, and each user has different tastes regarding
3280	documentation for C<ev_default_init>.	3954	warning options. "Warn-free" code therefore cannot be a goal except when
		3955	targeting a specific compiler and compiler-version.
3281		3956
3282	All of the following are about amortised time: If an array needs to be	3957	Another reason is that some compiler warnings require elaborate
3283	extended, libev needs to realloc and move the whole array, but this	3958	workarounds, or other changes to the code that make it less clear and less
3284	happens asymptotically never with higher number of elements, so O(1) might	3959	maintainable.
3285	mean it might do a lengthy realloc operation in rare cases, but on average
3286	it is much faster and asymptotically approaches constant time.
3287		3960
3288	=over 4	3961	And of course, some compiler warnings are just plain stupid, or simply
		3962	wrong (because they don't actually warn about the condition their message
		3963	seems to warn about). For example, certain older gcc versions had some
		3964	warnings that resulted an extreme number of false positives. These have
		3965	been fixed, but some people still insist on making code warn-free with
		3966	such buggy versions.
3289		3967
3290	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3968	While libev is written to generate as few warnings as possible,
		3969	"warn-free" code is not a goal, and it is recommended not to build libev
		3970	with any compiler warnings enabled unless you are prepared to cope with
		3971	them (e.g. by ignoring them). Remember that warnings are just that:
		3972	warnings, not errors, or proof of bugs.
3291		3973
3292	This means that, when you have a watcher that triggers in one hour and
3293	there are 100 watchers that would trigger before that then inserting will
3294	have to skip roughly seven (C<ld 100>) of these watchers.
3295		3974
3296	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3975	=head2 VALGRIND
3297		3976
3298	That means that changing a timer costs less than removing/adding them	3977	Valgrind has a special section here because it is a popular tool that is
3299	as only the relative motion in the event queue has to be paid for.	3978	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3300		3979
3301	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3980	If you think you found a bug (memory leak, uninitialised data access etc.)
		3981	in libev, then check twice: If valgrind reports something like:
3302		3982
3303	These just add the watcher into an array or at the head of a list.	3983	==2274== definitely lost: 0 bytes in 0 blocks.
		3984	==2274== possibly lost: 0 bytes in 0 blocks.
		3985	==2274== still reachable: 256 bytes in 1 blocks.
3304		3986
3305	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3987	Then there is no memory leak, just as memory accounted to global variables
		3988	is not a memleak - the memory is still being referenced, and didn't leak.
3306		3989
3307	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3990	Similarly, under some circumstances, valgrind might report kernel bugs
		3991	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3992	although an acceptable workaround has been found here), or it might be
		3993	confused.
3308		3994
3309	These watchers are stored in lists then need to be walked to find the	3995	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3310	correct watcher to remove. The lists are usually short (you don't usually	3996	make it into some kind of religion.
3311	have many watchers waiting for the same fd or signal).
3312		3997
3313	=item Finding the next timer in each loop iteration: O(1)	3998	If you are unsure about something, feel free to contact the mailing list
		3999	with the full valgrind report and an explanation on why you think this
		4000	is a bug in libev (best check the archives, too :). However, don't be
		4001	annoyed when you get a brisk "this is no bug" answer and take the chance
		4002	of learning how to interpret valgrind properly.
3314		4003
3315	By virtue of using a binary or 4-heap, the next timer is always found at a	4004	If you need, for some reason, empty reports from valgrind for your project
3316	fixed position in the storage array.	4005	I suggest using suppression lists.
3317		4006
3318	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3319		4007
3320	A change means an I/O watcher gets started or stopped, which requires	4008	=head1 PORTABILITY NOTES
3321	libev to recalculate its status (and possibly tell the kernel, depending
3322	on backend and whether C<ev_io_set> was used).
3323		4009
3324	=item Activating one watcher (putting it into the pending state): O(1)
3325
3326	=item Priority handling: O(number_of_priorities)
3327
3328	Priorities are implemented by allocating some space for each
3329	priority. When doing priority-based operations, libev usually has to
3330	linearly search all the priorities, but starting/stopping and activating
3331	watchers becomes O(1) w.r.t. priority handling.
3332
3333	=item Sending an ev_async: O(1)
3334
3335	=item Processing ev_async_send: O(number_of_async_watchers)
3336
3337	=item Processing signals: O(max_signal_number)
3338
3339	Sending involves a system call I<iff> there were no other C<ev_async_send>
3340	calls in the current loop iteration. Checking for async and signal events
3341	involves iterating over all running async watchers or all signal numbers.
3342
3343	=back
3344
3345
3346	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4010	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3347		4011
3348	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4012	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3349	requires, and its I/O model is fundamentally incompatible with the POSIX	4013	requires, and its I/O model is fundamentally incompatible with the POSIX
3350	model. Libev still offers limited functionality on this platform in	4014	model. Libev still offers limited functionality on this platform in
3351	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4015	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3358	way (note also that glib is the slowest event library known to man).	4022	way (note also that glib is the slowest event library known to man).
3359		4023
3360	There is no supported compilation method available on windows except	4024	There is no supported compilation method available on windows except
3361	embedding it into other applications.	4025	embedding it into other applications.
3362		4026
		4027	Sensible signal handling is officially unsupported by Microsoft - libev
		4028	tries its best, but under most conditions, signals will simply not work.
		4029
3363	Not a libev limitation but worth mentioning: windows apparently doesn't	4030	Not a libev limitation but worth mentioning: windows apparently doesn't
3364	accept large writes: instead of resulting in a partial write, windows will	4031	accept large writes: instead of resulting in a partial write, windows will
3365	either accept everything or return C<ENOBUFS> if the buffer is too large,	4032	either accept everything or return C<ENOBUFS> if the buffer is too large,
3366	so make sure you only write small amounts into your sockets (less than a	4033	so make sure you only write small amounts into your sockets (less than a
3367	megabyte seems safe, but thsi apparently depends on the amount of memory	4034	megabyte seems safe, but this apparently depends on the amount of memory
3368	available).	4035	available).
3369		4036
3370	Due to the many, low, and arbitrary limits on the win32 platform and	4037	Due to the many, low, and arbitrary limits on the win32 platform and
3371	the abysmal performance of winsockets, using a large number of sockets	4038	the abysmal performance of winsockets, using a large number of sockets
3372	is not recommended (and not reasonable). If your program needs to use	4039	is not recommended (and not reasonable). If your program needs to use
3373	more than a hundred or so sockets, then likely it needs to use a totally	4040	more than a hundred or so sockets, then likely it needs to use a totally
3374	different implementation for windows, as libev offers the POSIX readiness	4041	different implementation for windows, as libev offers the POSIX readiness
3375	notification model, which cannot be implemented efficiently on windows	4042	notification model, which cannot be implemented efficiently on windows
3376	(Microsoft monopoly games).	4043	(due to Microsoft monopoly games).
3377		4044
3378	A typical way to use libev under windows is to embed it (see the embedding	4045	A typical way to use libev under windows is to embed it (see the embedding
3379	section for details) and use the following F<evwrap.h> header file instead	4046	section for details) and use the following F<evwrap.h> header file instead
3380	of F<ev.h>:	4047	of F<ev.h>:
3381		4048
…		…
3383	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	4050	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3384		4051
3385	#include "ev.h"	4052	#include "ev.h"
3386		4053
3387	And compile the following F<evwrap.c> file into your project (make sure	4054	And compile the following F<evwrap.c> file into your project (make sure
3388	you do I<not> compile the F<ev.c> or any other embedded soruce files!):	4055	you do I<not> compile the F<ev.c> or any other embedded source files!):
3389		4056
3390	#include "evwrap.h"	4057	#include "evwrap.h"
3391	#include "ev.c"	4058	#include "ev.c"
3392		4059
3393	=over 4	4060	=over 4
…		…
3417		4084
3418	Early versions of winsocket's select only supported waiting for a maximum	4085	Early versions of winsocket's select only supported waiting for a maximum
3419	of C<64> handles (probably owning to the fact that all windows kernels	4086	of C<64> handles (probably owning to the fact that all windows kernels
3420	can only wait for C<64> things at the same time internally; Microsoft	4087	can only wait for C<64> things at the same time internally; Microsoft
3421	recommends spawning a chain of threads and wait for 63 handles and the	4088	recommends spawning a chain of threads and wait for 63 handles and the
3422	previous thread in each. Great).	4089	previous thread in each. Sounds great!).
3423		4090
3424	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4091	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3425	to some high number (e.g. C<2048>) before compiling the winsocket select	4092	to some high number (e.g. C<2048>) before compiling the winsocket select
3426	call (which might be in libev or elsewhere, for example, perl does its own	4093	call (which might be in libev or elsewhere, for example, perl and many
3427	select emulation on windows).	4094	other interpreters do their own select emulation on windows).
3428		4095
3429	Another limit is the number of file descriptors in the Microsoft runtime	4096	Another limit is the number of file descriptors in the Microsoft runtime
3430	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4097	libraries, which by default is C<64> (there must be a hidden I<64>
3431	or something like this inside Microsoft). You can increase this by calling	4098	fetish or something like this inside Microsoft). You can increase this
3432	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4099	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3433	arbitrary limit), but is broken in many versions of the Microsoft runtime	4100	(another arbitrary limit), but is broken in many versions of the Microsoft
3434	libraries.
3435
3436	This might get you to about C<512> or C<2048> sockets (depending on	4101	runtime libraries. This might get you to about C<512> or C<2048> sockets
3437	windows version and/or the phase of the moon). To get more, you need to	4102	(depending on windows version and/or the phase of the moon). To get more,
3438	wrap all I/O functions and provide your own fd management, but the cost of	4103	you need to wrap all I/O functions and provide your own fd management, but
3439	calling select (O(n²)) will likely make this unworkable.	4104	the cost of calling select (O(n²)) will likely make this unworkable.
3440		4105
3441	=back	4106	=back
3442		4107
3443
3444	=head1 PORTABILITY REQUIREMENTS	4108	=head2 PORTABILITY REQUIREMENTS
3445		4109
3446	In addition to a working ISO-C implementation, libev relies on a few	4110	In addition to a working ISO-C implementation and of course the
3447	additional extensions:	4111	backend-specific APIs, libev relies on a few additional extensions:
3448		4112
3449	=over 4	4113	=over 4
3450		4114
3451	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	4115	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3452	calling conventions regardless of C<ev_watcher_type *>.	4116	calling conventions regardless of C<ev_watcher_type *>.
…		…
3458	calls them using an C<ev_watcher *> internally.	4122	calls them using an C<ev_watcher *> internally.
3459		4123
3460	=item C<sig_atomic_t volatile> must be thread-atomic as well	4124	=item C<sig_atomic_t volatile> must be thread-atomic as well
3461		4125
3462	The type C<sig_atomic_t volatile> (or whatever is defined as	4126	The type C<sig_atomic_t volatile> (or whatever is defined as
3463	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	4127	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3464	threads. This is not part of the specification for C<sig_atomic_t>, but is	4128	threads. This is not part of the specification for C<sig_atomic_t>, but is
3465	believed to be sufficiently portable.	4129	believed to be sufficiently portable.
3466		4130
3467	=item C<sigprocmask> must work in a threaded environment	4131	=item C<sigprocmask> must work in a threaded environment
3468		4132
…		…
3477	except the initial one, and run the default loop in the initial thread as	4141	except the initial one, and run the default loop in the initial thread as
3478	well.	4142	well.
3479		4143
3480	=item C<long> must be large enough for common memory allocation sizes	4144	=item C<long> must be large enough for common memory allocation sizes
3481		4145
3482	To improve portability and simplify using libev, libev uses C<long>	4146	To improve portability and simplify its API, libev uses C<long> internally
3483	internally instead of C<size_t> when allocating its data structures. On	4147	instead of C<size_t> when allocating its data structures. On non-POSIX
3484	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4148	systems (Microsoft...) this might be unexpectedly low, but is still at
3485	is still at least 31 bits everywhere, which is enough for hundreds of	4149	least 31 bits everywhere, which is enough for hundreds of millions of
3486	millions of watchers.	4150	watchers.
3487		4151
3488	=item C<double> must hold a time value in seconds with enough accuracy	4152	=item C<double> must hold a time value in seconds with enough accuracy
3489		4153
3490	The type C<double> is used to represent timestamps. It is required to	4154	The type C<double> is used to represent timestamps. It is required to
3491	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4155	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
3492	enough for at least into the year 4000. This requirement is fulfilled by	4156	enough for at least into the year 4000. This requirement is fulfilled by
3493	implementations implementing IEEE 754 (basically all existing ones).	4157	implementations implementing IEEE 754, which is basically all existing
		4158	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4159	2200.
3494		4160
3495	=back	4161	=back
3496		4162
3497	If you know of other additional requirements drop me a note.	4163	If you know of other additional requirements drop me a note.
3498		4164
3499		4165
3500	=head1 COMPILER WARNINGS	4166	=head1 ALGORITHMIC COMPLEXITIES
3501		4167
3502	Depending on your compiler and compiler settings, you might get no or a	4168	In this section the complexities of (many of) the algorithms used inside
3503	lot of warnings when compiling libev code. Some people are apparently	4169	libev will be documented. For complexity discussions about backends see
3504	scared by this.	4170	the documentation for C<ev_default_init>.
3505		4171
3506	However, these are unavoidable for many reasons. For one, each compiler	4172	All of the following are about amortised time: If an array needs to be
3507	has different warnings, and each user has different tastes regarding	4173	extended, libev needs to realloc and move the whole array, but this
3508	warning options. "Warn-free" code therefore cannot be a goal except when	4174	happens asymptotically rarer with higher number of elements, so O(1) might
3509	targeting a specific compiler and compiler-version.	4175	mean that libev does a lengthy realloc operation in rare cases, but on
		4176	average it is much faster and asymptotically approaches constant time.
3510		4177
3511	Another reason is that some compiler warnings require elaborate	4178	=over 4
3512	workarounds, or other changes to the code that make it less clear and less
3513	maintainable.
3514		4179
3515	And of course, some compiler warnings are just plain stupid, or simply	4180	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3516	wrong (because they don't actually warn about the condition their message
3517	seems to warn about).
3518		4181
3519	While libev is written to generate as few warnings as possible,	4182	This means that, when you have a watcher that triggers in one hour and
3520	"warn-free" code is not a goal, and it is recommended not to build libev	4183	there are 100 watchers that would trigger before that, then inserting will
3521	with any compiler warnings enabled unless you are prepared to cope with	4184	have to skip roughly seven (C<ld 100>) of these watchers.
3522	them (e.g. by ignoring them). Remember that warnings are just that:
3523	warnings, not errors, or proof of bugs.
3524		4185
		4186	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3525		4187
3526	=head1 VALGRIND	4188	That means that changing a timer costs less than removing/adding them,
		4189	as only the relative motion in the event queue has to be paid for.
3527		4190
3528	Valgrind has a special section here because it is a popular tool that is	4191	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3529	highly useful, but valgrind reports are very hard to interpret.
3530		4192
3531	If you think you found a bug (memory leak, uninitialised data access etc.)	4193	These just add the watcher into an array or at the head of a list.
3532	in libev, then check twice: If valgrind reports something like:
3533		4194
3534	==2274== definitely lost: 0 bytes in 0 blocks.	4195	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3535	==2274== possibly lost: 0 bytes in 0 blocks.
3536	==2274== still reachable: 256 bytes in 1 blocks.
3537		4196
3538	Then there is no memory leak. Similarly, under some circumstances,	4197	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3539	valgrind might report kernel bugs as if it were a bug in libev, or it
3540	might be confused (it is a very good tool, but only a tool).
3541		4198
3542	If you are unsure about something, feel free to contact the mailing list	4199	These watchers are stored in lists, so they need to be walked to find the
3543	with the full valgrind report and an explanation on why you think this is	4200	correct watcher to remove. The lists are usually short (you don't usually
3544	a bug in libev. However, don't be annoyed when you get a brisk "this is	4201	have many watchers waiting for the same fd or signal: one is typical, two
3545	no bug" answer and take the chance of learning how to interpret valgrind	4202	is rare).
3546	properly.
3547		4203
3548	If you need, for some reason, empty reports from valgrind for your project	4204	=item Finding the next timer in each loop iteration: O(1)
3549	I suggest using suppression lists.
3550		4205
		4206	By virtue of using a binary or 4-heap, the next timer is always found at a
		4207	fixed position in the storage array.
		4208
		4209	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4210
		4211	A change means an I/O watcher gets started or stopped, which requires
		4212	libev to recalculate its status (and possibly tell the kernel, depending
		4213	on backend and whether C<ev_io_set> was used).
		4214
		4215	=item Activating one watcher (putting it into the pending state): O(1)
		4216
		4217	=item Priority handling: O(number_of_priorities)
		4218
		4219	Priorities are implemented by allocating some space for each
		4220	priority. When doing priority-based operations, libev usually has to
		4221	linearly search all the priorities, but starting/stopping and activating
		4222	watchers becomes O(1) with respect to priority handling.
		4223
		4224	=item Sending an ev_async: O(1)
		4225
		4226	=item Processing ev_async_send: O(number_of_async_watchers)
		4227
		4228	=item Processing signals: O(max_signal_number)
		4229
		4230	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4231	calls in the current loop iteration. Checking for async and signal events
		4232	involves iterating over all running async watchers or all signal numbers.
		4233
		4234	=back
		4235
		4236
		4237	=head1 GLOSSARY
		4238
		4239	=over 4
		4240
		4241	=item active
		4242
		4243	A watcher is active as long as it has been started (has been attached to
		4244	an event loop) but not yet stopped (disassociated from the event loop).
		4245
		4246	=item application
		4247
		4248	In this document, an application is whatever is using libev.
		4249
		4250	=item callback
		4251
		4252	The address of a function that is called when some event has been
		4253	detected. Callbacks are being passed the event loop, the watcher that
		4254	received the event, and the actual event bitset.
		4255
		4256	=item callback invocation
		4257
		4258	The act of calling the callback associated with a watcher.
		4259
		4260	=item event
		4261
		4262	A change of state of some external event, such as data now being available
		4263	for reading on a file descriptor, time having passed or simply not having
		4264	any other events happening anymore.
		4265
		4266	In libev, events are represented as single bits (such as C<EV_READ> or
		4267	C<EV_TIMEOUT>).
		4268
		4269	=item event library
		4270
		4271	A software package implementing an event model and loop.
		4272
		4273	=item event loop
		4274
		4275	An entity that handles and processes external events and converts them
		4276	into callback invocations.
		4277
		4278	=item event model
		4279
		4280	The model used to describe how an event loop handles and processes
		4281	watchers and events.
		4282
		4283	=item pending
		4284
		4285	A watcher is pending as soon as the corresponding event has been detected,
		4286	and stops being pending as soon as the watcher will be invoked or its
		4287	pending status is explicitly cleared by the application.
		4288
		4289	A watcher can be pending, but not active. Stopping a watcher also clears
		4290	its pending status.
		4291
		4292	=item real time
		4293
		4294	The physical time that is observed. It is apparently strictly monotonic :)
		4295
		4296	=item wall-clock time
		4297
		4298	The time and date as shown on clocks. Unlike real time, it can actually
		4299	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4300	clock.
		4301
		4302	=item watcher
		4303
		4304	A data structure that describes interest in certain events. Watchers need
		4305	to be started (attached to an event loop) before they can receive events.
		4306
		4307	=item watcher invocation
		4308
		4309	The act of calling the callback associated with a watcher.
		4310
		4311	=back
3551		4312
3552	=head1 AUTHOR	4313	=head1 AUTHOR
3553		4314
3554	Marc Lehmann <libev@schmorp.de>.	4315	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3555		4316

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