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…		…
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
		14	#include <stdio.h> // for puts
		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
18		20
19	// all watcher callbacks have a similar signature	21	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	22	// this callback is called when data is readable on stdin
21	static void	23	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	25	{
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
…		…
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	42	}
…		…
60		62
61	// unloop was called, so exit	63	// unloop was called, so exit
62	return 0;	64	return 0;
63	}	65	}
64		66
65	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
66		70
67	The newest version of this document is also available as an html-formatted	71	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	72	web page you might find easier to navigate when reading it for the first
69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.	73	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		74
		75	While this document tries to be as complete as possible in documenting
		76	libev, its usage and the rationale behind its design, it is not a tutorial
		77	on event-based programming, nor will it introduce event-based programming
		78	with libev.
		79
		80	Familarity with event based programming techniques in general is assumed
		81	throughout this document.
		82
		83	=head1 ABOUT LIBEV
70		84
71	Libev is an event loop: you register interest in certain events (such as a	85	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	86	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	87	these event sources and provide your program with events.
74		88
…		…
103	Libev is very configurable. In this manual the default (and most common)	117	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	118	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	119	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	120	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	121	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	122	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	123	this argument.
110		124
111	=head2 TIME REPRESENTATION	125	=head2 TIME REPRESENTATION
112		126
113	Libev represents time as a single floating point number, representing the	127	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	128	the (fractional) number of seconds since the (POSIX) epoch (somewhere
115	the beginning of 1970, details are complicated, don't ask). This type is	129	near the beginning of 1970, details are complicated, don't ask). This
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	130	type is called C<ev_tstamp>, which is what you should use too. It usually
117	to the C<double> type in C, and when you need to do any calculations on	131	aliases to the C<double> type in C. When you need to do any calculations
118	it, you should treat it as some floating point value. Unlike the name	132	on it, you should treat it as some floating point value. Unlike the name
119	component C<stamp> might indicate, it is also used for time differences	133	component C<stamp> might indicate, it is also used for time differences
120	throughout libev.	134	throughout libev.
121		135
122	=head1 ERROR HANDLING	136	=head1 ERROR HANDLING
123		137
…		…
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	228	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
215	recommended ones.	229	recommended ones.
216		230
217	See the description of C<ev_embed> watchers for more info.	231	See the description of C<ev_embed> watchers for more info.
218		232
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	233	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
220		234
221	Sets the allocation function to use (the prototype is similar - the	235	Sets the allocation function to use (the prototype is similar - the
222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	236	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
223	used to allocate and free memory (no surprises here). If it returns zero	237	used to allocate and free memory (no surprises here). If it returns zero
224	when memory needs to be allocated (C<size != 0>), the library might abort	238	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	264	}
251		265
252	...	266	...
253	ev_set_allocator (persistent_realloc);	267	ev_set_allocator (persistent_realloc);
254		268
255	=item ev_set_syserr_cb (void (*cb)(const char *msg));	269	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
256		270
257	Set the callback function to call on a retryable system call error (such	271	Set the callback function to call on a retryable system call error (such
258	as failed select, poll, epoll_wait). The message is a printable string	272	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	273	indicating the system call or subsystem causing the problem. If this
260	callback is set, then libev will expect it to remedy the situation, no	274	callback is set, then libev will expect it to remedy the situation, no
…		…
276		290
277	=back	291	=back
278		292
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	293	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
280		294
281	An event loop is described by a C<struct ev_loop *>. The library knows two	295	An event loop is described by a C<struct ev_loop *> (the C<struct>
282	types of such loops, the I<default> loop, which supports signals and child	296	is I<not> optional in this case, as there is also an C<ev_loop>
283	events, and dynamically created loops which do not.	297	I<function>).
		298
		299	The library knows two types of such loops, the I<default> loop, which
		300	supports signals and child events, and dynamically created loops which do
		301	not.
284		302
285	=over 4	303	=over 4
286		304
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	305	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		306
…		…
294	If you don't know what event loop to use, use the one returned from this	312	If you don't know what event loop to use, use the one returned from this
295	function.	313	function.
296		314
297	Note that this function is I<not> thread-safe, so if you want to use it	315	Note that this function is I<not> thread-safe, so if you want to use it
298	from multiple threads, you have to lock (note also that this is unlikely,	316	from multiple threads, you have to lock (note also that this is unlikely,
299	as loops cannot bes hared easily between threads anyway).	317	as loops cannot be shared easily between threads anyway).
300		318
301	The default loop is the only loop that can handle C<ev_signal> and	319	The default loop is the only loop that can handle C<ev_signal> and
302	C<ev_child> watchers, and to do this, it always registers a handler	320	C<ev_child> watchers, and to do this, it always registers a handler
303	for C<SIGCHLD>. If this is a problem for your application you can either	321	for C<SIGCHLD>. If this is a problem for your application you can either
304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	322	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
…		…
359	writing a server, you should C<accept ()> in a loop to accept as many	377	writing a server, you should C<accept ()> in a loop to accept as many
360	connections as possible during one iteration. You might also want to have	378	connections as possible during one iteration. You might also want to have
361	a look at C<ev_set_io_collect_interval ()> to increase the amount of	379	a look at C<ev_set_io_collect_interval ()> to increase the amount of
362	readiness notifications you get per iteration.	380	readiness notifications you get per iteration.
363		381
		382	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		383	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		384	C<exceptfds> set on that platform).
		385
364	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	386	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
365		387
366	And this is your standard poll(2) backend. It's more complicated	388	And this is your standard poll(2) backend. It's more complicated
367	than select, but handles sparse fds better and has no artificial	389	than select, but handles sparse fds better and has no artificial
368	limit on the number of fds you can use (except it will slow down	390	limit on the number of fds you can use (except it will slow down
369	considerably with a lot of inactive fds). It scales similarly to select,	391	considerably with a lot of inactive fds). It scales similarly to select,
370	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for	392	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
371	performance tips.	393	performance tips.
372		394
		395	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		396	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		397
373	=item C<EVBACKEND_EPOLL> (value 4, Linux)	398	=item C<EVBACKEND_EPOLL> (value 4, Linux)
374		399
375	For few fds, this backend is a bit little slower than poll and select,	400	For few fds, this backend is a bit little slower than poll and select,
376	but it scales phenomenally better. While poll and select usually scale	401	but it scales phenomenally better. While poll and select usually scale
377	like O(total_fds) where n is the total number of fds (or the highest fd),	402	like O(total_fds) where n is the total number of fds (or the highest fd),
378	epoll scales either O(1) or O(active_fds). The epoll design has a number	403	epoll scales either O(1) or O(active_fds).
379	of shortcomings, such as silently dropping events in some hard-to-detect	404
380	cases and requiring a system call per fd change, no fork support and bad	405	The epoll mechanism deserves honorable mention as the most misdesigned
381	support for dup.	406	of the more advanced event mechanisms: mere annoyances include silently
		407	dropping file descriptors, requiring a system call per change per file
		408	descriptor (and unnecessary guessing of parameters), problems with dup and
		409	so on. The biggest issue is fork races, however - if a program forks then
		410	I<both> parent and child process have to recreate the epoll set, which can
		411	take considerable time (one syscall per file descriptor) and is of course
		412	hard to detect.
		413
		414	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		415	of course I<doesn't>, and epoll just loves to report events for totally
		416	I<different> file descriptors (even already closed ones, so one cannot
		417	even remove them from the set) than registered in the set (especially
		418	on SMP systems). Libev tries to counter these spurious notifications by
		419	employing an additional generation counter and comparing that against the
		420	events to filter out spurious ones, recreating the set when required.
382		421
383	While stopping, setting and starting an I/O watcher in the same iteration	422	While stopping, setting and starting an I/O watcher in the same iteration
384	will result in some caching, there is still a system call per such incident	423	will result in some caching, there is still a system call per such
385	(because the fd could point to a different file description now), so its	424	incident (because the same I<file descriptor> could point to a different
386	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	425	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
387	very well if you register events for both fds.	426	file descriptors might not work very well if you register events for both
388		427	file descriptors.
389	Please note that epoll sometimes generates spurious notifications, so you
390	need to use non-blocking I/O or other means to avoid blocking when no data
391	(or space) is available.
392		428
393	Best performance from this backend is achieved by not unregistering all	429	Best performance from this backend is achieved by not unregistering all
394	watchers for a file descriptor until it has been closed, if possible, i.e.	430	watchers for a file descriptor until it has been closed, if possible,
395	keep at least one watcher active per fd at all times.	431	i.e. keep at least one watcher active per fd at all times. Stopping and
		432	starting a watcher (without re-setting it) also usually doesn't cause
		433	extra overhead. A fork can both result in spurious notifications as well
		434	as in libev having to destroy and recreate the epoll object, which can
		435	take considerable time and thus should be avoided.
		436
		437	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		438	faster than epoll for maybe up to a hundred file descriptors, depending on
		439	the usage. So sad.
396		440
397	While nominally embeddable in other event loops, this feature is broken in	441	While nominally embeddable in other event loops, this feature is broken in
398	all kernel versions tested so far.	442	all kernel versions tested so far.
		443
		444	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		445	C<EVBACKEND_POLL>.
399		446
400	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	447	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
401		448
402	Kqueue deserves special mention, as at the time of this writing, it	449	Kqueue deserves special mention, as at the time of this writing, it
403	was broken on all BSDs except NetBSD (usually it doesn't work reliably	450	was broken on all BSDs except NetBSD (usually it doesn't work reliably
404	with anything but sockets and pipes, except on Darwin, where of course	451	with anything but sockets and pipes, except on Darwin, where of course
405	it's completely useless). For this reason it's not being "auto-detected"	452	it's completely useless). Unlike epoll, however, whose brokenness
		453	is by design, these kqueue bugs can (and eventually will) be fixed
		454	without API changes to existing programs. For this reason it's not being
406	unless you explicitly specify it explicitly in the flags (i.e. using	455	"auto-detected" unless you explicitly specify it in the flags (i.e. using
407	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	456	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
408	system like NetBSD.	457	system like NetBSD.
409		458
410	You still can embed kqueue into a normal poll or select backend and use it	459	You still can embed kqueue into a normal poll or select backend and use it
411	only for sockets (after having made sure that sockets work with kqueue on	460	only for sockets (after having made sure that sockets work with kqueue on
…		…
413		462
414	It scales in the same way as the epoll backend, but the interface to the	463	It scales in the same way as the epoll backend, but the interface to the
415	kernel is more efficient (which says nothing about its actual speed, of	464	kernel is more efficient (which says nothing about its actual speed, of
416	course). While stopping, setting and starting an I/O watcher does never	465	course). While stopping, setting and starting an I/O watcher does never
417	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	466	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
418	two event changes per incident, support for C<fork ()> is very bad and it	467	two event changes per incident. Support for C<fork ()> is very bad (but
419	drops fds silently in similarly hard-to-detect cases.	468	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		469	cases
420		470
421	This backend usually performs well under most conditions.	471	This backend usually performs well under most conditions.
422		472
423	While nominally embeddable in other event loops, this doesn't work	473	While nominally embeddable in other event loops, this doesn't work
424	everywhere, so you might need to test for this. And since it is broken	474	everywhere, so you might need to test for this. And since it is broken
425	almost everywhere, you should only use it when you have a lot of sockets	475	almost everywhere, you should only use it when you have a lot of sockets
426	(for which it usually works), by embedding it into another event loop	476	(for which it usually works), by embedding it into another event loop
427	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	477	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
428	sockets.	478	also broken on OS X)) and, did I mention it, using it only for sockets.
		479
		480	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		481	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		482	C<NOTE_EOF>.
429		483
430	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	484	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
431		485
432	This is not implemented yet (and might never be, unless you send me an	486	This is not implemented yet (and might never be, unless you send me an
433	implementation). According to reports, C</dev/poll> only supports sockets	487	implementation). According to reports, C</dev/poll> only supports sockets
…		…
446	While this backend scales well, it requires one system call per active	500	While this backend scales well, it requires one system call per active
447	file descriptor per loop iteration. For small and medium numbers of file	501	file descriptor per loop iteration. For small and medium numbers of file
448	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	502	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
449	might perform better.	503	might perform better.
450		504
451	On the positive side, ignoring the spurious readiness notifications, this	505	On the positive side, with the exception of the spurious readiness
452	backend actually performed to specification in all tests and is fully	506	notifications, this backend actually performed fully to specification
453	embeddable, which is a rare feat among the OS-specific backends.	507	in all tests and is fully embeddable, which is a rare feat among the
		508	OS-specific backends (I vastly prefer correctness over speed hacks).
		509
		510	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		511	C<EVBACKEND_POLL>.
454		512
455	=item C<EVBACKEND_ALL>	513	=item C<EVBACKEND_ALL>
456		514
457	Try all backends (even potentially broken ones that wouldn't be tried	515	Try all backends (even potentially broken ones that wouldn't be tried
458	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	516	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
464		522
465	If one or more of these are or'ed into the flags value, then only these	523	If one or more of these are or'ed into the flags value, then only these
466	backends will be tried (in the reverse order as listed here). If none are	524	backends will be tried (in the reverse order as listed here). If none are
467	specified, all backends in C<ev_recommended_backends ()> will be tried.	525	specified, all backends in C<ev_recommended_backends ()> will be tried.
468		526
469	The most typical usage is like this:	527	Example: This is the most typical usage.
470		528
471	if (!ev_default_loop (0))	529	if (!ev_default_loop (0))
472	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	530	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
473		531
474	Restrict libev to the select and poll backends, and do not allow	532	Example: Restrict libev to the select and poll backends, and do not allow
475	environment settings to be taken into account:	533	environment settings to be taken into account:
476		534
477	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	535	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
478		536
479	Use whatever libev has to offer, but make sure that kqueue is used if	537	Example: Use whatever libev has to offer, but make sure that kqueue is
480	available (warning, breaks stuff, best use only with your own private	538	used if available (warning, breaks stuff, best use only with your own
481	event loop and only if you know the OS supports your types of fds):	539	private event loop and only if you know the OS supports your types of
		540	fds):
482		541
483	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	542	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
484		543
485	=item struct ev_loop *ev_loop_new (unsigned int flags)	544	=item struct ev_loop *ev_loop_new (unsigned int flags)
486		545
…		…
507	responsibility to either stop all watchers cleanly yourself I<before>	566	responsibility to either stop all watchers cleanly yourself I<before>
508	calling this function, or cope with the fact afterwards (which is usually	567	calling this function, or cope with the fact afterwards (which is usually
509	the easiest thing, you can just ignore the watchers and/or C<free ()> them	568	the easiest thing, you can just ignore the watchers and/or C<free ()> them
510	for example).	569	for example).
511		570
512	Note that certain global state, such as signal state, will not be freed by	571	Note that certain global state, such as signal state (and installed signal
513	this function, and related watchers (such as signal and child watchers)	572	handlers), will not be freed by this function, and related watchers (such
514	would need to be stopped manually.	573	as signal and child watchers) would need to be stopped manually.
515		574
516	In general it is not advisable to call this function except in the	575	In general it is not advisable to call this function except in the
517	rare occasion where you really need to free e.g. the signal handling	576	rare occasion where you really need to free e.g. the signal handling
518	pipe fds. If you need dynamically allocated loops it is better to use	577	pipe fds. If you need dynamically allocated loops it is better to use
519	C<ev_loop_new> and C<ev_loop_destroy>).	578	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
544		603
545	=item ev_loop_fork (loop)	604	=item ev_loop_fork (loop)
546		605
547	Like C<ev_default_fork>, but acts on an event loop created by	606	Like C<ev_default_fork>, but acts on an event loop created by
548	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	607	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
549	after fork, and how you do this is entirely your own problem.	608	after fork that you want to re-use in the child, and how you do this is
		609	entirely your own problem.
550		610
551	=item int ev_is_default_loop (loop)	611	=item int ev_is_default_loop (loop)
552		612
553	Returns true when the given loop actually is the default loop, false otherwise.	613	Returns true when the given loop is, in fact, the default loop, and false
		614	otherwise.
554		615
555	=item unsigned int ev_loop_count (loop)	616	=item unsigned int ev_loop_count (loop)
556		617
557	Returns the count of loop iterations for the loop, which is identical to	618	Returns the count of loop iterations for the loop, which is identical to
558	the number of times libev did poll for new events. It starts at C<0> and	619	the number of times libev did poll for new events. It starts at C<0> and
559	happily wraps around with enough iterations.	620	happily wraps around with enough iterations.
560		621
561	This value can sometimes be useful as a generation counter of sorts (it	622	This value can sometimes be useful as a generation counter of sorts (it
562	"ticks" the number of loop iterations), as it roughly corresponds with	623	"ticks" the number of loop iterations), as it roughly corresponds with
563	C<ev_prepare> and C<ev_check> calls.	624	C<ev_prepare> and C<ev_check> calls.
		625
		626	=item unsigned int ev_loop_depth (loop)
		627
		628	Returns the number of times C<ev_loop> was entered minus the number of
		629	times C<ev_loop> was exited, in other words, the recursion depth.
		630
		631	Outside C<ev_loop>, this number is zero. In a callback, this number is
		632	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),
		633	in which case it is higher.
		634
		635	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread
		636	etc.), doesn't count as exit.
564		637
565	=item unsigned int ev_backend (loop)	638	=item unsigned int ev_backend (loop)
566		639
567	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	640	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
568	use.	641	use.
…		…
573	received events and started processing them. This timestamp does not	646	received events and started processing them. This timestamp does not
574	change as long as callbacks are being processed, and this is also the base	647	change as long as callbacks are being processed, and this is also the base
575	time used for relative timers. You can treat it as the timestamp of the	648	time used for relative timers. You can treat it as the timestamp of the
576	event occurring (or more correctly, libev finding out about it).	649	event occurring (or more correctly, libev finding out about it).
577		650
		651	=item ev_now_update (loop)
		652
		653	Establishes the current time by querying the kernel, updating the time
		654	returned by C<ev_now ()> in the progress. This is a costly operation and
		655	is usually done automatically within C<ev_loop ()>.
		656
		657	This function is rarely useful, but when some event callback runs for a
		658	very long time without entering the event loop, updating libev's idea of
		659	the current time is a good idea.
		660
		661	See also L<The special problem of time updates> in the C<ev_timer> section.
		662
		663	=item ev_suspend (loop)
		664
		665	=item ev_resume (loop)
		666
		667	These two functions suspend and resume a loop, for use when the loop is
		668	not used for a while and timeouts should not be processed.
		669
		670	A typical use case would be an interactive program such as a game: When
		671	the user presses C<^Z> to suspend the game and resumes it an hour later it
		672	would be best to handle timeouts as if no time had actually passed while
		673	the program was suspended. This can be achieved by calling C<ev_suspend>
		674	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		675	C<ev_resume> directly afterwards to resume timer processing.
		676
		677	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		678	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		679	will be rescheduled (that is, they will lose any events that would have
		680	occured while suspended).
		681
		682	After calling C<ev_suspend> you B<must not> call I<any> function on the
		683	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		684	without a previous call to C<ev_suspend>.
		685
		686	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		687	event loop time (see C<ev_now_update>).
		688
578	=item ev_loop (loop, int flags)	689	=item ev_loop (loop, int flags)
579		690
580	Finally, this is it, the event handler. This function usually is called	691	Finally, this is it, the event handler. This function usually is called
581	after you initialised all your watchers and you want to start handling	692	after you initialised all your watchers and you want to start handling
582	events.	693	events.
…		…
584	If the flags argument is specified as C<0>, it will not return until	695	If the flags argument is specified as C<0>, it will not return until
585	either no event watchers are active anymore or C<ev_unloop> was called.	696	either no event watchers are active anymore or C<ev_unloop> was called.
586		697
587	Please note that an explicit C<ev_unloop> is usually better than	698	Please note that an explicit C<ev_unloop> is usually better than
588	relying on all watchers to be stopped when deciding when a program has	699	relying on all watchers to be stopped when deciding when a program has
589	finished (especially in interactive programs), but having a program that	700	finished (especially in interactive programs), but having a program
590	automatically loops as long as it has to and no longer by virtue of	701	that automatically loops as long as it has to and no longer by virtue
591	relying on its watchers stopping correctly is a thing of beauty.	702	of relying on its watchers stopping correctly, that is truly a thing of
		703	beauty.
592		704
593	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	705	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
594	those events and any outstanding ones, but will not block your process in	706	those events and any already outstanding ones, but will not block your
595	case there are no events and will return after one iteration of the loop.	707	process in case there are no events and will return after one iteration of
		708	the loop.
596		709
597	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	710	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
598	necessary) and will handle those and any outstanding ones. It will block	711	necessary) and will handle those and any already outstanding ones. It
599	your process until at least one new event arrives, and will return after	712	will block your process until at least one new event arrives (which could
600	one iteration of the loop. This is useful if you are waiting for some	713	be an event internal to libev itself, so there is no guarantee that a
601	external event in conjunction with something not expressible using other	714	user-registered callback will be called), and will return after one
		715	iteration of the loop.
		716
		717	This is useful if you are waiting for some external event in conjunction
		718	with something not expressible using other libev watchers (i.e. "roll your
602	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	719	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
603	usually a better approach for this kind of thing.	720	usually a better approach for this kind of thing.
604		721
605	Here are the gory details of what C<ev_loop> does:	722	Here are the gory details of what C<ev_loop> does:
606		723
607	- Before the first iteration, call any pending watchers.	724	- Before the first iteration, call any pending watchers.
…		…
617	any active watchers at all will result in not sleeping).	734	any active watchers at all will result in not sleeping).
618	- Sleep if the I/O and timer collect interval say so.	735	- Sleep if the I/O and timer collect interval say so.
619	- Block the process, waiting for any events.	736	- Block the process, waiting for any events.
620	- Queue all outstanding I/O (fd) events.	737	- Queue all outstanding I/O (fd) events.
621	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	738	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
622	- Queue all outstanding timers.	739	- Queue all expired timers.
623	- Queue all outstanding periodics.	740	- Queue all expired periodics.
624	- Unless any events are pending now, queue all idle watchers.	741	- Unless any events are pending now, queue all idle watchers.
625	- Queue all check watchers.	742	- Queue all check watchers.
626	- Call all queued watchers in reverse order (i.e. check watchers first).	743	- Call all queued watchers in reverse order (i.e. check watchers first).
627	Signals and child watchers are implemented as I/O watchers, and will	744	Signals and child watchers are implemented as I/O watchers, and will
628	be handled here by queueing them when their watcher gets executed.	745	be handled here by queueing them when their watcher gets executed.
…		…
645	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	762	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
646	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	763	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
647		764
648	This "unloop state" will be cleared when entering C<ev_loop> again.	765	This "unloop state" will be cleared when entering C<ev_loop> again.
649		766
		767	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		768
650	=item ev_ref (loop)	769	=item ev_ref (loop)
651		770
652	=item ev_unref (loop)	771	=item ev_unref (loop)
653		772
654	Ref/unref can be used to add or remove a reference count on the event	773	Ref/unref can be used to add or remove a reference count on the event
655	loop: Every watcher keeps one reference, and as long as the reference	774	loop: Every watcher keeps one reference, and as long as the reference
656	count is nonzero, C<ev_loop> will not return on its own. If you have	775	count is nonzero, C<ev_loop> will not return on its own.
		776
657	a watcher you never unregister that should not keep C<ev_loop> from	777	If you have a watcher you never unregister that should not keep C<ev_loop>
658	returning, ev_unref() after starting, and ev_ref() before stopping it. For	778	from returning, call ev_unref() after starting, and ev_ref() before
		779	stopping it.
		780
659	example, libev itself uses this for its internal signal pipe: It is not	781	As an example, libev itself uses this for its internal signal pipe: It
660	visible to the libev user and should not keep C<ev_loop> from exiting if	782	is not visible to the libev user and should not keep C<ev_loop> from
661	no event watchers registered by it are active. It is also an excellent	783	exiting if no event watchers registered by it are active. It is also an
662	way to do this for generic recurring timers or from within third-party	784	excellent way to do this for generic recurring timers or from within
663	libraries. Just remember to I<unref after start> and I<ref before stop>	785	third-party libraries. Just remember to I<unref after start> and I<ref
664	(but only if the watcher wasn't active before, or was active before,	786	before stop> (but only if the watcher wasn't active before, or was active
665	respectively).	787	before, respectively. Note also that libev might stop watchers itself
		788	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		789	in the callback).
666		790
667	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	791	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
668	running when nothing else is active.	792	running when nothing else is active.
669		793
670	struct ev_signal exitsig;	794	ev_signal exitsig;
671	ev_signal_init (&exitsig, sig_cb, SIGINT);	795	ev_signal_init (&exitsig, sig_cb, SIGINT);
672	ev_signal_start (loop, &exitsig);	796	ev_signal_start (loop, &exitsig);
673	evf_unref (loop);	797	evf_unref (loop);
674		798
675	Example: For some weird reason, unregister the above signal handler again.	799	Example: For some weird reason, unregister the above signal handler again.
…		…
689	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	813	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
690	allows libev to delay invocation of I/O and timer/periodic callbacks	814	allows libev to delay invocation of I/O and timer/periodic callbacks
691	to increase efficiency of loop iterations (or to increase power-saving	815	to increase efficiency of loop iterations (or to increase power-saving
692	opportunities).	816	opportunities).
693		817
694	The background is that sometimes your program runs just fast enough to	818	The idea is that sometimes your program runs just fast enough to handle
695	handle one (or very few) event(s) per loop iteration. While this makes	819	one (or very few) event(s) per loop iteration. While this makes the
696	the program responsive, it also wastes a lot of CPU time to poll for new	820	program responsive, it also wastes a lot of CPU time to poll for new
697	events, especially with backends like C<select ()> which have a high	821	events, especially with backends like C<select ()> which have a high
698	overhead for the actual polling but can deliver many events at once.	822	overhead for the actual polling but can deliver many events at once.
699		823
700	By setting a higher I<io collect interval> you allow libev to spend more	824	By setting a higher I<io collect interval> you allow libev to spend more
701	time collecting I/O events, so you can handle more events per iteration,	825	time collecting I/O events, so you can handle more events per iteration,
702	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	826	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
703	C<ev_timer>) will be not affected. Setting this to a non-null value will	827	C<ev_timer>) will be not affected. Setting this to a non-null value will
704	introduce an additional C<ev_sleep ()> call into most loop iterations.	828	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		829	sleep time ensures that libev will not poll for I/O events more often then
		830	once per this interval, on average.
705		831
706	Likewise, by setting a higher I<timeout collect interval> you allow libev	832	Likewise, by setting a higher I<timeout collect interval> you allow libev
707	to spend more time collecting timeouts, at the expense of increased	833	to spend more time collecting timeouts, at the expense of increased
708	latency (the watcher callback will be called later). C<ev_io> watchers	834	latency/jitter/inexactness (the watcher callback will be called
709	will not be affected. Setting this to a non-null value will not introduce	835	later). C<ev_io> watchers will not be affected. Setting this to a non-null
710	any overhead in libev.	836	value will not introduce any overhead in libev.
711		837
712	Many (busy) programs can usually benefit by setting the I/O collect	838	Many (busy) programs can usually benefit by setting the I/O collect
713	interval to a value near C<0.1> or so, which is often enough for	839	interval to a value near C<0.1> or so, which is often enough for
714	interactive servers (of course not for games), likewise for timeouts. It	840	interactive servers (of course not for games), likewise for timeouts. It
715	usually doesn't make much sense to set it to a lower value than C<0.01>,	841	usually doesn't make much sense to set it to a lower value than C<0.01>,
716	as this approaches the timing granularity of most systems.	842	as this approaches the timing granularity of most systems. Note that if
		843	you do transactions with the outside world and you can't increase the
		844	parallelity, then this setting will limit your transaction rate (if you
		845	need to poll once per transaction and the I/O collect interval is 0.01,
		846	then you can't do more than 100 transations per second).
717		847
718	Setting the I<timeout collect interval> can improve the opportunity for	848	Setting the I<timeout collect interval> can improve the opportunity for
719	saving power, as the program will "bundle" timer callback invocations that	849	saving power, as the program will "bundle" timer callback invocations that
720	are "near" in time together, by delaying some, thus reducing the number of	850	are "near" in time together, by delaying some, thus reducing the number of
721	times the process sleeps and wakes up again. Another useful technique to	851	times the process sleeps and wakes up again. Another useful technique to
722	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	852	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
723	they fire on, say, one-second boundaries only.	853	they fire on, say, one-second boundaries only.
724		854
		855	Example: we only need 0.1s timeout granularity, and we wish not to poll
		856	more often than 100 times per second:
		857
		858	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		859	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		860
		861	=item ev_invoke_pending (loop)
		862
		863	This call will simply invoke all pending watchers while resetting their
		864	pending state. Normally, C<ev_loop> does this automatically when required,
		865	but when overriding the invoke callback this call comes handy.
		866
		867	=item 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
725	=item ev_loop_verify (loop)	908	=item ev_loop_verify (loop)
726		909
727	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
728	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
729	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
730	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 ()>.
731		915
732	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
733	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
734	data structures consistent.	918	data structures consistent.
735		919
736	=back	920	=back
737		921
738		922
739	=head1 ANATOMY OF A WATCHER	923	=head1 ANATOMY OF A WATCHER
740		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
741	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
742	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
743	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:
744		932
745	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)
746	{	934	{
747	ev_io_stop (w);	935	ev_io_stop (w);
748	ev_unloop (loop, EVUNLOOP_ALL);	936	ev_unloop (loop, EVUNLOOP_ALL);
749	}	937	}
750		938
751	struct ev_loop *loop = ev_default_loop (0);	939	struct ev_loop *loop = ev_default_loop (0);
		940
752	struct ev_io stdin_watcher;	941	ev_io stdin_watcher;
		942
753	ev_init (&stdin_watcher, my_cb);	943	ev_init (&stdin_watcher, my_cb);
754	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	944	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
755	ev_io_start (loop, &stdin_watcher);	945	ev_io_start (loop, &stdin_watcher);
		946
756	ev_loop (loop, 0);	947	ev_loop (loop, 0);
757		948
758	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
759	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
760	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).
761		955
762	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
763	(watcher *, callback)>, which expects a callback to be provided. This	957	(watcher *, callback)>, which expects a callback to be provided. This
764	callback gets invoked each time the event occurs (or, in the case of I/O	958	callback gets invoked each time the event occurs (or, in the case of I/O
765	watchers, each time the event loop detects that the file descriptor given	959	watchers, each time the event loop detects that the file descriptor given
766	is readable and/or writable).	960	is readable and/or writable).
767		961
768	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 *, ...) >>
769	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
770	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<<
771	(watcher *, callback, ...) >>.	965	ev_TYPE_init (watcher *, callback, ...) >>.
772		966
773	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
774	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
775	*) >>), 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
776	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	970	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
777		971
778	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
779	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
780	reinitialise it or call its C<set> macro.	974	reinitialise it or call its C<ev_TYPE_set> macro.
781		975
782	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
783	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
784	third argument.	978	third argument.
785		979
…		…
843		1037
844	=item C<EV_ASYNC>	1038	=item C<EV_ASYNC>
845		1039
846	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>).
847		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
848	=item C<EV_ERROR>	1047	=item C<EV_ERROR>
849		1048
850	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
851	happen because the watcher could not be properly started because libev	1050	happen because the watcher could not be properly started because libev
852	ran out of memory, a file descriptor was found to be closed or any other	1051	ran out of memory, a file descriptor was found to be closed or any other
		1052	problem. Libev considers these application bugs.
		1053
853	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
854	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.
855		1058
856	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
857	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
858	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
859	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
860	programs, though, so beware.	1063	programs, though, as the fd could already be closed and reused for another
		1064	thing, so beware.
861		1065
862	=back	1066	=back
863		1067
864	=head2 GENERIC WATCHER FUNCTIONS	1068	=head2 GENERIC WATCHER FUNCTIONS
865
866	In the following description, C<TYPE> stands for the watcher type,
867	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
868		1069
869	=over 4	1070	=over 4
870		1071
871	=item C<ev_init> (ev_TYPE *watcher, callback)	1072	=item C<ev_init> (ev_TYPE *watcher, callback)
872		1073
…		…
878	which rolls both calls into one.	1079	which rolls both calls into one.
879		1080
880	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
881	(or never started) and there are no pending events outstanding.	1082	(or never started) and there are no pending events outstanding.
882		1083
883	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,
884	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);
885		1092
886	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1093	=item C<ev_TYPE_set> (ev_TYPE *, [args])
887		1094
888	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
889	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
…		…
892	difference to the C<ev_init> macro).	1099	difference to the C<ev_init> macro).
893		1100
894	Although some watcher types do not have type-specific arguments	1101	Although some watcher types do not have type-specific arguments
895	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	1102	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
896		1103
		1104	See C<ev_init>, above, for an example.
		1105
897	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1106	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
898		1107
899	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
900	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
901	a watcher. The same limitations apply, of course.	1110	a watcher. The same limitations apply, of course.
902		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
903	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1116	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
904		1117
905	Starts (activates) the given watcher. Only active watchers will receive	1118	Starts (activates) the given watcher. Only active watchers will receive
906	events. If the watcher is already active nothing will happen.	1119	events. If the watcher is already active nothing will happen.
907		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
908	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1126	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
909		1127
910	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
911	status. It is possible that stopped watchers are pending (for example,	1131	It is possible that stopped watchers are pending - for example,
912	non-repeating timers are being stopped when they become pending), but	1132	non-repeating timers are being stopped when they become pending - but
913	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1133	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
914	you want to free or reuse the memory used by the watcher it is therefore a	1134	pending. If you want to free or reuse the memory used by the watcher it is
915	good idea to always call its C<ev_TYPE_stop> function.	1135	therefore a good idea to always call its C<ev_TYPE_stop> function.
916		1136
917	=item bool ev_is_active (ev_TYPE *watcher)	1137	=item bool ev_is_active (ev_TYPE *watcher)
918		1138
919	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
920	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
…		…
946	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>
947	(default: C<-2>). Pending watchers with higher priority will be invoked	1167	(default: C<-2>). Pending watchers with higher priority will be invoked
948	before watchers with lower priority, but priority will not keep watchers	1168	before watchers with lower priority, but priority will not keep watchers
949	from being executed (except for C<ev_idle> watchers).	1169	from being executed (except for C<ev_idle> watchers).
950		1170
951	This means that priorities are I<only> used for ordering callback
952	invocation after new events have been received. This is useful, for
953	example, to reduce latency after idling, or more often, to bind two
954	watchers on the same event and make sure one is called first.
955
956	If you need to suppress invocation when higher priority events are pending	1171	If you need to suppress invocation when higher priority events are pending
957	you need to look at C<ev_idle> watchers, which provide this functionality.	1172	you need to look at C<ev_idle> watchers, which provide this functionality.
958		1173
959	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
960	pending.	1175	pending.
961		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
962	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
963	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 :).
964		1183
965	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
966	fine, as long as you do not mind that the priority value you query might	1185	priorities.
967	or might not have been adjusted to be within valid range.
968		1186
969	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1187	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
970		1188
971	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
972	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
973	can deal with that fact.	1191	can deal with that fact, as both are simply passed through to the
		1192	callback.
974		1193
975	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1194	=item int ev_clear_pending (loop, ev_TYPE *watcher)
976		1195
977	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
978	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
979	watcher isn't pending it does nothing and returns C<0>.	1198	watcher isn't pending it does nothing and returns C<0>.
980		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
981	=back	1203	=back
982		1204
983		1205
984	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1206	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
985		1207
986	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
987	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
988	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
989	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
990	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
991	data:	1213	data:
992		1214
993	struct my_io	1215	struct my_io
994	{	1216	{
995	struct ev_io io;	1217	ev_io io;
996	int otherfd;	1218	int otherfd;
997	void *somedata;	1219	void *somedata;
998	struct whatever *mostinteresting;	1220	struct whatever *mostinteresting;
999	}	1221	};
		1222
		1223	...
		1224	struct my_io w;
		1225	ev_io_init (&w.io, my_cb, fd, EV_READ);
1000		1226
1001	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
1002	can cast it back to your own type:	1228	can cast it back to your own type:
1003		1229
1004	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)
1005	{	1231	{
1006	struct my_io *w = (struct my_io *)w_;	1232	struct my_io *w = (struct my_io *)w_;
1007	...	1233	...
1008	}	1234	}
1009		1235
1010	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
1011	instead have been omitted.	1237	instead have been omitted.
1012		1238
1013	Another common scenario is having some data structure with multiple	1239	Another common scenario is to use some data structure with multiple
1014	watchers:	1240	embedded watchers:
1015		1241
1016	struct my_biggy	1242	struct my_biggy
1017	{	1243	{
1018	int some_data;	1244	int some_data;
1019	ev_timer t1;	1245	ev_timer t1;
1020	ev_timer t2;	1246	ev_timer t2;
1021	}	1247	}
1022		1248
1023	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
1024	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):
1025		1254
1026	#include <stddef.h>	1255	#include <stddef.h>
1027		1256
1028	static void	1257	static void
1029	t1_cb (EV_P_ struct ev_timer *w, int revents)	1258	t1_cb (EV_P_ ev_timer *w, int revents)
1030	{	1259	{
1031	struct my_biggy big = (struct my_biggy *	1260	struct my_biggy big = (struct my_biggy *)
1032	(((char *)w) - offsetof (struct my_biggy, t1));	1261	(((char *)w) - offsetof (struct my_biggy, t1));
1033	}	1262	}
1034		1263
1035	static void	1264	static void
1036	t2_cb (EV_P_ struct ev_timer *w, int revents)	1265	t2_cb (EV_P_ ev_timer *w, int revents)
1037	{	1266	{
1038	struct my_biggy big = (struct my_biggy *	1267	struct my_biggy big = (struct my_biggy *)
1039	(((char *)w) - offsetof (struct my_biggy, t2));	1268	(((char *)w) - offsetof (struct my_biggy, t2));
1040	}	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.
1041		1373
1042		1374
1043	=head1 WATCHER TYPES	1375	=head1 WATCHER TYPES
1044		1376
1045	This section describes each watcher in detail, but will not repeat	1377	This section describes each watcher in detail, but will not repeat
…		…
1069	In general you can register as many read and/or write event watchers per	1401	In general you can register as many read and/or write event watchers per
1070	fd as you want (as long as you don't confuse yourself). Setting all file	1402	fd as you want (as long as you don't confuse yourself). Setting all file
1071	descriptors to non-blocking mode is also usually a good idea (but not	1403	descriptors to non-blocking mode is also usually a good idea (but not
1072	required if you know what you are doing).	1404	required if you know what you are doing).
1073		1405
1074	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
1075	(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
1076	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.
1077		1411
1078	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
1079	receive "spurious" readiness notifications, that is your callback might	1413	receive "spurious" readiness notifications, that is your callback might
1080	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1414	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1081	because there is no data. Not only are some backends known to create a	1415	because there is no data. Not only are some backends known to create a
1082	lot of those (for example Solaris ports), it is very easy to get into	1416	lot of those (for example Solaris ports), it is very easy to get into
1083	this situation even with a relatively standard program structure. Thus	1417	this situation even with a relatively standard program structure. Thus
1084	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1418	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1085	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1419	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1086		1420
1087	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
1088	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
1089	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
1090	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
1091	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.
1092		1430
1093	=head3 The special problem of disappearing file descriptors	1431	=head3 The special problem of disappearing file descriptors
1094		1432
1095	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
1096	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,
1097	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
1098	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
1099	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
1100	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
1101	fact, a different file descriptor.	1439	fact, a different file descriptor.
1102		1440
…		…
1133	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1471	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1134	C<EVBACKEND_POLL>.	1472	C<EVBACKEND_POLL>.
1135		1473
1136	=head3 The special problem of SIGPIPE	1474	=head3 The special problem of SIGPIPE
1137		1475
1138	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>:
1139	when reading from a pipe whose other end has been closed, your program	1477	when writing to a pipe whose other end has been closed, your program gets
1140	gets send a SIGPIPE, which, by default, aborts your program. For most	1478	sent a SIGPIPE, which, by default, aborts your program. For most programs
1141	programs this is sensible behaviour, for daemons, this is usually	1479	this is sensible behaviour, for daemons, this is usually undesirable.
1142	undesirable.
1143		1480
1144	So when you encounter spurious, unexplained daemon exits, make sure you	1481	So when you encounter spurious, unexplained daemon exits, make sure you
1145	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1482	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1146	somewhere, as that would have given you a big clue).	1483	somewhere, as that would have given you a big clue).
1147		1484
…		…
1153	=item ev_io_init (ev_io *, callback, int fd, int events)	1490	=item ev_io_init (ev_io *, callback, int fd, int events)
1154		1491
1155	=item ev_io_set (ev_io *, int fd, int events)	1492	=item ev_io_set (ev_io *, int fd, int events)
1156		1493
1157	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
1158	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
1159	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.
1160		1497
1161	=item int fd [read-only]	1498	=item int fd [read-only]
1162		1499
1163	The file descriptor being watched.	1500	The file descriptor being watched.
1164		1501
…		…
1173	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
1174	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
1175	attempt to read a whole line in the callback.	1512	attempt to read a whole line in the callback.
1176		1513
1177	static void	1514	static void
1178	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)
1179	{	1516	{
1180	ev_io_stop (loop, w);	1517	ev_io_stop (loop, w);
1181	.. 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
1182	}	1519	}
1183		1520
1184	...	1521	...
1185	struct ev_loop *loop = ev_default_init (0);	1522	struct ev_loop *loop = ev_default_init (0);
1186	struct ev_io stdin_readable;	1523	ev_io stdin_readable;
1187	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);
1188	ev_io_start (loop, &stdin_readable);	1525	ev_io_start (loop, &stdin_readable);
1189	ev_loop (loop, 0);	1526	ev_loop (loop, 0);
1190		1527
1191		1528
…		…
1194	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
1195	given time, and optionally repeating in regular intervals after that.	1532	given time, and optionally repeating in regular intervals after that.
1196		1533
1197	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
1198	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
1199	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
1200	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1537	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1201	monotonic clock option helps a lot here).	1538	monotonic clock option helps a lot here).
		1539
		1540	The callback is guaranteed to be invoked only I<after> its timeout has
		1541	passed (not I<at>, so on systems with very low-resolution clocks this
		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 :)
		1721
		1722	=head3 The special problem of time updates
		1723
		1724	Establishing the current time is a costly operation (it usually takes at
		1725	least two system calls): EV therefore updates its idea of the current
		1726	time only before and after C<ev_loop> collects new events, which causes a
		1727	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1728	lots of events in one iteration.
1202		1729
1203	The relative timeouts are calculated relative to the C<ev_now ()>	1730	The relative timeouts are calculated relative to the C<ev_now ()>
1204	time. This is usually the right thing as this timestamp refers to the time	1731	time. This is usually the right thing as this timestamp refers to the time
1205	of the event triggering whatever timeout you are modifying/starting. If	1732	of the event triggering whatever timeout you are modifying/starting. If
1206	you suspect event processing to be delayed and you I<need> to base the timeout	1733	you suspect event processing to be delayed and you I<need> to base the
1207	on the current time, use something like this to adjust for this:	1734	timeout on the current time, use something like this to adjust for this:
1208		1735
1209	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1736	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1210		1737
1211	The callback is guaranteed to be invoked only after its timeout has passed,	1738	If the event loop is suspended for a long time, you can also force an
1212	but if multiple timers become ready during the same loop iteration then	1739	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1213	order of execution is undefined.	1740	()>.
1214		1741
1215	=head3 Watcher-Specific Functions and Data Members	1742	=head3 Watcher-Specific Functions and Data Members
1216		1743
1217	=over 4	1744	=over 4
1218		1745
…		…
1242	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).
1243		1770
1244	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
1245	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.
1246		1773
1247	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
1248	example: Imagine you have a TCP connection and you want a so-called idle	1775	usage example.
1249	timeout, that is, you want to be called when there have been, say, 60
1250	seconds of inactivity on the socket. The easiest way to do this is to
1251	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1252	C<ev_timer_again> each time you successfully read or write some data. If
1253	you go into an idle state where you do not expect data to travel on the
1254	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1255	automatically restart it if need be.
1256
1257	That means you can ignore the C<after> value and C<ev_timer_start>
1258	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1259
1260	ev_timer_init (timer, callback, 0., 5.);
1261	ev_timer_again (loop, timer);
1262	...
1263	timer->again = 17.;
1264	ev_timer_again (loop, timer);
1265	...
1266	timer->again = 10.;
1267	ev_timer_again (loop, timer);
1268
1269	This is more slightly efficient then stopping/starting the timer each time
1270	you want to modify its timeout value.
1271		1776
1272	=item ev_tstamp repeat [read-write]	1777	=item ev_tstamp repeat [read-write]
1273		1778
1274	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
1275	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),
1276	which is also when any modifications are taken into account.	1781	which is also when any modifications are taken into account.
1277		1782
1278	=back	1783	=back
1279		1784
1280	=head3 Examples	1785	=head3 Examples
1281		1786
1282	Example: Create a timer that fires after 60 seconds.	1787	Example: Create a timer that fires after 60 seconds.
1283		1788
1284	static void	1789	static void
1285	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)
1286	{	1791	{
1287	.. one minute over, w is actually stopped right here	1792	.. one minute over, w is actually stopped right here
1288	}	1793	}
1289		1794
1290	struct ev_timer mytimer;	1795	ev_timer mytimer;
1291	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1796	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1292	ev_timer_start (loop, &mytimer);	1797	ev_timer_start (loop, &mytimer);
1293		1798
1294	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
1295	inactivity.	1800	inactivity.
1296		1801
1297	static void	1802	static void
1298	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1803	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1299	{	1804	{
1300	.. ten seconds without any activity	1805	.. ten seconds without any activity
1301	}	1806	}
1302		1807
1303	struct ev_timer mytimer;	1808	ev_timer mytimer;
1304	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 */
1305	ev_timer_again (&mytimer); /* start timer */	1810	ev_timer_again (&mytimer); /* start timer */
1306	ev_loop (loop, 0);	1811	ev_loop (loop, 0);
1307		1812
1308	// 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":
…		…
1313	=head2 C<ev_periodic> - to cron or not to cron?	1818	=head2 C<ev_periodic> - to cron or not to cron?
1314		1819
1315	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
1316	(and unfortunately a bit complex).	1821	(and unfortunately a bit complex).
1317		1822
1318	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
1319	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
1320	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
1321	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
1322	+ 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
1323	clock to January of the previous year, then it will take more than year	1828	wrist-watch).
1324	to trigger the event (unlike an C<ev_timer>, which would still trigger
1325	roughly 10 seconds later as it uses a relative timeout).
1326		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
1327	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
1328	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
1329	complicated, rules.	1840	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1841	those cannot react to time jumps.
1330		1842
1331	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
1332	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
1333	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).
1334		1848
1335	=head3 Watcher-Specific Functions and Data Members	1849	=head3 Watcher-Specific Functions and Data Members
1336		1850
1337	=over 4	1851	=over 4
1338		1852
1339	=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)
1340		1854
1341	=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)
1342		1856
1343	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
1344	operation, and we will explain them from simplest to complex:	1858	operation, and we will explain them from simplest to most complex:
1345		1859
1346	=over 4	1860	=over 4
1347		1861
1348	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1862	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1349		1863
1350	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
1351	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
1352	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
1353	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.
1354		1869
1355	=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)
1356		1871
1357	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
1358	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
1359	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.
1360		1876
1361	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
1362	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
1363	the hour:	1879	hour, on the hour (with respect to UTC):
1364		1880
1365	ev_periodic_set (&periodic, 0., 3600., 0);	1881	ev_periodic_set (&periodic, 0., 3600., 0);
1366		1882
1367	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,
1368	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
1369	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
1370	by 3600.	1886	by 3600.
1371		1887
1372	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
1373	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
1374	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.
1375		1891
1376	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
1377	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
1378	this value, and in fact is often specified as zero.	1894	this value, and in fact is often specified as zero.
1379		1895
1380	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
1381	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
1382	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
1383	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).
1384		1900
1385	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1901	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1386		1902
1387	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
1388	ignored. Instead, each time the periodic watcher gets scheduled, the	1904	ignored. Instead, each time the periodic watcher gets scheduled, the
1389	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
1390	current time as second argument.	1906	current time as second argument.
1391		1907
1392	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,
1393	ever, or make ANY event loop modifications whatsoever>.	1909	or make ANY other event loop modifications whatsoever, unless explicitly
		1910	allowed by documentation here>.
1394		1911
1395	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
1396	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
1397	only event loop modification you are allowed to do).	1914	only event loop modification you are allowed to do).
1398		1915
1399	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1916	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1400	*w, ev_tstamp now)>, e.g.:	1917	*w, ev_tstamp now)>, e.g.:
1401		1918
		1919	static ev_tstamp
1402	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1920	my_rescheduler (ev_periodic *w, ev_tstamp now)
1403	{	1921	{
1404	return now + 60.;	1922	return now + 60.;
1405	}	1923	}
1406		1924
1407	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
…		…
1427	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
1428	program when the crontabs have changed).	1946	program when the crontabs have changed).
1429		1947
1430	=item ev_tstamp ev_periodic_at (ev_periodic *)	1948	=item ev_tstamp ev_periodic_at (ev_periodic *)
1431		1949
1432	When active, returns the absolute time that the watcher is supposed to	1950	When active, returns the absolute time that the watcher is supposed
1433	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.
1434		1954
1435	=item ev_tstamp offset [read-write]	1955	=item ev_tstamp offset [read-write]
1436		1956
1437	When repeating, this contains the offset value, otherwise this is the	1957	When repeating, this contains the offset value, otherwise this is the
1438	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	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).
1439		1960
1440	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
1441	timer fires or C<ev_periodic_again> is being called.	1962	timer fires or C<ev_periodic_again> is being called.
1442		1963
1443	=item ev_tstamp interval [read-write]	1964	=item ev_tstamp interval [read-write]
1444		1965
1445	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
1446	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
1447	called.	1968	called.
1448		1969
1449	=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]
1450		1971
1451	The current reschedule callback, or C<0>, if this functionality is	1972	The current reschedule callback, or C<0>, if this functionality is
1452	switched off. Can be changed any time, but changes only take effect when	1973	switched off. Can be changed any time, but changes only take effect when
1453	the periodic timer fires or C<ev_periodic_again> is being called.	1974	the periodic timer fires or C<ev_periodic_again> is being called.
1454		1975
1455	=back	1976	=back
1456		1977
1457	=head3 Examples	1978	=head3 Examples
1458		1979
1459	Example: Call a callback every hour, or, more precisely, whenever the	1980	Example: Call a callback every hour, or, more precisely, whenever the
1460	system clock is divisible by 3600. The callback invocation times have	1981	system time is divisible by 3600. The callback invocation times have
1461	potentially a lot of jitter, but good long-term stability.	1982	potentially a lot of jitter, but good long-term stability.
1462		1983
1463	static void	1984	static void
1464	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1985	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1465	{	1986	{
1466	... 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)
1467	}	1988	}
1468		1989
1469	struct ev_periodic hourly_tick;	1990	ev_periodic hourly_tick;
1470	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1991	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1471	ev_periodic_start (loop, &hourly_tick);	1992	ev_periodic_start (loop, &hourly_tick);
1472		1993
1473	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:
1474		1995
1475	#include <math.h>	1996	#include <math.h>
1476		1997
1477	static ev_tstamp	1998	static ev_tstamp
1478	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1999	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1479	{	2000	{
1480	return fmod (now, 3600.) + 3600.;	2001	return now + (3600. - fmod (now, 3600.));
1481	}	2002	}
1482		2003
1483	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);
1484		2005
1485	Example: Call a callback every hour, starting now:	2006	Example: Call a callback every hour, starting now:
1486		2007
1487	struct ev_periodic hourly_tick;	2008	ev_periodic hourly_tick;
1488	ev_periodic_init (&hourly_tick, clock_cb,	2009	ev_periodic_init (&hourly_tick, clock_cb,
1489	fmod (ev_now (loop), 3600.), 3600., 0);	2010	fmod (ev_now (loop), 3600.), 3600., 0);
1490	ev_periodic_start (loop, &hourly_tick);	2011	ev_periodic_start (loop, &hourly_tick);
1491		2012
1492		2013
…		…
1495	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
1496	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
1497	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
1498	normal event processing, like any other event.	2019	normal event processing, like any other event.
1499		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
1500	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
1501	first watcher gets started will libev actually register a signal watcher	2026	first watcher gets started will libev actually register a signal handler
1502	with the kernel (thus it coexists with your own signal handlers as long	2027	with the kernel (thus it coexists with your own signal handlers as long as
1503	as you don't register any with libev). Similarly, when the last signal	2028	you don't register any with libev for the same signal). Similarly, when
1504	watcher for a signal is stopped libev will reset the signal handler to	2029	the last signal watcher for a signal is stopped, libev will reset the
1505	SIG_DFL (regardless of what it was set to before).	2030	signal handler to SIG_DFL (regardless of what it was set to before).
1506		2031
1507	If possible and supported, libev will install its handlers with	2032	If possible and supported, libev will install its handlers with
1508	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
1509	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
1510	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
…		…
1527		2052
1528	=back	2053	=back
1529		2054
1530	=head3 Examples	2055	=head3 Examples
1531		2056
1532	Example: Try to exit cleanly on SIGINT and SIGTERM.	2057	Example: Try to exit cleanly on SIGINT.
1533		2058
1534	static void	2059	static void
1535	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2060	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1536	{	2061	{
1537	ev_unloop (loop, EVUNLOOP_ALL);	2062	ev_unloop (loop, EVUNLOOP_ALL);
1538	}	2063	}
1539		2064
1540	struct ev_signal signal_watcher;	2065	ev_signal signal_watcher;
1541	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2066	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1542	ev_signal_start (loop, &sigint_cb);	2067	ev_signal_start (loop, &signal_watcher);
1543		2068
1544		2069
1545	=head2 C<ev_child> - watch out for process status changes	2070	=head2 C<ev_child> - watch out for process status changes
1546		2071
1547	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
1548	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
1549	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
1550	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
1551	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.
1552		2080
1553	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
1554	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)
1555		2087
1556	=head3 Process Interaction	2088	=head3 Process Interaction
1557		2089
1558	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
1559	initialised. This is necessary to guarantee proper behaviour even if	2091	initialised. This is necessary to guarantee proper behaviour even if
…		…
1569	handler, you can override it easily by installing your own handler for	2101	handler, you can override it easily by installing your own handler for
1570	C<SIGCHLD> after initialising the default loop, and making sure the	2102	C<SIGCHLD> after initialising the default loop, and making sure the
1571	default loop never gets destroyed. You are encouraged, however, to use an	2103	default loop never gets destroyed. You are encouraged, however, to use an
1572	event-based approach to child reaping and thus use libev's support for	2104	event-based approach to child reaping and thus use libev's support for
1573	that, so other libev users can use C<ev_child> watchers freely.	2105	that, so other libev users can use C<ev_child> watchers freely.
		2106
		2107	=head3 Stopping the Child Watcher
		2108
		2109	Currently, the child watcher never gets stopped, even when the
		2110	child terminates, so normally one needs to stop the watcher in the
		2111	callback. Future versions of libev might stop the watcher automatically
		2112	when a child exit is detected.
1574		2113
1575	=head3 Watcher-Specific Functions and Data Members	2114	=head3 Watcher-Specific Functions and Data Members
1576		2115
1577	=over 4	2116	=over 4
1578		2117
…		…
1610	its completion.	2149	its completion.
1611		2150
1612	ev_child cw;	2151	ev_child cw;
1613		2152
1614	static void	2153	static void
1615	child_cb (EV_P_ struct ev_child *w, int revents)	2154	child_cb (EV_P_ ev_child *w, int revents)
1616	{	2155	{
1617	ev_child_stop (EV_A_ w);	2156	ev_child_stop (EV_A_ w);
1618	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);
1619	}	2158	}
1620		2159
…		…
1635		2174
1636		2175
1637	=head2 C<ev_stat> - did the file attributes just change?	2176	=head2 C<ev_stat> - did the file attributes just change?
1638		2177
1639	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
1640	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)
1641	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.
1642		2182
1643	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
1644	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
1645	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
1646	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
1647	the stat buffer having unspecified contents.	2187	least one) and all the other fields of the stat buffer having unspecified
		2188	contents.
1648		2189
1649	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
1650	relative and your working directory changes, the behaviour is undefined.	2192	your working directory changes, then the behaviour is undefined.
1651		2193
1652	Since there is no standard to do this, the portable implementation simply	2194	Since there is no portable change notification interface available, the
1653	calls C<stat (2)> regularly on the path to see if it changed somehow. You	2195	portable implementation simply calls C<stat(2)> regularly on the path
1654	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
1655	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
1656	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
1657	five seconds, although this might change dynamically). Libev will also	2199	(which you can expect to be around five seconds, although this might
1658	impose a minimum interval which is currently around C<0.1>, but thats	2200	change dynamically). Libev will also impose a minimum interval which is
1659	usually overkill.	2201	currently around C<0.1>, but that's usually overkill.
1660		2202
1661	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,
1662	as even with OS-supported change notifications, this can be	2204	as even with OS-supported change notifications, this can be
1663	resource-intensive.	2205	resource-intensive.
1664		2206
1665	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
1666	implemented (implementing kqueue support is left as an exercise for the	2208	is the Linux inotify interface (implementing kqueue support is left as an
1667	reader, note, however, that the author sees no way of implementing ev_stat	2209	exercise for the reader. Note, however, that the author sees no way of
1668	semantics with kqueue). Inotify will be used to give hints only and should	2210	implementing C<ev_stat> semantics with kqueue, except as a hint).
1669	not change the semantics of C<ev_stat> watchers, which means that libev
1670	sometimes needs to fall back to regular polling again even with inotify,
1671	but changes are usually detected immediately, and if the file exists there
1672	will be no polling.
1673		2211
1674	=head3 ABI Issues (Largefile Support)	2212	=head3 ABI Issues (Largefile Support)
1675		2213
1676	Libev by default (unless the user overrides this) uses the default	2214	Libev by default (unless the user overrides this) uses the default
1677	compilation environment, which means that on systems with large file	2215	compilation environment, which means that on systems with large file
1678	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
1679	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
1680	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
1681	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
1682	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
1683	most noticeably disabled with ev_stat and large file support.	2221	most noticeably displayed with ev_stat and large file support.
1684		2222
1685	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
1686	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
1687	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
1688	to exchange stat structures with application programs compiled using the	2226	to exchange stat structures with application programs compiled using the
1689	default compilation environment.	2227	default compilation environment.
1690		2228
1691	=head3 Inotify	2229	=head3 Inotify and Kqueue
1692		2230
1693	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
1694	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
1695	change detection where possible. The inotify descriptor will be created lazily	2233	inotify descriptor will be created lazily when the first C<ev_stat>
1696	when the first C<ev_stat> watcher is being started.	2234	watcher is being started.
1697		2235
1698	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
1699	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
1700	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
1701	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.
1702		2244
1703	(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
1704	implement this functionality, due to the requirement of having a file	2246	implement this functionality, due to the requirement of having a file
1705	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.
1706		2267
1707	=head3 The special problem of stat time resolution	2268	=head3 The special problem of stat time resolution
1708		2269
1709	The C<stat ()> system call only supports full-second resolution portably, and	2270	The C<stat ()> system call only supports full-second resolution portably,
1710	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
1711	only support whole seconds.	2272	still only support whole seconds.
1712		2273
1713	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
1714	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
1715	calls your callback, which does something. When there is another update	2276	calls your callback, which does something. When there is another update
1716	within the same second, C<ev_stat> will be unable to detect it as the stat	2277	within the same second, C<ev_stat> will be unable to detect unless the
1717	data does not change.	2278	stat data does change in other ways (e.g. file size).
1718		2279
1719	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
1720	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
1721	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);
1722	ev_timer_again (loop, w)>).	2283	ev_timer_again (loop, w)>).
…		…
1742	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
1743	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
1744	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
1745	path for as long as the watcher is active.	2306	path for as long as the watcher is active.
1746		2307
1747	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,
1748	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
1749	was detected).	2310	last change was detected).
1750		2311
1751	=item ev_stat_stat (loop, ev_stat *)	2312	=item ev_stat_stat (loop, ev_stat *)
1752		2313
1753	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
1754	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
…		…
1837		2398
1838		2399
1839	=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...
1840		2401
1841	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
1842	priority are pending (prepare, check and other idle watchers do not	2403	priority are pending (prepare, check and other idle watchers do not count
1843	count).	2404	as receiving "events").
1844		2405
1845	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
1846	(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
1847	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
1848	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
…		…
1859		2420
1860	=head3 Watcher-Specific Functions and Data Members	2421	=head3 Watcher-Specific Functions and Data Members
1861		2422
1862	=over 4	2423	=over 4
1863		2424
1864	=item ev_idle_init (ev_signal *, callback)	2425	=item ev_idle_init (ev_idle *, callback)
1865		2426
1866	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
1867	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,
1868	believe me.	2429	believe me.
1869		2430
…		…
1873		2434
1874	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
1875	callback, free it. Also, use no error checking, as usual.	2436	callback, free it. Also, use no error checking, as usual.
1876		2437
1877	static void	2438	static void
1878	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2439	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1879	{	2440	{
1880	free (w);	2441	free (w);
1881	// now do something you wanted to do when the program has	2442	// now do something you wanted to do when the program has
1882	// no longer anything immediate to do.	2443	// no longer anything immediate to do.
1883	}	2444	}
1884		2445
1885	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2446	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1886	ev_idle_init (idle_watcher, idle_cb);	2447	ev_idle_init (idle_watcher, idle_cb);
1887	ev_idle_start (loop, idle_cb);	2448	ev_idle_start (loop, idle_watcher);
1888		2449
1889		2450
1890	=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!
1891		2452
1892	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:
1893	prepare watchers get invoked before the process blocks and check watchers	2454	prepare watchers get invoked before the process blocks and check watchers
1894	afterwards.	2455	afterwards.
1895		2456
1896	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
1897	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>
…		…
1900	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,
1901	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
1902	called in pairs bracketing the blocking call.	2463	called in pairs bracketing the blocking call.
1903		2464
1904	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
1905	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
1906	variable changes, implement your own watchers, integrate net-snmp or a	2467	variable changes, implement your own watchers, integrate net-snmp or a
1907	coroutine library and lots more. They are also occasionally useful if	2468	coroutine library and lots more. They are also occasionally useful if
1908	you cache some data and want to flush it before blocking (for example,	2469	you cache some data and want to flush it before blocking (for example,
1909	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2470	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1910	watcher).	2471	watcher).
1911		2472
1912	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
1913	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
1914	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
1915	provide just this functionality). Then, in the check watcher you check for	2476	libraries provide exactly this functionality). Then, in the check watcher,
1916	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
1917	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
1918	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
1919	because you never know, you know?).	2480	nevertheless, because you never know, you know?).
1920		2481
1921	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
1922	coroutines into libev programs, by yielding to other active coroutines	2483	coroutines into libev programs, by yielding to other active coroutines
1923	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
1924	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
…		…
1927	loop from blocking if lower-priority coroutines are active, thus mapping	2488	loop from blocking if lower-priority coroutines are active, thus mapping
1928	low-priority coroutines to idle/background tasks).	2489	low-priority coroutines to idle/background tasks).
1929		2490
1930	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>)
1931	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
1932	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
1933	too) should not activate ("feed") events into libev. While libev fully	2496	activate ("feed") events into libev. While libev fully supports this, they
1934	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
1935	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
1936	(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
1937	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
1938	coexist peacefully with others).	2501	others).
1939		2502
1940	=head3 Watcher-Specific Functions and Data Members	2503	=head3 Watcher-Specific Functions and Data Members
1941		2504
1942	=over 4	2505	=over 4
1943		2506
…		…
1945		2508
1946	=item ev_check_init (ev_check *, callback)	2509	=item ev_check_init (ev_check *, callback)
1947		2510
1948	Initialises and configures the prepare or check watcher - they have no	2511	Initialises and configures the prepare or check watcher - they have no
1949	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2512	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1950	macros, but using them is utterly, utterly and completely pointless.	2513	macros, but using them is utterly, utterly, utterly and completely
		2514	pointless.
1951		2515
1952	=back	2516	=back
1953		2517
1954	=head3 Examples	2518	=head3 Examples
1955		2519
…		…
1968		2532
1969	static ev_io iow [nfd];	2533	static ev_io iow [nfd];
1970	static ev_timer tw;	2534	static ev_timer tw;
1971		2535
1972	static void	2536	static void
1973	io_cb (ev_loop *loop, ev_io *w, int revents)	2537	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1974	{	2538	{
1975	}	2539	}
1976		2540
1977	// create io watchers for each fd and a timer before blocking	2541	// create io watchers for each fd and a timer before blocking
1978	static void	2542	static void
1979	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2543	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1980	{	2544	{
1981	int timeout = 3600000;	2545	int timeout = 3600000;
1982	struct pollfd fds [nfd];	2546	struct pollfd fds [nfd];
1983	// actual code will need to loop here and realloc etc.	2547	// actual code will need to loop here and realloc etc.
1984	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2548	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1985		2549
1986	/* 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 */
1987	ev_timer_init (&tw, 0, timeout * 1e-3);	2551	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
1988	ev_timer_start (loop, &tw);	2552	ev_timer_start (loop, &tw);
1989		2553
1990	// create one ev_io per pollfd	2554	// create one ev_io per pollfd
1991	for (int i = 0; i < nfd; ++i)	2555	for (int i = 0; i < nfd; ++i)
1992	{	2556	{
…		…
1999	}	2563	}
2000	}	2564	}
2001		2565
2002	// stop all watchers after blocking	2566	// stop all watchers after blocking
2003	static void	2567	static void
2004	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2568	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2005	{	2569	{
2006	ev_timer_stop (loop, &tw);	2570	ev_timer_stop (loop, &tw);
2007		2571
2008	for (int i = 0; i < nfd; ++i)	2572	for (int i = 0; i < nfd; ++i)
2009	{	2573	{
…		…
2048	}	2612	}
2049		2613
2050	// do not ever call adns_afterpoll	2614	// do not ever call adns_afterpoll
2051		2615
2052	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
2053	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
2054	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
2055	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
2056	this.	2620	this approach, effectively embedding EV as a client into the horrible
		2621	libglib event loop.
2057		2622
2058	static gint	2623	static gint
2059	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2624	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2060	{	2625	{
2061	int got_events = 0;	2626	int got_events = 0;
…		…
2092	prioritise I/O.	2657	prioritise I/O.
2093		2658
2094	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
2095	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
2096	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
2097	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
2098	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
2099	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
2100	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 :)
2101		2667
2102	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
2103	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),
2104	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
2105	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
2106	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.
2107		2673
2108	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
2109	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
2110	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
2111	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
2112	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
2113	to C<0>, in which case the embed watcher will automatically execute the	2679	to give the embedded loop strictly lower priority for example).
2114	embedded loop sweep.
2115		2680
2116	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
2117	callback will be invoked whenever some events have been handled. You can	2682	will automatically execute the embedded loop sweep whenever necessary.
2118	set the callback to C<0> to avoid having to specify one if you are not
2119	interested in that.
2120		2683
2121	Also, there have not currently been made special provisions for forking:	2684	Fork detection will be handled transparently while the C<ev_embed> watcher
2122	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2685	is active, i.e., the embedded loop will automatically be forked when the
2123	but you will also have to stop and restart any C<ev_embed> watchers	2686	embedding loop forks. In other cases, the user is responsible for calling
2124	yourself.	2687	C<ev_loop_fork> on the embedded loop.
2125		2688
2126	Unfortunately, not all backends are embeddable, only the ones returned by	2689	Unfortunately, not all backends are embeddable: only the ones returned by
2127	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2690	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2128	portable one.	2691	portable one.
2129		2692
2130	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
2131	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
2132	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
2133	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.
2134		2705
2135	=head3 Watcher-Specific Functions and Data Members	2706	=head3 Watcher-Specific Functions and Data Members
2136		2707
2137	=over 4	2708	=over 4
2138		2709
…		…
2166	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
2167	used).	2738	used).
2168		2739
2169	struct ev_loop *loop_hi = ev_default_init (0);	2740	struct ev_loop *loop_hi = ev_default_init (0);
2170	struct ev_loop *loop_lo = 0;	2741	struct ev_loop *loop_lo = 0;
2171	struct ev_embed embed;	2742	ev_embed embed;
2172		2743
2173	// see if there is a chance of getting one that works	2744	// see if there is a chance of getting one that works
2174	// (remember that a flags value of 0 means autodetection)	2745	// (remember that a flags value of 0 means autodetection)
2175	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2746	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2176	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2747	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2190	kqueue implementation). Store the kqueue/socket-only event loop in	2761	kqueue implementation). Store the kqueue/socket-only event loop in
2191	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2762	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2192		2763
2193	struct ev_loop *loop = ev_default_init (0);	2764	struct ev_loop *loop = ev_default_init (0);
2194	struct ev_loop *loop_socket = 0;	2765	struct ev_loop *loop_socket = 0;
2195	struct ev_embed embed;	2766	ev_embed embed;
2196		2767
2197	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2768	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2198	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2769	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2199	{	2770	{
2200	ev_embed_init (&embed, 0, loop_socket);	2771	ev_embed_init (&embed, 0, loop_socket);
…		…
2215	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,
2216	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
2217	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
2218	handlers will be invoked, too, of course.	2789	handlers will be invoked, too, of course.
2219		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
2220	=head3 Watcher-Specific Functions and Data Members	2824	=head3 Watcher-Specific Functions and Data Members
2221		2825
2222	=over 4	2826	=over 4
2223		2827
2224	=item ev_fork_init (ev_signal *, callback)	2828	=item ev_fork_init (ev_signal *, callback)
…		…
2256	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
2257	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
2258	need elaborate support such as pthreads.	2862	need elaborate support such as pthreads.
2259		2863
2260	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
2261	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
2262	queue:	2866	queue:
2263		2867
2264	=over 4	2868	=over 4
2265		2869
2266	=item queueing from a signal handler context	2870	=item queueing from a signal handler context
2267		2871
2268	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
2269	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
2270	some fictitious SIGUSR1 handler:	2874	an example that does that for some fictitious SIGUSR1 handler:
2271		2875
2272	static ev_async mysig;	2876	static ev_async mysig;
2273		2877
2274	static void	2878	static void
2275	sigusr1_handler (void)	2879	sigusr1_handler (void)
…		…
2341	=over 4	2945	=over 4
2342		2946
2343	=item ev_async_init (ev_async *, callback)	2947	=item ev_async_init (ev_async *, callback)
2344		2948
2345	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
2346	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,
2347	believe me.	2951	trust me.
2348		2952
2349	=item ev_async_send (loop, ev_async *)	2953	=item ev_async_send (loop, ev_async *)
2350		2954
2351	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
2352	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
2353	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
2354	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
2355	section below on what exactly this means).	2959	section below on what exactly this means).
2356		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
2357	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
2358	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
2359	calls to C<ev_async_send>.	2968	repeated calls to C<ev_async_send> for the same event loop.
2360		2969
2361	=item bool = ev_async_pending (ev_async *)	2970	=item bool = ev_async_pending (ev_async *)
2362		2971
2363	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
2364	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
…		…
2367	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
2368	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,
2369	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
2370	quickly check whether invoking the loop might be a good idea.	2979	quickly check whether invoking the loop might be a good idea.
2371		2980
2372	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,
2373	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.
2374		2985
2375	=back	2986	=back
2376		2987
2377		2988
2378	=head1 OTHER FUNCTIONS	2989	=head1 OTHER FUNCTIONS
…		…
2382	=over 4	2993	=over 4
2383		2994
2384	=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)
2385		2996
2386	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
2387	callback on whichever event happens first and automatically stop both	2998	callback on whichever event happens first and automatically stops both
2388	watchers. This is useful if you want to wait for a single event on an fd	2999	watchers. This is useful if you want to wait for a single event on an fd
2389	or timeout without having to allocate/configure/start/stop/free one or	3000	or timeout without having to allocate/configure/start/stop/free one or
2390	more watchers yourself.	3001	more watchers yourself.
2391		3002
2392	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
2393	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
2394	C<events> set will be created and started.	3005	the given C<fd> and C<events> set will be created and started.
2395		3006
2396	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
2397	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
2398	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.
2399	dubious value.
2400		3010
2401	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
2402	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
2403	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>
2404	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.
2405		3019
2406	static void stdin_ready (int revents, void *arg)	3020	static void stdin_ready (int revents, void *arg)
2407	{	3021	{
		3022	if (revents & EV_READ)
		3023	/* stdin might have data for us, joy! */;
2408	if (revents & EV_TIMEOUT)	3024	else if (revents & EV_TIMEOUT)
2409	/* doh, nothing entered */;	3025	/* doh, nothing entered */;
2410	else if (revents & EV_READ)
2411	/* stdin might have data for us, joy! */;
2412	}	3026	}
2413		3027
2414	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3028	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2415		3029
2416	=item ev_feed_event (ev_loop *, watcher *, int revents)	3030	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2417		3031
2418	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
2419	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
2420	initialised but not necessarily started event watcher).	3034	initialised but not necessarily started event watcher).
2421		3035
2422	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3036	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2423		3037
2424	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
2425	the given events it.	3039	the given events it.
2426		3040
2427	=item ev_feed_signal_event (ev_loop *loop, int signum)	3041	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2428		3042
2429	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
2430	loop!).	3044	loop!).
2431		3045
2432	=back	3046	=back
…		…
2554		3168
2555	myclass obj;	3169	myclass obj;
2556	ev::io iow;	3170	ev::io iow;
2557	iow.set <myclass, &myclass::io_cb> (&obj);	3171	iow.set <myclass, &myclass::io_cb> (&obj);
2558		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
2559	=item w->set<function> (void *data = 0)	3203	=item w->set<function> (void *data = 0)
2560		3204
2561	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
2562	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
2563	C<data> member and is free for you to use.	3207	C<data> member and is free for you to use.
2564		3208
2565	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)>.
2566		3210
2567	See the method-C<set> above for more details.	3211	See the method-C<set> above for more details.
2568		3212
2569	Example:	3213	Example: Use a plain function as callback.
2570		3214
2571	static void io_cb (ev::io &w, int revents) { }	3215	static void io_cb (ev::io &w, int revents) { }
2572	iow.set <io_cb> ();	3216	iow.set <io_cb> ();
2573		3217
2574	=item w->set (struct ev_loop *)	3218	=item w->set (struct ev_loop *)
…		…
2612	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
2613	the constructor.	3257	the constructor.
2614		3258
2615	class myclass	3259	class myclass
2616	{	3260	{
2617	ev::io io; void io_cb (ev::io &w, int revents);	3261	ev::io io ; void io_cb (ev::io &w, int revents);
2618	ev:idle idle void idle_cb (ev::idle &w, int revents);	3262	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2619		3263
2620	myclass (int fd)	3264	myclass (int fd)
2621	{	3265	{
2622	io .set <myclass, &myclass::io_cb > (this);	3266	io .set <myclass, &myclass::io_cb > (this);
2623	idle.set <myclass, &myclass::idle_cb> (this);	3267	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2639	=item Perl	3283	=item Perl
2640		3284
2641	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
2642	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,
2643	there are additional modules that implement libev-compatible interfaces	3287	there are additional modules that implement libev-compatible interfaces
2644	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3288	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2645	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3289	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3290	and C<EV::Glib>).
2646		3291
2647	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
2648	L<http://software.schmorp.de/pkg/EV>.	3293	L<http://software.schmorp.de/pkg/EV>.
2649		3294
2650	=item Python	3295	=item Python
2651		3296
2652	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
2653	seems to be quite complete and well-documented. Note, however, that the	3298	seems to be quite complete and well-documented.
2654	patch they require for libev is outright dangerous as it breaks the ABI
2655	for everybody else, and therefore, should never be applied in an installed
2656	libev (if python requires an incompatible ABI then it needs to embed
2657	libev).
2658		3299
2659	=item Ruby	3300	=item Ruby
2660		3301
2661	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
2662	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
2663	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
2664	L<http://rev.rubyforge.org/>.	3305	L<http://rev.rubyforge.org/>.
2665		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
2666	=item D	3315	=item D
2667		3316
2668	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
2669	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/>.
2670		3324
2671	=back	3325	=back
2672		3326
2673		3327
2674	=head1 MACRO MAGIC	3328	=head1 MACRO MAGIC
…		…
2775		3429
2776	#define EV_STANDALONE 1	3430	#define EV_STANDALONE 1
2777	#include "ev.h"	3431	#include "ev.h"
2778		3432
2779	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++
2780	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
2781	as a bug).	3435	as a bug).
2782		3436
2783	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
2784	in your include path (e.g. in libev/ when using -Ilibev):	3438	in your include path (e.g. in libev/ when using -Ilibev):
2785		3439
…		…
2829		3483
2830	=head2 PREPROCESSOR SYMBOLS/MACROS	3484	=head2 PREPROCESSOR SYMBOLS/MACROS
2831		3485
2832	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
2833	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
2834	autoconf is noted for every option.	3488	autoconf is documented for every option.
2835		3489
2836	=over 4	3490	=over 4
2837		3491
2838	=item EV_STANDALONE	3492	=item EV_STANDALONE
2839		3493
…		…
2841	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
2842	implementations for some libevent functions (such as logging, which is not	3496	implementations for some libevent functions (such as logging, which is not
2843	supported). It will also not define any of the structs usually found in	3497	supported). It will also not define any of the structs usually found in
2844	F<event.h> that are not directly supported by the libev core alone.	3498	F<event.h> that are not directly supported by the libev core alone.
2845		3499
		3500	In stanbdalone mode, libev will still try to automatically deduce the
		3501	configuration, but has to be more conservative.
		3502
2846	=item EV_USE_MONOTONIC	3503	=item EV_USE_MONOTONIC
2847		3504
2848	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
2849	monotonic clock option at both compile time and runtime. Otherwise no use	3506	monotonic clock option at both compile time and runtime. Otherwise no
2850	of the monotonic clock option will be attempted. If you enable this, you	3507	use of the monotonic clock option will be attempted. If you enable this,
2851	usually have to link against librt or something similar. Enabling it when	3508	you usually have to link against librt or something similar. Enabling it
2852	the functionality isn't available is safe, though, although you have	3509	when the functionality isn't available is safe, though, although you have
2853	to make sure you link against any libraries where the C<clock_gettime>	3510	to make sure you link against any libraries where the C<clock_gettime>
2854	function is hiding in (often F<-lrt>).	3511	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2855		3512
2856	=item EV_USE_REALTIME	3513	=item EV_USE_REALTIME
2857		3514
2858	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
2859	real-time clock option at compile time (and assume its availability at	3516	real-time clock option at compile time (and assume its availability
2860	runtime if successful). Otherwise no use of the real-time clock option will	3517	at runtime if successful). Otherwise no use of the real-time clock
2861	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3518	option will be attempted. This effectively replaces C<gettimeofday>
2862	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3519	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2863	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>).
2864		3534
2865	=item EV_USE_NANOSLEEP	3535	=item EV_USE_NANOSLEEP
2866		3536
2867	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
2868	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 ()>.
…		…
2884		3554
2885	=item EV_SELECT_USE_FD_SET	3555	=item EV_SELECT_USE_FD_SET
2886		3556
2887	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>
2888	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
2889	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
2890	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
2891	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
2892	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,
2893	influence the size of the C<fd_set> used.	3563	configures the maximum size of the C<fd_set>.
2894		3564
2895	=item EV_SELECT_IS_WINSOCKET	3565	=item EV_SELECT_IS_WINSOCKET
2896		3566
2897	When defined to C<1>, the select backend will assume that	3567	When defined to C<1>, the select backend will assume that
2898	select/socket/connect etc. don't understand file descriptors but	3568	select/socket/connect etc. don't understand file descriptors but
…		…
3009	When doing priority-based operations, libev usually has to linearly search	3679	When doing priority-based operations, libev usually has to linearly search
3010	all the priorities, so having many of them (hundreds) uses a lot of space	3680	all the priorities, so having many of them (hundreds) uses a lot of space
3011	and time, so using the defaults of five priorities (-2 .. +2) is usually	3681	and time, so using the defaults of five priorities (-2 .. +2) is usually
3012	fine.	3682	fine.
3013		3683
3014	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
3015	C<0> will save some memory and CPU.	3685	both to C<0> will save some memory and CPU.
3016		3686
3017	=item EV_PERIODIC_ENABLE	3687	=item EV_PERIODIC_ENABLE
3018		3688
3019	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
3020	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
…		…
3027	code.	3697	code.
3028		3698
3029	=item EV_EMBED_ENABLE	3699	=item EV_EMBED_ENABLE
3030		3700
3031	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
3032	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.
3033		3704
3034	=item EV_STAT_ENABLE	3705	=item EV_STAT_ENABLE
3035		3706
3036	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
3037	defined to be C<0>, then they are not.	3708	defined to be C<0>, then they are not.
…		…
3047	defined to be C<0>, then they are not.	3718	defined to be C<0>, then they are not.
3048		3719
3049	=item EV_MINIMAL	3720	=item EV_MINIMAL
3050		3721
3051	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
3052	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
3053	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
3054	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.
3055		3736
3056	=item EV_PID_HASHSIZE	3737	=item EV_PID_HASHSIZE
3057		3738
3058	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
3059	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
…		…
3069	two).	3750	two).
3070		3751
3071	=item EV_USE_4HEAP	3752	=item EV_USE_4HEAP
3072		3753
3073	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
3074	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
3075	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
3076	noticeably faster performance with many (thousands) of watchers.	3757	faster performance with many (thousands) of watchers.
3077		3758
3078	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>
3079	(disabled).	3760	(disabled).
3080		3761
3081	=item EV_HEAP_CACHE_AT	3762	=item EV_HEAP_CACHE_AT
3082		3763
3083	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
3084	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
3085	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>),
3086	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,
3087	but avoids random read accesses on heap changes. This improves performance	3768	but avoids random read accesses on heap changes. This improves performance
3088	noticeably with with many (hundreds) of watchers.	3769	noticeably with many (hundreds) of watchers.
3089		3770
3090	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>
3091	(disabled).	3772	(disabled).
3092		3773
3093	=item EV_VERIFY	3774	=item EV_VERIFY
…		…
3099	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
3100	verification code will be called very frequently, which will slow down	3781	verification code will be called very frequently, which will slow down
3101	libev considerably.	3782	libev considerably.
3102		3783
3103	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
3104	C<0.>	3785	C<0>.
3105		3786
3106	=item EV_COMMON	3787	=item EV_COMMON
3107		3788
3108	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
3109	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
…		…
3126	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
3127	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
3128	their default definitions. One possible use for overriding these is to	3809	their default definitions. One possible use for overriding these is to
3129	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3810	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3130	method calls instead of plain function calls in C++.	3811	method calls instead of plain function calls in C++.
		3812
		3813	=back
3131		3814
3132	=head2 EXPORTED API SYMBOLS	3815	=head2 EXPORTED API SYMBOLS
3133		3816
3134	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
3135	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
…		…
3182	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:
3183		3866
3184	#include "ev_cpp.h"	3867	#include "ev_cpp.h"
3185	#include "ev.c"	3868	#include "ev.c"
3186		3869
		3870	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3187		3871
3188	=head1 THREADS AND COROUTINES	3872	=head2 THREADS AND COROUTINES
3189		3873
3190	=head2 THREADS	3874	=head3 THREADS
3191		3875
3192	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
3193	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
3194	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
3195	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.
3196		3883
3197	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
3198	parallel from multiple threads, calls with the same loop parameter must be	3885	concurrently from multiple threads, calls with the same loop parameter
3199	done serially (but can be done from different threads, as long as only one	3886	must be done serially (but can be done from different threads, as long as
3200	thread ever is inside a call at any point in time, e.g. by using a mutex	3887	only one thread ever is inside a call at any point in time, e.g. by using
3201	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".
3202		3894
3203	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
3204	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
3205	help you. I can give some generic advice however:	3897	help you, but here is some generic advice:
3206		3898
3207	=over 4	3899	=over 4
3208		3900
3209	=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
3210	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.
…		…
3222		3914
3223	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
3224	better than you currently do :-)	3916	better than you currently do :-)
3225		3917
3226	=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
3227	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
3228	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.
3229		3928
3230	=back	3929	=back
3231		3930
		3931	=head4 THREAD LOCKING EXAMPLE
		3932
3232	=head2 COROUTINES	3933	=head3 COROUTINES
3233		3934
3234	Libev is much more accommodating to coroutines ("cooperative threads"):	3935	Libev is very accommodating to coroutines ("cooperative threads"):
3235	libev fully supports nesting calls to it's functions from different	3936	libev fully supports nesting calls to its functions from different
3236	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3937	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3237	different coroutines and switch freely between both coroutines running the	3938	different coroutines, and switch freely between both coroutines running the
3238	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
3239	you must not do this from C<ev_periodic> reschedule callbacks.	3940	you must not do this from C<ev_periodic> reschedule callbacks.
3240		3941
3241	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
3242	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
3243	switches.	3944	they do not call any callbacks.
3244		3945
		3946	=head2 COMPILER WARNINGS
3245		3947
3246	=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.
3247		3951
3248	In this section the complexities of (many of) the algorithms used inside	3952	However, these are unavoidable for many reasons. For one, each compiler
3249	libev will be explained. For complexity discussions about backends see the	3953	has different warnings, and each user has different tastes regarding
3250	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.
3251		3956
3252	All of the following are about amortised time: If an array needs to be	3957	Another reason is that some compiler warnings require elaborate
3253	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
3254	happens asymptotically never with higher number of elements, so O(1) might	3959	maintainable.
3255	mean it might do a lengthy realloc operation in rare cases, but on average
3256	it is much faster and asymptotically approaches constant time.
3257		3960
3258	=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.
3259		3967
3260	=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.
3261		3973
3262	This means that, when you have a watcher that triggers in one hour and
3263	there are 100 watchers that would trigger before that then inserting will
3264	have to skip roughly seven (C<ld 100>) of these watchers.
3265		3974
3266	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3975	=head2 VALGRIND
3267		3976
3268	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
3269	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.
3270		3979
3271	=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:
3272		3982
3273	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.
3274		3986
3275	=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.
3276		3989
3277	=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.
3278		3994
3279	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
3280	correct watcher to remove. The lists are usually short (you don't usually	3996	make it into some kind of religion.
3281	have many watchers waiting for the same fd or signal).
3282		3997
3283	=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.
3284		4003
3285	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
3286	fixed position in the storage array.	4005	I suggest using suppression lists.
3287		4006
3288	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3289		4007
3290	A change means an I/O watcher gets started or stopped, which requires	4008	=head1 PORTABILITY NOTES
3291	libev to recalculate its status (and possibly tell the kernel, depending
3292	on backend and whether C<ev_io_set> was used).
3293		4009
3294	=item Activating one watcher (putting it into the pending state): O(1)
3295
3296	=item Priority handling: O(number_of_priorities)
3297
3298	Priorities are implemented by allocating some space for each
3299	priority. When doing priority-based operations, libev usually has to
3300	linearly search all the priorities, but starting/stopping and activating
3301	watchers becomes O(1) w.r.t. priority handling.
3302
3303	=item Sending an ev_async: O(1)
3304
3305	=item Processing ev_async_send: O(number_of_async_watchers)
3306
3307	=item Processing signals: O(max_signal_number)
3308
3309	Sending involves a system call I<iff> there were no other C<ev_async_send>
3310	calls in the current loop iteration. Checking for async and signal events
3311	involves iterating over all running async watchers or all signal numbers.
3312
3313	=back
3314
3315
3316	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4010	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3317		4011
3318	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
3319	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
3320	model. Libev still offers limited functionality on this platform in	4014	model. Libev still offers limited functionality on this platform in
3321	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
…		…
3328	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).
3329		4023
3330	There is no supported compilation method available on windows except	4024	There is no supported compilation method available on windows except
3331	embedding it into other applications.	4025	embedding it into other applications.
3332		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
3333	Not a libev limitation but worth mentioning: windows apparently doesn't	4030	Not a libev limitation but worth mentioning: windows apparently doesn't
3334	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
3335	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,
3336	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
3337	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
3338	available).	4035	available).
3339		4036
3340	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
3341	the abysmal performance of winsockets, using a large number of sockets	4038	the abysmal performance of winsockets, using a large number of sockets
3342	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
3343	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
3344	different implementation for windows, as libev offers the POSIX readiness	4041	different implementation for windows, as libev offers the POSIX readiness
3345	notification model, which cannot be implemented efficiently on windows	4042	notification model, which cannot be implemented efficiently on windows
3346	(Microsoft monopoly games).	4043	(due to Microsoft monopoly games).
3347		4044
3348	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
3349	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
3350	of F<ev.h>:	4047	of F<ev.h>:
3351		4048
…		…
3353	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	4050	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3354		4051
3355	#include "ev.h"	4052	#include "ev.h"
3356		4053
3357	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
3358	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!):
3359		4056
3360	#include "evwrap.h"	4057	#include "evwrap.h"
3361	#include "ev.c"	4058	#include "ev.c"
3362		4059
3363	=over 4	4060	=over 4
…		…
3387		4084
3388	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
3389	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
3390	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
3391	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
3392	previous thread in each. Great).	4089	previous thread in each. Sounds great!).
3393		4090
3394	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>
3395	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
3396	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
3397	select emulation on windows).	4094	other interpreters do their own select emulation on windows).
3398		4095
3399	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
3400	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>
3401	or something like this inside Microsoft). You can increase this by calling	4098	fetish or something like this inside Microsoft). You can increase this
3402	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4099	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3403	arbitrary limit), but is broken in many versions of the Microsoft runtime	4100	(another arbitrary limit), but is broken in many versions of the Microsoft
3404	libraries.
3405
3406	This might get you to about C<512> or C<2048> sockets (depending on	4101	runtime libraries. This might get you to about C<512> or C<2048> sockets
3407	windows version and/or the phase of the moon). To get more, you need to	4102	(depending on windows version and/or the phase of the moon). To get more,
3408	wrap all I/O functions and provide your own fd management, but the cost of	4103	you need to wrap all I/O functions and provide your own fd management, but
3409	calling select (O(n²)) will likely make this unworkable.	4104	the cost of calling select (O(n²)) will likely make this unworkable.
3410		4105
3411	=back	4106	=back
3412		4107
3413
3414	=head1 PORTABILITY REQUIREMENTS	4108	=head2 PORTABILITY REQUIREMENTS
3415		4109
3416	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
3417	additional extensions:	4111	backend-specific APIs, libev relies on a few additional extensions:
3418		4112
3419	=over 4	4113	=over 4
3420		4114
3421	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	4115	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3422	calling conventions regardless of C<ev_watcher_type *>.	4116	calling conventions regardless of C<ev_watcher_type *>.
…		…
3428	calls them using an C<ev_watcher *> internally.	4122	calls them using an C<ev_watcher *> internally.
3429		4123
3430	=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
3431		4125
3432	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
3433	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
3434	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
3435	believed to be sufficiently portable.	4129	believed to be sufficiently portable.
3436		4130
3437	=item C<sigprocmask> must work in a threaded environment	4131	=item C<sigprocmask> must work in a threaded environment
3438		4132
…		…
3447	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
3448	well.	4142	well.
3449		4143
3450	=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
3451		4145
3452	To improve portability and simplify using libev, libev uses C<long>	4146	To improve portability and simplify its API, libev uses C<long> internally
3453	internally instead of C<size_t> when allocating its data structures. On	4147	instead of C<size_t> when allocating its data structures. On non-POSIX
3454	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4148	systems (Microsoft...) this might be unexpectedly low, but is still at
3455	is still at least 31 bits everywhere, which is enough for hundreds of	4149	least 31 bits everywhere, which is enough for hundreds of millions of
3456	millions of watchers.	4150	watchers.
3457		4151
3458	=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
3459		4153
3460	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
3461	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
3462	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
3463	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.
3464		4160
3465	=back	4161	=back
3466		4162
3467	If you know of other additional requirements drop me a note.	4163	If you know of other additional requirements drop me a note.
3468		4164
3469		4165
3470	=head1 COMPILER WARNINGS	4166	=head1 ALGORITHMIC COMPLEXITIES
3471		4167
3472	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
3473	lot of warnings when compiling libev code. Some people are apparently	4169	libev will be documented. For complexity discussions about backends see
3474	scared by this.	4170	the documentation for C<ev_default_init>.
3475		4171
3476	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
3477	has different warnings, and each user has different tastes regarding	4173	extended, libev needs to realloc and move the whole array, but this
3478	warning options. "Warn-free" code therefore cannot be a goal except when	4174	happens asymptotically rarer with higher number of elements, so O(1) might
3479	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.
3480		4177
3481	Another reason is that some compiler warnings require elaborate	4178	=over 4
3482	workarounds, or other changes to the code that make it less clear and less
3483	maintainable.
3484		4179
3485	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)
3486	wrong (because they don't actually warn about the condition their message
3487	seems to warn about).
3488		4181
3489	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
3490	"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
3491	with any compiler warnings enabled unless you are prepared to cope with	4184	have to skip roughly seven (C<ld 100>) of these watchers.
3492	them (e.g. by ignoring them). Remember that warnings are just that:
3493	warnings, not errors, or proof of bugs.
3494		4185
		4186	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3495		4187
3496	=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.
3497		4190
3498	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)
3499	highly useful, but valgrind reports are very hard to interpret.
3500		4192
3501	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.
3502	in libev, then check twice: If valgrind reports something like:
3503		4194
3504	==2274== definitely lost: 0 bytes in 0 blocks.	4195	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3505	==2274== possibly lost: 0 bytes in 0 blocks.
3506	==2274== still reachable: 256 bytes in 1 blocks.
3507		4196
3508	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))
3509	valgrind might report kernel bugs as if it were a bug in libev, or it
3510	might be confused (it is a very good tool, but only a tool).
3511		4198
3512	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
3513	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
3514	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
3515	no bug" answer and take the chance of learning how to interpret valgrind	4202	is rare).
3516	properly.
3517		4203
3518	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)
3519	I suggest using suppression lists.
3520		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
3521		4312
3522	=head1 AUTHOR	4313	=head1 AUTHOR
3523		4314
3524	Marc Lehmann <libev@schmorp.de>.	4315	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3525		4316

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