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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
725	=item ev_loop_verify (loop)	861	=item ev_loop_verify (loop)
726		862
727	This function only does something when C<EV_VERIFY> support has been	863	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	864	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	865	through all internal structures and checks them for validity. If anything
730	an error message to standard error and call C<abort ()>.	866	is found to be inconsistent, it will print an error message to standard
		867	error and call C<abort ()>.
731		868
732	This can be used to catch bugs inside libev itself: under normal	869	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	870	circumstances, this function will never abort as of course libev keeps its
734	data structures consistent.	871	data structures consistent.
735		872
736	=back	873	=back
737		874
738		875
739	=head1 ANATOMY OF A WATCHER	876	=head1 ANATOMY OF A WATCHER
740		877
		878	In the following description, uppercase C<TYPE> in names stands for the
		879	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		880	watchers and C<ev_io_start> for I/O watchers.
		881
741	A watcher is a structure that you create and register to record your	882	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	883	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:	884	become readable, you would create an C<ev_io> watcher for that:
744		885
745	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	886	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
746	{	887	{
747	ev_io_stop (w);	888	ev_io_stop (w);
748	ev_unloop (loop, EVUNLOOP_ALL);	889	ev_unloop (loop, EVUNLOOP_ALL);
749	}	890	}
750		891
751	struct ev_loop *loop = ev_default_loop (0);	892	struct ev_loop *loop = ev_default_loop (0);
		893
752	struct ev_io stdin_watcher;	894	ev_io stdin_watcher;
		895
753	ev_init (&stdin_watcher, my_cb);	896	ev_init (&stdin_watcher, my_cb);
754	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	897	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
755	ev_io_start (loop, &stdin_watcher);	898	ev_io_start (loop, &stdin_watcher);
		899
756	ev_loop (loop, 0);	900	ev_loop (loop, 0);
757		901
758	As you can see, you are responsible for allocating the memory for your	902	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,	903	watcher structures (and it is I<usually> a bad idea to do this on the
760	although this can sometimes be quite valid).	904	stack).
		905
		906	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		907	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
761		908
762	Each watcher structure must be initialised by a call to C<ev_init	909	Each watcher structure must be initialised by a call to C<ev_init
763	(watcher *, callback)>, which expects a callback to be provided. This	910	(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	911	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	912	watchers, each time the event loop detects that the file descriptor given
766	is readable and/or writable).	913	is readable and/or writable).
767		914
768	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	915	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	916	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	917	is also a macro to combine initialisation and setting in one call: C<<
771	(watcher *, callback, ...) >>.	918	ev_TYPE_init (watcher *, callback, ...) >>.
772		919
773	To make the watcher actually watch out for events, you have to start it	920	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	921	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	922	*) >>), and you can stop watching for events at any time by calling the
776	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	923	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
777		924
778	As long as your watcher is active (has been started but not stopped) you	925	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	926	must not touch the values stored in it. Most specifically you must never
780	reinitialise it or call its C<set> macro.	927	reinitialise it or call its C<ev_TYPE_set> macro.
781		928
782	Each and every callback receives the event loop pointer as first, the	929	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	930	registered watcher structure as second, and a bitset of received events as
784	third argument.	931	third argument.
785		932
…		…
843		990
844	=item C<EV_ASYNC>	991	=item C<EV_ASYNC>
845		992
846	The given async watcher has been asynchronously notified (see C<ev_async>).	993	The given async watcher has been asynchronously notified (see C<ev_async>).
847		994
		995	=item C<EV_CUSTOM>
		996
		997	Not ever sent (or otherwise used) by libev itself, but can be freely used
		998	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		999
848	=item C<EV_ERROR>	1000	=item C<EV_ERROR>
849		1001
850	An unspecified error has occurred, the watcher has been stopped. This might	1002	An unspecified error has occurred, the watcher has been stopped. This might
851	happen because the watcher could not be properly started because libev	1003	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	1004	ran out of memory, a file descriptor was found to be closed or any other
		1005	problem. Libev considers these application bugs.
		1006
853	problem. You best act on it by reporting the problem and somehow coping	1007	You best act on it by reporting the problem and somehow coping with the
854	with the watcher being stopped.	1008	watcher being stopped. Note that well-written programs should not receive
		1009	an error ever, so when your watcher receives it, this usually indicates a
		1010	bug in your program.
855		1011
856	Libev will usually signal a few "dummy" events together with an error,	1012	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	1013	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	1014	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	1015	the error from read() or write(). This will not work in multi-threaded
860	programs, though, so beware.	1016	programs, though, as the fd could already be closed and reused for another
		1017	thing, so beware.
861		1018
862	=back	1019	=back
863		1020
864	=head2 GENERIC WATCHER FUNCTIONS	1021	=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		1022
869	=over 4	1023	=over 4
870		1024
871	=item C<ev_init> (ev_TYPE *watcher, callback)	1025	=item C<ev_init> (ev_TYPE *watcher, callback)
872		1026
…		…
878	which rolls both calls into one.	1032	which rolls both calls into one.
879		1033
880	You can reinitialise a watcher at any time as long as it has been stopped	1034	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.	1035	(or never started) and there are no pending events outstanding.
882		1036
883	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1037	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
884	int revents)>.	1038	int revents)>.
		1039
		1040	Example: Initialise an C<ev_io> watcher in two steps.
		1041
		1042	ev_io w;
		1043	ev_init (&w, my_cb);
		1044	ev_io_set (&w, STDIN_FILENO, EV_READ);
885		1045
886	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1046	=item C<ev_TYPE_set> (ev_TYPE *, [args])
887		1047
888	This macro initialises the type-specific parts of a watcher. You need to	1048	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	1049	call C<ev_init> at least once before you call this macro, but you can
…		…
892	difference to the C<ev_init> macro).	1052	difference to the C<ev_init> macro).
893		1053
894	Although some watcher types do not have type-specific arguments	1054	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.	1055	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
896		1056
		1057	See C<ev_init>, above, for an example.
		1058
897	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1059	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
898		1060
899	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1061	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	1062	calls into a single call. This is the most convenient method to initialise
901	a watcher. The same limitations apply, of course.	1063	a watcher. The same limitations apply, of course.
902		1064
		1065	Example: Initialise and set an C<ev_io> watcher in one step.
		1066
		1067	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1068
903	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1069	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
904		1070
905	Starts (activates) the given watcher. Only active watchers will receive	1071	Starts (activates) the given watcher. Only active watchers will receive
906	events. If the watcher is already active nothing will happen.	1072	events. If the watcher is already active nothing will happen.
907		1073
		1074	Example: Start the C<ev_io> watcher that is being abused as example in this
		1075	whole section.
		1076
		1077	ev_io_start (EV_DEFAULT_UC, &w);
		1078
908	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1079	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
909		1080
910	Stops the given watcher again (if active) and clears the pending	1081	Stops the given watcher if active, and clears the pending status (whether
		1082	the watcher was active or not).
		1083
911	status. It is possible that stopped watchers are pending (for example,	1084	It is possible that stopped watchers are pending - for example,
912	non-repeating timers are being stopped when they become pending), but	1085	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	1086	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	1087	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.	1088	therefore a good idea to always call its C<ev_TYPE_stop> function.
916		1089
917	=item bool ev_is_active (ev_TYPE *watcher)	1090	=item bool ev_is_active (ev_TYPE *watcher)
918		1091
919	Returns a true value iff the watcher is active (i.e. it has been started	1092	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	1093	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>	1119	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
947	(default: C<-2>). Pending watchers with higher priority will be invoked	1120	(default: C<-2>). Pending watchers with higher priority will be invoked
948	before watchers with lower priority, but priority will not keep watchers	1121	before watchers with lower priority, but priority will not keep watchers
949	from being executed (except for C<ev_idle> watchers).	1122	from being executed (except for C<ev_idle> watchers).
950		1123
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	1124	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.	1125	you need to look at C<ev_idle> watchers, which provide this functionality.
958		1126
959	You I<must not> change the priority of a watcher as long as it is active or	1127	You I<must not> change the priority of a watcher as long as it is active or
960	pending.	1128	pending.
961		1129
		1130	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1131	fine, as long as you do not mind that the priority value you query might
		1132	or might not have been clamped to the valid range.
		1133
962	The default priority used by watchers when no priority has been set is	1134	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 :).	1135	always C<0>, which is supposed to not be too high and not be too low :).
964		1136
965	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1137	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	1138	priorities.
967	or might not have been adjusted to be within valid range.
968		1139
969	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1140	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
970		1141
971	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1142	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	1143	C<loop> nor C<revents> need to be valid as long as the watcher callback
973	can deal with that fact.	1144	can deal with that fact, as both are simply passed through to the
		1145	callback.
974		1146
975	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1147	=item int ev_clear_pending (loop, ev_TYPE *watcher)
976		1148
977	If the watcher is pending, this function returns clears its pending status	1149	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	1150	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>.	1151	watcher isn't pending it does nothing and returns C<0>.
980		1152
		1153	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1154	callback to be invoked, which can be accomplished with this function.
		1155
981	=back	1156	=back
982		1157
983		1158
984	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1159	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
985		1160
986	Each watcher has, by default, a member C<void *data> that you can change	1161	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	1162	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	1163	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	1164	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	1165	member, you can also "subclass" the watcher type and provide your own
991	data:	1166	data:
992		1167
993	struct my_io	1168	struct my_io
994	{	1169	{
995	struct ev_io io;	1170	ev_io io;
996	int otherfd;	1171	int otherfd;
997	void *somedata;	1172	void *somedata;
998	struct whatever *mostinteresting;	1173	struct whatever *mostinteresting;
999	}	1174	};
		1175
		1176	...
		1177	struct my_io w;
		1178	ev_io_init (&w.io, my_cb, fd, EV_READ);
1000		1179
1001	And since your callback will be called with a pointer to the watcher, you	1180	And since your callback will be called with a pointer to the watcher, you
1002	can cast it back to your own type:	1181	can cast it back to your own type:
1003		1182
1004	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1183	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1005	{	1184	{
1006	struct my_io *w = (struct my_io *)w_;	1185	struct my_io *w = (struct my_io *)w_;
1007	...	1186	...
1008	}	1187	}
1009		1188
1010	More interesting and less C-conformant ways of casting your callback type	1189	More interesting and less C-conformant ways of casting your callback type
1011	instead have been omitted.	1190	instead have been omitted.
1012		1191
1013	Another common scenario is having some data structure with multiple	1192	Another common scenario is to use some data structure with multiple
1014	watchers:	1193	embedded watchers:
1015		1194
1016	struct my_biggy	1195	struct my_biggy
1017	{	1196	{
1018	int some_data;	1197	int some_data;
1019	ev_timer t1;	1198	ev_timer t1;
1020	ev_timer t2;	1199	ev_timer t2;
1021	}	1200	}
1022		1201
1023	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1202	In this case getting the pointer to C<my_biggy> is a bit more
1024	you need to use C<offsetof>:	1203	complicated: Either you store the address of your C<my_biggy> struct
		1204	in the C<data> member of the watcher (for woozies), or you need to use
		1205	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1206	programmers):
1025		1207
1026	#include <stddef.h>	1208	#include <stddef.h>
1027		1209
1028	static void	1210	static void
1029	t1_cb (EV_P_ struct ev_timer *w, int revents)	1211	t1_cb (EV_P_ ev_timer *w, int revents)
1030	{	1212	{
1031	struct my_biggy big = (struct my_biggy *	1213	struct my_biggy big = (struct my_biggy *)
1032	(((char *)w) - offsetof (struct my_biggy, t1));	1214	(((char *)w) - offsetof (struct my_biggy, t1));
1033	}	1215	}
1034		1216
1035	static void	1217	static void
1036	t2_cb (EV_P_ struct ev_timer *w, int revents)	1218	t2_cb (EV_P_ ev_timer *w, int revents)
1037	{	1219	{
1038	struct my_biggy big = (struct my_biggy *	1220	struct my_biggy big = (struct my_biggy *)
1039	(((char *)w) - offsetof (struct my_biggy, t2));	1221	(((char *)w) - offsetof (struct my_biggy, t2));
1040	}	1222	}
		1223
		1224	=head2 WATCHER PRIORITY MODELS
		1225
		1226	Many event loops support I<watcher priorities>, which are usually small
		1227	integers that influence the ordering of event callback invocation
		1228	between watchers in some way, all else being equal.
		1229
		1230	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1231	description for the more technical details such as the actual priority
		1232	range.
		1233
		1234	There are two common ways how these these priorities are being interpreted
		1235	by event loops:
		1236
		1237	In the more common lock-out model, higher priorities "lock out" invocation
		1238	of lower priority watchers, which means as long as higher priority
		1239	watchers receive events, lower priority watchers are not being invoked.
		1240
		1241	The less common only-for-ordering model uses priorities solely to order
		1242	callback invocation within a single event loop iteration: Higher priority
		1243	watchers are invoked before lower priority ones, but they all get invoked
		1244	before polling for new events.
		1245
		1246	Libev uses the second (only-for-ordering) model for all its watchers
		1247	except for idle watchers (which use the lock-out model).
		1248
		1249	The rationale behind this is that implementing the lock-out model for
		1250	watchers is not well supported by most kernel interfaces, and most event
		1251	libraries will just poll for the same events again and again as long as
		1252	their callbacks have not been executed, which is very inefficient in the
		1253	common case of one high-priority watcher locking out a mass of lower
		1254	priority ones.
		1255
		1256	Static (ordering) priorities are most useful when you have two or more
		1257	watchers handling the same resource: a typical usage example is having an
		1258	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1259	timeouts. Under load, data might be received while the program handles
		1260	other jobs, but since timers normally get invoked first, the timeout
		1261	handler will be executed before checking for data. In that case, giving
		1262	the timer a lower priority than the I/O watcher ensures that I/O will be
		1263	handled first even under adverse conditions (which is usually, but not
		1264	always, what you want).
		1265
		1266	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1267	will only be executed when no same or higher priority watchers have
		1268	received events, they can be used to implement the "lock-out" model when
		1269	required.
		1270
		1271	For example, to emulate how many other event libraries handle priorities,
		1272	you can associate an C<ev_idle> watcher to each such watcher, and in
		1273	the normal watcher callback, you just start the idle watcher. The real
		1274	processing is done in the idle watcher callback. This causes libev to
		1275	continously poll and process kernel event data for the watcher, but when
		1276	the lock-out case is known to be rare (which in turn is rare :), this is
		1277	workable.
		1278
		1279	Usually, however, the lock-out model implemented that way will perform
		1280	miserably under the type of load it was designed to handle. In that case,
		1281	it might be preferable to stop the real watcher before starting the
		1282	idle watcher, so the kernel will not have to process the event in case
		1283	the actual processing will be delayed for considerable time.
		1284
		1285	Here is an example of an I/O watcher that should run at a strictly lower
		1286	priority than the default, and which should only process data when no
		1287	other events are pending:
		1288
		1289	ev_idle idle; // actual processing watcher
		1290	ev_io io; // actual event watcher
		1291
		1292	static void
		1293	io_cb (EV_P_ ev_io *w, int revents)
		1294	{
		1295	// stop the I/O watcher, we received the event, but
		1296	// are not yet ready to handle it.
		1297	ev_io_stop (EV_A_ w);
		1298
		1299	// start the idle watcher to ahndle the actual event.
		1300	// it will not be executed as long as other watchers
		1301	// with the default priority are receiving events.
		1302	ev_idle_start (EV_A_ &idle);
		1303	}
		1304
		1305	static void
		1306	idle_cb (EV_P_ ev_idle *w, int revents)
		1307	{
		1308	// actual processing
		1309	read (STDIN_FILENO, ...);
		1310
		1311	// have to start the I/O watcher again, as
		1312	// we have handled the event
		1313	ev_io_start (EV_P_ &io);
		1314	}
		1315
		1316	// initialisation
		1317	ev_idle_init (&idle, idle_cb);
		1318	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1319	ev_io_start (EV_DEFAULT_ &io);
		1320
		1321	In the "real" world, it might also be beneficial to start a timer, so that
		1322	low-priority connections can not be locked out forever under load. This
		1323	enables your program to keep a lower latency for important connections
		1324	during short periods of high load, while not completely locking out less
		1325	important ones.
1041		1326
1042		1327
1043	=head1 WATCHER TYPES	1328	=head1 WATCHER TYPES
1044		1329
1045	This section describes each watcher in detail, but will not repeat	1330	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	1354	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	1355	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	1356	descriptors to non-blocking mode is also usually a good idea (but not
1072	required if you know what you are doing).	1357	required if you know what you are doing).
1073		1358
1074	If you must do this, then force the use of a known-to-be-good backend	1359	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	1360	known-to-be-good backend (at the time of this writing, this includes only
1076	C<EVBACKEND_POLL>).	1361	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1362	descriptors for which non-blocking operation makes no sense (such as
		1363	files) - libev doesn't guarentee any specific behaviour in that case.
1077		1364
1078	Another thing you have to watch out for is that it is quite easy to	1365	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	1366	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	1367	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	1368	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	1369	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	1370	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	1371	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.	1372	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1086		1373
1087	If you cannot run the fd in non-blocking mode (for example you should not	1374	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	1375	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	1376	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	1377	interface such as poll (fortunately in our Xlib example, Xlib already
1091	its own, so its quite safe to use).	1378	does this on its own, so its quite safe to use). Some people additionally
		1379	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1380	indefinitely.
		1381
		1382	But really, best use non-blocking mode.
1092		1383
1093	=head3 The special problem of disappearing file descriptors	1384	=head3 The special problem of disappearing file descriptors
1094		1385
1095	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1386	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,	1387	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	1388	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	1389	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	1390	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	1391	registered with libev, there is no efficient way to see that this is, in
1101	fact, a different file descriptor.	1392	fact, a different file descriptor.
1102		1393
…		…
1133	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1424	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1134	C<EVBACKEND_POLL>.	1425	C<EVBACKEND_POLL>.
1135		1426
1136	=head3 The special problem of SIGPIPE	1427	=head3 The special problem of SIGPIPE
1137		1428
1138	While not really specific to libev, it is easy to forget about SIGPIPE:	1429	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	1430	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	1431	sent a SIGPIPE, which, by default, aborts your program. For most programs
1141	programs this is sensible behaviour, for daemons, this is usually	1432	this is sensible behaviour, for daemons, this is usually undesirable.
1142	undesirable.
1143		1433
1144	So when you encounter spurious, unexplained daemon exits, make sure you	1434	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	1435	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).	1436	somewhere, as that would have given you a big clue).
1147		1437
…		…
1153	=item ev_io_init (ev_io *, callback, int fd, int events)	1443	=item ev_io_init (ev_io *, callback, int fd, int events)
1154		1444
1155	=item ev_io_set (ev_io *, int fd, int events)	1445	=item ev_io_set (ev_io *, int fd, int events)
1156		1446
1157	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1447	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	1448	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.	1449	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1160		1450
1161	=item int fd [read-only]	1451	=item int fd [read-only]
1162		1452
1163	The file descriptor being watched.	1453	The file descriptor being watched.
1164		1454
…		…
1173	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1463	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	1464	readable, but only once. Since it is likely line-buffered, you could
1175	attempt to read a whole line in the callback.	1465	attempt to read a whole line in the callback.
1176		1466
1177	static void	1467	static void
1178	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1468	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1179	{	1469	{
1180	ev_io_stop (loop, w);	1470	ev_io_stop (loop, w);
1181	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1471	.. read from stdin here (or from w->fd) and handle any I/O errors
1182	}	1472	}
1183		1473
1184	...	1474	...
1185	struct ev_loop *loop = ev_default_init (0);	1475	struct ev_loop *loop = ev_default_init (0);
1186	struct ev_io stdin_readable;	1476	ev_io stdin_readable;
1187	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1477	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1188	ev_io_start (loop, &stdin_readable);	1478	ev_io_start (loop, &stdin_readable);
1189	ev_loop (loop, 0);	1479	ev_loop (loop, 0);
1190		1480
1191		1481
…		…
1194	Timer watchers are simple relative timers that generate an event after a	1484	Timer watchers are simple relative timers that generate an event after a
1195	given time, and optionally repeating in regular intervals after that.	1485	given time, and optionally repeating in regular intervals after that.
1196		1486
1197	The timers are based on real time, that is, if you register an event that	1487	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	1488	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	1489	year, it will still time out after (roughly) one hour. "Roughly" because
1200	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1490	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1201	monotonic clock option helps a lot here).	1491	monotonic clock option helps a lot here).
		1492
		1493	The callback is guaranteed to be invoked only I<after> its timeout has
		1494	passed (not I<at>, so on systems with very low-resolution clocks this
		1495	might introduce a small delay). If multiple timers become ready during the
		1496	same loop iteration then the ones with earlier time-out values are invoked
		1497	before ones of the same priority with later time-out values (but this is
		1498	no longer true when a callback calls C<ev_loop> recursively).
		1499
		1500	=head3 Be smart about timeouts
		1501
		1502	Many real-world problems involve some kind of timeout, usually for error
		1503	recovery. A typical example is an HTTP request - if the other side hangs,
		1504	you want to raise some error after a while.
		1505
		1506	What follows are some ways to handle this problem, from obvious and
		1507	inefficient to smart and efficient.
		1508
		1509	In the following, a 60 second activity timeout is assumed - a timeout that
		1510	gets reset to 60 seconds each time there is activity (e.g. each time some
		1511	data or other life sign was received).
		1512
		1513	=over 4
		1514
		1515	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1516
		1517	This is the most obvious, but not the most simple way: In the beginning,
		1518	start the watcher:
		1519
		1520	ev_timer_init (timer, callback, 60., 0.);
		1521	ev_timer_start (loop, timer);
		1522
		1523	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1524	and start it again:
		1525
		1526	ev_timer_stop (loop, timer);
		1527	ev_timer_set (timer, 60., 0.);
		1528	ev_timer_start (loop, timer);
		1529
		1530	This is relatively simple to implement, but means that each time there is
		1531	some activity, libev will first have to remove the timer from its internal
		1532	data structure and then add it again. Libev tries to be fast, but it's
		1533	still not a constant-time operation.
		1534
		1535	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1536
		1537	This is the easiest way, and involves using C<ev_timer_again> instead of
		1538	C<ev_timer_start>.
		1539
		1540	To implement this, configure an C<ev_timer> with a C<repeat> value
		1541	of C<60> and then call C<ev_timer_again> at start and each time you
		1542	successfully read or write some data. If you go into an idle state where
		1543	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1544	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1545
		1546	That means you can ignore both the C<ev_timer_start> function and the
		1547	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1548	member and C<ev_timer_again>.
		1549
		1550	At start:
		1551
		1552	ev_init (timer, callback);
		1553	timer->repeat = 60.;
		1554	ev_timer_again (loop, timer);
		1555
		1556	Each time there is some activity:
		1557
		1558	ev_timer_again (loop, timer);
		1559
		1560	It is even possible to change the time-out on the fly, regardless of
		1561	whether the watcher is active or not:
		1562
		1563	timer->repeat = 30.;
		1564	ev_timer_again (loop, timer);
		1565
		1566	This is slightly more efficient then stopping/starting the timer each time
		1567	you want to modify its timeout value, as libev does not have to completely
		1568	remove and re-insert the timer from/into its internal data structure.
		1569
		1570	It is, however, even simpler than the "obvious" way to do it.
		1571
		1572	=item 3. Let the timer time out, but then re-arm it as required.
		1573
		1574	This method is more tricky, but usually most efficient: Most timeouts are
		1575	relatively long compared to the intervals between other activity - in
		1576	our example, within 60 seconds, there are usually many I/O events with
		1577	associated activity resets.
		1578
		1579	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1580	but remember the time of last activity, and check for a real timeout only
		1581	within the callback:
		1582
		1583	ev_tstamp last_activity; // time of last activity
		1584
		1585	static void
		1586	callback (EV_P_ ev_timer *w, int revents)
		1587	{
		1588	ev_tstamp now = ev_now (EV_A);
		1589	ev_tstamp timeout = last_activity + 60.;
		1590
		1591	// if last_activity + 60. is older than now, we did time out
		1592	if (timeout < now)
		1593	{
		1594	// timeout occured, take action
		1595	}
		1596	else
		1597	{
		1598	// callback was invoked, but there was some activity, re-arm
		1599	// the watcher to fire in last_activity + 60, which is
		1600	// guaranteed to be in the future, so "again" is positive:
		1601	w->repeat = timeout - now;
		1602	ev_timer_again (EV_A_ w);
		1603	}
		1604	}
		1605
		1606	To summarise the callback: first calculate the real timeout (defined
		1607	as "60 seconds after the last activity"), then check if that time has
		1608	been reached, which means something I<did>, in fact, time out. Otherwise
		1609	the callback was invoked too early (C<timeout> is in the future), so
		1610	re-schedule the timer to fire at that future time, to see if maybe we have
		1611	a timeout then.
		1612
		1613	Note how C<ev_timer_again> is used, taking advantage of the
		1614	C<ev_timer_again> optimisation when the timer is already running.
		1615
		1616	This scheme causes more callback invocations (about one every 60 seconds
		1617	minus half the average time between activity), but virtually no calls to
		1618	libev to change the timeout.
		1619
		1620	To start the timer, simply initialise the watcher and set C<last_activity>
		1621	to the current time (meaning we just have some activity :), then call the
		1622	callback, which will "do the right thing" and start the timer:
		1623
		1624	ev_init (timer, callback);
		1625	last_activity = ev_now (loop);
		1626	callback (loop, timer, EV_TIMEOUT);
		1627
		1628	And when there is some activity, simply store the current time in
		1629	C<last_activity>, no libev calls at all:
		1630
		1631	last_actiivty = ev_now (loop);
		1632
		1633	This technique is slightly more complex, but in most cases where the
		1634	time-out is unlikely to be triggered, much more efficient.
		1635
		1636	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1637	callback :) - just change the timeout and invoke the callback, which will
		1638	fix things for you.
		1639
		1640	=item 4. Wee, just use a double-linked list for your timeouts.
		1641
		1642	If there is not one request, but many thousands (millions...), all
		1643	employing some kind of timeout with the same timeout value, then one can
		1644	do even better:
		1645
		1646	When starting the timeout, calculate the timeout value and put the timeout
		1647	at the I<end> of the list.
		1648
		1649	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1650	the list is expected to fire (for example, using the technique #3).
		1651
		1652	When there is some activity, remove the timer from the list, recalculate
		1653	the timeout, append it to the end of the list again, and make sure to
		1654	update the C<ev_timer> if it was taken from the beginning of the list.
		1655
		1656	This way, one can manage an unlimited number of timeouts in O(1) time for
		1657	starting, stopping and updating the timers, at the expense of a major
		1658	complication, and having to use a constant timeout. The constant timeout
		1659	ensures that the list stays sorted.
		1660
		1661	=back
		1662
		1663	So which method the best?
		1664
		1665	Method #2 is a simple no-brain-required solution that is adequate in most
		1666	situations. Method #3 requires a bit more thinking, but handles many cases
		1667	better, and isn't very complicated either. In most case, choosing either
		1668	one is fine, with #3 being better in typical situations.
		1669
		1670	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1671	rather complicated, but extremely efficient, something that really pays
		1672	off after the first million or so of active timers, i.e. it's usually
		1673	overkill :)
		1674
		1675	=head3 The special problem of time updates
		1676
		1677	Establishing the current time is a costly operation (it usually takes at
		1678	least two system calls): EV therefore updates its idea of the current
		1679	time only before and after C<ev_loop> collects new events, which causes a
		1680	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1681	lots of events in one iteration.
1202		1682
1203	The relative timeouts are calculated relative to the C<ev_now ()>	1683	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	1684	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	1685	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	1686	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:	1687	timeout on the current time, use something like this to adjust for this:
1208		1688
1209	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1689	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1210		1690
1211	The callback is guaranteed to be invoked only after its timeout has passed,	1691	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	1692	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1213	order of execution is undefined.	1693	()>.
1214		1694
1215	=head3 Watcher-Specific Functions and Data Members	1695	=head3 Watcher-Specific Functions and Data Members
1216		1696
1217	=over 4	1697	=over 4
1218		1698
…		…
1242	If the timer is started but non-repeating, stop it (as if it timed out).	1722	If the timer is started but non-repeating, stop it (as if it timed out).
1243		1723
1244	If the timer is repeating, either start it if necessary (with the	1724	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.	1725	C<repeat> value), or reset the running timer to the C<repeat> value.
1246		1726
1247	This sounds a bit complicated, but here is a useful and typical	1727	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	1728	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		1729
1272	=item ev_tstamp repeat [read-write]	1730	=item ev_tstamp repeat [read-write]
1273		1731
1274	The current C<repeat> value. Will be used each time the watcher times out	1732	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),	1733	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.	1734	which is also when any modifications are taken into account.
1277		1735
1278	=back	1736	=back
1279		1737
1280	=head3 Examples	1738	=head3 Examples
1281		1739
1282	Example: Create a timer that fires after 60 seconds.	1740	Example: Create a timer that fires after 60 seconds.
1283		1741
1284	static void	1742	static void
1285	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1743	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1286	{	1744	{
1287	.. one minute over, w is actually stopped right here	1745	.. one minute over, w is actually stopped right here
1288	}	1746	}
1289		1747
1290	struct ev_timer mytimer;	1748	ev_timer mytimer;
1291	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1749	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1292	ev_timer_start (loop, &mytimer);	1750	ev_timer_start (loop, &mytimer);
1293		1751
1294	Example: Create a timeout timer that times out after 10 seconds of	1752	Example: Create a timeout timer that times out after 10 seconds of
1295	inactivity.	1753	inactivity.
1296		1754
1297	static void	1755	static void
1298	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1756	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1299	{	1757	{
1300	.. ten seconds without any activity	1758	.. ten seconds without any activity
1301	}	1759	}
1302		1760
1303	struct ev_timer mytimer;	1761	ev_timer mytimer;
1304	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1762	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1305	ev_timer_again (&mytimer); /* start timer */	1763	ev_timer_again (&mytimer); /* start timer */
1306	ev_loop (loop, 0);	1764	ev_loop (loop, 0);
1307		1765
1308	// and in some piece of code that gets executed on any "activity":	1766	// and in some piece of code that gets executed on any "activity":
…		…
1313	=head2 C<ev_periodic> - to cron or not to cron?	1771	=head2 C<ev_periodic> - to cron or not to cron?
1314		1772
1315	Periodic watchers are also timers of a kind, but they are very versatile	1773	Periodic watchers are also timers of a kind, but they are very versatile
1316	(and unfortunately a bit complex).	1774	(and unfortunately a bit complex).
1317		1775
1318	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1776	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	1777	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	1778	(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 ()	1779	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	1780	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	1781	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		1782
		1783	You can tell a periodic watcher to trigger after some specific point
		1784	in time: for example, if you tell a periodic watcher to trigger "in 10
		1785	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1786	not a delay) and then reset your system clock to January of the previous
		1787	year, then it will take a year or more to trigger the event (unlike an
		1788	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1789	it, as it uses a relative timeout).
		1790
1327	C<ev_periodic>s can also be used to implement vastly more complex timers,	1791	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	1792	timers, such as triggering an event on each "midnight, local time", or
1329	complicated, rules.	1793	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1794	those cannot react to time jumps.
1330		1795
1331	As with timers, the callback is guaranteed to be invoked only when the	1796	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	1797	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.	1798	timers become ready during the same loop iteration then the ones with
		1799	earlier time-out values are invoked before ones with later time-out values
		1800	(but this is no longer true when a callback calls C<ev_loop> recursively).
1334		1801
1335	=head3 Watcher-Specific Functions and Data Members	1802	=head3 Watcher-Specific Functions and Data Members
1336		1803
1337	=over 4	1804	=over 4
1338		1805
1339	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1806	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1340		1807
1341	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1808	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1342		1809
1343	Lots of arguments, lets sort it out... There are basically three modes of	1810	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:	1811	operation, and we will explain them from simplest to most complex:
1345		1812
1346	=over 4	1813	=over 4
1347		1814
1348	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1815	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1349		1816
1350	In this configuration the watcher triggers an event after the wall clock	1817	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	1818	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	1819	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.	1820	will be stopped and invoked when the system clock reaches or surpasses
		1821	this point in time.
1354		1822
1355	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1823	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1356		1824
1357	In this mode the watcher will always be scheduled to time out at the next	1825	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)	1826	C<offset + N * interval> time (for some integer N, which can also be
1359	and then repeat, regardless of any time jumps.	1827	negative) and then repeat, regardless of any time jumps. The C<offset>
		1828	argument is merely an offset into the C<interval> periods.
1360		1829
1361	This can be used to create timers that do not drift with respect to system	1830	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	1831	system clock, for example, here is an C<ev_periodic> that triggers each
1363	the hour:	1832	hour, on the hour (with respect to UTC):
1364		1833
1365	ev_periodic_set (&periodic, 0., 3600., 0);	1834	ev_periodic_set (&periodic, 0., 3600., 0);
1366		1835
1367	This doesn't mean there will always be 3600 seconds in between triggers,	1836	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	1837	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	1838	full hour (UTC), or more correctly, when the system time is evenly divisible
1370	by 3600.	1839	by 3600.
1371		1840
1372	Another way to think about it (for the mathematically inclined) is that	1841	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	1842	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.	1843	time where C<time = offset (mod interval)>, regardless of any time jumps.
1375		1844
1376	For numerical stability it is preferable that the C<at> value is near	1845	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	1846	C<ev_now ()> (the current time), but there is no range requirement for
1378	this value, and in fact is often specified as zero.	1847	this value, and in fact is often specified as zero.
1379		1848
1380	Note also that there is an upper limit to how often a timer can fire (CPU	1849	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	1850	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	1851	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).	1852	millisecond (if the OS supports it and the machine is fast enough).
1384		1853
1385	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1854	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1386		1855
1387	In this mode the values for C<interval> and C<at> are both being	1856	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	1857	ignored. Instead, each time the periodic watcher gets scheduled, the
1389	reschedule callback will be called with the watcher as first, and the	1858	reschedule callback will be called with the watcher as first, and the
1390	current time as second argument.	1859	current time as second argument.
1391		1860
1392	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1861	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1393	ever, or make ANY event loop modifications whatsoever>.	1862	or make ANY other event loop modifications whatsoever, unless explicitly
		1863	allowed by documentation here>.
1394		1864
1395	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1865	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	1866	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1397	only event loop modification you are allowed to do).	1867	only event loop modification you are allowed to do).
1398		1868
1399	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1869	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1400	*w, ev_tstamp now)>, e.g.:	1870	*w, ev_tstamp now)>, e.g.:
1401		1871
		1872	static ev_tstamp
1402	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1873	my_rescheduler (ev_periodic *w, ev_tstamp now)
1403	{	1874	{
1404	return now + 60.;	1875	return now + 60.;
1405	}	1876	}
1406		1877
1407	It must return the next time to trigger, based on the passed time value	1878	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	1898	a different time than the last time it was called (e.g. in a crond like
1428	program when the crontabs have changed).	1899	program when the crontabs have changed).
1429		1900
1430	=item ev_tstamp ev_periodic_at (ev_periodic *)	1901	=item ev_tstamp ev_periodic_at (ev_periodic *)
1431		1902
1432	When active, returns the absolute time that the watcher is supposed to	1903	When active, returns the absolute time that the watcher is supposed
1433	trigger next.	1904	to trigger next. This is not the same as the C<offset> argument to
		1905	C<ev_periodic_set>, but indeed works even in interval and manual
		1906	rescheduling modes.
1434		1907
1435	=item ev_tstamp offset [read-write]	1908	=item ev_tstamp offset [read-write]
1436		1909
1437	When repeating, this contains the offset value, otherwise this is the	1910	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>).	1911	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		1912	although libev might modify this value for better numerical stability).
1439		1913
1440	Can be modified any time, but changes only take effect when the periodic	1914	Can be modified any time, but changes only take effect when the periodic
1441	timer fires or C<ev_periodic_again> is being called.	1915	timer fires or C<ev_periodic_again> is being called.
1442		1916
1443	=item ev_tstamp interval [read-write]	1917	=item ev_tstamp interval [read-write]
1444		1918
1445	The current interval value. Can be modified any time, but changes only	1919	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	1920	take effect when the periodic timer fires or C<ev_periodic_again> is being
1447	called.	1921	called.
1448		1922
1449	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1923	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1450		1924
1451	The current reschedule callback, or C<0>, if this functionality is	1925	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	1926	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.	1927	the periodic timer fires or C<ev_periodic_again> is being called.
1454		1928
1455	=back	1929	=back
1456		1930
1457	=head3 Examples	1931	=head3 Examples
1458		1932
1459	Example: Call a callback every hour, or, more precisely, whenever the	1933	Example: Call a callback every hour, or, more precisely, whenever the
1460	system clock is divisible by 3600. The callback invocation times have	1934	system time is divisible by 3600. The callback invocation times have
1461	potentially a lot of jitter, but good long-term stability.	1935	potentially a lot of jitter, but good long-term stability.
1462		1936
1463	static void	1937	static void
1464	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1938	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1465	{	1939	{
1466	... its now a full hour (UTC, or TAI or whatever your clock follows)	1940	... its now a full hour (UTC, or TAI or whatever your clock follows)
1467	}	1941	}
1468		1942
1469	struct ev_periodic hourly_tick;	1943	ev_periodic hourly_tick;
1470	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1944	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1471	ev_periodic_start (loop, &hourly_tick);	1945	ev_periodic_start (loop, &hourly_tick);
1472		1946
1473	Example: The same as above, but use a reschedule callback to do it:	1947	Example: The same as above, but use a reschedule callback to do it:
1474		1948
1475	#include <math.h>	1949	#include <math.h>
1476		1950
1477	static ev_tstamp	1951	static ev_tstamp
1478	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1952	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1479	{	1953	{
1480	return fmod (now, 3600.) + 3600.;	1954	return now + (3600. - fmod (now, 3600.));
1481	}	1955	}
1482		1956
1483	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1957	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1484		1958
1485	Example: Call a callback every hour, starting now:	1959	Example: Call a callback every hour, starting now:
1486		1960
1487	struct ev_periodic hourly_tick;	1961	ev_periodic hourly_tick;
1488	ev_periodic_init (&hourly_tick, clock_cb,	1962	ev_periodic_init (&hourly_tick, clock_cb,
1489	fmod (ev_now (loop), 3600.), 3600., 0);	1963	fmod (ev_now (loop), 3600.), 3600., 0);
1490	ev_periodic_start (loop, &hourly_tick);	1964	ev_periodic_start (loop, &hourly_tick);
1491		1965
1492		1966
…		…
1495	Signal watchers will trigger an event when the process receives a specific	1969	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	1970	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	1971	will try it's best to deliver signals synchronously, i.e. as part of the
1498	normal event processing, like any other event.	1972	normal event processing, like any other event.
1499		1973
		1974	If you want signals asynchronously, just use C<sigaction> as you would
		1975	do without libev and forget about sharing the signal. You can even use
		1976	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1977
1500	You can configure as many watchers as you like per signal. Only when the	1978	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	1979	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	1980	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	1981	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	1982	the last signal watcher for a signal is stopped, libev will reset the
1505	SIG_DFL (regardless of what it was set to before).	1983	signal handler to SIG_DFL (regardless of what it was set to before).
1506		1984
1507	If possible and supported, libev will install its handlers with	1985	If possible and supported, libev will install its handlers with
1508	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	1986	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	1987	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	1988	signals you can block all signals in an C<ev_check> watcher and unblock
…		…
1527		2005
1528	=back	2006	=back
1529		2007
1530	=head3 Examples	2008	=head3 Examples
1531		2009
1532	Example: Try to exit cleanly on SIGINT and SIGTERM.	2010	Example: Try to exit cleanly on SIGINT.
1533		2011
1534	static void	2012	static void
1535	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2013	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1536	{	2014	{
1537	ev_unloop (loop, EVUNLOOP_ALL);	2015	ev_unloop (loop, EVUNLOOP_ALL);
1538	}	2016	}
1539		2017
1540	struct ev_signal signal_watcher;	2018	ev_signal signal_watcher;
1541	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2019	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1542	ev_signal_start (loop, &sigint_cb);	2020	ev_signal_start (loop, &signal_watcher);
1543		2021
1544		2022
1545	=head2 C<ev_child> - watch out for process status changes	2023	=head2 C<ev_child> - watch out for process status changes
1546		2024
1547	Child watchers trigger when your process receives a SIGCHLD in response to	2025	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	2026	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	2027	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	2028	has been forked (which implies it might have already exited), as long
1551	loop isn't entered (or is continued from a watcher).	2029	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2030	forking and then immediately registering a watcher for the child is fine,
		2031	but forking and registering a watcher a few event loop iterations later or
		2032	in the next callback invocation is not.
1552		2033
1553	Only the default event loop is capable of handling signals, and therefore	2034	Only the default event loop is capable of handling signals, and therefore
1554	you can only register child watchers in the default event loop.	2035	you can only register child watchers in the default event loop.
		2036
		2037	Due to some design glitches inside libev, child watchers will always be
		2038	handled at maximum priority (their priority is set to EV_MAXPRI by libev)
1555		2039
1556	=head3 Process Interaction	2040	=head3 Process Interaction
1557		2041
1558	Libev grabs C<SIGCHLD> as soon as the default event loop is	2042	Libev grabs C<SIGCHLD> as soon as the default event loop is
1559	initialised. This is necessary to guarantee proper behaviour even if	2043	initialised. This is necessary to guarantee proper behaviour even if
…		…
1569	handler, you can override it easily by installing your own handler for	2053	handler, you can override it easily by installing your own handler for
1570	C<SIGCHLD> after initialising the default loop, and making sure the	2054	C<SIGCHLD> after initialising the default loop, and making sure the
1571	default loop never gets destroyed. You are encouraged, however, to use an	2055	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	2056	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.	2057	that, so other libev users can use C<ev_child> watchers freely.
		2058
		2059	=head3 Stopping the Child Watcher
		2060
		2061	Currently, the child watcher never gets stopped, even when the
		2062	child terminates, so normally one needs to stop the watcher in the
		2063	callback. Future versions of libev might stop the watcher automatically
		2064	when a child exit is detected.
1574		2065
1575	=head3 Watcher-Specific Functions and Data Members	2066	=head3 Watcher-Specific Functions and Data Members
1576		2067
1577	=over 4	2068	=over 4
1578		2069
…		…
1610	its completion.	2101	its completion.
1611		2102
1612	ev_child cw;	2103	ev_child cw;
1613		2104
1614	static void	2105	static void
1615	child_cb (EV_P_ struct ev_child *w, int revents)	2106	child_cb (EV_P_ ev_child *w, int revents)
1616	{	2107	{
1617	ev_child_stop (EV_A_ w);	2108	ev_child_stop (EV_A_ w);
1618	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2109	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1619	}	2110	}
1620		2111
…		…
1635		2126
1636		2127
1637	=head2 C<ev_stat> - did the file attributes just change?	2128	=head2 C<ev_stat> - did the file attributes just change?
1638		2129
1639	This watches a file system path for attribute changes. That is, it calls	2130	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	2131	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.	2132	and sees if it changed compared to the last time, invoking the callback if
		2133	it did.
1642		2134
1643	The path does not need to exist: changing from "path exists" to "path does	2135	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	2136	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	2137	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	2138	C<st_nlink> field being zero (which is otherwise always forced to be at
1647	the stat buffer having unspecified contents.	2139	least one) and all the other fields of the stat buffer having unspecified
		2140	contents.
1648		2141
1649	The path I<should> be absolute and I<must not> end in a slash. If it is	2142	The path I<must not> end in a slash or contain special components such as
		2143	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.	2144	your working directory changes, then the behaviour is undefined.
1651		2145
1652	Since there is no standard to do this, the portable implementation simply	2146	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	2147	portable implementation simply calls C<stat(2)> regularly on the path
1654	can specify a recommended polling interval for this case. If you specify	2148	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,	2149	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	2150	recommended!) then a I<suitable, unspecified default> value will be used
1657	five seconds, although this might change dynamically). Libev will also	2151	(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	2152	change dynamically). Libev will also impose a minimum interval which is
1659	usually overkill.	2153	currently around C<0.1>, but that's usually overkill.
1660		2154
1661	This watcher type is not meant for massive numbers of stat watchers,	2155	This watcher type is not meant for massive numbers of stat watchers,
1662	as even with OS-supported change notifications, this can be	2156	as even with OS-supported change notifications, this can be
1663	resource-intensive.	2157	resource-intensive.
1664		2158
1665	At the time of this writing, only the Linux inotify interface is	2159	At the time of this writing, the only OS-specific interface implemented
1666	implemented (implementing kqueue support is left as an exercise for the	2160	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	2161	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	2162	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		2163
1674	=head3 ABI Issues (Largefile Support)	2164	=head3 ABI Issues (Largefile Support)
1675		2165
1676	Libev by default (unless the user overrides this) uses the default	2166	Libev by default (unless the user overrides this) uses the default
1677	compilation environment, which means that on systems with large file	2167	compilation environment, which means that on systems with large file
1678	support disabled by default, you get the 32 bit version of the stat	2168	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	2169	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	2170	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	2171	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	2172	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.	2173	most noticeably displayed with ev_stat and large file support.
1684		2174
1685	The solution for this is to lobby your distribution maker to make large	2175	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	2176	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	2177	optional. Libev cannot simply switch on large file support because it has
1688	to exchange stat structures with application programs compiled using the	2178	to exchange stat structures with application programs compiled using the
1689	default compilation environment.	2179	default compilation environment.
1690		2180
1691	=head3 Inotify	2181	=head3 Inotify and Kqueue
1692		2182
1693	When C<inotify (7)> support has been compiled into libev (generally only	2183	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	2184	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	2185	inotify descriptor will be created lazily when the first C<ev_stat>
1696	when the first C<ev_stat> watcher is being started.	2186	watcher is being started.
1697		2187
1698	Inotify presence does not change the semantics of C<ev_stat> watchers	2188	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	2189	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	2190	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.	2191	there are many cases where libev has to resort to regular C<stat> polling,
		2192	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2193	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2194	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2195	xfs are fully working) libev usually gets away without polling.
1702		2196
1703	(There is no support for kqueue, as apparently it cannot be used to	2197	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	2198	implement this functionality, due to the requirement of having a file
1705	descriptor open on the object at all times).	2199	descriptor open on the object at all times, and detecting renames, unlinks
		2200	etc. is difficult.
		2201
		2202	=head3 C<stat ()> is a synchronous operation
		2203
		2204	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2205	the process. The exception are C<ev_stat> watchers - those call C<stat
		2206	()>, which is a synchronous operation.
		2207
		2208	For local paths, this usually doesn't matter: unless the system is very
		2209	busy or the intervals between stat's are large, a stat call will be fast,
		2210	as the path data is usually in memory already (except when starting the
		2211	watcher).
		2212
		2213	For networked file systems, calling C<stat ()> can block an indefinite
		2214	time due to network issues, and even under good conditions, a stat call
		2215	often takes multiple milliseconds.
		2216
		2217	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2218	paths, although this is fully supported by libev.
1706		2219
1707	=head3 The special problem of stat time resolution	2220	=head3 The special problem of stat time resolution
1708		2221
1709	The C<stat ()> system call only supports full-second resolution portably, and	2222	The C<stat ()> system call only supports full-second resolution portably,
1710	even on systems where the resolution is higher, many file systems still	2223	and even on systems where the resolution is higher, most file systems
1711	only support whole seconds.	2224	still only support whole seconds.
1712		2225
1713	That means that, if the time is the only thing that changes, you can	2226	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	2227	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	2228	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	2229	within the same second, C<ev_stat> will be unable to detect unless the
1717	data does not change.	2230	stat data does change in other ways (e.g. file size).
1718		2231
1719	The solution to this is to delay acting on a change for slightly more	2232	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	2233	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);	2234	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1722	ev_timer_again (loop, w)>).	2235	ev_timer_again (loop, w)>).
…		…
1742	C<path>. The C<interval> is a hint on how quickly a change is expected to	2255	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	2256	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	2257	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.	2258	path for as long as the watcher is active.
1746		2259
1747	The callback will receive C<EV_STAT> when a change was detected, relative	2260	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	2261	relative to the attributes at the time the watcher was started (or the
1749	was detected).	2262	last change was detected).
1750		2263
1751	=item ev_stat_stat (loop, ev_stat *)	2264	=item ev_stat_stat (loop, ev_stat *)
1752		2265
1753	Updates the stat buffer immediately with new values. If you change the	2266	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	2267	watched path in your callback, you could call this function to avoid
…		…
1837		2350
1838		2351
1839	=head2 C<ev_idle> - when you've got nothing better to do...	2352	=head2 C<ev_idle> - when you've got nothing better to do...
1840		2353
1841	Idle watchers trigger events when no other events of the same or higher	2354	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	2355	priority are pending (prepare, check and other idle watchers do not count
1843	count).	2356	as receiving "events").
1844		2357
1845	That is, as long as your process is busy handling sockets or timeouts	2358	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	2359	(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	2360	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	2361	are pending), the idle watchers are being called once per event loop
…		…
1859		2372
1860	=head3 Watcher-Specific Functions and Data Members	2373	=head3 Watcher-Specific Functions and Data Members
1861		2374
1862	=over 4	2375	=over 4
1863		2376
1864	=item ev_idle_init (ev_signal *, callback)	2377	=item ev_idle_init (ev_idle *, callback)
1865		2378
1866	Initialises and configures the idle watcher - it has no parameters of any	2379	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,	2380	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1868	believe me.	2381	believe me.
1869		2382
…		…
1873		2386
1874	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2387	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1875	callback, free it. Also, use no error checking, as usual.	2388	callback, free it. Also, use no error checking, as usual.
1876		2389
1877	static void	2390	static void
1878	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2391	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1879	{	2392	{
1880	free (w);	2393	free (w);
1881	// now do something you wanted to do when the program has	2394	// now do something you wanted to do when the program has
1882	// no longer anything immediate to do.	2395	// no longer anything immediate to do.
1883	}	2396	}
1884		2397
1885	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2398	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1886	ev_idle_init (idle_watcher, idle_cb);	2399	ev_idle_init (idle_watcher, idle_cb);
1887	ev_idle_start (loop, idle_cb);	2400	ev_idle_start (loop, idle_watcher);
1888		2401
1889		2402
1890	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2403	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1891		2404
1892	Prepare and check watchers are usually (but not always) used in tandem:	2405	Prepare and check watchers are usually (but not always) used in pairs:
1893	prepare watchers get invoked before the process blocks and check watchers	2406	prepare watchers get invoked before the process blocks and check watchers
1894	afterwards.	2407	afterwards.
1895		2408
1896	You I<must not> call C<ev_loop> or similar functions that enter	2409	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>	2410	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,	2413	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	2414	C<ev_check> so if you have one watcher of each kind they will always be
1902	called in pairs bracketing the blocking call.	2415	called in pairs bracketing the blocking call.
1903		2416
1904	Their main purpose is to integrate other event mechanisms into libev and	2417	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	2418	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	2419	variable changes, implement your own watchers, integrate net-snmp or a
1907	coroutine library and lots more. They are also occasionally useful if	2420	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,	2421	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>	2422	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1910	watcher).	2423	watcher).
1911		2424
1912	This is done by examining in each prepare call which file descriptors need	2425	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	2426	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	2427	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	2428	libraries provide exactly this functionality). Then, in the check watcher,
1916	any events that occurred (by checking the pending status of all watchers	2429	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	2430	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,	2431	I/O and timer callbacks will never actually be called (but must be valid
1919	because you never know, you know?).	2432	nevertheless, because you never know, you know?).
1920		2433
1921	As another example, the Perl Coro module uses these hooks to integrate	2434	As another example, the Perl Coro module uses these hooks to integrate
1922	coroutines into libev programs, by yielding to other active coroutines	2435	coroutines into libev programs, by yielding to other active coroutines
1923	during each prepare and only letting the process block if no coroutines	2436	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	2437	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	2440	loop from blocking if lower-priority coroutines are active, thus mapping
1928	low-priority coroutines to idle/background tasks).	2441	low-priority coroutines to idle/background tasks).
1929		2442
1930	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2443	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	2444	priority, to ensure that they are being run before any other watchers
		2445	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2446
1932	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2447	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	2448	activate ("feed") events into libev. While libev fully supports this, they
1934	supports this, they might get executed before other C<ev_check> watchers	2449	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	2450	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	2451	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	2452	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1938	coexist peacefully with others).	2453	others).
1939		2454
1940	=head3 Watcher-Specific Functions and Data Members	2455	=head3 Watcher-Specific Functions and Data Members
1941		2456
1942	=over 4	2457	=over 4
1943		2458
…		…
1945		2460
1946	=item ev_check_init (ev_check *, callback)	2461	=item ev_check_init (ev_check *, callback)
1947		2462
1948	Initialises and configures the prepare or check watcher - they have no	2463	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>	2464	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.	2465	macros, but using them is utterly, utterly, utterly and completely
		2466	pointless.
1951		2467
1952	=back	2468	=back
1953		2469
1954	=head3 Examples	2470	=head3 Examples
1955		2471
…		…
1968		2484
1969	static ev_io iow [nfd];	2485	static ev_io iow [nfd];
1970	static ev_timer tw;	2486	static ev_timer tw;
1971		2487
1972	static void	2488	static void
1973	io_cb (ev_loop *loop, ev_io *w, int revents)	2489	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1974	{	2490	{
1975	}	2491	}
1976		2492
1977	// create io watchers for each fd and a timer before blocking	2493	// create io watchers for each fd and a timer before blocking
1978	static void	2494	static void
1979	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2495	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1980	{	2496	{
1981	int timeout = 3600000;	2497	int timeout = 3600000;
1982	struct pollfd fds [nfd];	2498	struct pollfd fds [nfd];
1983	// actual code will need to loop here and realloc etc.	2499	// actual code will need to loop here and realloc etc.
1984	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2500	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1985		2501
1986	/* the callback is illegal, but won't be called as we stop during check */	2502	/* the callback is illegal, but won't be called as we stop during check */
1987	ev_timer_init (&tw, 0, timeout * 1e-3);	2503	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
1988	ev_timer_start (loop, &tw);	2504	ev_timer_start (loop, &tw);
1989		2505
1990	// create one ev_io per pollfd	2506	// create one ev_io per pollfd
1991	for (int i = 0; i < nfd; ++i)	2507	for (int i = 0; i < nfd; ++i)
1992	{	2508	{
…		…
1999	}	2515	}
2000	}	2516	}
2001		2517
2002	// stop all watchers after blocking	2518	// stop all watchers after blocking
2003	static void	2519	static void
2004	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2520	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2005	{	2521	{
2006	ev_timer_stop (loop, &tw);	2522	ev_timer_stop (loop, &tw);
2007		2523
2008	for (int i = 0; i < nfd; ++i)	2524	for (int i = 0; i < nfd; ++i)
2009	{	2525	{
…		…
2048	}	2564	}
2049		2565
2050	// do not ever call adns_afterpoll	2566	// do not ever call adns_afterpoll
2051		2567
2052	Method 4: Do not use a prepare or check watcher because the module you	2568	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	2569	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	2570	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	2571	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2056	this.	2572	this approach, effectively embedding EV as a client into the horrible
		2573	libglib event loop.
2057		2574
2058	static gint	2575	static gint
2059	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2576	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2060	{	2577	{
2061	int got_events = 0;	2578	int got_events = 0;
…		…
2092	prioritise I/O.	2609	prioritise I/O.
2093		2610
2094	As an example for a bug workaround, the kqueue backend might only support	2611	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	2612	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	2613	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	2614	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	2615	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	2616	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.	2617	C<kevent>, but at least you can use both mechanisms for what they are
		2618	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2101		2619
2102	As for prioritising I/O: rarely you have the case where some fds have	2620	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	2621	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	2622	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	2623	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.	2624	the rest in a second one, and embed the second one in the first.
2107		2625
2108	As long as the watcher is active, the callback will be invoked every time	2626	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	2627	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	2628	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	2629	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	2630	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	2631	to give the embedded loop strictly lower priority for example).
2114	embedded loop sweep.
2115		2632
2116	As long as the watcher is started it will automatically handle events. The	2633	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	2634	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		2635
2121	Also, there have not currently been made special provisions for forking:	2636	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,	2637	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	2638	embedding loop forks. In other cases, the user is responsible for calling
2124	yourself.	2639	C<ev_loop_fork> on the embedded loop.
2125		2640
2126	Unfortunately, not all backends are embeddable, only the ones returned by	2641	Unfortunately, not all backends are embeddable: only the ones returned by
2127	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2642	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2128	portable one.	2643	portable one.
2129		2644
2130	So when you want to use this feature you will always have to be prepared	2645	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	2646	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	2647	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.	2648	create it, and if that fails, use the normal loop for everything.
		2649
		2650	=head3 C<ev_embed> and fork
		2651
		2652	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2653	automatically be applied to the embedded loop as well, so no special
		2654	fork handling is required in that case. When the watcher is not running,
		2655	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2656	as applicable.
2134		2657
2135	=head3 Watcher-Specific Functions and Data Members	2658	=head3 Watcher-Specific Functions and Data Members
2136		2659
2137	=over 4	2660	=over 4
2138		2661
…		…
2166	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2689	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2167	used).	2690	used).
2168		2691
2169	struct ev_loop *loop_hi = ev_default_init (0);	2692	struct ev_loop *loop_hi = ev_default_init (0);
2170	struct ev_loop *loop_lo = 0;	2693	struct ev_loop *loop_lo = 0;
2171	struct ev_embed embed;	2694	ev_embed embed;
2172		2695
2173	// see if there is a chance of getting one that works	2696	// see if there is a chance of getting one that works
2174	// (remember that a flags value of 0 means autodetection)	2697	// (remember that a flags value of 0 means autodetection)
2175	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2698	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2176	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2699	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2190	kqueue implementation). Store the kqueue/socket-only event loop in	2713	kqueue implementation). Store the kqueue/socket-only event loop in
2191	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2714	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2192		2715
2193	struct ev_loop *loop = ev_default_init (0);	2716	struct ev_loop *loop = ev_default_init (0);
2194	struct ev_loop *loop_socket = 0;	2717	struct ev_loop *loop_socket = 0;
2195	struct ev_embed embed;	2718	ev_embed embed;
2196		2719
2197	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2720	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2198	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2721	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2199	{	2722	{
2200	ev_embed_init (&embed, 0, loop_socket);	2723	ev_embed_init (&embed, 0, loop_socket);
…		…
2215	event loop blocks next and before C<ev_check> watchers are being called,	2738	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	2739	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	2740	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2218	handlers will be invoked, too, of course.	2741	handlers will be invoked, too, of course.
2219		2742
		2743	=head3 The special problem of life after fork - how is it possible?
		2744
		2745	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2746	up/change the process environment, followed by a call to C<exec()>. This
		2747	sequence should be handled by libev without any problems.
		2748
		2749	This changes when the application actually wants to do event handling
		2750	in the child, or both parent in child, in effect "continuing" after the
		2751	fork.
		2752
		2753	The default mode of operation (for libev, with application help to detect
		2754	forks) is to duplicate all the state in the child, as would be expected
		2755	when I<either> the parent I<or> the child process continues.
		2756
		2757	When both processes want to continue using libev, then this is usually the
		2758	wrong result. In that case, usually one process (typically the parent) is
		2759	supposed to continue with all watchers in place as before, while the other
		2760	process typically wants to start fresh, i.e. without any active watchers.
		2761
		2762	The cleanest and most efficient way to achieve that with libev is to
		2763	simply create a new event loop, which of course will be "empty", and
		2764	use that for new watchers. This has the advantage of not touching more
		2765	memory than necessary, and thus avoiding the copy-on-write, and the
		2766	disadvantage of having to use multiple event loops (which do not support
		2767	signal watchers).
		2768
		2769	When this is not possible, or you want to use the default loop for
		2770	other reasons, then in the process that wants to start "fresh", call
		2771	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2772	the default loop will "orphan" (not stop) all registered watchers, so you
		2773	have to be careful not to execute code that modifies those watchers. Note
		2774	also that in that case, you have to re-register any signal watchers.
		2775
2220	=head3 Watcher-Specific Functions and Data Members	2776	=head3 Watcher-Specific Functions and Data Members
2221		2777
2222	=over 4	2778	=over 4
2223		2779
2224	=item ev_fork_init (ev_signal *, callback)	2780	=item ev_fork_init (ev_signal *, callback)
…		…
2256	is that the author does not know of a simple (or any) algorithm for a	2812	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	2813	multiple-writer-single-reader queue that works in all cases and doesn't
2258	need elaborate support such as pthreads.	2814	need elaborate support such as pthreads.
2259		2815
2260	That means that if you want to queue data, you have to provide your own	2816	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	2817	queue. But at least I can tell you how to implement locking around your
2262	queue:	2818	queue:
2263		2819
2264	=over 4	2820	=over 4
2265		2821
2266	=item queueing from a signal handler context	2822	=item queueing from a signal handler context
2267		2823
2268	To implement race-free queueing, you simply add to the queue in the signal	2824	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	2825	handler but you block the signal handler in the watcher callback. Here is
2270	some fictitious SIGUSR1 handler:	2826	an example that does that for some fictitious SIGUSR1 handler:
2271		2827
2272	static ev_async mysig;	2828	static ev_async mysig;
2273		2829
2274	static void	2830	static void
2275	sigusr1_handler (void)	2831	sigusr1_handler (void)
…		…
2341	=over 4	2897	=over 4
2342		2898
2343	=item ev_async_init (ev_async *, callback)	2899	=item ev_async_init (ev_async *, callback)
2344		2900
2345	Initialises and configures the async watcher - it has no parameters of any	2901	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,	2902	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2347	believe me.	2903	trust me.
2348		2904
2349	=item ev_async_send (loop, ev_async *)	2905	=item ev_async_send (loop, ev_async *)
2350		2906
2351	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2907	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	2908	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	2909	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	2910	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2355	section below on what exactly this means).	2911	section below on what exactly this means).
2356		2912
		2913	Note that, as with other watchers in libev, multiple events might get
		2914	compressed into a single callback invocation (another way to look at this
		2915	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		2916	reset when the event loop detects that).
		2917
2357	This call incurs the overhead of a system call only once per loop iteration,	2918	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	2919	iteration, so while the overhead might be noticeable, it doesn't apply to
2359	calls to C<ev_async_send>.	2920	repeated calls to C<ev_async_send> for the same event loop.
2360		2921
2361	=item bool = ev_async_pending (ev_async *)	2922	=item bool = ev_async_pending (ev_async *)
2362		2923
2363	Returns a non-zero value when C<ev_async_send> has been called on the	2924	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	2925	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	2928	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,	2929	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	2930	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.	2931	quickly check whether invoking the loop might be a good idea.
2371		2932
2372	Not that this does I<not> check whether the watcher itself is pending, only	2933	Not that this does I<not> check whether the watcher itself is pending,
2373	whether it has been requested to make this watcher pending.	2934	only whether it has been requested to make this watcher pending: there
		2935	is a time window between the event loop checking and resetting the async
		2936	notification, and the callback being invoked.
2374		2937
2375	=back	2938	=back
2376		2939
2377		2940
2378	=head1 OTHER FUNCTIONS	2941	=head1 OTHER FUNCTIONS
…		…
2382	=over 4	2945	=over 4
2383		2946
2384	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2947	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2385		2948
2386	This function combines a simple timer and an I/O watcher, calls your	2949	This function combines a simple timer and an I/O watcher, calls your
2387	callback on whichever event happens first and automatically stop both	2950	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	2951	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	2952	or timeout without having to allocate/configure/start/stop/free one or
2390	more watchers yourself.	2953	more watchers yourself.
2391		2954
2392	If C<fd> is less than 0, then no I/O watcher will be started and events	2955	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	2956	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2394	C<events> set will be created and started.	2957	the given C<fd> and C<events> set will be created and started.
2395		2958
2396	If C<timeout> is less than 0, then no timeout watcher will be	2959	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	2960	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	2961	repeat = 0) will be started. C<0> is a valid timeout.
2399	dubious value.
2400		2962
2401	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2963	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	2964	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>	2965	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2404	value passed to C<ev_once>:	2966	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2967	a timeout and an io event at the same time - you probably should give io
		2968	events precedence.
		2969
		2970	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2405		2971
2406	static void stdin_ready (int revents, void *arg)	2972	static void stdin_ready (int revents, void *arg)
2407	{	2973	{
		2974	if (revents & EV_READ)
		2975	/* stdin might have data for us, joy! */;
2408	if (revents & EV_TIMEOUT)	2976	else if (revents & EV_TIMEOUT)
2409	/* doh, nothing entered */;	2977	/* doh, nothing entered */;
2410	else if (revents & EV_READ)
2411	/* stdin might have data for us, joy! */;
2412	}	2978	}
2413		2979
2414	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2980	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2415		2981
2416	=item ev_feed_event (ev_loop *, watcher *, int revents)	2982	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2417		2983
2418	Feeds the given event set into the event loop, as if the specified event	2984	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	2985	had happened for the specified watcher (which must be a pointer to an
2420	initialised but not necessarily started event watcher).	2986	initialised but not necessarily started event watcher).
2421		2987
2422	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2988	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2423		2989
2424	Feed an event on the given fd, as if a file descriptor backend detected	2990	Feed an event on the given fd, as if a file descriptor backend detected
2425	the given events it.	2991	the given events it.
2426		2992
2427	=item ev_feed_signal_event (ev_loop *loop, int signum)	2993	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2428		2994
2429	Feed an event as if the given signal occurred (C<loop> must be the default	2995	Feed an event as if the given signal occurred (C<loop> must be the default
2430	loop!).	2996	loop!).
2431		2997
2432	=back	2998	=back
…		…
2554		3120
2555	myclass obj;	3121	myclass obj;
2556	ev::io iow;	3122	ev::io iow;
2557	iow.set <myclass, &myclass::io_cb> (&obj);	3123	iow.set <myclass, &myclass::io_cb> (&obj);
2558		3124
		3125	=item w->set (object *)
		3126
		3127	This is an B<experimental> feature that might go away in a future version.
		3128
		3129	This is a variation of a method callback - leaving out the method to call
		3130	will default the method to C<operator ()>, which makes it possible to use
		3131	functor objects without having to manually specify the C<operator ()> all
		3132	the time. Incidentally, you can then also leave out the template argument
		3133	list.
		3134
		3135	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3136	int revents)>.
		3137
		3138	See the method-C<set> above for more details.
		3139
		3140	Example: use a functor object as callback.
		3141
		3142	struct myfunctor
		3143	{
		3144	void operator() (ev::io &w, int revents)
		3145	{
		3146	...
		3147	}
		3148	}
		3149
		3150	myfunctor f;
		3151
		3152	ev::io w;
		3153	w.set (&f);
		3154
2559	=item w->set<function> (void *data = 0)	3155	=item w->set<function> (void *data = 0)
2560		3156
2561	Also sets a callback, but uses a static method or plain function as	3157	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	3158	callback. The optional C<data> argument will be stored in the watcher's
2563	C<data> member and is free for you to use.	3159	C<data> member and is free for you to use.
2564		3160
2565	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3161	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2566		3162
2567	See the method-C<set> above for more details.	3163	See the method-C<set> above for more details.
2568		3164
2569	Example:	3165	Example: Use a plain function as callback.
2570		3166
2571	static void io_cb (ev::io &w, int revents) { }	3167	static void io_cb (ev::io &w, int revents) { }
2572	iow.set <io_cb> ();	3168	iow.set <io_cb> ();
2573		3169
2574	=item w->set (struct ev_loop *)	3170	=item w->set (struct ev_loop *)
…		…
2612	Example: Define a class with an IO and idle watcher, start one of them in	3208	Example: Define a class with an IO and idle watcher, start one of them in
2613	the constructor.	3209	the constructor.
2614		3210
2615	class myclass	3211	class myclass
2616	{	3212	{
2617	ev::io io; void io_cb (ev::io &w, int revents);	3213	ev::io io ; void io_cb (ev::io &w, int revents);
2618	ev:idle idle void idle_cb (ev::idle &w, int revents);	3214	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2619		3215
2620	myclass (int fd)	3216	myclass (int fd)
2621	{	3217	{
2622	io .set <myclass, &myclass::io_cb > (this);	3218	io .set <myclass, &myclass::io_cb > (this);
2623	idle.set <myclass, &myclass::idle_cb> (this);	3219	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2639	=item Perl	3235	=item Perl
2640		3236
2641	The EV module implements the full libev API and is actually used to test	3237	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,	3238	libev. EV is developed together with libev. Apart from the EV core module,
2643	there are additional modules that implement libev-compatible interfaces	3239	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	3240	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>).	3241	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3242	and C<EV::Glib>).
2646		3243
2647	It can be found and installed via CPAN, its homepage is at	3244	It can be found and installed via CPAN, its homepage is at
2648	L<http://software.schmorp.de/pkg/EV>.	3245	L<http://software.schmorp.de/pkg/EV>.
2649		3246
2650	=item Python	3247	=item Python
2651		3248
2652	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3249	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	3250	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		3251
2659	=item Ruby	3252	=item Ruby
2660		3253
2661	Tony Arcieri has written a ruby extension that offers access to a subset	3254	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	3255	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	3256	more on top of it. It can be found via gem servers. Its homepage is at
2664	L<http://rev.rubyforge.org/>.	3257	L<http://rev.rubyforge.org/>.
2665		3258
		3259	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3260	makes rev work even on mingw.
		3261
		3262	=item Haskell
		3263
		3264	A haskell binding to libev is available at
		3265	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3266
2666	=item D	3267	=item D
2667		3268
2668	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3269	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>.	3270	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3271
		3272	=item Ocaml
		3273
		3274	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3275	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2670		3276
2671	=back	3277	=back
2672		3278
2673		3279
2674	=head1 MACRO MAGIC	3280	=head1 MACRO MAGIC
…		…
2775		3381
2776	#define EV_STANDALONE 1	3382	#define EV_STANDALONE 1
2777	#include "ev.h"	3383	#include "ev.h"
2778		3384
2779	Both header files and implementation files can be compiled with a C++	3385	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	3386	compiler (at least, that's a stated goal, and breakage will be treated
2781	as a bug).	3387	as a bug).
2782		3388
2783	You need the following files in your source tree, or in a directory	3389	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):	3390	in your include path (e.g. in libev/ when using -Ilibev):
2785		3391
…		…
2829		3435
2830	=head2 PREPROCESSOR SYMBOLS/MACROS	3436	=head2 PREPROCESSOR SYMBOLS/MACROS
2831		3437
2832	Libev can be configured via a variety of preprocessor symbols you have to	3438	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	3439	define before including any of its files. The default in the absence of
2834	autoconf is noted for every option.	3440	autoconf is documented for every option.
2835		3441
2836	=over 4	3442	=over 4
2837		3443
2838	=item EV_STANDALONE	3444	=item EV_STANDALONE
2839		3445
…		…
2841	keeps libev from including F<config.h>, and it also defines dummy	3447	keeps libev from including F<config.h>, and it also defines dummy
2842	implementations for some libevent functions (such as logging, which is not	3448	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	3449	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.	3450	F<event.h> that are not directly supported by the libev core alone.
2845		3451
		3452	In stanbdalone mode, libev will still try to automatically deduce the
		3453	configuration, but has to be more conservative.
		3454
2846	=item EV_USE_MONOTONIC	3455	=item EV_USE_MONOTONIC
2847		3456
2848	If defined to be C<1>, libev will try to detect the availability of the	3457	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	3458	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	3459	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	3460	you usually have to link against librt or something similar. Enabling it
2852	the functionality isn't available is safe, though, although you have	3461	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>	3462	to make sure you link against any libraries where the C<clock_gettime>
2854	function is hiding in (often F<-lrt>).	3463	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2855		3464
2856	=item EV_USE_REALTIME	3465	=item EV_USE_REALTIME
2857		3466
2858	If defined to be C<1>, libev will try to detect the availability of the	3467	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	3468	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	3469	at runtime if successful). Otherwise no use of the real-time clock
2861	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3470	option will be attempted. This effectively replaces C<gettimeofday>
2862	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3471	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2863	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3472	correctness. See the note about libraries in the description of
		3473	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3474	C<EV_USE_CLOCK_SYSCALL>.
		3475
		3476	=item EV_USE_CLOCK_SYSCALL
		3477
		3478	If defined to be C<1>, libev will try to use a direct syscall instead
		3479	of calling the system-provided C<clock_gettime> function. This option
		3480	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3481	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3482	programs needlessly. Using a direct syscall is slightly slower (in
		3483	theory), because no optimised vdso implementation can be used, but avoids
		3484	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3485	higher, as it simplifies linking (no need for C<-lrt>).
2864		3486
2865	=item EV_USE_NANOSLEEP	3487	=item EV_USE_NANOSLEEP
2866		3488
2867	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3489	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 ()>.	3490	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2884		3506
2885	=item EV_SELECT_USE_FD_SET	3507	=item EV_SELECT_USE_FD_SET
2886		3508
2887	If defined to C<1>, then the select backend will use the system C<fd_set>	3509	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	3510	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	3511	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	3512	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	3513	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	3514	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2893	influence the size of the C<fd_set> used.	3515	configures the maximum size of the C<fd_set>.
2894		3516
2895	=item EV_SELECT_IS_WINSOCKET	3517	=item EV_SELECT_IS_WINSOCKET
2896		3518
2897	When defined to C<1>, the select backend will assume that	3519	When defined to C<1>, the select backend will assume that
2898	select/socket/connect etc. don't understand file descriptors but	3520	select/socket/connect etc. don't understand file descriptors but
…		…
3009	When doing priority-based operations, libev usually has to linearly search	3631	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	3632	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	3633	and time, so using the defaults of five priorities (-2 .. +2) is usually
3012	fine.	3634	fine.
3013		3635
3014	If your embedding application does not need any priorities, defining these both to	3636	If your embedding application does not need any priorities, defining these
3015	C<0> will save some memory and CPU.	3637	both to C<0> will save some memory and CPU.
3016		3638
3017	=item EV_PERIODIC_ENABLE	3639	=item EV_PERIODIC_ENABLE
3018		3640
3019	If undefined or defined to be C<1>, then periodic timers are supported. If	3641	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	3642	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3027	code.	3649	code.
3028		3650
3029	=item EV_EMBED_ENABLE	3651	=item EV_EMBED_ENABLE
3030		3652
3031	If undefined or defined to be C<1>, then embed watchers are supported. If	3653	If undefined or defined to be C<1>, then embed watchers are supported. If
3032	defined to be C<0>, then they are not.	3654	defined to be C<0>, then they are not. Embed watchers rely on most other
		3655	watcher types, which therefore must not be disabled.
3033		3656
3034	=item EV_STAT_ENABLE	3657	=item EV_STAT_ENABLE
3035		3658
3036	If undefined or defined to be C<1>, then stat watchers are supported. If	3659	If undefined or defined to be C<1>, then stat watchers are supported. If
3037	defined to be C<0>, then they are not.	3660	defined to be C<0>, then they are not.
…		…
3069	two).	3692	two).
3070		3693
3071	=item EV_USE_4HEAP	3694	=item EV_USE_4HEAP
3072		3695
3073	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3696	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	3697	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	3698	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3076	noticeably faster performance with many (thousands) of watchers.	3699	faster performance with many (thousands) of watchers.
3077		3700
3078	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3701	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3079	(disabled).	3702	(disabled).
3080		3703
3081	=item EV_HEAP_CACHE_AT	3704	=item EV_HEAP_CACHE_AT
3082		3705
3083	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3706	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	3707	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>),	3708	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,	3709	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	3710	but avoids random read accesses on heap changes. This improves performance
3088	noticeably with with many (hundreds) of watchers.	3711	noticeably with many (hundreds) of watchers.
3089		3712
3090	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3713	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3091	(disabled).	3714	(disabled).
3092		3715
3093	=item EV_VERIFY	3716	=item EV_VERIFY
…		…
3099	called once per loop, which can slow down libev. If set to C<3>, then the	3722	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	3723	verification code will be called very frequently, which will slow down
3101	libev considerably.	3724	libev considerably.
3102		3725
3103	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3726	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3104	C<0.>	3727	C<0>.
3105		3728
3106	=item EV_COMMON	3729	=item EV_COMMON
3107		3730
3108	By default, all watchers have a C<void *data> member. By redefining	3731	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	3732	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	3749	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	3750	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	3751	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	3752	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++.	3753	method calls instead of plain function calls in C++.
		3754
		3755	=back
3131		3756
3132	=head2 EXPORTED API SYMBOLS	3757	=head2 EXPORTED API SYMBOLS
3133		3758
3134	If you need to re-export the API (e.g. via a DLL) and you need a list of	3759	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	3760	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:	3807	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3183		3808
3184	#include "ev_cpp.h"	3809	#include "ev_cpp.h"
3185	#include "ev.c"	3810	#include "ev.c"
3186		3811
		3812	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3187		3813
3188	=head1 THREADS AND COROUTINES	3814	=head2 THREADS AND COROUTINES
3189		3815
3190	=head2 THREADS	3816	=head3 THREADS
3191		3817
3192	Libev itself is completely thread-safe, but it uses no locking. This	3818	All libev functions are reentrant and thread-safe unless explicitly
		3819	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	3820	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	3821	are no concurrent calls into any libev function with the same loop
3195	parameter.	3822	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3823	of course): libev guarantees that different event loops share no data
		3824	structures that need any locking.
3196		3825
3197	Or put differently: calls with different loop parameters can be done in	3826	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	3827	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	3828	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	3829	only one thread ever is inside a call at any point in time, e.g. by using
3201	per loop).	3830	a mutex per loop).
		3831
		3832	Specifically to support threads (and signal handlers), libev implements
		3833	so-called C<ev_async> watchers, which allow some limited form of
		3834	concurrency on the same event loop, namely waking it up "from the
		3835	outside".
3202		3836
3203	If you want to know which design (one loop, locking, or multiple loops	3837	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	3838	without or something else still) is best for your problem, then I cannot
3205	help you. I can give some generic advice however:	3839	help you, but here is some generic advice:
3206		3840
3207	=over 4	3841	=over 4
3208		3842
3209	=item * most applications have a main thread: use the default libev loop	3843	=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.	3844	in that thread, or create a separate thread running only the default loop.
…		…
3222		3856
3223	Choosing a model is hard - look around, learn, know that usually you can do	3857	Choosing a model is hard - look around, learn, know that usually you can do
3224	better than you currently do :-)	3858	better than you currently do :-)
3225		3859
3226	=item * often you need to talk to some other thread which blocks in the	3860	=item * often you need to talk to some other thread which blocks in the
		3861	event loop.
		3862
3227	event loop - C<ev_async> watchers can be used to wake them up from other	3863	C<ev_async> watchers can be used to wake them up from other threads safely
3228	threads safely (or from signal contexts...).	3864	(or from signal contexts...).
		3865
		3866	An example use would be to communicate signals or other events that only
		3867	work in the default loop by registering the signal watcher with the
		3868	default loop and triggering an C<ev_async> watcher from the default loop
		3869	watcher callback into the event loop interested in the signal.
3229		3870
3230	=back	3871	=back
3231		3872
3232	=head2 COROUTINES	3873	=head3 COROUTINES
3233		3874
3234	Libev is much more accommodating to coroutines ("cooperative threads"):	3875	Libev is very accommodating to coroutines ("cooperative threads"):
3235	libev fully supports nesting calls to it's functions from different	3876	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	3877	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	3878	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	3879	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.	3880	you must not do this from C<ev_periodic> reschedule callbacks.
3240		3881
3241	Care has been invested into making sure that libev does not keep local	3882	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	3883	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3243	switches.	3884	they do not call any callbacks.
3244		3885
		3886	=head2 COMPILER WARNINGS
3245		3887
3246	=head1 COMPLEXITIES	3888	Depending on your compiler and compiler settings, you might get no or a
		3889	lot of warnings when compiling libev code. Some people are apparently
		3890	scared by this.
3247		3891
3248	In this section the complexities of (many of) the algorithms used inside	3892	However, these are unavoidable for many reasons. For one, each compiler
3249	libev will be explained. For complexity discussions about backends see the	3893	has different warnings, and each user has different tastes regarding
3250	documentation for C<ev_default_init>.	3894	warning options. "Warn-free" code therefore cannot be a goal except when
		3895	targeting a specific compiler and compiler-version.
3251		3896
3252	All of the following are about amortised time: If an array needs to be	3897	Another reason is that some compiler warnings require elaborate
3253	extended, libev needs to realloc and move the whole array, but this	3898	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	3899	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		3900
3258	=over 4	3901	And of course, some compiler warnings are just plain stupid, or simply
		3902	wrong (because they don't actually warn about the condition their message
		3903	seems to warn about). For example, certain older gcc versions had some
		3904	warnings that resulted an extreme number of false positives. These have
		3905	been fixed, but some people still insist on making code warn-free with
		3906	such buggy versions.
3259		3907
3260	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3908	While libev is written to generate as few warnings as possible,
		3909	"warn-free" code is not a goal, and it is recommended not to build libev
		3910	with any compiler warnings enabled unless you are prepared to cope with
		3911	them (e.g. by ignoring them). Remember that warnings are just that:
		3912	warnings, not errors, or proof of bugs.
3261		3913
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		3914
3266	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3915	=head2 VALGRIND
3267		3916
3268	That means that changing a timer costs less than removing/adding them	3917	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.	3918	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3270		3919
3271	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3920	If you think you found a bug (memory leak, uninitialised data access etc.)
		3921	in libev, then check twice: If valgrind reports something like:
3272		3922
3273	These just add the watcher into an array or at the head of a list.	3923	==2274== definitely lost: 0 bytes in 0 blocks.
		3924	==2274== possibly lost: 0 bytes in 0 blocks.
		3925	==2274== still reachable: 256 bytes in 1 blocks.
3274		3926
3275	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3927	Then there is no memory leak, just as memory accounted to global variables
		3928	is not a memleak - the memory is still being referenced, and didn't leak.
3276		3929
3277	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3930	Similarly, under some circumstances, valgrind might report kernel bugs
		3931	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3932	although an acceptable workaround has been found here), or it might be
		3933	confused.
3278		3934
3279	These watchers are stored in lists then need to be walked to find the	3935	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	3936	make it into some kind of religion.
3281	have many watchers waiting for the same fd or signal).
3282		3937
3283	=item Finding the next timer in each loop iteration: O(1)	3938	If you are unsure about something, feel free to contact the mailing list
		3939	with the full valgrind report and an explanation on why you think this
		3940	is a bug in libev (best check the archives, too :). However, don't be
		3941	annoyed when you get a brisk "this is no bug" answer and take the chance
		3942	of learning how to interpret valgrind properly.
3284		3943
3285	By virtue of using a binary or 4-heap, the next timer is always found at a	3944	If you need, for some reason, empty reports from valgrind for your project
3286	fixed position in the storage array.	3945	I suggest using suppression lists.
3287		3946
3288	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3289		3947
3290	A change means an I/O watcher gets started or stopped, which requires	3948	=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		3949
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	3950	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3317		3951
3318	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3952	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	3953	requires, and its I/O model is fundamentally incompatible with the POSIX
3320	model. Libev still offers limited functionality on this platform in	3954	model. Libev still offers limited functionality on this platform in
3321	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3955	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).	3962	way (note also that glib is the slowest event library known to man).
3329		3963
3330	There is no supported compilation method available on windows except	3964	There is no supported compilation method available on windows except
3331	embedding it into other applications.	3965	embedding it into other applications.
3332		3966
		3967	Sensible signal handling is officially unsupported by Microsoft - libev
		3968	tries its best, but under most conditions, signals will simply not work.
		3969
3333	Not a libev limitation but worth mentioning: windows apparently doesn't	3970	Not a libev limitation but worth mentioning: windows apparently doesn't
3334	accept large writes: instead of resulting in a partial write, windows will	3971	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,	3972	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	3973	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	3974	megabyte seems safe, but this apparently depends on the amount of memory
3338	available).	3975	available).
3339		3976
3340	Due to the many, low, and arbitrary limits on the win32 platform and	3977	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	3978	the abysmal performance of winsockets, using a large number of sockets
3342	is not recommended (and not reasonable). If your program needs to use	3979	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	3980	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	3981	different implementation for windows, as libev offers the POSIX readiness
3345	notification model, which cannot be implemented efficiently on windows	3982	notification model, which cannot be implemented efficiently on windows
3346	(Microsoft monopoly games).	3983	(due to Microsoft monopoly games).
3347		3984
3348	A typical way to use libev under windows is to embed it (see the embedding	3985	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	3986	section for details) and use the following F<evwrap.h> header file instead
3350	of F<ev.h>:	3987	of F<ev.h>:
3351		3988
…		…
3353	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	3990	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3354		3991
3355	#include "ev.h"	3992	#include "ev.h"
3356		3993
3357	And compile the following F<evwrap.c> file into your project (make sure	3994	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!):	3995	you do I<not> compile the F<ev.c> or any other embedded source files!):
3359		3996
3360	#include "evwrap.h"	3997	#include "evwrap.h"
3361	#include "ev.c"	3998	#include "ev.c"
3362		3999
3363	=over 4	4000	=over 4
…		…
3387		4024
3388	Early versions of winsocket's select only supported waiting for a maximum	4025	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	4026	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	4027	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	4028	recommends spawning a chain of threads and wait for 63 handles and the
3392	previous thread in each. Great).	4029	previous thread in each. Sounds great!).
3393		4030
3394	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4031	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	4032	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	4033	call (which might be in libev or elsewhere, for example, perl and many
3397	select emulation on windows).	4034	other interpreters do their own select emulation on windows).
3398		4035
3399	Another limit is the number of file descriptors in the Microsoft runtime	4036	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	4037	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	4038	fetish or something like this inside Microsoft). You can increase this
3402	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4039	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	4040	(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	4041	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	4042	(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	4043	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.	4044	the cost of calling select (O(n²)) will likely make this unworkable.
3410		4045
3411	=back	4046	=back
3412		4047
3413
3414	=head1 PORTABILITY REQUIREMENTS	4048	=head2 PORTABILITY REQUIREMENTS
3415		4049
3416	In addition to a working ISO-C implementation, libev relies on a few	4050	In addition to a working ISO-C implementation and of course the
3417	additional extensions:	4051	backend-specific APIs, libev relies on a few additional extensions:
3418		4052
3419	=over 4	4053	=over 4
3420		4054
3421	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	4055	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3422	calling conventions regardless of C<ev_watcher_type *>.	4056	calling conventions regardless of C<ev_watcher_type *>.
…		…
3428	calls them using an C<ev_watcher *> internally.	4062	calls them using an C<ev_watcher *> internally.
3429		4063
3430	=item C<sig_atomic_t volatile> must be thread-atomic as well	4064	=item C<sig_atomic_t volatile> must be thread-atomic as well
3431		4065
3432	The type C<sig_atomic_t volatile> (or whatever is defined as	4066	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	4067	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	4068	threads. This is not part of the specification for C<sig_atomic_t>, but is
3435	believed to be sufficiently portable.	4069	believed to be sufficiently portable.
3436		4070
3437	=item C<sigprocmask> must work in a threaded environment	4071	=item C<sigprocmask> must work in a threaded environment
3438		4072
…		…
3447	except the initial one, and run the default loop in the initial thread as	4081	except the initial one, and run the default loop in the initial thread as
3448	well.	4082	well.
3449		4083
3450	=item C<long> must be large enough for common memory allocation sizes	4084	=item C<long> must be large enough for common memory allocation sizes
3451		4085
3452	To improve portability and simplify using libev, libev uses C<long>	4086	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	4087	instead of C<size_t> when allocating its data structures. On non-POSIX
3454	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4088	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	4089	least 31 bits everywhere, which is enough for hundreds of millions of
3456	millions of watchers.	4090	watchers.
3457		4091
3458	=item C<double> must hold a time value in seconds with enough accuracy	4092	=item C<double> must hold a time value in seconds with enough accuracy
3459		4093
3460	The type C<double> is used to represent timestamps. It is required to	4094	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	4095	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	4096	enough for at least into the year 4000. This requirement is fulfilled by
3463	implementations implementing IEEE 754 (basically all existing ones).	4097	implementations implementing IEEE 754, which is basically all existing
		4098	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4099	2200.
3464		4100
3465	=back	4101	=back
3466		4102
3467	If you know of other additional requirements drop me a note.	4103	If you know of other additional requirements drop me a note.
3468		4104
3469		4105
3470	=head1 COMPILER WARNINGS	4106	=head1 ALGORITHMIC COMPLEXITIES
3471		4107
3472	Depending on your compiler and compiler settings, you might get no or a	4108	In this section the complexities of (many of) the algorithms used inside
3473	lot of warnings when compiling libev code. Some people are apparently	4109	libev will be documented. For complexity discussions about backends see
3474	scared by this.	4110	the documentation for C<ev_default_init>.
3475		4111
3476	However, these are unavoidable for many reasons. For one, each compiler	4112	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	4113	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	4114	happens asymptotically rarer with higher number of elements, so O(1) might
3479	targeting a specific compiler and compiler-version.	4115	mean that libev does a lengthy realloc operation in rare cases, but on
		4116	average it is much faster and asymptotically approaches constant time.
3480		4117
3481	Another reason is that some compiler warnings require elaborate	4118	=over 4
3482	workarounds, or other changes to the code that make it less clear and less
3483	maintainable.
3484		4119
3485	And of course, some compiler warnings are just plain stupid, or simply	4120	=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		4121
3489	While libev is written to generate as few warnings as possible,	4122	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	4123	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	4124	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		4125
		4126	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3495		4127
3496	=head1 VALGRIND	4128	That means that changing a timer costs less than removing/adding them,
		4129	as only the relative motion in the event queue has to be paid for.
3497		4130
3498	Valgrind has a special section here because it is a popular tool that is	4131	=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		4132
3501	If you think you found a bug (memory leak, uninitialised data access etc.)	4133	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		4134
3504	==2274== definitely lost: 0 bytes in 0 blocks.	4135	=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		4136
3508	Then there is no memory leak. Similarly, under some circumstances,	4137	=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		4138
3512	If you are unsure about something, feel free to contact the mailing list	4139	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	4140	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	4141	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	4142	is rare).
3516	properly.
3517		4143
3518	If you need, for some reason, empty reports from valgrind for your project	4144	=item Finding the next timer in each loop iteration: O(1)
3519	I suggest using suppression lists.
3520		4145
		4146	By virtue of using a binary or 4-heap, the next timer is always found at a
		4147	fixed position in the storage array.
		4148
		4149	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4150
		4151	A change means an I/O watcher gets started or stopped, which requires
		4152	libev to recalculate its status (and possibly tell the kernel, depending
		4153	on backend and whether C<ev_io_set> was used).
		4154
		4155	=item Activating one watcher (putting it into the pending state): O(1)
		4156
		4157	=item Priority handling: O(number_of_priorities)
		4158
		4159	Priorities are implemented by allocating some space for each
		4160	priority. When doing priority-based operations, libev usually has to
		4161	linearly search all the priorities, but starting/stopping and activating
		4162	watchers becomes O(1) with respect to priority handling.
		4163
		4164	=item Sending an ev_async: O(1)
		4165
		4166	=item Processing ev_async_send: O(number_of_async_watchers)
		4167
		4168	=item Processing signals: O(max_signal_number)
		4169
		4170	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4171	calls in the current loop iteration. Checking for async and signal events
		4172	involves iterating over all running async watchers or all signal numbers.
		4173
		4174	=back
		4175
		4176
		4177	=head1 GLOSSARY
		4178
		4179	=over 4
		4180
		4181	=item active
		4182
		4183	A watcher is active as long as it has been started (has been attached to
		4184	an event loop) but not yet stopped (disassociated from the event loop).
		4185
		4186	=item application
		4187
		4188	In this document, an application is whatever is using libev.
		4189
		4190	=item callback
		4191
		4192	The address of a function that is called when some event has been
		4193	detected. Callbacks are being passed the event loop, the watcher that
		4194	received the event, and the actual event bitset.
		4195
		4196	=item callback invocation
		4197
		4198	The act of calling the callback associated with a watcher.
		4199
		4200	=item event
		4201
		4202	A change of state of some external event, such as data now being available
		4203	for reading on a file descriptor, time having passed or simply not having
		4204	any other events happening anymore.
		4205
		4206	In libev, events are represented as single bits (such as C<EV_READ> or
		4207	C<EV_TIMEOUT>).
		4208
		4209	=item event library
		4210
		4211	A software package implementing an event model and loop.
		4212
		4213	=item event loop
		4214
		4215	An entity that handles and processes external events and converts them
		4216	into callback invocations.
		4217
		4218	=item event model
		4219
		4220	The model used to describe how an event loop handles and processes
		4221	watchers and events.
		4222
		4223	=item pending
		4224
		4225	A watcher is pending as soon as the corresponding event has been detected,
		4226	and stops being pending as soon as the watcher will be invoked or its
		4227	pending status is explicitly cleared by the application.
		4228
		4229	A watcher can be pending, but not active. Stopping a watcher also clears
		4230	its pending status.
		4231
		4232	=item real time
		4233
		4234	The physical time that is observed. It is apparently strictly monotonic :)
		4235
		4236	=item wall-clock time
		4237
		4238	The time and date as shown on clocks. Unlike real time, it can actually
		4239	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4240	clock.
		4241
		4242	=item watcher
		4243
		4244	A data structure that describes interest in certain events. Watchers need
		4245	to be started (attached to an event loop) before they can receive events.
		4246
		4247	=item watcher invocation
		4248
		4249	The act of calling the callback associated with a watcher.
		4250
		4251	=back
3521		4252
3522	=head1 AUTHOR	4253	=head1 AUTHOR
3523		4254
3524	Marc Lehmann <libev@schmorp.de>.	4255	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3525		4256

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