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…		…
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
		14	#include <stdio.h> // for puts
		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
18		20
19	// all watcher callbacks have a similar signature	21	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	22	// this callback is called when data is readable on stdin
21	static void	23	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	25	{
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
…		…
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	42	}
…		…
60		62
61	// unloop was called, so exit	63	// unloop was called, so exit
62	return 0;	64	return 0;
63	}	65	}
64		66
65	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
66		70
67	The newest version of this document is also available as an html-formatted	71	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	72	web page you might find easier to navigate when reading it for the first
69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.	73	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		74
		75	While this document tries to be as complete as possible in documenting
		76	libev, its usage and the rationale behind its design, it is not a tutorial
		77	on event-based programming, nor will it introduce event-based programming
		78	with libev.
		79
		80	Familarity with event based programming techniques in general is assumed
		81	throughout this document.
		82
		83	=head1 ABOUT LIBEV
70		84
71	Libev is an event loop: you register interest in certain events (such as a	85	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	86	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	87	these event sources and provide your program with events.
74		88
…		…
103	Libev is very configurable. In this manual the default (and most common)	117	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	118	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	119	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	120	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	121	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	122	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	123	this argument.
110		124
111	=head2 TIME REPRESENTATION	125	=head2 TIME REPRESENTATION
112		126
113	Libev represents time as a single floating point number, representing the	127	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	128	the (fractional) number of seconds since the (POSIX) epoch (somewhere
115	the beginning of 1970, details are complicated, don't ask). This type is	129	near the beginning of 1970, details are complicated, don't ask). This
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	130	type is called C<ev_tstamp>, which is what you should use too. It usually
117	to the C<double> type in C, and when you need to do any calculations on	131	aliases to the C<double> type in C. When you need to do any calculations
118	it, you should treat it as some floating point value. Unlike the name	132	on it, you should treat it as some floating point value. Unlike the name
119	component C<stamp> might indicate, it is also used for time differences	133	component C<stamp> might indicate, it is also used for time differences
120	throughout libev.	134	throughout libev.
121		135
122	=head1 ERROR HANDLING	136	=head1 ERROR HANDLING
123		137
…		…
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	228	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
215	recommended ones.	229	recommended ones.
216		230
217	See the description of C<ev_embed> watchers for more info.	231	See the description of C<ev_embed> watchers for more info.
218		232
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	233	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
220		234
221	Sets the allocation function to use (the prototype is similar - the	235	Sets the allocation function to use (the prototype is similar - the
222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	236	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
223	used to allocate and free memory (no surprises here). If it returns zero	237	used to allocate and free memory (no surprises here). If it returns zero
224	when memory needs to be allocated (C<size != 0>), the library might abort	238	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	264	}
251		265
252	...	266	...
253	ev_set_allocator (persistent_realloc);	267	ev_set_allocator (persistent_realloc);
254		268
255	=item ev_set_syserr_cb (void (*cb)(const char *msg));	269	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
256		270
257	Set the callback function to call on a retryable system call error (such	271	Set the callback function to call on a retryable system call error (such
258	as failed select, poll, epoll_wait). The message is a printable string	272	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	273	indicating the system call or subsystem causing the problem. If this
260	callback is set, then libev will expect it to remedy the situation, no	274	callback is set, then libev will expect it to remedy the situation, no
…		…
276		290
277	=back	291	=back
278		292
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	293	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
280		294
281	An event loop is described by a C<struct ev_loop *>. The library knows two	295	An event loop is described by a C<struct ev_loop *> (the C<struct>
282	types of such loops, the I<default> loop, which supports signals and child	296	is I<not> optional in this case, as there is also an C<ev_loop>
283	events, and dynamically created loops which do not.	297	I<function>).
		298
		299	The library knows two types of such loops, the I<default> loop, which
		300	supports signals and child events, and dynamically created loops which do
		301	not.
284		302
285	=over 4	303	=over 4
286		304
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	305	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		306
…		…
294	If you don't know what event loop to use, use the one returned from this	312	If you don't know what event loop to use, use the one returned from this
295	function.	313	function.
296		314
297	Note that this function is I<not> thread-safe, so if you want to use it	315	Note that this function is I<not> thread-safe, so if you want to use it
298	from multiple threads, you have to lock (note also that this is unlikely,	316	from multiple threads, you have to lock (note also that this is unlikely,
299	as loops cannot bes hared easily between threads anyway).	317	as loops cannot be shared easily between threads anyway).
300		318
301	The default loop is the only loop that can handle C<ev_signal> and	319	The default loop is the only loop that can handle C<ev_signal> and
302	C<ev_child> watchers, and to do this, it always registers a handler	320	C<ev_child> watchers, and to do this, it always registers a handler
303	for C<SIGCHLD>. If this is a problem for your application you can either	321	for C<SIGCHLD>. If this is a problem for your application you can either
304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	322	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
…		…
359	writing a server, you should C<accept ()> in a loop to accept as many	377	writing a server, you should C<accept ()> in a loop to accept as many
360	connections as possible during one iteration. You might also want to have	378	connections as possible during one iteration. You might also want to have
361	a look at C<ev_set_io_collect_interval ()> to increase the amount of	379	a look at C<ev_set_io_collect_interval ()> to increase the amount of
362	readiness notifications you get per iteration.	380	readiness notifications you get per iteration.
363		381
		382	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		383	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		384	C<exceptfds> set on that platform).
		385
364	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	386	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
365		387
366	And this is your standard poll(2) backend. It's more complicated	388	And this is your standard poll(2) backend. It's more complicated
367	than select, but handles sparse fds better and has no artificial	389	than select, but handles sparse fds better and has no artificial
368	limit on the number of fds you can use (except it will slow down	390	limit on the number of fds you can use (except it will slow down
369	considerably with a lot of inactive fds). It scales similarly to select,	391	considerably with a lot of inactive fds). It scales similarly to select,
370	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for	392	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
371	performance tips.	393	performance tips.
372		394
		395	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		396	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		397
373	=item C<EVBACKEND_EPOLL> (value 4, Linux)	398	=item C<EVBACKEND_EPOLL> (value 4, Linux)
374		399
375	For few fds, this backend is a bit little slower than poll and select,	400	For few fds, this backend is a bit little slower than poll and select,
376	but it scales phenomenally better. While poll and select usually scale	401	but it scales phenomenally better. While poll and select usually scale
377	like O(total_fds) where n is the total number of fds (or the highest fd),	402	like O(total_fds) where n is the total number of fds (or the highest fd),
378	epoll scales either O(1) or O(active_fds). The epoll design has a number	403	epoll scales either O(1) or O(active_fds).
379	of shortcomings, such as silently dropping events in some hard-to-detect	404
380	cases and requiring a system call per fd change, no fork support and bad	405	The epoll mechanism deserves honorable mention as the most misdesigned
381	support for dup.	406	of the more advanced event mechanisms: mere annoyances include silently
		407	dropping file descriptors, requiring a system call per change per file
		408	descriptor (and unnecessary guessing of parameters), problems with dup and
		409	so on. The biggest issue is fork races, however - if a program forks then
		410	I<both> parent and child process have to recreate the epoll set, which can
		411	take considerable time (one syscall per file descriptor) and is of course
		412	hard to detect.
		413
		414	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		415	of course I<doesn't>, and epoll just loves to report events for totally
		416	I<different> file descriptors (even already closed ones, so one cannot
		417	even remove them from the set) than registered in the set (especially
		418	on SMP systems). Libev tries to counter these spurious notifications by
		419	employing an additional generation counter and comparing that against the
		420	events to filter out spurious ones, recreating the set when required.
382		421
383	While stopping, setting and starting an I/O watcher in the same iteration	422	While stopping, setting and starting an I/O watcher in the same iteration
384	will result in some caching, there is still a system call per such incident	423	will result in some caching, there is still a system call per such
385	(because the fd could point to a different file description now), so its	424	incident (because the same I<file descriptor> could point to a different
386	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	425	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
387	very well if you register events for both fds.	426	file descriptors might not work very well if you register events for both
388		427	file descriptors.
389	Please note that epoll sometimes generates spurious notifications, so you
390	need to use non-blocking I/O or other means to avoid blocking when no data
391	(or space) is available.
392		428
393	Best performance from this backend is achieved by not unregistering all	429	Best performance from this backend is achieved by not unregistering all
394	watchers for a file descriptor until it has been closed, if possible, i.e.	430	watchers for a file descriptor until it has been closed, if possible,
395	keep at least one watcher active per fd at all times.	431	i.e. keep at least one watcher active per fd at all times. Stopping and
		432	starting a watcher (without re-setting it) also usually doesn't cause
		433	extra overhead. A fork can both result in spurious notifications as well
		434	as in libev having to destroy and recreate the epoll object, which can
		435	take considerable time and thus should be avoided.
		436
		437	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		438	faster than epoll for maybe up to a hundred file descriptors, depending on
		439	the usage. So sad.
396		440
397	While nominally embeddable in other event loops, this feature is broken in	441	While nominally embeddable in other event loops, this feature is broken in
398	all kernel versions tested so far.	442	all kernel versions tested so far.
		443
		444	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		445	C<EVBACKEND_POLL>.
399		446
400	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	447	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
401		448
402	Kqueue deserves special mention, as at the time of this writing, it	449	Kqueue deserves special mention, as at the time of this writing, it
403	was broken on all BSDs except NetBSD (usually it doesn't work reliably	450	was broken on all BSDs except NetBSD (usually it doesn't work reliably
404	with anything but sockets and pipes, except on Darwin, where of course	451	with anything but sockets and pipes, except on Darwin, where of course
405	it's completely useless). For this reason it's not being "auto-detected"	452	it's completely useless). Unlike epoll, however, whose brokenness
		453	is by design, these kqueue bugs can (and eventually will) be fixed
		454	without API changes to existing programs. For this reason it's not being
406	unless you explicitly specify it explicitly in the flags (i.e. using	455	"auto-detected" unless you explicitly specify it in the flags (i.e. using
407	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	456	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
408	system like NetBSD.	457	system like NetBSD.
409		458
410	You still can embed kqueue into a normal poll or select backend and use it	459	You still can embed kqueue into a normal poll or select backend and use it
411	only for sockets (after having made sure that sockets work with kqueue on	460	only for sockets (after having made sure that sockets work with kqueue on
…		…
413		462
414	It scales in the same way as the epoll backend, but the interface to the	463	It scales in the same way as the epoll backend, but the interface to the
415	kernel is more efficient (which says nothing about its actual speed, of	464	kernel is more efficient (which says nothing about its actual speed, of
416	course). While stopping, setting and starting an I/O watcher does never	465	course). While stopping, setting and starting an I/O watcher does never
417	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	466	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
418	two event changes per incident, support for C<fork ()> is very bad and it	467	two event changes per incident. Support for C<fork ()> is very bad (but
419	drops fds silently in similarly hard-to-detect cases.	468	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		469	cases
420		470
421	This backend usually performs well under most conditions.	471	This backend usually performs well under most conditions.
422		472
423	While nominally embeddable in other event loops, this doesn't work	473	While nominally embeddable in other event loops, this doesn't work
424	everywhere, so you might need to test for this. And since it is broken	474	everywhere, so you might need to test for this. And since it is broken
425	almost everywhere, you should only use it when you have a lot of sockets	475	almost everywhere, you should only use it when you have a lot of sockets
426	(for which it usually works), by embedding it into another event loop	476	(for which it usually works), by embedding it into another event loop
427	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	477	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
428	sockets.	478	also broken on OS X)) and, did I mention it, using it only for sockets.
		479
		480	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		481	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		482	C<NOTE_EOF>.
429		483
430	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	484	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
431		485
432	This is not implemented yet (and might never be, unless you send me an	486	This is not implemented yet (and might never be, unless you send me an
433	implementation). According to reports, C</dev/poll> only supports sockets	487	implementation). According to reports, C</dev/poll> only supports sockets
…		…
446	While this backend scales well, it requires one system call per active	500	While this backend scales well, it requires one system call per active
447	file descriptor per loop iteration. For small and medium numbers of file	501	file descriptor per loop iteration. For small and medium numbers of file
448	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	502	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
449	might perform better.	503	might perform better.
450		504
451	On the positive side, ignoring the spurious readiness notifications, this	505	On the positive side, with the exception of the spurious readiness
452	backend actually performed to specification in all tests and is fully	506	notifications, this backend actually performed fully to specification
453	embeddable, which is a rare feat among the OS-specific backends.	507	in all tests and is fully embeddable, which is a rare feat among the
		508	OS-specific backends (I vastly prefer correctness over speed hacks).
		509
		510	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		511	C<EVBACKEND_POLL>.
454		512
455	=item C<EVBACKEND_ALL>	513	=item C<EVBACKEND_ALL>
456		514
457	Try all backends (even potentially broken ones that wouldn't be tried	515	Try all backends (even potentially broken ones that wouldn't be tried
458	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	516	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
464		522
465	If one or more of these are or'ed into the flags value, then only these	523	If one or more of these are or'ed into the flags value, then only these
466	backends will be tried (in the reverse order as listed here). If none are	524	backends will be tried (in the reverse order as listed here). If none are
467	specified, all backends in C<ev_recommended_backends ()> will be tried.	525	specified, all backends in C<ev_recommended_backends ()> will be tried.
468		526
469	The most typical usage is like this:	527	Example: This is the most typical usage.
470		528
471	if (!ev_default_loop (0))	529	if (!ev_default_loop (0))
472	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	530	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
473		531
474	Restrict libev to the select and poll backends, and do not allow	532	Example: Restrict libev to the select and poll backends, and do not allow
475	environment settings to be taken into account:	533	environment settings to be taken into account:
476		534
477	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	535	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
478		536
479	Use whatever libev has to offer, but make sure that kqueue is used if	537	Example: Use whatever libev has to offer, but make sure that kqueue is
480	available (warning, breaks stuff, best use only with your own private	538	used if available (warning, breaks stuff, best use only with your own
481	event loop and only if you know the OS supports your types of fds):	539	private event loop and only if you know the OS supports your types of
		540	fds):
482		541
483	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	542	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
484		543
485	=item struct ev_loop *ev_loop_new (unsigned int flags)	544	=item struct ev_loop *ev_loop_new (unsigned int flags)
486		545
…		…
507	responsibility to either stop all watchers cleanly yourself I<before>	566	responsibility to either stop all watchers cleanly yourself I<before>
508	calling this function, or cope with the fact afterwards (which is usually	567	calling this function, or cope with the fact afterwards (which is usually
509	the easiest thing, you can just ignore the watchers and/or C<free ()> them	568	the easiest thing, you can just ignore the watchers and/or C<free ()> them
510	for example).	569	for example).
511		570
512	Note that certain global state, such as signal state, will not be freed by	571	Note that certain global state, such as signal state (and installed signal
513	this function, and related watchers (such as signal and child watchers)	572	handlers), will not be freed by this function, and related watchers (such
514	would need to be stopped manually.	573	as signal and child watchers) would need to be stopped manually.
515		574
516	In general it is not advisable to call this function except in the	575	In general it is not advisable to call this function except in the
517	rare occasion where you really need to free e.g. the signal handling	576	rare occasion where you really need to free e.g. the signal handling
518	pipe fds. If you need dynamically allocated loops it is better to use	577	pipe fds. If you need dynamically allocated loops it is better to use
519	C<ev_loop_new> and C<ev_loop_destroy>).	578	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
544		603
545	=item ev_loop_fork (loop)	604	=item ev_loop_fork (loop)
546		605
547	Like C<ev_default_fork>, but acts on an event loop created by	606	Like C<ev_default_fork>, but acts on an event loop created by
548	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	607	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
549	after fork, and how you do this is entirely your own problem.	608	after fork that you want to re-use in the child, and how you do this is
		609	entirely your own problem.
550		610
551	=item int ev_is_default_loop (loop)	611	=item int ev_is_default_loop (loop)
552		612
553	Returns true when the given loop actually is the default loop, false otherwise.	613	Returns true when the given loop is, in fact, the default loop, and false
		614	otherwise.
554		615
555	=item unsigned int ev_loop_count (loop)	616	=item unsigned int ev_loop_count (loop)
556		617
557	Returns the count of loop iterations for the loop, which is identical to	618	Returns the count of loop iterations for the loop, which is identical to
558	the number of times libev did poll for new events. It starts at C<0> and	619	the number of times libev did poll for new events. It starts at C<0> and
559	happily wraps around with enough iterations.	620	happily wraps around with enough iterations.
560		621
561	This value can sometimes be useful as a generation counter of sorts (it	622	This value can sometimes be useful as a generation counter of sorts (it
562	"ticks" the number of loop iterations), as it roughly corresponds with	623	"ticks" the number of loop iterations), as it roughly corresponds with
563	C<ev_prepare> and C<ev_check> calls.	624	C<ev_prepare> and C<ev_check> calls.
		625
		626	=item unsigned int ev_loop_depth (loop)
		627
		628	Returns the number of times C<ev_loop> was entered minus the number of
		629	times C<ev_loop> was exited, in other words, the recursion depth.
		630
		631	Outside C<ev_loop>, this number is zero. In a callback, this number is
		632	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),
		633	in which case it is higher.
		634
		635	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread
		636	etc.), doesn't count as exit.
564		637
565	=item unsigned int ev_backend (loop)	638	=item unsigned int ev_backend (loop)
566		639
567	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	640	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
568	use.	641	use.
…		…
573	received events and started processing them. This timestamp does not	646	received events and started processing them. This timestamp does not
574	change as long as callbacks are being processed, and this is also the base	647	change as long as callbacks are being processed, and this is also the base
575	time used for relative timers. You can treat it as the timestamp of the	648	time used for relative timers. You can treat it as the timestamp of the
576	event occurring (or more correctly, libev finding out about it).	649	event occurring (or more correctly, libev finding out about it).
577		650
		651	=item ev_now_update (loop)
		652
		653	Establishes the current time by querying the kernel, updating the time
		654	returned by C<ev_now ()> in the progress. This is a costly operation and
		655	is usually done automatically within C<ev_loop ()>.
		656
		657	This function is rarely useful, but when some event callback runs for a
		658	very long time without entering the event loop, updating libev's idea of
		659	the current time is a good idea.
		660
		661	See also L<The special problem of time updates> in the C<ev_timer> section.
		662
		663	=item ev_suspend (loop)
		664
		665	=item ev_resume (loop)
		666
		667	These two functions suspend and resume a loop, for use when the loop is
		668	not used for a while and timeouts should not be processed.
		669
		670	A typical use case would be an interactive program such as a game: When
		671	the user presses C<^Z> to suspend the game and resumes it an hour later it
		672	would be best to handle timeouts as if no time had actually passed while
		673	the program was suspended. This can be achieved by calling C<ev_suspend>
		674	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		675	C<ev_resume> directly afterwards to resume timer processing.
		676
		677	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		678	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		679	will be rescheduled (that is, they will lose any events that would have
		680	occured while suspended).
		681
		682	After calling C<ev_suspend> you B<must not> call I<any> function on the
		683	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		684	without a previous call to C<ev_suspend>.
		685
		686	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		687	event loop time (see C<ev_now_update>).
		688
578	=item ev_loop (loop, int flags)	689	=item ev_loop (loop, int flags)
579		690
580	Finally, this is it, the event handler. This function usually is called	691	Finally, this is it, the event handler. This function usually is called
581	after you initialised all your watchers and you want to start handling	692	after you initialised all your watchers and you want to start handling
582	events.	693	events.
…		…
584	If the flags argument is specified as C<0>, it will not return until	695	If the flags argument is specified as C<0>, it will not return until
585	either no event watchers are active anymore or C<ev_unloop> was called.	696	either no event watchers are active anymore or C<ev_unloop> was called.
586		697
587	Please note that an explicit C<ev_unloop> is usually better than	698	Please note that an explicit C<ev_unloop> is usually better than
588	relying on all watchers to be stopped when deciding when a program has	699	relying on all watchers to be stopped when deciding when a program has
589	finished (especially in interactive programs), but having a program that	700	finished (especially in interactive programs), but having a program
590	automatically loops as long as it has to and no longer by virtue of	701	that automatically loops as long as it has to and no longer by virtue
591	relying on its watchers stopping correctly is a thing of beauty.	702	of relying on its watchers stopping correctly, that is truly a thing of
		703	beauty.
592		704
593	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	705	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
594	those events and any outstanding ones, but will not block your process in	706	those events and any already outstanding ones, but will not block your
595	case there are no events and will return after one iteration of the loop.	707	process in case there are no events and will return after one iteration of
		708	the loop.
596		709
597	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	710	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
598	necessary) and will handle those and any outstanding ones. It will block	711	necessary) and will handle those and any already outstanding ones. It
599	your process until at least one new event arrives, and will return after	712	will block your process until at least one new event arrives (which could
600	one iteration of the loop. This is useful if you are waiting for some	713	be an event internal to libev itself, so there is no guarantee that a
601	external event in conjunction with something not expressible using other	714	user-registered callback will be called), and will return after one
		715	iteration of the loop.
		716
		717	This is useful if you are waiting for some external event in conjunction
		718	with something not expressible using other libev watchers (i.e. "roll your
602	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	719	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
603	usually a better approach for this kind of thing.	720	usually a better approach for this kind of thing.
604		721
605	Here are the gory details of what C<ev_loop> does:	722	Here are the gory details of what C<ev_loop> does:
606		723
607	- Before the first iteration, call any pending watchers.	724	- Before the first iteration, call any pending watchers.
…		…
617	any active watchers at all will result in not sleeping).	734	any active watchers at all will result in not sleeping).
618	- Sleep if the I/O and timer collect interval say so.	735	- Sleep if the I/O and timer collect interval say so.
619	- Block the process, waiting for any events.	736	- Block the process, waiting for any events.
620	- Queue all outstanding I/O (fd) events.	737	- Queue all outstanding I/O (fd) events.
621	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	738	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
622	- Queue all outstanding timers.	739	- Queue all expired timers.
623	- Queue all outstanding periodics.	740	- Queue all expired periodics.
624	- Unless any events are pending now, queue all idle watchers.	741	- Unless any events are pending now, queue all idle watchers.
625	- Queue all check watchers.	742	- Queue all check watchers.
626	- Call all queued watchers in reverse order (i.e. check watchers first).	743	- Call all queued watchers in reverse order (i.e. check watchers first).
627	Signals and child watchers are implemented as I/O watchers, and will	744	Signals and child watchers are implemented as I/O watchers, and will
628	be handled here by queueing them when their watcher gets executed.	745	be handled here by queueing them when their watcher gets executed.
…		…
645	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	762	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
646	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	763	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
647		764
648	This "unloop state" will be cleared when entering C<ev_loop> again.	765	This "unloop state" will be cleared when entering C<ev_loop> again.
649		766
		767	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		768
650	=item ev_ref (loop)	769	=item ev_ref (loop)
651		770
652	=item ev_unref (loop)	771	=item ev_unref (loop)
653		772
654	Ref/unref can be used to add or remove a reference count on the event	773	Ref/unref can be used to add or remove a reference count on the event
655	loop: Every watcher keeps one reference, and as long as the reference	774	loop: Every watcher keeps one reference, and as long as the reference
656	count is nonzero, C<ev_loop> will not return on its own. If you have	775	count is nonzero, C<ev_loop> will not return on its own.
		776
657	a watcher you never unregister that should not keep C<ev_loop> from	777	If you have a watcher you never unregister that should not keep C<ev_loop>
658	returning, ev_unref() after starting, and ev_ref() before stopping it. For	778	from returning, call ev_unref() after starting, and ev_ref() before
		779	stopping it.
		780
659	example, libev itself uses this for its internal signal pipe: It is not	781	As an example, libev itself uses this for its internal signal pipe: It
660	visible to the libev user and should not keep C<ev_loop> from exiting if	782	is not visible to the libev user and should not keep C<ev_loop> from
661	no event watchers registered by it are active. It is also an excellent	783	exiting if no event watchers registered by it are active. It is also an
662	way to do this for generic recurring timers or from within third-party	784	excellent way to do this for generic recurring timers or from within
663	libraries. Just remember to I<unref after start> and I<ref before stop>	785	third-party libraries. Just remember to I<unref after start> and I<ref
664	(but only if the watcher wasn't active before, or was active before,	786	before stop> (but only if the watcher wasn't active before, or was active
665	respectively).	787	before, respectively. Note also that libev might stop watchers itself
		788	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		789	in the callback).
666		790
667	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	791	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
668	running when nothing else is active.	792	running when nothing else is active.
669		793
670	struct ev_signal exitsig;	794	ev_signal exitsig;
671	ev_signal_init (&exitsig, sig_cb, SIGINT);	795	ev_signal_init (&exitsig, sig_cb, SIGINT);
672	ev_signal_start (loop, &exitsig);	796	ev_signal_start (loop, &exitsig);
673	evf_unref (loop);	797	evf_unref (loop);
674		798
675	Example: For some weird reason, unregister the above signal handler again.	799	Example: For some weird reason, unregister the above signal handler again.
…		…
689	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	813	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
690	allows libev to delay invocation of I/O and timer/periodic callbacks	814	allows libev to delay invocation of I/O and timer/periodic callbacks
691	to increase efficiency of loop iterations (or to increase power-saving	815	to increase efficiency of loop iterations (or to increase power-saving
692	opportunities).	816	opportunities).
693		817
694	The background is that sometimes your program runs just fast enough to	818	The idea is that sometimes your program runs just fast enough to handle
695	handle one (or very few) event(s) per loop iteration. While this makes	819	one (or very few) event(s) per loop iteration. While this makes the
696	the program responsive, it also wastes a lot of CPU time to poll for new	820	program responsive, it also wastes a lot of CPU time to poll for new
697	events, especially with backends like C<select ()> which have a high	821	events, especially with backends like C<select ()> which have a high
698	overhead for the actual polling but can deliver many events at once.	822	overhead for the actual polling but can deliver many events at once.
699		823
700	By setting a higher I<io collect interval> you allow libev to spend more	824	By setting a higher I<io collect interval> you allow libev to spend more
701	time collecting I/O events, so you can handle more events per iteration,	825	time collecting I/O events, so you can handle more events per iteration,
702	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	826	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
703	C<ev_timer>) will be not affected. Setting this to a non-null value will	827	C<ev_timer>) will be not affected. Setting this to a non-null value will
704	introduce an additional C<ev_sleep ()> call into most loop iterations.	828	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		829	sleep time ensures that libev will not poll for I/O events more often then
		830	once per this interval, on average.
705		831
706	Likewise, by setting a higher I<timeout collect interval> you allow libev	832	Likewise, by setting a higher I<timeout collect interval> you allow libev
707	to spend more time collecting timeouts, at the expense of increased	833	to spend more time collecting timeouts, at the expense of increased
708	latency (the watcher callback will be called later). C<ev_io> watchers	834	latency/jitter/inexactness (the watcher callback will be called
709	will not be affected. Setting this to a non-null value will not introduce	835	later). C<ev_io> watchers will not be affected. Setting this to a non-null
710	any overhead in libev.	836	value will not introduce any overhead in libev.
711		837
712	Many (busy) programs can usually benefit by setting the I/O collect	838	Many (busy) programs can usually benefit by setting the I/O collect
713	interval to a value near C<0.1> or so, which is often enough for	839	interval to a value near C<0.1> or so, which is often enough for
714	interactive servers (of course not for games), likewise for timeouts. It	840	interactive servers (of course not for games), likewise for timeouts. It
715	usually doesn't make much sense to set it to a lower value than C<0.01>,	841	usually doesn't make much sense to set it to a lower value than C<0.01>,
716	as this approaches the timing granularity of most systems.	842	as this approaches the timing granularity of most systems. Note that if
		843	you do transactions with the outside world and you can't increase the
		844	parallelity, then this setting will limit your transaction rate (if you
		845	need to poll once per transaction and the I/O collect interval is 0.01,
		846	then you can't do more than 100 transations per second).
717		847
718	Setting the I<timeout collect interval> can improve the opportunity for	848	Setting the I<timeout collect interval> can improve the opportunity for
719	saving power, as the program will "bundle" timer callback invocations that	849	saving power, as the program will "bundle" timer callback invocations that
720	are "near" in time together, by delaying some, thus reducing the number of	850	are "near" in time together, by delaying some, thus reducing the number of
721	times the process sleeps and wakes up again. Another useful technique to	851	times the process sleeps and wakes up again. Another useful technique to
722	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	852	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
723	they fire on, say, one-second boundaries only.	853	they fire on, say, one-second boundaries only.
724		854
		855	Example: we only need 0.1s timeout granularity, and we wish not to poll
		856	more often than 100 times per second:
		857
		858	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		859	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		860
		861	=item ev_invoke_pending (loop)
		862
		863	This call will simply invoke all pending watchers while resetting their
		864	pending state. Normally, C<ev_loop> does this automatically when required,
		865	but when overriding the invoke callback this call comes handy.
		866
		867	=item int ev_pending_count (loop)
		868
		869	Returns the number of pending watchers - zero indicates that no watchers
		870	are pending.
		871
		872	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		873
		874	This overrides the invoke pending functionality of the loop: Instead of
		875	invoking all pending watchers when there are any, C<ev_loop> will call
		876	this callback instead. This is useful, for example, when you want to
		877	invoke the actual watchers inside another context (another thread etc.).
		878
		879	If you want to reset the callback, use C<ev_invoke_pending> as new
		880	callback.
		881
		882	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		883
		884	Sometimes you want to share the same loop between multiple threads. This
		885	can be done relatively simply by putting mutex_lock/unlock calls around
		886	each call to a libev function.
		887
		888	However, C<ev_loop> can run an indefinite time, so it is not feasible to
		889	wait for it to return. One way around this is to wake up the loop via
		890	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>
		891	and I<acquire> callbacks on the loop.
		892
		893	When set, then C<release> will be called just before the thread is
		894	suspended waiting for new events, and C<acquire> is called just
		895	afterwards.
		896
		897	Ideally, C<release> will just call your mutex_unlock function, and
		898	C<acquire> will just call the mutex_lock function again.
		899
		900	While event loop modifications are allowed between invocations of
		901	C<release> and C<acquire> (that's their only purpose after all), no
		902	modifications done will affect the event loop, i.e. adding watchers will
		903	have no effect on the set of file descriptors being watched, or the time
		904	waited. USe an C<ev_async> watcher to wake up C<ev_loop> when you want it
		905	to take note of any changes you made.
		906
		907	In theory, threads executing C<ev_loop> will be async-cancel safe between
		908	invocations of C<release> and C<acquire>.
		909
		910	See also the locking example in the C<THREADS> section later in this
		911	document.
		912
		913	=item ev_set_userdata (loop, void *data)
		914
		915	=item ev_userdata (loop)
		916
		917	Set and retrieve a single C<void *> associated with a loop. When
		918	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		919	C<0.>
		920
		921	These two functions can be used to associate arbitrary data with a loop,
		922	and are intended solely for the C<invoke_pending_cb>, C<release> and
		923	C<acquire> callbacks described above, but of course can be (ab-)used for
		924	any other purpose as well.
		925
725	=item ev_loop_verify (loop)	926	=item ev_loop_verify (loop)
726		927
727	This function only does something when C<EV_VERIFY> support has been	928	This function only does something when C<EV_VERIFY> support has been
728	compiled in. It tries to go through all internal structures and checks	929	compiled in, which is the default for non-minimal builds. It tries to go
729	them for validity. If anything is found to be inconsistent, it will print	930	through all internal structures and checks them for validity. If anything
730	an error message to standard error and call C<abort ()>.	931	is found to be inconsistent, it will print an error message to standard
		932	error and call C<abort ()>.
731		933
732	This can be used to catch bugs inside libev itself: under normal	934	This can be used to catch bugs inside libev itself: under normal
733	circumstances, this function will never abort as of course libev keeps its	935	circumstances, this function will never abort as of course libev keeps its
734	data structures consistent.	936	data structures consistent.
735		937
736	=back	938	=back
737		939
738		940
739	=head1 ANATOMY OF A WATCHER	941	=head1 ANATOMY OF A WATCHER
740		942
		943	In the following description, uppercase C<TYPE> in names stands for the
		944	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		945	watchers and C<ev_io_start> for I/O watchers.
		946
741	A watcher is a structure that you create and register to record your	947	A watcher is a structure that you create and register to record your
742	interest in some event. For instance, if you want to wait for STDIN to	948	interest in some event. For instance, if you want to wait for STDIN to
743	become readable, you would create an C<ev_io> watcher for that:	949	become readable, you would create an C<ev_io> watcher for that:
744		950
745	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	951	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
746	{	952	{
747	ev_io_stop (w);	953	ev_io_stop (w);
748	ev_unloop (loop, EVUNLOOP_ALL);	954	ev_unloop (loop, EVUNLOOP_ALL);
749	}	955	}
750		956
751	struct ev_loop *loop = ev_default_loop (0);	957	struct ev_loop *loop = ev_default_loop (0);
		958
752	struct ev_io stdin_watcher;	959	ev_io stdin_watcher;
		960
753	ev_init (&stdin_watcher, my_cb);	961	ev_init (&stdin_watcher, my_cb);
754	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	962	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
755	ev_io_start (loop, &stdin_watcher);	963	ev_io_start (loop, &stdin_watcher);
		964
756	ev_loop (loop, 0);	965	ev_loop (loop, 0);
757		966
758	As you can see, you are responsible for allocating the memory for your	967	As you can see, you are responsible for allocating the memory for your
759	watcher structures (and it is usually a bad idea to do this on the stack,	968	watcher structures (and it is I<usually> a bad idea to do this on the
760	although this can sometimes be quite valid).	969	stack).
		970
		971	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		972	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
761		973
762	Each watcher structure must be initialised by a call to C<ev_init	974	Each watcher structure must be initialised by a call to C<ev_init
763	(watcher *, callback)>, which expects a callback to be provided. This	975	(watcher *, callback)>, which expects a callback to be provided. This
764	callback gets invoked each time the event occurs (or, in the case of I/O	976	callback gets invoked each time the event occurs (or, in the case of I/O
765	watchers, each time the event loop detects that the file descriptor given	977	watchers, each time the event loop detects that the file descriptor given
766	is readable and/or writable).	978	is readable and/or writable).
767		979
768	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	980	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
769	with arguments specific to this watcher type. There is also a macro	981	macro to configure it, with arguments specific to the watcher type. There
770	to combine initialisation and setting in one call: C<< ev_<type>_init	982	is also a macro to combine initialisation and setting in one call: C<<
771	(watcher *, callback, ...) >>.	983	ev_TYPE_init (watcher *, callback, ...) >>.
772		984
773	To make the watcher actually watch out for events, you have to start it	985	To make the watcher actually watch out for events, you have to start it
774	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	986	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
775	*) >>), and you can stop watching for events at any time by calling the	987	*) >>), and you can stop watching for events at any time by calling the
776	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	988	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
777		989
778	As long as your watcher is active (has been started but not stopped) you	990	As long as your watcher is active (has been started but not stopped) you
779	must not touch the values stored in it. Most specifically you must never	991	must not touch the values stored in it. Most specifically you must never
780	reinitialise it or call its C<set> macro.	992	reinitialise it or call its C<ev_TYPE_set> macro.
781		993
782	Each and every callback receives the event loop pointer as first, the	994	Each and every callback receives the event loop pointer as first, the
783	registered watcher structure as second, and a bitset of received events as	995	registered watcher structure as second, and a bitset of received events as
784	third argument.	996	third argument.
785		997
…		…
843		1055
844	=item C<EV_ASYNC>	1056	=item C<EV_ASYNC>
845		1057
846	The given async watcher has been asynchronously notified (see C<ev_async>).	1058	The given async watcher has been asynchronously notified (see C<ev_async>).
847		1059
		1060	=item C<EV_CUSTOM>
		1061
		1062	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1063	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		1064
848	=item C<EV_ERROR>	1065	=item C<EV_ERROR>
849		1066
850	An unspecified error has occurred, the watcher has been stopped. This might	1067	An unspecified error has occurred, the watcher has been stopped. This might
851	happen because the watcher could not be properly started because libev	1068	happen because the watcher could not be properly started because libev
852	ran out of memory, a file descriptor was found to be closed or any other	1069	ran out of memory, a file descriptor was found to be closed or any other
		1070	problem. Libev considers these application bugs.
		1071
853	problem. You best act on it by reporting the problem and somehow coping	1072	You best act on it by reporting the problem and somehow coping with the
854	with the watcher being stopped.	1073	watcher being stopped. Note that well-written programs should not receive
		1074	an error ever, so when your watcher receives it, this usually indicates a
		1075	bug in your program.
855		1076
856	Libev will usually signal a few "dummy" events together with an error,	1077	Libev will usually signal a few "dummy" events together with an error, for
857	for example it might indicate that a fd is readable or writable, and if	1078	example it might indicate that a fd is readable or writable, and if your
858	your callbacks is well-written it can just attempt the operation and cope	1079	callbacks is well-written it can just attempt the operation and cope with
859	with the error from read() or write(). This will not work in multi-threaded	1080	the error from read() or write(). This will not work in multi-threaded
860	programs, though, so beware.	1081	programs, though, as the fd could already be closed and reused for another
		1082	thing, so beware.
861		1083
862	=back	1084	=back
863		1085
864	=head2 GENERIC WATCHER FUNCTIONS	1086	=head2 GENERIC WATCHER FUNCTIONS
865
866	In the following description, C<TYPE> stands for the watcher type,
867	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
868		1087
869	=over 4	1088	=over 4
870		1089
871	=item C<ev_init> (ev_TYPE *watcher, callback)	1090	=item C<ev_init> (ev_TYPE *watcher, callback)
872		1091
…		…
878	which rolls both calls into one.	1097	which rolls both calls into one.
879		1098
880	You can reinitialise a watcher at any time as long as it has been stopped	1099	You can reinitialise a watcher at any time as long as it has been stopped
881	(or never started) and there are no pending events outstanding.	1100	(or never started) and there are no pending events outstanding.
882		1101
883	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1102	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
884	int revents)>.	1103	int revents)>.
		1104
		1105	Example: Initialise an C<ev_io> watcher in two steps.
		1106
		1107	ev_io w;
		1108	ev_init (&w, my_cb);
		1109	ev_io_set (&w, STDIN_FILENO, EV_READ);
885		1110
886	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1111	=item C<ev_TYPE_set> (ev_TYPE *, [args])
887		1112
888	This macro initialises the type-specific parts of a watcher. You need to	1113	This macro initialises the type-specific parts of a watcher. You need to
889	call C<ev_init> at least once before you call this macro, but you can	1114	call C<ev_init> at least once before you call this macro, but you can
…		…
892	difference to the C<ev_init> macro).	1117	difference to the C<ev_init> macro).
893		1118
894	Although some watcher types do not have type-specific arguments	1119	Although some watcher types do not have type-specific arguments
895	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	1120	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
896		1121
		1122	See C<ev_init>, above, for an example.
		1123
897	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1124	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
898		1125
899	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1126	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
900	calls into a single call. This is the most convenient method to initialise	1127	calls into a single call. This is the most convenient method to initialise
901	a watcher. The same limitations apply, of course.	1128	a watcher. The same limitations apply, of course.
902		1129
		1130	Example: Initialise and set an C<ev_io> watcher in one step.
		1131
		1132	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1133
903	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1134	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
904		1135
905	Starts (activates) the given watcher. Only active watchers will receive	1136	Starts (activates) the given watcher. Only active watchers will receive
906	events. If the watcher is already active nothing will happen.	1137	events. If the watcher is already active nothing will happen.
907		1138
		1139	Example: Start the C<ev_io> watcher that is being abused as example in this
		1140	whole section.
		1141
		1142	ev_io_start (EV_DEFAULT_UC, &w);
		1143
908	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1144	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
909		1145
910	Stops the given watcher again (if active) and clears the pending	1146	Stops the given watcher if active, and clears the pending status (whether
		1147	the watcher was active or not).
		1148
911	status. It is possible that stopped watchers are pending (for example,	1149	It is possible that stopped watchers are pending - for example,
912	non-repeating timers are being stopped when they become pending), but	1150	non-repeating timers are being stopped when they become pending - but
913	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1151	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
914	you want to free or reuse the memory used by the watcher it is therefore a	1152	pending. If you want to free or reuse the memory used by the watcher it is
915	good idea to always call its C<ev_TYPE_stop> function.	1153	therefore a good idea to always call its C<ev_TYPE_stop> function.
916		1154
917	=item bool ev_is_active (ev_TYPE *watcher)	1155	=item bool ev_is_active (ev_TYPE *watcher)
918		1156
919	Returns a true value iff the watcher is active (i.e. it has been started	1157	Returns a true value iff the watcher is active (i.e. it has been started
920	and not yet been stopped). As long as a watcher is active you must not modify	1158	and not yet been stopped). As long as a watcher is active you must not modify
…		…
946	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1184	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
947	(default: C<-2>). Pending watchers with higher priority will be invoked	1185	(default: C<-2>). Pending watchers with higher priority will be invoked
948	before watchers with lower priority, but priority will not keep watchers	1186	before watchers with lower priority, but priority will not keep watchers
949	from being executed (except for C<ev_idle> watchers).	1187	from being executed (except for C<ev_idle> watchers).
950		1188
951	This means that priorities are I<only> used for ordering callback
952	invocation after new events have been received. This is useful, for
953	example, to reduce latency after idling, or more often, to bind two
954	watchers on the same event and make sure one is called first.
955
956	If you need to suppress invocation when higher priority events are pending	1189	If you need to suppress invocation when higher priority events are pending
957	you need to look at C<ev_idle> watchers, which provide this functionality.	1190	you need to look at C<ev_idle> watchers, which provide this functionality.
958		1191
959	You I<must not> change the priority of a watcher as long as it is active or	1192	You I<must not> change the priority of a watcher as long as it is active or
960	pending.	1193	pending.
961		1194
		1195	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1196	fine, as long as you do not mind that the priority value you query might
		1197	or might not have been clamped to the valid range.
		1198
962	The default priority used by watchers when no priority has been set is	1199	The default priority used by watchers when no priority has been set is
963	always C<0>, which is supposed to not be too high and not be too low :).	1200	always C<0>, which is supposed to not be too high and not be too low :).
964		1201
965	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1202	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
966	fine, as long as you do not mind that the priority value you query might	1203	priorities.
967	or might not have been adjusted to be within valid range.
968		1204
969	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1205	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
970		1206
971	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1207	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
972	C<loop> nor C<revents> need to be valid as long as the watcher callback	1208	C<loop> nor C<revents> need to be valid as long as the watcher callback
973	can deal with that fact.	1209	can deal with that fact, as both are simply passed through to the
		1210	callback.
974		1211
975	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1212	=item int ev_clear_pending (loop, ev_TYPE *watcher)
976		1213
977	If the watcher is pending, this function returns clears its pending status	1214	If the watcher is pending, this function clears its pending status and
978	and returns its C<revents> bitset (as if its callback was invoked). If the	1215	returns its C<revents> bitset (as if its callback was invoked). If the
979	watcher isn't pending it does nothing and returns C<0>.	1216	watcher isn't pending it does nothing and returns C<0>.
980		1217
		1218	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1219	callback to be invoked, which can be accomplished with this function.
		1220
981	=back	1221	=back
982		1222
983		1223
984	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1224	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
985		1225
986	Each watcher has, by default, a member C<void *data> that you can change	1226	Each watcher has, by default, a member C<void *data> that you can change
987	and read at any time, libev will completely ignore it. This can be used	1227	and read at any time: libev will completely ignore it. This can be used
988	to associate arbitrary data with your watcher. If you need more data and	1228	to associate arbitrary data with your watcher. If you need more data and
989	don't want to allocate memory and store a pointer to it in that data	1229	don't want to allocate memory and store a pointer to it in that data
990	member, you can also "subclass" the watcher type and provide your own	1230	member, you can also "subclass" the watcher type and provide your own
991	data:	1231	data:
992		1232
993	struct my_io	1233	struct my_io
994	{	1234	{
995	struct ev_io io;	1235	ev_io io;
996	int otherfd;	1236	int otherfd;
997	void *somedata;	1237	void *somedata;
998	struct whatever *mostinteresting;	1238	struct whatever *mostinteresting;
999	}	1239	};
		1240
		1241	...
		1242	struct my_io w;
		1243	ev_io_init (&w.io, my_cb, fd, EV_READ);
1000		1244
1001	And since your callback will be called with a pointer to the watcher, you	1245	And since your callback will be called with a pointer to the watcher, you
1002	can cast it back to your own type:	1246	can cast it back to your own type:
1003		1247
1004	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1248	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1005	{	1249	{
1006	struct my_io *w = (struct my_io *)w_;	1250	struct my_io *w = (struct my_io *)w_;
1007	...	1251	...
1008	}	1252	}
1009		1253
1010	More interesting and less C-conformant ways of casting your callback type	1254	More interesting and less C-conformant ways of casting your callback type
1011	instead have been omitted.	1255	instead have been omitted.
1012		1256
1013	Another common scenario is having some data structure with multiple	1257	Another common scenario is to use some data structure with multiple
1014	watchers:	1258	embedded watchers:
1015		1259
1016	struct my_biggy	1260	struct my_biggy
1017	{	1261	{
1018	int some_data;	1262	int some_data;
1019	ev_timer t1;	1263	ev_timer t1;
1020	ev_timer t2;	1264	ev_timer t2;
1021	}	1265	}
1022		1266
1023	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1267	In this case getting the pointer to C<my_biggy> is a bit more
1024	you need to use C<offsetof>:	1268	complicated: Either you store the address of your C<my_biggy> struct
		1269	in the C<data> member of the watcher (for woozies), or you need to use
		1270	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1271	programmers):
1025		1272
1026	#include <stddef.h>	1273	#include <stddef.h>
1027		1274
1028	static void	1275	static void
1029	t1_cb (EV_P_ struct ev_timer *w, int revents)	1276	t1_cb (EV_P_ ev_timer *w, int revents)
1030	{	1277	{
1031	struct my_biggy big = (struct my_biggy *	1278	struct my_biggy big = (struct my_biggy *)
1032	(((char *)w) - offsetof (struct my_biggy, t1));	1279	(((char *)w) - offsetof (struct my_biggy, t1));
1033	}	1280	}
1034		1281
1035	static void	1282	static void
1036	t2_cb (EV_P_ struct ev_timer *w, int revents)	1283	t2_cb (EV_P_ ev_timer *w, int revents)
1037	{	1284	{
1038	struct my_biggy big = (struct my_biggy *	1285	struct my_biggy big = (struct my_biggy *)
1039	(((char *)w) - offsetof (struct my_biggy, t2));	1286	(((char *)w) - offsetof (struct my_biggy, t2));
1040	}	1287	}
		1288
		1289	=head2 WATCHER PRIORITY MODELS
		1290
		1291	Many event loops support I<watcher priorities>, which are usually small
		1292	integers that influence the ordering of event callback invocation
		1293	between watchers in some way, all else being equal.
		1294
		1295	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1296	description for the more technical details such as the actual priority
		1297	range.
		1298
		1299	There are two common ways how these these priorities are being interpreted
		1300	by event loops:
		1301
		1302	In the more common lock-out model, higher priorities "lock out" invocation
		1303	of lower priority watchers, which means as long as higher priority
		1304	watchers receive events, lower priority watchers are not being invoked.
		1305
		1306	The less common only-for-ordering model uses priorities solely to order
		1307	callback invocation within a single event loop iteration: Higher priority
		1308	watchers are invoked before lower priority ones, but they all get invoked
		1309	before polling for new events.
		1310
		1311	Libev uses the second (only-for-ordering) model for all its watchers
		1312	except for idle watchers (which use the lock-out model).
		1313
		1314	The rationale behind this is that implementing the lock-out model for
		1315	watchers is not well supported by most kernel interfaces, and most event
		1316	libraries will just poll for the same events again and again as long as
		1317	their callbacks have not been executed, which is very inefficient in the
		1318	common case of one high-priority watcher locking out a mass of lower
		1319	priority ones.
		1320
		1321	Static (ordering) priorities are most useful when you have two or more
		1322	watchers handling the same resource: a typical usage example is having an
		1323	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1324	timeouts. Under load, data might be received while the program handles
		1325	other jobs, but since timers normally get invoked first, the timeout
		1326	handler will be executed before checking for data. In that case, giving
		1327	the timer a lower priority than the I/O watcher ensures that I/O will be
		1328	handled first even under adverse conditions (which is usually, but not
		1329	always, what you want).
		1330
		1331	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1332	will only be executed when no same or higher priority watchers have
		1333	received events, they can be used to implement the "lock-out" model when
		1334	required.
		1335
		1336	For example, to emulate how many other event libraries handle priorities,
		1337	you can associate an C<ev_idle> watcher to each such watcher, and in
		1338	the normal watcher callback, you just start the idle watcher. The real
		1339	processing is done in the idle watcher callback. This causes libev to
		1340	continously poll and process kernel event data for the watcher, but when
		1341	the lock-out case is known to be rare (which in turn is rare :), this is
		1342	workable.
		1343
		1344	Usually, however, the lock-out model implemented that way will perform
		1345	miserably under the type of load it was designed to handle. In that case,
		1346	it might be preferable to stop the real watcher before starting the
		1347	idle watcher, so the kernel will not have to process the event in case
		1348	the actual processing will be delayed for considerable time.
		1349
		1350	Here is an example of an I/O watcher that should run at a strictly lower
		1351	priority than the default, and which should only process data when no
		1352	other events are pending:
		1353
		1354	ev_idle idle; // actual processing watcher
		1355	ev_io io; // actual event watcher
		1356
		1357	static void
		1358	io_cb (EV_P_ ev_io *w, int revents)
		1359	{
		1360	// stop the I/O watcher, we received the event, but
		1361	// are not yet ready to handle it.
		1362	ev_io_stop (EV_A_ w);
		1363
		1364	// start the idle watcher to ahndle the actual event.
		1365	// it will not be executed as long as other watchers
		1366	// with the default priority are receiving events.
		1367	ev_idle_start (EV_A_ &idle);
		1368	}
		1369
		1370	static void
		1371	idle_cb (EV_P_ ev_idle *w, int revents)
		1372	{
		1373	// actual processing
		1374	read (STDIN_FILENO, ...);
		1375
		1376	// have to start the I/O watcher again, as
		1377	// we have handled the event
		1378	ev_io_start (EV_P_ &io);
		1379	}
		1380
		1381	// initialisation
		1382	ev_idle_init (&idle, idle_cb);
		1383	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1384	ev_io_start (EV_DEFAULT_ &io);
		1385
		1386	In the "real" world, it might also be beneficial to start a timer, so that
		1387	low-priority connections can not be locked out forever under load. This
		1388	enables your program to keep a lower latency for important connections
		1389	during short periods of high load, while not completely locking out less
		1390	important ones.
1041		1391
1042		1392
1043	=head1 WATCHER TYPES	1393	=head1 WATCHER TYPES
1044		1394
1045	This section describes each watcher in detail, but will not repeat	1395	This section describes each watcher in detail, but will not repeat
…		…
1069	In general you can register as many read and/or write event watchers per	1419	In general you can register as many read and/or write event watchers per
1070	fd as you want (as long as you don't confuse yourself). Setting all file	1420	fd as you want (as long as you don't confuse yourself). Setting all file
1071	descriptors to non-blocking mode is also usually a good idea (but not	1421	descriptors to non-blocking mode is also usually a good idea (but not
1072	required if you know what you are doing).	1422	required if you know what you are doing).
1073		1423
1074	If you must do this, then force the use of a known-to-be-good backend	1424	If you cannot use non-blocking mode, then force the use of a
1075	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1425	known-to-be-good backend (at the time of this writing, this includes only
1076	C<EVBACKEND_POLL>).	1426	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1427	descriptors for which non-blocking operation makes no sense (such as
		1428	files) - libev doesn't guarentee any specific behaviour in that case.
1077		1429
1078	Another thing you have to watch out for is that it is quite easy to	1430	Another thing you have to watch out for is that it is quite easy to
1079	receive "spurious" readiness notifications, that is your callback might	1431	receive "spurious" readiness notifications, that is your callback might
1080	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1432	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1081	because there is no data. Not only are some backends known to create a	1433	because there is no data. Not only are some backends known to create a
1082	lot of those (for example Solaris ports), it is very easy to get into	1434	lot of those (for example Solaris ports), it is very easy to get into
1083	this situation even with a relatively standard program structure. Thus	1435	this situation even with a relatively standard program structure. Thus
1084	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1436	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1085	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1437	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1086		1438
1087	If you cannot run the fd in non-blocking mode (for example you should not	1439	If you cannot run the fd in non-blocking mode (for example you should
1088	play around with an Xlib connection), then you have to separately re-test	1440	not play around with an Xlib connection), then you have to separately
1089	whether a file descriptor is really ready with a known-to-be good interface	1441	re-test whether a file descriptor is really ready with a known-to-be good
1090	such as poll (fortunately in our Xlib example, Xlib already does this on	1442	interface such as poll (fortunately in our Xlib example, Xlib already
1091	its own, so its quite safe to use).	1443	does this on its own, so its quite safe to use). Some people additionally
		1444	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1445	indefinitely.
		1446
		1447	But really, best use non-blocking mode.
1092		1448
1093	=head3 The special problem of disappearing file descriptors	1449	=head3 The special problem of disappearing file descriptors
1094		1450
1095	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1451	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1096	descriptor (either by calling C<close> explicitly or by any other means,	1452	descriptor (either due to calling C<close> explicitly or any other means,
1097	such as C<dup>). The reason is that you register interest in some file	1453	such as C<dup2>). The reason is that you register interest in some file
1098	descriptor, but when it goes away, the operating system will silently drop	1454	descriptor, but when it goes away, the operating system will silently drop
1099	this interest. If another file descriptor with the same number then is	1455	this interest. If another file descriptor with the same number then is
1100	registered with libev, there is no efficient way to see that this is, in	1456	registered with libev, there is no efficient way to see that this is, in
1101	fact, a different file descriptor.	1457	fact, a different file descriptor.
1102		1458
…		…
1133	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1489	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1134	C<EVBACKEND_POLL>.	1490	C<EVBACKEND_POLL>.
1135		1491
1136	=head3 The special problem of SIGPIPE	1492	=head3 The special problem of SIGPIPE
1137		1493
1138	While not really specific to libev, it is easy to forget about SIGPIPE:	1494	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1139	when writing to a pipe whose other end has been closed, your program gets	1495	when writing to a pipe whose other end has been closed, your program gets
1140	send a SIGPIPE, which, by default, aborts your program. For most programs	1496	sent a SIGPIPE, which, by default, aborts your program. For most programs
1141	this is sensible behaviour, for daemons, this is usually undesirable.	1497	this is sensible behaviour, for daemons, this is usually undesirable.
1142		1498
1143	So when you encounter spurious, unexplained daemon exits, make sure you	1499	So when you encounter spurious, unexplained daemon exits, make sure you
1144	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1500	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1145	somewhere, as that would have given you a big clue).	1501	somewhere, as that would have given you a big clue).
…		…
1152	=item ev_io_init (ev_io *, callback, int fd, int events)	1508	=item ev_io_init (ev_io *, callback, int fd, int events)
1153		1509
1154	=item ev_io_set (ev_io *, int fd, int events)	1510	=item ev_io_set (ev_io *, int fd, int events)
1155		1511
1156	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1512	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1157	receive events for and events is either C<EV_READ>, C<EV_WRITE> or	1513	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1158	C<EV_READ | EV_WRITE> to receive the given events.	1514	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1159		1515
1160	=item int fd [read-only]	1516	=item int fd [read-only]
1161		1517
1162	The file descriptor being watched.	1518	The file descriptor being watched.
1163		1519
…		…
1172	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1528	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1173	readable, but only once. Since it is likely line-buffered, you could	1529	readable, but only once. Since it is likely line-buffered, you could
1174	attempt to read a whole line in the callback.	1530	attempt to read a whole line in the callback.
1175		1531
1176	static void	1532	static void
1177	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1533	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1178	{	1534	{
1179	ev_io_stop (loop, w);	1535	ev_io_stop (loop, w);
1180	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1536	.. read from stdin here (or from w->fd) and handle any I/O errors
1181	}	1537	}
1182		1538
1183	...	1539	...
1184	struct ev_loop *loop = ev_default_init (0);	1540	struct ev_loop *loop = ev_default_init (0);
1185	struct ev_io stdin_readable;	1541	ev_io stdin_readable;
1186	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1542	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1187	ev_io_start (loop, &stdin_readable);	1543	ev_io_start (loop, &stdin_readable);
1188	ev_loop (loop, 0);	1544	ev_loop (loop, 0);
1189		1545
1190		1546
…		…
1193	Timer watchers are simple relative timers that generate an event after a	1549	Timer watchers are simple relative timers that generate an event after a
1194	given time, and optionally repeating in regular intervals after that.	1550	given time, and optionally repeating in regular intervals after that.
1195		1551
1196	The timers are based on real time, that is, if you register an event that	1552	The timers are based on real time, that is, if you register an event that
1197	times out after an hour and you reset your system clock to January last	1553	times out after an hour and you reset your system clock to January last
1198	year, it will still time out after (roughly) and hour. "Roughly" because	1554	year, it will still time out after (roughly) one hour. "Roughly" because
1199	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1555	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1200	monotonic clock option helps a lot here).	1556	monotonic clock option helps a lot here).
1201		1557
1202	The callback is guaranteed to be invoked only after its timeout has passed,	1558	The callback is guaranteed to be invoked only I<after> its timeout has
1203	but if multiple timers become ready during the same loop iteration then	1559	passed (not I<at>, so on systems with very low-resolution clocks this
1204	order of execution is undefined.	1560	might introduce a small delay). If multiple timers become ready during the
		1561	same loop iteration then the ones with earlier time-out values are invoked
		1562	before ones of the same priority with later time-out values (but this is
		1563	no longer true when a callback calls C<ev_loop> recursively).
		1564
		1565	=head3 Be smart about timeouts
		1566
		1567	Many real-world problems involve some kind of timeout, usually for error
		1568	recovery. A typical example is an HTTP request - if the other side hangs,
		1569	you want to raise some error after a while.
		1570
		1571	What follows are some ways to handle this problem, from obvious and
		1572	inefficient to smart and efficient.
		1573
		1574	In the following, a 60 second activity timeout is assumed - a timeout that
		1575	gets reset to 60 seconds each time there is activity (e.g. each time some
		1576	data or other life sign was received).
		1577
		1578	=over 4
		1579
		1580	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1581
		1582	This is the most obvious, but not the most simple way: In the beginning,
		1583	start the watcher:
		1584
		1585	ev_timer_init (timer, callback, 60., 0.);
		1586	ev_timer_start (loop, timer);
		1587
		1588	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1589	and start it again:
		1590
		1591	ev_timer_stop (loop, timer);
		1592	ev_timer_set (timer, 60., 0.);
		1593	ev_timer_start (loop, timer);
		1594
		1595	This is relatively simple to implement, but means that each time there is
		1596	some activity, libev will first have to remove the timer from its internal
		1597	data structure and then add it again. Libev tries to be fast, but it's
		1598	still not a constant-time operation.
		1599
		1600	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1601
		1602	This is the easiest way, and involves using C<ev_timer_again> instead of
		1603	C<ev_timer_start>.
		1604
		1605	To implement this, configure an C<ev_timer> with a C<repeat> value
		1606	of C<60> and then call C<ev_timer_again> at start and each time you
		1607	successfully read or write some data. If you go into an idle state where
		1608	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1609	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1610
		1611	That means you can ignore both the C<ev_timer_start> function and the
		1612	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1613	member and C<ev_timer_again>.
		1614
		1615	At start:
		1616
		1617	ev_init (timer, callback);
		1618	timer->repeat = 60.;
		1619	ev_timer_again (loop, timer);
		1620
		1621	Each time there is some activity:
		1622
		1623	ev_timer_again (loop, timer);
		1624
		1625	It is even possible to change the time-out on the fly, regardless of
		1626	whether the watcher is active or not:
		1627
		1628	timer->repeat = 30.;
		1629	ev_timer_again (loop, timer);
		1630
		1631	This is slightly more efficient then stopping/starting the timer each time
		1632	you want to modify its timeout value, as libev does not have to completely
		1633	remove and re-insert the timer from/into its internal data structure.
		1634
		1635	It is, however, even simpler than the "obvious" way to do it.
		1636
		1637	=item 3. Let the timer time out, but then re-arm it as required.
		1638
		1639	This method is more tricky, but usually most efficient: Most timeouts are
		1640	relatively long compared to the intervals between other activity - in
		1641	our example, within 60 seconds, there are usually many I/O events with
		1642	associated activity resets.
		1643
		1644	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1645	but remember the time of last activity, and check for a real timeout only
		1646	within the callback:
		1647
		1648	ev_tstamp last_activity; // time of last activity
		1649
		1650	static void
		1651	callback (EV_P_ ev_timer *w, int revents)
		1652	{
		1653	ev_tstamp now = ev_now (EV_A);
		1654	ev_tstamp timeout = last_activity + 60.;
		1655
		1656	// if last_activity + 60. is older than now, we did time out
		1657	if (timeout < now)
		1658	{
		1659	// timeout occured, take action
		1660	}
		1661	else
		1662	{
		1663	// callback was invoked, but there was some activity, re-arm
		1664	// the watcher to fire in last_activity + 60, which is
		1665	// guaranteed to be in the future, so "again" is positive:
		1666	w->repeat = timeout - now;
		1667	ev_timer_again (EV_A_ w);
		1668	}
		1669	}
		1670
		1671	To summarise the callback: first calculate the real timeout (defined
		1672	as "60 seconds after the last activity"), then check if that time has
		1673	been reached, which means something I<did>, in fact, time out. Otherwise
		1674	the callback was invoked too early (C<timeout> is in the future), so
		1675	re-schedule the timer to fire at that future time, to see if maybe we have
		1676	a timeout then.
		1677
		1678	Note how C<ev_timer_again> is used, taking advantage of the
		1679	C<ev_timer_again> optimisation when the timer is already running.
		1680
		1681	This scheme causes more callback invocations (about one every 60 seconds
		1682	minus half the average time between activity), but virtually no calls to
		1683	libev to change the timeout.
		1684
		1685	To start the timer, simply initialise the watcher and set C<last_activity>
		1686	to the current time (meaning we just have some activity :), then call the
		1687	callback, which will "do the right thing" and start the timer:
		1688
		1689	ev_init (timer, callback);
		1690	last_activity = ev_now (loop);
		1691	callback (loop, timer, EV_TIMEOUT);
		1692
		1693	And when there is some activity, simply store the current time in
		1694	C<last_activity>, no libev calls at all:
		1695
		1696	last_actiivty = ev_now (loop);
		1697
		1698	This technique is slightly more complex, but in most cases where the
		1699	time-out is unlikely to be triggered, much more efficient.
		1700
		1701	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1702	callback :) - just change the timeout and invoke the callback, which will
		1703	fix things for you.
		1704
		1705	=item 4. Wee, just use a double-linked list for your timeouts.
		1706
		1707	If there is not one request, but many thousands (millions...), all
		1708	employing some kind of timeout with the same timeout value, then one can
		1709	do even better:
		1710
		1711	When starting the timeout, calculate the timeout value and put the timeout
		1712	at the I<end> of the list.
		1713
		1714	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1715	the list is expected to fire (for example, using the technique #3).
		1716
		1717	When there is some activity, remove the timer from the list, recalculate
		1718	the timeout, append it to the end of the list again, and make sure to
		1719	update the C<ev_timer> if it was taken from the beginning of the list.
		1720
		1721	This way, one can manage an unlimited number of timeouts in O(1) time for
		1722	starting, stopping and updating the timers, at the expense of a major
		1723	complication, and having to use a constant timeout. The constant timeout
		1724	ensures that the list stays sorted.
		1725
		1726	=back
		1727
		1728	So which method the best?
		1729
		1730	Method #2 is a simple no-brain-required solution that is adequate in most
		1731	situations. Method #3 requires a bit more thinking, but handles many cases
		1732	better, and isn't very complicated either. In most case, choosing either
		1733	one is fine, with #3 being better in typical situations.
		1734
		1735	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1736	rather complicated, but extremely efficient, something that really pays
		1737	off after the first million or so of active timers, i.e. it's usually
		1738	overkill :)
1205		1739
1206	=head3 The special problem of time updates	1740	=head3 The special problem of time updates
1207		1741
1208	Requesting the current time is a costly operation (it usually takes at	1742	Establishing the current time is a costly operation (it usually takes at
1209	least two syscalls): EV therefore updates it's idea of the current time	1743	least two system calls): EV therefore updates its idea of the current
1210	only before and after C<ev_loop> polls for new events, which causes the	1744	time only before and after C<ev_loop> collects new events, which causes a
1211	difference between C<ev_now ()> and C<ev_time ()>.	1745	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1746	lots of events in one iteration.
1212		1747
1213	The relative timeouts are calculated relative to the C<ev_now ()>	1748	The relative timeouts are calculated relative to the C<ev_now ()>
1214	time. This is usually the right thing as this timestamp refers to the time	1749	time. This is usually the right thing as this timestamp refers to the time
1215	of the event triggering whatever timeout you are modifying/starting. If	1750	of the event triggering whatever timeout you are modifying/starting. If
1216	you suspect event processing to be delayed and you I<need> to base the	1751	you suspect event processing to be delayed and you I<need> to base the
1217	timeout on the current time, use something like this to adjust for this:	1752	timeout on the current time, use something like this to adjust for this:
1218		1753
1219	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1754	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1220		1755
		1756	If the event loop is suspended for a long time, you can also force an
		1757	update of the time returned by C<ev_now ()> by calling C<ev_now_update
		1758	()>.
		1759
		1760	=head3 The special problems of suspended animation
		1761
		1762	When you leave the server world it is quite customary to hit machines that
		1763	can suspend/hibernate - what happens to the clocks during such a suspend?
		1764
		1765	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1766	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1767	to run until the system is suspended, but they will not advance while the
		1768	system is suspended. That means, on resume, it will be as if the program
		1769	was frozen for a few seconds, but the suspend time will not be counted
		1770	towards C<ev_timer> when a monotonic clock source is used. The real time
		1771	clock advanced as expected, but if it is used as sole clocksource, then a
		1772	long suspend would be detected as a time jump by libev, and timers would
		1773	be adjusted accordingly.
		1774
		1775	I would not be surprised to see different behaviour in different between
		1776	operating systems, OS versions or even different hardware.
		1777
		1778	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1779	time jump in the monotonic clocks and the realtime clock. If the program
		1780	is suspended for a very long time, and monotonic clock sources are in use,
		1781	then you can expect C<ev_timer>s to expire as the full suspension time
		1782	will be counted towards the timers. When no monotonic clock source is in
		1783	use, then libev will again assume a timejump and adjust accordingly.
		1784
		1785	It might be beneficial for this latter case to call C<ev_suspend>
		1786	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1787	deterministic behaviour in this case (you can do nothing against
		1788	C<SIGSTOP>).
		1789
1221	=head3 Watcher-Specific Functions and Data Members	1790	=head3 Watcher-Specific Functions and Data Members
1222		1791
1223	=over 4	1792	=over 4
1224		1793
1225	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1794	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1248	If the timer is started but non-repeating, stop it (as if it timed out).	1817	If the timer is started but non-repeating, stop it (as if it timed out).
1249		1818
1250	If the timer is repeating, either start it if necessary (with the	1819	If the timer is repeating, either start it if necessary (with the
1251	C<repeat> value), or reset the running timer to the C<repeat> value.	1820	C<repeat> value), or reset the running timer to the C<repeat> value.
1252		1821
1253	This sounds a bit complicated, but here is a useful and typical	1822	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1254	example: Imagine you have a TCP connection and you want a so-called idle	1823	usage example.
1255	timeout, that is, you want to be called when there have been, say, 60
1256	seconds of inactivity on the socket. The easiest way to do this is to
1257	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1258	C<ev_timer_again> each time you successfully read or write some data. If
1259	you go into an idle state where you do not expect data to travel on the
1260	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1261	automatically restart it if need be.
1262		1824
1263	That means you can ignore the C<after> value and C<ev_timer_start>	1825	=item ev_timer_remaining (loop, ev_timer *)
1264	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1265		1826
1266	ev_timer_init (timer, callback, 0., 5.);	1827	Returns the remaining time until a timer fires. If the timer is active,
1267	ev_timer_again (loop, timer);	1828	then this time is relative to the current event loop time, otherwise it's
1268	...	1829	the timeout value currently configured.
1269	timer->again = 17.;
1270	ev_timer_again (loop, timer);
1271	...
1272	timer->again = 10.;
1273	ev_timer_again (loop, timer);
1274		1830
1275	This is more slightly efficient then stopping/starting the timer each time	1831	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1276	you want to modify its timeout value.	1832	C<5>. When the timer is started and one second passes, C<ev_timer_remain>
		1833	will return C<4>. When the timer expires and is restarted, it will return
		1834	roughly C<7> (likely slightly less as callback invocation takes some time,
		1835	too), and so on.
1277		1836
1278	=item ev_tstamp repeat [read-write]	1837	=item ev_tstamp repeat [read-write]
1279		1838
1280	The current C<repeat> value. Will be used each time the watcher times out	1839	The current C<repeat> value. Will be used each time the watcher times out
1281	or C<ev_timer_again> is called and determines the next timeout (if any),	1840	or C<ev_timer_again> is called, and determines the next timeout (if any),
1282	which is also when any modifications are taken into account.	1841	which is also when any modifications are taken into account.
1283		1842
1284	=back	1843	=back
1285		1844
1286	=head3 Examples	1845	=head3 Examples
1287		1846
1288	Example: Create a timer that fires after 60 seconds.	1847	Example: Create a timer that fires after 60 seconds.
1289		1848
1290	static void	1849	static void
1291	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1850	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1292	{	1851	{
1293	.. one minute over, w is actually stopped right here	1852	.. one minute over, w is actually stopped right here
1294	}	1853	}
1295		1854
1296	struct ev_timer mytimer;	1855	ev_timer mytimer;
1297	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1856	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1298	ev_timer_start (loop, &mytimer);	1857	ev_timer_start (loop, &mytimer);
1299		1858
1300	Example: Create a timeout timer that times out after 10 seconds of	1859	Example: Create a timeout timer that times out after 10 seconds of
1301	inactivity.	1860	inactivity.
1302		1861
1303	static void	1862	static void
1304	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1863	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1305	{	1864	{
1306	.. ten seconds without any activity	1865	.. ten seconds without any activity
1307	}	1866	}
1308		1867
1309	struct ev_timer mytimer;	1868	ev_timer mytimer;
1310	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1869	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1311	ev_timer_again (&mytimer); /* start timer */	1870	ev_timer_again (&mytimer); /* start timer */
1312	ev_loop (loop, 0);	1871	ev_loop (loop, 0);
1313		1872
1314	// and in some piece of code that gets executed on any "activity":	1873	// and in some piece of code that gets executed on any "activity":
…		…
1319	=head2 C<ev_periodic> - to cron or not to cron?	1878	=head2 C<ev_periodic> - to cron or not to cron?
1320		1879
1321	Periodic watchers are also timers of a kind, but they are very versatile	1880	Periodic watchers are also timers of a kind, but they are very versatile
1322	(and unfortunately a bit complex).	1881	(and unfortunately a bit complex).
1323		1882
1324	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1883	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1325	but on wall clock time (absolute time). You can tell a periodic watcher	1884	relative time, the physical time that passes) but on wall clock time
1326	to trigger after some specific point in time. For example, if you tell a	1885	(absolute time, the thing you can read on your calender or clock). The
1327	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	1886	difference is that wall clock time can run faster or slower than real
1328	+ 10.>, that is, an absolute time not a delay) and then reset your system	1887	time, and time jumps are not uncommon (e.g. when you adjust your
1329	clock to January of the previous year, then it will take more than year	1888	wrist-watch).
1330	to trigger the event (unlike an C<ev_timer>, which would still trigger
1331	roughly 10 seconds later as it uses a relative timeout).
1332		1889
		1890	You can tell a periodic watcher to trigger after some specific point
		1891	in time: for example, if you tell a periodic watcher to trigger "in 10
		1892	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1893	not a delay) and then reset your system clock to January of the previous
		1894	year, then it will take a year or more to trigger the event (unlike an
		1895	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1896	it, as it uses a relative timeout).
		1897
1333	C<ev_periodic>s can also be used to implement vastly more complex timers,	1898	C<ev_periodic> watchers can also be used to implement vastly more complex
1334	such as triggering an event on each "midnight, local time", or other	1899	timers, such as triggering an event on each "midnight, local time", or
1335	complicated, rules.	1900	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1901	those cannot react to time jumps.
1336		1902
1337	As with timers, the callback is guaranteed to be invoked only when the	1903	As with timers, the callback is guaranteed to be invoked only when the
1338	time (C<at>) has passed, but if multiple periodic timers become ready	1904	point in time where it is supposed to trigger has passed. If multiple
1339	during the same loop iteration then order of execution is undefined.	1905	timers become ready during the same loop iteration then the ones with
		1906	earlier time-out values are invoked before ones with later time-out values
		1907	(but this is no longer true when a callback calls C<ev_loop> recursively).
1340		1908
1341	=head3 Watcher-Specific Functions and Data Members	1909	=head3 Watcher-Specific Functions and Data Members
1342		1910
1343	=over 4	1911	=over 4
1344		1912
1345	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1913	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1346		1914
1347	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1915	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1348		1916
1349	Lots of arguments, lets sort it out... There are basically three modes of	1917	Lots of arguments, let's sort it out... There are basically three modes of
1350	operation, and we will explain them from simplest to complex:	1918	operation, and we will explain them from simplest to most complex:
1351		1919
1352	=over 4	1920	=over 4
1353		1921
1354	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1922	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1355		1923
1356	In this configuration the watcher triggers an event after the wall clock	1924	In this configuration the watcher triggers an event after the wall clock
1357	time C<at> has passed and doesn't repeat. It will not adjust when a time	1925	time C<offset> has passed. It will not repeat and will not adjust when a
1358	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1926	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1359	run when the system time reaches or surpasses this time.	1927	will be stopped and invoked when the system clock reaches or surpasses
		1928	this point in time.
1360		1929
1361	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1930	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1362		1931
1363	In this mode the watcher will always be scheduled to time out at the next	1932	In this mode the watcher will always be scheduled to time out at the next
1364	C<at + N * interval> time (for some integer N, which can also be negative)	1933	C<offset + N * interval> time (for some integer N, which can also be
1365	and then repeat, regardless of any time jumps.	1934	negative) and then repeat, regardless of any time jumps. The C<offset>
		1935	argument is merely an offset into the C<interval> periods.
1366		1936
1367	This can be used to create timers that do not drift with respect to system	1937	This can be used to create timers that do not drift with respect to the
1368	time, for example, here is a C<ev_periodic> that triggers each hour, on	1938	system clock, for example, here is an C<ev_periodic> that triggers each
1369	the hour:	1939	hour, on the hour (with respect to UTC):
1370		1940
1371	ev_periodic_set (&periodic, 0., 3600., 0);	1941	ev_periodic_set (&periodic, 0., 3600., 0);
1372		1942
1373	This doesn't mean there will always be 3600 seconds in between triggers,	1943	This doesn't mean there will always be 3600 seconds in between triggers,
1374	but only that the callback will be called when the system time shows a	1944	but only that the callback will be called when the system time shows a
1375	full hour (UTC), or more correctly, when the system time is evenly divisible	1945	full hour (UTC), or more correctly, when the system time is evenly divisible
1376	by 3600.	1946	by 3600.
1377		1947
1378	Another way to think about it (for the mathematically inclined) is that	1948	Another way to think about it (for the mathematically inclined) is that
1379	C<ev_periodic> will try to run the callback in this mode at the next possible	1949	C<ev_periodic> will try to run the callback in this mode at the next possible
1380	time where C<time = at (mod interval)>, regardless of any time jumps.	1950	time where C<time = offset (mod interval)>, regardless of any time jumps.
1381		1951
1382	For numerical stability it is preferable that the C<at> value is near	1952	For numerical stability it is preferable that the C<offset> value is near
1383	C<ev_now ()> (the current time), but there is no range requirement for	1953	C<ev_now ()> (the current time), but there is no range requirement for
1384	this value, and in fact is often specified as zero.	1954	this value, and in fact is often specified as zero.
1385		1955
1386	Note also that there is an upper limit to how often a timer can fire (CPU	1956	Note also that there is an upper limit to how often a timer can fire (CPU
1387	speed for example), so if C<interval> is very small then timing stability	1957	speed for example), so if C<interval> is very small then timing stability
1388	will of course deteriorate. Libev itself tries to be exact to be about one	1958	will of course deteriorate. Libev itself tries to be exact to be about one
1389	millisecond (if the OS supports it and the machine is fast enough).	1959	millisecond (if the OS supports it and the machine is fast enough).
1390		1960
1391	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1961	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1392		1962
1393	In this mode the values for C<interval> and C<at> are both being	1963	In this mode the values for C<interval> and C<offset> are both being
1394	ignored. Instead, each time the periodic watcher gets scheduled, the	1964	ignored. Instead, each time the periodic watcher gets scheduled, the
1395	reschedule callback will be called with the watcher as first, and the	1965	reschedule callback will be called with the watcher as first, and the
1396	current time as second argument.	1966	current time as second argument.
1397		1967
1398	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1968	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1399	ever, or make ANY event loop modifications whatsoever>.	1969	or make ANY other event loop modifications whatsoever, unless explicitly
		1970	allowed by documentation here>.
1400		1971
1401	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1972	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1402	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	1973	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1403	only event loop modification you are allowed to do).	1974	only event loop modification you are allowed to do).
1404		1975
1405	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1976	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1406	*w, ev_tstamp now)>, e.g.:	1977	*w, ev_tstamp now)>, e.g.:
1407		1978
		1979	static ev_tstamp
1408	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1980	my_rescheduler (ev_periodic *w, ev_tstamp now)
1409	{	1981	{
1410	return now + 60.;	1982	return now + 60.;
1411	}	1983	}
1412		1984
1413	It must return the next time to trigger, based on the passed time value	1985	It must return the next time to trigger, based on the passed time value
…		…
1433	a different time than the last time it was called (e.g. in a crond like	2005	a different time than the last time it was called (e.g. in a crond like
1434	program when the crontabs have changed).	2006	program when the crontabs have changed).
1435		2007
1436	=item ev_tstamp ev_periodic_at (ev_periodic *)	2008	=item ev_tstamp ev_periodic_at (ev_periodic *)
1437		2009
1438	When active, returns the absolute time that the watcher is supposed to	2010	When active, returns the absolute time that the watcher is supposed
1439	trigger next.	2011	to trigger next. This is not the same as the C<offset> argument to
		2012	C<ev_periodic_set>, but indeed works even in interval and manual
		2013	rescheduling modes.
1440		2014
1441	=item ev_tstamp offset [read-write]	2015	=item ev_tstamp offset [read-write]
1442		2016
1443	When repeating, this contains the offset value, otherwise this is the	2017	When repeating, this contains the offset value, otherwise this is the
1444	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2018	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2019	although libev might modify this value for better numerical stability).
1445		2020
1446	Can be modified any time, but changes only take effect when the periodic	2021	Can be modified any time, but changes only take effect when the periodic
1447	timer fires or C<ev_periodic_again> is being called.	2022	timer fires or C<ev_periodic_again> is being called.
1448		2023
1449	=item ev_tstamp interval [read-write]	2024	=item ev_tstamp interval [read-write]
1450		2025
1451	The current interval value. Can be modified any time, but changes only	2026	The current interval value. Can be modified any time, but changes only
1452	take effect when the periodic timer fires or C<ev_periodic_again> is being	2027	take effect when the periodic timer fires or C<ev_periodic_again> is being
1453	called.	2028	called.
1454		2029
1455	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2030	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1456		2031
1457	The current reschedule callback, or C<0>, if this functionality is	2032	The current reschedule callback, or C<0>, if this functionality is
1458	switched off. Can be changed any time, but changes only take effect when	2033	switched off. Can be changed any time, but changes only take effect when
1459	the periodic timer fires or C<ev_periodic_again> is being called.	2034	the periodic timer fires or C<ev_periodic_again> is being called.
1460		2035
1461	=back	2036	=back
1462		2037
1463	=head3 Examples	2038	=head3 Examples
1464		2039
1465	Example: Call a callback every hour, or, more precisely, whenever the	2040	Example: Call a callback every hour, or, more precisely, whenever the
1466	system clock is divisible by 3600. The callback invocation times have	2041	system time is divisible by 3600. The callback invocation times have
1467	potentially a lot of jitter, but good long-term stability.	2042	potentially a lot of jitter, but good long-term stability.
1468		2043
1469	static void	2044	static void
1470	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2045	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1471	{	2046	{
1472	... its now a full hour (UTC, or TAI or whatever your clock follows)	2047	... its now a full hour (UTC, or TAI or whatever your clock follows)
1473	}	2048	}
1474		2049
1475	struct ev_periodic hourly_tick;	2050	ev_periodic hourly_tick;
1476	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2051	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1477	ev_periodic_start (loop, &hourly_tick);	2052	ev_periodic_start (loop, &hourly_tick);
1478		2053
1479	Example: The same as above, but use a reschedule callback to do it:	2054	Example: The same as above, but use a reschedule callback to do it:
1480		2055
1481	#include <math.h>	2056	#include <math.h>
1482		2057
1483	static ev_tstamp	2058	static ev_tstamp
1484	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2059	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1485	{	2060	{
1486	return fmod (now, 3600.) + 3600.;	2061	return now + (3600. - fmod (now, 3600.));
1487	}	2062	}
1488		2063
1489	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2064	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1490		2065
1491	Example: Call a callback every hour, starting now:	2066	Example: Call a callback every hour, starting now:
1492		2067
1493	struct ev_periodic hourly_tick;	2068	ev_periodic hourly_tick;
1494	ev_periodic_init (&hourly_tick, clock_cb,	2069	ev_periodic_init (&hourly_tick, clock_cb,
1495	fmod (ev_now (loop), 3600.), 3600., 0);	2070	fmod (ev_now (loop), 3600.), 3600., 0);
1496	ev_periodic_start (loop, &hourly_tick);	2071	ev_periodic_start (loop, &hourly_tick);
1497		2072
1498		2073
…		…
1501	Signal watchers will trigger an event when the process receives a specific	2076	Signal watchers will trigger an event when the process receives a specific
1502	signal one or more times. Even though signals are very asynchronous, libev	2077	signal one or more times. Even though signals are very asynchronous, libev
1503	will try it's best to deliver signals synchronously, i.e. as part of the	2078	will try it's best to deliver signals synchronously, i.e. as part of the
1504	normal event processing, like any other event.	2079	normal event processing, like any other event.
1505		2080
		2081	Note that only the default loop supports registering signal watchers
		2082	currently.
		2083
		2084	If you want signals asynchronously, just use C<sigaction> as you would
		2085	do without libev and forget about sharing the signal. You can even use
		2086	C<ev_async> from a signal handler to synchronously wake up an event loop.
		2087
1506	You can configure as many watchers as you like per signal. Only when the	2088	You can configure as many watchers as you like per signal. Only when the
1507	first watcher gets started will libev actually register a signal watcher	2089	first watcher gets started will libev actually register something with
1508	with the kernel (thus it coexists with your own signal handlers as long	2090	the kernel (thus it coexists with your own signal handlers as long as you
1509	as you don't register any with libev). Similarly, when the last signal	2091	don't register any with libev for the same signal).
1510	watcher for a signal is stopped libev will reset the signal handler to	2092
1511	SIG_DFL (regardless of what it was set to before).	2093	Both the signal mask state (C<sigprocmask>) and the signal handler state
		2094	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2095	sotpping it again), that is, libev might or might not block the signal,
		2096	and might or might not set or restore the installed signal handler.
1512		2097
1513	If possible and supported, libev will install its handlers with	2098	If possible and supported, libev will install its handlers with
1514	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2099	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1515	interrupted. If you have a problem with system calls getting interrupted by	2100	not be unduly interrupted. If you have a problem with system calls getting
1516	signals you can block all signals in an C<ev_check> watcher and unblock	2101	interrupted by signals you can block all signals in an C<ev_check> watcher
1517	them in an C<ev_prepare> watcher.	2102	and unblock them in an C<ev_prepare> watcher.
1518		2103
1519	=head3 Watcher-Specific Functions and Data Members	2104	=head3 Watcher-Specific Functions and Data Members
1520		2105
1521	=over 4	2106	=over 4
1522		2107
…		…
1533		2118
1534	=back	2119	=back
1535		2120
1536	=head3 Examples	2121	=head3 Examples
1537		2122
1538	Example: Try to exit cleanly on SIGINT and SIGTERM.	2123	Example: Try to exit cleanly on SIGINT.
1539		2124
1540	static void	2125	static void
1541	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2126	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1542	{	2127	{
1543	ev_unloop (loop, EVUNLOOP_ALL);	2128	ev_unloop (loop, EVUNLOOP_ALL);
1544	}	2129	}
1545		2130
1546	struct ev_signal signal_watcher;	2131	ev_signal signal_watcher;
1547	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2132	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1548	ev_signal_start (loop, &sigint_cb);	2133	ev_signal_start (loop, &signal_watcher);
1549		2134
1550		2135
1551	=head2 C<ev_child> - watch out for process status changes	2136	=head2 C<ev_child> - watch out for process status changes
1552		2137
1553	Child watchers trigger when your process receives a SIGCHLD in response to	2138	Child watchers trigger when your process receives a SIGCHLD in response to
1554	some child status changes (most typically when a child of yours dies). It	2139	some child status changes (most typically when a child of yours dies or
1555	is permissible to install a child watcher I<after> the child has been	2140	exits). It is permissible to install a child watcher I<after> the child
1556	forked (which implies it might have already exited), as long as the event	2141	has been forked (which implies it might have already exited), as long
1557	loop isn't entered (or is continued from a watcher).	2142	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2143	forking and then immediately registering a watcher for the child is fine,
		2144	but forking and registering a watcher a few event loop iterations later or
		2145	in the next callback invocation is not.
1558		2146
1559	Only the default event loop is capable of handling signals, and therefore	2147	Only the default event loop is capable of handling signals, and therefore
1560	you can only register child watchers in the default event loop.	2148	you can only register child watchers in the default event loop.
1561		2149
		2150	Due to some design glitches inside libev, child watchers will always be
		2151	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2152	libev)
		2153
1562	=head3 Process Interaction	2154	=head3 Process Interaction
1563		2155
1564	Libev grabs C<SIGCHLD> as soon as the default event loop is	2156	Libev grabs C<SIGCHLD> as soon as the default event loop is
1565	initialised. This is necessary to guarantee proper behaviour even if	2157	initialised. This is necessary to guarantee proper behaviour even if the
1566	the first child watcher is started after the child exits. The occurrence	2158	first child watcher is started after the child exits. The occurrence
1567	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2159	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1568	synchronously as part of the event loop processing. Libev always reaps all	2160	synchronously as part of the event loop processing. Libev always reaps all
1569	children, even ones not watched.	2161	children, even ones not watched.
1570		2162
1571	=head3 Overriding the Built-In Processing	2163	=head3 Overriding the Built-In Processing
…		…
1581	=head3 Stopping the Child Watcher	2173	=head3 Stopping the Child Watcher
1582		2174
1583	Currently, the child watcher never gets stopped, even when the	2175	Currently, the child watcher never gets stopped, even when the
1584	child terminates, so normally one needs to stop the watcher in the	2176	child terminates, so normally one needs to stop the watcher in the
1585	callback. Future versions of libev might stop the watcher automatically	2177	callback. Future versions of libev might stop the watcher automatically
1586	when a child exit is detected.	2178	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2179	problem).
1587		2180
1588	=head3 Watcher-Specific Functions and Data Members	2181	=head3 Watcher-Specific Functions and Data Members
1589		2182
1590	=over 4	2183	=over 4
1591		2184
…		…
1623	its completion.	2216	its completion.
1624		2217
1625	ev_child cw;	2218	ev_child cw;
1626		2219
1627	static void	2220	static void
1628	child_cb (EV_P_ struct ev_child *w, int revents)	2221	child_cb (EV_P_ ev_child *w, int revents)
1629	{	2222	{
1630	ev_child_stop (EV_A_ w);	2223	ev_child_stop (EV_A_ w);
1631	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2224	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1632	}	2225	}
1633		2226
…		…
1648		2241
1649		2242
1650	=head2 C<ev_stat> - did the file attributes just change?	2243	=head2 C<ev_stat> - did the file attributes just change?
1651		2244
1652	This watches a file system path for attribute changes. That is, it calls	2245	This watches a file system path for attribute changes. That is, it calls
1653	C<stat> regularly (or when the OS says it changed) and sees if it changed	2246	C<stat> on that path in regular intervals (or when the OS says it changed)
1654	compared to the last time, invoking the callback if it did.	2247	and sees if it changed compared to the last time, invoking the callback if
		2248	it did.
1655		2249
1656	The path does not need to exist: changing from "path exists" to "path does	2250	The path does not need to exist: changing from "path exists" to "path does
1657	not exist" is a status change like any other. The condition "path does	2251	not exist" is a status change like any other. The condition "path does not
1658	not exist" is signified by the C<st_nlink> field being zero (which is	2252	exist" (or more correctly "path cannot be stat'ed") is signified by the
1659	otherwise always forced to be at least one) and all the other fields of	2253	C<st_nlink> field being zero (which is otherwise always forced to be at
1660	the stat buffer having unspecified contents.	2254	least one) and all the other fields of the stat buffer having unspecified
		2255	contents.
1661		2256
1662	The path I<should> be absolute and I<must not> end in a slash. If it is	2257	The path I<must not> end in a slash or contain special components such as
		2258	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1663	relative and your working directory changes, the behaviour is undefined.	2259	your working directory changes, then the behaviour is undefined.
1664		2260
1665	Since there is no standard to do this, the portable implementation simply	2261	Since there is no portable change notification interface available, the
1666	calls C<stat (2)> regularly on the path to see if it changed somehow. You	2262	portable implementation simply calls C<stat(2)> regularly on the path
1667	can specify a recommended polling interval for this case. If you specify	2263	to see if it changed somehow. You can specify a recommended polling
1668	a polling interval of C<0> (highly recommended!) then a I<suitable,	2264	interval for this case. If you specify a polling interval of C<0> (highly
1669	unspecified default> value will be used (which you can expect to be around	2265	recommended!) then a I<suitable, unspecified default> value will be used
1670	five seconds, although this might change dynamically). Libev will also	2266	(which you can expect to be around five seconds, although this might
1671	impose a minimum interval which is currently around C<0.1>, but thats	2267	change dynamically). Libev will also impose a minimum interval which is
1672	usually overkill.	2268	currently around C<0.1>, but that's usually overkill.
1673		2269
1674	This watcher type is not meant for massive numbers of stat watchers,	2270	This watcher type is not meant for massive numbers of stat watchers,
1675	as even with OS-supported change notifications, this can be	2271	as even with OS-supported change notifications, this can be
1676	resource-intensive.	2272	resource-intensive.
1677		2273
1678	At the time of this writing, only the Linux inotify interface is	2274	At the time of this writing, the only OS-specific interface implemented
1679	implemented (implementing kqueue support is left as an exercise for the	2275	is the Linux inotify interface (implementing kqueue support is left as an
1680	reader, note, however, that the author sees no way of implementing ev_stat	2276	exercise for the reader. Note, however, that the author sees no way of
1681	semantics with kqueue). Inotify will be used to give hints only and should	2277	implementing C<ev_stat> semantics with kqueue, except as a hint).
1682	not change the semantics of C<ev_stat> watchers, which means that libev
1683	sometimes needs to fall back to regular polling again even with inotify,
1684	but changes are usually detected immediately, and if the file exists there
1685	will be no polling.
1686		2278
1687	=head3 ABI Issues (Largefile Support)	2279	=head3 ABI Issues (Largefile Support)
1688		2280
1689	Libev by default (unless the user overrides this) uses the default	2281	Libev by default (unless the user overrides this) uses the default
1690	compilation environment, which means that on systems with large file	2282	compilation environment, which means that on systems with large file
1691	support disabled by default, you get the 32 bit version of the stat	2283	support disabled by default, you get the 32 bit version of the stat
1692	structure. When using the library from programs that change the ABI to	2284	structure. When using the library from programs that change the ABI to
1693	use 64 bit file offsets the programs will fail. In that case you have to	2285	use 64 bit file offsets the programs will fail. In that case you have to
1694	compile libev with the same flags to get binary compatibility. This is	2286	compile libev with the same flags to get binary compatibility. This is
1695	obviously the case with any flags that change the ABI, but the problem is	2287	obviously the case with any flags that change the ABI, but the problem is
1696	most noticeably disabled with ev_stat and large file support.	2288	most noticeably displayed with ev_stat and large file support.
1697		2289
1698	The solution for this is to lobby your distribution maker to make large	2290	The solution for this is to lobby your distribution maker to make large
1699	file interfaces available by default (as e.g. FreeBSD does) and not	2291	file interfaces available by default (as e.g. FreeBSD does) and not
1700	optional. Libev cannot simply switch on large file support because it has	2292	optional. Libev cannot simply switch on large file support because it has
1701	to exchange stat structures with application programs compiled using the	2293	to exchange stat structures with application programs compiled using the
1702	default compilation environment.	2294	default compilation environment.
1703		2295
1704	=head3 Inotify	2296	=head3 Inotify and Kqueue
1705		2297
1706	When C<inotify (7)> support has been compiled into libev (generally only	2298	When C<inotify (7)> support has been compiled into libev and present at
1707	available on Linux) and present at runtime, it will be used to speed up	2299	runtime, it will be used to speed up change detection where possible. The
1708	change detection where possible. The inotify descriptor will be created lazily	2300	inotify descriptor will be created lazily when the first C<ev_stat>
1709	when the first C<ev_stat> watcher is being started.	2301	watcher is being started.
1710		2302
1711	Inotify presence does not change the semantics of C<ev_stat> watchers	2303	Inotify presence does not change the semantics of C<ev_stat> watchers
1712	except that changes might be detected earlier, and in some cases, to avoid	2304	except that changes might be detected earlier, and in some cases, to avoid
1713	making regular C<stat> calls. Even in the presence of inotify support	2305	making regular C<stat> calls. Even in the presence of inotify support
1714	there are many cases where libev has to resort to regular C<stat> polling.	2306	there are many cases where libev has to resort to regular C<stat> polling,
		2307	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2308	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2309	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2310	xfs are fully working) libev usually gets away without polling.
1715		2311
1716	(There is no support for kqueue, as apparently it cannot be used to	2312	There is no support for kqueue, as apparently it cannot be used to
1717	implement this functionality, due to the requirement of having a file	2313	implement this functionality, due to the requirement of having a file
1718	descriptor open on the object at all times).	2314	descriptor open on the object at all times, and detecting renames, unlinks
		2315	etc. is difficult.
		2316
		2317	=head3 C<stat ()> is a synchronous operation
		2318
		2319	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2320	the process. The exception are C<ev_stat> watchers - those call C<stat
		2321	()>, which is a synchronous operation.
		2322
		2323	For local paths, this usually doesn't matter: unless the system is very
		2324	busy or the intervals between stat's are large, a stat call will be fast,
		2325	as the path data is usually in memory already (except when starting the
		2326	watcher).
		2327
		2328	For networked file systems, calling C<stat ()> can block an indefinite
		2329	time due to network issues, and even under good conditions, a stat call
		2330	often takes multiple milliseconds.
		2331
		2332	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2333	paths, although this is fully supported by libev.
1719		2334
1720	=head3 The special problem of stat time resolution	2335	=head3 The special problem of stat time resolution
1721		2336
1722	The C<stat ()> system call only supports full-second resolution portably, and	2337	The C<stat ()> system call only supports full-second resolution portably,
1723	even on systems where the resolution is higher, many file systems still	2338	and even on systems where the resolution is higher, most file systems
1724	only support whole seconds.	2339	still only support whole seconds.
1725		2340
1726	That means that, if the time is the only thing that changes, you can	2341	That means that, if the time is the only thing that changes, you can
1727	easily miss updates: on the first update, C<ev_stat> detects a change and	2342	easily miss updates: on the first update, C<ev_stat> detects a change and
1728	calls your callback, which does something. When there is another update	2343	calls your callback, which does something. When there is another update
1729	within the same second, C<ev_stat> will be unable to detect it as the stat	2344	within the same second, C<ev_stat> will be unable to detect unless the
1730	data does not change.	2345	stat data does change in other ways (e.g. file size).
1731		2346
1732	The solution to this is to delay acting on a change for slightly more	2347	The solution to this is to delay acting on a change for slightly more
1733	than a second (or till slightly after the next full second boundary), using	2348	than a second (or till slightly after the next full second boundary), using
1734	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2349	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1735	ev_timer_again (loop, w)>).	2350	ev_timer_again (loop, w)>).
…		…
1755	C<path>. The C<interval> is a hint on how quickly a change is expected to	2370	C<path>. The C<interval> is a hint on how quickly a change is expected to
1756	be detected and should normally be specified as C<0> to let libev choose	2371	be detected and should normally be specified as C<0> to let libev choose
1757	a suitable value. The memory pointed to by C<path> must point to the same	2372	a suitable value. The memory pointed to by C<path> must point to the same
1758	path for as long as the watcher is active.	2373	path for as long as the watcher is active.
1759		2374
1760	The callback will receive C<EV_STAT> when a change was detected, relative	2375	The callback will receive an C<EV_STAT> event when a change was detected,
1761	to the attributes at the time the watcher was started (or the last change	2376	relative to the attributes at the time the watcher was started (or the
1762	was detected).	2377	last change was detected).
1763		2378
1764	=item ev_stat_stat (loop, ev_stat *)	2379	=item ev_stat_stat (loop, ev_stat *)
1765		2380
1766	Updates the stat buffer immediately with new values. If you change the	2381	Updates the stat buffer immediately with new values. If you change the
1767	watched path in your callback, you could call this function to avoid	2382	watched path in your callback, you could call this function to avoid
…		…
1850		2465
1851		2466
1852	=head2 C<ev_idle> - when you've got nothing better to do...	2467	=head2 C<ev_idle> - when you've got nothing better to do...
1853		2468
1854	Idle watchers trigger events when no other events of the same or higher	2469	Idle watchers trigger events when no other events of the same or higher
1855	priority are pending (prepare, check and other idle watchers do not	2470	priority are pending (prepare, check and other idle watchers do not count
1856	count).	2471	as receiving "events").
1857		2472
1858	That is, as long as your process is busy handling sockets or timeouts	2473	That is, as long as your process is busy handling sockets or timeouts
1859	(or even signals, imagine) of the same or higher priority it will not be	2474	(or even signals, imagine) of the same or higher priority it will not be
1860	triggered. But when your process is idle (or only lower-priority watchers	2475	triggered. But when your process is idle (or only lower-priority watchers
1861	are pending), the idle watchers are being called once per event loop	2476	are pending), the idle watchers are being called once per event loop
…		…
1872		2487
1873	=head3 Watcher-Specific Functions and Data Members	2488	=head3 Watcher-Specific Functions and Data Members
1874		2489
1875	=over 4	2490	=over 4
1876		2491
1877	=item ev_idle_init (ev_signal *, callback)	2492	=item ev_idle_init (ev_idle *, callback)
1878		2493
1879	Initialises and configures the idle watcher - it has no parameters of any	2494	Initialises and configures the idle watcher - it has no parameters of any
1880	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2495	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1881	believe me.	2496	believe me.
1882		2497
…		…
1886		2501
1887	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2502	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1888	callback, free it. Also, use no error checking, as usual.	2503	callback, free it. Also, use no error checking, as usual.
1889		2504
1890	static void	2505	static void
1891	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2506	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1892	{	2507	{
1893	free (w);	2508	free (w);
1894	// now do something you wanted to do when the program has	2509	// now do something you wanted to do when the program has
1895	// no longer anything immediate to do.	2510	// no longer anything immediate to do.
1896	}	2511	}
1897		2512
1898	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2513	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1899	ev_idle_init (idle_watcher, idle_cb);	2514	ev_idle_init (idle_watcher, idle_cb);
1900	ev_idle_start (loop, idle_cb);	2515	ev_idle_start (loop, idle_watcher);
1901		2516
1902		2517
1903	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2518	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1904		2519
1905	Prepare and check watchers are usually (but not always) used in tandem:	2520	Prepare and check watchers are usually (but not always) used in pairs:
1906	prepare watchers get invoked before the process blocks and check watchers	2521	prepare watchers get invoked before the process blocks and check watchers
1907	afterwards.	2522	afterwards.
1908		2523
1909	You I<must not> call C<ev_loop> or similar functions that enter	2524	You I<must not> call C<ev_loop> or similar functions that enter
1910	the current event loop from either C<ev_prepare> or C<ev_check>	2525	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1913	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2528	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1914	C<ev_check> so if you have one watcher of each kind they will always be	2529	C<ev_check> so if you have one watcher of each kind they will always be
1915	called in pairs bracketing the blocking call.	2530	called in pairs bracketing the blocking call.
1916		2531
1917	Their main purpose is to integrate other event mechanisms into libev and	2532	Their main purpose is to integrate other event mechanisms into libev and
1918	their use is somewhat advanced. This could be used, for example, to track	2533	their use is somewhat advanced. They could be used, for example, to track
1919	variable changes, implement your own watchers, integrate net-snmp or a	2534	variable changes, implement your own watchers, integrate net-snmp or a
1920	coroutine library and lots more. They are also occasionally useful if	2535	coroutine library and lots more. They are also occasionally useful if
1921	you cache some data and want to flush it before blocking (for example,	2536	you cache some data and want to flush it before blocking (for example,
1922	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2537	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1923	watcher).	2538	watcher).
1924		2539
1925	This is done by examining in each prepare call which file descriptors need	2540	This is done by examining in each prepare call which file descriptors
1926	to be watched by the other library, registering C<ev_io> watchers for	2541	need to be watched by the other library, registering C<ev_io> watchers
1927	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2542	for them and starting an C<ev_timer> watcher for any timeouts (many
1928	provide just this functionality). Then, in the check watcher you check for	2543	libraries provide exactly this functionality). Then, in the check watcher,
1929	any events that occurred (by checking the pending status of all watchers	2544	you check for any events that occurred (by checking the pending status
1930	and stopping them) and call back into the library. The I/O and timer	2545	of all watchers and stopping them) and call back into the library. The
1931	callbacks will never actually be called (but must be valid nevertheless,	2546	I/O and timer callbacks will never actually be called (but must be valid
1932	because you never know, you know?).	2547	nevertheless, because you never know, you know?).
1933		2548
1934	As another example, the Perl Coro module uses these hooks to integrate	2549	As another example, the Perl Coro module uses these hooks to integrate
1935	coroutines into libev programs, by yielding to other active coroutines	2550	coroutines into libev programs, by yielding to other active coroutines
1936	during each prepare and only letting the process block if no coroutines	2551	during each prepare and only letting the process block if no coroutines
1937	are ready to run (it's actually more complicated: it only runs coroutines	2552	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1940	loop from blocking if lower-priority coroutines are active, thus mapping	2555	loop from blocking if lower-priority coroutines are active, thus mapping
1941	low-priority coroutines to idle/background tasks).	2556	low-priority coroutines to idle/background tasks).
1942		2557
1943	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2558	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1944	priority, to ensure that they are being run before any other watchers	2559	priority, to ensure that they are being run before any other watchers
		2560	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2561
1945	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2562	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1946	too) should not activate ("feed") events into libev. While libev fully	2563	activate ("feed") events into libev. While libev fully supports this, they
1947	supports this, they might get executed before other C<ev_check> watchers	2564	might get executed before other C<ev_check> watchers did their job. As
1948	did their job. As C<ev_check> watchers are often used to embed other	2565	C<ev_check> watchers are often used to embed other (non-libev) event
1949	(non-libev) event loops those other event loops might be in an unusable	2566	loops those other event loops might be in an unusable state until their
1950	state until their C<ev_check> watcher ran (always remind yourself to	2567	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1951	coexist peacefully with others).	2568	others).
1952		2569
1953	=head3 Watcher-Specific Functions and Data Members	2570	=head3 Watcher-Specific Functions and Data Members
1954		2571
1955	=over 4	2572	=over 4
1956		2573
…		…
1958		2575
1959	=item ev_check_init (ev_check *, callback)	2576	=item ev_check_init (ev_check *, callback)
1960		2577
1961	Initialises and configures the prepare or check watcher - they have no	2578	Initialises and configures the prepare or check watcher - they have no
1962	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2579	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1963	macros, but using them is utterly, utterly and completely pointless.	2580	macros, but using them is utterly, utterly, utterly and completely
		2581	pointless.
1964		2582
1965	=back	2583	=back
1966		2584
1967	=head3 Examples	2585	=head3 Examples
1968		2586
…		…
1981		2599
1982	static ev_io iow [nfd];	2600	static ev_io iow [nfd];
1983	static ev_timer tw;	2601	static ev_timer tw;
1984		2602
1985	static void	2603	static void
1986	io_cb (ev_loop *loop, ev_io *w, int revents)	2604	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1987	{	2605	{
1988	}	2606	}
1989		2607
1990	// create io watchers for each fd and a timer before blocking	2608	// create io watchers for each fd and a timer before blocking
1991	static void	2609	static void
1992	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2610	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1993	{	2611	{
1994	int timeout = 3600000;	2612	int timeout = 3600000;
1995	struct pollfd fds [nfd];	2613	struct pollfd fds [nfd];
1996	// actual code will need to loop here and realloc etc.	2614	// actual code will need to loop here and realloc etc.
1997	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2615	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1998		2616
1999	/* the callback is illegal, but won't be called as we stop during check */	2617	/* the callback is illegal, but won't be called as we stop during check */
2000	ev_timer_init (&tw, 0, timeout * 1e-3);	2618	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2001	ev_timer_start (loop, &tw);	2619	ev_timer_start (loop, &tw);
2002		2620
2003	// create one ev_io per pollfd	2621	// create one ev_io per pollfd
2004	for (int i = 0; i < nfd; ++i)	2622	for (int i = 0; i < nfd; ++i)
2005	{	2623	{
…		…
2012	}	2630	}
2013	}	2631	}
2014		2632
2015	// stop all watchers after blocking	2633	// stop all watchers after blocking
2016	static void	2634	static void
2017	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2635	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2018	{	2636	{
2019	ev_timer_stop (loop, &tw);	2637	ev_timer_stop (loop, &tw);
2020		2638
2021	for (int i = 0; i < nfd; ++i)	2639	for (int i = 0; i < nfd; ++i)
2022	{	2640	{
…		…
2061	}	2679	}
2062		2680
2063	// do not ever call adns_afterpoll	2681	// do not ever call adns_afterpoll
2064		2682
2065	Method 4: Do not use a prepare or check watcher because the module you	2683	Method 4: Do not use a prepare or check watcher because the module you
2066	want to embed is too inflexible to support it. Instead, you can override	2684	want to embed is not flexible enough to support it. Instead, you can
2067	their poll function. The drawback with this solution is that the main	2685	override their poll function. The drawback with this solution is that the
2068	loop is now no longer controllable by EV. The C<Glib::EV> module does	2686	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2069	this.	2687	this approach, effectively embedding EV as a client into the horrible
		2688	libglib event loop.
2070		2689
2071	static gint	2690	static gint
2072	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2691	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2073	{	2692	{
2074	int got_events = 0;	2693	int got_events = 0;
…		…
2105	prioritise I/O.	2724	prioritise I/O.
2106		2725
2107	As an example for a bug workaround, the kqueue backend might only support	2726	As an example for a bug workaround, the kqueue backend might only support
2108	sockets on some platform, so it is unusable as generic backend, but you	2727	sockets on some platform, so it is unusable as generic backend, but you
2109	still want to make use of it because you have many sockets and it scales	2728	still want to make use of it because you have many sockets and it scales
2110	so nicely. In this case, you would create a kqueue-based loop and embed it	2729	so nicely. In this case, you would create a kqueue-based loop and embed
2111	into your default loop (which might use e.g. poll). Overall operation will	2730	it into your default loop (which might use e.g. poll). Overall operation
2112	be a bit slower because first libev has to poll and then call kevent, but	2731	will be a bit slower because first libev has to call C<poll> and then
2113	at least you can use both at what they are best.	2732	C<kevent>, but at least you can use both mechanisms for what they are
		2733	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2114		2734
2115	As for prioritising I/O: rarely you have the case where some fds have	2735	As for prioritising I/O: under rare circumstances you have the case where
2116	to be watched and handled very quickly (with low latency), and even	2736	some fds have to be watched and handled very quickly (with low latency),
2117	priorities and idle watchers might have too much overhead. In this case	2737	and even priorities and idle watchers might have too much overhead. In
2118	you would put all the high priority stuff in one loop and all the rest in	2738	this case you would put all the high priority stuff in one loop and all
2119	a second one, and embed the second one in the first.	2739	the rest in a second one, and embed the second one in the first.
2120		2740
2121	As long as the watcher is active, the callback will be invoked every time	2741	As long as the watcher is active, the callback will be invoked every
2122	there might be events pending in the embedded loop. The callback must then	2742	time there might be events pending in the embedded loop. The callback
2123	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2743	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2124	their callbacks (you could also start an idle watcher to give the embedded	2744	sweep and invoke their callbacks (the callback doesn't need to invoke the
2125	loop strictly lower priority for example). You can also set the callback	2745	C<ev_embed_sweep> function directly, it could also start an idle watcher
2126	to C<0>, in which case the embed watcher will automatically execute the	2746	to give the embedded loop strictly lower priority for example).
2127	embedded loop sweep.
2128		2747
2129	As long as the watcher is started it will automatically handle events. The	2748	You can also set the callback to C<0>, in which case the embed watcher
2130	callback will be invoked whenever some events have been handled. You can	2749	will automatically execute the embedded loop sweep whenever necessary.
2131	set the callback to C<0> to avoid having to specify one if you are not
2132	interested in that.
2133		2750
2134	Also, there have not currently been made special provisions for forking:	2751	Fork detection will be handled transparently while the C<ev_embed> watcher
2135	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2752	is active, i.e., the embedded loop will automatically be forked when the
2136	but you will also have to stop and restart any C<ev_embed> watchers	2753	embedding loop forks. In other cases, the user is responsible for calling
2137	yourself.	2754	C<ev_loop_fork> on the embedded loop.
2138		2755
2139	Unfortunately, not all backends are embeddable, only the ones returned by	2756	Unfortunately, not all backends are embeddable: only the ones returned by
2140	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2757	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2141	portable one.	2758	portable one.
2142		2759
2143	So when you want to use this feature you will always have to be prepared	2760	So when you want to use this feature you will always have to be prepared
2144	that you cannot get an embeddable loop. The recommended way to get around	2761	that you cannot get an embeddable loop. The recommended way to get around
2145	this is to have a separate variables for your embeddable loop, try to	2762	this is to have a separate variables for your embeddable loop, try to
2146	create it, and if that fails, use the normal loop for everything.	2763	create it, and if that fails, use the normal loop for everything.
		2764
		2765	=head3 C<ev_embed> and fork
		2766
		2767	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2768	automatically be applied to the embedded loop as well, so no special
		2769	fork handling is required in that case. When the watcher is not running,
		2770	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2771	as applicable.
2147		2772
2148	=head3 Watcher-Specific Functions and Data Members	2773	=head3 Watcher-Specific Functions and Data Members
2149		2774
2150	=over 4	2775	=over 4
2151		2776
…		…
2179	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2804	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2180	used).	2805	used).
2181		2806
2182	struct ev_loop *loop_hi = ev_default_init (0);	2807	struct ev_loop *loop_hi = ev_default_init (0);
2183	struct ev_loop *loop_lo = 0;	2808	struct ev_loop *loop_lo = 0;
2184	struct ev_embed embed;	2809	ev_embed embed;
2185		2810
2186	// see if there is a chance of getting one that works	2811	// see if there is a chance of getting one that works
2187	// (remember that a flags value of 0 means autodetection)	2812	// (remember that a flags value of 0 means autodetection)
2188	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2813	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2189	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2814	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2203	kqueue implementation). Store the kqueue/socket-only event loop in	2828	kqueue implementation). Store the kqueue/socket-only event loop in
2204	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2829	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2205		2830
2206	struct ev_loop *loop = ev_default_init (0);	2831	struct ev_loop *loop = ev_default_init (0);
2207	struct ev_loop *loop_socket = 0;	2832	struct ev_loop *loop_socket = 0;
2208	struct ev_embed embed;	2833	ev_embed embed;
2209		2834
2210	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2835	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2211	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2836	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2212	{	2837	{
2213	ev_embed_init (&embed, 0, loop_socket);	2838	ev_embed_init (&embed, 0, loop_socket);
…		…
2228	event loop blocks next and before C<ev_check> watchers are being called,	2853	event loop blocks next and before C<ev_check> watchers are being called,
2229	and only in the child after the fork. If whoever good citizen calling	2854	and only in the child after the fork. If whoever good citizen calling
2230	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2855	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2231	handlers will be invoked, too, of course.	2856	handlers will be invoked, too, of course.
2232		2857
		2858	=head3 The special problem of life after fork - how is it possible?
		2859
		2860	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2861	up/change the process environment, followed by a call to C<exec()>. This
		2862	sequence should be handled by libev without any problems.
		2863
		2864	This changes when the application actually wants to do event handling
		2865	in the child, or both parent in child, in effect "continuing" after the
		2866	fork.
		2867
		2868	The default mode of operation (for libev, with application help to detect
		2869	forks) is to duplicate all the state in the child, as would be expected
		2870	when I<either> the parent I<or> the child process continues.
		2871
		2872	When both processes want to continue using libev, then this is usually the
		2873	wrong result. In that case, usually one process (typically the parent) is
		2874	supposed to continue with all watchers in place as before, while the other
		2875	process typically wants to start fresh, i.e. without any active watchers.
		2876
		2877	The cleanest and most efficient way to achieve that with libev is to
		2878	simply create a new event loop, which of course will be "empty", and
		2879	use that for new watchers. This has the advantage of not touching more
		2880	memory than necessary, and thus avoiding the copy-on-write, and the
		2881	disadvantage of having to use multiple event loops (which do not support
		2882	signal watchers).
		2883
		2884	When this is not possible, or you want to use the default loop for
		2885	other reasons, then in the process that wants to start "fresh", call
		2886	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2887	the default loop will "orphan" (not stop) all registered watchers, so you
		2888	have to be careful not to execute code that modifies those watchers. Note
		2889	also that in that case, you have to re-register any signal watchers.
		2890
2233	=head3 Watcher-Specific Functions and Data Members	2891	=head3 Watcher-Specific Functions and Data Members
2234		2892
2235	=over 4	2893	=over 4
2236		2894
2237	=item ev_fork_init (ev_signal *, callback)	2895	=item ev_fork_init (ev_signal *, callback)
…		…
2269	is that the author does not know of a simple (or any) algorithm for a	2927	is that the author does not know of a simple (or any) algorithm for a
2270	multiple-writer-single-reader queue that works in all cases and doesn't	2928	multiple-writer-single-reader queue that works in all cases and doesn't
2271	need elaborate support such as pthreads.	2929	need elaborate support such as pthreads.
2272		2930
2273	That means that if you want to queue data, you have to provide your own	2931	That means that if you want to queue data, you have to provide your own
2274	queue. But at least I can tell you would implement locking around your	2932	queue. But at least I can tell you how to implement locking around your
2275	queue:	2933	queue:
2276		2934
2277	=over 4	2935	=over 4
2278		2936
2279	=item queueing from a signal handler context	2937	=item queueing from a signal handler context
2280		2938
2281	To implement race-free queueing, you simply add to the queue in the signal	2939	To implement race-free queueing, you simply add to the queue in the signal
2282	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2940	handler but you block the signal handler in the watcher callback. Here is
2283	some fictitious SIGUSR1 handler:	2941	an example that does that for some fictitious SIGUSR1 handler:
2284		2942
2285	static ev_async mysig;	2943	static ev_async mysig;
2286		2944
2287	static void	2945	static void
2288	sigusr1_handler (void)	2946	sigusr1_handler (void)
…		…
2354	=over 4	3012	=over 4
2355		3013
2356	=item ev_async_init (ev_async *, callback)	3014	=item ev_async_init (ev_async *, callback)
2357		3015
2358	Initialises and configures the async watcher - it has no parameters of any	3016	Initialises and configures the async watcher - it has no parameters of any
2359	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3017	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2360	believe me.	3018	trust me.
2361		3019
2362	=item ev_async_send (loop, ev_async *)	3020	=item ev_async_send (loop, ev_async *)
2363		3021
2364	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3022	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2365	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3023	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2366	C<ev_feed_event>, this call is safe to do in other threads, signal or	3024	C<ev_feed_event>, this call is safe to do from other threads, signal or
2367	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3025	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2368	section below on what exactly this means).	3026	section below on what exactly this means).
2369		3027
		3028	Note that, as with other watchers in libev, multiple events might get
		3029	compressed into a single callback invocation (another way to look at this
		3030	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3031	reset when the event loop detects that).
		3032
2370	This call incurs the overhead of a system call only once per loop iteration,	3033	This call incurs the overhead of a system call only once per event loop
2371	so while the overhead might be noticeable, it doesn't apply to repeated	3034	iteration, so while the overhead might be noticeable, it doesn't apply to
2372	calls to C<ev_async_send>.	3035	repeated calls to C<ev_async_send> for the same event loop.
2373		3036
2374	=item bool = ev_async_pending (ev_async *)	3037	=item bool = ev_async_pending (ev_async *)
2375		3038
2376	Returns a non-zero value when C<ev_async_send> has been called on the	3039	Returns a non-zero value when C<ev_async_send> has been called on the
2377	watcher but the event has not yet been processed (or even noted) by the	3040	watcher but the event has not yet been processed (or even noted) by the
…		…
2380	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3043	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2381	the loop iterates next and checks for the watcher to have become active,	3044	the loop iterates next and checks for the watcher to have become active,
2382	it will reset the flag again. C<ev_async_pending> can be used to very	3045	it will reset the flag again. C<ev_async_pending> can be used to very
2383	quickly check whether invoking the loop might be a good idea.	3046	quickly check whether invoking the loop might be a good idea.
2384		3047
2385	Not that this does I<not> check whether the watcher itself is pending, only	3048	Not that this does I<not> check whether the watcher itself is pending,
2386	whether it has been requested to make this watcher pending.	3049	only whether it has been requested to make this watcher pending: there
		3050	is a time window between the event loop checking and resetting the async
		3051	notification, and the callback being invoked.
2387		3052
2388	=back	3053	=back
2389		3054
2390		3055
2391	=head1 OTHER FUNCTIONS	3056	=head1 OTHER FUNCTIONS
…		…
2395	=over 4	3060	=over 4
2396		3061
2397	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3062	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2398		3063
2399	This function combines a simple timer and an I/O watcher, calls your	3064	This function combines a simple timer and an I/O watcher, calls your
2400	callback on whichever event happens first and automatically stop both	3065	callback on whichever event happens first and automatically stops both
2401	watchers. This is useful if you want to wait for a single event on an fd	3066	watchers. This is useful if you want to wait for a single event on an fd
2402	or timeout without having to allocate/configure/start/stop/free one or	3067	or timeout without having to allocate/configure/start/stop/free one or
2403	more watchers yourself.	3068	more watchers yourself.
2404		3069
2405	If C<fd> is less than 0, then no I/O watcher will be started and events	3070	If C<fd> is less than 0, then no I/O watcher will be started and the
2406	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	3071	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2407	C<events> set will be created and started.	3072	the given C<fd> and C<events> set will be created and started.
2408		3073
2409	If C<timeout> is less than 0, then no timeout watcher will be	3074	If C<timeout> is less than 0, then no timeout watcher will be
2410	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3075	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2411	repeat = 0) will be started. While C<0> is a valid timeout, it is of	3076	repeat = 0) will be started. C<0> is a valid timeout.
2412	dubious value.
2413		3077
2414	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3078	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2415	passed an C<revents> set like normal event callbacks (a combination of	3079	passed an C<revents> set like normal event callbacks (a combination of
2416	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3080	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2417	value passed to C<ev_once>:	3081	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3082	a timeout and an io event at the same time - you probably should give io
		3083	events precedence.
		3084
		3085	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2418		3086
2419	static void stdin_ready (int revents, void *arg)	3087	static void stdin_ready (int revents, void *arg)
2420	{	3088	{
		3089	if (revents & EV_READ)
		3090	/* stdin might have data for us, joy! */;
2421	if (revents & EV_TIMEOUT)	3091	else if (revents & EV_TIMEOUT)
2422	/* doh, nothing entered */;	3092	/* doh, nothing entered */;
2423	else if (revents & EV_READ)
2424	/* stdin might have data for us, joy! */;
2425	}	3093	}
2426		3094
2427	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3095	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2428		3096
2429	=item ev_feed_event (ev_loop *, watcher *, int revents)	3097	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2430		3098
2431	Feeds the given event set into the event loop, as if the specified event	3099	Feeds the given event set into the event loop, as if the specified event
2432	had happened for the specified watcher (which must be a pointer to an	3100	had happened for the specified watcher (which must be a pointer to an
2433	initialised but not necessarily started event watcher).	3101	initialised but not necessarily started event watcher).
2434		3102
2435	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3103	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2436		3104
2437	Feed an event on the given fd, as if a file descriptor backend detected	3105	Feed an event on the given fd, as if a file descriptor backend detected
2438	the given events it.	3106	the given events it.
2439		3107
2440	=item ev_feed_signal_event (ev_loop *loop, int signum)	3108	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2441		3109
2442	Feed an event as if the given signal occurred (C<loop> must be the default	3110	Feed an event as if the given signal occurred (C<loop> must be the default
2443	loop!).	3111	loop!).
2444		3112
2445	=back	3113	=back
…		…
2567		3235
2568	myclass obj;	3236	myclass obj;
2569	ev::io iow;	3237	ev::io iow;
2570	iow.set <myclass, &myclass::io_cb> (&obj);	3238	iow.set <myclass, &myclass::io_cb> (&obj);
2571		3239
		3240	=item w->set (object *)
		3241
		3242	This is an B<experimental> feature that might go away in a future version.
		3243
		3244	This is a variation of a method callback - leaving out the method to call
		3245	will default the method to C<operator ()>, which makes it possible to use
		3246	functor objects without having to manually specify the C<operator ()> all
		3247	the time. Incidentally, you can then also leave out the template argument
		3248	list.
		3249
		3250	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3251	int revents)>.
		3252
		3253	See the method-C<set> above for more details.
		3254
		3255	Example: use a functor object as callback.
		3256
		3257	struct myfunctor
		3258	{
		3259	void operator() (ev::io &w, int revents)
		3260	{
		3261	...
		3262	}
		3263	}
		3264
		3265	myfunctor f;
		3266
		3267	ev::io w;
		3268	w.set (&f);
		3269
2572	=item w->set<function> (void *data = 0)	3270	=item w->set<function> (void *data = 0)
2573		3271
2574	Also sets a callback, but uses a static method or plain function as	3272	Also sets a callback, but uses a static method or plain function as
2575	callback. The optional C<data> argument will be stored in the watcher's	3273	callback. The optional C<data> argument will be stored in the watcher's
2576	C<data> member and is free for you to use.	3274	C<data> member and is free for you to use.
2577		3275
2578	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3276	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2579		3277
2580	See the method-C<set> above for more details.	3278	See the method-C<set> above for more details.
2581		3279
2582	Example:	3280	Example: Use a plain function as callback.
2583		3281
2584	static void io_cb (ev::io &w, int revents) { }	3282	static void io_cb (ev::io &w, int revents) { }
2585	iow.set <io_cb> ();	3283	iow.set <io_cb> ();
2586		3284
2587	=item w->set (struct ev_loop *)	3285	=item w->set (struct ev_loop *)
…		…
2625	Example: Define a class with an IO and idle watcher, start one of them in	3323	Example: Define a class with an IO and idle watcher, start one of them in
2626	the constructor.	3324	the constructor.
2627		3325
2628	class myclass	3326	class myclass
2629	{	3327	{
2630	ev::io io; void io_cb (ev::io &w, int revents);	3328	ev::io io ; void io_cb (ev::io &w, int revents);
2631	ev:idle idle void idle_cb (ev::idle &w, int revents);	3329	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2632		3330
2633	myclass (int fd)	3331	myclass (int fd)
2634	{	3332	{
2635	io .set <myclass, &myclass::io_cb > (this);	3333	io .set <myclass, &myclass::io_cb > (this);
2636	idle.set <myclass, &myclass::idle_cb> (this);	3334	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2652	=item Perl	3350	=item Perl
2653		3351
2654	The EV module implements the full libev API and is actually used to test	3352	The EV module implements the full libev API and is actually used to test
2655	libev. EV is developed together with libev. Apart from the EV core module,	3353	libev. EV is developed together with libev. Apart from the EV core module,
2656	there are additional modules that implement libev-compatible interfaces	3354	there are additional modules that implement libev-compatible interfaces
2657	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3355	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2658	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3356	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3357	and C<EV::Glib>).
2659		3358
2660	It can be found and installed via CPAN, its homepage is at	3359	It can be found and installed via CPAN, its homepage is at
2661	L<http://software.schmorp.de/pkg/EV>.	3360	L<http://software.schmorp.de/pkg/EV>.
2662		3361
2663	=item Python	3362	=item Python
2664		3363
2665	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3364	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2666	seems to be quite complete and well-documented. Note, however, that the	3365	seems to be quite complete and well-documented.
2667	patch they require for libev is outright dangerous as it breaks the ABI
2668	for everybody else, and therefore, should never be applied in an installed
2669	libev (if python requires an incompatible ABI then it needs to embed
2670	libev).
2671		3366
2672	=item Ruby	3367	=item Ruby
2673		3368
2674	Tony Arcieri has written a ruby extension that offers access to a subset	3369	Tony Arcieri has written a ruby extension that offers access to a subset
2675	of the libev API and adds file handle abstractions, asynchronous DNS and	3370	of the libev API and adds file handle abstractions, asynchronous DNS and
2676	more on top of it. It can be found via gem servers. Its homepage is at	3371	more on top of it. It can be found via gem servers. Its homepage is at
2677	L<http://rev.rubyforge.org/>.	3372	L<http://rev.rubyforge.org/>.
2678		3373
		3374	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3375	makes rev work even on mingw.
		3376
		3377	=item Haskell
		3378
		3379	A haskell binding to libev is available at
		3380	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3381
2679	=item D	3382	=item D
2680		3383
2681	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3384	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2682	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3385	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3386
		3387	=item Ocaml
		3388
		3389	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3390	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2683		3391
2684	=back	3392	=back
2685		3393
2686		3394
2687	=head1 MACRO MAGIC	3395	=head1 MACRO MAGIC
…		…
2788		3496
2789	#define EV_STANDALONE 1	3497	#define EV_STANDALONE 1
2790	#include "ev.h"	3498	#include "ev.h"
2791		3499
2792	Both header files and implementation files can be compiled with a C++	3500	Both header files and implementation files can be compiled with a C++
2793	compiler (at least, thats a stated goal, and breakage will be treated	3501	compiler (at least, that's a stated goal, and breakage will be treated
2794	as a bug).	3502	as a bug).
2795		3503
2796	You need the following files in your source tree, or in a directory	3504	You need the following files in your source tree, or in a directory
2797	in your include path (e.g. in libev/ when using -Ilibev):	3505	in your include path (e.g. in libev/ when using -Ilibev):
2798		3506
…		…
2842		3550
2843	=head2 PREPROCESSOR SYMBOLS/MACROS	3551	=head2 PREPROCESSOR SYMBOLS/MACROS
2844		3552
2845	Libev can be configured via a variety of preprocessor symbols you have to	3553	Libev can be configured via a variety of preprocessor symbols you have to
2846	define before including any of its files. The default in the absence of	3554	define before including any of its files. The default in the absence of
2847	autoconf is noted for every option.	3555	autoconf is documented for every option.
2848		3556
2849	=over 4	3557	=over 4
2850		3558
2851	=item EV_STANDALONE	3559	=item EV_STANDALONE
2852		3560
…		…
2854	keeps libev from including F<config.h>, and it also defines dummy	3562	keeps libev from including F<config.h>, and it also defines dummy
2855	implementations for some libevent functions (such as logging, which is not	3563	implementations for some libevent functions (such as logging, which is not
2856	supported). It will also not define any of the structs usually found in	3564	supported). It will also not define any of the structs usually found in
2857	F<event.h> that are not directly supported by the libev core alone.	3565	F<event.h> that are not directly supported by the libev core alone.
2858		3566
		3567	In stanbdalone mode, libev will still try to automatically deduce the
		3568	configuration, but has to be more conservative.
		3569
2859	=item EV_USE_MONOTONIC	3570	=item EV_USE_MONOTONIC
2860		3571
2861	If defined to be C<1>, libev will try to detect the availability of the	3572	If defined to be C<1>, libev will try to detect the availability of the
2862	monotonic clock option at both compile time and runtime. Otherwise no use	3573	monotonic clock option at both compile time and runtime. Otherwise no
2863	of the monotonic clock option will be attempted. If you enable this, you	3574	use of the monotonic clock option will be attempted. If you enable this,
2864	usually have to link against librt or something similar. Enabling it when	3575	you usually have to link against librt or something similar. Enabling it
2865	the functionality isn't available is safe, though, although you have	3576	when the functionality isn't available is safe, though, although you have
2866	to make sure you link against any libraries where the C<clock_gettime>	3577	to make sure you link against any libraries where the C<clock_gettime>
2867	function is hiding in (often F<-lrt>).	3578	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2868		3579
2869	=item EV_USE_REALTIME	3580	=item EV_USE_REALTIME
2870		3581
2871	If defined to be C<1>, libev will try to detect the availability of the	3582	If defined to be C<1>, libev will try to detect the availability of the
2872	real-time clock option at compile time (and assume its availability at	3583	real-time clock option at compile time (and assume its availability
2873	runtime if successful). Otherwise no use of the real-time clock option will	3584	at runtime if successful). Otherwise no use of the real-time clock
2874	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3585	option will be attempted. This effectively replaces C<gettimeofday>
2875	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3586	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2876	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3587	correctness. See the note about libraries in the description of
		3588	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3589	C<EV_USE_CLOCK_SYSCALL>.
		3590
		3591	=item EV_USE_CLOCK_SYSCALL
		3592
		3593	If defined to be C<1>, libev will try to use a direct syscall instead
		3594	of calling the system-provided C<clock_gettime> function. This option
		3595	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3596	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3597	programs needlessly. Using a direct syscall is slightly slower (in
		3598	theory), because no optimised vdso implementation can be used, but avoids
		3599	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3600	higher, as it simplifies linking (no need for C<-lrt>).
2877		3601
2878	=item EV_USE_NANOSLEEP	3602	=item EV_USE_NANOSLEEP
2879		3603
2880	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3604	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2881	and will use it for delays. Otherwise it will use C<select ()>.	3605	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2897		3621
2898	=item EV_SELECT_USE_FD_SET	3622	=item EV_SELECT_USE_FD_SET
2899		3623
2900	If defined to C<1>, then the select backend will use the system C<fd_set>	3624	If defined to C<1>, then the select backend will use the system C<fd_set>
2901	structure. This is useful if libev doesn't compile due to a missing	3625	structure. This is useful if libev doesn't compile due to a missing
2902	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3626	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2903	exotic systems. This usually limits the range of file descriptors to some	3627	on exotic systems. This usually limits the range of file descriptors to
2904	low limit such as 1024 or might have other limitations (winsocket only	3628	some low limit such as 1024 or might have other limitations (winsocket
2905	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3629	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2906	influence the size of the C<fd_set> used.	3630	configures the maximum size of the C<fd_set>.
2907		3631
2908	=item EV_SELECT_IS_WINSOCKET	3632	=item EV_SELECT_IS_WINSOCKET
2909		3633
2910	When defined to C<1>, the select backend will assume that	3634	When defined to C<1>, the select backend will assume that
2911	select/socket/connect etc. don't understand file descriptors but	3635	select/socket/connect etc. don't understand file descriptors but
…		…
3022	When doing priority-based operations, libev usually has to linearly search	3746	When doing priority-based operations, libev usually has to linearly search
3023	all the priorities, so having many of them (hundreds) uses a lot of space	3747	all the priorities, so having many of them (hundreds) uses a lot of space
3024	and time, so using the defaults of five priorities (-2 .. +2) is usually	3748	and time, so using the defaults of five priorities (-2 .. +2) is usually
3025	fine.	3749	fine.
3026		3750
3027	If your embedding application does not need any priorities, defining these both to	3751	If your embedding application does not need any priorities, defining these
3028	C<0> will save some memory and CPU.	3752	both to C<0> will save some memory and CPU.
3029		3753
3030	=item EV_PERIODIC_ENABLE	3754	=item EV_PERIODIC_ENABLE
3031		3755
3032	If undefined or defined to be C<1>, then periodic timers are supported. If	3756	If undefined or defined to be C<1>, then periodic timers are supported. If
3033	defined to be C<0>, then they are not. Disabling them saves a few kB of	3757	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3040	code.	3764	code.
3041		3765
3042	=item EV_EMBED_ENABLE	3766	=item EV_EMBED_ENABLE
3043		3767
3044	If undefined or defined to be C<1>, then embed watchers are supported. If	3768	If undefined or defined to be C<1>, then embed watchers are supported. If
3045	defined to be C<0>, then they are not.	3769	defined to be C<0>, then they are not. Embed watchers rely on most other
		3770	watcher types, which therefore must not be disabled.
3046		3771
3047	=item EV_STAT_ENABLE	3772	=item EV_STAT_ENABLE
3048		3773
3049	If undefined or defined to be C<1>, then stat watchers are supported. If	3774	If undefined or defined to be C<1>, then stat watchers are supported. If
3050	defined to be C<0>, then they are not.	3775	defined to be C<0>, then they are not.
…		…
3060	defined to be C<0>, then they are not.	3785	defined to be C<0>, then they are not.
3061		3786
3062	=item EV_MINIMAL	3787	=item EV_MINIMAL
3063		3788
3064	If you need to shave off some kilobytes of code at the expense of some	3789	If you need to shave off some kilobytes of code at the expense of some
3065	speed, define this symbol to C<1>. Currently this is used to override some	3790	speed (but with the full API), define this symbol to C<1>. Currently this
3066	inlining decisions, saves roughly 30% code size on amd64. It also selects a	3791	is used to override some inlining decisions, saves roughly 30% code size
3067	much smaller 2-heap for timer management over the default 4-heap.	3792	on amd64. It also selects a much smaller 2-heap for timer management over
		3793	the default 4-heap.
		3794
		3795	You can save even more by disabling watcher types you do not need
		3796	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>
		3797	(C<-DNDEBUG>) will usually reduce code size a lot.
		3798
		3799	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to
		3800	provide a bare-bones event library. See C<ev.h> for details on what parts
		3801	of the API are still available, and do not complain if this subset changes
		3802	over time.
3068		3803
3069	=item EV_PID_HASHSIZE	3804	=item EV_PID_HASHSIZE
3070		3805
3071	C<ev_child> watchers use a small hash table to distribute workload by	3806	C<ev_child> watchers use a small hash table to distribute workload by
3072	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3807	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
3082	two).	3817	two).
3083		3818
3084	=item EV_USE_4HEAP	3819	=item EV_USE_4HEAP
3085		3820
3086	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3821	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3087	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3822	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3088	to C<1>. The 4-heap uses more complicated (longer) code but has	3823	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3089	noticeably faster performance with many (thousands) of watchers.	3824	faster performance with many (thousands) of watchers.
3090		3825
3091	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3826	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3092	(disabled).	3827	(disabled).
3093		3828
3094	=item EV_HEAP_CACHE_AT	3829	=item EV_HEAP_CACHE_AT
3095		3830
3096	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3831	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3097	timer and periodics heap, libev can cache the timestamp (I<at>) within	3832	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3098	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3833	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3099	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3834	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3100	but avoids random read accesses on heap changes. This improves performance	3835	but avoids random read accesses on heap changes. This improves performance
3101	noticeably with with many (hundreds) of watchers.	3836	noticeably with many (hundreds) of watchers.
3102		3837
3103	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3838	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3104	(disabled).	3839	(disabled).
3105		3840
3106	=item EV_VERIFY	3841	=item EV_VERIFY
…		…
3112	called once per loop, which can slow down libev. If set to C<3>, then the	3847	called once per loop, which can slow down libev. If set to C<3>, then the
3113	verification code will be called very frequently, which will slow down	3848	verification code will be called very frequently, which will slow down
3114	libev considerably.	3849	libev considerably.
3115		3850
3116	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3851	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3117	C<0.>	3852	C<0>.
3118		3853
3119	=item EV_COMMON	3854	=item EV_COMMON
3120		3855
3121	By default, all watchers have a C<void *data> member. By redefining	3856	By default, all watchers have a C<void *data> member. By redefining
3122	this macro to a something else you can include more and other types of	3857	this macro to a something else you can include more and other types of
…		…
3139	and the way callbacks are invoked and set. Must expand to a struct member	3874	and the way callbacks are invoked and set. Must expand to a struct member
3140	definition and a statement, respectively. See the F<ev.h> header file for	3875	definition and a statement, respectively. See the F<ev.h> header file for
3141	their default definitions. One possible use for overriding these is to	3876	their default definitions. One possible use for overriding these is to
3142	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3877	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3143	method calls instead of plain function calls in C++.	3878	method calls instead of plain function calls in C++.
		3879
		3880	=back
3144		3881
3145	=head2 EXPORTED API SYMBOLS	3882	=head2 EXPORTED API SYMBOLS
3146		3883
3147	If you need to re-export the API (e.g. via a DLL) and you need a list of	3884	If you need to re-export the API (e.g. via a DLL) and you need a list of
3148	exported symbols, you can use the provided F<Symbol.*> files which list	3885	exported symbols, you can use the provided F<Symbol.*> files which list
…		…
3195	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3932	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3196		3933
3197	#include "ev_cpp.h"	3934	#include "ev_cpp.h"
3198	#include "ev.c"	3935	#include "ev.c"
3199		3936
		3937	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3200		3938
3201	=head1 THREADS AND COROUTINES	3939	=head2 THREADS AND COROUTINES
3202		3940
3203	=head2 THREADS	3941	=head3 THREADS
3204		3942
3205	Libev itself is completely thread-safe, but it uses no locking. This	3943	All libev functions are reentrant and thread-safe unless explicitly
		3944	documented otherwise, but libev implements no locking itself. This means
3206	means that you can use as many loops as you want in parallel, as long as	3945	that you can use as many loops as you want in parallel, as long as there
3207	only one thread ever calls into one libev function with the same loop	3946	are no concurrent calls into any libev function with the same loop
3208	parameter.	3947	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3948	of course): libev guarantees that different event loops share no data
		3949	structures that need any locking.
3209		3950
3210	Or put differently: calls with different loop parameters can be done in	3951	Or to put it differently: calls with different loop parameters can be done
3211	parallel from multiple threads, calls with the same loop parameter must be	3952	concurrently from multiple threads, calls with the same loop parameter
3212	done serially (but can be done from different threads, as long as only one	3953	must be done serially (but can be done from different threads, as long as
3213	thread ever is inside a call at any point in time, e.g. by using a mutex	3954	only one thread ever is inside a call at any point in time, e.g. by using
3214	per loop).	3955	a mutex per loop).
		3956
		3957	Specifically to support threads (and signal handlers), libev implements
		3958	so-called C<ev_async> watchers, which allow some limited form of
		3959	concurrency on the same event loop, namely waking it up "from the
		3960	outside".
3215		3961
3216	If you want to know which design (one loop, locking, or multiple loops	3962	If you want to know which design (one loop, locking, or multiple loops
3217	without or something else still) is best for your problem, then I cannot	3963	without or something else still) is best for your problem, then I cannot
3218	help you. I can give some generic advice however:	3964	help you, but here is some generic advice:
3219		3965
3220	=over 4	3966	=over 4
3221		3967
3222	=item * most applications have a main thread: use the default libev loop	3968	=item * most applications have a main thread: use the default libev loop
3223	in that thread, or create a separate thread running only the default loop.	3969	in that thread, or create a separate thread running only the default loop.
…		…
3235		3981
3236	Choosing a model is hard - look around, learn, know that usually you can do	3982	Choosing a model is hard - look around, learn, know that usually you can do
3237	better than you currently do :-)	3983	better than you currently do :-)
3238		3984
3239	=item * often you need to talk to some other thread which blocks in the	3985	=item * often you need to talk to some other thread which blocks in the
		3986	event loop.
		3987
3240	event loop - C<ev_async> watchers can be used to wake them up from other	3988	C<ev_async> watchers can be used to wake them up from other threads safely
3241	threads safely (or from signal contexts...).	3989	(or from signal contexts...).
		3990
		3991	An example use would be to communicate signals or other events that only
		3992	work in the default loop by registering the signal watcher with the
		3993	default loop and triggering an C<ev_async> watcher from the default loop
		3994	watcher callback into the event loop interested in the signal.
3242		3995
3243	=back	3996	=back
3244		3997
		3998	=head4 THREAD LOCKING EXAMPLE
		3999
		4000	Here is a fictitious example of how to run an event loop in a different
		4001	thread than where callbacks are being invoked and watchers are
		4002	created/added/removed.
		4003
		4004	For a real-world example, see the C<EV::Loop::Async> perl module,
		4005	which uses exactly this technique (which is suited for many high-level
		4006	languages).
		4007
		4008	The example uses a pthread mutex to protect the loop data, a condition
		4009	variable to wait for callback invocations, an async watcher to notify the
		4010	event loop thread and an unspecified mechanism to wake up the main thread.
		4011
		4012	First, you need to associate some data with the event loop:
		4013
		4014	typedef struct {
		4015	mutex_t lock; /* global loop lock */
		4016	ev_async async_w;
		4017	thread_t tid;
		4018	cond_t invoke_cv;
		4019	} userdata;
		4020
		4021	void prepare_loop (EV_P)
		4022	{
		4023	// for simplicity, we use a static userdata struct.
		4024	static userdata u;
		4025
		4026	ev_async_init (&u->async_w, async_cb);
		4027	ev_async_start (EV_A_ &u->async_w);
		4028
		4029	pthread_mutex_init (&u->lock, 0);
		4030	pthread_cond_init (&u->invoke_cv, 0);
		4031
		4032	// now associate this with the loop
		4033	ev_set_userdata (EV_A_ u);
		4034	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4035	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4036
		4037	// then create the thread running ev_loop
		4038	pthread_create (&u->tid, 0, l_run, EV_A);
		4039	}
		4040
		4041	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4042	solely to wake up the event loop so it takes notice of any new watchers
		4043	that might have been added:
		4044
		4045	static void
		4046	async_cb (EV_P_ ev_async *w, int revents)
		4047	{
		4048	// just used for the side effects
		4049	}
		4050
		4051	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4052	protecting the loop data, respectively.
		4053
		4054	static void
		4055	l_release (EV_P)
		4056	{
		4057	userdata *u = ev_userdata (EV_A);
		4058	pthread_mutex_unlock (&u->lock);
		4059	}
		4060
		4061	static void
		4062	l_acquire (EV_P)
		4063	{
		4064	userdata *u = ev_userdata (EV_A);
		4065	pthread_mutex_lock (&u->lock);
		4066	}
		4067
		4068	The event loop thread first acquires the mutex, and then jumps straight
		4069	into C<ev_loop>:
		4070
		4071	void *
		4072	l_run (void *thr_arg)
		4073	{
		4074	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4075
		4076	l_acquire (EV_A);
		4077	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4078	ev_loop (EV_A_ 0);
		4079	l_release (EV_A);
		4080
		4081	return 0;
		4082	}
		4083
		4084	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4085	signal the main thread via some unspecified mechanism (signals? pipe
		4086	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4087	have been called (in a while loop because a) spurious wakeups are possible
		4088	and b) skipping inter-thread-communication when there are no pending
		4089	watchers is very beneficial):
		4090
		4091	static void
		4092	l_invoke (EV_P)
		4093	{
		4094	userdata *u = ev_userdata (EV_A);
		4095
		4096	while (ev_pending_count (EV_A))
		4097	{
		4098	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4099	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4100	}
		4101	}
		4102
		4103	Now, whenever the main thread gets told to invoke pending watchers, it
		4104	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4105	thread to continue:
		4106
		4107	static void
		4108	real_invoke_pending (EV_P)
		4109	{
		4110	userdata *u = ev_userdata (EV_A);
		4111
		4112	pthread_mutex_lock (&u->lock);
		4113	ev_invoke_pending (EV_A);
		4114	pthread_cond_signal (&u->invoke_cv);
		4115	pthread_mutex_unlock (&u->lock);
		4116	}
		4117
		4118	Whenever you want to start/stop a watcher or do other modifications to an
		4119	event loop, you will now have to lock:
		4120
		4121	ev_timer timeout_watcher;
		4122	userdata *u = ev_userdata (EV_A);
		4123
		4124	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4125
		4126	pthread_mutex_lock (&u->lock);
		4127	ev_timer_start (EV_A_ &timeout_watcher);
		4128	ev_async_send (EV_A_ &u->async_w);
		4129	pthread_mutex_unlock (&u->lock);
		4130
		4131	Note that sending the C<ev_async> watcher is required because otherwise
		4132	an event loop currently blocking in the kernel will have no knowledge
		4133	about the newly added timer. By waking up the loop it will pick up any new
		4134	watchers in the next event loop iteration.
		4135
3245	=head2 COROUTINES	4136	=head3 COROUTINES
3246		4137
3247	Libev is much more accommodating to coroutines ("cooperative threads"):	4138	Libev is very accommodating to coroutines ("cooperative threads"):
3248	libev fully supports nesting calls to it's functions from different	4139	libev fully supports nesting calls to its functions from different
3249	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4140	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3250	different coroutines and switch freely between both coroutines running the	4141	different coroutines, and switch freely between both coroutines running
3251	loop, as long as you don't confuse yourself). The only exception is that	4142	the loop, as long as you don't confuse yourself). The only exception is
3252	you must not do this from C<ev_periodic> reschedule callbacks.	4143	that you must not do this from C<ev_periodic> reschedule callbacks.
3253		4144
3254	Care has been invested into making sure that libev does not keep local	4145	Care has been taken to ensure that libev does not keep local state inside
3255	state inside C<ev_loop>, and other calls do not usually allow coroutine	4146	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3256	switches.	4147	they do not call any callbacks.
3257		4148
		4149	=head2 COMPILER WARNINGS
3258		4150
3259	=head1 COMPLEXITIES	4151	Depending on your compiler and compiler settings, you might get no or a
		4152	lot of warnings when compiling libev code. Some people are apparently
		4153	scared by this.
3260		4154
3261	In this section the complexities of (many of) the algorithms used inside	4155	However, these are unavoidable for many reasons. For one, each compiler
3262	libev will be explained. For complexity discussions about backends see the	4156	has different warnings, and each user has different tastes regarding
3263	documentation for C<ev_default_init>.	4157	warning options. "Warn-free" code therefore cannot be a goal except when
		4158	targeting a specific compiler and compiler-version.
3264		4159
3265	All of the following are about amortised time: If an array needs to be	4160	Another reason is that some compiler warnings require elaborate
3266	extended, libev needs to realloc and move the whole array, but this	4161	workarounds, or other changes to the code that make it less clear and less
3267	happens asymptotically never with higher number of elements, so O(1) might	4162	maintainable.
3268	mean it might do a lengthy realloc operation in rare cases, but on average
3269	it is much faster and asymptotically approaches constant time.
3270		4163
3271	=over 4	4164	And of course, some compiler warnings are just plain stupid, or simply
		4165	wrong (because they don't actually warn about the condition their message
		4166	seems to warn about). For example, certain older gcc versions had some
		4167	warnings that resulted an extreme number of false positives. These have
		4168	been fixed, but some people still insist on making code warn-free with
		4169	such buggy versions.
3272		4170
3273	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	4171	While libev is written to generate as few warnings as possible,
		4172	"warn-free" code is not a goal, and it is recommended not to build libev
		4173	with any compiler warnings enabled unless you are prepared to cope with
		4174	them (e.g. by ignoring them). Remember that warnings are just that:
		4175	warnings, not errors, or proof of bugs.
3274		4176
3275	This means that, when you have a watcher that triggers in one hour and
3276	there are 100 watchers that would trigger before that then inserting will
3277	have to skip roughly seven (C<ld 100>) of these watchers.
3278		4177
3279	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	4178	=head2 VALGRIND
3280		4179
3281	That means that changing a timer costs less than removing/adding them	4180	Valgrind has a special section here because it is a popular tool that is
3282	as only the relative motion in the event queue has to be paid for.	4181	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3283		4182
3284	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	4183	If you think you found a bug (memory leak, uninitialised data access etc.)
		4184	in libev, then check twice: If valgrind reports something like:
3285		4185
3286	These just add the watcher into an array or at the head of a list.	4186	==2274== definitely lost: 0 bytes in 0 blocks.
		4187	==2274== possibly lost: 0 bytes in 0 blocks.
		4188	==2274== still reachable: 256 bytes in 1 blocks.
3287		4189
3288	=item Stopping check/prepare/idle/fork/async watchers: O(1)	4190	Then there is no memory leak, just as memory accounted to global variables
		4191	is not a memleak - the memory is still being referenced, and didn't leak.
3289		4192
3290	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	4193	Similarly, under some circumstances, valgrind might report kernel bugs
		4194	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		4195	although an acceptable workaround has been found here), or it might be
		4196	confused.
3291		4197
3292	These watchers are stored in lists then need to be walked to find the	4198	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3293	correct watcher to remove. The lists are usually short (you don't usually	4199	make it into some kind of religion.
3294	have many watchers waiting for the same fd or signal).
3295		4200
3296	=item Finding the next timer in each loop iteration: O(1)	4201	If you are unsure about something, feel free to contact the mailing list
		4202	with the full valgrind report and an explanation on why you think this
		4203	is a bug in libev (best check the archives, too :). However, don't be
		4204	annoyed when you get a brisk "this is no bug" answer and take the chance
		4205	of learning how to interpret valgrind properly.
3297		4206
3298	By virtue of using a binary or 4-heap, the next timer is always found at a	4207	If you need, for some reason, empty reports from valgrind for your project
3299	fixed position in the storage array.	4208	I suggest using suppression lists.
3300		4209
3301	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3302		4210
3303	A change means an I/O watcher gets started or stopped, which requires	4211	=head1 PORTABILITY NOTES
3304	libev to recalculate its status (and possibly tell the kernel, depending
3305	on backend and whether C<ev_io_set> was used).
3306		4212
3307	=item Activating one watcher (putting it into the pending state): O(1)
3308
3309	=item Priority handling: O(number_of_priorities)
3310
3311	Priorities are implemented by allocating some space for each
3312	priority. When doing priority-based operations, libev usually has to
3313	linearly search all the priorities, but starting/stopping and activating
3314	watchers becomes O(1) w.r.t. priority handling.
3315
3316	=item Sending an ev_async: O(1)
3317
3318	=item Processing ev_async_send: O(number_of_async_watchers)
3319
3320	=item Processing signals: O(max_signal_number)
3321
3322	Sending involves a system call I<iff> there were no other C<ev_async_send>
3323	calls in the current loop iteration. Checking for async and signal events
3324	involves iterating over all running async watchers or all signal numbers.
3325
3326	=back
3327
3328
3329	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4213	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3330		4214
3331	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4215	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3332	requires, and its I/O model is fundamentally incompatible with the POSIX	4216	requires, and its I/O model is fundamentally incompatible with the POSIX
3333	model. Libev still offers limited functionality on this platform in	4217	model. Libev still offers limited functionality on this platform in
3334	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4218	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3341	way (note also that glib is the slowest event library known to man).	4225	way (note also that glib is the slowest event library known to man).
3342		4226
3343	There is no supported compilation method available on windows except	4227	There is no supported compilation method available on windows except
3344	embedding it into other applications.	4228	embedding it into other applications.
3345		4229
		4230	Sensible signal handling is officially unsupported by Microsoft - libev
		4231	tries its best, but under most conditions, signals will simply not work.
		4232
3346	Not a libev limitation but worth mentioning: windows apparently doesn't	4233	Not a libev limitation but worth mentioning: windows apparently doesn't
3347	accept large writes: instead of resulting in a partial write, windows will	4234	accept large writes: instead of resulting in a partial write, windows will
3348	either accept everything or return C<ENOBUFS> if the buffer is too large,	4235	either accept everything or return C<ENOBUFS> if the buffer is too large,
3349	so make sure you only write small amounts into your sockets (less than a	4236	so make sure you only write small amounts into your sockets (less than a
3350	megabyte seems safe, but thsi apparently depends on the amount of memory	4237	megabyte seems safe, but this apparently depends on the amount of memory
3351	available).	4238	available).
3352		4239
3353	Due to the many, low, and arbitrary limits on the win32 platform and	4240	Due to the many, low, and arbitrary limits on the win32 platform and
3354	the abysmal performance of winsockets, using a large number of sockets	4241	the abysmal performance of winsockets, using a large number of sockets
3355	is not recommended (and not reasonable). If your program needs to use	4242	is not recommended (and not reasonable). If your program needs to use
3356	more than a hundred or so sockets, then likely it needs to use a totally	4243	more than a hundred or so sockets, then likely it needs to use a totally
3357	different implementation for windows, as libev offers the POSIX readiness	4244	different implementation for windows, as libev offers the POSIX readiness
3358	notification model, which cannot be implemented efficiently on windows	4245	notification model, which cannot be implemented efficiently on windows
3359	(Microsoft monopoly games).	4246	(due to Microsoft monopoly games).
3360		4247
3361	A typical way to use libev under windows is to embed it (see the embedding	4248	A typical way to use libev under windows is to embed it (see the embedding
3362	section for details) and use the following F<evwrap.h> header file instead	4249	section for details) and use the following F<evwrap.h> header file instead
3363	of F<ev.h>:	4250	of F<ev.h>:
3364		4251
…		…
3366	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	4253	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3367		4254
3368	#include "ev.h"	4255	#include "ev.h"
3369		4256
3370	And compile the following F<evwrap.c> file into your project (make sure	4257	And compile the following F<evwrap.c> file into your project (make sure
3371	you do I<not> compile the F<ev.c> or any other embedded soruce files!):	4258	you do I<not> compile the F<ev.c> or any other embedded source files!):
3372		4259
3373	#include "evwrap.h"	4260	#include "evwrap.h"
3374	#include "ev.c"	4261	#include "ev.c"
3375		4262
3376	=over 4	4263	=over 4
…		…
3400		4287
3401	Early versions of winsocket's select only supported waiting for a maximum	4288	Early versions of winsocket's select only supported waiting for a maximum
3402	of C<64> handles (probably owning to the fact that all windows kernels	4289	of C<64> handles (probably owning to the fact that all windows kernels
3403	can only wait for C<64> things at the same time internally; Microsoft	4290	can only wait for C<64> things at the same time internally; Microsoft
3404	recommends spawning a chain of threads and wait for 63 handles and the	4291	recommends spawning a chain of threads and wait for 63 handles and the
3405	previous thread in each. Great).	4292	previous thread in each. Sounds great!).
3406		4293
3407	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4294	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3408	to some high number (e.g. C<2048>) before compiling the winsocket select	4295	to some high number (e.g. C<2048>) before compiling the winsocket select
3409	call (which might be in libev or elsewhere, for example, perl does its own	4296	call (which might be in libev or elsewhere, for example, perl and many
3410	select emulation on windows).	4297	other interpreters do their own select emulation on windows).
3411		4298
3412	Another limit is the number of file descriptors in the Microsoft runtime	4299	Another limit is the number of file descriptors in the Microsoft runtime
3413	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4300	libraries, which by default is C<64> (there must be a hidden I<64>
3414	or something like this inside Microsoft). You can increase this by calling	4301	fetish or something like this inside Microsoft). You can increase this
3415	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4302	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3416	arbitrary limit), but is broken in many versions of the Microsoft runtime	4303	(another arbitrary limit), but is broken in many versions of the Microsoft
3417	libraries.
3418
3419	This might get you to about C<512> or C<2048> sockets (depending on	4304	runtime libraries. This might get you to about C<512> or C<2048> sockets
3420	windows version and/or the phase of the moon). To get more, you need to	4305	(depending on windows version and/or the phase of the moon). To get more,
3421	wrap all I/O functions and provide your own fd management, but the cost of	4306	you need to wrap all I/O functions and provide your own fd management, but
3422	calling select (O(n²)) will likely make this unworkable.	4307	the cost of calling select (O(n²)) will likely make this unworkable.
3423		4308
3424	=back	4309	=back
3425		4310
3426
3427	=head1 PORTABILITY REQUIREMENTS	4311	=head2 PORTABILITY REQUIREMENTS
3428		4312
3429	In addition to a working ISO-C implementation, libev relies on a few	4313	In addition to a working ISO-C implementation and of course the
3430	additional extensions:	4314	backend-specific APIs, libev relies on a few additional extensions:
3431		4315
3432	=over 4	4316	=over 4
3433		4317
3434	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	4318	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3435	calling conventions regardless of C<ev_watcher_type *>.	4319	calling conventions regardless of C<ev_watcher_type *>.
…		…
3441	calls them using an C<ev_watcher *> internally.	4325	calls them using an C<ev_watcher *> internally.
3442		4326
3443	=item C<sig_atomic_t volatile> must be thread-atomic as well	4327	=item C<sig_atomic_t volatile> must be thread-atomic as well
3444		4328
3445	The type C<sig_atomic_t volatile> (or whatever is defined as	4329	The type C<sig_atomic_t volatile> (or whatever is defined as
3446	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	4330	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3447	threads. This is not part of the specification for C<sig_atomic_t>, but is	4331	threads. This is not part of the specification for C<sig_atomic_t>, but is
3448	believed to be sufficiently portable.	4332	believed to be sufficiently portable.
3449		4333
3450	=item C<sigprocmask> must work in a threaded environment	4334	=item C<sigprocmask> must work in a threaded environment
3451		4335
…		…
3460	except the initial one, and run the default loop in the initial thread as	4344	except the initial one, and run the default loop in the initial thread as
3461	well.	4345	well.
3462		4346
3463	=item C<long> must be large enough for common memory allocation sizes	4347	=item C<long> must be large enough for common memory allocation sizes
3464		4348
3465	To improve portability and simplify using libev, libev uses C<long>	4349	To improve portability and simplify its API, libev uses C<long> internally
3466	internally instead of C<size_t> when allocating its data structures. On	4350	instead of C<size_t> when allocating its data structures. On non-POSIX
3467	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4351	systems (Microsoft...) this might be unexpectedly low, but is still at
3468	is still at least 31 bits everywhere, which is enough for hundreds of	4352	least 31 bits everywhere, which is enough for hundreds of millions of
3469	millions of watchers.	4353	watchers.
3470		4354
3471	=item C<double> must hold a time value in seconds with enough accuracy	4355	=item C<double> must hold a time value in seconds with enough accuracy
3472		4356
3473	The type C<double> is used to represent timestamps. It is required to	4357	The type C<double> is used to represent timestamps. It is required to
3474	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4358	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
3475	enough for at least into the year 4000. This requirement is fulfilled by	4359	enough for at least into the year 4000. This requirement is fulfilled by
3476	implementations implementing IEEE 754 (basically all existing ones).	4360	implementations implementing IEEE 754, which is basically all existing
		4361	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4362	2200.
3477		4363
3478	=back	4364	=back
3479		4365
3480	If you know of other additional requirements drop me a note.	4366	If you know of other additional requirements drop me a note.
3481		4367
3482		4368
3483	=head1 COMPILER WARNINGS	4369	=head1 ALGORITHMIC COMPLEXITIES
3484		4370
3485	Depending on your compiler and compiler settings, you might get no or a	4371	In this section the complexities of (many of) the algorithms used inside
3486	lot of warnings when compiling libev code. Some people are apparently	4372	libev will be documented. For complexity discussions about backends see
3487	scared by this.	4373	the documentation for C<ev_default_init>.
3488		4374
3489	However, these are unavoidable for many reasons. For one, each compiler	4375	All of the following are about amortised time: If an array needs to be
3490	has different warnings, and each user has different tastes regarding	4376	extended, libev needs to realloc and move the whole array, but this
3491	warning options. "Warn-free" code therefore cannot be a goal except when	4377	happens asymptotically rarer with higher number of elements, so O(1) might
3492	targeting a specific compiler and compiler-version.	4378	mean that libev does a lengthy realloc operation in rare cases, but on
		4379	average it is much faster and asymptotically approaches constant time.
3493		4380
3494	Another reason is that some compiler warnings require elaborate	4381	=over 4
3495	workarounds, or other changes to the code that make it less clear and less
3496	maintainable.
3497		4382
3498	And of course, some compiler warnings are just plain stupid, or simply	4383	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3499	wrong (because they don't actually warn about the condition their message
3500	seems to warn about).
3501		4384
3502	While libev is written to generate as few warnings as possible,	4385	This means that, when you have a watcher that triggers in one hour and
3503	"warn-free" code is not a goal, and it is recommended not to build libev	4386	there are 100 watchers that would trigger before that, then inserting will
3504	with any compiler warnings enabled unless you are prepared to cope with	4387	have to skip roughly seven (C<ld 100>) of these watchers.
3505	them (e.g. by ignoring them). Remember that warnings are just that:
3506	warnings, not errors, or proof of bugs.
3507		4388
		4389	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3508		4390
3509	=head1 VALGRIND	4391	That means that changing a timer costs less than removing/adding them,
		4392	as only the relative motion in the event queue has to be paid for.
3510		4393
3511	Valgrind has a special section here because it is a popular tool that is	4394	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3512	highly useful, but valgrind reports are very hard to interpret.
3513		4395
3514	If you think you found a bug (memory leak, uninitialised data access etc.)	4396	These just add the watcher into an array or at the head of a list.
3515	in libev, then check twice: If valgrind reports something like:
3516		4397
3517	==2274== definitely lost: 0 bytes in 0 blocks.	4398	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3518	==2274== possibly lost: 0 bytes in 0 blocks.
3519	==2274== still reachable: 256 bytes in 1 blocks.
3520		4399
3521	Then there is no memory leak. Similarly, under some circumstances,	4400	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3522	valgrind might report kernel bugs as if it were a bug in libev, or it
3523	might be confused (it is a very good tool, but only a tool).
3524		4401
3525	If you are unsure about something, feel free to contact the mailing list	4402	These watchers are stored in lists, so they need to be walked to find the
3526	with the full valgrind report and an explanation on why you think this is	4403	correct watcher to remove. The lists are usually short (you don't usually
3527	a bug in libev. However, don't be annoyed when you get a brisk "this is	4404	have many watchers waiting for the same fd or signal: one is typical, two
3528	no bug" answer and take the chance of learning how to interpret valgrind	4405	is rare).
3529	properly.
3530		4406
3531	If you need, for some reason, empty reports from valgrind for your project	4407	=item Finding the next timer in each loop iteration: O(1)
3532	I suggest using suppression lists.
3533		4408
		4409	By virtue of using a binary or 4-heap, the next timer is always found at a
		4410	fixed position in the storage array.
		4411
		4412	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4413
		4414	A change means an I/O watcher gets started or stopped, which requires
		4415	libev to recalculate its status (and possibly tell the kernel, depending
		4416	on backend and whether C<ev_io_set> was used).
		4417
		4418	=item Activating one watcher (putting it into the pending state): O(1)
		4419
		4420	=item Priority handling: O(number_of_priorities)
		4421
		4422	Priorities are implemented by allocating some space for each
		4423	priority. When doing priority-based operations, libev usually has to
		4424	linearly search all the priorities, but starting/stopping and activating
		4425	watchers becomes O(1) with respect to priority handling.
		4426
		4427	=item Sending an ev_async: O(1)
		4428
		4429	=item Processing ev_async_send: O(number_of_async_watchers)
		4430
		4431	=item Processing signals: O(max_signal_number)
		4432
		4433	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4434	calls in the current loop iteration. Checking for async and signal events
		4435	involves iterating over all running async watchers or all signal numbers.
		4436
		4437	=back
		4438
		4439
		4440	=head1 GLOSSARY
		4441
		4442	=over 4
		4443
		4444	=item active
		4445
		4446	A watcher is active as long as it has been started (has been attached to
		4447	an event loop) but not yet stopped (disassociated from the event loop).
		4448
		4449	=item application
		4450
		4451	In this document, an application is whatever is using libev.
		4452
		4453	=item callback
		4454
		4455	The address of a function that is called when some event has been
		4456	detected. Callbacks are being passed the event loop, the watcher that
		4457	received the event, and the actual event bitset.
		4458
		4459	=item callback invocation
		4460
		4461	The act of calling the callback associated with a watcher.
		4462
		4463	=item event
		4464
		4465	A change of state of some external event, such as data now being available
		4466	for reading on a file descriptor, time having passed or simply not having
		4467	any other events happening anymore.
		4468
		4469	In libev, events are represented as single bits (such as C<EV_READ> or
		4470	C<EV_TIMEOUT>).
		4471
		4472	=item event library
		4473
		4474	A software package implementing an event model and loop.
		4475
		4476	=item event loop
		4477
		4478	An entity that handles and processes external events and converts them
		4479	into callback invocations.
		4480
		4481	=item event model
		4482
		4483	The model used to describe how an event loop handles and processes
		4484	watchers and events.
		4485
		4486	=item pending
		4487
		4488	A watcher is pending as soon as the corresponding event has been detected,
		4489	and stops being pending as soon as the watcher will be invoked or its
		4490	pending status is explicitly cleared by the application.
		4491
		4492	A watcher can be pending, but not active. Stopping a watcher also clears
		4493	its pending status.
		4494
		4495	=item real time
		4496
		4497	The physical time that is observed. It is apparently strictly monotonic :)
		4498
		4499	=item wall-clock time
		4500
		4501	The time and date as shown on clocks. Unlike real time, it can actually
		4502	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4503	clock.
		4504
		4505	=item watcher
		4506
		4507	A data structure that describes interest in certain events. Watchers need
		4508	to be started (attached to an event loop) before they can receive events.
		4509
		4510	=item watcher invocation
		4511
		4512	The act of calling the callback associated with a watcher.
		4513
		4514	=back
3534		4515
3535	=head1 AUTHOR	4516	=head1 AUTHOR
3536		4517
3537	Marc Lehmann <libev@schmorp.de>.	4518	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3538		4519

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