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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
…		…
573	received events and started processing them. This timestamp does not	634	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	635	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	636	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).	637	event occurring (or more correctly, libev finding out about it).
577		638
		639	=item ev_now_update (loop)
		640
		641	Establishes the current time by querying the kernel, updating the time
		642	returned by C<ev_now ()> in the progress. This is a costly operation and
		643	is usually done automatically within C<ev_loop ()>.
		644
		645	This function is rarely useful, but when some event callback runs for a
		646	very long time without entering the event loop, updating libev's idea of
		647	the current time is a good idea.
		648
		649	See also L<The special problem of time updates> in the C<ev_timer> section.
		650
		651	=item ev_suspend (loop)
		652
		653	=item ev_resume (loop)
		654
		655	These two functions suspend and resume a loop, for use when the loop is
		656	not used for a while and timeouts should not be processed.
		657
		658	A typical use case would be an interactive program such as a game: When
		659	the user presses C<^Z> to suspend the game and resumes it an hour later it
		660	would be best to handle timeouts as if no time had actually passed while
		661	the program was suspended. This can be achieved by calling C<ev_suspend>
		662	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		663	C<ev_resume> directly afterwards to resume timer processing.
		664
		665	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		666	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		667	will be rescheduled (that is, they will lose any events that would have
		668	occured while suspended).
		669
		670	After calling C<ev_suspend> you B<must not> call I<any> function on the
		671	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		672	without a previous call to C<ev_suspend>.
		673
		674	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		675	event loop time (see C<ev_now_update>).
		676
578	=item ev_loop (loop, int flags)	677	=item ev_loop (loop, int flags)
579		678
580	Finally, this is it, the event handler. This function usually is called	679	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	680	after you initialised all your watchers and you want to start handling
582	events.	681	events.
…		…
584	If the flags argument is specified as C<0>, it will not return until	683	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.	684	either no event watchers are active anymore or C<ev_unloop> was called.
586		685
587	Please note that an explicit C<ev_unloop> is usually better than	686	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	687	relying on all watchers to be stopped when deciding when a program has
589	finished (especially in interactive programs), but having a program that	688	finished (especially in interactive programs), but having a program
590	automatically loops as long as it has to and no longer by virtue of	689	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.	690	of relying on its watchers stopping correctly, that is truly a thing of
		691	beauty.
592		692
593	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	693	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	694	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.	695	process in case there are no events and will return after one iteration of
		696	the loop.
596		697
597	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	698	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	699	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	700	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	701	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	702	user-registered callback will be called), and will return after one
		703	iteration of the loop.
		704
		705	This is useful if you are waiting for some external event in conjunction
		706	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	707	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.	708	usually a better approach for this kind of thing.
604		709
605	Here are the gory details of what C<ev_loop> does:	710	Here are the gory details of what C<ev_loop> does:
606		711
607	- Before the first iteration, call any pending watchers.	712	- Before the first iteration, call any pending watchers.
608	* If EVFLAG_FORKCHECK was used, check for a fork.	713	* If EVFLAG_FORKCHECK was used, check for a fork.
609	- If a fork was detected, queue and call all fork watchers.	714	- If a fork was detected (by any means), queue and call all fork watchers.
610	- Queue and call all prepare watchers.	715	- Queue and call all prepare watchers.
611	- If we have been forked, recreate the kernel state.	716	- If we have been forked, detach and recreate the kernel state
		717	as to not disturb the other process.
612	- Update the kernel state with all outstanding changes.	718	- Update the kernel state with all outstanding changes.
613	- Update the "event loop time".	719	- Update the "event loop time" (ev_now ()).
614	- Calculate for how long to sleep or block, if at all	720	- Calculate for how long to sleep or block, if at all
615	(active idle watchers, EVLOOP_NONBLOCK or not having	721	(active idle watchers, EVLOOP_NONBLOCK or not having
616	any active watchers at all will result in not sleeping).	722	any active watchers at all will result in not sleeping).
617	- Sleep if the I/O and timer collect interval say so.	723	- Sleep if the I/O and timer collect interval say so.
618	- Block the process, waiting for any events.	724	- Block the process, waiting for any events.
619	- Queue all outstanding I/O (fd) events.	725	- Queue all outstanding I/O (fd) events.
620	- Update the "event loop time" and do time jump handling.	726	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
621	- Queue all outstanding timers.	727	- Queue all expired timers.
622	- Queue all outstanding periodics.	728	- Queue all expired periodics.
623	- If no events are pending now, queue all idle watchers.	729	- Unless any events are pending now, queue all idle watchers.
624	- Queue all check watchers.	730	- Queue all check watchers.
625	- Call all queued watchers in reverse order (i.e. check watchers first).	731	- Call all queued watchers in reverse order (i.e. check watchers first).
626	Signals and child watchers are implemented as I/O watchers, and will	732	Signals and child watchers are implemented as I/O watchers, and will
627	be handled here by queueing them when their watcher gets executed.	733	be handled here by queueing them when their watcher gets executed.
628	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	734	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
633	anymore.	739	anymore.
634		740
635	... queue jobs here, make sure they register event watchers as long	741	... queue jobs here, make sure they register event watchers as long
636	... as they still have work to do (even an idle watcher will do..)	742	... as they still have work to do (even an idle watcher will do..)
637	ev_loop (my_loop, 0);	743	ev_loop (my_loop, 0);
638	... jobs done. yeah!	744	... jobs done or somebody called unloop. yeah!
639		745
640	=item ev_unloop (loop, how)	746	=item ev_unloop (loop, how)
641		747
642	Can be used to make a call to C<ev_loop> return early (but only after it	748	Can be used to make a call to C<ev_loop> return early (but only after it
643	has processed all outstanding events). The C<how> argument must be either	749	has processed all outstanding events). The C<how> argument must be either
644	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	750	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
645	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	751	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
646		752
647	This "unloop state" will be cleared when entering C<ev_loop> again.	753	This "unloop state" will be cleared when entering C<ev_loop> again.
648		754
		755	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		756
649	=item ev_ref (loop)	757	=item ev_ref (loop)
650		758
651	=item ev_unref (loop)	759	=item ev_unref (loop)
652		760
653	Ref/unref can be used to add or remove a reference count on the event	761	Ref/unref can be used to add or remove a reference count on the event
654	loop: Every watcher keeps one reference, and as long as the reference	762	loop: Every watcher keeps one reference, and as long as the reference
655	count is nonzero, C<ev_loop> will not return on its own. If you have	763	count is nonzero, C<ev_loop> will not return on its own.
		764
656	a watcher you never unregister that should not keep C<ev_loop> from	765	If you have a watcher you never unregister that should not keep C<ev_loop>
657	returning, ev_unref() after starting, and ev_ref() before stopping it. For	766	from returning, call ev_unref() after starting, and ev_ref() before
		767	stopping it.
		768
658	example, libev itself uses this for its internal signal pipe: It is not	769	As an example, libev itself uses this for its internal signal pipe: It
659	visible to the libev user and should not keep C<ev_loop> from exiting if	770	is not visible to the libev user and should not keep C<ev_loop> from
660	no event watchers registered by it are active. It is also an excellent	771	exiting if no event watchers registered by it are active. It is also an
661	way to do this for generic recurring timers or from within third-party	772	excellent way to do this for generic recurring timers or from within
662	libraries. Just remember to I<unref after start> and I<ref before stop>	773	third-party libraries. Just remember to I<unref after start> and I<ref
663	(but only if the watcher wasn't active before, or was active before,	774	before stop> (but only if the watcher wasn't active before, or was active
664	respectively).	775	before, respectively. Note also that libev might stop watchers itself
		776	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		777	in the callback).
665		778
666	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	779	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
667	running when nothing else is active.	780	running when nothing else is active.
668		781
669	struct ev_signal exitsig;	782	ev_signal exitsig;
670	ev_signal_init (&exitsig, sig_cb, SIGINT);	783	ev_signal_init (&exitsig, sig_cb, SIGINT);
671	ev_signal_start (loop, &exitsig);	784	ev_signal_start (loop, &exitsig);
672	evf_unref (loop);	785	evf_unref (loop);
673		786
674	Example: For some weird reason, unregister the above signal handler again.	787	Example: For some weird reason, unregister the above signal handler again.
…		…
679	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	792	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
680		793
681	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	794	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
682		795
683	These advanced functions influence the time that libev will spend waiting	796	These advanced functions influence the time that libev will spend waiting
684	for events. Both are by default C<0>, meaning that libev will try to	797	for events. Both time intervals are by default C<0>, meaning that libev
685	invoke timer/periodic callbacks and I/O callbacks with minimum latency.	798	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		799	latency.
686		800
687	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	801	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
688	allows libev to delay invocation of I/O and timer/periodic callbacks to	802	allows libev to delay invocation of I/O and timer/periodic callbacks
689	increase efficiency of loop iterations.	803	to increase efficiency of loop iterations (or to increase power-saving
		804	opportunities).
690		805
691	The background is that sometimes your program runs just fast enough to	806	The idea is that sometimes your program runs just fast enough to handle
692	handle one (or very few) event(s) per loop iteration. While this makes	807	one (or very few) event(s) per loop iteration. While this makes the
693	the program responsive, it also wastes a lot of CPU time to poll for new	808	program responsive, it also wastes a lot of CPU time to poll for new
694	events, especially with backends like C<select ()> which have a high	809	events, especially with backends like C<select ()> which have a high
695	overhead for the actual polling but can deliver many events at once.	810	overhead for the actual polling but can deliver many events at once.
696		811
697	By setting a higher I<io collect interval> you allow libev to spend more	812	By setting a higher I<io collect interval> you allow libev to spend more
698	time collecting I/O events, so you can handle more events per iteration,	813	time collecting I/O events, so you can handle more events per iteration,
…		…
700	C<ev_timer>) will be not affected. Setting this to a non-null value will	815	C<ev_timer>) will be not affected. Setting this to a non-null value will
701	introduce an additional C<ev_sleep ()> call into most loop iterations.	816	introduce an additional C<ev_sleep ()> call into most loop iterations.
702		817
703	Likewise, by setting a higher I<timeout collect interval> you allow libev	818	Likewise, by setting a higher I<timeout collect interval> you allow libev
704	to spend more time collecting timeouts, at the expense of increased	819	to spend more time collecting timeouts, at the expense of increased
705	latency (the watcher callback will be called later). C<ev_io> watchers	820	latency/jitter/inexactness (the watcher callback will be called
706	will not be affected. Setting this to a non-null value will not introduce	821	later). C<ev_io> watchers will not be affected. Setting this to a non-null
707	any overhead in libev.	822	value will not introduce any overhead in libev.
708		823
709	Many (busy) programs can usually benefit by setting the I/O collect	824	Many (busy) programs can usually benefit by setting the I/O collect
710	interval to a value near C<0.1> or so, which is often enough for	825	interval to a value near C<0.1> or so, which is often enough for
711	interactive servers (of course not for games), likewise for timeouts. It	826	interactive servers (of course not for games), likewise for timeouts. It
712	usually doesn't make much sense to set it to a lower value than C<0.01>,	827	usually doesn't make much sense to set it to a lower value than C<0.01>,
713	as this approaches the timing granularity of most systems.	828	as this approaches the timing granularity of most systems.
714		829
		830	Setting the I<timeout collect interval> can improve the opportunity for
		831	saving power, as the program will "bundle" timer callback invocations that
		832	are "near" in time together, by delaying some, thus reducing the number of
		833	times the process sleeps and wakes up again. Another useful technique to
		834	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		835	they fire on, say, one-second boundaries only.
		836
715	=item ev_loop_verify (loop)	837	=item ev_loop_verify (loop)
716		838
717	This function only does something when C<EV_VERIFY> support has been	839	This function only does something when C<EV_VERIFY> support has been
718	compiled in. It tries to go through all internal structures and checks	840	compiled in, which is the default for non-minimal builds. It tries to go
719	them for validity. If anything is found to be inconsistent, it will print	841	through all internal structures and checks them for validity. If anything
720	an error message to standard error and call C<abort ()>.	842	is found to be inconsistent, it will print an error message to standard
		843	error and call C<abort ()>.
721		844
722	This can be used to catch bugs inside libev itself: under normal	845	This can be used to catch bugs inside libev itself: under normal
723	circumstances, this function will never abort as of course libev keeps its	846	circumstances, this function will never abort as of course libev keeps its
724	data structures consistent.	847	data structures consistent.
725		848
726	=back	849	=back
727		850
728		851
729	=head1 ANATOMY OF A WATCHER	852	=head1 ANATOMY OF A WATCHER
730		853
		854	In the following description, uppercase C<TYPE> in names stands for the
		855	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		856	watchers and C<ev_io_start> for I/O watchers.
		857
731	A watcher is a structure that you create and register to record your	858	A watcher is a structure that you create and register to record your
732	interest in some event. For instance, if you want to wait for STDIN to	859	interest in some event. For instance, if you want to wait for STDIN to
733	become readable, you would create an C<ev_io> watcher for that:	860	become readable, you would create an C<ev_io> watcher for that:
734		861
735	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	862	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
736	{	863	{
737	ev_io_stop (w);	864	ev_io_stop (w);
738	ev_unloop (loop, EVUNLOOP_ALL);	865	ev_unloop (loop, EVUNLOOP_ALL);
739	}	866	}
740		867
741	struct ev_loop *loop = ev_default_loop (0);	868	struct ev_loop *loop = ev_default_loop (0);
		869
742	struct ev_io stdin_watcher;	870	ev_io stdin_watcher;
		871
743	ev_init (&stdin_watcher, my_cb);	872	ev_init (&stdin_watcher, my_cb);
744	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	873	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
745	ev_io_start (loop, &stdin_watcher);	874	ev_io_start (loop, &stdin_watcher);
		875
746	ev_loop (loop, 0);	876	ev_loop (loop, 0);
747		877
748	As you can see, you are responsible for allocating the memory for your	878	As you can see, you are responsible for allocating the memory for your
749	watcher structures (and it is usually a bad idea to do this on the stack,	879	watcher structures (and it is I<usually> a bad idea to do this on the
750	although this can sometimes be quite valid).	880	stack).
		881
		882	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		883	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
751		884
752	Each watcher structure must be initialised by a call to C<ev_init	885	Each watcher structure must be initialised by a call to C<ev_init
753	(watcher *, callback)>, which expects a callback to be provided. This	886	(watcher *, callback)>, which expects a callback to be provided. This
754	callback gets invoked each time the event occurs (or, in the case of I/O	887	callback gets invoked each time the event occurs (or, in the case of I/O
755	watchers, each time the event loop detects that the file descriptor given	888	watchers, each time the event loop detects that the file descriptor given
756	is readable and/or writable).	889	is readable and/or writable).
757		890
758	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	891	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
759	with arguments specific to this watcher type. There is also a macro	892	macro to configure it, with arguments specific to the watcher type. There
760	to combine initialisation and setting in one call: C<< ev_<type>_init	893	is also a macro to combine initialisation and setting in one call: C<<
761	(watcher *, callback, ...) >>.	894	ev_TYPE_init (watcher *, callback, ...) >>.
762		895
763	To make the watcher actually watch out for events, you have to start it	896	To make the watcher actually watch out for events, you have to start it
764	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	897	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
765	*) >>), and you can stop watching for events at any time by calling the	898	*) >>), and you can stop watching for events at any time by calling the
766	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	899	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
767		900
768	As long as your watcher is active (has been started but not stopped) you	901	As long as your watcher is active (has been started but not stopped) you
769	must not touch the values stored in it. Most specifically you must never	902	must not touch the values stored in it. Most specifically you must never
770	reinitialise it or call its C<set> macro.	903	reinitialise it or call its C<ev_TYPE_set> macro.
771		904
772	Each and every callback receives the event loop pointer as first, the	905	Each and every callback receives the event loop pointer as first, the
773	registered watcher structure as second, and a bitset of received events as	906	registered watcher structure as second, and a bitset of received events as
774	third argument.	907	third argument.
775		908
…		…
833		966
834	=item C<EV_ASYNC>	967	=item C<EV_ASYNC>
835		968
836	The given async watcher has been asynchronously notified (see C<ev_async>).	969	The given async watcher has been asynchronously notified (see C<ev_async>).
837		970
		971	=item C<EV_CUSTOM>
		972
		973	Not ever sent (or otherwise used) by libev itself, but can be freely used
		974	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		975
838	=item C<EV_ERROR>	976	=item C<EV_ERROR>
839		977
840	An unspecified error has occurred, the watcher has been stopped. This might	978	An unspecified error has occurred, the watcher has been stopped. This might
841	happen because the watcher could not be properly started because libev	979	happen because the watcher could not be properly started because libev
842	ran out of memory, a file descriptor was found to be closed or any other	980	ran out of memory, a file descriptor was found to be closed or any other
		981	problem. Libev considers these application bugs.
		982
843	problem. You best act on it by reporting the problem and somehow coping	983	You best act on it by reporting the problem and somehow coping with the
844	with the watcher being stopped.	984	watcher being stopped. Note that well-written programs should not receive
		985	an error ever, so when your watcher receives it, this usually indicates a
		986	bug in your program.
845		987
846	Libev will usually signal a few "dummy" events together with an error,	988	Libev will usually signal a few "dummy" events together with an error, for
847	for example it might indicate that a fd is readable or writable, and if	989	example it might indicate that a fd is readable or writable, and if your
848	your callbacks is well-written it can just attempt the operation and cope	990	callbacks is well-written it can just attempt the operation and cope with
849	with the error from read() or write(). This will not work in multi-threaded	991	the error from read() or write(). This will not work in multi-threaded
850	programs, though, so beware.	992	programs, though, as the fd could already be closed and reused for another
		993	thing, so beware.
851		994
852	=back	995	=back
853		996
854	=head2 GENERIC WATCHER FUNCTIONS	997	=head2 GENERIC WATCHER FUNCTIONS
855
856	In the following description, C<TYPE> stands for the watcher type,
857	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
858		998
859	=over 4	999	=over 4
860		1000
861	=item C<ev_init> (ev_TYPE *watcher, callback)	1001	=item C<ev_init> (ev_TYPE *watcher, callback)
862		1002
…		…
868	which rolls both calls into one.	1008	which rolls both calls into one.
869		1009
870	You can reinitialise a watcher at any time as long as it has been stopped	1010	You can reinitialise a watcher at any time as long as it has been stopped
871	(or never started) and there are no pending events outstanding.	1011	(or never started) and there are no pending events outstanding.
872		1012
873	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1013	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
874	int revents)>.	1014	int revents)>.
		1015
		1016	Example: Initialise an C<ev_io> watcher in two steps.
		1017
		1018	ev_io w;
		1019	ev_init (&w, my_cb);
		1020	ev_io_set (&w, STDIN_FILENO, EV_READ);
875		1021
876	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1022	=item C<ev_TYPE_set> (ev_TYPE *, [args])
877		1023
878	This macro initialises the type-specific parts of a watcher. You need to	1024	This macro initialises the type-specific parts of a watcher. You need to
879	call C<ev_init> at least once before you call this macro, but you can	1025	call C<ev_init> at least once before you call this macro, but you can
…		…
882	difference to the C<ev_init> macro).	1028	difference to the C<ev_init> macro).
883		1029
884	Although some watcher types do not have type-specific arguments	1030	Although some watcher types do not have type-specific arguments
885	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	1031	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
886		1032
		1033	See C<ev_init>, above, for an example.
		1034
887	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1035	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
888		1036
889	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1037	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
890	calls into a single call. This is the most convenient method to initialise	1038	calls into a single call. This is the most convenient method to initialise
891	a watcher. The same limitations apply, of course.	1039	a watcher. The same limitations apply, of course.
892		1040
		1041	Example: Initialise and set an C<ev_io> watcher in one step.
		1042
		1043	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1044
893	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1045	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
894		1046
895	Starts (activates) the given watcher. Only active watchers will receive	1047	Starts (activates) the given watcher. Only active watchers will receive
896	events. If the watcher is already active nothing will happen.	1048	events. If the watcher is already active nothing will happen.
897		1049
		1050	Example: Start the C<ev_io> watcher that is being abused as example in this
		1051	whole section.
		1052
		1053	ev_io_start (EV_DEFAULT_UC, &w);
		1054
898	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1055	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
899		1056
900	Stops the given watcher again (if active) and clears the pending	1057	Stops the given watcher if active, and clears the pending status (whether
		1058	the watcher was active or not).
		1059
901	status. It is possible that stopped watchers are pending (for example,	1060	It is possible that stopped watchers are pending - for example,
902	non-repeating timers are being stopped when they become pending), but	1061	non-repeating timers are being stopped when they become pending - but
903	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1062	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
904	you want to free or reuse the memory used by the watcher it is therefore a	1063	pending. If you want to free or reuse the memory used by the watcher it is
905	good idea to always call its C<ev_TYPE_stop> function.	1064	therefore a good idea to always call its C<ev_TYPE_stop> function.
906		1065
907	=item bool ev_is_active (ev_TYPE *watcher)	1066	=item bool ev_is_active (ev_TYPE *watcher)
908		1067
909	Returns a true value iff the watcher is active (i.e. it has been started	1068	Returns a true value iff the watcher is active (i.e. it has been started
910	and not yet been stopped). As long as a watcher is active you must not modify	1069	and not yet been stopped). As long as a watcher is active you must not modify
…		…
936	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1095	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
937	(default: C<-2>). Pending watchers with higher priority will be invoked	1096	(default: C<-2>). Pending watchers with higher priority will be invoked
938	before watchers with lower priority, but priority will not keep watchers	1097	before watchers with lower priority, but priority will not keep watchers
939	from being executed (except for C<ev_idle> watchers).	1098	from being executed (except for C<ev_idle> watchers).
940		1099
941	This means that priorities are I<only> used for ordering callback
942	invocation after new events have been received. This is useful, for
943	example, to reduce latency after idling, or more often, to bind two
944	watchers on the same event and make sure one is called first.
945
946	If you need to suppress invocation when higher priority events are pending	1100	If you need to suppress invocation when higher priority events are pending
947	you need to look at C<ev_idle> watchers, which provide this functionality.	1101	you need to look at C<ev_idle> watchers, which provide this functionality.
948		1102
949	You I<must not> change the priority of a watcher as long as it is active or	1103	You I<must not> change the priority of a watcher as long as it is active or
950	pending.	1104	pending.
951		1105
		1106	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1107	fine, as long as you do not mind that the priority value you query might
		1108	or might not have been clamped to the valid range.
		1109
952	The default priority used by watchers when no priority has been set is	1110	The default priority used by watchers when no priority has been set is
953	always C<0>, which is supposed to not be too high and not be too low :).	1111	always C<0>, which is supposed to not be too high and not be too low :).
954		1112
955	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1113	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
956	fine, as long as you do not mind that the priority value you query might	1114	priorities.
957	or might not have been adjusted to be within valid range.
958		1115
959	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1116	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
960		1117
961	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1118	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
962	C<loop> nor C<revents> need to be valid as long as the watcher callback	1119	C<loop> nor C<revents> need to be valid as long as the watcher callback
963	can deal with that fact.	1120	can deal with that fact, as both are simply passed through to the
		1121	callback.
964		1122
965	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1123	=item int ev_clear_pending (loop, ev_TYPE *watcher)
966		1124
967	If the watcher is pending, this function returns clears its pending status	1125	If the watcher is pending, this function clears its pending status and
968	and returns its C<revents> bitset (as if its callback was invoked). If the	1126	returns its C<revents> bitset (as if its callback was invoked). If the
969	watcher isn't pending it does nothing and returns C<0>.	1127	watcher isn't pending it does nothing and returns C<0>.
970		1128
		1129	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1130	callback to be invoked, which can be accomplished with this function.
		1131
971	=back	1132	=back
972		1133
973		1134
974	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1135	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
975		1136
976	Each watcher has, by default, a member C<void *data> that you can change	1137	Each watcher has, by default, a member C<void *data> that you can change
977	and read at any time, libev will completely ignore it. This can be used	1138	and read at any time: libev will completely ignore it. This can be used
978	to associate arbitrary data with your watcher. If you need more data and	1139	to associate arbitrary data with your watcher. If you need more data and
979	don't want to allocate memory and store a pointer to it in that data	1140	don't want to allocate memory and store a pointer to it in that data
980	member, you can also "subclass" the watcher type and provide your own	1141	member, you can also "subclass" the watcher type and provide your own
981	data:	1142	data:
982		1143
983	struct my_io	1144	struct my_io
984	{	1145	{
985	struct ev_io io;	1146	ev_io io;
986	int otherfd;	1147	int otherfd;
987	void *somedata;	1148	void *somedata;
988	struct whatever *mostinteresting;	1149	struct whatever *mostinteresting;
989	}	1150	};
		1151
		1152	...
		1153	struct my_io w;
		1154	ev_io_init (&w.io, my_cb, fd, EV_READ);
990		1155
991	And since your callback will be called with a pointer to the watcher, you	1156	And since your callback will be called with a pointer to the watcher, you
992	can cast it back to your own type:	1157	can cast it back to your own type:
993		1158
994	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1159	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
995	{	1160	{
996	struct my_io *w = (struct my_io *)w_;	1161	struct my_io *w = (struct my_io *)w_;
997	...	1162	...
998	}	1163	}
999		1164
1000	More interesting and less C-conformant ways of casting your callback type	1165	More interesting and less C-conformant ways of casting your callback type
1001	instead have been omitted.	1166	instead have been omitted.
1002		1167
1003	Another common scenario is having some data structure with multiple	1168	Another common scenario is to use some data structure with multiple
1004	watchers:	1169	embedded watchers:
1005		1170
1006	struct my_biggy	1171	struct my_biggy
1007	{	1172	{
1008	int some_data;	1173	int some_data;
1009	ev_timer t1;	1174	ev_timer t1;
1010	ev_timer t2;	1175	ev_timer t2;
1011	}	1176	}
1012		1177
1013	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1178	In this case getting the pointer to C<my_biggy> is a bit more
1014	you need to use C<offsetof>:	1179	complicated: Either you store the address of your C<my_biggy> struct
		1180	in the C<data> member of the watcher (for woozies), or you need to use
		1181	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1182	programmers):
1015		1183
1016	#include <stddef.h>	1184	#include <stddef.h>
1017		1185
1018	static void	1186	static void
1019	t1_cb (EV_P_ struct ev_timer *w, int revents)	1187	t1_cb (EV_P_ ev_timer *w, int revents)
1020	{	1188	{
1021	struct my_biggy big = (struct my_biggy *	1189	struct my_biggy big = (struct my_biggy *)
1022	(((char *)w) - offsetof (struct my_biggy, t1));	1190	(((char *)w) - offsetof (struct my_biggy, t1));
1023	}	1191	}
1024		1192
1025	static void	1193	static void
1026	t2_cb (EV_P_ struct ev_timer *w, int revents)	1194	t2_cb (EV_P_ ev_timer *w, int revents)
1027	{	1195	{
1028	struct my_biggy big = (struct my_biggy *	1196	struct my_biggy big = (struct my_biggy *)
1029	(((char *)w) - offsetof (struct my_biggy, t2));	1197	(((char *)w) - offsetof (struct my_biggy, t2));
1030	}	1198	}
		1199
		1200	=head2 WATCHER PRIORITY MODELS
		1201
		1202	Many event loops support I<watcher priorities>, which are usually small
		1203	integers that influence the ordering of event callback invocation
		1204	between watchers in some way, all else being equal.
		1205
		1206	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1207	description for the more technical details such as the actual priority
		1208	range.
		1209
		1210	There are two common ways how these these priorities are being interpreted
		1211	by event loops:
		1212
		1213	In the more common lock-out model, higher priorities "lock out" invocation
		1214	of lower priority watchers, which means as long as higher priority
		1215	watchers receive events, lower priority watchers are not being invoked.
		1216
		1217	The less common only-for-ordering model uses priorities solely to order
		1218	callback invocation within a single event loop iteration: Higher priority
		1219	watchers are invoked before lower priority ones, but they all get invoked
		1220	before polling for new events.
		1221
		1222	Libev uses the second (only-for-ordering) model for all its watchers
		1223	except for idle watchers (which use the lock-out model).
		1224
		1225	The rationale behind this is that implementing the lock-out model for
		1226	watchers is not well supported by most kernel interfaces, and most event
		1227	libraries will just poll for the same events again and again as long as
		1228	their callbacks have not been executed, which is very inefficient in the
		1229	common case of one high-priority watcher locking out a mass of lower
		1230	priority ones.
		1231
		1232	Static (ordering) priorities are most useful when you have two or more
		1233	watchers handling the same resource: a typical usage example is having an
		1234	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1235	timeouts. Under load, data might be received while the program handles
		1236	other jobs, but since timers normally get invoked first, the timeout
		1237	handler will be executed before checking for data. In that case, giving
		1238	the timer a lower priority than the I/O watcher ensures that I/O will be
		1239	handled first even under adverse conditions (which is usually, but not
		1240	always, what you want).
		1241
		1242	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1243	will only be executed when no same or higher priority watchers have
		1244	received events, they can be used to implement the "lock-out" model when
		1245	required.
		1246
		1247	For example, to emulate how many other event libraries handle priorities,
		1248	you can associate an C<ev_idle> watcher to each such watcher, and in
		1249	the normal watcher callback, you just start the idle watcher. The real
		1250	processing is done in the idle watcher callback. This causes libev to
		1251	continously poll and process kernel event data for the watcher, but when
		1252	the lock-out case is known to be rare (which in turn is rare :), this is
		1253	workable.
		1254
		1255	Usually, however, the lock-out model implemented that way will perform
		1256	miserably under the type of load it was designed to handle. In that case,
		1257	it might be preferable to stop the real watcher before starting the
		1258	idle watcher, so the kernel will not have to process the event in case
		1259	the actual processing will be delayed for considerable time.
		1260
		1261	Here is an example of an I/O watcher that should run at a strictly lower
		1262	priority than the default, and which should only process data when no
		1263	other events are pending:
		1264
		1265	ev_idle idle; // actual processing watcher
		1266	ev_io io; // actual event watcher
		1267
		1268	static void
		1269	io_cb (EV_P_ ev_io *w, int revents)
		1270	{
		1271	// stop the I/O watcher, we received the event, but
		1272	// are not yet ready to handle it.
		1273	ev_io_stop (EV_A_ w);
		1274
		1275	// start the idle watcher to ahndle the actual event.
		1276	// it will not be executed as long as other watchers
		1277	// with the default priority are receiving events.
		1278	ev_idle_start (EV_A_ &idle);
		1279	}
		1280
		1281	static void
		1282	idle_cb (EV_P_ ev_idle *w, int revents)
		1283	{
		1284	// actual processing
		1285	read (STDIN_FILENO, ...);
		1286
		1287	// have to start the I/O watcher again, as
		1288	// we have handled the event
		1289	ev_io_start (EV_P_ &io);
		1290	}
		1291
		1292	// initialisation
		1293	ev_idle_init (&idle, idle_cb);
		1294	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1295	ev_io_start (EV_DEFAULT_ &io);
		1296
		1297	In the "real" world, it might also be beneficial to start a timer, so that
		1298	low-priority connections can not be locked out forever under load. This
		1299	enables your program to keep a lower latency for important connections
		1300	during short periods of high load, while not completely locking out less
		1301	important ones.
1031		1302
1032		1303
1033	=head1 WATCHER TYPES	1304	=head1 WATCHER TYPES
1034		1305
1035	This section describes each watcher in detail, but will not repeat	1306	This section describes each watcher in detail, but will not repeat
…		…
1059	In general you can register as many read and/or write event watchers per	1330	In general you can register as many read and/or write event watchers per
1060	fd as you want (as long as you don't confuse yourself). Setting all file	1331	fd as you want (as long as you don't confuse yourself). Setting all file
1061	descriptors to non-blocking mode is also usually a good idea (but not	1332	descriptors to non-blocking mode is also usually a good idea (but not
1062	required if you know what you are doing).	1333	required if you know what you are doing).
1063		1334
1064	If you must do this, then force the use of a known-to-be-good backend	1335	If you cannot use non-blocking mode, then force the use of a
1065	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1336	known-to-be-good backend (at the time of this writing, this includes only
1066	C<EVBACKEND_POLL>).	1337	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1338	descriptors for which non-blocking operation makes no sense (such as
		1339	files) - libev doesn't guarentee any specific behaviour in that case.
1067		1340
1068	Another thing you have to watch out for is that it is quite easy to	1341	Another thing you have to watch out for is that it is quite easy to
1069	receive "spurious" readiness notifications, that is your callback might	1342	receive "spurious" readiness notifications, that is your callback might
1070	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1343	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1071	because there is no data. Not only are some backends known to create a	1344	because there is no data. Not only are some backends known to create a
1072	lot of those (for example Solaris ports), it is very easy to get into	1345	lot of those (for example Solaris ports), it is very easy to get into
1073	this situation even with a relatively standard program structure. Thus	1346	this situation even with a relatively standard program structure. Thus
1074	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1347	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1075	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1348	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1076		1349
1077	If you cannot run the fd in non-blocking mode (for example you should not	1350	If you cannot run the fd in non-blocking mode (for example you should
1078	play around with an Xlib connection), then you have to separately re-test	1351	not play around with an Xlib connection), then you have to separately
1079	whether a file descriptor is really ready with a known-to-be good interface	1352	re-test whether a file descriptor is really ready with a known-to-be good
1080	such as poll (fortunately in our Xlib example, Xlib already does this on	1353	interface such as poll (fortunately in our Xlib example, Xlib already
1081	its own, so its quite safe to use).	1354	does this on its own, so its quite safe to use). Some people additionally
		1355	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1356	indefinitely.
		1357
		1358	But really, best use non-blocking mode.
1082		1359
1083	=head3 The special problem of disappearing file descriptors	1360	=head3 The special problem of disappearing file descriptors
1084		1361
1085	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1362	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1086	descriptor (either by calling C<close> explicitly or by any other means,	1363	descriptor (either due to calling C<close> explicitly or any other means,
1087	such as C<dup>). The reason is that you register interest in some file	1364	such as C<dup2>). The reason is that you register interest in some file
1088	descriptor, but when it goes away, the operating system will silently drop	1365	descriptor, but when it goes away, the operating system will silently drop
1089	this interest. If another file descriptor with the same number then is	1366	this interest. If another file descriptor with the same number then is
1090	registered with libev, there is no efficient way to see that this is, in	1367	registered with libev, there is no efficient way to see that this is, in
1091	fact, a different file descriptor.	1368	fact, a different file descriptor.
1092		1369
…		…
1123	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1400	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1124	C<EVBACKEND_POLL>.	1401	C<EVBACKEND_POLL>.
1125		1402
1126	=head3 The special problem of SIGPIPE	1403	=head3 The special problem of SIGPIPE
1127		1404
1128	While not really specific to libev, it is easy to forget about SIGPIPE:	1405	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1129	when reading from a pipe whose other end has been closed, your program	1406	when writing to a pipe whose other end has been closed, your program gets
1130	gets send a SIGPIPE, which, by default, aborts your program. For most	1407	sent a SIGPIPE, which, by default, aborts your program. For most programs
1131	programs this is sensible behaviour, for daemons, this is usually	1408	this is sensible behaviour, for daemons, this is usually undesirable.
1132	undesirable.
1133		1409
1134	So when you encounter spurious, unexplained daemon exits, make sure you	1410	So when you encounter spurious, unexplained daemon exits, make sure you
1135	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1411	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1136	somewhere, as that would have given you a big clue).	1412	somewhere, as that would have given you a big clue).
1137		1413
…		…
1143	=item ev_io_init (ev_io *, callback, int fd, int events)	1419	=item ev_io_init (ev_io *, callback, int fd, int events)
1144		1420
1145	=item ev_io_set (ev_io *, int fd, int events)	1421	=item ev_io_set (ev_io *, int fd, int events)
1146		1422
1147	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1423	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1148	receive events for and events is either C<EV_READ>, C<EV_WRITE> or	1424	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1149	C<EV_READ | EV_WRITE> to receive the given events.	1425	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1150		1426
1151	=item int fd [read-only]	1427	=item int fd [read-only]
1152		1428
1153	The file descriptor being watched.	1429	The file descriptor being watched.
1154		1430
…		…
1163	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1439	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1164	readable, but only once. Since it is likely line-buffered, you could	1440	readable, but only once. Since it is likely line-buffered, you could
1165	attempt to read a whole line in the callback.	1441	attempt to read a whole line in the callback.
1166		1442
1167	static void	1443	static void
1168	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1444	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1169	{	1445	{
1170	ev_io_stop (loop, w);	1446	ev_io_stop (loop, w);
1171	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1447	.. read from stdin here (or from w->fd) and handle any I/O errors
1172	}	1448	}
1173		1449
1174	...	1450	...
1175	struct ev_loop *loop = ev_default_init (0);	1451	struct ev_loop *loop = ev_default_init (0);
1176	struct ev_io stdin_readable;	1452	ev_io stdin_readable;
1177	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1453	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1178	ev_io_start (loop, &stdin_readable);	1454	ev_io_start (loop, &stdin_readable);
1179	ev_loop (loop, 0);	1455	ev_loop (loop, 0);
1180		1456
1181		1457
…		…
1184	Timer watchers are simple relative timers that generate an event after a	1460	Timer watchers are simple relative timers that generate an event after a
1185	given time, and optionally repeating in regular intervals after that.	1461	given time, and optionally repeating in regular intervals after that.
1186		1462
1187	The timers are based on real time, that is, if you register an event that	1463	The timers are based on real time, that is, if you register an event that
1188	times out after an hour and you reset your system clock to January last	1464	times out after an hour and you reset your system clock to January last
1189	year, it will still time out after (roughly) and hour. "Roughly" because	1465	year, it will still time out after (roughly) one hour. "Roughly" because
1190	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1466	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1191	monotonic clock option helps a lot here).	1467	monotonic clock option helps a lot here).
		1468
		1469	The callback is guaranteed to be invoked only I<after> its timeout has
		1470	passed (not I<at>, so on systems with very low-resolution clocks this
		1471	might introduce a small delay). If multiple timers become ready during the
		1472	same loop iteration then the ones with earlier time-out values are invoked
		1473	before ones with later time-out values (but this is no longer true when a
		1474	callback calls C<ev_loop> recursively).
		1475
		1476	=head3 Be smart about timeouts
		1477
		1478	Many real-world problems involve some kind of timeout, usually for error
		1479	recovery. A typical example is an HTTP request - if the other side hangs,
		1480	you want to raise some error after a while.
		1481
		1482	What follows are some ways to handle this problem, from obvious and
		1483	inefficient to smart and efficient.
		1484
		1485	In the following, a 60 second activity timeout is assumed - a timeout that
		1486	gets reset to 60 seconds each time there is activity (e.g. each time some
		1487	data or other life sign was received).
		1488
		1489	=over 4
		1490
		1491	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1492
		1493	This is the most obvious, but not the most simple way: In the beginning,
		1494	start the watcher:
		1495
		1496	ev_timer_init (timer, callback, 60., 0.);
		1497	ev_timer_start (loop, timer);
		1498
		1499	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1500	and start it again:
		1501
		1502	ev_timer_stop (loop, timer);
		1503	ev_timer_set (timer, 60., 0.);
		1504	ev_timer_start (loop, timer);
		1505
		1506	This is relatively simple to implement, but means that each time there is
		1507	some activity, libev will first have to remove the timer from its internal
		1508	data structure and then add it again. Libev tries to be fast, but it's
		1509	still not a constant-time operation.
		1510
		1511	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1512
		1513	This is the easiest way, and involves using C<ev_timer_again> instead of
		1514	C<ev_timer_start>.
		1515
		1516	To implement this, configure an C<ev_timer> with a C<repeat> value
		1517	of C<60> and then call C<ev_timer_again> at start and each time you
		1518	successfully read or write some data. If you go into an idle state where
		1519	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1520	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1521
		1522	That means you can ignore both the C<ev_timer_start> function and the
		1523	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1524	member and C<ev_timer_again>.
		1525
		1526	At start:
		1527
		1528	ev_init (timer, callback);
		1529	timer->repeat = 60.;
		1530	ev_timer_again (loop, timer);
		1531
		1532	Each time there is some activity:
		1533
		1534	ev_timer_again (loop, timer);
		1535
		1536	It is even possible to change the time-out on the fly, regardless of
		1537	whether the watcher is active or not:
		1538
		1539	timer->repeat = 30.;
		1540	ev_timer_again (loop, timer);
		1541
		1542	This is slightly more efficient then stopping/starting the timer each time
		1543	you want to modify its timeout value, as libev does not have to completely
		1544	remove and re-insert the timer from/into its internal data structure.
		1545
		1546	It is, however, even simpler than the "obvious" way to do it.
		1547
		1548	=item 3. Let the timer time out, but then re-arm it as required.
		1549
		1550	This method is more tricky, but usually most efficient: Most timeouts are
		1551	relatively long compared to the intervals between other activity - in
		1552	our example, within 60 seconds, there are usually many I/O events with
		1553	associated activity resets.
		1554
		1555	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1556	but remember the time of last activity, and check for a real timeout only
		1557	within the callback:
		1558
		1559	ev_tstamp last_activity; // time of last activity
		1560
		1561	static void
		1562	callback (EV_P_ ev_timer *w, int revents)
		1563	{
		1564	ev_tstamp now = ev_now (EV_A);
		1565	ev_tstamp timeout = last_activity + 60.;
		1566
		1567	// if last_activity + 60. is older than now, we did time out
		1568	if (timeout < now)
		1569	{
		1570	// timeout occured, take action
		1571	}
		1572	else
		1573	{
		1574	// callback was invoked, but there was some activity, re-arm
		1575	// the watcher to fire in last_activity + 60, which is
		1576	// guaranteed to be in the future, so "again" is positive:
		1577	w->repeat = timeout - now;
		1578	ev_timer_again (EV_A_ w);
		1579	}
		1580	}
		1581
		1582	To summarise the callback: first calculate the real timeout (defined
		1583	as "60 seconds after the last activity"), then check if that time has
		1584	been reached, which means something I<did>, in fact, time out. Otherwise
		1585	the callback was invoked too early (C<timeout> is in the future), so
		1586	re-schedule the timer to fire at that future time, to see if maybe we have
		1587	a timeout then.
		1588
		1589	Note how C<ev_timer_again> is used, taking advantage of the
		1590	C<ev_timer_again> optimisation when the timer is already running.
		1591
		1592	This scheme causes more callback invocations (about one every 60 seconds
		1593	minus half the average time between activity), but virtually no calls to
		1594	libev to change the timeout.
		1595
		1596	To start the timer, simply initialise the watcher and set C<last_activity>
		1597	to the current time (meaning we just have some activity :), then call the
		1598	callback, which will "do the right thing" and start the timer:
		1599
		1600	ev_init (timer, callback);
		1601	last_activity = ev_now (loop);
		1602	callback (loop, timer, EV_TIMEOUT);
		1603
		1604	And when there is some activity, simply store the current time in
		1605	C<last_activity>, no libev calls at all:
		1606
		1607	last_actiivty = ev_now (loop);
		1608
		1609	This technique is slightly more complex, but in most cases where the
		1610	time-out is unlikely to be triggered, much more efficient.
		1611
		1612	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1613	callback :) - just change the timeout and invoke the callback, which will
		1614	fix things for you.
		1615
		1616	=item 4. Wee, just use a double-linked list for your timeouts.
		1617
		1618	If there is not one request, but many thousands (millions...), all
		1619	employing some kind of timeout with the same timeout value, then one can
		1620	do even better:
		1621
		1622	When starting the timeout, calculate the timeout value and put the timeout
		1623	at the I<end> of the list.
		1624
		1625	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1626	the list is expected to fire (for example, using the technique #3).
		1627
		1628	When there is some activity, remove the timer from the list, recalculate
		1629	the timeout, append it to the end of the list again, and make sure to
		1630	update the C<ev_timer> if it was taken from the beginning of the list.
		1631
		1632	This way, one can manage an unlimited number of timeouts in O(1) time for
		1633	starting, stopping and updating the timers, at the expense of a major
		1634	complication, and having to use a constant timeout. The constant timeout
		1635	ensures that the list stays sorted.
		1636
		1637	=back
		1638
		1639	So which method the best?
		1640
		1641	Method #2 is a simple no-brain-required solution that is adequate in most
		1642	situations. Method #3 requires a bit more thinking, but handles many cases
		1643	better, and isn't very complicated either. In most case, choosing either
		1644	one is fine, with #3 being better in typical situations.
		1645
		1646	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1647	rather complicated, but extremely efficient, something that really pays
		1648	off after the first million or so of active timers, i.e. it's usually
		1649	overkill :)
		1650
		1651	=head3 The special problem of time updates
		1652
		1653	Establishing the current time is a costly operation (it usually takes at
		1654	least two system calls): EV therefore updates its idea of the current
		1655	time only before and after C<ev_loop> collects new events, which causes a
		1656	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1657	lots of events in one iteration.
1192		1658
1193	The relative timeouts are calculated relative to the C<ev_now ()>	1659	The relative timeouts are calculated relative to the C<ev_now ()>
1194	time. This is usually the right thing as this timestamp refers to the time	1660	time. This is usually the right thing as this timestamp refers to the time
1195	of the event triggering whatever timeout you are modifying/starting. If	1661	of the event triggering whatever timeout you are modifying/starting. If
1196	you suspect event processing to be delayed and you I<need> to base the timeout	1662	you suspect event processing to be delayed and you I<need> to base the
1197	on the current time, use something like this to adjust for this:	1663	timeout on the current time, use something like this to adjust for this:
1198		1664
1199	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1665	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1200		1666
1201	The callback is guaranteed to be invoked only after its timeout has passed,	1667	If the event loop is suspended for a long time, you can also force an
1202	but if multiple timers become ready during the same loop iteration then	1668	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1203	order of execution is undefined.	1669	()>.
1204		1670
1205	=head3 Watcher-Specific Functions and Data Members	1671	=head3 Watcher-Specific Functions and Data Members
1206		1672
1207	=over 4	1673	=over 4
1208		1674
…		…
1232	If the timer is started but non-repeating, stop it (as if it timed out).	1698	If the timer is started but non-repeating, stop it (as if it timed out).
1233		1699
1234	If the timer is repeating, either start it if necessary (with the	1700	If the timer is repeating, either start it if necessary (with the
1235	C<repeat> value), or reset the running timer to the C<repeat> value.	1701	C<repeat> value), or reset the running timer to the C<repeat> value.
1236		1702
1237	This sounds a bit complicated, but here is a useful and typical	1703	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1238	example: Imagine you have a TCP connection and you want a so-called idle	1704	usage example.
1239	timeout, that is, you want to be called when there have been, say, 60
1240	seconds of inactivity on the socket. The easiest way to do this is to
1241	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1242	C<ev_timer_again> each time you successfully read or write some data. If
1243	you go into an idle state where you do not expect data to travel on the
1244	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1245	automatically restart it if need be.
1246
1247	That means you can ignore the C<after> value and C<ev_timer_start>
1248	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1249
1250	ev_timer_init (timer, callback, 0., 5.);
1251	ev_timer_again (loop, timer);
1252	...
1253	timer->again = 17.;
1254	ev_timer_again (loop, timer);
1255	...
1256	timer->again = 10.;
1257	ev_timer_again (loop, timer);
1258
1259	This is more slightly efficient then stopping/starting the timer each time
1260	you want to modify its timeout value.
1261		1705
1262	=item ev_tstamp repeat [read-write]	1706	=item ev_tstamp repeat [read-write]
1263		1707
1264	The current C<repeat> value. Will be used each time the watcher times out	1708	The current C<repeat> value. Will be used each time the watcher times out
1265	or C<ev_timer_again> is called and determines the next timeout (if any),	1709	or C<ev_timer_again> is called, and determines the next timeout (if any),
1266	which is also when any modifications are taken into account.	1710	which is also when any modifications are taken into account.
1267		1711
1268	=back	1712	=back
1269		1713
1270	=head3 Examples	1714	=head3 Examples
1271		1715
1272	Example: Create a timer that fires after 60 seconds.	1716	Example: Create a timer that fires after 60 seconds.
1273		1717
1274	static void	1718	static void
1275	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1719	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1276	{	1720	{
1277	.. one minute over, w is actually stopped right here	1721	.. one minute over, w is actually stopped right here
1278	}	1722	}
1279		1723
1280	struct ev_timer mytimer;	1724	ev_timer mytimer;
1281	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1725	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1282	ev_timer_start (loop, &mytimer);	1726	ev_timer_start (loop, &mytimer);
1283		1727
1284	Example: Create a timeout timer that times out after 10 seconds of	1728	Example: Create a timeout timer that times out after 10 seconds of
1285	inactivity.	1729	inactivity.
1286		1730
1287	static void	1731	static void
1288	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1732	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1289	{	1733	{
1290	.. ten seconds without any activity	1734	.. ten seconds without any activity
1291	}	1735	}
1292		1736
1293	struct ev_timer mytimer;	1737	ev_timer mytimer;
1294	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1738	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1295	ev_timer_again (&mytimer); /* start timer */	1739	ev_timer_again (&mytimer); /* start timer */
1296	ev_loop (loop, 0);	1740	ev_loop (loop, 0);
1297		1741
1298	// and in some piece of code that gets executed on any "activity":	1742	// and in some piece of code that gets executed on any "activity":
…		…
1303	=head2 C<ev_periodic> - to cron or not to cron?	1747	=head2 C<ev_periodic> - to cron or not to cron?
1304		1748
1305	Periodic watchers are also timers of a kind, but they are very versatile	1749	Periodic watchers are also timers of a kind, but they are very versatile
1306	(and unfortunately a bit complex).	1750	(and unfortunately a bit complex).
1307		1751
1308	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1752	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1309	but on wall clock time (absolute time). You can tell a periodic watcher	1753	relative time, the physical time that passes) but on wall clock time
1310	to trigger after some specific point in time. For example, if you tell a	1754	(absolute time, the thing you can read on your calender or clock). The
1311	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	1755	difference is that wall clock time can run faster or slower than real
1312	+ 10.>, that is, an absolute time not a delay) and then reset your system	1756	time, and time jumps are not uncommon (e.g. when you adjust your
1313	clock to January of the previous year, then it will take more than year	1757	wrist-watch).
1314	to trigger the event (unlike an C<ev_timer>, which would still trigger
1315	roughly 10 seconds later as it uses a relative timeout).
1316		1758
		1759	You can tell a periodic watcher to trigger after some specific point
		1760	in time: for example, if you tell a periodic watcher to trigger "in 10
		1761	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1762	not a delay) and then reset your system clock to January of the previous
		1763	year, then it will take a year or more to trigger the event (unlike an
		1764	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1765	it, as it uses a relative timeout).
		1766
1317	C<ev_periodic>s can also be used to implement vastly more complex timers,	1767	C<ev_periodic> watchers can also be used to implement vastly more complex
1318	such as triggering an event on each "midnight, local time", or other	1768	timers, such as triggering an event on each "midnight, local time", or
1319	complicated, rules.	1769	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1770	those cannot react to time jumps.
1320		1771
1321	As with timers, the callback is guaranteed to be invoked only when the	1772	As with timers, the callback is guaranteed to be invoked only when the
1322	time (C<at>) has passed, but if multiple periodic timers become ready	1773	point in time where it is supposed to trigger has passed. If multiple
1323	during the same loop iteration then order of execution is undefined.	1774	timers become ready during the same loop iteration then the ones with
		1775	earlier time-out values are invoked before ones with later time-out values
		1776	(but this is no longer true when a callback calls C<ev_loop> recursively).
1324		1777
1325	=head3 Watcher-Specific Functions and Data Members	1778	=head3 Watcher-Specific Functions and Data Members
1326		1779
1327	=over 4	1780	=over 4
1328		1781
1329	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1782	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1330		1783
1331	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1784	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1332		1785
1333	Lots of arguments, lets sort it out... There are basically three modes of	1786	Lots of arguments, let's sort it out... There are basically three modes of
1334	operation, and we will explain them from simplest to complex:	1787	operation, and we will explain them from simplest to most complex:
1335		1788
1336	=over 4	1789	=over 4
1337		1790
1338	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1791	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1339		1792
1340	In this configuration the watcher triggers an event after the wall clock	1793	In this configuration the watcher triggers an event after the wall clock
1341	time C<at> has passed and doesn't repeat. It will not adjust when a time	1794	time C<offset> has passed. It will not repeat and will not adjust when a
1342	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1795	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1343	run when the system time reaches or surpasses this time.	1796	will be stopped and invoked when the system clock reaches or surpasses
		1797	this point in time.
1344		1798
1345	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1799	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1346		1800
1347	In this mode the watcher will always be scheduled to time out at the next	1801	In this mode the watcher will always be scheduled to time out at the next
1348	C<at + N * interval> time (for some integer N, which can also be negative)	1802	C<offset + N * interval> time (for some integer N, which can also be
1349	and then repeat, regardless of any time jumps.	1803	negative) and then repeat, regardless of any time jumps. The C<offset>
		1804	argument is merely an offset into the C<interval> periods.
1350		1805
1351	This can be used to create timers that do not drift with respect to system	1806	This can be used to create timers that do not drift with respect to the
1352	time, for example, here is a C<ev_periodic> that triggers each hour, on	1807	system clock, for example, here is an C<ev_periodic> that triggers each
1353	the hour:	1808	hour, on the hour (with respect to UTC):
1354		1809
1355	ev_periodic_set (&periodic, 0., 3600., 0);	1810	ev_periodic_set (&periodic, 0., 3600., 0);
1356		1811
1357	This doesn't mean there will always be 3600 seconds in between triggers,	1812	This doesn't mean there will always be 3600 seconds in between triggers,
1358	but only that the callback will be called when the system time shows a	1813	but only that the callback will be called when the system time shows a
1359	full hour (UTC), or more correctly, when the system time is evenly divisible	1814	full hour (UTC), or more correctly, when the system time is evenly divisible
1360	by 3600.	1815	by 3600.
1361		1816
1362	Another way to think about it (for the mathematically inclined) is that	1817	Another way to think about it (for the mathematically inclined) is that
1363	C<ev_periodic> will try to run the callback in this mode at the next possible	1818	C<ev_periodic> will try to run the callback in this mode at the next possible
1364	time where C<time = at (mod interval)>, regardless of any time jumps.	1819	time where C<time = offset (mod interval)>, regardless of any time jumps.
1365		1820
1366	For numerical stability it is preferable that the C<at> value is near	1821	For numerical stability it is preferable that the C<offset> value is near
1367	C<ev_now ()> (the current time), but there is no range requirement for	1822	C<ev_now ()> (the current time), but there is no range requirement for
1368	this value, and in fact is often specified as zero.	1823	this value, and in fact is often specified as zero.
1369		1824
1370	Note also that there is an upper limit to how often a timer can fire (CPU	1825	Note also that there is an upper limit to how often a timer can fire (CPU
1371	speed for example), so if C<interval> is very small then timing stability	1826	speed for example), so if C<interval> is very small then timing stability
1372	will of course deteriorate. Libev itself tries to be exact to be about one	1827	will of course deteriorate. Libev itself tries to be exact to be about one
1373	millisecond (if the OS supports it and the machine is fast enough).	1828	millisecond (if the OS supports it and the machine is fast enough).
1374		1829
1375	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1830	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1376		1831
1377	In this mode the values for C<interval> and C<at> are both being	1832	In this mode the values for C<interval> and C<offset> are both being
1378	ignored. Instead, each time the periodic watcher gets scheduled, the	1833	ignored. Instead, each time the periodic watcher gets scheduled, the
1379	reschedule callback will be called with the watcher as first, and the	1834	reschedule callback will be called with the watcher as first, and the
1380	current time as second argument.	1835	current time as second argument.
1381		1836
1382	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1837	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1383	ever, or make ANY event loop modifications whatsoever>.	1838	or make ANY other event loop modifications whatsoever, unless explicitly
		1839	allowed by documentation here>.
1384		1840
1385	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1841	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1386	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	1842	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1387	only event loop modification you are allowed to do).	1843	only event loop modification you are allowed to do).
1388		1844
1389	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1845	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1390	*w, ev_tstamp now)>, e.g.:	1846	*w, ev_tstamp now)>, e.g.:
1391		1847
		1848	static ev_tstamp
1392	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1849	my_rescheduler (ev_periodic *w, ev_tstamp now)
1393	{	1850	{
1394	return now + 60.;	1851	return now + 60.;
1395	}	1852	}
1396		1853
1397	It must return the next time to trigger, based on the passed time value	1854	It must return the next time to trigger, based on the passed time value
…		…
1417	a different time than the last time it was called (e.g. in a crond like	1874	a different time than the last time it was called (e.g. in a crond like
1418	program when the crontabs have changed).	1875	program when the crontabs have changed).
1419		1876
1420	=item ev_tstamp ev_periodic_at (ev_periodic *)	1877	=item ev_tstamp ev_periodic_at (ev_periodic *)
1421		1878
1422	When active, returns the absolute time that the watcher is supposed to	1879	When active, returns the absolute time that the watcher is supposed
1423	trigger next.	1880	to trigger next. This is not the same as the C<offset> argument to
		1881	C<ev_periodic_set>, but indeed works even in interval and manual
		1882	rescheduling modes.
1424		1883
1425	=item ev_tstamp offset [read-write]	1884	=item ev_tstamp offset [read-write]
1426		1885
1427	When repeating, this contains the offset value, otherwise this is the	1886	When repeating, this contains the offset value, otherwise this is the
1428	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1887	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		1888	although libev might modify this value for better numerical stability).
1429		1889
1430	Can be modified any time, but changes only take effect when the periodic	1890	Can be modified any time, but changes only take effect when the periodic
1431	timer fires or C<ev_periodic_again> is being called.	1891	timer fires or C<ev_periodic_again> is being called.
1432		1892
1433	=item ev_tstamp interval [read-write]	1893	=item ev_tstamp interval [read-write]
1434		1894
1435	The current interval value. Can be modified any time, but changes only	1895	The current interval value. Can be modified any time, but changes only
1436	take effect when the periodic timer fires or C<ev_periodic_again> is being	1896	take effect when the periodic timer fires or C<ev_periodic_again> is being
1437	called.	1897	called.
1438		1898
1439	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1899	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1440		1900
1441	The current reschedule callback, or C<0>, if this functionality is	1901	The current reschedule callback, or C<0>, if this functionality is
1442	switched off. Can be changed any time, but changes only take effect when	1902	switched off. Can be changed any time, but changes only take effect when
1443	the periodic timer fires or C<ev_periodic_again> is being called.	1903	the periodic timer fires or C<ev_periodic_again> is being called.
1444		1904
1445	=back	1905	=back
1446		1906
1447	=head3 Examples	1907	=head3 Examples
1448		1908
1449	Example: Call a callback every hour, or, more precisely, whenever the	1909	Example: Call a callback every hour, or, more precisely, whenever the
1450	system clock is divisible by 3600. The callback invocation times have	1910	system time is divisible by 3600. The callback invocation times have
1451	potentially a lot of jitter, but good long-term stability.	1911	potentially a lot of jitter, but good long-term stability.
1452		1912
1453	static void	1913	static void
1454	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1914	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1455	{	1915	{
1456	... its now a full hour (UTC, or TAI or whatever your clock follows)	1916	... its now a full hour (UTC, or TAI or whatever your clock follows)
1457	}	1917	}
1458		1918
1459	struct ev_periodic hourly_tick;	1919	ev_periodic hourly_tick;
1460	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1920	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1461	ev_periodic_start (loop, &hourly_tick);	1921	ev_periodic_start (loop, &hourly_tick);
1462		1922
1463	Example: The same as above, but use a reschedule callback to do it:	1923	Example: The same as above, but use a reschedule callback to do it:
1464		1924
1465	#include <math.h>	1925	#include <math.h>
1466		1926
1467	static ev_tstamp	1927	static ev_tstamp
1468	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1928	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1469	{	1929	{
1470	return fmod (now, 3600.) + 3600.;	1930	return now + (3600. - fmod (now, 3600.));
1471	}	1931	}
1472		1932
1473	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1933	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1474		1934
1475	Example: Call a callback every hour, starting now:	1935	Example: Call a callback every hour, starting now:
1476		1936
1477	struct ev_periodic hourly_tick;	1937	ev_periodic hourly_tick;
1478	ev_periodic_init (&hourly_tick, clock_cb,	1938	ev_periodic_init (&hourly_tick, clock_cb,
1479	fmod (ev_now (loop), 3600.), 3600., 0);	1939	fmod (ev_now (loop), 3600.), 3600., 0);
1480	ev_periodic_start (loop, &hourly_tick);	1940	ev_periodic_start (loop, &hourly_tick);
1481		1941
1482		1942
…		…
1485	Signal watchers will trigger an event when the process receives a specific	1945	Signal watchers will trigger an event when the process receives a specific
1486	signal one or more times. Even though signals are very asynchronous, libev	1946	signal one or more times. Even though signals are very asynchronous, libev
1487	will try it's best to deliver signals synchronously, i.e. as part of the	1947	will try it's best to deliver signals synchronously, i.e. as part of the
1488	normal event processing, like any other event.	1948	normal event processing, like any other event.
1489		1949
		1950	If you want signals asynchronously, just use C<sigaction> as you would
		1951	do without libev and forget about sharing the signal. You can even use
		1952	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1953
1490	You can configure as many watchers as you like per signal. Only when the	1954	You can configure as many watchers as you like per signal. Only when the
1491	first watcher gets started will libev actually register a signal watcher	1955	first watcher gets started will libev actually register a signal handler
1492	with the kernel (thus it coexists with your own signal handlers as long	1956	with the kernel (thus it coexists with your own signal handlers as long as
1493	as you don't register any with libev). Similarly, when the last signal	1957	you don't register any with libev for the same signal). Similarly, when
1494	watcher for a signal is stopped libev will reset the signal handler to	1958	the last signal watcher for a signal is stopped, libev will reset the
1495	SIG_DFL (regardless of what it was set to before).	1959	signal handler to SIG_DFL (regardless of what it was set to before).
1496		1960
1497	If possible and supported, libev will install its handlers with	1961	If possible and supported, libev will install its handlers with
1498	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	1962	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1499	interrupted. If you have a problem with system calls getting interrupted by	1963	interrupted. If you have a problem with system calls getting interrupted by
1500	signals you can block all signals in an C<ev_check> watcher and unblock	1964	signals you can block all signals in an C<ev_check> watcher and unblock
…		…
1517		1981
1518	=back	1982	=back
1519		1983
1520	=head3 Examples	1984	=head3 Examples
1521		1985
1522	Example: Try to exit cleanly on SIGINT and SIGTERM.	1986	Example: Try to exit cleanly on SIGINT.
1523		1987
1524	static void	1988	static void
1525	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1989	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1526	{	1990	{
1527	ev_unloop (loop, EVUNLOOP_ALL);	1991	ev_unloop (loop, EVUNLOOP_ALL);
1528	}	1992	}
1529		1993
1530	struct ev_signal signal_watcher;	1994	ev_signal signal_watcher;
1531	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1995	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1532	ev_signal_start (loop, &sigint_cb);	1996	ev_signal_start (loop, &signal_watcher);
1533		1997
1534		1998
1535	=head2 C<ev_child> - watch out for process status changes	1999	=head2 C<ev_child> - watch out for process status changes
1536		2000
1537	Child watchers trigger when your process receives a SIGCHLD in response to	2001	Child watchers trigger when your process receives a SIGCHLD in response to
1538	some child status changes (most typically when a child of yours dies). It	2002	some child status changes (most typically when a child of yours dies or
1539	is permissible to install a child watcher I<after> the child has been	2003	exits). It is permissible to install a child watcher I<after> the child
1540	forked (which implies it might have already exited), as long as the event	2004	has been forked (which implies it might have already exited), as long
1541	loop isn't entered (or is continued from a watcher).	2005	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2006	forking and then immediately registering a watcher for the child is fine,
		2007	but forking and registering a watcher a few event loop iterations later or
		2008	in the next callback invocation is not.
1542		2009
1543	Only the default event loop is capable of handling signals, and therefore	2010	Only the default event loop is capable of handling signals, and therefore
1544	you can only register child watchers in the default event loop.	2011	you can only register child watchers in the default event loop.
1545		2012
1546	=head3 Process Interaction	2013	=head3 Process Interaction
…		…
1559	handler, you can override it easily by installing your own handler for	2026	handler, you can override it easily by installing your own handler for
1560	C<SIGCHLD> after initialising the default loop, and making sure the	2027	C<SIGCHLD> after initialising the default loop, and making sure the
1561	default loop never gets destroyed. You are encouraged, however, to use an	2028	default loop never gets destroyed. You are encouraged, however, to use an
1562	event-based approach to child reaping and thus use libev's support for	2029	event-based approach to child reaping and thus use libev's support for
1563	that, so other libev users can use C<ev_child> watchers freely.	2030	that, so other libev users can use C<ev_child> watchers freely.
		2031
		2032	=head3 Stopping the Child Watcher
		2033
		2034	Currently, the child watcher never gets stopped, even when the
		2035	child terminates, so normally one needs to stop the watcher in the
		2036	callback. Future versions of libev might stop the watcher automatically
		2037	when a child exit is detected.
1564		2038
1565	=head3 Watcher-Specific Functions and Data Members	2039	=head3 Watcher-Specific Functions and Data Members
1566		2040
1567	=over 4	2041	=over 4
1568		2042
…		…
1600	its completion.	2074	its completion.
1601		2075
1602	ev_child cw;	2076	ev_child cw;
1603		2077
1604	static void	2078	static void
1605	child_cb (EV_P_ struct ev_child *w, int revents)	2079	child_cb (EV_P_ ev_child *w, int revents)
1606	{	2080	{
1607	ev_child_stop (EV_A_ w);	2081	ev_child_stop (EV_A_ w);
1608	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2082	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1609	}	2083	}
1610		2084
…		…
1625		2099
1626		2100
1627	=head2 C<ev_stat> - did the file attributes just change?	2101	=head2 C<ev_stat> - did the file attributes just change?
1628		2102
1629	This watches a file system path for attribute changes. That is, it calls	2103	This watches a file system path for attribute changes. That is, it calls
1630	C<stat> regularly (or when the OS says it changed) and sees if it changed	2104	C<stat> on that path in regular intervals (or when the OS says it changed)
1631	compared to the last time, invoking the callback if it did.	2105	and sees if it changed compared to the last time, invoking the callback if
		2106	it did.
1632		2107
1633	The path does not need to exist: changing from "path exists" to "path does	2108	The path does not need to exist: changing from "path exists" to "path does
1634	not exist" is a status change like any other. The condition "path does	2109	not exist" is a status change like any other. The condition "path does not
1635	not exist" is signified by the C<st_nlink> field being zero (which is	2110	exist" (or more correctly "path cannot be stat'ed") is signified by the
1636	otherwise always forced to be at least one) and all the other fields of	2111	C<st_nlink> field being zero (which is otherwise always forced to be at
1637	the stat buffer having unspecified contents.	2112	least one) and all the other fields of the stat buffer having unspecified
		2113	contents.
1638		2114
1639	The path I<should> be absolute and I<must not> end in a slash. If it is	2115	The path I<must not> end in a slash or contain special components such as
		2116	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1640	relative and your working directory changes, the behaviour is undefined.	2117	your working directory changes, then the behaviour is undefined.
1641		2118
1642	Since there is no standard to do this, the portable implementation simply	2119	Since there is no portable change notification interface available, the
1643	calls C<stat (2)> regularly on the path to see if it changed somehow. You	2120	portable implementation simply calls C<stat(2)> regularly on the path
1644	can specify a recommended polling interval for this case. If you specify	2121	to see if it changed somehow. You can specify a recommended polling
1645	a polling interval of C<0> (highly recommended!) then a I<suitable,	2122	interval for this case. If you specify a polling interval of C<0> (highly
1646	unspecified default> value will be used (which you can expect to be around	2123	recommended!) then a I<suitable, unspecified default> value will be used
1647	five seconds, although this might change dynamically). Libev will also	2124	(which you can expect to be around five seconds, although this might
1648	impose a minimum interval which is currently around C<0.1>, but thats	2125	change dynamically). Libev will also impose a minimum interval which is
1649	usually overkill.	2126	currently around C<0.1>, but that's usually overkill.
1650		2127
1651	This watcher type is not meant for massive numbers of stat watchers,	2128	This watcher type is not meant for massive numbers of stat watchers,
1652	as even with OS-supported change notifications, this can be	2129	as even with OS-supported change notifications, this can be
1653	resource-intensive.	2130	resource-intensive.
1654		2131
1655	At the time of this writing, only the Linux inotify interface is	2132	At the time of this writing, the only OS-specific interface implemented
1656	implemented (implementing kqueue support is left as an exercise for the	2133	is the Linux inotify interface (implementing kqueue support is left as an
1657	reader, note, however, that the author sees no way of implementing ev_stat	2134	exercise for the reader. Note, however, that the author sees no way of
1658	semantics with kqueue). Inotify will be used to give hints only and should	2135	implementing C<ev_stat> semantics with kqueue, except as a hint).
1659	not change the semantics of C<ev_stat> watchers, which means that libev
1660	sometimes needs to fall back to regular polling again even with inotify,
1661	but changes are usually detected immediately, and if the file exists there
1662	will be no polling.
1663		2136
1664	=head3 ABI Issues (Largefile Support)	2137	=head3 ABI Issues (Largefile Support)
1665		2138
1666	Libev by default (unless the user overrides this) uses the default	2139	Libev by default (unless the user overrides this) uses the default
1667	compilation environment, which means that on systems with optionally	2140	compilation environment, which means that on systems with large file
1668	disabled large file support, you get the 32 bit version of the stat	2141	support disabled by default, you get the 32 bit version of the stat
1669	structure. When using the library from programs that change the ABI to	2142	structure. When using the library from programs that change the ABI to
1670	use 64 bit file offsets the programs will fail. In that case you have to	2143	use 64 bit file offsets the programs will fail. In that case you have to
1671	compile libev with the same flags to get binary compatibility. This is	2144	compile libev with the same flags to get binary compatibility. This is
1672	obviously the case with any flags that change the ABI, but the problem is	2145	obviously the case with any flags that change the ABI, but the problem is
1673	most noticeably with ev_stat and large file support.	2146	most noticeably displayed with ev_stat and large file support.
1674		2147
1675	=head3 Inotify	2148	The solution for this is to lobby your distribution maker to make large
		2149	file interfaces available by default (as e.g. FreeBSD does) and not
		2150	optional. Libev cannot simply switch on large file support because it has
		2151	to exchange stat structures with application programs compiled using the
		2152	default compilation environment.
1676		2153
		2154	=head3 Inotify and Kqueue
		2155
1677	When C<inotify (7)> support has been compiled into libev (generally only	2156	When C<inotify (7)> support has been compiled into libev and present at
1678	available on Linux) and present at runtime, it will be used to speed up	2157	runtime, it will be used to speed up change detection where possible. The
1679	change detection where possible. The inotify descriptor will be created lazily	2158	inotify descriptor will be created lazily when the first C<ev_stat>
1680	when the first C<ev_stat> watcher is being started.	2159	watcher is being started.
1681		2160
1682	Inotify presence does not change the semantics of C<ev_stat> watchers	2161	Inotify presence does not change the semantics of C<ev_stat> watchers
1683	except that changes might be detected earlier, and in some cases, to avoid	2162	except that changes might be detected earlier, and in some cases, to avoid
1684	making regular C<stat> calls. Even in the presence of inotify support	2163	making regular C<stat> calls. Even in the presence of inotify support
1685	there are many cases where libev has to resort to regular C<stat> polling.	2164	there are many cases where libev has to resort to regular C<stat> polling,
		2165	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2166	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2167	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2168	xfs are fully working) libev usually gets away without polling.
1686		2169
1687	(There is no support for kqueue, as apparently it cannot be used to	2170	There is no support for kqueue, as apparently it cannot be used to
1688	implement this functionality, due to the requirement of having a file	2171	implement this functionality, due to the requirement of having a file
1689	descriptor open on the object at all times).	2172	descriptor open on the object at all times, and detecting renames, unlinks
		2173	etc. is difficult.
		2174
		2175	=head3 C<stat ()> is a synchronous operation
		2176
		2177	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2178	the process. The exception are C<ev_stat> watchers - those call C<stat
		2179	()>, which is a synchronous operation.
		2180
		2181	For local paths, this usually doesn't matter: unless the system is very
		2182	busy or the intervals between stat's are large, a stat call will be fast,
		2183	as the path data is usually in memory already (except when starting the
		2184	watcher).
		2185
		2186	For networked file systems, calling C<stat ()> can block an indefinite
		2187	time due to network issues, and even under good conditions, a stat call
		2188	often takes multiple milliseconds.
		2189
		2190	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2191	paths, although this is fully supported by libev.
1690		2192
1691	=head3 The special problem of stat time resolution	2193	=head3 The special problem of stat time resolution
1692		2194
1693	The C<stat ()> system call only supports full-second resolution portably, and	2195	The C<stat ()> system call only supports full-second resolution portably,
1694	even on systems where the resolution is higher, many file systems still	2196	and even on systems where the resolution is higher, most file systems
1695	only support whole seconds.	2197	still only support whole seconds.
1696		2198
1697	That means that, if the time is the only thing that changes, you can	2199	That means that, if the time is the only thing that changes, you can
1698	easily miss updates: on the first update, C<ev_stat> detects a change and	2200	easily miss updates: on the first update, C<ev_stat> detects a change and
1699	calls your callback, which does something. When there is another update	2201	calls your callback, which does something. When there is another update
1700	within the same second, C<ev_stat> will be unable to detect it as the stat	2202	within the same second, C<ev_stat> will be unable to detect unless the
1701	data does not change.	2203	stat data does change in other ways (e.g. file size).
1702		2204
1703	The solution to this is to delay acting on a change for slightly more	2205	The solution to this is to delay acting on a change for slightly more
1704	than a second (or till slightly after the next full second boundary), using	2206	than a second (or till slightly after the next full second boundary), using
1705	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2207	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1706	ev_timer_again (loop, w)>).	2208	ev_timer_again (loop, w)>).
…		…
1726	C<path>. The C<interval> is a hint on how quickly a change is expected to	2228	C<path>. The C<interval> is a hint on how quickly a change is expected to
1727	be detected and should normally be specified as C<0> to let libev choose	2229	be detected and should normally be specified as C<0> to let libev choose
1728	a suitable value. The memory pointed to by C<path> must point to the same	2230	a suitable value. The memory pointed to by C<path> must point to the same
1729	path for as long as the watcher is active.	2231	path for as long as the watcher is active.
1730		2232
1731	The callback will receive C<EV_STAT> when a change was detected, relative	2233	The callback will receive an C<EV_STAT> event when a change was detected,
1732	to the attributes at the time the watcher was started (or the last change	2234	relative to the attributes at the time the watcher was started (or the
1733	was detected).	2235	last change was detected).
1734		2236
1735	=item ev_stat_stat (loop, ev_stat *)	2237	=item ev_stat_stat (loop, ev_stat *)
1736		2238
1737	Updates the stat buffer immediately with new values. If you change the	2239	Updates the stat buffer immediately with new values. If you change the
1738	watched path in your callback, you could call this function to avoid	2240	watched path in your callback, you could call this function to avoid
…		…
1821		2323
1822		2324
1823	=head2 C<ev_idle> - when you've got nothing better to do...	2325	=head2 C<ev_idle> - when you've got nothing better to do...
1824		2326
1825	Idle watchers trigger events when no other events of the same or higher	2327	Idle watchers trigger events when no other events of the same or higher
1826	priority are pending (prepare, check and other idle watchers do not	2328	priority are pending (prepare, check and other idle watchers do not count
1827	count).	2329	as receiving "events").
1828		2330
1829	That is, as long as your process is busy handling sockets or timeouts	2331	That is, as long as your process is busy handling sockets or timeouts
1830	(or even signals, imagine) of the same or higher priority it will not be	2332	(or even signals, imagine) of the same or higher priority it will not be
1831	triggered. But when your process is idle (or only lower-priority watchers	2333	triggered. But when your process is idle (or only lower-priority watchers
1832	are pending), the idle watchers are being called once per event loop	2334	are pending), the idle watchers are being called once per event loop
…		…
1843		2345
1844	=head3 Watcher-Specific Functions and Data Members	2346	=head3 Watcher-Specific Functions and Data Members
1845		2347
1846	=over 4	2348	=over 4
1847		2349
1848	=item ev_idle_init (ev_signal *, callback)	2350	=item ev_idle_init (ev_idle *, callback)
1849		2351
1850	Initialises and configures the idle watcher - it has no parameters of any	2352	Initialises and configures the idle watcher - it has no parameters of any
1851	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2353	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1852	believe me.	2354	believe me.
1853		2355
…		…
1857		2359
1858	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2360	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1859	callback, free it. Also, use no error checking, as usual.	2361	callback, free it. Also, use no error checking, as usual.
1860		2362
1861	static void	2363	static void
1862	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2364	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1863	{	2365	{
1864	free (w);	2366	free (w);
1865	// now do something you wanted to do when the program has	2367	// now do something you wanted to do when the program has
1866	// no longer anything immediate to do.	2368	// no longer anything immediate to do.
1867	}	2369	}
1868		2370
1869	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2371	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1870	ev_idle_init (idle_watcher, idle_cb);	2372	ev_idle_init (idle_watcher, idle_cb);
1871	ev_idle_start (loop, idle_cb);	2373	ev_idle_start (loop, idle_watcher);
1872		2374
1873		2375
1874	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2376	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1875		2377
1876	Prepare and check watchers are usually (but not always) used in tandem:	2378	Prepare and check watchers are usually (but not always) used in pairs:
1877	prepare watchers get invoked before the process blocks and check watchers	2379	prepare watchers get invoked before the process blocks and check watchers
1878	afterwards.	2380	afterwards.
1879		2381
1880	You I<must not> call C<ev_loop> or similar functions that enter	2382	You I<must not> call C<ev_loop> or similar functions that enter
1881	the current event loop from either C<ev_prepare> or C<ev_check>	2383	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1884	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2386	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1885	C<ev_check> so if you have one watcher of each kind they will always be	2387	C<ev_check> so if you have one watcher of each kind they will always be
1886	called in pairs bracketing the blocking call.	2388	called in pairs bracketing the blocking call.
1887		2389
1888	Their main purpose is to integrate other event mechanisms into libev and	2390	Their main purpose is to integrate other event mechanisms into libev and
1889	their use is somewhat advanced. This could be used, for example, to track	2391	their use is somewhat advanced. They could be used, for example, to track
1890	variable changes, implement your own watchers, integrate net-snmp or a	2392	variable changes, implement your own watchers, integrate net-snmp or a
1891	coroutine library and lots more. They are also occasionally useful if	2393	coroutine library and lots more. They are also occasionally useful if
1892	you cache some data and want to flush it before blocking (for example,	2394	you cache some data and want to flush it before blocking (for example,
1893	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2395	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1894	watcher).	2396	watcher).
1895		2397
1896	This is done by examining in each prepare call which file descriptors need	2398	This is done by examining in each prepare call which file descriptors
1897	to be watched by the other library, registering C<ev_io> watchers for	2399	need to be watched by the other library, registering C<ev_io> watchers
1898	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2400	for them and starting an C<ev_timer> watcher for any timeouts (many
1899	provide just this functionality). Then, in the check watcher you check for	2401	libraries provide exactly this functionality). Then, in the check watcher,
1900	any events that occurred (by checking the pending status of all watchers	2402	you check for any events that occurred (by checking the pending status
1901	and stopping them) and call back into the library. The I/O and timer	2403	of all watchers and stopping them) and call back into the library. The
1902	callbacks will never actually be called (but must be valid nevertheless,	2404	I/O and timer callbacks will never actually be called (but must be valid
1903	because you never know, you know?).	2405	nevertheless, because you never know, you know?).
1904		2406
1905	As another example, the Perl Coro module uses these hooks to integrate	2407	As another example, the Perl Coro module uses these hooks to integrate
1906	coroutines into libev programs, by yielding to other active coroutines	2408	coroutines into libev programs, by yielding to other active coroutines
1907	during each prepare and only letting the process block if no coroutines	2409	during each prepare and only letting the process block if no coroutines
1908	are ready to run (it's actually more complicated: it only runs coroutines	2410	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1911	loop from blocking if lower-priority coroutines are active, thus mapping	2413	loop from blocking if lower-priority coroutines are active, thus mapping
1912	low-priority coroutines to idle/background tasks).	2414	low-priority coroutines to idle/background tasks).
1913		2415
1914	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2416	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1915	priority, to ensure that they are being run before any other watchers	2417	priority, to ensure that they are being run before any other watchers
		2418	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2419
1916	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2420	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1917	too) should not activate ("feed") events into libev. While libev fully	2421	activate ("feed") events into libev. While libev fully supports this, they
1918	supports this, they might get executed before other C<ev_check> watchers	2422	might get executed before other C<ev_check> watchers did their job. As
1919	did their job. As C<ev_check> watchers are often used to embed other	2423	C<ev_check> watchers are often used to embed other (non-libev) event
1920	(non-libev) event loops those other event loops might be in an unusable	2424	loops those other event loops might be in an unusable state until their
1921	state until their C<ev_check> watcher ran (always remind yourself to	2425	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1922	coexist peacefully with others).	2426	others).
1923		2427
1924	=head3 Watcher-Specific Functions and Data Members	2428	=head3 Watcher-Specific Functions and Data Members
1925		2429
1926	=over 4	2430	=over 4
1927		2431
…		…
1929		2433
1930	=item ev_check_init (ev_check *, callback)	2434	=item ev_check_init (ev_check *, callback)
1931		2435
1932	Initialises and configures the prepare or check watcher - they have no	2436	Initialises and configures the prepare or check watcher - they have no
1933	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2437	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1934	macros, but using them is utterly, utterly and completely pointless.	2438	macros, but using them is utterly, utterly, utterly and completely
		2439	pointless.
1935		2440
1936	=back	2441	=back
1937		2442
1938	=head3 Examples	2443	=head3 Examples
1939		2444
…		…
1952		2457
1953	static ev_io iow [nfd];	2458	static ev_io iow [nfd];
1954	static ev_timer tw;	2459	static ev_timer tw;
1955		2460
1956	static void	2461	static void
1957	io_cb (ev_loop *loop, ev_io *w, int revents)	2462	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1958	{	2463	{
1959	}	2464	}
1960		2465
1961	// create io watchers for each fd and a timer before blocking	2466	// create io watchers for each fd and a timer before blocking
1962	static void	2467	static void
1963	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2468	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1964	{	2469	{
1965	int timeout = 3600000;	2470	int timeout = 3600000;
1966	struct pollfd fds [nfd];	2471	struct pollfd fds [nfd];
1967	// actual code will need to loop here and realloc etc.	2472	// actual code will need to loop here and realloc etc.
1968	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2473	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1969		2474
1970	/* the callback is illegal, but won't be called as we stop during check */	2475	/* the callback is illegal, but won't be called as we stop during check */
1971	ev_timer_init (&tw, 0, timeout * 1e-3);	2476	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
1972	ev_timer_start (loop, &tw);	2477	ev_timer_start (loop, &tw);
1973		2478
1974	// create one ev_io per pollfd	2479	// create one ev_io per pollfd
1975	for (int i = 0; i < nfd; ++i)	2480	for (int i = 0; i < nfd; ++i)
1976	{	2481	{
…		…
1983	}	2488	}
1984	}	2489	}
1985		2490
1986	// stop all watchers after blocking	2491	// stop all watchers after blocking
1987	static void	2492	static void
1988	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2493	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1989	{	2494	{
1990	ev_timer_stop (loop, &tw);	2495	ev_timer_stop (loop, &tw);
1991		2496
1992	for (int i = 0; i < nfd; ++i)	2497	for (int i = 0; i < nfd; ++i)
1993	{	2498	{
…		…
2032	}	2537	}
2033		2538
2034	// do not ever call adns_afterpoll	2539	// do not ever call adns_afterpoll
2035		2540
2036	Method 4: Do not use a prepare or check watcher because the module you	2541	Method 4: Do not use a prepare or check watcher because the module you
2037	want to embed is too inflexible to support it. Instead, you can override	2542	want to embed is not flexible enough to support it. Instead, you can
2038	their poll function. The drawback with this solution is that the main	2543	override their poll function. The drawback with this solution is that the
2039	loop is now no longer controllable by EV. The C<Glib::EV> module does	2544	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2040	this.	2545	this approach, effectively embedding EV as a client into the horrible
		2546	libglib event loop.
2041		2547
2042	static gint	2548	static gint
2043	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2549	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2044	{	2550	{
2045	int got_events = 0;	2551	int got_events = 0;
…		…
2076	prioritise I/O.	2582	prioritise I/O.
2077		2583
2078	As an example for a bug workaround, the kqueue backend might only support	2584	As an example for a bug workaround, the kqueue backend might only support
2079	sockets on some platform, so it is unusable as generic backend, but you	2585	sockets on some platform, so it is unusable as generic backend, but you
2080	still want to make use of it because you have many sockets and it scales	2586	still want to make use of it because you have many sockets and it scales
2081	so nicely. In this case, you would create a kqueue-based loop and embed it	2587	so nicely. In this case, you would create a kqueue-based loop and embed
2082	into your default loop (which might use e.g. poll). Overall operation will	2588	it into your default loop (which might use e.g. poll). Overall operation
2083	be a bit slower because first libev has to poll and then call kevent, but	2589	will be a bit slower because first libev has to call C<poll> and then
2084	at least you can use both at what they are best.	2590	C<kevent>, but at least you can use both mechanisms for what they are
		2591	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2085		2592
2086	As for prioritising I/O: rarely you have the case where some fds have	2593	As for prioritising I/O: under rare circumstances you have the case where
2087	to be watched and handled very quickly (with low latency), and even	2594	some fds have to be watched and handled very quickly (with low latency),
2088	priorities and idle watchers might have too much overhead. In this case	2595	and even priorities and idle watchers might have too much overhead. In
2089	you would put all the high priority stuff in one loop and all the rest in	2596	this case you would put all the high priority stuff in one loop and all
2090	a second one, and embed the second one in the first.	2597	the rest in a second one, and embed the second one in the first.
2091		2598
2092	As long as the watcher is active, the callback will be invoked every time	2599	As long as the watcher is active, the callback will be invoked every
2093	there might be events pending in the embedded loop. The callback must then	2600	time there might be events pending in the embedded loop. The callback
2094	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2601	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2095	their callbacks (you could also start an idle watcher to give the embedded	2602	sweep and invoke their callbacks (the callback doesn't need to invoke the
2096	loop strictly lower priority for example). You can also set the callback	2603	C<ev_embed_sweep> function directly, it could also start an idle watcher
2097	to C<0>, in which case the embed watcher will automatically execute the	2604	to give the embedded loop strictly lower priority for example).
2098	embedded loop sweep.
2099		2605
2100	As long as the watcher is started it will automatically handle events. The	2606	You can also set the callback to C<0>, in which case the embed watcher
2101	callback will be invoked whenever some events have been handled. You can	2607	will automatically execute the embedded loop sweep whenever necessary.
2102	set the callback to C<0> to avoid having to specify one if you are not
2103	interested in that.
2104		2608
2105	Also, there have not currently been made special provisions for forking:	2609	Fork detection will be handled transparently while the C<ev_embed> watcher
2106	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2610	is active, i.e., the embedded loop will automatically be forked when the
2107	but you will also have to stop and restart any C<ev_embed> watchers	2611	embedding loop forks. In other cases, the user is responsible for calling
2108	yourself.	2612	C<ev_loop_fork> on the embedded loop.
2109		2613
2110	Unfortunately, not all backends are embeddable, only the ones returned by	2614	Unfortunately, not all backends are embeddable: only the ones returned by
2111	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2615	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2112	portable one.	2616	portable one.
2113		2617
2114	So when you want to use this feature you will always have to be prepared	2618	So when you want to use this feature you will always have to be prepared
2115	that you cannot get an embeddable loop. The recommended way to get around	2619	that you cannot get an embeddable loop. The recommended way to get around
2116	this is to have a separate variables for your embeddable loop, try to	2620	this is to have a separate variables for your embeddable loop, try to
2117	create it, and if that fails, use the normal loop for everything.	2621	create it, and if that fails, use the normal loop for everything.
		2622
		2623	=head3 C<ev_embed> and fork
		2624
		2625	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2626	automatically be applied to the embedded loop as well, so no special
		2627	fork handling is required in that case. When the watcher is not running,
		2628	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2629	as applicable.
2118		2630
2119	=head3 Watcher-Specific Functions and Data Members	2631	=head3 Watcher-Specific Functions and Data Members
2120		2632
2121	=over 4	2633	=over 4
2122		2634
…		…
2150	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2662	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2151	used).	2663	used).
2152		2664
2153	struct ev_loop *loop_hi = ev_default_init (0);	2665	struct ev_loop *loop_hi = ev_default_init (0);
2154	struct ev_loop *loop_lo = 0;	2666	struct ev_loop *loop_lo = 0;
2155	struct ev_embed embed;	2667	ev_embed embed;
2156		2668
2157	// see if there is a chance of getting one that works	2669	// see if there is a chance of getting one that works
2158	// (remember that a flags value of 0 means autodetection)	2670	// (remember that a flags value of 0 means autodetection)
2159	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2671	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2160	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2672	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2174	kqueue implementation). Store the kqueue/socket-only event loop in	2686	kqueue implementation). Store the kqueue/socket-only event loop in
2175	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2687	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2176		2688
2177	struct ev_loop *loop = ev_default_init (0);	2689	struct ev_loop *loop = ev_default_init (0);
2178	struct ev_loop *loop_socket = 0;	2690	struct ev_loop *loop_socket = 0;
2179	struct ev_embed embed;	2691	ev_embed embed;
2180		2692
2181	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2693	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2182	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2694	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2183	{	2695	{
2184	ev_embed_init (&embed, 0, loop_socket);	2696	ev_embed_init (&embed, 0, loop_socket);
…		…
2199	event loop blocks next and before C<ev_check> watchers are being called,	2711	event loop blocks next and before C<ev_check> watchers are being called,
2200	and only in the child after the fork. If whoever good citizen calling	2712	and only in the child after the fork. If whoever good citizen calling
2201	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2713	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2202	handlers will be invoked, too, of course.	2714	handlers will be invoked, too, of course.
2203		2715
		2716	=head3 The special problem of life after fork - how is it possible?
		2717
		2718	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2719	up/change the process environment, followed by a call to C<exec()>. This
		2720	sequence should be handled by libev without any problems.
		2721
		2722	This changes when the application actually wants to do event handling
		2723	in the child, or both parent in child, in effect "continuing" after the
		2724	fork.
		2725
		2726	The default mode of operation (for libev, with application help to detect
		2727	forks) is to duplicate all the state in the child, as would be expected
		2728	when I<either> the parent I<or> the child process continues.
		2729
		2730	When both processes want to continue using libev, then this is usually the
		2731	wrong result. In that case, usually one process (typically the parent) is
		2732	supposed to continue with all watchers in place as before, while the other
		2733	process typically wants to start fresh, i.e. without any active watchers.
		2734
		2735	The cleanest and most efficient way to achieve that with libev is to
		2736	simply create a new event loop, which of course will be "empty", and
		2737	use that for new watchers. This has the advantage of not touching more
		2738	memory than necessary, and thus avoiding the copy-on-write, and the
		2739	disadvantage of having to use multiple event loops (which do not support
		2740	signal watchers).
		2741
		2742	When this is not possible, or you want to use the default loop for
		2743	other reasons, then in the process that wants to start "fresh", call
		2744	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2745	the default loop will "orphan" (not stop) all registered watchers, so you
		2746	have to be careful not to execute code that modifies those watchers. Note
		2747	also that in that case, you have to re-register any signal watchers.
		2748
2204	=head3 Watcher-Specific Functions and Data Members	2749	=head3 Watcher-Specific Functions and Data Members
2205		2750
2206	=over 4	2751	=over 4
2207		2752
2208	=item ev_fork_init (ev_signal *, callback)	2753	=item ev_fork_init (ev_signal *, callback)
…		…
2240	is that the author does not know of a simple (or any) algorithm for a	2785	is that the author does not know of a simple (or any) algorithm for a
2241	multiple-writer-single-reader queue that works in all cases and doesn't	2786	multiple-writer-single-reader queue that works in all cases and doesn't
2242	need elaborate support such as pthreads.	2787	need elaborate support such as pthreads.
2243		2788
2244	That means that if you want to queue data, you have to provide your own	2789	That means that if you want to queue data, you have to provide your own
2245	queue. But at least I can tell you would implement locking around your	2790	queue. But at least I can tell you how to implement locking around your
2246	queue:	2791	queue:
2247		2792
2248	=over 4	2793	=over 4
2249		2794
2250	=item queueing from a signal handler context	2795	=item queueing from a signal handler context
2251		2796
2252	To implement race-free queueing, you simply add to the queue in the signal	2797	To implement race-free queueing, you simply add to the queue in the signal
2253	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2798	handler but you block the signal handler in the watcher callback. Here is
2254	some fictitious SIGUSR1 handler:	2799	an example that does that for some fictitious SIGUSR1 handler:
2255		2800
2256	static ev_async mysig;	2801	static ev_async mysig;
2257		2802
2258	static void	2803	static void
2259	sigusr1_handler (void)	2804	sigusr1_handler (void)
…		…
2325	=over 4	2870	=over 4
2326		2871
2327	=item ev_async_init (ev_async *, callback)	2872	=item ev_async_init (ev_async *, callback)
2328		2873
2329	Initialises and configures the async watcher - it has no parameters of any	2874	Initialises and configures the async watcher - it has no parameters of any
2330	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2875	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2331	believe me.	2876	trust me.
2332		2877
2333	=item ev_async_send (loop, ev_async *)	2878	=item ev_async_send (loop, ev_async *)
2334		2879
2335	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2880	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2336	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2881	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2337	C<ev_feed_event>, this call is safe to do in other threads, signal or	2882	C<ev_feed_event>, this call is safe to do from other threads, signal or
2338	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	2883	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2339	section below on what exactly this means).	2884	section below on what exactly this means).
2340		2885
		2886	Note that, as with other watchers in libev, multiple events might get
		2887	compressed into a single callback invocation (another way to look at this
		2888	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		2889	reset when the event loop detects that).
		2890
2341	This call incurs the overhead of a system call only once per loop iteration,	2891	This call incurs the overhead of a system call only once per event loop
2342	so while the overhead might be noticeable, it doesn't apply to repeated	2892	iteration, so while the overhead might be noticeable, it doesn't apply to
2343	calls to C<ev_async_send>.	2893	repeated calls to C<ev_async_send> for the same event loop.
2344		2894
2345	=item bool = ev_async_pending (ev_async *)	2895	=item bool = ev_async_pending (ev_async *)
2346		2896
2347	Returns a non-zero value when C<ev_async_send> has been called on the	2897	Returns a non-zero value when C<ev_async_send> has been called on the
2348	watcher but the event has not yet been processed (or even noted) by the	2898	watcher but the event has not yet been processed (or even noted) by the
…		…
2351	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	2901	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2352	the loop iterates next and checks for the watcher to have become active,	2902	the loop iterates next and checks for the watcher to have become active,
2353	it will reset the flag again. C<ev_async_pending> can be used to very	2903	it will reset the flag again. C<ev_async_pending> can be used to very
2354	quickly check whether invoking the loop might be a good idea.	2904	quickly check whether invoking the loop might be a good idea.
2355		2905
2356	Not that this does I<not> check whether the watcher itself is pending, only	2906	Not that this does I<not> check whether the watcher itself is pending,
2357	whether it has been requested to make this watcher pending.	2907	only whether it has been requested to make this watcher pending: there
		2908	is a time window between the event loop checking and resetting the async
		2909	notification, and the callback being invoked.
2358		2910
2359	=back	2911	=back
2360		2912
2361		2913
2362	=head1 OTHER FUNCTIONS	2914	=head1 OTHER FUNCTIONS
…		…
2366	=over 4	2918	=over 4
2367		2919
2368	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2920	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2369		2921
2370	This function combines a simple timer and an I/O watcher, calls your	2922	This function combines a simple timer and an I/O watcher, calls your
2371	callback on whichever event happens first and automatically stop both	2923	callback on whichever event happens first and automatically stops both
2372	watchers. This is useful if you want to wait for a single event on an fd	2924	watchers. This is useful if you want to wait for a single event on an fd
2373	or timeout without having to allocate/configure/start/stop/free one or	2925	or timeout without having to allocate/configure/start/stop/free one or
2374	more watchers yourself.	2926	more watchers yourself.
2375		2927
2376	If C<fd> is less than 0, then no I/O watcher will be started and events	2928	If C<fd> is less than 0, then no I/O watcher will be started and the
2377	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2929	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2378	C<events> set will be created and started.	2930	the given C<fd> and C<events> set will be created and started.
2379		2931
2380	If C<timeout> is less than 0, then no timeout watcher will be	2932	If C<timeout> is less than 0, then no timeout watcher will be
2381	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2933	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2382	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2934	repeat = 0) will be started. C<0> is a valid timeout.
2383	dubious value.
2384		2935
2385	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2936	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2386	passed an C<revents> set like normal event callbacks (a combination of	2937	passed an C<revents> set like normal event callbacks (a combination of
2387	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2938	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2388	value passed to C<ev_once>:	2939	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2940	a timeout and an io event at the same time - you probably should give io
		2941	events precedence.
		2942
		2943	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2389		2944
2390	static void stdin_ready (int revents, void *arg)	2945	static void stdin_ready (int revents, void *arg)
2391	{	2946	{
		2947	if (revents & EV_READ)
		2948	/* stdin might have data for us, joy! */;
2392	if (revents & EV_TIMEOUT)	2949	else if (revents & EV_TIMEOUT)
2393	/* doh, nothing entered */;	2950	/* doh, nothing entered */;
2394	else if (revents & EV_READ)
2395	/* stdin might have data for us, joy! */;
2396	}	2951	}
2397		2952
2398	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2953	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2399		2954
2400	=item ev_feed_event (ev_loop *, watcher *, int revents)	2955	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2401		2956
2402	Feeds the given event set into the event loop, as if the specified event	2957	Feeds the given event set into the event loop, as if the specified event
2403	had happened for the specified watcher (which must be a pointer to an	2958	had happened for the specified watcher (which must be a pointer to an
2404	initialised but not necessarily started event watcher).	2959	initialised but not necessarily started event watcher).
2405		2960
2406	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2961	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2407		2962
2408	Feed an event on the given fd, as if a file descriptor backend detected	2963	Feed an event on the given fd, as if a file descriptor backend detected
2409	the given events it.	2964	the given events it.
2410		2965
2411	=item ev_feed_signal_event (ev_loop *loop, int signum)	2966	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2412		2967
2413	Feed an event as if the given signal occurred (C<loop> must be the default	2968	Feed an event as if the given signal occurred (C<loop> must be the default
2414	loop!).	2969	loop!).
2415		2970
2416	=back	2971	=back
…		…
2538		3093
2539	myclass obj;	3094	myclass obj;
2540	ev::io iow;	3095	ev::io iow;
2541	iow.set <myclass, &myclass::io_cb> (&obj);	3096	iow.set <myclass, &myclass::io_cb> (&obj);
2542		3097
		3098	=item w->set (object *)
		3099
		3100	This is an B<experimental> feature that might go away in a future version.
		3101
		3102	This is a variation of a method callback - leaving out the method to call
		3103	will default the method to C<operator ()>, which makes it possible to use
		3104	functor objects without having to manually specify the C<operator ()> all
		3105	the time. Incidentally, you can then also leave out the template argument
		3106	list.
		3107
		3108	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3109	int revents)>.
		3110
		3111	See the method-C<set> above for more details.
		3112
		3113	Example: use a functor object as callback.
		3114
		3115	struct myfunctor
		3116	{
		3117	void operator() (ev::io &w, int revents)
		3118	{
		3119	...
		3120	}
		3121	}
		3122
		3123	myfunctor f;
		3124
		3125	ev::io w;
		3126	w.set (&f);
		3127
2543	=item w->set<function> (void *data = 0)	3128	=item w->set<function> (void *data = 0)
2544		3129
2545	Also sets a callback, but uses a static method or plain function as	3130	Also sets a callback, but uses a static method or plain function as
2546	callback. The optional C<data> argument will be stored in the watcher's	3131	callback. The optional C<data> argument will be stored in the watcher's
2547	C<data> member and is free for you to use.	3132	C<data> member and is free for you to use.
2548		3133
2549	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3134	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2550		3135
2551	See the method-C<set> above for more details.	3136	See the method-C<set> above for more details.
2552		3137
2553	Example:	3138	Example: Use a plain function as callback.
2554		3139
2555	static void io_cb (ev::io &w, int revents) { }	3140	static void io_cb (ev::io &w, int revents) { }
2556	iow.set <io_cb> ();	3141	iow.set <io_cb> ();
2557		3142
2558	=item w->set (struct ev_loop *)	3143	=item w->set (struct ev_loop *)
…		…
2596	Example: Define a class with an IO and idle watcher, start one of them in	3181	Example: Define a class with an IO and idle watcher, start one of them in
2597	the constructor.	3182	the constructor.
2598		3183
2599	class myclass	3184	class myclass
2600	{	3185	{
2601	ev::io io; void io_cb (ev::io &w, int revents);	3186	ev::io io ; void io_cb (ev::io &w, int revents);
2602	ev:idle idle void idle_cb (ev::idle &w, int revents);	3187	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2603		3188
2604	myclass (int fd)	3189	myclass (int fd)
2605	{	3190	{
2606	io .set <myclass, &myclass::io_cb > (this);	3191	io .set <myclass, &myclass::io_cb > (this);
2607	idle.set <myclass, &myclass::idle_cb> (this);	3192	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2623	=item Perl	3208	=item Perl
2624		3209
2625	The EV module implements the full libev API and is actually used to test	3210	The EV module implements the full libev API and is actually used to test
2626	libev. EV is developed together with libev. Apart from the EV core module,	3211	libev. EV is developed together with libev. Apart from the EV core module,
2627	there are additional modules that implement libev-compatible interfaces	3212	there are additional modules that implement libev-compatible interfaces
2628	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3213	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2629	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3214	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3215	and C<EV::Glib>).
2630		3216
2631	It can be found and installed via CPAN, its homepage is found at	3217	It can be found and installed via CPAN, its homepage is at
2632	L<http://software.schmorp.de/pkg/EV>.	3218	L<http://software.schmorp.de/pkg/EV>.
		3219
		3220	=item Python
		3221
		3222	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		3223	seems to be quite complete and well-documented.
2633		3224
2634	=item Ruby	3225	=item Ruby
2635		3226
2636	Tony Arcieri has written a ruby extension that offers access to a subset	3227	Tony Arcieri has written a ruby extension that offers access to a subset
2637	of the libev API and adds file handle abstractions, asynchronous DNS and	3228	of the libev API and adds file handle abstractions, asynchronous DNS and
2638	more on top of it. It can be found via gem servers. Its homepage is at	3229	more on top of it. It can be found via gem servers. Its homepage is at
2639	L<http://rev.rubyforge.org/>.	3230	L<http://rev.rubyforge.org/>.
2640		3231
		3232	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3233	makes rev work even on mingw.
		3234
		3235	=item Haskell
		3236
		3237	A haskell binding to libev is available at
		3238	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3239
2641	=item D	3240	=item D
2642		3241
2643	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3242	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2644	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	3243	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3244
		3245	=item Ocaml
		3246
		3247	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3248	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2645		3249
2646	=back	3250	=back
2647		3251
2648		3252
2649	=head1 MACRO MAGIC	3253	=head1 MACRO MAGIC
…		…
2750		3354
2751	#define EV_STANDALONE 1	3355	#define EV_STANDALONE 1
2752	#include "ev.h"	3356	#include "ev.h"
2753		3357
2754	Both header files and implementation files can be compiled with a C++	3358	Both header files and implementation files can be compiled with a C++
2755	compiler (at least, thats a stated goal, and breakage will be treated	3359	compiler (at least, that's a stated goal, and breakage will be treated
2756	as a bug).	3360	as a bug).
2757		3361
2758	You need the following files in your source tree, or in a directory	3362	You need the following files in your source tree, or in a directory
2759	in your include path (e.g. in libev/ when using -Ilibev):	3363	in your include path (e.g. in libev/ when using -Ilibev):
2760		3364
…		…
2804		3408
2805	=head2 PREPROCESSOR SYMBOLS/MACROS	3409	=head2 PREPROCESSOR SYMBOLS/MACROS
2806		3410
2807	Libev can be configured via a variety of preprocessor symbols you have to	3411	Libev can be configured via a variety of preprocessor symbols you have to
2808	define before including any of its files. The default in the absence of	3412	define before including any of its files. The default in the absence of
2809	autoconf is noted for every option.	3413	autoconf is documented for every option.
2810		3414
2811	=over 4	3415	=over 4
2812		3416
2813	=item EV_STANDALONE	3417	=item EV_STANDALONE
2814		3418
…		…
2816	keeps libev from including F<config.h>, and it also defines dummy	3420	keeps libev from including F<config.h>, and it also defines dummy
2817	implementations for some libevent functions (such as logging, which is not	3421	implementations for some libevent functions (such as logging, which is not
2818	supported). It will also not define any of the structs usually found in	3422	supported). It will also not define any of the structs usually found in
2819	F<event.h> that are not directly supported by the libev core alone.	3423	F<event.h> that are not directly supported by the libev core alone.
2820		3424
		3425	In stanbdalone mode, libev will still try to automatically deduce the
		3426	configuration, but has to be more conservative.
		3427
2821	=item EV_USE_MONOTONIC	3428	=item EV_USE_MONOTONIC
2822		3429
2823	If defined to be C<1>, libev will try to detect the availability of the	3430	If defined to be C<1>, libev will try to detect the availability of the
2824	monotonic clock option at both compile time and runtime. Otherwise no use	3431	monotonic clock option at both compile time and runtime. Otherwise no
2825	of the monotonic clock option will be attempted. If you enable this, you	3432	use of the monotonic clock option will be attempted. If you enable this,
2826	usually have to link against librt or something similar. Enabling it when	3433	you usually have to link against librt or something similar. Enabling it
2827	the functionality isn't available is safe, though, although you have	3434	when the functionality isn't available is safe, though, although you have
2828	to make sure you link against any libraries where the C<clock_gettime>	3435	to make sure you link against any libraries where the C<clock_gettime>
2829	function is hiding in (often F<-lrt>).	3436	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2830		3437
2831	=item EV_USE_REALTIME	3438	=item EV_USE_REALTIME
2832		3439
2833	If defined to be C<1>, libev will try to detect the availability of the	3440	If defined to be C<1>, libev will try to detect the availability of the
2834	real-time clock option at compile time (and assume its availability at	3441	real-time clock option at compile time (and assume its availability
2835	runtime if successful). Otherwise no use of the real-time clock option will	3442	at runtime if successful). Otherwise no use of the real-time clock
2836	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3443	option will be attempted. This effectively replaces C<gettimeofday>
2837	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3444	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2838	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3445	correctness. See the note about libraries in the description of
		3446	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3447	C<EV_USE_CLOCK_SYSCALL>.
		3448
		3449	=item EV_USE_CLOCK_SYSCALL
		3450
		3451	If defined to be C<1>, libev will try to use a direct syscall instead
		3452	of calling the system-provided C<clock_gettime> function. This option
		3453	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3454	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3455	programs needlessly. Using a direct syscall is slightly slower (in
		3456	theory), because no optimised vdso implementation can be used, but avoids
		3457	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3458	higher, as it simplifies linking (no need for C<-lrt>).
2839		3459
2840	=item EV_USE_NANOSLEEP	3460	=item EV_USE_NANOSLEEP
2841		3461
2842	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3462	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2843	and will use it for delays. Otherwise it will use C<select ()>.	3463	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2859		3479
2860	=item EV_SELECT_USE_FD_SET	3480	=item EV_SELECT_USE_FD_SET
2861		3481
2862	If defined to C<1>, then the select backend will use the system C<fd_set>	3482	If defined to C<1>, then the select backend will use the system C<fd_set>
2863	structure. This is useful if libev doesn't compile due to a missing	3483	structure. This is useful if libev doesn't compile due to a missing
2864	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3484	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2865	exotic systems. This usually limits the range of file descriptors to some	3485	on exotic systems. This usually limits the range of file descriptors to
2866	low limit such as 1024 or might have other limitations (winsocket only	3486	some low limit such as 1024 or might have other limitations (winsocket
2867	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3487	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2868	influence the size of the C<fd_set> used.	3488	configures the maximum size of the C<fd_set>.
2869		3489
2870	=item EV_SELECT_IS_WINSOCKET	3490	=item EV_SELECT_IS_WINSOCKET
2871		3491
2872	When defined to C<1>, the select backend will assume that	3492	When defined to C<1>, the select backend will assume that
2873	select/socket/connect etc. don't understand file descriptors but	3493	select/socket/connect etc. don't understand file descriptors but
…		…
2984	When doing priority-based operations, libev usually has to linearly search	3604	When doing priority-based operations, libev usually has to linearly search
2985	all the priorities, so having many of them (hundreds) uses a lot of space	3605	all the priorities, so having many of them (hundreds) uses a lot of space
2986	and time, so using the defaults of five priorities (-2 .. +2) is usually	3606	and time, so using the defaults of five priorities (-2 .. +2) is usually
2987	fine.	3607	fine.
2988		3608
2989	If your embedding application does not need any priorities, defining these both to	3609	If your embedding application does not need any priorities, defining these
2990	C<0> will save some memory and CPU.	3610	both to C<0> will save some memory and CPU.
2991		3611
2992	=item EV_PERIODIC_ENABLE	3612	=item EV_PERIODIC_ENABLE
2993		3613
2994	If undefined or defined to be C<1>, then periodic timers are supported. If	3614	If undefined or defined to be C<1>, then periodic timers are supported. If
2995	defined to be C<0>, then they are not. Disabling them saves a few kB of	3615	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3002	code.	3622	code.
3003		3623
3004	=item EV_EMBED_ENABLE	3624	=item EV_EMBED_ENABLE
3005		3625
3006	If undefined or defined to be C<1>, then embed watchers are supported. If	3626	If undefined or defined to be C<1>, then embed watchers are supported. If
3007	defined to be C<0>, then they are not.	3627	defined to be C<0>, then they are not. Embed watchers rely on most other
		3628	watcher types, which therefore must not be disabled.
3008		3629
3009	=item EV_STAT_ENABLE	3630	=item EV_STAT_ENABLE
3010		3631
3011	If undefined or defined to be C<1>, then stat watchers are supported. If	3632	If undefined or defined to be C<1>, then stat watchers are supported. If
3012	defined to be C<0>, then they are not.	3633	defined to be C<0>, then they are not.
…		…
3044	two).	3665	two).
3045		3666
3046	=item EV_USE_4HEAP	3667	=item EV_USE_4HEAP
3047		3668
3048	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3669	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3049	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3670	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3050	to C<1>. The 4-heap uses more complicated (longer) code but has	3671	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3051	noticeably faster performance with many (thousands) of watchers.	3672	faster performance with many (thousands) of watchers.
3052		3673
3053	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3674	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3054	(disabled).	3675	(disabled).
3055		3676
3056	=item EV_HEAP_CACHE_AT	3677	=item EV_HEAP_CACHE_AT
3057		3678
3058	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3679	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3059	timer and periodics heap, libev can cache the timestamp (I<at>) within	3680	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3060	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3681	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3061	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3682	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3062	but avoids random read accesses on heap changes. This improves performance	3683	but avoids random read accesses on heap changes. This improves performance
3063	noticeably with with many (hundreds) of watchers.	3684	noticeably with many (hundreds) of watchers.
3064		3685
3065	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3686	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3066	(disabled).	3687	(disabled).
3067		3688
3068	=item EV_VERIFY	3689	=item EV_VERIFY
…		…
3074	called once per loop, which can slow down libev. If set to C<3>, then the	3695	called once per loop, which can slow down libev. If set to C<3>, then the
3075	verification code will be called very frequently, which will slow down	3696	verification code will be called very frequently, which will slow down
3076	libev considerably.	3697	libev considerably.
3077		3698
3078	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3699	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3079	C<0.>	3700	C<0>.
3080		3701
3081	=item EV_COMMON	3702	=item EV_COMMON
3082		3703
3083	By default, all watchers have a C<void *data> member. By redefining	3704	By default, all watchers have a C<void *data> member. By redefining
3084	this macro to a something else you can include more and other types of	3705	this macro to a something else you can include more and other types of
…		…
3101	and the way callbacks are invoked and set. Must expand to a struct member	3722	and the way callbacks are invoked and set. Must expand to a struct member
3102	definition and a statement, respectively. See the F<ev.h> header file for	3723	definition and a statement, respectively. See the F<ev.h> header file for
3103	their default definitions. One possible use for overriding these is to	3724	their default definitions. One possible use for overriding these is to
3104	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3725	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3105	method calls instead of plain function calls in C++.	3726	method calls instead of plain function calls in C++.
		3727
		3728	=back
3106		3729
3107	=head2 EXPORTED API SYMBOLS	3730	=head2 EXPORTED API SYMBOLS
3108		3731
3109	If you need to re-export the API (e.g. via a DLL) and you need a list of	3732	If you need to re-export the API (e.g. via a DLL) and you need a list of
3110	exported symbols, you can use the provided F<Symbol.*> files which list	3733	exported symbols, you can use the provided F<Symbol.*> files which list
…		…
3157	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3780	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3158		3781
3159	#include "ev_cpp.h"	3782	#include "ev_cpp.h"
3160	#include "ev.c"	3783	#include "ev.c"
3161		3784
		3785	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3162		3786
3163	=head1 THREADS AND COROUTINES	3787	=head2 THREADS AND COROUTINES
3164		3788
3165	=head2 THREADS	3789	=head3 THREADS
3166		3790
3167	Libev itself is completely thread-safe, but it uses no locking. This	3791	All libev functions are reentrant and thread-safe unless explicitly
		3792	documented otherwise, but libev implements no locking itself. This means
3168	means that you can use as many loops as you want in parallel, as long as	3793	that you can use as many loops as you want in parallel, as long as there
3169	only one thread ever calls into one libev function with the same loop	3794	are no concurrent calls into any libev function with the same loop
3170	parameter.	3795	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3796	of course): libev guarantees that different event loops share no data
		3797	structures that need any locking.
3171		3798
3172	Or put differently: calls with different loop parameters can be done in	3799	Or to put it differently: calls with different loop parameters can be done
3173	parallel from multiple threads, calls with the same loop parameter must be	3800	concurrently from multiple threads, calls with the same loop parameter
3174	done serially (but can be done from different threads, as long as only one	3801	must be done serially (but can be done from different threads, as long as
3175	thread ever is inside a call at any point in time, e.g. by using a mutex	3802	only one thread ever is inside a call at any point in time, e.g. by using
3176	per loop).	3803	a mutex per loop).
3177		3804
3178	If you want to know which design is best for your problem, then I cannot	3805	Specifically to support threads (and signal handlers), libev implements
		3806	so-called C<ev_async> watchers, which allow some limited form of
		3807	concurrency on the same event loop, namely waking it up "from the
		3808	outside".
		3809
		3810	If you want to know which design (one loop, locking, or multiple loops
		3811	without or something else still) is best for your problem, then I cannot
3179	help you but by giving some generic advice:	3812	help you, but here is some generic advice:
3180		3813
3181	=over 4	3814	=over 4
3182		3815
3183	=item * most applications have a main thread: use the default libev loop	3816	=item * most applications have a main thread: use the default libev loop
3184	in that thread, or create a separate thread running only the default loop.	3817	in that thread, or create a separate thread running only the default loop.
…		…
3196		3829
3197	Choosing a model is hard - look around, learn, know that usually you can do	3830	Choosing a model is hard - look around, learn, know that usually you can do
3198	better than you currently do :-)	3831	better than you currently do :-)
3199		3832
3200	=item * often you need to talk to some other thread which blocks in the	3833	=item * often you need to talk to some other thread which blocks in the
		3834	event loop.
		3835
3201	event loop - C<ev_async> watchers can be used to wake them up from other	3836	C<ev_async> watchers can be used to wake them up from other threads safely
3202	threads safely (or from signal contexts...).	3837	(or from signal contexts...).
		3838
		3839	An example use would be to communicate signals or other events that only
		3840	work in the default loop by registering the signal watcher with the
		3841	default loop and triggering an C<ev_async> watcher from the default loop
		3842	watcher callback into the event loop interested in the signal.
3203		3843
3204	=back	3844	=back
3205		3845
3206	=head2 COROUTINES	3846	=head3 COROUTINES
3207		3847
3208	Libev is much more accommodating to coroutines ("cooperative threads"):	3848	Libev is very accommodating to coroutines ("cooperative threads"):
3209	libev fully supports nesting calls to it's functions from different	3849	libev fully supports nesting calls to its functions from different
3210	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3850	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3211	different coroutines and switch freely between both coroutines running the	3851	different coroutines, and switch freely between both coroutines running the
3212	loop, as long as you don't confuse yourself). The only exception is that	3852	loop, as long as you don't confuse yourself). The only exception is that
3213	you must not do this from C<ev_periodic> reschedule callbacks.	3853	you must not do this from C<ev_periodic> reschedule callbacks.
3214		3854
3215	Care has been invested into making sure that libev does not keep local	3855	Care has been taken to ensure that libev does not keep local state inside
3216	state inside C<ev_loop>, and other calls do not usually allow coroutine	3856	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3217	switches.	3857	they do not call any callbacks.
3218		3858
		3859	=head2 COMPILER WARNINGS
3219		3860
3220	=head1 COMPLEXITIES	3861	Depending on your compiler and compiler settings, you might get no or a
		3862	lot of warnings when compiling libev code. Some people are apparently
		3863	scared by this.
3221		3864
3222	In this section the complexities of (many of) the algorithms used inside	3865	However, these are unavoidable for many reasons. For one, each compiler
3223	libev will be explained. For complexity discussions about backends see the	3866	has different warnings, and each user has different tastes regarding
3224	documentation for C<ev_default_init>.	3867	warning options. "Warn-free" code therefore cannot be a goal except when
		3868	targeting a specific compiler and compiler-version.
3225		3869
3226	All of the following are about amortised time: If an array needs to be	3870	Another reason is that some compiler warnings require elaborate
3227	extended, libev needs to realloc and move the whole array, but this	3871	workarounds, or other changes to the code that make it less clear and less
3228	happens asymptotically never with higher number of elements, so O(1) might	3872	maintainable.
3229	mean it might do a lengthy realloc operation in rare cases, but on average
3230	it is much faster and asymptotically approaches constant time.
3231		3873
3232	=over 4	3874	And of course, some compiler warnings are just plain stupid, or simply
		3875	wrong (because they don't actually warn about the condition their message
		3876	seems to warn about). For example, certain older gcc versions had some
		3877	warnings that resulted an extreme number of false positives. These have
		3878	been fixed, but some people still insist on making code warn-free with
		3879	such buggy versions.
3233		3880
3234	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3881	While libev is written to generate as few warnings as possible,
		3882	"warn-free" code is not a goal, and it is recommended not to build libev
		3883	with any compiler warnings enabled unless you are prepared to cope with
		3884	them (e.g. by ignoring them). Remember that warnings are just that:
		3885	warnings, not errors, or proof of bugs.
3235		3886
3236	This means that, when you have a watcher that triggers in one hour and
3237	there are 100 watchers that would trigger before that then inserting will
3238	have to skip roughly seven (C<ld 100>) of these watchers.
3239		3887
3240	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3888	=head2 VALGRIND
3241		3889
3242	That means that changing a timer costs less than removing/adding them	3890	Valgrind has a special section here because it is a popular tool that is
3243	as only the relative motion in the event queue has to be paid for.	3891	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3244		3892
3245	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3893	If you think you found a bug (memory leak, uninitialised data access etc.)
		3894	in libev, then check twice: If valgrind reports something like:
3246		3895
3247	These just add the watcher into an array or at the head of a list.	3896	==2274== definitely lost: 0 bytes in 0 blocks.
		3897	==2274== possibly lost: 0 bytes in 0 blocks.
		3898	==2274== still reachable: 256 bytes in 1 blocks.
3248		3899
3249	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3900	Then there is no memory leak, just as memory accounted to global variables
		3901	is not a memleak - the memory is still being referenced, and didn't leak.
3250		3902
3251	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3903	Similarly, under some circumstances, valgrind might report kernel bugs
		3904	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3905	although an acceptable workaround has been found here), or it might be
		3906	confused.
3252		3907
3253	These watchers are stored in lists then need to be walked to find the	3908	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3254	correct watcher to remove. The lists are usually short (you don't usually	3909	make it into some kind of religion.
3255	have many watchers waiting for the same fd or signal).
3256		3910
3257	=item Finding the next timer in each loop iteration: O(1)	3911	If you are unsure about something, feel free to contact the mailing list
		3912	with the full valgrind report and an explanation on why you think this
		3913	is a bug in libev (best check the archives, too :). However, don't be
		3914	annoyed when you get a brisk "this is no bug" answer and take the chance
		3915	of learning how to interpret valgrind properly.
3258		3916
3259	By virtue of using a binary or 4-heap, the next timer is always found at a	3917	If you need, for some reason, empty reports from valgrind for your project
3260	fixed position in the storage array.	3918	I suggest using suppression lists.
3261		3919
3262	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3263		3920
3264	A change means an I/O watcher gets started or stopped, which requires	3921	=head1 PORTABILITY NOTES
3265	libev to recalculate its status (and possibly tell the kernel, depending
3266	on backend and whether C<ev_io_set> was used).
3267		3922
3268	=item Activating one watcher (putting it into the pending state): O(1)
3269
3270	=item Priority handling: O(number_of_priorities)
3271
3272	Priorities are implemented by allocating some space for each
3273	priority. When doing priority-based operations, libev usually has to
3274	linearly search all the priorities, but starting/stopping and activating
3275	watchers becomes O(1) w.r.t. priority handling.
3276
3277	=item Sending an ev_async: O(1)
3278
3279	=item Processing ev_async_send: O(number_of_async_watchers)
3280
3281	=item Processing signals: O(max_signal_number)
3282
3283	Sending involves a system call I<iff> there were no other C<ev_async_send>
3284	calls in the current loop iteration. Checking for async and signal events
3285	involves iterating over all running async watchers or all signal numbers.
3286
3287	=back
3288
3289
3290	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	3923	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3291		3924
3292	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3925	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3293	requires, and its I/O model is fundamentally incompatible with the POSIX	3926	requires, and its I/O model is fundamentally incompatible with the POSIX
3294	model. Libev still offers limited functionality on this platform in	3927	model. Libev still offers limited functionality on this platform in
3295	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3928	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3302	way (note also that glib is the slowest event library known to man).	3935	way (note also that glib is the slowest event library known to man).
3303		3936
3304	There is no supported compilation method available on windows except	3937	There is no supported compilation method available on windows except
3305	embedding it into other applications.	3938	embedding it into other applications.
3306		3939
		3940	Sensible signal handling is officially unsupported by Microsoft - libev
		3941	tries its best, but under most conditions, signals will simply not work.
		3942
3307	Not a libev limitation but worth mentioning: windows apparently doesn't	3943	Not a libev limitation but worth mentioning: windows apparently doesn't
3308	accept large writes: instead of resulting in a partial write, windows will	3944	accept large writes: instead of resulting in a partial write, windows will
3309	either accept everything or return C<ENOBUFS> if the buffer is too large,	3945	either accept everything or return C<ENOBUFS> if the buffer is too large,
3310	so make sure you only write small amounts into your sockets (less than a	3946	so make sure you only write small amounts into your sockets (less than a
3311	megabyte seems safe, but thsi apparently depends on the amount of memory	3947	megabyte seems safe, but this apparently depends on the amount of memory
3312	available).	3948	available).
3313		3949
3314	Due to the many, low, and arbitrary limits on the win32 platform and	3950	Due to the many, low, and arbitrary limits on the win32 platform and
3315	the abysmal performance of winsockets, using a large number of sockets	3951	the abysmal performance of winsockets, using a large number of sockets
3316	is not recommended (and not reasonable). If your program needs to use	3952	is not recommended (and not reasonable). If your program needs to use
3317	more than a hundred or so sockets, then likely it needs to use a totally	3953	more than a hundred or so sockets, then likely it needs to use a totally
3318	different implementation for windows, as libev offers the POSIX readiness	3954	different implementation for windows, as libev offers the POSIX readiness
3319	notification model, which cannot be implemented efficiently on windows	3955	notification model, which cannot be implemented efficiently on windows
3320	(Microsoft monopoly games).	3956	(due to Microsoft monopoly games).
		3957
		3958	A typical way to use libev under windows is to embed it (see the embedding
		3959	section for details) and use the following F<evwrap.h> header file instead
		3960	of F<ev.h>:
		3961
		3962	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3963	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3964
		3965	#include "ev.h"
		3966
		3967	And compile the following F<evwrap.c> file into your project (make sure
		3968	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3969
		3970	#include "evwrap.h"
		3971	#include "ev.c"
3321		3972
3322	=over 4	3973	=over 4
3323		3974
3324	=item The winsocket select function	3975	=item The winsocket select function
3325		3976
3326	The winsocket C<select> function doesn't follow POSIX in that it	3977	The winsocket C<select> function doesn't follow POSIX in that it
3327	requires socket I<handles> and not socket I<file descriptors> (it is	3978	requires socket I<handles> and not socket I<file descriptors> (it is
3328	also extremely buggy). This makes select very inefficient, and also	3979	also extremely buggy). This makes select very inefficient, and also
3329	requires a mapping from file descriptors to socket handles. See the	3980	requires a mapping from file descriptors to socket handles (the Microsoft
		3981	C runtime provides the function C<_open_osfhandle> for this). See the
3330	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and	3982	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
3331	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.	3983	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3332		3984
3333	The configuration for a "naked" win32 using the Microsoft runtime	3985	The configuration for a "naked" win32 using the Microsoft runtime
3334	libraries and raw winsocket select is:	3986	libraries and raw winsocket select is:
…		…
3345		3997
3346	Early versions of winsocket's select only supported waiting for a maximum	3998	Early versions of winsocket's select only supported waiting for a maximum
3347	of C<64> handles (probably owning to the fact that all windows kernels	3999	of C<64> handles (probably owning to the fact that all windows kernels
3348	can only wait for C<64> things at the same time internally; Microsoft	4000	can only wait for C<64> things at the same time internally; Microsoft
3349	recommends spawning a chain of threads and wait for 63 handles and the	4001	recommends spawning a chain of threads and wait for 63 handles and the
3350	previous thread in each. Great).	4002	previous thread in each. Sounds great!).
3351		4003
3352	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4004	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3353	to some high number (e.g. C<2048>) before compiling the winsocket select	4005	to some high number (e.g. C<2048>) before compiling the winsocket select
3354	call (which might be in libev or elsewhere, for example, perl does its own	4006	call (which might be in libev or elsewhere, for example, perl and many
3355	select emulation on windows).	4007	other interpreters do their own select emulation on windows).
3356		4008
3357	Another limit is the number of file descriptors in the Microsoft runtime	4009	Another limit is the number of file descriptors in the Microsoft runtime
3358	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4010	libraries, which by default is C<64> (there must be a hidden I<64>
3359	or something like this inside Microsoft). You can increase this by calling	4011	fetish or something like this inside Microsoft). You can increase this
3360	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4012	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3361	arbitrary limit), but is broken in many versions of the Microsoft runtime	4013	(another arbitrary limit), but is broken in many versions of the Microsoft
3362	libraries.
3363
3364	This might get you to about C<512> or C<2048> sockets (depending on	4014	runtime libraries. This might get you to about C<512> or C<2048> sockets
3365	windows version and/or the phase of the moon). To get more, you need to	4015	(depending on windows version and/or the phase of the moon). To get more,
3366	wrap all I/O functions and provide your own fd management, but the cost of	4016	you need to wrap all I/O functions and provide your own fd management, but
3367	calling select (O(n²)) will likely make this unworkable.	4017	the cost of calling select (O(n²)) will likely make this unworkable.
3368		4018
3369	=back	4019	=back
3370		4020
3371
3372	=head1 PORTABILITY REQUIREMENTS	4021	=head2 PORTABILITY REQUIREMENTS
3373		4022
3374	In addition to a working ISO-C implementation, libev relies on a few	4023	In addition to a working ISO-C implementation and of course the
3375	additional extensions:	4024	backend-specific APIs, libev relies on a few additional extensions:
3376		4025
3377	=over 4	4026	=over 4
3378		4027
3379	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	4028	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3380	calling conventions regardless of C<ev_watcher_type *>.	4029	calling conventions regardless of C<ev_watcher_type *>.
…		…
3386	calls them using an C<ev_watcher *> internally.	4035	calls them using an C<ev_watcher *> internally.
3387		4036
3388	=item C<sig_atomic_t volatile> must be thread-atomic as well	4037	=item C<sig_atomic_t volatile> must be thread-atomic as well
3389		4038
3390	The type C<sig_atomic_t volatile> (or whatever is defined as	4039	The type C<sig_atomic_t volatile> (or whatever is defined as
3391	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	4040	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3392	threads. This is not part of the specification for C<sig_atomic_t>, but is	4041	threads. This is not part of the specification for C<sig_atomic_t>, but is
3393	believed to be sufficiently portable.	4042	believed to be sufficiently portable.
3394		4043
3395	=item C<sigprocmask> must work in a threaded environment	4044	=item C<sigprocmask> must work in a threaded environment
3396		4045
…		…
3405	except the initial one, and run the default loop in the initial thread as	4054	except the initial one, and run the default loop in the initial thread as
3406	well.	4055	well.
3407		4056
3408	=item C<long> must be large enough for common memory allocation sizes	4057	=item C<long> must be large enough for common memory allocation sizes
3409		4058
3410	To improve portability and simplify using libev, libev uses C<long>	4059	To improve portability and simplify its API, libev uses C<long> internally
3411	internally instead of C<size_t> when allocating its data structures. On	4060	instead of C<size_t> when allocating its data structures. On non-POSIX
3412	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4061	systems (Microsoft...) this might be unexpectedly low, but is still at
3413	is still at least 31 bits everywhere, which is enough for hundreds of	4062	least 31 bits everywhere, which is enough for hundreds of millions of
3414	millions of watchers.	4063	watchers.
3415		4064
3416	=item C<double> must hold a time value in seconds with enough accuracy	4065	=item C<double> must hold a time value in seconds with enough accuracy
3417		4066
3418	The type C<double> is used to represent timestamps. It is required to	4067	The type C<double> is used to represent timestamps. It is required to
3419	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4068	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3423	=back	4072	=back
3424		4073
3425	If you know of other additional requirements drop me a note.	4074	If you know of other additional requirements drop me a note.
3426		4075
3427		4076
3428	=head1 COMPILER WARNINGS	4077	=head1 ALGORITHMIC COMPLEXITIES
3429		4078
3430	Depending on your compiler and compiler settings, you might get no or a	4079	In this section the complexities of (many of) the algorithms used inside
3431	lot of warnings when compiling libev code. Some people are apparently	4080	libev will be documented. For complexity discussions about backends see
3432	scared by this.	4081	the documentation for C<ev_default_init>.
3433		4082
3434	However, these are unavoidable for many reasons. For one, each compiler	4083	All of the following are about amortised time: If an array needs to be
3435	has different warnings, and each user has different tastes regarding	4084	extended, libev needs to realloc and move the whole array, but this
3436	warning options. "Warn-free" code therefore cannot be a goal except when	4085	happens asymptotically rarer with higher number of elements, so O(1) might
3437	targeting a specific compiler and compiler-version.	4086	mean that libev does a lengthy realloc operation in rare cases, but on
		4087	average it is much faster and asymptotically approaches constant time.
3438		4088
3439	Another reason is that some compiler warnings require elaborate	4089	=over 4
3440	workarounds, or other changes to the code that make it less clear and less
3441	maintainable.
3442		4090
3443	And of course, some compiler warnings are just plain stupid, or simply	4091	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3444	wrong (because they don't actually warn about the condition their message
3445	seems to warn about).
3446		4092
3447	While libev is written to generate as few warnings as possible,	4093	This means that, when you have a watcher that triggers in one hour and
3448	"warn-free" code is not a goal, and it is recommended not to build libev	4094	there are 100 watchers that would trigger before that, then inserting will
3449	with any compiler warnings enabled unless you are prepared to cope with	4095	have to skip roughly seven (C<ld 100>) of these watchers.
3450	them (e.g. by ignoring them). Remember that warnings are just that:
3451	warnings, not errors, or proof of bugs.
3452		4096
		4097	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3453		4098
3454	=head1 VALGRIND	4099	That means that changing a timer costs less than removing/adding them,
		4100	as only the relative motion in the event queue has to be paid for.
3455		4101
3456	Valgrind has a special section here because it is a popular tool that is	4102	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3457	highly useful, but valgrind reports are very hard to interpret.
3458		4103
3459	If you think you found a bug (memory leak, uninitialised data access etc.)	4104	These just add the watcher into an array or at the head of a list.
3460	in libev, then check twice: If valgrind reports something like:
3461		4105
3462	==2274== definitely lost: 0 bytes in 0 blocks.	4106	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3463	==2274== possibly lost: 0 bytes in 0 blocks.
3464	==2274== still reachable: 256 bytes in 1 blocks.
3465		4107
3466	Then there is no memory leak. Similarly, under some circumstances,	4108	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3467	valgrind might report kernel bugs as if it were a bug in libev, or it
3468	might be confused (it is a very good tool, but only a tool).
3469		4109
3470	If you are unsure about something, feel free to contact the mailing list	4110	These watchers are stored in lists, so they need to be walked to find the
3471	with the full valgrind report and an explanation on why you think this is	4111	correct watcher to remove. The lists are usually short (you don't usually
3472	a bug in libev. However, don't be annoyed when you get a brisk "this is	4112	have many watchers waiting for the same fd or signal: one is typical, two
3473	no bug" answer and take the chance of learning how to interpret valgrind	4113	is rare).
3474	properly.
3475		4114
3476	If you need, for some reason, empty reports from valgrind for your project	4115	=item Finding the next timer in each loop iteration: O(1)
3477	I suggest using suppression lists.
3478		4116
		4117	By virtue of using a binary or 4-heap, the next timer is always found at a
		4118	fixed position in the storage array.
		4119
		4120	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4121
		4122	A change means an I/O watcher gets started or stopped, which requires
		4123	libev to recalculate its status (and possibly tell the kernel, depending
		4124	on backend and whether C<ev_io_set> was used).
		4125
		4126	=item Activating one watcher (putting it into the pending state): O(1)
		4127
		4128	=item Priority handling: O(number_of_priorities)
		4129
		4130	Priorities are implemented by allocating some space for each
		4131	priority. When doing priority-based operations, libev usually has to
		4132	linearly search all the priorities, but starting/stopping and activating
		4133	watchers becomes O(1) with respect to priority handling.
		4134
		4135	=item Sending an ev_async: O(1)
		4136
		4137	=item Processing ev_async_send: O(number_of_async_watchers)
		4138
		4139	=item Processing signals: O(max_signal_number)
		4140
		4141	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4142	calls in the current loop iteration. Checking for async and signal events
		4143	involves iterating over all running async watchers or all signal numbers.
		4144
		4145	=back
		4146
		4147
		4148	=head1 GLOSSARY
		4149
		4150	=over 4
		4151
		4152	=item active
		4153
		4154	A watcher is active as long as it has been started (has been attached to
		4155	an event loop) but not yet stopped (disassociated from the event loop).
		4156
		4157	=item application
		4158
		4159	In this document, an application is whatever is using libev.
		4160
		4161	=item callback
		4162
		4163	The address of a function that is called when some event has been
		4164	detected. Callbacks are being passed the event loop, the watcher that
		4165	received the event, and the actual event bitset.
		4166
		4167	=item callback invocation
		4168
		4169	The act of calling the callback associated with a watcher.
		4170
		4171	=item event
		4172
		4173	A change of state of some external event, such as data now being available
		4174	for reading on a file descriptor, time having passed or simply not having
		4175	any other events happening anymore.
		4176
		4177	In libev, events are represented as single bits (such as C<EV_READ> or
		4178	C<EV_TIMEOUT>).
		4179
		4180	=item event library
		4181
		4182	A software package implementing an event model and loop.
		4183
		4184	=item event loop
		4185
		4186	An entity that handles and processes external events and converts them
		4187	into callback invocations.
		4188
		4189	=item event model
		4190
		4191	The model used to describe how an event loop handles and processes
		4192	watchers and events.
		4193
		4194	=item pending
		4195
		4196	A watcher is pending as soon as the corresponding event has been detected,
		4197	and stops being pending as soon as the watcher will be invoked or its
		4198	pending status is explicitly cleared by the application.
		4199
		4200	A watcher can be pending, but not active. Stopping a watcher also clears
		4201	its pending status.
		4202
		4203	=item real time
		4204
		4205	The physical time that is observed. It is apparently strictly monotonic :)
		4206
		4207	=item wall-clock time
		4208
		4209	The time and date as shown on clocks. Unlike real time, it can actually
		4210	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4211	clock.
		4212
		4213	=item watcher
		4214
		4215	A data structure that describes interest in certain events. Watchers need
		4216	to be started (attached to an event loop) before they can receive events.
		4217
		4218	=item watcher invocation
		4219
		4220	The act of calling the callback associated with a watcher.
		4221
		4222	=back
3479		4223
3480	=head1 AUTHOR	4224	=head1 AUTHOR
3481		4225
3482	Marc Lehmann <libev@schmorp.de>.	4226	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3483		4227

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