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…		…
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
		14	#include <stdio.h> // for puts
		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
18		20
19	// all watcher callbacks have a similar signature	21	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	22	// this callback is called when data is readable on stdin
21	static void	23	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	25	{
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
…		…
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	42	}
…		…
60		62
61	// unloop was called, so exit	63	// unloop was called, so exit
62	return 0;	64	return 0;
63	}	65	}
64		66
65	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
66		70
67	The newest version of this document is also available as an html-formatted	71	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	72	web page you might find easier to navigate when reading it for the first
69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.	73	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		74
		75	While this document tries to be as complete as possible in documenting
		76	libev, its usage and the rationale behind its design, it is not a tutorial
		77	on event-based programming, nor will it introduce event-based programming
		78	with libev.
		79
		80	Familarity with event based programming techniques in general is assumed
		81	throughout this document.
		82
		83	=head1 ABOUT LIBEV
70		84
71	Libev is an event loop: you register interest in certain events (such as a	85	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	86	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	87	these event sources and provide your program with events.
74		88
…		…
103	Libev is very configurable. In this manual the default (and most common)	117	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	118	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	119	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	120	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	121	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	122	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	123	this argument.
110		124
111	=head2 TIME REPRESENTATION	125	=head2 TIME REPRESENTATION
112		126
113	Libev represents time as a single floating point number, representing the	127	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	128	the (fractional) number of seconds since the (POSIX) epoch (somewhere
115	the beginning of 1970, details are complicated, don't ask). This type is	129	near the beginning of 1970, details are complicated, don't ask). This
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	130	type is called C<ev_tstamp>, which is what you should use too. It usually
117	to the C<double> type in C, and when you need to do any calculations on	131	aliases to the C<double> type in C. When you need to do any calculations
118	it, you should treat it as some floating point value. Unlike the name	132	on it, you should treat it as some floating point value. Unlike the name
119	component C<stamp> might indicate, it is also used for time differences	133	component C<stamp> might indicate, it is also used for time differences
120	throughout libev.	134	throughout libev.
121		135
122	=head1 ERROR HANDLING	136	=head1 ERROR HANDLING
123		137
…		…
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	228	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
215	recommended ones.	229	recommended ones.
216		230
217	See the description of C<ev_embed> watchers for more info.	231	See the description of C<ev_embed> watchers for more info.
218		232
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	233	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
220		234
221	Sets the allocation function to use (the prototype is similar - the	235	Sets the allocation function to use (the prototype is similar - the
222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	236	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
223	used to allocate and free memory (no surprises here). If it returns zero	237	used to allocate and free memory (no surprises here). If it returns zero
224	when memory needs to be allocated (C<size != 0>), the library might abort	238	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	264	}
251		265
252	...	266	...
253	ev_set_allocator (persistent_realloc);	267	ev_set_allocator (persistent_realloc);
254		268
255	=item ev_set_syserr_cb (void (*cb)(const char *msg));	269	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
256		270
257	Set the callback function to call on a retryable system call error (such	271	Set the callback function to call on a retryable system call error (such
258	as failed select, poll, epoll_wait). The message is a printable string	272	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	273	indicating the system call or subsystem causing the problem. If this
260	callback is set, then libev will expect it to remedy the situation, no	274	callback is set, then libev will expect it to remedy the situation, no
…		…
276		290
277	=back	291	=back
278		292
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	293	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
280		294
281	An event loop is described by a C<struct ev_loop *>. The library knows two	295	An event loop is described by a C<struct ev_loop *> (the C<struct>
282	types of such loops, the I<default> loop, which supports signals and child	296	is I<not> optional in this case, as there is also an C<ev_loop>
283	events, and dynamically created loops which do not.	297	I<function>).
		298
		299	The library knows two types of such loops, the I<default> loop, which
		300	supports signals and child events, and dynamically created loops which do
		301	not.
284		302
285	=over 4	303	=over 4
286		304
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	305	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		306
…		…
294	If you don't know what event loop to use, use the one returned from this	312	If you don't know what event loop to use, use the one returned from this
295	function.	313	function.
296		314
297	Note that this function is I<not> thread-safe, so if you want to use it	315	Note that this function is I<not> thread-safe, so if you want to use it
298	from multiple threads, you have to lock (note also that this is unlikely,	316	from multiple threads, you have to lock (note also that this is unlikely,
299	as loops cannot bes hared easily between threads anyway).	317	as loops cannot be shared easily between threads anyway).
300		318
301	The default loop is the only loop that can handle C<ev_signal> and	319	The default loop is the only loop that can handle C<ev_signal> and
302	C<ev_child> watchers, and to do this, it always registers a handler	320	C<ev_child> watchers, and to do this, it always registers a handler
303	for C<SIGCHLD>. If this is a problem for your application you can either	321	for C<SIGCHLD>. If this is a problem for your application you can either
304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	322	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
…		…
359	writing a server, you should C<accept ()> in a loop to accept as many	377	writing a server, you should C<accept ()> in a loop to accept as many
360	connections as possible during one iteration. You might also want to have	378	connections as possible during one iteration. You might also want to have
361	a look at C<ev_set_io_collect_interval ()> to increase the amount of	379	a look at C<ev_set_io_collect_interval ()> to increase the amount of
362	readiness notifications you get per iteration.	380	readiness notifications you get per iteration.
363		381
		382	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		383	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		384	C<exceptfds> set on that platform).
		385
364	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	386	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
365		387
366	And this is your standard poll(2) backend. It's more complicated	388	And this is your standard poll(2) backend. It's more complicated
367	than select, but handles sparse fds better and has no artificial	389	than select, but handles sparse fds better and has no artificial
368	limit on the number of fds you can use (except it will slow down	390	limit on the number of fds you can use (except it will slow down
369	considerably with a lot of inactive fds). It scales similarly to select,	391	considerably with a lot of inactive fds). It scales similarly to select,
370	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for	392	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
371	performance tips.	393	performance tips.
372		394
		395	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		396	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		397
373	=item C<EVBACKEND_EPOLL> (value 4, Linux)	398	=item C<EVBACKEND_EPOLL> (value 4, Linux)
374		399
375	For few fds, this backend is a bit little slower than poll and select,	400	For few fds, this backend is a bit little slower than poll and select,
376	but it scales phenomenally better. While poll and select usually scale	401	but it scales phenomenally better. While poll and select usually scale
377	like O(total_fds) where n is the total number of fds (or the highest fd),	402	like O(total_fds) where n is the total number of fds (or the highest fd),
378	epoll scales either O(1) or O(active_fds). The epoll design has a number	403	epoll scales either O(1) or O(active_fds).
379	of shortcomings, such as silently dropping events in some hard-to-detect	404
380	cases and requiring a system call per fd change, no fork support and bad	405	The epoll mechanism deserves honorable mention as the most misdesigned
381	support for dup.	406	of the more advanced event mechanisms: mere annoyances include silently
		407	dropping file descriptors, requiring a system call per change per file
		408	descriptor (and unnecessary guessing of parameters), problems with dup and
		409	so on. The biggest issue is fork races, however - if a program forks then
		410	I<both> parent and child process have to recreate the epoll set, which can
		411	take considerable time (one syscall per file descriptor) and is of course
		412	hard to detect.
		413
		414	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		415	of course I<doesn't>, and epoll just loves to report events for totally
		416	I<different> file descriptors (even already closed ones, so one cannot
		417	even remove them from the set) than registered in the set (especially
		418	on SMP systems). Libev tries to counter these spurious notifications by
		419	employing an additional generation counter and comparing that against the
		420	events to filter out spurious ones, recreating the set when required.
382		421
383	While stopping, setting and starting an I/O watcher in the same iteration	422	While stopping, setting and starting an I/O watcher in the same iteration
384	will result in some caching, there is still a system call per such incident	423	will result in some caching, there is still a system call per such
385	(because the fd could point to a different file description now), so its	424	incident (because the same I<file descriptor> could point to a different
386	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	425	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
387	very well if you register events for both fds.	426	file descriptors might not work very well if you register events for both
388		427	file descriptors.
389	Please note that epoll sometimes generates spurious notifications, so you
390	need to use non-blocking I/O or other means to avoid blocking when no data
391	(or space) is available.
392		428
393	Best performance from this backend is achieved by not unregistering all	429	Best performance from this backend is achieved by not unregistering all
394	watchers for a file descriptor until it has been closed, if possible, i.e.	430	watchers for a file descriptor until it has been closed, if possible,
395	keep at least one watcher active per fd at all times.	431	i.e. keep at least one watcher active per fd at all times. Stopping and
		432	starting a watcher (without re-setting it) also usually doesn't cause
		433	extra overhead. A fork can both result in spurious notifications as well
		434	as in libev having to destroy and recreate the epoll object, which can
		435	take considerable time and thus should be avoided.
		436
		437	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		438	faster than epoll for maybe up to a hundred file descriptors, depending on
		439	the usage. So sad.
396		440
397	While nominally embeddable in other event loops, this feature is broken in	441	While nominally embeddable in other event loops, this feature is broken in
398	all kernel versions tested so far.	442	all kernel versions tested so far.
		443
		444	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		445	C<EVBACKEND_POLL>.
399		446
400	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	447	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
401		448
402	Kqueue deserves special mention, as at the time of this writing, it	449	Kqueue deserves special mention, as at the time of this writing, it
403	was broken on all BSDs except NetBSD (usually it doesn't work reliably	450	was broken on all BSDs except NetBSD (usually it doesn't work reliably
404	with anything but sockets and pipes, except on Darwin, where of course	451	with anything but sockets and pipes, except on Darwin, where of course
405	it's completely useless). For this reason it's not being "auto-detected"	452	it's completely useless). Unlike epoll, however, whose brokenness
		453	is by design, these kqueue bugs can (and eventually will) be fixed
		454	without API changes to existing programs. For this reason it's not being
406	unless you explicitly specify it explicitly in the flags (i.e. using	455	"auto-detected" unless you explicitly specify it in the flags (i.e. using
407	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	456	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
408	system like NetBSD.	457	system like NetBSD.
409		458
410	You still can embed kqueue into a normal poll or select backend and use it	459	You still can embed kqueue into a normal poll or select backend and use it
411	only for sockets (after having made sure that sockets work with kqueue on	460	only for sockets (after having made sure that sockets work with kqueue on
…		…
413		462
414	It scales in the same way as the epoll backend, but the interface to the	463	It scales in the same way as the epoll backend, but the interface to the
415	kernel is more efficient (which says nothing about its actual speed, of	464	kernel is more efficient (which says nothing about its actual speed, of
416	course). While stopping, setting and starting an I/O watcher does never	465	course). While stopping, setting and starting an I/O watcher does never
417	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	466	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
418	two event changes per incident, support for C<fork ()> is very bad and it	467	two event changes per incident. Support for C<fork ()> is very bad (but
419	drops fds silently in similarly hard-to-detect cases.	468	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		469	cases
420		470
421	This backend usually performs well under most conditions.	471	This backend usually performs well under most conditions.
422		472
423	While nominally embeddable in other event loops, this doesn't work	473	While nominally embeddable in other event loops, this doesn't work
424	everywhere, so you might need to test for this. And since it is broken	474	everywhere, so you might need to test for this. And since it is broken
425	almost everywhere, you should only use it when you have a lot of sockets	475	almost everywhere, you should only use it when you have a lot of sockets
426	(for which it usually works), by embedding it into another event loop	476	(for which it usually works), by embedding it into another event loop
427	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	477	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
428	sockets.	478	also broken on OS X)) and, did I mention it, using it only for sockets.
		479
		480	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		481	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		482	C<NOTE_EOF>.
429		483
430	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	484	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
431		485
432	This is not implemented yet (and might never be, unless you send me an	486	This is not implemented yet (and might never be, unless you send me an
433	implementation). According to reports, C</dev/poll> only supports sockets	487	implementation). According to reports, C</dev/poll> only supports sockets
…		…
446	While this backend scales well, it requires one system call per active	500	While this backend scales well, it requires one system call per active
447	file descriptor per loop iteration. For small and medium numbers of file	501	file descriptor per loop iteration. For small and medium numbers of file
448	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	502	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
449	might perform better.	503	might perform better.
450		504
451	On the positive side, ignoring the spurious readiness notifications, this	505	On the positive side, with the exception of the spurious readiness
452	backend actually performed to specification in all tests and is fully	506	notifications, this backend actually performed fully to specification
453	embeddable, which is a rare feat among the OS-specific backends.	507	in all tests and is fully embeddable, which is a rare feat among the
		508	OS-specific backends (I vastly prefer correctness over speed hacks).
		509
		510	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		511	C<EVBACKEND_POLL>.
454		512
455	=item C<EVBACKEND_ALL>	513	=item C<EVBACKEND_ALL>
456		514
457	Try all backends (even potentially broken ones that wouldn't be tried	515	Try all backends (even potentially broken ones that wouldn't be tried
458	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	516	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
464		522
465	If one or more of these are or'ed into the flags value, then only these	523	If one or more of these are or'ed into the flags value, then only these
466	backends will be tried (in the reverse order as listed here). If none are	524	backends will be tried (in the reverse order as listed here). If none are
467	specified, all backends in C<ev_recommended_backends ()> will be tried.	525	specified, all backends in C<ev_recommended_backends ()> will be tried.
468		526
469	The most typical usage is like this:	527	Example: This is the most typical usage.
470		528
471	if (!ev_default_loop (0))	529	if (!ev_default_loop (0))
472	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	530	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
473		531
474	Restrict libev to the select and poll backends, and do not allow	532	Example: Restrict libev to the select and poll backends, and do not allow
475	environment settings to be taken into account:	533	environment settings to be taken into account:
476		534
477	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	535	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
478		536
479	Use whatever libev has to offer, but make sure that kqueue is used if	537	Example: Use whatever libev has to offer, but make sure that kqueue is
480	available (warning, breaks stuff, best use only with your own private	538	used if available (warning, breaks stuff, best use only with your own
481	event loop and only if you know the OS supports your types of fds):	539	private event loop and only if you know the OS supports your types of
		540	fds):
482		541
483	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	542	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
484		543
485	=item struct ev_loop *ev_loop_new (unsigned int flags)	544	=item struct ev_loop *ev_loop_new (unsigned int flags)
486		545
…		…
507	responsibility to either stop all watchers cleanly yourself I<before>	566	responsibility to either stop all watchers cleanly yourself I<before>
508	calling this function, or cope with the fact afterwards (which is usually	567	calling this function, or cope with the fact afterwards (which is usually
509	the easiest thing, you can just ignore the watchers and/or C<free ()> them	568	the easiest thing, you can just ignore the watchers and/or C<free ()> them
510	for example).	569	for example).
511		570
512	Note that certain global state, such as signal state, will not be freed by	571	Note that certain global state, such as signal state (and installed signal
513	this function, and related watchers (such as signal and child watchers)	572	handlers), will not be freed by this function, and related watchers (such
514	would need to be stopped manually.	573	as signal and child watchers) would need to be stopped manually.
515		574
516	In general it is not advisable to call this function except in the	575	In general it is not advisable to call this function except in the
517	rare occasion where you really need to free e.g. the signal handling	576	rare occasion where you really need to free e.g. the signal handling
518	pipe fds. If you need dynamically allocated loops it is better to use	577	pipe fds. If you need dynamically allocated loops it is better to use
519	C<ev_loop_new> and C<ev_loop_destroy>).	578	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
544		603
545	=item ev_loop_fork (loop)	604	=item ev_loop_fork (loop)
546		605
547	Like C<ev_default_fork>, but acts on an event loop created by	606	Like C<ev_default_fork>, but acts on an event loop created by
548	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	607	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
549	after fork, and how you do this is entirely your own problem.	608	after fork that you want to re-use in the child, and how you do this is
		609	entirely your own problem.
550		610
551	=item int ev_is_default_loop (loop)	611	=item int ev_is_default_loop (loop)
552		612
553	Returns true when the given loop actually is the default loop, false otherwise.	613	Returns true when the given loop is, in fact, the default loop, and false
		614	otherwise.
554		615
555	=item unsigned int ev_loop_count (loop)	616	=item unsigned int ev_loop_count (loop)
556		617
557	Returns the count of loop iterations for the loop, which is identical to	618	Returns the count of loop iterations for the loop, which is identical to
558	the number of times libev did poll for new events. It starts at C<0> and	619	the number of times libev did poll for new events. It starts at C<0> and
559	happily wraps around with enough iterations.	620	happily wraps around with enough iterations.
560		621
561	This value can sometimes be useful as a generation counter of sorts (it	622	This value can sometimes be useful as a generation counter of sorts (it
562	"ticks" the number of loop iterations), as it roughly corresponds with	623	"ticks" the number of loop iterations), as it roughly corresponds with
563	C<ev_prepare> and C<ev_check> calls.	624	C<ev_prepare> and C<ev_check> calls.
		625
		626	=item unsigned int ev_loop_depth (loop)
		627
		628	Returns the number of times C<ev_loop> was entered minus the number of
		629	times C<ev_loop> was exited, in other words, the recursion depth.
		630
		631	Outside C<ev_loop>, this number is zero. In a callback, this number is
		632	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),
		633	in which case it is higher.
		634
		635	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread
		636	etc.), doesn't count as exit.
564		637
565	=item unsigned int ev_backend (loop)	638	=item unsigned int ev_backend (loop)
566		639
567	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	640	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
568	use.	641	use.
…		…
583		656
584	This function is rarely useful, but when some event callback runs for a	657	This function is rarely useful, but when some event callback runs for a
585	very long time without entering the event loop, updating libev's idea of	658	very long time without entering the event loop, updating libev's idea of
586	the current time is a good idea.	659	the current time is a good idea.
587		660
588	See also "The special problem of time updates" in the C<ev_timer> section.	661	See also L<The special problem of time updates> in the C<ev_timer> section.
		662
		663	=item ev_suspend (loop)
		664
		665	=item ev_resume (loop)
		666
		667	These two functions suspend and resume a loop, for use when the loop is
		668	not used for a while and timeouts should not be processed.
		669
		670	A typical use case would be an interactive program such as a game: When
		671	the user presses C<^Z> to suspend the game and resumes it an hour later it
		672	would be best to handle timeouts as if no time had actually passed while
		673	the program was suspended. This can be achieved by calling C<ev_suspend>
		674	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		675	C<ev_resume> directly afterwards to resume timer processing.
		676
		677	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		678	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		679	will be rescheduled (that is, they will lose any events that would have
		680	occured while suspended).
		681
		682	After calling C<ev_suspend> you B<must not> call I<any> function on the
		683	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		684	without a previous call to C<ev_suspend>.
		685
		686	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		687	event loop time (see C<ev_now_update>).
589		688
590	=item ev_loop (loop, int flags)	689	=item ev_loop (loop, int flags)
591		690
592	Finally, this is it, the event handler. This function usually is called	691	Finally, this is it, the event handler. This function usually is called
593	after you initialised all your watchers and you want to start handling	692	after you initialised all your watchers and you want to start handling
…		…
596	If the flags argument is specified as C<0>, it will not return until	695	If the flags argument is specified as C<0>, it will not return until
597	either no event watchers are active anymore or C<ev_unloop> was called.	696	either no event watchers are active anymore or C<ev_unloop> was called.
598		697
599	Please note that an explicit C<ev_unloop> is usually better than	698	Please note that an explicit C<ev_unloop> is usually better than
600	relying on all watchers to be stopped when deciding when a program has	699	relying on all watchers to be stopped when deciding when a program has
601	finished (especially in interactive programs), but having a program that	700	finished (especially in interactive programs), but having a program
602	automatically loops as long as it has to and no longer by virtue of	701	that automatically loops as long as it has to and no longer by virtue
603	relying on its watchers stopping correctly is a thing of beauty.	702	of relying on its watchers stopping correctly, that is truly a thing of
		703	beauty.
604		704
605	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	705	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
606	those events and any outstanding ones, but will not block your process in	706	those events and any already outstanding ones, but will not block your
607	case there are no events and will return after one iteration of the loop.	707	process in case there are no events and will return after one iteration of
		708	the loop.
608		709
609	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	710	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
610	necessary) and will handle those and any outstanding ones. It will block	711	necessary) and will handle those and any already outstanding ones. It
611	your process until at least one new event arrives, and will return after	712	will block your process until at least one new event arrives (which could
612	one iteration of the loop. This is useful if you are waiting for some	713	be an event internal to libev itself, so there is no guarantee that a
613	external event in conjunction with something not expressible using other	714	user-registered callback will be called), and will return after one
		715	iteration of the loop.
		716
		717	This is useful if you are waiting for some external event in conjunction
		718	with something not expressible using other libev watchers (i.e. "roll your
614	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	719	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
615	usually a better approach for this kind of thing.	720	usually a better approach for this kind of thing.
616		721
617	Here are the gory details of what C<ev_loop> does:	722	Here are the gory details of what C<ev_loop> does:
618		723
619	- Before the first iteration, call any pending watchers.	724	- Before the first iteration, call any pending watchers.
…		…
629	any active watchers at all will result in not sleeping).	734	any active watchers at all will result in not sleeping).
630	- Sleep if the I/O and timer collect interval say so.	735	- Sleep if the I/O and timer collect interval say so.
631	- Block the process, waiting for any events.	736	- Block the process, waiting for any events.
632	- Queue all outstanding I/O (fd) events.	737	- Queue all outstanding I/O (fd) events.
633	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	738	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
634	- Queue all outstanding timers.	739	- Queue all expired timers.
635	- Queue all outstanding periodics.	740	- Queue all expired periodics.
636	- Unless any events are pending now, queue all idle watchers.	741	- Unless any events are pending now, queue all idle watchers.
637	- Queue all check watchers.	742	- Queue all check watchers.
638	- Call all queued watchers in reverse order (i.e. check watchers first).	743	- Call all queued watchers in reverse order (i.e. check watchers first).
639	Signals and child watchers are implemented as I/O watchers, and will	744	Signals and child watchers are implemented as I/O watchers, and will
640	be handled here by queueing them when their watcher gets executed.	745	be handled here by queueing them when their watcher gets executed.
…		…
657	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	762	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
658	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	763	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
659		764
660	This "unloop state" will be cleared when entering C<ev_loop> again.	765	This "unloop state" will be cleared when entering C<ev_loop> again.
661		766
		767	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		768
662	=item ev_ref (loop)	769	=item ev_ref (loop)
663		770
664	=item ev_unref (loop)	771	=item ev_unref (loop)
665		772
666	Ref/unref can be used to add or remove a reference count on the event	773	Ref/unref can be used to add or remove a reference count on the event
667	loop: Every watcher keeps one reference, and as long as the reference	774	loop: Every watcher keeps one reference, and as long as the reference
668	count is nonzero, C<ev_loop> will not return on its own. If you have	775	count is nonzero, C<ev_loop> will not return on its own.
		776
669	a watcher you never unregister that should not keep C<ev_loop> from	777	If you have a watcher you never unregister that should not keep C<ev_loop>
670	returning, ev_unref() after starting, and ev_ref() before stopping it. For	778	from returning, call ev_unref() after starting, and ev_ref() before
		779	stopping it.
		780
671	example, libev itself uses this for its internal signal pipe: It is not	781	As an example, libev itself uses this for its internal signal pipe: It
672	visible to the libev user and should not keep C<ev_loop> from exiting if	782	is not visible to the libev user and should not keep C<ev_loop> from
673	no event watchers registered by it are active. It is also an excellent	783	exiting if no event watchers registered by it are active. It is also an
674	way to do this for generic recurring timers or from within third-party	784	excellent way to do this for generic recurring timers or from within
675	libraries. Just remember to I<unref after start> and I<ref before stop>	785	third-party libraries. Just remember to I<unref after start> and I<ref
676	(but only if the watcher wasn't active before, or was active before,	786	before stop> (but only if the watcher wasn't active before, or was active
677	respectively).	787	before, respectively. Note also that libev might stop watchers itself
		788	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		789	in the callback).
678		790
679	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	791	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
680	running when nothing else is active.	792	running when nothing else is active.
681		793
682	struct ev_signal exitsig;	794	ev_signal exitsig;
683	ev_signal_init (&exitsig, sig_cb, SIGINT);	795	ev_signal_init (&exitsig, sig_cb, SIGINT);
684	ev_signal_start (loop, &exitsig);	796	ev_signal_start (loop, &exitsig);
685	evf_unref (loop);	797	evf_unref (loop);
686		798
687	Example: For some weird reason, unregister the above signal handler again.	799	Example: For some weird reason, unregister the above signal handler again.
…		…
701	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	813	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
702	allows libev to delay invocation of I/O and timer/periodic callbacks	814	allows libev to delay invocation of I/O and timer/periodic callbacks
703	to increase efficiency of loop iterations (or to increase power-saving	815	to increase efficiency of loop iterations (or to increase power-saving
704	opportunities).	816	opportunities).
705		817
706	The background is that sometimes your program runs just fast enough to	818	The idea is that sometimes your program runs just fast enough to handle
707	handle one (or very few) event(s) per loop iteration. While this makes	819	one (or very few) event(s) per loop iteration. While this makes the
708	the program responsive, it also wastes a lot of CPU time to poll for new	820	program responsive, it also wastes a lot of CPU time to poll for new
709	events, especially with backends like C<select ()> which have a high	821	events, especially with backends like C<select ()> which have a high
710	overhead for the actual polling but can deliver many events at once.	822	overhead for the actual polling but can deliver many events at once.
711		823
712	By setting a higher I<io collect interval> you allow libev to spend more	824	By setting a higher I<io collect interval> you allow libev to spend more
713	time collecting I/O events, so you can handle more events per iteration,	825	time collecting I/O events, so you can handle more events per iteration,
714	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	826	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
715	C<ev_timer>) will be not affected. Setting this to a non-null value will	827	C<ev_timer>) will be not affected. Setting this to a non-null value will
716	introduce an additional C<ev_sleep ()> call into most loop iterations.	828	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		829	sleep time ensures that libev will not poll for I/O events more often then
		830	once per this interval, on average.
717		831
718	Likewise, by setting a higher I<timeout collect interval> you allow libev	832	Likewise, by setting a higher I<timeout collect interval> you allow libev
719	to spend more time collecting timeouts, at the expense of increased	833	to spend more time collecting timeouts, at the expense of increased
720	latency (the watcher callback will be called later). C<ev_io> watchers	834	latency/jitter/inexactness (the watcher callback will be called
721	will not be affected. Setting this to a non-null value will not introduce	835	later). C<ev_io> watchers will not be affected. Setting this to a non-null
722	any overhead in libev.	836	value will not introduce any overhead in libev.
723		837
724	Many (busy) programs can usually benefit by setting the I/O collect	838	Many (busy) programs can usually benefit by setting the I/O collect
725	interval to a value near C<0.1> or so, which is often enough for	839	interval to a value near C<0.1> or so, which is often enough for
726	interactive servers (of course not for games), likewise for timeouts. It	840	interactive servers (of course not for games), likewise for timeouts. It
727	usually doesn't make much sense to set it to a lower value than C<0.01>,	841	usually doesn't make much sense to set it to a lower value than C<0.01>,
728	as this approaches the timing granularity of most systems.	842	as this approaches the timing granularity of most systems. Note that if
		843	you do transactions with the outside world and you can't increase the
		844	parallelity, then this setting will limit your transaction rate (if you
		845	need to poll once per transaction and the I/O collect interval is 0.01,
		846	then you can't do more than 100 transations per second).
729		847
730	Setting the I<timeout collect interval> can improve the opportunity for	848	Setting the I<timeout collect interval> can improve the opportunity for
731	saving power, as the program will "bundle" timer callback invocations that	849	saving power, as the program will "bundle" timer callback invocations that
732	are "near" in time together, by delaying some, thus reducing the number of	850	are "near" in time together, by delaying some, thus reducing the number of
733	times the process sleeps and wakes up again. Another useful technique to	851	times the process sleeps and wakes up again. Another useful technique to
734	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	852	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
735	they fire on, say, one-second boundaries only.	853	they fire on, say, one-second boundaries only.
736		854
		855	Example: we only need 0.1s timeout granularity, and we wish not to poll
		856	more often than 100 times per second:
		857
		858	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		859	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		860
737	=item ev_loop_verify (loop)	861	=item ev_loop_verify (loop)
738		862
739	This function only does something when C<EV_VERIFY> support has been	863	This function only does something when C<EV_VERIFY> support has been
740	compiled in. It tries to go through all internal structures and checks	864	compiled in, which is the default for non-minimal builds. It tries to go
741	them for validity. If anything is found to be inconsistent, it will print	865	through all internal structures and checks them for validity. If anything
742	an error message to standard error and call C<abort ()>.	866	is found to be inconsistent, it will print an error message to standard
		867	error and call C<abort ()>.
743		868
744	This can be used to catch bugs inside libev itself: under normal	869	This can be used to catch bugs inside libev itself: under normal
745	circumstances, this function will never abort as of course libev keeps its	870	circumstances, this function will never abort as of course libev keeps its
746	data structures consistent.	871	data structures consistent.
747		872
748	=back	873	=back
749		874
750		875
751	=head1 ANATOMY OF A WATCHER	876	=head1 ANATOMY OF A WATCHER
752		877
		878	In the following description, uppercase C<TYPE> in names stands for the
		879	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		880	watchers and C<ev_io_start> for I/O watchers.
		881
753	A watcher is a structure that you create and register to record your	882	A watcher is a structure that you create and register to record your
754	interest in some event. For instance, if you want to wait for STDIN to	883	interest in some event. For instance, if you want to wait for STDIN to
755	become readable, you would create an C<ev_io> watcher for that:	884	become readable, you would create an C<ev_io> watcher for that:
756		885
757	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	886	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
758	{	887	{
759	ev_io_stop (w);	888	ev_io_stop (w);
760	ev_unloop (loop, EVUNLOOP_ALL);	889	ev_unloop (loop, EVUNLOOP_ALL);
761	}	890	}
762		891
763	struct ev_loop *loop = ev_default_loop (0);	892	struct ev_loop *loop = ev_default_loop (0);
		893
764	struct ev_io stdin_watcher;	894	ev_io stdin_watcher;
		895
765	ev_init (&stdin_watcher, my_cb);	896	ev_init (&stdin_watcher, my_cb);
766	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	897	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
767	ev_io_start (loop, &stdin_watcher);	898	ev_io_start (loop, &stdin_watcher);
		899
768	ev_loop (loop, 0);	900	ev_loop (loop, 0);
769		901
770	As you can see, you are responsible for allocating the memory for your	902	As you can see, you are responsible for allocating the memory for your
771	watcher structures (and it is usually a bad idea to do this on the stack,	903	watcher structures (and it is I<usually> a bad idea to do this on the
772	although this can sometimes be quite valid).	904	stack).
		905
		906	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		907	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
773		908
774	Each watcher structure must be initialised by a call to C<ev_init	909	Each watcher structure must be initialised by a call to C<ev_init
775	(watcher *, callback)>, which expects a callback to be provided. This	910	(watcher *, callback)>, which expects a callback to be provided. This
776	callback gets invoked each time the event occurs (or, in the case of I/O	911	callback gets invoked each time the event occurs (or, in the case of I/O
777	watchers, each time the event loop detects that the file descriptor given	912	watchers, each time the event loop detects that the file descriptor given
778	is readable and/or writable).	913	is readable and/or writable).
779		914
780	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	915	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
781	with arguments specific to this watcher type. There is also a macro	916	macro to configure it, with arguments specific to the watcher type. There
782	to combine initialisation and setting in one call: C<< ev_<type>_init	917	is also a macro to combine initialisation and setting in one call: C<<
783	(watcher *, callback, ...) >>.	918	ev_TYPE_init (watcher *, callback, ...) >>.
784		919
785	To make the watcher actually watch out for events, you have to start it	920	To make the watcher actually watch out for events, you have to start it
786	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	921	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
787	*) >>), and you can stop watching for events at any time by calling the	922	*) >>), and you can stop watching for events at any time by calling the
788	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	923	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
789		924
790	As long as your watcher is active (has been started but not stopped) you	925	As long as your watcher is active (has been started but not stopped) you
791	must not touch the values stored in it. Most specifically you must never	926	must not touch the values stored in it. Most specifically you must never
792	reinitialise it or call its C<set> macro.	927	reinitialise it or call its C<ev_TYPE_set> macro.
793		928
794	Each and every callback receives the event loop pointer as first, the	929	Each and every callback receives the event loop pointer as first, the
795	registered watcher structure as second, and a bitset of received events as	930	registered watcher structure as second, and a bitset of received events as
796	third argument.	931	third argument.
797		932
…		…
855		990
856	=item C<EV_ASYNC>	991	=item C<EV_ASYNC>
857		992
858	The given async watcher has been asynchronously notified (see C<ev_async>).	993	The given async watcher has been asynchronously notified (see C<ev_async>).
859		994
		995	=item C<EV_CUSTOM>
		996
		997	Not ever sent (or otherwise used) by libev itself, but can be freely used
		998	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		999
860	=item C<EV_ERROR>	1000	=item C<EV_ERROR>
861		1001
862	An unspecified error has occurred, the watcher has been stopped. This might	1002	An unspecified error has occurred, the watcher has been stopped. This might
863	happen because the watcher could not be properly started because libev	1003	happen because the watcher could not be properly started because libev
864	ran out of memory, a file descriptor was found to be closed or any other	1004	ran out of memory, a file descriptor was found to be closed or any other
		1005	problem. Libev considers these application bugs.
		1006
865	problem. You best act on it by reporting the problem and somehow coping	1007	You best act on it by reporting the problem and somehow coping with the
866	with the watcher being stopped.	1008	watcher being stopped. Note that well-written programs should not receive
		1009	an error ever, so when your watcher receives it, this usually indicates a
		1010	bug in your program.
867		1011
868	Libev will usually signal a few "dummy" events together with an error,	1012	Libev will usually signal a few "dummy" events together with an error, for
869	for example it might indicate that a fd is readable or writable, and if	1013	example it might indicate that a fd is readable or writable, and if your
870	your callbacks is well-written it can just attempt the operation and cope	1014	callbacks is well-written it can just attempt the operation and cope with
871	with the error from read() or write(). This will not work in multi-threaded	1015	the error from read() or write(). This will not work in multi-threaded
872	programs, though, so beware.	1016	programs, though, as the fd could already be closed and reused for another
		1017	thing, so beware.
873		1018
874	=back	1019	=back
875		1020
876	=head2 GENERIC WATCHER FUNCTIONS	1021	=head2 GENERIC WATCHER FUNCTIONS
877
878	In the following description, C<TYPE> stands for the watcher type,
879	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
880		1022
881	=over 4	1023	=over 4
882		1024
883	=item C<ev_init> (ev_TYPE *watcher, callback)	1025	=item C<ev_init> (ev_TYPE *watcher, callback)
884		1026
…		…
890	which rolls both calls into one.	1032	which rolls both calls into one.
891		1033
892	You can reinitialise a watcher at any time as long as it has been stopped	1034	You can reinitialise a watcher at any time as long as it has been stopped
893	(or never started) and there are no pending events outstanding.	1035	(or never started) and there are no pending events outstanding.
894		1036
895	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1037	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
896	int revents)>.	1038	int revents)>.
		1039
		1040	Example: Initialise an C<ev_io> watcher in two steps.
		1041
		1042	ev_io w;
		1043	ev_init (&w, my_cb);
		1044	ev_io_set (&w, STDIN_FILENO, EV_READ);
897		1045
898	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1046	=item C<ev_TYPE_set> (ev_TYPE *, [args])
899		1047
900	This macro initialises the type-specific parts of a watcher. You need to	1048	This macro initialises the type-specific parts of a watcher. You need to
901	call C<ev_init> at least once before you call this macro, but you can	1049	call C<ev_init> at least once before you call this macro, but you can
…		…
904	difference to the C<ev_init> macro).	1052	difference to the C<ev_init> macro).
905		1053
906	Although some watcher types do not have type-specific arguments	1054	Although some watcher types do not have type-specific arguments
907	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	1055	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
908		1056
		1057	See C<ev_init>, above, for an example.
		1058
909	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1059	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
910		1060
911	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1061	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
912	calls into a single call. This is the most convenient method to initialise	1062	calls into a single call. This is the most convenient method to initialise
913	a watcher. The same limitations apply, of course.	1063	a watcher. The same limitations apply, of course.
914		1064
		1065	Example: Initialise and set an C<ev_io> watcher in one step.
		1066
		1067	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1068
915	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1069	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
916		1070
917	Starts (activates) the given watcher. Only active watchers will receive	1071	Starts (activates) the given watcher. Only active watchers will receive
918	events. If the watcher is already active nothing will happen.	1072	events. If the watcher is already active nothing will happen.
919		1073
		1074	Example: Start the C<ev_io> watcher that is being abused as example in this
		1075	whole section.
		1076
		1077	ev_io_start (EV_DEFAULT_UC, &w);
		1078
920	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1079	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
921		1080
922	Stops the given watcher again (if active) and clears the pending	1081	Stops the given watcher if active, and clears the pending status (whether
		1082	the watcher was active or not).
		1083
923	status. It is possible that stopped watchers are pending (for example,	1084	It is possible that stopped watchers are pending - for example,
924	non-repeating timers are being stopped when they become pending), but	1085	non-repeating timers are being stopped when they become pending - but
925	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1086	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
926	you want to free or reuse the memory used by the watcher it is therefore a	1087	pending. If you want to free or reuse the memory used by the watcher it is
927	good idea to always call its C<ev_TYPE_stop> function.	1088	therefore a good idea to always call its C<ev_TYPE_stop> function.
928		1089
929	=item bool ev_is_active (ev_TYPE *watcher)	1090	=item bool ev_is_active (ev_TYPE *watcher)
930		1091
931	Returns a true value iff the watcher is active (i.e. it has been started	1092	Returns a true value iff the watcher is active (i.e. it has been started
932	and not yet been stopped). As long as a watcher is active you must not modify	1093	and not yet been stopped). As long as a watcher is active you must not modify
…		…
958	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1119	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
959	(default: C<-2>). Pending watchers with higher priority will be invoked	1120	(default: C<-2>). Pending watchers with higher priority will be invoked
960	before watchers with lower priority, but priority will not keep watchers	1121	before watchers with lower priority, but priority will not keep watchers
961	from being executed (except for C<ev_idle> watchers).	1122	from being executed (except for C<ev_idle> watchers).
962		1123
963	This means that priorities are I<only> used for ordering callback
964	invocation after new events have been received. This is useful, for
965	example, to reduce latency after idling, or more often, to bind two
966	watchers on the same event and make sure one is called first.
967
968	If you need to suppress invocation when higher priority events are pending	1124	If you need to suppress invocation when higher priority events are pending
969	you need to look at C<ev_idle> watchers, which provide this functionality.	1125	you need to look at C<ev_idle> watchers, which provide this functionality.
970		1126
971	You I<must not> change the priority of a watcher as long as it is active or	1127	You I<must not> change the priority of a watcher as long as it is active or
972	pending.	1128	pending.
973		1129
		1130	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1131	fine, as long as you do not mind that the priority value you query might
		1132	or might not have been clamped to the valid range.
		1133
974	The default priority used by watchers when no priority has been set is	1134	The default priority used by watchers when no priority has been set is
975	always C<0>, which is supposed to not be too high and not be too low :).	1135	always C<0>, which is supposed to not be too high and not be too low :).
976		1136
977	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1137	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
978	fine, as long as you do not mind that the priority value you query might	1138	priorities.
979	or might not have been adjusted to be within valid range.
980		1139
981	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1140	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
982		1141
983	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1142	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
984	C<loop> nor C<revents> need to be valid as long as the watcher callback	1143	C<loop> nor C<revents> need to be valid as long as the watcher callback
985	can deal with that fact.	1144	can deal with that fact, as both are simply passed through to the
		1145	callback.
986		1146
987	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1147	=item int ev_clear_pending (loop, ev_TYPE *watcher)
988		1148
989	If the watcher is pending, this function returns clears its pending status	1149	If the watcher is pending, this function clears its pending status and
990	and returns its C<revents> bitset (as if its callback was invoked). If the	1150	returns its C<revents> bitset (as if its callback was invoked). If the
991	watcher isn't pending it does nothing and returns C<0>.	1151	watcher isn't pending it does nothing and returns C<0>.
992		1152
		1153	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1154	callback to be invoked, which can be accomplished with this function.
		1155
993	=back	1156	=back
994		1157
995		1158
996	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1159	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
997		1160
998	Each watcher has, by default, a member C<void *data> that you can change	1161	Each watcher has, by default, a member C<void *data> that you can change
999	and read at any time, libev will completely ignore it. This can be used	1162	and read at any time: libev will completely ignore it. This can be used
1000	to associate arbitrary data with your watcher. If you need more data and	1163	to associate arbitrary data with your watcher. If you need more data and
1001	don't want to allocate memory and store a pointer to it in that data	1164	don't want to allocate memory and store a pointer to it in that data
1002	member, you can also "subclass" the watcher type and provide your own	1165	member, you can also "subclass" the watcher type and provide your own
1003	data:	1166	data:
1004		1167
1005	struct my_io	1168	struct my_io
1006	{	1169	{
1007	struct ev_io io;	1170	ev_io io;
1008	int otherfd;	1171	int otherfd;
1009	void *somedata;	1172	void *somedata;
1010	struct whatever *mostinteresting;	1173	struct whatever *mostinteresting;
1011	};	1174	};
1012		1175
…		…
1015	ev_io_init (&w.io, my_cb, fd, EV_READ);	1178	ev_io_init (&w.io, my_cb, fd, EV_READ);
1016		1179
1017	And since your callback will be called with a pointer to the watcher, you	1180	And since your callback will be called with a pointer to the watcher, you
1018	can cast it back to your own type:	1181	can cast it back to your own type:
1019		1182
1020	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1183	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1021	{	1184	{
1022	struct my_io *w = (struct my_io *)w_;	1185	struct my_io *w = (struct my_io *)w_;
1023	...	1186	...
1024	}	1187	}
1025		1188
…		…
1036	ev_timer t2;	1199	ev_timer t2;
1037	}	1200	}
1038		1201
1039	In this case getting the pointer to C<my_biggy> is a bit more	1202	In this case getting the pointer to C<my_biggy> is a bit more
1040	complicated: Either you store the address of your C<my_biggy> struct	1203	complicated: Either you store the address of your C<my_biggy> struct
1041	in the C<data> member of the watcher, or you need to use some pointer	1204	in the C<data> member of the watcher (for woozies), or you need to use
1042	arithmetic using C<offsetof> inside your watchers:	1205	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1206	programmers):
1043		1207
1044	#include <stddef.h>	1208	#include <stddef.h>
1045		1209
1046	static void	1210	static void
1047	t1_cb (EV_P_ struct ev_timer *w, int revents)	1211	t1_cb (EV_P_ ev_timer *w, int revents)
1048	{	1212	{
1049	struct my_biggy big = (struct my_biggy *	1213	struct my_biggy big = (struct my_biggy *)
1050	(((char *)w) - offsetof (struct my_biggy, t1));	1214	(((char *)w) - offsetof (struct my_biggy, t1));
1051	}	1215	}
1052		1216
1053	static void	1217	static void
1054	t2_cb (EV_P_ struct ev_timer *w, int revents)	1218	t2_cb (EV_P_ ev_timer *w, int revents)
1055	{	1219	{
1056	struct my_biggy big = (struct my_biggy *	1220	struct my_biggy big = (struct my_biggy *)
1057	(((char *)w) - offsetof (struct my_biggy, t2));	1221	(((char *)w) - offsetof (struct my_biggy, t2));
1058	}	1222	}
		1223
		1224	=head2 WATCHER PRIORITY MODELS
		1225
		1226	Many event loops support I<watcher priorities>, which are usually small
		1227	integers that influence the ordering of event callback invocation
		1228	between watchers in some way, all else being equal.
		1229
		1230	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1231	description for the more technical details such as the actual priority
		1232	range.
		1233
		1234	There are two common ways how these these priorities are being interpreted
		1235	by event loops:
		1236
		1237	In the more common lock-out model, higher priorities "lock out" invocation
		1238	of lower priority watchers, which means as long as higher priority
		1239	watchers receive events, lower priority watchers are not being invoked.
		1240
		1241	The less common only-for-ordering model uses priorities solely to order
		1242	callback invocation within a single event loop iteration: Higher priority
		1243	watchers are invoked before lower priority ones, but they all get invoked
		1244	before polling for new events.
		1245
		1246	Libev uses the second (only-for-ordering) model for all its watchers
		1247	except for idle watchers (which use the lock-out model).
		1248
		1249	The rationale behind this is that implementing the lock-out model for
		1250	watchers is not well supported by most kernel interfaces, and most event
		1251	libraries will just poll for the same events again and again as long as
		1252	their callbacks have not been executed, which is very inefficient in the
		1253	common case of one high-priority watcher locking out a mass of lower
		1254	priority ones.
		1255
		1256	Static (ordering) priorities are most useful when you have two or more
		1257	watchers handling the same resource: a typical usage example is having an
		1258	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1259	timeouts. Under load, data might be received while the program handles
		1260	other jobs, but since timers normally get invoked first, the timeout
		1261	handler will be executed before checking for data. In that case, giving
		1262	the timer a lower priority than the I/O watcher ensures that I/O will be
		1263	handled first even under adverse conditions (which is usually, but not
		1264	always, what you want).
		1265
		1266	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1267	will only be executed when no same or higher priority watchers have
		1268	received events, they can be used to implement the "lock-out" model when
		1269	required.
		1270
		1271	For example, to emulate how many other event libraries handle priorities,
		1272	you can associate an C<ev_idle> watcher to each such watcher, and in
		1273	the normal watcher callback, you just start the idle watcher. The real
		1274	processing is done in the idle watcher callback. This causes libev to
		1275	continously poll and process kernel event data for the watcher, but when
		1276	the lock-out case is known to be rare (which in turn is rare :), this is
		1277	workable.
		1278
		1279	Usually, however, the lock-out model implemented that way will perform
		1280	miserably under the type of load it was designed to handle. In that case,
		1281	it might be preferable to stop the real watcher before starting the
		1282	idle watcher, so the kernel will not have to process the event in case
		1283	the actual processing will be delayed for considerable time.
		1284
		1285	Here is an example of an I/O watcher that should run at a strictly lower
		1286	priority than the default, and which should only process data when no
		1287	other events are pending:
		1288
		1289	ev_idle idle; // actual processing watcher
		1290	ev_io io; // actual event watcher
		1291
		1292	static void
		1293	io_cb (EV_P_ ev_io *w, int revents)
		1294	{
		1295	// stop the I/O watcher, we received the event, but
		1296	// are not yet ready to handle it.
		1297	ev_io_stop (EV_A_ w);
		1298
		1299	// start the idle watcher to ahndle the actual event.
		1300	// it will not be executed as long as other watchers
		1301	// with the default priority are receiving events.
		1302	ev_idle_start (EV_A_ &idle);
		1303	}
		1304
		1305	static void
		1306	idle_cb (EV_P_ ev_idle *w, int revents)
		1307	{
		1308	// actual processing
		1309	read (STDIN_FILENO, ...);
		1310
		1311	// have to start the I/O watcher again, as
		1312	// we have handled the event
		1313	ev_io_start (EV_P_ &io);
		1314	}
		1315
		1316	// initialisation
		1317	ev_idle_init (&idle, idle_cb);
		1318	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1319	ev_io_start (EV_DEFAULT_ &io);
		1320
		1321	In the "real" world, it might also be beneficial to start a timer, so that
		1322	low-priority connections can not be locked out forever under load. This
		1323	enables your program to keep a lower latency for important connections
		1324	during short periods of high load, while not completely locking out less
		1325	important ones.
1059		1326
1060		1327
1061	=head1 WATCHER TYPES	1328	=head1 WATCHER TYPES
1062		1329
1063	This section describes each watcher in detail, but will not repeat	1330	This section describes each watcher in detail, but will not repeat
…		…
1087	In general you can register as many read and/or write event watchers per	1354	In general you can register as many read and/or write event watchers per
1088	fd as you want (as long as you don't confuse yourself). Setting all file	1355	fd as you want (as long as you don't confuse yourself). Setting all file
1089	descriptors to non-blocking mode is also usually a good idea (but not	1356	descriptors to non-blocking mode is also usually a good idea (but not
1090	required if you know what you are doing).	1357	required if you know what you are doing).
1091		1358
1092	If you must do this, then force the use of a known-to-be-good backend	1359	If you cannot use non-blocking mode, then force the use of a
1093	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1360	known-to-be-good backend (at the time of this writing, this includes only
1094	C<EVBACKEND_POLL>).	1361	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1362	descriptors for which non-blocking operation makes no sense (such as
		1363	files) - libev doesn't guarentee any specific behaviour in that case.
1095		1364
1096	Another thing you have to watch out for is that it is quite easy to	1365	Another thing you have to watch out for is that it is quite easy to
1097	receive "spurious" readiness notifications, that is your callback might	1366	receive "spurious" readiness notifications, that is your callback might
1098	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1367	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1099	because there is no data. Not only are some backends known to create a	1368	because there is no data. Not only are some backends known to create a
1100	lot of those (for example Solaris ports), it is very easy to get into	1369	lot of those (for example Solaris ports), it is very easy to get into
1101	this situation even with a relatively standard program structure. Thus	1370	this situation even with a relatively standard program structure. Thus
1102	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1371	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1103	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1372	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1104		1373
1105	If you cannot run the fd in non-blocking mode (for example you should not	1374	If you cannot run the fd in non-blocking mode (for example you should
1106	play around with an Xlib connection), then you have to separately re-test	1375	not play around with an Xlib connection), then you have to separately
1107	whether a file descriptor is really ready with a known-to-be good interface	1376	re-test whether a file descriptor is really ready with a known-to-be good
1108	such as poll (fortunately in our Xlib example, Xlib already does this on	1377	interface such as poll (fortunately in our Xlib example, Xlib already
1109	its own, so its quite safe to use).	1378	does this on its own, so its quite safe to use). Some people additionally
		1379	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1380	indefinitely.
		1381
		1382	But really, best use non-blocking mode.
1110		1383
1111	=head3 The special problem of disappearing file descriptors	1384	=head3 The special problem of disappearing file descriptors
1112		1385
1113	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1386	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1114	descriptor (either by calling C<close> explicitly or by any other means,	1387	descriptor (either due to calling C<close> explicitly or any other means,
1115	such as C<dup>). The reason is that you register interest in some file	1388	such as C<dup2>). The reason is that you register interest in some file
1116	descriptor, but when it goes away, the operating system will silently drop	1389	descriptor, but when it goes away, the operating system will silently drop
1117	this interest. If another file descriptor with the same number then is	1390	this interest. If another file descriptor with the same number then is
1118	registered with libev, there is no efficient way to see that this is, in	1391	registered with libev, there is no efficient way to see that this is, in
1119	fact, a different file descriptor.	1392	fact, a different file descriptor.
1120		1393
…		…
1151	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1424	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1152	C<EVBACKEND_POLL>.	1425	C<EVBACKEND_POLL>.
1153		1426
1154	=head3 The special problem of SIGPIPE	1427	=head3 The special problem of SIGPIPE
1155		1428
1156	While not really specific to libev, it is easy to forget about SIGPIPE:	1429	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1157	when writing to a pipe whose other end has been closed, your program gets	1430	when writing to a pipe whose other end has been closed, your program gets
1158	send a SIGPIPE, which, by default, aborts your program. For most programs	1431	sent a SIGPIPE, which, by default, aborts your program. For most programs
1159	this is sensible behaviour, for daemons, this is usually undesirable.	1432	this is sensible behaviour, for daemons, this is usually undesirable.
1160		1433
1161	So when you encounter spurious, unexplained daemon exits, make sure you	1434	So when you encounter spurious, unexplained daemon exits, make sure you
1162	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1435	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1163	somewhere, as that would have given you a big clue).	1436	somewhere, as that would have given you a big clue).
…		…
1170	=item ev_io_init (ev_io *, callback, int fd, int events)	1443	=item ev_io_init (ev_io *, callback, int fd, int events)
1171		1444
1172	=item ev_io_set (ev_io *, int fd, int events)	1445	=item ev_io_set (ev_io *, int fd, int events)
1173		1446
1174	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1447	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1175	receive events for and events is either C<EV_READ>, C<EV_WRITE> or	1448	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1176	C<EV_READ | EV_WRITE> to receive the given events.	1449	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1177		1450
1178	=item int fd [read-only]	1451	=item int fd [read-only]
1179		1452
1180	The file descriptor being watched.	1453	The file descriptor being watched.
1181		1454
…		…
1190	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1463	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1191	readable, but only once. Since it is likely line-buffered, you could	1464	readable, but only once. Since it is likely line-buffered, you could
1192	attempt to read a whole line in the callback.	1465	attempt to read a whole line in the callback.
1193		1466
1194	static void	1467	static void
1195	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1468	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1196	{	1469	{
1197	ev_io_stop (loop, w);	1470	ev_io_stop (loop, w);
1198	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1471	.. read from stdin here (or from w->fd) and handle any I/O errors
1199	}	1472	}
1200		1473
1201	...	1474	...
1202	struct ev_loop *loop = ev_default_init (0);	1475	struct ev_loop *loop = ev_default_init (0);
1203	struct ev_io stdin_readable;	1476	ev_io stdin_readable;
1204	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1477	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1205	ev_io_start (loop, &stdin_readable);	1478	ev_io_start (loop, &stdin_readable);
1206	ev_loop (loop, 0);	1479	ev_loop (loop, 0);
1207		1480
1208		1481
…		…
1211	Timer watchers are simple relative timers that generate an event after a	1484	Timer watchers are simple relative timers that generate an event after a
1212	given time, and optionally repeating in regular intervals after that.	1485	given time, and optionally repeating in regular intervals after that.
1213		1486
1214	The timers are based on real time, that is, if you register an event that	1487	The timers are based on real time, that is, if you register an event that
1215	times out after an hour and you reset your system clock to January last	1488	times out after an hour and you reset your system clock to January last
1216	year, it will still time out after (roughly) and hour. "Roughly" because	1489	year, it will still time out after (roughly) one hour. "Roughly" because
1217	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1490	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1218	monotonic clock option helps a lot here).	1491	monotonic clock option helps a lot here).
1219		1492
1220	The callback is guaranteed to be invoked only after its timeout has passed,	1493	The callback is guaranteed to be invoked only I<after> its timeout has
1221	but if multiple timers become ready during the same loop iteration then	1494	passed (not I<at>, so on systems with very low-resolution clocks this
1222	order of execution is undefined.	1495	might introduce a small delay). If multiple timers become ready during the
		1496	same loop iteration then the ones with earlier time-out values are invoked
		1497	before ones of the same priority with later time-out values (but this is
		1498	no longer true when a callback calls C<ev_loop> recursively).
		1499
		1500	=head3 Be smart about timeouts
		1501
		1502	Many real-world problems involve some kind of timeout, usually for error
		1503	recovery. A typical example is an HTTP request - if the other side hangs,
		1504	you want to raise some error after a while.
		1505
		1506	What follows are some ways to handle this problem, from obvious and
		1507	inefficient to smart and efficient.
		1508
		1509	In the following, a 60 second activity timeout is assumed - a timeout that
		1510	gets reset to 60 seconds each time there is activity (e.g. each time some
		1511	data or other life sign was received).
		1512
		1513	=over 4
		1514
		1515	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1516
		1517	This is the most obvious, but not the most simple way: In the beginning,
		1518	start the watcher:
		1519
		1520	ev_timer_init (timer, callback, 60., 0.);
		1521	ev_timer_start (loop, timer);
		1522
		1523	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1524	and start it again:
		1525
		1526	ev_timer_stop (loop, timer);
		1527	ev_timer_set (timer, 60., 0.);
		1528	ev_timer_start (loop, timer);
		1529
		1530	This is relatively simple to implement, but means that each time there is
		1531	some activity, libev will first have to remove the timer from its internal
		1532	data structure and then add it again. Libev tries to be fast, but it's
		1533	still not a constant-time operation.
		1534
		1535	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1536
		1537	This is the easiest way, and involves using C<ev_timer_again> instead of
		1538	C<ev_timer_start>.
		1539
		1540	To implement this, configure an C<ev_timer> with a C<repeat> value
		1541	of C<60> and then call C<ev_timer_again> at start and each time you
		1542	successfully read or write some data. If you go into an idle state where
		1543	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1544	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1545
		1546	That means you can ignore both the C<ev_timer_start> function and the
		1547	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1548	member and C<ev_timer_again>.
		1549
		1550	At start:
		1551
		1552	ev_init (timer, callback);
		1553	timer->repeat = 60.;
		1554	ev_timer_again (loop, timer);
		1555
		1556	Each time there is some activity:
		1557
		1558	ev_timer_again (loop, timer);
		1559
		1560	It is even possible to change the time-out on the fly, regardless of
		1561	whether the watcher is active or not:
		1562
		1563	timer->repeat = 30.;
		1564	ev_timer_again (loop, timer);
		1565
		1566	This is slightly more efficient then stopping/starting the timer each time
		1567	you want to modify its timeout value, as libev does not have to completely
		1568	remove and re-insert the timer from/into its internal data structure.
		1569
		1570	It is, however, even simpler than the "obvious" way to do it.
		1571
		1572	=item 3. Let the timer time out, but then re-arm it as required.
		1573
		1574	This method is more tricky, but usually most efficient: Most timeouts are
		1575	relatively long compared to the intervals between other activity - in
		1576	our example, within 60 seconds, there are usually many I/O events with
		1577	associated activity resets.
		1578
		1579	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1580	but remember the time of last activity, and check for a real timeout only
		1581	within the callback:
		1582
		1583	ev_tstamp last_activity; // time of last activity
		1584
		1585	static void
		1586	callback (EV_P_ ev_timer *w, int revents)
		1587	{
		1588	ev_tstamp now = ev_now (EV_A);
		1589	ev_tstamp timeout = last_activity + 60.;
		1590
		1591	// if last_activity + 60. is older than now, we did time out
		1592	if (timeout < now)
		1593	{
		1594	// timeout occured, take action
		1595	}
		1596	else
		1597	{
		1598	// callback was invoked, but there was some activity, re-arm
		1599	// the watcher to fire in last_activity + 60, which is
		1600	// guaranteed to be in the future, so "again" is positive:
		1601	w->repeat = timeout - now;
		1602	ev_timer_again (EV_A_ w);
		1603	}
		1604	}
		1605
		1606	To summarise the callback: first calculate the real timeout (defined
		1607	as "60 seconds after the last activity"), then check if that time has
		1608	been reached, which means something I<did>, in fact, time out. Otherwise
		1609	the callback was invoked too early (C<timeout> is in the future), so
		1610	re-schedule the timer to fire at that future time, to see if maybe we have
		1611	a timeout then.
		1612
		1613	Note how C<ev_timer_again> is used, taking advantage of the
		1614	C<ev_timer_again> optimisation when the timer is already running.
		1615
		1616	This scheme causes more callback invocations (about one every 60 seconds
		1617	minus half the average time between activity), but virtually no calls to
		1618	libev to change the timeout.
		1619
		1620	To start the timer, simply initialise the watcher and set C<last_activity>
		1621	to the current time (meaning we just have some activity :), then call the
		1622	callback, which will "do the right thing" and start the timer:
		1623
		1624	ev_init (timer, callback);
		1625	last_activity = ev_now (loop);
		1626	callback (loop, timer, EV_TIMEOUT);
		1627
		1628	And when there is some activity, simply store the current time in
		1629	C<last_activity>, no libev calls at all:
		1630
		1631	last_actiivty = ev_now (loop);
		1632
		1633	This technique is slightly more complex, but in most cases where the
		1634	time-out is unlikely to be triggered, much more efficient.
		1635
		1636	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1637	callback :) - just change the timeout and invoke the callback, which will
		1638	fix things for you.
		1639
		1640	=item 4. Wee, just use a double-linked list for your timeouts.
		1641
		1642	If there is not one request, but many thousands (millions...), all
		1643	employing some kind of timeout with the same timeout value, then one can
		1644	do even better:
		1645
		1646	When starting the timeout, calculate the timeout value and put the timeout
		1647	at the I<end> of the list.
		1648
		1649	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1650	the list is expected to fire (for example, using the technique #3).
		1651
		1652	When there is some activity, remove the timer from the list, recalculate
		1653	the timeout, append it to the end of the list again, and make sure to
		1654	update the C<ev_timer> if it was taken from the beginning of the list.
		1655
		1656	This way, one can manage an unlimited number of timeouts in O(1) time for
		1657	starting, stopping and updating the timers, at the expense of a major
		1658	complication, and having to use a constant timeout. The constant timeout
		1659	ensures that the list stays sorted.
		1660
		1661	=back
		1662
		1663	So which method the best?
		1664
		1665	Method #2 is a simple no-brain-required solution that is adequate in most
		1666	situations. Method #3 requires a bit more thinking, but handles many cases
		1667	better, and isn't very complicated either. In most case, choosing either
		1668	one is fine, with #3 being better in typical situations.
		1669
		1670	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1671	rather complicated, but extremely efficient, something that really pays
		1672	off after the first million or so of active timers, i.e. it's usually
		1673	overkill :)
1223		1674
1224	=head3 The special problem of time updates	1675	=head3 The special problem of time updates
1225		1676
1226	Establishing the current time is a costly operation (it usually takes at	1677	Establishing the current time is a costly operation (it usually takes at
1227	least two system calls): EV therefore updates its idea of the current	1678	least two system calls): EV therefore updates its idea of the current
1228	time only before and after C<ev_loop> polls for new events, which causes	1679	time only before and after C<ev_loop> collects new events, which causes a
1229	a growing difference between C<ev_now ()> and C<ev_time ()> when handling	1680	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1230	lots of events.	1681	lots of events in one iteration.
1231		1682
1232	The relative timeouts are calculated relative to the C<ev_now ()>	1683	The relative timeouts are calculated relative to the C<ev_now ()>
1233	time. This is usually the right thing as this timestamp refers to the time	1684	time. This is usually the right thing as this timestamp refers to the time
1234	of the event triggering whatever timeout you are modifying/starting. If	1685	of the event triggering whatever timeout you are modifying/starting. If
1235	you suspect event processing to be delayed and you I<need> to base the	1686	you suspect event processing to be delayed and you I<need> to base the
…		…
1271	If the timer is started but non-repeating, stop it (as if it timed out).	1722	If the timer is started but non-repeating, stop it (as if it timed out).
1272		1723
1273	If the timer is repeating, either start it if necessary (with the	1724	If the timer is repeating, either start it if necessary (with the
1274	C<repeat> value), or reset the running timer to the C<repeat> value.	1725	C<repeat> value), or reset the running timer to the C<repeat> value.
1275		1726
1276	This sounds a bit complicated, but here is a useful and typical	1727	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1277	example: Imagine you have a TCP connection and you want a so-called idle	1728	usage example.
1278	timeout, that is, you want to be called when there have been, say, 60
1279	seconds of inactivity on the socket. The easiest way to do this is to
1280	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1281	C<ev_timer_again> each time you successfully read or write some data. If
1282	you go into an idle state where you do not expect data to travel on the
1283	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1284	automatically restart it if need be.
1285
1286	That means you can ignore the C<after> value and C<ev_timer_start>
1287	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1288
1289	ev_timer_init (timer, callback, 0., 5.);
1290	ev_timer_again (loop, timer);
1291	...
1292	timer->again = 17.;
1293	ev_timer_again (loop, timer);
1294	...
1295	timer->again = 10.;
1296	ev_timer_again (loop, timer);
1297
1298	This is more slightly efficient then stopping/starting the timer each time
1299	you want to modify its timeout value.
1300		1729
1301	=item ev_tstamp repeat [read-write]	1730	=item ev_tstamp repeat [read-write]
1302		1731
1303	The current C<repeat> value. Will be used each time the watcher times out	1732	The current C<repeat> value. Will be used each time the watcher times out
1304	or C<ev_timer_again> is called and determines the next timeout (if any),	1733	or C<ev_timer_again> is called, and determines the next timeout (if any),
1305	which is also when any modifications are taken into account.	1734	which is also when any modifications are taken into account.
1306		1735
1307	=back	1736	=back
1308		1737
1309	=head3 Examples	1738	=head3 Examples
1310		1739
1311	Example: Create a timer that fires after 60 seconds.	1740	Example: Create a timer that fires after 60 seconds.
1312		1741
1313	static void	1742	static void
1314	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1743	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1315	{	1744	{
1316	.. one minute over, w is actually stopped right here	1745	.. one minute over, w is actually stopped right here
1317	}	1746	}
1318		1747
1319	struct ev_timer mytimer;	1748	ev_timer mytimer;
1320	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1749	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1321	ev_timer_start (loop, &mytimer);	1750	ev_timer_start (loop, &mytimer);
1322		1751
1323	Example: Create a timeout timer that times out after 10 seconds of	1752	Example: Create a timeout timer that times out after 10 seconds of
1324	inactivity.	1753	inactivity.
1325		1754
1326	static void	1755	static void
1327	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1756	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1328	{	1757	{
1329	.. ten seconds without any activity	1758	.. ten seconds without any activity
1330	}	1759	}
1331		1760
1332	struct ev_timer mytimer;	1761	ev_timer mytimer;
1333	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1762	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1334	ev_timer_again (&mytimer); /* start timer */	1763	ev_timer_again (&mytimer); /* start timer */
1335	ev_loop (loop, 0);	1764	ev_loop (loop, 0);
1336		1765
1337	// and in some piece of code that gets executed on any "activity":	1766	// and in some piece of code that gets executed on any "activity":
…		…
1342	=head2 C<ev_periodic> - to cron or not to cron?	1771	=head2 C<ev_periodic> - to cron or not to cron?
1343		1772
1344	Periodic watchers are also timers of a kind, but they are very versatile	1773	Periodic watchers are also timers of a kind, but they are very versatile
1345	(and unfortunately a bit complex).	1774	(and unfortunately a bit complex).
1346		1775
1347	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1776	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1348	but on wall clock time (absolute time). You can tell a periodic watcher	1777	relative time, the physical time that passes) but on wall clock time
1349	to trigger after some specific point in time. For example, if you tell a	1778	(absolute time, the thing you can read on your calender or clock). The
1350	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	1779	difference is that wall clock time can run faster or slower than real
1351	+ 10.>, that is, an absolute time not a delay) and then reset your system	1780	time, and time jumps are not uncommon (e.g. when you adjust your
1352	clock to January of the previous year, then it will take more than year	1781	wrist-watch).
1353	to trigger the event (unlike an C<ev_timer>, which would still trigger
1354	roughly 10 seconds later as it uses a relative timeout).
1355		1782
		1783	You can tell a periodic watcher to trigger after some specific point
		1784	in time: for example, if you tell a periodic watcher to trigger "in 10
		1785	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1786	not a delay) and then reset your system clock to January of the previous
		1787	year, then it will take a year or more to trigger the event (unlike an
		1788	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1789	it, as it uses a relative timeout).
		1790
1356	C<ev_periodic>s can also be used to implement vastly more complex timers,	1791	C<ev_periodic> watchers can also be used to implement vastly more complex
1357	such as triggering an event on each "midnight, local time", or other	1792	timers, such as triggering an event on each "midnight, local time", or
1358	complicated, rules.	1793	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1794	those cannot react to time jumps.
1359		1795
1360	As with timers, the callback is guaranteed to be invoked only when the	1796	As with timers, the callback is guaranteed to be invoked only when the
1361	time (C<at>) has passed, but if multiple periodic timers become ready	1797	point in time where it is supposed to trigger has passed. If multiple
1362	during the same loop iteration then order of execution is undefined.	1798	timers become ready during the same loop iteration then the ones with
		1799	earlier time-out values are invoked before ones with later time-out values
		1800	(but this is no longer true when a callback calls C<ev_loop> recursively).
1363		1801
1364	=head3 Watcher-Specific Functions and Data Members	1802	=head3 Watcher-Specific Functions and Data Members
1365		1803
1366	=over 4	1804	=over 4
1367		1805
1368	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1806	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1369		1807
1370	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1808	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1371		1809
1372	Lots of arguments, lets sort it out... There are basically three modes of	1810	Lots of arguments, let's sort it out... There are basically three modes of
1373	operation, and we will explain them from simplest to complex:	1811	operation, and we will explain them from simplest to most complex:
1374		1812
1375	=over 4	1813	=over 4
1376		1814
1377	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1815	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1378		1816
1379	In this configuration the watcher triggers an event after the wall clock	1817	In this configuration the watcher triggers an event after the wall clock
1380	time C<at> has passed and doesn't repeat. It will not adjust when a time	1818	time C<offset> has passed. It will not repeat and will not adjust when a
1381	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1819	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1382	run when the system time reaches or surpasses this time.	1820	will be stopped and invoked when the system clock reaches or surpasses
		1821	this point in time.
1383		1822
1384	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1823	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1385		1824
1386	In this mode the watcher will always be scheduled to time out at the next	1825	In this mode the watcher will always be scheduled to time out at the next
1387	C<at + N * interval> time (for some integer N, which can also be negative)	1826	C<offset + N * interval> time (for some integer N, which can also be
1388	and then repeat, regardless of any time jumps.	1827	negative) and then repeat, regardless of any time jumps. The C<offset>
		1828	argument is merely an offset into the C<interval> periods.
1389		1829
1390	This can be used to create timers that do not drift with respect to system	1830	This can be used to create timers that do not drift with respect to the
1391	time, for example, here is a C<ev_periodic> that triggers each hour, on	1831	system clock, for example, here is an C<ev_periodic> that triggers each
1392	the hour:	1832	hour, on the hour (with respect to UTC):
1393		1833
1394	ev_periodic_set (&periodic, 0., 3600., 0);	1834	ev_periodic_set (&periodic, 0., 3600., 0);
1395		1835
1396	This doesn't mean there will always be 3600 seconds in between triggers,	1836	This doesn't mean there will always be 3600 seconds in between triggers,
1397	but only that the callback will be called when the system time shows a	1837	but only that the callback will be called when the system time shows a
1398	full hour (UTC), or more correctly, when the system time is evenly divisible	1838	full hour (UTC), or more correctly, when the system time is evenly divisible
1399	by 3600.	1839	by 3600.
1400		1840
1401	Another way to think about it (for the mathematically inclined) is that	1841	Another way to think about it (for the mathematically inclined) is that
1402	C<ev_periodic> will try to run the callback in this mode at the next possible	1842	C<ev_periodic> will try to run the callback in this mode at the next possible
1403	time where C<time = at (mod interval)>, regardless of any time jumps.	1843	time where C<time = offset (mod interval)>, regardless of any time jumps.
1404		1844
1405	For numerical stability it is preferable that the C<at> value is near	1845	For numerical stability it is preferable that the C<offset> value is near
1406	C<ev_now ()> (the current time), but there is no range requirement for	1846	C<ev_now ()> (the current time), but there is no range requirement for
1407	this value, and in fact is often specified as zero.	1847	this value, and in fact is often specified as zero.
1408		1848
1409	Note also that there is an upper limit to how often a timer can fire (CPU	1849	Note also that there is an upper limit to how often a timer can fire (CPU
1410	speed for example), so if C<interval> is very small then timing stability	1850	speed for example), so if C<interval> is very small then timing stability
1411	will of course deteriorate. Libev itself tries to be exact to be about one	1851	will of course deteriorate. Libev itself tries to be exact to be about one
1412	millisecond (if the OS supports it and the machine is fast enough).	1852	millisecond (if the OS supports it and the machine is fast enough).
1413		1853
1414	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1854	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1415		1855
1416	In this mode the values for C<interval> and C<at> are both being	1856	In this mode the values for C<interval> and C<offset> are both being
1417	ignored. Instead, each time the periodic watcher gets scheduled, the	1857	ignored. Instead, each time the periodic watcher gets scheduled, the
1418	reschedule callback will be called with the watcher as first, and the	1858	reschedule callback will be called with the watcher as first, and the
1419	current time as second argument.	1859	current time as second argument.
1420		1860
1421	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1861	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1422	ever, or make ANY event loop modifications whatsoever>.	1862	or make ANY other event loop modifications whatsoever, unless explicitly
		1863	allowed by documentation here>.
1423		1864
1424	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1865	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1425	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	1866	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1426	only event loop modification you are allowed to do).	1867	only event loop modification you are allowed to do).
1427		1868
1428	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1869	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1429	*w, ev_tstamp now)>, e.g.:	1870	*w, ev_tstamp now)>, e.g.:
1430		1871
		1872	static ev_tstamp
1431	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1873	my_rescheduler (ev_periodic *w, ev_tstamp now)
1432	{	1874	{
1433	return now + 60.;	1875	return now + 60.;
1434	}	1876	}
1435		1877
1436	It must return the next time to trigger, based on the passed time value	1878	It must return the next time to trigger, based on the passed time value
…		…
1456	a different time than the last time it was called (e.g. in a crond like	1898	a different time than the last time it was called (e.g. in a crond like
1457	program when the crontabs have changed).	1899	program when the crontabs have changed).
1458		1900
1459	=item ev_tstamp ev_periodic_at (ev_periodic *)	1901	=item ev_tstamp ev_periodic_at (ev_periodic *)
1460		1902
1461	When active, returns the absolute time that the watcher is supposed to	1903	When active, returns the absolute time that the watcher is supposed
1462	trigger next.	1904	to trigger next. This is not the same as the C<offset> argument to
		1905	C<ev_periodic_set>, but indeed works even in interval and manual
		1906	rescheduling modes.
1463		1907
1464	=item ev_tstamp offset [read-write]	1908	=item ev_tstamp offset [read-write]
1465		1909
1466	When repeating, this contains the offset value, otherwise this is the	1910	When repeating, this contains the offset value, otherwise this is the
1467	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1911	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		1912	although libev might modify this value for better numerical stability).
1468		1913
1469	Can be modified any time, but changes only take effect when the periodic	1914	Can be modified any time, but changes only take effect when the periodic
1470	timer fires or C<ev_periodic_again> is being called.	1915	timer fires or C<ev_periodic_again> is being called.
1471		1916
1472	=item ev_tstamp interval [read-write]	1917	=item ev_tstamp interval [read-write]
1473		1918
1474	The current interval value. Can be modified any time, but changes only	1919	The current interval value. Can be modified any time, but changes only
1475	take effect when the periodic timer fires or C<ev_periodic_again> is being	1920	take effect when the periodic timer fires or C<ev_periodic_again> is being
1476	called.	1921	called.
1477		1922
1478	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1923	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1479		1924
1480	The current reschedule callback, or C<0>, if this functionality is	1925	The current reschedule callback, or C<0>, if this functionality is
1481	switched off. Can be changed any time, but changes only take effect when	1926	switched off. Can be changed any time, but changes only take effect when
1482	the periodic timer fires or C<ev_periodic_again> is being called.	1927	the periodic timer fires or C<ev_periodic_again> is being called.
1483		1928
1484	=back	1929	=back
1485		1930
1486	=head3 Examples	1931	=head3 Examples
1487		1932
1488	Example: Call a callback every hour, or, more precisely, whenever the	1933	Example: Call a callback every hour, or, more precisely, whenever the
1489	system clock is divisible by 3600. The callback invocation times have	1934	system time is divisible by 3600. The callback invocation times have
1490	potentially a lot of jitter, but good long-term stability.	1935	potentially a lot of jitter, but good long-term stability.
1491		1936
1492	static void	1937	static void
1493	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1938	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1494	{	1939	{
1495	... its now a full hour (UTC, or TAI or whatever your clock follows)	1940	... its now a full hour (UTC, or TAI or whatever your clock follows)
1496	}	1941	}
1497		1942
1498	struct ev_periodic hourly_tick;	1943	ev_periodic hourly_tick;
1499	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1944	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1500	ev_periodic_start (loop, &hourly_tick);	1945	ev_periodic_start (loop, &hourly_tick);
1501		1946
1502	Example: The same as above, but use a reschedule callback to do it:	1947	Example: The same as above, but use a reschedule callback to do it:
1503		1948
1504	#include <math.h>	1949	#include <math.h>
1505		1950
1506	static ev_tstamp	1951	static ev_tstamp
1507	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1952	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1508	{	1953	{
1509	return fmod (now, 3600.) + 3600.;	1954	return now + (3600. - fmod (now, 3600.));
1510	}	1955	}
1511		1956
1512	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1957	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1513		1958
1514	Example: Call a callback every hour, starting now:	1959	Example: Call a callback every hour, starting now:
1515		1960
1516	struct ev_periodic hourly_tick;	1961	ev_periodic hourly_tick;
1517	ev_periodic_init (&hourly_tick, clock_cb,	1962	ev_periodic_init (&hourly_tick, clock_cb,
1518	fmod (ev_now (loop), 3600.), 3600., 0);	1963	fmod (ev_now (loop), 3600.), 3600., 0);
1519	ev_periodic_start (loop, &hourly_tick);	1964	ev_periodic_start (loop, &hourly_tick);
1520		1965
1521		1966
…		…
1524	Signal watchers will trigger an event when the process receives a specific	1969	Signal watchers will trigger an event when the process receives a specific
1525	signal one or more times. Even though signals are very asynchronous, libev	1970	signal one or more times. Even though signals are very asynchronous, libev
1526	will try it's best to deliver signals synchronously, i.e. as part of the	1971	will try it's best to deliver signals synchronously, i.e. as part of the
1527	normal event processing, like any other event.	1972	normal event processing, like any other event.
1528		1973
		1974	If you want signals asynchronously, just use C<sigaction> as you would
		1975	do without libev and forget about sharing the signal. You can even use
		1976	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1977
1529	You can configure as many watchers as you like per signal. Only when the	1978	You can configure as many watchers as you like per signal. Only when the
1530	first watcher gets started will libev actually register a signal watcher	1979	first watcher gets started will libev actually register a signal handler
1531	with the kernel (thus it coexists with your own signal handlers as long	1980	with the kernel (thus it coexists with your own signal handlers as long as
1532	as you don't register any with libev). Similarly, when the last signal	1981	you don't register any with libev for the same signal). Similarly, when
1533	watcher for a signal is stopped libev will reset the signal handler to	1982	the last signal watcher for a signal is stopped, libev will reset the
1534	SIG_DFL (regardless of what it was set to before).	1983	signal handler to SIG_DFL (regardless of what it was set to before).
1535		1984
1536	If possible and supported, libev will install its handlers with	1985	If possible and supported, libev will install its handlers with
1537	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	1986	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1538	interrupted. If you have a problem with system calls getting interrupted by	1987	interrupted. If you have a problem with system calls getting interrupted by
1539	signals you can block all signals in an C<ev_check> watcher and unblock	1988	signals you can block all signals in an C<ev_check> watcher and unblock
…		…
1556		2005
1557	=back	2006	=back
1558		2007
1559	=head3 Examples	2008	=head3 Examples
1560		2009
1561	Example: Try to exit cleanly on SIGINT and SIGTERM.	2010	Example: Try to exit cleanly on SIGINT.
1562		2011
1563	static void	2012	static void
1564	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2013	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1565	{	2014	{
1566	ev_unloop (loop, EVUNLOOP_ALL);	2015	ev_unloop (loop, EVUNLOOP_ALL);
1567	}	2016	}
1568		2017
1569	struct ev_signal signal_watcher;	2018	ev_signal signal_watcher;
1570	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2019	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1571	ev_signal_start (loop, &sigint_cb);	2020	ev_signal_start (loop, &signal_watcher);
1572		2021
1573		2022
1574	=head2 C<ev_child> - watch out for process status changes	2023	=head2 C<ev_child> - watch out for process status changes
1575		2024
1576	Child watchers trigger when your process receives a SIGCHLD in response to	2025	Child watchers trigger when your process receives a SIGCHLD in response to
1577	some child status changes (most typically when a child of yours dies). It	2026	some child status changes (most typically when a child of yours dies or
1578	is permissible to install a child watcher I<after> the child has been	2027	exits). It is permissible to install a child watcher I<after> the child
1579	forked (which implies it might have already exited), as long as the event	2028	has been forked (which implies it might have already exited), as long
1580	loop isn't entered (or is continued from a watcher).	2029	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2030	forking and then immediately registering a watcher for the child is fine,
		2031	but forking and registering a watcher a few event loop iterations later or
		2032	in the next callback invocation is not.
1581		2033
1582	Only the default event loop is capable of handling signals, and therefore	2034	Only the default event loop is capable of handling signals, and therefore
1583	you can only register child watchers in the default event loop.	2035	you can only register child watchers in the default event loop.
		2036
		2037	Due to some design glitches inside libev, child watchers will always be
		2038	handled at maximum priority (their priority is set to EV_MAXPRI by libev)
1584		2039
1585	=head3 Process Interaction	2040	=head3 Process Interaction
1586		2041
1587	Libev grabs C<SIGCHLD> as soon as the default event loop is	2042	Libev grabs C<SIGCHLD> as soon as the default event loop is
1588	initialised. This is necessary to guarantee proper behaviour even if	2043	initialised. This is necessary to guarantee proper behaviour even if
…		…
1646	its completion.	2101	its completion.
1647		2102
1648	ev_child cw;	2103	ev_child cw;
1649		2104
1650	static void	2105	static void
1651	child_cb (EV_P_ struct ev_child *w, int revents)	2106	child_cb (EV_P_ ev_child *w, int revents)
1652	{	2107	{
1653	ev_child_stop (EV_A_ w);	2108	ev_child_stop (EV_A_ w);
1654	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2109	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1655	}	2110	}
1656		2111
…		…
1671		2126
1672		2127
1673	=head2 C<ev_stat> - did the file attributes just change?	2128	=head2 C<ev_stat> - did the file attributes just change?
1674		2129
1675	This watches a file system path for attribute changes. That is, it calls	2130	This watches a file system path for attribute changes. That is, it calls
1676	C<stat> regularly (or when the OS says it changed) and sees if it changed	2131	C<stat> on that path in regular intervals (or when the OS says it changed)
1677	compared to the last time, invoking the callback if it did.	2132	and sees if it changed compared to the last time, invoking the callback if
		2133	it did.
1678		2134
1679	The path does not need to exist: changing from "path exists" to "path does	2135	The path does not need to exist: changing from "path exists" to "path does
1680	not exist" is a status change like any other. The condition "path does	2136	not exist" is a status change like any other. The condition "path does not
1681	not exist" is signified by the C<st_nlink> field being zero (which is	2137	exist" (or more correctly "path cannot be stat'ed") is signified by the
1682	otherwise always forced to be at least one) and all the other fields of	2138	C<st_nlink> field being zero (which is otherwise always forced to be at
1683	the stat buffer having unspecified contents.	2139	least one) and all the other fields of the stat buffer having unspecified
		2140	contents.
1684		2141
1685	The path I<should> be absolute and I<must not> end in a slash. If it is	2142	The path I<must not> end in a slash or contain special components such as
		2143	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1686	relative and your working directory changes, the behaviour is undefined.	2144	your working directory changes, then the behaviour is undefined.
1687		2145
1688	Since there is no standard to do this, the portable implementation simply	2146	Since there is no portable change notification interface available, the
1689	calls C<stat (2)> regularly on the path to see if it changed somehow. You	2147	portable implementation simply calls C<stat(2)> regularly on the path
1690	can specify a recommended polling interval for this case. If you specify	2148	to see if it changed somehow. You can specify a recommended polling
1691	a polling interval of C<0> (highly recommended!) then a I<suitable,	2149	interval for this case. If you specify a polling interval of C<0> (highly
1692	unspecified default> value will be used (which you can expect to be around	2150	recommended!) then a I<suitable, unspecified default> value will be used
1693	five seconds, although this might change dynamically). Libev will also	2151	(which you can expect to be around five seconds, although this might
1694	impose a minimum interval which is currently around C<0.1>, but thats	2152	change dynamically). Libev will also impose a minimum interval which is
1695	usually overkill.	2153	currently around C<0.1>, but that's usually overkill.
1696		2154
1697	This watcher type is not meant for massive numbers of stat watchers,	2155	This watcher type is not meant for massive numbers of stat watchers,
1698	as even with OS-supported change notifications, this can be	2156	as even with OS-supported change notifications, this can be
1699	resource-intensive.	2157	resource-intensive.
1700		2158
1701	At the time of this writing, only the Linux inotify interface is	2159	At the time of this writing, the only OS-specific interface implemented
1702	implemented (implementing kqueue support is left as an exercise for the	2160	is the Linux inotify interface (implementing kqueue support is left as an
1703	reader, note, however, that the author sees no way of implementing ev_stat	2161	exercise for the reader. Note, however, that the author sees no way of
1704	semantics with kqueue). Inotify will be used to give hints only and should	2162	implementing C<ev_stat> semantics with kqueue, except as a hint).
1705	not change the semantics of C<ev_stat> watchers, which means that libev
1706	sometimes needs to fall back to regular polling again even with inotify,
1707	but changes are usually detected immediately, and if the file exists there
1708	will be no polling.
1709		2163
1710	=head3 ABI Issues (Largefile Support)	2164	=head3 ABI Issues (Largefile Support)
1711		2165
1712	Libev by default (unless the user overrides this) uses the default	2166	Libev by default (unless the user overrides this) uses the default
1713	compilation environment, which means that on systems with large file	2167	compilation environment, which means that on systems with large file
1714	support disabled by default, you get the 32 bit version of the stat	2168	support disabled by default, you get the 32 bit version of the stat
1715	structure. When using the library from programs that change the ABI to	2169	structure. When using the library from programs that change the ABI to
1716	use 64 bit file offsets the programs will fail. In that case you have to	2170	use 64 bit file offsets the programs will fail. In that case you have to
1717	compile libev with the same flags to get binary compatibility. This is	2171	compile libev with the same flags to get binary compatibility. This is
1718	obviously the case with any flags that change the ABI, but the problem is	2172	obviously the case with any flags that change the ABI, but the problem is
1719	most noticeably disabled with ev_stat and large file support.	2173	most noticeably displayed with ev_stat and large file support.
1720		2174
1721	The solution for this is to lobby your distribution maker to make large	2175	The solution for this is to lobby your distribution maker to make large
1722	file interfaces available by default (as e.g. FreeBSD does) and not	2176	file interfaces available by default (as e.g. FreeBSD does) and not
1723	optional. Libev cannot simply switch on large file support because it has	2177	optional. Libev cannot simply switch on large file support because it has
1724	to exchange stat structures with application programs compiled using the	2178	to exchange stat structures with application programs compiled using the
1725	default compilation environment.	2179	default compilation environment.
1726		2180
1727	=head3 Inotify	2181	=head3 Inotify and Kqueue
1728		2182
1729	When C<inotify (7)> support has been compiled into libev (generally only	2183	When C<inotify (7)> support has been compiled into libev and present at
1730	available on Linux) and present at runtime, it will be used to speed up	2184	runtime, it will be used to speed up change detection where possible. The
1731	change detection where possible. The inotify descriptor will be created lazily	2185	inotify descriptor will be created lazily when the first C<ev_stat>
1732	when the first C<ev_stat> watcher is being started.	2186	watcher is being started.
1733		2187
1734	Inotify presence does not change the semantics of C<ev_stat> watchers	2188	Inotify presence does not change the semantics of C<ev_stat> watchers
1735	except that changes might be detected earlier, and in some cases, to avoid	2189	except that changes might be detected earlier, and in some cases, to avoid
1736	making regular C<stat> calls. Even in the presence of inotify support	2190	making regular C<stat> calls. Even in the presence of inotify support
1737	there are many cases where libev has to resort to regular C<stat> polling.	2191	there are many cases where libev has to resort to regular C<stat> polling,
		2192	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2193	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2194	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2195	xfs are fully working) libev usually gets away without polling.
1738		2196
1739	(There is no support for kqueue, as apparently it cannot be used to	2197	There is no support for kqueue, as apparently it cannot be used to
1740	implement this functionality, due to the requirement of having a file	2198	implement this functionality, due to the requirement of having a file
1741	descriptor open on the object at all times).	2199	descriptor open on the object at all times, and detecting renames, unlinks
		2200	etc. is difficult.
		2201
		2202	=head3 C<stat ()> is a synchronous operation
		2203
		2204	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2205	the process. The exception are C<ev_stat> watchers - those call C<stat
		2206	()>, which is a synchronous operation.
		2207
		2208	For local paths, this usually doesn't matter: unless the system is very
		2209	busy or the intervals between stat's are large, a stat call will be fast,
		2210	as the path data is usually in memory already (except when starting the
		2211	watcher).
		2212
		2213	For networked file systems, calling C<stat ()> can block an indefinite
		2214	time due to network issues, and even under good conditions, a stat call
		2215	often takes multiple milliseconds.
		2216
		2217	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2218	paths, although this is fully supported by libev.
1742		2219
1743	=head3 The special problem of stat time resolution	2220	=head3 The special problem of stat time resolution
1744		2221
1745	The C<stat ()> system call only supports full-second resolution portably, and	2222	The C<stat ()> system call only supports full-second resolution portably,
1746	even on systems where the resolution is higher, many file systems still	2223	and even on systems where the resolution is higher, most file systems
1747	only support whole seconds.	2224	still only support whole seconds.
1748		2225
1749	That means that, if the time is the only thing that changes, you can	2226	That means that, if the time is the only thing that changes, you can
1750	easily miss updates: on the first update, C<ev_stat> detects a change and	2227	easily miss updates: on the first update, C<ev_stat> detects a change and
1751	calls your callback, which does something. When there is another update	2228	calls your callback, which does something. When there is another update
1752	within the same second, C<ev_stat> will be unable to detect it as the stat	2229	within the same second, C<ev_stat> will be unable to detect unless the
1753	data does not change.	2230	stat data does change in other ways (e.g. file size).
1754		2231
1755	The solution to this is to delay acting on a change for slightly more	2232	The solution to this is to delay acting on a change for slightly more
1756	than a second (or till slightly after the next full second boundary), using	2233	than a second (or till slightly after the next full second boundary), using
1757	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2234	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1758	ev_timer_again (loop, w)>).	2235	ev_timer_again (loop, w)>).
…		…
1778	C<path>. The C<interval> is a hint on how quickly a change is expected to	2255	C<path>. The C<interval> is a hint on how quickly a change is expected to
1779	be detected and should normally be specified as C<0> to let libev choose	2256	be detected and should normally be specified as C<0> to let libev choose
1780	a suitable value. The memory pointed to by C<path> must point to the same	2257	a suitable value. The memory pointed to by C<path> must point to the same
1781	path for as long as the watcher is active.	2258	path for as long as the watcher is active.
1782		2259
1783	The callback will receive C<EV_STAT> when a change was detected, relative	2260	The callback will receive an C<EV_STAT> event when a change was detected,
1784	to the attributes at the time the watcher was started (or the last change	2261	relative to the attributes at the time the watcher was started (or the
1785	was detected).	2262	last change was detected).
1786		2263
1787	=item ev_stat_stat (loop, ev_stat *)	2264	=item ev_stat_stat (loop, ev_stat *)
1788		2265
1789	Updates the stat buffer immediately with new values. If you change the	2266	Updates the stat buffer immediately with new values. If you change the
1790	watched path in your callback, you could call this function to avoid	2267	watched path in your callback, you could call this function to avoid
…		…
1873		2350
1874		2351
1875	=head2 C<ev_idle> - when you've got nothing better to do...	2352	=head2 C<ev_idle> - when you've got nothing better to do...
1876		2353
1877	Idle watchers trigger events when no other events of the same or higher	2354	Idle watchers trigger events when no other events of the same or higher
1878	priority are pending (prepare, check and other idle watchers do not	2355	priority are pending (prepare, check and other idle watchers do not count
1879	count).	2356	as receiving "events").
1880		2357
1881	That is, as long as your process is busy handling sockets or timeouts	2358	That is, as long as your process is busy handling sockets or timeouts
1882	(or even signals, imagine) of the same or higher priority it will not be	2359	(or even signals, imagine) of the same or higher priority it will not be
1883	triggered. But when your process is idle (or only lower-priority watchers	2360	triggered. But when your process is idle (or only lower-priority watchers
1884	are pending), the idle watchers are being called once per event loop	2361	are pending), the idle watchers are being called once per event loop
…		…
1895		2372
1896	=head3 Watcher-Specific Functions and Data Members	2373	=head3 Watcher-Specific Functions and Data Members
1897		2374
1898	=over 4	2375	=over 4
1899		2376
1900	=item ev_idle_init (ev_signal *, callback)	2377	=item ev_idle_init (ev_idle *, callback)
1901		2378
1902	Initialises and configures the idle watcher - it has no parameters of any	2379	Initialises and configures the idle watcher - it has no parameters of any
1903	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2380	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1904	believe me.	2381	believe me.
1905		2382
…		…
1909		2386
1910	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2387	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1911	callback, free it. Also, use no error checking, as usual.	2388	callback, free it. Also, use no error checking, as usual.
1912		2389
1913	static void	2390	static void
1914	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2391	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1915	{	2392	{
1916	free (w);	2393	free (w);
1917	// now do something you wanted to do when the program has	2394	// now do something you wanted to do when the program has
1918	// no longer anything immediate to do.	2395	// no longer anything immediate to do.
1919	}	2396	}
1920		2397
1921	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2398	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1922	ev_idle_init (idle_watcher, idle_cb);	2399	ev_idle_init (idle_watcher, idle_cb);
1923	ev_idle_start (loop, idle_cb);	2400	ev_idle_start (loop, idle_watcher);
1924		2401
1925		2402
1926	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2403	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1927		2404
1928	Prepare and check watchers are usually (but not always) used in tandem:	2405	Prepare and check watchers are usually (but not always) used in pairs:
1929	prepare watchers get invoked before the process blocks and check watchers	2406	prepare watchers get invoked before the process blocks and check watchers
1930	afterwards.	2407	afterwards.
1931		2408
1932	You I<must not> call C<ev_loop> or similar functions that enter	2409	You I<must not> call C<ev_loop> or similar functions that enter
1933	the current event loop from either C<ev_prepare> or C<ev_check>	2410	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1936	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2413	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1937	C<ev_check> so if you have one watcher of each kind they will always be	2414	C<ev_check> so if you have one watcher of each kind they will always be
1938	called in pairs bracketing the blocking call.	2415	called in pairs bracketing the blocking call.
1939		2416
1940	Their main purpose is to integrate other event mechanisms into libev and	2417	Their main purpose is to integrate other event mechanisms into libev and
1941	their use is somewhat advanced. This could be used, for example, to track	2418	their use is somewhat advanced. They could be used, for example, to track
1942	variable changes, implement your own watchers, integrate net-snmp or a	2419	variable changes, implement your own watchers, integrate net-snmp or a
1943	coroutine library and lots more. They are also occasionally useful if	2420	coroutine library and lots more. They are also occasionally useful if
1944	you cache some data and want to flush it before blocking (for example,	2421	you cache some data and want to flush it before blocking (for example,
1945	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2422	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1946	watcher).	2423	watcher).
1947		2424
1948	This is done by examining in each prepare call which file descriptors need	2425	This is done by examining in each prepare call which file descriptors
1949	to be watched by the other library, registering C<ev_io> watchers for	2426	need to be watched by the other library, registering C<ev_io> watchers
1950	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2427	for them and starting an C<ev_timer> watcher for any timeouts (many
1951	provide just this functionality). Then, in the check watcher you check for	2428	libraries provide exactly this functionality). Then, in the check watcher,
1952	any events that occurred (by checking the pending status of all watchers	2429	you check for any events that occurred (by checking the pending status
1953	and stopping them) and call back into the library. The I/O and timer	2430	of all watchers and stopping them) and call back into the library. The
1954	callbacks will never actually be called (but must be valid nevertheless,	2431	I/O and timer callbacks will never actually be called (but must be valid
1955	because you never know, you know?).	2432	nevertheless, because you never know, you know?).
1956		2433
1957	As another example, the Perl Coro module uses these hooks to integrate	2434	As another example, the Perl Coro module uses these hooks to integrate
1958	coroutines into libev programs, by yielding to other active coroutines	2435	coroutines into libev programs, by yielding to other active coroutines
1959	during each prepare and only letting the process block if no coroutines	2436	during each prepare and only letting the process block if no coroutines
1960	are ready to run (it's actually more complicated: it only runs coroutines	2437	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1963	loop from blocking if lower-priority coroutines are active, thus mapping	2440	loop from blocking if lower-priority coroutines are active, thus mapping
1964	low-priority coroutines to idle/background tasks).	2441	low-priority coroutines to idle/background tasks).
1965		2442
1966	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2443	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1967	priority, to ensure that they are being run before any other watchers	2444	priority, to ensure that they are being run before any other watchers
		2445	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2446
1968	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2447	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1969	too) should not activate ("feed") events into libev. While libev fully	2448	activate ("feed") events into libev. While libev fully supports this, they
1970	supports this, they might get executed before other C<ev_check> watchers	2449	might get executed before other C<ev_check> watchers did their job. As
1971	did their job. As C<ev_check> watchers are often used to embed other	2450	C<ev_check> watchers are often used to embed other (non-libev) event
1972	(non-libev) event loops those other event loops might be in an unusable	2451	loops those other event loops might be in an unusable state until their
1973	state until their C<ev_check> watcher ran (always remind yourself to	2452	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1974	coexist peacefully with others).	2453	others).
1975		2454
1976	=head3 Watcher-Specific Functions and Data Members	2455	=head3 Watcher-Specific Functions and Data Members
1977		2456
1978	=over 4	2457	=over 4
1979		2458
…		…
1981		2460
1982	=item ev_check_init (ev_check *, callback)	2461	=item ev_check_init (ev_check *, callback)
1983		2462
1984	Initialises and configures the prepare or check watcher - they have no	2463	Initialises and configures the prepare or check watcher - they have no
1985	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2464	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1986	macros, but using them is utterly, utterly and completely pointless.	2465	macros, but using them is utterly, utterly, utterly and completely
		2466	pointless.
1987		2467
1988	=back	2468	=back
1989		2469
1990	=head3 Examples	2470	=head3 Examples
1991		2471
…		…
2004		2484
2005	static ev_io iow [nfd];	2485	static ev_io iow [nfd];
2006	static ev_timer tw;	2486	static ev_timer tw;
2007		2487
2008	static void	2488	static void
2009	io_cb (ev_loop *loop, ev_io *w, int revents)	2489	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2010	{	2490	{
2011	}	2491	}
2012		2492
2013	// create io watchers for each fd and a timer before blocking	2493	// create io watchers for each fd and a timer before blocking
2014	static void	2494	static void
2015	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2495	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2016	{	2496	{
2017	int timeout = 3600000;	2497	int timeout = 3600000;
2018	struct pollfd fds [nfd];	2498	struct pollfd fds [nfd];
2019	// actual code will need to loop here and realloc etc.	2499	// actual code will need to loop here and realloc etc.
2020	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2500	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2021		2501
2022	/* the callback is illegal, but won't be called as we stop during check */	2502	/* the callback is illegal, but won't be called as we stop during check */
2023	ev_timer_init (&tw, 0, timeout * 1e-3);	2503	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2024	ev_timer_start (loop, &tw);	2504	ev_timer_start (loop, &tw);
2025		2505
2026	// create one ev_io per pollfd	2506	// create one ev_io per pollfd
2027	for (int i = 0; i < nfd; ++i)	2507	for (int i = 0; i < nfd; ++i)
2028	{	2508	{
…		…
2035	}	2515	}
2036	}	2516	}
2037		2517
2038	// stop all watchers after blocking	2518	// stop all watchers after blocking
2039	static void	2519	static void
2040	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2520	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2041	{	2521	{
2042	ev_timer_stop (loop, &tw);	2522	ev_timer_stop (loop, &tw);
2043		2523
2044	for (int i = 0; i < nfd; ++i)	2524	for (int i = 0; i < nfd; ++i)
2045	{	2525	{
…		…
2084	}	2564	}
2085		2565
2086	// do not ever call adns_afterpoll	2566	// do not ever call adns_afterpoll
2087		2567
2088	Method 4: Do not use a prepare or check watcher because the module you	2568	Method 4: Do not use a prepare or check watcher because the module you
2089	want to embed is too inflexible to support it. Instead, you can override	2569	want to embed is not flexible enough to support it. Instead, you can
2090	their poll function. The drawback with this solution is that the main	2570	override their poll function. The drawback with this solution is that the
2091	loop is now no longer controllable by EV. The C<Glib::EV> module does	2571	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2092	this.	2572	this approach, effectively embedding EV as a client into the horrible
		2573	libglib event loop.
2093		2574
2094	static gint	2575	static gint
2095	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2576	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2096	{	2577	{
2097	int got_events = 0;	2578	int got_events = 0;
…		…
2128	prioritise I/O.	2609	prioritise I/O.
2129		2610
2130	As an example for a bug workaround, the kqueue backend might only support	2611	As an example for a bug workaround, the kqueue backend might only support
2131	sockets on some platform, so it is unusable as generic backend, but you	2612	sockets on some platform, so it is unusable as generic backend, but you
2132	still want to make use of it because you have many sockets and it scales	2613	still want to make use of it because you have many sockets and it scales
2133	so nicely. In this case, you would create a kqueue-based loop and embed it	2614	so nicely. In this case, you would create a kqueue-based loop and embed
2134	into your default loop (which might use e.g. poll). Overall operation will	2615	it into your default loop (which might use e.g. poll). Overall operation
2135	be a bit slower because first libev has to poll and then call kevent, but	2616	will be a bit slower because first libev has to call C<poll> and then
2136	at least you can use both at what they are best.	2617	C<kevent>, but at least you can use both mechanisms for what they are
		2618	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2137		2619
2138	As for prioritising I/O: rarely you have the case where some fds have	2620	As for prioritising I/O: under rare circumstances you have the case where
2139	to be watched and handled very quickly (with low latency), and even	2621	some fds have to be watched and handled very quickly (with low latency),
2140	priorities and idle watchers might have too much overhead. In this case	2622	and even priorities and idle watchers might have too much overhead. In
2141	you would put all the high priority stuff in one loop and all the rest in	2623	this case you would put all the high priority stuff in one loop and all
2142	a second one, and embed the second one in the first.	2624	the rest in a second one, and embed the second one in the first.
2143		2625
2144	As long as the watcher is active, the callback will be invoked every time	2626	As long as the watcher is active, the callback will be invoked every
2145	there might be events pending in the embedded loop. The callback must then	2627	time there might be events pending in the embedded loop. The callback
2146	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2628	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2147	their callbacks (you could also start an idle watcher to give the embedded	2629	sweep and invoke their callbacks (the callback doesn't need to invoke the
2148	loop strictly lower priority for example). You can also set the callback	2630	C<ev_embed_sweep> function directly, it could also start an idle watcher
2149	to C<0>, in which case the embed watcher will automatically execute the	2631	to give the embedded loop strictly lower priority for example).
2150	embedded loop sweep.
2151		2632
2152	As long as the watcher is started it will automatically handle events. The	2633	You can also set the callback to C<0>, in which case the embed watcher
2153	callback will be invoked whenever some events have been handled. You can	2634	will automatically execute the embedded loop sweep whenever necessary.
2154	set the callback to C<0> to avoid having to specify one if you are not
2155	interested in that.
2156		2635
2157	Also, there have not currently been made special provisions for forking:	2636	Fork detection will be handled transparently while the C<ev_embed> watcher
2158	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2637	is active, i.e., the embedded loop will automatically be forked when the
2159	but you will also have to stop and restart any C<ev_embed> watchers	2638	embedding loop forks. In other cases, the user is responsible for calling
2160	yourself.	2639	C<ev_loop_fork> on the embedded loop.
2161		2640
2162	Unfortunately, not all backends are embeddable, only the ones returned by	2641	Unfortunately, not all backends are embeddable: only the ones returned by
2163	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2642	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2164	portable one.	2643	portable one.
2165		2644
2166	So when you want to use this feature you will always have to be prepared	2645	So when you want to use this feature you will always have to be prepared
2167	that you cannot get an embeddable loop. The recommended way to get around	2646	that you cannot get an embeddable loop. The recommended way to get around
2168	this is to have a separate variables for your embeddable loop, try to	2647	this is to have a separate variables for your embeddable loop, try to
2169	create it, and if that fails, use the normal loop for everything.	2648	create it, and if that fails, use the normal loop for everything.
		2649
		2650	=head3 C<ev_embed> and fork
		2651
		2652	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2653	automatically be applied to the embedded loop as well, so no special
		2654	fork handling is required in that case. When the watcher is not running,
		2655	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2656	as applicable.
2170		2657
2171	=head3 Watcher-Specific Functions and Data Members	2658	=head3 Watcher-Specific Functions and Data Members
2172		2659
2173	=over 4	2660	=over 4
2174		2661
…		…
2202	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2689	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2203	used).	2690	used).
2204		2691
2205	struct ev_loop *loop_hi = ev_default_init (0);	2692	struct ev_loop *loop_hi = ev_default_init (0);
2206	struct ev_loop *loop_lo = 0;	2693	struct ev_loop *loop_lo = 0;
2207	struct ev_embed embed;	2694	ev_embed embed;
2208		2695
2209	// see if there is a chance of getting one that works	2696	// see if there is a chance of getting one that works
2210	// (remember that a flags value of 0 means autodetection)	2697	// (remember that a flags value of 0 means autodetection)
2211	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2698	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2212	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2699	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2226	kqueue implementation). Store the kqueue/socket-only event loop in	2713	kqueue implementation). Store the kqueue/socket-only event loop in
2227	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2714	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2228		2715
2229	struct ev_loop *loop = ev_default_init (0);	2716	struct ev_loop *loop = ev_default_init (0);
2230	struct ev_loop *loop_socket = 0;	2717	struct ev_loop *loop_socket = 0;
2231	struct ev_embed embed;	2718	ev_embed embed;
2232		2719
2233	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2720	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2234	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2721	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2235	{	2722	{
2236	ev_embed_init (&embed, 0, loop_socket);	2723	ev_embed_init (&embed, 0, loop_socket);
…		…
2251	event loop blocks next and before C<ev_check> watchers are being called,	2738	event loop blocks next and before C<ev_check> watchers are being called,
2252	and only in the child after the fork. If whoever good citizen calling	2739	and only in the child after the fork. If whoever good citizen calling
2253	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2740	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2254	handlers will be invoked, too, of course.	2741	handlers will be invoked, too, of course.
2255		2742
		2743	=head3 The special problem of life after fork - how is it possible?
		2744
		2745	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2746	up/change the process environment, followed by a call to C<exec()>. This
		2747	sequence should be handled by libev without any problems.
		2748
		2749	This changes when the application actually wants to do event handling
		2750	in the child, or both parent in child, in effect "continuing" after the
		2751	fork.
		2752
		2753	The default mode of operation (for libev, with application help to detect
		2754	forks) is to duplicate all the state in the child, as would be expected
		2755	when I<either> the parent I<or> the child process continues.
		2756
		2757	When both processes want to continue using libev, then this is usually the
		2758	wrong result. In that case, usually one process (typically the parent) is
		2759	supposed to continue with all watchers in place as before, while the other
		2760	process typically wants to start fresh, i.e. without any active watchers.
		2761
		2762	The cleanest and most efficient way to achieve that with libev is to
		2763	simply create a new event loop, which of course will be "empty", and
		2764	use that for new watchers. This has the advantage of not touching more
		2765	memory than necessary, and thus avoiding the copy-on-write, and the
		2766	disadvantage of having to use multiple event loops (which do not support
		2767	signal watchers).
		2768
		2769	When this is not possible, or you want to use the default loop for
		2770	other reasons, then in the process that wants to start "fresh", call
		2771	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2772	the default loop will "orphan" (not stop) all registered watchers, so you
		2773	have to be careful not to execute code that modifies those watchers. Note
		2774	also that in that case, you have to re-register any signal watchers.
		2775
2256	=head3 Watcher-Specific Functions and Data Members	2776	=head3 Watcher-Specific Functions and Data Members
2257		2777
2258	=over 4	2778	=over 4
2259		2779
2260	=item ev_fork_init (ev_signal *, callback)	2780	=item ev_fork_init (ev_signal *, callback)
…		…
2292	is that the author does not know of a simple (or any) algorithm for a	2812	is that the author does not know of a simple (or any) algorithm for a
2293	multiple-writer-single-reader queue that works in all cases and doesn't	2813	multiple-writer-single-reader queue that works in all cases and doesn't
2294	need elaborate support such as pthreads.	2814	need elaborate support such as pthreads.
2295		2815
2296	That means that if you want to queue data, you have to provide your own	2816	That means that if you want to queue data, you have to provide your own
2297	queue. But at least I can tell you would implement locking around your	2817	queue. But at least I can tell you how to implement locking around your
2298	queue:	2818	queue:
2299		2819
2300	=over 4	2820	=over 4
2301		2821
2302	=item queueing from a signal handler context	2822	=item queueing from a signal handler context
2303		2823
2304	To implement race-free queueing, you simply add to the queue in the signal	2824	To implement race-free queueing, you simply add to the queue in the signal
2305	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2825	handler but you block the signal handler in the watcher callback. Here is
2306	some fictitious SIGUSR1 handler:	2826	an example that does that for some fictitious SIGUSR1 handler:
2307		2827
2308	static ev_async mysig;	2828	static ev_async mysig;
2309		2829
2310	static void	2830	static void
2311	sigusr1_handler (void)	2831	sigusr1_handler (void)
…		…
2377	=over 4	2897	=over 4
2378		2898
2379	=item ev_async_init (ev_async *, callback)	2899	=item ev_async_init (ev_async *, callback)
2380		2900
2381	Initialises and configures the async watcher - it has no parameters of any	2901	Initialises and configures the async watcher - it has no parameters of any
2382	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2902	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2383	believe me.	2903	trust me.
2384		2904
2385	=item ev_async_send (loop, ev_async *)	2905	=item ev_async_send (loop, ev_async *)
2386		2906
2387	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2907	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2388	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2908	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2389	C<ev_feed_event>, this call is safe to do in other threads, signal or	2909	C<ev_feed_event>, this call is safe to do from other threads, signal or
2390	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	2910	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2391	section below on what exactly this means).	2911	section below on what exactly this means).
2392		2912
		2913	Note that, as with other watchers in libev, multiple events might get
		2914	compressed into a single callback invocation (another way to look at this
		2915	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		2916	reset when the event loop detects that).
		2917
2393	This call incurs the overhead of a system call only once per loop iteration,	2918	This call incurs the overhead of a system call only once per event loop
2394	so while the overhead might be noticeable, it doesn't apply to repeated	2919	iteration, so while the overhead might be noticeable, it doesn't apply to
2395	calls to C<ev_async_send>.	2920	repeated calls to C<ev_async_send> for the same event loop.
2396		2921
2397	=item bool = ev_async_pending (ev_async *)	2922	=item bool = ev_async_pending (ev_async *)
2398		2923
2399	Returns a non-zero value when C<ev_async_send> has been called on the	2924	Returns a non-zero value when C<ev_async_send> has been called on the
2400	watcher but the event has not yet been processed (or even noted) by the	2925	watcher but the event has not yet been processed (or even noted) by the
…		…
2403	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	2928	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2404	the loop iterates next and checks for the watcher to have become active,	2929	the loop iterates next and checks for the watcher to have become active,
2405	it will reset the flag again. C<ev_async_pending> can be used to very	2930	it will reset the flag again. C<ev_async_pending> can be used to very
2406	quickly check whether invoking the loop might be a good idea.	2931	quickly check whether invoking the loop might be a good idea.
2407		2932
2408	Not that this does I<not> check whether the watcher itself is pending, only	2933	Not that this does I<not> check whether the watcher itself is pending,
2409	whether it has been requested to make this watcher pending.	2934	only whether it has been requested to make this watcher pending: there
		2935	is a time window between the event loop checking and resetting the async
		2936	notification, and the callback being invoked.
2410		2937
2411	=back	2938	=back
2412		2939
2413		2940
2414	=head1 OTHER FUNCTIONS	2941	=head1 OTHER FUNCTIONS
…		…
2418	=over 4	2945	=over 4
2419		2946
2420	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2947	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2421		2948
2422	This function combines a simple timer and an I/O watcher, calls your	2949	This function combines a simple timer and an I/O watcher, calls your
2423	callback on whichever event happens first and automatically stop both	2950	callback on whichever event happens first and automatically stops both
2424	watchers. This is useful if you want to wait for a single event on an fd	2951	watchers. This is useful if you want to wait for a single event on an fd
2425	or timeout without having to allocate/configure/start/stop/free one or	2952	or timeout without having to allocate/configure/start/stop/free one or
2426	more watchers yourself.	2953	more watchers yourself.
2427		2954
2428	If C<fd> is less than 0, then no I/O watcher will be started and events	2955	If C<fd> is less than 0, then no I/O watcher will be started and the
2429	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2956	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2430	C<events> set will be created and started.	2957	the given C<fd> and C<events> set will be created and started.
2431		2958
2432	If C<timeout> is less than 0, then no timeout watcher will be	2959	If C<timeout> is less than 0, then no timeout watcher will be
2433	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2960	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2434	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2961	repeat = 0) will be started. C<0> is a valid timeout.
2435	dubious value.
2436		2962
2437	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2963	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2438	passed an C<revents> set like normal event callbacks (a combination of	2964	passed an C<revents> set like normal event callbacks (a combination of
2439	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2965	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2440	value passed to C<ev_once>:	2966	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2967	a timeout and an io event at the same time - you probably should give io
		2968	events precedence.
		2969
		2970	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2441		2971
2442	static void stdin_ready (int revents, void *arg)	2972	static void stdin_ready (int revents, void *arg)
2443	{	2973	{
		2974	if (revents & EV_READ)
		2975	/* stdin might have data for us, joy! */;
2444	if (revents & EV_TIMEOUT)	2976	else if (revents & EV_TIMEOUT)
2445	/* doh, nothing entered */;	2977	/* doh, nothing entered */;
2446	else if (revents & EV_READ)
2447	/* stdin might have data for us, joy! */;
2448	}	2978	}
2449		2979
2450	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2980	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2451		2981
2452	=item ev_feed_event (ev_loop *, watcher *, int revents)	2982	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2453		2983
2454	Feeds the given event set into the event loop, as if the specified event	2984	Feeds the given event set into the event loop, as if the specified event
2455	had happened for the specified watcher (which must be a pointer to an	2985	had happened for the specified watcher (which must be a pointer to an
2456	initialised but not necessarily started event watcher).	2986	initialised but not necessarily started event watcher).
2457		2987
2458	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2988	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2459		2989
2460	Feed an event on the given fd, as if a file descriptor backend detected	2990	Feed an event on the given fd, as if a file descriptor backend detected
2461	the given events it.	2991	the given events it.
2462		2992
2463	=item ev_feed_signal_event (ev_loop *loop, int signum)	2993	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2464		2994
2465	Feed an event as if the given signal occurred (C<loop> must be the default	2995	Feed an event as if the given signal occurred (C<loop> must be the default
2466	loop!).	2996	loop!).
2467		2997
2468	=back	2998	=back
…		…
2590		3120
2591	myclass obj;	3121	myclass obj;
2592	ev::io iow;	3122	ev::io iow;
2593	iow.set <myclass, &myclass::io_cb> (&obj);	3123	iow.set <myclass, &myclass::io_cb> (&obj);
2594		3124
		3125	=item w->set (object *)
		3126
		3127	This is an B<experimental> feature that might go away in a future version.
		3128
		3129	This is a variation of a method callback - leaving out the method to call
		3130	will default the method to C<operator ()>, which makes it possible to use
		3131	functor objects without having to manually specify the C<operator ()> all
		3132	the time. Incidentally, you can then also leave out the template argument
		3133	list.
		3134
		3135	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3136	int revents)>.
		3137
		3138	See the method-C<set> above for more details.
		3139
		3140	Example: use a functor object as callback.
		3141
		3142	struct myfunctor
		3143	{
		3144	void operator() (ev::io &w, int revents)
		3145	{
		3146	...
		3147	}
		3148	}
		3149
		3150	myfunctor f;
		3151
		3152	ev::io w;
		3153	w.set (&f);
		3154
2595	=item w->set<function> (void *data = 0)	3155	=item w->set<function> (void *data = 0)
2596		3156
2597	Also sets a callback, but uses a static method or plain function as	3157	Also sets a callback, but uses a static method or plain function as
2598	callback. The optional C<data> argument will be stored in the watcher's	3158	callback. The optional C<data> argument will be stored in the watcher's
2599	C<data> member and is free for you to use.	3159	C<data> member and is free for you to use.
2600		3160
2601	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3161	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2602		3162
2603	See the method-C<set> above for more details.	3163	See the method-C<set> above for more details.
2604		3164
2605	Example:	3165	Example: Use a plain function as callback.
2606		3166
2607	static void io_cb (ev::io &w, int revents) { }	3167	static void io_cb (ev::io &w, int revents) { }
2608	iow.set <io_cb> ();	3168	iow.set <io_cb> ();
2609		3169
2610	=item w->set (struct ev_loop *)	3170	=item w->set (struct ev_loop *)
…		…
2648	Example: Define a class with an IO and idle watcher, start one of them in	3208	Example: Define a class with an IO and idle watcher, start one of them in
2649	the constructor.	3209	the constructor.
2650		3210
2651	class myclass	3211	class myclass
2652	{	3212	{
2653	ev::io io; void io_cb (ev::io &w, int revents);	3213	ev::io io ; void io_cb (ev::io &w, int revents);
2654	ev:idle idle void idle_cb (ev::idle &w, int revents);	3214	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2655		3215
2656	myclass (int fd)	3216	myclass (int fd)
2657	{	3217	{
2658	io .set <myclass, &myclass::io_cb > (this);	3218	io .set <myclass, &myclass::io_cb > (this);
2659	idle.set <myclass, &myclass::idle_cb> (this);	3219	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2675	=item Perl	3235	=item Perl
2676		3236
2677	The EV module implements the full libev API and is actually used to test	3237	The EV module implements the full libev API and is actually used to test
2678	libev. EV is developed together with libev. Apart from the EV core module,	3238	libev. EV is developed together with libev. Apart from the EV core module,
2679	there are additional modules that implement libev-compatible interfaces	3239	there are additional modules that implement libev-compatible interfaces
2680	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3240	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2681	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3241	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3242	and C<EV::Glib>).
2682		3243
2683	It can be found and installed via CPAN, its homepage is at	3244	It can be found and installed via CPAN, its homepage is at
2684	L<http://software.schmorp.de/pkg/EV>.	3245	L<http://software.schmorp.de/pkg/EV>.
2685		3246
2686	=item Python	3247	=item Python
2687		3248
2688	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3249	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2689	seems to be quite complete and well-documented. Note, however, that the	3250	seems to be quite complete and well-documented.
2690	patch they require for libev is outright dangerous as it breaks the ABI
2691	for everybody else, and therefore, should never be applied in an installed
2692	libev (if python requires an incompatible ABI then it needs to embed
2693	libev).
2694		3251
2695	=item Ruby	3252	=item Ruby
2696		3253
2697	Tony Arcieri has written a ruby extension that offers access to a subset	3254	Tony Arcieri has written a ruby extension that offers access to a subset
2698	of the libev API and adds file handle abstractions, asynchronous DNS and	3255	of the libev API and adds file handle abstractions, asynchronous DNS and
2699	more on top of it. It can be found via gem servers. Its homepage is at	3256	more on top of it. It can be found via gem servers. Its homepage is at
2700	L<http://rev.rubyforge.org/>.	3257	L<http://rev.rubyforge.org/>.
2701		3258
		3259	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3260	makes rev work even on mingw.
		3261
		3262	=item Haskell
		3263
		3264	A haskell binding to libev is available at
		3265	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3266
2702	=item D	3267	=item D
2703		3268
2704	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3269	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2705	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3270	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3271
		3272	=item Ocaml
		3273
		3274	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3275	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2706		3276
2707	=back	3277	=back
2708		3278
2709		3279
2710	=head1 MACRO MAGIC	3280	=head1 MACRO MAGIC
…		…
2811		3381
2812	#define EV_STANDALONE 1	3382	#define EV_STANDALONE 1
2813	#include "ev.h"	3383	#include "ev.h"
2814		3384
2815	Both header files and implementation files can be compiled with a C++	3385	Both header files and implementation files can be compiled with a C++
2816	compiler (at least, thats a stated goal, and breakage will be treated	3386	compiler (at least, that's a stated goal, and breakage will be treated
2817	as a bug).	3387	as a bug).
2818		3388
2819	You need the following files in your source tree, or in a directory	3389	You need the following files in your source tree, or in a directory
2820	in your include path (e.g. in libev/ when using -Ilibev):	3390	in your include path (e.g. in libev/ when using -Ilibev):
2821		3391
…		…
2865		3435
2866	=head2 PREPROCESSOR SYMBOLS/MACROS	3436	=head2 PREPROCESSOR SYMBOLS/MACROS
2867		3437
2868	Libev can be configured via a variety of preprocessor symbols you have to	3438	Libev can be configured via a variety of preprocessor symbols you have to
2869	define before including any of its files. The default in the absence of	3439	define before including any of its files. The default in the absence of
2870	autoconf is noted for every option.	3440	autoconf is documented for every option.
2871		3441
2872	=over 4	3442	=over 4
2873		3443
2874	=item EV_STANDALONE	3444	=item EV_STANDALONE
2875		3445
…		…
2877	keeps libev from including F<config.h>, and it also defines dummy	3447	keeps libev from including F<config.h>, and it also defines dummy
2878	implementations for some libevent functions (such as logging, which is not	3448	implementations for some libevent functions (such as logging, which is not
2879	supported). It will also not define any of the structs usually found in	3449	supported). It will also not define any of the structs usually found in
2880	F<event.h> that are not directly supported by the libev core alone.	3450	F<event.h> that are not directly supported by the libev core alone.
2881		3451
		3452	In stanbdalone mode, libev will still try to automatically deduce the
		3453	configuration, but has to be more conservative.
		3454
2882	=item EV_USE_MONOTONIC	3455	=item EV_USE_MONOTONIC
2883		3456
2884	If defined to be C<1>, libev will try to detect the availability of the	3457	If defined to be C<1>, libev will try to detect the availability of the
2885	monotonic clock option at both compile time and runtime. Otherwise no use	3458	monotonic clock option at both compile time and runtime. Otherwise no
2886	of the monotonic clock option will be attempted. If you enable this, you	3459	use of the monotonic clock option will be attempted. If you enable this,
2887	usually have to link against librt or something similar. Enabling it when	3460	you usually have to link against librt or something similar. Enabling it
2888	the functionality isn't available is safe, though, although you have	3461	when the functionality isn't available is safe, though, although you have
2889	to make sure you link against any libraries where the C<clock_gettime>	3462	to make sure you link against any libraries where the C<clock_gettime>
2890	function is hiding in (often F<-lrt>).	3463	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2891		3464
2892	=item EV_USE_REALTIME	3465	=item EV_USE_REALTIME
2893		3466
2894	If defined to be C<1>, libev will try to detect the availability of the	3467	If defined to be C<1>, libev will try to detect the availability of the
2895	real-time clock option at compile time (and assume its availability at	3468	real-time clock option at compile time (and assume its availability
2896	runtime if successful). Otherwise no use of the real-time clock option will	3469	at runtime if successful). Otherwise no use of the real-time clock
2897	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3470	option will be attempted. This effectively replaces C<gettimeofday>
2898	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3471	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2899	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3472	correctness. See the note about libraries in the description of
		3473	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3474	C<EV_USE_CLOCK_SYSCALL>.
		3475
		3476	=item EV_USE_CLOCK_SYSCALL
		3477
		3478	If defined to be C<1>, libev will try to use a direct syscall instead
		3479	of calling the system-provided C<clock_gettime> function. This option
		3480	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3481	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3482	programs needlessly. Using a direct syscall is slightly slower (in
		3483	theory), because no optimised vdso implementation can be used, but avoids
		3484	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3485	higher, as it simplifies linking (no need for C<-lrt>).
2900		3486
2901	=item EV_USE_NANOSLEEP	3487	=item EV_USE_NANOSLEEP
2902		3488
2903	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3489	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2904	and will use it for delays. Otherwise it will use C<select ()>.	3490	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2920		3506
2921	=item EV_SELECT_USE_FD_SET	3507	=item EV_SELECT_USE_FD_SET
2922		3508
2923	If defined to C<1>, then the select backend will use the system C<fd_set>	3509	If defined to C<1>, then the select backend will use the system C<fd_set>
2924	structure. This is useful if libev doesn't compile due to a missing	3510	structure. This is useful if libev doesn't compile due to a missing
2925	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3511	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2926	exotic systems. This usually limits the range of file descriptors to some	3512	on exotic systems. This usually limits the range of file descriptors to
2927	low limit such as 1024 or might have other limitations (winsocket only	3513	some low limit such as 1024 or might have other limitations (winsocket
2928	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3514	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2929	influence the size of the C<fd_set> used.	3515	configures the maximum size of the C<fd_set>.
2930		3516
2931	=item EV_SELECT_IS_WINSOCKET	3517	=item EV_SELECT_IS_WINSOCKET
2932		3518
2933	When defined to C<1>, the select backend will assume that	3519	When defined to C<1>, the select backend will assume that
2934	select/socket/connect etc. don't understand file descriptors but	3520	select/socket/connect etc. don't understand file descriptors but
…		…
3045	When doing priority-based operations, libev usually has to linearly search	3631	When doing priority-based operations, libev usually has to linearly search
3046	all the priorities, so having many of them (hundreds) uses a lot of space	3632	all the priorities, so having many of them (hundreds) uses a lot of space
3047	and time, so using the defaults of five priorities (-2 .. +2) is usually	3633	and time, so using the defaults of five priorities (-2 .. +2) is usually
3048	fine.	3634	fine.
3049		3635
3050	If your embedding application does not need any priorities, defining these both to	3636	If your embedding application does not need any priorities, defining these
3051	C<0> will save some memory and CPU.	3637	both to C<0> will save some memory and CPU.
3052		3638
3053	=item EV_PERIODIC_ENABLE	3639	=item EV_PERIODIC_ENABLE
3054		3640
3055	If undefined or defined to be C<1>, then periodic timers are supported. If	3641	If undefined or defined to be C<1>, then periodic timers are supported. If
3056	defined to be C<0>, then they are not. Disabling them saves a few kB of	3642	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3063	code.	3649	code.
3064		3650
3065	=item EV_EMBED_ENABLE	3651	=item EV_EMBED_ENABLE
3066		3652
3067	If undefined or defined to be C<1>, then embed watchers are supported. If	3653	If undefined or defined to be C<1>, then embed watchers are supported. If
3068	defined to be C<0>, then they are not.	3654	defined to be C<0>, then they are not. Embed watchers rely on most other
		3655	watcher types, which therefore must not be disabled.
3069		3656
3070	=item EV_STAT_ENABLE	3657	=item EV_STAT_ENABLE
3071		3658
3072	If undefined or defined to be C<1>, then stat watchers are supported. If	3659	If undefined or defined to be C<1>, then stat watchers are supported. If
3073	defined to be C<0>, then they are not.	3660	defined to be C<0>, then they are not.
…		…
3105	two).	3692	two).
3106		3693
3107	=item EV_USE_4HEAP	3694	=item EV_USE_4HEAP
3108		3695
3109	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3696	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3110	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3697	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3111	to C<1>. The 4-heap uses more complicated (longer) code but has	3698	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3112	noticeably faster performance with many (thousands) of watchers.	3699	faster performance with many (thousands) of watchers.
3113		3700
3114	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3701	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3115	(disabled).	3702	(disabled).
3116		3703
3117	=item EV_HEAP_CACHE_AT	3704	=item EV_HEAP_CACHE_AT
3118		3705
3119	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3706	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3120	timer and periodics heap, libev can cache the timestamp (I<at>) within	3707	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3121	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3708	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3122	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3709	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3123	but avoids random read accesses on heap changes. This improves performance	3710	but avoids random read accesses on heap changes. This improves performance
3124	noticeably with with many (hundreds) of watchers.	3711	noticeably with many (hundreds) of watchers.
3125		3712
3126	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3713	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3127	(disabled).	3714	(disabled).
3128		3715
3129	=item EV_VERIFY	3716	=item EV_VERIFY
…		…
3135	called once per loop, which can slow down libev. If set to C<3>, then the	3722	called once per loop, which can slow down libev. If set to C<3>, then the
3136	verification code will be called very frequently, which will slow down	3723	verification code will be called very frequently, which will slow down
3137	libev considerably.	3724	libev considerably.
3138		3725
3139	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3726	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3140	C<0.>	3727	C<0>.
3141		3728
3142	=item EV_COMMON	3729	=item EV_COMMON
3143		3730
3144	By default, all watchers have a C<void *data> member. By redefining	3731	By default, all watchers have a C<void *data> member. By redefining
3145	this macro to a something else you can include more and other types of	3732	this macro to a something else you can include more and other types of
…		…
3162	and the way callbacks are invoked and set. Must expand to a struct member	3749	and the way callbacks are invoked and set. Must expand to a struct member
3163	definition and a statement, respectively. See the F<ev.h> header file for	3750	definition and a statement, respectively. See the F<ev.h> header file for
3164	their default definitions. One possible use for overriding these is to	3751	their default definitions. One possible use for overriding these is to
3165	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3752	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3166	method calls instead of plain function calls in C++.	3753	method calls instead of plain function calls in C++.
		3754
		3755	=back
3167		3756
3168	=head2 EXPORTED API SYMBOLS	3757	=head2 EXPORTED API SYMBOLS
3169		3758
3170	If you need to re-export the API (e.g. via a DLL) and you need a list of	3759	If you need to re-export the API (e.g. via a DLL) and you need a list of
3171	exported symbols, you can use the provided F<Symbol.*> files which list	3760	exported symbols, you can use the provided F<Symbol.*> files which list
…		…
3218	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3807	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3219		3808
3220	#include "ev_cpp.h"	3809	#include "ev_cpp.h"
3221	#include "ev.c"	3810	#include "ev.c"
3222		3811
		3812	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3223		3813
3224	=head1 THREADS AND COROUTINES	3814	=head2 THREADS AND COROUTINES
3225		3815
3226	=head2 THREADS	3816	=head3 THREADS
3227		3817
3228	Libev itself is completely thread-safe, but it uses no locking. This	3818	All libev functions are reentrant and thread-safe unless explicitly
		3819	documented otherwise, but libev implements no locking itself. This means
3229	means that you can use as many loops as you want in parallel, as long as	3820	that you can use as many loops as you want in parallel, as long as there
3230	only one thread ever calls into one libev function with the same loop	3821	are no concurrent calls into any libev function with the same loop
3231	parameter.	3822	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3823	of course): libev guarantees that different event loops share no data
		3824	structures that need any locking.
3232		3825
3233	Or put differently: calls with different loop parameters can be done in	3826	Or to put it differently: calls with different loop parameters can be done
3234	parallel from multiple threads, calls with the same loop parameter must be	3827	concurrently from multiple threads, calls with the same loop parameter
3235	done serially (but can be done from different threads, as long as only one	3828	must be done serially (but can be done from different threads, as long as
3236	thread ever is inside a call at any point in time, e.g. by using a mutex	3829	only one thread ever is inside a call at any point in time, e.g. by using
3237	per loop).	3830	a mutex per loop).
		3831
		3832	Specifically to support threads (and signal handlers), libev implements
		3833	so-called C<ev_async> watchers, which allow some limited form of
		3834	concurrency on the same event loop, namely waking it up "from the
		3835	outside".
3238		3836
3239	If you want to know which design (one loop, locking, or multiple loops	3837	If you want to know which design (one loop, locking, or multiple loops
3240	without or something else still) is best for your problem, then I cannot	3838	without or something else still) is best for your problem, then I cannot
3241	help you. I can give some generic advice however:	3839	help you, but here is some generic advice:
3242		3840
3243	=over 4	3841	=over 4
3244		3842
3245	=item * most applications have a main thread: use the default libev loop	3843	=item * most applications have a main thread: use the default libev loop
3246	in that thread, or create a separate thread running only the default loop.	3844	in that thread, or create a separate thread running only the default loop.
…		…
3258		3856
3259	Choosing a model is hard - look around, learn, know that usually you can do	3857	Choosing a model is hard - look around, learn, know that usually you can do
3260	better than you currently do :-)	3858	better than you currently do :-)
3261		3859
3262	=item * often you need to talk to some other thread which blocks in the	3860	=item * often you need to talk to some other thread which blocks in the
		3861	event loop.
		3862
3263	event loop - C<ev_async> watchers can be used to wake them up from other	3863	C<ev_async> watchers can be used to wake them up from other threads safely
3264	threads safely (or from signal contexts...).	3864	(or from signal contexts...).
		3865
		3866	An example use would be to communicate signals or other events that only
		3867	work in the default loop by registering the signal watcher with the
		3868	default loop and triggering an C<ev_async> watcher from the default loop
		3869	watcher callback into the event loop interested in the signal.
3265		3870
3266	=back	3871	=back
3267		3872
3268	=head2 COROUTINES	3873	=head3 COROUTINES
3269		3874
3270	Libev is much more accommodating to coroutines ("cooperative threads"):	3875	Libev is very accommodating to coroutines ("cooperative threads"):
3271	libev fully supports nesting calls to it's functions from different	3876	libev fully supports nesting calls to its functions from different
3272	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3877	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3273	different coroutines and switch freely between both coroutines running the	3878	different coroutines, and switch freely between both coroutines running the
3274	loop, as long as you don't confuse yourself). The only exception is that	3879	loop, as long as you don't confuse yourself). The only exception is that
3275	you must not do this from C<ev_periodic> reschedule callbacks.	3880	you must not do this from C<ev_periodic> reschedule callbacks.
3276		3881
3277	Care has been invested into making sure that libev does not keep local	3882	Care has been taken to ensure that libev does not keep local state inside
3278	state inside C<ev_loop>, and other calls do not usually allow coroutine	3883	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3279	switches.	3884	they do not call any callbacks.
3280		3885
		3886	=head2 COMPILER WARNINGS
3281		3887
3282	=head1 COMPLEXITIES	3888	Depending on your compiler and compiler settings, you might get no or a
		3889	lot of warnings when compiling libev code. Some people are apparently
		3890	scared by this.
3283		3891
3284	In this section the complexities of (many of) the algorithms used inside	3892	However, these are unavoidable for many reasons. For one, each compiler
3285	libev will be explained. For complexity discussions about backends see the	3893	has different warnings, and each user has different tastes regarding
3286	documentation for C<ev_default_init>.	3894	warning options. "Warn-free" code therefore cannot be a goal except when
		3895	targeting a specific compiler and compiler-version.
3287		3896
3288	All of the following are about amortised time: If an array needs to be	3897	Another reason is that some compiler warnings require elaborate
3289	extended, libev needs to realloc and move the whole array, but this	3898	workarounds, or other changes to the code that make it less clear and less
3290	happens asymptotically never with higher number of elements, so O(1) might	3899	maintainable.
3291	mean it might do a lengthy realloc operation in rare cases, but on average
3292	it is much faster and asymptotically approaches constant time.
3293		3900
3294	=over 4	3901	And of course, some compiler warnings are just plain stupid, or simply
		3902	wrong (because they don't actually warn about the condition their message
		3903	seems to warn about). For example, certain older gcc versions had some
		3904	warnings that resulted an extreme number of false positives. These have
		3905	been fixed, but some people still insist on making code warn-free with
		3906	such buggy versions.
3295		3907
3296	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3908	While libev is written to generate as few warnings as possible,
		3909	"warn-free" code is not a goal, and it is recommended not to build libev
		3910	with any compiler warnings enabled unless you are prepared to cope with
		3911	them (e.g. by ignoring them). Remember that warnings are just that:
		3912	warnings, not errors, or proof of bugs.
3297		3913
3298	This means that, when you have a watcher that triggers in one hour and
3299	there are 100 watchers that would trigger before that then inserting will
3300	have to skip roughly seven (C<ld 100>) of these watchers.
3301		3914
3302	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3915	=head2 VALGRIND
3303		3916
3304	That means that changing a timer costs less than removing/adding them	3917	Valgrind has a special section here because it is a popular tool that is
3305	as only the relative motion in the event queue has to be paid for.	3918	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3306		3919
3307	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3920	If you think you found a bug (memory leak, uninitialised data access etc.)
		3921	in libev, then check twice: If valgrind reports something like:
3308		3922
3309	These just add the watcher into an array or at the head of a list.	3923	==2274== definitely lost: 0 bytes in 0 blocks.
		3924	==2274== possibly lost: 0 bytes in 0 blocks.
		3925	==2274== still reachable: 256 bytes in 1 blocks.
3310		3926
3311	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3927	Then there is no memory leak, just as memory accounted to global variables
		3928	is not a memleak - the memory is still being referenced, and didn't leak.
3312		3929
3313	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3930	Similarly, under some circumstances, valgrind might report kernel bugs
		3931	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3932	although an acceptable workaround has been found here), or it might be
		3933	confused.
3314		3934
3315	These watchers are stored in lists then need to be walked to find the	3935	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3316	correct watcher to remove. The lists are usually short (you don't usually	3936	make it into some kind of religion.
3317	have many watchers waiting for the same fd or signal).
3318		3937
3319	=item Finding the next timer in each loop iteration: O(1)	3938	If you are unsure about something, feel free to contact the mailing list
		3939	with the full valgrind report and an explanation on why you think this
		3940	is a bug in libev (best check the archives, too :). However, don't be
		3941	annoyed when you get a brisk "this is no bug" answer and take the chance
		3942	of learning how to interpret valgrind properly.
3320		3943
3321	By virtue of using a binary or 4-heap, the next timer is always found at a	3944	If you need, for some reason, empty reports from valgrind for your project
3322	fixed position in the storage array.	3945	I suggest using suppression lists.
3323		3946
3324	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3325		3947
3326	A change means an I/O watcher gets started or stopped, which requires	3948	=head1 PORTABILITY NOTES
3327	libev to recalculate its status (and possibly tell the kernel, depending
3328	on backend and whether C<ev_io_set> was used).
3329		3949
3330	=item Activating one watcher (putting it into the pending state): O(1)
3331
3332	=item Priority handling: O(number_of_priorities)
3333
3334	Priorities are implemented by allocating some space for each
3335	priority. When doing priority-based operations, libev usually has to
3336	linearly search all the priorities, but starting/stopping and activating
3337	watchers becomes O(1) w.r.t. priority handling.
3338
3339	=item Sending an ev_async: O(1)
3340
3341	=item Processing ev_async_send: O(number_of_async_watchers)
3342
3343	=item Processing signals: O(max_signal_number)
3344
3345	Sending involves a system call I<iff> there were no other C<ev_async_send>
3346	calls in the current loop iteration. Checking for async and signal events
3347	involves iterating over all running async watchers or all signal numbers.
3348
3349	=back
3350
3351
3352	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	3950	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3353		3951
3354	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3952	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3355	requires, and its I/O model is fundamentally incompatible with the POSIX	3953	requires, and its I/O model is fundamentally incompatible with the POSIX
3356	model. Libev still offers limited functionality on this platform in	3954	model. Libev still offers limited functionality on this platform in
3357	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3955	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3364	way (note also that glib is the slowest event library known to man).	3962	way (note also that glib is the slowest event library known to man).
3365		3963
3366	There is no supported compilation method available on windows except	3964	There is no supported compilation method available on windows except
3367	embedding it into other applications.	3965	embedding it into other applications.
3368		3966
		3967	Sensible signal handling is officially unsupported by Microsoft - libev
		3968	tries its best, but under most conditions, signals will simply not work.
		3969
3369	Not a libev limitation but worth mentioning: windows apparently doesn't	3970	Not a libev limitation but worth mentioning: windows apparently doesn't
3370	accept large writes: instead of resulting in a partial write, windows will	3971	accept large writes: instead of resulting in a partial write, windows will
3371	either accept everything or return C<ENOBUFS> if the buffer is too large,	3972	either accept everything or return C<ENOBUFS> if the buffer is too large,
3372	so make sure you only write small amounts into your sockets (less than a	3973	so make sure you only write small amounts into your sockets (less than a
3373	megabyte seems safe, but thsi apparently depends on the amount of memory	3974	megabyte seems safe, but this apparently depends on the amount of memory
3374	available).	3975	available).
3375		3976
3376	Due to the many, low, and arbitrary limits on the win32 platform and	3977	Due to the many, low, and arbitrary limits on the win32 platform and
3377	the abysmal performance of winsockets, using a large number of sockets	3978	the abysmal performance of winsockets, using a large number of sockets
3378	is not recommended (and not reasonable). If your program needs to use	3979	is not recommended (and not reasonable). If your program needs to use
3379	more than a hundred or so sockets, then likely it needs to use a totally	3980	more than a hundred or so sockets, then likely it needs to use a totally
3380	different implementation for windows, as libev offers the POSIX readiness	3981	different implementation for windows, as libev offers the POSIX readiness
3381	notification model, which cannot be implemented efficiently on windows	3982	notification model, which cannot be implemented efficiently on windows
3382	(Microsoft monopoly games).	3983	(due to Microsoft monopoly games).
3383		3984
3384	A typical way to use libev under windows is to embed it (see the embedding	3985	A typical way to use libev under windows is to embed it (see the embedding
3385	section for details) and use the following F<evwrap.h> header file instead	3986	section for details) and use the following F<evwrap.h> header file instead
3386	of F<ev.h>:	3987	of F<ev.h>:
3387		3988
…		…
3389	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	3990	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3390		3991
3391	#include "ev.h"	3992	#include "ev.h"
3392		3993
3393	And compile the following F<evwrap.c> file into your project (make sure	3994	And compile the following F<evwrap.c> file into your project (make sure
3394	you do I<not> compile the F<ev.c> or any other embedded soruce files!):	3995	you do I<not> compile the F<ev.c> or any other embedded source files!):
3395		3996
3396	#include "evwrap.h"	3997	#include "evwrap.h"
3397	#include "ev.c"	3998	#include "ev.c"
3398		3999
3399	=over 4	4000	=over 4
…		…
3423		4024
3424	Early versions of winsocket's select only supported waiting for a maximum	4025	Early versions of winsocket's select only supported waiting for a maximum
3425	of C<64> handles (probably owning to the fact that all windows kernels	4026	of C<64> handles (probably owning to the fact that all windows kernels
3426	can only wait for C<64> things at the same time internally; Microsoft	4027	can only wait for C<64> things at the same time internally; Microsoft
3427	recommends spawning a chain of threads and wait for 63 handles and the	4028	recommends spawning a chain of threads and wait for 63 handles and the
3428	previous thread in each. Great).	4029	previous thread in each. Sounds great!).
3429		4030
3430	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4031	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3431	to some high number (e.g. C<2048>) before compiling the winsocket select	4032	to some high number (e.g. C<2048>) before compiling the winsocket select
3432	call (which might be in libev or elsewhere, for example, perl does its own	4033	call (which might be in libev or elsewhere, for example, perl and many
3433	select emulation on windows).	4034	other interpreters do their own select emulation on windows).
3434		4035
3435	Another limit is the number of file descriptors in the Microsoft runtime	4036	Another limit is the number of file descriptors in the Microsoft runtime
3436	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4037	libraries, which by default is C<64> (there must be a hidden I<64>
3437	or something like this inside Microsoft). You can increase this by calling	4038	fetish or something like this inside Microsoft). You can increase this
3438	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4039	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3439	arbitrary limit), but is broken in many versions of the Microsoft runtime	4040	(another arbitrary limit), but is broken in many versions of the Microsoft
3440	libraries.
3441
3442	This might get you to about C<512> or C<2048> sockets (depending on	4041	runtime libraries. This might get you to about C<512> or C<2048> sockets
3443	windows version and/or the phase of the moon). To get more, you need to	4042	(depending on windows version and/or the phase of the moon). To get more,
3444	wrap all I/O functions and provide your own fd management, but the cost of	4043	you need to wrap all I/O functions and provide your own fd management, but
3445	calling select (O(n²)) will likely make this unworkable.	4044	the cost of calling select (O(n²)) will likely make this unworkable.
3446		4045
3447	=back	4046	=back
3448		4047
3449
3450	=head1 PORTABILITY REQUIREMENTS	4048	=head2 PORTABILITY REQUIREMENTS
3451		4049
3452	In addition to a working ISO-C implementation, libev relies on a few	4050	In addition to a working ISO-C implementation and of course the
3453	additional extensions:	4051	backend-specific APIs, libev relies on a few additional extensions:
3454		4052
3455	=over 4	4053	=over 4
3456		4054
3457	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	4055	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3458	calling conventions regardless of C<ev_watcher_type *>.	4056	calling conventions regardless of C<ev_watcher_type *>.
…		…
3464	calls them using an C<ev_watcher *> internally.	4062	calls them using an C<ev_watcher *> internally.
3465		4063
3466	=item C<sig_atomic_t volatile> must be thread-atomic as well	4064	=item C<sig_atomic_t volatile> must be thread-atomic as well
3467		4065
3468	The type C<sig_atomic_t volatile> (or whatever is defined as	4066	The type C<sig_atomic_t volatile> (or whatever is defined as
3469	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	4067	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3470	threads. This is not part of the specification for C<sig_atomic_t>, but is	4068	threads. This is not part of the specification for C<sig_atomic_t>, but is
3471	believed to be sufficiently portable.	4069	believed to be sufficiently portable.
3472		4070
3473	=item C<sigprocmask> must work in a threaded environment	4071	=item C<sigprocmask> must work in a threaded environment
3474		4072
…		…
3483	except the initial one, and run the default loop in the initial thread as	4081	except the initial one, and run the default loop in the initial thread as
3484	well.	4082	well.
3485		4083
3486	=item C<long> must be large enough for common memory allocation sizes	4084	=item C<long> must be large enough for common memory allocation sizes
3487		4085
3488	To improve portability and simplify using libev, libev uses C<long>	4086	To improve portability and simplify its API, libev uses C<long> internally
3489	internally instead of C<size_t> when allocating its data structures. On	4087	instead of C<size_t> when allocating its data structures. On non-POSIX
3490	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4088	systems (Microsoft...) this might be unexpectedly low, but is still at
3491	is still at least 31 bits everywhere, which is enough for hundreds of	4089	least 31 bits everywhere, which is enough for hundreds of millions of
3492	millions of watchers.	4090	watchers.
3493		4091
3494	=item C<double> must hold a time value in seconds with enough accuracy	4092	=item C<double> must hold a time value in seconds with enough accuracy
3495		4093
3496	The type C<double> is used to represent timestamps. It is required to	4094	The type C<double> is used to represent timestamps. It is required to
3497	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4095	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
3498	enough for at least into the year 4000. This requirement is fulfilled by	4096	enough for at least into the year 4000. This requirement is fulfilled by
3499	implementations implementing IEEE 754 (basically all existing ones).	4097	implementations implementing IEEE 754, which is basically all existing
		4098	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4099	2200.
3500		4100
3501	=back	4101	=back
3502		4102
3503	If you know of other additional requirements drop me a note.	4103	If you know of other additional requirements drop me a note.
3504		4104
3505		4105
3506	=head1 COMPILER WARNINGS	4106	=head1 ALGORITHMIC COMPLEXITIES
3507		4107
3508	Depending on your compiler and compiler settings, you might get no or a	4108	In this section the complexities of (many of) the algorithms used inside
3509	lot of warnings when compiling libev code. Some people are apparently	4109	libev will be documented. For complexity discussions about backends see
3510	scared by this.	4110	the documentation for C<ev_default_init>.
3511		4111
3512	However, these are unavoidable for many reasons. For one, each compiler	4112	All of the following are about amortised time: If an array needs to be
3513	has different warnings, and each user has different tastes regarding	4113	extended, libev needs to realloc and move the whole array, but this
3514	warning options. "Warn-free" code therefore cannot be a goal except when	4114	happens asymptotically rarer with higher number of elements, so O(1) might
3515	targeting a specific compiler and compiler-version.	4115	mean that libev does a lengthy realloc operation in rare cases, but on
		4116	average it is much faster and asymptotically approaches constant time.
3516		4117
3517	Another reason is that some compiler warnings require elaborate	4118	=over 4
3518	workarounds, or other changes to the code that make it less clear and less
3519	maintainable.
3520		4119
3521	And of course, some compiler warnings are just plain stupid, or simply	4120	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3522	wrong (because they don't actually warn about the condition their message
3523	seems to warn about).
3524		4121
3525	While libev is written to generate as few warnings as possible,	4122	This means that, when you have a watcher that triggers in one hour and
3526	"warn-free" code is not a goal, and it is recommended not to build libev	4123	there are 100 watchers that would trigger before that, then inserting will
3527	with any compiler warnings enabled unless you are prepared to cope with	4124	have to skip roughly seven (C<ld 100>) of these watchers.
3528	them (e.g. by ignoring them). Remember that warnings are just that:
3529	warnings, not errors, or proof of bugs.
3530		4125
		4126	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3531		4127
3532	=head1 VALGRIND	4128	That means that changing a timer costs less than removing/adding them,
		4129	as only the relative motion in the event queue has to be paid for.
3533		4130
3534	Valgrind has a special section here because it is a popular tool that is	4131	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3535	highly useful, but valgrind reports are very hard to interpret.
3536		4132
3537	If you think you found a bug (memory leak, uninitialised data access etc.)	4133	These just add the watcher into an array or at the head of a list.
3538	in libev, then check twice: If valgrind reports something like:
3539		4134
3540	==2274== definitely lost: 0 bytes in 0 blocks.	4135	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3541	==2274== possibly lost: 0 bytes in 0 blocks.
3542	==2274== still reachable: 256 bytes in 1 blocks.
3543		4136
3544	Then there is no memory leak. Similarly, under some circumstances,	4137	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3545	valgrind might report kernel bugs as if it were a bug in libev, or it
3546	might be confused (it is a very good tool, but only a tool).
3547		4138
3548	If you are unsure about something, feel free to contact the mailing list	4139	These watchers are stored in lists, so they need to be walked to find the
3549	with the full valgrind report and an explanation on why you think this is	4140	correct watcher to remove. The lists are usually short (you don't usually
3550	a bug in libev. However, don't be annoyed when you get a brisk "this is	4141	have many watchers waiting for the same fd or signal: one is typical, two
3551	no bug" answer and take the chance of learning how to interpret valgrind	4142	is rare).
3552	properly.
3553		4143
3554	If you need, for some reason, empty reports from valgrind for your project	4144	=item Finding the next timer in each loop iteration: O(1)
3555	I suggest using suppression lists.
3556		4145
		4146	By virtue of using a binary or 4-heap, the next timer is always found at a
		4147	fixed position in the storage array.
		4148
		4149	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4150
		4151	A change means an I/O watcher gets started or stopped, which requires
		4152	libev to recalculate its status (and possibly tell the kernel, depending
		4153	on backend and whether C<ev_io_set> was used).
		4154
		4155	=item Activating one watcher (putting it into the pending state): O(1)
		4156
		4157	=item Priority handling: O(number_of_priorities)
		4158
		4159	Priorities are implemented by allocating some space for each
		4160	priority. When doing priority-based operations, libev usually has to
		4161	linearly search all the priorities, but starting/stopping and activating
		4162	watchers becomes O(1) with respect to priority handling.
		4163
		4164	=item Sending an ev_async: O(1)
		4165
		4166	=item Processing ev_async_send: O(number_of_async_watchers)
		4167
		4168	=item Processing signals: O(max_signal_number)
		4169
		4170	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4171	calls in the current loop iteration. Checking for async and signal events
		4172	involves iterating over all running async watchers or all signal numbers.
		4173
		4174	=back
		4175
		4176
		4177	=head1 GLOSSARY
		4178
		4179	=over 4
		4180
		4181	=item active
		4182
		4183	A watcher is active as long as it has been started (has been attached to
		4184	an event loop) but not yet stopped (disassociated from the event loop).
		4185
		4186	=item application
		4187
		4188	In this document, an application is whatever is using libev.
		4189
		4190	=item callback
		4191
		4192	The address of a function that is called when some event has been
		4193	detected. Callbacks are being passed the event loop, the watcher that
		4194	received the event, and the actual event bitset.
		4195
		4196	=item callback invocation
		4197
		4198	The act of calling the callback associated with a watcher.
		4199
		4200	=item event
		4201
		4202	A change of state of some external event, such as data now being available
		4203	for reading on a file descriptor, time having passed or simply not having
		4204	any other events happening anymore.
		4205
		4206	In libev, events are represented as single bits (such as C<EV_READ> or
		4207	C<EV_TIMEOUT>).
		4208
		4209	=item event library
		4210
		4211	A software package implementing an event model and loop.
		4212
		4213	=item event loop
		4214
		4215	An entity that handles and processes external events and converts them
		4216	into callback invocations.
		4217
		4218	=item event model
		4219
		4220	The model used to describe how an event loop handles and processes
		4221	watchers and events.
		4222
		4223	=item pending
		4224
		4225	A watcher is pending as soon as the corresponding event has been detected,
		4226	and stops being pending as soon as the watcher will be invoked or its
		4227	pending status is explicitly cleared by the application.
		4228
		4229	A watcher can be pending, but not active. Stopping a watcher also clears
		4230	its pending status.
		4231
		4232	=item real time
		4233
		4234	The physical time that is observed. It is apparently strictly monotonic :)
		4235
		4236	=item wall-clock time
		4237
		4238	The time and date as shown on clocks. Unlike real time, it can actually
		4239	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4240	clock.
		4241
		4242	=item watcher
		4243
		4244	A data structure that describes interest in certain events. Watchers need
		4245	to be started (attached to an event loop) before they can receive events.
		4246
		4247	=item watcher invocation
		4248
		4249	The act of calling the callback associated with a watcher.
		4250
		4251	=back
3557		4252
3558	=head1 AUTHOR	4253	=head1 AUTHOR
3559		4254
3560	Marc Lehmann <libev@schmorp.de>.	4255	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3561		4256

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