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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
…		…
84	=head2 FEATURES	98	=head2 FEATURES
85		99
86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	100	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	101	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	102	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	103	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
90	with customised rescheduling (C<ev_periodic>), synchronous signals	104	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
91	(C<ev_signal>), process status change events (C<ev_child>), and event	105	timers (C<ev_timer>), absolute timers with customised rescheduling
92	watchers dealing with the event loop mechanism itself (C<ev_idle>,	106	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
93	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	107	change events (C<ev_child>), and event watchers dealing with the event
94	file watchers (C<ev_stat>) and even limited support for fork events	108	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
95	(C<ev_fork>).	109	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		110	limited support for fork events (C<ev_fork>).
96		111
97	It also is quite fast (see this	112	It also is quite fast (see this
98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	113	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
99	for example).	114	for example).
100		115
…		…
103	Libev is very configurable. In this manual the default (and most common)	118	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	119	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	120	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	121	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	122	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	123	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	124	this argument.
110		125
111	=head2 TIME REPRESENTATION	126	=head2 TIME REPRESENTATION
112		127
113	Libev represents time as a single floating point number, representing the	128	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	129	the (fractional) number of seconds since the (POSIX) epoch (somewhere
115	the beginning of 1970, details are complicated, don't ask). This type is	130	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	131	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	132	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	133	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	134	component C<stamp> might indicate, it is also used for time differences
120	throughout libev.	135	throughout libev.
121		136
122	=head1 ERROR HANDLING	137	=head1 ERROR HANDLING
123		138
…		…
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	229	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
215	recommended ones.	230	recommended ones.
216		231
217	See the description of C<ev_embed> watchers for more info.	232	See the description of C<ev_embed> watchers for more info.
218		233
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	234	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
220		235
221	Sets the allocation function to use (the prototype is similar - the	236	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	237	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	238	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	239	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	265	}
251		266
252	...	267	...
253	ev_set_allocator (persistent_realloc);	268	ev_set_allocator (persistent_realloc);
254		269
255	=item ev_set_syserr_cb (void (*cb)(const char *msg));	270	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
256		271
257	Set the callback function to call on a retryable system call error (such	272	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	273	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	274	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	275	callback is set, then libev will expect it to remedy the situation, no
…		…
276		291
277	=back	292	=back
278		293
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	294	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
280		295
281	An event loop is described by a C<struct ev_loop *>. The library knows two	296	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	297	is I<not> optional in this case, as there is also an C<ev_loop>
283	events, and dynamically created loops which do not.	298	I<function>).
		299
		300	The library knows two types of such loops, the I<default> loop, which
		301	supports signals and child events, and dynamically created loops which do
		302	not.
284		303
285	=over 4	304	=over 4
286		305
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	306	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		307
…		…
294	If you don't know what event loop to use, use the one returned from this	313	If you don't know what event loop to use, use the one returned from this
295	function.	314	function.
296		315
297	Note that this function is I<not> thread-safe, so if you want to use it	316	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,	317	from multiple threads, you have to lock (note also that this is unlikely,
299	as loops cannot bes hared easily between threads anyway).	318	as loops cannot be shared easily between threads anyway).
300		319
301	The default loop is the only loop that can handle C<ev_signal> and	320	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	321	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	322	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	323	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
…		…
344	flag.	363	flag.
345		364
346	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	365	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
347	environment variable.	366	environment variable.
348		367
		368	=item C<EVFLAG_NOINOTIFY>
		369
		370	When this flag is specified, then libev will not attempt to use the
		371	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and
		372	testing, this flag can be useful to conserve inotify file descriptors, as
		373	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		374
		375	=item C<EVFLAG_NOSIGNALFD>
		376
		377	When this flag is specified, then libev will not attempt to use the
		378	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This is
		379	probably only useful to work around any bugs in libev. Consequently, this
		380	flag might go away once the signalfd functionality is considered stable,
		381	so it's useful mostly in environment variables and not in program code.
		382
349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	383	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
350		384
351	This is your standard select(2) backend. Not I<completely> standard, as	385	This is your standard select(2) backend. Not I<completely> standard, as
352	libev tries to roll its own fd_set with no limits on the number of fds,	386	libev tries to roll its own fd_set with no limits on the number of fds,
353	but if that fails, expect a fairly low limit on the number of fds when	387	but if that fails, expect a fairly low limit on the number of fds when
…		…
359	writing a server, you should C<accept ()> in a loop to accept as many	393	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	394	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	395	a look at C<ev_set_io_collect_interval ()> to increase the amount of
362	readiness notifications you get per iteration.	396	readiness notifications you get per iteration.
363		397
		398	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		399	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		400	C<exceptfds> set on that platform).
		401
364	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	402	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
365		403
366	And this is your standard poll(2) backend. It's more complicated	404	And this is your standard poll(2) backend. It's more complicated
367	than select, but handles sparse fds better and has no artificial	405	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	406	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,	407	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	408	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
371	performance tips.	409	performance tips.
372		410
		411	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		412	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		413
373	=item C<EVBACKEND_EPOLL> (value 4, Linux)	414	=item C<EVBACKEND_EPOLL> (value 4, Linux)
374		415
375	For few fds, this backend is a bit little slower than poll and select,	416	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	417	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),	418	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	419	epoll scales either O(1) or O(active_fds).
379	of shortcomings, such as silently dropping events in some hard-to-detect	420
380	cases and requiring a system call per fd change, no fork support and bad	421	The epoll mechanism deserves honorable mention as the most misdesigned
381	support for dup.	422	of the more advanced event mechanisms: mere annoyances include silently
		423	dropping file descriptors, requiring a system call per change per file
		424	descriptor (and unnecessary guessing of parameters), problems with dup and
		425	so on. The biggest issue is fork races, however - if a program forks then
		426	I<both> parent and child process have to recreate the epoll set, which can
		427	take considerable time (one syscall per file descriptor) and is of course
		428	hard to detect.
		429
		430	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		431	of course I<doesn't>, and epoll just loves to report events for totally
		432	I<different> file descriptors (even already closed ones, so one cannot
		433	even remove them from the set) than registered in the set (especially
		434	on SMP systems). Libev tries to counter these spurious notifications by
		435	employing an additional generation counter and comparing that against the
		436	events to filter out spurious ones, recreating the set when required.
382		437
383	While stopping, setting and starting an I/O watcher in the same iteration	438	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	439	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	440	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	441	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
387	very well if you register events for both fds.	442	file descriptors might not work very well if you register events for both
388		443	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		444
393	Best performance from this backend is achieved by not unregistering all	445	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.	446	watchers for a file descriptor until it has been closed, if possible,
395	keep at least one watcher active per fd at all times.	447	i.e. keep at least one watcher active per fd at all times. Stopping and
		448	starting a watcher (without re-setting it) also usually doesn't cause
		449	extra overhead. A fork can both result in spurious notifications as well
		450	as in libev having to destroy and recreate the epoll object, which can
		451	take considerable time and thus should be avoided.
		452
		453	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		454	faster than epoll for maybe up to a hundred file descriptors, depending on
		455	the usage. So sad.
396		456
397	While nominally embeddable in other event loops, this feature is broken in	457	While nominally embeddable in other event loops, this feature is broken in
398	all kernel versions tested so far.	458	all kernel versions tested so far.
		459
		460	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		461	C<EVBACKEND_POLL>.
399		462
400	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	463	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
401		464
402	Kqueue deserves special mention, as at the time of this writing, it	465	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	466	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	467	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"	468	it's completely useless). Unlike epoll, however, whose brokenness
		469	is by design, these kqueue bugs can (and eventually will) be fixed
		470	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	471	"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)	472	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
408	system like NetBSD.	473	system like NetBSD.
409		474
410	You still can embed kqueue into a normal poll or select backend and use it	475	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	476	only for sockets (after having made sure that sockets work with kqueue on
…		…
413		478
414	It scales in the same way as the epoll backend, but the interface to the	479	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	480	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	481	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	482	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	483	two event changes per incident. Support for C<fork ()> is very bad (but
419	drops fds silently in similarly hard-to-detect cases.	484	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		485	cases
420		486
421	This backend usually performs well under most conditions.	487	This backend usually performs well under most conditions.
422		488
423	While nominally embeddable in other event loops, this doesn't work	489	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	490	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	491	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	492	(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	493	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
428	sockets.	494	also broken on OS X)) and, did I mention it, using it only for sockets.
		495
		496	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		497	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		498	C<NOTE_EOF>.
429		499
430	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	500	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
431		501
432	This is not implemented yet (and might never be, unless you send me an	502	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	503	implementation). According to reports, C</dev/poll> only supports sockets
…		…
446	While this backend scales well, it requires one system call per active	516	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	517	file descriptor per loop iteration. For small and medium numbers of file
448	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	518	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
449	might perform better.	519	might perform better.
450		520
451	On the positive side, ignoring the spurious readiness notifications, this	521	On the positive side, with the exception of the spurious readiness
452	backend actually performed to specification in all tests and is fully	522	notifications, this backend actually performed fully to specification
453	embeddable, which is a rare feat among the OS-specific backends.	523	in all tests and is fully embeddable, which is a rare feat among the
		524	OS-specific backends (I vastly prefer correctness over speed hacks).
		525
		526	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		527	C<EVBACKEND_POLL>.
454		528
455	=item C<EVBACKEND_ALL>	529	=item C<EVBACKEND_ALL>
456		530
457	Try all backends (even potentially broken ones that wouldn't be tried	531	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	532	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
460		534
461	It is definitely not recommended to use this flag.	535	It is definitely not recommended to use this flag.
462		536
463	=back	537	=back
464		538
465	If one or more of these are or'ed into the flags value, then only these	539	If one or more of the backend flags are or'ed into the flags value,
466	backends will be tried (in the reverse order as listed here). If none are	540	then only these backends will be tried (in the reverse order as listed
467	specified, all backends in C<ev_recommended_backends ()> will be tried.	541	here). If none are specified, all backends in C<ev_recommended_backends
		542	()> will be tried.
468		543
469	The most typical usage is like this:	544	Example: This is the most typical usage.
470		545
471	if (!ev_default_loop (0))	546	if (!ev_default_loop (0))
472	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	547	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
473		548
474	Restrict libev to the select and poll backends, and do not allow	549	Example: Restrict libev to the select and poll backends, and do not allow
475	environment settings to be taken into account:	550	environment settings to be taken into account:
476		551
477	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	552	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
478		553
479	Use whatever libev has to offer, but make sure that kqueue is used if	554	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	555	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):	556	private event loop and only if you know the OS supports your types of
		557	fds):
482		558
483	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	559	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
484		560
485	=item struct ev_loop *ev_loop_new (unsigned int flags)	561	=item struct ev_loop *ev_loop_new (unsigned int flags)
486		562
…		…
507	responsibility to either stop all watchers cleanly yourself I<before>	583	responsibility to either stop all watchers cleanly yourself I<before>
508	calling this function, or cope with the fact afterwards (which is usually	584	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	585	the easiest thing, you can just ignore the watchers and/or C<free ()> them
510	for example).	586	for example).
511		587
512	Note that certain global state, such as signal state, will not be freed by	588	Note that certain global state, such as signal state (and installed signal
513	this function, and related watchers (such as signal and child watchers)	589	handlers), will not be freed by this function, and related watchers (such
514	would need to be stopped manually.	590	as signal and child watchers) would need to be stopped manually.
515		591
516	In general it is not advisable to call this function except in the	592	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	593	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	594	pipe fds. If you need dynamically allocated loops it is better to use
519	C<ev_loop_new> and C<ev_loop_destroy>).	595	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
544		620
545	=item ev_loop_fork (loop)	621	=item ev_loop_fork (loop)
546		622
547	Like C<ev_default_fork>, but acts on an event loop created by	623	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	624	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.	625	after fork that you want to re-use in the child, and how you do this is
		626	entirely your own problem.
550		627
551	=item int ev_is_default_loop (loop)	628	=item int ev_is_default_loop (loop)
552		629
553	Returns true when the given loop actually is the default loop, false otherwise.	630	Returns true when the given loop is, in fact, the default loop, and false
		631	otherwise.
554		632
555	=item unsigned int ev_loop_count (loop)	633	=item unsigned int ev_loop_count (loop)
556		634
557	Returns the count of loop iterations for the loop, which is identical to	635	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	636	the number of times libev did poll for new events. It starts at C<0> and
559	happily wraps around with enough iterations.	637	happily wraps around with enough iterations.
560		638
561	This value can sometimes be useful as a generation counter of sorts (it	639	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	640	"ticks" the number of loop iterations), as it roughly corresponds with
563	C<ev_prepare> and C<ev_check> calls.	641	C<ev_prepare> and C<ev_check> calls.
		642
		643	=item unsigned int ev_loop_depth (loop)
		644
		645	Returns the number of times C<ev_loop> was entered minus the number of
		646	times C<ev_loop> was exited, in other words, the recursion depth.
		647
		648	Outside C<ev_loop>, this number is zero. In a callback, this number is
		649	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),
		650	in which case it is higher.
		651
		652	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread
		653	etc.), doesn't count as exit.
564		654
565	=item unsigned int ev_backend (loop)	655	=item unsigned int ev_backend (loop)
566		656
567	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	657	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
568	use.	658	use.
…		…
573	received events and started processing them. This timestamp does not	663	received events and started processing them. This timestamp does not
574	change as long as callbacks are being processed, and this is also the base	664	change as long as callbacks are being processed, and this is also the base
575	time used for relative timers. You can treat it as the timestamp of the	665	time used for relative timers. You can treat it as the timestamp of the
576	event occurring (or more correctly, libev finding out about it).	666	event occurring (or more correctly, libev finding out about it).
577		667
		668	=item ev_now_update (loop)
		669
		670	Establishes the current time by querying the kernel, updating the time
		671	returned by C<ev_now ()> in the progress. This is a costly operation and
		672	is usually done automatically within C<ev_loop ()>.
		673
		674	This function is rarely useful, but when some event callback runs for a
		675	very long time without entering the event loop, updating libev's idea of
		676	the current time is a good idea.
		677
		678	See also L<The special problem of time updates> in the C<ev_timer> section.
		679
		680	=item ev_suspend (loop)
		681
		682	=item ev_resume (loop)
		683
		684	These two functions suspend and resume a loop, for use when the loop is
		685	not used for a while and timeouts should not be processed.
		686
		687	A typical use case would be an interactive program such as a game: When
		688	the user presses C<^Z> to suspend the game and resumes it an hour later it
		689	would be best to handle timeouts as if no time had actually passed while
		690	the program was suspended. This can be achieved by calling C<ev_suspend>
		691	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		692	C<ev_resume> directly afterwards to resume timer processing.
		693
		694	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		695	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		696	will be rescheduled (that is, they will lose any events that would have
		697	occured while suspended).
		698
		699	After calling C<ev_suspend> you B<must not> call I<any> function on the
		700	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		701	without a previous call to C<ev_suspend>.
		702
		703	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		704	event loop time (see C<ev_now_update>).
		705
578	=item ev_loop (loop, int flags)	706	=item ev_loop (loop, int flags)
579		707
580	Finally, this is it, the event handler. This function usually is called	708	Finally, this is it, the event handler. This function usually is called
581	after you initialised all your watchers and you want to start handling	709	after you initialised all your watchers and you want to start handling
582	events.	710	events.
…		…
584	If the flags argument is specified as C<0>, it will not return until	712	If the flags argument is specified as C<0>, it will not return until
585	either no event watchers are active anymore or C<ev_unloop> was called.	713	either no event watchers are active anymore or C<ev_unloop> was called.
586		714
587	Please note that an explicit C<ev_unloop> is usually better than	715	Please note that an explicit C<ev_unloop> is usually better than
588	relying on all watchers to be stopped when deciding when a program has	716	relying on all watchers to be stopped when deciding when a program has
589	finished (especially in interactive programs), but having a program that	717	finished (especially in interactive programs), but having a program
590	automatically loops as long as it has to and no longer by virtue of	718	that automatically loops as long as it has to and no longer by virtue
591	relying on its watchers stopping correctly is a thing of beauty.	719	of relying on its watchers stopping correctly, that is truly a thing of
		720	beauty.
592		721
593	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	722	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
594	those events and any outstanding ones, but will not block your process in	723	those events and any already outstanding ones, but will not block your
595	case there are no events and will return after one iteration of the loop.	724	process in case there are no events and will return after one iteration of
		725	the loop.
596		726
597	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	727	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
598	necessary) and will handle those and any outstanding ones. It will block	728	necessary) and will handle those and any already outstanding ones. It
599	your process until at least one new event arrives, and will return after	729	will block your process until at least one new event arrives (which could
600	one iteration of the loop. This is useful if you are waiting for some	730	be an event internal to libev itself, so there is no guarantee that a
601	external event in conjunction with something not expressible using other	731	user-registered callback will be called), and will return after one
		732	iteration of the loop.
		733
		734	This is useful if you are waiting for some external event in conjunction
		735	with something not expressible using other libev watchers (i.e. "roll your
602	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	736	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
603	usually a better approach for this kind of thing.	737	usually a better approach for this kind of thing.
604		738
605	Here are the gory details of what C<ev_loop> does:	739	Here are the gory details of what C<ev_loop> does:
606		740
607	- Before the first iteration, call any pending watchers.	741	- Before the first iteration, call any pending watchers.
…		…
617	any active watchers at all will result in not sleeping).	751	any active watchers at all will result in not sleeping).
618	- Sleep if the I/O and timer collect interval say so.	752	- Sleep if the I/O and timer collect interval say so.
619	- Block the process, waiting for any events.	753	- Block the process, waiting for any events.
620	- Queue all outstanding I/O (fd) events.	754	- Queue all outstanding I/O (fd) events.
621	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	755	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
622	- Queue all outstanding timers.	756	- Queue all expired timers.
623	- Queue all outstanding periodics.	757	- Queue all expired periodics.
624	- Unless any events are pending now, queue all idle watchers.	758	- Unless any events are pending now, queue all idle watchers.
625	- Queue all check watchers.	759	- Queue all check watchers.
626	- Call all queued watchers in reverse order (i.e. check watchers first).	760	- Call all queued watchers in reverse order (i.e. check watchers first).
627	Signals and child watchers are implemented as I/O watchers, and will	761	Signals and child watchers are implemented as I/O watchers, and will
628	be handled here by queueing them when their watcher gets executed.	762	be handled here by queueing them when their watcher gets executed.
…		…
645	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	779	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
646	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	780	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
647		781
648	This "unloop state" will be cleared when entering C<ev_loop> again.	782	This "unloop state" will be cleared when entering C<ev_loop> again.
649		783
		784	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		785
650	=item ev_ref (loop)	786	=item ev_ref (loop)
651		787
652	=item ev_unref (loop)	788	=item ev_unref (loop)
653		789
654	Ref/unref can be used to add or remove a reference count on the event	790	Ref/unref can be used to add or remove a reference count on the event
655	loop: Every watcher keeps one reference, and as long as the reference	791	loop: Every watcher keeps one reference, and as long as the reference
656	count is nonzero, C<ev_loop> will not return on its own. If you have	792	count is nonzero, C<ev_loop> will not return on its own.
		793
657	a watcher you never unregister that should not keep C<ev_loop> from	794	If you have a watcher you never unregister that should not keep C<ev_loop>
658	returning, ev_unref() after starting, and ev_ref() before stopping it. For	795	from returning, call ev_unref() after starting, and ev_ref() before
		796	stopping it.
		797
659	example, libev itself uses this for its internal signal pipe: It is not	798	As an example, libev itself uses this for its internal signal pipe: It
660	visible to the libev user and should not keep C<ev_loop> from exiting if	799	is not visible to the libev user and should not keep C<ev_loop> from
661	no event watchers registered by it are active. It is also an excellent	800	exiting if no event watchers registered by it are active. It is also an
662	way to do this for generic recurring timers or from within third-party	801	excellent way to do this for generic recurring timers or from within
663	libraries. Just remember to I<unref after start> and I<ref before stop>	802	third-party libraries. Just remember to I<unref after start> and I<ref
664	(but only if the watcher wasn't active before, or was active before,	803	before stop> (but only if the watcher wasn't active before, or was active
665	respectively).	804	before, respectively. Note also that libev might stop watchers itself
		805	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		806	in the callback).
666		807
667	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	808	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
668	running when nothing else is active.	809	running when nothing else is active.
669		810
670	struct ev_signal exitsig;	811	ev_signal exitsig;
671	ev_signal_init (&exitsig, sig_cb, SIGINT);	812	ev_signal_init (&exitsig, sig_cb, SIGINT);
672	ev_signal_start (loop, &exitsig);	813	ev_signal_start (loop, &exitsig);
673	evf_unref (loop);	814	evf_unref (loop);
674		815
675	Example: For some weird reason, unregister the above signal handler again.	816	Example: For some weird reason, unregister the above signal handler again.
…		…
689	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	830	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
690	allows libev to delay invocation of I/O and timer/periodic callbacks	831	allows libev to delay invocation of I/O and timer/periodic callbacks
691	to increase efficiency of loop iterations (or to increase power-saving	832	to increase efficiency of loop iterations (or to increase power-saving
692	opportunities).	833	opportunities).
693		834
694	The background is that sometimes your program runs just fast enough to	835	The idea is that sometimes your program runs just fast enough to handle
695	handle one (or very few) event(s) per loop iteration. While this makes	836	one (or very few) event(s) per loop iteration. While this makes the
696	the program responsive, it also wastes a lot of CPU time to poll for new	837	program responsive, it also wastes a lot of CPU time to poll for new
697	events, especially with backends like C<select ()> which have a high	838	events, especially with backends like C<select ()> which have a high
698	overhead for the actual polling but can deliver many events at once.	839	overhead for the actual polling but can deliver many events at once.
699		840
700	By setting a higher I<io collect interval> you allow libev to spend more	841	By setting a higher I<io collect interval> you allow libev to spend more
701	time collecting I/O events, so you can handle more events per iteration,	842	time collecting I/O events, so you can handle more events per iteration,
702	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	843	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
703	C<ev_timer>) will be not affected. Setting this to a non-null value will	844	C<ev_timer>) will be not affected. Setting this to a non-null value will
704	introduce an additional C<ev_sleep ()> call into most loop iterations.	845	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		846	sleep time ensures that libev will not poll for I/O events more often then
		847	once per this interval, on average.
705		848
706	Likewise, by setting a higher I<timeout collect interval> you allow libev	849	Likewise, by setting a higher I<timeout collect interval> you allow libev
707	to spend more time collecting timeouts, at the expense of increased	850	to spend more time collecting timeouts, at the expense of increased
708	latency (the watcher callback will be called later). C<ev_io> watchers	851	latency/jitter/inexactness (the watcher callback will be called
709	will not be affected. Setting this to a non-null value will not introduce	852	later). C<ev_io> watchers will not be affected. Setting this to a non-null
710	any overhead in libev.	853	value will not introduce any overhead in libev.
711		854
712	Many (busy) programs can usually benefit by setting the I/O collect	855	Many (busy) programs can usually benefit by setting the I/O collect
713	interval to a value near C<0.1> or so, which is often enough for	856	interval to a value near C<0.1> or so, which is often enough for
714	interactive servers (of course not for games), likewise for timeouts. It	857	interactive servers (of course not for games), likewise for timeouts. It
715	usually doesn't make much sense to set it to a lower value than C<0.01>,	858	usually doesn't make much sense to set it to a lower value than C<0.01>,
716	as this approaches the timing granularity of most systems.	859	as this approaches the timing granularity of most systems. Note that if
		860	you do transactions with the outside world and you can't increase the
		861	parallelity, then this setting will limit your transaction rate (if you
		862	need to poll once per transaction and the I/O collect interval is 0.01,
		863	then you can't do more than 100 transations per second).
717		864
718	Setting the I<timeout collect interval> can improve the opportunity for	865	Setting the I<timeout collect interval> can improve the opportunity for
719	saving power, as the program will "bundle" timer callback invocations that	866	saving power, as the program will "bundle" timer callback invocations that
720	are "near" in time together, by delaying some, thus reducing the number of	867	are "near" in time together, by delaying some, thus reducing the number of
721	times the process sleeps and wakes up again. Another useful technique to	868	times the process sleeps and wakes up again. Another useful technique to
722	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	869	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
723	they fire on, say, one-second boundaries only.	870	they fire on, say, one-second boundaries only.
724		871
		872	Example: we only need 0.1s timeout granularity, and we wish not to poll
		873	more often than 100 times per second:
		874
		875	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		876	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		877
		878	=item ev_invoke_pending (loop)
		879
		880	This call will simply invoke all pending watchers while resetting their
		881	pending state. Normally, C<ev_loop> does this automatically when required,
		882	but when overriding the invoke callback this call comes handy.
		883
		884	=item int ev_pending_count (loop)
		885
		886	Returns the number of pending watchers - zero indicates that no watchers
		887	are pending.
		888
		889	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		890
		891	This overrides the invoke pending functionality of the loop: Instead of
		892	invoking all pending watchers when there are any, C<ev_loop> will call
		893	this callback instead. This is useful, for example, when you want to
		894	invoke the actual watchers inside another context (another thread etc.).
		895
		896	If you want to reset the callback, use C<ev_invoke_pending> as new
		897	callback.
		898
		899	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		900
		901	Sometimes you want to share the same loop between multiple threads. This
		902	can be done relatively simply by putting mutex_lock/unlock calls around
		903	each call to a libev function.
		904
		905	However, C<ev_loop> can run an indefinite time, so it is not feasible to
		906	wait for it to return. One way around this is to wake up the loop via
		907	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>
		908	and I<acquire> callbacks on the loop.
		909
		910	When set, then C<release> will be called just before the thread is
		911	suspended waiting for new events, and C<acquire> is called just
		912	afterwards.
		913
		914	Ideally, C<release> will just call your mutex_unlock function, and
		915	C<acquire> will just call the mutex_lock function again.
		916
		917	While event loop modifications are allowed between invocations of
		918	C<release> and C<acquire> (that's their only purpose after all), no
		919	modifications done will affect the event loop, i.e. adding watchers will
		920	have no effect on the set of file descriptors being watched, or the time
		921	waited. USe an C<ev_async> watcher to wake up C<ev_loop> when you want it
		922	to take note of any changes you made.
		923
		924	In theory, threads executing C<ev_loop> will be async-cancel safe between
		925	invocations of C<release> and C<acquire>.
		926
		927	See also the locking example in the C<THREADS> section later in this
		928	document.
		929
		930	=item ev_set_userdata (loop, void *data)
		931
		932	=item ev_userdata (loop)
		933
		934	Set and retrieve a single C<void *> associated with a loop. When
		935	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		936	C<0.>
		937
		938	These two functions can be used to associate arbitrary data with a loop,
		939	and are intended solely for the C<invoke_pending_cb>, C<release> and
		940	C<acquire> callbacks described above, but of course can be (ab-)used for
		941	any other purpose as well.
		942
725	=item ev_loop_verify (loop)	943	=item ev_loop_verify (loop)
726		944
727	This function only does something when C<EV_VERIFY> support has been	945	This function only does something when C<EV_VERIFY> support has been
728	compiled in. It tries to go through all internal structures and checks	946	compiled in, which is the default for non-minimal builds. It tries to go
729	them for validity. If anything is found to be inconsistent, it will print	947	through all internal structures and checks them for validity. If anything
730	an error message to standard error and call C<abort ()>.	948	is found to be inconsistent, it will print an error message to standard
		949	error and call C<abort ()>.
731		950
732	This can be used to catch bugs inside libev itself: under normal	951	This can be used to catch bugs inside libev itself: under normal
733	circumstances, this function will never abort as of course libev keeps its	952	circumstances, this function will never abort as of course libev keeps its
734	data structures consistent.	953	data structures consistent.
735		954
736	=back	955	=back
737		956
738		957
739	=head1 ANATOMY OF A WATCHER	958	=head1 ANATOMY OF A WATCHER
740		959
		960	In the following description, uppercase C<TYPE> in names stands for the
		961	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		962	watchers and C<ev_io_start> for I/O watchers.
		963
741	A watcher is a structure that you create and register to record your	964	A watcher is a structure that you create and register to record your
742	interest in some event. For instance, if you want to wait for STDIN to	965	interest in some event. For instance, if you want to wait for STDIN to
743	become readable, you would create an C<ev_io> watcher for that:	966	become readable, you would create an C<ev_io> watcher for that:
744		967
745	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	968	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
746	{	969	{
747	ev_io_stop (w);	970	ev_io_stop (w);
748	ev_unloop (loop, EVUNLOOP_ALL);	971	ev_unloop (loop, EVUNLOOP_ALL);
749	}	972	}
750		973
751	struct ev_loop *loop = ev_default_loop (0);	974	struct ev_loop *loop = ev_default_loop (0);
		975
752	struct ev_io stdin_watcher;	976	ev_io stdin_watcher;
		977
753	ev_init (&stdin_watcher, my_cb);	978	ev_init (&stdin_watcher, my_cb);
754	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	979	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
755	ev_io_start (loop, &stdin_watcher);	980	ev_io_start (loop, &stdin_watcher);
		981
756	ev_loop (loop, 0);	982	ev_loop (loop, 0);
757		983
758	As you can see, you are responsible for allocating the memory for your	984	As you can see, you are responsible for allocating the memory for your
759	watcher structures (and it is usually a bad idea to do this on the stack,	985	watcher structures (and it is I<usually> a bad idea to do this on the
760	although this can sometimes be quite valid).	986	stack).
		987
		988	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		989	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
761		990
762	Each watcher structure must be initialised by a call to C<ev_init	991	Each watcher structure must be initialised by a call to C<ev_init
763	(watcher *, callback)>, which expects a callback to be provided. This	992	(watcher *, callback)>, which expects a callback to be provided. This
764	callback gets invoked each time the event occurs (or, in the case of I/O	993	callback gets invoked each time the event occurs (or, in the case of I/O
765	watchers, each time the event loop detects that the file descriptor given	994	watchers, each time the event loop detects that the file descriptor given
766	is readable and/or writable).	995	is readable and/or writable).
767		996
768	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	997	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
769	with arguments specific to this watcher type. There is also a macro	998	macro to configure it, with arguments specific to the watcher type. There
770	to combine initialisation and setting in one call: C<< ev_<type>_init	999	is also a macro to combine initialisation and setting in one call: C<<
771	(watcher *, callback, ...) >>.	1000	ev_TYPE_init (watcher *, callback, ...) >>.
772		1001
773	To make the watcher actually watch out for events, you have to start it	1002	To make the watcher actually watch out for events, you have to start it
774	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	1003	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
775	*) >>), and you can stop watching for events at any time by calling the	1004	*) >>), and you can stop watching for events at any time by calling the
776	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1005	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
777		1006
778	As long as your watcher is active (has been started but not stopped) you	1007	As long as your watcher is active (has been started but not stopped) you
779	must not touch the values stored in it. Most specifically you must never	1008	must not touch the values stored in it. Most specifically you must never
780	reinitialise it or call its C<set> macro.	1009	reinitialise it or call its C<ev_TYPE_set> macro.
781		1010
782	Each and every callback receives the event loop pointer as first, the	1011	Each and every callback receives the event loop pointer as first, the
783	registered watcher structure as second, and a bitset of received events as	1012	registered watcher structure as second, and a bitset of received events as
784	third argument.	1013	third argument.
785		1014
…		…
843		1072
844	=item C<EV_ASYNC>	1073	=item C<EV_ASYNC>
845		1074
846	The given async watcher has been asynchronously notified (see C<ev_async>).	1075	The given async watcher has been asynchronously notified (see C<ev_async>).
847		1076
		1077	=item C<EV_CUSTOM>
		1078
		1079	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1080	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		1081
848	=item C<EV_ERROR>	1082	=item C<EV_ERROR>
849		1083
850	An unspecified error has occurred, the watcher has been stopped. This might	1084	An unspecified error has occurred, the watcher has been stopped. This might
851	happen because the watcher could not be properly started because libev	1085	happen because the watcher could not be properly started because libev
852	ran out of memory, a file descriptor was found to be closed or any other	1086	ran out of memory, a file descriptor was found to be closed or any other
		1087	problem. Libev considers these application bugs.
		1088
853	problem. You best act on it by reporting the problem and somehow coping	1089	You best act on it by reporting the problem and somehow coping with the
854	with the watcher being stopped.	1090	watcher being stopped. Note that well-written programs should not receive
		1091	an error ever, so when your watcher receives it, this usually indicates a
		1092	bug in your program.
855		1093
856	Libev will usually signal a few "dummy" events together with an error,	1094	Libev will usually signal a few "dummy" events together with an error, for
857	for example it might indicate that a fd is readable or writable, and if	1095	example it might indicate that a fd is readable or writable, and if your
858	your callbacks is well-written it can just attempt the operation and cope	1096	callbacks is well-written it can just attempt the operation and cope with
859	with the error from read() or write(). This will not work in multi-threaded	1097	the error from read() or write(). This will not work in multi-threaded
860	programs, though, so beware.	1098	programs, though, as the fd could already be closed and reused for another
		1099	thing, so beware.
861		1100
862	=back	1101	=back
863		1102
864	=head2 GENERIC WATCHER FUNCTIONS	1103	=head2 GENERIC WATCHER FUNCTIONS
865
866	In the following description, C<TYPE> stands for the watcher type,
867	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
868		1104
869	=over 4	1105	=over 4
870		1106
871	=item C<ev_init> (ev_TYPE *watcher, callback)	1107	=item C<ev_init> (ev_TYPE *watcher, callback)
872		1108
…		…
878	which rolls both calls into one.	1114	which rolls both calls into one.
879		1115
880	You can reinitialise a watcher at any time as long as it has been stopped	1116	You can reinitialise a watcher at any time as long as it has been stopped
881	(or never started) and there are no pending events outstanding.	1117	(or never started) and there are no pending events outstanding.
882		1118
883	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1119	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
884	int revents)>.	1120	int revents)>.
		1121
		1122	Example: Initialise an C<ev_io> watcher in two steps.
		1123
		1124	ev_io w;
		1125	ev_init (&w, my_cb);
		1126	ev_io_set (&w, STDIN_FILENO, EV_READ);
885		1127
886	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1128	=item C<ev_TYPE_set> (ev_TYPE *, [args])
887		1129
888	This macro initialises the type-specific parts of a watcher. You need to	1130	This macro initialises the type-specific parts of a watcher. You need to
889	call C<ev_init> at least once before you call this macro, but you can	1131	call C<ev_init> at least once before you call this macro, but you can
…		…
892	difference to the C<ev_init> macro).	1134	difference to the C<ev_init> macro).
893		1135
894	Although some watcher types do not have type-specific arguments	1136	Although some watcher types do not have type-specific arguments
895	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	1137	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
896		1138
		1139	See C<ev_init>, above, for an example.
		1140
897	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1141	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
898		1142
899	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1143	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
900	calls into a single call. This is the most convenient method to initialise	1144	calls into a single call. This is the most convenient method to initialise
901	a watcher. The same limitations apply, of course.	1145	a watcher. The same limitations apply, of course.
902		1146
		1147	Example: Initialise and set an C<ev_io> watcher in one step.
		1148
		1149	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1150
903	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1151	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
904		1152
905	Starts (activates) the given watcher. Only active watchers will receive	1153	Starts (activates) the given watcher. Only active watchers will receive
906	events. If the watcher is already active nothing will happen.	1154	events. If the watcher is already active nothing will happen.
907		1155
		1156	Example: Start the C<ev_io> watcher that is being abused as example in this
		1157	whole section.
		1158
		1159	ev_io_start (EV_DEFAULT_UC, &w);
		1160
908	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1161	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
909		1162
910	Stops the given watcher again (if active) and clears the pending	1163	Stops the given watcher if active, and clears the pending status (whether
		1164	the watcher was active or not).
		1165
911	status. It is possible that stopped watchers are pending (for example,	1166	It is possible that stopped watchers are pending - for example,
912	non-repeating timers are being stopped when they become pending), but	1167	non-repeating timers are being stopped when they become pending - but
913	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1168	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
914	you want to free or reuse the memory used by the watcher it is therefore a	1169	pending. If you want to free or reuse the memory used by the watcher it is
915	good idea to always call its C<ev_TYPE_stop> function.	1170	therefore a good idea to always call its C<ev_TYPE_stop> function.
916		1171
917	=item bool ev_is_active (ev_TYPE *watcher)	1172	=item bool ev_is_active (ev_TYPE *watcher)
918		1173
919	Returns a true value iff the watcher is active (i.e. it has been started	1174	Returns a true value iff the watcher is active (i.e. it has been started
920	and not yet been stopped). As long as a watcher is active you must not modify	1175	and not yet been stopped). As long as a watcher is active you must not modify
…		…
946	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1201	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
947	(default: C<-2>). Pending watchers with higher priority will be invoked	1202	(default: C<-2>). Pending watchers with higher priority will be invoked
948	before watchers with lower priority, but priority will not keep watchers	1203	before watchers with lower priority, but priority will not keep watchers
949	from being executed (except for C<ev_idle> watchers).	1204	from being executed (except for C<ev_idle> watchers).
950		1205
951	This means that priorities are I<only> used for ordering callback
952	invocation after new events have been received. This is useful, for
953	example, to reduce latency after idling, or more often, to bind two
954	watchers on the same event and make sure one is called first.
955
956	If you need to suppress invocation when higher priority events are pending	1206	If you need to suppress invocation when higher priority events are pending
957	you need to look at C<ev_idle> watchers, which provide this functionality.	1207	you need to look at C<ev_idle> watchers, which provide this functionality.
958		1208
959	You I<must not> change the priority of a watcher as long as it is active or	1209	You I<must not> change the priority of a watcher as long as it is active or
960	pending.	1210	pending.
961		1211
		1212	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1213	fine, as long as you do not mind that the priority value you query might
		1214	or might not have been clamped to the valid range.
		1215
962	The default priority used by watchers when no priority has been set is	1216	The default priority used by watchers when no priority has been set is
963	always C<0>, which is supposed to not be too high and not be too low :).	1217	always C<0>, which is supposed to not be too high and not be too low :).
964		1218
965	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1219	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
966	fine, as long as you do not mind that the priority value you query might	1220	priorities.
967	or might not have been adjusted to be within valid range.
968		1221
969	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1222	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
970		1223
971	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1224	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
972	C<loop> nor C<revents> need to be valid as long as the watcher callback	1225	C<loop> nor C<revents> need to be valid as long as the watcher callback
973	can deal with that fact.	1226	can deal with that fact, as both are simply passed through to the
		1227	callback.
974		1228
975	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1229	=item int ev_clear_pending (loop, ev_TYPE *watcher)
976		1230
977	If the watcher is pending, this function returns clears its pending status	1231	If the watcher is pending, this function clears its pending status and
978	and returns its C<revents> bitset (as if its callback was invoked). If the	1232	returns its C<revents> bitset (as if its callback was invoked). If the
979	watcher isn't pending it does nothing and returns C<0>.	1233	watcher isn't pending it does nothing and returns C<0>.
980		1234
		1235	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1236	callback to be invoked, which can be accomplished with this function.
		1237
981	=back	1238	=back
982		1239
983		1240
984	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1241	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
985		1242
986	Each watcher has, by default, a member C<void *data> that you can change	1243	Each watcher has, by default, a member C<void *data> that you can change
987	and read at any time, libev will completely ignore it. This can be used	1244	and read at any time: libev will completely ignore it. This can be used
988	to associate arbitrary data with your watcher. If you need more data and	1245	to associate arbitrary data with your watcher. If you need more data and
989	don't want to allocate memory and store a pointer to it in that data	1246	don't want to allocate memory and store a pointer to it in that data
990	member, you can also "subclass" the watcher type and provide your own	1247	member, you can also "subclass" the watcher type and provide your own
991	data:	1248	data:
992		1249
993	struct my_io	1250	struct my_io
994	{	1251	{
995	struct ev_io io;	1252	ev_io io;
996	int otherfd;	1253	int otherfd;
997	void *somedata;	1254	void *somedata;
998	struct whatever *mostinteresting;	1255	struct whatever *mostinteresting;
999	}	1256	};
		1257
		1258	...
		1259	struct my_io w;
		1260	ev_io_init (&w.io, my_cb, fd, EV_READ);
1000		1261
1001	And since your callback will be called with a pointer to the watcher, you	1262	And since your callback will be called with a pointer to the watcher, you
1002	can cast it back to your own type:	1263	can cast it back to your own type:
1003		1264
1004	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1265	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1005	{	1266	{
1006	struct my_io *w = (struct my_io *)w_;	1267	struct my_io *w = (struct my_io *)w_;
1007	...	1268	...
1008	}	1269	}
1009		1270
1010	More interesting and less C-conformant ways of casting your callback type	1271	More interesting and less C-conformant ways of casting your callback type
1011	instead have been omitted.	1272	instead have been omitted.
1012		1273
1013	Another common scenario is having some data structure with multiple	1274	Another common scenario is to use some data structure with multiple
1014	watchers:	1275	embedded watchers:
1015		1276
1016	struct my_biggy	1277	struct my_biggy
1017	{	1278	{
1018	int some_data;	1279	int some_data;
1019	ev_timer t1;	1280	ev_timer t1;
1020	ev_timer t2;	1281	ev_timer t2;
1021	}	1282	}
1022		1283
1023	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1284	In this case getting the pointer to C<my_biggy> is a bit more
1024	you need to use C<offsetof>:	1285	complicated: Either you store the address of your C<my_biggy> struct
		1286	in the C<data> member of the watcher (for woozies), or you need to use
		1287	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1288	programmers):
1025		1289
1026	#include <stddef.h>	1290	#include <stddef.h>
1027		1291
1028	static void	1292	static void
1029	t1_cb (EV_P_ struct ev_timer *w, int revents)	1293	t1_cb (EV_P_ ev_timer *w, int revents)
1030	{	1294	{
1031	struct my_biggy big = (struct my_biggy *	1295	struct my_biggy big = (struct my_biggy *)
1032	(((char *)w) - offsetof (struct my_biggy, t1));	1296	(((char *)w) - offsetof (struct my_biggy, t1));
1033	}	1297	}
1034		1298
1035	static void	1299	static void
1036	t2_cb (EV_P_ struct ev_timer *w, int revents)	1300	t2_cb (EV_P_ ev_timer *w, int revents)
1037	{	1301	{
1038	struct my_biggy big = (struct my_biggy *	1302	struct my_biggy big = (struct my_biggy *)
1039	(((char *)w) - offsetof (struct my_biggy, t2));	1303	(((char *)w) - offsetof (struct my_biggy, t2));
1040	}	1304	}
		1305
		1306	=head2 WATCHER PRIORITY MODELS
		1307
		1308	Many event loops support I<watcher priorities>, which are usually small
		1309	integers that influence the ordering of event callback invocation
		1310	between watchers in some way, all else being equal.
		1311
		1312	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1313	description for the more technical details such as the actual priority
		1314	range.
		1315
		1316	There are two common ways how these these priorities are being interpreted
		1317	by event loops:
		1318
		1319	In the more common lock-out model, higher priorities "lock out" invocation
		1320	of lower priority watchers, which means as long as higher priority
		1321	watchers receive events, lower priority watchers are not being invoked.
		1322
		1323	The less common only-for-ordering model uses priorities solely to order
		1324	callback invocation within a single event loop iteration: Higher priority
		1325	watchers are invoked before lower priority ones, but they all get invoked
		1326	before polling for new events.
		1327
		1328	Libev uses the second (only-for-ordering) model for all its watchers
		1329	except for idle watchers (which use the lock-out model).
		1330
		1331	The rationale behind this is that implementing the lock-out model for
		1332	watchers is not well supported by most kernel interfaces, and most event
		1333	libraries will just poll for the same events again and again as long as
		1334	their callbacks have not been executed, which is very inefficient in the
		1335	common case of one high-priority watcher locking out a mass of lower
		1336	priority ones.
		1337
		1338	Static (ordering) priorities are most useful when you have two or more
		1339	watchers handling the same resource: a typical usage example is having an
		1340	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1341	timeouts. Under load, data might be received while the program handles
		1342	other jobs, but since timers normally get invoked first, the timeout
		1343	handler will be executed before checking for data. In that case, giving
		1344	the timer a lower priority than the I/O watcher ensures that I/O will be
		1345	handled first even under adverse conditions (which is usually, but not
		1346	always, what you want).
		1347
		1348	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1349	will only be executed when no same or higher priority watchers have
		1350	received events, they can be used to implement the "lock-out" model when
		1351	required.
		1352
		1353	For example, to emulate how many other event libraries handle priorities,
		1354	you can associate an C<ev_idle> watcher to each such watcher, and in
		1355	the normal watcher callback, you just start the idle watcher. The real
		1356	processing is done in the idle watcher callback. This causes libev to
		1357	continously poll and process kernel event data for the watcher, but when
		1358	the lock-out case is known to be rare (which in turn is rare :), this is
		1359	workable.
		1360
		1361	Usually, however, the lock-out model implemented that way will perform
		1362	miserably under the type of load it was designed to handle. In that case,
		1363	it might be preferable to stop the real watcher before starting the
		1364	idle watcher, so the kernel will not have to process the event in case
		1365	the actual processing will be delayed for considerable time.
		1366
		1367	Here is an example of an I/O watcher that should run at a strictly lower
		1368	priority than the default, and which should only process data when no
		1369	other events are pending:
		1370
		1371	ev_idle idle; // actual processing watcher
		1372	ev_io io; // actual event watcher
		1373
		1374	static void
		1375	io_cb (EV_P_ ev_io *w, int revents)
		1376	{
		1377	// stop the I/O watcher, we received the event, but
		1378	// are not yet ready to handle it.
		1379	ev_io_stop (EV_A_ w);
		1380
		1381	// start the idle watcher to ahndle the actual event.
		1382	// it will not be executed as long as other watchers
		1383	// with the default priority are receiving events.
		1384	ev_idle_start (EV_A_ &idle);
		1385	}
		1386
		1387	static void
		1388	idle_cb (EV_P_ ev_idle *w, int revents)
		1389	{
		1390	// actual processing
		1391	read (STDIN_FILENO, ...);
		1392
		1393	// have to start the I/O watcher again, as
		1394	// we have handled the event
		1395	ev_io_start (EV_P_ &io);
		1396	}
		1397
		1398	// initialisation
		1399	ev_idle_init (&idle, idle_cb);
		1400	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1401	ev_io_start (EV_DEFAULT_ &io);
		1402
		1403	In the "real" world, it might also be beneficial to start a timer, so that
		1404	low-priority connections can not be locked out forever under load. This
		1405	enables your program to keep a lower latency for important connections
		1406	during short periods of high load, while not completely locking out less
		1407	important ones.
1041		1408
1042		1409
1043	=head1 WATCHER TYPES	1410	=head1 WATCHER TYPES
1044		1411
1045	This section describes each watcher in detail, but will not repeat	1412	This section describes each watcher in detail, but will not repeat
…		…
1069	In general you can register as many read and/or write event watchers per	1436	In general you can register as many read and/or write event watchers per
1070	fd as you want (as long as you don't confuse yourself). Setting all file	1437	fd as you want (as long as you don't confuse yourself). Setting all file
1071	descriptors to non-blocking mode is also usually a good idea (but not	1438	descriptors to non-blocking mode is also usually a good idea (but not
1072	required if you know what you are doing).	1439	required if you know what you are doing).
1073		1440
1074	If you must do this, then force the use of a known-to-be-good backend	1441	If you cannot use non-blocking mode, then force the use of a
1075	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1442	known-to-be-good backend (at the time of this writing, this includes only
1076	C<EVBACKEND_POLL>).	1443	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1444	descriptors for which non-blocking operation makes no sense (such as
		1445	files) - libev doesn't guarentee any specific behaviour in that case.
1077		1446
1078	Another thing you have to watch out for is that it is quite easy to	1447	Another thing you have to watch out for is that it is quite easy to
1079	receive "spurious" readiness notifications, that is your callback might	1448	receive "spurious" readiness notifications, that is your callback might
1080	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1449	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1081	because there is no data. Not only are some backends known to create a	1450	because there is no data. Not only are some backends known to create a
1082	lot of those (for example Solaris ports), it is very easy to get into	1451	lot of those (for example Solaris ports), it is very easy to get into
1083	this situation even with a relatively standard program structure. Thus	1452	this situation even with a relatively standard program structure. Thus
1084	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1453	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1085	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1454	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1086		1455
1087	If you cannot run the fd in non-blocking mode (for example you should not	1456	If you cannot run the fd in non-blocking mode (for example you should
1088	play around with an Xlib connection), then you have to separately re-test	1457	not play around with an Xlib connection), then you have to separately
1089	whether a file descriptor is really ready with a known-to-be good interface	1458	re-test whether a file descriptor is really ready with a known-to-be good
1090	such as poll (fortunately in our Xlib example, Xlib already does this on	1459	interface such as poll (fortunately in our Xlib example, Xlib already
1091	its own, so its quite safe to use).	1460	does this on its own, so its quite safe to use). Some people additionally
		1461	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1462	indefinitely.
		1463
		1464	But really, best use non-blocking mode.
1092		1465
1093	=head3 The special problem of disappearing file descriptors	1466	=head3 The special problem of disappearing file descriptors
1094		1467
1095	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1468	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1096	descriptor (either by calling C<close> explicitly or by any other means,	1469	descriptor (either due to calling C<close> explicitly or any other means,
1097	such as C<dup>). The reason is that you register interest in some file	1470	such as C<dup2>). The reason is that you register interest in some file
1098	descriptor, but when it goes away, the operating system will silently drop	1471	descriptor, but when it goes away, the operating system will silently drop
1099	this interest. If another file descriptor with the same number then is	1472	this interest. If another file descriptor with the same number then is
1100	registered with libev, there is no efficient way to see that this is, in	1473	registered with libev, there is no efficient way to see that this is, in
1101	fact, a different file descriptor.	1474	fact, a different file descriptor.
1102		1475
…		…
1133	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1506	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1134	C<EVBACKEND_POLL>.	1507	C<EVBACKEND_POLL>.
1135		1508
1136	=head3 The special problem of SIGPIPE	1509	=head3 The special problem of SIGPIPE
1137		1510
1138	While not really specific to libev, it is easy to forget about SIGPIPE:	1511	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1139	when reading from a pipe whose other end has been closed, your program	1512	when writing to a pipe whose other end has been closed, your program gets
1140	gets send a SIGPIPE, which, by default, aborts your program. For most	1513	sent a SIGPIPE, which, by default, aborts your program. For most programs
1141	programs this is sensible behaviour, for daemons, this is usually	1514	this is sensible behaviour, for daemons, this is usually undesirable.
1142	undesirable.
1143		1515
1144	So when you encounter spurious, unexplained daemon exits, make sure you	1516	So when you encounter spurious, unexplained daemon exits, make sure you
1145	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1517	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1146	somewhere, as that would have given you a big clue).	1518	somewhere, as that would have given you a big clue).
1147		1519
…		…
1153	=item ev_io_init (ev_io *, callback, int fd, int events)	1525	=item ev_io_init (ev_io *, callback, int fd, int events)
1154		1526
1155	=item ev_io_set (ev_io *, int fd, int events)	1527	=item ev_io_set (ev_io *, int fd, int events)
1156		1528
1157	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1529	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1158	receive events for and events is either C<EV_READ>, C<EV_WRITE> or	1530	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1159	C<EV_READ | EV_WRITE> to receive the given events.	1531	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1160		1532
1161	=item int fd [read-only]	1533	=item int fd [read-only]
1162		1534
1163	The file descriptor being watched.	1535	The file descriptor being watched.
1164		1536
…		…
1173	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1545	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1174	readable, but only once. Since it is likely line-buffered, you could	1546	readable, but only once. Since it is likely line-buffered, you could
1175	attempt to read a whole line in the callback.	1547	attempt to read a whole line in the callback.
1176		1548
1177	static void	1549	static void
1178	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1550	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1179	{	1551	{
1180	ev_io_stop (loop, w);	1552	ev_io_stop (loop, w);
1181	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1553	.. read from stdin here (or from w->fd) and handle any I/O errors
1182	}	1554	}
1183		1555
1184	...	1556	...
1185	struct ev_loop *loop = ev_default_init (0);	1557	struct ev_loop *loop = ev_default_init (0);
1186	struct ev_io stdin_readable;	1558	ev_io stdin_readable;
1187	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1559	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1188	ev_io_start (loop, &stdin_readable);	1560	ev_io_start (loop, &stdin_readable);
1189	ev_loop (loop, 0);	1561	ev_loop (loop, 0);
1190		1562
1191		1563
…		…
1194	Timer watchers are simple relative timers that generate an event after a	1566	Timer watchers are simple relative timers that generate an event after a
1195	given time, and optionally repeating in regular intervals after that.	1567	given time, and optionally repeating in regular intervals after that.
1196		1568
1197	The timers are based on real time, that is, if you register an event that	1569	The timers are based on real time, that is, if you register an event that
1198	times out after an hour and you reset your system clock to January last	1570	times out after an hour and you reset your system clock to January last
1199	year, it will still time out after (roughly) and hour. "Roughly" because	1571	year, it will still time out after (roughly) one hour. "Roughly" because
1200	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1572	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1201	monotonic clock option helps a lot here).	1573	monotonic clock option helps a lot here).
		1574
		1575	The callback is guaranteed to be invoked only I<after> its timeout has
		1576	passed (not I<at>, so on systems with very low-resolution clocks this
		1577	might introduce a small delay). If multiple timers become ready during the
		1578	same loop iteration then the ones with earlier time-out values are invoked
		1579	before ones of the same priority with later time-out values (but this is
		1580	no longer true when a callback calls C<ev_loop> recursively).
		1581
		1582	=head3 Be smart about timeouts
		1583
		1584	Many real-world problems involve some kind of timeout, usually for error
		1585	recovery. A typical example is an HTTP request - if the other side hangs,
		1586	you want to raise some error after a while.
		1587
		1588	What follows are some ways to handle this problem, from obvious and
		1589	inefficient to smart and efficient.
		1590
		1591	In the following, a 60 second activity timeout is assumed - a timeout that
		1592	gets reset to 60 seconds each time there is activity (e.g. each time some
		1593	data or other life sign was received).
		1594
		1595	=over 4
		1596
		1597	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1598
		1599	This is the most obvious, but not the most simple way: In the beginning,
		1600	start the watcher:
		1601
		1602	ev_timer_init (timer, callback, 60., 0.);
		1603	ev_timer_start (loop, timer);
		1604
		1605	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1606	and start it again:
		1607
		1608	ev_timer_stop (loop, timer);
		1609	ev_timer_set (timer, 60., 0.);
		1610	ev_timer_start (loop, timer);
		1611
		1612	This is relatively simple to implement, but means that each time there is
		1613	some activity, libev will first have to remove the timer from its internal
		1614	data structure and then add it again. Libev tries to be fast, but it's
		1615	still not a constant-time operation.
		1616
		1617	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1618
		1619	This is the easiest way, and involves using C<ev_timer_again> instead of
		1620	C<ev_timer_start>.
		1621
		1622	To implement this, configure an C<ev_timer> with a C<repeat> value
		1623	of C<60> and then call C<ev_timer_again> at start and each time you
		1624	successfully read or write some data. If you go into an idle state where
		1625	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1626	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1627
		1628	That means you can ignore both the C<ev_timer_start> function and the
		1629	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1630	member and C<ev_timer_again>.
		1631
		1632	At start:
		1633
		1634	ev_init (timer, callback);
		1635	timer->repeat = 60.;
		1636	ev_timer_again (loop, timer);
		1637
		1638	Each time there is some activity:
		1639
		1640	ev_timer_again (loop, timer);
		1641
		1642	It is even possible to change the time-out on the fly, regardless of
		1643	whether the watcher is active or not:
		1644
		1645	timer->repeat = 30.;
		1646	ev_timer_again (loop, timer);
		1647
		1648	This is slightly more efficient then stopping/starting the timer each time
		1649	you want to modify its timeout value, as libev does not have to completely
		1650	remove and re-insert the timer from/into its internal data structure.
		1651
		1652	It is, however, even simpler than the "obvious" way to do it.
		1653
		1654	=item 3. Let the timer time out, but then re-arm it as required.
		1655
		1656	This method is more tricky, but usually most efficient: Most timeouts are
		1657	relatively long compared to the intervals between other activity - in
		1658	our example, within 60 seconds, there are usually many I/O events with
		1659	associated activity resets.
		1660
		1661	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1662	but remember the time of last activity, and check for a real timeout only
		1663	within the callback:
		1664
		1665	ev_tstamp last_activity; // time of last activity
		1666
		1667	static void
		1668	callback (EV_P_ ev_timer *w, int revents)
		1669	{
		1670	ev_tstamp now = ev_now (EV_A);
		1671	ev_tstamp timeout = last_activity + 60.;
		1672
		1673	// if last_activity + 60. is older than now, we did time out
		1674	if (timeout < now)
		1675	{
		1676	// timeout occured, take action
		1677	}
		1678	else
		1679	{
		1680	// callback was invoked, but there was some activity, re-arm
		1681	// the watcher to fire in last_activity + 60, which is
		1682	// guaranteed to be in the future, so "again" is positive:
		1683	w->repeat = timeout - now;
		1684	ev_timer_again (EV_A_ w);
		1685	}
		1686	}
		1687
		1688	To summarise the callback: first calculate the real timeout (defined
		1689	as "60 seconds after the last activity"), then check if that time has
		1690	been reached, which means something I<did>, in fact, time out. Otherwise
		1691	the callback was invoked too early (C<timeout> is in the future), so
		1692	re-schedule the timer to fire at that future time, to see if maybe we have
		1693	a timeout then.
		1694
		1695	Note how C<ev_timer_again> is used, taking advantage of the
		1696	C<ev_timer_again> optimisation when the timer is already running.
		1697
		1698	This scheme causes more callback invocations (about one every 60 seconds
		1699	minus half the average time between activity), but virtually no calls to
		1700	libev to change the timeout.
		1701
		1702	To start the timer, simply initialise the watcher and set C<last_activity>
		1703	to the current time (meaning we just have some activity :), then call the
		1704	callback, which will "do the right thing" and start the timer:
		1705
		1706	ev_init (timer, callback);
		1707	last_activity = ev_now (loop);
		1708	callback (loop, timer, EV_TIMEOUT);
		1709
		1710	And when there is some activity, simply store the current time in
		1711	C<last_activity>, no libev calls at all:
		1712
		1713	last_actiivty = ev_now (loop);
		1714
		1715	This technique is slightly more complex, but in most cases where the
		1716	time-out is unlikely to be triggered, much more efficient.
		1717
		1718	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1719	callback :) - just change the timeout and invoke the callback, which will
		1720	fix things for you.
		1721
		1722	=item 4. Wee, just use a double-linked list for your timeouts.
		1723
		1724	If there is not one request, but many thousands (millions...), all
		1725	employing some kind of timeout with the same timeout value, then one can
		1726	do even better:
		1727
		1728	When starting the timeout, calculate the timeout value and put the timeout
		1729	at the I<end> of the list.
		1730
		1731	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1732	the list is expected to fire (for example, using the technique #3).
		1733
		1734	When there is some activity, remove the timer from the list, recalculate
		1735	the timeout, append it to the end of the list again, and make sure to
		1736	update the C<ev_timer> if it was taken from the beginning of the list.
		1737
		1738	This way, one can manage an unlimited number of timeouts in O(1) time for
		1739	starting, stopping and updating the timers, at the expense of a major
		1740	complication, and having to use a constant timeout. The constant timeout
		1741	ensures that the list stays sorted.
		1742
		1743	=back
		1744
		1745	So which method the best?
		1746
		1747	Method #2 is a simple no-brain-required solution that is adequate in most
		1748	situations. Method #3 requires a bit more thinking, but handles many cases
		1749	better, and isn't very complicated either. In most case, choosing either
		1750	one is fine, with #3 being better in typical situations.
		1751
		1752	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1753	rather complicated, but extremely efficient, something that really pays
		1754	off after the first million or so of active timers, i.e. it's usually
		1755	overkill :)
		1756
		1757	=head3 The special problem of time updates
		1758
		1759	Establishing the current time is a costly operation (it usually takes at
		1760	least two system calls): EV therefore updates its idea of the current
		1761	time only before and after C<ev_loop> collects new events, which causes a
		1762	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1763	lots of events in one iteration.
1202		1764
1203	The relative timeouts are calculated relative to the C<ev_now ()>	1765	The relative timeouts are calculated relative to the C<ev_now ()>
1204	time. This is usually the right thing as this timestamp refers to the time	1766	time. This is usually the right thing as this timestamp refers to the time
1205	of the event triggering whatever timeout you are modifying/starting. If	1767	of the event triggering whatever timeout you are modifying/starting. If
1206	you suspect event processing to be delayed and you I<need> to base the timeout	1768	you suspect event processing to be delayed and you I<need> to base the
1207	on the current time, use something like this to adjust for this:	1769	timeout on the current time, use something like this to adjust for this:
1208		1770
1209	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1771	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1210		1772
1211	The callback is guaranteed to be invoked only after its timeout has passed,	1773	If the event loop is suspended for a long time, you can also force an
1212	but if multiple timers become ready during the same loop iteration then	1774	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1213	order of execution is undefined.	1775	()>.
		1776
		1777	=head3 The special problems of suspended animation
		1778
		1779	When you leave the server world it is quite customary to hit machines that
		1780	can suspend/hibernate - what happens to the clocks during such a suspend?
		1781
		1782	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1783	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1784	to run until the system is suspended, but they will not advance while the
		1785	system is suspended. That means, on resume, it will be as if the program
		1786	was frozen for a few seconds, but the suspend time will not be counted
		1787	towards C<ev_timer> when a monotonic clock source is used. The real time
		1788	clock advanced as expected, but if it is used as sole clocksource, then a
		1789	long suspend would be detected as a time jump by libev, and timers would
		1790	be adjusted accordingly.
		1791
		1792	I would not be surprised to see different behaviour in different between
		1793	operating systems, OS versions or even different hardware.
		1794
		1795	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1796	time jump in the monotonic clocks and the realtime clock. If the program
		1797	is suspended for a very long time, and monotonic clock sources are in use,
		1798	then you can expect C<ev_timer>s to expire as the full suspension time
		1799	will be counted towards the timers. When no monotonic clock source is in
		1800	use, then libev will again assume a timejump and adjust accordingly.
		1801
		1802	It might be beneficial for this latter case to call C<ev_suspend>
		1803	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1804	deterministic behaviour in this case (you can do nothing against
		1805	C<SIGSTOP>).
1214		1806
1215	=head3 Watcher-Specific Functions and Data Members	1807	=head3 Watcher-Specific Functions and Data Members
1216		1808
1217	=over 4	1809	=over 4
1218		1810
…		…
1242	If the timer is started but non-repeating, stop it (as if it timed out).	1834	If the timer is started but non-repeating, stop it (as if it timed out).
1243		1835
1244	If the timer is repeating, either start it if necessary (with the	1836	If the timer is repeating, either start it if necessary (with the
1245	C<repeat> value), or reset the running timer to the C<repeat> value.	1837	C<repeat> value), or reset the running timer to the C<repeat> value.
1246		1838
1247	This sounds a bit complicated, but here is a useful and typical	1839	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1248	example: Imagine you have a TCP connection and you want a so-called idle	1840	usage example.
1249	timeout, that is, you want to be called when there have been, say, 60
1250	seconds of inactivity on the socket. The easiest way to do this is to
1251	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1252	C<ev_timer_again> each time you successfully read or write some data. If
1253	you go into an idle state where you do not expect data to travel on the
1254	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1255	automatically restart it if need be.
1256		1841
1257	That means you can ignore the C<after> value and C<ev_timer_start>	1842	=item ev_timer_remaining (loop, ev_timer *)
1258	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1259		1843
1260	ev_timer_init (timer, callback, 0., 5.);	1844	Returns the remaining time until a timer fires. If the timer is active,
1261	ev_timer_again (loop, timer);	1845	then this time is relative to the current event loop time, otherwise it's
1262	...	1846	the timeout value currently configured.
1263	timer->again = 17.;
1264	ev_timer_again (loop, timer);
1265	...
1266	timer->again = 10.;
1267	ev_timer_again (loop, timer);
1268		1847
1269	This is more slightly efficient then stopping/starting the timer each time	1848	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1270	you want to modify its timeout value.	1849	C<5>. When the timer is started and one second passes, C<ev_timer_remain>
		1850	will return C<4>. When the timer expires and is restarted, it will return
		1851	roughly C<7> (likely slightly less as callback invocation takes some time,
		1852	too), and so on.
1271		1853
1272	=item ev_tstamp repeat [read-write]	1854	=item ev_tstamp repeat [read-write]
1273		1855
1274	The current C<repeat> value. Will be used each time the watcher times out	1856	The current C<repeat> value. Will be used each time the watcher times out
1275	or C<ev_timer_again> is called and determines the next timeout (if any),	1857	or C<ev_timer_again> is called, and determines the next timeout (if any),
1276	which is also when any modifications are taken into account.	1858	which is also when any modifications are taken into account.
1277		1859
1278	=back	1860	=back
1279		1861
1280	=head3 Examples	1862	=head3 Examples
1281		1863
1282	Example: Create a timer that fires after 60 seconds.	1864	Example: Create a timer that fires after 60 seconds.
1283		1865
1284	static void	1866	static void
1285	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1867	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1286	{	1868	{
1287	.. one minute over, w is actually stopped right here	1869	.. one minute over, w is actually stopped right here
1288	}	1870	}
1289		1871
1290	struct ev_timer mytimer;	1872	ev_timer mytimer;
1291	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1873	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1292	ev_timer_start (loop, &mytimer);	1874	ev_timer_start (loop, &mytimer);
1293		1875
1294	Example: Create a timeout timer that times out after 10 seconds of	1876	Example: Create a timeout timer that times out after 10 seconds of
1295	inactivity.	1877	inactivity.
1296		1878
1297	static void	1879	static void
1298	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1880	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1299	{	1881	{
1300	.. ten seconds without any activity	1882	.. ten seconds without any activity
1301	}	1883	}
1302		1884
1303	struct ev_timer mytimer;	1885	ev_timer mytimer;
1304	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1886	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1305	ev_timer_again (&mytimer); /* start timer */	1887	ev_timer_again (&mytimer); /* start timer */
1306	ev_loop (loop, 0);	1888	ev_loop (loop, 0);
1307		1889
1308	// and in some piece of code that gets executed on any "activity":	1890	// and in some piece of code that gets executed on any "activity":
…		…
1313	=head2 C<ev_periodic> - to cron or not to cron?	1895	=head2 C<ev_periodic> - to cron or not to cron?
1314		1896
1315	Periodic watchers are also timers of a kind, but they are very versatile	1897	Periodic watchers are also timers of a kind, but they are very versatile
1316	(and unfortunately a bit complex).	1898	(and unfortunately a bit complex).
1317		1899
1318	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1900	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1319	but on wall clock time (absolute time). You can tell a periodic watcher	1901	relative time, the physical time that passes) but on wall clock time
1320	to trigger after some specific point in time. For example, if you tell a	1902	(absolute time, the thing you can read on your calender or clock). The
1321	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	1903	difference is that wall clock time can run faster or slower than real
1322	+ 10.>, that is, an absolute time not a delay) and then reset your system	1904	time, and time jumps are not uncommon (e.g. when you adjust your
1323	clock to January of the previous year, then it will take more than year	1905	wrist-watch).
1324	to trigger the event (unlike an C<ev_timer>, which would still trigger
1325	roughly 10 seconds later as it uses a relative timeout).
1326		1906
		1907	You can tell a periodic watcher to trigger after some specific point
		1908	in time: for example, if you tell a periodic watcher to trigger "in 10
		1909	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1910	not a delay) and then reset your system clock to January of the previous
		1911	year, then it will take a year or more to trigger the event (unlike an
		1912	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1913	it, as it uses a relative timeout).
		1914
1327	C<ev_periodic>s can also be used to implement vastly more complex timers,	1915	C<ev_periodic> watchers can also be used to implement vastly more complex
1328	such as triggering an event on each "midnight, local time", or other	1916	timers, such as triggering an event on each "midnight, local time", or
1329	complicated, rules.	1917	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1918	those cannot react to time jumps.
1330		1919
1331	As with timers, the callback is guaranteed to be invoked only when the	1920	As with timers, the callback is guaranteed to be invoked only when the
1332	time (C<at>) has passed, but if multiple periodic timers become ready	1921	point in time where it is supposed to trigger has passed. If multiple
1333	during the same loop iteration then order of execution is undefined.	1922	timers become ready during the same loop iteration then the ones with
		1923	earlier time-out values are invoked before ones with later time-out values
		1924	(but this is no longer true when a callback calls C<ev_loop> recursively).
1334		1925
1335	=head3 Watcher-Specific Functions and Data Members	1926	=head3 Watcher-Specific Functions and Data Members
1336		1927
1337	=over 4	1928	=over 4
1338		1929
1339	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1930	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1340		1931
1341	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1932	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1342		1933
1343	Lots of arguments, lets sort it out... There are basically three modes of	1934	Lots of arguments, let's sort it out... There are basically three modes of
1344	operation, and we will explain them from simplest to complex:	1935	operation, and we will explain them from simplest to most complex:
1345		1936
1346	=over 4	1937	=over 4
1347		1938
1348	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1939	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1349		1940
1350	In this configuration the watcher triggers an event after the wall clock	1941	In this configuration the watcher triggers an event after the wall clock
1351	time C<at> has passed and doesn't repeat. It will not adjust when a time	1942	time C<offset> has passed. It will not repeat and will not adjust when a
1352	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1943	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1353	run when the system time reaches or surpasses this time.	1944	will be stopped and invoked when the system clock reaches or surpasses
		1945	this point in time.
1354		1946
1355	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1947	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1356		1948
1357	In this mode the watcher will always be scheduled to time out at the next	1949	In this mode the watcher will always be scheduled to time out at the next
1358	C<at + N * interval> time (for some integer N, which can also be negative)	1950	C<offset + N * interval> time (for some integer N, which can also be
1359	and then repeat, regardless of any time jumps.	1951	negative) and then repeat, regardless of any time jumps. The C<offset>
		1952	argument is merely an offset into the C<interval> periods.
1360		1953
1361	This can be used to create timers that do not drift with respect to system	1954	This can be used to create timers that do not drift with respect to the
1362	time, for example, here is a C<ev_periodic> that triggers each hour, on	1955	system clock, for example, here is an C<ev_periodic> that triggers each
1363	the hour:	1956	hour, on the hour (with respect to UTC):
1364		1957
1365	ev_periodic_set (&periodic, 0., 3600., 0);	1958	ev_periodic_set (&periodic, 0., 3600., 0);
1366		1959
1367	This doesn't mean there will always be 3600 seconds in between triggers,	1960	This doesn't mean there will always be 3600 seconds in between triggers,
1368	but only that the callback will be called when the system time shows a	1961	but only that the callback will be called when the system time shows a
1369	full hour (UTC), or more correctly, when the system time is evenly divisible	1962	full hour (UTC), or more correctly, when the system time is evenly divisible
1370	by 3600.	1963	by 3600.
1371		1964
1372	Another way to think about it (for the mathematically inclined) is that	1965	Another way to think about it (for the mathematically inclined) is that
1373	C<ev_periodic> will try to run the callback in this mode at the next possible	1966	C<ev_periodic> will try to run the callback in this mode at the next possible
1374	time where C<time = at (mod interval)>, regardless of any time jumps.	1967	time where C<time = offset (mod interval)>, regardless of any time jumps.
1375		1968
1376	For numerical stability it is preferable that the C<at> value is near	1969	For numerical stability it is preferable that the C<offset> value is near
1377	C<ev_now ()> (the current time), but there is no range requirement for	1970	C<ev_now ()> (the current time), but there is no range requirement for
1378	this value, and in fact is often specified as zero.	1971	this value, and in fact is often specified as zero.
1379		1972
1380	Note also that there is an upper limit to how often a timer can fire (CPU	1973	Note also that there is an upper limit to how often a timer can fire (CPU
1381	speed for example), so if C<interval> is very small then timing stability	1974	speed for example), so if C<interval> is very small then timing stability
1382	will of course deteriorate. Libev itself tries to be exact to be about one	1975	will of course deteriorate. Libev itself tries to be exact to be about one
1383	millisecond (if the OS supports it and the machine is fast enough).	1976	millisecond (if the OS supports it and the machine is fast enough).
1384		1977
1385	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1978	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1386		1979
1387	In this mode the values for C<interval> and C<at> are both being	1980	In this mode the values for C<interval> and C<offset> are both being
1388	ignored. Instead, each time the periodic watcher gets scheduled, the	1981	ignored. Instead, each time the periodic watcher gets scheduled, the
1389	reschedule callback will be called with the watcher as first, and the	1982	reschedule callback will be called with the watcher as first, and the
1390	current time as second argument.	1983	current time as second argument.
1391		1984
1392	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1985	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1393	ever, or make ANY event loop modifications whatsoever>.	1986	or make ANY other event loop modifications whatsoever, unless explicitly
		1987	allowed by documentation here>.
1394		1988
1395	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1989	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1396	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	1990	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1397	only event loop modification you are allowed to do).	1991	only event loop modification you are allowed to do).
1398		1992
1399	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1993	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1400	*w, ev_tstamp now)>, e.g.:	1994	*w, ev_tstamp now)>, e.g.:
1401		1995
		1996	static ev_tstamp
1402	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1997	my_rescheduler (ev_periodic *w, ev_tstamp now)
1403	{	1998	{
1404	return now + 60.;	1999	return now + 60.;
1405	}	2000	}
1406		2001
1407	It must return the next time to trigger, based on the passed time value	2002	It must return the next time to trigger, based on the passed time value
…		…
1427	a different time than the last time it was called (e.g. in a crond like	2022	a different time than the last time it was called (e.g. in a crond like
1428	program when the crontabs have changed).	2023	program when the crontabs have changed).
1429		2024
1430	=item ev_tstamp ev_periodic_at (ev_periodic *)	2025	=item ev_tstamp ev_periodic_at (ev_periodic *)
1431		2026
1432	When active, returns the absolute time that the watcher is supposed to	2027	When active, returns the absolute time that the watcher is supposed
1433	trigger next.	2028	to trigger next. This is not the same as the C<offset> argument to
		2029	C<ev_periodic_set>, but indeed works even in interval and manual
		2030	rescheduling modes.
1434		2031
1435	=item ev_tstamp offset [read-write]	2032	=item ev_tstamp offset [read-write]
1436		2033
1437	When repeating, this contains the offset value, otherwise this is the	2034	When repeating, this contains the offset value, otherwise this is the
1438	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2035	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2036	although libev might modify this value for better numerical stability).
1439		2037
1440	Can be modified any time, but changes only take effect when the periodic	2038	Can be modified any time, but changes only take effect when the periodic
1441	timer fires or C<ev_periodic_again> is being called.	2039	timer fires or C<ev_periodic_again> is being called.
1442		2040
1443	=item ev_tstamp interval [read-write]	2041	=item ev_tstamp interval [read-write]
1444		2042
1445	The current interval value. Can be modified any time, but changes only	2043	The current interval value. Can be modified any time, but changes only
1446	take effect when the periodic timer fires or C<ev_periodic_again> is being	2044	take effect when the periodic timer fires or C<ev_periodic_again> is being
1447	called.	2045	called.
1448		2046
1449	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2047	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1450		2048
1451	The current reschedule callback, or C<0>, if this functionality is	2049	The current reschedule callback, or C<0>, if this functionality is
1452	switched off. Can be changed any time, but changes only take effect when	2050	switched off. Can be changed any time, but changes only take effect when
1453	the periodic timer fires or C<ev_periodic_again> is being called.	2051	the periodic timer fires or C<ev_periodic_again> is being called.
1454		2052
1455	=back	2053	=back
1456		2054
1457	=head3 Examples	2055	=head3 Examples
1458		2056
1459	Example: Call a callback every hour, or, more precisely, whenever the	2057	Example: Call a callback every hour, or, more precisely, whenever the
1460	system clock is divisible by 3600. The callback invocation times have	2058	system time is divisible by 3600. The callback invocation times have
1461	potentially a lot of jitter, but good long-term stability.	2059	potentially a lot of jitter, but good long-term stability.
1462		2060
1463	static void	2061	static void
1464	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2062	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1465	{	2063	{
1466	... its now a full hour (UTC, or TAI or whatever your clock follows)	2064	... its now a full hour (UTC, or TAI or whatever your clock follows)
1467	}	2065	}
1468		2066
1469	struct ev_periodic hourly_tick;	2067	ev_periodic hourly_tick;
1470	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2068	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1471	ev_periodic_start (loop, &hourly_tick);	2069	ev_periodic_start (loop, &hourly_tick);
1472		2070
1473	Example: The same as above, but use a reschedule callback to do it:	2071	Example: The same as above, but use a reschedule callback to do it:
1474		2072
1475	#include <math.h>	2073	#include <math.h>
1476		2074
1477	static ev_tstamp	2075	static ev_tstamp
1478	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2076	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1479	{	2077	{
1480	return fmod (now, 3600.) + 3600.;	2078	return now + (3600. - fmod (now, 3600.));
1481	}	2079	}
1482		2080
1483	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2081	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1484		2082
1485	Example: Call a callback every hour, starting now:	2083	Example: Call a callback every hour, starting now:
1486		2084
1487	struct ev_periodic hourly_tick;	2085	ev_periodic hourly_tick;
1488	ev_periodic_init (&hourly_tick, clock_cb,	2086	ev_periodic_init (&hourly_tick, clock_cb,
1489	fmod (ev_now (loop), 3600.), 3600., 0);	2087	fmod (ev_now (loop), 3600.), 3600., 0);
1490	ev_periodic_start (loop, &hourly_tick);	2088	ev_periodic_start (loop, &hourly_tick);
1491		2089
1492		2090
…		…
1495	Signal watchers will trigger an event when the process receives a specific	2093	Signal watchers will trigger an event when the process receives a specific
1496	signal one or more times. Even though signals are very asynchronous, libev	2094	signal one or more times. Even though signals are very asynchronous, libev
1497	will try it's best to deliver signals synchronously, i.e. as part of the	2095	will try it's best to deliver signals synchronously, i.e. as part of the
1498	normal event processing, like any other event.	2096	normal event processing, like any other event.
1499		2097
		2098	If you want signals to be delivered truly asynchronously, just use
		2099	C<sigaction> as you would do without libev and forget about sharing
		2100	the signal. You can even use C<ev_async> from a signal handler to
		2101	synchronously wake up an event loop.
		2102
1500	You can configure as many watchers as you like per signal. Only when the	2103	You can configure as many watchers as you like for the same signal, but
		2104	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2105	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2106	C<SIGINT> in both the default loop and another loop at the same time. At
		2107	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2108
1501	first watcher gets started will libev actually register a signal watcher	2109	When the first watcher gets started will libev actually register something
1502	with the kernel (thus it coexists with your own signal handlers as long	2110	with the kernel (thus it coexists with your own signal handlers as long as
1503	as you don't register any with libev). Similarly, when the last signal	2111	you don't register any with libev for the same signal).
1504	watcher for a signal is stopped libev will reset the signal handler to	2112
1505	SIG_DFL (regardless of what it was set to before).	2113	Both the signal mask state (C<sigprocmask>) and the signal handler state
		2114	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2115	sotpping it again), that is, libev might or might not block the signal,
		2116	and might or might not set or restore the installed signal handler.
1506		2117
1507	If possible and supported, libev will install its handlers with	2118	If possible and supported, libev will install its handlers with
1508	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2119	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1509	interrupted. If you have a problem with system calls getting interrupted by	2120	not be unduly interrupted. If you have a problem with system calls getting
1510	signals you can block all signals in an C<ev_check> watcher and unblock	2121	interrupted by signals you can block all signals in an C<ev_check> watcher
1511	them in an C<ev_prepare> watcher.	2122	and unblock them in an C<ev_prepare> watcher.
1512		2123
1513	=head3 Watcher-Specific Functions and Data Members	2124	=head3 Watcher-Specific Functions and Data Members
1514		2125
1515	=over 4	2126	=over 4
1516		2127
…		…
1527		2138
1528	=back	2139	=back
1529		2140
1530	=head3 Examples	2141	=head3 Examples
1531		2142
1532	Example: Try to exit cleanly on SIGINT and SIGTERM.	2143	Example: Try to exit cleanly on SIGINT.
1533		2144
1534	static void	2145	static void
1535	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2146	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1536	{	2147	{
1537	ev_unloop (loop, EVUNLOOP_ALL);	2148	ev_unloop (loop, EVUNLOOP_ALL);
1538	}	2149	}
1539		2150
1540	struct ev_signal signal_watcher;	2151	ev_signal signal_watcher;
1541	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2152	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1542	ev_signal_start (loop, &sigint_cb);	2153	ev_signal_start (loop, &signal_watcher);
1543		2154
1544		2155
1545	=head2 C<ev_child> - watch out for process status changes	2156	=head2 C<ev_child> - watch out for process status changes
1546		2157
1547	Child watchers trigger when your process receives a SIGCHLD in response to	2158	Child watchers trigger when your process receives a SIGCHLD in response to
1548	some child status changes (most typically when a child of yours dies). It	2159	some child status changes (most typically when a child of yours dies or
1549	is permissible to install a child watcher I<after> the child has been	2160	exits). It is permissible to install a child watcher I<after> the child
1550	forked (which implies it might have already exited), as long as the event	2161	has been forked (which implies it might have already exited), as long
1551	loop isn't entered (or is continued from a watcher).	2162	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2163	forking and then immediately registering a watcher for the child is fine,
		2164	but forking and registering a watcher a few event loop iterations later or
		2165	in the next callback invocation is not.
1552		2166
1553	Only the default event loop is capable of handling signals, and therefore	2167	Only the default event loop is capable of handling signals, and therefore
1554	you can only register child watchers in the default event loop.	2168	you can only register child watchers in the default event loop.
1555		2169
		2170	Due to some design glitches inside libev, child watchers will always be
		2171	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2172	libev)
		2173
1556	=head3 Process Interaction	2174	=head3 Process Interaction
1557		2175
1558	Libev grabs C<SIGCHLD> as soon as the default event loop is	2176	Libev grabs C<SIGCHLD> as soon as the default event loop is
1559	initialised. This is necessary to guarantee proper behaviour even if	2177	initialised. This is necessary to guarantee proper behaviour even if the
1560	the first child watcher is started after the child exits. The occurrence	2178	first child watcher is started after the child exits. The occurrence
1561	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2179	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1562	synchronously as part of the event loop processing. Libev always reaps all	2180	synchronously as part of the event loop processing. Libev always reaps all
1563	children, even ones not watched.	2181	children, even ones not watched.
1564		2182
1565	=head3 Overriding the Built-In Processing	2183	=head3 Overriding the Built-In Processing
…		…
1569	handler, you can override it easily by installing your own handler for	2187	handler, you can override it easily by installing your own handler for
1570	C<SIGCHLD> after initialising the default loop, and making sure the	2188	C<SIGCHLD> after initialising the default loop, and making sure the
1571	default loop never gets destroyed. You are encouraged, however, to use an	2189	default loop never gets destroyed. You are encouraged, however, to use an
1572	event-based approach to child reaping and thus use libev's support for	2190	event-based approach to child reaping and thus use libev's support for
1573	that, so other libev users can use C<ev_child> watchers freely.	2191	that, so other libev users can use C<ev_child> watchers freely.
		2192
		2193	=head3 Stopping the Child Watcher
		2194
		2195	Currently, the child watcher never gets stopped, even when the
		2196	child terminates, so normally one needs to stop the watcher in the
		2197	callback. Future versions of libev might stop the watcher automatically
		2198	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2199	problem).
1574		2200
1575	=head3 Watcher-Specific Functions and Data Members	2201	=head3 Watcher-Specific Functions and Data Members
1576		2202
1577	=over 4	2203	=over 4
1578		2204
…		…
1610	its completion.	2236	its completion.
1611		2237
1612	ev_child cw;	2238	ev_child cw;
1613		2239
1614	static void	2240	static void
1615	child_cb (EV_P_ struct ev_child *w, int revents)	2241	child_cb (EV_P_ ev_child *w, int revents)
1616	{	2242	{
1617	ev_child_stop (EV_A_ w);	2243	ev_child_stop (EV_A_ w);
1618	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2244	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1619	}	2245	}
1620		2246
…		…
1635		2261
1636		2262
1637	=head2 C<ev_stat> - did the file attributes just change?	2263	=head2 C<ev_stat> - did the file attributes just change?
1638		2264
1639	This watches a file system path for attribute changes. That is, it calls	2265	This watches a file system path for attribute changes. That is, it calls
1640	C<stat> regularly (or when the OS says it changed) and sees if it changed	2266	C<stat> on that path in regular intervals (or when the OS says it changed)
1641	compared to the last time, invoking the callback if it did.	2267	and sees if it changed compared to the last time, invoking the callback if
		2268	it did.
1642		2269
1643	The path does not need to exist: changing from "path exists" to "path does	2270	The path does not need to exist: changing from "path exists" to "path does
1644	not exist" is a status change like any other. The condition "path does	2271	not exist" is a status change like any other. The condition "path does not
1645	not exist" is signified by the C<st_nlink> field being zero (which is	2272	exist" (or more correctly "path cannot be stat'ed") is signified by the
1646	otherwise always forced to be at least one) and all the other fields of	2273	C<st_nlink> field being zero (which is otherwise always forced to be at
1647	the stat buffer having unspecified contents.	2274	least one) and all the other fields of the stat buffer having unspecified
		2275	contents.
1648		2276
1649	The path I<should> be absolute and I<must not> end in a slash. If it is	2277	The path I<must not> end in a slash or contain special components such as
		2278	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1650	relative and your working directory changes, the behaviour is undefined.	2279	your working directory changes, then the behaviour is undefined.
1651		2280
1652	Since there is no standard to do this, the portable implementation simply	2281	Since there is no portable change notification interface available, the
1653	calls C<stat (2)> regularly on the path to see if it changed somehow. You	2282	portable implementation simply calls C<stat(2)> regularly on the path
1654	can specify a recommended polling interval for this case. If you specify	2283	to see if it changed somehow. You can specify a recommended polling
1655	a polling interval of C<0> (highly recommended!) then a I<suitable,	2284	interval for this case. If you specify a polling interval of C<0> (highly
1656	unspecified default> value will be used (which you can expect to be around	2285	recommended!) then a I<suitable, unspecified default> value will be used
1657	five seconds, although this might change dynamically). Libev will also	2286	(which you can expect to be around five seconds, although this might
1658	impose a minimum interval which is currently around C<0.1>, but thats	2287	change dynamically). Libev will also impose a minimum interval which is
1659	usually overkill.	2288	currently around C<0.1>, but that's usually overkill.
1660		2289
1661	This watcher type is not meant for massive numbers of stat watchers,	2290	This watcher type is not meant for massive numbers of stat watchers,
1662	as even with OS-supported change notifications, this can be	2291	as even with OS-supported change notifications, this can be
1663	resource-intensive.	2292	resource-intensive.
1664		2293
1665	At the time of this writing, only the Linux inotify interface is	2294	At the time of this writing, the only OS-specific interface implemented
1666	implemented (implementing kqueue support is left as an exercise for the	2295	is the Linux inotify interface (implementing kqueue support is left as an
1667	reader, note, however, that the author sees no way of implementing ev_stat	2296	exercise for the reader. Note, however, that the author sees no way of
1668	semantics with kqueue). Inotify will be used to give hints only and should	2297	implementing C<ev_stat> semantics with kqueue, except as a hint).
1669	not change the semantics of C<ev_stat> watchers, which means that libev
1670	sometimes needs to fall back to regular polling again even with inotify,
1671	but changes are usually detected immediately, and if the file exists there
1672	will be no polling.
1673		2298
1674	=head3 ABI Issues (Largefile Support)	2299	=head3 ABI Issues (Largefile Support)
1675		2300
1676	Libev by default (unless the user overrides this) uses the default	2301	Libev by default (unless the user overrides this) uses the default
1677	compilation environment, which means that on systems with large file	2302	compilation environment, which means that on systems with large file
1678	support disabled by default, you get the 32 bit version of the stat	2303	support disabled by default, you get the 32 bit version of the stat
1679	structure. When using the library from programs that change the ABI to	2304	structure. When using the library from programs that change the ABI to
1680	use 64 bit file offsets the programs will fail. In that case you have to	2305	use 64 bit file offsets the programs will fail. In that case you have to
1681	compile libev with the same flags to get binary compatibility. This is	2306	compile libev with the same flags to get binary compatibility. This is
1682	obviously the case with any flags that change the ABI, but the problem is	2307	obviously the case with any flags that change the ABI, but the problem is
1683	most noticeably disabled with ev_stat and large file support.	2308	most noticeably displayed with ev_stat and large file support.
1684		2309
1685	The solution for this is to lobby your distribution maker to make large	2310	The solution for this is to lobby your distribution maker to make large
1686	file interfaces available by default (as e.g. FreeBSD does) and not	2311	file interfaces available by default (as e.g. FreeBSD does) and not
1687	optional. Libev cannot simply switch on large file support because it has	2312	optional. Libev cannot simply switch on large file support because it has
1688	to exchange stat structures with application programs compiled using the	2313	to exchange stat structures with application programs compiled using the
1689	default compilation environment.	2314	default compilation environment.
1690		2315
1691	=head3 Inotify	2316	=head3 Inotify and Kqueue
1692		2317
1693	When C<inotify (7)> support has been compiled into libev (generally only	2318	When C<inotify (7)> support has been compiled into libev and present at
1694	available on Linux) and present at runtime, it will be used to speed up	2319	runtime, it will be used to speed up change detection where possible. The
1695	change detection where possible. The inotify descriptor will be created lazily	2320	inotify descriptor will be created lazily when the first C<ev_stat>
1696	when the first C<ev_stat> watcher is being started.	2321	watcher is being started.
1697		2322
1698	Inotify presence does not change the semantics of C<ev_stat> watchers	2323	Inotify presence does not change the semantics of C<ev_stat> watchers
1699	except that changes might be detected earlier, and in some cases, to avoid	2324	except that changes might be detected earlier, and in some cases, to avoid
1700	making regular C<stat> calls. Even in the presence of inotify support	2325	making regular C<stat> calls. Even in the presence of inotify support
1701	there are many cases where libev has to resort to regular C<stat> polling.	2326	there are many cases where libev has to resort to regular C<stat> polling,
		2327	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2328	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2329	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2330	xfs are fully working) libev usually gets away without polling.
1702		2331
1703	(There is no support for kqueue, as apparently it cannot be used to	2332	There is no support for kqueue, as apparently it cannot be used to
1704	implement this functionality, due to the requirement of having a file	2333	implement this functionality, due to the requirement of having a file
1705	descriptor open on the object at all times).	2334	descriptor open on the object at all times, and detecting renames, unlinks
		2335	etc. is difficult.
		2336
		2337	=head3 C<stat ()> is a synchronous operation
		2338
		2339	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2340	the process. The exception are C<ev_stat> watchers - those call C<stat
		2341	()>, which is a synchronous operation.
		2342
		2343	For local paths, this usually doesn't matter: unless the system is very
		2344	busy or the intervals between stat's are large, a stat call will be fast,
		2345	as the path data is usually in memory already (except when starting the
		2346	watcher).
		2347
		2348	For networked file systems, calling C<stat ()> can block an indefinite
		2349	time due to network issues, and even under good conditions, a stat call
		2350	often takes multiple milliseconds.
		2351
		2352	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2353	paths, although this is fully supported by libev.
1706		2354
1707	=head3 The special problem of stat time resolution	2355	=head3 The special problem of stat time resolution
1708		2356
1709	The C<stat ()> system call only supports full-second resolution portably, and	2357	The C<stat ()> system call only supports full-second resolution portably,
1710	even on systems where the resolution is higher, many file systems still	2358	and even on systems where the resolution is higher, most file systems
1711	only support whole seconds.	2359	still only support whole seconds.
1712		2360
1713	That means that, if the time is the only thing that changes, you can	2361	That means that, if the time is the only thing that changes, you can
1714	easily miss updates: on the first update, C<ev_stat> detects a change and	2362	easily miss updates: on the first update, C<ev_stat> detects a change and
1715	calls your callback, which does something. When there is another update	2363	calls your callback, which does something. When there is another update
1716	within the same second, C<ev_stat> will be unable to detect it as the stat	2364	within the same second, C<ev_stat> will be unable to detect unless the
1717	data does not change.	2365	stat data does change in other ways (e.g. file size).
1718		2366
1719	The solution to this is to delay acting on a change for slightly more	2367	The solution to this is to delay acting on a change for slightly more
1720	than a second (or till slightly after the next full second boundary), using	2368	than a second (or till slightly after the next full second boundary), using
1721	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2369	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1722	ev_timer_again (loop, w)>).	2370	ev_timer_again (loop, w)>).
…		…
1742	C<path>. The C<interval> is a hint on how quickly a change is expected to	2390	C<path>. The C<interval> is a hint on how quickly a change is expected to
1743	be detected and should normally be specified as C<0> to let libev choose	2391	be detected and should normally be specified as C<0> to let libev choose
1744	a suitable value. The memory pointed to by C<path> must point to the same	2392	a suitable value. The memory pointed to by C<path> must point to the same
1745	path for as long as the watcher is active.	2393	path for as long as the watcher is active.
1746		2394
1747	The callback will receive C<EV_STAT> when a change was detected, relative	2395	The callback will receive an C<EV_STAT> event when a change was detected,
1748	to the attributes at the time the watcher was started (or the last change	2396	relative to the attributes at the time the watcher was started (or the
1749	was detected).	2397	last change was detected).
1750		2398
1751	=item ev_stat_stat (loop, ev_stat *)	2399	=item ev_stat_stat (loop, ev_stat *)
1752		2400
1753	Updates the stat buffer immediately with new values. If you change the	2401	Updates the stat buffer immediately with new values. If you change the
1754	watched path in your callback, you could call this function to avoid	2402	watched path in your callback, you could call this function to avoid
…		…
1837		2485
1838		2486
1839	=head2 C<ev_idle> - when you've got nothing better to do...	2487	=head2 C<ev_idle> - when you've got nothing better to do...
1840		2488
1841	Idle watchers trigger events when no other events of the same or higher	2489	Idle watchers trigger events when no other events of the same or higher
1842	priority are pending (prepare, check and other idle watchers do not	2490	priority are pending (prepare, check and other idle watchers do not count
1843	count).	2491	as receiving "events").
1844		2492
1845	That is, as long as your process is busy handling sockets or timeouts	2493	That is, as long as your process is busy handling sockets or timeouts
1846	(or even signals, imagine) of the same or higher priority it will not be	2494	(or even signals, imagine) of the same or higher priority it will not be
1847	triggered. But when your process is idle (or only lower-priority watchers	2495	triggered. But when your process is idle (or only lower-priority watchers
1848	are pending), the idle watchers are being called once per event loop	2496	are pending), the idle watchers are being called once per event loop
…		…
1859		2507
1860	=head3 Watcher-Specific Functions and Data Members	2508	=head3 Watcher-Specific Functions and Data Members
1861		2509
1862	=over 4	2510	=over 4
1863		2511
1864	=item ev_idle_init (ev_signal *, callback)	2512	=item ev_idle_init (ev_idle *, callback)
1865		2513
1866	Initialises and configures the idle watcher - it has no parameters of any	2514	Initialises and configures the idle watcher - it has no parameters of any
1867	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2515	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1868	believe me.	2516	believe me.
1869		2517
…		…
1873		2521
1874	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2522	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1875	callback, free it. Also, use no error checking, as usual.	2523	callback, free it. Also, use no error checking, as usual.
1876		2524
1877	static void	2525	static void
1878	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2526	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1879	{	2527	{
1880	free (w);	2528	free (w);
1881	// now do something you wanted to do when the program has	2529	// now do something you wanted to do when the program has
1882	// no longer anything immediate to do.	2530	// no longer anything immediate to do.
1883	}	2531	}
1884		2532
1885	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2533	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1886	ev_idle_init (idle_watcher, idle_cb);	2534	ev_idle_init (idle_watcher, idle_cb);
1887	ev_idle_start (loop, idle_cb);	2535	ev_idle_start (loop, idle_watcher);
1888		2536
1889		2537
1890	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2538	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1891		2539
1892	Prepare and check watchers are usually (but not always) used in tandem:	2540	Prepare and check watchers are usually (but not always) used in pairs:
1893	prepare watchers get invoked before the process blocks and check watchers	2541	prepare watchers get invoked before the process blocks and check watchers
1894	afterwards.	2542	afterwards.
1895		2543
1896	You I<must not> call C<ev_loop> or similar functions that enter	2544	You I<must not> call C<ev_loop> or similar functions that enter
1897	the current event loop from either C<ev_prepare> or C<ev_check>	2545	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1900	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2548	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1901	C<ev_check> so if you have one watcher of each kind they will always be	2549	C<ev_check> so if you have one watcher of each kind they will always be
1902	called in pairs bracketing the blocking call.	2550	called in pairs bracketing the blocking call.
1903		2551
1904	Their main purpose is to integrate other event mechanisms into libev and	2552	Their main purpose is to integrate other event mechanisms into libev and
1905	their use is somewhat advanced. This could be used, for example, to track	2553	their use is somewhat advanced. They could be used, for example, to track
1906	variable changes, implement your own watchers, integrate net-snmp or a	2554	variable changes, implement your own watchers, integrate net-snmp or a
1907	coroutine library and lots more. They are also occasionally useful if	2555	coroutine library and lots more. They are also occasionally useful if
1908	you cache some data and want to flush it before blocking (for example,	2556	you cache some data and want to flush it before blocking (for example,
1909	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2557	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1910	watcher).	2558	watcher).
1911		2559
1912	This is done by examining in each prepare call which file descriptors need	2560	This is done by examining in each prepare call which file descriptors
1913	to be watched by the other library, registering C<ev_io> watchers for	2561	need to be watched by the other library, registering C<ev_io> watchers
1914	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2562	for them and starting an C<ev_timer> watcher for any timeouts (many
1915	provide just this functionality). Then, in the check watcher you check for	2563	libraries provide exactly this functionality). Then, in the check watcher,
1916	any events that occurred (by checking the pending status of all watchers	2564	you check for any events that occurred (by checking the pending status
1917	and stopping them) and call back into the library. The I/O and timer	2565	of all watchers and stopping them) and call back into the library. The
1918	callbacks will never actually be called (but must be valid nevertheless,	2566	I/O and timer callbacks will never actually be called (but must be valid
1919	because you never know, you know?).	2567	nevertheless, because you never know, you know?).
1920		2568
1921	As another example, the Perl Coro module uses these hooks to integrate	2569	As another example, the Perl Coro module uses these hooks to integrate
1922	coroutines into libev programs, by yielding to other active coroutines	2570	coroutines into libev programs, by yielding to other active coroutines
1923	during each prepare and only letting the process block if no coroutines	2571	during each prepare and only letting the process block if no coroutines
1924	are ready to run (it's actually more complicated: it only runs coroutines	2572	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1927	loop from blocking if lower-priority coroutines are active, thus mapping	2575	loop from blocking if lower-priority coroutines are active, thus mapping
1928	low-priority coroutines to idle/background tasks).	2576	low-priority coroutines to idle/background tasks).
1929		2577
1930	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2578	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1931	priority, to ensure that they are being run before any other watchers	2579	priority, to ensure that they are being run before any other watchers
		2580	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2581
1932	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2582	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1933	too) should not activate ("feed") events into libev. While libev fully	2583	activate ("feed") events into libev. While libev fully supports this, they
1934	supports this, they might get executed before other C<ev_check> watchers	2584	might get executed before other C<ev_check> watchers did their job. As
1935	did their job. As C<ev_check> watchers are often used to embed other	2585	C<ev_check> watchers are often used to embed other (non-libev) event
1936	(non-libev) event loops those other event loops might be in an unusable	2586	loops those other event loops might be in an unusable state until their
1937	state until their C<ev_check> watcher ran (always remind yourself to	2587	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1938	coexist peacefully with others).	2588	others).
1939		2589
1940	=head3 Watcher-Specific Functions and Data Members	2590	=head3 Watcher-Specific Functions and Data Members
1941		2591
1942	=over 4	2592	=over 4
1943		2593
…		…
1945		2595
1946	=item ev_check_init (ev_check *, callback)	2596	=item ev_check_init (ev_check *, callback)
1947		2597
1948	Initialises and configures the prepare or check watcher - they have no	2598	Initialises and configures the prepare or check watcher - they have no
1949	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2599	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1950	macros, but using them is utterly, utterly and completely pointless.	2600	macros, but using them is utterly, utterly, utterly and completely
		2601	pointless.
1951		2602
1952	=back	2603	=back
1953		2604
1954	=head3 Examples	2605	=head3 Examples
1955		2606
…		…
1968		2619
1969	static ev_io iow [nfd];	2620	static ev_io iow [nfd];
1970	static ev_timer tw;	2621	static ev_timer tw;
1971		2622
1972	static void	2623	static void
1973	io_cb (ev_loop *loop, ev_io *w, int revents)	2624	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1974	{	2625	{
1975	}	2626	}
1976		2627
1977	// create io watchers for each fd and a timer before blocking	2628	// create io watchers for each fd and a timer before blocking
1978	static void	2629	static void
1979	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2630	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1980	{	2631	{
1981	int timeout = 3600000;	2632	int timeout = 3600000;
1982	struct pollfd fds [nfd];	2633	struct pollfd fds [nfd];
1983	// actual code will need to loop here and realloc etc.	2634	// actual code will need to loop here and realloc etc.
1984	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2635	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1985		2636
1986	/* the callback is illegal, but won't be called as we stop during check */	2637	/* the callback is illegal, but won't be called as we stop during check */
1987	ev_timer_init (&tw, 0, timeout * 1e-3);	2638	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
1988	ev_timer_start (loop, &tw);	2639	ev_timer_start (loop, &tw);
1989		2640
1990	// create one ev_io per pollfd	2641	// create one ev_io per pollfd
1991	for (int i = 0; i < nfd; ++i)	2642	for (int i = 0; i < nfd; ++i)
1992	{	2643	{
…		…
1999	}	2650	}
2000	}	2651	}
2001		2652
2002	// stop all watchers after blocking	2653	// stop all watchers after blocking
2003	static void	2654	static void
2004	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2655	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2005	{	2656	{
2006	ev_timer_stop (loop, &tw);	2657	ev_timer_stop (loop, &tw);
2007		2658
2008	for (int i = 0; i < nfd; ++i)	2659	for (int i = 0; i < nfd; ++i)
2009	{	2660	{
…		…
2048	}	2699	}
2049		2700
2050	// do not ever call adns_afterpoll	2701	// do not ever call adns_afterpoll
2051		2702
2052	Method 4: Do not use a prepare or check watcher because the module you	2703	Method 4: Do not use a prepare or check watcher because the module you
2053	want to embed is too inflexible to support it. Instead, you can override	2704	want to embed is not flexible enough to support it. Instead, you can
2054	their poll function. The drawback with this solution is that the main	2705	override their poll function. The drawback with this solution is that the
2055	loop is now no longer controllable by EV. The C<Glib::EV> module does	2706	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2056	this.	2707	this approach, effectively embedding EV as a client into the horrible
		2708	libglib event loop.
2057		2709
2058	static gint	2710	static gint
2059	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2711	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2060	{	2712	{
2061	int got_events = 0;	2713	int got_events = 0;
…		…
2092	prioritise I/O.	2744	prioritise I/O.
2093		2745
2094	As an example for a bug workaround, the kqueue backend might only support	2746	As an example for a bug workaround, the kqueue backend might only support
2095	sockets on some platform, so it is unusable as generic backend, but you	2747	sockets on some platform, so it is unusable as generic backend, but you
2096	still want to make use of it because you have many sockets and it scales	2748	still want to make use of it because you have many sockets and it scales
2097	so nicely. In this case, you would create a kqueue-based loop and embed it	2749	so nicely. In this case, you would create a kqueue-based loop and embed
2098	into your default loop (which might use e.g. poll). Overall operation will	2750	it into your default loop (which might use e.g. poll). Overall operation
2099	be a bit slower because first libev has to poll and then call kevent, but	2751	will be a bit slower because first libev has to call C<poll> and then
2100	at least you can use both at what they are best.	2752	C<kevent>, but at least you can use both mechanisms for what they are
		2753	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2101		2754
2102	As for prioritising I/O: rarely you have the case where some fds have	2755	As for prioritising I/O: under rare circumstances you have the case where
2103	to be watched and handled very quickly (with low latency), and even	2756	some fds have to be watched and handled very quickly (with low latency),
2104	priorities and idle watchers might have too much overhead. In this case	2757	and even priorities and idle watchers might have too much overhead. In
2105	you would put all the high priority stuff in one loop and all the rest in	2758	this case you would put all the high priority stuff in one loop and all
2106	a second one, and embed the second one in the first.	2759	the rest in a second one, and embed the second one in the first.
2107		2760
2108	As long as the watcher is active, the callback will be invoked every time	2761	As long as the watcher is active, the callback will be invoked every
2109	there might be events pending in the embedded loop. The callback must then	2762	time there might be events pending in the embedded loop. The callback
2110	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2763	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2111	their callbacks (you could also start an idle watcher to give the embedded	2764	sweep and invoke their callbacks (the callback doesn't need to invoke the
2112	loop strictly lower priority for example). You can also set the callback	2765	C<ev_embed_sweep> function directly, it could also start an idle watcher
2113	to C<0>, in which case the embed watcher will automatically execute the	2766	to give the embedded loop strictly lower priority for example).
2114	embedded loop sweep.
2115		2767
2116	As long as the watcher is started it will automatically handle events. The	2768	You can also set the callback to C<0>, in which case the embed watcher
2117	callback will be invoked whenever some events have been handled. You can	2769	will automatically execute the embedded loop sweep whenever necessary.
2118	set the callback to C<0> to avoid having to specify one if you are not
2119	interested in that.
2120		2770
2121	Also, there have not currently been made special provisions for forking:	2771	Fork detection will be handled transparently while the C<ev_embed> watcher
2122	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2772	is active, i.e., the embedded loop will automatically be forked when the
2123	but you will also have to stop and restart any C<ev_embed> watchers	2773	embedding loop forks. In other cases, the user is responsible for calling
2124	yourself.	2774	C<ev_loop_fork> on the embedded loop.
2125		2775
2126	Unfortunately, not all backends are embeddable, only the ones returned by	2776	Unfortunately, not all backends are embeddable: only the ones returned by
2127	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2777	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2128	portable one.	2778	portable one.
2129		2779
2130	So when you want to use this feature you will always have to be prepared	2780	So when you want to use this feature you will always have to be prepared
2131	that you cannot get an embeddable loop. The recommended way to get around	2781	that you cannot get an embeddable loop. The recommended way to get around
2132	this is to have a separate variables for your embeddable loop, try to	2782	this is to have a separate variables for your embeddable loop, try to
2133	create it, and if that fails, use the normal loop for everything.	2783	create it, and if that fails, use the normal loop for everything.
		2784
		2785	=head3 C<ev_embed> and fork
		2786
		2787	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2788	automatically be applied to the embedded loop as well, so no special
		2789	fork handling is required in that case. When the watcher is not running,
		2790	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2791	as applicable.
2134		2792
2135	=head3 Watcher-Specific Functions and Data Members	2793	=head3 Watcher-Specific Functions and Data Members
2136		2794
2137	=over 4	2795	=over 4
2138		2796
…		…
2166	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2824	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2167	used).	2825	used).
2168		2826
2169	struct ev_loop *loop_hi = ev_default_init (0);	2827	struct ev_loop *loop_hi = ev_default_init (0);
2170	struct ev_loop *loop_lo = 0;	2828	struct ev_loop *loop_lo = 0;
2171	struct ev_embed embed;	2829	ev_embed embed;
2172		2830
2173	// see if there is a chance of getting one that works	2831	// see if there is a chance of getting one that works
2174	// (remember that a flags value of 0 means autodetection)	2832	// (remember that a flags value of 0 means autodetection)
2175	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2833	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2176	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2834	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2190	kqueue implementation). Store the kqueue/socket-only event loop in	2848	kqueue implementation). Store the kqueue/socket-only event loop in
2191	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2849	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2192		2850
2193	struct ev_loop *loop = ev_default_init (0);	2851	struct ev_loop *loop = ev_default_init (0);
2194	struct ev_loop *loop_socket = 0;	2852	struct ev_loop *loop_socket = 0;
2195	struct ev_embed embed;	2853	ev_embed embed;
2196		2854
2197	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2855	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2198	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2856	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2199	{	2857	{
2200	ev_embed_init (&embed, 0, loop_socket);	2858	ev_embed_init (&embed, 0, loop_socket);
…		…
2215	event loop blocks next and before C<ev_check> watchers are being called,	2873	event loop blocks next and before C<ev_check> watchers are being called,
2216	and only in the child after the fork. If whoever good citizen calling	2874	and only in the child after the fork. If whoever good citizen calling
2217	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2875	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2218	handlers will be invoked, too, of course.	2876	handlers will be invoked, too, of course.
2219		2877
		2878	=head3 The special problem of life after fork - how is it possible?
		2879
		2880	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2881	up/change the process environment, followed by a call to C<exec()>. This
		2882	sequence should be handled by libev without any problems.
		2883
		2884	This changes when the application actually wants to do event handling
		2885	in the child, or both parent in child, in effect "continuing" after the
		2886	fork.
		2887
		2888	The default mode of operation (for libev, with application help to detect
		2889	forks) is to duplicate all the state in the child, as would be expected
		2890	when I<either> the parent I<or> the child process continues.
		2891
		2892	When both processes want to continue using libev, then this is usually the
		2893	wrong result. In that case, usually one process (typically the parent) is
		2894	supposed to continue with all watchers in place as before, while the other
		2895	process typically wants to start fresh, i.e. without any active watchers.
		2896
		2897	The cleanest and most efficient way to achieve that with libev is to
		2898	simply create a new event loop, which of course will be "empty", and
		2899	use that for new watchers. This has the advantage of not touching more
		2900	memory than necessary, and thus avoiding the copy-on-write, and the
		2901	disadvantage of having to use multiple event loops (which do not support
		2902	signal watchers).
		2903
		2904	When this is not possible, or you want to use the default loop for
		2905	other reasons, then in the process that wants to start "fresh", call
		2906	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2907	the default loop will "orphan" (not stop) all registered watchers, so you
		2908	have to be careful not to execute code that modifies those watchers. Note
		2909	also that in that case, you have to re-register any signal watchers.
		2910
2220	=head3 Watcher-Specific Functions and Data Members	2911	=head3 Watcher-Specific Functions and Data Members
2221		2912
2222	=over 4	2913	=over 4
2223		2914
2224	=item ev_fork_init (ev_signal *, callback)	2915	=item ev_fork_init (ev_signal *, callback)
…		…
2256	is that the author does not know of a simple (or any) algorithm for a	2947	is that the author does not know of a simple (or any) algorithm for a
2257	multiple-writer-single-reader queue that works in all cases and doesn't	2948	multiple-writer-single-reader queue that works in all cases and doesn't
2258	need elaborate support such as pthreads.	2949	need elaborate support such as pthreads.
2259		2950
2260	That means that if you want to queue data, you have to provide your own	2951	That means that if you want to queue data, you have to provide your own
2261	queue. But at least I can tell you would implement locking around your	2952	queue. But at least I can tell you how to implement locking around your
2262	queue:	2953	queue:
2263		2954
2264	=over 4	2955	=over 4
2265		2956
2266	=item queueing from a signal handler context	2957	=item queueing from a signal handler context
2267		2958
2268	To implement race-free queueing, you simply add to the queue in the signal	2959	To implement race-free queueing, you simply add to the queue in the signal
2269	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2960	handler but you block the signal handler in the watcher callback. Here is
2270	some fictitious SIGUSR1 handler:	2961	an example that does that for some fictitious SIGUSR1 handler:
2271		2962
2272	static ev_async mysig;	2963	static ev_async mysig;
2273		2964
2274	static void	2965	static void
2275	sigusr1_handler (void)	2966	sigusr1_handler (void)
…		…
2341	=over 4	3032	=over 4
2342		3033
2343	=item ev_async_init (ev_async *, callback)	3034	=item ev_async_init (ev_async *, callback)
2344		3035
2345	Initialises and configures the async watcher - it has no parameters of any	3036	Initialises and configures the async watcher - it has no parameters of any
2346	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3037	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2347	believe me.	3038	trust me.
2348		3039
2349	=item ev_async_send (loop, ev_async *)	3040	=item ev_async_send (loop, ev_async *)
2350		3041
2351	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3042	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2352	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3043	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2353	C<ev_feed_event>, this call is safe to do in other threads, signal or	3044	C<ev_feed_event>, this call is safe to do from other threads, signal or
2354	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3045	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2355	section below on what exactly this means).	3046	section below on what exactly this means).
2356		3047
		3048	Note that, as with other watchers in libev, multiple events might get
		3049	compressed into a single callback invocation (another way to look at this
		3050	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3051	reset when the event loop detects that).
		3052
2357	This call incurs the overhead of a system call only once per loop iteration,	3053	This call incurs the overhead of a system call only once per event loop
2358	so while the overhead might be noticeable, it doesn't apply to repeated	3054	iteration, so while the overhead might be noticeable, it doesn't apply to
2359	calls to C<ev_async_send>.	3055	repeated calls to C<ev_async_send> for the same event loop.
2360		3056
2361	=item bool = ev_async_pending (ev_async *)	3057	=item bool = ev_async_pending (ev_async *)
2362		3058
2363	Returns a non-zero value when C<ev_async_send> has been called on the	3059	Returns a non-zero value when C<ev_async_send> has been called on the
2364	watcher but the event has not yet been processed (or even noted) by the	3060	watcher but the event has not yet been processed (or even noted) by the
…		…
2367	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3063	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2368	the loop iterates next and checks for the watcher to have become active,	3064	the loop iterates next and checks for the watcher to have become active,
2369	it will reset the flag again. C<ev_async_pending> can be used to very	3065	it will reset the flag again. C<ev_async_pending> can be used to very
2370	quickly check whether invoking the loop might be a good idea.	3066	quickly check whether invoking the loop might be a good idea.
2371		3067
2372	Not that this does I<not> check whether the watcher itself is pending, only	3068	Not that this does I<not> check whether the watcher itself is pending,
2373	whether it has been requested to make this watcher pending.	3069	only whether it has been requested to make this watcher pending: there
		3070	is a time window between the event loop checking and resetting the async
		3071	notification, and the callback being invoked.
2374		3072
2375	=back	3073	=back
2376		3074
2377		3075
2378	=head1 OTHER FUNCTIONS	3076	=head1 OTHER FUNCTIONS
…		…
2382	=over 4	3080	=over 4
2383		3081
2384	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3082	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2385		3083
2386	This function combines a simple timer and an I/O watcher, calls your	3084	This function combines a simple timer and an I/O watcher, calls your
2387	callback on whichever event happens first and automatically stop both	3085	callback on whichever event happens first and automatically stops both
2388	watchers. This is useful if you want to wait for a single event on an fd	3086	watchers. This is useful if you want to wait for a single event on an fd
2389	or timeout without having to allocate/configure/start/stop/free one or	3087	or timeout without having to allocate/configure/start/stop/free one or
2390	more watchers yourself.	3088	more watchers yourself.
2391		3089
2392	If C<fd> is less than 0, then no I/O watcher will be started and events	3090	If C<fd> is less than 0, then no I/O watcher will be started and the
2393	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	3091	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2394	C<events> set will be created and started.	3092	the given C<fd> and C<events> set will be created and started.
2395		3093
2396	If C<timeout> is less than 0, then no timeout watcher will be	3094	If C<timeout> is less than 0, then no timeout watcher will be
2397	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3095	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2398	repeat = 0) will be started. While C<0> is a valid timeout, it is of	3096	repeat = 0) will be started. C<0> is a valid timeout.
2399	dubious value.
2400		3097
2401	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3098	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2402	passed an C<revents> set like normal event callbacks (a combination of	3099	passed an C<revents> set like normal event callbacks (a combination of
2403	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3100	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2404	value passed to C<ev_once>:	3101	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3102	a timeout and an io event at the same time - you probably should give io
		3103	events precedence.
		3104
		3105	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2405		3106
2406	static void stdin_ready (int revents, void *arg)	3107	static void stdin_ready (int revents, void *arg)
2407	{	3108	{
		3109	if (revents & EV_READ)
		3110	/* stdin might have data for us, joy! */;
2408	if (revents & EV_TIMEOUT)	3111	else if (revents & EV_TIMEOUT)
2409	/* doh, nothing entered */;	3112	/* doh, nothing entered */;
2410	else if (revents & EV_READ)
2411	/* stdin might have data for us, joy! */;
2412	}	3113	}
2413		3114
2414	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3115	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2415		3116
2416	=item ev_feed_event (ev_loop *, watcher *, int revents)	3117	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2417		3118
2418	Feeds the given event set into the event loop, as if the specified event	3119	Feeds the given event set into the event loop, as if the specified event
2419	had happened for the specified watcher (which must be a pointer to an	3120	had happened for the specified watcher (which must be a pointer to an
2420	initialised but not necessarily started event watcher).	3121	initialised but not necessarily started event watcher).
2421		3122
2422	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3123	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2423		3124
2424	Feed an event on the given fd, as if a file descriptor backend detected	3125	Feed an event on the given fd, as if a file descriptor backend detected
2425	the given events it.	3126	the given events it.
2426		3127
2427	=item ev_feed_signal_event (ev_loop *loop, int signum)	3128	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2428		3129
2429	Feed an event as if the given signal occurred (C<loop> must be the default	3130	Feed an event as if the given signal occurred (C<loop> must be the default
2430	loop!).	3131	loop!).
2431		3132
2432	=back	3133	=back
…		…
2554		3255
2555	myclass obj;	3256	myclass obj;
2556	ev::io iow;	3257	ev::io iow;
2557	iow.set <myclass, &myclass::io_cb> (&obj);	3258	iow.set <myclass, &myclass::io_cb> (&obj);
2558		3259
		3260	=item w->set (object *)
		3261
		3262	This is an B<experimental> feature that might go away in a future version.
		3263
		3264	This is a variation of a method callback - leaving out the method to call
		3265	will default the method to C<operator ()>, which makes it possible to use
		3266	functor objects without having to manually specify the C<operator ()> all
		3267	the time. Incidentally, you can then also leave out the template argument
		3268	list.
		3269
		3270	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3271	int revents)>.
		3272
		3273	See the method-C<set> above for more details.
		3274
		3275	Example: use a functor object as callback.
		3276
		3277	struct myfunctor
		3278	{
		3279	void operator() (ev::io &w, int revents)
		3280	{
		3281	...
		3282	}
		3283	}
		3284
		3285	myfunctor f;
		3286
		3287	ev::io w;
		3288	w.set (&f);
		3289
2559	=item w->set<function> (void *data = 0)	3290	=item w->set<function> (void *data = 0)
2560		3291
2561	Also sets a callback, but uses a static method or plain function as	3292	Also sets a callback, but uses a static method or plain function as
2562	callback. The optional C<data> argument will be stored in the watcher's	3293	callback. The optional C<data> argument will be stored in the watcher's
2563	C<data> member and is free for you to use.	3294	C<data> member and is free for you to use.
2564		3295
2565	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3296	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2566		3297
2567	See the method-C<set> above for more details.	3298	See the method-C<set> above for more details.
2568		3299
2569	Example:	3300	Example: Use a plain function as callback.
2570		3301
2571	static void io_cb (ev::io &w, int revents) { }	3302	static void io_cb (ev::io &w, int revents) { }
2572	iow.set <io_cb> ();	3303	iow.set <io_cb> ();
2573		3304
2574	=item w->set (struct ev_loop *)	3305	=item w->set (struct ev_loop *)
…		…
2612	Example: Define a class with an IO and idle watcher, start one of them in	3343	Example: Define a class with an IO and idle watcher, start one of them in
2613	the constructor.	3344	the constructor.
2614		3345
2615	class myclass	3346	class myclass
2616	{	3347	{
2617	ev::io io; void io_cb (ev::io &w, int revents);	3348	ev::io io ; void io_cb (ev::io &w, int revents);
2618	ev:idle idle void idle_cb (ev::idle &w, int revents);	3349	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2619		3350
2620	myclass (int fd)	3351	myclass (int fd)
2621	{	3352	{
2622	io .set <myclass, &myclass::io_cb > (this);	3353	io .set <myclass, &myclass::io_cb > (this);
2623	idle.set <myclass, &myclass::idle_cb> (this);	3354	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2639	=item Perl	3370	=item Perl
2640		3371
2641	The EV module implements the full libev API and is actually used to test	3372	The EV module implements the full libev API and is actually used to test
2642	libev. EV is developed together with libev. Apart from the EV core module,	3373	libev. EV is developed together with libev. Apart from the EV core module,
2643	there are additional modules that implement libev-compatible interfaces	3374	there are additional modules that implement libev-compatible interfaces
2644	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3375	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2645	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3376	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3377	and C<EV::Glib>).
2646		3378
2647	It can be found and installed via CPAN, its homepage is at	3379	It can be found and installed via CPAN, its homepage is at
2648	L<http://software.schmorp.de/pkg/EV>.	3380	L<http://software.schmorp.de/pkg/EV>.
2649		3381
2650	=item Python	3382	=item Python
2651		3383
2652	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3384	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2653	seems to be quite complete and well-documented. Note, however, that the	3385	seems to be quite complete and well-documented.
2654	patch they require for libev is outright dangerous as it breaks the ABI
2655	for everybody else, and therefore, should never be applied in an installed
2656	libev (if python requires an incompatible ABI then it needs to embed
2657	libev).
2658		3386
2659	=item Ruby	3387	=item Ruby
2660		3388
2661	Tony Arcieri has written a ruby extension that offers access to a subset	3389	Tony Arcieri has written a ruby extension that offers access to a subset
2662	of the libev API and adds file handle abstractions, asynchronous DNS and	3390	of the libev API and adds file handle abstractions, asynchronous DNS and
2663	more on top of it. It can be found via gem servers. Its homepage is at	3391	more on top of it. It can be found via gem servers. Its homepage is at
2664	L<http://rev.rubyforge.org/>.	3392	L<http://rev.rubyforge.org/>.
2665		3393
		3394	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3395	makes rev work even on mingw.
		3396
		3397	=item Haskell
		3398
		3399	A haskell binding to libev is available at
		3400	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3401
2666	=item D	3402	=item D
2667		3403
2668	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3404	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2669	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3405	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3406
		3407	=item Ocaml
		3408
		3409	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3410	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3411
		3412	=item Lua
		3413
		3414	Brian Maher has written a partial interface to libev
		3415	for lua (only C<ev_io> and C<ev_timer>), to be found at
		3416	L<http://github.com/brimworks/lua-ev>.
2670		3417
2671	=back	3418	=back
2672		3419
2673		3420
2674	=head1 MACRO MAGIC	3421	=head1 MACRO MAGIC
…		…
2775		3522
2776	#define EV_STANDALONE 1	3523	#define EV_STANDALONE 1
2777	#include "ev.h"	3524	#include "ev.h"
2778		3525
2779	Both header files and implementation files can be compiled with a C++	3526	Both header files and implementation files can be compiled with a C++
2780	compiler (at least, thats a stated goal, and breakage will be treated	3527	compiler (at least, that's a stated goal, and breakage will be treated
2781	as a bug).	3528	as a bug).
2782		3529
2783	You need the following files in your source tree, or in a directory	3530	You need the following files in your source tree, or in a directory
2784	in your include path (e.g. in libev/ when using -Ilibev):	3531	in your include path (e.g. in libev/ when using -Ilibev):
2785		3532
…		…
2829		3576
2830	=head2 PREPROCESSOR SYMBOLS/MACROS	3577	=head2 PREPROCESSOR SYMBOLS/MACROS
2831		3578
2832	Libev can be configured via a variety of preprocessor symbols you have to	3579	Libev can be configured via a variety of preprocessor symbols you have to
2833	define before including any of its files. The default in the absence of	3580	define before including any of its files. The default in the absence of
2834	autoconf is noted for every option.	3581	autoconf is documented for every option.
2835		3582
2836	=over 4	3583	=over 4
2837		3584
2838	=item EV_STANDALONE	3585	=item EV_STANDALONE
2839		3586
…		…
2841	keeps libev from including F<config.h>, and it also defines dummy	3588	keeps libev from including F<config.h>, and it also defines dummy
2842	implementations for some libevent functions (such as logging, which is not	3589	implementations for some libevent functions (such as logging, which is not
2843	supported). It will also not define any of the structs usually found in	3590	supported). It will also not define any of the structs usually found in
2844	F<event.h> that are not directly supported by the libev core alone.	3591	F<event.h> that are not directly supported by the libev core alone.
2845		3592
		3593	In standalone mode, libev will still try to automatically deduce the
		3594	configuration, but has to be more conservative.
		3595
2846	=item EV_USE_MONOTONIC	3596	=item EV_USE_MONOTONIC
2847		3597
2848	If defined to be C<1>, libev will try to detect the availability of the	3598	If defined to be C<1>, libev will try to detect the availability of the
2849	monotonic clock option at both compile time and runtime. Otherwise no use	3599	monotonic clock option at both compile time and runtime. Otherwise no
2850	of the monotonic clock option will be attempted. If you enable this, you	3600	use of the monotonic clock option will be attempted. If you enable this,
2851	usually have to link against librt or something similar. Enabling it when	3601	you usually have to link against librt or something similar. Enabling it
2852	the functionality isn't available is safe, though, although you have	3602	when the functionality isn't available is safe, though, although you have
2853	to make sure you link against any libraries where the C<clock_gettime>	3603	to make sure you link against any libraries where the C<clock_gettime>
2854	function is hiding in (often F<-lrt>).	3604	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2855		3605
2856	=item EV_USE_REALTIME	3606	=item EV_USE_REALTIME
2857		3607
2858	If defined to be C<1>, libev will try to detect the availability of the	3608	If defined to be C<1>, libev will try to detect the availability of the
2859	real-time clock option at compile time (and assume its availability at	3609	real-time clock option at compile time (and assume its availability
2860	runtime if successful). Otherwise no use of the real-time clock option will	3610	at runtime if successful). Otherwise no use of the real-time clock
2861	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3611	option will be attempted. This effectively replaces C<gettimeofday>
2862	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3612	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2863	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3613	correctness. See the note about libraries in the description of
		3614	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3615	C<EV_USE_CLOCK_SYSCALL>.
		3616
		3617	=item EV_USE_CLOCK_SYSCALL
		3618
		3619	If defined to be C<1>, libev will try to use a direct syscall instead
		3620	of calling the system-provided C<clock_gettime> function. This option
		3621	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3622	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3623	programs needlessly. Using a direct syscall is slightly slower (in
		3624	theory), because no optimised vdso implementation can be used, but avoids
		3625	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3626	higher, as it simplifies linking (no need for C<-lrt>).
2864		3627
2865	=item EV_USE_NANOSLEEP	3628	=item EV_USE_NANOSLEEP
2866		3629
2867	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3630	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2868	and will use it for delays. Otherwise it will use C<select ()>.	3631	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2884		3647
2885	=item EV_SELECT_USE_FD_SET	3648	=item EV_SELECT_USE_FD_SET
2886		3649
2887	If defined to C<1>, then the select backend will use the system C<fd_set>	3650	If defined to C<1>, then the select backend will use the system C<fd_set>
2888	structure. This is useful if libev doesn't compile due to a missing	3651	structure. This is useful if libev doesn't compile due to a missing
2889	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3652	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2890	exotic systems. This usually limits the range of file descriptors to some	3653	on exotic systems. This usually limits the range of file descriptors to
2891	low limit such as 1024 or might have other limitations (winsocket only	3654	some low limit such as 1024 or might have other limitations (winsocket
2892	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3655	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2893	influence the size of the C<fd_set> used.	3656	configures the maximum size of the C<fd_set>.
2894		3657
2895	=item EV_SELECT_IS_WINSOCKET	3658	=item EV_SELECT_IS_WINSOCKET
2896		3659
2897	When defined to C<1>, the select backend will assume that	3660	When defined to C<1>, the select backend will assume that
2898	select/socket/connect etc. don't understand file descriptors but	3661	select/socket/connect etc. don't understand file descriptors but
…		…
3009	When doing priority-based operations, libev usually has to linearly search	3772	When doing priority-based operations, libev usually has to linearly search
3010	all the priorities, so having many of them (hundreds) uses a lot of space	3773	all the priorities, so having many of them (hundreds) uses a lot of space
3011	and time, so using the defaults of five priorities (-2 .. +2) is usually	3774	and time, so using the defaults of five priorities (-2 .. +2) is usually
3012	fine.	3775	fine.
3013		3776
3014	If your embedding application does not need any priorities, defining these both to	3777	If your embedding application does not need any priorities, defining these
3015	C<0> will save some memory and CPU.	3778	both to C<0> will save some memory and CPU.
3016		3779
3017	=item EV_PERIODIC_ENABLE	3780	=item EV_PERIODIC_ENABLE
3018		3781
3019	If undefined or defined to be C<1>, then periodic timers are supported. If	3782	If undefined or defined to be C<1>, then periodic timers are supported. If
3020	defined to be C<0>, then they are not. Disabling them saves a few kB of	3783	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3027	code.	3790	code.
3028		3791
3029	=item EV_EMBED_ENABLE	3792	=item EV_EMBED_ENABLE
3030		3793
3031	If undefined or defined to be C<1>, then embed watchers are supported. If	3794	If undefined or defined to be C<1>, then embed watchers are supported. If
3032	defined to be C<0>, then they are not.	3795	defined to be C<0>, then they are not. Embed watchers rely on most other
		3796	watcher types, which therefore must not be disabled.
3033		3797
3034	=item EV_STAT_ENABLE	3798	=item EV_STAT_ENABLE
3035		3799
3036	If undefined or defined to be C<1>, then stat watchers are supported. If	3800	If undefined or defined to be C<1>, then stat watchers are supported. If
3037	defined to be C<0>, then they are not.	3801	defined to be C<0>, then they are not.
…		…
3047	defined to be C<0>, then they are not.	3811	defined to be C<0>, then they are not.
3048		3812
3049	=item EV_MINIMAL	3813	=item EV_MINIMAL
3050		3814
3051	If you need to shave off some kilobytes of code at the expense of some	3815	If you need to shave off some kilobytes of code at the expense of some
3052	speed, define this symbol to C<1>. Currently this is used to override some	3816	speed (but with the full API), define this symbol to C<1>. Currently this
3053	inlining decisions, saves roughly 30% code size on amd64. It also selects a	3817	is used to override some inlining decisions, saves roughly 30% code size
3054	much smaller 2-heap for timer management over the default 4-heap.	3818	on amd64. It also selects a much smaller 2-heap for timer management over
		3819	the default 4-heap.
		3820
		3821	You can save even more by disabling watcher types you do not need
		3822	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>
		3823	(C<-DNDEBUG>) will usually reduce code size a lot.
		3824
		3825	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to
		3826	provide a bare-bones event library. See C<ev.h> for details on what parts
		3827	of the API are still available, and do not complain if this subset changes
		3828	over time.
		3829
		3830	=item EV_NSIG
		3831
		3832	The highest supported signal number, +1 (or, the number of
		3833	signals): Normally, libev tries to deduce the maximum number of signals
		3834	automatically, but sometimes this fails, in which case it can be
		3835	specified. Also, using a lower number than detected (C<32> should be
		3836	good for about any system in existance) can save some memory, as libev
		3837	statically allocates some 12-24 bytes per signal number.
3055		3838
3056	=item EV_PID_HASHSIZE	3839	=item EV_PID_HASHSIZE
3057		3840
3058	C<ev_child> watchers use a small hash table to distribute workload by	3841	C<ev_child> watchers use a small hash table to distribute workload by
3059	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3842	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
3069	two).	3852	two).
3070		3853
3071	=item EV_USE_4HEAP	3854	=item EV_USE_4HEAP
3072		3855
3073	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3856	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3074	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3857	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3075	to C<1>. The 4-heap uses more complicated (longer) code but has	3858	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3076	noticeably faster performance with many (thousands) of watchers.	3859	faster performance with many (thousands) of watchers.
3077		3860
3078	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3861	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3079	(disabled).	3862	(disabled).
3080		3863
3081	=item EV_HEAP_CACHE_AT	3864	=item EV_HEAP_CACHE_AT
3082		3865
3083	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3866	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3084	timer and periodics heap, libev can cache the timestamp (I<at>) within	3867	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3085	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3868	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3086	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3869	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3087	but avoids random read accesses on heap changes. This improves performance	3870	but avoids random read accesses on heap changes. This improves performance
3088	noticeably with with many (hundreds) of watchers.	3871	noticeably with many (hundreds) of watchers.
3089		3872
3090	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3873	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3091	(disabled).	3874	(disabled).
3092		3875
3093	=item EV_VERIFY	3876	=item EV_VERIFY
…		…
3099	called once per loop, which can slow down libev. If set to C<3>, then the	3882	called once per loop, which can slow down libev. If set to C<3>, then the
3100	verification code will be called very frequently, which will slow down	3883	verification code will be called very frequently, which will slow down
3101	libev considerably.	3884	libev considerably.
3102		3885
3103	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3886	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3104	C<0.>	3887	C<0>.
3105		3888
3106	=item EV_COMMON	3889	=item EV_COMMON
3107		3890
3108	By default, all watchers have a C<void *data> member. By redefining	3891	By default, all watchers have a C<void *data> member. By redefining
3109	this macro to a something else you can include more and other types of	3892	this macro to a something else you can include more and other types of
…		…
3126	and the way callbacks are invoked and set. Must expand to a struct member	3909	and the way callbacks are invoked and set. Must expand to a struct member
3127	definition and a statement, respectively. See the F<ev.h> header file for	3910	definition and a statement, respectively. See the F<ev.h> header file for
3128	their default definitions. One possible use for overriding these is to	3911	their default definitions. One possible use for overriding these is to
3129	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3912	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3130	method calls instead of plain function calls in C++.	3913	method calls instead of plain function calls in C++.
		3914
		3915	=back
3131		3916
3132	=head2 EXPORTED API SYMBOLS	3917	=head2 EXPORTED API SYMBOLS
3133		3918
3134	If you need to re-export the API (e.g. via a DLL) and you need a list of	3919	If you need to re-export the API (e.g. via a DLL) and you need a list of
3135	exported symbols, you can use the provided F<Symbol.*> files which list	3920	exported symbols, you can use the provided F<Symbol.*> files which list
…		…
3182	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3967	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3183		3968
3184	#include "ev_cpp.h"	3969	#include "ev_cpp.h"
3185	#include "ev.c"	3970	#include "ev.c"
3186		3971
		3972	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3187		3973
3188	=head1 THREADS AND COROUTINES	3974	=head2 THREADS AND COROUTINES
3189		3975
3190	=head2 THREADS	3976	=head3 THREADS
3191		3977
3192	Libev itself is completely thread-safe, but it uses no locking. This	3978	All libev functions are reentrant and thread-safe unless explicitly
		3979	documented otherwise, but libev implements no locking itself. This means
3193	means that you can use as many loops as you want in parallel, as long as	3980	that you can use as many loops as you want in parallel, as long as there
3194	only one thread ever calls into one libev function with the same loop	3981	are no concurrent calls into any libev function with the same loop
3195	parameter.	3982	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3983	of course): libev guarantees that different event loops share no data
		3984	structures that need any locking.
3196		3985
3197	Or put differently: calls with different loop parameters can be done in	3986	Or to put it differently: calls with different loop parameters can be done
3198	parallel from multiple threads, calls with the same loop parameter must be	3987	concurrently from multiple threads, calls with the same loop parameter
3199	done serially (but can be done from different threads, as long as only one	3988	must be done serially (but can be done from different threads, as long as
3200	thread ever is inside a call at any point in time, e.g. by using a mutex	3989	only one thread ever is inside a call at any point in time, e.g. by using
3201	per loop).	3990	a mutex per loop).
		3991
		3992	Specifically to support threads (and signal handlers), libev implements
		3993	so-called C<ev_async> watchers, which allow some limited form of
		3994	concurrency on the same event loop, namely waking it up "from the
		3995	outside".
3202		3996
3203	If you want to know which design (one loop, locking, or multiple loops	3997	If you want to know which design (one loop, locking, or multiple loops
3204	without or something else still) is best for your problem, then I cannot	3998	without or something else still) is best for your problem, then I cannot
3205	help you. I can give some generic advice however:	3999	help you, but here is some generic advice:
3206		4000
3207	=over 4	4001	=over 4
3208		4002
3209	=item * most applications have a main thread: use the default libev loop	4003	=item * most applications have a main thread: use the default libev loop
3210	in that thread, or create a separate thread running only the default loop.	4004	in that thread, or create a separate thread running only the default loop.
…		…
3222		4016
3223	Choosing a model is hard - look around, learn, know that usually you can do	4017	Choosing a model is hard - look around, learn, know that usually you can do
3224	better than you currently do :-)	4018	better than you currently do :-)
3225		4019
3226	=item * often you need to talk to some other thread which blocks in the	4020	=item * often you need to talk to some other thread which blocks in the
		4021	event loop.
		4022
3227	event loop - C<ev_async> watchers can be used to wake them up from other	4023	C<ev_async> watchers can be used to wake them up from other threads safely
3228	threads safely (or from signal contexts...).	4024	(or from signal contexts...).
		4025
		4026	An example use would be to communicate signals or other events that only
		4027	work in the default loop by registering the signal watcher with the
		4028	default loop and triggering an C<ev_async> watcher from the default loop
		4029	watcher callback into the event loop interested in the signal.
3229		4030
3230	=back	4031	=back
3231		4032
		4033	=head4 THREAD LOCKING EXAMPLE
		4034
		4035	Here is a fictitious example of how to run an event loop in a different
		4036	thread than where callbacks are being invoked and watchers are
		4037	created/added/removed.
		4038
		4039	For a real-world example, see the C<EV::Loop::Async> perl module,
		4040	which uses exactly this technique (which is suited for many high-level
		4041	languages).
		4042
		4043	The example uses a pthread mutex to protect the loop data, a condition
		4044	variable to wait for callback invocations, an async watcher to notify the
		4045	event loop thread and an unspecified mechanism to wake up the main thread.
		4046
		4047	First, you need to associate some data with the event loop:
		4048
		4049	typedef struct {
		4050	mutex_t lock; /* global loop lock */
		4051	ev_async async_w;
		4052	thread_t tid;
		4053	cond_t invoke_cv;
		4054	} userdata;
		4055
		4056	void prepare_loop (EV_P)
		4057	{
		4058	// for simplicity, we use a static userdata struct.
		4059	static userdata u;
		4060
		4061	ev_async_init (&u->async_w, async_cb);
		4062	ev_async_start (EV_A_ &u->async_w);
		4063
		4064	pthread_mutex_init (&u->lock, 0);
		4065	pthread_cond_init (&u->invoke_cv, 0);
		4066
		4067	// now associate this with the loop
		4068	ev_set_userdata (EV_A_ u);
		4069	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4070	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4071
		4072	// then create the thread running ev_loop
		4073	pthread_create (&u->tid, 0, l_run, EV_A);
		4074	}
		4075
		4076	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4077	solely to wake up the event loop so it takes notice of any new watchers
		4078	that might have been added:
		4079
		4080	static void
		4081	async_cb (EV_P_ ev_async *w, int revents)
		4082	{
		4083	// just used for the side effects
		4084	}
		4085
		4086	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4087	protecting the loop data, respectively.
		4088
		4089	static void
		4090	l_release (EV_P)
		4091	{
		4092	userdata *u = ev_userdata (EV_A);
		4093	pthread_mutex_unlock (&u->lock);
		4094	}
		4095
		4096	static void
		4097	l_acquire (EV_P)
		4098	{
		4099	userdata *u = ev_userdata (EV_A);
		4100	pthread_mutex_lock (&u->lock);
		4101	}
		4102
		4103	The event loop thread first acquires the mutex, and then jumps straight
		4104	into C<ev_loop>:
		4105
		4106	void *
		4107	l_run (void *thr_arg)
		4108	{
		4109	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4110
		4111	l_acquire (EV_A);
		4112	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4113	ev_loop (EV_A_ 0);
		4114	l_release (EV_A);
		4115
		4116	return 0;
		4117	}
		4118
		4119	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4120	signal the main thread via some unspecified mechanism (signals? pipe
		4121	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4122	have been called (in a while loop because a) spurious wakeups are possible
		4123	and b) skipping inter-thread-communication when there are no pending
		4124	watchers is very beneficial):
		4125
		4126	static void
		4127	l_invoke (EV_P)
		4128	{
		4129	userdata *u = ev_userdata (EV_A);
		4130
		4131	while (ev_pending_count (EV_A))
		4132	{
		4133	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4134	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4135	}
		4136	}
		4137
		4138	Now, whenever the main thread gets told to invoke pending watchers, it
		4139	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4140	thread to continue:
		4141
		4142	static void
		4143	real_invoke_pending (EV_P)
		4144	{
		4145	userdata *u = ev_userdata (EV_A);
		4146
		4147	pthread_mutex_lock (&u->lock);
		4148	ev_invoke_pending (EV_A);
		4149	pthread_cond_signal (&u->invoke_cv);
		4150	pthread_mutex_unlock (&u->lock);
		4151	}
		4152
		4153	Whenever you want to start/stop a watcher or do other modifications to an
		4154	event loop, you will now have to lock:
		4155
		4156	ev_timer timeout_watcher;
		4157	userdata *u = ev_userdata (EV_A);
		4158
		4159	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4160
		4161	pthread_mutex_lock (&u->lock);
		4162	ev_timer_start (EV_A_ &timeout_watcher);
		4163	ev_async_send (EV_A_ &u->async_w);
		4164	pthread_mutex_unlock (&u->lock);
		4165
		4166	Note that sending the C<ev_async> watcher is required because otherwise
		4167	an event loop currently blocking in the kernel will have no knowledge
		4168	about the newly added timer. By waking up the loop it will pick up any new
		4169	watchers in the next event loop iteration.
		4170
3232	=head2 COROUTINES	4171	=head3 COROUTINES
3233		4172
3234	Libev is much more accommodating to coroutines ("cooperative threads"):	4173	Libev is very accommodating to coroutines ("cooperative threads"):
3235	libev fully supports nesting calls to it's functions from different	4174	libev fully supports nesting calls to its functions from different
3236	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4175	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3237	different coroutines and switch freely between both coroutines running the	4176	different coroutines, and switch freely between both coroutines running
3238	loop, as long as you don't confuse yourself). The only exception is that	4177	the loop, as long as you don't confuse yourself). The only exception is
3239	you must not do this from C<ev_periodic> reschedule callbacks.	4178	that you must not do this from C<ev_periodic> reschedule callbacks.
3240		4179
3241	Care has been invested into making sure that libev does not keep local	4180	Care has been taken to ensure that libev does not keep local state inside
3242	state inside C<ev_loop>, and other calls do not usually allow coroutine	4181	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3243	switches.	4182	they do not call any callbacks.
3244		4183
		4184	=head2 COMPILER WARNINGS
3245		4185
3246	=head1 COMPLEXITIES	4186	Depending on your compiler and compiler settings, you might get no or a
		4187	lot of warnings when compiling libev code. Some people are apparently
		4188	scared by this.
3247		4189
3248	In this section the complexities of (many of) the algorithms used inside	4190	However, these are unavoidable for many reasons. For one, each compiler
3249	libev will be explained. For complexity discussions about backends see the	4191	has different warnings, and each user has different tastes regarding
3250	documentation for C<ev_default_init>.	4192	warning options. "Warn-free" code therefore cannot be a goal except when
		4193	targeting a specific compiler and compiler-version.
3251		4194
3252	All of the following are about amortised time: If an array needs to be	4195	Another reason is that some compiler warnings require elaborate
3253	extended, libev needs to realloc and move the whole array, but this	4196	workarounds, or other changes to the code that make it less clear and less
3254	happens asymptotically never with higher number of elements, so O(1) might	4197	maintainable.
3255	mean it might do a lengthy realloc operation in rare cases, but on average
3256	it is much faster and asymptotically approaches constant time.
3257		4198
3258	=over 4	4199	And of course, some compiler warnings are just plain stupid, or simply
		4200	wrong (because they don't actually warn about the condition their message
		4201	seems to warn about). For example, certain older gcc versions had some
		4202	warnings that resulted an extreme number of false positives. These have
		4203	been fixed, but some people still insist on making code warn-free with
		4204	such buggy versions.
3259		4205
3260	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	4206	While libev is written to generate as few warnings as possible,
		4207	"warn-free" code is not a goal, and it is recommended not to build libev
		4208	with any compiler warnings enabled unless you are prepared to cope with
		4209	them (e.g. by ignoring them). Remember that warnings are just that:
		4210	warnings, not errors, or proof of bugs.
3261		4211
3262	This means that, when you have a watcher that triggers in one hour and
3263	there are 100 watchers that would trigger before that then inserting will
3264	have to skip roughly seven (C<ld 100>) of these watchers.
3265		4212
3266	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	4213	=head2 VALGRIND
3267		4214
3268	That means that changing a timer costs less than removing/adding them	4215	Valgrind has a special section here because it is a popular tool that is
3269	as only the relative motion in the event queue has to be paid for.	4216	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3270		4217
3271	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	4218	If you think you found a bug (memory leak, uninitialised data access etc.)
		4219	in libev, then check twice: If valgrind reports something like:
3272		4220
3273	These just add the watcher into an array or at the head of a list.	4221	==2274== definitely lost: 0 bytes in 0 blocks.
		4222	==2274== possibly lost: 0 bytes in 0 blocks.
		4223	==2274== still reachable: 256 bytes in 1 blocks.
3274		4224
3275	=item Stopping check/prepare/idle/fork/async watchers: O(1)	4225	Then there is no memory leak, just as memory accounted to global variables
		4226	is not a memleak - the memory is still being referenced, and didn't leak.
3276		4227
3277	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	4228	Similarly, under some circumstances, valgrind might report kernel bugs
		4229	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		4230	although an acceptable workaround has been found here), or it might be
		4231	confused.
3278		4232
3279	These watchers are stored in lists then need to be walked to find the	4233	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3280	correct watcher to remove. The lists are usually short (you don't usually	4234	make it into some kind of religion.
3281	have many watchers waiting for the same fd or signal).
3282		4235
3283	=item Finding the next timer in each loop iteration: O(1)	4236	If you are unsure about something, feel free to contact the mailing list
		4237	with the full valgrind report and an explanation on why you think this
		4238	is a bug in libev (best check the archives, too :). However, don't be
		4239	annoyed when you get a brisk "this is no bug" answer and take the chance
		4240	of learning how to interpret valgrind properly.
3284		4241
3285	By virtue of using a binary or 4-heap, the next timer is always found at a	4242	If you need, for some reason, empty reports from valgrind for your project
3286	fixed position in the storage array.	4243	I suggest using suppression lists.
3287		4244
3288	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3289		4245
3290	A change means an I/O watcher gets started or stopped, which requires	4246	=head1 PORTABILITY NOTES
3291	libev to recalculate its status (and possibly tell the kernel, depending
3292	on backend and whether C<ev_io_set> was used).
3293		4247
3294	=item Activating one watcher (putting it into the pending state): O(1)
3295
3296	=item Priority handling: O(number_of_priorities)
3297
3298	Priorities are implemented by allocating some space for each
3299	priority. When doing priority-based operations, libev usually has to
3300	linearly search all the priorities, but starting/stopping and activating
3301	watchers becomes O(1) w.r.t. priority handling.
3302
3303	=item Sending an ev_async: O(1)
3304
3305	=item Processing ev_async_send: O(number_of_async_watchers)
3306
3307	=item Processing signals: O(max_signal_number)
3308
3309	Sending involves a system call I<iff> there were no other C<ev_async_send>
3310	calls in the current loop iteration. Checking for async and signal events
3311	involves iterating over all running async watchers or all signal numbers.
3312
3313	=back
3314
3315
3316	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4248	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3317		4249
3318	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4250	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3319	requires, and its I/O model is fundamentally incompatible with the POSIX	4251	requires, and its I/O model is fundamentally incompatible with the POSIX
3320	model. Libev still offers limited functionality on this platform in	4252	model. Libev still offers limited functionality on this platform in
3321	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4253	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3328	way (note also that glib is the slowest event library known to man).	4260	way (note also that glib is the slowest event library known to man).
3329		4261
3330	There is no supported compilation method available on windows except	4262	There is no supported compilation method available on windows except
3331	embedding it into other applications.	4263	embedding it into other applications.
3332		4264
		4265	Sensible signal handling is officially unsupported by Microsoft - libev
		4266	tries its best, but under most conditions, signals will simply not work.
		4267
3333	Not a libev limitation but worth mentioning: windows apparently doesn't	4268	Not a libev limitation but worth mentioning: windows apparently doesn't
3334	accept large writes: instead of resulting in a partial write, windows will	4269	accept large writes: instead of resulting in a partial write, windows will
3335	either accept everything or return C<ENOBUFS> if the buffer is too large,	4270	either accept everything or return C<ENOBUFS> if the buffer is too large,
3336	so make sure you only write small amounts into your sockets (less than a	4271	so make sure you only write small amounts into your sockets (less than a
3337	megabyte seems safe, but thsi apparently depends on the amount of memory	4272	megabyte seems safe, but this apparently depends on the amount of memory
3338	available).	4273	available).
3339		4274
3340	Due to the many, low, and arbitrary limits on the win32 platform and	4275	Due to the many, low, and arbitrary limits on the win32 platform and
3341	the abysmal performance of winsockets, using a large number of sockets	4276	the abysmal performance of winsockets, using a large number of sockets
3342	is not recommended (and not reasonable). If your program needs to use	4277	is not recommended (and not reasonable). If your program needs to use
3343	more than a hundred or so sockets, then likely it needs to use a totally	4278	more than a hundred or so sockets, then likely it needs to use a totally
3344	different implementation for windows, as libev offers the POSIX readiness	4279	different implementation for windows, as libev offers the POSIX readiness
3345	notification model, which cannot be implemented efficiently on windows	4280	notification model, which cannot be implemented efficiently on windows
3346	(Microsoft monopoly games).	4281	(due to Microsoft monopoly games).
3347		4282
3348	A typical way to use libev under windows is to embed it (see the embedding	4283	A typical way to use libev under windows is to embed it (see the embedding
3349	section for details) and use the following F<evwrap.h> header file instead	4284	section for details) and use the following F<evwrap.h> header file instead
3350	of F<ev.h>:	4285	of F<ev.h>:
3351		4286
…		…
3353	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	4288	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3354		4289
3355	#include "ev.h"	4290	#include "ev.h"
3356		4291
3357	And compile the following F<evwrap.c> file into your project (make sure	4292	And compile the following F<evwrap.c> file into your project (make sure
3358	you do I<not> compile the F<ev.c> or any other embedded soruce files!):	4293	you do I<not> compile the F<ev.c> or any other embedded source files!):
3359		4294
3360	#include "evwrap.h"	4295	#include "evwrap.h"
3361	#include "ev.c"	4296	#include "ev.c"
3362		4297
3363	=over 4	4298	=over 4
…		…
3387		4322
3388	Early versions of winsocket's select only supported waiting for a maximum	4323	Early versions of winsocket's select only supported waiting for a maximum
3389	of C<64> handles (probably owning to the fact that all windows kernels	4324	of C<64> handles (probably owning to the fact that all windows kernels
3390	can only wait for C<64> things at the same time internally; Microsoft	4325	can only wait for C<64> things at the same time internally; Microsoft
3391	recommends spawning a chain of threads and wait for 63 handles and the	4326	recommends spawning a chain of threads and wait for 63 handles and the
3392	previous thread in each. Great).	4327	previous thread in each. Sounds great!).
3393		4328
3394	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4329	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3395	to some high number (e.g. C<2048>) before compiling the winsocket select	4330	to some high number (e.g. C<2048>) before compiling the winsocket select
3396	call (which might be in libev or elsewhere, for example, perl does its own	4331	call (which might be in libev or elsewhere, for example, perl and many
3397	select emulation on windows).	4332	other interpreters do their own select emulation on windows).
3398		4333
3399	Another limit is the number of file descriptors in the Microsoft runtime	4334	Another limit is the number of file descriptors in the Microsoft runtime
3400	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4335	libraries, which by default is C<64> (there must be a hidden I<64>
3401	or something like this inside Microsoft). You can increase this by calling	4336	fetish or something like this inside Microsoft). You can increase this
3402	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4337	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3403	arbitrary limit), but is broken in many versions of the Microsoft runtime	4338	(another arbitrary limit), but is broken in many versions of the Microsoft
3404	libraries.
3405
3406	This might get you to about C<512> or C<2048> sockets (depending on	4339	runtime libraries. This might get you to about C<512> or C<2048> sockets
3407	windows version and/or the phase of the moon). To get more, you need to	4340	(depending on windows version and/or the phase of the moon). To get more,
3408	wrap all I/O functions and provide your own fd management, but the cost of	4341	you need to wrap all I/O functions and provide your own fd management, but
3409	calling select (O(n²)) will likely make this unworkable.	4342	the cost of calling select (O(n²)) will likely make this unworkable.
3410		4343
3411	=back	4344	=back
3412		4345
3413
3414	=head1 PORTABILITY REQUIREMENTS	4346	=head2 PORTABILITY REQUIREMENTS
3415		4347
3416	In addition to a working ISO-C implementation, libev relies on a few	4348	In addition to a working ISO-C implementation and of course the
3417	additional extensions:	4349	backend-specific APIs, libev relies on a few additional extensions:
3418		4350
3419	=over 4	4351	=over 4
3420		4352
3421	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	4353	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3422	calling conventions regardless of C<ev_watcher_type *>.	4354	calling conventions regardless of C<ev_watcher_type *>.
…		…
3428	calls them using an C<ev_watcher *> internally.	4360	calls them using an C<ev_watcher *> internally.
3429		4361
3430	=item C<sig_atomic_t volatile> must be thread-atomic as well	4362	=item C<sig_atomic_t volatile> must be thread-atomic as well
3431		4363
3432	The type C<sig_atomic_t volatile> (or whatever is defined as	4364	The type C<sig_atomic_t volatile> (or whatever is defined as
3433	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	4365	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3434	threads. This is not part of the specification for C<sig_atomic_t>, but is	4366	threads. This is not part of the specification for C<sig_atomic_t>, but is
3435	believed to be sufficiently portable.	4367	believed to be sufficiently portable.
3436		4368
3437	=item C<sigprocmask> must work in a threaded environment	4369	=item C<sigprocmask> must work in a threaded environment
3438		4370
…		…
3447	except the initial one, and run the default loop in the initial thread as	4379	except the initial one, and run the default loop in the initial thread as
3448	well.	4380	well.
3449		4381
3450	=item C<long> must be large enough for common memory allocation sizes	4382	=item C<long> must be large enough for common memory allocation sizes
3451		4383
3452	To improve portability and simplify using libev, libev uses C<long>	4384	To improve portability and simplify its API, libev uses C<long> internally
3453	internally instead of C<size_t> when allocating its data structures. On	4385	instead of C<size_t> when allocating its data structures. On non-POSIX
3454	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4386	systems (Microsoft...) this might be unexpectedly low, but is still at
3455	is still at least 31 bits everywhere, which is enough for hundreds of	4387	least 31 bits everywhere, which is enough for hundreds of millions of
3456	millions of watchers.	4388	watchers.
3457		4389
3458	=item C<double> must hold a time value in seconds with enough accuracy	4390	=item C<double> must hold a time value in seconds with enough accuracy
3459		4391
3460	The type C<double> is used to represent timestamps. It is required to	4392	The type C<double> is used to represent timestamps. It is required to
3461	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4393	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
3462	enough for at least into the year 4000. This requirement is fulfilled by	4394	enough for at least into the year 4000. This requirement is fulfilled by
3463	implementations implementing IEEE 754 (basically all existing ones).	4395	implementations implementing IEEE 754, which is basically all existing
		4396	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4397	2200.
3464		4398
3465	=back	4399	=back
3466		4400
3467	If you know of other additional requirements drop me a note.	4401	If you know of other additional requirements drop me a note.
3468		4402
3469		4403
3470	=head1 COMPILER WARNINGS	4404	=head1 ALGORITHMIC COMPLEXITIES
3471		4405
3472	Depending on your compiler and compiler settings, you might get no or a	4406	In this section the complexities of (many of) the algorithms used inside
3473	lot of warnings when compiling libev code. Some people are apparently	4407	libev will be documented. For complexity discussions about backends see
3474	scared by this.	4408	the documentation for C<ev_default_init>.
3475		4409
3476	However, these are unavoidable for many reasons. For one, each compiler	4410	All of the following are about amortised time: If an array needs to be
3477	has different warnings, and each user has different tastes regarding	4411	extended, libev needs to realloc and move the whole array, but this
3478	warning options. "Warn-free" code therefore cannot be a goal except when	4412	happens asymptotically rarer with higher number of elements, so O(1) might
3479	targeting a specific compiler and compiler-version.	4413	mean that libev does a lengthy realloc operation in rare cases, but on
		4414	average it is much faster and asymptotically approaches constant time.
3480		4415
3481	Another reason is that some compiler warnings require elaborate	4416	=over 4
3482	workarounds, or other changes to the code that make it less clear and less
3483	maintainable.
3484		4417
3485	And of course, some compiler warnings are just plain stupid, or simply	4418	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3486	wrong (because they don't actually warn about the condition their message
3487	seems to warn about).
3488		4419
3489	While libev is written to generate as few warnings as possible,	4420	This means that, when you have a watcher that triggers in one hour and
3490	"warn-free" code is not a goal, and it is recommended not to build libev	4421	there are 100 watchers that would trigger before that, then inserting will
3491	with any compiler warnings enabled unless you are prepared to cope with	4422	have to skip roughly seven (C<ld 100>) of these watchers.
3492	them (e.g. by ignoring them). Remember that warnings are just that:
3493	warnings, not errors, or proof of bugs.
3494		4423
		4424	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3495		4425
3496	=head1 VALGRIND	4426	That means that changing a timer costs less than removing/adding them,
		4427	as only the relative motion in the event queue has to be paid for.
3497		4428
3498	Valgrind has a special section here because it is a popular tool that is	4429	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3499	highly useful, but valgrind reports are very hard to interpret.
3500		4430
3501	If you think you found a bug (memory leak, uninitialised data access etc.)	4431	These just add the watcher into an array or at the head of a list.
3502	in libev, then check twice: If valgrind reports something like:
3503		4432
3504	==2274== definitely lost: 0 bytes in 0 blocks.	4433	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3505	==2274== possibly lost: 0 bytes in 0 blocks.
3506	==2274== still reachable: 256 bytes in 1 blocks.
3507		4434
3508	Then there is no memory leak. Similarly, under some circumstances,	4435	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3509	valgrind might report kernel bugs as if it were a bug in libev, or it
3510	might be confused (it is a very good tool, but only a tool).
3511		4436
3512	If you are unsure about something, feel free to contact the mailing list	4437	These watchers are stored in lists, so they need to be walked to find the
3513	with the full valgrind report and an explanation on why you think this is	4438	correct watcher to remove. The lists are usually short (you don't usually
3514	a bug in libev. However, don't be annoyed when you get a brisk "this is	4439	have many watchers waiting for the same fd or signal: one is typical, two
3515	no bug" answer and take the chance of learning how to interpret valgrind	4440	is rare).
3516	properly.
3517		4441
3518	If you need, for some reason, empty reports from valgrind for your project	4442	=item Finding the next timer in each loop iteration: O(1)
3519	I suggest using suppression lists.
3520		4443
		4444	By virtue of using a binary or 4-heap, the next timer is always found at a
		4445	fixed position in the storage array.
		4446
		4447	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4448
		4449	A change means an I/O watcher gets started or stopped, which requires
		4450	libev to recalculate its status (and possibly tell the kernel, depending
		4451	on backend and whether C<ev_io_set> was used).
		4452
		4453	=item Activating one watcher (putting it into the pending state): O(1)
		4454
		4455	=item Priority handling: O(number_of_priorities)
		4456
		4457	Priorities are implemented by allocating some space for each
		4458	priority. When doing priority-based operations, libev usually has to
		4459	linearly search all the priorities, but starting/stopping and activating
		4460	watchers becomes O(1) with respect to priority handling.
		4461
		4462	=item Sending an ev_async: O(1)
		4463
		4464	=item Processing ev_async_send: O(number_of_async_watchers)
		4465
		4466	=item Processing signals: O(max_signal_number)
		4467
		4468	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4469	calls in the current loop iteration. Checking for async and signal events
		4470	involves iterating over all running async watchers or all signal numbers.
		4471
		4472	=back
		4473
		4474
		4475	=head1 GLOSSARY
		4476
		4477	=over 4
		4478
		4479	=item active
		4480
		4481	A watcher is active as long as it has been started (has been attached to
		4482	an event loop) but not yet stopped (disassociated from the event loop).
		4483
		4484	=item application
		4485
		4486	In this document, an application is whatever is using libev.
		4487
		4488	=item callback
		4489
		4490	The address of a function that is called when some event has been
		4491	detected. Callbacks are being passed the event loop, the watcher that
		4492	received the event, and the actual event bitset.
		4493
		4494	=item callback invocation
		4495
		4496	The act of calling the callback associated with a watcher.
		4497
		4498	=item event
		4499
		4500	A change of state of some external event, such as data now being available
		4501	for reading on a file descriptor, time having passed or simply not having
		4502	any other events happening anymore.
		4503
		4504	In libev, events are represented as single bits (such as C<EV_READ> or
		4505	C<EV_TIMEOUT>).
		4506
		4507	=item event library
		4508
		4509	A software package implementing an event model and loop.
		4510
		4511	=item event loop
		4512
		4513	An entity that handles and processes external events and converts them
		4514	into callback invocations.
		4515
		4516	=item event model
		4517
		4518	The model used to describe how an event loop handles and processes
		4519	watchers and events.
		4520
		4521	=item pending
		4522
		4523	A watcher is pending as soon as the corresponding event has been detected,
		4524	and stops being pending as soon as the watcher will be invoked or its
		4525	pending status is explicitly cleared by the application.
		4526
		4527	A watcher can be pending, but not active. Stopping a watcher also clears
		4528	its pending status.
		4529
		4530	=item real time
		4531
		4532	The physical time that is observed. It is apparently strictly monotonic :)
		4533
		4534	=item wall-clock time
		4535
		4536	The time and date as shown on clocks. Unlike real time, it can actually
		4537	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4538	clock.
		4539
		4540	=item watcher
		4541
		4542	A data structure that describes interest in certain events. Watchers need
		4543	to be started (attached to an event loop) before they can receive events.
		4544
		4545	=item watcher invocation
		4546
		4547	The act of calling the callback associated with a watcher.
		4548
		4549	=back
3521		4550
3522	=head1 AUTHOR	4551	=head1 AUTHOR
3523		4552
3524	Marc Lehmann <libev@schmorp.de>.	4553	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3525		4554

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