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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_NOSIGFD>
		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)
		415
		416	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		417	kernels).
374		418
375	For few fds, this backend is a bit little slower than poll and select,	419	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	420	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),	421	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	422	epoll scales either O(1) or O(active_fds).
379	of shortcomings, such as silently dropping events in some hard-to-detect	423
380	cases and requiring a system call per fd change, no fork support and bad	424	The epoll mechanism deserves honorable mention as the most misdesigned
381	support for dup.	425	of the more advanced event mechanisms: mere annoyances include silently
		426	dropping file descriptors, requiring a system call per change per file
		427	descriptor (and unnecessary guessing of parameters), problems with dup and
		428	so on. The biggest issue is fork races, however - if a program forks then
		429	I<both> parent and child process have to recreate the epoll set, which can
		430	take considerable time (one syscall per file descriptor) and is of course
		431	hard to detect.
		432
		433	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		434	of course I<doesn't>, and epoll just loves to report events for totally
		435	I<different> file descriptors (even already closed ones, so one cannot
		436	even remove them from the set) than registered in the set (especially
		437	on SMP systems). Libev tries to counter these spurious notifications by
		438	employing an additional generation counter and comparing that against the
		439	events to filter out spurious ones, recreating the set when required.
382		440
383	While stopping, setting and starting an I/O watcher in the same iteration	441	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	442	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	443	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	444	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
387	very well if you register events for both fds.	445	file descriptors might not work very well if you register events for both
388		446	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		447
393	Best performance from this backend is achieved by not unregistering all	448	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.	449	watchers for a file descriptor until it has been closed, if possible,
395	keep at least one watcher active per fd at all times.	450	i.e. keep at least one watcher active per fd at all times. Stopping and
		451	starting a watcher (without re-setting it) also usually doesn't cause
		452	extra overhead. A fork can both result in spurious notifications as well
		453	as in libev having to destroy and recreate the epoll object, which can
		454	take considerable time and thus should be avoided.
		455
		456	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		457	faster than epoll for maybe up to a hundred file descriptors, depending on
		458	the usage. So sad.
396		459
397	While nominally embeddable in other event loops, this feature is broken in	460	While nominally embeddable in other event loops, this feature is broken in
398	all kernel versions tested so far.	461	all kernel versions tested so far.
		462
		463	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		464	C<EVBACKEND_POLL>.
399		465
400	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	466	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
401		467
402	Kqueue deserves special mention, as at the time of this writing, it	468	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	469	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	470	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"	471	it's completely useless). Unlike epoll, however, whose brokenness
		472	is by design, these kqueue bugs can (and eventually will) be fixed
		473	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	474	"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)	475	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
408	system like NetBSD.	476	system like NetBSD.
409		477
410	You still can embed kqueue into a normal poll or select backend and use it	478	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	479	only for sockets (after having made sure that sockets work with kqueue on
…		…
413		481
414	It scales in the same way as the epoll backend, but the interface to the	482	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	483	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	484	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	485	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	486	two event changes per incident. Support for C<fork ()> is very bad (but
419	drops fds silently in similarly hard-to-detect cases.	487	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		488	cases
420		489
421	This backend usually performs well under most conditions.	490	This backend usually performs well under most conditions.
422		491
423	While nominally embeddable in other event loops, this doesn't work	492	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	493	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	494	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	495	(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	496	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
428	sockets.	497	also broken on OS X)) and, did I mention it, using it only for sockets.
		498
		499	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		500	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		501	C<NOTE_EOF>.
429		502
430	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	503	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
431		504
432	This is not implemented yet (and might never be, unless you send me an	505	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	506	implementation). According to reports, C</dev/poll> only supports sockets
…		…
446	While this backend scales well, it requires one system call per active	519	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	520	file descriptor per loop iteration. For small and medium numbers of file
448	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	521	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
449	might perform better.	522	might perform better.
450		523
451	On the positive side, ignoring the spurious readiness notifications, this	524	On the positive side, with the exception of the spurious readiness
452	backend actually performed to specification in all tests and is fully	525	notifications, this backend actually performed fully to specification
453	embeddable, which is a rare feat among the OS-specific backends.	526	in all tests and is fully embeddable, which is a rare feat among the
		527	OS-specific backends (I vastly prefer correctness over speed hacks).
		528
		529	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		530	C<EVBACKEND_POLL>.
454		531
455	=item C<EVBACKEND_ALL>	532	=item C<EVBACKEND_ALL>
456		533
457	Try all backends (even potentially broken ones that wouldn't be tried	534	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	535	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
460		537
461	It is definitely not recommended to use this flag.	538	It is definitely not recommended to use this flag.
462		539
463	=back	540	=back
464		541
465	If one or more of these are or'ed into the flags value, then only these	542	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	543	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.	544	here). If none are specified, all backends in C<ev_recommended_backends
		545	()> will be tried.
468		546
469	The most typical usage is like this:	547	Example: This is the most typical usage.
470		548
471	if (!ev_default_loop (0))	549	if (!ev_default_loop (0))
472	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	550	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
473		551
474	Restrict libev to the select and poll backends, and do not allow	552	Example: Restrict libev to the select and poll backends, and do not allow
475	environment settings to be taken into account:	553	environment settings to be taken into account:
476		554
477	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	555	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
478		556
479	Use whatever libev has to offer, but make sure that kqueue is used if	557	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	558	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):	559	private event loop and only if you know the OS supports your types of
		560	fds):
482		561
483	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	562	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
484		563
485	=item struct ev_loop *ev_loop_new (unsigned int flags)	564	=item struct ev_loop *ev_loop_new (unsigned int flags)
486		565
…		…
507	responsibility to either stop all watchers cleanly yourself I<before>	586	responsibility to either stop all watchers cleanly yourself I<before>
508	calling this function, or cope with the fact afterwards (which is usually	587	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	588	the easiest thing, you can just ignore the watchers and/or C<free ()> them
510	for example).	589	for example).
511		590
512	Note that certain global state, such as signal state, will not be freed by	591	Note that certain global state, such as signal state (and installed signal
513	this function, and related watchers (such as signal and child watchers)	592	handlers), will not be freed by this function, and related watchers (such
514	would need to be stopped manually.	593	as signal and child watchers) would need to be stopped manually.
515		594
516	In general it is not advisable to call this function except in the	595	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	596	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	597	pipe fds. If you need dynamically allocated loops it is better to use
519	C<ev_loop_new> and C<ev_loop_destroy>).	598	C<ev_loop_new> and C<ev_loop_destroy>.
520		599
521	=item ev_loop_destroy (loop)	600	=item ev_loop_destroy (loop)
522		601
523	Like C<ev_default_destroy>, but destroys an event loop created by an	602	Like C<ev_default_destroy>, but destroys an event loop created by an
524	earlier call to C<ev_loop_new>.	603	earlier call to C<ev_loop_new>.
…		…
544		623
545	=item ev_loop_fork (loop)	624	=item ev_loop_fork (loop)
546		625
547	Like C<ev_default_fork>, but acts on an event loop created by	626	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	627	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.	628	after fork that you want to re-use in the child, and how you do this is
		629	entirely your own problem.
550		630
551	=item int ev_is_default_loop (loop)	631	=item int ev_is_default_loop (loop)
552		632
553	Returns true when the given loop actually is the default loop, false otherwise.	633	Returns true when the given loop is, in fact, the default loop, and false
		634	otherwise.
554		635
555	=item unsigned int ev_loop_count (loop)	636	=item unsigned int ev_loop_count (loop)
556		637
557	Returns the count of loop iterations for the loop, which is identical to	638	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	639	the number of times libev did poll for new events. It starts at C<0> and
559	happily wraps around with enough iterations.	640	happily wraps around with enough iterations.
560		641
561	This value can sometimes be useful as a generation counter of sorts (it	642	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	643	"ticks" the number of loop iterations), as it roughly corresponds with
563	C<ev_prepare> and C<ev_check> calls.	644	C<ev_prepare> and C<ev_check> calls.
		645
		646	=item unsigned int ev_loop_depth (loop)
		647
		648	Returns the number of times C<ev_loop> was entered minus the number of
		649	times C<ev_loop> was exited, in other words, the recursion depth.
		650
		651	Outside C<ev_loop>, this number is zero. In a callback, this number is
		652	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),
		653	in which case it is higher.
		654
		655	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread
		656	etc.), doesn't count as exit.
564		657
565	=item unsigned int ev_backend (loop)	658	=item unsigned int ev_backend (loop)
566		659
567	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	660	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
568	use.	661	use.
…		…
573	received events and started processing them. This timestamp does not	666	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	667	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	668	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).	669	event occurring (or more correctly, libev finding out about it).
577		670
		671	=item ev_now_update (loop)
		672
		673	Establishes the current time by querying the kernel, updating the time
		674	returned by C<ev_now ()> in the progress. This is a costly operation and
		675	is usually done automatically within C<ev_loop ()>.
		676
		677	This function is rarely useful, but when some event callback runs for a
		678	very long time without entering the event loop, updating libev's idea of
		679	the current time is a good idea.
		680
		681	See also L<The special problem of time updates> in the C<ev_timer> section.
		682
		683	=item ev_suspend (loop)
		684
		685	=item ev_resume (loop)
		686
		687	These two functions suspend and resume a loop, for use when the loop is
		688	not used for a while and timeouts should not be processed.
		689
		690	A typical use case would be an interactive program such as a game: When
		691	the user presses C<^Z> to suspend the game and resumes it an hour later it
		692	would be best to handle timeouts as if no time had actually passed while
		693	the program was suspended. This can be achieved by calling C<ev_suspend>
		694	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		695	C<ev_resume> directly afterwards to resume timer processing.
		696
		697	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		698	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		699	will be rescheduled (that is, they will lose any events that would have
		700	occured while suspended).
		701
		702	After calling C<ev_suspend> you B<must not> call I<any> function on the
		703	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		704	without a previous call to C<ev_suspend>.
		705
		706	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		707	event loop time (see C<ev_now_update>).
		708
578	=item ev_loop (loop, int flags)	709	=item ev_loop (loop, int flags)
579		710
580	Finally, this is it, the event handler. This function usually is called	711	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	712	after you have initialised all your watchers and you want to start
582	events.	713	handling events.
583		714
584	If the flags argument is specified as C<0>, it will not return until	715	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.	716	either no event watchers are active anymore or C<ev_unloop> was called.
586		717
587	Please note that an explicit C<ev_unloop> is usually better than	718	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	719	relying on all watchers to be stopped when deciding when a program has
589	finished (especially in interactive programs), but having a program that	720	finished (especially in interactive programs), but having a program
590	automatically loops as long as it has to and no longer by virtue of	721	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.	722	of relying on its watchers stopping correctly, that is truly a thing of
		723	beauty.
592		724
593	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	725	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	726	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.	727	process in case there are no events and will return after one iteration of
		728	the loop.
596		729
597	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	730	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	731	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	732	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	733	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	734	user-registered callback will be called), and will return after one
		735	iteration of the loop.
		736
		737	This is useful if you are waiting for some external event in conjunction
		738	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	739	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.	740	usually a better approach for this kind of thing.
604		741
605	Here are the gory details of what C<ev_loop> does:	742	Here are the gory details of what C<ev_loop> does:
606		743
607	- Before the first iteration, call any pending watchers.	744	- Before the first iteration, call any pending watchers.
608	* If EVFLAG_FORKCHECK was used, check for a fork.	745	* If EVFLAG_FORKCHECK was used, check for a fork.
609	- If a fork was detected, queue and call all fork watchers.	746	- If a fork was detected (by any means), queue and call all fork watchers.
610	- Queue and call all prepare watchers.	747	- Queue and call all prepare watchers.
611	- If we have been forked, recreate the kernel state.	748	- If we have been forked, detach and recreate the kernel state
		749	as to not disturb the other process.
612	- Update the kernel state with all outstanding changes.	750	- Update the kernel state with all outstanding changes.
613	- Update the "event loop time".	751	- Update the "event loop time" (ev_now ()).
614	- Calculate for how long to sleep or block, if at all	752	- Calculate for how long to sleep or block, if at all
615	(active idle watchers, EVLOOP_NONBLOCK or not having	753	(active idle watchers, EVLOOP_NONBLOCK or not having
616	any active watchers at all will result in not sleeping).	754	any active watchers at all will result in not sleeping).
617	- Sleep if the I/O and timer collect interval say so.	755	- Sleep if the I/O and timer collect interval say so.
618	- Block the process, waiting for any events.	756	- Block the process, waiting for any events.
619	- Queue all outstanding I/O (fd) events.	757	- Queue all outstanding I/O (fd) events.
620	- Update the "event loop time" and do time jump handling.	758	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
621	- Queue all outstanding timers.	759	- Queue all expired timers.
622	- Queue all outstanding periodics.	760	- Queue all expired periodics.
623	- If no events are pending now, queue all idle watchers.	761	- Unless any events are pending now, queue all idle watchers.
624	- Queue all check watchers.	762	- Queue all check watchers.
625	- Call all queued watchers in reverse order (i.e. check watchers first).	763	- Call all queued watchers in reverse order (i.e. check watchers first).
626	Signals and child watchers are implemented as I/O watchers, and will	764	Signals and child watchers are implemented as I/O watchers, and will
627	be handled here by queueing them when their watcher gets executed.	765	be handled here by queueing them when their watcher gets executed.
628	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	766	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
633	anymore.	771	anymore.
634		772
635	... queue jobs here, make sure they register event watchers as long	773	... queue jobs here, make sure they register event watchers as long
636	... as they still have work to do (even an idle watcher will do..)	774	... as they still have work to do (even an idle watcher will do..)
637	ev_loop (my_loop, 0);	775	ev_loop (my_loop, 0);
638	... jobs done. yeah!	776	... jobs done or somebody called unloop. yeah!
639		777
640	=item ev_unloop (loop, how)	778	=item ev_unloop (loop, how)
641		779
642	Can be used to make a call to C<ev_loop> return early (but only after it	780	Can be used to make a call to C<ev_loop> return early (but only after it
643	has processed all outstanding events). The C<how> argument must be either	781	has processed all outstanding events). The C<how> argument must be either
644	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	782	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
645	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	783	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
646		784
647	This "unloop state" will be cleared when entering C<ev_loop> again.	785	This "unloop state" will be cleared when entering C<ev_loop> again.
648		786
		787	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		788
649	=item ev_ref (loop)	789	=item ev_ref (loop)
650		790
651	=item ev_unref (loop)	791	=item ev_unref (loop)
652		792
653	Ref/unref can be used to add or remove a reference count on the event	793	Ref/unref can be used to add or remove a reference count on the event
654	loop: Every watcher keeps one reference, and as long as the reference	794	loop: Every watcher keeps one reference, and as long as the reference
655	count is nonzero, C<ev_loop> will not return on its own. If you have	795	count is nonzero, C<ev_loop> will not return on its own.
		796
656	a watcher you never unregister that should not keep C<ev_loop> from	797	If you have a watcher you never unregister that should not keep C<ev_loop>
657	returning, ev_unref() after starting, and ev_ref() before stopping it. For	798	from returning, call ev_unref() after starting, and ev_ref() before
		799	stopping it.
		800
658	example, libev itself uses this for its internal signal pipe: It is not	801	As an example, libev itself uses this for its internal signal pipe: It
659	visible to the libev user and should not keep C<ev_loop> from exiting if	802	is not visible to the libev user and should not keep C<ev_loop> from
660	no event watchers registered by it are active. It is also an excellent	803	exiting if no event watchers registered by it are active. It is also an
661	way to do this for generic recurring timers or from within third-party	804	excellent way to do this for generic recurring timers or from within
662	libraries. Just remember to I<unref after start> and I<ref before stop>	805	third-party libraries. Just remember to I<unref after start> and I<ref
663	(but only if the watcher wasn't active before, or was active before,	806	before stop> (but only if the watcher wasn't active before, or was active
664	respectively).	807	before, respectively. Note also that libev might stop watchers itself
		808	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		809	in the callback).
665		810
666	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	811	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
667	running when nothing else is active.	812	running when nothing else is active.
668		813
669	struct ev_signal exitsig;	814	ev_signal exitsig;
670	ev_signal_init (&exitsig, sig_cb, SIGINT);	815	ev_signal_init (&exitsig, sig_cb, SIGINT);
671	ev_signal_start (loop, &exitsig);	816	ev_signal_start (loop, &exitsig);
672	evf_unref (loop);	817	evf_unref (loop);
673		818
674	Example: For some weird reason, unregister the above signal handler again.	819	Example: For some weird reason, unregister the above signal handler again.
…		…
679	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	824	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
680		825
681	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	826	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
682		827
683	These advanced functions influence the time that libev will spend waiting	828	These advanced functions influence the time that libev will spend waiting
684	for events. Both are by default C<0>, meaning that libev will try to	829	for events. Both time intervals are by default C<0>, meaning that libev
685	invoke timer/periodic callbacks and I/O callbacks with minimum latency.	830	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		831	latency.
686		832
687	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	833	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
688	allows libev to delay invocation of I/O and timer/periodic callbacks to	834	allows libev to delay invocation of I/O and timer/periodic callbacks
689	increase efficiency of loop iterations.	835	to increase efficiency of loop iterations (or to increase power-saving
		836	opportunities).
690		837
691	The background is that sometimes your program runs just fast enough to	838	The idea is that sometimes your program runs just fast enough to handle
692	handle one (or very few) event(s) per loop iteration. While this makes	839	one (or very few) event(s) per loop iteration. While this makes the
693	the program responsive, it also wastes a lot of CPU time to poll for new	840	program responsive, it also wastes a lot of CPU time to poll for new
694	events, especially with backends like C<select ()> which have a high	841	events, especially with backends like C<select ()> which have a high
695	overhead for the actual polling but can deliver many events at once.	842	overhead for the actual polling but can deliver many events at once.
696		843
697	By setting a higher I<io collect interval> you allow libev to spend more	844	By setting a higher I<io collect interval> you allow libev to spend more
698	time collecting I/O events, so you can handle more events per iteration,	845	time collecting I/O events, so you can handle more events per iteration,
699	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	846	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
700	C<ev_timer>) will be not affected. Setting this to a non-null value will	847	C<ev_timer>) will be not affected. Setting this to a non-null value will
701	introduce an additional C<ev_sleep ()> call into most loop iterations.	848	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		849	sleep time ensures that libev will not poll for I/O events more often then
		850	once per this interval, on average.
702		851
703	Likewise, by setting a higher I<timeout collect interval> you allow libev	852	Likewise, by setting a higher I<timeout collect interval> you allow libev
704	to spend more time collecting timeouts, at the expense of increased	853	to spend more time collecting timeouts, at the expense of increased
705	latency (the watcher callback will be called later). C<ev_io> watchers	854	latency/jitter/inexactness (the watcher callback will be called
706	will not be affected. Setting this to a non-null value will not introduce	855	later). C<ev_io> watchers will not be affected. Setting this to a non-null
707	any overhead in libev.	856	value will not introduce any overhead in libev.
708		857
709	Many (busy) programs can usually benefit by setting the I/O collect	858	Many (busy) programs can usually benefit by setting the I/O collect
710	interval to a value near C<0.1> or so, which is often enough for	859	interval to a value near C<0.1> or so, which is often enough for
711	interactive servers (of course not for games), likewise for timeouts. It	860	interactive servers (of course not for games), likewise for timeouts. It
712	usually doesn't make much sense to set it to a lower value than C<0.01>,	861	usually doesn't make much sense to set it to a lower value than C<0.01>,
713	as this approaches the timing granularity of most systems.	862	as this approaches the timing granularity of most systems. Note that if
		863	you do transactions with the outside world and you can't increase the
		864	parallelity, then this setting will limit your transaction rate (if you
		865	need to poll once per transaction and the I/O collect interval is 0.01,
		866	then you can't do more than 100 transations per second).
		867
		868	Setting the I<timeout collect interval> can improve the opportunity for
		869	saving power, as the program will "bundle" timer callback invocations that
		870	are "near" in time together, by delaying some, thus reducing the number of
		871	times the process sleeps and wakes up again. Another useful technique to
		872	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		873	they fire on, say, one-second boundaries only.
		874
		875	Example: we only need 0.1s timeout granularity, and we wish not to poll
		876	more often than 100 times per second:
		877
		878	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		879	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		880
		881	=item ev_invoke_pending (loop)
		882
		883	This call will simply invoke all pending watchers while resetting their
		884	pending state. Normally, C<ev_loop> does this automatically when required,
		885	but when overriding the invoke callback this call comes handy.
		886
		887	=item int ev_pending_count (loop)
		888
		889	Returns the number of pending watchers - zero indicates that no watchers
		890	are pending.
		891
		892	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		893
		894	This overrides the invoke pending functionality of the loop: Instead of
		895	invoking all pending watchers when there are any, C<ev_loop> will call
		896	this callback instead. This is useful, for example, when you want to
		897	invoke the actual watchers inside another context (another thread etc.).
		898
		899	If you want to reset the callback, use C<ev_invoke_pending> as new
		900	callback.
		901
		902	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		903
		904	Sometimes you want to share the same loop between multiple threads. This
		905	can be done relatively simply by putting mutex_lock/unlock calls around
		906	each call to a libev function.
		907
		908	However, C<ev_loop> can run an indefinite time, so it is not feasible to
		909	wait for it to return. One way around this is to wake up the loop via
		910	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>
		911	and I<acquire> callbacks on the loop.
		912
		913	When set, then C<release> will be called just before the thread is
		914	suspended waiting for new events, and C<acquire> is called just
		915	afterwards.
		916
		917	Ideally, C<release> will just call your mutex_unlock function, and
		918	C<acquire> will just call the mutex_lock function again.
		919
		920	While event loop modifications are allowed between invocations of
		921	C<release> and C<acquire> (that's their only purpose after all), no
		922	modifications done will affect the event loop, i.e. adding watchers will
		923	have no effect on the set of file descriptors being watched, or the time
		924	waited. USe an C<ev_async> watcher to wake up C<ev_loop> when you want it
		925	to take note of any changes you made.
		926
		927	In theory, threads executing C<ev_loop> will be async-cancel safe between
		928	invocations of C<release> and C<acquire>.
		929
		930	See also the locking example in the C<THREADS> section later in this
		931	document.
		932
		933	=item ev_set_userdata (loop, void *data)
		934
		935	=item ev_userdata (loop)
		936
		937	Set and retrieve a single C<void *> associated with a loop. When
		938	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		939	C<0.>
		940
		941	These two functions can be used to associate arbitrary data with a loop,
		942	and are intended solely for the C<invoke_pending_cb>, C<release> and
		943	C<acquire> callbacks described above, but of course can be (ab-)used for
		944	any other purpose as well.
714		945
715	=item ev_loop_verify (loop)	946	=item ev_loop_verify (loop)
716		947
717	This function only does something when C<EV_VERIFY> support has been	948	This function only does something when C<EV_VERIFY> support has been
718	compiled in. It tries to go through all internal structures and checks	949	compiled in, which is the default for non-minimal builds. It tries to go
719	them for validity. If anything is found to be inconsistent, it will print	950	through all internal structures and checks them for validity. If anything
720	an error message to standard error and call C<abort ()>.	951	is found to be inconsistent, it will print an error message to standard
		952	error and call C<abort ()>.
721		953
722	This can be used to catch bugs inside libev itself: under normal	954	This can be used to catch bugs inside libev itself: under normal
723	circumstances, this function will never abort as of course libev keeps its	955	circumstances, this function will never abort as of course libev keeps its
724	data structures consistent.	956	data structures consistent.
725		957
726	=back	958	=back
727		959
728		960
729	=head1 ANATOMY OF A WATCHER	961	=head1 ANATOMY OF A WATCHER
730		962
		963	In the following description, uppercase C<TYPE> in names stands for the
		964	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		965	watchers and C<ev_io_start> for I/O watchers.
		966
731	A watcher is a structure that you create and register to record your	967	A watcher is a structure that you create and register to record your
732	interest in some event. For instance, if you want to wait for STDIN to	968	interest in some event. For instance, if you want to wait for STDIN to
733	become readable, you would create an C<ev_io> watcher for that:	969	become readable, you would create an C<ev_io> watcher for that:
734		970
735	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	971	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
736	{	972	{
737	ev_io_stop (w);	973	ev_io_stop (w);
738	ev_unloop (loop, EVUNLOOP_ALL);	974	ev_unloop (loop, EVUNLOOP_ALL);
739	}	975	}
740		976
741	struct ev_loop *loop = ev_default_loop (0);	977	struct ev_loop *loop = ev_default_loop (0);
		978
742	struct ev_io stdin_watcher;	979	ev_io stdin_watcher;
		980
743	ev_init (&stdin_watcher, my_cb);	981	ev_init (&stdin_watcher, my_cb);
744	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	982	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
745	ev_io_start (loop, &stdin_watcher);	983	ev_io_start (loop, &stdin_watcher);
		984
746	ev_loop (loop, 0);	985	ev_loop (loop, 0);
747		986
748	As you can see, you are responsible for allocating the memory for your	987	As you can see, you are responsible for allocating the memory for your
749	watcher structures (and it is usually a bad idea to do this on the stack,	988	watcher structures (and it is I<usually> a bad idea to do this on the
750	although this can sometimes be quite valid).	989	stack).
		990
		991	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		992	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
751		993
752	Each watcher structure must be initialised by a call to C<ev_init	994	Each watcher structure must be initialised by a call to C<ev_init
753	(watcher *, callback)>, which expects a callback to be provided. This	995	(watcher *, callback)>, which expects a callback to be provided. This
754	callback gets invoked each time the event occurs (or, in the case of I/O	996	callback gets invoked each time the event occurs (or, in the case of I/O
755	watchers, each time the event loop detects that the file descriptor given	997	watchers, each time the event loop detects that the file descriptor given
756	is readable and/or writable).	998	is readable and/or writable).
757		999
758	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1000	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
759	with arguments specific to this watcher type. There is also a macro	1001	macro to configure it, with arguments specific to the watcher type. There
760	to combine initialisation and setting in one call: C<< ev_<type>_init	1002	is also a macro to combine initialisation and setting in one call: C<<
761	(watcher *, callback, ...) >>.	1003	ev_TYPE_init (watcher *, callback, ...) >>.
762		1004
763	To make the watcher actually watch out for events, you have to start it	1005	To make the watcher actually watch out for events, you have to start it
764	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	1006	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
765	*) >>), and you can stop watching for events at any time by calling the	1007	*) >>), and you can stop watching for events at any time by calling the
766	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1008	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
767		1009
768	As long as your watcher is active (has been started but not stopped) you	1010	As long as your watcher is active (has been started but not stopped) you
769	must not touch the values stored in it. Most specifically you must never	1011	must not touch the values stored in it. Most specifically you must never
770	reinitialise it or call its C<set> macro.	1012	reinitialise it or call its C<ev_TYPE_set> macro.
771		1013
772	Each and every callback receives the event loop pointer as first, the	1014	Each and every callback receives the event loop pointer as first, the
773	registered watcher structure as second, and a bitset of received events as	1015	registered watcher structure as second, and a bitset of received events as
774	third argument.	1016	third argument.
775		1017
…		…
833		1075
834	=item C<EV_ASYNC>	1076	=item C<EV_ASYNC>
835		1077
836	The given async watcher has been asynchronously notified (see C<ev_async>).	1078	The given async watcher has been asynchronously notified (see C<ev_async>).
837		1079
		1080	=item C<EV_CUSTOM>
		1081
		1082	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1083	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		1084
838	=item C<EV_ERROR>	1085	=item C<EV_ERROR>
839		1086
840	An unspecified error has occurred, the watcher has been stopped. This might	1087	An unspecified error has occurred, the watcher has been stopped. This might
841	happen because the watcher could not be properly started because libev	1088	happen because the watcher could not be properly started because libev
842	ran out of memory, a file descriptor was found to be closed or any other	1089	ran out of memory, a file descriptor was found to be closed or any other
		1090	problem. Libev considers these application bugs.
		1091
843	problem. You best act on it by reporting the problem and somehow coping	1092	You best act on it by reporting the problem and somehow coping with the
844	with the watcher being stopped.	1093	watcher being stopped. Note that well-written programs should not receive
		1094	an error ever, so when your watcher receives it, this usually indicates a
		1095	bug in your program.
845		1096
846	Libev will usually signal a few "dummy" events together with an error,	1097	Libev will usually signal a few "dummy" events together with an error, for
847	for example it might indicate that a fd is readable or writable, and if	1098	example it might indicate that a fd is readable or writable, and if your
848	your callbacks is well-written it can just attempt the operation and cope	1099	callbacks is well-written it can just attempt the operation and cope with
849	with the error from read() or write(). This will not work in multi-threaded	1100	the error from read() or write(). This will not work in multi-threaded
850	programs, though, so beware.	1101	programs, though, as the fd could already be closed and reused for another
		1102	thing, so beware.
851		1103
852	=back	1104	=back
853		1105
854	=head2 GENERIC WATCHER FUNCTIONS	1106	=head2 GENERIC WATCHER FUNCTIONS
855
856	In the following description, C<TYPE> stands for the watcher type,
857	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
858		1107
859	=over 4	1108	=over 4
860		1109
861	=item C<ev_init> (ev_TYPE *watcher, callback)	1110	=item C<ev_init> (ev_TYPE *watcher, callback)
862		1111
…		…
868	which rolls both calls into one.	1117	which rolls both calls into one.
869		1118
870	You can reinitialise a watcher at any time as long as it has been stopped	1119	You can reinitialise a watcher at any time as long as it has been stopped
871	(or never started) and there are no pending events outstanding.	1120	(or never started) and there are no pending events outstanding.
872		1121
873	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1122	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
874	int revents)>.	1123	int revents)>.
		1124
		1125	Example: Initialise an C<ev_io> watcher in two steps.
		1126
		1127	ev_io w;
		1128	ev_init (&w, my_cb);
		1129	ev_io_set (&w, STDIN_FILENO, EV_READ);
875		1130
876	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1131	=item C<ev_TYPE_set> (ev_TYPE *, [args])
877		1132
878	This macro initialises the type-specific parts of a watcher. You need to	1133	This macro initialises the type-specific parts of a watcher. You need to
879	call C<ev_init> at least once before you call this macro, but you can	1134	call C<ev_init> at least once before you call this macro, but you can
…		…
882	difference to the C<ev_init> macro).	1137	difference to the C<ev_init> macro).
883		1138
884	Although some watcher types do not have type-specific arguments	1139	Although some watcher types do not have type-specific arguments
885	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	1140	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
886		1141
		1142	See C<ev_init>, above, for an example.
		1143
887	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1144	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
888		1145
889	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1146	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
890	calls into a single call. This is the most convenient method to initialise	1147	calls into a single call. This is the most convenient method to initialise
891	a watcher. The same limitations apply, of course.	1148	a watcher. The same limitations apply, of course.
892		1149
		1150	Example: Initialise and set an C<ev_io> watcher in one step.
		1151
		1152	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1153
893	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1154	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
894		1155
895	Starts (activates) the given watcher. Only active watchers will receive	1156	Starts (activates) the given watcher. Only active watchers will receive
896	events. If the watcher is already active nothing will happen.	1157	events. If the watcher is already active nothing will happen.
897		1158
		1159	Example: Start the C<ev_io> watcher that is being abused as example in this
		1160	whole section.
		1161
		1162	ev_io_start (EV_DEFAULT_UC, &w);
		1163
898	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1164	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
899		1165
900	Stops the given watcher again (if active) and clears the pending	1166	Stops the given watcher if active, and clears the pending status (whether
		1167	the watcher was active or not).
		1168
901	status. It is possible that stopped watchers are pending (for example,	1169	It is possible that stopped watchers are pending - for example,
902	non-repeating timers are being stopped when they become pending), but	1170	non-repeating timers are being stopped when they become pending - but
903	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1171	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
904	you want to free or reuse the memory used by the watcher it is therefore a	1172	pending. If you want to free or reuse the memory used by the watcher it is
905	good idea to always call its C<ev_TYPE_stop> function.	1173	therefore a good idea to always call its C<ev_TYPE_stop> function.
906		1174
907	=item bool ev_is_active (ev_TYPE *watcher)	1175	=item bool ev_is_active (ev_TYPE *watcher)
908		1176
909	Returns a true value iff the watcher is active (i.e. it has been started	1177	Returns a true value iff the watcher is active (i.e. it has been started
910	and not yet been stopped). As long as a watcher is active you must not modify	1178	and not yet been stopped). As long as a watcher is active you must not modify
…		…
936	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1204	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
937	(default: C<-2>). Pending watchers with higher priority will be invoked	1205	(default: C<-2>). Pending watchers with higher priority will be invoked
938	before watchers with lower priority, but priority will not keep watchers	1206	before watchers with lower priority, but priority will not keep watchers
939	from being executed (except for C<ev_idle> watchers).	1207	from being executed (except for C<ev_idle> watchers).
940		1208
941	This means that priorities are I<only> used for ordering callback
942	invocation after new events have been received. This is useful, for
943	example, to reduce latency after idling, or more often, to bind two
944	watchers on the same event and make sure one is called first.
945
946	If you need to suppress invocation when higher priority events are pending	1209	If you need to suppress invocation when higher priority events are pending
947	you need to look at C<ev_idle> watchers, which provide this functionality.	1210	you need to look at C<ev_idle> watchers, which provide this functionality.
948		1211
949	You I<must not> change the priority of a watcher as long as it is active or	1212	You I<must not> change the priority of a watcher as long as it is active or
950	pending.	1213	pending.
951		1214
		1215	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1216	fine, as long as you do not mind that the priority value you query might
		1217	or might not have been clamped to the valid range.
		1218
952	The default priority used by watchers when no priority has been set is	1219	The default priority used by watchers when no priority has been set is
953	always C<0>, which is supposed to not be too high and not be too low :).	1220	always C<0>, which is supposed to not be too high and not be too low :).
954		1221
955	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1222	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
956	fine, as long as you do not mind that the priority value you query might	1223	priorities.
957	or might not have been adjusted to be within valid range.
958		1224
959	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1225	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
960		1226
961	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1227	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
962	C<loop> nor C<revents> need to be valid as long as the watcher callback	1228	C<loop> nor C<revents> need to be valid as long as the watcher callback
963	can deal with that fact.	1229	can deal with that fact, as both are simply passed through to the
		1230	callback.
964		1231
965	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1232	=item int ev_clear_pending (loop, ev_TYPE *watcher)
966		1233
967	If the watcher is pending, this function returns clears its pending status	1234	If the watcher is pending, this function clears its pending status and
968	and returns its C<revents> bitset (as if its callback was invoked). If the	1235	returns its C<revents> bitset (as if its callback was invoked). If the
969	watcher isn't pending it does nothing and returns C<0>.	1236	watcher isn't pending it does nothing and returns C<0>.
970		1237
		1238	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1239	callback to be invoked, which can be accomplished with this function.
		1240
		1241	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
		1242
		1243	Feeds the given event set into the event loop, as if the specified event
		1244	had happened for the specified watcher (which must be a pointer to an
		1245	initialised but not necessarily started event watcher). Obviously you must
		1246	not free the watcher as long as it has pending events.
		1247
		1248	Stopping the watcher, letting libev invoke it, or calling
		1249	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1250	not started in the first place.
		1251
		1252	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1253	functions that do not need a watcher.
		1254
971	=back	1255	=back
972		1256
973		1257
974	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1258	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
975		1259
976	Each watcher has, by default, a member C<void *data> that you can change	1260	Each watcher has, by default, a member C<void *data> that you can change
977	and read at any time, libev will completely ignore it. This can be used	1261	and read at any time: libev will completely ignore it. This can be used
978	to associate arbitrary data with your watcher. If you need more data and	1262	to associate arbitrary data with your watcher. If you need more data and
979	don't want to allocate memory and store a pointer to it in that data	1263	don't want to allocate memory and store a pointer to it in that data
980	member, you can also "subclass" the watcher type and provide your own	1264	member, you can also "subclass" the watcher type and provide your own
981	data:	1265	data:
982		1266
983	struct my_io	1267	struct my_io
984	{	1268	{
985	struct ev_io io;	1269	ev_io io;
986	int otherfd;	1270	int otherfd;
987	void *somedata;	1271	void *somedata;
988	struct whatever *mostinteresting;	1272	struct whatever *mostinteresting;
989	}	1273	};
		1274
		1275	...
		1276	struct my_io w;
		1277	ev_io_init (&w.io, my_cb, fd, EV_READ);
990		1278
991	And since your callback will be called with a pointer to the watcher, you	1279	And since your callback will be called with a pointer to the watcher, you
992	can cast it back to your own type:	1280	can cast it back to your own type:
993		1281
994	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1282	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
995	{	1283	{
996	struct my_io *w = (struct my_io *)w_;	1284	struct my_io *w = (struct my_io *)w_;
997	...	1285	...
998	}	1286	}
999		1287
1000	More interesting and less C-conformant ways of casting your callback type	1288	More interesting and less C-conformant ways of casting your callback type
1001	instead have been omitted.	1289	instead have been omitted.
1002		1290
1003	Another common scenario is having some data structure with multiple	1291	Another common scenario is to use some data structure with multiple
1004	watchers:	1292	embedded watchers:
1005		1293
1006	struct my_biggy	1294	struct my_biggy
1007	{	1295	{
1008	int some_data;	1296	int some_data;
1009	ev_timer t1;	1297	ev_timer t1;
1010	ev_timer t2;	1298	ev_timer t2;
1011	}	1299	}
1012		1300
1013	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1301	In this case getting the pointer to C<my_biggy> is a bit more
1014	you need to use C<offsetof>:	1302	complicated: Either you store the address of your C<my_biggy> struct
		1303	in the C<data> member of the watcher (for woozies), or you need to use
		1304	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1305	programmers):
1015		1306
1016	#include <stddef.h>	1307	#include <stddef.h>
1017		1308
1018	static void	1309	static void
1019	t1_cb (EV_P_ struct ev_timer *w, int revents)	1310	t1_cb (EV_P_ ev_timer *w, int revents)
1020	{	1311	{
1021	struct my_biggy big = (struct my_biggy *	1312	struct my_biggy big = (struct my_biggy *)
1022	(((char *)w) - offsetof (struct my_biggy, t1));	1313	(((char *)w) - offsetof (struct my_biggy, t1));
1023	}	1314	}
1024		1315
1025	static void	1316	static void
1026	t2_cb (EV_P_ struct ev_timer *w, int revents)	1317	t2_cb (EV_P_ ev_timer *w, int revents)
1027	{	1318	{
1028	struct my_biggy big = (struct my_biggy *	1319	struct my_biggy big = (struct my_biggy *)
1029	(((char *)w) - offsetof (struct my_biggy, t2));	1320	(((char *)w) - offsetof (struct my_biggy, t2));
1030	}	1321	}
		1322
		1323	=head2 WATCHER PRIORITY MODELS
		1324
		1325	Many event loops support I<watcher priorities>, which are usually small
		1326	integers that influence the ordering of event callback invocation
		1327	between watchers in some way, all else being equal.
		1328
		1329	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1330	description for the more technical details such as the actual priority
		1331	range.
		1332
		1333	There are two common ways how these these priorities are being interpreted
		1334	by event loops:
		1335
		1336	In the more common lock-out model, higher priorities "lock out" invocation
		1337	of lower priority watchers, which means as long as higher priority
		1338	watchers receive events, lower priority watchers are not being invoked.
		1339
		1340	The less common only-for-ordering model uses priorities solely to order
		1341	callback invocation within a single event loop iteration: Higher priority
		1342	watchers are invoked before lower priority ones, but they all get invoked
		1343	before polling for new events.
		1344
		1345	Libev uses the second (only-for-ordering) model for all its watchers
		1346	except for idle watchers (which use the lock-out model).
		1347
		1348	The rationale behind this is that implementing the lock-out model for
		1349	watchers is not well supported by most kernel interfaces, and most event
		1350	libraries will just poll for the same events again and again as long as
		1351	their callbacks have not been executed, which is very inefficient in the
		1352	common case of one high-priority watcher locking out a mass of lower
		1353	priority ones.
		1354
		1355	Static (ordering) priorities are most useful when you have two or more
		1356	watchers handling the same resource: a typical usage example is having an
		1357	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1358	timeouts. Under load, data might be received while the program handles
		1359	other jobs, but since timers normally get invoked first, the timeout
		1360	handler will be executed before checking for data. In that case, giving
		1361	the timer a lower priority than the I/O watcher ensures that I/O will be
		1362	handled first even under adverse conditions (which is usually, but not
		1363	always, what you want).
		1364
		1365	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1366	will only be executed when no same or higher priority watchers have
		1367	received events, they can be used to implement the "lock-out" model when
		1368	required.
		1369
		1370	For example, to emulate how many other event libraries handle priorities,
		1371	you can associate an C<ev_idle> watcher to each such watcher, and in
		1372	the normal watcher callback, you just start the idle watcher. The real
		1373	processing is done in the idle watcher callback. This causes libev to
		1374	continously poll and process kernel event data for the watcher, but when
		1375	the lock-out case is known to be rare (which in turn is rare :), this is
		1376	workable.
		1377
		1378	Usually, however, the lock-out model implemented that way will perform
		1379	miserably under the type of load it was designed to handle. In that case,
		1380	it might be preferable to stop the real watcher before starting the
		1381	idle watcher, so the kernel will not have to process the event in case
		1382	the actual processing will be delayed for considerable time.
		1383
		1384	Here is an example of an I/O watcher that should run at a strictly lower
		1385	priority than the default, and which should only process data when no
		1386	other events are pending:
		1387
		1388	ev_idle idle; // actual processing watcher
		1389	ev_io io; // actual event watcher
		1390
		1391	static void
		1392	io_cb (EV_P_ ev_io *w, int revents)
		1393	{
		1394	// stop the I/O watcher, we received the event, but
		1395	// are not yet ready to handle it.
		1396	ev_io_stop (EV_A_ w);
		1397
		1398	// start the idle watcher to ahndle the actual event.
		1399	// it will not be executed as long as other watchers
		1400	// with the default priority are receiving events.
		1401	ev_idle_start (EV_A_ &idle);
		1402	}
		1403
		1404	static void
		1405	idle_cb (EV_P_ ev_idle *w, int revents)
		1406	{
		1407	// actual processing
		1408	read (STDIN_FILENO, ...);
		1409
		1410	// have to start the I/O watcher again, as
		1411	// we have handled the event
		1412	ev_io_start (EV_P_ &io);
		1413	}
		1414
		1415	// initialisation
		1416	ev_idle_init (&idle, idle_cb);
		1417	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1418	ev_io_start (EV_DEFAULT_ &io);
		1419
		1420	In the "real" world, it might also be beneficial to start a timer, so that
		1421	low-priority connections can not be locked out forever under load. This
		1422	enables your program to keep a lower latency for important connections
		1423	during short periods of high load, while not completely locking out less
		1424	important ones.
1031		1425
1032		1426
1033	=head1 WATCHER TYPES	1427	=head1 WATCHER TYPES
1034		1428
1035	This section describes each watcher in detail, but will not repeat	1429	This section describes each watcher in detail, but will not repeat
…		…
1059	In general you can register as many read and/or write event watchers per	1453	In general you can register as many read and/or write event watchers per
1060	fd as you want (as long as you don't confuse yourself). Setting all file	1454	fd as you want (as long as you don't confuse yourself). Setting all file
1061	descriptors to non-blocking mode is also usually a good idea (but not	1455	descriptors to non-blocking mode is also usually a good idea (but not
1062	required if you know what you are doing).	1456	required if you know what you are doing).
1063		1457
1064	If you must do this, then force the use of a known-to-be-good backend	1458	If you cannot use non-blocking mode, then force the use of a
1065	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1459	known-to-be-good backend (at the time of this writing, this includes only
1066	C<EVBACKEND_POLL>).	1460	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1461	descriptors for which non-blocking operation makes no sense (such as
		1462	files) - libev doesn't guarentee any specific behaviour in that case.
1067		1463
1068	Another thing you have to watch out for is that it is quite easy to	1464	Another thing you have to watch out for is that it is quite easy to
1069	receive "spurious" readiness notifications, that is your callback might	1465	receive "spurious" readiness notifications, that is your callback might
1070	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1466	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1071	because there is no data. Not only are some backends known to create a	1467	because there is no data. Not only are some backends known to create a
1072	lot of those (for example Solaris ports), it is very easy to get into	1468	lot of those (for example Solaris ports), it is very easy to get into
1073	this situation even with a relatively standard program structure. Thus	1469	this situation even with a relatively standard program structure. Thus
1074	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1470	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1075	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1471	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1076		1472
1077	If you cannot run the fd in non-blocking mode (for example you should not	1473	If you cannot run the fd in non-blocking mode (for example you should
1078	play around with an Xlib connection), then you have to separately re-test	1474	not play around with an Xlib connection), then you have to separately
1079	whether a file descriptor is really ready with a known-to-be good interface	1475	re-test whether a file descriptor is really ready with a known-to-be good
1080	such as poll (fortunately in our Xlib example, Xlib already does this on	1476	interface such as poll (fortunately in our Xlib example, Xlib already
1081	its own, so its quite safe to use).	1477	does this on its own, so its quite safe to use). Some people additionally
		1478	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1479	indefinitely.
		1480
		1481	But really, best use non-blocking mode.
1082		1482
1083	=head3 The special problem of disappearing file descriptors	1483	=head3 The special problem of disappearing file descriptors
1084		1484
1085	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1485	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1086	descriptor (either by calling C<close> explicitly or by any other means,	1486	descriptor (either due to calling C<close> explicitly or any other means,
1087	such as C<dup>). The reason is that you register interest in some file	1487	such as C<dup2>). The reason is that you register interest in some file
1088	descriptor, but when it goes away, the operating system will silently drop	1488	descriptor, but when it goes away, the operating system will silently drop
1089	this interest. If another file descriptor with the same number then is	1489	this interest. If another file descriptor with the same number then is
1090	registered with libev, there is no efficient way to see that this is, in	1490	registered with libev, there is no efficient way to see that this is, in
1091	fact, a different file descriptor.	1491	fact, a different file descriptor.
1092		1492
…		…
1123	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1523	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1124	C<EVBACKEND_POLL>.	1524	C<EVBACKEND_POLL>.
1125		1525
1126	=head3 The special problem of SIGPIPE	1526	=head3 The special problem of SIGPIPE
1127		1527
1128	While not really specific to libev, it is easy to forget about SIGPIPE:	1528	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1129	when reading from a pipe whose other end has been closed, your program	1529	when writing to a pipe whose other end has been closed, your program gets
1130	gets send a SIGPIPE, which, by default, aborts your program. For most	1530	sent a SIGPIPE, which, by default, aborts your program. For most programs
1131	programs this is sensible behaviour, for daemons, this is usually	1531	this is sensible behaviour, for daemons, this is usually undesirable.
1132	undesirable.
1133		1532
1134	So when you encounter spurious, unexplained daemon exits, make sure you	1533	So when you encounter spurious, unexplained daemon exits, make sure you
1135	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1534	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1136	somewhere, as that would have given you a big clue).	1535	somewhere, as that would have given you a big clue).
1137		1536
…		…
1143	=item ev_io_init (ev_io *, callback, int fd, int events)	1542	=item ev_io_init (ev_io *, callback, int fd, int events)
1144		1543
1145	=item ev_io_set (ev_io *, int fd, int events)	1544	=item ev_io_set (ev_io *, int fd, int events)
1146		1545
1147	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1546	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1148	receive events for and events is either C<EV_READ>, C<EV_WRITE> or	1547	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1149	C<EV_READ | EV_WRITE> to receive the given events.	1548	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1150		1549
1151	=item int fd [read-only]	1550	=item int fd [read-only]
1152		1551
1153	The file descriptor being watched.	1552	The file descriptor being watched.
1154		1553
…		…
1163	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1562	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1164	readable, but only once. Since it is likely line-buffered, you could	1563	readable, but only once. Since it is likely line-buffered, you could
1165	attempt to read a whole line in the callback.	1564	attempt to read a whole line in the callback.
1166		1565
1167	static void	1566	static void
1168	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1567	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1169	{	1568	{
1170	ev_io_stop (loop, w);	1569	ev_io_stop (loop, w);
1171	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1570	.. read from stdin here (or from w->fd) and handle any I/O errors
1172	}	1571	}
1173		1572
1174	...	1573	...
1175	struct ev_loop *loop = ev_default_init (0);	1574	struct ev_loop *loop = ev_default_init (0);
1176	struct ev_io stdin_readable;	1575	ev_io stdin_readable;
1177	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1576	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1178	ev_io_start (loop, &stdin_readable);	1577	ev_io_start (loop, &stdin_readable);
1179	ev_loop (loop, 0);	1578	ev_loop (loop, 0);
1180		1579
1181		1580
…		…
1184	Timer watchers are simple relative timers that generate an event after a	1583	Timer watchers are simple relative timers that generate an event after a
1185	given time, and optionally repeating in regular intervals after that.	1584	given time, and optionally repeating in regular intervals after that.
1186		1585
1187	The timers are based on real time, that is, if you register an event that	1586	The timers are based on real time, that is, if you register an event that
1188	times out after an hour and you reset your system clock to January last	1587	times out after an hour and you reset your system clock to January last
1189	year, it will still time out after (roughly) and hour. "Roughly" because	1588	year, it will still time out after (roughly) one hour. "Roughly" because
1190	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1589	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1191	monotonic clock option helps a lot here).	1590	monotonic clock option helps a lot here).
		1591
		1592	The callback is guaranteed to be invoked only I<after> its timeout has
		1593	passed (not I<at>, so on systems with very low-resolution clocks this
		1594	might introduce a small delay). If multiple timers become ready during the
		1595	same loop iteration then the ones with earlier time-out values are invoked
		1596	before ones of the same priority with later time-out values (but this is
		1597	no longer true when a callback calls C<ev_loop> recursively).
		1598
		1599	=head3 Be smart about timeouts
		1600
		1601	Many real-world problems involve some kind of timeout, usually for error
		1602	recovery. A typical example is an HTTP request - if the other side hangs,
		1603	you want to raise some error after a while.
		1604
		1605	What follows are some ways to handle this problem, from obvious and
		1606	inefficient to smart and efficient.
		1607
		1608	In the following, a 60 second activity timeout is assumed - a timeout that
		1609	gets reset to 60 seconds each time there is activity (e.g. each time some
		1610	data or other life sign was received).
		1611
		1612	=over 4
		1613
		1614	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1615
		1616	This is the most obvious, but not the most simple way: In the beginning,
		1617	start the watcher:
		1618
		1619	ev_timer_init (timer, callback, 60., 0.);
		1620	ev_timer_start (loop, timer);
		1621
		1622	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1623	and start it again:
		1624
		1625	ev_timer_stop (loop, timer);
		1626	ev_timer_set (timer, 60., 0.);
		1627	ev_timer_start (loop, timer);
		1628
		1629	This is relatively simple to implement, but means that each time there is
		1630	some activity, libev will first have to remove the timer from its internal
		1631	data structure and then add it again. Libev tries to be fast, but it's
		1632	still not a constant-time operation.
		1633
		1634	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1635
		1636	This is the easiest way, and involves using C<ev_timer_again> instead of
		1637	C<ev_timer_start>.
		1638
		1639	To implement this, configure an C<ev_timer> with a C<repeat> value
		1640	of C<60> and then call C<ev_timer_again> at start and each time you
		1641	successfully read or write some data. If you go into an idle state where
		1642	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1643	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1644
		1645	That means you can ignore both the C<ev_timer_start> function and the
		1646	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1647	member and C<ev_timer_again>.
		1648
		1649	At start:
		1650
		1651	ev_init (timer, callback);
		1652	timer->repeat = 60.;
		1653	ev_timer_again (loop, timer);
		1654
		1655	Each time there is some activity:
		1656
		1657	ev_timer_again (loop, timer);
		1658
		1659	It is even possible to change the time-out on the fly, regardless of
		1660	whether the watcher is active or not:
		1661
		1662	timer->repeat = 30.;
		1663	ev_timer_again (loop, timer);
		1664
		1665	This is slightly more efficient then stopping/starting the timer each time
		1666	you want to modify its timeout value, as libev does not have to completely
		1667	remove and re-insert the timer from/into its internal data structure.
		1668
		1669	It is, however, even simpler than the "obvious" way to do it.
		1670
		1671	=item 3. Let the timer time out, but then re-arm it as required.
		1672
		1673	This method is more tricky, but usually most efficient: Most timeouts are
		1674	relatively long compared to the intervals between other activity - in
		1675	our example, within 60 seconds, there are usually many I/O events with
		1676	associated activity resets.
		1677
		1678	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1679	but remember the time of last activity, and check for a real timeout only
		1680	within the callback:
		1681
		1682	ev_tstamp last_activity; // time of last activity
		1683
		1684	static void
		1685	callback (EV_P_ ev_timer *w, int revents)
		1686	{
		1687	ev_tstamp now = ev_now (EV_A);
		1688	ev_tstamp timeout = last_activity + 60.;
		1689
		1690	// if last_activity + 60. is older than now, we did time out
		1691	if (timeout < now)
		1692	{
		1693	// timeout occured, take action
		1694	}
		1695	else
		1696	{
		1697	// callback was invoked, but there was some activity, re-arm
		1698	// the watcher to fire in last_activity + 60, which is
		1699	// guaranteed to be in the future, so "again" is positive:
		1700	w->repeat = timeout - now;
		1701	ev_timer_again (EV_A_ w);
		1702	}
		1703	}
		1704
		1705	To summarise the callback: first calculate the real timeout (defined
		1706	as "60 seconds after the last activity"), then check if that time has
		1707	been reached, which means something I<did>, in fact, time out. Otherwise
		1708	the callback was invoked too early (C<timeout> is in the future), so
		1709	re-schedule the timer to fire at that future time, to see if maybe we have
		1710	a timeout then.
		1711
		1712	Note how C<ev_timer_again> is used, taking advantage of the
		1713	C<ev_timer_again> optimisation when the timer is already running.
		1714
		1715	This scheme causes more callback invocations (about one every 60 seconds
		1716	minus half the average time between activity), but virtually no calls to
		1717	libev to change the timeout.
		1718
		1719	To start the timer, simply initialise the watcher and set C<last_activity>
		1720	to the current time (meaning we just have some activity :), then call the
		1721	callback, which will "do the right thing" and start the timer:
		1722
		1723	ev_init (timer, callback);
		1724	last_activity = ev_now (loop);
		1725	callback (loop, timer, EV_TIMEOUT);
		1726
		1727	And when there is some activity, simply store the current time in
		1728	C<last_activity>, no libev calls at all:
		1729
		1730	last_actiivty = ev_now (loop);
		1731
		1732	This technique is slightly more complex, but in most cases where the
		1733	time-out is unlikely to be triggered, much more efficient.
		1734
		1735	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1736	callback :) - just change the timeout and invoke the callback, which will
		1737	fix things for you.
		1738
		1739	=item 4. Wee, just use a double-linked list for your timeouts.
		1740
		1741	If there is not one request, but many thousands (millions...), all
		1742	employing some kind of timeout with the same timeout value, then one can
		1743	do even better:
		1744
		1745	When starting the timeout, calculate the timeout value and put the timeout
		1746	at the I<end> of the list.
		1747
		1748	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1749	the list is expected to fire (for example, using the technique #3).
		1750
		1751	When there is some activity, remove the timer from the list, recalculate
		1752	the timeout, append it to the end of the list again, and make sure to
		1753	update the C<ev_timer> if it was taken from the beginning of the list.
		1754
		1755	This way, one can manage an unlimited number of timeouts in O(1) time for
		1756	starting, stopping and updating the timers, at the expense of a major
		1757	complication, and having to use a constant timeout. The constant timeout
		1758	ensures that the list stays sorted.
		1759
		1760	=back
		1761
		1762	So which method the best?
		1763
		1764	Method #2 is a simple no-brain-required solution that is adequate in most
		1765	situations. Method #3 requires a bit more thinking, but handles many cases
		1766	better, and isn't very complicated either. In most case, choosing either
		1767	one is fine, with #3 being better in typical situations.
		1768
		1769	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1770	rather complicated, but extremely efficient, something that really pays
		1771	off after the first million or so of active timers, i.e. it's usually
		1772	overkill :)
		1773
		1774	=head3 The special problem of time updates
		1775
		1776	Establishing the current time is a costly operation (it usually takes at
		1777	least two system calls): EV therefore updates its idea of the current
		1778	time only before and after C<ev_loop> collects new events, which causes a
		1779	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1780	lots of events in one iteration.
1192		1781
1193	The relative timeouts are calculated relative to the C<ev_now ()>	1782	The relative timeouts are calculated relative to the C<ev_now ()>
1194	time. This is usually the right thing as this timestamp refers to the time	1783	time. This is usually the right thing as this timestamp refers to the time
1195	of the event triggering whatever timeout you are modifying/starting. If	1784	of the event triggering whatever timeout you are modifying/starting. If
1196	you suspect event processing to be delayed and you I<need> to base the timeout	1785	you suspect event processing to be delayed and you I<need> to base the
1197	on the current time, use something like this to adjust for this:	1786	timeout on the current time, use something like this to adjust for this:
1198		1787
1199	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1788	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1200		1789
1201	The callback is guaranteed to be invoked only after its timeout has passed,	1790	If the event loop is suspended for a long time, you can also force an
1202	but if multiple timers become ready during the same loop iteration then	1791	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1203	order of execution is undefined.	1792	()>.
		1793
		1794	=head3 The special problems of suspended animation
		1795
		1796	When you leave the server world it is quite customary to hit machines that
		1797	can suspend/hibernate - what happens to the clocks during such a suspend?
		1798
		1799	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1800	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1801	to run until the system is suspended, but they will not advance while the
		1802	system is suspended. That means, on resume, it will be as if the program
		1803	was frozen for a few seconds, but the suspend time will not be counted
		1804	towards C<ev_timer> when a monotonic clock source is used. The real time
		1805	clock advanced as expected, but if it is used as sole clocksource, then a
		1806	long suspend would be detected as a time jump by libev, and timers would
		1807	be adjusted accordingly.
		1808
		1809	I would not be surprised to see different behaviour in different between
		1810	operating systems, OS versions or even different hardware.
		1811
		1812	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1813	time jump in the monotonic clocks and the realtime clock. If the program
		1814	is suspended for a very long time, and monotonic clock sources are in use,
		1815	then you can expect C<ev_timer>s to expire as the full suspension time
		1816	will be counted towards the timers. When no monotonic clock source is in
		1817	use, then libev will again assume a timejump and adjust accordingly.
		1818
		1819	It might be beneficial for this latter case to call C<ev_suspend>
		1820	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1821	deterministic behaviour in this case (you can do nothing against
		1822	C<SIGSTOP>).
1204		1823
1205	=head3 Watcher-Specific Functions and Data Members	1824	=head3 Watcher-Specific Functions and Data Members
1206		1825
1207	=over 4	1826	=over 4
1208		1827
…		…
1232	If the timer is started but non-repeating, stop it (as if it timed out).	1851	If the timer is started but non-repeating, stop it (as if it timed out).
1233		1852
1234	If the timer is repeating, either start it if necessary (with the	1853	If the timer is repeating, either start it if necessary (with the
1235	C<repeat> value), or reset the running timer to the C<repeat> value.	1854	C<repeat> value), or reset the running timer to the C<repeat> value.
1236		1855
1237	This sounds a bit complicated, but here is a useful and typical	1856	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1238	example: Imagine you have a TCP connection and you want a so-called idle	1857	usage example.
1239	timeout, that is, you want to be called when there have been, say, 60
1240	seconds of inactivity on the socket. The easiest way to do this is to
1241	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1242	C<ev_timer_again> each time you successfully read or write some data. If
1243	you go into an idle state where you do not expect data to travel on the
1244	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1245	automatically restart it if need be.
1246		1858
1247	That means you can ignore the C<after> value and C<ev_timer_start>	1859	=item ev_timer_remaining (loop, ev_timer *)
1248	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1249		1860
1250	ev_timer_init (timer, callback, 0., 5.);	1861	Returns the remaining time until a timer fires. If the timer is active,
1251	ev_timer_again (loop, timer);	1862	then this time is relative to the current event loop time, otherwise it's
1252	...	1863	the timeout value currently configured.
1253	timer->again = 17.;
1254	ev_timer_again (loop, timer);
1255	...
1256	timer->again = 10.;
1257	ev_timer_again (loop, timer);
1258		1864
1259	This is more slightly efficient then stopping/starting the timer each time	1865	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1260	you want to modify its timeout value.	1866	C<5>. When the timer is started and one second passes, C<ev_timer_remain>
		1867	will return C<4>. When the timer expires and is restarted, it will return
		1868	roughly C<7> (likely slightly less as callback invocation takes some time,
		1869	too), and so on.
1261		1870
1262	=item ev_tstamp repeat [read-write]	1871	=item ev_tstamp repeat [read-write]
1263		1872
1264	The current C<repeat> value. Will be used each time the watcher times out	1873	The current C<repeat> value. Will be used each time the watcher times out
1265	or C<ev_timer_again> is called and determines the next timeout (if any),	1874	or C<ev_timer_again> is called, and determines the next timeout (if any),
1266	which is also when any modifications are taken into account.	1875	which is also when any modifications are taken into account.
1267		1876
1268	=back	1877	=back
1269		1878
1270	=head3 Examples	1879	=head3 Examples
1271		1880
1272	Example: Create a timer that fires after 60 seconds.	1881	Example: Create a timer that fires after 60 seconds.
1273		1882
1274	static void	1883	static void
1275	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1884	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1276	{	1885	{
1277	.. one minute over, w is actually stopped right here	1886	.. one minute over, w is actually stopped right here
1278	}	1887	}
1279		1888
1280	struct ev_timer mytimer;	1889	ev_timer mytimer;
1281	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1890	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1282	ev_timer_start (loop, &mytimer);	1891	ev_timer_start (loop, &mytimer);
1283		1892
1284	Example: Create a timeout timer that times out after 10 seconds of	1893	Example: Create a timeout timer that times out after 10 seconds of
1285	inactivity.	1894	inactivity.
1286		1895
1287	static void	1896	static void
1288	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1897	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1289	{	1898	{
1290	.. ten seconds without any activity	1899	.. ten seconds without any activity
1291	}	1900	}
1292		1901
1293	struct ev_timer mytimer;	1902	ev_timer mytimer;
1294	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1903	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1295	ev_timer_again (&mytimer); /* start timer */	1904	ev_timer_again (&mytimer); /* start timer */
1296	ev_loop (loop, 0);	1905	ev_loop (loop, 0);
1297		1906
1298	// and in some piece of code that gets executed on any "activity":	1907	// and in some piece of code that gets executed on any "activity":
…		…
1303	=head2 C<ev_periodic> - to cron or not to cron?	1912	=head2 C<ev_periodic> - to cron or not to cron?
1304		1913
1305	Periodic watchers are also timers of a kind, but they are very versatile	1914	Periodic watchers are also timers of a kind, but they are very versatile
1306	(and unfortunately a bit complex).	1915	(and unfortunately a bit complex).
1307		1916
1308	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1917	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1309	but on wall clock time (absolute time). You can tell a periodic watcher	1918	relative time, the physical time that passes) but on wall clock time
1310	to trigger after some specific point in time. For example, if you tell a	1919	(absolute time, the thing you can read on your calender or clock). The
1311	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	1920	difference is that wall clock time can run faster or slower than real
1312	+ 10.>, that is, an absolute time not a delay) and then reset your system	1921	time, and time jumps are not uncommon (e.g. when you adjust your
1313	clock to January of the previous year, then it will take more than year	1922	wrist-watch).
1314	to trigger the event (unlike an C<ev_timer>, which would still trigger
1315	roughly 10 seconds later as it uses a relative timeout).
1316		1923
		1924	You can tell a periodic watcher to trigger after some specific point
		1925	in time: for example, if you tell a periodic watcher to trigger "in 10
		1926	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1927	not a delay) and then reset your system clock to January of the previous
		1928	year, then it will take a year or more to trigger the event (unlike an
		1929	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1930	it, as it uses a relative timeout).
		1931
1317	C<ev_periodic>s can also be used to implement vastly more complex timers,	1932	C<ev_periodic> watchers can also be used to implement vastly more complex
1318	such as triggering an event on each "midnight, local time", or other	1933	timers, such as triggering an event on each "midnight, local time", or
1319	complicated, rules.	1934	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1935	those cannot react to time jumps.
1320		1936
1321	As with timers, the callback is guaranteed to be invoked only when the	1937	As with timers, the callback is guaranteed to be invoked only when the
1322	time (C<at>) has passed, but if multiple periodic timers become ready	1938	point in time where it is supposed to trigger has passed. If multiple
1323	during the same loop iteration then order of execution is undefined.	1939	timers become ready during the same loop iteration then the ones with
		1940	earlier time-out values are invoked before ones with later time-out values
		1941	(but this is no longer true when a callback calls C<ev_loop> recursively).
1324		1942
1325	=head3 Watcher-Specific Functions and Data Members	1943	=head3 Watcher-Specific Functions and Data Members
1326		1944
1327	=over 4	1945	=over 4
1328		1946
1329	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1947	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1330		1948
1331	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1949	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1332		1950
1333	Lots of arguments, lets sort it out... There are basically three modes of	1951	Lots of arguments, let's sort it out... There are basically three modes of
1334	operation, and we will explain them from simplest to complex:	1952	operation, and we will explain them from simplest to most complex:
1335		1953
1336	=over 4	1954	=over 4
1337		1955
1338	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1956	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1339		1957
1340	In this configuration the watcher triggers an event after the wall clock	1958	In this configuration the watcher triggers an event after the wall clock
1341	time C<at> has passed and doesn't repeat. It will not adjust when a time	1959	time C<offset> has passed. It will not repeat and will not adjust when a
1342	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1960	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1343	run when the system time reaches or surpasses this time.	1961	will be stopped and invoked when the system clock reaches or surpasses
		1962	this point in time.
1344		1963
1345	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1964	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1346		1965
1347	In this mode the watcher will always be scheduled to time out at the next	1966	In this mode the watcher will always be scheduled to time out at the next
1348	C<at + N * interval> time (for some integer N, which can also be negative)	1967	C<offset + N * interval> time (for some integer N, which can also be
1349	and then repeat, regardless of any time jumps.	1968	negative) and then repeat, regardless of any time jumps. The C<offset>
		1969	argument is merely an offset into the C<interval> periods.
1350		1970
1351	This can be used to create timers that do not drift with respect to system	1971	This can be used to create timers that do not drift with respect to the
1352	time, for example, here is a C<ev_periodic> that triggers each hour, on	1972	system clock, for example, here is an C<ev_periodic> that triggers each
1353	the hour:	1973	hour, on the hour (with respect to UTC):
1354		1974
1355	ev_periodic_set (&periodic, 0., 3600., 0);	1975	ev_periodic_set (&periodic, 0., 3600., 0);
1356		1976
1357	This doesn't mean there will always be 3600 seconds in between triggers,	1977	This doesn't mean there will always be 3600 seconds in between triggers,
1358	but only that the callback will be called when the system time shows a	1978	but only that the callback will be called when the system time shows a
1359	full hour (UTC), or more correctly, when the system time is evenly divisible	1979	full hour (UTC), or more correctly, when the system time is evenly divisible
1360	by 3600.	1980	by 3600.
1361		1981
1362	Another way to think about it (for the mathematically inclined) is that	1982	Another way to think about it (for the mathematically inclined) is that
1363	C<ev_periodic> will try to run the callback in this mode at the next possible	1983	C<ev_periodic> will try to run the callback in this mode at the next possible
1364	time where C<time = at (mod interval)>, regardless of any time jumps.	1984	time where C<time = offset (mod interval)>, regardless of any time jumps.
1365		1985
1366	For numerical stability it is preferable that the C<at> value is near	1986	For numerical stability it is preferable that the C<offset> value is near
1367	C<ev_now ()> (the current time), but there is no range requirement for	1987	C<ev_now ()> (the current time), but there is no range requirement for
1368	this value, and in fact is often specified as zero.	1988	this value, and in fact is often specified as zero.
1369		1989
1370	Note also that there is an upper limit to how often a timer can fire (CPU	1990	Note also that there is an upper limit to how often a timer can fire (CPU
1371	speed for example), so if C<interval> is very small then timing stability	1991	speed for example), so if C<interval> is very small then timing stability
1372	will of course deteriorate. Libev itself tries to be exact to be about one	1992	will of course deteriorate. Libev itself tries to be exact to be about one
1373	millisecond (if the OS supports it and the machine is fast enough).	1993	millisecond (if the OS supports it and the machine is fast enough).
1374		1994
1375	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1995	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1376		1996
1377	In this mode the values for C<interval> and C<at> are both being	1997	In this mode the values for C<interval> and C<offset> are both being
1378	ignored. Instead, each time the periodic watcher gets scheduled, the	1998	ignored. Instead, each time the periodic watcher gets scheduled, the
1379	reschedule callback will be called with the watcher as first, and the	1999	reschedule callback will be called with the watcher as first, and the
1380	current time as second argument.	2000	current time as second argument.
1381		2001
1382	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2002	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1383	ever, or make ANY event loop modifications whatsoever>.	2003	or make ANY other event loop modifications whatsoever, unless explicitly
		2004	allowed by documentation here>.
1384		2005
1385	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2006	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1386	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2007	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1387	only event loop modification you are allowed to do).	2008	only event loop modification you are allowed to do).
1388		2009
1389	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	2010	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1390	*w, ev_tstamp now)>, e.g.:	2011	*w, ev_tstamp now)>, e.g.:
1391		2012
		2013	static ev_tstamp
1392	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	2014	my_rescheduler (ev_periodic *w, ev_tstamp now)
1393	{	2015	{
1394	return now + 60.;	2016	return now + 60.;
1395	}	2017	}
1396		2018
1397	It must return the next time to trigger, based on the passed time value	2019	It must return the next time to trigger, based on the passed time value
…		…
1417	a different time than the last time it was called (e.g. in a crond like	2039	a different time than the last time it was called (e.g. in a crond like
1418	program when the crontabs have changed).	2040	program when the crontabs have changed).
1419		2041
1420	=item ev_tstamp ev_periodic_at (ev_periodic *)	2042	=item ev_tstamp ev_periodic_at (ev_periodic *)
1421		2043
1422	When active, returns the absolute time that the watcher is supposed to	2044	When active, returns the absolute time that the watcher is supposed
1423	trigger next.	2045	to trigger next. This is not the same as the C<offset> argument to
		2046	C<ev_periodic_set>, but indeed works even in interval and manual
		2047	rescheduling modes.
1424		2048
1425	=item ev_tstamp offset [read-write]	2049	=item ev_tstamp offset [read-write]
1426		2050
1427	When repeating, this contains the offset value, otherwise this is the	2051	When repeating, this contains the offset value, otherwise this is the
1428	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2052	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2053	although libev might modify this value for better numerical stability).
1429		2054
1430	Can be modified any time, but changes only take effect when the periodic	2055	Can be modified any time, but changes only take effect when the periodic
1431	timer fires or C<ev_periodic_again> is being called.	2056	timer fires or C<ev_periodic_again> is being called.
1432		2057
1433	=item ev_tstamp interval [read-write]	2058	=item ev_tstamp interval [read-write]
1434		2059
1435	The current interval value. Can be modified any time, but changes only	2060	The current interval value. Can be modified any time, but changes only
1436	take effect when the periodic timer fires or C<ev_periodic_again> is being	2061	take effect when the periodic timer fires or C<ev_periodic_again> is being
1437	called.	2062	called.
1438		2063
1439	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2064	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1440		2065
1441	The current reschedule callback, or C<0>, if this functionality is	2066	The current reschedule callback, or C<0>, if this functionality is
1442	switched off. Can be changed any time, but changes only take effect when	2067	switched off. Can be changed any time, but changes only take effect when
1443	the periodic timer fires or C<ev_periodic_again> is being called.	2068	the periodic timer fires or C<ev_periodic_again> is being called.
1444		2069
1445	=back	2070	=back
1446		2071
1447	=head3 Examples	2072	=head3 Examples
1448		2073
1449	Example: Call a callback every hour, or, more precisely, whenever the	2074	Example: Call a callback every hour, or, more precisely, whenever the
1450	system clock is divisible by 3600. The callback invocation times have	2075	system time is divisible by 3600. The callback invocation times have
1451	potentially a lot of jitter, but good long-term stability.	2076	potentially a lot of jitter, but good long-term stability.
1452		2077
1453	static void	2078	static void
1454	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2079	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1455	{	2080	{
1456	... its now a full hour (UTC, or TAI or whatever your clock follows)	2081	... its now a full hour (UTC, or TAI or whatever your clock follows)
1457	}	2082	}
1458		2083
1459	struct ev_periodic hourly_tick;	2084	ev_periodic hourly_tick;
1460	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2085	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1461	ev_periodic_start (loop, &hourly_tick);	2086	ev_periodic_start (loop, &hourly_tick);
1462		2087
1463	Example: The same as above, but use a reschedule callback to do it:	2088	Example: The same as above, but use a reschedule callback to do it:
1464		2089
1465	#include <math.h>	2090	#include <math.h>
1466		2091
1467	static ev_tstamp	2092	static ev_tstamp
1468	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2093	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1469	{	2094	{
1470	return fmod (now, 3600.) + 3600.;	2095	return now + (3600. - fmod (now, 3600.));
1471	}	2096	}
1472		2097
1473	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2098	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1474		2099
1475	Example: Call a callback every hour, starting now:	2100	Example: Call a callback every hour, starting now:
1476		2101
1477	struct ev_periodic hourly_tick;	2102	ev_periodic hourly_tick;
1478	ev_periodic_init (&hourly_tick, clock_cb,	2103	ev_periodic_init (&hourly_tick, clock_cb,
1479	fmod (ev_now (loop), 3600.), 3600., 0);	2104	fmod (ev_now (loop), 3600.), 3600., 0);
1480	ev_periodic_start (loop, &hourly_tick);	2105	ev_periodic_start (loop, &hourly_tick);
1481		2106
1482		2107
…		…
1485	Signal watchers will trigger an event when the process receives a specific	2110	Signal watchers will trigger an event when the process receives a specific
1486	signal one or more times. Even though signals are very asynchronous, libev	2111	signal one or more times. Even though signals are very asynchronous, libev
1487	will try it's best to deliver signals synchronously, i.e. as part of the	2112	will try it's best to deliver signals synchronously, i.e. as part of the
1488	normal event processing, like any other event.	2113	normal event processing, like any other event.
1489		2114
		2115	If you want signals to be delivered truly asynchronously, just use
		2116	C<sigaction> as you would do without libev and forget about sharing
		2117	the signal. You can even use C<ev_async> from a signal handler to
		2118	synchronously wake up an event loop.
		2119
1490	You can configure as many watchers as you like per signal. Only when the	2120	You can configure as many watchers as you like for the same signal, but
		2121	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2122	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2123	C<SIGINT> in both the default loop and another loop at the same time. At
		2124	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2125
1491	first watcher gets started will libev actually register a signal watcher	2126	When the first watcher gets started will libev actually register something
1492	with the kernel (thus it coexists with your own signal handlers as long	2127	with the kernel (thus it coexists with your own signal handlers as long as
1493	as you don't register any with libev). Similarly, when the last signal	2128	you don't register any with libev for the same signal).
1494	watcher for a signal is stopped libev will reset the signal handler to
1495	SIG_DFL (regardless of what it was set to before).
1496		2129
1497	If possible and supported, libev will install its handlers with	2130	If possible and supported, libev will install its handlers with
1498	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2131	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1499	interrupted. If you have a problem with system calls getting interrupted by	2132	not be unduly interrupted. If you have a problem with system calls getting
1500	signals you can block all signals in an C<ev_check> watcher and unblock	2133	interrupted by signals you can block all signals in an C<ev_check> watcher
1501	them in an C<ev_prepare> watcher.	2134	and unblock them in an C<ev_prepare> watcher.
		2135
		2136	=head3 The special problem of inheritance over execve
		2137
		2138	Both the signal mask (C<sigprocmask>) and the signal disposition
		2139	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2140	stopping it again), that is, libev might or might not block the signal,
		2141	and might or might not set or restore the installed signal handler.
		2142
		2143	While this does not matter for the signal disposition (libev never
		2144	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2145	C<execve>), this matters for the signal mask: many programs do not expect
		2146	certain signals to be blocked.
		2147
		2148	This means that before calling C<exec> (from the child) you should reset
		2149	the signal mask to whatever "default" you expect (all clear is a good
		2150	choice usually).
		2151
		2152	The simplest way to ensure that the signal mask is reset in the child is
		2153	to install a fork handler with C<pthread_atfork> that resets it. That will
		2154	catch fork calls done by libraries (such as the libc) as well.
		2155
		2156	In current versions of libev, you can also ensure that the signal mask is
		2157	not blocking any signals (except temporarily, so thread users watch out)
		2158	by specifying the C<EVFLAG_NOSIGFD> when creating the event loop. This
		2159	is not guaranteed for future versions, however.
1502		2160
1503	=head3 Watcher-Specific Functions and Data Members	2161	=head3 Watcher-Specific Functions and Data Members
1504		2162
1505	=over 4	2163	=over 4
1506		2164
…		…
1517		2175
1518	=back	2176	=back
1519		2177
1520	=head3 Examples	2178	=head3 Examples
1521		2179
1522	Example: Try to exit cleanly on SIGINT and SIGTERM.	2180	Example: Try to exit cleanly on SIGINT.
1523		2181
1524	static void	2182	static void
1525	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2183	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1526	{	2184	{
1527	ev_unloop (loop, EVUNLOOP_ALL);	2185	ev_unloop (loop, EVUNLOOP_ALL);
1528	}	2186	}
1529		2187
1530	struct ev_signal signal_watcher;	2188	ev_signal signal_watcher;
1531	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2189	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1532	ev_signal_start (loop, &sigint_cb);	2190	ev_signal_start (loop, &signal_watcher);
1533		2191
1534		2192
1535	=head2 C<ev_child> - watch out for process status changes	2193	=head2 C<ev_child> - watch out for process status changes
1536		2194
1537	Child watchers trigger when your process receives a SIGCHLD in response to	2195	Child watchers trigger when your process receives a SIGCHLD in response to
1538	some child status changes (most typically when a child of yours dies). It	2196	some child status changes (most typically when a child of yours dies or
1539	is permissible to install a child watcher I<after> the child has been	2197	exits). It is permissible to install a child watcher I<after> the child
1540	forked (which implies it might have already exited), as long as the event	2198	has been forked (which implies it might have already exited), as long
1541	loop isn't entered (or is continued from a watcher).	2199	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2200	forking and then immediately registering a watcher for the child is fine,
		2201	but forking and registering a watcher a few event loop iterations later or
		2202	in the next callback invocation is not.
1542		2203
1543	Only the default event loop is capable of handling signals, and therefore	2204	Only the default event loop is capable of handling signals, and therefore
1544	you can only register child watchers in the default event loop.	2205	you can only register child watchers in the default event loop.
1545		2206
		2207	Due to some design glitches inside libev, child watchers will always be
		2208	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2209	libev)
		2210
1546	=head3 Process Interaction	2211	=head3 Process Interaction
1547		2212
1548	Libev grabs C<SIGCHLD> as soon as the default event loop is	2213	Libev grabs C<SIGCHLD> as soon as the default event loop is
1549	initialised. This is necessary to guarantee proper behaviour even if	2214	initialised. This is necessary to guarantee proper behaviour even if the
1550	the first child watcher is started after the child exits. The occurrence	2215	first child watcher is started after the child exits. The occurrence
1551	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2216	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1552	synchronously as part of the event loop processing. Libev always reaps all	2217	synchronously as part of the event loop processing. Libev always reaps all
1553	children, even ones not watched.	2218	children, even ones not watched.
1554		2219
1555	=head3 Overriding the Built-In Processing	2220	=head3 Overriding the Built-In Processing
…		…
1559	handler, you can override it easily by installing your own handler for	2224	handler, you can override it easily by installing your own handler for
1560	C<SIGCHLD> after initialising the default loop, and making sure the	2225	C<SIGCHLD> after initialising the default loop, and making sure the
1561	default loop never gets destroyed. You are encouraged, however, to use an	2226	default loop never gets destroyed. You are encouraged, however, to use an
1562	event-based approach to child reaping and thus use libev's support for	2227	event-based approach to child reaping and thus use libev's support for
1563	that, so other libev users can use C<ev_child> watchers freely.	2228	that, so other libev users can use C<ev_child> watchers freely.
		2229
		2230	=head3 Stopping the Child Watcher
		2231
		2232	Currently, the child watcher never gets stopped, even when the
		2233	child terminates, so normally one needs to stop the watcher in the
		2234	callback. Future versions of libev might stop the watcher automatically
		2235	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2236	problem).
1564		2237
1565	=head3 Watcher-Specific Functions and Data Members	2238	=head3 Watcher-Specific Functions and Data Members
1566		2239
1567	=over 4	2240	=over 4
1568		2241
…		…
1600	its completion.	2273	its completion.
1601		2274
1602	ev_child cw;	2275	ev_child cw;
1603		2276
1604	static void	2277	static void
1605	child_cb (EV_P_ struct ev_child *w, int revents)	2278	child_cb (EV_P_ ev_child *w, int revents)
1606	{	2279	{
1607	ev_child_stop (EV_A_ w);	2280	ev_child_stop (EV_A_ w);
1608	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2281	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1609	}	2282	}
1610		2283
…		…
1625		2298
1626		2299
1627	=head2 C<ev_stat> - did the file attributes just change?	2300	=head2 C<ev_stat> - did the file attributes just change?
1628		2301
1629	This watches a file system path for attribute changes. That is, it calls	2302	This watches a file system path for attribute changes. That is, it calls
1630	C<stat> regularly (or when the OS says it changed) and sees if it changed	2303	C<stat> on that path in regular intervals (or when the OS says it changed)
1631	compared to the last time, invoking the callback if it did.	2304	and sees if it changed compared to the last time, invoking the callback if
		2305	it did.
1632		2306
1633	The path does not need to exist: changing from "path exists" to "path does	2307	The path does not need to exist: changing from "path exists" to "path does
1634	not exist" is a status change like any other. The condition "path does	2308	not exist" is a status change like any other. The condition "path does not
1635	not exist" is signified by the C<st_nlink> field being zero (which is	2309	exist" (or more correctly "path cannot be stat'ed") is signified by the
1636	otherwise always forced to be at least one) and all the other fields of	2310	C<st_nlink> field being zero (which is otherwise always forced to be at
1637	the stat buffer having unspecified contents.	2311	least one) and all the other fields of the stat buffer having unspecified
		2312	contents.
1638		2313
1639	The path I<should> be absolute and I<must not> end in a slash. If it is	2314	The path I<must not> end in a slash or contain special components such as
		2315	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1640	relative and your working directory changes, the behaviour is undefined.	2316	your working directory changes, then the behaviour is undefined.
1641		2317
1642	Since there is no standard to do this, the portable implementation simply	2318	Since there is no portable change notification interface available, the
1643	calls C<stat (2)> regularly on the path to see if it changed somehow. You	2319	portable implementation simply calls C<stat(2)> regularly on the path
1644	can specify a recommended polling interval for this case. If you specify	2320	to see if it changed somehow. You can specify a recommended polling
1645	a polling interval of C<0> (highly recommended!) then a I<suitable,	2321	interval for this case. If you specify a polling interval of C<0> (highly
1646	unspecified default> value will be used (which you can expect to be around	2322	recommended!) then a I<suitable, unspecified default> value will be used
1647	five seconds, although this might change dynamically). Libev will also	2323	(which you can expect to be around five seconds, although this might
1648	impose a minimum interval which is currently around C<0.1>, but thats	2324	change dynamically). Libev will also impose a minimum interval which is
1649	usually overkill.	2325	currently around C<0.1>, but that's usually overkill.
1650		2326
1651	This watcher type is not meant for massive numbers of stat watchers,	2327	This watcher type is not meant for massive numbers of stat watchers,
1652	as even with OS-supported change notifications, this can be	2328	as even with OS-supported change notifications, this can be
1653	resource-intensive.	2329	resource-intensive.
1654		2330
1655	At the time of this writing, only the Linux inotify interface is	2331	At the time of this writing, the only OS-specific interface implemented
1656	implemented (implementing kqueue support is left as an exercise for the	2332	is the Linux inotify interface (implementing kqueue support is left as an
1657	reader, note, however, that the author sees no way of implementing ev_stat	2333	exercise for the reader. Note, however, that the author sees no way of
1658	semantics with kqueue). Inotify will be used to give hints only and should	2334	implementing C<ev_stat> semantics with kqueue, except as a hint).
1659	not change the semantics of C<ev_stat> watchers, which means that libev
1660	sometimes needs to fall back to regular polling again even with inotify,
1661	but changes are usually detected immediately, and if the file exists there
1662	will be no polling.
1663		2335
1664	=head3 ABI Issues (Largefile Support)	2336	=head3 ABI Issues (Largefile Support)
1665		2337
1666	Libev by default (unless the user overrides this) uses the default	2338	Libev by default (unless the user overrides this) uses the default
1667	compilation environment, which means that on systems with optionally	2339	compilation environment, which means that on systems with large file
1668	disabled large file support, you get the 32 bit version of the stat	2340	support disabled by default, you get the 32 bit version of the stat
1669	structure. When using the library from programs that change the ABI to	2341	structure. When using the library from programs that change the ABI to
1670	use 64 bit file offsets the programs will fail. In that case you have to	2342	use 64 bit file offsets the programs will fail. In that case you have to
1671	compile libev with the same flags to get binary compatibility. This is	2343	compile libev with the same flags to get binary compatibility. This is
1672	obviously the case with any flags that change the ABI, but the problem is	2344	obviously the case with any flags that change the ABI, but the problem is
1673	most noticeably with ev_stat and large file support.	2345	most noticeably displayed with ev_stat and large file support.
1674		2346
1675	=head3 Inotify	2347	The solution for this is to lobby your distribution maker to make large
		2348	file interfaces available by default (as e.g. FreeBSD does) and not
		2349	optional. Libev cannot simply switch on large file support because it has
		2350	to exchange stat structures with application programs compiled using the
		2351	default compilation environment.
1676		2352
		2353	=head3 Inotify and Kqueue
		2354
1677	When C<inotify (7)> support has been compiled into libev (generally only	2355	When C<inotify (7)> support has been compiled into libev and present at
1678	available on Linux) and present at runtime, it will be used to speed up	2356	runtime, it will be used to speed up change detection where possible. The
1679	change detection where possible. The inotify descriptor will be created lazily	2357	inotify descriptor will be created lazily when the first C<ev_stat>
1680	when the first C<ev_stat> watcher is being started.	2358	watcher is being started.
1681		2359
1682	Inotify presence does not change the semantics of C<ev_stat> watchers	2360	Inotify presence does not change the semantics of C<ev_stat> watchers
1683	except that changes might be detected earlier, and in some cases, to avoid	2361	except that changes might be detected earlier, and in some cases, to avoid
1684	making regular C<stat> calls. Even in the presence of inotify support	2362	making regular C<stat> calls. Even in the presence of inotify support
1685	there are many cases where libev has to resort to regular C<stat> polling.	2363	there are many cases where libev has to resort to regular C<stat> polling,
		2364	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2365	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2366	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2367	xfs are fully working) libev usually gets away without polling.
1686		2368
1687	(There is no support for kqueue, as apparently it cannot be used to	2369	There is no support for kqueue, as apparently it cannot be used to
1688	implement this functionality, due to the requirement of having a file	2370	implement this functionality, due to the requirement of having a file
1689	descriptor open on the object at all times).	2371	descriptor open on the object at all times, and detecting renames, unlinks
		2372	etc. is difficult.
		2373
		2374	=head3 C<stat ()> is a synchronous operation
		2375
		2376	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2377	the process. The exception are C<ev_stat> watchers - those call C<stat
		2378	()>, which is a synchronous operation.
		2379
		2380	For local paths, this usually doesn't matter: unless the system is very
		2381	busy or the intervals between stat's are large, a stat call will be fast,
		2382	as the path data is usually in memory already (except when starting the
		2383	watcher).
		2384
		2385	For networked file systems, calling C<stat ()> can block an indefinite
		2386	time due to network issues, and even under good conditions, a stat call
		2387	often takes multiple milliseconds.
		2388
		2389	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2390	paths, although this is fully supported by libev.
1690		2391
1691	=head3 The special problem of stat time resolution	2392	=head3 The special problem of stat time resolution
1692		2393
1693	The C<stat ()> system call only supports full-second resolution portably, and	2394	The C<stat ()> system call only supports full-second resolution portably,
1694	even on systems where the resolution is higher, many file systems still	2395	and even on systems where the resolution is higher, most file systems
1695	only support whole seconds.	2396	still only support whole seconds.
1696		2397
1697	That means that, if the time is the only thing that changes, you can	2398	That means that, if the time is the only thing that changes, you can
1698	easily miss updates: on the first update, C<ev_stat> detects a change and	2399	easily miss updates: on the first update, C<ev_stat> detects a change and
1699	calls your callback, which does something. When there is another update	2400	calls your callback, which does something. When there is another update
1700	within the same second, C<ev_stat> will be unable to detect it as the stat	2401	within the same second, C<ev_stat> will be unable to detect unless the
1701	data does not change.	2402	stat data does change in other ways (e.g. file size).
1702		2403
1703	The solution to this is to delay acting on a change for slightly more	2404	The solution to this is to delay acting on a change for slightly more
1704	than a second (or till slightly after the next full second boundary), using	2405	than a second (or till slightly after the next full second boundary), using
1705	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2406	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1706	ev_timer_again (loop, w)>).	2407	ev_timer_again (loop, w)>).
…		…
1726	C<path>. The C<interval> is a hint on how quickly a change is expected to	2427	C<path>. The C<interval> is a hint on how quickly a change is expected to
1727	be detected and should normally be specified as C<0> to let libev choose	2428	be detected and should normally be specified as C<0> to let libev choose
1728	a suitable value. The memory pointed to by C<path> must point to the same	2429	a suitable value. The memory pointed to by C<path> must point to the same
1729	path for as long as the watcher is active.	2430	path for as long as the watcher is active.
1730		2431
1731	The callback will receive C<EV_STAT> when a change was detected, relative	2432	The callback will receive an C<EV_STAT> event when a change was detected,
1732	to the attributes at the time the watcher was started (or the last change	2433	relative to the attributes at the time the watcher was started (or the
1733	was detected).	2434	last change was detected).
1734		2435
1735	=item ev_stat_stat (loop, ev_stat *)	2436	=item ev_stat_stat (loop, ev_stat *)
1736		2437
1737	Updates the stat buffer immediately with new values. If you change the	2438	Updates the stat buffer immediately with new values. If you change the
1738	watched path in your callback, you could call this function to avoid	2439	watched path in your callback, you could call this function to avoid
…		…
1821		2522
1822		2523
1823	=head2 C<ev_idle> - when you've got nothing better to do...	2524	=head2 C<ev_idle> - when you've got nothing better to do...
1824		2525
1825	Idle watchers trigger events when no other events of the same or higher	2526	Idle watchers trigger events when no other events of the same or higher
1826	priority are pending (prepare, check and other idle watchers do not	2527	priority are pending (prepare, check and other idle watchers do not count
1827	count).	2528	as receiving "events").
1828		2529
1829	That is, as long as your process is busy handling sockets or timeouts	2530	That is, as long as your process is busy handling sockets or timeouts
1830	(or even signals, imagine) of the same or higher priority it will not be	2531	(or even signals, imagine) of the same or higher priority it will not be
1831	triggered. But when your process is idle (or only lower-priority watchers	2532	triggered. But when your process is idle (or only lower-priority watchers
1832	are pending), the idle watchers are being called once per event loop	2533	are pending), the idle watchers are being called once per event loop
…		…
1843		2544
1844	=head3 Watcher-Specific Functions and Data Members	2545	=head3 Watcher-Specific Functions and Data Members
1845		2546
1846	=over 4	2547	=over 4
1847		2548
1848	=item ev_idle_init (ev_signal *, callback)	2549	=item ev_idle_init (ev_idle *, callback)
1849		2550
1850	Initialises and configures the idle watcher - it has no parameters of any	2551	Initialises and configures the idle watcher - it has no parameters of any
1851	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2552	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1852	believe me.	2553	believe me.
1853		2554
…		…
1857		2558
1858	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2559	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1859	callback, free it. Also, use no error checking, as usual.	2560	callback, free it. Also, use no error checking, as usual.
1860		2561
1861	static void	2562	static void
1862	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2563	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1863	{	2564	{
1864	free (w);	2565	free (w);
1865	// now do something you wanted to do when the program has	2566	// now do something you wanted to do when the program has
1866	// no longer anything immediate to do.	2567	// no longer anything immediate to do.
1867	}	2568	}
1868		2569
1869	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2570	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1870	ev_idle_init (idle_watcher, idle_cb);	2571	ev_idle_init (idle_watcher, idle_cb);
1871	ev_idle_start (loop, idle_cb);	2572	ev_idle_start (loop, idle_watcher);
1872		2573
1873		2574
1874	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2575	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1875		2576
1876	Prepare and check watchers are usually (but not always) used in tandem:	2577	Prepare and check watchers are usually (but not always) used in pairs:
1877	prepare watchers get invoked before the process blocks and check watchers	2578	prepare watchers get invoked before the process blocks and check watchers
1878	afterwards.	2579	afterwards.
1879		2580
1880	You I<must not> call C<ev_loop> or similar functions that enter	2581	You I<must not> call C<ev_loop> or similar functions that enter
1881	the current event loop from either C<ev_prepare> or C<ev_check>	2582	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1884	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2585	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1885	C<ev_check> so if you have one watcher of each kind they will always be	2586	C<ev_check> so if you have one watcher of each kind they will always be
1886	called in pairs bracketing the blocking call.	2587	called in pairs bracketing the blocking call.
1887		2588
1888	Their main purpose is to integrate other event mechanisms into libev and	2589	Their main purpose is to integrate other event mechanisms into libev and
1889	their use is somewhat advanced. This could be used, for example, to track	2590	their use is somewhat advanced. They could be used, for example, to track
1890	variable changes, implement your own watchers, integrate net-snmp or a	2591	variable changes, implement your own watchers, integrate net-snmp or a
1891	coroutine library and lots more. They are also occasionally useful if	2592	coroutine library and lots more. They are also occasionally useful if
1892	you cache some data and want to flush it before blocking (for example,	2593	you cache some data and want to flush it before blocking (for example,
1893	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2594	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1894	watcher).	2595	watcher).
1895		2596
1896	This is done by examining in each prepare call which file descriptors need	2597	This is done by examining in each prepare call which file descriptors
1897	to be watched by the other library, registering C<ev_io> watchers for	2598	need to be watched by the other library, registering C<ev_io> watchers
1898	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2599	for them and starting an C<ev_timer> watcher for any timeouts (many
1899	provide just this functionality). Then, in the check watcher you check for	2600	libraries provide exactly this functionality). Then, in the check watcher,
1900	any events that occurred (by checking the pending status of all watchers	2601	you check for any events that occurred (by checking the pending status
1901	and stopping them) and call back into the library. The I/O and timer	2602	of all watchers and stopping them) and call back into the library. The
1902	callbacks will never actually be called (but must be valid nevertheless,	2603	I/O and timer callbacks will never actually be called (but must be valid
1903	because you never know, you know?).	2604	nevertheless, because you never know, you know?).
1904		2605
1905	As another example, the Perl Coro module uses these hooks to integrate	2606	As another example, the Perl Coro module uses these hooks to integrate
1906	coroutines into libev programs, by yielding to other active coroutines	2607	coroutines into libev programs, by yielding to other active coroutines
1907	during each prepare and only letting the process block if no coroutines	2608	during each prepare and only letting the process block if no coroutines
1908	are ready to run (it's actually more complicated: it only runs coroutines	2609	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1911	loop from blocking if lower-priority coroutines are active, thus mapping	2612	loop from blocking if lower-priority coroutines are active, thus mapping
1912	low-priority coroutines to idle/background tasks).	2613	low-priority coroutines to idle/background tasks).
1913		2614
1914	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2615	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1915	priority, to ensure that they are being run before any other watchers	2616	priority, to ensure that they are being run before any other watchers
		2617	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2618
1916	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2619	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1917	too) should not activate ("feed") events into libev. While libev fully	2620	activate ("feed") events into libev. While libev fully supports this, they
1918	supports this, they might get executed before other C<ev_check> watchers	2621	might get executed before other C<ev_check> watchers did their job. As
1919	did their job. As C<ev_check> watchers are often used to embed other	2622	C<ev_check> watchers are often used to embed other (non-libev) event
1920	(non-libev) event loops those other event loops might be in an unusable	2623	loops those other event loops might be in an unusable state until their
1921	state until their C<ev_check> watcher ran (always remind yourself to	2624	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1922	coexist peacefully with others).	2625	others).
1923		2626
1924	=head3 Watcher-Specific Functions and Data Members	2627	=head3 Watcher-Specific Functions and Data Members
1925		2628
1926	=over 4	2629	=over 4
1927		2630
…		…
1929		2632
1930	=item ev_check_init (ev_check *, callback)	2633	=item ev_check_init (ev_check *, callback)
1931		2634
1932	Initialises and configures the prepare or check watcher - they have no	2635	Initialises and configures the prepare or check watcher - they have no
1933	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2636	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1934	macros, but using them is utterly, utterly and completely pointless.	2637	macros, but using them is utterly, utterly, utterly and completely
		2638	pointless.
1935		2639
1936	=back	2640	=back
1937		2641
1938	=head3 Examples	2642	=head3 Examples
1939		2643
…		…
1952		2656
1953	static ev_io iow [nfd];	2657	static ev_io iow [nfd];
1954	static ev_timer tw;	2658	static ev_timer tw;
1955		2659
1956	static void	2660	static void
1957	io_cb (ev_loop *loop, ev_io *w, int revents)	2661	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1958	{	2662	{
1959	}	2663	}
1960		2664
1961	// create io watchers for each fd and a timer before blocking	2665	// create io watchers for each fd and a timer before blocking
1962	static void	2666	static void
1963	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2667	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1964	{	2668	{
1965	int timeout = 3600000;	2669	int timeout = 3600000;
1966	struct pollfd fds [nfd];	2670	struct pollfd fds [nfd];
1967	// actual code will need to loop here and realloc etc.	2671	// actual code will need to loop here and realloc etc.
1968	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2672	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1969		2673
1970	/* the callback is illegal, but won't be called as we stop during check */	2674	/* the callback is illegal, but won't be called as we stop during check */
1971	ev_timer_init (&tw, 0, timeout * 1e-3);	2675	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
1972	ev_timer_start (loop, &tw);	2676	ev_timer_start (loop, &tw);
1973		2677
1974	// create one ev_io per pollfd	2678	// create one ev_io per pollfd
1975	for (int i = 0; i < nfd; ++i)	2679	for (int i = 0; i < nfd; ++i)
1976	{	2680	{
…		…
1983	}	2687	}
1984	}	2688	}
1985		2689
1986	// stop all watchers after blocking	2690	// stop all watchers after blocking
1987	static void	2691	static void
1988	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2692	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1989	{	2693	{
1990	ev_timer_stop (loop, &tw);	2694	ev_timer_stop (loop, &tw);
1991		2695
1992	for (int i = 0; i < nfd; ++i)	2696	for (int i = 0; i < nfd; ++i)
1993	{	2697	{
…		…
2032	}	2736	}
2033		2737
2034	// do not ever call adns_afterpoll	2738	// do not ever call adns_afterpoll
2035		2739
2036	Method 4: Do not use a prepare or check watcher because the module you	2740	Method 4: Do not use a prepare or check watcher because the module you
2037	want to embed is too inflexible to support it. Instead, you can override	2741	want to embed is not flexible enough to support it. Instead, you can
2038	their poll function. The drawback with this solution is that the main	2742	override their poll function. The drawback with this solution is that the
2039	loop is now no longer controllable by EV. The C<Glib::EV> module does	2743	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2040	this.	2744	this approach, effectively embedding EV as a client into the horrible
		2745	libglib event loop.
2041		2746
2042	static gint	2747	static gint
2043	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2748	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2044	{	2749	{
2045	int got_events = 0;	2750	int got_events = 0;
…		…
2076	prioritise I/O.	2781	prioritise I/O.
2077		2782
2078	As an example for a bug workaround, the kqueue backend might only support	2783	As an example for a bug workaround, the kqueue backend might only support
2079	sockets on some platform, so it is unusable as generic backend, but you	2784	sockets on some platform, so it is unusable as generic backend, but you
2080	still want to make use of it because you have many sockets and it scales	2785	still want to make use of it because you have many sockets and it scales
2081	so nicely. In this case, you would create a kqueue-based loop and embed it	2786	so nicely. In this case, you would create a kqueue-based loop and embed
2082	into your default loop (which might use e.g. poll). Overall operation will	2787	it into your default loop (which might use e.g. poll). Overall operation
2083	be a bit slower because first libev has to poll and then call kevent, but	2788	will be a bit slower because first libev has to call C<poll> and then
2084	at least you can use both at what they are best.	2789	C<kevent>, but at least you can use both mechanisms for what they are
		2790	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2085		2791
2086	As for prioritising I/O: rarely you have the case where some fds have	2792	As for prioritising I/O: under rare circumstances you have the case where
2087	to be watched and handled very quickly (with low latency), and even	2793	some fds have to be watched and handled very quickly (with low latency),
2088	priorities and idle watchers might have too much overhead. In this case	2794	and even priorities and idle watchers might have too much overhead. In
2089	you would put all the high priority stuff in one loop and all the rest in	2795	this case you would put all the high priority stuff in one loop and all
2090	a second one, and embed the second one in the first.	2796	the rest in a second one, and embed the second one in the first.
2091		2797
2092	As long as the watcher is active, the callback will be invoked every time	2798	As long as the watcher is active, the callback will be invoked every
2093	there might be events pending in the embedded loop. The callback must then	2799	time there might be events pending in the embedded loop. The callback
2094	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2800	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2095	their callbacks (you could also start an idle watcher to give the embedded	2801	sweep and invoke their callbacks (the callback doesn't need to invoke the
2096	loop strictly lower priority for example). You can also set the callback	2802	C<ev_embed_sweep> function directly, it could also start an idle watcher
2097	to C<0>, in which case the embed watcher will automatically execute the	2803	to give the embedded loop strictly lower priority for example).
2098	embedded loop sweep.
2099		2804
2100	As long as the watcher is started it will automatically handle events. The	2805	You can also set the callback to C<0>, in which case the embed watcher
2101	callback will be invoked whenever some events have been handled. You can	2806	will automatically execute the embedded loop sweep whenever necessary.
2102	set the callback to C<0> to avoid having to specify one if you are not
2103	interested in that.
2104		2807
2105	Also, there have not currently been made special provisions for forking:	2808	Fork detection will be handled transparently while the C<ev_embed> watcher
2106	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2809	is active, i.e., the embedded loop will automatically be forked when the
2107	but you will also have to stop and restart any C<ev_embed> watchers	2810	embedding loop forks. In other cases, the user is responsible for calling
2108	yourself.	2811	C<ev_loop_fork> on the embedded loop.
2109		2812
2110	Unfortunately, not all backends are embeddable, only the ones returned by	2813	Unfortunately, not all backends are embeddable: only the ones returned by
2111	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2814	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2112	portable one.	2815	portable one.
2113		2816
2114	So when you want to use this feature you will always have to be prepared	2817	So when you want to use this feature you will always have to be prepared
2115	that you cannot get an embeddable loop. The recommended way to get around	2818	that you cannot get an embeddable loop. The recommended way to get around
2116	this is to have a separate variables for your embeddable loop, try to	2819	this is to have a separate variables for your embeddable loop, try to
2117	create it, and if that fails, use the normal loop for everything.	2820	create it, and if that fails, use the normal loop for everything.
		2821
		2822	=head3 C<ev_embed> and fork
		2823
		2824	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2825	automatically be applied to the embedded loop as well, so no special
		2826	fork handling is required in that case. When the watcher is not running,
		2827	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2828	as applicable.
2118		2829
2119	=head3 Watcher-Specific Functions and Data Members	2830	=head3 Watcher-Specific Functions and Data Members
2120		2831
2121	=over 4	2832	=over 4
2122		2833
…		…
2150	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2861	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2151	used).	2862	used).
2152		2863
2153	struct ev_loop *loop_hi = ev_default_init (0);	2864	struct ev_loop *loop_hi = ev_default_init (0);
2154	struct ev_loop *loop_lo = 0;	2865	struct ev_loop *loop_lo = 0;
2155	struct ev_embed embed;	2866	ev_embed embed;
2156		2867
2157	// see if there is a chance of getting one that works	2868	// see if there is a chance of getting one that works
2158	// (remember that a flags value of 0 means autodetection)	2869	// (remember that a flags value of 0 means autodetection)
2159	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2870	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2160	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2871	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2174	kqueue implementation). Store the kqueue/socket-only event loop in	2885	kqueue implementation). Store the kqueue/socket-only event loop in
2175	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2886	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2176		2887
2177	struct ev_loop *loop = ev_default_init (0);	2888	struct ev_loop *loop = ev_default_init (0);
2178	struct ev_loop *loop_socket = 0;	2889	struct ev_loop *loop_socket = 0;
2179	struct ev_embed embed;	2890	ev_embed embed;
2180		2891
2181	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2892	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2182	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2893	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2183	{	2894	{
2184	ev_embed_init (&embed, 0, loop_socket);	2895	ev_embed_init (&embed, 0, loop_socket);
…		…
2199	event loop blocks next and before C<ev_check> watchers are being called,	2910	event loop blocks next and before C<ev_check> watchers are being called,
2200	and only in the child after the fork. If whoever good citizen calling	2911	and only in the child after the fork. If whoever good citizen calling
2201	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2912	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2202	handlers will be invoked, too, of course.	2913	handlers will be invoked, too, of course.
2203		2914
		2915	=head3 The special problem of life after fork - how is it possible?
		2916
		2917	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2918	up/change the process environment, followed by a call to C<exec()>. This
		2919	sequence should be handled by libev without any problems.
		2920
		2921	This changes when the application actually wants to do event handling
		2922	in the child, or both parent in child, in effect "continuing" after the
		2923	fork.
		2924
		2925	The default mode of operation (for libev, with application help to detect
		2926	forks) is to duplicate all the state in the child, as would be expected
		2927	when I<either> the parent I<or> the child process continues.
		2928
		2929	When both processes want to continue using libev, then this is usually the
		2930	wrong result. In that case, usually one process (typically the parent) is
		2931	supposed to continue with all watchers in place as before, while the other
		2932	process typically wants to start fresh, i.e. without any active watchers.
		2933
		2934	The cleanest and most efficient way to achieve that with libev is to
		2935	simply create a new event loop, which of course will be "empty", and
		2936	use that for new watchers. This has the advantage of not touching more
		2937	memory than necessary, and thus avoiding the copy-on-write, and the
		2938	disadvantage of having to use multiple event loops (which do not support
		2939	signal watchers).
		2940
		2941	When this is not possible, or you want to use the default loop for
		2942	other reasons, then in the process that wants to start "fresh", call
		2943	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2944	the default loop will "orphan" (not stop) all registered watchers, so you
		2945	have to be careful not to execute code that modifies those watchers. Note
		2946	also that in that case, you have to re-register any signal watchers.
		2947
2204	=head3 Watcher-Specific Functions and Data Members	2948	=head3 Watcher-Specific Functions and Data Members
2205		2949
2206	=over 4	2950	=over 4
2207		2951
2208	=item ev_fork_init (ev_signal *, callback)	2952	=item ev_fork_init (ev_signal *, callback)
…		…
2240	is that the author does not know of a simple (or any) algorithm for a	2984	is that the author does not know of a simple (or any) algorithm for a
2241	multiple-writer-single-reader queue that works in all cases and doesn't	2985	multiple-writer-single-reader queue that works in all cases and doesn't
2242	need elaborate support such as pthreads.	2986	need elaborate support such as pthreads.
2243		2987
2244	That means that if you want to queue data, you have to provide your own	2988	That means that if you want to queue data, you have to provide your own
2245	queue. But at least I can tell you would implement locking around your	2989	queue. But at least I can tell you how to implement locking around your
2246	queue:	2990	queue:
2247		2991
2248	=over 4	2992	=over 4
2249		2993
2250	=item queueing from a signal handler context	2994	=item queueing from a signal handler context
2251		2995
2252	To implement race-free queueing, you simply add to the queue in the signal	2996	To implement race-free queueing, you simply add to the queue in the signal
2253	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2997	handler but you block the signal handler in the watcher callback. Here is
2254	some fictitious SIGUSR1 handler:	2998	an example that does that for some fictitious SIGUSR1 handler:
2255		2999
2256	static ev_async mysig;	3000	static ev_async mysig;
2257		3001
2258	static void	3002	static void
2259	sigusr1_handler (void)	3003	sigusr1_handler (void)
…		…
2325	=over 4	3069	=over 4
2326		3070
2327	=item ev_async_init (ev_async *, callback)	3071	=item ev_async_init (ev_async *, callback)
2328		3072
2329	Initialises and configures the async watcher - it has no parameters of any	3073	Initialises and configures the async watcher - it has no parameters of any
2330	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3074	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2331	believe me.	3075	trust me.
2332		3076
2333	=item ev_async_send (loop, ev_async *)	3077	=item ev_async_send (loop, ev_async *)
2334		3078
2335	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3079	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2336	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3080	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2337	C<ev_feed_event>, this call is safe to do in other threads, signal or	3081	C<ev_feed_event>, this call is safe to do from other threads, signal or
2338	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3082	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2339	section below on what exactly this means).	3083	section below on what exactly this means).
2340		3084
		3085	Note that, as with other watchers in libev, multiple events might get
		3086	compressed into a single callback invocation (another way to look at this
		3087	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3088	reset when the event loop detects that).
		3089
2341	This call incurs the overhead of a system call only once per loop iteration,	3090	This call incurs the overhead of a system call only once per event loop
2342	so while the overhead might be noticeable, it doesn't apply to repeated	3091	iteration, so while the overhead might be noticeable, it doesn't apply to
2343	calls to C<ev_async_send>.	3092	repeated calls to C<ev_async_send> for the same event loop.
2344		3093
2345	=item bool = ev_async_pending (ev_async *)	3094	=item bool = ev_async_pending (ev_async *)
2346		3095
2347	Returns a non-zero value when C<ev_async_send> has been called on the	3096	Returns a non-zero value when C<ev_async_send> has been called on the
2348	watcher but the event has not yet been processed (or even noted) by the	3097	watcher but the event has not yet been processed (or even noted) by the
…		…
2351	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3100	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2352	the loop iterates next and checks for the watcher to have become active,	3101	the loop iterates next and checks for the watcher to have become active,
2353	it will reset the flag again. C<ev_async_pending> can be used to very	3102	it will reset the flag again. C<ev_async_pending> can be used to very
2354	quickly check whether invoking the loop might be a good idea.	3103	quickly check whether invoking the loop might be a good idea.
2355		3104
2356	Not that this does I<not> check whether the watcher itself is pending, only	3105	Not that this does I<not> check whether the watcher itself is pending,
2357	whether it has been requested to make this watcher pending.	3106	only whether it has been requested to make this watcher pending: there
		3107	is a time window between the event loop checking and resetting the async
		3108	notification, and the callback being invoked.
2358		3109
2359	=back	3110	=back
2360		3111
2361		3112
2362	=head1 OTHER FUNCTIONS	3113	=head1 OTHER FUNCTIONS
…		…
2366	=over 4	3117	=over 4
2367		3118
2368	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3119	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2369		3120
2370	This function combines a simple timer and an I/O watcher, calls your	3121	This function combines a simple timer and an I/O watcher, calls your
2371	callback on whichever event happens first and automatically stop both	3122	callback on whichever event happens first and automatically stops both
2372	watchers. This is useful if you want to wait for a single event on an fd	3123	watchers. This is useful if you want to wait for a single event on an fd
2373	or timeout without having to allocate/configure/start/stop/free one or	3124	or timeout without having to allocate/configure/start/stop/free one or
2374	more watchers yourself.	3125	more watchers yourself.
2375		3126
2376	If C<fd> is less than 0, then no I/O watcher will be started and events	3127	If C<fd> is less than 0, then no I/O watcher will be started and the
2377	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	3128	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2378	C<events> set will be created and started.	3129	the given C<fd> and C<events> set will be created and started.
2379		3130
2380	If C<timeout> is less than 0, then no timeout watcher will be	3131	If C<timeout> is less than 0, then no timeout watcher will be
2381	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3132	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2382	repeat = 0) will be started. While C<0> is a valid timeout, it is of	3133	repeat = 0) will be started. C<0> is a valid timeout.
2383	dubious value.
2384		3134
2385	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3135	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2386	passed an C<revents> set like normal event callbacks (a combination of	3136	passed an C<revents> set like normal event callbacks (a combination of
2387	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3137	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2388	value passed to C<ev_once>:	3138	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3139	a timeout and an io event at the same time - you probably should give io
		3140	events precedence.
		3141
		3142	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2389		3143
2390	static void stdin_ready (int revents, void *arg)	3144	static void stdin_ready (int revents, void *arg)
2391	{	3145	{
		3146	if (revents & EV_READ)
		3147	/* stdin might have data for us, joy! */;
2392	if (revents & EV_TIMEOUT)	3148	else if (revents & EV_TIMEOUT)
2393	/* doh, nothing entered */;	3149	/* doh, nothing entered */;
2394	else if (revents & EV_READ)
2395	/* stdin might have data for us, joy! */;
2396	}	3150	}
2397		3151
2398	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3152	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2399		3153
2400	=item ev_feed_event (ev_loop *, watcher *, int revents)
2401
2402	Feeds the given event set into the event loop, as if the specified event
2403	had happened for the specified watcher (which must be a pointer to an
2404	initialised but not necessarily started event watcher).
2405
2406	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3154	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2407		3155
2408	Feed an event on the given fd, as if a file descriptor backend detected	3156	Feed an event on the given fd, as if a file descriptor backend detected
2409	the given events it.	3157	the given events it.
2410		3158
2411	=item ev_feed_signal_event (ev_loop *loop, int signum)	3159	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2412		3160
2413	Feed an event as if the given signal occurred (C<loop> must be the default	3161	Feed an event as if the given signal occurred (C<loop> must be the default
2414	loop!).	3162	loop!).
2415		3163
2416	=back	3164	=back
…		…
2538		3286
2539	myclass obj;	3287	myclass obj;
2540	ev::io iow;	3288	ev::io iow;
2541	iow.set <myclass, &myclass::io_cb> (&obj);	3289	iow.set <myclass, &myclass::io_cb> (&obj);
2542		3290
		3291	=item w->set (object *)
		3292
		3293	This is an B<experimental> feature that might go away in a future version.
		3294
		3295	This is a variation of a method callback - leaving out the method to call
		3296	will default the method to C<operator ()>, which makes it possible to use
		3297	functor objects without having to manually specify the C<operator ()> all
		3298	the time. Incidentally, you can then also leave out the template argument
		3299	list.
		3300
		3301	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3302	int revents)>.
		3303
		3304	See the method-C<set> above for more details.
		3305
		3306	Example: use a functor object as callback.
		3307
		3308	struct myfunctor
		3309	{
		3310	void operator() (ev::io &w, int revents)
		3311	{
		3312	...
		3313	}
		3314	}
		3315
		3316	myfunctor f;
		3317
		3318	ev::io w;
		3319	w.set (&f);
		3320
2543	=item w->set<function> (void *data = 0)	3321	=item w->set<function> (void *data = 0)
2544		3322
2545	Also sets a callback, but uses a static method or plain function as	3323	Also sets a callback, but uses a static method or plain function as
2546	callback. The optional C<data> argument will be stored in the watcher's	3324	callback. The optional C<data> argument will be stored in the watcher's
2547	C<data> member and is free for you to use.	3325	C<data> member and is free for you to use.
2548		3326
2549	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3327	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2550		3328
2551	See the method-C<set> above for more details.	3329	See the method-C<set> above for more details.
2552		3330
2553	Example:	3331	Example: Use a plain function as callback.
2554		3332
2555	static void io_cb (ev::io &w, int revents) { }	3333	static void io_cb (ev::io &w, int revents) { }
2556	iow.set <io_cb> ();	3334	iow.set <io_cb> ();
2557		3335
2558	=item w->set (struct ev_loop *)	3336	=item w->set (struct ev_loop *)
…		…
2596	Example: Define a class with an IO and idle watcher, start one of them in	3374	Example: Define a class with an IO and idle watcher, start one of them in
2597	the constructor.	3375	the constructor.
2598		3376
2599	class myclass	3377	class myclass
2600	{	3378	{
2601	ev::io io; void io_cb (ev::io &w, int revents);	3379	ev::io io ; void io_cb (ev::io &w, int revents);
2602	ev:idle idle void idle_cb (ev::idle &w, int revents);	3380	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2603		3381
2604	myclass (int fd)	3382	myclass (int fd)
2605	{	3383	{
2606	io .set <myclass, &myclass::io_cb > (this);	3384	io .set <myclass, &myclass::io_cb > (this);
2607	idle.set <myclass, &myclass::idle_cb> (this);	3385	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2623	=item Perl	3401	=item Perl
2624		3402
2625	The EV module implements the full libev API and is actually used to test	3403	The EV module implements the full libev API and is actually used to test
2626	libev. EV is developed together with libev. Apart from the EV core module,	3404	libev. EV is developed together with libev. Apart from the EV core module,
2627	there are additional modules that implement libev-compatible interfaces	3405	there are additional modules that implement libev-compatible interfaces
2628	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3406	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2629	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3407	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3408	and C<EV::Glib>).
2630		3409
2631	It can be found and installed via CPAN, its homepage is at	3410	It can be found and installed via CPAN, its homepage is at
2632	L<http://software.schmorp.de/pkg/EV>.	3411	L<http://software.schmorp.de/pkg/EV>.
2633		3412
2634	=item Python	3413	=item Python
2635		3414
2636	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3415	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2637	seems to be quite complete and well-documented. Note, however, that the	3416	seems to be quite complete and well-documented.
2638	patch they require for libev is outright dangerous as it breaks the ABI
2639	for everybody else, and therefore, should never be applied in an installed
2640	libev (if python requires an incompatible ABI then it needs to embed
2641	libev).
2642		3417
2643	=item Ruby	3418	=item Ruby
2644		3419
2645	Tony Arcieri has written a ruby extension that offers access to a subset	3420	Tony Arcieri has written a ruby extension that offers access to a subset
2646	of the libev API and adds file handle abstractions, asynchronous DNS and	3421	of the libev API and adds file handle abstractions, asynchronous DNS and
2647	more on top of it. It can be found via gem servers. Its homepage is at	3422	more on top of it. It can be found via gem servers. Its homepage is at
2648	L<http://rev.rubyforge.org/>.	3423	L<http://rev.rubyforge.org/>.
2649		3424
		3425	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3426	makes rev work even on mingw.
		3427
		3428	=item Haskell
		3429
		3430	A haskell binding to libev is available at
		3431	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3432
2650	=item D	3433	=item D
2651		3434
2652	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3435	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2653	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	3436	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3437
		3438	=item Ocaml
		3439
		3440	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3441	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3442
		3443	=item Lua
		3444
		3445	Brian Maher has written a partial interface to libev
		3446	for lua (only C<ev_io> and C<ev_timer>), to be found at
		3447	L<http://github.com/brimworks/lua-ev>.
2654		3448
2655	=back	3449	=back
2656		3450
2657		3451
2658	=head1 MACRO MAGIC	3452	=head1 MACRO MAGIC
…		…
2759		3553
2760	#define EV_STANDALONE 1	3554	#define EV_STANDALONE 1
2761	#include "ev.h"	3555	#include "ev.h"
2762		3556
2763	Both header files and implementation files can be compiled with a C++	3557	Both header files and implementation files can be compiled with a C++
2764	compiler (at least, thats a stated goal, and breakage will be treated	3558	compiler (at least, that's a stated goal, and breakage will be treated
2765	as a bug).	3559	as a bug).
2766		3560
2767	You need the following files in your source tree, or in a directory	3561	You need the following files in your source tree, or in a directory
2768	in your include path (e.g. in libev/ when using -Ilibev):	3562	in your include path (e.g. in libev/ when using -Ilibev):
2769		3563
…		…
2813		3607
2814	=head2 PREPROCESSOR SYMBOLS/MACROS	3608	=head2 PREPROCESSOR SYMBOLS/MACROS
2815		3609
2816	Libev can be configured via a variety of preprocessor symbols you have to	3610	Libev can be configured via a variety of preprocessor symbols you have to
2817	define before including any of its files. The default in the absence of	3611	define before including any of its files. The default in the absence of
2818	autoconf is noted for every option.	3612	autoconf is documented for every option.
2819		3613
2820	=over 4	3614	=over 4
2821		3615
2822	=item EV_STANDALONE	3616	=item EV_STANDALONE
2823		3617
…		…
2825	keeps libev from including F<config.h>, and it also defines dummy	3619	keeps libev from including F<config.h>, and it also defines dummy
2826	implementations for some libevent functions (such as logging, which is not	3620	implementations for some libevent functions (such as logging, which is not
2827	supported). It will also not define any of the structs usually found in	3621	supported). It will also not define any of the structs usually found in
2828	F<event.h> that are not directly supported by the libev core alone.	3622	F<event.h> that are not directly supported by the libev core alone.
2829		3623
		3624	In standalone mode, libev will still try to automatically deduce the
		3625	configuration, but has to be more conservative.
		3626
2830	=item EV_USE_MONOTONIC	3627	=item EV_USE_MONOTONIC
2831		3628
2832	If defined to be C<1>, libev will try to detect the availability of the	3629	If defined to be C<1>, libev will try to detect the availability of the
2833	monotonic clock option at both compile time and runtime. Otherwise no use	3630	monotonic clock option at both compile time and runtime. Otherwise no
2834	of the monotonic clock option will be attempted. If you enable this, you	3631	use of the monotonic clock option will be attempted. If you enable this,
2835	usually have to link against librt or something similar. Enabling it when	3632	you usually have to link against librt or something similar. Enabling it
2836	the functionality isn't available is safe, though, although you have	3633	when the functionality isn't available is safe, though, although you have
2837	to make sure you link against any libraries where the C<clock_gettime>	3634	to make sure you link against any libraries where the C<clock_gettime>
2838	function is hiding in (often F<-lrt>).	3635	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2839		3636
2840	=item EV_USE_REALTIME	3637	=item EV_USE_REALTIME
2841		3638
2842	If defined to be C<1>, libev will try to detect the availability of the	3639	If defined to be C<1>, libev will try to detect the availability of the
2843	real-time clock option at compile time (and assume its availability at	3640	real-time clock option at compile time (and assume its availability
2844	runtime if successful). Otherwise no use of the real-time clock option will	3641	at runtime if successful). Otherwise no use of the real-time clock
2845	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3642	option will be attempted. This effectively replaces C<gettimeofday>
2846	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3643	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2847	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3644	correctness. See the note about libraries in the description of
		3645	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3646	C<EV_USE_CLOCK_SYSCALL>.
		3647
		3648	=item EV_USE_CLOCK_SYSCALL
		3649
		3650	If defined to be C<1>, libev will try to use a direct syscall instead
		3651	of calling the system-provided C<clock_gettime> function. This option
		3652	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3653	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3654	programs needlessly. Using a direct syscall is slightly slower (in
		3655	theory), because no optimised vdso implementation can be used, but avoids
		3656	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3657	higher, as it simplifies linking (no need for C<-lrt>).
2848		3658
2849	=item EV_USE_NANOSLEEP	3659	=item EV_USE_NANOSLEEP
2850		3660
2851	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3661	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2852	and will use it for delays. Otherwise it will use C<select ()>.	3662	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2868		3678
2869	=item EV_SELECT_USE_FD_SET	3679	=item EV_SELECT_USE_FD_SET
2870		3680
2871	If defined to C<1>, then the select backend will use the system C<fd_set>	3681	If defined to C<1>, then the select backend will use the system C<fd_set>
2872	structure. This is useful if libev doesn't compile due to a missing	3682	structure. This is useful if libev doesn't compile due to a missing
2873	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3683	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2874	exotic systems. This usually limits the range of file descriptors to some	3684	on exotic systems. This usually limits the range of file descriptors to
2875	low limit such as 1024 or might have other limitations (winsocket only	3685	some low limit such as 1024 or might have other limitations (winsocket
2876	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3686	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2877	influence the size of the C<fd_set> used.	3687	configures the maximum size of the C<fd_set>.
2878		3688
2879	=item EV_SELECT_IS_WINSOCKET	3689	=item EV_SELECT_IS_WINSOCKET
2880		3690
2881	When defined to C<1>, the select backend will assume that	3691	When defined to C<1>, the select backend will assume that
2882	select/socket/connect etc. don't understand file descriptors but	3692	select/socket/connect etc. don't understand file descriptors but
…		…
2884	be used is the winsock select). This means that it will call	3694	be used is the winsock select). This means that it will call
2885	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3695	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2886	it is assumed that all these functions actually work on fds, even	3696	it is assumed that all these functions actually work on fds, even
2887	on win32. Should not be defined on non-win32 platforms.	3697	on win32. Should not be defined on non-win32 platforms.
2888		3698
2889	=item EV_FD_TO_WIN32_HANDLE	3699	=item EV_FD_TO_WIN32_HANDLE(fd)
2890		3700
2891	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3701	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
2892	file descriptors to socket handles. When not defining this symbol (the	3702	file descriptors to socket handles. When not defining this symbol (the
2893	default), then libev will call C<_get_osfhandle>, which is usually	3703	default), then libev will call C<_get_osfhandle>, which is usually
2894	correct. In some cases, programs use their own file descriptor management,	3704	correct. In some cases, programs use their own file descriptor management,
2895	in which case they can provide this function to map fds to socket handles.	3705	in which case they can provide this function to map fds to socket handles.
		3706
		3707	=item EV_WIN32_HANDLE_TO_FD(handle)
		3708
		3709	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3710	using the standard C<_open_osfhandle> function. For programs implementing
		3711	their own fd to handle mapping, overwriting this function makes it easier
		3712	to do so. This can be done by defining this macro to an appropriate value.
		3713
		3714	=item EV_WIN32_CLOSE_FD(fd)
		3715
		3716	If programs implement their own fd to handle mapping on win32, then this
		3717	macro can be used to override the C<close> function, useful to unregister
		3718	file descriptors again. Note that the replacement function has to close
		3719	the underlying OS handle.
2896		3720
2897	=item EV_USE_POLL	3721	=item EV_USE_POLL
2898		3722
2899	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3723	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2900	backend. Otherwise it will be enabled on non-win32 platforms. It	3724	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
2993	When doing priority-based operations, libev usually has to linearly search	3817	When doing priority-based operations, libev usually has to linearly search
2994	all the priorities, so having many of them (hundreds) uses a lot of space	3818	all the priorities, so having many of them (hundreds) uses a lot of space
2995	and time, so using the defaults of five priorities (-2 .. +2) is usually	3819	and time, so using the defaults of five priorities (-2 .. +2) is usually
2996	fine.	3820	fine.
2997		3821
2998	If your embedding application does not need any priorities, defining these both to	3822	If your embedding application does not need any priorities, defining these
2999	C<0> will save some memory and CPU.	3823	both to C<0> will save some memory and CPU.
3000		3824
3001	=item EV_PERIODIC_ENABLE	3825	=item EV_PERIODIC_ENABLE
3002		3826
3003	If undefined or defined to be C<1>, then periodic timers are supported. If	3827	If undefined or defined to be C<1>, then periodic timers are supported. If
3004	defined to be C<0>, then they are not. Disabling them saves a few kB of	3828	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3011	code.	3835	code.
3012		3836
3013	=item EV_EMBED_ENABLE	3837	=item EV_EMBED_ENABLE
3014		3838
3015	If undefined or defined to be C<1>, then embed watchers are supported. If	3839	If undefined or defined to be C<1>, then embed watchers are supported. If
3016	defined to be C<0>, then they are not.	3840	defined to be C<0>, then they are not. Embed watchers rely on most other
		3841	watcher types, which therefore must not be disabled.
3017		3842
3018	=item EV_STAT_ENABLE	3843	=item EV_STAT_ENABLE
3019		3844
3020	If undefined or defined to be C<1>, then stat watchers are supported. If	3845	If undefined or defined to be C<1>, then stat watchers are supported. If
3021	defined to be C<0>, then they are not.	3846	defined to be C<0>, then they are not.
…		…
3031	defined to be C<0>, then they are not.	3856	defined to be C<0>, then they are not.
3032		3857
3033	=item EV_MINIMAL	3858	=item EV_MINIMAL
3034		3859
3035	If you need to shave off some kilobytes of code at the expense of some	3860	If you need to shave off some kilobytes of code at the expense of some
3036	speed, define this symbol to C<1>. Currently this is used to override some	3861	speed (but with the full API), define this symbol to C<1>. Currently this
3037	inlining decisions, saves roughly 30% code size on amd64. It also selects a	3862	is used to override some inlining decisions, saves roughly 30% code size
3038	much smaller 2-heap for timer management over the default 4-heap.	3863	on amd64. It also selects a much smaller 2-heap for timer management over
		3864	the default 4-heap.
		3865
		3866	You can save even more by disabling watcher types you do not need
		3867	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>
		3868	(C<-DNDEBUG>) will usually reduce code size a lot.
		3869
		3870	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to
		3871	provide a bare-bones event library. See C<ev.h> for details on what parts
		3872	of the API are still available, and do not complain if this subset changes
		3873	over time.
		3874
		3875	=item EV_NSIG
		3876
		3877	The highest supported signal number, +1 (or, the number of
		3878	signals): Normally, libev tries to deduce the maximum number of signals
		3879	automatically, but sometimes this fails, in which case it can be
		3880	specified. Also, using a lower number than detected (C<32> should be
		3881	good for about any system in existance) can save some memory, as libev
		3882	statically allocates some 12-24 bytes per signal number.
3039		3883
3040	=item EV_PID_HASHSIZE	3884	=item EV_PID_HASHSIZE
3041		3885
3042	C<ev_child> watchers use a small hash table to distribute workload by	3886	C<ev_child> watchers use a small hash table to distribute workload by
3043	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3887	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
3053	two).	3897	two).
3054		3898
3055	=item EV_USE_4HEAP	3899	=item EV_USE_4HEAP
3056		3900
3057	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3901	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3058	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3902	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3059	to C<1>. The 4-heap uses more complicated (longer) code but has	3903	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3060	noticeably faster performance with many (thousands) of watchers.	3904	faster performance with many (thousands) of watchers.
3061		3905
3062	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3906	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3063	(disabled).	3907	(disabled).
3064		3908
3065	=item EV_HEAP_CACHE_AT	3909	=item EV_HEAP_CACHE_AT
3066		3910
3067	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3911	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3068	timer and periodics heap, libev can cache the timestamp (I<at>) within	3912	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3069	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3913	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3070	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3914	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3071	but avoids random read accesses on heap changes. This improves performance	3915	but avoids random read accesses on heap changes. This improves performance
3072	noticeably with with many (hundreds) of watchers.	3916	noticeably with many (hundreds) of watchers.
3073		3917
3074	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3918	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3075	(disabled).	3919	(disabled).
3076		3920
3077	=item EV_VERIFY	3921	=item EV_VERIFY
…		…
3083	called once per loop, which can slow down libev. If set to C<3>, then the	3927	called once per loop, which can slow down libev. If set to C<3>, then the
3084	verification code will be called very frequently, which will slow down	3928	verification code will be called very frequently, which will slow down
3085	libev considerably.	3929	libev considerably.
3086		3930
3087	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3931	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3088	C<0.>	3932	C<0>.
3089		3933
3090	=item EV_COMMON	3934	=item EV_COMMON
3091		3935
3092	By default, all watchers have a C<void *data> member. By redefining	3936	By default, all watchers have a C<void *data> member. By redefining
3093	this macro to a something else you can include more and other types of	3937	this macro to a something else you can include more and other types of
…		…
3110	and the way callbacks are invoked and set. Must expand to a struct member	3954	and the way callbacks are invoked and set. Must expand to a struct member
3111	definition and a statement, respectively. See the F<ev.h> header file for	3955	definition and a statement, respectively. See the F<ev.h> header file for
3112	their default definitions. One possible use for overriding these is to	3956	their default definitions. One possible use for overriding these is to
3113	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3957	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3114	method calls instead of plain function calls in C++.	3958	method calls instead of plain function calls in C++.
		3959
		3960	=back
3115		3961
3116	=head2 EXPORTED API SYMBOLS	3962	=head2 EXPORTED API SYMBOLS
3117		3963
3118	If you need to re-export the API (e.g. via a DLL) and you need a list of	3964	If you need to re-export the API (e.g. via a DLL) and you need a list of
3119	exported symbols, you can use the provided F<Symbol.*> files which list	3965	exported symbols, you can use the provided F<Symbol.*> files which list
…		…
3166	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4012	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3167		4013
3168	#include "ev_cpp.h"	4014	#include "ev_cpp.h"
3169	#include "ev.c"	4015	#include "ev.c"
3170		4016
		4017	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3171		4018
3172	=head1 THREADS AND COROUTINES	4019	=head2 THREADS AND COROUTINES
3173		4020
3174	=head2 THREADS	4021	=head3 THREADS
3175		4022
3176	Libev itself is completely thread-safe, but it uses no locking. This	4023	All libev functions are reentrant and thread-safe unless explicitly
		4024	documented otherwise, but libev implements no locking itself. This means
3177	means that you can use as many loops as you want in parallel, as long as	4025	that you can use as many loops as you want in parallel, as long as there
3178	only one thread ever calls into one libev function with the same loop	4026	are no concurrent calls into any libev function with the same loop
3179	parameter.	4027	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		4028	of course): libev guarantees that different event loops share no data
		4029	structures that need any locking.
3180		4030
3181	Or put differently: calls with different loop parameters can be done in	4031	Or to put it differently: calls with different loop parameters can be done
3182	parallel from multiple threads, calls with the same loop parameter must be	4032	concurrently from multiple threads, calls with the same loop parameter
3183	done serially (but can be done from different threads, as long as only one	4033	must be done serially (but can be done from different threads, as long as
3184	thread ever is inside a call at any point in time, e.g. by using a mutex	4034	only one thread ever is inside a call at any point in time, e.g. by using
3185	per loop).	4035	a mutex per loop).
3186		4036
3187	If you want to know which design is best for your problem, then I cannot	4037	Specifically to support threads (and signal handlers), libev implements
		4038	so-called C<ev_async> watchers, which allow some limited form of
		4039	concurrency on the same event loop, namely waking it up "from the
		4040	outside".
		4041
		4042	If you want to know which design (one loop, locking, or multiple loops
		4043	without or something else still) is best for your problem, then I cannot
3188	help you but by giving some generic advice:	4044	help you, but here is some generic advice:
3189		4045
3190	=over 4	4046	=over 4
3191		4047
3192	=item * most applications have a main thread: use the default libev loop	4048	=item * most applications have a main thread: use the default libev loop
3193	in that thread, or create a separate thread running only the default loop.	4049	in that thread, or create a separate thread running only the default loop.
…		…
3205		4061
3206	Choosing a model is hard - look around, learn, know that usually you can do	4062	Choosing a model is hard - look around, learn, know that usually you can do
3207	better than you currently do :-)	4063	better than you currently do :-)
3208		4064
3209	=item * often you need to talk to some other thread which blocks in the	4065	=item * often you need to talk to some other thread which blocks in the
		4066	event loop.
		4067
3210	event loop - C<ev_async> watchers can be used to wake them up from other	4068	C<ev_async> watchers can be used to wake them up from other threads safely
3211	threads safely (or from signal contexts...).	4069	(or from signal contexts...).
		4070
		4071	An example use would be to communicate signals or other events that only
		4072	work in the default loop by registering the signal watcher with the
		4073	default loop and triggering an C<ev_async> watcher from the default loop
		4074	watcher callback into the event loop interested in the signal.
3212		4075
3213	=back	4076	=back
3214		4077
		4078	=head4 THREAD LOCKING EXAMPLE
		4079
		4080	Here is a fictitious example of how to run an event loop in a different
		4081	thread than where callbacks are being invoked and watchers are
		4082	created/added/removed.
		4083
		4084	For a real-world example, see the C<EV::Loop::Async> perl module,
		4085	which uses exactly this technique (which is suited for many high-level
		4086	languages).
		4087
		4088	The example uses a pthread mutex to protect the loop data, a condition
		4089	variable to wait for callback invocations, an async watcher to notify the
		4090	event loop thread and an unspecified mechanism to wake up the main thread.
		4091
		4092	First, you need to associate some data with the event loop:
		4093
		4094	typedef struct {
		4095	mutex_t lock; /* global loop lock */
		4096	ev_async async_w;
		4097	thread_t tid;
		4098	cond_t invoke_cv;
		4099	} userdata;
		4100
		4101	void prepare_loop (EV_P)
		4102	{
		4103	// for simplicity, we use a static userdata struct.
		4104	static userdata u;
		4105
		4106	ev_async_init (&u->async_w, async_cb);
		4107	ev_async_start (EV_A_ &u->async_w);
		4108
		4109	pthread_mutex_init (&u->lock, 0);
		4110	pthread_cond_init (&u->invoke_cv, 0);
		4111
		4112	// now associate this with the loop
		4113	ev_set_userdata (EV_A_ u);
		4114	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4115	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4116
		4117	// then create the thread running ev_loop
		4118	pthread_create (&u->tid, 0, l_run, EV_A);
		4119	}
		4120
		4121	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4122	solely to wake up the event loop so it takes notice of any new watchers
		4123	that might have been added:
		4124
		4125	static void
		4126	async_cb (EV_P_ ev_async *w, int revents)
		4127	{
		4128	// just used for the side effects
		4129	}
		4130
		4131	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4132	protecting the loop data, respectively.
		4133
		4134	static void
		4135	l_release (EV_P)
		4136	{
		4137	userdata *u = ev_userdata (EV_A);
		4138	pthread_mutex_unlock (&u->lock);
		4139	}
		4140
		4141	static void
		4142	l_acquire (EV_P)
		4143	{
		4144	userdata *u = ev_userdata (EV_A);
		4145	pthread_mutex_lock (&u->lock);
		4146	}
		4147
		4148	The event loop thread first acquires the mutex, and then jumps straight
		4149	into C<ev_loop>:
		4150
		4151	void *
		4152	l_run (void *thr_arg)
		4153	{
		4154	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4155
		4156	l_acquire (EV_A);
		4157	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4158	ev_loop (EV_A_ 0);
		4159	l_release (EV_A);
		4160
		4161	return 0;
		4162	}
		4163
		4164	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4165	signal the main thread via some unspecified mechanism (signals? pipe
		4166	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4167	have been called (in a while loop because a) spurious wakeups are possible
		4168	and b) skipping inter-thread-communication when there are no pending
		4169	watchers is very beneficial):
		4170
		4171	static void
		4172	l_invoke (EV_P)
		4173	{
		4174	userdata *u = ev_userdata (EV_A);
		4175
		4176	while (ev_pending_count (EV_A))
		4177	{
		4178	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4179	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4180	}
		4181	}
		4182
		4183	Now, whenever the main thread gets told to invoke pending watchers, it
		4184	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4185	thread to continue:
		4186
		4187	static void
		4188	real_invoke_pending (EV_P)
		4189	{
		4190	userdata *u = ev_userdata (EV_A);
		4191
		4192	pthread_mutex_lock (&u->lock);
		4193	ev_invoke_pending (EV_A);
		4194	pthread_cond_signal (&u->invoke_cv);
		4195	pthread_mutex_unlock (&u->lock);
		4196	}
		4197
		4198	Whenever you want to start/stop a watcher or do other modifications to an
		4199	event loop, you will now have to lock:
		4200
		4201	ev_timer timeout_watcher;
		4202	userdata *u = ev_userdata (EV_A);
		4203
		4204	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4205
		4206	pthread_mutex_lock (&u->lock);
		4207	ev_timer_start (EV_A_ &timeout_watcher);
		4208	ev_async_send (EV_A_ &u->async_w);
		4209	pthread_mutex_unlock (&u->lock);
		4210
		4211	Note that sending the C<ev_async> watcher is required because otherwise
		4212	an event loop currently blocking in the kernel will have no knowledge
		4213	about the newly added timer. By waking up the loop it will pick up any new
		4214	watchers in the next event loop iteration.
		4215
3215	=head2 COROUTINES	4216	=head3 COROUTINES
3216		4217
3217	Libev is much more accommodating to coroutines ("cooperative threads"):	4218	Libev is very accommodating to coroutines ("cooperative threads"):
3218	libev fully supports nesting calls to it's functions from different	4219	libev fully supports nesting calls to its functions from different
3219	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4220	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3220	different coroutines and switch freely between both coroutines running the	4221	different coroutines, and switch freely between both coroutines running
3221	loop, as long as you don't confuse yourself). The only exception is that	4222	the loop, as long as you don't confuse yourself). The only exception is
3222	you must not do this from C<ev_periodic> reschedule callbacks.	4223	that you must not do this from C<ev_periodic> reschedule callbacks.
3223		4224
3224	Care has been invested into making sure that libev does not keep local	4225	Care has been taken to ensure that libev does not keep local state inside
3225	state inside C<ev_loop>, and other calls do not usually allow coroutine	4226	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3226	switches.	4227	they do not call any callbacks.
3227		4228
		4229	=head2 COMPILER WARNINGS
3228		4230
3229	=head1 COMPLEXITIES	4231	Depending on your compiler and compiler settings, you might get no or a
		4232	lot of warnings when compiling libev code. Some people are apparently
		4233	scared by this.
3230		4234
3231	In this section the complexities of (many of) the algorithms used inside	4235	However, these are unavoidable for many reasons. For one, each compiler
3232	libev will be explained. For complexity discussions about backends see the	4236	has different warnings, and each user has different tastes regarding
3233	documentation for C<ev_default_init>.	4237	warning options. "Warn-free" code therefore cannot be a goal except when
		4238	targeting a specific compiler and compiler-version.
3234		4239
3235	All of the following are about amortised time: If an array needs to be	4240	Another reason is that some compiler warnings require elaborate
3236	extended, libev needs to realloc and move the whole array, but this	4241	workarounds, or other changes to the code that make it less clear and less
3237	happens asymptotically never with higher number of elements, so O(1) might	4242	maintainable.
3238	mean it might do a lengthy realloc operation in rare cases, but on average
3239	it is much faster and asymptotically approaches constant time.
3240		4243
3241	=over 4	4244	And of course, some compiler warnings are just plain stupid, or simply
		4245	wrong (because they don't actually warn about the condition their message
		4246	seems to warn about). For example, certain older gcc versions had some
		4247	warnings that resulted an extreme number of false positives. These have
		4248	been fixed, but some people still insist on making code warn-free with
		4249	such buggy versions.
3242		4250
3243	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	4251	While libev is written to generate as few warnings as possible,
		4252	"warn-free" code is not a goal, and it is recommended not to build libev
		4253	with any compiler warnings enabled unless you are prepared to cope with
		4254	them (e.g. by ignoring them). Remember that warnings are just that:
		4255	warnings, not errors, or proof of bugs.
3244		4256
3245	This means that, when you have a watcher that triggers in one hour and
3246	there are 100 watchers that would trigger before that then inserting will
3247	have to skip roughly seven (C<ld 100>) of these watchers.
3248		4257
3249	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	4258	=head2 VALGRIND
3250		4259
3251	That means that changing a timer costs less than removing/adding them	4260	Valgrind has a special section here because it is a popular tool that is
3252	as only the relative motion in the event queue has to be paid for.	4261	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3253		4262
3254	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	4263	If you think you found a bug (memory leak, uninitialised data access etc.)
		4264	in libev, then check twice: If valgrind reports something like:
3255		4265
3256	These just add the watcher into an array or at the head of a list.	4266	==2274== definitely lost: 0 bytes in 0 blocks.
		4267	==2274== possibly lost: 0 bytes in 0 blocks.
		4268	==2274== still reachable: 256 bytes in 1 blocks.
3257		4269
3258	=item Stopping check/prepare/idle/fork/async watchers: O(1)	4270	Then there is no memory leak, just as memory accounted to global variables
		4271	is not a memleak - the memory is still being referenced, and didn't leak.
3259		4272
3260	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	4273	Similarly, under some circumstances, valgrind might report kernel bugs
		4274	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		4275	although an acceptable workaround has been found here), or it might be
		4276	confused.
3261		4277
3262	These watchers are stored in lists then need to be walked to find the	4278	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3263	correct watcher to remove. The lists are usually short (you don't usually	4279	make it into some kind of religion.
3264	have many watchers waiting for the same fd or signal).
3265		4280
3266	=item Finding the next timer in each loop iteration: O(1)	4281	If you are unsure about something, feel free to contact the mailing list
		4282	with the full valgrind report and an explanation on why you think this
		4283	is a bug in libev (best check the archives, too :). However, don't be
		4284	annoyed when you get a brisk "this is no bug" answer and take the chance
		4285	of learning how to interpret valgrind properly.
3267		4286
3268	By virtue of using a binary or 4-heap, the next timer is always found at a	4287	If you need, for some reason, empty reports from valgrind for your project
3269	fixed position in the storage array.	4288	I suggest using suppression lists.
3270		4289
3271	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3272		4290
3273	A change means an I/O watcher gets started or stopped, which requires	4291	=head1 PORTABILITY NOTES
3274	libev to recalculate its status (and possibly tell the kernel, depending
3275	on backend and whether C<ev_io_set> was used).
3276		4292
3277	=item Activating one watcher (putting it into the pending state): O(1)
3278
3279	=item Priority handling: O(number_of_priorities)
3280
3281	Priorities are implemented by allocating some space for each
3282	priority. When doing priority-based operations, libev usually has to
3283	linearly search all the priorities, but starting/stopping and activating
3284	watchers becomes O(1) w.r.t. priority handling.
3285
3286	=item Sending an ev_async: O(1)
3287
3288	=item Processing ev_async_send: O(number_of_async_watchers)
3289
3290	=item Processing signals: O(max_signal_number)
3291
3292	Sending involves a system call I<iff> there were no other C<ev_async_send>
3293	calls in the current loop iteration. Checking for async and signal events
3294	involves iterating over all running async watchers or all signal numbers.
3295
3296	=back
3297
3298
3299	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4293	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3300		4294
3301	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4295	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3302	requires, and its I/O model is fundamentally incompatible with the POSIX	4296	requires, and its I/O model is fundamentally incompatible with the POSIX
3303	model. Libev still offers limited functionality on this platform in	4297	model. Libev still offers limited functionality on this platform in
3304	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4298	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3311	way (note also that glib is the slowest event library known to man).	4305	way (note also that glib is the slowest event library known to man).
3312		4306
3313	There is no supported compilation method available on windows except	4307	There is no supported compilation method available on windows except
3314	embedding it into other applications.	4308	embedding it into other applications.
3315		4309
		4310	Sensible signal handling is officially unsupported by Microsoft - libev
		4311	tries its best, but under most conditions, signals will simply not work.
		4312
3316	Not a libev limitation but worth mentioning: windows apparently doesn't	4313	Not a libev limitation but worth mentioning: windows apparently doesn't
3317	accept large writes: instead of resulting in a partial write, windows will	4314	accept large writes: instead of resulting in a partial write, windows will
3318	either accept everything or return C<ENOBUFS> if the buffer is too large,	4315	either accept everything or return C<ENOBUFS> if the buffer is too large,
3319	so make sure you only write small amounts into your sockets (less than a	4316	so make sure you only write small amounts into your sockets (less than a
3320	megabyte seems safe, but thsi apparently depends on the amount of memory	4317	megabyte seems safe, but this apparently depends on the amount of memory
3321	available).	4318	available).
3322		4319
3323	Due to the many, low, and arbitrary limits on the win32 platform and	4320	Due to the many, low, and arbitrary limits on the win32 platform and
3324	the abysmal performance of winsockets, using a large number of sockets	4321	the abysmal performance of winsockets, using a large number of sockets
3325	is not recommended (and not reasonable). If your program needs to use	4322	is not recommended (and not reasonable). If your program needs to use
3326	more than a hundred or so sockets, then likely it needs to use a totally	4323	more than a hundred or so sockets, then likely it needs to use a totally
3327	different implementation for windows, as libev offers the POSIX readiness	4324	different implementation for windows, as libev offers the POSIX readiness
3328	notification model, which cannot be implemented efficiently on windows	4325	notification model, which cannot be implemented efficiently on windows
3329	(Microsoft monopoly games).	4326	(due to Microsoft monopoly games).
3330		4327
3331	A typical way to use libev under windows is to embed it (see the embedding	4328	A typical way to use libev under windows is to embed it (see the embedding
3332	section for details) and use the following F<evwrap.h> header file instead	4329	section for details) and use the following F<evwrap.h> header file instead
3333	of F<ev.h>:	4330	of F<ev.h>:
3334		4331
…		…
3336	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	4333	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3337		4334
3338	#include "ev.h"	4335	#include "ev.h"
3339		4336
3340	And compile the following F<evwrap.c> file into your project (make sure	4337	And compile the following F<evwrap.c> file into your project (make sure
3341	you do I<not> compile the F<ev.c> or any other embedded soruce files!):	4338	you do I<not> compile the F<ev.c> or any other embedded source files!):
3342		4339
3343	#include "evwrap.h"	4340	#include "evwrap.h"
3344	#include "ev.c"	4341	#include "ev.c"
3345		4342
3346	=over 4	4343	=over 4
…		…
3370		4367
3371	Early versions of winsocket's select only supported waiting for a maximum	4368	Early versions of winsocket's select only supported waiting for a maximum
3372	of C<64> handles (probably owning to the fact that all windows kernels	4369	of C<64> handles (probably owning to the fact that all windows kernels
3373	can only wait for C<64> things at the same time internally; Microsoft	4370	can only wait for C<64> things at the same time internally; Microsoft
3374	recommends spawning a chain of threads and wait for 63 handles and the	4371	recommends spawning a chain of threads and wait for 63 handles and the
3375	previous thread in each. Great).	4372	previous thread in each. Sounds great!).
3376		4373
3377	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4374	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3378	to some high number (e.g. C<2048>) before compiling the winsocket select	4375	to some high number (e.g. C<2048>) before compiling the winsocket select
3379	call (which might be in libev or elsewhere, for example, perl does its own	4376	call (which might be in libev or elsewhere, for example, perl and many
3380	select emulation on windows).	4377	other interpreters do their own select emulation on windows).
3381		4378
3382	Another limit is the number of file descriptors in the Microsoft runtime	4379	Another limit is the number of file descriptors in the Microsoft runtime
3383	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4380	libraries, which by default is C<64> (there must be a hidden I<64>
3384	or something like this inside Microsoft). You can increase this by calling	4381	fetish or something like this inside Microsoft). You can increase this
3385	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4382	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3386	arbitrary limit), but is broken in many versions of the Microsoft runtime	4383	(another arbitrary limit), but is broken in many versions of the Microsoft
3387	libraries.
3388
3389	This might get you to about C<512> or C<2048> sockets (depending on	4384	runtime libraries. This might get you to about C<512> or C<2048> sockets
3390	windows version and/or the phase of the moon). To get more, you need to	4385	(depending on windows version and/or the phase of the moon). To get more,
3391	wrap all I/O functions and provide your own fd management, but the cost of	4386	you need to wrap all I/O functions and provide your own fd management, but
3392	calling select (O(n²)) will likely make this unworkable.	4387	the cost of calling select (O(n²)) will likely make this unworkable.
3393		4388
3394	=back	4389	=back
3395		4390
3396
3397	=head1 PORTABILITY REQUIREMENTS	4391	=head2 PORTABILITY REQUIREMENTS
3398		4392
3399	In addition to a working ISO-C implementation, libev relies on a few	4393	In addition to a working ISO-C implementation and of course the
3400	additional extensions:	4394	backend-specific APIs, libev relies on a few additional extensions:
3401		4395
3402	=over 4	4396	=over 4
3403		4397
3404	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	4398	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3405	calling conventions regardless of C<ev_watcher_type *>.	4399	calling conventions regardless of C<ev_watcher_type *>.
…		…
3411	calls them using an C<ev_watcher *> internally.	4405	calls them using an C<ev_watcher *> internally.
3412		4406
3413	=item C<sig_atomic_t volatile> must be thread-atomic as well	4407	=item C<sig_atomic_t volatile> must be thread-atomic as well
3414		4408
3415	The type C<sig_atomic_t volatile> (or whatever is defined as	4409	The type C<sig_atomic_t volatile> (or whatever is defined as
3416	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	4410	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3417	threads. This is not part of the specification for C<sig_atomic_t>, but is	4411	threads. This is not part of the specification for C<sig_atomic_t>, but is
3418	believed to be sufficiently portable.	4412	believed to be sufficiently portable.
3419		4413
3420	=item C<sigprocmask> must work in a threaded environment	4414	=item C<sigprocmask> must work in a threaded environment
3421		4415
…		…
3430	except the initial one, and run the default loop in the initial thread as	4424	except the initial one, and run the default loop in the initial thread as
3431	well.	4425	well.
3432		4426
3433	=item C<long> must be large enough for common memory allocation sizes	4427	=item C<long> must be large enough for common memory allocation sizes
3434		4428
3435	To improve portability and simplify using libev, libev uses C<long>	4429	To improve portability and simplify its API, libev uses C<long> internally
3436	internally instead of C<size_t> when allocating its data structures. On	4430	instead of C<size_t> when allocating its data structures. On non-POSIX
3437	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4431	systems (Microsoft...) this might be unexpectedly low, but is still at
3438	is still at least 31 bits everywhere, which is enough for hundreds of	4432	least 31 bits everywhere, which is enough for hundreds of millions of
3439	millions of watchers.	4433	watchers.
3440		4434
3441	=item C<double> must hold a time value in seconds with enough accuracy	4435	=item C<double> must hold a time value in seconds with enough accuracy
3442		4436
3443	The type C<double> is used to represent timestamps. It is required to	4437	The type C<double> is used to represent timestamps. It is required to
3444	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4438	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
3445	enough for at least into the year 4000. This requirement is fulfilled by	4439	enough for at least into the year 4000. This requirement is fulfilled by
3446	implementations implementing IEEE 754 (basically all existing ones).	4440	implementations implementing IEEE 754, which is basically all existing
		4441	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4442	2200.
3447		4443
3448	=back	4444	=back
3449		4445
3450	If you know of other additional requirements drop me a note.	4446	If you know of other additional requirements drop me a note.
3451		4447
3452		4448
3453	=head1 COMPILER WARNINGS	4449	=head1 ALGORITHMIC COMPLEXITIES
3454		4450
3455	Depending on your compiler and compiler settings, you might get no or a	4451	In this section the complexities of (many of) the algorithms used inside
3456	lot of warnings when compiling libev code. Some people are apparently	4452	libev will be documented. For complexity discussions about backends see
3457	scared by this.	4453	the documentation for C<ev_default_init>.
3458		4454
3459	However, these are unavoidable for many reasons. For one, each compiler	4455	All of the following are about amortised time: If an array needs to be
3460	has different warnings, and each user has different tastes regarding	4456	extended, libev needs to realloc and move the whole array, but this
3461	warning options. "Warn-free" code therefore cannot be a goal except when	4457	happens asymptotically rarer with higher number of elements, so O(1) might
3462	targeting a specific compiler and compiler-version.	4458	mean that libev does a lengthy realloc operation in rare cases, but on
		4459	average it is much faster and asymptotically approaches constant time.
3463		4460
3464	Another reason is that some compiler warnings require elaborate	4461	=over 4
3465	workarounds, or other changes to the code that make it less clear and less
3466	maintainable.
3467		4462
3468	And of course, some compiler warnings are just plain stupid, or simply	4463	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3469	wrong (because they don't actually warn about the condition their message
3470	seems to warn about).
3471		4464
3472	While libev is written to generate as few warnings as possible,	4465	This means that, when you have a watcher that triggers in one hour and
3473	"warn-free" code is not a goal, and it is recommended not to build libev	4466	there are 100 watchers that would trigger before that, then inserting will
3474	with any compiler warnings enabled unless you are prepared to cope with	4467	have to skip roughly seven (C<ld 100>) of these watchers.
3475	them (e.g. by ignoring them). Remember that warnings are just that:
3476	warnings, not errors, or proof of bugs.
3477		4468
		4469	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3478		4470
3479	=head1 VALGRIND	4471	That means that changing a timer costs less than removing/adding them,
		4472	as only the relative motion in the event queue has to be paid for.
3480		4473
3481	Valgrind has a special section here because it is a popular tool that is	4474	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3482	highly useful, but valgrind reports are very hard to interpret.
3483		4475
3484	If you think you found a bug (memory leak, uninitialised data access etc.)	4476	These just add the watcher into an array or at the head of a list.
3485	in libev, then check twice: If valgrind reports something like:
3486		4477
3487	==2274== definitely lost: 0 bytes in 0 blocks.	4478	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3488	==2274== possibly lost: 0 bytes in 0 blocks.
3489	==2274== still reachable: 256 bytes in 1 blocks.
3490		4479
3491	Then there is no memory leak. Similarly, under some circumstances,	4480	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3492	valgrind might report kernel bugs as if it were a bug in libev, or it
3493	might be confused (it is a very good tool, but only a tool).
3494		4481
3495	If you are unsure about something, feel free to contact the mailing list	4482	These watchers are stored in lists, so they need to be walked to find the
3496	with the full valgrind report and an explanation on why you think this is	4483	correct watcher to remove. The lists are usually short (you don't usually
3497	a bug in libev. However, don't be annoyed when you get a brisk "this is	4484	have many watchers waiting for the same fd or signal: one is typical, two
3498	no bug" answer and take the chance of learning how to interpret valgrind	4485	is rare).
3499	properly.
3500		4486
3501	If you need, for some reason, empty reports from valgrind for your project	4487	=item Finding the next timer in each loop iteration: O(1)
3502	I suggest using suppression lists.
3503		4488
		4489	By virtue of using a binary or 4-heap, the next timer is always found at a
		4490	fixed position in the storage array.
		4491
		4492	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4493
		4494	A change means an I/O watcher gets started or stopped, which requires
		4495	libev to recalculate its status (and possibly tell the kernel, depending
		4496	on backend and whether C<ev_io_set> was used).
		4497
		4498	=item Activating one watcher (putting it into the pending state): O(1)
		4499
		4500	=item Priority handling: O(number_of_priorities)
		4501
		4502	Priorities are implemented by allocating some space for each
		4503	priority. When doing priority-based operations, libev usually has to
		4504	linearly search all the priorities, but starting/stopping and activating
		4505	watchers becomes O(1) with respect to priority handling.
		4506
		4507	=item Sending an ev_async: O(1)
		4508
		4509	=item Processing ev_async_send: O(number_of_async_watchers)
		4510
		4511	=item Processing signals: O(max_signal_number)
		4512
		4513	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4514	calls in the current loop iteration. Checking for async and signal events
		4515	involves iterating over all running async watchers or all signal numbers.
		4516
		4517	=back
		4518
		4519
		4520	=head1 GLOSSARY
		4521
		4522	=over 4
		4523
		4524	=item active
		4525
		4526	A watcher is active as long as it has been started (has been attached to
		4527	an event loop) but not yet stopped (disassociated from the event loop).
		4528
		4529	=item application
		4530
		4531	In this document, an application is whatever is using libev.
		4532
		4533	=item callback
		4534
		4535	The address of a function that is called when some event has been
		4536	detected. Callbacks are being passed the event loop, the watcher that
		4537	received the event, and the actual event bitset.
		4538
		4539	=item callback invocation
		4540
		4541	The act of calling the callback associated with a watcher.
		4542
		4543	=item event
		4544
		4545	A change of state of some external event, such as data now being available
		4546	for reading on a file descriptor, time having passed or simply not having
		4547	any other events happening anymore.
		4548
		4549	In libev, events are represented as single bits (such as C<EV_READ> or
		4550	C<EV_TIMEOUT>).
		4551
		4552	=item event library
		4553
		4554	A software package implementing an event model and loop.
		4555
		4556	=item event loop
		4557
		4558	An entity that handles and processes external events and converts them
		4559	into callback invocations.
		4560
		4561	=item event model
		4562
		4563	The model used to describe how an event loop handles and processes
		4564	watchers and events.
		4565
		4566	=item pending
		4567
		4568	A watcher is pending as soon as the corresponding event has been detected,
		4569	and stops being pending as soon as the watcher will be invoked or its
		4570	pending status is explicitly cleared by the application.
		4571
		4572	A watcher can be pending, but not active. Stopping a watcher also clears
		4573	its pending status.
		4574
		4575	=item real time
		4576
		4577	The physical time that is observed. It is apparently strictly monotonic :)
		4578
		4579	=item wall-clock time
		4580
		4581	The time and date as shown on clocks. Unlike real time, it can actually
		4582	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4583	clock.
		4584
		4585	=item watcher
		4586
		4587	A data structure that describes interest in certain events. Watchers need
		4588	to be started (attached to an event loop) before they can receive events.
		4589
		4590	=item watcher invocation
		4591
		4592	The act of calling the callback associated with a watcher.
		4593
		4594	=back
3504		4595
3505	=head1 AUTHOR	4596	=head1 AUTHOR
3506		4597
3507	Marc Lehmann <libev@schmorp.de>.	4598	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3508		4599

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