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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
…		…
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<struct 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
…		…
326	useful to try out specific backends to test their performance, or to work	345	useful to try out specific backends to test their performance, or to work
327	around bugs.	346	around bugs.
328		347
329	=item C<EVFLAG_FORKCHECK>	348	=item C<EVFLAG_FORKCHECK>
330		349
331	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	350	Instead of calling C<ev_loop_fork> manually after a fork, you can also
332	a fork, you can also make libev check for a fork in each iteration by	351	make libev check for a fork in each iteration by enabling this flag.
333	enabling this flag.
334		352
335	This works by calling C<getpid ()> on every iteration of the loop,	353	This works by calling C<getpid ()> on every iteration of the loop,
336	and thus this might slow down your event loop if you do a lot of loop	354	and thus this might slow down your event loop if you do a lot of loop
337	iterations and little real work, but is usually not noticeable (on my	355	iterations and little real work, but is usually not noticeable (on my
338	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	356	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
…		…
344	flag.	362	flag.
345		363
346	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	364	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
347	environment variable.	365	environment variable.
348		366
		367	=item C<EVFLAG_NOINOTIFY>
		368
		369	When this flag is specified, then libev will not attempt to use the
		370	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and
		371	testing, this flag can be useful to conserve inotify file descriptors, as
		372	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		373
		374	=item C<EVFLAG_SIGNALFD>
		375
		376	When this flag is specified, then libev will attempt to use the
		377	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API
		378	delivers signals synchronously, which makes it both faster and might make
		379	it possible to get the queued signal data. It can also simplify signal
		380	handling with threads, as long as you properly block signals in your
		381	threads that are not interested in handling them.
		382
		383	Signalfd will not be used by default as this changes your signal mask, and
		384	there are a lot of shoddy libraries and programs (glib's threadpool for
		385	example) that can't properly initialise their signal masks.
		386
349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	387	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
350		388
351	This is your standard select(2) backend. Not I<completely> standard, as	389	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,	390	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	391	but if that fails, expect a fairly low limit on the number of fds when
…		…
377	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and	415	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
378	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	416	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
379		417
380	=item C<EVBACKEND_EPOLL> (value 4, Linux)	418	=item C<EVBACKEND_EPOLL> (value 4, Linux)
381		419
		420	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		421	kernels).
		422
382	For few fds, this backend is a bit little slower than poll and select,	423	For few fds, this backend is a bit little slower than poll and select,
383	but it scales phenomenally better. While poll and select usually scale	424	but it scales phenomenally better. While poll and select usually scale
384	like O(total_fds) where n is the total number of fds (or the highest fd),	425	like O(total_fds) where n is the total number of fds (or the highest fd),
385	epoll scales either O(1) or O(active_fds). The epoll design has a number	426	epoll scales either O(1) or O(active_fds).
386	of shortcomings, such as silently dropping events in some hard-to-detect	427
387	cases and requiring a system call per fd change, no fork support and bad	428	The epoll mechanism deserves honorable mention as the most misdesigned
388	support for dup.	429	of the more advanced event mechanisms: mere annoyances include silently
		430	dropping file descriptors, requiring a system call per change per file
		431	descriptor (and unnecessary guessing of parameters), problems with dup and
		432	so on. The biggest issue is fork races, however - if a program forks then
		433	I<both> parent and child process have to recreate the epoll set, which can
		434	take considerable time (one syscall per file descriptor) and is of course
		435	hard to detect.
		436
		437	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		438	of course I<doesn't>, and epoll just loves to report events for totally
		439	I<different> file descriptors (even already closed ones, so one cannot
		440	even remove them from the set) than registered in the set (especially
		441	on SMP systems). Libev tries to counter these spurious notifications by
		442	employing an additional generation counter and comparing that against the
		443	events to filter out spurious ones, recreating the set when required.
389		444
390	While stopping, setting and starting an I/O watcher in the same iteration	445	While stopping, setting and starting an I/O watcher in the same iteration
391	will result in some caching, there is still a system call per such incident	446	will result in some caching, there is still a system call per such
392	(because the fd could point to a different file description now), so its	447	incident (because the same I<file descriptor> could point to a different
393	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	448	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
394	very well if you register events for both fds.	449	file descriptors might not work very well if you register events for both
395		450	file descriptors.
396	Please note that epoll sometimes generates spurious notifications, so you
397	need to use non-blocking I/O or other means to avoid blocking when no data
398	(or space) is available.
399		451
400	Best performance from this backend is achieved by not unregistering all	452	Best performance from this backend is achieved by not unregistering all
401	watchers for a file descriptor until it has been closed, if possible,	453	watchers for a file descriptor until it has been closed, if possible,
402	i.e. keep at least one watcher active per fd at all times. Stopping and	454	i.e. keep at least one watcher active per fd at all times. Stopping and
403	starting a watcher (without re-setting it) also usually doesn't cause	455	starting a watcher (without re-setting it) also usually doesn't cause
404	extra overhead.	456	extra overhead. A fork can both result in spurious notifications as well
		457	as in libev having to destroy and recreate the epoll object, which can
		458	take considerable time and thus should be avoided.
		459
		460	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		461	faster than epoll for maybe up to a hundred file descriptors, depending on
		462	the usage. So sad.
405		463
406	While nominally embeddable in other event loops, this feature is broken in	464	While nominally embeddable in other event loops, this feature is broken in
407	all kernel versions tested so far.	465	all kernel versions tested so far.
408		466
409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	467	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
410	C<EVBACKEND_POLL>.	468	C<EVBACKEND_POLL>.
411		469
412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	470	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
413		471
414	Kqueue deserves special mention, as at the time of this writing, it was	472	Kqueue deserves special mention, as at the time of this writing, it
415	broken on all BSDs except NetBSD (usually it doesn't work reliably with	473	was broken on all BSDs except NetBSD (usually it doesn't work reliably
416	anything but sockets and pipes, except on Darwin, where of course it's	474	with anything but sockets and pipes, except on Darwin, where of course
417	completely useless). For this reason it's not being "auto-detected" unless	475	it's completely useless). Unlike epoll, however, whose brokenness
418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or	476	is by design, these kqueue bugs can (and eventually will) be fixed
419	libev was compiled on a known-to-be-good (-enough) system like NetBSD.	477	without API changes to existing programs. For this reason it's not being
		478	"auto-detected" unless you explicitly specify it in the flags (i.e. using
		479	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		480	system like NetBSD.
420		481
421	You still can embed kqueue into a normal poll or select backend and use it	482	You still can embed kqueue into a normal poll or select backend and use it
422	only for sockets (after having made sure that sockets work with kqueue on	483	only for sockets (after having made sure that sockets work with kqueue on
423	the target platform). See C<ev_embed> watchers for more info.	484	the target platform). See C<ev_embed> watchers for more info.
424		485
425	It scales in the same way as the epoll backend, but the interface to the	486	It scales in the same way as the epoll backend, but the interface to the
426	kernel is more efficient (which says nothing about its actual speed, of	487	kernel is more efficient (which says nothing about its actual speed, of
427	course). While stopping, setting and starting an I/O watcher does never	488	course). While stopping, setting and starting an I/O watcher does never
428	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	489	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
429	two event changes per incident. Support for C<fork ()> is very bad and it	490	two event changes per incident. Support for C<fork ()> is very bad (but
430	drops fds silently in similarly hard-to-detect cases.	491	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		492	cases
431		493
432	This backend usually performs well under most conditions.	494	This backend usually performs well under most conditions.
433		495
434	While nominally embeddable in other event loops, this doesn't work	496	While nominally embeddable in other event loops, this doesn't work
435	everywhere, so you might need to test for this. And since it is broken	497	everywhere, so you might need to test for this. And since it is broken
436	almost everywhere, you should only use it when you have a lot of sockets	498	almost everywhere, you should only use it when you have a lot of sockets
437	(for which it usually works), by embedding it into another event loop	499	(for which it usually works), by embedding it into another event loop
438	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,	500	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
439	using it only for sockets.	501	also broken on OS X)) and, did I mention it, using it only for sockets.
440		502
441	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	503	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
442	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with	504	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
443	C<NOTE_EOF>.	505	C<NOTE_EOF>.
444		506
…		…
464	might perform better.	526	might perform better.
465		527
466	On the positive side, with the exception of the spurious readiness	528	On the positive side, with the exception of the spurious readiness
467	notifications, this backend actually performed fully to specification	529	notifications, this backend actually performed fully to specification
468	in all tests and is fully embeddable, which is a rare feat among the	530	in all tests and is fully embeddable, which is a rare feat among the
469	OS-specific backends.	531	OS-specific backends (I vastly prefer correctness over speed hacks).
470		532
471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	533	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
472	C<EVBACKEND_POLL>.	534	C<EVBACKEND_POLL>.
473		535
474	=item C<EVBACKEND_ALL>	536	=item C<EVBACKEND_ALL>
…		…
479		541
480	It is definitely not recommended to use this flag.	542	It is definitely not recommended to use this flag.
481		543
482	=back	544	=back
483		545
484	If one or more of these are or'ed into the flags value, then only these	546	If one or more of the backend flags are or'ed into the flags value,
485	backends will be tried (in the reverse order as listed here). If none are	547	then only these backends will be tried (in the reverse order as listed
486	specified, all backends in C<ev_recommended_backends ()> will be tried.	548	here). If none are specified, all backends in C<ev_recommended_backends
		549	()> will be tried.
487		550
488	Example: This is the most typical usage.	551	Example: This is the most typical usage.
489		552
490	if (!ev_default_loop (0))	553	if (!ev_default_loop (0))
491	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	554	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
503	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	566	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
504		567
505	=item struct ev_loop *ev_loop_new (unsigned int flags)	568	=item struct ev_loop *ev_loop_new (unsigned int flags)
506		569
507	Similar to C<ev_default_loop>, but always creates a new event loop that is	570	Similar to C<ev_default_loop>, but always creates a new event loop that is
508	always distinct from the default loop. Unlike the default loop, it cannot	571	always distinct from the default loop.
509	handle signal and child watchers, and attempts to do so will be greeted by
510	undefined behaviour (or a failed assertion if assertions are enabled).
511		572
512	Note that this function I<is> thread-safe, and the recommended way to use	573	Note that this function I<is> thread-safe, and one common way to use
513	libev with threads is indeed to create one loop per thread, and using the	574	libev with threads is indeed to create one loop per thread, and using the
514	default loop in the "main" or "initial" thread.	575	default loop in the "main" or "initial" thread.
515		576
516	Example: Try to create a event loop that uses epoll and nothing else.	577	Example: Try to create a event loop that uses epoll and nothing else.
517		578
…		…
519	if (!epoller)	580	if (!epoller)
520	fatal ("no epoll found here, maybe it hides under your chair");	581	fatal ("no epoll found here, maybe it hides under your chair");
521		582
522	=item ev_default_destroy ()	583	=item ev_default_destroy ()
523		584
524	Destroys the default loop again (frees all memory and kernel state	585	Destroys the default loop (frees all memory and kernel state etc.). None
525	etc.). None of the active event watchers will be stopped in the normal	586	of the active event watchers will be stopped in the normal sense, so
526	sense, so e.g. C<ev_is_active> might still return true. It is your	587	e.g. C<ev_is_active> might still return true. It is your responsibility to
527	responsibility to either stop all watchers cleanly yourself I<before>	588	either stop all watchers cleanly yourself I<before> calling this function,
528	calling this function, or cope with the fact afterwards (which is usually	589	or cope with the fact afterwards (which is usually the easiest thing, you
529	the easiest thing, you can just ignore the watchers and/or C<free ()> them	590	can just ignore the watchers and/or C<free ()> them for example).
530	for example).
531		591
532	Note that certain global state, such as signal state, will not be freed by	592	Note that certain global state, such as signal state (and installed signal
533	this function, and related watchers (such as signal and child watchers)	593	handlers), will not be freed by this function, and related watchers (such
534	would need to be stopped manually.	594	as signal and child watchers) would need to be stopped manually.
535		595
536	In general it is not advisable to call this function except in the	596	In general it is not advisable to call this function except in the
537	rare occasion where you really need to free e.g. the signal handling	597	rare occasion where you really need to free e.g. the signal handling
538	pipe fds. If you need dynamically allocated loops it is better to use	598	pipe fds. If you need dynamically allocated loops it is better to use
539	C<ev_loop_new> and C<ev_loop_destroy>).	599	C<ev_loop_new> and C<ev_loop_destroy>.
540		600
541	=item ev_loop_destroy (loop)	601	=item ev_loop_destroy (loop)
542		602
543	Like C<ev_default_destroy>, but destroys an event loop created by an	603	Like C<ev_default_destroy>, but destroys an event loop created by an
544	earlier call to C<ev_loop_new>.	604	earlier call to C<ev_loop_new>.
…		…
550	name, you can call it anytime, but it makes most sense after forking, in	610	name, you can call it anytime, but it makes most sense after forking, in
551	the child process (or both child and parent, but that again makes little	611	the child process (or both child and parent, but that again makes little
552	sense). You I<must> call it in the child before using any of the libev	612	sense). You I<must> call it in the child before using any of the libev
553	functions, and it will only take effect at the next C<ev_loop> iteration.	613	functions, and it will only take effect at the next C<ev_loop> iteration.
554		614
		615	Again, you I<have> to call it on I<any> loop that you want to re-use after
		616	a fork, I<even if you do not plan to use the loop in the parent>. This is
		617	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		618	during fork.
		619
555	On the other hand, you only need to call this function in the child	620	On the other hand, you only need to call this function in the child
556	process if and only if you want to use the event library in the child. If	621	process if and only if you want to use the event loop in the child. If you
557	you just fork+exec, you don't have to call it at all.	622	just fork+exec or create a new loop in the child, you don't have to call
		623	it at all.
558		624
559	The function itself is quite fast and it's usually not a problem to call	625	The function itself is quite fast and it's usually not a problem to call
560	it just in case after a fork. To make this easy, the function will fit in	626	it just in case after a fork. To make this easy, the function will fit in
561	quite nicely into a call to C<pthread_atfork>:	627	quite nicely into a call to C<pthread_atfork>:
562		628
…		…
564		630
565	=item ev_loop_fork (loop)	631	=item ev_loop_fork (loop)
566		632
567	Like C<ev_default_fork>, but acts on an event loop created by	633	Like C<ev_default_fork>, but acts on an event loop created by
568	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	634	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
569	after fork that you want to re-use in the child, and how you do this is	635	after fork that you want to re-use in the child, and how you keep track of
570	entirely your own problem.	636	them is entirely your own problem.
571		637
572	=item int ev_is_default_loop (loop)	638	=item int ev_is_default_loop (loop)
573		639
574	Returns true when the given loop is, in fact, the default loop, and false	640	Returns true when the given loop is, in fact, the default loop, and false
575	otherwise.	641	otherwise.
576		642
577	=item unsigned int ev_loop_count (loop)	643	=item unsigned int ev_iteration (loop)
578		644
579	Returns the count of loop iterations for the loop, which is identical to	645	Returns the current iteration count for the loop, which is identical to
580	the number of times libev did poll for new events. It starts at C<0> and	646	the number of times libev did poll for new events. It starts at C<0> and
581	happily wraps around with enough iterations.	647	happily wraps around with enough iterations.
582		648
583	This value can sometimes be useful as a generation counter of sorts (it	649	This value can sometimes be useful as a generation counter of sorts (it
584	"ticks" the number of loop iterations), as it roughly corresponds with	650	"ticks" the number of loop iterations), as it roughly corresponds with
585	C<ev_prepare> and C<ev_check> calls.	651	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		652	prepare and check phases.
		653
		654	=item unsigned int ev_depth (loop)
		655
		656	Returns the number of times C<ev_loop> was entered minus the number of
		657	times C<ev_loop> was exited, in other words, the recursion depth.
		658
		659	Outside C<ev_loop>, this number is zero. In a callback, this number is
		660	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),
		661	in which case it is higher.
		662
		663	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread
		664	etc.), doesn't count as "exit" - consider this as a hint to avoid such
		665	ungentleman behaviour unless it's really convenient.
586		666
587	=item unsigned int ev_backend (loop)	667	=item unsigned int ev_backend (loop)
588		668
589	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	669	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
590	use.	670	use.
…		…
605		685
606	This function is rarely useful, but when some event callback runs for a	686	This function is rarely useful, but when some event callback runs for a
607	very long time without entering the event loop, updating libev's idea of	687	very long time without entering the event loop, updating libev's idea of
608	the current time is a good idea.	688	the current time is a good idea.
609		689
610	See also "The special problem of time updates" in the C<ev_timer> section.	690	See also L<The special problem of time updates> in the C<ev_timer> section.
		691
		692	=item ev_suspend (loop)
		693
		694	=item ev_resume (loop)
		695
		696	These two functions suspend and resume a loop, for use when the loop is
		697	not used for a while and timeouts should not be processed.
		698
		699	A typical use case would be an interactive program such as a game: When
		700	the user presses C<^Z> to suspend the game and resumes it an hour later it
		701	would be best to handle timeouts as if no time had actually passed while
		702	the program was suspended. This can be achieved by calling C<ev_suspend>
		703	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		704	C<ev_resume> directly afterwards to resume timer processing.
		705
		706	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		707	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		708	will be rescheduled (that is, they will lose any events that would have
		709	occured while suspended).
		710
		711	After calling C<ev_suspend> you B<must not> call I<any> function on the
		712	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		713	without a previous call to C<ev_suspend>.
		714
		715	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		716	event loop time (see C<ev_now_update>).
611		717
612	=item ev_loop (loop, int flags)	718	=item ev_loop (loop, int flags)
613		719
614	Finally, this is it, the event handler. This function usually is called	720	Finally, this is it, the event handler. This function usually is called
615	after you initialised all your watchers and you want to start handling	721	after you have initialised all your watchers and you want to start
616	events.	722	handling events.
617		723
618	If the flags argument is specified as C<0>, it will not return until	724	If the flags argument is specified as C<0>, it will not return until
619	either no event watchers are active anymore or C<ev_unloop> was called.	725	either no event watchers are active anymore or C<ev_unloop> was called.
620		726
621	Please note that an explicit C<ev_unloop> is usually better than	727	Please note that an explicit C<ev_unloop> is usually better than
…		…
631	the loop.	737	the loop.
632		738
633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	739	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
634	necessary) and will handle those and any already outstanding ones. It	740	necessary) and will handle those and any already outstanding ones. It
635	will block your process until at least one new event arrives (which could	741	will block your process until at least one new event arrives (which could
636	be an event internal to libev itself, so there is no guarentee that a	742	be an event internal to libev itself, so there is no guarantee that a
637	user-registered callback will be called), and will return after one	743	user-registered callback will be called), and will return after one
638	iteration of the loop.	744	iteration of the loop.
639		745
640	This is useful if you are waiting for some external event in conjunction	746	This is useful if you are waiting for some external event in conjunction
641	with something not expressible using other libev watchers (i.e. "roll your	747	with something not expressible using other libev watchers (i.e. "roll your
…		…
685	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	791	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
686	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	792	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
687		793
688	This "unloop state" will be cleared when entering C<ev_loop> again.	794	This "unloop state" will be cleared when entering C<ev_loop> again.
689		795
		796	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		797
690	=item ev_ref (loop)	798	=item ev_ref (loop)
691		799
692	=item ev_unref (loop)	800	=item ev_unref (loop)
693		801
694	Ref/unref can be used to add or remove a reference count on the event	802	Ref/unref can be used to add or remove a reference count on the event
695	loop: Every watcher keeps one reference, and as long as the reference	803	loop: Every watcher keeps one reference, and as long as the reference
696	count is nonzero, C<ev_loop> will not return on its own.	804	count is nonzero, C<ev_loop> will not return on its own.
697		805
698	If you have a watcher you never unregister that should not keep C<ev_loop>	806	This is useful when you have a watcher that you never intend to
699	from returning, call ev_unref() after starting, and ev_ref() before	807	unregister, but that nevertheless should not keep C<ev_loop> from
		808	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
700	stopping it.	809	before stopping it.
701		810
702	As an example, libev itself uses this for its internal signal pipe: It is	811	As an example, libev itself uses this for its internal signal pipe: It
703	not visible to the libev user and should not keep C<ev_loop> from exiting	812	is not visible to the libev user and should not keep C<ev_loop> from
704	if no event watchers registered by it are active. It is also an excellent	813	exiting if no event watchers registered by it are active. It is also an
705	way to do this for generic recurring timers or from within third-party	814	excellent way to do this for generic recurring timers or from within
706	libraries. Just remember to I<unref after start> and I<ref before stop>	815	third-party libraries. Just remember to I<unref after start> and I<ref
707	(but only if the watcher wasn't active before, or was active before,	816	before stop> (but only if the watcher wasn't active before, or was active
708	respectively).	817	before, respectively. Note also that libev might stop watchers itself
		818	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		819	in the callback).
709		820
710	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	821	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
711	running when nothing else is active.	822	running when nothing else is active.
712		823
713	struct ev_signal exitsig;	824	ev_signal exitsig;
714	ev_signal_init (&exitsig, sig_cb, SIGINT);	825	ev_signal_init (&exitsig, sig_cb, SIGINT);
715	ev_signal_start (loop, &exitsig);	826	ev_signal_start (loop, &exitsig);
716	evf_unref (loop);	827	evf_unref (loop);
717		828
718	Example: For some weird reason, unregister the above signal handler again.	829	Example: For some weird reason, unregister the above signal handler again.
…		…
742		853
743	By setting a higher I<io collect interval> you allow libev to spend more	854	By setting a higher I<io collect interval> you allow libev to spend more
744	time collecting I/O events, so you can handle more events per iteration,	855	time collecting I/O events, so you can handle more events per iteration,
745	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	856	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
746	C<ev_timer>) will be not affected. Setting this to a non-null value will	857	C<ev_timer>) will be not affected. Setting this to a non-null value will
747	introduce an additional C<ev_sleep ()> call into most loop iterations.	858	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		859	sleep time ensures that libev will not poll for I/O events more often then
		860	once per this interval, on average.
748		861
749	Likewise, by setting a higher I<timeout collect interval> you allow libev	862	Likewise, by setting a higher I<timeout collect interval> you allow libev
750	to spend more time collecting timeouts, at the expense of increased	863	to spend more time collecting timeouts, at the expense of increased
751	latency/jitter/inexactness (the watcher callback will be called	864	latency/jitter/inexactness (the watcher callback will be called
752	later). C<ev_io> watchers will not be affected. Setting this to a non-null	865	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
754		867
755	Many (busy) programs can usually benefit by setting the I/O collect	868	Many (busy) programs can usually benefit by setting the I/O collect
756	interval to a value near C<0.1> or so, which is often enough for	869	interval to a value near C<0.1> or so, which is often enough for
757	interactive servers (of course not for games), likewise for timeouts. It	870	interactive servers (of course not for games), likewise for timeouts. It
758	usually doesn't make much sense to set it to a lower value than C<0.01>,	871	usually doesn't make much sense to set it to a lower value than C<0.01>,
759	as this approaches the timing granularity of most systems.	872	as this approaches the timing granularity of most systems. Note that if
		873	you do transactions with the outside world and you can't increase the
		874	parallelity, then this setting will limit your transaction rate (if you
		875	need to poll once per transaction and the I/O collect interval is 0.01,
		876	then you can't do more than 100 transations per second).
760		877
761	Setting the I<timeout collect interval> can improve the opportunity for	878	Setting the I<timeout collect interval> can improve the opportunity for
762	saving power, as the program will "bundle" timer callback invocations that	879	saving power, as the program will "bundle" timer callback invocations that
763	are "near" in time together, by delaying some, thus reducing the number of	880	are "near" in time together, by delaying some, thus reducing the number of
764	times the process sleeps and wakes up again. Another useful technique to	881	times the process sleeps and wakes up again. Another useful technique to
765	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	882	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
766	they fire on, say, one-second boundaries only.	883	they fire on, say, one-second boundaries only.
767		884
		885	Example: we only need 0.1s timeout granularity, and we wish not to poll
		886	more often than 100 times per second:
		887
		888	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		889	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		890
		891	=item ev_invoke_pending (loop)
		892
		893	This call will simply invoke all pending watchers while resetting their
		894	pending state. Normally, C<ev_loop> does this automatically when required,
		895	but when overriding the invoke callback this call comes handy.
		896
		897	=item int ev_pending_count (loop)
		898
		899	Returns the number of pending watchers - zero indicates that no watchers
		900	are pending.
		901
		902	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		903
		904	This overrides the invoke pending functionality of the loop: Instead of
		905	invoking all pending watchers when there are any, C<ev_loop> will call
		906	this callback instead. This is useful, for example, when you want to
		907	invoke the actual watchers inside another context (another thread etc.).
		908
		909	If you want to reset the callback, use C<ev_invoke_pending> as new
		910	callback.
		911
		912	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		913
		914	Sometimes you want to share the same loop between multiple threads. This
		915	can be done relatively simply by putting mutex_lock/unlock calls around
		916	each call to a libev function.
		917
		918	However, C<ev_loop> can run an indefinite time, so it is not feasible to
		919	wait for it to return. One way around this is to wake up the loop via
		920	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>
		921	and I<acquire> callbacks on the loop.
		922
		923	When set, then C<release> will be called just before the thread is
		924	suspended waiting for new events, and C<acquire> is called just
		925	afterwards.
		926
		927	Ideally, C<release> will just call your mutex_unlock function, and
		928	C<acquire> will just call the mutex_lock function again.
		929
		930	While event loop modifications are allowed between invocations of
		931	C<release> and C<acquire> (that's their only purpose after all), no
		932	modifications done will affect the event loop, i.e. adding watchers will
		933	have no effect on the set of file descriptors being watched, or the time
		934	waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it
		935	to take note of any changes you made.
		936
		937	In theory, threads executing C<ev_loop> will be async-cancel safe between
		938	invocations of C<release> and C<acquire>.
		939
		940	See also the locking example in the C<THREADS> section later in this
		941	document.
		942
		943	=item ev_set_userdata (loop, void *data)
		944
		945	=item ev_userdata (loop)
		946
		947	Set and retrieve a single C<void *> associated with a loop. When
		948	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		949	C<0.>
		950
		951	These two functions can be used to associate arbitrary data with a loop,
		952	and are intended solely for the C<invoke_pending_cb>, C<release> and
		953	C<acquire> callbacks described above, but of course can be (ab-)used for
		954	any other purpose as well.
		955
768	=item ev_loop_verify (loop)	956	=item ev_loop_verify (loop)
769		957
770	This function only does something when C<EV_VERIFY> support has been	958	This function only does something when C<EV_VERIFY> support has been
771	compiled in. which is the default for non-minimal builds. It tries to go	959	compiled in, which is the default for non-minimal builds. It tries to go
772	through all internal structures and checks them for validity. If anything	960	through all internal structures and checks them for validity. If anything
773	is found to be inconsistent, it will print an error message to standard	961	is found to be inconsistent, it will print an error message to standard
774	error and call C<abort ()>.	962	error and call C<abort ()>.
775		963
776	This can be used to catch bugs inside libev itself: under normal	964	This can be used to catch bugs inside libev itself: under normal
…		…
780	=back	968	=back
781		969
782		970
783	=head1 ANATOMY OF A WATCHER	971	=head1 ANATOMY OF A WATCHER
784		972
		973	In the following description, uppercase C<TYPE> in names stands for the
		974	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		975	watchers and C<ev_io_start> for I/O watchers.
		976
785	A watcher is a structure that you create and register to record your	977	A watcher is a structure that you create and register to record your
786	interest in some event. For instance, if you want to wait for STDIN to	978	interest in some event. For instance, if you want to wait for STDIN to
787	become readable, you would create an C<ev_io> watcher for that:	979	become readable, you would create an C<ev_io> watcher for that:
788		980
789	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	981	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
790	{	982	{
791	ev_io_stop (w);	983	ev_io_stop (w);
792	ev_unloop (loop, EVUNLOOP_ALL);	984	ev_unloop (loop, EVUNLOOP_ALL);
793	}	985	}
794		986
795	struct ev_loop *loop = ev_default_loop (0);	987	struct ev_loop *loop = ev_default_loop (0);
		988
796	struct ev_io stdin_watcher;	989	ev_io stdin_watcher;
		990
797	ev_init (&stdin_watcher, my_cb);	991	ev_init (&stdin_watcher, my_cb);
798	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	992	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
799	ev_io_start (loop, &stdin_watcher);	993	ev_io_start (loop, &stdin_watcher);
		994
800	ev_loop (loop, 0);	995	ev_loop (loop, 0);
801		996
802	As you can see, you are responsible for allocating the memory for your	997	As you can see, you are responsible for allocating the memory for your
803	watcher structures (and it is usually a bad idea to do this on the stack,	998	watcher structures (and it is I<usually> a bad idea to do this on the
804	although this can sometimes be quite valid).	999	stack).
		1000
		1001	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		1002	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
805		1003
806	Each watcher structure must be initialised by a call to C<ev_init	1004	Each watcher structure must be initialised by a call to C<ev_init
807	(watcher *, callback)>, which expects a callback to be provided. This	1005	(watcher *, callback)>, which expects a callback to be provided. This
808	callback gets invoked each time the event occurs (or, in the case of I/O	1006	callback gets invoked each time the event occurs (or, in the case of I/O
809	watchers, each time the event loop detects that the file descriptor given	1007	watchers, each time the event loop detects that the file descriptor given
810	is readable and/or writable).	1008	is readable and/or writable).
811		1009
812	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1010	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
813	with arguments specific to this watcher type. There is also a macro	1011	macro to configure it, with arguments specific to the watcher type. There
814	to combine initialisation and setting in one call: C<< ev_<type>_init	1012	is also a macro to combine initialisation and setting in one call: C<<
815	(watcher *, callback, ...) >>.	1013	ev_TYPE_init (watcher *, callback, ...) >>.
816		1014
817	To make the watcher actually watch out for events, you have to start it	1015	To make the watcher actually watch out for events, you have to start it
818	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	1016	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
819	*) >>), and you can stop watching for events at any time by calling the	1017	*) >>), and you can stop watching for events at any time by calling the
820	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1018	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
821		1019
822	As long as your watcher is active (has been started but not stopped) you	1020	As long as your watcher is active (has been started but not stopped) you
823	must not touch the values stored in it. Most specifically you must never	1021	must not touch the values stored in it. Most specifically you must never
824	reinitialise it or call its C<set> macro.	1022	reinitialise it or call its C<ev_TYPE_set> macro.
825		1023
826	Each and every callback receives the event loop pointer as first, the	1024	Each and every callback receives the event loop pointer as first, the
827	registered watcher structure as second, and a bitset of received events as	1025	registered watcher structure as second, and a bitset of received events as
828	third argument.	1026	third argument.
829		1027
…		…
838	=item C<EV_WRITE>	1036	=item C<EV_WRITE>
839		1037
840	The file descriptor in the C<ev_io> watcher has become readable and/or	1038	The file descriptor in the C<ev_io> watcher has become readable and/or
841	writable.	1039	writable.
842		1040
843	=item C<EV_TIMEOUT>	1041	=item C<EV_TIMER>
844		1042
845	The C<ev_timer> watcher has timed out.	1043	The C<ev_timer> watcher has timed out.
846		1044
847	=item C<EV_PERIODIC>	1045	=item C<EV_PERIODIC>
848		1046
…		…
887		1085
888	=item C<EV_ASYNC>	1086	=item C<EV_ASYNC>
889		1087
890	The given async watcher has been asynchronously notified (see C<ev_async>).	1088	The given async watcher has been asynchronously notified (see C<ev_async>).
891		1089
		1090	=item C<EV_CUSTOM>
		1091
		1092	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1093	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		1094
892	=item C<EV_ERROR>	1095	=item C<EV_ERROR>
893		1096
894	An unspecified error has occurred, the watcher has been stopped. This might	1097	An unspecified error has occurred, the watcher has been stopped. This might
895	happen because the watcher could not be properly started because libev	1098	happen because the watcher could not be properly started because libev
896	ran out of memory, a file descriptor was found to be closed or any other	1099	ran out of memory, a file descriptor was found to be closed or any other
		1100	problem. Libev considers these application bugs.
		1101
897	problem. You best act on it by reporting the problem and somehow coping	1102	You best act on it by reporting the problem and somehow coping with the
898	with the watcher being stopped.	1103	watcher being stopped. Note that well-written programs should not receive
		1104	an error ever, so when your watcher receives it, this usually indicates a
		1105	bug in your program.
899		1106
900	Libev will usually signal a few "dummy" events together with an error, for	1107	Libev will usually signal a few "dummy" events together with an error, for
901	example it might indicate that a fd is readable or writable, and if your	1108	example it might indicate that a fd is readable or writable, and if your
902	callbacks is well-written it can just attempt the operation and cope with	1109	callbacks is well-written it can just attempt the operation and cope with
903	the error from read() or write(). This will not work in multi-threaded	1110	the error from read() or write(). This will not work in multi-threaded
…		…
906		1113
907	=back	1114	=back
908		1115
909	=head2 GENERIC WATCHER FUNCTIONS	1116	=head2 GENERIC WATCHER FUNCTIONS
910		1117
911	In the following description, C<TYPE> stands for the watcher type,
912	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
913
914	=over 4	1118	=over 4
915		1119
916	=item C<ev_init> (ev_TYPE *watcher, callback)	1120	=item C<ev_init> (ev_TYPE *watcher, callback)
917		1121
918	This macro initialises the generic portion of a watcher. The contents	1122	This macro initialises the generic portion of a watcher. The contents
…		…
923	which rolls both calls into one.	1127	which rolls both calls into one.
924		1128
925	You can reinitialise a watcher at any time as long as it has been stopped	1129	You can reinitialise a watcher at any time as long as it has been stopped
926	(or never started) and there are no pending events outstanding.	1130	(or never started) and there are no pending events outstanding.
927		1131
928	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1132	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
929	int revents)>.	1133	int revents)>.
930		1134
931	Example: Initialise an C<ev_io> watcher in two steps.	1135	Example: Initialise an C<ev_io> watcher in two steps.
932		1136
933	ev_io w;	1137	ev_io w;
934	ev_init (&w, my_cb);	1138	ev_init (&w, my_cb);
935	ev_io_set (&w, STDIN_FILENO, EV_READ);	1139	ev_io_set (&w, STDIN_FILENO, EV_READ);
936		1140
937	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1141	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
938		1142
939	This macro initialises the type-specific parts of a watcher. You need to	1143	This macro initialises the type-specific parts of a watcher. You need to
940	call C<ev_init> at least once before you call this macro, but you can	1144	call C<ev_init> at least once before you call this macro, but you can
941	call C<ev_TYPE_set> any number of times. You must not, however, call this	1145	call C<ev_TYPE_set> any number of times. You must not, however, call this
942	macro on a watcher that is active (it can be pending, however, which is a	1146	macro on a watcher that is active (it can be pending, however, which is a
…		…
955		1159
956	Example: Initialise and set an C<ev_io> watcher in one step.	1160	Example: Initialise and set an C<ev_io> watcher in one step.
957		1161
958	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1162	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
959		1163
960	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1164	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
961		1165
962	Starts (activates) the given watcher. Only active watchers will receive	1166	Starts (activates) the given watcher. Only active watchers will receive
963	events. If the watcher is already active nothing will happen.	1167	events. If the watcher is already active nothing will happen.
964		1168
965	Example: Start the C<ev_io> watcher that is being abused as example in this	1169	Example: Start the C<ev_io> watcher that is being abused as example in this
966	whole section.	1170	whole section.
967		1171
968	ev_io_start (EV_DEFAULT_UC, &w);	1172	ev_io_start (EV_DEFAULT_UC, &w);
969		1173
970	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1174	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
971		1175
972	Stops the given watcher again (if active) and clears the pending	1176	Stops the given watcher if active, and clears the pending status (whether
		1177	the watcher was active or not).
		1178
973	status. It is possible that stopped watchers are pending (for example,	1179	It is possible that stopped watchers are pending - for example,
974	non-repeating timers are being stopped when they become pending), but	1180	non-repeating timers are being stopped when they become pending - but
975	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1181	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
976	you want to free or reuse the memory used by the watcher it is therefore a	1182	pending. If you want to free or reuse the memory used by the watcher it is
977	good idea to always call its C<ev_TYPE_stop> function.	1183	therefore a good idea to always call its C<ev_TYPE_stop> function.
978		1184
979	=item bool ev_is_active (ev_TYPE *watcher)	1185	=item bool ev_is_active (ev_TYPE *watcher)
980		1186
981	Returns a true value iff the watcher is active (i.e. it has been started	1187	Returns a true value iff the watcher is active (i.e. it has been started
982	and not yet been stopped). As long as a watcher is active you must not modify	1188	and not yet been stopped). As long as a watcher is active you must not modify
…		…
998	=item ev_cb_set (ev_TYPE *watcher, callback)	1204	=item ev_cb_set (ev_TYPE *watcher, callback)
999		1205
1000	Change the callback. You can change the callback at virtually any time	1206	Change the callback. You can change the callback at virtually any time
1001	(modulo threads).	1207	(modulo threads).
1002		1208
1003	=item ev_set_priority (ev_TYPE *watcher, priority)	1209	=item ev_set_priority (ev_TYPE *watcher, int priority)
1004		1210
1005	=item int ev_priority (ev_TYPE *watcher)	1211	=item int ev_priority (ev_TYPE *watcher)
1006		1212
1007	Set and query the priority of the watcher. The priority is a small	1213	Set and query the priority of the watcher. The priority is a small
1008	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1214	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1009	(default: C<-2>). Pending watchers with higher priority will be invoked	1215	(default: C<-2>). Pending watchers with higher priority will be invoked
1010	before watchers with lower priority, but priority will not keep watchers	1216	before watchers with lower priority, but priority will not keep watchers
1011	from being executed (except for C<ev_idle> watchers).	1217	from being executed (except for C<ev_idle> watchers).
1012		1218
1013	This means that priorities are I<only> used for ordering callback
1014	invocation after new events have been received. This is useful, for
1015	example, to reduce latency after idling, or more often, to bind two
1016	watchers on the same event and make sure one is called first.
1017
1018	If you need to suppress invocation when higher priority events are pending	1219	If you need to suppress invocation when higher priority events are pending
1019	you need to look at C<ev_idle> watchers, which provide this functionality.	1220	you need to look at C<ev_idle> watchers, which provide this functionality.
1020		1221
1021	You I<must not> change the priority of a watcher as long as it is active or	1222	You I<must not> change the priority of a watcher as long as it is active or
1022	pending.	1223	pending.
1023		1224
		1225	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1226	fine, as long as you do not mind that the priority value you query might
		1227	or might not have been clamped to the valid range.
		1228
1024	The default priority used by watchers when no priority has been set is	1229	The default priority used by watchers when no priority has been set is
1025	always C<0>, which is supposed to not be too high and not be too low :).	1230	always C<0>, which is supposed to not be too high and not be too low :).
1026		1231
1027	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1232	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1028	fine, as long as you do not mind that the priority value you query might	1233	priorities.
1029	or might not have been adjusted to be within valid range.
1030		1234
1031	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1235	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1032		1236
1033	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1237	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1034	C<loop> nor C<revents> need to be valid as long as the watcher callback	1238	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1041	returns its C<revents> bitset (as if its callback was invoked). If the	1245	returns its C<revents> bitset (as if its callback was invoked). If the
1042	watcher isn't pending it does nothing and returns C<0>.	1246	watcher isn't pending it does nothing and returns C<0>.
1043		1247
1044	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1248	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1045	callback to be invoked, which can be accomplished with this function.	1249	callback to be invoked, which can be accomplished with this function.
		1250
		1251	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1252
		1253	Feeds the given event set into the event loop, as if the specified event
		1254	had happened for the specified watcher (which must be a pointer to an
		1255	initialised but not necessarily started event watcher). Obviously you must
		1256	not free the watcher as long as it has pending events.
		1257
		1258	Stopping the watcher, letting libev invoke it, or calling
		1259	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1260	not started in the first place.
		1261
		1262	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1263	functions that do not need a watcher.
1046		1264
1047	=back	1265	=back
1048		1266
1049		1267
1050	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1268	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
1056	member, you can also "subclass" the watcher type and provide your own	1274	member, you can also "subclass" the watcher type and provide your own
1057	data:	1275	data:
1058		1276
1059	struct my_io	1277	struct my_io
1060	{	1278	{
1061	struct ev_io io;	1279	ev_io io;
1062	int otherfd;	1280	int otherfd;
1063	void *somedata;	1281	void *somedata;
1064	struct whatever *mostinteresting;	1282	struct whatever *mostinteresting;
1065	};	1283	};
1066		1284
…		…
1069	ev_io_init (&w.io, my_cb, fd, EV_READ);	1287	ev_io_init (&w.io, my_cb, fd, EV_READ);
1070		1288
1071	And since your callback will be called with a pointer to the watcher, you	1289	And since your callback will be called with a pointer to the watcher, you
1072	can cast it back to your own type:	1290	can cast it back to your own type:
1073		1291
1074	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1292	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1075	{	1293	{
1076	struct my_io *w = (struct my_io *)w_;	1294	struct my_io *w = (struct my_io *)w_;
1077	...	1295	...
1078	}	1296	}
1079		1297
…		…
1097	programmers):	1315	programmers):
1098		1316
1099	#include <stddef.h>	1317	#include <stddef.h>
1100		1318
1101	static void	1319	static void
1102	t1_cb (EV_P_ struct ev_timer *w, int revents)	1320	t1_cb (EV_P_ ev_timer *w, int revents)
1103	{	1321	{
1104	struct my_biggy big = (struct my_biggy *	1322	struct my_biggy big = (struct my_biggy *)
1105	(((char *)w) - offsetof (struct my_biggy, t1));	1323	(((char *)w) - offsetof (struct my_biggy, t1));
1106	}	1324	}
1107		1325
1108	static void	1326	static void
1109	t2_cb (EV_P_ struct ev_timer *w, int revents)	1327	t2_cb (EV_P_ ev_timer *w, int revents)
1110	{	1328	{
1111	struct my_biggy big = (struct my_biggy *	1329	struct my_biggy big = (struct my_biggy *)
1112	(((char *)w) - offsetof (struct my_biggy, t2));	1330	(((char *)w) - offsetof (struct my_biggy, t2));
1113	}	1331	}
		1332
		1333	=head2 WATCHER PRIORITY MODELS
		1334
		1335	Many event loops support I<watcher priorities>, which are usually small
		1336	integers that influence the ordering of event callback invocation
		1337	between watchers in some way, all else being equal.
		1338
		1339	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1340	description for the more technical details such as the actual priority
		1341	range.
		1342
		1343	There are two common ways how these these priorities are being interpreted
		1344	by event loops:
		1345
		1346	In the more common lock-out model, higher priorities "lock out" invocation
		1347	of lower priority watchers, which means as long as higher priority
		1348	watchers receive events, lower priority watchers are not being invoked.
		1349
		1350	The less common only-for-ordering model uses priorities solely to order
		1351	callback invocation within a single event loop iteration: Higher priority
		1352	watchers are invoked before lower priority ones, but they all get invoked
		1353	before polling for new events.
		1354
		1355	Libev uses the second (only-for-ordering) model for all its watchers
		1356	except for idle watchers (which use the lock-out model).
		1357
		1358	The rationale behind this is that implementing the lock-out model for
		1359	watchers is not well supported by most kernel interfaces, and most event
		1360	libraries will just poll for the same events again and again as long as
		1361	their callbacks have not been executed, which is very inefficient in the
		1362	common case of one high-priority watcher locking out a mass of lower
		1363	priority ones.
		1364
		1365	Static (ordering) priorities are most useful when you have two or more
		1366	watchers handling the same resource: a typical usage example is having an
		1367	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1368	timeouts. Under load, data might be received while the program handles
		1369	other jobs, but since timers normally get invoked first, the timeout
		1370	handler will be executed before checking for data. In that case, giving
		1371	the timer a lower priority than the I/O watcher ensures that I/O will be
		1372	handled first even under adverse conditions (which is usually, but not
		1373	always, what you want).
		1374
		1375	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1376	will only be executed when no same or higher priority watchers have
		1377	received events, they can be used to implement the "lock-out" model when
		1378	required.
		1379
		1380	For example, to emulate how many other event libraries handle priorities,
		1381	you can associate an C<ev_idle> watcher to each such watcher, and in
		1382	the normal watcher callback, you just start the idle watcher. The real
		1383	processing is done in the idle watcher callback. This causes libev to
		1384	continously poll and process kernel event data for the watcher, but when
		1385	the lock-out case is known to be rare (which in turn is rare :), this is
		1386	workable.
		1387
		1388	Usually, however, the lock-out model implemented that way will perform
		1389	miserably under the type of load it was designed to handle. In that case,
		1390	it might be preferable to stop the real watcher before starting the
		1391	idle watcher, so the kernel will not have to process the event in case
		1392	the actual processing will be delayed for considerable time.
		1393
		1394	Here is an example of an I/O watcher that should run at a strictly lower
		1395	priority than the default, and which should only process data when no
		1396	other events are pending:
		1397
		1398	ev_idle idle; // actual processing watcher
		1399	ev_io io; // actual event watcher
		1400
		1401	static void
		1402	io_cb (EV_P_ ev_io *w, int revents)
		1403	{
		1404	// stop the I/O watcher, we received the event, but
		1405	// are not yet ready to handle it.
		1406	ev_io_stop (EV_A_ w);
		1407
		1408	// start the idle watcher to ahndle the actual event.
		1409	// it will not be executed as long as other watchers
		1410	// with the default priority are receiving events.
		1411	ev_idle_start (EV_A_ &idle);
		1412	}
		1413
		1414	static void
		1415	idle_cb (EV_P_ ev_idle *w, int revents)
		1416	{
		1417	// actual processing
		1418	read (STDIN_FILENO, ...);
		1419
		1420	// have to start the I/O watcher again, as
		1421	// we have handled the event
		1422	ev_io_start (EV_P_ &io);
		1423	}
		1424
		1425	// initialisation
		1426	ev_idle_init (&idle, idle_cb);
		1427	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1428	ev_io_start (EV_DEFAULT_ &io);
		1429
		1430	In the "real" world, it might also be beneficial to start a timer, so that
		1431	low-priority connections can not be locked out forever under load. This
		1432	enables your program to keep a lower latency for important connections
		1433	during short periods of high load, while not completely locking out less
		1434	important ones.
1114		1435
1115		1436
1116	=head1 WATCHER TYPES	1437	=head1 WATCHER TYPES
1117		1438
1118	This section describes each watcher in detail, but will not repeat	1439	This section describes each watcher in detail, but will not repeat
…		…
1144	descriptors to non-blocking mode is also usually a good idea (but not	1465	descriptors to non-blocking mode is also usually a good idea (but not
1145	required if you know what you are doing).	1466	required if you know what you are doing).
1146		1467
1147	If you cannot use non-blocking mode, then force the use of a	1468	If you cannot use non-blocking mode, then force the use of a
1148	known-to-be-good backend (at the time of this writing, this includes only	1469	known-to-be-good backend (at the time of this writing, this includes only
1149	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).	1470	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1471	descriptors for which non-blocking operation makes no sense (such as
		1472	files) - libev doesn't guarentee any specific behaviour in that case.
1150		1473
1151	Another thing you have to watch out for is that it is quite easy to	1474	Another thing you have to watch out for is that it is quite easy to
1152	receive "spurious" readiness notifications, that is your callback might	1475	receive "spurious" readiness notifications, that is your callback might
1153	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1476	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1154	because there is no data. Not only are some backends known to create a	1477	because there is no data. Not only are some backends known to create a
…		…
1219		1542
1220	So when you encounter spurious, unexplained daemon exits, make sure you	1543	So when you encounter spurious, unexplained daemon exits, make sure you
1221	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1544	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1222	somewhere, as that would have given you a big clue).	1545	somewhere, as that would have given you a big clue).
1223		1546
		1547	=head3 The special problem of accept()ing when you can't
		1548
		1549	Many implementations of the POSIX C<accept> function (for example,
		1550	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1551	connection from the pending queue in all error cases.
		1552
		1553	For example, larger servers often run out of file descriptors (because
		1554	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1555	rejecting the connection, leading to libev signalling readiness on
		1556	the next iteration again (the connection still exists after all), and
		1557	typically causing the program to loop at 100% CPU usage.
		1558
		1559	Unfortunately, the set of errors that cause this issue differs between
		1560	operating systems, there is usually little the app can do to remedy the
		1561	situation, and no known thread-safe method of removing the connection to
		1562	cope with overload is known (to me).
		1563
		1564	One of the easiest ways to handle this situation is to just ignore it
		1565	- when the program encounters an overload, it will just loop until the
		1566	situation is over. While this is a form of busy waiting, no OS offers an
		1567	event-based way to handle this situation, so it's the best one can do.
		1568
		1569	A better way to handle the situation is to log any errors other than
		1570	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1571	messages, and continue as usual, which at least gives the user an idea of
		1572	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1573	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1574	usage.
		1575
		1576	If your program is single-threaded, then you could also keep a dummy file
		1577	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1578	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1579	close that fd, and create a new dummy fd. This will gracefully refuse
		1580	clients under typical overload conditions.
		1581
		1582	The last way to handle it is to simply log the error and C<exit>, as
		1583	is often done with C<malloc> failures, but this results in an easy
		1584	opportunity for a DoS attack.
1224		1585
1225	=head3 Watcher-Specific Functions	1586	=head3 Watcher-Specific Functions
1226		1587
1227	=over 4	1588	=over 4
1228		1589
…		…
1249	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1610	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1250	readable, but only once. Since it is likely line-buffered, you could	1611	readable, but only once. Since it is likely line-buffered, you could
1251	attempt to read a whole line in the callback.	1612	attempt to read a whole line in the callback.
1252		1613
1253	static void	1614	static void
1254	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1615	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1255	{	1616	{
1256	ev_io_stop (loop, w);	1617	ev_io_stop (loop, w);
1257	.. read from stdin here (or from w->fd) and handle any I/O errors	1618	.. read from stdin here (or from w->fd) and handle any I/O errors
1258	}	1619	}
1259		1620
1260	...	1621	...
1261	struct ev_loop *loop = ev_default_init (0);	1622	struct ev_loop *loop = ev_default_init (0);
1262	struct ev_io stdin_readable;	1623	ev_io stdin_readable;
1263	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1624	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1264	ev_io_start (loop, &stdin_readable);	1625	ev_io_start (loop, &stdin_readable);
1265	ev_loop (loop, 0);	1626	ev_loop (loop, 0);
1266		1627
1267		1628
…		…
1275	year, it will still time out after (roughly) one hour. "Roughly" because	1636	year, it will still time out after (roughly) one hour. "Roughly" because
1276	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1637	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1277	monotonic clock option helps a lot here).	1638	monotonic clock option helps a lot here).
1278		1639
1279	The callback is guaranteed to be invoked only I<after> its timeout has	1640	The callback is guaranteed to be invoked only I<after> its timeout has
1280	passed, but if multiple timers become ready during the same loop iteration	1641	passed (not I<at>, so on systems with very low-resolution clocks this
1281	then order of execution is undefined.	1642	might introduce a small delay). If multiple timers become ready during the
		1643	same loop iteration then the ones with earlier time-out values are invoked
		1644	before ones of the same priority with later time-out values (but this is
		1645	no longer true when a callback calls C<ev_loop> recursively).
		1646
		1647	=head3 Be smart about timeouts
		1648
		1649	Many real-world problems involve some kind of timeout, usually for error
		1650	recovery. A typical example is an HTTP request - if the other side hangs,
		1651	you want to raise some error after a while.
		1652
		1653	What follows are some ways to handle this problem, from obvious and
		1654	inefficient to smart and efficient.
		1655
		1656	In the following, a 60 second activity timeout is assumed - a timeout that
		1657	gets reset to 60 seconds each time there is activity (e.g. each time some
		1658	data or other life sign was received).
		1659
		1660	=over 4
		1661
		1662	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1663
		1664	This is the most obvious, but not the most simple way: In the beginning,
		1665	start the watcher:
		1666
		1667	ev_timer_init (timer, callback, 60., 0.);
		1668	ev_timer_start (loop, timer);
		1669
		1670	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1671	and start it again:
		1672
		1673	ev_timer_stop (loop, timer);
		1674	ev_timer_set (timer, 60., 0.);
		1675	ev_timer_start (loop, timer);
		1676
		1677	This is relatively simple to implement, but means that each time there is
		1678	some activity, libev will first have to remove the timer from its internal
		1679	data structure and then add it again. Libev tries to be fast, but it's
		1680	still not a constant-time operation.
		1681
		1682	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1683
		1684	This is the easiest way, and involves using C<ev_timer_again> instead of
		1685	C<ev_timer_start>.
		1686
		1687	To implement this, configure an C<ev_timer> with a C<repeat> value
		1688	of C<60> and then call C<ev_timer_again> at start and each time you
		1689	successfully read or write some data. If you go into an idle state where
		1690	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1691	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1692
		1693	That means you can ignore both the C<ev_timer_start> function and the
		1694	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1695	member and C<ev_timer_again>.
		1696
		1697	At start:
		1698
		1699	ev_init (timer, callback);
		1700	timer->repeat = 60.;
		1701	ev_timer_again (loop, timer);
		1702
		1703	Each time there is some activity:
		1704
		1705	ev_timer_again (loop, timer);
		1706
		1707	It is even possible to change the time-out on the fly, regardless of
		1708	whether the watcher is active or not:
		1709
		1710	timer->repeat = 30.;
		1711	ev_timer_again (loop, timer);
		1712
		1713	This is slightly more efficient then stopping/starting the timer each time
		1714	you want to modify its timeout value, as libev does not have to completely
		1715	remove and re-insert the timer from/into its internal data structure.
		1716
		1717	It is, however, even simpler than the "obvious" way to do it.
		1718
		1719	=item 3. Let the timer time out, but then re-arm it as required.
		1720
		1721	This method is more tricky, but usually most efficient: Most timeouts are
		1722	relatively long compared to the intervals between other activity - in
		1723	our example, within 60 seconds, there are usually many I/O events with
		1724	associated activity resets.
		1725
		1726	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1727	but remember the time of last activity, and check for a real timeout only
		1728	within the callback:
		1729
		1730	ev_tstamp last_activity; // time of last activity
		1731
		1732	static void
		1733	callback (EV_P_ ev_timer *w, int revents)
		1734	{
		1735	ev_tstamp now = ev_now (EV_A);
		1736	ev_tstamp timeout = last_activity + 60.;
		1737
		1738	// if last_activity + 60. is older than now, we did time out
		1739	if (timeout < now)
		1740	{
		1741	// timeout occured, take action
		1742	}
		1743	else
		1744	{
		1745	// callback was invoked, but there was some activity, re-arm
		1746	// the watcher to fire in last_activity + 60, which is
		1747	// guaranteed to be in the future, so "again" is positive:
		1748	w->repeat = timeout - now;
		1749	ev_timer_again (EV_A_ w);
		1750	}
		1751	}
		1752
		1753	To summarise the callback: first calculate the real timeout (defined
		1754	as "60 seconds after the last activity"), then check if that time has
		1755	been reached, which means something I<did>, in fact, time out. Otherwise
		1756	the callback was invoked too early (C<timeout> is in the future), so
		1757	re-schedule the timer to fire at that future time, to see if maybe we have
		1758	a timeout then.
		1759
		1760	Note how C<ev_timer_again> is used, taking advantage of the
		1761	C<ev_timer_again> optimisation when the timer is already running.
		1762
		1763	This scheme causes more callback invocations (about one every 60 seconds
		1764	minus half the average time between activity), but virtually no calls to
		1765	libev to change the timeout.
		1766
		1767	To start the timer, simply initialise the watcher and set C<last_activity>
		1768	to the current time (meaning we just have some activity :), then call the
		1769	callback, which will "do the right thing" and start the timer:
		1770
		1771	ev_init (timer, callback);
		1772	last_activity = ev_now (loop);
		1773	callback (loop, timer, EV_TIMER);
		1774
		1775	And when there is some activity, simply store the current time in
		1776	C<last_activity>, no libev calls at all:
		1777
		1778	last_actiivty = ev_now (loop);
		1779
		1780	This technique is slightly more complex, but in most cases where the
		1781	time-out is unlikely to be triggered, much more efficient.
		1782
		1783	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1784	callback :) - just change the timeout and invoke the callback, which will
		1785	fix things for you.
		1786
		1787	=item 4. Wee, just use a double-linked list for your timeouts.
		1788
		1789	If there is not one request, but many thousands (millions...), all
		1790	employing some kind of timeout with the same timeout value, then one can
		1791	do even better:
		1792
		1793	When starting the timeout, calculate the timeout value and put the timeout
		1794	at the I<end> of the list.
		1795
		1796	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1797	the list is expected to fire (for example, using the technique #3).
		1798
		1799	When there is some activity, remove the timer from the list, recalculate
		1800	the timeout, append it to the end of the list again, and make sure to
		1801	update the C<ev_timer> if it was taken from the beginning of the list.
		1802
		1803	This way, one can manage an unlimited number of timeouts in O(1) time for
		1804	starting, stopping and updating the timers, at the expense of a major
		1805	complication, and having to use a constant timeout. The constant timeout
		1806	ensures that the list stays sorted.
		1807
		1808	=back
		1809
		1810	So which method the best?
		1811
		1812	Method #2 is a simple no-brain-required solution that is adequate in most
		1813	situations. Method #3 requires a bit more thinking, but handles many cases
		1814	better, and isn't very complicated either. In most case, choosing either
		1815	one is fine, with #3 being better in typical situations.
		1816
		1817	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1818	rather complicated, but extremely efficient, something that really pays
		1819	off after the first million or so of active timers, i.e. it's usually
		1820	overkill :)
1282		1821
1283	=head3 The special problem of time updates	1822	=head3 The special problem of time updates
1284		1823
1285	Establishing the current time is a costly operation (it usually takes at	1824	Establishing the current time is a costly operation (it usually takes at
1286	least two system calls): EV therefore updates its idea of the current	1825	least two system calls): EV therefore updates its idea of the current
…		…
1298		1837
1299	If the event loop is suspended for a long time, you can also force an	1838	If the event loop is suspended for a long time, you can also force an
1300	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1839	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1301	()>.	1840	()>.
1302		1841
		1842	=head3 The special problems of suspended animation
		1843
		1844	When you leave the server world it is quite customary to hit machines that
		1845	can suspend/hibernate - what happens to the clocks during such a suspend?
		1846
		1847	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1848	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1849	to run until the system is suspended, but they will not advance while the
		1850	system is suspended. That means, on resume, it will be as if the program
		1851	was frozen for a few seconds, but the suspend time will not be counted
		1852	towards C<ev_timer> when a monotonic clock source is used. The real time
		1853	clock advanced as expected, but if it is used as sole clocksource, then a
		1854	long suspend would be detected as a time jump by libev, and timers would
		1855	be adjusted accordingly.
		1856
		1857	I would not be surprised to see different behaviour in different between
		1858	operating systems, OS versions or even different hardware.
		1859
		1860	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1861	time jump in the monotonic clocks and the realtime clock. If the program
		1862	is suspended for a very long time, and monotonic clock sources are in use,
		1863	then you can expect C<ev_timer>s to expire as the full suspension time
		1864	will be counted towards the timers. When no monotonic clock source is in
		1865	use, then libev will again assume a timejump and adjust accordingly.
		1866
		1867	It might be beneficial for this latter case to call C<ev_suspend>
		1868	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1869	deterministic behaviour in this case (you can do nothing against
		1870	C<SIGSTOP>).
		1871
1303	=head3 Watcher-Specific Functions and Data Members	1872	=head3 Watcher-Specific Functions and Data Members
1304		1873
1305	=over 4	1874	=over 4
1306		1875
1307	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1876	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1330	If the timer is started but non-repeating, stop it (as if it timed out).	1899	If the timer is started but non-repeating, stop it (as if it timed out).
1331		1900
1332	If the timer is repeating, either start it if necessary (with the	1901	If the timer is repeating, either start it if necessary (with the
1333	C<repeat> value), or reset the running timer to the C<repeat> value.	1902	C<repeat> value), or reset the running timer to the C<repeat> value.
1334		1903
1335	This sounds a bit complicated, but here is a useful and typical	1904	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1336	example: Imagine you have a TCP connection and you want a so-called idle	1905	usage example.
1337	timeout, that is, you want to be called when there have been, say, 60
1338	seconds of inactivity on the socket. The easiest way to do this is to
1339	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1340	C<ev_timer_again> each time you successfully read or write some data. If
1341	you go into an idle state where you do not expect data to travel on the
1342	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1343	automatically restart it if need be.
1344		1906
1345	That means you can ignore the C<after> value and C<ev_timer_start>	1907	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1346	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1347		1908
1348	ev_timer_init (timer, callback, 0., 5.);	1909	Returns the remaining time until a timer fires. If the timer is active,
1349	ev_timer_again (loop, timer);	1910	then this time is relative to the current event loop time, otherwise it's
1350	...	1911	the timeout value currently configured.
1351	timer->again = 17.;
1352	ev_timer_again (loop, timer);
1353	...
1354	timer->again = 10.;
1355	ev_timer_again (loop, timer);
1356		1912
1357	This is more slightly efficient then stopping/starting the timer each time	1913	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1358	you want to modify its timeout value.	1914	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
1359		1915	will return C<4>. When the timer expires and is restarted, it will return
1360	Note, however, that it is often even more efficient to remember the	1916	roughly C<7> (likely slightly less as callback invocation takes some time,
1361	time of the last activity and let the timer time-out naturally. In the	1917	too), and so on.
1362	callback, you then check whether the time-out is real, or, if there was
1363	some activity, you reschedule the watcher to time-out in "last_activity +
1364	timeout - ev_now ()" seconds.
1365		1918
1366	=item ev_tstamp repeat [read-write]	1919	=item ev_tstamp repeat [read-write]
1367		1920
1368	The current C<repeat> value. Will be used each time the watcher times out	1921	The current C<repeat> value. Will be used each time the watcher times out
1369	or C<ev_timer_again> is called, and determines the next timeout (if any),	1922	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1374	=head3 Examples	1927	=head3 Examples
1375		1928
1376	Example: Create a timer that fires after 60 seconds.	1929	Example: Create a timer that fires after 60 seconds.
1377		1930
1378	static void	1931	static void
1379	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1932	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1380	{	1933	{
1381	.. one minute over, w is actually stopped right here	1934	.. one minute over, w is actually stopped right here
1382	}	1935	}
1383		1936
1384	struct ev_timer mytimer;	1937	ev_timer mytimer;
1385	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1938	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1386	ev_timer_start (loop, &mytimer);	1939	ev_timer_start (loop, &mytimer);
1387		1940
1388	Example: Create a timeout timer that times out after 10 seconds of	1941	Example: Create a timeout timer that times out after 10 seconds of
1389	inactivity.	1942	inactivity.
1390		1943
1391	static void	1944	static void
1392	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1945	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1393	{	1946	{
1394	.. ten seconds without any activity	1947	.. ten seconds without any activity
1395	}	1948	}
1396		1949
1397	struct ev_timer mytimer;	1950	ev_timer mytimer;
1398	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1951	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1399	ev_timer_again (&mytimer); /* start timer */	1952	ev_timer_again (&mytimer); /* start timer */
1400	ev_loop (loop, 0);	1953	ev_loop (loop, 0);
1401		1954
1402	// and in some piece of code that gets executed on any "activity":	1955	// and in some piece of code that gets executed on any "activity":
…		…
1407	=head2 C<ev_periodic> - to cron or not to cron?	1960	=head2 C<ev_periodic> - to cron or not to cron?
1408		1961
1409	Periodic watchers are also timers of a kind, but they are very versatile	1962	Periodic watchers are also timers of a kind, but they are very versatile
1410	(and unfortunately a bit complex).	1963	(and unfortunately a bit complex).
1411		1964
1412	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1965	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1413	but on wall clock time (absolute time). You can tell a periodic watcher	1966	relative time, the physical time that passes) but on wall clock time
1414	to trigger after some specific point in time. For example, if you tell a	1967	(absolute time, the thing you can read on your calender or clock). The
1415	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	1968	difference is that wall clock time can run faster or slower than real
1416	+ 10.>, that is, an absolute time not a delay) and then reset your system	1969	time, and time jumps are not uncommon (e.g. when you adjust your
1417	clock to January of the previous year, then it will take more than year	1970	wrist-watch).
1418	to trigger the event (unlike an C<ev_timer>, which would still trigger
1419	roughly 10 seconds later as it uses a relative timeout).
1420		1971
		1972	You can tell a periodic watcher to trigger after some specific point
		1973	in time: for example, if you tell a periodic watcher to trigger "in 10
		1974	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1975	not a delay) and then reset your system clock to January of the previous
		1976	year, then it will take a year or more to trigger the event (unlike an
		1977	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1978	it, as it uses a relative timeout).
		1979
1421	C<ev_periodic>s can also be used to implement vastly more complex timers,	1980	C<ev_periodic> watchers can also be used to implement vastly more complex
1422	such as triggering an event on each "midnight, local time", or other	1981	timers, such as triggering an event on each "midnight, local time", or
1423	complicated rules.	1982	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1983	those cannot react to time jumps.
1424		1984
1425	As with timers, the callback is guaranteed to be invoked only when the	1985	As with timers, the callback is guaranteed to be invoked only when the
1426	time (C<at>) has passed, but if multiple periodic timers become ready	1986	point in time where it is supposed to trigger has passed. If multiple
1427	during the same loop iteration, then order of execution is undefined.	1987	timers become ready during the same loop iteration then the ones with
		1988	earlier time-out values are invoked before ones with later time-out values
		1989	(but this is no longer true when a callback calls C<ev_loop> recursively).
1428		1990
1429	=head3 Watcher-Specific Functions and Data Members	1991	=head3 Watcher-Specific Functions and Data Members
1430		1992
1431	=over 4	1993	=over 4
1432		1994
1433	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1995	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1434		1996
1435	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1997	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1436		1998
1437	Lots of arguments, lets sort it out... There are basically three modes of	1999	Lots of arguments, let's sort it out... There are basically three modes of
1438	operation, and we will explain them from simplest to most complex:	2000	operation, and we will explain them from simplest to most complex:
1439		2001
1440	=over 4	2002	=over 4
1441		2003
1442	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2004	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1443		2005
1444	In this configuration the watcher triggers an event after the wall clock	2006	In this configuration the watcher triggers an event after the wall clock
1445	time C<at> has passed. It will not repeat and will not adjust when a time	2007	time C<offset> has passed. It will not repeat and will not adjust when a
1446	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2008	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1447	only run when the system clock reaches or surpasses this time.	2009	will be stopped and invoked when the system clock reaches or surpasses
		2010	this point in time.
1448		2011
1449	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2012	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1450		2013
1451	In this mode the watcher will always be scheduled to time out at the next	2014	In this mode the watcher will always be scheduled to time out at the next
1452	C<at + N * interval> time (for some integer N, which can also be negative)	2015	C<offset + N * interval> time (for some integer N, which can also be
1453	and then repeat, regardless of any time jumps.	2016	negative) and then repeat, regardless of any time jumps. The C<offset>
		2017	argument is merely an offset into the C<interval> periods.
1454		2018
1455	This can be used to create timers that do not drift with respect to the	2019	This can be used to create timers that do not drift with respect to the
1456	system clock, for example, here is a C<ev_periodic> that triggers each	2020	system clock, for example, here is an C<ev_periodic> that triggers each
1457	hour, on the hour:	2021	hour, on the hour (with respect to UTC):
1458		2022
1459	ev_periodic_set (&periodic, 0., 3600., 0);	2023	ev_periodic_set (&periodic, 0., 3600., 0);
1460		2024
1461	This doesn't mean there will always be 3600 seconds in between triggers,	2025	This doesn't mean there will always be 3600 seconds in between triggers,
1462	but only that the callback will be called when the system time shows a	2026	but only that the callback will be called when the system time shows a
1463	full hour (UTC), or more correctly, when the system time is evenly divisible	2027	full hour (UTC), or more correctly, when the system time is evenly divisible
1464	by 3600.	2028	by 3600.
1465		2029
1466	Another way to think about it (for the mathematically inclined) is that	2030	Another way to think about it (for the mathematically inclined) is that
1467	C<ev_periodic> will try to run the callback in this mode at the next possible	2031	C<ev_periodic> will try to run the callback in this mode at the next possible
1468	time where C<time = at (mod interval)>, regardless of any time jumps.	2032	time where C<time = offset (mod interval)>, regardless of any time jumps.
1469		2033
1470	For numerical stability it is preferable that the C<at> value is near	2034	For numerical stability it is preferable that the C<offset> value is near
1471	C<ev_now ()> (the current time), but there is no range requirement for	2035	C<ev_now ()> (the current time), but there is no range requirement for
1472	this value, and in fact is often specified as zero.	2036	this value, and in fact is often specified as zero.
1473		2037
1474	Note also that there is an upper limit to how often a timer can fire (CPU	2038	Note also that there is an upper limit to how often a timer can fire (CPU
1475	speed for example), so if C<interval> is very small then timing stability	2039	speed for example), so if C<interval> is very small then timing stability
1476	will of course deteriorate. Libev itself tries to be exact to be about one	2040	will of course deteriorate. Libev itself tries to be exact to be about one
1477	millisecond (if the OS supports it and the machine is fast enough).	2041	millisecond (if the OS supports it and the machine is fast enough).
1478		2042
1479	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2043	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1480		2044
1481	In this mode the values for C<interval> and C<at> are both being	2045	In this mode the values for C<interval> and C<offset> are both being
1482	ignored. Instead, each time the periodic watcher gets scheduled, the	2046	ignored. Instead, each time the periodic watcher gets scheduled, the
1483	reschedule callback will be called with the watcher as first, and the	2047	reschedule callback will be called with the watcher as first, and the
1484	current time as second argument.	2048	current time as second argument.
1485		2049
1486	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2050	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1487	ever, or make ANY event loop modifications whatsoever>.	2051	or make ANY other event loop modifications whatsoever, unless explicitly
		2052	allowed by documentation here>.
1488		2053
1489	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2054	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1490	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2055	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1491	only event loop modification you are allowed to do).	2056	only event loop modification you are allowed to do).
1492		2057
1493	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	2058	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1494	*w, ev_tstamp now)>, e.g.:	2059	*w, ev_tstamp now)>, e.g.:
1495		2060
		2061	static ev_tstamp
1496	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	2062	my_rescheduler (ev_periodic *w, ev_tstamp now)
1497	{	2063	{
1498	return now + 60.;	2064	return now + 60.;
1499	}	2065	}
1500		2066
1501	It must return the next time to trigger, based on the passed time value	2067	It must return the next time to trigger, based on the passed time value
…		…
1521	a different time than the last time it was called (e.g. in a crond like	2087	a different time than the last time it was called (e.g. in a crond like
1522	program when the crontabs have changed).	2088	program when the crontabs have changed).
1523		2089
1524	=item ev_tstamp ev_periodic_at (ev_periodic *)	2090	=item ev_tstamp ev_periodic_at (ev_periodic *)
1525		2091
1526	When active, returns the absolute time that the watcher is supposed to	2092	When active, returns the absolute time that the watcher is supposed
1527	trigger next.	2093	to trigger next. This is not the same as the C<offset> argument to
		2094	C<ev_periodic_set>, but indeed works even in interval and manual
		2095	rescheduling modes.
1528		2096
1529	=item ev_tstamp offset [read-write]	2097	=item ev_tstamp offset [read-write]
1530		2098
1531	When repeating, this contains the offset value, otherwise this is the	2099	When repeating, this contains the offset value, otherwise this is the
1532	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2100	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2101	although libev might modify this value for better numerical stability).
1533		2102
1534	Can be modified any time, but changes only take effect when the periodic	2103	Can be modified any time, but changes only take effect when the periodic
1535	timer fires or C<ev_periodic_again> is being called.	2104	timer fires or C<ev_periodic_again> is being called.
1536		2105
1537	=item ev_tstamp interval [read-write]	2106	=item ev_tstamp interval [read-write]
1538		2107
1539	The current interval value. Can be modified any time, but changes only	2108	The current interval value. Can be modified any time, but changes only
1540	take effect when the periodic timer fires or C<ev_periodic_again> is being	2109	take effect when the periodic timer fires or C<ev_periodic_again> is being
1541	called.	2110	called.
1542		2111
1543	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2112	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1544		2113
1545	The current reschedule callback, or C<0>, if this functionality is	2114	The current reschedule callback, or C<0>, if this functionality is
1546	switched off. Can be changed any time, but changes only take effect when	2115	switched off. Can be changed any time, but changes only take effect when
1547	the periodic timer fires or C<ev_periodic_again> is being called.	2116	the periodic timer fires or C<ev_periodic_again> is being called.
1548		2117
…		…
1553	Example: Call a callback every hour, or, more precisely, whenever the	2122	Example: Call a callback every hour, or, more precisely, whenever the
1554	system time is divisible by 3600. The callback invocation times have	2123	system time is divisible by 3600. The callback invocation times have
1555	potentially a lot of jitter, but good long-term stability.	2124	potentially a lot of jitter, but good long-term stability.
1556		2125
1557	static void	2126	static void
1558	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2127	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1559	{	2128	{
1560	... its now a full hour (UTC, or TAI or whatever your clock follows)	2129	... its now a full hour (UTC, or TAI or whatever your clock follows)
1561	}	2130	}
1562		2131
1563	struct ev_periodic hourly_tick;	2132	ev_periodic hourly_tick;
1564	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2133	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1565	ev_periodic_start (loop, &hourly_tick);	2134	ev_periodic_start (loop, &hourly_tick);
1566		2135
1567	Example: The same as above, but use a reschedule callback to do it:	2136	Example: The same as above, but use a reschedule callback to do it:
1568		2137
1569	#include <math.h>	2138	#include <math.h>
1570		2139
1571	static ev_tstamp	2140	static ev_tstamp
1572	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2141	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1573	{	2142	{
1574	return now + (3600. - fmod (now, 3600.));	2143	return now + (3600. - fmod (now, 3600.));
1575	}	2144	}
1576		2145
1577	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2146	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1578		2147
1579	Example: Call a callback every hour, starting now:	2148	Example: Call a callback every hour, starting now:
1580		2149
1581	struct ev_periodic hourly_tick;	2150	ev_periodic hourly_tick;
1582	ev_periodic_init (&hourly_tick, clock_cb,	2151	ev_periodic_init (&hourly_tick, clock_cb,
1583	fmod (ev_now (loop), 3600.), 3600., 0);	2152	fmod (ev_now (loop), 3600.), 3600., 0);
1584	ev_periodic_start (loop, &hourly_tick);	2153	ev_periodic_start (loop, &hourly_tick);
1585		2154
1586		2155
…		…
1589	Signal watchers will trigger an event when the process receives a specific	2158	Signal watchers will trigger an event when the process receives a specific
1590	signal one or more times. Even though signals are very asynchronous, libev	2159	signal one or more times. Even though signals are very asynchronous, libev
1591	will try it's best to deliver signals synchronously, i.e. as part of the	2160	will try it's best to deliver signals synchronously, i.e. as part of the
1592	normal event processing, like any other event.	2161	normal event processing, like any other event.
1593		2162
1594	If you want signals asynchronously, just use C<sigaction> as you would	2163	If you want signals to be delivered truly asynchronously, just use
1595	do without libev and forget about sharing the signal. You can even use	2164	C<sigaction> as you would do without libev and forget about sharing
1596	C<ev_async> from a signal handler to synchronously wake up an event loop.	2165	the signal. You can even use C<ev_async> from a signal handler to
		2166	synchronously wake up an event loop.
1597		2167
1598	You can configure as many watchers as you like per signal. Only when the	2168	You can configure as many watchers as you like for the same signal, but
		2169	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2170	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2171	C<SIGINT> in both the default loop and another loop at the same time. At
		2172	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2173
1599	first watcher gets started will libev actually register a signal handler	2174	When the first watcher gets started will libev actually register something
1600	with the kernel (thus it coexists with your own signal handlers as long as	2175	with the kernel (thus it coexists with your own signal handlers as long as
1601	you don't register any with libev for the same signal). Similarly, when	2176	you don't register any with libev for the same signal).
1602	the last signal watcher for a signal is stopped, libev will reset the
1603	signal handler to SIG_DFL (regardless of what it was set to before).
1604		2177
1605	If possible and supported, libev will install its handlers with	2178	If possible and supported, libev will install its handlers with
1606	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2179	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1607	interrupted. If you have a problem with system calls getting interrupted by	2180	not be unduly interrupted. If you have a problem with system calls getting
1608	signals you can block all signals in an C<ev_check> watcher and unblock	2181	interrupted by signals you can block all signals in an C<ev_check> watcher
1609	them in an C<ev_prepare> watcher.	2182	and unblock them in an C<ev_prepare> watcher.
		2183
		2184	=head3 The special problem of inheritance over fork/execve/pthread_create
		2185
		2186	Both the signal mask (C<sigprocmask>) and the signal disposition
		2187	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2188	stopping it again), that is, libev might or might not block the signal,
		2189	and might or might not set or restore the installed signal handler.
		2190
		2191	While this does not matter for the signal disposition (libev never
		2192	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2193	C<execve>), this matters for the signal mask: many programs do not expect
		2194	certain signals to be blocked.
		2195
		2196	This means that before calling C<exec> (from the child) you should reset
		2197	the signal mask to whatever "default" you expect (all clear is a good
		2198	choice usually).
		2199
		2200	The simplest way to ensure that the signal mask is reset in the child is
		2201	to install a fork handler with C<pthread_atfork> that resets it. That will
		2202	catch fork calls done by libraries (such as the libc) as well.
		2203
		2204	In current versions of libev, the signal will not be blocked indefinitely
		2205	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2206	the window of opportunity for problems, it will not go away, as libev
		2207	I<has> to modify the signal mask, at least temporarily.
		2208
		2209	So I can't stress this enough: I<If you do not reset your signal mask when
		2210	you expect it to be empty, you have a race condition in your code>. This
		2211	is not a libev-specific thing, this is true for most event libraries.
1610		2212
1611	=head3 Watcher-Specific Functions and Data Members	2213	=head3 Watcher-Specific Functions and Data Members
1612		2214
1613	=over 4	2215	=over 4
1614		2216
…		…
1625		2227
1626	=back	2228	=back
1627		2229
1628	=head3 Examples	2230	=head3 Examples
1629		2231
1630	Example: Try to exit cleanly on SIGINT and SIGTERM.	2232	Example: Try to exit cleanly on SIGINT.
1631		2233
1632	static void	2234	static void
1633	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2235	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1634	{	2236	{
1635	ev_unloop (loop, EVUNLOOP_ALL);	2237	ev_unloop (loop, EVUNLOOP_ALL);
1636	}	2238	}
1637		2239
1638	struct ev_signal signal_watcher;	2240	ev_signal signal_watcher;
1639	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2241	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1640	ev_signal_start (loop, &sigint_cb);	2242	ev_signal_start (loop, &signal_watcher);
1641		2243
1642		2244
1643	=head2 C<ev_child> - watch out for process status changes	2245	=head2 C<ev_child> - watch out for process status changes
1644		2246
1645	Child watchers trigger when your process receives a SIGCHLD in response to	2247	Child watchers trigger when your process receives a SIGCHLD in response to
1646	some child status changes (most typically when a child of yours dies or	2248	some child status changes (most typically when a child of yours dies or
1647	exits). It is permissible to install a child watcher I<after> the child	2249	exits). It is permissible to install a child watcher I<after> the child
1648	has been forked (which implies it might have already exited), as long	2250	has been forked (which implies it might have already exited), as long
1649	as the event loop isn't entered (or is continued from a watcher), i.e.,	2251	as the event loop isn't entered (or is continued from a watcher), i.e.,
1650	forking and then immediately registering a watcher for the child is fine,	2252	forking and then immediately registering a watcher for the child is fine,
1651	but forking and registering a watcher a few event loop iterations later is	2253	but forking and registering a watcher a few event loop iterations later or
1652	not.	2254	in the next callback invocation is not.
1653		2255
1654	Only the default event loop is capable of handling signals, and therefore	2256	Only the default event loop is capable of handling signals, and therefore
1655	you can only register child watchers in the default event loop.	2257	you can only register child watchers in the default event loop.
1656		2258
		2259	Due to some design glitches inside libev, child watchers will always be
		2260	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2261	libev)
		2262
1657	=head3 Process Interaction	2263	=head3 Process Interaction
1658		2264
1659	Libev grabs C<SIGCHLD> as soon as the default event loop is	2265	Libev grabs C<SIGCHLD> as soon as the default event loop is
1660	initialised. This is necessary to guarantee proper behaviour even if	2266	initialised. This is necessary to guarantee proper behaviour even if the
1661	the first child watcher is started after the child exits. The occurrence	2267	first child watcher is started after the child exits. The occurrence
1662	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2268	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1663	synchronously as part of the event loop processing. Libev always reaps all	2269	synchronously as part of the event loop processing. Libev always reaps all
1664	children, even ones not watched.	2270	children, even ones not watched.
1665		2271
1666	=head3 Overriding the Built-In Processing	2272	=head3 Overriding the Built-In Processing
…		…
1676	=head3 Stopping the Child Watcher	2282	=head3 Stopping the Child Watcher
1677		2283
1678	Currently, the child watcher never gets stopped, even when the	2284	Currently, the child watcher never gets stopped, even when the
1679	child terminates, so normally one needs to stop the watcher in the	2285	child terminates, so normally one needs to stop the watcher in the
1680	callback. Future versions of libev might stop the watcher automatically	2286	callback. Future versions of libev might stop the watcher automatically
1681	when a child exit is detected.	2287	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2288	problem).
1682		2289
1683	=head3 Watcher-Specific Functions and Data Members	2290	=head3 Watcher-Specific Functions and Data Members
1684		2291
1685	=over 4	2292	=over 4
1686		2293
…		…
1718	its completion.	2325	its completion.
1719		2326
1720	ev_child cw;	2327	ev_child cw;
1721		2328
1722	static void	2329	static void
1723	child_cb (EV_P_ struct ev_child *w, int revents)	2330	child_cb (EV_P_ ev_child *w, int revents)
1724	{	2331	{
1725	ev_child_stop (EV_A_ w);	2332	ev_child_stop (EV_A_ w);
1726	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2333	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1727	}	2334	}
1728		2335
…		…
1743		2350
1744		2351
1745	=head2 C<ev_stat> - did the file attributes just change?	2352	=head2 C<ev_stat> - did the file attributes just change?
1746		2353
1747	This watches a file system path for attribute changes. That is, it calls	2354	This watches a file system path for attribute changes. That is, it calls
1748	C<stat> regularly (or when the OS says it changed) and sees if it changed	2355	C<stat> on that path in regular intervals (or when the OS says it changed)
1749	compared to the last time, invoking the callback if it did.	2356	and sees if it changed compared to the last time, invoking the callback if
		2357	it did.
1750		2358
1751	The path does not need to exist: changing from "path exists" to "path does	2359	The path does not need to exist: changing from "path exists" to "path does
1752	not exist" is a status change like any other. The condition "path does	2360	not exist" is a status change like any other. The condition "path does not
1753	not exist" is signified by the C<st_nlink> field being zero (which is	2361	exist" (or more correctly "path cannot be stat'ed") is signified by the
1754	otherwise always forced to be at least one) and all the other fields of	2362	C<st_nlink> field being zero (which is otherwise always forced to be at
1755	the stat buffer having unspecified contents.	2363	least one) and all the other fields of the stat buffer having unspecified
		2364	contents.
1756		2365
1757	The path I<should> be absolute and I<must not> end in a slash. If it is	2366	The path I<must not> end in a slash or contain special components such as
		2367	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1758	relative and your working directory changes, the behaviour is undefined.	2368	your working directory changes, then the behaviour is undefined.
1759		2369
1760	Since there is no standard kernel interface to do this, the portable	2370	Since there is no portable change notification interface available, the
1761	implementation simply calls C<stat (2)> regularly on the path to see if	2371	portable implementation simply calls C<stat(2)> regularly on the path
1762	it changed somehow. You can specify a recommended polling interval for	2372	to see if it changed somehow. You can specify a recommended polling
1763	this case. If you specify a polling interval of C<0> (highly recommended!)	2373	interval for this case. If you specify a polling interval of C<0> (highly
1764	then a I<suitable, unspecified default> value will be used (which	2374	recommended!) then a I<suitable, unspecified default> value will be used
1765	you can expect to be around five seconds, although this might change	2375	(which you can expect to be around five seconds, although this might
1766	dynamically). Libev will also impose a minimum interval which is currently	2376	change dynamically). Libev will also impose a minimum interval which is
1767	around C<0.1>, but thats usually overkill.	2377	currently around C<0.1>, but that's usually overkill.
1768		2378
1769	This watcher type is not meant for massive numbers of stat watchers,	2379	This watcher type is not meant for massive numbers of stat watchers,
1770	as even with OS-supported change notifications, this can be	2380	as even with OS-supported change notifications, this can be
1771	resource-intensive.	2381	resource-intensive.
1772		2382
1773	At the time of this writing, the only OS-specific interface implemented	2383	At the time of this writing, the only OS-specific interface implemented
1774	is the Linux inotify interface (implementing kqueue support is left as	2384	is the Linux inotify interface (implementing kqueue support is left as an
1775	an exercise for the reader. Note, however, that the author sees no way	2385	exercise for the reader. Note, however, that the author sees no way of
1776	of implementing C<ev_stat> semantics with kqueue).	2386	implementing C<ev_stat> semantics with kqueue, except as a hint).
1777		2387
1778	=head3 ABI Issues (Largefile Support)	2388	=head3 ABI Issues (Largefile Support)
1779		2389
1780	Libev by default (unless the user overrides this) uses the default	2390	Libev by default (unless the user overrides this) uses the default
1781	compilation environment, which means that on systems with large file	2391	compilation environment, which means that on systems with large file
1782	support disabled by default, you get the 32 bit version of the stat	2392	support disabled by default, you get the 32 bit version of the stat
1783	structure. When using the library from programs that change the ABI to	2393	structure. When using the library from programs that change the ABI to
1784	use 64 bit file offsets the programs will fail. In that case you have to	2394	use 64 bit file offsets the programs will fail. In that case you have to
1785	compile libev with the same flags to get binary compatibility. This is	2395	compile libev with the same flags to get binary compatibility. This is
1786	obviously the case with any flags that change the ABI, but the problem is	2396	obviously the case with any flags that change the ABI, but the problem is
1787	most noticeably disabled with ev_stat and large file support.	2397	most noticeably displayed with ev_stat and large file support.
1788		2398
1789	The solution for this is to lobby your distribution maker to make large	2399	The solution for this is to lobby your distribution maker to make large
1790	file interfaces available by default (as e.g. FreeBSD does) and not	2400	file interfaces available by default (as e.g. FreeBSD does) and not
1791	optional. Libev cannot simply switch on large file support because it has	2401	optional. Libev cannot simply switch on large file support because it has
1792	to exchange stat structures with application programs compiled using the	2402	to exchange stat structures with application programs compiled using the
1793	default compilation environment.	2403	default compilation environment.
1794		2404
1795	=head3 Inotify and Kqueue	2405	=head3 Inotify and Kqueue
1796		2406
1797	When C<inotify (7)> support has been compiled into libev (generally only	2407	When C<inotify (7)> support has been compiled into libev and present at
1798	available with Linux) and present at runtime, it will be used to speed up	2408	runtime, it will be used to speed up change detection where possible. The
1799	change detection where possible. The inotify descriptor will be created lazily	2409	inotify descriptor will be created lazily when the first C<ev_stat>
1800	when the first C<ev_stat> watcher is being started.	2410	watcher is being started.
1801		2411
1802	Inotify presence does not change the semantics of C<ev_stat> watchers	2412	Inotify presence does not change the semantics of C<ev_stat> watchers
1803	except that changes might be detected earlier, and in some cases, to avoid	2413	except that changes might be detected earlier, and in some cases, to avoid
1804	making regular C<stat> calls. Even in the presence of inotify support	2414	making regular C<stat> calls. Even in the presence of inotify support
1805	there are many cases where libev has to resort to regular C<stat> polling,	2415	there are many cases where libev has to resort to regular C<stat> polling,
1806	but as long as the path exists, libev usually gets away without polling.	2416	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2417	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2418	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2419	xfs are fully working) libev usually gets away without polling.
1807		2420
1808	There is no support for kqueue, as apparently it cannot be used to	2421	There is no support for kqueue, as apparently it cannot be used to
1809	implement this functionality, due to the requirement of having a file	2422	implement this functionality, due to the requirement of having a file
1810	descriptor open on the object at all times, and detecting renames, unlinks	2423	descriptor open on the object at all times, and detecting renames, unlinks
1811	etc. is difficult.	2424	etc. is difficult.
1812		2425
		2426	=head3 C<stat ()> is a synchronous operation
		2427
		2428	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2429	the process. The exception are C<ev_stat> watchers - those call C<stat
		2430	()>, which is a synchronous operation.
		2431
		2432	For local paths, this usually doesn't matter: unless the system is very
		2433	busy or the intervals between stat's are large, a stat call will be fast,
		2434	as the path data is usually in memory already (except when starting the
		2435	watcher).
		2436
		2437	For networked file systems, calling C<stat ()> can block an indefinite
		2438	time due to network issues, and even under good conditions, a stat call
		2439	often takes multiple milliseconds.
		2440
		2441	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2442	paths, although this is fully supported by libev.
		2443
1813	=head3 The special problem of stat time resolution	2444	=head3 The special problem of stat time resolution
1814		2445
1815	The C<stat ()> system call only supports full-second resolution portably, and	2446	The C<stat ()> system call only supports full-second resolution portably,
1816	even on systems where the resolution is higher, most file systems still	2447	and even on systems where the resolution is higher, most file systems
1817	only support whole seconds.	2448	still only support whole seconds.
1818		2449
1819	That means that, if the time is the only thing that changes, you can	2450	That means that, if the time is the only thing that changes, you can
1820	easily miss updates: on the first update, C<ev_stat> detects a change and	2451	easily miss updates: on the first update, C<ev_stat> detects a change and
1821	calls your callback, which does something. When there is another update	2452	calls your callback, which does something. When there is another update
1822	within the same second, C<ev_stat> will be unable to detect unless the	2453	within the same second, C<ev_stat> will be unable to detect unless the
…		…
1965		2596
1966	=head3 Watcher-Specific Functions and Data Members	2597	=head3 Watcher-Specific Functions and Data Members
1967		2598
1968	=over 4	2599	=over 4
1969		2600
1970	=item ev_idle_init (ev_signal *, callback)	2601	=item ev_idle_init (ev_idle *, callback)
1971		2602
1972	Initialises and configures the idle watcher - it has no parameters of any	2603	Initialises and configures the idle watcher - it has no parameters of any
1973	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2604	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1974	believe me.	2605	believe me.
1975		2606
…		…
1979		2610
1980	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2611	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1981	callback, free it. Also, use no error checking, as usual.	2612	callback, free it. Also, use no error checking, as usual.
1982		2613
1983	static void	2614	static void
1984	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2615	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1985	{	2616	{
1986	free (w);	2617	free (w);
1987	// now do something you wanted to do when the program has	2618	// now do something you wanted to do when the program has
1988	// no longer anything immediate to do.	2619	// no longer anything immediate to do.
1989	}	2620	}
1990		2621
1991	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2622	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1992	ev_idle_init (idle_watcher, idle_cb);	2623	ev_idle_init (idle_watcher, idle_cb);
1993	ev_idle_start (loop, idle_cb);	2624	ev_idle_start (loop, idle_watcher);
1994		2625
1995		2626
1996	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2627	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1997		2628
1998	Prepare and check watchers are usually (but not always) used in pairs:	2629	Prepare and check watchers are usually (but not always) used in pairs:
…		…
2077		2708
2078	static ev_io iow [nfd];	2709	static ev_io iow [nfd];
2079	static ev_timer tw;	2710	static ev_timer tw;
2080		2711
2081	static void	2712	static void
2082	io_cb (ev_loop *loop, ev_io *w, int revents)	2713	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2083	{	2714	{
2084	}	2715	}
2085		2716
2086	// create io watchers for each fd and a timer before blocking	2717	// create io watchers for each fd and a timer before blocking
2087	static void	2718	static void
2088	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2719	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2089	{	2720	{
2090	int timeout = 3600000;	2721	int timeout = 3600000;
2091	struct pollfd fds [nfd];	2722	struct pollfd fds [nfd];
2092	// actual code will need to loop here and realloc etc.	2723	// actual code will need to loop here and realloc etc.
2093	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2724	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2094		2725
2095	/* the callback is illegal, but won't be called as we stop during check */	2726	/* the callback is illegal, but won't be called as we stop during check */
2096	ev_timer_init (&tw, 0, timeout * 1e-3);	2727	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2097	ev_timer_start (loop, &tw);	2728	ev_timer_start (loop, &tw);
2098		2729
2099	// create one ev_io per pollfd	2730	// create one ev_io per pollfd
2100	for (int i = 0; i < nfd; ++i)	2731	for (int i = 0; i < nfd; ++i)
2101	{	2732	{
…		…
2108	}	2739	}
2109	}	2740	}
2110		2741
2111	// stop all watchers after blocking	2742	// stop all watchers after blocking
2112	static void	2743	static void
2113	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2744	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2114	{	2745	{
2115	ev_timer_stop (loop, &tw);	2746	ev_timer_stop (loop, &tw);
2116		2747
2117	for (int i = 0; i < nfd; ++i)	2748	for (int i = 0; i < nfd; ++i)
2118	{	2749	{
…		…
2214	some fds have to be watched and handled very quickly (with low latency),	2845	some fds have to be watched and handled very quickly (with low latency),
2215	and even priorities and idle watchers might have too much overhead. In	2846	and even priorities and idle watchers might have too much overhead. In
2216	this case you would put all the high priority stuff in one loop and all	2847	this case you would put all the high priority stuff in one loop and all
2217	the rest in a second one, and embed the second one in the first.	2848	the rest in a second one, and embed the second one in the first.
2218		2849
2219	As long as the watcher is active, the callback will be invoked every time	2850	As long as the watcher is active, the callback will be invoked every
2220	there might be events pending in the embedded loop. The callback must then	2851	time there might be events pending in the embedded loop. The callback
2221	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2852	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2222	their callbacks (you could also start an idle watcher to give the embedded	2853	sweep and invoke their callbacks (the callback doesn't need to invoke the
2223	loop strictly lower priority for example). You can also set the callback	2854	C<ev_embed_sweep> function directly, it could also start an idle watcher
2224	to C<0>, in which case the embed watcher will automatically execute the	2855	to give the embedded loop strictly lower priority for example).
2225	embedded loop sweep.
2226		2856
2227	As long as the watcher is started it will automatically handle events. The	2857	You can also set the callback to C<0>, in which case the embed watcher
2228	callback will be invoked whenever some events have been handled. You can	2858	will automatically execute the embedded loop sweep whenever necessary.
2229	set the callback to C<0> to avoid having to specify one if you are not
2230	interested in that.
2231		2859
2232	Also, there have not currently been made special provisions for forking:	2860	Fork detection will be handled transparently while the C<ev_embed> watcher
2233	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2861	is active, i.e., the embedded loop will automatically be forked when the
2234	but you will also have to stop and restart any C<ev_embed> watchers	2862	embedding loop forks. In other cases, the user is responsible for calling
2235	yourself - but you can use a fork watcher to handle this automatically,	2863	C<ev_loop_fork> on the embedded loop.
2236	and future versions of libev might do just that.
2237		2864
2238	Unfortunately, not all backends are embeddable: only the ones returned by	2865	Unfortunately, not all backends are embeddable: only the ones returned by
2239	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2866	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2240	portable one.	2867	portable one.
2241		2868
2242	So when you want to use this feature you will always have to be prepared	2869	So when you want to use this feature you will always have to be prepared
2243	that you cannot get an embeddable loop. The recommended way to get around	2870	that you cannot get an embeddable loop. The recommended way to get around
2244	this is to have a separate variables for your embeddable loop, try to	2871	this is to have a separate variables for your embeddable loop, try to
2245	create it, and if that fails, use the normal loop for everything.	2872	create it, and if that fails, use the normal loop for everything.
		2873
		2874	=head3 C<ev_embed> and fork
		2875
		2876	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2877	automatically be applied to the embedded loop as well, so no special
		2878	fork handling is required in that case. When the watcher is not running,
		2879	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2880	as applicable.
2246		2881
2247	=head3 Watcher-Specific Functions and Data Members	2882	=head3 Watcher-Specific Functions and Data Members
2248		2883
2249	=over 4	2884	=over 4
2250		2885
…		…
2278	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2913	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2279	used).	2914	used).
2280		2915
2281	struct ev_loop *loop_hi = ev_default_init (0);	2916	struct ev_loop *loop_hi = ev_default_init (0);
2282	struct ev_loop *loop_lo = 0;	2917	struct ev_loop *loop_lo = 0;
2283	struct ev_embed embed;	2918	ev_embed embed;
2284		2919
2285	// see if there is a chance of getting one that works	2920	// see if there is a chance of getting one that works
2286	// (remember that a flags value of 0 means autodetection)	2921	// (remember that a flags value of 0 means autodetection)
2287	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2922	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2288	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2923	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2302	kqueue implementation). Store the kqueue/socket-only event loop in	2937	kqueue implementation). Store the kqueue/socket-only event loop in
2303	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2938	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2304		2939
2305	struct ev_loop *loop = ev_default_init (0);	2940	struct ev_loop *loop = ev_default_init (0);
2306	struct ev_loop *loop_socket = 0;	2941	struct ev_loop *loop_socket = 0;
2307	struct ev_embed embed;	2942	ev_embed embed;
2308		2943
2309	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2944	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2310	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2945	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2311	{	2946	{
2312	ev_embed_init (&embed, 0, loop_socket);	2947	ev_embed_init (&embed, 0, loop_socket);
…		…
2327	event loop blocks next and before C<ev_check> watchers are being called,	2962	event loop blocks next and before C<ev_check> watchers are being called,
2328	and only in the child after the fork. If whoever good citizen calling	2963	and only in the child after the fork. If whoever good citizen calling
2329	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2964	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2330	handlers will be invoked, too, of course.	2965	handlers will be invoked, too, of course.
2331		2966
		2967	=head3 The special problem of life after fork - how is it possible?
		2968
		2969	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2970	up/change the process environment, followed by a call to C<exec()>. This
		2971	sequence should be handled by libev without any problems.
		2972
		2973	This changes when the application actually wants to do event handling
		2974	in the child, or both parent in child, in effect "continuing" after the
		2975	fork.
		2976
		2977	The default mode of operation (for libev, with application help to detect
		2978	forks) is to duplicate all the state in the child, as would be expected
		2979	when I<either> the parent I<or> the child process continues.
		2980
		2981	When both processes want to continue using libev, then this is usually the
		2982	wrong result. In that case, usually one process (typically the parent) is
		2983	supposed to continue with all watchers in place as before, while the other
		2984	process typically wants to start fresh, i.e. without any active watchers.
		2985
		2986	The cleanest and most efficient way to achieve that with libev is to
		2987	simply create a new event loop, which of course will be "empty", and
		2988	use that for new watchers. This has the advantage of not touching more
		2989	memory than necessary, and thus avoiding the copy-on-write, and the
		2990	disadvantage of having to use multiple event loops (which do not support
		2991	signal watchers).
		2992
		2993	When this is not possible, or you want to use the default loop for
		2994	other reasons, then in the process that wants to start "fresh", call
		2995	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2996	the default loop will "orphan" (not stop) all registered watchers, so you
		2997	have to be careful not to execute code that modifies those watchers. Note
		2998	also that in that case, you have to re-register any signal watchers.
		2999
2332	=head3 Watcher-Specific Functions and Data Members	3000	=head3 Watcher-Specific Functions and Data Members
2333		3001
2334	=over 4	3002	=over 4
2335		3003
2336	=item ev_fork_init (ev_signal *, callback)	3004	=item ev_fork_init (ev_signal *, callback)
…		…
2365	=head3 Queueing	3033	=head3 Queueing
2366		3034
2367	C<ev_async> does not support queueing of data in any way. The reason	3035	C<ev_async> does not support queueing of data in any way. The reason
2368	is that the author does not know of a simple (or any) algorithm for a	3036	is that the author does not know of a simple (or any) algorithm for a
2369	multiple-writer-single-reader queue that works in all cases and doesn't	3037	multiple-writer-single-reader queue that works in all cases and doesn't
2370	need elaborate support such as pthreads.	3038	need elaborate support such as pthreads or unportable memory access
		3039	semantics.
2371		3040
2372	That means that if you want to queue data, you have to provide your own	3041	That means that if you want to queue data, you have to provide your own
2373	queue. But at least I can tell you how to implement locking around your	3042	queue. But at least I can tell you how to implement locking around your
2374	queue:	3043	queue:
2375		3044
2376	=over 4	3045	=over 4
2377		3046
2378	=item queueing from a signal handler context	3047	=item queueing from a signal handler context
2379		3048
2380	To implement race-free queueing, you simply add to the queue in the signal	3049	To implement race-free queueing, you simply add to the queue in the signal
2381	handler but you block the signal handler in the watcher callback. Here is an example that does that for	3050	handler but you block the signal handler in the watcher callback. Here is
2382	some fictitious SIGUSR1 handler:	3051	an example that does that for some fictitious SIGUSR1 handler:
2383		3052
2384	static ev_async mysig;	3053	static ev_async mysig;
2385		3054
2386	static void	3055	static void
2387	sigusr1_handler (void)	3056	sigusr1_handler (void)
…		…
2453	=over 4	3122	=over 4
2454		3123
2455	=item ev_async_init (ev_async *, callback)	3124	=item ev_async_init (ev_async *, callback)
2456		3125
2457	Initialises and configures the async watcher - it has no parameters of any	3126	Initialises and configures the async watcher - it has no parameters of any
2458	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3127	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2459	trust me.	3128	trust me.
2460		3129
2461	=item ev_async_send (loop, ev_async *)	3130	=item ev_async_send (loop, ev_async *)
2462		3131
2463	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3132	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2464	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3133	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2465	C<ev_feed_event>, this call is safe to do from other threads, signal or	3134	C<ev_feed_event>, this call is safe to do from other threads, signal or
2466	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3135	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2467	section below on what exactly this means).	3136	section below on what exactly this means).
2468		3137
		3138	Note that, as with other watchers in libev, multiple events might get
		3139	compressed into a single callback invocation (another way to look at this
		3140	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3141	reset when the event loop detects that).
		3142
2469	This call incurs the overhead of a system call only once per loop iteration,	3143	This call incurs the overhead of a system call only once per event loop
2470	so while the overhead might be noticeable, it doesn't apply to repeated	3144	iteration, so while the overhead might be noticeable, it doesn't apply to
2471	calls to C<ev_async_send>.	3145	repeated calls to C<ev_async_send> for the same event loop.
2472		3146
2473	=item bool = ev_async_pending (ev_async *)	3147	=item bool = ev_async_pending (ev_async *)
2474		3148
2475	Returns a non-zero value when C<ev_async_send> has been called on the	3149	Returns a non-zero value when C<ev_async_send> has been called on the
2476	watcher but the event has not yet been processed (or even noted) by the	3150	watcher but the event has not yet been processed (or even noted) by the
…		…
2479	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3153	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2480	the loop iterates next and checks for the watcher to have become active,	3154	the loop iterates next and checks for the watcher to have become active,
2481	it will reset the flag again. C<ev_async_pending> can be used to very	3155	it will reset the flag again. C<ev_async_pending> can be used to very
2482	quickly check whether invoking the loop might be a good idea.	3156	quickly check whether invoking the loop might be a good idea.
2483		3157
2484	Not that this does I<not> check whether the watcher itself is pending, only	3158	Not that this does I<not> check whether the watcher itself is pending,
2485	whether it has been requested to make this watcher pending.	3159	only whether it has been requested to make this watcher pending: there
		3160	is a time window between the event loop checking and resetting the async
		3161	notification, and the callback being invoked.
2486		3162
2487	=back	3163	=back
2488		3164
2489		3165
2490	=head1 OTHER FUNCTIONS	3166	=head1 OTHER FUNCTIONS
…		…
2494	=over 4	3170	=over 4
2495		3171
2496	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3172	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2497		3173
2498	This function combines a simple timer and an I/O watcher, calls your	3174	This function combines a simple timer and an I/O watcher, calls your
2499	callback on whichever event happens first and automatically stop both	3175	callback on whichever event happens first and automatically stops both
2500	watchers. This is useful if you want to wait for a single event on an fd	3176	watchers. This is useful if you want to wait for a single event on an fd
2501	or timeout without having to allocate/configure/start/stop/free one or	3177	or timeout without having to allocate/configure/start/stop/free one or
2502	more watchers yourself.	3178	more watchers yourself.
2503		3179
2504	If C<fd> is less than 0, then no I/O watcher will be started and events	3180	If C<fd> is less than 0, then no I/O watcher will be started and the
2505	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	3181	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2506	C<events> set will be created and started.	3182	the given C<fd> and C<events> set will be created and started.
2507		3183
2508	If C<timeout> is less than 0, then no timeout watcher will be	3184	If C<timeout> is less than 0, then no timeout watcher will be
2509	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3185	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2510	repeat = 0) will be started. While C<0> is a valid timeout, it is of	3186	repeat = 0) will be started. C<0> is a valid timeout.
2511	dubious value.
2512		3187
2513	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3188	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2514	passed an C<revents> set like normal event callbacks (a combination of	3189	passed an C<revents> set like normal event callbacks (a combination of
2515	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3190	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2516	value passed to C<ev_once>:	3191	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3192	a timeout and an io event at the same time - you probably should give io
		3193	events precedence.
		3194
		3195	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2517		3196
2518	static void stdin_ready (int revents, void *arg)	3197	static void stdin_ready (int revents, void *arg)
2519	{	3198	{
		3199	if (revents & EV_READ)
		3200	/* stdin might have data for us, joy! */;
2520	if (revents & EV_TIMEOUT)	3201	else if (revents & EV_TIMER)
2521	/* doh, nothing entered */;	3202	/* doh, nothing entered */;
2522	else if (revents & EV_READ)
2523	/* stdin might have data for us, joy! */;
2524	}	3203	}
2525		3204
2526	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3205	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2527		3206
2528	=item ev_feed_event (ev_loop *, watcher *, int revents)
2529
2530	Feeds the given event set into the event loop, as if the specified event
2531	had happened for the specified watcher (which must be a pointer to an
2532	initialised but not necessarily started event watcher).
2533
2534	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3207	=item ev_feed_fd_event (loop, int fd, int revents)
2535		3208
2536	Feed an event on the given fd, as if a file descriptor backend detected	3209	Feed an event on the given fd, as if a file descriptor backend detected
2537	the given events it.	3210	the given events it.
2538		3211
2539	=item ev_feed_signal_event (ev_loop *loop, int signum)	3212	=item ev_feed_signal_event (loop, int signum)
2540		3213
2541	Feed an event as if the given signal occurred (C<loop> must be the default	3214	Feed an event as if the given signal occurred (C<loop> must be the default
2542	loop!).	3215	loop!).
2543		3216
2544	=back	3217	=back
…		…
2624		3297
2625	=over 4	3298	=over 4
2626		3299
2627	=item ev::TYPE::TYPE ()	3300	=item ev::TYPE::TYPE ()
2628		3301
2629	=item ev::TYPE::TYPE (struct ev_loop *)	3302	=item ev::TYPE::TYPE (loop)
2630		3303
2631	=item ev::TYPE::~TYPE	3304	=item ev::TYPE::~TYPE
2632		3305
2633	The constructor (optionally) takes an event loop to associate the watcher	3306	The constructor (optionally) takes an event loop to associate the watcher
2634	with. If it is omitted, it will use C<EV_DEFAULT>.	3307	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2666		3339
2667	myclass obj;	3340	myclass obj;
2668	ev::io iow;	3341	ev::io iow;
2669	iow.set <myclass, &myclass::io_cb> (&obj);	3342	iow.set <myclass, &myclass::io_cb> (&obj);
2670		3343
		3344	=item w->set (object *)
		3345
		3346	This is an B<experimental> feature that might go away in a future version.
		3347
		3348	This is a variation of a method callback - leaving out the method to call
		3349	will default the method to C<operator ()>, which makes it possible to use
		3350	functor objects without having to manually specify the C<operator ()> all
		3351	the time. Incidentally, you can then also leave out the template argument
		3352	list.
		3353
		3354	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3355	int revents)>.
		3356
		3357	See the method-C<set> above for more details.
		3358
		3359	Example: use a functor object as callback.
		3360
		3361	struct myfunctor
		3362	{
		3363	void operator() (ev::io &w, int revents)
		3364	{
		3365	...
		3366	}
		3367	}
		3368
		3369	myfunctor f;
		3370
		3371	ev::io w;
		3372	w.set (&f);
		3373
2671	=item w->set<function> (void *data = 0)	3374	=item w->set<function> (void *data = 0)
2672		3375
2673	Also sets a callback, but uses a static method or plain function as	3376	Also sets a callback, but uses a static method or plain function as
2674	callback. The optional C<data> argument will be stored in the watcher's	3377	callback. The optional C<data> argument will be stored in the watcher's
2675	C<data> member and is free for you to use.	3378	C<data> member and is free for you to use.
…		…
2681	Example: Use a plain function as callback.	3384	Example: Use a plain function as callback.
2682		3385
2683	static void io_cb (ev::io &w, int revents) { }	3386	static void io_cb (ev::io &w, int revents) { }
2684	iow.set <io_cb> ();	3387	iow.set <io_cb> ();
2685		3388
2686	=item w->set (struct ev_loop *)	3389	=item w->set (loop)
2687		3390
2688	Associates a different C<struct ev_loop> with this watcher. You can only	3391	Associates a different C<struct ev_loop> with this watcher. You can only
2689	do this when the watcher is inactive (and not pending either).	3392	do this when the watcher is inactive (and not pending either).
2690		3393
2691	=item w->set ([arguments])	3394	=item w->set ([arguments])
…		…
2761	L<http://software.schmorp.de/pkg/EV>.	3464	L<http://software.schmorp.de/pkg/EV>.
2762		3465
2763	=item Python	3466	=item Python
2764		3467
2765	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3468	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2766	seems to be quite complete and well-documented. Note, however, that the	3469	seems to be quite complete and well-documented.
2767	patch they require for libev is outright dangerous as it breaks the ABI
2768	for everybody else, and therefore, should never be applied in an installed
2769	libev (if python requires an incompatible ABI then it needs to embed
2770	libev).
2771		3470
2772	=item Ruby	3471	=item Ruby
2773		3472
2774	Tony Arcieri has written a ruby extension that offers access to a subset	3473	Tony Arcieri has written a ruby extension that offers access to a subset
2775	of the libev API and adds file handle abstractions, asynchronous DNS and	3474	of the libev API and adds file handle abstractions, asynchronous DNS and
2776	more on top of it. It can be found via gem servers. Its homepage is at	3475	more on top of it. It can be found via gem servers. Its homepage is at
2777	L<http://rev.rubyforge.org/>.	3476	L<http://rev.rubyforge.org/>.
2778		3477
		3478	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3479	makes rev work even on mingw.
		3480
		3481	=item Haskell
		3482
		3483	A haskell binding to libev is available at
		3484	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3485
2779	=item D	3486	=item D
2780		3487
2781	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3488	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2782	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3489	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3490
		3491	=item Ocaml
		3492
		3493	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3494	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3495
		3496	=item Lua
		3497
		3498	Brian Maher has written a partial interface to libev for lua (at the
		3499	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3500	L<http://github.com/brimworks/lua-ev>.
2783		3501
2784	=back	3502	=back
2785		3503
2786		3504
2787	=head1 MACRO MAGIC	3505	=head1 MACRO MAGIC
…		…
2888		3606
2889	#define EV_STANDALONE 1	3607	#define EV_STANDALONE 1
2890	#include "ev.h"	3608	#include "ev.h"
2891		3609
2892	Both header files and implementation files can be compiled with a C++	3610	Both header files and implementation files can be compiled with a C++
2893	compiler (at least, thats a stated goal, and breakage will be treated	3611	compiler (at least, that's a stated goal, and breakage will be treated
2894	as a bug).	3612	as a bug).
2895		3613
2896	You need the following files in your source tree, or in a directory	3614	You need the following files in your source tree, or in a directory
2897	in your include path (e.g. in libev/ when using -Ilibev):	3615	in your include path (e.g. in libev/ when using -Ilibev):
2898		3616
…		…
2941	libev.m4	3659	libev.m4
2942		3660
2943	=head2 PREPROCESSOR SYMBOLS/MACROS	3661	=head2 PREPROCESSOR SYMBOLS/MACROS
2944		3662
2945	Libev can be configured via a variety of preprocessor symbols you have to	3663	Libev can be configured via a variety of preprocessor symbols you have to
2946	define before including any of its files. The default in the absence of	3664	define before including (or compiling) any of its files. The default in
2947	autoconf is documented for every option.	3665	the absence of autoconf is documented for every option.
		3666
		3667	Symbols marked with "(h)" do not change the ABI, and can have different
		3668	values when compiling libev vs. including F<ev.h>, so it is permissible
		3669	to redefine them before including F<ev.h> without breaking compatibility
		3670	to a compiled library. All other symbols change the ABI, which means all
		3671	users of libev and the libev code itself must be compiled with compatible
		3672	settings.
2948		3673
2949	=over 4	3674	=over 4
2950		3675
2951	=item EV_STANDALONE	3676	=item EV_STANDALONE (h)
2952		3677
2953	Must always be C<1> if you do not use autoconf configuration, which	3678	Must always be C<1> if you do not use autoconf configuration, which
2954	keeps libev from including F<config.h>, and it also defines dummy	3679	keeps libev from including F<config.h>, and it also defines dummy
2955	implementations for some libevent functions (such as logging, which is not	3680	implementations for some libevent functions (such as logging, which is not
2956	supported). It will also not define any of the structs usually found in	3681	supported). It will also not define any of the structs usually found in
2957	F<event.h> that are not directly supported by the libev core alone.	3682	F<event.h> that are not directly supported by the libev core alone.
2958		3683
		3684	In standalone mode, libev will still try to automatically deduce the
		3685	configuration, but has to be more conservative.
		3686
2959	=item EV_USE_MONOTONIC	3687	=item EV_USE_MONOTONIC
2960		3688
2961	If defined to be C<1>, libev will try to detect the availability of the	3689	If defined to be C<1>, libev will try to detect the availability of the
2962	monotonic clock option at both compile time and runtime. Otherwise no use	3690	monotonic clock option at both compile time and runtime. Otherwise no
2963	of the monotonic clock option will be attempted. If you enable this, you	3691	use of the monotonic clock option will be attempted. If you enable this,
2964	usually have to link against librt or something similar. Enabling it when	3692	you usually have to link against librt or something similar. Enabling it
2965	the functionality isn't available is safe, though, although you have	3693	when the functionality isn't available is safe, though, although you have
2966	to make sure you link against any libraries where the C<clock_gettime>	3694	to make sure you link against any libraries where the C<clock_gettime>
2967	function is hiding in (often F<-lrt>).	3695	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2968		3696
2969	=item EV_USE_REALTIME	3697	=item EV_USE_REALTIME
2970		3698
2971	If defined to be C<1>, libev will try to detect the availability of the	3699	If defined to be C<1>, libev will try to detect the availability of the
2972	real-time clock option at compile time (and assume its availability at	3700	real-time clock option at compile time (and assume its availability
2973	runtime if successful). Otherwise no use of the real-time clock option will	3701	at runtime if successful). Otherwise no use of the real-time clock
2974	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3702	option will be attempted. This effectively replaces C<gettimeofday>
2975	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3703	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2976	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3704	correctness. See the note about libraries in the description of
		3705	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3706	C<EV_USE_CLOCK_SYSCALL>.
		3707
		3708	=item EV_USE_CLOCK_SYSCALL
		3709
		3710	If defined to be C<1>, libev will try to use a direct syscall instead
		3711	of calling the system-provided C<clock_gettime> function. This option
		3712	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3713	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3714	programs needlessly. Using a direct syscall is slightly slower (in
		3715	theory), because no optimised vdso implementation can be used, but avoids
		3716	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3717	higher, as it simplifies linking (no need for C<-lrt>).
2977		3718
2978	=item EV_USE_NANOSLEEP	3719	=item EV_USE_NANOSLEEP
2979		3720
2980	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3721	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2981	and will use it for delays. Otherwise it will use C<select ()>.	3722	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2997		3738
2998	=item EV_SELECT_USE_FD_SET	3739	=item EV_SELECT_USE_FD_SET
2999		3740
3000	If defined to C<1>, then the select backend will use the system C<fd_set>	3741	If defined to C<1>, then the select backend will use the system C<fd_set>
3001	structure. This is useful if libev doesn't compile due to a missing	3742	structure. This is useful if libev doesn't compile due to a missing
3002	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3743	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3003	exotic systems. This usually limits the range of file descriptors to some	3744	on exotic systems. This usually limits the range of file descriptors to
3004	low limit such as 1024 or might have other limitations (winsocket only	3745	some low limit such as 1024 or might have other limitations (winsocket
3005	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3746	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3006	influence the size of the C<fd_set> used.	3747	configures the maximum size of the C<fd_set>.
3007		3748
3008	=item EV_SELECT_IS_WINSOCKET	3749	=item EV_SELECT_IS_WINSOCKET
3009		3750
3010	When defined to C<1>, the select backend will assume that	3751	When defined to C<1>, the select backend will assume that
3011	select/socket/connect etc. don't understand file descriptors but	3752	select/socket/connect etc. don't understand file descriptors but
…		…
3013	be used is the winsock select). This means that it will call	3754	be used is the winsock select). This means that it will call
3014	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3755	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3015	it is assumed that all these functions actually work on fds, even	3756	it is assumed that all these functions actually work on fds, even
3016	on win32. Should not be defined on non-win32 platforms.	3757	on win32. Should not be defined on non-win32 platforms.
3017		3758
3018	=item EV_FD_TO_WIN32_HANDLE	3759	=item EV_FD_TO_WIN32_HANDLE(fd)
3019		3760
3020	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3761	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3021	file descriptors to socket handles. When not defining this symbol (the	3762	file descriptors to socket handles. When not defining this symbol (the
3022	default), then libev will call C<_get_osfhandle>, which is usually	3763	default), then libev will call C<_get_osfhandle>, which is usually
3023	correct. In some cases, programs use their own file descriptor management,	3764	correct. In some cases, programs use their own file descriptor management,
3024	in which case they can provide this function to map fds to socket handles.	3765	in which case they can provide this function to map fds to socket handles.
		3766
		3767	=item EV_WIN32_HANDLE_TO_FD(handle)
		3768
		3769	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3770	using the standard C<_open_osfhandle> function. For programs implementing
		3771	their own fd to handle mapping, overwriting this function makes it easier
		3772	to do so. This can be done by defining this macro to an appropriate value.
		3773
		3774	=item EV_WIN32_CLOSE_FD(fd)
		3775
		3776	If programs implement their own fd to handle mapping on win32, then this
		3777	macro can be used to override the C<close> function, useful to unregister
		3778	file descriptors again. Note that the replacement function has to close
		3779	the underlying OS handle.
3025		3780
3026	=item EV_USE_POLL	3781	=item EV_USE_POLL
3027		3782
3028	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3783	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3029	backend. Otherwise it will be enabled on non-win32 platforms. It	3784	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3076	as well as for signal and thread safety in C<ev_async> watchers.	3831	as well as for signal and thread safety in C<ev_async> watchers.
3077		3832
3078	In the absence of this define, libev will use C<sig_atomic_t volatile>	3833	In the absence of this define, libev will use C<sig_atomic_t volatile>
3079	(from F<signal.h>), which is usually good enough on most platforms.	3834	(from F<signal.h>), which is usually good enough on most platforms.
3080		3835
3081	=item EV_H	3836	=item EV_H (h)
3082		3837
3083	The name of the F<ev.h> header file used to include it. The default if	3838	The name of the F<ev.h> header file used to include it. The default if
3084	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	3839	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3085	used to virtually rename the F<ev.h> header file in case of conflicts.	3840	used to virtually rename the F<ev.h> header file in case of conflicts.
3086		3841
3087	=item EV_CONFIG_H	3842	=item EV_CONFIG_H (h)
3088		3843
3089	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	3844	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3090	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	3845	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3091	C<EV_H>, above.	3846	C<EV_H>, above.
3092		3847
3093	=item EV_EVENT_H	3848	=item EV_EVENT_H (h)
3094		3849
3095	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	3850	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3096	of how the F<event.h> header can be found, the default is C<"event.h">.	3851	of how the F<event.h> header can be found, the default is C<"event.h">.
3097		3852
3098	=item EV_PROTOTYPES	3853	=item EV_PROTOTYPES (h)
3099		3854
3100	If defined to be C<0>, then F<ev.h> will not define any function	3855	If defined to be C<0>, then F<ev.h> will not define any function
3101	prototypes, but still define all the structs and other symbols. This is	3856	prototypes, but still define all the structs and other symbols. This is
3102	occasionally useful if you want to provide your own wrapper functions	3857	occasionally useful if you want to provide your own wrapper functions
3103	around libev functions.	3858	around libev functions.
…		…
3125	fine.	3880	fine.
3126		3881
3127	If your embedding application does not need any priorities, defining these	3882	If your embedding application does not need any priorities, defining these
3128	both to C<0> will save some memory and CPU.	3883	both to C<0> will save some memory and CPU.
3129		3884
3130	=item EV_PERIODIC_ENABLE	3885	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		3886	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		3887	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3131		3888
3132	If undefined or defined to be C<1>, then periodic timers are supported. If	3889	If undefined or defined to be C<1> (and the platform supports it), then
3133	defined to be C<0>, then they are not. Disabling them saves a few kB of	3890	the respective watcher type is supported. If defined to be C<0>, then it
3134	code.	3891	is not. Disabling watcher types mainly saves codesize.
3135		3892
3136	=item EV_IDLE_ENABLE	3893	=item EV_FEATURES
3137
3138	If undefined or defined to be C<1>, then idle watchers are supported. If
3139	defined to be C<0>, then they are not. Disabling them saves a few kB of
3140	code.
3141
3142	=item EV_EMBED_ENABLE
3143
3144	If undefined or defined to be C<1>, then embed watchers are supported. If
3145	defined to be C<0>, then they are not. Embed watchers rely on most other
3146	watcher types, which therefore must not be disabled.
3147
3148	=item EV_STAT_ENABLE
3149
3150	If undefined or defined to be C<1>, then stat watchers are supported. If
3151	defined to be C<0>, then they are not.
3152
3153	=item EV_FORK_ENABLE
3154
3155	If undefined or defined to be C<1>, then fork watchers are supported. If
3156	defined to be C<0>, then they are not.
3157
3158	=item EV_ASYNC_ENABLE
3159
3160	If undefined or defined to be C<1>, then async watchers are supported. If
3161	defined to be C<0>, then they are not.
3162
3163	=item EV_MINIMAL
3164		3894
3165	If you need to shave off some kilobytes of code at the expense of some	3895	If you need to shave off some kilobytes of code at the expense of some
3166	speed, define this symbol to C<1>. Currently this is used to override some	3896	speed (but with the full API), you can define this symbol to request
3167	inlining decisions, saves roughly 30% code size on amd64. It also selects a	3897	certain subsets of functionality. The default is to enable all features
3168	much smaller 2-heap for timer management over the default 4-heap.	3898	that can be enabled on the platform.
		3899
		3900	A typical way to use this symbol is to define it to C<0> (or to a bitset
		3901	with some broad features you want) and then selectively re-enable
		3902	additional parts you want, for example if you want everything minimal,
		3903	but multiple event loop support, async and child watchers and the poll
		3904	backend, use this:
		3905
		3906	#define EV_FEATURES 0
		3907	#define EV_MULTIPLICITY 1
		3908	#define EV_USE_POLL 1
		3909	#define EV_CHILD_ENABLE 1
		3910	#define EV_ASYNC_ENABLE 1
		3911
		3912	The actual value is a bitset, it can be a combination of the following
		3913	values:
		3914
		3915	=over 4
		3916
		3917	=item C<1> - faster/larger code
		3918
		3919	Use larger code to speed up some operations.
		3920
		3921	Currently this is used to override some inlining decisions (enlarging the roughly
		3922	30% code size on amd64.
		3923
		3924	When optimising for size, use of compiler flags such as C<-Os> with
		3925	gcc recommended, as well as C<-DNDEBUG>, as libev contains a number of
		3926	assertions.
		3927
		3928	=item C<2> - faster/larger data structures
		3929
		3930	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		3931	hash table sizes and so on. This will usually further increase codesize
		3932	and can additionally have an effect on the size of data structures at
		3933	runtime.
		3934
		3935	=item C<4> - full API configuration
		3936
		3937	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		3938	enables multiplicity (C<EV_MULTIPLICITY>=1).
		3939
		3940	=item C<8> - full API
		3941
		3942	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		3943	details on which parts of the API are still available without this
		3944	feature, and do not complain if this subset changes over time.
		3945
		3946	=item C<16> - enable all optional watcher types
		3947
		3948	Enables all optional watcher types. If you want to selectively enable
		3949	only some watcher types other than I/O and timers (e.g. prepare,
		3950	embed, async, child...) you can enable them manually by defining
		3951	C<EV_watchertype_ENABLE> to C<1> instead.
		3952
		3953	=item C<32> - enable all backends
		3954
		3955	This enables all backends - without this feature, you need to enable at
		3956	least one backend manually (C<EV_USE_SELECT> is a good choice).
		3957
		3958	=item C<64> - enable OS-specific "helper" APIs
		3959
		3960	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		3961	default.
		3962
		3963	=back
		3964
		3965	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		3966	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		3967	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		3968	watchers, timers and monotonic clock support.
		3969
		3970	With an intelligent-enough linker (gcc+binutils are intelligent enough
		3971	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		3972	your program might be left out as well - a binary starting a timer and an
		3973	I/O watcher then might come out at only 5Kb.
		3974
		3975	=item EV_AVOID_STDIO
		3976
		3977	If this is set to C<1> at compiletime, then libev will avoid using stdio
		3978	functions (printf, scanf, perror etc.). This will increase the codesize
		3979	somewhat, but if your program doesn't otherwise depend on stdio and your
		3980	libc allows it, this avoids linking in the stdio library which is quite
		3981	big.
		3982
		3983	Note that error messages might become less precise when this option is
		3984	enabled.
		3985
		3986	=item EV_NSIG
		3987
		3988	The highest supported signal number, +1 (or, the number of
		3989	signals): Normally, libev tries to deduce the maximum number of signals
		3990	automatically, but sometimes this fails, in which case it can be
		3991	specified. Also, using a lower number than detected (C<32> should be
		3992	good for about any system in existance) can save some memory, as libev
		3993	statically allocates some 12-24 bytes per signal number.
3169		3994
3170	=item EV_PID_HASHSIZE	3995	=item EV_PID_HASHSIZE
3171		3996
3172	C<ev_child> watchers use a small hash table to distribute workload by	3997	C<ev_child> watchers use a small hash table to distribute workload by
3173	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3998	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3174	than enough. If you need to manage thousands of children you might want to	3999	usually more than enough. If you need to manage thousands of children you
3175	increase this value (I<must> be a power of two).	4000	might want to increase this value (I<must> be a power of two).
3176		4001
3177	=item EV_INOTIFY_HASHSIZE	4002	=item EV_INOTIFY_HASHSIZE
3178		4003
3179	C<ev_stat> watchers use a small hash table to distribute workload by	4004	C<ev_stat> watchers use a small hash table to distribute workload by
3180	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4005	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3181	usually more than enough. If you need to manage thousands of C<ev_stat>	4006	disabled), usually more than enough. If you need to manage thousands of
3182	watchers you might want to increase this value (I<must> be a power of	4007	C<ev_stat> watchers you might want to increase this value (I<must> be a
3183	two).	4008	power of two).
3184		4009
3185	=item EV_USE_4HEAP	4010	=item EV_USE_4HEAP
3186		4011
3187	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4012	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3188	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4013	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3189	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4014	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3190	faster performance with many (thousands) of watchers.	4015	faster performance with many (thousands) of watchers.
3191		4016
3192	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4017	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3193	(disabled).	4018	will be C<0>.
3194		4019
3195	=item EV_HEAP_CACHE_AT	4020	=item EV_HEAP_CACHE_AT
3196		4021
3197	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4022	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3198	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4023	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3199	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4024	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3200	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4025	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3201	but avoids random read accesses on heap changes. This improves performance	4026	but avoids random read accesses on heap changes. This improves performance
3202	noticeably with many (hundreds) of watchers.	4027	noticeably with many (hundreds) of watchers.
3203		4028
3204	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4029	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3205	(disabled).	4030	will be C<0>.
3206		4031
3207	=item EV_VERIFY	4032	=item EV_VERIFY
3208		4033
3209	Controls how much internal verification (see C<ev_loop_verify ()>) will	4034	Controls how much internal verification (see C<ev_loop_verify ()>) will
3210	be done: If set to C<0>, no internal verification code will be compiled	4035	be done: If set to C<0>, no internal verification code will be compiled
…		…
3212	called. If set to C<2>, then the internal verification code will be	4037	called. If set to C<2>, then the internal verification code will be
3213	called once per loop, which can slow down libev. If set to C<3>, then the	4038	called once per loop, which can slow down libev. If set to C<3>, then the
3214	verification code will be called very frequently, which will slow down	4039	verification code will be called very frequently, which will slow down
3215	libev considerably.	4040	libev considerably.
3216		4041
3217	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4042	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3218	C<0>.	4043	will be C<0>.
3219		4044
3220	=item EV_COMMON	4045	=item EV_COMMON
3221		4046
3222	By default, all watchers have a C<void *data> member. By redefining	4047	By default, all watchers have a C<void *data> member. By redefining
3223	this macro to a something else you can include more and other types of	4048	this macro to a something else you can include more and other types of
…		…
3281	file.	4106	file.
3282		4107
3283	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4108	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3284	that everybody includes and which overrides some configure choices:	4109	that everybody includes and which overrides some configure choices:
3285		4110
3286	#define EV_MINIMAL 1	4111	#define EV_FEATURES 8
3287	#define EV_USE_POLL 0	4112	#define EV_USE_SELECT 1
3288	#define EV_MULTIPLICITY 0
3289	#define EV_PERIODIC_ENABLE 0	4113	#define EV_PREPARE_ENABLE 1
		4114	#define EV_IDLE_ENABLE 1
3290	#define EV_STAT_ENABLE 0	4115	#define EV_SIGNAL_ENABLE 1
3291	#define EV_FORK_ENABLE 0	4116	#define EV_CHILD_ENABLE 1
		4117	#define EV_USE_STDEXCEPT 0
3292	#define EV_CONFIG_H <config.h>	4118	#define EV_CONFIG_H <config.h>
3293	#define EV_MINPRI 0
3294	#define EV_MAXPRI 0
3295		4119
3296	#include "ev++.h"	4120	#include "ev++.h"
3297		4121
3298	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4122	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3299		4123
3300	#include "ev_cpp.h"	4124	#include "ev_cpp.h"
3301	#include "ev.c"	4125	#include "ev.c"
3302		4126
		4127	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3303		4128
3304	=head1 THREADS AND COROUTINES	4129	=head2 THREADS AND COROUTINES
3305		4130
3306	=head2 THREADS	4131	=head3 THREADS
3307		4132
3308	Libev itself is thread-safe (unless the opposite is specifically	4133	All libev functions are reentrant and thread-safe unless explicitly
3309	documented for a function), but it uses no locking itself. This means that	4134	documented otherwise, but libev implements no locking itself. This means
3310	you can use as many loops as you want in parallel, as long as only one	4135	that you can use as many loops as you want in parallel, as long as there
3311	thread ever calls into one libev function with the same loop parameter:	4136	are no concurrent calls into any libev function with the same loop
		4137	parameter (C<ev_default_*> calls have an implicit default loop parameter,
3312	libev guarantees that different event loops share no data structures that	4138	of course): libev guarantees that different event loops share no data
3313	need locking.	4139	structures that need any locking.
3314		4140
3315	Or to put it differently: calls with different loop parameters can be done	4141	Or to put it differently: calls with different loop parameters can be done
3316	concurrently from multiple threads, calls with the same loop parameter	4142	concurrently from multiple threads, calls with the same loop parameter
3317	must be done serially (but can be done from different threads, as long as	4143	must be done serially (but can be done from different threads, as long as
3318	only one thread ever is inside a call at any point in time, e.g. by using	4144	only one thread ever is inside a call at any point in time, e.g. by using
3319	a mutex per loop).	4145	a mutex per loop).
3320		4146
3321	Specifically to support threads (and signal handlers), libev implements	4147	Specifically to support threads (and signal handlers), libev implements
3322	so-called C<ev_async> watchers, which allow some limited form of	4148	so-called C<ev_async> watchers, which allow some limited form of
3323	concurrency on the same event loop.	4149	concurrency on the same event loop, namely waking it up "from the
		4150	outside".
3324		4151
3325	If you want to know which design (one loop, locking, or multiple loops	4152	If you want to know which design (one loop, locking, or multiple loops
3326	without or something else still) is best for your problem, then I cannot	4153	without or something else still) is best for your problem, then I cannot
3327	help you. I can give some generic advice however:	4154	help you, but here is some generic advice:
3328		4155
3329	=over 4	4156	=over 4
3330		4157
3331	=item * most applications have a main thread: use the default libev loop	4158	=item * most applications have a main thread: use the default libev loop
3332	in that thread, or create a separate thread running only the default loop.	4159	in that thread, or create a separate thread running only the default loop.
…		…
3356	default loop and triggering an C<ev_async> watcher from the default loop	4183	default loop and triggering an C<ev_async> watcher from the default loop
3357	watcher callback into the event loop interested in the signal.	4184	watcher callback into the event loop interested in the signal.
3358		4185
3359	=back	4186	=back
3360		4187
		4188	=head4 THREAD LOCKING EXAMPLE
		4189
		4190	Here is a fictitious example of how to run an event loop in a different
		4191	thread than where callbacks are being invoked and watchers are
		4192	created/added/removed.
		4193
		4194	For a real-world example, see the C<EV::Loop::Async> perl module,
		4195	which uses exactly this technique (which is suited for many high-level
		4196	languages).
		4197
		4198	The example uses a pthread mutex to protect the loop data, a condition
		4199	variable to wait for callback invocations, an async watcher to notify the
		4200	event loop thread and an unspecified mechanism to wake up the main thread.
		4201
		4202	First, you need to associate some data with the event loop:
		4203
		4204	typedef struct {
		4205	mutex_t lock; /* global loop lock */
		4206	ev_async async_w;
		4207	thread_t tid;
		4208	cond_t invoke_cv;
		4209	} userdata;
		4210
		4211	void prepare_loop (EV_P)
		4212	{
		4213	// for simplicity, we use a static userdata struct.
		4214	static userdata u;
		4215
		4216	ev_async_init (&u->async_w, async_cb);
		4217	ev_async_start (EV_A_ &u->async_w);
		4218
		4219	pthread_mutex_init (&u->lock, 0);
		4220	pthread_cond_init (&u->invoke_cv, 0);
		4221
		4222	// now associate this with the loop
		4223	ev_set_userdata (EV_A_ u);
		4224	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4225	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4226
		4227	// then create the thread running ev_loop
		4228	pthread_create (&u->tid, 0, l_run, EV_A);
		4229	}
		4230
		4231	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4232	solely to wake up the event loop so it takes notice of any new watchers
		4233	that might have been added:
		4234
		4235	static void
		4236	async_cb (EV_P_ ev_async *w, int revents)
		4237	{
		4238	// just used for the side effects
		4239	}
		4240
		4241	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4242	protecting the loop data, respectively.
		4243
		4244	static void
		4245	l_release (EV_P)
		4246	{
		4247	userdata *u = ev_userdata (EV_A);
		4248	pthread_mutex_unlock (&u->lock);
		4249	}
		4250
		4251	static void
		4252	l_acquire (EV_P)
		4253	{
		4254	userdata *u = ev_userdata (EV_A);
		4255	pthread_mutex_lock (&u->lock);
		4256	}
		4257
		4258	The event loop thread first acquires the mutex, and then jumps straight
		4259	into C<ev_loop>:
		4260
		4261	void *
		4262	l_run (void *thr_arg)
		4263	{
		4264	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4265
		4266	l_acquire (EV_A);
		4267	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4268	ev_loop (EV_A_ 0);
		4269	l_release (EV_A);
		4270
		4271	return 0;
		4272	}
		4273
		4274	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4275	signal the main thread via some unspecified mechanism (signals? pipe
		4276	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4277	have been called (in a while loop because a) spurious wakeups are possible
		4278	and b) skipping inter-thread-communication when there are no pending
		4279	watchers is very beneficial):
		4280
		4281	static void
		4282	l_invoke (EV_P)
		4283	{
		4284	userdata *u = ev_userdata (EV_A);
		4285
		4286	while (ev_pending_count (EV_A))
		4287	{
		4288	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4289	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4290	}
		4291	}
		4292
		4293	Now, whenever the main thread gets told to invoke pending watchers, it
		4294	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4295	thread to continue:
		4296
		4297	static void
		4298	real_invoke_pending (EV_P)
		4299	{
		4300	userdata *u = ev_userdata (EV_A);
		4301
		4302	pthread_mutex_lock (&u->lock);
		4303	ev_invoke_pending (EV_A);
		4304	pthread_cond_signal (&u->invoke_cv);
		4305	pthread_mutex_unlock (&u->lock);
		4306	}
		4307
		4308	Whenever you want to start/stop a watcher or do other modifications to an
		4309	event loop, you will now have to lock:
		4310
		4311	ev_timer timeout_watcher;
		4312	userdata *u = ev_userdata (EV_A);
		4313
		4314	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4315
		4316	pthread_mutex_lock (&u->lock);
		4317	ev_timer_start (EV_A_ &timeout_watcher);
		4318	ev_async_send (EV_A_ &u->async_w);
		4319	pthread_mutex_unlock (&u->lock);
		4320
		4321	Note that sending the C<ev_async> watcher is required because otherwise
		4322	an event loop currently blocking in the kernel will have no knowledge
		4323	about the newly added timer. By waking up the loop it will pick up any new
		4324	watchers in the next event loop iteration.
		4325
3361	=head2 COROUTINES	4326	=head3 COROUTINES
3362		4327
3363	Libev is much more accommodating to coroutines ("cooperative threads"):	4328	Libev is very accommodating to coroutines ("cooperative threads"):
3364	libev fully supports nesting calls to it's functions from different	4329	libev fully supports nesting calls to its functions from different
3365	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4330	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3366	different coroutines and switch freely between both coroutines running the	4331	different coroutines, and switch freely between both coroutines running
3367	loop, as long as you don't confuse yourself). The only exception is that	4332	the loop, as long as you don't confuse yourself). The only exception is
3368	you must not do this from C<ev_periodic> reschedule callbacks.	4333	that you must not do this from C<ev_periodic> reschedule callbacks.
3369		4334
3370	Care has been taken to ensure that libev does not keep local state inside	4335	Care has been taken to ensure that libev does not keep local state inside
3371	C<ev_loop>, and other calls do not usually allow coroutine switches.	4336	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		4337	they do not call any callbacks.
3372		4338
		4339	=head2 COMPILER WARNINGS
3373		4340
3374	=head1 COMPLEXITIES	4341	Depending on your compiler and compiler settings, you might get no or a
		4342	lot of warnings when compiling libev code. Some people are apparently
		4343	scared by this.
3375		4344
3376	In this section the complexities of (many of) the algorithms used inside	4345	However, these are unavoidable for many reasons. For one, each compiler
3377	libev will be explained. For complexity discussions about backends see the	4346	has different warnings, and each user has different tastes regarding
3378	documentation for C<ev_default_init>.	4347	warning options. "Warn-free" code therefore cannot be a goal except when
		4348	targeting a specific compiler and compiler-version.
3379		4349
3380	All of the following are about amortised time: If an array needs to be	4350	Another reason is that some compiler warnings require elaborate
3381	extended, libev needs to realloc and move the whole array, but this	4351	workarounds, or other changes to the code that make it less clear and less
3382	happens asymptotically never with higher number of elements, so O(1) might	4352	maintainable.
3383	mean it might do a lengthy realloc operation in rare cases, but on average
3384	it is much faster and asymptotically approaches constant time.
3385		4353
3386	=over 4	4354	And of course, some compiler warnings are just plain stupid, or simply
		4355	wrong (because they don't actually warn about the condition their message
		4356	seems to warn about). For example, certain older gcc versions had some
		4357	warnings that resulted an extreme number of false positives. These have
		4358	been fixed, but some people still insist on making code warn-free with
		4359	such buggy versions.
3387		4360
3388	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	4361	While libev is written to generate as few warnings as possible,
		4362	"warn-free" code is not a goal, and it is recommended not to build libev
		4363	with any compiler warnings enabled unless you are prepared to cope with
		4364	them (e.g. by ignoring them). Remember that warnings are just that:
		4365	warnings, not errors, or proof of bugs.
3389		4366
3390	This means that, when you have a watcher that triggers in one hour and
3391	there are 100 watchers that would trigger before that then inserting will
3392	have to skip roughly seven (C<ld 100>) of these watchers.
3393		4367
3394	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	4368	=head2 VALGRIND
3395		4369
3396	That means that changing a timer costs less than removing/adding them	4370	Valgrind has a special section here because it is a popular tool that is
3397	as only the relative motion in the event queue has to be paid for.	4371	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3398		4372
3399	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	4373	If you think you found a bug (memory leak, uninitialised data access etc.)
		4374	in libev, then check twice: If valgrind reports something like:
3400		4375
3401	These just add the watcher into an array or at the head of a list.	4376	==2274== definitely lost: 0 bytes in 0 blocks.
		4377	==2274== possibly lost: 0 bytes in 0 blocks.
		4378	==2274== still reachable: 256 bytes in 1 blocks.
3402		4379
3403	=item Stopping check/prepare/idle/fork/async watchers: O(1)	4380	Then there is no memory leak, just as memory accounted to global variables
		4381	is not a memleak - the memory is still being referenced, and didn't leak.
3404		4382
3405	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	4383	Similarly, under some circumstances, valgrind might report kernel bugs
		4384	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		4385	although an acceptable workaround has been found here), or it might be
		4386	confused.
3406		4387
3407	These watchers are stored in lists then need to be walked to find the	4388	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3408	correct watcher to remove. The lists are usually short (you don't usually	4389	make it into some kind of religion.
3409	have many watchers waiting for the same fd or signal).
3410		4390
3411	=item Finding the next timer in each loop iteration: O(1)	4391	If you are unsure about something, feel free to contact the mailing list
		4392	with the full valgrind report and an explanation on why you think this
		4393	is a bug in libev (best check the archives, too :). However, don't be
		4394	annoyed when you get a brisk "this is no bug" answer and take the chance
		4395	of learning how to interpret valgrind properly.
3412		4396
3413	By virtue of using a binary or 4-heap, the next timer is always found at a	4397	If you need, for some reason, empty reports from valgrind for your project
3414	fixed position in the storage array.	4398	I suggest using suppression lists.
3415		4399
3416	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3417		4400
3418	A change means an I/O watcher gets started or stopped, which requires	4401	=head1 PORTABILITY NOTES
3419	libev to recalculate its status (and possibly tell the kernel, depending
3420	on backend and whether C<ev_io_set> was used).
3421		4402
3422	=item Activating one watcher (putting it into the pending state): O(1)
3423
3424	=item Priority handling: O(number_of_priorities)
3425
3426	Priorities are implemented by allocating some space for each
3427	priority. When doing priority-based operations, libev usually has to
3428	linearly search all the priorities, but starting/stopping and activating
3429	watchers becomes O(1) with respect to priority handling.
3430
3431	=item Sending an ev_async: O(1)
3432
3433	=item Processing ev_async_send: O(number_of_async_watchers)
3434
3435	=item Processing signals: O(max_signal_number)
3436
3437	Sending involves a system call I<iff> there were no other C<ev_async_send>
3438	calls in the current loop iteration. Checking for async and signal events
3439	involves iterating over all running async watchers or all signal numbers.
3440
3441	=back
3442
3443
3444	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4403	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3445		4404
3446	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4405	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3447	requires, and its I/O model is fundamentally incompatible with the POSIX	4406	requires, and its I/O model is fundamentally incompatible with the POSIX
3448	model. Libev still offers limited functionality on this platform in	4407	model. Libev still offers limited functionality on this platform in
3449	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4408	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3456	way (note also that glib is the slowest event library known to man).	4415	way (note also that glib is the slowest event library known to man).
3457		4416
3458	There is no supported compilation method available on windows except	4417	There is no supported compilation method available on windows except
3459	embedding it into other applications.	4418	embedding it into other applications.
3460		4419
		4420	Sensible signal handling is officially unsupported by Microsoft - libev
		4421	tries its best, but under most conditions, signals will simply not work.
		4422
3461	Not a libev limitation but worth mentioning: windows apparently doesn't	4423	Not a libev limitation but worth mentioning: windows apparently doesn't
3462	accept large writes: instead of resulting in a partial write, windows will	4424	accept large writes: instead of resulting in a partial write, windows will
3463	either accept everything or return C<ENOBUFS> if the buffer is too large,	4425	either accept everything or return C<ENOBUFS> if the buffer is too large,
3464	so make sure you only write small amounts into your sockets (less than a	4426	so make sure you only write small amounts into your sockets (less than a
3465	megabyte seems safe, but this apparently depends on the amount of memory	4427	megabyte seems safe, but this apparently depends on the amount of memory
…		…
3469	the abysmal performance of winsockets, using a large number of sockets	4431	the abysmal performance of winsockets, using a large number of sockets
3470	is not recommended (and not reasonable). If your program needs to use	4432	is not recommended (and not reasonable). If your program needs to use
3471	more than a hundred or so sockets, then likely it needs to use a totally	4433	more than a hundred or so sockets, then likely it needs to use a totally
3472	different implementation for windows, as libev offers the POSIX readiness	4434	different implementation for windows, as libev offers the POSIX readiness
3473	notification model, which cannot be implemented efficiently on windows	4435	notification model, which cannot be implemented efficiently on windows
3474	(Microsoft monopoly games).	4436	(due to Microsoft monopoly games).
3475		4437
3476	A typical way to use libev under windows is to embed it (see the embedding	4438	A typical way to use libev under windows is to embed it (see the embedding
3477	section for details) and use the following F<evwrap.h> header file instead	4439	section for details) and use the following F<evwrap.h> header file instead
3478	of F<ev.h>:	4440	of F<ev.h>:
3479		4441
…		…
3515		4477
3516	Early versions of winsocket's select only supported waiting for a maximum	4478	Early versions of winsocket's select only supported waiting for a maximum
3517	of C<64> handles (probably owning to the fact that all windows kernels	4479	of C<64> handles (probably owning to the fact that all windows kernels
3518	can only wait for C<64> things at the same time internally; Microsoft	4480	can only wait for C<64> things at the same time internally; Microsoft
3519	recommends spawning a chain of threads and wait for 63 handles and the	4481	recommends spawning a chain of threads and wait for 63 handles and the
3520	previous thread in each. Great).	4482	previous thread in each. Sounds great!).
3521		4483
3522	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4484	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3523	to some high number (e.g. C<2048>) before compiling the winsocket select	4485	to some high number (e.g. C<2048>) before compiling the winsocket select
3524	call (which might be in libev or elsewhere, for example, perl does its own	4486	call (which might be in libev or elsewhere, for example, perl and many
3525	select emulation on windows).	4487	other interpreters do their own select emulation on windows).
3526		4488
3527	Another limit is the number of file descriptors in the Microsoft runtime	4489	Another limit is the number of file descriptors in the Microsoft runtime
3528	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4490	libraries, which by default is C<64> (there must be a hidden I<64>
3529	or something like this inside Microsoft). You can increase this by calling	4491	fetish or something like this inside Microsoft). You can increase this
3530	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4492	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3531	arbitrary limit), but is broken in many versions of the Microsoft runtime	4493	(another arbitrary limit), but is broken in many versions of the Microsoft
3532	libraries.
3533
3534	This might get you to about C<512> or C<2048> sockets (depending on	4494	runtime libraries. This might get you to about C<512> or C<2048> sockets
3535	windows version and/or the phase of the moon). To get more, you need to	4495	(depending on windows version and/or the phase of the moon). To get more,
3536	wrap all I/O functions and provide your own fd management, but the cost of	4496	you need to wrap all I/O functions and provide your own fd management, but
3537	calling select (O(n²)) will likely make this unworkable.	4497	the cost of calling select (O(n²)) will likely make this unworkable.
3538		4498
3539	=back	4499	=back
3540		4500
3541
3542	=head1 PORTABILITY REQUIREMENTS	4501	=head2 PORTABILITY REQUIREMENTS
3543		4502
3544	In addition to a working ISO-C implementation, libev relies on a few	4503	In addition to a working ISO-C implementation and of course the
3545	additional extensions:	4504	backend-specific APIs, libev relies on a few additional extensions:
3546		4505
3547	=over 4	4506	=over 4
3548		4507
3549	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	4508	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3550	calling conventions regardless of C<ev_watcher_type *>.	4509	calling conventions regardless of C<ev_watcher_type *>.
…		…
3575	except the initial one, and run the default loop in the initial thread as	4534	except the initial one, and run the default loop in the initial thread as
3576	well.	4535	well.
3577		4536
3578	=item C<long> must be large enough for common memory allocation sizes	4537	=item C<long> must be large enough for common memory allocation sizes
3579		4538
3580	To improve portability and simplify using libev, libev uses C<long>	4539	To improve portability and simplify its API, libev uses C<long> internally
3581	internally instead of C<size_t> when allocating its data structures. On	4540	instead of C<size_t> when allocating its data structures. On non-POSIX
3582	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4541	systems (Microsoft...) this might be unexpectedly low, but is still at
3583	is still at least 31 bits everywhere, which is enough for hundreds of	4542	least 31 bits everywhere, which is enough for hundreds of millions of
3584	millions of watchers.	4543	watchers.
3585		4544
3586	=item C<double> must hold a time value in seconds with enough accuracy	4545	=item C<double> must hold a time value in seconds with enough accuracy
3587		4546
3588	The type C<double> is used to represent timestamps. It is required to	4547	The type C<double> is used to represent timestamps. It is required to
3589	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4548	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
3590	enough for at least into the year 4000. This requirement is fulfilled by	4549	enough for at least into the year 4000. This requirement is fulfilled by
3591	implementations implementing IEEE 754 (basically all existing ones).	4550	implementations implementing IEEE 754, which is basically all existing
		4551	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4552	2200.
3592		4553
3593	=back	4554	=back
3594		4555
3595	If you know of other additional requirements drop me a note.	4556	If you know of other additional requirements drop me a note.
3596		4557
3597		4558
3598	=head1 COMPILER WARNINGS	4559	=head1 ALGORITHMIC COMPLEXITIES
3599		4560
3600	Depending on your compiler and compiler settings, you might get no or a	4561	In this section the complexities of (many of) the algorithms used inside
3601	lot of warnings when compiling libev code. Some people are apparently	4562	libev will be documented. For complexity discussions about backends see
3602	scared by this.	4563	the documentation for C<ev_default_init>.
3603		4564
3604	However, these are unavoidable for many reasons. For one, each compiler	4565	All of the following are about amortised time: If an array needs to be
3605	has different warnings, and each user has different tastes regarding	4566	extended, libev needs to realloc and move the whole array, but this
3606	warning options. "Warn-free" code therefore cannot be a goal except when	4567	happens asymptotically rarer with higher number of elements, so O(1) might
3607	targeting a specific compiler and compiler-version.	4568	mean that libev does a lengthy realloc operation in rare cases, but on
		4569	average it is much faster and asymptotically approaches constant time.
3608		4570
3609	Another reason is that some compiler warnings require elaborate	4571	=over 4
3610	workarounds, or other changes to the code that make it less clear and less
3611	maintainable.
3612		4572
3613	And of course, some compiler warnings are just plain stupid, or simply	4573	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3614	wrong (because they don't actually warn about the condition their message
3615	seems to warn about).
3616		4574
3617	While libev is written to generate as few warnings as possible,	4575	This means that, when you have a watcher that triggers in one hour and
3618	"warn-free" code is not a goal, and it is recommended not to build libev	4576	there are 100 watchers that would trigger before that, then inserting will
3619	with any compiler warnings enabled unless you are prepared to cope with	4577	have to skip roughly seven (C<ld 100>) of these watchers.
3620	them (e.g. by ignoring them). Remember that warnings are just that:
3621	warnings, not errors, or proof of bugs.
3622		4578
		4579	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3623		4580
3624	=head1 VALGRIND	4581	That means that changing a timer costs less than removing/adding them,
		4582	as only the relative motion in the event queue has to be paid for.
3625		4583
3626	Valgrind has a special section here because it is a popular tool that is	4584	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3627	highly useful, but valgrind reports are very hard to interpret.
3628		4585
3629	If you think you found a bug (memory leak, uninitialised data access etc.)	4586	These just add the watcher into an array or at the head of a list.
3630	in libev, then check twice: If valgrind reports something like:
3631		4587
3632	==2274== definitely lost: 0 bytes in 0 blocks.	4588	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3633	==2274== possibly lost: 0 bytes in 0 blocks.
3634	==2274== still reachable: 256 bytes in 1 blocks.
3635		4589
3636	Then there is no memory leak. Similarly, under some circumstances,	4590	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3637	valgrind might report kernel bugs as if it were a bug in libev, or it
3638	might be confused (it is a very good tool, but only a tool).
3639		4591
3640	If you are unsure about something, feel free to contact the mailing list	4592	These watchers are stored in lists, so they need to be walked to find the
3641	with the full valgrind report and an explanation on why you think this is	4593	correct watcher to remove. The lists are usually short (you don't usually
3642	a bug in libev. However, don't be annoyed when you get a brisk "this is	4594	have many watchers waiting for the same fd or signal: one is typical, two
3643	no bug" answer and take the chance of learning how to interpret valgrind	4595	is rare).
3644	properly.
3645		4596
3646	If you need, for some reason, empty reports from valgrind for your project	4597	=item Finding the next timer in each loop iteration: O(1)
3647	I suggest using suppression lists.
3648		4598
		4599	By virtue of using a binary or 4-heap, the next timer is always found at a
		4600	fixed position in the storage array.
		4601
		4602	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4603
		4604	A change means an I/O watcher gets started or stopped, which requires
		4605	libev to recalculate its status (and possibly tell the kernel, depending
		4606	on backend and whether C<ev_io_set> was used).
		4607
		4608	=item Activating one watcher (putting it into the pending state): O(1)
		4609
		4610	=item Priority handling: O(number_of_priorities)
		4611
		4612	Priorities are implemented by allocating some space for each
		4613	priority. When doing priority-based operations, libev usually has to
		4614	linearly search all the priorities, but starting/stopping and activating
		4615	watchers becomes O(1) with respect to priority handling.
		4616
		4617	=item Sending an ev_async: O(1)
		4618
		4619	=item Processing ev_async_send: O(number_of_async_watchers)
		4620
		4621	=item Processing signals: O(max_signal_number)
		4622
		4623	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4624	calls in the current loop iteration. Checking for async and signal events
		4625	involves iterating over all running async watchers or all signal numbers.
		4626
		4627	=back
		4628
		4629
		4630	=head1 PORTING FROM LIBEV 3.X TO 4.X
		4631
		4632	The major version 4 introduced some minor incompatible changes to the API.
		4633
		4634	At the moment, the C<ev.h> header file tries to implement superficial
		4635	compatibility, so most programs should still compile. Those might be
		4636	removed in later versions of libev, so better update early than late.
		4637
		4638	=over 4
		4639
		4640	=item C<ev_loop_count> renamed to C<ev_iteration>
		4641
		4642	=item C<ev_loop_depth> renamed to C<ev_depth>
		4643
		4644	=item C<ev_loop_verify> renamed to C<ev_verify>
		4645
		4646	Most functions working on C<struct ev_loop> objects don't have an
		4647	C<ev_loop_> prefix, so it was removed. Note that C<ev_loop_fork> is
		4648	still called C<ev_loop_fork> because it would otherwise clash with the
		4649	C<ev_fork> typedef.
		4650
		4651	=item C<EV_TIMEOUT> renamed to C<EV_TIMER> in C<revents>
		4652
		4653	This is a simple rename - all other watcher types use their name
		4654	as revents flag, and now C<ev_timer> does, too.
		4655
		4656	Both C<EV_TIMER> and C<EV_TIMEOUT> symbols were present in 3.x versions
		4657	and continue to be present for the forseeable future, so this is mostly a
		4658	documentation change.
		4659
		4660	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		4661
		4662	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		4663	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		4664	and work, but the library code will of course be larger.
		4665
		4666	=back
		4667
		4668
		4669	=head1 GLOSSARY
		4670
		4671	=over 4
		4672
		4673	=item active
		4674
		4675	A watcher is active as long as it has been started (has been attached to
		4676	an event loop) but not yet stopped (disassociated from the event loop).
		4677
		4678	=item application
		4679
		4680	In this document, an application is whatever is using libev.
		4681
		4682	=item callback
		4683
		4684	The address of a function that is called when some event has been
		4685	detected. Callbacks are being passed the event loop, the watcher that
		4686	received the event, and the actual event bitset.
		4687
		4688	=item callback invocation
		4689
		4690	The act of calling the callback associated with a watcher.
		4691
		4692	=item event
		4693
		4694	A change of state of some external event, such as data now being available
		4695	for reading on a file descriptor, time having passed or simply not having
		4696	any other events happening anymore.
		4697
		4698	In libev, events are represented as single bits (such as C<EV_READ> or
		4699	C<EV_TIMER>).
		4700
		4701	=item event library
		4702
		4703	A software package implementing an event model and loop.
		4704
		4705	=item event loop
		4706
		4707	An entity that handles and processes external events and converts them
		4708	into callback invocations.
		4709
		4710	=item event model
		4711
		4712	The model used to describe how an event loop handles and processes
		4713	watchers and events.
		4714
		4715	=item pending
		4716
		4717	A watcher is pending as soon as the corresponding event has been detected,
		4718	and stops being pending as soon as the watcher will be invoked or its
		4719	pending status is explicitly cleared by the application.
		4720
		4721	A watcher can be pending, but not active. Stopping a watcher also clears
		4722	its pending status.
		4723
		4724	=item real time
		4725
		4726	The physical time that is observed. It is apparently strictly monotonic :)
		4727
		4728	=item wall-clock time
		4729
		4730	The time and date as shown on clocks. Unlike real time, it can actually
		4731	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4732	clock.
		4733
		4734	=item watcher
		4735
		4736	A data structure that describes interest in certain events. Watchers need
		4737	to be started (attached to an event loop) before they can receive events.
		4738
		4739	=item watcher invocation
		4740
		4741	The act of calling the callback associated with a watcher.
		4742
		4743	=back
3649		4744
3650	=head1 AUTHOR	4745	=head1 AUTHOR
3651		4746
3652	Marc Lehmann <libev@schmorp.de>.	4747	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3653		4748

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