ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.196 by root, Tue Oct 21 20:04:14 2008 UTC vs.
Revision 1.299 by sf-exg, Sat Aug 28 21:42:12 2010 UTC

…		…
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	Familiarity 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 (in practise
115	the beginning of 1970, details are complicated, don't ask). This type is	130	somewhere near the beginning of 1970, details are complicated, don't
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	131	ask). This type is called C<ev_tstamp>, which is what you should use
117	to the C<double> type in C, and when you need to do any calculations on	132	too. It usually aliases to the C<double> type in C. When you need to do
118	it, you should treat it as some floating point value. Unlike the name	133	any calculations on it, you should treat it as some floating point value.
		134
119	component C<stamp> might indicate, it is also used for time differences	135	Unlike the name component C<stamp> might indicate, it is also used for
120	throughout libev.	136	time differences (e.g. delays) throughout libev.
121		137
122	=head1 ERROR HANDLING	138	=head1 ERROR HANDLING
123		139
124	Libev knows three classes of errors: operating system errors, usage errors	140	Libev knows three classes of errors: operating system errors, usage errors
125	and internal errors (bugs).	141	and internal errors (bugs).
…		…
176	as this indicates an incompatible change. Minor versions are usually	192	as this indicates an incompatible change. Minor versions are usually
177	compatible to older versions, so a larger minor version alone is usually	193	compatible to older versions, so a larger minor version alone is usually
178	not a problem.	194	not a problem.
179		195
180	Example: Make sure we haven't accidentally been linked against the wrong	196	Example: Make sure we haven't accidentally been linked against the wrong
181	version.	197	version (note, however, that this will not detect ABI mismatches :).
182		198
183	assert (("libev version mismatch",	199	assert (("libev version mismatch",
184	ev_version_major () == EV_VERSION_MAJOR	200	ev_version_major () == EV_VERSION_MAJOR
185	&& ev_version_minor () >= EV_VERSION_MINOR));	201	&& ev_version_minor () >= EV_VERSION_MINOR));
186		202
…		…
276		292
277	=back	293	=back
278		294
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	295	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
280		296
281	An event loop is described by a C<struct ev_loop *>. The library knows two	297	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	298	is I<not> optional in this case, as there is also an C<ev_loop>
283	events, and dynamically created loops which do not.	299	I<function>).
		300
		301	The library knows two types of such loops, the I<default> loop, which
		302	supports signals and child events, and dynamically created loops which do
		303	not.
284		304
285	=over 4	305	=over 4
286		306
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	307	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		308
…		…
294	If you don't know what event loop to use, use the one returned from this	314	If you don't know what event loop to use, use the one returned from this
295	function.	315	function.
296		316
297	Note that this function is I<not> thread-safe, so if you want to use it	317	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,	318	from multiple threads, you have to lock (note also that this is unlikely,
299	as loops cannot bes hared easily between threads anyway).	319	as loops cannot be shared easily between threads anyway).
300		320
301	The default loop is the only loop that can handle C<ev_signal> and	321	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	322	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	323	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	324	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	346	useful to try out specific backends to test their performance, or to work
327	around bugs.	347	around bugs.
328		348
329	=item C<EVFLAG_FORKCHECK>	349	=item C<EVFLAG_FORKCHECK>
330		350
331	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	351	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	352	make libev check for a fork in each iteration by enabling this flag.
333	enabling this flag.
334		353
335	This works by calling C<getpid ()> on every iteration of the loop,	354	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	355	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	356	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	357	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
…		…
344	flag.	363	flag.
345		364
346	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	365	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
347	environment variable.	366	environment variable.
348		367
		368	=item C<EVFLAG_NOINOTIFY>
		369
		370	When this flag is specified, then libev will not attempt to use the
		371	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and
		372	testing, this flag can be useful to conserve inotify file descriptors, as
		373	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		374
		375	=item C<EVFLAG_SIGNALFD>
		376
		377	When this flag is specified, then libev will attempt to use the
		378	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API
		379	delivers signals synchronously, which makes it both faster and might make
		380	it possible to get the queued signal data. It can also simplify signal
		381	handling with threads, as long as you properly block signals in your
		382	threads that are not interested in handling them.
		383
		384	Signalfd will not be used by default as this changes your signal mask, and
		385	there are a lot of shoddy libraries and programs (glib's threadpool for
		386	example) that can't properly initialise their signal masks.
		387
349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	388	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
350		389
351	This is your standard select(2) backend. Not I<completely> standard, as	390	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,	391	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	392	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	416	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
378	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	417	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
379		418
380	=item C<EVBACKEND_EPOLL> (value 4, Linux)	419	=item C<EVBACKEND_EPOLL> (value 4, Linux)
381		420
		421	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		422	kernels).
		423
382	For few fds, this backend is a bit little slower than poll and select,	424	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	425	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),	426	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	427	epoll scales either O(1) or O(active_fds).
386	of shortcomings, such as silently dropping events in some hard-to-detect	428
387	cases and requiring a system call per fd change, no fork support and bad	429	The epoll mechanism deserves honorable mention as the most misdesigned
388	support for dup.	430	of the more advanced event mechanisms: mere annoyances include silently
		431	dropping file descriptors, requiring a system call per change per file
		432	descriptor (and unnecessary guessing of parameters), problems with dup and
		433	so on. The biggest issue is fork races, however - if a program forks then
		434	I<both> parent and child process have to recreate the epoll set, which can
		435	take considerable time (one syscall per file descriptor) and is of course
		436	hard to detect.
		437
		438	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		439	of course I<doesn't>, and epoll just loves to report events for totally
		440	I<different> file descriptors (even already closed ones, so one cannot
		441	even remove them from the set) than registered in the set (especially
		442	on SMP systems). Libev tries to counter these spurious notifications by
		443	employing an additional generation counter and comparing that against the
		444	events to filter out spurious ones, recreating the set when required.
389		445
390	While stopping, setting and starting an I/O watcher in the same iteration	446	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	447	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	448	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	449	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
394	very well if you register events for both fds.	450	file descriptors might not work very well if you register events for both
395		451	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		452
400	Best performance from this backend is achieved by not unregistering all	453	Best performance from this backend is achieved by not unregistering all
401	watchers for a file descriptor until it has been closed, if possible,	454	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	455	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	456	starting a watcher (without re-setting it) also usually doesn't cause
404	extra overhead.	457	extra overhead. A fork can both result in spurious notifications as well
		458	as in libev having to destroy and recreate the epoll object, which can
		459	take considerable time and thus should be avoided.
		460
		461	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		462	faster than epoll for maybe up to a hundred file descriptors, depending on
		463	the usage. So sad.
405		464
406	While nominally embeddable in other event loops, this feature is broken in	465	While nominally embeddable in other event loops, this feature is broken in
407	all kernel versions tested so far.	466	all kernel versions tested so far.
408		467
409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	468	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
410	C<EVBACKEND_POLL>.	469	C<EVBACKEND_POLL>.
411		470
412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	471	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
413		472
414	Kqueue deserves special mention, as at the time of this writing, it was	473	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	474	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	475	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	476	it's completely useless). Unlike epoll, however, whose brokenness
418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or	477	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.	478	without API changes to existing programs. For this reason it's not being
		479	"auto-detected" unless you explicitly specify it in the flags (i.e. using
		480	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		481	system like NetBSD.
420		482
421	You still can embed kqueue into a normal poll or select backend and use it	483	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	484	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.	485	the target platform). See C<ev_embed> watchers for more info.
424		486
425	It scales in the same way as the epoll backend, but the interface to the	487	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	488	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	489	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	490	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	491	two event changes per incident. Support for C<fork ()> is very bad (but
430	drops fds silently in similarly hard-to-detect cases.	492	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		493	cases
431		494
432	This backend usually performs well under most conditions.	495	This backend usually performs well under most conditions.
433		496
434	While nominally embeddable in other event loops, this doesn't work	497	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	498	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	499	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	500	(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,	501	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
439	using it only for sockets.	502	also broken on OS X)) and, did I mention it, using it only for sockets.
440		503
441	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	504	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	505	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
443	C<NOTE_EOF>.	506	C<NOTE_EOF>.
444		507
…		…
464	might perform better.	527	might perform better.
465		528
466	On the positive side, with the exception of the spurious readiness	529	On the positive side, with the exception of the spurious readiness
467	notifications, this backend actually performed fully to specification	530	notifications, this backend actually performed fully to specification
468	in all tests and is fully embeddable, which is a rare feat among the	531	in all tests and is fully embeddable, which is a rare feat among the
469	OS-specific backends.	532	OS-specific backends (I vastly prefer correctness over speed hacks).
470		533
471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	534	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
472	C<EVBACKEND_POLL>.	535	C<EVBACKEND_POLL>.
473		536
474	=item C<EVBACKEND_ALL>	537	=item C<EVBACKEND_ALL>
…		…
479		542
480	It is definitely not recommended to use this flag.	543	It is definitely not recommended to use this flag.
481		544
482	=back	545	=back
483		546
484	If one or more of these are or'ed into the flags value, then only these	547	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	548	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.	549	here). If none are specified, all backends in C<ev_recommended_backends
		550	()> will be tried.
487		551
488	Example: This is the most typical usage.	552	Example: This is the most typical usage.
489		553
490	if (!ev_default_loop (0))	554	if (!ev_default_loop (0))
491	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	555	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
503	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	567	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
504		568
505	=item struct ev_loop *ev_loop_new (unsigned int flags)	569	=item struct ev_loop *ev_loop_new (unsigned int flags)
506		570
507	Similar to C<ev_default_loop>, but always creates a new event loop that is	571	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	572	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		573
512	Note that this function I<is> thread-safe, and the recommended way to use	574	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	575	libev with threads is indeed to create one loop per thread, and using the
514	default loop in the "main" or "initial" thread.	576	default loop in the "main" or "initial" thread.
515		577
516	Example: Try to create a event loop that uses epoll and nothing else.	578	Example: Try to create a event loop that uses epoll and nothing else.
517		579
…		…
519	if (!epoller)	581	if (!epoller)
520	fatal ("no epoll found here, maybe it hides under your chair");	582	fatal ("no epoll found here, maybe it hides under your chair");
521		583
522	=item ev_default_destroy ()	584	=item ev_default_destroy ()
523		585
524	Destroys the default loop again (frees all memory and kernel state	586	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	587	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	588	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>	589	either stop all watchers cleanly yourself I<before> calling this function,
528	calling this function, or cope with the fact afterwards (which is usually	590	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	591	can just ignore the watchers and/or C<free ()> them for example).
530	for example).
531		592
532	Note that certain global state, such as signal state, will not be freed by	593	Note that certain global state, such as signal state (and installed signal
533	this function, and related watchers (such as signal and child watchers)	594	handlers), will not be freed by this function, and related watchers (such
534	would need to be stopped manually.	595	as signal and child watchers) would need to be stopped manually.
535		596
536	In general it is not advisable to call this function except in the	597	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	598	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	599	pipe fds. If you need dynamically allocated loops it is better to use
539	C<ev_loop_new> and C<ev_loop_destroy>).	600	C<ev_loop_new> and C<ev_loop_destroy>.
540		601
541	=item ev_loop_destroy (loop)	602	=item ev_loop_destroy (loop)
542		603
543	Like C<ev_default_destroy>, but destroys an event loop created by an	604	Like C<ev_default_destroy>, but destroys an event loop created by an
544	earlier call to C<ev_loop_new>.	605	earlier call to C<ev_loop_new>.
…		…
550	name, you can call it anytime, but it makes most sense after forking, in	611	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	612	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	613	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.	614	functions, and it will only take effect at the next C<ev_loop> iteration.
554		615
		616	Again, you I<have> to call it on I<any> loop that you want to re-use after
		617	a fork, I<even if you do not plan to use the loop in the parent>. This is
		618	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		619	during fork.
		620
555	On the other hand, you only need to call this function in the child	621	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	622	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.	623	just fork+exec or create a new loop in the child, you don't have to call
		624	it at all.
558		625
559	The function itself is quite fast and it's usually not a problem to call	626	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	627	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>:	628	quite nicely into a call to C<pthread_atfork>:
562		629
…		…
564		631
565	=item ev_loop_fork (loop)	632	=item ev_loop_fork (loop)
566		633
567	Like C<ev_default_fork>, but acts on an event loop created by	634	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	635	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	636	after fork that you want to re-use in the child, and how you keep track of
570	entirely your own problem.	637	them is entirely your own problem.
571		638
572	=item int ev_is_default_loop (loop)	639	=item int ev_is_default_loop (loop)
573		640
574	Returns true when the given loop is, in fact, the default loop, and false	641	Returns true when the given loop is, in fact, the default loop, and false
575	otherwise.	642	otherwise.
576		643
577	=item unsigned int ev_loop_count (loop)	644	=item unsigned int ev_iteration (loop)
578		645
579	Returns the count of loop iterations for the loop, which is identical to	646	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	647	the number of times libev did poll for new events. It starts at C<0> and
581	happily wraps around with enough iterations.	648	happily wraps around with enough iterations.
582		649
583	This value can sometimes be useful as a generation counter of sorts (it	650	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	651	"ticks" the number of loop iterations), as it roughly corresponds with
585	C<ev_prepare> and C<ev_check> calls.	652	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		653	prepare and check phases.
		654
		655	=item unsigned int ev_depth (loop)
		656
		657	Returns the number of times C<ev_loop> was entered minus the number of
		658	times C<ev_loop> was exited, in other words, the recursion depth.
		659
		660	Outside C<ev_loop>, this number is zero. In a callback, this number is
		661	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),
		662	in which case it is higher.
		663
		664	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread
		665	etc.), doesn't count as "exit" - consider this as a hint to avoid such
		666	ungentleman behaviour unless it's really convenient.
586		667
587	=item unsigned int ev_backend (loop)	668	=item unsigned int ev_backend (loop)
588		669
589	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	670	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
590	use.	671	use.
…		…
605		686
606	This function is rarely useful, but when some event callback runs for a	687	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	688	very long time without entering the event loop, updating libev's idea of
608	the current time is a good idea.	689	the current time is a good idea.
609		690
610	See also "The special problem of time updates" in the C<ev_timer> section.	691	See also L<The special problem of time updates> in the C<ev_timer> section.
		692
		693	=item ev_suspend (loop)
		694
		695	=item ev_resume (loop)
		696
		697	These two functions suspend and resume a loop, for use when the loop is
		698	not used for a while and timeouts should not be processed.
		699
		700	A typical use case would be an interactive program such as a game: When
		701	the user presses C<^Z> to suspend the game and resumes it an hour later it
		702	would be best to handle timeouts as if no time had actually passed while
		703	the program was suspended. This can be achieved by calling C<ev_suspend>
		704	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		705	C<ev_resume> directly afterwards to resume timer processing.
		706
		707	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		708	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		709	will be rescheduled (that is, they will lose any events that would have
		710	occurred while suspended).
		711
		712	After calling C<ev_suspend> you B<must not> call I<any> function on the
		713	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		714	without a previous call to C<ev_suspend>.
		715
		716	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		717	event loop time (see C<ev_now_update>).
611		718
612	=item ev_loop (loop, int flags)	719	=item ev_loop (loop, int flags)
613		720
614	Finally, this is it, the event handler. This function usually is called	721	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	722	after you have initialised all your watchers and you want to start
616	events.	723	handling events.
617		724
618	If the flags argument is specified as C<0>, it will not return until	725	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.	726	either no event watchers are active anymore or C<ev_unloop> was called.
620		727
621	Please note that an explicit C<ev_unloop> is usually better than	728	Please note that an explicit C<ev_unloop> is usually better than
…		…
631	the loop.	738	the loop.
632		739
633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	740	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	741	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	742	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	743	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	744	user-registered callback will be called), and will return after one
638	iteration of the loop.	745	iteration of the loop.
639		746
640	This is useful if you are waiting for some external event in conjunction	747	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	748	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	792	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.	793	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
687		794
688	This "unloop state" will be cleared when entering C<ev_loop> again.	795	This "unloop state" will be cleared when entering C<ev_loop> again.
689		796
690	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	797	It is safe to call C<ev_unloop> from outside any C<ev_loop> calls.
691		798
692	=item ev_ref (loop)	799	=item ev_ref (loop)
693		800
694	=item ev_unref (loop)	801	=item ev_unref (loop)
695		802
696	Ref/unref can be used to add or remove a reference count on the event	803	Ref/unref can be used to add or remove a reference count on the event
697	loop: Every watcher keeps one reference, and as long as the reference	804	loop: Every watcher keeps one reference, and as long as the reference
698	count is nonzero, C<ev_loop> will not return on its own.	805	count is nonzero, C<ev_loop> will not return on its own.
699		806
700	If you have a watcher you never unregister that should not keep C<ev_loop>	807	This is useful when you have a watcher that you never intend to
701	from returning, call ev_unref() after starting, and ev_ref() before	808	unregister, but that nevertheless should not keep C<ev_loop> from
		809	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
702	stopping it.	810	before stopping it.
703		811
704	As an example, libev itself uses this for its internal signal pipe: It is	812	As an example, libev itself uses this for its internal signal pipe: It
705	not visible to the libev user and should not keep C<ev_loop> from exiting	813	is not visible to the libev user and should not keep C<ev_loop> from
706	if no event watchers registered by it are active. It is also an excellent	814	exiting if no event watchers registered by it are active. It is also an
707	way to do this for generic recurring timers or from within third-party	815	excellent way to do this for generic recurring timers or from within
708	libraries. Just remember to I<unref after start> and I<ref before stop>	816	third-party libraries. Just remember to I<unref after start> and I<ref
709	(but only if the watcher wasn't active before, or was active before,	817	before stop> (but only if the watcher wasn't active before, or was active
710	respectively).	818	before, respectively. Note also that libev might stop watchers itself
		819	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		820	in the callback).
711		821
712	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	822	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
713	running when nothing else is active.	823	running when nothing else is active.
714		824
715	struct ev_signal exitsig;	825	ev_signal exitsig;
716	ev_signal_init (&exitsig, sig_cb, SIGINT);	826	ev_signal_init (&exitsig, sig_cb, SIGINT);
717	ev_signal_start (loop, &exitsig);	827	ev_signal_start (loop, &exitsig);
718	evf_unref (loop);	828	evf_unref (loop);
719		829
720	Example: For some weird reason, unregister the above signal handler again.	830	Example: For some weird reason, unregister the above signal handler again.
…		…
744		854
745	By setting a higher I<io collect interval> you allow libev to spend more	855	By setting a higher I<io collect interval> you allow libev to spend more
746	time collecting I/O events, so you can handle more events per iteration,	856	time collecting I/O events, so you can handle more events per iteration,
747	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	857	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
748	C<ev_timer>) will be not affected. Setting this to a non-null value will	858	C<ev_timer>) will be not affected. Setting this to a non-null value will
749	introduce an additional C<ev_sleep ()> call into most loop iterations.	859	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		860	sleep time ensures that libev will not poll for I/O events more often then
		861	once per this interval, on average.
750		862
751	Likewise, by setting a higher I<timeout collect interval> you allow libev	863	Likewise, by setting a higher I<timeout collect interval> you allow libev
752	to spend more time collecting timeouts, at the expense of increased	864	to spend more time collecting timeouts, at the expense of increased
753	latency/jitter/inexactness (the watcher callback will be called	865	latency/jitter/inexactness (the watcher callback will be called
754	later). C<ev_io> watchers will not be affected. Setting this to a non-null	866	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
756		868
757	Many (busy) programs can usually benefit by setting the I/O collect	869	Many (busy) programs can usually benefit by setting the I/O collect
758	interval to a value near C<0.1> or so, which is often enough for	870	interval to a value near C<0.1> or so, which is often enough for
759	interactive servers (of course not for games), likewise for timeouts. It	871	interactive servers (of course not for games), likewise for timeouts. It
760	usually doesn't make much sense to set it to a lower value than C<0.01>,	872	usually doesn't make much sense to set it to a lower value than C<0.01>,
761	as this approaches the timing granularity of most systems.	873	as this approaches the timing granularity of most systems. Note that if
		874	you do transactions with the outside world and you can't increase the
		875	parallelity, then this setting will limit your transaction rate (if you
		876	need to poll once per transaction and the I/O collect interval is 0.01,
		877	then you can't do more than 100 transactions per second).
762		878
763	Setting the I<timeout collect interval> can improve the opportunity for	879	Setting the I<timeout collect interval> can improve the opportunity for
764	saving power, as the program will "bundle" timer callback invocations that	880	saving power, as the program will "bundle" timer callback invocations that
765	are "near" in time together, by delaying some, thus reducing the number of	881	are "near" in time together, by delaying some, thus reducing the number of
766	times the process sleeps and wakes up again. Another useful technique to	882	times the process sleeps and wakes up again. Another useful technique to
767	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	883	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
768	they fire on, say, one-second boundaries only.	884	they fire on, say, one-second boundaries only.
769		885
		886	Example: we only need 0.1s timeout granularity, and we wish not to poll
		887	more often than 100 times per second:
		888
		889	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		890	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		891
		892	=item ev_invoke_pending (loop)
		893
		894	This call will simply invoke all pending watchers while resetting their
		895	pending state. Normally, C<ev_loop> does this automatically when required,
		896	but when overriding the invoke callback this call comes handy.
		897
		898	=item int ev_pending_count (loop)
		899
		900	Returns the number of pending watchers - zero indicates that no watchers
		901	are pending.
		902
		903	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		904
		905	This overrides the invoke pending functionality of the loop: Instead of
		906	invoking all pending watchers when there are any, C<ev_loop> will call
		907	this callback instead. This is useful, for example, when you want to
		908	invoke the actual watchers inside another context (another thread etc.).
		909
		910	If you want to reset the callback, use C<ev_invoke_pending> as new
		911	callback.
		912
		913	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		914
		915	Sometimes you want to share the same loop between multiple threads. This
		916	can be done relatively simply by putting mutex_lock/unlock calls around
		917	each call to a libev function.
		918
		919	However, C<ev_loop> can run an indefinite time, so it is not feasible to
		920	wait for it to return. One way around this is to wake up the loop via
		921	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>
		922	and I<acquire> callbacks on the loop.
		923
		924	When set, then C<release> will be called just before the thread is
		925	suspended waiting for new events, and C<acquire> is called just
		926	afterwards.
		927
		928	Ideally, C<release> will just call your mutex_unlock function, and
		929	C<acquire> will just call the mutex_lock function again.
		930
		931	While event loop modifications are allowed between invocations of
		932	C<release> and C<acquire> (that's their only purpose after all), no
		933	modifications done will affect the event loop, i.e. adding watchers will
		934	have no effect on the set of file descriptors being watched, or the time
		935	waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it
		936	to take note of any changes you made.
		937
		938	In theory, threads executing C<ev_loop> will be async-cancel safe between
		939	invocations of C<release> and C<acquire>.
		940
		941	See also the locking example in the C<THREADS> section later in this
		942	document.
		943
		944	=item ev_set_userdata (loop, void *data)
		945
		946	=item ev_userdata (loop)
		947
		948	Set and retrieve a single C<void *> associated with a loop. When
		949	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		950	C<0.>
		951
		952	These two functions can be used to associate arbitrary data with a loop,
		953	and are intended solely for the C<invoke_pending_cb>, C<release> and
		954	C<acquire> callbacks described above, but of course can be (ab-)used for
		955	any other purpose as well.
		956
770	=item ev_loop_verify (loop)	957	=item ev_loop_verify (loop)
771		958
772	This function only does something when C<EV_VERIFY> support has been	959	This function only does something when C<EV_VERIFY> support has been
773	compiled in. which is the default for non-minimal builds. It tries to go	960	compiled in, which is the default for non-minimal builds. It tries to go
774	through all internal structures and checks them for validity. If anything	961	through all internal structures and checks them for validity. If anything
775	is found to be inconsistent, it will print an error message to standard	962	is found to be inconsistent, it will print an error message to standard
776	error and call C<abort ()>.	963	error and call C<abort ()>.
777		964
778	This can be used to catch bugs inside libev itself: under normal	965	This can be used to catch bugs inside libev itself: under normal
…		…
782	=back	969	=back
783		970
784		971
785	=head1 ANATOMY OF A WATCHER	972	=head1 ANATOMY OF A WATCHER
786		973
		974	In the following description, uppercase C<TYPE> in names stands for the
		975	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		976	watchers and C<ev_io_start> for I/O watchers.
		977
787	A watcher is a structure that you create and register to record your	978	A watcher is a structure that you create and register to record your
788	interest in some event. For instance, if you want to wait for STDIN to	979	interest in some event. For instance, if you want to wait for STDIN to
789	become readable, you would create an C<ev_io> watcher for that:	980	become readable, you would create an C<ev_io> watcher for that:
790		981
791	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	982	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
792	{	983	{
793	ev_io_stop (w);	984	ev_io_stop (w);
794	ev_unloop (loop, EVUNLOOP_ALL);	985	ev_unloop (loop, EVUNLOOP_ALL);
795	}	986	}
796		987
797	struct ev_loop *loop = ev_default_loop (0);	988	struct ev_loop *loop = ev_default_loop (0);
		989
798	struct ev_io stdin_watcher;	990	ev_io stdin_watcher;
		991
799	ev_init (&stdin_watcher, my_cb);	992	ev_init (&stdin_watcher, my_cb);
800	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	993	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
801	ev_io_start (loop, &stdin_watcher);	994	ev_io_start (loop, &stdin_watcher);
		995
802	ev_loop (loop, 0);	996	ev_loop (loop, 0);
803		997
804	As you can see, you are responsible for allocating the memory for your	998	As you can see, you are responsible for allocating the memory for your
805	watcher structures (and it is usually a bad idea to do this on the stack,	999	watcher structures (and it is I<usually> a bad idea to do this on the
806	although this can sometimes be quite valid).	1000	stack).
		1001
		1002	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		1003	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
807		1004
808	Each watcher structure must be initialised by a call to C<ev_init	1005	Each watcher structure must be initialised by a call to C<ev_init
809	(watcher *, callback)>, which expects a callback to be provided. This	1006	(watcher *, callback)>, which expects a callback to be provided. This
810	callback gets invoked each time the event occurs (or, in the case of I/O	1007	callback gets invoked each time the event occurs (or, in the case of I/O
811	watchers, each time the event loop detects that the file descriptor given	1008	watchers, each time the event loop detects that the file descriptor given
812	is readable and/or writable).	1009	is readable and/or writable).
813		1010
814	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1011	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
815	with arguments specific to this watcher type. There is also a macro	1012	macro to configure it, with arguments specific to the watcher type. There
816	to combine initialisation and setting in one call: C<< ev_<type>_init	1013	is also a macro to combine initialisation and setting in one call: C<<
817	(watcher *, callback, ...) >>.	1014	ev_TYPE_init (watcher *, callback, ...) >>.
818		1015
819	To make the watcher actually watch out for events, you have to start it	1016	To make the watcher actually watch out for events, you have to start it
820	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	1017	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
821	*) >>), and you can stop watching for events at any time by calling the	1018	*) >>), and you can stop watching for events at any time by calling the
822	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1019	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
823		1020
824	As long as your watcher is active (has been started but not stopped) you	1021	As long as your watcher is active (has been started but not stopped) you
825	must not touch the values stored in it. Most specifically you must never	1022	must not touch the values stored in it. Most specifically you must never
826	reinitialise it or call its C<set> macro.	1023	reinitialise it or call its C<ev_TYPE_set> macro.
827		1024
828	Each and every callback receives the event loop pointer as first, the	1025	Each and every callback receives the event loop pointer as first, the
829	registered watcher structure as second, and a bitset of received events as	1026	registered watcher structure as second, and a bitset of received events as
830	third argument.	1027	third argument.
831		1028
…		…
840	=item C<EV_WRITE>	1037	=item C<EV_WRITE>
841		1038
842	The file descriptor in the C<ev_io> watcher has become readable and/or	1039	The file descriptor in the C<ev_io> watcher has become readable and/or
843	writable.	1040	writable.
844		1041
845	=item C<EV_TIMEOUT>	1042	=item C<EV_TIMER>
846		1043
847	The C<ev_timer> watcher has timed out.	1044	The C<ev_timer> watcher has timed out.
848		1045
849	=item C<EV_PERIODIC>	1046	=item C<EV_PERIODIC>
850		1047
…		…
889		1086
890	=item C<EV_ASYNC>	1087	=item C<EV_ASYNC>
891		1088
892	The given async watcher has been asynchronously notified (see C<ev_async>).	1089	The given async watcher has been asynchronously notified (see C<ev_async>).
893		1090
		1091	=item C<EV_CUSTOM>
		1092
		1093	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1094	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		1095
894	=item C<EV_ERROR>	1096	=item C<EV_ERROR>
895		1097
896	An unspecified error has occurred, the watcher has been stopped. This might	1098	An unspecified error has occurred, the watcher has been stopped. This might
897	happen because the watcher could not be properly started because libev	1099	happen because the watcher could not be properly started because libev
898	ran out of memory, a file descriptor was found to be closed or any other	1100	ran out of memory, a file descriptor was found to be closed or any other
		1101	problem. Libev considers these application bugs.
		1102
899	problem. You best act on it by reporting the problem and somehow coping	1103	You best act on it by reporting the problem and somehow coping with the
900	with the watcher being stopped.	1104	watcher being stopped. Note that well-written programs should not receive
		1105	an error ever, so when your watcher receives it, this usually indicates a
		1106	bug in your program.
901		1107
902	Libev will usually signal a few "dummy" events together with an error, for	1108	Libev will usually signal a few "dummy" events together with an error, for
903	example it might indicate that a fd is readable or writable, and if your	1109	example it might indicate that a fd is readable or writable, and if your
904	callbacks is well-written it can just attempt the operation and cope with	1110	callbacks is well-written it can just attempt the operation and cope with
905	the error from read() or write(). This will not work in multi-threaded	1111	the error from read() or write(). This will not work in multi-threaded
…		…
908		1114
909	=back	1115	=back
910		1116
911	=head2 GENERIC WATCHER FUNCTIONS	1117	=head2 GENERIC WATCHER FUNCTIONS
912		1118
913	In the following description, C<TYPE> stands for the watcher type,
914	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
915
916	=over 4	1119	=over 4
917		1120
918	=item C<ev_init> (ev_TYPE *watcher, callback)	1121	=item C<ev_init> (ev_TYPE *watcher, callback)
919		1122
920	This macro initialises the generic portion of a watcher. The contents	1123	This macro initialises the generic portion of a watcher. The contents
…		…
925	which rolls both calls into one.	1128	which rolls both calls into one.
926		1129
927	You can reinitialise a watcher at any time as long as it has been stopped	1130	You can reinitialise a watcher at any time as long as it has been stopped
928	(or never started) and there are no pending events outstanding.	1131	(or never started) and there are no pending events outstanding.
929		1132
930	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1133	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
931	int revents)>.	1134	int revents)>.
932		1135
933	Example: Initialise an C<ev_io> watcher in two steps.	1136	Example: Initialise an C<ev_io> watcher in two steps.
934		1137
935	ev_io w;	1138	ev_io w;
936	ev_init (&w, my_cb);	1139	ev_init (&w, my_cb);
937	ev_io_set (&w, STDIN_FILENO, EV_READ);	1140	ev_io_set (&w, STDIN_FILENO, EV_READ);
938		1141
939	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1142	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
940		1143
941	This macro initialises the type-specific parts of a watcher. You need to	1144	This macro initialises the type-specific parts of a watcher. You need to
942	call C<ev_init> at least once before you call this macro, but you can	1145	call C<ev_init> at least once before you call this macro, but you can
943	call C<ev_TYPE_set> any number of times. You must not, however, call this	1146	call C<ev_TYPE_set> any number of times. You must not, however, call this
944	macro on a watcher that is active (it can be pending, however, which is a	1147	macro on a watcher that is active (it can be pending, however, which is a
…		…
957		1160
958	Example: Initialise and set an C<ev_io> watcher in one step.	1161	Example: Initialise and set an C<ev_io> watcher in one step.
959		1162
960	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1163	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
961		1164
962	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1165	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
963		1166
964	Starts (activates) the given watcher. Only active watchers will receive	1167	Starts (activates) the given watcher. Only active watchers will receive
965	events. If the watcher is already active nothing will happen.	1168	events. If the watcher is already active nothing will happen.
966		1169
967	Example: Start the C<ev_io> watcher that is being abused as example in this	1170	Example: Start the C<ev_io> watcher that is being abused as example in this
968	whole section.	1171	whole section.
969		1172
970	ev_io_start (EV_DEFAULT_UC, &w);	1173	ev_io_start (EV_DEFAULT_UC, &w);
971		1174
972	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1175	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
973		1176
974	Stops the given watcher if active, and clears the pending status (whether	1177	Stops the given watcher if active, and clears the pending status (whether
975	the watcher was active or not).	1178	the watcher was active or not).
976		1179
977	It is possible that stopped watchers are pending - for example,	1180	It is possible that stopped watchers are pending - for example,
…		…
1002	=item ev_cb_set (ev_TYPE *watcher, callback)	1205	=item ev_cb_set (ev_TYPE *watcher, callback)
1003		1206
1004	Change the callback. You can change the callback at virtually any time	1207	Change the callback. You can change the callback at virtually any time
1005	(modulo threads).	1208	(modulo threads).
1006		1209
1007	=item ev_set_priority (ev_TYPE *watcher, priority)	1210	=item ev_set_priority (ev_TYPE *watcher, int priority)
1008		1211
1009	=item int ev_priority (ev_TYPE *watcher)	1212	=item int ev_priority (ev_TYPE *watcher)
1010		1213
1011	Set and query the priority of the watcher. The priority is a small	1214	Set and query the priority of the watcher. The priority is a small
1012	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1215	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1013	(default: C<-2>). Pending watchers with higher priority will be invoked	1216	(default: C<-2>). Pending watchers with higher priority will be invoked
1014	before watchers with lower priority, but priority will not keep watchers	1217	before watchers with lower priority, but priority will not keep watchers
1015	from being executed (except for C<ev_idle> watchers).	1218	from being executed (except for C<ev_idle> watchers).
1016		1219
1017	This means that priorities are I<only> used for ordering callback
1018	invocation after new events have been received. This is useful, for
1019	example, to reduce latency after idling, or more often, to bind two
1020	watchers on the same event and make sure one is called first.
1021
1022	If you need to suppress invocation when higher priority events are pending	1220	If you need to suppress invocation when higher priority events are pending
1023	you need to look at C<ev_idle> watchers, which provide this functionality.	1221	you need to look at C<ev_idle> watchers, which provide this functionality.
1024		1222
1025	You I<must not> change the priority of a watcher as long as it is active or	1223	You I<must not> change the priority of a watcher as long as it is active or
1026	pending.	1224	pending.
1027		1225
		1226	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1227	fine, as long as you do not mind that the priority value you query might
		1228	or might not have been clamped to the valid range.
		1229
1028	The default priority used by watchers when no priority has been set is	1230	The default priority used by watchers when no priority has been set is
1029	always C<0>, which is supposed to not be too high and not be too low :).	1231	always C<0>, which is supposed to not be too high and not be too low :).
1030		1232
1031	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1233	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1032	fine, as long as you do not mind that the priority value you query might	1234	priorities.
1033	or might not have been adjusted to be within valid range.
1034		1235
1035	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1236	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1036		1237
1037	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1238	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1038	C<loop> nor C<revents> need to be valid as long as the watcher callback	1239	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1045	returns its C<revents> bitset (as if its callback was invoked). If the	1246	returns its C<revents> bitset (as if its callback was invoked). If the
1046	watcher isn't pending it does nothing and returns C<0>.	1247	watcher isn't pending it does nothing and returns C<0>.
1047		1248
1048	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1249	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1049	callback to be invoked, which can be accomplished with this function.	1250	callback to be invoked, which can be accomplished with this function.
		1251
		1252	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1253
		1254	Feeds the given event set into the event loop, as if the specified event
		1255	had happened for the specified watcher (which must be a pointer to an
		1256	initialised but not necessarily started event watcher). Obviously you must
		1257	not free the watcher as long as it has pending events.
		1258
		1259	Stopping the watcher, letting libev invoke it, or calling
		1260	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1261	not started in the first place.
		1262
		1263	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1264	functions that do not need a watcher.
1050		1265
1051	=back	1266	=back
1052		1267
1053		1268
1054	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1269	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
1060	member, you can also "subclass" the watcher type and provide your own	1275	member, you can also "subclass" the watcher type and provide your own
1061	data:	1276	data:
1062		1277
1063	struct my_io	1278	struct my_io
1064	{	1279	{
1065	struct ev_io io;	1280	ev_io io;
1066	int otherfd;	1281	int otherfd;
1067	void *somedata;	1282	void *somedata;
1068	struct whatever *mostinteresting;	1283	struct whatever *mostinteresting;
1069	};	1284	};
1070		1285
…		…
1073	ev_io_init (&w.io, my_cb, fd, EV_READ);	1288	ev_io_init (&w.io, my_cb, fd, EV_READ);
1074		1289
1075	And since your callback will be called with a pointer to the watcher, you	1290	And since your callback will be called with a pointer to the watcher, you
1076	can cast it back to your own type:	1291	can cast it back to your own type:
1077		1292
1078	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1293	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1079	{	1294	{
1080	struct my_io *w = (struct my_io *)w_;	1295	struct my_io *w = (struct my_io *)w_;
1081	...	1296	...
1082	}	1297	}
1083		1298
…		…
1101	programmers):	1316	programmers):
1102		1317
1103	#include <stddef.h>	1318	#include <stddef.h>
1104		1319
1105	static void	1320	static void
1106	t1_cb (EV_P_ struct ev_timer *w, int revents)	1321	t1_cb (EV_P_ ev_timer *w, int revents)
1107	{	1322	{
1108	struct my_biggy big = (struct my_biggy *	1323	struct my_biggy big = (struct my_biggy *)
1109	(((char *)w) - offsetof (struct my_biggy, t1));	1324	(((char *)w) - offsetof (struct my_biggy, t1));
1110	}	1325	}
1111		1326
1112	static void	1327	static void
1113	t2_cb (EV_P_ struct ev_timer *w, int revents)	1328	t2_cb (EV_P_ ev_timer *w, int revents)
1114	{	1329	{
1115	struct my_biggy big = (struct my_biggy *	1330	struct my_biggy big = (struct my_biggy *)
1116	(((char *)w) - offsetof (struct my_biggy, t2));	1331	(((char *)w) - offsetof (struct my_biggy, t2));
1117	}	1332	}
		1333
		1334	=head2 WATCHER PRIORITY MODELS
		1335
		1336	Many event loops support I<watcher priorities>, which are usually small
		1337	integers that influence the ordering of event callback invocation
		1338	between watchers in some way, all else being equal.
		1339
		1340	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1341	description for the more technical details such as the actual priority
		1342	range.
		1343
		1344	There are two common ways how these these priorities are being interpreted
		1345	by event loops:
		1346
		1347	In the more common lock-out model, higher priorities "lock out" invocation
		1348	of lower priority watchers, which means as long as higher priority
		1349	watchers receive events, lower priority watchers are not being invoked.
		1350
		1351	The less common only-for-ordering model uses priorities solely to order
		1352	callback invocation within a single event loop iteration: Higher priority
		1353	watchers are invoked before lower priority ones, but they all get invoked
		1354	before polling for new events.
		1355
		1356	Libev uses the second (only-for-ordering) model for all its watchers
		1357	except for idle watchers (which use the lock-out model).
		1358
		1359	The rationale behind this is that implementing the lock-out model for
		1360	watchers is not well supported by most kernel interfaces, and most event
		1361	libraries will just poll for the same events again and again as long as
		1362	their callbacks have not been executed, which is very inefficient in the
		1363	common case of one high-priority watcher locking out a mass of lower
		1364	priority ones.
		1365
		1366	Static (ordering) priorities are most useful when you have two or more
		1367	watchers handling the same resource: a typical usage example is having an
		1368	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1369	timeouts. Under load, data might be received while the program handles
		1370	other jobs, but since timers normally get invoked first, the timeout
		1371	handler will be executed before checking for data. In that case, giving
		1372	the timer a lower priority than the I/O watcher ensures that I/O will be
		1373	handled first even under adverse conditions (which is usually, but not
		1374	always, what you want).
		1375
		1376	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1377	will only be executed when no same or higher priority watchers have
		1378	received events, they can be used to implement the "lock-out" model when
		1379	required.
		1380
		1381	For example, to emulate how many other event libraries handle priorities,
		1382	you can associate an C<ev_idle> watcher to each such watcher, and in
		1383	the normal watcher callback, you just start the idle watcher. The real
		1384	processing is done in the idle watcher callback. This causes libev to
		1385	continuously poll and process kernel event data for the watcher, but when
		1386	the lock-out case is known to be rare (which in turn is rare :), this is
		1387	workable.
		1388
		1389	Usually, however, the lock-out model implemented that way will perform
		1390	miserably under the type of load it was designed to handle. In that case,
		1391	it might be preferable to stop the real watcher before starting the
		1392	idle watcher, so the kernel will not have to process the event in case
		1393	the actual processing will be delayed for considerable time.
		1394
		1395	Here is an example of an I/O watcher that should run at a strictly lower
		1396	priority than the default, and which should only process data when no
		1397	other events are pending:
		1398
		1399	ev_idle idle; // actual processing watcher
		1400	ev_io io; // actual event watcher
		1401
		1402	static void
		1403	io_cb (EV_P_ ev_io *w, int revents)
		1404	{
		1405	// stop the I/O watcher, we received the event, but
		1406	// are not yet ready to handle it.
		1407	ev_io_stop (EV_A_ w);
		1408
		1409	// start the idle watcher to handle the actual event.
		1410	// it will not be executed as long as other watchers
		1411	// with the default priority are receiving events.
		1412	ev_idle_start (EV_A_ &idle);
		1413	}
		1414
		1415	static void
		1416	idle_cb (EV_P_ ev_idle *w, int revents)
		1417	{
		1418	// actual processing
		1419	read (STDIN_FILENO, ...);
		1420
		1421	// have to start the I/O watcher again, as
		1422	// we have handled the event
		1423	ev_io_start (EV_P_ &io);
		1424	}
		1425
		1426	// initialisation
		1427	ev_idle_init (&idle, idle_cb);
		1428	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1429	ev_io_start (EV_DEFAULT_ &io);
		1430
		1431	In the "real" world, it might also be beneficial to start a timer, so that
		1432	low-priority connections can not be locked out forever under load. This
		1433	enables your program to keep a lower latency for important connections
		1434	during short periods of high load, while not completely locking out less
		1435	important ones.
1118		1436
1119		1437
1120	=head1 WATCHER TYPES	1438	=head1 WATCHER TYPES
1121		1439
1122	This section describes each watcher in detail, but will not repeat	1440	This section describes each watcher in detail, but will not repeat
…		…
1148	descriptors to non-blocking mode is also usually a good idea (but not	1466	descriptors to non-blocking mode is also usually a good idea (but not
1149	required if you know what you are doing).	1467	required if you know what you are doing).
1150		1468
1151	If you cannot use non-blocking mode, then force the use of a	1469	If you cannot use non-blocking mode, then force the use of a
1152	known-to-be-good backend (at the time of this writing, this includes only	1470	known-to-be-good backend (at the time of this writing, this includes only
1153	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).	1471	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1472	descriptors for which non-blocking operation makes no sense (such as
		1473	files) - libev doesn't guarantee any specific behaviour in that case.
1154		1474
1155	Another thing you have to watch out for is that it is quite easy to	1475	Another thing you have to watch out for is that it is quite easy to
1156	receive "spurious" readiness notifications, that is your callback might	1476	receive "spurious" readiness notifications, that is your callback might
1157	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1477	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1158	because there is no data. Not only are some backends known to create a	1478	because there is no data. Not only are some backends known to create a
…		…
1223		1543
1224	So when you encounter spurious, unexplained daemon exits, make sure you	1544	So when you encounter spurious, unexplained daemon exits, make sure you
1225	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1545	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1226	somewhere, as that would have given you a big clue).	1546	somewhere, as that would have given you a big clue).
1227		1547
		1548	=head3 The special problem of accept()ing when you can't
		1549
		1550	Many implementations of the POSIX C<accept> function (for example,
		1551	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1552	connection from the pending queue in all error cases.
		1553
		1554	For example, larger servers often run out of file descriptors (because
		1555	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1556	rejecting the connection, leading to libev signalling readiness on
		1557	the next iteration again (the connection still exists after all), and
		1558	typically causing the program to loop at 100% CPU usage.
		1559
		1560	Unfortunately, the set of errors that cause this issue differs between
		1561	operating systems, there is usually little the app can do to remedy the
		1562	situation, and no known thread-safe method of removing the connection to
		1563	cope with overload is known (to me).
		1564
		1565	One of the easiest ways to handle this situation is to just ignore it
		1566	- when the program encounters an overload, it will just loop until the
		1567	situation is over. While this is a form of busy waiting, no OS offers an
		1568	event-based way to handle this situation, so it's the best one can do.
		1569
		1570	A better way to handle the situation is to log any errors other than
		1571	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1572	messages, and continue as usual, which at least gives the user an idea of
		1573	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1574	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1575	usage.
		1576
		1577	If your program is single-threaded, then you could also keep a dummy file
		1578	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1579	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1580	close that fd, and create a new dummy fd. This will gracefully refuse
		1581	clients under typical overload conditions.
		1582
		1583	The last way to handle it is to simply log the error and C<exit>, as
		1584	is often done with C<malloc> failures, but this results in an easy
		1585	opportunity for a DoS attack.
1228		1586
1229	=head3 Watcher-Specific Functions	1587	=head3 Watcher-Specific Functions
1230		1588
1231	=over 4	1589	=over 4
1232		1590
…		…
1253	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1611	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1254	readable, but only once. Since it is likely line-buffered, you could	1612	readable, but only once. Since it is likely line-buffered, you could
1255	attempt to read a whole line in the callback.	1613	attempt to read a whole line in the callback.
1256		1614
1257	static void	1615	static void
1258	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1616	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1259	{	1617	{
1260	ev_io_stop (loop, w);	1618	ev_io_stop (loop, w);
1261	.. read from stdin here (or from w->fd) and handle any I/O errors	1619	.. read from stdin here (or from w->fd) and handle any I/O errors
1262	}	1620	}
1263		1621
1264	...	1622	...
1265	struct ev_loop *loop = ev_default_init (0);	1623	struct ev_loop *loop = ev_default_init (0);
1266	struct ev_io stdin_readable;	1624	ev_io stdin_readable;
1267	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1625	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1268	ev_io_start (loop, &stdin_readable);	1626	ev_io_start (loop, &stdin_readable);
1269	ev_loop (loop, 0);	1627	ev_loop (loop, 0);
1270		1628
1271		1629
…		…
1279	year, it will still time out after (roughly) one hour. "Roughly" because	1637	year, it will still time out after (roughly) one hour. "Roughly" because
1280	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1638	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1281	monotonic clock option helps a lot here).	1639	monotonic clock option helps a lot here).
1282		1640
1283	The callback is guaranteed to be invoked only I<after> its timeout has	1641	The callback is guaranteed to be invoked only I<after> its timeout has
1284	passed, but if multiple timers become ready during the same loop iteration	1642	passed (not I<at>, so on systems with very low-resolution clocks this
1285	then order of execution is undefined.	1643	might introduce a small delay). If multiple timers become ready during the
		1644	same loop iteration then the ones with earlier time-out values are invoked
		1645	before ones of the same priority with later time-out values (but this is
		1646	no longer true when a callback calls C<ev_loop> recursively).
		1647
		1648	=head3 Be smart about timeouts
		1649
		1650	Many real-world problems involve some kind of timeout, usually for error
		1651	recovery. A typical example is an HTTP request - if the other side hangs,
		1652	you want to raise some error after a while.
		1653
		1654	What follows are some ways to handle this problem, from obvious and
		1655	inefficient to smart and efficient.
		1656
		1657	In the following, a 60 second activity timeout is assumed - a timeout that
		1658	gets reset to 60 seconds each time there is activity (e.g. each time some
		1659	data or other life sign was received).
		1660
		1661	=over 4
		1662
		1663	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1664
		1665	This is the most obvious, but not the most simple way: In the beginning,
		1666	start the watcher:
		1667
		1668	ev_timer_init (timer, callback, 60., 0.);
		1669	ev_timer_start (loop, timer);
		1670
		1671	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1672	and start it again:
		1673
		1674	ev_timer_stop (loop, timer);
		1675	ev_timer_set (timer, 60., 0.);
		1676	ev_timer_start (loop, timer);
		1677
		1678	This is relatively simple to implement, but means that each time there is
		1679	some activity, libev will first have to remove the timer from its internal
		1680	data structure and then add it again. Libev tries to be fast, but it's
		1681	still not a constant-time operation.
		1682
		1683	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1684
		1685	This is the easiest way, and involves using C<ev_timer_again> instead of
		1686	C<ev_timer_start>.
		1687
		1688	To implement this, configure an C<ev_timer> with a C<repeat> value
		1689	of C<60> and then call C<ev_timer_again> at start and each time you
		1690	successfully read or write some data. If you go into an idle state where
		1691	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1692	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1693
		1694	That means you can ignore both the C<ev_timer_start> function and the
		1695	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1696	member and C<ev_timer_again>.
		1697
		1698	At start:
		1699
		1700	ev_init (timer, callback);
		1701	timer->repeat = 60.;
		1702	ev_timer_again (loop, timer);
		1703
		1704	Each time there is some activity:
		1705
		1706	ev_timer_again (loop, timer);
		1707
		1708	It is even possible to change the time-out on the fly, regardless of
		1709	whether the watcher is active or not:
		1710
		1711	timer->repeat = 30.;
		1712	ev_timer_again (loop, timer);
		1713
		1714	This is slightly more efficient then stopping/starting the timer each time
		1715	you want to modify its timeout value, as libev does not have to completely
		1716	remove and re-insert the timer from/into its internal data structure.
		1717
		1718	It is, however, even simpler than the "obvious" way to do it.
		1719
		1720	=item 3. Let the timer time out, but then re-arm it as required.
		1721
		1722	This method is more tricky, but usually most efficient: Most timeouts are
		1723	relatively long compared to the intervals between other activity - in
		1724	our example, within 60 seconds, there are usually many I/O events with
		1725	associated activity resets.
		1726
		1727	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1728	but remember the time of last activity, and check for a real timeout only
		1729	within the callback:
		1730
		1731	ev_tstamp last_activity; // time of last activity
		1732
		1733	static void
		1734	callback (EV_P_ ev_timer *w, int revents)
		1735	{
		1736	ev_tstamp now = ev_now (EV_A);
		1737	ev_tstamp timeout = last_activity + 60.;
		1738
		1739	// if last_activity + 60. is older than now, we did time out
		1740	if (timeout < now)
		1741	{
		1742	// timeout occurred, take action
		1743	}
		1744	else
		1745	{
		1746	// callback was invoked, but there was some activity, re-arm
		1747	// the watcher to fire in last_activity + 60, which is
		1748	// guaranteed to be in the future, so "again" is positive:
		1749	w->repeat = timeout - now;
		1750	ev_timer_again (EV_A_ w);
		1751	}
		1752	}
		1753
		1754	To summarise the callback: first calculate the real timeout (defined
		1755	as "60 seconds after the last activity"), then check if that time has
		1756	been reached, which means something I<did>, in fact, time out. Otherwise
		1757	the callback was invoked too early (C<timeout> is in the future), so
		1758	re-schedule the timer to fire at that future time, to see if maybe we have
		1759	a timeout then.
		1760
		1761	Note how C<ev_timer_again> is used, taking advantage of the
		1762	C<ev_timer_again> optimisation when the timer is already running.
		1763
		1764	This scheme causes more callback invocations (about one every 60 seconds
		1765	minus half the average time between activity), but virtually no calls to
		1766	libev to change the timeout.
		1767
		1768	To start the timer, simply initialise the watcher and set C<last_activity>
		1769	to the current time (meaning we just have some activity :), then call the
		1770	callback, which will "do the right thing" and start the timer:
		1771
		1772	ev_init (timer, callback);
		1773	last_activity = ev_now (loop);
		1774	callback (loop, timer, EV_TIMER);
		1775
		1776	And when there is some activity, simply store the current time in
		1777	C<last_activity>, no libev calls at all:
		1778
		1779	last_activity = ev_now (loop);
		1780
		1781	This technique is slightly more complex, but in most cases where the
		1782	time-out is unlikely to be triggered, much more efficient.
		1783
		1784	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1785	callback :) - just change the timeout and invoke the callback, which will
		1786	fix things for you.
		1787
		1788	=item 4. Wee, just use a double-linked list for your timeouts.
		1789
		1790	If there is not one request, but many thousands (millions...), all
		1791	employing some kind of timeout with the same timeout value, then one can
		1792	do even better:
		1793
		1794	When starting the timeout, calculate the timeout value and put the timeout
		1795	at the I<end> of the list.
		1796
		1797	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1798	the list is expected to fire (for example, using the technique #3).
		1799
		1800	When there is some activity, remove the timer from the list, recalculate
		1801	the timeout, append it to the end of the list again, and make sure to
		1802	update the C<ev_timer> if it was taken from the beginning of the list.
		1803
		1804	This way, one can manage an unlimited number of timeouts in O(1) time for
		1805	starting, stopping and updating the timers, at the expense of a major
		1806	complication, and having to use a constant timeout. The constant timeout
		1807	ensures that the list stays sorted.
		1808
		1809	=back
		1810
		1811	So which method the best?
		1812
		1813	Method #2 is a simple no-brain-required solution that is adequate in most
		1814	situations. Method #3 requires a bit more thinking, but handles many cases
		1815	better, and isn't very complicated either. In most case, choosing either
		1816	one is fine, with #3 being better in typical situations.
		1817
		1818	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1819	rather complicated, but extremely efficient, something that really pays
		1820	off after the first million or so of active timers, i.e. it's usually
		1821	overkill :)
1286		1822
1287	=head3 The special problem of time updates	1823	=head3 The special problem of time updates
1288		1824
1289	Establishing the current time is a costly operation (it usually takes at	1825	Establishing the current time is a costly operation (it usually takes at
1290	least two system calls): EV therefore updates its idea of the current	1826	least two system calls): EV therefore updates its idea of the current
…		…
1302		1838
1303	If the event loop is suspended for a long time, you can also force an	1839	If the event loop is suspended for a long time, you can also force an
1304	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1840	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1305	()>.	1841	()>.
1306		1842
		1843	=head3 The special problems of suspended animation
		1844
		1845	When you leave the server world it is quite customary to hit machines that
		1846	can suspend/hibernate - what happens to the clocks during such a suspend?
		1847
		1848	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1849	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1850	to run until the system is suspended, but they will not advance while the
		1851	system is suspended. That means, on resume, it will be as if the program
		1852	was frozen for a few seconds, but the suspend time will not be counted
		1853	towards C<ev_timer> when a monotonic clock source is used. The real time
		1854	clock advanced as expected, but if it is used as sole clocksource, then a
		1855	long suspend would be detected as a time jump by libev, and timers would
		1856	be adjusted accordingly.
		1857
		1858	I would not be surprised to see different behaviour in different between
		1859	operating systems, OS versions or even different hardware.
		1860
		1861	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1862	time jump in the monotonic clocks and the realtime clock. If the program
		1863	is suspended for a very long time, and monotonic clock sources are in use,
		1864	then you can expect C<ev_timer>s to expire as the full suspension time
		1865	will be counted towards the timers. When no monotonic clock source is in
		1866	use, then libev will again assume a timejump and adjust accordingly.
		1867
		1868	It might be beneficial for this latter case to call C<ev_suspend>
		1869	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1870	deterministic behaviour in this case (you can do nothing against
		1871	C<SIGSTOP>).
		1872
1307	=head3 Watcher-Specific Functions and Data Members	1873	=head3 Watcher-Specific Functions and Data Members
1308		1874
1309	=over 4	1875	=over 4
1310		1876
1311	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1877	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1334	If the timer is started but non-repeating, stop it (as if it timed out).	1900	If the timer is started but non-repeating, stop it (as if it timed out).
1335		1901
1336	If the timer is repeating, either start it if necessary (with the	1902	If the timer is repeating, either start it if necessary (with the
1337	C<repeat> value), or reset the running timer to the C<repeat> value.	1903	C<repeat> value), or reset the running timer to the C<repeat> value.
1338		1904
1339	This sounds a bit complicated, but here is a useful and typical	1905	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1340	example: Imagine you have a TCP connection and you want a so-called idle	1906	usage example.
1341	timeout, that is, you want to be called when there have been, say, 60
1342	seconds of inactivity on the socket. The easiest way to do this is to
1343	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1344	C<ev_timer_again> each time you successfully read or write some data. If
1345	you go into an idle state where you do not expect data to travel on the
1346	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1347	automatically restart it if need be.
1348		1907
1349	That means you can ignore the C<after> value and C<ev_timer_start>	1908	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1350	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1351		1909
1352	ev_timer_init (timer, callback, 0., 5.);	1910	Returns the remaining time until a timer fires. If the timer is active,
1353	ev_timer_again (loop, timer);	1911	then this time is relative to the current event loop time, otherwise it's
1354	...	1912	the timeout value currently configured.
1355	timer->again = 17.;
1356	ev_timer_again (loop, timer);
1357	...
1358	timer->again = 10.;
1359	ev_timer_again (loop, timer);
1360		1913
1361	This is more slightly efficient then stopping/starting the timer each time	1914	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1362	you want to modify its timeout value.	1915	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
1363		1916	will return C<4>. When the timer expires and is restarted, it will return
1364	Note, however, that it is often even more efficient to remember the	1917	roughly C<7> (likely slightly less as callback invocation takes some time,
1365	time of the last activity and let the timer time-out naturally. In the	1918	too), and so on.
1366	callback, you then check whether the time-out is real, or, if there was
1367	some activity, you reschedule the watcher to time-out in "last_activity +
1368	timeout - ev_now ()" seconds.
1369		1919
1370	=item ev_tstamp repeat [read-write]	1920	=item ev_tstamp repeat [read-write]
1371		1921
1372	The current C<repeat> value. Will be used each time the watcher times out	1922	The current C<repeat> value. Will be used each time the watcher times out
1373	or C<ev_timer_again> is called, and determines the next timeout (if any),	1923	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1378	=head3 Examples	1928	=head3 Examples
1379		1929
1380	Example: Create a timer that fires after 60 seconds.	1930	Example: Create a timer that fires after 60 seconds.
1381		1931
1382	static void	1932	static void
1383	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1933	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1384	{	1934	{
1385	.. one minute over, w is actually stopped right here	1935	.. one minute over, w is actually stopped right here
1386	}	1936	}
1387		1937
1388	struct ev_timer mytimer;	1938	ev_timer mytimer;
1389	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1939	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1390	ev_timer_start (loop, &mytimer);	1940	ev_timer_start (loop, &mytimer);
1391		1941
1392	Example: Create a timeout timer that times out after 10 seconds of	1942	Example: Create a timeout timer that times out after 10 seconds of
1393	inactivity.	1943	inactivity.
1394		1944
1395	static void	1945	static void
1396	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1946	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1397	{	1947	{
1398	.. ten seconds without any activity	1948	.. ten seconds without any activity
1399	}	1949	}
1400		1950
1401	struct ev_timer mytimer;	1951	ev_timer mytimer;
1402	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1952	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1403	ev_timer_again (&mytimer); /* start timer */	1953	ev_timer_again (&mytimer); /* start timer */
1404	ev_loop (loop, 0);	1954	ev_loop (loop, 0);
1405		1955
1406	// and in some piece of code that gets executed on any "activity":	1956	// and in some piece of code that gets executed on any "activity":
…		…
1411	=head2 C<ev_periodic> - to cron or not to cron?	1961	=head2 C<ev_periodic> - to cron or not to cron?
1412		1962
1413	Periodic watchers are also timers of a kind, but they are very versatile	1963	Periodic watchers are also timers of a kind, but they are very versatile
1414	(and unfortunately a bit complex).	1964	(and unfortunately a bit complex).
1415		1965
1416	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1966	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1417	but on wall clock time (absolute time). You can tell a periodic watcher	1967	relative time, the physical time that passes) but on wall clock time
1418	to trigger after some specific point in time. For example, if you tell a	1968	(absolute time, the thing you can read on your calender or clock). The
1419	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	1969	difference is that wall clock time can run faster or slower than real
1420	+ 10.>, that is, an absolute time not a delay) and then reset your system	1970	time, and time jumps are not uncommon (e.g. when you adjust your
1421	clock to January of the previous year, then it will take more than year	1971	wrist-watch).
1422	to trigger the event (unlike an C<ev_timer>, which would still trigger
1423	roughly 10 seconds later as it uses a relative timeout).
1424		1972
		1973	You can tell a periodic watcher to trigger after some specific point
		1974	in time: for example, if you tell a periodic watcher to trigger "in 10
		1975	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1976	not a delay) and then reset your system clock to January of the previous
		1977	year, then it will take a year or more to trigger the event (unlike an
		1978	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1979	it, as it uses a relative timeout).
		1980
1425	C<ev_periodic>s can also be used to implement vastly more complex timers,	1981	C<ev_periodic> watchers can also be used to implement vastly more complex
1426	such as triggering an event on each "midnight, local time", or other	1982	timers, such as triggering an event on each "midnight, local time", or
1427	complicated rules.	1983	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1984	those cannot react to time jumps.
1428		1985
1429	As with timers, the callback is guaranteed to be invoked only when the	1986	As with timers, the callback is guaranteed to be invoked only when the
1430	time (C<at>) has passed, but if multiple periodic timers become ready	1987	point in time where it is supposed to trigger has passed. If multiple
1431	during the same loop iteration, then order of execution is undefined.	1988	timers become ready during the same loop iteration then the ones with
		1989	earlier time-out values are invoked before ones with later time-out values
		1990	(but this is no longer true when a callback calls C<ev_loop> recursively).
1432		1991
1433	=head3 Watcher-Specific Functions and Data Members	1992	=head3 Watcher-Specific Functions and Data Members
1434		1993
1435	=over 4	1994	=over 4
1436		1995
1437	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1996	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1438		1997
1439	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1998	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1440		1999
1441	Lots of arguments, lets sort it out... There are basically three modes of	2000	Lots of arguments, let's sort it out... There are basically three modes of
1442	operation, and we will explain them from simplest to most complex:	2001	operation, and we will explain them from simplest to most complex:
1443		2002
1444	=over 4	2003	=over 4
1445		2004
1446	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2005	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1447		2006
1448	In this configuration the watcher triggers an event after the wall clock	2007	In this configuration the watcher triggers an event after the wall clock
1449	time C<at> has passed. It will not repeat and will not adjust when a time	2008	time C<offset> has passed. It will not repeat and will not adjust when a
1450	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2009	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1451	only run when the system clock reaches or surpasses this time.	2010	will be stopped and invoked when the system clock reaches or surpasses
		2011	this point in time.
1452		2012
1453	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2013	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1454		2014
1455	In this mode the watcher will always be scheduled to time out at the next	2015	In this mode the watcher will always be scheduled to time out at the next
1456	C<at + N * interval> time (for some integer N, which can also be negative)	2016	C<offset + N * interval> time (for some integer N, which can also be
1457	and then repeat, regardless of any time jumps.	2017	negative) and then repeat, regardless of any time jumps. The C<offset>
		2018	argument is merely an offset into the C<interval> periods.
1458		2019
1459	This can be used to create timers that do not drift with respect to the	2020	This can be used to create timers that do not drift with respect to the
1460	system clock, for example, here is a C<ev_periodic> that triggers each	2021	system clock, for example, here is an C<ev_periodic> that triggers each
1461	hour, on the hour:	2022	hour, on the hour (with respect to UTC):
1462		2023
1463	ev_periodic_set (&periodic, 0., 3600., 0);	2024	ev_periodic_set (&periodic, 0., 3600., 0);
1464		2025
1465	This doesn't mean there will always be 3600 seconds in between triggers,	2026	This doesn't mean there will always be 3600 seconds in between triggers,
1466	but only that the callback will be called when the system time shows a	2027	but only that the callback will be called when the system time shows a
1467	full hour (UTC), or more correctly, when the system time is evenly divisible	2028	full hour (UTC), or more correctly, when the system time is evenly divisible
1468	by 3600.	2029	by 3600.
1469		2030
1470	Another way to think about it (for the mathematically inclined) is that	2031	Another way to think about it (for the mathematically inclined) is that
1471	C<ev_periodic> will try to run the callback in this mode at the next possible	2032	C<ev_periodic> will try to run the callback in this mode at the next possible
1472	time where C<time = at (mod interval)>, regardless of any time jumps.	2033	time where C<time = offset (mod interval)>, regardless of any time jumps.
1473		2034
1474	For numerical stability it is preferable that the C<at> value is near	2035	For numerical stability it is preferable that the C<offset> value is near
1475	C<ev_now ()> (the current time), but there is no range requirement for	2036	C<ev_now ()> (the current time), but there is no range requirement for
1476	this value, and in fact is often specified as zero.	2037	this value, and in fact is often specified as zero.
1477		2038
1478	Note also that there is an upper limit to how often a timer can fire (CPU	2039	Note also that there is an upper limit to how often a timer can fire (CPU
1479	speed for example), so if C<interval> is very small then timing stability	2040	speed for example), so if C<interval> is very small then timing stability
1480	will of course deteriorate. Libev itself tries to be exact to be about one	2041	will of course deteriorate. Libev itself tries to be exact to be about one
1481	millisecond (if the OS supports it and the machine is fast enough).	2042	millisecond (if the OS supports it and the machine is fast enough).
1482		2043
1483	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2044	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1484		2045
1485	In this mode the values for C<interval> and C<at> are both being	2046	In this mode the values for C<interval> and C<offset> are both being
1486	ignored. Instead, each time the periodic watcher gets scheduled, the	2047	ignored. Instead, each time the periodic watcher gets scheduled, the
1487	reschedule callback will be called with the watcher as first, and the	2048	reschedule callback will be called with the watcher as first, and the
1488	current time as second argument.	2049	current time as second argument.
1489		2050
1490	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2051	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1491	ever, or make ANY event loop modifications whatsoever>.	2052	or make ANY other event loop modifications whatsoever, unless explicitly
		2053	allowed by documentation here>.
1492		2054
1493	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2055	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1494	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2056	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1495	only event loop modification you are allowed to do).	2057	only event loop modification you are allowed to do).
1496		2058
1497	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	2059	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1498	*w, ev_tstamp now)>, e.g.:	2060	*w, ev_tstamp now)>, e.g.:
1499		2061
		2062	static ev_tstamp
1500	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	2063	my_rescheduler (ev_periodic *w, ev_tstamp now)
1501	{	2064	{
1502	return now + 60.;	2065	return now + 60.;
1503	}	2066	}
1504		2067
1505	It must return the next time to trigger, based on the passed time value	2068	It must return the next time to trigger, based on the passed time value
…		…
1525	a different time than the last time it was called (e.g. in a crond like	2088	a different time than the last time it was called (e.g. in a crond like
1526	program when the crontabs have changed).	2089	program when the crontabs have changed).
1527		2090
1528	=item ev_tstamp ev_periodic_at (ev_periodic *)	2091	=item ev_tstamp ev_periodic_at (ev_periodic *)
1529		2092
1530	When active, returns the absolute time that the watcher is supposed to	2093	When active, returns the absolute time that the watcher is supposed
1531	trigger next.	2094	to trigger next. This is not the same as the C<offset> argument to
		2095	C<ev_periodic_set>, but indeed works even in interval and manual
		2096	rescheduling modes.
1532		2097
1533	=item ev_tstamp offset [read-write]	2098	=item ev_tstamp offset [read-write]
1534		2099
1535	When repeating, this contains the offset value, otherwise this is the	2100	When repeating, this contains the offset value, otherwise this is the
1536	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2101	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2102	although libev might modify this value for better numerical stability).
1537		2103
1538	Can be modified any time, but changes only take effect when the periodic	2104	Can be modified any time, but changes only take effect when the periodic
1539	timer fires or C<ev_periodic_again> is being called.	2105	timer fires or C<ev_periodic_again> is being called.
1540		2106
1541	=item ev_tstamp interval [read-write]	2107	=item ev_tstamp interval [read-write]
1542		2108
1543	The current interval value. Can be modified any time, but changes only	2109	The current interval value. Can be modified any time, but changes only
1544	take effect when the periodic timer fires or C<ev_periodic_again> is being	2110	take effect when the periodic timer fires or C<ev_periodic_again> is being
1545	called.	2111	called.
1546		2112
1547	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2113	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1548		2114
1549	The current reschedule callback, or C<0>, if this functionality is	2115	The current reschedule callback, or C<0>, if this functionality is
1550	switched off. Can be changed any time, but changes only take effect when	2116	switched off. Can be changed any time, but changes only take effect when
1551	the periodic timer fires or C<ev_periodic_again> is being called.	2117	the periodic timer fires or C<ev_periodic_again> is being called.
1552		2118
…		…
1557	Example: Call a callback every hour, or, more precisely, whenever the	2123	Example: Call a callback every hour, or, more precisely, whenever the
1558	system time is divisible by 3600. The callback invocation times have	2124	system time is divisible by 3600. The callback invocation times have
1559	potentially a lot of jitter, but good long-term stability.	2125	potentially a lot of jitter, but good long-term stability.
1560		2126
1561	static void	2127	static void
1562	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2128	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1563	{	2129	{
1564	... its now a full hour (UTC, or TAI or whatever your clock follows)	2130	... its now a full hour (UTC, or TAI or whatever your clock follows)
1565	}	2131	}
1566		2132
1567	struct ev_periodic hourly_tick;	2133	ev_periodic hourly_tick;
1568	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2134	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1569	ev_periodic_start (loop, &hourly_tick);	2135	ev_periodic_start (loop, &hourly_tick);
1570		2136
1571	Example: The same as above, but use a reschedule callback to do it:	2137	Example: The same as above, but use a reschedule callback to do it:
1572		2138
1573	#include <math.h>	2139	#include <math.h>
1574		2140
1575	static ev_tstamp	2141	static ev_tstamp
1576	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2142	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1577	{	2143	{
1578	return now + (3600. - fmod (now, 3600.));	2144	return now + (3600. - fmod (now, 3600.));
1579	}	2145	}
1580		2146
1581	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2147	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1582		2148
1583	Example: Call a callback every hour, starting now:	2149	Example: Call a callback every hour, starting now:
1584		2150
1585	struct ev_periodic hourly_tick;	2151	ev_periodic hourly_tick;
1586	ev_periodic_init (&hourly_tick, clock_cb,	2152	ev_periodic_init (&hourly_tick, clock_cb,
1587	fmod (ev_now (loop), 3600.), 3600., 0);	2153	fmod (ev_now (loop), 3600.), 3600., 0);
1588	ev_periodic_start (loop, &hourly_tick);	2154	ev_periodic_start (loop, &hourly_tick);
1589		2155
1590		2156
…		…
1593	Signal watchers will trigger an event when the process receives a specific	2159	Signal watchers will trigger an event when the process receives a specific
1594	signal one or more times. Even though signals are very asynchronous, libev	2160	signal one or more times. Even though signals are very asynchronous, libev
1595	will try it's best to deliver signals synchronously, i.e. as part of the	2161	will try it's best to deliver signals synchronously, i.e. as part of the
1596	normal event processing, like any other event.	2162	normal event processing, like any other event.
1597		2163
1598	If you want signals asynchronously, just use C<sigaction> as you would	2164	If you want signals to be delivered truly asynchronously, just use
1599	do without libev and forget about sharing the signal. You can even use	2165	C<sigaction> as you would do without libev and forget about sharing
1600	C<ev_async> from a signal handler to synchronously wake up an event loop.	2166	the signal. You can even use C<ev_async> from a signal handler to
		2167	synchronously wake up an event loop.
1601		2168
1602	You can configure as many watchers as you like per signal. Only when the	2169	You can configure as many watchers as you like for the same signal, but
		2170	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2171	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2172	C<SIGINT> in both the default loop and another loop at the same time. At
		2173	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2174
1603	first watcher gets started will libev actually register a signal handler	2175	When the first watcher gets started will libev actually register something
1604	with the kernel (thus it coexists with your own signal handlers as long as	2176	with the kernel (thus it coexists with your own signal handlers as long as
1605	you don't register any with libev for the same signal). Similarly, when	2177	you don't register any with libev for the same signal).
1606	the last signal watcher for a signal is stopped, libev will reset the
1607	signal handler to SIG_DFL (regardless of what it was set to before).
1608		2178
1609	If possible and supported, libev will install its handlers with	2179	If possible and supported, libev will install its handlers with
1610	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2180	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1611	interrupted. If you have a problem with system calls getting interrupted by	2181	not be unduly interrupted. If you have a problem with system calls getting
1612	signals you can block all signals in an C<ev_check> watcher and unblock	2182	interrupted by signals you can block all signals in an C<ev_check> watcher
1613	them in an C<ev_prepare> watcher.	2183	and unblock them in an C<ev_prepare> watcher.
		2184
		2185	=head3 The special problem of inheritance over fork/execve/pthread_create
		2186
		2187	Both the signal mask (C<sigprocmask>) and the signal disposition
		2188	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2189	stopping it again), that is, libev might or might not block the signal,
		2190	and might or might not set or restore the installed signal handler.
		2191
		2192	While this does not matter for the signal disposition (libev never
		2193	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2194	C<execve>), this matters for the signal mask: many programs do not expect
		2195	certain signals to be blocked.
		2196
		2197	This means that before calling C<exec> (from the child) you should reset
		2198	the signal mask to whatever "default" you expect (all clear is a good
		2199	choice usually).
		2200
		2201	The simplest way to ensure that the signal mask is reset in the child is
		2202	to install a fork handler with C<pthread_atfork> that resets it. That will
		2203	catch fork calls done by libraries (such as the libc) as well.
		2204
		2205	In current versions of libev, the signal will not be blocked indefinitely
		2206	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2207	the window of opportunity for problems, it will not go away, as libev
		2208	I<has> to modify the signal mask, at least temporarily.
		2209
		2210	So I can't stress this enough: I<If you do not reset your signal mask when
		2211	you expect it to be empty, you have a race condition in your code>. This
		2212	is not a libev-specific thing, this is true for most event libraries.
1614		2213
1615	=head3 Watcher-Specific Functions and Data Members	2214	=head3 Watcher-Specific Functions and Data Members
1616		2215
1617	=over 4	2216	=over 4
1618		2217
…		…
1632	=head3 Examples	2231	=head3 Examples
1633		2232
1634	Example: Try to exit cleanly on SIGINT.	2233	Example: Try to exit cleanly on SIGINT.
1635		2234
1636	static void	2235	static void
1637	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2236	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1638	{	2237	{
1639	ev_unloop (loop, EVUNLOOP_ALL);	2238	ev_unloop (loop, EVUNLOOP_ALL);
1640	}	2239	}
1641		2240
1642	struct ev_signal signal_watcher;	2241	ev_signal signal_watcher;
1643	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2242	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1644	ev_signal_start (loop, &signal_watcher);	2243	ev_signal_start (loop, &signal_watcher);
1645		2244
1646		2245
1647	=head2 C<ev_child> - watch out for process status changes	2246	=head2 C<ev_child> - watch out for process status changes
…		…
1650	some child status changes (most typically when a child of yours dies or	2249	some child status changes (most typically when a child of yours dies or
1651	exits). It is permissible to install a child watcher I<after> the child	2250	exits). It is permissible to install a child watcher I<after> the child
1652	has been forked (which implies it might have already exited), as long	2251	has been forked (which implies it might have already exited), as long
1653	as the event loop isn't entered (or is continued from a watcher), i.e.,	2252	as the event loop isn't entered (or is continued from a watcher), i.e.,
1654	forking and then immediately registering a watcher for the child is fine,	2253	forking and then immediately registering a watcher for the child is fine,
1655	but forking and registering a watcher a few event loop iterations later is	2254	but forking and registering a watcher a few event loop iterations later or
1656	not.	2255	in the next callback invocation is not.
1657		2256
1658	Only the default event loop is capable of handling signals, and therefore	2257	Only the default event loop is capable of handling signals, and therefore
1659	you can only register child watchers in the default event loop.	2258	you can only register child watchers in the default event loop.
1660		2259
		2260	Due to some design glitches inside libev, child watchers will always be
		2261	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2262	libev)
		2263
1661	=head3 Process Interaction	2264	=head3 Process Interaction
1662		2265
1663	Libev grabs C<SIGCHLD> as soon as the default event loop is	2266	Libev grabs C<SIGCHLD> as soon as the default event loop is
1664	initialised. This is necessary to guarantee proper behaviour even if	2267	initialised. This is necessary to guarantee proper behaviour even if the
1665	the first child watcher is started after the child exits. The occurrence	2268	first child watcher is started after the child exits. The occurrence
1666	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2269	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1667	synchronously as part of the event loop processing. Libev always reaps all	2270	synchronously as part of the event loop processing. Libev always reaps all
1668	children, even ones not watched.	2271	children, even ones not watched.
1669		2272
1670	=head3 Overriding the Built-In Processing	2273	=head3 Overriding the Built-In Processing
…		…
1680	=head3 Stopping the Child Watcher	2283	=head3 Stopping the Child Watcher
1681		2284
1682	Currently, the child watcher never gets stopped, even when the	2285	Currently, the child watcher never gets stopped, even when the
1683	child terminates, so normally one needs to stop the watcher in the	2286	child terminates, so normally one needs to stop the watcher in the
1684	callback. Future versions of libev might stop the watcher automatically	2287	callback. Future versions of libev might stop the watcher automatically
1685	when a child exit is detected.	2288	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2289	problem).
1686		2290
1687	=head3 Watcher-Specific Functions and Data Members	2291	=head3 Watcher-Specific Functions and Data Members
1688		2292
1689	=over 4	2293	=over 4
1690		2294
…		…
1722	its completion.	2326	its completion.
1723		2327
1724	ev_child cw;	2328	ev_child cw;
1725		2329
1726	static void	2330	static void
1727	child_cb (EV_P_ struct ev_child *w, int revents)	2331	child_cb (EV_P_ ev_child *w, int revents)
1728	{	2332	{
1729	ev_child_stop (EV_A_ w);	2333	ev_child_stop (EV_A_ w);
1730	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2334	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1731	}	2335	}
1732		2336
…		…
1747		2351
1748		2352
1749	=head2 C<ev_stat> - did the file attributes just change?	2353	=head2 C<ev_stat> - did the file attributes just change?
1750		2354
1751	This watches a file system path for attribute changes. That is, it calls	2355	This watches a file system path for attribute changes. That is, it calls
1752	C<stat> regularly (or when the OS says it changed) and sees if it changed	2356	C<stat> on that path in regular intervals (or when the OS says it changed)
1753	compared to the last time, invoking the callback if it did.	2357	and sees if it changed compared to the last time, invoking the callback if
		2358	it did.
1754		2359
1755	The path does not need to exist: changing from "path exists" to "path does	2360	The path does not need to exist: changing from "path exists" to "path does
1756	not exist" is a status change like any other. The condition "path does	2361	not exist" is a status change like any other. The condition "path does not
1757	not exist" is signified by the C<st_nlink> field being zero (which is	2362	exist" (or more correctly "path cannot be stat'ed") is signified by the
1758	otherwise always forced to be at least one) and all the other fields of	2363	C<st_nlink> field being zero (which is otherwise always forced to be at
1759	the stat buffer having unspecified contents.	2364	least one) and all the other fields of the stat buffer having unspecified
		2365	contents.
1760		2366
1761	The path I<should> be absolute and I<must not> end in a slash. If it is	2367	The path I<must not> end in a slash or contain special components such as
		2368	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1762	relative and your working directory changes, the behaviour is undefined.	2369	your working directory changes, then the behaviour is undefined.
1763		2370
1764	Since there is no standard kernel interface to do this, the portable	2371	Since there is no portable change notification interface available, the
1765	implementation simply calls C<stat (2)> regularly on the path to see if	2372	portable implementation simply calls C<stat(2)> regularly on the path
1766	it changed somehow. You can specify a recommended polling interval for	2373	to see if it changed somehow. You can specify a recommended polling
1767	this case. If you specify a polling interval of C<0> (highly recommended!)	2374	interval for this case. If you specify a polling interval of C<0> (highly
1768	then a I<suitable, unspecified default> value will be used (which	2375	recommended!) then a I<suitable, unspecified default> value will be used
1769	you can expect to be around five seconds, although this might change	2376	(which you can expect to be around five seconds, although this might
1770	dynamically). Libev will also impose a minimum interval which is currently	2377	change dynamically). Libev will also impose a minimum interval which is
1771	around C<0.1>, but thats usually overkill.	2378	currently around C<0.1>, but that's usually overkill.
1772		2379
1773	This watcher type is not meant for massive numbers of stat watchers,	2380	This watcher type is not meant for massive numbers of stat watchers,
1774	as even with OS-supported change notifications, this can be	2381	as even with OS-supported change notifications, this can be
1775	resource-intensive.	2382	resource-intensive.
1776		2383
1777	At the time of this writing, the only OS-specific interface implemented	2384	At the time of this writing, the only OS-specific interface implemented
1778	is the Linux inotify interface (implementing kqueue support is left as	2385	is the Linux inotify interface (implementing kqueue support is left as an
1779	an exercise for the reader. Note, however, that the author sees no way	2386	exercise for the reader. Note, however, that the author sees no way of
1780	of implementing C<ev_stat> semantics with kqueue).	2387	implementing C<ev_stat> semantics with kqueue, except as a hint).
1781		2388
1782	=head3 ABI Issues (Largefile Support)	2389	=head3 ABI Issues (Largefile Support)
1783		2390
1784	Libev by default (unless the user overrides this) uses the default	2391	Libev by default (unless the user overrides this) uses the default
1785	compilation environment, which means that on systems with large file	2392	compilation environment, which means that on systems with large file
1786	support disabled by default, you get the 32 bit version of the stat	2393	support disabled by default, you get the 32 bit version of the stat
1787	structure. When using the library from programs that change the ABI to	2394	structure. When using the library from programs that change the ABI to
1788	use 64 bit file offsets the programs will fail. In that case you have to	2395	use 64 bit file offsets the programs will fail. In that case you have to
1789	compile libev with the same flags to get binary compatibility. This is	2396	compile libev with the same flags to get binary compatibility. This is
1790	obviously the case with any flags that change the ABI, but the problem is	2397	obviously the case with any flags that change the ABI, but the problem is
1791	most noticeably disabled with ev_stat and large file support.	2398	most noticeably displayed with ev_stat and large file support.
1792		2399
1793	The solution for this is to lobby your distribution maker to make large	2400	The solution for this is to lobby your distribution maker to make large
1794	file interfaces available by default (as e.g. FreeBSD does) and not	2401	file interfaces available by default (as e.g. FreeBSD does) and not
1795	optional. Libev cannot simply switch on large file support because it has	2402	optional. Libev cannot simply switch on large file support because it has
1796	to exchange stat structures with application programs compiled using the	2403	to exchange stat structures with application programs compiled using the
1797	default compilation environment.	2404	default compilation environment.
1798		2405
1799	=head3 Inotify and Kqueue	2406	=head3 Inotify and Kqueue
1800		2407
1801	When C<inotify (7)> support has been compiled into libev (generally	2408	When C<inotify (7)> support has been compiled into libev and present at
1802	only available with Linux 2.6.25 or above due to bugs in earlier	2409	runtime, it will be used to speed up change detection where possible. The
1803	implementations) and present at runtime, it will be used to speed up	2410	inotify descriptor will be created lazily when the first C<ev_stat>
1804	change detection where possible. The inotify descriptor will be created	2411	watcher is being started.
1805	lazily when the first C<ev_stat> watcher is being started.
1806		2412
1807	Inotify presence does not change the semantics of C<ev_stat> watchers	2413	Inotify presence does not change the semantics of C<ev_stat> watchers
1808	except that changes might be detected earlier, and in some cases, to avoid	2414	except that changes might be detected earlier, and in some cases, to avoid
1809	making regular C<stat> calls. Even in the presence of inotify support	2415	making regular C<stat> calls. Even in the presence of inotify support
1810	there are many cases where libev has to resort to regular C<stat> polling,	2416	there are many cases where libev has to resort to regular C<stat> polling,
1811	but as long as the path exists, libev usually gets away without polling.	2417	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2418	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2419	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2420	xfs are fully working) libev usually gets away without polling.
1812		2421
1813	There is no support for kqueue, as apparently it cannot be used to	2422	There is no support for kqueue, as apparently it cannot be used to
1814	implement this functionality, due to the requirement of having a file	2423	implement this functionality, due to the requirement of having a file
1815	descriptor open on the object at all times, and detecting renames, unlinks	2424	descriptor open on the object at all times, and detecting renames, unlinks
1816	etc. is difficult.	2425	etc. is difficult.
1817		2426
		2427	=head3 C<stat ()> is a synchronous operation
		2428
		2429	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2430	the process. The exception are C<ev_stat> watchers - those call C<stat
		2431	()>, which is a synchronous operation.
		2432
		2433	For local paths, this usually doesn't matter: unless the system is very
		2434	busy or the intervals between stat's are large, a stat call will be fast,
		2435	as the path data is usually in memory already (except when starting the
		2436	watcher).
		2437
		2438	For networked file systems, calling C<stat ()> can block an indefinite
		2439	time due to network issues, and even under good conditions, a stat call
		2440	often takes multiple milliseconds.
		2441
		2442	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2443	paths, although this is fully supported by libev.
		2444
1818	=head3 The special problem of stat time resolution	2445	=head3 The special problem of stat time resolution
1819		2446
1820	The C<stat ()> system call only supports full-second resolution portably, and	2447	The C<stat ()> system call only supports full-second resolution portably,
1821	even on systems where the resolution is higher, most file systems still	2448	and even on systems where the resolution is higher, most file systems
1822	only support whole seconds.	2449	still only support whole seconds.
1823		2450
1824	That means that, if the time is the only thing that changes, you can	2451	That means that, if the time is the only thing that changes, you can
1825	easily miss updates: on the first update, C<ev_stat> detects a change and	2452	easily miss updates: on the first update, C<ev_stat> detects a change and
1826	calls your callback, which does something. When there is another update	2453	calls your callback, which does something. When there is another update
1827	within the same second, C<ev_stat> will be unable to detect unless the	2454	within the same second, C<ev_stat> will be unable to detect unless the
…		…
1970		2597
1971	=head3 Watcher-Specific Functions and Data Members	2598	=head3 Watcher-Specific Functions and Data Members
1972		2599
1973	=over 4	2600	=over 4
1974		2601
1975	=item ev_idle_init (ev_signal *, callback)	2602	=item ev_idle_init (ev_idle *, callback)
1976		2603
1977	Initialises and configures the idle watcher - it has no parameters of any	2604	Initialises and configures the idle watcher - it has no parameters of any
1978	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2605	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1979	believe me.	2606	believe me.
1980		2607
…		…
1984		2611
1985	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2612	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1986	callback, free it. Also, use no error checking, as usual.	2613	callback, free it. Also, use no error checking, as usual.
1987		2614
1988	static void	2615	static void
1989	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2616	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1990	{	2617	{
1991	free (w);	2618	free (w);
1992	// now do something you wanted to do when the program has	2619	// now do something you wanted to do when the program has
1993	// no longer anything immediate to do.	2620	// no longer anything immediate to do.
1994	}	2621	}
1995		2622
1996	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2623	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1997	ev_idle_init (idle_watcher, idle_cb);	2624	ev_idle_init (idle_watcher, idle_cb);
1998	ev_idle_start (loop, idle_cb);	2625	ev_idle_start (loop, idle_watcher);
1999		2626
2000		2627
2001	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2628	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2002		2629
2003	Prepare and check watchers are usually (but not always) used in pairs:	2630	Prepare and check watchers are usually (but not always) used in pairs:
…		…
2082		2709
2083	static ev_io iow [nfd];	2710	static ev_io iow [nfd];
2084	static ev_timer tw;	2711	static ev_timer tw;
2085		2712
2086	static void	2713	static void
2087	io_cb (ev_loop *loop, ev_io *w, int revents)	2714	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2088	{	2715	{
2089	}	2716	}
2090		2717
2091	// create io watchers for each fd and a timer before blocking	2718	// create io watchers for each fd and a timer before blocking
2092	static void	2719	static void
2093	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2720	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2094	{	2721	{
2095	int timeout = 3600000;	2722	int timeout = 3600000;
2096	struct pollfd fds [nfd];	2723	struct pollfd fds [nfd];
2097	// actual code will need to loop here and realloc etc.	2724	// actual code will need to loop here and realloc etc.
2098	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2725	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2099		2726
2100	/* the callback is illegal, but won't be called as we stop during check */	2727	/* the callback is illegal, but won't be called as we stop during check */
2101	ev_timer_init (&tw, 0, timeout * 1e-3);	2728	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2102	ev_timer_start (loop, &tw);	2729	ev_timer_start (loop, &tw);
2103		2730
2104	// create one ev_io per pollfd	2731	// create one ev_io per pollfd
2105	for (int i = 0; i < nfd; ++i)	2732	for (int i = 0; i < nfd; ++i)
2106	{	2733	{
…		…
2113	}	2740	}
2114	}	2741	}
2115		2742
2116	// stop all watchers after blocking	2743	// stop all watchers after blocking
2117	static void	2744	static void
2118	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2745	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2119	{	2746	{
2120	ev_timer_stop (loop, &tw);	2747	ev_timer_stop (loop, &tw);
2121		2748
2122	for (int i = 0; i < nfd; ++i)	2749	for (int i = 0; i < nfd; ++i)
2123	{	2750	{
…		…
2219	some fds have to be watched and handled very quickly (with low latency),	2846	some fds have to be watched and handled very quickly (with low latency),
2220	and even priorities and idle watchers might have too much overhead. In	2847	and even priorities and idle watchers might have too much overhead. In
2221	this case you would put all the high priority stuff in one loop and all	2848	this case you would put all the high priority stuff in one loop and all
2222	the rest in a second one, and embed the second one in the first.	2849	the rest in a second one, and embed the second one in the first.
2223		2850
2224	As long as the watcher is active, the callback will be invoked every time	2851	As long as the watcher is active, the callback will be invoked every
2225	there might be events pending in the embedded loop. The callback must then	2852	time there might be events pending in the embedded loop. The callback
2226	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2853	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2227	their callbacks (you could also start an idle watcher to give the embedded	2854	sweep and invoke their callbacks (the callback doesn't need to invoke the
2228	loop strictly lower priority for example). You can also set the callback	2855	C<ev_embed_sweep> function directly, it could also start an idle watcher
2229	to C<0>, in which case the embed watcher will automatically execute the	2856	to give the embedded loop strictly lower priority for example).
2230	embedded loop sweep.
2231		2857
2232	As long as the watcher is started it will automatically handle events. The	2858	You can also set the callback to C<0>, in which case the embed watcher
2233	callback will be invoked whenever some events have been handled. You can	2859	will automatically execute the embedded loop sweep whenever necessary.
2234	set the callback to C<0> to avoid having to specify one if you are not
2235	interested in that.
2236		2860
2237	Also, there have not currently been made special provisions for forking:	2861	Fork detection will be handled transparently while the C<ev_embed> watcher
2238	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2862	is active, i.e., the embedded loop will automatically be forked when the
2239	but you will also have to stop and restart any C<ev_embed> watchers	2863	embedding loop forks. In other cases, the user is responsible for calling
2240	yourself - but you can use a fork watcher to handle this automatically,	2864	C<ev_loop_fork> on the embedded loop.
2241	and future versions of libev might do just that.
2242		2865
2243	Unfortunately, not all backends are embeddable: only the ones returned by	2866	Unfortunately, not all backends are embeddable: only the ones returned by
2244	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2867	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2245	portable one.	2868	portable one.
2246		2869
…		…
2291	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2914	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2292	used).	2915	used).
2293		2916
2294	struct ev_loop *loop_hi = ev_default_init (0);	2917	struct ev_loop *loop_hi = ev_default_init (0);
2295	struct ev_loop *loop_lo = 0;	2918	struct ev_loop *loop_lo = 0;
2296	struct ev_embed embed;	2919	ev_embed embed;
2297		2920
2298	// see if there is a chance of getting one that works	2921	// see if there is a chance of getting one that works
2299	// (remember that a flags value of 0 means autodetection)	2922	// (remember that a flags value of 0 means autodetection)
2300	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2923	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2301	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2924	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2315	kqueue implementation). Store the kqueue/socket-only event loop in	2938	kqueue implementation). Store the kqueue/socket-only event loop in
2316	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2939	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2317		2940
2318	struct ev_loop *loop = ev_default_init (0);	2941	struct ev_loop *loop = ev_default_init (0);
2319	struct ev_loop *loop_socket = 0;	2942	struct ev_loop *loop_socket = 0;
2320	struct ev_embed embed;	2943	ev_embed embed;
2321		2944
2322	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2945	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2323	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2946	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2324	{	2947	{
2325	ev_embed_init (&embed, 0, loop_socket);	2948	ev_embed_init (&embed, 0, loop_socket);
…		…
2340	event loop blocks next and before C<ev_check> watchers are being called,	2963	event loop blocks next and before C<ev_check> watchers are being called,
2341	and only in the child after the fork. If whoever good citizen calling	2964	and only in the child after the fork. If whoever good citizen calling
2342	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2965	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2343	handlers will be invoked, too, of course.	2966	handlers will be invoked, too, of course.
2344		2967
		2968	=head3 The special problem of life after fork - how is it possible?
		2969
		2970	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2971	up/change the process environment, followed by a call to C<exec()>. This
		2972	sequence should be handled by libev without any problems.
		2973
		2974	This changes when the application actually wants to do event handling
		2975	in the child, or both parent in child, in effect "continuing" after the
		2976	fork.
		2977
		2978	The default mode of operation (for libev, with application help to detect
		2979	forks) is to duplicate all the state in the child, as would be expected
		2980	when I<either> the parent I<or> the child process continues.
		2981
		2982	When both processes want to continue using libev, then this is usually the
		2983	wrong result. In that case, usually one process (typically the parent) is
		2984	supposed to continue with all watchers in place as before, while the other
		2985	process typically wants to start fresh, i.e. without any active watchers.
		2986
		2987	The cleanest and most efficient way to achieve that with libev is to
		2988	simply create a new event loop, which of course will be "empty", and
		2989	use that for new watchers. This has the advantage of not touching more
		2990	memory than necessary, and thus avoiding the copy-on-write, and the
		2991	disadvantage of having to use multiple event loops (which do not support
		2992	signal watchers).
		2993
		2994	When this is not possible, or you want to use the default loop for
		2995	other reasons, then in the process that wants to start "fresh", call
		2996	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2997	the default loop will "orphan" (not stop) all registered watchers, so you
		2998	have to be careful not to execute code that modifies those watchers. Note
		2999	also that in that case, you have to re-register any signal watchers.
		3000
2345	=head3 Watcher-Specific Functions and Data Members	3001	=head3 Watcher-Specific Functions and Data Members
2346		3002
2347	=over 4	3003	=over 4
2348		3004
2349	=item ev_fork_init (ev_signal *, callback)	3005	=item ev_fork_init (ev_signal *, callback)
…		…
2378	=head3 Queueing	3034	=head3 Queueing
2379		3035
2380	C<ev_async> does not support queueing of data in any way. The reason	3036	C<ev_async> does not support queueing of data in any way. The reason
2381	is that the author does not know of a simple (or any) algorithm for a	3037	is that the author does not know of a simple (or any) algorithm for a
2382	multiple-writer-single-reader queue that works in all cases and doesn't	3038	multiple-writer-single-reader queue that works in all cases and doesn't
2383	need elaborate support such as pthreads.	3039	need elaborate support such as pthreads or unportable memory access
		3040	semantics.
2384		3041
2385	That means that if you want to queue data, you have to provide your own	3042	That means that if you want to queue data, you have to provide your own
2386	queue. But at least I can tell you how to implement locking around your	3043	queue. But at least I can tell you how to implement locking around your
2387	queue:	3044	queue:
2388		3045
…		…
2466	=over 4	3123	=over 4
2467		3124
2468	=item ev_async_init (ev_async *, callback)	3125	=item ev_async_init (ev_async *, callback)
2469		3126
2470	Initialises and configures the async watcher - it has no parameters of any	3127	Initialises and configures the async watcher - it has no parameters of any
2471	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3128	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2472	trust me.	3129	trust me.
2473		3130
2474	=item ev_async_send (loop, ev_async *)	3131	=item ev_async_send (loop, ev_async *)
2475		3132
2476	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3133	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2477	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3134	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2478	C<ev_feed_event>, this call is safe to do from other threads, signal or	3135	C<ev_feed_event>, this call is safe to do from other threads, signal or
2479	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3136	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2480	section below on what exactly this means).	3137	section below on what exactly this means).
2481		3138
		3139	Note that, as with other watchers in libev, multiple events might get
		3140	compressed into a single callback invocation (another way to look at this
		3141	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3142	reset when the event loop detects that).
		3143
2482	This call incurs the overhead of a system call only once per loop iteration,	3144	This call incurs the overhead of a system call only once per event loop
2483	so while the overhead might be noticeable, it doesn't apply to repeated	3145	iteration, so while the overhead might be noticeable, it doesn't apply to
2484	calls to C<ev_async_send>.	3146	repeated calls to C<ev_async_send> for the same event loop.
2485		3147
2486	=item bool = ev_async_pending (ev_async *)	3148	=item bool = ev_async_pending (ev_async *)
2487		3149
2488	Returns a non-zero value when C<ev_async_send> has been called on the	3150	Returns a non-zero value when C<ev_async_send> has been called on the
2489	watcher but the event has not yet been processed (or even noted) by the	3151	watcher but the event has not yet been processed (or even noted) by the
…		…
2492	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3154	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2493	the loop iterates next and checks for the watcher to have become active,	3155	the loop iterates next and checks for the watcher to have become active,
2494	it will reset the flag again. C<ev_async_pending> can be used to very	3156	it will reset the flag again. C<ev_async_pending> can be used to very
2495	quickly check whether invoking the loop might be a good idea.	3157	quickly check whether invoking the loop might be a good idea.
2496		3158
2497	Not that this does I<not> check whether the watcher itself is pending, only	3159	Not that this does I<not> check whether the watcher itself is pending,
2498	whether it has been requested to make this watcher pending.	3160	only whether it has been requested to make this watcher pending: there
		3161	is a time window between the event loop checking and resetting the async
		3162	notification, and the callback being invoked.
2499		3163
2500	=back	3164	=back
2501		3165
2502		3166
2503	=head1 OTHER FUNCTIONS	3167	=head1 OTHER FUNCTIONS
…		…
2520		3184
2521	If C<timeout> is less than 0, then no timeout watcher will be	3185	If C<timeout> is less than 0, then no timeout watcher will be
2522	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3186	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2523	repeat = 0) will be started. C<0> is a valid timeout.	3187	repeat = 0) will be started. C<0> is a valid timeout.
2524		3188
2525	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3189	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2526	passed an C<revents> set like normal event callbacks (a combination of	3190	passed an C<revents> set like normal event callbacks (a combination of
2527	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3191	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2528	value passed to C<ev_once>. Note that it is possible to receive I<both>	3192	value passed to C<ev_once>. Note that it is possible to receive I<both>
2529	a timeout and an io event at the same time - you probably should give io	3193	a timeout and an io event at the same time - you probably should give io
2530	events precedence.	3194	events precedence.
2531		3195
2532	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3196	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2533		3197
2534	static void stdin_ready (int revents, void *arg)	3198	static void stdin_ready (int revents, void *arg)
2535	{	3199	{
2536	if (revents & EV_READ)	3200	if (revents & EV_READ)
2537	/* stdin might have data for us, joy! */;	3201	/* stdin might have data for us, joy! */;
2538	else if (revents & EV_TIMEOUT)	3202	else if (revents & EV_TIMER)
2539	/* doh, nothing entered */;	3203	/* doh, nothing entered */;
2540	}	3204	}
2541		3205
2542	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3206	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2543		3207
2544	=item ev_feed_event (ev_loop *, watcher *, int revents)
2545
2546	Feeds the given event set into the event loop, as if the specified event
2547	had happened for the specified watcher (which must be a pointer to an
2548	initialised but not necessarily started event watcher).
2549
2550	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3208	=item ev_feed_fd_event (loop, int fd, int revents)
2551		3209
2552	Feed an event on the given fd, as if a file descriptor backend detected	3210	Feed an event on the given fd, as if a file descriptor backend detected
2553	the given events it.	3211	the given events it.
2554		3212
2555	=item ev_feed_signal_event (ev_loop *loop, int signum)	3213	=item ev_feed_signal_event (loop, int signum)
2556		3214
2557	Feed an event as if the given signal occurred (C<loop> must be the default	3215	Feed an event as if the given signal occurred (C<loop> must be the default
2558	loop!).	3216	loop!).
2559		3217
2560	=back	3218	=back
…		…
2640		3298
2641	=over 4	3299	=over 4
2642		3300
2643	=item ev::TYPE::TYPE ()	3301	=item ev::TYPE::TYPE ()
2644		3302
2645	=item ev::TYPE::TYPE (struct ev_loop *)	3303	=item ev::TYPE::TYPE (loop)
2646		3304
2647	=item ev::TYPE::~TYPE	3305	=item ev::TYPE::~TYPE
2648		3306
2649	The constructor (optionally) takes an event loop to associate the watcher	3307	The constructor (optionally) takes an event loop to associate the watcher
2650	with. If it is omitted, it will use C<EV_DEFAULT>.	3308	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2682		3340
2683	myclass obj;	3341	myclass obj;
2684	ev::io iow;	3342	ev::io iow;
2685	iow.set <myclass, &myclass::io_cb> (&obj);	3343	iow.set <myclass, &myclass::io_cb> (&obj);
2686		3344
		3345	=item w->set (object *)
		3346
		3347	This is a variation of a method callback - leaving out the method to call
		3348	will default the method to C<operator ()>, which makes it possible to use
		3349	functor objects without having to manually specify the C<operator ()> all
		3350	the time. Incidentally, you can then also leave out the template argument
		3351	list.
		3352
		3353	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3354	int revents)>.
		3355
		3356	See the method-C<set> above for more details.
		3357
		3358	Example: use a functor object as callback.
		3359
		3360	struct myfunctor
		3361	{
		3362	void operator() (ev::io &w, int revents)
		3363	{
		3364	...
		3365	}
		3366	}
		3367
		3368	myfunctor f;
		3369
		3370	ev::io w;
		3371	w.set (&f);
		3372
2687	=item w->set<function> (void *data = 0)	3373	=item w->set<function> (void *data = 0)
2688		3374
2689	Also sets a callback, but uses a static method or plain function as	3375	Also sets a callback, but uses a static method or plain function as
2690	callback. The optional C<data> argument will be stored in the watcher's	3376	callback. The optional C<data> argument will be stored in the watcher's
2691	C<data> member and is free for you to use.	3377	C<data> member and is free for you to use.
…		…
2697	Example: Use a plain function as callback.	3383	Example: Use a plain function as callback.
2698		3384
2699	static void io_cb (ev::io &w, int revents) { }	3385	static void io_cb (ev::io &w, int revents) { }
2700	iow.set <io_cb> ();	3386	iow.set <io_cb> ();
2701		3387
2702	=item w->set (struct ev_loop *)	3388	=item w->set (loop)
2703		3389
2704	Associates a different C<struct ev_loop> with this watcher. You can only	3390	Associates a different C<struct ev_loop> with this watcher. You can only
2705	do this when the watcher is inactive (and not pending either).	3391	do this when the watcher is inactive (and not pending either).
2706		3392
2707	=item w->set ([arguments])	3393	=item w->set ([arguments])
…		…
2777	L<http://software.schmorp.de/pkg/EV>.	3463	L<http://software.schmorp.de/pkg/EV>.
2778		3464
2779	=item Python	3465	=item Python
2780		3466
2781	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3467	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2782	seems to be quite complete and well-documented. Note, however, that the	3468	seems to be quite complete and well-documented.
2783	patch they require for libev is outright dangerous as it breaks the ABI
2784	for everybody else, and therefore, should never be applied in an installed
2785	libev (if python requires an incompatible ABI then it needs to embed
2786	libev).
2787		3469
2788	=item Ruby	3470	=item Ruby
2789		3471
2790	Tony Arcieri has written a ruby extension that offers access to a subset	3472	Tony Arcieri has written a ruby extension that offers access to a subset
2791	of the libev API and adds file handle abstractions, asynchronous DNS and	3473	of the libev API and adds file handle abstractions, asynchronous DNS and
2792	more on top of it. It can be found via gem servers. Its homepage is at	3474	more on top of it. It can be found via gem servers. Its homepage is at
2793	L<http://rev.rubyforge.org/>.	3475	L<http://rev.rubyforge.org/>.
2794		3476
		3477	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3478	makes rev work even on mingw.
		3479
		3480	=item Haskell
		3481
		3482	A haskell binding to libev is available at
		3483	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3484
2795	=item D	3485	=item D
2796		3486
2797	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3487	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2798	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3488	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3489
		3490	=item Ocaml
		3491
		3492	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3493	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3494
		3495	=item Lua
		3496
		3497	Brian Maher has written a partial interface to libev for lua (at the
		3498	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3499	L<http://github.com/brimworks/lua-ev>.
2799		3500
2800	=back	3501	=back
2801		3502
2802		3503
2803	=head1 MACRO MAGIC	3504	=head1 MACRO MAGIC
…		…
2904		3605
2905	#define EV_STANDALONE 1	3606	#define EV_STANDALONE 1
2906	#include "ev.h"	3607	#include "ev.h"
2907		3608
2908	Both header files and implementation files can be compiled with a C++	3609	Both header files and implementation files can be compiled with a C++
2909	compiler (at least, thats a stated goal, and breakage will be treated	3610	compiler (at least, that's a stated goal, and breakage will be treated
2910	as a bug).	3611	as a bug).
2911		3612
2912	You need the following files in your source tree, or in a directory	3613	You need the following files in your source tree, or in a directory
2913	in your include path (e.g. in libev/ when using -Ilibev):	3614	in your include path (e.g. in libev/ when using -Ilibev):
2914		3615
…		…
2957	libev.m4	3658	libev.m4
2958		3659
2959	=head2 PREPROCESSOR SYMBOLS/MACROS	3660	=head2 PREPROCESSOR SYMBOLS/MACROS
2960		3661
2961	Libev can be configured via a variety of preprocessor symbols you have to	3662	Libev can be configured via a variety of preprocessor symbols you have to
2962	define before including any of its files. The default in the absence of	3663	define before including (or compiling) any of its files. The default in
2963	autoconf is documented for every option.	3664	the absence of autoconf is documented for every option.
		3665
		3666	Symbols marked with "(h)" do not change the ABI, and can have different
		3667	values when compiling libev vs. including F<ev.h>, so it is permissible
		3668	to redefine them before including F<ev.h> without breaking compatibility
		3669	to a compiled library. All other symbols change the ABI, which means all
		3670	users of libev and the libev code itself must be compiled with compatible
		3671	settings.
2964		3672
2965	=over 4	3673	=over 4
2966		3674
2967	=item EV_STANDALONE	3675	=item EV_STANDALONE (h)
2968		3676
2969	Must always be C<1> if you do not use autoconf configuration, which	3677	Must always be C<1> if you do not use autoconf configuration, which
2970	keeps libev from including F<config.h>, and it also defines dummy	3678	keeps libev from including F<config.h>, and it also defines dummy
2971	implementations for some libevent functions (such as logging, which is not	3679	implementations for some libevent functions (such as logging, which is not
2972	supported). It will also not define any of the structs usually found in	3680	supported). It will also not define any of the structs usually found in
2973	F<event.h> that are not directly supported by the libev core alone.	3681	F<event.h> that are not directly supported by the libev core alone.
2974		3682
		3683	In standalone mode, libev will still try to automatically deduce the
		3684	configuration, but has to be more conservative.
		3685
2975	=item EV_USE_MONOTONIC	3686	=item EV_USE_MONOTONIC
2976		3687
2977	If defined to be C<1>, libev will try to detect the availability of the	3688	If defined to be C<1>, libev will try to detect the availability of the
2978	monotonic clock option at both compile time and runtime. Otherwise no use	3689	monotonic clock option at both compile time and runtime. Otherwise no
2979	of the monotonic clock option will be attempted. If you enable this, you	3690	use of the monotonic clock option will be attempted. If you enable this,
2980	usually have to link against librt or something similar. Enabling it when	3691	you usually have to link against librt or something similar. Enabling it
2981	the functionality isn't available is safe, though, although you have	3692	when the functionality isn't available is safe, though, although you have
2982	to make sure you link against any libraries where the C<clock_gettime>	3693	to make sure you link against any libraries where the C<clock_gettime>
2983	function is hiding in (often F<-lrt>).	3694	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2984		3695
2985	=item EV_USE_REALTIME	3696	=item EV_USE_REALTIME
2986		3697
2987	If defined to be C<1>, libev will try to detect the availability of the	3698	If defined to be C<1>, libev will try to detect the availability of the
2988	real-time clock option at compile time (and assume its availability at	3699	real-time clock option at compile time (and assume its availability
2989	runtime if successful). Otherwise no use of the real-time clock option will	3700	at runtime if successful). Otherwise no use of the real-time clock
2990	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3701	option will be attempted. This effectively replaces C<gettimeofday>
2991	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3702	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2992	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3703	correctness. See the note about libraries in the description of
		3704	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3705	C<EV_USE_CLOCK_SYSCALL>.
		3706
		3707	=item EV_USE_CLOCK_SYSCALL
		3708
		3709	If defined to be C<1>, libev will try to use a direct syscall instead
		3710	of calling the system-provided C<clock_gettime> function. This option
		3711	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3712	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3713	programs needlessly. Using a direct syscall is slightly slower (in
		3714	theory), because no optimised vdso implementation can be used, but avoids
		3715	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3716	higher, as it simplifies linking (no need for C<-lrt>).
2993		3717
2994	=item EV_USE_NANOSLEEP	3718	=item EV_USE_NANOSLEEP
2995		3719
2996	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3720	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2997	and will use it for delays. Otherwise it will use C<select ()>.	3721	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3013		3737
3014	=item EV_SELECT_USE_FD_SET	3738	=item EV_SELECT_USE_FD_SET
3015		3739
3016	If defined to C<1>, then the select backend will use the system C<fd_set>	3740	If defined to C<1>, then the select backend will use the system C<fd_set>
3017	structure. This is useful if libev doesn't compile due to a missing	3741	structure. This is useful if libev doesn't compile due to a missing
3018	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3742	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3019	exotic systems. This usually limits the range of file descriptors to some	3743	on exotic systems. This usually limits the range of file descriptors to
3020	low limit such as 1024 or might have other limitations (winsocket only	3744	some low limit such as 1024 or might have other limitations (winsocket
3021	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3745	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3022	influence the size of the C<fd_set> used.	3746	configures the maximum size of the C<fd_set>.
3023		3747
3024	=item EV_SELECT_IS_WINSOCKET	3748	=item EV_SELECT_IS_WINSOCKET
3025		3749
3026	When defined to C<1>, the select backend will assume that	3750	When defined to C<1>, the select backend will assume that
3027	select/socket/connect etc. don't understand file descriptors but	3751	select/socket/connect etc. don't understand file descriptors but
…		…
3029	be used is the winsock select). This means that it will call	3753	be used is the winsock select). This means that it will call
3030	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3754	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3031	it is assumed that all these functions actually work on fds, even	3755	it is assumed that all these functions actually work on fds, even
3032	on win32. Should not be defined on non-win32 platforms.	3756	on win32. Should not be defined on non-win32 platforms.
3033		3757
3034	=item EV_FD_TO_WIN32_HANDLE	3758	=item EV_FD_TO_WIN32_HANDLE(fd)
3035		3759
3036	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3760	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3037	file descriptors to socket handles. When not defining this symbol (the	3761	file descriptors to socket handles. When not defining this symbol (the
3038	default), then libev will call C<_get_osfhandle>, which is usually	3762	default), then libev will call C<_get_osfhandle>, which is usually
3039	correct. In some cases, programs use their own file descriptor management,	3763	correct. In some cases, programs use their own file descriptor management,
3040	in which case they can provide this function to map fds to socket handles.	3764	in which case they can provide this function to map fds to socket handles.
		3765
		3766	=item EV_WIN32_HANDLE_TO_FD(handle)
		3767
		3768	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3769	using the standard C<_open_osfhandle> function. For programs implementing
		3770	their own fd to handle mapping, overwriting this function makes it easier
		3771	to do so. This can be done by defining this macro to an appropriate value.
		3772
		3773	=item EV_WIN32_CLOSE_FD(fd)
		3774
		3775	If programs implement their own fd to handle mapping on win32, then this
		3776	macro can be used to override the C<close> function, useful to unregister
		3777	file descriptors again. Note that the replacement function has to close
		3778	the underlying OS handle.
3041		3779
3042	=item EV_USE_POLL	3780	=item EV_USE_POLL
3043		3781
3044	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3782	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3045	backend. Otherwise it will be enabled on non-win32 platforms. It	3783	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3092	as well as for signal and thread safety in C<ev_async> watchers.	3830	as well as for signal and thread safety in C<ev_async> watchers.
3093		3831
3094	In the absence of this define, libev will use C<sig_atomic_t volatile>	3832	In the absence of this define, libev will use C<sig_atomic_t volatile>
3095	(from F<signal.h>), which is usually good enough on most platforms.	3833	(from F<signal.h>), which is usually good enough on most platforms.
3096		3834
3097	=item EV_H	3835	=item EV_H (h)
3098		3836
3099	The name of the F<ev.h> header file used to include it. The default if	3837	The name of the F<ev.h> header file used to include it. The default if
3100	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	3838	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3101	used to virtually rename the F<ev.h> header file in case of conflicts.	3839	used to virtually rename the F<ev.h> header file in case of conflicts.
3102		3840
3103	=item EV_CONFIG_H	3841	=item EV_CONFIG_H (h)
3104		3842
3105	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	3843	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3106	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	3844	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3107	C<EV_H>, above.	3845	C<EV_H>, above.
3108		3846
3109	=item EV_EVENT_H	3847	=item EV_EVENT_H (h)
3110		3848
3111	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	3849	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3112	of how the F<event.h> header can be found, the default is C<"event.h">.	3850	of how the F<event.h> header can be found, the default is C<"event.h">.
3113		3851
3114	=item EV_PROTOTYPES	3852	=item EV_PROTOTYPES (h)
3115		3853
3116	If defined to be C<0>, then F<ev.h> will not define any function	3854	If defined to be C<0>, then F<ev.h> will not define any function
3117	prototypes, but still define all the structs and other symbols. This is	3855	prototypes, but still define all the structs and other symbols. This is
3118	occasionally useful if you want to provide your own wrapper functions	3856	occasionally useful if you want to provide your own wrapper functions
3119	around libev functions.	3857	around libev functions.
…		…
3141	fine.	3879	fine.
3142		3880
3143	If your embedding application does not need any priorities, defining these	3881	If your embedding application does not need any priorities, defining these
3144	both to C<0> will save some memory and CPU.	3882	both to C<0> will save some memory and CPU.
3145		3883
3146	=item EV_PERIODIC_ENABLE	3884	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		3885	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		3886	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3147		3887
3148	If undefined or defined to be C<1>, then periodic timers are supported. If	3888	If undefined or defined to be C<1> (and the platform supports it), then
3149	defined to be C<0>, then they are not. Disabling them saves a few kB of	3889	the respective watcher type is supported. If defined to be C<0>, then it
3150	code.	3890	is not. Disabling watcher types mainly saves code size.
3151		3891
3152	=item EV_IDLE_ENABLE	3892	=item EV_FEATURES
3153
3154	If undefined or defined to be C<1>, then idle watchers are supported. If
3155	defined to be C<0>, then they are not. Disabling them saves a few kB of
3156	code.
3157
3158	=item EV_EMBED_ENABLE
3159
3160	If undefined or defined to be C<1>, then embed watchers are supported. If
3161	defined to be C<0>, then they are not. Embed watchers rely on most other
3162	watcher types, which therefore must not be disabled.
3163
3164	=item EV_STAT_ENABLE
3165
3166	If undefined or defined to be C<1>, then stat watchers are supported. If
3167	defined to be C<0>, then they are not.
3168
3169	=item EV_FORK_ENABLE
3170
3171	If undefined or defined to be C<1>, then fork watchers are supported. If
3172	defined to be C<0>, then they are not.
3173
3174	=item EV_ASYNC_ENABLE
3175
3176	If undefined or defined to be C<1>, then async watchers are supported. If
3177	defined to be C<0>, then they are not.
3178
3179	=item EV_MINIMAL
3180		3893
3181	If you need to shave off some kilobytes of code at the expense of some	3894	If you need to shave off some kilobytes of code at the expense of some
3182	speed, define this symbol to C<1>. Currently this is used to override some	3895	speed (but with the full API), you can define this symbol to request
3183	inlining decisions, saves roughly 30% code size on amd64. It also selects a	3896	certain subsets of functionality. The default is to enable all features
3184	much smaller 2-heap for timer management over the default 4-heap.	3897	that can be enabled on the platform.
		3898
		3899	A typical way to use this symbol is to define it to C<0> (or to a bitset
		3900	with some broad features you want) and then selectively re-enable
		3901	additional parts you want, for example if you want everything minimal,
		3902	but multiple event loop support, async and child watchers and the poll
		3903	backend, use this:
		3904
		3905	#define EV_FEATURES 0
		3906	#define EV_MULTIPLICITY 1
		3907	#define EV_USE_POLL 1
		3908	#define EV_CHILD_ENABLE 1
		3909	#define EV_ASYNC_ENABLE 1
		3910
		3911	The actual value is a bitset, it can be a combination of the following
		3912	values:
		3913
		3914	=over 4
		3915
		3916	=item C<1> - faster/larger code
		3917
		3918	Use larger code to speed up some operations.
		3919
		3920	Currently this is used to override some inlining decisions (enlarging the
		3921	code size by roughly 30% on amd64).
		3922
		3923	When optimising for size, use of compiler flags such as C<-Os> with
		3924	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		3925	assertions.
		3926
		3927	=item C<2> - faster/larger data structures
		3928
		3929	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		3930	hash table sizes and so on. This will usually further increase code size
		3931	and can additionally have an effect on the size of data structures at
		3932	runtime.
		3933
		3934	=item C<4> - full API configuration
		3935
		3936	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		3937	enables multiplicity (C<EV_MULTIPLICITY>=1).
		3938
		3939	=item C<8> - full API
		3940
		3941	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		3942	details on which parts of the API are still available without this
		3943	feature, and do not complain if this subset changes over time.
		3944
		3945	=item C<16> - enable all optional watcher types
		3946
		3947	Enables all optional watcher types. If you want to selectively enable
		3948	only some watcher types other than I/O and timers (e.g. prepare,
		3949	embed, async, child...) you can enable them manually by defining
		3950	C<EV_watchertype_ENABLE> to C<1> instead.
		3951
		3952	=item C<32> - enable all backends
		3953
		3954	This enables all backends - without this feature, you need to enable at
		3955	least one backend manually (C<EV_USE_SELECT> is a good choice).
		3956
		3957	=item C<64> - enable OS-specific "helper" APIs
		3958
		3959	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		3960	default.
		3961
		3962	=back
		3963
		3964	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		3965	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		3966	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		3967	watchers, timers and monotonic clock support.
		3968
		3969	With an intelligent-enough linker (gcc+binutils are intelligent enough
		3970	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		3971	your program might be left out as well - a binary starting a timer and an
		3972	I/O watcher then might come out at only 5Kb.
		3973
		3974	=item EV_AVOID_STDIO
		3975
		3976	If this is set to C<1> at compiletime, then libev will avoid using stdio
		3977	functions (printf, scanf, perror etc.). This will increase the code size
		3978	somewhat, but if your program doesn't otherwise depend on stdio and your
		3979	libc allows it, this avoids linking in the stdio library which is quite
		3980	big.
		3981
		3982	Note that error messages might become less precise when this option is
		3983	enabled.
		3984
		3985	=item EV_NSIG
		3986
		3987	The highest supported signal number, +1 (or, the number of
		3988	signals): Normally, libev tries to deduce the maximum number of signals
		3989	automatically, but sometimes this fails, in which case it can be
		3990	specified. Also, using a lower number than detected (C<32> should be
		3991	good for about any system in existence) can save some memory, as libev
		3992	statically allocates some 12-24 bytes per signal number.
3185		3993
3186	=item EV_PID_HASHSIZE	3994	=item EV_PID_HASHSIZE
3187		3995
3188	C<ev_child> watchers use a small hash table to distribute workload by	3996	C<ev_child> watchers use a small hash table to distribute workload by
3189	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3997	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3190	than enough. If you need to manage thousands of children you might want to	3998	usually more than enough. If you need to manage thousands of children you
3191	increase this value (I<must> be a power of two).	3999	might want to increase this value (I<must> be a power of two).
3192		4000
3193	=item EV_INOTIFY_HASHSIZE	4001	=item EV_INOTIFY_HASHSIZE
3194		4002
3195	C<ev_stat> watchers use a small hash table to distribute workload by	4003	C<ev_stat> watchers use a small hash table to distribute workload by
3196	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4004	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3197	usually more than enough. If you need to manage thousands of C<ev_stat>	4005	disabled), usually more than enough. If you need to manage thousands of
3198	watchers you might want to increase this value (I<must> be a power of	4006	C<ev_stat> watchers you might want to increase this value (I<must> be a
3199	two).	4007	power of two).
3200		4008
3201	=item EV_USE_4HEAP	4009	=item EV_USE_4HEAP
3202		4010
3203	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4011	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3204	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4012	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3205	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4013	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3206	faster performance with many (thousands) of watchers.	4014	faster performance with many (thousands) of watchers.
3207		4015
3208	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4016	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3209	(disabled).	4017	will be C<0>.
3210		4018
3211	=item EV_HEAP_CACHE_AT	4019	=item EV_HEAP_CACHE_AT
3212		4020
3213	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4021	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3214	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4022	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3215	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4023	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3216	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4024	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3217	but avoids random read accesses on heap changes. This improves performance	4025	but avoids random read accesses on heap changes. This improves performance
3218	noticeably with many (hundreds) of watchers.	4026	noticeably with many (hundreds) of watchers.
3219		4027
3220	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4028	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3221	(disabled).	4029	will be C<0>.
3222		4030
3223	=item EV_VERIFY	4031	=item EV_VERIFY
3224		4032
3225	Controls how much internal verification (see C<ev_loop_verify ()>) will	4033	Controls how much internal verification (see C<ev_loop_verify ()>) will
3226	be done: If set to C<0>, no internal verification code will be compiled	4034	be done: If set to C<0>, no internal verification code will be compiled
…		…
3228	called. If set to C<2>, then the internal verification code will be	4036	called. If set to C<2>, then the internal verification code will be
3229	called once per loop, which can slow down libev. If set to C<3>, then the	4037	called once per loop, which can slow down libev. If set to C<3>, then the
3230	verification code will be called very frequently, which will slow down	4038	verification code will be called very frequently, which will slow down
3231	libev considerably.	4039	libev considerably.
3232		4040
3233	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4041	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3234	C<0>.	4042	will be C<0>.
3235		4043
3236	=item EV_COMMON	4044	=item EV_COMMON
3237		4045
3238	By default, all watchers have a C<void *data> member. By redefining	4046	By default, all watchers have a C<void *data> member. By redefining
3239	this macro to a something else you can include more and other types of	4047	this macro to a something else you can include more and other types of
…		…
3297	file.	4105	file.
3298		4106
3299	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4107	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3300	that everybody includes and which overrides some configure choices:	4108	that everybody includes and which overrides some configure choices:
3301		4109
3302	#define EV_MINIMAL 1	4110	#define EV_FEATURES 8
3303	#define EV_USE_POLL 0	4111	#define EV_USE_SELECT 1
3304	#define EV_MULTIPLICITY 0
3305	#define EV_PERIODIC_ENABLE 0	4112	#define EV_PREPARE_ENABLE 1
		4113	#define EV_IDLE_ENABLE 1
3306	#define EV_STAT_ENABLE 0	4114	#define EV_SIGNAL_ENABLE 1
3307	#define EV_FORK_ENABLE 0	4115	#define EV_CHILD_ENABLE 1
		4116	#define EV_USE_STDEXCEPT 0
3308	#define EV_CONFIG_H <config.h>	4117	#define EV_CONFIG_H <config.h>
3309	#define EV_MINPRI 0
3310	#define EV_MAXPRI 0
3311		4118
3312	#include "ev++.h"	4119	#include "ev++.h"
3313		4120
3314	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4121	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3315		4122
…		…
3375	default loop and triggering an C<ev_async> watcher from the default loop	4182	default loop and triggering an C<ev_async> watcher from the default loop
3376	watcher callback into the event loop interested in the signal.	4183	watcher callback into the event loop interested in the signal.
3377		4184
3378	=back	4185	=back
3379		4186
		4187	=head4 THREAD LOCKING EXAMPLE
		4188
		4189	Here is a fictitious example of how to run an event loop in a different
		4190	thread than where callbacks are being invoked and watchers are
		4191	created/added/removed.
		4192
		4193	For a real-world example, see the C<EV::Loop::Async> perl module,
		4194	which uses exactly this technique (which is suited for many high-level
		4195	languages).
		4196
		4197	The example uses a pthread mutex to protect the loop data, a condition
		4198	variable to wait for callback invocations, an async watcher to notify the
		4199	event loop thread and an unspecified mechanism to wake up the main thread.
		4200
		4201	First, you need to associate some data with the event loop:
		4202
		4203	typedef struct {
		4204	mutex_t lock; /* global loop lock */
		4205	ev_async async_w;
		4206	thread_t tid;
		4207	cond_t invoke_cv;
		4208	} userdata;
		4209
		4210	void prepare_loop (EV_P)
		4211	{
		4212	// for simplicity, we use a static userdata struct.
		4213	static userdata u;
		4214
		4215	ev_async_init (&u->async_w, async_cb);
		4216	ev_async_start (EV_A_ &u->async_w);
		4217
		4218	pthread_mutex_init (&u->lock, 0);
		4219	pthread_cond_init (&u->invoke_cv, 0);
		4220
		4221	// now associate this with the loop
		4222	ev_set_userdata (EV_A_ u);
		4223	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4224	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4225
		4226	// then create the thread running ev_loop
		4227	pthread_create (&u->tid, 0, l_run, EV_A);
		4228	}
		4229
		4230	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4231	solely to wake up the event loop so it takes notice of any new watchers
		4232	that might have been added:
		4233
		4234	static void
		4235	async_cb (EV_P_ ev_async *w, int revents)
		4236	{
		4237	// just used for the side effects
		4238	}
		4239
		4240	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4241	protecting the loop data, respectively.
		4242
		4243	static void
		4244	l_release (EV_P)
		4245	{
		4246	userdata *u = ev_userdata (EV_A);
		4247	pthread_mutex_unlock (&u->lock);
		4248	}
		4249
		4250	static void
		4251	l_acquire (EV_P)
		4252	{
		4253	userdata *u = ev_userdata (EV_A);
		4254	pthread_mutex_lock (&u->lock);
		4255	}
		4256
		4257	The event loop thread first acquires the mutex, and then jumps straight
		4258	into C<ev_loop>:
		4259
		4260	void *
		4261	l_run (void *thr_arg)
		4262	{
		4263	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4264
		4265	l_acquire (EV_A);
		4266	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4267	ev_loop (EV_A_ 0);
		4268	l_release (EV_A);
		4269
		4270	return 0;
		4271	}
		4272
		4273	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4274	signal the main thread via some unspecified mechanism (signals? pipe
		4275	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4276	have been called (in a while loop because a) spurious wakeups are possible
		4277	and b) skipping inter-thread-communication when there are no pending
		4278	watchers is very beneficial):
		4279
		4280	static void
		4281	l_invoke (EV_P)
		4282	{
		4283	userdata *u = ev_userdata (EV_A);
		4284
		4285	while (ev_pending_count (EV_A))
		4286	{
		4287	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4288	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4289	}
		4290	}
		4291
		4292	Now, whenever the main thread gets told to invoke pending watchers, it
		4293	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4294	thread to continue:
		4295
		4296	static void
		4297	real_invoke_pending (EV_P)
		4298	{
		4299	userdata *u = ev_userdata (EV_A);
		4300
		4301	pthread_mutex_lock (&u->lock);
		4302	ev_invoke_pending (EV_A);
		4303	pthread_cond_signal (&u->invoke_cv);
		4304	pthread_mutex_unlock (&u->lock);
		4305	}
		4306
		4307	Whenever you want to start/stop a watcher or do other modifications to an
		4308	event loop, you will now have to lock:
		4309
		4310	ev_timer timeout_watcher;
		4311	userdata *u = ev_userdata (EV_A);
		4312
		4313	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4314
		4315	pthread_mutex_lock (&u->lock);
		4316	ev_timer_start (EV_A_ &timeout_watcher);
		4317	ev_async_send (EV_A_ &u->async_w);
		4318	pthread_mutex_unlock (&u->lock);
		4319
		4320	Note that sending the C<ev_async> watcher is required because otherwise
		4321	an event loop currently blocking in the kernel will have no knowledge
		4322	about the newly added timer. By waking up the loop it will pick up any new
		4323	watchers in the next event loop iteration.
		4324
3380	=head3 COROUTINES	4325	=head3 COROUTINES
3381		4326
3382	Libev is very accommodating to coroutines ("cooperative threads"):	4327	Libev is very accommodating to coroutines ("cooperative threads"):
3383	libev fully supports nesting calls to its functions from different	4328	libev fully supports nesting calls to its functions from different
3384	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4329	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3385	different coroutines, and switch freely between both coroutines running the	4330	different coroutines, and switch freely between both coroutines running
3386	loop, as long as you don't confuse yourself). The only exception is that	4331	the loop, as long as you don't confuse yourself). The only exception is
3387	you must not do this from C<ev_periodic> reschedule callbacks.	4332	that you must not do this from C<ev_periodic> reschedule callbacks.
3388		4333
3389	Care has been taken to ensure that libev does not keep local state inside	4334	Care has been taken to ensure that libev does not keep local state inside
3390	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4335	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3391	they do not clal any callbacks.	4336	they do not call any callbacks.
3392		4337
3393	=head2 COMPILER WARNINGS	4338	=head2 COMPILER WARNINGS
3394		4339
3395	Depending on your compiler and compiler settings, you might get no or a	4340	Depending on your compiler and compiler settings, you might get no or a
3396	lot of warnings when compiling libev code. Some people are apparently	4341	lot of warnings when compiling libev code. Some people are apparently
…		…
3430	==2274== definitely lost: 0 bytes in 0 blocks.	4375	==2274== definitely lost: 0 bytes in 0 blocks.
3431	==2274== possibly lost: 0 bytes in 0 blocks.	4376	==2274== possibly lost: 0 bytes in 0 blocks.
3432	==2274== still reachable: 256 bytes in 1 blocks.	4377	==2274== still reachable: 256 bytes in 1 blocks.
3433		4378
3434	Then there is no memory leak, just as memory accounted to global variables	4379	Then there is no memory leak, just as memory accounted to global variables
3435	is not a memleak - the memory is still being refernced, and didn't leak.	4380	is not a memleak - the memory is still being referenced, and didn't leak.
3436		4381
3437	Similarly, under some circumstances, valgrind might report kernel bugs	4382	Similarly, under some circumstances, valgrind might report kernel bugs
3438	as if it were a bug in libev (e.g. in realloc or in the poll backend,	4383	as if it were a bug in libev (e.g. in realloc or in the poll backend,
3439	although an acceptable workaround has been found here), or it might be	4384	although an acceptable workaround has been found here), or it might be
3440	confused.	4385	confused.
…		…
3469	way (note also that glib is the slowest event library known to man).	4414	way (note also that glib is the slowest event library known to man).
3470		4415
3471	There is no supported compilation method available on windows except	4416	There is no supported compilation method available on windows except
3472	embedding it into other applications.	4417	embedding it into other applications.
3473		4418
		4419	Sensible signal handling is officially unsupported by Microsoft - libev
		4420	tries its best, but under most conditions, signals will simply not work.
		4421
3474	Not a libev limitation but worth mentioning: windows apparently doesn't	4422	Not a libev limitation but worth mentioning: windows apparently doesn't
3475	accept large writes: instead of resulting in a partial write, windows will	4423	accept large writes: instead of resulting in a partial write, windows will
3476	either accept everything or return C<ENOBUFS> if the buffer is too large,	4424	either accept everything or return C<ENOBUFS> if the buffer is too large,
3477	so make sure you only write small amounts into your sockets (less than a	4425	so make sure you only write small amounts into your sockets (less than a
3478	megabyte seems safe, but this apparently depends on the amount of memory	4426	megabyte seems safe, but this apparently depends on the amount of memory
…		…
3482	the abysmal performance of winsockets, using a large number of sockets	4430	the abysmal performance of winsockets, using a large number of sockets
3483	is not recommended (and not reasonable). If your program needs to use	4431	is not recommended (and not reasonable). If your program needs to use
3484	more than a hundred or so sockets, then likely it needs to use a totally	4432	more than a hundred or so sockets, then likely it needs to use a totally
3485	different implementation for windows, as libev offers the POSIX readiness	4433	different implementation for windows, as libev offers the POSIX readiness
3486	notification model, which cannot be implemented efficiently on windows	4434	notification model, which cannot be implemented efficiently on windows
3487	(Microsoft monopoly games).	4435	(due to Microsoft monopoly games).
3488		4436
3489	A typical way to use libev under windows is to embed it (see the embedding	4437	A typical way to use libev under windows is to embed it (see the embedding
3490	section for details) and use the following F<evwrap.h> header file instead	4438	section for details) and use the following F<evwrap.h> header file instead
3491	of F<ev.h>:	4439	of F<ev.h>:
3492		4440
…		…
3528		4476
3529	Early versions of winsocket's select only supported waiting for a maximum	4477	Early versions of winsocket's select only supported waiting for a maximum
3530	of C<64> handles (probably owning to the fact that all windows kernels	4478	of C<64> handles (probably owning to the fact that all windows kernels
3531	can only wait for C<64> things at the same time internally; Microsoft	4479	can only wait for C<64> things at the same time internally; Microsoft
3532	recommends spawning a chain of threads and wait for 63 handles and the	4480	recommends spawning a chain of threads and wait for 63 handles and the
3533	previous thread in each. Great).	4481	previous thread in each. Sounds great!).
3534		4482
3535	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4483	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3536	to some high number (e.g. C<2048>) before compiling the winsocket select	4484	to some high number (e.g. C<2048>) before compiling the winsocket select
3537	call (which might be in libev or elsewhere, for example, perl does its own	4485	call (which might be in libev or elsewhere, for example, perl and many
3538	select emulation on windows).	4486	other interpreters do their own select emulation on windows).
3539		4487
3540	Another limit is the number of file descriptors in the Microsoft runtime	4488	Another limit is the number of file descriptors in the Microsoft runtime
3541	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4489	libraries, which by default is C<64> (there must be a hidden I<64>
3542	or something like this inside Microsoft). You can increase this by calling	4490	fetish or something like this inside Microsoft). You can increase this
3543	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4491	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3544	arbitrary limit), but is broken in many versions of the Microsoft runtime	4492	(another arbitrary limit), but is broken in many versions of the Microsoft
3545	libraries.
3546
3547	This might get you to about C<512> or C<2048> sockets (depending on	4493	runtime libraries. This might get you to about C<512> or C<2048> sockets
3548	windows version and/or the phase of the moon). To get more, you need to	4494	(depending on windows version and/or the phase of the moon). To get more,
3549	wrap all I/O functions and provide your own fd management, but the cost of	4495	you need to wrap all I/O functions and provide your own fd management, but
3550	calling select (O(n²)) will likely make this unworkable.	4496	the cost of calling select (O(n²)) will likely make this unworkable.
3551		4497
3552	=back	4498	=back
3553		4499
3554	=head2 PORTABILITY REQUIREMENTS	4500	=head2 PORTABILITY REQUIREMENTS
3555		4501
…		…
3598	=item C<double> must hold a time value in seconds with enough accuracy	4544	=item C<double> must hold a time value in seconds with enough accuracy
3599		4545
3600	The type C<double> is used to represent timestamps. It is required to	4546	The type C<double> is used to represent timestamps. It is required to
3601	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4547	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
3602	enough for at least into the year 4000. This requirement is fulfilled by	4548	enough for at least into the year 4000. This requirement is fulfilled by
3603	implementations implementing IEEE 754 (basically all existing ones).	4549	implementations implementing IEEE 754, which is basically all existing
		4550	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4551	2200.
3604		4552
3605	=back	4553	=back
3606		4554
3607	If you know of other additional requirements drop me a note.	4555	If you know of other additional requirements drop me a note.
3608		4556
…		…
3676	involves iterating over all running async watchers or all signal numbers.	4624	involves iterating over all running async watchers or all signal numbers.
3677		4625
3678	=back	4626	=back
3679		4627
3680		4628
		4629	=head1 PORTING FROM LIBEV 3.X TO 4.X
		4630
		4631	The major version 4 introduced some minor incompatible changes to the API.
		4632
		4633	At the moment, the C<ev.h> header file tries to implement superficial
		4634	compatibility, so most programs should still compile. Those might be
		4635	removed in later versions of libev, so better update early than late.
		4636
		4637	=over 4
		4638
		4639	=item C<ev_loop_count> renamed to C<ev_iteration>
		4640
		4641	=item C<ev_loop_depth> renamed to C<ev_depth>
		4642
		4643	=item C<ev_loop_verify> renamed to C<ev_verify>
		4644
		4645	Most functions working on C<struct ev_loop> objects don't have an
		4646	C<ev_loop_> prefix, so it was removed. Note that C<ev_loop_fork> is
		4647	still called C<ev_loop_fork> because it would otherwise clash with the
		4648	C<ev_fork> typedef.
		4649
		4650	=item C<EV_TIMEOUT> renamed to C<EV_TIMER> in C<revents>
		4651
		4652	This is a simple rename - all other watcher types use their name
		4653	as revents flag, and now C<ev_timer> does, too.
		4654
		4655	Both C<EV_TIMER> and C<EV_TIMEOUT> symbols were present in 3.x versions
		4656	and continue to be present for the foreseeable future, so this is mostly a
		4657	documentation change.
		4658
		4659	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		4660
		4661	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		4662	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		4663	and work, but the library code will of course be larger.
		4664
		4665	=back
		4666
		4667
		4668	=head1 GLOSSARY
		4669
		4670	=over 4
		4671
		4672	=item active
		4673
		4674	A watcher is active as long as it has been started (has been attached to
		4675	an event loop) but not yet stopped (disassociated from the event loop).
		4676
		4677	=item application
		4678
		4679	In this document, an application is whatever is using libev.
		4680
		4681	=item callback
		4682
		4683	The address of a function that is called when some event has been
		4684	detected. Callbacks are being passed the event loop, the watcher that
		4685	received the event, and the actual event bitset.
		4686
		4687	=item callback invocation
		4688
		4689	The act of calling the callback associated with a watcher.
		4690
		4691	=item event
		4692
		4693	A change of state of some external event, such as data now being available
		4694	for reading on a file descriptor, time having passed or simply not having
		4695	any other events happening anymore.
		4696
		4697	In libev, events are represented as single bits (such as C<EV_READ> or
		4698	C<EV_TIMER>).
		4699
		4700	=item event library
		4701
		4702	A software package implementing an event model and loop.
		4703
		4704	=item event loop
		4705
		4706	An entity that handles and processes external events and converts them
		4707	into callback invocations.
		4708
		4709	=item event model
		4710
		4711	The model used to describe how an event loop handles and processes
		4712	watchers and events.
		4713
		4714	=item pending
		4715
		4716	A watcher is pending as soon as the corresponding event has been detected,
		4717	and stops being pending as soon as the watcher will be invoked or its
		4718	pending status is explicitly cleared by the application.
		4719
		4720	A watcher can be pending, but not active. Stopping a watcher also clears
		4721	its pending status.
		4722
		4723	=item real time
		4724
		4725	The physical time that is observed. It is apparently strictly monotonic :)
		4726
		4727	=item wall-clock time
		4728
		4729	The time and date as shown on clocks. Unlike real time, it can actually
		4730	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4731	clock.
		4732
		4733	=item watcher
		4734
		4735	A data structure that describes interest in certain events. Watchers need
		4736	to be started (attached to an event loop) before they can receive events.
		4737
		4738	=item watcher invocation
		4739
		4740	The act of calling the callback associated with a watcher.
		4741
		4742	=back
		4743
3681	=head1 AUTHOR	4744	=head1 AUTHOR
3682		4745
3683	Marc Lehmann <libev@schmorp.de>.	4746	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3684		4747

Diff Legend

–	Removed lines
+	Added lines
<	Changed lines
>	Changed lines