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…		…
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
		14	#include <stdio.h> // for puts
		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
18		20
19	// all watcher callbacks have a similar signature	21	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	22	// this callback is called when data is readable on stdin
21	static void	23	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	25	{
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
…		…
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	42	}
…		…
60		62
61	// unloop was called, so exit	63	// unloop was called, so exit
62	return 0;	64	return 0;
63	}	65	}
64		66
65	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
66		70
67	The newest version of this document is also available as an html-formatted	71	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	72	web page you might find easier to navigate when reading it for the first
69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.	73	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		74
		75	While this document tries to be as complete as possible in documenting
		76	libev, its usage and the rationale behind its design, it is not a tutorial
		77	on event-based programming, nor will it introduce event-based programming
		78	with libev.
		79
		80	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
…		…
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	230	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
215	recommended ones.	231	recommended ones.
216		232
217	See the description of C<ev_embed> watchers for more info.	233	See the description of C<ev_embed> watchers for more info.
218		234
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	235	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
220		236
221	Sets the allocation function to use (the prototype is similar - the	237	Sets the allocation function to use (the prototype is similar - the
222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	238	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
223	used to allocate and free memory (no surprises here). If it returns zero	239	used to allocate and free memory (no surprises here). If it returns zero
224	when memory needs to be allocated (C<size != 0>), the library might abort	240	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	266	}
251		267
252	...	268	...
253	ev_set_allocator (persistent_realloc);	269	ev_set_allocator (persistent_realloc);
254		270
255	=item ev_set_syserr_cb (void (*cb)(const char *msg));	271	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
256		272
257	Set the callback function to call on a retryable system call error (such	273	Set the callback function to call on a retryable system call error (such
258	as failed select, poll, epoll_wait). The message is a printable string	274	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	275	indicating the system call or subsystem causing the problem. If this
260	callback is set, then libev will expect it to remedy the situation, no	276	callback is set, then libev will expect it to remedy the situation, no
…		…
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. Last
		445	not least, it also refuses to work with some file descriptors which work
		446	perfectly fine with C<select> (files, many character devices...).
389		447
390	While stopping, setting and starting an I/O watcher in the same iteration	448	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	449	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	450	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	451	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
394	very well if you register events for both fds.	452	file descriptors might not work very well if you register events for both
395		453	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		454
400	Best performance from this backend is achieved by not unregistering all	455	Best performance from this backend is achieved by not unregistering all
401	watchers for a file descriptor until it has been closed, if possible, i.e.	456	watchers for a file descriptor until it has been closed, if possible,
402	keep at least one watcher active per fd at all times.	457	i.e. keep at least one watcher active per fd at all times. Stopping and
		458	starting a watcher (without re-setting it) also usually doesn't cause
		459	extra overhead. A fork can both result in spurious notifications as well
		460	as in libev having to destroy and recreate the epoll object, which can
		461	take considerable time and thus should be avoided.
		462
		463	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		464	faster than epoll for maybe up to a hundred file descriptors, depending on
		465	the usage. So sad.
403		466
404	While nominally embeddable in other event loops, this feature is broken in	467	While nominally embeddable in other event loops, this feature is broken in
405	all kernel versions tested so far.	468	all kernel versions tested so far.
406		469
407	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	470	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
…		…
410	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	473	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
411		474
412	Kqueue deserves special mention, as at the time of this writing, it	475	Kqueue deserves special mention, as at the time of this writing, it
413	was broken on all BSDs except NetBSD (usually it doesn't work reliably	476	was broken on all BSDs except NetBSD (usually it doesn't work reliably
414	with anything but sockets and pipes, except on Darwin, where of course	477	with anything but sockets and pipes, except on Darwin, where of course
415	it's completely useless). For this reason it's not being "auto-detected"	478	it's completely useless). Unlike epoll, however, whose brokenness
		479	is by design, these kqueue bugs can (and eventually will) be fixed
		480	without API changes to existing programs. For this reason it's not being
416	unless you explicitly specify it explicitly in the flags (i.e. using	481	"auto-detected" unless you explicitly specify it in the flags (i.e. using
417	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	482	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
418	system like NetBSD.	483	system like NetBSD.
419		484
420	You still can embed kqueue into a normal poll or select backend and use it	485	You still can embed kqueue into a normal poll or select backend and use it
421	only for sockets (after having made sure that sockets work with kqueue on	486	only for sockets (after having made sure that sockets work with kqueue on
…		…
423		488
424	It scales in the same way as the epoll backend, but the interface to the	489	It scales in the same way as the epoll backend, but the interface to the
425	kernel is more efficient (which says nothing about its actual speed, of	490	kernel is more efficient (which says nothing about its actual speed, of
426	course). While stopping, setting and starting an I/O watcher does never	491	course). While stopping, setting and starting an I/O watcher does never
427	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	492	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
428	two event changes per incident, support for C<fork ()> is very bad and it	493	two event changes per incident. Support for C<fork ()> is very bad (but
429	drops fds silently in similarly hard-to-detect cases.	494	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		495	cases
430		496
431	This backend usually performs well under most conditions.	497	This backend usually performs well under most conditions.
432		498
433	While nominally embeddable in other event loops, this doesn't work	499	While nominally embeddable in other event loops, this doesn't work
434	everywhere, so you might need to test for this. And since it is broken	500	everywhere, so you might need to test for this. And since it is broken
435	almost everywhere, you should only use it when you have a lot of sockets	501	almost everywhere, you should only use it when you have a lot of sockets
436	(for which it usually works), by embedding it into another event loop	502	(for which it usually works), by embedding it into another event loop
437	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	503	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
438	sockets.	504	also broken on OS X)) and, did I mention it, using it only for sockets.
439		505
440	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	506	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
441	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with	507	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
442	C<NOTE_EOF>.	508	C<NOTE_EOF>.
443		509
…		…
460	While this backend scales well, it requires one system call per active	526	While this backend scales well, it requires one system call per active
461	file descriptor per loop iteration. For small and medium numbers of file	527	file descriptor per loop iteration. For small and medium numbers of file
462	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	528	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
463	might perform better.	529	might perform better.
464		530
465	On the positive side, ignoring the spurious readiness notifications, this	531	On the positive side, with the exception of the spurious readiness
466	backend actually performed to specification in all tests and is fully	532	notifications, this backend actually performed fully to specification
467	embeddable, which is a rare feat among the OS-specific backends.	533	in all tests and is fully embeddable, which is a rare feat among the
		534	OS-specific backends (I vastly prefer correctness over speed hacks).
468		535
469	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	536	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
470	C<EVBACKEND_POLL>.	537	C<EVBACKEND_POLL>.
471		538
472	=item C<EVBACKEND_ALL>	539	=item C<EVBACKEND_ALL>
…		…
477		544
478	It is definitely not recommended to use this flag.	545	It is definitely not recommended to use this flag.
479		546
480	=back	547	=back
481		548
482	If one or more of these are or'ed into the flags value, then only these	549	If one or more of the backend flags are or'ed into the flags value,
483	backends will be tried (in the reverse order as listed here). If none are	550	then only these backends will be tried (in the reverse order as listed
484	specified, all backends in C<ev_recommended_backends ()> will be tried.	551	here). If none are specified, all backends in C<ev_recommended_backends
		552	()> will be tried.
485		553
486	The most typical usage is like this:	554	Example: This is the most typical usage.
487		555
488	if (!ev_default_loop (0))	556	if (!ev_default_loop (0))
489	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	557	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
490		558
491	Restrict libev to the select and poll backends, and do not allow	559	Example: Restrict libev to the select and poll backends, and do not allow
492	environment settings to be taken into account:	560	environment settings to be taken into account:
493		561
494	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	562	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
495		563
496	Use whatever libev has to offer, but make sure that kqueue is used if	564	Example: Use whatever libev has to offer, but make sure that kqueue is
497	available (warning, breaks stuff, best use only with your own private	565	used if available (warning, breaks stuff, best use only with your own
498	event loop and only if you know the OS supports your types of fds):	566	private event loop and only if you know the OS supports your types of
		567	fds):
499		568
500	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	569	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
501		570
502	=item struct ev_loop *ev_loop_new (unsigned int flags)	571	=item struct ev_loop *ev_loop_new (unsigned int flags)
503		572
504	Similar to C<ev_default_loop>, but always creates a new event loop that is	573	Similar to C<ev_default_loop>, but always creates a new event loop that is
505	always distinct from the default loop. Unlike the default loop, it cannot	574	always distinct from the default loop.
506	handle signal and child watchers, and attempts to do so will be greeted by
507	undefined behaviour (or a failed assertion if assertions are enabled).
508		575
509	Note that this function I<is> thread-safe, and the recommended way to use	576	Note that this function I<is> thread-safe, and one common way to use
510	libev with threads is indeed to create one loop per thread, and using the	577	libev with threads is indeed to create one loop per thread, and using the
511	default loop in the "main" or "initial" thread.	578	default loop in the "main" or "initial" thread.
512		579
513	Example: Try to create a event loop that uses epoll and nothing else.	580	Example: Try to create a event loop that uses epoll and nothing else.
514		581
…		…
516	if (!epoller)	583	if (!epoller)
517	fatal ("no epoll found here, maybe it hides under your chair");	584	fatal ("no epoll found here, maybe it hides under your chair");
518		585
519	=item ev_default_destroy ()	586	=item ev_default_destroy ()
520		587
521	Destroys the default loop again (frees all memory and kernel state	588	Destroys the default loop (frees all memory and kernel state etc.). None
522	etc.). None of the active event watchers will be stopped in the normal	589	of the active event watchers will be stopped in the normal sense, so
523	sense, so e.g. C<ev_is_active> might still return true. It is your	590	e.g. C<ev_is_active> might still return true. It is your responsibility to
524	responsibility to either stop all watchers cleanly yourself I<before>	591	either stop all watchers cleanly yourself I<before> calling this function,
525	calling this function, or cope with the fact afterwards (which is usually	592	or cope with the fact afterwards (which is usually the easiest thing, you
526	the easiest thing, you can just ignore the watchers and/or C<free ()> them	593	can just ignore the watchers and/or C<free ()> them for example).
527	for example).
528		594
529	Note that certain global state, such as signal state, will not be freed by	595	Note that certain global state, such as signal state (and installed signal
530	this function, and related watchers (such as signal and child watchers)	596	handlers), will not be freed by this function, and related watchers (such
531	would need to be stopped manually.	597	as signal and child watchers) would need to be stopped manually.
532		598
533	In general it is not advisable to call this function except in the	599	In general it is not advisable to call this function except in the
534	rare occasion where you really need to free e.g. the signal handling	600	rare occasion where you really need to free e.g. the signal handling
535	pipe fds. If you need dynamically allocated loops it is better to use	601	pipe fds. If you need dynamically allocated loops it is better to use
536	C<ev_loop_new> and C<ev_loop_destroy>).	602	C<ev_loop_new> and C<ev_loop_destroy>.
537		603
538	=item ev_loop_destroy (loop)	604	=item ev_loop_destroy (loop)
539		605
540	Like C<ev_default_destroy>, but destroys an event loop created by an	606	Like C<ev_default_destroy>, but destroys an event loop created by an
541	earlier call to C<ev_loop_new>.	607	earlier call to C<ev_loop_new>.
…		…
547	name, you can call it anytime, but it makes most sense after forking, in	613	name, you can call it anytime, but it makes most sense after forking, in
548	the child process (or both child and parent, but that again makes little	614	the child process (or both child and parent, but that again makes little
549	sense). You I<must> call it in the child before using any of the libev	615	sense). You I<must> call it in the child before using any of the libev
550	functions, and it will only take effect at the next C<ev_loop> iteration.	616	functions, and it will only take effect at the next C<ev_loop> iteration.
551		617
		618	Again, you I<have> to call it on I<any> loop that you want to re-use after
		619	a fork, I<even if you do not plan to use the loop in the parent>. This is
		620	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		621	during fork.
		622
552	On the other hand, you only need to call this function in the child	623	On the other hand, you only need to call this function in the child
553	process if and only if you want to use the event library in the child. If	624	process if and only if you want to use the event loop in the child. If you
554	you just fork+exec, you don't have to call it at all.	625	just fork+exec or create a new loop in the child, you don't have to call
		626	it at all.
555		627
556	The function itself is quite fast and it's usually not a problem to call	628	The function itself is quite fast and it's usually not a problem to call
557	it just in case after a fork. To make this easy, the function will fit in	629	it just in case after a fork. To make this easy, the function will fit in
558	quite nicely into a call to C<pthread_atfork>:	630	quite nicely into a call to C<pthread_atfork>:
559		631
…		…
561		633
562	=item ev_loop_fork (loop)	634	=item ev_loop_fork (loop)
563		635
564	Like C<ev_default_fork>, but acts on an event loop created by	636	Like C<ev_default_fork>, but acts on an event loop created by
565	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	637	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
566	after fork, and how you do this is entirely your own problem.	638	after fork that you want to re-use in the child, and how you keep track of
		639	them is entirely your own problem.
567		640
568	=item int ev_is_default_loop (loop)	641	=item int ev_is_default_loop (loop)
569		642
570	Returns true when the given loop actually is the default loop, false otherwise.	643	Returns true when the given loop is, in fact, the default loop, and false
		644	otherwise.
571		645
572	=item unsigned int ev_loop_count (loop)	646	=item unsigned int ev_iteration (loop)
573		647
574	Returns the count of loop iterations for the loop, which is identical to	648	Returns the current iteration count for the loop, which is identical to
575	the number of times libev did poll for new events. It starts at C<0> and	649	the number of times libev did poll for new events. It starts at C<0> and
576	happily wraps around with enough iterations.	650	happily wraps around with enough iterations.
577		651
578	This value can sometimes be useful as a generation counter of sorts (it	652	This value can sometimes be useful as a generation counter of sorts (it
579	"ticks" the number of loop iterations), as it roughly corresponds with	653	"ticks" the number of loop iterations), as it roughly corresponds with
580	C<ev_prepare> and C<ev_check> calls.	654	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		655	prepare and check phases.
		656
		657	=item unsigned int ev_depth (loop)
		658
		659	Returns the number of times C<ev_loop> was entered minus the number of
		660	times C<ev_loop> was exited, in other words, the recursion depth.
		661
		662	Outside C<ev_loop>, this number is zero. In a callback, this number is
		663	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),
		664	in which case it is higher.
		665
		666	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread
		667	etc.), doesn't count as "exit" - consider this as a hint to avoid such
		668	ungentleman behaviour unless it's really convenient.
581		669
582	=item unsigned int ev_backend (loop)	670	=item unsigned int ev_backend (loop)
583		671
584	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	672	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
585	use.	673	use.
…		…
600		688
601	This function is rarely useful, but when some event callback runs for a	689	This function is rarely useful, but when some event callback runs for a
602	very long time without entering the event loop, updating libev's idea of	690	very long time without entering the event loop, updating libev's idea of
603	the current time is a good idea.	691	the current time is a good idea.
604		692
605	See also "The special problem of time updates" in the C<ev_timer> section.	693	See also L<The special problem of time updates> in the C<ev_timer> section.
		694
		695	=item ev_suspend (loop)
		696
		697	=item ev_resume (loop)
		698
		699	These two functions suspend and resume a loop, for use when the loop is
		700	not used for a while and timeouts should not be processed.
		701
		702	A typical use case would be an interactive program such as a game: When
		703	the user presses C<^Z> to suspend the game and resumes it an hour later it
		704	would be best to handle timeouts as if no time had actually passed while
		705	the program was suspended. This can be achieved by calling C<ev_suspend>
		706	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		707	C<ev_resume> directly afterwards to resume timer processing.
		708
		709	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		710	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		711	will be rescheduled (that is, they will lose any events that would have
		712	occurred while suspended).
		713
		714	After calling C<ev_suspend> you B<must not> call I<any> function on the
		715	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		716	without a previous call to C<ev_suspend>.
		717
		718	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		719	event loop time (see C<ev_now_update>).
606		720
607	=item ev_loop (loop, int flags)	721	=item ev_loop (loop, int flags)
608		722
609	Finally, this is it, the event handler. This function usually is called	723	Finally, this is it, the event handler. This function usually is called
610	after you initialised all your watchers and you want to start handling	724	after you have initialised all your watchers and you want to start
611	events.	725	handling events.
612		726
613	If the flags argument is specified as C<0>, it will not return until	727	If the flags argument is specified as C<0>, it will not return until
614	either no event watchers are active anymore or C<ev_unloop> was called.	728	either no event watchers are active anymore or C<ev_unloop> was called.
615		729
616	Please note that an explicit C<ev_unloop> is usually better than	730	Please note that an explicit C<ev_unloop> is usually better than
617	relying on all watchers to be stopped when deciding when a program has	731	relying on all watchers to be stopped when deciding when a program has
618	finished (especially in interactive programs), but having a program that	732	finished (especially in interactive programs), but having a program
619	automatically loops as long as it has to and no longer by virtue of	733	that automatically loops as long as it has to and no longer by virtue
620	relying on its watchers stopping correctly is a thing of beauty.	734	of relying on its watchers stopping correctly, that is truly a thing of
		735	beauty.
621		736
622	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	737	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
623	those events and any outstanding ones, but will not block your process in	738	those events and any already outstanding ones, but will not block your
624	case there are no events and will return after one iteration of the loop.	739	process in case there are no events and will return after one iteration of
		740	the loop.
625		741
626	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	742	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
627	necessary) and will handle those and any outstanding ones. It will block	743	necessary) and will handle those and any already outstanding ones. It
628	your process until at least one new event arrives, and will return after	744	will block your process until at least one new event arrives (which could
629	one iteration of the loop. This is useful if you are waiting for some	745	be an event internal to libev itself, so there is no guarantee that a
630	external event in conjunction with something not expressible using other	746	user-registered callback will be called), and will return after one
		747	iteration of the loop.
		748
		749	This is useful if you are waiting for some external event in conjunction
		750	with something not expressible using other libev watchers (i.e. "roll your
631	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	751	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
632	usually a better approach for this kind of thing.	752	usually a better approach for this kind of thing.
633		753
634	Here are the gory details of what C<ev_loop> does:	754	Here are the gory details of what C<ev_loop> does:
635		755
636	- Before the first iteration, call any pending watchers.	756	- Before the first iteration, call any pending watchers.
…		…
646	any active watchers at all will result in not sleeping).	766	any active watchers at all will result in not sleeping).
647	- Sleep if the I/O and timer collect interval say so.	767	- Sleep if the I/O and timer collect interval say so.
648	- Block the process, waiting for any events.	768	- Block the process, waiting for any events.
649	- Queue all outstanding I/O (fd) events.	769	- Queue all outstanding I/O (fd) events.
650	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	770	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
651	- Queue all outstanding timers.	771	- Queue all expired timers.
652	- Queue all outstanding periodics.	772	- Queue all expired periodics.
653	- Unless any events are pending now, queue all idle watchers.	773	- Unless any events are pending now, queue all idle watchers.
654	- Queue all check watchers.	774	- Queue all check watchers.
655	- Call all queued watchers in reverse order (i.e. check watchers first).	775	- Call all queued watchers in reverse order (i.e. check watchers first).
656	Signals and child watchers are implemented as I/O watchers, and will	776	Signals and child watchers are implemented as I/O watchers, and will
657	be handled here by queueing them when their watcher gets executed.	777	be handled here by queueing them when their watcher gets executed.
…		…
674	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	794	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
675	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	795	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
676		796
677	This "unloop state" will be cleared when entering C<ev_loop> again.	797	This "unloop state" will be cleared when entering C<ev_loop> again.
678		798
		799	It is safe to call C<ev_unloop> from outside any C<ev_loop> calls.
		800
679	=item ev_ref (loop)	801	=item ev_ref (loop)
680		802
681	=item ev_unref (loop)	803	=item ev_unref (loop)
682		804
683	Ref/unref can be used to add or remove a reference count on the event	805	Ref/unref can be used to add or remove a reference count on the event
684	loop: Every watcher keeps one reference, and as long as the reference	806	loop: Every watcher keeps one reference, and as long as the reference
685	count is nonzero, C<ev_loop> will not return on its own. If you have	807	count is nonzero, C<ev_loop> will not return on its own.
686	a watcher you never unregister that should not keep C<ev_loop> from	808
687	returning, ev_unref() after starting, and ev_ref() before stopping it. For	809	This is useful when you have a watcher that you never intend to
		810	unregister, but that nevertheless should not keep C<ev_loop> from
		811	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
		812	before stopping it.
		813
688	example, libev itself uses this for its internal signal pipe: It is not	814	As an example, libev itself uses this for its internal signal pipe: It
689	visible to the libev user and should not keep C<ev_loop> from exiting if	815	is not visible to the libev user and should not keep C<ev_loop> from
690	no event watchers registered by it are active. It is also an excellent	816	exiting if no event watchers registered by it are active. It is also an
691	way to do this for generic recurring timers or from within third-party	817	excellent way to do this for generic recurring timers or from within
692	libraries. Just remember to I<unref after start> and I<ref before stop>	818	third-party libraries. Just remember to I<unref after start> and I<ref
693	(but only if the watcher wasn't active before, or was active before,	819	before stop> (but only if the watcher wasn't active before, or was active
694	respectively).	820	before, respectively. Note also that libev might stop watchers itself
		821	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		822	in the callback).
695		823
696	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	824	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
697	running when nothing else is active.	825	running when nothing else is active.
698		826
699	struct ev_signal exitsig;	827	ev_signal exitsig;
700	ev_signal_init (&exitsig, sig_cb, SIGINT);	828	ev_signal_init (&exitsig, sig_cb, SIGINT);
701	ev_signal_start (loop, &exitsig);	829	ev_signal_start (loop, &exitsig);
702	evf_unref (loop);	830	evf_unref (loop);
703		831
704	Example: For some weird reason, unregister the above signal handler again.	832	Example: For some weird reason, unregister the above signal handler again.
…		…
718	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	846	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
719	allows libev to delay invocation of I/O and timer/periodic callbacks	847	allows libev to delay invocation of I/O and timer/periodic callbacks
720	to increase efficiency of loop iterations (or to increase power-saving	848	to increase efficiency of loop iterations (or to increase power-saving
721	opportunities).	849	opportunities).
722		850
723	The background is that sometimes your program runs just fast enough to	851	The idea is that sometimes your program runs just fast enough to handle
724	handle one (or very few) event(s) per loop iteration. While this makes	852	one (or very few) event(s) per loop iteration. While this makes the
725	the program responsive, it also wastes a lot of CPU time to poll for new	853	program responsive, it also wastes a lot of CPU time to poll for new
726	events, especially with backends like C<select ()> which have a high	854	events, especially with backends like C<select ()> which have a high
727	overhead for the actual polling but can deliver many events at once.	855	overhead for the actual polling but can deliver many events at once.
728		856
729	By setting a higher I<io collect interval> you allow libev to spend more	857	By setting a higher I<io collect interval> you allow libev to spend more
730	time collecting I/O events, so you can handle more events per iteration,	858	time collecting I/O events, so you can handle more events per iteration,
731	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	859	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
732	C<ev_timer>) will be not affected. Setting this to a non-null value will	860	C<ev_timer>) will be not affected. Setting this to a non-null value will
733	introduce an additional C<ev_sleep ()> call into most loop iterations.	861	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		862	sleep time ensures that libev will not poll for I/O events more often then
		863	once per this interval, on average.
734		864
735	Likewise, by setting a higher I<timeout collect interval> you allow libev	865	Likewise, by setting a higher I<timeout collect interval> you allow libev
736	to spend more time collecting timeouts, at the expense of increased	866	to spend more time collecting timeouts, at the expense of increased
737	latency (the watcher callback will be called later). C<ev_io> watchers	867	latency/jitter/inexactness (the watcher callback will be called
738	will not be affected. Setting this to a non-null value will not introduce	868	later). C<ev_io> watchers will not be affected. Setting this to a non-null
739	any overhead in libev.	869	value will not introduce any overhead in libev.
740		870
741	Many (busy) programs can usually benefit by setting the I/O collect	871	Many (busy) programs can usually benefit by setting the I/O collect
742	interval to a value near C<0.1> or so, which is often enough for	872	interval to a value near C<0.1> or so, which is often enough for
743	interactive servers (of course not for games), likewise for timeouts. It	873	interactive servers (of course not for games), likewise for timeouts. It
744	usually doesn't make much sense to set it to a lower value than C<0.01>,	874	usually doesn't make much sense to set it to a lower value than C<0.01>,
745	as this approaches the timing granularity of most systems.	875	as this approaches the timing granularity of most systems. Note that if
		876	you do transactions with the outside world and you can't increase the
		877	parallelity, then this setting will limit your transaction rate (if you
		878	need to poll once per transaction and the I/O collect interval is 0.01,
		879	then you can't do more than 100 transactions per second).
746		880
747	Setting the I<timeout collect interval> can improve the opportunity for	881	Setting the I<timeout collect interval> can improve the opportunity for
748	saving power, as the program will "bundle" timer callback invocations that	882	saving power, as the program will "bundle" timer callback invocations that
749	are "near" in time together, by delaying some, thus reducing the number of	883	are "near" in time together, by delaying some, thus reducing the number of
750	times the process sleeps and wakes up again. Another useful technique to	884	times the process sleeps and wakes up again. Another useful technique to
751	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	885	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
752	they fire on, say, one-second boundaries only.	886	they fire on, say, one-second boundaries only.
753		887
		888	Example: we only need 0.1s timeout granularity, and we wish not to poll
		889	more often than 100 times per second:
		890
		891	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		892	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		893
		894	=item ev_invoke_pending (loop)
		895
		896	This call will simply invoke all pending watchers while resetting their
		897	pending state. Normally, C<ev_loop> does this automatically when required,
		898	but when overriding the invoke callback this call comes handy.
		899
		900	=item int ev_pending_count (loop)
		901
		902	Returns the number of pending watchers - zero indicates that no watchers
		903	are pending.
		904
		905	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		906
		907	This overrides the invoke pending functionality of the loop: Instead of
		908	invoking all pending watchers when there are any, C<ev_loop> will call
		909	this callback instead. This is useful, for example, when you want to
		910	invoke the actual watchers inside another context (another thread etc.).
		911
		912	If you want to reset the callback, use C<ev_invoke_pending> as new
		913	callback.
		914
		915	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		916
		917	Sometimes you want to share the same loop between multiple threads. This
		918	can be done relatively simply by putting mutex_lock/unlock calls around
		919	each call to a libev function.
		920
		921	However, C<ev_loop> can run an indefinite time, so it is not feasible to
		922	wait for it to return. One way around this is to wake up the loop via
		923	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>
		924	and I<acquire> callbacks on the loop.
		925
		926	When set, then C<release> will be called just before the thread is
		927	suspended waiting for new events, and C<acquire> is called just
		928	afterwards.
		929
		930	Ideally, C<release> will just call your mutex_unlock function, and
		931	C<acquire> will just call the mutex_lock function again.
		932
		933	While event loop modifications are allowed between invocations of
		934	C<release> and C<acquire> (that's their only purpose after all), no
		935	modifications done will affect the event loop, i.e. adding watchers will
		936	have no effect on the set of file descriptors being watched, or the time
		937	waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it
		938	to take note of any changes you made.
		939
		940	In theory, threads executing C<ev_loop> will be async-cancel safe between
		941	invocations of C<release> and C<acquire>.
		942
		943	See also the locking example in the C<THREADS> section later in this
		944	document.
		945
		946	=item ev_set_userdata (loop, void *data)
		947
		948	=item ev_userdata (loop)
		949
		950	Set and retrieve a single C<void *> associated with a loop. When
		951	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		952	C<0.>
		953
		954	These two functions can be used to associate arbitrary data with a loop,
		955	and are intended solely for the C<invoke_pending_cb>, C<release> and
		956	C<acquire> callbacks described above, but of course can be (ab-)used for
		957	any other purpose as well.
		958
754	=item ev_loop_verify (loop)	959	=item ev_loop_verify (loop)
755		960
756	This function only does something when C<EV_VERIFY> support has been	961	This function only does something when C<EV_VERIFY> support has been
757	compiled in. It tries to go through all internal structures and checks	962	compiled in, which is the default for non-minimal builds. It tries to go
758	them for validity. If anything is found to be inconsistent, it will print	963	through all internal structures and checks them for validity. If anything
759	an error message to standard error and call C<abort ()>.	964	is found to be inconsistent, it will print an error message to standard
		965	error and call C<abort ()>.
760		966
761	This can be used to catch bugs inside libev itself: under normal	967	This can be used to catch bugs inside libev itself: under normal
762	circumstances, this function will never abort as of course libev keeps its	968	circumstances, this function will never abort as of course libev keeps its
763	data structures consistent.	969	data structures consistent.
764		970
765	=back	971	=back
766		972
767		973
768	=head1 ANATOMY OF A WATCHER	974	=head1 ANATOMY OF A WATCHER
769		975
		976	In the following description, uppercase C<TYPE> in names stands for the
		977	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		978	watchers and C<ev_io_start> for I/O watchers.
		979
770	A watcher is a structure that you create and register to record your	980	A watcher is a structure that you create and register to record your
771	interest in some event. For instance, if you want to wait for STDIN to	981	interest in some event. For instance, if you want to wait for STDIN to
772	become readable, you would create an C<ev_io> watcher for that:	982	become readable, you would create an C<ev_io> watcher for that:
773		983
774	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	984	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
775	{	985	{
776	ev_io_stop (w);	986	ev_io_stop (w);
777	ev_unloop (loop, EVUNLOOP_ALL);	987	ev_unloop (loop, EVUNLOOP_ALL);
778	}	988	}
779		989
780	struct ev_loop *loop = ev_default_loop (0);	990	struct ev_loop *loop = ev_default_loop (0);
		991
781	struct ev_io stdin_watcher;	992	ev_io stdin_watcher;
		993
782	ev_init (&stdin_watcher, my_cb);	994	ev_init (&stdin_watcher, my_cb);
783	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	995	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
784	ev_io_start (loop, &stdin_watcher);	996	ev_io_start (loop, &stdin_watcher);
		997
785	ev_loop (loop, 0);	998	ev_loop (loop, 0);
786		999
787	As you can see, you are responsible for allocating the memory for your	1000	As you can see, you are responsible for allocating the memory for your
788	watcher structures (and it is usually a bad idea to do this on the stack,	1001	watcher structures (and it is I<usually> a bad idea to do this on the
789	although this can sometimes be quite valid).	1002	stack).
		1003
		1004	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		1005	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
790		1006
791	Each watcher structure must be initialised by a call to C<ev_init	1007	Each watcher structure must be initialised by a call to C<ev_init
792	(watcher *, callback)>, which expects a callback to be provided. This	1008	(watcher *, callback)>, which expects a callback to be provided. This
793	callback gets invoked each time the event occurs (or, in the case of I/O	1009	callback gets invoked each time the event occurs (or, in the case of I/O
794	watchers, each time the event loop detects that the file descriptor given	1010	watchers, each time the event loop detects that the file descriptor given
795	is readable and/or writable).	1011	is readable and/or writable).
796		1012
797	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1013	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
798	with arguments specific to this watcher type. There is also a macro	1014	macro to configure it, with arguments specific to the watcher type. There
799	to combine initialisation and setting in one call: C<< ev_<type>_init	1015	is also a macro to combine initialisation and setting in one call: C<<
800	(watcher *, callback, ...) >>.	1016	ev_TYPE_init (watcher *, callback, ...) >>.
801		1017
802	To make the watcher actually watch out for events, you have to start it	1018	To make the watcher actually watch out for events, you have to start it
803	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	1019	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
804	*) >>), and you can stop watching for events at any time by calling the	1020	*) >>), and you can stop watching for events at any time by calling the
805	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1021	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
806		1022
807	As long as your watcher is active (has been started but not stopped) you	1023	As long as your watcher is active (has been started but not stopped) you
808	must not touch the values stored in it. Most specifically you must never	1024	must not touch the values stored in it. Most specifically you must never
809	reinitialise it or call its C<set> macro.	1025	reinitialise it or call its C<ev_TYPE_set> macro.
810		1026
811	Each and every callback receives the event loop pointer as first, the	1027	Each and every callback receives the event loop pointer as first, the
812	registered watcher structure as second, and a bitset of received events as	1028	registered watcher structure as second, and a bitset of received events as
813	third argument.	1029	third argument.
814		1030
…		…
823	=item C<EV_WRITE>	1039	=item C<EV_WRITE>
824		1040
825	The file descriptor in the C<ev_io> watcher has become readable and/or	1041	The file descriptor in the C<ev_io> watcher has become readable and/or
826	writable.	1042	writable.
827		1043
828	=item C<EV_TIMEOUT>	1044	=item C<EV_TIMER>
829		1045
830	The C<ev_timer> watcher has timed out.	1046	The C<ev_timer> watcher has timed out.
831		1047
832	=item C<EV_PERIODIC>	1048	=item C<EV_PERIODIC>
833		1049
…		…
872		1088
873	=item C<EV_ASYNC>	1089	=item C<EV_ASYNC>
874		1090
875	The given async watcher has been asynchronously notified (see C<ev_async>).	1091	The given async watcher has been asynchronously notified (see C<ev_async>).
876		1092
		1093	=item C<EV_CUSTOM>
		1094
		1095	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1096	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		1097
877	=item C<EV_ERROR>	1098	=item C<EV_ERROR>
878		1099
879	An unspecified error has occurred, the watcher has been stopped. This might	1100	An unspecified error has occurred, the watcher has been stopped. This might
880	happen because the watcher could not be properly started because libev	1101	happen because the watcher could not be properly started because libev
881	ran out of memory, a file descriptor was found to be closed or any other	1102	ran out of memory, a file descriptor was found to be closed or any other
		1103	problem. Libev considers these application bugs.
		1104
882	problem. You best act on it by reporting the problem and somehow coping	1105	You best act on it by reporting the problem and somehow coping with the
883	with the watcher being stopped.	1106	watcher being stopped. Note that well-written programs should not receive
		1107	an error ever, so when your watcher receives it, this usually indicates a
		1108	bug in your program.
884		1109
885	Libev will usually signal a few "dummy" events together with an error,	1110	Libev will usually signal a few "dummy" events together with an error, for
886	for example it might indicate that a fd is readable or writable, and if	1111	example it might indicate that a fd is readable or writable, and if your
887	your callbacks is well-written it can just attempt the operation and cope	1112	callbacks is well-written it can just attempt the operation and cope with
888	with the error from read() or write(). This will not work in multi-threaded	1113	the error from read() or write(). This will not work in multi-threaded
889	programs, though, so beware.	1114	programs, though, as the fd could already be closed and reused for another
		1115	thing, so beware.
890		1116
891	=back	1117	=back
892		1118
893	=head2 GENERIC WATCHER FUNCTIONS	1119	=head2 GENERIC WATCHER FUNCTIONS
894
895	In the following description, C<TYPE> stands for the watcher type,
896	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
897		1120
898	=over 4	1121	=over 4
899		1122
900	=item C<ev_init> (ev_TYPE *watcher, callback)	1123	=item C<ev_init> (ev_TYPE *watcher, callback)
901		1124
…		…
907	which rolls both calls into one.	1130	which rolls both calls into one.
908		1131
909	You can reinitialise a watcher at any time as long as it has been stopped	1132	You can reinitialise a watcher at any time as long as it has been stopped
910	(or never started) and there are no pending events outstanding.	1133	(or never started) and there are no pending events outstanding.
911		1134
912	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1135	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
913	int revents)>.	1136	int revents)>.
914		1137
		1138	Example: Initialise an C<ev_io> watcher in two steps.
		1139
		1140	ev_io w;
		1141	ev_init (&w, my_cb);
		1142	ev_io_set (&w, STDIN_FILENO, EV_READ);
		1143
915	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1144	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
916		1145
917	This macro initialises the type-specific parts of a watcher. You need to	1146	This macro initialises the type-specific parts of a watcher. You need to
918	call C<ev_init> at least once before you call this macro, but you can	1147	call C<ev_init> at least once before you call this macro, but you can
919	call C<ev_TYPE_set> any number of times. You must not, however, call this	1148	call C<ev_TYPE_set> any number of times. You must not, however, call this
920	macro on a watcher that is active (it can be pending, however, which is a	1149	macro on a watcher that is active (it can be pending, however, which is a
921	difference to the C<ev_init> macro).	1150	difference to the C<ev_init> macro).
922		1151
923	Although some watcher types do not have type-specific arguments	1152	Although some watcher types do not have type-specific arguments
924	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	1153	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
925		1154
		1155	See C<ev_init>, above, for an example.
		1156
926	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1157	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
927		1158
928	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1159	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
929	calls into a single call. This is the most convenient method to initialise	1160	calls into a single call. This is the most convenient method to initialise
930	a watcher. The same limitations apply, of course.	1161	a watcher. The same limitations apply, of course.
931		1162
		1163	Example: Initialise and set an C<ev_io> watcher in one step.
		1164
		1165	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1166
932	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1167	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
933		1168
934	Starts (activates) the given watcher. Only active watchers will receive	1169	Starts (activates) the given watcher. Only active watchers will receive
935	events. If the watcher is already active nothing will happen.	1170	events. If the watcher is already active nothing will happen.
936		1171
		1172	Example: Start the C<ev_io> watcher that is being abused as example in this
		1173	whole section.
		1174
		1175	ev_io_start (EV_DEFAULT_UC, &w);
		1176
937	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1177	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
938		1178
939	Stops the given watcher again (if active) and clears the pending	1179	Stops the given watcher if active, and clears the pending status (whether
		1180	the watcher was active or not).
		1181
940	status. It is possible that stopped watchers are pending (for example,	1182	It is possible that stopped watchers are pending - for example,
941	non-repeating timers are being stopped when they become pending), but	1183	non-repeating timers are being stopped when they become pending - but
942	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1184	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
943	you want to free or reuse the memory used by the watcher it is therefore a	1185	pending. If you want to free or reuse the memory used by the watcher it is
944	good idea to always call its C<ev_TYPE_stop> function.	1186	therefore a good idea to always call its C<ev_TYPE_stop> function.
945		1187
946	=item bool ev_is_active (ev_TYPE *watcher)	1188	=item bool ev_is_active (ev_TYPE *watcher)
947		1189
948	Returns a true value iff the watcher is active (i.e. it has been started	1190	Returns a true value iff the watcher is active (i.e. it has been started
949	and not yet been stopped). As long as a watcher is active you must not modify	1191	and not yet been stopped). As long as a watcher is active you must not modify
…		…
965	=item ev_cb_set (ev_TYPE *watcher, callback)	1207	=item ev_cb_set (ev_TYPE *watcher, callback)
966		1208
967	Change the callback. You can change the callback at virtually any time	1209	Change the callback. You can change the callback at virtually any time
968	(modulo threads).	1210	(modulo threads).
969		1211
970	=item ev_set_priority (ev_TYPE *watcher, priority)	1212	=item ev_set_priority (ev_TYPE *watcher, int priority)
971		1213
972	=item int ev_priority (ev_TYPE *watcher)	1214	=item int ev_priority (ev_TYPE *watcher)
973		1215
974	Set and query the priority of the watcher. The priority is a small	1216	Set and query the priority of the watcher. The priority is a small
975	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1217	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
976	(default: C<-2>). Pending watchers with higher priority will be invoked	1218	(default: C<-2>). Pending watchers with higher priority will be invoked
977	before watchers with lower priority, but priority will not keep watchers	1219	before watchers with lower priority, but priority will not keep watchers
978	from being executed (except for C<ev_idle> watchers).	1220	from being executed (except for C<ev_idle> watchers).
979		1221
980	This means that priorities are I<only> used for ordering callback
981	invocation after new events have been received. This is useful, for
982	example, to reduce latency after idling, or more often, to bind two
983	watchers on the same event and make sure one is called first.
984
985	If you need to suppress invocation when higher priority events are pending	1222	If you need to suppress invocation when higher priority events are pending
986	you need to look at C<ev_idle> watchers, which provide this functionality.	1223	you need to look at C<ev_idle> watchers, which provide this functionality.
987		1224
988	You I<must not> change the priority of a watcher as long as it is active or	1225	You I<must not> change the priority of a watcher as long as it is active or
989	pending.	1226	pending.
990		1227
		1228	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1229	fine, as long as you do not mind that the priority value you query might
		1230	or might not have been clamped to the valid range.
		1231
991	The default priority used by watchers when no priority has been set is	1232	The default priority used by watchers when no priority has been set is
992	always C<0>, which is supposed to not be too high and not be too low :).	1233	always C<0>, which is supposed to not be too high and not be too low :).
993		1234
994	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1235	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
995	fine, as long as you do not mind that the priority value you query might	1236	priorities.
996	or might not have been adjusted to be within valid range.
997		1237
998	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1238	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
999		1239
1000	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1240	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1001	C<loop> nor C<revents> need to be valid as long as the watcher callback	1241	C<loop> nor C<revents> need to be valid as long as the watcher callback
1002	can deal with that fact.	1242	can deal with that fact, as both are simply passed through to the
		1243	callback.
1003		1244
1004	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1245	=item int ev_clear_pending (loop, ev_TYPE *watcher)
1005		1246
1006	If the watcher is pending, this function returns clears its pending status	1247	If the watcher is pending, this function clears its pending status and
1007	and returns its C<revents> bitset (as if its callback was invoked). If the	1248	returns its C<revents> bitset (as if its callback was invoked). If the
1008	watcher isn't pending it does nothing and returns C<0>.	1249	watcher isn't pending it does nothing and returns C<0>.
1009		1250
		1251	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1252	callback to be invoked, which can be accomplished with this function.
		1253
		1254	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1255
		1256	Feeds the given event set into the event loop, as if the specified event
		1257	had happened for the specified watcher (which must be a pointer to an
		1258	initialised but not necessarily started event watcher). Obviously you must
		1259	not free the watcher as long as it has pending events.
		1260
		1261	Stopping the watcher, letting libev invoke it, or calling
		1262	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1263	not started in the first place.
		1264
		1265	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1266	functions that do not need a watcher.
		1267
1010	=back	1268	=back
1011		1269
1012		1270
1013	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1271	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1014		1272
1015	Each watcher has, by default, a member C<void *data> that you can change	1273	Each watcher has, by default, a member C<void *data> that you can change
1016	and read at any time, libev will completely ignore it. This can be used	1274	and read at any time: libev will completely ignore it. This can be used
1017	to associate arbitrary data with your watcher. If you need more data and	1275	to associate arbitrary data with your watcher. If you need more data and
1018	don't want to allocate memory and store a pointer to it in that data	1276	don't want to allocate memory and store a pointer to it in that data
1019	member, you can also "subclass" the watcher type and provide your own	1277	member, you can also "subclass" the watcher type and provide your own
1020	data:	1278	data:
1021		1279
1022	struct my_io	1280	struct my_io
1023	{	1281	{
1024	struct ev_io io;	1282	ev_io io;
1025	int otherfd;	1283	int otherfd;
1026	void *somedata;	1284	void *somedata;
1027	struct whatever *mostinteresting;	1285	struct whatever *mostinteresting;
1028	};	1286	};
1029		1287
…		…
1032	ev_io_init (&w.io, my_cb, fd, EV_READ);	1290	ev_io_init (&w.io, my_cb, fd, EV_READ);
1033		1291
1034	And since your callback will be called with a pointer to the watcher, you	1292	And since your callback will be called with a pointer to the watcher, you
1035	can cast it back to your own type:	1293	can cast it back to your own type:
1036		1294
1037	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1295	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1038	{	1296	{
1039	struct my_io *w = (struct my_io *)w_;	1297	struct my_io *w = (struct my_io *)w_;
1040	...	1298	...
1041	}	1299	}
1042		1300
…		…
1053	ev_timer t2;	1311	ev_timer t2;
1054	}	1312	}
1055		1313
1056	In this case getting the pointer to C<my_biggy> is a bit more	1314	In this case getting the pointer to C<my_biggy> is a bit more
1057	complicated: Either you store the address of your C<my_biggy> struct	1315	complicated: Either you store the address of your C<my_biggy> struct
1058	in the C<data> member of the watcher, or you need to use some pointer	1316	in the C<data> member of the watcher (for woozies), or you need to use
1059	arithmetic using C<offsetof> inside your watchers:	1317	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1318	programmers):
1060		1319
1061	#include <stddef.h>	1320	#include <stddef.h>
1062		1321
1063	static void	1322	static void
1064	t1_cb (EV_P_ struct ev_timer *w, int revents)	1323	t1_cb (EV_P_ ev_timer *w, int revents)
1065	{	1324	{
1066	struct my_biggy big = (struct my_biggy *	1325	struct my_biggy big = (struct my_biggy *)
1067	(((char *)w) - offsetof (struct my_biggy, t1));	1326	(((char *)w) - offsetof (struct my_biggy, t1));
1068	}	1327	}
1069		1328
1070	static void	1329	static void
1071	t2_cb (EV_P_ struct ev_timer *w, int revents)	1330	t2_cb (EV_P_ ev_timer *w, int revents)
1072	{	1331	{
1073	struct my_biggy big = (struct my_biggy *	1332	struct my_biggy big = (struct my_biggy *)
1074	(((char *)w) - offsetof (struct my_biggy, t2));	1333	(((char *)w) - offsetof (struct my_biggy, t2));
1075	}	1334	}
		1335
		1336	=head2 WATCHER PRIORITY MODELS
		1337
		1338	Many event loops support I<watcher priorities>, which are usually small
		1339	integers that influence the ordering of event callback invocation
		1340	between watchers in some way, all else being equal.
		1341
		1342	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1343	description for the more technical details such as the actual priority
		1344	range.
		1345
		1346	There are two common ways how these these priorities are being interpreted
		1347	by event loops:
		1348
		1349	In the more common lock-out model, higher priorities "lock out" invocation
		1350	of lower priority watchers, which means as long as higher priority
		1351	watchers receive events, lower priority watchers are not being invoked.
		1352
		1353	The less common only-for-ordering model uses priorities solely to order
		1354	callback invocation within a single event loop iteration: Higher priority
		1355	watchers are invoked before lower priority ones, but they all get invoked
		1356	before polling for new events.
		1357
		1358	Libev uses the second (only-for-ordering) model for all its watchers
		1359	except for idle watchers (which use the lock-out model).
		1360
		1361	The rationale behind this is that implementing the lock-out model for
		1362	watchers is not well supported by most kernel interfaces, and most event
		1363	libraries will just poll for the same events again and again as long as
		1364	their callbacks have not been executed, which is very inefficient in the
		1365	common case of one high-priority watcher locking out a mass of lower
		1366	priority ones.
		1367
		1368	Static (ordering) priorities are most useful when you have two or more
		1369	watchers handling the same resource: a typical usage example is having an
		1370	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1371	timeouts. Under load, data might be received while the program handles
		1372	other jobs, but since timers normally get invoked first, the timeout
		1373	handler will be executed before checking for data. In that case, giving
		1374	the timer a lower priority than the I/O watcher ensures that I/O will be
		1375	handled first even under adverse conditions (which is usually, but not
		1376	always, what you want).
		1377
		1378	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1379	will only be executed when no same or higher priority watchers have
		1380	received events, they can be used to implement the "lock-out" model when
		1381	required.
		1382
		1383	For example, to emulate how many other event libraries handle priorities,
		1384	you can associate an C<ev_idle> watcher to each such watcher, and in
		1385	the normal watcher callback, you just start the idle watcher. The real
		1386	processing is done in the idle watcher callback. This causes libev to
		1387	continuously poll and process kernel event data for the watcher, but when
		1388	the lock-out case is known to be rare (which in turn is rare :), this is
		1389	workable.
		1390
		1391	Usually, however, the lock-out model implemented that way will perform
		1392	miserably under the type of load it was designed to handle. In that case,
		1393	it might be preferable to stop the real watcher before starting the
		1394	idle watcher, so the kernel will not have to process the event in case
		1395	the actual processing will be delayed for considerable time.
		1396
		1397	Here is an example of an I/O watcher that should run at a strictly lower
		1398	priority than the default, and which should only process data when no
		1399	other events are pending:
		1400
		1401	ev_idle idle; // actual processing watcher
		1402	ev_io io; // actual event watcher
		1403
		1404	static void
		1405	io_cb (EV_P_ ev_io *w, int revents)
		1406	{
		1407	// stop the I/O watcher, we received the event, but
		1408	// are not yet ready to handle it.
		1409	ev_io_stop (EV_A_ w);
		1410
		1411	// start the idle watcher to handle the actual event.
		1412	// it will not be executed as long as other watchers
		1413	// with the default priority are receiving events.
		1414	ev_idle_start (EV_A_ &idle);
		1415	}
		1416
		1417	static void
		1418	idle_cb (EV_P_ ev_idle *w, int revents)
		1419	{
		1420	// actual processing
		1421	read (STDIN_FILENO, ...);
		1422
		1423	// have to start the I/O watcher again, as
		1424	// we have handled the event
		1425	ev_io_start (EV_P_ &io);
		1426	}
		1427
		1428	// initialisation
		1429	ev_idle_init (&idle, idle_cb);
		1430	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1431	ev_io_start (EV_DEFAULT_ &io);
		1432
		1433	In the "real" world, it might also be beneficial to start a timer, so that
		1434	low-priority connections can not be locked out forever under load. This
		1435	enables your program to keep a lower latency for important connections
		1436	during short periods of high load, while not completely locking out less
		1437	important ones.
1076		1438
1077		1439
1078	=head1 WATCHER TYPES	1440	=head1 WATCHER TYPES
1079		1441
1080	This section describes each watcher in detail, but will not repeat	1442	This section describes each watcher in detail, but will not repeat
…		…
1104	In general you can register as many read and/or write event watchers per	1466	In general you can register as many read and/or write event watchers per
1105	fd as you want (as long as you don't confuse yourself). Setting all file	1467	fd as you want (as long as you don't confuse yourself). Setting all file
1106	descriptors to non-blocking mode is also usually a good idea (but not	1468	descriptors to non-blocking mode is also usually a good idea (but not
1107	required if you know what you are doing).	1469	required if you know what you are doing).
1108		1470
1109	If you must do this, then force the use of a known-to-be-good backend	1471	If you cannot use non-blocking mode, then force the use of a
1110	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1472	known-to-be-good backend (at the time of this writing, this includes only
1111	C<EVBACKEND_POLL>).	1473	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1474	descriptors for which non-blocking operation makes no sense (such as
		1475	files) - libev doesn't guarantee any specific behaviour in that case.
1112		1476
1113	Another thing you have to watch out for is that it is quite easy to	1477	Another thing you have to watch out for is that it is quite easy to
1114	receive "spurious" readiness notifications, that is your callback might	1478	receive "spurious" readiness notifications, that is your callback might
1115	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1479	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1116	because there is no data. Not only are some backends known to create a	1480	because there is no data. Not only are some backends known to create a
1117	lot of those (for example Solaris ports), it is very easy to get into	1481	lot of those (for example Solaris ports), it is very easy to get into
1118	this situation even with a relatively standard program structure. Thus	1482	this situation even with a relatively standard program structure. Thus
1119	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1483	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1120	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1484	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1121		1485
1122	If you cannot run the fd in non-blocking mode (for example you should not	1486	If you cannot run the fd in non-blocking mode (for example you should
1123	play around with an Xlib connection), then you have to separately re-test	1487	not play around with an Xlib connection), then you have to separately
1124	whether a file descriptor is really ready with a known-to-be good interface	1488	re-test whether a file descriptor is really ready with a known-to-be good
1125	such as poll (fortunately in our Xlib example, Xlib already does this on	1489	interface such as poll (fortunately in our Xlib example, Xlib already
1126	its own, so its quite safe to use).	1490	does this on its own, so its quite safe to use). Some people additionally
		1491	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1492	indefinitely.
		1493
		1494	But really, best use non-blocking mode.
1127		1495
1128	=head3 The special problem of disappearing file descriptors	1496	=head3 The special problem of disappearing file descriptors
1129		1497
1130	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1498	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1131	descriptor (either by calling C<close> explicitly or by any other means,	1499	descriptor (either due to calling C<close> explicitly or any other means,
1132	such as C<dup>). The reason is that you register interest in some file	1500	such as C<dup2>). The reason is that you register interest in some file
1133	descriptor, but when it goes away, the operating system will silently drop	1501	descriptor, but when it goes away, the operating system will silently drop
1134	this interest. If another file descriptor with the same number then is	1502	this interest. If another file descriptor with the same number then is
1135	registered with libev, there is no efficient way to see that this is, in	1503	registered with libev, there is no efficient way to see that this is, in
1136	fact, a different file descriptor.	1504	fact, a different file descriptor.
1137		1505
…		…
1168	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1536	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1169	C<EVBACKEND_POLL>.	1537	C<EVBACKEND_POLL>.
1170		1538
1171	=head3 The special problem of SIGPIPE	1539	=head3 The special problem of SIGPIPE
1172		1540
1173	While not really specific to libev, it is easy to forget about SIGPIPE:	1541	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1174	when writing to a pipe whose other end has been closed, your program gets	1542	when writing to a pipe whose other end has been closed, your program gets
1175	send a SIGPIPE, which, by default, aborts your program. For most programs	1543	sent a SIGPIPE, which, by default, aborts your program. For most programs
1176	this is sensible behaviour, for daemons, this is usually undesirable.	1544	this is sensible behaviour, for daemons, this is usually undesirable.
1177		1545
1178	So when you encounter spurious, unexplained daemon exits, make sure you	1546	So when you encounter spurious, unexplained daemon exits, make sure you
1179	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1547	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1180	somewhere, as that would have given you a big clue).	1548	somewhere, as that would have given you a big clue).
1181		1549
		1550	=head3 The special problem of accept()ing when you can't
		1551
		1552	Many implementations of the POSIX C<accept> function (for example,
		1553	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1554	connection from the pending queue in all error cases.
		1555
		1556	For example, larger servers often run out of file descriptors (because
		1557	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1558	rejecting the connection, leading to libev signalling readiness on
		1559	the next iteration again (the connection still exists after all), and
		1560	typically causing the program to loop at 100% CPU usage.
		1561
		1562	Unfortunately, the set of errors that cause this issue differs between
		1563	operating systems, there is usually little the app can do to remedy the
		1564	situation, and no known thread-safe method of removing the connection to
		1565	cope with overload is known (to me).
		1566
		1567	One of the easiest ways to handle this situation is to just ignore it
		1568	- when the program encounters an overload, it will just loop until the
		1569	situation is over. While this is a form of busy waiting, no OS offers an
		1570	event-based way to handle this situation, so it's the best one can do.
		1571
		1572	A better way to handle the situation is to log any errors other than
		1573	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1574	messages, and continue as usual, which at least gives the user an idea of
		1575	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1576	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1577	usage.
		1578
		1579	If your program is single-threaded, then you could also keep a dummy file
		1580	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1581	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1582	close that fd, and create a new dummy fd. This will gracefully refuse
		1583	clients under typical overload conditions.
		1584
		1585	The last way to handle it is to simply log the error and C<exit>, as
		1586	is often done with C<malloc> failures, but this results in an easy
		1587	opportunity for a DoS attack.
1182		1588
1183	=head3 Watcher-Specific Functions	1589	=head3 Watcher-Specific Functions
1184		1590
1185	=over 4	1591	=over 4
1186		1592
1187	=item ev_io_init (ev_io *, callback, int fd, int events)	1593	=item ev_io_init (ev_io *, callback, int fd, int events)
1188		1594
1189	=item ev_io_set (ev_io *, int fd, int events)	1595	=item ev_io_set (ev_io *, int fd, int events)
1190		1596
1191	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1597	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1192	receive events for and events is either C<EV_READ>, C<EV_WRITE> or	1598	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1193	C<EV_READ | EV_WRITE> to receive the given events.	1599	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1194		1600
1195	=item int fd [read-only]	1601	=item int fd [read-only]
1196		1602
1197	The file descriptor being watched.	1603	The file descriptor being watched.
1198		1604
…		…
1207	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1613	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1208	readable, but only once. Since it is likely line-buffered, you could	1614	readable, but only once. Since it is likely line-buffered, you could
1209	attempt to read a whole line in the callback.	1615	attempt to read a whole line in the callback.
1210		1616
1211	static void	1617	static void
1212	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1618	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1213	{	1619	{
1214	ev_io_stop (loop, w);	1620	ev_io_stop (loop, w);
1215	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1621	.. read from stdin here (or from w->fd) and handle any I/O errors
1216	}	1622	}
1217		1623
1218	...	1624	...
1219	struct ev_loop *loop = ev_default_init (0);	1625	struct ev_loop *loop = ev_default_init (0);
1220	struct ev_io stdin_readable;	1626	ev_io stdin_readable;
1221	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1627	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1222	ev_io_start (loop, &stdin_readable);	1628	ev_io_start (loop, &stdin_readable);
1223	ev_loop (loop, 0);	1629	ev_loop (loop, 0);
1224		1630
1225		1631
…		…
1228	Timer watchers are simple relative timers that generate an event after a	1634	Timer watchers are simple relative timers that generate an event after a
1229	given time, and optionally repeating in regular intervals after that.	1635	given time, and optionally repeating in regular intervals after that.
1230		1636
1231	The timers are based on real time, that is, if you register an event that	1637	The timers are based on real time, that is, if you register an event that
1232	times out after an hour and you reset your system clock to January last	1638	times out after an hour and you reset your system clock to January last
1233	year, it will still time out after (roughly) and hour. "Roughly" because	1639	year, it will still time out after (roughly) one hour. "Roughly" because
1234	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1640	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1235	monotonic clock option helps a lot here).	1641	monotonic clock option helps a lot here).
1236		1642
1237	The callback is guaranteed to be invoked only after its timeout has passed,	1643	The callback is guaranteed to be invoked only I<after> its timeout has
1238	but if multiple timers become ready during the same loop iteration then	1644	passed (not I<at>, so on systems with very low-resolution clocks this
1239	order of execution is undefined.	1645	might introduce a small delay). If multiple timers become ready during the
		1646	same loop iteration then the ones with earlier time-out values are invoked
		1647	before ones of the same priority with later time-out values (but this is
		1648	no longer true when a callback calls C<ev_loop> recursively).
		1649
		1650	=head3 Be smart about timeouts
		1651
		1652	Many real-world problems involve some kind of timeout, usually for error
		1653	recovery. A typical example is an HTTP request - if the other side hangs,
		1654	you want to raise some error after a while.
		1655
		1656	What follows are some ways to handle this problem, from obvious and
		1657	inefficient to smart and efficient.
		1658
		1659	In the following, a 60 second activity timeout is assumed - a timeout that
		1660	gets reset to 60 seconds each time there is activity (e.g. each time some
		1661	data or other life sign was received).
		1662
		1663	=over 4
		1664
		1665	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1666
		1667	This is the most obvious, but not the most simple way: In the beginning,
		1668	start the watcher:
		1669
		1670	ev_timer_init (timer, callback, 60., 0.);
		1671	ev_timer_start (loop, timer);
		1672
		1673	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1674	and start it again:
		1675
		1676	ev_timer_stop (loop, timer);
		1677	ev_timer_set (timer, 60., 0.);
		1678	ev_timer_start (loop, timer);
		1679
		1680	This is relatively simple to implement, but means that each time there is
		1681	some activity, libev will first have to remove the timer from its internal
		1682	data structure and then add it again. Libev tries to be fast, but it's
		1683	still not a constant-time operation.
		1684
		1685	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1686
		1687	This is the easiest way, and involves using C<ev_timer_again> instead of
		1688	C<ev_timer_start>.
		1689
		1690	To implement this, configure an C<ev_timer> with a C<repeat> value
		1691	of C<60> and then call C<ev_timer_again> at start and each time you
		1692	successfully read or write some data. If you go into an idle state where
		1693	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1694	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1695
		1696	That means you can ignore both the C<ev_timer_start> function and the
		1697	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1698	member and C<ev_timer_again>.
		1699
		1700	At start:
		1701
		1702	ev_init (timer, callback);
		1703	timer->repeat = 60.;
		1704	ev_timer_again (loop, timer);
		1705
		1706	Each time there is some activity:
		1707
		1708	ev_timer_again (loop, timer);
		1709
		1710	It is even possible to change the time-out on the fly, regardless of
		1711	whether the watcher is active or not:
		1712
		1713	timer->repeat = 30.;
		1714	ev_timer_again (loop, timer);
		1715
		1716	This is slightly more efficient then stopping/starting the timer each time
		1717	you want to modify its timeout value, as libev does not have to completely
		1718	remove and re-insert the timer from/into its internal data structure.
		1719
		1720	It is, however, even simpler than the "obvious" way to do it.
		1721
		1722	=item 3. Let the timer time out, but then re-arm it as required.
		1723
		1724	This method is more tricky, but usually most efficient: Most timeouts are
		1725	relatively long compared to the intervals between other activity - in
		1726	our example, within 60 seconds, there are usually many I/O events with
		1727	associated activity resets.
		1728
		1729	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1730	but remember the time of last activity, and check for a real timeout only
		1731	within the callback:
		1732
		1733	ev_tstamp last_activity; // time of last activity
		1734
		1735	static void
		1736	callback (EV_P_ ev_timer *w, int revents)
		1737	{
		1738	ev_tstamp now = ev_now (EV_A);
		1739	ev_tstamp timeout = last_activity + 60.;
		1740
		1741	// if last_activity + 60. is older than now, we did time out
		1742	if (timeout < now)
		1743	{
		1744	// timeout occurred, take action
		1745	}
		1746	else
		1747	{
		1748	// callback was invoked, but there was some activity, re-arm
		1749	// the watcher to fire in last_activity + 60, which is
		1750	// guaranteed to be in the future, so "again" is positive:
		1751	w->repeat = timeout - now;
		1752	ev_timer_again (EV_A_ w);
		1753	}
		1754	}
		1755
		1756	To summarise the callback: first calculate the real timeout (defined
		1757	as "60 seconds after the last activity"), then check if that time has
		1758	been reached, which means something I<did>, in fact, time out. Otherwise
		1759	the callback was invoked too early (C<timeout> is in the future), so
		1760	re-schedule the timer to fire at that future time, to see if maybe we have
		1761	a timeout then.
		1762
		1763	Note how C<ev_timer_again> is used, taking advantage of the
		1764	C<ev_timer_again> optimisation when the timer is already running.
		1765
		1766	This scheme causes more callback invocations (about one every 60 seconds
		1767	minus half the average time between activity), but virtually no calls to
		1768	libev to change the timeout.
		1769
		1770	To start the timer, simply initialise the watcher and set C<last_activity>
		1771	to the current time (meaning we just have some activity :), then call the
		1772	callback, which will "do the right thing" and start the timer:
		1773
		1774	ev_init (timer, callback);
		1775	last_activity = ev_now (loop);
		1776	callback (loop, timer, EV_TIMER);
		1777
		1778	And when there is some activity, simply store the current time in
		1779	C<last_activity>, no libev calls at all:
		1780
		1781	last_activity = ev_now (loop);
		1782
		1783	This technique is slightly more complex, but in most cases where the
		1784	time-out is unlikely to be triggered, much more efficient.
		1785
		1786	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1787	callback :) - just change the timeout and invoke the callback, which will
		1788	fix things for you.
		1789
		1790	=item 4. Wee, just use a double-linked list for your timeouts.
		1791
		1792	If there is not one request, but many thousands (millions...), all
		1793	employing some kind of timeout with the same timeout value, then one can
		1794	do even better:
		1795
		1796	When starting the timeout, calculate the timeout value and put the timeout
		1797	at the I<end> of the list.
		1798
		1799	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1800	the list is expected to fire (for example, using the technique #3).
		1801
		1802	When there is some activity, remove the timer from the list, recalculate
		1803	the timeout, append it to the end of the list again, and make sure to
		1804	update the C<ev_timer> if it was taken from the beginning of the list.
		1805
		1806	This way, one can manage an unlimited number of timeouts in O(1) time for
		1807	starting, stopping and updating the timers, at the expense of a major
		1808	complication, and having to use a constant timeout. The constant timeout
		1809	ensures that the list stays sorted.
		1810
		1811	=back
		1812
		1813	So which method the best?
		1814
		1815	Method #2 is a simple no-brain-required solution that is adequate in most
		1816	situations. Method #3 requires a bit more thinking, but handles many cases
		1817	better, and isn't very complicated either. In most case, choosing either
		1818	one is fine, with #3 being better in typical situations.
		1819
		1820	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1821	rather complicated, but extremely efficient, something that really pays
		1822	off after the first million or so of active timers, i.e. it's usually
		1823	overkill :)
1240		1824
1241	=head3 The special problem of time updates	1825	=head3 The special problem of time updates
1242		1826
1243	Establishing the current time is a costly operation (it usually takes at	1827	Establishing the current time is a costly operation (it usually takes at
1244	least two system calls): EV therefore updates its idea of the current	1828	least two system calls): EV therefore updates its idea of the current
1245	time only before and after C<ev_loop> polls for new events, which causes	1829	time only before and after C<ev_loop> collects new events, which causes a
1246	a growing difference between C<ev_now ()> and C<ev_time ()> when handling	1830	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1247	lots of events.	1831	lots of events in one iteration.
1248		1832
1249	The relative timeouts are calculated relative to the C<ev_now ()>	1833	The relative timeouts are calculated relative to the C<ev_now ()>
1250	time. This is usually the right thing as this timestamp refers to the time	1834	time. This is usually the right thing as this timestamp refers to the time
1251	of the event triggering whatever timeout you are modifying/starting. If	1835	of the event triggering whatever timeout you are modifying/starting. If
1252	you suspect event processing to be delayed and you I<need> to base the	1836	you suspect event processing to be delayed and you I<need> to base the
…		…
1256		1840
1257	If the event loop is suspended for a long time, you can also force an	1841	If the event loop is suspended for a long time, you can also force an
1258	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1842	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1259	()>.	1843	()>.
1260		1844
		1845	=head3 The special problems of suspended animation
		1846
		1847	When you leave the server world it is quite customary to hit machines that
		1848	can suspend/hibernate - what happens to the clocks during such a suspend?
		1849
		1850	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1851	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1852	to run until the system is suspended, but they will not advance while the
		1853	system is suspended. That means, on resume, it will be as if the program
		1854	was frozen for a few seconds, but the suspend time will not be counted
		1855	towards C<ev_timer> when a monotonic clock source is used. The real time
		1856	clock advanced as expected, but if it is used as sole clocksource, then a
		1857	long suspend would be detected as a time jump by libev, and timers would
		1858	be adjusted accordingly.
		1859
		1860	I would not be surprised to see different behaviour in different between
		1861	operating systems, OS versions or even different hardware.
		1862
		1863	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1864	time jump in the monotonic clocks and the realtime clock. If the program
		1865	is suspended for a very long time, and monotonic clock sources are in use,
		1866	then you can expect C<ev_timer>s to expire as the full suspension time
		1867	will be counted towards the timers. When no monotonic clock source is in
		1868	use, then libev will again assume a timejump and adjust accordingly.
		1869
		1870	It might be beneficial for this latter case to call C<ev_suspend>
		1871	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1872	deterministic behaviour in this case (you can do nothing against
		1873	C<SIGSTOP>).
		1874
1261	=head3 Watcher-Specific Functions and Data Members	1875	=head3 Watcher-Specific Functions and Data Members
1262		1876
1263	=over 4	1877	=over 4
1264		1878
1265	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1879	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1288	If the timer is started but non-repeating, stop it (as if it timed out).	1902	If the timer is started but non-repeating, stop it (as if it timed out).
1289		1903
1290	If the timer is repeating, either start it if necessary (with the	1904	If the timer is repeating, either start it if necessary (with the
1291	C<repeat> value), or reset the running timer to the C<repeat> value.	1905	C<repeat> value), or reset the running timer to the C<repeat> value.
1292		1906
1293	This sounds a bit complicated, but here is a useful and typical	1907	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1294	example: Imagine you have a TCP connection and you want a so-called idle	1908	usage example.
1295	timeout, that is, you want to be called when there have been, say, 60
1296	seconds of inactivity on the socket. The easiest way to do this is to
1297	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1298	C<ev_timer_again> each time you successfully read or write some data. If
1299	you go into an idle state where you do not expect data to travel on the
1300	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1301	automatically restart it if need be.
1302		1909
1303	That means you can ignore the C<after> value and C<ev_timer_start>	1910	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1304	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1305		1911
1306	ev_timer_init (timer, callback, 0., 5.);	1912	Returns the remaining time until a timer fires. If the timer is active,
1307	ev_timer_again (loop, timer);	1913	then this time is relative to the current event loop time, otherwise it's
1308	...	1914	the timeout value currently configured.
1309	timer->again = 17.;
1310	ev_timer_again (loop, timer);
1311	...
1312	timer->again = 10.;
1313	ev_timer_again (loop, timer);
1314		1915
1315	This is more slightly efficient then stopping/starting the timer each time	1916	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1316	you want to modify its timeout value.	1917	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		1918	will return C<4>. When the timer expires and is restarted, it will return
		1919	roughly C<7> (likely slightly less as callback invocation takes some time,
		1920	too), and so on.
1317		1921
1318	=item ev_tstamp repeat [read-write]	1922	=item ev_tstamp repeat [read-write]
1319		1923
1320	The current C<repeat> value. Will be used each time the watcher times out	1924	The current C<repeat> value. Will be used each time the watcher times out
1321	or C<ev_timer_again> is called and determines the next timeout (if any),	1925	or C<ev_timer_again> is called, and determines the next timeout (if any),
1322	which is also when any modifications are taken into account.	1926	which is also when any modifications are taken into account.
1323		1927
1324	=back	1928	=back
1325		1929
1326	=head3 Examples	1930	=head3 Examples
1327		1931
1328	Example: Create a timer that fires after 60 seconds.	1932	Example: Create a timer that fires after 60 seconds.
1329		1933
1330	static void	1934	static void
1331	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1935	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1332	{	1936	{
1333	.. one minute over, w is actually stopped right here	1937	.. one minute over, w is actually stopped right here
1334	}	1938	}
1335		1939
1336	struct ev_timer mytimer;	1940	ev_timer mytimer;
1337	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1941	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1338	ev_timer_start (loop, &mytimer);	1942	ev_timer_start (loop, &mytimer);
1339		1943
1340	Example: Create a timeout timer that times out after 10 seconds of	1944	Example: Create a timeout timer that times out after 10 seconds of
1341	inactivity.	1945	inactivity.
1342		1946
1343	static void	1947	static void
1344	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1948	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1345	{	1949	{
1346	.. ten seconds without any activity	1950	.. ten seconds without any activity
1347	}	1951	}
1348		1952
1349	struct ev_timer mytimer;	1953	ev_timer mytimer;
1350	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1954	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1351	ev_timer_again (&mytimer); /* start timer */	1955	ev_timer_again (&mytimer); /* start timer */
1352	ev_loop (loop, 0);	1956	ev_loop (loop, 0);
1353		1957
1354	// and in some piece of code that gets executed on any "activity":	1958	// and in some piece of code that gets executed on any "activity":
…		…
1359	=head2 C<ev_periodic> - to cron or not to cron?	1963	=head2 C<ev_periodic> - to cron or not to cron?
1360		1964
1361	Periodic watchers are also timers of a kind, but they are very versatile	1965	Periodic watchers are also timers of a kind, but they are very versatile
1362	(and unfortunately a bit complex).	1966	(and unfortunately a bit complex).
1363		1967
1364	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1968	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1365	but on wall clock time (absolute time). You can tell a periodic watcher	1969	relative time, the physical time that passes) but on wall clock time
1366	to trigger after some specific point in time. For example, if you tell a	1970	(absolute time, the thing you can read on your calender or clock). The
1367	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	1971	difference is that wall clock time can run faster or slower than real
1368	+ 10.>, that is, an absolute time not a delay) and then reset your system	1972	time, and time jumps are not uncommon (e.g. when you adjust your
1369	clock to January of the previous year, then it will take more than year	1973	wrist-watch).
1370	to trigger the event (unlike an C<ev_timer>, which would still trigger
1371	roughly 10 seconds later as it uses a relative timeout).
1372		1974
		1975	You can tell a periodic watcher to trigger after some specific point
		1976	in time: for example, if you tell a periodic watcher to trigger "in 10
		1977	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1978	not a delay) and then reset your system clock to January of the previous
		1979	year, then it will take a year or more to trigger the event (unlike an
		1980	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1981	it, as it uses a relative timeout).
		1982
1373	C<ev_periodic>s can also be used to implement vastly more complex timers,	1983	C<ev_periodic> watchers can also be used to implement vastly more complex
1374	such as triggering an event on each "midnight, local time", or other	1984	timers, such as triggering an event on each "midnight, local time", or
1375	complicated, rules.	1985	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1986	those cannot react to time jumps.
1376		1987
1377	As with timers, the callback is guaranteed to be invoked only when the	1988	As with timers, the callback is guaranteed to be invoked only when the
1378	time (C<at>) has passed, but if multiple periodic timers become ready	1989	point in time where it is supposed to trigger has passed. If multiple
1379	during the same loop iteration then order of execution is undefined.	1990	timers become ready during the same loop iteration then the ones with
		1991	earlier time-out values are invoked before ones with later time-out values
		1992	(but this is no longer true when a callback calls C<ev_loop> recursively).
1380		1993
1381	=head3 Watcher-Specific Functions and Data Members	1994	=head3 Watcher-Specific Functions and Data Members
1382		1995
1383	=over 4	1996	=over 4
1384		1997
1385	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1998	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1386		1999
1387	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2000	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1388		2001
1389	Lots of arguments, lets sort it out... There are basically three modes of	2002	Lots of arguments, let's sort it out... There are basically three modes of
1390	operation, and we will explain them from simplest to complex:	2003	operation, and we will explain them from simplest to most complex:
1391		2004
1392	=over 4	2005	=over 4
1393		2006
1394	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2007	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1395		2008
1396	In this configuration the watcher triggers an event after the wall clock	2009	In this configuration the watcher triggers an event after the wall clock
1397	time C<at> has passed and doesn't repeat. It will not adjust when a time	2010	time C<offset> has passed. It will not repeat and will not adjust when a
1398	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2011	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1399	run when the system time reaches or surpasses this time.	2012	will be stopped and invoked when the system clock reaches or surpasses
		2013	this point in time.
1400		2014
1401	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2015	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1402		2016
1403	In this mode the watcher will always be scheduled to time out at the next	2017	In this mode the watcher will always be scheduled to time out at the next
1404	C<at + N * interval> time (for some integer N, which can also be negative)	2018	C<offset + N * interval> time (for some integer N, which can also be
1405	and then repeat, regardless of any time jumps.	2019	negative) and then repeat, regardless of any time jumps. The C<offset>
		2020	argument is merely an offset into the C<interval> periods.
1406		2021
1407	This can be used to create timers that do not drift with respect to system	2022	This can be used to create timers that do not drift with respect to the
1408	time, for example, here is a C<ev_periodic> that triggers each hour, on	2023	system clock, for example, here is an C<ev_periodic> that triggers each
1409	the hour:	2024	hour, on the hour (with respect to UTC):
1410		2025
1411	ev_periodic_set (&periodic, 0., 3600., 0);	2026	ev_periodic_set (&periodic, 0., 3600., 0);
1412		2027
1413	This doesn't mean there will always be 3600 seconds in between triggers,	2028	This doesn't mean there will always be 3600 seconds in between triggers,
1414	but only that the callback will be called when the system time shows a	2029	but only that the callback will be called when the system time shows a
1415	full hour (UTC), or more correctly, when the system time is evenly divisible	2030	full hour (UTC), or more correctly, when the system time is evenly divisible
1416	by 3600.	2031	by 3600.
1417		2032
1418	Another way to think about it (for the mathematically inclined) is that	2033	Another way to think about it (for the mathematically inclined) is that
1419	C<ev_periodic> will try to run the callback in this mode at the next possible	2034	C<ev_periodic> will try to run the callback in this mode at the next possible
1420	time where C<time = at (mod interval)>, regardless of any time jumps.	2035	time where C<time = offset (mod interval)>, regardless of any time jumps.
1421		2036
1422	For numerical stability it is preferable that the C<at> value is near	2037	For numerical stability it is preferable that the C<offset> value is near
1423	C<ev_now ()> (the current time), but there is no range requirement for	2038	C<ev_now ()> (the current time), but there is no range requirement for
1424	this value, and in fact is often specified as zero.	2039	this value, and in fact is often specified as zero.
1425		2040
1426	Note also that there is an upper limit to how often a timer can fire (CPU	2041	Note also that there is an upper limit to how often a timer can fire (CPU
1427	speed for example), so if C<interval> is very small then timing stability	2042	speed for example), so if C<interval> is very small then timing stability
1428	will of course deteriorate. Libev itself tries to be exact to be about one	2043	will of course deteriorate. Libev itself tries to be exact to be about one
1429	millisecond (if the OS supports it and the machine is fast enough).	2044	millisecond (if the OS supports it and the machine is fast enough).
1430		2045
1431	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2046	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1432		2047
1433	In this mode the values for C<interval> and C<at> are both being	2048	In this mode the values for C<interval> and C<offset> are both being
1434	ignored. Instead, each time the periodic watcher gets scheduled, the	2049	ignored. Instead, each time the periodic watcher gets scheduled, the
1435	reschedule callback will be called with the watcher as first, and the	2050	reschedule callback will be called with the watcher as first, and the
1436	current time as second argument.	2051	current time as second argument.
1437		2052
1438	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2053	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1439	ever, or make ANY event loop modifications whatsoever>.	2054	or make ANY other event loop modifications whatsoever, unless explicitly
		2055	allowed by documentation here>.
1440		2056
1441	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2057	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1442	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2058	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1443	only event loop modification you are allowed to do).	2059	only event loop modification you are allowed to do).
1444		2060
1445	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	2061	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1446	*w, ev_tstamp now)>, e.g.:	2062	*w, ev_tstamp now)>, e.g.:
1447		2063
		2064	static ev_tstamp
1448	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	2065	my_rescheduler (ev_periodic *w, ev_tstamp now)
1449	{	2066	{
1450	return now + 60.;	2067	return now + 60.;
1451	}	2068	}
1452		2069
1453	It must return the next time to trigger, based on the passed time value	2070	It must return the next time to trigger, based on the passed time value
…		…
1473	a different time than the last time it was called (e.g. in a crond like	2090	a different time than the last time it was called (e.g. in a crond like
1474	program when the crontabs have changed).	2091	program when the crontabs have changed).
1475		2092
1476	=item ev_tstamp ev_periodic_at (ev_periodic *)	2093	=item ev_tstamp ev_periodic_at (ev_periodic *)
1477		2094
1478	When active, returns the absolute time that the watcher is supposed to	2095	When active, returns the absolute time that the watcher is supposed
1479	trigger next.	2096	to trigger next. This is not the same as the C<offset> argument to
		2097	C<ev_periodic_set>, but indeed works even in interval and manual
		2098	rescheduling modes.
1480		2099
1481	=item ev_tstamp offset [read-write]	2100	=item ev_tstamp offset [read-write]
1482		2101
1483	When repeating, this contains the offset value, otherwise this is the	2102	When repeating, this contains the offset value, otherwise this is the
1484	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2103	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2104	although libev might modify this value for better numerical stability).
1485		2105
1486	Can be modified any time, but changes only take effect when the periodic	2106	Can be modified any time, but changes only take effect when the periodic
1487	timer fires or C<ev_periodic_again> is being called.	2107	timer fires or C<ev_periodic_again> is being called.
1488		2108
1489	=item ev_tstamp interval [read-write]	2109	=item ev_tstamp interval [read-write]
1490		2110
1491	The current interval value. Can be modified any time, but changes only	2111	The current interval value. Can be modified any time, but changes only
1492	take effect when the periodic timer fires or C<ev_periodic_again> is being	2112	take effect when the periodic timer fires or C<ev_periodic_again> is being
1493	called.	2113	called.
1494		2114
1495	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2115	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1496		2116
1497	The current reschedule callback, or C<0>, if this functionality is	2117	The current reschedule callback, or C<0>, if this functionality is
1498	switched off. Can be changed any time, but changes only take effect when	2118	switched off. Can be changed any time, but changes only take effect when
1499	the periodic timer fires or C<ev_periodic_again> is being called.	2119	the periodic timer fires or C<ev_periodic_again> is being called.
1500		2120
1501	=back	2121	=back
1502		2122
1503	=head3 Examples	2123	=head3 Examples
1504		2124
1505	Example: Call a callback every hour, or, more precisely, whenever the	2125	Example: Call a callback every hour, or, more precisely, whenever the
1506	system clock is divisible by 3600. The callback invocation times have	2126	system time is divisible by 3600. The callback invocation times have
1507	potentially a lot of jitter, but good long-term stability.	2127	potentially a lot of jitter, but good long-term stability.
1508		2128
1509	static void	2129	static void
1510	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2130	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1511	{	2131	{
1512	... its now a full hour (UTC, or TAI or whatever your clock follows)	2132	... its now a full hour (UTC, or TAI or whatever your clock follows)
1513	}	2133	}
1514		2134
1515	struct ev_periodic hourly_tick;	2135	ev_periodic hourly_tick;
1516	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2136	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1517	ev_periodic_start (loop, &hourly_tick);	2137	ev_periodic_start (loop, &hourly_tick);
1518		2138
1519	Example: The same as above, but use a reschedule callback to do it:	2139	Example: The same as above, but use a reschedule callback to do it:
1520		2140
1521	#include <math.h>	2141	#include <math.h>
1522		2142
1523	static ev_tstamp	2143	static ev_tstamp
1524	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2144	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1525	{	2145	{
1526	return fmod (now, 3600.) + 3600.;	2146	return now + (3600. - fmod (now, 3600.));
1527	}	2147	}
1528		2148
1529	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2149	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1530		2150
1531	Example: Call a callback every hour, starting now:	2151	Example: Call a callback every hour, starting now:
1532		2152
1533	struct ev_periodic hourly_tick;	2153	ev_periodic hourly_tick;
1534	ev_periodic_init (&hourly_tick, clock_cb,	2154	ev_periodic_init (&hourly_tick, clock_cb,
1535	fmod (ev_now (loop), 3600.), 3600., 0);	2155	fmod (ev_now (loop), 3600.), 3600., 0);
1536	ev_periodic_start (loop, &hourly_tick);	2156	ev_periodic_start (loop, &hourly_tick);
1537		2157
1538		2158
…		…
1541	Signal watchers will trigger an event when the process receives a specific	2161	Signal watchers will trigger an event when the process receives a specific
1542	signal one or more times. Even though signals are very asynchronous, libev	2162	signal one or more times. Even though signals are very asynchronous, libev
1543	will try it's best to deliver signals synchronously, i.e. as part of the	2163	will try it's best to deliver signals synchronously, i.e. as part of the
1544	normal event processing, like any other event.	2164	normal event processing, like any other event.
1545		2165
		2166	If you want signals to be delivered truly asynchronously, just use
		2167	C<sigaction> as you would do without libev and forget about sharing
		2168	the signal. You can even use C<ev_async> from a signal handler to
		2169	synchronously wake up an event loop.
		2170
1546	You can configure as many watchers as you like per signal. Only when the	2171	You can configure as many watchers as you like for the same signal, but
		2172	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2173	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2174	C<SIGINT> in both the default loop and another loop at the same time. At
		2175	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2176
1547	first watcher gets started will libev actually register a signal watcher	2177	When the first watcher gets started will libev actually register something
1548	with the kernel (thus it coexists with your own signal handlers as long	2178	with the kernel (thus it coexists with your own signal handlers as long as
1549	as you don't register any with libev). Similarly, when the last signal	2179	you don't register any with libev for the same signal).
1550	watcher for a signal is stopped libev will reset the signal handler to
1551	SIG_DFL (regardless of what it was set to before).
1552		2180
1553	If possible and supported, libev will install its handlers with	2181	If possible and supported, libev will install its handlers with
1554	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2182	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1555	interrupted. If you have a problem with system calls getting interrupted by	2183	not be unduly interrupted. If you have a problem with system calls getting
1556	signals you can block all signals in an C<ev_check> watcher and unblock	2184	interrupted by signals you can block all signals in an C<ev_check> watcher
1557	them in an C<ev_prepare> watcher.	2185	and unblock them in an C<ev_prepare> watcher.
		2186
		2187	=head3 The special problem of inheritance over fork/execve/pthread_create
		2188
		2189	Both the signal mask (C<sigprocmask>) and the signal disposition
		2190	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2191	stopping it again), that is, libev might or might not block the signal,
		2192	and might or might not set or restore the installed signal handler.
		2193
		2194	While this does not matter for the signal disposition (libev never
		2195	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2196	C<execve>), this matters for the signal mask: many programs do not expect
		2197	certain signals to be blocked.
		2198
		2199	This means that before calling C<exec> (from the child) you should reset
		2200	the signal mask to whatever "default" you expect (all clear is a good
		2201	choice usually).
		2202
		2203	The simplest way to ensure that the signal mask is reset in the child is
		2204	to install a fork handler with C<pthread_atfork> that resets it. That will
		2205	catch fork calls done by libraries (such as the libc) as well.
		2206
		2207	In current versions of libev, the signal will not be blocked indefinitely
		2208	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2209	the window of opportunity for problems, it will not go away, as libev
		2210	I<has> to modify the signal mask, at least temporarily.
		2211
		2212	So I can't stress this enough: I<If you do not reset your signal mask when
		2213	you expect it to be empty, you have a race condition in your code>. This
		2214	is not a libev-specific thing, this is true for most event libraries.
1558		2215
1559	=head3 Watcher-Specific Functions and Data Members	2216	=head3 Watcher-Specific Functions and Data Members
1560		2217
1561	=over 4	2218	=over 4
1562		2219
…		…
1573		2230
1574	=back	2231	=back
1575		2232
1576	=head3 Examples	2233	=head3 Examples
1577		2234
1578	Example: Try to exit cleanly on SIGINT and SIGTERM.	2235	Example: Try to exit cleanly on SIGINT.
1579		2236
1580	static void	2237	static void
1581	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2238	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1582	{	2239	{
1583	ev_unloop (loop, EVUNLOOP_ALL);	2240	ev_unloop (loop, EVUNLOOP_ALL);
1584	}	2241	}
1585		2242
1586	struct ev_signal signal_watcher;	2243	ev_signal signal_watcher;
1587	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2244	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1588	ev_signal_start (loop, &sigint_cb);	2245	ev_signal_start (loop, &signal_watcher);
1589		2246
1590		2247
1591	=head2 C<ev_child> - watch out for process status changes	2248	=head2 C<ev_child> - watch out for process status changes
1592		2249
1593	Child watchers trigger when your process receives a SIGCHLD in response to	2250	Child watchers trigger when your process receives a SIGCHLD in response to
1594	some child status changes (most typically when a child of yours dies). It	2251	some child status changes (most typically when a child of yours dies or
1595	is permissible to install a child watcher I<after> the child has been	2252	exits). It is permissible to install a child watcher I<after> the child
1596	forked (which implies it might have already exited), as long as the event	2253	has been forked (which implies it might have already exited), as long
1597	loop isn't entered (or is continued from a watcher).	2254	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2255	forking and then immediately registering a watcher for the child is fine,
		2256	but forking and registering a watcher a few event loop iterations later or
		2257	in the next callback invocation is not.
1598		2258
1599	Only the default event loop is capable of handling signals, and therefore	2259	Only the default event loop is capable of handling signals, and therefore
1600	you can only register child watchers in the default event loop.	2260	you can only register child watchers in the default event loop.
1601		2261
		2262	Due to some design glitches inside libev, child watchers will always be
		2263	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2264	libev)
		2265
1602	=head3 Process Interaction	2266	=head3 Process Interaction
1603		2267
1604	Libev grabs C<SIGCHLD> as soon as the default event loop is	2268	Libev grabs C<SIGCHLD> as soon as the default event loop is
1605	initialised. This is necessary to guarantee proper behaviour even if	2269	initialised. This is necessary to guarantee proper behaviour even if the
1606	the first child watcher is started after the child exits. The occurrence	2270	first child watcher is started after the child exits. The occurrence
1607	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2271	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1608	synchronously as part of the event loop processing. Libev always reaps all	2272	synchronously as part of the event loop processing. Libev always reaps all
1609	children, even ones not watched.	2273	children, even ones not watched.
1610		2274
1611	=head3 Overriding the Built-In Processing	2275	=head3 Overriding the Built-In Processing
…		…
1621	=head3 Stopping the Child Watcher	2285	=head3 Stopping the Child Watcher
1622		2286
1623	Currently, the child watcher never gets stopped, even when the	2287	Currently, the child watcher never gets stopped, even when the
1624	child terminates, so normally one needs to stop the watcher in the	2288	child terminates, so normally one needs to stop the watcher in the
1625	callback. Future versions of libev might stop the watcher automatically	2289	callback. Future versions of libev might stop the watcher automatically
1626	when a child exit is detected.	2290	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2291	problem).
1627		2292
1628	=head3 Watcher-Specific Functions and Data Members	2293	=head3 Watcher-Specific Functions and Data Members
1629		2294
1630	=over 4	2295	=over 4
1631		2296
…		…
1663	its completion.	2328	its completion.
1664		2329
1665	ev_child cw;	2330	ev_child cw;
1666		2331
1667	static void	2332	static void
1668	child_cb (EV_P_ struct ev_child *w, int revents)	2333	child_cb (EV_P_ ev_child *w, int revents)
1669	{	2334	{
1670	ev_child_stop (EV_A_ w);	2335	ev_child_stop (EV_A_ w);
1671	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2336	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1672	}	2337	}
1673		2338
…		…
1688		2353
1689		2354
1690	=head2 C<ev_stat> - did the file attributes just change?	2355	=head2 C<ev_stat> - did the file attributes just change?
1691		2356
1692	This watches a file system path for attribute changes. That is, it calls	2357	This watches a file system path for attribute changes. That is, it calls
1693	C<stat> regularly (or when the OS says it changed) and sees if it changed	2358	C<stat> on that path in regular intervals (or when the OS says it changed)
1694	compared to the last time, invoking the callback if it did.	2359	and sees if it changed compared to the last time, invoking the callback if
		2360	it did.
1695		2361
1696	The path does not need to exist: changing from "path exists" to "path does	2362	The path does not need to exist: changing from "path exists" to "path does
1697	not exist" is a status change like any other. The condition "path does	2363	not exist" is a status change like any other. The condition "path does not
1698	not exist" is signified by the C<st_nlink> field being zero (which is	2364	exist" (or more correctly "path cannot be stat'ed") is signified by the
1699	otherwise always forced to be at least one) and all the other fields of	2365	C<st_nlink> field being zero (which is otherwise always forced to be at
1700	the stat buffer having unspecified contents.	2366	least one) and all the other fields of the stat buffer having unspecified
		2367	contents.
1701		2368
1702	The path I<should> be absolute and I<must not> end in a slash. If it is	2369	The path I<must not> end in a slash or contain special components such as
		2370	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1703	relative and your working directory changes, the behaviour is undefined.	2371	your working directory changes, then the behaviour is undefined.
1704		2372
1705	Since there is no standard to do this, the portable implementation simply	2373	Since there is no portable change notification interface available, the
1706	calls C<stat (2)> regularly on the path to see if it changed somehow. You	2374	portable implementation simply calls C<stat(2)> regularly on the path
1707	can specify a recommended polling interval for this case. If you specify	2375	to see if it changed somehow. You can specify a recommended polling
1708	a polling interval of C<0> (highly recommended!) then a I<suitable,	2376	interval for this case. If you specify a polling interval of C<0> (highly
1709	unspecified default> value will be used (which you can expect to be around	2377	recommended!) then a I<suitable, unspecified default> value will be used
1710	five seconds, although this might change dynamically). Libev will also	2378	(which you can expect to be around five seconds, although this might
1711	impose a minimum interval which is currently around C<0.1>, but thats	2379	change dynamically). Libev will also impose a minimum interval which is
1712	usually overkill.	2380	currently around C<0.1>, but that's usually overkill.
1713		2381
1714	This watcher type is not meant for massive numbers of stat watchers,	2382	This watcher type is not meant for massive numbers of stat watchers,
1715	as even with OS-supported change notifications, this can be	2383	as even with OS-supported change notifications, this can be
1716	resource-intensive.	2384	resource-intensive.
1717		2385
1718	At the time of this writing, only the Linux inotify interface is	2386	At the time of this writing, the only OS-specific interface implemented
1719	implemented (implementing kqueue support is left as an exercise for the	2387	is the Linux inotify interface (implementing kqueue support is left as an
1720	reader, note, however, that the author sees no way of implementing ev_stat	2388	exercise for the reader. Note, however, that the author sees no way of
1721	semantics with kqueue). Inotify will be used to give hints only and should	2389	implementing C<ev_stat> semantics with kqueue, except as a hint).
1722	not change the semantics of C<ev_stat> watchers, which means that libev
1723	sometimes needs to fall back to regular polling again even with inotify,
1724	but changes are usually detected immediately, and if the file exists there
1725	will be no polling.
1726		2390
1727	=head3 ABI Issues (Largefile Support)	2391	=head3 ABI Issues (Largefile Support)
1728		2392
1729	Libev by default (unless the user overrides this) uses the default	2393	Libev by default (unless the user overrides this) uses the default
1730	compilation environment, which means that on systems with large file	2394	compilation environment, which means that on systems with large file
1731	support disabled by default, you get the 32 bit version of the stat	2395	support disabled by default, you get the 32 bit version of the stat
1732	structure. When using the library from programs that change the ABI to	2396	structure. When using the library from programs that change the ABI to
1733	use 64 bit file offsets the programs will fail. In that case you have to	2397	use 64 bit file offsets the programs will fail. In that case you have to
1734	compile libev with the same flags to get binary compatibility. This is	2398	compile libev with the same flags to get binary compatibility. This is
1735	obviously the case with any flags that change the ABI, but the problem is	2399	obviously the case with any flags that change the ABI, but the problem is
1736	most noticeably disabled with ev_stat and large file support.	2400	most noticeably displayed with ev_stat and large file support.
1737		2401
1738	The solution for this is to lobby your distribution maker to make large	2402	The solution for this is to lobby your distribution maker to make large
1739	file interfaces available by default (as e.g. FreeBSD does) and not	2403	file interfaces available by default (as e.g. FreeBSD does) and not
1740	optional. Libev cannot simply switch on large file support because it has	2404	optional. Libev cannot simply switch on large file support because it has
1741	to exchange stat structures with application programs compiled using the	2405	to exchange stat structures with application programs compiled using the
1742	default compilation environment.	2406	default compilation environment.
1743		2407
1744	=head3 Inotify	2408	=head3 Inotify and Kqueue
1745		2409
1746	When C<inotify (7)> support has been compiled into libev (generally only	2410	When C<inotify (7)> support has been compiled into libev and present at
1747	available on Linux) and present at runtime, it will be used to speed up	2411	runtime, it will be used to speed up change detection where possible. The
1748	change detection where possible. The inotify descriptor will be created lazily	2412	inotify descriptor will be created lazily when the first C<ev_stat>
1749	when the first C<ev_stat> watcher is being started.	2413	watcher is being started.
1750		2414
1751	Inotify presence does not change the semantics of C<ev_stat> watchers	2415	Inotify presence does not change the semantics of C<ev_stat> watchers
1752	except that changes might be detected earlier, and in some cases, to avoid	2416	except that changes might be detected earlier, and in some cases, to avoid
1753	making regular C<stat> calls. Even in the presence of inotify support	2417	making regular C<stat> calls. Even in the presence of inotify support
1754	there are many cases where libev has to resort to regular C<stat> polling.	2418	there are many cases where libev has to resort to regular C<stat> polling,
		2419	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2420	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2421	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2422	xfs are fully working) libev usually gets away without polling.
1755		2423
1756	(There is no support for kqueue, as apparently it cannot be used to	2424	There is no support for kqueue, as apparently it cannot be used to
1757	implement this functionality, due to the requirement of having a file	2425	implement this functionality, due to the requirement of having a file
1758	descriptor open on the object at all times).	2426	descriptor open on the object at all times, and detecting renames, unlinks
		2427	etc. is difficult.
		2428
		2429	=head3 C<stat ()> is a synchronous operation
		2430
		2431	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2432	the process. The exception are C<ev_stat> watchers - those call C<stat
		2433	()>, which is a synchronous operation.
		2434
		2435	For local paths, this usually doesn't matter: unless the system is very
		2436	busy or the intervals between stat's are large, a stat call will be fast,
		2437	as the path data is usually in memory already (except when starting the
		2438	watcher).
		2439
		2440	For networked file systems, calling C<stat ()> can block an indefinite
		2441	time due to network issues, and even under good conditions, a stat call
		2442	often takes multiple milliseconds.
		2443
		2444	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2445	paths, although this is fully supported by libev.
1759		2446
1760	=head3 The special problem of stat time resolution	2447	=head3 The special problem of stat time resolution
1761		2448
1762	The C<stat ()> system call only supports full-second resolution portably, and	2449	The C<stat ()> system call only supports full-second resolution portably,
1763	even on systems where the resolution is higher, many file systems still	2450	and even on systems where the resolution is higher, most file systems
1764	only support whole seconds.	2451	still only support whole seconds.
1765		2452
1766	That means that, if the time is the only thing that changes, you can	2453	That means that, if the time is the only thing that changes, you can
1767	easily miss updates: on the first update, C<ev_stat> detects a change and	2454	easily miss updates: on the first update, C<ev_stat> detects a change and
1768	calls your callback, which does something. When there is another update	2455	calls your callback, which does something. When there is another update
1769	within the same second, C<ev_stat> will be unable to detect it as the stat	2456	within the same second, C<ev_stat> will be unable to detect unless the
1770	data does not change.	2457	stat data does change in other ways (e.g. file size).
1771		2458
1772	The solution to this is to delay acting on a change for slightly more	2459	The solution to this is to delay acting on a change for slightly more
1773	than a second (or till slightly after the next full second boundary), using	2460	than a second (or till slightly after the next full second boundary), using
1774	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2461	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1775	ev_timer_again (loop, w)>).	2462	ev_timer_again (loop, w)>).
…		…
1795	C<path>. The C<interval> is a hint on how quickly a change is expected to	2482	C<path>. The C<interval> is a hint on how quickly a change is expected to
1796	be detected and should normally be specified as C<0> to let libev choose	2483	be detected and should normally be specified as C<0> to let libev choose
1797	a suitable value. The memory pointed to by C<path> must point to the same	2484	a suitable value. The memory pointed to by C<path> must point to the same
1798	path for as long as the watcher is active.	2485	path for as long as the watcher is active.
1799		2486
1800	The callback will receive C<EV_STAT> when a change was detected, relative	2487	The callback will receive an C<EV_STAT> event when a change was detected,
1801	to the attributes at the time the watcher was started (or the last change	2488	relative to the attributes at the time the watcher was started (or the
1802	was detected).	2489	last change was detected).
1803		2490
1804	=item ev_stat_stat (loop, ev_stat *)	2491	=item ev_stat_stat (loop, ev_stat *)
1805		2492
1806	Updates the stat buffer immediately with new values. If you change the	2493	Updates the stat buffer immediately with new values. If you change the
1807	watched path in your callback, you could call this function to avoid	2494	watched path in your callback, you could call this function to avoid
…		…
1890		2577
1891		2578
1892	=head2 C<ev_idle> - when you've got nothing better to do...	2579	=head2 C<ev_idle> - when you've got nothing better to do...
1893		2580
1894	Idle watchers trigger events when no other events of the same or higher	2581	Idle watchers trigger events when no other events of the same or higher
1895	priority are pending (prepare, check and other idle watchers do not	2582	priority are pending (prepare, check and other idle watchers do not count
1896	count).	2583	as receiving "events").
1897		2584
1898	That is, as long as your process is busy handling sockets or timeouts	2585	That is, as long as your process is busy handling sockets or timeouts
1899	(or even signals, imagine) of the same or higher priority it will not be	2586	(or even signals, imagine) of the same or higher priority it will not be
1900	triggered. But when your process is idle (or only lower-priority watchers	2587	triggered. But when your process is idle (or only lower-priority watchers
1901	are pending), the idle watchers are being called once per event loop	2588	are pending), the idle watchers are being called once per event loop
…		…
1912		2599
1913	=head3 Watcher-Specific Functions and Data Members	2600	=head3 Watcher-Specific Functions and Data Members
1914		2601
1915	=over 4	2602	=over 4
1916		2603
1917	=item ev_idle_init (ev_signal *, callback)	2604	=item ev_idle_init (ev_idle *, callback)
1918		2605
1919	Initialises and configures the idle watcher - it has no parameters of any	2606	Initialises and configures the idle watcher - it has no parameters of any
1920	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2607	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1921	believe me.	2608	believe me.
1922		2609
…		…
1926		2613
1927	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2614	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1928	callback, free it. Also, use no error checking, as usual.	2615	callback, free it. Also, use no error checking, as usual.
1929		2616
1930	static void	2617	static void
1931	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2618	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1932	{	2619	{
1933	free (w);	2620	free (w);
1934	// now do something you wanted to do when the program has	2621	// now do something you wanted to do when the program has
1935	// no longer anything immediate to do.	2622	// no longer anything immediate to do.
1936	}	2623	}
1937		2624
1938	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2625	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1939	ev_idle_init (idle_watcher, idle_cb);	2626	ev_idle_init (idle_watcher, idle_cb);
1940	ev_idle_start (loop, idle_cb);	2627	ev_idle_start (loop, idle_watcher);
1941		2628
1942		2629
1943	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2630	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1944		2631
1945	Prepare and check watchers are usually (but not always) used in tandem:	2632	Prepare and check watchers are usually (but not always) used in pairs:
1946	prepare watchers get invoked before the process blocks and check watchers	2633	prepare watchers get invoked before the process blocks and check watchers
1947	afterwards.	2634	afterwards.
1948		2635
1949	You I<must not> call C<ev_loop> or similar functions that enter	2636	You I<must not> call C<ev_loop> or similar functions that enter
1950	the current event loop from either C<ev_prepare> or C<ev_check>	2637	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1953	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2640	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1954	C<ev_check> so if you have one watcher of each kind they will always be	2641	C<ev_check> so if you have one watcher of each kind they will always be
1955	called in pairs bracketing the blocking call.	2642	called in pairs bracketing the blocking call.
1956		2643
1957	Their main purpose is to integrate other event mechanisms into libev and	2644	Their main purpose is to integrate other event mechanisms into libev and
1958	their use is somewhat advanced. This could be used, for example, to track	2645	their use is somewhat advanced. They could be used, for example, to track
1959	variable changes, implement your own watchers, integrate net-snmp or a	2646	variable changes, implement your own watchers, integrate net-snmp or a
1960	coroutine library and lots more. They are also occasionally useful if	2647	coroutine library and lots more. They are also occasionally useful if
1961	you cache some data and want to flush it before blocking (for example,	2648	you cache some data and want to flush it before blocking (for example,
1962	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2649	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1963	watcher).	2650	watcher).
1964		2651
1965	This is done by examining in each prepare call which file descriptors need	2652	This is done by examining in each prepare call which file descriptors
1966	to be watched by the other library, registering C<ev_io> watchers for	2653	need to be watched by the other library, registering C<ev_io> watchers
1967	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2654	for them and starting an C<ev_timer> watcher for any timeouts (many
1968	provide just this functionality). Then, in the check watcher you check for	2655	libraries provide exactly this functionality). Then, in the check watcher,
1969	any events that occurred (by checking the pending status of all watchers	2656	you check for any events that occurred (by checking the pending status
1970	and stopping them) and call back into the library. The I/O and timer	2657	of all watchers and stopping them) and call back into the library. The
1971	callbacks will never actually be called (but must be valid nevertheless,	2658	I/O and timer callbacks will never actually be called (but must be valid
1972	because you never know, you know?).	2659	nevertheless, because you never know, you know?).
1973		2660
1974	As another example, the Perl Coro module uses these hooks to integrate	2661	As another example, the Perl Coro module uses these hooks to integrate
1975	coroutines into libev programs, by yielding to other active coroutines	2662	coroutines into libev programs, by yielding to other active coroutines
1976	during each prepare and only letting the process block if no coroutines	2663	during each prepare and only letting the process block if no coroutines
1977	are ready to run (it's actually more complicated: it only runs coroutines	2664	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1980	loop from blocking if lower-priority coroutines are active, thus mapping	2667	loop from blocking if lower-priority coroutines are active, thus mapping
1981	low-priority coroutines to idle/background tasks).	2668	low-priority coroutines to idle/background tasks).
1982		2669
1983	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2670	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1984	priority, to ensure that they are being run before any other watchers	2671	priority, to ensure that they are being run before any other watchers
		2672	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2673
1985	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2674	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1986	too) should not activate ("feed") events into libev. While libev fully	2675	activate ("feed") events into libev. While libev fully supports this, they
1987	supports this, they might get executed before other C<ev_check> watchers	2676	might get executed before other C<ev_check> watchers did their job. As
1988	did their job. As C<ev_check> watchers are often used to embed other	2677	C<ev_check> watchers are often used to embed other (non-libev) event
1989	(non-libev) event loops those other event loops might be in an unusable	2678	loops those other event loops might be in an unusable state until their
1990	state until their C<ev_check> watcher ran (always remind yourself to	2679	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1991	coexist peacefully with others).	2680	others).
1992		2681
1993	=head3 Watcher-Specific Functions and Data Members	2682	=head3 Watcher-Specific Functions and Data Members
1994		2683
1995	=over 4	2684	=over 4
1996		2685
…		…
1998		2687
1999	=item ev_check_init (ev_check *, callback)	2688	=item ev_check_init (ev_check *, callback)
2000		2689
2001	Initialises and configures the prepare or check watcher - they have no	2690	Initialises and configures the prepare or check watcher - they have no
2002	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2691	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
2003	macros, but using them is utterly, utterly and completely pointless.	2692	macros, but using them is utterly, utterly, utterly and completely
		2693	pointless.
2004		2694
2005	=back	2695	=back
2006		2696
2007	=head3 Examples	2697	=head3 Examples
2008		2698
…		…
2021		2711
2022	static ev_io iow [nfd];	2712	static ev_io iow [nfd];
2023	static ev_timer tw;	2713	static ev_timer tw;
2024		2714
2025	static void	2715	static void
2026	io_cb (ev_loop *loop, ev_io *w, int revents)	2716	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2027	{	2717	{
2028	}	2718	}
2029		2719
2030	// create io watchers for each fd and a timer before blocking	2720	// create io watchers for each fd and a timer before blocking
2031	static void	2721	static void
2032	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2722	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2033	{	2723	{
2034	int timeout = 3600000;	2724	int timeout = 3600000;
2035	struct pollfd fds [nfd];	2725	struct pollfd fds [nfd];
2036	// actual code will need to loop here and realloc etc.	2726	// actual code will need to loop here and realloc etc.
2037	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2727	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2038		2728
2039	/* the callback is illegal, but won't be called as we stop during check */	2729	/* the callback is illegal, but won't be called as we stop during check */
2040	ev_timer_init (&tw, 0, timeout * 1e-3);	2730	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2041	ev_timer_start (loop, &tw);	2731	ev_timer_start (loop, &tw);
2042		2732
2043	// create one ev_io per pollfd	2733	// create one ev_io per pollfd
2044	for (int i = 0; i < nfd; ++i)	2734	for (int i = 0; i < nfd; ++i)
2045	{	2735	{
…		…
2052	}	2742	}
2053	}	2743	}
2054		2744
2055	// stop all watchers after blocking	2745	// stop all watchers after blocking
2056	static void	2746	static void
2057	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2747	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2058	{	2748	{
2059	ev_timer_stop (loop, &tw);	2749	ev_timer_stop (loop, &tw);
2060		2750
2061	for (int i = 0; i < nfd; ++i)	2751	for (int i = 0; i < nfd; ++i)
2062	{	2752	{
…		…
2101	}	2791	}
2102		2792
2103	// do not ever call adns_afterpoll	2793	// do not ever call adns_afterpoll
2104		2794
2105	Method 4: Do not use a prepare or check watcher because the module you	2795	Method 4: Do not use a prepare or check watcher because the module you
2106	want to embed is too inflexible to support it. Instead, you can override	2796	want to embed is not flexible enough to support it. Instead, you can
2107	their poll function. The drawback with this solution is that the main	2797	override their poll function. The drawback with this solution is that the
2108	loop is now no longer controllable by EV. The C<Glib::EV> module does	2798	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2109	this.	2799	this approach, effectively embedding EV as a client into the horrible
		2800	libglib event loop.
2110		2801
2111	static gint	2802	static gint
2112	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2803	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2113	{	2804	{
2114	int got_events = 0;	2805	int got_events = 0;
…		…
2145	prioritise I/O.	2836	prioritise I/O.
2146		2837
2147	As an example for a bug workaround, the kqueue backend might only support	2838	As an example for a bug workaround, the kqueue backend might only support
2148	sockets on some platform, so it is unusable as generic backend, but you	2839	sockets on some platform, so it is unusable as generic backend, but you
2149	still want to make use of it because you have many sockets and it scales	2840	still want to make use of it because you have many sockets and it scales
2150	so nicely. In this case, you would create a kqueue-based loop and embed it	2841	so nicely. In this case, you would create a kqueue-based loop and embed
2151	into your default loop (which might use e.g. poll). Overall operation will	2842	it into your default loop (which might use e.g. poll). Overall operation
2152	be a bit slower because first libev has to poll and then call kevent, but	2843	will be a bit slower because first libev has to call C<poll> and then
2153	at least you can use both at what they are best.	2844	C<kevent>, but at least you can use both mechanisms for what they are
		2845	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2154		2846
2155	As for prioritising I/O: rarely you have the case where some fds have	2847	As for prioritising I/O: under rare circumstances you have the case where
2156	to be watched and handled very quickly (with low latency), and even	2848	some fds have to be watched and handled very quickly (with low latency),
2157	priorities and idle watchers might have too much overhead. In this case	2849	and even priorities and idle watchers might have too much overhead. In
2158	you would put all the high priority stuff in one loop and all the rest in	2850	this case you would put all the high priority stuff in one loop and all
2159	a second one, and embed the second one in the first.	2851	the rest in a second one, and embed the second one in the first.
2160		2852
2161	As long as the watcher is active, the callback will be invoked every time	2853	As long as the watcher is active, the callback will be invoked every
2162	there might be events pending in the embedded loop. The callback must then	2854	time there might be events pending in the embedded loop. The callback
2163	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2855	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2164	their callbacks (you could also start an idle watcher to give the embedded	2856	sweep and invoke their callbacks (the callback doesn't need to invoke the
2165	loop strictly lower priority for example). You can also set the callback	2857	C<ev_embed_sweep> function directly, it could also start an idle watcher
2166	to C<0>, in which case the embed watcher will automatically execute the	2858	to give the embedded loop strictly lower priority for example).
2167	embedded loop sweep.
2168		2859
2169	As long as the watcher is started it will automatically handle events. The	2860	You can also set the callback to C<0>, in which case the embed watcher
2170	callback will be invoked whenever some events have been handled. You can	2861	will automatically execute the embedded loop sweep whenever necessary.
2171	set the callback to C<0> to avoid having to specify one if you are not
2172	interested in that.
2173		2862
2174	Also, there have not currently been made special provisions for forking:	2863	Fork detection will be handled transparently while the C<ev_embed> watcher
2175	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2864	is active, i.e., the embedded loop will automatically be forked when the
2176	but you will also have to stop and restart any C<ev_embed> watchers	2865	embedding loop forks. In other cases, the user is responsible for calling
2177	yourself.	2866	C<ev_loop_fork> on the embedded loop.
2178		2867
2179	Unfortunately, not all backends are embeddable, only the ones returned by	2868	Unfortunately, not all backends are embeddable: only the ones returned by
2180	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2869	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2181	portable one.	2870	portable one.
2182		2871
2183	So when you want to use this feature you will always have to be prepared	2872	So when you want to use this feature you will always have to be prepared
2184	that you cannot get an embeddable loop. The recommended way to get around	2873	that you cannot get an embeddable loop. The recommended way to get around
2185	this is to have a separate variables for your embeddable loop, try to	2874	this is to have a separate variables for your embeddable loop, try to
2186	create it, and if that fails, use the normal loop for everything.	2875	create it, and if that fails, use the normal loop for everything.
		2876
		2877	=head3 C<ev_embed> and fork
		2878
		2879	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2880	automatically be applied to the embedded loop as well, so no special
		2881	fork handling is required in that case. When the watcher is not running,
		2882	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2883	as applicable.
2187		2884
2188	=head3 Watcher-Specific Functions and Data Members	2885	=head3 Watcher-Specific Functions and Data Members
2189		2886
2190	=over 4	2887	=over 4
2191		2888
…		…
2219	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2916	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2220	used).	2917	used).
2221		2918
2222	struct ev_loop *loop_hi = ev_default_init (0);	2919	struct ev_loop *loop_hi = ev_default_init (0);
2223	struct ev_loop *loop_lo = 0;	2920	struct ev_loop *loop_lo = 0;
2224	struct ev_embed embed;	2921	ev_embed embed;
2225		2922
2226	// see if there is a chance of getting one that works	2923	// see if there is a chance of getting one that works
2227	// (remember that a flags value of 0 means autodetection)	2924	// (remember that a flags value of 0 means autodetection)
2228	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2925	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2229	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2926	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2243	kqueue implementation). Store the kqueue/socket-only event loop in	2940	kqueue implementation). Store the kqueue/socket-only event loop in
2244	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2941	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2245		2942
2246	struct ev_loop *loop = ev_default_init (0);	2943	struct ev_loop *loop = ev_default_init (0);
2247	struct ev_loop *loop_socket = 0;	2944	struct ev_loop *loop_socket = 0;
2248	struct ev_embed embed;	2945	ev_embed embed;
2249		2946
2250	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2947	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2251	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2948	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2252	{	2949	{
2253	ev_embed_init (&embed, 0, loop_socket);	2950	ev_embed_init (&embed, 0, loop_socket);
…		…
2268	event loop blocks next and before C<ev_check> watchers are being called,	2965	event loop blocks next and before C<ev_check> watchers are being called,
2269	and only in the child after the fork. If whoever good citizen calling	2966	and only in the child after the fork. If whoever good citizen calling
2270	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2967	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2271	handlers will be invoked, too, of course.	2968	handlers will be invoked, too, of course.
2272		2969
		2970	=head3 The special problem of life after fork - how is it possible?
		2971
		2972	Most uses of C<fork()> consist of forking, then some simple calls to set
		2973	up/change the process environment, followed by a call to C<exec()>. This
		2974	sequence should be handled by libev without any problems.
		2975
		2976	This changes when the application actually wants to do event handling
		2977	in the child, or both parent in child, in effect "continuing" after the
		2978	fork.
		2979
		2980	The default mode of operation (for libev, with application help to detect
		2981	forks) is to duplicate all the state in the child, as would be expected
		2982	when I<either> the parent I<or> the child process continues.
		2983
		2984	When both processes want to continue using libev, then this is usually the
		2985	wrong result. In that case, usually one process (typically the parent) is
		2986	supposed to continue with all watchers in place as before, while the other
		2987	process typically wants to start fresh, i.e. without any active watchers.
		2988
		2989	The cleanest and most efficient way to achieve that with libev is to
		2990	simply create a new event loop, which of course will be "empty", and
		2991	use that for new watchers. This has the advantage of not touching more
		2992	memory than necessary, and thus avoiding the copy-on-write, and the
		2993	disadvantage of having to use multiple event loops (which do not support
		2994	signal watchers).
		2995
		2996	When this is not possible, or you want to use the default loop for
		2997	other reasons, then in the process that wants to start "fresh", call
		2998	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2999	the default loop will "orphan" (not stop) all registered watchers, so you
		3000	have to be careful not to execute code that modifies those watchers. Note
		3001	also that in that case, you have to re-register any signal watchers.
		3002
2273	=head3 Watcher-Specific Functions and Data Members	3003	=head3 Watcher-Specific Functions and Data Members
2274		3004
2275	=over 4	3005	=over 4
2276		3006
2277	=item ev_fork_init (ev_signal *, callback)	3007	=item ev_fork_init (ev_signal *, callback)
…		…
2281	believe me.	3011	believe me.
2282		3012
2283	=back	3013	=back
2284		3014
2285		3015
2286	=head2 C<ev_async> - how to wake up another event loop	3016	=head2 C<ev_async> - how to wake up an event loop
2287		3017
2288	In general, you cannot use an C<ev_loop> from multiple threads or other	3018	In general, you cannot use an C<ev_loop> from multiple threads or other
2289	asynchronous sources such as signal handlers (as opposed to multiple event	3019	asynchronous sources such as signal handlers (as opposed to multiple event
2290	loops - those are of course safe to use in different threads).	3020	loops - those are of course safe to use in different threads).
2291		3021
2292	Sometimes, however, you need to wake up another event loop you do not	3022	Sometimes, however, you need to wake up an event loop you do not control,
2293	control, for example because it belongs to another thread. This is what	3023	for example because it belongs to another thread. This is what C<ev_async>
2294	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3024	watchers do: as long as the C<ev_async> watcher is active, you can signal
2295	can signal it by calling C<ev_async_send>, which is thread- and signal	3025	it by calling C<ev_async_send>, which is thread- and signal safe.
2296	safe.
2297		3026
2298	This functionality is very similar to C<ev_signal> watchers, as signals,	3027	This functionality is very similar to C<ev_signal> watchers, as signals,
2299	too, are asynchronous in nature, and signals, too, will be compressed	3028	too, are asynchronous in nature, and signals, too, will be compressed
2300	(i.e. the number of callback invocations may be less than the number of	3029	(i.e. the number of callback invocations may be less than the number of
2301	C<ev_async_sent> calls).	3030	C<ev_async_sent> calls).
…		…
2306	=head3 Queueing	3035	=head3 Queueing
2307		3036
2308	C<ev_async> does not support queueing of data in any way. The reason	3037	C<ev_async> does not support queueing of data in any way. The reason
2309	is that the author does not know of a simple (or any) algorithm for a	3038	is that the author does not know of a simple (or any) algorithm for a
2310	multiple-writer-single-reader queue that works in all cases and doesn't	3039	multiple-writer-single-reader queue that works in all cases and doesn't
2311	need elaborate support such as pthreads.	3040	need elaborate support such as pthreads or unportable memory access
		3041	semantics.
2312		3042
2313	That means that if you want to queue data, you have to provide your own	3043	That means that if you want to queue data, you have to provide your own
2314	queue. But at least I can tell you would implement locking around your	3044	queue. But at least I can tell you how to implement locking around your
2315	queue:	3045	queue:
2316		3046
2317	=over 4	3047	=over 4
2318		3048
2319	=item queueing from a signal handler context	3049	=item queueing from a signal handler context
2320		3050
2321	To implement race-free queueing, you simply add to the queue in the signal	3051	To implement race-free queueing, you simply add to the queue in the signal
2322	handler but you block the signal handler in the watcher callback. Here is an example that does that for	3052	handler but you block the signal handler in the watcher callback. Here is
2323	some fictitious SIGUSR1 handler:	3053	an example that does that for some fictitious SIGUSR1 handler:
2324		3054
2325	static ev_async mysig;	3055	static ev_async mysig;
2326		3056
2327	static void	3057	static void
2328	sigusr1_handler (void)	3058	sigusr1_handler (void)
…		…
2394	=over 4	3124	=over 4
2395		3125
2396	=item ev_async_init (ev_async *, callback)	3126	=item ev_async_init (ev_async *, callback)
2397		3127
2398	Initialises and configures the async watcher - it has no parameters of any	3128	Initialises and configures the async watcher - it has no parameters of any
2399	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3129	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2400	believe me.	3130	trust me.
2401		3131
2402	=item ev_async_send (loop, ev_async *)	3132	=item ev_async_send (loop, ev_async *)
2403		3133
2404	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3134	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2405	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3135	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2406	C<ev_feed_event>, this call is safe to do in other threads, signal or	3136	C<ev_feed_event>, this call is safe to do from other threads, signal or
2407	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3137	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2408	section below on what exactly this means).	3138	section below on what exactly this means).
2409		3139
		3140	Note that, as with other watchers in libev, multiple events might get
		3141	compressed into a single callback invocation (another way to look at this
		3142	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3143	reset when the event loop detects that).
		3144
2410	This call incurs the overhead of a system call only once per loop iteration,	3145	This call incurs the overhead of a system call only once per event loop
2411	so while the overhead might be noticeable, it doesn't apply to repeated	3146	iteration, so while the overhead might be noticeable, it doesn't apply to
2412	calls to C<ev_async_send>.	3147	repeated calls to C<ev_async_send> for the same event loop.
2413		3148
2414	=item bool = ev_async_pending (ev_async *)	3149	=item bool = ev_async_pending (ev_async *)
2415		3150
2416	Returns a non-zero value when C<ev_async_send> has been called on the	3151	Returns a non-zero value when C<ev_async_send> has been called on the
2417	watcher but the event has not yet been processed (or even noted) by the	3152	watcher but the event has not yet been processed (or even noted) by the
…		…
2420	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3155	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2421	the loop iterates next and checks for the watcher to have become active,	3156	the loop iterates next and checks for the watcher to have become active,
2422	it will reset the flag again. C<ev_async_pending> can be used to very	3157	it will reset the flag again. C<ev_async_pending> can be used to very
2423	quickly check whether invoking the loop might be a good idea.	3158	quickly check whether invoking the loop might be a good idea.
2424		3159
2425	Not that this does I<not> check whether the watcher itself is pending, only	3160	Not that this does I<not> check whether the watcher itself is pending,
2426	whether it has been requested to make this watcher pending.	3161	only whether it has been requested to make this watcher pending: there
		3162	is a time window between the event loop checking and resetting the async
		3163	notification, and the callback being invoked.
2427		3164
2428	=back	3165	=back
2429		3166
2430		3167
2431	=head1 OTHER FUNCTIONS	3168	=head1 OTHER FUNCTIONS
…		…
2435	=over 4	3172	=over 4
2436		3173
2437	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3174	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2438		3175
2439	This function combines a simple timer and an I/O watcher, calls your	3176	This function combines a simple timer and an I/O watcher, calls your
2440	callback on whichever event happens first and automatically stop both	3177	callback on whichever event happens first and automatically stops both
2441	watchers. This is useful if you want to wait for a single event on an fd	3178	watchers. This is useful if you want to wait for a single event on an fd
2442	or timeout without having to allocate/configure/start/stop/free one or	3179	or timeout without having to allocate/configure/start/stop/free one or
2443	more watchers yourself.	3180	more watchers yourself.
2444		3181
2445	If C<fd> is less than 0, then no I/O watcher will be started and events	3182	If C<fd> is less than 0, then no I/O watcher will be started and the
2446	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	3183	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2447	C<events> set will be created and started.	3184	the given C<fd> and C<events> set will be created and started.
2448		3185
2449	If C<timeout> is less than 0, then no timeout watcher will be	3186	If C<timeout> is less than 0, then no timeout watcher will be
2450	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3187	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2451	repeat = 0) will be started. While C<0> is a valid timeout, it is of	3188	repeat = 0) will be started. C<0> is a valid timeout.
2452	dubious value.
2453		3189
2454	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3190	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2455	passed an C<revents> set like normal event callbacks (a combination of	3191	passed an C<revents> set like normal event callbacks (a combination of
2456	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3192	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2457	value passed to C<ev_once>:	3193	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3194	a timeout and an io event at the same time - you probably should give io
		3195	events precedence.
		3196
		3197	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2458		3198
2459	static void stdin_ready (int revents, void *arg)	3199	static void stdin_ready (int revents, void *arg)
2460	{	3200	{
		3201	if (revents & EV_READ)
		3202	/* stdin might have data for us, joy! */;
2461	if (revents & EV_TIMEOUT)	3203	else if (revents & EV_TIMER)
2462	/* doh, nothing entered */;	3204	/* doh, nothing entered */;
2463	else if (revents & EV_READ)
2464	/* stdin might have data for us, joy! */;
2465	}	3205	}
2466		3206
2467	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3207	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2468		3208
2469	=item ev_feed_event (ev_loop *, watcher *, int revents)
2470
2471	Feeds the given event set into the event loop, as if the specified event
2472	had happened for the specified watcher (which must be a pointer to an
2473	initialised but not necessarily started event watcher).
2474
2475	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3209	=item ev_feed_fd_event (loop, int fd, int revents)
2476		3210
2477	Feed an event on the given fd, as if a file descriptor backend detected	3211	Feed an event on the given fd, as if a file descriptor backend detected
2478	the given events it.	3212	the given events it.
2479		3213
2480	=item ev_feed_signal_event (ev_loop *loop, int signum)	3214	=item ev_feed_signal_event (loop, int signum)
2481		3215
2482	Feed an event as if the given signal occurred (C<loop> must be the default	3216	Feed an event as if the given signal occurred (C<loop> must be the default
2483	loop!).	3217	loop!).
2484		3218
2485	=back	3219	=back
…		…
2565		3299
2566	=over 4	3300	=over 4
2567		3301
2568	=item ev::TYPE::TYPE ()	3302	=item ev::TYPE::TYPE ()
2569		3303
2570	=item ev::TYPE::TYPE (struct ev_loop *)	3304	=item ev::TYPE::TYPE (loop)
2571		3305
2572	=item ev::TYPE::~TYPE	3306	=item ev::TYPE::~TYPE
2573		3307
2574	The constructor (optionally) takes an event loop to associate the watcher	3308	The constructor (optionally) takes an event loop to associate the watcher
2575	with. If it is omitted, it will use C<EV_DEFAULT>.	3309	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2607		3341
2608	myclass obj;	3342	myclass obj;
2609	ev::io iow;	3343	ev::io iow;
2610	iow.set <myclass, &myclass::io_cb> (&obj);	3344	iow.set <myclass, &myclass::io_cb> (&obj);
2611		3345
		3346	=item w->set (object *)
		3347
		3348	This is a variation of a method callback - leaving out the method to call
		3349	will default the method to C<operator ()>, which makes it possible to use
		3350	functor objects without having to manually specify the C<operator ()> all
		3351	the time. Incidentally, you can then also leave out the template argument
		3352	list.
		3353
		3354	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3355	int revents)>.
		3356
		3357	See the method-C<set> above for more details.
		3358
		3359	Example: use a functor object as callback.
		3360
		3361	struct myfunctor
		3362	{
		3363	void operator() (ev::io &w, int revents)
		3364	{
		3365	...
		3366	}
		3367	}
		3368
		3369	myfunctor f;
		3370
		3371	ev::io w;
		3372	w.set (&f);
		3373
2612	=item w->set<function> (void *data = 0)	3374	=item w->set<function> (void *data = 0)
2613		3375
2614	Also sets a callback, but uses a static method or plain function as	3376	Also sets a callback, but uses a static method or plain function as
2615	callback. The optional C<data> argument will be stored in the watcher's	3377	callback. The optional C<data> argument will be stored in the watcher's
2616	C<data> member and is free for you to use.	3378	C<data> member and is free for you to use.
2617		3379
2618	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3380	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2619		3381
2620	See the method-C<set> above for more details.	3382	See the method-C<set> above for more details.
2621		3383
2622	Example:	3384	Example: Use a plain function as callback.
2623		3385
2624	static void io_cb (ev::io &w, int revents) { }	3386	static void io_cb (ev::io &w, int revents) { }
2625	iow.set <io_cb> ();	3387	iow.set <io_cb> ();
2626		3388
2627	=item w->set (struct ev_loop *)	3389	=item w->set (loop)
2628		3390
2629	Associates a different C<struct ev_loop> with this watcher. You can only	3391	Associates a different C<struct ev_loop> with this watcher. You can only
2630	do this when the watcher is inactive (and not pending either).	3392	do this when the watcher is inactive (and not pending either).
2631		3393
2632	=item w->set ([arguments])	3394	=item w->set ([arguments])
…		…
2665	Example: Define a class with an IO and idle watcher, start one of them in	3427	Example: Define a class with an IO and idle watcher, start one of them in
2666	the constructor.	3428	the constructor.
2667		3429
2668	class myclass	3430	class myclass
2669	{	3431	{
2670	ev::io io; void io_cb (ev::io &w, int revents);	3432	ev::io io ; void io_cb (ev::io &w, int revents);
2671	ev:idle idle void idle_cb (ev::idle &w, int revents);	3433	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2672		3434
2673	myclass (int fd)	3435	myclass (int fd)
2674	{	3436	{
2675	io .set <myclass, &myclass::io_cb > (this);	3437	io .set <myclass, &myclass::io_cb > (this);
2676	idle.set <myclass, &myclass::idle_cb> (this);	3438	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2692	=item Perl	3454	=item Perl
2693		3455
2694	The EV module implements the full libev API and is actually used to test	3456	The EV module implements the full libev API and is actually used to test
2695	libev. EV is developed together with libev. Apart from the EV core module,	3457	libev. EV is developed together with libev. Apart from the EV core module,
2696	there are additional modules that implement libev-compatible interfaces	3458	there are additional modules that implement libev-compatible interfaces
2697	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3459	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2698	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3460	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3461	and C<EV::Glib>).
2699		3462
2700	It can be found and installed via CPAN, its homepage is at	3463	It can be found and installed via CPAN, its homepage is at
2701	L<http://software.schmorp.de/pkg/EV>.	3464	L<http://software.schmorp.de/pkg/EV>.
2702		3465
2703	=item Python	3466	=item Python
2704		3467
2705	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3468	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2706	seems to be quite complete and well-documented. Note, however, that the	3469	seems to be quite complete and well-documented.
2707	patch they require for libev is outright dangerous as it breaks the ABI
2708	for everybody else, and therefore, should never be applied in an installed
2709	libev (if python requires an incompatible ABI then it needs to embed
2710	libev).
2711		3470
2712	=item Ruby	3471	=item Ruby
2713		3472
2714	Tony Arcieri has written a ruby extension that offers access to a subset	3473	Tony Arcieri has written a ruby extension that offers access to a subset
2715	of the libev API and adds file handle abstractions, asynchronous DNS and	3474	of the libev API and adds file handle abstractions, asynchronous DNS and
2716	more on top of it. It can be found via gem servers. Its homepage is at	3475	more on top of it. It can be found via gem servers. Its homepage is at
2717	L<http://rev.rubyforge.org/>.	3476	L<http://rev.rubyforge.org/>.
2718		3477
		3478	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3479	makes rev work even on mingw.
		3480
		3481	=item Haskell
		3482
		3483	A haskell binding to libev is available at
		3484	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3485
2719	=item D	3486	=item D
2720		3487
2721	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3488	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2722	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3489	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3490
		3491	=item Ocaml
		3492
		3493	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3494	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3495
		3496	=item Lua
		3497
		3498	Brian Maher has written a partial interface to libev for lua (at the
		3499	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3500	L<http://github.com/brimworks/lua-ev>.
2723		3501
2724	=back	3502	=back
2725		3503
2726		3504
2727	=head1 MACRO MAGIC	3505	=head1 MACRO MAGIC
…		…
2828		3606
2829	#define EV_STANDALONE 1	3607	#define EV_STANDALONE 1
2830	#include "ev.h"	3608	#include "ev.h"
2831		3609
2832	Both header files and implementation files can be compiled with a C++	3610	Both header files and implementation files can be compiled with a C++
2833	compiler (at least, thats a stated goal, and breakage will be treated	3611	compiler (at least, that's a stated goal, and breakage will be treated
2834	as a bug).	3612	as a bug).
2835		3613
2836	You need the following files in your source tree, or in a directory	3614	You need the following files in your source tree, or in a directory
2837	in your include path (e.g. in libev/ when using -Ilibev):	3615	in your include path (e.g. in libev/ when using -Ilibev):
2838		3616
…		…
2881	libev.m4	3659	libev.m4
2882		3660
2883	=head2 PREPROCESSOR SYMBOLS/MACROS	3661	=head2 PREPROCESSOR SYMBOLS/MACROS
2884		3662
2885	Libev can be configured via a variety of preprocessor symbols you have to	3663	Libev can be configured via a variety of preprocessor symbols you have to
2886	define before including any of its files. The default in the absence of	3664	define before including (or compiling) any of its files. The default in
2887	autoconf is noted for every option.	3665	the absence of autoconf is documented for every option.
		3666
		3667	Symbols marked with "(h)" do not change the ABI, and can have different
		3668	values when compiling libev vs. including F<ev.h>, so it is permissible
		3669	to redefine them before including F<ev.h> without breaking compatibility
		3670	to a compiled library. All other symbols change the ABI, which means all
		3671	users of libev and the libev code itself must be compiled with compatible
		3672	settings.
2888		3673
2889	=over 4	3674	=over 4
2890		3675
2891	=item EV_STANDALONE	3676	=item EV_STANDALONE (h)
2892		3677
2893	Must always be C<1> if you do not use autoconf configuration, which	3678	Must always be C<1> if you do not use autoconf configuration, which
2894	keeps libev from including F<config.h>, and it also defines dummy	3679	keeps libev from including F<config.h>, and it also defines dummy
2895	implementations for some libevent functions (such as logging, which is not	3680	implementations for some libevent functions (such as logging, which is not
2896	supported). It will also not define any of the structs usually found in	3681	supported). It will also not define any of the structs usually found in
2897	F<event.h> that are not directly supported by the libev core alone.	3682	F<event.h> that are not directly supported by the libev core alone.
2898		3683
		3684	In standalone mode, libev will still try to automatically deduce the
		3685	configuration, but has to be more conservative.
		3686
2899	=item EV_USE_MONOTONIC	3687	=item EV_USE_MONOTONIC
2900		3688
2901	If defined to be C<1>, libev will try to detect the availability of the	3689	If defined to be C<1>, libev will try to detect the availability of the
2902	monotonic clock option at both compile time and runtime. Otherwise no use	3690	monotonic clock option at both compile time and runtime. Otherwise no
2903	of the monotonic clock option will be attempted. If you enable this, you	3691	use of the monotonic clock option will be attempted. If you enable this,
2904	usually have to link against librt or something similar. Enabling it when	3692	you usually have to link against librt or something similar. Enabling it
2905	the functionality isn't available is safe, though, although you have	3693	when the functionality isn't available is safe, though, although you have
2906	to make sure you link against any libraries where the C<clock_gettime>	3694	to make sure you link against any libraries where the C<clock_gettime>
2907	function is hiding in (often F<-lrt>).	3695	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2908		3696
2909	=item EV_USE_REALTIME	3697	=item EV_USE_REALTIME
2910		3698
2911	If defined to be C<1>, libev will try to detect the availability of the	3699	If defined to be C<1>, libev will try to detect the availability of the
2912	real-time clock option at compile time (and assume its availability at	3700	real-time clock option at compile time (and assume its availability
2913	runtime if successful). Otherwise no use of the real-time clock option will	3701	at runtime if successful). Otherwise no use of the real-time clock
2914	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3702	option will be attempted. This effectively replaces C<gettimeofday>
2915	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3703	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2916	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3704	correctness. See the note about libraries in the description of
		3705	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3706	C<EV_USE_CLOCK_SYSCALL>.
		3707
		3708	=item EV_USE_CLOCK_SYSCALL
		3709
		3710	If defined to be C<1>, libev will try to use a direct syscall instead
		3711	of calling the system-provided C<clock_gettime> function. This option
		3712	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3713	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3714	programs needlessly. Using a direct syscall is slightly slower (in
		3715	theory), because no optimised vdso implementation can be used, but avoids
		3716	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3717	higher, as it simplifies linking (no need for C<-lrt>).
2917		3718
2918	=item EV_USE_NANOSLEEP	3719	=item EV_USE_NANOSLEEP
2919		3720
2920	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3721	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2921	and will use it for delays. Otherwise it will use C<select ()>.	3722	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2937		3738
2938	=item EV_SELECT_USE_FD_SET	3739	=item EV_SELECT_USE_FD_SET
2939		3740
2940	If defined to C<1>, then the select backend will use the system C<fd_set>	3741	If defined to C<1>, then the select backend will use the system C<fd_set>
2941	structure. This is useful if libev doesn't compile due to a missing	3742	structure. This is useful if libev doesn't compile due to a missing
2942	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3743	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2943	exotic systems. This usually limits the range of file descriptors to some	3744	on exotic systems. This usually limits the range of file descriptors to
2944	low limit such as 1024 or might have other limitations (winsocket only	3745	some low limit such as 1024 or might have other limitations (winsocket
2945	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3746	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2946	influence the size of the C<fd_set> used.	3747	configures the maximum size of the C<fd_set>.
2947		3748
2948	=item EV_SELECT_IS_WINSOCKET	3749	=item EV_SELECT_IS_WINSOCKET
2949		3750
2950	When defined to C<1>, the select backend will assume that	3751	When defined to C<1>, the select backend will assume that
2951	select/socket/connect etc. don't understand file descriptors but	3752	select/socket/connect etc. don't understand file descriptors but
…		…
2953	be used is the winsock select). This means that it will call	3754	be used is the winsock select). This means that it will call
2954	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3755	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2955	it is assumed that all these functions actually work on fds, even	3756	it is assumed that all these functions actually work on fds, even
2956	on win32. Should not be defined on non-win32 platforms.	3757	on win32. Should not be defined on non-win32 platforms.
2957		3758
2958	=item EV_FD_TO_WIN32_HANDLE	3759	=item EV_FD_TO_WIN32_HANDLE(fd)
2959		3760
2960	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3761	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
2961	file descriptors to socket handles. When not defining this symbol (the	3762	file descriptors to socket handles. When not defining this symbol (the
2962	default), then libev will call C<_get_osfhandle>, which is usually	3763	default), then libev will call C<_get_osfhandle>, which is usually
2963	correct. In some cases, programs use their own file descriptor management,	3764	correct. In some cases, programs use their own file descriptor management,
2964	in which case they can provide this function to map fds to socket handles.	3765	in which case they can provide this function to map fds to socket handles.
		3766
		3767	=item EV_WIN32_HANDLE_TO_FD(handle)
		3768
		3769	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3770	using the standard C<_open_osfhandle> function. For programs implementing
		3771	their own fd to handle mapping, overwriting this function makes it easier
		3772	to do so. This can be done by defining this macro to an appropriate value.
		3773
		3774	=item EV_WIN32_CLOSE_FD(fd)
		3775
		3776	If programs implement their own fd to handle mapping on win32, then this
		3777	macro can be used to override the C<close> function, useful to unregister
		3778	file descriptors again. Note that the replacement function has to close
		3779	the underlying OS handle.
2965		3780
2966	=item EV_USE_POLL	3781	=item EV_USE_POLL
2967		3782
2968	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3783	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2969	backend. Otherwise it will be enabled on non-win32 platforms. It	3784	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3016	as well as for signal and thread safety in C<ev_async> watchers.	3831	as well as for signal and thread safety in C<ev_async> watchers.
3017		3832
3018	In the absence of this define, libev will use C<sig_atomic_t volatile>	3833	In the absence of this define, libev will use C<sig_atomic_t volatile>
3019	(from F<signal.h>), which is usually good enough on most platforms.	3834	(from F<signal.h>), which is usually good enough on most platforms.
3020		3835
3021	=item EV_H	3836	=item EV_H (h)
3022		3837
3023	The name of the F<ev.h> header file used to include it. The default if	3838	The name of the F<ev.h> header file used to include it. The default if
3024	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	3839	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3025	used to virtually rename the F<ev.h> header file in case of conflicts.	3840	used to virtually rename the F<ev.h> header file in case of conflicts.
3026		3841
3027	=item EV_CONFIG_H	3842	=item EV_CONFIG_H (h)
3028		3843
3029	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	3844	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3030	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	3845	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3031	C<EV_H>, above.	3846	C<EV_H>, above.
3032		3847
3033	=item EV_EVENT_H	3848	=item EV_EVENT_H (h)
3034		3849
3035	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	3850	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3036	of how the F<event.h> header can be found, the default is C<"event.h">.	3851	of how the F<event.h> header can be found, the default is C<"event.h">.
3037		3852
3038	=item EV_PROTOTYPES	3853	=item EV_PROTOTYPES (h)
3039		3854
3040	If defined to be C<0>, then F<ev.h> will not define any function	3855	If defined to be C<0>, then F<ev.h> will not define any function
3041	prototypes, but still define all the structs and other symbols. This is	3856	prototypes, but still define all the structs and other symbols. This is
3042	occasionally useful if you want to provide your own wrapper functions	3857	occasionally useful if you want to provide your own wrapper functions
3043	around libev functions.	3858	around libev functions.
…		…
3062	When doing priority-based operations, libev usually has to linearly search	3877	When doing priority-based operations, libev usually has to linearly search
3063	all the priorities, so having many of them (hundreds) uses a lot of space	3878	all the priorities, so having many of them (hundreds) uses a lot of space
3064	and time, so using the defaults of five priorities (-2 .. +2) is usually	3879	and time, so using the defaults of five priorities (-2 .. +2) is usually
3065	fine.	3880	fine.
3066		3881
3067	If your embedding application does not need any priorities, defining these both to	3882	If your embedding application does not need any priorities, defining these
3068	C<0> will save some memory and CPU.	3883	both to C<0> will save some memory and CPU.
3069		3884
3070	=item EV_PERIODIC_ENABLE	3885	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		3886	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		3887	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3071		3888
3072	If undefined or defined to be C<1>, then periodic timers are supported. If	3889	If undefined or defined to be C<1> (and the platform supports it), then
3073	defined to be C<0>, then they are not. Disabling them saves a few kB of	3890	the respective watcher type is supported. If defined to be C<0>, then it
3074	code.	3891	is not. Disabling watcher types mainly saves code size.
3075		3892
3076	=item EV_IDLE_ENABLE	3893	=item EV_FEATURES
3077
3078	If undefined or defined to be C<1>, then idle watchers are supported. If
3079	defined to be C<0>, then they are not. Disabling them saves a few kB of
3080	code.
3081
3082	=item EV_EMBED_ENABLE
3083
3084	If undefined or defined to be C<1>, then embed watchers are supported. If
3085	defined to be C<0>, then they are not.
3086
3087	=item EV_STAT_ENABLE
3088
3089	If undefined or defined to be C<1>, then stat watchers are supported. If
3090	defined to be C<0>, then they are not.
3091
3092	=item EV_FORK_ENABLE
3093
3094	If undefined or defined to be C<1>, then fork watchers are supported. If
3095	defined to be C<0>, then they are not.
3096
3097	=item EV_ASYNC_ENABLE
3098
3099	If undefined or defined to be C<1>, then async watchers are supported. If
3100	defined to be C<0>, then they are not.
3101
3102	=item EV_MINIMAL
3103		3894
3104	If you need to shave off some kilobytes of code at the expense of some	3895	If you need to shave off some kilobytes of code at the expense of some
3105	speed, define this symbol to C<1>. Currently this is used to override some	3896	speed (but with the full API), you can define this symbol to request
3106	inlining decisions, saves roughly 30% code size on amd64. It also selects a	3897	certain subsets of functionality. The default is to enable all features
3107	much smaller 2-heap for timer management over the default 4-heap.	3898	that can be enabled on the platform.
		3899
		3900	A typical way to use this symbol is to define it to C<0> (or to a bitset
		3901	with some broad features you want) and then selectively re-enable
		3902	additional parts you want, for example if you want everything minimal,
		3903	but multiple event loop support, async and child watchers and the poll
		3904	backend, use this:
		3905
		3906	#define EV_FEATURES 0
		3907	#define EV_MULTIPLICITY 1
		3908	#define EV_USE_POLL 1
		3909	#define EV_CHILD_ENABLE 1
		3910	#define EV_ASYNC_ENABLE 1
		3911
		3912	The actual value is a bitset, it can be a combination of the following
		3913	values:
		3914
		3915	=over 4
		3916
		3917	=item C<1> - faster/larger code
		3918
		3919	Use larger code to speed up some operations.
		3920
		3921	Currently this is used to override some inlining decisions (enlarging the
		3922	code size by roughly 30% on amd64).
		3923
		3924	When optimising for size, use of compiler flags such as C<-Os> with
		3925	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		3926	assertions.
		3927
		3928	=item C<2> - faster/larger data structures
		3929
		3930	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		3931	hash table sizes and so on. This will usually further increase code size
		3932	and can additionally have an effect on the size of data structures at
		3933	runtime.
		3934
		3935	=item C<4> - full API configuration
		3936
		3937	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		3938	enables multiplicity (C<EV_MULTIPLICITY>=1).
		3939
		3940	=item C<8> - full API
		3941
		3942	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		3943	details on which parts of the API are still available without this
		3944	feature, and do not complain if this subset changes over time.
		3945
		3946	=item C<16> - enable all optional watcher types
		3947
		3948	Enables all optional watcher types. If you want to selectively enable
		3949	only some watcher types other than I/O and timers (e.g. prepare,
		3950	embed, async, child...) you can enable them manually by defining
		3951	C<EV_watchertype_ENABLE> to C<1> instead.
		3952
		3953	=item C<32> - enable all backends
		3954
		3955	This enables all backends - without this feature, you need to enable at
		3956	least one backend manually (C<EV_USE_SELECT> is a good choice).
		3957
		3958	=item C<64> - enable OS-specific "helper" APIs
		3959
		3960	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		3961	default.
		3962
		3963	=back
		3964
		3965	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		3966	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		3967	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		3968	watchers, timers and monotonic clock support.
		3969
		3970	With an intelligent-enough linker (gcc+binutils are intelligent enough
		3971	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		3972	your program might be left out as well - a binary starting a timer and an
		3973	I/O watcher then might come out at only 5Kb.
		3974
		3975	=item EV_AVOID_STDIO
		3976
		3977	If this is set to C<1> at compiletime, then libev will avoid using stdio
		3978	functions (printf, scanf, perror etc.). This will increase the code size
		3979	somewhat, but if your program doesn't otherwise depend on stdio and your
		3980	libc allows it, this avoids linking in the stdio library which is quite
		3981	big.
		3982
		3983	Note that error messages might become less precise when this option is
		3984	enabled.
		3985
		3986	=item EV_NSIG
		3987
		3988	The highest supported signal number, +1 (or, the number of
		3989	signals): Normally, libev tries to deduce the maximum number of signals
		3990	automatically, but sometimes this fails, in which case it can be
		3991	specified. Also, using a lower number than detected (C<32> should be
		3992	good for about any system in existence) can save some memory, as libev
		3993	statically allocates some 12-24 bytes per signal number.
3108		3994
3109	=item EV_PID_HASHSIZE	3995	=item EV_PID_HASHSIZE
3110		3996
3111	C<ev_child> watchers use a small hash table to distribute workload by	3997	C<ev_child> watchers use a small hash table to distribute workload by
3112	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3998	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3113	than enough. If you need to manage thousands of children you might want to	3999	usually more than enough. If you need to manage thousands of children you
3114	increase this value (I<must> be a power of two).	4000	might want to increase this value (I<must> be a power of two).
3115		4001
3116	=item EV_INOTIFY_HASHSIZE	4002	=item EV_INOTIFY_HASHSIZE
3117		4003
3118	C<ev_stat> watchers use a small hash table to distribute workload by	4004	C<ev_stat> watchers use a small hash table to distribute workload by
3119	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4005	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3120	usually more than enough. If you need to manage thousands of C<ev_stat>	4006	disabled), usually more than enough. If you need to manage thousands of
3121	watchers you might want to increase this value (I<must> be a power of	4007	C<ev_stat> watchers you might want to increase this value (I<must> be a
3122	two).	4008	power of two).
3123		4009
3124	=item EV_USE_4HEAP	4010	=item EV_USE_4HEAP
3125		4011
3126	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4012	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3127	timer and periodics heap, libev uses a 4-heap when this symbol is defined	4013	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3128	to C<1>. The 4-heap uses more complicated (longer) code but has	4014	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3129	noticeably faster performance with many (thousands) of watchers.	4015	faster performance with many (thousands) of watchers.
3130		4016
3131	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4017	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3132	(disabled).	4018	will be C<0>.
3133		4019
3134	=item EV_HEAP_CACHE_AT	4020	=item EV_HEAP_CACHE_AT
3135		4021
3136	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4022	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3137	timer and periodics heap, libev can cache the timestamp (I<at>) within	4023	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3138	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4024	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3139	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4025	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3140	but avoids random read accesses on heap changes. This improves performance	4026	but avoids random read accesses on heap changes. This improves performance
3141	noticeably with with many (hundreds) of watchers.	4027	noticeably with many (hundreds) of watchers.
3142		4028
3143	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4029	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3144	(disabled).	4030	will be C<0>.
3145		4031
3146	=item EV_VERIFY	4032	=item EV_VERIFY
3147		4033
3148	Controls how much internal verification (see C<ev_loop_verify ()>) will	4034	Controls how much internal verification (see C<ev_loop_verify ()>) will
3149	be done: If set to C<0>, no internal verification code will be compiled	4035	be done: If set to C<0>, no internal verification code will be compiled
…		…
3151	called. If set to C<2>, then the internal verification code will be	4037	called. If set to C<2>, then the internal verification code will be
3152	called once per loop, which can slow down libev. If set to C<3>, then the	4038	called once per loop, which can slow down libev. If set to C<3>, then the
3153	verification code will be called very frequently, which will slow down	4039	verification code will be called very frequently, which will slow down
3154	libev considerably.	4040	libev considerably.
3155		4041
3156	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4042	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3157	C<0.>	4043	will be C<0>.
3158		4044
3159	=item EV_COMMON	4045	=item EV_COMMON
3160		4046
3161	By default, all watchers have a C<void *data> member. By redefining	4047	By default, all watchers have a C<void *data> member. By redefining
3162	this macro to a something else you can include more and other types of	4048	this macro to something else you can include more and other types of
3163	members. You have to define it each time you include one of the files,	4049	members. You have to define it each time you include one of the files,
3164	though, and it must be identical each time.	4050	though, and it must be identical each time.
3165		4051
3166	For example, the perl EV module uses something like this:	4052	For example, the perl EV module uses something like this:
3167		4053
…		…
3179	and the way callbacks are invoked and set. Must expand to a struct member	4065	and the way callbacks are invoked and set. Must expand to a struct member
3180	definition and a statement, respectively. See the F<ev.h> header file for	4066	definition and a statement, respectively. See the F<ev.h> header file for
3181	their default definitions. One possible use for overriding these is to	4067	their default definitions. One possible use for overriding these is to
3182	avoid the C<struct ev_loop *> as first argument in all cases, or to use	4068	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3183	method calls instead of plain function calls in C++.	4069	method calls instead of plain function calls in C++.
		4070
		4071	=back
3184		4072
3185	=head2 EXPORTED API SYMBOLS	4073	=head2 EXPORTED API SYMBOLS
3186		4074
3187	If you need to re-export the API (e.g. via a DLL) and you need a list of	4075	If you need to re-export the API (e.g. via a DLL) and you need a list of
3188	exported symbols, you can use the provided F<Symbol.*> files which list	4076	exported symbols, you can use the provided F<Symbol.*> files which list
…		…
3218	file.	4106	file.
3219		4107
3220	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4108	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3221	that everybody includes and which overrides some configure choices:	4109	that everybody includes and which overrides some configure choices:
3222		4110
3223	#define EV_MINIMAL 1	4111	#define EV_FEATURES 8
3224	#define EV_USE_POLL 0	4112	#define EV_USE_SELECT 1
3225	#define EV_MULTIPLICITY 0
3226	#define EV_PERIODIC_ENABLE 0	4113	#define EV_PREPARE_ENABLE 1
		4114	#define EV_IDLE_ENABLE 1
3227	#define EV_STAT_ENABLE 0	4115	#define EV_SIGNAL_ENABLE 1
3228	#define EV_FORK_ENABLE 0	4116	#define EV_CHILD_ENABLE 1
		4117	#define EV_USE_STDEXCEPT 0
3229	#define EV_CONFIG_H <config.h>	4118	#define EV_CONFIG_H <config.h>
3230	#define EV_MINPRI 0
3231	#define EV_MAXPRI 0
3232		4119
3233	#include "ev++.h"	4120	#include "ev++.h"
3234		4121
3235	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4122	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3236		4123
3237	#include "ev_cpp.h"	4124	#include "ev_cpp.h"
3238	#include "ev.c"	4125	#include "ev.c"
3239		4126
		4127	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3240		4128
3241	=head1 THREADS AND COROUTINES	4129	=head2 THREADS AND COROUTINES
3242		4130
3243	=head2 THREADS	4131	=head3 THREADS
3244		4132
3245	Libev itself is thread-safe (unless the opposite is specifically	4133	All libev functions are reentrant and thread-safe unless explicitly
3246	documented for a function), but it uses no locking itself. This means that	4134	documented otherwise, but libev implements no locking itself. This means
3247	you can use as many loops as you want in parallel, as long as only one	4135	that you can use as many loops as you want in parallel, as long as there
3248	thread ever calls into one libev function with the same loop parameter:	4136	are no concurrent calls into any libev function with the same loop
		4137	parameter (C<ev_default_*> calls have an implicit default loop parameter,
3249	libev guarentees that different event loops share no data structures that	4138	of course): libev guarantees that different event loops share no data
3250	need locking.	4139	structures that need any locking.
3251		4140
3252	Or to put it differently: calls with different loop parameters can be done	4141	Or to put it differently: calls with different loop parameters can be done
3253	concurrently from multiple threads, calls with the same loop parameter	4142	concurrently from multiple threads, calls with the same loop parameter
3254	must be done serially (but can be done from different threads, as long as	4143	must be done serially (but can be done from different threads, as long as
3255	only one thread ever is inside a call at any point in time, e.g. by using	4144	only one thread ever is inside a call at any point in time, e.g. by using
3256	a mutex per loop).	4145	a mutex per loop).
3257		4146
3258	Specifically to support threads (and signal handlers), libev implements	4147	Specifically to support threads (and signal handlers), libev implements
3259	so-called C<ev_async> watchers, which allow some limited form of	4148	so-called C<ev_async> watchers, which allow some limited form of
3260	concurrency on the same event loop.	4149	concurrency on the same event loop, namely waking it up "from the
		4150	outside".
3261		4151
3262	If you want to know which design (one loop, locking, or multiple loops	4152	If you want to know which design (one loop, locking, or multiple loops
3263	without or something else still) is best for your problem, then I cannot	4153	without or something else still) is best for your problem, then I cannot
3264	help you. I can give some generic advice however:	4154	help you, but here is some generic advice:
3265		4155
3266	=over 4	4156	=over 4
3267		4157
3268	=item * most applications have a main thread: use the default libev loop	4158	=item * most applications have a main thread: use the default libev loop
3269	in that thread, or create a separate thread running only the default loop.	4159	in that thread, or create a separate thread running only the default loop.
…		…
3281		4171
3282	Choosing a model is hard - look around, learn, know that usually you can do	4172	Choosing a model is hard - look around, learn, know that usually you can do
3283	better than you currently do :-)	4173	better than you currently do :-)
3284		4174
3285	=item * often you need to talk to some other thread which blocks in the	4175	=item * often you need to talk to some other thread which blocks in the
		4176	event loop.
		4177
3286	event loop - C<ev_async> watchers can be used to wake them up from other	4178	C<ev_async> watchers can be used to wake them up from other threads safely
3287	threads safely (or from signal contexts...).	4179	(or from signal contexts...).
3288		4180
3289	=item * some watcher types are only supported in the default loop - use	4181	An example use would be to communicate signals or other events that only
3290	C<ev_async> watchers to tell your other loops about any such events.	4182	work in the default loop by registering the signal watcher with the
		4183	default loop and triggering an C<ev_async> watcher from the default loop
		4184	watcher callback into the event loop interested in the signal.
3291		4185
3292	=back	4186	=back
3293		4187
		4188	=head4 THREAD LOCKING EXAMPLE
		4189
		4190	Here is a fictitious example of how to run an event loop in a different
		4191	thread than where callbacks are being invoked and watchers are
		4192	created/added/removed.
		4193
		4194	For a real-world example, see the C<EV::Loop::Async> perl module,
		4195	which uses exactly this technique (which is suited for many high-level
		4196	languages).
		4197
		4198	The example uses a pthread mutex to protect the loop data, a condition
		4199	variable to wait for callback invocations, an async watcher to notify the
		4200	event loop thread and an unspecified mechanism to wake up the main thread.
		4201
		4202	First, you need to associate some data with the event loop:
		4203
		4204	typedef struct {
		4205	mutex_t lock; /* global loop lock */
		4206	ev_async async_w;
		4207	thread_t tid;
		4208	cond_t invoke_cv;
		4209	} userdata;
		4210
		4211	void prepare_loop (EV_P)
		4212	{
		4213	// for simplicity, we use a static userdata struct.
		4214	static userdata u;
		4215
		4216	ev_async_init (&u->async_w, async_cb);
		4217	ev_async_start (EV_A_ &u->async_w);
		4218
		4219	pthread_mutex_init (&u->lock, 0);
		4220	pthread_cond_init (&u->invoke_cv, 0);
		4221
		4222	// now associate this with the loop
		4223	ev_set_userdata (EV_A_ u);
		4224	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4225	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4226
		4227	// then create the thread running ev_loop
		4228	pthread_create (&u->tid, 0, l_run, EV_A);
		4229	}
		4230
		4231	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4232	solely to wake up the event loop so it takes notice of any new watchers
		4233	that might have been added:
		4234
		4235	static void
		4236	async_cb (EV_P_ ev_async *w, int revents)
		4237	{
		4238	// just used for the side effects
		4239	}
		4240
		4241	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4242	protecting the loop data, respectively.
		4243
		4244	static void
		4245	l_release (EV_P)
		4246	{
		4247	userdata *u = ev_userdata (EV_A);
		4248	pthread_mutex_unlock (&u->lock);
		4249	}
		4250
		4251	static void
		4252	l_acquire (EV_P)
		4253	{
		4254	userdata *u = ev_userdata (EV_A);
		4255	pthread_mutex_lock (&u->lock);
		4256	}
		4257
		4258	The event loop thread first acquires the mutex, and then jumps straight
		4259	into C<ev_loop>:
		4260
		4261	void *
		4262	l_run (void *thr_arg)
		4263	{
		4264	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4265
		4266	l_acquire (EV_A);
		4267	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4268	ev_loop (EV_A_ 0);
		4269	l_release (EV_A);
		4270
		4271	return 0;
		4272	}
		4273
		4274	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4275	signal the main thread via some unspecified mechanism (signals? pipe
		4276	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4277	have been called (in a while loop because a) spurious wakeups are possible
		4278	and b) skipping inter-thread-communication when there are no pending
		4279	watchers is very beneficial):
		4280
		4281	static void
		4282	l_invoke (EV_P)
		4283	{
		4284	userdata *u = ev_userdata (EV_A);
		4285
		4286	while (ev_pending_count (EV_A))
		4287	{
		4288	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4289	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4290	}
		4291	}
		4292
		4293	Now, whenever the main thread gets told to invoke pending watchers, it
		4294	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4295	thread to continue:
		4296
		4297	static void
		4298	real_invoke_pending (EV_P)
		4299	{
		4300	userdata *u = ev_userdata (EV_A);
		4301
		4302	pthread_mutex_lock (&u->lock);
		4303	ev_invoke_pending (EV_A);
		4304	pthread_cond_signal (&u->invoke_cv);
		4305	pthread_mutex_unlock (&u->lock);
		4306	}
		4307
		4308	Whenever you want to start/stop a watcher or do other modifications to an
		4309	event loop, you will now have to lock:
		4310
		4311	ev_timer timeout_watcher;
		4312	userdata *u = ev_userdata (EV_A);
		4313
		4314	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4315
		4316	pthread_mutex_lock (&u->lock);
		4317	ev_timer_start (EV_A_ &timeout_watcher);
		4318	ev_async_send (EV_A_ &u->async_w);
		4319	pthread_mutex_unlock (&u->lock);
		4320
		4321	Note that sending the C<ev_async> watcher is required because otherwise
		4322	an event loop currently blocking in the kernel will have no knowledge
		4323	about the newly added timer. By waking up the loop it will pick up any new
		4324	watchers in the next event loop iteration.
		4325
3294	=head2 COROUTINES	4326	=head3 COROUTINES
3295		4327
3296	Libev is much more accommodating to coroutines ("cooperative threads"):	4328	Libev is very accommodating to coroutines ("cooperative threads"):
3297	libev fully supports nesting calls to it's functions from different	4329	libev fully supports nesting calls to its functions from different
3298	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4330	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3299	different coroutines and switch freely between both coroutines running the	4331	different coroutines, and switch freely between both coroutines running
3300	loop, as long as you don't confuse yourself). The only exception is that	4332	the loop, as long as you don't confuse yourself). The only exception is
3301	you must not do this from C<ev_periodic> reschedule callbacks.	4333	that you must not do this from C<ev_periodic> reschedule callbacks.
3302		4334
3303	Care has been invested into making sure that libev does not keep local	4335	Care has been taken to ensure that libev does not keep local state inside
3304	state inside C<ev_loop>, and other calls do not usually allow coroutine	4336	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3305	switches.	4337	they do not call any callbacks.
3306		4338
		4339	=head2 COMPILER WARNINGS
3307		4340
3308	=head1 COMPLEXITIES	4341	Depending on your compiler and compiler settings, you might get no or a
		4342	lot of warnings when compiling libev code. Some people are apparently
		4343	scared by this.
3309		4344
3310	In this section the complexities of (many of) the algorithms used inside	4345	However, these are unavoidable for many reasons. For one, each compiler
3311	libev will be explained. For complexity discussions about backends see the	4346	has different warnings, and each user has different tastes regarding
3312	documentation for C<ev_default_init>.	4347	warning options. "Warn-free" code therefore cannot be a goal except when
		4348	targeting a specific compiler and compiler-version.
3313		4349
3314	All of the following are about amortised time: If an array needs to be	4350	Another reason is that some compiler warnings require elaborate
3315	extended, libev needs to realloc and move the whole array, but this	4351	workarounds, or other changes to the code that make it less clear and less
3316	happens asymptotically never with higher number of elements, so O(1) might	4352	maintainable.
3317	mean it might do a lengthy realloc operation in rare cases, but on average
3318	it is much faster and asymptotically approaches constant time.
3319		4353
3320	=over 4	4354	And of course, some compiler warnings are just plain stupid, or simply
		4355	wrong (because they don't actually warn about the condition their message
		4356	seems to warn about). For example, certain older gcc versions had some
		4357	warnings that resulted in an extreme number of false positives. These have
		4358	been fixed, but some people still insist on making code warn-free with
		4359	such buggy versions.
3321		4360
3322	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	4361	While libev is written to generate as few warnings as possible,
		4362	"warn-free" code is not a goal, and it is recommended not to build libev
		4363	with any compiler warnings enabled unless you are prepared to cope with
		4364	them (e.g. by ignoring them). Remember that warnings are just that:
		4365	warnings, not errors, or proof of bugs.
3323		4366
3324	This means that, when you have a watcher that triggers in one hour and
3325	there are 100 watchers that would trigger before that then inserting will
3326	have to skip roughly seven (C<ld 100>) of these watchers.
3327		4367
3328	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	4368	=head2 VALGRIND
3329		4369
3330	That means that changing a timer costs less than removing/adding them	4370	Valgrind has a special section here because it is a popular tool that is
3331	as only the relative motion in the event queue has to be paid for.	4371	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3332		4372
3333	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	4373	If you think you found a bug (memory leak, uninitialised data access etc.)
		4374	in libev, then check twice: If valgrind reports something like:
3334		4375
3335	These just add the watcher into an array or at the head of a list.	4376	==2274== definitely lost: 0 bytes in 0 blocks.
		4377	==2274== possibly lost: 0 bytes in 0 blocks.
		4378	==2274== still reachable: 256 bytes in 1 blocks.
3336		4379
3337	=item Stopping check/prepare/idle/fork/async watchers: O(1)	4380	Then there is no memory leak, just as memory accounted to global variables
		4381	is not a memleak - the memory is still being referenced, and didn't leak.
3338		4382
3339	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	4383	Similarly, under some circumstances, valgrind might report kernel bugs
		4384	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		4385	although an acceptable workaround has been found here), or it might be
		4386	confused.
3340		4387
3341	These watchers are stored in lists then need to be walked to find the	4388	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3342	correct watcher to remove. The lists are usually short (you don't usually	4389	make it into some kind of religion.
3343	have many watchers waiting for the same fd or signal).
3344		4390
3345	=item Finding the next timer in each loop iteration: O(1)	4391	If you are unsure about something, feel free to contact the mailing list
		4392	with the full valgrind report and an explanation on why you think this
		4393	is a bug in libev (best check the archives, too :). However, don't be
		4394	annoyed when you get a brisk "this is no bug" answer and take the chance
		4395	of learning how to interpret valgrind properly.
3346		4396
3347	By virtue of using a binary or 4-heap, the next timer is always found at a	4397	If you need, for some reason, empty reports from valgrind for your project
3348	fixed position in the storage array.	4398	I suggest using suppression lists.
3349		4399
3350	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3351		4400
3352	A change means an I/O watcher gets started or stopped, which requires	4401	=head1 PORTABILITY NOTES
3353	libev to recalculate its status (and possibly tell the kernel, depending
3354	on backend and whether C<ev_io_set> was used).
3355		4402
3356	=item Activating one watcher (putting it into the pending state): O(1)	4403	=head2 GNU/LINUX 32 BIT LIMITATIONS
3357		4404
3358	=item Priority handling: O(number_of_priorities)	4405	GNU/Linux is the only common platform that supports 64 bit file/large file
		4406	interfaces but I<disables> them by default.
3359		4407
3360	Priorities are implemented by allocating some space for each	4408	That means that libev compiled in the default environment doesn't support
3361	priority. When doing priority-based operations, libev usually has to	4409	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
3362	linearly search all the priorities, but starting/stopping and activating
3363	watchers becomes O(1) w.r.t. priority handling.
3364		4410
3365	=item Sending an ev_async: O(1)	4411	Unfortunately, many programs try to work around this GNU/Linux issue
		4412	by enabling the large file API, which makes them incompatible with the
		4413	standard libev compiled for their system.
3366		4414
3367	=item Processing ev_async_send: O(number_of_async_watchers)	4415	Likewise, libev cannot enable the large file API itself as this would
		4416	suddenly make it incompatible to the default compile time environment,
		4417	i.e. all programs not using special compile switches.
3368		4418
3369	=item Processing signals: O(max_signal_number)	4419	=head2 OS/X AND DARWIN BUGS
3370		4420
3371	Sending involves a system call I<iff> there were no other C<ev_async_send>	4421	The whole thing is a bug if you ask me - basically any system interface
3372	calls in the current loop iteration. Checking for async and signal events	4422	you touch is broken, whether it is locales, poll, kqueue or even the
3373	involves iterating over all running async watchers or all signal numbers.	4423	OpenGL drivers.
3374		4424
3375	=back	4425	=head3 C<kqueue> is buggy
3376		4426
		4427	The kqueue syscall is broken in all known versions - most versions support
		4428	only sockets, many support pipes.
3377		4429
		4430	Libev tries to work around this by not using C<kqueue> by default on
		4431	this rotten platform, but of course you can still ask for it when creating
		4432	a loop.
		4433
		4434	=head3 C<poll> is buggy
		4435
		4436	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4437	implementation by something calling C<kqueue> internally around the 10.5.6
		4438	release, so now C<kqueue> I<and> C<poll> are broken.
		4439
		4440	Libev tries to work around this by not using C<poll> by default on
		4441	this rotten platform, but of course you can still ask for it when creating
		4442	a loop.
		4443
		4444	=head3 C<select> is buggy
		4445
		4446	All that's left is C<select>, and of course Apple found a way to fuck this
		4447	one up as well: On OS/X, C<select> actively limits the number of file
		4448	descriptors you can pass in to 1024 - your program suddenly crashes when
		4449	you use more.
		4450
		4451	There is an undocumented "workaround" for this - defining
		4452	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4453	work on OS/X.
		4454
		4455	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4456
		4457	=head3 C<errno> reentrancy
		4458
		4459	The default compile environment on Solaris is unfortunately so
		4460	thread-unsafe that you can't even use components/libraries compiled
		4461	without C<-D_REENTRANT> (as long as they use C<errno>), which, of course,
		4462	isn't defined by default.
		4463
		4464	If you want to use libev in threaded environments you have to make sure
		4465	it's compiled with C<_REENTRANT> defined.
		4466
		4467	=head3 Event port backend
		4468
		4469	The scalable event interface for Solaris is called "event ports". Unfortunately,
		4470	this mechanism is very buggy. If you run into high CPU usage, your program
		4471	freezes or you get a large number of spurious wakeups, make sure you have
		4472	all the relevant and latest kernel patches applied. No, I don't know which
		4473	ones, but there are multiple ones.
		4474
		4475	If you can't get it to work, you can try running the program by setting
		4476	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4477	C<select> backends.
		4478
		4479	=head2 AIX POLL BUG
		4480
		4481	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4482	this by trying to avoid the poll backend altogether (i.e. it's not even
		4483	compiled in), which normally isn't a big problem as C<select> works fine
		4484	with large bitsets, and AIX is dead anyway.
		4485
3378	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4486	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4487
		4488	=head3 General issues
3379		4489
3380	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4490	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3381	requires, and its I/O model is fundamentally incompatible with the POSIX	4491	requires, and its I/O model is fundamentally incompatible with the POSIX
3382	model. Libev still offers limited functionality on this platform in	4492	model. Libev still offers limited functionality on this platform in
3383	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4493	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3384	descriptors. This only applies when using Win32 natively, not when using	4494	descriptors. This only applies when using Win32 natively, not when using
3385	e.g. cygwin.	4495	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4496	as every compielr comes with a slightly differently broken/incompatible
		4497	environment.
3386		4498
3387	Lifting these limitations would basically require the full	4499	Lifting these limitations would basically require the full
3388	re-implementation of the I/O system. If you are into these kinds of	4500	re-implementation of the I/O system. If you are into this kind of thing,
3389	things, then note that glib does exactly that for you in a very portable	4501	then note that glib does exactly that for you in a very portable way (note
3390	way (note also that glib is the slowest event library known to man).	4502	also that glib is the slowest event library known to man).
3391		4503
3392	There is no supported compilation method available on windows except	4504	There is no supported compilation method available on windows except
3393	embedding it into other applications.	4505	embedding it into other applications.
		4506
		4507	Sensible signal handling is officially unsupported by Microsoft - libev
		4508	tries its best, but under most conditions, signals will simply not work.
3394		4509
3395	Not a libev limitation but worth mentioning: windows apparently doesn't	4510	Not a libev limitation but worth mentioning: windows apparently doesn't
3396	accept large writes: instead of resulting in a partial write, windows will	4511	accept large writes: instead of resulting in a partial write, windows will
3397	either accept everything or return C<ENOBUFS> if the buffer is too large,	4512	either accept everything or return C<ENOBUFS> if the buffer is too large,
3398	so make sure you only write small amounts into your sockets (less than a	4513	so make sure you only write small amounts into your sockets (less than a
3399	megabyte seems safe, but thsi apparently depends on the amount of memory	4514	megabyte seems safe, but this apparently depends on the amount of memory
3400	available).	4515	available).
3401		4516
3402	Due to the many, low, and arbitrary limits on the win32 platform and	4517	Due to the many, low, and arbitrary limits on the win32 platform and
3403	the abysmal performance of winsockets, using a large number of sockets	4518	the abysmal performance of winsockets, using a large number of sockets
3404	is not recommended (and not reasonable). If your program needs to use	4519	is not recommended (and not reasonable). If your program needs to use
3405	more than a hundred or so sockets, then likely it needs to use a totally	4520	more than a hundred or so sockets, then likely it needs to use a totally
3406	different implementation for windows, as libev offers the POSIX readiness	4521	different implementation for windows, as libev offers the POSIX readiness
3407	notification model, which cannot be implemented efficiently on windows	4522	notification model, which cannot be implemented efficiently on windows
3408	(Microsoft monopoly games).	4523	(due to Microsoft monopoly games).
3409		4524
3410	A typical way to use libev under windows is to embed it (see the embedding	4525	A typical way to use libev under windows is to embed it (see the embedding
3411	section for details) and use the following F<evwrap.h> header file instead	4526	section for details) and use the following F<evwrap.h> header file instead
3412	of F<ev.h>:	4527	of F<ev.h>:
3413		4528
…		…
3415	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	4530	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3416		4531
3417	#include "ev.h"	4532	#include "ev.h"
3418		4533
3419	And compile the following F<evwrap.c> file into your project (make sure	4534	And compile the following F<evwrap.c> file into your project (make sure
3420	you do I<not> compile the F<ev.c> or any other embedded soruce files!):	4535	you do I<not> compile the F<ev.c> or any other embedded source files!):
3421		4536
3422	#include "evwrap.h"	4537	#include "evwrap.h"
3423	#include "ev.c"	4538	#include "ev.c"
3424		4539
3425	=over 4
3426
3427	=item The winsocket select function	4540	=head3 The winsocket C<select> function
3428		4541
3429	The winsocket C<select> function doesn't follow POSIX in that it	4542	The winsocket C<select> function doesn't follow POSIX in that it
3430	requires socket I<handles> and not socket I<file descriptors> (it is	4543	requires socket I<handles> and not socket I<file descriptors> (it is
3431	also extremely buggy). This makes select very inefficient, and also	4544	also extremely buggy). This makes select very inefficient, and also
3432	requires a mapping from file descriptors to socket handles (the Microsoft	4545	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3441	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4554	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3442		4555
3443	Note that winsockets handling of fd sets is O(n), so you can easily get a	4556	Note that winsockets handling of fd sets is O(n), so you can easily get a
3444	complexity in the O(n²) range when using win32.	4557	complexity in the O(n²) range when using win32.
3445		4558
3446	=item Limited number of file descriptors	4559	=head3 Limited number of file descriptors
3447		4560
3448	Windows has numerous arbitrary (and low) limits on things.	4561	Windows has numerous arbitrary (and low) limits on things.
3449		4562
3450	Early versions of winsocket's select only supported waiting for a maximum	4563	Early versions of winsocket's select only supported waiting for a maximum
3451	of C<64> handles (probably owning to the fact that all windows kernels	4564	of C<64> handles (probably owning to the fact that all windows kernels
3452	can only wait for C<64> things at the same time internally; Microsoft	4565	can only wait for C<64> things at the same time internally; Microsoft
3453	recommends spawning a chain of threads and wait for 63 handles and the	4566	recommends spawning a chain of threads and wait for 63 handles and the
3454	previous thread in each. Great).	4567	previous thread in each. Sounds great!).
3455		4568
3456	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4569	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3457	to some high number (e.g. C<2048>) before compiling the winsocket select	4570	to some high number (e.g. C<2048>) before compiling the winsocket select
3458	call (which might be in libev or elsewhere, for example, perl does its own	4571	call (which might be in libev or elsewhere, for example, perl and many
3459	select emulation on windows).	4572	other interpreters do their own select emulation on windows).
3460		4573
3461	Another limit is the number of file descriptors in the Microsoft runtime	4574	Another limit is the number of file descriptors in the Microsoft runtime
3462	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4575	libraries, which by default is C<64> (there must be a hidden I<64>
3463	or something like this inside Microsoft). You can increase this by calling	4576	fetish or something like this inside Microsoft). You can increase this
3464	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4577	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3465	arbitrary limit), but is broken in many versions of the Microsoft runtime	4578	(another arbitrary limit), but is broken in many versions of the Microsoft
3466	libraries.
3467
3468	This might get you to about C<512> or C<2048> sockets (depending on	4579	runtime libraries. This might get you to about C<512> or C<2048> sockets
3469	windows version and/or the phase of the moon). To get more, you need to	4580	(depending on windows version and/or the phase of the moon). To get more,
3470	wrap all I/O functions and provide your own fd management, but the cost of	4581	you need to wrap all I/O functions and provide your own fd management, but
3471	calling select (O(n²)) will likely make this unworkable.	4582	the cost of calling select (O(n²)) will likely make this unworkable.
3472		4583
3473	=back
3474
3475
3476	=head1 PORTABILITY REQUIREMENTS	4584	=head2 PORTABILITY REQUIREMENTS
3477		4585
3478	In addition to a working ISO-C implementation, libev relies on a few	4586	In addition to a working ISO-C implementation and of course the
3479	additional extensions:	4587	backend-specific APIs, libev relies on a few additional extensions:
3480		4588
3481	=over 4	4589	=over 4
3482		4590
3483	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	4591	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3484	calling conventions regardless of C<ev_watcher_type *>.	4592	calling conventions regardless of C<ev_watcher_type *>.
…		…
3490	calls them using an C<ev_watcher *> internally.	4598	calls them using an C<ev_watcher *> internally.
3491		4599
3492	=item C<sig_atomic_t volatile> must be thread-atomic as well	4600	=item C<sig_atomic_t volatile> must be thread-atomic as well
3493		4601
3494	The type C<sig_atomic_t volatile> (or whatever is defined as	4602	The type C<sig_atomic_t volatile> (or whatever is defined as
3495	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	4603	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3496	threads. This is not part of the specification for C<sig_atomic_t>, but is	4604	threads. This is not part of the specification for C<sig_atomic_t>, but is
3497	believed to be sufficiently portable.	4605	believed to be sufficiently portable.
3498		4606
3499	=item C<sigprocmask> must work in a threaded environment	4607	=item C<sigprocmask> must work in a threaded environment
3500		4608
…		…
3509	except the initial one, and run the default loop in the initial thread as	4617	except the initial one, and run the default loop in the initial thread as
3510	well.	4618	well.
3511		4619
3512	=item C<long> must be large enough for common memory allocation sizes	4620	=item C<long> must be large enough for common memory allocation sizes
3513		4621
3514	To improve portability and simplify using libev, libev uses C<long>	4622	To improve portability and simplify its API, libev uses C<long> internally
3515	internally instead of C<size_t> when allocating its data structures. On	4623	instead of C<size_t> when allocating its data structures. On non-POSIX
3516	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4624	systems (Microsoft...) this might be unexpectedly low, but is still at
3517	is still at least 31 bits everywhere, which is enough for hundreds of	4625	least 31 bits everywhere, which is enough for hundreds of millions of
3518	millions of watchers.	4626	watchers.
3519		4627
3520	=item C<double> must hold a time value in seconds with enough accuracy	4628	=item C<double> must hold a time value in seconds with enough accuracy
3521		4629
3522	The type C<double> is used to represent timestamps. It is required to	4630	The type C<double> is used to represent timestamps. It is required to
3523	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4631	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
3524	enough for at least into the year 4000. This requirement is fulfilled by	4632	enough for at least into the year 4000. This requirement is fulfilled by
3525	implementations implementing IEEE 754 (basically all existing ones).	4633	implementations implementing IEEE 754, which is basically all existing
		4634	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4635	2200.
3526		4636
3527	=back	4637	=back
3528		4638
3529	If you know of other additional requirements drop me a note.	4639	If you know of other additional requirements drop me a note.
3530		4640
3531		4641
3532	=head1 COMPILER WARNINGS	4642	=head1 ALGORITHMIC COMPLEXITIES
3533		4643
3534	Depending on your compiler and compiler settings, you might get no or a	4644	In this section the complexities of (many of) the algorithms used inside
3535	lot of warnings when compiling libev code. Some people are apparently	4645	libev will be documented. For complexity discussions about backends see
3536	scared by this.	4646	the documentation for C<ev_default_init>.
3537		4647
3538	However, these are unavoidable for many reasons. For one, each compiler	4648	All of the following are about amortised time: If an array needs to be
3539	has different warnings, and each user has different tastes regarding	4649	extended, libev needs to realloc and move the whole array, but this
3540	warning options. "Warn-free" code therefore cannot be a goal except when	4650	happens asymptotically rarer with higher number of elements, so O(1) might
3541	targeting a specific compiler and compiler-version.	4651	mean that libev does a lengthy realloc operation in rare cases, but on
		4652	average it is much faster and asymptotically approaches constant time.
3542		4653
3543	Another reason is that some compiler warnings require elaborate	4654	=over 4
3544	workarounds, or other changes to the code that make it less clear and less
3545	maintainable.
3546		4655
3547	And of course, some compiler warnings are just plain stupid, or simply	4656	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3548	wrong (because they don't actually warn about the condition their message
3549	seems to warn about).
3550		4657
3551	While libev is written to generate as few warnings as possible,	4658	This means that, when you have a watcher that triggers in one hour and
3552	"warn-free" code is not a goal, and it is recommended not to build libev	4659	there are 100 watchers that would trigger before that, then inserting will
3553	with any compiler warnings enabled unless you are prepared to cope with	4660	have to skip roughly seven (C<ld 100>) of these watchers.
3554	them (e.g. by ignoring them). Remember that warnings are just that:
3555	warnings, not errors, or proof of bugs.
3556		4661
		4662	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3557		4663
3558	=head1 VALGRIND	4664	That means that changing a timer costs less than removing/adding them,
		4665	as only the relative motion in the event queue has to be paid for.
3559		4666
3560	Valgrind has a special section here because it is a popular tool that is	4667	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3561	highly useful, but valgrind reports are very hard to interpret.
3562		4668
3563	If you think you found a bug (memory leak, uninitialised data access etc.)	4669	These just add the watcher into an array or at the head of a list.
3564	in libev, then check twice: If valgrind reports something like:
3565		4670
3566	==2274== definitely lost: 0 bytes in 0 blocks.	4671	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3567	==2274== possibly lost: 0 bytes in 0 blocks.
3568	==2274== still reachable: 256 bytes in 1 blocks.
3569		4672
3570	Then there is no memory leak. Similarly, under some circumstances,	4673	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3571	valgrind might report kernel bugs as if it were a bug in libev, or it
3572	might be confused (it is a very good tool, but only a tool).
3573		4674
3574	If you are unsure about something, feel free to contact the mailing list	4675	These watchers are stored in lists, so they need to be walked to find the
3575	with the full valgrind report and an explanation on why you think this is	4676	correct watcher to remove. The lists are usually short (you don't usually
3576	a bug in libev. However, don't be annoyed when you get a brisk "this is	4677	have many watchers waiting for the same fd or signal: one is typical, two
3577	no bug" answer and take the chance of learning how to interpret valgrind	4678	is rare).
3578	properly.
3579		4679
3580	If you need, for some reason, empty reports from valgrind for your project	4680	=item Finding the next timer in each loop iteration: O(1)
3581	I suggest using suppression lists.
3582		4681
		4682	By virtue of using a binary or 4-heap, the next timer is always found at a
		4683	fixed position in the storage array.
		4684
		4685	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4686
		4687	A change means an I/O watcher gets started or stopped, which requires
		4688	libev to recalculate its status (and possibly tell the kernel, depending
		4689	on backend and whether C<ev_io_set> was used).
		4690
		4691	=item Activating one watcher (putting it into the pending state): O(1)
		4692
		4693	=item Priority handling: O(number_of_priorities)
		4694
		4695	Priorities are implemented by allocating some space for each
		4696	priority. When doing priority-based operations, libev usually has to
		4697	linearly search all the priorities, but starting/stopping and activating
		4698	watchers becomes O(1) with respect to priority handling.
		4699
		4700	=item Sending an ev_async: O(1)
		4701
		4702	=item Processing ev_async_send: O(number_of_async_watchers)
		4703
		4704	=item Processing signals: O(max_signal_number)
		4705
		4706	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4707	calls in the current loop iteration. Checking for async and signal events
		4708	involves iterating over all running async watchers or all signal numbers.
		4709
		4710	=back
		4711
		4712
		4713	=head1 PORTING FROM LIBEV 3.X TO 4.X
		4714
		4715	The major version 4 introduced some minor incompatible changes to the API.
		4716
		4717	At the moment, the C<ev.h> header file tries to implement superficial
		4718	compatibility, so most programs should still compile. Those might be
		4719	removed in later versions of libev, so better update early than late.
		4720
		4721	=over 4
		4722
		4723	=item C<ev_loop_count> renamed to C<ev_iteration>
		4724
		4725	=item C<ev_loop_depth> renamed to C<ev_depth>
		4726
		4727	=item C<ev_loop_verify> renamed to C<ev_verify>
		4728
		4729	Most functions working on C<struct ev_loop> objects don't have an
		4730	C<ev_loop_> prefix, so it was removed. Note that C<ev_loop_fork> is
		4731	still called C<ev_loop_fork> because it would otherwise clash with the
		4732	C<ev_fork> typedef.
		4733
		4734	=item C<EV_TIMEOUT> renamed to C<EV_TIMER> in C<revents>
		4735
		4736	This is a simple rename - all other watcher types use their name
		4737	as revents flag, and now C<ev_timer> does, too.
		4738
		4739	Both C<EV_TIMER> and C<EV_TIMEOUT> symbols were present in 3.x versions
		4740	and continue to be present for the foreseeable future, so this is mostly a
		4741	documentation change.
		4742
		4743	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		4744
		4745	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		4746	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		4747	and work, but the library code will of course be larger.
		4748
		4749	=back
		4750
		4751
		4752	=head1 GLOSSARY
		4753
		4754	=over 4
		4755
		4756	=item active
		4757
		4758	A watcher is active as long as it has been started (has been attached to
		4759	an event loop) but not yet stopped (disassociated from the event loop).
		4760
		4761	=item application
		4762
		4763	In this document, an application is whatever is using libev.
		4764
		4765	=item callback
		4766
		4767	The address of a function that is called when some event has been
		4768	detected. Callbacks are being passed the event loop, the watcher that
		4769	received the event, and the actual event bitset.
		4770
		4771	=item callback invocation
		4772
		4773	The act of calling the callback associated with a watcher.
		4774
		4775	=item event
		4776
		4777	A change of state of some external event, such as data now being available
		4778	for reading on a file descriptor, time having passed or simply not having
		4779	any other events happening anymore.
		4780
		4781	In libev, events are represented as single bits (such as C<EV_READ> or
		4782	C<EV_TIMER>).
		4783
		4784	=item event library
		4785
		4786	A software package implementing an event model and loop.
		4787
		4788	=item event loop
		4789
		4790	An entity that handles and processes external events and converts them
		4791	into callback invocations.
		4792
		4793	=item event model
		4794
		4795	The model used to describe how an event loop handles and processes
		4796	watchers and events.
		4797
		4798	=item pending
		4799
		4800	A watcher is pending as soon as the corresponding event has been detected,
		4801	and stops being pending as soon as the watcher will be invoked or its
		4802	pending status is explicitly cleared by the application.
		4803
		4804	A watcher can be pending, but not active. Stopping a watcher also clears
		4805	its pending status.
		4806
		4807	=item real time
		4808
		4809	The physical time that is observed. It is apparently strictly monotonic :)
		4810
		4811	=item wall-clock time
		4812
		4813	The time and date as shown on clocks. Unlike real time, it can actually
		4814	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4815	clock.
		4816
		4817	=item watcher
		4818
		4819	A data structure that describes interest in certain events. Watchers need
		4820	to be started (attached to an event loop) before they can receive events.
		4821
		4822	=item watcher invocation
		4823
		4824	The act of calling the callback associated with a watcher.
		4825
		4826	=back
3583		4827
3584	=head1 AUTHOR	4828	=head1 AUTHOR
3585		4829
3586	Marc Lehmann <libev@schmorp.de>.	4830	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3587		4831

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