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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);
28		30
29	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_run's to stop iterating
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_break (EV_A_ EVBREAK_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_run to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_break (EV_A_ EVBREAK_ONE);
40	}	42	}
41		43
42	int	44	int
43	main (void)	45	main (void)
44	{	46	{
45	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
46	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = EV_DEFAULT;
47		49
48	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
…		…
54	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
57		59
58	// now wait for events to arrive	60	// now wait for events to arrive
59	ev_loop (loop, 0);	61	ev_run (loop, 0);
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 WHAT TO READ WHEN IN A HURRY
		84
		85	This manual tries to be very detailed, but unfortunately, this also makes
		86	it very long. If you just want to know the basics of libev, I suggest
		87	reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and
		88	look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and
		89	C<ev_timer> sections in L<WATCHER TYPES>.
		90
		91	=head1 ABOUT LIBEV
70		92
71	Libev is an event loop: you register interest in certain events (such as a	93	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	94	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	95	these event sources and provide your program with events.
74		96
…		…
84	=head2 FEATURES	106	=head2 FEATURES
85		107
86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	108	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	109	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	110	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	111	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
90	with customised rescheduling (C<ev_periodic>), synchronous signals	112	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	113	timers (C<ev_timer>), absolute timers with customised rescheduling
92	watchers dealing with the event loop mechanism itself (C<ev_idle>,	114	(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	115	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	116	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
95	(C<ev_fork>).	117	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		118	limited support for fork events (C<ev_fork>).
96		119
97	It also is quite fast (see this	120	It also is quite fast (see this
98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	121	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
99	for example).	122	for example).
100		123
…		…
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	131	name C<loop> (which is always of type C<struct ev_loop *>) will not have
109	this argument.	132	this argument.
110		133
111	=head2 TIME REPRESENTATION	134	=head2 TIME REPRESENTATION
112		135
113	Libev represents time as a single floating point number, representing the	136	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	137	the (fractional) number of seconds since the (POSIX) epoch (in practice
115	the beginning of 1970, details are complicated, don't ask). This type is	138	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	139	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	140	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	141	any calculations on it, you should treat it as some floating point value.
		142
119	component C<stamp> might indicate, it is also used for time differences	143	Unlike the name component C<stamp> might indicate, it is also used for
120	throughout libev.	144	time differences (e.g. delays) throughout libev.
121		145
122	=head1 ERROR HANDLING	146	=head1 ERROR HANDLING
123		147
124	Libev knows three classes of errors: operating system errors, usage errors	148	Libev knows three classes of errors: operating system errors, usage errors
125	and internal errors (bugs).	149	and internal errors (bugs).
…		…
149		173
150	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
151		175
152	Returns the current time as libev would use it. Please note that the	176	Returns the current time as libev would use it. Please note that the
153	C<ev_now> function is usually faster and also often returns the timestamp	177	C<ev_now> function is usually faster and also often returns the timestamp
154	you actually want to know.	178	you actually want to know. Also interesting is the combination of
		179	C<ev_update_now> and C<ev_now>.
155		180
156	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
157		182
158	Sleep for the given interval: The current thread will be blocked until	183	Sleep for the given interval: The current thread will be blocked until
159	either it is interrupted or the given time interval has passed. Basically	184	either it is interrupted or the given time interval has passed. Basically
…		…
176	as this indicates an incompatible change. Minor versions are usually	201	as this indicates an incompatible change. Minor versions are usually
177	compatible to older versions, so a larger minor version alone is usually	202	compatible to older versions, so a larger minor version alone is usually
178	not a problem.	203	not a problem.
179		204
180	Example: Make sure we haven't accidentally been linked against the wrong	205	Example: Make sure we haven't accidentally been linked against the wrong
181	version.	206	version (note, however, that this will not detect other ABI mismatches,
		207	such as LFS or reentrancy).
182		208
183	assert (("libev version mismatch",	209	assert (("libev version mismatch",
184	ev_version_major () == EV_VERSION_MAJOR	210	ev_version_major () == EV_VERSION_MAJOR
185	&& ev_version_minor () >= EV_VERSION_MINOR));	211	&& ev_version_minor () >= EV_VERSION_MINOR));
186		212
…		…
197	assert (("sorry, no epoll, no sex",	223	assert (("sorry, no epoll, no sex",
198	ev_supported_backends () & EVBACKEND_EPOLL));	224	ev_supported_backends () & EVBACKEND_EPOLL));
199		225
200	=item unsigned int ev_recommended_backends ()	226	=item unsigned int ev_recommended_backends ()
201		227
202	Return the set of all backends compiled into this binary of libev and also	228	Return the set of all backends compiled into this binary of libev and
203	recommended for this platform. This set is often smaller than the one	229	also recommended for this platform, meaning it will work for most file
		230	descriptor types. This set is often smaller than the one returned by
204	returned by C<ev_supported_backends>, as for example kqueue is broken on	231	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
205	most BSDs and will not be auto-detected unless you explicitly request it	232	and will not be auto-detected unless you explicitly request it (assuming
206	(assuming you know what you are doing). This is the set of backends that	233	you know what you are doing). This is the set of backends that libev will
207	libev will probe for if you specify no backends explicitly.	234	probe for if you specify no backends explicitly.
208		235
209	=item unsigned int ev_embeddable_backends ()	236	=item unsigned int ev_embeddable_backends ()
210		237
211	Returns the set of backends that are embeddable in other event loops. This	238	Returns the set of backends that are embeddable in other event loops. This
212	is the theoretical, all-platform, value. To find which backends	239	value is platform-specific but can include backends not available on the
213	might be supported on the current system, you would need to look at	240	current system. To find which embeddable backends might be supported on
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	241	the current system, you would need to look at C<ev_embeddable_backends ()
215	recommended ones.	242	& ev_supported_backends ()>, likewise for recommended ones.
216		243
217	See the description of C<ev_embed> watchers for more info.	244	See the description of C<ev_embed> watchers for more info.
218		245
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	246	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
220		247
221	Sets the allocation function to use (the prototype is similar - the	248	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	249	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	250	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	251	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	277	}
251		278
252	...	279	...
253	ev_set_allocator (persistent_realloc);	280	ev_set_allocator (persistent_realloc);
254		281
255	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	282	=item ev_set_syserr_cb (void (*cb)(const char *msg))
256		283
257	Set the callback function to call on a retryable system call error (such	284	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	285	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	286	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	287	callback is set, then libev will expect it to remedy the situation, no
…		…
272	}	299	}
273		300
274	...	301	...
275	ev_set_syserr_cb (fatal_error);	302	ev_set_syserr_cb (fatal_error);
276		303
		304	=item ev_feed_signal (int signum)
		305
		306	This function can be used to "simulate" a signal receive. It is completely
		307	safe to call this function at any time, from any context, including signal
		308	handlers or random threads.
		309
		310	Its main use is to customise signal handling in your process, especially
		311	in the presence of threads. For example, you could block signals
		312	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		313	creating any loops), and in one thread, use C<sigwait> or any other
		314	mechanism to wait for signals, then "deliver" them to libev by calling
		315	C<ev_feed_signal>.
		316
277	=back	317	=back
278		318
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	319	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
280		320
281	An event loop is described by a C<struct ev_loop *>. The library knows two	321	An event loop is described by a C<struct ev_loop *> (the C<struct> is
282	types of such loops, the I<default> loop, which supports signals and child	322	I<not> optional in this case unless libev 3 compatibility is disabled, as
283	events, and dynamically created loops which do not.	323	libev 3 had an C<ev_loop> function colliding with the struct name).
		324
		325	The library knows two types of such loops, the I<default> loop, which
		326	supports child process events, and dynamically created event loops which
		327	do not.
284		328
285	=over 4	329	=over 4
286		330
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	331	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		332
289	This will initialise the default event loop if it hasn't been initialised	333	This returns the "default" event loop object, which is what you should
290	yet and return it. If the default loop could not be initialised, returns	334	normally use when you just need "the event loop". Event loop objects and
291	false. If it already was initialised it simply returns it (and ignores the	335	the C<flags> parameter are described in more detail in the entry for
292	flags. If that is troubling you, check C<ev_backend ()> afterwards).	336	C<ev_loop_new>.
		337
		338	If the default loop is already initialised then this function simply
		339	returns it (and ignores the flags. If that is troubling you, check
		340	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		341	flags, which should almost always be C<0>, unless the caller is also the
		342	one calling C<ev_run> or otherwise qualifies as "the main program".
293		343
294	If you don't know what event loop to use, use the one returned from this	344	If you don't know what event loop to use, use the one returned from this
295	function.	345	function (or via the C<EV_DEFAULT> macro).
296		346
297	Note that this function is I<not> thread-safe, so if you want to use it	347	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,	348	from multiple threads, you have to employ some kind of mutex (note also
299	as loops cannot bes hared easily between threads anyway).	349	that this case is unlikely, as loops cannot be shared easily between
		350	threads anyway).
300		351
301	The default loop is the only loop that can handle C<ev_signal> and	352	The default loop is the only loop that can handle C<ev_child> watchers,
302	C<ev_child> watchers, and to do this, it always registers a handler	353	and to do this, it always registers a handler for C<SIGCHLD>. If this is
303	for C<SIGCHLD>. If this is a problem for your application you can either	354	a problem for your application you can either create a dynamic loop with
304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	355	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
305	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	356	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
306	C<ev_default_init>.	357
		358	Example: This is the most typical usage.
		359
		360	if (!ev_default_loop (0))
		361	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		362
		363	Example: Restrict libev to the select and poll backends, and do not allow
		364	environment settings to be taken into account:
		365
		366	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		367
		368	=item struct ev_loop *ev_loop_new (unsigned int flags)
		369
		370	This will create and initialise a new event loop object. If the loop
		371	could not be initialised, returns false.
		372
		373	This function is thread-safe, and one common way to use libev with
		374	threads is indeed to create one loop per thread, and using the default
		375	loop in the "main" or "initial" thread.
307		376
308	The flags argument can be used to specify special behaviour or specific	377	The flags argument can be used to specify special behaviour or specific
309	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	378	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
310		379
311	The following flags are supported:	380	The following flags are supported:
…		…
326	useful to try out specific backends to test their performance, or to work	395	useful to try out specific backends to test their performance, or to work
327	around bugs.	396	around bugs.
328		397
329	=item C<EVFLAG_FORKCHECK>	398	=item C<EVFLAG_FORKCHECK>
330		399
331	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	400	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	401	make libev check for a fork in each iteration by enabling this flag.
333	enabling this flag.
334		402
335	This works by calling C<getpid ()> on every iteration of the loop,	403	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	404	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	405	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	406	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
…		…
344	flag.	412	flag.
345		413
346	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	414	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
347	environment variable.	415	environment variable.
348		416
		417	=item C<EVFLAG_NOINOTIFY>
		418
		419	When this flag is specified, then libev will not attempt to use the
		420	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
		421	testing, this flag can be useful to conserve inotify file descriptors, as
		422	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		423
		424	=item C<EVFLAG_SIGNALFD>
		425
		426	When this flag is specified, then libev will attempt to use the
		427	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
		428	delivers signals synchronously, which makes it both faster and might make
		429	it possible to get the queued signal data. It can also simplify signal
		430	handling with threads, as long as you properly block signals in your
		431	threads that are not interested in handling them.
		432
		433	Signalfd will not be used by default as this changes your signal mask, and
		434	there are a lot of shoddy libraries and programs (glib's threadpool for
		435	example) that can't properly initialise their signal masks.
		436
		437	=item C<EVFLAG_NOSIGMASK>
		438
		439	When this flag is specified, then libev will avoid to modify the signal
		440	mask. Specifically, this means you ahve to make sure signals are unblocked
		441	when you want to receive them.
		442
		443	This behaviour is useful when you want to do your own signal handling, or
		444	want to handle signals only in specific threads and want to avoid libev
		445	unblocking the signals.
		446
		447	It's also required by POSIX in a threaded program, as libev calls
		448	C<sigprocmask>, whose behaviour is officially unspecified.
		449
		450	This flag's behaviour will become the default in future versions of libev.
		451
349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	452	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
350		453
351	This is your standard select(2) backend. Not I<completely> standard, as	454	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,	455	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	456	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	480	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
378	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	481	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
379		482
380	=item C<EVBACKEND_EPOLL> (value 4, Linux)	483	=item C<EVBACKEND_EPOLL> (value 4, Linux)
381		484
		485	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		486	kernels).
		487
382	For few fds, this backend is a bit little slower than poll and select,	488	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	489	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),	490	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	491	epoll scales either O(1) or O(active_fds).
386	of shortcomings, such as silently dropping events in some hard-to-detect	492
387	cases and requiring a system call per fd change, no fork support and bad	493	The epoll mechanism deserves honorable mention as the most misdesigned
388	support for dup.	494	of the more advanced event mechanisms: mere annoyances include silently
		495	dropping file descriptors, requiring a system call per change per file
		496	descriptor (and unnecessary guessing of parameters), problems with dup,
		497	returning before the timeout value, resulting in additional iterations
		498	(and only giving 5ms accuracy while select on the same platform gives
		499	0.1ms) and so on. The biggest issue is fork races, however - if a program
		500	forks then I<both> parent and child process have to recreate the epoll
		501	set, which can take considerable time (one syscall per file descriptor)
		502	and is of course hard to detect.
		503
		504	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		505	of course I<doesn't>, and epoll just loves to report events for totally
		506	I<different> file descriptors (even already closed ones, so one cannot
		507	even remove them from the set) than registered in the set (especially
		508	on SMP systems). Libev tries to counter these spurious notifications by
		509	employing an additional generation counter and comparing that against the
		510	events to filter out spurious ones, recreating the set when required. Last
		511	not least, it also refuses to work with some file descriptors which work
		512	perfectly fine with C<select> (files, many character devices...).
		513
		514	Epoll is truly the train wreck analog among event poll mechanisms,
		515	a frankenpoll, cobbled together in a hurry, no thought to design or
		516	interaction with others.
389		517
390	While stopping, setting and starting an I/O watcher in the same iteration	518	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	519	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	520	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	521	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
394	very well if you register events for both fds.	522	file descriptors might not work very well if you register events for both
395		523	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		524
400	Best performance from this backend is achieved by not unregistering all	525	Best performance from this backend is achieved by not unregistering all
401	watchers for a file descriptor until it has been closed, if possible,	526	watchers for a file descriptor until it has been closed, if possible,
402	i.e. keep at least one watcher active per fd at all times. Stopping and	527	i.e. keep at least one watcher active per fd at all times. Stopping and
403	starting a watcher (without re-setting it) also usually doesn't cause	528	starting a watcher (without re-setting it) also usually doesn't cause
404	extra overhead.	529	extra overhead. A fork can both result in spurious notifications as well
		530	as in libev having to destroy and recreate the epoll object, which can
		531	take considerable time and thus should be avoided.
		532
		533	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		534	faster than epoll for maybe up to a hundred file descriptors, depending on
		535	the usage. So sad.
405		536
406	While nominally embeddable in other event loops, this feature is broken in	537	While nominally embeddable in other event loops, this feature is broken in
407	all kernel versions tested so far.	538	all kernel versions tested so far.
408		539
409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	540	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
410	C<EVBACKEND_POLL>.	541	C<EVBACKEND_POLL>.
411		542
412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	543	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
413		544
414	Kqueue deserves special mention, as at the time of this writing, it was	545	Kqueue deserves special mention, as at the time of this writing, it
415	broken on all BSDs except NetBSD (usually it doesn't work reliably with	546	was broken on all BSDs except NetBSD (usually it doesn't work reliably
416	anything but sockets and pipes, except on Darwin, where of course it's	547	with anything but sockets and pipes, except on Darwin, where of course
417	completely useless). For this reason it's not being "auto-detected" unless	548	it's completely useless). Unlike epoll, however, whose brokenness
418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or	549	is by design, these kqueue bugs can (and eventually will) be fixed
419	libev was compiled on a known-to-be-good (-enough) system like NetBSD.	550	without API changes to existing programs. For this reason it's not being
		551	"auto-detected" unless you explicitly specify it in the flags (i.e. using
		552	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		553	system like NetBSD.
420		554
421	You still can embed kqueue into a normal poll or select backend and use it	555	You still can embed kqueue into a normal poll or select backend and use it
422	only for sockets (after having made sure that sockets work with kqueue on	556	only for sockets (after having made sure that sockets work with kqueue on
423	the target platform). See C<ev_embed> watchers for more info.	557	the target platform). See C<ev_embed> watchers for more info.
424		558
425	It scales in the same way as the epoll backend, but the interface to the	559	It scales in the same way as the epoll backend, but the interface to the
426	kernel is more efficient (which says nothing about its actual speed, of	560	kernel is more efficient (which says nothing about its actual speed, of
427	course). While stopping, setting and starting an I/O watcher does never	561	course). While stopping, setting and starting an I/O watcher does never
428	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	562	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
429	two event changes per incident. Support for C<fork ()> is very bad and it	563	two event changes per incident. Support for C<fork ()> is very bad (but
430	drops fds silently in similarly hard-to-detect cases.	564	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		565	cases
431		566
432	This backend usually performs well under most conditions.	567	This backend usually performs well under most conditions.
433		568
434	While nominally embeddable in other event loops, this doesn't work	569	While nominally embeddable in other event loops, this doesn't work
435	everywhere, so you might need to test for this. And since it is broken	570	everywhere, so you might need to test for this. And since it is broken
436	almost everywhere, you should only use it when you have a lot of sockets	571	almost everywhere, you should only use it when you have a lot of sockets
437	(for which it usually works), by embedding it into another event loop	572	(for which it usually works), by embedding it into another event loop
438	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,	573	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
439	using it only for sockets.	574	also broken on OS X)) and, did I mention it, using it only for sockets.
440		575
441	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	576	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
442	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with	577	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
443	C<NOTE_EOF>.	578	C<NOTE_EOF>.
444		579
…		…
452	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	587	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
453		588
454	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	589	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
455	it's really slow, but it still scales very well (O(active_fds)).	590	it's really slow, but it still scales very well (O(active_fds)).
456		591
457	Please note that Solaris event ports can deliver a lot of spurious
458	notifications, so you need to use non-blocking I/O or other means to avoid
459	blocking when no data (or space) is available.
460
461	While this backend scales well, it requires one system call per active	592	While this backend scales well, it requires one system call per active
462	file descriptor per loop iteration. For small and medium numbers of file	593	file descriptor per loop iteration. For small and medium numbers of file
463	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	594	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
464	might perform better.	595	might perform better.
465		596
466	On the positive side, with the exception of the spurious readiness	597	On the positive side, this backend actually performed fully to
467	notifications, this backend actually performed fully to specification
468	in all tests and is fully embeddable, which is a rare feat among the	598	specification in all tests and is fully embeddable, which is a rare feat
469	OS-specific backends.	599	among the OS-specific backends (I vastly prefer correctness over speed
		600	hacks).
		601
		602	On the negative side, the interface is I<bizarre> - so bizarre that
		603	even sun itself gets it wrong in their code examples: The event polling
		604	function sometimes returning events to the caller even though an error
		605	occurred, but with no indication whether it has done so or not (yes, it's
		606	even documented that way) - deadly for edge-triggered interfaces where
		607	you absolutely have to know whether an event occurred or not because you
		608	have to re-arm the watcher.
		609
		610	Fortunately libev seems to be able to work around these idiocies.
470		611
471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	612	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
472	C<EVBACKEND_POLL>.	613	C<EVBACKEND_POLL>.
473		614
474	=item C<EVBACKEND_ALL>	615	=item C<EVBACKEND_ALL>
475		616
476	Try all backends (even potentially broken ones that wouldn't be tried	617	Try all backends (even potentially broken ones that wouldn't be tried
477	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	618	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
478	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	619	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
479		620
480	It is definitely not recommended to use this flag.	621	It is definitely not recommended to use this flag, use whatever
		622	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		623	at all.
		624
		625	=item C<EVBACKEND_MASK>
		626
		627	Not a backend at all, but a mask to select all backend bits from a
		628	C<flags> value, in case you want to mask out any backends from a flags
		629	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
481		630
482	=back	631	=back
483		632
484	If one or more of these are or'ed into the flags value, then only these	633	If one or more of the backend flags are or'ed into the flags value,
485	backends will be tried (in the reverse order as listed here). If none are	634	then only these backends will be tried (in the reverse order as listed
486	specified, all backends in C<ev_recommended_backends ()> will be tried.	635	here). If none are specified, all backends in C<ev_recommended_backends
487		636	()> will be tried.
488	Example: This is the most typical usage.
489
490	if (!ev_default_loop (0))
491	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
492
493	Example: Restrict libev to the select and poll backends, and do not allow
494	environment settings to be taken into account:
495
496	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
497
498	Example: Use whatever libev has to offer, but make sure that kqueue is
499	used if available (warning, breaks stuff, best use only with your own
500	private event loop and only if you know the OS supports your types of
501	fds):
502
503	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
504
505	=item struct ev_loop *ev_loop_new (unsigned int flags)
506
507	Similar to C<ev_default_loop>, but always creates a new event loop that is
508	always distinct from the default loop. Unlike the default loop, it cannot
509	handle signal and child watchers, and attempts to do so will be greeted by
510	undefined behaviour (or a failed assertion if assertions are enabled).
511
512	Note that this function I<is> thread-safe, and the recommended way to use
513	libev with threads is indeed to create one loop per thread, and using the
514	default loop in the "main" or "initial" thread.
515		637
516	Example: Try to create a event loop that uses epoll and nothing else.	638	Example: Try to create a event loop that uses epoll and nothing else.
517		639
518	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	640	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
519	if (!epoller)	641	if (!epoller)
520	fatal ("no epoll found here, maybe it hides under your chair");	642	fatal ("no epoll found here, maybe it hides under your chair");
521		643
		644	Example: Use whatever libev has to offer, but make sure that kqueue is
		645	used if available.
		646
		647	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		648
522	=item ev_default_destroy ()	649	=item ev_loop_destroy (loop)
523		650
524	Destroys the default loop again (frees all memory and kernel state	651	Destroys an event loop object (frees all memory and kernel state
525	etc.). None of the active event watchers will be stopped in the normal	652	etc.). None of the active event watchers will be stopped in the normal
526	sense, so e.g. C<ev_is_active> might still return true. It is your	653	sense, so e.g. C<ev_is_active> might still return true. It is your
527	responsibility to either stop all watchers cleanly yourself I<before>	654	responsibility to either stop all watchers cleanly yourself I<before>
528	calling this function, or cope with the fact afterwards (which is usually	655	calling this function, or cope with the fact afterwards (which is usually
529	the easiest thing, you can just ignore the watchers and/or C<free ()> them	656	the easiest thing, you can just ignore the watchers and/or C<free ()> them
530	for example).	657	for example).
531		658
532	Note that certain global state, such as signal state, will not be freed by	659	Note that certain global state, such as signal state (and installed signal
533	this function, and related watchers (such as signal and child watchers)	660	handlers), will not be freed by this function, and related watchers (such
534	would need to be stopped manually.	661	as signal and child watchers) would need to be stopped manually.
535		662
536	In general it is not advisable to call this function except in the	663	This function is normally used on loop objects allocated by
537	rare occasion where you really need to free e.g. the signal handling	664	C<ev_loop_new>, but it can also be used on the default loop returned by
		665	C<ev_default_loop>, in which case it is not thread-safe.
		666
		667	Note that it is not advisable to call this function on the default loop
		668	except in the rare occasion where you really need to free its resources.
538	pipe fds. If you need dynamically allocated loops it is better to use	669	If you need dynamically allocated loops it is better to use C<ev_loop_new>
539	C<ev_loop_new> and C<ev_loop_destroy>).	670	and C<ev_loop_destroy>.
540		671
541	=item ev_loop_destroy (loop)	672	=item ev_loop_fork (loop)
542		673
543	Like C<ev_default_destroy>, but destroys an event loop created by an
544	earlier call to C<ev_loop_new>.
545
546	=item ev_default_fork ()
547
548	This function sets a flag that causes subsequent C<ev_loop> iterations	674	This function sets a flag that causes subsequent C<ev_run> iterations to
549	to reinitialise the kernel state for backends that have one. Despite the	675	reinitialise the kernel state for backends that have one. Despite the
550	name, you can call it anytime, but it makes most sense after forking, in	676	name, you can call it anytime, but it makes most sense after forking, in
551	the child process (or both child and parent, but that again makes little	677	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
552	sense). You I<must> call it in the child before using any of the libev	678	child before resuming or calling C<ev_run>.
553	functions, and it will only take effect at the next C<ev_loop> iteration.	679
		680	Again, you I<have> to call it on I<any> loop that you want to re-use after
		681	a fork, I<even if you do not plan to use the loop in the parent>. This is
		682	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		683	during fork.
554		684
555	On the other hand, you only need to call this function in the child	685	On the other hand, you only need to call this function in the child
556	process if and only if you want to use the event library in the child. If	686	process if and only if you want to use the event loop in the child. If
557	you just fork+exec, you don't have to call it at all.	687	you just fork+exec or create a new loop in the child, you don't have to
		688	call it at all (in fact, C<epoll> is so badly broken that it makes a
		689	difference, but libev will usually detect this case on its own and do a
		690	costly reset of the backend).
558		691
559	The function itself is quite fast and it's usually not a problem to call	692	The function itself is quite fast and it's usually not a problem to call
560	it just in case after a fork. To make this easy, the function will fit in	693	it just in case after a fork.
561	quite nicely into a call to C<pthread_atfork>:
562		694
		695	Example: Automate calling C<ev_loop_fork> on the default loop when
		696	using pthreads.
		697
		698	static void
		699	post_fork_child (void)
		700	{
		701	ev_loop_fork (EV_DEFAULT);
		702	}
		703
		704	...
563	pthread_atfork (0, 0, ev_default_fork);	705	pthread_atfork (0, 0, post_fork_child);
564
565	=item ev_loop_fork (loop)
566
567	Like C<ev_default_fork>, but acts on an event loop created by
568	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
569	after fork that you want to re-use in the child, and how you do this is
570	entirely your own problem.
571		706
572	=item int ev_is_default_loop (loop)	707	=item int ev_is_default_loop (loop)
573		708
574	Returns true when the given loop is, in fact, the default loop, and false	709	Returns true when the given loop is, in fact, the default loop, and false
575	otherwise.	710	otherwise.
576		711
577	=item unsigned int ev_loop_count (loop)	712	=item unsigned int ev_iteration (loop)
578		713
579	Returns the count of loop iterations for the loop, which is identical to	714	Returns the current iteration count for the event loop, which is identical
580	the number of times libev did poll for new events. It starts at C<0> and	715	to the number of times libev did poll for new events. It starts at C<0>
581	happily wraps around with enough iterations.	716	and happily wraps around with enough iterations.
582		717
583	This value can sometimes be useful as a generation counter of sorts (it	718	This value can sometimes be useful as a generation counter of sorts (it
584	"ticks" the number of loop iterations), as it roughly corresponds with	719	"ticks" the number of loop iterations), as it roughly corresponds with
585	C<ev_prepare> and C<ev_check> calls.	720	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		721	prepare and check phases.
		722
		723	=item unsigned int ev_depth (loop)
		724
		725	Returns the number of times C<ev_run> was entered minus the number of
		726	times C<ev_run> was exited normally, in other words, the recursion depth.
		727
		728	Outside C<ev_run>, this number is zero. In a callback, this number is
		729	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		730	in which case it is higher.
		731
		732	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
		733	throwing an exception etc.), doesn't count as "exit" - consider this
		734	as a hint to avoid such ungentleman-like behaviour unless it's really
		735	convenient, in which case it is fully supported.
586		736
587	=item unsigned int ev_backend (loop)	737	=item unsigned int ev_backend (loop)
588		738
589	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	739	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
590	use.	740	use.
…		…
599		749
600	=item ev_now_update (loop)	750	=item ev_now_update (loop)
601		751
602	Establishes the current time by querying the kernel, updating the time	752	Establishes the current time by querying the kernel, updating the time
603	returned by C<ev_now ()> in the progress. This is a costly operation and	753	returned by C<ev_now ()> in the progress. This is a costly operation and
604	is usually done automatically within C<ev_loop ()>.	754	is usually done automatically within C<ev_run ()>.
605		755
606	This function is rarely useful, but when some event callback runs for a	756	This function is rarely useful, but when some event callback runs for a
607	very long time without entering the event loop, updating libev's idea of	757	very long time without entering the event loop, updating libev's idea of
608	the current time is a good idea.	758	the current time is a good idea.
609		759
610	See also "The special problem of time updates" in the C<ev_timer> section.	760	See also L<The special problem of time updates> in the C<ev_timer> section.
611		761
		762	=item ev_suspend (loop)
		763
		764	=item ev_resume (loop)
		765
		766	These two functions suspend and resume an event loop, for use when the
		767	loop is not used for a while and timeouts should not be processed.
		768
		769	A typical use case would be an interactive program such as a game: When
		770	the user presses C<^Z> to suspend the game and resumes it an hour later it
		771	would be best to handle timeouts as if no time had actually passed while
		772	the program was suspended. This can be achieved by calling C<ev_suspend>
		773	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		774	C<ev_resume> directly afterwards to resume timer processing.
		775
		776	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		777	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		778	will be rescheduled (that is, they will lose any events that would have
		779	occurred while suspended).
		780
		781	After calling C<ev_suspend> you B<must not> call I<any> function on the
		782	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		783	without a previous call to C<ev_suspend>.
		784
		785	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		786	event loop time (see C<ev_now_update>).
		787
612	=item ev_loop (loop, int flags)	788	=item ev_run (loop, int flags)
613		789
614	Finally, this is it, the event handler. This function usually is called	790	Finally, this is it, the event handler. This function usually is called
615	after you initialised all your watchers and you want to start handling	791	after you have initialised all your watchers and you want to start
616	events.	792	handling events. It will ask the operating system for any new events, call
		793	the watcher callbacks, an then repeat the whole process indefinitely: This
		794	is why event loops are called I<loops>.
617		795
618	If the flags argument is specified as C<0>, it will not return until	796	If the flags argument is specified as C<0>, it will keep handling events
619	either no event watchers are active anymore or C<ev_unloop> was called.	797	until either no event watchers are active anymore or C<ev_break> was
		798	called.
620		799
621	Please note that an explicit C<ev_unloop> is usually better than	800	Please note that an explicit C<ev_break> is usually better than
622	relying on all watchers to be stopped when deciding when a program has	801	relying on all watchers to be stopped when deciding when a program has
623	finished (especially in interactive programs), but having a program	802	finished (especially in interactive programs), but having a program
624	that automatically loops as long as it has to and no longer by virtue	803	that automatically loops as long as it has to and no longer by virtue
625	of relying on its watchers stopping correctly, that is truly a thing of	804	of relying on its watchers stopping correctly, that is truly a thing of
626	beauty.	805	beauty.
627		806
		807	This function is also I<mostly> exception-safe - you can break out of
		808	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		809	exception and so on. This does not decrement the C<ev_depth> value, nor
		810	will it clear any outstanding C<EVBREAK_ONE> breaks.
		811
628	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	812	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
629	those events and any already outstanding ones, but will not block your	813	those events and any already outstanding ones, but will not wait and
630	process in case there are no events and will return after one iteration of	814	block your process in case there are no events and will return after one
631	the loop.	815	iteration of the loop. This is sometimes useful to poll and handle new
		816	events while doing lengthy calculations, to keep the program responsive.
632		817
633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	818	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
634	necessary) and will handle those and any already outstanding ones. It	819	necessary) and will handle those and any already outstanding ones. It
635	will block your process until at least one new event arrives (which could	820	will block your process until at least one new event arrives (which could
636	be an event internal to libev itself, so there is no guarentee that a	821	be an event internal to libev itself, so there is no guarantee that a
637	user-registered callback will be called), and will return after one	822	user-registered callback will be called), and will return after one
638	iteration of the loop.	823	iteration of the loop.
639		824
640	This is useful if you are waiting for some external event in conjunction	825	This is useful if you are waiting for some external event in conjunction
641	with something not expressible using other libev watchers (i.e. "roll your	826	with something not expressible using other libev watchers (i.e. "roll your
642	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	827	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
643	usually a better approach for this kind of thing.	828	usually a better approach for this kind of thing.
644		829
645	Here are the gory details of what C<ev_loop> does:	830	Here are the gory details of what C<ev_run> does:
646		831
		832	- Increment loop depth.
		833	- Reset the ev_break status.
647	- Before the first iteration, call any pending watchers.	834	- Before the first iteration, call any pending watchers.
		835	LOOP:
648	* If EVFLAG_FORKCHECK was used, check for a fork.	836	- If EVFLAG_FORKCHECK was used, check for a fork.
649	- If a fork was detected (by any means), queue and call all fork watchers.	837	- If a fork was detected (by any means), queue and call all fork watchers.
650	- Queue and call all prepare watchers.	838	- Queue and call all prepare watchers.
		839	- If ev_break was called, goto FINISH.
651	- If we have been forked, detach and recreate the kernel state	840	- If we have been forked, detach and recreate the kernel state
652	as to not disturb the other process.	841	as to not disturb the other process.
653	- Update the kernel state with all outstanding changes.	842	- Update the kernel state with all outstanding changes.
654	- Update the "event loop time" (ev_now ()).	843	- Update the "event loop time" (ev_now ()).
655	- Calculate for how long to sleep or block, if at all	844	- Calculate for how long to sleep or block, if at all
656	(active idle watchers, EVLOOP_NONBLOCK or not having	845	(active idle watchers, EVRUN_NOWAIT or not having
657	any active watchers at all will result in not sleeping).	846	any active watchers at all will result in not sleeping).
658	- Sleep if the I/O and timer collect interval say so.	847	- Sleep if the I/O and timer collect interval say so.
		848	- Increment loop iteration counter.
659	- Block the process, waiting for any events.	849	- Block the process, waiting for any events.
660	- Queue all outstanding I/O (fd) events.	850	- Queue all outstanding I/O (fd) events.
661	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	851	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
662	- Queue all expired timers.	852	- Queue all expired timers.
663	- Queue all expired periodics.	853	- Queue all expired periodics.
664	- Unless any events are pending now, queue all idle watchers.	854	- Queue all idle watchers with priority higher than that of pending events.
665	- Queue all check watchers.	855	- Queue all check watchers.
666	- Call all queued watchers in reverse order (i.e. check watchers first).	856	- Call all queued watchers in reverse order (i.e. check watchers first).
667	Signals and child watchers are implemented as I/O watchers, and will	857	Signals and child watchers are implemented as I/O watchers, and will
668	be handled here by queueing them when their watcher gets executed.	858	be handled here by queueing them when their watcher gets executed.
669	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	859	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
670	were used, or there are no active watchers, return, otherwise	860	were used, or there are no active watchers, goto FINISH, otherwise
671	continue with step *.	861	continue with step LOOP.
		862	FINISH:
		863	- Reset the ev_break status iff it was EVBREAK_ONE.
		864	- Decrement the loop depth.
		865	- Return.
672		866
673	Example: Queue some jobs and then loop until no events are outstanding	867	Example: Queue some jobs and then loop until no events are outstanding
674	anymore.	868	anymore.
675		869
676	... queue jobs here, make sure they register event watchers as long	870	... queue jobs here, make sure they register event watchers as long
677	... as they still have work to do (even an idle watcher will do..)	871	... as they still have work to do (even an idle watcher will do..)
678	ev_loop (my_loop, 0);	872	ev_run (my_loop, 0);
679	... jobs done or somebody called unloop. yeah!	873	... jobs done or somebody called unloop. yeah!
680		874
681	=item ev_unloop (loop, how)	875	=item ev_break (loop, how)
682		876
683	Can be used to make a call to C<ev_loop> return early (but only after it	877	Can be used to make a call to C<ev_run> return early (but only after it
684	has processed all outstanding events). The C<how> argument must be either	878	has processed all outstanding events). The C<how> argument must be either
685	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	879	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
686	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	880	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
687		881
688	This "unloop state" will be cleared when entering C<ev_loop> again.	882	This "break state" will be cleared on the next call to C<ev_run>.
		883
		884	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		885	which case it will have no effect.
689		886
690	=item ev_ref (loop)	887	=item ev_ref (loop)
691		888
692	=item ev_unref (loop)	889	=item ev_unref (loop)
693		890
694	Ref/unref can be used to add or remove a reference count on the event	891	Ref/unref can be used to add or remove a reference count on the event
695	loop: Every watcher keeps one reference, and as long as the reference	892	loop: Every watcher keeps one reference, and as long as the reference
696	count is nonzero, C<ev_loop> will not return on its own.	893	count is nonzero, C<ev_run> will not return on its own.
697		894
698	If you have a watcher you never unregister that should not keep C<ev_loop>	895	This is useful when you have a watcher that you never intend to
699	from returning, call ev_unref() after starting, and ev_ref() before	896	unregister, but that nevertheless should not keep C<ev_run> from
		897	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
700	stopping it.	898	before stopping it.
701		899
702	As an example, libev itself uses this for its internal signal pipe: It is	900	As an example, libev itself uses this for its internal signal pipe: It
703	not visible to the libev user and should not keep C<ev_loop> from exiting	901	is not visible to the libev user and should not keep C<ev_run> from
704	if no event watchers registered by it are active. It is also an excellent	902	exiting if no event watchers registered by it are active. It is also an
705	way to do this for generic recurring timers or from within third-party	903	excellent way to do this for generic recurring timers or from within
706	libraries. Just remember to I<unref after start> and I<ref before stop>	904	third-party libraries. Just remember to I<unref after start> and I<ref
707	(but only if the watcher wasn't active before, or was active before,	905	before stop> (but only if the watcher wasn't active before, or was active
708	respectively).	906	before, respectively. Note also that libev might stop watchers itself
		907	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		908	in the callback).
709		909
710	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	910	Example: Create a signal watcher, but keep it from keeping C<ev_run>
711	running when nothing else is active.	911	running when nothing else is active.
712		912
713	struct ev_signal exitsig;	913	ev_signal exitsig;
714	ev_signal_init (&exitsig, sig_cb, SIGINT);	914	ev_signal_init (&exitsig, sig_cb, SIGINT);
715	ev_signal_start (loop, &exitsig);	915	ev_signal_start (loop, &exitsig);
716	evf_unref (loop);	916	ev_unref (loop);
717		917
718	Example: For some weird reason, unregister the above signal handler again.	918	Example: For some weird reason, unregister the above signal handler again.
719		919
720	ev_ref (loop);	920	ev_ref (loop);
721	ev_signal_stop (loop, &exitsig);	921	ev_signal_stop (loop, &exitsig);
…		…
742		942
743	By setting a higher I<io collect interval> you allow libev to spend more	943	By setting a higher I<io collect interval> you allow libev to spend more
744	time collecting I/O events, so you can handle more events per iteration,	944	time collecting I/O events, so you can handle more events per iteration,
745	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	945	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
746	C<ev_timer>) will be not affected. Setting this to a non-null value will	946	C<ev_timer>) will be not affected. Setting this to a non-null value will
747	introduce an additional C<ev_sleep ()> call into most loop iterations.	947	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		948	sleep time ensures that libev will not poll for I/O events more often then
		949	once per this interval, on average.
748		950
749	Likewise, by setting a higher I<timeout collect interval> you allow libev	951	Likewise, by setting a higher I<timeout collect interval> you allow libev
750	to spend more time collecting timeouts, at the expense of increased	952	to spend more time collecting timeouts, at the expense of increased
751	latency/jitter/inexactness (the watcher callback will be called	953	latency/jitter/inexactness (the watcher callback will be called
752	later). C<ev_io> watchers will not be affected. Setting this to a non-null	954	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
754		956
755	Many (busy) programs can usually benefit by setting the I/O collect	957	Many (busy) programs can usually benefit by setting the I/O collect
756	interval to a value near C<0.1> or so, which is often enough for	958	interval to a value near C<0.1> or so, which is often enough for
757	interactive servers (of course not for games), likewise for timeouts. It	959	interactive servers (of course not for games), likewise for timeouts. It
758	usually doesn't make much sense to set it to a lower value than C<0.01>,	960	usually doesn't make much sense to set it to a lower value than C<0.01>,
759	as this approaches the timing granularity of most systems.	961	as this approaches the timing granularity of most systems. Note that if
		962	you do transactions with the outside world and you can't increase the
		963	parallelity, then this setting will limit your transaction rate (if you
		964	need to poll once per transaction and the I/O collect interval is 0.01,
		965	then you can't do more than 100 transactions per second).
760		966
761	Setting the I<timeout collect interval> can improve the opportunity for	967	Setting the I<timeout collect interval> can improve the opportunity for
762	saving power, as the program will "bundle" timer callback invocations that	968	saving power, as the program will "bundle" timer callback invocations that
763	are "near" in time together, by delaying some, thus reducing the number of	969	are "near" in time together, by delaying some, thus reducing the number of
764	times the process sleeps and wakes up again. Another useful technique to	970	times the process sleeps and wakes up again. Another useful technique to
765	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	971	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
766	they fire on, say, one-second boundaries only.	972	they fire on, say, one-second boundaries only.
767		973
		974	Example: we only need 0.1s timeout granularity, and we wish not to poll
		975	more often than 100 times per second:
		976
		977	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		978	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		979
		980	=item ev_invoke_pending (loop)
		981
		982	This call will simply invoke all pending watchers while resetting their
		983	pending state. Normally, C<ev_run> does this automatically when required,
		984	but when overriding the invoke callback this call comes handy. This
		985	function can be invoked from a watcher - this can be useful for example
		986	when you want to do some lengthy calculation and want to pass further
		987	event handling to another thread (you still have to make sure only one
		988	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		989
		990	=item int ev_pending_count (loop)
		991
		992	Returns the number of pending watchers - zero indicates that no watchers
		993	are pending.
		994
		995	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		996
		997	This overrides the invoke pending functionality of the loop: Instead of
		998	invoking all pending watchers when there are any, C<ev_run> will call
		999	this callback instead. This is useful, for example, when you want to
		1000	invoke the actual watchers inside another context (another thread etc.).
		1001
		1002	If you want to reset the callback, use C<ev_invoke_pending> as new
		1003	callback.
		1004
		1005	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		1006
		1007	Sometimes you want to share the same loop between multiple threads. This
		1008	can be done relatively simply by putting mutex_lock/unlock calls around
		1009	each call to a libev function.
		1010
		1011	However, C<ev_run> can run an indefinite time, so it is not feasible
		1012	to wait for it to return. One way around this is to wake up the event
		1013	loop via C<ev_break> and C<av_async_send>, another way is to set these
		1014	I<release> and I<acquire> callbacks on the loop.
		1015
		1016	When set, then C<release> will be called just before the thread is
		1017	suspended waiting for new events, and C<acquire> is called just
		1018	afterwards.
		1019
		1020	Ideally, C<release> will just call your mutex_unlock function, and
		1021	C<acquire> will just call the mutex_lock function again.
		1022
		1023	While event loop modifications are allowed between invocations of
		1024	C<release> and C<acquire> (that's their only purpose after all), no
		1025	modifications done will affect the event loop, i.e. adding watchers will
		1026	have no effect on the set of file descriptors being watched, or the time
		1027	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		1028	to take note of any changes you made.
		1029
		1030	In theory, threads executing C<ev_run> will be async-cancel safe between
		1031	invocations of C<release> and C<acquire>.
		1032
		1033	See also the locking example in the C<THREADS> section later in this
		1034	document.
		1035
		1036	=item ev_set_userdata (loop, void *data)
		1037
		1038	=item void *ev_userdata (loop)
		1039
		1040	Set and retrieve a single C<void *> associated with a loop. When
		1041	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		1042	C<0>.
		1043
		1044	These two functions can be used to associate arbitrary data with a loop,
		1045	and are intended solely for the C<invoke_pending_cb>, C<release> and
		1046	C<acquire> callbacks described above, but of course can be (ab-)used for
		1047	any other purpose as well.
		1048
768	=item ev_loop_verify (loop)	1049	=item ev_verify (loop)
769		1050
770	This function only does something when C<EV_VERIFY> support has been	1051	This function only does something when C<EV_VERIFY> support has been
771	compiled in. which is the default for non-minimal builds. It tries to go	1052	compiled in, which is the default for non-minimal builds. It tries to go
772	through all internal structures and checks them for validity. If anything	1053	through all internal structures and checks them for validity. If anything
773	is found to be inconsistent, it will print an error message to standard	1054	is found to be inconsistent, it will print an error message to standard
774	error and call C<abort ()>.	1055	error and call C<abort ()>.
775		1056
776	This can be used to catch bugs inside libev itself: under normal	1057	This can be used to catch bugs inside libev itself: under normal
…		…
780	=back	1061	=back
781		1062
782		1063
783	=head1 ANATOMY OF A WATCHER	1064	=head1 ANATOMY OF A WATCHER
784		1065
		1066	In the following description, uppercase C<TYPE> in names stands for the
		1067	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		1068	watchers and C<ev_io_start> for I/O watchers.
		1069
785	A watcher is a structure that you create and register to record your	1070	A watcher is an opaque structure that you allocate and register to record
786	interest in some event. For instance, if you want to wait for STDIN to	1071	your interest in some event. To make a concrete example, imagine you want
787	become readable, you would create an C<ev_io> watcher for that:	1072	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1073	for that:
788		1074
789	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1075	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
790	{	1076	{
791	ev_io_stop (w);	1077	ev_io_stop (w);
792	ev_unloop (loop, EVUNLOOP_ALL);	1078	ev_break (loop, EVBREAK_ALL);
793	}	1079	}
794		1080
795	struct ev_loop *loop = ev_default_loop (0);	1081	struct ev_loop *loop = ev_default_loop (0);
		1082
796	struct ev_io stdin_watcher;	1083	ev_io stdin_watcher;
		1084
797	ev_init (&stdin_watcher, my_cb);	1085	ev_init (&stdin_watcher, my_cb);
798	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1086	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
799	ev_io_start (loop, &stdin_watcher);	1087	ev_io_start (loop, &stdin_watcher);
		1088
800	ev_loop (loop, 0);	1089	ev_run (loop, 0);
801		1090
802	As you can see, you are responsible for allocating the memory for your	1091	As you can see, you are responsible for allocating the memory for your
803	watcher structures (and it is usually a bad idea to do this on the stack,	1092	watcher structures (and it is I<usually> a bad idea to do this on the
804	although this can sometimes be quite valid).	1093	stack).
805		1094
		1095	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		1096	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
		1097
806	Each watcher structure must be initialised by a call to C<ev_init	1098	Each watcher structure must be initialised by a call to C<ev_init (watcher
807	(watcher *, callback)>, which expects a callback to be provided. This	1099	*, callback)>, which expects a callback to be provided. This callback is
808	callback gets invoked each time the event occurs (or, in the case of I/O	1100	invoked each time the event occurs (or, in the case of I/O watchers, each
809	watchers, each time the event loop detects that the file descriptor given	1101	time the event loop detects that the file descriptor given is readable
810	is readable and/or writable).	1102	and/or writable).
811		1103
812	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1104	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
813	with arguments specific to this watcher type. There is also a macro	1105	macro to configure it, with arguments specific to the watcher type. There
814	to combine initialisation and setting in one call: C<< ev_<type>_init	1106	is also a macro to combine initialisation and setting in one call: C<<
815	(watcher *, callback, ...) >>.	1107	ev_TYPE_init (watcher *, callback, ...) >>.
816		1108
817	To make the watcher actually watch out for events, you have to start it	1109	To make the watcher actually watch out for events, you have to start it
818	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	1110	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
819	*) >>), and you can stop watching for events at any time by calling the	1111	*) >>), and you can stop watching for events at any time by calling the
820	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1112	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
821		1113
822	As long as your watcher is active (has been started but not stopped) you	1114	As long as your watcher is active (has been started but not stopped) you
823	must not touch the values stored in it. Most specifically you must never	1115	must not touch the values stored in it. Most specifically you must never
824	reinitialise it or call its C<set> macro.	1116	reinitialise it or call its C<ev_TYPE_set> macro.
825		1117
826	Each and every callback receives the event loop pointer as first, the	1118	Each and every callback receives the event loop pointer as first, the
827	registered watcher structure as second, and a bitset of received events as	1119	registered watcher structure as second, and a bitset of received events as
828	third argument.	1120	third argument.
829		1121
…		…
838	=item C<EV_WRITE>	1130	=item C<EV_WRITE>
839		1131
840	The file descriptor in the C<ev_io> watcher has become readable and/or	1132	The file descriptor in the C<ev_io> watcher has become readable and/or
841	writable.	1133	writable.
842		1134
843	=item C<EV_TIMEOUT>	1135	=item C<EV_TIMER>
844		1136
845	The C<ev_timer> watcher has timed out.	1137	The C<ev_timer> watcher has timed out.
846		1138
847	=item C<EV_PERIODIC>	1139	=item C<EV_PERIODIC>
848		1140
…		…
866		1158
867	=item C<EV_PREPARE>	1159	=item C<EV_PREPARE>
868		1160
869	=item C<EV_CHECK>	1161	=item C<EV_CHECK>
870		1162
871	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1163	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
872	to gather new events, and all C<ev_check> watchers are invoked just after	1164	to gather new events, and all C<ev_check> watchers are invoked just after
873	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1165	C<ev_run> has gathered them, but before it invokes any callbacks for any
874	received events. Callbacks of both watcher types can start and stop as	1166	received events. Callbacks of both watcher types can start and stop as
875	many watchers as they want, and all of them will be taken into account	1167	many watchers as they want, and all of them will be taken into account
876	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1168	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
877	C<ev_loop> from blocking).	1169	C<ev_run> from blocking).
878		1170
879	=item C<EV_EMBED>	1171	=item C<EV_EMBED>
880		1172
881	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1173	The embedded event loop specified in the C<ev_embed> watcher needs attention.
882		1174
883	=item C<EV_FORK>	1175	=item C<EV_FORK>
884		1176
885	The event loop has been resumed in the child process after fork (see	1177	The event loop has been resumed in the child process after fork (see
886	C<ev_fork>).	1178	C<ev_fork>).
887		1179
		1180	=item C<EV_CLEANUP>
		1181
		1182	The event loop is about to be destroyed (see C<ev_cleanup>).
		1183
888	=item C<EV_ASYNC>	1184	=item C<EV_ASYNC>
889		1185
890	The given async watcher has been asynchronously notified (see C<ev_async>).	1186	The given async watcher has been asynchronously notified (see C<ev_async>).
		1187
		1188	=item C<EV_CUSTOM>
		1189
		1190	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1191	by libev users to signal watchers (e.g. via C<ev_feed_event>).
891		1192
892	=item C<EV_ERROR>	1193	=item C<EV_ERROR>
893		1194
894	An unspecified error has occurred, the watcher has been stopped. This might	1195	An unspecified error has occurred, the watcher has been stopped. This might
895	happen because the watcher could not be properly started because libev	1196	happen because the watcher could not be properly started because libev
896	ran out of memory, a file descriptor was found to be closed or any other	1197	ran out of memory, a file descriptor was found to be closed or any other
		1198	problem. Libev considers these application bugs.
		1199
897	problem. You best act on it by reporting the problem and somehow coping	1200	You best act on it by reporting the problem and somehow coping with the
898	with the watcher being stopped.	1201	watcher being stopped. Note that well-written programs should not receive
		1202	an error ever, so when your watcher receives it, this usually indicates a
		1203	bug in your program.
899		1204
900	Libev will usually signal a few "dummy" events together with an error, for	1205	Libev will usually signal a few "dummy" events together with an error, for
901	example it might indicate that a fd is readable or writable, and if your	1206	example it might indicate that a fd is readable or writable, and if your
902	callbacks is well-written it can just attempt the operation and cope with	1207	callbacks is well-written it can just attempt the operation and cope with
903	the error from read() or write(). This will not work in multi-threaded	1208	the error from read() or write(). This will not work in multi-threaded
…		…
906		1211
907	=back	1212	=back
908		1213
909	=head2 GENERIC WATCHER FUNCTIONS	1214	=head2 GENERIC WATCHER FUNCTIONS
910		1215
911	In the following description, C<TYPE> stands for the watcher type,
912	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
913
914	=over 4	1216	=over 4
915		1217
916	=item C<ev_init> (ev_TYPE *watcher, callback)	1218	=item C<ev_init> (ev_TYPE *watcher, callback)
917		1219
918	This macro initialises the generic portion of a watcher. The contents	1220	This macro initialises the generic portion of a watcher. The contents
…		…
923	which rolls both calls into one.	1225	which rolls both calls into one.
924		1226
925	You can reinitialise a watcher at any time as long as it has been stopped	1227	You can reinitialise a watcher at any time as long as it has been stopped
926	(or never started) and there are no pending events outstanding.	1228	(or never started) and there are no pending events outstanding.
927		1229
928	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1230	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
929	int revents)>.	1231	int revents)>.
930		1232
931	Example: Initialise an C<ev_io> watcher in two steps.	1233	Example: Initialise an C<ev_io> watcher in two steps.
932		1234
933	ev_io w;	1235	ev_io w;
934	ev_init (&w, my_cb);	1236	ev_init (&w, my_cb);
935	ev_io_set (&w, STDIN_FILENO, EV_READ);	1237	ev_io_set (&w, STDIN_FILENO, EV_READ);
936		1238
937	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1239	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
938		1240
939	This macro initialises the type-specific parts of a watcher. You need to	1241	This macro initialises the type-specific parts of a watcher. You need to
940	call C<ev_init> at least once before you call this macro, but you can	1242	call C<ev_init> at least once before you call this macro, but you can
941	call C<ev_TYPE_set> any number of times. You must not, however, call this	1243	call C<ev_TYPE_set> any number of times. You must not, however, call this
942	macro on a watcher that is active (it can be pending, however, which is a	1244	macro on a watcher that is active (it can be pending, however, which is a
…		…
955		1257
956	Example: Initialise and set an C<ev_io> watcher in one step.	1258	Example: Initialise and set an C<ev_io> watcher in one step.
957		1259
958	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1260	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
959		1261
960	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1262	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
961		1263
962	Starts (activates) the given watcher. Only active watchers will receive	1264	Starts (activates) the given watcher. Only active watchers will receive
963	events. If the watcher is already active nothing will happen.	1265	events. If the watcher is already active nothing will happen.
964		1266
965	Example: Start the C<ev_io> watcher that is being abused as example in this	1267	Example: Start the C<ev_io> watcher that is being abused as example in this
966	whole section.	1268	whole section.
967		1269
968	ev_io_start (EV_DEFAULT_UC, &w);	1270	ev_io_start (EV_DEFAULT_UC, &w);
969		1271
970	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1272	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
971		1273
972	Stops the given watcher again (if active) and clears the pending	1274	Stops the given watcher if active, and clears the pending status (whether
		1275	the watcher was active or not).
		1276
973	status. It is possible that stopped watchers are pending (for example,	1277	It is possible that stopped watchers are pending - for example,
974	non-repeating timers are being stopped when they become pending), but	1278	non-repeating timers are being stopped when they become pending - but
975	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1279	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
976	you want to free or reuse the memory used by the watcher it is therefore a	1280	pending. If you want to free or reuse the memory used by the watcher it is
977	good idea to always call its C<ev_TYPE_stop> function.	1281	therefore a good idea to always call its C<ev_TYPE_stop> function.
978		1282
979	=item bool ev_is_active (ev_TYPE *watcher)	1283	=item bool ev_is_active (ev_TYPE *watcher)
980		1284
981	Returns a true value iff the watcher is active (i.e. it has been started	1285	Returns a true value iff the watcher is active (i.e. it has been started
982	and not yet been stopped). As long as a watcher is active you must not modify	1286	and not yet been stopped). As long as a watcher is active you must not modify
…		…
998	=item ev_cb_set (ev_TYPE *watcher, callback)	1302	=item ev_cb_set (ev_TYPE *watcher, callback)
999		1303
1000	Change the callback. You can change the callback at virtually any time	1304	Change the callback. You can change the callback at virtually any time
1001	(modulo threads).	1305	(modulo threads).
1002		1306
1003	=item ev_set_priority (ev_TYPE *watcher, priority)	1307	=item ev_set_priority (ev_TYPE *watcher, int priority)
1004		1308
1005	=item int ev_priority (ev_TYPE *watcher)	1309	=item int ev_priority (ev_TYPE *watcher)
1006		1310
1007	Set and query the priority of the watcher. The priority is a small	1311	Set and query the priority of the watcher. The priority is a small
1008	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1312	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1009	(default: C<-2>). Pending watchers with higher priority will be invoked	1313	(default: C<-2>). Pending watchers with higher priority will be invoked
1010	before watchers with lower priority, but priority will not keep watchers	1314	before watchers with lower priority, but priority will not keep watchers
1011	from being executed (except for C<ev_idle> watchers).	1315	from being executed (except for C<ev_idle> watchers).
1012		1316
1013	This means that priorities are I<only> used for ordering callback
1014	invocation after new events have been received. This is useful, for
1015	example, to reduce latency after idling, or more often, to bind two
1016	watchers on the same event and make sure one is called first.
1017
1018	If you need to suppress invocation when higher priority events are pending	1317	If you need to suppress invocation when higher priority events are pending
1019	you need to look at C<ev_idle> watchers, which provide this functionality.	1318	you need to look at C<ev_idle> watchers, which provide this functionality.
1020		1319
1021	You I<must not> change the priority of a watcher as long as it is active or	1320	You I<must not> change the priority of a watcher as long as it is active or
1022	pending.	1321	pending.
1023		1322
		1323	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1324	fine, as long as you do not mind that the priority value you query might
		1325	or might not have been clamped to the valid range.
		1326
1024	The default priority used by watchers when no priority has been set is	1327	The default priority used by watchers when no priority has been set is
1025	always C<0>, which is supposed to not be too high and not be too low :).	1328	always C<0>, which is supposed to not be too high and not be too low :).
1026		1329
1027	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1330	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1028	fine, as long as you do not mind that the priority value you query might	1331	priorities.
1029	or might not have been adjusted to be within valid range.
1030		1332
1031	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1333	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1032		1334
1033	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1335	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1034	C<loop> nor C<revents> need to be valid as long as the watcher callback	1336	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1042	watcher isn't pending it does nothing and returns C<0>.	1344	watcher isn't pending it does nothing and returns C<0>.
1043		1345
1044	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1346	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1045	callback to be invoked, which can be accomplished with this function.	1347	callback to be invoked, which can be accomplished with this function.
1046		1348
		1349	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1350
		1351	Feeds the given event set into the event loop, as if the specified event
		1352	had happened for the specified watcher (which must be a pointer to an
		1353	initialised but not necessarily started event watcher). Obviously you must
		1354	not free the watcher as long as it has pending events.
		1355
		1356	Stopping the watcher, letting libev invoke it, or calling
		1357	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1358	not started in the first place.
		1359
		1360	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1361	functions that do not need a watcher.
		1362
1047	=back	1363	=back
1048		1364
		1365	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
		1366	OWN COMPOSITE WATCHERS> idioms.
1049		1367
1050	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1368	=head2 WATCHER STATES
1051		1369
1052	Each watcher has, by default, a member C<void *data> that you can change	1370	There are various watcher states mentioned throughout this manual -
1053	and read at any time: libev will completely ignore it. This can be used	1371	active, pending and so on. In this section these states and the rules to
1054	to associate arbitrary data with your watcher. If you need more data and	1372	transition between them will be described in more detail - and while these
1055	don't want to allocate memory and store a pointer to it in that data	1373	rules might look complicated, they usually do "the right thing".
1056	member, you can also "subclass" the watcher type and provide your own
1057	data:
1058		1374
1059	struct my_io	1375	=over 4
		1376
		1377	=item initialiased
		1378
		1379	Before a watcher can be registered with the event looop it has to be
		1380	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1381	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1382
		1383	In this state it is simply some block of memory that is suitable for use
		1384	in an event loop. It can be moved around, freed, reused etc. at will.
		1385
		1386	=item started/running/active
		1387
		1388	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1389	property of the event loop, and is actively waiting for events. While in
		1390	this state it cannot be accessed (except in a few documented ways), moved,
		1391	freed or anything else - the only legal thing is to keep a pointer to it,
		1392	and call libev functions on it that are documented to work on active watchers.
		1393
		1394	=item pending
		1395
		1396	If a watcher is active and libev determines that an event it is interested
		1397	in has occurred (such as a timer expiring), it will become pending. It will
		1398	stay in this pending state until either it is stopped or its callback is
		1399	about to be invoked, so it is not normally pending inside the watcher
		1400	callback.
		1401
		1402	The watcher might or might not be active while it is pending (for example,
		1403	an expired non-repeating timer can be pending but no longer active). If it
		1404	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1405	but it is still property of the event loop at this time, so cannot be
		1406	moved, freed or reused. And if it is active the rules described in the
		1407	previous item still apply.
		1408
		1409	It is also possible to feed an event on a watcher that is not active (e.g.
		1410	via C<ev_feed_event>), in which case it becomes pending without being
		1411	active.
		1412
		1413	=item stopped
		1414
		1415	A watcher can be stopped implicitly by libev (in which case it might still
		1416	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1417	latter will clear any pending state the watcher might be in, regardless
		1418	of whether it was active or not, so stopping a watcher explicitly before
		1419	freeing it is often a good idea.
		1420
		1421	While stopped (and not pending) the watcher is essentially in the
		1422	initialised state, that is it can be reused, moved, modified in any way
		1423	you wish.
		1424
		1425	=back
		1426
		1427	=head2 WATCHER PRIORITY MODELS
		1428
		1429	Many event loops support I<watcher priorities>, which are usually small
		1430	integers that influence the ordering of event callback invocation
		1431	between watchers in some way, all else being equal.
		1432
		1433	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1434	description for the more technical details such as the actual priority
		1435	range.
		1436
		1437	There are two common ways how these these priorities are being interpreted
		1438	by event loops:
		1439
		1440	In the more common lock-out model, higher priorities "lock out" invocation
		1441	of lower priority watchers, which means as long as higher priority
		1442	watchers receive events, lower priority watchers are not being invoked.
		1443
		1444	The less common only-for-ordering model uses priorities solely to order
		1445	callback invocation within a single event loop iteration: Higher priority
		1446	watchers are invoked before lower priority ones, but they all get invoked
		1447	before polling for new events.
		1448
		1449	Libev uses the second (only-for-ordering) model for all its watchers
		1450	except for idle watchers (which use the lock-out model).
		1451
		1452	The rationale behind this is that implementing the lock-out model for
		1453	watchers is not well supported by most kernel interfaces, and most event
		1454	libraries will just poll for the same events again and again as long as
		1455	their callbacks have not been executed, which is very inefficient in the
		1456	common case of one high-priority watcher locking out a mass of lower
		1457	priority ones.
		1458
		1459	Static (ordering) priorities are most useful when you have two or more
		1460	watchers handling the same resource: a typical usage example is having an
		1461	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1462	timeouts. Under load, data might be received while the program handles
		1463	other jobs, but since timers normally get invoked first, the timeout
		1464	handler will be executed before checking for data. In that case, giving
		1465	the timer a lower priority than the I/O watcher ensures that I/O will be
		1466	handled first even under adverse conditions (which is usually, but not
		1467	always, what you want).
		1468
		1469	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1470	will only be executed when no same or higher priority watchers have
		1471	received events, they can be used to implement the "lock-out" model when
		1472	required.
		1473
		1474	For example, to emulate how many other event libraries handle priorities,
		1475	you can associate an C<ev_idle> watcher to each such watcher, and in
		1476	the normal watcher callback, you just start the idle watcher. The real
		1477	processing is done in the idle watcher callback. This causes libev to
		1478	continuously poll and process kernel event data for the watcher, but when
		1479	the lock-out case is known to be rare (which in turn is rare :), this is
		1480	workable.
		1481
		1482	Usually, however, the lock-out model implemented that way will perform
		1483	miserably under the type of load it was designed to handle. In that case,
		1484	it might be preferable to stop the real watcher before starting the
		1485	idle watcher, so the kernel will not have to process the event in case
		1486	the actual processing will be delayed for considerable time.
		1487
		1488	Here is an example of an I/O watcher that should run at a strictly lower
		1489	priority than the default, and which should only process data when no
		1490	other events are pending:
		1491
		1492	ev_idle idle; // actual processing watcher
		1493	ev_io io; // actual event watcher
		1494
		1495	static void
		1496	io_cb (EV_P_ ev_io *w, int revents)
1060	{	1497	{
1061	struct ev_io io;	1498	// stop the I/O watcher, we received the event, but
1062	int otherfd;	1499	// are not yet ready to handle it.
1063	void *somedata;	1500	ev_io_stop (EV_A_ w);
1064	struct whatever *mostinteresting;	1501
		1502	// start the idle watcher to handle the actual event.
		1503	// it will not be executed as long as other watchers
		1504	// with the default priority are receiving events.
		1505	ev_idle_start (EV_A_ &idle);
1065	};	1506	}
1066		1507
1067	...	1508	static void
1068	struct my_io w;	1509	idle_cb (EV_P_ ev_idle *w, int revents)
1069	ev_io_init (&w.io, my_cb, fd, EV_READ);
1070
1071	And since your callback will be called with a pointer to the watcher, you
1072	can cast it back to your own type:
1073
1074	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
1075	{	1510	{
1076	struct my_io *w = (struct my_io *)w_;	1511	// actual processing
1077	...	1512	read (STDIN_FILENO, ...);
		1513
		1514	// have to start the I/O watcher again, as
		1515	// we have handled the event
		1516	ev_io_start (EV_P_ &io);
1078	}	1517	}
1079		1518
1080	More interesting and less C-conformant ways of casting your callback type	1519	// initialisation
1081	instead have been omitted.	1520	ev_idle_init (&idle, idle_cb);
		1521	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1522	ev_io_start (EV_DEFAULT_ &io);
1082		1523
1083	Another common scenario is to use some data structure with multiple	1524	In the "real" world, it might also be beneficial to start a timer, so that
1084	embedded watchers:	1525	low-priority connections can not be locked out forever under load. This
1085		1526	enables your program to keep a lower latency for important connections
1086	struct my_biggy	1527	during short periods of high load, while not completely locking out less
1087	{	1528	important ones.
1088	int some_data;
1089	ev_timer t1;
1090	ev_timer t2;
1091	}
1092
1093	In this case getting the pointer to C<my_biggy> is a bit more
1094	complicated: Either you store the address of your C<my_biggy> struct
1095	in the C<data> member of the watcher (for woozies), or you need to use
1096	some pointer arithmetic using C<offsetof> inside your watchers (for real
1097	programmers):
1098
1099	#include <stddef.h>
1100
1101	static void
1102	t1_cb (EV_P_ struct ev_timer *w, int revents)
1103	{
1104	struct my_biggy big = (struct my_biggy *
1105	(((char *)w) - offsetof (struct my_biggy, t1));
1106	}
1107
1108	static void
1109	t2_cb (EV_P_ struct ev_timer *w, int revents)
1110	{
1111	struct my_biggy big = (struct my_biggy *
1112	(((char *)w) - offsetof (struct my_biggy, t2));
1113	}
1114		1529
1115		1530
1116	=head1 WATCHER TYPES	1531	=head1 WATCHER TYPES
1117		1532
1118	This section describes each watcher in detail, but will not repeat	1533	This section describes each watcher in detail, but will not repeat
…		…
1142	In general you can register as many read and/or write event watchers per	1557	In general you can register as many read and/or write event watchers per
1143	fd as you want (as long as you don't confuse yourself). Setting all file	1558	fd as you want (as long as you don't confuse yourself). Setting all file
1144	descriptors to non-blocking mode is also usually a good idea (but not	1559	descriptors to non-blocking mode is also usually a good idea (but not
1145	required if you know what you are doing).	1560	required if you know what you are doing).
1146		1561
1147	If you cannot use non-blocking mode, then force the use of a
1148	known-to-be-good backend (at the time of this writing, this includes only
1149	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1150
1151	Another thing you have to watch out for is that it is quite easy to	1562	Another thing you have to watch out for is that it is quite easy to
1152	receive "spurious" readiness notifications, that is your callback might	1563	receive "spurious" readiness notifications, that is, your callback might
1153	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1564	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1154	because there is no data. Not only are some backends known to create a	1565	because there is no data. It is very easy to get into this situation even
1155	lot of those (for example Solaris ports), it is very easy to get into	1566	with a relatively standard program structure. Thus it is best to always
1156	this situation even with a relatively standard program structure. Thus	1567	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1157	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1158	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1568	preferable to a program hanging until some data arrives.
1159		1569
1160	If you cannot run the fd in non-blocking mode (for example you should	1570	If you cannot run the fd in non-blocking mode (for example you should
1161	not play around with an Xlib connection), then you have to separately	1571	not play around with an Xlib connection), then you have to separately
1162	re-test whether a file descriptor is really ready with a known-to-be good	1572	re-test whether a file descriptor is really ready with a known-to-be good
1163	interface such as poll (fortunately in our Xlib example, Xlib already	1573	interface such as poll (fortunately in the case of Xlib, it already does
1164	does this on its own, so its quite safe to use). Some people additionally	1574	this on its own, so its quite safe to use). Some people additionally
1165	use C<SIGALRM> and an interval timer, just to be sure you won't block	1575	use C<SIGALRM> and an interval timer, just to be sure you won't block
1166	indefinitely.	1576	indefinitely.
1167		1577
1168	But really, best use non-blocking mode.	1578	But really, best use non-blocking mode.
1169		1579
…		…
1197		1607
1198	There is no workaround possible except not registering events	1608	There is no workaround possible except not registering events
1199	for potentially C<dup ()>'ed file descriptors, or to resort to	1609	for potentially C<dup ()>'ed file descriptors, or to resort to
1200	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1610	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1201		1611
		1612	=head3 The special problem of files
		1613
		1614	Many people try to use C<select> (or libev) on file descriptors
		1615	representing files, and expect it to become ready when their program
		1616	doesn't block on disk accesses (which can take a long time on their own).
		1617
		1618	However, this cannot ever work in the "expected" way - you get a readiness
		1619	notification as soon as the kernel knows whether and how much data is
		1620	there, and in the case of open files, that's always the case, so you
		1621	always get a readiness notification instantly, and your read (or possibly
		1622	write) will still block on the disk I/O.
		1623
		1624	Another way to view it is that in the case of sockets, pipes, character
		1625	devices and so on, there is another party (the sender) that delivers data
		1626	on its own, but in the case of files, there is no such thing: the disk
		1627	will not send data on its own, simply because it doesn't know what you
		1628	wish to read - you would first have to request some data.
		1629
		1630	Since files are typically not-so-well supported by advanced notification
		1631	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1632	to files, even though you should not use it. The reason for this is
		1633	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1634	usually a tty, often a pipe, but also sometimes files or special devices
		1635	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1636	F</dev/urandom>), and even though the file might better be served with
		1637	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1638	it "just works" instead of freezing.
		1639
		1640	So avoid file descriptors pointing to files when you know it (e.g. use
		1641	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1642	when you rarely read from a file instead of from a socket, and want to
		1643	reuse the same code path.
		1644
1202	=head3 The special problem of fork	1645	=head3 The special problem of fork
1203		1646
1204	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1647	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1205	useless behaviour. Libev fully supports fork, but needs to be told about	1648	useless behaviour. Libev fully supports fork, but needs to be told about
1206	it in the child.	1649	it in the child if you want to continue to use it in the child.
1207		1650
1208	To support fork in your programs, you either have to call	1651	To support fork in your child processes, you have to call C<ev_loop_fork
1209	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1652	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1210	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1653	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1211	C<EVBACKEND_POLL>.
1212		1654
1213	=head3 The special problem of SIGPIPE	1655	=head3 The special problem of SIGPIPE
1214		1656
1215	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1657	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1216	when writing to a pipe whose other end has been closed, your program gets	1658	when writing to a pipe whose other end has been closed, your program gets
…		…
1219		1661
1220	So when you encounter spurious, unexplained daemon exits, make sure you	1662	So when you encounter spurious, unexplained daemon exits, make sure you
1221	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1663	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1222	somewhere, as that would have given you a big clue).	1664	somewhere, as that would have given you a big clue).
1223		1665
		1666	=head3 The special problem of accept()ing when you can't
		1667
		1668	Many implementations of the POSIX C<accept> function (for example,
		1669	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1670	connection from the pending queue in all error cases.
		1671
		1672	For example, larger servers often run out of file descriptors (because
		1673	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1674	rejecting the connection, leading to libev signalling readiness on
		1675	the next iteration again (the connection still exists after all), and
		1676	typically causing the program to loop at 100% CPU usage.
		1677
		1678	Unfortunately, the set of errors that cause this issue differs between
		1679	operating systems, there is usually little the app can do to remedy the
		1680	situation, and no known thread-safe method of removing the connection to
		1681	cope with overload is known (to me).
		1682
		1683	One of the easiest ways to handle this situation is to just ignore it
		1684	- when the program encounters an overload, it will just loop until the
		1685	situation is over. While this is a form of busy waiting, no OS offers an
		1686	event-based way to handle this situation, so it's the best one can do.
		1687
		1688	A better way to handle the situation is to log any errors other than
		1689	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1690	messages, and continue as usual, which at least gives the user an idea of
		1691	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1692	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1693	usage.
		1694
		1695	If your program is single-threaded, then you could also keep a dummy file
		1696	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1697	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1698	close that fd, and create a new dummy fd. This will gracefully refuse
		1699	clients under typical overload conditions.
		1700
		1701	The last way to handle it is to simply log the error and C<exit>, as
		1702	is often done with C<malloc> failures, but this results in an easy
		1703	opportunity for a DoS attack.
1224		1704
1225	=head3 Watcher-Specific Functions	1705	=head3 Watcher-Specific Functions
1226		1706
1227	=over 4	1707	=over 4
1228		1708
…		…
1249	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1729	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1250	readable, but only once. Since it is likely line-buffered, you could	1730	readable, but only once. Since it is likely line-buffered, you could
1251	attempt to read a whole line in the callback.	1731	attempt to read a whole line in the callback.
1252		1732
1253	static void	1733	static void
1254	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1734	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1255	{	1735	{
1256	ev_io_stop (loop, w);	1736	ev_io_stop (loop, w);
1257	.. read from stdin here (or from w->fd) and handle any I/O errors	1737	.. read from stdin here (or from w->fd) and handle any I/O errors
1258	}	1738	}
1259		1739
1260	...	1740	...
1261	struct ev_loop *loop = ev_default_init (0);	1741	struct ev_loop *loop = ev_default_init (0);
1262	struct ev_io stdin_readable;	1742	ev_io stdin_readable;
1263	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1743	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1264	ev_io_start (loop, &stdin_readable);	1744	ev_io_start (loop, &stdin_readable);
1265	ev_loop (loop, 0);	1745	ev_run (loop, 0);
1266		1746
1267		1747
1268	=head2 C<ev_timer> - relative and optionally repeating timeouts	1748	=head2 C<ev_timer> - relative and optionally repeating timeouts
1269		1749
1270	Timer watchers are simple relative timers that generate an event after a	1750	Timer watchers are simple relative timers that generate an event after a
…		…
1275	year, it will still time out after (roughly) one hour. "Roughly" because	1755	year, it will still time out after (roughly) one hour. "Roughly" because
1276	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1756	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1277	monotonic clock option helps a lot here).	1757	monotonic clock option helps a lot here).
1278		1758
1279	The callback is guaranteed to be invoked only I<after> its timeout has	1759	The callback is guaranteed to be invoked only I<after> its timeout has
1280	passed, but if multiple timers become ready during the same loop iteration	1760	passed (not I<at>, so on systems with very low-resolution clocks this
1281	then order of execution is undefined.	1761	might introduce a small delay). If multiple timers become ready during the
		1762	same loop iteration then the ones with earlier time-out values are invoked
		1763	before ones of the same priority with later time-out values (but this is
		1764	no longer true when a callback calls C<ev_run> recursively).
		1765
		1766	=head3 Be smart about timeouts
		1767
		1768	Many real-world problems involve some kind of timeout, usually for error
		1769	recovery. A typical example is an HTTP request - if the other side hangs,
		1770	you want to raise some error after a while.
		1771
		1772	What follows are some ways to handle this problem, from obvious and
		1773	inefficient to smart and efficient.
		1774
		1775	In the following, a 60 second activity timeout is assumed - a timeout that
		1776	gets reset to 60 seconds each time there is activity (e.g. each time some
		1777	data or other life sign was received).
		1778
		1779	=over 4
		1780
		1781	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1782
		1783	This is the most obvious, but not the most simple way: In the beginning,
		1784	start the watcher:
		1785
		1786	ev_timer_init (timer, callback, 60., 0.);
		1787	ev_timer_start (loop, timer);
		1788
		1789	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1790	and start it again:
		1791
		1792	ev_timer_stop (loop, timer);
		1793	ev_timer_set (timer, 60., 0.);
		1794	ev_timer_start (loop, timer);
		1795
		1796	This is relatively simple to implement, but means that each time there is
		1797	some activity, libev will first have to remove the timer from its internal
		1798	data structure and then add it again. Libev tries to be fast, but it's
		1799	still not a constant-time operation.
		1800
		1801	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1802
		1803	This is the easiest way, and involves using C<ev_timer_again> instead of
		1804	C<ev_timer_start>.
		1805
		1806	To implement this, configure an C<ev_timer> with a C<repeat> value
		1807	of C<60> and then call C<ev_timer_again> at start and each time you
		1808	successfully read or write some data. If you go into an idle state where
		1809	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1810	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1811
		1812	That means you can ignore both the C<ev_timer_start> function and the
		1813	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1814	member and C<ev_timer_again>.
		1815
		1816	At start:
		1817
		1818	ev_init (timer, callback);
		1819	timer->repeat = 60.;
		1820	ev_timer_again (loop, timer);
		1821
		1822	Each time there is some activity:
		1823
		1824	ev_timer_again (loop, timer);
		1825
		1826	It is even possible to change the time-out on the fly, regardless of
		1827	whether the watcher is active or not:
		1828
		1829	timer->repeat = 30.;
		1830	ev_timer_again (loop, timer);
		1831
		1832	This is slightly more efficient then stopping/starting the timer each time
		1833	you want to modify its timeout value, as libev does not have to completely
		1834	remove and re-insert the timer from/into its internal data structure.
		1835
		1836	It is, however, even simpler than the "obvious" way to do it.
		1837
		1838	=item 3. Let the timer time out, but then re-arm it as required.
		1839
		1840	This method is more tricky, but usually most efficient: Most timeouts are
		1841	relatively long compared to the intervals between other activity - in
		1842	our example, within 60 seconds, there are usually many I/O events with
		1843	associated activity resets.
		1844
		1845	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1846	but remember the time of last activity, and check for a real timeout only
		1847	within the callback:
		1848
		1849	ev_tstamp last_activity; // time of last activity
		1850
		1851	static void
		1852	callback (EV_P_ ev_timer *w, int revents)
		1853	{
		1854	ev_tstamp now = ev_now (EV_A);
		1855	ev_tstamp timeout = last_activity + 60.;
		1856
		1857	// if last_activity + 60. is older than now, we did time out
		1858	if (timeout < now)
		1859	{
		1860	// timeout occurred, take action
		1861	}
		1862	else
		1863	{
		1864	// callback was invoked, but there was some activity, re-arm
		1865	// the watcher to fire in last_activity + 60, which is
		1866	// guaranteed to be in the future, so "again" is positive:
		1867	w->repeat = timeout - now;
		1868	ev_timer_again (EV_A_ w);
		1869	}
		1870	}
		1871
		1872	To summarise the callback: first calculate the real timeout (defined
		1873	as "60 seconds after the last activity"), then check if that time has
		1874	been reached, which means something I<did>, in fact, time out. Otherwise
		1875	the callback was invoked too early (C<timeout> is in the future), so
		1876	re-schedule the timer to fire at that future time, to see if maybe we have
		1877	a timeout then.
		1878
		1879	Note how C<ev_timer_again> is used, taking advantage of the
		1880	C<ev_timer_again> optimisation when the timer is already running.
		1881
		1882	This scheme causes more callback invocations (about one every 60 seconds
		1883	minus half the average time between activity), but virtually no calls to
		1884	libev to change the timeout.
		1885
		1886	To start the timer, simply initialise the watcher and set C<last_activity>
		1887	to the current time (meaning we just have some activity :), then call the
		1888	callback, which will "do the right thing" and start the timer:
		1889
		1890	ev_init (timer, callback);
		1891	last_activity = ev_now (loop);
		1892	callback (loop, timer, EV_TIMER);
		1893
		1894	And when there is some activity, simply store the current time in
		1895	C<last_activity>, no libev calls at all:
		1896
		1897	last_activity = ev_now (loop);
		1898
		1899	This technique is slightly more complex, but in most cases where the
		1900	time-out is unlikely to be triggered, much more efficient.
		1901
		1902	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1903	callback :) - just change the timeout and invoke the callback, which will
		1904	fix things for you.
		1905
		1906	=item 4. Wee, just use a double-linked list for your timeouts.
		1907
		1908	If there is not one request, but many thousands (millions...), all
		1909	employing some kind of timeout with the same timeout value, then one can
		1910	do even better:
		1911
		1912	When starting the timeout, calculate the timeout value and put the timeout
		1913	at the I<end> of the list.
		1914
		1915	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1916	the list is expected to fire (for example, using the technique #3).
		1917
		1918	When there is some activity, remove the timer from the list, recalculate
		1919	the timeout, append it to the end of the list again, and make sure to
		1920	update the C<ev_timer> if it was taken from the beginning of the list.
		1921
		1922	This way, one can manage an unlimited number of timeouts in O(1) time for
		1923	starting, stopping and updating the timers, at the expense of a major
		1924	complication, and having to use a constant timeout. The constant timeout
		1925	ensures that the list stays sorted.
		1926
		1927	=back
		1928
		1929	So which method the best?
		1930
		1931	Method #2 is a simple no-brain-required solution that is adequate in most
		1932	situations. Method #3 requires a bit more thinking, but handles many cases
		1933	better, and isn't very complicated either. In most case, choosing either
		1934	one is fine, with #3 being better in typical situations.
		1935
		1936	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1937	rather complicated, but extremely efficient, something that really pays
		1938	off after the first million or so of active timers, i.e. it's usually
		1939	overkill :)
1282		1940
1283	=head3 The special problem of time updates	1941	=head3 The special problem of time updates
1284		1942
1285	Establishing the current time is a costly operation (it usually takes at	1943	Establishing the current time is a costly operation (it usually takes at
1286	least two system calls): EV therefore updates its idea of the current	1944	least two system calls): EV therefore updates its idea of the current
1287	time only before and after C<ev_loop> collects new events, which causes a	1945	time only before and after C<ev_run> collects new events, which causes a
1288	growing difference between C<ev_now ()> and C<ev_time ()> when handling	1946	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1289	lots of events in one iteration.	1947	lots of events in one iteration.
1290		1948
1291	The relative timeouts are calculated relative to the C<ev_now ()>	1949	The relative timeouts are calculated relative to the C<ev_now ()>
1292	time. This is usually the right thing as this timestamp refers to the time	1950	time. This is usually the right thing as this timestamp refers to the time
…		…
1298		1956
1299	If the event loop is suspended for a long time, you can also force an	1957	If the event loop is suspended for a long time, you can also force an
1300	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1958	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1301	()>.	1959	()>.
1302		1960
		1961	=head3 The special problems of suspended animation
		1962
		1963	When you leave the server world it is quite customary to hit machines that
		1964	can suspend/hibernate - what happens to the clocks during such a suspend?
		1965
		1966	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1967	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1968	to run until the system is suspended, but they will not advance while the
		1969	system is suspended. That means, on resume, it will be as if the program
		1970	was frozen for a few seconds, but the suspend time will not be counted
		1971	towards C<ev_timer> when a monotonic clock source is used. The real time
		1972	clock advanced as expected, but if it is used as sole clocksource, then a
		1973	long suspend would be detected as a time jump by libev, and timers would
		1974	be adjusted accordingly.
		1975
		1976	I would not be surprised to see different behaviour in different between
		1977	operating systems, OS versions or even different hardware.
		1978
		1979	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1980	time jump in the monotonic clocks and the realtime clock. If the program
		1981	is suspended for a very long time, and monotonic clock sources are in use,
		1982	then you can expect C<ev_timer>s to expire as the full suspension time
		1983	will be counted towards the timers. When no monotonic clock source is in
		1984	use, then libev will again assume a timejump and adjust accordingly.
		1985
		1986	It might be beneficial for this latter case to call C<ev_suspend>
		1987	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1988	deterministic behaviour in this case (you can do nothing against
		1989	C<SIGSTOP>).
		1990
1303	=head3 Watcher-Specific Functions and Data Members	1991	=head3 Watcher-Specific Functions and Data Members
1304		1992
1305	=over 4	1993	=over 4
1306		1994
1307	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1995	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1330	If the timer is started but non-repeating, stop it (as if it timed out).	2018	If the timer is started but non-repeating, stop it (as if it timed out).
1331		2019
1332	If the timer is repeating, either start it if necessary (with the	2020	If the timer is repeating, either start it if necessary (with the
1333	C<repeat> value), or reset the running timer to the C<repeat> value.	2021	C<repeat> value), or reset the running timer to the C<repeat> value.
1334		2022
1335	This sounds a bit complicated, but here is a useful and typical	2023	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1336	example: Imagine you have a TCP connection and you want a so-called idle	2024	usage example.
1337	timeout, that is, you want to be called when there have been, say, 60
1338	seconds of inactivity on the socket. The easiest way to do this is to
1339	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1340	C<ev_timer_again> each time you successfully read or write some data. If
1341	you go into an idle state where you do not expect data to travel on the
1342	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1343	automatically restart it if need be.
1344		2025
1345	That means you can ignore the C<after> value and C<ev_timer_start>	2026	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1346	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1347		2027
1348	ev_timer_init (timer, callback, 0., 5.);	2028	Returns the remaining time until a timer fires. If the timer is active,
1349	ev_timer_again (loop, timer);	2029	then this time is relative to the current event loop time, otherwise it's
1350	...	2030	the timeout value currently configured.
1351	timer->again = 17.;
1352	ev_timer_again (loop, timer);
1353	...
1354	timer->again = 10.;
1355	ev_timer_again (loop, timer);
1356		2031
1357	This is more slightly efficient then stopping/starting the timer each time	2032	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1358	you want to modify its timeout value.	2033	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
1359		2034	will return C<4>. When the timer expires and is restarted, it will return
1360	Note, however, that it is often even more efficient to remember the	2035	roughly C<7> (likely slightly less as callback invocation takes some time,
1361	time of the last activity and let the timer time-out naturally. In the	2036	too), and so on.
1362	callback, you then check whether the time-out is real, or, if there was
1363	some activity, you reschedule the watcher to time-out in "last_activity +
1364	timeout - ev_now ()" seconds.
1365		2037
1366	=item ev_tstamp repeat [read-write]	2038	=item ev_tstamp repeat [read-write]
1367		2039
1368	The current C<repeat> value. Will be used each time the watcher times out	2040	The current C<repeat> value. Will be used each time the watcher times out
1369	or C<ev_timer_again> is called, and determines the next timeout (if any),	2041	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1374	=head3 Examples	2046	=head3 Examples
1375		2047
1376	Example: Create a timer that fires after 60 seconds.	2048	Example: Create a timer that fires after 60 seconds.
1377		2049
1378	static void	2050	static void
1379	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2051	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1380	{	2052	{
1381	.. one minute over, w is actually stopped right here	2053	.. one minute over, w is actually stopped right here
1382	}	2054	}
1383		2055
1384	struct ev_timer mytimer;	2056	ev_timer mytimer;
1385	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	2057	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1386	ev_timer_start (loop, &mytimer);	2058	ev_timer_start (loop, &mytimer);
1387		2059
1388	Example: Create a timeout timer that times out after 10 seconds of	2060	Example: Create a timeout timer that times out after 10 seconds of
1389	inactivity.	2061	inactivity.
1390		2062
1391	static void	2063	static void
1392	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2064	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1393	{	2065	{
1394	.. ten seconds without any activity	2066	.. ten seconds without any activity
1395	}	2067	}
1396		2068
1397	struct ev_timer mytimer;	2069	ev_timer mytimer;
1398	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2070	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1399	ev_timer_again (&mytimer); /* start timer */	2071	ev_timer_again (&mytimer); /* start timer */
1400	ev_loop (loop, 0);	2072	ev_run (loop, 0);
1401		2073
1402	// and in some piece of code that gets executed on any "activity":	2074	// and in some piece of code that gets executed on any "activity":
1403	// reset the timeout to start ticking again at 10 seconds	2075	// reset the timeout to start ticking again at 10 seconds
1404	ev_timer_again (&mytimer);	2076	ev_timer_again (&mytimer);
1405		2077
…		…
1407	=head2 C<ev_periodic> - to cron or not to cron?	2079	=head2 C<ev_periodic> - to cron or not to cron?
1408		2080
1409	Periodic watchers are also timers of a kind, but they are very versatile	2081	Periodic watchers are also timers of a kind, but they are very versatile
1410	(and unfortunately a bit complex).	2082	(and unfortunately a bit complex).
1411		2083
1412	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2084	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1413	but on wall clock time (absolute time). You can tell a periodic watcher	2085	relative time, the physical time that passes) but on wall clock time
1414	to trigger after some specific point in time. For example, if you tell a	2086	(absolute time, the thing you can read on your calender or clock). The
1415	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	2087	difference is that wall clock time can run faster or slower than real
1416	+ 10.>, that is, an absolute time not a delay) and then reset your system	2088	time, and time jumps are not uncommon (e.g. when you adjust your
1417	clock to January of the previous year, then it will take more than year	2089	wrist-watch).
1418	to trigger the event (unlike an C<ev_timer>, which would still trigger
1419	roughly 10 seconds later as it uses a relative timeout).
1420		2090
		2091	You can tell a periodic watcher to trigger after some specific point
		2092	in time: for example, if you tell a periodic watcher to trigger "in 10
		2093	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2094	not a delay) and then reset your system clock to January of the previous
		2095	year, then it will take a year or more to trigger the event (unlike an
		2096	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2097	it, as it uses a relative timeout).
		2098
1421	C<ev_periodic>s can also be used to implement vastly more complex timers,	2099	C<ev_periodic> watchers can also be used to implement vastly more complex
1422	such as triggering an event on each "midnight, local time", or other	2100	timers, such as triggering an event on each "midnight, local time", or
1423	complicated rules.	2101	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2102	those cannot react to time jumps.
1424		2103
1425	As with timers, the callback is guaranteed to be invoked only when the	2104	As with timers, the callback is guaranteed to be invoked only when the
1426	time (C<at>) has passed, but if multiple periodic timers become ready	2105	point in time where it is supposed to trigger has passed. If multiple
1427	during the same loop iteration, then order of execution is undefined.	2106	timers become ready during the same loop iteration then the ones with
		2107	earlier time-out values are invoked before ones with later time-out values
		2108	(but this is no longer true when a callback calls C<ev_run> recursively).
1428		2109
1429	=head3 Watcher-Specific Functions and Data Members	2110	=head3 Watcher-Specific Functions and Data Members
1430		2111
1431	=over 4	2112	=over 4
1432		2113
1433	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2114	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1434		2115
1435	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2116	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1436		2117
1437	Lots of arguments, lets sort it out... There are basically three modes of	2118	Lots of arguments, let's sort it out... There are basically three modes of
1438	operation, and we will explain them from simplest to most complex:	2119	operation, and we will explain them from simplest to most complex:
1439		2120
1440	=over 4	2121	=over 4
1441		2122
1442	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2123	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1443		2124
1444	In this configuration the watcher triggers an event after the wall clock	2125	In this configuration the watcher triggers an event after the wall clock
1445	time C<at> has passed. It will not repeat and will not adjust when a time	2126	time C<offset> has passed. It will not repeat and will not adjust when a
1446	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2127	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1447	only run when the system clock reaches or surpasses this time.	2128	will be stopped and invoked when the system clock reaches or surpasses
		2129	this point in time.
1448		2130
1449	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2131	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1450		2132
1451	In this mode the watcher will always be scheduled to time out at the next	2133	In this mode the watcher will always be scheduled to time out at the next
1452	C<at + N * interval> time (for some integer N, which can also be negative)	2134	C<offset + N * interval> time (for some integer N, which can also be
1453	and then repeat, regardless of any time jumps.	2135	negative) and then repeat, regardless of any time jumps. The C<offset>
		2136	argument is merely an offset into the C<interval> periods.
1454		2137
1455	This can be used to create timers that do not drift with respect to the	2138	This can be used to create timers that do not drift with respect to the
1456	system clock, for example, here is a C<ev_periodic> that triggers each	2139	system clock, for example, here is an C<ev_periodic> that triggers each
1457	hour, on the hour:	2140	hour, on the hour (with respect to UTC):
1458		2141
1459	ev_periodic_set (&periodic, 0., 3600., 0);	2142	ev_periodic_set (&periodic, 0., 3600., 0);
1460		2143
1461	This doesn't mean there will always be 3600 seconds in between triggers,	2144	This doesn't mean there will always be 3600 seconds in between triggers,
1462	but only that the callback will be called when the system time shows a	2145	but only that the callback will be called when the system time shows a
1463	full hour (UTC), or more correctly, when the system time is evenly divisible	2146	full hour (UTC), or more correctly, when the system time is evenly divisible
1464	by 3600.	2147	by 3600.
1465		2148
1466	Another way to think about it (for the mathematically inclined) is that	2149	Another way to think about it (for the mathematically inclined) is that
1467	C<ev_periodic> will try to run the callback in this mode at the next possible	2150	C<ev_periodic> will try to run the callback in this mode at the next possible
1468	time where C<time = at (mod interval)>, regardless of any time jumps.	2151	time where C<time = offset (mod interval)>, regardless of any time jumps.
1469		2152
1470	For numerical stability it is preferable that the C<at> value is near	2153	For numerical stability it is preferable that the C<offset> value is near
1471	C<ev_now ()> (the current time), but there is no range requirement for	2154	C<ev_now ()> (the current time), but there is no range requirement for
1472	this value, and in fact is often specified as zero.	2155	this value, and in fact is often specified as zero.
1473		2156
1474	Note also that there is an upper limit to how often a timer can fire (CPU	2157	Note also that there is an upper limit to how often a timer can fire (CPU
1475	speed for example), so if C<interval> is very small then timing stability	2158	speed for example), so if C<interval> is very small then timing stability
1476	will of course deteriorate. Libev itself tries to be exact to be about one	2159	will of course deteriorate. Libev itself tries to be exact to be about one
1477	millisecond (if the OS supports it and the machine is fast enough).	2160	millisecond (if the OS supports it and the machine is fast enough).
1478		2161
1479	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2162	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1480		2163
1481	In this mode the values for C<interval> and C<at> are both being	2164	In this mode the values for C<interval> and C<offset> are both being
1482	ignored. Instead, each time the periodic watcher gets scheduled, the	2165	ignored. Instead, each time the periodic watcher gets scheduled, the
1483	reschedule callback will be called with the watcher as first, and the	2166	reschedule callback will be called with the watcher as first, and the
1484	current time as second argument.	2167	current time as second argument.
1485		2168
1486	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2169	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1487	ever, or make ANY event loop modifications whatsoever>.	2170	or make ANY other event loop modifications whatsoever, unless explicitly
		2171	allowed by documentation here>.
1488		2172
1489	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2173	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1490	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2174	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1491	only event loop modification you are allowed to do).	2175	only event loop modification you are allowed to do).
1492		2176
1493	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	2177	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1494	*w, ev_tstamp now)>, e.g.:	2178	*w, ev_tstamp now)>, e.g.:
1495		2179
		2180	static ev_tstamp
1496	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	2181	my_rescheduler (ev_periodic *w, ev_tstamp now)
1497	{	2182	{
1498	return now + 60.;	2183	return now + 60.;
1499	}	2184	}
1500		2185
1501	It must return the next time to trigger, based on the passed time value	2186	It must return the next time to trigger, based on the passed time value
…		…
1521	a different time than the last time it was called (e.g. in a crond like	2206	a different time than the last time it was called (e.g. in a crond like
1522	program when the crontabs have changed).	2207	program when the crontabs have changed).
1523		2208
1524	=item ev_tstamp ev_periodic_at (ev_periodic *)	2209	=item ev_tstamp ev_periodic_at (ev_periodic *)
1525		2210
1526	When active, returns the absolute time that the watcher is supposed to	2211	When active, returns the absolute time that the watcher is supposed
1527	trigger next.	2212	to trigger next. This is not the same as the C<offset> argument to
		2213	C<ev_periodic_set>, but indeed works even in interval and manual
		2214	rescheduling modes.
1528		2215
1529	=item ev_tstamp offset [read-write]	2216	=item ev_tstamp offset [read-write]
1530		2217
1531	When repeating, this contains the offset value, otherwise this is the	2218	When repeating, this contains the offset value, otherwise this is the
1532	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2219	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2220	although libev might modify this value for better numerical stability).
1533		2221
1534	Can be modified any time, but changes only take effect when the periodic	2222	Can be modified any time, but changes only take effect when the periodic
1535	timer fires or C<ev_periodic_again> is being called.	2223	timer fires or C<ev_periodic_again> is being called.
1536		2224
1537	=item ev_tstamp interval [read-write]	2225	=item ev_tstamp interval [read-write]
1538		2226
1539	The current interval value. Can be modified any time, but changes only	2227	The current interval value. Can be modified any time, but changes only
1540	take effect when the periodic timer fires or C<ev_periodic_again> is being	2228	take effect when the periodic timer fires or C<ev_periodic_again> is being
1541	called.	2229	called.
1542		2230
1543	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2231	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1544		2232
1545	The current reschedule callback, or C<0>, if this functionality is	2233	The current reschedule callback, or C<0>, if this functionality is
1546	switched off. Can be changed any time, but changes only take effect when	2234	switched off. Can be changed any time, but changes only take effect when
1547	the periodic timer fires or C<ev_periodic_again> is being called.	2235	the periodic timer fires or C<ev_periodic_again> is being called.
1548		2236
…		…
1553	Example: Call a callback every hour, or, more precisely, whenever the	2241	Example: Call a callback every hour, or, more precisely, whenever the
1554	system time is divisible by 3600. The callback invocation times have	2242	system time is divisible by 3600. The callback invocation times have
1555	potentially a lot of jitter, but good long-term stability.	2243	potentially a lot of jitter, but good long-term stability.
1556		2244
1557	static void	2245	static void
1558	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2246	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1559	{	2247	{
1560	... its now a full hour (UTC, or TAI or whatever your clock follows)	2248	... its now a full hour (UTC, or TAI or whatever your clock follows)
1561	}	2249	}
1562		2250
1563	struct ev_periodic hourly_tick;	2251	ev_periodic hourly_tick;
1564	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2252	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1565	ev_periodic_start (loop, &hourly_tick);	2253	ev_periodic_start (loop, &hourly_tick);
1566		2254
1567	Example: The same as above, but use a reschedule callback to do it:	2255	Example: The same as above, but use a reschedule callback to do it:
1568		2256
1569	#include <math.h>	2257	#include <math.h>
1570		2258
1571	static ev_tstamp	2259	static ev_tstamp
1572	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2260	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1573	{	2261	{
1574	return now + (3600. - fmod (now, 3600.));	2262	return now + (3600. - fmod (now, 3600.));
1575	}	2263	}
1576		2264
1577	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2265	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1578		2266
1579	Example: Call a callback every hour, starting now:	2267	Example: Call a callback every hour, starting now:
1580		2268
1581	struct ev_periodic hourly_tick;	2269	ev_periodic hourly_tick;
1582	ev_periodic_init (&hourly_tick, clock_cb,	2270	ev_periodic_init (&hourly_tick, clock_cb,
1583	fmod (ev_now (loop), 3600.), 3600., 0);	2271	fmod (ev_now (loop), 3600.), 3600., 0);
1584	ev_periodic_start (loop, &hourly_tick);	2272	ev_periodic_start (loop, &hourly_tick);
1585		2273
1586		2274
1587	=head2 C<ev_signal> - signal me when a signal gets signalled!	2275	=head2 C<ev_signal> - signal me when a signal gets signalled!
1588		2276
1589	Signal watchers will trigger an event when the process receives a specific	2277	Signal watchers will trigger an event when the process receives a specific
1590	signal one or more times. Even though signals are very asynchronous, libev	2278	signal one or more times. Even though signals are very asynchronous, libev
1591	will try it's best to deliver signals synchronously, i.e. as part of the	2279	will try its best to deliver signals synchronously, i.e. as part of the
1592	normal event processing, like any other event.	2280	normal event processing, like any other event.
1593		2281
1594	If you want signals asynchronously, just use C<sigaction> as you would	2282	If you want signals to be delivered truly asynchronously, just use
1595	do without libev and forget about sharing the signal. You can even use	2283	C<sigaction> as you would do without libev and forget about sharing
1596	C<ev_async> from a signal handler to synchronously wake up an event loop.	2284	the signal. You can even use C<ev_async> from a signal handler to
		2285	synchronously wake up an event loop.
1597		2286
1598	You can configure as many watchers as you like per signal. Only when the	2287	You can configure as many watchers as you like for the same signal, but
		2288	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2289	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2290	C<SIGINT> in both the default loop and another loop at the same time. At
		2291	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2292
1599	first watcher gets started will libev actually register a signal handler	2293	When the first watcher gets started will libev actually register something
1600	with the kernel (thus it coexists with your own signal handlers as long as	2294	with the kernel (thus it coexists with your own signal handlers as long as
1601	you don't register any with libev for the same signal). Similarly, when	2295	you don't register any with libev for the same signal).
1602	the last signal watcher for a signal is stopped, libev will reset the
1603	signal handler to SIG_DFL (regardless of what it was set to before).
1604		2296
1605	If possible and supported, libev will install its handlers with	2297	If possible and supported, libev will install its handlers with
1606	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2298	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1607	interrupted. If you have a problem with system calls getting interrupted by	2299	not be unduly interrupted. If you have a problem with system calls getting
1608	signals you can block all signals in an C<ev_check> watcher and unblock	2300	interrupted by signals you can block all signals in an C<ev_check> watcher
1609	them in an C<ev_prepare> watcher.	2301	and unblock them in an C<ev_prepare> watcher.
		2302
		2303	=head3 The special problem of inheritance over fork/execve/pthread_create
		2304
		2305	Both the signal mask (C<sigprocmask>) and the signal disposition
		2306	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2307	stopping it again), that is, libev might or might not block the signal,
		2308	and might or might not set or restore the installed signal handler (but
		2309	see C<EVFLAG_NOSIGMASK>).
		2310
		2311	While this does not matter for the signal disposition (libev never
		2312	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2313	C<execve>), this matters for the signal mask: many programs do not expect
		2314	certain signals to be blocked.
		2315
		2316	This means that before calling C<exec> (from the child) you should reset
		2317	the signal mask to whatever "default" you expect (all clear is a good
		2318	choice usually).
		2319
		2320	The simplest way to ensure that the signal mask is reset in the child is
		2321	to install a fork handler with C<pthread_atfork> that resets it. That will
		2322	catch fork calls done by libraries (such as the libc) as well.
		2323
		2324	In current versions of libev, the signal will not be blocked indefinitely
		2325	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2326	the window of opportunity for problems, it will not go away, as libev
		2327	I<has> to modify the signal mask, at least temporarily.
		2328
		2329	So I can't stress this enough: I<If you do not reset your signal mask when
		2330	you expect it to be empty, you have a race condition in your code>. This
		2331	is not a libev-specific thing, this is true for most event libraries.
		2332
		2333	=head3 The special problem of threads signal handling
		2334
		2335	POSIX threads has problematic signal handling semantics, specifically,
		2336	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2337	threads in a process block signals, which is hard to achieve.
		2338
		2339	When you want to use sigwait (or mix libev signal handling with your own
		2340	for the same signals), you can tackle this problem by globally blocking
		2341	all signals before creating any threads (or creating them with a fully set
		2342	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2343	loops. Then designate one thread as "signal receiver thread" which handles
		2344	these signals. You can pass on any signals that libev might be interested
		2345	in by calling C<ev_feed_signal>.
1610		2346
1611	=head3 Watcher-Specific Functions and Data Members	2347	=head3 Watcher-Specific Functions and Data Members
1612		2348
1613	=over 4	2349	=over 4
1614		2350
…		…
1628	=head3 Examples	2364	=head3 Examples
1629		2365
1630	Example: Try to exit cleanly on SIGINT.	2366	Example: Try to exit cleanly on SIGINT.
1631		2367
1632	static void	2368	static void
1633	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2369	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1634	{	2370	{
1635	ev_unloop (loop, EVUNLOOP_ALL);	2371	ev_break (loop, EVBREAK_ALL);
1636	}	2372	}
1637		2373
1638	struct ev_signal signal_watcher;	2374	ev_signal signal_watcher;
1639	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2375	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1640	ev_signal_start (loop, &signal_watcher);	2376	ev_signal_start (loop, &signal_watcher);
1641		2377
1642		2378
1643	=head2 C<ev_child> - watch out for process status changes	2379	=head2 C<ev_child> - watch out for process status changes
…		…
1646	some child status changes (most typically when a child of yours dies or	2382	some child status changes (most typically when a child of yours dies or
1647	exits). It is permissible to install a child watcher I<after> the child	2383	exits). It is permissible to install a child watcher I<after> the child
1648	has been forked (which implies it might have already exited), as long	2384	has been forked (which implies it might have already exited), as long
1649	as the event loop isn't entered (or is continued from a watcher), i.e.,	2385	as the event loop isn't entered (or is continued from a watcher), i.e.,
1650	forking and then immediately registering a watcher for the child is fine,	2386	forking and then immediately registering a watcher for the child is fine,
1651	but forking and registering a watcher a few event loop iterations later is	2387	but forking and registering a watcher a few event loop iterations later or
1652	not.	2388	in the next callback invocation is not.
1653		2389
1654	Only the default event loop is capable of handling signals, and therefore	2390	Only the default event loop is capable of handling signals, and therefore
1655	you can only register child watchers in the default event loop.	2391	you can only register child watchers in the default event loop.
1656		2392
		2393	Due to some design glitches inside libev, child watchers will always be
		2394	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2395	libev)
		2396
1657	=head3 Process Interaction	2397	=head3 Process Interaction
1658		2398
1659	Libev grabs C<SIGCHLD> as soon as the default event loop is	2399	Libev grabs C<SIGCHLD> as soon as the default event loop is
1660	initialised. This is necessary to guarantee proper behaviour even if	2400	initialised. This is necessary to guarantee proper behaviour even if the
1661	the first child watcher is started after the child exits. The occurrence	2401	first child watcher is started after the child exits. The occurrence
1662	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2402	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1663	synchronously as part of the event loop processing. Libev always reaps all	2403	synchronously as part of the event loop processing. Libev always reaps all
1664	children, even ones not watched.	2404	children, even ones not watched.
1665		2405
1666	=head3 Overriding the Built-In Processing	2406	=head3 Overriding the Built-In Processing
…		…
1676	=head3 Stopping the Child Watcher	2416	=head3 Stopping the Child Watcher
1677		2417
1678	Currently, the child watcher never gets stopped, even when the	2418	Currently, the child watcher never gets stopped, even when the
1679	child terminates, so normally one needs to stop the watcher in the	2419	child terminates, so normally one needs to stop the watcher in the
1680	callback. Future versions of libev might stop the watcher automatically	2420	callback. Future versions of libev might stop the watcher automatically
1681	when a child exit is detected.	2421	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2422	problem).
1682		2423
1683	=head3 Watcher-Specific Functions and Data Members	2424	=head3 Watcher-Specific Functions and Data Members
1684		2425
1685	=over 4	2426	=over 4
1686		2427
…		…
1718	its completion.	2459	its completion.
1719		2460
1720	ev_child cw;	2461	ev_child cw;
1721		2462
1722	static void	2463	static void
1723	child_cb (EV_P_ struct ev_child *w, int revents)	2464	child_cb (EV_P_ ev_child *w, int revents)
1724	{	2465	{
1725	ev_child_stop (EV_A_ w);	2466	ev_child_stop (EV_A_ w);
1726	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2467	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1727	}	2468	}
1728		2469
…		…
1743		2484
1744		2485
1745	=head2 C<ev_stat> - did the file attributes just change?	2486	=head2 C<ev_stat> - did the file attributes just change?
1746		2487
1747	This watches a file system path for attribute changes. That is, it calls	2488	This watches a file system path for attribute changes. That is, it calls
1748	C<stat> regularly (or when the OS says it changed) and sees if it changed	2489	C<stat> on that path in regular intervals (or when the OS says it changed)
1749	compared to the last time, invoking the callback if it did.	2490	and sees if it changed compared to the last time, invoking the callback if
		2491	it did.
1750		2492
1751	The path does not need to exist: changing from "path exists" to "path does	2493	The path does not need to exist: changing from "path exists" to "path does
1752	not exist" is a status change like any other. The condition "path does	2494	not exist" is a status change like any other. The condition "path does not
1753	not exist" is signified by the C<st_nlink> field being zero (which is	2495	exist" (or more correctly "path cannot be stat'ed") is signified by the
1754	otherwise always forced to be at least one) and all the other fields of	2496	C<st_nlink> field being zero (which is otherwise always forced to be at
1755	the stat buffer having unspecified contents.	2497	least one) and all the other fields of the stat buffer having unspecified
		2498	contents.
1756		2499
1757	The path I<should> be absolute and I<must not> end in a slash. If it is	2500	The path I<must not> end in a slash or contain special components such as
		2501	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1758	relative and your working directory changes, the behaviour is undefined.	2502	your working directory changes, then the behaviour is undefined.
1759		2503
1760	Since there is no standard kernel interface to do this, the portable	2504	Since there is no portable change notification interface available, the
1761	implementation simply calls C<stat (2)> regularly on the path to see if	2505	portable implementation simply calls C<stat(2)> regularly on the path
1762	it changed somehow. You can specify a recommended polling interval for	2506	to see if it changed somehow. You can specify a recommended polling
1763	this case. If you specify a polling interval of C<0> (highly recommended!)	2507	interval for this case. If you specify a polling interval of C<0> (highly
1764	then a I<suitable, unspecified default> value will be used (which	2508	recommended!) then a I<suitable, unspecified default> value will be used
1765	you can expect to be around five seconds, although this might change	2509	(which you can expect to be around five seconds, although this might
1766	dynamically). Libev will also impose a minimum interval which is currently	2510	change dynamically). Libev will also impose a minimum interval which is
1767	around C<0.1>, but thats usually overkill.	2511	currently around C<0.1>, but that's usually overkill.
1768		2512
1769	This watcher type is not meant for massive numbers of stat watchers,	2513	This watcher type is not meant for massive numbers of stat watchers,
1770	as even with OS-supported change notifications, this can be	2514	as even with OS-supported change notifications, this can be
1771	resource-intensive.	2515	resource-intensive.
1772		2516
1773	At the time of this writing, the only OS-specific interface implemented	2517	At the time of this writing, the only OS-specific interface implemented
1774	is the Linux inotify interface (implementing kqueue support is left as	2518	is the Linux inotify interface (implementing kqueue support is left as an
1775	an exercise for the reader. Note, however, that the author sees no way	2519	exercise for the reader. Note, however, that the author sees no way of
1776	of implementing C<ev_stat> semantics with kqueue).	2520	implementing C<ev_stat> semantics with kqueue, except as a hint).
1777		2521
1778	=head3 ABI Issues (Largefile Support)	2522	=head3 ABI Issues (Largefile Support)
1779		2523
1780	Libev by default (unless the user overrides this) uses the default	2524	Libev by default (unless the user overrides this) uses the default
1781	compilation environment, which means that on systems with large file	2525	compilation environment, which means that on systems with large file
1782	support disabled by default, you get the 32 bit version of the stat	2526	support disabled by default, you get the 32 bit version of the stat
1783	structure. When using the library from programs that change the ABI to	2527	structure. When using the library from programs that change the ABI to
1784	use 64 bit file offsets the programs will fail. In that case you have to	2528	use 64 bit file offsets the programs will fail. In that case you have to
1785	compile libev with the same flags to get binary compatibility. This is	2529	compile libev with the same flags to get binary compatibility. This is
1786	obviously the case with any flags that change the ABI, but the problem is	2530	obviously the case with any flags that change the ABI, but the problem is
1787	most noticeably disabled with ev_stat and large file support.	2531	most noticeably displayed with ev_stat and large file support.
1788		2532
1789	The solution for this is to lobby your distribution maker to make large	2533	The solution for this is to lobby your distribution maker to make large
1790	file interfaces available by default (as e.g. FreeBSD does) and not	2534	file interfaces available by default (as e.g. FreeBSD does) and not
1791	optional. Libev cannot simply switch on large file support because it has	2535	optional. Libev cannot simply switch on large file support because it has
1792	to exchange stat structures with application programs compiled using the	2536	to exchange stat structures with application programs compiled using the
1793	default compilation environment.	2537	default compilation environment.
1794		2538
1795	=head3 Inotify and Kqueue	2539	=head3 Inotify and Kqueue
1796		2540
1797	When C<inotify (7)> support has been compiled into libev (generally only	2541	When C<inotify (7)> support has been compiled into libev and present at
1798	available with Linux) and present at runtime, it will be used to speed up	2542	runtime, it will be used to speed up change detection where possible. The
1799	change detection where possible. The inotify descriptor will be created lazily	2543	inotify descriptor will be created lazily when the first C<ev_stat>
1800	when the first C<ev_stat> watcher is being started.	2544	watcher is being started.
1801		2545
1802	Inotify presence does not change the semantics of C<ev_stat> watchers	2546	Inotify presence does not change the semantics of C<ev_stat> watchers
1803	except that changes might be detected earlier, and in some cases, to avoid	2547	except that changes might be detected earlier, and in some cases, to avoid
1804	making regular C<stat> calls. Even in the presence of inotify support	2548	making regular C<stat> calls. Even in the presence of inotify support
1805	there are many cases where libev has to resort to regular C<stat> polling,	2549	there are many cases where libev has to resort to regular C<stat> polling,
1806	but as long as the path exists, libev usually gets away without polling.	2550	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2551	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2552	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2553	xfs are fully working) libev usually gets away without polling.
1807		2554
1808	There is no support for kqueue, as apparently it cannot be used to	2555	There is no support for kqueue, as apparently it cannot be used to
1809	implement this functionality, due to the requirement of having a file	2556	implement this functionality, due to the requirement of having a file
1810	descriptor open on the object at all times, and detecting renames, unlinks	2557	descriptor open on the object at all times, and detecting renames, unlinks
1811	etc. is difficult.	2558	etc. is difficult.
1812		2559
		2560	=head3 C<stat ()> is a synchronous operation
		2561
		2562	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2563	the process. The exception are C<ev_stat> watchers - those call C<stat
		2564	()>, which is a synchronous operation.
		2565
		2566	For local paths, this usually doesn't matter: unless the system is very
		2567	busy or the intervals between stat's are large, a stat call will be fast,
		2568	as the path data is usually in memory already (except when starting the
		2569	watcher).
		2570
		2571	For networked file systems, calling C<stat ()> can block an indefinite
		2572	time due to network issues, and even under good conditions, a stat call
		2573	often takes multiple milliseconds.
		2574
		2575	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2576	paths, although this is fully supported by libev.
		2577
1813	=head3 The special problem of stat time resolution	2578	=head3 The special problem of stat time resolution
1814		2579
1815	The C<stat ()> system call only supports full-second resolution portably, and	2580	The C<stat ()> system call only supports full-second resolution portably,
1816	even on systems where the resolution is higher, most file systems still	2581	and even on systems where the resolution is higher, most file systems
1817	only support whole seconds.	2582	still only support whole seconds.
1818		2583
1819	That means that, if the time is the only thing that changes, you can	2584	That means that, if the time is the only thing that changes, you can
1820	easily miss updates: on the first update, C<ev_stat> detects a change and	2585	easily miss updates: on the first update, C<ev_stat> detects a change and
1821	calls your callback, which does something. When there is another update	2586	calls your callback, which does something. When there is another update
1822	within the same second, C<ev_stat> will be unable to detect unless the	2587	within the same second, C<ev_stat> will be unable to detect unless the
…		…
1965		2730
1966	=head3 Watcher-Specific Functions and Data Members	2731	=head3 Watcher-Specific Functions and Data Members
1967		2732
1968	=over 4	2733	=over 4
1969		2734
1970	=item ev_idle_init (ev_signal *, callback)	2735	=item ev_idle_init (ev_idle *, callback)
1971		2736
1972	Initialises and configures the idle watcher - it has no parameters of any	2737	Initialises and configures the idle watcher - it has no parameters of any
1973	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2738	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1974	believe me.	2739	believe me.
1975		2740
…		…
1979		2744
1980	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2745	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1981	callback, free it. Also, use no error checking, as usual.	2746	callback, free it. Also, use no error checking, as usual.
1982		2747
1983	static void	2748	static void
1984	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2749	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1985	{	2750	{
1986	free (w);	2751	free (w);
1987	// now do something you wanted to do when the program has	2752	// now do something you wanted to do when the program has
1988	// no longer anything immediate to do.	2753	// no longer anything immediate to do.
1989	}	2754	}
1990		2755
1991	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2756	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1992	ev_idle_init (idle_watcher, idle_cb);	2757	ev_idle_init (idle_watcher, idle_cb);
1993	ev_idle_start (loop, idle_cb);	2758	ev_idle_start (loop, idle_watcher);
1994		2759
1995		2760
1996	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2761	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1997		2762
1998	Prepare and check watchers are usually (but not always) used in pairs:	2763	Prepare and check watchers are usually (but not always) used in pairs:
1999	prepare watchers get invoked before the process blocks and check watchers	2764	prepare watchers get invoked before the process blocks and check watchers
2000	afterwards.	2765	afterwards.
2001		2766
2002	You I<must not> call C<ev_loop> or similar functions that enter	2767	You I<must not> call C<ev_run> or similar functions that enter
2003	the current event loop from either C<ev_prepare> or C<ev_check>	2768	the current event loop from either C<ev_prepare> or C<ev_check>
2004	watchers. Other loops than the current one are fine, however. The	2769	watchers. Other loops than the current one are fine, however. The
2005	rationale behind this is that you do not need to check for recursion in	2770	rationale behind this is that you do not need to check for recursion in
2006	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2771	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2007	C<ev_check> so if you have one watcher of each kind they will always be	2772	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2077		2842
2078	static ev_io iow [nfd];	2843	static ev_io iow [nfd];
2079	static ev_timer tw;	2844	static ev_timer tw;
2080		2845
2081	static void	2846	static void
2082	io_cb (ev_loop *loop, ev_io *w, int revents)	2847	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2083	{	2848	{
2084	}	2849	}
2085		2850
2086	// create io watchers for each fd and a timer before blocking	2851	// create io watchers for each fd and a timer before blocking
2087	static void	2852	static void
2088	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2853	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2089	{	2854	{
2090	int timeout = 3600000;	2855	int timeout = 3600000;
2091	struct pollfd fds [nfd];	2856	struct pollfd fds [nfd];
2092	// actual code will need to loop here and realloc etc.	2857	// actual code will need to loop here and realloc etc.
2093	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2858	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2094		2859
2095	/* the callback is illegal, but won't be called as we stop during check */	2860	/* the callback is illegal, but won't be called as we stop during check */
2096	ev_timer_init (&tw, 0, timeout * 1e-3);	2861	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2097	ev_timer_start (loop, &tw);	2862	ev_timer_start (loop, &tw);
2098		2863
2099	// create one ev_io per pollfd	2864	// create one ev_io per pollfd
2100	for (int i = 0; i < nfd; ++i)	2865	for (int i = 0; i < nfd; ++i)
2101	{	2866	{
…		…
2108	}	2873	}
2109	}	2874	}
2110		2875
2111	// stop all watchers after blocking	2876	// stop all watchers after blocking
2112	static void	2877	static void
2113	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2878	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2114	{	2879	{
2115	ev_timer_stop (loop, &tw);	2880	ev_timer_stop (loop, &tw);
2116		2881
2117	for (int i = 0; i < nfd; ++i)	2882	for (int i = 0; i < nfd; ++i)
2118	{	2883	{
…		…
2175		2940
2176	if (timeout >= 0)	2941	if (timeout >= 0)
2177	// create/start timer	2942	// create/start timer
2178		2943
2179	// poll	2944	// poll
2180	ev_loop (EV_A_ 0);	2945	ev_run (EV_A_ 0);
2181		2946
2182	// stop timer again	2947	// stop timer again
2183	if (timeout >= 0)	2948	if (timeout >= 0)
2184	ev_timer_stop (EV_A_ &to);	2949	ev_timer_stop (EV_A_ &to);
2185		2950
…		…
2214	some fds have to be watched and handled very quickly (with low latency),	2979	some fds have to be watched and handled very quickly (with low latency),
2215	and even priorities and idle watchers might have too much overhead. In	2980	and even priorities and idle watchers might have too much overhead. In
2216	this case you would put all the high priority stuff in one loop and all	2981	this case you would put all the high priority stuff in one loop and all
2217	the rest in a second one, and embed the second one in the first.	2982	the rest in a second one, and embed the second one in the first.
2218		2983
2219	As long as the watcher is active, the callback will be invoked every time	2984	As long as the watcher is active, the callback will be invoked every
2220	there might be events pending in the embedded loop. The callback must then	2985	time there might be events pending in the embedded loop. The callback
2221	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2986	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2222	their callbacks (you could also start an idle watcher to give the embedded	2987	sweep and invoke their callbacks (the callback doesn't need to invoke the
2223	loop strictly lower priority for example). You can also set the callback	2988	C<ev_embed_sweep> function directly, it could also start an idle watcher
2224	to C<0>, in which case the embed watcher will automatically execute the	2989	to give the embedded loop strictly lower priority for example).
2225	embedded loop sweep.
2226		2990
2227	As long as the watcher is started it will automatically handle events. The	2991	You can also set the callback to C<0>, in which case the embed watcher
2228	callback will be invoked whenever some events have been handled. You can	2992	will automatically execute the embedded loop sweep whenever necessary.
2229	set the callback to C<0> to avoid having to specify one if you are not
2230	interested in that.
2231		2993
2232	Also, there have not currently been made special provisions for forking:	2994	Fork detection will be handled transparently while the C<ev_embed> watcher
2233	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2995	is active, i.e., the embedded loop will automatically be forked when the
2234	but you will also have to stop and restart any C<ev_embed> watchers	2996	embedding loop forks. In other cases, the user is responsible for calling
2235	yourself - but you can use a fork watcher to handle this automatically,	2997	C<ev_loop_fork> on the embedded loop.
2236	and future versions of libev might do just that.
2237		2998
2238	Unfortunately, not all backends are embeddable: only the ones returned by	2999	Unfortunately, not all backends are embeddable: only the ones returned by
2239	C<ev_embeddable_backends> are, which, unfortunately, does not include any	3000	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2240	portable one.	3001	portable one.
2241		3002
…		…
2267	if you do not want that, you need to temporarily stop the embed watcher).	3028	if you do not want that, you need to temporarily stop the embed watcher).
2268		3029
2269	=item ev_embed_sweep (loop, ev_embed *)	3030	=item ev_embed_sweep (loop, ev_embed *)
2270		3031
2271	Make a single, non-blocking sweep over the embedded loop. This works	3032	Make a single, non-blocking sweep over the embedded loop. This works
2272	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3033	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2273	appropriate way for embedded loops.	3034	appropriate way for embedded loops.
2274		3035
2275	=item struct ev_loop *other [read-only]	3036	=item struct ev_loop *other [read-only]
2276		3037
2277	The embedded event loop.	3038	The embedded event loop.
…		…
2286	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	3047	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2287	used).	3048	used).
2288		3049
2289	struct ev_loop *loop_hi = ev_default_init (0);	3050	struct ev_loop *loop_hi = ev_default_init (0);
2290	struct ev_loop *loop_lo = 0;	3051	struct ev_loop *loop_lo = 0;
2291	struct ev_embed embed;	3052	ev_embed embed;
2292		3053
2293	// see if there is a chance of getting one that works	3054	// see if there is a chance of getting one that works
2294	// (remember that a flags value of 0 means autodetection)	3055	// (remember that a flags value of 0 means autodetection)
2295	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3056	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2296	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3057	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2310	kqueue implementation). Store the kqueue/socket-only event loop in	3071	kqueue implementation). Store the kqueue/socket-only event loop in
2311	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3072	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2312		3073
2313	struct ev_loop *loop = ev_default_init (0);	3074	struct ev_loop *loop = ev_default_init (0);
2314	struct ev_loop *loop_socket = 0;	3075	struct ev_loop *loop_socket = 0;
2315	struct ev_embed embed;	3076	ev_embed embed;
2316		3077
2317	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3078	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2318	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3079	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2319	{	3080	{
2320	ev_embed_init (&embed, 0, loop_socket);	3081	ev_embed_init (&embed, 0, loop_socket);
…		…
2335	event loop blocks next and before C<ev_check> watchers are being called,	3096	event loop blocks next and before C<ev_check> watchers are being called,
2336	and only in the child after the fork. If whoever good citizen calling	3097	and only in the child after the fork. If whoever good citizen calling
2337	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3098	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2338	handlers will be invoked, too, of course.	3099	handlers will be invoked, too, of course.
2339		3100
		3101	=head3 The special problem of life after fork - how is it possible?
		3102
		3103	Most uses of C<fork()> consist of forking, then some simple calls to set
		3104	up/change the process environment, followed by a call to C<exec()>. This
		3105	sequence should be handled by libev without any problems.
		3106
		3107	This changes when the application actually wants to do event handling
		3108	in the child, or both parent in child, in effect "continuing" after the
		3109	fork.
		3110
		3111	The default mode of operation (for libev, with application help to detect
		3112	forks) is to duplicate all the state in the child, as would be expected
		3113	when I<either> the parent I<or> the child process continues.
		3114
		3115	When both processes want to continue using libev, then this is usually the
		3116	wrong result. In that case, usually one process (typically the parent) is
		3117	supposed to continue with all watchers in place as before, while the other
		3118	process typically wants to start fresh, i.e. without any active watchers.
		3119
		3120	The cleanest and most efficient way to achieve that with libev is to
		3121	simply create a new event loop, which of course will be "empty", and
		3122	use that for new watchers. This has the advantage of not touching more
		3123	memory than necessary, and thus avoiding the copy-on-write, and the
		3124	disadvantage of having to use multiple event loops (which do not support
		3125	signal watchers).
		3126
		3127	When this is not possible, or you want to use the default loop for
		3128	other reasons, then in the process that wants to start "fresh", call
		3129	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3130	Destroying the default loop will "orphan" (not stop) all registered
		3131	watchers, so you have to be careful not to execute code that modifies
		3132	those watchers. Note also that in that case, you have to re-register any
		3133	signal watchers.
		3134
2340	=head3 Watcher-Specific Functions and Data Members	3135	=head3 Watcher-Specific Functions and Data Members
2341		3136
2342	=over 4	3137	=over 4
2343		3138
2344	=item ev_fork_init (ev_signal *, callback)	3139	=item ev_fork_init (ev_fork *, callback)
2345		3140
2346	Initialises and configures the fork watcher - it has no parameters of any	3141	Initialises and configures the fork watcher - it has no parameters of any
2347	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3142	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2348	believe me.	3143	really.
2349		3144
2350	=back	3145	=back
2351		3146
2352		3147
		3148	=head2 C<ev_cleanup> - even the best things end
		3149
		3150	Cleanup watchers are called just before the event loop is being destroyed
		3151	by a call to C<ev_loop_destroy>.
		3152
		3153	While there is no guarantee that the event loop gets destroyed, cleanup
		3154	watchers provide a convenient method to install cleanup hooks for your
		3155	program, worker threads and so on - you just to make sure to destroy the
		3156	loop when you want them to be invoked.
		3157
		3158	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3159	all other watchers, they do not keep a reference to the event loop (which
		3160	makes a lot of sense if you think about it). Like all other watchers, you
		3161	can call libev functions in the callback, except C<ev_cleanup_start>.
		3162
		3163	=head3 Watcher-Specific Functions and Data Members
		3164
		3165	=over 4
		3166
		3167	=item ev_cleanup_init (ev_cleanup *, callback)
		3168
		3169	Initialises and configures the cleanup watcher - it has no parameters of
		3170	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3171	pointless, I assure you.
		3172
		3173	=back
		3174
		3175	Example: Register an atexit handler to destroy the default loop, so any
		3176	cleanup functions are called.
		3177
		3178	static void
		3179	program_exits (void)
		3180	{
		3181	ev_loop_destroy (EV_DEFAULT_UC);
		3182	}
		3183
		3184	...
		3185	atexit (program_exits);
		3186
		3187
2353	=head2 C<ev_async> - how to wake up another event loop	3188	=head2 C<ev_async> - how to wake up an event loop
2354		3189
2355	In general, you cannot use an C<ev_loop> from multiple threads or other	3190	In general, you cannot use an C<ev_run> from multiple threads or other
2356	asynchronous sources such as signal handlers (as opposed to multiple event	3191	asynchronous sources such as signal handlers (as opposed to multiple event
2357	loops - those are of course safe to use in different threads).	3192	loops - those are of course safe to use in different threads).
2358		3193
2359	Sometimes, however, you need to wake up another event loop you do not	3194	Sometimes, however, you need to wake up an event loop you do not control,
2360	control, for example because it belongs to another thread. This is what	3195	for example because it belongs to another thread. This is what C<ev_async>
2361	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3196	watchers do: as long as the C<ev_async> watcher is active, you can signal
2362	can signal it by calling C<ev_async_send>, which is thread- and signal	3197	it by calling C<ev_async_send>, which is thread- and signal safe.
2363	safe.
2364		3198
2365	This functionality is very similar to C<ev_signal> watchers, as signals,	3199	This functionality is very similar to C<ev_signal> watchers, as signals,
2366	too, are asynchronous in nature, and signals, too, will be compressed	3200	too, are asynchronous in nature, and signals, too, will be compressed
2367	(i.e. the number of callback invocations may be less than the number of	3201	(i.e. the number of callback invocations may be less than the number of
2368	C<ev_async_sent> calls).	3202	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
		3203	of "global async watchers" by using a watcher on an otherwise unused
		3204	signal, and C<ev_feed_signal> to signal this watcher from another thread,
		3205	even without knowing which loop owns the signal.
2369		3206
2370	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3207	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
2371	just the default loop.	3208	just the default loop.
2372		3209
2373	=head3 Queueing	3210	=head3 Queueing
2374		3211
2375	C<ev_async> does not support queueing of data in any way. The reason	3212	C<ev_async> does not support queueing of data in any way. The reason
2376	is that the author does not know of a simple (or any) algorithm for a	3213	is that the author does not know of a simple (or any) algorithm for a
2377	multiple-writer-single-reader queue that works in all cases and doesn't	3214	multiple-writer-single-reader queue that works in all cases and doesn't
2378	need elaborate support such as pthreads.	3215	need elaborate support such as pthreads or unportable memory access
		3216	semantics.
2379		3217
2380	That means that if you want to queue data, you have to provide your own	3218	That means that if you want to queue data, you have to provide your own
2381	queue. But at least I can tell you how to implement locking around your	3219	queue. But at least I can tell you how to implement locking around your
2382	queue:	3220	queue:
2383		3221
2384	=over 4	3222	=over 4
2385		3223
2386	=item queueing from a signal handler context	3224	=item queueing from a signal handler context
2387		3225
2388	To implement race-free queueing, you simply add to the queue in the signal	3226	To implement race-free queueing, you simply add to the queue in the signal
2389	handler but you block the signal handler in the watcher callback. Here is an example that does that for	3227	handler but you block the signal handler in the watcher callback. Here is
2390	some fictitious SIGUSR1 handler:	3228	an example that does that for some fictitious SIGUSR1 handler:
2391		3229
2392	static ev_async mysig;	3230	static ev_async mysig;
2393		3231
2394	static void	3232	static void
2395	sigusr1_handler (void)	3233	sigusr1_handler (void)
…		…
2461	=over 4	3299	=over 4
2462		3300
2463	=item ev_async_init (ev_async *, callback)	3301	=item ev_async_init (ev_async *, callback)
2464		3302
2465	Initialises and configures the async watcher - it has no parameters of any	3303	Initialises and configures the async watcher - it has no parameters of any
2466	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3304	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2467	trust me.	3305	trust me.
2468		3306
2469	=item ev_async_send (loop, ev_async *)	3307	=item ev_async_send (loop, ev_async *)
2470		3308
2471	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3309	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2472	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3310	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2473	C<ev_feed_event>, this call is safe to do from other threads, signal or	3311	C<ev_feed_event>, this call is safe to do from other threads, signal or
2474	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3312	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2475	section below on what exactly this means).	3313	section below on what exactly this means).
2476		3314
		3315	Note that, as with other watchers in libev, multiple events might get
		3316	compressed into a single callback invocation (another way to look at this
		3317	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3318	reset when the event loop detects that).
		3319
2477	This call incurs the overhead of a system call only once per loop iteration,	3320	This call incurs the overhead of a system call only once per event loop
2478	so while the overhead might be noticeable, it doesn't apply to repeated	3321	iteration, so while the overhead might be noticeable, it doesn't apply to
2479	calls to C<ev_async_send>.	3322	repeated calls to C<ev_async_send> for the same event loop.
2480		3323
2481	=item bool = ev_async_pending (ev_async *)	3324	=item bool = ev_async_pending (ev_async *)
2482		3325
2483	Returns a non-zero value when C<ev_async_send> has been called on the	3326	Returns a non-zero value when C<ev_async_send> has been called on the
2484	watcher but the event has not yet been processed (or even noted) by the	3327	watcher but the event has not yet been processed (or even noted) by the
…		…
2487	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3330	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2488	the loop iterates next and checks for the watcher to have become active,	3331	the loop iterates next and checks for the watcher to have become active,
2489	it will reset the flag again. C<ev_async_pending> can be used to very	3332	it will reset the flag again. C<ev_async_pending> can be used to very
2490	quickly check whether invoking the loop might be a good idea.	3333	quickly check whether invoking the loop might be a good idea.
2491		3334
2492	Not that this does I<not> check whether the watcher itself is pending, only	3335	Not that this does I<not> check whether the watcher itself is pending,
2493	whether it has been requested to make this watcher pending.	3336	only whether it has been requested to make this watcher pending: there
		3337	is a time window between the event loop checking and resetting the async
		3338	notification, and the callback being invoked.
2494		3339
2495	=back	3340	=back
2496		3341
2497		3342
2498	=head1 OTHER FUNCTIONS	3343	=head1 OTHER FUNCTIONS
…		…
2502	=over 4	3347	=over 4
2503		3348
2504	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3349	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2505		3350
2506	This function combines a simple timer and an I/O watcher, calls your	3351	This function combines a simple timer and an I/O watcher, calls your
2507	callback on whichever event happens first and automatically stop both	3352	callback on whichever event happens first and automatically stops both
2508	watchers. This is useful if you want to wait for a single event on an fd	3353	watchers. This is useful if you want to wait for a single event on an fd
2509	or timeout without having to allocate/configure/start/stop/free one or	3354	or timeout without having to allocate/configure/start/stop/free one or
2510	more watchers yourself.	3355	more watchers yourself.
2511		3356
2512	If C<fd> is less than 0, then no I/O watcher will be started and events	3357	If C<fd> is less than 0, then no I/O watcher will be started and the
2513	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	3358	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2514	C<events> set will be created and started.	3359	the given C<fd> and C<events> set will be created and started.
2515		3360
2516	If C<timeout> is less than 0, then no timeout watcher will be	3361	If C<timeout> is less than 0, then no timeout watcher will be
2517	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3362	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2518	repeat = 0) will be started. While C<0> is a valid timeout, it is of	3363	repeat = 0) will be started. C<0> is a valid timeout.
2519	dubious value.
2520		3364
2521	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3365	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2522	passed an C<revents> set like normal event callbacks (a combination of	3366	passed an C<revents> set like normal event callbacks (a combination of
2523	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3367	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2524	value passed to C<ev_once>:	3368	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3369	a timeout and an io event at the same time - you probably should give io
		3370	events precedence.
		3371
		3372	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2525		3373
2526	static void stdin_ready (int revents, void *arg)	3374	static void stdin_ready (int revents, void *arg)
2527	{	3375	{
		3376	if (revents & EV_READ)
		3377	/* stdin might have data for us, joy! */;
2528	if (revents & EV_TIMEOUT)	3378	else if (revents & EV_TIMER)
2529	/* doh, nothing entered */;	3379	/* doh, nothing entered */;
2530	else if (revents & EV_READ)
2531	/* stdin might have data for us, joy! */;
2532	}	3380	}
2533		3381
2534	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3382	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2535		3383
2536	=item ev_feed_event (ev_loop *, watcher *, int revents)
2537
2538	Feeds the given event set into the event loop, as if the specified event
2539	had happened for the specified watcher (which must be a pointer to an
2540	initialised but not necessarily started event watcher).
2541
2542	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3384	=item ev_feed_fd_event (loop, int fd, int revents)
2543		3385
2544	Feed an event on the given fd, as if a file descriptor backend detected	3386	Feed an event on the given fd, as if a file descriptor backend detected
2545	the given events it.	3387	the given events it.
2546		3388
2547	=item ev_feed_signal_event (ev_loop *loop, int signum)	3389	=item ev_feed_signal_event (loop, int signum)
2548		3390
2549	Feed an event as if the given signal occurred (C<loop> must be the default	3391	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
2550	loop!).	3392	which is async-safe.
2551		3393
2552	=back	3394	=back
		3395
		3396
		3397	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3398
		3399	This section explains some common idioms that are not immediately
		3400	obvious. Note that examples are sprinkled over the whole manual, and this
		3401	section only contains stuff that wouldn't fit anywhere else.
		3402
		3403	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3404
		3405	Each watcher has, by default, a C<void *data> member that you can read
		3406	or modify at any time: libev will completely ignore it. This can be used
		3407	to associate arbitrary data with your watcher. If you need more data and
		3408	don't want to allocate memory separately and store a pointer to it in that
		3409	data member, you can also "subclass" the watcher type and provide your own
		3410	data:
		3411
		3412	struct my_io
		3413	{
		3414	ev_io io;
		3415	int otherfd;
		3416	void *somedata;
		3417	struct whatever *mostinteresting;
		3418	};
		3419
		3420	...
		3421	struct my_io w;
		3422	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3423
		3424	And since your callback will be called with a pointer to the watcher, you
		3425	can cast it back to your own type:
		3426
		3427	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3428	{
		3429	struct my_io *w = (struct my_io *)w_;
		3430	...
		3431	}
		3432
		3433	More interesting and less C-conformant ways of casting your callback
		3434	function type instead have been omitted.
		3435
		3436	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3437
		3438	Another common scenario is to use some data structure with multiple
		3439	embedded watchers, in effect creating your own watcher that combines
		3440	multiple libev event sources into one "super-watcher":
		3441
		3442	struct my_biggy
		3443	{
		3444	int some_data;
		3445	ev_timer t1;
		3446	ev_timer t2;
		3447	}
		3448
		3449	In this case getting the pointer to C<my_biggy> is a bit more
		3450	complicated: Either you store the address of your C<my_biggy> struct in
		3451	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3452	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3453	real programmers):
		3454
		3455	#include <stddef.h>
		3456
		3457	static void
		3458	t1_cb (EV_P_ ev_timer *w, int revents)
		3459	{
		3460	struct my_biggy big = (struct my_biggy *)
		3461	(((char *)w) - offsetof (struct my_biggy, t1));
		3462	}
		3463
		3464	static void
		3465	t2_cb (EV_P_ ev_timer *w, int revents)
		3466	{
		3467	struct my_biggy big = (struct my_biggy *)
		3468	(((char *)w) - offsetof (struct my_biggy, t2));
		3469	}
		3470
		3471	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3472
		3473	Often (especially in GUI toolkits) there are places where you have
		3474	I<modal> interaction, which is most easily implemented by recursively
		3475	invoking C<ev_run>.
		3476
		3477	This brings the problem of exiting - a callback might want to finish the
		3478	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3479	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3480	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3481	other combination: In these cases, C<ev_break> will not work alone.
		3482
		3483	The solution is to maintain "break this loop" variable for each C<ev_run>
		3484	invocation, and use a loop around C<ev_run> until the condition is
		3485	triggered, using C<EVRUN_ONCE>:
		3486
		3487	// main loop
		3488	int exit_main_loop = 0;
		3489
		3490	while (!exit_main_loop)
		3491	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3492
		3493	// in a model watcher
		3494	int exit_nested_loop = 0;
		3495
		3496	while (!exit_nested_loop)
		3497	ev_run (EV_A_ EVRUN_ONCE);
		3498
		3499	To exit from any of these loops, just set the corresponding exit variable:
		3500
		3501	// exit modal loop
		3502	exit_nested_loop = 1;
		3503
		3504	// exit main program, after modal loop is finished
		3505	exit_main_loop = 1;
		3506
		3507	// exit both
		3508	exit_main_loop = exit_nested_loop = 1;
		3509
		3510	=head2 THREAD LOCKING EXAMPLE
		3511
		3512	Here is a fictitious example of how to run an event loop in a different
		3513	thread from where callbacks are being invoked and watchers are
		3514	created/added/removed.
		3515
		3516	For a real-world example, see the C<EV::Loop::Async> perl module,
		3517	which uses exactly this technique (which is suited for many high-level
		3518	languages).
		3519
		3520	The example uses a pthread mutex to protect the loop data, a condition
		3521	variable to wait for callback invocations, an async watcher to notify the
		3522	event loop thread and an unspecified mechanism to wake up the main thread.
		3523
		3524	First, you need to associate some data with the event loop:
		3525
		3526	typedef struct {
		3527	mutex_t lock; /* global loop lock */
		3528	ev_async async_w;
		3529	thread_t tid;
		3530	cond_t invoke_cv;
		3531	} userdata;
		3532
		3533	void prepare_loop (EV_P)
		3534	{
		3535	// for simplicity, we use a static userdata struct.
		3536	static userdata u;
		3537
		3538	ev_async_init (&u->async_w, async_cb);
		3539	ev_async_start (EV_A_ &u->async_w);
		3540
		3541	pthread_mutex_init (&u->lock, 0);
		3542	pthread_cond_init (&u->invoke_cv, 0);
		3543
		3544	// now associate this with the loop
		3545	ev_set_userdata (EV_A_ u);
		3546	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3547	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3548
		3549	// then create the thread running ev_loop
		3550	pthread_create (&u->tid, 0, l_run, EV_A);
		3551	}
		3552
		3553	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3554	solely to wake up the event loop so it takes notice of any new watchers
		3555	that might have been added:
		3556
		3557	static void
		3558	async_cb (EV_P_ ev_async *w, int revents)
		3559	{
		3560	// just used for the side effects
		3561	}
		3562
		3563	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3564	protecting the loop data, respectively.
		3565
		3566	static void
		3567	l_release (EV_P)
		3568	{
		3569	userdata *u = ev_userdata (EV_A);
		3570	pthread_mutex_unlock (&u->lock);
		3571	}
		3572
		3573	static void
		3574	l_acquire (EV_P)
		3575	{
		3576	userdata *u = ev_userdata (EV_A);
		3577	pthread_mutex_lock (&u->lock);
		3578	}
		3579
		3580	The event loop thread first acquires the mutex, and then jumps straight
		3581	into C<ev_run>:
		3582
		3583	void *
		3584	l_run (void *thr_arg)
		3585	{
		3586	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3587
		3588	l_acquire (EV_A);
		3589	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3590	ev_run (EV_A_ 0);
		3591	l_release (EV_A);
		3592
		3593	return 0;
		3594	}
		3595
		3596	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3597	signal the main thread via some unspecified mechanism (signals? pipe
		3598	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3599	have been called (in a while loop because a) spurious wakeups are possible
		3600	and b) skipping inter-thread-communication when there are no pending
		3601	watchers is very beneficial):
		3602
		3603	static void
		3604	l_invoke (EV_P)
		3605	{
		3606	userdata *u = ev_userdata (EV_A);
		3607
		3608	while (ev_pending_count (EV_A))
		3609	{
		3610	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3611	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3612	}
		3613	}
		3614
		3615	Now, whenever the main thread gets told to invoke pending watchers, it
		3616	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3617	thread to continue:
		3618
		3619	static void
		3620	real_invoke_pending (EV_P)
		3621	{
		3622	userdata *u = ev_userdata (EV_A);
		3623
		3624	pthread_mutex_lock (&u->lock);
		3625	ev_invoke_pending (EV_A);
		3626	pthread_cond_signal (&u->invoke_cv);
		3627	pthread_mutex_unlock (&u->lock);
		3628	}
		3629
		3630	Whenever you want to start/stop a watcher or do other modifications to an
		3631	event loop, you will now have to lock:
		3632
		3633	ev_timer timeout_watcher;
		3634	userdata *u = ev_userdata (EV_A);
		3635
		3636	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3637
		3638	pthread_mutex_lock (&u->lock);
		3639	ev_timer_start (EV_A_ &timeout_watcher);
		3640	ev_async_send (EV_A_ &u->async_w);
		3641	pthread_mutex_unlock (&u->lock);
		3642
		3643	Note that sending the C<ev_async> watcher is required because otherwise
		3644	an event loop currently blocking in the kernel will have no knowledge
		3645	about the newly added timer. By waking up the loop it will pick up any new
		3646	watchers in the next event loop iteration.
		3647
		3648	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3649
		3650	While the overhead of a callback that e.g. schedules a thread is small, it
		3651	is still an overhead. If you embed libev, and your main usage is with some
		3652	kind of threads or coroutines, you might want to customise libev so that
		3653	doesn't need callbacks anymore.
		3654
		3655	Imagine you have coroutines that you can switch to using a function
		3656	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3657	and that due to some magic, the currently active coroutine is stored in a
		3658	global called C<current_coro>. Then you can build your own "wait for libev
		3659	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3660	the differing C<;> conventions):
		3661
		3662	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3663	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3664
		3665	That means instead of having a C callback function, you store the
		3666	coroutine to switch to in each watcher, and instead of having libev call
		3667	your callback, you instead have it switch to that coroutine.
		3668
		3669	A coroutine might now wait for an event with a function called
		3670	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3671	matter when, or whether the watcher is active or not when this function is
		3672	called):
		3673
		3674	void
		3675	wait_for_event (ev_watcher *w)
		3676	{
		3677	ev_cb_set (w) = current_coro;
		3678	switch_to (libev_coro);
		3679	}
		3680
		3681	That basically suspends the coroutine inside C<wait_for_event> and
		3682	continues the libev coroutine, which, when appropriate, switches back to
		3683	this or any other coroutine. I am sure if you sue this your own :)
		3684
		3685	You can do similar tricks if you have, say, threads with an event queue -
		3686	instead of storing a coroutine, you store the queue object and instead of
		3687	switching to a coroutine, you push the watcher onto the queue and notify
		3688	any waiters.
		3689
		3690	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3691	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3692
		3693	// my_ev.h
		3694	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3695	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3696	#include "../libev/ev.h"
		3697
		3698	// my_ev.c
		3699	#define EV_H "my_ev.h"
		3700	#include "../libev/ev.c"
		3701
		3702	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3703	F<my_ev.c> into your project. When properly specifying include paths, you
		3704	can even use F<ev.h> as header file name directly.
2553		3705
2554		3706
2555	=head1 LIBEVENT EMULATION	3707	=head1 LIBEVENT EMULATION
2556		3708
2557	Libev offers a compatibility emulation layer for libevent. It cannot	3709	Libev offers a compatibility emulation layer for libevent. It cannot
2558	emulate the internals of libevent, so here are some usage hints:	3710	emulate the internals of libevent, so here are some usage hints:
2559		3711
2560	=over 4	3712	=over 4
		3713
		3714	=item * Only the libevent-1.4.1-beta API is being emulated.
		3715
		3716	This was the newest libevent version available when libev was implemented,
		3717	and is still mostly unchanged in 2010.
2561		3718
2562	=item * Use it by including <event.h>, as usual.	3719	=item * Use it by including <event.h>, as usual.
2563		3720
2564	=item * The following members are fully supported: ev_base, ev_callback,	3721	=item * The following members are fully supported: ev_base, ev_callback,
2565	ev_arg, ev_fd, ev_res, ev_events.	3722	ev_arg, ev_fd, ev_res, ev_events.
…		…
2571	=item * Priorities are not currently supported. Initialising priorities	3728	=item * Priorities are not currently supported. Initialising priorities
2572	will fail and all watchers will have the same priority, even though there	3729	will fail and all watchers will have the same priority, even though there
2573	is an ev_pri field.	3730	is an ev_pri field.
2574		3731
2575	=item * In libevent, the last base created gets the signals, in libev, the	3732	=item * In libevent, the last base created gets the signals, in libev, the
2576	first base created (== the default loop) gets the signals.	3733	base that registered the signal gets the signals.
2577		3734
2578	=item * Other members are not supported.	3735	=item * Other members are not supported.
2579		3736
2580	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3737	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2581	to use the libev header file and library.	3738	to use the libev header file and library.
…		…
2600	Care has been taken to keep the overhead low. The only data member the C++	3757	Care has been taken to keep the overhead low. The only data member the C++
2601	classes add (compared to plain C-style watchers) is the event loop pointer	3758	classes add (compared to plain C-style watchers) is the event loop pointer
2602	that the watcher is associated with (or no additional members at all if	3759	that the watcher is associated with (or no additional members at all if
2603	you disable C<EV_MULTIPLICITY> when embedding libev).	3760	you disable C<EV_MULTIPLICITY> when embedding libev).
2604		3761
2605	Currently, functions, and static and non-static member functions can be	3762	Currently, functions, static and non-static member functions and classes
2606	used as callbacks. Other types should be easy to add as long as they only	3763	with C<operator ()> can be used as callbacks. Other types should be easy
2607	need one additional pointer for context. If you need support for other	3764	to add as long as they only need one additional pointer for context. If
2608	types of functors please contact the author (preferably after implementing	3765	you need support for other types of functors please contact the author
2609	it).	3766	(preferably after implementing it).
2610		3767
2611	Here is a list of things available in the C<ev> namespace:	3768	Here is a list of things available in the C<ev> namespace:
2612		3769
2613	=over 4	3770	=over 4
2614		3771
…		…
2632		3789
2633	=over 4	3790	=over 4
2634		3791
2635	=item ev::TYPE::TYPE ()	3792	=item ev::TYPE::TYPE ()
2636		3793
2637	=item ev::TYPE::TYPE (struct ev_loop *)	3794	=item ev::TYPE::TYPE (loop)
2638		3795
2639	=item ev::TYPE::~TYPE	3796	=item ev::TYPE::~TYPE
2640		3797
2641	The constructor (optionally) takes an event loop to associate the watcher	3798	The constructor (optionally) takes an event loop to associate the watcher
2642	with. If it is omitted, it will use C<EV_DEFAULT>.	3799	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2674		3831
2675	myclass obj;	3832	myclass obj;
2676	ev::io iow;	3833	ev::io iow;
2677	iow.set <myclass, &myclass::io_cb> (&obj);	3834	iow.set <myclass, &myclass::io_cb> (&obj);
2678		3835
		3836	=item w->set (object *)
		3837
		3838	This is a variation of a method callback - leaving out the method to call
		3839	will default the method to C<operator ()>, which makes it possible to use
		3840	functor objects without having to manually specify the C<operator ()> all
		3841	the time. Incidentally, you can then also leave out the template argument
		3842	list.
		3843
		3844	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3845	int revents)>.
		3846
		3847	See the method-C<set> above for more details.
		3848
		3849	Example: use a functor object as callback.
		3850
		3851	struct myfunctor
		3852	{
		3853	void operator() (ev::io &w, int revents)
		3854	{
		3855	...
		3856	}
		3857	}
		3858
		3859	myfunctor f;
		3860
		3861	ev::io w;
		3862	w.set (&f);
		3863
2679	=item w->set<function> (void *data = 0)	3864	=item w->set<function> (void *data = 0)
2680		3865
2681	Also sets a callback, but uses a static method or plain function as	3866	Also sets a callback, but uses a static method or plain function as
2682	callback. The optional C<data> argument will be stored in the watcher's	3867	callback. The optional C<data> argument will be stored in the watcher's
2683	C<data> member and is free for you to use.	3868	C<data> member and is free for you to use.
…		…
2689	Example: Use a plain function as callback.	3874	Example: Use a plain function as callback.
2690		3875
2691	static void io_cb (ev::io &w, int revents) { }	3876	static void io_cb (ev::io &w, int revents) { }
2692	iow.set <io_cb> ();	3877	iow.set <io_cb> ();
2693		3878
2694	=item w->set (struct ev_loop *)	3879	=item w->set (loop)
2695		3880
2696	Associates a different C<struct ev_loop> with this watcher. You can only	3881	Associates a different C<struct ev_loop> with this watcher. You can only
2697	do this when the watcher is inactive (and not pending either).	3882	do this when the watcher is inactive (and not pending either).
2698		3883
2699	=item w->set ([arguments])	3884	=item w->set ([arguments])
2700		3885
2701	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3886	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
2702	called at least once. Unlike the C counterpart, an active watcher gets	3887	method or a suitable start method must be called at least once. Unlike the
2703	automatically stopped and restarted when reconfiguring it with this	3888	C counterpart, an active watcher gets automatically stopped and restarted
2704	method.	3889	when reconfiguring it with this method.
2705		3890
2706	=item w->start ()	3891	=item w->start ()
2707		3892
2708	Starts the watcher. Note that there is no C<loop> argument, as the	3893	Starts the watcher. Note that there is no C<loop> argument, as the
2709	constructor already stores the event loop.	3894	constructor already stores the event loop.
2710		3895
		3896	=item w->start ([arguments])
		3897
		3898	Instead of calling C<set> and C<start> methods separately, it is often
		3899	convenient to wrap them in one call. Uses the same type of arguments as
		3900	the configure C<set> method of the watcher.
		3901
2711	=item w->stop ()	3902	=item w->stop ()
2712		3903
2713	Stops the watcher if it is active. Again, no C<loop> argument.	3904	Stops the watcher if it is active. Again, no C<loop> argument.
2714		3905
2715	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3906	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2727		3918
2728	=back	3919	=back
2729		3920
2730	=back	3921	=back
2731		3922
2732	Example: Define a class with an IO and idle watcher, start one of them in	3923	Example: Define a class with two I/O and idle watchers, start the I/O
2733	the constructor.	3924	watchers in the constructor.
2734		3925
2735	class myclass	3926	class myclass
2736	{	3927	{
2737	ev::io io ; void io_cb (ev::io &w, int revents);	3928	ev::io io ; void io_cb (ev::io &w, int revents);
		3929	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
2738	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3930	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2739		3931
2740	myclass (int fd)	3932	myclass (int fd)
2741	{	3933	{
2742	io .set <myclass, &myclass::io_cb > (this);	3934	io .set <myclass, &myclass::io_cb > (this);
		3935	io2 .set <myclass, &myclass::io2_cb > (this);
2743	idle.set <myclass, &myclass::idle_cb> (this);	3936	idle.set <myclass, &myclass::idle_cb> (this);
2744		3937
2745	io.start (fd, ev::READ);	3938	io.set (fd, ev::WRITE); // configure the watcher
		3939	io.start (); // start it whenever convenient
		3940
		3941	io2.start (fd, ev::READ); // set + start in one call
2746	}	3942	}
2747	};	3943	};
2748		3944
2749		3945
2750	=head1 OTHER LANGUAGE BINDINGS	3946	=head1 OTHER LANGUAGE BINDINGS
…		…
2769	L<http://software.schmorp.de/pkg/EV>.	3965	L<http://software.schmorp.de/pkg/EV>.
2770		3966
2771	=item Python	3967	=item Python
2772		3968
2773	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3969	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2774	seems to be quite complete and well-documented. Note, however, that the	3970	seems to be quite complete and well-documented.
2775	patch they require for libev is outright dangerous as it breaks the ABI
2776	for everybody else, and therefore, should never be applied in an installed
2777	libev (if python requires an incompatible ABI then it needs to embed
2778	libev).
2779		3971
2780	=item Ruby	3972	=item Ruby
2781		3973
2782	Tony Arcieri has written a ruby extension that offers access to a subset	3974	Tony Arcieri has written a ruby extension that offers access to a subset
2783	of the libev API and adds file handle abstractions, asynchronous DNS and	3975	of the libev API and adds file handle abstractions, asynchronous DNS and
2784	more on top of it. It can be found via gem servers. Its homepage is at	3976	more on top of it. It can be found via gem servers. Its homepage is at
2785	L<http://rev.rubyforge.org/>.	3977	L<http://rev.rubyforge.org/>.
2786		3978
		3979	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3980	makes rev work even on mingw.
		3981
		3982	=item Haskell
		3983
		3984	A haskell binding to libev is available at
		3985	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3986
2787	=item D	3987	=item D
2788		3988
2789	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3989	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2790	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3990	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3991
		3992	=item Ocaml
		3993
		3994	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3995	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3996
		3997	=item Lua
		3998
		3999	Brian Maher has written a partial interface to libev for lua (at the
		4000	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		4001	L<http://github.com/brimworks/lua-ev>.
2791		4002
2792	=back	4003	=back
2793		4004
2794		4005
2795	=head1 MACRO MAGIC	4006	=head1 MACRO MAGIC
…		…
2809	loop argument"). The C<EV_A> form is used when this is the sole argument,	4020	loop argument"). The C<EV_A> form is used when this is the sole argument,
2810	C<EV_A_> is used when other arguments are following. Example:	4021	C<EV_A_> is used when other arguments are following. Example:
2811		4022
2812	ev_unref (EV_A);	4023	ev_unref (EV_A);
2813	ev_timer_add (EV_A_ watcher);	4024	ev_timer_add (EV_A_ watcher);
2814	ev_loop (EV_A_ 0);	4025	ev_run (EV_A_ 0);
2815		4026
2816	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4027	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2817	which is often provided by the following macro.	4028	which is often provided by the following macro.
2818		4029
2819	=item C<EV_P>, C<EV_P_>	4030	=item C<EV_P>, C<EV_P_>
…		…
2859	}	4070	}
2860		4071
2861	ev_check check;	4072	ev_check check;
2862	ev_check_init (&check, check_cb);	4073	ev_check_init (&check, check_cb);
2863	ev_check_start (EV_DEFAULT_ &check);	4074	ev_check_start (EV_DEFAULT_ &check);
2864	ev_loop (EV_DEFAULT_ 0);	4075	ev_run (EV_DEFAULT_ 0);
2865		4076
2866	=head1 EMBEDDING	4077	=head1 EMBEDDING
2867		4078
2868	Libev can (and often is) directly embedded into host	4079	Libev can (and often is) directly embedded into host
2869	applications. Examples of applications that embed it include the Deliantra	4080	applications. Examples of applications that embed it include the Deliantra
…		…
2896		4107
2897	#define EV_STANDALONE 1	4108	#define EV_STANDALONE 1
2898	#include "ev.h"	4109	#include "ev.h"
2899		4110
2900	Both header files and implementation files can be compiled with a C++	4111	Both header files and implementation files can be compiled with a C++
2901	compiler (at least, thats a stated goal, and breakage will be treated	4112	compiler (at least, that's a stated goal, and breakage will be treated
2902	as a bug).	4113	as a bug).
2903		4114
2904	You need the following files in your source tree, or in a directory	4115	You need the following files in your source tree, or in a directory
2905	in your include path (e.g. in libev/ when using -Ilibev):	4116	in your include path (e.g. in libev/ when using -Ilibev):
2906		4117
…		…
2949	libev.m4	4160	libev.m4
2950		4161
2951	=head2 PREPROCESSOR SYMBOLS/MACROS	4162	=head2 PREPROCESSOR SYMBOLS/MACROS
2952		4163
2953	Libev can be configured via a variety of preprocessor symbols you have to	4164	Libev can be configured via a variety of preprocessor symbols you have to
2954	define before including any of its files. The default in the absence of	4165	define before including (or compiling) any of its files. The default in
2955	autoconf is documented for every option.	4166	the absence of autoconf is documented for every option.
		4167
		4168	Symbols marked with "(h)" do not change the ABI, and can have different
		4169	values when compiling libev vs. including F<ev.h>, so it is permissible
		4170	to redefine them before including F<ev.h> without breaking compatibility
		4171	to a compiled library. All other symbols change the ABI, which means all
		4172	users of libev and the libev code itself must be compiled with compatible
		4173	settings.
2956		4174
2957	=over 4	4175	=over 4
2958		4176
		4177	=item EV_COMPAT3 (h)
		4178
		4179	Backwards compatibility is a major concern for libev. This is why this
		4180	release of libev comes with wrappers for the functions and symbols that
		4181	have been renamed between libev version 3 and 4.
		4182
		4183	You can disable these wrappers (to test compatibility with future
		4184	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4185	sources. This has the additional advantage that you can drop the C<struct>
		4186	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4187	typedef in that case.
		4188
		4189	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4190	and in some even more future version the compatibility code will be
		4191	removed completely.
		4192
2959	=item EV_STANDALONE	4193	=item EV_STANDALONE (h)
2960		4194
2961	Must always be C<1> if you do not use autoconf configuration, which	4195	Must always be C<1> if you do not use autoconf configuration, which
2962	keeps libev from including F<config.h>, and it also defines dummy	4196	keeps libev from including F<config.h>, and it also defines dummy
2963	implementations for some libevent functions (such as logging, which is not	4197	implementations for some libevent functions (such as logging, which is not
2964	supported). It will also not define any of the structs usually found in	4198	supported). It will also not define any of the structs usually found in
2965	F<event.h> that are not directly supported by the libev core alone.	4199	F<event.h> that are not directly supported by the libev core alone.
2966		4200
		4201	In standalone mode, libev will still try to automatically deduce the
		4202	configuration, but has to be more conservative.
		4203
2967	=item EV_USE_MONOTONIC	4204	=item EV_USE_MONOTONIC
2968		4205
2969	If defined to be C<1>, libev will try to detect the availability of the	4206	If defined to be C<1>, libev will try to detect the availability of the
2970	monotonic clock option at both compile time and runtime. Otherwise no use	4207	monotonic clock option at both compile time and runtime. Otherwise no
2971	of the monotonic clock option will be attempted. If you enable this, you	4208	use of the monotonic clock option will be attempted. If you enable this,
2972	usually have to link against librt or something similar. Enabling it when	4209	you usually have to link against librt or something similar. Enabling it
2973	the functionality isn't available is safe, though, although you have	4210	when the functionality isn't available is safe, though, although you have
2974	to make sure you link against any libraries where the C<clock_gettime>	4211	to make sure you link against any libraries where the C<clock_gettime>
2975	function is hiding in (often F<-lrt>).	4212	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2976		4213
2977	=item EV_USE_REALTIME	4214	=item EV_USE_REALTIME
2978		4215
2979	If defined to be C<1>, libev will try to detect the availability of the	4216	If defined to be C<1>, libev will try to detect the availability of the
2980	real-time clock option at compile time (and assume its availability at	4217	real-time clock option at compile time (and assume its availability
2981	runtime if successful). Otherwise no use of the real-time clock option will	4218	at runtime if successful). Otherwise no use of the real-time clock
2982	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	4219	option will be attempted. This effectively replaces C<gettimeofday>
2983	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	4220	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2984	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	4221	correctness. See the note about libraries in the description of
		4222	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		4223	C<EV_USE_CLOCK_SYSCALL>.
		4224
		4225	=item EV_USE_CLOCK_SYSCALL
		4226
		4227	If defined to be C<1>, libev will try to use a direct syscall instead
		4228	of calling the system-provided C<clock_gettime> function. This option
		4229	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		4230	unconditionally pulls in C<libpthread>, slowing down single-threaded
		4231	programs needlessly. Using a direct syscall is slightly slower (in
		4232	theory), because no optimised vdso implementation can be used, but avoids
		4233	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		4234	higher, as it simplifies linking (no need for C<-lrt>).
2985		4235
2986	=item EV_USE_NANOSLEEP	4236	=item EV_USE_NANOSLEEP
2987		4237
2988	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	4238	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2989	and will use it for delays. Otherwise it will use C<select ()>.	4239	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3005		4255
3006	=item EV_SELECT_USE_FD_SET	4256	=item EV_SELECT_USE_FD_SET
3007		4257
3008	If defined to C<1>, then the select backend will use the system C<fd_set>	4258	If defined to C<1>, then the select backend will use the system C<fd_set>
3009	structure. This is useful if libev doesn't compile due to a missing	4259	structure. This is useful if libev doesn't compile due to a missing
3010	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	4260	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3011	exotic systems. This usually limits the range of file descriptors to some	4261	on exotic systems. This usually limits the range of file descriptors to
3012	low limit such as 1024 or might have other limitations (winsocket only	4262	some low limit such as 1024 or might have other limitations (winsocket
3013	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	4263	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3014	influence the size of the C<fd_set> used.	4264	configures the maximum size of the C<fd_set>.
3015		4265
3016	=item EV_SELECT_IS_WINSOCKET	4266	=item EV_SELECT_IS_WINSOCKET
3017		4267
3018	When defined to C<1>, the select backend will assume that	4268	When defined to C<1>, the select backend will assume that
3019	select/socket/connect etc. don't understand file descriptors but	4269	select/socket/connect etc. don't understand file descriptors but
…		…
3021	be used is the winsock select). This means that it will call	4271	be used is the winsock select). This means that it will call
3022	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4272	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3023	it is assumed that all these functions actually work on fds, even	4273	it is assumed that all these functions actually work on fds, even
3024	on win32. Should not be defined on non-win32 platforms.	4274	on win32. Should not be defined on non-win32 platforms.
3025		4275
3026	=item EV_FD_TO_WIN32_HANDLE	4276	=item EV_FD_TO_WIN32_HANDLE(fd)
3027		4277
3028	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4278	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3029	file descriptors to socket handles. When not defining this symbol (the	4279	file descriptors to socket handles. When not defining this symbol (the
3030	default), then libev will call C<_get_osfhandle>, which is usually	4280	default), then libev will call C<_get_osfhandle>, which is usually
3031	correct. In some cases, programs use their own file descriptor management,	4281	correct. In some cases, programs use their own file descriptor management,
3032	in which case they can provide this function to map fds to socket handles.	4282	in which case they can provide this function to map fds to socket handles.
		4283
		4284	=item EV_WIN32_HANDLE_TO_FD(handle)
		4285
		4286	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4287	using the standard C<_open_osfhandle> function. For programs implementing
		4288	their own fd to handle mapping, overwriting this function makes it easier
		4289	to do so. This can be done by defining this macro to an appropriate value.
		4290
		4291	=item EV_WIN32_CLOSE_FD(fd)
		4292
		4293	If programs implement their own fd to handle mapping on win32, then this
		4294	macro can be used to override the C<close> function, useful to unregister
		4295	file descriptors again. Note that the replacement function has to close
		4296	the underlying OS handle.
3033		4297
3034	=item EV_USE_POLL	4298	=item EV_USE_POLL
3035		4299
3036	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4300	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3037	backend. Otherwise it will be enabled on non-win32 platforms. It	4301	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3084	as well as for signal and thread safety in C<ev_async> watchers.	4348	as well as for signal and thread safety in C<ev_async> watchers.
3085		4349
3086	In the absence of this define, libev will use C<sig_atomic_t volatile>	4350	In the absence of this define, libev will use C<sig_atomic_t volatile>
3087	(from F<signal.h>), which is usually good enough on most platforms.	4351	(from F<signal.h>), which is usually good enough on most platforms.
3088		4352
3089	=item EV_H	4353	=item EV_H (h)
3090		4354
3091	The name of the F<ev.h> header file used to include it. The default if	4355	The name of the F<ev.h> header file used to include it. The default if
3092	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4356	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3093	used to virtually rename the F<ev.h> header file in case of conflicts.	4357	used to virtually rename the F<ev.h> header file in case of conflicts.
3094		4358
3095	=item EV_CONFIG_H	4359	=item EV_CONFIG_H (h)
3096		4360
3097	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4361	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3098	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4362	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3099	C<EV_H>, above.	4363	C<EV_H>, above.
3100		4364
3101	=item EV_EVENT_H	4365	=item EV_EVENT_H (h)
3102		4366
3103	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4367	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3104	of how the F<event.h> header can be found, the default is C<"event.h">.	4368	of how the F<event.h> header can be found, the default is C<"event.h">.
3105		4369
3106	=item EV_PROTOTYPES	4370	=item EV_PROTOTYPES (h)
3107		4371
3108	If defined to be C<0>, then F<ev.h> will not define any function	4372	If defined to be C<0>, then F<ev.h> will not define any function
3109	prototypes, but still define all the structs and other symbols. This is	4373	prototypes, but still define all the structs and other symbols. This is
3110	occasionally useful if you want to provide your own wrapper functions	4374	occasionally useful if you want to provide your own wrapper functions
3111	around libev functions.	4375	around libev functions.
…		…
3133	fine.	4397	fine.
3134		4398
3135	If your embedding application does not need any priorities, defining these	4399	If your embedding application does not need any priorities, defining these
3136	both to C<0> will save some memory and CPU.	4400	both to C<0> will save some memory and CPU.
3137		4401
3138	=item EV_PERIODIC_ENABLE	4402	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4403	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4404	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3139		4405
3140	If undefined or defined to be C<1>, then periodic timers are supported. If	4406	If undefined or defined to be C<1> (and the platform supports it), then
3141	defined to be C<0>, then they are not. Disabling them saves a few kB of	4407	the respective watcher type is supported. If defined to be C<0>, then it
3142	code.	4408	is not. Disabling watcher types mainly saves code size.
3143		4409
3144	=item EV_IDLE_ENABLE	4410	=item EV_FEATURES
3145
3146	If undefined or defined to be C<1>, then idle watchers are supported. If
3147	defined to be C<0>, then they are not. Disabling them saves a few kB of
3148	code.
3149
3150	=item EV_EMBED_ENABLE
3151
3152	If undefined or defined to be C<1>, then embed watchers are supported. If
3153	defined to be C<0>, then they are not. Embed watchers rely on most other
3154	watcher types, which therefore must not be disabled.
3155
3156	=item EV_STAT_ENABLE
3157
3158	If undefined or defined to be C<1>, then stat watchers are supported. If
3159	defined to be C<0>, then they are not.
3160
3161	=item EV_FORK_ENABLE
3162
3163	If undefined or defined to be C<1>, then fork watchers are supported. If
3164	defined to be C<0>, then they are not.
3165
3166	=item EV_ASYNC_ENABLE
3167
3168	If undefined or defined to be C<1>, then async watchers are supported. If
3169	defined to be C<0>, then they are not.
3170
3171	=item EV_MINIMAL
3172		4411
3173	If you need to shave off some kilobytes of code at the expense of some	4412	If you need to shave off some kilobytes of code at the expense of some
3174	speed, define this symbol to C<1>. Currently this is used to override some	4413	speed (but with the full API), you can define this symbol to request
3175	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4414	certain subsets of functionality. The default is to enable all features
3176	much smaller 2-heap for timer management over the default 4-heap.	4415	that can be enabled on the platform.
		4416
		4417	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4418	with some broad features you want) and then selectively re-enable
		4419	additional parts you want, for example if you want everything minimal,
		4420	but multiple event loop support, async and child watchers and the poll
		4421	backend, use this:
		4422
		4423	#define EV_FEATURES 0
		4424	#define EV_MULTIPLICITY 1
		4425	#define EV_USE_POLL 1
		4426	#define EV_CHILD_ENABLE 1
		4427	#define EV_ASYNC_ENABLE 1
		4428
		4429	The actual value is a bitset, it can be a combination of the following
		4430	values:
		4431
		4432	=over 4
		4433
		4434	=item C<1> - faster/larger code
		4435
		4436	Use larger code to speed up some operations.
		4437
		4438	Currently this is used to override some inlining decisions (enlarging the
		4439	code size by roughly 30% on amd64).
		4440
		4441	When optimising for size, use of compiler flags such as C<-Os> with
		4442	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4443	assertions.
		4444
		4445	=item C<2> - faster/larger data structures
		4446
		4447	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4448	hash table sizes and so on. This will usually further increase code size
		4449	and can additionally have an effect on the size of data structures at
		4450	runtime.
		4451
		4452	=item C<4> - full API configuration
		4453
		4454	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4455	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4456
		4457	=item C<8> - full API
		4458
		4459	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4460	details on which parts of the API are still available without this
		4461	feature, and do not complain if this subset changes over time.
		4462
		4463	=item C<16> - enable all optional watcher types
		4464
		4465	Enables all optional watcher types. If you want to selectively enable
		4466	only some watcher types other than I/O and timers (e.g. prepare,
		4467	embed, async, child...) you can enable them manually by defining
		4468	C<EV_watchertype_ENABLE> to C<1> instead.
		4469
		4470	=item C<32> - enable all backends
		4471
		4472	This enables all backends - without this feature, you need to enable at
		4473	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4474
		4475	=item C<64> - enable OS-specific "helper" APIs
		4476
		4477	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4478	default.
		4479
		4480	=back
		4481
		4482	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4483	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4484	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4485	watchers, timers and monotonic clock support.
		4486
		4487	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4488	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4489	your program might be left out as well - a binary starting a timer and an
		4490	I/O watcher then might come out at only 5Kb.
		4491
		4492	=item EV_AVOID_STDIO
		4493
		4494	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4495	functions (printf, scanf, perror etc.). This will increase the code size
		4496	somewhat, but if your program doesn't otherwise depend on stdio and your
		4497	libc allows it, this avoids linking in the stdio library which is quite
		4498	big.
		4499
		4500	Note that error messages might become less precise when this option is
		4501	enabled.
		4502
		4503	=item EV_NSIG
		4504
		4505	The highest supported signal number, +1 (or, the number of
		4506	signals): Normally, libev tries to deduce the maximum number of signals
		4507	automatically, but sometimes this fails, in which case it can be
		4508	specified. Also, using a lower number than detected (C<32> should be
		4509	good for about any system in existence) can save some memory, as libev
		4510	statically allocates some 12-24 bytes per signal number.
3177		4511
3178	=item EV_PID_HASHSIZE	4512	=item EV_PID_HASHSIZE
3179		4513
3180	C<ev_child> watchers use a small hash table to distribute workload by	4514	C<ev_child> watchers use a small hash table to distribute workload by
3181	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4515	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3182	than enough. If you need to manage thousands of children you might want to	4516	usually more than enough. If you need to manage thousands of children you
3183	increase this value (I<must> be a power of two).	4517	might want to increase this value (I<must> be a power of two).
3184		4518
3185	=item EV_INOTIFY_HASHSIZE	4519	=item EV_INOTIFY_HASHSIZE
3186		4520
3187	C<ev_stat> watchers use a small hash table to distribute workload by	4521	C<ev_stat> watchers use a small hash table to distribute workload by
3188	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4522	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3189	usually more than enough. If you need to manage thousands of C<ev_stat>	4523	disabled), usually more than enough. If you need to manage thousands of
3190	watchers you might want to increase this value (I<must> be a power of	4524	C<ev_stat> watchers you might want to increase this value (I<must> be a
3191	two).	4525	power of two).
3192		4526
3193	=item EV_USE_4HEAP	4527	=item EV_USE_4HEAP
3194		4528
3195	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4529	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3196	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4530	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3197	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4531	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3198	faster performance with many (thousands) of watchers.	4532	faster performance with many (thousands) of watchers.
3199		4533
3200	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4534	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3201	(disabled).	4535	will be C<0>.
3202		4536
3203	=item EV_HEAP_CACHE_AT	4537	=item EV_HEAP_CACHE_AT
3204		4538
3205	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4539	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3206	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4540	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3207	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4541	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3208	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4542	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3209	but avoids random read accesses on heap changes. This improves performance	4543	but avoids random read accesses on heap changes. This improves performance
3210	noticeably with many (hundreds) of watchers.	4544	noticeably with many (hundreds) of watchers.
3211		4545
3212	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4546	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3213	(disabled).	4547	will be C<0>.
3214		4548
3215	=item EV_VERIFY	4549	=item EV_VERIFY
3216		4550
3217	Controls how much internal verification (see C<ev_loop_verify ()>) will	4551	Controls how much internal verification (see C<ev_verify ()>) will
3218	be done: If set to C<0>, no internal verification code will be compiled	4552	be done: If set to C<0>, no internal verification code will be compiled
3219	in. If set to C<1>, then verification code will be compiled in, but not	4553	in. If set to C<1>, then verification code will be compiled in, but not
3220	called. If set to C<2>, then the internal verification code will be	4554	called. If set to C<2>, then the internal verification code will be
3221	called once per loop, which can slow down libev. If set to C<3>, then the	4555	called once per loop, which can slow down libev. If set to C<3>, then the
3222	verification code will be called very frequently, which will slow down	4556	verification code will be called very frequently, which will slow down
3223	libev considerably.	4557	libev considerably.
3224		4558
3225	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4559	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3226	C<0>.	4560	will be C<0>.
3227		4561
3228	=item EV_COMMON	4562	=item EV_COMMON
3229		4563
3230	By default, all watchers have a C<void *data> member. By redefining	4564	By default, all watchers have a C<void *data> member. By redefining
3231	this macro to a something else you can include more and other types of	4565	this macro to something else you can include more and other types of
3232	members. You have to define it each time you include one of the files,	4566	members. You have to define it each time you include one of the files,
3233	though, and it must be identical each time.	4567	though, and it must be identical each time.
3234		4568
3235	For example, the perl EV module uses something like this:	4569	For example, the perl EV module uses something like this:
3236		4570
…		…
3289	file.	4623	file.
3290		4624
3291	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4625	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3292	that everybody includes and which overrides some configure choices:	4626	that everybody includes and which overrides some configure choices:
3293		4627
3294	#define EV_MINIMAL 1	4628	#define EV_FEATURES 8
3295	#define EV_USE_POLL 0	4629	#define EV_USE_SELECT 1
3296	#define EV_MULTIPLICITY 0
3297	#define EV_PERIODIC_ENABLE 0	4630	#define EV_PREPARE_ENABLE 1
		4631	#define EV_IDLE_ENABLE 1
3298	#define EV_STAT_ENABLE 0	4632	#define EV_SIGNAL_ENABLE 1
3299	#define EV_FORK_ENABLE 0	4633	#define EV_CHILD_ENABLE 1
		4634	#define EV_USE_STDEXCEPT 0
3300	#define EV_CONFIG_H <config.h>	4635	#define EV_CONFIG_H <config.h>
3301	#define EV_MINPRI 0
3302	#define EV_MAXPRI 0
3303		4636
3304	#include "ev++.h"	4637	#include "ev++.h"
3305		4638
3306	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4639	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3307		4640
3308	#include "ev_cpp.h"	4641	#include "ev_cpp.h"
3309	#include "ev.c"	4642	#include "ev.c"
3310		4643
3311	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4644	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3312		4645
3313	=head2 THREADS AND COROUTINES	4646	=head2 THREADS AND COROUTINES
3314		4647
3315	=head3 THREADS	4648	=head3 THREADS
3316		4649
3317	All libev functions are reentrant and thread-safe unless explicitly	4650	All libev functions are reentrant and thread-safe unless explicitly
3318	documented otherwise, but it uses no locking itself. This means that you	4651	documented otherwise, but libev implements no locking itself. This means
3319	can use as many loops as you want in parallel, as long as there are no	4652	that you can use as many loops as you want in parallel, as long as there
3320	concurrent calls into any libev function with the same loop parameter	4653	are no concurrent calls into any libev function with the same loop
3321	(C<ev_default_*> calls have an implicit default loop parameter, of	4654	parameter (C<ev_default_*> calls have an implicit default loop parameter,
3322	course): libev guarantees that different event loops share no data	4655	of course): libev guarantees that different event loops share no data
3323	structures that need any locking.	4656	structures that need any locking.
3324		4657
3325	Or to put it differently: calls with different loop parameters can be done	4658	Or to put it differently: calls with different loop parameters can be done
3326	concurrently from multiple threads, calls with the same loop parameter	4659	concurrently from multiple threads, calls with the same loop parameter
3327	must be done serially (but can be done from different threads, as long as	4660	must be done serially (but can be done from different threads, as long as
…		…
3367	default loop and triggering an C<ev_async> watcher from the default loop	4700	default loop and triggering an C<ev_async> watcher from the default loop
3368	watcher callback into the event loop interested in the signal.	4701	watcher callback into the event loop interested in the signal.
3369		4702
3370	=back	4703	=back
3371		4704
		4705	See also L<THREAD LOCKING EXAMPLE>.
		4706
3372	=head3 COROUTINES	4707	=head3 COROUTINES
3373		4708
3374	Libev is much more accommodating to coroutines ("cooperative threads"):	4709	Libev is very accommodating to coroutines ("cooperative threads"):
3375	libev fully supports nesting calls to it's functions from different	4710	libev fully supports nesting calls to its functions from different
3376	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4711	coroutines (e.g. you can call C<ev_run> on the same loop from two
3377	different coroutines and switch freely between both coroutines running the	4712	different coroutines, and switch freely between both coroutines running
3378	loop, as long as you don't confuse yourself). The only exception is that	4713	the loop, as long as you don't confuse yourself). The only exception is
3379	you must not do this from C<ev_periodic> reschedule callbacks.	4714	that you must not do this from C<ev_periodic> reschedule callbacks.
3380		4715
3381	Care has been taken to ensure that libev does not keep local state inside	4716	Care has been taken to ensure that libev does not keep local state inside
3382	C<ev_loop>, and other calls do not usually allow coroutine switches.	4717	C<ev_run>, and other calls do not usually allow for coroutine switches as
		4718	they do not call any callbacks.
3383		4719
3384	=head2 COMPILER WARNINGS	4720	=head2 COMPILER WARNINGS
3385		4721
3386	Depending on your compiler and compiler settings, you might get no or a	4722	Depending on your compiler and compiler settings, you might get no or a
3387	lot of warnings when compiling libev code. Some people are apparently	4723	lot of warnings when compiling libev code. Some people are apparently
…		…
3397	maintainable.	4733	maintainable.
3398		4734
3399	And of course, some compiler warnings are just plain stupid, or simply	4735	And of course, some compiler warnings are just plain stupid, or simply
3400	wrong (because they don't actually warn about the condition their message	4736	wrong (because they don't actually warn about the condition their message
3401	seems to warn about). For example, certain older gcc versions had some	4737	seems to warn about). For example, certain older gcc versions had some
3402	warnings that resulted an extreme number of false positives. These have	4738	warnings that resulted in an extreme number of false positives. These have
3403	been fixed, but some people still insist on making code warn-free with	4739	been fixed, but some people still insist on making code warn-free with
3404	such buggy versions.	4740	such buggy versions.
3405		4741
3406	While libev is written to generate as few warnings as possible,	4742	While libev is written to generate as few warnings as possible,
3407	"warn-free" code is not a goal, and it is recommended not to build libev	4743	"warn-free" code is not a goal, and it is recommended not to build libev
3408	with any compiler warnings enabled unless you are prepared to cope with	4744	with any compiler warnings enabled unless you are prepared to cope with
3409	them (e.g. by ignoring them). Remember that warnings are just that:	4745	them (e.g. by ignoring them). Remember that warnings are just that:
3410	warnings, not errors, or proof of bugs.	4746	warnings, not errors, or proof of bugs.
3411		4747
3412		4748
3413	=head1 VALGRIND	4749	=head2 VALGRIND
3414		4750
3415	Valgrind has a special section here because it is a popular tool that is	4751	Valgrind has a special section here because it is a popular tool that is
3416	highly useful. Unfortunately, valgrind reports are very hard to interpret.	4752	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3417		4753
3418	If you think you found a bug (memory leak, uninitialised data access etc.)	4754	If you think you found a bug (memory leak, uninitialised data access etc.)
…		…
3421	==2274== definitely lost: 0 bytes in 0 blocks.	4757	==2274== definitely lost: 0 bytes in 0 blocks.
3422	==2274== possibly lost: 0 bytes in 0 blocks.	4758	==2274== possibly lost: 0 bytes in 0 blocks.
3423	==2274== still reachable: 256 bytes in 1 blocks.	4759	==2274== still reachable: 256 bytes in 1 blocks.
3424		4760
3425	Then there is no memory leak, just as memory accounted to global variables	4761	Then there is no memory leak, just as memory accounted to global variables
3426	is not a memleak - the memory is still being refernced, and didn't leak.	4762	is not a memleak - the memory is still being referenced, and didn't leak.
3427		4763
3428	Similarly, under some circumstances, valgrind might report kernel bugs	4764	Similarly, under some circumstances, valgrind might report kernel bugs
3429	as if it were a bug in libev (e.g. in realloc or in the poll backend,	4765	as if it were a bug in libev (e.g. in realloc or in the poll backend,
3430	although an acceptable workaround has been found here), or it might be	4766	although an acceptable workaround has been found here), or it might be
3431	confused.	4767	confused.
…		…
3441		4777
3442	If you need, for some reason, empty reports from valgrind for your project	4778	If you need, for some reason, empty reports from valgrind for your project
3443	I suggest using suppression lists.	4779	I suggest using suppression lists.
3444		4780
3445		4781
3446
3447	=head1 COMPLEXITIES
3448
3449	In this section the complexities of (many of) the algorithms used inside
3450	libev will be explained. For complexity discussions about backends see the
3451	documentation for C<ev_default_init>.
3452
3453	All of the following are about amortised time: If an array needs to be
3454	extended, libev needs to realloc and move the whole array, but this
3455	happens asymptotically never with higher number of elements, so O(1) might
3456	mean it might do a lengthy realloc operation in rare cases, but on average
3457	it is much faster and asymptotically approaches constant time.
3458
3459	=over 4
3460
3461	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3462
3463	This means that, when you have a watcher that triggers in one hour and
3464	there are 100 watchers that would trigger before that then inserting will
3465	have to skip roughly seven (C<ld 100>) of these watchers.
3466
3467	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3468
3469	That means that changing a timer costs less than removing/adding them
3470	as only the relative motion in the event queue has to be paid for.
3471
3472	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3473
3474	These just add the watcher into an array or at the head of a list.
3475
3476	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3477
3478	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3479
3480	These watchers are stored in lists then need to be walked to find the
3481	correct watcher to remove. The lists are usually short (you don't usually
3482	have many watchers waiting for the same fd or signal).
3483
3484	=item Finding the next timer in each loop iteration: O(1)
3485
3486	By virtue of using a binary or 4-heap, the next timer is always found at a
3487	fixed position in the storage array.
3488
3489	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3490
3491	A change means an I/O watcher gets started or stopped, which requires
3492	libev to recalculate its status (and possibly tell the kernel, depending
3493	on backend and whether C<ev_io_set> was used).
3494
3495	=item Activating one watcher (putting it into the pending state): O(1)
3496
3497	=item Priority handling: O(number_of_priorities)
3498
3499	Priorities are implemented by allocating some space for each
3500	priority. When doing priority-based operations, libev usually has to
3501	linearly search all the priorities, but starting/stopping and activating
3502	watchers becomes O(1) with respect to priority handling.
3503
3504	=item Sending an ev_async: O(1)
3505
3506	=item Processing ev_async_send: O(number_of_async_watchers)
3507
3508	=item Processing signals: O(max_signal_number)
3509
3510	Sending involves a system call I<iff> there were no other C<ev_async_send>
3511	calls in the current loop iteration. Checking for async and signal events
3512	involves iterating over all running async watchers or all signal numbers.
3513
3514	=back
3515
3516
3517	=head1 PORTABILITY	4782	=head1 PORTABILITY NOTES
		4783
		4784	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4785
		4786	GNU/Linux is the only common platform that supports 64 bit file/large file
		4787	interfaces but I<disables> them by default.
		4788
		4789	That means that libev compiled in the default environment doesn't support
		4790	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4791
		4792	Unfortunately, many programs try to work around this GNU/Linux issue
		4793	by enabling the large file API, which makes them incompatible with the
		4794	standard libev compiled for their system.
		4795
		4796	Likewise, libev cannot enable the large file API itself as this would
		4797	suddenly make it incompatible to the default compile time environment,
		4798	i.e. all programs not using special compile switches.
		4799
		4800	=head2 OS/X AND DARWIN BUGS
		4801
		4802	The whole thing is a bug if you ask me - basically any system interface
		4803	you touch is broken, whether it is locales, poll, kqueue or even the
		4804	OpenGL drivers.
		4805
		4806	=head3 C<kqueue> is buggy
		4807
		4808	The kqueue syscall is broken in all known versions - most versions support
		4809	only sockets, many support pipes.
		4810
		4811	Libev tries to work around this by not using C<kqueue> by default on this
		4812	rotten platform, but of course you can still ask for it when creating a
		4813	loop - embedding a socket-only kqueue loop into a select-based one is
		4814	probably going to work well.
		4815
		4816	=head3 C<poll> is buggy
		4817
		4818	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4819	implementation by something calling C<kqueue> internally around the 10.5.6
		4820	release, so now C<kqueue> I<and> C<poll> are broken.
		4821
		4822	Libev tries to work around this by not using C<poll> by default on
		4823	this rotten platform, but of course you can still ask for it when creating
		4824	a loop.
		4825
		4826	=head3 C<select> is buggy
		4827
		4828	All that's left is C<select>, and of course Apple found a way to fuck this
		4829	one up as well: On OS/X, C<select> actively limits the number of file
		4830	descriptors you can pass in to 1024 - your program suddenly crashes when
		4831	you use more.
		4832
		4833	There is an undocumented "workaround" for this - defining
		4834	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4835	work on OS/X.
		4836
		4837	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4838
		4839	=head3 C<errno> reentrancy
		4840
		4841	The default compile environment on Solaris is unfortunately so
		4842	thread-unsafe that you can't even use components/libraries compiled
		4843	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4844	defined by default. A valid, if stupid, implementation choice.
		4845
		4846	If you want to use libev in threaded environments you have to make sure
		4847	it's compiled with C<_REENTRANT> defined.
		4848
		4849	=head3 Event port backend
		4850
		4851	The scalable event interface for Solaris is called "event
		4852	ports". Unfortunately, this mechanism is very buggy in all major
		4853	releases. If you run into high CPU usage, your program freezes or you get
		4854	a large number of spurious wakeups, make sure you have all the relevant
		4855	and latest kernel patches applied. No, I don't know which ones, but there
		4856	are multiple ones to apply, and afterwards, event ports actually work
		4857	great.
		4858
		4859	If you can't get it to work, you can try running the program by setting
		4860	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4861	C<select> backends.
		4862
		4863	=head2 AIX POLL BUG
		4864
		4865	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4866	this by trying to avoid the poll backend altogether (i.e. it's not even
		4867	compiled in), which normally isn't a big problem as C<select> works fine
		4868	with large bitsets on AIX, and AIX is dead anyway.
3518		4869
3519	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4870	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4871
		4872	=head3 General issues
3520		4873
3521	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4874	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3522	requires, and its I/O model is fundamentally incompatible with the POSIX	4875	requires, and its I/O model is fundamentally incompatible with the POSIX
3523	model. Libev still offers limited functionality on this platform in	4876	model. Libev still offers limited functionality on this platform in
3524	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4877	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3525	descriptors. This only applies when using Win32 natively, not when using	4878	descriptors. This only applies when using Win32 natively, not when using
3526	e.g. cygwin.	4879	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4880	as every compielr comes with a slightly differently broken/incompatible
		4881	environment.
3527		4882
3528	Lifting these limitations would basically require the full	4883	Lifting these limitations would basically require the full
3529	re-implementation of the I/O system. If you are into these kinds of	4884	re-implementation of the I/O system. If you are into this kind of thing,
3530	things, then note that glib does exactly that for you in a very portable	4885	then note that glib does exactly that for you in a very portable way (note
3531	way (note also that glib is the slowest event library known to man).	4886	also that glib is the slowest event library known to man).
3532		4887
3533	There is no supported compilation method available on windows except	4888	There is no supported compilation method available on windows except
3534	embedding it into other applications.	4889	embedding it into other applications.
		4890
		4891	Sensible signal handling is officially unsupported by Microsoft - libev
		4892	tries its best, but under most conditions, signals will simply not work.
3535		4893
3536	Not a libev limitation but worth mentioning: windows apparently doesn't	4894	Not a libev limitation but worth mentioning: windows apparently doesn't
3537	accept large writes: instead of resulting in a partial write, windows will	4895	accept large writes: instead of resulting in a partial write, windows will
3538	either accept everything or return C<ENOBUFS> if the buffer is too large,	4896	either accept everything or return C<ENOBUFS> if the buffer is too large,
3539	so make sure you only write small amounts into your sockets (less than a	4897	so make sure you only write small amounts into your sockets (less than a
…		…
3544	the abysmal performance of winsockets, using a large number of sockets	4902	the abysmal performance of winsockets, using a large number of sockets
3545	is not recommended (and not reasonable). If your program needs to use	4903	is not recommended (and not reasonable). If your program needs to use
3546	more than a hundred or so sockets, then likely it needs to use a totally	4904	more than a hundred or so sockets, then likely it needs to use a totally
3547	different implementation for windows, as libev offers the POSIX readiness	4905	different implementation for windows, as libev offers the POSIX readiness
3548	notification model, which cannot be implemented efficiently on windows	4906	notification model, which cannot be implemented efficiently on windows
3549	(Microsoft monopoly games).	4907	(due to Microsoft monopoly games).
3550		4908
3551	A typical way to use libev under windows is to embed it (see the embedding	4909	A typical way to use libev under windows is to embed it (see the embedding
3552	section for details) and use the following F<evwrap.h> header file instead	4910	section for details) and use the following F<evwrap.h> header file instead
3553	of F<ev.h>:	4911	of F<ev.h>:
3554		4912
…		…
3561	you do I<not> compile the F<ev.c> or any other embedded source files!):	4919	you do I<not> compile the F<ev.c> or any other embedded source files!):
3562		4920
3563	#include "evwrap.h"	4921	#include "evwrap.h"
3564	#include "ev.c"	4922	#include "ev.c"
3565		4923
3566	=over 4
3567
3568	=item The winsocket select function	4924	=head3 The winsocket C<select> function
3569		4925
3570	The winsocket C<select> function doesn't follow POSIX in that it	4926	The winsocket C<select> function doesn't follow POSIX in that it
3571	requires socket I<handles> and not socket I<file descriptors> (it is	4927	requires socket I<handles> and not socket I<file descriptors> (it is
3572	also extremely buggy). This makes select very inefficient, and also	4928	also extremely buggy). This makes select very inefficient, and also
3573	requires a mapping from file descriptors to socket handles (the Microsoft	4929	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3582	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4938	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3583		4939
3584	Note that winsockets handling of fd sets is O(n), so you can easily get a	4940	Note that winsockets handling of fd sets is O(n), so you can easily get a
3585	complexity in the O(n²) range when using win32.	4941	complexity in the O(n²) range when using win32.
3586		4942
3587	=item Limited number of file descriptors	4943	=head3 Limited number of file descriptors
3588		4944
3589	Windows has numerous arbitrary (and low) limits on things.	4945	Windows has numerous arbitrary (and low) limits on things.
3590		4946
3591	Early versions of winsocket's select only supported waiting for a maximum	4947	Early versions of winsocket's select only supported waiting for a maximum
3592	of C<64> handles (probably owning to the fact that all windows kernels	4948	of C<64> handles (probably owning to the fact that all windows kernels
3593	can only wait for C<64> things at the same time internally; Microsoft	4949	can only wait for C<64> things at the same time internally; Microsoft
3594	recommends spawning a chain of threads and wait for 63 handles and the	4950	recommends spawning a chain of threads and wait for 63 handles and the
3595	previous thread in each. Great).	4951	previous thread in each. Sounds great!).
3596		4952
3597	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4953	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3598	to some high number (e.g. C<2048>) before compiling the winsocket select	4954	to some high number (e.g. C<2048>) before compiling the winsocket select
3599	call (which might be in libev or elsewhere, for example, perl does its own	4955	call (which might be in libev or elsewhere, for example, perl and many
3600	select emulation on windows).	4956	other interpreters do their own select emulation on windows).
3601		4957
3602	Another limit is the number of file descriptors in the Microsoft runtime	4958	Another limit is the number of file descriptors in the Microsoft runtime
3603	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4959	libraries, which by default is C<64> (there must be a hidden I<64>
3604	or something like this inside Microsoft). You can increase this by calling	4960	fetish or something like this inside Microsoft). You can increase this
3605	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4961	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3606	arbitrary limit), but is broken in many versions of the Microsoft runtime	4962	(another arbitrary limit), but is broken in many versions of the Microsoft
3607	libraries.
3608
3609	This might get you to about C<512> or C<2048> sockets (depending on	4963	runtime libraries. This might get you to about C<512> or C<2048> sockets
3610	windows version and/or the phase of the moon). To get more, you need to	4964	(depending on windows version and/or the phase of the moon). To get more,
3611	wrap all I/O functions and provide your own fd management, but the cost of	4965	you need to wrap all I/O functions and provide your own fd management, but
3612	calling select (O(n²)) will likely make this unworkable.	4966	the cost of calling select (O(n²)) will likely make this unworkable.
3613
3614	=back
3615		4967
3616	=head2 PORTABILITY REQUIREMENTS	4968	=head2 PORTABILITY REQUIREMENTS
3617		4969
3618	In addition to a working ISO-C implementation and of course the	4970	In addition to a working ISO-C implementation and of course the
3619	backend-specific APIs, libev relies on a few additional extensions:	4971	backend-specific APIs, libev relies on a few additional extensions:
…		…
3626	Libev assumes not only that all watcher pointers have the same internal	4978	Libev assumes not only that all watcher pointers have the same internal
3627	structure (guaranteed by POSIX but not by ISO C for example), but it also	4979	structure (guaranteed by POSIX but not by ISO C for example), but it also
3628	assumes that the same (machine) code can be used to call any watcher	4980	assumes that the same (machine) code can be used to call any watcher
3629	callback: The watcher callbacks have different type signatures, but libev	4981	callback: The watcher callbacks have different type signatures, but libev
3630	calls them using an C<ev_watcher *> internally.	4982	calls them using an C<ev_watcher *> internally.
		4983
		4984	=item pointer accesses must be thread-atomic
		4985
		4986	Accessing a pointer value must be atomic, it must both be readable and
		4987	writable in one piece - this is the case on all current architectures.
3631		4988
3632	=item C<sig_atomic_t volatile> must be thread-atomic as well	4989	=item C<sig_atomic_t volatile> must be thread-atomic as well
3633		4990
3634	The type C<sig_atomic_t volatile> (or whatever is defined as	4991	The type C<sig_atomic_t volatile> (or whatever is defined as
3635	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	4992	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
3658	watchers.	5015	watchers.
3659		5016
3660	=item C<double> must hold a time value in seconds with enough accuracy	5017	=item C<double> must hold a time value in seconds with enough accuracy
3661		5018
3662	The type C<double> is used to represent timestamps. It is required to	5019	The type C<double> is used to represent timestamps. It is required to
3663	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5020	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3664	enough for at least into the year 4000. This requirement is fulfilled by	5021	good enough for at least into the year 4000 with millisecond accuracy
		5022	(the design goal for libev). This requirement is overfulfilled by
3665	implementations implementing IEEE 754 (basically all existing ones).	5023	implementations using IEEE 754, which is basically all existing ones. With
		5024	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
3666		5025
3667	=back	5026	=back
3668		5027
3669	If you know of other additional requirements drop me a note.	5028	If you know of other additional requirements drop me a note.
3670		5029
3671		5030
		5031	=head1 ALGORITHMIC COMPLEXITIES
		5032
		5033	In this section the complexities of (many of) the algorithms used inside
		5034	libev will be documented. For complexity discussions about backends see
		5035	the documentation for C<ev_default_init>.
		5036
		5037	All of the following are about amortised time: If an array needs to be
		5038	extended, libev needs to realloc and move the whole array, but this
		5039	happens asymptotically rarer with higher number of elements, so O(1) might
		5040	mean that libev does a lengthy realloc operation in rare cases, but on
		5041	average it is much faster and asymptotically approaches constant time.
		5042
		5043	=over 4
		5044
		5045	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		5046
		5047	This means that, when you have a watcher that triggers in one hour and
		5048	there are 100 watchers that would trigger before that, then inserting will
		5049	have to skip roughly seven (C<ld 100>) of these watchers.
		5050
		5051	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		5052
		5053	That means that changing a timer costs less than removing/adding them,
		5054	as only the relative motion in the event queue has to be paid for.
		5055
		5056	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		5057
		5058	These just add the watcher into an array or at the head of a list.
		5059
		5060	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		5061
		5062	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		5063
		5064	These watchers are stored in lists, so they need to be walked to find the
		5065	correct watcher to remove. The lists are usually short (you don't usually
		5066	have many watchers waiting for the same fd or signal: one is typical, two
		5067	is rare).
		5068
		5069	=item Finding the next timer in each loop iteration: O(1)
		5070
		5071	By virtue of using a binary or 4-heap, the next timer is always found at a
		5072	fixed position in the storage array.
		5073
		5074	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		5075
		5076	A change means an I/O watcher gets started or stopped, which requires
		5077	libev to recalculate its status (and possibly tell the kernel, depending
		5078	on backend and whether C<ev_io_set> was used).
		5079
		5080	=item Activating one watcher (putting it into the pending state): O(1)
		5081
		5082	=item Priority handling: O(number_of_priorities)
		5083
		5084	Priorities are implemented by allocating some space for each
		5085	priority. When doing priority-based operations, libev usually has to
		5086	linearly search all the priorities, but starting/stopping and activating
		5087	watchers becomes O(1) with respect to priority handling.
		5088
		5089	=item Sending an ev_async: O(1)
		5090
		5091	=item Processing ev_async_send: O(number_of_async_watchers)
		5092
		5093	=item Processing signals: O(max_signal_number)
		5094
		5095	Sending involves a system call I<iff> there were no other C<ev_async_send>
		5096	calls in the current loop iteration. Checking for async and signal events
		5097	involves iterating over all running async watchers or all signal numbers.
		5098
		5099	=back
		5100
		5101
		5102	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5103
		5104	The major version 4 introduced some incompatible changes to the API.
		5105
		5106	At the moment, the C<ev.h> header file provides compatibility definitions
		5107	for all changes, so most programs should still compile. The compatibility
		5108	layer might be removed in later versions of libev, so better update to the
		5109	new API early than late.
		5110
		5111	=over 4
		5112
		5113	=item C<EV_COMPAT3> backwards compatibility mechanism
		5114
		5115	The backward compatibility mechanism can be controlled by
		5116	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5117	section.
		5118
		5119	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5120
		5121	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5122
		5123	ev_loop_destroy (EV_DEFAULT_UC);
		5124	ev_loop_fork (EV_DEFAULT);
		5125
		5126	=item function/symbol renames
		5127
		5128	A number of functions and symbols have been renamed:
		5129
		5130	ev_loop => ev_run
		5131	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5132	EVLOOP_ONESHOT => EVRUN_ONCE
		5133
		5134	ev_unloop => ev_break
		5135	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5136	EVUNLOOP_ONE => EVBREAK_ONE
		5137	EVUNLOOP_ALL => EVBREAK_ALL
		5138
		5139	EV_TIMEOUT => EV_TIMER
		5140
		5141	ev_loop_count => ev_iteration
		5142	ev_loop_depth => ev_depth
		5143	ev_loop_verify => ev_verify
		5144
		5145	Most functions working on C<struct ev_loop> objects don't have an
		5146	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5147	associated constants have been renamed to not collide with the C<struct
		5148	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5149	as all other watcher types. Note that C<ev_loop_fork> is still called
		5150	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5151	typedef.
		5152
		5153	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5154
		5155	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5156	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5157	and work, but the library code will of course be larger.
		5158
		5159	=back
		5160
		5161
		5162	=head1 GLOSSARY
		5163
		5164	=over 4
		5165
		5166	=item active
		5167
		5168	A watcher is active as long as it has been started and not yet stopped.
		5169	See L<WATCHER STATES> for details.
		5170
		5171	=item application
		5172
		5173	In this document, an application is whatever is using libev.
		5174
		5175	=item backend
		5176
		5177	The part of the code dealing with the operating system interfaces.
		5178
		5179	=item callback
		5180
		5181	The address of a function that is called when some event has been
		5182	detected. Callbacks are being passed the event loop, the watcher that
		5183	received the event, and the actual event bitset.
		5184
		5185	=item callback/watcher invocation
		5186
		5187	The act of calling the callback associated with a watcher.
		5188
		5189	=item event
		5190
		5191	A change of state of some external event, such as data now being available
		5192	for reading on a file descriptor, time having passed or simply not having
		5193	any other events happening anymore.
		5194
		5195	In libev, events are represented as single bits (such as C<EV_READ> or
		5196	C<EV_TIMER>).
		5197
		5198	=item event library
		5199
		5200	A software package implementing an event model and loop.
		5201
		5202	=item event loop
		5203
		5204	An entity that handles and processes external events and converts them
		5205	into callback invocations.
		5206
		5207	=item event model
		5208
		5209	The model used to describe how an event loop handles and processes
		5210	watchers and events.
		5211
		5212	=item pending
		5213
		5214	A watcher is pending as soon as the corresponding event has been
		5215	detected. See L<WATCHER STATES> for details.
		5216
		5217	=item real time
		5218
		5219	The physical time that is observed. It is apparently strictly monotonic :)
		5220
		5221	=item wall-clock time
		5222
		5223	The time and date as shown on clocks. Unlike real time, it can actually
		5224	be wrong and jump forwards and backwards, e.g. when the you adjust your
		5225	clock.
		5226
		5227	=item watcher
		5228
		5229	A data structure that describes interest in certain events. Watchers need
		5230	to be started (attached to an event loop) before they can receive events.
		5231
		5232	=back
		5233
3672	=head1 AUTHOR	5234	=head1 AUTHOR
3673		5235
3674	Marc Lehmann <libev@schmorp.de>.	5236	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5237	Magnusson and Emanuele Giaquinta.
3675		5238

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