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…		…
8		8
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
		14	#include <stdio.h> // for puts
13		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;
…		…
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_ 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	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
…		…
103	Libev is very configurable. In this manual the default (and most common)	126	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	127	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	128	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	129	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	130	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<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
…		…
274	...	301	...
275	ev_set_syserr_cb (fatal_error);	302	ev_set_syserr_cb (fatal_error);
276		303
277	=back	304	=back
278		305
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	306	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
280		307
281	An event loop is described by a C<struct ev_loop *> (the C<struct>	308	An event loop is described by a C<struct ev_loop *> (the C<struct> is
282	is I<not> optional in this case, as there is also an C<ev_loop>	309	I<not> optional in this case unless libev 3 compatibility is disabled, as
283	I<function>).	310	libev 3 had an C<ev_loop> function colliding with the struct name).
284		311
285	The library knows two types of such loops, the I<default> loop, which	312	The library knows two types of such loops, the I<default> loop, which
286	supports signals and child events, and dynamically created loops which do	313	supports child process events, and dynamically created event loops which
287	not.	314	do not.
288		315
289	=over 4	316	=over 4
290		317
291	=item struct ev_loop *ev_default_loop (unsigned int flags)	318	=item struct ev_loop *ev_default_loop (unsigned int flags)
292		319
293	This will initialise the default event loop if it hasn't been initialised	320	This returns the "default" event loop object, which is what you should
294	yet and return it. If the default loop could not be initialised, returns	321	normally use when you just need "the event loop". Event loop objects and
295	false. If it already was initialised it simply returns it (and ignores the	322	the C<flags> parameter are described in more detail in the entry for
296	flags. If that is troubling you, check C<ev_backend ()> afterwards).	323	C<ev_loop_new>.
		324
		325	If the default loop is already initialised then this function simply
		326	returns it (and ignores the flags. If that is troubling you, check
		327	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		328	flags, which should almost always be C<0>, unless the caller is also the
		329	one calling C<ev_run> or otherwise qualifies as "the main program".
297		330
298	If you don't know what event loop to use, use the one returned from this	331	If you don't know what event loop to use, use the one returned from this
299	function.	332	function (or via the C<EV_DEFAULT> macro).
300		333
301	Note that this function is I<not> thread-safe, so if you want to use it	334	Note that this function is I<not> thread-safe, so if you want to use it
302	from multiple threads, you have to lock (note also that this is unlikely,	335	from multiple threads, you have to employ some kind of mutex (note also
303	as loops cannot be shared easily between threads anyway).	336	that this case is unlikely, as loops cannot be shared easily between
		337	threads anyway).
304		338
305	The default loop is the only loop that can handle C<ev_signal> and	339	The default loop is the only loop that can handle C<ev_child> watchers,
306	C<ev_child> watchers, and to do this, it always registers a handler	340	and to do this, it always registers a handler for C<SIGCHLD>. If this is
307	for C<SIGCHLD>. If this is a problem for your application you can either	341	a problem for your application you can either create a dynamic loop with
308	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	342	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
309	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	343	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
310	C<ev_default_init>.	344
		345	Example: This is the most typical usage.
		346
		347	if (!ev_default_loop (0))
		348	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		349
		350	Example: Restrict libev to the select and poll backends, and do not allow
		351	environment settings to be taken into account:
		352
		353	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		354
		355	=item struct ev_loop *ev_loop_new (unsigned int flags)
		356
		357	This will create and initialise a new event loop object. If the loop
		358	could not be initialised, returns false.
		359
		360	This function is thread-safe, and one common way to use libev with
		361	threads is indeed to create one loop per thread, and using the default
		362	loop in the "main" or "initial" thread.
311		363
312	The flags argument can be used to specify special behaviour or specific	364	The flags argument can be used to specify special behaviour or specific
313	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	365	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
314		366
315	The following flags are supported:	367	The following flags are supported:
…		…
330	useful to try out specific backends to test their performance, or to work	382	useful to try out specific backends to test their performance, or to work
331	around bugs.	383	around bugs.
332		384
333	=item C<EVFLAG_FORKCHECK>	385	=item C<EVFLAG_FORKCHECK>
334		386
335	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	387	Instead of calling C<ev_loop_fork> manually after a fork, you can also
336	a fork, you can also make libev check for a fork in each iteration by	388	make libev check for a fork in each iteration by enabling this flag.
337	enabling this flag.
338		389
339	This works by calling C<getpid ()> on every iteration of the loop,	390	This works by calling C<getpid ()> on every iteration of the loop,
340	and thus this might slow down your event loop if you do a lot of loop	391	and thus this might slow down your event loop if you do a lot of loop
341	iterations and little real work, but is usually not noticeable (on my	392	iterations and little real work, but is usually not noticeable (on my
342	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	393	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
…		…
348	flag.	399	flag.
349		400
350	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	401	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
351	environment variable.	402	environment variable.
352		403
		404	=item C<EVFLAG_NOINOTIFY>
		405
		406	When this flag is specified, then libev will not attempt to use the
		407	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
		408	testing, this flag can be useful to conserve inotify file descriptors, as
		409	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		410
		411	=item C<EVFLAG_SIGNALFD>
		412
		413	When this flag is specified, then libev will attempt to use the
		414	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
		415	delivers signals synchronously, which makes it both faster and might make
		416	it possible to get the queued signal data. It can also simplify signal
		417	handling with threads, as long as you properly block signals in your
		418	threads that are not interested in handling them.
		419
		420	Signalfd will not be used by default as this changes your signal mask, and
		421	there are a lot of shoddy libraries and programs (glib's threadpool for
		422	example) that can't properly initialise their signal masks.
		423
353	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	424	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
354		425
355	This is your standard select(2) backend. Not I<completely> standard, as	426	This is your standard select(2) backend. Not I<completely> standard, as
356	libev tries to roll its own fd_set with no limits on the number of fds,	427	libev tries to roll its own fd_set with no limits on the number of fds,
357	but if that fails, expect a fairly low limit on the number of fds when	428	but if that fails, expect a fairly low limit on the number of fds when
…		…
381	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and	452	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
382	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	453	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
383		454
384	=item C<EVBACKEND_EPOLL> (value 4, Linux)	455	=item C<EVBACKEND_EPOLL> (value 4, Linux)
385		456
		457	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		458	kernels).
		459
386	For few fds, this backend is a bit little slower than poll and select,	460	For few fds, this backend is a bit little slower than poll and select,
387	but it scales phenomenally better. While poll and select usually scale	461	but it scales phenomenally better. While poll and select usually scale
388	like O(total_fds) where n is the total number of fds (or the highest fd),	462	like O(total_fds) where n is the total number of fds (or the highest fd),
389	epoll scales either O(1) or O(active_fds).	463	epoll scales either O(1) or O(active_fds).
390		464
391	The epoll mechanism deserves honorable mention as the most misdesigned	465	The epoll mechanism deserves honorable mention as the most misdesigned
392	of the more advanced event mechanisms: mere annoyances include silently	466	of the more advanced event mechanisms: mere annoyances include silently
393	dropping file descriptors, requiring a system call per change per file	467	dropping file descriptors, requiring a system call per change per file
394	descriptor (and unnecessary guessing of parameters), problems with dup and	468	descriptor (and unnecessary guessing of parameters), problems with dup,
		469	returning before the timeout value, resulting in additional iterations
		470	(and only giving 5ms accuracy while select on the same platform gives
395	so on. The biggest issue is fork races, however - if a program forks then	471	0.1ms) and so on. The biggest issue is fork races, however - if a program
396	I<both> parent and child process have to recreate the epoll set, which can	472	forks then I<both> parent and child process have to recreate the epoll
397	take considerable time (one syscall per file descriptor) and is of course	473	set, which can take considerable time (one syscall per file descriptor)
398	hard to detect.	474	and is of course hard to detect.
399		475
400	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	476	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
401	of course I<doesn't>, and epoll just loves to report events for totally	477	of course I<doesn't>, and epoll just loves to report events for totally
402	I<different> file descriptors (even already closed ones, so one cannot	478	I<different> file descriptors (even already closed ones, so one cannot
403	even remove them from the set) than registered in the set (especially	479	even remove them from the set) than registered in the set (especially
404	on SMP systems). Libev tries to counter these spurious notifications by	480	on SMP systems). Libev tries to counter these spurious notifications by
405	employing an additional generation counter and comparing that against the	481	employing an additional generation counter and comparing that against the
406	events to filter out spurious ones, recreating the set when required.	482	events to filter out spurious ones, recreating the set when required. Last
		483	not least, it also refuses to work with some file descriptors which work
		484	perfectly fine with C<select> (files, many character devices...).
		485
		486	Epoll is truly the train wreck analog among event poll mechanisms.
407		487
408	While stopping, setting and starting an I/O watcher in the same iteration	488	While stopping, setting and starting an I/O watcher in the same iteration
409	will result in some caching, there is still a system call per such	489	will result in some caching, there is still a system call per such
410	incident (because the same I<file descriptor> could point to a different	490	incident (because the same I<file descriptor> could point to a different
411	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	491	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
418	starting a watcher (without re-setting it) also usually doesn't cause	498	starting a watcher (without re-setting it) also usually doesn't cause
419	extra overhead. A fork can both result in spurious notifications as well	499	extra overhead. A fork can both result in spurious notifications as well
420	as in libev having to destroy and recreate the epoll object, which can	500	as in libev having to destroy and recreate the epoll object, which can
421	take considerable time and thus should be avoided.	501	take considerable time and thus should be avoided.
422		502
423	All this means that, in practise, C<EVBACKEND_SELECT> can be as fast or	503	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
424	faster then epoll for maybe up to a hundred file descriptors, depending on	504	faster than epoll for maybe up to a hundred file descriptors, depending on
425	the usage. So sad.	505	the usage. So sad.
426		506
427	While nominally embeddable in other event loops, this feature is broken in	507	While nominally embeddable in other event loops, this feature is broken in
428	all kernel versions tested so far.	508	all kernel versions tested so far.
429		509
…		…
458		538
459	While nominally embeddable in other event loops, this doesn't work	539	While nominally embeddable in other event loops, this doesn't work
460	everywhere, so you might need to test for this. And since it is broken	540	everywhere, so you might need to test for this. And since it is broken
461	almost everywhere, you should only use it when you have a lot of sockets	541	almost everywhere, you should only use it when you have a lot of sockets
462	(for which it usually works), by embedding it into another event loop	542	(for which it usually works), by embedding it into another event loop
463	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,	543	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
464	using it only for sockets.	544	also broken on OS X)) and, did I mention it, using it only for sockets.
465		545
466	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	546	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
467	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with	547	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
468	C<NOTE_EOF>.	548	C<NOTE_EOF>.
469		549
…		…
504		584
505	It is definitely not recommended to use this flag.	585	It is definitely not recommended to use this flag.
506		586
507	=back	587	=back
508		588
509	If one or more of these are or'ed into the flags value, then only these	589	If one or more of the backend flags are or'ed into the flags value,
510	backends will be tried (in the reverse order as listed here). If none are	590	then only these backends will be tried (in the reverse order as listed
511	specified, all backends in C<ev_recommended_backends ()> will be tried.	591	here). If none are specified, all backends in C<ev_recommended_backends
512		592	()> will be tried.
513	Example: This is the most typical usage.
514
515	if (!ev_default_loop (0))
516	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
517
518	Example: Restrict libev to the select and poll backends, and do not allow
519	environment settings to be taken into account:
520
521	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
522
523	Example: Use whatever libev has to offer, but make sure that kqueue is
524	used if available (warning, breaks stuff, best use only with your own
525	private event loop and only if you know the OS supports your types of
526	fds):
527
528	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
529
530	=item struct ev_loop *ev_loop_new (unsigned int flags)
531
532	Similar to C<ev_default_loop>, but always creates a new event loop that is
533	always distinct from the default loop. Unlike the default loop, it cannot
534	handle signal and child watchers, and attempts to do so will be greeted by
535	undefined behaviour (or a failed assertion if assertions are enabled).
536
537	Note that this function I<is> thread-safe, and the recommended way to use
538	libev with threads is indeed to create one loop per thread, and using the
539	default loop in the "main" or "initial" thread.
540		593
541	Example: Try to create a event loop that uses epoll and nothing else.	594	Example: Try to create a event loop that uses epoll and nothing else.
542		595
543	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	596	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
544	if (!epoller)	597	if (!epoller)
545	fatal ("no epoll found here, maybe it hides under your chair");	598	fatal ("no epoll found here, maybe it hides under your chair");
546		599
		600	Example: Use whatever libev has to offer, but make sure that kqueue is
		601	used if available.
		602
		603	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		604
547	=item ev_default_destroy ()	605	=item ev_loop_destroy (loop)
548		606
549	Destroys the default loop again (frees all memory and kernel state	607	Destroys an event loop object (frees all memory and kernel state
550	etc.). None of the active event watchers will be stopped in the normal	608	etc.). None of the active event watchers will be stopped in the normal
551	sense, so e.g. C<ev_is_active> might still return true. It is your	609	sense, so e.g. C<ev_is_active> might still return true. It is your
552	responsibility to either stop all watchers cleanly yourself I<before>	610	responsibility to either stop all watchers cleanly yourself I<before>
553	calling this function, or cope with the fact afterwards (which is usually	611	calling this function, or cope with the fact afterwards (which is usually
554	the easiest thing, you can just ignore the watchers and/or C<free ()> them	612	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
556		614
557	Note that certain global state, such as signal state (and installed signal	615	Note that certain global state, such as signal state (and installed signal
558	handlers), will not be freed by this function, and related watchers (such	616	handlers), will not be freed by this function, and related watchers (such
559	as signal and child watchers) would need to be stopped manually.	617	as signal and child watchers) would need to be stopped manually.
560		618
561	In general it is not advisable to call this function except in the	619	This function is normally used on loop objects allocated by
562	rare occasion where you really need to free e.g. the signal handling	620	C<ev_loop_new>, but it can also be used on the default loop returned by
		621	C<ev_default_loop>, in which case it is not thread-safe.
		622
		623	Note that it is not advisable to call this function on the default loop
		624	except in the rare occasion where you really need to free its resources.
563	pipe fds. If you need dynamically allocated loops it is better to use	625	If you need dynamically allocated loops it is better to use C<ev_loop_new>
564	C<ev_loop_new> and C<ev_loop_destroy>).	626	and C<ev_loop_destroy>.
565		627
566	=item ev_loop_destroy (loop)	628	=item ev_loop_fork (loop)
567		629
568	Like C<ev_default_destroy>, but destroys an event loop created by an
569	earlier call to C<ev_loop_new>.
570
571	=item ev_default_fork ()
572
573	This function sets a flag that causes subsequent C<ev_loop> iterations	630	This function sets a flag that causes subsequent C<ev_run> iterations to
574	to reinitialise the kernel state for backends that have one. Despite the	631	reinitialise the kernel state for backends that have one. Despite the
575	name, you can call it anytime, but it makes most sense after forking, in	632	name, you can call it anytime, but it makes most sense after forking, in
576	the child process (or both child and parent, but that again makes little	633	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
577	sense). You I<must> call it in the child before using any of the libev	634	child before resuming or calling C<ev_run>.
578	functions, and it will only take effect at the next C<ev_loop> iteration.	635
		636	Again, you I<have> to call it on I<any> loop that you want to re-use after
		637	a fork, I<even if you do not plan to use the loop in the parent>. This is
		638	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		639	during fork.
579		640
580	On the other hand, you only need to call this function in the child	641	On the other hand, you only need to call this function in the child
581	process if and only if you want to use the event library in the child. If	642	process if and only if you want to use the event loop in the child. If
582	you just fork+exec, you don't have to call it at all.	643	you just fork+exec or create a new loop in the child, you don't have to
		644	call it at all (in fact, C<epoll> is so badly broken that it makes a
		645	difference, but libev will usually detect this case on its own and do a
		646	costly reset of the backend).
583		647
584	The function itself is quite fast and it's usually not a problem to call	648	The function itself is quite fast and it's usually not a problem to call
585	it just in case after a fork. To make this easy, the function will fit in	649	it just in case after a fork.
586	quite nicely into a call to C<pthread_atfork>:
587		650
		651	Example: Automate calling C<ev_loop_fork> on the default loop when
		652	using pthreads.
		653
		654	static void
		655	post_fork_child (void)
		656	{
		657	ev_loop_fork (EV_DEFAULT);
		658	}
		659
		660	...
588	pthread_atfork (0, 0, ev_default_fork);	661	pthread_atfork (0, 0, post_fork_child);
589
590	=item ev_loop_fork (loop)
591
592	Like C<ev_default_fork>, but acts on an event loop created by
593	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
594	after fork that you want to re-use in the child, and how you do this is
595	entirely your own problem.
596		662
597	=item int ev_is_default_loop (loop)	663	=item int ev_is_default_loop (loop)
598		664
599	Returns true when the given loop is, in fact, the default loop, and false	665	Returns true when the given loop is, in fact, the default loop, and false
600	otherwise.	666	otherwise.
601		667
602	=item unsigned int ev_loop_count (loop)	668	=item unsigned int ev_iteration (loop)
603		669
604	Returns the count of loop iterations for the loop, which is identical to	670	Returns the current iteration count for the event loop, which is identical
605	the number of times libev did poll for new events. It starts at C<0> and	671	to the number of times libev did poll for new events. It starts at C<0>
606	happily wraps around with enough iterations.	672	and happily wraps around with enough iterations.
607		673
608	This value can sometimes be useful as a generation counter of sorts (it	674	This value can sometimes be useful as a generation counter of sorts (it
609	"ticks" the number of loop iterations), as it roughly corresponds with	675	"ticks" the number of loop iterations), as it roughly corresponds with
610	C<ev_prepare> and C<ev_check> calls.	676	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		677	prepare and check phases.
		678
		679	=item unsigned int ev_depth (loop)
		680
		681	Returns the number of times C<ev_run> was entered minus the number of
		682	times C<ev_run> was exited normally, in other words, the recursion depth.
		683
		684	Outside C<ev_run>, this number is zero. In a callback, this number is
		685	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		686	in which case it is higher.
		687
		688	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
		689	throwing an exception etc.), doesn't count as "exit" - consider this
		690	as a hint to avoid such ungentleman-like behaviour unless it's really
		691	convenient, in which case it is fully supported.
611		692
612	=item unsigned int ev_backend (loop)	693	=item unsigned int ev_backend (loop)
613		694
614	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	695	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
615	use.	696	use.
…		…
624		705
625	=item ev_now_update (loop)	706	=item ev_now_update (loop)
626		707
627	Establishes the current time by querying the kernel, updating the time	708	Establishes the current time by querying the kernel, updating the time
628	returned by C<ev_now ()> in the progress. This is a costly operation and	709	returned by C<ev_now ()> in the progress. This is a costly operation and
629	is usually done automatically within C<ev_loop ()>.	710	is usually done automatically within C<ev_run ()>.
630		711
631	This function is rarely useful, but when some event callback runs for a	712	This function is rarely useful, but when some event callback runs for a
632	very long time without entering the event loop, updating libev's idea of	713	very long time without entering the event loop, updating libev's idea of
633	the current time is a good idea.	714	the current time is a good idea.
634		715
635	See also "The special problem of time updates" in the C<ev_timer> section.	716	See also L<The special problem of time updates> in the C<ev_timer> section.
636		717
		718	=item ev_suspend (loop)
		719
		720	=item ev_resume (loop)
		721
		722	These two functions suspend and resume an event loop, for use when the
		723	loop is not used for a while and timeouts should not be processed.
		724
		725	A typical use case would be an interactive program such as a game: When
		726	the user presses C<^Z> to suspend the game and resumes it an hour later it
		727	would be best to handle timeouts as if no time had actually passed while
		728	the program was suspended. This can be achieved by calling C<ev_suspend>
		729	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		730	C<ev_resume> directly afterwards to resume timer processing.
		731
		732	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		733	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		734	will be rescheduled (that is, they will lose any events that would have
		735	occurred while suspended).
		736
		737	After calling C<ev_suspend> you B<must not> call I<any> function on the
		738	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		739	without a previous call to C<ev_suspend>.
		740
		741	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		742	event loop time (see C<ev_now_update>).
		743
637	=item ev_loop (loop, int flags)	744	=item ev_run (loop, int flags)
638		745
639	Finally, this is it, the event handler. This function usually is called	746	Finally, this is it, the event handler. This function usually is called
640	after you initialised all your watchers and you want to start handling	747	after you have initialised all your watchers and you want to start
641	events.	748	handling events. It will ask the operating system for any new events, call
		749	the watcher callbacks, an then repeat the whole process indefinitely: This
		750	is why event loops are called I<loops>.
642		751
643	If the flags argument is specified as C<0>, it will not return until	752	If the flags argument is specified as C<0>, it will keep handling events
644	either no event watchers are active anymore or C<ev_unloop> was called.	753	until either no event watchers are active anymore or C<ev_break> was
		754	called.
645		755
646	Please note that an explicit C<ev_unloop> is usually better than	756	Please note that an explicit C<ev_break> is usually better than
647	relying on all watchers to be stopped when deciding when a program has	757	relying on all watchers to be stopped when deciding when a program has
648	finished (especially in interactive programs), but having a program	758	finished (especially in interactive programs), but having a program
649	that automatically loops as long as it has to and no longer by virtue	759	that automatically loops as long as it has to and no longer by virtue
650	of relying on its watchers stopping correctly, that is truly a thing of	760	of relying on its watchers stopping correctly, that is truly a thing of
651	beauty.	761	beauty.
652		762
		763	This function is also I<mostly> exception-safe - you can break out of
		764	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		765	exception and so on. This does not decrement the C<ev_depth> value, nor
		766	will it clear any outstanding C<EVBREAK_ONE> breaks.
		767
653	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	768	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
654	those events and any already outstanding ones, but will not block your	769	those events and any already outstanding ones, but will not wait and
655	process in case there are no events and will return after one iteration of	770	block your process in case there are no events and will return after one
656	the loop.	771	iteration of the loop. This is sometimes useful to poll and handle new
		772	events while doing lengthy calculations, to keep the program responsive.
657		773
658	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	774	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
659	necessary) and will handle those and any already outstanding ones. It	775	necessary) and will handle those and any already outstanding ones. It
660	will block your process until at least one new event arrives (which could	776	will block your process until at least one new event arrives (which could
661	be an event internal to libev itself, so there is no guarantee that a	777	be an event internal to libev itself, so there is no guarantee that a
662	user-registered callback will be called), and will return after one	778	user-registered callback will be called), and will return after one
663	iteration of the loop.	779	iteration of the loop.
664		780
665	This is useful if you are waiting for some external event in conjunction	781	This is useful if you are waiting for some external event in conjunction
666	with something not expressible using other libev watchers (i.e. "roll your	782	with something not expressible using other libev watchers (i.e. "roll your
667	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	783	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
668	usually a better approach for this kind of thing.	784	usually a better approach for this kind of thing.
669		785
670	Here are the gory details of what C<ev_loop> does:	786	Here are the gory details of what C<ev_run> does:
671		787
		788	- Increment loop depth.
		789	- Reset the ev_break status.
672	- Before the first iteration, call any pending watchers.	790	- Before the first iteration, call any pending watchers.
		791	LOOP:
673	* If EVFLAG_FORKCHECK was used, check for a fork.	792	- If EVFLAG_FORKCHECK was used, check for a fork.
674	- If a fork was detected (by any means), queue and call all fork watchers.	793	- If a fork was detected (by any means), queue and call all fork watchers.
675	- Queue and call all prepare watchers.	794	- Queue and call all prepare watchers.
		795	- If ev_break was called, goto FINISH.
676	- If we have been forked, detach and recreate the kernel state	796	- If we have been forked, detach and recreate the kernel state
677	as to not disturb the other process.	797	as to not disturb the other process.
678	- Update the kernel state with all outstanding changes.	798	- Update the kernel state with all outstanding changes.
679	- Update the "event loop time" (ev_now ()).	799	- Update the "event loop time" (ev_now ()).
680	- Calculate for how long to sleep or block, if at all	800	- Calculate for how long to sleep or block, if at all
681	(active idle watchers, EVLOOP_NONBLOCK or not having	801	(active idle watchers, EVRUN_NOWAIT or not having
682	any active watchers at all will result in not sleeping).	802	any active watchers at all will result in not sleeping).
683	- Sleep if the I/O and timer collect interval say so.	803	- Sleep if the I/O and timer collect interval say so.
		804	- Increment loop iteration counter.
684	- Block the process, waiting for any events.	805	- Block the process, waiting for any events.
685	- Queue all outstanding I/O (fd) events.	806	- Queue all outstanding I/O (fd) events.
686	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	807	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
687	- Queue all expired timers.	808	- Queue all expired timers.
688	- Queue all expired periodics.	809	- Queue all expired periodics.
689	- Unless any events are pending now, queue all idle watchers.	810	- Queue all idle watchers with priority higher than that of pending events.
690	- Queue all check watchers.	811	- Queue all check watchers.
691	- Call all queued watchers in reverse order (i.e. check watchers first).	812	- Call all queued watchers in reverse order (i.e. check watchers first).
692	Signals and child watchers are implemented as I/O watchers, and will	813	Signals and child watchers are implemented as I/O watchers, and will
693	be handled here by queueing them when their watcher gets executed.	814	be handled here by queueing them when their watcher gets executed.
694	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	815	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
695	were used, or there are no active watchers, return, otherwise	816	were used, or there are no active watchers, goto FINISH, otherwise
696	continue with step *.	817	continue with step LOOP.
		818	FINISH:
		819	- Reset the ev_break status iff it was EVBREAK_ONE.
		820	- Decrement the loop depth.
		821	- Return.
697		822
698	Example: Queue some jobs and then loop until no events are outstanding	823	Example: Queue some jobs and then loop until no events are outstanding
699	anymore.	824	anymore.
700		825
701	... queue jobs here, make sure they register event watchers as long	826	... queue jobs here, make sure they register event watchers as long
702	... as they still have work to do (even an idle watcher will do..)	827	... as they still have work to do (even an idle watcher will do..)
703	ev_loop (my_loop, 0);	828	ev_run (my_loop, 0);
704	... jobs done or somebody called unloop. yeah!	829	... jobs done or somebody called unloop. yeah!
705		830
706	=item ev_unloop (loop, how)	831	=item ev_break (loop, how)
707		832
708	Can be used to make a call to C<ev_loop> return early (but only after it	833	Can be used to make a call to C<ev_run> return early (but only after it
709	has processed all outstanding events). The C<how> argument must be either	834	has processed all outstanding events). The C<how> argument must be either
710	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	835	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
711	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	836	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
712		837
713	This "unloop state" will be cleared when entering C<ev_loop> again.	838	This "break state" will be cleared on the next call to C<ev_run>.
714		839
715	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	840	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		841	which case it will have no effect.
716		842
717	=item ev_ref (loop)	843	=item ev_ref (loop)
718		844
719	=item ev_unref (loop)	845	=item ev_unref (loop)
720		846
721	Ref/unref can be used to add or remove a reference count on the event	847	Ref/unref can be used to add or remove a reference count on the event
722	loop: Every watcher keeps one reference, and as long as the reference	848	loop: Every watcher keeps one reference, and as long as the reference
723	count is nonzero, C<ev_loop> will not return on its own.	849	count is nonzero, C<ev_run> will not return on its own.
724		850
725	If you have a watcher you never unregister that should not keep C<ev_loop>	851	This is useful when you have a watcher that you never intend to
726	from returning, call ev_unref() after starting, and ev_ref() before	852	unregister, but that nevertheless should not keep C<ev_run> from
		853	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
727	stopping it.	854	before stopping it.
728		855
729	As an example, libev itself uses this for its internal signal pipe: It is	856	As an example, libev itself uses this for its internal signal pipe: It
730	not visible to the libev user and should not keep C<ev_loop> from exiting	857	is not visible to the libev user and should not keep C<ev_run> from
731	if no event watchers registered by it are active. It is also an excellent	858	exiting if no event watchers registered by it are active. It is also an
732	way to do this for generic recurring timers or from within third-party	859	excellent way to do this for generic recurring timers or from within
733	libraries. Just remember to I<unref after start> and I<ref before stop>	860	third-party libraries. Just remember to I<unref after start> and I<ref
734	(but only if the watcher wasn't active before, or was active before,	861	before stop> (but only if the watcher wasn't active before, or was active
735	respectively).	862	before, respectively. Note also that libev might stop watchers itself
		863	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		864	in the callback).
736		865
737	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	866	Example: Create a signal watcher, but keep it from keeping C<ev_run>
738	running when nothing else is active.	867	running when nothing else is active.
739		868
740	ev_signal exitsig;	869	ev_signal exitsig;
741	ev_signal_init (&exitsig, sig_cb, SIGINT);	870	ev_signal_init (&exitsig, sig_cb, SIGINT);
742	ev_signal_start (loop, &exitsig);	871	ev_signal_start (loop, &exitsig);
…		…
769		898
770	By setting a higher I<io collect interval> you allow libev to spend more	899	By setting a higher I<io collect interval> you allow libev to spend more
771	time collecting I/O events, so you can handle more events per iteration,	900	time collecting I/O events, so you can handle more events per iteration,
772	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	901	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
773	C<ev_timer>) will be not affected. Setting this to a non-null value will	902	C<ev_timer>) will be not affected. Setting this to a non-null value will
774	introduce an additional C<ev_sleep ()> call into most loop iterations.	903	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		904	sleep time ensures that libev will not poll for I/O events more often then
		905	once per this interval, on average.
775		906
776	Likewise, by setting a higher I<timeout collect interval> you allow libev	907	Likewise, by setting a higher I<timeout collect interval> you allow libev
777	to spend more time collecting timeouts, at the expense of increased	908	to spend more time collecting timeouts, at the expense of increased
778	latency/jitter/inexactness (the watcher callback will be called	909	latency/jitter/inexactness (the watcher callback will be called
779	later). C<ev_io> watchers will not be affected. Setting this to a non-null	910	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
781		912
782	Many (busy) programs can usually benefit by setting the I/O collect	913	Many (busy) programs can usually benefit by setting the I/O collect
783	interval to a value near C<0.1> or so, which is often enough for	914	interval to a value near C<0.1> or so, which is often enough for
784	interactive servers (of course not for games), likewise for timeouts. It	915	interactive servers (of course not for games), likewise for timeouts. It
785	usually doesn't make much sense to set it to a lower value than C<0.01>,	916	usually doesn't make much sense to set it to a lower value than C<0.01>,
786	as this approaches the timing granularity of most systems.	917	as this approaches the timing granularity of most systems. Note that if
		918	you do transactions with the outside world and you can't increase the
		919	parallelity, then this setting will limit your transaction rate (if you
		920	need to poll once per transaction and the I/O collect interval is 0.01,
		921	then you can't do more than 100 transactions per second).
787		922
788	Setting the I<timeout collect interval> can improve the opportunity for	923	Setting the I<timeout collect interval> can improve the opportunity for
789	saving power, as the program will "bundle" timer callback invocations that	924	saving power, as the program will "bundle" timer callback invocations that
790	are "near" in time together, by delaying some, thus reducing the number of	925	are "near" in time together, by delaying some, thus reducing the number of
791	times the process sleeps and wakes up again. Another useful technique to	926	times the process sleeps and wakes up again. Another useful technique to
792	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	927	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
793	they fire on, say, one-second boundaries only.	928	they fire on, say, one-second boundaries only.
794		929
		930	Example: we only need 0.1s timeout granularity, and we wish not to poll
		931	more often than 100 times per second:
		932
		933	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		934	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		935
		936	=item ev_invoke_pending (loop)
		937
		938	This call will simply invoke all pending watchers while resetting their
		939	pending state. Normally, C<ev_run> does this automatically when required,
		940	but when overriding the invoke callback this call comes handy. This
		941	function can be invoked from a watcher - this can be useful for example
		942	when you want to do some lengthy calculation and want to pass further
		943	event handling to another thread (you still have to make sure only one
		944	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		945
		946	=item int ev_pending_count (loop)
		947
		948	Returns the number of pending watchers - zero indicates that no watchers
		949	are pending.
		950
		951	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		952
		953	This overrides the invoke pending functionality of the loop: Instead of
		954	invoking all pending watchers when there are any, C<ev_run> will call
		955	this callback instead. This is useful, for example, when you want to
		956	invoke the actual watchers inside another context (another thread etc.).
		957
		958	If you want to reset the callback, use C<ev_invoke_pending> as new
		959	callback.
		960
		961	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		962
		963	Sometimes you want to share the same loop between multiple threads. This
		964	can be done relatively simply by putting mutex_lock/unlock calls around
		965	each call to a libev function.
		966
		967	However, C<ev_run> can run an indefinite time, so it is not feasible
		968	to wait for it to return. One way around this is to wake up the event
		969	loop via C<ev_break> and C<av_async_send>, another way is to set these
		970	I<release> and I<acquire> callbacks on the loop.
		971
		972	When set, then C<release> will be called just before the thread is
		973	suspended waiting for new events, and C<acquire> is called just
		974	afterwards.
		975
		976	Ideally, C<release> will just call your mutex_unlock function, and
		977	C<acquire> will just call the mutex_lock function again.
		978
		979	While event loop modifications are allowed between invocations of
		980	C<release> and C<acquire> (that's their only purpose after all), no
		981	modifications done will affect the event loop, i.e. adding watchers will
		982	have no effect on the set of file descriptors being watched, or the time
		983	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		984	to take note of any changes you made.
		985
		986	In theory, threads executing C<ev_run> will be async-cancel safe between
		987	invocations of C<release> and C<acquire>.
		988
		989	See also the locking example in the C<THREADS> section later in this
		990	document.
		991
		992	=item ev_set_userdata (loop, void *data)
		993
		994	=item void *ev_userdata (loop)
		995
		996	Set and retrieve a single C<void *> associated with a loop. When
		997	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		998	C<0>.
		999
		1000	These two functions can be used to associate arbitrary data with a loop,
		1001	and are intended solely for the C<invoke_pending_cb>, C<release> and
		1002	C<acquire> callbacks described above, but of course can be (ab-)used for
		1003	any other purpose as well.
		1004
795	=item ev_loop_verify (loop)	1005	=item ev_verify (loop)
796		1006
797	This function only does something when C<EV_VERIFY> support has been	1007	This function only does something when C<EV_VERIFY> support has been
798	compiled in, which is the default for non-minimal builds. It tries to go	1008	compiled in, which is the default for non-minimal builds. It tries to go
799	through all internal structures and checks them for validity. If anything	1009	through all internal structures and checks them for validity. If anything
800	is found to be inconsistent, it will print an error message to standard	1010	is found to be inconsistent, it will print an error message to standard
…		…
811		1021
812	In the following description, uppercase C<TYPE> in names stands for the	1022	In the following description, uppercase C<TYPE> in names stands for the
813	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1023	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
814	watchers and C<ev_io_start> for I/O watchers.	1024	watchers and C<ev_io_start> for I/O watchers.
815		1025
816	A watcher is a structure that you create and register to record your	1026	A watcher is an opaque structure that you allocate and register to record
817	interest in some event. For instance, if you want to wait for STDIN to	1027	your interest in some event. To make a concrete example, imagine you want
818	become readable, you would create an C<ev_io> watcher for that:	1028	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1029	for that:
819		1030
820	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1031	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
821	{	1032	{
822	ev_io_stop (w);	1033	ev_io_stop (w);
823	ev_unloop (loop, EVUNLOOP_ALL);	1034	ev_break (loop, EVBREAK_ALL);
824	}	1035	}
825		1036
826	struct ev_loop *loop = ev_default_loop (0);	1037	struct ev_loop *loop = ev_default_loop (0);
827		1038
828	ev_io stdin_watcher;	1039	ev_io stdin_watcher;
829		1040
830	ev_init (&stdin_watcher, my_cb);	1041	ev_init (&stdin_watcher, my_cb);
831	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1042	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
832	ev_io_start (loop, &stdin_watcher);	1043	ev_io_start (loop, &stdin_watcher);
833		1044
834	ev_loop (loop, 0);	1045	ev_run (loop, 0);
835		1046
836	As you can see, you are responsible for allocating the memory for your	1047	As you can see, you are responsible for allocating the memory for your
837	watcher structures (and it is I<usually> a bad idea to do this on the	1048	watcher structures (and it is I<usually> a bad idea to do this on the
838	stack).	1049	stack).
839		1050
840	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1051	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
841	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1052	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
842		1053
843	Each watcher structure must be initialised by a call to C<ev_init	1054	Each watcher structure must be initialised by a call to C<ev_init (watcher
844	(watcher *, callback)>, which expects a callback to be provided. This	1055	*, callback)>, which expects a callback to be provided. This callback is
845	callback gets invoked each time the event occurs (or, in the case of I/O	1056	invoked each time the event occurs (or, in the case of I/O watchers, each
846	watchers, each time the event loop detects that the file descriptor given	1057	time the event loop detects that the file descriptor given is readable
847	is readable and/or writable).	1058	and/or writable).
848		1059
849	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1060	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
850	macro to configure it, with arguments specific to the watcher type. There	1061	macro to configure it, with arguments specific to the watcher type. There
851	is also a macro to combine initialisation and setting in one call: C<<	1062	is also a macro to combine initialisation and setting in one call: C<<
852	ev_TYPE_init (watcher *, callback, ...) >>.	1063	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
875	=item C<EV_WRITE>	1086	=item C<EV_WRITE>
876		1087
877	The file descriptor in the C<ev_io> watcher has become readable and/or	1088	The file descriptor in the C<ev_io> watcher has become readable and/or
878	writable.	1089	writable.
879		1090
880	=item C<EV_TIMEOUT>	1091	=item C<EV_TIMER>
881		1092
882	The C<ev_timer> watcher has timed out.	1093	The C<ev_timer> watcher has timed out.
883		1094
884	=item C<EV_PERIODIC>	1095	=item C<EV_PERIODIC>
885		1096
…		…
903		1114
904	=item C<EV_PREPARE>	1115	=item C<EV_PREPARE>
905		1116
906	=item C<EV_CHECK>	1117	=item C<EV_CHECK>
907		1118
908	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1119	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
909	to gather new events, and all C<ev_check> watchers are invoked just after	1120	to gather new events, and all C<ev_check> watchers are invoked just after
910	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1121	C<ev_run> has gathered them, but before it invokes any callbacks for any
911	received events. Callbacks of both watcher types can start and stop as	1122	received events. Callbacks of both watcher types can start and stop as
912	many watchers as they want, and all of them will be taken into account	1123	many watchers as they want, and all of them will be taken into account
913	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1124	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
914	C<ev_loop> from blocking).	1125	C<ev_run> from blocking).
915		1126
916	=item C<EV_EMBED>	1127	=item C<EV_EMBED>
917		1128
918	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1129	The embedded event loop specified in the C<ev_embed> watcher needs attention.
919		1130
920	=item C<EV_FORK>	1131	=item C<EV_FORK>
921		1132
922	The event loop has been resumed in the child process after fork (see	1133	The event loop has been resumed in the child process after fork (see
923	C<ev_fork>).	1134	C<ev_fork>).
924		1135
		1136	=item C<EV_CLEANUP>
		1137
		1138	The event loop is about to be destroyed (see C<ev_cleanup>).
		1139
925	=item C<EV_ASYNC>	1140	=item C<EV_ASYNC>
926		1141
927	The given async watcher has been asynchronously notified (see C<ev_async>).	1142	The given async watcher has been asynchronously notified (see C<ev_async>).
		1143
		1144	=item C<EV_CUSTOM>
		1145
		1146	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1147	by libev users to signal watchers (e.g. via C<ev_feed_event>).
928		1148
929	=item C<EV_ERROR>	1149	=item C<EV_ERROR>
930		1150
931	An unspecified error has occurred, the watcher has been stopped. This might	1151	An unspecified error has occurred, the watcher has been stopped. This might
932	happen because the watcher could not be properly started because libev	1152	happen because the watcher could not be properly started because libev
…		…
970		1190
971	ev_io w;	1191	ev_io w;
972	ev_init (&w, my_cb);	1192	ev_init (&w, my_cb);
973	ev_io_set (&w, STDIN_FILENO, EV_READ);	1193	ev_io_set (&w, STDIN_FILENO, EV_READ);
974		1194
975	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1195	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
976		1196
977	This macro initialises the type-specific parts of a watcher. You need to	1197	This macro initialises the type-specific parts of a watcher. You need to
978	call C<ev_init> at least once before you call this macro, but you can	1198	call C<ev_init> at least once before you call this macro, but you can
979	call C<ev_TYPE_set> any number of times. You must not, however, call this	1199	call C<ev_TYPE_set> any number of times. You must not, however, call this
980	macro on a watcher that is active (it can be pending, however, which is a	1200	macro on a watcher that is active (it can be pending, however, which is a
…		…
993		1213
994	Example: Initialise and set an C<ev_io> watcher in one step.	1214	Example: Initialise and set an C<ev_io> watcher in one step.
995		1215
996	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1216	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
997		1217
998	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1218	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
999		1219
1000	Starts (activates) the given watcher. Only active watchers will receive	1220	Starts (activates) the given watcher. Only active watchers will receive
1001	events. If the watcher is already active nothing will happen.	1221	events. If the watcher is already active nothing will happen.
1002		1222
1003	Example: Start the C<ev_io> watcher that is being abused as example in this	1223	Example: Start the C<ev_io> watcher that is being abused as example in this
1004	whole section.	1224	whole section.
1005		1225
1006	ev_io_start (EV_DEFAULT_UC, &w);	1226	ev_io_start (EV_DEFAULT_UC, &w);
1007		1227
1008	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1228	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1009		1229
1010	Stops the given watcher if active, and clears the pending status (whether	1230	Stops the given watcher if active, and clears the pending status (whether
1011	the watcher was active or not).	1231	the watcher was active or not).
1012		1232
1013	It is possible that stopped watchers are pending - for example,	1233	It is possible that stopped watchers are pending - for example,
…		…
1038	=item ev_cb_set (ev_TYPE *watcher, callback)	1258	=item ev_cb_set (ev_TYPE *watcher, callback)
1039		1259
1040	Change the callback. You can change the callback at virtually any time	1260	Change the callback. You can change the callback at virtually any time
1041	(modulo threads).	1261	(modulo threads).
1042		1262
1043	=item ev_set_priority (ev_TYPE *watcher, priority)	1263	=item ev_set_priority (ev_TYPE *watcher, int priority)
1044		1264
1045	=item int ev_priority (ev_TYPE *watcher)	1265	=item int ev_priority (ev_TYPE *watcher)
1046		1266
1047	Set and query the priority of the watcher. The priority is a small	1267	Set and query the priority of the watcher. The priority is a small
1048	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1268	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1049	(default: C<-2>). Pending watchers with higher priority will be invoked	1269	(default: C<-2>). Pending watchers with higher priority will be invoked
1050	before watchers with lower priority, but priority will not keep watchers	1270	before watchers with lower priority, but priority will not keep watchers
1051	from being executed (except for C<ev_idle> watchers).	1271	from being executed (except for C<ev_idle> watchers).
1052		1272
1053	This means that priorities are I<only> used for ordering callback
1054	invocation after new events have been received. This is useful, for
1055	example, to reduce latency after idling, or more often, to bind two
1056	watchers on the same event and make sure one is called first.
1057
1058	If you need to suppress invocation when higher priority events are pending	1273	If you need to suppress invocation when higher priority events are pending
1059	you need to look at C<ev_idle> watchers, which provide this functionality.	1274	you need to look at C<ev_idle> watchers, which provide this functionality.
1060		1275
1061	You I<must not> change the priority of a watcher as long as it is active or	1276	You I<must not> change the priority of a watcher as long as it is active or
1062	pending.	1277	pending.
1063
1064	The default priority used by watchers when no priority has been set is
1065	always C<0>, which is supposed to not be too high and not be too low :).
1066		1278
1067	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1279	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1068	fine, as long as you do not mind that the priority value you query might	1280	fine, as long as you do not mind that the priority value you query might
1069	or might not have been clamped to the valid range.	1281	or might not have been clamped to the valid range.
		1282
		1283	The default priority used by watchers when no priority has been set is
		1284	always C<0>, which is supposed to not be too high and not be too low :).
		1285
		1286	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
		1287	priorities.
1070		1288
1071	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1289	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1072		1290
1073	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1291	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1074	C<loop> nor C<revents> need to be valid as long as the watcher callback	1292	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1082	watcher isn't pending it does nothing and returns C<0>.	1300	watcher isn't pending it does nothing and returns C<0>.
1083		1301
1084	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1302	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1085	callback to be invoked, which can be accomplished with this function.	1303	callback to be invoked, which can be accomplished with this function.
1086		1304
		1305	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1306
		1307	Feeds the given event set into the event loop, as if the specified event
		1308	had happened for the specified watcher (which must be a pointer to an
		1309	initialised but not necessarily started event watcher). Obviously you must
		1310	not free the watcher as long as it has pending events.
		1311
		1312	Stopping the watcher, letting libev invoke it, or calling
		1313	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1314	not started in the first place.
		1315
		1316	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1317	functions that do not need a watcher.
		1318
1087	=back	1319	=back
1088
1089		1320
1090	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1321	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1091		1322
1092	Each watcher has, by default, a member C<void *data> that you can change	1323	Each watcher has, by default, a member C<void *data> that you can change
1093	and read at any time: libev will completely ignore it. This can be used	1324	and read at any time: libev will completely ignore it. This can be used
…		…
1139	#include <stddef.h>	1370	#include <stddef.h>
1140		1371
1141	static void	1372	static void
1142	t1_cb (EV_P_ ev_timer *w, int revents)	1373	t1_cb (EV_P_ ev_timer *w, int revents)
1143	{	1374	{
1144	struct my_biggy big = (struct my_biggy *	1375	struct my_biggy big = (struct my_biggy *)
1145	(((char *)w) - offsetof (struct my_biggy, t1));	1376	(((char *)w) - offsetof (struct my_biggy, t1));
1146	}	1377	}
1147		1378
1148	static void	1379	static void
1149	t2_cb (EV_P_ ev_timer *w, int revents)	1380	t2_cb (EV_P_ ev_timer *w, int revents)
1150	{	1381	{
1151	struct my_biggy big = (struct my_biggy *	1382	struct my_biggy big = (struct my_biggy *)
1152	(((char *)w) - offsetof (struct my_biggy, t2));	1383	(((char *)w) - offsetof (struct my_biggy, t2));
1153	}	1384	}
		1385
		1386	=head2 WATCHER STATES
		1387
		1388	There are various watcher states mentioned throughout this manual -
		1389	active, pending and so on. In this section these states and the rules to
		1390	transition between them will be described in more detail - and while these
		1391	rules might look complicated, they usually do "the right thing".
		1392
		1393	=over 4
		1394
		1395	=item initialiased
		1396
		1397	Before a watcher can be registered with the event looop it has to be
		1398	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1399	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1400
		1401	In this state it is simply some block of memory that is suitable for use
		1402	in an event loop. It can be moved around, freed, reused etc. at will.
		1403
		1404	=item started/running/active
		1405
		1406	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1407	property of the event loop, and is actively waiting for events. While in
		1408	this state it cannot be accessed (except in a few documented ways), moved,
		1409	freed or anything else - the only legal thing is to keep a pointer to it,
		1410	and call libev functions on it that are documented to work on active watchers.
		1411
		1412	=item pending
		1413
		1414	If a watcher is active and libev determines that an event it is interested
		1415	in has occurred (such as a timer expiring), it will become pending. It will
		1416	stay in this pending state until either it is stopped or its callback is
		1417	about to be invoked, so it is not normally pending inside the watcher
		1418	callback.
		1419
		1420	The watcher might or might not be active while it is pending (for example,
		1421	an expired non-repeating timer can be pending but no longer active). If it
		1422	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1423	but it is still property of the event loop at this time, so cannot be
		1424	moved, freed or reused. And if it is active the rules described in the
		1425	previous item still apply.
		1426
		1427	It is also possible to feed an event on a watcher that is not active (e.g.
		1428	via C<ev_feed_event>), in which case it becomes pending without being
		1429	active.
		1430
		1431	=item stopped
		1432
		1433	A watcher can be stopped implicitly by libev (in which case it might still
		1434	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1435	latter will clear any pending state the watcher might be in, regardless
		1436	of whether it was active or not, so stopping a watcher explicitly before
		1437	freeing it is often a good idea.
		1438
		1439	While stopped (and not pending) the watcher is essentially in the
		1440	initialised state, that is it can be reused, moved, modified in any way
		1441	you wish.
		1442
		1443	=back
		1444
		1445	=head2 WATCHER PRIORITY MODELS
		1446
		1447	Many event loops support I<watcher priorities>, which are usually small
		1448	integers that influence the ordering of event callback invocation
		1449	between watchers in some way, all else being equal.
		1450
		1451	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1452	description for the more technical details such as the actual priority
		1453	range.
		1454
		1455	There are two common ways how these these priorities are being interpreted
		1456	by event loops:
		1457
		1458	In the more common lock-out model, higher priorities "lock out" invocation
		1459	of lower priority watchers, which means as long as higher priority
		1460	watchers receive events, lower priority watchers are not being invoked.
		1461
		1462	The less common only-for-ordering model uses priorities solely to order
		1463	callback invocation within a single event loop iteration: Higher priority
		1464	watchers are invoked before lower priority ones, but they all get invoked
		1465	before polling for new events.
		1466
		1467	Libev uses the second (only-for-ordering) model for all its watchers
		1468	except for idle watchers (which use the lock-out model).
		1469
		1470	The rationale behind this is that implementing the lock-out model for
		1471	watchers is not well supported by most kernel interfaces, and most event
		1472	libraries will just poll for the same events again and again as long as
		1473	their callbacks have not been executed, which is very inefficient in the
		1474	common case of one high-priority watcher locking out a mass of lower
		1475	priority ones.
		1476
		1477	Static (ordering) priorities are most useful when you have two or more
		1478	watchers handling the same resource: a typical usage example is having an
		1479	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1480	timeouts. Under load, data might be received while the program handles
		1481	other jobs, but since timers normally get invoked first, the timeout
		1482	handler will be executed before checking for data. In that case, giving
		1483	the timer a lower priority than the I/O watcher ensures that I/O will be
		1484	handled first even under adverse conditions (which is usually, but not
		1485	always, what you want).
		1486
		1487	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1488	will only be executed when no same or higher priority watchers have
		1489	received events, they can be used to implement the "lock-out" model when
		1490	required.
		1491
		1492	For example, to emulate how many other event libraries handle priorities,
		1493	you can associate an C<ev_idle> watcher to each such watcher, and in
		1494	the normal watcher callback, you just start the idle watcher. The real
		1495	processing is done in the idle watcher callback. This causes libev to
		1496	continuously poll and process kernel event data for the watcher, but when
		1497	the lock-out case is known to be rare (which in turn is rare :), this is
		1498	workable.
		1499
		1500	Usually, however, the lock-out model implemented that way will perform
		1501	miserably under the type of load it was designed to handle. In that case,
		1502	it might be preferable to stop the real watcher before starting the
		1503	idle watcher, so the kernel will not have to process the event in case
		1504	the actual processing will be delayed for considerable time.
		1505
		1506	Here is an example of an I/O watcher that should run at a strictly lower
		1507	priority than the default, and which should only process data when no
		1508	other events are pending:
		1509
		1510	ev_idle idle; // actual processing watcher
		1511	ev_io io; // actual event watcher
		1512
		1513	static void
		1514	io_cb (EV_P_ ev_io *w, int revents)
		1515	{
		1516	// stop the I/O watcher, we received the event, but
		1517	// are not yet ready to handle it.
		1518	ev_io_stop (EV_A_ w);
		1519
		1520	// start the idle watcher to handle the actual event.
		1521	// it will not be executed as long as other watchers
		1522	// with the default priority are receiving events.
		1523	ev_idle_start (EV_A_ &idle);
		1524	}
		1525
		1526	static void
		1527	idle_cb (EV_P_ ev_idle *w, int revents)
		1528	{
		1529	// actual processing
		1530	read (STDIN_FILENO, ...);
		1531
		1532	// have to start the I/O watcher again, as
		1533	// we have handled the event
		1534	ev_io_start (EV_P_ &io);
		1535	}
		1536
		1537	// initialisation
		1538	ev_idle_init (&idle, idle_cb);
		1539	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1540	ev_io_start (EV_DEFAULT_ &io);
		1541
		1542	In the "real" world, it might also be beneficial to start a timer, so that
		1543	low-priority connections can not be locked out forever under load. This
		1544	enables your program to keep a lower latency for important connections
		1545	during short periods of high load, while not completely locking out less
		1546	important ones.
1154		1547
1155		1548
1156	=head1 WATCHER TYPES	1549	=head1 WATCHER TYPES
1157		1550
1158	This section describes each watcher in detail, but will not repeat	1551	This section describes each watcher in detail, but will not repeat
…		…
1184	descriptors to non-blocking mode is also usually a good idea (but not	1577	descriptors to non-blocking mode is also usually a good idea (but not
1185	required if you know what you are doing).	1578	required if you know what you are doing).
1186		1579
1187	If you cannot use non-blocking mode, then force the use of a	1580	If you cannot use non-blocking mode, then force the use of a
1188	known-to-be-good backend (at the time of this writing, this includes only	1581	known-to-be-good backend (at the time of this writing, this includes only
1189	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).	1582	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1583	descriptors for which non-blocking operation makes no sense (such as
		1584	files) - libev doesn't guarantee any specific behaviour in that case.
1190		1585
1191	Another thing you have to watch out for is that it is quite easy to	1586	Another thing you have to watch out for is that it is quite easy to
1192	receive "spurious" readiness notifications, that is your callback might	1587	receive "spurious" readiness notifications, that is your callback might
1193	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1588	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1194	because there is no data. Not only are some backends known to create a	1589	because there is no data. Not only are some backends known to create a
…		…
1259		1654
1260	So when you encounter spurious, unexplained daemon exits, make sure you	1655	So when you encounter spurious, unexplained daemon exits, make sure you
1261	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1656	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1262	somewhere, as that would have given you a big clue).	1657	somewhere, as that would have given you a big clue).
1263		1658
		1659	=head3 The special problem of accept()ing when you can't
		1660
		1661	Many implementations of the POSIX C<accept> function (for example,
		1662	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1663	connection from the pending queue in all error cases.
		1664
		1665	For example, larger servers often run out of file descriptors (because
		1666	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1667	rejecting the connection, leading to libev signalling readiness on
		1668	the next iteration again (the connection still exists after all), and
		1669	typically causing the program to loop at 100% CPU usage.
		1670
		1671	Unfortunately, the set of errors that cause this issue differs between
		1672	operating systems, there is usually little the app can do to remedy the
		1673	situation, and no known thread-safe method of removing the connection to
		1674	cope with overload is known (to me).
		1675
		1676	One of the easiest ways to handle this situation is to just ignore it
		1677	- when the program encounters an overload, it will just loop until the
		1678	situation is over. While this is a form of busy waiting, no OS offers an
		1679	event-based way to handle this situation, so it's the best one can do.
		1680
		1681	A better way to handle the situation is to log any errors other than
		1682	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1683	messages, and continue as usual, which at least gives the user an idea of
		1684	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1685	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1686	usage.
		1687
		1688	If your program is single-threaded, then you could also keep a dummy file
		1689	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1690	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1691	close that fd, and create a new dummy fd. This will gracefully refuse
		1692	clients under typical overload conditions.
		1693
		1694	The last way to handle it is to simply log the error and C<exit>, as
		1695	is often done with C<malloc> failures, but this results in an easy
		1696	opportunity for a DoS attack.
1264		1697
1265	=head3 Watcher-Specific Functions	1698	=head3 Watcher-Specific Functions
1266		1699
1267	=over 4	1700	=over 4
1268		1701
…		…
1300	...	1733	...
1301	struct ev_loop *loop = ev_default_init (0);	1734	struct ev_loop *loop = ev_default_init (0);
1302	ev_io stdin_readable;	1735	ev_io stdin_readable;
1303	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1736	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1304	ev_io_start (loop, &stdin_readable);	1737	ev_io_start (loop, &stdin_readable);
1305	ev_loop (loop, 0);	1738	ev_run (loop, 0);
1306		1739
1307		1740
1308	=head2 C<ev_timer> - relative and optionally repeating timeouts	1741	=head2 C<ev_timer> - relative and optionally repeating timeouts
1309		1742
1310	Timer watchers are simple relative timers that generate an event after a	1743	Timer watchers are simple relative timers that generate an event after a
…		…
1315	year, it will still time out after (roughly) one hour. "Roughly" because	1748	year, it will still time out after (roughly) one hour. "Roughly" because
1316	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1749	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1317	monotonic clock option helps a lot here).	1750	monotonic clock option helps a lot here).
1318		1751
1319	The callback is guaranteed to be invoked only I<after> its timeout has	1752	The callback is guaranteed to be invoked only I<after> its timeout has
1320	passed, but if multiple timers become ready during the same loop iteration	1753	passed (not I<at>, so on systems with very low-resolution clocks this
1321	then order of execution is undefined.	1754	might introduce a small delay). If multiple timers become ready during the
		1755	same loop iteration then the ones with earlier time-out values are invoked
		1756	before ones of the same priority with later time-out values (but this is
		1757	no longer true when a callback calls C<ev_run> recursively).
1322		1758
1323	=head3 Be smart about timeouts	1759	=head3 Be smart about timeouts
1324		1760
1325	Many real-world problems involve some kind of timeout, usually for error	1761	Many real-world problems involve some kind of timeout, usually for error
1326	recovery. A typical example is an HTTP request - if the other side hangs,	1762	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1370	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>	1806	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
1371	member and C<ev_timer_again>.	1807	member and C<ev_timer_again>.
1372		1808
1373	At start:	1809	At start:
1374		1810
1375	ev_timer_init (timer, callback);	1811	ev_init (timer, callback);
1376	timer->repeat = 60.;	1812	timer->repeat = 60.;
1377	ev_timer_again (loop, timer);	1813	ev_timer_again (loop, timer);
1378		1814
1379	Each time there is some activity:	1815	Each time there is some activity:
1380		1816
…		…
1412	ev_tstamp timeout = last_activity + 60.;	1848	ev_tstamp timeout = last_activity + 60.;
1413		1849
1414	// if last_activity + 60. is older than now, we did time out	1850	// if last_activity + 60. is older than now, we did time out
1415	if (timeout < now)	1851	if (timeout < now)
1416	{	1852	{
1417	// timeout occured, take action	1853	// timeout occurred, take action
1418	}	1854	}
1419	else	1855	else
1420	{	1856	{
1421	// callback was invoked, but there was some activity, re-arm	1857	// callback was invoked, but there was some activity, re-arm
1422	// the watcher to fire in last_activity + 60, which is	1858	// the watcher to fire in last_activity + 60, which is
1423	// guaranteed to be in the future, so "again" is positive:	1859	// guaranteed to be in the future, so "again" is positive:
1424	w->again = timeout - now;	1860	w->repeat = timeout - now;
1425	ev_timer_again (EV_A_ w);	1861	ev_timer_again (EV_A_ w);
1426	}	1862	}
1427	}	1863	}
1428		1864
1429	To summarise the callback: first calculate the real timeout (defined	1865	To summarise the callback: first calculate the real timeout (defined
…		…
1442		1878
1443	To start the timer, simply initialise the watcher and set C<last_activity>	1879	To start the timer, simply initialise the watcher and set C<last_activity>
1444	to the current time (meaning we just have some activity :), then call the	1880	to the current time (meaning we just have some activity :), then call the
1445	callback, which will "do the right thing" and start the timer:	1881	callback, which will "do the right thing" and start the timer:
1446		1882
1447	ev_timer_init (timer, callback);	1883	ev_init (timer, callback);
1448	last_activity = ev_now (loop);	1884	last_activity = ev_now (loop);
1449	callback (loop, timer, EV_TIMEOUT);	1885	callback (loop, timer, EV_TIMER);
1450		1886
1451	And when there is some activity, simply store the current time in	1887	And when there is some activity, simply store the current time in
1452	C<last_activity>, no libev calls at all:	1888	C<last_activity>, no libev calls at all:
1453		1889
1454	last_actiivty = ev_now (loop);	1890	last_activity = ev_now (loop);
1455		1891
1456	This technique is slightly more complex, but in most cases where the	1892	This technique is slightly more complex, but in most cases where the
1457	time-out is unlikely to be triggered, much more efficient.	1893	time-out is unlikely to be triggered, much more efficient.
1458		1894
1459	Changing the timeout is trivial as well (if it isn't hard-coded in the	1895	Changing the timeout is trivial as well (if it isn't hard-coded in the
…		…
1497		1933
1498	=head3 The special problem of time updates	1934	=head3 The special problem of time updates
1499		1935
1500	Establishing the current time is a costly operation (it usually takes at	1936	Establishing the current time is a costly operation (it usually takes at
1501	least two system calls): EV therefore updates its idea of the current	1937	least two system calls): EV therefore updates its idea of the current
1502	time only before and after C<ev_loop> collects new events, which causes a	1938	time only before and after C<ev_run> collects new events, which causes a
1503	growing difference between C<ev_now ()> and C<ev_time ()> when handling	1939	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1504	lots of events in one iteration.	1940	lots of events in one iteration.
1505		1941
1506	The relative timeouts are calculated relative to the C<ev_now ()>	1942	The relative timeouts are calculated relative to the C<ev_now ()>
1507	time. This is usually the right thing as this timestamp refers to the time	1943	time. This is usually the right thing as this timestamp refers to the time
…		…
1513		1949
1514	If the event loop is suspended for a long time, you can also force an	1950	If the event loop is suspended for a long time, you can also force an
1515	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1951	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1516	()>.	1952	()>.
1517		1953
		1954	=head3 The special problems of suspended animation
		1955
		1956	When you leave the server world it is quite customary to hit machines that
		1957	can suspend/hibernate - what happens to the clocks during such a suspend?
		1958
		1959	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1960	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1961	to run until the system is suspended, but they will not advance while the
		1962	system is suspended. That means, on resume, it will be as if the program
		1963	was frozen for a few seconds, but the suspend time will not be counted
		1964	towards C<ev_timer> when a monotonic clock source is used. The real time
		1965	clock advanced as expected, but if it is used as sole clocksource, then a
		1966	long suspend would be detected as a time jump by libev, and timers would
		1967	be adjusted accordingly.
		1968
		1969	I would not be surprised to see different behaviour in different between
		1970	operating systems, OS versions or even different hardware.
		1971
		1972	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1973	time jump in the monotonic clocks and the realtime clock. If the program
		1974	is suspended for a very long time, and monotonic clock sources are in use,
		1975	then you can expect C<ev_timer>s to expire as the full suspension time
		1976	will be counted towards the timers. When no monotonic clock source is in
		1977	use, then libev will again assume a timejump and adjust accordingly.
		1978
		1979	It might be beneficial for this latter case to call C<ev_suspend>
		1980	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1981	deterministic behaviour in this case (you can do nothing against
		1982	C<SIGSTOP>).
		1983
1518	=head3 Watcher-Specific Functions and Data Members	1984	=head3 Watcher-Specific Functions and Data Members
1519		1985
1520	=over 4	1986	=over 4
1521		1987
1522	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1988	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1545	If the timer is started but non-repeating, stop it (as if it timed out).	2011	If the timer is started but non-repeating, stop it (as if it timed out).
1546		2012
1547	If the timer is repeating, either start it if necessary (with the	2013	If the timer is repeating, either start it if necessary (with the
1548	C<repeat> value), or reset the running timer to the C<repeat> value.	2014	C<repeat> value), or reset the running timer to the C<repeat> value.
1549		2015
1550	This sounds a bit complicated, see "Be smart about timeouts", above, for a	2016	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1551	usage example.	2017	usage example.
		2018
		2019	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2020
		2021	Returns the remaining time until a timer fires. If the timer is active,
		2022	then this time is relative to the current event loop time, otherwise it's
		2023	the timeout value currently configured.
		2024
		2025	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2026	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2027	will return C<4>. When the timer expires and is restarted, it will return
		2028	roughly C<7> (likely slightly less as callback invocation takes some time,
		2029	too), and so on.
1552		2030
1553	=item ev_tstamp repeat [read-write]	2031	=item ev_tstamp repeat [read-write]
1554		2032
1555	The current C<repeat> value. Will be used each time the watcher times out	2033	The current C<repeat> value. Will be used each time the watcher times out
1556	or C<ev_timer_again> is called, and determines the next timeout (if any),	2034	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1582	}	2060	}
1583		2061
1584	ev_timer mytimer;	2062	ev_timer mytimer;
1585	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2063	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1586	ev_timer_again (&mytimer); /* start timer */	2064	ev_timer_again (&mytimer); /* start timer */
1587	ev_loop (loop, 0);	2065	ev_run (loop, 0);
1588		2066
1589	// and in some piece of code that gets executed on any "activity":	2067	// and in some piece of code that gets executed on any "activity":
1590	// reset the timeout to start ticking again at 10 seconds	2068	// reset the timeout to start ticking again at 10 seconds
1591	ev_timer_again (&mytimer);	2069	ev_timer_again (&mytimer);
1592		2070
…		…
1594	=head2 C<ev_periodic> - to cron or not to cron?	2072	=head2 C<ev_periodic> - to cron or not to cron?
1595		2073
1596	Periodic watchers are also timers of a kind, but they are very versatile	2074	Periodic watchers are also timers of a kind, but they are very versatile
1597	(and unfortunately a bit complex).	2075	(and unfortunately a bit complex).
1598		2076
1599	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2077	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1600	but on wall clock time (absolute time). You can tell a periodic watcher	2078	relative time, the physical time that passes) but on wall clock time
1601	to trigger after some specific point in time. For example, if you tell a	2079	(absolute time, the thing you can read on your calender or clock). The
1602	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	2080	difference is that wall clock time can run faster or slower than real
1603	+ 10.>, that is, an absolute time not a delay) and then reset your system	2081	time, and time jumps are not uncommon (e.g. when you adjust your
1604	clock to January of the previous year, then it will take more than year	2082	wrist-watch).
1605	to trigger the event (unlike an C<ev_timer>, which would still trigger
1606	roughly 10 seconds later as it uses a relative timeout).
1607		2083
		2084	You can tell a periodic watcher to trigger after some specific point
		2085	in time: for example, if you tell a periodic watcher to trigger "in 10
		2086	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2087	not a delay) and then reset your system clock to January of the previous
		2088	year, then it will take a year or more to trigger the event (unlike an
		2089	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2090	it, as it uses a relative timeout).
		2091
1608	C<ev_periodic>s can also be used to implement vastly more complex timers,	2092	C<ev_periodic> watchers can also be used to implement vastly more complex
1609	such as triggering an event on each "midnight, local time", or other	2093	timers, such as triggering an event on each "midnight, local time", or
1610	complicated rules.	2094	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2095	those cannot react to time jumps.
1611		2096
1612	As with timers, the callback is guaranteed to be invoked only when the	2097	As with timers, the callback is guaranteed to be invoked only when the
1613	time (C<at>) has passed, but if multiple periodic timers become ready	2098	point in time where it is supposed to trigger has passed. If multiple
1614	during the same loop iteration, then order of execution is undefined.	2099	timers become ready during the same loop iteration then the ones with
		2100	earlier time-out values are invoked before ones with later time-out values
		2101	(but this is no longer true when a callback calls C<ev_run> recursively).
1615		2102
1616	=head3 Watcher-Specific Functions and Data Members	2103	=head3 Watcher-Specific Functions and Data Members
1617		2104
1618	=over 4	2105	=over 4
1619		2106
1620	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2107	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1621		2108
1622	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2109	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1623		2110
1624	Lots of arguments, lets sort it out... There are basically three modes of	2111	Lots of arguments, let's sort it out... There are basically three modes of
1625	operation, and we will explain them from simplest to most complex:	2112	operation, and we will explain them from simplest to most complex:
1626		2113
1627	=over 4	2114	=over 4
1628		2115
1629	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2116	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1630		2117
1631	In this configuration the watcher triggers an event after the wall clock	2118	In this configuration the watcher triggers an event after the wall clock
1632	time C<at> has passed. It will not repeat and will not adjust when a time	2119	time C<offset> has passed. It will not repeat and will not adjust when a
1633	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2120	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1634	only run when the system clock reaches or surpasses this time.	2121	will be stopped and invoked when the system clock reaches or surpasses
		2122	this point in time.
1635		2123
1636	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2124	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1637		2125
1638	In this mode the watcher will always be scheduled to time out at the next	2126	In this mode the watcher will always be scheduled to time out at the next
1639	C<at + N * interval> time (for some integer N, which can also be negative)	2127	C<offset + N * interval> time (for some integer N, which can also be
1640	and then repeat, regardless of any time jumps.	2128	negative) and then repeat, regardless of any time jumps. The C<offset>
		2129	argument is merely an offset into the C<interval> periods.
1641		2130
1642	This can be used to create timers that do not drift with respect to the	2131	This can be used to create timers that do not drift with respect to the
1643	system clock, for example, here is a C<ev_periodic> that triggers each	2132	system clock, for example, here is an C<ev_periodic> that triggers each
1644	hour, on the hour:	2133	hour, on the hour (with respect to UTC):
1645		2134
1646	ev_periodic_set (&periodic, 0., 3600., 0);	2135	ev_periodic_set (&periodic, 0., 3600., 0);
1647		2136
1648	This doesn't mean there will always be 3600 seconds in between triggers,	2137	This doesn't mean there will always be 3600 seconds in between triggers,
1649	but only that the callback will be called when the system time shows a	2138	but only that the callback will be called when the system time shows a
1650	full hour (UTC), or more correctly, when the system time is evenly divisible	2139	full hour (UTC), or more correctly, when the system time is evenly divisible
1651	by 3600.	2140	by 3600.
1652		2141
1653	Another way to think about it (for the mathematically inclined) is that	2142	Another way to think about it (for the mathematically inclined) is that
1654	C<ev_periodic> will try to run the callback in this mode at the next possible	2143	C<ev_periodic> will try to run the callback in this mode at the next possible
1655	time where C<time = at (mod interval)>, regardless of any time jumps.	2144	time where C<time = offset (mod interval)>, regardless of any time jumps.
1656		2145
1657	For numerical stability it is preferable that the C<at> value is near	2146	For numerical stability it is preferable that the C<offset> value is near
1658	C<ev_now ()> (the current time), but there is no range requirement for	2147	C<ev_now ()> (the current time), but there is no range requirement for
1659	this value, and in fact is often specified as zero.	2148	this value, and in fact is often specified as zero.
1660		2149
1661	Note also that there is an upper limit to how often a timer can fire (CPU	2150	Note also that there is an upper limit to how often a timer can fire (CPU
1662	speed for example), so if C<interval> is very small then timing stability	2151	speed for example), so if C<interval> is very small then timing stability
1663	will of course deteriorate. Libev itself tries to be exact to be about one	2152	will of course deteriorate. Libev itself tries to be exact to be about one
1664	millisecond (if the OS supports it and the machine is fast enough).	2153	millisecond (if the OS supports it and the machine is fast enough).
1665		2154
1666	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2155	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1667		2156
1668	In this mode the values for C<interval> and C<at> are both being	2157	In this mode the values for C<interval> and C<offset> are both being
1669	ignored. Instead, each time the periodic watcher gets scheduled, the	2158	ignored. Instead, each time the periodic watcher gets scheduled, the
1670	reschedule callback will be called with the watcher as first, and the	2159	reschedule callback will be called with the watcher as first, and the
1671	current time as second argument.	2160	current time as second argument.
1672		2161
1673	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2162	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1674	ever, or make ANY event loop modifications whatsoever>.	2163	or make ANY other event loop modifications whatsoever, unless explicitly
		2164	allowed by documentation here>.
1675		2165
1676	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2166	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1677	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2167	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1678	only event loop modification you are allowed to do).	2168	only event loop modification you are allowed to do).
1679		2169
…		…
1709	a different time than the last time it was called (e.g. in a crond like	2199	a different time than the last time it was called (e.g. in a crond like
1710	program when the crontabs have changed).	2200	program when the crontabs have changed).
1711		2201
1712	=item ev_tstamp ev_periodic_at (ev_periodic *)	2202	=item ev_tstamp ev_periodic_at (ev_periodic *)
1713		2203
1714	When active, returns the absolute time that the watcher is supposed to	2204	When active, returns the absolute time that the watcher is supposed
1715	trigger next.	2205	to trigger next. This is not the same as the C<offset> argument to
		2206	C<ev_periodic_set>, but indeed works even in interval and manual
		2207	rescheduling modes.
1716		2208
1717	=item ev_tstamp offset [read-write]	2209	=item ev_tstamp offset [read-write]
1718		2210
1719	When repeating, this contains the offset value, otherwise this is the	2211	When repeating, this contains the offset value, otherwise this is the
1720	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2212	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2213	although libev might modify this value for better numerical stability).
1721		2214
1722	Can be modified any time, but changes only take effect when the periodic	2215	Can be modified any time, but changes only take effect when the periodic
1723	timer fires or C<ev_periodic_again> is being called.	2216	timer fires or C<ev_periodic_again> is being called.
1724		2217
1725	=item ev_tstamp interval [read-write]	2218	=item ev_tstamp interval [read-write]
…		…
1741	Example: Call a callback every hour, or, more precisely, whenever the	2234	Example: Call a callback every hour, or, more precisely, whenever the
1742	system time is divisible by 3600. The callback invocation times have	2235	system time is divisible by 3600. The callback invocation times have
1743	potentially a lot of jitter, but good long-term stability.	2236	potentially a lot of jitter, but good long-term stability.
1744		2237
1745	static void	2238	static void
1746	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2239	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1747	{	2240	{
1748	... its now a full hour (UTC, or TAI or whatever your clock follows)	2241	... its now a full hour (UTC, or TAI or whatever your clock follows)
1749	}	2242	}
1750		2243
1751	ev_periodic hourly_tick;	2244	ev_periodic hourly_tick;
…		…
1774		2267
1775	=head2 C<ev_signal> - signal me when a signal gets signalled!	2268	=head2 C<ev_signal> - signal me when a signal gets signalled!
1776		2269
1777	Signal watchers will trigger an event when the process receives a specific	2270	Signal watchers will trigger an event when the process receives a specific
1778	signal one or more times. Even though signals are very asynchronous, libev	2271	signal one or more times. Even though signals are very asynchronous, libev
1779	will try it's best to deliver signals synchronously, i.e. as part of the	2272	will try its best to deliver signals synchronously, i.e. as part of the
1780	normal event processing, like any other event.	2273	normal event processing, like any other event.
1781		2274
1782	If you want signals asynchronously, just use C<sigaction> as you would	2275	If you want signals to be delivered truly asynchronously, just use
1783	do without libev and forget about sharing the signal. You can even use	2276	C<sigaction> as you would do without libev and forget about sharing
1784	C<ev_async> from a signal handler to synchronously wake up an event loop.	2277	the signal. You can even use C<ev_async> from a signal handler to
		2278	synchronously wake up an event loop.
1785		2279
1786	You can configure as many watchers as you like per signal. Only when the	2280	You can configure as many watchers as you like for the same signal, but
		2281	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2282	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2283	C<SIGINT> in both the default loop and another loop at the same time. At
		2284	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2285
1787	first watcher gets started will libev actually register a signal handler	2286	When the first watcher gets started will libev actually register something
1788	with the kernel (thus it coexists with your own signal handlers as long as	2287	with the kernel (thus it coexists with your own signal handlers as long as
1789	you don't register any with libev for the same signal). Similarly, when	2288	you don't register any with libev for the same signal).
1790	the last signal watcher for a signal is stopped, libev will reset the
1791	signal handler to SIG_DFL (regardless of what it was set to before).
1792		2289
1793	If possible and supported, libev will install its handlers with	2290	If possible and supported, libev will install its handlers with
1794	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2291	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1795	interrupted. If you have a problem with system calls getting interrupted by	2292	not be unduly interrupted. If you have a problem with system calls getting
1796	signals you can block all signals in an C<ev_check> watcher and unblock	2293	interrupted by signals you can block all signals in an C<ev_check> watcher
1797	them in an C<ev_prepare> watcher.	2294	and unblock them in an C<ev_prepare> watcher.
		2295
		2296	=head3 The special problem of inheritance over fork/execve/pthread_create
		2297
		2298	Both the signal mask (C<sigprocmask>) and the signal disposition
		2299	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2300	stopping it again), that is, libev might or might not block the signal,
		2301	and might or might not set or restore the installed signal handler.
		2302
		2303	While this does not matter for the signal disposition (libev never
		2304	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2305	C<execve>), this matters for the signal mask: many programs do not expect
		2306	certain signals to be blocked.
		2307
		2308	This means that before calling C<exec> (from the child) you should reset
		2309	the signal mask to whatever "default" you expect (all clear is a good
		2310	choice usually).
		2311
		2312	The simplest way to ensure that the signal mask is reset in the child is
		2313	to install a fork handler with C<pthread_atfork> that resets it. That will
		2314	catch fork calls done by libraries (such as the libc) as well.
		2315
		2316	In current versions of libev, the signal will not be blocked indefinitely
		2317	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2318	the window of opportunity for problems, it will not go away, as libev
		2319	I<has> to modify the signal mask, at least temporarily.
		2320
		2321	So I can't stress this enough: I<If you do not reset your signal mask when
		2322	you expect it to be empty, you have a race condition in your code>. This
		2323	is not a libev-specific thing, this is true for most event libraries.
1798		2324
1799	=head3 Watcher-Specific Functions and Data Members	2325	=head3 Watcher-Specific Functions and Data Members
1800		2326
1801	=over 4	2327	=over 4
1802		2328
…		…
1818	Example: Try to exit cleanly on SIGINT.	2344	Example: Try to exit cleanly on SIGINT.
1819		2345
1820	static void	2346	static void
1821	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2347	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1822	{	2348	{
1823	ev_unloop (loop, EVUNLOOP_ALL);	2349	ev_break (loop, EVBREAK_ALL);
1824	}	2350	}
1825		2351
1826	ev_signal signal_watcher;	2352	ev_signal signal_watcher;
1827	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2353	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1828	ev_signal_start (loop, &signal_watcher);	2354	ev_signal_start (loop, &signal_watcher);
…		…
1834	some child status changes (most typically when a child of yours dies or	2360	some child status changes (most typically when a child of yours dies or
1835	exits). It is permissible to install a child watcher I<after> the child	2361	exits). It is permissible to install a child watcher I<after> the child
1836	has been forked (which implies it might have already exited), as long	2362	has been forked (which implies it might have already exited), as long
1837	as the event loop isn't entered (or is continued from a watcher), i.e.,	2363	as the event loop isn't entered (or is continued from a watcher), i.e.,
1838	forking and then immediately registering a watcher for the child is fine,	2364	forking and then immediately registering a watcher for the child is fine,
1839	but forking and registering a watcher a few event loop iterations later is	2365	but forking and registering a watcher a few event loop iterations later or
1840	not.	2366	in the next callback invocation is not.
1841		2367
1842	Only the default event loop is capable of handling signals, and therefore	2368	Only the default event loop is capable of handling signals, and therefore
1843	you can only register child watchers in the default event loop.	2369	you can only register child watchers in the default event loop.
1844		2370
		2371	Due to some design glitches inside libev, child watchers will always be
		2372	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2373	libev)
		2374
1845	=head3 Process Interaction	2375	=head3 Process Interaction
1846		2376
1847	Libev grabs C<SIGCHLD> as soon as the default event loop is	2377	Libev grabs C<SIGCHLD> as soon as the default event loop is
1848	initialised. This is necessary to guarantee proper behaviour even if	2378	initialised. This is necessary to guarantee proper behaviour even if the
1849	the first child watcher is started after the child exits. The occurrence	2379	first child watcher is started after the child exits. The occurrence
1850	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2380	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1851	synchronously as part of the event loop processing. Libev always reaps all	2381	synchronously as part of the event loop processing. Libev always reaps all
1852	children, even ones not watched.	2382	children, even ones not watched.
1853		2383
1854	=head3 Overriding the Built-In Processing	2384	=head3 Overriding the Built-In Processing
…		…
1864	=head3 Stopping the Child Watcher	2394	=head3 Stopping the Child Watcher
1865		2395
1866	Currently, the child watcher never gets stopped, even when the	2396	Currently, the child watcher never gets stopped, even when the
1867	child terminates, so normally one needs to stop the watcher in the	2397	child terminates, so normally one needs to stop the watcher in the
1868	callback. Future versions of libev might stop the watcher automatically	2398	callback. Future versions of libev might stop the watcher automatically
1869	when a child exit is detected.	2399	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2400	problem).
1870		2401
1871	=head3 Watcher-Specific Functions and Data Members	2402	=head3 Watcher-Specific Functions and Data Members
1872		2403
1873	=over 4	2404	=over 4
1874		2405
…		…
2010	the process. The exception are C<ev_stat> watchers - those call C<stat	2541	the process. The exception are C<ev_stat> watchers - those call C<stat
2011	()>, which is a synchronous operation.	2542	()>, which is a synchronous operation.
2012		2543
2013	For local paths, this usually doesn't matter: unless the system is very	2544	For local paths, this usually doesn't matter: unless the system is very
2014	busy or the intervals between stat's are large, a stat call will be fast,	2545	busy or the intervals between stat's are large, a stat call will be fast,
2015	as the path data is suually in memory already (except when starting the	2546	as the path data is usually in memory already (except when starting the
2016	watcher).	2547	watcher).
2017		2548
2018	For networked file systems, calling C<stat ()> can block an indefinite	2549	For networked file systems, calling C<stat ()> can block an indefinite
2019	time due to network issues, and even under good conditions, a stat call	2550	time due to network issues, and even under good conditions, a stat call
2020	often takes multiple milliseconds.	2551	often takes multiple milliseconds.
…		…
2177		2708
2178	=head3 Watcher-Specific Functions and Data Members	2709	=head3 Watcher-Specific Functions and Data Members
2179		2710
2180	=over 4	2711	=over 4
2181		2712
2182	=item ev_idle_init (ev_signal *, callback)	2713	=item ev_idle_init (ev_idle *, callback)
2183		2714
2184	Initialises and configures the idle watcher - it has no parameters of any	2715	Initialises and configures the idle watcher - it has no parameters of any
2185	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2716	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
2186	believe me.	2717	believe me.
2187		2718
…		…
2200	// no longer anything immediate to do.	2731	// no longer anything immediate to do.
2201	}	2732	}
2202		2733
2203	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2734	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2204	ev_idle_init (idle_watcher, idle_cb);	2735	ev_idle_init (idle_watcher, idle_cb);
2205	ev_idle_start (loop, idle_cb);	2736	ev_idle_start (loop, idle_watcher);
2206		2737
2207		2738
2208	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2739	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2209		2740
2210	Prepare and check watchers are usually (but not always) used in pairs:	2741	Prepare and check watchers are usually (but not always) used in pairs:
2211	prepare watchers get invoked before the process blocks and check watchers	2742	prepare watchers get invoked before the process blocks and check watchers
2212	afterwards.	2743	afterwards.
2213		2744
2214	You I<must not> call C<ev_loop> or similar functions that enter	2745	You I<must not> call C<ev_run> or similar functions that enter
2215	the current event loop from either C<ev_prepare> or C<ev_check>	2746	the current event loop from either C<ev_prepare> or C<ev_check>
2216	watchers. Other loops than the current one are fine, however. The	2747	watchers. Other loops than the current one are fine, however. The
2217	rationale behind this is that you do not need to check for recursion in	2748	rationale behind this is that you do not need to check for recursion in
2218	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2749	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2219	C<ev_check> so if you have one watcher of each kind they will always be	2750	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2303	struct pollfd fds [nfd];	2834	struct pollfd fds [nfd];
2304	// actual code will need to loop here and realloc etc.	2835	// actual code will need to loop here and realloc etc.
2305	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2836	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2306		2837
2307	/* the callback is illegal, but won't be called as we stop during check */	2838	/* the callback is illegal, but won't be called as we stop during check */
2308	ev_timer_init (&tw, 0, timeout * 1e-3);	2839	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2309	ev_timer_start (loop, &tw);	2840	ev_timer_start (loop, &tw);
2310		2841
2311	// create one ev_io per pollfd	2842	// create one ev_io per pollfd
2312	for (int i = 0; i < nfd; ++i)	2843	for (int i = 0; i < nfd; ++i)
2313	{	2844	{
…		…
2387		2918
2388	if (timeout >= 0)	2919	if (timeout >= 0)
2389	// create/start timer	2920	// create/start timer
2390		2921
2391	// poll	2922	// poll
2392	ev_loop (EV_A_ 0);	2923	ev_run (EV_A_ 0);
2393		2924
2394	// stop timer again	2925	// stop timer again
2395	if (timeout >= 0)	2926	if (timeout >= 0)
2396	ev_timer_stop (EV_A_ &to);	2927	ev_timer_stop (EV_A_ &to);
2397		2928
…		…
2426	some fds have to be watched and handled very quickly (with low latency),	2957	some fds have to be watched and handled very quickly (with low latency),
2427	and even priorities and idle watchers might have too much overhead. In	2958	and even priorities and idle watchers might have too much overhead. In
2428	this case you would put all the high priority stuff in one loop and all	2959	this case you would put all the high priority stuff in one loop and all
2429	the rest in a second one, and embed the second one in the first.	2960	the rest in a second one, and embed the second one in the first.
2430		2961
2431	As long as the watcher is active, the callback will be invoked every time	2962	As long as the watcher is active, the callback will be invoked every
2432	there might be events pending in the embedded loop. The callback must then	2963	time there might be events pending in the embedded loop. The callback
2433	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2964	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2434	their callbacks (you could also start an idle watcher to give the embedded	2965	sweep and invoke their callbacks (the callback doesn't need to invoke the
2435	loop strictly lower priority for example). You can also set the callback	2966	C<ev_embed_sweep> function directly, it could also start an idle watcher
2436	to C<0>, in which case the embed watcher will automatically execute the	2967	to give the embedded loop strictly lower priority for example).
2437	embedded loop sweep.
2438		2968
2439	As long as the watcher is started it will automatically handle events. The	2969	You can also set the callback to C<0>, in which case the embed watcher
2440	callback will be invoked whenever some events have been handled. You can	2970	will automatically execute the embedded loop sweep whenever necessary.
2441	set the callback to C<0> to avoid having to specify one if you are not
2442	interested in that.
2443		2971
2444	Also, there have not currently been made special provisions for forking:	2972	Fork detection will be handled transparently while the C<ev_embed> watcher
2445	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2973	is active, i.e., the embedded loop will automatically be forked when the
2446	but you will also have to stop and restart any C<ev_embed> watchers	2974	embedding loop forks. In other cases, the user is responsible for calling
2447	yourself - but you can use a fork watcher to handle this automatically,	2975	C<ev_loop_fork> on the embedded loop.
2448	and future versions of libev might do just that.
2449		2976
2450	Unfortunately, not all backends are embeddable: only the ones returned by	2977	Unfortunately, not all backends are embeddable: only the ones returned by
2451	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2978	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2452	portable one.	2979	portable one.
2453		2980
…		…
2479	if you do not want that, you need to temporarily stop the embed watcher).	3006	if you do not want that, you need to temporarily stop the embed watcher).
2480		3007
2481	=item ev_embed_sweep (loop, ev_embed *)	3008	=item ev_embed_sweep (loop, ev_embed *)
2482		3009
2483	Make a single, non-blocking sweep over the embedded loop. This works	3010	Make a single, non-blocking sweep over the embedded loop. This works
2484	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3011	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2485	appropriate way for embedded loops.	3012	appropriate way for embedded loops.
2486		3013
2487	=item struct ev_loop *other [read-only]	3014	=item struct ev_loop *other [read-only]
2488		3015
2489	The embedded event loop.	3016	The embedded event loop.
…		…
2547	event loop blocks next and before C<ev_check> watchers are being called,	3074	event loop blocks next and before C<ev_check> watchers are being called,
2548	and only in the child after the fork. If whoever good citizen calling	3075	and only in the child after the fork. If whoever good citizen calling
2549	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3076	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2550	handlers will be invoked, too, of course.	3077	handlers will be invoked, too, of course.
2551		3078
		3079	=head3 The special problem of life after fork - how is it possible?
		3080
		3081	Most uses of C<fork()> consist of forking, then some simple calls to set
		3082	up/change the process environment, followed by a call to C<exec()>. This
		3083	sequence should be handled by libev without any problems.
		3084
		3085	This changes when the application actually wants to do event handling
		3086	in the child, or both parent in child, in effect "continuing" after the
		3087	fork.
		3088
		3089	The default mode of operation (for libev, with application help to detect
		3090	forks) is to duplicate all the state in the child, as would be expected
		3091	when I<either> the parent I<or> the child process continues.
		3092
		3093	When both processes want to continue using libev, then this is usually the
		3094	wrong result. In that case, usually one process (typically the parent) is
		3095	supposed to continue with all watchers in place as before, while the other
		3096	process typically wants to start fresh, i.e. without any active watchers.
		3097
		3098	The cleanest and most efficient way to achieve that with libev is to
		3099	simply create a new event loop, which of course will be "empty", and
		3100	use that for new watchers. This has the advantage of not touching more
		3101	memory than necessary, and thus avoiding the copy-on-write, and the
		3102	disadvantage of having to use multiple event loops (which do not support
		3103	signal watchers).
		3104
		3105	When this is not possible, or you want to use the default loop for
		3106	other reasons, then in the process that wants to start "fresh", call
		3107	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3108	Destroying the default loop will "orphan" (not stop) all registered
		3109	watchers, so you have to be careful not to execute code that modifies
		3110	those watchers. Note also that in that case, you have to re-register any
		3111	signal watchers.
		3112
2552	=head3 Watcher-Specific Functions and Data Members	3113	=head3 Watcher-Specific Functions and Data Members
2553		3114
2554	=over 4	3115	=over 4
2555		3116
2556	=item ev_fork_init (ev_signal *, callback)	3117	=item ev_fork_init (ev_fork *, callback)
2557		3118
2558	Initialises and configures the fork watcher - it has no parameters of any	3119	Initialises and configures the fork watcher - it has no parameters of any
2559	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3120	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2560	believe me.	3121	really.
2561		3122
2562	=back	3123	=back
2563		3124
2564		3125
		3126	=head2 C<ev_cleanup> - even the best things end
		3127
		3128	Cleanup watchers are called just before the event loop is being destroyed
		3129	by a call to C<ev_loop_destroy>.
		3130
		3131	While there is no guarantee that the event loop gets destroyed, cleanup
		3132	watchers provide a convenient method to install cleanup hooks for your
		3133	program, worker threads and so on - you just to make sure to destroy the
		3134	loop when you want them to be invoked.
		3135
		3136	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3137	all other watchers, they do not keep a reference to the event loop (which
		3138	makes a lot of sense if you think about it). Like all other watchers, you
		3139	can call libev functions in the callback, except C<ev_cleanup_start>.
		3140
		3141	=head3 Watcher-Specific Functions and Data Members
		3142
		3143	=over 4
		3144
		3145	=item ev_cleanup_init (ev_cleanup *, callback)
		3146
		3147	Initialises and configures the cleanup watcher - it has no parameters of
		3148	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3149	pointless, I assure you.
		3150
		3151	=back
		3152
		3153	Example: Register an atexit handler to destroy the default loop, so any
		3154	cleanup functions are called.
		3155
		3156	static void
		3157	program_exits (void)
		3158	{
		3159	ev_loop_destroy (EV_DEFAULT_UC);
		3160	}
		3161
		3162	...
		3163	atexit (program_exits);
		3164
		3165
2565	=head2 C<ev_async> - how to wake up another event loop	3166	=head2 C<ev_async> - how to wake up an event loop
2566		3167
2567	In general, you cannot use an C<ev_loop> from multiple threads or other	3168	In general, you cannot use an C<ev_run> from multiple threads or other
2568	asynchronous sources such as signal handlers (as opposed to multiple event	3169	asynchronous sources such as signal handlers (as opposed to multiple event
2569	loops - those are of course safe to use in different threads).	3170	loops - those are of course safe to use in different threads).
2570		3171
2571	Sometimes, however, you need to wake up another event loop you do not	3172	Sometimes, however, you need to wake up an event loop you do not control,
2572	control, for example because it belongs to another thread. This is what	3173	for example because it belongs to another thread. This is what C<ev_async>
2573	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3174	watchers do: as long as the C<ev_async> watcher is active, you can signal
2574	can signal it by calling C<ev_async_send>, which is thread- and signal	3175	it by calling C<ev_async_send>, which is thread- and signal safe.
2575	safe.
2576		3176
2577	This functionality is very similar to C<ev_signal> watchers, as signals,	3177	This functionality is very similar to C<ev_signal> watchers, as signals,
2578	too, are asynchronous in nature, and signals, too, will be compressed	3178	too, are asynchronous in nature, and signals, too, will be compressed
2579	(i.e. the number of callback invocations may be less than the number of	3179	(i.e. the number of callback invocations may be less than the number of
2580	C<ev_async_sent> calls).	3180	C<ev_async_sent> calls).
…		…
2585	=head3 Queueing	3185	=head3 Queueing
2586		3186
2587	C<ev_async> does not support queueing of data in any way. The reason	3187	C<ev_async> does not support queueing of data in any way. The reason
2588	is that the author does not know of a simple (or any) algorithm for a	3188	is that the author does not know of a simple (or any) algorithm for a
2589	multiple-writer-single-reader queue that works in all cases and doesn't	3189	multiple-writer-single-reader queue that works in all cases and doesn't
2590	need elaborate support such as pthreads.	3190	need elaborate support such as pthreads or unportable memory access
		3191	semantics.
2591		3192
2592	That means that if you want to queue data, you have to provide your own	3193	That means that if you want to queue data, you have to provide your own
2593	queue. But at least I can tell you how to implement locking around your	3194	queue. But at least I can tell you how to implement locking around your
2594	queue:	3195	queue:
2595		3196
…		…
2684	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3285	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2685	C<ev_feed_event>, this call is safe to do from other threads, signal or	3286	C<ev_feed_event>, this call is safe to do from other threads, signal or
2686	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3287	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2687	section below on what exactly this means).	3288	section below on what exactly this means).
2688		3289
		3290	Note that, as with other watchers in libev, multiple events might get
		3291	compressed into a single callback invocation (another way to look at this
		3292	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3293	reset when the event loop detects that).
		3294
2689	This call incurs the overhead of a system call only once per loop iteration,	3295	This call incurs the overhead of a system call only once per event loop
2690	so while the overhead might be noticeable, it doesn't apply to repeated	3296	iteration, so while the overhead might be noticeable, it doesn't apply to
2691	calls to C<ev_async_send>.	3297	repeated calls to C<ev_async_send> for the same event loop.
2692		3298
2693	=item bool = ev_async_pending (ev_async *)	3299	=item bool = ev_async_pending (ev_async *)
2694		3300
2695	Returns a non-zero value when C<ev_async_send> has been called on the	3301	Returns a non-zero value when C<ev_async_send> has been called on the
2696	watcher but the event has not yet been processed (or even noted) by the	3302	watcher but the event has not yet been processed (or even noted) by the
…		…
2699	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3305	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2700	the loop iterates next and checks for the watcher to have become active,	3306	the loop iterates next and checks for the watcher to have become active,
2701	it will reset the flag again. C<ev_async_pending> can be used to very	3307	it will reset the flag again. C<ev_async_pending> can be used to very
2702	quickly check whether invoking the loop might be a good idea.	3308	quickly check whether invoking the loop might be a good idea.
2703		3309
2704	Not that this does I<not> check whether the watcher itself is pending, only	3310	Not that this does I<not> check whether the watcher itself is pending,
2705	whether it has been requested to make this watcher pending.	3311	only whether it has been requested to make this watcher pending: there
		3312	is a time window between the event loop checking and resetting the async
		3313	notification, and the callback being invoked.
2706		3314
2707	=back	3315	=back
2708		3316
2709		3317
2710	=head1 OTHER FUNCTIONS	3318	=head1 OTHER FUNCTIONS
…		…
2727		3335
2728	If C<timeout> is less than 0, then no timeout watcher will be	3336	If C<timeout> is less than 0, then no timeout watcher will be
2729	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3337	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2730	repeat = 0) will be started. C<0> is a valid timeout.	3338	repeat = 0) will be started. C<0> is a valid timeout.
2731		3339
2732	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3340	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2733	passed an C<revents> set like normal event callbacks (a combination of	3341	passed an C<revents> set like normal event callbacks (a combination of
2734	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3342	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2735	value passed to C<ev_once>. Note that it is possible to receive I<both>	3343	value passed to C<ev_once>. Note that it is possible to receive I<both>
2736	a timeout and an io event at the same time - you probably should give io	3344	a timeout and an io event at the same time - you probably should give io
2737	events precedence.	3345	events precedence.
2738		3346
2739	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3347	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2740		3348
2741	static void stdin_ready (int revents, void *arg)	3349	static void stdin_ready (int revents, void *arg)
2742	{	3350	{
2743	if (revents & EV_READ)	3351	if (revents & EV_READ)
2744	/* stdin might have data for us, joy! */;	3352	/* stdin might have data for us, joy! */;
2745	else if (revents & EV_TIMEOUT)	3353	else if (revents & EV_TIMER)
2746	/* doh, nothing entered */;	3354	/* doh, nothing entered */;
2747	}	3355	}
2748		3356
2749	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3357	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2750		3358
2751	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2752
2753	Feeds the given event set into the event loop, as if the specified event
2754	had happened for the specified watcher (which must be a pointer to an
2755	initialised but not necessarily started event watcher).
2756
2757	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3359	=item ev_feed_fd_event (loop, int fd, int revents)
2758		3360
2759	Feed an event on the given fd, as if a file descriptor backend detected	3361	Feed an event on the given fd, as if a file descriptor backend detected
2760	the given events it.	3362	the given events it.
2761		3363
2762	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3364	=item ev_feed_signal_event (loop, int signum)
2763		3365
2764	Feed an event as if the given signal occurred (C<loop> must be the default	3366	Feed an event as if the given signal occurred (C<loop> must be the default
2765	loop!).	3367	loop!).
2766		3368
2767	=back	3369	=back
2768		3370
2769		3371
		3372	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3373
		3374	This section explains some common idioms that are not immediately
		3375	obvious. Note that examples are sprinkled over the whole manual, and this
		3376	section only contains stuff that wouldn't fit anywhere else.
		3377
		3378	=over 4
		3379
		3380	=item Model/nested event loop invocations and exit conditions.
		3381
		3382	Often (especially in GUI toolkits) there are places where you have
		3383	I<modal> interaction, which is most easily implemented by recursively
		3384	invoking C<ev_run>.
		3385
		3386	This brings the problem of exiting - a callback might want to finish the
		3387	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3388	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3389	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3390	other combination: In these cases, C<ev_break> will not work alone.
		3391
		3392	The solution is to maintain "break this loop" variable for each C<ev_run>
		3393	invocation, and use a loop around C<ev_run> until the condition is
		3394	triggered, using C<EVRUN_ONCE>:
		3395
		3396	// main loop
		3397	int exit_main_loop = 0;
		3398
		3399	while (!exit_main_loop)
		3400	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3401
		3402	// in a model watcher
		3403	int exit_nested_loop = 0;
		3404
		3405	while (!exit_nested_loop)
		3406	ev_run (EV_A_ EVRUN_ONCE);
		3407
		3408	To exit from any of these loops, just set the corresponding exit variable:
		3409
		3410	// exit modal loop
		3411	exit_nested_loop = 1;
		3412
		3413	// exit main program, after modal loop is finished
		3414	exit_main_loop = 1;
		3415
		3416	// exit both
		3417	exit_main_loop = exit_nested_loop = 1;
		3418
		3419	=back
		3420
		3421
2770	=head1 LIBEVENT EMULATION	3422	=head1 LIBEVENT EMULATION
2771		3423
2772	Libev offers a compatibility emulation layer for libevent. It cannot	3424	Libev offers a compatibility emulation layer for libevent. It cannot
2773	emulate the internals of libevent, so here are some usage hints:	3425	emulate the internals of libevent, so here are some usage hints:
2774		3426
2775	=over 4	3427	=over 4
		3428
		3429	=item * Only the libevent-1.4.1-beta API is being emulated.
		3430
		3431	This was the newest libevent version available when libev was implemented,
		3432	and is still mostly uncanged in 2010.
2776		3433
2777	=item * Use it by including <event.h>, as usual.	3434	=item * Use it by including <event.h>, as usual.
2778		3435
2779	=item * The following members are fully supported: ev_base, ev_callback,	3436	=item * The following members are fully supported: ev_base, ev_callback,
2780	ev_arg, ev_fd, ev_res, ev_events.	3437	ev_arg, ev_fd, ev_res, ev_events.
…		…
2786	=item * Priorities are not currently supported. Initialising priorities	3443	=item * Priorities are not currently supported. Initialising priorities
2787	will fail and all watchers will have the same priority, even though there	3444	will fail and all watchers will have the same priority, even though there
2788	is an ev_pri field.	3445	is an ev_pri field.
2789		3446
2790	=item * In libevent, the last base created gets the signals, in libev, the	3447	=item * In libevent, the last base created gets the signals, in libev, the
2791	first base created (== the default loop) gets the signals.	3448	base that registered the signal gets the signals.
2792		3449
2793	=item * Other members are not supported.	3450	=item * Other members are not supported.
2794		3451
2795	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3452	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2796	to use the libev header file and library.	3453	to use the libev header file and library.
…		…
2815	Care has been taken to keep the overhead low. The only data member the C++	3472	Care has been taken to keep the overhead low. The only data member the C++
2816	classes add (compared to plain C-style watchers) is the event loop pointer	3473	classes add (compared to plain C-style watchers) is the event loop pointer
2817	that the watcher is associated with (or no additional members at all if	3474	that the watcher is associated with (or no additional members at all if
2818	you disable C<EV_MULTIPLICITY> when embedding libev).	3475	you disable C<EV_MULTIPLICITY> when embedding libev).
2819		3476
2820	Currently, functions, and static and non-static member functions can be	3477	Currently, functions, static and non-static member functions and classes
2821	used as callbacks. Other types should be easy to add as long as they only	3478	with C<operator ()> can be used as callbacks. Other types should be easy
2822	need one additional pointer for context. If you need support for other	3479	to add as long as they only need one additional pointer for context. If
2823	types of functors please contact the author (preferably after implementing	3480	you need support for other types of functors please contact the author
2824	it).	3481	(preferably after implementing it).
2825		3482
2826	Here is a list of things available in the C<ev> namespace:	3483	Here is a list of things available in the C<ev> namespace:
2827		3484
2828	=over 4	3485	=over 4
2829		3486
…		…
2847		3504
2848	=over 4	3505	=over 4
2849		3506
2850	=item ev::TYPE::TYPE ()	3507	=item ev::TYPE::TYPE ()
2851		3508
2852	=item ev::TYPE::TYPE (struct ev_loop *)	3509	=item ev::TYPE::TYPE (loop)
2853		3510
2854	=item ev::TYPE::~TYPE	3511	=item ev::TYPE::~TYPE
2855		3512
2856	The constructor (optionally) takes an event loop to associate the watcher	3513	The constructor (optionally) takes an event loop to associate the watcher
2857	with. If it is omitted, it will use C<EV_DEFAULT>.	3514	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2889		3546
2890	myclass obj;	3547	myclass obj;
2891	ev::io iow;	3548	ev::io iow;
2892	iow.set <myclass, &myclass::io_cb> (&obj);	3549	iow.set <myclass, &myclass::io_cb> (&obj);
2893		3550
		3551	=item w->set (object *)
		3552
		3553	This is a variation of a method callback - leaving out the method to call
		3554	will default the method to C<operator ()>, which makes it possible to use
		3555	functor objects without having to manually specify the C<operator ()> all
		3556	the time. Incidentally, you can then also leave out the template argument
		3557	list.
		3558
		3559	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3560	int revents)>.
		3561
		3562	See the method-C<set> above for more details.
		3563
		3564	Example: use a functor object as callback.
		3565
		3566	struct myfunctor
		3567	{
		3568	void operator() (ev::io &w, int revents)
		3569	{
		3570	...
		3571	}
		3572	}
		3573
		3574	myfunctor f;
		3575
		3576	ev::io w;
		3577	w.set (&f);
		3578
2894	=item w->set<function> (void *data = 0)	3579	=item w->set<function> (void *data = 0)
2895		3580
2896	Also sets a callback, but uses a static method or plain function as	3581	Also sets a callback, but uses a static method or plain function as
2897	callback. The optional C<data> argument will be stored in the watcher's	3582	callback. The optional C<data> argument will be stored in the watcher's
2898	C<data> member and is free for you to use.	3583	C<data> member and is free for you to use.
…		…
2904	Example: Use a plain function as callback.	3589	Example: Use a plain function as callback.
2905		3590
2906	static void io_cb (ev::io &w, int revents) { }	3591	static void io_cb (ev::io &w, int revents) { }
2907	iow.set <io_cb> ();	3592	iow.set <io_cb> ();
2908		3593
2909	=item w->set (struct ev_loop *)	3594	=item w->set (loop)
2910		3595
2911	Associates a different C<struct ev_loop> with this watcher. You can only	3596	Associates a different C<struct ev_loop> with this watcher. You can only
2912	do this when the watcher is inactive (and not pending either).	3597	do this when the watcher is inactive (and not pending either).
2913		3598
2914	=item w->set ([arguments])	3599	=item w->set ([arguments])
2915		3600
2916	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3601	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
2917	called at least once. Unlike the C counterpart, an active watcher gets	3602	method or a suitable start method must be called at least once. Unlike the
2918	automatically stopped and restarted when reconfiguring it with this	3603	C counterpart, an active watcher gets automatically stopped and restarted
2919	method.	3604	when reconfiguring it with this method.
2920		3605
2921	=item w->start ()	3606	=item w->start ()
2922		3607
2923	Starts the watcher. Note that there is no C<loop> argument, as the	3608	Starts the watcher. Note that there is no C<loop> argument, as the
2924	constructor already stores the event loop.	3609	constructor already stores the event loop.
2925		3610
		3611	=item w->start ([arguments])
		3612
		3613	Instead of calling C<set> and C<start> methods separately, it is often
		3614	convenient to wrap them in one call. Uses the same type of arguments as
		3615	the configure C<set> method of the watcher.
		3616
2926	=item w->stop ()	3617	=item w->stop ()
2927		3618
2928	Stops the watcher if it is active. Again, no C<loop> argument.	3619	Stops the watcher if it is active. Again, no C<loop> argument.
2929		3620
2930	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3621	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2942		3633
2943	=back	3634	=back
2944		3635
2945	=back	3636	=back
2946		3637
2947	Example: Define a class with an IO and idle watcher, start one of them in	3638	Example: Define a class with two I/O and idle watchers, start the I/O
2948	the constructor.	3639	watchers in the constructor.
2949		3640
2950	class myclass	3641	class myclass
2951	{	3642	{
2952	ev::io io ; void io_cb (ev::io &w, int revents);	3643	ev::io io ; void io_cb (ev::io &w, int revents);
		3644	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
2953	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3645	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2954		3646
2955	myclass (int fd)	3647	myclass (int fd)
2956	{	3648	{
2957	io .set <myclass, &myclass::io_cb > (this);	3649	io .set <myclass, &myclass::io_cb > (this);
		3650	io2 .set <myclass, &myclass::io2_cb > (this);
2958	idle.set <myclass, &myclass::idle_cb> (this);	3651	idle.set <myclass, &myclass::idle_cb> (this);
2959		3652
2960	io.start (fd, ev::READ);	3653	io.set (fd, ev::WRITE); // configure the watcher
		3654	io.start (); // start it whenever convenient
		3655
		3656	io2.start (fd, ev::READ); // set + start in one call
2961	}	3657	}
2962	};	3658	};
2963		3659
2964		3660
2965	=head1 OTHER LANGUAGE BINDINGS	3661	=head1 OTHER LANGUAGE BINDINGS
…		…
2984	L<http://software.schmorp.de/pkg/EV>.	3680	L<http://software.schmorp.de/pkg/EV>.
2985		3681
2986	=item Python	3682	=item Python
2987		3683
2988	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3684	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2989	seems to be quite complete and well-documented. Note, however, that the	3685	seems to be quite complete and well-documented.
2990	patch they require for libev is outright dangerous as it breaks the ABI
2991	for everybody else, and therefore, should never be applied in an installed
2992	libev (if python requires an incompatible ABI then it needs to embed
2993	libev).
2994		3686
2995	=item Ruby	3687	=item Ruby
2996		3688
2997	Tony Arcieri has written a ruby extension that offers access to a subset	3689	Tony Arcieri has written a ruby extension that offers access to a subset
2998	of the libev API and adds file handle abstractions, asynchronous DNS and	3690	of the libev API and adds file handle abstractions, asynchronous DNS and
2999	more on top of it. It can be found via gem servers. Its homepage is at	3691	more on top of it. It can be found via gem servers. Its homepage is at
3000	L<http://rev.rubyforge.org/>.	3692	L<http://rev.rubyforge.org/>.
3001		3693
		3694	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3695	makes rev work even on mingw.
		3696
		3697	=item Haskell
		3698
		3699	A haskell binding to libev is available at
		3700	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3701
3002	=item D	3702	=item D
3003		3703
3004	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3704	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3005	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3705	be found at L<http://proj.llucax.com.ar/wiki/evd>.
3006		3706
3007	=item Ocaml	3707	=item Ocaml
3008		3708
3009	Erkki Seppala has written Ocaml bindings for libev, to be found at	3709	Erkki Seppala has written Ocaml bindings for libev, to be found at
3010	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	3710	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3711
		3712	=item Lua
		3713
		3714	Brian Maher has written a partial interface to libev for lua (at the
		3715	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3716	L<http://github.com/brimworks/lua-ev>.
3011		3717
3012	=back	3718	=back
3013		3719
3014		3720
3015	=head1 MACRO MAGIC	3721	=head1 MACRO MAGIC
…		…
3029	loop argument"). The C<EV_A> form is used when this is the sole argument,	3735	loop argument"). The C<EV_A> form is used when this is the sole argument,
3030	C<EV_A_> is used when other arguments are following. Example:	3736	C<EV_A_> is used when other arguments are following. Example:
3031		3737
3032	ev_unref (EV_A);	3738	ev_unref (EV_A);
3033	ev_timer_add (EV_A_ watcher);	3739	ev_timer_add (EV_A_ watcher);
3034	ev_loop (EV_A_ 0);	3740	ev_run (EV_A_ 0);
3035		3741
3036	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3742	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3037	which is often provided by the following macro.	3743	which is often provided by the following macro.
3038		3744
3039	=item C<EV_P>, C<EV_P_>	3745	=item C<EV_P>, C<EV_P_>
…		…
3079	}	3785	}
3080		3786
3081	ev_check check;	3787	ev_check check;
3082	ev_check_init (&check, check_cb);	3788	ev_check_init (&check, check_cb);
3083	ev_check_start (EV_DEFAULT_ &check);	3789	ev_check_start (EV_DEFAULT_ &check);
3084	ev_loop (EV_DEFAULT_ 0);	3790	ev_run (EV_DEFAULT_ 0);
3085		3791
3086	=head1 EMBEDDING	3792	=head1 EMBEDDING
3087		3793
3088	Libev can (and often is) directly embedded into host	3794	Libev can (and often is) directly embedded into host
3089	applications. Examples of applications that embed it include the Deliantra	3795	applications. Examples of applications that embed it include the Deliantra
…		…
3169	libev.m4	3875	libev.m4
3170		3876
3171	=head2 PREPROCESSOR SYMBOLS/MACROS	3877	=head2 PREPROCESSOR SYMBOLS/MACROS
3172		3878
3173	Libev can be configured via a variety of preprocessor symbols you have to	3879	Libev can be configured via a variety of preprocessor symbols you have to
3174	define before including any of its files. The default in the absence of	3880	define before including (or compiling) any of its files. The default in
3175	autoconf is documented for every option.	3881	the absence of autoconf is documented for every option.
		3882
		3883	Symbols marked with "(h)" do not change the ABI, and can have different
		3884	values when compiling libev vs. including F<ev.h>, so it is permissible
		3885	to redefine them before including F<ev.h> without breaking compatibility
		3886	to a compiled library. All other symbols change the ABI, which means all
		3887	users of libev and the libev code itself must be compiled with compatible
		3888	settings.
3176		3889
3177	=over 4	3890	=over 4
3178		3891
		3892	=item EV_COMPAT3 (h)
		3893
		3894	Backwards compatibility is a major concern for libev. This is why this
		3895	release of libev comes with wrappers for the functions and symbols that
		3896	have been renamed between libev version 3 and 4.
		3897
		3898	You can disable these wrappers (to test compatibility with future
		3899	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		3900	sources. This has the additional advantage that you can drop the C<struct>
		3901	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		3902	typedef in that case.
		3903
		3904	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		3905	and in some even more future version the compatibility code will be
		3906	removed completely.
		3907
3179	=item EV_STANDALONE	3908	=item EV_STANDALONE (h)
3180		3909
3181	Must always be C<1> if you do not use autoconf configuration, which	3910	Must always be C<1> if you do not use autoconf configuration, which
3182	keeps libev from including F<config.h>, and it also defines dummy	3911	keeps libev from including F<config.h>, and it also defines dummy
3183	implementations for some libevent functions (such as logging, which is not	3912	implementations for some libevent functions (such as logging, which is not
3184	supported). It will also not define any of the structs usually found in	3913	supported). It will also not define any of the structs usually found in
3185	F<event.h> that are not directly supported by the libev core alone.	3914	F<event.h> that are not directly supported by the libev core alone.
3186		3915
		3916	In standalone mode, libev will still try to automatically deduce the
		3917	configuration, but has to be more conservative.
		3918
3187	=item EV_USE_MONOTONIC	3919	=item EV_USE_MONOTONIC
3188		3920
3189	If defined to be C<1>, libev will try to detect the availability of the	3921	If defined to be C<1>, libev will try to detect the availability of the
3190	monotonic clock option at both compile time and runtime. Otherwise no use	3922	monotonic clock option at both compile time and runtime. Otherwise no
3191	of the monotonic clock option will be attempted. If you enable this, you	3923	use of the monotonic clock option will be attempted. If you enable this,
3192	usually have to link against librt or something similar. Enabling it when	3924	you usually have to link against librt or something similar. Enabling it
3193	the functionality isn't available is safe, though, although you have	3925	when the functionality isn't available is safe, though, although you have
3194	to make sure you link against any libraries where the C<clock_gettime>	3926	to make sure you link against any libraries where the C<clock_gettime>
3195	function is hiding in (often F<-lrt>).	3927	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
3196		3928
3197	=item EV_USE_REALTIME	3929	=item EV_USE_REALTIME
3198		3930
3199	If defined to be C<1>, libev will try to detect the availability of the	3931	If defined to be C<1>, libev will try to detect the availability of the
3200	real-time clock option at compile time (and assume its availability at	3932	real-time clock option at compile time (and assume its availability
3201	runtime if successful). Otherwise no use of the real-time clock option will	3933	at runtime if successful). Otherwise no use of the real-time clock
3202	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3934	option will be attempted. This effectively replaces C<gettimeofday>
3203	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3935	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
3204	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3936	correctness. See the note about libraries in the description of
		3937	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3938	C<EV_USE_CLOCK_SYSCALL>.
		3939
		3940	=item EV_USE_CLOCK_SYSCALL
		3941
		3942	If defined to be C<1>, libev will try to use a direct syscall instead
		3943	of calling the system-provided C<clock_gettime> function. This option
		3944	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3945	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3946	programs needlessly. Using a direct syscall is slightly slower (in
		3947	theory), because no optimised vdso implementation can be used, but avoids
		3948	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3949	higher, as it simplifies linking (no need for C<-lrt>).
3205		3950
3206	=item EV_USE_NANOSLEEP	3951	=item EV_USE_NANOSLEEP
3207		3952
3208	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3953	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
3209	and will use it for delays. Otherwise it will use C<select ()>.	3954	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3225		3970
3226	=item EV_SELECT_USE_FD_SET	3971	=item EV_SELECT_USE_FD_SET
3227		3972
3228	If defined to C<1>, then the select backend will use the system C<fd_set>	3973	If defined to C<1>, then the select backend will use the system C<fd_set>
3229	structure. This is useful if libev doesn't compile due to a missing	3974	structure. This is useful if libev doesn't compile due to a missing
3230	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3975	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3231	exotic systems. This usually limits the range of file descriptors to some	3976	on exotic systems. This usually limits the range of file descriptors to
3232	low limit such as 1024 or might have other limitations (winsocket only	3977	some low limit such as 1024 or might have other limitations (winsocket
3233	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3978	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3234	influence the size of the C<fd_set> used.	3979	configures the maximum size of the C<fd_set>.
3235		3980
3236	=item EV_SELECT_IS_WINSOCKET	3981	=item EV_SELECT_IS_WINSOCKET
3237		3982
3238	When defined to C<1>, the select backend will assume that	3983	When defined to C<1>, the select backend will assume that
3239	select/socket/connect etc. don't understand file descriptors but	3984	select/socket/connect etc. don't understand file descriptors but
…		…
3241	be used is the winsock select). This means that it will call	3986	be used is the winsock select). This means that it will call
3242	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3987	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3243	it is assumed that all these functions actually work on fds, even	3988	it is assumed that all these functions actually work on fds, even
3244	on win32. Should not be defined on non-win32 platforms.	3989	on win32. Should not be defined on non-win32 platforms.
3245		3990
3246	=item EV_FD_TO_WIN32_HANDLE	3991	=item EV_FD_TO_WIN32_HANDLE(fd)
3247		3992
3248	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3993	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3249	file descriptors to socket handles. When not defining this symbol (the	3994	file descriptors to socket handles. When not defining this symbol (the
3250	default), then libev will call C<_get_osfhandle>, which is usually	3995	default), then libev will call C<_get_osfhandle>, which is usually
3251	correct. In some cases, programs use their own file descriptor management,	3996	correct. In some cases, programs use their own file descriptor management,
3252	in which case they can provide this function to map fds to socket handles.	3997	in which case they can provide this function to map fds to socket handles.
		3998
		3999	=item EV_WIN32_HANDLE_TO_FD(handle)
		4000
		4001	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4002	using the standard C<_open_osfhandle> function. For programs implementing
		4003	their own fd to handle mapping, overwriting this function makes it easier
		4004	to do so. This can be done by defining this macro to an appropriate value.
		4005
		4006	=item EV_WIN32_CLOSE_FD(fd)
		4007
		4008	If programs implement their own fd to handle mapping on win32, then this
		4009	macro can be used to override the C<close> function, useful to unregister
		4010	file descriptors again. Note that the replacement function has to close
		4011	the underlying OS handle.
3253		4012
3254	=item EV_USE_POLL	4013	=item EV_USE_POLL
3255		4014
3256	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4015	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3257	backend. Otherwise it will be enabled on non-win32 platforms. It	4016	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3304	as well as for signal and thread safety in C<ev_async> watchers.	4063	as well as for signal and thread safety in C<ev_async> watchers.
3305		4064
3306	In the absence of this define, libev will use C<sig_atomic_t volatile>	4065	In the absence of this define, libev will use C<sig_atomic_t volatile>
3307	(from F<signal.h>), which is usually good enough on most platforms.	4066	(from F<signal.h>), which is usually good enough on most platforms.
3308		4067
3309	=item EV_H	4068	=item EV_H (h)
3310		4069
3311	The name of the F<ev.h> header file used to include it. The default if	4070	The name of the F<ev.h> header file used to include it. The default if
3312	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4071	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3313	used to virtually rename the F<ev.h> header file in case of conflicts.	4072	used to virtually rename the F<ev.h> header file in case of conflicts.
3314		4073
3315	=item EV_CONFIG_H	4074	=item EV_CONFIG_H (h)
3316		4075
3317	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4076	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3318	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4077	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3319	C<EV_H>, above.	4078	C<EV_H>, above.
3320		4079
3321	=item EV_EVENT_H	4080	=item EV_EVENT_H (h)
3322		4081
3323	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4082	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3324	of how the F<event.h> header can be found, the default is C<"event.h">.	4083	of how the F<event.h> header can be found, the default is C<"event.h">.
3325		4084
3326	=item EV_PROTOTYPES	4085	=item EV_PROTOTYPES (h)
3327		4086
3328	If defined to be C<0>, then F<ev.h> will not define any function	4087	If defined to be C<0>, then F<ev.h> will not define any function
3329	prototypes, but still define all the structs and other symbols. This is	4088	prototypes, but still define all the structs and other symbols. This is
3330	occasionally useful if you want to provide your own wrapper functions	4089	occasionally useful if you want to provide your own wrapper functions
3331	around libev functions.	4090	around libev functions.
…		…
3353	fine.	4112	fine.
3354		4113
3355	If your embedding application does not need any priorities, defining these	4114	If your embedding application does not need any priorities, defining these
3356	both to C<0> will save some memory and CPU.	4115	both to C<0> will save some memory and CPU.
3357		4116
3358	=item EV_PERIODIC_ENABLE	4117	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4118	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4119	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3359		4120
3360	If undefined or defined to be C<1>, then periodic timers are supported. If	4121	If undefined or defined to be C<1> (and the platform supports it), then
3361	defined to be C<0>, then they are not. Disabling them saves a few kB of	4122	the respective watcher type is supported. If defined to be C<0>, then it
3362	code.	4123	is not. Disabling watcher types mainly saves code size.
3363		4124
3364	=item EV_IDLE_ENABLE	4125	=item EV_FEATURES
3365
3366	If undefined or defined to be C<1>, then idle watchers are supported. If
3367	defined to be C<0>, then they are not. Disabling them saves a few kB of
3368	code.
3369
3370	=item EV_EMBED_ENABLE
3371
3372	If undefined or defined to be C<1>, then embed watchers are supported. If
3373	defined to be C<0>, then they are not. Embed watchers rely on most other
3374	watcher types, which therefore must not be disabled.
3375
3376	=item EV_STAT_ENABLE
3377
3378	If undefined or defined to be C<1>, then stat watchers are supported. If
3379	defined to be C<0>, then they are not.
3380
3381	=item EV_FORK_ENABLE
3382
3383	If undefined or defined to be C<1>, then fork watchers are supported. If
3384	defined to be C<0>, then they are not.
3385
3386	=item EV_ASYNC_ENABLE
3387
3388	If undefined or defined to be C<1>, then async watchers are supported. If
3389	defined to be C<0>, then they are not.
3390
3391	=item EV_MINIMAL
3392		4126
3393	If you need to shave off some kilobytes of code at the expense of some	4127	If you need to shave off some kilobytes of code at the expense of some
3394	speed, define this symbol to C<1>. Currently this is used to override some	4128	speed (but with the full API), you can define this symbol to request
3395	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4129	certain subsets of functionality. The default is to enable all features
3396	much smaller 2-heap for timer management over the default 4-heap.	4130	that can be enabled on the platform.
		4131
		4132	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4133	with some broad features you want) and then selectively re-enable
		4134	additional parts you want, for example if you want everything minimal,
		4135	but multiple event loop support, async and child watchers and the poll
		4136	backend, use this:
		4137
		4138	#define EV_FEATURES 0
		4139	#define EV_MULTIPLICITY 1
		4140	#define EV_USE_POLL 1
		4141	#define EV_CHILD_ENABLE 1
		4142	#define EV_ASYNC_ENABLE 1
		4143
		4144	The actual value is a bitset, it can be a combination of the following
		4145	values:
		4146
		4147	=over 4
		4148
		4149	=item C<1> - faster/larger code
		4150
		4151	Use larger code to speed up some operations.
		4152
		4153	Currently this is used to override some inlining decisions (enlarging the
		4154	code size by roughly 30% on amd64).
		4155
		4156	When optimising for size, use of compiler flags such as C<-Os> with
		4157	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4158	assertions.
		4159
		4160	=item C<2> - faster/larger data structures
		4161
		4162	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4163	hash table sizes and so on. This will usually further increase code size
		4164	and can additionally have an effect on the size of data structures at
		4165	runtime.
		4166
		4167	=item C<4> - full API configuration
		4168
		4169	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4170	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4171
		4172	=item C<8> - full API
		4173
		4174	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4175	details on which parts of the API are still available without this
		4176	feature, and do not complain if this subset changes over time.
		4177
		4178	=item C<16> - enable all optional watcher types
		4179
		4180	Enables all optional watcher types. If you want to selectively enable
		4181	only some watcher types other than I/O and timers (e.g. prepare,
		4182	embed, async, child...) you can enable them manually by defining
		4183	C<EV_watchertype_ENABLE> to C<1> instead.
		4184
		4185	=item C<32> - enable all backends
		4186
		4187	This enables all backends - without this feature, you need to enable at
		4188	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4189
		4190	=item C<64> - enable OS-specific "helper" APIs
		4191
		4192	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4193	default.
		4194
		4195	=back
		4196
		4197	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4198	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4199	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4200	watchers, timers and monotonic clock support.
		4201
		4202	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4203	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4204	your program might be left out as well - a binary starting a timer and an
		4205	I/O watcher then might come out at only 5Kb.
		4206
		4207	=item EV_AVOID_STDIO
		4208
		4209	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4210	functions (printf, scanf, perror etc.). This will increase the code size
		4211	somewhat, but if your program doesn't otherwise depend on stdio and your
		4212	libc allows it, this avoids linking in the stdio library which is quite
		4213	big.
		4214
		4215	Note that error messages might become less precise when this option is
		4216	enabled.
		4217
		4218	=item EV_NSIG
		4219
		4220	The highest supported signal number, +1 (or, the number of
		4221	signals): Normally, libev tries to deduce the maximum number of signals
		4222	automatically, but sometimes this fails, in which case it can be
		4223	specified. Also, using a lower number than detected (C<32> should be
		4224	good for about any system in existence) can save some memory, as libev
		4225	statically allocates some 12-24 bytes per signal number.
3397		4226
3398	=item EV_PID_HASHSIZE	4227	=item EV_PID_HASHSIZE
3399		4228
3400	C<ev_child> watchers use a small hash table to distribute workload by	4229	C<ev_child> watchers use a small hash table to distribute workload by
3401	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4230	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3402	than enough. If you need to manage thousands of children you might want to	4231	usually more than enough. If you need to manage thousands of children you
3403	increase this value (I<must> be a power of two).	4232	might want to increase this value (I<must> be a power of two).
3404		4233
3405	=item EV_INOTIFY_HASHSIZE	4234	=item EV_INOTIFY_HASHSIZE
3406		4235
3407	C<ev_stat> watchers use a small hash table to distribute workload by	4236	C<ev_stat> watchers use a small hash table to distribute workload by
3408	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4237	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3409	usually more than enough. If you need to manage thousands of C<ev_stat>	4238	disabled), usually more than enough. If you need to manage thousands of
3410	watchers you might want to increase this value (I<must> be a power of	4239	C<ev_stat> watchers you might want to increase this value (I<must> be a
3411	two).	4240	power of two).
3412		4241
3413	=item EV_USE_4HEAP	4242	=item EV_USE_4HEAP
3414		4243
3415	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4244	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3416	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4245	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3417	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4246	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3418	faster performance with many (thousands) of watchers.	4247	faster performance with many (thousands) of watchers.
3419		4248
3420	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4249	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3421	(disabled).	4250	will be C<0>.
3422		4251
3423	=item EV_HEAP_CACHE_AT	4252	=item EV_HEAP_CACHE_AT
3424		4253
3425	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4254	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3426	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4255	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3427	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4256	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3428	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4257	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3429	but avoids random read accesses on heap changes. This improves performance	4258	but avoids random read accesses on heap changes. This improves performance
3430	noticeably with many (hundreds) of watchers.	4259	noticeably with many (hundreds) of watchers.
3431		4260
3432	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4261	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3433	(disabled).	4262	will be C<0>.
3434		4263
3435	=item EV_VERIFY	4264	=item EV_VERIFY
3436		4265
3437	Controls how much internal verification (see C<ev_loop_verify ()>) will	4266	Controls how much internal verification (see C<ev_verify ()>) will
3438	be done: If set to C<0>, no internal verification code will be compiled	4267	be done: If set to C<0>, no internal verification code will be compiled
3439	in. If set to C<1>, then verification code will be compiled in, but not	4268	in. If set to C<1>, then verification code will be compiled in, but not
3440	called. If set to C<2>, then the internal verification code will be	4269	called. If set to C<2>, then the internal verification code will be
3441	called once per loop, which can slow down libev. If set to C<3>, then the	4270	called once per loop, which can slow down libev. If set to C<3>, then the
3442	verification code will be called very frequently, which will slow down	4271	verification code will be called very frequently, which will slow down
3443	libev considerably.	4272	libev considerably.
3444		4273
3445	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4274	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3446	C<0>.	4275	will be C<0>.
3447		4276
3448	=item EV_COMMON	4277	=item EV_COMMON
3449		4278
3450	By default, all watchers have a C<void *data> member. By redefining	4279	By default, all watchers have a C<void *data> member. By redefining
3451	this macro to a something else you can include more and other types of	4280	this macro to something else you can include more and other types of
3452	members. You have to define it each time you include one of the files,	4281	members. You have to define it each time you include one of the files,
3453	though, and it must be identical each time.	4282	though, and it must be identical each time.
3454		4283
3455	For example, the perl EV module uses something like this:	4284	For example, the perl EV module uses something like this:
3456		4285
…		…
3509	file.	4338	file.
3510		4339
3511	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4340	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3512	that everybody includes and which overrides some configure choices:	4341	that everybody includes and which overrides some configure choices:
3513		4342
3514	#define EV_MINIMAL 1	4343	#define EV_FEATURES 8
3515	#define EV_USE_POLL 0	4344	#define EV_USE_SELECT 1
3516	#define EV_MULTIPLICITY 0
3517	#define EV_PERIODIC_ENABLE 0	4345	#define EV_PREPARE_ENABLE 1
		4346	#define EV_IDLE_ENABLE 1
3518	#define EV_STAT_ENABLE 0	4347	#define EV_SIGNAL_ENABLE 1
3519	#define EV_FORK_ENABLE 0	4348	#define EV_CHILD_ENABLE 1
		4349	#define EV_USE_STDEXCEPT 0
3520	#define EV_CONFIG_H <config.h>	4350	#define EV_CONFIG_H <config.h>
3521	#define EV_MINPRI 0
3522	#define EV_MAXPRI 0
3523		4351
3524	#include "ev++.h"	4352	#include "ev++.h"
3525		4353
3526	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4354	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3527		4355
…		…
3587	default loop and triggering an C<ev_async> watcher from the default loop	4415	default loop and triggering an C<ev_async> watcher from the default loop
3588	watcher callback into the event loop interested in the signal.	4416	watcher callback into the event loop interested in the signal.
3589		4417
3590	=back	4418	=back
3591		4419
		4420	=head4 THREAD LOCKING EXAMPLE
		4421
		4422	Here is a fictitious example of how to run an event loop in a different
		4423	thread than where callbacks are being invoked and watchers are
		4424	created/added/removed.
		4425
		4426	For a real-world example, see the C<EV::Loop::Async> perl module,
		4427	which uses exactly this technique (which is suited for many high-level
		4428	languages).
		4429
		4430	The example uses a pthread mutex to protect the loop data, a condition
		4431	variable to wait for callback invocations, an async watcher to notify the
		4432	event loop thread and an unspecified mechanism to wake up the main thread.
		4433
		4434	First, you need to associate some data with the event loop:
		4435
		4436	typedef struct {
		4437	mutex_t lock; /* global loop lock */
		4438	ev_async async_w;
		4439	thread_t tid;
		4440	cond_t invoke_cv;
		4441	} userdata;
		4442
		4443	void prepare_loop (EV_P)
		4444	{
		4445	// for simplicity, we use a static userdata struct.
		4446	static userdata u;
		4447
		4448	ev_async_init (&u->async_w, async_cb);
		4449	ev_async_start (EV_A_ &u->async_w);
		4450
		4451	pthread_mutex_init (&u->lock, 0);
		4452	pthread_cond_init (&u->invoke_cv, 0);
		4453
		4454	// now associate this with the loop
		4455	ev_set_userdata (EV_A_ u);
		4456	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4457	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4458
		4459	// then create the thread running ev_loop
		4460	pthread_create (&u->tid, 0, l_run, EV_A);
		4461	}
		4462
		4463	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4464	solely to wake up the event loop so it takes notice of any new watchers
		4465	that might have been added:
		4466
		4467	static void
		4468	async_cb (EV_P_ ev_async *w, int revents)
		4469	{
		4470	// just used for the side effects
		4471	}
		4472
		4473	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4474	protecting the loop data, respectively.
		4475
		4476	static void
		4477	l_release (EV_P)
		4478	{
		4479	userdata *u = ev_userdata (EV_A);
		4480	pthread_mutex_unlock (&u->lock);
		4481	}
		4482
		4483	static void
		4484	l_acquire (EV_P)
		4485	{
		4486	userdata *u = ev_userdata (EV_A);
		4487	pthread_mutex_lock (&u->lock);
		4488	}
		4489
		4490	The event loop thread first acquires the mutex, and then jumps straight
		4491	into C<ev_run>:
		4492
		4493	void *
		4494	l_run (void *thr_arg)
		4495	{
		4496	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4497
		4498	l_acquire (EV_A);
		4499	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4500	ev_run (EV_A_ 0);
		4501	l_release (EV_A);
		4502
		4503	return 0;
		4504	}
		4505
		4506	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4507	signal the main thread via some unspecified mechanism (signals? pipe
		4508	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4509	have been called (in a while loop because a) spurious wakeups are possible
		4510	and b) skipping inter-thread-communication when there are no pending
		4511	watchers is very beneficial):
		4512
		4513	static void
		4514	l_invoke (EV_P)
		4515	{
		4516	userdata *u = ev_userdata (EV_A);
		4517
		4518	while (ev_pending_count (EV_A))
		4519	{
		4520	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4521	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4522	}
		4523	}
		4524
		4525	Now, whenever the main thread gets told to invoke pending watchers, it
		4526	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4527	thread to continue:
		4528
		4529	static void
		4530	real_invoke_pending (EV_P)
		4531	{
		4532	userdata *u = ev_userdata (EV_A);
		4533
		4534	pthread_mutex_lock (&u->lock);
		4535	ev_invoke_pending (EV_A);
		4536	pthread_cond_signal (&u->invoke_cv);
		4537	pthread_mutex_unlock (&u->lock);
		4538	}
		4539
		4540	Whenever you want to start/stop a watcher or do other modifications to an
		4541	event loop, you will now have to lock:
		4542
		4543	ev_timer timeout_watcher;
		4544	userdata *u = ev_userdata (EV_A);
		4545
		4546	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4547
		4548	pthread_mutex_lock (&u->lock);
		4549	ev_timer_start (EV_A_ &timeout_watcher);
		4550	ev_async_send (EV_A_ &u->async_w);
		4551	pthread_mutex_unlock (&u->lock);
		4552
		4553	Note that sending the C<ev_async> watcher is required because otherwise
		4554	an event loop currently blocking in the kernel will have no knowledge
		4555	about the newly added timer. By waking up the loop it will pick up any new
		4556	watchers in the next event loop iteration.
		4557
3592	=head3 COROUTINES	4558	=head3 COROUTINES
3593		4559
3594	Libev is very accommodating to coroutines ("cooperative threads"):	4560	Libev is very accommodating to coroutines ("cooperative threads"):
3595	libev fully supports nesting calls to its functions from different	4561	libev fully supports nesting calls to its functions from different
3596	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4562	coroutines (e.g. you can call C<ev_run> on the same loop from two
3597	different coroutines, and switch freely between both coroutines running the	4563	different coroutines, and switch freely between both coroutines running
3598	loop, as long as you don't confuse yourself). The only exception is that	4564	the loop, as long as you don't confuse yourself). The only exception is
3599	you must not do this from C<ev_periodic> reschedule callbacks.	4565	that you must not do this from C<ev_periodic> reschedule callbacks.
3600		4566
3601	Care has been taken to ensure that libev does not keep local state inside	4567	Care has been taken to ensure that libev does not keep local state inside
3602	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4568	C<ev_run>, and other calls do not usually allow for coroutine switches as
3603	they do not call any callbacks.	4569	they do not call any callbacks.
3604		4570
3605	=head2 COMPILER WARNINGS	4571	=head2 COMPILER WARNINGS
3606		4572
3607	Depending on your compiler and compiler settings, you might get no or a	4573	Depending on your compiler and compiler settings, you might get no or a
…		…
3618	maintainable.	4584	maintainable.
3619		4585
3620	And of course, some compiler warnings are just plain stupid, or simply	4586	And of course, some compiler warnings are just plain stupid, or simply
3621	wrong (because they don't actually warn about the condition their message	4587	wrong (because they don't actually warn about the condition their message
3622	seems to warn about). For example, certain older gcc versions had some	4588	seems to warn about). For example, certain older gcc versions had some
3623	warnings that resulted an extreme number of false positives. These have	4589	warnings that resulted in an extreme number of false positives. These have
3624	been fixed, but some people still insist on making code warn-free with	4590	been fixed, but some people still insist on making code warn-free with
3625	such buggy versions.	4591	such buggy versions.
3626		4592
3627	While libev is written to generate as few warnings as possible,	4593	While libev is written to generate as few warnings as possible,
3628	"warn-free" code is not a goal, and it is recommended not to build libev	4594	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3664	I suggest using suppression lists.	4630	I suggest using suppression lists.
3665		4631
3666		4632
3667	=head1 PORTABILITY NOTES	4633	=head1 PORTABILITY NOTES
3668		4634
		4635	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4636
		4637	GNU/Linux is the only common platform that supports 64 bit file/large file
		4638	interfaces but I<disables> them by default.
		4639
		4640	That means that libev compiled in the default environment doesn't support
		4641	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4642
		4643	Unfortunately, many programs try to work around this GNU/Linux issue
		4644	by enabling the large file API, which makes them incompatible with the
		4645	standard libev compiled for their system.
		4646
		4647	Likewise, libev cannot enable the large file API itself as this would
		4648	suddenly make it incompatible to the default compile time environment,
		4649	i.e. all programs not using special compile switches.
		4650
		4651	=head2 OS/X AND DARWIN BUGS
		4652
		4653	The whole thing is a bug if you ask me - basically any system interface
		4654	you touch is broken, whether it is locales, poll, kqueue or even the
		4655	OpenGL drivers.
		4656
		4657	=head3 C<kqueue> is buggy
		4658
		4659	The kqueue syscall is broken in all known versions - most versions support
		4660	only sockets, many support pipes.
		4661
		4662	Libev tries to work around this by not using C<kqueue> by default on this
		4663	rotten platform, but of course you can still ask for it when creating a
		4664	loop - embedding a socket-only kqueue loop into a select-based one is
		4665	probably going to work well.
		4666
		4667	=head3 C<poll> is buggy
		4668
		4669	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4670	implementation by something calling C<kqueue> internally around the 10.5.6
		4671	release, so now C<kqueue> I<and> C<poll> are broken.
		4672
		4673	Libev tries to work around this by not using C<poll> by default on
		4674	this rotten platform, but of course you can still ask for it when creating
		4675	a loop.
		4676
		4677	=head3 C<select> is buggy
		4678
		4679	All that's left is C<select>, and of course Apple found a way to fuck this
		4680	one up as well: On OS/X, C<select> actively limits the number of file
		4681	descriptors you can pass in to 1024 - your program suddenly crashes when
		4682	you use more.
		4683
		4684	There is an undocumented "workaround" for this - defining
		4685	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4686	work on OS/X.
		4687
		4688	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4689
		4690	=head3 C<errno> reentrancy
		4691
		4692	The default compile environment on Solaris is unfortunately so
		4693	thread-unsafe that you can't even use components/libraries compiled
		4694	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4695	defined by default. A valid, if stupid, implementation choice.
		4696
		4697	If you want to use libev in threaded environments you have to make sure
		4698	it's compiled with C<_REENTRANT> defined.
		4699
		4700	=head3 Event port backend
		4701
		4702	The scalable event interface for Solaris is called "event
		4703	ports". Unfortunately, this mechanism is very buggy in all major
		4704	releases. If you run into high CPU usage, your program freezes or you get
		4705	a large number of spurious wakeups, make sure you have all the relevant
		4706	and latest kernel patches applied. No, I don't know which ones, but there
		4707	are multiple ones to apply, and afterwards, event ports actually work
		4708	great.
		4709
		4710	If you can't get it to work, you can try running the program by setting
		4711	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4712	C<select> backends.
		4713
		4714	=head2 AIX POLL BUG
		4715
		4716	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4717	this by trying to avoid the poll backend altogether (i.e. it's not even
		4718	compiled in), which normally isn't a big problem as C<select> works fine
		4719	with large bitsets on AIX, and AIX is dead anyway.
		4720
3669	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4721	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4722
		4723	=head3 General issues
3670		4724
3671	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4725	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3672	requires, and its I/O model is fundamentally incompatible with the POSIX	4726	requires, and its I/O model is fundamentally incompatible with the POSIX
3673	model. Libev still offers limited functionality on this platform in	4727	model. Libev still offers limited functionality on this platform in
3674	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4728	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3675	descriptors. This only applies when using Win32 natively, not when using	4729	descriptors. This only applies when using Win32 natively, not when using
3676	e.g. cygwin.	4730	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4731	as every compielr comes with a slightly differently broken/incompatible
		4732	environment.
3677		4733
3678	Lifting these limitations would basically require the full	4734	Lifting these limitations would basically require the full
3679	re-implementation of the I/O system. If you are into these kinds of	4735	re-implementation of the I/O system. If you are into this kind of thing,
3680	things, then note that glib does exactly that for you in a very portable	4736	then note that glib does exactly that for you in a very portable way (note
3681	way (note also that glib is the slowest event library known to man).	4737	also that glib is the slowest event library known to man).
3682		4738
3683	There is no supported compilation method available on windows except	4739	There is no supported compilation method available on windows except
3684	embedding it into other applications.	4740	embedding it into other applications.
		4741
		4742	Sensible signal handling is officially unsupported by Microsoft - libev
		4743	tries its best, but under most conditions, signals will simply not work.
3685		4744
3686	Not a libev limitation but worth mentioning: windows apparently doesn't	4745	Not a libev limitation but worth mentioning: windows apparently doesn't
3687	accept large writes: instead of resulting in a partial write, windows will	4746	accept large writes: instead of resulting in a partial write, windows will
3688	either accept everything or return C<ENOBUFS> if the buffer is too large,	4747	either accept everything or return C<ENOBUFS> if the buffer is too large,
3689	so make sure you only write small amounts into your sockets (less than a	4748	so make sure you only write small amounts into your sockets (less than a
…		…
3694	the abysmal performance of winsockets, using a large number of sockets	4753	the abysmal performance of winsockets, using a large number of sockets
3695	is not recommended (and not reasonable). If your program needs to use	4754	is not recommended (and not reasonable). If your program needs to use
3696	more than a hundred or so sockets, then likely it needs to use a totally	4755	more than a hundred or so sockets, then likely it needs to use a totally
3697	different implementation for windows, as libev offers the POSIX readiness	4756	different implementation for windows, as libev offers the POSIX readiness
3698	notification model, which cannot be implemented efficiently on windows	4757	notification model, which cannot be implemented efficiently on windows
3699	(Microsoft monopoly games).	4758	(due to Microsoft monopoly games).
3700		4759
3701	A typical way to use libev under windows is to embed it (see the embedding	4760	A typical way to use libev under windows is to embed it (see the embedding
3702	section for details) and use the following F<evwrap.h> header file instead	4761	section for details) and use the following F<evwrap.h> header file instead
3703	of F<ev.h>:	4762	of F<ev.h>:
3704		4763
…		…
3711	you do I<not> compile the F<ev.c> or any other embedded source files!):	4770	you do I<not> compile the F<ev.c> or any other embedded source files!):
3712		4771
3713	#include "evwrap.h"	4772	#include "evwrap.h"
3714	#include "ev.c"	4773	#include "ev.c"
3715		4774
3716	=over 4
3717
3718	=item The winsocket select function	4775	=head3 The winsocket C<select> function
3719		4776
3720	The winsocket C<select> function doesn't follow POSIX in that it	4777	The winsocket C<select> function doesn't follow POSIX in that it
3721	requires socket I<handles> and not socket I<file descriptors> (it is	4778	requires socket I<handles> and not socket I<file descriptors> (it is
3722	also extremely buggy). This makes select very inefficient, and also	4779	also extremely buggy). This makes select very inefficient, and also
3723	requires a mapping from file descriptors to socket handles (the Microsoft	4780	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3732	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4789	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3733		4790
3734	Note that winsockets handling of fd sets is O(n), so you can easily get a	4791	Note that winsockets handling of fd sets is O(n), so you can easily get a
3735	complexity in the O(n²) range when using win32.	4792	complexity in the O(n²) range when using win32.
3736		4793
3737	=item Limited number of file descriptors	4794	=head3 Limited number of file descriptors
3738		4795
3739	Windows has numerous arbitrary (and low) limits on things.	4796	Windows has numerous arbitrary (and low) limits on things.
3740		4797
3741	Early versions of winsocket's select only supported waiting for a maximum	4798	Early versions of winsocket's select only supported waiting for a maximum
3742	of C<64> handles (probably owning to the fact that all windows kernels	4799	of C<64> handles (probably owning to the fact that all windows kernels
3743	can only wait for C<64> things at the same time internally; Microsoft	4800	can only wait for C<64> things at the same time internally; Microsoft
3744	recommends spawning a chain of threads and wait for 63 handles and the	4801	recommends spawning a chain of threads and wait for 63 handles and the
3745	previous thread in each. Great).	4802	previous thread in each. Sounds great!).
3746		4803
3747	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4804	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3748	to some high number (e.g. C<2048>) before compiling the winsocket select	4805	to some high number (e.g. C<2048>) before compiling the winsocket select
3749	call (which might be in libev or elsewhere, for example, perl does its own	4806	call (which might be in libev or elsewhere, for example, perl and many
3750	select emulation on windows).	4807	other interpreters do their own select emulation on windows).
3751		4808
3752	Another limit is the number of file descriptors in the Microsoft runtime	4809	Another limit is the number of file descriptors in the Microsoft runtime
3753	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4810	libraries, which by default is C<64> (there must be a hidden I<64>
3754	or something like this inside Microsoft). You can increase this by calling	4811	fetish or something like this inside Microsoft). You can increase this
3755	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4812	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3756	arbitrary limit), but is broken in many versions of the Microsoft runtime	4813	(another arbitrary limit), but is broken in many versions of the Microsoft
3757	libraries.
3758
3759	This might get you to about C<512> or C<2048> sockets (depending on	4814	runtime libraries. This might get you to about C<512> or C<2048> sockets
3760	windows version and/or the phase of the moon). To get more, you need to	4815	(depending on windows version and/or the phase of the moon). To get more,
3761	wrap all I/O functions and provide your own fd management, but the cost of	4816	you need to wrap all I/O functions and provide your own fd management, but
3762	calling select (O(n²)) will likely make this unworkable.	4817	the cost of calling select (O(n²)) will likely make this unworkable.
3763
3764	=back
3765		4818
3766	=head2 PORTABILITY REQUIREMENTS	4819	=head2 PORTABILITY REQUIREMENTS
3767		4820
3768	In addition to a working ISO-C implementation and of course the	4821	In addition to a working ISO-C implementation and of course the
3769	backend-specific APIs, libev relies on a few additional extensions:	4822	backend-specific APIs, libev relies on a few additional extensions:
…		…
3776	Libev assumes not only that all watcher pointers have the same internal	4829	Libev assumes not only that all watcher pointers have the same internal
3777	structure (guaranteed by POSIX but not by ISO C for example), but it also	4830	structure (guaranteed by POSIX but not by ISO C for example), but it also
3778	assumes that the same (machine) code can be used to call any watcher	4831	assumes that the same (machine) code can be used to call any watcher
3779	callback: The watcher callbacks have different type signatures, but libev	4832	callback: The watcher callbacks have different type signatures, but libev
3780	calls them using an C<ev_watcher *> internally.	4833	calls them using an C<ev_watcher *> internally.
		4834
		4835	=item pointer accesses must be thread-atomic
		4836
		4837	Accessing a pointer value must be atomic, it must both be readable and
		4838	writable in one piece - this is the case on all current architectures.
3781		4839
3782	=item C<sig_atomic_t volatile> must be thread-atomic as well	4840	=item C<sig_atomic_t volatile> must be thread-atomic as well
3783		4841
3784	The type C<sig_atomic_t volatile> (or whatever is defined as	4842	The type C<sig_atomic_t volatile> (or whatever is defined as
3785	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	4843	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
3808	watchers.	4866	watchers.
3809		4867
3810	=item C<double> must hold a time value in seconds with enough accuracy	4868	=item C<double> must hold a time value in seconds with enough accuracy
3811		4869
3812	The type C<double> is used to represent timestamps. It is required to	4870	The type C<double> is used to represent timestamps. It is required to
3813	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4871	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3814	enough for at least into the year 4000. This requirement is fulfilled by	4872	good enough for at least into the year 4000 with millisecond accuracy
		4873	(the design goal for libev). This requirement is overfulfilled by
3815	implementations implementing IEEE 754 (basically all existing ones).	4874	implementations using IEEE 754, which is basically all existing ones. With
		4875	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
3816		4876
3817	=back	4877	=back
3818		4878
3819	If you know of other additional requirements drop me a note.	4879	If you know of other additional requirements drop me a note.
3820		4880
…		…
3888	involves iterating over all running async watchers or all signal numbers.	4948	involves iterating over all running async watchers or all signal numbers.
3889		4949
3890	=back	4950	=back
3891		4951
3892		4952
		4953	=head1 PORTING FROM LIBEV 3.X TO 4.X
		4954
		4955	The major version 4 introduced some incompatible changes to the API.
		4956
		4957	At the moment, the C<ev.h> header file provides compatibility definitions
		4958	for all changes, so most programs should still compile. The compatibility
		4959	layer might be removed in later versions of libev, so better update to the
		4960	new API early than late.
		4961
		4962	=over 4
		4963
		4964	=item C<EV_COMPAT3> backwards compatibility mechanism
		4965
		4966	The backward compatibility mechanism can be controlled by
		4967	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		4968	section.
		4969
		4970	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		4971
		4972	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		4973
		4974	ev_loop_destroy (EV_DEFAULT_UC);
		4975	ev_loop_fork (EV_DEFAULT);
		4976
		4977	=item function/symbol renames
		4978
		4979	A number of functions and symbols have been renamed:
		4980
		4981	ev_loop => ev_run
		4982	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		4983	EVLOOP_ONESHOT => EVRUN_ONCE
		4984
		4985	ev_unloop => ev_break
		4986	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		4987	EVUNLOOP_ONE => EVBREAK_ONE
		4988	EVUNLOOP_ALL => EVBREAK_ALL
		4989
		4990	EV_TIMEOUT => EV_TIMER
		4991
		4992	ev_loop_count => ev_iteration
		4993	ev_loop_depth => ev_depth
		4994	ev_loop_verify => ev_verify
		4995
		4996	Most functions working on C<struct ev_loop> objects don't have an
		4997	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		4998	associated constants have been renamed to not collide with the C<struct
		4999	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5000	as all other watcher types. Note that C<ev_loop_fork> is still called
		5001	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5002	typedef.
		5003
		5004	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5005
		5006	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5007	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5008	and work, but the library code will of course be larger.
		5009
		5010	=back
		5011
		5012
		5013	=head1 GLOSSARY
		5014
		5015	=over 4
		5016
		5017	=item active
		5018
		5019	A watcher is active as long as it has been started and not yet stopped.
		5020	See L<WATCHER STATES> for details.
		5021
		5022	=item application
		5023
		5024	In this document, an application is whatever is using libev.
		5025
		5026	=item backend
		5027
		5028	The part of the code dealing with the operating system interfaces.
		5029
		5030	=item callback
		5031
		5032	The address of a function that is called when some event has been
		5033	detected. Callbacks are being passed the event loop, the watcher that
		5034	received the event, and the actual event bitset.
		5035
		5036	=item callback/watcher invocation
		5037
		5038	The act of calling the callback associated with a watcher.
		5039
		5040	=item event
		5041
		5042	A change of state of some external event, such as data now being available
		5043	for reading on a file descriptor, time having passed or simply not having
		5044	any other events happening anymore.
		5045
		5046	In libev, events are represented as single bits (such as C<EV_READ> or
		5047	C<EV_TIMER>).
		5048
		5049	=item event library
		5050
		5051	A software package implementing an event model and loop.
		5052
		5053	=item event loop
		5054
		5055	An entity that handles and processes external events and converts them
		5056	into callback invocations.
		5057
		5058	=item event model
		5059
		5060	The model used to describe how an event loop handles and processes
		5061	watchers and events.
		5062
		5063	=item pending
		5064
		5065	A watcher is pending as soon as the corresponding event has been
		5066	detected. See L<WATCHER STATES> for details.
		5067
		5068	=item real time
		5069
		5070	The physical time that is observed. It is apparently strictly monotonic :)
		5071
		5072	=item wall-clock time
		5073
		5074	The time and date as shown on clocks. Unlike real time, it can actually
		5075	be wrong and jump forwards and backwards, e.g. when the you adjust your
		5076	clock.
		5077
		5078	=item watcher
		5079
		5080	A data structure that describes interest in certain events. Watchers need
		5081	to be started (attached to an event loop) before they can receive events.
		5082
		5083	=back
		5084
3893	=head1 AUTHOR	5085	=head1 AUTHOR
3894		5086
3895	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5087	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5088	Magnusson and Emanuele Giaquinta.
3896		5089

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