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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
…		…
417	i.e. keep at least one watcher active per fd at all times. Stopping and	497	i.e. keep at least one watcher active per fd at all times. Stopping and
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.
		502
		503	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		504	faster than epoll for maybe up to a hundred file descriptors, depending on
		505	the usage. So sad.
422		506
423	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
424	all kernel versions tested so far.	508	all kernel versions tested so far.
425		509
426	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	510	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
…		…
454		538
455	While nominally embeddable in other event loops, this doesn't work	539	While nominally embeddable in other event loops, this doesn't work
456	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
457	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
458	(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
459	(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
460	using it only for sockets.	544	also broken on OS X)) and, did I mention it, using it only for sockets.
461		545
462	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
463	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
464	C<NOTE_EOF>.	548	C<NOTE_EOF>.
465		549
…		…
500		584
501	It is definitely not recommended to use this flag.	585	It is definitely not recommended to use this flag.
502		586
503	=back	587	=back
504		588
505	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,
506	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
507	specified, all backends in C<ev_recommended_backends ()> will be tried.	591	here). If none are specified, all backends in C<ev_recommended_backends
508		592	()> will be tried.
509	Example: This is the most typical usage.
510
511	if (!ev_default_loop (0))
512	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
513
514	Example: Restrict libev to the select and poll backends, and do not allow
515	environment settings to be taken into account:
516
517	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
518
519	Example: Use whatever libev has to offer, but make sure that kqueue is
520	used if available (warning, breaks stuff, best use only with your own
521	private event loop and only if you know the OS supports your types of
522	fds):
523
524	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
525
526	=item struct ev_loop *ev_loop_new (unsigned int flags)
527
528	Similar to C<ev_default_loop>, but always creates a new event loop that is
529	always distinct from the default loop. Unlike the default loop, it cannot
530	handle signal and child watchers, and attempts to do so will be greeted by
531	undefined behaviour (or a failed assertion if assertions are enabled).
532
533	Note that this function I<is> thread-safe, and the recommended way to use
534	libev with threads is indeed to create one loop per thread, and using the
535	default loop in the "main" or "initial" thread.
536		593
537	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.
538		595
539	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	596	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
540	if (!epoller)	597	if (!epoller)
541	fatal ("no epoll found here, maybe it hides under your chair");	598	fatal ("no epoll found here, maybe it hides under your chair");
542		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
543	=item ev_default_destroy ()	605	=item ev_loop_destroy (loop)
544		606
545	Destroys the default loop again (frees all memory and kernel state	607	Destroys an event loop object (frees all memory and kernel state
546	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
547	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
548	responsibility to either stop all watchers cleanly yourself I<before>	610	responsibility to either stop all watchers cleanly yourself I<before>
549	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
550	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
…		…
552		614
553	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
554	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
555	as signal and child watchers) would need to be stopped manually.	617	as signal and child watchers) would need to be stopped manually.
556		618
557	In general it is not advisable to call this function except in the	619	This function is normally used on loop objects allocated by
558	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.
559	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>
560	C<ev_loop_new> and C<ev_loop_destroy>).	626	and C<ev_loop_destroy>.
561		627
562	=item ev_loop_destroy (loop)	628	=item ev_loop_fork (loop)
563		629
564	Like C<ev_default_destroy>, but destroys an event loop created by an
565	earlier call to C<ev_loop_new>.
566
567	=item ev_default_fork ()
568
569	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
570	to reinitialise the kernel state for backends that have one. Despite the	631	reinitialise the kernel state for backends that have one. Despite the
571	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
572	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
573	sense). You I<must> call it in the child before using any of the libev	634	child before resuming or calling C<ev_run>.
574	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.
575		640
576	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
577	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
578	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).
579		647
580	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
581	it just in case after a fork. To make this easy, the function will fit in	649	it just in case after a fork.
582	quite nicely into a call to C<pthread_atfork>:
583		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	...
584	pthread_atfork (0, 0, ev_default_fork);	661	pthread_atfork (0, 0, post_fork_child);
585
586	=item ev_loop_fork (loop)
587
588	Like C<ev_default_fork>, but acts on an event loop created by
589	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
590	after fork that you want to re-use in the child, and how you do this is
591	entirely your own problem.
592		662
593	=item int ev_is_default_loop (loop)	663	=item int ev_is_default_loop (loop)
594		664
595	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
596	otherwise.	666	otherwise.
597		667
598	=item unsigned int ev_loop_count (loop)	668	=item unsigned int ev_iteration (loop)
599		669
600	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
601	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>
602	happily wraps around with enough iterations.	672	and happily wraps around with enough iterations.
603		673
604	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
605	"ticks" the number of loop iterations), as it roughly corresponds with	675	"ticks" the number of loop iterations), as it roughly corresponds with
606	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.
607		692
608	=item unsigned int ev_backend (loop)	693	=item unsigned int ev_backend (loop)
609		694
610	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
611	use.	696	use.
…		…
620		705
621	=item ev_now_update (loop)	706	=item ev_now_update (loop)
622		707
623	Establishes the current time by querying the kernel, updating the time	708	Establishes the current time by querying the kernel, updating the time
624	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
625	is usually done automatically within C<ev_loop ()>.	710	is usually done automatically within C<ev_run ()>.
626		711
627	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
628	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
629	the current time is a good idea.	714	the current time is a good idea.
630		715
631	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.
632		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
633	=item ev_loop (loop, int flags)	744	=item ev_run (loop, int flags)
634		745
635	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
636	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
637	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>.
638		751
639	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
640	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.
641		755
642	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
643	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
644	finished (especially in interactive programs), but having a program	758	finished (especially in interactive programs), but having a program
645	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
646	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
647	beauty.	761	beauty.
648		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
649	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
650	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
651	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
652	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.
653		773
654	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
655	necessary) and will handle those and any already outstanding ones. It	775	necessary) and will handle those and any already outstanding ones. It
656	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
657	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
658	user-registered callback will be called), and will return after one	778	user-registered callback will be called), and will return after one
659	iteration of the loop.	779	iteration of the loop.
660		780
661	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
662	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
663	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
664	usually a better approach for this kind of thing.	784	usually a better approach for this kind of thing.
665		785
666	Here are the gory details of what C<ev_loop> does:	786	Here are the gory details of what C<ev_run> does:
667		787
		788	- Increment loop depth.
		789	- Reset the ev_break status.
668	- Before the first iteration, call any pending watchers.	790	- Before the first iteration, call any pending watchers.
		791	LOOP:
669	* If EVFLAG_FORKCHECK was used, check for a fork.	792	- If EVFLAG_FORKCHECK was used, check for a fork.
670	- 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.
671	- Queue and call all prepare watchers.	794	- Queue and call all prepare watchers.
		795	- If ev_break was called, goto FINISH.
672	- If we have been forked, detach and recreate the kernel state	796	- If we have been forked, detach and recreate the kernel state
673	as to not disturb the other process.	797	as to not disturb the other process.
674	- Update the kernel state with all outstanding changes.	798	- Update the kernel state with all outstanding changes.
675	- Update the "event loop time" (ev_now ()).	799	- Update the "event loop time" (ev_now ()).
676	- Calculate for how long to sleep or block, if at all	800	- Calculate for how long to sleep or block, if at all
677	(active idle watchers, EVLOOP_NONBLOCK or not having	801	(active idle watchers, EVRUN_NOWAIT or not having
678	any active watchers at all will result in not sleeping).	802	any active watchers at all will result in not sleeping).
679	- 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.
680	- Block the process, waiting for any events.	805	- Block the process, waiting for any events.
681	- Queue all outstanding I/O (fd) events.	806	- Queue all outstanding I/O (fd) events.
682	- 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.
683	- Queue all expired timers.	808	- Queue all expired timers.
684	- Queue all expired periodics.	809	- Queue all expired periodics.
685	- Unless any events are pending now, queue all idle watchers.	810	- Queue all idle watchers with priority higher than that of pending events.
686	- Queue all check watchers.	811	- Queue all check watchers.
687	- 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).
688	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
689	be handled here by queueing them when their watcher gets executed.	814	be handled here by queueing them when their watcher gets executed.
690	- 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
691	were used, or there are no active watchers, return, otherwise	816	were used, or there are no active watchers, goto FINISH, otherwise
692	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.
693		822
694	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
695	anymore.	824	anymore.
696		825
697	... queue jobs here, make sure they register event watchers as long	826	... queue jobs here, make sure they register event watchers as long
698	... 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..)
699	ev_loop (my_loop, 0);	828	ev_run (my_loop, 0);
700	... jobs done or somebody called unloop. yeah!	829	... jobs done or somebody called unloop. yeah!
701		830
702	=item ev_unloop (loop, how)	831	=item ev_break (loop, how)
703		832
704	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
705	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
706	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
707	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.
708		837
709	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>.
710		839
711	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.
712		842
713	=item ev_ref (loop)	843	=item ev_ref (loop)
714		844
715	=item ev_unref (loop)	845	=item ev_unref (loop)
716		846
717	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
718	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
719	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.
720		850
721	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
722	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>
723	stopping it.	854	before stopping it.
724		855
725	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
726	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
727	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
728	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
729	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
730	(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
731	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).
732		865
733	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>
734	running when nothing else is active.	867	running when nothing else is active.
735		868
736	ev_signal exitsig;	869	ev_signal exitsig;
737	ev_signal_init (&exitsig, sig_cb, SIGINT);	870	ev_signal_init (&exitsig, sig_cb, SIGINT);
738	ev_signal_start (loop, &exitsig);	871	ev_signal_start (loop, &exitsig);
…		…
765		898
766	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
767	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,
768	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
769	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
770	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.
771		906
772	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
773	to spend more time collecting timeouts, at the expense of increased	908	to spend more time collecting timeouts, at the expense of increased
774	latency/jitter/inexactness (the watcher callback will be called	909	latency/jitter/inexactness (the watcher callback will be called
775	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
…		…
777		912
778	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
779	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
780	interactive servers (of course not for games), likewise for timeouts. It	915	interactive servers (of course not for games), likewise for timeouts. It
781	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>,
782	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).
783		922
784	Setting the I<timeout collect interval> can improve the opportunity for	923	Setting the I<timeout collect interval> can improve the opportunity for
785	saving power, as the program will "bundle" timer callback invocations that	924	saving power, as the program will "bundle" timer callback invocations that
786	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
787	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
788	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
789	they fire on, say, one-second boundaries only.	928	they fire on, say, one-second boundaries only.
790		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
791	=item ev_loop_verify (loop)	1005	=item ev_verify (loop)
792		1006
793	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
794	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
795	through all internal structures and checks them for validity. If anything	1009	through all internal structures and checks them for validity. If anything
796	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
…		…
807		1021
808	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
809	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
810	watchers and C<ev_io_start> for I/O watchers.	1024	watchers and C<ev_io_start> for I/O watchers.
811		1025
812	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
813	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
814	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:
815		1030
816	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)
817	{	1032	{
818	ev_io_stop (w);	1033	ev_io_stop (w);
819	ev_unloop (loop, EVUNLOOP_ALL);	1034	ev_break (loop, EVBREAK_ALL);
820	}	1035	}
821		1036
822	struct ev_loop *loop = ev_default_loop (0);	1037	struct ev_loop *loop = ev_default_loop (0);
823		1038
824	ev_io stdin_watcher;	1039	ev_io stdin_watcher;
825		1040
826	ev_init (&stdin_watcher, my_cb);	1041	ev_init (&stdin_watcher, my_cb);
827	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1042	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
828	ev_io_start (loop, &stdin_watcher);	1043	ev_io_start (loop, &stdin_watcher);
829		1044
830	ev_loop (loop, 0);	1045	ev_run (loop, 0);
831		1046
832	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
833	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
834	stack).	1049	stack).
835		1050
836	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>
837	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).
838		1053
839	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
840	(watcher *, callback)>, which expects a callback to be provided. This	1055	*, callback)>, which expects a callback to be provided. This callback is
841	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
842	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
843	is readable and/or writable).	1058	and/or writable).
844		1059
845	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 *, ...) >>
846	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
847	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<<
848	ev_TYPE_init (watcher *, callback, ...) >>.	1063	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
871	=item C<EV_WRITE>	1086	=item C<EV_WRITE>
872		1087
873	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
874	writable.	1089	writable.
875		1090
876	=item C<EV_TIMEOUT>	1091	=item C<EV_TIMER>
877		1092
878	The C<ev_timer> watcher has timed out.	1093	The C<ev_timer> watcher has timed out.
879		1094
880	=item C<EV_PERIODIC>	1095	=item C<EV_PERIODIC>
881		1096
…		…
899		1114
900	=item C<EV_PREPARE>	1115	=item C<EV_PREPARE>
901		1116
902	=item C<EV_CHECK>	1117	=item C<EV_CHECK>
903		1118
904	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
905	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
906	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
907	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
908	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
909	(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
910	C<ev_loop> from blocking).	1125	C<ev_run> from blocking).
911		1126
912	=item C<EV_EMBED>	1127	=item C<EV_EMBED>
913		1128
914	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.
915		1130
916	=item C<EV_FORK>	1131	=item C<EV_FORK>
917		1132
918	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
919	C<ev_fork>).	1134	C<ev_fork>).
920		1135
		1136	=item C<EV_CLEANUP>
		1137
		1138	The event loop is about to be destroyed (see C<ev_cleanup>).
		1139
921	=item C<EV_ASYNC>	1140	=item C<EV_ASYNC>
922		1141
923	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>).
924		1148
925	=item C<EV_ERROR>	1149	=item C<EV_ERROR>
926		1150
927	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
928	happen because the watcher could not be properly started because libev	1152	happen because the watcher could not be properly started because libev
…		…
966		1190
967	ev_io w;	1191	ev_io w;
968	ev_init (&w, my_cb);	1192	ev_init (&w, my_cb);
969	ev_io_set (&w, STDIN_FILENO, EV_READ);	1193	ev_io_set (&w, STDIN_FILENO, EV_READ);
970		1194
971	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1195	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
972		1196
973	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
974	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
975	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
976	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
…		…
989		1213
990	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.
991		1215
992	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1216	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
993		1217
994	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1218	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
995		1219
996	Starts (activates) the given watcher. Only active watchers will receive	1220	Starts (activates) the given watcher. Only active watchers will receive
997	events. If the watcher is already active nothing will happen.	1221	events. If the watcher is already active nothing will happen.
998		1222
999	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
1000	whole section.	1224	whole section.
1001		1225
1002	ev_io_start (EV_DEFAULT_UC, &w);	1226	ev_io_start (EV_DEFAULT_UC, &w);
1003		1227
1004	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1228	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1005		1229
1006	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
1007	the watcher was active or not).	1231	the watcher was active or not).
1008		1232
1009	It is possible that stopped watchers are pending - for example,	1233	It is possible that stopped watchers are pending - for example,
…		…
1034	=item ev_cb_set (ev_TYPE *watcher, callback)	1258	=item ev_cb_set (ev_TYPE *watcher, callback)
1035		1259
1036	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
1037	(modulo threads).	1261	(modulo threads).
1038		1262
1039	=item ev_set_priority (ev_TYPE *watcher, priority)	1263	=item ev_set_priority (ev_TYPE *watcher, int priority)
1040		1264
1041	=item int ev_priority (ev_TYPE *watcher)	1265	=item int ev_priority (ev_TYPE *watcher)
1042		1266
1043	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
1044	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>
1045	(default: C<-2>). Pending watchers with higher priority will be invoked	1269	(default: C<-2>). Pending watchers with higher priority will be invoked
1046	before watchers with lower priority, but priority will not keep watchers	1270	before watchers with lower priority, but priority will not keep watchers
1047	from being executed (except for C<ev_idle> watchers).	1271	from being executed (except for C<ev_idle> watchers).
1048		1272
1049	This means that priorities are I<only> used for ordering callback
1050	invocation after new events have been received. This is useful, for
1051	example, to reduce latency after idling, or more often, to bind two
1052	watchers on the same event and make sure one is called first.
1053
1054	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
1055	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.
1056		1275
1057	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
1058	pending.	1277	pending.
1059
1060	The default priority used by watchers when no priority has been set is
1061	always C<0>, which is supposed to not be too high and not be too low :).
1062		1278
1063	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
1064	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
1065	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.
1066		1288
1067	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1289	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1068		1290
1069	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
1070	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
…		…
1078	watcher isn't pending it does nothing and returns C<0>.	1300	watcher isn't pending it does nothing and returns C<0>.
1079		1301
1080	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
1081	callback to be invoked, which can be accomplished with this function.	1303	callback to be invoked, which can be accomplished with this function.
1082		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
1083	=back	1319	=back
1084
1085		1320
1086	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1321	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1087		1322
1088	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
1089	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
…		…
1135	#include <stddef.h>	1370	#include <stddef.h>
1136		1371
1137	static void	1372	static void
1138	t1_cb (EV_P_ ev_timer *w, int revents)	1373	t1_cb (EV_P_ ev_timer *w, int revents)
1139	{	1374	{
1140	struct my_biggy big = (struct my_biggy *	1375	struct my_biggy big = (struct my_biggy *)
1141	(((char *)w) - offsetof (struct my_biggy, t1));	1376	(((char *)w) - offsetof (struct my_biggy, t1));
1142	}	1377	}
1143		1378
1144	static void	1379	static void
1145	t2_cb (EV_P_ ev_timer *w, int revents)	1380	t2_cb (EV_P_ ev_timer *w, int revents)
1146	{	1381	{
1147	struct my_biggy big = (struct my_biggy *	1382	struct my_biggy big = (struct my_biggy *)
1148	(((char *)w) - offsetof (struct my_biggy, t2));	1383	(((char *)w) - offsetof (struct my_biggy, t2));
1149	}	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.
1150		1547
1151		1548
1152	=head1 WATCHER TYPES	1549	=head1 WATCHER TYPES
1153		1550
1154	This section describes each watcher in detail, but will not repeat	1551	This section describes each watcher in detail, but will not repeat
…		…
1180	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
1181	required if you know what you are doing).	1578	required if you know what you are doing).
1182		1579
1183	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
1184	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
1185	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.
1186		1585
1187	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
1188	receive "spurious" readiness notifications, that is your callback might	1587	receive "spurious" readiness notifications, that is your callback might
1189	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
1190	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
…		…
1255		1654
1256	So when you encounter spurious, unexplained daemon exits, make sure you	1655	So when you encounter spurious, unexplained daemon exits, make sure you
1257	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
1258	somewhere, as that would have given you a big clue).	1657	somewhere, as that would have given you a big clue).
1259		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.
1260		1697
1261	=head3 Watcher-Specific Functions	1698	=head3 Watcher-Specific Functions
1262		1699
1263	=over 4	1700	=over 4
1264		1701
…		…
1296	...	1733	...
1297	struct ev_loop *loop = ev_default_init (0);	1734	struct ev_loop *loop = ev_default_init (0);
1298	ev_io stdin_readable;	1735	ev_io stdin_readable;
1299	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);
1300	ev_io_start (loop, &stdin_readable);	1737	ev_io_start (loop, &stdin_readable);
1301	ev_loop (loop, 0);	1738	ev_run (loop, 0);
1302		1739
1303		1740
1304	=head2 C<ev_timer> - relative and optionally repeating timeouts	1741	=head2 C<ev_timer> - relative and optionally repeating timeouts
1305		1742
1306	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
…		…
1311	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
1312	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1749	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1313	monotonic clock option helps a lot here).	1750	monotonic clock option helps a lot here).
1314		1751
1315	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
1316	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
1317	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).
1318		1758
1319	=head3 Be smart about timeouts	1759	=head3 Be smart about timeouts
1320		1760
1321	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
1322	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,
…		…
1366	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>
1367	member and C<ev_timer_again>.	1807	member and C<ev_timer_again>.
1368		1808
1369	At start:	1809	At start:
1370		1810
1371	ev_timer_init (timer, callback);	1811	ev_init (timer, callback);
1372	timer->repeat = 60.;	1812	timer->repeat = 60.;
1373	ev_timer_again (loop, timer);	1813	ev_timer_again (loop, timer);
1374		1814
1375	Each time there is some activity:	1815	Each time there is some activity:
1376		1816
…		…
1408	ev_tstamp timeout = last_activity + 60.;	1848	ev_tstamp timeout = last_activity + 60.;
1409		1849
1410	// 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
1411	if (timeout < now)	1851	if (timeout < now)
1412	{	1852	{
1413	// timeout occured, take action	1853	// timeout occurred, take action
1414	}	1854	}
1415	else	1855	else
1416	{	1856	{
1417	// callback was invoked, but there was some activity, re-arm	1857	// callback was invoked, but there was some activity, re-arm
1418	// the watcher to fire in last_activity + 60, which is	1858	// the watcher to fire in last_activity + 60, which is
1419	// guaranteed to be in the future, so "again" is positive:	1859	// guaranteed to be in the future, so "again" is positive:
1420	w->again = timeout - now;	1860	w->repeat = timeout - now;
1421	ev_timer_again (EV_A_ w);	1861	ev_timer_again (EV_A_ w);
1422	}	1862	}
1423	}	1863	}
1424		1864
1425	To summarise the callback: first calculate the real timeout (defined	1865	To summarise the callback: first calculate the real timeout (defined
…		…
1438		1878
1439	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>
1440	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
1441	callback, which will "do the right thing" and start the timer:	1881	callback, which will "do the right thing" and start the timer:
1442		1882
1443	ev_timer_init (timer, callback);	1883	ev_init (timer, callback);
1444	last_activity = ev_now (loop);	1884	last_activity = ev_now (loop);
1445	callback (loop, timer, EV_TIMEOUT);	1885	callback (loop, timer, EV_TIMER);
1446		1886
1447	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
1448	C<last_activity>, no libev calls at all:	1888	C<last_activity>, no libev calls at all:
1449		1889
1450	last_actiivty = ev_now (loop);	1890	last_activity = ev_now (loop);
1451		1891
1452	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
1453	time-out is unlikely to be triggered, much more efficient.	1893	time-out is unlikely to be triggered, much more efficient.
1454		1894
1455	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
…		…
1493		1933
1494	=head3 The special problem of time updates	1934	=head3 The special problem of time updates
1495		1935
1496	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
1497	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
1498	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
1499	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
1500	lots of events in one iteration.	1940	lots of events in one iteration.
1501		1941
1502	The relative timeouts are calculated relative to the C<ev_now ()>	1942	The relative timeouts are calculated relative to the C<ev_now ()>
1503	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
…		…
1509		1949
1510	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
1511	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
1512	()>.	1952	()>.
1513		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
1514	=head3 Watcher-Specific Functions and Data Members	1984	=head3 Watcher-Specific Functions and Data Members
1515		1985
1516	=over 4	1986	=over 4
1517		1987
1518	=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)
…		…
1541	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).
1542		2012
1543	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
1544	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.
1545		2015
1546	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
1547	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.
1548		2030
1549	=item ev_tstamp repeat [read-write]	2031	=item ev_tstamp repeat [read-write]
1550		2032
1551	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
1552	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),
…		…
1578	}	2060	}
1579		2061
1580	ev_timer mytimer;	2062	ev_timer mytimer;
1581	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 */
1582	ev_timer_again (&mytimer); /* start timer */	2064	ev_timer_again (&mytimer); /* start timer */
1583	ev_loop (loop, 0);	2065	ev_run (loop, 0);
1584		2066
1585	// 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":
1586	// reset the timeout to start ticking again at 10 seconds	2068	// reset the timeout to start ticking again at 10 seconds
1587	ev_timer_again (&mytimer);	2069	ev_timer_again (&mytimer);
1588		2070
…		…
1590	=head2 C<ev_periodic> - to cron or not to cron?	2072	=head2 C<ev_periodic> - to cron or not to cron?
1591		2073
1592	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
1593	(and unfortunately a bit complex).	2075	(and unfortunately a bit complex).
1594		2076
1595	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
1596	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
1597	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
1598	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
1599	+ 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
1600	clock to January of the previous year, then it will take more than year	2082	wrist-watch).
1601	to trigger the event (unlike an C<ev_timer>, which would still trigger
1602	roughly 10 seconds later as it uses a relative timeout).
1603		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
1604	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
1605	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
1606	complicated rules.	2094	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2095	those cannot react to time jumps.
1607		2096
1608	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
1609	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
1610	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).
1611		2102
1612	=head3 Watcher-Specific Functions and Data Members	2103	=head3 Watcher-Specific Functions and Data Members
1613		2104
1614	=over 4	2105	=over 4
1615		2106
1616	=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)
1617		2108
1618	=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)
1619		2110
1620	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
1621	operation, and we will explain them from simplest to most complex:	2112	operation, and we will explain them from simplest to most complex:
1622		2113
1623	=over 4	2114	=over 4
1624		2115
1625	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2116	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1626		2117
1627	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
1628	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
1629	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
1630	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.
1631		2123
1632	=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)
1633		2125
1634	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
1635	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
1636	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.
1637		2130
1638	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
1639	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
1640	hour, on the hour:	2133	hour, on the hour (with respect to UTC):
1641		2134
1642	ev_periodic_set (&periodic, 0., 3600., 0);	2135	ev_periodic_set (&periodic, 0., 3600., 0);
1643		2136
1644	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,
1645	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
1646	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
1647	by 3600.	2140	by 3600.
1648		2141
1649	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
1650	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
1651	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.
1652		2145
1653	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
1654	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
1655	this value, and in fact is often specified as zero.	2148	this value, and in fact is often specified as zero.
1656		2149
1657	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
1658	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
1659	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
1660	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).
1661		2154
1662	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2155	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1663		2156
1664	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
1665	ignored. Instead, each time the periodic watcher gets scheduled, the	2158	ignored. Instead, each time the periodic watcher gets scheduled, the
1666	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
1667	current time as second argument.	2160	current time as second argument.
1668		2161
1669	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,
1670	ever, or make ANY event loop modifications whatsoever>.	2163	or make ANY other event loop modifications whatsoever, unless explicitly
		2164	allowed by documentation here>.
1671		2165
1672	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
1673	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
1674	only event loop modification you are allowed to do).	2168	only event loop modification you are allowed to do).
1675		2169
…		…
1705	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
1706	program when the crontabs have changed).	2200	program when the crontabs have changed).
1707		2201
1708	=item ev_tstamp ev_periodic_at (ev_periodic *)	2202	=item ev_tstamp ev_periodic_at (ev_periodic *)
1709		2203
1710	When active, returns the absolute time that the watcher is supposed to	2204	When active, returns the absolute time that the watcher is supposed
1711	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.
1712		2208
1713	=item ev_tstamp offset [read-write]	2209	=item ev_tstamp offset [read-write]
1714		2210
1715	When repeating, this contains the offset value, otherwise this is the	2211	When repeating, this contains the offset value, otherwise this is the
1716	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).
1717		2214
1718	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
1719	timer fires or C<ev_periodic_again> is being called.	2216	timer fires or C<ev_periodic_again> is being called.
1720		2217
1721	=item ev_tstamp interval [read-write]	2218	=item ev_tstamp interval [read-write]
…		…
1737	Example: Call a callback every hour, or, more precisely, whenever the	2234	Example: Call a callback every hour, or, more precisely, whenever the
1738	system time is divisible by 3600. The callback invocation times have	2235	system time is divisible by 3600. The callback invocation times have
1739	potentially a lot of jitter, but good long-term stability.	2236	potentially a lot of jitter, but good long-term stability.
1740		2237
1741	static void	2238	static void
1742	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2239	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1743	{	2240	{
1744	... 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)
1745	}	2242	}
1746		2243
1747	ev_periodic hourly_tick;	2244	ev_periodic hourly_tick;
…		…
1770		2267
1771	=head2 C<ev_signal> - signal me when a signal gets signalled!	2268	=head2 C<ev_signal> - signal me when a signal gets signalled!
1772		2269
1773	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
1774	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
1775	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
1776	normal event processing, like any other event.	2273	normal event processing, like any other event.
1777		2274
1778	If you want signals asynchronously, just use C<sigaction> as you would	2275	If you want signals to be delivered truly asynchronously, just use
1779	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
1780	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.
1781		2279
1782	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
1783	first watcher gets started will libev actually register a signal handler	2286	When the first watcher gets started will libev actually register something
1784	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
1785	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).
1786	the last signal watcher for a signal is stopped, libev will reset the
1787	signal handler to SIG_DFL (regardless of what it was set to before).
1788		2289
1789	If possible and supported, libev will install its handlers with	2290	If possible and supported, libev will install its handlers with
1790	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2291	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1791	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
1792	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
1793	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.
1794		2324
1795	=head3 Watcher-Specific Functions and Data Members	2325	=head3 Watcher-Specific Functions and Data Members
1796		2326
1797	=over 4	2327	=over 4
1798		2328
…		…
1814	Example: Try to exit cleanly on SIGINT.	2344	Example: Try to exit cleanly on SIGINT.
1815		2345
1816	static void	2346	static void
1817	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2347	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1818	{	2348	{
1819	ev_unloop (loop, EVUNLOOP_ALL);	2349	ev_break (loop, EVBREAK_ALL);
1820	}	2350	}
1821		2351
1822	ev_signal signal_watcher;	2352	ev_signal signal_watcher;
1823	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2353	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1824	ev_signal_start (loop, &signal_watcher);	2354	ev_signal_start (loop, &signal_watcher);
…		…
1830	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
1831	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
1832	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
1833	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.,
1834	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,
1835	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
1836	not.	2366	in the next callback invocation is not.
1837		2367
1838	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
1839	you can only register child watchers in the default event loop.	2369	you can only register child watchers in the default event loop.
1840		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
1841	=head3 Process Interaction	2375	=head3 Process Interaction
1842		2376
1843	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
1844	initialised. This is necessary to guarantee proper behaviour even if	2378	initialised. This is necessary to guarantee proper behaviour even if the
1845	the first child watcher is started after the child exits. The occurrence	2379	first child watcher is started after the child exits. The occurrence
1846	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2380	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1847	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
1848	children, even ones not watched.	2382	children, even ones not watched.
1849		2383
1850	=head3 Overriding the Built-In Processing	2384	=head3 Overriding the Built-In Processing
…		…
1860	=head3 Stopping the Child Watcher	2394	=head3 Stopping the Child Watcher
1861		2395
1862	Currently, the child watcher never gets stopped, even when the	2396	Currently, the child watcher never gets stopped, even when the
1863	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
1864	callback. Future versions of libev might stop the watcher automatically	2398	callback. Future versions of libev might stop the watcher automatically
1865	when a child exit is detected.	2399	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2400	problem).
1866		2401
1867	=head3 Watcher-Specific Functions and Data Members	2402	=head3 Watcher-Specific Functions and Data Members
1868		2403
1869	=over 4	2404	=over 4
1870		2405
…		…
1997		2532
1998	There is no support for kqueue, as apparently it cannot be used to	2533	There is no support for kqueue, as apparently it cannot be used to
1999	implement this functionality, due to the requirement of having a file	2534	implement this functionality, due to the requirement of having a file
2000	descriptor open on the object at all times, and detecting renames, unlinks	2535	descriptor open on the object at all times, and detecting renames, unlinks
2001	etc. is difficult.	2536	etc. is difficult.
		2537
		2538	=head3 C<stat ()> is a synchronous operation
		2539
		2540	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2541	the process. The exception are C<ev_stat> watchers - those call C<stat
		2542	()>, which is a synchronous operation.
		2543
		2544	For local paths, this usually doesn't matter: unless the system is very
		2545	busy or the intervals between stat's are large, a stat call will be fast,
		2546	as the path data is usually in memory already (except when starting the
		2547	watcher).
		2548
		2549	For networked file systems, calling C<stat ()> can block an indefinite
		2550	time due to network issues, and even under good conditions, a stat call
		2551	often takes multiple milliseconds.
		2552
		2553	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2554	paths, although this is fully supported by libev.
2002		2555
2003	=head3 The special problem of stat time resolution	2556	=head3 The special problem of stat time resolution
2004		2557
2005	The C<stat ()> system call only supports full-second resolution portably,	2558	The C<stat ()> system call only supports full-second resolution portably,
2006	and even on systems where the resolution is higher, most file systems	2559	and even on systems where the resolution is higher, most file systems
…		…
2155		2708
2156	=head3 Watcher-Specific Functions and Data Members	2709	=head3 Watcher-Specific Functions and Data Members
2157		2710
2158	=over 4	2711	=over 4
2159		2712
2160	=item ev_idle_init (ev_signal *, callback)	2713	=item ev_idle_init (ev_idle *, callback)
2161		2714
2162	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
2163	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,
2164	believe me.	2717	believe me.
2165		2718
…		…
2178	// no longer anything immediate to do.	2731	// no longer anything immediate to do.
2179	}	2732	}
2180		2733
2181	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2734	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2182	ev_idle_init (idle_watcher, idle_cb);	2735	ev_idle_init (idle_watcher, idle_cb);
2183	ev_idle_start (loop, idle_cb);	2736	ev_idle_start (loop, idle_watcher);
2184		2737
2185		2738
2186	=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!
2187		2740
2188	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:
2189	prepare watchers get invoked before the process blocks and check watchers	2742	prepare watchers get invoked before the process blocks and check watchers
2190	afterwards.	2743	afterwards.
2191		2744
2192	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
2193	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>
2194	watchers. Other loops than the current one are fine, however. The	2747	watchers. Other loops than the current one are fine, however. The
2195	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
2196	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,
2197	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
…		…
2281	struct pollfd fds [nfd];	2834	struct pollfd fds [nfd];
2282	// actual code will need to loop here and realloc etc.	2835	// actual code will need to loop here and realloc etc.
2283	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2836	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2284		2837
2285	/* 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 */
2286	ev_timer_init (&tw, 0, timeout * 1e-3);	2839	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2287	ev_timer_start (loop, &tw);	2840	ev_timer_start (loop, &tw);
2288		2841
2289	// create one ev_io per pollfd	2842	// create one ev_io per pollfd
2290	for (int i = 0; i < nfd; ++i)	2843	for (int i = 0; i < nfd; ++i)
2291	{	2844	{
…		…
2365		2918
2366	if (timeout >= 0)	2919	if (timeout >= 0)
2367	// create/start timer	2920	// create/start timer
2368		2921
2369	// poll	2922	// poll
2370	ev_loop (EV_A_ 0);	2923	ev_run (EV_A_ 0);
2371		2924
2372	// stop timer again	2925	// stop timer again
2373	if (timeout >= 0)	2926	if (timeout >= 0)
2374	ev_timer_stop (EV_A_ &to);	2927	ev_timer_stop (EV_A_ &to);
2375		2928
…		…
2404	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),
2405	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
2406	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
2407	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.
2408		2961
2409	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
2410	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
2411	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
2412	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
2413	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
2414	to C<0>, in which case the embed watcher will automatically execute the	2967	to give the embedded loop strictly lower priority for example).
2415	embedded loop sweep.
2416		2968
2417	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
2418	callback will be invoked whenever some events have been handled. You can	2970	will automatically execute the embedded loop sweep whenever necessary.
2419	set the callback to C<0> to avoid having to specify one if you are not
2420	interested in that.
2421		2971
2422	Also, there have not currently been made special provisions for forking:	2972	Fork detection will be handled transparently while the C<ev_embed> watcher
2423	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
2424	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
2425	yourself - but you can use a fork watcher to handle this automatically,	2975	C<ev_loop_fork> on the embedded loop.
2426	and future versions of libev might do just that.
2427		2976
2428	Unfortunately, not all backends are embeddable: only the ones returned by	2977	Unfortunately, not all backends are embeddable: only the ones returned by
2429	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2978	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2430	portable one.	2979	portable one.
2431		2980
…		…
2457	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).
2458		3007
2459	=item ev_embed_sweep (loop, ev_embed *)	3008	=item ev_embed_sweep (loop, ev_embed *)
2460		3009
2461	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
2462	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
2463	appropriate way for embedded loops.	3012	appropriate way for embedded loops.
2464		3013
2465	=item struct ev_loop *other [read-only]	3014	=item struct ev_loop *other [read-only]
2466		3015
2467	The embedded event loop.	3016	The embedded event loop.
…		…
2525	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,
2526	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
2527	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
2528	handlers will be invoked, too, of course.	3077	handlers will be invoked, too, of course.
2529		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
2530	=head3 Watcher-Specific Functions and Data Members	3113	=head3 Watcher-Specific Functions and Data Members
2531		3114
2532	=over 4	3115	=over 4
2533		3116
2534	=item ev_fork_init (ev_signal *, callback)	3117	=item ev_fork_init (ev_fork *, callback)
2535		3118
2536	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
2537	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,
2538	believe me.	3121	really.
2539		3122
2540	=back	3123	=back
2541		3124
2542		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
2543	=head2 C<ev_async> - how to wake up another event loop	3166	=head2 C<ev_async> - how to wake up an event loop
2544		3167
2545	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
2546	asynchronous sources such as signal handlers (as opposed to multiple event	3169	asynchronous sources such as signal handlers (as opposed to multiple event
2547	loops - those are of course safe to use in different threads).	3170	loops - those are of course safe to use in different threads).
2548		3171
2549	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,
2550	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>
2551	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
2552	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.
2553	safe.
2554		3176
2555	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,
2556	too, are asynchronous in nature, and signals, too, will be compressed	3178	too, are asynchronous in nature, and signals, too, will be compressed
2557	(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
2558	C<ev_async_sent> calls).	3180	C<ev_async_sent> calls).
…		…
2563	=head3 Queueing	3185	=head3 Queueing
2564		3186
2565	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
2566	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
2567	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
2568	need elaborate support such as pthreads.	3190	need elaborate support such as pthreads or unportable memory access
		3191	semantics.
2569		3192
2570	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
2571	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
2572	queue:	3195	queue:
2573		3196
…		…
2662	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
2663	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
2664	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
2665	section below on what exactly this means).	3288	section below on what exactly this means).
2666		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
2667	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
2668	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
2669	calls to C<ev_async_send>.	3297	repeated calls to C<ev_async_send> for the same event loop.
2670		3298
2671	=item bool = ev_async_pending (ev_async *)	3299	=item bool = ev_async_pending (ev_async *)
2672		3300
2673	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
2674	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
…		…
2677	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
2678	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,
2679	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
2680	quickly check whether invoking the loop might be a good idea.	3308	quickly check whether invoking the loop might be a good idea.
2681		3309
2682	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,
2683	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.
2684		3314
2685	=back	3315	=back
2686		3316
2687		3317
2688	=head1 OTHER FUNCTIONS	3318	=head1 OTHER FUNCTIONS
…		…
2705		3335
2706	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
2707	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
2708	repeat = 0) will be started. C<0> is a valid timeout.	3338	repeat = 0) will be started. C<0> is a valid timeout.
2709		3339
2710	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
2711	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
2712	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>
2713	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>
2714	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
2715	events precedence.	3345	events precedence.
2716		3346
2717	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.
2718		3348
2719	static void stdin_ready (int revents, void *arg)	3349	static void stdin_ready (int revents, void *arg)
2720	{	3350	{
2721	if (revents & EV_READ)	3351	if (revents & EV_READ)
2722	/* stdin might have data for us, joy! */;	3352	/* stdin might have data for us, joy! */;
2723	else if (revents & EV_TIMEOUT)	3353	else if (revents & EV_TIMER)
2724	/* doh, nothing entered */;	3354	/* doh, nothing entered */;
2725	}	3355	}
2726		3356
2727	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3357	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2728		3358
2729	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2730
2731	Feeds the given event set into the event loop, as if the specified event
2732	had happened for the specified watcher (which must be a pointer to an
2733	initialised but not necessarily started event watcher).
2734
2735	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3359	=item ev_feed_fd_event (loop, int fd, int revents)
2736		3360
2737	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
2738	the given events it.	3362	the given events it.
2739		3363
2740	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3364	=item ev_feed_signal_event (loop, int signum)
2741		3365
2742	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
2743	loop!).	3367	loop!).
2744		3368
2745	=back	3369	=back
…		…
2764	=item * Priorities are not currently supported. Initialising priorities	3388	=item * Priorities are not currently supported. Initialising priorities
2765	will fail and all watchers will have the same priority, even though there	3389	will fail and all watchers will have the same priority, even though there
2766	is an ev_pri field.	3390	is an ev_pri field.
2767		3391
2768	=item * In libevent, the last base created gets the signals, in libev, the	3392	=item * In libevent, the last base created gets the signals, in libev, the
2769	first base created (== the default loop) gets the signals.	3393	base that registered the signal gets the signals.
2770		3394
2771	=item * Other members are not supported.	3395	=item * Other members are not supported.
2772		3396
2773	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3397	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2774	to use the libev header file and library.	3398	to use the libev header file and library.
…		…
2825		3449
2826	=over 4	3450	=over 4
2827		3451
2828	=item ev::TYPE::TYPE ()	3452	=item ev::TYPE::TYPE ()
2829		3453
2830	=item ev::TYPE::TYPE (struct ev_loop *)	3454	=item ev::TYPE::TYPE (loop)
2831		3455
2832	=item ev::TYPE::~TYPE	3456	=item ev::TYPE::~TYPE
2833		3457
2834	The constructor (optionally) takes an event loop to associate the watcher	3458	The constructor (optionally) takes an event loop to associate the watcher
2835	with. If it is omitted, it will use C<EV_DEFAULT>.	3459	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2867		3491
2868	myclass obj;	3492	myclass obj;
2869	ev::io iow;	3493	ev::io iow;
2870	iow.set <myclass, &myclass::io_cb> (&obj);	3494	iow.set <myclass, &myclass::io_cb> (&obj);
2871		3495
		3496	=item w->set (object *)
		3497
		3498	This is a variation of a method callback - leaving out the method to call
		3499	will default the method to C<operator ()>, which makes it possible to use
		3500	functor objects without having to manually specify the C<operator ()> all
		3501	the time. Incidentally, you can then also leave out the template argument
		3502	list.
		3503
		3504	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3505	int revents)>.
		3506
		3507	See the method-C<set> above for more details.
		3508
		3509	Example: use a functor object as callback.
		3510
		3511	struct myfunctor
		3512	{
		3513	void operator() (ev::io &w, int revents)
		3514	{
		3515	...
		3516	}
		3517	}
		3518
		3519	myfunctor f;
		3520
		3521	ev::io w;
		3522	w.set (&f);
		3523
2872	=item w->set<function> (void *data = 0)	3524	=item w->set<function> (void *data = 0)
2873		3525
2874	Also sets a callback, but uses a static method or plain function as	3526	Also sets a callback, but uses a static method or plain function as
2875	callback. The optional C<data> argument will be stored in the watcher's	3527	callback. The optional C<data> argument will be stored in the watcher's
2876	C<data> member and is free for you to use.	3528	C<data> member and is free for you to use.
…		…
2882	Example: Use a plain function as callback.	3534	Example: Use a plain function as callback.
2883		3535
2884	static void io_cb (ev::io &w, int revents) { }	3536	static void io_cb (ev::io &w, int revents) { }
2885	iow.set <io_cb> ();	3537	iow.set <io_cb> ();
2886		3538
2887	=item w->set (struct ev_loop *)	3539	=item w->set (loop)
2888		3540
2889	Associates a different C<struct ev_loop> with this watcher. You can only	3541	Associates a different C<struct ev_loop> with this watcher. You can only
2890	do this when the watcher is inactive (and not pending either).	3542	do this when the watcher is inactive (and not pending either).
2891		3543
2892	=item w->set ([arguments])	3544	=item w->set ([arguments])
2893		3545
2894	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3546	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
2895	called at least once. Unlike the C counterpart, an active watcher gets	3547	method or a suitable start method must be called at least once. Unlike the
2896	automatically stopped and restarted when reconfiguring it with this	3548	C counterpart, an active watcher gets automatically stopped and restarted
2897	method.	3549	when reconfiguring it with this method.
2898		3550
2899	=item w->start ()	3551	=item w->start ()
2900		3552
2901	Starts the watcher. Note that there is no C<loop> argument, as the	3553	Starts the watcher. Note that there is no C<loop> argument, as the
2902	constructor already stores the event loop.	3554	constructor already stores the event loop.
2903		3555
		3556	=item w->start ([arguments])
		3557
		3558	Instead of calling C<set> and C<start> methods separately, it is often
		3559	convenient to wrap them in one call. Uses the same type of arguments as
		3560	the configure C<set> method of the watcher.
		3561
2904	=item w->stop ()	3562	=item w->stop ()
2905		3563
2906	Stops the watcher if it is active. Again, no C<loop> argument.	3564	Stops the watcher if it is active. Again, no C<loop> argument.
2907		3565
2908	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3566	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2920		3578
2921	=back	3579	=back
2922		3580
2923	=back	3581	=back
2924		3582
2925	Example: Define a class with an IO and idle watcher, start one of them in	3583	Example: Define a class with two I/O and idle watchers, start the I/O
2926	the constructor.	3584	watchers in the constructor.
2927		3585
2928	class myclass	3586	class myclass
2929	{	3587	{
2930	ev::io io ; void io_cb (ev::io &w, int revents);	3588	ev::io io ; void io_cb (ev::io &w, int revents);
		3589	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
2931	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3590	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2932		3591
2933	myclass (int fd)	3592	myclass (int fd)
2934	{	3593	{
2935	io .set <myclass, &myclass::io_cb > (this);	3594	io .set <myclass, &myclass::io_cb > (this);
		3595	io2 .set <myclass, &myclass::io2_cb > (this);
2936	idle.set <myclass, &myclass::idle_cb> (this);	3596	idle.set <myclass, &myclass::idle_cb> (this);
2937		3597
2938	io.start (fd, ev::READ);	3598	io.set (fd, ev::WRITE); // configure the watcher
		3599	io.start (); // start it whenever convenient
		3600
		3601	io2.start (fd, ev::READ); // set + start in one call
2939	}	3602	}
2940	};	3603	};
2941		3604
2942		3605
2943	=head1 OTHER LANGUAGE BINDINGS	3606	=head1 OTHER LANGUAGE BINDINGS
…		…
2962	L<http://software.schmorp.de/pkg/EV>.	3625	L<http://software.schmorp.de/pkg/EV>.
2963		3626
2964	=item Python	3627	=item Python
2965		3628
2966	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3629	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2967	seems to be quite complete and well-documented. Note, however, that the	3630	seems to be quite complete and well-documented.
2968	patch they require for libev is outright dangerous as it breaks the ABI
2969	for everybody else, and therefore, should never be applied in an installed
2970	libev (if python requires an incompatible ABI then it needs to embed
2971	libev).
2972		3631
2973	=item Ruby	3632	=item Ruby
2974		3633
2975	Tony Arcieri has written a ruby extension that offers access to a subset	3634	Tony Arcieri has written a ruby extension that offers access to a subset
2976	of the libev API and adds file handle abstractions, asynchronous DNS and	3635	of the libev API and adds file handle abstractions, asynchronous DNS and
2977	more on top of it. It can be found via gem servers. Its homepage is at	3636	more on top of it. It can be found via gem servers. Its homepage is at
2978	L<http://rev.rubyforge.org/>.	3637	L<http://rev.rubyforge.org/>.
2979		3638
		3639	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3640	makes rev work even on mingw.
		3641
		3642	=item Haskell
		3643
		3644	A haskell binding to libev is available at
		3645	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3646
2980	=item D	3647	=item D
2981		3648
2982	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3649	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2983	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3650	be found at L<http://proj.llucax.com.ar/wiki/evd>.
2984		3651
2985	=item Ocaml	3652	=item Ocaml
2986		3653
2987	Erkki Seppala has written Ocaml bindings for libev, to be found at	3654	Erkki Seppala has written Ocaml bindings for libev, to be found at
2988	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	3655	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3656
		3657	=item Lua
		3658
		3659	Brian Maher has written a partial interface to libev for lua (at the
		3660	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3661	L<http://github.com/brimworks/lua-ev>.
2989		3662
2990	=back	3663	=back
2991		3664
2992		3665
2993	=head1 MACRO MAGIC	3666	=head1 MACRO MAGIC
…		…
3007	loop argument"). The C<EV_A> form is used when this is the sole argument,	3680	loop argument"). The C<EV_A> form is used when this is the sole argument,
3008	C<EV_A_> is used when other arguments are following. Example:	3681	C<EV_A_> is used when other arguments are following. Example:
3009		3682
3010	ev_unref (EV_A);	3683	ev_unref (EV_A);
3011	ev_timer_add (EV_A_ watcher);	3684	ev_timer_add (EV_A_ watcher);
3012	ev_loop (EV_A_ 0);	3685	ev_run (EV_A_ 0);
3013		3686
3014	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3687	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3015	which is often provided by the following macro.	3688	which is often provided by the following macro.
3016		3689
3017	=item C<EV_P>, C<EV_P_>	3690	=item C<EV_P>, C<EV_P_>
…		…
3057	}	3730	}
3058		3731
3059	ev_check check;	3732	ev_check check;
3060	ev_check_init (&check, check_cb);	3733	ev_check_init (&check, check_cb);
3061	ev_check_start (EV_DEFAULT_ &check);	3734	ev_check_start (EV_DEFAULT_ &check);
3062	ev_loop (EV_DEFAULT_ 0);	3735	ev_run (EV_DEFAULT_ 0);
3063		3736
3064	=head1 EMBEDDING	3737	=head1 EMBEDDING
3065		3738
3066	Libev can (and often is) directly embedded into host	3739	Libev can (and often is) directly embedded into host
3067	applications. Examples of applications that embed it include the Deliantra	3740	applications. Examples of applications that embed it include the Deliantra
…		…
3147	libev.m4	3820	libev.m4
3148		3821
3149	=head2 PREPROCESSOR SYMBOLS/MACROS	3822	=head2 PREPROCESSOR SYMBOLS/MACROS
3150		3823
3151	Libev can be configured via a variety of preprocessor symbols you have to	3824	Libev can be configured via a variety of preprocessor symbols you have to
3152	define before including any of its files. The default in the absence of	3825	define before including (or compiling) any of its files. The default in
3153	autoconf is documented for every option.	3826	the absence of autoconf is documented for every option.
		3827
		3828	Symbols marked with "(h)" do not change the ABI, and can have different
		3829	values when compiling libev vs. including F<ev.h>, so it is permissible
		3830	to redefine them before including F<ev.h> without breaking compatibility
		3831	to a compiled library. All other symbols change the ABI, which means all
		3832	users of libev and the libev code itself must be compiled with compatible
		3833	settings.
3154		3834
3155	=over 4	3835	=over 4
3156		3836
		3837	=item EV_COMPAT3 (h)
		3838
		3839	Backwards compatibility is a major concern for libev. This is why this
		3840	release of libev comes with wrappers for the functions and symbols that
		3841	have been renamed between libev version 3 and 4.
		3842
		3843	You can disable these wrappers (to test compatibility with future
		3844	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		3845	sources. This has the additional advantage that you can drop the C<struct>
		3846	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		3847	typedef in that case.
		3848
		3849	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		3850	and in some even more future version the compatibility code will be
		3851	removed completely.
		3852
3157	=item EV_STANDALONE	3853	=item EV_STANDALONE (h)
3158		3854
3159	Must always be C<1> if you do not use autoconf configuration, which	3855	Must always be C<1> if you do not use autoconf configuration, which
3160	keeps libev from including F<config.h>, and it also defines dummy	3856	keeps libev from including F<config.h>, and it also defines dummy
3161	implementations for some libevent functions (such as logging, which is not	3857	implementations for some libevent functions (such as logging, which is not
3162	supported). It will also not define any of the structs usually found in	3858	supported). It will also not define any of the structs usually found in
3163	F<event.h> that are not directly supported by the libev core alone.	3859	F<event.h> that are not directly supported by the libev core alone.
3164		3860
		3861	In standalone mode, libev will still try to automatically deduce the
		3862	configuration, but has to be more conservative.
		3863
3165	=item EV_USE_MONOTONIC	3864	=item EV_USE_MONOTONIC
3166		3865
3167	If defined to be C<1>, libev will try to detect the availability of the	3866	If defined to be C<1>, libev will try to detect the availability of the
3168	monotonic clock option at both compile time and runtime. Otherwise no use	3867	monotonic clock option at both compile time and runtime. Otherwise no
3169	of the monotonic clock option will be attempted. If you enable this, you	3868	use of the monotonic clock option will be attempted. If you enable this,
3170	usually have to link against librt or something similar. Enabling it when	3869	you usually have to link against librt or something similar. Enabling it
3171	the functionality isn't available is safe, though, although you have	3870	when the functionality isn't available is safe, though, although you have
3172	to make sure you link against any libraries where the C<clock_gettime>	3871	to make sure you link against any libraries where the C<clock_gettime>
3173	function is hiding in (often F<-lrt>).	3872	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
3174		3873
3175	=item EV_USE_REALTIME	3874	=item EV_USE_REALTIME
3176		3875
3177	If defined to be C<1>, libev will try to detect the availability of the	3876	If defined to be C<1>, libev will try to detect the availability of the
3178	real-time clock option at compile time (and assume its availability at	3877	real-time clock option at compile time (and assume its availability
3179	runtime if successful). Otherwise no use of the real-time clock option will	3878	at runtime if successful). Otherwise no use of the real-time clock
3180	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3879	option will be attempted. This effectively replaces C<gettimeofday>
3181	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3880	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
3182	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3881	correctness. See the note about libraries in the description of
		3882	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3883	C<EV_USE_CLOCK_SYSCALL>.
		3884
		3885	=item EV_USE_CLOCK_SYSCALL
		3886
		3887	If defined to be C<1>, libev will try to use a direct syscall instead
		3888	of calling the system-provided C<clock_gettime> function. This option
		3889	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3890	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3891	programs needlessly. Using a direct syscall is slightly slower (in
		3892	theory), because no optimised vdso implementation can be used, but avoids
		3893	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3894	higher, as it simplifies linking (no need for C<-lrt>).
3183		3895
3184	=item EV_USE_NANOSLEEP	3896	=item EV_USE_NANOSLEEP
3185		3897
3186	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3898	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
3187	and will use it for delays. Otherwise it will use C<select ()>.	3899	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3203		3915
3204	=item EV_SELECT_USE_FD_SET	3916	=item EV_SELECT_USE_FD_SET
3205		3917
3206	If defined to C<1>, then the select backend will use the system C<fd_set>	3918	If defined to C<1>, then the select backend will use the system C<fd_set>
3207	structure. This is useful if libev doesn't compile due to a missing	3919	structure. This is useful if libev doesn't compile due to a missing
3208	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3920	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3209	exotic systems. This usually limits the range of file descriptors to some	3921	on exotic systems. This usually limits the range of file descriptors to
3210	low limit such as 1024 or might have other limitations (winsocket only	3922	some low limit such as 1024 or might have other limitations (winsocket
3211	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3923	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3212	influence the size of the C<fd_set> used.	3924	configures the maximum size of the C<fd_set>.
3213		3925
3214	=item EV_SELECT_IS_WINSOCKET	3926	=item EV_SELECT_IS_WINSOCKET
3215		3927
3216	When defined to C<1>, the select backend will assume that	3928	When defined to C<1>, the select backend will assume that
3217	select/socket/connect etc. don't understand file descriptors but	3929	select/socket/connect etc. don't understand file descriptors but
…		…
3219	be used is the winsock select). This means that it will call	3931	be used is the winsock select). This means that it will call
3220	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3932	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3221	it is assumed that all these functions actually work on fds, even	3933	it is assumed that all these functions actually work on fds, even
3222	on win32. Should not be defined on non-win32 platforms.	3934	on win32. Should not be defined on non-win32 platforms.
3223		3935
3224	=item EV_FD_TO_WIN32_HANDLE	3936	=item EV_FD_TO_WIN32_HANDLE(fd)
3225		3937
3226	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3938	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3227	file descriptors to socket handles. When not defining this symbol (the	3939	file descriptors to socket handles. When not defining this symbol (the
3228	default), then libev will call C<_get_osfhandle>, which is usually	3940	default), then libev will call C<_get_osfhandle>, which is usually
3229	correct. In some cases, programs use their own file descriptor management,	3941	correct. In some cases, programs use their own file descriptor management,
3230	in which case they can provide this function to map fds to socket handles.	3942	in which case they can provide this function to map fds to socket handles.
		3943
		3944	=item EV_WIN32_HANDLE_TO_FD(handle)
		3945
		3946	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3947	using the standard C<_open_osfhandle> function. For programs implementing
		3948	their own fd to handle mapping, overwriting this function makes it easier
		3949	to do so. This can be done by defining this macro to an appropriate value.
		3950
		3951	=item EV_WIN32_CLOSE_FD(fd)
		3952
		3953	If programs implement their own fd to handle mapping on win32, then this
		3954	macro can be used to override the C<close> function, useful to unregister
		3955	file descriptors again. Note that the replacement function has to close
		3956	the underlying OS handle.
3231		3957
3232	=item EV_USE_POLL	3958	=item EV_USE_POLL
3233		3959
3234	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3960	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3235	backend. Otherwise it will be enabled on non-win32 platforms. It	3961	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3282	as well as for signal and thread safety in C<ev_async> watchers.	4008	as well as for signal and thread safety in C<ev_async> watchers.
3283		4009
3284	In the absence of this define, libev will use C<sig_atomic_t volatile>	4010	In the absence of this define, libev will use C<sig_atomic_t volatile>
3285	(from F<signal.h>), which is usually good enough on most platforms.	4011	(from F<signal.h>), which is usually good enough on most platforms.
3286		4012
3287	=item EV_H	4013	=item EV_H (h)
3288		4014
3289	The name of the F<ev.h> header file used to include it. The default if	4015	The name of the F<ev.h> header file used to include it. The default if
3290	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4016	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3291	used to virtually rename the F<ev.h> header file in case of conflicts.	4017	used to virtually rename the F<ev.h> header file in case of conflicts.
3292		4018
3293	=item EV_CONFIG_H	4019	=item EV_CONFIG_H (h)
3294		4020
3295	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4021	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3296	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4022	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3297	C<EV_H>, above.	4023	C<EV_H>, above.
3298		4024
3299	=item EV_EVENT_H	4025	=item EV_EVENT_H (h)
3300		4026
3301	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4027	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3302	of how the F<event.h> header can be found, the default is C<"event.h">.	4028	of how the F<event.h> header can be found, the default is C<"event.h">.
3303		4029
3304	=item EV_PROTOTYPES	4030	=item EV_PROTOTYPES (h)
3305		4031
3306	If defined to be C<0>, then F<ev.h> will not define any function	4032	If defined to be C<0>, then F<ev.h> will not define any function
3307	prototypes, but still define all the structs and other symbols. This is	4033	prototypes, but still define all the structs and other symbols. This is
3308	occasionally useful if you want to provide your own wrapper functions	4034	occasionally useful if you want to provide your own wrapper functions
3309	around libev functions.	4035	around libev functions.
…		…
3331	fine.	4057	fine.
3332		4058
3333	If your embedding application does not need any priorities, defining these	4059	If your embedding application does not need any priorities, defining these
3334	both to C<0> will save some memory and CPU.	4060	both to C<0> will save some memory and CPU.
3335		4061
3336	=item EV_PERIODIC_ENABLE	4062	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4063	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4064	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3337		4065
3338	If undefined or defined to be C<1>, then periodic timers are supported. If	4066	If undefined or defined to be C<1> (and the platform supports it), then
3339	defined to be C<0>, then they are not. Disabling them saves a few kB of	4067	the respective watcher type is supported. If defined to be C<0>, then it
3340	code.	4068	is not. Disabling watcher types mainly saves code size.
3341		4069
3342	=item EV_IDLE_ENABLE	4070	=item EV_FEATURES
3343
3344	If undefined or defined to be C<1>, then idle watchers are supported. If
3345	defined to be C<0>, then they are not. Disabling them saves a few kB of
3346	code.
3347
3348	=item EV_EMBED_ENABLE
3349
3350	If undefined or defined to be C<1>, then embed watchers are supported. If
3351	defined to be C<0>, then they are not. Embed watchers rely on most other
3352	watcher types, which therefore must not be disabled.
3353
3354	=item EV_STAT_ENABLE
3355
3356	If undefined or defined to be C<1>, then stat watchers are supported. If
3357	defined to be C<0>, then they are not.
3358
3359	=item EV_FORK_ENABLE
3360
3361	If undefined or defined to be C<1>, then fork watchers are supported. If
3362	defined to be C<0>, then they are not.
3363
3364	=item EV_ASYNC_ENABLE
3365
3366	If undefined or defined to be C<1>, then async watchers are supported. If
3367	defined to be C<0>, then they are not.
3368
3369	=item EV_MINIMAL
3370		4071
3371	If you need to shave off some kilobytes of code at the expense of some	4072	If you need to shave off some kilobytes of code at the expense of some
3372	speed, define this symbol to C<1>. Currently this is used to override some	4073	speed (but with the full API), you can define this symbol to request
3373	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4074	certain subsets of functionality. The default is to enable all features
3374	much smaller 2-heap for timer management over the default 4-heap.	4075	that can be enabled on the platform.
		4076
		4077	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4078	with some broad features you want) and then selectively re-enable
		4079	additional parts you want, for example if you want everything minimal,
		4080	but multiple event loop support, async and child watchers and the poll
		4081	backend, use this:
		4082
		4083	#define EV_FEATURES 0
		4084	#define EV_MULTIPLICITY 1
		4085	#define EV_USE_POLL 1
		4086	#define EV_CHILD_ENABLE 1
		4087	#define EV_ASYNC_ENABLE 1
		4088
		4089	The actual value is a bitset, it can be a combination of the following
		4090	values:
		4091
		4092	=over 4
		4093
		4094	=item C<1> - faster/larger code
		4095
		4096	Use larger code to speed up some operations.
		4097
		4098	Currently this is used to override some inlining decisions (enlarging the
		4099	code size by roughly 30% on amd64).
		4100
		4101	When optimising for size, use of compiler flags such as C<-Os> with
		4102	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4103	assertions.
		4104
		4105	=item C<2> - faster/larger data structures
		4106
		4107	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4108	hash table sizes and so on. This will usually further increase code size
		4109	and can additionally have an effect on the size of data structures at
		4110	runtime.
		4111
		4112	=item C<4> - full API configuration
		4113
		4114	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4115	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4116
		4117	=item C<8> - full API
		4118
		4119	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4120	details on which parts of the API are still available without this
		4121	feature, and do not complain if this subset changes over time.
		4122
		4123	=item C<16> - enable all optional watcher types
		4124
		4125	Enables all optional watcher types. If you want to selectively enable
		4126	only some watcher types other than I/O and timers (e.g. prepare,
		4127	embed, async, child...) you can enable them manually by defining
		4128	C<EV_watchertype_ENABLE> to C<1> instead.
		4129
		4130	=item C<32> - enable all backends
		4131
		4132	This enables all backends - without this feature, you need to enable at
		4133	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4134
		4135	=item C<64> - enable OS-specific "helper" APIs
		4136
		4137	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4138	default.
		4139
		4140	=back
		4141
		4142	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4143	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4144	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4145	watchers, timers and monotonic clock support.
		4146
		4147	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4148	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4149	your program might be left out as well - a binary starting a timer and an
		4150	I/O watcher then might come out at only 5Kb.
		4151
		4152	=item EV_AVOID_STDIO
		4153
		4154	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4155	functions (printf, scanf, perror etc.). This will increase the code size
		4156	somewhat, but if your program doesn't otherwise depend on stdio and your
		4157	libc allows it, this avoids linking in the stdio library which is quite
		4158	big.
		4159
		4160	Note that error messages might become less precise when this option is
		4161	enabled.
		4162
		4163	=item EV_NSIG
		4164
		4165	The highest supported signal number, +1 (or, the number of
		4166	signals): Normally, libev tries to deduce the maximum number of signals
		4167	automatically, but sometimes this fails, in which case it can be
		4168	specified. Also, using a lower number than detected (C<32> should be
		4169	good for about any system in existence) can save some memory, as libev
		4170	statically allocates some 12-24 bytes per signal number.
3375		4171
3376	=item EV_PID_HASHSIZE	4172	=item EV_PID_HASHSIZE
3377		4173
3378	C<ev_child> watchers use a small hash table to distribute workload by	4174	C<ev_child> watchers use a small hash table to distribute workload by
3379	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4175	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3380	than enough. If you need to manage thousands of children you might want to	4176	usually more than enough. If you need to manage thousands of children you
3381	increase this value (I<must> be a power of two).	4177	might want to increase this value (I<must> be a power of two).
3382		4178
3383	=item EV_INOTIFY_HASHSIZE	4179	=item EV_INOTIFY_HASHSIZE
3384		4180
3385	C<ev_stat> watchers use a small hash table to distribute workload by	4181	C<ev_stat> watchers use a small hash table to distribute workload by
3386	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4182	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3387	usually more than enough. If you need to manage thousands of C<ev_stat>	4183	disabled), usually more than enough. If you need to manage thousands of
3388	watchers you might want to increase this value (I<must> be a power of	4184	C<ev_stat> watchers you might want to increase this value (I<must> be a
3389	two).	4185	power of two).
3390		4186
3391	=item EV_USE_4HEAP	4187	=item EV_USE_4HEAP
3392		4188
3393	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4189	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3394	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4190	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3395	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4191	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3396	faster performance with many (thousands) of watchers.	4192	faster performance with many (thousands) of watchers.
3397		4193
3398	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4194	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3399	(disabled).	4195	will be C<0>.
3400		4196
3401	=item EV_HEAP_CACHE_AT	4197	=item EV_HEAP_CACHE_AT
3402		4198
3403	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4199	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3404	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4200	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3405	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4201	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3406	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4202	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3407	but avoids random read accesses on heap changes. This improves performance	4203	but avoids random read accesses on heap changes. This improves performance
3408	noticeably with many (hundreds) of watchers.	4204	noticeably with many (hundreds) of watchers.
3409		4205
3410	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4206	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3411	(disabled).	4207	will be C<0>.
3412		4208
3413	=item EV_VERIFY	4209	=item EV_VERIFY
3414		4210
3415	Controls how much internal verification (see C<ev_loop_verify ()>) will	4211	Controls how much internal verification (see C<ev_verify ()>) will
3416	be done: If set to C<0>, no internal verification code will be compiled	4212	be done: If set to C<0>, no internal verification code will be compiled
3417	in. If set to C<1>, then verification code will be compiled in, but not	4213	in. If set to C<1>, then verification code will be compiled in, but not
3418	called. If set to C<2>, then the internal verification code will be	4214	called. If set to C<2>, then the internal verification code will be
3419	called once per loop, which can slow down libev. If set to C<3>, then the	4215	called once per loop, which can slow down libev. If set to C<3>, then the
3420	verification code will be called very frequently, which will slow down	4216	verification code will be called very frequently, which will slow down
3421	libev considerably.	4217	libev considerably.
3422		4218
3423	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4219	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3424	C<0>.	4220	will be C<0>.
3425		4221
3426	=item EV_COMMON	4222	=item EV_COMMON
3427		4223
3428	By default, all watchers have a C<void *data> member. By redefining	4224	By default, all watchers have a C<void *data> member. By redefining
3429	this macro to a something else you can include more and other types of	4225	this macro to something else you can include more and other types of
3430	members. You have to define it each time you include one of the files,	4226	members. You have to define it each time you include one of the files,
3431	though, and it must be identical each time.	4227	though, and it must be identical each time.
3432		4228
3433	For example, the perl EV module uses something like this:	4229	For example, the perl EV module uses something like this:
3434		4230
…		…
3487	file.	4283	file.
3488		4284
3489	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4285	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3490	that everybody includes and which overrides some configure choices:	4286	that everybody includes and which overrides some configure choices:
3491		4287
3492	#define EV_MINIMAL 1	4288	#define EV_FEATURES 8
3493	#define EV_USE_POLL 0	4289	#define EV_USE_SELECT 1
3494	#define EV_MULTIPLICITY 0
3495	#define EV_PERIODIC_ENABLE 0	4290	#define EV_PREPARE_ENABLE 1
		4291	#define EV_IDLE_ENABLE 1
3496	#define EV_STAT_ENABLE 0	4292	#define EV_SIGNAL_ENABLE 1
3497	#define EV_FORK_ENABLE 0	4293	#define EV_CHILD_ENABLE 1
		4294	#define EV_USE_STDEXCEPT 0
3498	#define EV_CONFIG_H <config.h>	4295	#define EV_CONFIG_H <config.h>
3499	#define EV_MINPRI 0
3500	#define EV_MAXPRI 0
3501		4296
3502	#include "ev++.h"	4297	#include "ev++.h"
3503		4298
3504	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4299	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3505		4300
…		…
3565	default loop and triggering an C<ev_async> watcher from the default loop	4360	default loop and triggering an C<ev_async> watcher from the default loop
3566	watcher callback into the event loop interested in the signal.	4361	watcher callback into the event loop interested in the signal.
3567		4362
3568	=back	4363	=back
3569		4364
		4365	=head4 THREAD LOCKING EXAMPLE
		4366
		4367	Here is a fictitious example of how to run an event loop in a different
		4368	thread than where callbacks are being invoked and watchers are
		4369	created/added/removed.
		4370
		4371	For a real-world example, see the C<EV::Loop::Async> perl module,
		4372	which uses exactly this technique (which is suited for many high-level
		4373	languages).
		4374
		4375	The example uses a pthread mutex to protect the loop data, a condition
		4376	variable to wait for callback invocations, an async watcher to notify the
		4377	event loop thread and an unspecified mechanism to wake up the main thread.
		4378
		4379	First, you need to associate some data with the event loop:
		4380
		4381	typedef struct {
		4382	mutex_t lock; /* global loop lock */
		4383	ev_async async_w;
		4384	thread_t tid;
		4385	cond_t invoke_cv;
		4386	} userdata;
		4387
		4388	void prepare_loop (EV_P)
		4389	{
		4390	// for simplicity, we use a static userdata struct.
		4391	static userdata u;
		4392
		4393	ev_async_init (&u->async_w, async_cb);
		4394	ev_async_start (EV_A_ &u->async_w);
		4395
		4396	pthread_mutex_init (&u->lock, 0);
		4397	pthread_cond_init (&u->invoke_cv, 0);
		4398
		4399	// now associate this with the loop
		4400	ev_set_userdata (EV_A_ u);
		4401	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4402	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4403
		4404	// then create the thread running ev_loop
		4405	pthread_create (&u->tid, 0, l_run, EV_A);
		4406	}
		4407
		4408	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4409	solely to wake up the event loop so it takes notice of any new watchers
		4410	that might have been added:
		4411
		4412	static void
		4413	async_cb (EV_P_ ev_async *w, int revents)
		4414	{
		4415	// just used for the side effects
		4416	}
		4417
		4418	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4419	protecting the loop data, respectively.
		4420
		4421	static void
		4422	l_release (EV_P)
		4423	{
		4424	userdata *u = ev_userdata (EV_A);
		4425	pthread_mutex_unlock (&u->lock);
		4426	}
		4427
		4428	static void
		4429	l_acquire (EV_P)
		4430	{
		4431	userdata *u = ev_userdata (EV_A);
		4432	pthread_mutex_lock (&u->lock);
		4433	}
		4434
		4435	The event loop thread first acquires the mutex, and then jumps straight
		4436	into C<ev_run>:
		4437
		4438	void *
		4439	l_run (void *thr_arg)
		4440	{
		4441	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4442
		4443	l_acquire (EV_A);
		4444	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4445	ev_run (EV_A_ 0);
		4446	l_release (EV_A);
		4447
		4448	return 0;
		4449	}
		4450
		4451	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4452	signal the main thread via some unspecified mechanism (signals? pipe
		4453	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4454	have been called (in a while loop because a) spurious wakeups are possible
		4455	and b) skipping inter-thread-communication when there are no pending
		4456	watchers is very beneficial):
		4457
		4458	static void
		4459	l_invoke (EV_P)
		4460	{
		4461	userdata *u = ev_userdata (EV_A);
		4462
		4463	while (ev_pending_count (EV_A))
		4464	{
		4465	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4466	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4467	}
		4468	}
		4469
		4470	Now, whenever the main thread gets told to invoke pending watchers, it
		4471	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4472	thread to continue:
		4473
		4474	static void
		4475	real_invoke_pending (EV_P)
		4476	{
		4477	userdata *u = ev_userdata (EV_A);
		4478
		4479	pthread_mutex_lock (&u->lock);
		4480	ev_invoke_pending (EV_A);
		4481	pthread_cond_signal (&u->invoke_cv);
		4482	pthread_mutex_unlock (&u->lock);
		4483	}
		4484
		4485	Whenever you want to start/stop a watcher or do other modifications to an
		4486	event loop, you will now have to lock:
		4487
		4488	ev_timer timeout_watcher;
		4489	userdata *u = ev_userdata (EV_A);
		4490
		4491	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4492
		4493	pthread_mutex_lock (&u->lock);
		4494	ev_timer_start (EV_A_ &timeout_watcher);
		4495	ev_async_send (EV_A_ &u->async_w);
		4496	pthread_mutex_unlock (&u->lock);
		4497
		4498	Note that sending the C<ev_async> watcher is required because otherwise
		4499	an event loop currently blocking in the kernel will have no knowledge
		4500	about the newly added timer. By waking up the loop it will pick up any new
		4501	watchers in the next event loop iteration.
		4502
3570	=head3 COROUTINES	4503	=head3 COROUTINES
3571		4504
3572	Libev is very accommodating to coroutines ("cooperative threads"):	4505	Libev is very accommodating to coroutines ("cooperative threads"):
3573	libev fully supports nesting calls to its functions from different	4506	libev fully supports nesting calls to its functions from different
3574	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4507	coroutines (e.g. you can call C<ev_run> on the same loop from two
3575	different coroutines, and switch freely between both coroutines running the	4508	different coroutines, and switch freely between both coroutines running
3576	loop, as long as you don't confuse yourself). The only exception is that	4509	the loop, as long as you don't confuse yourself). The only exception is
3577	you must not do this from C<ev_periodic> reschedule callbacks.	4510	that you must not do this from C<ev_periodic> reschedule callbacks.
3578		4511
3579	Care has been taken to ensure that libev does not keep local state inside	4512	Care has been taken to ensure that libev does not keep local state inside
3580	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4513	C<ev_run>, and other calls do not usually allow for coroutine switches as
3581	they do not call any callbacks.	4514	they do not call any callbacks.
3582		4515
3583	=head2 COMPILER WARNINGS	4516	=head2 COMPILER WARNINGS
3584		4517
3585	Depending on your compiler and compiler settings, you might get no or a	4518	Depending on your compiler and compiler settings, you might get no or a
…		…
3596	maintainable.	4529	maintainable.
3597		4530
3598	And of course, some compiler warnings are just plain stupid, or simply	4531	And of course, some compiler warnings are just plain stupid, or simply
3599	wrong (because they don't actually warn about the condition their message	4532	wrong (because they don't actually warn about the condition their message
3600	seems to warn about). For example, certain older gcc versions had some	4533	seems to warn about). For example, certain older gcc versions had some
3601	warnings that resulted an extreme number of false positives. These have	4534	warnings that resulted in an extreme number of false positives. These have
3602	been fixed, but some people still insist on making code warn-free with	4535	been fixed, but some people still insist on making code warn-free with
3603	such buggy versions.	4536	such buggy versions.
3604		4537
3605	While libev is written to generate as few warnings as possible,	4538	While libev is written to generate as few warnings as possible,
3606	"warn-free" code is not a goal, and it is recommended not to build libev	4539	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3642	I suggest using suppression lists.	4575	I suggest using suppression lists.
3643		4576
3644		4577
3645	=head1 PORTABILITY NOTES	4578	=head1 PORTABILITY NOTES
3646		4579
		4580	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4581
		4582	GNU/Linux is the only common platform that supports 64 bit file/large file
		4583	interfaces but I<disables> them by default.
		4584
		4585	That means that libev compiled in the default environment doesn't support
		4586	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4587
		4588	Unfortunately, many programs try to work around this GNU/Linux issue
		4589	by enabling the large file API, which makes them incompatible with the
		4590	standard libev compiled for their system.
		4591
		4592	Likewise, libev cannot enable the large file API itself as this would
		4593	suddenly make it incompatible to the default compile time environment,
		4594	i.e. all programs not using special compile switches.
		4595
		4596	=head2 OS/X AND DARWIN BUGS
		4597
		4598	The whole thing is a bug if you ask me - basically any system interface
		4599	you touch is broken, whether it is locales, poll, kqueue or even the
		4600	OpenGL drivers.
		4601
		4602	=head3 C<kqueue> is buggy
		4603
		4604	The kqueue syscall is broken in all known versions - most versions support
		4605	only sockets, many support pipes.
		4606
		4607	Libev tries to work around this by not using C<kqueue> by default on this
		4608	rotten platform, but of course you can still ask for it when creating a
		4609	loop - embedding a socket-only kqueue loop into a select-based one is
		4610	probably going to work well.
		4611
		4612	=head3 C<poll> is buggy
		4613
		4614	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4615	implementation by something calling C<kqueue> internally around the 10.5.6
		4616	release, so now C<kqueue> I<and> C<poll> are broken.
		4617
		4618	Libev tries to work around this by not using C<poll> by default on
		4619	this rotten platform, but of course you can still ask for it when creating
		4620	a loop.
		4621
		4622	=head3 C<select> is buggy
		4623
		4624	All that's left is C<select>, and of course Apple found a way to fuck this
		4625	one up as well: On OS/X, C<select> actively limits the number of file
		4626	descriptors you can pass in to 1024 - your program suddenly crashes when
		4627	you use more.
		4628
		4629	There is an undocumented "workaround" for this - defining
		4630	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4631	work on OS/X.
		4632
		4633	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4634
		4635	=head3 C<errno> reentrancy
		4636
		4637	The default compile environment on Solaris is unfortunately so
		4638	thread-unsafe that you can't even use components/libraries compiled
		4639	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4640	defined by default. A valid, if stupid, implementation choice.
		4641
		4642	If you want to use libev in threaded environments you have to make sure
		4643	it's compiled with C<_REENTRANT> defined.
		4644
		4645	=head3 Event port backend
		4646
		4647	The scalable event interface for Solaris is called "event
		4648	ports". Unfortunately, this mechanism is very buggy in all major
		4649	releases. If you run into high CPU usage, your program freezes or you get
		4650	a large number of spurious wakeups, make sure you have all the relevant
		4651	and latest kernel patches applied. No, I don't know which ones, but there
		4652	are multiple ones to apply, and afterwards, event ports actually work
		4653	great.
		4654
		4655	If you can't get it to work, you can try running the program by setting
		4656	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4657	C<select> backends.
		4658
		4659	=head2 AIX POLL BUG
		4660
		4661	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4662	this by trying to avoid the poll backend altogether (i.e. it's not even
		4663	compiled in), which normally isn't a big problem as C<select> works fine
		4664	with large bitsets on AIX, and AIX is dead anyway.
		4665
3647	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4666	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4667
		4668	=head3 General issues
3648		4669
3649	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4670	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3650	requires, and its I/O model is fundamentally incompatible with the POSIX	4671	requires, and its I/O model is fundamentally incompatible with the POSIX
3651	model. Libev still offers limited functionality on this platform in	4672	model. Libev still offers limited functionality on this platform in
3652	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4673	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3653	descriptors. This only applies when using Win32 natively, not when using	4674	descriptors. This only applies when using Win32 natively, not when using
3654	e.g. cygwin.	4675	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4676	as every compielr comes with a slightly differently broken/incompatible
		4677	environment.
3655		4678
3656	Lifting these limitations would basically require the full	4679	Lifting these limitations would basically require the full
3657	re-implementation of the I/O system. If you are into these kinds of	4680	re-implementation of the I/O system. If you are into this kind of thing,
3658	things, then note that glib does exactly that for you in a very portable	4681	then note that glib does exactly that for you in a very portable way (note
3659	way (note also that glib is the slowest event library known to man).	4682	also that glib is the slowest event library known to man).
3660		4683
3661	There is no supported compilation method available on windows except	4684	There is no supported compilation method available on windows except
3662	embedding it into other applications.	4685	embedding it into other applications.
		4686
		4687	Sensible signal handling is officially unsupported by Microsoft - libev
		4688	tries its best, but under most conditions, signals will simply not work.
3663		4689
3664	Not a libev limitation but worth mentioning: windows apparently doesn't	4690	Not a libev limitation but worth mentioning: windows apparently doesn't
3665	accept large writes: instead of resulting in a partial write, windows will	4691	accept large writes: instead of resulting in a partial write, windows will
3666	either accept everything or return C<ENOBUFS> if the buffer is too large,	4692	either accept everything or return C<ENOBUFS> if the buffer is too large,
3667	so make sure you only write small amounts into your sockets (less than a	4693	so make sure you only write small amounts into your sockets (less than a
…		…
3672	the abysmal performance of winsockets, using a large number of sockets	4698	the abysmal performance of winsockets, using a large number of sockets
3673	is not recommended (and not reasonable). If your program needs to use	4699	is not recommended (and not reasonable). If your program needs to use
3674	more than a hundred or so sockets, then likely it needs to use a totally	4700	more than a hundred or so sockets, then likely it needs to use a totally
3675	different implementation for windows, as libev offers the POSIX readiness	4701	different implementation for windows, as libev offers the POSIX readiness
3676	notification model, which cannot be implemented efficiently on windows	4702	notification model, which cannot be implemented efficiently on windows
3677	(Microsoft monopoly games).	4703	(due to Microsoft monopoly games).
3678		4704
3679	A typical way to use libev under windows is to embed it (see the embedding	4705	A typical way to use libev under windows is to embed it (see the embedding
3680	section for details) and use the following F<evwrap.h> header file instead	4706	section for details) and use the following F<evwrap.h> header file instead
3681	of F<ev.h>:	4707	of F<ev.h>:
3682		4708
…		…
3689	you do I<not> compile the F<ev.c> or any other embedded source files!):	4715	you do I<not> compile the F<ev.c> or any other embedded source files!):
3690		4716
3691	#include "evwrap.h"	4717	#include "evwrap.h"
3692	#include "ev.c"	4718	#include "ev.c"
3693		4719
3694	=over 4
3695
3696	=item The winsocket select function	4720	=head3 The winsocket C<select> function
3697		4721
3698	The winsocket C<select> function doesn't follow POSIX in that it	4722	The winsocket C<select> function doesn't follow POSIX in that it
3699	requires socket I<handles> and not socket I<file descriptors> (it is	4723	requires socket I<handles> and not socket I<file descriptors> (it is
3700	also extremely buggy). This makes select very inefficient, and also	4724	also extremely buggy). This makes select very inefficient, and also
3701	requires a mapping from file descriptors to socket handles (the Microsoft	4725	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3710	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4734	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3711		4735
3712	Note that winsockets handling of fd sets is O(n), so you can easily get a	4736	Note that winsockets handling of fd sets is O(n), so you can easily get a
3713	complexity in the O(n²) range when using win32.	4737	complexity in the O(n²) range when using win32.
3714		4738
3715	=item Limited number of file descriptors	4739	=head3 Limited number of file descriptors
3716		4740
3717	Windows has numerous arbitrary (and low) limits on things.	4741	Windows has numerous arbitrary (and low) limits on things.
3718		4742
3719	Early versions of winsocket's select only supported waiting for a maximum	4743	Early versions of winsocket's select only supported waiting for a maximum
3720	of C<64> handles (probably owning to the fact that all windows kernels	4744	of C<64> handles (probably owning to the fact that all windows kernels
3721	can only wait for C<64> things at the same time internally; Microsoft	4745	can only wait for C<64> things at the same time internally; Microsoft
3722	recommends spawning a chain of threads and wait for 63 handles and the	4746	recommends spawning a chain of threads and wait for 63 handles and the
3723	previous thread in each. Great).	4747	previous thread in each. Sounds great!).
3724		4748
3725	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4749	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3726	to some high number (e.g. C<2048>) before compiling the winsocket select	4750	to some high number (e.g. C<2048>) before compiling the winsocket select
3727	call (which might be in libev or elsewhere, for example, perl does its own	4751	call (which might be in libev or elsewhere, for example, perl and many
3728	select emulation on windows).	4752	other interpreters do their own select emulation on windows).
3729		4753
3730	Another limit is the number of file descriptors in the Microsoft runtime	4754	Another limit is the number of file descriptors in the Microsoft runtime
3731	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4755	libraries, which by default is C<64> (there must be a hidden I<64>
3732	or something like this inside Microsoft). You can increase this by calling	4756	fetish or something like this inside Microsoft). You can increase this
3733	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4757	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3734	arbitrary limit), but is broken in many versions of the Microsoft runtime	4758	(another arbitrary limit), but is broken in many versions of the Microsoft
3735	libraries.
3736
3737	This might get you to about C<512> or C<2048> sockets (depending on	4759	runtime libraries. This might get you to about C<512> or C<2048> sockets
3738	windows version and/or the phase of the moon). To get more, you need to	4760	(depending on windows version and/or the phase of the moon). To get more,
3739	wrap all I/O functions and provide your own fd management, but the cost of	4761	you need to wrap all I/O functions and provide your own fd management, but
3740	calling select (O(n²)) will likely make this unworkable.	4762	the cost of calling select (O(n²)) will likely make this unworkable.
3741
3742	=back
3743		4763
3744	=head2 PORTABILITY REQUIREMENTS	4764	=head2 PORTABILITY REQUIREMENTS
3745		4765
3746	In addition to a working ISO-C implementation and of course the	4766	In addition to a working ISO-C implementation and of course the
3747	backend-specific APIs, libev relies on a few additional extensions:	4767	backend-specific APIs, libev relies on a few additional extensions:
…		…
3754	Libev assumes not only that all watcher pointers have the same internal	4774	Libev assumes not only that all watcher pointers have the same internal
3755	structure (guaranteed by POSIX but not by ISO C for example), but it also	4775	structure (guaranteed by POSIX but not by ISO C for example), but it also
3756	assumes that the same (machine) code can be used to call any watcher	4776	assumes that the same (machine) code can be used to call any watcher
3757	callback: The watcher callbacks have different type signatures, but libev	4777	callback: The watcher callbacks have different type signatures, but libev
3758	calls them using an C<ev_watcher *> internally.	4778	calls them using an C<ev_watcher *> internally.
		4779
		4780	=item pointer accesses must be thread-atomic
		4781
		4782	Accessing a pointer value must be atomic, it must both be readable and
		4783	writable in one piece - this is the case on all current architectures.
3759		4784
3760	=item C<sig_atomic_t volatile> must be thread-atomic as well	4785	=item C<sig_atomic_t volatile> must be thread-atomic as well
3761		4786
3762	The type C<sig_atomic_t volatile> (or whatever is defined as	4787	The type C<sig_atomic_t volatile> (or whatever is defined as
3763	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	4788	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
3786	watchers.	4811	watchers.
3787		4812
3788	=item C<double> must hold a time value in seconds with enough accuracy	4813	=item C<double> must hold a time value in seconds with enough accuracy
3789		4814
3790	The type C<double> is used to represent timestamps. It is required to	4815	The type C<double> is used to represent timestamps. It is required to
3791	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4816	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3792	enough for at least into the year 4000. This requirement is fulfilled by	4817	good enough for at least into the year 4000 with millisecond accuracy
		4818	(the design goal for libev). This requirement is overfulfilled by
3793	implementations implementing IEEE 754 (basically all existing ones).	4819	implementations using IEEE 754, which is basically all existing ones. With
		4820	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
3794		4821
3795	=back	4822	=back
3796		4823
3797	If you know of other additional requirements drop me a note.	4824	If you know of other additional requirements drop me a note.
3798		4825
…		…
3866	involves iterating over all running async watchers or all signal numbers.	4893	involves iterating over all running async watchers or all signal numbers.
3867		4894
3868	=back	4895	=back
3869		4896
3870		4897
		4898	=head1 PORTING FROM LIBEV 3.X TO 4.X
		4899
		4900	The major version 4 introduced some incompatible changes to the API.
		4901
		4902	At the moment, the C<ev.h> header file provides compatibility definitions
		4903	for all changes, so most programs should still compile. The compatibility
		4904	layer might be removed in later versions of libev, so better update to the
		4905	new API early than late.
		4906
		4907	=over 4
		4908
		4909	=item C<EV_COMPAT3> backwards compatibility mechanism
		4910
		4911	The backward compatibility mechanism can be controlled by
		4912	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		4913	section.
		4914
		4915	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		4916
		4917	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		4918
		4919	ev_loop_destroy (EV_DEFAULT_UC);
		4920	ev_loop_fork (EV_DEFAULT);
		4921
		4922	=item function/symbol renames
		4923
		4924	A number of functions and symbols have been renamed:
		4925
		4926	ev_loop => ev_run
		4927	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		4928	EVLOOP_ONESHOT => EVRUN_ONCE
		4929
		4930	ev_unloop => ev_break
		4931	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		4932	EVUNLOOP_ONE => EVBREAK_ONE
		4933	EVUNLOOP_ALL => EVBREAK_ALL
		4934
		4935	EV_TIMEOUT => EV_TIMER
		4936
		4937	ev_loop_count => ev_iteration
		4938	ev_loop_depth => ev_depth
		4939	ev_loop_verify => ev_verify
		4940
		4941	Most functions working on C<struct ev_loop> objects don't have an
		4942	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		4943	associated constants have been renamed to not collide with the C<struct
		4944	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		4945	as all other watcher types. Note that C<ev_loop_fork> is still called
		4946	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		4947	typedef.
		4948
		4949	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		4950
		4951	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		4952	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		4953	and work, but the library code will of course be larger.
		4954
		4955	=back
		4956
		4957
		4958	=head1 GLOSSARY
		4959
		4960	=over 4
		4961
		4962	=item active
		4963
		4964	A watcher is active as long as it has been started and not yet stopped.
		4965	See L<WATCHER STATES> for details.
		4966
		4967	=item application
		4968
		4969	In this document, an application is whatever is using libev.
		4970
		4971	=item backend
		4972
		4973	The part of the code dealing with the operating system interfaces.
		4974
		4975	=item callback
		4976
		4977	The address of a function that is called when some event has been
		4978	detected. Callbacks are being passed the event loop, the watcher that
		4979	received the event, and the actual event bitset.
		4980
		4981	=item callback/watcher invocation
		4982
		4983	The act of calling the callback associated with a watcher.
		4984
		4985	=item event
		4986
		4987	A change of state of some external event, such as data now being available
		4988	for reading on a file descriptor, time having passed or simply not having
		4989	any other events happening anymore.
		4990
		4991	In libev, events are represented as single bits (such as C<EV_READ> or
		4992	C<EV_TIMER>).
		4993
		4994	=item event library
		4995
		4996	A software package implementing an event model and loop.
		4997
		4998	=item event loop
		4999
		5000	An entity that handles and processes external events and converts them
		5001	into callback invocations.
		5002
		5003	=item event model
		5004
		5005	The model used to describe how an event loop handles and processes
		5006	watchers and events.
		5007
		5008	=item pending
		5009
		5010	A watcher is pending as soon as the corresponding event has been
		5011	detected. See L<WATCHER STATES> for details.
		5012
		5013	=item real time
		5014
		5015	The physical time that is observed. It is apparently strictly monotonic :)
		5016
		5017	=item wall-clock time
		5018
		5019	The time and date as shown on clocks. Unlike real time, it can actually
		5020	be wrong and jump forwards and backwards, e.g. when the you adjust your
		5021	clock.
		5022
		5023	=item watcher
		5024
		5025	A data structure that describes interest in certain events. Watchers need
		5026	to be started (attached to an event loop) before they can receive events.
		5027
		5028	=back
		5029
3871	=head1 AUTHOR	5030	=head1 AUTHOR
3872		5031
3873	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5032	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5033	Magnusson and Emanuele Giaquinta.
3874		5034

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