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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	// break 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
159	either it is interrupted or the given time interval has passed. Basically	184	until either it is interrupted or the given time interval has
		185	passed (approximately - it might return a bit earlier even if not
		186	interrupted). Returns immediately if C<< interval <= 0 >>.
		187
160	this is a sub-second-resolution C<sleep ()>.	188	Basically this is a sub-second-resolution C<sleep ()>.
		189
		190	The range of the C<interval> is limited - libev only guarantees to work
		191	with sleep times of up to one day (C<< interval <= 86400 >>).
161		192
162	=item int ev_version_major ()	193	=item int ev_version_major ()
163		194
164	=item int ev_version_minor ()	195	=item int ev_version_minor ()
165		196
…		…
176	as this indicates an incompatible change. Minor versions are usually	207	as this indicates an incompatible change. Minor versions are usually
177	compatible to older versions, so a larger minor version alone is usually	208	compatible to older versions, so a larger minor version alone is usually
178	not a problem.	209	not a problem.
179		210
180	Example: Make sure we haven't accidentally been linked against the wrong	211	Example: Make sure we haven't accidentally been linked against the wrong
181	version.	212	version (note, however, that this will not detect other ABI mismatches,
		213	such as LFS or reentrancy).
182		214
183	assert (("libev version mismatch",	215	assert (("libev version mismatch",
184	ev_version_major () == EV_VERSION_MAJOR	216	ev_version_major () == EV_VERSION_MAJOR
185	&& ev_version_minor () >= EV_VERSION_MINOR));	217	&& ev_version_minor () >= EV_VERSION_MINOR));
186		218
…		…
197	assert (("sorry, no epoll, no sex",	229	assert (("sorry, no epoll, no sex",
198	ev_supported_backends () & EVBACKEND_EPOLL));	230	ev_supported_backends () & EVBACKEND_EPOLL));
199		231
200	=item unsigned int ev_recommended_backends ()	232	=item unsigned int ev_recommended_backends ()
201		233
202	Return the set of all backends compiled into this binary of libev and also	234	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	235	also recommended for this platform, meaning it will work for most file
		236	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	237	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	238	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	239	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.	240	probe for if you specify no backends explicitly.
208		241
209	=item unsigned int ev_embeddable_backends ()	242	=item unsigned int ev_embeddable_backends ()
210		243
211	Returns the set of backends that are embeddable in other event loops. This	244	Returns the set of backends that are embeddable in other event loops. This
212	is the theoretical, all-platform, value. To find which backends	245	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	246	current system. To find which embeddable backends might be supported on
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	247	the current system, you would need to look at C<ev_embeddable_backends ()
215	recommended ones.	248	& ev_supported_backends ()>, likewise for recommended ones.
216		249
217	See the description of C<ev_embed> watchers for more info.	250	See the description of C<ev_embed> watchers for more info.
218		251
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	252	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
220		253
221	Sets the allocation function to use (the prototype is similar - the	254	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	255	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	256	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	257	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	283	}
251		284
252	...	285	...
253	ev_set_allocator (persistent_realloc);	286	ev_set_allocator (persistent_realloc);
254		287
255	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	288	=item ev_set_syserr_cb (void (*cb)(const char *msg))
256		289
257	Set the callback function to call on a retryable system call error (such	290	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	291	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	292	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	293	callback is set, then libev will expect it to remedy the situation, no
…		…
272	}	305	}
273		306
274	...	307	...
275	ev_set_syserr_cb (fatal_error);	308	ev_set_syserr_cb (fatal_error);
276		309
		310	=item ev_feed_signal (int signum)
		311
		312	This function can be used to "simulate" a signal receive. It is completely
		313	safe to call this function at any time, from any context, including signal
		314	handlers or random threads.
		315
		316	Its main use is to customise signal handling in your process, especially
		317	in the presence of threads. For example, you could block signals
		318	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		319	creating any loops), and in one thread, use C<sigwait> or any other
		320	mechanism to wait for signals, then "deliver" them to libev by calling
		321	C<ev_feed_signal>.
		322
277	=back	323	=back
278		324
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	325	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
280		326
281	An event loop is described by a C<struct ev_loop *> (the C<struct>	327	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>	328	I<not> optional in this case unless libev 3 compatibility is disabled, as
283	I<function>).	329	libev 3 had an C<ev_loop> function colliding with the struct name).
284		330
285	The library knows two types of such loops, the I<default> loop, which	331	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	332	supports child process events, and dynamically created event loops which
287	not.	333	do not.
288		334
289	=over 4	335	=over 4
290		336
291	=item struct ev_loop *ev_default_loop (unsigned int flags)	337	=item struct ev_loop *ev_default_loop (unsigned int flags)
292		338
293	This will initialise the default event loop if it hasn't been initialised	339	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	340	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	341	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).	342	C<ev_loop_new>.
		343
		344	If the default loop is already initialised then this function simply
		345	returns it (and ignores the flags. If that is troubling you, check
		346	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		347	flags, which should almost always be C<0>, unless the caller is also the
		348	one calling C<ev_run> or otherwise qualifies as "the main program".
297		349
298	If you don't know what event loop to use, use the one returned from this	350	If you don't know what event loop to use, use the one returned from this
299	function.	351	function (or via the C<EV_DEFAULT> macro).
300		352
301	Note that this function is I<not> thread-safe, so if you want to use it	353	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,	354	from multiple threads, you have to employ some kind of mutex (note also
303	as loops cannot bes hared easily between threads anyway).	355	that this case is unlikely, as loops cannot be shared easily between
		356	threads anyway).
304		357
305	The default loop is the only loop that can handle C<ev_signal> and	358	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	359	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	360	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	361	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	362	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
310	C<ev_default_init>.	363
		364	Example: This is the most typical usage.
		365
		366	if (!ev_default_loop (0))
		367	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		368
		369	Example: Restrict libev to the select and poll backends, and do not allow
		370	environment settings to be taken into account:
		371
		372	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		373
		374	=item struct ev_loop *ev_loop_new (unsigned int flags)
		375
		376	This will create and initialise a new event loop object. If the loop
		377	could not be initialised, returns false.
		378
		379	This function is thread-safe, and one common way to use libev with
		380	threads is indeed to create one loop per thread, and using the default
		381	loop in the "main" or "initial" thread.
311		382
312	The flags argument can be used to specify special behaviour or specific	383	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>).	384	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
314		385
315	The following flags are supported:	386	The following flags are supported:
…		…
330	useful to try out specific backends to test their performance, or to work	401	useful to try out specific backends to test their performance, or to work
331	around bugs.	402	around bugs.
332		403
333	=item C<EVFLAG_FORKCHECK>	404	=item C<EVFLAG_FORKCHECK>
334		405
335	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	406	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	407	make libev check for a fork in each iteration by enabling this flag.
337	enabling this flag.
338		408
339	This works by calling C<getpid ()> on every iteration of the loop,	409	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	410	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	411	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	412	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
…		…
348	flag.	418	flag.
349		419
350	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	420	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
351	environment variable.	421	environment variable.
352		422
		423	=item C<EVFLAG_NOINOTIFY>
		424
		425	When this flag is specified, then libev will not attempt to use the
		426	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
		427	testing, this flag can be useful to conserve inotify file descriptors, as
		428	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		429
		430	=item C<EVFLAG_SIGNALFD>
		431
		432	When this flag is specified, then libev will attempt to use the
		433	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
		434	delivers signals synchronously, which makes it both faster and might make
		435	it possible to get the queued signal data. It can also simplify signal
		436	handling with threads, as long as you properly block signals in your
		437	threads that are not interested in handling them.
		438
		439	Signalfd will not be used by default as this changes your signal mask, and
		440	there are a lot of shoddy libraries and programs (glib's threadpool for
		441	example) that can't properly initialise their signal masks.
		442
		443	=item C<EVFLAG_NOSIGMASK>
		444
		445	When this flag is specified, then libev will avoid to modify the signal
		446	mask. Specifically, this means you ahve to make sure signals are unblocked
		447	when you want to receive them.
		448
		449	This behaviour is useful when you want to do your own signal handling, or
		450	want to handle signals only in specific threads and want to avoid libev
		451	unblocking the signals.
		452
		453	It's also required by POSIX in a threaded program, as libev calls
		454	C<sigprocmask>, whose behaviour is officially unspecified.
		455
		456	This flag's behaviour will become the default in future versions of libev.
		457
353	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	458	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
354		459
355	This is your standard select(2) backend. Not I<completely> standard, as	460	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,	461	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	462	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	486	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
382	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	487	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
383		488
384	=item C<EVBACKEND_EPOLL> (value 4, Linux)	489	=item C<EVBACKEND_EPOLL> (value 4, Linux)
385		490
		491	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		492	kernels).
		493
386	For few fds, this backend is a bit little slower than poll and select,	494	For few fds, this backend is a bit little slower than poll and select, but
387	but it scales phenomenally better. While poll and select usually scale	495	it scales phenomenally better. While poll and select usually scale like
388	like O(total_fds) where n is the total number of fds (or the highest fd),	496	O(total_fds) where total_fds is the total number of fds (or the highest
389	epoll scales either O(1) or O(active_fds). The epoll design has a number	497	fd), epoll scales either O(1) or O(active_fds).
390	of shortcomings, such as silently dropping events in some hard-to-detect	498
391	cases and requiring a system call per fd change, no fork support and bad	499	The epoll mechanism deserves honorable mention as the most misdesigned
392	support for dup.	500	of the more advanced event mechanisms: mere annoyances include silently
		501	dropping file descriptors, requiring a system call per change per file
		502	descriptor (and unnecessary guessing of parameters), problems with dup,
		503	returning before the timeout value, resulting in additional iterations
		504	(and only giving 5ms accuracy while select on the same platform gives
		505	0.1ms) and so on. The biggest issue is fork races, however - if a program
		506	forks then I<both> parent and child process have to recreate the epoll
		507	set, which can take considerable time (one syscall per file descriptor)
		508	and is of course hard to detect.
		509
		510	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
		511	but of course I<doesn't>, and epoll just loves to report events for
		512	totally I<different> file descriptors (even already closed ones, so
		513	one cannot even remove them from the set) than registered in the set
		514	(especially on SMP systems). Libev tries to counter these spurious
		515	notifications by employing an additional generation counter and comparing
		516	that against the events to filter out spurious ones, recreating the set
		517	when required. Epoll also errornously rounds down timeouts, but gives you
		518	no way to know when and by how much, so sometimes you have to busy-wait
		519	because epoll returns immediately despite a nonzero timeout. And last
		520	not least, it also refuses to work with some file descriptors which work
		521	perfectly fine with C<select> (files, many character devices...).
		522
		523	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		524	cobbled together in a hurry, no thought to design or interaction with
		525	others. Oh, the pain, will it ever stop...
393		526
394	While stopping, setting and starting an I/O watcher in the same iteration	527	While stopping, setting and starting an I/O watcher in the same iteration
395	will result in some caching, there is still a system call per such incident	528	will result in some caching, there is still a system call per such
396	(because the fd could point to a different file description now), so its	529	incident (because the same I<file descriptor> could point to a different
397	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	530	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
398	very well if you register events for both fds.	531	file descriptors might not work very well if you register events for both
399		532	file descriptors.
400	Please note that epoll sometimes generates spurious notifications, so you
401	need to use non-blocking I/O or other means to avoid blocking when no data
402	(or space) is available.
403		533
404	Best performance from this backend is achieved by not unregistering all	534	Best performance from this backend is achieved by not unregistering all
405	watchers for a file descriptor until it has been closed, if possible,	535	watchers for a file descriptor until it has been closed, if possible,
406	i.e. keep at least one watcher active per fd at all times. Stopping and	536	i.e. keep at least one watcher active per fd at all times. Stopping and
407	starting a watcher (without re-setting it) also usually doesn't cause	537	starting a watcher (without re-setting it) also usually doesn't cause
408	extra overhead.	538	extra overhead. A fork can both result in spurious notifications as well
		539	as in libev having to destroy and recreate the epoll object, which can
		540	take considerable time and thus should be avoided.
		541
		542	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		543	faster than epoll for maybe up to a hundred file descriptors, depending on
		544	the usage. So sad.
409		545
410	While nominally embeddable in other event loops, this feature is broken in	546	While nominally embeddable in other event loops, this feature is broken in
411	all kernel versions tested so far.	547	all kernel versions tested so far.
412		548
413	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	549	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
414	C<EVBACKEND_POLL>.	550	C<EVBACKEND_POLL>.
415		551
416	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	552	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
417		553
418	Kqueue deserves special mention, as at the time of this writing, it was	554	Kqueue deserves special mention, as at the time of this writing, it
419	broken on all BSDs except NetBSD (usually it doesn't work reliably with	555	was broken on all BSDs except NetBSD (usually it doesn't work reliably
420	anything but sockets and pipes, except on Darwin, where of course it's	556	with anything but sockets and pipes, except on Darwin, where of course
421	completely useless). For this reason it's not being "auto-detected" unless	557	it's completely useless). Unlike epoll, however, whose brokenness
422	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or	558	is by design, these kqueue bugs can (and eventually will) be fixed
423	libev was compiled on a known-to-be-good (-enough) system like NetBSD.	559	without API changes to existing programs. For this reason it's not being
		560	"auto-detected" unless you explicitly specify it in the flags (i.e. using
		561	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		562	system like NetBSD.
424		563
425	You still can embed kqueue into a normal poll or select backend and use it	564	You still can embed kqueue into a normal poll or select backend and use it
426	only for sockets (after having made sure that sockets work with kqueue on	565	only for sockets (after having made sure that sockets work with kqueue on
427	the target platform). See C<ev_embed> watchers for more info.	566	the target platform). See C<ev_embed> watchers for more info.
428		567
429	It scales in the same way as the epoll backend, but the interface to the	568	It scales in the same way as the epoll backend, but the interface to the
430	kernel is more efficient (which says nothing about its actual speed, of	569	kernel is more efficient (which says nothing about its actual speed, of
431	course). While stopping, setting and starting an I/O watcher does never	570	course). While stopping, setting and starting an I/O watcher does never
432	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	571	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
433	two event changes per incident. Support for C<fork ()> is very bad and it	572	two event changes per incident. Support for C<fork ()> is very bad (but
434	drops fds silently in similarly hard-to-detect cases.	573	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		574	cases
435		575
436	This backend usually performs well under most conditions.	576	This backend usually performs well under most conditions.
437		577
438	While nominally embeddable in other event loops, this doesn't work	578	While nominally embeddable in other event loops, this doesn't work
439	everywhere, so you might need to test for this. And since it is broken	579	everywhere, so you might need to test for this. And since it is broken
440	almost everywhere, you should only use it when you have a lot of sockets	580	almost everywhere, you should only use it when you have a lot of sockets
441	(for which it usually works), by embedding it into another event loop	581	(for which it usually works), by embedding it into another event loop
442	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,	582	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
443	using it only for sockets.	583	also broken on OS X)) and, did I mention it, using it only for sockets.
444		584
445	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	585	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
446	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with	586	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
447	C<NOTE_EOF>.	587	C<NOTE_EOF>.
448		588
…		…
456	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	596	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
457		597
458	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	598	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
459	it's really slow, but it still scales very well (O(active_fds)).	599	it's really slow, but it still scales very well (O(active_fds)).
460		600
461	Please note that Solaris event ports can deliver a lot of spurious
462	notifications, so you need to use non-blocking I/O or other means to avoid
463	blocking when no data (or space) is available.
464
465	While this backend scales well, it requires one system call per active	601	While this backend scales well, it requires one system call per active
466	file descriptor per loop iteration. For small and medium numbers of file	602	file descriptor per loop iteration. For small and medium numbers of file
467	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	603	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
468	might perform better.	604	might perform better.
469		605
470	On the positive side, with the exception of the spurious readiness	606	On the positive side, this backend actually performed fully to
471	notifications, this backend actually performed fully to specification
472	in all tests and is fully embeddable, which is a rare feat among the	607	specification in all tests and is fully embeddable, which is a rare feat
473	OS-specific backends.	608	among the OS-specific backends (I vastly prefer correctness over speed
		609	hacks).
		610
		611	On the negative side, the interface is I<bizarre> - so bizarre that
		612	even sun itself gets it wrong in their code examples: The event polling
		613	function sometimes returning events to the caller even though an error
		614	occurred, but with no indication whether it has done so or not (yes, it's
		615	even documented that way) - deadly for edge-triggered interfaces where
		616	you absolutely have to know whether an event occurred or not because you
		617	have to re-arm the watcher.
		618
		619	Fortunately libev seems to be able to work around these idiocies.
474		620
475	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	621	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
476	C<EVBACKEND_POLL>.	622	C<EVBACKEND_POLL>.
477		623
478	=item C<EVBACKEND_ALL>	624	=item C<EVBACKEND_ALL>
479		625
480	Try all backends (even potentially broken ones that wouldn't be tried	626	Try all backends (even potentially broken ones that wouldn't be tried
481	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	627	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
482	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	628	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
483		629
484	It is definitely not recommended to use this flag.	630	It is definitely not recommended to use this flag, use whatever
		631	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		632	at all.
		633
		634	=item C<EVBACKEND_MASK>
		635
		636	Not a backend at all, but a mask to select all backend bits from a
		637	C<flags> value, in case you want to mask out any backends from a flags
		638	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
485		639
486	=back	640	=back
487		641
488	If one or more of these are or'ed into the flags value, then only these	642	If one or more of the backend flags are or'ed into the flags value,
489	backends will be tried (in the reverse order as listed here). If none are	643	then only these backends will be tried (in the reverse order as listed
490	specified, all backends in C<ev_recommended_backends ()> will be tried.	644	here). If none are specified, all backends in C<ev_recommended_backends
491		645	()> will be tried.
492	Example: This is the most typical usage.
493
494	if (!ev_default_loop (0))
495	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
496
497	Example: Restrict libev to the select and poll backends, and do not allow
498	environment settings to be taken into account:
499
500	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
501
502	Example: Use whatever libev has to offer, but make sure that kqueue is
503	used if available (warning, breaks stuff, best use only with your own
504	private event loop and only if you know the OS supports your types of
505	fds):
506
507	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
508
509	=item struct ev_loop *ev_loop_new (unsigned int flags)
510
511	Similar to C<ev_default_loop>, but always creates a new event loop that is
512	always distinct from the default loop. Unlike the default loop, it cannot
513	handle signal and child watchers, and attempts to do so will be greeted by
514	undefined behaviour (or a failed assertion if assertions are enabled).
515
516	Note that this function I<is> thread-safe, and the recommended way to use
517	libev with threads is indeed to create one loop per thread, and using the
518	default loop in the "main" or "initial" thread.
519		646
520	Example: Try to create a event loop that uses epoll and nothing else.	647	Example: Try to create a event loop that uses epoll and nothing else.
521		648
522	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	649	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
523	if (!epoller)	650	if (!epoller)
524	fatal ("no epoll found here, maybe it hides under your chair");	651	fatal ("no epoll found here, maybe it hides under your chair");
525		652
		653	Example: Use whatever libev has to offer, but make sure that kqueue is
		654	used if available.
		655
		656	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		657
526	=item ev_default_destroy ()	658	=item ev_loop_destroy (loop)
527		659
528	Destroys the default loop again (frees all memory and kernel state	660	Destroys an event loop object (frees all memory and kernel state
529	etc.). None of the active event watchers will be stopped in the normal	661	etc.). None of the active event watchers will be stopped in the normal
530	sense, so e.g. C<ev_is_active> might still return true. It is your	662	sense, so e.g. C<ev_is_active> might still return true. It is your
531	responsibility to either stop all watchers cleanly yourself I<before>	663	responsibility to either stop all watchers cleanly yourself I<before>
532	calling this function, or cope with the fact afterwards (which is usually	664	calling this function, or cope with the fact afterwards (which is usually
533	the easiest thing, you can just ignore the watchers and/or C<free ()> them	665	the easiest thing, you can just ignore the watchers and/or C<free ()> them
534	for example).	666	for example).
535		667
536	Note that certain global state, such as signal state, will not be freed by	668	Note that certain global state, such as signal state (and installed signal
537	this function, and related watchers (such as signal and child watchers)	669	handlers), will not be freed by this function, and related watchers (such
538	would need to be stopped manually.	670	as signal and child watchers) would need to be stopped manually.
539		671
540	In general it is not advisable to call this function except in the	672	This function is normally used on loop objects allocated by
541	rare occasion where you really need to free e.g. the signal handling	673	C<ev_loop_new>, but it can also be used on the default loop returned by
		674	C<ev_default_loop>, in which case it is not thread-safe.
		675
		676	Note that it is not advisable to call this function on the default loop
		677	except in the rare occasion where you really need to free its resources.
542	pipe fds. If you need dynamically allocated loops it is better to use	678	If you need dynamically allocated loops it is better to use C<ev_loop_new>
543	C<ev_loop_new> and C<ev_loop_destroy>).	679	and C<ev_loop_destroy>.
544		680
545	=item ev_loop_destroy (loop)	681	=item ev_loop_fork (loop)
546		682
547	Like C<ev_default_destroy>, but destroys an event loop created by an
548	earlier call to C<ev_loop_new>.
549
550	=item ev_default_fork ()
551
552	This function sets a flag that causes subsequent C<ev_loop> iterations	683	This function sets a flag that causes subsequent C<ev_run> iterations to
553	to reinitialise the kernel state for backends that have one. Despite the	684	reinitialise the kernel state for backends that have one. Despite the
554	name, you can call it anytime, but it makes most sense after forking, in	685	name, you can call it anytime, but it makes most sense after forking, in
555	the child process (or both child and parent, but that again makes little	686	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
556	sense). You I<must> call it in the child before using any of the libev	687	child before resuming or calling C<ev_run>.
557	functions, and it will only take effect at the next C<ev_loop> iteration.	688
		689	Again, you I<have> to call it on I<any> loop that you want to re-use after
		690	a fork, I<even if you do not plan to use the loop in the parent>. This is
		691	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		692	during fork.
558		693
559	On the other hand, you only need to call this function in the child	694	On the other hand, you only need to call this function in the child
560	process if and only if you want to use the event library in the child. If	695	process if and only if you want to use the event loop in the child. If
561	you just fork+exec, you don't have to call it at all.	696	you just fork+exec or create a new loop in the child, you don't have to
		697	call it at all (in fact, C<epoll> is so badly broken that it makes a
		698	difference, but libev will usually detect this case on its own and do a
		699	costly reset of the backend).
562		700
563	The function itself is quite fast and it's usually not a problem to call	701	The function itself is quite fast and it's usually not a problem to call
564	it just in case after a fork. To make this easy, the function will fit in	702	it just in case after a fork.
565	quite nicely into a call to C<pthread_atfork>:
566		703
		704	Example: Automate calling C<ev_loop_fork> on the default loop when
		705	using pthreads.
		706
		707	static void
		708	post_fork_child (void)
		709	{
		710	ev_loop_fork (EV_DEFAULT);
		711	}
		712
		713	...
567	pthread_atfork (0, 0, ev_default_fork);	714	pthread_atfork (0, 0, post_fork_child);
568
569	=item ev_loop_fork (loop)
570
571	Like C<ev_default_fork>, but acts on an event loop created by
572	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
573	after fork that you want to re-use in the child, and how you do this is
574	entirely your own problem.
575		715
576	=item int ev_is_default_loop (loop)	716	=item int ev_is_default_loop (loop)
577		717
578	Returns true when the given loop is, in fact, the default loop, and false	718	Returns true when the given loop is, in fact, the default loop, and false
579	otherwise.	719	otherwise.
580		720
581	=item unsigned int ev_loop_count (loop)	721	=item unsigned int ev_iteration (loop)
582		722
583	Returns the count of loop iterations for the loop, which is identical to	723	Returns the current iteration count for the event loop, which is identical
584	the number of times libev did poll for new events. It starts at C<0> and	724	to the number of times libev did poll for new events. It starts at C<0>
585	happily wraps around with enough iterations.	725	and happily wraps around with enough iterations.
586		726
587	This value can sometimes be useful as a generation counter of sorts (it	727	This value can sometimes be useful as a generation counter of sorts (it
588	"ticks" the number of loop iterations), as it roughly corresponds with	728	"ticks" the number of loop iterations), as it roughly corresponds with
589	C<ev_prepare> and C<ev_check> calls.	729	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		730	prepare and check phases.
		731
		732	=item unsigned int ev_depth (loop)
		733
		734	Returns the number of times C<ev_run> was entered minus the number of
		735	times C<ev_run> was exited normally, in other words, the recursion depth.
		736
		737	Outside C<ev_run>, this number is zero. In a callback, this number is
		738	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		739	in which case it is higher.
		740
		741	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
		742	throwing an exception etc.), doesn't count as "exit" - consider this
		743	as a hint to avoid such ungentleman-like behaviour unless it's really
		744	convenient, in which case it is fully supported.
590		745
591	=item unsigned int ev_backend (loop)	746	=item unsigned int ev_backend (loop)
592		747
593	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	748	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
594	use.	749	use.
…		…
603		758
604	=item ev_now_update (loop)	759	=item ev_now_update (loop)
605		760
606	Establishes the current time by querying the kernel, updating the time	761	Establishes the current time by querying the kernel, updating the time
607	returned by C<ev_now ()> in the progress. This is a costly operation and	762	returned by C<ev_now ()> in the progress. This is a costly operation and
608	is usually done automatically within C<ev_loop ()>.	763	is usually done automatically within C<ev_run ()>.
609		764
610	This function is rarely useful, but when some event callback runs for a	765	This function is rarely useful, but when some event callback runs for a
611	very long time without entering the event loop, updating libev's idea of	766	very long time without entering the event loop, updating libev's idea of
612	the current time is a good idea.	767	the current time is a good idea.
613		768
614	See also "The special problem of time updates" in the C<ev_timer> section.	769	See also L<The special problem of time updates> in the C<ev_timer> section.
615		770
		771	=item ev_suspend (loop)
		772
		773	=item ev_resume (loop)
		774
		775	These two functions suspend and resume an event loop, for use when the
		776	loop is not used for a while and timeouts should not be processed.
		777
		778	A typical use case would be an interactive program such as a game: When
		779	the user presses C<^Z> to suspend the game and resumes it an hour later it
		780	would be best to handle timeouts as if no time had actually passed while
		781	the program was suspended. This can be achieved by calling C<ev_suspend>
		782	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		783	C<ev_resume> directly afterwards to resume timer processing.
		784
		785	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		786	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		787	will be rescheduled (that is, they will lose any events that would have
		788	occurred while suspended).
		789
		790	After calling C<ev_suspend> you B<must not> call I<any> function on the
		791	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		792	without a previous call to C<ev_suspend>.
		793
		794	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		795	event loop time (see C<ev_now_update>).
		796
616	=item ev_loop (loop, int flags)	797	=item ev_run (loop, int flags)
617		798
618	Finally, this is it, the event handler. This function usually is called	799	Finally, this is it, the event handler. This function usually is called
619	after you initialised all your watchers and you want to start handling	800	after you have initialised all your watchers and you want to start
620	events.	801	handling events. It will ask the operating system for any new events, call
		802	the watcher callbacks, an then repeat the whole process indefinitely: This
		803	is why event loops are called I<loops>.
621		804
622	If the flags argument is specified as C<0>, it will not return until	805	If the flags argument is specified as C<0>, it will keep handling events
623	either no event watchers are active anymore or C<ev_unloop> was called.	806	until either no event watchers are active anymore or C<ev_break> was
		807	called.
624		808
625	Please note that an explicit C<ev_unloop> is usually better than	809	Please note that an explicit C<ev_break> is usually better than
626	relying on all watchers to be stopped when deciding when a program has	810	relying on all watchers to be stopped when deciding when a program has
627	finished (especially in interactive programs), but having a program	811	finished (especially in interactive programs), but having a program
628	that automatically loops as long as it has to and no longer by virtue	812	that automatically loops as long as it has to and no longer by virtue
629	of relying on its watchers stopping correctly, that is truly a thing of	813	of relying on its watchers stopping correctly, that is truly a thing of
630	beauty.	814	beauty.
631		815
		816	This function is also I<mostly> exception-safe - you can break out of
		817	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		818	exception and so on. This does not decrement the C<ev_depth> value, nor
		819	will it clear any outstanding C<EVBREAK_ONE> breaks.
		820
632	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	821	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
633	those events and any already outstanding ones, but will not block your	822	those events and any already outstanding ones, but will not wait and
634	process in case there are no events and will return after one iteration of	823	block your process in case there are no events and will return after one
635	the loop.	824	iteration of the loop. This is sometimes useful to poll and handle new
		825	events while doing lengthy calculations, to keep the program responsive.
636		826
637	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	827	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
638	necessary) and will handle those and any already outstanding ones. It	828	necessary) and will handle those and any already outstanding ones. It
639	will block your process until at least one new event arrives (which could	829	will block your process until at least one new event arrives (which could
640	be an event internal to libev itself, so there is no guarentee that a	830	be an event internal to libev itself, so there is no guarantee that a
641	user-registered callback will be called), and will return after one	831	user-registered callback will be called), and will return after one
642	iteration of the loop.	832	iteration of the loop.
643		833
644	This is useful if you are waiting for some external event in conjunction	834	This is useful if you are waiting for some external event in conjunction
645	with something not expressible using other libev watchers (i.e. "roll your	835	with something not expressible using other libev watchers (i.e. "roll your
646	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	836	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
647	usually a better approach for this kind of thing.	837	usually a better approach for this kind of thing.
648		838
649	Here are the gory details of what C<ev_loop> does:	839	Here are the gory details of what C<ev_run> does (this is for your
		840	understanding, not a guarantee that things will work exactly like this in
		841	future versions):
650		842
		843	- Increment loop depth.
		844	- Reset the ev_break status.
651	- Before the first iteration, call any pending watchers.	845	- Before the first iteration, call any pending watchers.
		846	LOOP:
652	* If EVFLAG_FORKCHECK was used, check for a fork.	847	- If EVFLAG_FORKCHECK was used, check for a fork.
653	- If a fork was detected (by any means), queue and call all fork watchers.	848	- If a fork was detected (by any means), queue and call all fork watchers.
654	- Queue and call all prepare watchers.	849	- Queue and call all prepare watchers.
		850	- If ev_break was called, goto FINISH.
655	- If we have been forked, detach and recreate the kernel state	851	- If we have been forked, detach and recreate the kernel state
656	as to not disturb the other process.	852	as to not disturb the other process.
657	- Update the kernel state with all outstanding changes.	853	- Update the kernel state with all outstanding changes.
658	- Update the "event loop time" (ev_now ()).	854	- Update the "event loop time" (ev_now ()).
659	- Calculate for how long to sleep or block, if at all	855	- Calculate for how long to sleep or block, if at all
660	(active idle watchers, EVLOOP_NONBLOCK or not having	856	(active idle watchers, EVRUN_NOWAIT or not having
661	any active watchers at all will result in not sleeping).	857	any active watchers at all will result in not sleeping).
662	- Sleep if the I/O and timer collect interval say so.	858	- Sleep if the I/O and timer collect interval say so.
		859	- Increment loop iteration counter.
663	- Block the process, waiting for any events.	860	- Block the process, waiting for any events.
664	- Queue all outstanding I/O (fd) events.	861	- Queue all outstanding I/O (fd) events.
665	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	862	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
666	- Queue all expired timers.	863	- Queue all expired timers.
667	- Queue all expired periodics.	864	- Queue all expired periodics.
668	- Unless any events are pending now, queue all idle watchers.	865	- Queue all idle watchers with priority higher than that of pending events.
669	- Queue all check watchers.	866	- Queue all check watchers.
670	- Call all queued watchers in reverse order (i.e. check watchers first).	867	- Call all queued watchers in reverse order (i.e. check watchers first).
671	Signals and child watchers are implemented as I/O watchers, and will	868	Signals and child watchers are implemented as I/O watchers, and will
672	be handled here by queueing them when their watcher gets executed.	869	be handled here by queueing them when their watcher gets executed.
673	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	870	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
674	were used, or there are no active watchers, return, otherwise	871	were used, or there are no active watchers, goto FINISH, otherwise
675	continue with step *.	872	continue with step LOOP.
		873	FINISH:
		874	- Reset the ev_break status iff it was EVBREAK_ONE.
		875	- Decrement the loop depth.
		876	- Return.
676		877
677	Example: Queue some jobs and then loop until no events are outstanding	878	Example: Queue some jobs and then loop until no events are outstanding
678	anymore.	879	anymore.
679		880
680	... queue jobs here, make sure they register event watchers as long	881	... queue jobs here, make sure they register event watchers as long
681	... as they still have work to do (even an idle watcher will do..)	882	... as they still have work to do (even an idle watcher will do..)
682	ev_loop (my_loop, 0);	883	ev_run (my_loop, 0);
683	... jobs done or somebody called unloop. yeah!	884	... jobs done or somebody called break. yeah!
684		885
685	=item ev_unloop (loop, how)	886	=item ev_break (loop, how)
686		887
687	Can be used to make a call to C<ev_loop> return early (but only after it	888	Can be used to make a call to C<ev_run> return early (but only after it
688	has processed all outstanding events). The C<how> argument must be either	889	has processed all outstanding events). The C<how> argument must be either
689	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	890	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
690	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	891	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
691		892
692	This "unloop state" will be cleared when entering C<ev_loop> again.	893	This "break state" will be cleared on the next call to C<ev_run>.
693		894
694	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	895	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		896	which case it will have no effect.
695		897
696	=item ev_ref (loop)	898	=item ev_ref (loop)
697		899
698	=item ev_unref (loop)	900	=item ev_unref (loop)
699		901
700	Ref/unref can be used to add or remove a reference count on the event	902	Ref/unref can be used to add or remove a reference count on the event
701	loop: Every watcher keeps one reference, and as long as the reference	903	loop: Every watcher keeps one reference, and as long as the reference
702	count is nonzero, C<ev_loop> will not return on its own.	904	count is nonzero, C<ev_run> will not return on its own.
703		905
704	If you have a watcher you never unregister that should not keep C<ev_loop>	906	This is useful when you have a watcher that you never intend to
705	from returning, call ev_unref() after starting, and ev_ref() before	907	unregister, but that nevertheless should not keep C<ev_run> from
		908	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
706	stopping it.	909	before stopping it.
707		910
708	As an example, libev itself uses this for its internal signal pipe: It is	911	As an example, libev itself uses this for its internal signal pipe: It
709	not visible to the libev user and should not keep C<ev_loop> from exiting	912	is not visible to the libev user and should not keep C<ev_run> from
710	if no event watchers registered by it are active. It is also an excellent	913	exiting if no event watchers registered by it are active. It is also an
711	way to do this for generic recurring timers or from within third-party	914	excellent way to do this for generic recurring timers or from within
712	libraries. Just remember to I<unref after start> and I<ref before stop>	915	third-party libraries. Just remember to I<unref after start> and I<ref
713	(but only if the watcher wasn't active before, or was active before,	916	before stop> (but only if the watcher wasn't active before, or was active
714	respectively).	917	before, respectively. Note also that libev might stop watchers itself
		918	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		919	in the callback).
715		920
716	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	921	Example: Create a signal watcher, but keep it from keeping C<ev_run>
717	running when nothing else is active.	922	running when nothing else is active.
718		923
719	ev_signal exitsig;	924	ev_signal exitsig;
720	ev_signal_init (&exitsig, sig_cb, SIGINT);	925	ev_signal_init (&exitsig, sig_cb, SIGINT);
721	ev_signal_start (loop, &exitsig);	926	ev_signal_start (loop, &exitsig);
722	evf_unref (loop);	927	ev_unref (loop);
723		928
724	Example: For some weird reason, unregister the above signal handler again.	929	Example: For some weird reason, unregister the above signal handler again.
725		930
726	ev_ref (loop);	931	ev_ref (loop);
727	ev_signal_stop (loop, &exitsig);	932	ev_signal_stop (loop, &exitsig);
…		…
747	overhead for the actual polling but can deliver many events at once.	952	overhead for the actual polling but can deliver many events at once.
748		953
749	By setting a higher I<io collect interval> you allow libev to spend more	954	By setting a higher I<io collect interval> you allow libev to spend more
750	time collecting I/O events, so you can handle more events per iteration,	955	time collecting I/O events, so you can handle more events per iteration,
751	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	956	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
752	C<ev_timer>) will be not affected. Setting this to a non-null value will	957	C<ev_timer>) will not be affected. Setting this to a non-null value will
753	introduce an additional C<ev_sleep ()> call into most loop iterations.	958	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		959	sleep time ensures that libev will not poll for I/O events more often then
		960	once per this interval, on average (as long as the host time resolution is
		961	good enough).
754		962
755	Likewise, by setting a higher I<timeout collect interval> you allow libev	963	Likewise, by setting a higher I<timeout collect interval> you allow libev
756	to spend more time collecting timeouts, at the expense of increased	964	to spend more time collecting timeouts, at the expense of increased
757	latency/jitter/inexactness (the watcher callback will be called	965	latency/jitter/inexactness (the watcher callback will be called
758	later). C<ev_io> watchers will not be affected. Setting this to a non-null	966	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
760		968
761	Many (busy) programs can usually benefit by setting the I/O collect	969	Many (busy) programs can usually benefit by setting the I/O collect
762	interval to a value near C<0.1> or so, which is often enough for	970	interval to a value near C<0.1> or so, which is often enough for
763	interactive servers (of course not for games), likewise for timeouts. It	971	interactive servers (of course not for games), likewise for timeouts. It
764	usually doesn't make much sense to set it to a lower value than C<0.01>,	972	usually doesn't make much sense to set it to a lower value than C<0.01>,
765	as this approaches the timing granularity of most systems.	973	as this approaches the timing granularity of most systems. Note that if
		974	you do transactions with the outside world and you can't increase the
		975	parallelity, then this setting will limit your transaction rate (if you
		976	need to poll once per transaction and the I/O collect interval is 0.01,
		977	then you can't do more than 100 transactions per second).
766		978
767	Setting the I<timeout collect interval> can improve the opportunity for	979	Setting the I<timeout collect interval> can improve the opportunity for
768	saving power, as the program will "bundle" timer callback invocations that	980	saving power, as the program will "bundle" timer callback invocations that
769	are "near" in time together, by delaying some, thus reducing the number of	981	are "near" in time together, by delaying some, thus reducing the number of
770	times the process sleeps and wakes up again. Another useful technique to	982	times the process sleeps and wakes up again. Another useful technique to
771	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	983	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
772	they fire on, say, one-second boundaries only.	984	they fire on, say, one-second boundaries only.
773		985
		986	Example: we only need 0.1s timeout granularity, and we wish not to poll
		987	more often than 100 times per second:
		988
		989	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		990	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		991
		992	=item ev_invoke_pending (loop)
		993
		994	This call will simply invoke all pending watchers while resetting their
		995	pending state. Normally, C<ev_run> does this automatically when required,
		996	but when overriding the invoke callback this call comes handy. This
		997	function can be invoked from a watcher - this can be useful for example
		998	when you want to do some lengthy calculation and want to pass further
		999	event handling to another thread (you still have to make sure only one
		1000	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		1001
		1002	=item int ev_pending_count (loop)
		1003
		1004	Returns the number of pending watchers - zero indicates that no watchers
		1005	are pending.
		1006
		1007	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		1008
		1009	This overrides the invoke pending functionality of the loop: Instead of
		1010	invoking all pending watchers when there are any, C<ev_run> will call
		1011	this callback instead. This is useful, for example, when you want to
		1012	invoke the actual watchers inside another context (another thread etc.).
		1013
		1014	If you want to reset the callback, use C<ev_invoke_pending> as new
		1015	callback.
		1016
		1017	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		1018
		1019	Sometimes you want to share the same loop between multiple threads. This
		1020	can be done relatively simply by putting mutex_lock/unlock calls around
		1021	each call to a libev function.
		1022
		1023	However, C<ev_run> can run an indefinite time, so it is not feasible
		1024	to wait for it to return. One way around this is to wake up the event
		1025	loop via C<ev_break> and C<av_async_send>, another way is to set these
		1026	I<release> and I<acquire> callbacks on the loop.
		1027
		1028	When set, then C<release> will be called just before the thread is
		1029	suspended waiting for new events, and C<acquire> is called just
		1030	afterwards.
		1031
		1032	Ideally, C<release> will just call your mutex_unlock function, and
		1033	C<acquire> will just call the mutex_lock function again.
		1034
		1035	While event loop modifications are allowed between invocations of
		1036	C<release> and C<acquire> (that's their only purpose after all), no
		1037	modifications done will affect the event loop, i.e. adding watchers will
		1038	have no effect on the set of file descriptors being watched, or the time
		1039	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		1040	to take note of any changes you made.
		1041
		1042	In theory, threads executing C<ev_run> will be async-cancel safe between
		1043	invocations of C<release> and C<acquire>.
		1044
		1045	See also the locking example in the C<THREADS> section later in this
		1046	document.
		1047
		1048	=item ev_set_userdata (loop, void *data)
		1049
		1050	=item void *ev_userdata (loop)
		1051
		1052	Set and retrieve a single C<void *> associated with a loop. When
		1053	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		1054	C<0>.
		1055
		1056	These two functions can be used to associate arbitrary data with a loop,
		1057	and are intended solely for the C<invoke_pending_cb>, C<release> and
		1058	C<acquire> callbacks described above, but of course can be (ab-)used for
		1059	any other purpose as well.
		1060
774	=item ev_loop_verify (loop)	1061	=item ev_verify (loop)
775		1062
776	This function only does something when C<EV_VERIFY> support has been	1063	This function only does something when C<EV_VERIFY> support has been
777	compiled in, which is the default for non-minimal builds. It tries to go	1064	compiled in, which is the default for non-minimal builds. It tries to go
778	through all internal structures and checks them for validity. If anything	1065	through all internal structures and checks them for validity. If anything
779	is found to be inconsistent, it will print an error message to standard	1066	is found to be inconsistent, it will print an error message to standard
…		…
790		1077
791	In the following description, uppercase C<TYPE> in names stands for the	1078	In the following description, uppercase C<TYPE> in names stands for the
792	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1079	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
793	watchers and C<ev_io_start> for I/O watchers.	1080	watchers and C<ev_io_start> for I/O watchers.
794		1081
795	A watcher is a structure that you create and register to record your	1082	A watcher is an opaque structure that you allocate and register to record
796	interest in some event. For instance, if you want to wait for STDIN to	1083	your interest in some event. To make a concrete example, imagine you want
797	become readable, you would create an C<ev_io> watcher for that:	1084	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1085	for that:
798		1086
799	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1087	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
800	{	1088	{
801	ev_io_stop (w);	1089	ev_io_stop (w);
802	ev_unloop (loop, EVUNLOOP_ALL);	1090	ev_break (loop, EVBREAK_ALL);
803	}	1091	}
804		1092
805	struct ev_loop *loop = ev_default_loop (0);	1093	struct ev_loop *loop = ev_default_loop (0);
806		1094
807	ev_io stdin_watcher;	1095	ev_io stdin_watcher;
808		1096
809	ev_init (&stdin_watcher, my_cb);	1097	ev_init (&stdin_watcher, my_cb);
810	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1098	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
811	ev_io_start (loop, &stdin_watcher);	1099	ev_io_start (loop, &stdin_watcher);
812		1100
813	ev_loop (loop, 0);	1101	ev_run (loop, 0);
814		1102
815	As you can see, you are responsible for allocating the memory for your	1103	As you can see, you are responsible for allocating the memory for your
816	watcher structures (and it is I<usually> a bad idea to do this on the	1104	watcher structures (and it is I<usually> a bad idea to do this on the
817	stack).	1105	stack).
818		1106
819	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1107	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
820	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1108	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
821		1109
822	Each watcher structure must be initialised by a call to C<ev_init	1110	Each watcher structure must be initialised by a call to C<ev_init (watcher
823	(watcher *, callback)>, which expects a callback to be provided. This	1111	*, callback)>, which expects a callback to be provided. This callback is
824	callback gets invoked each time the event occurs (or, in the case of I/O	1112	invoked each time the event occurs (or, in the case of I/O watchers, each
825	watchers, each time the event loop detects that the file descriptor given	1113	time the event loop detects that the file descriptor given is readable
826	is readable and/or writable).	1114	and/or writable).
827		1115
828	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1116	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
829	macro to configure it, with arguments specific to the watcher type. There	1117	macro to configure it, with arguments specific to the watcher type. There
830	is also a macro to combine initialisation and setting in one call: C<<	1118	is also a macro to combine initialisation and setting in one call: C<<
831	ev_TYPE_init (watcher *, callback, ...) >>.	1119	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
854	=item C<EV_WRITE>	1142	=item C<EV_WRITE>
855		1143
856	The file descriptor in the C<ev_io> watcher has become readable and/or	1144	The file descriptor in the C<ev_io> watcher has become readable and/or
857	writable.	1145	writable.
858		1146
859	=item C<EV_TIMEOUT>	1147	=item C<EV_TIMER>
860		1148
861	The C<ev_timer> watcher has timed out.	1149	The C<ev_timer> watcher has timed out.
862		1150
863	=item C<EV_PERIODIC>	1151	=item C<EV_PERIODIC>
864		1152
…		…
882		1170
883	=item C<EV_PREPARE>	1171	=item C<EV_PREPARE>
884		1172
885	=item C<EV_CHECK>	1173	=item C<EV_CHECK>
886		1174
887	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1175	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
888	to gather new events, and all C<ev_check> watchers are invoked just after	1176	to gather new events, and all C<ev_check> watchers are invoked just after
889	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1177	C<ev_run> has gathered them, but before it invokes any callbacks for any
890	received events. Callbacks of both watcher types can start and stop as	1178	received events. Callbacks of both watcher types can start and stop as
891	many watchers as they want, and all of them will be taken into account	1179	many watchers as they want, and all of them will be taken into account
892	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1180	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
893	C<ev_loop> from blocking).	1181	C<ev_run> from blocking).
894		1182
895	=item C<EV_EMBED>	1183	=item C<EV_EMBED>
896		1184
897	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1185	The embedded event loop specified in the C<ev_embed> watcher needs attention.
898		1186
899	=item C<EV_FORK>	1187	=item C<EV_FORK>
900		1188
901	The event loop has been resumed in the child process after fork (see	1189	The event loop has been resumed in the child process after fork (see
902	C<ev_fork>).	1190	C<ev_fork>).
903		1191
		1192	=item C<EV_CLEANUP>
		1193
		1194	The event loop is about to be destroyed (see C<ev_cleanup>).
		1195
904	=item C<EV_ASYNC>	1196	=item C<EV_ASYNC>
905		1197
906	The given async watcher has been asynchronously notified (see C<ev_async>).	1198	The given async watcher has been asynchronously notified (see C<ev_async>).
		1199
		1200	=item C<EV_CUSTOM>
		1201
		1202	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1203	by libev users to signal watchers (e.g. via C<ev_feed_event>).
907		1204
908	=item C<EV_ERROR>	1205	=item C<EV_ERROR>
909		1206
910	An unspecified error has occurred, the watcher has been stopped. This might	1207	An unspecified error has occurred, the watcher has been stopped. This might
911	happen because the watcher could not be properly started because libev	1208	happen because the watcher could not be properly started because libev
…		…
949		1246
950	ev_io w;	1247	ev_io w;
951	ev_init (&w, my_cb);	1248	ev_init (&w, my_cb);
952	ev_io_set (&w, STDIN_FILENO, EV_READ);	1249	ev_io_set (&w, STDIN_FILENO, EV_READ);
953		1250
954	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1251	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
955		1252
956	This macro initialises the type-specific parts of a watcher. You need to	1253	This macro initialises the type-specific parts of a watcher. You need to
957	call C<ev_init> at least once before you call this macro, but you can	1254	call C<ev_init> at least once before you call this macro, but you can
958	call C<ev_TYPE_set> any number of times. You must not, however, call this	1255	call C<ev_TYPE_set> any number of times. You must not, however, call this
959	macro on a watcher that is active (it can be pending, however, which is a	1256	macro on a watcher that is active (it can be pending, however, which is a
…		…
972		1269
973	Example: Initialise and set an C<ev_io> watcher in one step.	1270	Example: Initialise and set an C<ev_io> watcher in one step.
974		1271
975	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1272	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
976		1273
977	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1274	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
978		1275
979	Starts (activates) the given watcher. Only active watchers will receive	1276	Starts (activates) the given watcher. Only active watchers will receive
980	events. If the watcher is already active nothing will happen.	1277	events. If the watcher is already active nothing will happen.
981		1278
982	Example: Start the C<ev_io> watcher that is being abused as example in this	1279	Example: Start the C<ev_io> watcher that is being abused as example in this
983	whole section.	1280	whole section.
984		1281
985	ev_io_start (EV_DEFAULT_UC, &w);	1282	ev_io_start (EV_DEFAULT_UC, &w);
986		1283
987	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1284	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
988		1285
989	Stops the given watcher if active, and clears the pending status (whether	1286	Stops the given watcher if active, and clears the pending status (whether
990	the watcher was active or not).	1287	the watcher was active or not).
991		1288
992	It is possible that stopped watchers are pending - for example,	1289	It is possible that stopped watchers are pending - for example,
…		…
1017	=item ev_cb_set (ev_TYPE *watcher, callback)	1314	=item ev_cb_set (ev_TYPE *watcher, callback)
1018		1315
1019	Change the callback. You can change the callback at virtually any time	1316	Change the callback. You can change the callback at virtually any time
1020	(modulo threads).	1317	(modulo threads).
1021		1318
1022	=item ev_set_priority (ev_TYPE *watcher, priority)	1319	=item ev_set_priority (ev_TYPE *watcher, int priority)
1023		1320
1024	=item int ev_priority (ev_TYPE *watcher)	1321	=item int ev_priority (ev_TYPE *watcher)
1025		1322
1026	Set and query the priority of the watcher. The priority is a small	1323	Set and query the priority of the watcher. The priority is a small
1027	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1324	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1028	(default: C<-2>). Pending watchers with higher priority will be invoked	1325	(default: C<-2>). Pending watchers with higher priority will be invoked
1029	before watchers with lower priority, but priority will not keep watchers	1326	before watchers with lower priority, but priority will not keep watchers
1030	from being executed (except for C<ev_idle> watchers).	1327	from being executed (except for C<ev_idle> watchers).
1031		1328
1032	This means that priorities are I<only> used for ordering callback
1033	invocation after new events have been received. This is useful, for
1034	example, to reduce latency after idling, or more often, to bind two
1035	watchers on the same event and make sure one is called first.
1036
1037	If you need to suppress invocation when higher priority events are pending	1329	If you need to suppress invocation when higher priority events are pending
1038	you need to look at C<ev_idle> watchers, which provide this functionality.	1330	you need to look at C<ev_idle> watchers, which provide this functionality.
1039		1331
1040	You I<must not> change the priority of a watcher as long as it is active or	1332	You I<must not> change the priority of a watcher as long as it is active or
1041	pending.	1333	pending.
1042
1043	The default priority used by watchers when no priority has been set is
1044	always C<0>, which is supposed to not be too high and not be too low :).
1045		1334
1046	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1335	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1047	fine, as long as you do not mind that the priority value you query might	1336	fine, as long as you do not mind that the priority value you query might
1048	or might not have been clamped to the valid range.	1337	or might not have been clamped to the valid range.
		1338
		1339	The default priority used by watchers when no priority has been set is
		1340	always C<0>, which is supposed to not be too high and not be too low :).
		1341
		1342	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
		1343	priorities.
1049		1344
1050	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1345	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1051		1346
1052	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1347	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1053	C<loop> nor C<revents> need to be valid as long as the watcher callback	1348	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1061	watcher isn't pending it does nothing and returns C<0>.	1356	watcher isn't pending it does nothing and returns C<0>.
1062		1357
1063	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1358	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1064	callback to be invoked, which can be accomplished with this function.	1359	callback to be invoked, which can be accomplished with this function.
1065		1360
		1361	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1362
		1363	Feeds the given event set into the event loop, as if the specified event
		1364	had happened for the specified watcher (which must be a pointer to an
		1365	initialised but not necessarily started event watcher). Obviously you must
		1366	not free the watcher as long as it has pending events.
		1367
		1368	Stopping the watcher, letting libev invoke it, or calling
		1369	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1370	not started in the first place.
		1371
		1372	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1373	functions that do not need a watcher.
		1374
1066	=back	1375	=back
1067		1376
		1377	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
		1378	OWN COMPOSITE WATCHERS> idioms.
1068		1379
1069	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1380	=head2 WATCHER STATES
1070		1381
1071	Each watcher has, by default, a member C<void *data> that you can change	1382	There are various watcher states mentioned throughout this manual -
1072	and read at any time: libev will completely ignore it. This can be used	1383	active, pending and so on. In this section these states and the rules to
1073	to associate arbitrary data with your watcher. If you need more data and	1384	transition between them will be described in more detail - and while these
1074	don't want to allocate memory and store a pointer to it in that data	1385	rules might look complicated, they usually do "the right thing".
1075	member, you can also "subclass" the watcher type and provide your own
1076	data:
1077		1386
1078	struct my_io	1387	=over 4
		1388
		1389	=item initialiased
		1390
		1391	Before a watcher can be registered with the event looop it has to be
		1392	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1393	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1394
		1395	In this state it is simply some block of memory that is suitable for
		1396	use in an event loop. It can be moved around, freed, reused etc. at
		1397	will - as long as you either keep the memory contents intact, or call
		1398	C<ev_TYPE_init> again.
		1399
		1400	=item started/running/active
		1401
		1402	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1403	property of the event loop, and is actively waiting for events. While in
		1404	this state it cannot be accessed (except in a few documented ways), moved,
		1405	freed or anything else - the only legal thing is to keep a pointer to it,
		1406	and call libev functions on it that are documented to work on active watchers.
		1407
		1408	=item pending
		1409
		1410	If a watcher is active and libev determines that an event it is interested
		1411	in has occurred (such as a timer expiring), it will become pending. It will
		1412	stay in this pending state until either it is stopped or its callback is
		1413	about to be invoked, so it is not normally pending inside the watcher
		1414	callback.
		1415
		1416	The watcher might or might not be active while it is pending (for example,
		1417	an expired non-repeating timer can be pending but no longer active). If it
		1418	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1419	but it is still property of the event loop at this time, so cannot be
		1420	moved, freed or reused. And if it is active the rules described in the
		1421	previous item still apply.
		1422
		1423	It is also possible to feed an event on a watcher that is not active (e.g.
		1424	via C<ev_feed_event>), in which case it becomes pending without being
		1425	active.
		1426
		1427	=item stopped
		1428
		1429	A watcher can be stopped implicitly by libev (in which case it might still
		1430	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1431	latter will clear any pending state the watcher might be in, regardless
		1432	of whether it was active or not, so stopping a watcher explicitly before
		1433	freeing it is often a good idea.
		1434
		1435	While stopped (and not pending) the watcher is essentially in the
		1436	initialised state, that is, it can be reused, moved, modified in any way
		1437	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1438	it again).
		1439
		1440	=back
		1441
		1442	=head2 WATCHER PRIORITY MODELS
		1443
		1444	Many event loops support I<watcher priorities>, which are usually small
		1445	integers that influence the ordering of event callback invocation
		1446	between watchers in some way, all else being equal.
		1447
		1448	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1449	description for the more technical details such as the actual priority
		1450	range.
		1451
		1452	There are two common ways how these these priorities are being interpreted
		1453	by event loops:
		1454
		1455	In the more common lock-out model, higher priorities "lock out" invocation
		1456	of lower priority watchers, which means as long as higher priority
		1457	watchers receive events, lower priority watchers are not being invoked.
		1458
		1459	The less common only-for-ordering model uses priorities solely to order
		1460	callback invocation within a single event loop iteration: Higher priority
		1461	watchers are invoked before lower priority ones, but they all get invoked
		1462	before polling for new events.
		1463
		1464	Libev uses the second (only-for-ordering) model for all its watchers
		1465	except for idle watchers (which use the lock-out model).
		1466
		1467	The rationale behind this is that implementing the lock-out model for
		1468	watchers is not well supported by most kernel interfaces, and most event
		1469	libraries will just poll for the same events again and again as long as
		1470	their callbacks have not been executed, which is very inefficient in the
		1471	common case of one high-priority watcher locking out a mass of lower
		1472	priority ones.
		1473
		1474	Static (ordering) priorities are most useful when you have two or more
		1475	watchers handling the same resource: a typical usage example is having an
		1476	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1477	timeouts. Under load, data might be received while the program handles
		1478	other jobs, but since timers normally get invoked first, the timeout
		1479	handler will be executed before checking for data. In that case, giving
		1480	the timer a lower priority than the I/O watcher ensures that I/O will be
		1481	handled first even under adverse conditions (which is usually, but not
		1482	always, what you want).
		1483
		1484	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1485	will only be executed when no same or higher priority watchers have
		1486	received events, they can be used to implement the "lock-out" model when
		1487	required.
		1488
		1489	For example, to emulate how many other event libraries handle priorities,
		1490	you can associate an C<ev_idle> watcher to each such watcher, and in
		1491	the normal watcher callback, you just start the idle watcher. The real
		1492	processing is done in the idle watcher callback. This causes libev to
		1493	continuously poll and process kernel event data for the watcher, but when
		1494	the lock-out case is known to be rare (which in turn is rare :), this is
		1495	workable.
		1496
		1497	Usually, however, the lock-out model implemented that way will perform
		1498	miserably under the type of load it was designed to handle. In that case,
		1499	it might be preferable to stop the real watcher before starting the
		1500	idle watcher, so the kernel will not have to process the event in case
		1501	the actual processing will be delayed for considerable time.
		1502
		1503	Here is an example of an I/O watcher that should run at a strictly lower
		1504	priority than the default, and which should only process data when no
		1505	other events are pending:
		1506
		1507	ev_idle idle; // actual processing watcher
		1508	ev_io io; // actual event watcher
		1509
		1510	static void
		1511	io_cb (EV_P_ ev_io *w, int revents)
1079	{	1512	{
1080	ev_io io;	1513	// stop the I/O watcher, we received the event, but
1081	int otherfd;	1514	// are not yet ready to handle it.
1082	void *somedata;	1515	ev_io_stop (EV_A_ w);
1083	struct whatever *mostinteresting;	1516
		1517	// start the idle watcher to handle the actual event.
		1518	// it will not be executed as long as other watchers
		1519	// with the default priority are receiving events.
		1520	ev_idle_start (EV_A_ &idle);
1084	};	1521	}
1085		1522
1086	...	1523	static void
1087	struct my_io w;	1524	idle_cb (EV_P_ ev_idle *w, int revents)
1088	ev_io_init (&w.io, my_cb, fd, EV_READ);
1089
1090	And since your callback will be called with a pointer to the watcher, you
1091	can cast it back to your own type:
1092
1093	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1094	{	1525	{
1095	struct my_io *w = (struct my_io *)w_;	1526	// actual processing
1096	...	1527	read (STDIN_FILENO, ...);
		1528
		1529	// have to start the I/O watcher again, as
		1530	// we have handled the event
		1531	ev_io_start (EV_P_ &io);
1097	}	1532	}
1098		1533
1099	More interesting and less C-conformant ways of casting your callback type	1534	// initialisation
1100	instead have been omitted.	1535	ev_idle_init (&idle, idle_cb);
		1536	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1537	ev_io_start (EV_DEFAULT_ &io);
1101		1538
1102	Another common scenario is to use some data structure with multiple	1539	In the "real" world, it might also be beneficial to start a timer, so that
1103	embedded watchers:	1540	low-priority connections can not be locked out forever under load. This
1104		1541	enables your program to keep a lower latency for important connections
1105	struct my_biggy	1542	during short periods of high load, while not completely locking out less
1106	{	1543	important ones.
1107	int some_data;
1108	ev_timer t1;
1109	ev_timer t2;
1110	}
1111
1112	In this case getting the pointer to C<my_biggy> is a bit more
1113	complicated: Either you store the address of your C<my_biggy> struct
1114	in the C<data> member of the watcher (for woozies), or you need to use
1115	some pointer arithmetic using C<offsetof> inside your watchers (for real
1116	programmers):
1117
1118	#include <stddef.h>
1119
1120	static void
1121	t1_cb (EV_P_ ev_timer *w, int revents)
1122	{
1123	struct my_biggy big = (struct my_biggy *
1124	(((char *)w) - offsetof (struct my_biggy, t1));
1125	}
1126
1127	static void
1128	t2_cb (EV_P_ ev_timer *w, int revents)
1129	{
1130	struct my_biggy big = (struct my_biggy *
1131	(((char *)w) - offsetof (struct my_biggy, t2));
1132	}
1133		1544
1134		1545
1135	=head1 WATCHER TYPES	1546	=head1 WATCHER TYPES
1136		1547
1137	This section describes each watcher in detail, but will not repeat	1548	This section describes each watcher in detail, but will not repeat
…		…
1161	In general you can register as many read and/or write event watchers per	1572	In general you can register as many read and/or write event watchers per
1162	fd as you want (as long as you don't confuse yourself). Setting all file	1573	fd as you want (as long as you don't confuse yourself). Setting all file
1163	descriptors to non-blocking mode is also usually a good idea (but not	1574	descriptors to non-blocking mode is also usually a good idea (but not
1164	required if you know what you are doing).	1575	required if you know what you are doing).
1165		1576
1166	If you cannot use non-blocking mode, then force the use of a
1167	known-to-be-good backend (at the time of this writing, this includes only
1168	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1169
1170	Another thing you have to watch out for is that it is quite easy to	1577	Another thing you have to watch out for is that it is quite easy to
1171	receive "spurious" readiness notifications, that is your callback might	1578	receive "spurious" readiness notifications, that is, your callback might
1172	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1579	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1173	because there is no data. Not only are some backends known to create a	1580	because there is no data. It is very easy to get into this situation even
1174	lot of those (for example Solaris ports), it is very easy to get into	1581	with a relatively standard program structure. Thus it is best to always
1175	this situation even with a relatively standard program structure. Thus	1582	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1176	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1177	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1583	preferable to a program hanging until some data arrives.
1178		1584
1179	If you cannot run the fd in non-blocking mode (for example you should	1585	If you cannot run the fd in non-blocking mode (for example you should
1180	not play around with an Xlib connection), then you have to separately	1586	not play around with an Xlib connection), then you have to separately
1181	re-test whether a file descriptor is really ready with a known-to-be good	1587	re-test whether a file descriptor is really ready with a known-to-be good
1182	interface such as poll (fortunately in our Xlib example, Xlib already	1588	interface such as poll (fortunately in the case of Xlib, it already does
1183	does this on its own, so its quite safe to use). Some people additionally	1589	this on its own, so its quite safe to use). Some people additionally
1184	use C<SIGALRM> and an interval timer, just to be sure you won't block	1590	use C<SIGALRM> and an interval timer, just to be sure you won't block
1185	indefinitely.	1591	indefinitely.
1186		1592
1187	But really, best use non-blocking mode.	1593	But really, best use non-blocking mode.
1188		1594
…		…
1216		1622
1217	There is no workaround possible except not registering events	1623	There is no workaround possible except not registering events
1218	for potentially C<dup ()>'ed file descriptors, or to resort to	1624	for potentially C<dup ()>'ed file descriptors, or to resort to
1219	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1625	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1220		1626
		1627	=head3 The special problem of files
		1628
		1629	Many people try to use C<select> (or libev) on file descriptors
		1630	representing files, and expect it to become ready when their program
		1631	doesn't block on disk accesses (which can take a long time on their own).
		1632
		1633	However, this cannot ever work in the "expected" way - you get a readiness
		1634	notification as soon as the kernel knows whether and how much data is
		1635	there, and in the case of open files, that's always the case, so you
		1636	always get a readiness notification instantly, and your read (or possibly
		1637	write) will still block on the disk I/O.
		1638
		1639	Another way to view it is that in the case of sockets, pipes, character
		1640	devices and so on, there is another party (the sender) that delivers data
		1641	on its own, but in the case of files, there is no such thing: the disk
		1642	will not send data on its own, simply because it doesn't know what you
		1643	wish to read - you would first have to request some data.
		1644
		1645	Since files are typically not-so-well supported by advanced notification
		1646	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1647	to files, even though you should not use it. The reason for this is
		1648	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1649	usually a tty, often a pipe, but also sometimes files or special devices
		1650	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1651	F</dev/urandom>), and even though the file might better be served with
		1652	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1653	it "just works" instead of freezing.
		1654
		1655	So avoid file descriptors pointing to files when you know it (e.g. use
		1656	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1657	when you rarely read from a file instead of from a socket, and want to
		1658	reuse the same code path.
		1659
1221	=head3 The special problem of fork	1660	=head3 The special problem of fork
1222		1661
1223	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1662	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1224	useless behaviour. Libev fully supports fork, but needs to be told about	1663	useless behaviour. Libev fully supports fork, but needs to be told about
1225	it in the child.	1664	it in the child if you want to continue to use it in the child.
1226		1665
1227	To support fork in your programs, you either have to call	1666	To support fork in your child processes, you have to call C<ev_loop_fork
1228	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1667	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1229	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1668	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1230	C<EVBACKEND_POLL>.
1231		1669
1232	=head3 The special problem of SIGPIPE	1670	=head3 The special problem of SIGPIPE
1233		1671
1234	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1672	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1235	when writing to a pipe whose other end has been closed, your program gets	1673	when writing to a pipe whose other end has been closed, your program gets
…		…
1238		1676
1239	So when you encounter spurious, unexplained daemon exits, make sure you	1677	So when you encounter spurious, unexplained daemon exits, make sure you
1240	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1678	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1241	somewhere, as that would have given you a big clue).	1679	somewhere, as that would have given you a big clue).
1242		1680
		1681	=head3 The special problem of accept()ing when you can't
		1682
		1683	Many implementations of the POSIX C<accept> function (for example,
		1684	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1685	connection from the pending queue in all error cases.
		1686
		1687	For example, larger servers often run out of file descriptors (because
		1688	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1689	rejecting the connection, leading to libev signalling readiness on
		1690	the next iteration again (the connection still exists after all), and
		1691	typically causing the program to loop at 100% CPU usage.
		1692
		1693	Unfortunately, the set of errors that cause this issue differs between
		1694	operating systems, there is usually little the app can do to remedy the
		1695	situation, and no known thread-safe method of removing the connection to
		1696	cope with overload is known (to me).
		1697
		1698	One of the easiest ways to handle this situation is to just ignore it
		1699	- when the program encounters an overload, it will just loop until the
		1700	situation is over. While this is a form of busy waiting, no OS offers an
		1701	event-based way to handle this situation, so it's the best one can do.
		1702
		1703	A better way to handle the situation is to log any errors other than
		1704	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1705	messages, and continue as usual, which at least gives the user an idea of
		1706	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1707	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1708	usage.
		1709
		1710	If your program is single-threaded, then you could also keep a dummy file
		1711	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1712	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1713	close that fd, and create a new dummy fd. This will gracefully refuse
		1714	clients under typical overload conditions.
		1715
		1716	The last way to handle it is to simply log the error and C<exit>, as
		1717	is often done with C<malloc> failures, but this results in an easy
		1718	opportunity for a DoS attack.
1243		1719
1244	=head3 Watcher-Specific Functions	1720	=head3 Watcher-Specific Functions
1245		1721
1246	=over 4	1722	=over 4
1247		1723
…		…
1279	...	1755	...
1280	struct ev_loop *loop = ev_default_init (0);	1756	struct ev_loop *loop = ev_default_init (0);
1281	ev_io stdin_readable;	1757	ev_io stdin_readable;
1282	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1758	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1283	ev_io_start (loop, &stdin_readable);	1759	ev_io_start (loop, &stdin_readable);
1284	ev_loop (loop, 0);	1760	ev_run (loop, 0);
1285		1761
1286		1762
1287	=head2 C<ev_timer> - relative and optionally repeating timeouts	1763	=head2 C<ev_timer> - relative and optionally repeating timeouts
1288		1764
1289	Timer watchers are simple relative timers that generate an event after a	1765	Timer watchers are simple relative timers that generate an event after a
…		…
1294	year, it will still time out after (roughly) one hour. "Roughly" because	1770	year, it will still time out after (roughly) one hour. "Roughly" because
1295	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1771	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1296	monotonic clock option helps a lot here).	1772	monotonic clock option helps a lot here).
1297		1773
1298	The callback is guaranteed to be invoked only I<after> its timeout has	1774	The callback is guaranteed to be invoked only I<after> its timeout has
1299	passed, but if multiple timers become ready during the same loop iteration	1775	passed (not I<at>, so on systems with very low-resolution clocks this
1300	then order of execution is undefined.	1776	might introduce a small delay). If multiple timers become ready during the
		1777	same loop iteration then the ones with earlier time-out values are invoked
		1778	before ones of the same priority with later time-out values (but this is
		1779	no longer true when a callback calls C<ev_run> recursively).
1301		1780
1302	=head3 Be smart about timeouts	1781	=head3 Be smart about timeouts
1303		1782
1304	Many real-world problems involve some kind of timeout, usually for error	1783	Many real-world problems involve some kind of timeout, usually for error
1305	recovery. A typical example is an HTTP request - if the other side hangs,	1784	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1349	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>	1828	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
1350	member and C<ev_timer_again>.	1829	member and C<ev_timer_again>.
1351		1830
1352	At start:	1831	At start:
1353		1832
1354	ev_timer_init (timer, callback);	1833	ev_init (timer, callback);
1355	timer->repeat = 60.;	1834	timer->repeat = 60.;
1356	ev_timer_again (loop, timer);	1835	ev_timer_again (loop, timer);
1357		1836
1358	Each time there is some activity:	1837	Each time there is some activity:
1359		1838
…		…
1391	ev_tstamp timeout = last_activity + 60.;	1870	ev_tstamp timeout = last_activity + 60.;
1392		1871
1393	// if last_activity + 60. is older than now, we did time out	1872	// if last_activity + 60. is older than now, we did time out
1394	if (timeout < now)	1873	if (timeout < now)
1395	{	1874	{
1396	// timeout occured, take action	1875	// timeout occurred, take action
1397	}	1876	}
1398	else	1877	else
1399	{	1878	{
1400	// callback was invoked, but there was some activity, re-arm	1879	// callback was invoked, but there was some activity, re-arm
1401	// the watcher to fire in last_activity + 60, which is	1880	// the watcher to fire in last_activity + 60, which is
1402	// guaranteed to be in the future, so "again" is positive:	1881	// guaranteed to be in the future, so "again" is positive:
1403	w->again = timeout - now;	1882	w->repeat = timeout - now;
1404	ev_timer_again (EV_A_ w);	1883	ev_timer_again (EV_A_ w);
1405	}	1884	}
1406	}	1885	}
1407		1886
1408	To summarise the callback: first calculate the real timeout (defined	1887	To summarise the callback: first calculate the real timeout (defined
…		…
1421		1900
1422	To start the timer, simply initialise the watcher and set C<last_activity>	1901	To start the timer, simply initialise the watcher and set C<last_activity>
1423	to the current time (meaning we just have some activity :), then call the	1902	to the current time (meaning we just have some activity :), then call the
1424	callback, which will "do the right thing" and start the timer:	1903	callback, which will "do the right thing" and start the timer:
1425		1904
1426	ev_timer_init (timer, callback);	1905	ev_init (timer, callback);
1427	last_activity = ev_now (loop);	1906	last_activity = ev_now (loop);
1428	callback (loop, timer, EV_TIMEOUT);	1907	callback (loop, timer, EV_TIMER);
1429		1908
1430	And when there is some activity, simply store the current time in	1909	And when there is some activity, simply store the current time in
1431	C<last_activity>, no libev calls at all:	1910	C<last_activity>, no libev calls at all:
1432		1911
1433	last_actiivty = ev_now (loop);	1912	last_activity = ev_now (loop);
1434		1913
1435	This technique is slightly more complex, but in most cases where the	1914	This technique is slightly more complex, but in most cases where the
1436	time-out is unlikely to be triggered, much more efficient.	1915	time-out is unlikely to be triggered, much more efficient.
1437		1916
1438	Changing the timeout is trivial as well (if it isn't hard-coded in the	1917	Changing the timeout is trivial as well (if it isn't hard-coded in the
…		…
1476		1955
1477	=head3 The special problem of time updates	1956	=head3 The special problem of time updates
1478		1957
1479	Establishing the current time is a costly operation (it usually takes at	1958	Establishing the current time is a costly operation (it usually takes at
1480	least two system calls): EV therefore updates its idea of the current	1959	least two system calls): EV therefore updates its idea of the current
1481	time only before and after C<ev_loop> collects new events, which causes a	1960	time only before and after C<ev_run> collects new events, which causes a
1482	growing difference between C<ev_now ()> and C<ev_time ()> when handling	1961	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1483	lots of events in one iteration.	1962	lots of events in one iteration.
1484		1963
1485	The relative timeouts are calculated relative to the C<ev_now ()>	1964	The relative timeouts are calculated relative to the C<ev_now ()>
1486	time. This is usually the right thing as this timestamp refers to the time	1965	time. This is usually the right thing as this timestamp refers to the time
…		…
1492		1971
1493	If the event loop is suspended for a long time, you can also force an	1972	If the event loop is suspended for a long time, you can also force an
1494	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1973	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1495	()>.	1974	()>.
1496		1975
		1976	=head3 The special problems of suspended animation
		1977
		1978	When you leave the server world it is quite customary to hit machines that
		1979	can suspend/hibernate - what happens to the clocks during such a suspend?
		1980
		1981	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1982	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1983	to run until the system is suspended, but they will not advance while the
		1984	system is suspended. That means, on resume, it will be as if the program
		1985	was frozen for a few seconds, but the suspend time will not be counted
		1986	towards C<ev_timer> when a monotonic clock source is used. The real time
		1987	clock advanced as expected, but if it is used as sole clocksource, then a
		1988	long suspend would be detected as a time jump by libev, and timers would
		1989	be adjusted accordingly.
		1990
		1991	I would not be surprised to see different behaviour in different between
		1992	operating systems, OS versions or even different hardware.
		1993
		1994	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1995	time jump in the monotonic clocks and the realtime clock. If the program
		1996	is suspended for a very long time, and monotonic clock sources are in use,
		1997	then you can expect C<ev_timer>s to expire as the full suspension time
		1998	will be counted towards the timers. When no monotonic clock source is in
		1999	use, then libev will again assume a timejump and adjust accordingly.
		2000
		2001	It might be beneficial for this latter case to call C<ev_suspend>
		2002	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		2003	deterministic behaviour in this case (you can do nothing against
		2004	C<SIGSTOP>).
		2005
1497	=head3 Watcher-Specific Functions and Data Members	2006	=head3 Watcher-Specific Functions and Data Members
1498		2007
1499	=over 4	2008	=over 4
1500		2009
1501	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2010	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1524	If the timer is started but non-repeating, stop it (as if it timed out).	2033	If the timer is started but non-repeating, stop it (as if it timed out).
1525		2034
1526	If the timer is repeating, either start it if necessary (with the	2035	If the timer is repeating, either start it if necessary (with the
1527	C<repeat> value), or reset the running timer to the C<repeat> value.	2036	C<repeat> value), or reset the running timer to the C<repeat> value.
1528		2037
1529	This sounds a bit complicated, see "Be smart about timeouts", above, for a	2038	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1530	usage example.	2039	usage example.
		2040
		2041	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2042
		2043	Returns the remaining time until a timer fires. If the timer is active,
		2044	then this time is relative to the current event loop time, otherwise it's
		2045	the timeout value currently configured.
		2046
		2047	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2048	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2049	will return C<4>. When the timer expires and is restarted, it will return
		2050	roughly C<7> (likely slightly less as callback invocation takes some time,
		2051	too), and so on.
1531		2052
1532	=item ev_tstamp repeat [read-write]	2053	=item ev_tstamp repeat [read-write]
1533		2054
1534	The current C<repeat> value. Will be used each time the watcher times out	2055	The current C<repeat> value. Will be used each time the watcher times out
1535	or C<ev_timer_again> is called, and determines the next timeout (if any),	2056	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1561	}	2082	}
1562		2083
1563	ev_timer mytimer;	2084	ev_timer mytimer;
1564	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2085	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1565	ev_timer_again (&mytimer); /* start timer */	2086	ev_timer_again (&mytimer); /* start timer */
1566	ev_loop (loop, 0);	2087	ev_run (loop, 0);
1567		2088
1568	// and in some piece of code that gets executed on any "activity":	2089	// and in some piece of code that gets executed on any "activity":
1569	// reset the timeout to start ticking again at 10 seconds	2090	// reset the timeout to start ticking again at 10 seconds
1570	ev_timer_again (&mytimer);	2091	ev_timer_again (&mytimer);
1571		2092
…		…
1573	=head2 C<ev_periodic> - to cron or not to cron?	2094	=head2 C<ev_periodic> - to cron or not to cron?
1574		2095
1575	Periodic watchers are also timers of a kind, but they are very versatile	2096	Periodic watchers are also timers of a kind, but they are very versatile
1576	(and unfortunately a bit complex).	2097	(and unfortunately a bit complex).
1577		2098
1578	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2099	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1579	but on wall clock time (absolute time). You can tell a periodic watcher	2100	relative time, the physical time that passes) but on wall clock time
1580	to trigger after some specific point in time. For example, if you tell a	2101	(absolute time, the thing you can read on your calender or clock). The
1581	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	2102	difference is that wall clock time can run faster or slower than real
1582	+ 10.>, that is, an absolute time not a delay) and then reset your system	2103	time, and time jumps are not uncommon (e.g. when you adjust your
1583	clock to January of the previous year, then it will take more than year	2104	wrist-watch).
1584	to trigger the event (unlike an C<ev_timer>, which would still trigger
1585	roughly 10 seconds later as it uses a relative timeout).
1586		2105
		2106	You can tell a periodic watcher to trigger after some specific point
		2107	in time: for example, if you tell a periodic watcher to trigger "in 10
		2108	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2109	not a delay) and then reset your system clock to January of the previous
		2110	year, then it will take a year or more to trigger the event (unlike an
		2111	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2112	it, as it uses a relative timeout).
		2113
1587	C<ev_periodic>s can also be used to implement vastly more complex timers,	2114	C<ev_periodic> watchers can also be used to implement vastly more complex
1588	such as triggering an event on each "midnight, local time", or other	2115	timers, such as triggering an event on each "midnight, local time", or
1589	complicated rules.	2116	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2117	those cannot react to time jumps.
1590		2118
1591	As with timers, the callback is guaranteed to be invoked only when the	2119	As with timers, the callback is guaranteed to be invoked only when the
1592	time (C<at>) has passed, but if multiple periodic timers become ready	2120	point in time where it is supposed to trigger has passed. If multiple
1593	during the same loop iteration, then order of execution is undefined.	2121	timers become ready during the same loop iteration then the ones with
		2122	earlier time-out values are invoked before ones with later time-out values
		2123	(but this is no longer true when a callback calls C<ev_run> recursively).
1594		2124
1595	=head3 Watcher-Specific Functions and Data Members	2125	=head3 Watcher-Specific Functions and Data Members
1596		2126
1597	=over 4	2127	=over 4
1598		2128
1599	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2129	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1600		2130
1601	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2131	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1602		2132
1603	Lots of arguments, lets sort it out... There are basically three modes of	2133	Lots of arguments, let's sort it out... There are basically three modes of
1604	operation, and we will explain them from simplest to most complex:	2134	operation, and we will explain them from simplest to most complex:
1605		2135
1606	=over 4	2136	=over 4
1607		2137
1608	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2138	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1609		2139
1610	In this configuration the watcher triggers an event after the wall clock	2140	In this configuration the watcher triggers an event after the wall clock
1611	time C<at> has passed. It will not repeat and will not adjust when a time	2141	time C<offset> has passed. It will not repeat and will not adjust when a
1612	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2142	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1613	only run when the system clock reaches or surpasses this time.	2143	will be stopped and invoked when the system clock reaches or surpasses
		2144	this point in time.
1614		2145
1615	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2146	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1616		2147
1617	In this mode the watcher will always be scheduled to time out at the next	2148	In this mode the watcher will always be scheduled to time out at the next
1618	C<at + N * interval> time (for some integer N, which can also be negative)	2149	C<offset + N * interval> time (for some integer N, which can also be
1619	and then repeat, regardless of any time jumps.	2150	negative) and then repeat, regardless of any time jumps. The C<offset>
		2151	argument is merely an offset into the C<interval> periods.
1620		2152
1621	This can be used to create timers that do not drift with respect to the	2153	This can be used to create timers that do not drift with respect to the
1622	system clock, for example, here is a C<ev_periodic> that triggers each	2154	system clock, for example, here is an C<ev_periodic> that triggers each
1623	hour, on the hour:	2155	hour, on the hour (with respect to UTC):
1624		2156
1625	ev_periodic_set (&periodic, 0., 3600., 0);	2157	ev_periodic_set (&periodic, 0., 3600., 0);
1626		2158
1627	This doesn't mean there will always be 3600 seconds in between triggers,	2159	This doesn't mean there will always be 3600 seconds in between triggers,
1628	but only that the callback will be called when the system time shows a	2160	but only that the callback will be called when the system time shows a
1629	full hour (UTC), or more correctly, when the system time is evenly divisible	2161	full hour (UTC), or more correctly, when the system time is evenly divisible
1630	by 3600.	2162	by 3600.
1631		2163
1632	Another way to think about it (for the mathematically inclined) is that	2164	Another way to think about it (for the mathematically inclined) is that
1633	C<ev_periodic> will try to run the callback in this mode at the next possible	2165	C<ev_periodic> will try to run the callback in this mode at the next possible
1634	time where C<time = at (mod interval)>, regardless of any time jumps.	2166	time where C<time = offset (mod interval)>, regardless of any time jumps.
1635		2167
1636	For numerical stability it is preferable that the C<at> value is near	2168	The C<interval> I<MUST> be positive, and for numerical stability, the
1637	C<ev_now ()> (the current time), but there is no range requirement for	2169	interval value should be higher than C<1/8192> (which is around 100
1638	this value, and in fact is often specified as zero.	2170	microseconds) and C<offset> should be higher than C<0> and should have
		2171	at most a similar magnitude as the current time (say, within a factor of
		2172	ten). Typical values for offset are, in fact, C<0> or something between
		2173	C<0> and C<interval>, which is also the recommended range.
1639		2174
1640	Note also that there is an upper limit to how often a timer can fire (CPU	2175	Note also that there is an upper limit to how often a timer can fire (CPU
1641	speed for example), so if C<interval> is very small then timing stability	2176	speed for example), so if C<interval> is very small then timing stability
1642	will of course deteriorate. Libev itself tries to be exact to be about one	2177	will of course deteriorate. Libev itself tries to be exact to be about one
1643	millisecond (if the OS supports it and the machine is fast enough).	2178	millisecond (if the OS supports it and the machine is fast enough).
1644		2179
1645	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2180	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1646		2181
1647	In this mode the values for C<interval> and C<at> are both being	2182	In this mode the values for C<interval> and C<offset> are both being
1648	ignored. Instead, each time the periodic watcher gets scheduled, the	2183	ignored. Instead, each time the periodic watcher gets scheduled, the
1649	reschedule callback will be called with the watcher as first, and the	2184	reschedule callback will be called with the watcher as first, and the
1650	current time as second argument.	2185	current time as second argument.
1651		2186
1652	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2187	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1653	ever, or make ANY event loop modifications whatsoever>.	2188	or make ANY other event loop modifications whatsoever, unless explicitly
		2189	allowed by documentation here>.
1654		2190
1655	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2191	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1656	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2192	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1657	only event loop modification you are allowed to do).	2193	only event loop modification you are allowed to do).
1658		2194
…		…
1688	a different time than the last time it was called (e.g. in a crond like	2224	a different time than the last time it was called (e.g. in a crond like
1689	program when the crontabs have changed).	2225	program when the crontabs have changed).
1690		2226
1691	=item ev_tstamp ev_periodic_at (ev_periodic *)	2227	=item ev_tstamp ev_periodic_at (ev_periodic *)
1692		2228
1693	When active, returns the absolute time that the watcher is supposed to	2229	When active, returns the absolute time that the watcher is supposed
1694	trigger next.	2230	to trigger next. This is not the same as the C<offset> argument to
		2231	C<ev_periodic_set>, but indeed works even in interval and manual
		2232	rescheduling modes.
1695		2233
1696	=item ev_tstamp offset [read-write]	2234	=item ev_tstamp offset [read-write]
1697		2235
1698	When repeating, this contains the offset value, otherwise this is the	2236	When repeating, this contains the offset value, otherwise this is the
1699	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2237	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2238	although libev might modify this value for better numerical stability).
1700		2239
1701	Can be modified any time, but changes only take effect when the periodic	2240	Can be modified any time, but changes only take effect when the periodic
1702	timer fires or C<ev_periodic_again> is being called.	2241	timer fires or C<ev_periodic_again> is being called.
1703		2242
1704	=item ev_tstamp interval [read-write]	2243	=item ev_tstamp interval [read-write]
…		…
1720	Example: Call a callback every hour, or, more precisely, whenever the	2259	Example: Call a callback every hour, or, more precisely, whenever the
1721	system time is divisible by 3600. The callback invocation times have	2260	system time is divisible by 3600. The callback invocation times have
1722	potentially a lot of jitter, but good long-term stability.	2261	potentially a lot of jitter, but good long-term stability.
1723		2262
1724	static void	2263	static void
1725	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2264	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1726	{	2265	{
1727	... its now a full hour (UTC, or TAI or whatever your clock follows)	2266	... its now a full hour (UTC, or TAI or whatever your clock follows)
1728	}	2267	}
1729		2268
1730	ev_periodic hourly_tick;	2269	ev_periodic hourly_tick;
…		…
1753		2292
1754	=head2 C<ev_signal> - signal me when a signal gets signalled!	2293	=head2 C<ev_signal> - signal me when a signal gets signalled!
1755		2294
1756	Signal watchers will trigger an event when the process receives a specific	2295	Signal watchers will trigger an event when the process receives a specific
1757	signal one or more times. Even though signals are very asynchronous, libev	2296	signal one or more times. Even though signals are very asynchronous, libev
1758	will try it's best to deliver signals synchronously, i.e. as part of the	2297	will try its best to deliver signals synchronously, i.e. as part of the
1759	normal event processing, like any other event.	2298	normal event processing, like any other event.
1760		2299
1761	If you want signals asynchronously, just use C<sigaction> as you would	2300	If you want signals to be delivered truly asynchronously, just use
1762	do without libev and forget about sharing the signal. You can even use	2301	C<sigaction> as you would do without libev and forget about sharing
1763	C<ev_async> from a signal handler to synchronously wake up an event loop.	2302	the signal. You can even use C<ev_async> from a signal handler to
		2303	synchronously wake up an event loop.
1764		2304
1765	You can configure as many watchers as you like per signal. Only when the	2305	You can configure as many watchers as you like for the same signal, but
		2306	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2307	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2308	C<SIGINT> in both the default loop and another loop at the same time. At
		2309	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2310
1766	first watcher gets started will libev actually register a signal handler	2311	When the first watcher gets started will libev actually register something
1767	with the kernel (thus it coexists with your own signal handlers as long as	2312	with the kernel (thus it coexists with your own signal handlers as long as
1768	you don't register any with libev for the same signal). Similarly, when	2313	you don't register any with libev for the same signal).
1769	the last signal watcher for a signal is stopped, libev will reset the
1770	signal handler to SIG_DFL (regardless of what it was set to before).
1771		2314
1772	If possible and supported, libev will install its handlers with	2315	If possible and supported, libev will install its handlers with
1773	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2316	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1774	interrupted. If you have a problem with system calls getting interrupted by	2317	not be unduly interrupted. If you have a problem with system calls getting
1775	signals you can block all signals in an C<ev_check> watcher and unblock	2318	interrupted by signals you can block all signals in an C<ev_check> watcher
1776	them in an C<ev_prepare> watcher.	2319	and unblock them in an C<ev_prepare> watcher.
		2320
		2321	=head3 The special problem of inheritance over fork/execve/pthread_create
		2322
		2323	Both the signal mask (C<sigprocmask>) and the signal disposition
		2324	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2325	stopping it again), that is, libev might or might not block the signal,
		2326	and might or might not set or restore the installed signal handler (but
		2327	see C<EVFLAG_NOSIGMASK>).
		2328
		2329	While this does not matter for the signal disposition (libev never
		2330	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2331	C<execve>), this matters for the signal mask: many programs do not expect
		2332	certain signals to be blocked.
		2333
		2334	This means that before calling C<exec> (from the child) you should reset
		2335	the signal mask to whatever "default" you expect (all clear is a good
		2336	choice usually).
		2337
		2338	The simplest way to ensure that the signal mask is reset in the child is
		2339	to install a fork handler with C<pthread_atfork> that resets it. That will
		2340	catch fork calls done by libraries (such as the libc) as well.
		2341
		2342	In current versions of libev, the signal will not be blocked indefinitely
		2343	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2344	the window of opportunity for problems, it will not go away, as libev
		2345	I<has> to modify the signal mask, at least temporarily.
		2346
		2347	So I can't stress this enough: I<If you do not reset your signal mask when
		2348	you expect it to be empty, you have a race condition in your code>. This
		2349	is not a libev-specific thing, this is true for most event libraries.
		2350
		2351	=head3 The special problem of threads signal handling
		2352
		2353	POSIX threads has problematic signal handling semantics, specifically,
		2354	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2355	threads in a process block signals, which is hard to achieve.
		2356
		2357	When you want to use sigwait (or mix libev signal handling with your own
		2358	for the same signals), you can tackle this problem by globally blocking
		2359	all signals before creating any threads (or creating them with a fully set
		2360	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2361	loops. Then designate one thread as "signal receiver thread" which handles
		2362	these signals. You can pass on any signals that libev might be interested
		2363	in by calling C<ev_feed_signal>.
1777		2364
1778	=head3 Watcher-Specific Functions and Data Members	2365	=head3 Watcher-Specific Functions and Data Members
1779		2366
1780	=over 4	2367	=over 4
1781		2368
…		…
1797	Example: Try to exit cleanly on SIGINT.	2384	Example: Try to exit cleanly on SIGINT.
1798		2385
1799	static void	2386	static void
1800	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2387	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1801	{	2388	{
1802	ev_unloop (loop, EVUNLOOP_ALL);	2389	ev_break (loop, EVBREAK_ALL);
1803	}	2390	}
1804		2391
1805	ev_signal signal_watcher;	2392	ev_signal signal_watcher;
1806	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2393	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1807	ev_signal_start (loop, &signal_watcher);	2394	ev_signal_start (loop, &signal_watcher);
…		…
1813	some child status changes (most typically when a child of yours dies or	2400	some child status changes (most typically when a child of yours dies or
1814	exits). It is permissible to install a child watcher I<after> the child	2401	exits). It is permissible to install a child watcher I<after> the child
1815	has been forked (which implies it might have already exited), as long	2402	has been forked (which implies it might have already exited), as long
1816	as the event loop isn't entered (or is continued from a watcher), i.e.,	2403	as the event loop isn't entered (or is continued from a watcher), i.e.,
1817	forking and then immediately registering a watcher for the child is fine,	2404	forking and then immediately registering a watcher for the child is fine,
1818	but forking and registering a watcher a few event loop iterations later is	2405	but forking and registering a watcher a few event loop iterations later or
1819	not.	2406	in the next callback invocation is not.
1820		2407
1821	Only the default event loop is capable of handling signals, and therefore	2408	Only the default event loop is capable of handling signals, and therefore
1822	you can only register child watchers in the default event loop.	2409	you can only register child watchers in the default event loop.
1823		2410
		2411	Due to some design glitches inside libev, child watchers will always be
		2412	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2413	libev)
		2414
1824	=head3 Process Interaction	2415	=head3 Process Interaction
1825		2416
1826	Libev grabs C<SIGCHLD> as soon as the default event loop is	2417	Libev grabs C<SIGCHLD> as soon as the default event loop is
1827	initialised. This is necessary to guarantee proper behaviour even if	2418	initialised. This is necessary to guarantee proper behaviour even if the
1828	the first child watcher is started after the child exits. The occurrence	2419	first child watcher is started after the child exits. The occurrence
1829	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2420	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1830	synchronously as part of the event loop processing. Libev always reaps all	2421	synchronously as part of the event loop processing. Libev always reaps all
1831	children, even ones not watched.	2422	children, even ones not watched.
1832		2423
1833	=head3 Overriding the Built-In Processing	2424	=head3 Overriding the Built-In Processing
…		…
1843	=head3 Stopping the Child Watcher	2434	=head3 Stopping the Child Watcher
1844		2435
1845	Currently, the child watcher never gets stopped, even when the	2436	Currently, the child watcher never gets stopped, even when the
1846	child terminates, so normally one needs to stop the watcher in the	2437	child terminates, so normally one needs to stop the watcher in the
1847	callback. Future versions of libev might stop the watcher automatically	2438	callback. Future versions of libev might stop the watcher automatically
1848	when a child exit is detected.	2439	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2440	problem).
1849		2441
1850	=head3 Watcher-Specific Functions and Data Members	2442	=head3 Watcher-Specific Functions and Data Members
1851		2443
1852	=over 4	2444	=over 4
1853		2445
…		…
1910		2502
1911		2503
1912	=head2 C<ev_stat> - did the file attributes just change?	2504	=head2 C<ev_stat> - did the file attributes just change?
1913		2505
1914	This watches a file system path for attribute changes. That is, it calls	2506	This watches a file system path for attribute changes. That is, it calls
1915	C<stat> regularly (or when the OS says it changed) and sees if it changed	2507	C<stat> on that path in regular intervals (or when the OS says it changed)
1916	compared to the last time, invoking the callback if it did.	2508	and sees if it changed compared to the last time, invoking the callback if
		2509	it did.
1917		2510
1918	The path does not need to exist: changing from "path exists" to "path does	2511	The path does not need to exist: changing from "path exists" to "path does
1919	not exist" is a status change like any other. The condition "path does	2512	not exist" is a status change like any other. The condition "path does not
1920	not exist" is signified by the C<st_nlink> field being zero (which is	2513	exist" (or more correctly "path cannot be stat'ed") is signified by the
1921	otherwise always forced to be at least one) and all the other fields of	2514	C<st_nlink> field being zero (which is otherwise always forced to be at
1922	the stat buffer having unspecified contents.	2515	least one) and all the other fields of the stat buffer having unspecified
		2516	contents.
1923		2517
1924	The path I<should> be absolute and I<must not> end in a slash. If it is	2518	The path I<must not> end in a slash or contain special components such as
		2519	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1925	relative and your working directory changes, the behaviour is undefined.	2520	your working directory changes, then the behaviour is undefined.
1926		2521
1927	Since there is no standard kernel interface to do this, the portable	2522	Since there is no portable change notification interface available, the
1928	implementation simply calls C<stat (2)> regularly on the path to see if	2523	portable implementation simply calls C<stat(2)> regularly on the path
1929	it changed somehow. You can specify a recommended polling interval for	2524	to see if it changed somehow. You can specify a recommended polling
1930	this case. If you specify a polling interval of C<0> (highly recommended!)	2525	interval for this case. If you specify a polling interval of C<0> (highly
1931	then a I<suitable, unspecified default> value will be used (which	2526	recommended!) then a I<suitable, unspecified default> value will be used
1932	you can expect to be around five seconds, although this might change	2527	(which you can expect to be around five seconds, although this might
1933	dynamically). Libev will also impose a minimum interval which is currently	2528	change dynamically). Libev will also impose a minimum interval which is
1934	around C<0.1>, but thats usually overkill.	2529	currently around C<0.1>, but that's usually overkill.
1935		2530
1936	This watcher type is not meant for massive numbers of stat watchers,	2531	This watcher type is not meant for massive numbers of stat watchers,
1937	as even with OS-supported change notifications, this can be	2532	as even with OS-supported change notifications, this can be
1938	resource-intensive.	2533	resource-intensive.
1939		2534
1940	At the time of this writing, the only OS-specific interface implemented	2535	At the time of this writing, the only OS-specific interface implemented
1941	is the Linux inotify interface (implementing kqueue support is left as	2536	is the Linux inotify interface (implementing kqueue support is left as an
1942	an exercise for the reader. Note, however, that the author sees no way	2537	exercise for the reader. Note, however, that the author sees no way of
1943	of implementing C<ev_stat> semantics with kqueue).	2538	implementing C<ev_stat> semantics with kqueue, except as a hint).
1944		2539
1945	=head3 ABI Issues (Largefile Support)	2540	=head3 ABI Issues (Largefile Support)
1946		2541
1947	Libev by default (unless the user overrides this) uses the default	2542	Libev by default (unless the user overrides this) uses the default
1948	compilation environment, which means that on systems with large file	2543	compilation environment, which means that on systems with large file
1949	support disabled by default, you get the 32 bit version of the stat	2544	support disabled by default, you get the 32 bit version of the stat
1950	structure. When using the library from programs that change the ABI to	2545	structure. When using the library from programs that change the ABI to
1951	use 64 bit file offsets the programs will fail. In that case you have to	2546	use 64 bit file offsets the programs will fail. In that case you have to
1952	compile libev with the same flags to get binary compatibility. This is	2547	compile libev with the same flags to get binary compatibility. This is
1953	obviously the case with any flags that change the ABI, but the problem is	2548	obviously the case with any flags that change the ABI, but the problem is
1954	most noticeably disabled with ev_stat and large file support.	2549	most noticeably displayed with ev_stat and large file support.
1955		2550
1956	The solution for this is to lobby your distribution maker to make large	2551	The solution for this is to lobby your distribution maker to make large
1957	file interfaces available by default (as e.g. FreeBSD does) and not	2552	file interfaces available by default (as e.g. FreeBSD does) and not
1958	optional. Libev cannot simply switch on large file support because it has	2553	optional. Libev cannot simply switch on large file support because it has
1959	to exchange stat structures with application programs compiled using the	2554	to exchange stat structures with application programs compiled using the
1960	default compilation environment.	2555	default compilation environment.
1961		2556
1962	=head3 Inotify and Kqueue	2557	=head3 Inotify and Kqueue
1963		2558
1964	When C<inotify (7)> support has been compiled into libev (generally	2559	When C<inotify (7)> support has been compiled into libev and present at
1965	only available with Linux 2.6.25 or above due to bugs in earlier	2560	runtime, it will be used to speed up change detection where possible. The
1966	implementations) and present at runtime, it will be used to speed up	2561	inotify descriptor will be created lazily when the first C<ev_stat>
1967	change detection where possible. The inotify descriptor will be created	2562	watcher is being started.
1968	lazily when the first C<ev_stat> watcher is being started.
1969		2563
1970	Inotify presence does not change the semantics of C<ev_stat> watchers	2564	Inotify presence does not change the semantics of C<ev_stat> watchers
1971	except that changes might be detected earlier, and in some cases, to avoid	2565	except that changes might be detected earlier, and in some cases, to avoid
1972	making regular C<stat> calls. Even in the presence of inotify support	2566	making regular C<stat> calls. Even in the presence of inotify support
1973	there are many cases where libev has to resort to regular C<stat> polling,	2567	there are many cases where libev has to resort to regular C<stat> polling,
1974	but as long as the path exists, libev usually gets away without polling.	2568	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2569	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2570	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2571	xfs are fully working) libev usually gets away without polling.
1975		2572
1976	There is no support for kqueue, as apparently it cannot be used to	2573	There is no support for kqueue, as apparently it cannot be used to
1977	implement this functionality, due to the requirement of having a file	2574	implement this functionality, due to the requirement of having a file
1978	descriptor open on the object at all times, and detecting renames, unlinks	2575	descriptor open on the object at all times, and detecting renames, unlinks
1979	etc. is difficult.	2576	etc. is difficult.
1980		2577
		2578	=head3 C<stat ()> is a synchronous operation
		2579
		2580	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2581	the process. The exception are C<ev_stat> watchers - those call C<stat
		2582	()>, which is a synchronous operation.
		2583
		2584	For local paths, this usually doesn't matter: unless the system is very
		2585	busy or the intervals between stat's are large, a stat call will be fast,
		2586	as the path data is usually in memory already (except when starting the
		2587	watcher).
		2588
		2589	For networked file systems, calling C<stat ()> can block an indefinite
		2590	time due to network issues, and even under good conditions, a stat call
		2591	often takes multiple milliseconds.
		2592
		2593	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2594	paths, although this is fully supported by libev.
		2595
1981	=head3 The special problem of stat time resolution	2596	=head3 The special problem of stat time resolution
1982		2597
1983	The C<stat ()> system call only supports full-second resolution portably, and	2598	The C<stat ()> system call only supports full-second resolution portably,
1984	even on systems where the resolution is higher, most file systems still	2599	and even on systems where the resolution is higher, most file systems
1985	only support whole seconds.	2600	still only support whole seconds.
1986		2601
1987	That means that, if the time is the only thing that changes, you can	2602	That means that, if the time is the only thing that changes, you can
1988	easily miss updates: on the first update, C<ev_stat> detects a change and	2603	easily miss updates: on the first update, C<ev_stat> detects a change and
1989	calls your callback, which does something. When there is another update	2604	calls your callback, which does something. When there is another update
1990	within the same second, C<ev_stat> will be unable to detect unless the	2605	within the same second, C<ev_stat> will be unable to detect unless the
…		…
2133		2748
2134	=head3 Watcher-Specific Functions and Data Members	2749	=head3 Watcher-Specific Functions and Data Members
2135		2750
2136	=over 4	2751	=over 4
2137		2752
2138	=item ev_idle_init (ev_signal *, callback)	2753	=item ev_idle_init (ev_idle *, callback)
2139		2754
2140	Initialises and configures the idle watcher - it has no parameters of any	2755	Initialises and configures the idle watcher - it has no parameters of any
2141	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2756	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
2142	believe me.	2757	believe me.
2143		2758
…		…
2156	// no longer anything immediate to do.	2771	// no longer anything immediate to do.
2157	}	2772	}
2158		2773
2159	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2774	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2160	ev_idle_init (idle_watcher, idle_cb);	2775	ev_idle_init (idle_watcher, idle_cb);
2161	ev_idle_start (loop, idle_cb);	2776	ev_idle_start (loop, idle_watcher);
2162		2777
2163		2778
2164	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2779	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2165		2780
2166	Prepare and check watchers are usually (but not always) used in pairs:	2781	Prepare and check watchers are usually (but not always) used in pairs:
2167	prepare watchers get invoked before the process blocks and check watchers	2782	prepare watchers get invoked before the process blocks and check watchers
2168	afterwards.	2783	afterwards.
2169		2784
2170	You I<must not> call C<ev_loop> or similar functions that enter	2785	You I<must not> call C<ev_run> or similar functions that enter
2171	the current event loop from either C<ev_prepare> or C<ev_check>	2786	the current event loop from either C<ev_prepare> or C<ev_check>
2172	watchers. Other loops than the current one are fine, however. The	2787	watchers. Other loops than the current one are fine, however. The
2173	rationale behind this is that you do not need to check for recursion in	2788	rationale behind this is that you do not need to check for recursion in
2174	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2789	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2175	C<ev_check> so if you have one watcher of each kind they will always be	2790	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2259	struct pollfd fds [nfd];	2874	struct pollfd fds [nfd];
2260	// actual code will need to loop here and realloc etc.	2875	// actual code will need to loop here and realloc etc.
2261	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2876	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2262		2877
2263	/* the callback is illegal, but won't be called as we stop during check */	2878	/* the callback is illegal, but won't be called as we stop during check */
2264	ev_timer_init (&tw, 0, timeout * 1e-3);	2879	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2265	ev_timer_start (loop, &tw);	2880	ev_timer_start (loop, &tw);
2266		2881
2267	// create one ev_io per pollfd	2882	// create one ev_io per pollfd
2268	for (int i = 0; i < nfd; ++i)	2883	for (int i = 0; i < nfd; ++i)
2269	{	2884	{
…		…
2343		2958
2344	if (timeout >= 0)	2959	if (timeout >= 0)
2345	// create/start timer	2960	// create/start timer
2346		2961
2347	// poll	2962	// poll
2348	ev_loop (EV_A_ 0);	2963	ev_run (EV_A_ 0);
2349		2964
2350	// stop timer again	2965	// stop timer again
2351	if (timeout >= 0)	2966	if (timeout >= 0)
2352	ev_timer_stop (EV_A_ &to);	2967	ev_timer_stop (EV_A_ &to);
2353		2968
…		…
2382	some fds have to be watched and handled very quickly (with low latency),	2997	some fds have to be watched and handled very quickly (with low latency),
2383	and even priorities and idle watchers might have too much overhead. In	2998	and even priorities and idle watchers might have too much overhead. In
2384	this case you would put all the high priority stuff in one loop and all	2999	this case you would put all the high priority stuff in one loop and all
2385	the rest in a second one, and embed the second one in the first.	3000	the rest in a second one, and embed the second one in the first.
2386		3001
2387	As long as the watcher is active, the callback will be invoked every time	3002	As long as the watcher is active, the callback will be invoked every
2388	there might be events pending in the embedded loop. The callback must then	3003	time there might be events pending in the embedded loop. The callback
2389	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	3004	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2390	their callbacks (you could also start an idle watcher to give the embedded	3005	sweep and invoke their callbacks (the callback doesn't need to invoke the
2391	loop strictly lower priority for example). You can also set the callback	3006	C<ev_embed_sweep> function directly, it could also start an idle watcher
2392	to C<0>, in which case the embed watcher will automatically execute the	3007	to give the embedded loop strictly lower priority for example).
2393	embedded loop sweep.
2394		3008
2395	As long as the watcher is started it will automatically handle events. The	3009	You can also set the callback to C<0>, in which case the embed watcher
2396	callback will be invoked whenever some events have been handled. You can	3010	will automatically execute the embedded loop sweep whenever necessary.
2397	set the callback to C<0> to avoid having to specify one if you are not
2398	interested in that.
2399		3011
2400	Also, there have not currently been made special provisions for forking:	3012	Fork detection will be handled transparently while the C<ev_embed> watcher
2401	when you fork, you not only have to call C<ev_loop_fork> on both loops,	3013	is active, i.e., the embedded loop will automatically be forked when the
2402	but you will also have to stop and restart any C<ev_embed> watchers	3014	embedding loop forks. In other cases, the user is responsible for calling
2403	yourself - but you can use a fork watcher to handle this automatically,	3015	C<ev_loop_fork> on the embedded loop.
2404	and future versions of libev might do just that.
2405		3016
2406	Unfortunately, not all backends are embeddable: only the ones returned by	3017	Unfortunately, not all backends are embeddable: only the ones returned by
2407	C<ev_embeddable_backends> are, which, unfortunately, does not include any	3018	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2408	portable one.	3019	portable one.
2409		3020
…		…
2435	if you do not want that, you need to temporarily stop the embed watcher).	3046	if you do not want that, you need to temporarily stop the embed watcher).
2436		3047
2437	=item ev_embed_sweep (loop, ev_embed *)	3048	=item ev_embed_sweep (loop, ev_embed *)
2438		3049
2439	Make a single, non-blocking sweep over the embedded loop. This works	3050	Make a single, non-blocking sweep over the embedded loop. This works
2440	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3051	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2441	appropriate way for embedded loops.	3052	appropriate way for embedded loops.
2442		3053
2443	=item struct ev_loop *other [read-only]	3054	=item struct ev_loop *other [read-only]
2444		3055
2445	The embedded event loop.	3056	The embedded event loop.
…		…
2503	event loop blocks next and before C<ev_check> watchers are being called,	3114	event loop blocks next and before C<ev_check> watchers are being called,
2504	and only in the child after the fork. If whoever good citizen calling	3115	and only in the child after the fork. If whoever good citizen calling
2505	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3116	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2506	handlers will be invoked, too, of course.	3117	handlers will be invoked, too, of course.
2507		3118
		3119	=head3 The special problem of life after fork - how is it possible?
		3120
		3121	Most uses of C<fork()> consist of forking, then some simple calls to set
		3122	up/change the process environment, followed by a call to C<exec()>. This
		3123	sequence should be handled by libev without any problems.
		3124
		3125	This changes when the application actually wants to do event handling
		3126	in the child, or both parent in child, in effect "continuing" after the
		3127	fork.
		3128
		3129	The default mode of operation (for libev, with application help to detect
		3130	forks) is to duplicate all the state in the child, as would be expected
		3131	when I<either> the parent I<or> the child process continues.
		3132
		3133	When both processes want to continue using libev, then this is usually the
		3134	wrong result. In that case, usually one process (typically the parent) is
		3135	supposed to continue with all watchers in place as before, while the other
		3136	process typically wants to start fresh, i.e. without any active watchers.
		3137
		3138	The cleanest and most efficient way to achieve that with libev is to
		3139	simply create a new event loop, which of course will be "empty", and
		3140	use that for new watchers. This has the advantage of not touching more
		3141	memory than necessary, and thus avoiding the copy-on-write, and the
		3142	disadvantage of having to use multiple event loops (which do not support
		3143	signal watchers).
		3144
		3145	When this is not possible, or you want to use the default loop for
		3146	other reasons, then in the process that wants to start "fresh", call
		3147	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3148	Destroying the default loop will "orphan" (not stop) all registered
		3149	watchers, so you have to be careful not to execute code that modifies
		3150	those watchers. Note also that in that case, you have to re-register any
		3151	signal watchers.
		3152
2508	=head3 Watcher-Specific Functions and Data Members	3153	=head3 Watcher-Specific Functions and Data Members
2509		3154
2510	=over 4	3155	=over 4
2511		3156
2512	=item ev_fork_init (ev_signal *, callback)	3157	=item ev_fork_init (ev_fork *, callback)
2513		3158
2514	Initialises and configures the fork watcher - it has no parameters of any	3159	Initialises and configures the fork watcher - it has no parameters of any
2515	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3160	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2516	believe me.	3161	really.
2517		3162
2518	=back	3163	=back
2519		3164
2520		3165
		3166	=head2 C<ev_cleanup> - even the best things end
		3167
		3168	Cleanup watchers are called just before the event loop is being destroyed
		3169	by a call to C<ev_loop_destroy>.
		3170
		3171	While there is no guarantee that the event loop gets destroyed, cleanup
		3172	watchers provide a convenient method to install cleanup hooks for your
		3173	program, worker threads and so on - you just to make sure to destroy the
		3174	loop when you want them to be invoked.
		3175
		3176	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3177	all other watchers, they do not keep a reference to the event loop (which
		3178	makes a lot of sense if you think about it). Like all other watchers, you
		3179	can call libev functions in the callback, except C<ev_cleanup_start>.
		3180
		3181	=head3 Watcher-Specific Functions and Data Members
		3182
		3183	=over 4
		3184
		3185	=item ev_cleanup_init (ev_cleanup *, callback)
		3186
		3187	Initialises and configures the cleanup watcher - it has no parameters of
		3188	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3189	pointless, I assure you.
		3190
		3191	=back
		3192
		3193	Example: Register an atexit handler to destroy the default loop, so any
		3194	cleanup functions are called.
		3195
		3196	static void
		3197	program_exits (void)
		3198	{
		3199	ev_loop_destroy (EV_DEFAULT_UC);
		3200	}
		3201
		3202	...
		3203	atexit (program_exits);
		3204
		3205
2521	=head2 C<ev_async> - how to wake up another event loop	3206	=head2 C<ev_async> - how to wake up an event loop
2522		3207
2523	In general, you cannot use an C<ev_loop> from multiple threads or other	3208	In general, you cannot use an C<ev_loop> from multiple threads or other
2524	asynchronous sources such as signal handlers (as opposed to multiple event	3209	asynchronous sources such as signal handlers (as opposed to multiple event
2525	loops - those are of course safe to use in different threads).	3210	loops - those are of course safe to use in different threads).
2526		3211
2527	Sometimes, however, you need to wake up another event loop you do not	3212	Sometimes, however, you need to wake up an event loop you do not control,
2528	control, for example because it belongs to another thread. This is what	3213	for example because it belongs to another thread. This is what C<ev_async>
2529	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3214	watchers do: as long as the C<ev_async> watcher is active, you can signal
2530	can signal it by calling C<ev_async_send>, which is thread- and signal	3215	it by calling C<ev_async_send>, which is thread- and signal safe.
2531	safe.
2532		3216
2533	This functionality is very similar to C<ev_signal> watchers, as signals,	3217	This functionality is very similar to C<ev_signal> watchers, as signals,
2534	too, are asynchronous in nature, and signals, too, will be compressed	3218	too, are asynchronous in nature, and signals, too, will be compressed
2535	(i.e. the number of callback invocations may be less than the number of	3219	(i.e. the number of callback invocations may be less than the number of
2536	C<ev_async_sent> calls).	3220	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
		3221	of "global async watchers" by using a watcher on an otherwise unused
		3222	signal, and C<ev_feed_signal> to signal this watcher from another thread,
		3223	even without knowing which loop owns the signal.
2537		3224
2538	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3225	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
2539	just the default loop.	3226	just the default loop.
2540		3227
2541	=head3 Queueing	3228	=head3 Queueing
2542		3229
2543	C<ev_async> does not support queueing of data in any way. The reason	3230	C<ev_async> does not support queueing of data in any way. The reason
2544	is that the author does not know of a simple (or any) algorithm for a	3231	is that the author does not know of a simple (or any) algorithm for a
2545	multiple-writer-single-reader queue that works in all cases and doesn't	3232	multiple-writer-single-reader queue that works in all cases and doesn't
2546	need elaborate support such as pthreads.	3233	need elaborate support such as pthreads or unportable memory access
		3234	semantics.
2547		3235
2548	That means that if you want to queue data, you have to provide your own	3236	That means that if you want to queue data, you have to provide your own
2549	queue. But at least I can tell you how to implement locking around your	3237	queue. But at least I can tell you how to implement locking around your
2550	queue:	3238	queue:
2551		3239
…		…
2629	=over 4	3317	=over 4
2630		3318
2631	=item ev_async_init (ev_async *, callback)	3319	=item ev_async_init (ev_async *, callback)
2632		3320
2633	Initialises and configures the async watcher - it has no parameters of any	3321	Initialises and configures the async watcher - it has no parameters of any
2634	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3322	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2635	trust me.	3323	trust me.
2636		3324
2637	=item ev_async_send (loop, ev_async *)	3325	=item ev_async_send (loop, ev_async *)
2638		3326
2639	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3327	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2640	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3328	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3329	returns.
		3330
2641	C<ev_feed_event>, this call is safe to do from other threads, signal or	3331	Unlike C<ev_feed_event>, this call is safe to do from other threads,
2642	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3332	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
2643	section below on what exactly this means).	3333	embedding section below on what exactly this means).
2644		3334
		3335	Note that, as with other watchers in libev, multiple events might get
		3336	compressed into a single callback invocation (another way to look at this
		3337	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3338	reset when the event loop detects that).
		3339
2645	This call incurs the overhead of a system call only once per loop iteration,	3340	This call incurs the overhead of a system call only once per event loop
2646	so while the overhead might be noticeable, it doesn't apply to repeated	3341	iteration, so while the overhead might be noticeable, it doesn't apply to
2647	calls to C<ev_async_send>.	3342	repeated calls to C<ev_async_send> for the same event loop.
2648		3343
2649	=item bool = ev_async_pending (ev_async *)	3344	=item bool = ev_async_pending (ev_async *)
2650		3345
2651	Returns a non-zero value when C<ev_async_send> has been called on the	3346	Returns a non-zero value when C<ev_async_send> has been called on the
2652	watcher but the event has not yet been processed (or even noted) by the	3347	watcher but the event has not yet been processed (or even noted) by the
…		…
2655	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3350	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2656	the loop iterates next and checks for the watcher to have become active,	3351	the loop iterates next and checks for the watcher to have become active,
2657	it will reset the flag again. C<ev_async_pending> can be used to very	3352	it will reset the flag again. C<ev_async_pending> can be used to very
2658	quickly check whether invoking the loop might be a good idea.	3353	quickly check whether invoking the loop might be a good idea.
2659		3354
2660	Not that this does I<not> check whether the watcher itself is pending, only	3355	Not that this does I<not> check whether the watcher itself is pending,
2661	whether it has been requested to make this watcher pending.	3356	only whether it has been requested to make this watcher pending: there
		3357	is a time window between the event loop checking and resetting the async
		3358	notification, and the callback being invoked.
2662		3359
2663	=back	3360	=back
2664		3361
2665		3362
2666	=head1 OTHER FUNCTIONS	3363	=head1 OTHER FUNCTIONS
…		…
2683		3380
2684	If C<timeout> is less than 0, then no timeout watcher will be	3381	If C<timeout> is less than 0, then no timeout watcher will be
2685	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3382	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2686	repeat = 0) will be started. C<0> is a valid timeout.	3383	repeat = 0) will be started. C<0> is a valid timeout.
2687		3384
2688	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3385	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2689	passed an C<revents> set like normal event callbacks (a combination of	3386	passed an C<revents> set like normal event callbacks (a combination of
2690	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3387	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2691	value passed to C<ev_once>. Note that it is possible to receive I<both>	3388	value passed to C<ev_once>. Note that it is possible to receive I<both>
2692	a timeout and an io event at the same time - you probably should give io	3389	a timeout and an io event at the same time - you probably should give io
2693	events precedence.	3390	events precedence.
2694		3391
2695	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3392	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2696		3393
2697	static void stdin_ready (int revents, void *arg)	3394	static void stdin_ready (int revents, void *arg)
2698	{	3395	{
2699	if (revents & EV_READ)	3396	if (revents & EV_READ)
2700	/* stdin might have data for us, joy! */;	3397	/* stdin might have data for us, joy! */;
2701	else if (revents & EV_TIMEOUT)	3398	else if (revents & EV_TIMER)
2702	/* doh, nothing entered */;	3399	/* doh, nothing entered */;
2703	}	3400	}
2704		3401
2705	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3402	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2706		3403
2707	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2708
2709	Feeds the given event set into the event loop, as if the specified event
2710	had happened for the specified watcher (which must be a pointer to an
2711	initialised but not necessarily started event watcher).
2712
2713	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3404	=item ev_feed_fd_event (loop, int fd, int revents)
2714		3405
2715	Feed an event on the given fd, as if a file descriptor backend detected	3406	Feed an event on the given fd, as if a file descriptor backend detected
2716	the given events it.	3407	the given events it.
2717		3408
2718	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3409	=item ev_feed_signal_event (loop, int signum)
2719		3410
2720	Feed an event as if the given signal occurred (C<loop> must be the default	3411	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
2721	loop!).	3412	which is async-safe.
2722		3413
2723	=back	3414	=back
		3415
		3416
		3417	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3418
		3419	This section explains some common idioms that are not immediately
		3420	obvious. Note that examples are sprinkled over the whole manual, and this
		3421	section only contains stuff that wouldn't fit anywhere else.
		3422
		3423	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3424
		3425	Each watcher has, by default, a C<void *data> member that you can read
		3426	or modify at any time: libev will completely ignore it. This can be used
		3427	to associate arbitrary data with your watcher. If you need more data and
		3428	don't want to allocate memory separately and store a pointer to it in that
		3429	data member, you can also "subclass" the watcher type and provide your own
		3430	data:
		3431
		3432	struct my_io
		3433	{
		3434	ev_io io;
		3435	int otherfd;
		3436	void *somedata;
		3437	struct whatever *mostinteresting;
		3438	};
		3439
		3440	...
		3441	struct my_io w;
		3442	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3443
		3444	And since your callback will be called with a pointer to the watcher, you
		3445	can cast it back to your own type:
		3446
		3447	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3448	{
		3449	struct my_io *w = (struct my_io *)w_;
		3450	...
		3451	}
		3452
		3453	More interesting and less C-conformant ways of casting your callback
		3454	function type instead have been omitted.
		3455
		3456	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3457
		3458	Another common scenario is to use some data structure with multiple
		3459	embedded watchers, in effect creating your own watcher that combines
		3460	multiple libev event sources into one "super-watcher":
		3461
		3462	struct my_biggy
		3463	{
		3464	int some_data;
		3465	ev_timer t1;
		3466	ev_timer t2;
		3467	}
		3468
		3469	In this case getting the pointer to C<my_biggy> is a bit more
		3470	complicated: Either you store the address of your C<my_biggy> struct in
		3471	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3472	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3473	real programmers):
		3474
		3475	#include <stddef.h>
		3476
		3477	static void
		3478	t1_cb (EV_P_ ev_timer *w, int revents)
		3479	{
		3480	struct my_biggy big = (struct my_biggy *)
		3481	(((char *)w) - offsetof (struct my_biggy, t1));
		3482	}
		3483
		3484	static void
		3485	t2_cb (EV_P_ ev_timer *w, int revents)
		3486	{
		3487	struct my_biggy big = (struct my_biggy *)
		3488	(((char *)w) - offsetof (struct my_biggy, t2));
		3489	}
		3490
		3491	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3492
		3493	Often (especially in GUI toolkits) there are places where you have
		3494	I<modal> interaction, which is most easily implemented by recursively
		3495	invoking C<ev_run>.
		3496
		3497	This brings the problem of exiting - a callback might want to finish the
		3498	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3499	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3500	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3501	other combination: In these cases, C<ev_break> will not work alone.
		3502
		3503	The solution is to maintain "break this loop" variable for each C<ev_run>
		3504	invocation, and use a loop around C<ev_run> until the condition is
		3505	triggered, using C<EVRUN_ONCE>:
		3506
		3507	// main loop
		3508	int exit_main_loop = 0;
		3509
		3510	while (!exit_main_loop)
		3511	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3512
		3513	// in a model watcher
		3514	int exit_nested_loop = 0;
		3515
		3516	while (!exit_nested_loop)
		3517	ev_run (EV_A_ EVRUN_ONCE);
		3518
		3519	To exit from any of these loops, just set the corresponding exit variable:
		3520
		3521	// exit modal loop
		3522	exit_nested_loop = 1;
		3523
		3524	// exit main program, after modal loop is finished
		3525	exit_main_loop = 1;
		3526
		3527	// exit both
		3528	exit_main_loop = exit_nested_loop = 1;
		3529
		3530	=head2 THREAD LOCKING EXAMPLE
		3531
		3532	Here is a fictitious example of how to run an event loop in a different
		3533	thread from where callbacks are being invoked and watchers are
		3534	created/added/removed.
		3535
		3536	For a real-world example, see the C<EV::Loop::Async> perl module,
		3537	which uses exactly this technique (which is suited for many high-level
		3538	languages).
		3539
		3540	The example uses a pthread mutex to protect the loop data, a condition
		3541	variable to wait for callback invocations, an async watcher to notify the
		3542	event loop thread and an unspecified mechanism to wake up the main thread.
		3543
		3544	First, you need to associate some data with the event loop:
		3545
		3546	typedef struct {
		3547	mutex_t lock; /* global loop lock */
		3548	ev_async async_w;
		3549	thread_t tid;
		3550	cond_t invoke_cv;
		3551	} userdata;
		3552
		3553	void prepare_loop (EV_P)
		3554	{
		3555	// for simplicity, we use a static userdata struct.
		3556	static userdata u;
		3557
		3558	ev_async_init (&u->async_w, async_cb);
		3559	ev_async_start (EV_A_ &u->async_w);
		3560
		3561	pthread_mutex_init (&u->lock, 0);
		3562	pthread_cond_init (&u->invoke_cv, 0);
		3563
		3564	// now associate this with the loop
		3565	ev_set_userdata (EV_A_ u);
		3566	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3567	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3568
		3569	// then create the thread running ev_run
		3570	pthread_create (&u->tid, 0, l_run, EV_A);
		3571	}
		3572
		3573	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3574	solely to wake up the event loop so it takes notice of any new watchers
		3575	that might have been added:
		3576
		3577	static void
		3578	async_cb (EV_P_ ev_async *w, int revents)
		3579	{
		3580	// just used for the side effects
		3581	}
		3582
		3583	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3584	protecting the loop data, respectively.
		3585
		3586	static void
		3587	l_release (EV_P)
		3588	{
		3589	userdata *u = ev_userdata (EV_A);
		3590	pthread_mutex_unlock (&u->lock);
		3591	}
		3592
		3593	static void
		3594	l_acquire (EV_P)
		3595	{
		3596	userdata *u = ev_userdata (EV_A);
		3597	pthread_mutex_lock (&u->lock);
		3598	}
		3599
		3600	The event loop thread first acquires the mutex, and then jumps straight
		3601	into C<ev_run>:
		3602
		3603	void *
		3604	l_run (void *thr_arg)
		3605	{
		3606	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3607
		3608	l_acquire (EV_A);
		3609	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3610	ev_run (EV_A_ 0);
		3611	l_release (EV_A);
		3612
		3613	return 0;
		3614	}
		3615
		3616	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3617	signal the main thread via some unspecified mechanism (signals? pipe
		3618	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3619	have been called (in a while loop because a) spurious wakeups are possible
		3620	and b) skipping inter-thread-communication when there are no pending
		3621	watchers is very beneficial):
		3622
		3623	static void
		3624	l_invoke (EV_P)
		3625	{
		3626	userdata *u = ev_userdata (EV_A);
		3627
		3628	while (ev_pending_count (EV_A))
		3629	{
		3630	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3631	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3632	}
		3633	}
		3634
		3635	Now, whenever the main thread gets told to invoke pending watchers, it
		3636	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3637	thread to continue:
		3638
		3639	static void
		3640	real_invoke_pending (EV_P)
		3641	{
		3642	userdata *u = ev_userdata (EV_A);
		3643
		3644	pthread_mutex_lock (&u->lock);
		3645	ev_invoke_pending (EV_A);
		3646	pthread_cond_signal (&u->invoke_cv);
		3647	pthread_mutex_unlock (&u->lock);
		3648	}
		3649
		3650	Whenever you want to start/stop a watcher or do other modifications to an
		3651	event loop, you will now have to lock:
		3652
		3653	ev_timer timeout_watcher;
		3654	userdata *u = ev_userdata (EV_A);
		3655
		3656	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3657
		3658	pthread_mutex_lock (&u->lock);
		3659	ev_timer_start (EV_A_ &timeout_watcher);
		3660	ev_async_send (EV_A_ &u->async_w);
		3661	pthread_mutex_unlock (&u->lock);
		3662
		3663	Note that sending the C<ev_async> watcher is required because otherwise
		3664	an event loop currently blocking in the kernel will have no knowledge
		3665	about the newly added timer. By waking up the loop it will pick up any new
		3666	watchers in the next event loop iteration.
		3667
		3668	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3669
		3670	While the overhead of a callback that e.g. schedules a thread is small, it
		3671	is still an overhead. If you embed libev, and your main usage is with some
		3672	kind of threads or coroutines, you might want to customise libev so that
		3673	doesn't need callbacks anymore.
		3674
		3675	Imagine you have coroutines that you can switch to using a function
		3676	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3677	and that due to some magic, the currently active coroutine is stored in a
		3678	global called C<current_coro>. Then you can build your own "wait for libev
		3679	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3680	the differing C<;> conventions):
		3681
		3682	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3683	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3684
		3685	That means instead of having a C callback function, you store the
		3686	coroutine to switch to in each watcher, and instead of having libev call
		3687	your callback, you instead have it switch to that coroutine.
		3688
		3689	A coroutine might now wait for an event with a function called
		3690	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3691	matter when, or whether the watcher is active or not when this function is
		3692	called):
		3693
		3694	void
		3695	wait_for_event (ev_watcher *w)
		3696	{
		3697	ev_cb_set (w) = current_coro;
		3698	switch_to (libev_coro);
		3699	}
		3700
		3701	That basically suspends the coroutine inside C<wait_for_event> and
		3702	continues the libev coroutine, which, when appropriate, switches back to
		3703	this or any other coroutine. I am sure if you sue this your own :)
		3704
		3705	You can do similar tricks if you have, say, threads with an event queue -
		3706	instead of storing a coroutine, you store the queue object and instead of
		3707	switching to a coroutine, you push the watcher onto the queue and notify
		3708	any waiters.
		3709
		3710	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3711	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3712
		3713	// my_ev.h
		3714	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3715	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3716	#include "../libev/ev.h"
		3717
		3718	// my_ev.c
		3719	#define EV_H "my_ev.h"
		3720	#include "../libev/ev.c"
		3721
		3722	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3723	F<my_ev.c> into your project. When properly specifying include paths, you
		3724	can even use F<ev.h> as header file name directly.
2724		3725
2725		3726
2726	=head1 LIBEVENT EMULATION	3727	=head1 LIBEVENT EMULATION
2727		3728
2728	Libev offers a compatibility emulation layer for libevent. It cannot	3729	Libev offers a compatibility emulation layer for libevent. It cannot
2729	emulate the internals of libevent, so here are some usage hints:	3730	emulate the internals of libevent, so here are some usage hints:
2730		3731
2731	=over 4	3732	=over 4
		3733
		3734	=item * Only the libevent-1.4.1-beta API is being emulated.
		3735
		3736	This was the newest libevent version available when libev was implemented,
		3737	and is still mostly unchanged in 2010.
2732		3738
2733	=item * Use it by including <event.h>, as usual.	3739	=item * Use it by including <event.h>, as usual.
2734		3740
2735	=item * The following members are fully supported: ev_base, ev_callback,	3741	=item * The following members are fully supported: ev_base, ev_callback,
2736	ev_arg, ev_fd, ev_res, ev_events.	3742	ev_arg, ev_fd, ev_res, ev_events.
…		…
2742	=item * Priorities are not currently supported. Initialising priorities	3748	=item * Priorities are not currently supported. Initialising priorities
2743	will fail and all watchers will have the same priority, even though there	3749	will fail and all watchers will have the same priority, even though there
2744	is an ev_pri field.	3750	is an ev_pri field.
2745		3751
2746	=item * In libevent, the last base created gets the signals, in libev, the	3752	=item * In libevent, the last base created gets the signals, in libev, the
2747	first base created (== the default loop) gets the signals.	3753	base that registered the signal gets the signals.
2748		3754
2749	=item * Other members are not supported.	3755	=item * Other members are not supported.
2750		3756
2751	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3757	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2752	to use the libev header file and library.	3758	to use the libev header file and library.
…		…
2771	Care has been taken to keep the overhead low. The only data member the C++	3777	Care has been taken to keep the overhead low. The only data member the C++
2772	classes add (compared to plain C-style watchers) is the event loop pointer	3778	classes add (compared to plain C-style watchers) is the event loop pointer
2773	that the watcher is associated with (or no additional members at all if	3779	that the watcher is associated with (or no additional members at all if
2774	you disable C<EV_MULTIPLICITY> when embedding libev).	3780	you disable C<EV_MULTIPLICITY> when embedding libev).
2775		3781
2776	Currently, functions, and static and non-static member functions can be	3782	Currently, functions, static and non-static member functions and classes
2777	used as callbacks. Other types should be easy to add as long as they only	3783	with C<operator ()> can be used as callbacks. Other types should be easy
2778	need one additional pointer for context. If you need support for other	3784	to add as long as they only need one additional pointer for context. If
2779	types of functors please contact the author (preferably after implementing	3785	you need support for other types of functors please contact the author
2780	it).	3786	(preferably after implementing it).
2781		3787
2782	Here is a list of things available in the C<ev> namespace:	3788	Here is a list of things available in the C<ev> namespace:
2783		3789
2784	=over 4	3790	=over 4
2785		3791
…		…
2803		3809
2804	=over 4	3810	=over 4
2805		3811
2806	=item ev::TYPE::TYPE ()	3812	=item ev::TYPE::TYPE ()
2807		3813
2808	=item ev::TYPE::TYPE (struct ev_loop *)	3814	=item ev::TYPE::TYPE (loop)
2809		3815
2810	=item ev::TYPE::~TYPE	3816	=item ev::TYPE::~TYPE
2811		3817
2812	The constructor (optionally) takes an event loop to associate the watcher	3818	The constructor (optionally) takes an event loop to associate the watcher
2813	with. If it is omitted, it will use C<EV_DEFAULT>.	3819	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2845		3851
2846	myclass obj;	3852	myclass obj;
2847	ev::io iow;	3853	ev::io iow;
2848	iow.set <myclass, &myclass::io_cb> (&obj);	3854	iow.set <myclass, &myclass::io_cb> (&obj);
2849		3855
		3856	=item w->set (object *)
		3857
		3858	This is a variation of a method callback - leaving out the method to call
		3859	will default the method to C<operator ()>, which makes it possible to use
		3860	functor objects without having to manually specify the C<operator ()> all
		3861	the time. Incidentally, you can then also leave out the template argument
		3862	list.
		3863
		3864	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3865	int revents)>.
		3866
		3867	See the method-C<set> above for more details.
		3868
		3869	Example: use a functor object as callback.
		3870
		3871	struct myfunctor
		3872	{
		3873	void operator() (ev::io &w, int revents)
		3874	{
		3875	...
		3876	}
		3877	}
		3878
		3879	myfunctor f;
		3880
		3881	ev::io w;
		3882	w.set (&f);
		3883
2850	=item w->set<function> (void *data = 0)	3884	=item w->set<function> (void *data = 0)
2851		3885
2852	Also sets a callback, but uses a static method or plain function as	3886	Also sets a callback, but uses a static method or plain function as
2853	callback. The optional C<data> argument will be stored in the watcher's	3887	callback. The optional C<data> argument will be stored in the watcher's
2854	C<data> member and is free for you to use.	3888	C<data> member and is free for you to use.
…		…
2860	Example: Use a plain function as callback.	3894	Example: Use a plain function as callback.
2861		3895
2862	static void io_cb (ev::io &w, int revents) { }	3896	static void io_cb (ev::io &w, int revents) { }
2863	iow.set <io_cb> ();	3897	iow.set <io_cb> ();
2864		3898
2865	=item w->set (struct ev_loop *)	3899	=item w->set (loop)
2866		3900
2867	Associates a different C<struct ev_loop> with this watcher. You can only	3901	Associates a different C<struct ev_loop> with this watcher. You can only
2868	do this when the watcher is inactive (and not pending either).	3902	do this when the watcher is inactive (and not pending either).
2869		3903
2870	=item w->set ([arguments])	3904	=item w->set ([arguments])
2871		3905
2872	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3906	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
2873	called at least once. Unlike the C counterpart, an active watcher gets	3907	method or a suitable start method must be called at least once. Unlike the
2874	automatically stopped and restarted when reconfiguring it with this	3908	C counterpart, an active watcher gets automatically stopped and restarted
2875	method.	3909	when reconfiguring it with this method.
2876		3910
2877	=item w->start ()	3911	=item w->start ()
2878		3912
2879	Starts the watcher. Note that there is no C<loop> argument, as the	3913	Starts the watcher. Note that there is no C<loop> argument, as the
2880	constructor already stores the event loop.	3914	constructor already stores the event loop.
2881		3915
		3916	=item w->start ([arguments])
		3917
		3918	Instead of calling C<set> and C<start> methods separately, it is often
		3919	convenient to wrap them in one call. Uses the same type of arguments as
		3920	the configure C<set> method of the watcher.
		3921
2882	=item w->stop ()	3922	=item w->stop ()
2883		3923
2884	Stops the watcher if it is active. Again, no C<loop> argument.	3924	Stops the watcher if it is active. Again, no C<loop> argument.
2885		3925
2886	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3926	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2898		3938
2899	=back	3939	=back
2900		3940
2901	=back	3941	=back
2902		3942
2903	Example: Define a class with an IO and idle watcher, start one of them in	3943	Example: Define a class with two I/O and idle watchers, start the I/O
2904	the constructor.	3944	watchers in the constructor.
2905		3945
2906	class myclass	3946	class myclass
2907	{	3947	{
2908	ev::io io ; void io_cb (ev::io &w, int revents);	3948	ev::io io ; void io_cb (ev::io &w, int revents);
		3949	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
2909	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3950	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2910		3951
2911	myclass (int fd)	3952	myclass (int fd)
2912	{	3953	{
2913	io .set <myclass, &myclass::io_cb > (this);	3954	io .set <myclass, &myclass::io_cb > (this);
		3955	io2 .set <myclass, &myclass::io2_cb > (this);
2914	idle.set <myclass, &myclass::idle_cb> (this);	3956	idle.set <myclass, &myclass::idle_cb> (this);
2915		3957
2916	io.start (fd, ev::READ);	3958	io.set (fd, ev::WRITE); // configure the watcher
		3959	io.start (); // start it whenever convenient
		3960
		3961	io2.start (fd, ev::READ); // set + start in one call
2917	}	3962	}
2918	};	3963	};
2919		3964
2920		3965
2921	=head1 OTHER LANGUAGE BINDINGS	3966	=head1 OTHER LANGUAGE BINDINGS
…		…
2940	L<http://software.schmorp.de/pkg/EV>.	3985	L<http://software.schmorp.de/pkg/EV>.
2941		3986
2942	=item Python	3987	=item Python
2943		3988
2944	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3989	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2945	seems to be quite complete and well-documented. Note, however, that the	3990	seems to be quite complete and well-documented.
2946	patch they require for libev is outright dangerous as it breaks the ABI
2947	for everybody else, and therefore, should never be applied in an installed
2948	libev (if python requires an incompatible ABI then it needs to embed
2949	libev).
2950		3991
2951	=item Ruby	3992	=item Ruby
2952		3993
2953	Tony Arcieri has written a ruby extension that offers access to a subset	3994	Tony Arcieri has written a ruby extension that offers access to a subset
2954	of the libev API and adds file handle abstractions, asynchronous DNS and	3995	of the libev API and adds file handle abstractions, asynchronous DNS and
2955	more on top of it. It can be found via gem servers. Its homepage is at	3996	more on top of it. It can be found via gem servers. Its homepage is at
2956	L<http://rev.rubyforge.org/>.	3997	L<http://rev.rubyforge.org/>.
2957		3998
		3999	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		4000	makes rev work even on mingw.
		4001
		4002	=item Haskell
		4003
		4004	A haskell binding to libev is available at
		4005	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		4006
2958	=item D	4007	=item D
2959		4008
2960	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4009	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2961	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4010	be found at L<http://proj.llucax.com.ar/wiki/evd>.
2962		4011
2963	=item Ocaml	4012	=item Ocaml
2964		4013
2965	Erkki Seppala has written Ocaml bindings for libev, to be found at	4014	Erkki Seppala has written Ocaml bindings for libev, to be found at
2966	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4015	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		4016
		4017	=item Lua
		4018
		4019	Brian Maher has written a partial interface to libev for lua (at the
		4020	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		4021	L<http://github.com/brimworks/lua-ev>.
2967		4022
2968	=back	4023	=back
2969		4024
2970		4025
2971	=head1 MACRO MAGIC	4026	=head1 MACRO MAGIC
…		…
2985	loop argument"). The C<EV_A> form is used when this is the sole argument,	4040	loop argument"). The C<EV_A> form is used when this is the sole argument,
2986	C<EV_A_> is used when other arguments are following. Example:	4041	C<EV_A_> is used when other arguments are following. Example:
2987		4042
2988	ev_unref (EV_A);	4043	ev_unref (EV_A);
2989	ev_timer_add (EV_A_ watcher);	4044	ev_timer_add (EV_A_ watcher);
2990	ev_loop (EV_A_ 0);	4045	ev_run (EV_A_ 0);
2991		4046
2992	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4047	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2993	which is often provided by the following macro.	4048	which is often provided by the following macro.
2994		4049
2995	=item C<EV_P>, C<EV_P_>	4050	=item C<EV_P>, C<EV_P_>
…		…
3035	}	4090	}
3036		4091
3037	ev_check check;	4092	ev_check check;
3038	ev_check_init (&check, check_cb);	4093	ev_check_init (&check, check_cb);
3039	ev_check_start (EV_DEFAULT_ &check);	4094	ev_check_start (EV_DEFAULT_ &check);
3040	ev_loop (EV_DEFAULT_ 0);	4095	ev_run (EV_DEFAULT_ 0);
3041		4096
3042	=head1 EMBEDDING	4097	=head1 EMBEDDING
3043		4098
3044	Libev can (and often is) directly embedded into host	4099	Libev can (and often is) directly embedded into host
3045	applications. Examples of applications that embed it include the Deliantra	4100	applications. Examples of applications that embed it include the Deliantra
…		…
3072		4127
3073	#define EV_STANDALONE 1	4128	#define EV_STANDALONE 1
3074	#include "ev.h"	4129	#include "ev.h"
3075		4130
3076	Both header files and implementation files can be compiled with a C++	4131	Both header files and implementation files can be compiled with a C++
3077	compiler (at least, thats a stated goal, and breakage will be treated	4132	compiler (at least, that's a stated goal, and breakage will be treated
3078	as a bug).	4133	as a bug).
3079		4134
3080	You need the following files in your source tree, or in a directory	4135	You need the following files in your source tree, or in a directory
3081	in your include path (e.g. in libev/ when using -Ilibev):	4136	in your include path (e.g. in libev/ when using -Ilibev):
3082		4137
…		…
3125	libev.m4	4180	libev.m4
3126		4181
3127	=head2 PREPROCESSOR SYMBOLS/MACROS	4182	=head2 PREPROCESSOR SYMBOLS/MACROS
3128		4183
3129	Libev can be configured via a variety of preprocessor symbols you have to	4184	Libev can be configured via a variety of preprocessor symbols you have to
3130	define before including any of its files. The default in the absence of	4185	define before including (or compiling) any of its files. The default in
3131	autoconf is documented for every option.	4186	the absence of autoconf is documented for every option.
		4187
		4188	Symbols marked with "(h)" do not change the ABI, and can have different
		4189	values when compiling libev vs. including F<ev.h>, so it is permissible
		4190	to redefine them before including F<ev.h> without breaking compatibility
		4191	to a compiled library. All other symbols change the ABI, which means all
		4192	users of libev and the libev code itself must be compiled with compatible
		4193	settings.
3132		4194
3133	=over 4	4195	=over 4
3134		4196
		4197	=item EV_COMPAT3 (h)
		4198
		4199	Backwards compatibility is a major concern for libev. This is why this
		4200	release of libev comes with wrappers for the functions and symbols that
		4201	have been renamed between libev version 3 and 4.
		4202
		4203	You can disable these wrappers (to test compatibility with future
		4204	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4205	sources. This has the additional advantage that you can drop the C<struct>
		4206	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4207	typedef in that case.
		4208
		4209	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4210	and in some even more future version the compatibility code will be
		4211	removed completely.
		4212
3135	=item EV_STANDALONE	4213	=item EV_STANDALONE (h)
3136		4214
3137	Must always be C<1> if you do not use autoconf configuration, which	4215	Must always be C<1> if you do not use autoconf configuration, which
3138	keeps libev from including F<config.h>, and it also defines dummy	4216	keeps libev from including F<config.h>, and it also defines dummy
3139	implementations for some libevent functions (such as logging, which is not	4217	implementations for some libevent functions (such as logging, which is not
3140	supported). It will also not define any of the structs usually found in	4218	supported). It will also not define any of the structs usually found in
3141	F<event.h> that are not directly supported by the libev core alone.	4219	F<event.h> that are not directly supported by the libev core alone.
3142		4220
		4221	In standalone mode, libev will still try to automatically deduce the
		4222	configuration, but has to be more conservative.
		4223
		4224	=item EV_USE_FLOOR
		4225
		4226	If defined to be C<1>, libev will use the C<floor ()> function for its
		4227	periodic reschedule calculations, otherwise libev will fall back on a
		4228	portable (slower) implementation. If you enable this, you usually have to
		4229	link against libm or something equivalent. Enabling this when the C<floor>
		4230	function is not available will fail, so the safe default is to not enable
		4231	this.
		4232
3143	=item EV_USE_MONOTONIC	4233	=item EV_USE_MONOTONIC
3144		4234
3145	If defined to be C<1>, libev will try to detect the availability of the	4235	If defined to be C<1>, libev will try to detect the availability of the
3146	monotonic clock option at both compile time and runtime. Otherwise no use	4236	monotonic clock option at both compile time and runtime. Otherwise no
3147	of the monotonic clock option will be attempted. If you enable this, you	4237	use of the monotonic clock option will be attempted. If you enable this,
3148	usually have to link against librt or something similar. Enabling it when	4238	you usually have to link against librt or something similar. Enabling it
3149	the functionality isn't available is safe, though, although you have	4239	when the functionality isn't available is safe, though, although you have
3150	to make sure you link against any libraries where the C<clock_gettime>	4240	to make sure you link against any libraries where the C<clock_gettime>
3151	function is hiding in (often F<-lrt>).	4241	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
3152		4242
3153	=item EV_USE_REALTIME	4243	=item EV_USE_REALTIME
3154		4244
3155	If defined to be C<1>, libev will try to detect the availability of the	4245	If defined to be C<1>, libev will try to detect the availability of the
3156	real-time clock option at compile time (and assume its availability at	4246	real-time clock option at compile time (and assume its availability
3157	runtime if successful). Otherwise no use of the real-time clock option will	4247	at runtime if successful). Otherwise no use of the real-time clock
3158	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	4248	option will be attempted. This effectively replaces C<gettimeofday>
3159	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	4249	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
3160	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	4250	correctness. See the note about libraries in the description of
		4251	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		4252	C<EV_USE_CLOCK_SYSCALL>.
		4253
		4254	=item EV_USE_CLOCK_SYSCALL
		4255
		4256	If defined to be C<1>, libev will try to use a direct syscall instead
		4257	of calling the system-provided C<clock_gettime> function. This option
		4258	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		4259	unconditionally pulls in C<libpthread>, slowing down single-threaded
		4260	programs needlessly. Using a direct syscall is slightly slower (in
		4261	theory), because no optimised vdso implementation can be used, but avoids
		4262	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		4263	higher, as it simplifies linking (no need for C<-lrt>).
3161		4264
3162	=item EV_USE_NANOSLEEP	4265	=item EV_USE_NANOSLEEP
3163		4266
3164	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	4267	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
3165	and will use it for delays. Otherwise it will use C<select ()>.	4268	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3181		4284
3182	=item EV_SELECT_USE_FD_SET	4285	=item EV_SELECT_USE_FD_SET
3183		4286
3184	If defined to C<1>, then the select backend will use the system C<fd_set>	4287	If defined to C<1>, then the select backend will use the system C<fd_set>
3185	structure. This is useful if libev doesn't compile due to a missing	4288	structure. This is useful if libev doesn't compile due to a missing
3186	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	4289	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3187	exotic systems. This usually limits the range of file descriptors to some	4290	on exotic systems. This usually limits the range of file descriptors to
3188	low limit such as 1024 or might have other limitations (winsocket only	4291	some low limit such as 1024 or might have other limitations (winsocket
3189	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	4292	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3190	influence the size of the C<fd_set> used.	4293	configures the maximum size of the C<fd_set>.
3191		4294
3192	=item EV_SELECT_IS_WINSOCKET	4295	=item EV_SELECT_IS_WINSOCKET
3193		4296
3194	When defined to C<1>, the select backend will assume that	4297	When defined to C<1>, the select backend will assume that
3195	select/socket/connect etc. don't understand file descriptors but	4298	select/socket/connect etc. don't understand file descriptors but
…		…
3197	be used is the winsock select). This means that it will call	4300	be used is the winsock select). This means that it will call
3198	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4301	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3199	it is assumed that all these functions actually work on fds, even	4302	it is assumed that all these functions actually work on fds, even
3200	on win32. Should not be defined on non-win32 platforms.	4303	on win32. Should not be defined on non-win32 platforms.
3201		4304
3202	=item EV_FD_TO_WIN32_HANDLE	4305	=item EV_FD_TO_WIN32_HANDLE(fd)
3203		4306
3204	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4307	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3205	file descriptors to socket handles. When not defining this symbol (the	4308	file descriptors to socket handles. When not defining this symbol (the
3206	default), then libev will call C<_get_osfhandle>, which is usually	4309	default), then libev will call C<_get_osfhandle>, which is usually
3207	correct. In some cases, programs use their own file descriptor management,	4310	correct. In some cases, programs use their own file descriptor management,
3208	in which case they can provide this function to map fds to socket handles.	4311	in which case they can provide this function to map fds to socket handles.
		4312
		4313	=item EV_WIN32_HANDLE_TO_FD(handle)
		4314
		4315	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4316	using the standard C<_open_osfhandle> function. For programs implementing
		4317	their own fd to handle mapping, overwriting this function makes it easier
		4318	to do so. This can be done by defining this macro to an appropriate value.
		4319
		4320	=item EV_WIN32_CLOSE_FD(fd)
		4321
		4322	If programs implement their own fd to handle mapping on win32, then this
		4323	macro can be used to override the C<close> function, useful to unregister
		4324	file descriptors again. Note that the replacement function has to close
		4325	the underlying OS handle.
3209		4326
3210	=item EV_USE_POLL	4327	=item EV_USE_POLL
3211		4328
3212	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4329	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3213	backend. Otherwise it will be enabled on non-win32 platforms. It	4330	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3260	as well as for signal and thread safety in C<ev_async> watchers.	4377	as well as for signal and thread safety in C<ev_async> watchers.
3261		4378
3262	In the absence of this define, libev will use C<sig_atomic_t volatile>	4379	In the absence of this define, libev will use C<sig_atomic_t volatile>
3263	(from F<signal.h>), which is usually good enough on most platforms.	4380	(from F<signal.h>), which is usually good enough on most platforms.
3264		4381
3265	=item EV_H	4382	=item EV_H (h)
3266		4383
3267	The name of the F<ev.h> header file used to include it. The default if	4384	The name of the F<ev.h> header file used to include it. The default if
3268	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4385	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3269	used to virtually rename the F<ev.h> header file in case of conflicts.	4386	used to virtually rename the F<ev.h> header file in case of conflicts.
3270		4387
3271	=item EV_CONFIG_H	4388	=item EV_CONFIG_H (h)
3272		4389
3273	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4390	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3274	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4391	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3275	C<EV_H>, above.	4392	C<EV_H>, above.
3276		4393
3277	=item EV_EVENT_H	4394	=item EV_EVENT_H (h)
3278		4395
3279	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4396	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3280	of how the F<event.h> header can be found, the default is C<"event.h">.	4397	of how the F<event.h> header can be found, the default is C<"event.h">.
3281		4398
3282	=item EV_PROTOTYPES	4399	=item EV_PROTOTYPES (h)
3283		4400
3284	If defined to be C<0>, then F<ev.h> will not define any function	4401	If defined to be C<0>, then F<ev.h> will not define any function
3285	prototypes, but still define all the structs and other symbols. This is	4402	prototypes, but still define all the structs and other symbols. This is
3286	occasionally useful if you want to provide your own wrapper functions	4403	occasionally useful if you want to provide your own wrapper functions
3287	around libev functions.	4404	around libev functions.
…		…
3309	fine.	4426	fine.
3310		4427
3311	If your embedding application does not need any priorities, defining these	4428	If your embedding application does not need any priorities, defining these
3312	both to C<0> will save some memory and CPU.	4429	both to C<0> will save some memory and CPU.
3313		4430
3314	=item EV_PERIODIC_ENABLE	4431	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4432	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4433	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3315		4434
3316	If undefined or defined to be C<1>, then periodic timers are supported. If	4435	If undefined or defined to be C<1> (and the platform supports it), then
3317	defined to be C<0>, then they are not. Disabling them saves a few kB of	4436	the respective watcher type is supported. If defined to be C<0>, then it
3318	code.	4437	is not. Disabling watcher types mainly saves code size.
3319		4438
3320	=item EV_IDLE_ENABLE	4439	=item EV_FEATURES
3321
3322	If undefined or defined to be C<1>, then idle watchers are supported. If
3323	defined to be C<0>, then they are not. Disabling them saves a few kB of
3324	code.
3325
3326	=item EV_EMBED_ENABLE
3327
3328	If undefined or defined to be C<1>, then embed watchers are supported. If
3329	defined to be C<0>, then they are not. Embed watchers rely on most other
3330	watcher types, which therefore must not be disabled.
3331
3332	=item EV_STAT_ENABLE
3333
3334	If undefined or defined to be C<1>, then stat watchers are supported. If
3335	defined to be C<0>, then they are not.
3336
3337	=item EV_FORK_ENABLE
3338
3339	If undefined or defined to be C<1>, then fork watchers are supported. If
3340	defined to be C<0>, then they are not.
3341
3342	=item EV_ASYNC_ENABLE
3343
3344	If undefined or defined to be C<1>, then async watchers are supported. If
3345	defined to be C<0>, then they are not.
3346
3347	=item EV_MINIMAL
3348		4440
3349	If you need to shave off some kilobytes of code at the expense of some	4441	If you need to shave off some kilobytes of code at the expense of some
3350	speed, define this symbol to C<1>. Currently this is used to override some	4442	speed (but with the full API), you can define this symbol to request
3351	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4443	certain subsets of functionality. The default is to enable all features
3352	much smaller 2-heap for timer management over the default 4-heap.	4444	that can be enabled on the platform.
		4445
		4446	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4447	with some broad features you want) and then selectively re-enable
		4448	additional parts you want, for example if you want everything minimal,
		4449	but multiple event loop support, async and child watchers and the poll
		4450	backend, use this:
		4451
		4452	#define EV_FEATURES 0
		4453	#define EV_MULTIPLICITY 1
		4454	#define EV_USE_POLL 1
		4455	#define EV_CHILD_ENABLE 1
		4456	#define EV_ASYNC_ENABLE 1
		4457
		4458	The actual value is a bitset, it can be a combination of the following
		4459	values:
		4460
		4461	=over 4
		4462
		4463	=item C<1> - faster/larger code
		4464
		4465	Use larger code to speed up some operations.
		4466
		4467	Currently this is used to override some inlining decisions (enlarging the
		4468	code size by roughly 30% on amd64).
		4469
		4470	When optimising for size, use of compiler flags such as C<-Os> with
		4471	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4472	assertions.
		4473
		4474	=item C<2> - faster/larger data structures
		4475
		4476	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4477	hash table sizes and so on. This will usually further increase code size
		4478	and can additionally have an effect on the size of data structures at
		4479	runtime.
		4480
		4481	=item C<4> - full API configuration
		4482
		4483	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4484	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4485
		4486	=item C<8> - full API
		4487
		4488	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4489	details on which parts of the API are still available without this
		4490	feature, and do not complain if this subset changes over time.
		4491
		4492	=item C<16> - enable all optional watcher types
		4493
		4494	Enables all optional watcher types. If you want to selectively enable
		4495	only some watcher types other than I/O and timers (e.g. prepare,
		4496	embed, async, child...) you can enable them manually by defining
		4497	C<EV_watchertype_ENABLE> to C<1> instead.
		4498
		4499	=item C<32> - enable all backends
		4500
		4501	This enables all backends - without this feature, you need to enable at
		4502	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4503
		4504	=item C<64> - enable OS-specific "helper" APIs
		4505
		4506	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4507	default.
		4508
		4509	=back
		4510
		4511	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4512	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4513	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4514	watchers, timers and monotonic clock support.
		4515
		4516	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4517	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4518	your program might be left out as well - a binary starting a timer and an
		4519	I/O watcher then might come out at only 5Kb.
		4520
		4521	=item EV_AVOID_STDIO
		4522
		4523	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4524	functions (printf, scanf, perror etc.). This will increase the code size
		4525	somewhat, but if your program doesn't otherwise depend on stdio and your
		4526	libc allows it, this avoids linking in the stdio library which is quite
		4527	big.
		4528
		4529	Note that error messages might become less precise when this option is
		4530	enabled.
		4531
		4532	=item EV_NSIG
		4533
		4534	The highest supported signal number, +1 (or, the number of
		4535	signals): Normally, libev tries to deduce the maximum number of signals
		4536	automatically, but sometimes this fails, in which case it can be
		4537	specified. Also, using a lower number than detected (C<32> should be
		4538	good for about any system in existence) can save some memory, as libev
		4539	statically allocates some 12-24 bytes per signal number.
3353		4540
3354	=item EV_PID_HASHSIZE	4541	=item EV_PID_HASHSIZE
3355		4542
3356	C<ev_child> watchers use a small hash table to distribute workload by	4543	C<ev_child> watchers use a small hash table to distribute workload by
3357	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4544	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3358	than enough. If you need to manage thousands of children you might want to	4545	usually more than enough. If you need to manage thousands of children you
3359	increase this value (I<must> be a power of two).	4546	might want to increase this value (I<must> be a power of two).
3360		4547
3361	=item EV_INOTIFY_HASHSIZE	4548	=item EV_INOTIFY_HASHSIZE
3362		4549
3363	C<ev_stat> watchers use a small hash table to distribute workload by	4550	C<ev_stat> watchers use a small hash table to distribute workload by
3364	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4551	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3365	usually more than enough. If you need to manage thousands of C<ev_stat>	4552	disabled), usually more than enough. If you need to manage thousands of
3366	watchers you might want to increase this value (I<must> be a power of	4553	C<ev_stat> watchers you might want to increase this value (I<must> be a
3367	two).	4554	power of two).
3368		4555
3369	=item EV_USE_4HEAP	4556	=item EV_USE_4HEAP
3370		4557
3371	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4558	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3372	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4559	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3373	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4560	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3374	faster performance with many (thousands) of watchers.	4561	faster performance with many (thousands) of watchers.
3375		4562
3376	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4563	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3377	(disabled).	4564	will be C<0>.
3378		4565
3379	=item EV_HEAP_CACHE_AT	4566	=item EV_HEAP_CACHE_AT
3380		4567
3381	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4568	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3382	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4569	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3383	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4570	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3384	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4571	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3385	but avoids random read accesses on heap changes. This improves performance	4572	but avoids random read accesses on heap changes. This improves performance
3386	noticeably with many (hundreds) of watchers.	4573	noticeably with many (hundreds) of watchers.
3387		4574
3388	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4575	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3389	(disabled).	4576	will be C<0>.
3390		4577
3391	=item EV_VERIFY	4578	=item EV_VERIFY
3392		4579
3393	Controls how much internal verification (see C<ev_loop_verify ()>) will	4580	Controls how much internal verification (see C<ev_verify ()>) will
3394	be done: If set to C<0>, no internal verification code will be compiled	4581	be done: If set to C<0>, no internal verification code will be compiled
3395	in. If set to C<1>, then verification code will be compiled in, but not	4582	in. If set to C<1>, then verification code will be compiled in, but not
3396	called. If set to C<2>, then the internal verification code will be	4583	called. If set to C<2>, then the internal verification code will be
3397	called once per loop, which can slow down libev. If set to C<3>, then the	4584	called once per loop, which can slow down libev. If set to C<3>, then the
3398	verification code will be called very frequently, which will slow down	4585	verification code will be called very frequently, which will slow down
3399	libev considerably.	4586	libev considerably.
3400		4587
3401	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4588	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3402	C<0>.	4589	will be C<0>.
3403		4590
3404	=item EV_COMMON	4591	=item EV_COMMON
3405		4592
3406	By default, all watchers have a C<void *data> member. By redefining	4593	By default, all watchers have a C<void *data> member. By redefining
3407	this macro to a something else you can include more and other types of	4594	this macro to something else you can include more and other types of
3408	members. You have to define it each time you include one of the files,	4595	members. You have to define it each time you include one of the files,
3409	though, and it must be identical each time.	4596	though, and it must be identical each time.
3410		4597
3411	For example, the perl EV module uses something like this:	4598	For example, the perl EV module uses something like this:
3412		4599
…		…
3465	file.	4652	file.
3466		4653
3467	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4654	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3468	that everybody includes and which overrides some configure choices:	4655	that everybody includes and which overrides some configure choices:
3469		4656
3470	#define EV_MINIMAL 1	4657	#define EV_FEATURES 8
3471	#define EV_USE_POLL 0	4658	#define EV_USE_SELECT 1
3472	#define EV_MULTIPLICITY 0
3473	#define EV_PERIODIC_ENABLE 0	4659	#define EV_PREPARE_ENABLE 1
		4660	#define EV_IDLE_ENABLE 1
3474	#define EV_STAT_ENABLE 0	4661	#define EV_SIGNAL_ENABLE 1
3475	#define EV_FORK_ENABLE 0	4662	#define EV_CHILD_ENABLE 1
		4663	#define EV_USE_STDEXCEPT 0
3476	#define EV_CONFIG_H <config.h>	4664	#define EV_CONFIG_H <config.h>
3477	#define EV_MINPRI 0
3478	#define EV_MAXPRI 0
3479		4665
3480	#include "ev++.h"	4666	#include "ev++.h"
3481		4667
3482	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4668	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3483		4669
3484	#include "ev_cpp.h"	4670	#include "ev_cpp.h"
3485	#include "ev.c"	4671	#include "ev.c"
3486		4672
3487	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4673	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3488		4674
3489	=head2 THREADS AND COROUTINES	4675	=head2 THREADS AND COROUTINES
3490		4676
3491	=head3 THREADS	4677	=head3 THREADS
3492		4678
…		…
3543	default loop and triggering an C<ev_async> watcher from the default loop	4729	default loop and triggering an C<ev_async> watcher from the default loop
3544	watcher callback into the event loop interested in the signal.	4730	watcher callback into the event loop interested in the signal.
3545		4731
3546	=back	4732	=back
3547		4733
		4734	See also L<THREAD LOCKING EXAMPLE>.
		4735
3548	=head3 COROUTINES	4736	=head3 COROUTINES
3549		4737
3550	Libev is very accommodating to coroutines ("cooperative threads"):	4738	Libev is very accommodating to coroutines ("cooperative threads"):
3551	libev fully supports nesting calls to its functions from different	4739	libev fully supports nesting calls to its functions from different
3552	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4740	coroutines (e.g. you can call C<ev_run> on the same loop from two
3553	different coroutines, and switch freely between both coroutines running the	4741	different coroutines, and switch freely between both coroutines running
3554	loop, as long as you don't confuse yourself). The only exception is that	4742	the loop, as long as you don't confuse yourself). The only exception is
3555	you must not do this from C<ev_periodic> reschedule callbacks.	4743	that you must not do this from C<ev_periodic> reschedule callbacks.
3556		4744
3557	Care has been taken to ensure that libev does not keep local state inside	4745	Care has been taken to ensure that libev does not keep local state inside
3558	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4746	C<ev_run>, and other calls do not usually allow for coroutine switches as
3559	they do not clal any callbacks.	4747	they do not call any callbacks.
3560		4748
3561	=head2 COMPILER WARNINGS	4749	=head2 COMPILER WARNINGS
3562		4750
3563	Depending on your compiler and compiler settings, you might get no or a	4751	Depending on your compiler and compiler settings, you might get no or a
3564	lot of warnings when compiling libev code. Some people are apparently	4752	lot of warnings when compiling libev code. Some people are apparently
…		…
3574	maintainable.	4762	maintainable.
3575		4763
3576	And of course, some compiler warnings are just plain stupid, or simply	4764	And of course, some compiler warnings are just plain stupid, or simply
3577	wrong (because they don't actually warn about the condition their message	4765	wrong (because they don't actually warn about the condition their message
3578	seems to warn about). For example, certain older gcc versions had some	4766	seems to warn about). For example, certain older gcc versions had some
3579	warnings that resulted an extreme number of false positives. These have	4767	warnings that resulted in an extreme number of false positives. These have
3580	been fixed, but some people still insist on making code warn-free with	4768	been fixed, but some people still insist on making code warn-free with
3581	such buggy versions.	4769	such buggy versions.
3582		4770
3583	While libev is written to generate as few warnings as possible,	4771	While libev is written to generate as few warnings as possible,
3584	"warn-free" code is not a goal, and it is recommended not to build libev	4772	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3598	==2274== definitely lost: 0 bytes in 0 blocks.	4786	==2274== definitely lost: 0 bytes in 0 blocks.
3599	==2274== possibly lost: 0 bytes in 0 blocks.	4787	==2274== possibly lost: 0 bytes in 0 blocks.
3600	==2274== still reachable: 256 bytes in 1 blocks.	4788	==2274== still reachable: 256 bytes in 1 blocks.
3601		4789
3602	Then there is no memory leak, just as memory accounted to global variables	4790	Then there is no memory leak, just as memory accounted to global variables
3603	is not a memleak - the memory is still being refernced, and didn't leak.	4791	is not a memleak - the memory is still being referenced, and didn't leak.
3604		4792
3605	Similarly, under some circumstances, valgrind might report kernel bugs	4793	Similarly, under some circumstances, valgrind might report kernel bugs
3606	as if it were a bug in libev (e.g. in realloc or in the poll backend,	4794	as if it were a bug in libev (e.g. in realloc or in the poll backend,
3607	although an acceptable workaround has been found here), or it might be	4795	although an acceptable workaround has been found here), or it might be
3608	confused.	4796	confused.
…		…
3620	I suggest using suppression lists.	4808	I suggest using suppression lists.
3621		4809
3622		4810
3623	=head1 PORTABILITY NOTES	4811	=head1 PORTABILITY NOTES
3624		4812
		4813	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4814
		4815	GNU/Linux is the only common platform that supports 64 bit file/large file
		4816	interfaces but I<disables> them by default.
		4817
		4818	That means that libev compiled in the default environment doesn't support
		4819	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4820
		4821	Unfortunately, many programs try to work around this GNU/Linux issue
		4822	by enabling the large file API, which makes them incompatible with the
		4823	standard libev compiled for their system.
		4824
		4825	Likewise, libev cannot enable the large file API itself as this would
		4826	suddenly make it incompatible to the default compile time environment,
		4827	i.e. all programs not using special compile switches.
		4828
		4829	=head2 OS/X AND DARWIN BUGS
		4830
		4831	The whole thing is a bug if you ask me - basically any system interface
		4832	you touch is broken, whether it is locales, poll, kqueue or even the
		4833	OpenGL drivers.
		4834
		4835	=head3 C<kqueue> is buggy
		4836
		4837	The kqueue syscall is broken in all known versions - most versions support
		4838	only sockets, many support pipes.
		4839
		4840	Libev tries to work around this by not using C<kqueue> by default on this
		4841	rotten platform, but of course you can still ask for it when creating a
		4842	loop - embedding a socket-only kqueue loop into a select-based one is
		4843	probably going to work well.
		4844
		4845	=head3 C<poll> is buggy
		4846
		4847	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4848	implementation by something calling C<kqueue> internally around the 10.5.6
		4849	release, so now C<kqueue> I<and> C<poll> are broken.
		4850
		4851	Libev tries to work around this by not using C<poll> by default on
		4852	this rotten platform, but of course you can still ask for it when creating
		4853	a loop.
		4854
		4855	=head3 C<select> is buggy
		4856
		4857	All that's left is C<select>, and of course Apple found a way to fuck this
		4858	one up as well: On OS/X, C<select> actively limits the number of file
		4859	descriptors you can pass in to 1024 - your program suddenly crashes when
		4860	you use more.
		4861
		4862	There is an undocumented "workaround" for this - defining
		4863	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4864	work on OS/X.
		4865
		4866	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4867
		4868	=head3 C<errno> reentrancy
		4869
		4870	The default compile environment on Solaris is unfortunately so
		4871	thread-unsafe that you can't even use components/libraries compiled
		4872	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4873	defined by default. A valid, if stupid, implementation choice.
		4874
		4875	If you want to use libev in threaded environments you have to make sure
		4876	it's compiled with C<_REENTRANT> defined.
		4877
		4878	=head3 Event port backend
		4879
		4880	The scalable event interface for Solaris is called "event
		4881	ports". Unfortunately, this mechanism is very buggy in all major
		4882	releases. If you run into high CPU usage, your program freezes or you get
		4883	a large number of spurious wakeups, make sure you have all the relevant
		4884	and latest kernel patches applied. No, I don't know which ones, but there
		4885	are multiple ones to apply, and afterwards, event ports actually work
		4886	great.
		4887
		4888	If you can't get it to work, you can try running the program by setting
		4889	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4890	C<select> backends.
		4891
		4892	=head2 AIX POLL BUG
		4893
		4894	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4895	this by trying to avoid the poll backend altogether (i.e. it's not even
		4896	compiled in), which normally isn't a big problem as C<select> works fine
		4897	with large bitsets on AIX, and AIX is dead anyway.
		4898
3625	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4899	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4900
		4901	=head3 General issues
3626		4902
3627	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4903	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3628	requires, and its I/O model is fundamentally incompatible with the POSIX	4904	requires, and its I/O model is fundamentally incompatible with the POSIX
3629	model. Libev still offers limited functionality on this platform in	4905	model. Libev still offers limited functionality on this platform in
3630	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4906	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3631	descriptors. This only applies when using Win32 natively, not when using	4907	descriptors. This only applies when using Win32 natively, not when using
3632	e.g. cygwin.	4908	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4909	as every compielr comes with a slightly differently broken/incompatible
		4910	environment.
3633		4911
3634	Lifting these limitations would basically require the full	4912	Lifting these limitations would basically require the full
3635	re-implementation of the I/O system. If you are into these kinds of	4913	re-implementation of the I/O system. If you are into this kind of thing,
3636	things, then note that glib does exactly that for you in a very portable	4914	then note that glib does exactly that for you in a very portable way (note
3637	way (note also that glib is the slowest event library known to man).	4915	also that glib is the slowest event library known to man).
3638		4916
3639	There is no supported compilation method available on windows except	4917	There is no supported compilation method available on windows except
3640	embedding it into other applications.	4918	embedding it into other applications.
		4919
		4920	Sensible signal handling is officially unsupported by Microsoft - libev
		4921	tries its best, but under most conditions, signals will simply not work.
3641		4922
3642	Not a libev limitation but worth mentioning: windows apparently doesn't	4923	Not a libev limitation but worth mentioning: windows apparently doesn't
3643	accept large writes: instead of resulting in a partial write, windows will	4924	accept large writes: instead of resulting in a partial write, windows will
3644	either accept everything or return C<ENOBUFS> if the buffer is too large,	4925	either accept everything or return C<ENOBUFS> if the buffer is too large,
3645	so make sure you only write small amounts into your sockets (less than a	4926	so make sure you only write small amounts into your sockets (less than a
…		…
3650	the abysmal performance of winsockets, using a large number of sockets	4931	the abysmal performance of winsockets, using a large number of sockets
3651	is not recommended (and not reasonable). If your program needs to use	4932	is not recommended (and not reasonable). If your program needs to use
3652	more than a hundred or so sockets, then likely it needs to use a totally	4933	more than a hundred or so sockets, then likely it needs to use a totally
3653	different implementation for windows, as libev offers the POSIX readiness	4934	different implementation for windows, as libev offers the POSIX readiness
3654	notification model, which cannot be implemented efficiently on windows	4935	notification model, which cannot be implemented efficiently on windows
3655	(Microsoft monopoly games).	4936	(due to Microsoft monopoly games).
3656		4937
3657	A typical way to use libev under windows is to embed it (see the embedding	4938	A typical way to use libev under windows is to embed it (see the embedding
3658	section for details) and use the following F<evwrap.h> header file instead	4939	section for details) and use the following F<evwrap.h> header file instead
3659	of F<ev.h>:	4940	of F<ev.h>:
3660		4941
…		…
3667	you do I<not> compile the F<ev.c> or any other embedded source files!):	4948	you do I<not> compile the F<ev.c> or any other embedded source files!):
3668		4949
3669	#include "evwrap.h"	4950	#include "evwrap.h"
3670	#include "ev.c"	4951	#include "ev.c"
3671		4952
3672	=over 4
3673
3674	=item The winsocket select function	4953	=head3 The winsocket C<select> function
3675		4954
3676	The winsocket C<select> function doesn't follow POSIX in that it	4955	The winsocket C<select> function doesn't follow POSIX in that it
3677	requires socket I<handles> and not socket I<file descriptors> (it is	4956	requires socket I<handles> and not socket I<file descriptors> (it is
3678	also extremely buggy). This makes select very inefficient, and also	4957	also extremely buggy). This makes select very inefficient, and also
3679	requires a mapping from file descriptors to socket handles (the Microsoft	4958	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3688	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4967	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3689		4968
3690	Note that winsockets handling of fd sets is O(n), so you can easily get a	4969	Note that winsockets handling of fd sets is O(n), so you can easily get a
3691	complexity in the O(n²) range when using win32.	4970	complexity in the O(n²) range when using win32.
3692		4971
3693	=item Limited number of file descriptors	4972	=head3 Limited number of file descriptors
3694		4973
3695	Windows has numerous arbitrary (and low) limits on things.	4974	Windows has numerous arbitrary (and low) limits on things.
3696		4975
3697	Early versions of winsocket's select only supported waiting for a maximum	4976	Early versions of winsocket's select only supported waiting for a maximum
3698	of C<64> handles (probably owning to the fact that all windows kernels	4977	of C<64> handles (probably owning to the fact that all windows kernels
3699	can only wait for C<64> things at the same time internally; Microsoft	4978	can only wait for C<64> things at the same time internally; Microsoft
3700	recommends spawning a chain of threads and wait for 63 handles and the	4979	recommends spawning a chain of threads and wait for 63 handles and the
3701	previous thread in each. Great).	4980	previous thread in each. Sounds great!).
3702		4981
3703	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4982	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3704	to some high number (e.g. C<2048>) before compiling the winsocket select	4983	to some high number (e.g. C<2048>) before compiling the winsocket select
3705	call (which might be in libev or elsewhere, for example, perl does its own	4984	call (which might be in libev or elsewhere, for example, perl and many
3706	select emulation on windows).	4985	other interpreters do their own select emulation on windows).
3707		4986
3708	Another limit is the number of file descriptors in the Microsoft runtime	4987	Another limit is the number of file descriptors in the Microsoft runtime
3709	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4988	libraries, which by default is C<64> (there must be a hidden I<64>
3710	or something like this inside Microsoft). You can increase this by calling	4989	fetish or something like this inside Microsoft). You can increase this
3711	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4990	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3712	arbitrary limit), but is broken in many versions of the Microsoft runtime	4991	(another arbitrary limit), but is broken in many versions of the Microsoft
3713	libraries.
3714
3715	This might get you to about C<512> or C<2048> sockets (depending on	4992	runtime libraries. This might get you to about C<512> or C<2048> sockets
3716	windows version and/or the phase of the moon). To get more, you need to	4993	(depending on windows version and/or the phase of the moon). To get more,
3717	wrap all I/O functions and provide your own fd management, but the cost of	4994	you need to wrap all I/O functions and provide your own fd management, but
3718	calling select (O(n²)) will likely make this unworkable.	4995	the cost of calling select (O(n²)) will likely make this unworkable.
3719
3720	=back
3721		4996
3722	=head2 PORTABILITY REQUIREMENTS	4997	=head2 PORTABILITY REQUIREMENTS
3723		4998
3724	In addition to a working ISO-C implementation and of course the	4999	In addition to a working ISO-C implementation and of course the
3725	backend-specific APIs, libev relies on a few additional extensions:	5000	backend-specific APIs, libev relies on a few additional extensions:
…		…
3732	Libev assumes not only that all watcher pointers have the same internal	5007	Libev assumes not only that all watcher pointers have the same internal
3733	structure (guaranteed by POSIX but not by ISO C for example), but it also	5008	structure (guaranteed by POSIX but not by ISO C for example), but it also
3734	assumes that the same (machine) code can be used to call any watcher	5009	assumes that the same (machine) code can be used to call any watcher
3735	callback: The watcher callbacks have different type signatures, but libev	5010	callback: The watcher callbacks have different type signatures, but libev
3736	calls them using an C<ev_watcher *> internally.	5011	calls them using an C<ev_watcher *> internally.
		5012
		5013	=item pointer accesses must be thread-atomic
		5014
		5015	Accessing a pointer value must be atomic, it must both be readable and
		5016	writable in one piece - this is the case on all current architectures.
3737		5017
3738	=item C<sig_atomic_t volatile> must be thread-atomic as well	5018	=item C<sig_atomic_t volatile> must be thread-atomic as well
3739		5019
3740	The type C<sig_atomic_t volatile> (or whatever is defined as	5020	The type C<sig_atomic_t volatile> (or whatever is defined as
3741	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5021	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
3764	watchers.	5044	watchers.
3765		5045
3766	=item C<double> must hold a time value in seconds with enough accuracy	5046	=item C<double> must hold a time value in seconds with enough accuracy
3767		5047
3768	The type C<double> is used to represent timestamps. It is required to	5048	The type C<double> is used to represent timestamps. It is required to
3769	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5049	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3770	enough for at least into the year 4000. This requirement is fulfilled by	5050	good enough for at least into the year 4000 with millisecond accuracy
		5051	(the design goal for libev). This requirement is overfulfilled by
3771	implementations implementing IEEE 754 (basically all existing ones).	5052	implementations using IEEE 754, which is basically all existing ones. With
		5053	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
3772		5054
3773	=back	5055	=back
3774		5056
3775	If you know of other additional requirements drop me a note.	5057	If you know of other additional requirements drop me a note.
3776		5058
…		…
3844	involves iterating over all running async watchers or all signal numbers.	5126	involves iterating over all running async watchers or all signal numbers.
3845		5127
3846	=back	5128	=back
3847		5129
3848		5130
		5131	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5132
		5133	The major version 4 introduced some incompatible changes to the API.
		5134
		5135	At the moment, the C<ev.h> header file provides compatibility definitions
		5136	for all changes, so most programs should still compile. The compatibility
		5137	layer might be removed in later versions of libev, so better update to the
		5138	new API early than late.
		5139
		5140	=over 4
		5141
		5142	=item C<EV_COMPAT3> backwards compatibility mechanism
		5143
		5144	The backward compatibility mechanism can be controlled by
		5145	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5146	section.
		5147
		5148	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5149
		5150	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5151
		5152	ev_loop_destroy (EV_DEFAULT_UC);
		5153	ev_loop_fork (EV_DEFAULT);
		5154
		5155	=item function/symbol renames
		5156
		5157	A number of functions and symbols have been renamed:
		5158
		5159	ev_loop => ev_run
		5160	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5161	EVLOOP_ONESHOT => EVRUN_ONCE
		5162
		5163	ev_unloop => ev_break
		5164	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5165	EVUNLOOP_ONE => EVBREAK_ONE
		5166	EVUNLOOP_ALL => EVBREAK_ALL
		5167
		5168	EV_TIMEOUT => EV_TIMER
		5169
		5170	ev_loop_count => ev_iteration
		5171	ev_loop_depth => ev_depth
		5172	ev_loop_verify => ev_verify
		5173
		5174	Most functions working on C<struct ev_loop> objects don't have an
		5175	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5176	associated constants have been renamed to not collide with the C<struct
		5177	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5178	as all other watcher types. Note that C<ev_loop_fork> is still called
		5179	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5180	typedef.
		5181
		5182	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5183
		5184	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5185	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5186	and work, but the library code will of course be larger.
		5187
		5188	=back
		5189
		5190
		5191	=head1 GLOSSARY
		5192
		5193	=over 4
		5194
		5195	=item active
		5196
		5197	A watcher is active as long as it has been started and not yet stopped.
		5198	See L<WATCHER STATES> for details.
		5199
		5200	=item application
		5201
		5202	In this document, an application is whatever is using libev.
		5203
		5204	=item backend
		5205
		5206	The part of the code dealing with the operating system interfaces.
		5207
		5208	=item callback
		5209
		5210	The address of a function that is called when some event has been
		5211	detected. Callbacks are being passed the event loop, the watcher that
		5212	received the event, and the actual event bitset.
		5213
		5214	=item callback/watcher invocation
		5215
		5216	The act of calling the callback associated with a watcher.
		5217
		5218	=item event
		5219
		5220	A change of state of some external event, such as data now being available
		5221	for reading on a file descriptor, time having passed or simply not having
		5222	any other events happening anymore.
		5223
		5224	In libev, events are represented as single bits (such as C<EV_READ> or
		5225	C<EV_TIMER>).
		5226
		5227	=item event library
		5228
		5229	A software package implementing an event model and loop.
		5230
		5231	=item event loop
		5232
		5233	An entity that handles and processes external events and converts them
		5234	into callback invocations.
		5235
		5236	=item event model
		5237
		5238	The model used to describe how an event loop handles and processes
		5239	watchers and events.
		5240
		5241	=item pending
		5242
		5243	A watcher is pending as soon as the corresponding event has been
		5244	detected. See L<WATCHER STATES> for details.
		5245
		5246	=item real time
		5247
		5248	The physical time that is observed. It is apparently strictly monotonic :)
		5249
		5250	=item wall-clock time
		5251
		5252	The time and date as shown on clocks. Unlike real time, it can actually
		5253	be wrong and jump forwards and backwards, e.g. when you adjust your
		5254	clock.
		5255
		5256	=item watcher
		5257
		5258	A data structure that describes interest in certain events. Watchers need
		5259	to be started (attached to an event loop) before they can receive events.
		5260
		5261	=back
		5262
3849	=head1 AUTHOR	5263	=head1 AUTHOR
3850		5264
3851	Marc Lehmann <libev@schmorp.de>.	5265	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5266	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
3852		5267

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