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…		…
8		8
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
		13
		14	#include <stdio.h> // for puts
13		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_TYPE	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
…		…
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
28		30
29	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_run's to stop iterating
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_break (EV_A_ EVBREAK_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_run to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_break (EV_A_ EVBREAK_ONE);
40	}	42	}
41		43
42	int	44	int
43	main (void)	45	main (void)
44	{	46	{
45	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
46	ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = EV_DEFAULT;
47		49
48	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
…		…
54	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
57		59
58	// now wait for events to arrive	60	// now wait for events to arrive
59	ev_loop (loop, 0);	61	ev_run (loop, 0);
60		62
61	// unloop was called, so exit	63	// unloop was called, so exit
62	return 0;	64	return 0;
63	}	65	}
64		66
65	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
66		70
67	The newest version of this document is also available as an html-formatted	71	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	72	web page you might find easier to navigate when reading it for the first
69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.	73	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		74
		75	While this document tries to be as complete as possible in documenting
		76	libev, its usage and the rationale behind its design, it is not a tutorial
		77	on event-based programming, nor will it introduce event-based programming
		78	with libev.
		79
		80	Familiarity with event based programming techniques in general is assumed
		81	throughout this document.
		82
		83	=head1 WHAT TO READ WHEN IN A HURRY
		84
		85	This manual tries to be very detailed, but unfortunately, this also makes
		86	it very long. If you just want to know the basics of libev, I suggest
		87	reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and
		88	look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and
		89	C<ev_timer> sections in L<WATCHER TYPES>.
		90
		91	=head1 ABOUT LIBEV
70		92
71	Libev is an event loop: you register interest in certain events (such as a	93	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	94	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	95	these event sources and provide your program with events.
74		96
…		…
84	=head2 FEATURES	106	=head2 FEATURES
85		107
86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	108	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	109	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	110	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	111	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
90	with customised rescheduling (C<ev_periodic>), synchronous signals	112	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
91	(C<ev_signal>), process status change events (C<ev_child>), and event	113	timers (C<ev_timer>), absolute timers with customised rescheduling
92	watchers dealing with the event loop mechanism itself (C<ev_idle>,	114	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
93	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	115	change events (C<ev_child>), and event watchers dealing with the event
94	file watchers (C<ev_stat>) and even limited support for fork events	116	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
95	(C<ev_fork>).	117	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		118	limited support for fork events (C<ev_fork>).
96		119
97	It also is quite fast (see this	120	It also is quite fast (see this
98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	121	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
99	for example).	122	for example).
100		123
…		…
103	Libev is very configurable. In this manual the default (and most common)	126	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	127	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	128	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	129	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	130	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<ev_loop *>) will not have	131	name C<loop> (which is always of type C<struct ev_loop *>) will not have
109	this argument.	132	this argument.
110		133
111	=head2 TIME REPRESENTATION	134	=head2 TIME REPRESENTATION
112		135
113	Libev represents time as a single floating point number, representing the	136	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	137	the (fractional) number of seconds since the (POSIX) epoch (in practice
115	the beginning of 1970, details are complicated, don't ask). This type is	138	somewhere near the beginning of 1970, details are complicated, don't
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	139	ask). This type is called C<ev_tstamp>, which is what you should use
117	to the C<double> type in C, and when you need to do any calculations on	140	too. It usually aliases to the C<double> type in C. When you need to do
118	it, you should treat it as some floating point value. Unlike the name	141	any calculations on it, you should treat it as some floating point value.
		142
119	component C<stamp> might indicate, it is also used for time differences	143	Unlike the name component C<stamp> might indicate, it is also used for
120	throughout libev.	144	time differences (e.g. delays) throughout libev.
121		145
122	=head1 ERROR HANDLING	146	=head1 ERROR HANDLING
123		147
124	Libev knows three classes of errors: operating system errors, usage errors	148	Libev knows three classes of errors: operating system errors, usage errors
125	and internal errors (bugs).	149	and internal errors (bugs).
…		…
149		173
150	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
151		175
152	Returns the current time as libev would use it. Please note that the	176	Returns the current time as libev would use it. Please note that the
153	C<ev_now> function is usually faster and also often returns the timestamp	177	C<ev_now> function is usually faster and also often returns the timestamp
154	you actually want to know.	178	you actually want to know. Also interesting is the combination of
		179	C<ev_update_now> and C<ev_now>.
155		180
156	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
157		182
158	Sleep for the given interval: The current thread will be blocked until	183	Sleep for the given interval: The current thread will be blocked until
159	either it is interrupted or the given time interval has passed. Basically	184	either it is interrupted or the given time interval has passed. Basically
…		…
176	as this indicates an incompatible change. Minor versions are usually	201	as this indicates an incompatible change. Minor versions are usually
177	compatible to older versions, so a larger minor version alone is usually	202	compatible to older versions, so a larger minor version alone is usually
178	not a problem.	203	not a problem.
179		204
180	Example: Make sure we haven't accidentally been linked against the wrong	205	Example: Make sure we haven't accidentally been linked against the wrong
181	version.	206	version (note, however, that this will not detect other ABI mismatches,
		207	such as LFS or reentrancy).
182		208
183	assert (("libev version mismatch",	209	assert (("libev version mismatch",
184	ev_version_major () == EV_VERSION_MAJOR	210	ev_version_major () == EV_VERSION_MAJOR
185	&& ev_version_minor () >= EV_VERSION_MINOR));	211	&& ev_version_minor () >= EV_VERSION_MINOR));
186		212
…		…
197	assert (("sorry, no epoll, no sex",	223	assert (("sorry, no epoll, no sex",
198	ev_supported_backends () & EVBACKEND_EPOLL));	224	ev_supported_backends () & EVBACKEND_EPOLL));
199		225
200	=item unsigned int ev_recommended_backends ()	226	=item unsigned int ev_recommended_backends ()
201		227
202	Return the set of all backends compiled into this binary of libev and also	228	Return the set of all backends compiled into this binary of libev and
203	recommended for this platform. This set is often smaller than the one	229	also recommended for this platform, meaning it will work for most file
		230	descriptor types. This set is often smaller than the one returned by
204	returned by C<ev_supported_backends>, as for example kqueue is broken on	231	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
205	most BSDs and will not be auto-detected unless you explicitly request it	232	and will not be auto-detected unless you explicitly request it (assuming
206	(assuming you know what you are doing). This is the set of backends that	233	you know what you are doing). This is the set of backends that libev will
207	libev will probe for if you specify no backends explicitly.	234	probe for if you specify no backends explicitly.
208		235
209	=item unsigned int ev_embeddable_backends ()	236	=item unsigned int ev_embeddable_backends ()
210		237
211	Returns the set of backends that are embeddable in other event loops. This	238	Returns the set of backends that are embeddable in other event loops. This
212	is the theoretical, all-platform, value. To find which backends	239	value is platform-specific but can include backends not available on the
213	might be supported on the current system, you would need to look at	240	current system. To find which embeddable backends might be supported on
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	241	the current system, you would need to look at C<ev_embeddable_backends ()
215	recommended ones.	242	& ev_supported_backends ()>, likewise for recommended ones.
216		243
217	See the description of C<ev_embed> watchers for more info.	244	See the description of C<ev_embed> watchers for more info.
218		245
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	246	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
220		247
221	Sets the allocation function to use (the prototype is similar - the	248	Sets the allocation function to use (the prototype is similar - the
222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	249	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
223	used to allocate and free memory (no surprises here). If it returns zero	250	used to allocate and free memory (no surprises here). If it returns zero
224	when memory needs to be allocated (C<size != 0>), the library might abort	251	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	277	}
251		278
252	...	279	...
253	ev_set_allocator (persistent_realloc);	280	ev_set_allocator (persistent_realloc);
254		281
255	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	282	=item ev_set_syserr_cb (void (*cb)(const char *msg))
256		283
257	Set the callback function to call on a retryable system call error (such	284	Set the callback function to call on a retryable system call error (such
258	as failed select, poll, epoll_wait). The message is a printable string	285	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	286	indicating the system call or subsystem causing the problem. If this
260	callback is set, then libev will expect it to remedy the situation, no	287	callback is set, then libev will expect it to remedy the situation, no
…		…
272	}	299	}
273		300
274	...	301	...
275	ev_set_syserr_cb (fatal_error);	302	ev_set_syserr_cb (fatal_error);
276		303
		304	=item ev_feed_signal (int signum)
		305
		306	This function can be used to "simulate" a signal receive. It is completely
		307	safe to call this function at any time, from any context, including signal
		308	handlers or random threads.
		309
		310	Its main use is to customise signal handling in your process, especially
		311	in the presence of threads. For example, you could block signals
		312	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		313	creating any loops), and in one thread, use C<sigwait> or any other
		314	mechanism to wait for signals, then "deliver" them to libev by calling
		315	C<ev_feed_signal>.
		316
277	=back	317	=back
278		318
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	319	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
280		320
281	An event loop is described by a C<struct ev_loop *> (the C<struct>	321	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>	322	I<not> optional in this case unless libev 3 compatibility is disabled, as
283	I<function>).	323	libev 3 had an C<ev_loop> function colliding with the struct name).
284		324
285	The library knows two types of such loops, the I<default> loop, which	325	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	326	supports child process events, and dynamically created event loops which
287	not.	327	do not.
288		328
289	=over 4	329	=over 4
290		330
291	=item struct ev_loop *ev_default_loop (unsigned int flags)	331	=item struct ev_loop *ev_default_loop (unsigned int flags)
292		332
293	This will initialise the default event loop if it hasn't been initialised	333	This returns the "default" event loop object, which is what you should
294	yet and return it. If the default loop could not be initialised, returns	334	normally use when you just need "the event loop". Event loop objects and
295	false. If it already was initialised it simply returns it (and ignores the	335	the C<flags> parameter are described in more detail in the entry for
296	flags. If that is troubling you, check C<ev_backend ()> afterwards).	336	C<ev_loop_new>.
		337
		338	If the default loop is already initialised then this function simply
		339	returns it (and ignores the flags. If that is troubling you, check
		340	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		341	flags, which should almost always be C<0>, unless the caller is also the
		342	one calling C<ev_run> or otherwise qualifies as "the main program".
297		343
298	If you don't know what event loop to use, use the one returned from this	344	If you don't know what event loop to use, use the one returned from this
299	function.	345	function (or via the C<EV_DEFAULT> macro).
300		346
301	Note that this function is I<not> thread-safe, so if you want to use it	347	Note that this function is I<not> thread-safe, so if you want to use it
302	from multiple threads, you have to lock (note also that this is unlikely,	348	from multiple threads, you have to employ some kind of mutex (note also
303	as loops cannot be shared easily between threads anyway).	349	that this case is unlikely, as loops cannot be shared easily between
		350	threads anyway).
304		351
305	The default loop is the only loop that can handle C<ev_signal> and	352	The default loop is the only loop that can handle C<ev_child> watchers,
306	C<ev_child> watchers, and to do this, it always registers a handler	353	and to do this, it always registers a handler for C<SIGCHLD>. If this is
307	for C<SIGCHLD>. If this is a problem for your application you can either	354	a problem for your application you can either create a dynamic loop with
308	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	355	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
309	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	356	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
310	C<ev_default_init>.	357
		358	Example: This is the most typical usage.
		359
		360	if (!ev_default_loop (0))
		361	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		362
		363	Example: Restrict libev to the select and poll backends, and do not allow
		364	environment settings to be taken into account:
		365
		366	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		367
		368	=item struct ev_loop *ev_loop_new (unsigned int flags)
		369
		370	This will create and initialise a new event loop object. If the loop
		371	could not be initialised, returns false.
		372
		373	This function is thread-safe, and one common way to use libev with
		374	threads is indeed to create one loop per thread, and using the default
		375	loop in the "main" or "initial" thread.
311		376
312	The flags argument can be used to specify special behaviour or specific	377	The flags argument can be used to specify special behaviour or specific
313	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	378	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
314		379
315	The following flags are supported:	380	The following flags are supported:
…		…
330	useful to try out specific backends to test their performance, or to work	395	useful to try out specific backends to test their performance, or to work
331	around bugs.	396	around bugs.
332		397
333	=item C<EVFLAG_FORKCHECK>	398	=item C<EVFLAG_FORKCHECK>
334		399
335	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	400	Instead of calling C<ev_loop_fork> manually after a fork, you can also
336	a fork, you can also make libev check for a fork in each iteration by	401	make libev check for a fork in each iteration by enabling this flag.
337	enabling this flag.
338		402
339	This works by calling C<getpid ()> on every iteration of the loop,	403	This works by calling C<getpid ()> on every iteration of the loop,
340	and thus this might slow down your event loop if you do a lot of loop	404	and thus this might slow down your event loop if you do a lot of loop
341	iterations and little real work, but is usually not noticeable (on my	405	iterations and little real work, but is usually not noticeable (on my
342	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	406	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
…		…
348	flag.	412	flag.
349		413
350	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	414	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
351	environment variable.	415	environment variable.
352		416
		417	=item C<EVFLAG_NOINOTIFY>
		418
		419	When this flag is specified, then libev will not attempt to use the
		420	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
		421	testing, this flag can be useful to conserve inotify file descriptors, as
		422	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		423
		424	=item C<EVFLAG_SIGNALFD>
		425
		426	When this flag is specified, then libev will attempt to use the
		427	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
		428	delivers signals synchronously, which makes it both faster and might make
		429	it possible to get the queued signal data. It can also simplify signal
		430	handling with threads, as long as you properly block signals in your
		431	threads that are not interested in handling them.
		432
		433	Signalfd will not be used by default as this changes your signal mask, and
		434	there are a lot of shoddy libraries and programs (glib's threadpool for
		435	example) that can't properly initialise their signal masks.
		436
		437	=item C<EVFLAG_NOSIGMASK>
		438
		439	When this flag is specified, then libev will avoid to modify the signal
		440	mask. Specifically, this means you ahve to make sure signals are unblocked
		441	when you want to receive them.
		442
		443	This behaviour is useful when you want to do your own signal handling, or
		444	want to handle signals only in specific threads and want to avoid libev
		445	unblocking the signals.
		446
		447	This flag's behaviour will become the default in future versions of libev.
		448
353	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	449	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
354		450
355	This is your standard select(2) backend. Not I<completely> standard, as	451	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,	452	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	453	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	477	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
382	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	478	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
383		479
384	=item C<EVBACKEND_EPOLL> (value 4, Linux)	480	=item C<EVBACKEND_EPOLL> (value 4, Linux)
385		481
		482	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		483	kernels).
		484
386	For few fds, this backend is a bit little slower than poll and select,	485	For few fds, this backend is a bit little slower than poll and select,
387	but it scales phenomenally better. While poll and select usually scale	486	but it scales phenomenally better. While poll and select usually scale
388	like O(total_fds) where n is the total number of fds (or the highest fd),	487	like O(total_fds) where n is the total number of fds (or the highest fd),
389	epoll scales either O(1) or O(active_fds).	488	epoll scales either O(1) or O(active_fds).
390		489
391	The epoll mechanism deserves honorable mention as the most misdesigned	490	The epoll mechanism deserves honorable mention as the most misdesigned
392	of the more advanced event mechanisms: mere annoyances include silently	491	of the more advanced event mechanisms: mere annoyances include silently
393	dropping file descriptors, requiring a system call per change per file	492	dropping file descriptors, requiring a system call per change per file
394	descriptor (and unnecessary guessing of parameters), problems with dup and	493	descriptor (and unnecessary guessing of parameters), problems with dup,
		494	returning before the timeout value, resulting in additional iterations
		495	(and only giving 5ms accuracy while select on the same platform gives
395	so on. The biggest issue is fork races, however - if a program forks then	496	0.1ms) and so on. The biggest issue is fork races, however - if a program
396	I<both> parent and child process have to recreate the epoll set, which can	497	forks then I<both> parent and child process have to recreate the epoll
397	take considerable time (one syscall per file descriptor) and is of course	498	set, which can take considerable time (one syscall per file descriptor)
398	hard to detect.	499	and is of course hard to detect.
399		500
400	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	501	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
401	of course I<doesn't>, and epoll just loves to report events for totally	502	of course I<doesn't>, and epoll just loves to report events for totally
402	I<different> file descriptors (even already closed ones, so one cannot	503	I<different> file descriptors (even already closed ones, so one cannot
403	even remove them from the set) than registered in the set (especially	504	even remove them from the set) than registered in the set (especially
404	on SMP systems). Libev tries to counter these spurious notifications by	505	on SMP systems). Libev tries to counter these spurious notifications by
405	employing an additional generation counter and comparing that against the	506	employing an additional generation counter and comparing that against the
406	events to filter out spurious ones, recreating the set when required.	507	events to filter out spurious ones, recreating the set when required. Last
		508	not least, it also refuses to work with some file descriptors which work
		509	perfectly fine with C<select> (files, many character devices...).
		510
		511	Epoll is truly the train wreck analog among event poll mechanisms.
407		512
408	While stopping, setting and starting an I/O watcher in the same iteration	513	While stopping, setting and starting an I/O watcher in the same iteration
409	will result in some caching, there is still a system call per such	514	will result in some caching, there is still a system call per such
410	incident (because the same I<file descriptor> could point to a different	515	incident (because the same I<file descriptor> could point to a different
411	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	516	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
458		563
459	While nominally embeddable in other event loops, this doesn't work	564	While nominally embeddable in other event loops, this doesn't work
460	everywhere, so you might need to test for this. And since it is broken	565	everywhere, so you might need to test for this. And since it is broken
461	almost everywhere, you should only use it when you have a lot of sockets	566	almost everywhere, you should only use it when you have a lot of sockets
462	(for which it usually works), by embedding it into another event loop	567	(for which it usually works), by embedding it into another event loop
463	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,	568	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
464	using it only for sockets.	569	also broken on OS X)) and, did I mention it, using it only for sockets.
465		570
466	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	571	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
467	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with	572	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
468	C<NOTE_EOF>.	573	C<NOTE_EOF>.
469		574
…		…
477	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	582	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
478		583
479	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	584	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
480	it's really slow, but it still scales very well (O(active_fds)).	585	it's really slow, but it still scales very well (O(active_fds)).
481		586
482	Please note that Solaris event ports can deliver a lot of spurious
483	notifications, so you need to use non-blocking I/O or other means to avoid
484	blocking when no data (or space) is available.
485
486	While this backend scales well, it requires one system call per active	587	While this backend scales well, it requires one system call per active
487	file descriptor per loop iteration. For small and medium numbers of file	588	file descriptor per loop iteration. For small and medium numbers of file
488	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	589	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
489	might perform better.	590	might perform better.
490		591
491	On the positive side, with the exception of the spurious readiness	592	On the positive side, this backend actually performed fully to
492	notifications, this backend actually performed fully to specification
493	in all tests and is fully embeddable, which is a rare feat among the	593	specification in all tests and is fully embeddable, which is a rare feat
494	OS-specific backends (I vastly prefer correctness over speed hacks).	594	among the OS-specific backends (I vastly prefer correctness over speed
		595	hacks).
		596
		597	On the negative side, the interface is I<bizarre> - so bizarre that
		598	even sun itself gets it wrong in their code examples: The event polling
		599	function sometimes returning events to the caller even though an error
		600	occured, but with no indication whether it has done so or not (yes, it's
		601	even documented that way) - deadly for edge-triggered interfaces where
		602	you absolutely have to know whether an event occured or not because you
		603	have to re-arm the watcher.
		604
		605	Fortunately libev seems to be able to work around these idiocies.
495		606
496	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	607	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
497	C<EVBACKEND_POLL>.	608	C<EVBACKEND_POLL>.
498		609
499	=item C<EVBACKEND_ALL>	610	=item C<EVBACKEND_ALL>
500		611
501	Try all backends (even potentially broken ones that wouldn't be tried	612	Try all backends (even potentially broken ones that wouldn't be tried
502	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	613	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
503	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	614	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
504		615
505	It is definitely not recommended to use this flag.	616	It is definitely not recommended to use this flag, use whatever
		617	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		618	at all.
		619
		620	=item C<EVBACKEND_MASK>
		621
		622	Not a backend at all, but a mask to select all backend bits from a
		623	C<flags> value, in case you want to mask out any backends from a flags
		624	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
506		625
507	=back	626	=back
508		627
509	If one or more of these are or'ed into the flags value, then only these	628	If one or more of the backend flags are or'ed into the flags value,
510	backends will be tried (in the reverse order as listed here). If none are	629	then only these backends will be tried (in the reverse order as listed
511	specified, all backends in C<ev_recommended_backends ()> will be tried.	630	here). If none are specified, all backends in C<ev_recommended_backends
512		631	()> will be tried.
513	Example: This is the most typical usage.
514
515	if (!ev_default_loop (0))
516	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
517
518	Example: Restrict libev to the select and poll backends, and do not allow
519	environment settings to be taken into account:
520
521	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
522
523	Example: Use whatever libev has to offer, but make sure that kqueue is
524	used if available (warning, breaks stuff, best use only with your own
525	private event loop and only if you know the OS supports your types of
526	fds):
527
528	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
529
530	=item struct ev_loop *ev_loop_new (unsigned int flags)
531
532	Similar to C<ev_default_loop>, but always creates a new event loop that is
533	always distinct from the default loop. Unlike the default loop, it cannot
534	handle signal and child watchers, and attempts to do so will be greeted by
535	undefined behaviour (or a failed assertion if assertions are enabled).
536
537	Note that this function I<is> thread-safe, and the recommended way to use
538	libev with threads is indeed to create one loop per thread, and using the
539	default loop in the "main" or "initial" thread.
540		632
541	Example: Try to create a event loop that uses epoll and nothing else.	633	Example: Try to create a event loop that uses epoll and nothing else.
542		634
543	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	635	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
544	if (!epoller)	636	if (!epoller)
545	fatal ("no epoll found here, maybe it hides under your chair");	637	fatal ("no epoll found here, maybe it hides under your chair");
546		638
		639	Example: Use whatever libev has to offer, but make sure that kqueue is
		640	used if available.
		641
		642	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		643
547	=item ev_default_destroy ()	644	=item ev_loop_destroy (loop)
548		645
549	Destroys the default loop again (frees all memory and kernel state	646	Destroys an event loop object (frees all memory and kernel state
550	etc.). None of the active event watchers will be stopped in the normal	647	etc.). None of the active event watchers will be stopped in the normal
551	sense, so e.g. C<ev_is_active> might still return true. It is your	648	sense, so e.g. C<ev_is_active> might still return true. It is your
552	responsibility to either stop all watchers cleanly yourself I<before>	649	responsibility to either stop all watchers cleanly yourself I<before>
553	calling this function, or cope with the fact afterwards (which is usually	650	calling this function, or cope with the fact afterwards (which is usually
554	the easiest thing, you can just ignore the watchers and/or C<free ()> them	651	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
556		653
557	Note that certain global state, such as signal state (and installed signal	654	Note that certain global state, such as signal state (and installed signal
558	handlers), will not be freed by this function, and related watchers (such	655	handlers), will not be freed by this function, and related watchers (such
559	as signal and child watchers) would need to be stopped manually.	656	as signal and child watchers) would need to be stopped manually.
560		657
561	In general it is not advisable to call this function except in the	658	This function is normally used on loop objects allocated by
562	rare occasion where you really need to free e.g. the signal handling	659	C<ev_loop_new>, but it can also be used on the default loop returned by
		660	C<ev_default_loop>, in which case it is not thread-safe.
		661
		662	Note that it is not advisable to call this function on the default loop
		663	except in the rare occasion where you really need to free its resources.
563	pipe fds. If you need dynamically allocated loops it is better to use	664	If you need dynamically allocated loops it is better to use C<ev_loop_new>
564	C<ev_loop_new> and C<ev_loop_destroy>).	665	and C<ev_loop_destroy>.
565		666
566	=item ev_loop_destroy (loop)	667	=item ev_loop_fork (loop)
567		668
568	Like C<ev_default_destroy>, but destroys an event loop created by an
569	earlier call to C<ev_loop_new>.
570
571	=item ev_default_fork ()
572
573	This function sets a flag that causes subsequent C<ev_loop> iterations	669	This function sets a flag that causes subsequent C<ev_run> iterations to
574	to reinitialise the kernel state for backends that have one. Despite the	670	reinitialise the kernel state for backends that have one. Despite the
575	name, you can call it anytime, but it makes most sense after forking, in	671	name, you can call it anytime, but it makes most sense after forking, in
576	the child process (or both child and parent, but that again makes little	672	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
577	sense). You I<must> call it in the child before using any of the libev	673	child before resuming or calling C<ev_run>.
578	functions, and it will only take effect at the next C<ev_loop> iteration.	674
		675	Again, you I<have> to call it on I<any> loop that you want to re-use after
		676	a fork, I<even if you do not plan to use the loop in the parent>. This is
		677	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		678	during fork.
579		679
580	On the other hand, you only need to call this function in the child	680	On the other hand, you only need to call this function in the child
581	process if and only if you want to use the event library in the child. If	681	process if and only if you want to use the event loop in the child. If
582	you just fork+exec, you don't have to call it at all.	682	you just fork+exec or create a new loop in the child, you don't have to
		683	call it at all (in fact, C<epoll> is so badly broken that it makes a
		684	difference, but libev will usually detect this case on its own and do a
		685	costly reset of the backend).
583		686
584	The function itself is quite fast and it's usually not a problem to call	687	The function itself is quite fast and it's usually not a problem to call
585	it just in case after a fork. To make this easy, the function will fit in	688	it just in case after a fork.
586	quite nicely into a call to C<pthread_atfork>:
587		689
		690	Example: Automate calling C<ev_loop_fork> on the default loop when
		691	using pthreads.
		692
		693	static void
		694	post_fork_child (void)
		695	{
		696	ev_loop_fork (EV_DEFAULT);
		697	}
		698
		699	...
588	pthread_atfork (0, 0, ev_default_fork);	700	pthread_atfork (0, 0, post_fork_child);
589
590	=item ev_loop_fork (loop)
591
592	Like C<ev_default_fork>, but acts on an event loop created by
593	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
594	after fork that you want to re-use in the child, and how you do this is
595	entirely your own problem.
596		701
597	=item int ev_is_default_loop (loop)	702	=item int ev_is_default_loop (loop)
598		703
599	Returns true when the given loop is, in fact, the default loop, and false	704	Returns true when the given loop is, in fact, the default loop, and false
600	otherwise.	705	otherwise.
601		706
602	=item unsigned int ev_loop_count (loop)	707	=item unsigned int ev_iteration (loop)
603		708
604	Returns the count of loop iterations for the loop, which is identical to	709	Returns the current iteration count for the event loop, which is identical
605	the number of times libev did poll for new events. It starts at C<0> and	710	to the number of times libev did poll for new events. It starts at C<0>
606	happily wraps around with enough iterations.	711	and happily wraps around with enough iterations.
607		712
608	This value can sometimes be useful as a generation counter of sorts (it	713	This value can sometimes be useful as a generation counter of sorts (it
609	"ticks" the number of loop iterations), as it roughly corresponds with	714	"ticks" the number of loop iterations), as it roughly corresponds with
610	C<ev_prepare> and C<ev_check> calls.	715	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		716	prepare and check phases.
		717
		718	=item unsigned int ev_depth (loop)
		719
		720	Returns the number of times C<ev_run> was entered minus the number of
		721	times C<ev_run> was exited normally, in other words, the recursion depth.
		722
		723	Outside C<ev_run>, this number is zero. In a callback, this number is
		724	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		725	in which case it is higher.
		726
		727	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
		728	throwing an exception etc.), doesn't count as "exit" - consider this
		729	as a hint to avoid such ungentleman-like behaviour unless it's really
		730	convenient, in which case it is fully supported.
611		731
612	=item unsigned int ev_backend (loop)	732	=item unsigned int ev_backend (loop)
613		733
614	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	734	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
615	use.	735	use.
…		…
624		744
625	=item ev_now_update (loop)	745	=item ev_now_update (loop)
626		746
627	Establishes the current time by querying the kernel, updating the time	747	Establishes the current time by querying the kernel, updating the time
628	returned by C<ev_now ()> in the progress. This is a costly operation and	748	returned by C<ev_now ()> in the progress. This is a costly operation and
629	is usually done automatically within C<ev_loop ()>.	749	is usually done automatically within C<ev_run ()>.
630		750
631	This function is rarely useful, but when some event callback runs for a	751	This function is rarely useful, but when some event callback runs for a
632	very long time without entering the event loop, updating libev's idea of	752	very long time without entering the event loop, updating libev's idea of
633	the current time is a good idea.	753	the current time is a good idea.
634		754
635	See also "The special problem of time updates" in the C<ev_timer> section.	755	See also L<The special problem of time updates> in the C<ev_timer> section.
636		756
		757	=item ev_suspend (loop)
		758
		759	=item ev_resume (loop)
		760
		761	These two functions suspend and resume an event loop, for use when the
		762	loop is not used for a while and timeouts should not be processed.
		763
		764	A typical use case would be an interactive program such as a game: When
		765	the user presses C<^Z> to suspend the game and resumes it an hour later it
		766	would be best to handle timeouts as if no time had actually passed while
		767	the program was suspended. This can be achieved by calling C<ev_suspend>
		768	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		769	C<ev_resume> directly afterwards to resume timer processing.
		770
		771	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		772	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		773	will be rescheduled (that is, they will lose any events that would have
		774	occurred while suspended).
		775
		776	After calling C<ev_suspend> you B<must not> call I<any> function on the
		777	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		778	without a previous call to C<ev_suspend>.
		779
		780	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		781	event loop time (see C<ev_now_update>).
		782
637	=item ev_loop (loop, int flags)	783	=item ev_run (loop, int flags)
638		784
639	Finally, this is it, the event handler. This function usually is called	785	Finally, this is it, the event handler. This function usually is called
640	after you initialised all your watchers and you want to start handling	786	after you have initialised all your watchers and you want to start
641	events.	787	handling events. It will ask the operating system for any new events, call
		788	the watcher callbacks, an then repeat the whole process indefinitely: This
		789	is why event loops are called I<loops>.
642		790
643	If the flags argument is specified as C<0>, it will not return until	791	If the flags argument is specified as C<0>, it will keep handling events
644	either no event watchers are active anymore or C<ev_unloop> was called.	792	until either no event watchers are active anymore or C<ev_break> was
		793	called.
645		794
646	Please note that an explicit C<ev_unloop> is usually better than	795	Please note that an explicit C<ev_break> is usually better than
647	relying on all watchers to be stopped when deciding when a program has	796	relying on all watchers to be stopped when deciding when a program has
648	finished (especially in interactive programs), but having a program	797	finished (especially in interactive programs), but having a program
649	that automatically loops as long as it has to and no longer by virtue	798	that automatically loops as long as it has to and no longer by virtue
650	of relying on its watchers stopping correctly, that is truly a thing of	799	of relying on its watchers stopping correctly, that is truly a thing of
651	beauty.	800	beauty.
652		801
		802	This function is also I<mostly> exception-safe - you can break out of
		803	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		804	exception and so on. This does not decrement the C<ev_depth> value, nor
		805	will it clear any outstanding C<EVBREAK_ONE> breaks.
		806
653	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	807	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
654	those events and any already outstanding ones, but will not block your	808	those events and any already outstanding ones, but will not wait and
655	process in case there are no events and will return after one iteration of	809	block your process in case there are no events and will return after one
656	the loop.	810	iteration of the loop. This is sometimes useful to poll and handle new
		811	events while doing lengthy calculations, to keep the program responsive.
657		812
658	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	813	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
659	necessary) and will handle those and any already outstanding ones. It	814	necessary) and will handle those and any already outstanding ones. It
660	will block your process until at least one new event arrives (which could	815	will block your process until at least one new event arrives (which could
661	be an event internal to libev itself, so there is no guarantee that a	816	be an event internal to libev itself, so there is no guarantee that a
662	user-registered callback will be called), and will return after one	817	user-registered callback will be called), and will return after one
663	iteration of the loop.	818	iteration of the loop.
664		819
665	This is useful if you are waiting for some external event in conjunction	820	This is useful if you are waiting for some external event in conjunction
666	with something not expressible using other libev watchers (i.e. "roll your	821	with something not expressible using other libev watchers (i.e. "roll your
667	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	822	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
668	usually a better approach for this kind of thing.	823	usually a better approach for this kind of thing.
669		824
670	Here are the gory details of what C<ev_loop> does:	825	Here are the gory details of what C<ev_run> does:
671		826
		827	- Increment loop depth.
		828	- Reset the ev_break status.
672	- Before the first iteration, call any pending watchers.	829	- Before the first iteration, call any pending watchers.
		830	LOOP:
673	* If EVFLAG_FORKCHECK was used, check for a fork.	831	- If EVFLAG_FORKCHECK was used, check for a fork.
674	- If a fork was detected (by any means), queue and call all fork watchers.	832	- If a fork was detected (by any means), queue and call all fork watchers.
675	- Queue and call all prepare watchers.	833	- Queue and call all prepare watchers.
		834	- If ev_break was called, goto FINISH.
676	- If we have been forked, detach and recreate the kernel state	835	- If we have been forked, detach and recreate the kernel state
677	as to not disturb the other process.	836	as to not disturb the other process.
678	- Update the kernel state with all outstanding changes.	837	- Update the kernel state with all outstanding changes.
679	- Update the "event loop time" (ev_now ()).	838	- Update the "event loop time" (ev_now ()).
680	- Calculate for how long to sleep or block, if at all	839	- Calculate for how long to sleep or block, if at all
681	(active idle watchers, EVLOOP_NONBLOCK or not having	840	(active idle watchers, EVRUN_NOWAIT or not having
682	any active watchers at all will result in not sleeping).	841	any active watchers at all will result in not sleeping).
683	- Sleep if the I/O and timer collect interval say so.	842	- Sleep if the I/O and timer collect interval say so.
		843	- Increment loop iteration counter.
684	- Block the process, waiting for any events.	844	- Block the process, waiting for any events.
685	- Queue all outstanding I/O (fd) events.	845	- Queue all outstanding I/O (fd) events.
686	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	846	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
687	- Queue all expired timers.	847	- Queue all expired timers.
688	- Queue all expired periodics.	848	- Queue all expired periodics.
689	- Unless any events are pending now, queue all idle watchers.	849	- Queue all idle watchers with priority higher than that of pending events.
690	- Queue all check watchers.	850	- Queue all check watchers.
691	- Call all queued watchers in reverse order (i.e. check watchers first).	851	- Call all queued watchers in reverse order (i.e. check watchers first).
692	Signals and child watchers are implemented as I/O watchers, and will	852	Signals and child watchers are implemented as I/O watchers, and will
693	be handled here by queueing them when their watcher gets executed.	853	be handled here by queueing them when their watcher gets executed.
694	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	854	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
695	were used, or there are no active watchers, return, otherwise	855	were used, or there are no active watchers, goto FINISH, otherwise
696	continue with step *.	856	continue with step LOOP.
		857	FINISH:
		858	- Reset the ev_break status iff it was EVBREAK_ONE.
		859	- Decrement the loop depth.
		860	- Return.
697		861
698	Example: Queue some jobs and then loop until no events are outstanding	862	Example: Queue some jobs and then loop until no events are outstanding
699	anymore.	863	anymore.
700		864
701	... queue jobs here, make sure they register event watchers as long	865	... queue jobs here, make sure they register event watchers as long
702	... as they still have work to do (even an idle watcher will do..)	866	... as they still have work to do (even an idle watcher will do..)
703	ev_loop (my_loop, 0);	867	ev_run (my_loop, 0);
704	... jobs done or somebody called unloop. yeah!	868	... jobs done or somebody called unloop. yeah!
705		869
706	=item ev_unloop (loop, how)	870	=item ev_break (loop, how)
707		871
708	Can be used to make a call to C<ev_loop> return early (but only after it	872	Can be used to make a call to C<ev_run> return early (but only after it
709	has processed all outstanding events). The C<how> argument must be either	873	has processed all outstanding events). The C<how> argument must be either
710	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	874	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
711	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	875	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
712		876
713	This "unloop state" will be cleared when entering C<ev_loop> again.	877	This "break state" will be cleared on the next call to C<ev_run>.
714		878
715	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	879	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		880	which case it will have no effect.
716		881
717	=item ev_ref (loop)	882	=item ev_ref (loop)
718		883
719	=item ev_unref (loop)	884	=item ev_unref (loop)
720		885
721	Ref/unref can be used to add or remove a reference count on the event	886	Ref/unref can be used to add or remove a reference count on the event
722	loop: Every watcher keeps one reference, and as long as the reference	887	loop: Every watcher keeps one reference, and as long as the reference
723	count is nonzero, C<ev_loop> will not return on its own.	888	count is nonzero, C<ev_run> will not return on its own.
724		889
725	If you have a watcher you never unregister that should not keep C<ev_loop>	890	This is useful when you have a watcher that you never intend to
726	from returning, call ev_unref() after starting, and ev_ref() before	891	unregister, but that nevertheless should not keep C<ev_run> from
		892	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
727	stopping it.	893	before stopping it.
728		894
729	As an example, libev itself uses this for its internal signal pipe: It is	895	As an example, libev itself uses this for its internal signal pipe: It
730	not visible to the libev user and should not keep C<ev_loop> from exiting	896	is not visible to the libev user and should not keep C<ev_run> from
731	if no event watchers registered by it are active. It is also an excellent	897	exiting if no event watchers registered by it are active. It is also an
732	way to do this for generic recurring timers or from within third-party	898	excellent way to do this for generic recurring timers or from within
733	libraries. Just remember to I<unref after start> and I<ref before stop>	899	third-party libraries. Just remember to I<unref after start> and I<ref
734	(but only if the watcher wasn't active before, or was active before,	900	before stop> (but only if the watcher wasn't active before, or was active
735	respectively).	901	before, respectively. Note also that libev might stop watchers itself
		902	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		903	in the callback).
736		904
737	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	905	Example: Create a signal watcher, but keep it from keeping C<ev_run>
738	running when nothing else is active.	906	running when nothing else is active.
739		907
740	ev_signal exitsig;	908	ev_signal exitsig;
741	ev_signal_init (&exitsig, sig_cb, SIGINT);	909	ev_signal_init (&exitsig, sig_cb, SIGINT);
742	ev_signal_start (loop, &exitsig);	910	ev_signal_start (loop, &exitsig);
743	evf_unref (loop);	911	ev_unref (loop);
744		912
745	Example: For some weird reason, unregister the above signal handler again.	913	Example: For some weird reason, unregister the above signal handler again.
746		914
747	ev_ref (loop);	915	ev_ref (loop);
748	ev_signal_stop (loop, &exitsig);	916	ev_signal_stop (loop, &exitsig);
…		…
769		937
770	By setting a higher I<io collect interval> you allow libev to spend more	938	By setting a higher I<io collect interval> you allow libev to spend more
771	time collecting I/O events, so you can handle more events per iteration,	939	time collecting I/O events, so you can handle more events per iteration,
772	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	940	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
773	C<ev_timer>) will be not affected. Setting this to a non-null value will	941	C<ev_timer>) will be not affected. Setting this to a non-null value will
774	introduce an additional C<ev_sleep ()> call into most loop iterations.	942	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		943	sleep time ensures that libev will not poll for I/O events more often then
		944	once per this interval, on average.
775		945
776	Likewise, by setting a higher I<timeout collect interval> you allow libev	946	Likewise, by setting a higher I<timeout collect interval> you allow libev
777	to spend more time collecting timeouts, at the expense of increased	947	to spend more time collecting timeouts, at the expense of increased
778	latency/jitter/inexactness (the watcher callback will be called	948	latency/jitter/inexactness (the watcher callback will be called
779	later). C<ev_io> watchers will not be affected. Setting this to a non-null	949	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
781		951
782	Many (busy) programs can usually benefit by setting the I/O collect	952	Many (busy) programs can usually benefit by setting the I/O collect
783	interval to a value near C<0.1> or so, which is often enough for	953	interval to a value near C<0.1> or so, which is often enough for
784	interactive servers (of course not for games), likewise for timeouts. It	954	interactive servers (of course not for games), likewise for timeouts. It
785	usually doesn't make much sense to set it to a lower value than C<0.01>,	955	usually doesn't make much sense to set it to a lower value than C<0.01>,
786	as this approaches the timing granularity of most systems.	956	as this approaches the timing granularity of most systems. Note that if
		957	you do transactions with the outside world and you can't increase the
		958	parallelity, then this setting will limit your transaction rate (if you
		959	need to poll once per transaction and the I/O collect interval is 0.01,
		960	then you can't do more than 100 transactions per second).
787		961
788	Setting the I<timeout collect interval> can improve the opportunity for	962	Setting the I<timeout collect interval> can improve the opportunity for
789	saving power, as the program will "bundle" timer callback invocations that	963	saving power, as the program will "bundle" timer callback invocations that
790	are "near" in time together, by delaying some, thus reducing the number of	964	are "near" in time together, by delaying some, thus reducing the number of
791	times the process sleeps and wakes up again. Another useful technique to	965	times the process sleeps and wakes up again. Another useful technique to
792	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	966	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
793	they fire on, say, one-second boundaries only.	967	they fire on, say, one-second boundaries only.
794		968
		969	Example: we only need 0.1s timeout granularity, and we wish not to poll
		970	more often than 100 times per second:
		971
		972	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		973	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		974
		975	=item ev_invoke_pending (loop)
		976
		977	This call will simply invoke all pending watchers while resetting their
		978	pending state. Normally, C<ev_run> does this automatically when required,
		979	but when overriding the invoke callback this call comes handy. This
		980	function can be invoked from a watcher - this can be useful for example
		981	when you want to do some lengthy calculation and want to pass further
		982	event handling to another thread (you still have to make sure only one
		983	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		984
		985	=item int ev_pending_count (loop)
		986
		987	Returns the number of pending watchers - zero indicates that no watchers
		988	are pending.
		989
		990	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		991
		992	This overrides the invoke pending functionality of the loop: Instead of
		993	invoking all pending watchers when there are any, C<ev_run> will call
		994	this callback instead. This is useful, for example, when you want to
		995	invoke the actual watchers inside another context (another thread etc.).
		996
		997	If you want to reset the callback, use C<ev_invoke_pending> as new
		998	callback.
		999
		1000	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		1001
		1002	Sometimes you want to share the same loop between multiple threads. This
		1003	can be done relatively simply by putting mutex_lock/unlock calls around
		1004	each call to a libev function.
		1005
		1006	However, C<ev_run> can run an indefinite time, so it is not feasible
		1007	to wait for it to return. One way around this is to wake up the event
		1008	loop via C<ev_break> and C<av_async_send>, another way is to set these
		1009	I<release> and I<acquire> callbacks on the loop.
		1010
		1011	When set, then C<release> will be called just before the thread is
		1012	suspended waiting for new events, and C<acquire> is called just
		1013	afterwards.
		1014
		1015	Ideally, C<release> will just call your mutex_unlock function, and
		1016	C<acquire> will just call the mutex_lock function again.
		1017
		1018	While event loop modifications are allowed between invocations of
		1019	C<release> and C<acquire> (that's their only purpose after all), no
		1020	modifications done will affect the event loop, i.e. adding watchers will
		1021	have no effect on the set of file descriptors being watched, or the time
		1022	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		1023	to take note of any changes you made.
		1024
		1025	In theory, threads executing C<ev_run> will be async-cancel safe between
		1026	invocations of C<release> and C<acquire>.
		1027
		1028	See also the locking example in the C<THREADS> section later in this
		1029	document.
		1030
		1031	=item ev_set_userdata (loop, void *data)
		1032
		1033	=item void *ev_userdata (loop)
		1034
		1035	Set and retrieve a single C<void *> associated with a loop. When
		1036	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		1037	C<0>.
		1038
		1039	These two functions can be used to associate arbitrary data with a loop,
		1040	and are intended solely for the C<invoke_pending_cb>, C<release> and
		1041	C<acquire> callbacks described above, but of course can be (ab-)used for
		1042	any other purpose as well.
		1043
795	=item ev_loop_verify (loop)	1044	=item ev_verify (loop)
796		1045
797	This function only does something when C<EV_VERIFY> support has been	1046	This function only does something when C<EV_VERIFY> support has been
798	compiled in, which is the default for non-minimal builds. It tries to go	1047	compiled in, which is the default for non-minimal builds. It tries to go
799	through all internal structures and checks them for validity. If anything	1048	through all internal structures and checks them for validity. If anything
800	is found to be inconsistent, it will print an error message to standard	1049	is found to be inconsistent, it will print an error message to standard
…		…
811		1060
812	In the following description, uppercase C<TYPE> in names stands for the	1061	In the following description, uppercase C<TYPE> in names stands for the
813	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1062	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
814	watchers and C<ev_io_start> for I/O watchers.	1063	watchers and C<ev_io_start> for I/O watchers.
815		1064
816	A watcher is a structure that you create and register to record your	1065	A watcher is an opaque structure that you allocate and register to record
817	interest in some event. For instance, if you want to wait for STDIN to	1066	your interest in some event. To make a concrete example, imagine you want
818	become readable, you would create an C<ev_io> watcher for that:	1067	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1068	for that:
819		1069
820	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1070	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
821	{	1071	{
822	ev_io_stop (w);	1072	ev_io_stop (w);
823	ev_unloop (loop, EVUNLOOP_ALL);	1073	ev_break (loop, EVBREAK_ALL);
824	}	1074	}
825		1075
826	struct ev_loop *loop = ev_default_loop (0);	1076	struct ev_loop *loop = ev_default_loop (0);
827		1077
828	ev_io stdin_watcher;	1078	ev_io stdin_watcher;
829		1079
830	ev_init (&stdin_watcher, my_cb);	1080	ev_init (&stdin_watcher, my_cb);
831	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1081	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
832	ev_io_start (loop, &stdin_watcher);	1082	ev_io_start (loop, &stdin_watcher);
833		1083
834	ev_loop (loop, 0);	1084	ev_run (loop, 0);
835		1085
836	As you can see, you are responsible for allocating the memory for your	1086	As you can see, you are responsible for allocating the memory for your
837	watcher structures (and it is I<usually> a bad idea to do this on the	1087	watcher structures (and it is I<usually> a bad idea to do this on the
838	stack).	1088	stack).
839		1089
840	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1090	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
841	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1091	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
842		1092
843	Each watcher structure must be initialised by a call to C<ev_init	1093	Each watcher structure must be initialised by a call to C<ev_init (watcher
844	(watcher *, callback)>, which expects a callback to be provided. This	1094	*, callback)>, which expects a callback to be provided. This callback is
845	callback gets invoked each time the event occurs (or, in the case of I/O	1095	invoked each time the event occurs (or, in the case of I/O watchers, each
846	watchers, each time the event loop detects that the file descriptor given	1096	time the event loop detects that the file descriptor given is readable
847	is readable and/or writable).	1097	and/or writable).
848		1098
849	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1099	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
850	macro to configure it, with arguments specific to the watcher type. There	1100	macro to configure it, with arguments specific to the watcher type. There
851	is also a macro to combine initialisation and setting in one call: C<<	1101	is also a macro to combine initialisation and setting in one call: C<<
852	ev_TYPE_init (watcher *, callback, ...) >>.	1102	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
875	=item C<EV_WRITE>	1125	=item C<EV_WRITE>
876		1126
877	The file descriptor in the C<ev_io> watcher has become readable and/or	1127	The file descriptor in the C<ev_io> watcher has become readable and/or
878	writable.	1128	writable.
879		1129
880	=item C<EV_TIMEOUT>	1130	=item C<EV_TIMER>
881		1131
882	The C<ev_timer> watcher has timed out.	1132	The C<ev_timer> watcher has timed out.
883		1133
884	=item C<EV_PERIODIC>	1134	=item C<EV_PERIODIC>
885		1135
…		…
903		1153
904	=item C<EV_PREPARE>	1154	=item C<EV_PREPARE>
905		1155
906	=item C<EV_CHECK>	1156	=item C<EV_CHECK>
907		1157
908	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1158	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
909	to gather new events, and all C<ev_check> watchers are invoked just after	1159	to gather new events, and all C<ev_check> watchers are invoked just after
910	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1160	C<ev_run> has gathered them, but before it invokes any callbacks for any
911	received events. Callbacks of both watcher types can start and stop as	1161	received events. Callbacks of both watcher types can start and stop as
912	many watchers as they want, and all of them will be taken into account	1162	many watchers as they want, and all of them will be taken into account
913	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1163	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
914	C<ev_loop> from blocking).	1164	C<ev_run> from blocking).
915		1165
916	=item C<EV_EMBED>	1166	=item C<EV_EMBED>
917		1167
918	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1168	The embedded event loop specified in the C<ev_embed> watcher needs attention.
919		1169
920	=item C<EV_FORK>	1170	=item C<EV_FORK>
921		1171
922	The event loop has been resumed in the child process after fork (see	1172	The event loop has been resumed in the child process after fork (see
923	C<ev_fork>).	1173	C<ev_fork>).
924		1174
		1175	=item C<EV_CLEANUP>
		1176
		1177	The event loop is about to be destroyed (see C<ev_cleanup>).
		1178
925	=item C<EV_ASYNC>	1179	=item C<EV_ASYNC>
926		1180
927	The given async watcher has been asynchronously notified (see C<ev_async>).	1181	The given async watcher has been asynchronously notified (see C<ev_async>).
		1182
		1183	=item C<EV_CUSTOM>
		1184
		1185	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1186	by libev users to signal watchers (e.g. via C<ev_feed_event>).
928		1187
929	=item C<EV_ERROR>	1188	=item C<EV_ERROR>
930		1189
931	An unspecified error has occurred, the watcher has been stopped. This might	1190	An unspecified error has occurred, the watcher has been stopped. This might
932	happen because the watcher could not be properly started because libev	1191	happen because the watcher could not be properly started because libev
…		…
970		1229
971	ev_io w;	1230	ev_io w;
972	ev_init (&w, my_cb);	1231	ev_init (&w, my_cb);
973	ev_io_set (&w, STDIN_FILENO, EV_READ);	1232	ev_io_set (&w, STDIN_FILENO, EV_READ);
974		1233
975	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1234	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
976		1235
977	This macro initialises the type-specific parts of a watcher. You need to	1236	This macro initialises the type-specific parts of a watcher. You need to
978	call C<ev_init> at least once before you call this macro, but you can	1237	call C<ev_init> at least once before you call this macro, but you can
979	call C<ev_TYPE_set> any number of times. You must not, however, call this	1238	call C<ev_TYPE_set> any number of times. You must not, however, call this
980	macro on a watcher that is active (it can be pending, however, which is a	1239	macro on a watcher that is active (it can be pending, however, which is a
…		…
993		1252
994	Example: Initialise and set an C<ev_io> watcher in one step.	1253	Example: Initialise and set an C<ev_io> watcher in one step.
995		1254
996	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1255	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
997		1256
998	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1257	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
999		1258
1000	Starts (activates) the given watcher. Only active watchers will receive	1259	Starts (activates) the given watcher. Only active watchers will receive
1001	events. If the watcher is already active nothing will happen.	1260	events. If the watcher is already active nothing will happen.
1002		1261
1003	Example: Start the C<ev_io> watcher that is being abused as example in this	1262	Example: Start the C<ev_io> watcher that is being abused as example in this
1004	whole section.	1263	whole section.
1005		1264
1006	ev_io_start (EV_DEFAULT_UC, &w);	1265	ev_io_start (EV_DEFAULT_UC, &w);
1007		1266
1008	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1267	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1009		1268
1010	Stops the given watcher if active, and clears the pending status (whether	1269	Stops the given watcher if active, and clears the pending status (whether
1011	the watcher was active or not).	1270	the watcher was active or not).
1012		1271
1013	It is possible that stopped watchers are pending - for example,	1272	It is possible that stopped watchers are pending - for example,
…		…
1038	=item ev_cb_set (ev_TYPE *watcher, callback)	1297	=item ev_cb_set (ev_TYPE *watcher, callback)
1039		1298
1040	Change the callback. You can change the callback at virtually any time	1299	Change the callback. You can change the callback at virtually any time
1041	(modulo threads).	1300	(modulo threads).
1042		1301
1043	=item ev_set_priority (ev_TYPE *watcher, priority)	1302	=item ev_set_priority (ev_TYPE *watcher, int priority)
1044		1303
1045	=item int ev_priority (ev_TYPE *watcher)	1304	=item int ev_priority (ev_TYPE *watcher)
1046		1305
1047	Set and query the priority of the watcher. The priority is a small	1306	Set and query the priority of the watcher. The priority is a small
1048	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1307	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1049	(default: C<-2>). Pending watchers with higher priority will be invoked	1308	(default: C<-2>). Pending watchers with higher priority will be invoked
1050	before watchers with lower priority, but priority will not keep watchers	1309	before watchers with lower priority, but priority will not keep watchers
1051	from being executed (except for C<ev_idle> watchers).	1310	from being executed (except for C<ev_idle> watchers).
1052		1311
1053	This means that priorities are I<only> used for ordering callback
1054	invocation after new events have been received. This is useful, for
1055	example, to reduce latency after idling, or more often, to bind two
1056	watchers on the same event and make sure one is called first.
1057
1058	If you need to suppress invocation when higher priority events are pending	1312	If you need to suppress invocation when higher priority events are pending
1059	you need to look at C<ev_idle> watchers, which provide this functionality.	1313	you need to look at C<ev_idle> watchers, which provide this functionality.
1060		1314
1061	You I<must not> change the priority of a watcher as long as it is active or	1315	You I<must not> change the priority of a watcher as long as it is active or
1062	pending.	1316	pending.
1063
1064	The default priority used by watchers when no priority has been set is
1065	always C<0>, which is supposed to not be too high and not be too low :).
1066		1317
1067	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1318	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1068	fine, as long as you do not mind that the priority value you query might	1319	fine, as long as you do not mind that the priority value you query might
1069	or might not have been clamped to the valid range.	1320	or might not have been clamped to the valid range.
		1321
		1322	The default priority used by watchers when no priority has been set is
		1323	always C<0>, which is supposed to not be too high and not be too low :).
		1324
		1325	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
		1326	priorities.
1070		1327
1071	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1328	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1072		1329
1073	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1330	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1074	C<loop> nor C<revents> need to be valid as long as the watcher callback	1331	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1082	watcher isn't pending it does nothing and returns C<0>.	1339	watcher isn't pending it does nothing and returns C<0>.
1083		1340
1084	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1341	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1085	callback to be invoked, which can be accomplished with this function.	1342	callback to be invoked, which can be accomplished with this function.
1086		1343
		1344	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1345
		1346	Feeds the given event set into the event loop, as if the specified event
		1347	had happened for the specified watcher (which must be a pointer to an
		1348	initialised but not necessarily started event watcher). Obviously you must
		1349	not free the watcher as long as it has pending events.
		1350
		1351	Stopping the watcher, letting libev invoke it, or calling
		1352	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1353	not started in the first place.
		1354
		1355	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1356	functions that do not need a watcher.
		1357
1087	=back	1358	=back
1088
1089		1359
1090	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1360	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1091		1361
1092	Each watcher has, by default, a member C<void *data> that you can change	1362	Each watcher has, by default, a member C<void *data> that you can change
1093	and read at any time: libev will completely ignore it. This can be used	1363	and read at any time: libev will completely ignore it. This can be used
…		…
1139	#include <stddef.h>	1409	#include <stddef.h>
1140		1410
1141	static void	1411	static void
1142	t1_cb (EV_P_ ev_timer *w, int revents)	1412	t1_cb (EV_P_ ev_timer *w, int revents)
1143	{	1413	{
1144	struct my_biggy big = (struct my_biggy *	1414	struct my_biggy big = (struct my_biggy *)
1145	(((char *)w) - offsetof (struct my_biggy, t1));	1415	(((char *)w) - offsetof (struct my_biggy, t1));
1146	}	1416	}
1147		1417
1148	static void	1418	static void
1149	t2_cb (EV_P_ ev_timer *w, int revents)	1419	t2_cb (EV_P_ ev_timer *w, int revents)
1150	{	1420	{
1151	struct my_biggy big = (struct my_biggy *	1421	struct my_biggy big = (struct my_biggy *)
1152	(((char *)w) - offsetof (struct my_biggy, t2));	1422	(((char *)w) - offsetof (struct my_biggy, t2));
1153	}	1423	}
		1424
		1425	=head2 WATCHER STATES
		1426
		1427	There are various watcher states mentioned throughout this manual -
		1428	active, pending and so on. In this section these states and the rules to
		1429	transition between them will be described in more detail - and while these
		1430	rules might look complicated, they usually do "the right thing".
		1431
		1432	=over 4
		1433
		1434	=item initialiased
		1435
		1436	Before a watcher can be registered with the event looop it has to be
		1437	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1438	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1439
		1440	In this state it is simply some block of memory that is suitable for use
		1441	in an event loop. It can be moved around, freed, reused etc. at will.
		1442
		1443	=item started/running/active
		1444
		1445	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1446	property of the event loop, and is actively waiting for events. While in
		1447	this state it cannot be accessed (except in a few documented ways), moved,
		1448	freed or anything else - the only legal thing is to keep a pointer to it,
		1449	and call libev functions on it that are documented to work on active watchers.
		1450
		1451	=item pending
		1452
		1453	If a watcher is active and libev determines that an event it is interested
		1454	in has occurred (such as a timer expiring), it will become pending. It will
		1455	stay in this pending state until either it is stopped or its callback is
		1456	about to be invoked, so it is not normally pending inside the watcher
		1457	callback.
		1458
		1459	The watcher might or might not be active while it is pending (for example,
		1460	an expired non-repeating timer can be pending but no longer active). If it
		1461	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1462	but it is still property of the event loop at this time, so cannot be
		1463	moved, freed or reused. And if it is active the rules described in the
		1464	previous item still apply.
		1465
		1466	It is also possible to feed an event on a watcher that is not active (e.g.
		1467	via C<ev_feed_event>), in which case it becomes pending without being
		1468	active.
		1469
		1470	=item stopped
		1471
		1472	A watcher can be stopped implicitly by libev (in which case it might still
		1473	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1474	latter will clear any pending state the watcher might be in, regardless
		1475	of whether it was active or not, so stopping a watcher explicitly before
		1476	freeing it is often a good idea.
		1477
		1478	While stopped (and not pending) the watcher is essentially in the
		1479	initialised state, that is it can be reused, moved, modified in any way
		1480	you wish.
		1481
		1482	=back
		1483
		1484	=head2 WATCHER PRIORITY MODELS
		1485
		1486	Many event loops support I<watcher priorities>, which are usually small
		1487	integers that influence the ordering of event callback invocation
		1488	between watchers in some way, all else being equal.
		1489
		1490	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1491	description for the more technical details such as the actual priority
		1492	range.
		1493
		1494	There are two common ways how these these priorities are being interpreted
		1495	by event loops:
		1496
		1497	In the more common lock-out model, higher priorities "lock out" invocation
		1498	of lower priority watchers, which means as long as higher priority
		1499	watchers receive events, lower priority watchers are not being invoked.
		1500
		1501	The less common only-for-ordering model uses priorities solely to order
		1502	callback invocation within a single event loop iteration: Higher priority
		1503	watchers are invoked before lower priority ones, but they all get invoked
		1504	before polling for new events.
		1505
		1506	Libev uses the second (only-for-ordering) model for all its watchers
		1507	except for idle watchers (which use the lock-out model).
		1508
		1509	The rationale behind this is that implementing the lock-out model for
		1510	watchers is not well supported by most kernel interfaces, and most event
		1511	libraries will just poll for the same events again and again as long as
		1512	their callbacks have not been executed, which is very inefficient in the
		1513	common case of one high-priority watcher locking out a mass of lower
		1514	priority ones.
		1515
		1516	Static (ordering) priorities are most useful when you have two or more
		1517	watchers handling the same resource: a typical usage example is having an
		1518	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1519	timeouts. Under load, data might be received while the program handles
		1520	other jobs, but since timers normally get invoked first, the timeout
		1521	handler will be executed before checking for data. In that case, giving
		1522	the timer a lower priority than the I/O watcher ensures that I/O will be
		1523	handled first even under adverse conditions (which is usually, but not
		1524	always, what you want).
		1525
		1526	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1527	will only be executed when no same or higher priority watchers have
		1528	received events, they can be used to implement the "lock-out" model when
		1529	required.
		1530
		1531	For example, to emulate how many other event libraries handle priorities,
		1532	you can associate an C<ev_idle> watcher to each such watcher, and in
		1533	the normal watcher callback, you just start the idle watcher. The real
		1534	processing is done in the idle watcher callback. This causes libev to
		1535	continuously poll and process kernel event data for the watcher, but when
		1536	the lock-out case is known to be rare (which in turn is rare :), this is
		1537	workable.
		1538
		1539	Usually, however, the lock-out model implemented that way will perform
		1540	miserably under the type of load it was designed to handle. In that case,
		1541	it might be preferable to stop the real watcher before starting the
		1542	idle watcher, so the kernel will not have to process the event in case
		1543	the actual processing will be delayed for considerable time.
		1544
		1545	Here is an example of an I/O watcher that should run at a strictly lower
		1546	priority than the default, and which should only process data when no
		1547	other events are pending:
		1548
		1549	ev_idle idle; // actual processing watcher
		1550	ev_io io; // actual event watcher
		1551
		1552	static void
		1553	io_cb (EV_P_ ev_io *w, int revents)
		1554	{
		1555	// stop the I/O watcher, we received the event, but
		1556	// are not yet ready to handle it.
		1557	ev_io_stop (EV_A_ w);
		1558
		1559	// start the idle watcher to handle the actual event.
		1560	// it will not be executed as long as other watchers
		1561	// with the default priority are receiving events.
		1562	ev_idle_start (EV_A_ &idle);
		1563	}
		1564
		1565	static void
		1566	idle_cb (EV_P_ ev_idle *w, int revents)
		1567	{
		1568	// actual processing
		1569	read (STDIN_FILENO, ...);
		1570
		1571	// have to start the I/O watcher again, as
		1572	// we have handled the event
		1573	ev_io_start (EV_P_ &io);
		1574	}
		1575
		1576	// initialisation
		1577	ev_idle_init (&idle, idle_cb);
		1578	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1579	ev_io_start (EV_DEFAULT_ &io);
		1580
		1581	In the "real" world, it might also be beneficial to start a timer, so that
		1582	low-priority connections can not be locked out forever under load. This
		1583	enables your program to keep a lower latency for important connections
		1584	during short periods of high load, while not completely locking out less
		1585	important ones.
1154		1586
1155		1587
1156	=head1 WATCHER TYPES	1588	=head1 WATCHER TYPES
1157		1589
1158	This section describes each watcher in detail, but will not repeat	1590	This section describes each watcher in detail, but will not repeat
…		…
1184	descriptors to non-blocking mode is also usually a good idea (but not	1616	descriptors to non-blocking mode is also usually a good idea (but not
1185	required if you know what you are doing).	1617	required if you know what you are doing).
1186		1618
1187	If you cannot use non-blocking mode, then force the use of a	1619	If you cannot use non-blocking mode, then force the use of a
1188	known-to-be-good backend (at the time of this writing, this includes only	1620	known-to-be-good backend (at the time of this writing, this includes only
1189	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).	1621	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1622	descriptors for which non-blocking operation makes no sense (such as
		1623	files) - libev doesn't guarantee any specific behaviour in that case.
1190		1624
1191	Another thing you have to watch out for is that it is quite easy to	1625	Another thing you have to watch out for is that it is quite easy to
1192	receive "spurious" readiness notifications, that is your callback might	1626	receive "spurious" readiness notifications, that is your callback might
1193	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1627	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1194	because there is no data. Not only are some backends known to create a	1628	because there is no data. Not only are some backends known to create a
…		…
1259		1693
1260	So when you encounter spurious, unexplained daemon exits, make sure you	1694	So when you encounter spurious, unexplained daemon exits, make sure you
1261	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1695	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1262	somewhere, as that would have given you a big clue).	1696	somewhere, as that would have given you a big clue).
1263		1697
		1698	=head3 The special problem of accept()ing when you can't
		1699
		1700	Many implementations of the POSIX C<accept> function (for example,
		1701	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1702	connection from the pending queue in all error cases.
		1703
		1704	For example, larger servers often run out of file descriptors (because
		1705	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1706	rejecting the connection, leading to libev signalling readiness on
		1707	the next iteration again (the connection still exists after all), and
		1708	typically causing the program to loop at 100% CPU usage.
		1709
		1710	Unfortunately, the set of errors that cause this issue differs between
		1711	operating systems, there is usually little the app can do to remedy the
		1712	situation, and no known thread-safe method of removing the connection to
		1713	cope with overload is known (to me).
		1714
		1715	One of the easiest ways to handle this situation is to just ignore it
		1716	- when the program encounters an overload, it will just loop until the
		1717	situation is over. While this is a form of busy waiting, no OS offers an
		1718	event-based way to handle this situation, so it's the best one can do.
		1719
		1720	A better way to handle the situation is to log any errors other than
		1721	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1722	messages, and continue as usual, which at least gives the user an idea of
		1723	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1724	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1725	usage.
		1726
		1727	If your program is single-threaded, then you could also keep a dummy file
		1728	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1729	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1730	close that fd, and create a new dummy fd. This will gracefully refuse
		1731	clients under typical overload conditions.
		1732
		1733	The last way to handle it is to simply log the error and C<exit>, as
		1734	is often done with C<malloc> failures, but this results in an easy
		1735	opportunity for a DoS attack.
1264		1736
1265	=head3 Watcher-Specific Functions	1737	=head3 Watcher-Specific Functions
1266		1738
1267	=over 4	1739	=over 4
1268		1740
…		…
1300	...	1772	...
1301	struct ev_loop *loop = ev_default_init (0);	1773	struct ev_loop *loop = ev_default_init (0);
1302	ev_io stdin_readable;	1774	ev_io stdin_readable;
1303	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1775	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1304	ev_io_start (loop, &stdin_readable);	1776	ev_io_start (loop, &stdin_readable);
1305	ev_loop (loop, 0);	1777	ev_run (loop, 0);
1306		1778
1307		1779
1308	=head2 C<ev_timer> - relative and optionally repeating timeouts	1780	=head2 C<ev_timer> - relative and optionally repeating timeouts
1309		1781
1310	Timer watchers are simple relative timers that generate an event after a	1782	Timer watchers are simple relative timers that generate an event after a
…		…
1315	year, it will still time out after (roughly) one hour. "Roughly" because	1787	year, it will still time out after (roughly) one hour. "Roughly" because
1316	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1788	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1317	monotonic clock option helps a lot here).	1789	monotonic clock option helps a lot here).
1318		1790
1319	The callback is guaranteed to be invoked only I<after> its timeout has	1791	The callback is guaranteed to be invoked only I<after> its timeout has
1320	passed, but if multiple timers become ready during the same loop iteration	1792	passed (not I<at>, so on systems with very low-resolution clocks this
1321	then order of execution is undefined.	1793	might introduce a small delay). If multiple timers become ready during the
		1794	same loop iteration then the ones with earlier time-out values are invoked
		1795	before ones of the same priority with later time-out values (but this is
		1796	no longer true when a callback calls C<ev_run> recursively).
1322		1797
1323	=head3 Be smart about timeouts	1798	=head3 Be smart about timeouts
1324		1799
1325	Many real-world problems involve some kind of timeout, usually for error	1800	Many real-world problems involve some kind of timeout, usually for error
1326	recovery. A typical example is an HTTP request - if the other side hangs,	1801	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1370	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>	1845	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
1371	member and C<ev_timer_again>.	1846	member and C<ev_timer_again>.
1372		1847
1373	At start:	1848	At start:
1374		1849
1375	ev_timer_init (timer, callback);	1850	ev_init (timer, callback);
1376	timer->repeat = 60.;	1851	timer->repeat = 60.;
1377	ev_timer_again (loop, timer);	1852	ev_timer_again (loop, timer);
1378		1853
1379	Each time there is some activity:	1854	Each time there is some activity:
1380		1855
…		…
1412	ev_tstamp timeout = last_activity + 60.;	1887	ev_tstamp timeout = last_activity + 60.;
1413		1888
1414	// if last_activity + 60. is older than now, we did time out	1889	// if last_activity + 60. is older than now, we did time out
1415	if (timeout < now)	1890	if (timeout < now)
1416	{	1891	{
1417	// timeout occured, take action	1892	// timeout occurred, take action
1418	}	1893	}
1419	else	1894	else
1420	{	1895	{
1421	// callback was invoked, but there was some activity, re-arm	1896	// callback was invoked, but there was some activity, re-arm
1422	// the watcher to fire in last_activity + 60, which is	1897	// the watcher to fire in last_activity + 60, which is
1423	// guaranteed to be in the future, so "again" is positive:	1898	// guaranteed to be in the future, so "again" is positive:
1424	w->again = timeout - now;	1899	w->repeat = timeout - now;
1425	ev_timer_again (EV_A_ w);	1900	ev_timer_again (EV_A_ w);
1426	}	1901	}
1427	}	1902	}
1428		1903
1429	To summarise the callback: first calculate the real timeout (defined	1904	To summarise the callback: first calculate the real timeout (defined
…		…
1442		1917
1443	To start the timer, simply initialise the watcher and set C<last_activity>	1918	To start the timer, simply initialise the watcher and set C<last_activity>
1444	to the current time (meaning we just have some activity :), then call the	1919	to the current time (meaning we just have some activity :), then call the
1445	callback, which will "do the right thing" and start the timer:	1920	callback, which will "do the right thing" and start the timer:
1446		1921
1447	ev_timer_init (timer, callback);	1922	ev_init (timer, callback);
1448	last_activity = ev_now (loop);	1923	last_activity = ev_now (loop);
1449	callback (loop, timer, EV_TIMEOUT);	1924	callback (loop, timer, EV_TIMER);
1450		1925
1451	And when there is some activity, simply store the current time in	1926	And when there is some activity, simply store the current time in
1452	C<last_activity>, no libev calls at all:	1927	C<last_activity>, no libev calls at all:
1453		1928
1454	last_actiivty = ev_now (loop);	1929	last_activity = ev_now (loop);
1455		1930
1456	This technique is slightly more complex, but in most cases where the	1931	This technique is slightly more complex, but in most cases where the
1457	time-out is unlikely to be triggered, much more efficient.	1932	time-out is unlikely to be triggered, much more efficient.
1458		1933
1459	Changing the timeout is trivial as well (if it isn't hard-coded in the	1934	Changing the timeout is trivial as well (if it isn't hard-coded in the
…		…
1497		1972
1498	=head3 The special problem of time updates	1973	=head3 The special problem of time updates
1499		1974
1500	Establishing the current time is a costly operation (it usually takes at	1975	Establishing the current time is a costly operation (it usually takes at
1501	least two system calls): EV therefore updates its idea of the current	1976	least two system calls): EV therefore updates its idea of the current
1502	time only before and after C<ev_loop> collects new events, which causes a	1977	time only before and after C<ev_run> collects new events, which causes a
1503	growing difference between C<ev_now ()> and C<ev_time ()> when handling	1978	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1504	lots of events in one iteration.	1979	lots of events in one iteration.
1505		1980
1506	The relative timeouts are calculated relative to the C<ev_now ()>	1981	The relative timeouts are calculated relative to the C<ev_now ()>
1507	time. This is usually the right thing as this timestamp refers to the time	1982	time. This is usually the right thing as this timestamp refers to the time
…		…
1513		1988
1514	If the event loop is suspended for a long time, you can also force an	1989	If the event loop is suspended for a long time, you can also force an
1515	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1990	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1516	()>.	1991	()>.
1517		1992
		1993	=head3 The special problems of suspended animation
		1994
		1995	When you leave the server world it is quite customary to hit machines that
		1996	can suspend/hibernate - what happens to the clocks during such a suspend?
		1997
		1998	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1999	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		2000	to run until the system is suspended, but they will not advance while the
		2001	system is suspended. That means, on resume, it will be as if the program
		2002	was frozen for a few seconds, but the suspend time will not be counted
		2003	towards C<ev_timer> when a monotonic clock source is used. The real time
		2004	clock advanced as expected, but if it is used as sole clocksource, then a
		2005	long suspend would be detected as a time jump by libev, and timers would
		2006	be adjusted accordingly.
		2007
		2008	I would not be surprised to see different behaviour in different between
		2009	operating systems, OS versions or even different hardware.
		2010
		2011	The other form of suspend (job control, or sending a SIGSTOP) will see a
		2012	time jump in the monotonic clocks and the realtime clock. If the program
		2013	is suspended for a very long time, and monotonic clock sources are in use,
		2014	then you can expect C<ev_timer>s to expire as the full suspension time
		2015	will be counted towards the timers. When no monotonic clock source is in
		2016	use, then libev will again assume a timejump and adjust accordingly.
		2017
		2018	It might be beneficial for this latter case to call C<ev_suspend>
		2019	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		2020	deterministic behaviour in this case (you can do nothing against
		2021	C<SIGSTOP>).
		2022
1518	=head3 Watcher-Specific Functions and Data Members	2023	=head3 Watcher-Specific Functions and Data Members
1519		2024
1520	=over 4	2025	=over 4
1521		2026
1522	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2027	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1545	If the timer is started but non-repeating, stop it (as if it timed out).	2050	If the timer is started but non-repeating, stop it (as if it timed out).
1546		2051
1547	If the timer is repeating, either start it if necessary (with the	2052	If the timer is repeating, either start it if necessary (with the
1548	C<repeat> value), or reset the running timer to the C<repeat> value.	2053	C<repeat> value), or reset the running timer to the C<repeat> value.
1549		2054
1550	This sounds a bit complicated, see "Be smart about timeouts", above, for a	2055	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1551	usage example.	2056	usage example.
		2057
		2058	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2059
		2060	Returns the remaining time until a timer fires. If the timer is active,
		2061	then this time is relative to the current event loop time, otherwise it's
		2062	the timeout value currently configured.
		2063
		2064	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2065	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2066	will return C<4>. When the timer expires and is restarted, it will return
		2067	roughly C<7> (likely slightly less as callback invocation takes some time,
		2068	too), and so on.
1552		2069
1553	=item ev_tstamp repeat [read-write]	2070	=item ev_tstamp repeat [read-write]
1554		2071
1555	The current C<repeat> value. Will be used each time the watcher times out	2072	The current C<repeat> value. Will be used each time the watcher times out
1556	or C<ev_timer_again> is called, and determines the next timeout (if any),	2073	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1582	}	2099	}
1583		2100
1584	ev_timer mytimer;	2101	ev_timer mytimer;
1585	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2102	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1586	ev_timer_again (&mytimer); /* start timer */	2103	ev_timer_again (&mytimer); /* start timer */
1587	ev_loop (loop, 0);	2104	ev_run (loop, 0);
1588		2105
1589	// and in some piece of code that gets executed on any "activity":	2106	// and in some piece of code that gets executed on any "activity":
1590	// reset the timeout to start ticking again at 10 seconds	2107	// reset the timeout to start ticking again at 10 seconds
1591	ev_timer_again (&mytimer);	2108	ev_timer_again (&mytimer);
1592		2109
…		…
1594	=head2 C<ev_periodic> - to cron or not to cron?	2111	=head2 C<ev_periodic> - to cron or not to cron?
1595		2112
1596	Periodic watchers are also timers of a kind, but they are very versatile	2113	Periodic watchers are also timers of a kind, but they are very versatile
1597	(and unfortunately a bit complex).	2114	(and unfortunately a bit complex).
1598		2115
1599	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2116	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1600	but on wall clock time (absolute time). You can tell a periodic watcher	2117	relative time, the physical time that passes) but on wall clock time
1601	to trigger after some specific point in time. For example, if you tell a	2118	(absolute time, the thing you can read on your calender or clock). The
1602	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	2119	difference is that wall clock time can run faster or slower than real
1603	+ 10.>, that is, an absolute time not a delay) and then reset your system	2120	time, and time jumps are not uncommon (e.g. when you adjust your
1604	clock to January of the previous year, then it will take more than year	2121	wrist-watch).
1605	to trigger the event (unlike an C<ev_timer>, which would still trigger
1606	roughly 10 seconds later as it uses a relative timeout).
1607		2122
		2123	You can tell a periodic watcher to trigger after some specific point
		2124	in time: for example, if you tell a periodic watcher to trigger "in 10
		2125	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2126	not a delay) and then reset your system clock to January of the previous
		2127	year, then it will take a year or more to trigger the event (unlike an
		2128	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2129	it, as it uses a relative timeout).
		2130
1608	C<ev_periodic>s can also be used to implement vastly more complex timers,	2131	C<ev_periodic> watchers can also be used to implement vastly more complex
1609	such as triggering an event on each "midnight, local time", or other	2132	timers, such as triggering an event on each "midnight, local time", or
1610	complicated rules.	2133	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2134	those cannot react to time jumps.
1611		2135
1612	As with timers, the callback is guaranteed to be invoked only when the	2136	As with timers, the callback is guaranteed to be invoked only when the
1613	time (C<at>) has passed, but if multiple periodic timers become ready	2137	point in time where it is supposed to trigger has passed. If multiple
1614	during the same loop iteration, then order of execution is undefined.	2138	timers become ready during the same loop iteration then the ones with
		2139	earlier time-out values are invoked before ones with later time-out values
		2140	(but this is no longer true when a callback calls C<ev_run> recursively).
1615		2141
1616	=head3 Watcher-Specific Functions and Data Members	2142	=head3 Watcher-Specific Functions and Data Members
1617		2143
1618	=over 4	2144	=over 4
1619		2145
1620	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2146	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1621		2147
1622	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2148	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1623		2149
1624	Lots of arguments, lets sort it out... There are basically three modes of	2150	Lots of arguments, let's sort it out... There are basically three modes of
1625	operation, and we will explain them from simplest to most complex:	2151	operation, and we will explain them from simplest to most complex:
1626		2152
1627	=over 4	2153	=over 4
1628		2154
1629	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2155	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1630		2156
1631	In this configuration the watcher triggers an event after the wall clock	2157	In this configuration the watcher triggers an event after the wall clock
1632	time C<at> has passed. It will not repeat and will not adjust when a time	2158	time C<offset> has passed. It will not repeat and will not adjust when a
1633	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2159	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1634	only run when the system clock reaches or surpasses this time.	2160	will be stopped and invoked when the system clock reaches or surpasses
		2161	this point in time.
1635		2162
1636	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2163	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1637		2164
1638	In this mode the watcher will always be scheduled to time out at the next	2165	In this mode the watcher will always be scheduled to time out at the next
1639	C<at + N * interval> time (for some integer N, which can also be negative)	2166	C<offset + N * interval> time (for some integer N, which can also be
1640	and then repeat, regardless of any time jumps.	2167	negative) and then repeat, regardless of any time jumps. The C<offset>
		2168	argument is merely an offset into the C<interval> periods.
1641		2169
1642	This can be used to create timers that do not drift with respect to the	2170	This can be used to create timers that do not drift with respect to the
1643	system clock, for example, here is a C<ev_periodic> that triggers each	2171	system clock, for example, here is an C<ev_periodic> that triggers each
1644	hour, on the hour:	2172	hour, on the hour (with respect to UTC):
1645		2173
1646	ev_periodic_set (&periodic, 0., 3600., 0);	2174	ev_periodic_set (&periodic, 0., 3600., 0);
1647		2175
1648	This doesn't mean there will always be 3600 seconds in between triggers,	2176	This doesn't mean there will always be 3600 seconds in between triggers,
1649	but only that the callback will be called when the system time shows a	2177	but only that the callback will be called when the system time shows a
1650	full hour (UTC), or more correctly, when the system time is evenly divisible	2178	full hour (UTC), or more correctly, when the system time is evenly divisible
1651	by 3600.	2179	by 3600.
1652		2180
1653	Another way to think about it (for the mathematically inclined) is that	2181	Another way to think about it (for the mathematically inclined) is that
1654	C<ev_periodic> will try to run the callback in this mode at the next possible	2182	C<ev_periodic> will try to run the callback in this mode at the next possible
1655	time where C<time = at (mod interval)>, regardless of any time jumps.	2183	time where C<time = offset (mod interval)>, regardless of any time jumps.
1656		2184
1657	For numerical stability it is preferable that the C<at> value is near	2185	For numerical stability it is preferable that the C<offset> value is near
1658	C<ev_now ()> (the current time), but there is no range requirement for	2186	C<ev_now ()> (the current time), but there is no range requirement for
1659	this value, and in fact is often specified as zero.	2187	this value, and in fact is often specified as zero.
1660		2188
1661	Note also that there is an upper limit to how often a timer can fire (CPU	2189	Note also that there is an upper limit to how often a timer can fire (CPU
1662	speed for example), so if C<interval> is very small then timing stability	2190	speed for example), so if C<interval> is very small then timing stability
1663	will of course deteriorate. Libev itself tries to be exact to be about one	2191	will of course deteriorate. Libev itself tries to be exact to be about one
1664	millisecond (if the OS supports it and the machine is fast enough).	2192	millisecond (if the OS supports it and the machine is fast enough).
1665		2193
1666	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2194	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1667		2195
1668	In this mode the values for C<interval> and C<at> are both being	2196	In this mode the values for C<interval> and C<offset> are both being
1669	ignored. Instead, each time the periodic watcher gets scheduled, the	2197	ignored. Instead, each time the periodic watcher gets scheduled, the
1670	reschedule callback will be called with the watcher as first, and the	2198	reschedule callback will be called with the watcher as first, and the
1671	current time as second argument.	2199	current time as second argument.
1672		2200
1673	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2201	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1674	ever, or make ANY event loop modifications whatsoever>.	2202	or make ANY other event loop modifications whatsoever, unless explicitly
		2203	allowed by documentation here>.
1675		2204
1676	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2205	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1677	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2206	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1678	only event loop modification you are allowed to do).	2207	only event loop modification you are allowed to do).
1679		2208
…		…
1709	a different time than the last time it was called (e.g. in a crond like	2238	a different time than the last time it was called (e.g. in a crond like
1710	program when the crontabs have changed).	2239	program when the crontabs have changed).
1711		2240
1712	=item ev_tstamp ev_periodic_at (ev_periodic *)	2241	=item ev_tstamp ev_periodic_at (ev_periodic *)
1713		2242
1714	When active, returns the absolute time that the watcher is supposed to	2243	When active, returns the absolute time that the watcher is supposed
1715	trigger next.	2244	to trigger next. This is not the same as the C<offset> argument to
		2245	C<ev_periodic_set>, but indeed works even in interval and manual
		2246	rescheduling modes.
1716		2247
1717	=item ev_tstamp offset [read-write]	2248	=item ev_tstamp offset [read-write]
1718		2249
1719	When repeating, this contains the offset value, otherwise this is the	2250	When repeating, this contains the offset value, otherwise this is the
1720	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2251	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2252	although libev might modify this value for better numerical stability).
1721		2253
1722	Can be modified any time, but changes only take effect when the periodic	2254	Can be modified any time, but changes only take effect when the periodic
1723	timer fires or C<ev_periodic_again> is being called.	2255	timer fires or C<ev_periodic_again> is being called.
1724		2256
1725	=item ev_tstamp interval [read-write]	2257	=item ev_tstamp interval [read-write]
…		…
1741	Example: Call a callback every hour, or, more precisely, whenever the	2273	Example: Call a callback every hour, or, more precisely, whenever the
1742	system time is divisible by 3600. The callback invocation times have	2274	system time is divisible by 3600. The callback invocation times have
1743	potentially a lot of jitter, but good long-term stability.	2275	potentially a lot of jitter, but good long-term stability.
1744		2276
1745	static void	2277	static void
1746	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2278	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1747	{	2279	{
1748	... its now a full hour (UTC, or TAI or whatever your clock follows)	2280	... its now a full hour (UTC, or TAI or whatever your clock follows)
1749	}	2281	}
1750		2282
1751	ev_periodic hourly_tick;	2283	ev_periodic hourly_tick;
…		…
1774		2306
1775	=head2 C<ev_signal> - signal me when a signal gets signalled!	2307	=head2 C<ev_signal> - signal me when a signal gets signalled!
1776		2308
1777	Signal watchers will trigger an event when the process receives a specific	2309	Signal watchers will trigger an event when the process receives a specific
1778	signal one or more times. Even though signals are very asynchronous, libev	2310	signal one or more times. Even though signals are very asynchronous, libev
1779	will try it's best to deliver signals synchronously, i.e. as part of the	2311	will try its best to deliver signals synchronously, i.e. as part of the
1780	normal event processing, like any other event.	2312	normal event processing, like any other event.
1781		2313
1782	If you want signals asynchronously, just use C<sigaction> as you would	2314	If you want signals to be delivered truly asynchronously, just use
1783	do without libev and forget about sharing the signal. You can even use	2315	C<sigaction> as you would do without libev and forget about sharing
1784	C<ev_async> from a signal handler to synchronously wake up an event loop.	2316	the signal. You can even use C<ev_async> from a signal handler to
		2317	synchronously wake up an event loop.
1785		2318
1786	You can configure as many watchers as you like per signal. Only when the	2319	You can configure as many watchers as you like for the same signal, but
		2320	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2321	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2322	C<SIGINT> in both the default loop and another loop at the same time. At
		2323	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2324
1787	first watcher gets started will libev actually register a signal handler	2325	When the first watcher gets started will libev actually register something
1788	with the kernel (thus it coexists with your own signal handlers as long as	2326	with the kernel (thus it coexists with your own signal handlers as long as
1789	you don't register any with libev for the same signal). Similarly, when	2327	you don't register any with libev for the same signal).
1790	the last signal watcher for a signal is stopped, libev will reset the
1791	signal handler to SIG_DFL (regardless of what it was set to before).
1792		2328
1793	If possible and supported, libev will install its handlers with	2329	If possible and supported, libev will install its handlers with
1794	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2330	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1795	interrupted. If you have a problem with system calls getting interrupted by	2331	not be unduly interrupted. If you have a problem with system calls getting
1796	signals you can block all signals in an C<ev_check> watcher and unblock	2332	interrupted by signals you can block all signals in an C<ev_check> watcher
1797	them in an C<ev_prepare> watcher.	2333	and unblock them in an C<ev_prepare> watcher.
		2334
		2335	=head3 The special problem of inheritance over fork/execve/pthread_create
		2336
		2337	Both the signal mask (C<sigprocmask>) and the signal disposition
		2338	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2339	stopping it again), that is, libev might or might not block the signal,
		2340	and might or might not set or restore the installed signal handler.
		2341
		2342	While this does not matter for the signal disposition (libev never
		2343	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2344	C<execve>), this matters for the signal mask: many programs do not expect
		2345	certain signals to be blocked.
		2346
		2347	This means that before calling C<exec> (from the child) you should reset
		2348	the signal mask to whatever "default" you expect (all clear is a good
		2349	choice usually).
		2350
		2351	The simplest way to ensure that the signal mask is reset in the child is
		2352	to install a fork handler with C<pthread_atfork> that resets it. That will
		2353	catch fork calls done by libraries (such as the libc) as well.
		2354
		2355	In current versions of libev, the signal will not be blocked indefinitely
		2356	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2357	the window of opportunity for problems, it will not go away, as libev
		2358	I<has> to modify the signal mask, at least temporarily.
		2359
		2360	So I can't stress this enough: I<If you do not reset your signal mask when
		2361	you expect it to be empty, you have a race condition in your code>. This
		2362	is not a libev-specific thing, this is true for most event libraries.
		2363
		2364	=head3 The special problem of threads signal handling
		2365
		2366	POSIX threads has problematic signal handling semantics, specifically,
		2367	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2368	threads in a process block signals, which is hard to achieve.
		2369
		2370	When you want to use sigwait (or mix libev signal handling with your own
		2371	for the same signals), you can tackle this problem by globally blocking
		2372	all signals before creating any threads (or creating them with a fully set
		2373	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2374	loops. Then designate one thread as "signal receiver thread" which handles
		2375	these signals. You can pass on any signals that libev might be interested
		2376	in by calling C<ev_feed_signal>.
1798		2377
1799	=head3 Watcher-Specific Functions and Data Members	2378	=head3 Watcher-Specific Functions and Data Members
1800		2379
1801	=over 4	2380	=over 4
1802		2381
…		…
1818	Example: Try to exit cleanly on SIGINT.	2397	Example: Try to exit cleanly on SIGINT.
1819		2398
1820	static void	2399	static void
1821	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2400	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1822	{	2401	{
1823	ev_unloop (loop, EVUNLOOP_ALL);	2402	ev_break (loop, EVBREAK_ALL);
1824	}	2403	}
1825		2404
1826	ev_signal signal_watcher;	2405	ev_signal signal_watcher;
1827	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2406	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1828	ev_signal_start (loop, &signal_watcher);	2407	ev_signal_start (loop, &signal_watcher);
…		…
1834	some child status changes (most typically when a child of yours dies or	2413	some child status changes (most typically when a child of yours dies or
1835	exits). It is permissible to install a child watcher I<after> the child	2414	exits). It is permissible to install a child watcher I<after> the child
1836	has been forked (which implies it might have already exited), as long	2415	has been forked (which implies it might have already exited), as long
1837	as the event loop isn't entered (or is continued from a watcher), i.e.,	2416	as the event loop isn't entered (or is continued from a watcher), i.e.,
1838	forking and then immediately registering a watcher for the child is fine,	2417	forking and then immediately registering a watcher for the child is fine,
1839	but forking and registering a watcher a few event loop iterations later is	2418	but forking and registering a watcher a few event loop iterations later or
1840	not.	2419	in the next callback invocation is not.
1841		2420
1842	Only the default event loop is capable of handling signals, and therefore	2421	Only the default event loop is capable of handling signals, and therefore
1843	you can only register child watchers in the default event loop.	2422	you can only register child watchers in the default event loop.
1844		2423
		2424	Due to some design glitches inside libev, child watchers will always be
		2425	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2426	libev)
		2427
1845	=head3 Process Interaction	2428	=head3 Process Interaction
1846		2429
1847	Libev grabs C<SIGCHLD> as soon as the default event loop is	2430	Libev grabs C<SIGCHLD> as soon as the default event loop is
1848	initialised. This is necessary to guarantee proper behaviour even if	2431	initialised. This is necessary to guarantee proper behaviour even if the
1849	the first child watcher is started after the child exits. The occurrence	2432	first child watcher is started after the child exits. The occurrence
1850	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2433	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1851	synchronously as part of the event loop processing. Libev always reaps all	2434	synchronously as part of the event loop processing. Libev always reaps all
1852	children, even ones not watched.	2435	children, even ones not watched.
1853		2436
1854	=head3 Overriding the Built-In Processing	2437	=head3 Overriding the Built-In Processing
…		…
1864	=head3 Stopping the Child Watcher	2447	=head3 Stopping the Child Watcher
1865		2448
1866	Currently, the child watcher never gets stopped, even when the	2449	Currently, the child watcher never gets stopped, even when the
1867	child terminates, so normally one needs to stop the watcher in the	2450	child terminates, so normally one needs to stop the watcher in the
1868	callback. Future versions of libev might stop the watcher automatically	2451	callback. Future versions of libev might stop the watcher automatically
1869	when a child exit is detected.	2452	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2453	problem).
1870		2454
1871	=head3 Watcher-Specific Functions and Data Members	2455	=head3 Watcher-Specific Functions and Data Members
1872		2456
1873	=over 4	2457	=over 4
1874		2458
…		…
2010	the process. The exception are C<ev_stat> watchers - those call C<stat	2594	the process. The exception are C<ev_stat> watchers - those call C<stat
2011	()>, which is a synchronous operation.	2595	()>, which is a synchronous operation.
2012		2596
2013	For local paths, this usually doesn't matter: unless the system is very	2597	For local paths, this usually doesn't matter: unless the system is very
2014	busy or the intervals between stat's are large, a stat call will be fast,	2598	busy or the intervals between stat's are large, a stat call will be fast,
2015	as the path data is suually in memory already (except when starting the	2599	as the path data is usually in memory already (except when starting the
2016	watcher).	2600	watcher).
2017		2601
2018	For networked file systems, calling C<stat ()> can block an indefinite	2602	For networked file systems, calling C<stat ()> can block an indefinite
2019	time due to network issues, and even under good conditions, a stat call	2603	time due to network issues, and even under good conditions, a stat call
2020	often takes multiple milliseconds.	2604	often takes multiple milliseconds.
…		…
2177		2761
2178	=head3 Watcher-Specific Functions and Data Members	2762	=head3 Watcher-Specific Functions and Data Members
2179		2763
2180	=over 4	2764	=over 4
2181		2765
2182	=item ev_idle_init (ev_signal *, callback)	2766	=item ev_idle_init (ev_idle *, callback)
2183		2767
2184	Initialises and configures the idle watcher - it has no parameters of any	2768	Initialises and configures the idle watcher - it has no parameters of any
2185	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2769	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
2186	believe me.	2770	believe me.
2187		2771
…		…
2200	// no longer anything immediate to do.	2784	// no longer anything immediate to do.
2201	}	2785	}
2202		2786
2203	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2787	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2204	ev_idle_init (idle_watcher, idle_cb);	2788	ev_idle_init (idle_watcher, idle_cb);
2205	ev_idle_start (loop, idle_cb);	2789	ev_idle_start (loop, idle_watcher);
2206		2790
2207		2791
2208	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2792	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2209		2793
2210	Prepare and check watchers are usually (but not always) used in pairs:	2794	Prepare and check watchers are usually (but not always) used in pairs:
2211	prepare watchers get invoked before the process blocks and check watchers	2795	prepare watchers get invoked before the process blocks and check watchers
2212	afterwards.	2796	afterwards.
2213		2797
2214	You I<must not> call C<ev_loop> or similar functions that enter	2798	You I<must not> call C<ev_run> or similar functions that enter
2215	the current event loop from either C<ev_prepare> or C<ev_check>	2799	the current event loop from either C<ev_prepare> or C<ev_check>
2216	watchers. Other loops than the current one are fine, however. The	2800	watchers. Other loops than the current one are fine, however. The
2217	rationale behind this is that you do not need to check for recursion in	2801	rationale behind this is that you do not need to check for recursion in
2218	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2802	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2219	C<ev_check> so if you have one watcher of each kind they will always be	2803	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2303	struct pollfd fds [nfd];	2887	struct pollfd fds [nfd];
2304	// actual code will need to loop here and realloc etc.	2888	// actual code will need to loop here and realloc etc.
2305	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2889	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2306		2890
2307	/* the callback is illegal, but won't be called as we stop during check */	2891	/* the callback is illegal, but won't be called as we stop during check */
2308	ev_timer_init (&tw, 0, timeout * 1e-3);	2892	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2309	ev_timer_start (loop, &tw);	2893	ev_timer_start (loop, &tw);
2310		2894
2311	// create one ev_io per pollfd	2895	// create one ev_io per pollfd
2312	for (int i = 0; i < nfd; ++i)	2896	for (int i = 0; i < nfd; ++i)
2313	{	2897	{
…		…
2387		2971
2388	if (timeout >= 0)	2972	if (timeout >= 0)
2389	// create/start timer	2973	// create/start timer
2390		2974
2391	// poll	2975	// poll
2392	ev_loop (EV_A_ 0);	2976	ev_run (EV_A_ 0);
2393		2977
2394	// stop timer again	2978	// stop timer again
2395	if (timeout >= 0)	2979	if (timeout >= 0)
2396	ev_timer_stop (EV_A_ &to);	2980	ev_timer_stop (EV_A_ &to);
2397		2981
…		…
2426	some fds have to be watched and handled very quickly (with low latency),	3010	some fds have to be watched and handled very quickly (with low latency),
2427	and even priorities and idle watchers might have too much overhead. In	3011	and even priorities and idle watchers might have too much overhead. In
2428	this case you would put all the high priority stuff in one loop and all	3012	this case you would put all the high priority stuff in one loop and all
2429	the rest in a second one, and embed the second one in the first.	3013	the rest in a second one, and embed the second one in the first.
2430		3014
2431	As long as the watcher is active, the callback will be invoked every time	3015	As long as the watcher is active, the callback will be invoked every
2432	there might be events pending in the embedded loop. The callback must then	3016	time there might be events pending in the embedded loop. The callback
2433	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	3017	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2434	their callbacks (you could also start an idle watcher to give the embedded	3018	sweep and invoke their callbacks (the callback doesn't need to invoke the
2435	loop strictly lower priority for example). You can also set the callback	3019	C<ev_embed_sweep> function directly, it could also start an idle watcher
2436	to C<0>, in which case the embed watcher will automatically execute the	3020	to give the embedded loop strictly lower priority for example).
2437	embedded loop sweep.
2438		3021
2439	As long as the watcher is started it will automatically handle events. The	3022	You can also set the callback to C<0>, in which case the embed watcher
2440	callback will be invoked whenever some events have been handled. You can	3023	will automatically execute the embedded loop sweep whenever necessary.
2441	set the callback to C<0> to avoid having to specify one if you are not
2442	interested in that.
2443		3024
2444	Also, there have not currently been made special provisions for forking:	3025	Fork detection will be handled transparently while the C<ev_embed> watcher
2445	when you fork, you not only have to call C<ev_loop_fork> on both loops,	3026	is active, i.e., the embedded loop will automatically be forked when the
2446	but you will also have to stop and restart any C<ev_embed> watchers	3027	embedding loop forks. In other cases, the user is responsible for calling
2447	yourself - but you can use a fork watcher to handle this automatically,	3028	C<ev_loop_fork> on the embedded loop.
2448	and future versions of libev might do just that.
2449		3029
2450	Unfortunately, not all backends are embeddable: only the ones returned by	3030	Unfortunately, not all backends are embeddable: only the ones returned by
2451	C<ev_embeddable_backends> are, which, unfortunately, does not include any	3031	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2452	portable one.	3032	portable one.
2453		3033
…		…
2479	if you do not want that, you need to temporarily stop the embed watcher).	3059	if you do not want that, you need to temporarily stop the embed watcher).
2480		3060
2481	=item ev_embed_sweep (loop, ev_embed *)	3061	=item ev_embed_sweep (loop, ev_embed *)
2482		3062
2483	Make a single, non-blocking sweep over the embedded loop. This works	3063	Make a single, non-blocking sweep over the embedded loop. This works
2484	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3064	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2485	appropriate way for embedded loops.	3065	appropriate way for embedded loops.
2486		3066
2487	=item struct ev_loop *other [read-only]	3067	=item struct ev_loop *other [read-only]
2488		3068
2489	The embedded event loop.	3069	The embedded event loop.
…		…
2547	event loop blocks next and before C<ev_check> watchers are being called,	3127	event loop blocks next and before C<ev_check> watchers are being called,
2548	and only in the child after the fork. If whoever good citizen calling	3128	and only in the child after the fork. If whoever good citizen calling
2549	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3129	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2550	handlers will be invoked, too, of course.	3130	handlers will be invoked, too, of course.
2551		3131
		3132	=head3 The special problem of life after fork - how is it possible?
		3133
		3134	Most uses of C<fork()> consist of forking, then some simple calls to set
		3135	up/change the process environment, followed by a call to C<exec()>. This
		3136	sequence should be handled by libev without any problems.
		3137
		3138	This changes when the application actually wants to do event handling
		3139	in the child, or both parent in child, in effect "continuing" after the
		3140	fork.
		3141
		3142	The default mode of operation (for libev, with application help to detect
		3143	forks) is to duplicate all the state in the child, as would be expected
		3144	when I<either> the parent I<or> the child process continues.
		3145
		3146	When both processes want to continue using libev, then this is usually the
		3147	wrong result. In that case, usually one process (typically the parent) is
		3148	supposed to continue with all watchers in place as before, while the other
		3149	process typically wants to start fresh, i.e. without any active watchers.
		3150
		3151	The cleanest and most efficient way to achieve that with libev is to
		3152	simply create a new event loop, which of course will be "empty", and
		3153	use that for new watchers. This has the advantage of not touching more
		3154	memory than necessary, and thus avoiding the copy-on-write, and the
		3155	disadvantage of having to use multiple event loops (which do not support
		3156	signal watchers).
		3157
		3158	When this is not possible, or you want to use the default loop for
		3159	other reasons, then in the process that wants to start "fresh", call
		3160	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3161	Destroying the default loop will "orphan" (not stop) all registered
		3162	watchers, so you have to be careful not to execute code that modifies
		3163	those watchers. Note also that in that case, you have to re-register any
		3164	signal watchers.
		3165
2552	=head3 Watcher-Specific Functions and Data Members	3166	=head3 Watcher-Specific Functions and Data Members
2553		3167
2554	=over 4	3168	=over 4
2555		3169
2556	=item ev_fork_init (ev_signal *, callback)	3170	=item ev_fork_init (ev_fork *, callback)
2557		3171
2558	Initialises and configures the fork watcher - it has no parameters of any	3172	Initialises and configures the fork watcher - it has no parameters of any
2559	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3173	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2560	believe me.	3174	really.
2561		3175
2562	=back	3176	=back
2563		3177
2564		3178
		3179	=head2 C<ev_cleanup> - even the best things end
		3180
		3181	Cleanup watchers are called just before the event loop is being destroyed
		3182	by a call to C<ev_loop_destroy>.
		3183
		3184	While there is no guarantee that the event loop gets destroyed, cleanup
		3185	watchers provide a convenient method to install cleanup hooks for your
		3186	program, worker threads and so on - you just to make sure to destroy the
		3187	loop when you want them to be invoked.
		3188
		3189	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3190	all other watchers, they do not keep a reference to the event loop (which
		3191	makes a lot of sense if you think about it). Like all other watchers, you
		3192	can call libev functions in the callback, except C<ev_cleanup_start>.
		3193
		3194	=head3 Watcher-Specific Functions and Data Members
		3195
		3196	=over 4
		3197
		3198	=item ev_cleanup_init (ev_cleanup *, callback)
		3199
		3200	Initialises and configures the cleanup watcher - it has no parameters of
		3201	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3202	pointless, I assure you.
		3203
		3204	=back
		3205
		3206	Example: Register an atexit handler to destroy the default loop, so any
		3207	cleanup functions are called.
		3208
		3209	static void
		3210	program_exits (void)
		3211	{
		3212	ev_loop_destroy (EV_DEFAULT_UC);
		3213	}
		3214
		3215	...
		3216	atexit (program_exits);
		3217
		3218
2565	=head2 C<ev_async> - how to wake up another event loop	3219	=head2 C<ev_async> - how to wake up an event loop
2566		3220
2567	In general, you cannot use an C<ev_loop> from multiple threads or other	3221	In general, you cannot use an C<ev_run> from multiple threads or other
2568	asynchronous sources such as signal handlers (as opposed to multiple event	3222	asynchronous sources such as signal handlers (as opposed to multiple event
2569	loops - those are of course safe to use in different threads).	3223	loops - those are of course safe to use in different threads).
2570		3224
2571	Sometimes, however, you need to wake up another event loop you do not	3225	Sometimes, however, you need to wake up an event loop you do not control,
2572	control, for example because it belongs to another thread. This is what	3226	for example because it belongs to another thread. This is what C<ev_async>
2573	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3227	watchers do: as long as the C<ev_async> watcher is active, you can signal
2574	can signal it by calling C<ev_async_send>, which is thread- and signal	3228	it by calling C<ev_async_send>, which is thread- and signal safe.
2575	safe.
2576		3229
2577	This functionality is very similar to C<ev_signal> watchers, as signals,	3230	This functionality is very similar to C<ev_signal> watchers, as signals,
2578	too, are asynchronous in nature, and signals, too, will be compressed	3231	too, are asynchronous in nature, and signals, too, will be compressed
2579	(i.e. the number of callback invocations may be less than the number of	3232	(i.e. the number of callback invocations may be less than the number of
2580	C<ev_async_sent> calls).	3233	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
		3234	of "global async watchers" by using a watcher on an otherwise unused
		3235	signal, and C<ev_feed_signal> to signal this watcher from another thread,
		3236	even without knowing which loop owns the signal.
2581		3237
2582	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3238	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
2583	just the default loop.	3239	just the default loop.
2584		3240
2585	=head3 Queueing	3241	=head3 Queueing
2586		3242
2587	C<ev_async> does not support queueing of data in any way. The reason	3243	C<ev_async> does not support queueing of data in any way. The reason
2588	is that the author does not know of a simple (or any) algorithm for a	3244	is that the author does not know of a simple (or any) algorithm for a
2589	multiple-writer-single-reader queue that works in all cases and doesn't	3245	multiple-writer-single-reader queue that works in all cases and doesn't
2590	need elaborate support such as pthreads.	3246	need elaborate support such as pthreads or unportable memory access
		3247	semantics.
2591		3248
2592	That means that if you want to queue data, you have to provide your own	3249	That means that if you want to queue data, you have to provide your own
2593	queue. But at least I can tell you how to implement locking around your	3250	queue. But at least I can tell you how to implement locking around your
2594	queue:	3251	queue:
2595		3252
…		…
2684	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3341	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2685	C<ev_feed_event>, this call is safe to do from other threads, signal or	3342	C<ev_feed_event>, this call is safe to do from other threads, signal or
2686	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3343	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2687	section below on what exactly this means).	3344	section below on what exactly this means).
2688		3345
		3346	Note that, as with other watchers in libev, multiple events might get
		3347	compressed into a single callback invocation (another way to look at this
		3348	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3349	reset when the event loop detects that).
		3350
2689	This call incurs the overhead of a system call only once per loop iteration,	3351	This call incurs the overhead of a system call only once per event loop
2690	so while the overhead might be noticeable, it doesn't apply to repeated	3352	iteration, so while the overhead might be noticeable, it doesn't apply to
2691	calls to C<ev_async_send>.	3353	repeated calls to C<ev_async_send> for the same event loop.
2692		3354
2693	=item bool = ev_async_pending (ev_async *)	3355	=item bool = ev_async_pending (ev_async *)
2694		3356
2695	Returns a non-zero value when C<ev_async_send> has been called on the	3357	Returns a non-zero value when C<ev_async_send> has been called on the
2696	watcher but the event has not yet been processed (or even noted) by the	3358	watcher but the event has not yet been processed (or even noted) by the
…		…
2699	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3361	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2700	the loop iterates next and checks for the watcher to have become active,	3362	the loop iterates next and checks for the watcher to have become active,
2701	it will reset the flag again. C<ev_async_pending> can be used to very	3363	it will reset the flag again. C<ev_async_pending> can be used to very
2702	quickly check whether invoking the loop might be a good idea.	3364	quickly check whether invoking the loop might be a good idea.
2703		3365
2704	Not that this does I<not> check whether the watcher itself is pending, only	3366	Not that this does I<not> check whether the watcher itself is pending,
2705	whether it has been requested to make this watcher pending.	3367	only whether it has been requested to make this watcher pending: there
		3368	is a time window between the event loop checking and resetting the async
		3369	notification, and the callback being invoked.
2706		3370
2707	=back	3371	=back
2708		3372
2709		3373
2710	=head1 OTHER FUNCTIONS	3374	=head1 OTHER FUNCTIONS
…		…
2727		3391
2728	If C<timeout> is less than 0, then no timeout watcher will be	3392	If C<timeout> is less than 0, then no timeout watcher will be
2729	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3393	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2730	repeat = 0) will be started. C<0> is a valid timeout.	3394	repeat = 0) will be started. C<0> is a valid timeout.
2731		3395
2732	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3396	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2733	passed an C<revents> set like normal event callbacks (a combination of	3397	passed an C<revents> set like normal event callbacks (a combination of
2734	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3398	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2735	value passed to C<ev_once>. Note that it is possible to receive I<both>	3399	value passed to C<ev_once>. Note that it is possible to receive I<both>
2736	a timeout and an io event at the same time - you probably should give io	3400	a timeout and an io event at the same time - you probably should give io
2737	events precedence.	3401	events precedence.
2738		3402
2739	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3403	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2740		3404
2741	static void stdin_ready (int revents, void *arg)	3405	static void stdin_ready (int revents, void *arg)
2742	{	3406	{
2743	if (revents & EV_READ)	3407	if (revents & EV_READ)
2744	/* stdin might have data for us, joy! */;	3408	/* stdin might have data for us, joy! */;
2745	else if (revents & EV_TIMEOUT)	3409	else if (revents & EV_TIMER)
2746	/* doh, nothing entered */;	3410	/* doh, nothing entered */;
2747	}	3411	}
2748		3412
2749	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3413	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2750		3414
2751	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2752
2753	Feeds the given event set into the event loop, as if the specified event
2754	had happened for the specified watcher (which must be a pointer to an
2755	initialised but not necessarily started event watcher).
2756
2757	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3415	=item ev_feed_fd_event (loop, int fd, int revents)
2758		3416
2759	Feed an event on the given fd, as if a file descriptor backend detected	3417	Feed an event on the given fd, as if a file descriptor backend detected
2760	the given events it.	3418	the given events it.
2761		3419
2762	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3420	=item ev_feed_signal_event (loop, int signum)
2763		3421
2764	Feed an event as if the given signal occurred (C<loop> must be the default	3422	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
2765	loop!).	3423	which is async-safe.
		3424
		3425	=back
		3426
		3427
		3428	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3429
		3430	This section explains some common idioms that are not immediately
		3431	obvious. Note that examples are sprinkled over the whole manual, and this
		3432	section only contains stuff that wouldn't fit anywhere else.
		3433
		3434	=over 4
		3435
		3436	=item Model/nested event loop invocations and exit conditions.
		3437
		3438	Often (especially in GUI toolkits) there are places where you have
		3439	I<modal> interaction, which is most easily implemented by recursively
		3440	invoking C<ev_run>.
		3441
		3442	This brings the problem of exiting - a callback might want to finish the
		3443	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3444	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3445	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3446	other combination: In these cases, C<ev_break> will not work alone.
		3447
		3448	The solution is to maintain "break this loop" variable for each C<ev_run>
		3449	invocation, and use a loop around C<ev_run> until the condition is
		3450	triggered, using C<EVRUN_ONCE>:
		3451
		3452	// main loop
		3453	int exit_main_loop = 0;
		3454
		3455	while (!exit_main_loop)
		3456	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3457
		3458	// in a model watcher
		3459	int exit_nested_loop = 0;
		3460
		3461	while (!exit_nested_loop)
		3462	ev_run (EV_A_ EVRUN_ONCE);
		3463
		3464	To exit from any of these loops, just set the corresponding exit variable:
		3465
		3466	// exit modal loop
		3467	exit_nested_loop = 1;
		3468
		3469	// exit main program, after modal loop is finished
		3470	exit_main_loop = 1;
		3471
		3472	// exit both
		3473	exit_main_loop = exit_nested_loop = 1;
2766		3474
2767	=back	3475	=back
2768		3476
2769		3477
2770	=head1 LIBEVENT EMULATION	3478	=head1 LIBEVENT EMULATION
2771		3479
2772	Libev offers a compatibility emulation layer for libevent. It cannot	3480	Libev offers a compatibility emulation layer for libevent. It cannot
2773	emulate the internals of libevent, so here are some usage hints:	3481	emulate the internals of libevent, so here are some usage hints:
2774		3482
2775	=over 4	3483	=over 4
		3484
		3485	=item * Only the libevent-1.4.1-beta API is being emulated.
		3486
		3487	This was the newest libevent version available when libev was implemented,
		3488	and is still mostly unchanged in 2010.
2776		3489
2777	=item * Use it by including <event.h>, as usual.	3490	=item * Use it by including <event.h>, as usual.
2778		3491
2779	=item * The following members are fully supported: ev_base, ev_callback,	3492	=item * The following members are fully supported: ev_base, ev_callback,
2780	ev_arg, ev_fd, ev_res, ev_events.	3493	ev_arg, ev_fd, ev_res, ev_events.
…		…
2786	=item * Priorities are not currently supported. Initialising priorities	3499	=item * Priorities are not currently supported. Initialising priorities
2787	will fail and all watchers will have the same priority, even though there	3500	will fail and all watchers will have the same priority, even though there
2788	is an ev_pri field.	3501	is an ev_pri field.
2789		3502
2790	=item * In libevent, the last base created gets the signals, in libev, the	3503	=item * In libevent, the last base created gets the signals, in libev, the
2791	first base created (== the default loop) gets the signals.	3504	base that registered the signal gets the signals.
2792		3505
2793	=item * Other members are not supported.	3506	=item * Other members are not supported.
2794		3507
2795	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3508	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2796	to use the libev header file and library.	3509	to use the libev header file and library.
…		…
2815	Care has been taken to keep the overhead low. The only data member the C++	3528	Care has been taken to keep the overhead low. The only data member the C++
2816	classes add (compared to plain C-style watchers) is the event loop pointer	3529	classes add (compared to plain C-style watchers) is the event loop pointer
2817	that the watcher is associated with (or no additional members at all if	3530	that the watcher is associated with (or no additional members at all if
2818	you disable C<EV_MULTIPLICITY> when embedding libev).	3531	you disable C<EV_MULTIPLICITY> when embedding libev).
2819		3532
2820	Currently, functions, and static and non-static member functions can be	3533	Currently, functions, static and non-static member functions and classes
2821	used as callbacks. Other types should be easy to add as long as they only	3534	with C<operator ()> can be used as callbacks. Other types should be easy
2822	need one additional pointer for context. If you need support for other	3535	to add as long as they only need one additional pointer for context. If
2823	types of functors please contact the author (preferably after implementing	3536	you need support for other types of functors please contact the author
2824	it).	3537	(preferably after implementing it).
2825		3538
2826	Here is a list of things available in the C<ev> namespace:	3539	Here is a list of things available in the C<ev> namespace:
2827		3540
2828	=over 4	3541	=over 4
2829		3542
…		…
2847		3560
2848	=over 4	3561	=over 4
2849		3562
2850	=item ev::TYPE::TYPE ()	3563	=item ev::TYPE::TYPE ()
2851		3564
2852	=item ev::TYPE::TYPE (struct ev_loop *)	3565	=item ev::TYPE::TYPE (loop)
2853		3566
2854	=item ev::TYPE::~TYPE	3567	=item ev::TYPE::~TYPE
2855		3568
2856	The constructor (optionally) takes an event loop to associate the watcher	3569	The constructor (optionally) takes an event loop to associate the watcher
2857	with. If it is omitted, it will use C<EV_DEFAULT>.	3570	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2889		3602
2890	myclass obj;	3603	myclass obj;
2891	ev::io iow;	3604	ev::io iow;
2892	iow.set <myclass, &myclass::io_cb> (&obj);	3605	iow.set <myclass, &myclass::io_cb> (&obj);
2893		3606
		3607	=item w->set (object *)
		3608
		3609	This is a variation of a method callback - leaving out the method to call
		3610	will default the method to C<operator ()>, which makes it possible to use
		3611	functor objects without having to manually specify the C<operator ()> all
		3612	the time. Incidentally, you can then also leave out the template argument
		3613	list.
		3614
		3615	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3616	int revents)>.
		3617
		3618	See the method-C<set> above for more details.
		3619
		3620	Example: use a functor object as callback.
		3621
		3622	struct myfunctor
		3623	{
		3624	void operator() (ev::io &w, int revents)
		3625	{
		3626	...
		3627	}
		3628	}
		3629
		3630	myfunctor f;
		3631
		3632	ev::io w;
		3633	w.set (&f);
		3634
2894	=item w->set<function> (void *data = 0)	3635	=item w->set<function> (void *data = 0)
2895		3636
2896	Also sets a callback, but uses a static method or plain function as	3637	Also sets a callback, but uses a static method or plain function as
2897	callback. The optional C<data> argument will be stored in the watcher's	3638	callback. The optional C<data> argument will be stored in the watcher's
2898	C<data> member and is free for you to use.	3639	C<data> member and is free for you to use.
…		…
2904	Example: Use a plain function as callback.	3645	Example: Use a plain function as callback.
2905		3646
2906	static void io_cb (ev::io &w, int revents) { }	3647	static void io_cb (ev::io &w, int revents) { }
2907	iow.set <io_cb> ();	3648	iow.set <io_cb> ();
2908		3649
2909	=item w->set (struct ev_loop *)	3650	=item w->set (loop)
2910		3651
2911	Associates a different C<struct ev_loop> with this watcher. You can only	3652	Associates a different C<struct ev_loop> with this watcher. You can only
2912	do this when the watcher is inactive (and not pending either).	3653	do this when the watcher is inactive (and not pending either).
2913		3654
2914	=item w->set ([arguments])	3655	=item w->set ([arguments])
2915		3656
2916	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3657	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
2917	called at least once. Unlike the C counterpart, an active watcher gets	3658	method or a suitable start method must be called at least once. Unlike the
2918	automatically stopped and restarted when reconfiguring it with this	3659	C counterpart, an active watcher gets automatically stopped and restarted
2919	method.	3660	when reconfiguring it with this method.
2920		3661
2921	=item w->start ()	3662	=item w->start ()
2922		3663
2923	Starts the watcher. Note that there is no C<loop> argument, as the	3664	Starts the watcher. Note that there is no C<loop> argument, as the
2924	constructor already stores the event loop.	3665	constructor already stores the event loop.
2925		3666
		3667	=item w->start ([arguments])
		3668
		3669	Instead of calling C<set> and C<start> methods separately, it is often
		3670	convenient to wrap them in one call. Uses the same type of arguments as
		3671	the configure C<set> method of the watcher.
		3672
2926	=item w->stop ()	3673	=item w->stop ()
2927		3674
2928	Stops the watcher if it is active. Again, no C<loop> argument.	3675	Stops the watcher if it is active. Again, no C<loop> argument.
2929		3676
2930	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3677	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2942		3689
2943	=back	3690	=back
2944		3691
2945	=back	3692	=back
2946		3693
2947	Example: Define a class with an IO and idle watcher, start one of them in	3694	Example: Define a class with two I/O and idle watchers, start the I/O
2948	the constructor.	3695	watchers in the constructor.
2949		3696
2950	class myclass	3697	class myclass
2951	{	3698	{
2952	ev::io io ; void io_cb (ev::io &w, int revents);	3699	ev::io io ; void io_cb (ev::io &w, int revents);
		3700	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
2953	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3701	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2954		3702
2955	myclass (int fd)	3703	myclass (int fd)
2956	{	3704	{
2957	io .set <myclass, &myclass::io_cb > (this);	3705	io .set <myclass, &myclass::io_cb > (this);
		3706	io2 .set <myclass, &myclass::io2_cb > (this);
2958	idle.set <myclass, &myclass::idle_cb> (this);	3707	idle.set <myclass, &myclass::idle_cb> (this);
2959		3708
2960	io.start (fd, ev::READ);	3709	io.set (fd, ev::WRITE); // configure the watcher
		3710	io.start (); // start it whenever convenient
		3711
		3712	io2.start (fd, ev::READ); // set + start in one call
2961	}	3713	}
2962	};	3714	};
2963		3715
2964		3716
2965	=head1 OTHER LANGUAGE BINDINGS	3717	=head1 OTHER LANGUAGE BINDINGS
…		…
2984	L<http://software.schmorp.de/pkg/EV>.	3736	L<http://software.schmorp.de/pkg/EV>.
2985		3737
2986	=item Python	3738	=item Python
2987		3739
2988	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3740	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2989	seems to be quite complete and well-documented. Note, however, that the	3741	seems to be quite complete and well-documented.
2990	patch they require for libev is outright dangerous as it breaks the ABI
2991	for everybody else, and therefore, should never be applied in an installed
2992	libev (if python requires an incompatible ABI then it needs to embed
2993	libev).
2994		3742
2995	=item Ruby	3743	=item Ruby
2996		3744
2997	Tony Arcieri has written a ruby extension that offers access to a subset	3745	Tony Arcieri has written a ruby extension that offers access to a subset
2998	of the libev API and adds file handle abstractions, asynchronous DNS and	3746	of the libev API and adds file handle abstractions, asynchronous DNS and
2999	more on top of it. It can be found via gem servers. Its homepage is at	3747	more on top of it. It can be found via gem servers. Its homepage is at
3000	L<http://rev.rubyforge.org/>.	3748	L<http://rev.rubyforge.org/>.
3001		3749
		3750	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3751	makes rev work even on mingw.
		3752
		3753	=item Haskell
		3754
		3755	A haskell binding to libev is available at
		3756	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3757
3002	=item D	3758	=item D
3003		3759
3004	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3760	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3005	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3761	be found at L<http://proj.llucax.com.ar/wiki/evd>.
3006		3762
3007	=item Ocaml	3763	=item Ocaml
3008		3764
3009	Erkki Seppala has written Ocaml bindings for libev, to be found at	3765	Erkki Seppala has written Ocaml bindings for libev, to be found at
3010	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	3766	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3767
		3768	=item Lua
		3769
		3770	Brian Maher has written a partial interface to libev for lua (at the
		3771	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3772	L<http://github.com/brimworks/lua-ev>.
3011		3773
3012	=back	3774	=back
3013		3775
3014		3776
3015	=head1 MACRO MAGIC	3777	=head1 MACRO MAGIC
…		…
3029	loop argument"). The C<EV_A> form is used when this is the sole argument,	3791	loop argument"). The C<EV_A> form is used when this is the sole argument,
3030	C<EV_A_> is used when other arguments are following. Example:	3792	C<EV_A_> is used when other arguments are following. Example:
3031		3793
3032	ev_unref (EV_A);	3794	ev_unref (EV_A);
3033	ev_timer_add (EV_A_ watcher);	3795	ev_timer_add (EV_A_ watcher);
3034	ev_loop (EV_A_ 0);	3796	ev_run (EV_A_ 0);
3035		3797
3036	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3798	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3037	which is often provided by the following macro.	3799	which is often provided by the following macro.
3038		3800
3039	=item C<EV_P>, C<EV_P_>	3801	=item C<EV_P>, C<EV_P_>
…		…
3079	}	3841	}
3080		3842
3081	ev_check check;	3843	ev_check check;
3082	ev_check_init (&check, check_cb);	3844	ev_check_init (&check, check_cb);
3083	ev_check_start (EV_DEFAULT_ &check);	3845	ev_check_start (EV_DEFAULT_ &check);
3084	ev_loop (EV_DEFAULT_ 0);	3846	ev_run (EV_DEFAULT_ 0);
3085		3847
3086	=head1 EMBEDDING	3848	=head1 EMBEDDING
3087		3849
3088	Libev can (and often is) directly embedded into host	3850	Libev can (and often is) directly embedded into host
3089	applications. Examples of applications that embed it include the Deliantra	3851	applications. Examples of applications that embed it include the Deliantra
…		…
3169	libev.m4	3931	libev.m4
3170		3932
3171	=head2 PREPROCESSOR SYMBOLS/MACROS	3933	=head2 PREPROCESSOR SYMBOLS/MACROS
3172		3934
3173	Libev can be configured via a variety of preprocessor symbols you have to	3935	Libev can be configured via a variety of preprocessor symbols you have to
3174	define before including any of its files. The default in the absence of	3936	define before including (or compiling) any of its files. The default in
3175	autoconf is documented for every option.	3937	the absence of autoconf is documented for every option.
		3938
		3939	Symbols marked with "(h)" do not change the ABI, and can have different
		3940	values when compiling libev vs. including F<ev.h>, so it is permissible
		3941	to redefine them before including F<ev.h> without breaking compatibility
		3942	to a compiled library. All other symbols change the ABI, which means all
		3943	users of libev and the libev code itself must be compiled with compatible
		3944	settings.
3176		3945
3177	=over 4	3946	=over 4
3178		3947
		3948	=item EV_COMPAT3 (h)
		3949
		3950	Backwards compatibility is a major concern for libev. This is why this
		3951	release of libev comes with wrappers for the functions and symbols that
		3952	have been renamed between libev version 3 and 4.
		3953
		3954	You can disable these wrappers (to test compatibility with future
		3955	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		3956	sources. This has the additional advantage that you can drop the C<struct>
		3957	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		3958	typedef in that case.
		3959
		3960	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		3961	and in some even more future version the compatibility code will be
		3962	removed completely.
		3963
3179	=item EV_STANDALONE	3964	=item EV_STANDALONE (h)
3180		3965
3181	Must always be C<1> if you do not use autoconf configuration, which	3966	Must always be C<1> if you do not use autoconf configuration, which
3182	keeps libev from including F<config.h>, and it also defines dummy	3967	keeps libev from including F<config.h>, and it also defines dummy
3183	implementations for some libevent functions (such as logging, which is not	3968	implementations for some libevent functions (such as logging, which is not
3184	supported). It will also not define any of the structs usually found in	3969	supported). It will also not define any of the structs usually found in
3185	F<event.h> that are not directly supported by the libev core alone.	3970	F<event.h> that are not directly supported by the libev core alone.
3186		3971
		3972	In standalone mode, libev will still try to automatically deduce the
		3973	configuration, but has to be more conservative.
		3974
3187	=item EV_USE_MONOTONIC	3975	=item EV_USE_MONOTONIC
3188		3976
3189	If defined to be C<1>, libev will try to detect the availability of the	3977	If defined to be C<1>, libev will try to detect the availability of the
3190	monotonic clock option at both compile time and runtime. Otherwise no use	3978	monotonic clock option at both compile time and runtime. Otherwise no
3191	of the monotonic clock option will be attempted. If you enable this, you	3979	use of the monotonic clock option will be attempted. If you enable this,
3192	usually have to link against librt or something similar. Enabling it when	3980	you usually have to link against librt or something similar. Enabling it
3193	the functionality isn't available is safe, though, although you have	3981	when the functionality isn't available is safe, though, although you have
3194	to make sure you link against any libraries where the C<clock_gettime>	3982	to make sure you link against any libraries where the C<clock_gettime>
3195	function is hiding in (often F<-lrt>).	3983	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
3196		3984
3197	=item EV_USE_REALTIME	3985	=item EV_USE_REALTIME
3198		3986
3199	If defined to be C<1>, libev will try to detect the availability of the	3987	If defined to be C<1>, libev will try to detect the availability of the
3200	real-time clock option at compile time (and assume its availability at	3988	real-time clock option at compile time (and assume its availability
3201	runtime if successful). Otherwise no use of the real-time clock option will	3989	at runtime if successful). Otherwise no use of the real-time clock
3202	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3990	option will be attempted. This effectively replaces C<gettimeofday>
3203	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3991	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
3204	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3992	correctness. See the note about libraries in the description of
		3993	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3994	C<EV_USE_CLOCK_SYSCALL>.
		3995
		3996	=item EV_USE_CLOCK_SYSCALL
		3997
		3998	If defined to be C<1>, libev will try to use a direct syscall instead
		3999	of calling the system-provided C<clock_gettime> function. This option
		4000	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		4001	unconditionally pulls in C<libpthread>, slowing down single-threaded
		4002	programs needlessly. Using a direct syscall is slightly slower (in
		4003	theory), because no optimised vdso implementation can be used, but avoids
		4004	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		4005	higher, as it simplifies linking (no need for C<-lrt>).
3205		4006
3206	=item EV_USE_NANOSLEEP	4007	=item EV_USE_NANOSLEEP
3207		4008
3208	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	4009	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
3209	and will use it for delays. Otherwise it will use C<select ()>.	4010	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3225		4026
3226	=item EV_SELECT_USE_FD_SET	4027	=item EV_SELECT_USE_FD_SET
3227		4028
3228	If defined to C<1>, then the select backend will use the system C<fd_set>	4029	If defined to C<1>, then the select backend will use the system C<fd_set>
3229	structure. This is useful if libev doesn't compile due to a missing	4030	structure. This is useful if libev doesn't compile due to a missing
3230	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	4031	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3231	exotic systems. This usually limits the range of file descriptors to some	4032	on exotic systems. This usually limits the range of file descriptors to
3232	low limit such as 1024 or might have other limitations (winsocket only	4033	some low limit such as 1024 or might have other limitations (winsocket
3233	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	4034	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3234	influence the size of the C<fd_set> used.	4035	configures the maximum size of the C<fd_set>.
3235		4036
3236	=item EV_SELECT_IS_WINSOCKET	4037	=item EV_SELECT_IS_WINSOCKET
3237		4038
3238	When defined to C<1>, the select backend will assume that	4039	When defined to C<1>, the select backend will assume that
3239	select/socket/connect etc. don't understand file descriptors but	4040	select/socket/connect etc. don't understand file descriptors but
…		…
3241	be used is the winsock select). This means that it will call	4042	be used is the winsock select). This means that it will call
3242	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4043	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3243	it is assumed that all these functions actually work on fds, even	4044	it is assumed that all these functions actually work on fds, even
3244	on win32. Should not be defined on non-win32 platforms.	4045	on win32. Should not be defined on non-win32 platforms.
3245		4046
3246	=item EV_FD_TO_WIN32_HANDLE	4047	=item EV_FD_TO_WIN32_HANDLE(fd)
3247		4048
3248	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4049	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3249	file descriptors to socket handles. When not defining this symbol (the	4050	file descriptors to socket handles. When not defining this symbol (the
3250	default), then libev will call C<_get_osfhandle>, which is usually	4051	default), then libev will call C<_get_osfhandle>, which is usually
3251	correct. In some cases, programs use their own file descriptor management,	4052	correct. In some cases, programs use their own file descriptor management,
3252	in which case they can provide this function to map fds to socket handles.	4053	in which case they can provide this function to map fds to socket handles.
		4054
		4055	=item EV_WIN32_HANDLE_TO_FD(handle)
		4056
		4057	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4058	using the standard C<_open_osfhandle> function. For programs implementing
		4059	their own fd to handle mapping, overwriting this function makes it easier
		4060	to do so. This can be done by defining this macro to an appropriate value.
		4061
		4062	=item EV_WIN32_CLOSE_FD(fd)
		4063
		4064	If programs implement their own fd to handle mapping on win32, then this
		4065	macro can be used to override the C<close> function, useful to unregister
		4066	file descriptors again. Note that the replacement function has to close
		4067	the underlying OS handle.
3253		4068
3254	=item EV_USE_POLL	4069	=item EV_USE_POLL
3255		4070
3256	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4071	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3257	backend. Otherwise it will be enabled on non-win32 platforms. It	4072	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3304	as well as for signal and thread safety in C<ev_async> watchers.	4119	as well as for signal and thread safety in C<ev_async> watchers.
3305		4120
3306	In the absence of this define, libev will use C<sig_atomic_t volatile>	4121	In the absence of this define, libev will use C<sig_atomic_t volatile>
3307	(from F<signal.h>), which is usually good enough on most platforms.	4122	(from F<signal.h>), which is usually good enough on most platforms.
3308		4123
3309	=item EV_H	4124	=item EV_H (h)
3310		4125
3311	The name of the F<ev.h> header file used to include it. The default if	4126	The name of the F<ev.h> header file used to include it. The default if
3312	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4127	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3313	used to virtually rename the F<ev.h> header file in case of conflicts.	4128	used to virtually rename the F<ev.h> header file in case of conflicts.
3314		4129
3315	=item EV_CONFIG_H	4130	=item EV_CONFIG_H (h)
3316		4131
3317	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4132	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3318	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4133	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3319	C<EV_H>, above.	4134	C<EV_H>, above.
3320		4135
3321	=item EV_EVENT_H	4136	=item EV_EVENT_H (h)
3322		4137
3323	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4138	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3324	of how the F<event.h> header can be found, the default is C<"event.h">.	4139	of how the F<event.h> header can be found, the default is C<"event.h">.
3325		4140
3326	=item EV_PROTOTYPES	4141	=item EV_PROTOTYPES (h)
3327		4142
3328	If defined to be C<0>, then F<ev.h> will not define any function	4143	If defined to be C<0>, then F<ev.h> will not define any function
3329	prototypes, but still define all the structs and other symbols. This is	4144	prototypes, but still define all the structs and other symbols. This is
3330	occasionally useful if you want to provide your own wrapper functions	4145	occasionally useful if you want to provide your own wrapper functions
3331	around libev functions.	4146	around libev functions.
…		…
3353	fine.	4168	fine.
3354		4169
3355	If your embedding application does not need any priorities, defining these	4170	If your embedding application does not need any priorities, defining these
3356	both to C<0> will save some memory and CPU.	4171	both to C<0> will save some memory and CPU.
3357		4172
3358	=item EV_PERIODIC_ENABLE	4173	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4174	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4175	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3359		4176
3360	If undefined or defined to be C<1>, then periodic timers are supported. If	4177	If undefined or defined to be C<1> (and the platform supports it), then
3361	defined to be C<0>, then they are not. Disabling them saves a few kB of	4178	the respective watcher type is supported. If defined to be C<0>, then it
3362	code.	4179	is not. Disabling watcher types mainly saves code size.
3363		4180
3364	=item EV_IDLE_ENABLE	4181	=item EV_FEATURES
3365
3366	If undefined or defined to be C<1>, then idle watchers are supported. If
3367	defined to be C<0>, then they are not. Disabling them saves a few kB of
3368	code.
3369
3370	=item EV_EMBED_ENABLE
3371
3372	If undefined or defined to be C<1>, then embed watchers are supported. If
3373	defined to be C<0>, then they are not. Embed watchers rely on most other
3374	watcher types, which therefore must not be disabled.
3375
3376	=item EV_STAT_ENABLE
3377
3378	If undefined or defined to be C<1>, then stat watchers are supported. If
3379	defined to be C<0>, then they are not.
3380
3381	=item EV_FORK_ENABLE
3382
3383	If undefined or defined to be C<1>, then fork watchers are supported. If
3384	defined to be C<0>, then they are not.
3385
3386	=item EV_ASYNC_ENABLE
3387
3388	If undefined or defined to be C<1>, then async watchers are supported. If
3389	defined to be C<0>, then they are not.
3390
3391	=item EV_MINIMAL
3392		4182
3393	If you need to shave off some kilobytes of code at the expense of some	4183	If you need to shave off some kilobytes of code at the expense of some
3394	speed, define this symbol to C<1>. Currently this is used to override some	4184	speed (but with the full API), you can define this symbol to request
3395	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4185	certain subsets of functionality. The default is to enable all features
3396	much smaller 2-heap for timer management over the default 4-heap.	4186	that can be enabled on the platform.
		4187
		4188	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4189	with some broad features you want) and then selectively re-enable
		4190	additional parts you want, for example if you want everything minimal,
		4191	but multiple event loop support, async and child watchers and the poll
		4192	backend, use this:
		4193
		4194	#define EV_FEATURES 0
		4195	#define EV_MULTIPLICITY 1
		4196	#define EV_USE_POLL 1
		4197	#define EV_CHILD_ENABLE 1
		4198	#define EV_ASYNC_ENABLE 1
		4199
		4200	The actual value is a bitset, it can be a combination of the following
		4201	values:
		4202
		4203	=over 4
		4204
		4205	=item C<1> - faster/larger code
		4206
		4207	Use larger code to speed up some operations.
		4208
		4209	Currently this is used to override some inlining decisions (enlarging the
		4210	code size by roughly 30% on amd64).
		4211
		4212	When optimising for size, use of compiler flags such as C<-Os> with
		4213	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4214	assertions.
		4215
		4216	=item C<2> - faster/larger data structures
		4217
		4218	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4219	hash table sizes and so on. This will usually further increase code size
		4220	and can additionally have an effect on the size of data structures at
		4221	runtime.
		4222
		4223	=item C<4> - full API configuration
		4224
		4225	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4226	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4227
		4228	=item C<8> - full API
		4229
		4230	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4231	details on which parts of the API are still available without this
		4232	feature, and do not complain if this subset changes over time.
		4233
		4234	=item C<16> - enable all optional watcher types
		4235
		4236	Enables all optional watcher types. If you want to selectively enable
		4237	only some watcher types other than I/O and timers (e.g. prepare,
		4238	embed, async, child...) you can enable them manually by defining
		4239	C<EV_watchertype_ENABLE> to C<1> instead.
		4240
		4241	=item C<32> - enable all backends
		4242
		4243	This enables all backends - without this feature, you need to enable at
		4244	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4245
		4246	=item C<64> - enable OS-specific "helper" APIs
		4247
		4248	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4249	default.
		4250
		4251	=back
		4252
		4253	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4254	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4255	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4256	watchers, timers and monotonic clock support.
		4257
		4258	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4259	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4260	your program might be left out as well - a binary starting a timer and an
		4261	I/O watcher then might come out at only 5Kb.
		4262
		4263	=item EV_AVOID_STDIO
		4264
		4265	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4266	functions (printf, scanf, perror etc.). This will increase the code size
		4267	somewhat, but if your program doesn't otherwise depend on stdio and your
		4268	libc allows it, this avoids linking in the stdio library which is quite
		4269	big.
		4270
		4271	Note that error messages might become less precise when this option is
		4272	enabled.
		4273
		4274	=item EV_NSIG
		4275
		4276	The highest supported signal number, +1 (or, the number of
		4277	signals): Normally, libev tries to deduce the maximum number of signals
		4278	automatically, but sometimes this fails, in which case it can be
		4279	specified. Also, using a lower number than detected (C<32> should be
		4280	good for about any system in existence) can save some memory, as libev
		4281	statically allocates some 12-24 bytes per signal number.
3397		4282
3398	=item EV_PID_HASHSIZE	4283	=item EV_PID_HASHSIZE
3399		4284
3400	C<ev_child> watchers use a small hash table to distribute workload by	4285	C<ev_child> watchers use a small hash table to distribute workload by
3401	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4286	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3402	than enough. If you need to manage thousands of children you might want to	4287	usually more than enough. If you need to manage thousands of children you
3403	increase this value (I<must> be a power of two).	4288	might want to increase this value (I<must> be a power of two).
3404		4289
3405	=item EV_INOTIFY_HASHSIZE	4290	=item EV_INOTIFY_HASHSIZE
3406		4291
3407	C<ev_stat> watchers use a small hash table to distribute workload by	4292	C<ev_stat> watchers use a small hash table to distribute workload by
3408	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4293	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3409	usually more than enough. If you need to manage thousands of C<ev_stat>	4294	disabled), usually more than enough. If you need to manage thousands of
3410	watchers you might want to increase this value (I<must> be a power of	4295	C<ev_stat> watchers you might want to increase this value (I<must> be a
3411	two).	4296	power of two).
3412		4297
3413	=item EV_USE_4HEAP	4298	=item EV_USE_4HEAP
3414		4299
3415	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4300	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3416	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4301	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3417	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4302	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3418	faster performance with many (thousands) of watchers.	4303	faster performance with many (thousands) of watchers.
3419		4304
3420	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4305	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3421	(disabled).	4306	will be C<0>.
3422		4307
3423	=item EV_HEAP_CACHE_AT	4308	=item EV_HEAP_CACHE_AT
3424		4309
3425	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4310	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3426	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4311	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3427	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4312	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3428	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4313	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3429	but avoids random read accesses on heap changes. This improves performance	4314	but avoids random read accesses on heap changes. This improves performance
3430	noticeably with many (hundreds) of watchers.	4315	noticeably with many (hundreds) of watchers.
3431		4316
3432	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4317	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3433	(disabled).	4318	will be C<0>.
3434		4319
3435	=item EV_VERIFY	4320	=item EV_VERIFY
3436		4321
3437	Controls how much internal verification (see C<ev_loop_verify ()>) will	4322	Controls how much internal verification (see C<ev_verify ()>) will
3438	be done: If set to C<0>, no internal verification code will be compiled	4323	be done: If set to C<0>, no internal verification code will be compiled
3439	in. If set to C<1>, then verification code will be compiled in, but not	4324	in. If set to C<1>, then verification code will be compiled in, but not
3440	called. If set to C<2>, then the internal verification code will be	4325	called. If set to C<2>, then the internal verification code will be
3441	called once per loop, which can slow down libev. If set to C<3>, then the	4326	called once per loop, which can slow down libev. If set to C<3>, then the
3442	verification code will be called very frequently, which will slow down	4327	verification code will be called very frequently, which will slow down
3443	libev considerably.	4328	libev considerably.
3444		4329
3445	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4330	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3446	C<0>.	4331	will be C<0>.
3447		4332
3448	=item EV_COMMON	4333	=item EV_COMMON
3449		4334
3450	By default, all watchers have a C<void *data> member. By redefining	4335	By default, all watchers have a C<void *data> member. By redefining
3451	this macro to a something else you can include more and other types of	4336	this macro to something else you can include more and other types of
3452	members. You have to define it each time you include one of the files,	4337	members. You have to define it each time you include one of the files,
3453	though, and it must be identical each time.	4338	though, and it must be identical each time.
3454		4339
3455	For example, the perl EV module uses something like this:	4340	For example, the perl EV module uses something like this:
3456		4341
…		…
3509	file.	4394	file.
3510		4395
3511	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4396	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3512	that everybody includes and which overrides some configure choices:	4397	that everybody includes and which overrides some configure choices:
3513		4398
3514	#define EV_MINIMAL 1	4399	#define EV_FEATURES 8
3515	#define EV_USE_POLL 0	4400	#define EV_USE_SELECT 1
3516	#define EV_MULTIPLICITY 0
3517	#define EV_PERIODIC_ENABLE 0	4401	#define EV_PREPARE_ENABLE 1
		4402	#define EV_IDLE_ENABLE 1
3518	#define EV_STAT_ENABLE 0	4403	#define EV_SIGNAL_ENABLE 1
3519	#define EV_FORK_ENABLE 0	4404	#define EV_CHILD_ENABLE 1
		4405	#define EV_USE_STDEXCEPT 0
3520	#define EV_CONFIG_H <config.h>	4406	#define EV_CONFIG_H <config.h>
3521	#define EV_MINPRI 0
3522	#define EV_MAXPRI 0
3523		4407
3524	#include "ev++.h"	4408	#include "ev++.h"
3525		4409
3526	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4410	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3527		4411
…		…
3587	default loop and triggering an C<ev_async> watcher from the default loop	4471	default loop and triggering an C<ev_async> watcher from the default loop
3588	watcher callback into the event loop interested in the signal.	4472	watcher callback into the event loop interested in the signal.
3589		4473
3590	=back	4474	=back
3591		4475
		4476	=head4 THREAD LOCKING EXAMPLE
		4477
		4478	Here is a fictitious example of how to run an event loop in a different
		4479	thread than where callbacks are being invoked and watchers are
		4480	created/added/removed.
		4481
		4482	For a real-world example, see the C<EV::Loop::Async> perl module,
		4483	which uses exactly this technique (which is suited for many high-level
		4484	languages).
		4485
		4486	The example uses a pthread mutex to protect the loop data, a condition
		4487	variable to wait for callback invocations, an async watcher to notify the
		4488	event loop thread and an unspecified mechanism to wake up the main thread.
		4489
		4490	First, you need to associate some data with the event loop:
		4491
		4492	typedef struct {
		4493	mutex_t lock; /* global loop lock */
		4494	ev_async async_w;
		4495	thread_t tid;
		4496	cond_t invoke_cv;
		4497	} userdata;
		4498
		4499	void prepare_loop (EV_P)
		4500	{
		4501	// for simplicity, we use a static userdata struct.
		4502	static userdata u;
		4503
		4504	ev_async_init (&u->async_w, async_cb);
		4505	ev_async_start (EV_A_ &u->async_w);
		4506
		4507	pthread_mutex_init (&u->lock, 0);
		4508	pthread_cond_init (&u->invoke_cv, 0);
		4509
		4510	// now associate this with the loop
		4511	ev_set_userdata (EV_A_ u);
		4512	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4513	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4514
		4515	// then create the thread running ev_loop
		4516	pthread_create (&u->tid, 0, l_run, EV_A);
		4517	}
		4518
		4519	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4520	solely to wake up the event loop so it takes notice of any new watchers
		4521	that might have been added:
		4522
		4523	static void
		4524	async_cb (EV_P_ ev_async *w, int revents)
		4525	{
		4526	// just used for the side effects
		4527	}
		4528
		4529	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4530	protecting the loop data, respectively.
		4531
		4532	static void
		4533	l_release (EV_P)
		4534	{
		4535	userdata *u = ev_userdata (EV_A);
		4536	pthread_mutex_unlock (&u->lock);
		4537	}
		4538
		4539	static void
		4540	l_acquire (EV_P)
		4541	{
		4542	userdata *u = ev_userdata (EV_A);
		4543	pthread_mutex_lock (&u->lock);
		4544	}
		4545
		4546	The event loop thread first acquires the mutex, and then jumps straight
		4547	into C<ev_run>:
		4548
		4549	void *
		4550	l_run (void *thr_arg)
		4551	{
		4552	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4553
		4554	l_acquire (EV_A);
		4555	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4556	ev_run (EV_A_ 0);
		4557	l_release (EV_A);
		4558
		4559	return 0;
		4560	}
		4561
		4562	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4563	signal the main thread via some unspecified mechanism (signals? pipe
		4564	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4565	have been called (in a while loop because a) spurious wakeups are possible
		4566	and b) skipping inter-thread-communication when there are no pending
		4567	watchers is very beneficial):
		4568
		4569	static void
		4570	l_invoke (EV_P)
		4571	{
		4572	userdata *u = ev_userdata (EV_A);
		4573
		4574	while (ev_pending_count (EV_A))
		4575	{
		4576	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4577	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4578	}
		4579	}
		4580
		4581	Now, whenever the main thread gets told to invoke pending watchers, it
		4582	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4583	thread to continue:
		4584
		4585	static void
		4586	real_invoke_pending (EV_P)
		4587	{
		4588	userdata *u = ev_userdata (EV_A);
		4589
		4590	pthread_mutex_lock (&u->lock);
		4591	ev_invoke_pending (EV_A);
		4592	pthread_cond_signal (&u->invoke_cv);
		4593	pthread_mutex_unlock (&u->lock);
		4594	}
		4595
		4596	Whenever you want to start/stop a watcher or do other modifications to an
		4597	event loop, you will now have to lock:
		4598
		4599	ev_timer timeout_watcher;
		4600	userdata *u = ev_userdata (EV_A);
		4601
		4602	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4603
		4604	pthread_mutex_lock (&u->lock);
		4605	ev_timer_start (EV_A_ &timeout_watcher);
		4606	ev_async_send (EV_A_ &u->async_w);
		4607	pthread_mutex_unlock (&u->lock);
		4608
		4609	Note that sending the C<ev_async> watcher is required because otherwise
		4610	an event loop currently blocking in the kernel will have no knowledge
		4611	about the newly added timer. By waking up the loop it will pick up any new
		4612	watchers in the next event loop iteration.
		4613
3592	=head3 COROUTINES	4614	=head3 COROUTINES
3593		4615
3594	Libev is very accommodating to coroutines ("cooperative threads"):	4616	Libev is very accommodating to coroutines ("cooperative threads"):
3595	libev fully supports nesting calls to its functions from different	4617	libev fully supports nesting calls to its functions from different
3596	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4618	coroutines (e.g. you can call C<ev_run> on the same loop from two
3597	different coroutines, and switch freely between both coroutines running the	4619	different coroutines, and switch freely between both coroutines running
3598	loop, as long as you don't confuse yourself). The only exception is that	4620	the loop, as long as you don't confuse yourself). The only exception is
3599	you must not do this from C<ev_periodic> reschedule callbacks.	4621	that you must not do this from C<ev_periodic> reschedule callbacks.
3600		4622
3601	Care has been taken to ensure that libev does not keep local state inside	4623	Care has been taken to ensure that libev does not keep local state inside
3602	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4624	C<ev_run>, and other calls do not usually allow for coroutine switches as
3603	they do not call any callbacks.	4625	they do not call any callbacks.
3604		4626
3605	=head2 COMPILER WARNINGS	4627	=head2 COMPILER WARNINGS
3606		4628
3607	Depending on your compiler and compiler settings, you might get no or a	4629	Depending on your compiler and compiler settings, you might get no or a
…		…
3618	maintainable.	4640	maintainable.
3619		4641
3620	And of course, some compiler warnings are just plain stupid, or simply	4642	And of course, some compiler warnings are just plain stupid, or simply
3621	wrong (because they don't actually warn about the condition their message	4643	wrong (because they don't actually warn about the condition their message
3622	seems to warn about). For example, certain older gcc versions had some	4644	seems to warn about). For example, certain older gcc versions had some
3623	warnings that resulted an extreme number of false positives. These have	4645	warnings that resulted in an extreme number of false positives. These have
3624	been fixed, but some people still insist on making code warn-free with	4646	been fixed, but some people still insist on making code warn-free with
3625	such buggy versions.	4647	such buggy versions.
3626		4648
3627	While libev is written to generate as few warnings as possible,	4649	While libev is written to generate as few warnings as possible,
3628	"warn-free" code is not a goal, and it is recommended not to build libev	4650	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3664	I suggest using suppression lists.	4686	I suggest using suppression lists.
3665		4687
3666		4688
3667	=head1 PORTABILITY NOTES	4689	=head1 PORTABILITY NOTES
3668		4690
		4691	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4692
		4693	GNU/Linux is the only common platform that supports 64 bit file/large file
		4694	interfaces but I<disables> them by default.
		4695
		4696	That means that libev compiled in the default environment doesn't support
		4697	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4698
		4699	Unfortunately, many programs try to work around this GNU/Linux issue
		4700	by enabling the large file API, which makes them incompatible with the
		4701	standard libev compiled for their system.
		4702
		4703	Likewise, libev cannot enable the large file API itself as this would
		4704	suddenly make it incompatible to the default compile time environment,
		4705	i.e. all programs not using special compile switches.
		4706
		4707	=head2 OS/X AND DARWIN BUGS
		4708
		4709	The whole thing is a bug if you ask me - basically any system interface
		4710	you touch is broken, whether it is locales, poll, kqueue or even the
		4711	OpenGL drivers.
		4712
		4713	=head3 C<kqueue> is buggy
		4714
		4715	The kqueue syscall is broken in all known versions - most versions support
		4716	only sockets, many support pipes.
		4717
		4718	Libev tries to work around this by not using C<kqueue> by default on this
		4719	rotten platform, but of course you can still ask for it when creating a
		4720	loop - embedding a socket-only kqueue loop into a select-based one is
		4721	probably going to work well.
		4722
		4723	=head3 C<poll> is buggy
		4724
		4725	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4726	implementation by something calling C<kqueue> internally around the 10.5.6
		4727	release, so now C<kqueue> I<and> C<poll> are broken.
		4728
		4729	Libev tries to work around this by not using C<poll> by default on
		4730	this rotten platform, but of course you can still ask for it when creating
		4731	a loop.
		4732
		4733	=head3 C<select> is buggy
		4734
		4735	All that's left is C<select>, and of course Apple found a way to fuck this
		4736	one up as well: On OS/X, C<select> actively limits the number of file
		4737	descriptors you can pass in to 1024 - your program suddenly crashes when
		4738	you use more.
		4739
		4740	There is an undocumented "workaround" for this - defining
		4741	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4742	work on OS/X.
		4743
		4744	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4745
		4746	=head3 C<errno> reentrancy
		4747
		4748	The default compile environment on Solaris is unfortunately so
		4749	thread-unsafe that you can't even use components/libraries compiled
		4750	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4751	defined by default. A valid, if stupid, implementation choice.
		4752
		4753	If you want to use libev in threaded environments you have to make sure
		4754	it's compiled with C<_REENTRANT> defined.
		4755
		4756	=head3 Event port backend
		4757
		4758	The scalable event interface for Solaris is called "event
		4759	ports". Unfortunately, this mechanism is very buggy in all major
		4760	releases. If you run into high CPU usage, your program freezes or you get
		4761	a large number of spurious wakeups, make sure you have all the relevant
		4762	and latest kernel patches applied. No, I don't know which ones, but there
		4763	are multiple ones to apply, and afterwards, event ports actually work
		4764	great.
		4765
		4766	If you can't get it to work, you can try running the program by setting
		4767	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4768	C<select> backends.
		4769
		4770	=head2 AIX POLL BUG
		4771
		4772	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4773	this by trying to avoid the poll backend altogether (i.e. it's not even
		4774	compiled in), which normally isn't a big problem as C<select> works fine
		4775	with large bitsets on AIX, and AIX is dead anyway.
		4776
3669	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4777	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4778
		4779	=head3 General issues
3670		4780
3671	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4781	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3672	requires, and its I/O model is fundamentally incompatible with the POSIX	4782	requires, and its I/O model is fundamentally incompatible with the POSIX
3673	model. Libev still offers limited functionality on this platform in	4783	model. Libev still offers limited functionality on this platform in
3674	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4784	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3675	descriptors. This only applies when using Win32 natively, not when using	4785	descriptors. This only applies when using Win32 natively, not when using
3676	e.g. cygwin.	4786	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4787	as every compielr comes with a slightly differently broken/incompatible
		4788	environment.
3677		4789
3678	Lifting these limitations would basically require the full	4790	Lifting these limitations would basically require the full
3679	re-implementation of the I/O system. If you are into these kinds of	4791	re-implementation of the I/O system. If you are into this kind of thing,
3680	things, then note that glib does exactly that for you in a very portable	4792	then note that glib does exactly that for you in a very portable way (note
3681	way (note also that glib is the slowest event library known to man).	4793	also that glib is the slowest event library known to man).
3682		4794
3683	There is no supported compilation method available on windows except	4795	There is no supported compilation method available on windows except
3684	embedding it into other applications.	4796	embedding it into other applications.
		4797
		4798	Sensible signal handling is officially unsupported by Microsoft - libev
		4799	tries its best, but under most conditions, signals will simply not work.
3685		4800
3686	Not a libev limitation but worth mentioning: windows apparently doesn't	4801	Not a libev limitation but worth mentioning: windows apparently doesn't
3687	accept large writes: instead of resulting in a partial write, windows will	4802	accept large writes: instead of resulting in a partial write, windows will
3688	either accept everything or return C<ENOBUFS> if the buffer is too large,	4803	either accept everything or return C<ENOBUFS> if the buffer is too large,
3689	so make sure you only write small amounts into your sockets (less than a	4804	so make sure you only write small amounts into your sockets (less than a
…		…
3694	the abysmal performance of winsockets, using a large number of sockets	4809	the abysmal performance of winsockets, using a large number of sockets
3695	is not recommended (and not reasonable). If your program needs to use	4810	is not recommended (and not reasonable). If your program needs to use
3696	more than a hundred or so sockets, then likely it needs to use a totally	4811	more than a hundred or so sockets, then likely it needs to use a totally
3697	different implementation for windows, as libev offers the POSIX readiness	4812	different implementation for windows, as libev offers the POSIX readiness
3698	notification model, which cannot be implemented efficiently on windows	4813	notification model, which cannot be implemented efficiently on windows
3699	(Microsoft monopoly games).	4814	(due to Microsoft monopoly games).
3700		4815
3701	A typical way to use libev under windows is to embed it (see the embedding	4816	A typical way to use libev under windows is to embed it (see the embedding
3702	section for details) and use the following F<evwrap.h> header file instead	4817	section for details) and use the following F<evwrap.h> header file instead
3703	of F<ev.h>:	4818	of F<ev.h>:
3704		4819
…		…
3711	you do I<not> compile the F<ev.c> or any other embedded source files!):	4826	you do I<not> compile the F<ev.c> or any other embedded source files!):
3712		4827
3713	#include "evwrap.h"	4828	#include "evwrap.h"
3714	#include "ev.c"	4829	#include "ev.c"
3715		4830
3716	=over 4
3717
3718	=item The winsocket select function	4831	=head3 The winsocket C<select> function
3719		4832
3720	The winsocket C<select> function doesn't follow POSIX in that it	4833	The winsocket C<select> function doesn't follow POSIX in that it
3721	requires socket I<handles> and not socket I<file descriptors> (it is	4834	requires socket I<handles> and not socket I<file descriptors> (it is
3722	also extremely buggy). This makes select very inefficient, and also	4835	also extremely buggy). This makes select very inefficient, and also
3723	requires a mapping from file descriptors to socket handles (the Microsoft	4836	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3732	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4845	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3733		4846
3734	Note that winsockets handling of fd sets is O(n), so you can easily get a	4847	Note that winsockets handling of fd sets is O(n), so you can easily get a
3735	complexity in the O(n²) range when using win32.	4848	complexity in the O(n²) range when using win32.
3736		4849
3737	=item Limited number of file descriptors	4850	=head3 Limited number of file descriptors
3738		4851
3739	Windows has numerous arbitrary (and low) limits on things.	4852	Windows has numerous arbitrary (and low) limits on things.
3740		4853
3741	Early versions of winsocket's select only supported waiting for a maximum	4854	Early versions of winsocket's select only supported waiting for a maximum
3742	of C<64> handles (probably owning to the fact that all windows kernels	4855	of C<64> handles (probably owning to the fact that all windows kernels
3743	can only wait for C<64> things at the same time internally; Microsoft	4856	can only wait for C<64> things at the same time internally; Microsoft
3744	recommends spawning a chain of threads and wait for 63 handles and the	4857	recommends spawning a chain of threads and wait for 63 handles and the
3745	previous thread in each. Great).	4858	previous thread in each. Sounds great!).
3746		4859
3747	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4860	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3748	to some high number (e.g. C<2048>) before compiling the winsocket select	4861	to some high number (e.g. C<2048>) before compiling the winsocket select
3749	call (which might be in libev or elsewhere, for example, perl does its own	4862	call (which might be in libev or elsewhere, for example, perl and many
3750	select emulation on windows).	4863	other interpreters do their own select emulation on windows).
3751		4864
3752	Another limit is the number of file descriptors in the Microsoft runtime	4865	Another limit is the number of file descriptors in the Microsoft runtime
3753	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4866	libraries, which by default is C<64> (there must be a hidden I<64>
3754	or something like this inside Microsoft). You can increase this by calling	4867	fetish or something like this inside Microsoft). You can increase this
3755	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4868	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3756	arbitrary limit), but is broken in many versions of the Microsoft runtime	4869	(another arbitrary limit), but is broken in many versions of the Microsoft
3757	libraries.
3758
3759	This might get you to about C<512> or C<2048> sockets (depending on	4870	runtime libraries. This might get you to about C<512> or C<2048> sockets
3760	windows version and/or the phase of the moon). To get more, you need to	4871	(depending on windows version and/or the phase of the moon). To get more,
3761	wrap all I/O functions and provide your own fd management, but the cost of	4872	you need to wrap all I/O functions and provide your own fd management, but
3762	calling select (O(n²)) will likely make this unworkable.	4873	the cost of calling select (O(n²)) will likely make this unworkable.
3763
3764	=back
3765		4874
3766	=head2 PORTABILITY REQUIREMENTS	4875	=head2 PORTABILITY REQUIREMENTS
3767		4876
3768	In addition to a working ISO-C implementation and of course the	4877	In addition to a working ISO-C implementation and of course the
3769	backend-specific APIs, libev relies on a few additional extensions:	4878	backend-specific APIs, libev relies on a few additional extensions:
…		…
3776	Libev assumes not only that all watcher pointers have the same internal	4885	Libev assumes not only that all watcher pointers have the same internal
3777	structure (guaranteed by POSIX but not by ISO C for example), but it also	4886	structure (guaranteed by POSIX but not by ISO C for example), but it also
3778	assumes that the same (machine) code can be used to call any watcher	4887	assumes that the same (machine) code can be used to call any watcher
3779	callback: The watcher callbacks have different type signatures, but libev	4888	callback: The watcher callbacks have different type signatures, but libev
3780	calls them using an C<ev_watcher *> internally.	4889	calls them using an C<ev_watcher *> internally.
		4890
		4891	=item pointer accesses must be thread-atomic
		4892
		4893	Accessing a pointer value must be atomic, it must both be readable and
		4894	writable in one piece - this is the case on all current architectures.
3781		4895
3782	=item C<sig_atomic_t volatile> must be thread-atomic as well	4896	=item C<sig_atomic_t volatile> must be thread-atomic as well
3783		4897
3784	The type C<sig_atomic_t volatile> (or whatever is defined as	4898	The type C<sig_atomic_t volatile> (or whatever is defined as
3785	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	4899	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
3808	watchers.	4922	watchers.
3809		4923
3810	=item C<double> must hold a time value in seconds with enough accuracy	4924	=item C<double> must hold a time value in seconds with enough accuracy
3811		4925
3812	The type C<double> is used to represent timestamps. It is required to	4926	The type C<double> is used to represent timestamps. It is required to
3813	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4927	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3814	enough for at least into the year 4000. This requirement is fulfilled by	4928	good enough for at least into the year 4000 with millisecond accuracy
		4929	(the design goal for libev). This requirement is overfulfilled by
3815	implementations implementing IEEE 754 (basically all existing ones).	4930	implementations using IEEE 754, which is basically all existing ones. With
		4931	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
3816		4932
3817	=back	4933	=back
3818		4934
3819	If you know of other additional requirements drop me a note.	4935	If you know of other additional requirements drop me a note.
3820		4936
…		…
3888	involves iterating over all running async watchers or all signal numbers.	5004	involves iterating over all running async watchers or all signal numbers.
3889		5005
3890	=back	5006	=back
3891		5007
3892		5008
		5009	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5010
		5011	The major version 4 introduced some incompatible changes to the API.
		5012
		5013	At the moment, the C<ev.h> header file provides compatibility definitions
		5014	for all changes, so most programs should still compile. The compatibility
		5015	layer might be removed in later versions of libev, so better update to the
		5016	new API early than late.
		5017
		5018	=over 4
		5019
		5020	=item C<EV_COMPAT3> backwards compatibility mechanism
		5021
		5022	The backward compatibility mechanism can be controlled by
		5023	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5024	section.
		5025
		5026	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5027
		5028	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5029
		5030	ev_loop_destroy (EV_DEFAULT_UC);
		5031	ev_loop_fork (EV_DEFAULT);
		5032
		5033	=item function/symbol renames
		5034
		5035	A number of functions and symbols have been renamed:
		5036
		5037	ev_loop => ev_run
		5038	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5039	EVLOOP_ONESHOT => EVRUN_ONCE
		5040
		5041	ev_unloop => ev_break
		5042	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5043	EVUNLOOP_ONE => EVBREAK_ONE
		5044	EVUNLOOP_ALL => EVBREAK_ALL
		5045
		5046	EV_TIMEOUT => EV_TIMER
		5047
		5048	ev_loop_count => ev_iteration
		5049	ev_loop_depth => ev_depth
		5050	ev_loop_verify => ev_verify
		5051
		5052	Most functions working on C<struct ev_loop> objects don't have an
		5053	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5054	associated constants have been renamed to not collide with the C<struct
		5055	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5056	as all other watcher types. Note that C<ev_loop_fork> is still called
		5057	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5058	typedef.
		5059
		5060	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5061
		5062	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5063	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5064	and work, but the library code will of course be larger.
		5065
		5066	=back
		5067
		5068
		5069	=head1 GLOSSARY
		5070
		5071	=over 4
		5072
		5073	=item active
		5074
		5075	A watcher is active as long as it has been started and not yet stopped.
		5076	See L<WATCHER STATES> for details.
		5077
		5078	=item application
		5079
		5080	In this document, an application is whatever is using libev.
		5081
		5082	=item backend
		5083
		5084	The part of the code dealing with the operating system interfaces.
		5085
		5086	=item callback
		5087
		5088	The address of a function that is called when some event has been
		5089	detected. Callbacks are being passed the event loop, the watcher that
		5090	received the event, and the actual event bitset.
		5091
		5092	=item callback/watcher invocation
		5093
		5094	The act of calling the callback associated with a watcher.
		5095
		5096	=item event
		5097
		5098	A change of state of some external event, such as data now being available
		5099	for reading on a file descriptor, time having passed or simply not having
		5100	any other events happening anymore.
		5101
		5102	In libev, events are represented as single bits (such as C<EV_READ> or
		5103	C<EV_TIMER>).
		5104
		5105	=item event library
		5106
		5107	A software package implementing an event model and loop.
		5108
		5109	=item event loop
		5110
		5111	An entity that handles and processes external events and converts them
		5112	into callback invocations.
		5113
		5114	=item event model
		5115
		5116	The model used to describe how an event loop handles and processes
		5117	watchers and events.
		5118
		5119	=item pending
		5120
		5121	A watcher is pending as soon as the corresponding event has been
		5122	detected. See L<WATCHER STATES> for details.
		5123
		5124	=item real time
		5125
		5126	The physical time that is observed. It is apparently strictly monotonic :)
		5127
		5128	=item wall-clock time
		5129
		5130	The time and date as shown on clocks. Unlike real time, it can actually
		5131	be wrong and jump forwards and backwards, e.g. when the you adjust your
		5132	clock.
		5133
		5134	=item watcher
		5135
		5136	A data structure that describes interest in certain events. Watchers need
		5137	to be started (attached to an event loop) before they can receive events.
		5138
		5139	=back
		5140
3893	=head1 AUTHOR	5141	=head1 AUTHOR
3894		5142
3895	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5143	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5144	Magnusson and Emanuele Giaquinta.
3896		5145

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