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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 bes hared 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). The epoll design has a number	488	epoll scales either O(1) or O(active_fds).
390	of shortcomings, such as silently dropping events in some hard-to-detect	489
391	cases and requiring a system call per fd change, no fork support and bad	490	The epoll mechanism deserves honorable mention as the most misdesigned
392	support for dup.	491	of the more advanced event mechanisms: mere annoyances include silently
		492	dropping file descriptors, requiring a system call per change per file
		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
		496	0.1ms) and so on. The biggest issue is fork races, however - if a program
		497	forks then I<both> parent and child process have to recreate the epoll
		498	set, which can take considerable time (one syscall per file descriptor)
		499	and is of course hard to detect.
		500
		501	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		502	of course I<doesn't>, and epoll just loves to report events for totally
		503	I<different> file descriptors (even already closed ones, so one cannot
		504	even remove them from the set) than registered in the set (especially
		505	on SMP systems). Libev tries to counter these spurious notifications by
		506	employing an additional generation counter and comparing that against the
		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,
		512	a frankenpoll, cobbled together in a hurry, no thought to design or
		513	interaction with others.
393		514
394	While stopping, setting and starting an I/O watcher in the same iteration	515	While stopping, setting and starting an I/O watcher in the same iteration
395	will result in some caching, there is still a system call per such incident	516	will result in some caching, there is still a system call per such
396	(because the fd could point to a different file description now), so its	517	incident (because the same I<file descriptor> could point to a different
397	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	518	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
398	very well if you register events for both fds.	519	file descriptors might not work very well if you register events for both
399		520	file descriptors.
400	Please note that epoll sometimes generates spurious notifications, so you
401	need to use non-blocking I/O or other means to avoid blocking when no data
402	(or space) is available.
403		521
404	Best performance from this backend is achieved by not unregistering all	522	Best performance from this backend is achieved by not unregistering all
405	watchers for a file descriptor until it has been closed, if possible,	523	watchers for a file descriptor until it has been closed, if possible,
406	i.e. keep at least one watcher active per fd at all times. Stopping and	524	i.e. keep at least one watcher active per fd at all times. Stopping and
407	starting a watcher (without re-setting it) also usually doesn't cause	525	starting a watcher (without re-setting it) also usually doesn't cause
408	extra overhead.	526	extra overhead. A fork can both result in spurious notifications as well
		527	as in libev having to destroy and recreate the epoll object, which can
		528	take considerable time and thus should be avoided.
		529
		530	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		531	faster than epoll for maybe up to a hundred file descriptors, depending on
		532	the usage. So sad.
409		533
410	While nominally embeddable in other event loops, this feature is broken in	534	While nominally embeddable in other event loops, this feature is broken in
411	all kernel versions tested so far.	535	all kernel versions tested so far.
412		536
413	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	537	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
414	C<EVBACKEND_POLL>.	538	C<EVBACKEND_POLL>.
415		539
416	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	540	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
417		541
418	Kqueue deserves special mention, as at the time of this writing, it was	542	Kqueue deserves special mention, as at the time of this writing, it
419	broken on all BSDs except NetBSD (usually it doesn't work reliably with	543	was broken on all BSDs except NetBSD (usually it doesn't work reliably
420	anything but sockets and pipes, except on Darwin, where of course it's	544	with anything but sockets and pipes, except on Darwin, where of course
421	completely useless). For this reason it's not being "auto-detected" unless	545	it's completely useless). Unlike epoll, however, whose brokenness
422	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or	546	is by design, these kqueue bugs can (and eventually will) be fixed
423	libev was compiled on a known-to-be-good (-enough) system like NetBSD.	547	without API changes to existing programs. For this reason it's not being
		548	"auto-detected" unless you explicitly specify it in the flags (i.e. using
		549	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		550	system like NetBSD.
424		551
425	You still can embed kqueue into a normal poll or select backend and use it	552	You still can embed kqueue into a normal poll or select backend and use it
426	only for sockets (after having made sure that sockets work with kqueue on	553	only for sockets (after having made sure that sockets work with kqueue on
427	the target platform). See C<ev_embed> watchers for more info.	554	the target platform). See C<ev_embed> watchers for more info.
428		555
429	It scales in the same way as the epoll backend, but the interface to the	556	It scales in the same way as the epoll backend, but the interface to the
430	kernel is more efficient (which says nothing about its actual speed, of	557	kernel is more efficient (which says nothing about its actual speed, of
431	course). While stopping, setting and starting an I/O watcher does never	558	course). While stopping, setting and starting an I/O watcher does never
432	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	559	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
433	two event changes per incident. Support for C<fork ()> is very bad and it	560	two event changes per incident. Support for C<fork ()> is very bad (but
434	drops fds silently in similarly hard-to-detect cases.	561	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		562	cases
435		563
436	This backend usually performs well under most conditions.	564	This backend usually performs well under most conditions.
437		565
438	While nominally embeddable in other event loops, this doesn't work	566	While nominally embeddable in other event loops, this doesn't work
439	everywhere, so you might need to test for this. And since it is broken	567	everywhere, so you might need to test for this. And since it is broken
440	almost everywhere, you should only use it when you have a lot of sockets	568	almost everywhere, you should only use it when you have a lot of sockets
441	(for which it usually works), by embedding it into another event loop	569	(for which it usually works), by embedding it into another event loop
442	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,	570	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
443	using it only for sockets.	571	also broken on OS X)) and, did I mention it, using it only for sockets.
444		572
445	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	573	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
446	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with	574	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
447	C<NOTE_EOF>.	575	C<NOTE_EOF>.
448		576
…		…
456	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	584	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
457		585
458	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	586	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
459	it's really slow, but it still scales very well (O(active_fds)).	587	it's really slow, but it still scales very well (O(active_fds)).
460		588
461	Please note that Solaris event ports can deliver a lot of spurious
462	notifications, so you need to use non-blocking I/O or other means to avoid
463	blocking when no data (or space) is available.
464
465	While this backend scales well, it requires one system call per active	589	While this backend scales well, it requires one system call per active
466	file descriptor per loop iteration. For small and medium numbers of file	590	file descriptor per loop iteration. For small and medium numbers of file
467	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	591	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
468	might perform better.	592	might perform better.
469		593
470	On the positive side, with the exception of the spurious readiness	594	On the positive side, this backend actually performed fully to
471	notifications, this backend actually performed fully to specification
472	in all tests and is fully embeddable, which is a rare feat among the	595	specification in all tests and is fully embeddable, which is a rare feat
473	OS-specific backends.	596	among the OS-specific backends (I vastly prefer correctness over speed
		597	hacks).
		598
		599	On the negative side, the interface is I<bizarre> - so bizarre that
		600	even sun itself gets it wrong in their code examples: The event polling
		601	function sometimes returning events to the caller even though an error
		602	occurred, but with no indication whether it has done so or not (yes, it's
		603	even documented that way) - deadly for edge-triggered interfaces where
		604	you absolutely have to know whether an event occurred or not because you
		605	have to re-arm the watcher.
		606
		607	Fortunately libev seems to be able to work around these idiocies.
474		608
475	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	609	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
476	C<EVBACKEND_POLL>.	610	C<EVBACKEND_POLL>.
477		611
478	=item C<EVBACKEND_ALL>	612	=item C<EVBACKEND_ALL>
479		613
480	Try all backends (even potentially broken ones that wouldn't be tried	614	Try all backends (even potentially broken ones that wouldn't be tried
481	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	615	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
482	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	616	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
483		617
484	It is definitely not recommended to use this flag.	618	It is definitely not recommended to use this flag, use whatever
		619	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		620	at all.
		621
		622	=item C<EVBACKEND_MASK>
		623
		624	Not a backend at all, but a mask to select all backend bits from a
		625	C<flags> value, in case you want to mask out any backends from a flags
		626	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
485		627
486	=back	628	=back
487		629
488	If one or more of these are or'ed into the flags value, then only these	630	If one or more of the backend flags are or'ed into the flags value,
489	backends will be tried (in the reverse order as listed here). If none are	631	then only these backends will be tried (in the reverse order as listed
490	specified, all backends in C<ev_recommended_backends ()> will be tried.	632	here). If none are specified, all backends in C<ev_recommended_backends
491		633	()> will be tried.
492	Example: This is the most typical usage.
493
494	if (!ev_default_loop (0))
495	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
496
497	Example: Restrict libev to the select and poll backends, and do not allow
498	environment settings to be taken into account:
499
500	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
501
502	Example: Use whatever libev has to offer, but make sure that kqueue is
503	used if available (warning, breaks stuff, best use only with your own
504	private event loop and only if you know the OS supports your types of
505	fds):
506
507	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
508
509	=item struct ev_loop *ev_loop_new (unsigned int flags)
510
511	Similar to C<ev_default_loop>, but always creates a new event loop that is
512	always distinct from the default loop. Unlike the default loop, it cannot
513	handle signal and child watchers, and attempts to do so will be greeted by
514	undefined behaviour (or a failed assertion if assertions are enabled).
515
516	Note that this function I<is> thread-safe, and the recommended way to use
517	libev with threads is indeed to create one loop per thread, and using the
518	default loop in the "main" or "initial" thread.
519		634
520	Example: Try to create a event loop that uses epoll and nothing else.	635	Example: Try to create a event loop that uses epoll and nothing else.
521		636
522	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	637	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
523	if (!epoller)	638	if (!epoller)
524	fatal ("no epoll found here, maybe it hides under your chair");	639	fatal ("no epoll found here, maybe it hides under your chair");
525		640
		641	Example: Use whatever libev has to offer, but make sure that kqueue is
		642	used if available.
		643
		644	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		645
526	=item ev_default_destroy ()	646	=item ev_loop_destroy (loop)
527		647
528	Destroys the default loop again (frees all memory and kernel state	648	Destroys an event loop object (frees all memory and kernel state
529	etc.). None of the active event watchers will be stopped in the normal	649	etc.). None of the active event watchers will be stopped in the normal
530	sense, so e.g. C<ev_is_active> might still return true. It is your	650	sense, so e.g. C<ev_is_active> might still return true. It is your
531	responsibility to either stop all watchers cleanly yourself I<before>	651	responsibility to either stop all watchers cleanly yourself I<before>
532	calling this function, or cope with the fact afterwards (which is usually	652	calling this function, or cope with the fact afterwards (which is usually
533	the easiest thing, you can just ignore the watchers and/or C<free ()> them	653	the easiest thing, you can just ignore the watchers and/or C<free ()> them
534	for example).	654	for example).
535		655
536	Note that certain global state, such as signal state, will not be freed by	656	Note that certain global state, such as signal state (and installed signal
537	this function, and related watchers (such as signal and child watchers)	657	handlers), will not be freed by this function, and related watchers (such
538	would need to be stopped manually.	658	as signal and child watchers) would need to be stopped manually.
539		659
540	In general it is not advisable to call this function except in the	660	This function is normally used on loop objects allocated by
541	rare occasion where you really need to free e.g. the signal handling	661	C<ev_loop_new>, but it can also be used on the default loop returned by
		662	C<ev_default_loop>, in which case it is not thread-safe.
		663
		664	Note that it is not advisable to call this function on the default loop
		665	except in the rare occasion where you really need to free its resources.
542	pipe fds. If you need dynamically allocated loops it is better to use	666	If you need dynamically allocated loops it is better to use C<ev_loop_new>
543	C<ev_loop_new> and C<ev_loop_destroy>).	667	and C<ev_loop_destroy>.
544		668
545	=item ev_loop_destroy (loop)	669	=item ev_loop_fork (loop)
546		670
547	Like C<ev_default_destroy>, but destroys an event loop created by an
548	earlier call to C<ev_loop_new>.
549
550	=item ev_default_fork ()
551
552	This function sets a flag that causes subsequent C<ev_loop> iterations	671	This function sets a flag that causes subsequent C<ev_run> iterations to
553	to reinitialise the kernel state for backends that have one. Despite the	672	reinitialise the kernel state for backends that have one. Despite the
554	name, you can call it anytime, but it makes most sense after forking, in	673	name, you can call it anytime, but it makes most sense after forking, in
555	the child process (or both child and parent, but that again makes little	674	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
556	sense). You I<must> call it in the child before using any of the libev	675	child before resuming or calling C<ev_run>.
557	functions, and it will only take effect at the next C<ev_loop> iteration.	676
		677	Again, you I<have> to call it on I<any> loop that you want to re-use after
		678	a fork, I<even if you do not plan to use the loop in the parent>. This is
		679	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		680	during fork.
558		681
559	On the other hand, you only need to call this function in the child	682	On the other hand, you only need to call this function in the child
560	process if and only if you want to use the event library in the child. If	683	process if and only if you want to use the event loop in the child. If
561	you just fork+exec, you don't have to call it at all.	684	you just fork+exec or create a new loop in the child, you don't have to
		685	call it at all (in fact, C<epoll> is so badly broken that it makes a
		686	difference, but libev will usually detect this case on its own and do a
		687	costly reset of the backend).
562		688
563	The function itself is quite fast and it's usually not a problem to call	689	The function itself is quite fast and it's usually not a problem to call
564	it just in case after a fork. To make this easy, the function will fit in	690	it just in case after a fork.
565	quite nicely into a call to C<pthread_atfork>:
566		691
		692	Example: Automate calling C<ev_loop_fork> on the default loop when
		693	using pthreads.
		694
		695	static void
		696	post_fork_child (void)
		697	{
		698	ev_loop_fork (EV_DEFAULT);
		699	}
		700
		701	...
567	pthread_atfork (0, 0, ev_default_fork);	702	pthread_atfork (0, 0, post_fork_child);
568
569	=item ev_loop_fork (loop)
570
571	Like C<ev_default_fork>, but acts on an event loop created by
572	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
573	after fork that you want to re-use in the child, and how you do this is
574	entirely your own problem.
575		703
576	=item int ev_is_default_loop (loop)	704	=item int ev_is_default_loop (loop)
577		705
578	Returns true when the given loop is, in fact, the default loop, and false	706	Returns true when the given loop is, in fact, the default loop, and false
579	otherwise.	707	otherwise.
580		708
581	=item unsigned int ev_loop_count (loop)	709	=item unsigned int ev_iteration (loop)
582		710
583	Returns the count of loop iterations for the loop, which is identical to	711	Returns the current iteration count for the event loop, which is identical
584	the number of times libev did poll for new events. It starts at C<0> and	712	to the number of times libev did poll for new events. It starts at C<0>
585	happily wraps around with enough iterations.	713	and happily wraps around with enough iterations.
586		714
587	This value can sometimes be useful as a generation counter of sorts (it	715	This value can sometimes be useful as a generation counter of sorts (it
588	"ticks" the number of loop iterations), as it roughly corresponds with	716	"ticks" the number of loop iterations), as it roughly corresponds with
589	C<ev_prepare> and C<ev_check> calls.	717	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		718	prepare and check phases.
		719
		720	=item unsigned int ev_depth (loop)
		721
		722	Returns the number of times C<ev_run> was entered minus the number of
		723	times C<ev_run> was exited normally, in other words, the recursion depth.
		724
		725	Outside C<ev_run>, this number is zero. In a callback, this number is
		726	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		727	in which case it is higher.
		728
		729	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
		730	throwing an exception etc.), doesn't count as "exit" - consider this
		731	as a hint to avoid such ungentleman-like behaviour unless it's really
		732	convenient, in which case it is fully supported.
590		733
591	=item unsigned int ev_backend (loop)	734	=item unsigned int ev_backend (loop)
592		735
593	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	736	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
594	use.	737	use.
…		…
603		746
604	=item ev_now_update (loop)	747	=item ev_now_update (loop)
605		748
606	Establishes the current time by querying the kernel, updating the time	749	Establishes the current time by querying the kernel, updating the time
607	returned by C<ev_now ()> in the progress. This is a costly operation and	750	returned by C<ev_now ()> in the progress. This is a costly operation and
608	is usually done automatically within C<ev_loop ()>.	751	is usually done automatically within C<ev_run ()>.
609		752
610	This function is rarely useful, but when some event callback runs for a	753	This function is rarely useful, but when some event callback runs for a
611	very long time without entering the event loop, updating libev's idea of	754	very long time without entering the event loop, updating libev's idea of
612	the current time is a good idea.	755	the current time is a good idea.
613		756
614	See also "The special problem of time updates" in the C<ev_timer> section.	757	See also L<The special problem of time updates> in the C<ev_timer> section.
615		758
		759	=item ev_suspend (loop)
		760
		761	=item ev_resume (loop)
		762
		763	These two functions suspend and resume an event loop, for use when the
		764	loop is not used for a while and timeouts should not be processed.
		765
		766	A typical use case would be an interactive program such as a game: When
		767	the user presses C<^Z> to suspend the game and resumes it an hour later it
		768	would be best to handle timeouts as if no time had actually passed while
		769	the program was suspended. This can be achieved by calling C<ev_suspend>
		770	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		771	C<ev_resume> directly afterwards to resume timer processing.
		772
		773	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		774	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		775	will be rescheduled (that is, they will lose any events that would have
		776	occurred while suspended).
		777
		778	After calling C<ev_suspend> you B<must not> call I<any> function on the
		779	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		780	without a previous call to C<ev_suspend>.
		781
		782	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		783	event loop time (see C<ev_now_update>).
		784
616	=item ev_loop (loop, int flags)	785	=item ev_run (loop, int flags)
617		786
618	Finally, this is it, the event handler. This function usually is called	787	Finally, this is it, the event handler. This function usually is called
619	after you initialised all your watchers and you want to start handling	788	after you have initialised all your watchers and you want to start
620	events.	789	handling events. It will ask the operating system for any new events, call
		790	the watcher callbacks, an then repeat the whole process indefinitely: This
		791	is why event loops are called I<loops>.
621		792
622	If the flags argument is specified as C<0>, it will not return until	793	If the flags argument is specified as C<0>, it will keep handling events
623	either no event watchers are active anymore or C<ev_unloop> was called.	794	until either no event watchers are active anymore or C<ev_break> was
		795	called.
624		796
625	Please note that an explicit C<ev_unloop> is usually better than	797	Please note that an explicit C<ev_break> is usually better than
626	relying on all watchers to be stopped when deciding when a program has	798	relying on all watchers to be stopped when deciding when a program has
627	finished (especially in interactive programs), but having a program	799	finished (especially in interactive programs), but having a program
628	that automatically loops as long as it has to and no longer by virtue	800	that automatically loops as long as it has to and no longer by virtue
629	of relying on its watchers stopping correctly, that is truly a thing of	801	of relying on its watchers stopping correctly, that is truly a thing of
630	beauty.	802	beauty.
631		803
		804	This function is also I<mostly> exception-safe - you can break out of
		805	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		806	exception and so on. This does not decrement the C<ev_depth> value, nor
		807	will it clear any outstanding C<EVBREAK_ONE> breaks.
		808
632	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	809	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
633	those events and any already outstanding ones, but will not block your	810	those events and any already outstanding ones, but will not wait and
634	process in case there are no events and will return after one iteration of	811	block your process in case there are no events and will return after one
635	the loop.	812	iteration of the loop. This is sometimes useful to poll and handle new
		813	events while doing lengthy calculations, to keep the program responsive.
636		814
637	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	815	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
638	necessary) and will handle those and any already outstanding ones. It	816	necessary) and will handle those and any already outstanding ones. It
639	will block your process until at least one new event arrives (which could	817	will block your process until at least one new event arrives (which could
640	be an event internal to libev itself, so there is no guarentee that a	818	be an event internal to libev itself, so there is no guarantee that a
641	user-registered callback will be called), and will return after one	819	user-registered callback will be called), and will return after one
642	iteration of the loop.	820	iteration of the loop.
643		821
644	This is useful if you are waiting for some external event in conjunction	822	This is useful if you are waiting for some external event in conjunction
645	with something not expressible using other libev watchers (i.e. "roll your	823	with something not expressible using other libev watchers (i.e. "roll your
646	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	824	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
647	usually a better approach for this kind of thing.	825	usually a better approach for this kind of thing.
648		826
649	Here are the gory details of what C<ev_loop> does:	827	Here are the gory details of what C<ev_run> does:
650		828
		829	- Increment loop depth.
		830	- Reset the ev_break status.
651	- Before the first iteration, call any pending watchers.	831	- Before the first iteration, call any pending watchers.
		832	LOOP:
652	* If EVFLAG_FORKCHECK was used, check for a fork.	833	- If EVFLAG_FORKCHECK was used, check for a fork.
653	- If a fork was detected (by any means), queue and call all fork watchers.	834	- If a fork was detected (by any means), queue and call all fork watchers.
654	- Queue and call all prepare watchers.	835	- Queue and call all prepare watchers.
		836	- If ev_break was called, goto FINISH.
655	- If we have been forked, detach and recreate the kernel state	837	- If we have been forked, detach and recreate the kernel state
656	as to not disturb the other process.	838	as to not disturb the other process.
657	- Update the kernel state with all outstanding changes.	839	- Update the kernel state with all outstanding changes.
658	- Update the "event loop time" (ev_now ()).	840	- Update the "event loop time" (ev_now ()).
659	- Calculate for how long to sleep or block, if at all	841	- Calculate for how long to sleep or block, if at all
660	(active idle watchers, EVLOOP_NONBLOCK or not having	842	(active idle watchers, EVRUN_NOWAIT or not having
661	any active watchers at all will result in not sleeping).	843	any active watchers at all will result in not sleeping).
662	- Sleep if the I/O and timer collect interval say so.	844	- Sleep if the I/O and timer collect interval say so.
		845	- Increment loop iteration counter.
663	- Block the process, waiting for any events.	846	- Block the process, waiting for any events.
664	- Queue all outstanding I/O (fd) events.	847	- Queue all outstanding I/O (fd) events.
665	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	848	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
666	- Queue all expired timers.	849	- Queue all expired timers.
667	- Queue all expired periodics.	850	- Queue all expired periodics.
668	- Unless any events are pending now, queue all idle watchers.	851	- Queue all idle watchers with priority higher than that of pending events.
669	- Queue all check watchers.	852	- Queue all check watchers.
670	- Call all queued watchers in reverse order (i.e. check watchers first).	853	- Call all queued watchers in reverse order (i.e. check watchers first).
671	Signals and child watchers are implemented as I/O watchers, and will	854	Signals and child watchers are implemented as I/O watchers, and will
672	be handled here by queueing them when their watcher gets executed.	855	be handled here by queueing them when their watcher gets executed.
673	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	856	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
674	were used, or there are no active watchers, return, otherwise	857	were used, or there are no active watchers, goto FINISH, otherwise
675	continue with step *.	858	continue with step LOOP.
		859	FINISH:
		860	- Reset the ev_break status iff it was EVBREAK_ONE.
		861	- Decrement the loop depth.
		862	- Return.
676		863
677	Example: Queue some jobs and then loop until no events are outstanding	864	Example: Queue some jobs and then loop until no events are outstanding
678	anymore.	865	anymore.
679		866
680	... queue jobs here, make sure they register event watchers as long	867	... queue jobs here, make sure they register event watchers as long
681	... as they still have work to do (even an idle watcher will do..)	868	... as they still have work to do (even an idle watcher will do..)
682	ev_loop (my_loop, 0);	869	ev_run (my_loop, 0);
683	... jobs done or somebody called unloop. yeah!	870	... jobs done or somebody called unloop. yeah!
684		871
685	=item ev_unloop (loop, how)	872	=item ev_break (loop, how)
686		873
687	Can be used to make a call to C<ev_loop> return early (but only after it	874	Can be used to make a call to C<ev_run> return early (but only after it
688	has processed all outstanding events). The C<how> argument must be either	875	has processed all outstanding events). The C<how> argument must be either
689	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	876	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
690	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	877	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
691		878
692	This "unloop state" will be cleared when entering C<ev_loop> again.	879	This "break state" will be cleared on the next call to C<ev_run>.
693		880
694	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	881	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		882	which case it will have no effect.
695		883
696	=item ev_ref (loop)	884	=item ev_ref (loop)
697		885
698	=item ev_unref (loop)	886	=item ev_unref (loop)
699		887
700	Ref/unref can be used to add or remove a reference count on the event	888	Ref/unref can be used to add or remove a reference count on the event
701	loop: Every watcher keeps one reference, and as long as the reference	889	loop: Every watcher keeps one reference, and as long as the reference
702	count is nonzero, C<ev_loop> will not return on its own.	890	count is nonzero, C<ev_run> will not return on its own.
703		891
704	If you have a watcher you never unregister that should not keep C<ev_loop>	892	This is useful when you have a watcher that you never intend to
705	from returning, call ev_unref() after starting, and ev_ref() before	893	unregister, but that nevertheless should not keep C<ev_run> from
		894	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
706	stopping it.	895	before stopping it.
707		896
708	As an example, libev itself uses this for its internal signal pipe: It is	897	As an example, libev itself uses this for its internal signal pipe: It
709	not visible to the libev user and should not keep C<ev_loop> from exiting	898	is not visible to the libev user and should not keep C<ev_run> from
710	if no event watchers registered by it are active. It is also an excellent	899	exiting if no event watchers registered by it are active. It is also an
711	way to do this for generic recurring timers or from within third-party	900	excellent way to do this for generic recurring timers or from within
712	libraries. Just remember to I<unref after start> and I<ref before stop>	901	third-party libraries. Just remember to I<unref after start> and I<ref
713	(but only if the watcher wasn't active before, or was active before,	902	before stop> (but only if the watcher wasn't active before, or was active
714	respectively).	903	before, respectively. Note also that libev might stop watchers itself
		904	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		905	in the callback).
715		906
716	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	907	Example: Create a signal watcher, but keep it from keeping C<ev_run>
717	running when nothing else is active.	908	running when nothing else is active.
718		909
719	ev_signal exitsig;	910	ev_signal exitsig;
720	ev_signal_init (&exitsig, sig_cb, SIGINT);	911	ev_signal_init (&exitsig, sig_cb, SIGINT);
721	ev_signal_start (loop, &exitsig);	912	ev_signal_start (loop, &exitsig);
722	evf_unref (loop);	913	ev_unref (loop);
723		914
724	Example: For some weird reason, unregister the above signal handler again.	915	Example: For some weird reason, unregister the above signal handler again.
725		916
726	ev_ref (loop);	917	ev_ref (loop);
727	ev_signal_stop (loop, &exitsig);	918	ev_signal_stop (loop, &exitsig);
…		…
748		939
749	By setting a higher I<io collect interval> you allow libev to spend more	940	By setting a higher I<io collect interval> you allow libev to spend more
750	time collecting I/O events, so you can handle more events per iteration,	941	time collecting I/O events, so you can handle more events per iteration,
751	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	942	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
752	C<ev_timer>) will be not affected. Setting this to a non-null value will	943	C<ev_timer>) will be not affected. Setting this to a non-null value will
753	introduce an additional C<ev_sleep ()> call into most loop iterations.	944	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		945	sleep time ensures that libev will not poll for I/O events more often then
		946	once per this interval, on average.
754		947
755	Likewise, by setting a higher I<timeout collect interval> you allow libev	948	Likewise, by setting a higher I<timeout collect interval> you allow libev
756	to spend more time collecting timeouts, at the expense of increased	949	to spend more time collecting timeouts, at the expense of increased
757	latency/jitter/inexactness (the watcher callback will be called	950	latency/jitter/inexactness (the watcher callback will be called
758	later). C<ev_io> watchers will not be affected. Setting this to a non-null	951	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
760		953
761	Many (busy) programs can usually benefit by setting the I/O collect	954	Many (busy) programs can usually benefit by setting the I/O collect
762	interval to a value near C<0.1> or so, which is often enough for	955	interval to a value near C<0.1> or so, which is often enough for
763	interactive servers (of course not for games), likewise for timeouts. It	956	interactive servers (of course not for games), likewise for timeouts. It
764	usually doesn't make much sense to set it to a lower value than C<0.01>,	957	usually doesn't make much sense to set it to a lower value than C<0.01>,
765	as this approaches the timing granularity of most systems.	958	as this approaches the timing granularity of most systems. Note that if
		959	you do transactions with the outside world and you can't increase the
		960	parallelity, then this setting will limit your transaction rate (if you
		961	need to poll once per transaction and the I/O collect interval is 0.01,
		962	then you can't do more than 100 transactions per second).
766		963
767	Setting the I<timeout collect interval> can improve the opportunity for	964	Setting the I<timeout collect interval> can improve the opportunity for
768	saving power, as the program will "bundle" timer callback invocations that	965	saving power, as the program will "bundle" timer callback invocations that
769	are "near" in time together, by delaying some, thus reducing the number of	966	are "near" in time together, by delaying some, thus reducing the number of
770	times the process sleeps and wakes up again. Another useful technique to	967	times the process sleeps and wakes up again. Another useful technique to
771	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	968	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
772	they fire on, say, one-second boundaries only.	969	they fire on, say, one-second boundaries only.
773		970
		971	Example: we only need 0.1s timeout granularity, and we wish not to poll
		972	more often than 100 times per second:
		973
		974	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		975	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		976
		977	=item ev_invoke_pending (loop)
		978
		979	This call will simply invoke all pending watchers while resetting their
		980	pending state. Normally, C<ev_run> does this automatically when required,
		981	but when overriding the invoke callback this call comes handy. This
		982	function can be invoked from a watcher - this can be useful for example
		983	when you want to do some lengthy calculation and want to pass further
		984	event handling to another thread (you still have to make sure only one
		985	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		986
		987	=item int ev_pending_count (loop)
		988
		989	Returns the number of pending watchers - zero indicates that no watchers
		990	are pending.
		991
		992	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		993
		994	This overrides the invoke pending functionality of the loop: Instead of
		995	invoking all pending watchers when there are any, C<ev_run> will call
		996	this callback instead. This is useful, for example, when you want to
		997	invoke the actual watchers inside another context (another thread etc.).
		998
		999	If you want to reset the callback, use C<ev_invoke_pending> as new
		1000	callback.
		1001
		1002	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		1003
		1004	Sometimes you want to share the same loop between multiple threads. This
		1005	can be done relatively simply by putting mutex_lock/unlock calls around
		1006	each call to a libev function.
		1007
		1008	However, C<ev_run> can run an indefinite time, so it is not feasible
		1009	to wait for it to return. One way around this is to wake up the event
		1010	loop via C<ev_break> and C<av_async_send>, another way is to set these
		1011	I<release> and I<acquire> callbacks on the loop.
		1012
		1013	When set, then C<release> will be called just before the thread is
		1014	suspended waiting for new events, and C<acquire> is called just
		1015	afterwards.
		1016
		1017	Ideally, C<release> will just call your mutex_unlock function, and
		1018	C<acquire> will just call the mutex_lock function again.
		1019
		1020	While event loop modifications are allowed between invocations of
		1021	C<release> and C<acquire> (that's their only purpose after all), no
		1022	modifications done will affect the event loop, i.e. adding watchers will
		1023	have no effect on the set of file descriptors being watched, or the time
		1024	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		1025	to take note of any changes you made.
		1026
		1027	In theory, threads executing C<ev_run> will be async-cancel safe between
		1028	invocations of C<release> and C<acquire>.
		1029
		1030	See also the locking example in the C<THREADS> section later in this
		1031	document.
		1032
		1033	=item ev_set_userdata (loop, void *data)
		1034
		1035	=item void *ev_userdata (loop)
		1036
		1037	Set and retrieve a single C<void *> associated with a loop. When
		1038	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		1039	C<0>.
		1040
		1041	These two functions can be used to associate arbitrary data with a loop,
		1042	and are intended solely for the C<invoke_pending_cb>, C<release> and
		1043	C<acquire> callbacks described above, but of course can be (ab-)used for
		1044	any other purpose as well.
		1045
774	=item ev_loop_verify (loop)	1046	=item ev_verify (loop)
775		1047
776	This function only does something when C<EV_VERIFY> support has been	1048	This function only does something when C<EV_VERIFY> support has been
777	compiled in, which is the default for non-minimal builds. It tries to go	1049	compiled in, which is the default for non-minimal builds. It tries to go
778	through all internal structures and checks them for validity. If anything	1050	through all internal structures and checks them for validity. If anything
779	is found to be inconsistent, it will print an error message to standard	1051	is found to be inconsistent, it will print an error message to standard
…		…
790		1062
791	In the following description, uppercase C<TYPE> in names stands for the	1063	In the following description, uppercase C<TYPE> in names stands for the
792	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1064	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
793	watchers and C<ev_io_start> for I/O watchers.	1065	watchers and C<ev_io_start> for I/O watchers.
794		1066
795	A watcher is a structure that you create and register to record your	1067	A watcher is an opaque structure that you allocate and register to record
796	interest in some event. For instance, if you want to wait for STDIN to	1068	your interest in some event. To make a concrete example, imagine you want
797	become readable, you would create an C<ev_io> watcher for that:	1069	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1070	for that:
798		1071
799	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1072	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
800	{	1073	{
801	ev_io_stop (w);	1074	ev_io_stop (w);
802	ev_unloop (loop, EVUNLOOP_ALL);	1075	ev_break (loop, EVBREAK_ALL);
803	}	1076	}
804		1077
805	struct ev_loop *loop = ev_default_loop (0);	1078	struct ev_loop *loop = ev_default_loop (0);
806		1079
807	ev_io stdin_watcher;	1080	ev_io stdin_watcher;
808		1081
809	ev_init (&stdin_watcher, my_cb);	1082	ev_init (&stdin_watcher, my_cb);
810	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1083	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
811	ev_io_start (loop, &stdin_watcher);	1084	ev_io_start (loop, &stdin_watcher);
812		1085
813	ev_loop (loop, 0);	1086	ev_run (loop, 0);
814		1087
815	As you can see, you are responsible for allocating the memory for your	1088	As you can see, you are responsible for allocating the memory for your
816	watcher structures (and it is I<usually> a bad idea to do this on the	1089	watcher structures (and it is I<usually> a bad idea to do this on the
817	stack).	1090	stack).
818		1091
819	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1092	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
820	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1093	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
821		1094
822	Each watcher structure must be initialised by a call to C<ev_init	1095	Each watcher structure must be initialised by a call to C<ev_init (watcher
823	(watcher *, callback)>, which expects a callback to be provided. This	1096	*, callback)>, which expects a callback to be provided. This callback is
824	callback gets invoked each time the event occurs (or, in the case of I/O	1097	invoked each time the event occurs (or, in the case of I/O watchers, each
825	watchers, each time the event loop detects that the file descriptor given	1098	time the event loop detects that the file descriptor given is readable
826	is readable and/or writable).	1099	and/or writable).
827		1100
828	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1101	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
829	macro to configure it, with arguments specific to the watcher type. There	1102	macro to configure it, with arguments specific to the watcher type. There
830	is also a macro to combine initialisation and setting in one call: C<<	1103	is also a macro to combine initialisation and setting in one call: C<<
831	ev_TYPE_init (watcher *, callback, ...) >>.	1104	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
854	=item C<EV_WRITE>	1127	=item C<EV_WRITE>
855		1128
856	The file descriptor in the C<ev_io> watcher has become readable and/or	1129	The file descriptor in the C<ev_io> watcher has become readable and/or
857	writable.	1130	writable.
858		1131
859	=item C<EV_TIMEOUT>	1132	=item C<EV_TIMER>
860		1133
861	The C<ev_timer> watcher has timed out.	1134	The C<ev_timer> watcher has timed out.
862		1135
863	=item C<EV_PERIODIC>	1136	=item C<EV_PERIODIC>
864		1137
…		…
882		1155
883	=item C<EV_PREPARE>	1156	=item C<EV_PREPARE>
884		1157
885	=item C<EV_CHECK>	1158	=item C<EV_CHECK>
886		1159
887	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1160	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
888	to gather new events, and all C<ev_check> watchers are invoked just after	1161	to gather new events, and all C<ev_check> watchers are invoked just after
889	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1162	C<ev_run> has gathered them, but before it invokes any callbacks for any
890	received events. Callbacks of both watcher types can start and stop as	1163	received events. Callbacks of both watcher types can start and stop as
891	many watchers as they want, and all of them will be taken into account	1164	many watchers as they want, and all of them will be taken into account
892	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1165	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
893	C<ev_loop> from blocking).	1166	C<ev_run> from blocking).
894		1167
895	=item C<EV_EMBED>	1168	=item C<EV_EMBED>
896		1169
897	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1170	The embedded event loop specified in the C<ev_embed> watcher needs attention.
898		1171
899	=item C<EV_FORK>	1172	=item C<EV_FORK>
900		1173
901	The event loop has been resumed in the child process after fork (see	1174	The event loop has been resumed in the child process after fork (see
902	C<ev_fork>).	1175	C<ev_fork>).
903		1176
		1177	=item C<EV_CLEANUP>
		1178
		1179	The event loop is about to be destroyed (see C<ev_cleanup>).
		1180
904	=item C<EV_ASYNC>	1181	=item C<EV_ASYNC>
905		1182
906	The given async watcher has been asynchronously notified (see C<ev_async>).	1183	The given async watcher has been asynchronously notified (see C<ev_async>).
		1184
		1185	=item C<EV_CUSTOM>
		1186
		1187	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1188	by libev users to signal watchers (e.g. via C<ev_feed_event>).
907		1189
908	=item C<EV_ERROR>	1190	=item C<EV_ERROR>
909		1191
910	An unspecified error has occurred, the watcher has been stopped. This might	1192	An unspecified error has occurred, the watcher has been stopped. This might
911	happen because the watcher could not be properly started because libev	1193	happen because the watcher could not be properly started because libev
…		…
949		1231
950	ev_io w;	1232	ev_io w;
951	ev_init (&w, my_cb);	1233	ev_init (&w, my_cb);
952	ev_io_set (&w, STDIN_FILENO, EV_READ);	1234	ev_io_set (&w, STDIN_FILENO, EV_READ);
953		1235
954	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1236	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
955		1237
956	This macro initialises the type-specific parts of a watcher. You need to	1238	This macro initialises the type-specific parts of a watcher. You need to
957	call C<ev_init> at least once before you call this macro, but you can	1239	call C<ev_init> at least once before you call this macro, but you can
958	call C<ev_TYPE_set> any number of times. You must not, however, call this	1240	call C<ev_TYPE_set> any number of times. You must not, however, call this
959	macro on a watcher that is active (it can be pending, however, which is a	1241	macro on a watcher that is active (it can be pending, however, which is a
…		…
972		1254
973	Example: Initialise and set an C<ev_io> watcher in one step.	1255	Example: Initialise and set an C<ev_io> watcher in one step.
974		1256
975	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1257	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
976		1258
977	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1259	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
978		1260
979	Starts (activates) the given watcher. Only active watchers will receive	1261	Starts (activates) the given watcher. Only active watchers will receive
980	events. If the watcher is already active nothing will happen.	1262	events. If the watcher is already active nothing will happen.
981		1263
982	Example: Start the C<ev_io> watcher that is being abused as example in this	1264	Example: Start the C<ev_io> watcher that is being abused as example in this
983	whole section.	1265	whole section.
984		1266
985	ev_io_start (EV_DEFAULT_UC, &w);	1267	ev_io_start (EV_DEFAULT_UC, &w);
986		1268
987	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1269	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
988		1270
989	Stops the given watcher if active, and clears the pending status (whether	1271	Stops the given watcher if active, and clears the pending status (whether
990	the watcher was active or not).	1272	the watcher was active or not).
991		1273
992	It is possible that stopped watchers are pending - for example,	1274	It is possible that stopped watchers are pending - for example,
…		…
1017	=item ev_cb_set (ev_TYPE *watcher, callback)	1299	=item ev_cb_set (ev_TYPE *watcher, callback)
1018		1300
1019	Change the callback. You can change the callback at virtually any time	1301	Change the callback. You can change the callback at virtually any time
1020	(modulo threads).	1302	(modulo threads).
1021		1303
1022	=item ev_set_priority (ev_TYPE *watcher, priority)	1304	=item ev_set_priority (ev_TYPE *watcher, int priority)
1023		1305
1024	=item int ev_priority (ev_TYPE *watcher)	1306	=item int ev_priority (ev_TYPE *watcher)
1025		1307
1026	Set and query the priority of the watcher. The priority is a small	1308	Set and query the priority of the watcher. The priority is a small
1027	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1309	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1028	(default: C<-2>). Pending watchers with higher priority will be invoked	1310	(default: C<-2>). Pending watchers with higher priority will be invoked
1029	before watchers with lower priority, but priority will not keep watchers	1311	before watchers with lower priority, but priority will not keep watchers
1030	from being executed (except for C<ev_idle> watchers).	1312	from being executed (except for C<ev_idle> watchers).
1031		1313
1032	This means that priorities are I<only> used for ordering callback
1033	invocation after new events have been received. This is useful, for
1034	example, to reduce latency after idling, or more often, to bind two
1035	watchers on the same event and make sure one is called first.
1036
1037	If you need to suppress invocation when higher priority events are pending	1314	If you need to suppress invocation when higher priority events are pending
1038	you need to look at C<ev_idle> watchers, which provide this functionality.	1315	you need to look at C<ev_idle> watchers, which provide this functionality.
1039		1316
1040	You I<must not> change the priority of a watcher as long as it is active or	1317	You I<must not> change the priority of a watcher as long as it is active or
1041	pending.	1318	pending.
1042		1319
		1320	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1321	fine, as long as you do not mind that the priority value you query might
		1322	or might not have been clamped to the valid range.
		1323
1043	The default priority used by watchers when no priority has been set is	1324	The default priority used by watchers when no priority has been set is
1044	always C<0>, which is supposed to not be too high and not be too low :).	1325	always C<0>, which is supposed to not be too high and not be too low :).
1045		1326
1046	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1327	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1047	fine, as long as you do not mind that the priority value you query might	1328	priorities.
1048	or might not have been adjusted to be within valid range.
1049		1329
1050	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1330	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1051		1331
1052	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1332	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1053	C<loop> nor C<revents> need to be valid as long as the watcher callback	1333	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1061	watcher isn't pending it does nothing and returns C<0>.	1341	watcher isn't pending it does nothing and returns C<0>.
1062		1342
1063	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1343	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1064	callback to be invoked, which can be accomplished with this function.	1344	callback to be invoked, which can be accomplished with this function.
1065		1345
		1346	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1347
		1348	Feeds the given event set into the event loop, as if the specified event
		1349	had happened for the specified watcher (which must be a pointer to an
		1350	initialised but not necessarily started event watcher). Obviously you must
		1351	not free the watcher as long as it has pending events.
		1352
		1353	Stopping the watcher, letting libev invoke it, or calling
		1354	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1355	not started in the first place.
		1356
		1357	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1358	functions that do not need a watcher.
		1359
1066	=back	1360	=back
1067		1361
		1362	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
		1363	OWN COMPOSITE WATCHERS> idioms.
1068		1364
1069	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1365	=head2 WATCHER STATES
1070		1366
1071	Each watcher has, by default, a member C<void *data> that you can change	1367	There are various watcher states mentioned throughout this manual -
1072	and read at any time: libev will completely ignore it. This can be used	1368	active, pending and so on. In this section these states and the rules to
1073	to associate arbitrary data with your watcher. If you need more data and	1369	transition between them will be described in more detail - and while these
1074	don't want to allocate memory and store a pointer to it in that data	1370	rules might look complicated, they usually do "the right thing".
1075	member, you can also "subclass" the watcher type and provide your own
1076	data:
1077		1371
1078	struct my_io	1372	=over 4
		1373
		1374	=item initialiased
		1375
		1376	Before a watcher can be registered with the event looop it has to be
		1377	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1378	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1379
		1380	In this state it is simply some block of memory that is suitable for use
		1381	in an event loop. It can be moved around, freed, reused etc. at will.
		1382
		1383	=item started/running/active
		1384
		1385	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1386	property of the event loop, and is actively waiting for events. While in
		1387	this state it cannot be accessed (except in a few documented ways), moved,
		1388	freed or anything else - the only legal thing is to keep a pointer to it,
		1389	and call libev functions on it that are documented to work on active watchers.
		1390
		1391	=item pending
		1392
		1393	If a watcher is active and libev determines that an event it is interested
		1394	in has occurred (such as a timer expiring), it will become pending. It will
		1395	stay in this pending state until either it is stopped or its callback is
		1396	about to be invoked, so it is not normally pending inside the watcher
		1397	callback.
		1398
		1399	The watcher might or might not be active while it is pending (for example,
		1400	an expired non-repeating timer can be pending but no longer active). If it
		1401	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1402	but it is still property of the event loop at this time, so cannot be
		1403	moved, freed or reused. And if it is active the rules described in the
		1404	previous item still apply.
		1405
		1406	It is also possible to feed an event on a watcher that is not active (e.g.
		1407	via C<ev_feed_event>), in which case it becomes pending without being
		1408	active.
		1409
		1410	=item stopped
		1411
		1412	A watcher can be stopped implicitly by libev (in which case it might still
		1413	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1414	latter will clear any pending state the watcher might be in, regardless
		1415	of whether it was active or not, so stopping a watcher explicitly before
		1416	freeing it is often a good idea.
		1417
		1418	While stopped (and not pending) the watcher is essentially in the
		1419	initialised state, that is it can be reused, moved, modified in any way
		1420	you wish.
		1421
		1422	=back
		1423
		1424	=head2 WATCHER PRIORITY MODELS
		1425
		1426	Many event loops support I<watcher priorities>, which are usually small
		1427	integers that influence the ordering of event callback invocation
		1428	between watchers in some way, all else being equal.
		1429
		1430	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1431	description for the more technical details such as the actual priority
		1432	range.
		1433
		1434	There are two common ways how these these priorities are being interpreted
		1435	by event loops:
		1436
		1437	In the more common lock-out model, higher priorities "lock out" invocation
		1438	of lower priority watchers, which means as long as higher priority
		1439	watchers receive events, lower priority watchers are not being invoked.
		1440
		1441	The less common only-for-ordering model uses priorities solely to order
		1442	callback invocation within a single event loop iteration: Higher priority
		1443	watchers are invoked before lower priority ones, but they all get invoked
		1444	before polling for new events.
		1445
		1446	Libev uses the second (only-for-ordering) model for all its watchers
		1447	except for idle watchers (which use the lock-out model).
		1448
		1449	The rationale behind this is that implementing the lock-out model for
		1450	watchers is not well supported by most kernel interfaces, and most event
		1451	libraries will just poll for the same events again and again as long as
		1452	their callbacks have not been executed, which is very inefficient in the
		1453	common case of one high-priority watcher locking out a mass of lower
		1454	priority ones.
		1455
		1456	Static (ordering) priorities are most useful when you have two or more
		1457	watchers handling the same resource: a typical usage example is having an
		1458	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1459	timeouts. Under load, data might be received while the program handles
		1460	other jobs, but since timers normally get invoked first, the timeout
		1461	handler will be executed before checking for data. In that case, giving
		1462	the timer a lower priority than the I/O watcher ensures that I/O will be
		1463	handled first even under adverse conditions (which is usually, but not
		1464	always, what you want).
		1465
		1466	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1467	will only be executed when no same or higher priority watchers have
		1468	received events, they can be used to implement the "lock-out" model when
		1469	required.
		1470
		1471	For example, to emulate how many other event libraries handle priorities,
		1472	you can associate an C<ev_idle> watcher to each such watcher, and in
		1473	the normal watcher callback, you just start the idle watcher. The real
		1474	processing is done in the idle watcher callback. This causes libev to
		1475	continuously poll and process kernel event data for the watcher, but when
		1476	the lock-out case is known to be rare (which in turn is rare :), this is
		1477	workable.
		1478
		1479	Usually, however, the lock-out model implemented that way will perform
		1480	miserably under the type of load it was designed to handle. In that case,
		1481	it might be preferable to stop the real watcher before starting the
		1482	idle watcher, so the kernel will not have to process the event in case
		1483	the actual processing will be delayed for considerable time.
		1484
		1485	Here is an example of an I/O watcher that should run at a strictly lower
		1486	priority than the default, and which should only process data when no
		1487	other events are pending:
		1488
		1489	ev_idle idle; // actual processing watcher
		1490	ev_io io; // actual event watcher
		1491
		1492	static void
		1493	io_cb (EV_P_ ev_io *w, int revents)
1079	{	1494	{
1080	ev_io io;	1495	// stop the I/O watcher, we received the event, but
1081	int otherfd;	1496	// are not yet ready to handle it.
1082	void *somedata;	1497	ev_io_stop (EV_A_ w);
1083	struct whatever *mostinteresting;	1498
		1499	// start the idle watcher to handle the actual event.
		1500	// it will not be executed as long as other watchers
		1501	// with the default priority are receiving events.
		1502	ev_idle_start (EV_A_ &idle);
1084	};	1503	}
1085		1504
1086	...	1505	static void
1087	struct my_io w;	1506	idle_cb (EV_P_ ev_idle *w, int revents)
1088	ev_io_init (&w.io, my_cb, fd, EV_READ);
1089
1090	And since your callback will be called with a pointer to the watcher, you
1091	can cast it back to your own type:
1092
1093	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1094	{	1507	{
1095	struct my_io *w = (struct my_io *)w_;	1508	// actual processing
1096	...	1509	read (STDIN_FILENO, ...);
		1510
		1511	// have to start the I/O watcher again, as
		1512	// we have handled the event
		1513	ev_io_start (EV_P_ &io);
1097	}	1514	}
1098		1515
1099	More interesting and less C-conformant ways of casting your callback type	1516	// initialisation
1100	instead have been omitted.	1517	ev_idle_init (&idle, idle_cb);
		1518	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1519	ev_io_start (EV_DEFAULT_ &io);
1101		1520
1102	Another common scenario is to use some data structure with multiple	1521	In the "real" world, it might also be beneficial to start a timer, so that
1103	embedded watchers:	1522	low-priority connections can not be locked out forever under load. This
1104		1523	enables your program to keep a lower latency for important connections
1105	struct my_biggy	1524	during short periods of high load, while not completely locking out less
1106	{	1525	important ones.
1107	int some_data;
1108	ev_timer t1;
1109	ev_timer t2;
1110	}
1111
1112	In this case getting the pointer to C<my_biggy> is a bit more
1113	complicated: Either you store the address of your C<my_biggy> struct
1114	in the C<data> member of the watcher (for woozies), or you need to use
1115	some pointer arithmetic using C<offsetof> inside your watchers (for real
1116	programmers):
1117
1118	#include <stddef.h>
1119
1120	static void
1121	t1_cb (EV_P_ ev_timer *w, int revents)
1122	{
1123	struct my_biggy big = (struct my_biggy *
1124	(((char *)w) - offsetof (struct my_biggy, t1));
1125	}
1126
1127	static void
1128	t2_cb (EV_P_ ev_timer *w, int revents)
1129	{
1130	struct my_biggy big = (struct my_biggy *
1131	(((char *)w) - offsetof (struct my_biggy, t2));
1132	}
1133		1526
1134		1527
1135	=head1 WATCHER TYPES	1528	=head1 WATCHER TYPES
1136		1529
1137	This section describes each watcher in detail, but will not repeat	1530	This section describes each watcher in detail, but will not repeat
…		…
1161	In general you can register as many read and/or write event watchers per	1554	In general you can register as many read and/or write event watchers per
1162	fd as you want (as long as you don't confuse yourself). Setting all file	1555	fd as you want (as long as you don't confuse yourself). Setting all file
1163	descriptors to non-blocking mode is also usually a good idea (but not	1556	descriptors to non-blocking mode is also usually a good idea (but not
1164	required if you know what you are doing).	1557	required if you know what you are doing).
1165		1558
1166	If you cannot use non-blocking mode, then force the use of a
1167	known-to-be-good backend (at the time of this writing, this includes only
1168	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1169
1170	Another thing you have to watch out for is that it is quite easy to	1559	Another thing you have to watch out for is that it is quite easy to
1171	receive "spurious" readiness notifications, that is your callback might	1560	receive "spurious" readiness notifications, that is, your callback might
1172	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1561	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1173	because there is no data. Not only are some backends known to create a	1562	because there is no data. It is very easy to get into this situation even
1174	lot of those (for example Solaris ports), it is very easy to get into	1563	with a relatively standard program structure. Thus it is best to always
1175	this situation even with a relatively standard program structure. Thus	1564	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1176	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1177	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1565	preferable to a program hanging until some data arrives.
1178		1566
1179	If you cannot run the fd in non-blocking mode (for example you should	1567	If you cannot run the fd in non-blocking mode (for example you should
1180	not play around with an Xlib connection), then you have to separately	1568	not play around with an Xlib connection), then you have to separately
1181	re-test whether a file descriptor is really ready with a known-to-be good	1569	re-test whether a file descriptor is really ready with a known-to-be good
1182	interface such as poll (fortunately in our Xlib example, Xlib already	1570	interface such as poll (fortunately in the case of Xlib, it already does
1183	does this on its own, so its quite safe to use). Some people additionally	1571	this on its own, so its quite safe to use). Some people additionally
1184	use C<SIGALRM> and an interval timer, just to be sure you won't block	1572	use C<SIGALRM> and an interval timer, just to be sure you won't block
1185	indefinitely.	1573	indefinitely.
1186		1574
1187	But really, best use non-blocking mode.	1575	But really, best use non-blocking mode.
1188		1576
…		…
1216		1604
1217	There is no workaround possible except not registering events	1605	There is no workaround possible except not registering events
1218	for potentially C<dup ()>'ed file descriptors, or to resort to	1606	for potentially C<dup ()>'ed file descriptors, or to resort to
1219	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1607	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1220		1608
		1609	=head3 The special problem of files
		1610
		1611	Many people try to use C<select> (or libev) on file descriptors
		1612	representing files, and expect it to become ready when their program
		1613	doesn't block on disk accesses (which can take a long time on their own).
		1614
		1615	However, this cannot ever work in the "expected" way - you get a readiness
		1616	notification as soon as the kernel knows whether and how much data is
		1617	there, and in the case of open files, that's always the case, so you
		1618	always get a readiness notification instantly, and your read (or possibly
		1619	write) will still block on the disk I/O.
		1620
		1621	Another way to view it is that in the case of sockets, pipes, character
		1622	devices and so on, there is another party (the sender) that delivers data
		1623	on it's own, but in the case of files, there is no such thing: the disk
		1624	will not send data on it's own, simply because it doesn't know what you
		1625	wish to read - you would first have to request some data.
		1626
		1627	Since files are typically not-so-well supported by advanced notification
		1628	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1629	to files, even though you should not use it. The reason for this is
		1630	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1631	usually a tty, often a pipe, but also sometimes files or special devices
		1632	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1633	F</dev/urandom>), and even though the file might better be served with
		1634	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1635	it "just works" instead of freezing.
		1636
		1637	So avoid file descriptors pointing to files when you know it (e.g. use
		1638	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1639	when you rarely read from a file instead of from a socket, and want to
		1640	reuse the same code path.
		1641
1221	=head3 The special problem of fork	1642	=head3 The special problem of fork
1222		1643
1223	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1644	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1224	useless behaviour. Libev fully supports fork, but needs to be told about	1645	useless behaviour. Libev fully supports fork, but needs to be told about
1225	it in the child.	1646	it in the child if you want to continue to use it in the child.
1226		1647
1227	To support fork in your programs, you either have to call	1648	To support fork in your child processes, you have to call C<ev_loop_fork
1228	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1649	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1229	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1650	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1230	C<EVBACKEND_POLL>.
1231		1651
1232	=head3 The special problem of SIGPIPE	1652	=head3 The special problem of SIGPIPE
1233		1653
1234	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1654	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1235	when writing to a pipe whose other end has been closed, your program gets	1655	when writing to a pipe whose other end has been closed, your program gets
…		…
1238		1658
1239	So when you encounter spurious, unexplained daemon exits, make sure you	1659	So when you encounter spurious, unexplained daemon exits, make sure you
1240	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1660	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1241	somewhere, as that would have given you a big clue).	1661	somewhere, as that would have given you a big clue).
1242		1662
		1663	=head3 The special problem of accept()ing when you can't
		1664
		1665	Many implementations of the POSIX C<accept> function (for example,
		1666	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1667	connection from the pending queue in all error cases.
		1668
		1669	For example, larger servers often run out of file descriptors (because
		1670	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1671	rejecting the connection, leading to libev signalling readiness on
		1672	the next iteration again (the connection still exists after all), and
		1673	typically causing the program to loop at 100% CPU usage.
		1674
		1675	Unfortunately, the set of errors that cause this issue differs between
		1676	operating systems, there is usually little the app can do to remedy the
		1677	situation, and no known thread-safe method of removing the connection to
		1678	cope with overload is known (to me).
		1679
		1680	One of the easiest ways to handle this situation is to just ignore it
		1681	- when the program encounters an overload, it will just loop until the
		1682	situation is over. While this is a form of busy waiting, no OS offers an
		1683	event-based way to handle this situation, so it's the best one can do.
		1684
		1685	A better way to handle the situation is to log any errors other than
		1686	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1687	messages, and continue as usual, which at least gives the user an idea of
		1688	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1689	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1690	usage.
		1691
		1692	If your program is single-threaded, then you could also keep a dummy file
		1693	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1694	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1695	close that fd, and create a new dummy fd. This will gracefully refuse
		1696	clients under typical overload conditions.
		1697
		1698	The last way to handle it is to simply log the error and C<exit>, as
		1699	is often done with C<malloc> failures, but this results in an easy
		1700	opportunity for a DoS attack.
1243		1701
1244	=head3 Watcher-Specific Functions	1702	=head3 Watcher-Specific Functions
1245		1703
1246	=over 4	1704	=over 4
1247		1705
…		…
1279	...	1737	...
1280	struct ev_loop *loop = ev_default_init (0);	1738	struct ev_loop *loop = ev_default_init (0);
1281	ev_io stdin_readable;	1739	ev_io stdin_readable;
1282	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1740	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1283	ev_io_start (loop, &stdin_readable);	1741	ev_io_start (loop, &stdin_readable);
1284	ev_loop (loop, 0);	1742	ev_run (loop, 0);
1285		1743
1286		1744
1287	=head2 C<ev_timer> - relative and optionally repeating timeouts	1745	=head2 C<ev_timer> - relative and optionally repeating timeouts
1288		1746
1289	Timer watchers are simple relative timers that generate an event after a	1747	Timer watchers are simple relative timers that generate an event after a
…		…
1294	year, it will still time out after (roughly) one hour. "Roughly" because	1752	year, it will still time out after (roughly) one hour. "Roughly" because
1295	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1753	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1296	monotonic clock option helps a lot here).	1754	monotonic clock option helps a lot here).
1297		1755
1298	The callback is guaranteed to be invoked only I<after> its timeout has	1756	The callback is guaranteed to be invoked only I<after> its timeout has
1299	passed, but if multiple timers become ready during the same loop iteration	1757	passed (not I<at>, so on systems with very low-resolution clocks this
1300	then order of execution is undefined.	1758	might introduce a small delay). If multiple timers become ready during the
		1759	same loop iteration then the ones with earlier time-out values are invoked
		1760	before ones of the same priority with later time-out values (but this is
		1761	no longer true when a callback calls C<ev_run> recursively).
1301		1762
1302	=head3 Be smart about timeouts	1763	=head3 Be smart about timeouts
1303		1764
1304	Many real-world problems involve some kind of timeout, usually for error	1765	Many real-world problems involve some kind of timeout, usually for error
1305	recovery. A typical example is an HTTP request - if the other side hangs,	1766	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1349	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>	1810	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
1350	member and C<ev_timer_again>.	1811	member and C<ev_timer_again>.
1351		1812
1352	At start:	1813	At start:
1353		1814
1354	ev_timer_init (timer, callback);	1815	ev_init (timer, callback);
1355	timer->repeat = 60.;	1816	timer->repeat = 60.;
1356	ev_timer_again (loop, timer);	1817	ev_timer_again (loop, timer);
1357		1818
1358	Each time there is some activity:	1819	Each time there is some activity:
1359		1820
…		…
1391	ev_tstamp timeout = last_activity + 60.;	1852	ev_tstamp timeout = last_activity + 60.;
1392		1853
1393	// if last_activity + 60. is older than now, we did time out	1854	// if last_activity + 60. is older than now, we did time out
1394	if (timeout < now)	1855	if (timeout < now)
1395	{	1856	{
1396	// timeout occured, take action	1857	// timeout occurred, take action
1397	}	1858	}
1398	else	1859	else
1399	{	1860	{
1400	// callback was invoked, but there was some activity, re-arm	1861	// callback was invoked, but there was some activity, re-arm
1401	// the watcher to fire in last_activity + 60, which is	1862	// the watcher to fire in last_activity + 60, which is
1402	// guaranteed to be in the future, so "again" is positive:	1863	// guaranteed to be in the future, so "again" is positive:
1403	w->again = timeout - now;	1864	w->repeat = timeout - now;
1404	ev_timer_again (EV_A_ w);	1865	ev_timer_again (EV_A_ w);
1405	}	1866	}
1406	}	1867	}
1407		1868
1408	To summarise the callback: first calculate the real timeout (defined	1869	To summarise the callback: first calculate the real timeout (defined
…		…
1421		1882
1422	To start the timer, simply initialise the watcher and set C<last_activity>	1883	To start the timer, simply initialise the watcher and set C<last_activity>
1423	to the current time (meaning we just have some activity :), then call the	1884	to the current time (meaning we just have some activity :), then call the
1424	callback, which will "do the right thing" and start the timer:	1885	callback, which will "do the right thing" and start the timer:
1425		1886
1426	ev_timer_init (timer, callback);	1887	ev_init (timer, callback);
1427	last_activity = ev_now (loop);	1888	last_activity = ev_now (loop);
1428	callback (loop, timer, EV_TIMEOUT);	1889	callback (loop, timer, EV_TIMER);
1429		1890
1430	And when there is some activity, simply store the current time in	1891	And when there is some activity, simply store the current time in
1431	C<last_activity>, no libev calls at all:	1892	C<last_activity>, no libev calls at all:
1432		1893
1433	last_actiivty = ev_now (loop);	1894	last_activity = ev_now (loop);
1434		1895
1435	This technique is slightly more complex, but in most cases where the	1896	This technique is slightly more complex, but in most cases where the
1436	time-out is unlikely to be triggered, much more efficient.	1897	time-out is unlikely to be triggered, much more efficient.
1437		1898
1438	Changing the timeout is trivial as well (if it isn't hard-coded in the	1899	Changing the timeout is trivial as well (if it isn't hard-coded in the
…		…
1476		1937
1477	=head3 The special problem of time updates	1938	=head3 The special problem of time updates
1478		1939
1479	Establishing the current time is a costly operation (it usually takes at	1940	Establishing the current time is a costly operation (it usually takes at
1480	least two system calls): EV therefore updates its idea of the current	1941	least two system calls): EV therefore updates its idea of the current
1481	time only before and after C<ev_loop> collects new events, which causes a	1942	time only before and after C<ev_run> collects new events, which causes a
1482	growing difference between C<ev_now ()> and C<ev_time ()> when handling	1943	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1483	lots of events in one iteration.	1944	lots of events in one iteration.
1484		1945
1485	The relative timeouts are calculated relative to the C<ev_now ()>	1946	The relative timeouts are calculated relative to the C<ev_now ()>
1486	time. This is usually the right thing as this timestamp refers to the time	1947	time. This is usually the right thing as this timestamp refers to the time
…		…
1492		1953
1493	If the event loop is suspended for a long time, you can also force an	1954	If the event loop is suspended for a long time, you can also force an
1494	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1955	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1495	()>.	1956	()>.
1496		1957
		1958	=head3 The special problems of suspended animation
		1959
		1960	When you leave the server world it is quite customary to hit machines that
		1961	can suspend/hibernate - what happens to the clocks during such a suspend?
		1962
		1963	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1964	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1965	to run until the system is suspended, but they will not advance while the
		1966	system is suspended. That means, on resume, it will be as if the program
		1967	was frozen for a few seconds, but the suspend time will not be counted
		1968	towards C<ev_timer> when a monotonic clock source is used. The real time
		1969	clock advanced as expected, but if it is used as sole clocksource, then a
		1970	long suspend would be detected as a time jump by libev, and timers would
		1971	be adjusted accordingly.
		1972
		1973	I would not be surprised to see different behaviour in different between
		1974	operating systems, OS versions or even different hardware.
		1975
		1976	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1977	time jump in the monotonic clocks and the realtime clock. If the program
		1978	is suspended for a very long time, and monotonic clock sources are in use,
		1979	then you can expect C<ev_timer>s to expire as the full suspension time
		1980	will be counted towards the timers. When no monotonic clock source is in
		1981	use, then libev will again assume a timejump and adjust accordingly.
		1982
		1983	It might be beneficial for this latter case to call C<ev_suspend>
		1984	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1985	deterministic behaviour in this case (you can do nothing against
		1986	C<SIGSTOP>).
		1987
1497	=head3 Watcher-Specific Functions and Data Members	1988	=head3 Watcher-Specific Functions and Data Members
1498		1989
1499	=over 4	1990	=over 4
1500		1991
1501	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1992	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1524	If the timer is started but non-repeating, stop it (as if it timed out).	2015	If the timer is started but non-repeating, stop it (as if it timed out).
1525		2016
1526	If the timer is repeating, either start it if necessary (with the	2017	If the timer is repeating, either start it if necessary (with the
1527	C<repeat> value), or reset the running timer to the C<repeat> value.	2018	C<repeat> value), or reset the running timer to the C<repeat> value.
1528		2019
1529	This sounds a bit complicated, see "Be smart about timeouts", above, for a	2020	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1530	usage example.	2021	usage example.
		2022
		2023	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2024
		2025	Returns the remaining time until a timer fires. If the timer is active,
		2026	then this time is relative to the current event loop time, otherwise it's
		2027	the timeout value currently configured.
		2028
		2029	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2030	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2031	will return C<4>. When the timer expires and is restarted, it will return
		2032	roughly C<7> (likely slightly less as callback invocation takes some time,
		2033	too), and so on.
1531		2034
1532	=item ev_tstamp repeat [read-write]	2035	=item ev_tstamp repeat [read-write]
1533		2036
1534	The current C<repeat> value. Will be used each time the watcher times out	2037	The current C<repeat> value. Will be used each time the watcher times out
1535	or C<ev_timer_again> is called, and determines the next timeout (if any),	2038	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1561	}	2064	}
1562		2065
1563	ev_timer mytimer;	2066	ev_timer mytimer;
1564	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2067	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1565	ev_timer_again (&mytimer); /* start timer */	2068	ev_timer_again (&mytimer); /* start timer */
1566	ev_loop (loop, 0);	2069	ev_run (loop, 0);
1567		2070
1568	// and in some piece of code that gets executed on any "activity":	2071	// and in some piece of code that gets executed on any "activity":
1569	// reset the timeout to start ticking again at 10 seconds	2072	// reset the timeout to start ticking again at 10 seconds
1570	ev_timer_again (&mytimer);	2073	ev_timer_again (&mytimer);
1571		2074
…		…
1573	=head2 C<ev_periodic> - to cron or not to cron?	2076	=head2 C<ev_periodic> - to cron or not to cron?
1574		2077
1575	Periodic watchers are also timers of a kind, but they are very versatile	2078	Periodic watchers are also timers of a kind, but they are very versatile
1576	(and unfortunately a bit complex).	2079	(and unfortunately a bit complex).
1577		2080
1578	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2081	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1579	but on wall clock time (absolute time). You can tell a periodic watcher	2082	relative time, the physical time that passes) but on wall clock time
1580	to trigger after some specific point in time. For example, if you tell a	2083	(absolute time, the thing you can read on your calender or clock). The
1581	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	2084	difference is that wall clock time can run faster or slower than real
1582	+ 10.>, that is, an absolute time not a delay) and then reset your system	2085	time, and time jumps are not uncommon (e.g. when you adjust your
1583	clock to January of the previous year, then it will take more than year	2086	wrist-watch).
1584	to trigger the event (unlike an C<ev_timer>, which would still trigger
1585	roughly 10 seconds later as it uses a relative timeout).
1586		2087
		2088	You can tell a periodic watcher to trigger after some specific point
		2089	in time: for example, if you tell a periodic watcher to trigger "in 10
		2090	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2091	not a delay) and then reset your system clock to January of the previous
		2092	year, then it will take a year or more to trigger the event (unlike an
		2093	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2094	it, as it uses a relative timeout).
		2095
1587	C<ev_periodic>s can also be used to implement vastly more complex timers,	2096	C<ev_periodic> watchers can also be used to implement vastly more complex
1588	such as triggering an event on each "midnight, local time", or other	2097	timers, such as triggering an event on each "midnight, local time", or
1589	complicated rules.	2098	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2099	those cannot react to time jumps.
1590		2100
1591	As with timers, the callback is guaranteed to be invoked only when the	2101	As with timers, the callback is guaranteed to be invoked only when the
1592	time (C<at>) has passed, but if multiple periodic timers become ready	2102	point in time where it is supposed to trigger has passed. If multiple
1593	during the same loop iteration, then order of execution is undefined.	2103	timers become ready during the same loop iteration then the ones with
		2104	earlier time-out values are invoked before ones with later time-out values
		2105	(but this is no longer true when a callback calls C<ev_run> recursively).
1594		2106
1595	=head3 Watcher-Specific Functions and Data Members	2107	=head3 Watcher-Specific Functions and Data Members
1596		2108
1597	=over 4	2109	=over 4
1598		2110
1599	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2111	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1600		2112
1601	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2113	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1602		2114
1603	Lots of arguments, lets sort it out... There are basically three modes of	2115	Lots of arguments, let's sort it out... There are basically three modes of
1604	operation, and we will explain them from simplest to most complex:	2116	operation, and we will explain them from simplest to most complex:
1605		2117
1606	=over 4	2118	=over 4
1607		2119
1608	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2120	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1609		2121
1610	In this configuration the watcher triggers an event after the wall clock	2122	In this configuration the watcher triggers an event after the wall clock
1611	time C<at> has passed. It will not repeat and will not adjust when a time	2123	time C<offset> has passed. It will not repeat and will not adjust when a
1612	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2124	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1613	only run when the system clock reaches or surpasses this time.	2125	will be stopped and invoked when the system clock reaches or surpasses
		2126	this point in time.
1614		2127
1615	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2128	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1616		2129
1617	In this mode the watcher will always be scheduled to time out at the next	2130	In this mode the watcher will always be scheduled to time out at the next
1618	C<at + N * interval> time (for some integer N, which can also be negative)	2131	C<offset + N * interval> time (for some integer N, which can also be
1619	and then repeat, regardless of any time jumps.	2132	negative) and then repeat, regardless of any time jumps. The C<offset>
		2133	argument is merely an offset into the C<interval> periods.
1620		2134
1621	This can be used to create timers that do not drift with respect to the	2135	This can be used to create timers that do not drift with respect to the
1622	system clock, for example, here is a C<ev_periodic> that triggers each	2136	system clock, for example, here is an C<ev_periodic> that triggers each
1623	hour, on the hour:	2137	hour, on the hour (with respect to UTC):
1624		2138
1625	ev_periodic_set (&periodic, 0., 3600., 0);	2139	ev_periodic_set (&periodic, 0., 3600., 0);
1626		2140
1627	This doesn't mean there will always be 3600 seconds in between triggers,	2141	This doesn't mean there will always be 3600 seconds in between triggers,
1628	but only that the callback will be called when the system time shows a	2142	but only that the callback will be called when the system time shows a
1629	full hour (UTC), or more correctly, when the system time is evenly divisible	2143	full hour (UTC), or more correctly, when the system time is evenly divisible
1630	by 3600.	2144	by 3600.
1631		2145
1632	Another way to think about it (for the mathematically inclined) is that	2146	Another way to think about it (for the mathematically inclined) is that
1633	C<ev_periodic> will try to run the callback in this mode at the next possible	2147	C<ev_periodic> will try to run the callback in this mode at the next possible
1634	time where C<time = at (mod interval)>, regardless of any time jumps.	2148	time where C<time = offset (mod interval)>, regardless of any time jumps.
1635		2149
1636	For numerical stability it is preferable that the C<at> value is near	2150	For numerical stability it is preferable that the C<offset> value is near
1637	C<ev_now ()> (the current time), but there is no range requirement for	2151	C<ev_now ()> (the current time), but there is no range requirement for
1638	this value, and in fact is often specified as zero.	2152	this value, and in fact is often specified as zero.
1639		2153
1640	Note also that there is an upper limit to how often a timer can fire (CPU	2154	Note also that there is an upper limit to how often a timer can fire (CPU
1641	speed for example), so if C<interval> is very small then timing stability	2155	speed for example), so if C<interval> is very small then timing stability
1642	will of course deteriorate. Libev itself tries to be exact to be about one	2156	will of course deteriorate. Libev itself tries to be exact to be about one
1643	millisecond (if the OS supports it and the machine is fast enough).	2157	millisecond (if the OS supports it and the machine is fast enough).
1644		2158
1645	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2159	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1646		2160
1647	In this mode the values for C<interval> and C<at> are both being	2161	In this mode the values for C<interval> and C<offset> are both being
1648	ignored. Instead, each time the periodic watcher gets scheduled, the	2162	ignored. Instead, each time the periodic watcher gets scheduled, the
1649	reschedule callback will be called with the watcher as first, and the	2163	reschedule callback will be called with the watcher as first, and the
1650	current time as second argument.	2164	current time as second argument.
1651		2165
1652	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2166	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1653	ever, or make ANY event loop modifications whatsoever>.	2167	or make ANY other event loop modifications whatsoever, unless explicitly
		2168	allowed by documentation here>.
1654		2169
1655	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2170	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1656	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2171	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1657	only event loop modification you are allowed to do).	2172	only event loop modification you are allowed to do).
1658		2173
…		…
1688	a different time than the last time it was called (e.g. in a crond like	2203	a different time than the last time it was called (e.g. in a crond like
1689	program when the crontabs have changed).	2204	program when the crontabs have changed).
1690		2205
1691	=item ev_tstamp ev_periodic_at (ev_periodic *)	2206	=item ev_tstamp ev_periodic_at (ev_periodic *)
1692		2207
1693	When active, returns the absolute time that the watcher is supposed to	2208	When active, returns the absolute time that the watcher is supposed
1694	trigger next.	2209	to trigger next. This is not the same as the C<offset> argument to
		2210	C<ev_periodic_set>, but indeed works even in interval and manual
		2211	rescheduling modes.
1695		2212
1696	=item ev_tstamp offset [read-write]	2213	=item ev_tstamp offset [read-write]
1697		2214
1698	When repeating, this contains the offset value, otherwise this is the	2215	When repeating, this contains the offset value, otherwise this is the
1699	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2216	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2217	although libev might modify this value for better numerical stability).
1700		2218
1701	Can be modified any time, but changes only take effect when the periodic	2219	Can be modified any time, but changes only take effect when the periodic
1702	timer fires or C<ev_periodic_again> is being called.	2220	timer fires or C<ev_periodic_again> is being called.
1703		2221
1704	=item ev_tstamp interval [read-write]	2222	=item ev_tstamp interval [read-write]
…		…
1720	Example: Call a callback every hour, or, more precisely, whenever the	2238	Example: Call a callback every hour, or, more precisely, whenever the
1721	system time is divisible by 3600. The callback invocation times have	2239	system time is divisible by 3600. The callback invocation times have
1722	potentially a lot of jitter, but good long-term stability.	2240	potentially a lot of jitter, but good long-term stability.
1723		2241
1724	static void	2242	static void
1725	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2243	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1726	{	2244	{
1727	... its now a full hour (UTC, or TAI or whatever your clock follows)	2245	... its now a full hour (UTC, or TAI or whatever your clock follows)
1728	}	2246	}
1729		2247
1730	ev_periodic hourly_tick;	2248	ev_periodic hourly_tick;
…		…
1753		2271
1754	=head2 C<ev_signal> - signal me when a signal gets signalled!	2272	=head2 C<ev_signal> - signal me when a signal gets signalled!
1755		2273
1756	Signal watchers will trigger an event when the process receives a specific	2274	Signal watchers will trigger an event when the process receives a specific
1757	signal one or more times. Even though signals are very asynchronous, libev	2275	signal one or more times. Even though signals are very asynchronous, libev
1758	will try it's best to deliver signals synchronously, i.e. as part of the	2276	will try its best to deliver signals synchronously, i.e. as part of the
1759	normal event processing, like any other event.	2277	normal event processing, like any other event.
1760		2278
1761	If you want signals asynchronously, just use C<sigaction> as you would	2279	If you want signals to be delivered truly asynchronously, just use
1762	do without libev and forget about sharing the signal. You can even use	2280	C<sigaction> as you would do without libev and forget about sharing
1763	C<ev_async> from a signal handler to synchronously wake up an event loop.	2281	the signal. You can even use C<ev_async> from a signal handler to
		2282	synchronously wake up an event loop.
1764		2283
1765	You can configure as many watchers as you like per signal. Only when the	2284	You can configure as many watchers as you like for the same signal, but
		2285	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2286	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2287	C<SIGINT> in both the default loop and another loop at the same time. At
		2288	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2289
1766	first watcher gets started will libev actually register a signal handler	2290	When the first watcher gets started will libev actually register something
1767	with the kernel (thus it coexists with your own signal handlers as long as	2291	with the kernel (thus it coexists with your own signal handlers as long as
1768	you don't register any with libev for the same signal). Similarly, when	2292	you don't register any with libev for the same signal).
1769	the last signal watcher for a signal is stopped, libev will reset the
1770	signal handler to SIG_DFL (regardless of what it was set to before).
1771		2293
1772	If possible and supported, libev will install its handlers with	2294	If possible and supported, libev will install its handlers with
1773	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2295	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1774	interrupted. If you have a problem with system calls getting interrupted by	2296	not be unduly interrupted. If you have a problem with system calls getting
1775	signals you can block all signals in an C<ev_check> watcher and unblock	2297	interrupted by signals you can block all signals in an C<ev_check> watcher
1776	them in an C<ev_prepare> watcher.	2298	and unblock them in an C<ev_prepare> watcher.
		2299
		2300	=head3 The special problem of inheritance over fork/execve/pthread_create
		2301
		2302	Both the signal mask (C<sigprocmask>) and the signal disposition
		2303	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2304	stopping it again), that is, libev might or might not block the signal,
		2305	and might or might not set or restore the installed signal handler.
		2306
		2307	While this does not matter for the signal disposition (libev never
		2308	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2309	C<execve>), this matters for the signal mask: many programs do not expect
		2310	certain signals to be blocked.
		2311
		2312	This means that before calling C<exec> (from the child) you should reset
		2313	the signal mask to whatever "default" you expect (all clear is a good
		2314	choice usually).
		2315
		2316	The simplest way to ensure that the signal mask is reset in the child is
		2317	to install a fork handler with C<pthread_atfork> that resets it. That will
		2318	catch fork calls done by libraries (such as the libc) as well.
		2319
		2320	In current versions of libev, the signal will not be blocked indefinitely
		2321	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2322	the window of opportunity for problems, it will not go away, as libev
		2323	I<has> to modify the signal mask, at least temporarily.
		2324
		2325	So I can't stress this enough: I<If you do not reset your signal mask when
		2326	you expect it to be empty, you have a race condition in your code>. This
		2327	is not a libev-specific thing, this is true for most event libraries.
		2328
		2329	=head3 The special problem of threads signal handling
		2330
		2331	POSIX threads has problematic signal handling semantics, specifically,
		2332	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2333	threads in a process block signals, which is hard to achieve.
		2334
		2335	When you want to use sigwait (or mix libev signal handling with your own
		2336	for the same signals), you can tackle this problem by globally blocking
		2337	all signals before creating any threads (or creating them with a fully set
		2338	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2339	loops. Then designate one thread as "signal receiver thread" which handles
		2340	these signals. You can pass on any signals that libev might be interested
		2341	in by calling C<ev_feed_signal>.
1777		2342
1778	=head3 Watcher-Specific Functions and Data Members	2343	=head3 Watcher-Specific Functions and Data Members
1779		2344
1780	=over 4	2345	=over 4
1781		2346
…		…
1797	Example: Try to exit cleanly on SIGINT.	2362	Example: Try to exit cleanly on SIGINT.
1798		2363
1799	static void	2364	static void
1800	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2365	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1801	{	2366	{
1802	ev_unloop (loop, EVUNLOOP_ALL);	2367	ev_break (loop, EVBREAK_ALL);
1803	}	2368	}
1804		2369
1805	ev_signal signal_watcher;	2370	ev_signal signal_watcher;
1806	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2371	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1807	ev_signal_start (loop, &signal_watcher);	2372	ev_signal_start (loop, &signal_watcher);
…		…
1813	some child status changes (most typically when a child of yours dies or	2378	some child status changes (most typically when a child of yours dies or
1814	exits). It is permissible to install a child watcher I<after> the child	2379	exits). It is permissible to install a child watcher I<after> the child
1815	has been forked (which implies it might have already exited), as long	2380	has been forked (which implies it might have already exited), as long
1816	as the event loop isn't entered (or is continued from a watcher), i.e.,	2381	as the event loop isn't entered (or is continued from a watcher), i.e.,
1817	forking and then immediately registering a watcher for the child is fine,	2382	forking and then immediately registering a watcher for the child is fine,
1818	but forking and registering a watcher a few event loop iterations later is	2383	but forking and registering a watcher a few event loop iterations later or
1819	not.	2384	in the next callback invocation is not.
1820		2385
1821	Only the default event loop is capable of handling signals, and therefore	2386	Only the default event loop is capable of handling signals, and therefore
1822	you can only register child watchers in the default event loop.	2387	you can only register child watchers in the default event loop.
1823		2388
		2389	Due to some design glitches inside libev, child watchers will always be
		2390	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2391	libev)
		2392
1824	=head3 Process Interaction	2393	=head3 Process Interaction
1825		2394
1826	Libev grabs C<SIGCHLD> as soon as the default event loop is	2395	Libev grabs C<SIGCHLD> as soon as the default event loop is
1827	initialised. This is necessary to guarantee proper behaviour even if	2396	initialised. This is necessary to guarantee proper behaviour even if the
1828	the first child watcher is started after the child exits. The occurrence	2397	first child watcher is started after the child exits. The occurrence
1829	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2398	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1830	synchronously as part of the event loop processing. Libev always reaps all	2399	synchronously as part of the event loop processing. Libev always reaps all
1831	children, even ones not watched.	2400	children, even ones not watched.
1832		2401
1833	=head3 Overriding the Built-In Processing	2402	=head3 Overriding the Built-In Processing
…		…
1843	=head3 Stopping the Child Watcher	2412	=head3 Stopping the Child Watcher
1844		2413
1845	Currently, the child watcher never gets stopped, even when the	2414	Currently, the child watcher never gets stopped, even when the
1846	child terminates, so normally one needs to stop the watcher in the	2415	child terminates, so normally one needs to stop the watcher in the
1847	callback. Future versions of libev might stop the watcher automatically	2416	callback. Future versions of libev might stop the watcher automatically
1848	when a child exit is detected.	2417	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2418	problem).
1849		2419
1850	=head3 Watcher-Specific Functions and Data Members	2420	=head3 Watcher-Specific Functions and Data Members
1851		2421
1852	=over 4	2422	=over 4
1853		2423
…		…
1910		2480
1911		2481
1912	=head2 C<ev_stat> - did the file attributes just change?	2482	=head2 C<ev_stat> - did the file attributes just change?
1913		2483
1914	This watches a file system path for attribute changes. That is, it calls	2484	This watches a file system path for attribute changes. That is, it calls
1915	C<stat> regularly (or when the OS says it changed) and sees if it changed	2485	C<stat> on that path in regular intervals (or when the OS says it changed)
1916	compared to the last time, invoking the callback if it did.	2486	and sees if it changed compared to the last time, invoking the callback if
		2487	it did.
1917		2488
1918	The path does not need to exist: changing from "path exists" to "path does	2489	The path does not need to exist: changing from "path exists" to "path does
1919	not exist" is a status change like any other. The condition "path does	2490	not exist" is a status change like any other. The condition "path does not
1920	not exist" is signified by the C<st_nlink> field being zero (which is	2491	exist" (or more correctly "path cannot be stat'ed") is signified by the
1921	otherwise always forced to be at least one) and all the other fields of	2492	C<st_nlink> field being zero (which is otherwise always forced to be at
1922	the stat buffer having unspecified contents.	2493	least one) and all the other fields of the stat buffer having unspecified
		2494	contents.
1923		2495
1924	The path I<should> be absolute and I<must not> end in a slash. If it is	2496	The path I<must not> end in a slash or contain special components such as
		2497	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1925	relative and your working directory changes, the behaviour is undefined.	2498	your working directory changes, then the behaviour is undefined.
1926		2499
1927	Since there is no standard kernel interface to do this, the portable	2500	Since there is no portable change notification interface available, the
1928	implementation simply calls C<stat (2)> regularly on the path to see if	2501	portable implementation simply calls C<stat(2)> regularly on the path
1929	it changed somehow. You can specify a recommended polling interval for	2502	to see if it changed somehow. You can specify a recommended polling
1930	this case. If you specify a polling interval of C<0> (highly recommended!)	2503	interval for this case. If you specify a polling interval of C<0> (highly
1931	then a I<suitable, unspecified default> value will be used (which	2504	recommended!) then a I<suitable, unspecified default> value will be used
1932	you can expect to be around five seconds, although this might change	2505	(which you can expect to be around five seconds, although this might
1933	dynamically). Libev will also impose a minimum interval which is currently	2506	change dynamically). Libev will also impose a minimum interval which is
1934	around C<0.1>, but thats usually overkill.	2507	currently around C<0.1>, but that's usually overkill.
1935		2508
1936	This watcher type is not meant for massive numbers of stat watchers,	2509	This watcher type is not meant for massive numbers of stat watchers,
1937	as even with OS-supported change notifications, this can be	2510	as even with OS-supported change notifications, this can be
1938	resource-intensive.	2511	resource-intensive.
1939		2512
1940	At the time of this writing, the only OS-specific interface implemented	2513	At the time of this writing, the only OS-specific interface implemented
1941	is the Linux inotify interface (implementing kqueue support is left as	2514	is the Linux inotify interface (implementing kqueue support is left as an
1942	an exercise for the reader. Note, however, that the author sees no way	2515	exercise for the reader. Note, however, that the author sees no way of
1943	of implementing C<ev_stat> semantics with kqueue).	2516	implementing C<ev_stat> semantics with kqueue, except as a hint).
1944		2517
1945	=head3 ABI Issues (Largefile Support)	2518	=head3 ABI Issues (Largefile Support)
1946		2519
1947	Libev by default (unless the user overrides this) uses the default	2520	Libev by default (unless the user overrides this) uses the default
1948	compilation environment, which means that on systems with large file	2521	compilation environment, which means that on systems with large file
1949	support disabled by default, you get the 32 bit version of the stat	2522	support disabled by default, you get the 32 bit version of the stat
1950	structure. When using the library from programs that change the ABI to	2523	structure. When using the library from programs that change the ABI to
1951	use 64 bit file offsets the programs will fail. In that case you have to	2524	use 64 bit file offsets the programs will fail. In that case you have to
1952	compile libev with the same flags to get binary compatibility. This is	2525	compile libev with the same flags to get binary compatibility. This is
1953	obviously the case with any flags that change the ABI, but the problem is	2526	obviously the case with any flags that change the ABI, but the problem is
1954	most noticeably disabled with ev_stat and large file support.	2527	most noticeably displayed with ev_stat and large file support.
1955		2528
1956	The solution for this is to lobby your distribution maker to make large	2529	The solution for this is to lobby your distribution maker to make large
1957	file interfaces available by default (as e.g. FreeBSD does) and not	2530	file interfaces available by default (as e.g. FreeBSD does) and not
1958	optional. Libev cannot simply switch on large file support because it has	2531	optional. Libev cannot simply switch on large file support because it has
1959	to exchange stat structures with application programs compiled using the	2532	to exchange stat structures with application programs compiled using the
1960	default compilation environment.	2533	default compilation environment.
1961		2534
1962	=head3 Inotify and Kqueue	2535	=head3 Inotify and Kqueue
1963		2536
1964	When C<inotify (7)> support has been compiled into libev (generally	2537	When C<inotify (7)> support has been compiled into libev and present at
1965	only available with Linux 2.6.25 or above due to bugs in earlier	2538	runtime, it will be used to speed up change detection where possible. The
1966	implementations) and present at runtime, it will be used to speed up	2539	inotify descriptor will be created lazily when the first C<ev_stat>
1967	change detection where possible. The inotify descriptor will be created	2540	watcher is being started.
1968	lazily when the first C<ev_stat> watcher is being started.
1969		2541
1970	Inotify presence does not change the semantics of C<ev_stat> watchers	2542	Inotify presence does not change the semantics of C<ev_stat> watchers
1971	except that changes might be detected earlier, and in some cases, to avoid	2543	except that changes might be detected earlier, and in some cases, to avoid
1972	making regular C<stat> calls. Even in the presence of inotify support	2544	making regular C<stat> calls. Even in the presence of inotify support
1973	there are many cases where libev has to resort to regular C<stat> polling,	2545	there are many cases where libev has to resort to regular C<stat> polling,
1974	but as long as the path exists, libev usually gets away without polling.	2546	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2547	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2548	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2549	xfs are fully working) libev usually gets away without polling.
1975		2550
1976	There is no support for kqueue, as apparently it cannot be used to	2551	There is no support for kqueue, as apparently it cannot be used to
1977	implement this functionality, due to the requirement of having a file	2552	implement this functionality, due to the requirement of having a file
1978	descriptor open on the object at all times, and detecting renames, unlinks	2553	descriptor open on the object at all times, and detecting renames, unlinks
1979	etc. is difficult.	2554	etc. is difficult.
1980		2555
		2556	=head3 C<stat ()> is a synchronous operation
		2557
		2558	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2559	the process. The exception are C<ev_stat> watchers - those call C<stat
		2560	()>, which is a synchronous operation.
		2561
		2562	For local paths, this usually doesn't matter: unless the system is very
		2563	busy or the intervals between stat's are large, a stat call will be fast,
		2564	as the path data is usually in memory already (except when starting the
		2565	watcher).
		2566
		2567	For networked file systems, calling C<stat ()> can block an indefinite
		2568	time due to network issues, and even under good conditions, a stat call
		2569	often takes multiple milliseconds.
		2570
		2571	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2572	paths, although this is fully supported by libev.
		2573
1981	=head3 The special problem of stat time resolution	2574	=head3 The special problem of stat time resolution
1982		2575
1983	The C<stat ()> system call only supports full-second resolution portably, and	2576	The C<stat ()> system call only supports full-second resolution portably,
1984	even on systems where the resolution is higher, most file systems still	2577	and even on systems where the resolution is higher, most file systems
1985	only support whole seconds.	2578	still only support whole seconds.
1986		2579
1987	That means that, if the time is the only thing that changes, you can	2580	That means that, if the time is the only thing that changes, you can
1988	easily miss updates: on the first update, C<ev_stat> detects a change and	2581	easily miss updates: on the first update, C<ev_stat> detects a change and
1989	calls your callback, which does something. When there is another update	2582	calls your callback, which does something. When there is another update
1990	within the same second, C<ev_stat> will be unable to detect unless the	2583	within the same second, C<ev_stat> will be unable to detect unless the
…		…
2133		2726
2134	=head3 Watcher-Specific Functions and Data Members	2727	=head3 Watcher-Specific Functions and Data Members
2135		2728
2136	=over 4	2729	=over 4
2137		2730
2138	=item ev_idle_init (ev_signal *, callback)	2731	=item ev_idle_init (ev_idle *, callback)
2139		2732
2140	Initialises and configures the idle watcher - it has no parameters of any	2733	Initialises and configures the idle watcher - it has no parameters of any
2141	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2734	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
2142	believe me.	2735	believe me.
2143		2736
…		…
2156	// no longer anything immediate to do.	2749	// no longer anything immediate to do.
2157	}	2750	}
2158		2751
2159	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2752	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2160	ev_idle_init (idle_watcher, idle_cb);	2753	ev_idle_init (idle_watcher, idle_cb);
2161	ev_idle_start (loop, idle_cb);	2754	ev_idle_start (loop, idle_watcher);
2162		2755
2163		2756
2164	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2757	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2165		2758
2166	Prepare and check watchers are usually (but not always) used in pairs:	2759	Prepare and check watchers are usually (but not always) used in pairs:
2167	prepare watchers get invoked before the process blocks and check watchers	2760	prepare watchers get invoked before the process blocks and check watchers
2168	afterwards.	2761	afterwards.
2169		2762
2170	You I<must not> call C<ev_loop> or similar functions that enter	2763	You I<must not> call C<ev_run> or similar functions that enter
2171	the current event loop from either C<ev_prepare> or C<ev_check>	2764	the current event loop from either C<ev_prepare> or C<ev_check>
2172	watchers. Other loops than the current one are fine, however. The	2765	watchers. Other loops than the current one are fine, however. The
2173	rationale behind this is that you do not need to check for recursion in	2766	rationale behind this is that you do not need to check for recursion in
2174	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2767	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2175	C<ev_check> so if you have one watcher of each kind they will always be	2768	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2259	struct pollfd fds [nfd];	2852	struct pollfd fds [nfd];
2260	// actual code will need to loop here and realloc etc.	2853	// actual code will need to loop here and realloc etc.
2261	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2854	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2262		2855
2263	/* the callback is illegal, but won't be called as we stop during check */	2856	/* the callback is illegal, but won't be called as we stop during check */
2264	ev_timer_init (&tw, 0, timeout * 1e-3);	2857	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2265	ev_timer_start (loop, &tw);	2858	ev_timer_start (loop, &tw);
2266		2859
2267	// create one ev_io per pollfd	2860	// create one ev_io per pollfd
2268	for (int i = 0; i < nfd; ++i)	2861	for (int i = 0; i < nfd; ++i)
2269	{	2862	{
…		…
2343		2936
2344	if (timeout >= 0)	2937	if (timeout >= 0)
2345	// create/start timer	2938	// create/start timer
2346		2939
2347	// poll	2940	// poll
2348	ev_loop (EV_A_ 0);	2941	ev_run (EV_A_ 0);
2349		2942
2350	// stop timer again	2943	// stop timer again
2351	if (timeout >= 0)	2944	if (timeout >= 0)
2352	ev_timer_stop (EV_A_ &to);	2945	ev_timer_stop (EV_A_ &to);
2353		2946
…		…
2382	some fds have to be watched and handled very quickly (with low latency),	2975	some fds have to be watched and handled very quickly (with low latency),
2383	and even priorities and idle watchers might have too much overhead. In	2976	and even priorities and idle watchers might have too much overhead. In
2384	this case you would put all the high priority stuff in one loop and all	2977	this case you would put all the high priority stuff in one loop and all
2385	the rest in a second one, and embed the second one in the first.	2978	the rest in a second one, and embed the second one in the first.
2386		2979
2387	As long as the watcher is active, the callback will be invoked every time	2980	As long as the watcher is active, the callback will be invoked every
2388	there might be events pending in the embedded loop. The callback must then	2981	time there might be events pending in the embedded loop. The callback
2389	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2982	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2390	their callbacks (you could also start an idle watcher to give the embedded	2983	sweep and invoke their callbacks (the callback doesn't need to invoke the
2391	loop strictly lower priority for example). You can also set the callback	2984	C<ev_embed_sweep> function directly, it could also start an idle watcher
2392	to C<0>, in which case the embed watcher will automatically execute the	2985	to give the embedded loop strictly lower priority for example).
2393	embedded loop sweep.
2394		2986
2395	As long as the watcher is started it will automatically handle events. The	2987	You can also set the callback to C<0>, in which case the embed watcher
2396	callback will be invoked whenever some events have been handled. You can	2988	will automatically execute the embedded loop sweep whenever necessary.
2397	set the callback to C<0> to avoid having to specify one if you are not
2398	interested in that.
2399		2989
2400	Also, there have not currently been made special provisions for forking:	2990	Fork detection will be handled transparently while the C<ev_embed> watcher
2401	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2991	is active, i.e., the embedded loop will automatically be forked when the
2402	but you will also have to stop and restart any C<ev_embed> watchers	2992	embedding loop forks. In other cases, the user is responsible for calling
2403	yourself - but you can use a fork watcher to handle this automatically,	2993	C<ev_loop_fork> on the embedded loop.
2404	and future versions of libev might do just that.
2405		2994
2406	Unfortunately, not all backends are embeddable: only the ones returned by	2995	Unfortunately, not all backends are embeddable: only the ones returned by
2407	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2996	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2408	portable one.	2997	portable one.
2409		2998
…		…
2435	if you do not want that, you need to temporarily stop the embed watcher).	3024	if you do not want that, you need to temporarily stop the embed watcher).
2436		3025
2437	=item ev_embed_sweep (loop, ev_embed *)	3026	=item ev_embed_sweep (loop, ev_embed *)
2438		3027
2439	Make a single, non-blocking sweep over the embedded loop. This works	3028	Make a single, non-blocking sweep over the embedded loop. This works
2440	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3029	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2441	appropriate way for embedded loops.	3030	appropriate way for embedded loops.
2442		3031
2443	=item struct ev_loop *other [read-only]	3032	=item struct ev_loop *other [read-only]
2444		3033
2445	The embedded event loop.	3034	The embedded event loop.
…		…
2503	event loop blocks next and before C<ev_check> watchers are being called,	3092	event loop blocks next and before C<ev_check> watchers are being called,
2504	and only in the child after the fork. If whoever good citizen calling	3093	and only in the child after the fork. If whoever good citizen calling
2505	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3094	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2506	handlers will be invoked, too, of course.	3095	handlers will be invoked, too, of course.
2507		3096
		3097	=head3 The special problem of life after fork - how is it possible?
		3098
		3099	Most uses of C<fork()> consist of forking, then some simple calls to set
		3100	up/change the process environment, followed by a call to C<exec()>. This
		3101	sequence should be handled by libev without any problems.
		3102
		3103	This changes when the application actually wants to do event handling
		3104	in the child, or both parent in child, in effect "continuing" after the
		3105	fork.
		3106
		3107	The default mode of operation (for libev, with application help to detect
		3108	forks) is to duplicate all the state in the child, as would be expected
		3109	when I<either> the parent I<or> the child process continues.
		3110
		3111	When both processes want to continue using libev, then this is usually the
		3112	wrong result. In that case, usually one process (typically the parent) is
		3113	supposed to continue with all watchers in place as before, while the other
		3114	process typically wants to start fresh, i.e. without any active watchers.
		3115
		3116	The cleanest and most efficient way to achieve that with libev is to
		3117	simply create a new event loop, which of course will be "empty", and
		3118	use that for new watchers. This has the advantage of not touching more
		3119	memory than necessary, and thus avoiding the copy-on-write, and the
		3120	disadvantage of having to use multiple event loops (which do not support
		3121	signal watchers).
		3122
		3123	When this is not possible, or you want to use the default loop for
		3124	other reasons, then in the process that wants to start "fresh", call
		3125	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3126	Destroying the default loop will "orphan" (not stop) all registered
		3127	watchers, so you have to be careful not to execute code that modifies
		3128	those watchers. Note also that in that case, you have to re-register any
		3129	signal watchers.
		3130
2508	=head3 Watcher-Specific Functions and Data Members	3131	=head3 Watcher-Specific Functions and Data Members
2509		3132
2510	=over 4	3133	=over 4
2511		3134
2512	=item ev_fork_init (ev_signal *, callback)	3135	=item ev_fork_init (ev_fork *, callback)
2513		3136
2514	Initialises and configures the fork watcher - it has no parameters of any	3137	Initialises and configures the fork watcher - it has no parameters of any
2515	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3138	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2516	believe me.	3139	really.
2517		3140
2518	=back	3141	=back
2519		3142
2520		3143
		3144	=head2 C<ev_cleanup> - even the best things end
		3145
		3146	Cleanup watchers are called just before the event loop is being destroyed
		3147	by a call to C<ev_loop_destroy>.
		3148
		3149	While there is no guarantee that the event loop gets destroyed, cleanup
		3150	watchers provide a convenient method to install cleanup hooks for your
		3151	program, worker threads and so on - you just to make sure to destroy the
		3152	loop when you want them to be invoked.
		3153
		3154	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3155	all other watchers, they do not keep a reference to the event loop (which
		3156	makes a lot of sense if you think about it). Like all other watchers, you
		3157	can call libev functions in the callback, except C<ev_cleanup_start>.
		3158
		3159	=head3 Watcher-Specific Functions and Data Members
		3160
		3161	=over 4
		3162
		3163	=item ev_cleanup_init (ev_cleanup *, callback)
		3164
		3165	Initialises and configures the cleanup watcher - it has no parameters of
		3166	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3167	pointless, I assure you.
		3168
		3169	=back
		3170
		3171	Example: Register an atexit handler to destroy the default loop, so any
		3172	cleanup functions are called.
		3173
		3174	static void
		3175	program_exits (void)
		3176	{
		3177	ev_loop_destroy (EV_DEFAULT_UC);
		3178	}
		3179
		3180	...
		3181	atexit (program_exits);
		3182
		3183
2521	=head2 C<ev_async> - how to wake up another event loop	3184	=head2 C<ev_async> - how to wake up an event loop
2522		3185
2523	In general, you cannot use an C<ev_loop> from multiple threads or other	3186	In general, you cannot use an C<ev_run> from multiple threads or other
2524	asynchronous sources such as signal handlers (as opposed to multiple event	3187	asynchronous sources such as signal handlers (as opposed to multiple event
2525	loops - those are of course safe to use in different threads).	3188	loops - those are of course safe to use in different threads).
2526		3189
2527	Sometimes, however, you need to wake up another event loop you do not	3190	Sometimes, however, you need to wake up an event loop you do not control,
2528	control, for example because it belongs to another thread. This is what	3191	for example because it belongs to another thread. This is what C<ev_async>
2529	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3192	watchers do: as long as the C<ev_async> watcher is active, you can signal
2530	can signal it by calling C<ev_async_send>, which is thread- and signal	3193	it by calling C<ev_async_send>, which is thread- and signal safe.
2531	safe.
2532		3194
2533	This functionality is very similar to C<ev_signal> watchers, as signals,	3195	This functionality is very similar to C<ev_signal> watchers, as signals,
2534	too, are asynchronous in nature, and signals, too, will be compressed	3196	too, are asynchronous in nature, and signals, too, will be compressed
2535	(i.e. the number of callback invocations may be less than the number of	3197	(i.e. the number of callback invocations may be less than the number of
2536	C<ev_async_sent> calls).	3198	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
		3199	of "global async watchers" by using a watcher on an otherwise unused
		3200	signal, and C<ev_feed_signal> to signal this watcher from another thread,
		3201	even without knowing which loop owns the signal.
2537		3202
2538	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3203	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
2539	just the default loop.	3204	just the default loop.
2540		3205
2541	=head3 Queueing	3206	=head3 Queueing
2542		3207
2543	C<ev_async> does not support queueing of data in any way. The reason	3208	C<ev_async> does not support queueing of data in any way. The reason
2544	is that the author does not know of a simple (or any) algorithm for a	3209	is that the author does not know of a simple (or any) algorithm for a
2545	multiple-writer-single-reader queue that works in all cases and doesn't	3210	multiple-writer-single-reader queue that works in all cases and doesn't
2546	need elaborate support such as pthreads.	3211	need elaborate support such as pthreads or unportable memory access
		3212	semantics.
2547		3213
2548	That means that if you want to queue data, you have to provide your own	3214	That means that if you want to queue data, you have to provide your own
2549	queue. But at least I can tell you how to implement locking around your	3215	queue. But at least I can tell you how to implement locking around your
2550	queue:	3216	queue:
2551		3217
…		…
2629	=over 4	3295	=over 4
2630		3296
2631	=item ev_async_init (ev_async *, callback)	3297	=item ev_async_init (ev_async *, callback)
2632		3298
2633	Initialises and configures the async watcher - it has no parameters of any	3299	Initialises and configures the async watcher - it has no parameters of any
2634	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3300	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2635	trust me.	3301	trust me.
2636		3302
2637	=item ev_async_send (loop, ev_async *)	3303	=item ev_async_send (loop, ev_async *)
2638		3304
2639	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3305	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2640	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3306	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2641	C<ev_feed_event>, this call is safe to do from other threads, signal or	3307	C<ev_feed_event>, this call is safe to do from other threads, signal or
2642	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3308	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2643	section below on what exactly this means).	3309	section below on what exactly this means).
2644		3310
		3311	Note that, as with other watchers in libev, multiple events might get
		3312	compressed into a single callback invocation (another way to look at this
		3313	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3314	reset when the event loop detects that).
		3315
2645	This call incurs the overhead of a system call only once per loop iteration,	3316	This call incurs the overhead of a system call only once per event loop
2646	so while the overhead might be noticeable, it doesn't apply to repeated	3317	iteration, so while the overhead might be noticeable, it doesn't apply to
2647	calls to C<ev_async_send>.	3318	repeated calls to C<ev_async_send> for the same event loop.
2648		3319
2649	=item bool = ev_async_pending (ev_async *)	3320	=item bool = ev_async_pending (ev_async *)
2650		3321
2651	Returns a non-zero value when C<ev_async_send> has been called on the	3322	Returns a non-zero value when C<ev_async_send> has been called on the
2652	watcher but the event has not yet been processed (or even noted) by the	3323	watcher but the event has not yet been processed (or even noted) by the
…		…
2655	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3326	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2656	the loop iterates next and checks for the watcher to have become active,	3327	the loop iterates next and checks for the watcher to have become active,
2657	it will reset the flag again. C<ev_async_pending> can be used to very	3328	it will reset the flag again. C<ev_async_pending> can be used to very
2658	quickly check whether invoking the loop might be a good idea.	3329	quickly check whether invoking the loop might be a good idea.
2659		3330
2660	Not that this does I<not> check whether the watcher itself is pending, only	3331	Not that this does I<not> check whether the watcher itself is pending,
2661	whether it has been requested to make this watcher pending.	3332	only whether it has been requested to make this watcher pending: there
		3333	is a time window between the event loop checking and resetting the async
		3334	notification, and the callback being invoked.
2662		3335
2663	=back	3336	=back
2664		3337
2665		3338
2666	=head1 OTHER FUNCTIONS	3339	=head1 OTHER FUNCTIONS
…		…
2683		3356
2684	If C<timeout> is less than 0, then no timeout watcher will be	3357	If C<timeout> is less than 0, then no timeout watcher will be
2685	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3358	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2686	repeat = 0) will be started. C<0> is a valid timeout.	3359	repeat = 0) will be started. C<0> is a valid timeout.
2687		3360
2688	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3361	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2689	passed an C<revents> set like normal event callbacks (a combination of	3362	passed an C<revents> set like normal event callbacks (a combination of
2690	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3363	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2691	value passed to C<ev_once>. Note that it is possible to receive I<both>	3364	value passed to C<ev_once>. Note that it is possible to receive I<both>
2692	a timeout and an io event at the same time - you probably should give io	3365	a timeout and an io event at the same time - you probably should give io
2693	events precedence.	3366	events precedence.
2694		3367
2695	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3368	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2696		3369
2697	static void stdin_ready (int revents, void *arg)	3370	static void stdin_ready (int revents, void *arg)
2698	{	3371	{
2699	if (revents & EV_READ)	3372	if (revents & EV_READ)
2700	/* stdin might have data for us, joy! */;	3373	/* stdin might have data for us, joy! */;
2701	else if (revents & EV_TIMEOUT)	3374	else if (revents & EV_TIMER)
2702	/* doh, nothing entered */;	3375	/* doh, nothing entered */;
2703	}	3376	}
2704		3377
2705	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3378	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2706		3379
2707	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2708
2709	Feeds the given event set into the event loop, as if the specified event
2710	had happened for the specified watcher (which must be a pointer to an
2711	initialised but not necessarily started event watcher).
2712
2713	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3380	=item ev_feed_fd_event (loop, int fd, int revents)
2714		3381
2715	Feed an event on the given fd, as if a file descriptor backend detected	3382	Feed an event on the given fd, as if a file descriptor backend detected
2716	the given events it.	3383	the given events it.
2717		3384
2718	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3385	=item ev_feed_signal_event (loop, int signum)
2719		3386
2720	Feed an event as if the given signal occurred (C<loop> must be the default	3387	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
2721	loop!).	3388	which is async-safe.
2722		3389
2723	=back	3390	=back
		3391
		3392
		3393	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3394
		3395	This section explains some common idioms that are not immediately
		3396	obvious. Note that examples are sprinkled over the whole manual, and this
		3397	section only contains stuff that wouldn't fit anywhere else.
		3398
		3399	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3400
		3401	Each watcher has, by default, a C<void *data> member that you can read
		3402	or modify at any time: libev will completely ignore it. This can be used
		3403	to associate arbitrary data with your watcher. If you need more data and
		3404	don't want to allocate memory separately and store a pointer to it in that
		3405	data member, you can also "subclass" the watcher type and provide your own
		3406	data:
		3407
		3408	struct my_io
		3409	{
		3410	ev_io io;
		3411	int otherfd;
		3412	void *somedata;
		3413	struct whatever *mostinteresting;
		3414	};
		3415
		3416	...
		3417	struct my_io w;
		3418	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3419
		3420	And since your callback will be called with a pointer to the watcher, you
		3421	can cast it back to your own type:
		3422
		3423	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3424	{
		3425	struct my_io *w = (struct my_io *)w_;
		3426	...
		3427	}
		3428
		3429	More interesting and less C-conformant ways of casting your callback
		3430	function type instead have been omitted.
		3431
		3432	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3433
		3434	Another common scenario is to use some data structure with multiple
		3435	embedded watchers, in effect creating your own watcher that combines
		3436	multiple libev event sources into one "super-watcher":
		3437
		3438	struct my_biggy
		3439	{
		3440	int some_data;
		3441	ev_timer t1;
		3442	ev_timer t2;
		3443	}
		3444
		3445	In this case getting the pointer to C<my_biggy> is a bit more
		3446	complicated: Either you store the address of your C<my_biggy> struct in
		3447	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3448	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3449	real programmers):
		3450
		3451	#include <stddef.h>
		3452
		3453	static void
		3454	t1_cb (EV_P_ ev_timer *w, int revents)
		3455	{
		3456	struct my_biggy big = (struct my_biggy *)
		3457	(((char *)w) - offsetof (struct my_biggy, t1));
		3458	}
		3459
		3460	static void
		3461	t2_cb (EV_P_ ev_timer *w, int revents)
		3462	{
		3463	struct my_biggy big = (struct my_biggy *)
		3464	(((char *)w) - offsetof (struct my_biggy, t2));
		3465	}
		3466
		3467	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3468
		3469	Often (especially in GUI toolkits) there are places where you have
		3470	I<modal> interaction, which is most easily implemented by recursively
		3471	invoking C<ev_run>.
		3472
		3473	This brings the problem of exiting - a callback might want to finish the
		3474	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3475	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3476	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3477	other combination: In these cases, C<ev_break> will not work alone.
		3478
		3479	The solution is to maintain "break this loop" variable for each C<ev_run>
		3480	invocation, and use a loop around C<ev_run> until the condition is
		3481	triggered, using C<EVRUN_ONCE>:
		3482
		3483	// main loop
		3484	int exit_main_loop = 0;
		3485
		3486	while (!exit_main_loop)
		3487	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3488
		3489	// in a model watcher
		3490	int exit_nested_loop = 0;
		3491
		3492	while (!exit_nested_loop)
		3493	ev_run (EV_A_ EVRUN_ONCE);
		3494
		3495	To exit from any of these loops, just set the corresponding exit variable:
		3496
		3497	// exit modal loop
		3498	exit_nested_loop = 1;
		3499
		3500	// exit main program, after modal loop is finished
		3501	exit_main_loop = 1;
		3502
		3503	// exit both
		3504	exit_main_loop = exit_nested_loop = 1;
		3505
		3506	=head2 THREAD LOCKING EXAMPLE
		3507
		3508	Here is a fictitious example of how to run an event loop in a different
		3509	thread than where callbacks are being invoked and watchers are
		3510	created/added/removed.
		3511
		3512	For a real-world example, see the C<EV::Loop::Async> perl module,
		3513	which uses exactly this technique (which is suited for many high-level
		3514	languages).
		3515
		3516	The example uses a pthread mutex to protect the loop data, a condition
		3517	variable to wait for callback invocations, an async watcher to notify the
		3518	event loop thread and an unspecified mechanism to wake up the main thread.
		3519
		3520	First, you need to associate some data with the event loop:
		3521
		3522	typedef struct {
		3523	mutex_t lock; /* global loop lock */
		3524	ev_async async_w;
		3525	thread_t tid;
		3526	cond_t invoke_cv;
		3527	} userdata;
		3528
		3529	void prepare_loop (EV_P)
		3530	{
		3531	// for simplicity, we use a static userdata struct.
		3532	static userdata u;
		3533
		3534	ev_async_init (&u->async_w, async_cb);
		3535	ev_async_start (EV_A_ &u->async_w);
		3536
		3537	pthread_mutex_init (&u->lock, 0);
		3538	pthread_cond_init (&u->invoke_cv, 0);
		3539
		3540	// now associate this with the loop
		3541	ev_set_userdata (EV_A_ u);
		3542	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3543	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3544
		3545	// then create the thread running ev_loop
		3546	pthread_create (&u->tid, 0, l_run, EV_A);
		3547	}
		3548
		3549	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3550	solely to wake up the event loop so it takes notice of any new watchers
		3551	that might have been added:
		3552
		3553	static void
		3554	async_cb (EV_P_ ev_async *w, int revents)
		3555	{
		3556	// just used for the side effects
		3557	}
		3558
		3559	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3560	protecting the loop data, respectively.
		3561
		3562	static void
		3563	l_release (EV_P)
		3564	{
		3565	userdata *u = ev_userdata (EV_A);
		3566	pthread_mutex_unlock (&u->lock);
		3567	}
		3568
		3569	static void
		3570	l_acquire (EV_P)
		3571	{
		3572	userdata *u = ev_userdata (EV_A);
		3573	pthread_mutex_lock (&u->lock);
		3574	}
		3575
		3576	The event loop thread first acquires the mutex, and then jumps straight
		3577	into C<ev_run>:
		3578
		3579	void *
		3580	l_run (void *thr_arg)
		3581	{
		3582	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3583
		3584	l_acquire (EV_A);
		3585	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3586	ev_run (EV_A_ 0);
		3587	l_release (EV_A);
		3588
		3589	return 0;
		3590	}
		3591
		3592	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3593	signal the main thread via some unspecified mechanism (signals? pipe
		3594	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3595	have been called (in a while loop because a) spurious wakeups are possible
		3596	and b) skipping inter-thread-communication when there are no pending
		3597	watchers is very beneficial):
		3598
		3599	static void
		3600	l_invoke (EV_P)
		3601	{
		3602	userdata *u = ev_userdata (EV_A);
		3603
		3604	while (ev_pending_count (EV_A))
		3605	{
		3606	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3607	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3608	}
		3609	}
		3610
		3611	Now, whenever the main thread gets told to invoke pending watchers, it
		3612	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3613	thread to continue:
		3614
		3615	static void
		3616	real_invoke_pending (EV_P)
		3617	{
		3618	userdata *u = ev_userdata (EV_A);
		3619
		3620	pthread_mutex_lock (&u->lock);
		3621	ev_invoke_pending (EV_A);
		3622	pthread_cond_signal (&u->invoke_cv);
		3623	pthread_mutex_unlock (&u->lock);
		3624	}
		3625
		3626	Whenever you want to start/stop a watcher or do other modifications to an
		3627	event loop, you will now have to lock:
		3628
		3629	ev_timer timeout_watcher;
		3630	userdata *u = ev_userdata (EV_A);
		3631
		3632	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3633
		3634	pthread_mutex_lock (&u->lock);
		3635	ev_timer_start (EV_A_ &timeout_watcher);
		3636	ev_async_send (EV_A_ &u->async_w);
		3637	pthread_mutex_unlock (&u->lock);
		3638
		3639	Note that sending the C<ev_async> watcher is required because otherwise
		3640	an event loop currently blocking in the kernel will have no knowledge
		3641	about the newly added timer. By waking up the loop it will pick up any new
		3642	watchers in the next event loop iteration.
		3643
		3644	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3645
		3646	While the overhead of a callback that e.g. schedules a thread is small, it
		3647	is still an overhead. If you embed libev, and your main usage is with some
		3648	kind of threads or coroutines, you might want to customise libev so that
		3649	doesn't need callbacks anymore.
		3650
		3651	Imagine you have coroutines that you can switch to using a function
		3652	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3653	and that due to some magic, the currently active coroutine is stored in a
		3654	global called C<current_coro>. Then you can build your own "wait for libev
		3655	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3656	the differing C<;> conventions):
		3657
		3658	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3659	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3660
		3661	That means instead of having a C callback function, you store the
		3662	coroutine to switch to in each watcher, and instead of having libev call
		3663	your callback, you instead have it switch to that coroutine.
		3664
		3665	A coroutine might now wait for an event with a function called
		3666	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3667	matter when, or whether the watcher is active or not when this function is
		3668	called):
		3669
		3670	void
		3671	wait_for_event (ev_watcher *w)
		3672	{
		3673	ev_cb_set (w) = current_coro;
		3674	switch_to (libev_coro);
		3675	}
		3676
		3677	That basically suspends the coroutine inside C<wait_for_event> and
		3678	continues the libev coroutine, which, when appropriate, switches back to
		3679	this or any other coroutine. I am sure if you sue this your own :)
		3680
		3681	You can do similar tricks if you have, say, threads with an event queue -
		3682	instead of storing a coroutine, you store the queue object and instead of
		3683	switching to a coroutine, you push the watcher onto the queue and notify
		3684	any waiters.
		3685
		3686	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3687	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3688
		3689	// my_ev.h
		3690	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3691	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3692	#include "../libev/ev.h"
		3693
		3694	// my_ev.c
		3695	#define EV_H "my_ev.h"
		3696	#include "../libev/ev.c"
		3697
		3698	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3699	F<my_ev.c> into your project. When properly specifying include paths, you
		3700	can even use F<ev.h> as header file name directly.
2724		3701
2725		3702
2726	=head1 LIBEVENT EMULATION	3703	=head1 LIBEVENT EMULATION
2727		3704
2728	Libev offers a compatibility emulation layer for libevent. It cannot	3705	Libev offers a compatibility emulation layer for libevent. It cannot
2729	emulate the internals of libevent, so here are some usage hints:	3706	emulate the internals of libevent, so here are some usage hints:
2730		3707
2731	=over 4	3708	=over 4
		3709
		3710	=item * Only the libevent-1.4.1-beta API is being emulated.
		3711
		3712	This was the newest libevent version available when libev was implemented,
		3713	and is still mostly unchanged in 2010.
2732		3714
2733	=item * Use it by including <event.h>, as usual.	3715	=item * Use it by including <event.h>, as usual.
2734		3716
2735	=item * The following members are fully supported: ev_base, ev_callback,	3717	=item * The following members are fully supported: ev_base, ev_callback,
2736	ev_arg, ev_fd, ev_res, ev_events.	3718	ev_arg, ev_fd, ev_res, ev_events.
…		…
2742	=item * Priorities are not currently supported. Initialising priorities	3724	=item * Priorities are not currently supported. Initialising priorities
2743	will fail and all watchers will have the same priority, even though there	3725	will fail and all watchers will have the same priority, even though there
2744	is an ev_pri field.	3726	is an ev_pri field.
2745		3727
2746	=item * In libevent, the last base created gets the signals, in libev, the	3728	=item * In libevent, the last base created gets the signals, in libev, the
2747	first base created (== the default loop) gets the signals.	3729	base that registered the signal gets the signals.
2748		3730
2749	=item * Other members are not supported.	3731	=item * Other members are not supported.
2750		3732
2751	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3733	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2752	to use the libev header file and library.	3734	to use the libev header file and library.
…		…
2771	Care has been taken to keep the overhead low. The only data member the C++	3753	Care has been taken to keep the overhead low. The only data member the C++
2772	classes add (compared to plain C-style watchers) is the event loop pointer	3754	classes add (compared to plain C-style watchers) is the event loop pointer
2773	that the watcher is associated with (or no additional members at all if	3755	that the watcher is associated with (or no additional members at all if
2774	you disable C<EV_MULTIPLICITY> when embedding libev).	3756	you disable C<EV_MULTIPLICITY> when embedding libev).
2775		3757
2776	Currently, functions, and static and non-static member functions can be	3758	Currently, functions, static and non-static member functions and classes
2777	used as callbacks. Other types should be easy to add as long as they only	3759	with C<operator ()> can be used as callbacks. Other types should be easy
2778	need one additional pointer for context. If you need support for other	3760	to add as long as they only need one additional pointer for context. If
2779	types of functors please contact the author (preferably after implementing	3761	you need support for other types of functors please contact the author
2780	it).	3762	(preferably after implementing it).
2781		3763
2782	Here is a list of things available in the C<ev> namespace:	3764	Here is a list of things available in the C<ev> namespace:
2783		3765
2784	=over 4	3766	=over 4
2785		3767
…		…
2803		3785
2804	=over 4	3786	=over 4
2805		3787
2806	=item ev::TYPE::TYPE ()	3788	=item ev::TYPE::TYPE ()
2807		3789
2808	=item ev::TYPE::TYPE (struct ev_loop *)	3790	=item ev::TYPE::TYPE (loop)
2809		3791
2810	=item ev::TYPE::~TYPE	3792	=item ev::TYPE::~TYPE
2811		3793
2812	The constructor (optionally) takes an event loop to associate the watcher	3794	The constructor (optionally) takes an event loop to associate the watcher
2813	with. If it is omitted, it will use C<EV_DEFAULT>.	3795	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2845		3827
2846	myclass obj;	3828	myclass obj;
2847	ev::io iow;	3829	ev::io iow;
2848	iow.set <myclass, &myclass::io_cb> (&obj);	3830	iow.set <myclass, &myclass::io_cb> (&obj);
2849		3831
		3832	=item w->set (object *)
		3833
		3834	This is a variation of a method callback - leaving out the method to call
		3835	will default the method to C<operator ()>, which makes it possible to use
		3836	functor objects without having to manually specify the C<operator ()> all
		3837	the time. Incidentally, you can then also leave out the template argument
		3838	list.
		3839
		3840	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3841	int revents)>.
		3842
		3843	See the method-C<set> above for more details.
		3844
		3845	Example: use a functor object as callback.
		3846
		3847	struct myfunctor
		3848	{
		3849	void operator() (ev::io &w, int revents)
		3850	{
		3851	...
		3852	}
		3853	}
		3854
		3855	myfunctor f;
		3856
		3857	ev::io w;
		3858	w.set (&f);
		3859
2850	=item w->set<function> (void *data = 0)	3860	=item w->set<function> (void *data = 0)
2851		3861
2852	Also sets a callback, but uses a static method or plain function as	3862	Also sets a callback, but uses a static method or plain function as
2853	callback. The optional C<data> argument will be stored in the watcher's	3863	callback. The optional C<data> argument will be stored in the watcher's
2854	C<data> member and is free for you to use.	3864	C<data> member and is free for you to use.
…		…
2860	Example: Use a plain function as callback.	3870	Example: Use a plain function as callback.
2861		3871
2862	static void io_cb (ev::io &w, int revents) { }	3872	static void io_cb (ev::io &w, int revents) { }
2863	iow.set <io_cb> ();	3873	iow.set <io_cb> ();
2864		3874
2865	=item w->set (struct ev_loop *)	3875	=item w->set (loop)
2866		3876
2867	Associates a different C<struct ev_loop> with this watcher. You can only	3877	Associates a different C<struct ev_loop> with this watcher. You can only
2868	do this when the watcher is inactive (and not pending either).	3878	do this when the watcher is inactive (and not pending either).
2869		3879
2870	=item w->set ([arguments])	3880	=item w->set ([arguments])
2871		3881
2872	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3882	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
2873	called at least once. Unlike the C counterpart, an active watcher gets	3883	method or a suitable start method must be called at least once. Unlike the
2874	automatically stopped and restarted when reconfiguring it with this	3884	C counterpart, an active watcher gets automatically stopped and restarted
2875	method.	3885	when reconfiguring it with this method.
2876		3886
2877	=item w->start ()	3887	=item w->start ()
2878		3888
2879	Starts the watcher. Note that there is no C<loop> argument, as the	3889	Starts the watcher. Note that there is no C<loop> argument, as the
2880	constructor already stores the event loop.	3890	constructor already stores the event loop.
2881		3891
		3892	=item w->start ([arguments])
		3893
		3894	Instead of calling C<set> and C<start> methods separately, it is often
		3895	convenient to wrap them in one call. Uses the same type of arguments as
		3896	the configure C<set> method of the watcher.
		3897
2882	=item w->stop ()	3898	=item w->stop ()
2883		3899
2884	Stops the watcher if it is active. Again, no C<loop> argument.	3900	Stops the watcher if it is active. Again, no C<loop> argument.
2885		3901
2886	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3902	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2898		3914
2899	=back	3915	=back
2900		3916
2901	=back	3917	=back
2902		3918
2903	Example: Define a class with an IO and idle watcher, start one of them in	3919	Example: Define a class with two I/O and idle watchers, start the I/O
2904	the constructor.	3920	watchers in the constructor.
2905		3921
2906	class myclass	3922	class myclass
2907	{	3923	{
2908	ev::io io ; void io_cb (ev::io &w, int revents);	3924	ev::io io ; void io_cb (ev::io &w, int revents);
		3925	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
2909	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3926	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2910		3927
2911	myclass (int fd)	3928	myclass (int fd)
2912	{	3929	{
2913	io .set <myclass, &myclass::io_cb > (this);	3930	io .set <myclass, &myclass::io_cb > (this);
		3931	io2 .set <myclass, &myclass::io2_cb > (this);
2914	idle.set <myclass, &myclass::idle_cb> (this);	3932	idle.set <myclass, &myclass::idle_cb> (this);
2915		3933
2916	io.start (fd, ev::READ);	3934	io.set (fd, ev::WRITE); // configure the watcher
		3935	io.start (); // start it whenever convenient
		3936
		3937	io2.start (fd, ev::READ); // set + start in one call
2917	}	3938	}
2918	};	3939	};
2919		3940
2920		3941
2921	=head1 OTHER LANGUAGE BINDINGS	3942	=head1 OTHER LANGUAGE BINDINGS
…		…
2940	L<http://software.schmorp.de/pkg/EV>.	3961	L<http://software.schmorp.de/pkg/EV>.
2941		3962
2942	=item Python	3963	=item Python
2943		3964
2944	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3965	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2945	seems to be quite complete and well-documented. Note, however, that the	3966	seems to be quite complete and well-documented.
2946	patch they require for libev is outright dangerous as it breaks the ABI
2947	for everybody else, and therefore, should never be applied in an installed
2948	libev (if python requires an incompatible ABI then it needs to embed
2949	libev).
2950		3967
2951	=item Ruby	3968	=item Ruby
2952		3969
2953	Tony Arcieri has written a ruby extension that offers access to a subset	3970	Tony Arcieri has written a ruby extension that offers access to a subset
2954	of the libev API and adds file handle abstractions, asynchronous DNS and	3971	of the libev API and adds file handle abstractions, asynchronous DNS and
2955	more on top of it. It can be found via gem servers. Its homepage is at	3972	more on top of it. It can be found via gem servers. Its homepage is at
2956	L<http://rev.rubyforge.org/>.	3973	L<http://rev.rubyforge.org/>.
2957		3974
		3975	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3976	makes rev work even on mingw.
		3977
		3978	=item Haskell
		3979
		3980	A haskell binding to libev is available at
		3981	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3982
2958	=item D	3983	=item D
2959		3984
2960	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3985	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2961	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3986	be found at L<http://proj.llucax.com.ar/wiki/evd>.
2962		3987
2963	=item Ocaml	3988	=item Ocaml
2964		3989
2965	Erkki Seppala has written Ocaml bindings for libev, to be found at	3990	Erkki Seppala has written Ocaml bindings for libev, to be found at
2966	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	3991	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3992
		3993	=item Lua
		3994
		3995	Brian Maher has written a partial interface to libev for lua (at the
		3996	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3997	L<http://github.com/brimworks/lua-ev>.
2967		3998
2968	=back	3999	=back
2969		4000
2970		4001
2971	=head1 MACRO MAGIC	4002	=head1 MACRO MAGIC
…		…
2985	loop argument"). The C<EV_A> form is used when this is the sole argument,	4016	loop argument"). The C<EV_A> form is used when this is the sole argument,
2986	C<EV_A_> is used when other arguments are following. Example:	4017	C<EV_A_> is used when other arguments are following. Example:
2987		4018
2988	ev_unref (EV_A);	4019	ev_unref (EV_A);
2989	ev_timer_add (EV_A_ watcher);	4020	ev_timer_add (EV_A_ watcher);
2990	ev_loop (EV_A_ 0);	4021	ev_run (EV_A_ 0);
2991		4022
2992	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4023	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2993	which is often provided by the following macro.	4024	which is often provided by the following macro.
2994		4025
2995	=item C<EV_P>, C<EV_P_>	4026	=item C<EV_P>, C<EV_P_>
…		…
3035	}	4066	}
3036		4067
3037	ev_check check;	4068	ev_check check;
3038	ev_check_init (&check, check_cb);	4069	ev_check_init (&check, check_cb);
3039	ev_check_start (EV_DEFAULT_ &check);	4070	ev_check_start (EV_DEFAULT_ &check);
3040	ev_loop (EV_DEFAULT_ 0);	4071	ev_run (EV_DEFAULT_ 0);
3041		4072
3042	=head1 EMBEDDING	4073	=head1 EMBEDDING
3043		4074
3044	Libev can (and often is) directly embedded into host	4075	Libev can (and often is) directly embedded into host
3045	applications. Examples of applications that embed it include the Deliantra	4076	applications. Examples of applications that embed it include the Deliantra
…		…
3072		4103
3073	#define EV_STANDALONE 1	4104	#define EV_STANDALONE 1
3074	#include "ev.h"	4105	#include "ev.h"
3075		4106
3076	Both header files and implementation files can be compiled with a C++	4107	Both header files and implementation files can be compiled with a C++
3077	compiler (at least, thats a stated goal, and breakage will be treated	4108	compiler (at least, that's a stated goal, and breakage will be treated
3078	as a bug).	4109	as a bug).
3079		4110
3080	You need the following files in your source tree, or in a directory	4111	You need the following files in your source tree, or in a directory
3081	in your include path (e.g. in libev/ when using -Ilibev):	4112	in your include path (e.g. in libev/ when using -Ilibev):
3082		4113
…		…
3125	libev.m4	4156	libev.m4
3126		4157
3127	=head2 PREPROCESSOR SYMBOLS/MACROS	4158	=head2 PREPROCESSOR SYMBOLS/MACROS
3128		4159
3129	Libev can be configured via a variety of preprocessor symbols you have to	4160	Libev can be configured via a variety of preprocessor symbols you have to
3130	define before including any of its files. The default in the absence of	4161	define before including (or compiling) any of its files. The default in
3131	autoconf is documented for every option.	4162	the absence of autoconf is documented for every option.
		4163
		4164	Symbols marked with "(h)" do not change the ABI, and can have different
		4165	values when compiling libev vs. including F<ev.h>, so it is permissible
		4166	to redefine them before including F<ev.h> without breaking compatibility
		4167	to a compiled library. All other symbols change the ABI, which means all
		4168	users of libev and the libev code itself must be compiled with compatible
		4169	settings.
3132		4170
3133	=over 4	4171	=over 4
3134		4172
		4173	=item EV_COMPAT3 (h)
		4174
		4175	Backwards compatibility is a major concern for libev. This is why this
		4176	release of libev comes with wrappers for the functions and symbols that
		4177	have been renamed between libev version 3 and 4.
		4178
		4179	You can disable these wrappers (to test compatibility with future
		4180	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4181	sources. This has the additional advantage that you can drop the C<struct>
		4182	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4183	typedef in that case.
		4184
		4185	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4186	and in some even more future version the compatibility code will be
		4187	removed completely.
		4188
3135	=item EV_STANDALONE	4189	=item EV_STANDALONE (h)
3136		4190
3137	Must always be C<1> if you do not use autoconf configuration, which	4191	Must always be C<1> if you do not use autoconf configuration, which
3138	keeps libev from including F<config.h>, and it also defines dummy	4192	keeps libev from including F<config.h>, and it also defines dummy
3139	implementations for some libevent functions (such as logging, which is not	4193	implementations for some libevent functions (such as logging, which is not
3140	supported). It will also not define any of the structs usually found in	4194	supported). It will also not define any of the structs usually found in
3141	F<event.h> that are not directly supported by the libev core alone.	4195	F<event.h> that are not directly supported by the libev core alone.
3142		4196
		4197	In standalone mode, libev will still try to automatically deduce the
		4198	configuration, but has to be more conservative.
		4199
3143	=item EV_USE_MONOTONIC	4200	=item EV_USE_MONOTONIC
3144		4201
3145	If defined to be C<1>, libev will try to detect the availability of the	4202	If defined to be C<1>, libev will try to detect the availability of the
3146	monotonic clock option at both compile time and runtime. Otherwise no use	4203	monotonic clock option at both compile time and runtime. Otherwise no
3147	of the monotonic clock option will be attempted. If you enable this, you	4204	use of the monotonic clock option will be attempted. If you enable this,
3148	usually have to link against librt or something similar. Enabling it when	4205	you usually have to link against librt or something similar. Enabling it
3149	the functionality isn't available is safe, though, although you have	4206	when the functionality isn't available is safe, though, although you have
3150	to make sure you link against any libraries where the C<clock_gettime>	4207	to make sure you link against any libraries where the C<clock_gettime>
3151	function is hiding in (often F<-lrt>).	4208	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
3152		4209
3153	=item EV_USE_REALTIME	4210	=item EV_USE_REALTIME
3154		4211
3155	If defined to be C<1>, libev will try to detect the availability of the	4212	If defined to be C<1>, libev will try to detect the availability of the
3156	real-time clock option at compile time (and assume its availability at	4213	real-time clock option at compile time (and assume its availability
3157	runtime if successful). Otherwise no use of the real-time clock option will	4214	at runtime if successful). Otherwise no use of the real-time clock
3158	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	4215	option will be attempted. This effectively replaces C<gettimeofday>
3159	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	4216	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
3160	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	4217	correctness. See the note about libraries in the description of
		4218	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		4219	C<EV_USE_CLOCK_SYSCALL>.
		4220
		4221	=item EV_USE_CLOCK_SYSCALL
		4222
		4223	If defined to be C<1>, libev will try to use a direct syscall instead
		4224	of calling the system-provided C<clock_gettime> function. This option
		4225	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		4226	unconditionally pulls in C<libpthread>, slowing down single-threaded
		4227	programs needlessly. Using a direct syscall is slightly slower (in
		4228	theory), because no optimised vdso implementation can be used, but avoids
		4229	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		4230	higher, as it simplifies linking (no need for C<-lrt>).
3161		4231
3162	=item EV_USE_NANOSLEEP	4232	=item EV_USE_NANOSLEEP
3163		4233
3164	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	4234	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
3165	and will use it for delays. Otherwise it will use C<select ()>.	4235	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3181		4251
3182	=item EV_SELECT_USE_FD_SET	4252	=item EV_SELECT_USE_FD_SET
3183		4253
3184	If defined to C<1>, then the select backend will use the system C<fd_set>	4254	If defined to C<1>, then the select backend will use the system C<fd_set>
3185	structure. This is useful if libev doesn't compile due to a missing	4255	structure. This is useful if libev doesn't compile due to a missing
3186	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	4256	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3187	exotic systems. This usually limits the range of file descriptors to some	4257	on exotic systems. This usually limits the range of file descriptors to
3188	low limit such as 1024 or might have other limitations (winsocket only	4258	some low limit such as 1024 or might have other limitations (winsocket
3189	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	4259	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3190	influence the size of the C<fd_set> used.	4260	configures the maximum size of the C<fd_set>.
3191		4261
3192	=item EV_SELECT_IS_WINSOCKET	4262	=item EV_SELECT_IS_WINSOCKET
3193		4263
3194	When defined to C<1>, the select backend will assume that	4264	When defined to C<1>, the select backend will assume that
3195	select/socket/connect etc. don't understand file descriptors but	4265	select/socket/connect etc. don't understand file descriptors but
…		…
3197	be used is the winsock select). This means that it will call	4267	be used is the winsock select). This means that it will call
3198	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4268	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3199	it is assumed that all these functions actually work on fds, even	4269	it is assumed that all these functions actually work on fds, even
3200	on win32. Should not be defined on non-win32 platforms.	4270	on win32. Should not be defined on non-win32 platforms.
3201		4271
3202	=item EV_FD_TO_WIN32_HANDLE	4272	=item EV_FD_TO_WIN32_HANDLE(fd)
3203		4273
3204	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4274	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3205	file descriptors to socket handles. When not defining this symbol (the	4275	file descriptors to socket handles. When not defining this symbol (the
3206	default), then libev will call C<_get_osfhandle>, which is usually	4276	default), then libev will call C<_get_osfhandle>, which is usually
3207	correct. In some cases, programs use their own file descriptor management,	4277	correct. In some cases, programs use their own file descriptor management,
3208	in which case they can provide this function to map fds to socket handles.	4278	in which case they can provide this function to map fds to socket handles.
		4279
		4280	=item EV_WIN32_HANDLE_TO_FD(handle)
		4281
		4282	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4283	using the standard C<_open_osfhandle> function. For programs implementing
		4284	their own fd to handle mapping, overwriting this function makes it easier
		4285	to do so. This can be done by defining this macro to an appropriate value.
		4286
		4287	=item EV_WIN32_CLOSE_FD(fd)
		4288
		4289	If programs implement their own fd to handle mapping on win32, then this
		4290	macro can be used to override the C<close> function, useful to unregister
		4291	file descriptors again. Note that the replacement function has to close
		4292	the underlying OS handle.
3209		4293
3210	=item EV_USE_POLL	4294	=item EV_USE_POLL
3211		4295
3212	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4296	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3213	backend. Otherwise it will be enabled on non-win32 platforms. It	4297	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3260	as well as for signal and thread safety in C<ev_async> watchers.	4344	as well as for signal and thread safety in C<ev_async> watchers.
3261		4345
3262	In the absence of this define, libev will use C<sig_atomic_t volatile>	4346	In the absence of this define, libev will use C<sig_atomic_t volatile>
3263	(from F<signal.h>), which is usually good enough on most platforms.	4347	(from F<signal.h>), which is usually good enough on most platforms.
3264		4348
3265	=item EV_H	4349	=item EV_H (h)
3266		4350
3267	The name of the F<ev.h> header file used to include it. The default if	4351	The name of the F<ev.h> header file used to include it. The default if
3268	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4352	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3269	used to virtually rename the F<ev.h> header file in case of conflicts.	4353	used to virtually rename the F<ev.h> header file in case of conflicts.
3270		4354
3271	=item EV_CONFIG_H	4355	=item EV_CONFIG_H (h)
3272		4356
3273	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4357	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3274	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4358	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3275	C<EV_H>, above.	4359	C<EV_H>, above.
3276		4360
3277	=item EV_EVENT_H	4361	=item EV_EVENT_H (h)
3278		4362
3279	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4363	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3280	of how the F<event.h> header can be found, the default is C<"event.h">.	4364	of how the F<event.h> header can be found, the default is C<"event.h">.
3281		4365
3282	=item EV_PROTOTYPES	4366	=item EV_PROTOTYPES (h)
3283		4367
3284	If defined to be C<0>, then F<ev.h> will not define any function	4368	If defined to be C<0>, then F<ev.h> will not define any function
3285	prototypes, but still define all the structs and other symbols. This is	4369	prototypes, but still define all the structs and other symbols. This is
3286	occasionally useful if you want to provide your own wrapper functions	4370	occasionally useful if you want to provide your own wrapper functions
3287	around libev functions.	4371	around libev functions.
…		…
3309	fine.	4393	fine.
3310		4394
3311	If your embedding application does not need any priorities, defining these	4395	If your embedding application does not need any priorities, defining these
3312	both to C<0> will save some memory and CPU.	4396	both to C<0> will save some memory and CPU.
3313		4397
3314	=item EV_PERIODIC_ENABLE	4398	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4399	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4400	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3315		4401
3316	If undefined or defined to be C<1>, then periodic timers are supported. If	4402	If undefined or defined to be C<1> (and the platform supports it), then
3317	defined to be C<0>, then they are not. Disabling them saves a few kB of	4403	the respective watcher type is supported. If defined to be C<0>, then it
3318	code.	4404	is not. Disabling watcher types mainly saves code size.
3319		4405
3320	=item EV_IDLE_ENABLE	4406	=item EV_FEATURES
3321
3322	If undefined or defined to be C<1>, then idle watchers are supported. If
3323	defined to be C<0>, then they are not. Disabling them saves a few kB of
3324	code.
3325
3326	=item EV_EMBED_ENABLE
3327
3328	If undefined or defined to be C<1>, then embed watchers are supported. If
3329	defined to be C<0>, then they are not. Embed watchers rely on most other
3330	watcher types, which therefore must not be disabled.
3331
3332	=item EV_STAT_ENABLE
3333
3334	If undefined or defined to be C<1>, then stat watchers are supported. If
3335	defined to be C<0>, then they are not.
3336
3337	=item EV_FORK_ENABLE
3338
3339	If undefined or defined to be C<1>, then fork watchers are supported. If
3340	defined to be C<0>, then they are not.
3341
3342	=item EV_ASYNC_ENABLE
3343
3344	If undefined or defined to be C<1>, then async watchers are supported. If
3345	defined to be C<0>, then they are not.
3346
3347	=item EV_MINIMAL
3348		4407
3349	If you need to shave off some kilobytes of code at the expense of some	4408	If you need to shave off some kilobytes of code at the expense of some
3350	speed, define this symbol to C<1>. Currently this is used to override some	4409	speed (but with the full API), you can define this symbol to request
3351	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4410	certain subsets of functionality. The default is to enable all features
3352	much smaller 2-heap for timer management over the default 4-heap.	4411	that can be enabled on the platform.
		4412
		4413	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4414	with some broad features you want) and then selectively re-enable
		4415	additional parts you want, for example if you want everything minimal,
		4416	but multiple event loop support, async and child watchers and the poll
		4417	backend, use this:
		4418
		4419	#define EV_FEATURES 0
		4420	#define EV_MULTIPLICITY 1
		4421	#define EV_USE_POLL 1
		4422	#define EV_CHILD_ENABLE 1
		4423	#define EV_ASYNC_ENABLE 1
		4424
		4425	The actual value is a bitset, it can be a combination of the following
		4426	values:
		4427
		4428	=over 4
		4429
		4430	=item C<1> - faster/larger code
		4431
		4432	Use larger code to speed up some operations.
		4433
		4434	Currently this is used to override some inlining decisions (enlarging the
		4435	code size by roughly 30% on amd64).
		4436
		4437	When optimising for size, use of compiler flags such as C<-Os> with
		4438	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4439	assertions.
		4440
		4441	=item C<2> - faster/larger data structures
		4442
		4443	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4444	hash table sizes and so on. This will usually further increase code size
		4445	and can additionally have an effect on the size of data structures at
		4446	runtime.
		4447
		4448	=item C<4> - full API configuration
		4449
		4450	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4451	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4452
		4453	=item C<8> - full API
		4454
		4455	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4456	details on which parts of the API are still available without this
		4457	feature, and do not complain if this subset changes over time.
		4458
		4459	=item C<16> - enable all optional watcher types
		4460
		4461	Enables all optional watcher types. If you want to selectively enable
		4462	only some watcher types other than I/O and timers (e.g. prepare,
		4463	embed, async, child...) you can enable them manually by defining
		4464	C<EV_watchertype_ENABLE> to C<1> instead.
		4465
		4466	=item C<32> - enable all backends
		4467
		4468	This enables all backends - without this feature, you need to enable at
		4469	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4470
		4471	=item C<64> - enable OS-specific "helper" APIs
		4472
		4473	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4474	default.
		4475
		4476	=back
		4477
		4478	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4479	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4480	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4481	watchers, timers and monotonic clock support.
		4482
		4483	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4484	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4485	your program might be left out as well - a binary starting a timer and an
		4486	I/O watcher then might come out at only 5Kb.
		4487
		4488	=item EV_AVOID_STDIO
		4489
		4490	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4491	functions (printf, scanf, perror etc.). This will increase the code size
		4492	somewhat, but if your program doesn't otherwise depend on stdio and your
		4493	libc allows it, this avoids linking in the stdio library which is quite
		4494	big.
		4495
		4496	Note that error messages might become less precise when this option is
		4497	enabled.
		4498
		4499	=item EV_NSIG
		4500
		4501	The highest supported signal number, +1 (or, the number of
		4502	signals): Normally, libev tries to deduce the maximum number of signals
		4503	automatically, but sometimes this fails, in which case it can be
		4504	specified. Also, using a lower number than detected (C<32> should be
		4505	good for about any system in existence) can save some memory, as libev
		4506	statically allocates some 12-24 bytes per signal number.
3353		4507
3354	=item EV_PID_HASHSIZE	4508	=item EV_PID_HASHSIZE
3355		4509
3356	C<ev_child> watchers use a small hash table to distribute workload by	4510	C<ev_child> watchers use a small hash table to distribute workload by
3357	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4511	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3358	than enough. If you need to manage thousands of children you might want to	4512	usually more than enough. If you need to manage thousands of children you
3359	increase this value (I<must> be a power of two).	4513	might want to increase this value (I<must> be a power of two).
3360		4514
3361	=item EV_INOTIFY_HASHSIZE	4515	=item EV_INOTIFY_HASHSIZE
3362		4516
3363	C<ev_stat> watchers use a small hash table to distribute workload by	4517	C<ev_stat> watchers use a small hash table to distribute workload by
3364	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4518	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3365	usually more than enough. If you need to manage thousands of C<ev_stat>	4519	disabled), usually more than enough. If you need to manage thousands of
3366	watchers you might want to increase this value (I<must> be a power of	4520	C<ev_stat> watchers you might want to increase this value (I<must> be a
3367	two).	4521	power of two).
3368		4522
3369	=item EV_USE_4HEAP	4523	=item EV_USE_4HEAP
3370		4524
3371	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4525	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3372	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4526	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3373	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4527	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3374	faster performance with many (thousands) of watchers.	4528	faster performance with many (thousands) of watchers.
3375		4529
3376	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4530	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3377	(disabled).	4531	will be C<0>.
3378		4532
3379	=item EV_HEAP_CACHE_AT	4533	=item EV_HEAP_CACHE_AT
3380		4534
3381	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4535	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3382	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4536	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3383	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4537	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3384	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4538	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3385	but avoids random read accesses on heap changes. This improves performance	4539	but avoids random read accesses on heap changes. This improves performance
3386	noticeably with many (hundreds) of watchers.	4540	noticeably with many (hundreds) of watchers.
3387		4541
3388	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4542	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3389	(disabled).	4543	will be C<0>.
3390		4544
3391	=item EV_VERIFY	4545	=item EV_VERIFY
3392		4546
3393	Controls how much internal verification (see C<ev_loop_verify ()>) will	4547	Controls how much internal verification (see C<ev_verify ()>) will
3394	be done: If set to C<0>, no internal verification code will be compiled	4548	be done: If set to C<0>, no internal verification code will be compiled
3395	in. If set to C<1>, then verification code will be compiled in, but not	4549	in. If set to C<1>, then verification code will be compiled in, but not
3396	called. If set to C<2>, then the internal verification code will be	4550	called. If set to C<2>, then the internal verification code will be
3397	called once per loop, which can slow down libev. If set to C<3>, then the	4551	called once per loop, which can slow down libev. If set to C<3>, then the
3398	verification code will be called very frequently, which will slow down	4552	verification code will be called very frequently, which will slow down
3399	libev considerably.	4553	libev considerably.
3400		4554
3401	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4555	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3402	C<0>.	4556	will be C<0>.
3403		4557
3404	=item EV_COMMON	4558	=item EV_COMMON
3405		4559
3406	By default, all watchers have a C<void *data> member. By redefining	4560	By default, all watchers have a C<void *data> member. By redefining
3407	this macro to a something else you can include more and other types of	4561	this macro to something else you can include more and other types of
3408	members. You have to define it each time you include one of the files,	4562	members. You have to define it each time you include one of the files,
3409	though, and it must be identical each time.	4563	though, and it must be identical each time.
3410		4564
3411	For example, the perl EV module uses something like this:	4565	For example, the perl EV module uses something like this:
3412		4566
…		…
3465	file.	4619	file.
3466		4620
3467	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4621	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3468	that everybody includes and which overrides some configure choices:	4622	that everybody includes and which overrides some configure choices:
3469		4623
3470	#define EV_MINIMAL 1	4624	#define EV_FEATURES 8
3471	#define EV_USE_POLL 0	4625	#define EV_USE_SELECT 1
3472	#define EV_MULTIPLICITY 0
3473	#define EV_PERIODIC_ENABLE 0	4626	#define EV_PREPARE_ENABLE 1
		4627	#define EV_IDLE_ENABLE 1
3474	#define EV_STAT_ENABLE 0	4628	#define EV_SIGNAL_ENABLE 1
3475	#define EV_FORK_ENABLE 0	4629	#define EV_CHILD_ENABLE 1
		4630	#define EV_USE_STDEXCEPT 0
3476	#define EV_CONFIG_H <config.h>	4631	#define EV_CONFIG_H <config.h>
3477	#define EV_MINPRI 0
3478	#define EV_MAXPRI 0
3479		4632
3480	#include "ev++.h"	4633	#include "ev++.h"
3481		4634
3482	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4635	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3483		4636
3484	#include "ev_cpp.h"	4637	#include "ev_cpp.h"
3485	#include "ev.c"	4638	#include "ev.c"
3486		4639
3487	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4640	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3488		4641
3489	=head2 THREADS AND COROUTINES	4642	=head2 THREADS AND COROUTINES
3490		4643
3491	=head3 THREADS	4644	=head3 THREADS
3492		4645
…		…
3543	default loop and triggering an C<ev_async> watcher from the default loop	4696	default loop and triggering an C<ev_async> watcher from the default loop
3544	watcher callback into the event loop interested in the signal.	4697	watcher callback into the event loop interested in the signal.
3545		4698
3546	=back	4699	=back
3547		4700
		4701	See also L<THREAD LOCKING EXAMPLE>.
		4702
3548	=head3 COROUTINES	4703	=head3 COROUTINES
3549		4704
3550	Libev is very accommodating to coroutines ("cooperative threads"):	4705	Libev is very accommodating to coroutines ("cooperative threads"):
3551	libev fully supports nesting calls to its functions from different	4706	libev fully supports nesting calls to its functions from different
3552	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4707	coroutines (e.g. you can call C<ev_run> on the same loop from two
3553	different coroutines, and switch freely between both coroutines running the	4708	different coroutines, and switch freely between both coroutines running
3554	loop, as long as you don't confuse yourself). The only exception is that	4709	the loop, as long as you don't confuse yourself). The only exception is
3555	you must not do this from C<ev_periodic> reschedule callbacks.	4710	that you must not do this from C<ev_periodic> reschedule callbacks.
3556		4711
3557	Care has been taken to ensure that libev does not keep local state inside	4712	Care has been taken to ensure that libev does not keep local state inside
3558	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4713	C<ev_run>, and other calls do not usually allow for coroutine switches as
3559	they do not clal any callbacks.	4714	they do not call any callbacks.
3560		4715
3561	=head2 COMPILER WARNINGS	4716	=head2 COMPILER WARNINGS
3562		4717
3563	Depending on your compiler and compiler settings, you might get no or a	4718	Depending on your compiler and compiler settings, you might get no or a
3564	lot of warnings when compiling libev code. Some people are apparently	4719	lot of warnings when compiling libev code. Some people are apparently
…		…
3574	maintainable.	4729	maintainable.
3575		4730
3576	And of course, some compiler warnings are just plain stupid, or simply	4731	And of course, some compiler warnings are just plain stupid, or simply
3577	wrong (because they don't actually warn about the condition their message	4732	wrong (because they don't actually warn about the condition their message
3578	seems to warn about). For example, certain older gcc versions had some	4733	seems to warn about). For example, certain older gcc versions had some
3579	warnings that resulted an extreme number of false positives. These have	4734	warnings that resulted in an extreme number of false positives. These have
3580	been fixed, but some people still insist on making code warn-free with	4735	been fixed, but some people still insist on making code warn-free with
3581	such buggy versions.	4736	such buggy versions.
3582		4737
3583	While libev is written to generate as few warnings as possible,	4738	While libev is written to generate as few warnings as possible,
3584	"warn-free" code is not a goal, and it is recommended not to build libev	4739	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3598	==2274== definitely lost: 0 bytes in 0 blocks.	4753	==2274== definitely lost: 0 bytes in 0 blocks.
3599	==2274== possibly lost: 0 bytes in 0 blocks.	4754	==2274== possibly lost: 0 bytes in 0 blocks.
3600	==2274== still reachable: 256 bytes in 1 blocks.	4755	==2274== still reachable: 256 bytes in 1 blocks.
3601		4756
3602	Then there is no memory leak, just as memory accounted to global variables	4757	Then there is no memory leak, just as memory accounted to global variables
3603	is not a memleak - the memory is still being refernced, and didn't leak.	4758	is not a memleak - the memory is still being referenced, and didn't leak.
3604		4759
3605	Similarly, under some circumstances, valgrind might report kernel bugs	4760	Similarly, under some circumstances, valgrind might report kernel bugs
3606	as if it were a bug in libev (e.g. in realloc or in the poll backend,	4761	as if it were a bug in libev (e.g. in realloc or in the poll backend,
3607	although an acceptable workaround has been found here), or it might be	4762	although an acceptable workaround has been found here), or it might be
3608	confused.	4763	confused.
…		…
3620	I suggest using suppression lists.	4775	I suggest using suppression lists.
3621		4776
3622		4777
3623	=head1 PORTABILITY NOTES	4778	=head1 PORTABILITY NOTES
3624		4779
		4780	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4781
		4782	GNU/Linux is the only common platform that supports 64 bit file/large file
		4783	interfaces but I<disables> them by default.
		4784
		4785	That means that libev compiled in the default environment doesn't support
		4786	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4787
		4788	Unfortunately, many programs try to work around this GNU/Linux issue
		4789	by enabling the large file API, which makes them incompatible with the
		4790	standard libev compiled for their system.
		4791
		4792	Likewise, libev cannot enable the large file API itself as this would
		4793	suddenly make it incompatible to the default compile time environment,
		4794	i.e. all programs not using special compile switches.
		4795
		4796	=head2 OS/X AND DARWIN BUGS
		4797
		4798	The whole thing is a bug if you ask me - basically any system interface
		4799	you touch is broken, whether it is locales, poll, kqueue or even the
		4800	OpenGL drivers.
		4801
		4802	=head3 C<kqueue> is buggy
		4803
		4804	The kqueue syscall is broken in all known versions - most versions support
		4805	only sockets, many support pipes.
		4806
		4807	Libev tries to work around this by not using C<kqueue> by default on this
		4808	rotten platform, but of course you can still ask for it when creating a
		4809	loop - embedding a socket-only kqueue loop into a select-based one is
		4810	probably going to work well.
		4811
		4812	=head3 C<poll> is buggy
		4813
		4814	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4815	implementation by something calling C<kqueue> internally around the 10.5.6
		4816	release, so now C<kqueue> I<and> C<poll> are broken.
		4817
		4818	Libev tries to work around this by not using C<poll> by default on
		4819	this rotten platform, but of course you can still ask for it when creating
		4820	a loop.
		4821
		4822	=head3 C<select> is buggy
		4823
		4824	All that's left is C<select>, and of course Apple found a way to fuck this
		4825	one up as well: On OS/X, C<select> actively limits the number of file
		4826	descriptors you can pass in to 1024 - your program suddenly crashes when
		4827	you use more.
		4828
		4829	There is an undocumented "workaround" for this - defining
		4830	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4831	work on OS/X.
		4832
		4833	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4834
		4835	=head3 C<errno> reentrancy
		4836
		4837	The default compile environment on Solaris is unfortunately so
		4838	thread-unsafe that you can't even use components/libraries compiled
		4839	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4840	defined by default. A valid, if stupid, implementation choice.
		4841
		4842	If you want to use libev in threaded environments you have to make sure
		4843	it's compiled with C<_REENTRANT> defined.
		4844
		4845	=head3 Event port backend
		4846
		4847	The scalable event interface for Solaris is called "event
		4848	ports". Unfortunately, this mechanism is very buggy in all major
		4849	releases. If you run into high CPU usage, your program freezes or you get
		4850	a large number of spurious wakeups, make sure you have all the relevant
		4851	and latest kernel patches applied. No, I don't know which ones, but there
		4852	are multiple ones to apply, and afterwards, event ports actually work
		4853	great.
		4854
		4855	If you can't get it to work, you can try running the program by setting
		4856	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4857	C<select> backends.
		4858
		4859	=head2 AIX POLL BUG
		4860
		4861	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4862	this by trying to avoid the poll backend altogether (i.e. it's not even
		4863	compiled in), which normally isn't a big problem as C<select> works fine
		4864	with large bitsets on AIX, and AIX is dead anyway.
		4865
3625	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4866	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4867
		4868	=head3 General issues
3626		4869
3627	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4870	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3628	requires, and its I/O model is fundamentally incompatible with the POSIX	4871	requires, and its I/O model is fundamentally incompatible with the POSIX
3629	model. Libev still offers limited functionality on this platform in	4872	model. Libev still offers limited functionality on this platform in
3630	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4873	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3631	descriptors. This only applies when using Win32 natively, not when using	4874	descriptors. This only applies when using Win32 natively, not when using
3632	e.g. cygwin.	4875	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4876	as every compielr comes with a slightly differently broken/incompatible
		4877	environment.
3633		4878
3634	Lifting these limitations would basically require the full	4879	Lifting these limitations would basically require the full
3635	re-implementation of the I/O system. If you are into these kinds of	4880	re-implementation of the I/O system. If you are into this kind of thing,
3636	things, then note that glib does exactly that for you in a very portable	4881	then note that glib does exactly that for you in a very portable way (note
3637	way (note also that glib is the slowest event library known to man).	4882	also that glib is the slowest event library known to man).
3638		4883
3639	There is no supported compilation method available on windows except	4884	There is no supported compilation method available on windows except
3640	embedding it into other applications.	4885	embedding it into other applications.
		4886
		4887	Sensible signal handling is officially unsupported by Microsoft - libev
		4888	tries its best, but under most conditions, signals will simply not work.
3641		4889
3642	Not a libev limitation but worth mentioning: windows apparently doesn't	4890	Not a libev limitation but worth mentioning: windows apparently doesn't
3643	accept large writes: instead of resulting in a partial write, windows will	4891	accept large writes: instead of resulting in a partial write, windows will
3644	either accept everything or return C<ENOBUFS> if the buffer is too large,	4892	either accept everything or return C<ENOBUFS> if the buffer is too large,
3645	so make sure you only write small amounts into your sockets (less than a	4893	so make sure you only write small amounts into your sockets (less than a
…		…
3650	the abysmal performance of winsockets, using a large number of sockets	4898	the abysmal performance of winsockets, using a large number of sockets
3651	is not recommended (and not reasonable). If your program needs to use	4899	is not recommended (and not reasonable). If your program needs to use
3652	more than a hundred or so sockets, then likely it needs to use a totally	4900	more than a hundred or so sockets, then likely it needs to use a totally
3653	different implementation for windows, as libev offers the POSIX readiness	4901	different implementation for windows, as libev offers the POSIX readiness
3654	notification model, which cannot be implemented efficiently on windows	4902	notification model, which cannot be implemented efficiently on windows
3655	(Microsoft monopoly games).	4903	(due to Microsoft monopoly games).
3656		4904
3657	A typical way to use libev under windows is to embed it (see the embedding	4905	A typical way to use libev under windows is to embed it (see the embedding
3658	section for details) and use the following F<evwrap.h> header file instead	4906	section for details) and use the following F<evwrap.h> header file instead
3659	of F<ev.h>:	4907	of F<ev.h>:
3660		4908
…		…
3667	you do I<not> compile the F<ev.c> or any other embedded source files!):	4915	you do I<not> compile the F<ev.c> or any other embedded source files!):
3668		4916
3669	#include "evwrap.h"	4917	#include "evwrap.h"
3670	#include "ev.c"	4918	#include "ev.c"
3671		4919
3672	=over 4
3673
3674	=item The winsocket select function	4920	=head3 The winsocket C<select> function
3675		4921
3676	The winsocket C<select> function doesn't follow POSIX in that it	4922	The winsocket C<select> function doesn't follow POSIX in that it
3677	requires socket I<handles> and not socket I<file descriptors> (it is	4923	requires socket I<handles> and not socket I<file descriptors> (it is
3678	also extremely buggy). This makes select very inefficient, and also	4924	also extremely buggy). This makes select very inefficient, and also
3679	requires a mapping from file descriptors to socket handles (the Microsoft	4925	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3688	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4934	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3689		4935
3690	Note that winsockets handling of fd sets is O(n), so you can easily get a	4936	Note that winsockets handling of fd sets is O(n), so you can easily get a
3691	complexity in the O(n²) range when using win32.	4937	complexity in the O(n²) range when using win32.
3692		4938
3693	=item Limited number of file descriptors	4939	=head3 Limited number of file descriptors
3694		4940
3695	Windows has numerous arbitrary (and low) limits on things.	4941	Windows has numerous arbitrary (and low) limits on things.
3696		4942
3697	Early versions of winsocket's select only supported waiting for a maximum	4943	Early versions of winsocket's select only supported waiting for a maximum
3698	of C<64> handles (probably owning to the fact that all windows kernels	4944	of C<64> handles (probably owning to the fact that all windows kernels
3699	can only wait for C<64> things at the same time internally; Microsoft	4945	can only wait for C<64> things at the same time internally; Microsoft
3700	recommends spawning a chain of threads and wait for 63 handles and the	4946	recommends spawning a chain of threads and wait for 63 handles and the
3701	previous thread in each. Great).	4947	previous thread in each. Sounds great!).
3702		4948
3703	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4949	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3704	to some high number (e.g. C<2048>) before compiling the winsocket select	4950	to some high number (e.g. C<2048>) before compiling the winsocket select
3705	call (which might be in libev or elsewhere, for example, perl does its own	4951	call (which might be in libev or elsewhere, for example, perl and many
3706	select emulation on windows).	4952	other interpreters do their own select emulation on windows).
3707		4953
3708	Another limit is the number of file descriptors in the Microsoft runtime	4954	Another limit is the number of file descriptors in the Microsoft runtime
3709	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4955	libraries, which by default is C<64> (there must be a hidden I<64>
3710	or something like this inside Microsoft). You can increase this by calling	4956	fetish or something like this inside Microsoft). You can increase this
3711	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4957	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3712	arbitrary limit), but is broken in many versions of the Microsoft runtime	4958	(another arbitrary limit), but is broken in many versions of the Microsoft
3713	libraries.
3714
3715	This might get you to about C<512> or C<2048> sockets (depending on	4959	runtime libraries. This might get you to about C<512> or C<2048> sockets
3716	windows version and/or the phase of the moon). To get more, you need to	4960	(depending on windows version and/or the phase of the moon). To get more,
3717	wrap all I/O functions and provide your own fd management, but the cost of	4961	you need to wrap all I/O functions and provide your own fd management, but
3718	calling select (O(n²)) will likely make this unworkable.	4962	the cost of calling select (O(n²)) will likely make this unworkable.
3719
3720	=back
3721		4963
3722	=head2 PORTABILITY REQUIREMENTS	4964	=head2 PORTABILITY REQUIREMENTS
3723		4965
3724	In addition to a working ISO-C implementation and of course the	4966	In addition to a working ISO-C implementation and of course the
3725	backend-specific APIs, libev relies on a few additional extensions:	4967	backend-specific APIs, libev relies on a few additional extensions:
…		…
3732	Libev assumes not only that all watcher pointers have the same internal	4974	Libev assumes not only that all watcher pointers have the same internal
3733	structure (guaranteed by POSIX but not by ISO C for example), but it also	4975	structure (guaranteed by POSIX but not by ISO C for example), but it also
3734	assumes that the same (machine) code can be used to call any watcher	4976	assumes that the same (machine) code can be used to call any watcher
3735	callback: The watcher callbacks have different type signatures, but libev	4977	callback: The watcher callbacks have different type signatures, but libev
3736	calls them using an C<ev_watcher *> internally.	4978	calls them using an C<ev_watcher *> internally.
		4979
		4980	=item pointer accesses must be thread-atomic
		4981
		4982	Accessing a pointer value must be atomic, it must both be readable and
		4983	writable in one piece - this is the case on all current architectures.
3737		4984
3738	=item C<sig_atomic_t volatile> must be thread-atomic as well	4985	=item C<sig_atomic_t volatile> must be thread-atomic as well
3739		4986
3740	The type C<sig_atomic_t volatile> (or whatever is defined as	4987	The type C<sig_atomic_t volatile> (or whatever is defined as
3741	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	4988	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
3764	watchers.	5011	watchers.
3765		5012
3766	=item C<double> must hold a time value in seconds with enough accuracy	5013	=item C<double> must hold a time value in seconds with enough accuracy
3767		5014
3768	The type C<double> is used to represent timestamps. It is required to	5015	The type C<double> is used to represent timestamps. It is required to
3769	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5016	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3770	enough for at least into the year 4000. This requirement is fulfilled by	5017	good enough for at least into the year 4000 with millisecond accuracy
		5018	(the design goal for libev). This requirement is overfulfilled by
3771	implementations implementing IEEE 754 (basically all existing ones).	5019	implementations using IEEE 754, which is basically all existing ones. With
		5020	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
3772		5021
3773	=back	5022	=back
3774		5023
3775	If you know of other additional requirements drop me a note.	5024	If you know of other additional requirements drop me a note.
3776		5025
…		…
3844	involves iterating over all running async watchers or all signal numbers.	5093	involves iterating over all running async watchers or all signal numbers.
3845		5094
3846	=back	5095	=back
3847		5096
3848		5097
		5098	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5099
		5100	The major version 4 introduced some incompatible changes to the API.
		5101
		5102	At the moment, the C<ev.h> header file provides compatibility definitions
		5103	for all changes, so most programs should still compile. The compatibility
		5104	layer might be removed in later versions of libev, so better update to the
		5105	new API early than late.
		5106
		5107	=over 4
		5108
		5109	=item C<EV_COMPAT3> backwards compatibility mechanism
		5110
		5111	The backward compatibility mechanism can be controlled by
		5112	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5113	section.
		5114
		5115	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5116
		5117	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5118
		5119	ev_loop_destroy (EV_DEFAULT_UC);
		5120	ev_loop_fork (EV_DEFAULT);
		5121
		5122	=item function/symbol renames
		5123
		5124	A number of functions and symbols have been renamed:
		5125
		5126	ev_loop => ev_run
		5127	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5128	EVLOOP_ONESHOT => EVRUN_ONCE
		5129
		5130	ev_unloop => ev_break
		5131	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5132	EVUNLOOP_ONE => EVBREAK_ONE
		5133	EVUNLOOP_ALL => EVBREAK_ALL
		5134
		5135	EV_TIMEOUT => EV_TIMER
		5136
		5137	ev_loop_count => ev_iteration
		5138	ev_loop_depth => ev_depth
		5139	ev_loop_verify => ev_verify
		5140
		5141	Most functions working on C<struct ev_loop> objects don't have an
		5142	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5143	associated constants have been renamed to not collide with the C<struct
		5144	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5145	as all other watcher types. Note that C<ev_loop_fork> is still called
		5146	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5147	typedef.
		5148
		5149	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5150
		5151	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5152	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5153	and work, but the library code will of course be larger.
		5154
		5155	=back
		5156
		5157
		5158	=head1 GLOSSARY
		5159
		5160	=over 4
		5161
		5162	=item active
		5163
		5164	A watcher is active as long as it has been started and not yet stopped.
		5165	See L<WATCHER STATES> for details.
		5166
		5167	=item application
		5168
		5169	In this document, an application is whatever is using libev.
		5170
		5171	=item backend
		5172
		5173	The part of the code dealing with the operating system interfaces.
		5174
		5175	=item callback
		5176
		5177	The address of a function that is called when some event has been
		5178	detected. Callbacks are being passed the event loop, the watcher that
		5179	received the event, and the actual event bitset.
		5180
		5181	=item callback/watcher invocation
		5182
		5183	The act of calling the callback associated with a watcher.
		5184
		5185	=item event
		5186
		5187	A change of state of some external event, such as data now being available
		5188	for reading on a file descriptor, time having passed or simply not having
		5189	any other events happening anymore.
		5190
		5191	In libev, events are represented as single bits (such as C<EV_READ> or
		5192	C<EV_TIMER>).
		5193
		5194	=item event library
		5195
		5196	A software package implementing an event model and loop.
		5197
		5198	=item event loop
		5199
		5200	An entity that handles and processes external events and converts them
		5201	into callback invocations.
		5202
		5203	=item event model
		5204
		5205	The model used to describe how an event loop handles and processes
		5206	watchers and events.
		5207
		5208	=item pending
		5209
		5210	A watcher is pending as soon as the corresponding event has been
		5211	detected. See L<WATCHER STATES> for details.
		5212
		5213	=item real time
		5214
		5215	The physical time that is observed. It is apparently strictly monotonic :)
		5216
		5217	=item wall-clock time
		5218
		5219	The time and date as shown on clocks. Unlike real time, it can actually
		5220	be wrong and jump forwards and backwards, e.g. when the you adjust your
		5221	clock.
		5222
		5223	=item watcher
		5224
		5225	A data structure that describes interest in certain events. Watchers need
		5226	to be started (attached to an event loop) before they can receive events.
		5227
		5228	=back
		5229
3849	=head1 AUTHOR	5230	=head1 AUTHOR
3850		5231
3851	Marc Lehmann <libev@schmorp.de>.	5232	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5233	Magnusson and Emanuele Giaquinta.
3852		5234

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