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…		…
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		13
		14	#include <stdio.h> // for puts
		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;
18		20
19	// all watcher callbacks have a similar signature	21	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	22	// this callback is called when data is readable on stdin
…		…
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
28		30
29	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_run's to stop iterating
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_break (EV_A_ EVBREAK_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_run to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_break (EV_A_ EVBREAK_ONE);
40	}	42	}
41		43
42	int	44	int
43	main (void)	45	main (void)
44	{	46	{
45	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
46	ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = EV_DEFAULT;
47		49
48	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
…		…
54	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
57		59
58	// now wait for events to arrive	60	// now wait for events to arrive
59	ev_loop (loop, 0);	61	ev_run (loop, 0);
60		62
61	// unloop was called, so exit	63	// break was called, so exit
62	return 0;	64	return 0;
63	}	65	}
64		66
65	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
66		70
67	The newest version of this document is also available as an html-formatted	71	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	72	web page you might find easier to navigate when reading it for the first
69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.	73	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		74
		75	While this document tries to be as complete as possible in documenting
		76	libev, its usage and the rationale behind its design, it is not a tutorial
		77	on event-based programming, nor will it introduce event-based programming
		78	with libev.
		79
		80	Familiarity with event based programming techniques in general is assumed
		81	throughout this document.
		82
		83	=head1 WHAT TO READ WHEN IN A HURRY
		84
		85	This manual tries to be very detailed, but unfortunately, this also makes
		86	it very long. If you just want to know the basics of libev, I suggest
		87	reading L</ANATOMY OF A WATCHER>, then the L</EXAMPLE PROGRAM> above and
		88	look up the missing functions in L</GLOBAL FUNCTIONS> and the C<ev_io> and
		89	C<ev_timer> sections in L</WATCHER TYPES>.
		90
		91	=head1 ABOUT LIBEV
70		92
71	Libev is an event loop: you register interest in certain events (such as a	93	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	94	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	95	these event sources and provide your program with events.
74		96
…		…
84	=head2 FEATURES	106	=head2 FEATURES
85		107
86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	108	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	109	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	110	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	111	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
90	with customised rescheduling (C<ev_periodic>), synchronous signals	112	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
91	(C<ev_signal>), process status change events (C<ev_child>), and event	113	timers (C<ev_timer>), absolute timers with customised rescheduling
92	watchers dealing with the event loop mechanism itself (C<ev_idle>,	114	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
93	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	115	change events (C<ev_child>), and event watchers dealing with the event
94	file watchers (C<ev_stat>) and even limited support for fork events	116	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
95	(C<ev_fork>).	117	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		118	limited support for fork events (C<ev_fork>).
96		119
97	It also is quite fast (see this	120	It also is quite fast (see this
98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	121	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
99	for example).	122	for example).
100		123
…		…
103	Libev is very configurable. In this manual the default (and most common)	126	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	127	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	128	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	129	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	130	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<ev_loop *>) will not have	131	name C<loop> (which is always of type C<struct ev_loop *>) will not have
109	this argument.	132	this argument.
110		133
111	=head2 TIME REPRESENTATION	134	=head2 TIME REPRESENTATION
112		135
113	Libev represents time as a single floating point number, representing the	136	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	137	the (fractional) number of seconds since the (POSIX) epoch (in practice
115	the beginning of 1970, details are complicated, don't ask). This type is	138	somewhere near the beginning of 1970, details are complicated, don't
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	139	ask). This type is called C<ev_tstamp>, which is what you should use
117	to the C<double> type in C, and when you need to do any calculations on	140	too. It usually aliases to the C<double> type in C. When you need to do
118	it, you should treat it as some floating point value. Unlike the name	141	any calculations on it, you should treat it as some floating point value.
		142
119	component C<stamp> might indicate, it is also used for time differences	143	Unlike the name component C<stamp> might indicate, it is also used for
120	throughout libev.	144	time differences (e.g. delays) throughout libev.
121		145
122	=head1 ERROR HANDLING	146	=head1 ERROR HANDLING
123		147
124	Libev knows three classes of errors: operating system errors, usage errors	148	Libev knows three classes of errors: operating system errors, usage errors
125	and internal errors (bugs).	149	and internal errors (bugs).
…		…
149		173
150	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
151		175
152	Returns the current time as libev would use it. Please note that the	176	Returns the current time as libev would use it. Please note that the
153	C<ev_now> function is usually faster and also often returns the timestamp	177	C<ev_now> function is usually faster and also often returns the timestamp
154	you actually want to know.	178	you actually want to know. Also interesting is the combination of
		179	C<ev_now_update> and C<ev_now>.
155		180
156	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
157		182
158	Sleep for the given interval: The current thread will be blocked until	183	Sleep for the given interval: The current thread will be blocked
159	either it is interrupted or the given time interval has passed. Basically	184	until either it is interrupted or the given time interval has
		185	passed (approximately - it might return a bit earlier even if not
		186	interrupted). Returns immediately if C<< interval <= 0 >>.
		187
160	this is a sub-second-resolution C<sleep ()>.	188	Basically this is a sub-second-resolution C<sleep ()>.
		189
		190	The range of the C<interval> is limited - libev only guarantees to work
		191	with sleep times of up to one day (C<< interval <= 86400 >>).
161		192
162	=item int ev_version_major ()	193	=item int ev_version_major ()
163		194
164	=item int ev_version_minor ()	195	=item int ev_version_minor ()
165		196
…		…
176	as this indicates an incompatible change. Minor versions are usually	207	as this indicates an incompatible change. Minor versions are usually
177	compatible to older versions, so a larger minor version alone is usually	208	compatible to older versions, so a larger minor version alone is usually
178	not a problem.	209	not a problem.
179		210
180	Example: Make sure we haven't accidentally been linked against the wrong	211	Example: Make sure we haven't accidentally been linked against the wrong
181	version.	212	version (note, however, that this will not detect other ABI mismatches,
		213	such as LFS or reentrancy).
182		214
183	assert (("libev version mismatch",	215	assert (("libev version mismatch",
184	ev_version_major () == EV_VERSION_MAJOR	216	ev_version_major () == EV_VERSION_MAJOR
185	&& ev_version_minor () >= EV_VERSION_MINOR));	217	&& ev_version_minor () >= EV_VERSION_MINOR));
186		218
…		…
197	assert (("sorry, no epoll, no sex",	229	assert (("sorry, no epoll, no sex",
198	ev_supported_backends () & EVBACKEND_EPOLL));	230	ev_supported_backends () & EVBACKEND_EPOLL));
199		231
200	=item unsigned int ev_recommended_backends ()	232	=item unsigned int ev_recommended_backends ()
201		233
202	Return the set of all backends compiled into this binary of libev and also	234	Return the set of all backends compiled into this binary of libev and
203	recommended for this platform. This set is often smaller than the one	235	also recommended for this platform, meaning it will work for most file
		236	descriptor types. This set is often smaller than the one returned by
204	returned by C<ev_supported_backends>, as for example kqueue is broken on	237	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
205	most BSDs and will not be auto-detected unless you explicitly request it	238	and will not be auto-detected unless you explicitly request it (assuming
206	(assuming you know what you are doing). This is the set of backends that	239	you know what you are doing). This is the set of backends that libev will
207	libev will probe for if you specify no backends explicitly.	240	probe for if you specify no backends explicitly.
208		241
209	=item unsigned int ev_embeddable_backends ()	242	=item unsigned int ev_embeddable_backends ()
210		243
211	Returns the set of backends that are embeddable in other event loops. This	244	Returns the set of backends that are embeddable in other event loops. This
212	is the theoretical, all-platform, value. To find which backends	245	value is platform-specific but can include backends not available on the
213	might be supported on the current system, you would need to look at	246	current system. To find which embeddable backends might be supported on
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	247	the current system, you would need to look at C<ev_embeddable_backends ()
215	recommended ones.	248	& ev_supported_backends ()>, likewise for recommended ones.
216		249
217	See the description of C<ev_embed> watchers for more info.	250	See the description of C<ev_embed> watchers for more info.
218		251
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	252	=item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())
220		253
221	Sets the allocation function to use (the prototype is similar - the	254	Sets the allocation function to use (the prototype is similar - the
222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	255	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
223	used to allocate and free memory (no surprises here). If it returns zero	256	used to allocate and free memory (no surprises here). If it returns zero
224	when memory needs to be allocated (C<size != 0>), the library might abort	257	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	283	}
251		284
252	...	285	...
253	ev_set_allocator (persistent_realloc);	286	ev_set_allocator (persistent_realloc);
254		287
255	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	288	=item ev_set_syserr_cb (void (*cb)(const char *msg) throw ())
256		289
257	Set the callback function to call on a retryable system call error (such	290	Set the callback function to call on a retryable system call error (such
258	as failed select, poll, epoll_wait). The message is a printable string	291	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	292	indicating the system call or subsystem causing the problem. If this
260	callback is set, then libev will expect it to remedy the situation, no	293	callback is set, then libev will expect it to remedy the situation, no
…		…
272	}	305	}
273		306
274	...	307	...
275	ev_set_syserr_cb (fatal_error);	308	ev_set_syserr_cb (fatal_error);
276		309
		310	=item ev_feed_signal (int signum)
		311
		312	This function can be used to "simulate" a signal receive. It is completely
		313	safe to call this function at any time, from any context, including signal
		314	handlers or random threads.
		315
		316	Its main use is to customise signal handling in your process, especially
		317	in the presence of threads. For example, you could block signals
		318	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		319	creating any loops), and in one thread, use C<sigwait> or any other
		320	mechanism to wait for signals, then "deliver" them to libev by calling
		321	C<ev_feed_signal>.
		322
277	=back	323	=back
278		324
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	325	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
280		326
281	An event loop is described by a C<ev_loop *>. The library knows two	327	An event loop is described by a C<struct ev_loop *> (the C<struct> is
282	types of such loops, the I<default> loop, which supports signals and child	328	I<not> optional in this case unless libev 3 compatibility is disabled, as
283	events, and dynamically created loops which do not.	329	libev 3 had an C<ev_loop> function colliding with the struct name).
		330
		331	The library knows two types of such loops, the I<default> loop, which
		332	supports child process events, and dynamically created event loops which
		333	do not.
284		334
285	=over 4	335	=over 4
286		336
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	337	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		338
289	This will initialise the default event loop if it hasn't been initialised	339	This returns the "default" event loop object, which is what you should
290	yet and return it. If the default loop could not be initialised, returns	340	normally use when you just need "the event loop". Event loop objects and
291	false. If it already was initialised it simply returns it (and ignores the	341	the C<flags> parameter are described in more detail in the entry for
292	flags. If that is troubling you, check C<ev_backend ()> afterwards).	342	C<ev_loop_new>.
		343
		344	If the default loop is already initialised then this function simply
		345	returns it (and ignores the flags. If that is troubling you, check
		346	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		347	flags, which should almost always be C<0>, unless the caller is also the
		348	one calling C<ev_run> or otherwise qualifies as "the main program".
293		349
294	If you don't know what event loop to use, use the one returned from this	350	If you don't know what event loop to use, use the one returned from this
295	function.	351	function (or via the C<EV_DEFAULT> macro).
296		352
297	Note that this function is I<not> thread-safe, so if you want to use it	353	Note that this function is I<not> thread-safe, so if you want to use it
298	from multiple threads, you have to lock (note also that this is unlikely,	354	from multiple threads, you have to employ some kind of mutex (note also
299	as loops cannot bes hared easily between threads anyway).	355	that this case is unlikely, as loops cannot be shared easily between
		356	threads anyway).
300		357
301	The default loop is the only loop that can handle C<ev_signal> and	358	The default loop is the only loop that can handle C<ev_child> watchers,
302	C<ev_child> watchers, and to do this, it always registers a handler	359	and to do this, it always registers a handler for C<SIGCHLD>. If this is
303	for C<SIGCHLD>. If this is a problem for your application you can either	360	a problem for your application you can either create a dynamic loop with
304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	361	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
305	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	362	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
306	C<ev_default_init>.	363
		364	Example: This is the most typical usage.
		365
		366	if (!ev_default_loop (0))
		367	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		368
		369	Example: Restrict libev to the select and poll backends, and do not allow
		370	environment settings to be taken into account:
		371
		372	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		373
		374	=item struct ev_loop *ev_loop_new (unsigned int flags)
		375
		376	This will create and initialise a new event loop object. If the loop
		377	could not be initialised, returns false.
		378
		379	This function is thread-safe, and one common way to use libev with
		380	threads is indeed to create one loop per thread, and using the default
		381	loop in the "main" or "initial" thread.
307		382
308	The flags argument can be used to specify special behaviour or specific	383	The flags argument can be used to specify special behaviour or specific
309	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	384	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
310		385
311	The following flags are supported:	386	The following flags are supported:
…		…
321		396
322	If this flag bit is or'ed into the flag value (or the program runs setuid	397	If this flag bit is or'ed into the flag value (or the program runs setuid
323	or setgid) then libev will I<not> look at the environment variable	398	or setgid) then libev will I<not> look at the environment variable
324	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	399	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
325	override the flags completely if it is found in the environment. This is	400	override the flags completely if it is found in the environment. This is
326	useful to try out specific backends to test their performance, or to work	401	useful to try out specific backends to test their performance, to work
327	around bugs.	402	around bugs, or to make libev threadsafe (accessing environment variables
		403	cannot be done in a threadsafe way, but usually it works if no other
		404	thread modifies them).
328		405
329	=item C<EVFLAG_FORKCHECK>	406	=item C<EVFLAG_FORKCHECK>
330		407
331	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	408	Instead of calling C<ev_loop_fork> manually after a fork, you can also
332	a fork, you can also make libev check for a fork in each iteration by	409	make libev check for a fork in each iteration by enabling this flag.
333	enabling this flag.
334		410
335	This works by calling C<getpid ()> on every iteration of the loop,	411	This works by calling C<getpid ()> on every iteration of the loop,
336	and thus this might slow down your event loop if you do a lot of loop	412	and thus this might slow down your event loop if you do a lot of loop
337	iterations and little real work, but is usually not noticeable (on my	413	iterations and little real work, but is usually not noticeable (on my
338	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	414	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
…		…
344	flag.	420	flag.
345		421
346	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	422	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
347	environment variable.	423	environment variable.
348		424
		425	=item C<EVFLAG_NOINOTIFY>
		426
		427	When this flag is specified, then libev will not attempt to use the
		428	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
		429	testing, this flag can be useful to conserve inotify file descriptors, as
		430	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		431
		432	=item C<EVFLAG_SIGNALFD>
		433
		434	When this flag is specified, then libev will attempt to use the
		435	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
		436	delivers signals synchronously, which makes it both faster and might make
		437	it possible to get the queued signal data. It can also simplify signal
		438	handling with threads, as long as you properly block signals in your
		439	threads that are not interested in handling them.
		440
		441	Signalfd will not be used by default as this changes your signal mask, and
		442	there are a lot of shoddy libraries and programs (glib's threadpool for
		443	example) that can't properly initialise their signal masks.
		444
		445	=item C<EVFLAG_NOSIGMASK>
		446
		447	When this flag is specified, then libev will avoid to modify the signal
		448	mask. Specifically, this means you have to make sure signals are unblocked
		449	when you want to receive them.
		450
		451	This behaviour is useful when you want to do your own signal handling, or
		452	want to handle signals only in specific threads and want to avoid libev
		453	unblocking the signals.
		454
		455	It's also required by POSIX in a threaded program, as libev calls
		456	C<sigprocmask>, whose behaviour is officially unspecified.
		457
		458	This flag's behaviour will become the default in future versions of libev.
		459
349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	460	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
350		461
351	This is your standard select(2) backend. Not I<completely> standard, as	462	This is your standard select(2) backend. Not I<completely> standard, as
352	libev tries to roll its own fd_set with no limits on the number of fds,	463	libev tries to roll its own fd_set with no limits on the number of fds,
353	but if that fails, expect a fairly low limit on the number of fds when	464	but if that fails, expect a fairly low limit on the number of fds when
…		…
377	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and	488	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
378	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	489	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
379		490
380	=item C<EVBACKEND_EPOLL> (value 4, Linux)	491	=item C<EVBACKEND_EPOLL> (value 4, Linux)
381		492
		493	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		494	kernels).
		495
382	For few fds, this backend is a bit little slower than poll and select,	496	For few fds, this backend is a bit little slower than poll and select, but
383	but it scales phenomenally better. While poll and select usually scale	497	it scales phenomenally better. While poll and select usually scale like
384	like O(total_fds) where n is the total number of fds (or the highest fd),	498	O(total_fds) where total_fds is the total number of fds (or the highest
385	epoll scales either O(1) or O(active_fds). The epoll design has a number	499	fd), epoll scales either O(1) or O(active_fds).
386	of shortcomings, such as silently dropping events in some hard-to-detect	500
387	cases and requiring a system call per fd change, no fork support and bad	501	The epoll mechanism deserves honorable mention as the most misdesigned
388	support for dup.	502	of the more advanced event mechanisms: mere annoyances include silently
		503	dropping file descriptors, requiring a system call per change per file
		504	descriptor (and unnecessary guessing of parameters), problems with dup,
		505	returning before the timeout value, resulting in additional iterations
		506	(and only giving 5ms accuracy while select on the same platform gives
		507	0.1ms) and so on. The biggest issue is fork races, however - if a program
		508	forks then I<both> parent and child process have to recreate the epoll
		509	set, which can take considerable time (one syscall per file descriptor)
		510	and is of course hard to detect.
		511
		512	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
		513	but of course I<doesn't>, and epoll just loves to report events for
		514	totally I<different> file descriptors (even already closed ones, so
		515	one cannot even remove them from the set) than registered in the set
		516	(especially on SMP systems). Libev tries to counter these spurious
		517	notifications by employing an additional generation counter and comparing
		518	that against the events to filter out spurious ones, recreating the set
		519	when required. Epoll also erroneously rounds down timeouts, but gives you
		520	no way to know when and by how much, so sometimes you have to busy-wait
		521	because epoll returns immediately despite a nonzero timeout. And last
		522	not least, it also refuses to work with some file descriptors which work
		523	perfectly fine with C<select> (files, many character devices...).
		524
		525	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		526	cobbled together in a hurry, no thought to design or interaction with
		527	others. Oh, the pain, will it ever stop...
389		528
390	While stopping, setting and starting an I/O watcher in the same iteration	529	While stopping, setting and starting an I/O watcher in the same iteration
391	will result in some caching, there is still a system call per such incident	530	will result in some caching, there is still a system call per such
392	(because the fd could point to a different file description now), so its	531	incident (because the same I<file descriptor> could point to a different
393	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	532	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
394	very well if you register events for both fds.	533	file descriptors might not work very well if you register events for both
395		534	file descriptors.
396	Please note that epoll sometimes generates spurious notifications, so you
397	need to use non-blocking I/O or other means to avoid blocking when no data
398	(or space) is available.
399		535
400	Best performance from this backend is achieved by not unregistering all	536	Best performance from this backend is achieved by not unregistering all
401	watchers for a file descriptor until it has been closed, if possible,	537	watchers for a file descriptor until it has been closed, if possible,
402	i.e. keep at least one watcher active per fd at all times. Stopping and	538	i.e. keep at least one watcher active per fd at all times. Stopping and
403	starting a watcher (without re-setting it) also usually doesn't cause	539	starting a watcher (without re-setting it) also usually doesn't cause
404	extra overhead.	540	extra overhead. A fork can both result in spurious notifications as well
		541	as in libev having to destroy and recreate the epoll object, which can
		542	take considerable time and thus should be avoided.
		543
		544	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		545	faster than epoll for maybe up to a hundred file descriptors, depending on
		546	the usage. So sad.
405		547
406	While nominally embeddable in other event loops, this feature is broken in	548	While nominally embeddable in other event loops, this feature is broken in
407	all kernel versions tested so far.	549	all kernel versions tested so far.
408		550
409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	551	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
410	C<EVBACKEND_POLL>.	552	C<EVBACKEND_POLL>.
411		553
412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	554	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
413		555
414	Kqueue deserves special mention, as at the time of this writing, it was	556	Kqueue deserves special mention, as at the time of this writing, it
415	broken on all BSDs except NetBSD (usually it doesn't work reliably with	557	was broken on all BSDs except NetBSD (usually it doesn't work reliably
416	anything but sockets and pipes, except on Darwin, where of course it's	558	with anything but sockets and pipes, except on Darwin, where of course
417	completely useless). For this reason it's not being "auto-detected" unless	559	it's completely useless). Unlike epoll, however, whose brokenness
418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or	560	is by design, these kqueue bugs can (and eventually will) be fixed
419	libev was compiled on a known-to-be-good (-enough) system like NetBSD.	561	without API changes to existing programs. For this reason it's not being
		562	"auto-detected" unless you explicitly specify it in the flags (i.e. using
		563	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		564	system like NetBSD.
420		565
421	You still can embed kqueue into a normal poll or select backend and use it	566	You still can embed kqueue into a normal poll or select backend and use it
422	only for sockets (after having made sure that sockets work with kqueue on	567	only for sockets (after having made sure that sockets work with kqueue on
423	the target platform). See C<ev_embed> watchers for more info.	568	the target platform). See C<ev_embed> watchers for more info.
424		569
425	It scales in the same way as the epoll backend, but the interface to the	570	It scales in the same way as the epoll backend, but the interface to the
426	kernel is more efficient (which says nothing about its actual speed, of	571	kernel is more efficient (which says nothing about its actual speed, of
427	course). While stopping, setting and starting an I/O watcher does never	572	course). While stopping, setting and starting an I/O watcher does never
428	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	573	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
429	two event changes per incident. Support for C<fork ()> is very bad and it	574	two event changes per incident. Support for C<fork ()> is very bad (you
		575	might have to leak fd's on fork, but it's more sane than epoll) and it
430	drops fds silently in similarly hard-to-detect cases.	576	drops fds silently in similarly hard-to-detect cases.
431		577
432	This backend usually performs well under most conditions.	578	This backend usually performs well under most conditions.
433		579
434	While nominally embeddable in other event loops, this doesn't work	580	While nominally embeddable in other event loops, this doesn't work
435	everywhere, so you might need to test for this. And since it is broken	581	everywhere, so you might need to test for this. And since it is broken
436	almost everywhere, you should only use it when you have a lot of sockets	582	almost everywhere, you should only use it when you have a lot of sockets
437	(for which it usually works), by embedding it into another event loop	583	(for which it usually works), by embedding it into another event loop
438	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,	584	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
439	using it only for sockets.	585	also broken on OS X)) and, did I mention it, using it only for sockets.
440		586
441	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	587	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
442	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with	588	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
443	C<NOTE_EOF>.	589	C<NOTE_EOF>.
444		590
…		…
452	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	598	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
453		599
454	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	600	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
455	it's really slow, but it still scales very well (O(active_fds)).	601	it's really slow, but it still scales very well (O(active_fds)).
456		602
457	Please note that Solaris event ports can deliver a lot of spurious
458	notifications, so you need to use non-blocking I/O or other means to avoid
459	blocking when no data (or space) is available.
460
461	While this backend scales well, it requires one system call per active	603	While this backend scales well, it requires one system call per active
462	file descriptor per loop iteration. For small and medium numbers of file	604	file descriptor per loop iteration. For small and medium numbers of file
463	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	605	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
464	might perform better.	606	might perform better.
465		607
466	On the positive side, with the exception of the spurious readiness	608	On the positive side, this backend actually performed fully to
467	notifications, this backend actually performed fully to specification
468	in all tests and is fully embeddable, which is a rare feat among the	609	specification in all tests and is fully embeddable, which is a rare feat
469	OS-specific backends.	610	among the OS-specific backends (I vastly prefer correctness over speed
		611	hacks).
		612
		613	On the negative side, the interface is I<bizarre> - so bizarre that
		614	even sun itself gets it wrong in their code examples: The event polling
		615	function sometimes returns events to the caller even though an error
		616	occurred, but with no indication whether it has done so or not (yes, it's
		617	even documented that way) - deadly for edge-triggered interfaces where you
		618	absolutely have to know whether an event occurred or not because you have
		619	to re-arm the watcher.
		620
		621	Fortunately libev seems to be able to work around these idiocies.
470		622
471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	623	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
472	C<EVBACKEND_POLL>.	624	C<EVBACKEND_POLL>.
473		625
474	=item C<EVBACKEND_ALL>	626	=item C<EVBACKEND_ALL>
475		627
476	Try all backends (even potentially broken ones that wouldn't be tried	628	Try all backends (even potentially broken ones that wouldn't be tried
477	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	629	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
478	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	630	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
479		631
480	It is definitely not recommended to use this flag.	632	It is definitely not recommended to use this flag, use whatever
		633	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		634	at all.
		635
		636	=item C<EVBACKEND_MASK>
		637
		638	Not a backend at all, but a mask to select all backend bits from a
		639	C<flags> value, in case you want to mask out any backends from a flags
		640	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
481		641
482	=back	642	=back
483		643
484	If one or more of these are or'ed into the flags value, then only these	644	If one or more of the backend flags are or'ed into the flags value,
485	backends will be tried (in the reverse order as listed here). If none are	645	then only these backends will be tried (in the reverse order as listed
486	specified, all backends in C<ev_recommended_backends ()> will be tried.	646	here). If none are specified, all backends in C<ev_recommended_backends
487		647	()> will be tried.
488	Example: This is the most typical usage.
489
490	if (!ev_default_loop (0))
491	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
492
493	Example: Restrict libev to the select and poll backends, and do not allow
494	environment settings to be taken into account:
495
496	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
497
498	Example: Use whatever libev has to offer, but make sure that kqueue is
499	used if available (warning, breaks stuff, best use only with your own
500	private event loop and only if you know the OS supports your types of
501	fds):
502
503	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
504
505	=item struct ev_loop *ev_loop_new (unsigned int flags)
506
507	Similar to C<ev_default_loop>, but always creates a new event loop that is
508	always distinct from the default loop. Unlike the default loop, it cannot
509	handle signal and child watchers, and attempts to do so will be greeted by
510	undefined behaviour (or a failed assertion if assertions are enabled).
511
512	Note that this function I<is> thread-safe, and the recommended way to use
513	libev with threads is indeed to create one loop per thread, and using the
514	default loop in the "main" or "initial" thread.
515		648
516	Example: Try to create a event loop that uses epoll and nothing else.	649	Example: Try to create a event loop that uses epoll and nothing else.
517		650
518	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	651	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
519	if (!epoller)	652	if (!epoller)
520	fatal ("no epoll found here, maybe it hides under your chair");	653	fatal ("no epoll found here, maybe it hides under your chair");
521		654
		655	Example: Use whatever libev has to offer, but make sure that kqueue is
		656	used if available.
		657
		658	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		659
522	=item ev_default_destroy ()	660	=item ev_loop_destroy (loop)
523		661
524	Destroys the default loop again (frees all memory and kernel state	662	Destroys an event loop object (frees all memory and kernel state
525	etc.). None of the active event watchers will be stopped in the normal	663	etc.). None of the active event watchers will be stopped in the normal
526	sense, so e.g. C<ev_is_active> might still return true. It is your	664	sense, so e.g. C<ev_is_active> might still return true. It is your
527	responsibility to either stop all watchers cleanly yourself I<before>	665	responsibility to either stop all watchers cleanly yourself I<before>
528	calling this function, or cope with the fact afterwards (which is usually	666	calling this function, or cope with the fact afterwards (which is usually
529	the easiest thing, you can just ignore the watchers and/or C<free ()> them	667	the easiest thing, you can just ignore the watchers and/or C<free ()> them
530	for example).	668	for example).
531		669
532	Note that certain global state, such as signal state, will not be freed by	670	Note that certain global state, such as signal state (and installed signal
533	this function, and related watchers (such as signal and child watchers)	671	handlers), will not be freed by this function, and related watchers (such
534	would need to be stopped manually.	672	as signal and child watchers) would need to be stopped manually.
535		673
536	In general it is not advisable to call this function except in the	674	This function is normally used on loop objects allocated by
537	rare occasion where you really need to free e.g. the signal handling	675	C<ev_loop_new>, but it can also be used on the default loop returned by
		676	C<ev_default_loop>, in which case it is not thread-safe.
		677
		678	Note that it is not advisable to call this function on the default loop
		679	except in the rare occasion where you really need to free its resources.
538	pipe fds. If you need dynamically allocated loops it is better to use	680	If you need dynamically allocated loops it is better to use C<ev_loop_new>
539	C<ev_loop_new> and C<ev_loop_destroy>).	681	and C<ev_loop_destroy>.
540		682
541	=item ev_loop_destroy (loop)	683	=item ev_loop_fork (loop)
542		684
543	Like C<ev_default_destroy>, but destroys an event loop created by an
544	earlier call to C<ev_loop_new>.
545
546	=item ev_default_fork ()
547
548	This function sets a flag that causes subsequent C<ev_loop> iterations	685	This function sets a flag that causes subsequent C<ev_run> iterations to
549	to reinitialise the kernel state for backends that have one. Despite the	686	reinitialise the kernel state for backends that have one. Despite the
550	name, you can call it anytime, but it makes most sense after forking, in	687	name, you can call it anytime, but it makes most sense after forking, in
551	the child process (or both child and parent, but that again makes little	688	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
552	sense). You I<must> call it in the child before using any of the libev	689	child before resuming or calling C<ev_run>.
553	functions, and it will only take effect at the next C<ev_loop> iteration.	690
		691	Again, you I<have> to call it on I<any> loop that you want to re-use after
		692	a fork, I<even if you do not plan to use the loop in the parent>. This is
		693	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		694	during fork.
554		695
555	On the other hand, you only need to call this function in the child	696	On the other hand, you only need to call this function in the child
556	process if and only if you want to use the event library in the child. If	697	process if and only if you want to use the event loop in the child. If
557	you just fork+exec, you don't have to call it at all.	698	you just fork+exec or create a new loop in the child, you don't have to
		699	call it at all (in fact, C<epoll> is so badly broken that it makes a
		700	difference, but libev will usually detect this case on its own and do a
		701	costly reset of the backend).
558		702
559	The function itself is quite fast and it's usually not a problem to call	703	The function itself is quite fast and it's usually not a problem to call
560	it just in case after a fork. To make this easy, the function will fit in	704	it just in case after a fork.
561	quite nicely into a call to C<pthread_atfork>:
562		705
		706	Example: Automate calling C<ev_loop_fork> on the default loop when
		707	using pthreads.
		708
		709	static void
		710	post_fork_child (void)
		711	{
		712	ev_loop_fork (EV_DEFAULT);
		713	}
		714
		715	...
563	pthread_atfork (0, 0, ev_default_fork);	716	pthread_atfork (0, 0, post_fork_child);
564
565	=item ev_loop_fork (loop)
566
567	Like C<ev_default_fork>, but acts on an event loop created by
568	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
569	after fork that you want to re-use in the child, and how you do this is
570	entirely your own problem.
571		717
572	=item int ev_is_default_loop (loop)	718	=item int ev_is_default_loop (loop)
573		719
574	Returns true when the given loop is, in fact, the default loop, and false	720	Returns true when the given loop is, in fact, the default loop, and false
575	otherwise.	721	otherwise.
576		722
577	=item unsigned int ev_loop_count (loop)	723	=item unsigned int ev_iteration (loop)
578		724
579	Returns the count of loop iterations for the loop, which is identical to	725	Returns the current iteration count for the event loop, which is identical
580	the number of times libev did poll for new events. It starts at C<0> and	726	to the number of times libev did poll for new events. It starts at C<0>
581	happily wraps around with enough iterations.	727	and happily wraps around with enough iterations.
582		728
583	This value can sometimes be useful as a generation counter of sorts (it	729	This value can sometimes be useful as a generation counter of sorts (it
584	"ticks" the number of loop iterations), as it roughly corresponds with	730	"ticks" the number of loop iterations), as it roughly corresponds with
585	C<ev_prepare> and C<ev_check> calls.	731	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		732	prepare and check phases.
		733
		734	=item unsigned int ev_depth (loop)
		735
		736	Returns the number of times C<ev_run> was entered minus the number of
		737	times C<ev_run> was exited normally, in other words, the recursion depth.
		738
		739	Outside C<ev_run>, this number is zero. In a callback, this number is
		740	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		741	in which case it is higher.
		742
		743	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
		744	throwing an exception etc.), doesn't count as "exit" - consider this
		745	as a hint to avoid such ungentleman-like behaviour unless it's really
		746	convenient, in which case it is fully supported.
586		747
587	=item unsigned int ev_backend (loop)	748	=item unsigned int ev_backend (loop)
588		749
589	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	750	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
590	use.	751	use.
…		…
599		760
600	=item ev_now_update (loop)	761	=item ev_now_update (loop)
601		762
602	Establishes the current time by querying the kernel, updating the time	763	Establishes the current time by querying the kernel, updating the time
603	returned by C<ev_now ()> in the progress. This is a costly operation and	764	returned by C<ev_now ()> in the progress. This is a costly operation and
604	is usually done automatically within C<ev_loop ()>.	765	is usually done automatically within C<ev_run ()>.
605		766
606	This function is rarely useful, but when some event callback runs for a	767	This function is rarely useful, but when some event callback runs for a
607	very long time without entering the event loop, updating libev's idea of	768	very long time without entering the event loop, updating libev's idea of
608	the current time is a good idea.	769	the current time is a good idea.
609		770
610	See also "The special problem of time updates" in the C<ev_timer> section.	771	See also L</The special problem of time updates> in the C<ev_timer> section.
611		772
		773	=item ev_suspend (loop)
		774
		775	=item ev_resume (loop)
		776
		777	These two functions suspend and resume an event loop, for use when the
		778	loop is not used for a while and timeouts should not be processed.
		779
		780	A typical use case would be an interactive program such as a game: When
		781	the user presses C<^Z> to suspend the game and resumes it an hour later it
		782	would be best to handle timeouts as if no time had actually passed while
		783	the program was suspended. This can be achieved by calling C<ev_suspend>
		784	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		785	C<ev_resume> directly afterwards to resume timer processing.
		786
		787	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		788	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		789	will be rescheduled (that is, they will lose any events that would have
		790	occurred while suspended).
		791
		792	After calling C<ev_suspend> you B<must not> call I<any> function on the
		793	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		794	without a previous call to C<ev_suspend>.
		795
		796	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		797	event loop time (see C<ev_now_update>).
		798
612	=item ev_loop (loop, int flags)	799	=item bool ev_run (loop, int flags)
613		800
614	Finally, this is it, the event handler. This function usually is called	801	Finally, this is it, the event handler. This function usually is called
615	after you initialised all your watchers and you want to start handling	802	after you have initialised all your watchers and you want to start
616	events.	803	handling events. It will ask the operating system for any new events, call
		804	the watcher callbacks, and then repeat the whole process indefinitely: This
		805	is why event loops are called I<loops>.
617		806
618	If the flags argument is specified as C<0>, it will not return until	807	If the flags argument is specified as C<0>, it will keep handling events
619	either no event watchers are active anymore or C<ev_unloop> was called.	808	until either no event watchers are active anymore or C<ev_break> was
		809	called.
620		810
		811	The return value is false if there are no more active watchers (which
		812	usually means "all jobs done" or "deadlock"), and true in all other cases
		813	(which usually means " you should call C<ev_run> again").
		814
621	Please note that an explicit C<ev_unloop> is usually better than	815	Please note that an explicit C<ev_break> is usually better than
622	relying on all watchers to be stopped when deciding when a program has	816	relying on all watchers to be stopped when deciding when a program has
623	finished (especially in interactive programs), but having a program	817	finished (especially in interactive programs), but having a program
624	that automatically loops as long as it has to and no longer by virtue	818	that automatically loops as long as it has to and no longer by virtue
625	of relying on its watchers stopping correctly, that is truly a thing of	819	of relying on its watchers stopping correctly, that is truly a thing of
626	beauty.	820	beauty.
627		821
		822	This function is I<mostly> exception-safe - you can break out of a
		823	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		824	exception and so on. This does not decrement the C<ev_depth> value, nor
		825	will it clear any outstanding C<EVBREAK_ONE> breaks.
		826
628	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	827	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
629	those events and any already outstanding ones, but will not block your	828	those events and any already outstanding ones, but will not wait and
630	process in case there are no events and will return after one iteration of	829	block your process in case there are no events and will return after one
631	the loop.	830	iteration of the loop. This is sometimes useful to poll and handle new
		831	events while doing lengthy calculations, to keep the program responsive.
632		832
633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	833	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
634	necessary) and will handle those and any already outstanding ones. It	834	necessary) and will handle those and any already outstanding ones. It
635	will block your process until at least one new event arrives (which could	835	will block your process until at least one new event arrives (which could
636	be an event internal to libev itself, so there is no guarentee that a	836	be an event internal to libev itself, so there is no guarantee that a
637	user-registered callback will be called), and will return after one	837	user-registered callback will be called), and will return after one
638	iteration of the loop.	838	iteration of the loop.
639		839
640	This is useful if you are waiting for some external event in conjunction	840	This is useful if you are waiting for some external event in conjunction
641	with something not expressible using other libev watchers (i.e. "roll your	841	with something not expressible using other libev watchers (i.e. "roll your
642	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	842	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
643	usually a better approach for this kind of thing.	843	usually a better approach for this kind of thing.
644		844
645	Here are the gory details of what C<ev_loop> does:	845	Here are the gory details of what C<ev_run> does (this is for your
		846	understanding, not a guarantee that things will work exactly like this in
		847	future versions):
646		848
		849	- Increment loop depth.
		850	- Reset the ev_break status.
647	- Before the first iteration, call any pending watchers.	851	- Before the first iteration, call any pending watchers.
		852	LOOP:
648	* If EVFLAG_FORKCHECK was used, check for a fork.	853	- If EVFLAG_FORKCHECK was used, check for a fork.
649	- If a fork was detected (by any means), queue and call all fork watchers.	854	- If a fork was detected (by any means), queue and call all fork watchers.
650	- Queue and call all prepare watchers.	855	- Queue and call all prepare watchers.
		856	- If ev_break was called, goto FINISH.
651	- If we have been forked, detach and recreate the kernel state	857	- If we have been forked, detach and recreate the kernel state
652	as to not disturb the other process.	858	as to not disturb the other process.
653	- Update the kernel state with all outstanding changes.	859	- Update the kernel state with all outstanding changes.
654	- Update the "event loop time" (ev_now ()).	860	- Update the "event loop time" (ev_now ()).
655	- Calculate for how long to sleep or block, if at all	861	- Calculate for how long to sleep or block, if at all
656	(active idle watchers, EVLOOP_NONBLOCK or not having	862	(active idle watchers, EVRUN_NOWAIT or not having
657	any active watchers at all will result in not sleeping).	863	any active watchers at all will result in not sleeping).
658	- Sleep if the I/O and timer collect interval say so.	864	- Sleep if the I/O and timer collect interval say so.
		865	- Increment loop iteration counter.
659	- Block the process, waiting for any events.	866	- Block the process, waiting for any events.
660	- Queue all outstanding I/O (fd) events.	867	- Queue all outstanding I/O (fd) events.
661	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	868	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
662	- Queue all expired timers.	869	- Queue all expired timers.
663	- Queue all expired periodics.	870	- Queue all expired periodics.
664	- Unless any events are pending now, queue all idle watchers.	871	- Queue all idle watchers with priority higher than that of pending events.
665	- Queue all check watchers.	872	- Queue all check watchers.
666	- Call all queued watchers in reverse order (i.e. check watchers first).	873	- Call all queued watchers in reverse order (i.e. check watchers first).
667	Signals and child watchers are implemented as I/O watchers, and will	874	Signals and child watchers are implemented as I/O watchers, and will
668	be handled here by queueing them when their watcher gets executed.	875	be handled here by queueing them when their watcher gets executed.
669	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	876	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
670	were used, or there are no active watchers, return, otherwise	877	were used, or there are no active watchers, goto FINISH, otherwise
671	continue with step *.	878	continue with step LOOP.
		879	FINISH:
		880	- Reset the ev_break status iff it was EVBREAK_ONE.
		881	- Decrement the loop depth.
		882	- Return.
672		883
673	Example: Queue some jobs and then loop until no events are outstanding	884	Example: Queue some jobs and then loop until no events are outstanding
674	anymore.	885	anymore.
675		886
676	... queue jobs here, make sure they register event watchers as long	887	... queue jobs here, make sure they register event watchers as long
677	... as they still have work to do (even an idle watcher will do..)	888	... as they still have work to do (even an idle watcher will do..)
678	ev_loop (my_loop, 0);	889	ev_run (my_loop, 0);
679	... jobs done or somebody called unloop. yeah!	890	... jobs done or somebody called break. yeah!
680		891
681	=item ev_unloop (loop, how)	892	=item ev_break (loop, how)
682		893
683	Can be used to make a call to C<ev_loop> return early (but only after it	894	Can be used to make a call to C<ev_run> return early (but only after it
684	has processed all outstanding events). The C<how> argument must be either	895	has processed all outstanding events). The C<how> argument must be either
685	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	896	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
686	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	897	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
687		898
688	This "unloop state" will be cleared when entering C<ev_loop> again.	899	This "break state" will be cleared on the next call to C<ev_run>.
689		900
690	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	901	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		902	which case it will have no effect.
691		903
692	=item ev_ref (loop)	904	=item ev_ref (loop)
693		905
694	=item ev_unref (loop)	906	=item ev_unref (loop)
695		907
696	Ref/unref can be used to add or remove a reference count on the event	908	Ref/unref can be used to add or remove a reference count on the event
697	loop: Every watcher keeps one reference, and as long as the reference	909	loop: Every watcher keeps one reference, and as long as the reference
698	count is nonzero, C<ev_loop> will not return on its own.	910	count is nonzero, C<ev_run> will not return on its own.
699		911
700	If you have a watcher you never unregister that should not keep C<ev_loop>	912	This is useful when you have a watcher that you never intend to
701	from returning, call ev_unref() after starting, and ev_ref() before	913	unregister, but that nevertheless should not keep C<ev_run> from
		914	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
702	stopping it.	915	before stopping it.
703		916
704	As an example, libev itself uses this for its internal signal pipe: It is	917	As an example, libev itself uses this for its internal signal pipe: It
705	not visible to the libev user and should not keep C<ev_loop> from exiting	918	is not visible to the libev user and should not keep C<ev_run> from
706	if no event watchers registered by it are active. It is also an excellent	919	exiting if no event watchers registered by it are active. It is also an
707	way to do this for generic recurring timers or from within third-party	920	excellent way to do this for generic recurring timers or from within
708	libraries. Just remember to I<unref after start> and I<ref before stop>	921	third-party libraries. Just remember to I<unref after start> and I<ref
709	(but only if the watcher wasn't active before, or was active before,	922	before stop> (but only if the watcher wasn't active before, or was active
710	respectively).	923	before, respectively. Note also that libev might stop watchers itself
		924	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		925	in the callback).
711		926
712	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	927	Example: Create a signal watcher, but keep it from keeping C<ev_run>
713	running when nothing else is active.	928	running when nothing else is active.
714		929
715	ev_signal exitsig;	930	ev_signal exitsig;
716	ev_signal_init (&exitsig, sig_cb, SIGINT);	931	ev_signal_init (&exitsig, sig_cb, SIGINT);
717	ev_signal_start (loop, &exitsig);	932	ev_signal_start (loop, &exitsig);
718	evf_unref (loop);	933	ev_unref (loop);
719		934
720	Example: For some weird reason, unregister the above signal handler again.	935	Example: For some weird reason, unregister the above signal handler again.
721		936
722	ev_ref (loop);	937	ev_ref (loop);
723	ev_signal_stop (loop, &exitsig);	938	ev_signal_stop (loop, &exitsig);
…		…
743	overhead for the actual polling but can deliver many events at once.	958	overhead for the actual polling but can deliver many events at once.
744		959
745	By setting a higher I<io collect interval> you allow libev to spend more	960	By setting a higher I<io collect interval> you allow libev to spend more
746	time collecting I/O events, so you can handle more events per iteration,	961	time collecting I/O events, so you can handle more events per iteration,
747	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	962	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
748	C<ev_timer>) will be not affected. Setting this to a non-null value will	963	C<ev_timer>) will not be affected. Setting this to a non-null value will
749	introduce an additional C<ev_sleep ()> call into most loop iterations.	964	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		965	sleep time ensures that libev will not poll for I/O events more often then
		966	once per this interval, on average (as long as the host time resolution is
		967	good enough).
750		968
751	Likewise, by setting a higher I<timeout collect interval> you allow libev	969	Likewise, by setting a higher I<timeout collect interval> you allow libev
752	to spend more time collecting timeouts, at the expense of increased	970	to spend more time collecting timeouts, at the expense of increased
753	latency/jitter/inexactness (the watcher callback will be called	971	latency/jitter/inexactness (the watcher callback will be called
754	later). C<ev_io> watchers will not be affected. Setting this to a non-null	972	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
756		974
757	Many (busy) programs can usually benefit by setting the I/O collect	975	Many (busy) programs can usually benefit by setting the I/O collect
758	interval to a value near C<0.1> or so, which is often enough for	976	interval to a value near C<0.1> or so, which is often enough for
759	interactive servers (of course not for games), likewise for timeouts. It	977	interactive servers (of course not for games), likewise for timeouts. It
760	usually doesn't make much sense to set it to a lower value than C<0.01>,	978	usually doesn't make much sense to set it to a lower value than C<0.01>,
761	as this approaches the timing granularity of most systems.	979	as this approaches the timing granularity of most systems. Note that if
		980	you do transactions with the outside world and you can't increase the
		981	parallelity, then this setting will limit your transaction rate (if you
		982	need to poll once per transaction and the I/O collect interval is 0.01,
		983	then you can't do more than 100 transactions per second).
762		984
763	Setting the I<timeout collect interval> can improve the opportunity for	985	Setting the I<timeout collect interval> can improve the opportunity for
764	saving power, as the program will "bundle" timer callback invocations that	986	saving power, as the program will "bundle" timer callback invocations that
765	are "near" in time together, by delaying some, thus reducing the number of	987	are "near" in time together, by delaying some, thus reducing the number of
766	times the process sleeps and wakes up again. Another useful technique to	988	times the process sleeps and wakes up again. Another useful technique to
767	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	989	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
768	they fire on, say, one-second boundaries only.	990	they fire on, say, one-second boundaries only.
769		991
		992	Example: we only need 0.1s timeout granularity, and we wish not to poll
		993	more often than 100 times per second:
		994
		995	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		996	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		997
		998	=item ev_invoke_pending (loop)
		999
		1000	This call will simply invoke all pending watchers while resetting their
		1001	pending state. Normally, C<ev_run> does this automatically when required,
		1002	but when overriding the invoke callback this call comes handy. This
		1003	function can be invoked from a watcher - this can be useful for example
		1004	when you want to do some lengthy calculation and want to pass further
		1005	event handling to another thread (you still have to make sure only one
		1006	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		1007
		1008	=item int ev_pending_count (loop)
		1009
		1010	Returns the number of pending watchers - zero indicates that no watchers
		1011	are pending.
		1012
		1013	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		1014
		1015	This overrides the invoke pending functionality of the loop: Instead of
		1016	invoking all pending watchers when there are any, C<ev_run> will call
		1017	this callback instead. This is useful, for example, when you want to
		1018	invoke the actual watchers inside another context (another thread etc.).
		1019
		1020	If you want to reset the callback, use C<ev_invoke_pending> as new
		1021	callback.
		1022
		1023	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
		1024
		1025	Sometimes you want to share the same loop between multiple threads. This
		1026	can be done relatively simply by putting mutex_lock/unlock calls around
		1027	each call to a libev function.
		1028
		1029	However, C<ev_run> can run an indefinite time, so it is not feasible
		1030	to wait for it to return. One way around this is to wake up the event
		1031	loop via C<ev_break> and C<ev_async_send>, another way is to set these
		1032	I<release> and I<acquire> callbacks on the loop.
		1033
		1034	When set, then C<release> will be called just before the thread is
		1035	suspended waiting for new events, and C<acquire> is called just
		1036	afterwards.
		1037
		1038	Ideally, C<release> will just call your mutex_unlock function, and
		1039	C<acquire> will just call the mutex_lock function again.
		1040
		1041	While event loop modifications are allowed between invocations of
		1042	C<release> and C<acquire> (that's their only purpose after all), no
		1043	modifications done will affect the event loop, i.e. adding watchers will
		1044	have no effect on the set of file descriptors being watched, or the time
		1045	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		1046	to take note of any changes you made.
		1047
		1048	In theory, threads executing C<ev_run> will be async-cancel safe between
		1049	invocations of C<release> and C<acquire>.
		1050
		1051	See also the locking example in the C<THREADS> section later in this
		1052	document.
		1053
		1054	=item ev_set_userdata (loop, void *data)
		1055
		1056	=item void *ev_userdata (loop)
		1057
		1058	Set and retrieve a single C<void *> associated with a loop. When
		1059	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		1060	C<0>.
		1061
		1062	These two functions can be used to associate arbitrary data with a loop,
		1063	and are intended solely for the C<invoke_pending_cb>, C<release> and
		1064	C<acquire> callbacks described above, but of course can be (ab-)used for
		1065	any other purpose as well.
		1066
770	=item ev_loop_verify (loop)	1067	=item ev_verify (loop)
771		1068
772	This function only does something when C<EV_VERIFY> support has been	1069	This function only does something when C<EV_VERIFY> support has been
773	compiled in. which is the default for non-minimal builds. It tries to go	1070	compiled in, which is the default for non-minimal builds. It tries to go
774	through all internal structures and checks them for validity. If anything	1071	through all internal structures and checks them for validity. If anything
775	is found to be inconsistent, it will print an error message to standard	1072	is found to be inconsistent, it will print an error message to standard
776	error and call C<abort ()>.	1073	error and call C<abort ()>.
777		1074
778	This can be used to catch bugs inside libev itself: under normal	1075	This can be used to catch bugs inside libev itself: under normal
…		…
782	=back	1079	=back
783		1080
784		1081
785	=head1 ANATOMY OF A WATCHER	1082	=head1 ANATOMY OF A WATCHER
786		1083
		1084	In the following description, uppercase C<TYPE> in names stands for the
		1085	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		1086	watchers and C<ev_io_start> for I/O watchers.
		1087
787	A watcher is a structure that you create and register to record your	1088	A watcher is an opaque structure that you allocate and register to record
788	interest in some event. For instance, if you want to wait for STDIN to	1089	your interest in some event. To make a concrete example, imagine you want
789	become readable, you would create an C<ev_io> watcher for that:	1090	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1091	for that:
790		1092
791	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1093	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
792	{	1094	{
793	ev_io_stop (w);	1095	ev_io_stop (w);
794	ev_unloop (loop, EVUNLOOP_ALL);	1096	ev_break (loop, EVBREAK_ALL);
795	}	1097	}
796		1098
797	struct ev_loop *loop = ev_default_loop (0);	1099	struct ev_loop *loop = ev_default_loop (0);
		1100
798	ev_io stdin_watcher;	1101	ev_io stdin_watcher;
		1102
799	ev_init (&stdin_watcher, my_cb);	1103	ev_init (&stdin_watcher, my_cb);
800	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1104	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
801	ev_io_start (loop, &stdin_watcher);	1105	ev_io_start (loop, &stdin_watcher);
		1106
802	ev_loop (loop, 0);	1107	ev_run (loop, 0);
803		1108
804	As you can see, you are responsible for allocating the memory for your	1109	As you can see, you are responsible for allocating the memory for your
805	watcher structures (and it is usually a bad idea to do this on the stack,	1110	watcher structures (and it is I<usually> a bad idea to do this on the
806	although this can sometimes be quite valid).	1111	stack).
807		1112
		1113	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		1114	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
		1115
808	Each watcher structure must be initialised by a call to C<ev_init	1116	Each watcher structure must be initialised by a call to C<ev_init (watcher
809	(watcher *, callback)>, which expects a callback to be provided. This	1117	*, callback)>, which expects a callback to be provided. This callback is
810	callback gets invoked each time the event occurs (or, in the case of I/O	1118	invoked each time the event occurs (or, in the case of I/O watchers, each
811	watchers, each time the event loop detects that the file descriptor given	1119	time the event loop detects that the file descriptor given is readable
812	is readable and/or writable).	1120	and/or writable).
813		1121
814	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1122	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
815	with arguments specific to this watcher type. There is also a macro	1123	macro to configure it, with arguments specific to the watcher type. There
816	to combine initialisation and setting in one call: C<< ev_<type>_init	1124	is also a macro to combine initialisation and setting in one call: C<<
817	(watcher *, callback, ...) >>.	1125	ev_TYPE_init (watcher *, callback, ...) >>.
818		1126
819	To make the watcher actually watch out for events, you have to start it	1127	To make the watcher actually watch out for events, you have to start it
820	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	1128	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
821	*) >>), and you can stop watching for events at any time by calling the	1129	*) >>), and you can stop watching for events at any time by calling the
822	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1130	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
823		1131
824	As long as your watcher is active (has been started but not stopped) you	1132	As long as your watcher is active (has been started but not stopped) you
825	must not touch the values stored in it. Most specifically you must never	1133	must not touch the values stored in it. Most specifically you must never
826	reinitialise it or call its C<set> macro.	1134	reinitialise it or call its C<ev_TYPE_set> macro.
827		1135
828	Each and every callback receives the event loop pointer as first, the	1136	Each and every callback receives the event loop pointer as first, the
829	registered watcher structure as second, and a bitset of received events as	1137	registered watcher structure as second, and a bitset of received events as
830	third argument.	1138	third argument.
831		1139
…		…
840	=item C<EV_WRITE>	1148	=item C<EV_WRITE>
841		1149
842	The file descriptor in the C<ev_io> watcher has become readable and/or	1150	The file descriptor in the C<ev_io> watcher has become readable and/or
843	writable.	1151	writable.
844		1152
845	=item C<EV_TIMEOUT>	1153	=item C<EV_TIMER>
846		1154
847	The C<ev_timer> watcher has timed out.	1155	The C<ev_timer> watcher has timed out.
848		1156
849	=item C<EV_PERIODIC>	1157	=item C<EV_PERIODIC>
850		1158
…		…
868		1176
869	=item C<EV_PREPARE>	1177	=item C<EV_PREPARE>
870		1178
871	=item C<EV_CHECK>	1179	=item C<EV_CHECK>
872		1180
873	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1181	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to
874	to gather new events, and all C<ev_check> watchers are invoked just after	1182	gather new events, and all C<ev_check> watchers are queued (not invoked)
875	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1183	just after C<ev_run> has gathered them, but before it queues any callbacks
		1184	for any received events. That means C<ev_prepare> watchers are the last
		1185	watchers invoked before the event loop sleeps or polls for new events, and
		1186	C<ev_check> watchers will be invoked before any other watchers of the same
		1187	or lower priority within an event loop iteration.
		1188
876	received events. Callbacks of both watcher types can start and stop as	1189	Callbacks of both watcher types can start and stop as many watchers as
877	many watchers as they want, and all of them will be taken into account	1190	they want, and all of them will be taken into account (for example, a
878	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1191	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
879	C<ev_loop> from blocking).	1192	blocking).
880		1193
881	=item C<EV_EMBED>	1194	=item C<EV_EMBED>
882		1195
883	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1196	The embedded event loop specified in the C<ev_embed> watcher needs attention.
884		1197
885	=item C<EV_FORK>	1198	=item C<EV_FORK>
886		1199
887	The event loop has been resumed in the child process after fork (see	1200	The event loop has been resumed in the child process after fork (see
888	C<ev_fork>).	1201	C<ev_fork>).
889		1202
		1203	=item C<EV_CLEANUP>
		1204
		1205	The event loop is about to be destroyed (see C<ev_cleanup>).
		1206
890	=item C<EV_ASYNC>	1207	=item C<EV_ASYNC>
891		1208
892	The given async watcher has been asynchronously notified (see C<ev_async>).	1209	The given async watcher has been asynchronously notified (see C<ev_async>).
		1210
		1211	=item C<EV_CUSTOM>
		1212
		1213	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1214	by libev users to signal watchers (e.g. via C<ev_feed_event>).
893		1215
894	=item C<EV_ERROR>	1216	=item C<EV_ERROR>
895		1217
896	An unspecified error has occurred, the watcher has been stopped. This might	1218	An unspecified error has occurred, the watcher has been stopped. This might
897	happen because the watcher could not be properly started because libev	1219	happen because the watcher could not be properly started because libev
…		…
912		1234
913	=back	1235	=back
914		1236
915	=head2 GENERIC WATCHER FUNCTIONS	1237	=head2 GENERIC WATCHER FUNCTIONS
916		1238
917	In the following description, C<TYPE> stands for the watcher type,
918	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
919
920	=over 4	1239	=over 4
921		1240
922	=item C<ev_init> (ev_TYPE *watcher, callback)	1241	=item C<ev_init> (ev_TYPE *watcher, callback)
923		1242
924	This macro initialises the generic portion of a watcher. The contents	1243	This macro initialises the generic portion of a watcher. The contents
…		…
938		1257
939	ev_io w;	1258	ev_io w;
940	ev_init (&w, my_cb);	1259	ev_init (&w, my_cb);
941	ev_io_set (&w, STDIN_FILENO, EV_READ);	1260	ev_io_set (&w, STDIN_FILENO, EV_READ);
942		1261
943	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1262	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
944		1263
945	This macro initialises the type-specific parts of a watcher. You need to	1264	This macro initialises the type-specific parts of a watcher. You need to
946	call C<ev_init> at least once before you call this macro, but you can	1265	call C<ev_init> at least once before you call this macro, but you can
947	call C<ev_TYPE_set> any number of times. You must not, however, call this	1266	call C<ev_TYPE_set> any number of times. You must not, however, call this
948	macro on a watcher that is active (it can be pending, however, which is a	1267	macro on a watcher that is active (it can be pending, however, which is a
…		…
961		1280
962	Example: Initialise and set an C<ev_io> watcher in one step.	1281	Example: Initialise and set an C<ev_io> watcher in one step.
963		1282
964	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1283	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
965		1284
966	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1285	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
967		1286
968	Starts (activates) the given watcher. Only active watchers will receive	1287	Starts (activates) the given watcher. Only active watchers will receive
969	events. If the watcher is already active nothing will happen.	1288	events. If the watcher is already active nothing will happen.
970		1289
971	Example: Start the C<ev_io> watcher that is being abused as example in this	1290	Example: Start the C<ev_io> watcher that is being abused as example in this
972	whole section.	1291	whole section.
973		1292
974	ev_io_start (EV_DEFAULT_UC, &w);	1293	ev_io_start (EV_DEFAULT_UC, &w);
975		1294
976	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1295	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
977		1296
978	Stops the given watcher if active, and clears the pending status (whether	1297	Stops the given watcher if active, and clears the pending status (whether
979	the watcher was active or not).	1298	the watcher was active or not).
980		1299
981	It is possible that stopped watchers are pending - for example,	1300	It is possible that stopped watchers are pending - for example,
…		…
1001		1320
1002	=item callback ev_cb (ev_TYPE *watcher)	1321	=item callback ev_cb (ev_TYPE *watcher)
1003		1322
1004	Returns the callback currently set on the watcher.	1323	Returns the callback currently set on the watcher.
1005		1324
1006	=item ev_cb_set (ev_TYPE *watcher, callback)	1325	=item ev_set_cb (ev_TYPE *watcher, callback)
1007		1326
1008	Change the callback. You can change the callback at virtually any time	1327	Change the callback. You can change the callback at virtually any time
1009	(modulo threads).	1328	(modulo threads).
1010		1329
1011	=item ev_set_priority (ev_TYPE *watcher, priority)	1330	=item ev_set_priority (ev_TYPE *watcher, int priority)
1012		1331
1013	=item int ev_priority (ev_TYPE *watcher)	1332	=item int ev_priority (ev_TYPE *watcher)
1014		1333
1015	Set and query the priority of the watcher. The priority is a small	1334	Set and query the priority of the watcher. The priority is a small
1016	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1335	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1017	(default: C<-2>). Pending watchers with higher priority will be invoked	1336	(default: C<-2>). Pending watchers with higher priority will be invoked
1018	before watchers with lower priority, but priority will not keep watchers	1337	before watchers with lower priority, but priority will not keep watchers
1019	from being executed (except for C<ev_idle> watchers).	1338	from being executed (except for C<ev_idle> watchers).
1020		1339
1021	This means that priorities are I<only> used for ordering callback
1022	invocation after new events have been received. This is useful, for
1023	example, to reduce latency after idling, or more often, to bind two
1024	watchers on the same event and make sure one is called first.
1025
1026	If you need to suppress invocation when higher priority events are pending	1340	If you need to suppress invocation when higher priority events are pending
1027	you need to look at C<ev_idle> watchers, which provide this functionality.	1341	you need to look at C<ev_idle> watchers, which provide this functionality.
1028		1342
1029	You I<must not> change the priority of a watcher as long as it is active or	1343	You I<must not> change the priority of a watcher as long as it is active or
1030	pending.	1344	pending.
1031		1345
		1346	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1347	fine, as long as you do not mind that the priority value you query might
		1348	or might not have been clamped to the valid range.
		1349
1032	The default priority used by watchers when no priority has been set is	1350	The default priority used by watchers when no priority has been set is
1033	always C<0>, which is supposed to not be too high and not be too low :).	1351	always C<0>, which is supposed to not be too high and not be too low :).
1034		1352
1035	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1353	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1036	fine, as long as you do not mind that the priority value you query might	1354	priorities.
1037	or might not have been adjusted to be within valid range.
1038		1355
1039	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1356	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1040		1357
1041	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1358	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1042	C<loop> nor C<revents> need to be valid as long as the watcher callback	1359	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1050	watcher isn't pending it does nothing and returns C<0>.	1367	watcher isn't pending it does nothing and returns C<0>.
1051		1368
1052	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1369	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1053	callback to be invoked, which can be accomplished with this function.	1370	callback to be invoked, which can be accomplished with this function.
1054		1371
		1372	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1373
		1374	Feeds the given event set into the event loop, as if the specified event
		1375	had happened for the specified watcher (which must be a pointer to an
		1376	initialised but not necessarily started event watcher). Obviously you must
		1377	not free the watcher as long as it has pending events.
		1378
		1379	Stopping the watcher, letting libev invoke it, or calling
		1380	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1381	not started in the first place.
		1382
		1383	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1384	functions that do not need a watcher.
		1385
1055	=back	1386	=back
1056		1387
		1388	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
		1389	OWN COMPOSITE WATCHERS> idioms.
1057		1390
1058	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1391	=head2 WATCHER STATES
1059		1392
1060	Each watcher has, by default, a member C<void *data> that you can change	1393	There are various watcher states mentioned throughout this manual -
1061	and read at any time: libev will completely ignore it. This can be used	1394	active, pending and so on. In this section these states and the rules to
1062	to associate arbitrary data with your watcher. If you need more data and	1395	transition between them will be described in more detail - and while these
1063	don't want to allocate memory and store a pointer to it in that data	1396	rules might look complicated, they usually do "the right thing".
1064	member, you can also "subclass" the watcher type and provide your own
1065	data:
1066		1397
1067	struct my_io	1398	=over 4
		1399
		1400	=item initialised
		1401
		1402	Before a watcher can be registered with the event loop it has to be
		1403	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1404	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1405
		1406	In this state it is simply some block of memory that is suitable for
		1407	use in an event loop. It can be moved around, freed, reused etc. at
		1408	will - as long as you either keep the memory contents intact, or call
		1409	C<ev_TYPE_init> again.
		1410
		1411	=item started/running/active
		1412
		1413	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1414	property of the event loop, and is actively waiting for events. While in
		1415	this state it cannot be accessed (except in a few documented ways), moved,
		1416	freed or anything else - the only legal thing is to keep a pointer to it,
		1417	and call libev functions on it that are documented to work on active watchers.
		1418
		1419	=item pending
		1420
		1421	If a watcher is active and libev determines that an event it is interested
		1422	in has occurred (such as a timer expiring), it will become pending. It will
		1423	stay in this pending state until either it is stopped or its callback is
		1424	about to be invoked, so it is not normally pending inside the watcher
		1425	callback.
		1426
		1427	The watcher might or might not be active while it is pending (for example,
		1428	an expired non-repeating timer can be pending but no longer active). If it
		1429	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1430	but it is still property of the event loop at this time, so cannot be
		1431	moved, freed or reused. And if it is active the rules described in the
		1432	previous item still apply.
		1433
		1434	It is also possible to feed an event on a watcher that is not active (e.g.
		1435	via C<ev_feed_event>), in which case it becomes pending without being
		1436	active.
		1437
		1438	=item stopped
		1439
		1440	A watcher can be stopped implicitly by libev (in which case it might still
		1441	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1442	latter will clear any pending state the watcher might be in, regardless
		1443	of whether it was active or not, so stopping a watcher explicitly before
		1444	freeing it is often a good idea.
		1445
		1446	While stopped (and not pending) the watcher is essentially in the
		1447	initialised state, that is, it can be reused, moved, modified in any way
		1448	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1449	it again).
		1450
		1451	=back
		1452
		1453	=head2 WATCHER PRIORITY MODELS
		1454
		1455	Many event loops support I<watcher priorities>, which are usually small
		1456	integers that influence the ordering of event callback invocation
		1457	between watchers in some way, all else being equal.
		1458
		1459	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1460	description for the more technical details such as the actual priority
		1461	range.
		1462
		1463	There are two common ways how these these priorities are being interpreted
		1464	by event loops:
		1465
		1466	In the more common lock-out model, higher priorities "lock out" invocation
		1467	of lower priority watchers, which means as long as higher priority
		1468	watchers receive events, lower priority watchers are not being invoked.
		1469
		1470	The less common only-for-ordering model uses priorities solely to order
		1471	callback invocation within a single event loop iteration: Higher priority
		1472	watchers are invoked before lower priority ones, but they all get invoked
		1473	before polling for new events.
		1474
		1475	Libev uses the second (only-for-ordering) model for all its watchers
		1476	except for idle watchers (which use the lock-out model).
		1477
		1478	The rationale behind this is that implementing the lock-out model for
		1479	watchers is not well supported by most kernel interfaces, and most event
		1480	libraries will just poll for the same events again and again as long as
		1481	their callbacks have not been executed, which is very inefficient in the
		1482	common case of one high-priority watcher locking out a mass of lower
		1483	priority ones.
		1484
		1485	Static (ordering) priorities are most useful when you have two or more
		1486	watchers handling the same resource: a typical usage example is having an
		1487	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1488	timeouts. Under load, data might be received while the program handles
		1489	other jobs, but since timers normally get invoked first, the timeout
		1490	handler will be executed before checking for data. In that case, giving
		1491	the timer a lower priority than the I/O watcher ensures that I/O will be
		1492	handled first even under adverse conditions (which is usually, but not
		1493	always, what you want).
		1494
		1495	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1496	will only be executed when no same or higher priority watchers have
		1497	received events, they can be used to implement the "lock-out" model when
		1498	required.
		1499
		1500	For example, to emulate how many other event libraries handle priorities,
		1501	you can associate an C<ev_idle> watcher to each such watcher, and in
		1502	the normal watcher callback, you just start the idle watcher. The real
		1503	processing is done in the idle watcher callback. This causes libev to
		1504	continuously poll and process kernel event data for the watcher, but when
		1505	the lock-out case is known to be rare (which in turn is rare :), this is
		1506	workable.
		1507
		1508	Usually, however, the lock-out model implemented that way will perform
		1509	miserably under the type of load it was designed to handle. In that case,
		1510	it might be preferable to stop the real watcher before starting the
		1511	idle watcher, so the kernel will not have to process the event in case
		1512	the actual processing will be delayed for considerable time.
		1513
		1514	Here is an example of an I/O watcher that should run at a strictly lower
		1515	priority than the default, and which should only process data when no
		1516	other events are pending:
		1517
		1518	ev_idle idle; // actual processing watcher
		1519	ev_io io; // actual event watcher
		1520
		1521	static void
		1522	io_cb (EV_P_ ev_io *w, int revents)
1068	{	1523	{
1069	ev_io io;	1524	// stop the I/O watcher, we received the event, but
1070	int otherfd;	1525	// are not yet ready to handle it.
1071	void *somedata;	1526	ev_io_stop (EV_A_ w);
1072	struct whatever *mostinteresting;	1527
		1528	// start the idle watcher to handle the actual event.
		1529	// it will not be executed as long as other watchers
		1530	// with the default priority are receiving events.
		1531	ev_idle_start (EV_A_ &idle);
1073	};	1532	}
1074		1533
1075	...	1534	static void
1076	struct my_io w;	1535	idle_cb (EV_P_ ev_idle *w, int revents)
1077	ev_io_init (&w.io, my_cb, fd, EV_READ);
1078
1079	And since your callback will be called with a pointer to the watcher, you
1080	can cast it back to your own type:
1081
1082	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1083	{	1536	{
1084	struct my_io *w = (struct my_io *)w_;	1537	// actual processing
1085	...	1538	read (STDIN_FILENO, ...);
		1539
		1540	// have to start the I/O watcher again, as
		1541	// we have handled the event
		1542	ev_io_start (EV_P_ &io);
1086	}	1543	}
1087		1544
1088	More interesting and less C-conformant ways of casting your callback type	1545	// initialisation
1089	instead have been omitted.	1546	ev_idle_init (&idle, idle_cb);
		1547	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1548	ev_io_start (EV_DEFAULT_ &io);
1090		1549
1091	Another common scenario is to use some data structure with multiple	1550	In the "real" world, it might also be beneficial to start a timer, so that
1092	embedded watchers:	1551	low-priority connections can not be locked out forever under load. This
1093		1552	enables your program to keep a lower latency for important connections
1094	struct my_biggy	1553	during short periods of high load, while not completely locking out less
1095	{	1554	important ones.
1096	int some_data;
1097	ev_timer t1;
1098	ev_timer t2;
1099	}
1100
1101	In this case getting the pointer to C<my_biggy> is a bit more
1102	complicated: Either you store the address of your C<my_biggy> struct
1103	in the C<data> member of the watcher (for woozies), or you need to use
1104	some pointer arithmetic using C<offsetof> inside your watchers (for real
1105	programmers):
1106
1107	#include <stddef.h>
1108
1109	static void
1110	t1_cb (EV_P_ ev_timer *w, int revents)
1111	{
1112	struct my_biggy big = (struct my_biggy *
1113	(((char *)w) - offsetof (struct my_biggy, t1));
1114	}
1115
1116	static void
1117	t2_cb (EV_P_ ev_timer *w, int revents)
1118	{
1119	struct my_biggy big = (struct my_biggy *
1120	(((char *)w) - offsetof (struct my_biggy, t2));
1121	}
1122		1555
1123		1556
1124	=head1 WATCHER TYPES	1557	=head1 WATCHER TYPES
1125		1558
1126	This section describes each watcher in detail, but will not repeat	1559	This section describes each watcher in detail, but will not repeat
…		…
1150	In general you can register as many read and/or write event watchers per	1583	In general you can register as many read and/or write event watchers per
1151	fd as you want (as long as you don't confuse yourself). Setting all file	1584	fd as you want (as long as you don't confuse yourself). Setting all file
1152	descriptors to non-blocking mode is also usually a good idea (but not	1585	descriptors to non-blocking mode is also usually a good idea (but not
1153	required if you know what you are doing).	1586	required if you know what you are doing).
1154		1587
1155	If you cannot use non-blocking mode, then force the use of a
1156	known-to-be-good backend (at the time of this writing, this includes only
1157	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1158
1159	Another thing you have to watch out for is that it is quite easy to	1588	Another thing you have to watch out for is that it is quite easy to
1160	receive "spurious" readiness notifications, that is your callback might	1589	receive "spurious" readiness notifications, that is, your callback might
1161	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1590	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1162	because there is no data. Not only are some backends known to create a	1591	because there is no data. It is very easy to get into this situation even
1163	lot of those (for example Solaris ports), it is very easy to get into	1592	with a relatively standard program structure. Thus it is best to always
1164	this situation even with a relatively standard program structure. Thus	1593	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1165	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1166	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1594	preferable to a program hanging until some data arrives.
1167		1595
1168	If you cannot run the fd in non-blocking mode (for example you should	1596	If you cannot run the fd in non-blocking mode (for example you should
1169	not play around with an Xlib connection), then you have to separately	1597	not play around with an Xlib connection), then you have to separately
1170	re-test whether a file descriptor is really ready with a known-to-be good	1598	re-test whether a file descriptor is really ready with a known-to-be good
1171	interface such as poll (fortunately in our Xlib example, Xlib already	1599	interface such as poll (fortunately in the case of Xlib, it already does
1172	does this on its own, so its quite safe to use). Some people additionally	1600	this on its own, so its quite safe to use). Some people additionally
1173	use C<SIGALRM> and an interval timer, just to be sure you won't block	1601	use C<SIGALRM> and an interval timer, just to be sure you won't block
1174	indefinitely.	1602	indefinitely.
1175		1603
1176	But really, best use non-blocking mode.	1604	But really, best use non-blocking mode.
1177		1605
…		…
1205		1633
1206	There is no workaround possible except not registering events	1634	There is no workaround possible except not registering events
1207	for potentially C<dup ()>'ed file descriptors, or to resort to	1635	for potentially C<dup ()>'ed file descriptors, or to resort to
1208	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1636	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1209		1637
		1638	=head3 The special problem of files
		1639
		1640	Many people try to use C<select> (or libev) on file descriptors
		1641	representing files, and expect it to become ready when their program
		1642	doesn't block on disk accesses (which can take a long time on their own).
		1643
		1644	However, this cannot ever work in the "expected" way - you get a readiness
		1645	notification as soon as the kernel knows whether and how much data is
		1646	there, and in the case of open files, that's always the case, so you
		1647	always get a readiness notification instantly, and your read (or possibly
		1648	write) will still block on the disk I/O.
		1649
		1650	Another way to view it is that in the case of sockets, pipes, character
		1651	devices and so on, there is another party (the sender) that delivers data
		1652	on its own, but in the case of files, there is no such thing: the disk
		1653	will not send data on its own, simply because it doesn't know what you
		1654	wish to read - you would first have to request some data.
		1655
		1656	Since files are typically not-so-well supported by advanced notification
		1657	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1658	to files, even though you should not use it. The reason for this is
		1659	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1660	usually a tty, often a pipe, but also sometimes files or special devices
		1661	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1662	F</dev/urandom>), and even though the file might better be served with
		1663	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1664	it "just works" instead of freezing.
		1665
		1666	So avoid file descriptors pointing to files when you know it (e.g. use
		1667	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1668	when you rarely read from a file instead of from a socket, and want to
		1669	reuse the same code path.
		1670
1210	=head3 The special problem of fork	1671	=head3 The special problem of fork
1211		1672
1212	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1673	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1213	useless behaviour. Libev fully supports fork, but needs to be told about	1674	useless behaviour. Libev fully supports fork, but needs to be told about
1214	it in the child.	1675	it in the child if you want to continue to use it in the child.
1215		1676
1216	To support fork in your programs, you either have to call	1677	To support fork in your child processes, you have to call C<ev_loop_fork
1217	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1678	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1218	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1679	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1219	C<EVBACKEND_POLL>.
1220		1680
1221	=head3 The special problem of SIGPIPE	1681	=head3 The special problem of SIGPIPE
1222		1682
1223	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1683	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1224	when writing to a pipe whose other end has been closed, your program gets	1684	when writing to a pipe whose other end has been closed, your program gets
…		…
1227		1687
1228	So when you encounter spurious, unexplained daemon exits, make sure you	1688	So when you encounter spurious, unexplained daemon exits, make sure you
1229	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1689	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1230	somewhere, as that would have given you a big clue).	1690	somewhere, as that would have given you a big clue).
1231		1691
		1692	=head3 The special problem of accept()ing when you can't
		1693
		1694	Many implementations of the POSIX C<accept> function (for example,
		1695	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1696	connection from the pending queue in all error cases.
		1697
		1698	For example, larger servers often run out of file descriptors (because
		1699	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1700	rejecting the connection, leading to libev signalling readiness on
		1701	the next iteration again (the connection still exists after all), and
		1702	typically causing the program to loop at 100% CPU usage.
		1703
		1704	Unfortunately, the set of errors that cause this issue differs between
		1705	operating systems, there is usually little the app can do to remedy the
		1706	situation, and no known thread-safe method of removing the connection to
		1707	cope with overload is known (to me).
		1708
		1709	One of the easiest ways to handle this situation is to just ignore it
		1710	- when the program encounters an overload, it will just loop until the
		1711	situation is over. While this is a form of busy waiting, no OS offers an
		1712	event-based way to handle this situation, so it's the best one can do.
		1713
		1714	A better way to handle the situation is to log any errors other than
		1715	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1716	messages, and continue as usual, which at least gives the user an idea of
		1717	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1718	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1719	usage.
		1720
		1721	If your program is single-threaded, then you could also keep a dummy file
		1722	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1723	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1724	close that fd, and create a new dummy fd. This will gracefully refuse
		1725	clients under typical overload conditions.
		1726
		1727	The last way to handle it is to simply log the error and C<exit>, as
		1728	is often done with C<malloc> failures, but this results in an easy
		1729	opportunity for a DoS attack.
1232		1730
1233	=head3 Watcher-Specific Functions	1731	=head3 Watcher-Specific Functions
1234		1732
1235	=over 4	1733	=over 4
1236		1734
…		…
1268	...	1766	...
1269	struct ev_loop *loop = ev_default_init (0);	1767	struct ev_loop *loop = ev_default_init (0);
1270	ev_io stdin_readable;	1768	ev_io stdin_readable;
1271	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1769	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1272	ev_io_start (loop, &stdin_readable);	1770	ev_io_start (loop, &stdin_readable);
1273	ev_loop (loop, 0);	1771	ev_run (loop, 0);
1274		1772
1275		1773
1276	=head2 C<ev_timer> - relative and optionally repeating timeouts	1774	=head2 C<ev_timer> - relative and optionally repeating timeouts
1277		1775
1278	Timer watchers are simple relative timers that generate an event after a	1776	Timer watchers are simple relative timers that generate an event after a
…		…
1283	year, it will still time out after (roughly) one hour. "Roughly" because	1781	year, it will still time out after (roughly) one hour. "Roughly" because
1284	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1782	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1285	monotonic clock option helps a lot here).	1783	monotonic clock option helps a lot here).
1286		1784
1287	The callback is guaranteed to be invoked only I<after> its timeout has	1785	The callback is guaranteed to be invoked only I<after> its timeout has
1288	passed, but if multiple timers become ready during the same loop iteration	1786	passed (not I<at>, so on systems with very low-resolution clocks this
1289	then order of execution is undefined.	1787	might introduce a small delay, see "the special problem of being too
		1788	early", below). If multiple timers become ready during the same loop
		1789	iteration then the ones with earlier time-out values are invoked before
		1790	ones of the same priority with later time-out values (but this is no
		1791	longer true when a callback calls C<ev_run> recursively).
1290		1792
1291	=head3 Be smart about timeouts	1793	=head3 Be smart about timeouts
1292		1794
1293	Many real-world problems invole some kind of time-out, usually for error	1795	Many real-world problems involve some kind of timeout, usually for error
1294	recovery. A typical example is an HTTP request - if the other side hangs,	1796	recovery. A typical example is an HTTP request - if the other side hangs,
1295	you want to raise some error after a while.	1797	you want to raise some error after a while.
1296		1798
1297	Here are some ways on how to handle this problem, from simple and	1799	What follows are some ways to handle this problem, from obvious and
1298	inefficient to very efficient.	1800	inefficient to smart and efficient.
1299		1801
1300	In the following examples a 60 second activity timeout is assumed - a	1802	In the following, a 60 second activity timeout is assumed - a timeout that
1301	timeout that gets reset to 60 seconds each time some data ("a lifesign")	1803	gets reset to 60 seconds each time there is activity (e.g. each time some
1302	was received.	1804	data or other life sign was received).
1303		1805
1304	=over 4	1806	=over 4
1305		1807
1306	=item 1. Use a timer and stop, reinitialise, start it on activity.	1808	=item 1. Use a timer and stop, reinitialise and start it on activity.
1307		1809
1308	This is the most obvious, but not the most simple way: In the beginning,	1810	This is the most obvious, but not the most simple way: In the beginning,
1309	start the watcher:	1811	start the watcher:
1310		1812
1311	ev_timer_init (timer, callback, 60., 0.);	1813	ev_timer_init (timer, callback, 60., 0.);
1312	ev_timer_start (loop, timer);	1814	ev_timer_start (loop, timer);
1313		1815
1314	Then, each time there is some activity, C<ev_timer_stop> the timer,	1816	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
1315	initialise it again, and start it:	1817	and start it again:
1316		1818
1317	ev_timer_stop (loop, timer);	1819	ev_timer_stop (loop, timer);
1318	ev_timer_set (timer, 60., 0.);	1820	ev_timer_set (timer, 60., 0.);
1319	ev_timer_start (loop, timer);	1821	ev_timer_start (loop, timer);
1320		1822
1321	This is relatively simple to implement, but means that each time there	1823	This is relatively simple to implement, but means that each time there is
1322	is some activity, libev will first have to remove the timer from it's	1824	some activity, libev will first have to remove the timer from its internal
1323	internal data strcuture and then add it again.	1825	data structure and then add it again. Libev tries to be fast, but it's
		1826	still not a constant-time operation.
1324		1827
1325	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.	1828	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
1326		1829
1327	This is the easiest way, and involves using C<ev_timer_again> instead of	1830	This is the easiest way, and involves using C<ev_timer_again> instead of
1328	C<ev_timer_start>.	1831	C<ev_timer_start>.
1329		1832
1330	For this, configure an C<ev_timer> with a C<repeat> value of C<60> and	1833	To implement this, configure an C<ev_timer> with a C<repeat> value
1331	then call C<ev_timer_again> at start and each time you successfully read	1834	of C<60> and then call C<ev_timer_again> at start and each time you
1332	or write some data. If you go into an idle state where you do not expect	1835	successfully read or write some data. If you go into an idle state where
1333	data to travel on the socket, you can C<ev_timer_stop> the timer, and	1836	you do not expect data to travel on the socket, you can C<ev_timer_stop>
1334	C<ev_timer_again> will automatically restart it if need be.	1837	the timer, and C<ev_timer_again> will automatically restart it if need be.
1335		1838
1336	That means you can ignore the C<after> value and C<ev_timer_start>	1839	That means you can ignore both the C<ev_timer_start> function and the
1337	altogether and only ever use the C<repeat> value and C<ev_timer_again>.	1840	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1841	member and C<ev_timer_again>.
1338		1842
1339	At start:	1843	At start:
1340		1844
1341	ev_timer_init (timer, callback, 0., 60.);	1845	ev_init (timer, callback);
		1846	timer->repeat = 60.;
1342	ev_timer_again (loop, timer);	1847	ev_timer_again (loop, timer);
1343		1848
1344	Each time you receive some data:	1849	Each time there is some activity:
1345		1850
1346	ev_timer_again (loop, timer);	1851	ev_timer_again (loop, timer);
1347		1852
1348	It is even possible to change the time-out on the fly:	1853	It is even possible to change the time-out on the fly, regardless of
		1854	whether the watcher is active or not:
1349		1855
1350	timer->repeat = 30.;	1856	timer->repeat = 30.;
1351	ev_timer_again (loop, timer);	1857	ev_timer_again (loop, timer);
1352		1858
1353	This is slightly more efficient then stopping/starting the timer each time	1859	This is slightly more efficient then stopping/starting the timer each time
1354	you want to modify its timeout value, as libev does not have to completely	1860	you want to modify its timeout value, as libev does not have to completely
1355	remove and re-insert the timer from/into it's internal data structure.	1861	remove and re-insert the timer from/into its internal data structure.
		1862
		1863	It is, however, even simpler than the "obvious" way to do it.
1356		1864
1357	=item 3. Let the timer time out, but then re-arm it as required.	1865	=item 3. Let the timer time out, but then re-arm it as required.
1358		1866
1359	This method is more tricky, but usually most efficient: Most timeouts are	1867	This method is more tricky, but usually most efficient: Most timeouts are
1360	relatively long compared to the loop iteration time - in our example,	1868	relatively long compared to the intervals between other activity - in
1361	within 60 seconds, there are usually many I/O events with associated	1869	our example, within 60 seconds, there are usually many I/O events with
1362	activity resets.	1870	associated activity resets.
1363		1871
1364	In this case, it would be more efficient to leave the C<ev_timer> alone,	1872	In this case, it would be more efficient to leave the C<ev_timer> alone,
1365	but remember the time of last activity, and check for a real timeout only	1873	but remember the time of last activity, and check for a real timeout only
1366	within the callback:	1874	within the callback:
1367		1875
		1876	ev_tstamp timeout = 60.;
1368	ev_tstamp last_activity; // time of last activity	1877	ev_tstamp last_activity; // time of last activity
		1878	ev_timer timer;
1369		1879
1370	static void	1880	static void
1371	callback (EV_P_ ev_timer *w, int revents)	1881	callback (EV_P_ ev_timer *w, int revents)
1372	{	1882	{
1373	ev_tstamp now = ev_now (EV_A);	1883	// calculate when the timeout would happen
1374	ev_tstamp timeout = last_activity + 60.;	1884	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1375		1885
1376	// if last_activity is older than now - timeout, we did time out	1886	// if negative, it means we the timeout already occurred
1377	if (timeout < now)	1887	if (after < 0.)
1378	{	1888	{
1379	// timeout occured, take action	1889	// timeout occurred, take action
1380	}	1890	}
1381	else	1891	else
1382	{	1892	{
1383	// callback was invoked, but there was some activity, re-arm	1893	// callback was invoked, but there was some recent
1384	// to fire in last_activity + 60.	1894	// activity. simply restart the timer to time out
1385	w->again = timeout - now;	1895	// after "after" seconds, which is the earliest time
		1896	// the timeout can occur.
		1897	ev_timer_set (w, after, 0.);
1386	ev_timer_again (EV_A_ w);	1898	ev_timer_start (EV_A_ w);
1387	}	1899	}
1388	}	1900	}
1389		1901
1390	To summarise the callback: first calculate the real time-out (defined as	1902	To summarise the callback: first calculate in how many seconds the
1391	"60 seconds after the last activity"), then check if that time has been	1903	timeout will occur (by calculating the absolute time when it would occur,
1392	reached, which means there was a real timeout. Otherwise the callback was	1904	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1393	invoked too early (timeout is in the future), so re-schedule the timer to	1905	(EV_A)> from that).
1394	fire at that future time.
1395		1906
1396	Note how C<ev_timer_again> is used, taking advantage of the	1907	If this value is negative, then we are already past the timeout, i.e. we
1397	C<ev_timer_again> optimisation when the timer is already running.	1908	timed out, and need to do whatever is needed in this case.
1398		1909
		1910	Otherwise, we now the earliest time at which the timeout would trigger,
		1911	and simply start the timer with this timeout value.
		1912
		1913	In other words, each time the callback is invoked it will check whether
		1914	the timeout occurred. If not, it will simply reschedule itself to check
		1915	again at the earliest time it could time out. Rinse. Repeat.
		1916
1399	This scheme causes more callback invocations (about one every 60 seconds),	1917	This scheme causes more callback invocations (about one every 60 seconds
1400	but virtually no calls to libev to change the timeout.	1918	minus half the average time between activity), but virtually no calls to
		1919	libev to change the timeout.
1401		1920
1402	To start the timer, simply intiialise the watcher and C<last_activity>,	1921	To start the machinery, simply initialise the watcher and set
1403	then call the callback:	1922	C<last_activity> to the current time (meaning there was some activity just
		1923	now), then call the callback, which will "do the right thing" and start
		1924	the timer:
1404		1925
		1926	last_activity = ev_now (EV_A);
1405	ev_timer_init (timer, callback);	1927	ev_init (&timer, callback);
		1928	callback (EV_A_ &timer, 0);
		1929
		1930	When there is some activity, simply store the current time in
		1931	C<last_activity>, no libev calls at all:
		1932
		1933	if (activity detected)
1406	last_activity = ev_now (loop);	1934	last_activity = ev_now (EV_A);
1407	callback (loop, timer, EV_TIMEOUT);
1408		1935
1409	And when there is some activity, simply remember the time in	1936	When your timeout value changes, then the timeout can be changed by simply
1410	C<last_activity>:	1937	providing a new value, stopping the timer and calling the callback, which
		1938	will again do the right thing (for example, time out immediately :).
1411		1939
1412	last_actiivty = ev_now (loop);	1940	timeout = new_value;
		1941	ev_timer_stop (EV_A_ &timer);
		1942	callback (EV_A_ &timer, 0);
1413		1943
1414	This technique is slightly more complex, but in most cases where the	1944	This technique is slightly more complex, but in most cases where the
1415	time-out is unlikely to be triggered, much more efficient.	1945	time-out is unlikely to be triggered, much more efficient.
1416		1946
		1947	=item 4. Wee, just use a double-linked list for your timeouts.
		1948
		1949	If there is not one request, but many thousands (millions...), all
		1950	employing some kind of timeout with the same timeout value, then one can
		1951	do even better:
		1952
		1953	When starting the timeout, calculate the timeout value and put the timeout
		1954	at the I<end> of the list.
		1955
		1956	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1957	the list is expected to fire (for example, using the technique #3).
		1958
		1959	When there is some activity, remove the timer from the list, recalculate
		1960	the timeout, append it to the end of the list again, and make sure to
		1961	update the C<ev_timer> if it was taken from the beginning of the list.
		1962
		1963	This way, one can manage an unlimited number of timeouts in O(1) time for
		1964	starting, stopping and updating the timers, at the expense of a major
		1965	complication, and having to use a constant timeout. The constant timeout
		1966	ensures that the list stays sorted.
		1967
1417	=back	1968	=back
1418		1969
		1970	So which method the best?
		1971
		1972	Method #2 is a simple no-brain-required solution that is adequate in most
		1973	situations. Method #3 requires a bit more thinking, but handles many cases
		1974	better, and isn't very complicated either. In most case, choosing either
		1975	one is fine, with #3 being better in typical situations.
		1976
		1977	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1978	rather complicated, but extremely efficient, something that really pays
		1979	off after the first million or so of active timers, i.e. it's usually
		1980	overkill :)
		1981
		1982	=head3 The special problem of being too early
		1983
		1984	If you ask a timer to call your callback after three seconds, then
		1985	you expect it to be invoked after three seconds - but of course, this
		1986	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		1987	guaranteed to any precision by libev - imagine somebody suspending the
		1988	process with a STOP signal for a few hours for example.
		1989
		1990	So, libev tries to invoke your callback as soon as possible I<after> the
		1991	delay has occurred, but cannot guarantee this.
		1992
		1993	A less obvious failure mode is calling your callback too early: many event
		1994	loops compare timestamps with a "elapsed delay >= requested delay", but
		1995	this can cause your callback to be invoked much earlier than you would
		1996	expect.
		1997
		1998	To see why, imagine a system with a clock that only offers full second
		1999	resolution (think windows if you can't come up with a broken enough OS
		2000	yourself). If you schedule a one-second timer at the time 500.9, then the
		2001	event loop will schedule your timeout to elapse at a system time of 500
		2002	(500.9 truncated to the resolution) + 1, or 501.
		2003
		2004	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2005	501" and invoke the callback 0.1s after it was started, even though a
		2006	one-second delay was requested - this is being "too early", despite best
		2007	intentions.
		2008
		2009	This is the reason why libev will never invoke the callback if the elapsed
		2010	delay equals the requested delay, but only when the elapsed delay is
		2011	larger than the requested delay. In the example above, libev would only invoke
		2012	the callback at system time 502, or 1.1s after the timer was started.
		2013
		2014	So, while libev cannot guarantee that your callback will be invoked
		2015	exactly when requested, it I<can> and I<does> guarantee that the requested
		2016	delay has actually elapsed, or in other words, it always errs on the "too
		2017	late" side of things.
		2018
1419	=head3 The special problem of time updates	2019	=head3 The special problem of time updates
1420		2020
1421	Establishing the current time is a costly operation (it usually takes at	2021	Establishing the current time is a costly operation (it usually takes
1422	least two system calls): EV therefore updates its idea of the current	2022	at least one system call): EV therefore updates its idea of the current
1423	time only before and after C<ev_loop> collects new events, which causes a	2023	time only before and after C<ev_run> collects new events, which causes a
1424	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2024	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1425	lots of events in one iteration.	2025	lots of events in one iteration.
1426		2026
1427	The relative timeouts are calculated relative to the C<ev_now ()>	2027	The relative timeouts are calculated relative to the C<ev_now ()>
1428	time. This is usually the right thing as this timestamp refers to the time	2028	time. This is usually the right thing as this timestamp refers to the time
…		…
1434		2034
1435	If the event loop is suspended for a long time, you can also force an	2035	If the event loop is suspended for a long time, you can also force an
1436	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2036	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1437	()>.	2037	()>.
1438		2038
		2039	=head3 The special problem of unsynchronised clocks
		2040
		2041	Modern systems have a variety of clocks - libev itself uses the normal
		2042	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2043	jumps).
		2044
		2045	Neither of these clocks is synchronised with each other or any other clock
		2046	on the system, so C<ev_time ()> might return a considerably different time
		2047	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2048	a call to C<gettimeofday> might return a second count that is one higher
		2049	than a directly following call to C<time>.
		2050
		2051	The moral of this is to only compare libev-related timestamps with
		2052	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2053	a second or so.
		2054
		2055	One more problem arises due to this lack of synchronisation: if libev uses
		2056	the system monotonic clock and you compare timestamps from C<ev_time>
		2057	or C<ev_now> from when you started your timer and when your callback is
		2058	invoked, you will find that sometimes the callback is a bit "early".
		2059
		2060	This is because C<ev_timer>s work in real time, not wall clock time, so
		2061	libev makes sure your callback is not invoked before the delay happened,
		2062	I<measured according to the real time>, not the system clock.
		2063
		2064	If your timeouts are based on a physical timescale (e.g. "time out this
		2065	connection after 100 seconds") then this shouldn't bother you as it is
		2066	exactly the right behaviour.
		2067
		2068	If you want to compare wall clock/system timestamps to your timers, then
		2069	you need to use C<ev_periodic>s, as these are based on the wall clock
		2070	time, where your comparisons will always generate correct results.
		2071
		2072	=head3 The special problems of suspended animation
		2073
		2074	When you leave the server world it is quite customary to hit machines that
		2075	can suspend/hibernate - what happens to the clocks during such a suspend?
		2076
		2077	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		2078	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		2079	to run until the system is suspended, but they will not advance while the
		2080	system is suspended. That means, on resume, it will be as if the program
		2081	was frozen for a few seconds, but the suspend time will not be counted
		2082	towards C<ev_timer> when a monotonic clock source is used. The real time
		2083	clock advanced as expected, but if it is used as sole clocksource, then a
		2084	long suspend would be detected as a time jump by libev, and timers would
		2085	be adjusted accordingly.
		2086
		2087	I would not be surprised to see different behaviour in different between
		2088	operating systems, OS versions or even different hardware.
		2089
		2090	The other form of suspend (job control, or sending a SIGSTOP) will see a
		2091	time jump in the monotonic clocks and the realtime clock. If the program
		2092	is suspended for a very long time, and monotonic clock sources are in use,
		2093	then you can expect C<ev_timer>s to expire as the full suspension time
		2094	will be counted towards the timers. When no monotonic clock source is in
		2095	use, then libev will again assume a timejump and adjust accordingly.
		2096
		2097	It might be beneficial for this latter case to call C<ev_suspend>
		2098	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		2099	deterministic behaviour in this case (you can do nothing against
		2100	C<SIGSTOP>).
		2101
1439	=head3 Watcher-Specific Functions and Data Members	2102	=head3 Watcher-Specific Functions and Data Members
1440		2103
1441	=over 4	2104	=over 4
1442		2105
1443	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2106	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1456	keep up with the timer (because it takes longer than those 10 seconds to	2119	keep up with the timer (because it takes longer than those 10 seconds to
1457	do stuff) the timer will not fire more than once per event loop iteration.	2120	do stuff) the timer will not fire more than once per event loop iteration.
1458		2121
1459	=item ev_timer_again (loop, ev_timer *)	2122	=item ev_timer_again (loop, ev_timer *)
1460		2123
1461	This will act as if the timer timed out and restart it again if it is	2124	This will act as if the timer timed out, and restarts it again if it is
1462	repeating. The exact semantics are:	2125	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2126	timeout to the C<repeat> value and calling C<ev_timer_start>.
1463		2127
		2128	The exact semantics are as in the following rules, all of which will be
		2129	applied to the watcher:
		2130
		2131	=over 4
		2132
1464	If the timer is pending, its pending status is cleared.	2133	=item If the timer is pending, the pending status is always cleared.
1465		2134
1466	If the timer is started but non-repeating, stop it (as if it timed out).	2135	=item If the timer is started but non-repeating, stop it (as if it timed
		2136	out, without invoking it).
1467		2137
1468	If the timer is repeating, either start it if necessary (with the	2138	=item If the timer is repeating, make the C<repeat> value the new timeout
1469	C<repeat> value), or reset the running timer to the C<repeat> value.	2139	and start the timer, if necessary.
1470		2140
		2141	=back
		2142
1471	This sounds a bit complicated, see "Be smart about timeouts", above, for a	2143	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
1472	usage example.	2144	usage example.
		2145
		2146	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2147
		2148	Returns the remaining time until a timer fires. If the timer is active,
		2149	then this time is relative to the current event loop time, otherwise it's
		2150	the timeout value currently configured.
		2151
		2152	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2153	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2154	will return C<4>. When the timer expires and is restarted, it will return
		2155	roughly C<7> (likely slightly less as callback invocation takes some time,
		2156	too), and so on.
1473		2157
1474	=item ev_tstamp repeat [read-write]	2158	=item ev_tstamp repeat [read-write]
1475		2159
1476	The current C<repeat> value. Will be used each time the watcher times out	2160	The current C<repeat> value. Will be used each time the watcher times out
1477	or C<ev_timer_again> is called, and determines the next timeout (if any),	2161	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1503	}	2187	}
1504		2188
1505	ev_timer mytimer;	2189	ev_timer mytimer;
1506	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2190	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1507	ev_timer_again (&mytimer); /* start timer */	2191	ev_timer_again (&mytimer); /* start timer */
1508	ev_loop (loop, 0);	2192	ev_run (loop, 0);
1509		2193
1510	// and in some piece of code that gets executed on any "activity":	2194	// and in some piece of code that gets executed on any "activity":
1511	// reset the timeout to start ticking again at 10 seconds	2195	// reset the timeout to start ticking again at 10 seconds
1512	ev_timer_again (&mytimer);	2196	ev_timer_again (&mytimer);
1513		2197
…		…
1515	=head2 C<ev_periodic> - to cron or not to cron?	2199	=head2 C<ev_periodic> - to cron or not to cron?
1516		2200
1517	Periodic watchers are also timers of a kind, but they are very versatile	2201	Periodic watchers are also timers of a kind, but they are very versatile
1518	(and unfortunately a bit complex).	2202	(and unfortunately a bit complex).
1519		2203
1520	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2204	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1521	but on wall clock time (absolute time). You can tell a periodic watcher	2205	relative time, the physical time that passes) but on wall clock time
1522	to trigger after some specific point in time. For example, if you tell a	2206	(absolute time, the thing you can read on your calender or clock). The
1523	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	2207	difference is that wall clock time can run faster or slower than real
1524	+ 10.>, that is, an absolute time not a delay) and then reset your system	2208	time, and time jumps are not uncommon (e.g. when you adjust your
1525	clock to January of the previous year, then it will take more than year	2209	wrist-watch).
1526	to trigger the event (unlike an C<ev_timer>, which would still trigger
1527	roughly 10 seconds later as it uses a relative timeout).
1528		2210
		2211	You can tell a periodic watcher to trigger after some specific point
		2212	in time: for example, if you tell a periodic watcher to trigger "in 10
		2213	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2214	not a delay) and then reset your system clock to January of the previous
		2215	year, then it will take a year or more to trigger the event (unlike an
		2216	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2217	it, as it uses a relative timeout).
		2218
1529	C<ev_periodic>s can also be used to implement vastly more complex timers,	2219	C<ev_periodic> watchers can also be used to implement vastly more complex
1530	such as triggering an event on each "midnight, local time", or other	2220	timers, such as triggering an event on each "midnight, local time", or
1531	complicated rules.	2221	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2222	those cannot react to time jumps.
1532		2223
1533	As with timers, the callback is guaranteed to be invoked only when the	2224	As with timers, the callback is guaranteed to be invoked only when the
1534	time (C<at>) has passed, but if multiple periodic timers become ready	2225	point in time where it is supposed to trigger has passed. If multiple
1535	during the same loop iteration, then order of execution is undefined.	2226	timers become ready during the same loop iteration then the ones with
		2227	earlier time-out values are invoked before ones with later time-out values
		2228	(but this is no longer true when a callback calls C<ev_run> recursively).
1536		2229
1537	=head3 Watcher-Specific Functions and Data Members	2230	=head3 Watcher-Specific Functions and Data Members
1538		2231
1539	=over 4	2232	=over 4
1540		2233
1541	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2234	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1542		2235
1543	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2236	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1544		2237
1545	Lots of arguments, lets sort it out... There are basically three modes of	2238	Lots of arguments, let's sort it out... There are basically three modes of
1546	operation, and we will explain them from simplest to most complex:	2239	operation, and we will explain them from simplest to most complex:
1547		2240
1548	=over 4	2241	=over 4
1549		2242
1550	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2243	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1551		2244
1552	In this configuration the watcher triggers an event after the wall clock	2245	In this configuration the watcher triggers an event after the wall clock
1553	time C<at> has passed. It will not repeat and will not adjust when a time	2246	time C<offset> has passed. It will not repeat and will not adjust when a
1554	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2247	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1555	only run when the system clock reaches or surpasses this time.	2248	will be stopped and invoked when the system clock reaches or surpasses
		2249	this point in time.
1556		2250
1557	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2251	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1558		2252
1559	In this mode the watcher will always be scheduled to time out at the next	2253	In this mode the watcher will always be scheduled to time out at the next
1560	C<at + N * interval> time (for some integer N, which can also be negative)	2254	C<offset + N * interval> time (for some integer N, which can also be
1561	and then repeat, regardless of any time jumps.	2255	negative) and then repeat, regardless of any time jumps. The C<offset>
		2256	argument is merely an offset into the C<interval> periods.
1562		2257
1563	This can be used to create timers that do not drift with respect to the	2258	This can be used to create timers that do not drift with respect to the
1564	system clock, for example, here is a C<ev_periodic> that triggers each	2259	system clock, for example, here is an C<ev_periodic> that triggers each
1565	hour, on the hour:	2260	hour, on the hour (with respect to UTC):
1566		2261
1567	ev_periodic_set (&periodic, 0., 3600., 0);	2262	ev_periodic_set (&periodic, 0., 3600., 0);
1568		2263
1569	This doesn't mean there will always be 3600 seconds in between triggers,	2264	This doesn't mean there will always be 3600 seconds in between triggers,
1570	but only that the callback will be called when the system time shows a	2265	but only that the callback will be called when the system time shows a
1571	full hour (UTC), or more correctly, when the system time is evenly divisible	2266	full hour (UTC), or more correctly, when the system time is evenly divisible
1572	by 3600.	2267	by 3600.
1573		2268
1574	Another way to think about it (for the mathematically inclined) is that	2269	Another way to think about it (for the mathematically inclined) is that
1575	C<ev_periodic> will try to run the callback in this mode at the next possible	2270	C<ev_periodic> will try to run the callback in this mode at the next possible
1576	time where C<time = at (mod interval)>, regardless of any time jumps.	2271	time where C<time = offset (mod interval)>, regardless of any time jumps.
1577		2272
1578	For numerical stability it is preferable that the C<at> value is near	2273	The C<interval> I<MUST> be positive, and for numerical stability, the
1579	C<ev_now ()> (the current time), but there is no range requirement for	2274	interval value should be higher than C<1/8192> (which is around 100
1580	this value, and in fact is often specified as zero.	2275	microseconds) and C<offset> should be higher than C<0> and should have
		2276	at most a similar magnitude as the current time (say, within a factor of
		2277	ten). Typical values for offset are, in fact, C<0> or something between
		2278	C<0> and C<interval>, which is also the recommended range.
1581		2279
1582	Note also that there is an upper limit to how often a timer can fire (CPU	2280	Note also that there is an upper limit to how often a timer can fire (CPU
1583	speed for example), so if C<interval> is very small then timing stability	2281	speed for example), so if C<interval> is very small then timing stability
1584	will of course deteriorate. Libev itself tries to be exact to be about one	2282	will of course deteriorate. Libev itself tries to be exact to be about one
1585	millisecond (if the OS supports it and the machine is fast enough).	2283	millisecond (if the OS supports it and the machine is fast enough).
1586		2284
1587	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2285	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1588		2286
1589	In this mode the values for C<interval> and C<at> are both being	2287	In this mode the values for C<interval> and C<offset> are both being
1590	ignored. Instead, each time the periodic watcher gets scheduled, the	2288	ignored. Instead, each time the periodic watcher gets scheduled, the
1591	reschedule callback will be called with the watcher as first, and the	2289	reschedule callback will be called with the watcher as first, and the
1592	current time as second argument.	2290	current time as second argument.
1593		2291
1594	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2292	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1595	ever, or make ANY event loop modifications whatsoever>.	2293	or make ANY other event loop modifications whatsoever, unless explicitly
		2294	allowed by documentation here>.
1596		2295
1597	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2296	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1598	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2297	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1599	only event loop modification you are allowed to do).	2298	only event loop modification you are allowed to do).
1600		2299
…		…
1630	a different time than the last time it was called (e.g. in a crond like	2329	a different time than the last time it was called (e.g. in a crond like
1631	program when the crontabs have changed).	2330	program when the crontabs have changed).
1632		2331
1633	=item ev_tstamp ev_periodic_at (ev_periodic *)	2332	=item ev_tstamp ev_periodic_at (ev_periodic *)
1634		2333
1635	When active, returns the absolute time that the watcher is supposed to	2334	When active, returns the absolute time that the watcher is supposed
1636	trigger next.	2335	to trigger next. This is not the same as the C<offset> argument to
		2336	C<ev_periodic_set>, but indeed works even in interval and manual
		2337	rescheduling modes.
1637		2338
1638	=item ev_tstamp offset [read-write]	2339	=item ev_tstamp offset [read-write]
1639		2340
1640	When repeating, this contains the offset value, otherwise this is the	2341	When repeating, this contains the offset value, otherwise this is the
1641	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2342	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2343	although libev might modify this value for better numerical stability).
1642		2344
1643	Can be modified any time, but changes only take effect when the periodic	2345	Can be modified any time, but changes only take effect when the periodic
1644	timer fires or C<ev_periodic_again> is being called.	2346	timer fires or C<ev_periodic_again> is being called.
1645		2347
1646	=item ev_tstamp interval [read-write]	2348	=item ev_tstamp interval [read-write]
…		…
1662	Example: Call a callback every hour, or, more precisely, whenever the	2364	Example: Call a callback every hour, or, more precisely, whenever the
1663	system time is divisible by 3600. The callback invocation times have	2365	system time is divisible by 3600. The callback invocation times have
1664	potentially a lot of jitter, but good long-term stability.	2366	potentially a lot of jitter, but good long-term stability.
1665		2367
1666	static void	2368	static void
1667	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2369	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1668	{	2370	{
1669	... its now a full hour (UTC, or TAI or whatever your clock follows)	2371	... its now a full hour (UTC, or TAI or whatever your clock follows)
1670	}	2372	}
1671		2373
1672	ev_periodic hourly_tick;	2374	ev_periodic hourly_tick;
…		…
1695		2397
1696	=head2 C<ev_signal> - signal me when a signal gets signalled!	2398	=head2 C<ev_signal> - signal me when a signal gets signalled!
1697		2399
1698	Signal watchers will trigger an event when the process receives a specific	2400	Signal watchers will trigger an event when the process receives a specific
1699	signal one or more times. Even though signals are very asynchronous, libev	2401	signal one or more times. Even though signals are very asynchronous, libev
1700	will try it's best to deliver signals synchronously, i.e. as part of the	2402	will try its best to deliver signals synchronously, i.e. as part of the
1701	normal event processing, like any other event.	2403	normal event processing, like any other event.
1702		2404
1703	If you want signals asynchronously, just use C<sigaction> as you would	2405	If you want signals to be delivered truly asynchronously, just use
1704	do without libev and forget about sharing the signal. You can even use	2406	C<sigaction> as you would do without libev and forget about sharing
1705	C<ev_async> from a signal handler to synchronously wake up an event loop.	2407	the signal. You can even use C<ev_async> from a signal handler to
		2408	synchronously wake up an event loop.
1706		2409
1707	You can configure as many watchers as you like per signal. Only when the	2410	You can configure as many watchers as you like for the same signal, but
		2411	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2412	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2413	C<SIGINT> in both the default loop and another loop at the same time. At
		2414	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2415
1708	first watcher gets started will libev actually register a signal handler	2416	When the first watcher gets started will libev actually register something
1709	with the kernel (thus it coexists with your own signal handlers as long as	2417	with the kernel (thus it coexists with your own signal handlers as long as
1710	you don't register any with libev for the same signal). Similarly, when	2418	you don't register any with libev for the same signal).
1711	the last signal watcher for a signal is stopped, libev will reset the
1712	signal handler to SIG_DFL (regardless of what it was set to before).
1713		2419
1714	If possible and supported, libev will install its handlers with	2420	If possible and supported, libev will install its handlers with
1715	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2421	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1716	interrupted. If you have a problem with system calls getting interrupted by	2422	not be unduly interrupted. If you have a problem with system calls getting
1717	signals you can block all signals in an C<ev_check> watcher and unblock	2423	interrupted by signals you can block all signals in an C<ev_check> watcher
1718	them in an C<ev_prepare> watcher.	2424	and unblock them in an C<ev_prepare> watcher.
		2425
		2426	=head3 The special problem of inheritance over fork/execve/pthread_create
		2427
		2428	Both the signal mask (C<sigprocmask>) and the signal disposition
		2429	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2430	stopping it again), that is, libev might or might not block the signal,
		2431	and might or might not set or restore the installed signal handler (but
		2432	see C<EVFLAG_NOSIGMASK>).
		2433
		2434	While this does not matter for the signal disposition (libev never
		2435	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2436	C<execve>), this matters for the signal mask: many programs do not expect
		2437	certain signals to be blocked.
		2438
		2439	This means that before calling C<exec> (from the child) you should reset
		2440	the signal mask to whatever "default" you expect (all clear is a good
		2441	choice usually).
		2442
		2443	The simplest way to ensure that the signal mask is reset in the child is
		2444	to install a fork handler with C<pthread_atfork> that resets it. That will
		2445	catch fork calls done by libraries (such as the libc) as well.
		2446
		2447	In current versions of libev, the signal will not be blocked indefinitely
		2448	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2449	the window of opportunity for problems, it will not go away, as libev
		2450	I<has> to modify the signal mask, at least temporarily.
		2451
		2452	So I can't stress this enough: I<If you do not reset your signal mask when
		2453	you expect it to be empty, you have a race condition in your code>. This
		2454	is not a libev-specific thing, this is true for most event libraries.
		2455
		2456	=head3 The special problem of threads signal handling
		2457
		2458	POSIX threads has problematic signal handling semantics, specifically,
		2459	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2460	threads in a process block signals, which is hard to achieve.
		2461
		2462	When you want to use sigwait (or mix libev signal handling with your own
		2463	for the same signals), you can tackle this problem by globally blocking
		2464	all signals before creating any threads (or creating them with a fully set
		2465	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2466	loops. Then designate one thread as "signal receiver thread" which handles
		2467	these signals. You can pass on any signals that libev might be interested
		2468	in by calling C<ev_feed_signal>.
1719		2469
1720	=head3 Watcher-Specific Functions and Data Members	2470	=head3 Watcher-Specific Functions and Data Members
1721		2471
1722	=over 4	2472	=over 4
1723		2473
…		…
1739	Example: Try to exit cleanly on SIGINT.	2489	Example: Try to exit cleanly on SIGINT.
1740		2490
1741	static void	2491	static void
1742	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2492	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1743	{	2493	{
1744	ev_unloop (loop, EVUNLOOP_ALL);	2494	ev_break (loop, EVBREAK_ALL);
1745	}	2495	}
1746		2496
1747	ev_signal signal_watcher;	2497	ev_signal signal_watcher;
1748	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2498	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1749	ev_signal_start (loop, &signal_watcher);	2499	ev_signal_start (loop, &signal_watcher);
…		…
1755	some child status changes (most typically when a child of yours dies or	2505	some child status changes (most typically when a child of yours dies or
1756	exits). It is permissible to install a child watcher I<after> the child	2506	exits). It is permissible to install a child watcher I<after> the child
1757	has been forked (which implies it might have already exited), as long	2507	has been forked (which implies it might have already exited), as long
1758	as the event loop isn't entered (or is continued from a watcher), i.e.,	2508	as the event loop isn't entered (or is continued from a watcher), i.e.,
1759	forking and then immediately registering a watcher for the child is fine,	2509	forking and then immediately registering a watcher for the child is fine,
1760	but forking and registering a watcher a few event loop iterations later is	2510	but forking and registering a watcher a few event loop iterations later or
1761	not.	2511	in the next callback invocation is not.
1762		2512
1763	Only the default event loop is capable of handling signals, and therefore	2513	Only the default event loop is capable of handling signals, and therefore
1764	you can only register child watchers in the default event loop.	2514	you can only register child watchers in the default event loop.
1765		2515
		2516	Due to some design glitches inside libev, child watchers will always be
		2517	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2518	libev)
		2519
1766	=head3 Process Interaction	2520	=head3 Process Interaction
1767		2521
1768	Libev grabs C<SIGCHLD> as soon as the default event loop is	2522	Libev grabs C<SIGCHLD> as soon as the default event loop is
1769	initialised. This is necessary to guarantee proper behaviour even if	2523	initialised. This is necessary to guarantee proper behaviour even if the
1770	the first child watcher is started after the child exits. The occurrence	2524	first child watcher is started after the child exits. The occurrence
1771	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2525	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1772	synchronously as part of the event loop processing. Libev always reaps all	2526	synchronously as part of the event loop processing. Libev always reaps all
1773	children, even ones not watched.	2527	children, even ones not watched.
1774		2528
1775	=head3 Overriding the Built-In Processing	2529	=head3 Overriding the Built-In Processing
…		…
1785	=head3 Stopping the Child Watcher	2539	=head3 Stopping the Child Watcher
1786		2540
1787	Currently, the child watcher never gets stopped, even when the	2541	Currently, the child watcher never gets stopped, even when the
1788	child terminates, so normally one needs to stop the watcher in the	2542	child terminates, so normally one needs to stop the watcher in the
1789	callback. Future versions of libev might stop the watcher automatically	2543	callback. Future versions of libev might stop the watcher automatically
1790	when a child exit is detected.	2544	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2545	problem).
1791		2546
1792	=head3 Watcher-Specific Functions and Data Members	2547	=head3 Watcher-Specific Functions and Data Members
1793		2548
1794	=over 4	2549	=over 4
1795		2550
…		…
1852		2607
1853		2608
1854	=head2 C<ev_stat> - did the file attributes just change?	2609	=head2 C<ev_stat> - did the file attributes just change?
1855		2610
1856	This watches a file system path for attribute changes. That is, it calls	2611	This watches a file system path for attribute changes. That is, it calls
1857	C<stat> regularly (or when the OS says it changed) and sees if it changed	2612	C<stat> on that path in regular intervals (or when the OS says it changed)
1858	compared to the last time, invoking the callback if it did.	2613	and sees if it changed compared to the last time, invoking the callback
		2614	if it did. Starting the watcher C<stat>'s the file, so only changes that
		2615	happen after the watcher has been started will be reported.
1859		2616
1860	The path does not need to exist: changing from "path exists" to "path does	2617	The path does not need to exist: changing from "path exists" to "path does
1861	not exist" is a status change like any other. The condition "path does	2618	not exist" is a status change like any other. The condition "path does not
1862	not exist" is signified by the C<st_nlink> field being zero (which is	2619	exist" (or more correctly "path cannot be stat'ed") is signified by the
1863	otherwise always forced to be at least one) and all the other fields of	2620	C<st_nlink> field being zero (which is otherwise always forced to be at
1864	the stat buffer having unspecified contents.	2621	least one) and all the other fields of the stat buffer having unspecified
		2622	contents.
1865		2623
1866	The path I<should> be absolute and I<must not> end in a slash. If it is	2624	The path I<must not> end in a slash or contain special components such as
		2625	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1867	relative and your working directory changes, the behaviour is undefined.	2626	your working directory changes, then the behaviour is undefined.
1868		2627
1869	Since there is no standard kernel interface to do this, the portable	2628	Since there is no portable change notification interface available, the
1870	implementation simply calls C<stat (2)> regularly on the path to see if	2629	portable implementation simply calls C<stat(2)> regularly on the path
1871	it changed somehow. You can specify a recommended polling interval for	2630	to see if it changed somehow. You can specify a recommended polling
1872	this case. If you specify a polling interval of C<0> (highly recommended!)	2631	interval for this case. If you specify a polling interval of C<0> (highly
1873	then a I<suitable, unspecified default> value will be used (which	2632	recommended!) then a I<suitable, unspecified default> value will be used
1874	you can expect to be around five seconds, although this might change	2633	(which you can expect to be around five seconds, although this might
1875	dynamically). Libev will also impose a minimum interval which is currently	2634	change dynamically). Libev will also impose a minimum interval which is
1876	around C<0.1>, but thats usually overkill.	2635	currently around C<0.1>, but that's usually overkill.
1877		2636
1878	This watcher type is not meant for massive numbers of stat watchers,	2637	This watcher type is not meant for massive numbers of stat watchers,
1879	as even with OS-supported change notifications, this can be	2638	as even with OS-supported change notifications, this can be
1880	resource-intensive.	2639	resource-intensive.
1881		2640
1882	At the time of this writing, the only OS-specific interface implemented	2641	At the time of this writing, the only OS-specific interface implemented
1883	is the Linux inotify interface (implementing kqueue support is left as	2642	is the Linux inotify interface (implementing kqueue support is left as an
1884	an exercise for the reader. Note, however, that the author sees no way	2643	exercise for the reader. Note, however, that the author sees no way of
1885	of implementing C<ev_stat> semantics with kqueue).	2644	implementing C<ev_stat> semantics with kqueue, except as a hint).
1886		2645
1887	=head3 ABI Issues (Largefile Support)	2646	=head3 ABI Issues (Largefile Support)
1888		2647
1889	Libev by default (unless the user overrides this) uses the default	2648	Libev by default (unless the user overrides this) uses the default
1890	compilation environment, which means that on systems with large file	2649	compilation environment, which means that on systems with large file
1891	support disabled by default, you get the 32 bit version of the stat	2650	support disabled by default, you get the 32 bit version of the stat
1892	structure. When using the library from programs that change the ABI to	2651	structure. When using the library from programs that change the ABI to
1893	use 64 bit file offsets the programs will fail. In that case you have to	2652	use 64 bit file offsets the programs will fail. In that case you have to
1894	compile libev with the same flags to get binary compatibility. This is	2653	compile libev with the same flags to get binary compatibility. This is
1895	obviously the case with any flags that change the ABI, but the problem is	2654	obviously the case with any flags that change the ABI, but the problem is
1896	most noticeably disabled with ev_stat and large file support.	2655	most noticeably displayed with ev_stat and large file support.
1897		2656
1898	The solution for this is to lobby your distribution maker to make large	2657	The solution for this is to lobby your distribution maker to make large
1899	file interfaces available by default (as e.g. FreeBSD does) and not	2658	file interfaces available by default (as e.g. FreeBSD does) and not
1900	optional. Libev cannot simply switch on large file support because it has	2659	optional. Libev cannot simply switch on large file support because it has
1901	to exchange stat structures with application programs compiled using the	2660	to exchange stat structures with application programs compiled using the
1902	default compilation environment.	2661	default compilation environment.
1903		2662
1904	=head3 Inotify and Kqueue	2663	=head3 Inotify and Kqueue
1905		2664
1906	When C<inotify (7)> support has been compiled into libev (generally	2665	When C<inotify (7)> support has been compiled into libev and present at
1907	only available with Linux 2.6.25 or above due to bugs in earlier	2666	runtime, it will be used to speed up change detection where possible. The
1908	implementations) and present at runtime, it will be used to speed up	2667	inotify descriptor will be created lazily when the first C<ev_stat>
1909	change detection where possible. The inotify descriptor will be created	2668	watcher is being started.
1910	lazily when the first C<ev_stat> watcher is being started.
1911		2669
1912	Inotify presence does not change the semantics of C<ev_stat> watchers	2670	Inotify presence does not change the semantics of C<ev_stat> watchers
1913	except that changes might be detected earlier, and in some cases, to avoid	2671	except that changes might be detected earlier, and in some cases, to avoid
1914	making regular C<stat> calls. Even in the presence of inotify support	2672	making regular C<stat> calls. Even in the presence of inotify support
1915	there are many cases where libev has to resort to regular C<stat> polling,	2673	there are many cases where libev has to resort to regular C<stat> polling,
1916	but as long as the path exists, libev usually gets away without polling.	2674	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2675	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2676	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2677	xfs are fully working) libev usually gets away without polling.
1917		2678
1918	There is no support for kqueue, as apparently it cannot be used to	2679	There is no support for kqueue, as apparently it cannot be used to
1919	implement this functionality, due to the requirement of having a file	2680	implement this functionality, due to the requirement of having a file
1920	descriptor open on the object at all times, and detecting renames, unlinks	2681	descriptor open on the object at all times, and detecting renames, unlinks
1921	etc. is difficult.	2682	etc. is difficult.
1922		2683
		2684	=head3 C<stat ()> is a synchronous operation
		2685
		2686	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2687	the process. The exception are C<ev_stat> watchers - those call C<stat
		2688	()>, which is a synchronous operation.
		2689
		2690	For local paths, this usually doesn't matter: unless the system is very
		2691	busy or the intervals between stat's are large, a stat call will be fast,
		2692	as the path data is usually in memory already (except when starting the
		2693	watcher).
		2694
		2695	For networked file systems, calling C<stat ()> can block an indefinite
		2696	time due to network issues, and even under good conditions, a stat call
		2697	often takes multiple milliseconds.
		2698
		2699	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2700	paths, although this is fully supported by libev.
		2701
1923	=head3 The special problem of stat time resolution	2702	=head3 The special problem of stat time resolution
1924		2703
1925	The C<stat ()> system call only supports full-second resolution portably, and	2704	The C<stat ()> system call only supports full-second resolution portably,
1926	even on systems where the resolution is higher, most file systems still	2705	and even on systems where the resolution is higher, most file systems
1927	only support whole seconds.	2706	still only support whole seconds.
1928		2707
1929	That means that, if the time is the only thing that changes, you can	2708	That means that, if the time is the only thing that changes, you can
1930	easily miss updates: on the first update, C<ev_stat> detects a change and	2709	easily miss updates: on the first update, C<ev_stat> detects a change and
1931	calls your callback, which does something. When there is another update	2710	calls your callback, which does something. When there is another update
1932	within the same second, C<ev_stat> will be unable to detect unless the	2711	within the same second, C<ev_stat> will be unable to detect unless the
…		…
2071	Apart from keeping your process non-blocking (which is a useful	2850	Apart from keeping your process non-blocking (which is a useful
2072	effect on its own sometimes), idle watchers are a good place to do	2851	effect on its own sometimes), idle watchers are a good place to do
2073	"pseudo-background processing", or delay processing stuff to after the	2852	"pseudo-background processing", or delay processing stuff to after the
2074	event loop has handled all outstanding events.	2853	event loop has handled all outstanding events.
2075		2854
		2855	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2856
		2857	As long as there is at least one active idle watcher, libev will never
		2858	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2859	For this to work, the idle watcher doesn't need to be invoked at all - the
		2860	lowest priority will do.
		2861
		2862	This mode of operation can be useful together with an C<ev_check> watcher,
		2863	to do something on each event loop iteration - for example to balance load
		2864	between different connections.
		2865
		2866	See L</Abusing an ev_check watcher for its side-effect> for a longer
		2867	example.
		2868
2076	=head3 Watcher-Specific Functions and Data Members	2869	=head3 Watcher-Specific Functions and Data Members
2077		2870
2078	=over 4	2871	=over 4
2079		2872
2080	=item ev_idle_init (ev_signal *, callback)	2873	=item ev_idle_init (ev_idle *, callback)
2081		2874
2082	Initialises and configures the idle watcher - it has no parameters of any	2875	Initialises and configures the idle watcher - it has no parameters of any
2083	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2876	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
2084	believe me.	2877	believe me.
2085		2878
…		…
2091	callback, free it. Also, use no error checking, as usual.	2884	callback, free it. Also, use no error checking, as usual.
2092		2885
2093	static void	2886	static void
2094	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	2887	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2095	{	2888	{
		2889	// stop the watcher
		2890	ev_idle_stop (loop, w);
		2891
		2892	// now we can free it
2096	free (w);	2893	free (w);
		2894
2097	// now do something you wanted to do when the program has	2895	// now do something you wanted to do when the program has
2098	// no longer anything immediate to do.	2896	// no longer anything immediate to do.
2099	}	2897	}
2100		2898
2101	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2899	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2102	ev_idle_init (idle_watcher, idle_cb);	2900	ev_idle_init (idle_watcher, idle_cb);
2103	ev_idle_start (loop, idle_cb);	2901	ev_idle_start (loop, idle_watcher);
2104		2902
2105		2903
2106	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2904	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2107		2905
2108	Prepare and check watchers are usually (but not always) used in pairs:	2906	Prepare and check watchers are often (but not always) used in pairs:
2109	prepare watchers get invoked before the process blocks and check watchers	2907	prepare watchers get invoked before the process blocks and check watchers
2110	afterwards.	2908	afterwards.
2111		2909
2112	You I<must not> call C<ev_loop> or similar functions that enter	2910	You I<must not> call C<ev_run> or similar functions that enter
2113	the current event loop from either C<ev_prepare> or C<ev_check>	2911	the current event loop from either C<ev_prepare> or C<ev_check>
2114	watchers. Other loops than the current one are fine, however. The	2912	watchers. Other loops than the current one are fine, however. The
2115	rationale behind this is that you do not need to check for recursion in	2913	rationale behind this is that you do not need to check for recursion in
2116	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2914	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2117	C<ev_check> so if you have one watcher of each kind they will always be	2915	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2141	with priority higher than or equal to the event loop and one coroutine	2939	with priority higher than or equal to the event loop and one coroutine
2142	of lower priority, but only once, using idle watchers to keep the event	2940	of lower priority, but only once, using idle watchers to keep the event
2143	loop from blocking if lower-priority coroutines are active, thus mapping	2941	loop from blocking if lower-priority coroutines are active, thus mapping
2144	low-priority coroutines to idle/background tasks).	2942	low-priority coroutines to idle/background tasks).
2145		2943
2146	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2944	When used for this purpose, it is recommended to give C<ev_check> watchers
2147	priority, to ensure that they are being run before any other watchers	2945	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2148	after the poll (this doesn't matter for C<ev_prepare> watchers).	2946	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		2947	watchers).
2149		2948
2150	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	2949	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2151	activate ("feed") events into libev. While libev fully supports this, they	2950	activate ("feed") events into libev. While libev fully supports this, they
2152	might get executed before other C<ev_check> watchers did their job. As	2951	might get executed before other C<ev_check> watchers did their job. As
2153	C<ev_check> watchers are often used to embed other (non-libev) event	2952	C<ev_check> watchers are often used to embed other (non-libev) event
2154	loops those other event loops might be in an unusable state until their	2953	loops those other event loops might be in an unusable state until their
2155	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	2954	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2156	others).	2955	others).
		2956
		2957	=head3 Abusing an C<ev_check> watcher for its side-effect
		2958
		2959	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		2960	useful because they are called once per event loop iteration. For
		2961	example, if you want to handle a large number of connections fairly, you
		2962	normally only do a bit of work for each active connection, and if there
		2963	is more work to do, you wait for the next event loop iteration, so other
		2964	connections have a chance of making progress.
		2965
		2966	Using an C<ev_check> watcher is almost enough: it will be called on the
		2967	next event loop iteration. However, that isn't as soon as possible -
		2968	without external events, your C<ev_check> watcher will not be invoked.
		2969
		2970	This is where C<ev_idle> watchers come in handy - all you need is a
		2971	single global idle watcher that is active as long as you have one active
		2972	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		2973	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		2974	invoked. Neither watcher alone can do that.
2157		2975
2158	=head3 Watcher-Specific Functions and Data Members	2976	=head3 Watcher-Specific Functions and Data Members
2159		2977
2160	=over 4	2978	=over 4
2161		2979
…		…
2201	struct pollfd fds [nfd];	3019	struct pollfd fds [nfd];
2202	// actual code will need to loop here and realloc etc.	3020	// actual code will need to loop here and realloc etc.
2203	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	3021	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2204		3022
2205	/* the callback is illegal, but won't be called as we stop during check */	3023	/* the callback is illegal, but won't be called as we stop during check */
2206	ev_timer_init (&tw, 0, timeout * 1e-3);	3024	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2207	ev_timer_start (loop, &tw);	3025	ev_timer_start (loop, &tw);
2208		3026
2209	// create one ev_io per pollfd	3027	// create one ev_io per pollfd
2210	for (int i = 0; i < nfd; ++i)	3028	for (int i = 0; i < nfd; ++i)
2211	{	3029	{
…		…
2285		3103
2286	if (timeout >= 0)	3104	if (timeout >= 0)
2287	// create/start timer	3105	// create/start timer
2288		3106
2289	// poll	3107	// poll
2290	ev_loop (EV_A_ 0);	3108	ev_run (EV_A_ 0);
2291		3109
2292	// stop timer again	3110	// stop timer again
2293	if (timeout >= 0)	3111	if (timeout >= 0)
2294	ev_timer_stop (EV_A_ &to);	3112	ev_timer_stop (EV_A_ &to);
2295		3113
…		…
2324	some fds have to be watched and handled very quickly (with low latency),	3142	some fds have to be watched and handled very quickly (with low latency),
2325	and even priorities and idle watchers might have too much overhead. In	3143	and even priorities and idle watchers might have too much overhead. In
2326	this case you would put all the high priority stuff in one loop and all	3144	this case you would put all the high priority stuff in one loop and all
2327	the rest in a second one, and embed the second one in the first.	3145	the rest in a second one, and embed the second one in the first.
2328		3146
2329	As long as the watcher is active, the callback will be invoked every time	3147	As long as the watcher is active, the callback will be invoked every
2330	there might be events pending in the embedded loop. The callback must then	3148	time there might be events pending in the embedded loop. The callback
2331	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	3149	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2332	their callbacks (you could also start an idle watcher to give the embedded	3150	sweep and invoke their callbacks (the callback doesn't need to invoke the
2333	loop strictly lower priority for example). You can also set the callback	3151	C<ev_embed_sweep> function directly, it could also start an idle watcher
2334	to C<0>, in which case the embed watcher will automatically execute the	3152	to give the embedded loop strictly lower priority for example).
2335	embedded loop sweep.
2336		3153
2337	As long as the watcher is started it will automatically handle events. The	3154	You can also set the callback to C<0>, in which case the embed watcher
2338	callback will be invoked whenever some events have been handled. You can	3155	will automatically execute the embedded loop sweep whenever necessary.
2339	set the callback to C<0> to avoid having to specify one if you are not
2340	interested in that.
2341		3156
2342	Also, there have not currently been made special provisions for forking:	3157	Fork detection will be handled transparently while the C<ev_embed> watcher
2343	when you fork, you not only have to call C<ev_loop_fork> on both loops,	3158	is active, i.e., the embedded loop will automatically be forked when the
2344	but you will also have to stop and restart any C<ev_embed> watchers	3159	embedding loop forks. In other cases, the user is responsible for calling
2345	yourself - but you can use a fork watcher to handle this automatically,	3160	C<ev_loop_fork> on the embedded loop.
2346	and future versions of libev might do just that.
2347		3161
2348	Unfortunately, not all backends are embeddable: only the ones returned by	3162	Unfortunately, not all backends are embeddable: only the ones returned by
2349	C<ev_embeddable_backends> are, which, unfortunately, does not include any	3163	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2350	portable one.	3164	portable one.
2351		3165
…		…
2366		3180
2367	=over 4	3181	=over 4
2368		3182
2369	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3183	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
2370		3184
2371	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3185	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
2372		3186
2373	Configures the watcher to embed the given loop, which must be	3187	Configures the watcher to embed the given loop, which must be
2374	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	3188	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2375	invoked automatically, otherwise it is the responsibility of the callback	3189	invoked automatically, otherwise it is the responsibility of the callback
2376	to invoke it (it will continue to be called until the sweep has been done,	3190	to invoke it (it will continue to be called until the sweep has been done,
2377	if you do not want that, you need to temporarily stop the embed watcher).	3191	if you do not want that, you need to temporarily stop the embed watcher).
2378		3192
2379	=item ev_embed_sweep (loop, ev_embed *)	3193	=item ev_embed_sweep (loop, ev_embed *)
2380		3194
2381	Make a single, non-blocking sweep over the embedded loop. This works	3195	Make a single, non-blocking sweep over the embedded loop. This works
2382	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3196	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2383	appropriate way for embedded loops.	3197	appropriate way for embedded loops.
2384		3198
2385	=item struct ev_loop *other [read-only]	3199	=item struct ev_loop *other [read-only]
2386		3200
2387	The embedded event loop.	3201	The embedded event loop.
…		…
2439		3253
2440	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3254	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2441		3255
2442	Fork watchers are called when a C<fork ()> was detected (usually because	3256	Fork watchers are called when a C<fork ()> was detected (usually because
2443	whoever is a good citizen cared to tell libev about it by calling	3257	whoever is a good citizen cared to tell libev about it by calling
2444	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the	3258	C<ev_loop_fork>). The invocation is done before the event loop blocks next
2445	event loop blocks next and before C<ev_check> watchers are being called,	3259	and before C<ev_check> watchers are being called, and only in the child
2446	and only in the child after the fork. If whoever good citizen calling	3260	after the fork. If whoever good citizen calling C<ev_default_fork> cheats
2447	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3261	and calls it in the wrong process, the fork handlers will be invoked, too,
2448	handlers will be invoked, too, of course.	3262	of course.
		3263
		3264	=head3 The special problem of life after fork - how is it possible?
		3265
		3266	Most uses of C<fork()> consist of forking, then some simple calls to set
		3267	up/change the process environment, followed by a call to C<exec()>. This
		3268	sequence should be handled by libev without any problems.
		3269
		3270	This changes when the application actually wants to do event handling
		3271	in the child, or both parent in child, in effect "continuing" after the
		3272	fork.
		3273
		3274	The default mode of operation (for libev, with application help to detect
		3275	forks) is to duplicate all the state in the child, as would be expected
		3276	when I<either> the parent I<or> the child process continues.
		3277
		3278	When both processes want to continue using libev, then this is usually the
		3279	wrong result. In that case, usually one process (typically the parent) is
		3280	supposed to continue with all watchers in place as before, while the other
		3281	process typically wants to start fresh, i.e. without any active watchers.
		3282
		3283	The cleanest and most efficient way to achieve that with libev is to
		3284	simply create a new event loop, which of course will be "empty", and
		3285	use that for new watchers. This has the advantage of not touching more
		3286	memory than necessary, and thus avoiding the copy-on-write, and the
		3287	disadvantage of having to use multiple event loops (which do not support
		3288	signal watchers).
		3289
		3290	When this is not possible, or you want to use the default loop for
		3291	other reasons, then in the process that wants to start "fresh", call
		3292	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3293	Destroying the default loop will "orphan" (not stop) all registered
		3294	watchers, so you have to be careful not to execute code that modifies
		3295	those watchers. Note also that in that case, you have to re-register any
		3296	signal watchers.
2449		3297
2450	=head3 Watcher-Specific Functions and Data Members	3298	=head3 Watcher-Specific Functions and Data Members
2451		3299
2452	=over 4	3300	=over 4
2453		3301
2454	=item ev_fork_init (ev_signal *, callback)	3302	=item ev_fork_init (ev_fork *, callback)
2455		3303
2456	Initialises and configures the fork watcher - it has no parameters of any	3304	Initialises and configures the fork watcher - it has no parameters of any
2457	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3305	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2458	believe me.	3306	really.
2459		3307
2460	=back	3308	=back
2461		3309
2462		3310
		3311	=head2 C<ev_cleanup> - even the best things end
		3312
		3313	Cleanup watchers are called just before the event loop is being destroyed
		3314	by a call to C<ev_loop_destroy>.
		3315
		3316	While there is no guarantee that the event loop gets destroyed, cleanup
		3317	watchers provide a convenient method to install cleanup hooks for your
		3318	program, worker threads and so on - you just to make sure to destroy the
		3319	loop when you want them to be invoked.
		3320
		3321	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3322	all other watchers, they do not keep a reference to the event loop (which
		3323	makes a lot of sense if you think about it). Like all other watchers, you
		3324	can call libev functions in the callback, except C<ev_cleanup_start>.
		3325
		3326	=head3 Watcher-Specific Functions and Data Members
		3327
		3328	=over 4
		3329
		3330	=item ev_cleanup_init (ev_cleanup *, callback)
		3331
		3332	Initialises and configures the cleanup watcher - it has no parameters of
		3333	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3334	pointless, I assure you.
		3335
		3336	=back
		3337
		3338	Example: Register an atexit handler to destroy the default loop, so any
		3339	cleanup functions are called.
		3340
		3341	static void
		3342	program_exits (void)
		3343	{
		3344	ev_loop_destroy (EV_DEFAULT_UC);
		3345	}
		3346
		3347	...
		3348	atexit (program_exits);
		3349
		3350
2463	=head2 C<ev_async> - how to wake up another event loop	3351	=head2 C<ev_async> - how to wake up an event loop
2464		3352
2465	In general, you cannot use an C<ev_loop> from multiple threads or other	3353	In general, you cannot use an C<ev_loop> from multiple threads or other
2466	asynchronous sources such as signal handlers (as opposed to multiple event	3354	asynchronous sources such as signal handlers (as opposed to multiple event
2467	loops - those are of course safe to use in different threads).	3355	loops - those are of course safe to use in different threads).
2468		3356
2469	Sometimes, however, you need to wake up another event loop you do not	3357	Sometimes, however, you need to wake up an event loop you do not control,
2470	control, for example because it belongs to another thread. This is what	3358	for example because it belongs to another thread. This is what C<ev_async>
2471	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3359	watchers do: as long as the C<ev_async> watcher is active, you can signal
2472	can signal it by calling C<ev_async_send>, which is thread- and signal	3360	it by calling C<ev_async_send>, which is thread- and signal safe.
2473	safe.
2474		3361
2475	This functionality is very similar to C<ev_signal> watchers, as signals,	3362	This functionality is very similar to C<ev_signal> watchers, as signals,
2476	too, are asynchronous in nature, and signals, too, will be compressed	3363	too, are asynchronous in nature, and signals, too, will be compressed
2477	(i.e. the number of callback invocations may be less than the number of	3364	(i.e. the number of callback invocations may be less than the number of
2478	C<ev_async_sent> calls).	3365	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
2479		3366	of "global async watchers" by using a watcher on an otherwise unused
2480	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3367	signal, and C<ev_feed_signal> to signal this watcher from another thread,
2481	just the default loop.	3368	even without knowing which loop owns the signal.
2482		3369
2483	=head3 Queueing	3370	=head3 Queueing
2484		3371
2485	C<ev_async> does not support queueing of data in any way. The reason	3372	C<ev_async> does not support queueing of data in any way. The reason
2486	is that the author does not know of a simple (or any) algorithm for a	3373	is that the author does not know of a simple (or any) algorithm for a
2487	multiple-writer-single-reader queue that works in all cases and doesn't	3374	multiple-writer-single-reader queue that works in all cases and doesn't
2488	need elaborate support such as pthreads.	3375	need elaborate support such as pthreads or unportable memory access
		3376	semantics.
2489		3377
2490	That means that if you want to queue data, you have to provide your own	3378	That means that if you want to queue data, you have to provide your own
2491	queue. But at least I can tell you how to implement locking around your	3379	queue. But at least I can tell you how to implement locking around your
2492	queue:	3380	queue:
2493		3381
…		…
2571	=over 4	3459	=over 4
2572		3460
2573	=item ev_async_init (ev_async *, callback)	3461	=item ev_async_init (ev_async *, callback)
2574		3462
2575	Initialises and configures the async watcher - it has no parameters of any	3463	Initialises and configures the async watcher - it has no parameters of any
2576	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3464	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2577	trust me.	3465	trust me.
2578		3466
2579	=item ev_async_send (loop, ev_async *)	3467	=item ev_async_send (loop, ev_async *)
2580		3468
2581	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3469	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2582	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3470	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3471	returns.
		3472
2583	C<ev_feed_event>, this call is safe to do from other threads, signal or	3473	Unlike C<ev_feed_event>, this call is safe to do from other threads,
2584	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3474	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
2585	section below on what exactly this means).	3475	embedding section below on what exactly this means).
2586		3476
2587	This call incurs the overhead of a system call only once per loop iteration,	3477	Note that, as with other watchers in libev, multiple events might get
2588	so while the overhead might be noticeable, it doesn't apply to repeated	3478	compressed into a single callback invocation (another way to look at
2589	calls to C<ev_async_send>.	3479	this is that C<ev_async> watchers are level-triggered: they are set on
		3480	C<ev_async_send>, reset when the event loop detects that).
		3481
		3482	This call incurs the overhead of at most one extra system call per event
		3483	loop iteration, if the event loop is blocked, and no syscall at all if
		3484	the event loop (or your program) is processing events. That means that
		3485	repeated calls are basically free (there is no need to avoid calls for
		3486	performance reasons) and that the overhead becomes smaller (typically
		3487	zero) under load.
2590		3488
2591	=item bool = ev_async_pending (ev_async *)	3489	=item bool = ev_async_pending (ev_async *)
2592		3490
2593	Returns a non-zero value when C<ev_async_send> has been called on the	3491	Returns a non-zero value when C<ev_async_send> has been called on the
2594	watcher but the event has not yet been processed (or even noted) by the	3492	watcher but the event has not yet been processed (or even noted) by the
…		…
2597	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3495	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2598	the loop iterates next and checks for the watcher to have become active,	3496	the loop iterates next and checks for the watcher to have become active,
2599	it will reset the flag again. C<ev_async_pending> can be used to very	3497	it will reset the flag again. C<ev_async_pending> can be used to very
2600	quickly check whether invoking the loop might be a good idea.	3498	quickly check whether invoking the loop might be a good idea.
2601		3499
2602	Not that this does I<not> check whether the watcher itself is pending, only	3500	Not that this does I<not> check whether the watcher itself is pending,
2603	whether it has been requested to make this watcher pending.	3501	only whether it has been requested to make this watcher pending: there
		3502	is a time window between the event loop checking and resetting the async
		3503	notification, and the callback being invoked.
2604		3504
2605	=back	3505	=back
2606		3506
2607		3507
2608	=head1 OTHER FUNCTIONS	3508	=head1 OTHER FUNCTIONS
…		…
2625		3525
2626	If C<timeout> is less than 0, then no timeout watcher will be	3526	If C<timeout> is less than 0, then no timeout watcher will be
2627	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3527	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2628	repeat = 0) will be started. C<0> is a valid timeout.	3528	repeat = 0) will be started. C<0> is a valid timeout.
2629		3529
2630	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3530	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2631	passed an C<revents> set like normal event callbacks (a combination of	3531	passed an C<revents> set like normal event callbacks (a combination of
2632	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3532	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2633	value passed to C<ev_once>. Note that it is possible to receive I<both>	3533	value passed to C<ev_once>. Note that it is possible to receive I<both>
2634	a timeout and an io event at the same time - you probably should give io	3534	a timeout and an io event at the same time - you probably should give io
2635	events precedence.	3535	events precedence.
2636		3536
2637	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3537	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2638		3538
2639	static void stdin_ready (int revents, void *arg)	3539	static void stdin_ready (int revents, void *arg)
2640	{	3540	{
2641	if (revents & EV_READ)	3541	if (revents & EV_READ)
2642	/* stdin might have data for us, joy! */;	3542	/* stdin might have data for us, joy! */;
2643	else if (revents & EV_TIMEOUT)	3543	else if (revents & EV_TIMER)
2644	/* doh, nothing entered */;	3544	/* doh, nothing entered */;
2645	}	3545	}
2646		3546
2647	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3547	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2648		3548
2649	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2650
2651	Feeds the given event set into the event loop, as if the specified event
2652	had happened for the specified watcher (which must be a pointer to an
2653	initialised but not necessarily started event watcher).
2654
2655	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3549	=item ev_feed_fd_event (loop, int fd, int revents)
2656		3550
2657	Feed an event on the given fd, as if a file descriptor backend detected	3551	Feed an event on the given fd, as if a file descriptor backend detected
2658	the given events it.	3552	the given events.
2659		3553
2660	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3554	=item ev_feed_signal_event (loop, int signum)
2661		3555
2662	Feed an event as if the given signal occurred (C<loop> must be the default	3556	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
2663	loop!).	3557	which is async-safe.
2664		3558
2665	=back	3559	=back
		3560
		3561
		3562	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3563
		3564	This section explains some common idioms that are not immediately
		3565	obvious. Note that examples are sprinkled over the whole manual, and this
		3566	section only contains stuff that wouldn't fit anywhere else.
		3567
		3568	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3569
		3570	Each watcher has, by default, a C<void *data> member that you can read
		3571	or modify at any time: libev will completely ignore it. This can be used
		3572	to associate arbitrary data with your watcher. If you need more data and
		3573	don't want to allocate memory separately and store a pointer to it in that
		3574	data member, you can also "subclass" the watcher type and provide your own
		3575	data:
		3576
		3577	struct my_io
		3578	{
		3579	ev_io io;
		3580	int otherfd;
		3581	void *somedata;
		3582	struct whatever *mostinteresting;
		3583	};
		3584
		3585	...
		3586	struct my_io w;
		3587	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3588
		3589	And since your callback will be called with a pointer to the watcher, you
		3590	can cast it back to your own type:
		3591
		3592	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3593	{
		3594	struct my_io *w = (struct my_io *)w_;
		3595	...
		3596	}
		3597
		3598	More interesting and less C-conformant ways of casting your callback
		3599	function type instead have been omitted.
		3600
		3601	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3602
		3603	Another common scenario is to use some data structure with multiple
		3604	embedded watchers, in effect creating your own watcher that combines
		3605	multiple libev event sources into one "super-watcher":
		3606
		3607	struct my_biggy
		3608	{
		3609	int some_data;
		3610	ev_timer t1;
		3611	ev_timer t2;
		3612	}
		3613
		3614	In this case getting the pointer to C<my_biggy> is a bit more
		3615	complicated: Either you store the address of your C<my_biggy> struct in
		3616	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3617	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3618	real programmers):
		3619
		3620	#include <stddef.h>
		3621
		3622	static void
		3623	t1_cb (EV_P_ ev_timer *w, int revents)
		3624	{
		3625	struct my_biggy big = (struct my_biggy *)
		3626	(((char *)w) - offsetof (struct my_biggy, t1));
		3627	}
		3628
		3629	static void
		3630	t2_cb (EV_P_ ev_timer *w, int revents)
		3631	{
		3632	struct my_biggy big = (struct my_biggy *)
		3633	(((char *)w) - offsetof (struct my_biggy, t2));
		3634	}
		3635
		3636	=head2 AVOIDING FINISHING BEFORE RETURNING
		3637
		3638	Often you have structures like this in event-based programs:
		3639
		3640	callback ()
		3641	{
		3642	free (request);
		3643	}
		3644
		3645	request = start_new_request (..., callback);
		3646
		3647	The intent is to start some "lengthy" operation. The C<request> could be
		3648	used to cancel the operation, or do other things with it.
		3649
		3650	It's not uncommon to have code paths in C<start_new_request> that
		3651	immediately invoke the callback, for example, to report errors. Or you add
		3652	some caching layer that finds that it can skip the lengthy aspects of the
		3653	operation and simply invoke the callback with the result.
		3654
		3655	The problem here is that this will happen I<before> C<start_new_request>
		3656	has returned, so C<request> is not set.
		3657
		3658	Even if you pass the request by some safer means to the callback, you
		3659	might want to do something to the request after starting it, such as
		3660	canceling it, which probably isn't working so well when the callback has
		3661	already been invoked.
		3662
		3663	A common way around all these issues is to make sure that
		3664	C<start_new_request> I<always> returns before the callback is invoked. If
		3665	C<start_new_request> immediately knows the result, it can artificially
		3666	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3667	example, or more sneakily, by reusing an existing (stopped) watcher and
		3668	pushing it into the pending queue:
		3669
		3670	ev_set_cb (watcher, callback);
		3671	ev_feed_event (EV_A_ watcher, 0);
		3672
		3673	This way, C<start_new_request> can safely return before the callback is
		3674	invoked, while not delaying callback invocation too much.
		3675
		3676	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3677
		3678	Often (especially in GUI toolkits) there are places where you have
		3679	I<modal> interaction, which is most easily implemented by recursively
		3680	invoking C<ev_run>.
		3681
		3682	This brings the problem of exiting - a callback might want to finish the
		3683	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3684	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3685	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3686	other combination: In these cases, a simple C<ev_break> will not work.
		3687
		3688	The solution is to maintain "break this loop" variable for each C<ev_run>
		3689	invocation, and use a loop around C<ev_run> until the condition is
		3690	triggered, using C<EVRUN_ONCE>:
		3691
		3692	// main loop
		3693	int exit_main_loop = 0;
		3694
		3695	while (!exit_main_loop)
		3696	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3697
		3698	// in a modal watcher
		3699	int exit_nested_loop = 0;
		3700
		3701	while (!exit_nested_loop)
		3702	ev_run (EV_A_ EVRUN_ONCE);
		3703
		3704	To exit from any of these loops, just set the corresponding exit variable:
		3705
		3706	// exit modal loop
		3707	exit_nested_loop = 1;
		3708
		3709	// exit main program, after modal loop is finished
		3710	exit_main_loop = 1;
		3711
		3712	// exit both
		3713	exit_main_loop = exit_nested_loop = 1;
		3714
		3715	=head2 THREAD LOCKING EXAMPLE
		3716
		3717	Here is a fictitious example of how to run an event loop in a different
		3718	thread from where callbacks are being invoked and watchers are
		3719	created/added/removed.
		3720
		3721	For a real-world example, see the C<EV::Loop::Async> perl module,
		3722	which uses exactly this technique (which is suited for many high-level
		3723	languages).
		3724
		3725	The example uses a pthread mutex to protect the loop data, a condition
		3726	variable to wait for callback invocations, an async watcher to notify the
		3727	event loop thread and an unspecified mechanism to wake up the main thread.
		3728
		3729	First, you need to associate some data with the event loop:
		3730
		3731	typedef struct {
		3732	mutex_t lock; /* global loop lock */
		3733	ev_async async_w;
		3734	thread_t tid;
		3735	cond_t invoke_cv;
		3736	} userdata;
		3737
		3738	void prepare_loop (EV_P)
		3739	{
		3740	// for simplicity, we use a static userdata struct.
		3741	static userdata u;
		3742
		3743	ev_async_init (&u->async_w, async_cb);
		3744	ev_async_start (EV_A_ &u->async_w);
		3745
		3746	pthread_mutex_init (&u->lock, 0);
		3747	pthread_cond_init (&u->invoke_cv, 0);
		3748
		3749	// now associate this with the loop
		3750	ev_set_userdata (EV_A_ u);
		3751	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3752	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3753
		3754	// then create the thread running ev_run
		3755	pthread_create (&u->tid, 0, l_run, EV_A);
		3756	}
		3757
		3758	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3759	solely to wake up the event loop so it takes notice of any new watchers
		3760	that might have been added:
		3761
		3762	static void
		3763	async_cb (EV_P_ ev_async *w, int revents)
		3764	{
		3765	// just used for the side effects
		3766	}
		3767
		3768	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3769	protecting the loop data, respectively.
		3770
		3771	static void
		3772	l_release (EV_P)
		3773	{
		3774	userdata *u = ev_userdata (EV_A);
		3775	pthread_mutex_unlock (&u->lock);
		3776	}
		3777
		3778	static void
		3779	l_acquire (EV_P)
		3780	{
		3781	userdata *u = ev_userdata (EV_A);
		3782	pthread_mutex_lock (&u->lock);
		3783	}
		3784
		3785	The event loop thread first acquires the mutex, and then jumps straight
		3786	into C<ev_run>:
		3787
		3788	void *
		3789	l_run (void *thr_arg)
		3790	{
		3791	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3792
		3793	l_acquire (EV_A);
		3794	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3795	ev_run (EV_A_ 0);
		3796	l_release (EV_A);
		3797
		3798	return 0;
		3799	}
		3800
		3801	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3802	signal the main thread via some unspecified mechanism (signals? pipe
		3803	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3804	have been called (in a while loop because a) spurious wakeups are possible
		3805	and b) skipping inter-thread-communication when there are no pending
		3806	watchers is very beneficial):
		3807
		3808	static void
		3809	l_invoke (EV_P)
		3810	{
		3811	userdata *u = ev_userdata (EV_A);
		3812
		3813	while (ev_pending_count (EV_A))
		3814	{
		3815	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3816	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3817	}
		3818	}
		3819
		3820	Now, whenever the main thread gets told to invoke pending watchers, it
		3821	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3822	thread to continue:
		3823
		3824	static void
		3825	real_invoke_pending (EV_P)
		3826	{
		3827	userdata *u = ev_userdata (EV_A);
		3828
		3829	pthread_mutex_lock (&u->lock);
		3830	ev_invoke_pending (EV_A);
		3831	pthread_cond_signal (&u->invoke_cv);
		3832	pthread_mutex_unlock (&u->lock);
		3833	}
		3834
		3835	Whenever you want to start/stop a watcher or do other modifications to an
		3836	event loop, you will now have to lock:
		3837
		3838	ev_timer timeout_watcher;
		3839	userdata *u = ev_userdata (EV_A);
		3840
		3841	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3842
		3843	pthread_mutex_lock (&u->lock);
		3844	ev_timer_start (EV_A_ &timeout_watcher);
		3845	ev_async_send (EV_A_ &u->async_w);
		3846	pthread_mutex_unlock (&u->lock);
		3847
		3848	Note that sending the C<ev_async> watcher is required because otherwise
		3849	an event loop currently blocking in the kernel will have no knowledge
		3850	about the newly added timer. By waking up the loop it will pick up any new
		3851	watchers in the next event loop iteration.
		3852
		3853	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3854
		3855	While the overhead of a callback that e.g. schedules a thread is small, it
		3856	is still an overhead. If you embed libev, and your main usage is with some
		3857	kind of threads or coroutines, you might want to customise libev so that
		3858	doesn't need callbacks anymore.
		3859
		3860	Imagine you have coroutines that you can switch to using a function
		3861	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3862	and that due to some magic, the currently active coroutine is stored in a
		3863	global called C<current_coro>. Then you can build your own "wait for libev
		3864	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3865	the differing C<;> conventions):
		3866
		3867	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3868	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3869
		3870	That means instead of having a C callback function, you store the
		3871	coroutine to switch to in each watcher, and instead of having libev call
		3872	your callback, you instead have it switch to that coroutine.
		3873
		3874	A coroutine might now wait for an event with a function called
		3875	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3876	matter when, or whether the watcher is active or not when this function is
		3877	called):
		3878
		3879	void
		3880	wait_for_event (ev_watcher *w)
		3881	{
		3882	ev_set_cb (w, current_coro);
		3883	switch_to (libev_coro);
		3884	}
		3885
		3886	That basically suspends the coroutine inside C<wait_for_event> and
		3887	continues the libev coroutine, which, when appropriate, switches back to
		3888	this or any other coroutine.
		3889
		3890	You can do similar tricks if you have, say, threads with an event queue -
		3891	instead of storing a coroutine, you store the queue object and instead of
		3892	switching to a coroutine, you push the watcher onto the queue and notify
		3893	any waiters.
		3894
		3895	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		3896	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3897
		3898	// my_ev.h
		3899	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3900	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3901	#include "../libev/ev.h"
		3902
		3903	// my_ev.c
		3904	#define EV_H "my_ev.h"
		3905	#include "../libev/ev.c"
		3906
		3907	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3908	F<my_ev.c> into your project. When properly specifying include paths, you
		3909	can even use F<ev.h> as header file name directly.
2666		3910
2667		3911
2668	=head1 LIBEVENT EMULATION	3912	=head1 LIBEVENT EMULATION
2669		3913
2670	Libev offers a compatibility emulation layer for libevent. It cannot	3914	Libev offers a compatibility emulation layer for libevent. It cannot
2671	emulate the internals of libevent, so here are some usage hints:	3915	emulate the internals of libevent, so here are some usage hints:
2672		3916
2673	=over 4	3917	=over 4
		3918
		3919	=item * Only the libevent-1.4.1-beta API is being emulated.
		3920
		3921	This was the newest libevent version available when libev was implemented,
		3922	and is still mostly unchanged in 2010.
2674		3923
2675	=item * Use it by including <event.h>, as usual.	3924	=item * Use it by including <event.h>, as usual.
2676		3925
2677	=item * The following members are fully supported: ev_base, ev_callback,	3926	=item * The following members are fully supported: ev_base, ev_callback,
2678	ev_arg, ev_fd, ev_res, ev_events.	3927	ev_arg, ev_fd, ev_res, ev_events.
…		…
2684	=item * Priorities are not currently supported. Initialising priorities	3933	=item * Priorities are not currently supported. Initialising priorities
2685	will fail and all watchers will have the same priority, even though there	3934	will fail and all watchers will have the same priority, even though there
2686	is an ev_pri field.	3935	is an ev_pri field.
2687		3936
2688	=item * In libevent, the last base created gets the signals, in libev, the	3937	=item * In libevent, the last base created gets the signals, in libev, the
2689	first base created (== the default loop) gets the signals.	3938	base that registered the signal gets the signals.
2690		3939
2691	=item * Other members are not supported.	3940	=item * Other members are not supported.
2692		3941
2693	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3942	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2694	to use the libev header file and library.	3943	to use the libev header file and library.
2695		3944
2696	=back	3945	=back
2697		3946
2698	=head1 C++ SUPPORT	3947	=head1 C++ SUPPORT
		3948
		3949	=head2 C API
		3950
		3951	The normal C API should work fine when used from C++: both ev.h and the
		3952	libev sources can be compiled as C++. Therefore, code that uses the C API
		3953	will work fine.
		3954
		3955	Proper exception specifications might have to be added to callbacks passed
		3956	to libev: exceptions may be thrown only from watcher callbacks, all
		3957	other callbacks (allocator, syserr, loop acquire/release and periodic
		3958	reschedule callbacks) must not throw exceptions, and might need a C<throw
		3959	()> specification. If you have code that needs to be compiled as both C
		3960	and C++ you can use the C<EV_THROW> macro for this:
		3961
		3962	static void
		3963	fatal_error (const char *msg) EV_THROW
		3964	{
		3965	perror (msg);
		3966	abort ();
		3967	}
		3968
		3969	...
		3970	ev_set_syserr_cb (fatal_error);
		3971
		3972	The only API functions that can currently throw exceptions are C<ev_run>,
		3973	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		3974	because it runs cleanup watchers).
		3975
		3976	Throwing exceptions in watcher callbacks is only supported if libev itself
		3977	is compiled with a C++ compiler or your C and C++ environments allow
		3978	throwing exceptions through C libraries (most do).
		3979
		3980	=head2 C++ API
2699		3981
2700	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3982	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2701	you to use some convenience methods to start/stop watchers and also change	3983	you to use some convenience methods to start/stop watchers and also change
2702	the callback model to a model using method callbacks on objects.	3984	the callback model to a model using method callbacks on objects.
2703		3985
2704	To use it,	3986	To use it,
2705		3987
2706	#include <ev++.h>	3988	#include <ev++.h>
2707		3989
2708	This automatically includes F<ev.h> and puts all of its definitions (many	3990	This automatically includes F<ev.h> and puts all of its definitions (many
2709	of them macros) into the global namespace. All C++ specific things are	3991	of them macros) into the global namespace. All C++ specific things are
2710	put into the C<ev> namespace. It should support all the same embedding	3992	put into the C<ev> namespace. It should support all the same embedding
…		…
2713	Care has been taken to keep the overhead low. The only data member the C++	3995	Care has been taken to keep the overhead low. The only data member the C++
2714	classes add (compared to plain C-style watchers) is the event loop pointer	3996	classes add (compared to plain C-style watchers) is the event loop pointer
2715	that the watcher is associated with (or no additional members at all if	3997	that the watcher is associated with (or no additional members at all if
2716	you disable C<EV_MULTIPLICITY> when embedding libev).	3998	you disable C<EV_MULTIPLICITY> when embedding libev).
2717		3999
2718	Currently, functions, and static and non-static member functions can be	4000	Currently, functions, static and non-static member functions and classes
2719	used as callbacks. Other types should be easy to add as long as they only	4001	with C<operator ()> can be used as callbacks. Other types should be easy
2720	need one additional pointer for context. If you need support for other	4002	to add as long as they only need one additional pointer for context. If
2721	types of functors please contact the author (preferably after implementing	4003	you need support for other types of functors please contact the author
2722	it).	4004	(preferably after implementing it).
		4005
		4006	For all this to work, your C++ compiler either has to use the same calling
		4007	conventions as your C compiler (for static member functions), or you have
		4008	to embed libev and compile libev itself as C++.
2723		4009
2724	Here is a list of things available in the C<ev> namespace:	4010	Here is a list of things available in the C<ev> namespace:
2725		4011
2726	=over 4	4012	=over 4
2727		4013
…		…
2737	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4023	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
2738		4024
2739	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4025	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
2740	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4026	the same name in the C<ev> namespace, with the exception of C<ev_signal>
2741	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4027	which is called C<ev::sig> to avoid clashes with the C<signal> macro
2742	defines by many implementations.	4028	defined by many implementations.
2743		4029
2744	All of those classes have these methods:	4030	All of those classes have these methods:
2745		4031
2746	=over 4	4032	=over 4
2747		4033
2748	=item ev::TYPE::TYPE ()	4034	=item ev::TYPE::TYPE ()
2749		4035
2750	=item ev::TYPE::TYPE (struct ev_loop *)	4036	=item ev::TYPE::TYPE (loop)
2751		4037
2752	=item ev::TYPE::~TYPE	4038	=item ev::TYPE::~TYPE
2753		4039
2754	The constructor (optionally) takes an event loop to associate the watcher	4040	The constructor (optionally) takes an event loop to associate the watcher
2755	with. If it is omitted, it will use C<EV_DEFAULT>.	4041	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2787		4073
2788	myclass obj;	4074	myclass obj;
2789	ev::io iow;	4075	ev::io iow;
2790	iow.set <myclass, &myclass::io_cb> (&obj);	4076	iow.set <myclass, &myclass::io_cb> (&obj);
2791		4077
		4078	=item w->set (object *)
		4079
		4080	This is a variation of a method callback - leaving out the method to call
		4081	will default the method to C<operator ()>, which makes it possible to use
		4082	functor objects without having to manually specify the C<operator ()> all
		4083	the time. Incidentally, you can then also leave out the template argument
		4084	list.
		4085
		4086	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		4087	int revents)>.
		4088
		4089	See the method-C<set> above for more details.
		4090
		4091	Example: use a functor object as callback.
		4092
		4093	struct myfunctor
		4094	{
		4095	void operator() (ev::io &w, int revents)
		4096	{
		4097	...
		4098	}
		4099	}
		4100
		4101	myfunctor f;
		4102
		4103	ev::io w;
		4104	w.set (&f);
		4105
2792	=item w->set<function> (void *data = 0)	4106	=item w->set<function> (void *data = 0)
2793		4107
2794	Also sets a callback, but uses a static method or plain function as	4108	Also sets a callback, but uses a static method or plain function as
2795	callback. The optional C<data> argument will be stored in the watcher's	4109	callback. The optional C<data> argument will be stored in the watcher's
2796	C<data> member and is free for you to use.	4110	C<data> member and is free for you to use.
…		…
2802	Example: Use a plain function as callback.	4116	Example: Use a plain function as callback.
2803		4117
2804	static void io_cb (ev::io &w, int revents) { }	4118	static void io_cb (ev::io &w, int revents) { }
2805	iow.set <io_cb> ();	4119	iow.set <io_cb> ();
2806		4120
2807	=item w->set (struct ev_loop *)	4121	=item w->set (loop)
2808		4122
2809	Associates a different C<struct ev_loop> with this watcher. You can only	4123	Associates a different C<struct ev_loop> with this watcher. You can only
2810	do this when the watcher is inactive (and not pending either).	4124	do this when the watcher is inactive (and not pending either).
2811		4125
2812	=item w->set ([arguments])	4126	=item w->set ([arguments])
2813		4127
2814	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4128	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
		4129	with the same arguments. Either this method or a suitable start method
2815	called at least once. Unlike the C counterpart, an active watcher gets	4130	must be called at least once. Unlike the C counterpart, an active watcher
2816	automatically stopped and restarted when reconfiguring it with this	4131	gets automatically stopped and restarted when reconfiguring it with this
2817	method.	4132	method.
		4133
		4134	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4135	clashing with the C<set (loop)> method.
2818		4136
2819	=item w->start ()	4137	=item w->start ()
2820		4138
2821	Starts the watcher. Note that there is no C<loop> argument, as the	4139	Starts the watcher. Note that there is no C<loop> argument, as the
2822	constructor already stores the event loop.	4140	constructor already stores the event loop.
2823		4141
		4142	=item w->start ([arguments])
		4143
		4144	Instead of calling C<set> and C<start> methods separately, it is often
		4145	convenient to wrap them in one call. Uses the same type of arguments as
		4146	the configure C<set> method of the watcher.
		4147
2824	=item w->stop ()	4148	=item w->stop ()
2825		4149
2826	Stops the watcher if it is active. Again, no C<loop> argument.	4150	Stops the watcher if it is active. Again, no C<loop> argument.
2827		4151
2828	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4152	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2840		4164
2841	=back	4165	=back
2842		4166
2843	=back	4167	=back
2844		4168
2845	Example: Define a class with an IO and idle watcher, start one of them in	4169	Example: Define a class with two I/O and idle watchers, start the I/O
2846	the constructor.	4170	watchers in the constructor.
2847		4171
2848	class myclass	4172	class myclass
2849	{	4173	{
2850	ev::io io ; void io_cb (ev::io &w, int revents);	4174	ev::io io ; void io_cb (ev::io &w, int revents);
		4175	ev::io io2 ; void io2_cb (ev::io &w, int revents);
2851	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4176	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2852		4177
2853	myclass (int fd)	4178	myclass (int fd)
2854	{	4179	{
2855	io .set <myclass, &myclass::io_cb > (this);	4180	io .set <myclass, &myclass::io_cb > (this);
		4181	io2 .set <myclass, &myclass::io2_cb > (this);
2856	idle.set <myclass, &myclass::idle_cb> (this);	4182	idle.set <myclass, &myclass::idle_cb> (this);
2857		4183
2858	io.start (fd, ev::READ);	4184	io.set (fd, ev::WRITE); // configure the watcher
		4185	io.start (); // start it whenever convenient
		4186
		4187	io2.start (fd, ev::READ); // set + start in one call
2859	}	4188	}
2860	};	4189	};
2861		4190
2862		4191
2863	=head1 OTHER LANGUAGE BINDINGS	4192	=head1 OTHER LANGUAGE BINDINGS
…		…
2882	L<http://software.schmorp.de/pkg/EV>.	4211	L<http://software.schmorp.de/pkg/EV>.
2883		4212
2884	=item Python	4213	=item Python
2885		4214
2886	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	4215	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2887	seems to be quite complete and well-documented. Note, however, that the	4216	seems to be quite complete and well-documented.
2888	patch they require for libev is outright dangerous as it breaks the ABI
2889	for everybody else, and therefore, should never be applied in an installed
2890	libev (if python requires an incompatible ABI then it needs to embed
2891	libev).
2892		4217
2893	=item Ruby	4218	=item Ruby
2894		4219
2895	Tony Arcieri has written a ruby extension that offers access to a subset	4220	Tony Arcieri has written a ruby extension that offers access to a subset
2896	of the libev API and adds file handle abstractions, asynchronous DNS and	4221	of the libev API and adds file handle abstractions, asynchronous DNS and
2897	more on top of it. It can be found via gem servers. Its homepage is at	4222	more on top of it. It can be found via gem servers. Its homepage is at
2898	L<http://rev.rubyforge.org/>.	4223	L<http://rev.rubyforge.org/>.
2899		4224
		4225	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		4226	makes rev work even on mingw.
		4227
		4228	=item Haskell
		4229
		4230	A haskell binding to libev is available at
		4231	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		4232
2900	=item D	4233	=item D
2901		4234
2902	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4235	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2903	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4236	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
		4237
		4238	=item Ocaml
		4239
		4240	Erkki Seppala has written Ocaml bindings for libev, to be found at
		4241	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		4242
		4243	=item Lua
		4244
		4245	Brian Maher has written a partial interface to libev for lua (at the
		4246	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		4247	L<http://github.com/brimworks/lua-ev>.
		4248
		4249	=item Javascript
		4250
		4251	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4252
		4253	=item Others
		4254
		4255	There are others, and I stopped counting.
2904		4256
2905	=back	4257	=back
2906		4258
2907		4259
2908	=head1 MACRO MAGIC	4260	=head1 MACRO MAGIC
…		…
2922	loop argument"). The C<EV_A> form is used when this is the sole argument,	4274	loop argument"). The C<EV_A> form is used when this is the sole argument,
2923	C<EV_A_> is used when other arguments are following. Example:	4275	C<EV_A_> is used when other arguments are following. Example:
2924		4276
2925	ev_unref (EV_A);	4277	ev_unref (EV_A);
2926	ev_timer_add (EV_A_ watcher);	4278	ev_timer_add (EV_A_ watcher);
2927	ev_loop (EV_A_ 0);	4279	ev_run (EV_A_ 0);
2928		4280
2929	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4281	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2930	which is often provided by the following macro.	4282	which is often provided by the following macro.
2931		4283
2932	=item C<EV_P>, C<EV_P_>	4284	=item C<EV_P>, C<EV_P_>
…		…
2945	suitable for use with C<EV_A>.	4297	suitable for use with C<EV_A>.
2946		4298
2947	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4299	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2948		4300
2949	Similar to the other two macros, this gives you the value of the default	4301	Similar to the other two macros, this gives you the value of the default
2950	loop, if multiple loops are supported ("ev loop default").	4302	loop, if multiple loops are supported ("ev loop default"). The default loop
		4303	will be initialised if it isn't already initialised.
		4304
		4305	For non-multiplicity builds, these macros do nothing, so you always have
		4306	to initialise the loop somewhere.
2951		4307
2952	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4308	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
2953		4309
2954	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4310	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
2955	default loop has been initialised (C<UC> == unchecked). Their behaviour	4311	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
2972	}	4328	}
2973		4329
2974	ev_check check;	4330	ev_check check;
2975	ev_check_init (&check, check_cb);	4331	ev_check_init (&check, check_cb);
2976	ev_check_start (EV_DEFAULT_ &check);	4332	ev_check_start (EV_DEFAULT_ &check);
2977	ev_loop (EV_DEFAULT_ 0);	4333	ev_run (EV_DEFAULT_ 0);
2978		4334
2979	=head1 EMBEDDING	4335	=head1 EMBEDDING
2980		4336
2981	Libev can (and often is) directly embedded into host	4337	Libev can (and often is) directly embedded into host
2982	applications. Examples of applications that embed it include the Deliantra	4338	applications. Examples of applications that embed it include the Deliantra
…		…
3009		4365
3010	#define EV_STANDALONE 1	4366	#define EV_STANDALONE 1
3011	#include "ev.h"	4367	#include "ev.h"
3012		4368
3013	Both header files and implementation files can be compiled with a C++	4369	Both header files and implementation files can be compiled with a C++
3014	compiler (at least, thats a stated goal, and breakage will be treated	4370	compiler (at least, that's a stated goal, and breakage will be treated
3015	as a bug).	4371	as a bug).
3016		4372
3017	You need the following files in your source tree, or in a directory	4373	You need the following files in your source tree, or in a directory
3018	in your include path (e.g. in libev/ when using -Ilibev):	4374	in your include path (e.g. in libev/ when using -Ilibev):
3019		4375
…		…
3062	libev.m4	4418	libev.m4
3063		4419
3064	=head2 PREPROCESSOR SYMBOLS/MACROS	4420	=head2 PREPROCESSOR SYMBOLS/MACROS
3065		4421
3066	Libev can be configured via a variety of preprocessor symbols you have to	4422	Libev can be configured via a variety of preprocessor symbols you have to
3067	define before including any of its files. The default in the absence of	4423	define before including (or compiling) any of its files. The default in
3068	autoconf is documented for every option.	4424	the absence of autoconf is documented for every option.
		4425
		4426	Symbols marked with "(h)" do not change the ABI, and can have different
		4427	values when compiling libev vs. including F<ev.h>, so it is permissible
		4428	to redefine them before including F<ev.h> without breaking compatibility
		4429	to a compiled library. All other symbols change the ABI, which means all
		4430	users of libev and the libev code itself must be compiled with compatible
		4431	settings.
3069		4432
3070	=over 4	4433	=over 4
3071		4434
		4435	=item EV_COMPAT3 (h)
		4436
		4437	Backwards compatibility is a major concern for libev. This is why this
		4438	release of libev comes with wrappers for the functions and symbols that
		4439	have been renamed between libev version 3 and 4.
		4440
		4441	You can disable these wrappers (to test compatibility with future
		4442	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4443	sources. This has the additional advantage that you can drop the C<struct>
		4444	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4445	typedef in that case.
		4446
		4447	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4448	and in some even more future version the compatibility code will be
		4449	removed completely.
		4450
3072	=item EV_STANDALONE	4451	=item EV_STANDALONE (h)
3073		4452
3074	Must always be C<1> if you do not use autoconf configuration, which	4453	Must always be C<1> if you do not use autoconf configuration, which
3075	keeps libev from including F<config.h>, and it also defines dummy	4454	keeps libev from including F<config.h>, and it also defines dummy
3076	implementations for some libevent functions (such as logging, which is not	4455	implementations for some libevent functions (such as logging, which is not
3077	supported). It will also not define any of the structs usually found in	4456	supported). It will also not define any of the structs usually found in
3078	F<event.h> that are not directly supported by the libev core alone.	4457	F<event.h> that are not directly supported by the libev core alone.
3079		4458
		4459	In standalone mode, libev will still try to automatically deduce the
		4460	configuration, but has to be more conservative.
		4461
		4462	=item EV_USE_FLOOR
		4463
		4464	If defined to be C<1>, libev will use the C<floor ()> function for its
		4465	periodic reschedule calculations, otherwise libev will fall back on a
		4466	portable (slower) implementation. If you enable this, you usually have to
		4467	link against libm or something equivalent. Enabling this when the C<floor>
		4468	function is not available will fail, so the safe default is to not enable
		4469	this.
		4470
3080	=item EV_USE_MONOTONIC	4471	=item EV_USE_MONOTONIC
3081		4472
3082	If defined to be C<1>, libev will try to detect the availability of the	4473	If defined to be C<1>, libev will try to detect the availability of the
3083	monotonic clock option at both compile time and runtime. Otherwise no use	4474	monotonic clock option at both compile time and runtime. Otherwise no
3084	of the monotonic clock option will be attempted. If you enable this, you	4475	use of the monotonic clock option will be attempted. If you enable this,
3085	usually have to link against librt or something similar. Enabling it when	4476	you usually have to link against librt or something similar. Enabling it
3086	the functionality isn't available is safe, though, although you have	4477	when the functionality isn't available is safe, though, although you have
3087	to make sure you link against any libraries where the C<clock_gettime>	4478	to make sure you link against any libraries where the C<clock_gettime>
3088	function is hiding in (often F<-lrt>).	4479	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
3089		4480
3090	=item EV_USE_REALTIME	4481	=item EV_USE_REALTIME
3091		4482
3092	If defined to be C<1>, libev will try to detect the availability of the	4483	If defined to be C<1>, libev will try to detect the availability of the
3093	real-time clock option at compile time (and assume its availability at	4484	real-time clock option at compile time (and assume its availability
3094	runtime if successful). Otherwise no use of the real-time clock option will	4485	at runtime if successful). Otherwise no use of the real-time clock
3095	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	4486	option will be attempted. This effectively replaces C<gettimeofday>
3096	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	4487	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
3097	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	4488	correctness. See the note about libraries in the description of
		4489	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		4490	C<EV_USE_CLOCK_SYSCALL>.
		4491
		4492	=item EV_USE_CLOCK_SYSCALL
		4493
		4494	If defined to be C<1>, libev will try to use a direct syscall instead
		4495	of calling the system-provided C<clock_gettime> function. This option
		4496	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		4497	unconditionally pulls in C<libpthread>, slowing down single-threaded
		4498	programs needlessly. Using a direct syscall is slightly slower (in
		4499	theory), because no optimised vdso implementation can be used, but avoids
		4500	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		4501	higher, as it simplifies linking (no need for C<-lrt>).
3098		4502
3099	=item EV_USE_NANOSLEEP	4503	=item EV_USE_NANOSLEEP
3100		4504
3101	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	4505	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
3102	and will use it for delays. Otherwise it will use C<select ()>.	4506	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3118		4522
3119	=item EV_SELECT_USE_FD_SET	4523	=item EV_SELECT_USE_FD_SET
3120		4524
3121	If defined to C<1>, then the select backend will use the system C<fd_set>	4525	If defined to C<1>, then the select backend will use the system C<fd_set>
3122	structure. This is useful if libev doesn't compile due to a missing	4526	structure. This is useful if libev doesn't compile due to a missing
3123	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	4527	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3124	exotic systems. This usually limits the range of file descriptors to some	4528	on exotic systems. This usually limits the range of file descriptors to
3125	low limit such as 1024 or might have other limitations (winsocket only	4529	some low limit such as 1024 or might have other limitations (winsocket
3126	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	4530	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3127	influence the size of the C<fd_set> used.	4531	configures the maximum size of the C<fd_set>.
3128		4532
3129	=item EV_SELECT_IS_WINSOCKET	4533	=item EV_SELECT_IS_WINSOCKET
3130		4534
3131	When defined to C<1>, the select backend will assume that	4535	When defined to C<1>, the select backend will assume that
3132	select/socket/connect etc. don't understand file descriptors but	4536	select/socket/connect etc. don't understand file descriptors but
…		…
3134	be used is the winsock select). This means that it will call	4538	be used is the winsock select). This means that it will call
3135	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4539	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3136	it is assumed that all these functions actually work on fds, even	4540	it is assumed that all these functions actually work on fds, even
3137	on win32. Should not be defined on non-win32 platforms.	4541	on win32. Should not be defined on non-win32 platforms.
3138		4542
3139	=item EV_FD_TO_WIN32_HANDLE	4543	=item EV_FD_TO_WIN32_HANDLE(fd)
3140		4544
3141	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4545	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3142	file descriptors to socket handles. When not defining this symbol (the	4546	file descriptors to socket handles. When not defining this symbol (the
3143	default), then libev will call C<_get_osfhandle>, which is usually	4547	default), then libev will call C<_get_osfhandle>, which is usually
3144	correct. In some cases, programs use their own file descriptor management,	4548	correct. In some cases, programs use their own file descriptor management,
3145	in which case they can provide this function to map fds to socket handles.	4549	in which case they can provide this function to map fds to socket handles.
		4550
		4551	=item EV_WIN32_HANDLE_TO_FD(handle)
		4552
		4553	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4554	using the standard C<_open_osfhandle> function. For programs implementing
		4555	their own fd to handle mapping, overwriting this function makes it easier
		4556	to do so. This can be done by defining this macro to an appropriate value.
		4557
		4558	=item EV_WIN32_CLOSE_FD(fd)
		4559
		4560	If programs implement their own fd to handle mapping on win32, then this
		4561	macro can be used to override the C<close> function, useful to unregister
		4562	file descriptors again. Note that the replacement function has to close
		4563	the underlying OS handle.
		4564
		4565	=item EV_USE_WSASOCKET
		4566
		4567	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4568	communication socket, which works better in some environments. Otherwise,
		4569	the normal C<socket> function will be used, which works better in other
		4570	environments.
3146		4571
3147	=item EV_USE_POLL	4572	=item EV_USE_POLL
3148		4573
3149	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4574	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3150	backend. Otherwise it will be enabled on non-win32 platforms. It	4575	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3186	If defined to be C<1>, libev will compile in support for the Linux inotify	4611	If defined to be C<1>, libev will compile in support for the Linux inotify
3187	interface to speed up C<ev_stat> watchers. Its actual availability will	4612	interface to speed up C<ev_stat> watchers. Its actual availability will
3188	be detected at runtime. If undefined, it will be enabled if the headers	4613	be detected at runtime. If undefined, it will be enabled if the headers
3189	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4614	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3190		4615
		4616	=item EV_NO_SMP
		4617
		4618	If defined to be C<1>, libev will assume that memory is always coherent
		4619	between threads, that is, threads can be used, but threads never run on
		4620	different cpus (or different cpu cores). This reduces dependencies
		4621	and makes libev faster.
		4622
		4623	=item EV_NO_THREADS
		4624
		4625	If defined to be C<1>, libev will assume that it will never be called from
		4626	different threads (that includes signal handlers), which is a stronger
		4627	assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes
		4628	libev faster.
		4629
3191	=item EV_ATOMIC_T	4630	=item EV_ATOMIC_T
3192		4631
3193	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4632	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3194	access is atomic with respect to other threads or signal contexts. No such	4633	access is atomic with respect to other threads or signal contexts. No
3195	type is easily found in the C language, so you can provide your own type	4634	such type is easily found in the C language, so you can provide your own
3196	that you know is safe for your purposes. It is used both for signal handler "locking"	4635	type that you know is safe for your purposes. It is used both for signal
3197	as well as for signal and thread safety in C<ev_async> watchers.	4636	handler "locking" as well as for signal and thread safety in C<ev_async>
		4637	watchers.
3198		4638
3199	In the absence of this define, libev will use C<sig_atomic_t volatile>	4639	In the absence of this define, libev will use C<sig_atomic_t volatile>
3200	(from F<signal.h>), which is usually good enough on most platforms.	4640	(from F<signal.h>), which is usually good enough on most platforms.
3201		4641
3202	=item EV_H	4642	=item EV_H (h)
3203		4643
3204	The name of the F<ev.h> header file used to include it. The default if	4644	The name of the F<ev.h> header file used to include it. The default if
3205	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4645	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3206	used to virtually rename the F<ev.h> header file in case of conflicts.	4646	used to virtually rename the F<ev.h> header file in case of conflicts.
3207		4647
3208	=item EV_CONFIG_H	4648	=item EV_CONFIG_H (h)
3209		4649
3210	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4650	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3211	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4651	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3212	C<EV_H>, above.	4652	C<EV_H>, above.
3213		4653
3214	=item EV_EVENT_H	4654	=item EV_EVENT_H (h)
3215		4655
3216	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4656	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3217	of how the F<event.h> header can be found, the default is C<"event.h">.	4657	of how the F<event.h> header can be found, the default is C<"event.h">.
3218		4658
3219	=item EV_PROTOTYPES	4659	=item EV_PROTOTYPES (h)
3220		4660
3221	If defined to be C<0>, then F<ev.h> will not define any function	4661	If defined to be C<0>, then F<ev.h> will not define any function
3222	prototypes, but still define all the structs and other symbols. This is	4662	prototypes, but still define all the structs and other symbols. This is
3223	occasionally useful if you want to provide your own wrapper functions	4663	occasionally useful if you want to provide your own wrapper functions
3224	around libev functions.	4664	around libev functions.
…		…
3229	will have the C<struct ev_loop *> as first argument, and you can create	4669	will have the C<struct ev_loop *> as first argument, and you can create
3230	additional independent event loops. Otherwise there will be no support	4670	additional independent event loops. Otherwise there will be no support
3231	for multiple event loops and there is no first event loop pointer	4671	for multiple event loops and there is no first event loop pointer
3232	argument. Instead, all functions act on the single default loop.	4672	argument. Instead, all functions act on the single default loop.
3233		4673
		4674	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4675	default loop when multiplicity is switched off - you always have to
		4676	initialise the loop manually in this case.
		4677
3234	=item EV_MINPRI	4678	=item EV_MINPRI
3235		4679
3236	=item EV_MAXPRI	4680	=item EV_MAXPRI
3237		4681
3238	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4682	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3246	fine.	4690	fine.
3247		4691
3248	If your embedding application does not need any priorities, defining these	4692	If your embedding application does not need any priorities, defining these
3249	both to C<0> will save some memory and CPU.	4693	both to C<0> will save some memory and CPU.
3250		4694
3251	=item EV_PERIODIC_ENABLE	4695	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4696	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4697	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3252		4698
3253	If undefined or defined to be C<1>, then periodic timers are supported. If	4699	If undefined or defined to be C<1> (and the platform supports it), then
3254	defined to be C<0>, then they are not. Disabling them saves a few kB of	4700	the respective watcher type is supported. If defined to be C<0>, then it
3255	code.	4701	is not. Disabling watcher types mainly saves code size.
3256		4702
3257	=item EV_IDLE_ENABLE	4703	=item EV_FEATURES
3258
3259	If undefined or defined to be C<1>, then idle watchers are supported. If
3260	defined to be C<0>, then they are not. Disabling them saves a few kB of
3261	code.
3262
3263	=item EV_EMBED_ENABLE
3264
3265	If undefined or defined to be C<1>, then embed watchers are supported. If
3266	defined to be C<0>, then they are not. Embed watchers rely on most other
3267	watcher types, which therefore must not be disabled.
3268
3269	=item EV_STAT_ENABLE
3270
3271	If undefined or defined to be C<1>, then stat watchers are supported. If
3272	defined to be C<0>, then they are not.
3273
3274	=item EV_FORK_ENABLE
3275
3276	If undefined or defined to be C<1>, then fork watchers are supported. If
3277	defined to be C<0>, then they are not.
3278
3279	=item EV_ASYNC_ENABLE
3280
3281	If undefined or defined to be C<1>, then async watchers are supported. If
3282	defined to be C<0>, then they are not.
3283
3284	=item EV_MINIMAL
3285		4704
3286	If you need to shave off some kilobytes of code at the expense of some	4705	If you need to shave off some kilobytes of code at the expense of some
3287	speed, define this symbol to C<1>. Currently this is used to override some	4706	speed (but with the full API), you can define this symbol to request
3288	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4707	certain subsets of functionality. The default is to enable all features
3289	much smaller 2-heap for timer management over the default 4-heap.	4708	that can be enabled on the platform.
		4709
		4710	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4711	with some broad features you want) and then selectively re-enable
		4712	additional parts you want, for example if you want everything minimal,
		4713	but multiple event loop support, async and child watchers and the poll
		4714	backend, use this:
		4715
		4716	#define EV_FEATURES 0
		4717	#define EV_MULTIPLICITY 1
		4718	#define EV_USE_POLL 1
		4719	#define EV_CHILD_ENABLE 1
		4720	#define EV_ASYNC_ENABLE 1
		4721
		4722	The actual value is a bitset, it can be a combination of the following
		4723	values (by default, all of these are enabled):
		4724
		4725	=over 4
		4726
		4727	=item C<1> - faster/larger code
		4728
		4729	Use larger code to speed up some operations.
		4730
		4731	Currently this is used to override some inlining decisions (enlarging the
		4732	code size by roughly 30% on amd64).
		4733
		4734	When optimising for size, use of compiler flags such as C<-Os> with
		4735	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4736	assertions.
		4737
		4738	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4739	(e.g. gcc with C<-Os>).
		4740
		4741	=item C<2> - faster/larger data structures
		4742
		4743	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4744	hash table sizes and so on. This will usually further increase code size
		4745	and can additionally have an effect on the size of data structures at
		4746	runtime.
		4747
		4748	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4749	(e.g. gcc with C<-Os>).
		4750
		4751	=item C<4> - full API configuration
		4752
		4753	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4754	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4755
		4756	=item C<8> - full API
		4757
		4758	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4759	details on which parts of the API are still available without this
		4760	feature, and do not complain if this subset changes over time.
		4761
		4762	=item C<16> - enable all optional watcher types
		4763
		4764	Enables all optional watcher types. If you want to selectively enable
		4765	only some watcher types other than I/O and timers (e.g. prepare,
		4766	embed, async, child...) you can enable them manually by defining
		4767	C<EV_watchertype_ENABLE> to C<1> instead.
		4768
		4769	=item C<32> - enable all backends
		4770
		4771	This enables all backends - without this feature, you need to enable at
		4772	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4773
		4774	=item C<64> - enable OS-specific "helper" APIs
		4775
		4776	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4777	default.
		4778
		4779	=back
		4780
		4781	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4782	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4783	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4784	watchers, timers and monotonic clock support.
		4785
		4786	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4787	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4788	your program might be left out as well - a binary starting a timer and an
		4789	I/O watcher then might come out at only 5Kb.
		4790
		4791	=item EV_API_STATIC
		4792
		4793	If this symbol is defined (by default it is not), then all identifiers
		4794	will have static linkage. This means that libev will not export any
		4795	identifiers, and you cannot link against libev anymore. This can be useful
		4796	when you embed libev, only want to use libev functions in a single file,
		4797	and do not want its identifiers to be visible.
		4798
		4799	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4800	wants to use libev.
		4801
		4802	This option only works when libev is compiled with a C compiler, as C++
		4803	doesn't support the required declaration syntax.
		4804
		4805	=item EV_AVOID_STDIO
		4806
		4807	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4808	functions (printf, scanf, perror etc.). This will increase the code size
		4809	somewhat, but if your program doesn't otherwise depend on stdio and your
		4810	libc allows it, this avoids linking in the stdio library which is quite
		4811	big.
		4812
		4813	Note that error messages might become less precise when this option is
		4814	enabled.
		4815
		4816	=item EV_NSIG
		4817
		4818	The highest supported signal number, +1 (or, the number of
		4819	signals): Normally, libev tries to deduce the maximum number of signals
		4820	automatically, but sometimes this fails, in which case it can be
		4821	specified. Also, using a lower number than detected (C<32> should be
		4822	good for about any system in existence) can save some memory, as libev
		4823	statically allocates some 12-24 bytes per signal number.
3290		4824
3291	=item EV_PID_HASHSIZE	4825	=item EV_PID_HASHSIZE
3292		4826
3293	C<ev_child> watchers use a small hash table to distribute workload by	4827	C<ev_child> watchers use a small hash table to distribute workload by
3294	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4828	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3295	than enough. If you need to manage thousands of children you might want to	4829	usually more than enough. If you need to manage thousands of children you
3296	increase this value (I<must> be a power of two).	4830	might want to increase this value (I<must> be a power of two).
3297		4831
3298	=item EV_INOTIFY_HASHSIZE	4832	=item EV_INOTIFY_HASHSIZE
3299		4833
3300	C<ev_stat> watchers use a small hash table to distribute workload by	4834	C<ev_stat> watchers use a small hash table to distribute workload by
3301	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4835	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3302	usually more than enough. If you need to manage thousands of C<ev_stat>	4836	disabled), usually more than enough. If you need to manage thousands of
3303	watchers you might want to increase this value (I<must> be a power of	4837	C<ev_stat> watchers you might want to increase this value (I<must> be a
3304	two).	4838	power of two).
3305		4839
3306	=item EV_USE_4HEAP	4840	=item EV_USE_4HEAP
3307		4841
3308	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4842	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3309	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4843	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3310	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4844	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3311	faster performance with many (thousands) of watchers.	4845	faster performance with many (thousands) of watchers.
3312		4846
3313	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4847	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3314	(disabled).	4848	will be C<0>.
3315		4849
3316	=item EV_HEAP_CACHE_AT	4850	=item EV_HEAP_CACHE_AT
3317		4851
3318	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4852	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3319	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4853	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3320	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4854	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3321	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4855	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3322	but avoids random read accesses on heap changes. This improves performance	4856	but avoids random read accesses on heap changes. This improves performance
3323	noticeably with many (hundreds) of watchers.	4857	noticeably with many (hundreds) of watchers.
3324		4858
3325	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4859	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3326	(disabled).	4860	will be C<0>.
3327		4861
3328	=item EV_VERIFY	4862	=item EV_VERIFY
3329		4863
3330	Controls how much internal verification (see C<ev_loop_verify ()>) will	4864	Controls how much internal verification (see C<ev_verify ()>) will
3331	be done: If set to C<0>, no internal verification code will be compiled	4865	be done: If set to C<0>, no internal verification code will be compiled
3332	in. If set to C<1>, then verification code will be compiled in, but not	4866	in. If set to C<1>, then verification code will be compiled in, but not
3333	called. If set to C<2>, then the internal verification code will be	4867	called. If set to C<2>, then the internal verification code will be
3334	called once per loop, which can slow down libev. If set to C<3>, then the	4868	called once per loop, which can slow down libev. If set to C<3>, then the
3335	verification code will be called very frequently, which will slow down	4869	verification code will be called very frequently, which will slow down
3336	libev considerably.	4870	libev considerably.
3337		4871
3338	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4872	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3339	C<0>.	4873	will be C<0>.
3340		4874
3341	=item EV_COMMON	4875	=item EV_COMMON
3342		4876
3343	By default, all watchers have a C<void *data> member. By redefining	4877	By default, all watchers have a C<void *data> member. By redefining
3344	this macro to a something else you can include more and other types of	4878	this macro to something else you can include more and other types of
3345	members. You have to define it each time you include one of the files,	4879	members. You have to define it each time you include one of the files,
3346	though, and it must be identical each time.	4880	though, and it must be identical each time.
3347		4881
3348	For example, the perl EV module uses something like this:	4882	For example, the perl EV module uses something like this:
3349		4883
…		…
3402	file.	4936	file.
3403		4937
3404	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4938	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3405	that everybody includes and which overrides some configure choices:	4939	that everybody includes and which overrides some configure choices:
3406		4940
3407	#define EV_MINIMAL 1	4941	#define EV_FEATURES 8
3408	#define EV_USE_POLL 0	4942	#define EV_USE_SELECT 1
3409	#define EV_MULTIPLICITY 0
3410	#define EV_PERIODIC_ENABLE 0	4943	#define EV_PREPARE_ENABLE 1
		4944	#define EV_IDLE_ENABLE 1
3411	#define EV_STAT_ENABLE 0	4945	#define EV_SIGNAL_ENABLE 1
3412	#define EV_FORK_ENABLE 0	4946	#define EV_CHILD_ENABLE 1
		4947	#define EV_USE_STDEXCEPT 0
3413	#define EV_CONFIG_H <config.h>	4948	#define EV_CONFIG_H <config.h>
3414	#define EV_MINPRI 0
3415	#define EV_MAXPRI 0
3416		4949
3417	#include "ev++.h"	4950	#include "ev++.h"
3418		4951
3419	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4952	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3420		4953
3421	#include "ev_cpp.h"	4954	#include "ev_cpp.h"
3422	#include "ev.c"	4955	#include "ev.c"
3423		4956
3424	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4957	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3425		4958
3426	=head2 THREADS AND COROUTINES	4959	=head2 THREADS AND COROUTINES
3427		4960
3428	=head3 THREADS	4961	=head3 THREADS
3429		4962
…		…
3480	default loop and triggering an C<ev_async> watcher from the default loop	5013	default loop and triggering an C<ev_async> watcher from the default loop
3481	watcher callback into the event loop interested in the signal.	5014	watcher callback into the event loop interested in the signal.
3482		5015
3483	=back	5016	=back
3484		5017
		5018	See also L</THREAD LOCKING EXAMPLE>.
		5019
3485	=head3 COROUTINES	5020	=head3 COROUTINES
3486		5021
3487	Libev is very accommodating to coroutines ("cooperative threads"):	5022	Libev is very accommodating to coroutines ("cooperative threads"):
3488	libev fully supports nesting calls to its functions from different	5023	libev fully supports nesting calls to its functions from different
3489	coroutines (e.g. you can call C<ev_loop> on the same loop from two	5024	coroutines (e.g. you can call C<ev_run> on the same loop from two
3490	different coroutines, and switch freely between both coroutines running the	5025	different coroutines, and switch freely between both coroutines running
3491	loop, as long as you don't confuse yourself). The only exception is that	5026	the loop, as long as you don't confuse yourself). The only exception is
3492	you must not do this from C<ev_periodic> reschedule callbacks.	5027	that you must not do this from C<ev_periodic> reschedule callbacks.
3493		5028
3494	Care has been taken to ensure that libev does not keep local state inside	5029	Care has been taken to ensure that libev does not keep local state inside
3495	C<ev_loop>, and other calls do not usually allow for coroutine switches as	5030	C<ev_run>, and other calls do not usually allow for coroutine switches as
3496	they do not clal any callbacks.	5031	they do not call any callbacks.
3497		5032
3498	=head2 COMPILER WARNINGS	5033	=head2 COMPILER WARNINGS
3499		5034
3500	Depending on your compiler and compiler settings, you might get no or a	5035	Depending on your compiler and compiler settings, you might get no or a
3501	lot of warnings when compiling libev code. Some people are apparently	5036	lot of warnings when compiling libev code. Some people are apparently
…		…
3511	maintainable.	5046	maintainable.
3512		5047
3513	And of course, some compiler warnings are just plain stupid, or simply	5048	And of course, some compiler warnings are just plain stupid, or simply
3514	wrong (because they don't actually warn about the condition their message	5049	wrong (because they don't actually warn about the condition their message
3515	seems to warn about). For example, certain older gcc versions had some	5050	seems to warn about). For example, certain older gcc versions had some
3516	warnings that resulted an extreme number of false positives. These have	5051	warnings that resulted in an extreme number of false positives. These have
3517	been fixed, but some people still insist on making code warn-free with	5052	been fixed, but some people still insist on making code warn-free with
3518	such buggy versions.	5053	such buggy versions.
3519		5054
3520	While libev is written to generate as few warnings as possible,	5055	While libev is written to generate as few warnings as possible,
3521	"warn-free" code is not a goal, and it is recommended not to build libev	5056	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3535	==2274== definitely lost: 0 bytes in 0 blocks.	5070	==2274== definitely lost: 0 bytes in 0 blocks.
3536	==2274== possibly lost: 0 bytes in 0 blocks.	5071	==2274== possibly lost: 0 bytes in 0 blocks.
3537	==2274== still reachable: 256 bytes in 1 blocks.	5072	==2274== still reachable: 256 bytes in 1 blocks.
3538		5073
3539	Then there is no memory leak, just as memory accounted to global variables	5074	Then there is no memory leak, just as memory accounted to global variables
3540	is not a memleak - the memory is still being refernced, and didn't leak.	5075	is not a memleak - the memory is still being referenced, and didn't leak.
3541		5076
3542	Similarly, under some circumstances, valgrind might report kernel bugs	5077	Similarly, under some circumstances, valgrind might report kernel bugs
3543	as if it were a bug in libev (e.g. in realloc or in the poll backend,	5078	as if it were a bug in libev (e.g. in realloc or in the poll backend,
3544	although an acceptable workaround has been found here), or it might be	5079	although an acceptable workaround has been found here), or it might be
3545	confused.	5080	confused.
…		…
3557	I suggest using suppression lists.	5092	I suggest using suppression lists.
3558		5093
3559		5094
3560	=head1 PORTABILITY NOTES	5095	=head1 PORTABILITY NOTES
3561		5096
		5097	=head2 GNU/LINUX 32 BIT LIMITATIONS
		5098
		5099	GNU/Linux is the only common platform that supports 64 bit file/large file
		5100	interfaces but I<disables> them by default.
		5101
		5102	That means that libev compiled in the default environment doesn't support
		5103	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		5104
		5105	Unfortunately, many programs try to work around this GNU/Linux issue
		5106	by enabling the large file API, which makes them incompatible with the
		5107	standard libev compiled for their system.
		5108
		5109	Likewise, libev cannot enable the large file API itself as this would
		5110	suddenly make it incompatible to the default compile time environment,
		5111	i.e. all programs not using special compile switches.
		5112
		5113	=head2 OS/X AND DARWIN BUGS
		5114
		5115	The whole thing is a bug if you ask me - basically any system interface
		5116	you touch is broken, whether it is locales, poll, kqueue or even the
		5117	OpenGL drivers.
		5118
		5119	=head3 C<kqueue> is buggy
		5120
		5121	The kqueue syscall is broken in all known versions - most versions support
		5122	only sockets, many support pipes.
		5123
		5124	Libev tries to work around this by not using C<kqueue> by default on this
		5125	rotten platform, but of course you can still ask for it when creating a
		5126	loop - embedding a socket-only kqueue loop into a select-based one is
		5127	probably going to work well.
		5128
		5129	=head3 C<poll> is buggy
		5130
		5131	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		5132	implementation by something calling C<kqueue> internally around the 10.5.6
		5133	release, so now C<kqueue> I<and> C<poll> are broken.
		5134
		5135	Libev tries to work around this by not using C<poll> by default on
		5136	this rotten platform, but of course you can still ask for it when creating
		5137	a loop.
		5138
		5139	=head3 C<select> is buggy
		5140
		5141	All that's left is C<select>, and of course Apple found a way to fuck this
		5142	one up as well: On OS/X, C<select> actively limits the number of file
		5143	descriptors you can pass in to 1024 - your program suddenly crashes when
		5144	you use more.
		5145
		5146	There is an undocumented "workaround" for this - defining
		5147	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		5148	work on OS/X.
		5149
		5150	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		5151
		5152	=head3 C<errno> reentrancy
		5153
		5154	The default compile environment on Solaris is unfortunately so
		5155	thread-unsafe that you can't even use components/libraries compiled
		5156	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		5157	defined by default. A valid, if stupid, implementation choice.
		5158
		5159	If you want to use libev in threaded environments you have to make sure
		5160	it's compiled with C<_REENTRANT> defined.
		5161
		5162	=head3 Event port backend
		5163
		5164	The scalable event interface for Solaris is called "event
		5165	ports". Unfortunately, this mechanism is very buggy in all major
		5166	releases. If you run into high CPU usage, your program freezes or you get
		5167	a large number of spurious wakeups, make sure you have all the relevant
		5168	and latest kernel patches applied. No, I don't know which ones, but there
		5169	are multiple ones to apply, and afterwards, event ports actually work
		5170	great.
		5171
		5172	If you can't get it to work, you can try running the program by setting
		5173	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		5174	C<select> backends.
		5175
		5176	=head2 AIX POLL BUG
		5177
		5178	AIX unfortunately has a broken C<poll.h> header. Libev works around
		5179	this by trying to avoid the poll backend altogether (i.e. it's not even
		5180	compiled in), which normally isn't a big problem as C<select> works fine
		5181	with large bitsets on AIX, and AIX is dead anyway.
		5182
3562	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5183	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		5184
		5185	=head3 General issues
3563		5186
3564	Win32 doesn't support any of the standards (e.g. POSIX) that libev	5187	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3565	requires, and its I/O model is fundamentally incompatible with the POSIX	5188	requires, and its I/O model is fundamentally incompatible with the POSIX
3566	model. Libev still offers limited functionality on this platform in	5189	model. Libev still offers limited functionality on this platform in
3567	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5190	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3568	descriptors. This only applies when using Win32 natively, not when using	5191	descriptors. This only applies when using Win32 natively, not when using
3569	e.g. cygwin.	5192	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		5193	as every compiler comes with a slightly differently broken/incompatible
		5194	environment.
3570		5195
3571	Lifting these limitations would basically require the full	5196	Lifting these limitations would basically require the full
3572	re-implementation of the I/O system. If you are into these kinds of	5197	re-implementation of the I/O system. If you are into this kind of thing,
3573	things, then note that glib does exactly that for you in a very portable	5198	then note that glib does exactly that for you in a very portable way (note
3574	way (note also that glib is the slowest event library known to man).	5199	also that glib is the slowest event library known to man).
3575		5200
3576	There is no supported compilation method available on windows except	5201	There is no supported compilation method available on windows except
3577	embedding it into other applications.	5202	embedding it into other applications.
		5203
		5204	Sensible signal handling is officially unsupported by Microsoft - libev
		5205	tries its best, but under most conditions, signals will simply not work.
3578		5206
3579	Not a libev limitation but worth mentioning: windows apparently doesn't	5207	Not a libev limitation but worth mentioning: windows apparently doesn't
3580	accept large writes: instead of resulting in a partial write, windows will	5208	accept large writes: instead of resulting in a partial write, windows will
3581	either accept everything or return C<ENOBUFS> if the buffer is too large,	5209	either accept everything or return C<ENOBUFS> if the buffer is too large,
3582	so make sure you only write small amounts into your sockets (less than a	5210	so make sure you only write small amounts into your sockets (less than a
…		…
3587	the abysmal performance of winsockets, using a large number of sockets	5215	the abysmal performance of winsockets, using a large number of sockets
3588	is not recommended (and not reasonable). If your program needs to use	5216	is not recommended (and not reasonable). If your program needs to use
3589	more than a hundred or so sockets, then likely it needs to use a totally	5217	more than a hundred or so sockets, then likely it needs to use a totally
3590	different implementation for windows, as libev offers the POSIX readiness	5218	different implementation for windows, as libev offers the POSIX readiness
3591	notification model, which cannot be implemented efficiently on windows	5219	notification model, which cannot be implemented efficiently on windows
3592	(Microsoft monopoly games).	5220	(due to Microsoft monopoly games).
3593		5221
3594	A typical way to use libev under windows is to embed it (see the embedding	5222	A typical way to use libev under windows is to embed it (see the embedding
3595	section for details) and use the following F<evwrap.h> header file instead	5223	section for details) and use the following F<evwrap.h> header file instead
3596	of F<ev.h>:	5224	of F<ev.h>:
3597		5225
…		…
3604	you do I<not> compile the F<ev.c> or any other embedded source files!):	5232	you do I<not> compile the F<ev.c> or any other embedded source files!):
3605		5233
3606	#include "evwrap.h"	5234	#include "evwrap.h"
3607	#include "ev.c"	5235	#include "ev.c"
3608		5236
3609	=over 4
3610
3611	=item The winsocket select function	5237	=head3 The winsocket C<select> function
3612		5238
3613	The winsocket C<select> function doesn't follow POSIX in that it	5239	The winsocket C<select> function doesn't follow POSIX in that it
3614	requires socket I<handles> and not socket I<file descriptors> (it is	5240	requires socket I<handles> and not socket I<file descriptors> (it is
3615	also extremely buggy). This makes select very inefficient, and also	5241	also extremely buggy). This makes select very inefficient, and also
3616	requires a mapping from file descriptors to socket handles (the Microsoft	5242	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3625	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	5251	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3626		5252
3627	Note that winsockets handling of fd sets is O(n), so you can easily get a	5253	Note that winsockets handling of fd sets is O(n), so you can easily get a
3628	complexity in the O(n²) range when using win32.	5254	complexity in the O(n²) range when using win32.
3629		5255
3630	=item Limited number of file descriptors	5256	=head3 Limited number of file descriptors
3631		5257
3632	Windows has numerous arbitrary (and low) limits on things.	5258	Windows has numerous arbitrary (and low) limits on things.
3633		5259
3634	Early versions of winsocket's select only supported waiting for a maximum	5260	Early versions of winsocket's select only supported waiting for a maximum
3635	of C<64> handles (probably owning to the fact that all windows kernels	5261	of C<64> handles (probably owning to the fact that all windows kernels
3636	can only wait for C<64> things at the same time internally; Microsoft	5262	can only wait for C<64> things at the same time internally; Microsoft
3637	recommends spawning a chain of threads and wait for 63 handles and the	5263	recommends spawning a chain of threads and wait for 63 handles and the
3638	previous thread in each. Great).	5264	previous thread in each. Sounds great!).
3639		5265
3640	Newer versions support more handles, but you need to define C<FD_SETSIZE>	5266	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3641	to some high number (e.g. C<2048>) before compiling the winsocket select	5267	to some high number (e.g. C<2048>) before compiling the winsocket select
3642	call (which might be in libev or elsewhere, for example, perl does its own	5268	call (which might be in libev or elsewhere, for example, perl and many
3643	select emulation on windows).	5269	other interpreters do their own select emulation on windows).
3644		5270
3645	Another limit is the number of file descriptors in the Microsoft runtime	5271	Another limit is the number of file descriptors in the Microsoft runtime
3646	libraries, which by default is C<64> (there must be a hidden I<64> fetish	5272	libraries, which by default is C<64> (there must be a hidden I<64>
3647	or something like this inside Microsoft). You can increase this by calling	5273	fetish or something like this inside Microsoft). You can increase this
3648	C<_setmaxstdio>, which can increase this limit to C<2048> (another	5274	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3649	arbitrary limit), but is broken in many versions of the Microsoft runtime	5275	(another arbitrary limit), but is broken in many versions of the Microsoft
3650	libraries.
3651
3652	This might get you to about C<512> or C<2048> sockets (depending on	5276	runtime libraries. This might get you to about C<512> or C<2048> sockets
3653	windows version and/or the phase of the moon). To get more, you need to	5277	(depending on windows version and/or the phase of the moon). To get more,
3654	wrap all I/O functions and provide your own fd management, but the cost of	5278	you need to wrap all I/O functions and provide your own fd management, but
3655	calling select (O(n²)) will likely make this unworkable.	5279	the cost of calling select (O(n²)) will likely make this unworkable.
3656
3657	=back
3658		5280
3659	=head2 PORTABILITY REQUIREMENTS	5281	=head2 PORTABILITY REQUIREMENTS
3660		5282
3661	In addition to a working ISO-C implementation and of course the	5283	In addition to a working ISO-C implementation and of course the
3662	backend-specific APIs, libev relies on a few additional extensions:	5284	backend-specific APIs, libev relies on a few additional extensions:
…		…
3669	Libev assumes not only that all watcher pointers have the same internal	5291	Libev assumes not only that all watcher pointers have the same internal
3670	structure (guaranteed by POSIX but not by ISO C for example), but it also	5292	structure (guaranteed by POSIX but not by ISO C for example), but it also
3671	assumes that the same (machine) code can be used to call any watcher	5293	assumes that the same (machine) code can be used to call any watcher
3672	callback: The watcher callbacks have different type signatures, but libev	5294	callback: The watcher callbacks have different type signatures, but libev
3673	calls them using an C<ev_watcher *> internally.	5295	calls them using an C<ev_watcher *> internally.
		5296
		5297	=item pointer accesses must be thread-atomic
		5298
		5299	Accessing a pointer value must be atomic, it must both be readable and
		5300	writable in one piece - this is the case on all current architectures.
3674		5301
3675	=item C<sig_atomic_t volatile> must be thread-atomic as well	5302	=item C<sig_atomic_t volatile> must be thread-atomic as well
3676		5303
3677	The type C<sig_atomic_t volatile> (or whatever is defined as	5304	The type C<sig_atomic_t volatile> (or whatever is defined as
3678	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5305	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
3687	thread" or will block signals process-wide, both behaviours would	5314	thread" or will block signals process-wide, both behaviours would
3688	be compatible with libev. Interaction between C<sigprocmask> and	5315	be compatible with libev. Interaction between C<sigprocmask> and
3689	C<pthread_sigmask> could complicate things, however.	5316	C<pthread_sigmask> could complicate things, however.
3690		5317
3691	The most portable way to handle signals is to block signals in all threads	5318	The most portable way to handle signals is to block signals in all threads
3692	except the initial one, and run the default loop in the initial thread as	5319	except the initial one, and run the signal handling loop in the initial
3693	well.	5320	thread as well.
3694		5321
3695	=item C<long> must be large enough for common memory allocation sizes	5322	=item C<long> must be large enough for common memory allocation sizes
3696		5323
3697	To improve portability and simplify its API, libev uses C<long> internally	5324	To improve portability and simplify its API, libev uses C<long> internally
3698	instead of C<size_t> when allocating its data structures. On non-POSIX	5325	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
3701	watchers.	5328	watchers.
3702		5329
3703	=item C<double> must hold a time value in seconds with enough accuracy	5330	=item C<double> must hold a time value in seconds with enough accuracy
3704		5331
3705	The type C<double> is used to represent timestamps. It is required to	5332	The type C<double> is used to represent timestamps. It is required to
3706	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5333	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3707	enough for at least into the year 4000. This requirement is fulfilled by	5334	good enough for at least into the year 4000 with millisecond accuracy
		5335	(the design goal for libev). This requirement is overfulfilled by
3708	implementations implementing IEEE 754 (basically all existing ones).	5336	implementations using IEEE 754, which is basically all existing ones.
		5337
		5338	With IEEE 754 doubles, you get microsecond accuracy until at least the
		5339	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5340	is either obsolete or somebody patched it to use C<long double> or
		5341	something like that, just kidding).
3709		5342
3710	=back	5343	=back
3711		5344
3712	If you know of other additional requirements drop me a note.	5345	If you know of other additional requirements drop me a note.
3713		5346
…		…
3775	=item Processing ev_async_send: O(number_of_async_watchers)	5408	=item Processing ev_async_send: O(number_of_async_watchers)
3776		5409
3777	=item Processing signals: O(max_signal_number)	5410	=item Processing signals: O(max_signal_number)
3778		5411
3779	Sending involves a system call I<iff> there were no other C<ev_async_send>	5412	Sending involves a system call I<iff> there were no other C<ev_async_send>
3780	calls in the current loop iteration. Checking for async and signal events	5413	calls in the current loop iteration and the loop is currently
		5414	blocked. Checking for async and signal events involves iterating over all
3781	involves iterating over all running async watchers or all signal numbers.	5415	running async watchers or all signal numbers.
3782		5416
3783	=back	5417	=back
3784		5418
3785		5419
		5420	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5421
		5422	The major version 4 introduced some incompatible changes to the API.
		5423
		5424	At the moment, the C<ev.h> header file provides compatibility definitions
		5425	for all changes, so most programs should still compile. The compatibility
		5426	layer might be removed in later versions of libev, so better update to the
		5427	new API early than late.
		5428
		5429	=over 4
		5430
		5431	=item C<EV_COMPAT3> backwards compatibility mechanism
		5432
		5433	The backward compatibility mechanism can be controlled by
		5434	C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING>
		5435	section.
		5436
		5437	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5438
		5439	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5440
		5441	ev_loop_destroy (EV_DEFAULT_UC);
		5442	ev_loop_fork (EV_DEFAULT);
		5443
		5444	=item function/symbol renames
		5445
		5446	A number of functions and symbols have been renamed:
		5447
		5448	ev_loop => ev_run
		5449	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5450	EVLOOP_ONESHOT => EVRUN_ONCE
		5451
		5452	ev_unloop => ev_break
		5453	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5454	EVUNLOOP_ONE => EVBREAK_ONE
		5455	EVUNLOOP_ALL => EVBREAK_ALL
		5456
		5457	EV_TIMEOUT => EV_TIMER
		5458
		5459	ev_loop_count => ev_iteration
		5460	ev_loop_depth => ev_depth
		5461	ev_loop_verify => ev_verify
		5462
		5463	Most functions working on C<struct ev_loop> objects don't have an
		5464	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5465	associated constants have been renamed to not collide with the C<struct
		5466	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5467	as all other watcher types. Note that C<ev_loop_fork> is still called
		5468	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5469	typedef.
		5470
		5471	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5472
		5473	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5474	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5475	and work, but the library code will of course be larger.
		5476
		5477	=back
		5478
		5479
		5480	=head1 GLOSSARY
		5481
		5482	=over 4
		5483
		5484	=item active
		5485
		5486	A watcher is active as long as it has been started and not yet stopped.
		5487	See L</WATCHER STATES> for details.
		5488
		5489	=item application
		5490
		5491	In this document, an application is whatever is using libev.
		5492
		5493	=item backend
		5494
		5495	The part of the code dealing with the operating system interfaces.
		5496
		5497	=item callback
		5498
		5499	The address of a function that is called when some event has been
		5500	detected. Callbacks are being passed the event loop, the watcher that
		5501	received the event, and the actual event bitset.
		5502
		5503	=item callback/watcher invocation
		5504
		5505	The act of calling the callback associated with a watcher.
		5506
		5507	=item event
		5508
		5509	A change of state of some external event, such as data now being available
		5510	for reading on a file descriptor, time having passed or simply not having
		5511	any other events happening anymore.
		5512
		5513	In libev, events are represented as single bits (such as C<EV_READ> or
		5514	C<EV_TIMER>).
		5515
		5516	=item event library
		5517
		5518	A software package implementing an event model and loop.
		5519
		5520	=item event loop
		5521
		5522	An entity that handles and processes external events and converts them
		5523	into callback invocations.
		5524
		5525	=item event model
		5526
		5527	The model used to describe how an event loop handles and processes
		5528	watchers and events.
		5529
		5530	=item pending
		5531
		5532	A watcher is pending as soon as the corresponding event has been
		5533	detected. See L</WATCHER STATES> for details.
		5534
		5535	=item real time
		5536
		5537	The physical time that is observed. It is apparently strictly monotonic :)
		5538
		5539	=item wall-clock time
		5540
		5541	The time and date as shown on clocks. Unlike real time, it can actually
		5542	be wrong and jump forwards and backwards, e.g. when you adjust your
		5543	clock.
		5544
		5545	=item watcher
		5546
		5547	A data structure that describes interest in certain events. Watchers need
		5548	to be started (attached to an event loop) before they can receive events.
		5549
		5550	=back
		5551
3786	=head1 AUTHOR	5552	=head1 AUTHOR
3787		5553
3788	Marc Lehmann <libev@schmorp.de>.	5554	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5555	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
3789		5556

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