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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	// unloop was called, so exit
62	return 0;	64	return 0;
63	}	65	}
64		66
65	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
66		70
67	The newest version of this document is also available as an html-formatted	71	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	72	web page you might find easier to navigate when reading it for the first
69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.	73	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		74
		75	While this document tries to be as complete as possible in documenting
		76	libev, its usage and the rationale behind its design, it is not a tutorial
		77	on event-based programming, nor will it introduce event-based programming
		78	with libev.
		79
		80	Familiarity with event based programming techniques in general is assumed
		81	throughout this document.
		82
		83	=head1 WHAT TO READ WHEN IN A HURRY
		84
		85	This manual tries to be very detailed, but unfortunately, this also makes
		86	it very long. If you just want to know the basics of libev, I suggest
		87	reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and
		88	look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and
		89	C<ev_timer> sections in L<WATCHER TYPES>.
		90
		91	=head1 ABOUT LIBEV
70		92
71	Libev is an event loop: you register interest in certain events (such as a	93	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	94	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	95	these event sources and provide your program with events.
74		96
…		…
84	=head2 FEATURES	106	=head2 FEATURES
85		107
86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	108	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	109	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	110	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	111	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
90	with customised rescheduling (C<ev_periodic>), synchronous signals	112	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
91	(C<ev_signal>), process status change events (C<ev_child>), and event	113	timers (C<ev_timer>), absolute timers with customised rescheduling
92	watchers dealing with the event loop mechanism itself (C<ev_idle>,	114	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
93	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	115	change events (C<ev_child>), and event watchers dealing with the event
94	file watchers (C<ev_stat>) and even limited support for fork events	116	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
95	(C<ev_fork>).	117	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		118	limited support for fork events (C<ev_fork>).
96		119
97	It also is quite fast (see this	120	It also is quite fast (see this
98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	121	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
99	for example).	122	for example).
100		123
…		…
103	Libev is very configurable. In this manual the default (and most common)	126	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	127	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	128	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	129	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	130	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<ev_loop *>) will not have	131	name C<loop> (which is always of type C<struct ev_loop *>) will not have
109	this argument.	132	this argument.
110		133
111	=head2 TIME REPRESENTATION	134	=head2 TIME REPRESENTATION
112		135
113	Libev represents time as a single floating point number, representing the	136	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	137	the (fractional) number of seconds since the (POSIX) epoch (in practice
115	the beginning of 1970, details are complicated, don't ask). This type is	138	somewhere near the beginning of 1970, details are complicated, don't
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	139	ask). This type is called C<ev_tstamp>, which is what you should use
117	to the C<double> type in C, and when you need to do any calculations on	140	too. It usually aliases to the C<double> type in C. When you need to do
118	it, you should treat it as some floating point value. Unlike the name	141	any calculations on it, you should treat it as some floating point value.
		142
119	component C<stamp> might indicate, it is also used for time differences	143	Unlike the name component C<stamp> might indicate, it is also used for
120	throughout libev.	144	time differences (e.g. delays) throughout libev.
121		145
122	=head1 ERROR HANDLING	146	=head1 ERROR HANDLING
123		147
124	Libev knows three classes of errors: operating system errors, usage errors	148	Libev knows three classes of errors: operating system errors, usage errors
125	and internal errors (bugs).	149	and internal errors (bugs).
…		…
149		173
150	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
151		175
152	Returns the current time as libev would use it. Please note that the	176	Returns the current time as libev would use it. Please note that the
153	C<ev_now> function is usually faster and also often returns the timestamp	177	C<ev_now> function is usually faster and also often returns the timestamp
154	you actually want to know.	178	you actually want to know. Also interesting is the combination of
		179	C<ev_update_now> and C<ev_now>.
155		180
156	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
157		182
158	Sleep for the given interval: The current thread will be blocked until	183	Sleep for the given interval: The current thread will be blocked until
159	either it is interrupted or the given time interval has passed. Basically	184	either it is interrupted or the given time interval has passed. Basically
…		…
176	as this indicates an incompatible change. Minor versions are usually	201	as this indicates an incompatible change. Minor versions are usually
177	compatible to older versions, so a larger minor version alone is usually	202	compatible to older versions, so a larger minor version alone is usually
178	not a problem.	203	not a problem.
179		204
180	Example: Make sure we haven't accidentally been linked against the wrong	205	Example: Make sure we haven't accidentally been linked against the wrong
181	version.	206	version (note, however, that this will not detect other ABI mismatches,
		207	such as LFS or reentrancy).
182		208
183	assert (("libev version mismatch",	209	assert (("libev version mismatch",
184	ev_version_major () == EV_VERSION_MAJOR	210	ev_version_major () == EV_VERSION_MAJOR
185	&& ev_version_minor () >= EV_VERSION_MINOR));	211	&& ev_version_minor () >= EV_VERSION_MINOR));
186		212
…		…
197	assert (("sorry, no epoll, no sex",	223	assert (("sorry, no epoll, no sex",
198	ev_supported_backends () & EVBACKEND_EPOLL));	224	ev_supported_backends () & EVBACKEND_EPOLL));
199		225
200	=item unsigned int ev_recommended_backends ()	226	=item unsigned int ev_recommended_backends ()
201		227
202	Return the set of all backends compiled into this binary of libev and also	228	Return the set of all backends compiled into this binary of libev and
203	recommended for this platform. This set is often smaller than the one	229	also recommended for this platform, meaning it will work for most file
		230	descriptor types. This set is often smaller than the one returned by
204	returned by C<ev_supported_backends>, as for example kqueue is broken on	231	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
205	most BSDs and will not be auto-detected unless you explicitly request it	232	and will not be auto-detected unless you explicitly request it (assuming
206	(assuming you know what you are doing). This is the set of backends that	233	you know what you are doing). This is the set of backends that libev will
207	libev will probe for if you specify no backends explicitly.	234	probe for if you specify no backends explicitly.
208		235
209	=item unsigned int ev_embeddable_backends ()	236	=item unsigned int ev_embeddable_backends ()
210		237
211	Returns the set of backends that are embeddable in other event loops. This	238	Returns the set of backends that are embeddable in other event loops. This
212	is the theoretical, all-platform, value. To find which backends	239	value is platform-specific but can include backends not available on the
213	might be supported on the current system, you would need to look at	240	current system. To find which embeddable backends might be supported on
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	241	the current system, you would need to look at C<ev_embeddable_backends ()
215	recommended ones.	242	& ev_supported_backends ()>, likewise for recommended ones.
216		243
217	See the description of C<ev_embed> watchers for more info.	244	See the description of C<ev_embed> watchers for more info.
218		245
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	246	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
220		247
221	Sets the allocation function to use (the prototype is similar - the	248	Sets the allocation function to use (the prototype is similar - the
222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	249	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
223	used to allocate and free memory (no surprises here). If it returns zero	250	used to allocate and free memory (no surprises here). If it returns zero
224	when memory needs to be allocated (C<size != 0>), the library might abort	251	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	277	}
251		278
252	...	279	...
253	ev_set_allocator (persistent_realloc);	280	ev_set_allocator (persistent_realloc);
254		281
255	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	282	=item ev_set_syserr_cb (void (*cb)(const char *msg))
256		283
257	Set the callback function to call on a retryable system call error (such	284	Set the callback function to call on a retryable system call error (such
258	as failed select, poll, epoll_wait). The message is a printable string	285	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	286	indicating the system call or subsystem causing the problem. If this
260	callback is set, then libev will expect it to remedy the situation, no	287	callback is set, then libev will expect it to remedy the situation, no
…		…
274	...	301	...
275	ev_set_syserr_cb (fatal_error);	302	ev_set_syserr_cb (fatal_error);
276		303
277	=back	304	=back
278		305
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	306	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
280		307
281	An event loop is described by a C<ev_loop *>. The library knows two	308	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	309	I<not> optional in this case unless libev 3 compatibility is disabled, as
283	events, and dynamically created loops which do not.	310	libev 3 had an C<ev_loop> function colliding with the struct name).
		311
		312	The library knows two types of such loops, the I<default> loop, which
		313	supports child process events, and dynamically created event loops which
		314	do not.
284		315
285	=over 4	316	=over 4
286		317
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	318	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		319
289	This will initialise the default event loop if it hasn't been initialised	320	This returns the "default" event loop object, which is what you should
290	yet and return it. If the default loop could not be initialised, returns	321	normally use when you just need "the event loop". Event loop objects and
291	false. If it already was initialised it simply returns it (and ignores the	322	the C<flags> parameter are described in more detail in the entry for
292	flags. If that is troubling you, check C<ev_backend ()> afterwards).	323	C<ev_loop_new>.
		324
		325	If the default loop is already initialised then this function simply
		326	returns it (and ignores the flags. If that is troubling you, check
		327	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		328	flags, which should almost always be C<0>, unless the caller is also the
		329	one calling C<ev_run> or otherwise qualifies as "the main program".
293		330
294	If you don't know what event loop to use, use the one returned from this	331	If you don't know what event loop to use, use the one returned from this
295	function.	332	function (or via the C<EV_DEFAULT> macro).
296		333
297	Note that this function is I<not> thread-safe, so if you want to use it	334	Note that this function is I<not> thread-safe, so if you want to use it
298	from multiple threads, you have to lock (note also that this is unlikely,	335	from multiple threads, you have to employ some kind of mutex (note also
299	as loops cannot bes hared easily between threads anyway).	336	that this case is unlikely, as loops cannot be shared easily between
		337	threads anyway).
300		338
301	The default loop is the only loop that can handle C<ev_signal> and	339	The default loop is the only loop that can handle C<ev_child> watchers,
302	C<ev_child> watchers, and to do this, it always registers a handler	340	and to do this, it always registers a handler for C<SIGCHLD>. If this is
303	for C<SIGCHLD>. If this is a problem for your application you can either	341	a problem for your application you can either create a dynamic loop with
304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	342	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
305	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	343	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
306	C<ev_default_init>.	344
		345	Example: This is the most typical usage.
		346
		347	if (!ev_default_loop (0))
		348	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		349
		350	Example: Restrict libev to the select and poll backends, and do not allow
		351	environment settings to be taken into account:
		352
		353	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		354
		355	=item struct ev_loop *ev_loop_new (unsigned int flags)
		356
		357	This will create and initialise a new event loop object. If the loop
		358	could not be initialised, returns false.
		359
		360	This function is thread-safe, and one common way to use libev with
		361	threads is indeed to create one loop per thread, and using the default
		362	loop in the "main" or "initial" thread.
307		363
308	The flags argument can be used to specify special behaviour or specific	364	The flags argument can be used to specify special behaviour or specific
309	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	365	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
310		366
311	The following flags are supported:	367	The following flags are supported:
…		…
326	useful to try out specific backends to test their performance, or to work	382	useful to try out specific backends to test their performance, or to work
327	around bugs.	383	around bugs.
328		384
329	=item C<EVFLAG_FORKCHECK>	385	=item C<EVFLAG_FORKCHECK>
330		386
331	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	387	Instead of calling C<ev_loop_fork> manually after a fork, you can also
332	a fork, you can also make libev check for a fork in each iteration by	388	make libev check for a fork in each iteration by enabling this flag.
333	enabling this flag.
334		389
335	This works by calling C<getpid ()> on every iteration of the loop,	390	This works by calling C<getpid ()> on every iteration of the loop,
336	and thus this might slow down your event loop if you do a lot of loop	391	and thus this might slow down your event loop if you do a lot of loop
337	iterations and little real work, but is usually not noticeable (on my	392	iterations and little real work, but is usually not noticeable (on my
338	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	393	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
…		…
344	flag.	399	flag.
345		400
346	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	401	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
347	environment variable.	402	environment variable.
348		403
		404	=item C<EVFLAG_NOINOTIFY>
		405
		406	When this flag is specified, then libev will not attempt to use the
		407	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
		408	testing, this flag can be useful to conserve inotify file descriptors, as
		409	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		410
		411	=item C<EVFLAG_SIGNALFD>
		412
		413	When this flag is specified, then libev will attempt to use the
		414	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
		415	delivers signals synchronously, which makes it both faster and might make
		416	it possible to get the queued signal data. It can also simplify signal
		417	handling with threads, as long as you properly block signals in your
		418	threads that are not interested in handling them.
		419
		420	Signalfd will not be used by default as this changes your signal mask, and
		421	there are a lot of shoddy libraries and programs (glib's threadpool for
		422	example) that can't properly initialise their signal masks.
		423
349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	424	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
350		425
351	This is your standard select(2) backend. Not I<completely> standard, as	426	This is your standard select(2) backend. Not I<completely> standard, as
352	libev tries to roll its own fd_set with no limits on the number of fds,	427	libev tries to roll its own fd_set with no limits on the number of fds,
353	but if that fails, expect a fairly low limit on the number of fds when	428	but if that fails, expect a fairly low limit on the number of fds when
…		…
377	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and	452	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
378	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	453	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
379		454
380	=item C<EVBACKEND_EPOLL> (value 4, Linux)	455	=item C<EVBACKEND_EPOLL> (value 4, Linux)
381		456
		457	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		458	kernels).
		459
382	For few fds, this backend is a bit little slower than poll and select,	460	For few fds, this backend is a bit little slower than poll and select,
383	but it scales phenomenally better. While poll and select usually scale	461	but it scales phenomenally better. While poll and select usually scale
384	like O(total_fds) where n is the total number of fds (or the highest fd),	462	like O(total_fds) where n is the total number of fds (or the highest fd),
385	epoll scales either O(1) or O(active_fds). The epoll design has a number	463	epoll scales either O(1) or O(active_fds).
386	of shortcomings, such as silently dropping events in some hard-to-detect	464
387	cases and requiring a system call per fd change, no fork support and bad	465	The epoll mechanism deserves honorable mention as the most misdesigned
388	support for dup.	466	of the more advanced event mechanisms: mere annoyances include silently
		467	dropping file descriptors, requiring a system call per change per file
		468	descriptor (and unnecessary guessing of parameters), problems with dup,
		469	returning before the timeout value, resulting in additional iterations
		470	(and only giving 5ms accuracy while select on the same platform gives
		471	0.1ms) and so on. The biggest issue is fork races, however - if a program
		472	forks then I<both> parent and child process have to recreate the epoll
		473	set, which can take considerable time (one syscall per file descriptor)
		474	and is of course hard to detect.
		475
		476	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		477	of course I<doesn't>, and epoll just loves to report events for totally
		478	I<different> file descriptors (even already closed ones, so one cannot
		479	even remove them from the set) than registered in the set (especially
		480	on SMP systems). Libev tries to counter these spurious notifications by
		481	employing an additional generation counter and comparing that against the
		482	events to filter out spurious ones, recreating the set when required. Last
		483	not least, it also refuses to work with some file descriptors which work
		484	perfectly fine with C<select> (files, many character devices...).
		485
		486	Epoll is truly the train wreck analog among event poll mechanisms.
389		487
390	While stopping, setting and starting an I/O watcher in the same iteration	488	While stopping, setting and starting an I/O watcher in the same iteration
391	will result in some caching, there is still a system call per such incident	489	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	490	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	491	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
394	very well if you register events for both fds.	492	file descriptors might not work very well if you register events for both
395		493	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		494
400	Best performance from this backend is achieved by not unregistering all	495	Best performance from this backend is achieved by not unregistering all
401	watchers for a file descriptor until it has been closed, if possible,	496	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	497	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	498	starting a watcher (without re-setting it) also usually doesn't cause
404	extra overhead.	499	extra overhead. A fork can both result in spurious notifications as well
		500	as in libev having to destroy and recreate the epoll object, which can
		501	take considerable time and thus should be avoided.
		502
		503	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		504	faster than epoll for maybe up to a hundred file descriptors, depending on
		505	the usage. So sad.
405		506
406	While nominally embeddable in other event loops, this feature is broken in	507	While nominally embeddable in other event loops, this feature is broken in
407	all kernel versions tested so far.	508	all kernel versions tested so far.
408		509
409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	510	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
410	C<EVBACKEND_POLL>.	511	C<EVBACKEND_POLL>.
411		512
412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	513	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
413		514
414	Kqueue deserves special mention, as at the time of this writing, it was	515	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	516	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	517	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	518	it's completely useless). Unlike epoll, however, whose brokenness
418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or	519	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.	520	without API changes to existing programs. For this reason it's not being
		521	"auto-detected" unless you explicitly specify it in the flags (i.e. using
		522	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		523	system like NetBSD.
420		524
421	You still can embed kqueue into a normal poll or select backend and use it	525	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	526	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.	527	the target platform). See C<ev_embed> watchers for more info.
424		528
425	It scales in the same way as the epoll backend, but the interface to the	529	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	530	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	531	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	532	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	533	two event changes per incident. Support for C<fork ()> is very bad (but
430	drops fds silently in similarly hard-to-detect cases.	534	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		535	cases
431		536
432	This backend usually performs well under most conditions.	537	This backend usually performs well under most conditions.
433		538
434	While nominally embeddable in other event loops, this doesn't work	539	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	540	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	541	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	542	(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,	543	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
439	using it only for sockets.	544	also broken on OS X)) and, did I mention it, using it only for sockets.
440		545
441	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	546	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
442	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with	547	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
443	C<NOTE_EOF>.	548	C<NOTE_EOF>.
444		549
…		…
464	might perform better.	569	might perform better.
465		570
466	On the positive side, with the exception of the spurious readiness	571	On the positive side, with the exception of the spurious readiness
467	notifications, this backend actually performed fully to specification	572	notifications, this backend actually performed fully to specification
468	in all tests and is fully embeddable, which is a rare feat among the	573	in all tests and is fully embeddable, which is a rare feat among the
469	OS-specific backends.	574	OS-specific backends (I vastly prefer correctness over speed hacks).
470		575
471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	576	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
472	C<EVBACKEND_POLL>.	577	C<EVBACKEND_POLL>.
473		578
474	=item C<EVBACKEND_ALL>	579	=item C<EVBACKEND_ALL>
…		…
479		584
480	It is definitely not recommended to use this flag.	585	It is definitely not recommended to use this flag.
481		586
482	=back	587	=back
483		588
484	If one or more of these are or'ed into the flags value, then only these	589	If one or more of the backend flags are or'ed into the flags value,
485	backends will be tried (in the reverse order as listed here). If none are	590	then only these backends will be tried (in the reverse order as listed
486	specified, all backends in C<ev_recommended_backends ()> will be tried.	591	here). If none are specified, all backends in C<ev_recommended_backends
487		592	()> 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		593
516	Example: Try to create a event loop that uses epoll and nothing else.	594	Example: Try to create a event loop that uses epoll and nothing else.
517		595
518	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	596	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
519	if (!epoller)	597	if (!epoller)
520	fatal ("no epoll found here, maybe it hides under your chair");	598	fatal ("no epoll found here, maybe it hides under your chair");
521		599
		600	Example: Use whatever libev has to offer, but make sure that kqueue is
		601	used if available.
		602
		603	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		604
522	=item ev_default_destroy ()	605	=item ev_loop_destroy (loop)
523		606
524	Destroys the default loop again (frees all memory and kernel state	607	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	608	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	609	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>	610	responsibility to either stop all watchers cleanly yourself I<before>
528	calling this function, or cope with the fact afterwards (which is usually	611	calling this function, or cope with the fact afterwards (which is usually
529	the easiest thing, you can just ignore the watchers and/or C<free ()> them	612	the easiest thing, you can just ignore the watchers and/or C<free ()> them
530	for example).	613	for example).
531		614
532	Note that certain global state, such as signal state, will not be freed by	615	Note that certain global state, such as signal state (and installed signal
533	this function, and related watchers (such as signal and child watchers)	616	handlers), will not be freed by this function, and related watchers (such
534	would need to be stopped manually.	617	as signal and child watchers) would need to be stopped manually.
535		618
536	In general it is not advisable to call this function except in the	619	This function is normally used on loop objects allocated by
537	rare occasion where you really need to free e.g. the signal handling	620	C<ev_loop_new>, but it can also be used on the default loop returned by
		621	C<ev_default_loop>, in which case it is not thread-safe.
		622
		623	Note that it is not advisable to call this function on the default loop
		624	except in the rare occasion where you really need to free its resources.
538	pipe fds. If you need dynamically allocated loops it is better to use	625	If you need dynamically allocated loops it is better to use C<ev_loop_new>
539	C<ev_loop_new> and C<ev_loop_destroy>).	626	and C<ev_loop_destroy>.
540		627
541	=item ev_loop_destroy (loop)	628	=item ev_loop_fork (loop)
542		629
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	630	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	631	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	632	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	633	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	634	child before resuming or calling C<ev_run>.
553	functions, and it will only take effect at the next C<ev_loop> iteration.	635
		636	Again, you I<have> to call it on I<any> loop that you want to re-use after
		637	a fork, I<even if you do not plan to use the loop in the parent>. This is
		638	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		639	during fork.
554		640
555	On the other hand, you only need to call this function in the child	641	On the other hand, you only need to call this function in the child
556	process if and only if you want to use the event library in the child. If	642	process if and only if you want to use the event loop in the child. If
557	you just fork+exec, you don't have to call it at all.	643	you just fork+exec or create a new loop in the child, you don't have to
		644	call it at all (in fact, C<epoll> is so badly broken that it makes a
		645	difference, but libev will usually detect this case on its own and do a
		646	costly reset of the backend).
558		647
559	The function itself is quite fast and it's usually not a problem to call	648	The function itself is quite fast and it's usually not a problem to call
560	it just in case after a fork. To make this easy, the function will fit in	649	it just in case after a fork.
561	quite nicely into a call to C<pthread_atfork>:
562		650
		651	Example: Automate calling C<ev_loop_fork> on the default loop when
		652	using pthreads.
		653
		654	static void
		655	post_fork_child (void)
		656	{
		657	ev_loop_fork (EV_DEFAULT);
		658	}
		659
		660	...
563	pthread_atfork (0, 0, ev_default_fork);	661	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		662
572	=item int ev_is_default_loop (loop)	663	=item int ev_is_default_loop (loop)
573		664
574	Returns true when the given loop is, in fact, the default loop, and false	665	Returns true when the given loop is, in fact, the default loop, and false
575	otherwise.	666	otherwise.
576		667
577	=item unsigned int ev_loop_count (loop)	668	=item unsigned int ev_iteration (loop)
578		669
579	Returns the count of loop iterations for the loop, which is identical to	670	Returns the current iteration count for the event loop, which is identical
580	the number of times libev did poll for new events. It starts at C<0> and	671	to the number of times libev did poll for new events. It starts at C<0>
581	happily wraps around with enough iterations.	672	and happily wraps around with enough iterations.
582		673
583	This value can sometimes be useful as a generation counter of sorts (it	674	This value can sometimes be useful as a generation counter of sorts (it
584	"ticks" the number of loop iterations), as it roughly corresponds with	675	"ticks" the number of loop iterations), as it roughly corresponds with
585	C<ev_prepare> and C<ev_check> calls.	676	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		677	prepare and check phases.
		678
		679	=item unsigned int ev_depth (loop)
		680
		681	Returns the number of times C<ev_run> was entered minus the number of
		682	times C<ev_run> was exited normally, in other words, the recursion depth.
		683
		684	Outside C<ev_run>, this number is zero. In a callback, this number is
		685	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		686	in which case it is higher.
		687
		688	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
		689	throwing an exception etc.), doesn't count as "exit" - consider this
		690	as a hint to avoid such ungentleman-like behaviour unless it's really
		691	convenient, in which case it is fully supported.
586		692
587	=item unsigned int ev_backend (loop)	693	=item unsigned int ev_backend (loop)
588		694
589	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	695	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
590	use.	696	use.
…		…
599		705
600	=item ev_now_update (loop)	706	=item ev_now_update (loop)
601		707
602	Establishes the current time by querying the kernel, updating the time	708	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	709	returned by C<ev_now ()> in the progress. This is a costly operation and
604	is usually done automatically within C<ev_loop ()>.	710	is usually done automatically within C<ev_run ()>.
605		711
606	This function is rarely useful, but when some event callback runs for a	712	This function is rarely useful, but when some event callback runs for a
607	very long time without entering the event loop, updating libev's idea of	713	very long time without entering the event loop, updating libev's idea of
608	the current time is a good idea.	714	the current time is a good idea.
609		715
610	See also "The special problem of time updates" in the C<ev_timer> section.	716	See also L<The special problem of time updates> in the C<ev_timer> section.
611		717
		718	=item ev_suspend (loop)
		719
		720	=item ev_resume (loop)
		721
		722	These two functions suspend and resume an event loop, for use when the
		723	loop is not used for a while and timeouts should not be processed.
		724
		725	A typical use case would be an interactive program such as a game: When
		726	the user presses C<^Z> to suspend the game and resumes it an hour later it
		727	would be best to handle timeouts as if no time had actually passed while
		728	the program was suspended. This can be achieved by calling C<ev_suspend>
		729	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		730	C<ev_resume> directly afterwards to resume timer processing.
		731
		732	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		733	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		734	will be rescheduled (that is, they will lose any events that would have
		735	occurred while suspended).
		736
		737	After calling C<ev_suspend> you B<must not> call I<any> function on the
		738	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		739	without a previous call to C<ev_suspend>.
		740
		741	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		742	event loop time (see C<ev_now_update>).
		743
612	=item ev_loop (loop, int flags)	744	=item ev_run (loop, int flags)
613		745
614	Finally, this is it, the event handler. This function usually is called	746	Finally, this is it, the event handler. This function usually is called
615	after you initialised all your watchers and you want to start handling	747	after you have initialised all your watchers and you want to start
616	events.	748	handling events. It will ask the operating system for any new events, call
		749	the watcher callbacks, an then repeat the whole process indefinitely: This
		750	is why event loops are called I<loops>.
617		751
618	If the flags argument is specified as C<0>, it will not return until	752	If the flags argument is specified as C<0>, it will keep handling events
619	either no event watchers are active anymore or C<ev_unloop> was called.	753	until either no event watchers are active anymore or C<ev_break> was
		754	called.
620		755
621	Please note that an explicit C<ev_unloop> is usually better than	756	Please note that an explicit C<ev_break> is usually better than
622	relying on all watchers to be stopped when deciding when a program has	757	relying on all watchers to be stopped when deciding when a program has
623	finished (especially in interactive programs), but having a program	758	finished (especially in interactive programs), but having a program
624	that automatically loops as long as it has to and no longer by virtue	759	that automatically loops as long as it has to and no longer by virtue
625	of relying on its watchers stopping correctly, that is truly a thing of	760	of relying on its watchers stopping correctly, that is truly a thing of
626	beauty.	761	beauty.
627		762
		763	This function is also I<mostly> exception-safe - you can break out of
		764	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		765	exception and so on. This does not decrement the C<ev_depth> value, nor
		766	will it clear any outstanding C<EVBREAK_ONE> breaks.
		767
628	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	768	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
629	those events and any already outstanding ones, but will not block your	769	those events and any already outstanding ones, but will not wait and
630	process in case there are no events and will return after one iteration of	770	block your process in case there are no events and will return after one
631	the loop.	771	iteration of the loop. This is sometimes useful to poll and handle new
		772	events while doing lengthy calculations, to keep the program responsive.
632		773
633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	774	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
634	necessary) and will handle those and any already outstanding ones. It	775	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	776	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	777	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	778	user-registered callback will be called), and will return after one
638	iteration of the loop.	779	iteration of the loop.
639		780
640	This is useful if you are waiting for some external event in conjunction	781	This is useful if you are waiting for some external event in conjunction
641	with something not expressible using other libev watchers (i.e. "roll your	782	with something not expressible using other libev watchers (i.e. "roll your
642	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	783	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
643	usually a better approach for this kind of thing.	784	usually a better approach for this kind of thing.
644		785
645	Here are the gory details of what C<ev_loop> does:	786	Here are the gory details of what C<ev_run> does:
646		787
		788	- Increment loop depth.
		789	- Reset the ev_break status.
647	- Before the first iteration, call any pending watchers.	790	- Before the first iteration, call any pending watchers.
		791	LOOP:
648	* If EVFLAG_FORKCHECK was used, check for a fork.	792	- If EVFLAG_FORKCHECK was used, check for a fork.
649	- If a fork was detected (by any means), queue and call all fork watchers.	793	- If a fork was detected (by any means), queue and call all fork watchers.
650	- Queue and call all prepare watchers.	794	- Queue and call all prepare watchers.
		795	- If ev_break was called, goto FINISH.
651	- If we have been forked, detach and recreate the kernel state	796	- If we have been forked, detach and recreate the kernel state
652	as to not disturb the other process.	797	as to not disturb the other process.
653	- Update the kernel state with all outstanding changes.	798	- Update the kernel state with all outstanding changes.
654	- Update the "event loop time" (ev_now ()).	799	- Update the "event loop time" (ev_now ()).
655	- Calculate for how long to sleep or block, if at all	800	- Calculate for how long to sleep or block, if at all
656	(active idle watchers, EVLOOP_NONBLOCK or not having	801	(active idle watchers, EVRUN_NOWAIT or not having
657	any active watchers at all will result in not sleeping).	802	any active watchers at all will result in not sleeping).
658	- Sleep if the I/O and timer collect interval say so.	803	- Sleep if the I/O and timer collect interval say so.
		804	- Increment loop iteration counter.
659	- Block the process, waiting for any events.	805	- Block the process, waiting for any events.
660	- Queue all outstanding I/O (fd) events.	806	- Queue all outstanding I/O (fd) events.
661	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	807	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
662	- Queue all expired timers.	808	- Queue all expired timers.
663	- Queue all expired periodics.	809	- Queue all expired periodics.
664	- Unless any events are pending now, queue all idle watchers.	810	- Queue all idle watchers with priority higher than that of pending events.
665	- Queue all check watchers.	811	- Queue all check watchers.
666	- Call all queued watchers in reverse order (i.e. check watchers first).	812	- Call all queued watchers in reverse order (i.e. check watchers first).
667	Signals and child watchers are implemented as I/O watchers, and will	813	Signals and child watchers are implemented as I/O watchers, and will
668	be handled here by queueing them when their watcher gets executed.	814	be handled here by queueing them when their watcher gets executed.
669	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	815	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
670	were used, or there are no active watchers, return, otherwise	816	were used, or there are no active watchers, goto FINISH, otherwise
671	continue with step *.	817	continue with step LOOP.
		818	FINISH:
		819	- Reset the ev_break status iff it was EVBREAK_ONE.
		820	- Decrement the loop depth.
		821	- Return.
672		822
673	Example: Queue some jobs and then loop until no events are outstanding	823	Example: Queue some jobs and then loop until no events are outstanding
674	anymore.	824	anymore.
675		825
676	... queue jobs here, make sure they register event watchers as long	826	... 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..)	827	... as they still have work to do (even an idle watcher will do..)
678	ev_loop (my_loop, 0);	828	ev_run (my_loop, 0);
679	... jobs done or somebody called unloop. yeah!	829	... jobs done or somebody called unloop. yeah!
680		830
681	=item ev_unloop (loop, how)	831	=item ev_break (loop, how)
682		832
683	Can be used to make a call to C<ev_loop> return early (but only after it	833	Can be used to make a call to C<ev_run> return early (but only after it
684	has processed all outstanding events). The C<how> argument must be either	834	has processed all outstanding events). The C<how> argument must be either
685	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	835	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
686	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	836	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
687		837
688	This "unloop state" will be cleared when entering C<ev_loop> again.	838	This "break state" will be cleared on the next call to C<ev_run>.
689		839
690	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	840	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		841	which case it will have no effect.
691		842
692	=item ev_ref (loop)	843	=item ev_ref (loop)
693		844
694	=item ev_unref (loop)	845	=item ev_unref (loop)
695		846
696	Ref/unref can be used to add or remove a reference count on the event	847	Ref/unref can be used to add or remove a reference count on the event
697	loop: Every watcher keeps one reference, and as long as the reference	848	loop: Every watcher keeps one reference, and as long as the reference
698	count is nonzero, C<ev_loop> will not return on its own.	849	count is nonzero, C<ev_run> will not return on its own.
699		850
700	If you have a watcher you never unregister that should not keep C<ev_loop>	851	This is useful when you have a watcher that you never intend to
701	from returning, call ev_unref() after starting, and ev_ref() before	852	unregister, but that nevertheless should not keep C<ev_run> from
		853	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
702	stopping it.	854	before stopping it.
703		855
704	As an example, libev itself uses this for its internal signal pipe: It is	856	As an example, libev itself uses this for its internal signal pipe: It
705	not visible to the libev user and should not keep C<ev_loop> from exiting	857	is not visible to the libev user and should not keep C<ev_run> from
706	if no event watchers registered by it are active. It is also an excellent	858	exiting if no event watchers registered by it are active. It is also an
707	way to do this for generic recurring timers or from within third-party	859	excellent way to do this for generic recurring timers or from within
708	libraries. Just remember to I<unref after start> and I<ref before stop>	860	third-party libraries. Just remember to I<unref after start> and I<ref
709	(but only if the watcher wasn't active before, or was active before,	861	before stop> (but only if the watcher wasn't active before, or was active
710	respectively).	862	before, respectively. Note also that libev might stop watchers itself
		863	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		864	in the callback).
711		865
712	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	866	Example: Create a signal watcher, but keep it from keeping C<ev_run>
713	running when nothing else is active.	867	running when nothing else is active.
714		868
715	ev_signal exitsig;	869	ev_signal exitsig;
716	ev_signal_init (&exitsig, sig_cb, SIGINT);	870	ev_signal_init (&exitsig, sig_cb, SIGINT);
717	ev_signal_start (loop, &exitsig);	871	ev_signal_start (loop, &exitsig);
…		…
744		898
745	By setting a higher I<io collect interval> you allow libev to spend more	899	By setting a higher I<io collect interval> you allow libev to spend more
746	time collecting I/O events, so you can handle more events per iteration,	900	time collecting I/O events, so you can handle more events per iteration,
747	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	901	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
748	C<ev_timer>) will be not affected. Setting this to a non-null value will	902	C<ev_timer>) will be not affected. Setting this to a non-null value will
749	introduce an additional C<ev_sleep ()> call into most loop iterations.	903	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		904	sleep time ensures that libev will not poll for I/O events more often then
		905	once per this interval, on average.
750		906
751	Likewise, by setting a higher I<timeout collect interval> you allow libev	907	Likewise, by setting a higher I<timeout collect interval> you allow libev
752	to spend more time collecting timeouts, at the expense of increased	908	to spend more time collecting timeouts, at the expense of increased
753	latency/jitter/inexactness (the watcher callback will be called	909	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	910	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
756		912
757	Many (busy) programs can usually benefit by setting the I/O collect	913	Many (busy) programs can usually benefit by setting the I/O collect
758	interval to a value near C<0.1> or so, which is often enough for	914	interval to a value near C<0.1> or so, which is often enough for
759	interactive servers (of course not for games), likewise for timeouts. It	915	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>,	916	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.	917	as this approaches the timing granularity of most systems. Note that if
		918	you do transactions with the outside world and you can't increase the
		919	parallelity, then this setting will limit your transaction rate (if you
		920	need to poll once per transaction and the I/O collect interval is 0.01,
		921	then you can't do more than 100 transactions per second).
762		922
763	Setting the I<timeout collect interval> can improve the opportunity for	923	Setting the I<timeout collect interval> can improve the opportunity for
764	saving power, as the program will "bundle" timer callback invocations that	924	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	925	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	926	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	927	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
768	they fire on, say, one-second boundaries only.	928	they fire on, say, one-second boundaries only.
769		929
		930	Example: we only need 0.1s timeout granularity, and we wish not to poll
		931	more often than 100 times per second:
		932
		933	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		934	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		935
		936	=item ev_invoke_pending (loop)
		937
		938	This call will simply invoke all pending watchers while resetting their
		939	pending state. Normally, C<ev_run> does this automatically when required,
		940	but when overriding the invoke callback this call comes handy. This
		941	function can be invoked from a watcher - this can be useful for example
		942	when you want to do some lengthy calculation and want to pass further
		943	event handling to another thread (you still have to make sure only one
		944	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		945
		946	=item int ev_pending_count (loop)
		947
		948	Returns the number of pending watchers - zero indicates that no watchers
		949	are pending.
		950
		951	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		952
		953	This overrides the invoke pending functionality of the loop: Instead of
		954	invoking all pending watchers when there are any, C<ev_run> will call
		955	this callback instead. This is useful, for example, when you want to
		956	invoke the actual watchers inside another context (another thread etc.).
		957
		958	If you want to reset the callback, use C<ev_invoke_pending> as new
		959	callback.
		960
		961	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		962
		963	Sometimes you want to share the same loop between multiple threads. This
		964	can be done relatively simply by putting mutex_lock/unlock calls around
		965	each call to a libev function.
		966
		967	However, C<ev_run> can run an indefinite time, so it is not feasible
		968	to wait for it to return. One way around this is to wake up the event
		969	loop via C<ev_break> and C<av_async_send>, another way is to set these
		970	I<release> and I<acquire> callbacks on the loop.
		971
		972	When set, then C<release> will be called just before the thread is
		973	suspended waiting for new events, and C<acquire> is called just
		974	afterwards.
		975
		976	Ideally, C<release> will just call your mutex_unlock function, and
		977	C<acquire> will just call the mutex_lock function again.
		978
		979	While event loop modifications are allowed between invocations of
		980	C<release> and C<acquire> (that's their only purpose after all), no
		981	modifications done will affect the event loop, i.e. adding watchers will
		982	have no effect on the set of file descriptors being watched, or the time
		983	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		984	to take note of any changes you made.
		985
		986	In theory, threads executing C<ev_run> will be async-cancel safe between
		987	invocations of C<release> and C<acquire>.
		988
		989	See also the locking example in the C<THREADS> section later in this
		990	document.
		991
		992	=item ev_set_userdata (loop, void *data)
		993
		994	=item void *ev_userdata (loop)
		995
		996	Set and retrieve a single C<void *> associated with a loop. When
		997	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		998	C<0>.
		999
		1000	These two functions can be used to associate arbitrary data with a loop,
		1001	and are intended solely for the C<invoke_pending_cb>, C<release> and
		1002	C<acquire> callbacks described above, but of course can be (ab-)used for
		1003	any other purpose as well.
		1004
770	=item ev_loop_verify (loop)	1005	=item ev_verify (loop)
771		1006
772	This function only does something when C<EV_VERIFY> support has been	1007	This function only does something when C<EV_VERIFY> support has been
773	compiled in. which is the default for non-minimal builds. It tries to go	1008	compiled in, which is the default for non-minimal builds. It tries to go
774	through all internal structures and checks them for validity. If anything	1009	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	1010	is found to be inconsistent, it will print an error message to standard
776	error and call C<abort ()>.	1011	error and call C<abort ()>.
777		1012
778	This can be used to catch bugs inside libev itself: under normal	1013	This can be used to catch bugs inside libev itself: under normal
…		…
782	=back	1017	=back
783		1018
784		1019
785	=head1 ANATOMY OF A WATCHER	1020	=head1 ANATOMY OF A WATCHER
786		1021
		1022	In the following description, uppercase C<TYPE> in names stands for the
		1023	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		1024	watchers and C<ev_io_start> for I/O watchers.
		1025
787	A watcher is a structure that you create and register to record your	1026	A watcher is an opaque structure that you allocate and register to record
788	interest in some event. For instance, if you want to wait for STDIN to	1027	your interest in some event. To make a concrete example, imagine you want
789	become readable, you would create an C<ev_io> watcher for that:	1028	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1029	for that:
790		1030
791	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1031	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
792	{	1032	{
793	ev_io_stop (w);	1033	ev_io_stop (w);
794	ev_unloop (loop, EVUNLOOP_ALL);	1034	ev_break (loop, EVBREAK_ALL);
795	}	1035	}
796		1036
797	struct ev_loop *loop = ev_default_loop (0);	1037	struct ev_loop *loop = ev_default_loop (0);
		1038
798	ev_io stdin_watcher;	1039	ev_io stdin_watcher;
		1040
799	ev_init (&stdin_watcher, my_cb);	1041	ev_init (&stdin_watcher, my_cb);
800	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1042	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
801	ev_io_start (loop, &stdin_watcher);	1043	ev_io_start (loop, &stdin_watcher);
		1044
802	ev_loop (loop, 0);	1045	ev_run (loop, 0);
803		1046
804	As you can see, you are responsible for allocating the memory for your	1047	As you can see, you are responsible for allocating the memory for your
805	watcher structures (and it is usually a bad idea to do this on the stack,	1048	watcher structures (and it is I<usually> a bad idea to do this on the
806	although this can sometimes be quite valid).	1049	stack).
807		1050
		1051	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		1052	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
		1053
808	Each watcher structure must be initialised by a call to C<ev_init	1054	Each watcher structure must be initialised by a call to C<ev_init (watcher
809	(watcher *, callback)>, which expects a callback to be provided. This	1055	*, 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	1056	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	1057	time the event loop detects that the file descriptor given is readable
812	is readable and/or writable).	1058	and/or writable).
813		1059
814	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1060	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	1061	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	1062	is also a macro to combine initialisation and setting in one call: C<<
817	(watcher *, callback, ...) >>.	1063	ev_TYPE_init (watcher *, callback, ...) >>.
818		1064
819	To make the watcher actually watch out for events, you have to start it	1065	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	1066	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	1067	*) >>), and you can stop watching for events at any time by calling the
822	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1068	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
823		1069
824	As long as your watcher is active (has been started but not stopped) you	1070	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	1071	must not touch the values stored in it. Most specifically you must never
826	reinitialise it or call its C<set> macro.	1072	reinitialise it or call its C<ev_TYPE_set> macro.
827		1073
828	Each and every callback receives the event loop pointer as first, the	1074	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	1075	registered watcher structure as second, and a bitset of received events as
830	third argument.	1076	third argument.
831		1077
…		…
840	=item C<EV_WRITE>	1086	=item C<EV_WRITE>
841		1087
842	The file descriptor in the C<ev_io> watcher has become readable and/or	1088	The file descriptor in the C<ev_io> watcher has become readable and/or
843	writable.	1089	writable.
844		1090
845	=item C<EV_TIMEOUT>	1091	=item C<EV_TIMER>
846		1092
847	The C<ev_timer> watcher has timed out.	1093	The C<ev_timer> watcher has timed out.
848		1094
849	=item C<EV_PERIODIC>	1095	=item C<EV_PERIODIC>
850		1096
…		…
868		1114
869	=item C<EV_PREPARE>	1115	=item C<EV_PREPARE>
870		1116
871	=item C<EV_CHECK>	1117	=item C<EV_CHECK>
872		1118
873	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1119	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
874	to gather new events, and all C<ev_check> watchers are invoked just after	1120	to gather new events, and all C<ev_check> watchers are invoked just after
875	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1121	C<ev_run> has gathered them, but before it invokes any callbacks for any
876	received events. Callbacks of both watcher types can start and stop as	1122	received events. Callbacks of both watcher types can start and stop as
877	many watchers as they want, and all of them will be taken into account	1123	many watchers as they want, and all of them will be taken into account
878	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1124	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
879	C<ev_loop> from blocking).	1125	C<ev_run> from blocking).
880		1126
881	=item C<EV_EMBED>	1127	=item C<EV_EMBED>
882		1128
883	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1129	The embedded event loop specified in the C<ev_embed> watcher needs attention.
884		1130
885	=item C<EV_FORK>	1131	=item C<EV_FORK>
886		1132
887	The event loop has been resumed in the child process after fork (see	1133	The event loop has been resumed in the child process after fork (see
888	C<ev_fork>).	1134	C<ev_fork>).
889		1135
		1136	=item C<EV_CLEANUP>
		1137
		1138	The event loop is about to be destroyed (see C<ev_cleanup>).
		1139
890	=item C<EV_ASYNC>	1140	=item C<EV_ASYNC>
891		1141
892	The given async watcher has been asynchronously notified (see C<ev_async>).	1142	The given async watcher has been asynchronously notified (see C<ev_async>).
		1143
		1144	=item C<EV_CUSTOM>
		1145
		1146	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1147	by libev users to signal watchers (e.g. via C<ev_feed_event>).
893		1148
894	=item C<EV_ERROR>	1149	=item C<EV_ERROR>
895		1150
896	An unspecified error has occurred, the watcher has been stopped. This might	1151	An unspecified error has occurred, the watcher has been stopped. This might
897	happen because the watcher could not be properly started because libev	1152	happen because the watcher could not be properly started because libev
…		…
912		1167
913	=back	1168	=back
914		1169
915	=head2 GENERIC WATCHER FUNCTIONS	1170	=head2 GENERIC WATCHER FUNCTIONS
916		1171
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	1172	=over 4
921		1173
922	=item C<ev_init> (ev_TYPE *watcher, callback)	1174	=item C<ev_init> (ev_TYPE *watcher, callback)
923		1175
924	This macro initialises the generic portion of a watcher. The contents	1176	This macro initialises the generic portion of a watcher. The contents
…		…
938		1190
939	ev_io w;	1191	ev_io w;
940	ev_init (&w, my_cb);	1192	ev_init (&w, my_cb);
941	ev_io_set (&w, STDIN_FILENO, EV_READ);	1193	ev_io_set (&w, STDIN_FILENO, EV_READ);
942		1194
943	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1195	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
944		1196
945	This macro initialises the type-specific parts of a watcher. You need to	1197	This macro initialises the type-specific parts of a watcher. You need to
946	call C<ev_init> at least once before you call this macro, but you can	1198	call C<ev_init> at least once before you call this macro, but you can
947	call C<ev_TYPE_set> any number of times. You must not, however, call this	1199	call C<ev_TYPE_set> any number of times. You must not, however, call this
948	macro on a watcher that is active (it can be pending, however, which is a	1200	macro on a watcher that is active (it can be pending, however, which is a
…		…
961		1213
962	Example: Initialise and set an C<ev_io> watcher in one step.	1214	Example: Initialise and set an C<ev_io> watcher in one step.
963		1215
964	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1216	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
965		1217
966	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1218	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
967		1219
968	Starts (activates) the given watcher. Only active watchers will receive	1220	Starts (activates) the given watcher. Only active watchers will receive
969	events. If the watcher is already active nothing will happen.	1221	events. If the watcher is already active nothing will happen.
970		1222
971	Example: Start the C<ev_io> watcher that is being abused as example in this	1223	Example: Start the C<ev_io> watcher that is being abused as example in this
972	whole section.	1224	whole section.
973		1225
974	ev_io_start (EV_DEFAULT_UC, &w);	1226	ev_io_start (EV_DEFAULT_UC, &w);
975		1227
976	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1228	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
977		1229
978	Stops the given watcher if active, and clears the pending status (whether	1230	Stops the given watcher if active, and clears the pending status (whether
979	the watcher was active or not).	1231	the watcher was active or not).
980		1232
981	It is possible that stopped watchers are pending - for example,	1233	It is possible that stopped watchers are pending - for example,
…		…
1006	=item ev_cb_set (ev_TYPE *watcher, callback)	1258	=item ev_cb_set (ev_TYPE *watcher, callback)
1007		1259
1008	Change the callback. You can change the callback at virtually any time	1260	Change the callback. You can change the callback at virtually any time
1009	(modulo threads).	1261	(modulo threads).
1010		1262
1011	=item ev_set_priority (ev_TYPE *watcher, priority)	1263	=item ev_set_priority (ev_TYPE *watcher, int priority)
1012		1264
1013	=item int ev_priority (ev_TYPE *watcher)	1265	=item int ev_priority (ev_TYPE *watcher)
1014		1266
1015	Set and query the priority of the watcher. The priority is a small	1267	Set and query the priority of the watcher. The priority is a small
1016	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1268	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1017	(default: C<-2>). Pending watchers with higher priority will be invoked	1269	(default: C<-2>). Pending watchers with higher priority will be invoked
1018	before watchers with lower priority, but priority will not keep watchers	1270	before watchers with lower priority, but priority will not keep watchers
1019	from being executed (except for C<ev_idle> watchers).	1271	from being executed (except for C<ev_idle> watchers).
1020		1272
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	1273	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.	1274	you need to look at C<ev_idle> watchers, which provide this functionality.
1028		1275
1029	You I<must not> change the priority of a watcher as long as it is active or	1276	You I<must not> change the priority of a watcher as long as it is active or
1030	pending.	1277	pending.
1031		1278
		1279	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1280	fine, as long as you do not mind that the priority value you query might
		1281	or might not have been clamped to the valid range.
		1282
1032	The default priority used by watchers when no priority has been set is	1283	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 :).	1284	always C<0>, which is supposed to not be too high and not be too low :).
1034		1285
1035	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1286	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	1287	priorities.
1037	or might not have been adjusted to be within valid range.
1038		1288
1039	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1289	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1040		1290
1041	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1291	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1042	C<loop> nor C<revents> need to be valid as long as the watcher callback	1292	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1050	watcher isn't pending it does nothing and returns C<0>.	1300	watcher isn't pending it does nothing and returns C<0>.
1051		1301
1052	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1302	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1053	callback to be invoked, which can be accomplished with this function.	1303	callback to be invoked, which can be accomplished with this function.
1054		1304
		1305	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1306
		1307	Feeds the given event set into the event loop, as if the specified event
		1308	had happened for the specified watcher (which must be a pointer to an
		1309	initialised but not necessarily started event watcher). Obviously you must
		1310	not free the watcher as long as it has pending events.
		1311
		1312	Stopping the watcher, letting libev invoke it, or calling
		1313	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1314	not started in the first place.
		1315
		1316	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1317	functions that do not need a watcher.
		1318
1055	=back	1319	=back
1056
1057		1320
1058	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1321	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1059		1322
1060	Each watcher has, by default, a member C<void *data> that you can change	1323	Each watcher has, by default, a member C<void *data> that you can change
1061	and read at any time: libev will completely ignore it. This can be used	1324	and read at any time: libev will completely ignore it. This can be used
…		…
1107	#include <stddef.h>	1370	#include <stddef.h>
1108		1371
1109	static void	1372	static void
1110	t1_cb (EV_P_ ev_timer *w, int revents)	1373	t1_cb (EV_P_ ev_timer *w, int revents)
1111	{	1374	{
1112	struct my_biggy big = (struct my_biggy *	1375	struct my_biggy big = (struct my_biggy *)
1113	(((char *)w) - offsetof (struct my_biggy, t1));	1376	(((char *)w) - offsetof (struct my_biggy, t1));
1114	}	1377	}
1115		1378
1116	static void	1379	static void
1117	t2_cb (EV_P_ ev_timer *w, int revents)	1380	t2_cb (EV_P_ ev_timer *w, int revents)
1118	{	1381	{
1119	struct my_biggy big = (struct my_biggy *	1382	struct my_biggy big = (struct my_biggy *)
1120	(((char *)w) - offsetof (struct my_biggy, t2));	1383	(((char *)w) - offsetof (struct my_biggy, t2));
1121	}	1384	}
		1385
		1386	=head2 WATCHER STATES
		1387
		1388	There are various watcher states mentioned throughout this manual -
		1389	active, pending and so on. In this section these states and the rules to
		1390	transition between them will be described in more detail - and while these
		1391	rules might look complicated, they usually do "the right thing".
		1392
		1393	=over 4
		1394
		1395	=item initialiased
		1396
		1397	Before a watcher can be registered with the event looop it has to be
		1398	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1399	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1400
		1401	In this state it is simply some block of memory that is suitable for use
		1402	in an event loop. It can be moved around, freed, reused etc. at will.
		1403
		1404	=item started/running/active
		1405
		1406	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1407	property of the event loop, and is actively waiting for events. While in
		1408	this state it cannot be accessed (except in a few documented ways), moved,
		1409	freed or anything else - the only legal thing is to keep a pointer to it,
		1410	and call libev functions on it that are documented to work on active watchers.
		1411
		1412	=item pending
		1413
		1414	If a watcher is active and libev determines that an event it is interested
		1415	in has occurred (such as a timer expiring), it will become pending. It will
		1416	stay in this pending state until either it is stopped or its callback is
		1417	about to be invoked, so it is not normally pending inside the watcher
		1418	callback.
		1419
		1420	The watcher might or might not be active while it is pending (for example,
		1421	an expired non-repeating timer can be pending but no longer active). If it
		1422	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1423	but it is still property of the event loop at this time, so cannot be
		1424	moved, freed or reused. And if it is active the rules described in the
		1425	previous item still apply.
		1426
		1427	It is also possible to feed an event on a watcher that is not active (e.g.
		1428	via C<ev_feed_event>), in which case it becomes pending without being
		1429	active.
		1430
		1431	=item stopped
		1432
		1433	A watcher can be stopped implicitly by libev (in which case it might still
		1434	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1435	latter will clear any pending state the watcher might be in, regardless
		1436	of whether it was active or not, so stopping a watcher explicitly before
		1437	freeing it is often a good idea.
		1438
		1439	While stopped (and not pending) the watcher is essentially in the
		1440	initialised state, that is it can be reused, moved, modified in any way
		1441	you wish.
		1442
		1443	=back
		1444
		1445	=head2 WATCHER PRIORITY MODELS
		1446
		1447	Many event loops support I<watcher priorities>, which are usually small
		1448	integers that influence the ordering of event callback invocation
		1449	between watchers in some way, all else being equal.
		1450
		1451	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1452	description for the more technical details such as the actual priority
		1453	range.
		1454
		1455	There are two common ways how these these priorities are being interpreted
		1456	by event loops:
		1457
		1458	In the more common lock-out model, higher priorities "lock out" invocation
		1459	of lower priority watchers, which means as long as higher priority
		1460	watchers receive events, lower priority watchers are not being invoked.
		1461
		1462	The less common only-for-ordering model uses priorities solely to order
		1463	callback invocation within a single event loop iteration: Higher priority
		1464	watchers are invoked before lower priority ones, but they all get invoked
		1465	before polling for new events.
		1466
		1467	Libev uses the second (only-for-ordering) model for all its watchers
		1468	except for idle watchers (which use the lock-out model).
		1469
		1470	The rationale behind this is that implementing the lock-out model for
		1471	watchers is not well supported by most kernel interfaces, and most event
		1472	libraries will just poll for the same events again and again as long as
		1473	their callbacks have not been executed, which is very inefficient in the
		1474	common case of one high-priority watcher locking out a mass of lower
		1475	priority ones.
		1476
		1477	Static (ordering) priorities are most useful when you have two or more
		1478	watchers handling the same resource: a typical usage example is having an
		1479	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1480	timeouts. Under load, data might be received while the program handles
		1481	other jobs, but since timers normally get invoked first, the timeout
		1482	handler will be executed before checking for data. In that case, giving
		1483	the timer a lower priority than the I/O watcher ensures that I/O will be
		1484	handled first even under adverse conditions (which is usually, but not
		1485	always, what you want).
		1486
		1487	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1488	will only be executed when no same or higher priority watchers have
		1489	received events, they can be used to implement the "lock-out" model when
		1490	required.
		1491
		1492	For example, to emulate how many other event libraries handle priorities,
		1493	you can associate an C<ev_idle> watcher to each such watcher, and in
		1494	the normal watcher callback, you just start the idle watcher. The real
		1495	processing is done in the idle watcher callback. This causes libev to
		1496	continuously poll and process kernel event data for the watcher, but when
		1497	the lock-out case is known to be rare (which in turn is rare :), this is
		1498	workable.
		1499
		1500	Usually, however, the lock-out model implemented that way will perform
		1501	miserably under the type of load it was designed to handle. In that case,
		1502	it might be preferable to stop the real watcher before starting the
		1503	idle watcher, so the kernel will not have to process the event in case
		1504	the actual processing will be delayed for considerable time.
		1505
		1506	Here is an example of an I/O watcher that should run at a strictly lower
		1507	priority than the default, and which should only process data when no
		1508	other events are pending:
		1509
		1510	ev_idle idle; // actual processing watcher
		1511	ev_io io; // actual event watcher
		1512
		1513	static void
		1514	io_cb (EV_P_ ev_io *w, int revents)
		1515	{
		1516	// stop the I/O watcher, we received the event, but
		1517	// are not yet ready to handle it.
		1518	ev_io_stop (EV_A_ w);
		1519
		1520	// start the idle watcher to handle the actual event.
		1521	// it will not be executed as long as other watchers
		1522	// with the default priority are receiving events.
		1523	ev_idle_start (EV_A_ &idle);
		1524	}
		1525
		1526	static void
		1527	idle_cb (EV_P_ ev_idle *w, int revents)
		1528	{
		1529	// actual processing
		1530	read (STDIN_FILENO, ...);
		1531
		1532	// have to start the I/O watcher again, as
		1533	// we have handled the event
		1534	ev_io_start (EV_P_ &io);
		1535	}
		1536
		1537	// initialisation
		1538	ev_idle_init (&idle, idle_cb);
		1539	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1540	ev_io_start (EV_DEFAULT_ &io);
		1541
		1542	In the "real" world, it might also be beneficial to start a timer, so that
		1543	low-priority connections can not be locked out forever under load. This
		1544	enables your program to keep a lower latency for important connections
		1545	during short periods of high load, while not completely locking out less
		1546	important ones.
1122		1547
1123		1548
1124	=head1 WATCHER TYPES	1549	=head1 WATCHER TYPES
1125		1550
1126	This section describes each watcher in detail, but will not repeat	1551	This section describes each watcher in detail, but will not repeat
…		…
1152	descriptors to non-blocking mode is also usually a good idea (but not	1577	descriptors to non-blocking mode is also usually a good idea (but not
1153	required if you know what you are doing).	1578	required if you know what you are doing).
1154		1579
1155	If you cannot use non-blocking mode, then force the use of a	1580	If you cannot use non-blocking mode, then force the use of a
1156	known-to-be-good backend (at the time of this writing, this includes only	1581	known-to-be-good backend (at the time of this writing, this includes only
1157	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).	1582	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1583	descriptors for which non-blocking operation makes no sense (such as
		1584	files) - libev doesn't guarantee any specific behaviour in that case.
1158		1585
1159	Another thing you have to watch out for is that it is quite easy to	1586	Another thing you have to watch out for is that it is quite easy to
1160	receive "spurious" readiness notifications, that is your callback might	1587	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	1588	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	1589	because there is no data. Not only are some backends known to create a
…		…
1227		1654
1228	So when you encounter spurious, unexplained daemon exits, make sure you	1655	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	1656	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).	1657	somewhere, as that would have given you a big clue).
1231		1658
		1659	=head3 The special problem of accept()ing when you can't
		1660
		1661	Many implementations of the POSIX C<accept> function (for example,
		1662	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1663	connection from the pending queue in all error cases.
		1664
		1665	For example, larger servers often run out of file descriptors (because
		1666	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1667	rejecting the connection, leading to libev signalling readiness on
		1668	the next iteration again (the connection still exists after all), and
		1669	typically causing the program to loop at 100% CPU usage.
		1670
		1671	Unfortunately, the set of errors that cause this issue differs between
		1672	operating systems, there is usually little the app can do to remedy the
		1673	situation, and no known thread-safe method of removing the connection to
		1674	cope with overload is known (to me).
		1675
		1676	One of the easiest ways to handle this situation is to just ignore it
		1677	- when the program encounters an overload, it will just loop until the
		1678	situation is over. While this is a form of busy waiting, no OS offers an
		1679	event-based way to handle this situation, so it's the best one can do.
		1680
		1681	A better way to handle the situation is to log any errors other than
		1682	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1683	messages, and continue as usual, which at least gives the user an idea of
		1684	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1685	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1686	usage.
		1687
		1688	If your program is single-threaded, then you could also keep a dummy file
		1689	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1690	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1691	close that fd, and create a new dummy fd. This will gracefully refuse
		1692	clients under typical overload conditions.
		1693
		1694	The last way to handle it is to simply log the error and C<exit>, as
		1695	is often done with C<malloc> failures, but this results in an easy
		1696	opportunity for a DoS attack.
1232		1697
1233	=head3 Watcher-Specific Functions	1698	=head3 Watcher-Specific Functions
1234		1699
1235	=over 4	1700	=over 4
1236		1701
…		…
1268	...	1733	...
1269	struct ev_loop *loop = ev_default_init (0);	1734	struct ev_loop *loop = ev_default_init (0);
1270	ev_io stdin_readable;	1735	ev_io stdin_readable;
1271	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1736	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1272	ev_io_start (loop, &stdin_readable);	1737	ev_io_start (loop, &stdin_readable);
1273	ev_loop (loop, 0);	1738	ev_run (loop, 0);
1274		1739
1275		1740
1276	=head2 C<ev_timer> - relative and optionally repeating timeouts	1741	=head2 C<ev_timer> - relative and optionally repeating timeouts
1277		1742
1278	Timer watchers are simple relative timers that generate an event after a	1743	Timer watchers are simple relative timers that generate an event after a
…		…
1283	year, it will still time out after (roughly) one hour. "Roughly" because	1748	year, it will still time out after (roughly) one hour. "Roughly" because
1284	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1749	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1285	monotonic clock option helps a lot here).	1750	monotonic clock option helps a lot here).
1286		1751
1287	The callback is guaranteed to be invoked only I<after> its timeout has	1752	The callback is guaranteed to be invoked only I<after> its timeout has
1288	passed, but if multiple timers become ready during the same loop iteration	1753	passed (not I<at>, so on systems with very low-resolution clocks this
1289	then order of execution is undefined.	1754	might introduce a small delay). If multiple timers become ready during the
		1755	same loop iteration then the ones with earlier time-out values are invoked
		1756	before ones of the same priority with later time-out values (but this is
		1757	no longer true when a callback calls C<ev_run> recursively).
1290		1758
1291	=head3 Be smart about timeouts	1759	=head3 Be smart about timeouts
1292		1760
1293	Many real-world problems invole some kind of time-out, usually for error	1761	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,	1762	recovery. A typical example is an HTTP request - if the other side hangs,
1295	you want to raise some error after a while.	1763	you want to raise some error after a while.
1296		1764
1297	Here are some ways on how to handle this problem, from simple and	1765	What follows are some ways to handle this problem, from obvious and
1298	inefficient to very efficient.	1766	inefficient to smart and efficient.
1299		1767
1300	In the following examples a 60 second activity timeout is assumed - a	1768	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")	1769	gets reset to 60 seconds each time there is activity (e.g. each time some
1302	was received.	1770	data or other life sign was received).
1303		1771
1304	=over 4	1772	=over 4
1305		1773
1306	=item 1. Use a timer and stop, reinitialise, start it on activity.	1774	=item 1. Use a timer and stop, reinitialise and start it on activity.
1307		1775
1308	This is the most obvious, but not the most simple way: In the beginning,	1776	This is the most obvious, but not the most simple way: In the beginning,
1309	start the watcher:	1777	start the watcher:
1310		1778
1311	ev_timer_init (timer, callback, 60., 0.);	1779	ev_timer_init (timer, callback, 60., 0.);
1312	ev_timer_start (loop, timer);	1780	ev_timer_start (loop, timer);
1313		1781
1314	Then, each time there is some activity, C<ev_timer_stop> the timer,	1782	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
1315	initialise it again, and start it:	1783	and start it again:
1316		1784
1317	ev_timer_stop (loop, timer);	1785	ev_timer_stop (loop, timer);
1318	ev_timer_set (timer, 60., 0.);	1786	ev_timer_set (timer, 60., 0.);
1319	ev_timer_start (loop, timer);	1787	ev_timer_start (loop, timer);
1320		1788
1321	This is relatively simple to implement, but means that each time there	1789	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	1790	some activity, libev will first have to remove the timer from its internal
1323	internal data strcuture and then add it again.	1791	data structure and then add it again. Libev tries to be fast, but it's
		1792	still not a constant-time operation.
1324		1793
1325	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.	1794	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
1326		1795
1327	This is the easiest way, and involves using C<ev_timer_again> instead of	1796	This is the easiest way, and involves using C<ev_timer_again> instead of
1328	C<ev_timer_start>.	1797	C<ev_timer_start>.
1329		1798
1330	For this, configure an C<ev_timer> with a C<repeat> value of C<60> and	1799	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	1800	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	1801	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	1802	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.	1803	the timer, and C<ev_timer_again> will automatically restart it if need be.
1335		1804
1336	That means you can ignore the C<after> value and C<ev_timer_start>	1805	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>.	1806	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1807	member and C<ev_timer_again>.
1338		1808
1339	At start:	1809	At start:
1340		1810
1341	ev_timer_init (timer, callback, 0., 60.);	1811	ev_init (timer, callback);
		1812	timer->repeat = 60.;
1342	ev_timer_again (loop, timer);	1813	ev_timer_again (loop, timer);
1343		1814
1344	Each time you receive some data:	1815	Each time there is some activity:
1345		1816
1346	ev_timer_again (loop, timer);	1817	ev_timer_again (loop, timer);
1347		1818
1348	It is even possible to change the time-out on the fly:	1819	It is even possible to change the time-out on the fly, regardless of
		1820	whether the watcher is active or not:
1349		1821
1350	timer->repeat = 30.;	1822	timer->repeat = 30.;
1351	ev_timer_again (loop, timer);	1823	ev_timer_again (loop, timer);
1352		1824
1353	This is slightly more efficient then stopping/starting the timer each time	1825	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	1826	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.	1827	remove and re-insert the timer from/into its internal data structure.
		1828
		1829	It is, however, even simpler than the "obvious" way to do it.
1356		1830
1357	=item 3. Let the timer time out, but then re-arm it as required.	1831	=item 3. Let the timer time out, but then re-arm it as required.
1358		1832
1359	This method is more tricky, but usually most efficient: Most timeouts are	1833	This method is more tricky, but usually most efficient: Most timeouts are
1360	relatively long compared to the loop iteration time - in our example,	1834	relatively long compared to the intervals between other activity - in
1361	within 60 seconds, there are usually many I/O events with associated	1835	our example, within 60 seconds, there are usually many I/O events with
1362	activity resets.	1836	associated activity resets.
1363		1837
1364	In this case, it would be more efficient to leave the C<ev_timer> alone,	1838	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	1839	but remember the time of last activity, and check for a real timeout only
1366	within the callback:	1840	within the callback:
1367		1841
1368	ev_tstamp last_activity; // time of last activity	1842	ev_tstamp last_activity; // time of last activity
1369		1843
1370	static void	1844	static void
1371	callback (EV_P_ ev_timer *w, int revents)	1845	callback (EV_P_ ev_timer *w, int revents)
1372	{	1846	{
1373	ev_tstamp now = ev_now (EV_A);	1847	ev_tstamp now = ev_now (EV_A);
1374	ev_tstamp timeout = last_activity + 60.;	1848	ev_tstamp timeout = last_activity + 60.;
1375		1849
1376	// if last_activity is older than now - timeout, we did time out	1850	// if last_activity + 60. is older than now, we did time out
1377	if (timeout < now)	1851	if (timeout < now)
1378	{	1852	{
1379	// timeout occured, take action	1853	// timeout occurred, take action
1380	}	1854	}
1381	else	1855	else
1382	{	1856	{
1383	// callback was invoked, but there was some activity, re-arm	1857	// callback was invoked, but there was some activity, re-arm
1384	// to fire in last_activity + 60.	1858	// the watcher to fire in last_activity + 60, which is
		1859	// guaranteed to be in the future, so "again" is positive:
1385	w->again = timeout - now;	1860	w->repeat = timeout - now;
1386	ev_timer_again (EV_A_ w);	1861	ev_timer_again (EV_A_ w);
1387	}	1862	}
1388	}	1863	}
1389		1864
1390	To summarise the callback: first calculate the real time-out (defined as	1865	To summarise the callback: first calculate the real timeout (defined
1391	"60 seconds after the last activity"), then check if that time has been	1866	as "60 seconds after the last activity"), then check if that time has
1392	reached, which means there was a real timeout. Otherwise the callback was	1867	been reached, which means something I<did>, in fact, time out. Otherwise
1393	invoked too early (timeout is in the future), so re-schedule the timer to	1868	the callback was invoked too early (C<timeout> is in the future), so
1394	fire at that future time.	1869	re-schedule the timer to fire at that future time, to see if maybe we have
		1870	a timeout then.
1395		1871
1396	Note how C<ev_timer_again> is used, taking advantage of the	1872	Note how C<ev_timer_again> is used, taking advantage of the
1397	C<ev_timer_again> optimisation when the timer is already running.	1873	C<ev_timer_again> optimisation when the timer is already running.
1398		1874
1399	This scheme causes more callback invocations (about one every 60 seconds),	1875	This scheme causes more callback invocations (about one every 60 seconds
1400	but virtually no calls to libev to change the timeout.	1876	minus half the average time between activity), but virtually no calls to
		1877	libev to change the timeout.
1401		1878
1402	To start the timer, simply intiialise the watcher and C<last_activity>,	1879	To start the timer, simply initialise the watcher and set C<last_activity>
1403	then call the callback:	1880	to the current time (meaning we just have some activity :), then call the
		1881	callback, which will "do the right thing" and start the timer:
1404		1882
1405	ev_timer_init (timer, callback);	1883	ev_init (timer, callback);
1406	last_activity = ev_now (loop);	1884	last_activity = ev_now (loop);
1407	callback (loop, timer, EV_TIMEOUT);	1885	callback (loop, timer, EV_TIMER);
1408		1886
1409	And when there is some activity, simply remember the time in	1887	And when there is some activity, simply store the current time in
1410	C<last_activity>:	1888	C<last_activity>, no libev calls at all:
1411		1889
1412	last_actiivty = ev_now (loop);	1890	last_activity = ev_now (loop);
1413		1891
1414	This technique is slightly more complex, but in most cases where the	1892	This technique is slightly more complex, but in most cases where the
1415	time-out is unlikely to be triggered, much more efficient.	1893	time-out is unlikely to be triggered, much more efficient.
1416		1894
		1895	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1896	callback :) - just change the timeout and invoke the callback, which will
		1897	fix things for you.
		1898
		1899	=item 4. Wee, just use a double-linked list for your timeouts.
		1900
		1901	If there is not one request, but many thousands (millions...), all
		1902	employing some kind of timeout with the same timeout value, then one can
		1903	do even better:
		1904
		1905	When starting the timeout, calculate the timeout value and put the timeout
		1906	at the I<end> of the list.
		1907
		1908	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1909	the list is expected to fire (for example, using the technique #3).
		1910
		1911	When there is some activity, remove the timer from the list, recalculate
		1912	the timeout, append it to the end of the list again, and make sure to
		1913	update the C<ev_timer> if it was taken from the beginning of the list.
		1914
		1915	This way, one can manage an unlimited number of timeouts in O(1) time for
		1916	starting, stopping and updating the timers, at the expense of a major
		1917	complication, and having to use a constant timeout. The constant timeout
		1918	ensures that the list stays sorted.
		1919
1417	=back	1920	=back
		1921
		1922	So which method the best?
		1923
		1924	Method #2 is a simple no-brain-required solution that is adequate in most
		1925	situations. Method #3 requires a bit more thinking, but handles many cases
		1926	better, and isn't very complicated either. In most case, choosing either
		1927	one is fine, with #3 being better in typical situations.
		1928
		1929	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1930	rather complicated, but extremely efficient, something that really pays
		1931	off after the first million or so of active timers, i.e. it's usually
		1932	overkill :)
1418		1933
1419	=head3 The special problem of time updates	1934	=head3 The special problem of time updates
1420		1935
1421	Establishing the current time is a costly operation (it usually takes at	1936	Establishing the current time is a costly operation (it usually takes at
1422	least two system calls): EV therefore updates its idea of the current	1937	least two system calls): EV therefore updates its idea of the current
1423	time only before and after C<ev_loop> collects new events, which causes a	1938	time only before and after C<ev_run> collects new events, which causes a
1424	growing difference between C<ev_now ()> and C<ev_time ()> when handling	1939	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1425	lots of events in one iteration.	1940	lots of events in one iteration.
1426		1941
1427	The relative timeouts are calculated relative to the C<ev_now ()>	1942	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	1943	time. This is usually the right thing as this timestamp refers to the time
…		…
1434		1949
1435	If the event loop is suspended for a long time, you can also force an	1950	If the event loop is suspended for a long time, you can also force an
1436	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1951	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1437	()>.	1952	()>.
1438		1953
		1954	=head3 The special problems of suspended animation
		1955
		1956	When you leave the server world it is quite customary to hit machines that
		1957	can suspend/hibernate - what happens to the clocks during such a suspend?
		1958
		1959	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1960	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1961	to run until the system is suspended, but they will not advance while the
		1962	system is suspended. That means, on resume, it will be as if the program
		1963	was frozen for a few seconds, but the suspend time will not be counted
		1964	towards C<ev_timer> when a monotonic clock source is used. The real time
		1965	clock advanced as expected, but if it is used as sole clocksource, then a
		1966	long suspend would be detected as a time jump by libev, and timers would
		1967	be adjusted accordingly.
		1968
		1969	I would not be surprised to see different behaviour in different between
		1970	operating systems, OS versions or even different hardware.
		1971
		1972	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1973	time jump in the monotonic clocks and the realtime clock. If the program
		1974	is suspended for a very long time, and monotonic clock sources are in use,
		1975	then you can expect C<ev_timer>s to expire as the full suspension time
		1976	will be counted towards the timers. When no monotonic clock source is in
		1977	use, then libev will again assume a timejump and adjust accordingly.
		1978
		1979	It might be beneficial for this latter case to call C<ev_suspend>
		1980	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1981	deterministic behaviour in this case (you can do nothing against
		1982	C<SIGSTOP>).
		1983
1439	=head3 Watcher-Specific Functions and Data Members	1984	=head3 Watcher-Specific Functions and Data Members
1440		1985
1441	=over 4	1986	=over 4
1442		1987
1443	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1988	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1466	If the timer is started but non-repeating, stop it (as if it timed out).	2011	If the timer is started but non-repeating, stop it (as if it timed out).
1467		2012
1468	If the timer is repeating, either start it if necessary (with the	2013	If the timer is repeating, either start it if necessary (with the
1469	C<repeat> value), or reset the running timer to the C<repeat> value.	2014	C<repeat> value), or reset the running timer to the C<repeat> value.
1470		2015
1471	This sounds a bit complicated, see "Be smart about timeouts", above, for a	2016	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1472	usage example.	2017	usage example.
		2018
		2019	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2020
		2021	Returns the remaining time until a timer fires. If the timer is active,
		2022	then this time is relative to the current event loop time, otherwise it's
		2023	the timeout value currently configured.
		2024
		2025	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2026	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2027	will return C<4>. When the timer expires and is restarted, it will return
		2028	roughly C<7> (likely slightly less as callback invocation takes some time,
		2029	too), and so on.
1473		2030
1474	=item ev_tstamp repeat [read-write]	2031	=item ev_tstamp repeat [read-write]
1475		2032
1476	The current C<repeat> value. Will be used each time the watcher times out	2033	The current C<repeat> value. Will be used each time the watcher times out
1477	or C<ev_timer_again> is called, and determines the next timeout (if any),	2034	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1503	}	2060	}
1504		2061
1505	ev_timer mytimer;	2062	ev_timer mytimer;
1506	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2063	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1507	ev_timer_again (&mytimer); /* start timer */	2064	ev_timer_again (&mytimer); /* start timer */
1508	ev_loop (loop, 0);	2065	ev_run (loop, 0);
1509		2066
1510	// and in some piece of code that gets executed on any "activity":	2067	// and in some piece of code that gets executed on any "activity":
1511	// reset the timeout to start ticking again at 10 seconds	2068	// reset the timeout to start ticking again at 10 seconds
1512	ev_timer_again (&mytimer);	2069	ev_timer_again (&mytimer);
1513		2070
…		…
1515	=head2 C<ev_periodic> - to cron or not to cron?	2072	=head2 C<ev_periodic> - to cron or not to cron?
1516		2073
1517	Periodic watchers are also timers of a kind, but they are very versatile	2074	Periodic watchers are also timers of a kind, but they are very versatile
1518	(and unfortunately a bit complex).	2075	(and unfortunately a bit complex).
1519		2076
1520	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2077	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1521	but on wall clock time (absolute time). You can tell a periodic watcher	2078	relative time, the physical time that passes) but on wall clock time
1522	to trigger after some specific point in time. For example, if you tell a	2079	(absolute time, the thing you can read on your calender or clock). The
1523	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	2080	difference is that wall clock time can run faster or slower than real
1524	+ 10.>, that is, an absolute time not a delay) and then reset your system	2081	time, and time jumps are not uncommon (e.g. when you adjust your
1525	clock to January of the previous year, then it will take more than year	2082	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		2083
		2084	You can tell a periodic watcher to trigger after some specific point
		2085	in time: for example, if you tell a periodic watcher to trigger "in 10
		2086	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2087	not a delay) and then reset your system clock to January of the previous
		2088	year, then it will take a year or more to trigger the event (unlike an
		2089	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2090	it, as it uses a relative timeout).
		2091
1529	C<ev_periodic>s can also be used to implement vastly more complex timers,	2092	C<ev_periodic> watchers can also be used to implement vastly more complex
1530	such as triggering an event on each "midnight, local time", or other	2093	timers, such as triggering an event on each "midnight, local time", or
1531	complicated rules.	2094	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2095	those cannot react to time jumps.
1532		2096
1533	As with timers, the callback is guaranteed to be invoked only when the	2097	As with timers, the callback is guaranteed to be invoked only when the
1534	time (C<at>) has passed, but if multiple periodic timers become ready	2098	point in time where it is supposed to trigger has passed. If multiple
1535	during the same loop iteration, then order of execution is undefined.	2099	timers become ready during the same loop iteration then the ones with
		2100	earlier time-out values are invoked before ones with later time-out values
		2101	(but this is no longer true when a callback calls C<ev_run> recursively).
1536		2102
1537	=head3 Watcher-Specific Functions and Data Members	2103	=head3 Watcher-Specific Functions and Data Members
1538		2104
1539	=over 4	2105	=over 4
1540		2106
1541	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2107	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1542		2108
1543	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2109	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1544		2110
1545	Lots of arguments, lets sort it out... There are basically three modes of	2111	Lots of arguments, let's sort it out... There are basically three modes of
1546	operation, and we will explain them from simplest to most complex:	2112	operation, and we will explain them from simplest to most complex:
1547		2113
1548	=over 4	2114	=over 4
1549		2115
1550	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2116	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1551		2117
1552	In this configuration the watcher triggers an event after the wall clock	2118	In this configuration the watcher triggers an event after the wall clock
1553	time C<at> has passed. It will not repeat and will not adjust when a time	2119	time C<offset> has passed. It will not repeat and will not adjust when a
1554	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2120	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1555	only run when the system clock reaches or surpasses this time.	2121	will be stopped and invoked when the system clock reaches or surpasses
		2122	this point in time.
1556		2123
1557	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2124	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1558		2125
1559	In this mode the watcher will always be scheduled to time out at the next	2126	In this mode the watcher will always be scheduled to time out at the next
1560	C<at + N * interval> time (for some integer N, which can also be negative)	2127	C<offset + N * interval> time (for some integer N, which can also be
1561	and then repeat, regardless of any time jumps.	2128	negative) and then repeat, regardless of any time jumps. The C<offset>
		2129	argument is merely an offset into the C<interval> periods.
1562		2130
1563	This can be used to create timers that do not drift with respect to the	2131	This can be used to create timers that do not drift with respect to the
1564	system clock, for example, here is a C<ev_periodic> that triggers each	2132	system clock, for example, here is an C<ev_periodic> that triggers each
1565	hour, on the hour:	2133	hour, on the hour (with respect to UTC):
1566		2134
1567	ev_periodic_set (&periodic, 0., 3600., 0);	2135	ev_periodic_set (&periodic, 0., 3600., 0);
1568		2136
1569	This doesn't mean there will always be 3600 seconds in between triggers,	2137	This doesn't mean there will always be 3600 seconds in between triggers,
1570	but only that the callback will be called when the system time shows a	2138	but only that the callback will be called when the system time shows a
1571	full hour (UTC), or more correctly, when the system time is evenly divisible	2139	full hour (UTC), or more correctly, when the system time is evenly divisible
1572	by 3600.	2140	by 3600.
1573		2141
1574	Another way to think about it (for the mathematically inclined) is that	2142	Another way to think about it (for the mathematically inclined) is that
1575	C<ev_periodic> will try to run the callback in this mode at the next possible	2143	C<ev_periodic> will try to run the callback in this mode at the next possible
1576	time where C<time = at (mod interval)>, regardless of any time jumps.	2144	time where C<time = offset (mod interval)>, regardless of any time jumps.
1577		2145
1578	For numerical stability it is preferable that the C<at> value is near	2146	For numerical stability it is preferable that the C<offset> value is near
1579	C<ev_now ()> (the current time), but there is no range requirement for	2147	C<ev_now ()> (the current time), but there is no range requirement for
1580	this value, and in fact is often specified as zero.	2148	this value, and in fact is often specified as zero.
1581		2149
1582	Note also that there is an upper limit to how often a timer can fire (CPU	2150	Note also that there is an upper limit to how often a timer can fire (CPU
1583	speed for example), so if C<interval> is very small then timing stability	2151	speed for example), so if C<interval> is very small then timing stability
1584	will of course deteriorate. Libev itself tries to be exact to be about one	2152	will of course deteriorate. Libev itself tries to be exact to be about one
1585	millisecond (if the OS supports it and the machine is fast enough).	2153	millisecond (if the OS supports it and the machine is fast enough).
1586		2154
1587	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2155	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1588		2156
1589	In this mode the values for C<interval> and C<at> are both being	2157	In this mode the values for C<interval> and C<offset> are both being
1590	ignored. Instead, each time the periodic watcher gets scheduled, the	2158	ignored. Instead, each time the periodic watcher gets scheduled, the
1591	reschedule callback will be called with the watcher as first, and the	2159	reschedule callback will be called with the watcher as first, and the
1592	current time as second argument.	2160	current time as second argument.
1593		2161
1594	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2162	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1595	ever, or make ANY event loop modifications whatsoever>.	2163	or make ANY other event loop modifications whatsoever, unless explicitly
		2164	allowed by documentation here>.
1596		2165
1597	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2166	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1598	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2167	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1599	only event loop modification you are allowed to do).	2168	only event loop modification you are allowed to do).
1600		2169
…		…
1630	a different time than the last time it was called (e.g. in a crond like	2199	a different time than the last time it was called (e.g. in a crond like
1631	program when the crontabs have changed).	2200	program when the crontabs have changed).
1632		2201
1633	=item ev_tstamp ev_periodic_at (ev_periodic *)	2202	=item ev_tstamp ev_periodic_at (ev_periodic *)
1634		2203
1635	When active, returns the absolute time that the watcher is supposed to	2204	When active, returns the absolute time that the watcher is supposed
1636	trigger next.	2205	to trigger next. This is not the same as the C<offset> argument to
		2206	C<ev_periodic_set>, but indeed works even in interval and manual
		2207	rescheduling modes.
1637		2208
1638	=item ev_tstamp offset [read-write]	2209	=item ev_tstamp offset [read-write]
1639		2210
1640	When repeating, this contains the offset value, otherwise this is the	2211	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>).	2212	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2213	although libev might modify this value for better numerical stability).
1642		2214
1643	Can be modified any time, but changes only take effect when the periodic	2215	Can be modified any time, but changes only take effect when the periodic
1644	timer fires or C<ev_periodic_again> is being called.	2216	timer fires or C<ev_periodic_again> is being called.
1645		2217
1646	=item ev_tstamp interval [read-write]	2218	=item ev_tstamp interval [read-write]
…		…
1662	Example: Call a callback every hour, or, more precisely, whenever the	2234	Example: Call a callback every hour, or, more precisely, whenever the
1663	system time is divisible by 3600. The callback invocation times have	2235	system time is divisible by 3600. The callback invocation times have
1664	potentially a lot of jitter, but good long-term stability.	2236	potentially a lot of jitter, but good long-term stability.
1665		2237
1666	static void	2238	static void
1667	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2239	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1668	{	2240	{
1669	... its now a full hour (UTC, or TAI or whatever your clock follows)	2241	... its now a full hour (UTC, or TAI or whatever your clock follows)
1670	}	2242	}
1671		2243
1672	ev_periodic hourly_tick;	2244	ev_periodic hourly_tick;
…		…
1695		2267
1696	=head2 C<ev_signal> - signal me when a signal gets signalled!	2268	=head2 C<ev_signal> - signal me when a signal gets signalled!
1697		2269
1698	Signal watchers will trigger an event when the process receives a specific	2270	Signal watchers will trigger an event when the process receives a specific
1699	signal one or more times. Even though signals are very asynchronous, libev	2271	signal one or more times. Even though signals are very asynchronous, libev
1700	will try it's best to deliver signals synchronously, i.e. as part of the	2272	will try its best to deliver signals synchronously, i.e. as part of the
1701	normal event processing, like any other event.	2273	normal event processing, like any other event.
1702		2274
1703	If you want signals asynchronously, just use C<sigaction> as you would	2275	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	2276	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.	2277	the signal. You can even use C<ev_async> from a signal handler to
		2278	synchronously wake up an event loop.
1706		2279
1707	You can configure as many watchers as you like per signal. Only when the	2280	You can configure as many watchers as you like for the same signal, but
		2281	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2282	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2283	C<SIGINT> in both the default loop and another loop at the same time. At
		2284	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2285
1708	first watcher gets started will libev actually register a signal handler	2286	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	2287	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	2288	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		2289
1714	If possible and supported, libev will install its handlers with	2290	If possible and supported, libev will install its handlers with
1715	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2291	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1716	interrupted. If you have a problem with system calls getting interrupted by	2292	not be unduly interrupted. If you have a problem with system calls getting
1717	signals you can block all signals in an C<ev_check> watcher and unblock	2293	interrupted by signals you can block all signals in an C<ev_check> watcher
1718	them in an C<ev_prepare> watcher.	2294	and unblock them in an C<ev_prepare> watcher.
		2295
		2296	=head3 The special problem of inheritance over fork/execve/pthread_create
		2297
		2298	Both the signal mask (C<sigprocmask>) and the signal disposition
		2299	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2300	stopping it again), that is, libev might or might not block the signal,
		2301	and might or might not set or restore the installed signal handler.
		2302
		2303	While this does not matter for the signal disposition (libev never
		2304	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2305	C<execve>), this matters for the signal mask: many programs do not expect
		2306	certain signals to be blocked.
		2307
		2308	This means that before calling C<exec> (from the child) you should reset
		2309	the signal mask to whatever "default" you expect (all clear is a good
		2310	choice usually).
		2311
		2312	The simplest way to ensure that the signal mask is reset in the child is
		2313	to install a fork handler with C<pthread_atfork> that resets it. That will
		2314	catch fork calls done by libraries (such as the libc) as well.
		2315
		2316	In current versions of libev, the signal will not be blocked indefinitely
		2317	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2318	the window of opportunity for problems, it will not go away, as libev
		2319	I<has> to modify the signal mask, at least temporarily.
		2320
		2321	So I can't stress this enough: I<If you do not reset your signal mask when
		2322	you expect it to be empty, you have a race condition in your code>. This
		2323	is not a libev-specific thing, this is true for most event libraries.
1719		2324
1720	=head3 Watcher-Specific Functions and Data Members	2325	=head3 Watcher-Specific Functions and Data Members
1721		2326
1722	=over 4	2327	=over 4
1723		2328
…		…
1739	Example: Try to exit cleanly on SIGINT.	2344	Example: Try to exit cleanly on SIGINT.
1740		2345
1741	static void	2346	static void
1742	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2347	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1743	{	2348	{
1744	ev_unloop (loop, EVUNLOOP_ALL);	2349	ev_break (loop, EVBREAK_ALL);
1745	}	2350	}
1746		2351
1747	ev_signal signal_watcher;	2352	ev_signal signal_watcher;
1748	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2353	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1749	ev_signal_start (loop, &signal_watcher);	2354	ev_signal_start (loop, &signal_watcher);
…		…
1755	some child status changes (most typically when a child of yours dies or	2360	some child status changes (most typically when a child of yours dies or
1756	exits). It is permissible to install a child watcher I<after> the child	2361	exits). It is permissible to install a child watcher I<after> the child
1757	has been forked (which implies it might have already exited), as long	2362	has been forked (which implies it might have already exited), as long
1758	as the event loop isn't entered (or is continued from a watcher), i.e.,	2363	as the event loop isn't entered (or is continued from a watcher), i.e.,
1759	forking and then immediately registering a watcher for the child is fine,	2364	forking and then immediately registering a watcher for the child is fine,
1760	but forking and registering a watcher a few event loop iterations later is	2365	but forking and registering a watcher a few event loop iterations later or
1761	not.	2366	in the next callback invocation is not.
1762		2367
1763	Only the default event loop is capable of handling signals, and therefore	2368	Only the default event loop is capable of handling signals, and therefore
1764	you can only register child watchers in the default event loop.	2369	you can only register child watchers in the default event loop.
1765		2370
		2371	Due to some design glitches inside libev, child watchers will always be
		2372	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2373	libev)
		2374
1766	=head3 Process Interaction	2375	=head3 Process Interaction
1767		2376
1768	Libev grabs C<SIGCHLD> as soon as the default event loop is	2377	Libev grabs C<SIGCHLD> as soon as the default event loop is
1769	initialised. This is necessary to guarantee proper behaviour even if	2378	initialised. This is necessary to guarantee proper behaviour even if the
1770	the first child watcher is started after the child exits. The occurrence	2379	first child watcher is started after the child exits. The occurrence
1771	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2380	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1772	synchronously as part of the event loop processing. Libev always reaps all	2381	synchronously as part of the event loop processing. Libev always reaps all
1773	children, even ones not watched.	2382	children, even ones not watched.
1774		2383
1775	=head3 Overriding the Built-In Processing	2384	=head3 Overriding the Built-In Processing
…		…
1785	=head3 Stopping the Child Watcher	2394	=head3 Stopping the Child Watcher
1786		2395
1787	Currently, the child watcher never gets stopped, even when the	2396	Currently, the child watcher never gets stopped, even when the
1788	child terminates, so normally one needs to stop the watcher in the	2397	child terminates, so normally one needs to stop the watcher in the
1789	callback. Future versions of libev might stop the watcher automatically	2398	callback. Future versions of libev might stop the watcher automatically
1790	when a child exit is detected.	2399	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2400	problem).
1791		2401
1792	=head3 Watcher-Specific Functions and Data Members	2402	=head3 Watcher-Specific Functions and Data Members
1793		2403
1794	=over 4	2404	=over 4
1795		2405
…		…
1852		2462
1853		2463
1854	=head2 C<ev_stat> - did the file attributes just change?	2464	=head2 C<ev_stat> - did the file attributes just change?
1855		2465
1856	This watches a file system path for attribute changes. That is, it calls	2466	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	2467	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.	2468	and sees if it changed compared to the last time, invoking the callback if
		2469	it did.
1859		2470
1860	The path does not need to exist: changing from "path exists" to "path does	2471	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	2472	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	2473	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	2474	C<st_nlink> field being zero (which is otherwise always forced to be at
1864	the stat buffer having unspecified contents.	2475	least one) and all the other fields of the stat buffer having unspecified
		2476	contents.
1865		2477
1866	The path I<should> be absolute and I<must not> end in a slash. If it is	2478	The path I<must not> end in a slash or contain special components such as
		2479	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.	2480	your working directory changes, then the behaviour is undefined.
1868		2481
1869	Since there is no standard kernel interface to do this, the portable	2482	Since there is no portable change notification interface available, the
1870	implementation simply calls C<stat (2)> regularly on the path to see if	2483	portable implementation simply calls C<stat(2)> regularly on the path
1871	it changed somehow. You can specify a recommended polling interval for	2484	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!)	2485	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	2486	recommended!) then a I<suitable, unspecified default> value will be used
1874	you can expect to be around five seconds, although this might change	2487	(which you can expect to be around five seconds, although this might
1875	dynamically). Libev will also impose a minimum interval which is currently	2488	change dynamically). Libev will also impose a minimum interval which is
1876	around C<0.1>, but thats usually overkill.	2489	currently around C<0.1>, but that's usually overkill.
1877		2490
1878	This watcher type is not meant for massive numbers of stat watchers,	2491	This watcher type is not meant for massive numbers of stat watchers,
1879	as even with OS-supported change notifications, this can be	2492	as even with OS-supported change notifications, this can be
1880	resource-intensive.	2493	resource-intensive.
1881		2494
1882	At the time of this writing, the only OS-specific interface implemented	2495	At the time of this writing, the only OS-specific interface implemented
1883	is the Linux inotify interface (implementing kqueue support is left as	2496	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	2497	exercise for the reader. Note, however, that the author sees no way of
1885	of implementing C<ev_stat> semantics with kqueue).	2498	implementing C<ev_stat> semantics with kqueue, except as a hint).
1886		2499
1887	=head3 ABI Issues (Largefile Support)	2500	=head3 ABI Issues (Largefile Support)
1888		2501
1889	Libev by default (unless the user overrides this) uses the default	2502	Libev by default (unless the user overrides this) uses the default
1890	compilation environment, which means that on systems with large file	2503	compilation environment, which means that on systems with large file
1891	support disabled by default, you get the 32 bit version of the stat	2504	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	2505	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	2506	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	2507	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	2508	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.	2509	most noticeably displayed with ev_stat and large file support.
1897		2510
1898	The solution for this is to lobby your distribution maker to make large	2511	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	2512	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	2513	optional. Libev cannot simply switch on large file support because it has
1901	to exchange stat structures with application programs compiled using the	2514	to exchange stat structures with application programs compiled using the
1902	default compilation environment.	2515	default compilation environment.
1903		2516
1904	=head3 Inotify and Kqueue	2517	=head3 Inotify and Kqueue
1905		2518
1906	When C<inotify (7)> support has been compiled into libev (generally	2519	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	2520	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	2521	inotify descriptor will be created lazily when the first C<ev_stat>
1909	change detection where possible. The inotify descriptor will be created	2522	watcher is being started.
1910	lazily when the first C<ev_stat> watcher is being started.
1911		2523
1912	Inotify presence does not change the semantics of C<ev_stat> watchers	2524	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	2525	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	2526	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,	2527	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.	2528	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2529	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2530	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2531	xfs are fully working) libev usually gets away without polling.
1917		2532
1918	There is no support for kqueue, as apparently it cannot be used to	2533	There is no support for kqueue, as apparently it cannot be used to
1919	implement this functionality, due to the requirement of having a file	2534	implement this functionality, due to the requirement of having a file
1920	descriptor open on the object at all times, and detecting renames, unlinks	2535	descriptor open on the object at all times, and detecting renames, unlinks
1921	etc. is difficult.	2536	etc. is difficult.
1922		2537
		2538	=head3 C<stat ()> is a synchronous operation
		2539
		2540	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2541	the process. The exception are C<ev_stat> watchers - those call C<stat
		2542	()>, which is a synchronous operation.
		2543
		2544	For local paths, this usually doesn't matter: unless the system is very
		2545	busy or the intervals between stat's are large, a stat call will be fast,
		2546	as the path data is usually in memory already (except when starting the
		2547	watcher).
		2548
		2549	For networked file systems, calling C<stat ()> can block an indefinite
		2550	time due to network issues, and even under good conditions, a stat call
		2551	often takes multiple milliseconds.
		2552
		2553	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2554	paths, although this is fully supported by libev.
		2555
1923	=head3 The special problem of stat time resolution	2556	=head3 The special problem of stat time resolution
1924		2557
1925	The C<stat ()> system call only supports full-second resolution portably, and	2558	The C<stat ()> system call only supports full-second resolution portably,
1926	even on systems where the resolution is higher, most file systems still	2559	and even on systems where the resolution is higher, most file systems
1927	only support whole seconds.	2560	still only support whole seconds.
1928		2561
1929	That means that, if the time is the only thing that changes, you can	2562	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	2563	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	2564	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	2565	within the same second, C<ev_stat> will be unable to detect unless the
…		…
2075		2708
2076	=head3 Watcher-Specific Functions and Data Members	2709	=head3 Watcher-Specific Functions and Data Members
2077		2710
2078	=over 4	2711	=over 4
2079		2712
2080	=item ev_idle_init (ev_signal *, callback)	2713	=item ev_idle_init (ev_idle *, callback)
2081		2714
2082	Initialises and configures the idle watcher - it has no parameters of any	2715	Initialises and configures the idle watcher - it has no parameters of any
2083	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2716	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
2084	believe me.	2717	believe me.
2085		2718
…		…
2098	// no longer anything immediate to do.	2731	// no longer anything immediate to do.
2099	}	2732	}
2100		2733
2101	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2734	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2102	ev_idle_init (idle_watcher, idle_cb);	2735	ev_idle_init (idle_watcher, idle_cb);
2103	ev_idle_start (loop, idle_cb);	2736	ev_idle_start (loop, idle_watcher);
2104		2737
2105		2738
2106	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2739	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2107		2740
2108	Prepare and check watchers are usually (but not always) used in pairs:	2741	Prepare and check watchers are usually (but not always) used in pairs:
2109	prepare watchers get invoked before the process blocks and check watchers	2742	prepare watchers get invoked before the process blocks and check watchers
2110	afterwards.	2743	afterwards.
2111		2744
2112	You I<must not> call C<ev_loop> or similar functions that enter	2745	You I<must not> call C<ev_run> or similar functions that enter
2113	the current event loop from either C<ev_prepare> or C<ev_check>	2746	the current event loop from either C<ev_prepare> or C<ev_check>
2114	watchers. Other loops than the current one are fine, however. The	2747	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	2748	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,	2749	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	2750	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2201	struct pollfd fds [nfd];	2834	struct pollfd fds [nfd];
2202	// actual code will need to loop here and realloc etc.	2835	// actual code will need to loop here and realloc etc.
2203	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2836	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2204		2837
2205	/* the callback is illegal, but won't be called as we stop during check */	2838	/* the callback is illegal, but won't be called as we stop during check */
2206	ev_timer_init (&tw, 0, timeout * 1e-3);	2839	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2207	ev_timer_start (loop, &tw);	2840	ev_timer_start (loop, &tw);
2208		2841
2209	// create one ev_io per pollfd	2842	// create one ev_io per pollfd
2210	for (int i = 0; i < nfd; ++i)	2843	for (int i = 0; i < nfd; ++i)
2211	{	2844	{
…		…
2285		2918
2286	if (timeout >= 0)	2919	if (timeout >= 0)
2287	// create/start timer	2920	// create/start timer
2288		2921
2289	// poll	2922	// poll
2290	ev_loop (EV_A_ 0);	2923	ev_run (EV_A_ 0);
2291		2924
2292	// stop timer again	2925	// stop timer again
2293	if (timeout >= 0)	2926	if (timeout >= 0)
2294	ev_timer_stop (EV_A_ &to);	2927	ev_timer_stop (EV_A_ &to);
2295		2928
…		…
2324	some fds have to be watched and handled very quickly (with low latency),	2957	some fds have to be watched and handled very quickly (with low latency),
2325	and even priorities and idle watchers might have too much overhead. In	2958	and even priorities and idle watchers might have too much overhead. In
2326	this case you would put all the high priority stuff in one loop and all	2959	this case you would put all the high priority stuff in one loop and all
2327	the rest in a second one, and embed the second one in the first.	2960	the rest in a second one, and embed the second one in the first.
2328		2961
2329	As long as the watcher is active, the callback will be invoked every time	2962	As long as the watcher is active, the callback will be invoked every
2330	there might be events pending in the embedded loop. The callback must then	2963	time there might be events pending in the embedded loop. The callback
2331	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2964	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2332	their callbacks (you could also start an idle watcher to give the embedded	2965	sweep and invoke their callbacks (the callback doesn't need to invoke the
2333	loop strictly lower priority for example). You can also set the callback	2966	C<ev_embed_sweep> function directly, it could also start an idle watcher
2334	to C<0>, in which case the embed watcher will automatically execute the	2967	to give the embedded loop strictly lower priority for example).
2335	embedded loop sweep.
2336		2968
2337	As long as the watcher is started it will automatically handle events. The	2969	You can also set the callback to C<0>, in which case the embed watcher
2338	callback will be invoked whenever some events have been handled. You can	2970	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		2971
2342	Also, there have not currently been made special provisions for forking:	2972	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,	2973	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	2974	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,	2975	C<ev_loop_fork> on the embedded loop.
2346	and future versions of libev might do just that.
2347		2976
2348	Unfortunately, not all backends are embeddable: only the ones returned by	2977	Unfortunately, not all backends are embeddable: only the ones returned by
2349	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2978	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2350	portable one.	2979	portable one.
2351		2980
…		…
2377	if you do not want that, you need to temporarily stop the embed watcher).	3006	if you do not want that, you need to temporarily stop the embed watcher).
2378		3007
2379	=item ev_embed_sweep (loop, ev_embed *)	3008	=item ev_embed_sweep (loop, ev_embed *)
2380		3009
2381	Make a single, non-blocking sweep over the embedded loop. This works	3010	Make a single, non-blocking sweep over the embedded loop. This works
2382	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3011	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2383	appropriate way for embedded loops.	3012	appropriate way for embedded loops.
2384		3013
2385	=item struct ev_loop *other [read-only]	3014	=item struct ev_loop *other [read-only]
2386		3015
2387	The embedded event loop.	3016	The embedded event loop.
…		…
2445	event loop blocks next and before C<ev_check> watchers are being called,	3074	event loop blocks next and before C<ev_check> watchers are being called,
2446	and only in the child after the fork. If whoever good citizen calling	3075	and only in the child after the fork. If whoever good citizen calling
2447	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3076	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2448	handlers will be invoked, too, of course.	3077	handlers will be invoked, too, of course.
2449		3078
		3079	=head3 The special problem of life after fork - how is it possible?
		3080
		3081	Most uses of C<fork()> consist of forking, then some simple calls to set
		3082	up/change the process environment, followed by a call to C<exec()>. This
		3083	sequence should be handled by libev without any problems.
		3084
		3085	This changes when the application actually wants to do event handling
		3086	in the child, or both parent in child, in effect "continuing" after the
		3087	fork.
		3088
		3089	The default mode of operation (for libev, with application help to detect
		3090	forks) is to duplicate all the state in the child, as would be expected
		3091	when I<either> the parent I<or> the child process continues.
		3092
		3093	When both processes want to continue using libev, then this is usually the
		3094	wrong result. In that case, usually one process (typically the parent) is
		3095	supposed to continue with all watchers in place as before, while the other
		3096	process typically wants to start fresh, i.e. without any active watchers.
		3097
		3098	The cleanest and most efficient way to achieve that with libev is to
		3099	simply create a new event loop, which of course will be "empty", and
		3100	use that for new watchers. This has the advantage of not touching more
		3101	memory than necessary, and thus avoiding the copy-on-write, and the
		3102	disadvantage of having to use multiple event loops (which do not support
		3103	signal watchers).
		3104
		3105	When this is not possible, or you want to use the default loop for
		3106	other reasons, then in the process that wants to start "fresh", call
		3107	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3108	Destroying the default loop will "orphan" (not stop) all registered
		3109	watchers, so you have to be careful not to execute code that modifies
		3110	those watchers. Note also that in that case, you have to re-register any
		3111	signal watchers.
		3112
2450	=head3 Watcher-Specific Functions and Data Members	3113	=head3 Watcher-Specific Functions and Data Members
2451		3114
2452	=over 4	3115	=over 4
2453		3116
2454	=item ev_fork_init (ev_signal *, callback)	3117	=item ev_fork_init (ev_fork *, callback)
2455		3118
2456	Initialises and configures the fork watcher - it has no parameters of any	3119	Initialises and configures the fork watcher - it has no parameters of any
2457	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3120	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2458	believe me.	3121	really.
2459		3122
2460	=back	3123	=back
2461		3124
2462		3125
		3126	=head2 C<ev_cleanup> - even the best things end
		3127
		3128	Cleanup watchers are called just before the event loop is being destroyed
		3129	by a call to C<ev_loop_destroy>.
		3130
		3131	While there is no guarantee that the event loop gets destroyed, cleanup
		3132	watchers provide a convenient method to install cleanup hooks for your
		3133	program, worker threads and so on - you just to make sure to destroy the
		3134	loop when you want them to be invoked.
		3135
		3136	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3137	all other watchers, they do not keep a reference to the event loop (which
		3138	makes a lot of sense if you think about it). Like all other watchers, you
		3139	can call libev functions in the callback, except C<ev_cleanup_start>.
		3140
		3141	=head3 Watcher-Specific Functions and Data Members
		3142
		3143	=over 4
		3144
		3145	=item ev_cleanup_init (ev_cleanup *, callback)
		3146
		3147	Initialises and configures the cleanup watcher - it has no parameters of
		3148	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3149	pointless, I assure you.
		3150
		3151	=back
		3152
		3153	Example: Register an atexit handler to destroy the default loop, so any
		3154	cleanup functions are called.
		3155
		3156	static void
		3157	program_exits (void)
		3158	{
		3159	ev_loop_destroy (EV_DEFAULT_UC);
		3160	}
		3161
		3162	...
		3163	atexit (program_exits);
		3164
		3165
2463	=head2 C<ev_async> - how to wake up another event loop	3166	=head2 C<ev_async> - how to wake up an event loop
2464		3167
2465	In general, you cannot use an C<ev_loop> from multiple threads or other	3168	In general, you cannot use an C<ev_run> from multiple threads or other
2466	asynchronous sources such as signal handlers (as opposed to multiple event	3169	asynchronous sources such as signal handlers (as opposed to multiple event
2467	loops - those are of course safe to use in different threads).	3170	loops - those are of course safe to use in different threads).
2468		3171
2469	Sometimes, however, you need to wake up another event loop you do not	3172	Sometimes, however, you need to wake up an event loop you do not control,
2470	control, for example because it belongs to another thread. This is what	3173	for example because it belongs to another thread. This is what C<ev_async>
2471	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3174	watchers do: as long as the C<ev_async> watcher is active, you can signal
2472	can signal it by calling C<ev_async_send>, which is thread- and signal	3175	it by calling C<ev_async_send>, which is thread- and signal safe.
2473	safe.
2474		3176
2475	This functionality is very similar to C<ev_signal> watchers, as signals,	3177	This functionality is very similar to C<ev_signal> watchers, as signals,
2476	too, are asynchronous in nature, and signals, too, will be compressed	3178	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	3179	(i.e. the number of callback invocations may be less than the number of
2478	C<ev_async_sent> calls).	3180	C<ev_async_sent> calls).
…		…
2483	=head3 Queueing	3185	=head3 Queueing
2484		3186
2485	C<ev_async> does not support queueing of data in any way. The reason	3187	C<ev_async> does not support queueing of data in any way. The reason
2486	is that the author does not know of a simple (or any) algorithm for a	3188	is that the author does not know of a simple (or any) algorithm for a
2487	multiple-writer-single-reader queue that works in all cases and doesn't	3189	multiple-writer-single-reader queue that works in all cases and doesn't
2488	need elaborate support such as pthreads.	3190	need elaborate support such as pthreads or unportable memory access
		3191	semantics.
2489		3192
2490	That means that if you want to queue data, you have to provide your own	3193	That means that if you want to queue data, you have to provide your own
2491	queue. But at least I can tell you how to implement locking around your	3194	queue. But at least I can tell you how to implement locking around your
2492	queue:	3195	queue:
2493		3196
…		…
2571	=over 4	3274	=over 4
2572		3275
2573	=item ev_async_init (ev_async *, callback)	3276	=item ev_async_init (ev_async *, callback)
2574		3277
2575	Initialises and configures the async watcher - it has no parameters of any	3278	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,	3279	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2577	trust me.	3280	trust me.
2578		3281
2579	=item ev_async_send (loop, ev_async *)	3282	=item ev_async_send (loop, ev_async *)
2580		3283
2581	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3284	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	3285	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2583	C<ev_feed_event>, this call is safe to do from other threads, signal or	3286	C<ev_feed_event>, this call is safe to do from other threads, signal or
2584	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3287	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2585	section below on what exactly this means).	3288	section below on what exactly this means).
2586		3289
		3290	Note that, as with other watchers in libev, multiple events might get
		3291	compressed into a single callback invocation (another way to look at this
		3292	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3293	reset when the event loop detects that).
		3294
2587	This call incurs the overhead of a system call only once per loop iteration,	3295	This call incurs the overhead of a system call only once per event loop
2588	so while the overhead might be noticeable, it doesn't apply to repeated	3296	iteration, so while the overhead might be noticeable, it doesn't apply to
2589	calls to C<ev_async_send>.	3297	repeated calls to C<ev_async_send> for the same event loop.
2590		3298
2591	=item bool = ev_async_pending (ev_async *)	3299	=item bool = ev_async_pending (ev_async *)
2592		3300
2593	Returns a non-zero value when C<ev_async_send> has been called on the	3301	Returns a non-zero value when C<ev_async_send> has been called on the
2594	watcher but the event has not yet been processed (or even noted) by the	3302	watcher but the event has not yet been processed (or even noted) by the
…		…
2597	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3305	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2598	the loop iterates next and checks for the watcher to have become active,	3306	the loop iterates next and checks for the watcher to have become active,
2599	it will reset the flag again. C<ev_async_pending> can be used to very	3307	it will reset the flag again. C<ev_async_pending> can be used to very
2600	quickly check whether invoking the loop might be a good idea.	3308	quickly check whether invoking the loop might be a good idea.
2601		3309
2602	Not that this does I<not> check whether the watcher itself is pending, only	3310	Not that this does I<not> check whether the watcher itself is pending,
2603	whether it has been requested to make this watcher pending.	3311	only whether it has been requested to make this watcher pending: there
		3312	is a time window between the event loop checking and resetting the async
		3313	notification, and the callback being invoked.
2604		3314
2605	=back	3315	=back
2606		3316
2607		3317
2608	=head1 OTHER FUNCTIONS	3318	=head1 OTHER FUNCTIONS
…		…
2625		3335
2626	If C<timeout> is less than 0, then no timeout watcher will be	3336	If C<timeout> is less than 0, then no timeout watcher will be
2627	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3337	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2628	repeat = 0) will be started. C<0> is a valid timeout.	3338	repeat = 0) will be started. C<0> is a valid timeout.
2629		3339
2630	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3340	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2631	passed an C<revents> set like normal event callbacks (a combination of	3341	passed an C<revents> set like normal event callbacks (a combination of
2632	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3342	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2633	value passed to C<ev_once>. Note that it is possible to receive I<both>	3343	value passed to C<ev_once>. Note that it is possible to receive I<both>
2634	a timeout and an io event at the same time - you probably should give io	3344	a timeout and an io event at the same time - you probably should give io
2635	events precedence.	3345	events precedence.
2636		3346
2637	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3347	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2638		3348
2639	static void stdin_ready (int revents, void *arg)	3349	static void stdin_ready (int revents, void *arg)
2640	{	3350	{
2641	if (revents & EV_READ)	3351	if (revents & EV_READ)
2642	/* stdin might have data for us, joy! */;	3352	/* stdin might have data for us, joy! */;
2643	else if (revents & EV_TIMEOUT)	3353	else if (revents & EV_TIMER)
2644	/* doh, nothing entered */;	3354	/* doh, nothing entered */;
2645	}	3355	}
2646		3356
2647	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3357	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2648		3358
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)	3359	=item ev_feed_fd_event (loop, int fd, int revents)
2656		3360
2657	Feed an event on the given fd, as if a file descriptor backend detected	3361	Feed an event on the given fd, as if a file descriptor backend detected
2658	the given events it.	3362	the given events it.
2659		3363
2660	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3364	=item ev_feed_signal_event (loop, int signum)
2661		3365
2662	Feed an event as if the given signal occurred (C<loop> must be the default	3366	Feed an event as if the given signal occurred (C<loop> must be the default
2663	loop!).	3367	loop!).
2664		3368
2665	=back	3369	=back
…		…
2684	=item * Priorities are not currently supported. Initialising priorities	3388	=item * Priorities are not currently supported. Initialising priorities
2685	will fail and all watchers will have the same priority, even though there	3389	will fail and all watchers will have the same priority, even though there
2686	is an ev_pri field.	3390	is an ev_pri field.
2687		3391
2688	=item * In libevent, the last base created gets the signals, in libev, the	3392	=item * In libevent, the last base created gets the signals, in libev, the
2689	first base created (== the default loop) gets the signals.	3393	base that registered the signal gets the signals.
2690		3394
2691	=item * Other members are not supported.	3395	=item * Other members are not supported.
2692		3396
2693	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3397	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2694	to use the libev header file and library.	3398	to use the libev header file and library.
…		…
2745		3449
2746	=over 4	3450	=over 4
2747		3451
2748	=item ev::TYPE::TYPE ()	3452	=item ev::TYPE::TYPE ()
2749		3453
2750	=item ev::TYPE::TYPE (struct ev_loop *)	3454	=item ev::TYPE::TYPE (loop)
2751		3455
2752	=item ev::TYPE::~TYPE	3456	=item ev::TYPE::~TYPE
2753		3457
2754	The constructor (optionally) takes an event loop to associate the watcher	3458	The constructor (optionally) takes an event loop to associate the watcher
2755	with. If it is omitted, it will use C<EV_DEFAULT>.	3459	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2787		3491
2788	myclass obj;	3492	myclass obj;
2789	ev::io iow;	3493	ev::io iow;
2790	iow.set <myclass, &myclass::io_cb> (&obj);	3494	iow.set <myclass, &myclass::io_cb> (&obj);
2791		3495
		3496	=item w->set (object *)
		3497
		3498	This is a variation of a method callback - leaving out the method to call
		3499	will default the method to C<operator ()>, which makes it possible to use
		3500	functor objects without having to manually specify the C<operator ()> all
		3501	the time. Incidentally, you can then also leave out the template argument
		3502	list.
		3503
		3504	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3505	int revents)>.
		3506
		3507	See the method-C<set> above for more details.
		3508
		3509	Example: use a functor object as callback.
		3510
		3511	struct myfunctor
		3512	{
		3513	void operator() (ev::io &w, int revents)
		3514	{
		3515	...
		3516	}
		3517	}
		3518
		3519	myfunctor f;
		3520
		3521	ev::io w;
		3522	w.set (&f);
		3523
2792	=item w->set<function> (void *data = 0)	3524	=item w->set<function> (void *data = 0)
2793		3525
2794	Also sets a callback, but uses a static method or plain function as	3526	Also sets a callback, but uses a static method or plain function as
2795	callback. The optional C<data> argument will be stored in the watcher's	3527	callback. The optional C<data> argument will be stored in the watcher's
2796	C<data> member and is free for you to use.	3528	C<data> member and is free for you to use.
…		…
2802	Example: Use a plain function as callback.	3534	Example: Use a plain function as callback.
2803		3535
2804	static void io_cb (ev::io &w, int revents) { }	3536	static void io_cb (ev::io &w, int revents) { }
2805	iow.set <io_cb> ();	3537	iow.set <io_cb> ();
2806		3538
2807	=item w->set (struct ev_loop *)	3539	=item w->set (loop)
2808		3540
2809	Associates a different C<struct ev_loop> with this watcher. You can only	3541	Associates a different C<struct ev_loop> with this watcher. You can only
2810	do this when the watcher is inactive (and not pending either).	3542	do this when the watcher is inactive (and not pending either).
2811		3543
2812	=item w->set ([arguments])	3544	=item w->set ([arguments])
2813		3545
2814	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3546	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
2815	called at least once. Unlike the C counterpart, an active watcher gets	3547	method or a suitable start method must be called at least once. Unlike the
2816	automatically stopped and restarted when reconfiguring it with this	3548	C counterpart, an active watcher gets automatically stopped and restarted
2817	method.	3549	when reconfiguring it with this method.
2818		3550
2819	=item w->start ()	3551	=item w->start ()
2820		3552
2821	Starts the watcher. Note that there is no C<loop> argument, as the	3553	Starts the watcher. Note that there is no C<loop> argument, as the
2822	constructor already stores the event loop.	3554	constructor already stores the event loop.
2823		3555
		3556	=item w->start ([arguments])
		3557
		3558	Instead of calling C<set> and C<start> methods separately, it is often
		3559	convenient to wrap them in one call. Uses the same type of arguments as
		3560	the configure C<set> method of the watcher.
		3561
2824	=item w->stop ()	3562	=item w->stop ()
2825		3563
2826	Stops the watcher if it is active. Again, no C<loop> argument.	3564	Stops the watcher if it is active. Again, no C<loop> argument.
2827		3565
2828	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3566	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2840		3578
2841	=back	3579	=back
2842		3580
2843	=back	3581	=back
2844		3582
2845	Example: Define a class with an IO and idle watcher, start one of them in	3583	Example: Define a class with two I/O and idle watchers, start the I/O
2846	the constructor.	3584	watchers in the constructor.
2847		3585
2848	class myclass	3586	class myclass
2849	{	3587	{
2850	ev::io io ; void io_cb (ev::io &w, int revents);	3588	ev::io io ; void io_cb (ev::io &w, int revents);
		3589	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
2851	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3590	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2852		3591
2853	myclass (int fd)	3592	myclass (int fd)
2854	{	3593	{
2855	io .set <myclass, &myclass::io_cb > (this);	3594	io .set <myclass, &myclass::io_cb > (this);
		3595	io2 .set <myclass, &myclass::io2_cb > (this);
2856	idle.set <myclass, &myclass::idle_cb> (this);	3596	idle.set <myclass, &myclass::idle_cb> (this);
2857		3597
2858	io.start (fd, ev::READ);	3598	io.set (fd, ev::WRITE); // configure the watcher
		3599	io.start (); // start it whenever convenient
		3600
		3601	io2.start (fd, ev::READ); // set + start in one call
2859	}	3602	}
2860	};	3603	};
2861		3604
2862		3605
2863	=head1 OTHER LANGUAGE BINDINGS	3606	=head1 OTHER LANGUAGE BINDINGS
…		…
2882	L<http://software.schmorp.de/pkg/EV>.	3625	L<http://software.schmorp.de/pkg/EV>.
2883		3626
2884	=item Python	3627	=item Python
2885		3628
2886	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3629	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2887	seems to be quite complete and well-documented. Note, however, that the	3630	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		3631
2893	=item Ruby	3632	=item Ruby
2894		3633
2895	Tony Arcieri has written a ruby extension that offers access to a subset	3634	Tony Arcieri has written a ruby extension that offers access to a subset
2896	of the libev API and adds file handle abstractions, asynchronous DNS and	3635	of the libev API and adds file handle abstractions, asynchronous DNS and
2897	more on top of it. It can be found via gem servers. Its homepage is at	3636	more on top of it. It can be found via gem servers. Its homepage is at
2898	L<http://rev.rubyforge.org/>.	3637	L<http://rev.rubyforge.org/>.
2899		3638
		3639	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3640	makes rev work even on mingw.
		3641
		3642	=item Haskell
		3643
		3644	A haskell binding to libev is available at
		3645	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3646
2900	=item D	3647	=item D
2901		3648
2902	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3649	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2903	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3650	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3651
		3652	=item Ocaml
		3653
		3654	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3655	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3656
		3657	=item Lua
		3658
		3659	Brian Maher has written a partial interface to libev for lua (at the
		3660	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3661	L<http://github.com/brimworks/lua-ev>.
2904		3662
2905	=back	3663	=back
2906		3664
2907		3665
2908	=head1 MACRO MAGIC	3666	=head1 MACRO MAGIC
…		…
2922	loop argument"). The C<EV_A> form is used when this is the sole argument,	3680	loop argument"). The C<EV_A> form is used when this is the sole argument,
2923	C<EV_A_> is used when other arguments are following. Example:	3681	C<EV_A_> is used when other arguments are following. Example:
2924		3682
2925	ev_unref (EV_A);	3683	ev_unref (EV_A);
2926	ev_timer_add (EV_A_ watcher);	3684	ev_timer_add (EV_A_ watcher);
2927	ev_loop (EV_A_ 0);	3685	ev_run (EV_A_ 0);
2928		3686
2929	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3687	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2930	which is often provided by the following macro.	3688	which is often provided by the following macro.
2931		3689
2932	=item C<EV_P>, C<EV_P_>	3690	=item C<EV_P>, C<EV_P_>
…		…
2972	}	3730	}
2973		3731
2974	ev_check check;	3732	ev_check check;
2975	ev_check_init (&check, check_cb);	3733	ev_check_init (&check, check_cb);
2976	ev_check_start (EV_DEFAULT_ &check);	3734	ev_check_start (EV_DEFAULT_ &check);
2977	ev_loop (EV_DEFAULT_ 0);	3735	ev_run (EV_DEFAULT_ 0);
2978		3736
2979	=head1 EMBEDDING	3737	=head1 EMBEDDING
2980		3738
2981	Libev can (and often is) directly embedded into host	3739	Libev can (and often is) directly embedded into host
2982	applications. Examples of applications that embed it include the Deliantra	3740	applications. Examples of applications that embed it include the Deliantra
…		…
3009		3767
3010	#define EV_STANDALONE 1	3768	#define EV_STANDALONE 1
3011	#include "ev.h"	3769	#include "ev.h"
3012		3770
3013	Both header files and implementation files can be compiled with a C++	3771	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	3772	compiler (at least, that's a stated goal, and breakage will be treated
3015	as a bug).	3773	as a bug).
3016		3774
3017	You need the following files in your source tree, or in a directory	3775	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):	3776	in your include path (e.g. in libev/ when using -Ilibev):
3019		3777
…		…
3062	libev.m4	3820	libev.m4
3063		3821
3064	=head2 PREPROCESSOR SYMBOLS/MACROS	3822	=head2 PREPROCESSOR SYMBOLS/MACROS
3065		3823
3066	Libev can be configured via a variety of preprocessor symbols you have to	3824	Libev can be configured via a variety of preprocessor symbols you have to
3067	define before including any of its files. The default in the absence of	3825	define before including (or compiling) any of its files. The default in
3068	autoconf is documented for every option.	3826	the absence of autoconf is documented for every option.
		3827
		3828	Symbols marked with "(h)" do not change the ABI, and can have different
		3829	values when compiling libev vs. including F<ev.h>, so it is permissible
		3830	to redefine them before including F<ev.h> without breaking compatibility
		3831	to a compiled library. All other symbols change the ABI, which means all
		3832	users of libev and the libev code itself must be compiled with compatible
		3833	settings.
3069		3834
3070	=over 4	3835	=over 4
3071		3836
		3837	=item EV_COMPAT3 (h)
		3838
		3839	Backwards compatibility is a major concern for libev. This is why this
		3840	release of libev comes with wrappers for the functions and symbols that
		3841	have been renamed between libev version 3 and 4.
		3842
		3843	You can disable these wrappers (to test compatibility with future
		3844	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		3845	sources. This has the additional advantage that you can drop the C<struct>
		3846	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		3847	typedef in that case.
		3848
		3849	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		3850	and in some even more future version the compatibility code will be
		3851	removed completely.
		3852
3072	=item EV_STANDALONE	3853	=item EV_STANDALONE (h)
3073		3854
3074	Must always be C<1> if you do not use autoconf configuration, which	3855	Must always be C<1> if you do not use autoconf configuration, which
3075	keeps libev from including F<config.h>, and it also defines dummy	3856	keeps libev from including F<config.h>, and it also defines dummy
3076	implementations for some libevent functions (such as logging, which is not	3857	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	3858	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.	3859	F<event.h> that are not directly supported by the libev core alone.
3079		3860
		3861	In standalone mode, libev will still try to automatically deduce the
		3862	configuration, but has to be more conservative.
		3863
3080	=item EV_USE_MONOTONIC	3864	=item EV_USE_MONOTONIC
3081		3865
3082	If defined to be C<1>, libev will try to detect the availability of the	3866	If defined to be C<1>, libev will try to detect the availability of the
3083	monotonic clock option at both compile time and runtime. Otherwise no use	3867	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	3868	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	3869	you usually have to link against librt or something similar. Enabling it
3086	the functionality isn't available is safe, though, although you have	3870	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>	3871	to make sure you link against any libraries where the C<clock_gettime>
3088	function is hiding in (often F<-lrt>).	3872	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
3089		3873
3090	=item EV_USE_REALTIME	3874	=item EV_USE_REALTIME
3091		3875
3092	If defined to be C<1>, libev will try to detect the availability of the	3876	If defined to be C<1>, libev will try to detect the availability of the
3093	real-time clock option at compile time (and assume its availability at	3877	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	3878	at runtime if successful). Otherwise no use of the real-time clock
3095	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3879	option will be attempted. This effectively replaces C<gettimeofday>
3096	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3880	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
3097	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3881	correctness. See the note about libraries in the description of
		3882	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3883	C<EV_USE_CLOCK_SYSCALL>.
		3884
		3885	=item EV_USE_CLOCK_SYSCALL
		3886
		3887	If defined to be C<1>, libev will try to use a direct syscall instead
		3888	of calling the system-provided C<clock_gettime> function. This option
		3889	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3890	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3891	programs needlessly. Using a direct syscall is slightly slower (in
		3892	theory), because no optimised vdso implementation can be used, but avoids
		3893	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3894	higher, as it simplifies linking (no need for C<-lrt>).
3098		3895
3099	=item EV_USE_NANOSLEEP	3896	=item EV_USE_NANOSLEEP
3100		3897
3101	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3898	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
3102	and will use it for delays. Otherwise it will use C<select ()>.	3899	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3118		3915
3119	=item EV_SELECT_USE_FD_SET	3916	=item EV_SELECT_USE_FD_SET
3120		3917
3121	If defined to C<1>, then the select backend will use the system C<fd_set>	3918	If defined to C<1>, then the select backend will use the system C<fd_set>
3122	structure. This is useful if libev doesn't compile due to a missing	3919	structure. This is useful if libev doesn't compile due to a missing
3123	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3920	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3124	exotic systems. This usually limits the range of file descriptors to some	3921	on exotic systems. This usually limits the range of file descriptors to
3125	low limit such as 1024 or might have other limitations (winsocket only	3922	some low limit such as 1024 or might have other limitations (winsocket
3126	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3923	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3127	influence the size of the C<fd_set> used.	3924	configures the maximum size of the C<fd_set>.
3128		3925
3129	=item EV_SELECT_IS_WINSOCKET	3926	=item EV_SELECT_IS_WINSOCKET
3130		3927
3131	When defined to C<1>, the select backend will assume that	3928	When defined to C<1>, the select backend will assume that
3132	select/socket/connect etc. don't understand file descriptors but	3929	select/socket/connect etc. don't understand file descriptors but
…		…
3134	be used is the winsock select). This means that it will call	3931	be used is the winsock select). This means that it will call
3135	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3932	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3136	it is assumed that all these functions actually work on fds, even	3933	it is assumed that all these functions actually work on fds, even
3137	on win32. Should not be defined on non-win32 platforms.	3934	on win32. Should not be defined on non-win32 platforms.
3138		3935
3139	=item EV_FD_TO_WIN32_HANDLE	3936	=item EV_FD_TO_WIN32_HANDLE(fd)
3140		3937
3141	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3938	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3142	file descriptors to socket handles. When not defining this symbol (the	3939	file descriptors to socket handles. When not defining this symbol (the
3143	default), then libev will call C<_get_osfhandle>, which is usually	3940	default), then libev will call C<_get_osfhandle>, which is usually
3144	correct. In some cases, programs use their own file descriptor management,	3941	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.	3942	in which case they can provide this function to map fds to socket handles.
		3943
		3944	=item EV_WIN32_HANDLE_TO_FD(handle)
		3945
		3946	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3947	using the standard C<_open_osfhandle> function. For programs implementing
		3948	their own fd to handle mapping, overwriting this function makes it easier
		3949	to do so. This can be done by defining this macro to an appropriate value.
		3950
		3951	=item EV_WIN32_CLOSE_FD(fd)
		3952
		3953	If programs implement their own fd to handle mapping on win32, then this
		3954	macro can be used to override the C<close> function, useful to unregister
		3955	file descriptors again. Note that the replacement function has to close
		3956	the underlying OS handle.
3146		3957
3147	=item EV_USE_POLL	3958	=item EV_USE_POLL
3148		3959
3149	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3960	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3150	backend. Otherwise it will be enabled on non-win32 platforms. It	3961	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3197	as well as for signal and thread safety in C<ev_async> watchers.	4008	as well as for signal and thread safety in C<ev_async> watchers.
3198		4009
3199	In the absence of this define, libev will use C<sig_atomic_t volatile>	4010	In the absence of this define, libev will use C<sig_atomic_t volatile>
3200	(from F<signal.h>), which is usually good enough on most platforms.	4011	(from F<signal.h>), which is usually good enough on most platforms.
3201		4012
3202	=item EV_H	4013	=item EV_H (h)
3203		4014
3204	The name of the F<ev.h> header file used to include it. The default if	4015	The name of the F<ev.h> header file used to include it. The default if
3205	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4016	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3206	used to virtually rename the F<ev.h> header file in case of conflicts.	4017	used to virtually rename the F<ev.h> header file in case of conflicts.
3207		4018
3208	=item EV_CONFIG_H	4019	=item EV_CONFIG_H (h)
3209		4020
3210	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4021	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3211	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4022	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3212	C<EV_H>, above.	4023	C<EV_H>, above.
3213		4024
3214	=item EV_EVENT_H	4025	=item EV_EVENT_H (h)
3215		4026
3216	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4027	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3217	of how the F<event.h> header can be found, the default is C<"event.h">.	4028	of how the F<event.h> header can be found, the default is C<"event.h">.
3218		4029
3219	=item EV_PROTOTYPES	4030	=item EV_PROTOTYPES (h)
3220		4031
3221	If defined to be C<0>, then F<ev.h> will not define any function	4032	If defined to be C<0>, then F<ev.h> will not define any function
3222	prototypes, but still define all the structs and other symbols. This is	4033	prototypes, but still define all the structs and other symbols. This is
3223	occasionally useful if you want to provide your own wrapper functions	4034	occasionally useful if you want to provide your own wrapper functions
3224	around libev functions.	4035	around libev functions.
…		…
3246	fine.	4057	fine.
3247		4058
3248	If your embedding application does not need any priorities, defining these	4059	If your embedding application does not need any priorities, defining these
3249	both to C<0> will save some memory and CPU.	4060	both to C<0> will save some memory and CPU.
3250		4061
3251	=item EV_PERIODIC_ENABLE	4062	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4063	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4064	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3252		4065
3253	If undefined or defined to be C<1>, then periodic timers are supported. If	4066	If undefined or defined to be C<1> (and the platform supports it), then
3254	defined to be C<0>, then they are not. Disabling them saves a few kB of	4067	the respective watcher type is supported. If defined to be C<0>, then it
3255	code.	4068	is not. Disabling watcher types mainly saves code size.
3256		4069
3257	=item EV_IDLE_ENABLE	4070	=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		4071
3286	If you need to shave off some kilobytes of code at the expense of some	4072	If you need to shave off some kilobytes of code at the expense of some
3287	speed, define this symbol to C<1>. Currently this is used to override some	4073	speed (but with the full API), you can define this symbol to request
3288	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4074	certain subsets of functionality. The default is to enable all features
3289	much smaller 2-heap for timer management over the default 4-heap.	4075	that can be enabled on the platform.
		4076
		4077	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4078	with some broad features you want) and then selectively re-enable
		4079	additional parts you want, for example if you want everything minimal,
		4080	but multiple event loop support, async and child watchers and the poll
		4081	backend, use this:
		4082
		4083	#define EV_FEATURES 0
		4084	#define EV_MULTIPLICITY 1
		4085	#define EV_USE_POLL 1
		4086	#define EV_CHILD_ENABLE 1
		4087	#define EV_ASYNC_ENABLE 1
		4088
		4089	The actual value is a bitset, it can be a combination of the following
		4090	values:
		4091
		4092	=over 4
		4093
		4094	=item C<1> - faster/larger code
		4095
		4096	Use larger code to speed up some operations.
		4097
		4098	Currently this is used to override some inlining decisions (enlarging the
		4099	code size by roughly 30% on amd64).
		4100
		4101	When optimising for size, use of compiler flags such as C<-Os> with
		4102	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4103	assertions.
		4104
		4105	=item C<2> - faster/larger data structures
		4106
		4107	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4108	hash table sizes and so on. This will usually further increase code size
		4109	and can additionally have an effect on the size of data structures at
		4110	runtime.
		4111
		4112	=item C<4> - full API configuration
		4113
		4114	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4115	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4116
		4117	=item C<8> - full API
		4118
		4119	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4120	details on which parts of the API are still available without this
		4121	feature, and do not complain if this subset changes over time.
		4122
		4123	=item C<16> - enable all optional watcher types
		4124
		4125	Enables all optional watcher types. If you want to selectively enable
		4126	only some watcher types other than I/O and timers (e.g. prepare,
		4127	embed, async, child...) you can enable them manually by defining
		4128	C<EV_watchertype_ENABLE> to C<1> instead.
		4129
		4130	=item C<32> - enable all backends
		4131
		4132	This enables all backends - without this feature, you need to enable at
		4133	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4134
		4135	=item C<64> - enable OS-specific "helper" APIs
		4136
		4137	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4138	default.
		4139
		4140	=back
		4141
		4142	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4143	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4144	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4145	watchers, timers and monotonic clock support.
		4146
		4147	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4148	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4149	your program might be left out as well - a binary starting a timer and an
		4150	I/O watcher then might come out at only 5Kb.
		4151
		4152	=item EV_AVOID_STDIO
		4153
		4154	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4155	functions (printf, scanf, perror etc.). This will increase the code size
		4156	somewhat, but if your program doesn't otherwise depend on stdio and your
		4157	libc allows it, this avoids linking in the stdio library which is quite
		4158	big.
		4159
		4160	Note that error messages might become less precise when this option is
		4161	enabled.
		4162
		4163	=item EV_NSIG
		4164
		4165	The highest supported signal number, +1 (or, the number of
		4166	signals): Normally, libev tries to deduce the maximum number of signals
		4167	automatically, but sometimes this fails, in which case it can be
		4168	specified. Also, using a lower number than detected (C<32> should be
		4169	good for about any system in existence) can save some memory, as libev
		4170	statically allocates some 12-24 bytes per signal number.
3290		4171
3291	=item EV_PID_HASHSIZE	4172	=item EV_PID_HASHSIZE
3292		4173
3293	C<ev_child> watchers use a small hash table to distribute workload by	4174	C<ev_child> watchers use a small hash table to distribute workload by
3294	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4175	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3295	than enough. If you need to manage thousands of children you might want to	4176	usually more than enough. If you need to manage thousands of children you
3296	increase this value (I<must> be a power of two).	4177	might want to increase this value (I<must> be a power of two).
3297		4178
3298	=item EV_INOTIFY_HASHSIZE	4179	=item EV_INOTIFY_HASHSIZE
3299		4180
3300	C<ev_stat> watchers use a small hash table to distribute workload by	4181	C<ev_stat> watchers use a small hash table to distribute workload by
3301	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4182	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3302	usually more than enough. If you need to manage thousands of C<ev_stat>	4183	disabled), usually more than enough. If you need to manage thousands of
3303	watchers you might want to increase this value (I<must> be a power of	4184	C<ev_stat> watchers you might want to increase this value (I<must> be a
3304	two).	4185	power of two).
3305		4186
3306	=item EV_USE_4HEAP	4187	=item EV_USE_4HEAP
3307		4188
3308	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4189	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3309	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4190	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3310	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4191	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3311	faster performance with many (thousands) of watchers.	4192	faster performance with many (thousands) of watchers.
3312		4193
3313	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4194	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3314	(disabled).	4195	will be C<0>.
3315		4196
3316	=item EV_HEAP_CACHE_AT	4197	=item EV_HEAP_CACHE_AT
3317		4198
3318	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4199	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3319	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4200	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3320	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4201	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3321	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4202	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3322	but avoids random read accesses on heap changes. This improves performance	4203	but avoids random read accesses on heap changes. This improves performance
3323	noticeably with many (hundreds) of watchers.	4204	noticeably with many (hundreds) of watchers.
3324		4205
3325	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4206	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3326	(disabled).	4207	will be C<0>.
3327		4208
3328	=item EV_VERIFY	4209	=item EV_VERIFY
3329		4210
3330	Controls how much internal verification (see C<ev_loop_verify ()>) will	4211	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	4212	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	4213	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	4214	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	4215	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	4216	verification code will be called very frequently, which will slow down
3336	libev considerably.	4217	libev considerably.
3337		4218
3338	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4219	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3339	C<0>.	4220	will be C<0>.
3340		4221
3341	=item EV_COMMON	4222	=item EV_COMMON
3342		4223
3343	By default, all watchers have a C<void *data> member. By redefining	4224	By default, all watchers have a C<void *data> member. By redefining
3344	this macro to a something else you can include more and other types of	4225	this macro to something else you can include more and other types of
3345	members. You have to define it each time you include one of the files,	4226	members. You have to define it each time you include one of the files,
3346	though, and it must be identical each time.	4227	though, and it must be identical each time.
3347		4228
3348	For example, the perl EV module uses something like this:	4229	For example, the perl EV module uses something like this:
3349		4230
…		…
3402	file.	4283	file.
3403		4284
3404	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4285	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3405	that everybody includes and which overrides some configure choices:	4286	that everybody includes and which overrides some configure choices:
3406		4287
3407	#define EV_MINIMAL 1	4288	#define EV_FEATURES 8
3408	#define EV_USE_POLL 0	4289	#define EV_USE_SELECT 1
3409	#define EV_MULTIPLICITY 0
3410	#define EV_PERIODIC_ENABLE 0	4290	#define EV_PREPARE_ENABLE 1
		4291	#define EV_IDLE_ENABLE 1
3411	#define EV_STAT_ENABLE 0	4292	#define EV_SIGNAL_ENABLE 1
3412	#define EV_FORK_ENABLE 0	4293	#define EV_CHILD_ENABLE 1
		4294	#define EV_USE_STDEXCEPT 0
3413	#define EV_CONFIG_H <config.h>	4295	#define EV_CONFIG_H <config.h>
3414	#define EV_MINPRI 0
3415	#define EV_MAXPRI 0
3416		4296
3417	#include "ev++.h"	4297	#include "ev++.h"
3418		4298
3419	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4299	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3420		4300
…		…
3480	default loop and triggering an C<ev_async> watcher from the default loop	4360	default loop and triggering an C<ev_async> watcher from the default loop
3481	watcher callback into the event loop interested in the signal.	4361	watcher callback into the event loop interested in the signal.
3482		4362
3483	=back	4363	=back
3484		4364
		4365	=head4 THREAD LOCKING EXAMPLE
		4366
		4367	Here is a fictitious example of how to run an event loop in a different
		4368	thread than where callbacks are being invoked and watchers are
		4369	created/added/removed.
		4370
		4371	For a real-world example, see the C<EV::Loop::Async> perl module,
		4372	which uses exactly this technique (which is suited for many high-level
		4373	languages).
		4374
		4375	The example uses a pthread mutex to protect the loop data, a condition
		4376	variable to wait for callback invocations, an async watcher to notify the
		4377	event loop thread and an unspecified mechanism to wake up the main thread.
		4378
		4379	First, you need to associate some data with the event loop:
		4380
		4381	typedef struct {
		4382	mutex_t lock; /* global loop lock */
		4383	ev_async async_w;
		4384	thread_t tid;
		4385	cond_t invoke_cv;
		4386	} userdata;
		4387
		4388	void prepare_loop (EV_P)
		4389	{
		4390	// for simplicity, we use a static userdata struct.
		4391	static userdata u;
		4392
		4393	ev_async_init (&u->async_w, async_cb);
		4394	ev_async_start (EV_A_ &u->async_w);
		4395
		4396	pthread_mutex_init (&u->lock, 0);
		4397	pthread_cond_init (&u->invoke_cv, 0);
		4398
		4399	// now associate this with the loop
		4400	ev_set_userdata (EV_A_ u);
		4401	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4402	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4403
		4404	// then create the thread running ev_loop
		4405	pthread_create (&u->tid, 0, l_run, EV_A);
		4406	}
		4407
		4408	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4409	solely to wake up the event loop so it takes notice of any new watchers
		4410	that might have been added:
		4411
		4412	static void
		4413	async_cb (EV_P_ ev_async *w, int revents)
		4414	{
		4415	// just used for the side effects
		4416	}
		4417
		4418	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4419	protecting the loop data, respectively.
		4420
		4421	static void
		4422	l_release (EV_P)
		4423	{
		4424	userdata *u = ev_userdata (EV_A);
		4425	pthread_mutex_unlock (&u->lock);
		4426	}
		4427
		4428	static void
		4429	l_acquire (EV_P)
		4430	{
		4431	userdata *u = ev_userdata (EV_A);
		4432	pthread_mutex_lock (&u->lock);
		4433	}
		4434
		4435	The event loop thread first acquires the mutex, and then jumps straight
		4436	into C<ev_run>:
		4437
		4438	void *
		4439	l_run (void *thr_arg)
		4440	{
		4441	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4442
		4443	l_acquire (EV_A);
		4444	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4445	ev_run (EV_A_ 0);
		4446	l_release (EV_A);
		4447
		4448	return 0;
		4449	}
		4450
		4451	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4452	signal the main thread via some unspecified mechanism (signals? pipe
		4453	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4454	have been called (in a while loop because a) spurious wakeups are possible
		4455	and b) skipping inter-thread-communication when there are no pending
		4456	watchers is very beneficial):
		4457
		4458	static void
		4459	l_invoke (EV_P)
		4460	{
		4461	userdata *u = ev_userdata (EV_A);
		4462
		4463	while (ev_pending_count (EV_A))
		4464	{
		4465	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4466	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4467	}
		4468	}
		4469
		4470	Now, whenever the main thread gets told to invoke pending watchers, it
		4471	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4472	thread to continue:
		4473
		4474	static void
		4475	real_invoke_pending (EV_P)
		4476	{
		4477	userdata *u = ev_userdata (EV_A);
		4478
		4479	pthread_mutex_lock (&u->lock);
		4480	ev_invoke_pending (EV_A);
		4481	pthread_cond_signal (&u->invoke_cv);
		4482	pthread_mutex_unlock (&u->lock);
		4483	}
		4484
		4485	Whenever you want to start/stop a watcher or do other modifications to an
		4486	event loop, you will now have to lock:
		4487
		4488	ev_timer timeout_watcher;
		4489	userdata *u = ev_userdata (EV_A);
		4490
		4491	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4492
		4493	pthread_mutex_lock (&u->lock);
		4494	ev_timer_start (EV_A_ &timeout_watcher);
		4495	ev_async_send (EV_A_ &u->async_w);
		4496	pthread_mutex_unlock (&u->lock);
		4497
		4498	Note that sending the C<ev_async> watcher is required because otherwise
		4499	an event loop currently blocking in the kernel will have no knowledge
		4500	about the newly added timer. By waking up the loop it will pick up any new
		4501	watchers in the next event loop iteration.
		4502
3485	=head3 COROUTINES	4503	=head3 COROUTINES
3486		4504
3487	Libev is very accommodating to coroutines ("cooperative threads"):	4505	Libev is very accommodating to coroutines ("cooperative threads"):
3488	libev fully supports nesting calls to its functions from different	4506	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	4507	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	4508	different coroutines, and switch freely between both coroutines running
3491	loop, as long as you don't confuse yourself). The only exception is that	4509	the loop, as long as you don't confuse yourself). The only exception is
3492	you must not do this from C<ev_periodic> reschedule callbacks.	4510	that you must not do this from C<ev_periodic> reschedule callbacks.
3493		4511
3494	Care has been taken to ensure that libev does not keep local state inside	4512	Care has been taken to ensure that libev does not keep local state inside
3495	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4513	C<ev_run>, and other calls do not usually allow for coroutine switches as
3496	they do not clal any callbacks.	4514	they do not call any callbacks.
3497		4515
3498	=head2 COMPILER WARNINGS	4516	=head2 COMPILER WARNINGS
3499		4517
3500	Depending on your compiler and compiler settings, you might get no or a	4518	Depending on your compiler and compiler settings, you might get no or a
3501	lot of warnings when compiling libev code. Some people are apparently	4519	lot of warnings when compiling libev code. Some people are apparently
…		…
3511	maintainable.	4529	maintainable.
3512		4530
3513	And of course, some compiler warnings are just plain stupid, or simply	4531	And of course, some compiler warnings are just plain stupid, or simply
3514	wrong (because they don't actually warn about the condition their message	4532	wrong (because they don't actually warn about the condition their message
3515	seems to warn about). For example, certain older gcc versions had some	4533	seems to warn about). For example, certain older gcc versions had some
3516	warnings that resulted an extreme number of false positives. These have	4534	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	4535	been fixed, but some people still insist on making code warn-free with
3518	such buggy versions.	4536	such buggy versions.
3519		4537
3520	While libev is written to generate as few warnings as possible,	4538	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	4539	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3535	==2274== definitely lost: 0 bytes in 0 blocks.	4553	==2274== definitely lost: 0 bytes in 0 blocks.
3536	==2274== possibly lost: 0 bytes in 0 blocks.	4554	==2274== possibly lost: 0 bytes in 0 blocks.
3537	==2274== still reachable: 256 bytes in 1 blocks.	4555	==2274== still reachable: 256 bytes in 1 blocks.
3538		4556
3539	Then there is no memory leak, just as memory accounted to global variables	4557	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.	4558	is not a memleak - the memory is still being referenced, and didn't leak.
3541		4559
3542	Similarly, under some circumstances, valgrind might report kernel bugs	4560	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,	4561	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	4562	although an acceptable workaround has been found here), or it might be
3545	confused.	4563	confused.
…		…
3557	I suggest using suppression lists.	4575	I suggest using suppression lists.
3558		4576
3559		4577
3560	=head1 PORTABILITY NOTES	4578	=head1 PORTABILITY NOTES
3561		4579
		4580	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4581
		4582	GNU/Linux is the only common platform that supports 64 bit file/large file
		4583	interfaces but I<disables> them by default.
		4584
		4585	That means that libev compiled in the default environment doesn't support
		4586	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4587
		4588	Unfortunately, many programs try to work around this GNU/Linux issue
		4589	by enabling the large file API, which makes them incompatible with the
		4590	standard libev compiled for their system.
		4591
		4592	Likewise, libev cannot enable the large file API itself as this would
		4593	suddenly make it incompatible to the default compile time environment,
		4594	i.e. all programs not using special compile switches.
		4595
		4596	=head2 OS/X AND DARWIN BUGS
		4597
		4598	The whole thing is a bug if you ask me - basically any system interface
		4599	you touch is broken, whether it is locales, poll, kqueue or even the
		4600	OpenGL drivers.
		4601
		4602	=head3 C<kqueue> is buggy
		4603
		4604	The kqueue syscall is broken in all known versions - most versions support
		4605	only sockets, many support pipes.
		4606
		4607	Libev tries to work around this by not using C<kqueue> by default on this
		4608	rotten platform, but of course you can still ask for it when creating a
		4609	loop - embedding a socket-only kqueue loop into a select-based one is
		4610	probably going to work well.
		4611
		4612	=head3 C<poll> is buggy
		4613
		4614	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4615	implementation by something calling C<kqueue> internally around the 10.5.6
		4616	release, so now C<kqueue> I<and> C<poll> are broken.
		4617
		4618	Libev tries to work around this by not using C<poll> by default on
		4619	this rotten platform, but of course you can still ask for it when creating
		4620	a loop.
		4621
		4622	=head3 C<select> is buggy
		4623
		4624	All that's left is C<select>, and of course Apple found a way to fuck this
		4625	one up as well: On OS/X, C<select> actively limits the number of file
		4626	descriptors you can pass in to 1024 - your program suddenly crashes when
		4627	you use more.
		4628
		4629	There is an undocumented "workaround" for this - defining
		4630	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4631	work on OS/X.
		4632
		4633	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4634
		4635	=head3 C<errno> reentrancy
		4636
		4637	The default compile environment on Solaris is unfortunately so
		4638	thread-unsafe that you can't even use components/libraries compiled
		4639	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4640	defined by default. A valid, if stupid, implementation choice.
		4641
		4642	If you want to use libev in threaded environments you have to make sure
		4643	it's compiled with C<_REENTRANT> defined.
		4644
		4645	=head3 Event port backend
		4646
		4647	The scalable event interface for Solaris is called "event
		4648	ports". Unfortunately, this mechanism is very buggy in all major
		4649	releases. If you run into high CPU usage, your program freezes or you get
		4650	a large number of spurious wakeups, make sure you have all the relevant
		4651	and latest kernel patches applied. No, I don't know which ones, but there
		4652	are multiple ones to apply, and afterwards, event ports actually work
		4653	great.
		4654
		4655	If you can't get it to work, you can try running the program by setting
		4656	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4657	C<select> backends.
		4658
		4659	=head2 AIX POLL BUG
		4660
		4661	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4662	this by trying to avoid the poll backend altogether (i.e. it's not even
		4663	compiled in), which normally isn't a big problem as C<select> works fine
		4664	with large bitsets on AIX, and AIX is dead anyway.
		4665
3562	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4666	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4667
		4668	=head3 General issues
3563		4669
3564	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4670	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3565	requires, and its I/O model is fundamentally incompatible with the POSIX	4671	requires, and its I/O model is fundamentally incompatible with the POSIX
3566	model. Libev still offers limited functionality on this platform in	4672	model. Libev still offers limited functionality on this platform in
3567	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4673	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3568	descriptors. This only applies when using Win32 natively, not when using	4674	descriptors. This only applies when using Win32 natively, not when using
3569	e.g. cygwin.	4675	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4676	as every compielr comes with a slightly differently broken/incompatible
		4677	environment.
3570		4678
3571	Lifting these limitations would basically require the full	4679	Lifting these limitations would basically require the full
3572	re-implementation of the I/O system. If you are into these kinds of	4680	re-implementation of the I/O system. If you are into this kind of thing,
3573	things, then note that glib does exactly that for you in a very portable	4681	then note that glib does exactly that for you in a very portable way (note
3574	way (note also that glib is the slowest event library known to man).	4682	also that glib is the slowest event library known to man).
3575		4683
3576	There is no supported compilation method available on windows except	4684	There is no supported compilation method available on windows except
3577	embedding it into other applications.	4685	embedding it into other applications.
		4686
		4687	Sensible signal handling is officially unsupported by Microsoft - libev
		4688	tries its best, but under most conditions, signals will simply not work.
3578		4689
3579	Not a libev limitation but worth mentioning: windows apparently doesn't	4690	Not a libev limitation but worth mentioning: windows apparently doesn't
3580	accept large writes: instead of resulting in a partial write, windows will	4691	accept large writes: instead of resulting in a partial write, windows will
3581	either accept everything or return C<ENOBUFS> if the buffer is too large,	4692	either accept everything or return C<ENOBUFS> if the buffer is too large,
3582	so make sure you only write small amounts into your sockets (less than a	4693	so make sure you only write small amounts into your sockets (less than a
…		…
3587	the abysmal performance of winsockets, using a large number of sockets	4698	the abysmal performance of winsockets, using a large number of sockets
3588	is not recommended (and not reasonable). If your program needs to use	4699	is not recommended (and not reasonable). If your program needs to use
3589	more than a hundred or so sockets, then likely it needs to use a totally	4700	more than a hundred or so sockets, then likely it needs to use a totally
3590	different implementation for windows, as libev offers the POSIX readiness	4701	different implementation for windows, as libev offers the POSIX readiness
3591	notification model, which cannot be implemented efficiently on windows	4702	notification model, which cannot be implemented efficiently on windows
3592	(Microsoft monopoly games).	4703	(due to Microsoft monopoly games).
3593		4704
3594	A typical way to use libev under windows is to embed it (see the embedding	4705	A typical way to use libev under windows is to embed it (see the embedding
3595	section for details) and use the following F<evwrap.h> header file instead	4706	section for details) and use the following F<evwrap.h> header file instead
3596	of F<ev.h>:	4707	of F<ev.h>:
3597		4708
…		…
3604	you do I<not> compile the F<ev.c> or any other embedded source files!):	4715	you do I<not> compile the F<ev.c> or any other embedded source files!):
3605		4716
3606	#include "evwrap.h"	4717	#include "evwrap.h"
3607	#include "ev.c"	4718	#include "ev.c"
3608		4719
3609	=over 4
3610
3611	=item The winsocket select function	4720	=head3 The winsocket C<select> function
3612		4721
3613	The winsocket C<select> function doesn't follow POSIX in that it	4722	The winsocket C<select> function doesn't follow POSIX in that it
3614	requires socket I<handles> and not socket I<file descriptors> (it is	4723	requires socket I<handles> and not socket I<file descriptors> (it is
3615	also extremely buggy). This makes select very inefficient, and also	4724	also extremely buggy). This makes select very inefficient, and also
3616	requires a mapping from file descriptors to socket handles (the Microsoft	4725	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 */	4734	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3626		4735
3627	Note that winsockets handling of fd sets is O(n), so you can easily get a	4736	Note that winsockets handling of fd sets is O(n), so you can easily get a
3628	complexity in the O(n²) range when using win32.	4737	complexity in the O(n²) range when using win32.
3629		4738
3630	=item Limited number of file descriptors	4739	=head3 Limited number of file descriptors
3631		4740
3632	Windows has numerous arbitrary (and low) limits on things.	4741	Windows has numerous arbitrary (and low) limits on things.
3633		4742
3634	Early versions of winsocket's select only supported waiting for a maximum	4743	Early versions of winsocket's select only supported waiting for a maximum
3635	of C<64> handles (probably owning to the fact that all windows kernels	4744	of C<64> handles (probably owning to the fact that all windows kernels
3636	can only wait for C<64> things at the same time internally; Microsoft	4745	can only wait for C<64> things at the same time internally; Microsoft
3637	recommends spawning a chain of threads and wait for 63 handles and the	4746	recommends spawning a chain of threads and wait for 63 handles and the
3638	previous thread in each. Great).	4747	previous thread in each. Sounds great!).
3639		4748
3640	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4749	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3641	to some high number (e.g. C<2048>) before compiling the winsocket select	4750	to some high number (e.g. C<2048>) before compiling the winsocket select
3642	call (which might be in libev or elsewhere, for example, perl does its own	4751	call (which might be in libev or elsewhere, for example, perl and many
3643	select emulation on windows).	4752	other interpreters do their own select emulation on windows).
3644		4753
3645	Another limit is the number of file descriptors in the Microsoft runtime	4754	Another limit is the number of file descriptors in the Microsoft runtime
3646	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4755	libraries, which by default is C<64> (there must be a hidden I<64>
3647	or something like this inside Microsoft). You can increase this by calling	4756	fetish or something like this inside Microsoft). You can increase this
3648	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4757	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	4758	(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	4759	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	4760	(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	4761	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.	4762	the cost of calling select (O(n²)) will likely make this unworkable.
3656
3657	=back
3658		4763
3659	=head2 PORTABILITY REQUIREMENTS	4764	=head2 PORTABILITY REQUIREMENTS
3660		4765
3661	In addition to a working ISO-C implementation and of course the	4766	In addition to a working ISO-C implementation and of course the
3662	backend-specific APIs, libev relies on a few additional extensions:	4767	backend-specific APIs, libev relies on a few additional extensions:
…		…
3669	Libev assumes not only that all watcher pointers have the same internal	4774	Libev assumes not only that all watcher pointers have the same internal
3670	structure (guaranteed by POSIX but not by ISO C for example), but it also	4775	structure (guaranteed by POSIX but not by ISO C for example), but it also
3671	assumes that the same (machine) code can be used to call any watcher	4776	assumes that the same (machine) code can be used to call any watcher
3672	callback: The watcher callbacks have different type signatures, but libev	4777	callback: The watcher callbacks have different type signatures, but libev
3673	calls them using an C<ev_watcher *> internally.	4778	calls them using an C<ev_watcher *> internally.
		4779
		4780	=item pointer accesses must be thread-atomic
		4781
		4782	Accessing a pointer value must be atomic, it must both be readable and
		4783	writable in one piece - this is the case on all current architectures.
3674		4784
3675	=item C<sig_atomic_t volatile> must be thread-atomic as well	4785	=item C<sig_atomic_t volatile> must be thread-atomic as well
3676		4786
3677	The type C<sig_atomic_t volatile> (or whatever is defined as	4787	The type C<sig_atomic_t volatile> (or whatever is defined as
3678	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	4788	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
3701	watchers.	4811	watchers.
3702		4812
3703	=item C<double> must hold a time value in seconds with enough accuracy	4813	=item C<double> must hold a time value in seconds with enough accuracy
3704		4814
3705	The type C<double> is used to represent timestamps. It is required to	4815	The type C<double> is used to represent timestamps. It is required to
3706	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4816	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3707	enough for at least into the year 4000. This requirement is fulfilled by	4817	good enough for at least into the year 4000 with millisecond accuracy
		4818	(the design goal for libev). This requirement is overfulfilled by
3708	implementations implementing IEEE 754 (basically all existing ones).	4819	implementations using IEEE 754, which is basically all existing ones. With
		4820	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
3709		4821
3710	=back	4822	=back
3711		4823
3712	If you know of other additional requirements drop me a note.	4824	If you know of other additional requirements drop me a note.
3713		4825
…		…
3781	involves iterating over all running async watchers or all signal numbers.	4893	involves iterating over all running async watchers or all signal numbers.
3782		4894
3783	=back	4895	=back
3784		4896
3785		4897
		4898	=head1 PORTING FROM LIBEV 3.X TO 4.X
		4899
		4900	The major version 4 introduced some incompatible changes to the API.
		4901
		4902	At the moment, the C<ev.h> header file provides compatibility definitions
		4903	for all changes, so most programs should still compile. The compatibility
		4904	layer might be removed in later versions of libev, so better update to the
		4905	new API early than late.
		4906
		4907	=over 4
		4908
		4909	=item C<EV_COMPAT3> backwards compatibility mechanism
		4910
		4911	The backward compatibility mechanism can be controlled by
		4912	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		4913	section.
		4914
		4915	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		4916
		4917	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		4918
		4919	ev_loop_destroy (EV_DEFAULT_UC);
		4920	ev_loop_fork (EV_DEFAULT);
		4921
		4922	=item function/symbol renames
		4923
		4924	A number of functions and symbols have been renamed:
		4925
		4926	ev_loop => ev_run
		4927	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		4928	EVLOOP_ONESHOT => EVRUN_ONCE
		4929
		4930	ev_unloop => ev_break
		4931	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		4932	EVUNLOOP_ONE => EVBREAK_ONE
		4933	EVUNLOOP_ALL => EVBREAK_ALL
		4934
		4935	EV_TIMEOUT => EV_TIMER
		4936
		4937	ev_loop_count => ev_iteration
		4938	ev_loop_depth => ev_depth
		4939	ev_loop_verify => ev_verify
		4940
		4941	Most functions working on C<struct ev_loop> objects don't have an
		4942	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		4943	associated constants have been renamed to not collide with the C<struct
		4944	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		4945	as all other watcher types. Note that C<ev_loop_fork> is still called
		4946	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		4947	typedef.
		4948
		4949	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		4950
		4951	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		4952	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		4953	and work, but the library code will of course be larger.
		4954
		4955	=back
		4956
		4957
		4958	=head1 GLOSSARY
		4959
		4960	=over 4
		4961
		4962	=item active
		4963
		4964	A watcher is active as long as it has been started and not yet stopped.
		4965	See L<WATCHER STATES> for details.
		4966
		4967	=item application
		4968
		4969	In this document, an application is whatever is using libev.
		4970
		4971	=item backend
		4972
		4973	The part of the code dealing with the operating system interfaces.
		4974
		4975	=item callback
		4976
		4977	The address of a function that is called when some event has been
		4978	detected. Callbacks are being passed the event loop, the watcher that
		4979	received the event, and the actual event bitset.
		4980
		4981	=item callback/watcher invocation
		4982
		4983	The act of calling the callback associated with a watcher.
		4984
		4985	=item event
		4986
		4987	A change of state of some external event, such as data now being available
		4988	for reading on a file descriptor, time having passed or simply not having
		4989	any other events happening anymore.
		4990
		4991	In libev, events are represented as single bits (such as C<EV_READ> or
		4992	C<EV_TIMER>).
		4993
		4994	=item event library
		4995
		4996	A software package implementing an event model and loop.
		4997
		4998	=item event loop
		4999
		5000	An entity that handles and processes external events and converts them
		5001	into callback invocations.
		5002
		5003	=item event model
		5004
		5005	The model used to describe how an event loop handles and processes
		5006	watchers and events.
		5007
		5008	=item pending
		5009
		5010	A watcher is pending as soon as the corresponding event has been
		5011	detected. See L<WATCHER STATES> for details.
		5012
		5013	=item real time
		5014
		5015	The physical time that is observed. It is apparently strictly monotonic :)
		5016
		5017	=item wall-clock time
		5018
		5019	The time and date as shown on clocks. Unlike real time, it can actually
		5020	be wrong and jump forwards and backwards, e.g. when the you adjust your
		5021	clock.
		5022
		5023	=item watcher
		5024
		5025	A data structure that describes interest in certain events. Watchers need
		5026	to be started (attached to an event loop) before they can receive events.
		5027
		5028	=back
		5029
3786	=head1 AUTHOR	5030	=head1 AUTHOR
3787		5031
3788	Marc Lehmann <libev@schmorp.de>.	5032	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5033	Magnusson and Emanuele Giaquinta.
3789		5034

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