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…		…
8		8
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
		13
		14	#include <stdio.h> // for puts
13		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_TYPE	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
…		…
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
28		30
29	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_run's to stop iterating
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_break (EV_A_ EVBREAK_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_run to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_break (EV_A_ EVBREAK_ONE);
40	}	42	}
41		43
42	int	44	int
43	main (void)	45	main (void)
44	{	46	{
45	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
46	ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = EV_DEFAULT;
47		49
48	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
…		…
54	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
57		59
58	// now wait for events to arrive	60	// now wait for events to arrive
59	ev_loop (loop, 0);	61	ev_run (loop, 0);
60		62
61	// unloop was called, so exit	63	// unloop was called, so exit
62	return 0;	64	return 0;
63	}	65	}
64		66
65	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
66		70
67	The newest version of this document is also available as an html-formatted	71	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	72	web page you might find easier to navigate when reading it for the first
69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.	73	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		74
		75	While this document tries to be as complete as possible in documenting
		76	libev, its usage and the rationale behind its design, it is not a tutorial
		77	on event-based programming, nor will it introduce event-based programming
		78	with libev.
		79
		80	Familiarity with event based programming techniques in general is assumed
		81	throughout this document.
		82
		83	=head1 WHAT TO READ WHEN IN A HURRY
		84
		85	This manual tries to be very detailed, but unfortunately, this also makes
		86	it very long. If you just want to know the basics of libev, I suggest
		87	reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and
		88	look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and
		89	C<ev_timer> sections in L<WATCHER TYPES>.
		90
		91	=head1 ABOUT LIBEV
70		92
71	Libev is an event loop: you register interest in certain events (such as a	93	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	94	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	95	these event sources and provide your program with events.
74		96
…		…
84	=head2 FEATURES	106	=head2 FEATURES
85		107
86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	108	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	109	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	110	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	111	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
90	with customised rescheduling (C<ev_periodic>), synchronous signals	112	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
91	(C<ev_signal>), process status change events (C<ev_child>), and event	113	timers (C<ev_timer>), absolute timers with customised rescheduling
92	watchers dealing with the event loop mechanism itself (C<ev_idle>,	114	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
93	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	115	change events (C<ev_child>), and event watchers dealing with the event
94	file watchers (C<ev_stat>) and even limited support for fork events	116	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
95	(C<ev_fork>).	117	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		118	limited support for fork events (C<ev_fork>).
96		119
97	It also is quite fast (see this	120	It also is quite fast (see this
98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	121	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
99	for example).	122	for example).
100		123
…		…
103	Libev is very configurable. In this manual the default (and most common)	126	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	127	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	128	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	129	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	130	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<ev_loop *>) will not have	131	name C<loop> (which is always of type C<struct ev_loop *>) will not have
109	this argument.	132	this argument.
110		133
111	=head2 TIME REPRESENTATION	134	=head2 TIME REPRESENTATION
112		135
113	Libev represents time as a single floating point number, representing the	136	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	137	the (fractional) number of seconds since the (POSIX) epoch (in practice
115	the beginning of 1970, details are complicated, don't ask). This type is	138	somewhere near the beginning of 1970, details are complicated, don't
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	139	ask). This type is called C<ev_tstamp>, which is what you should use
117	to the C<double> type in C, and when you need to do any calculations on	140	too. It usually aliases to the C<double> type in C. When you need to do
118	it, you should treat it as some floating point value. Unlike the name	141	any calculations on it, you should treat it as some floating point value.
		142
119	component C<stamp> might indicate, it is also used for time differences	143	Unlike the name component C<stamp> might indicate, it is also used for
120	throughout libev.	144	time differences (e.g. delays) throughout libev.
121		145
122	=head1 ERROR HANDLING	146	=head1 ERROR HANDLING
123		147
124	Libev knows three classes of errors: operating system errors, usage errors	148	Libev knows three classes of errors: operating system errors, usage errors
125	and internal errors (bugs).	149	and internal errors (bugs).
…		…
149		173
150	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
151		175
152	Returns the current time as libev would use it. Please note that the	176	Returns the current time as libev would use it. Please note that the
153	C<ev_now> function is usually faster and also often returns the timestamp	177	C<ev_now> function is usually faster and also often returns the timestamp
154	you actually want to know.	178	you actually want to know. Also interesting is the combination of
		179	C<ev_update_now> and C<ev_now>.
155		180
156	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
157		182
158	Sleep for the given interval: The current thread will be blocked until	183	Sleep for the given interval: The current thread will be blocked until
159	either it is interrupted or the given time interval has passed. Basically	184	either it is interrupted or the given time interval has passed. Basically
…		…
176	as this indicates an incompatible change. Minor versions are usually	201	as this indicates an incompatible change. Minor versions are usually
177	compatible to older versions, so a larger minor version alone is usually	202	compatible to older versions, so a larger minor version alone is usually
178	not a problem.	203	not a problem.
179		204
180	Example: Make sure we haven't accidentally been linked against the wrong	205	Example: Make sure we haven't accidentally been linked against the wrong
181	version.	206	version (note, however, that this will not detect other ABI mismatches,
		207	such as LFS or reentrancy).
182		208
183	assert (("libev version mismatch",	209	assert (("libev version mismatch",
184	ev_version_major () == EV_VERSION_MAJOR	210	ev_version_major () == EV_VERSION_MAJOR
185	&& ev_version_minor () >= EV_VERSION_MINOR));	211	&& ev_version_minor () >= EV_VERSION_MINOR));
186		212
…		…
197	assert (("sorry, no epoll, no sex",	223	assert (("sorry, no epoll, no sex",
198	ev_supported_backends () & EVBACKEND_EPOLL));	224	ev_supported_backends () & EVBACKEND_EPOLL));
199		225
200	=item unsigned int ev_recommended_backends ()	226	=item unsigned int ev_recommended_backends ()
201		227
202	Return the set of all backends compiled into this binary of libev and also	228	Return the set of all backends compiled into this binary of libev and
203	recommended for this platform. This set is often smaller than the one	229	also recommended for this platform, meaning it will work for most file
		230	descriptor types. This set is often smaller than the one returned by
204	returned by C<ev_supported_backends>, as for example kqueue is broken on	231	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
205	most BSDs and will not be auto-detected unless you explicitly request it	232	and will not be auto-detected unless you explicitly request it (assuming
206	(assuming you know what you are doing). This is the set of backends that	233	you know what you are doing). This is the set of backends that libev will
207	libev will probe for if you specify no backends explicitly.	234	probe for if you specify no backends explicitly.
208		235
209	=item unsigned int ev_embeddable_backends ()	236	=item unsigned int ev_embeddable_backends ()
210		237
211	Returns the set of backends that are embeddable in other event loops. This	238	Returns the set of backends that are embeddable in other event loops. This
212	is the theoretical, all-platform, value. To find which backends	239	value is platform-specific but can include backends not available on the
213	might be supported on the current system, you would need to look at	240	current system. To find which embeddable backends might be supported on
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	241	the current system, you would need to look at C<ev_embeddable_backends ()
215	recommended ones.	242	& ev_supported_backends ()>, likewise for recommended ones.
216		243
217	See the description of C<ev_embed> watchers for more info.	244	See the description of C<ev_embed> watchers for more info.
218		245
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	246	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
220		247
221	Sets the allocation function to use (the prototype is similar - the	248	Sets the allocation function to use (the prototype is similar - the
222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	249	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
223	used to allocate and free memory (no surprises here). If it returns zero	250	used to allocate and free memory (no surprises here). If it returns zero
224	when memory needs to be allocated (C<size != 0>), the library might abort	251	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	277	}
251		278
252	...	279	...
253	ev_set_allocator (persistent_realloc);	280	ev_set_allocator (persistent_realloc);
254		281
255	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	282	=item ev_set_syserr_cb (void (*cb)(const char *msg))
256		283
257	Set the callback function to call on a retryable system call error (such	284	Set the callback function to call on a retryable system call error (such
258	as failed select, poll, epoll_wait). The message is a printable string	285	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	286	indicating the system call or subsystem causing the problem. If this
260	callback is set, then libev will expect it to remedy the situation, no	287	callback is set, then libev will expect it to remedy the situation, no
…		…
272	}	299	}
273		300
274	...	301	...
275	ev_set_syserr_cb (fatal_error);	302	ev_set_syserr_cb (fatal_error);
276		303
		304	=item ev_feed_signal (int signum)
		305
		306	This function can be used to "simulate" a signal receive. It is completely
		307	safe to call this function at any time, from any context, including signal
		308	handlers or random threads.
		309
		310	It's main use is to customise signal handling in your process, especially
		311	in the presence of threads. For example, you could block signals
		312	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		313	creating any loops), and in one thread, use C<sigwait> or any other
		314	mechanism to wait for signals, then "deliver" them to libev by calling
		315	C<ev_feed_signal>.
		316
277	=back	317	=back
278		318
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	319	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
280		320
281	An event loop is described by a C<struct ev_loop *> (the C<struct>	321	An event loop is described by a C<struct ev_loop *> (the C<struct> is
282	is I<not> optional in this case, as there is also an C<ev_loop>	322	I<not> optional in this case unless libev 3 compatibility is disabled, as
283	I<function>).	323	libev 3 had an C<ev_loop> function colliding with the struct name).
284		324
285	The library knows two types of such loops, the I<default> loop, which	325	The library knows two types of such loops, the I<default> loop, which
286	supports signals and child events, and dynamically created loops which do	326	supports child process events, and dynamically created event loops which
287	not.	327	do not.
288		328
289	=over 4	329	=over 4
290		330
291	=item struct ev_loop *ev_default_loop (unsigned int flags)	331	=item struct ev_loop *ev_default_loop (unsigned int flags)
292		332
293	This will initialise the default event loop if it hasn't been initialised	333	This returns the "default" event loop object, which is what you should
294	yet and return it. If the default loop could not be initialised, returns	334	normally use when you just need "the event loop". Event loop objects and
295	false. If it already was initialised it simply returns it (and ignores the	335	the C<flags> parameter are described in more detail in the entry for
296	flags. If that is troubling you, check C<ev_backend ()> afterwards).	336	C<ev_loop_new>.
		337
		338	If the default loop is already initialised then this function simply
		339	returns it (and ignores the flags. If that is troubling you, check
		340	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		341	flags, which should almost always be C<0>, unless the caller is also the
		342	one calling C<ev_run> or otherwise qualifies as "the main program".
297		343
298	If you don't know what event loop to use, use the one returned from this	344	If you don't know what event loop to use, use the one returned from this
299	function.	345	function (or via the C<EV_DEFAULT> macro).
300		346
301	Note that this function is I<not> thread-safe, so if you want to use it	347	Note that this function is I<not> thread-safe, so if you want to use it
302	from multiple threads, you have to lock (note also that this is unlikely,	348	from multiple threads, you have to employ some kind of mutex (note also
303	as loops cannot bes hared easily between threads anyway).	349	that this case is unlikely, as loops cannot be shared easily between
		350	threads anyway).
304		351
305	The default loop is the only loop that can handle C<ev_signal> and	352	The default loop is the only loop that can handle C<ev_child> watchers,
306	C<ev_child> watchers, and to do this, it always registers a handler	353	and to do this, it always registers a handler for C<SIGCHLD>. If this is
307	for C<SIGCHLD>. If this is a problem for your application you can either	354	a problem for your application you can either create a dynamic loop with
308	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	355	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
309	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	356	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
310	C<ev_default_init>.	357
		358	Example: This is the most typical usage.
		359
		360	if (!ev_default_loop (0))
		361	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		362
		363	Example: Restrict libev to the select and poll backends, and do not allow
		364	environment settings to be taken into account:
		365
		366	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		367
		368	=item struct ev_loop *ev_loop_new (unsigned int flags)
		369
		370	This will create and initialise a new event loop object. If the loop
		371	could not be initialised, returns false.
		372
		373	This function is thread-safe, and one common way to use libev with
		374	threads is indeed to create one loop per thread, and using the default
		375	loop in the "main" or "initial" thread.
311		376
312	The flags argument can be used to specify special behaviour or specific	377	The flags argument can be used to specify special behaviour or specific
313	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	378	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
314		379
315	The following flags are supported:	380	The following flags are supported:
…		…
330	useful to try out specific backends to test their performance, or to work	395	useful to try out specific backends to test their performance, or to work
331	around bugs.	396	around bugs.
332		397
333	=item C<EVFLAG_FORKCHECK>	398	=item C<EVFLAG_FORKCHECK>
334		399
335	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	400	Instead of calling C<ev_loop_fork> manually after a fork, you can also
336	a fork, you can also make libev check for a fork in each iteration by	401	make libev check for a fork in each iteration by enabling this flag.
337	enabling this flag.
338		402
339	This works by calling C<getpid ()> on every iteration of the loop,	403	This works by calling C<getpid ()> on every iteration of the loop,
340	and thus this might slow down your event loop if you do a lot of loop	404	and thus this might slow down your event loop if you do a lot of loop
341	iterations and little real work, but is usually not noticeable (on my	405	iterations and little real work, but is usually not noticeable (on my
342	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	406	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
…		…
348	flag.	412	flag.
349		413
350	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	414	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
351	environment variable.	415	environment variable.
352		416
		417	=item C<EVFLAG_NOINOTIFY>
		418
		419	When this flag is specified, then libev will not attempt to use the
		420	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
		421	testing, this flag can be useful to conserve inotify file descriptors, as
		422	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		423
		424	=item C<EVFLAG_SIGNALFD>
		425
		426	When this flag is specified, then libev will attempt to use the
		427	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
		428	delivers signals synchronously, which makes it both faster and might make
		429	it possible to get the queued signal data. It can also simplify signal
		430	handling with threads, as long as you properly block signals in your
		431	threads that are not interested in handling them.
		432
		433	Signalfd will not be used by default as this changes your signal mask, and
		434	there are a lot of shoddy libraries and programs (glib's threadpool for
		435	example) that can't properly initialise their signal masks.
		436
		437	=item C<EVFLAG_NOSIGMASK>
		438
		439	When this flag is specified, then libev will avoid to modify the signal
		440	mask. Specifically, this means you ahve to make sure signals are unblocked
		441	when you want to receive them.
		442
		443	This behaviour is useful when you want to do your own signal handling, or
		444	want to handle signals only in specific threads and want to avoid libev
		445	unblocking the signals.
		446
		447	This flag's behaviour will become the default in future versions of libev.
		448
353	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	449	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
354		450
355	This is your standard select(2) backend. Not I<completely> standard, as	451	This is your standard select(2) backend. Not I<completely> standard, as
356	libev tries to roll its own fd_set with no limits on the number of fds,	452	libev tries to roll its own fd_set with no limits on the number of fds,
357	but if that fails, expect a fairly low limit on the number of fds when	453	but if that fails, expect a fairly low limit on the number of fds when
…		…
381	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and	477	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
382	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	478	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
383		479
384	=item C<EVBACKEND_EPOLL> (value 4, Linux)	480	=item C<EVBACKEND_EPOLL> (value 4, Linux)
385		481
		482	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		483	kernels).
		484
386	For few fds, this backend is a bit little slower than poll and select,	485	For few fds, this backend is a bit little slower than poll and select,
387	but it scales phenomenally better. While poll and select usually scale	486	but it scales phenomenally better. While poll and select usually scale
388	like O(total_fds) where n is the total number of fds (or the highest fd),	487	like O(total_fds) where n is the total number of fds (or the highest fd),
389	epoll scales either O(1) or O(active_fds). The epoll design has a number	488	epoll scales either O(1) or O(active_fds).
390	of shortcomings, such as silently dropping events in some hard-to-detect
391	cases and requiring a system call per fd change, no fork support and bad
392	support for dup.
393		489
		490	The epoll mechanism deserves honorable mention as the most misdesigned
		491	of the more advanced event mechanisms: mere annoyances include silently
		492	dropping file descriptors, requiring a system call per change per file
		493	descriptor (and unnecessary guessing of parameters), problems with dup,
		494	returning before the timeout value, resulting in additional iterations
		495	(and only giving 5ms accuracy while select on the same platform gives
		496	0.1ms) and so on. The biggest issue is fork races, however - if a program
		497	forks then I<both> parent and child process have to recreate the epoll
		498	set, which can take considerable time (one syscall per file descriptor)
		499	and is of course hard to detect.
		500
394	Epoll is also notoriously buggy - embedding epoll fds should work, but	501	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
395	of course doesn't, and epoll just loves to report events for totally	502	of course I<doesn't>, and epoll just loves to report events for totally
396	I<different> file descriptors (even already closed ones) than registered	503	I<different> file descriptors (even already closed ones, so one cannot
397	in the set (especially on SMP systems). Libev tries to counter these	504	even remove them from the set) than registered in the set (especially
398	spurious notifications by employing an additional generation counter and	505	on SMP systems). Libev tries to counter these spurious notifications by
399	comparing that against the events to filter out spurious ones.	506	employing an additional generation counter and comparing that against the
		507	events to filter out spurious ones, recreating the set when required. Last
		508	not least, it also refuses to work with some file descriptors which work
		509	perfectly fine with C<select> (files, many character devices...).
		510
		511	Epoll is truly the train wreck analog among event poll mechanisms.
400		512
401	While stopping, setting and starting an I/O watcher in the same iteration	513	While stopping, setting and starting an I/O watcher in the same iteration
402	will result in some caching, there is still a system call per such incident	514	will result in some caching, there is still a system call per such
403	(because the fd could point to a different file description now), so its	515	incident (because the same I<file descriptor> could point to a different
404	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	516	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
405	very well if you register events for both fds.	517	file descriptors might not work very well if you register events for both
		518	file descriptors.
406		519
407	Best performance from this backend is achieved by not unregistering all	520	Best performance from this backend is achieved by not unregistering all
408	watchers for a file descriptor until it has been closed, if possible,	521	watchers for a file descriptor until it has been closed, if possible,
409	i.e. keep at least one watcher active per fd at all times. Stopping and	522	i.e. keep at least one watcher active per fd at all times. Stopping and
410	starting a watcher (without re-setting it) also usually doesn't cause	523	starting a watcher (without re-setting it) also usually doesn't cause
411	extra overhead.	524	extra overhead. A fork can both result in spurious notifications as well
		525	as in libev having to destroy and recreate the epoll object, which can
		526	take considerable time and thus should be avoided.
		527
		528	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		529	faster than epoll for maybe up to a hundred file descriptors, depending on
		530	the usage. So sad.
412		531
413	While nominally embeddable in other event loops, this feature is broken in	532	While nominally embeddable in other event loops, this feature is broken in
414	all kernel versions tested so far.	533	all kernel versions tested so far.
415		534
416	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	535	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
417	C<EVBACKEND_POLL>.	536	C<EVBACKEND_POLL>.
418		537
419	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	538	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
420		539
421	Kqueue deserves special mention, as at the time of this writing, it was	540	Kqueue deserves special mention, as at the time of this writing, it
422	broken on all BSDs except NetBSD (usually it doesn't work reliably with	541	was broken on all BSDs except NetBSD (usually it doesn't work reliably
423	anything but sockets and pipes, except on Darwin, where of course it's	542	with anything but sockets and pipes, except on Darwin, where of course
424	completely useless). For this reason it's not being "auto-detected" unless	543	it's completely useless). Unlike epoll, however, whose brokenness
425	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or	544	is by design, these kqueue bugs can (and eventually will) be fixed
426	libev was compiled on a known-to-be-good (-enough) system like NetBSD.	545	without API changes to existing programs. For this reason it's not being
		546	"auto-detected" unless you explicitly specify it in the flags (i.e. using
		547	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		548	system like NetBSD.
427		549
428	You still can embed kqueue into a normal poll or select backend and use it	550	You still can embed kqueue into a normal poll or select backend and use it
429	only for sockets (after having made sure that sockets work with kqueue on	551	only for sockets (after having made sure that sockets work with kqueue on
430	the target platform). See C<ev_embed> watchers for more info.	552	the target platform). See C<ev_embed> watchers for more info.
431		553
432	It scales in the same way as the epoll backend, but the interface to the	554	It scales in the same way as the epoll backend, but the interface to the
433	kernel is more efficient (which says nothing about its actual speed, of	555	kernel is more efficient (which says nothing about its actual speed, of
434	course). While stopping, setting and starting an I/O watcher does never	556	course). While stopping, setting and starting an I/O watcher does never
435	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	557	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
436	two event changes per incident. Support for C<fork ()> is very bad and it	558	two event changes per incident. Support for C<fork ()> is very bad (but
437	drops fds silently in similarly hard-to-detect cases.	559	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		560	cases
438		561
439	This backend usually performs well under most conditions.	562	This backend usually performs well under most conditions.
440		563
441	While nominally embeddable in other event loops, this doesn't work	564	While nominally embeddable in other event loops, this doesn't work
442	everywhere, so you might need to test for this. And since it is broken	565	everywhere, so you might need to test for this. And since it is broken
443	almost everywhere, you should only use it when you have a lot of sockets	566	almost everywhere, you should only use it when you have a lot of sockets
444	(for which it usually works), by embedding it into another event loop	567	(for which it usually works), by embedding it into another event loop
445	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,	568	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
446	using it only for sockets.	569	also broken on OS X)) and, did I mention it, using it only for sockets.
447		570
448	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	571	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
449	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with	572	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
450	C<NOTE_EOF>.	573	C<NOTE_EOF>.
451		574
…		…
471	might perform better.	594	might perform better.
472		595
473	On the positive side, with the exception of the spurious readiness	596	On the positive side, with the exception of the spurious readiness
474	notifications, this backend actually performed fully to specification	597	notifications, this backend actually performed fully to specification
475	in all tests and is fully embeddable, which is a rare feat among the	598	in all tests and is fully embeddable, which is a rare feat among the
476	OS-specific backends.	599	OS-specific backends (I vastly prefer correctness over speed hacks).
477		600
478	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	601	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
479	C<EVBACKEND_POLL>.	602	C<EVBACKEND_POLL>.
480		603
481	=item C<EVBACKEND_ALL>	604	=item C<EVBACKEND_ALL>
482		605
483	Try all backends (even potentially broken ones that wouldn't be tried	606	Try all backends (even potentially broken ones that wouldn't be tried
484	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	607	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
485	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	608	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
486		609
487	It is definitely not recommended to use this flag.	610	It is definitely not recommended to use this flag, use whatever
		611	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		612	at all.
		613
		614	=item C<EVBACKEND_MASK>
		615
		616	Not a backend at all, but a mask to select all backend bits from a
		617	C<flags> value, in case you want to mask out any backends from a flags
		618	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
488		619
489	=back	620	=back
490		621
491	If one or more of these are or'ed into the flags value, then only these	622	If one or more of the backend flags are or'ed into the flags value,
492	backends will be tried (in the reverse order as listed here). If none are	623	then only these backends will be tried (in the reverse order as listed
493	specified, all backends in C<ev_recommended_backends ()> will be tried.	624	here). If none are specified, all backends in C<ev_recommended_backends
494		625	()> will be tried.
495	Example: This is the most typical usage.
496
497	if (!ev_default_loop (0))
498	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
499
500	Example: Restrict libev to the select and poll backends, and do not allow
501	environment settings to be taken into account:
502
503	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
504
505	Example: Use whatever libev has to offer, but make sure that kqueue is
506	used if available (warning, breaks stuff, best use only with your own
507	private event loop and only if you know the OS supports your types of
508	fds):
509
510	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
511
512	=item struct ev_loop *ev_loop_new (unsigned int flags)
513
514	Similar to C<ev_default_loop>, but always creates a new event loop that is
515	always distinct from the default loop. Unlike the default loop, it cannot
516	handle signal and child watchers, and attempts to do so will be greeted by
517	undefined behaviour (or a failed assertion if assertions are enabled).
518
519	Note that this function I<is> thread-safe, and the recommended way to use
520	libev with threads is indeed to create one loop per thread, and using the
521	default loop in the "main" or "initial" thread.
522		626
523	Example: Try to create a event loop that uses epoll and nothing else.	627	Example: Try to create a event loop that uses epoll and nothing else.
524		628
525	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	629	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
526	if (!epoller)	630	if (!epoller)
527	fatal ("no epoll found here, maybe it hides under your chair");	631	fatal ("no epoll found here, maybe it hides under your chair");
528		632
		633	Example: Use whatever libev has to offer, but make sure that kqueue is
		634	used if available.
		635
		636	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		637
529	=item ev_default_destroy ()	638	=item ev_loop_destroy (loop)
530		639
531	Destroys the default loop again (frees all memory and kernel state	640	Destroys an event loop object (frees all memory and kernel state
532	etc.). None of the active event watchers will be stopped in the normal	641	etc.). None of the active event watchers will be stopped in the normal
533	sense, so e.g. C<ev_is_active> might still return true. It is your	642	sense, so e.g. C<ev_is_active> might still return true. It is your
534	responsibility to either stop all watchers cleanly yourself I<before>	643	responsibility to either stop all watchers cleanly yourself I<before>
535	calling this function, or cope with the fact afterwards (which is usually	644	calling this function, or cope with the fact afterwards (which is usually
536	the easiest thing, you can just ignore the watchers and/or C<free ()> them	645	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
538		647
539	Note that certain global state, such as signal state (and installed signal	648	Note that certain global state, such as signal state (and installed signal
540	handlers), will not be freed by this function, and related watchers (such	649	handlers), will not be freed by this function, and related watchers (such
541	as signal and child watchers) would need to be stopped manually.	650	as signal and child watchers) would need to be stopped manually.
542		651
543	In general it is not advisable to call this function except in the	652	This function is normally used on loop objects allocated by
544	rare occasion where you really need to free e.g. the signal handling	653	C<ev_loop_new>, but it can also be used on the default loop returned by
		654	C<ev_default_loop>, in which case it is not thread-safe.
		655
		656	Note that it is not advisable to call this function on the default loop
		657	except in the rare occasion where you really need to free its resources.
545	pipe fds. If you need dynamically allocated loops it is better to use	658	If you need dynamically allocated loops it is better to use C<ev_loop_new>
546	C<ev_loop_new> and C<ev_loop_destroy>).	659	and C<ev_loop_destroy>.
547		660
548	=item ev_loop_destroy (loop)	661	=item ev_loop_fork (loop)
549		662
550	Like C<ev_default_destroy>, but destroys an event loop created by an
551	earlier call to C<ev_loop_new>.
552
553	=item ev_default_fork ()
554
555	This function sets a flag that causes subsequent C<ev_loop> iterations	663	This function sets a flag that causes subsequent C<ev_run> iterations to
556	to reinitialise the kernel state for backends that have one. Despite the	664	reinitialise the kernel state for backends that have one. Despite the
557	name, you can call it anytime, but it makes most sense after forking, in	665	name, you can call it anytime, but it makes most sense after forking, in
558	the child process (or both child and parent, but that again makes little	666	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
559	sense). You I<must> call it in the child before using any of the libev	667	child before resuming or calling C<ev_run>.
560	functions, and it will only take effect at the next C<ev_loop> iteration.	668
		669	Again, you I<have> to call it on I<any> loop that you want to re-use after
		670	a fork, I<even if you do not plan to use the loop in the parent>. This is
		671	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		672	during fork.
561		673
562	On the other hand, you only need to call this function in the child	674	On the other hand, you only need to call this function in the child
563	process if and only if you want to use the event library in the child. If	675	process if and only if you want to use the event loop in the child. If
564	you just fork+exec, you don't have to call it at all.	676	you just fork+exec or create a new loop in the child, you don't have to
		677	call it at all (in fact, C<epoll> is so badly broken that it makes a
		678	difference, but libev will usually detect this case on its own and do a
		679	costly reset of the backend).
565		680
566	The function itself is quite fast and it's usually not a problem to call	681	The function itself is quite fast and it's usually not a problem to call
567	it just in case after a fork. To make this easy, the function will fit in	682	it just in case after a fork.
568	quite nicely into a call to C<pthread_atfork>:
569		683
		684	Example: Automate calling C<ev_loop_fork> on the default loop when
		685	using pthreads.
		686
		687	static void
		688	post_fork_child (void)
		689	{
		690	ev_loop_fork (EV_DEFAULT);
		691	}
		692
		693	...
570	pthread_atfork (0, 0, ev_default_fork);	694	pthread_atfork (0, 0, post_fork_child);
571
572	=item ev_loop_fork (loop)
573
574	Like C<ev_default_fork>, but acts on an event loop created by
575	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
576	after fork that you want to re-use in the child, and how you do this is
577	entirely your own problem.
578		695
579	=item int ev_is_default_loop (loop)	696	=item int ev_is_default_loop (loop)
580		697
581	Returns true when the given loop is, in fact, the default loop, and false	698	Returns true when the given loop is, in fact, the default loop, and false
582	otherwise.	699	otherwise.
583		700
584	=item unsigned int ev_loop_count (loop)	701	=item unsigned int ev_iteration (loop)
585		702
586	Returns the count of loop iterations for the loop, which is identical to	703	Returns the current iteration count for the event loop, which is identical
587	the number of times libev did poll for new events. It starts at C<0> and	704	to the number of times libev did poll for new events. It starts at C<0>
588	happily wraps around with enough iterations.	705	and happily wraps around with enough iterations.
589		706
590	This value can sometimes be useful as a generation counter of sorts (it	707	This value can sometimes be useful as a generation counter of sorts (it
591	"ticks" the number of loop iterations), as it roughly corresponds with	708	"ticks" the number of loop iterations), as it roughly corresponds with
592	C<ev_prepare> and C<ev_check> calls.	709	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		710	prepare and check phases.
		711
		712	=item unsigned int ev_depth (loop)
		713
		714	Returns the number of times C<ev_run> was entered minus the number of
		715	times C<ev_run> was exited normally, in other words, the recursion depth.
		716
		717	Outside C<ev_run>, this number is zero. In a callback, this number is
		718	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		719	in which case it is higher.
		720
		721	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
		722	throwing an exception etc.), doesn't count as "exit" - consider this
		723	as a hint to avoid such ungentleman-like behaviour unless it's really
		724	convenient, in which case it is fully supported.
593		725
594	=item unsigned int ev_backend (loop)	726	=item unsigned int ev_backend (loop)
595		727
596	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	728	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
597	use.	729	use.
…		…
606		738
607	=item ev_now_update (loop)	739	=item ev_now_update (loop)
608		740
609	Establishes the current time by querying the kernel, updating the time	741	Establishes the current time by querying the kernel, updating the time
610	returned by C<ev_now ()> in the progress. This is a costly operation and	742	returned by C<ev_now ()> in the progress. This is a costly operation and
611	is usually done automatically within C<ev_loop ()>.	743	is usually done automatically within C<ev_run ()>.
612		744
613	This function is rarely useful, but when some event callback runs for a	745	This function is rarely useful, but when some event callback runs for a
614	very long time without entering the event loop, updating libev's idea of	746	very long time without entering the event loop, updating libev's idea of
615	the current time is a good idea.	747	the current time is a good idea.
616		748
617	See also "The special problem of time updates" in the C<ev_timer> section.	749	See also L<The special problem of time updates> in the C<ev_timer> section.
618		750
		751	=item ev_suspend (loop)
		752
		753	=item ev_resume (loop)
		754
		755	These two functions suspend and resume an event loop, for use when the
		756	loop is not used for a while and timeouts should not be processed.
		757
		758	A typical use case would be an interactive program such as a game: When
		759	the user presses C<^Z> to suspend the game and resumes it an hour later it
		760	would be best to handle timeouts as if no time had actually passed while
		761	the program was suspended. This can be achieved by calling C<ev_suspend>
		762	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		763	C<ev_resume> directly afterwards to resume timer processing.
		764
		765	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		766	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		767	will be rescheduled (that is, they will lose any events that would have
		768	occurred while suspended).
		769
		770	After calling C<ev_suspend> you B<must not> call I<any> function on the
		771	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		772	without a previous call to C<ev_suspend>.
		773
		774	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		775	event loop time (see C<ev_now_update>).
		776
619	=item ev_loop (loop, int flags)	777	=item ev_run (loop, int flags)
620		778
621	Finally, this is it, the event handler. This function usually is called	779	Finally, this is it, the event handler. This function usually is called
622	after you initialised all your watchers and you want to start handling	780	after you have initialised all your watchers and you want to start
623	events.	781	handling events. It will ask the operating system for any new events, call
		782	the watcher callbacks, an then repeat the whole process indefinitely: This
		783	is why event loops are called I<loops>.
624		784
625	If the flags argument is specified as C<0>, it will not return until	785	If the flags argument is specified as C<0>, it will keep handling events
626	either no event watchers are active anymore or C<ev_unloop> was called.	786	until either no event watchers are active anymore or C<ev_break> was
		787	called.
627		788
628	Please note that an explicit C<ev_unloop> is usually better than	789	Please note that an explicit C<ev_break> is usually better than
629	relying on all watchers to be stopped when deciding when a program has	790	relying on all watchers to be stopped when deciding when a program has
630	finished (especially in interactive programs), but having a program	791	finished (especially in interactive programs), but having a program
631	that automatically loops as long as it has to and no longer by virtue	792	that automatically loops as long as it has to and no longer by virtue
632	of relying on its watchers stopping correctly, that is truly a thing of	793	of relying on its watchers stopping correctly, that is truly a thing of
633	beauty.	794	beauty.
634		795
		796	This function is also I<mostly> exception-safe - you can break out of
		797	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		798	exception and so on. This does not decrement the C<ev_depth> value, nor
		799	will it clear any outstanding C<EVBREAK_ONE> breaks.
		800
635	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	801	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
636	those events and any already outstanding ones, but will not block your	802	those events and any already outstanding ones, but will not wait and
637	process in case there are no events and will return after one iteration of	803	block your process in case there are no events and will return after one
638	the loop.	804	iteration of the loop. This is sometimes useful to poll and handle new
		805	events while doing lengthy calculations, to keep the program responsive.
639		806
640	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	807	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
641	necessary) and will handle those and any already outstanding ones. It	808	necessary) and will handle those and any already outstanding ones. It
642	will block your process until at least one new event arrives (which could	809	will block your process until at least one new event arrives (which could
643	be an event internal to libev itself, so there is no guarentee that a	810	be an event internal to libev itself, so there is no guarantee that a
644	user-registered callback will be called), and will return after one	811	user-registered callback will be called), and will return after one
645	iteration of the loop.	812	iteration of the loop.
646		813
647	This is useful if you are waiting for some external event in conjunction	814	This is useful if you are waiting for some external event in conjunction
648	with something not expressible using other libev watchers (i.e. "roll your	815	with something not expressible using other libev watchers (i.e. "roll your
649	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	816	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
650	usually a better approach for this kind of thing.	817	usually a better approach for this kind of thing.
651		818
652	Here are the gory details of what C<ev_loop> does:	819	Here are the gory details of what C<ev_run> does:
653		820
		821	- Increment loop depth.
		822	- Reset the ev_break status.
654	- Before the first iteration, call any pending watchers.	823	- Before the first iteration, call any pending watchers.
		824	LOOP:
655	* If EVFLAG_FORKCHECK was used, check for a fork.	825	- If EVFLAG_FORKCHECK was used, check for a fork.
656	- If a fork was detected (by any means), queue and call all fork watchers.	826	- If a fork was detected (by any means), queue and call all fork watchers.
657	- Queue and call all prepare watchers.	827	- Queue and call all prepare watchers.
		828	- If ev_break was called, goto FINISH.
658	- If we have been forked, detach and recreate the kernel state	829	- If we have been forked, detach and recreate the kernel state
659	as to not disturb the other process.	830	as to not disturb the other process.
660	- Update the kernel state with all outstanding changes.	831	- Update the kernel state with all outstanding changes.
661	- Update the "event loop time" (ev_now ()).	832	- Update the "event loop time" (ev_now ()).
662	- Calculate for how long to sleep or block, if at all	833	- Calculate for how long to sleep or block, if at all
663	(active idle watchers, EVLOOP_NONBLOCK or not having	834	(active idle watchers, EVRUN_NOWAIT or not having
664	any active watchers at all will result in not sleeping).	835	any active watchers at all will result in not sleeping).
665	- Sleep if the I/O and timer collect interval say so.	836	- Sleep if the I/O and timer collect interval say so.
		837	- Increment loop iteration counter.
666	- Block the process, waiting for any events.	838	- Block the process, waiting for any events.
667	- Queue all outstanding I/O (fd) events.	839	- Queue all outstanding I/O (fd) events.
668	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	840	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
669	- Queue all expired timers.	841	- Queue all expired timers.
670	- Queue all expired periodics.	842	- Queue all expired periodics.
671	- Unless any events are pending now, queue all idle watchers.	843	- Queue all idle watchers with priority higher than that of pending events.
672	- Queue all check watchers.	844	- Queue all check watchers.
673	- Call all queued watchers in reverse order (i.e. check watchers first).	845	- Call all queued watchers in reverse order (i.e. check watchers first).
674	Signals and child watchers are implemented as I/O watchers, and will	846	Signals and child watchers are implemented as I/O watchers, and will
675	be handled here by queueing them when their watcher gets executed.	847	be handled here by queueing them when their watcher gets executed.
676	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	848	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
677	were used, or there are no active watchers, return, otherwise	849	were used, or there are no active watchers, goto FINISH, otherwise
678	continue with step *.	850	continue with step LOOP.
		851	FINISH:
		852	- Reset the ev_break status iff it was EVBREAK_ONE.
		853	- Decrement the loop depth.
		854	- Return.
679		855
680	Example: Queue some jobs and then loop until no events are outstanding	856	Example: Queue some jobs and then loop until no events are outstanding
681	anymore.	857	anymore.
682		858
683	... queue jobs here, make sure they register event watchers as long	859	... queue jobs here, make sure they register event watchers as long
684	... as they still have work to do (even an idle watcher will do..)	860	... as they still have work to do (even an idle watcher will do..)
685	ev_loop (my_loop, 0);	861	ev_run (my_loop, 0);
686	... jobs done or somebody called unloop. yeah!	862	... jobs done or somebody called unloop. yeah!
687		863
688	=item ev_unloop (loop, how)	864	=item ev_break (loop, how)
689		865
690	Can be used to make a call to C<ev_loop> return early (but only after it	866	Can be used to make a call to C<ev_run> return early (but only after it
691	has processed all outstanding events). The C<how> argument must be either	867	has processed all outstanding events). The C<how> argument must be either
692	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	868	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
693	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	869	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
694		870
695	This "unloop state" will be cleared when entering C<ev_loop> again.	871	This "break state" will be cleared on the next call to C<ev_run>.
696		872
697	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	873	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		874	which case it will have no effect.
698		875
699	=item ev_ref (loop)	876	=item ev_ref (loop)
700		877
701	=item ev_unref (loop)	878	=item ev_unref (loop)
702		879
703	Ref/unref can be used to add or remove a reference count on the event	880	Ref/unref can be used to add or remove a reference count on the event
704	loop: Every watcher keeps one reference, and as long as the reference	881	loop: Every watcher keeps one reference, and as long as the reference
705	count is nonzero, C<ev_loop> will not return on its own.	882	count is nonzero, C<ev_run> will not return on its own.
706		883
707	If you have a watcher you never unregister that should not keep C<ev_loop>	884	This is useful when you have a watcher that you never intend to
708	from returning, call ev_unref() after starting, and ev_ref() before	885	unregister, but that nevertheless should not keep C<ev_run> from
		886	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
709	stopping it.	887	before stopping it.
710		888
711	As an example, libev itself uses this for its internal signal pipe: It is	889	As an example, libev itself uses this for its internal signal pipe: It
712	not visible to the libev user and should not keep C<ev_loop> from exiting	890	is not visible to the libev user and should not keep C<ev_run> from
713	if no event watchers registered by it are active. It is also an excellent	891	exiting if no event watchers registered by it are active. It is also an
714	way to do this for generic recurring timers or from within third-party	892	excellent way to do this for generic recurring timers or from within
715	libraries. Just remember to I<unref after start> and I<ref before stop>	893	third-party libraries. Just remember to I<unref after start> and I<ref
716	(but only if the watcher wasn't active before, or was active before,	894	before stop> (but only if the watcher wasn't active before, or was active
717	respectively).	895	before, respectively. Note also that libev might stop watchers itself
		896	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		897	in the callback).
718		898
719	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	899	Example: Create a signal watcher, but keep it from keeping C<ev_run>
720	running when nothing else is active.	900	running when nothing else is active.
721		901
722	ev_signal exitsig;	902	ev_signal exitsig;
723	ev_signal_init (&exitsig, sig_cb, SIGINT);	903	ev_signal_init (&exitsig, sig_cb, SIGINT);
724	ev_signal_start (loop, &exitsig);	904	ev_signal_start (loop, &exitsig);
725	evf_unref (loop);	905	ev_unref (loop);
726		906
727	Example: For some weird reason, unregister the above signal handler again.	907	Example: For some weird reason, unregister the above signal handler again.
728		908
729	ev_ref (loop);	909	ev_ref (loop);
730	ev_signal_stop (loop, &exitsig);	910	ev_signal_stop (loop, &exitsig);
…		…
751		931
752	By setting a higher I<io collect interval> you allow libev to spend more	932	By setting a higher I<io collect interval> you allow libev to spend more
753	time collecting I/O events, so you can handle more events per iteration,	933	time collecting I/O events, so you can handle more events per iteration,
754	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	934	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
755	C<ev_timer>) will be not affected. Setting this to a non-null value will	935	C<ev_timer>) will be not affected. Setting this to a non-null value will
756	introduce an additional C<ev_sleep ()> call into most loop iterations.	936	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		937	sleep time ensures that libev will not poll for I/O events more often then
		938	once per this interval, on average.
757		939
758	Likewise, by setting a higher I<timeout collect interval> you allow libev	940	Likewise, by setting a higher I<timeout collect interval> you allow libev
759	to spend more time collecting timeouts, at the expense of increased	941	to spend more time collecting timeouts, at the expense of increased
760	latency/jitter/inexactness (the watcher callback will be called	942	latency/jitter/inexactness (the watcher callback will be called
761	later). C<ev_io> watchers will not be affected. Setting this to a non-null	943	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
763		945
764	Many (busy) programs can usually benefit by setting the I/O collect	946	Many (busy) programs can usually benefit by setting the I/O collect
765	interval to a value near C<0.1> or so, which is often enough for	947	interval to a value near C<0.1> or so, which is often enough for
766	interactive servers (of course not for games), likewise for timeouts. It	948	interactive servers (of course not for games), likewise for timeouts. It
767	usually doesn't make much sense to set it to a lower value than C<0.01>,	949	usually doesn't make much sense to set it to a lower value than C<0.01>,
768	as this approaches the timing granularity of most systems.	950	as this approaches the timing granularity of most systems. Note that if
		951	you do transactions with the outside world and you can't increase the
		952	parallelity, then this setting will limit your transaction rate (if you
		953	need to poll once per transaction and the I/O collect interval is 0.01,
		954	then you can't do more than 100 transactions per second).
769		955
770	Setting the I<timeout collect interval> can improve the opportunity for	956	Setting the I<timeout collect interval> can improve the opportunity for
771	saving power, as the program will "bundle" timer callback invocations that	957	saving power, as the program will "bundle" timer callback invocations that
772	are "near" in time together, by delaying some, thus reducing the number of	958	are "near" in time together, by delaying some, thus reducing the number of
773	times the process sleeps and wakes up again. Another useful technique to	959	times the process sleeps and wakes up again. Another useful technique to
774	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	960	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
775	they fire on, say, one-second boundaries only.	961	they fire on, say, one-second boundaries only.
776		962
		963	Example: we only need 0.1s timeout granularity, and we wish not to poll
		964	more often than 100 times per second:
		965
		966	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		967	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		968
		969	=item ev_invoke_pending (loop)
		970
		971	This call will simply invoke all pending watchers while resetting their
		972	pending state. Normally, C<ev_run> does this automatically when required,
		973	but when overriding the invoke callback this call comes handy. This
		974	function can be invoked from a watcher - this can be useful for example
		975	when you want to do some lengthy calculation and want to pass further
		976	event handling to another thread (you still have to make sure only one
		977	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		978
		979	=item int ev_pending_count (loop)
		980
		981	Returns the number of pending watchers - zero indicates that no watchers
		982	are pending.
		983
		984	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		985
		986	This overrides the invoke pending functionality of the loop: Instead of
		987	invoking all pending watchers when there are any, C<ev_run> will call
		988	this callback instead. This is useful, for example, when you want to
		989	invoke the actual watchers inside another context (another thread etc.).
		990
		991	If you want to reset the callback, use C<ev_invoke_pending> as new
		992	callback.
		993
		994	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		995
		996	Sometimes you want to share the same loop between multiple threads. This
		997	can be done relatively simply by putting mutex_lock/unlock calls around
		998	each call to a libev function.
		999
		1000	However, C<ev_run> can run an indefinite time, so it is not feasible
		1001	to wait for it to return. One way around this is to wake up the event
		1002	loop via C<ev_break> and C<av_async_send>, another way is to set these
		1003	I<release> and I<acquire> callbacks on the loop.
		1004
		1005	When set, then C<release> will be called just before the thread is
		1006	suspended waiting for new events, and C<acquire> is called just
		1007	afterwards.
		1008
		1009	Ideally, C<release> will just call your mutex_unlock function, and
		1010	C<acquire> will just call the mutex_lock function again.
		1011
		1012	While event loop modifications are allowed between invocations of
		1013	C<release> and C<acquire> (that's their only purpose after all), no
		1014	modifications done will affect the event loop, i.e. adding watchers will
		1015	have no effect on the set of file descriptors being watched, or the time
		1016	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		1017	to take note of any changes you made.
		1018
		1019	In theory, threads executing C<ev_run> will be async-cancel safe between
		1020	invocations of C<release> and C<acquire>.
		1021
		1022	See also the locking example in the C<THREADS> section later in this
		1023	document.
		1024
		1025	=item ev_set_userdata (loop, void *data)
		1026
		1027	=item void *ev_userdata (loop)
		1028
		1029	Set and retrieve a single C<void *> associated with a loop. When
		1030	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		1031	C<0>.
		1032
		1033	These two functions can be used to associate arbitrary data with a loop,
		1034	and are intended solely for the C<invoke_pending_cb>, C<release> and
		1035	C<acquire> callbacks described above, but of course can be (ab-)used for
		1036	any other purpose as well.
		1037
777	=item ev_loop_verify (loop)	1038	=item ev_verify (loop)
778		1039
779	This function only does something when C<EV_VERIFY> support has been	1040	This function only does something when C<EV_VERIFY> support has been
780	compiled in, which is the default for non-minimal builds. It tries to go	1041	compiled in, which is the default for non-minimal builds. It tries to go
781	through all internal structures and checks them for validity. If anything	1042	through all internal structures and checks them for validity. If anything
782	is found to be inconsistent, it will print an error message to standard	1043	is found to be inconsistent, it will print an error message to standard
…		…
793		1054
794	In the following description, uppercase C<TYPE> in names stands for the	1055	In the following description, uppercase C<TYPE> in names stands for the
795	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1056	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
796	watchers and C<ev_io_start> for I/O watchers.	1057	watchers and C<ev_io_start> for I/O watchers.
797		1058
798	A watcher is a structure that you create and register to record your	1059	A watcher is an opaque structure that you allocate and register to record
799	interest in some event. For instance, if you want to wait for STDIN to	1060	your interest in some event. To make a concrete example, imagine you want
800	become readable, you would create an C<ev_io> watcher for that:	1061	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1062	for that:
801		1063
802	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1064	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
803	{	1065	{
804	ev_io_stop (w);	1066	ev_io_stop (w);
805	ev_unloop (loop, EVUNLOOP_ALL);	1067	ev_break (loop, EVBREAK_ALL);
806	}	1068	}
807		1069
808	struct ev_loop *loop = ev_default_loop (0);	1070	struct ev_loop *loop = ev_default_loop (0);
809		1071
810	ev_io stdin_watcher;	1072	ev_io stdin_watcher;
811		1073
812	ev_init (&stdin_watcher, my_cb);	1074	ev_init (&stdin_watcher, my_cb);
813	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1075	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
814	ev_io_start (loop, &stdin_watcher);	1076	ev_io_start (loop, &stdin_watcher);
815		1077
816	ev_loop (loop, 0);	1078	ev_run (loop, 0);
817		1079
818	As you can see, you are responsible for allocating the memory for your	1080	As you can see, you are responsible for allocating the memory for your
819	watcher structures (and it is I<usually> a bad idea to do this on the	1081	watcher structures (and it is I<usually> a bad idea to do this on the
820	stack).	1082	stack).
821		1083
822	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1084	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
823	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1085	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
824		1086
825	Each watcher structure must be initialised by a call to C<ev_init	1087	Each watcher structure must be initialised by a call to C<ev_init (watcher
826	(watcher *, callback)>, which expects a callback to be provided. This	1088	*, callback)>, which expects a callback to be provided. This callback is
827	callback gets invoked each time the event occurs (or, in the case of I/O	1089	invoked each time the event occurs (or, in the case of I/O watchers, each
828	watchers, each time the event loop detects that the file descriptor given	1090	time the event loop detects that the file descriptor given is readable
829	is readable and/or writable).	1091	and/or writable).
830		1092
831	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1093	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
832	macro to configure it, with arguments specific to the watcher type. There	1094	macro to configure it, with arguments specific to the watcher type. There
833	is also a macro to combine initialisation and setting in one call: C<<	1095	is also a macro to combine initialisation and setting in one call: C<<
834	ev_TYPE_init (watcher *, callback, ...) >>.	1096	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
857	=item C<EV_WRITE>	1119	=item C<EV_WRITE>
858		1120
859	The file descriptor in the C<ev_io> watcher has become readable and/or	1121	The file descriptor in the C<ev_io> watcher has become readable and/or
860	writable.	1122	writable.
861		1123
862	=item C<EV_TIMEOUT>	1124	=item C<EV_TIMER>
863		1125
864	The C<ev_timer> watcher has timed out.	1126	The C<ev_timer> watcher has timed out.
865		1127
866	=item C<EV_PERIODIC>	1128	=item C<EV_PERIODIC>
867		1129
…		…
885		1147
886	=item C<EV_PREPARE>	1148	=item C<EV_PREPARE>
887		1149
888	=item C<EV_CHECK>	1150	=item C<EV_CHECK>
889		1151
890	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1152	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
891	to gather new events, and all C<ev_check> watchers are invoked just after	1153	to gather new events, and all C<ev_check> watchers are invoked just after
892	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1154	C<ev_run> has gathered them, but before it invokes any callbacks for any
893	received events. Callbacks of both watcher types can start and stop as	1155	received events. Callbacks of both watcher types can start and stop as
894	many watchers as they want, and all of them will be taken into account	1156	many watchers as they want, and all of them will be taken into account
895	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1157	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
896	C<ev_loop> from blocking).	1158	C<ev_run> from blocking).
897		1159
898	=item C<EV_EMBED>	1160	=item C<EV_EMBED>
899		1161
900	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1162	The embedded event loop specified in the C<ev_embed> watcher needs attention.
901		1163
902	=item C<EV_FORK>	1164	=item C<EV_FORK>
903		1165
904	The event loop has been resumed in the child process after fork (see	1166	The event loop has been resumed in the child process after fork (see
905	C<ev_fork>).	1167	C<ev_fork>).
906		1168
		1169	=item C<EV_CLEANUP>
		1170
		1171	The event loop is about to be destroyed (see C<ev_cleanup>).
		1172
907	=item C<EV_ASYNC>	1173	=item C<EV_ASYNC>
908		1174
909	The given async watcher has been asynchronously notified (see C<ev_async>).	1175	The given async watcher has been asynchronously notified (see C<ev_async>).
		1176
		1177	=item C<EV_CUSTOM>
		1178
		1179	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1180	by libev users to signal watchers (e.g. via C<ev_feed_event>).
910		1181
911	=item C<EV_ERROR>	1182	=item C<EV_ERROR>
912		1183
913	An unspecified error has occurred, the watcher has been stopped. This might	1184	An unspecified error has occurred, the watcher has been stopped. This might
914	happen because the watcher could not be properly started because libev	1185	happen because the watcher could not be properly started because libev
…		…
952		1223
953	ev_io w;	1224	ev_io w;
954	ev_init (&w, my_cb);	1225	ev_init (&w, my_cb);
955	ev_io_set (&w, STDIN_FILENO, EV_READ);	1226	ev_io_set (&w, STDIN_FILENO, EV_READ);
956		1227
957	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1228	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
958		1229
959	This macro initialises the type-specific parts of a watcher. You need to	1230	This macro initialises the type-specific parts of a watcher. You need to
960	call C<ev_init> at least once before you call this macro, but you can	1231	call C<ev_init> at least once before you call this macro, but you can
961	call C<ev_TYPE_set> any number of times. You must not, however, call this	1232	call C<ev_TYPE_set> any number of times. You must not, however, call this
962	macro on a watcher that is active (it can be pending, however, which is a	1233	macro on a watcher that is active (it can be pending, however, which is a
…		…
975		1246
976	Example: Initialise and set an C<ev_io> watcher in one step.	1247	Example: Initialise and set an C<ev_io> watcher in one step.
977		1248
978	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1249	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
979		1250
980	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1251	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
981		1252
982	Starts (activates) the given watcher. Only active watchers will receive	1253	Starts (activates) the given watcher. Only active watchers will receive
983	events. If the watcher is already active nothing will happen.	1254	events. If the watcher is already active nothing will happen.
984		1255
985	Example: Start the C<ev_io> watcher that is being abused as example in this	1256	Example: Start the C<ev_io> watcher that is being abused as example in this
986	whole section.	1257	whole section.
987		1258
988	ev_io_start (EV_DEFAULT_UC, &w);	1259	ev_io_start (EV_DEFAULT_UC, &w);
989		1260
990	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1261	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
991		1262
992	Stops the given watcher if active, and clears the pending status (whether	1263	Stops the given watcher if active, and clears the pending status (whether
993	the watcher was active or not).	1264	the watcher was active or not).
994		1265
995	It is possible that stopped watchers are pending - for example,	1266	It is possible that stopped watchers are pending - for example,
…		…
1020	=item ev_cb_set (ev_TYPE *watcher, callback)	1291	=item ev_cb_set (ev_TYPE *watcher, callback)
1021		1292
1022	Change the callback. You can change the callback at virtually any time	1293	Change the callback. You can change the callback at virtually any time
1023	(modulo threads).	1294	(modulo threads).
1024		1295
1025	=item ev_set_priority (ev_TYPE *watcher, priority)	1296	=item ev_set_priority (ev_TYPE *watcher, int priority)
1026		1297
1027	=item int ev_priority (ev_TYPE *watcher)	1298	=item int ev_priority (ev_TYPE *watcher)
1028		1299
1029	Set and query the priority of the watcher. The priority is a small	1300	Set and query the priority of the watcher. The priority is a small
1030	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1301	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1031	(default: C<-2>). Pending watchers with higher priority will be invoked	1302	(default: C<-2>). Pending watchers with higher priority will be invoked
1032	before watchers with lower priority, but priority will not keep watchers	1303	before watchers with lower priority, but priority will not keep watchers
1033	from being executed (except for C<ev_idle> watchers).	1304	from being executed (except for C<ev_idle> watchers).
1034		1305
1035	This means that priorities are I<only> used for ordering callback
1036	invocation after new events have been received. This is useful, for
1037	example, to reduce latency after idling, or more often, to bind two
1038	watchers on the same event and make sure one is called first.
1039
1040	If you need to suppress invocation when higher priority events are pending	1306	If you need to suppress invocation when higher priority events are pending
1041	you need to look at C<ev_idle> watchers, which provide this functionality.	1307	you need to look at C<ev_idle> watchers, which provide this functionality.
1042		1308
1043	You I<must not> change the priority of a watcher as long as it is active or	1309	You I<must not> change the priority of a watcher as long as it is active or
1044	pending.	1310	pending.
1045
1046	The default priority used by watchers when no priority has been set is
1047	always C<0>, which is supposed to not be too high and not be too low :).
1048		1311
1049	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1312	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1050	fine, as long as you do not mind that the priority value you query might	1313	fine, as long as you do not mind that the priority value you query might
1051	or might not have been clamped to the valid range.	1314	or might not have been clamped to the valid range.
		1315
		1316	The default priority used by watchers when no priority has been set is
		1317	always C<0>, which is supposed to not be too high and not be too low :).
		1318
		1319	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
		1320	priorities.
1052		1321
1053	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1322	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1054		1323
1055	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1324	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1056	C<loop> nor C<revents> need to be valid as long as the watcher callback	1325	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1064	watcher isn't pending it does nothing and returns C<0>.	1333	watcher isn't pending it does nothing and returns C<0>.
1065		1334
1066	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1335	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1067	callback to be invoked, which can be accomplished with this function.	1336	callback to be invoked, which can be accomplished with this function.
1068		1337
		1338	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1339
		1340	Feeds the given event set into the event loop, as if the specified event
		1341	had happened for the specified watcher (which must be a pointer to an
		1342	initialised but not necessarily started event watcher). Obviously you must
		1343	not free the watcher as long as it has pending events.
		1344
		1345	Stopping the watcher, letting libev invoke it, or calling
		1346	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1347	not started in the first place.
		1348
		1349	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1350	functions that do not need a watcher.
		1351
1069	=back	1352	=back
1070
1071		1353
1072	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1354	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1073		1355
1074	Each watcher has, by default, a member C<void *data> that you can change	1356	Each watcher has, by default, a member C<void *data> that you can change
1075	and read at any time: libev will completely ignore it. This can be used	1357	and read at any time: libev will completely ignore it. This can be used
…		…
1121	#include <stddef.h>	1403	#include <stddef.h>
1122		1404
1123	static void	1405	static void
1124	t1_cb (EV_P_ ev_timer *w, int revents)	1406	t1_cb (EV_P_ ev_timer *w, int revents)
1125	{	1407	{
1126	struct my_biggy big = (struct my_biggy *	1408	struct my_biggy big = (struct my_biggy *)
1127	(((char *)w) - offsetof (struct my_biggy, t1));	1409	(((char *)w) - offsetof (struct my_biggy, t1));
1128	}	1410	}
1129		1411
1130	static void	1412	static void
1131	t2_cb (EV_P_ ev_timer *w, int revents)	1413	t2_cb (EV_P_ ev_timer *w, int revents)
1132	{	1414	{
1133	struct my_biggy big = (struct my_biggy *	1415	struct my_biggy big = (struct my_biggy *)
1134	(((char *)w) - offsetof (struct my_biggy, t2));	1416	(((char *)w) - offsetof (struct my_biggy, t2));
1135	}	1417	}
		1418
		1419	=head2 WATCHER STATES
		1420
		1421	There are various watcher states mentioned throughout this manual -
		1422	active, pending and so on. In this section these states and the rules to
		1423	transition between them will be described in more detail - and while these
		1424	rules might look complicated, they usually do "the right thing".
		1425
		1426	=over 4
		1427
		1428	=item initialiased
		1429
		1430	Before a watcher can be registered with the event looop it has to be
		1431	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1432	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1433
		1434	In this state it is simply some block of memory that is suitable for use
		1435	in an event loop. It can be moved around, freed, reused etc. at will.
		1436
		1437	=item started/running/active
		1438
		1439	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1440	property of the event loop, and is actively waiting for events. While in
		1441	this state it cannot be accessed (except in a few documented ways), moved,
		1442	freed or anything else - the only legal thing is to keep a pointer to it,
		1443	and call libev functions on it that are documented to work on active watchers.
		1444
		1445	=item pending
		1446
		1447	If a watcher is active and libev determines that an event it is interested
		1448	in has occurred (such as a timer expiring), it will become pending. It will
		1449	stay in this pending state until either it is stopped or its callback is
		1450	about to be invoked, so it is not normally pending inside the watcher
		1451	callback.
		1452
		1453	The watcher might or might not be active while it is pending (for example,
		1454	an expired non-repeating timer can be pending but no longer active). If it
		1455	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1456	but it is still property of the event loop at this time, so cannot be
		1457	moved, freed or reused. And if it is active the rules described in the
		1458	previous item still apply.
		1459
		1460	It is also possible to feed an event on a watcher that is not active (e.g.
		1461	via C<ev_feed_event>), in which case it becomes pending without being
		1462	active.
		1463
		1464	=item stopped
		1465
		1466	A watcher can be stopped implicitly by libev (in which case it might still
		1467	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1468	latter will clear any pending state the watcher might be in, regardless
		1469	of whether it was active or not, so stopping a watcher explicitly before
		1470	freeing it is often a good idea.
		1471
		1472	While stopped (and not pending) the watcher is essentially in the
		1473	initialised state, that is it can be reused, moved, modified in any way
		1474	you wish.
		1475
		1476	=back
		1477
		1478	=head2 WATCHER PRIORITY MODELS
		1479
		1480	Many event loops support I<watcher priorities>, which are usually small
		1481	integers that influence the ordering of event callback invocation
		1482	between watchers in some way, all else being equal.
		1483
		1484	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1485	description for the more technical details such as the actual priority
		1486	range.
		1487
		1488	There are two common ways how these these priorities are being interpreted
		1489	by event loops:
		1490
		1491	In the more common lock-out model, higher priorities "lock out" invocation
		1492	of lower priority watchers, which means as long as higher priority
		1493	watchers receive events, lower priority watchers are not being invoked.
		1494
		1495	The less common only-for-ordering model uses priorities solely to order
		1496	callback invocation within a single event loop iteration: Higher priority
		1497	watchers are invoked before lower priority ones, but they all get invoked
		1498	before polling for new events.
		1499
		1500	Libev uses the second (only-for-ordering) model for all its watchers
		1501	except for idle watchers (which use the lock-out model).
		1502
		1503	The rationale behind this is that implementing the lock-out model for
		1504	watchers is not well supported by most kernel interfaces, and most event
		1505	libraries will just poll for the same events again and again as long as
		1506	their callbacks have not been executed, which is very inefficient in the
		1507	common case of one high-priority watcher locking out a mass of lower
		1508	priority ones.
		1509
		1510	Static (ordering) priorities are most useful when you have two or more
		1511	watchers handling the same resource: a typical usage example is having an
		1512	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1513	timeouts. Under load, data might be received while the program handles
		1514	other jobs, but since timers normally get invoked first, the timeout
		1515	handler will be executed before checking for data. In that case, giving
		1516	the timer a lower priority than the I/O watcher ensures that I/O will be
		1517	handled first even under adverse conditions (which is usually, but not
		1518	always, what you want).
		1519
		1520	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1521	will only be executed when no same or higher priority watchers have
		1522	received events, they can be used to implement the "lock-out" model when
		1523	required.
		1524
		1525	For example, to emulate how many other event libraries handle priorities,
		1526	you can associate an C<ev_idle> watcher to each such watcher, and in
		1527	the normal watcher callback, you just start the idle watcher. The real
		1528	processing is done in the idle watcher callback. This causes libev to
		1529	continuously poll and process kernel event data for the watcher, but when
		1530	the lock-out case is known to be rare (which in turn is rare :), this is
		1531	workable.
		1532
		1533	Usually, however, the lock-out model implemented that way will perform
		1534	miserably under the type of load it was designed to handle. In that case,
		1535	it might be preferable to stop the real watcher before starting the
		1536	idle watcher, so the kernel will not have to process the event in case
		1537	the actual processing will be delayed for considerable time.
		1538
		1539	Here is an example of an I/O watcher that should run at a strictly lower
		1540	priority than the default, and which should only process data when no
		1541	other events are pending:
		1542
		1543	ev_idle idle; // actual processing watcher
		1544	ev_io io; // actual event watcher
		1545
		1546	static void
		1547	io_cb (EV_P_ ev_io *w, int revents)
		1548	{
		1549	// stop the I/O watcher, we received the event, but
		1550	// are not yet ready to handle it.
		1551	ev_io_stop (EV_A_ w);
		1552
		1553	// start the idle watcher to handle the actual event.
		1554	// it will not be executed as long as other watchers
		1555	// with the default priority are receiving events.
		1556	ev_idle_start (EV_A_ &idle);
		1557	}
		1558
		1559	static void
		1560	idle_cb (EV_P_ ev_idle *w, int revents)
		1561	{
		1562	// actual processing
		1563	read (STDIN_FILENO, ...);
		1564
		1565	// have to start the I/O watcher again, as
		1566	// we have handled the event
		1567	ev_io_start (EV_P_ &io);
		1568	}
		1569
		1570	// initialisation
		1571	ev_idle_init (&idle, idle_cb);
		1572	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1573	ev_io_start (EV_DEFAULT_ &io);
		1574
		1575	In the "real" world, it might also be beneficial to start a timer, so that
		1576	low-priority connections can not be locked out forever under load. This
		1577	enables your program to keep a lower latency for important connections
		1578	during short periods of high load, while not completely locking out less
		1579	important ones.
1136		1580
1137		1581
1138	=head1 WATCHER TYPES	1582	=head1 WATCHER TYPES
1139		1583
1140	This section describes each watcher in detail, but will not repeat	1584	This section describes each watcher in detail, but will not repeat
…		…
1166	descriptors to non-blocking mode is also usually a good idea (but not	1610	descriptors to non-blocking mode is also usually a good idea (but not
1167	required if you know what you are doing).	1611	required if you know what you are doing).
1168		1612
1169	If you cannot use non-blocking mode, then force the use of a	1613	If you cannot use non-blocking mode, then force the use of a
1170	known-to-be-good backend (at the time of this writing, this includes only	1614	known-to-be-good backend (at the time of this writing, this includes only
1171	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).	1615	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1616	descriptors for which non-blocking operation makes no sense (such as
		1617	files) - libev doesn't guarantee any specific behaviour in that case.
1172		1618
1173	Another thing you have to watch out for is that it is quite easy to	1619	Another thing you have to watch out for is that it is quite easy to
1174	receive "spurious" readiness notifications, that is your callback might	1620	receive "spurious" readiness notifications, that is your callback might
1175	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1621	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1176	because there is no data. Not only are some backends known to create a	1622	because there is no data. Not only are some backends known to create a
…		…
1241		1687
1242	So when you encounter spurious, unexplained daemon exits, make sure you	1688	So when you encounter spurious, unexplained daemon exits, make sure you
1243	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1689	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1244	somewhere, as that would have given you a big clue).	1690	somewhere, as that would have given you a big clue).
1245		1691
		1692	=head3 The special problem of accept()ing when you can't
		1693
		1694	Many implementations of the POSIX C<accept> function (for example,
		1695	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1696	connection from the pending queue in all error cases.
		1697
		1698	For example, larger servers often run out of file descriptors (because
		1699	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1700	rejecting the connection, leading to libev signalling readiness on
		1701	the next iteration again (the connection still exists after all), and
		1702	typically causing the program to loop at 100% CPU usage.
		1703
		1704	Unfortunately, the set of errors that cause this issue differs between
		1705	operating systems, there is usually little the app can do to remedy the
		1706	situation, and no known thread-safe method of removing the connection to
		1707	cope with overload is known (to me).
		1708
		1709	One of the easiest ways to handle this situation is to just ignore it
		1710	- when the program encounters an overload, it will just loop until the
		1711	situation is over. While this is a form of busy waiting, no OS offers an
		1712	event-based way to handle this situation, so it's the best one can do.
		1713
		1714	A better way to handle the situation is to log any errors other than
		1715	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1716	messages, and continue as usual, which at least gives the user an idea of
		1717	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1718	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1719	usage.
		1720
		1721	If your program is single-threaded, then you could also keep a dummy file
		1722	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1723	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1724	close that fd, and create a new dummy fd. This will gracefully refuse
		1725	clients under typical overload conditions.
		1726
		1727	The last way to handle it is to simply log the error and C<exit>, as
		1728	is often done with C<malloc> failures, but this results in an easy
		1729	opportunity for a DoS attack.
1246		1730
1247	=head3 Watcher-Specific Functions	1731	=head3 Watcher-Specific Functions
1248		1732
1249	=over 4	1733	=over 4
1250		1734
…		…
1282	...	1766	...
1283	struct ev_loop *loop = ev_default_init (0);	1767	struct ev_loop *loop = ev_default_init (0);
1284	ev_io stdin_readable;	1768	ev_io stdin_readable;
1285	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1769	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1286	ev_io_start (loop, &stdin_readable);	1770	ev_io_start (loop, &stdin_readable);
1287	ev_loop (loop, 0);	1771	ev_run (loop, 0);
1288		1772
1289		1773
1290	=head2 C<ev_timer> - relative and optionally repeating timeouts	1774	=head2 C<ev_timer> - relative and optionally repeating timeouts
1291		1775
1292	Timer watchers are simple relative timers that generate an event after a	1776	Timer watchers are simple relative timers that generate an event after a
…		…
1297	year, it will still time out after (roughly) one hour. "Roughly" because	1781	year, it will still time out after (roughly) one hour. "Roughly" because
1298	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1782	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1299	monotonic clock option helps a lot here).	1783	monotonic clock option helps a lot here).
1300		1784
1301	The callback is guaranteed to be invoked only I<after> its timeout has	1785	The callback is guaranteed to be invoked only I<after> its timeout has
1302	passed, but if multiple timers become ready during the same loop iteration	1786	passed (not I<at>, so on systems with very low-resolution clocks this
1303	then order of execution is undefined.	1787	might introduce a small delay). If multiple timers become ready during the
		1788	same loop iteration then the ones with earlier time-out values are invoked
		1789	before ones of the same priority with later time-out values (but this is
		1790	no longer true when a callback calls C<ev_run> recursively).
1304		1791
1305	=head3 Be smart about timeouts	1792	=head3 Be smart about timeouts
1306		1793
1307	Many real-world problems involve some kind of timeout, usually for error	1794	Many real-world problems involve some kind of timeout, usually for error
1308	recovery. A typical example is an HTTP request - if the other side hangs,	1795	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1352	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>	1839	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
1353	member and C<ev_timer_again>.	1840	member and C<ev_timer_again>.
1354		1841
1355	At start:	1842	At start:
1356		1843
1357	ev_timer_init (timer, callback);	1844	ev_init (timer, callback);
1358	timer->repeat = 60.;	1845	timer->repeat = 60.;
1359	ev_timer_again (loop, timer);	1846	ev_timer_again (loop, timer);
1360		1847
1361	Each time there is some activity:	1848	Each time there is some activity:
1362		1849
…		…
1394	ev_tstamp timeout = last_activity + 60.;	1881	ev_tstamp timeout = last_activity + 60.;
1395		1882
1396	// if last_activity + 60. is older than now, we did time out	1883	// if last_activity + 60. is older than now, we did time out
1397	if (timeout < now)	1884	if (timeout < now)
1398	{	1885	{
1399	// timeout occured, take action	1886	// timeout occurred, take action
1400	}	1887	}
1401	else	1888	else
1402	{	1889	{
1403	// callback was invoked, but there was some activity, re-arm	1890	// callback was invoked, but there was some activity, re-arm
1404	// the watcher to fire in last_activity + 60, which is	1891	// the watcher to fire in last_activity + 60, which is
1405	// guaranteed to be in the future, so "again" is positive:	1892	// guaranteed to be in the future, so "again" is positive:
1406	w->again = timeout - now;	1893	w->repeat = timeout - now;
1407	ev_timer_again (EV_A_ w);	1894	ev_timer_again (EV_A_ w);
1408	}	1895	}
1409	}	1896	}
1410		1897
1411	To summarise the callback: first calculate the real timeout (defined	1898	To summarise the callback: first calculate the real timeout (defined
…		…
1424		1911
1425	To start the timer, simply initialise the watcher and set C<last_activity>	1912	To start the timer, simply initialise the watcher and set C<last_activity>
1426	to the current time (meaning we just have some activity :), then call the	1913	to the current time (meaning we just have some activity :), then call the
1427	callback, which will "do the right thing" and start the timer:	1914	callback, which will "do the right thing" and start the timer:
1428		1915
1429	ev_timer_init (timer, callback);	1916	ev_init (timer, callback);
1430	last_activity = ev_now (loop);	1917	last_activity = ev_now (loop);
1431	callback (loop, timer, EV_TIMEOUT);	1918	callback (loop, timer, EV_TIMER);
1432		1919
1433	And when there is some activity, simply store the current time in	1920	And when there is some activity, simply store the current time in
1434	C<last_activity>, no libev calls at all:	1921	C<last_activity>, no libev calls at all:
1435		1922
1436	last_actiivty = ev_now (loop);	1923	last_activity = ev_now (loop);
1437		1924
1438	This technique is slightly more complex, but in most cases where the	1925	This technique is slightly more complex, but in most cases where the
1439	time-out is unlikely to be triggered, much more efficient.	1926	time-out is unlikely to be triggered, much more efficient.
1440		1927
1441	Changing the timeout is trivial as well (if it isn't hard-coded in the	1928	Changing the timeout is trivial as well (if it isn't hard-coded in the
…		…
1479		1966
1480	=head3 The special problem of time updates	1967	=head3 The special problem of time updates
1481		1968
1482	Establishing the current time is a costly operation (it usually takes at	1969	Establishing the current time is a costly operation (it usually takes at
1483	least two system calls): EV therefore updates its idea of the current	1970	least two system calls): EV therefore updates its idea of the current
1484	time only before and after C<ev_loop> collects new events, which causes a	1971	time only before and after C<ev_run> collects new events, which causes a
1485	growing difference between C<ev_now ()> and C<ev_time ()> when handling	1972	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1486	lots of events in one iteration.	1973	lots of events in one iteration.
1487		1974
1488	The relative timeouts are calculated relative to the C<ev_now ()>	1975	The relative timeouts are calculated relative to the C<ev_now ()>
1489	time. This is usually the right thing as this timestamp refers to the time	1976	time. This is usually the right thing as this timestamp refers to the time
…		…
1495		1982
1496	If the event loop is suspended for a long time, you can also force an	1983	If the event loop is suspended for a long time, you can also force an
1497	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1984	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1498	()>.	1985	()>.
1499		1986
		1987	=head3 The special problems of suspended animation
		1988
		1989	When you leave the server world it is quite customary to hit machines that
		1990	can suspend/hibernate - what happens to the clocks during such a suspend?
		1991
		1992	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1993	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1994	to run until the system is suspended, but they will not advance while the
		1995	system is suspended. That means, on resume, it will be as if the program
		1996	was frozen for a few seconds, but the suspend time will not be counted
		1997	towards C<ev_timer> when a monotonic clock source is used. The real time
		1998	clock advanced as expected, but if it is used as sole clocksource, then a
		1999	long suspend would be detected as a time jump by libev, and timers would
		2000	be adjusted accordingly.
		2001
		2002	I would not be surprised to see different behaviour in different between
		2003	operating systems, OS versions or even different hardware.
		2004
		2005	The other form of suspend (job control, or sending a SIGSTOP) will see a
		2006	time jump in the monotonic clocks and the realtime clock. If the program
		2007	is suspended for a very long time, and monotonic clock sources are in use,
		2008	then you can expect C<ev_timer>s to expire as the full suspension time
		2009	will be counted towards the timers. When no monotonic clock source is in
		2010	use, then libev will again assume a timejump and adjust accordingly.
		2011
		2012	It might be beneficial for this latter case to call C<ev_suspend>
		2013	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		2014	deterministic behaviour in this case (you can do nothing against
		2015	C<SIGSTOP>).
		2016
1500	=head3 Watcher-Specific Functions and Data Members	2017	=head3 Watcher-Specific Functions and Data Members
1501		2018
1502	=over 4	2019	=over 4
1503		2020
1504	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2021	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1527	If the timer is started but non-repeating, stop it (as if it timed out).	2044	If the timer is started but non-repeating, stop it (as if it timed out).
1528		2045
1529	If the timer is repeating, either start it if necessary (with the	2046	If the timer is repeating, either start it if necessary (with the
1530	C<repeat> value), or reset the running timer to the C<repeat> value.	2047	C<repeat> value), or reset the running timer to the C<repeat> value.
1531		2048
1532	This sounds a bit complicated, see "Be smart about timeouts", above, for a	2049	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1533	usage example.	2050	usage example.
		2051
		2052	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2053
		2054	Returns the remaining time until a timer fires. If the timer is active,
		2055	then this time is relative to the current event loop time, otherwise it's
		2056	the timeout value currently configured.
		2057
		2058	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2059	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2060	will return C<4>. When the timer expires and is restarted, it will return
		2061	roughly C<7> (likely slightly less as callback invocation takes some time,
		2062	too), and so on.
1534		2063
1535	=item ev_tstamp repeat [read-write]	2064	=item ev_tstamp repeat [read-write]
1536		2065
1537	The current C<repeat> value. Will be used each time the watcher times out	2066	The current C<repeat> value. Will be used each time the watcher times out
1538	or C<ev_timer_again> is called, and determines the next timeout (if any),	2067	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1564	}	2093	}
1565		2094
1566	ev_timer mytimer;	2095	ev_timer mytimer;
1567	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2096	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1568	ev_timer_again (&mytimer); /* start timer */	2097	ev_timer_again (&mytimer); /* start timer */
1569	ev_loop (loop, 0);	2098	ev_run (loop, 0);
1570		2099
1571	// and in some piece of code that gets executed on any "activity":	2100	// and in some piece of code that gets executed on any "activity":
1572	// reset the timeout to start ticking again at 10 seconds	2101	// reset the timeout to start ticking again at 10 seconds
1573	ev_timer_again (&mytimer);	2102	ev_timer_again (&mytimer);
1574		2103
…		…
1576	=head2 C<ev_periodic> - to cron or not to cron?	2105	=head2 C<ev_periodic> - to cron or not to cron?
1577		2106
1578	Periodic watchers are also timers of a kind, but they are very versatile	2107	Periodic watchers are also timers of a kind, but they are very versatile
1579	(and unfortunately a bit complex).	2108	(and unfortunately a bit complex).
1580		2109
1581	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2110	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1582	but on wall clock time (absolute time). You can tell a periodic watcher	2111	relative time, the physical time that passes) but on wall clock time
1583	to trigger after some specific point in time. For example, if you tell a	2112	(absolute time, the thing you can read on your calender or clock). The
1584	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	2113	difference is that wall clock time can run faster or slower than real
1585	+ 10.>, that is, an absolute time not a delay) and then reset your system	2114	time, and time jumps are not uncommon (e.g. when you adjust your
1586	clock to January of the previous year, then it will take more than year	2115	wrist-watch).
1587	to trigger the event (unlike an C<ev_timer>, which would still trigger
1588	roughly 10 seconds later as it uses a relative timeout).
1589		2116
		2117	You can tell a periodic watcher to trigger after some specific point
		2118	in time: for example, if you tell a periodic watcher to trigger "in 10
		2119	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2120	not a delay) and then reset your system clock to January of the previous
		2121	year, then it will take a year or more to trigger the event (unlike an
		2122	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2123	it, as it uses a relative timeout).
		2124
1590	C<ev_periodic>s can also be used to implement vastly more complex timers,	2125	C<ev_periodic> watchers can also be used to implement vastly more complex
1591	such as triggering an event on each "midnight, local time", or other	2126	timers, such as triggering an event on each "midnight, local time", or
1592	complicated rules.	2127	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2128	those cannot react to time jumps.
1593		2129
1594	As with timers, the callback is guaranteed to be invoked only when the	2130	As with timers, the callback is guaranteed to be invoked only when the
1595	time (C<at>) has passed, but if multiple periodic timers become ready	2131	point in time where it is supposed to trigger has passed. If multiple
1596	during the same loop iteration, then order of execution is undefined.	2132	timers become ready during the same loop iteration then the ones with
		2133	earlier time-out values are invoked before ones with later time-out values
		2134	(but this is no longer true when a callback calls C<ev_run> recursively).
1597		2135
1598	=head3 Watcher-Specific Functions and Data Members	2136	=head3 Watcher-Specific Functions and Data Members
1599		2137
1600	=over 4	2138	=over 4
1601		2139
1602	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2140	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1603		2141
1604	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2142	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1605		2143
1606	Lots of arguments, lets sort it out... There are basically three modes of	2144	Lots of arguments, let's sort it out... There are basically three modes of
1607	operation, and we will explain them from simplest to most complex:	2145	operation, and we will explain them from simplest to most complex:
1608		2146
1609	=over 4	2147	=over 4
1610		2148
1611	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2149	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1612		2150
1613	In this configuration the watcher triggers an event after the wall clock	2151	In this configuration the watcher triggers an event after the wall clock
1614	time C<at> has passed. It will not repeat and will not adjust when a time	2152	time C<offset> has passed. It will not repeat and will not adjust when a
1615	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2153	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1616	only run when the system clock reaches or surpasses this time.	2154	will be stopped and invoked when the system clock reaches or surpasses
		2155	this point in time.
1617		2156
1618	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2157	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1619		2158
1620	In this mode the watcher will always be scheduled to time out at the next	2159	In this mode the watcher will always be scheduled to time out at the next
1621	C<at + N * interval> time (for some integer N, which can also be negative)	2160	C<offset + N * interval> time (for some integer N, which can also be
1622	and then repeat, regardless of any time jumps.	2161	negative) and then repeat, regardless of any time jumps. The C<offset>
		2162	argument is merely an offset into the C<interval> periods.
1623		2163
1624	This can be used to create timers that do not drift with respect to the	2164	This can be used to create timers that do not drift with respect to the
1625	system clock, for example, here is a C<ev_periodic> that triggers each	2165	system clock, for example, here is an C<ev_periodic> that triggers each
1626	hour, on the hour:	2166	hour, on the hour (with respect to UTC):
1627		2167
1628	ev_periodic_set (&periodic, 0., 3600., 0);	2168	ev_periodic_set (&periodic, 0., 3600., 0);
1629		2169
1630	This doesn't mean there will always be 3600 seconds in between triggers,	2170	This doesn't mean there will always be 3600 seconds in between triggers,
1631	but only that the callback will be called when the system time shows a	2171	but only that the callback will be called when the system time shows a
1632	full hour (UTC), or more correctly, when the system time is evenly divisible	2172	full hour (UTC), or more correctly, when the system time is evenly divisible
1633	by 3600.	2173	by 3600.
1634		2174
1635	Another way to think about it (for the mathematically inclined) is that	2175	Another way to think about it (for the mathematically inclined) is that
1636	C<ev_periodic> will try to run the callback in this mode at the next possible	2176	C<ev_periodic> will try to run the callback in this mode at the next possible
1637	time where C<time = at (mod interval)>, regardless of any time jumps.	2177	time where C<time = offset (mod interval)>, regardless of any time jumps.
1638		2178
1639	For numerical stability it is preferable that the C<at> value is near	2179	For numerical stability it is preferable that the C<offset> value is near
1640	C<ev_now ()> (the current time), but there is no range requirement for	2180	C<ev_now ()> (the current time), but there is no range requirement for
1641	this value, and in fact is often specified as zero.	2181	this value, and in fact is often specified as zero.
1642		2182
1643	Note also that there is an upper limit to how often a timer can fire (CPU	2183	Note also that there is an upper limit to how often a timer can fire (CPU
1644	speed for example), so if C<interval> is very small then timing stability	2184	speed for example), so if C<interval> is very small then timing stability
1645	will of course deteriorate. Libev itself tries to be exact to be about one	2185	will of course deteriorate. Libev itself tries to be exact to be about one
1646	millisecond (if the OS supports it and the machine is fast enough).	2186	millisecond (if the OS supports it and the machine is fast enough).
1647		2187
1648	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2188	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1649		2189
1650	In this mode the values for C<interval> and C<at> are both being	2190	In this mode the values for C<interval> and C<offset> are both being
1651	ignored. Instead, each time the periodic watcher gets scheduled, the	2191	ignored. Instead, each time the periodic watcher gets scheduled, the
1652	reschedule callback will be called with the watcher as first, and the	2192	reschedule callback will be called with the watcher as first, and the
1653	current time as second argument.	2193	current time as second argument.
1654		2194
1655	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2195	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1656	ever, or make ANY event loop modifications whatsoever>.	2196	or make ANY other event loop modifications whatsoever, unless explicitly
		2197	allowed by documentation here>.
1657		2198
1658	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2199	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1659	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2200	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1660	only event loop modification you are allowed to do).	2201	only event loop modification you are allowed to do).
1661		2202
…		…
1691	a different time than the last time it was called (e.g. in a crond like	2232	a different time than the last time it was called (e.g. in a crond like
1692	program when the crontabs have changed).	2233	program when the crontabs have changed).
1693		2234
1694	=item ev_tstamp ev_periodic_at (ev_periodic *)	2235	=item ev_tstamp ev_periodic_at (ev_periodic *)
1695		2236
1696	When active, returns the absolute time that the watcher is supposed to	2237	When active, returns the absolute time that the watcher is supposed
1697	trigger next.	2238	to trigger next. This is not the same as the C<offset> argument to
		2239	C<ev_periodic_set>, but indeed works even in interval and manual
		2240	rescheduling modes.
1698		2241
1699	=item ev_tstamp offset [read-write]	2242	=item ev_tstamp offset [read-write]
1700		2243
1701	When repeating, this contains the offset value, otherwise this is the	2244	When repeating, this contains the offset value, otherwise this is the
1702	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2245	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2246	although libev might modify this value for better numerical stability).
1703		2247
1704	Can be modified any time, but changes only take effect when the periodic	2248	Can be modified any time, but changes only take effect when the periodic
1705	timer fires or C<ev_periodic_again> is being called.	2249	timer fires or C<ev_periodic_again> is being called.
1706		2250
1707	=item ev_tstamp interval [read-write]	2251	=item ev_tstamp interval [read-write]
…		…
1723	Example: Call a callback every hour, or, more precisely, whenever the	2267	Example: Call a callback every hour, or, more precisely, whenever the
1724	system time is divisible by 3600. The callback invocation times have	2268	system time is divisible by 3600. The callback invocation times have
1725	potentially a lot of jitter, but good long-term stability.	2269	potentially a lot of jitter, but good long-term stability.
1726		2270
1727	static void	2271	static void
1728	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2272	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1729	{	2273	{
1730	... its now a full hour (UTC, or TAI or whatever your clock follows)	2274	... its now a full hour (UTC, or TAI or whatever your clock follows)
1731	}	2275	}
1732		2276
1733	ev_periodic hourly_tick;	2277	ev_periodic hourly_tick;
…		…
1756		2300
1757	=head2 C<ev_signal> - signal me when a signal gets signalled!	2301	=head2 C<ev_signal> - signal me when a signal gets signalled!
1758		2302
1759	Signal watchers will trigger an event when the process receives a specific	2303	Signal watchers will trigger an event when the process receives a specific
1760	signal one or more times. Even though signals are very asynchronous, libev	2304	signal one or more times. Even though signals are very asynchronous, libev
1761	will try it's best to deliver signals synchronously, i.e. as part of the	2305	will try its best to deliver signals synchronously, i.e. as part of the
1762	normal event processing, like any other event.	2306	normal event processing, like any other event.
1763		2307
1764	If you want signals asynchronously, just use C<sigaction> as you would	2308	If you want signals to be delivered truly asynchronously, just use
1765	do without libev and forget about sharing the signal. You can even use	2309	C<sigaction> as you would do without libev and forget about sharing
1766	C<ev_async> from a signal handler to synchronously wake up an event loop.	2310	the signal. You can even use C<ev_async> from a signal handler to
		2311	synchronously wake up an event loop.
1767		2312
1768	You can configure as many watchers as you like per signal. Only when the	2313	You can configure as many watchers as you like for the same signal, but
		2314	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2315	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2316	C<SIGINT> in both the default loop and another loop at the same time. At
		2317	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2318
1769	first watcher gets started will libev actually register a signal handler	2319	When the first watcher gets started will libev actually register something
1770	with the kernel (thus it coexists with your own signal handlers as long as	2320	with the kernel (thus it coexists with your own signal handlers as long as
1771	you don't register any with libev for the same signal). Similarly, when	2321	you don't register any with libev for the same signal).
1772	the last signal watcher for a signal is stopped, libev will reset the
1773	signal handler to SIG_DFL (regardless of what it was set to before).
1774		2322
1775	If possible and supported, libev will install its handlers with	2323	If possible and supported, libev will install its handlers with
1776	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2324	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1777	interrupted. If you have a problem with system calls getting interrupted by	2325	not be unduly interrupted. If you have a problem with system calls getting
1778	signals you can block all signals in an C<ev_check> watcher and unblock	2326	interrupted by signals you can block all signals in an C<ev_check> watcher
1779	them in an C<ev_prepare> watcher.	2327	and unblock them in an C<ev_prepare> watcher.
		2328
		2329	=head3 The special problem of inheritance over fork/execve/pthread_create
		2330
		2331	Both the signal mask (C<sigprocmask>) and the signal disposition
		2332	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2333	stopping it again), that is, libev might or might not block the signal,
		2334	and might or might not set or restore the installed signal handler.
		2335
		2336	While this does not matter for the signal disposition (libev never
		2337	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2338	C<execve>), this matters for the signal mask: many programs do not expect
		2339	certain signals to be blocked.
		2340
		2341	This means that before calling C<exec> (from the child) you should reset
		2342	the signal mask to whatever "default" you expect (all clear is a good
		2343	choice usually).
		2344
		2345	The simplest way to ensure that the signal mask is reset in the child is
		2346	to install a fork handler with C<pthread_atfork> that resets it. That will
		2347	catch fork calls done by libraries (such as the libc) as well.
		2348
		2349	In current versions of libev, the signal will not be blocked indefinitely
		2350	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2351	the window of opportunity for problems, it will not go away, as libev
		2352	I<has> to modify the signal mask, at least temporarily.
		2353
		2354	So I can't stress this enough: I<If you do not reset your signal mask when
		2355	you expect it to be empty, you have a race condition in your code>. This
		2356	is not a libev-specific thing, this is true for most event libraries.
		2357
		2358	=head3 The special problem of threads signal handling
		2359
		2360	POSIX threads has problematic signal handling semantics, specifically,
		2361	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2362	threads in a process block signals, which is hard to achieve.
		2363
		2364	When you want to use sigwait (or mix libev signal handling with your own
		2365	for the same signals), you can tackle this problem by globally blocking
		2366	all signals before creating any threads (or creating them with a fully set
		2367	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2368	loops. Then designate one thread as "signal receiver thread" which handles
		2369	these signals. You can pass on any signals that libev might be interested
		2370	in by calling C<ev_feed_signal>.
1780		2371
1781	=head3 Watcher-Specific Functions and Data Members	2372	=head3 Watcher-Specific Functions and Data Members
1782		2373
1783	=over 4	2374	=over 4
1784		2375
…		…
1800	Example: Try to exit cleanly on SIGINT.	2391	Example: Try to exit cleanly on SIGINT.
1801		2392
1802	static void	2393	static void
1803	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2394	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1804	{	2395	{
1805	ev_unloop (loop, EVUNLOOP_ALL);	2396	ev_break (loop, EVBREAK_ALL);
1806	}	2397	}
1807		2398
1808	ev_signal signal_watcher;	2399	ev_signal signal_watcher;
1809	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2400	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1810	ev_signal_start (loop, &signal_watcher);	2401	ev_signal_start (loop, &signal_watcher);
…		…
1816	some child status changes (most typically when a child of yours dies or	2407	some child status changes (most typically when a child of yours dies or
1817	exits). It is permissible to install a child watcher I<after> the child	2408	exits). It is permissible to install a child watcher I<after> the child
1818	has been forked (which implies it might have already exited), as long	2409	has been forked (which implies it might have already exited), as long
1819	as the event loop isn't entered (or is continued from a watcher), i.e.,	2410	as the event loop isn't entered (or is continued from a watcher), i.e.,
1820	forking and then immediately registering a watcher for the child is fine,	2411	forking and then immediately registering a watcher for the child is fine,
1821	but forking and registering a watcher a few event loop iterations later is	2412	but forking and registering a watcher a few event loop iterations later or
1822	not.	2413	in the next callback invocation is not.
1823		2414
1824	Only the default event loop is capable of handling signals, and therefore	2415	Only the default event loop is capable of handling signals, and therefore
1825	you can only register child watchers in the default event loop.	2416	you can only register child watchers in the default event loop.
1826		2417
		2418	Due to some design glitches inside libev, child watchers will always be
		2419	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2420	libev)
		2421
1827	=head3 Process Interaction	2422	=head3 Process Interaction
1828		2423
1829	Libev grabs C<SIGCHLD> as soon as the default event loop is	2424	Libev grabs C<SIGCHLD> as soon as the default event loop is
1830	initialised. This is necessary to guarantee proper behaviour even if	2425	initialised. This is necessary to guarantee proper behaviour even if the
1831	the first child watcher is started after the child exits. The occurrence	2426	first child watcher is started after the child exits. The occurrence
1832	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2427	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1833	synchronously as part of the event loop processing. Libev always reaps all	2428	synchronously as part of the event loop processing. Libev always reaps all
1834	children, even ones not watched.	2429	children, even ones not watched.
1835		2430
1836	=head3 Overriding the Built-In Processing	2431	=head3 Overriding the Built-In Processing
…		…
1846	=head3 Stopping the Child Watcher	2441	=head3 Stopping the Child Watcher
1847		2442
1848	Currently, the child watcher never gets stopped, even when the	2443	Currently, the child watcher never gets stopped, even when the
1849	child terminates, so normally one needs to stop the watcher in the	2444	child terminates, so normally one needs to stop the watcher in the
1850	callback. Future versions of libev might stop the watcher automatically	2445	callback. Future versions of libev might stop the watcher automatically
1851	when a child exit is detected.	2446	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2447	problem).
1852		2448
1853	=head3 Watcher-Specific Functions and Data Members	2449	=head3 Watcher-Specific Functions and Data Members
1854		2450
1855	=over 4	2451	=over 4
1856		2452
…		…
1913		2509
1914		2510
1915	=head2 C<ev_stat> - did the file attributes just change?	2511	=head2 C<ev_stat> - did the file attributes just change?
1916		2512
1917	This watches a file system path for attribute changes. That is, it calls	2513	This watches a file system path for attribute changes. That is, it calls
1918	C<stat> regularly (or when the OS says it changed) and sees if it changed	2514	C<stat> on that path in regular intervals (or when the OS says it changed)
1919	compared to the last time, invoking the callback if it did.	2515	and sees if it changed compared to the last time, invoking the callback if
		2516	it did.
1920		2517
1921	The path does not need to exist: changing from "path exists" to "path does	2518	The path does not need to exist: changing from "path exists" to "path does
1922	not exist" is a status change like any other. The condition "path does	2519	not exist" is a status change like any other. The condition "path does not
1923	not exist" is signified by the C<st_nlink> field being zero (which is	2520	exist" (or more correctly "path cannot be stat'ed") is signified by the
1924	otherwise always forced to be at least one) and all the other fields of	2521	C<st_nlink> field being zero (which is otherwise always forced to be at
1925	the stat buffer having unspecified contents.	2522	least one) and all the other fields of the stat buffer having unspecified
		2523	contents.
1926		2524
1927	The path I<should> be absolute and I<must not> end in a slash. If it is	2525	The path I<must not> end in a slash or contain special components such as
		2526	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1928	relative and your working directory changes, the behaviour is undefined.	2527	your working directory changes, then the behaviour is undefined.
1929		2528
1930	Since there is no standard kernel interface to do this, the portable	2529	Since there is no portable change notification interface available, the
1931	implementation simply calls C<stat (2)> regularly on the path to see if	2530	portable implementation simply calls C<stat(2)> regularly on the path
1932	it changed somehow. You can specify a recommended polling interval for	2531	to see if it changed somehow. You can specify a recommended polling
1933	this case. If you specify a polling interval of C<0> (highly recommended!)	2532	interval for this case. If you specify a polling interval of C<0> (highly
1934	then a I<suitable, unspecified default> value will be used (which	2533	recommended!) then a I<suitable, unspecified default> value will be used
1935	you can expect to be around five seconds, although this might change	2534	(which you can expect to be around five seconds, although this might
1936	dynamically). Libev will also impose a minimum interval which is currently	2535	change dynamically). Libev will also impose a minimum interval which is
1937	around C<0.1>, but thats usually overkill.	2536	currently around C<0.1>, but that's usually overkill.
1938		2537
1939	This watcher type is not meant for massive numbers of stat watchers,	2538	This watcher type is not meant for massive numbers of stat watchers,
1940	as even with OS-supported change notifications, this can be	2539	as even with OS-supported change notifications, this can be
1941	resource-intensive.	2540	resource-intensive.
1942		2541
1943	At the time of this writing, the only OS-specific interface implemented	2542	At the time of this writing, the only OS-specific interface implemented
1944	is the Linux inotify interface (implementing kqueue support is left as	2543	is the Linux inotify interface (implementing kqueue support is left as an
1945	an exercise for the reader. Note, however, that the author sees no way	2544	exercise for the reader. Note, however, that the author sees no way of
1946	of implementing C<ev_stat> semantics with kqueue).	2545	implementing C<ev_stat> semantics with kqueue, except as a hint).
1947		2546
1948	=head3 ABI Issues (Largefile Support)	2547	=head3 ABI Issues (Largefile Support)
1949		2548
1950	Libev by default (unless the user overrides this) uses the default	2549	Libev by default (unless the user overrides this) uses the default
1951	compilation environment, which means that on systems with large file	2550	compilation environment, which means that on systems with large file
1952	support disabled by default, you get the 32 bit version of the stat	2551	support disabled by default, you get the 32 bit version of the stat
1953	structure. When using the library from programs that change the ABI to	2552	structure. When using the library from programs that change the ABI to
1954	use 64 bit file offsets the programs will fail. In that case you have to	2553	use 64 bit file offsets the programs will fail. In that case you have to
1955	compile libev with the same flags to get binary compatibility. This is	2554	compile libev with the same flags to get binary compatibility. This is
1956	obviously the case with any flags that change the ABI, but the problem is	2555	obviously the case with any flags that change the ABI, but the problem is
1957	most noticeably disabled with ev_stat and large file support.	2556	most noticeably displayed with ev_stat and large file support.
1958		2557
1959	The solution for this is to lobby your distribution maker to make large	2558	The solution for this is to lobby your distribution maker to make large
1960	file interfaces available by default (as e.g. FreeBSD does) and not	2559	file interfaces available by default (as e.g. FreeBSD does) and not
1961	optional. Libev cannot simply switch on large file support because it has	2560	optional. Libev cannot simply switch on large file support because it has
1962	to exchange stat structures with application programs compiled using the	2561	to exchange stat structures with application programs compiled using the
1963	default compilation environment.	2562	default compilation environment.
1964		2563
1965	=head3 Inotify and Kqueue	2564	=head3 Inotify and Kqueue
1966		2565
1967	When C<inotify (7)> support has been compiled into libev (generally	2566	When C<inotify (7)> support has been compiled into libev and present at
1968	only available with Linux 2.6.25 or above due to bugs in earlier	2567	runtime, it will be used to speed up change detection where possible. The
1969	implementations) and present at runtime, it will be used to speed up	2568	inotify descriptor will be created lazily when the first C<ev_stat>
1970	change detection where possible. The inotify descriptor will be created	2569	watcher is being started.
1971	lazily when the first C<ev_stat> watcher is being started.
1972		2570
1973	Inotify presence does not change the semantics of C<ev_stat> watchers	2571	Inotify presence does not change the semantics of C<ev_stat> watchers
1974	except that changes might be detected earlier, and in some cases, to avoid	2572	except that changes might be detected earlier, and in some cases, to avoid
1975	making regular C<stat> calls. Even in the presence of inotify support	2573	making regular C<stat> calls. Even in the presence of inotify support
1976	there are many cases where libev has to resort to regular C<stat> polling,	2574	there are many cases where libev has to resort to regular C<stat> polling,
1977	but as long as the path exists, libev usually gets away without polling.	2575	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2576	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2577	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2578	xfs are fully working) libev usually gets away without polling.
1978		2579
1979	There is no support for kqueue, as apparently it cannot be used to	2580	There is no support for kqueue, as apparently it cannot be used to
1980	implement this functionality, due to the requirement of having a file	2581	implement this functionality, due to the requirement of having a file
1981	descriptor open on the object at all times, and detecting renames, unlinks	2582	descriptor open on the object at all times, and detecting renames, unlinks
1982	etc. is difficult.	2583	etc. is difficult.
1983		2584
		2585	=head3 C<stat ()> is a synchronous operation
		2586
		2587	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2588	the process. The exception are C<ev_stat> watchers - those call C<stat
		2589	()>, which is a synchronous operation.
		2590
		2591	For local paths, this usually doesn't matter: unless the system is very
		2592	busy or the intervals between stat's are large, a stat call will be fast,
		2593	as the path data is usually in memory already (except when starting the
		2594	watcher).
		2595
		2596	For networked file systems, calling C<stat ()> can block an indefinite
		2597	time due to network issues, and even under good conditions, a stat call
		2598	often takes multiple milliseconds.
		2599
		2600	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2601	paths, although this is fully supported by libev.
		2602
1984	=head3 The special problem of stat time resolution	2603	=head3 The special problem of stat time resolution
1985		2604
1986	The C<stat ()> system call only supports full-second resolution portably, and	2605	The C<stat ()> system call only supports full-second resolution portably,
1987	even on systems where the resolution is higher, most file systems still	2606	and even on systems where the resolution is higher, most file systems
1988	only support whole seconds.	2607	still only support whole seconds.
1989		2608
1990	That means that, if the time is the only thing that changes, you can	2609	That means that, if the time is the only thing that changes, you can
1991	easily miss updates: on the first update, C<ev_stat> detects a change and	2610	easily miss updates: on the first update, C<ev_stat> detects a change and
1992	calls your callback, which does something. When there is another update	2611	calls your callback, which does something. When there is another update
1993	within the same second, C<ev_stat> will be unable to detect unless the	2612	within the same second, C<ev_stat> will be unable to detect unless the
…		…
2136		2755
2137	=head3 Watcher-Specific Functions and Data Members	2756	=head3 Watcher-Specific Functions and Data Members
2138		2757
2139	=over 4	2758	=over 4
2140		2759
2141	=item ev_idle_init (ev_signal *, callback)	2760	=item ev_idle_init (ev_idle *, callback)
2142		2761
2143	Initialises and configures the idle watcher - it has no parameters of any	2762	Initialises and configures the idle watcher - it has no parameters of any
2144	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2763	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
2145	believe me.	2764	believe me.
2146		2765
…		…
2159	// no longer anything immediate to do.	2778	// no longer anything immediate to do.
2160	}	2779	}
2161		2780
2162	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2781	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2163	ev_idle_init (idle_watcher, idle_cb);	2782	ev_idle_init (idle_watcher, idle_cb);
2164	ev_idle_start (loop, idle_cb);	2783	ev_idle_start (loop, idle_watcher);
2165		2784
2166		2785
2167	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2786	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2168		2787
2169	Prepare and check watchers are usually (but not always) used in pairs:	2788	Prepare and check watchers are usually (but not always) used in pairs:
2170	prepare watchers get invoked before the process blocks and check watchers	2789	prepare watchers get invoked before the process blocks and check watchers
2171	afterwards.	2790	afterwards.
2172		2791
2173	You I<must not> call C<ev_loop> or similar functions that enter	2792	You I<must not> call C<ev_run> or similar functions that enter
2174	the current event loop from either C<ev_prepare> or C<ev_check>	2793	the current event loop from either C<ev_prepare> or C<ev_check>
2175	watchers. Other loops than the current one are fine, however. The	2794	watchers. Other loops than the current one are fine, however. The
2176	rationale behind this is that you do not need to check for recursion in	2795	rationale behind this is that you do not need to check for recursion in
2177	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2796	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2178	C<ev_check> so if you have one watcher of each kind they will always be	2797	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2262	struct pollfd fds [nfd];	2881	struct pollfd fds [nfd];
2263	// actual code will need to loop here and realloc etc.	2882	// actual code will need to loop here and realloc etc.
2264	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2883	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2265		2884
2266	/* the callback is illegal, but won't be called as we stop during check */	2885	/* the callback is illegal, but won't be called as we stop during check */
2267	ev_timer_init (&tw, 0, timeout * 1e-3);	2886	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2268	ev_timer_start (loop, &tw);	2887	ev_timer_start (loop, &tw);
2269		2888
2270	// create one ev_io per pollfd	2889	// create one ev_io per pollfd
2271	for (int i = 0; i < nfd; ++i)	2890	for (int i = 0; i < nfd; ++i)
2272	{	2891	{
…		…
2346		2965
2347	if (timeout >= 0)	2966	if (timeout >= 0)
2348	// create/start timer	2967	// create/start timer
2349		2968
2350	// poll	2969	// poll
2351	ev_loop (EV_A_ 0);	2970	ev_run (EV_A_ 0);
2352		2971
2353	// stop timer again	2972	// stop timer again
2354	if (timeout >= 0)	2973	if (timeout >= 0)
2355	ev_timer_stop (EV_A_ &to);	2974	ev_timer_stop (EV_A_ &to);
2356		2975
…		…
2385	some fds have to be watched and handled very quickly (with low latency),	3004	some fds have to be watched and handled very quickly (with low latency),
2386	and even priorities and idle watchers might have too much overhead. In	3005	and even priorities and idle watchers might have too much overhead. In
2387	this case you would put all the high priority stuff in one loop and all	3006	this case you would put all the high priority stuff in one loop and all
2388	the rest in a second one, and embed the second one in the first.	3007	the rest in a second one, and embed the second one in the first.
2389		3008
2390	As long as the watcher is active, the callback will be invoked every time	3009	As long as the watcher is active, the callback will be invoked every
2391	there might be events pending in the embedded loop. The callback must then	3010	time there might be events pending in the embedded loop. The callback
2392	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	3011	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2393	their callbacks (you could also start an idle watcher to give the embedded	3012	sweep and invoke their callbacks (the callback doesn't need to invoke the
2394	loop strictly lower priority for example). You can also set the callback	3013	C<ev_embed_sweep> function directly, it could also start an idle watcher
2395	to C<0>, in which case the embed watcher will automatically execute the	3014	to give the embedded loop strictly lower priority for example).
2396	embedded loop sweep.
2397		3015
2398	As long as the watcher is started it will automatically handle events. The	3016	You can also set the callback to C<0>, in which case the embed watcher
2399	callback will be invoked whenever some events have been handled. You can	3017	will automatically execute the embedded loop sweep whenever necessary.
2400	set the callback to C<0> to avoid having to specify one if you are not
2401	interested in that.
2402		3018
2403	Also, there have not currently been made special provisions for forking:	3019	Fork detection will be handled transparently while the C<ev_embed> watcher
2404	when you fork, you not only have to call C<ev_loop_fork> on both loops,	3020	is active, i.e., the embedded loop will automatically be forked when the
2405	but you will also have to stop and restart any C<ev_embed> watchers	3021	embedding loop forks. In other cases, the user is responsible for calling
2406	yourself - but you can use a fork watcher to handle this automatically,	3022	C<ev_loop_fork> on the embedded loop.
2407	and future versions of libev might do just that.
2408		3023
2409	Unfortunately, not all backends are embeddable: only the ones returned by	3024	Unfortunately, not all backends are embeddable: only the ones returned by
2410	C<ev_embeddable_backends> are, which, unfortunately, does not include any	3025	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2411	portable one.	3026	portable one.
2412		3027
…		…
2438	if you do not want that, you need to temporarily stop the embed watcher).	3053	if you do not want that, you need to temporarily stop the embed watcher).
2439		3054
2440	=item ev_embed_sweep (loop, ev_embed *)	3055	=item ev_embed_sweep (loop, ev_embed *)
2441		3056
2442	Make a single, non-blocking sweep over the embedded loop. This works	3057	Make a single, non-blocking sweep over the embedded loop. This works
2443	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3058	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2444	appropriate way for embedded loops.	3059	appropriate way for embedded loops.
2445		3060
2446	=item struct ev_loop *other [read-only]	3061	=item struct ev_loop *other [read-only]
2447		3062
2448	The embedded event loop.	3063	The embedded event loop.
…		…
2506	event loop blocks next and before C<ev_check> watchers are being called,	3121	event loop blocks next and before C<ev_check> watchers are being called,
2507	and only in the child after the fork. If whoever good citizen calling	3122	and only in the child after the fork. If whoever good citizen calling
2508	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3123	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2509	handlers will be invoked, too, of course.	3124	handlers will be invoked, too, of course.
2510		3125
		3126	=head3 The special problem of life after fork - how is it possible?
		3127
		3128	Most uses of C<fork()> consist of forking, then some simple calls to set
		3129	up/change the process environment, followed by a call to C<exec()>. This
		3130	sequence should be handled by libev without any problems.
		3131
		3132	This changes when the application actually wants to do event handling
		3133	in the child, or both parent in child, in effect "continuing" after the
		3134	fork.
		3135
		3136	The default mode of operation (for libev, with application help to detect
		3137	forks) is to duplicate all the state in the child, as would be expected
		3138	when I<either> the parent I<or> the child process continues.
		3139
		3140	When both processes want to continue using libev, then this is usually the
		3141	wrong result. In that case, usually one process (typically the parent) is
		3142	supposed to continue with all watchers in place as before, while the other
		3143	process typically wants to start fresh, i.e. without any active watchers.
		3144
		3145	The cleanest and most efficient way to achieve that with libev is to
		3146	simply create a new event loop, which of course will be "empty", and
		3147	use that for new watchers. This has the advantage of not touching more
		3148	memory than necessary, and thus avoiding the copy-on-write, and the
		3149	disadvantage of having to use multiple event loops (which do not support
		3150	signal watchers).
		3151
		3152	When this is not possible, or you want to use the default loop for
		3153	other reasons, then in the process that wants to start "fresh", call
		3154	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3155	Destroying the default loop will "orphan" (not stop) all registered
		3156	watchers, so you have to be careful not to execute code that modifies
		3157	those watchers. Note also that in that case, you have to re-register any
		3158	signal watchers.
		3159
2511	=head3 Watcher-Specific Functions and Data Members	3160	=head3 Watcher-Specific Functions and Data Members
2512		3161
2513	=over 4	3162	=over 4
2514		3163
2515	=item ev_fork_init (ev_signal *, callback)	3164	=item ev_fork_init (ev_fork *, callback)
2516		3165
2517	Initialises and configures the fork watcher - it has no parameters of any	3166	Initialises and configures the fork watcher - it has no parameters of any
2518	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3167	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2519	believe me.	3168	really.
2520		3169
2521	=back	3170	=back
2522		3171
2523		3172
		3173	=head2 C<ev_cleanup> - even the best things end
		3174
		3175	Cleanup watchers are called just before the event loop is being destroyed
		3176	by a call to C<ev_loop_destroy>.
		3177
		3178	While there is no guarantee that the event loop gets destroyed, cleanup
		3179	watchers provide a convenient method to install cleanup hooks for your
		3180	program, worker threads and so on - you just to make sure to destroy the
		3181	loop when you want them to be invoked.
		3182
		3183	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3184	all other watchers, they do not keep a reference to the event loop (which
		3185	makes a lot of sense if you think about it). Like all other watchers, you
		3186	can call libev functions in the callback, except C<ev_cleanup_start>.
		3187
		3188	=head3 Watcher-Specific Functions and Data Members
		3189
		3190	=over 4
		3191
		3192	=item ev_cleanup_init (ev_cleanup *, callback)
		3193
		3194	Initialises and configures the cleanup watcher - it has no parameters of
		3195	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3196	pointless, I assure you.
		3197
		3198	=back
		3199
		3200	Example: Register an atexit handler to destroy the default loop, so any
		3201	cleanup functions are called.
		3202
		3203	static void
		3204	program_exits (void)
		3205	{
		3206	ev_loop_destroy (EV_DEFAULT_UC);
		3207	}
		3208
		3209	...
		3210	atexit (program_exits);
		3211
		3212
2524	=head2 C<ev_async> - how to wake up another event loop	3213	=head2 C<ev_async> - how to wake up an event loop
2525		3214
2526	In general, you cannot use an C<ev_loop> from multiple threads or other	3215	In general, you cannot use an C<ev_run> from multiple threads or other
2527	asynchronous sources such as signal handlers (as opposed to multiple event	3216	asynchronous sources such as signal handlers (as opposed to multiple event
2528	loops - those are of course safe to use in different threads).	3217	loops - those are of course safe to use in different threads).
2529		3218
2530	Sometimes, however, you need to wake up another event loop you do not	3219	Sometimes, however, you need to wake up an event loop you do not control,
2531	control, for example because it belongs to another thread. This is what	3220	for example because it belongs to another thread. This is what C<ev_async>
2532	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3221	watchers do: as long as the C<ev_async> watcher is active, you can signal
2533	can signal it by calling C<ev_async_send>, which is thread- and signal	3222	it by calling C<ev_async_send>, which is thread- and signal safe.
2534	safe.
2535		3223
2536	This functionality is very similar to C<ev_signal> watchers, as signals,	3224	This functionality is very similar to C<ev_signal> watchers, as signals,
2537	too, are asynchronous in nature, and signals, too, will be compressed	3225	too, are asynchronous in nature, and signals, too, will be compressed
2538	(i.e. the number of callback invocations may be less than the number of	3226	(i.e. the number of callback invocations may be less than the number of
2539	C<ev_async_sent> calls).	3227	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
		3228	of "global async watchers" by using a watcher on an otherwise unused
		3229	signal, and C<ev_feed_signal> to signal this watcher from another thread,
		3230	even without knowing which loop owns the signal.
2540		3231
2541	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3232	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
2542	just the default loop.	3233	just the default loop.
2543		3234
2544	=head3 Queueing	3235	=head3 Queueing
2545		3236
2546	C<ev_async> does not support queueing of data in any way. The reason	3237	C<ev_async> does not support queueing of data in any way. The reason
2547	is that the author does not know of a simple (or any) algorithm for a	3238	is that the author does not know of a simple (or any) algorithm for a
2548	multiple-writer-single-reader queue that works in all cases and doesn't	3239	multiple-writer-single-reader queue that works in all cases and doesn't
2549	need elaborate support such as pthreads.	3240	need elaborate support such as pthreads or unportable memory access
		3241	semantics.
2550		3242
2551	That means that if you want to queue data, you have to provide your own	3243	That means that if you want to queue data, you have to provide your own
2552	queue. But at least I can tell you how to implement locking around your	3244	queue. But at least I can tell you how to implement locking around your
2553	queue:	3245	queue:
2554		3246
…		…
2632	=over 4	3324	=over 4
2633		3325
2634	=item ev_async_init (ev_async *, callback)	3326	=item ev_async_init (ev_async *, callback)
2635		3327
2636	Initialises and configures the async watcher - it has no parameters of any	3328	Initialises and configures the async watcher - it has no parameters of any
2637	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3329	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2638	trust me.	3330	trust me.
2639		3331
2640	=item ev_async_send (loop, ev_async *)	3332	=item ev_async_send (loop, ev_async *)
2641		3333
2642	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3334	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2643	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3335	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2644	C<ev_feed_event>, this call is safe to do from other threads, signal or	3336	C<ev_feed_event>, this call is safe to do from other threads, signal or
2645	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3337	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2646	section below on what exactly this means).	3338	section below on what exactly this means).
2647		3339
		3340	Note that, as with other watchers in libev, multiple events might get
		3341	compressed into a single callback invocation (another way to look at this
		3342	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3343	reset when the event loop detects that).
		3344
2648	This call incurs the overhead of a system call only once per loop iteration,	3345	This call incurs the overhead of a system call only once per event loop
2649	so while the overhead might be noticeable, it doesn't apply to repeated	3346	iteration, so while the overhead might be noticeable, it doesn't apply to
2650	calls to C<ev_async_send>.	3347	repeated calls to C<ev_async_send> for the same event loop.
2651		3348
2652	=item bool = ev_async_pending (ev_async *)	3349	=item bool = ev_async_pending (ev_async *)
2653		3350
2654	Returns a non-zero value when C<ev_async_send> has been called on the	3351	Returns a non-zero value when C<ev_async_send> has been called on the
2655	watcher but the event has not yet been processed (or even noted) by the	3352	watcher but the event has not yet been processed (or even noted) by the
…		…
2658	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3355	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2659	the loop iterates next and checks for the watcher to have become active,	3356	the loop iterates next and checks for the watcher to have become active,
2660	it will reset the flag again. C<ev_async_pending> can be used to very	3357	it will reset the flag again. C<ev_async_pending> can be used to very
2661	quickly check whether invoking the loop might be a good idea.	3358	quickly check whether invoking the loop might be a good idea.
2662		3359
2663	Not that this does I<not> check whether the watcher itself is pending, only	3360	Not that this does I<not> check whether the watcher itself is pending,
2664	whether it has been requested to make this watcher pending.	3361	only whether it has been requested to make this watcher pending: there
		3362	is a time window between the event loop checking and resetting the async
		3363	notification, and the callback being invoked.
2665		3364
2666	=back	3365	=back
2667		3366
2668		3367
2669	=head1 OTHER FUNCTIONS	3368	=head1 OTHER FUNCTIONS
…		…
2686		3385
2687	If C<timeout> is less than 0, then no timeout watcher will be	3386	If C<timeout> is less than 0, then no timeout watcher will be
2688	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3387	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2689	repeat = 0) will be started. C<0> is a valid timeout.	3388	repeat = 0) will be started. C<0> is a valid timeout.
2690		3389
2691	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3390	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2692	passed an C<revents> set like normal event callbacks (a combination of	3391	passed an C<revents> set like normal event callbacks (a combination of
2693	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3392	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2694	value passed to C<ev_once>. Note that it is possible to receive I<both>	3393	value passed to C<ev_once>. Note that it is possible to receive I<both>
2695	a timeout and an io event at the same time - you probably should give io	3394	a timeout and an io event at the same time - you probably should give io
2696	events precedence.	3395	events precedence.
2697		3396
2698	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3397	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2699		3398
2700	static void stdin_ready (int revents, void *arg)	3399	static void stdin_ready (int revents, void *arg)
2701	{	3400	{
2702	if (revents & EV_READ)	3401	if (revents & EV_READ)
2703	/* stdin might have data for us, joy! */;	3402	/* stdin might have data for us, joy! */;
2704	else if (revents & EV_TIMEOUT)	3403	else if (revents & EV_TIMER)
2705	/* doh, nothing entered */;	3404	/* doh, nothing entered */;
2706	}	3405	}
2707		3406
2708	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3407	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2709		3408
2710	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2711
2712	Feeds the given event set into the event loop, as if the specified event
2713	had happened for the specified watcher (which must be a pointer to an
2714	initialised but not necessarily started event watcher).
2715
2716	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3409	=item ev_feed_fd_event (loop, int fd, int revents)
2717		3410
2718	Feed an event on the given fd, as if a file descriptor backend detected	3411	Feed an event on the given fd, as if a file descriptor backend detected
2719	the given events it.	3412	the given events it.
2720		3413
2721	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3414	=item ev_feed_signal_event (loop, int signum)
2722		3415
2723	Feed an event as if the given signal occurred (C<loop> must be the default	3416	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
2724	loop!).	3417	which is async-safe.
		3418
		3419	=back
		3420
		3421
		3422	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3423
		3424	This section explains some common idioms that are not immediately
		3425	obvious. Note that examples are sprinkled over the whole manual, and this
		3426	section only contains stuff that wouldn't fit anywhere else.
		3427
		3428	=over 4
		3429
		3430	=item Model/nested event loop invocations and exit conditions.
		3431
		3432	Often (especially in GUI toolkits) there are places where you have
		3433	I<modal> interaction, which is most easily implemented by recursively
		3434	invoking C<ev_run>.
		3435
		3436	This brings the problem of exiting - a callback might want to finish the
		3437	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3438	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3439	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3440	other combination: In these cases, C<ev_break> will not work alone.
		3441
		3442	The solution is to maintain "break this loop" variable for each C<ev_run>
		3443	invocation, and use a loop around C<ev_run> until the condition is
		3444	triggered, using C<EVRUN_ONCE>:
		3445
		3446	// main loop
		3447	int exit_main_loop = 0;
		3448
		3449	while (!exit_main_loop)
		3450	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3451
		3452	// in a model watcher
		3453	int exit_nested_loop = 0;
		3454
		3455	while (!exit_nested_loop)
		3456	ev_run (EV_A_ EVRUN_ONCE);
		3457
		3458	To exit from any of these loops, just set the corresponding exit variable:
		3459
		3460	// exit modal loop
		3461	exit_nested_loop = 1;
		3462
		3463	// exit main program, after modal loop is finished
		3464	exit_main_loop = 1;
		3465
		3466	// exit both
		3467	exit_main_loop = exit_nested_loop = 1;
2725		3468
2726	=back	3469	=back
2727		3470
2728		3471
2729	=head1 LIBEVENT EMULATION	3472	=head1 LIBEVENT EMULATION
2730		3473
2731	Libev offers a compatibility emulation layer for libevent. It cannot	3474	Libev offers a compatibility emulation layer for libevent. It cannot
2732	emulate the internals of libevent, so here are some usage hints:	3475	emulate the internals of libevent, so here are some usage hints:
2733		3476
2734	=over 4	3477	=over 4
		3478
		3479	=item * Only the libevent-1.4.1-beta API is being emulated.
		3480
		3481	This was the newest libevent version available when libev was implemented,
		3482	and is still mostly unchanged in 2010.
2735		3483
2736	=item * Use it by including <event.h>, as usual.	3484	=item * Use it by including <event.h>, as usual.
2737		3485
2738	=item * The following members are fully supported: ev_base, ev_callback,	3486	=item * The following members are fully supported: ev_base, ev_callback,
2739	ev_arg, ev_fd, ev_res, ev_events.	3487	ev_arg, ev_fd, ev_res, ev_events.
…		…
2745	=item * Priorities are not currently supported. Initialising priorities	3493	=item * Priorities are not currently supported. Initialising priorities
2746	will fail and all watchers will have the same priority, even though there	3494	will fail and all watchers will have the same priority, even though there
2747	is an ev_pri field.	3495	is an ev_pri field.
2748		3496
2749	=item * In libevent, the last base created gets the signals, in libev, the	3497	=item * In libevent, the last base created gets the signals, in libev, the
2750	first base created (== the default loop) gets the signals.	3498	base that registered the signal gets the signals.
2751		3499
2752	=item * Other members are not supported.	3500	=item * Other members are not supported.
2753		3501
2754	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3502	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2755	to use the libev header file and library.	3503	to use the libev header file and library.
…		…
2774	Care has been taken to keep the overhead low. The only data member the C++	3522	Care has been taken to keep the overhead low. The only data member the C++
2775	classes add (compared to plain C-style watchers) is the event loop pointer	3523	classes add (compared to plain C-style watchers) is the event loop pointer
2776	that the watcher is associated with (or no additional members at all if	3524	that the watcher is associated with (or no additional members at all if
2777	you disable C<EV_MULTIPLICITY> when embedding libev).	3525	you disable C<EV_MULTIPLICITY> when embedding libev).
2778		3526
2779	Currently, functions, and static and non-static member functions can be	3527	Currently, functions, static and non-static member functions and classes
2780	used as callbacks. Other types should be easy to add as long as they only	3528	with C<operator ()> can be used as callbacks. Other types should be easy
2781	need one additional pointer for context. If you need support for other	3529	to add as long as they only need one additional pointer for context. If
2782	types of functors please contact the author (preferably after implementing	3530	you need support for other types of functors please contact the author
2783	it).	3531	(preferably after implementing it).
2784		3532
2785	Here is a list of things available in the C<ev> namespace:	3533	Here is a list of things available in the C<ev> namespace:
2786		3534
2787	=over 4	3535	=over 4
2788		3536
…		…
2806		3554
2807	=over 4	3555	=over 4
2808		3556
2809	=item ev::TYPE::TYPE ()	3557	=item ev::TYPE::TYPE ()
2810		3558
2811	=item ev::TYPE::TYPE (struct ev_loop *)	3559	=item ev::TYPE::TYPE (loop)
2812		3560
2813	=item ev::TYPE::~TYPE	3561	=item ev::TYPE::~TYPE
2814		3562
2815	The constructor (optionally) takes an event loop to associate the watcher	3563	The constructor (optionally) takes an event loop to associate the watcher
2816	with. If it is omitted, it will use C<EV_DEFAULT>.	3564	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2848		3596
2849	myclass obj;	3597	myclass obj;
2850	ev::io iow;	3598	ev::io iow;
2851	iow.set <myclass, &myclass::io_cb> (&obj);	3599	iow.set <myclass, &myclass::io_cb> (&obj);
2852		3600
		3601	=item w->set (object *)
		3602
		3603	This is a variation of a method callback - leaving out the method to call
		3604	will default the method to C<operator ()>, which makes it possible to use
		3605	functor objects without having to manually specify the C<operator ()> all
		3606	the time. Incidentally, you can then also leave out the template argument
		3607	list.
		3608
		3609	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3610	int revents)>.
		3611
		3612	See the method-C<set> above for more details.
		3613
		3614	Example: use a functor object as callback.
		3615
		3616	struct myfunctor
		3617	{
		3618	void operator() (ev::io &w, int revents)
		3619	{
		3620	...
		3621	}
		3622	}
		3623
		3624	myfunctor f;
		3625
		3626	ev::io w;
		3627	w.set (&f);
		3628
2853	=item w->set<function> (void *data = 0)	3629	=item w->set<function> (void *data = 0)
2854		3630
2855	Also sets a callback, but uses a static method or plain function as	3631	Also sets a callback, but uses a static method or plain function as
2856	callback. The optional C<data> argument will be stored in the watcher's	3632	callback. The optional C<data> argument will be stored in the watcher's
2857	C<data> member and is free for you to use.	3633	C<data> member and is free for you to use.
…		…
2863	Example: Use a plain function as callback.	3639	Example: Use a plain function as callback.
2864		3640
2865	static void io_cb (ev::io &w, int revents) { }	3641	static void io_cb (ev::io &w, int revents) { }
2866	iow.set <io_cb> ();	3642	iow.set <io_cb> ();
2867		3643
2868	=item w->set (struct ev_loop *)	3644	=item w->set (loop)
2869		3645
2870	Associates a different C<struct ev_loop> with this watcher. You can only	3646	Associates a different C<struct ev_loop> with this watcher. You can only
2871	do this when the watcher is inactive (and not pending either).	3647	do this when the watcher is inactive (and not pending either).
2872		3648
2873	=item w->set ([arguments])	3649	=item w->set ([arguments])
2874		3650
2875	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3651	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
2876	called at least once. Unlike the C counterpart, an active watcher gets	3652	method or a suitable start method must be called at least once. Unlike the
2877	automatically stopped and restarted when reconfiguring it with this	3653	C counterpart, an active watcher gets automatically stopped and restarted
2878	method.	3654	when reconfiguring it with this method.
2879		3655
2880	=item w->start ()	3656	=item w->start ()
2881		3657
2882	Starts the watcher. Note that there is no C<loop> argument, as the	3658	Starts the watcher. Note that there is no C<loop> argument, as the
2883	constructor already stores the event loop.	3659	constructor already stores the event loop.
2884		3660
		3661	=item w->start ([arguments])
		3662
		3663	Instead of calling C<set> and C<start> methods separately, it is often
		3664	convenient to wrap them in one call. Uses the same type of arguments as
		3665	the configure C<set> method of the watcher.
		3666
2885	=item w->stop ()	3667	=item w->stop ()
2886		3668
2887	Stops the watcher if it is active. Again, no C<loop> argument.	3669	Stops the watcher if it is active. Again, no C<loop> argument.
2888		3670
2889	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3671	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2901		3683
2902	=back	3684	=back
2903		3685
2904	=back	3686	=back
2905		3687
2906	Example: Define a class with an IO and idle watcher, start one of them in	3688	Example: Define a class with two I/O and idle watchers, start the I/O
2907	the constructor.	3689	watchers in the constructor.
2908		3690
2909	class myclass	3691	class myclass
2910	{	3692	{
2911	ev::io io ; void io_cb (ev::io &w, int revents);	3693	ev::io io ; void io_cb (ev::io &w, int revents);
		3694	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
2912	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3695	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2913		3696
2914	myclass (int fd)	3697	myclass (int fd)
2915	{	3698	{
2916	io .set <myclass, &myclass::io_cb > (this);	3699	io .set <myclass, &myclass::io_cb > (this);
		3700	io2 .set <myclass, &myclass::io2_cb > (this);
2917	idle.set <myclass, &myclass::idle_cb> (this);	3701	idle.set <myclass, &myclass::idle_cb> (this);
2918		3702
2919	io.start (fd, ev::READ);	3703	io.set (fd, ev::WRITE); // configure the watcher
		3704	io.start (); // start it whenever convenient
		3705
		3706	io2.start (fd, ev::READ); // set + start in one call
2920	}	3707	}
2921	};	3708	};
2922		3709
2923		3710
2924	=head1 OTHER LANGUAGE BINDINGS	3711	=head1 OTHER LANGUAGE BINDINGS
…		…
2943	L<http://software.schmorp.de/pkg/EV>.	3730	L<http://software.schmorp.de/pkg/EV>.
2944		3731
2945	=item Python	3732	=item Python
2946		3733
2947	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3734	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2948	seems to be quite complete and well-documented. Note, however, that the	3735	seems to be quite complete and well-documented.
2949	patch they require for libev is outright dangerous as it breaks the ABI
2950	for everybody else, and therefore, should never be applied in an installed
2951	libev (if python requires an incompatible ABI then it needs to embed
2952	libev).
2953		3736
2954	=item Ruby	3737	=item Ruby
2955		3738
2956	Tony Arcieri has written a ruby extension that offers access to a subset	3739	Tony Arcieri has written a ruby extension that offers access to a subset
2957	of the libev API and adds file handle abstractions, asynchronous DNS and	3740	of the libev API and adds file handle abstractions, asynchronous DNS and
2958	more on top of it. It can be found via gem servers. Its homepage is at	3741	more on top of it. It can be found via gem servers. Its homepage is at
2959	L<http://rev.rubyforge.org/>.	3742	L<http://rev.rubyforge.org/>.
2960		3743
		3744	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3745	makes rev work even on mingw.
		3746
		3747	=item Haskell
		3748
		3749	A haskell binding to libev is available at
		3750	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3751
2961	=item D	3752	=item D
2962		3753
2963	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3754	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2964	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3755	be found at L<http://proj.llucax.com.ar/wiki/evd>.
2965		3756
2966	=item Ocaml	3757	=item Ocaml
2967		3758
2968	Erkki Seppala has written Ocaml bindings for libev, to be found at	3759	Erkki Seppala has written Ocaml bindings for libev, to be found at
2969	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	3760	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3761
		3762	=item Lua
		3763
		3764	Brian Maher has written a partial interface to libev for lua (at the
		3765	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3766	L<http://github.com/brimworks/lua-ev>.
2970		3767
2971	=back	3768	=back
2972		3769
2973		3770
2974	=head1 MACRO MAGIC	3771	=head1 MACRO MAGIC
…		…
2988	loop argument"). The C<EV_A> form is used when this is the sole argument,	3785	loop argument"). The C<EV_A> form is used when this is the sole argument,
2989	C<EV_A_> is used when other arguments are following. Example:	3786	C<EV_A_> is used when other arguments are following. Example:
2990		3787
2991	ev_unref (EV_A);	3788	ev_unref (EV_A);
2992	ev_timer_add (EV_A_ watcher);	3789	ev_timer_add (EV_A_ watcher);
2993	ev_loop (EV_A_ 0);	3790	ev_run (EV_A_ 0);
2994		3791
2995	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3792	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2996	which is often provided by the following macro.	3793	which is often provided by the following macro.
2997		3794
2998	=item C<EV_P>, C<EV_P_>	3795	=item C<EV_P>, C<EV_P_>
…		…
3038	}	3835	}
3039		3836
3040	ev_check check;	3837	ev_check check;
3041	ev_check_init (&check, check_cb);	3838	ev_check_init (&check, check_cb);
3042	ev_check_start (EV_DEFAULT_ &check);	3839	ev_check_start (EV_DEFAULT_ &check);
3043	ev_loop (EV_DEFAULT_ 0);	3840	ev_run (EV_DEFAULT_ 0);
3044		3841
3045	=head1 EMBEDDING	3842	=head1 EMBEDDING
3046		3843
3047	Libev can (and often is) directly embedded into host	3844	Libev can (and often is) directly embedded into host
3048	applications. Examples of applications that embed it include the Deliantra	3845	applications. Examples of applications that embed it include the Deliantra
…		…
3075		3872
3076	#define EV_STANDALONE 1	3873	#define EV_STANDALONE 1
3077	#include "ev.h"	3874	#include "ev.h"
3078		3875
3079	Both header files and implementation files can be compiled with a C++	3876	Both header files and implementation files can be compiled with a C++
3080	compiler (at least, thats a stated goal, and breakage will be treated	3877	compiler (at least, that's a stated goal, and breakage will be treated
3081	as a bug).	3878	as a bug).
3082		3879
3083	You need the following files in your source tree, or in a directory	3880	You need the following files in your source tree, or in a directory
3084	in your include path (e.g. in libev/ when using -Ilibev):	3881	in your include path (e.g. in libev/ when using -Ilibev):
3085		3882
…		…
3128	libev.m4	3925	libev.m4
3129		3926
3130	=head2 PREPROCESSOR SYMBOLS/MACROS	3927	=head2 PREPROCESSOR SYMBOLS/MACROS
3131		3928
3132	Libev can be configured via a variety of preprocessor symbols you have to	3929	Libev can be configured via a variety of preprocessor symbols you have to
3133	define before including any of its files. The default in the absence of	3930	define before including (or compiling) any of its files. The default in
3134	autoconf is documented for every option.	3931	the absence of autoconf is documented for every option.
		3932
		3933	Symbols marked with "(h)" do not change the ABI, and can have different
		3934	values when compiling libev vs. including F<ev.h>, so it is permissible
		3935	to redefine them before including F<ev.h> without breaking compatibility
		3936	to a compiled library. All other symbols change the ABI, which means all
		3937	users of libev and the libev code itself must be compiled with compatible
		3938	settings.
3135		3939
3136	=over 4	3940	=over 4
3137		3941
		3942	=item EV_COMPAT3 (h)
		3943
		3944	Backwards compatibility is a major concern for libev. This is why this
		3945	release of libev comes with wrappers for the functions and symbols that
		3946	have been renamed between libev version 3 and 4.
		3947
		3948	You can disable these wrappers (to test compatibility with future
		3949	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		3950	sources. This has the additional advantage that you can drop the C<struct>
		3951	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		3952	typedef in that case.
		3953
		3954	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		3955	and in some even more future version the compatibility code will be
		3956	removed completely.
		3957
3138	=item EV_STANDALONE	3958	=item EV_STANDALONE (h)
3139		3959
3140	Must always be C<1> if you do not use autoconf configuration, which	3960	Must always be C<1> if you do not use autoconf configuration, which
3141	keeps libev from including F<config.h>, and it also defines dummy	3961	keeps libev from including F<config.h>, and it also defines dummy
3142	implementations for some libevent functions (such as logging, which is not	3962	implementations for some libevent functions (such as logging, which is not
3143	supported). It will also not define any of the structs usually found in	3963	supported). It will also not define any of the structs usually found in
3144	F<event.h> that are not directly supported by the libev core alone.	3964	F<event.h> that are not directly supported by the libev core alone.
3145		3965
		3966	In standalone mode, libev will still try to automatically deduce the
		3967	configuration, but has to be more conservative.
		3968
3146	=item EV_USE_MONOTONIC	3969	=item EV_USE_MONOTONIC
3147		3970
3148	If defined to be C<1>, libev will try to detect the availability of the	3971	If defined to be C<1>, libev will try to detect the availability of the
3149	monotonic clock option at both compile time and runtime. Otherwise no use	3972	monotonic clock option at both compile time and runtime. Otherwise no
3150	of the monotonic clock option will be attempted. If you enable this, you	3973	use of the monotonic clock option will be attempted. If you enable this,
3151	usually have to link against librt or something similar. Enabling it when	3974	you usually have to link against librt or something similar. Enabling it
3152	the functionality isn't available is safe, though, although you have	3975	when the functionality isn't available is safe, though, although you have
3153	to make sure you link against any libraries where the C<clock_gettime>	3976	to make sure you link against any libraries where the C<clock_gettime>
3154	function is hiding in (often F<-lrt>).	3977	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
3155		3978
3156	=item EV_USE_REALTIME	3979	=item EV_USE_REALTIME
3157		3980
3158	If defined to be C<1>, libev will try to detect the availability of the	3981	If defined to be C<1>, libev will try to detect the availability of the
3159	real-time clock option at compile time (and assume its availability at	3982	real-time clock option at compile time (and assume its availability
3160	runtime if successful). Otherwise no use of the real-time clock option will	3983	at runtime if successful). Otherwise no use of the real-time clock
3161	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3984	option will be attempted. This effectively replaces C<gettimeofday>
3162	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3985	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
3163	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3986	correctness. See the note about libraries in the description of
		3987	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3988	C<EV_USE_CLOCK_SYSCALL>.
		3989
		3990	=item EV_USE_CLOCK_SYSCALL
		3991
		3992	If defined to be C<1>, libev will try to use a direct syscall instead
		3993	of calling the system-provided C<clock_gettime> function. This option
		3994	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3995	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3996	programs needlessly. Using a direct syscall is slightly slower (in
		3997	theory), because no optimised vdso implementation can be used, but avoids
		3998	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3999	higher, as it simplifies linking (no need for C<-lrt>).
3164		4000
3165	=item EV_USE_NANOSLEEP	4001	=item EV_USE_NANOSLEEP
3166		4002
3167	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	4003	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
3168	and will use it for delays. Otherwise it will use C<select ()>.	4004	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3184		4020
3185	=item EV_SELECT_USE_FD_SET	4021	=item EV_SELECT_USE_FD_SET
3186		4022
3187	If defined to C<1>, then the select backend will use the system C<fd_set>	4023	If defined to C<1>, then the select backend will use the system C<fd_set>
3188	structure. This is useful if libev doesn't compile due to a missing	4024	structure. This is useful if libev doesn't compile due to a missing
3189	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	4025	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3190	exotic systems. This usually limits the range of file descriptors to some	4026	on exotic systems. This usually limits the range of file descriptors to
3191	low limit such as 1024 or might have other limitations (winsocket only	4027	some low limit such as 1024 or might have other limitations (winsocket
3192	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	4028	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3193	influence the size of the C<fd_set> used.	4029	configures the maximum size of the C<fd_set>.
3194		4030
3195	=item EV_SELECT_IS_WINSOCKET	4031	=item EV_SELECT_IS_WINSOCKET
3196		4032
3197	When defined to C<1>, the select backend will assume that	4033	When defined to C<1>, the select backend will assume that
3198	select/socket/connect etc. don't understand file descriptors but	4034	select/socket/connect etc. don't understand file descriptors but
…		…
3200	be used is the winsock select). This means that it will call	4036	be used is the winsock select). This means that it will call
3201	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4037	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3202	it is assumed that all these functions actually work on fds, even	4038	it is assumed that all these functions actually work on fds, even
3203	on win32. Should not be defined on non-win32 platforms.	4039	on win32. Should not be defined on non-win32 platforms.
3204		4040
3205	=item EV_FD_TO_WIN32_HANDLE	4041	=item EV_FD_TO_WIN32_HANDLE(fd)
3206		4042
3207	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4043	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3208	file descriptors to socket handles. When not defining this symbol (the	4044	file descriptors to socket handles. When not defining this symbol (the
3209	default), then libev will call C<_get_osfhandle>, which is usually	4045	default), then libev will call C<_get_osfhandle>, which is usually
3210	correct. In some cases, programs use their own file descriptor management,	4046	correct. In some cases, programs use their own file descriptor management,
3211	in which case they can provide this function to map fds to socket handles.	4047	in which case they can provide this function to map fds to socket handles.
		4048
		4049	=item EV_WIN32_HANDLE_TO_FD(handle)
		4050
		4051	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4052	using the standard C<_open_osfhandle> function. For programs implementing
		4053	their own fd to handle mapping, overwriting this function makes it easier
		4054	to do so. This can be done by defining this macro to an appropriate value.
		4055
		4056	=item EV_WIN32_CLOSE_FD(fd)
		4057
		4058	If programs implement their own fd to handle mapping on win32, then this
		4059	macro can be used to override the C<close> function, useful to unregister
		4060	file descriptors again. Note that the replacement function has to close
		4061	the underlying OS handle.
3212		4062
3213	=item EV_USE_POLL	4063	=item EV_USE_POLL
3214		4064
3215	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4065	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3216	backend. Otherwise it will be enabled on non-win32 platforms. It	4066	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3263	as well as for signal and thread safety in C<ev_async> watchers.	4113	as well as for signal and thread safety in C<ev_async> watchers.
3264		4114
3265	In the absence of this define, libev will use C<sig_atomic_t volatile>	4115	In the absence of this define, libev will use C<sig_atomic_t volatile>
3266	(from F<signal.h>), which is usually good enough on most platforms.	4116	(from F<signal.h>), which is usually good enough on most platforms.
3267		4117
3268	=item EV_H	4118	=item EV_H (h)
3269		4119
3270	The name of the F<ev.h> header file used to include it. The default if	4120	The name of the F<ev.h> header file used to include it. The default if
3271	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4121	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3272	used to virtually rename the F<ev.h> header file in case of conflicts.	4122	used to virtually rename the F<ev.h> header file in case of conflicts.
3273		4123
3274	=item EV_CONFIG_H	4124	=item EV_CONFIG_H (h)
3275		4125
3276	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4126	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3277	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4127	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3278	C<EV_H>, above.	4128	C<EV_H>, above.
3279		4129
3280	=item EV_EVENT_H	4130	=item EV_EVENT_H (h)
3281		4131
3282	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4132	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3283	of how the F<event.h> header can be found, the default is C<"event.h">.	4133	of how the F<event.h> header can be found, the default is C<"event.h">.
3284		4134
3285	=item EV_PROTOTYPES	4135	=item EV_PROTOTYPES (h)
3286		4136
3287	If defined to be C<0>, then F<ev.h> will not define any function	4137	If defined to be C<0>, then F<ev.h> will not define any function
3288	prototypes, but still define all the structs and other symbols. This is	4138	prototypes, but still define all the structs and other symbols. This is
3289	occasionally useful if you want to provide your own wrapper functions	4139	occasionally useful if you want to provide your own wrapper functions
3290	around libev functions.	4140	around libev functions.
…		…
3312	fine.	4162	fine.
3313		4163
3314	If your embedding application does not need any priorities, defining these	4164	If your embedding application does not need any priorities, defining these
3315	both to C<0> will save some memory and CPU.	4165	both to C<0> will save some memory and CPU.
3316		4166
3317	=item EV_PERIODIC_ENABLE	4167	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4168	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4169	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3318		4170
3319	If undefined or defined to be C<1>, then periodic timers are supported. If	4171	If undefined or defined to be C<1> (and the platform supports it), then
3320	defined to be C<0>, then they are not. Disabling them saves a few kB of	4172	the respective watcher type is supported. If defined to be C<0>, then it
3321	code.	4173	is not. Disabling watcher types mainly saves code size.
3322		4174
3323	=item EV_IDLE_ENABLE	4175	=item EV_FEATURES
3324
3325	If undefined or defined to be C<1>, then idle watchers are supported. If
3326	defined to be C<0>, then they are not. Disabling them saves a few kB of
3327	code.
3328
3329	=item EV_EMBED_ENABLE
3330
3331	If undefined or defined to be C<1>, then embed watchers are supported. If
3332	defined to be C<0>, then they are not. Embed watchers rely on most other
3333	watcher types, which therefore must not be disabled.
3334
3335	=item EV_STAT_ENABLE
3336
3337	If undefined or defined to be C<1>, then stat watchers are supported. If
3338	defined to be C<0>, then they are not.
3339
3340	=item EV_FORK_ENABLE
3341
3342	If undefined or defined to be C<1>, then fork watchers are supported. If
3343	defined to be C<0>, then they are not.
3344
3345	=item EV_ASYNC_ENABLE
3346
3347	If undefined or defined to be C<1>, then async watchers are supported. If
3348	defined to be C<0>, then they are not.
3349
3350	=item EV_MINIMAL
3351		4176
3352	If you need to shave off some kilobytes of code at the expense of some	4177	If you need to shave off some kilobytes of code at the expense of some
3353	speed, define this symbol to C<1>. Currently this is used to override some	4178	speed (but with the full API), you can define this symbol to request
3354	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4179	certain subsets of functionality. The default is to enable all features
3355	much smaller 2-heap for timer management over the default 4-heap.	4180	that can be enabled on the platform.
		4181
		4182	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4183	with some broad features you want) and then selectively re-enable
		4184	additional parts you want, for example if you want everything minimal,
		4185	but multiple event loop support, async and child watchers and the poll
		4186	backend, use this:
		4187
		4188	#define EV_FEATURES 0
		4189	#define EV_MULTIPLICITY 1
		4190	#define EV_USE_POLL 1
		4191	#define EV_CHILD_ENABLE 1
		4192	#define EV_ASYNC_ENABLE 1
		4193
		4194	The actual value is a bitset, it can be a combination of the following
		4195	values:
		4196
		4197	=over 4
		4198
		4199	=item C<1> - faster/larger code
		4200
		4201	Use larger code to speed up some operations.
		4202
		4203	Currently this is used to override some inlining decisions (enlarging the
		4204	code size by roughly 30% on amd64).
		4205
		4206	When optimising for size, use of compiler flags such as C<-Os> with
		4207	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4208	assertions.
		4209
		4210	=item C<2> - faster/larger data structures
		4211
		4212	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4213	hash table sizes and so on. This will usually further increase code size
		4214	and can additionally have an effect on the size of data structures at
		4215	runtime.
		4216
		4217	=item C<4> - full API configuration
		4218
		4219	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4220	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4221
		4222	=item C<8> - full API
		4223
		4224	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4225	details on which parts of the API are still available without this
		4226	feature, and do not complain if this subset changes over time.
		4227
		4228	=item C<16> - enable all optional watcher types
		4229
		4230	Enables all optional watcher types. If you want to selectively enable
		4231	only some watcher types other than I/O and timers (e.g. prepare,
		4232	embed, async, child...) you can enable them manually by defining
		4233	C<EV_watchertype_ENABLE> to C<1> instead.
		4234
		4235	=item C<32> - enable all backends
		4236
		4237	This enables all backends - without this feature, you need to enable at
		4238	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4239
		4240	=item C<64> - enable OS-specific "helper" APIs
		4241
		4242	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4243	default.
		4244
		4245	=back
		4246
		4247	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4248	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4249	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4250	watchers, timers and monotonic clock support.
		4251
		4252	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4253	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4254	your program might be left out as well - a binary starting a timer and an
		4255	I/O watcher then might come out at only 5Kb.
		4256
		4257	=item EV_AVOID_STDIO
		4258
		4259	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4260	functions (printf, scanf, perror etc.). This will increase the code size
		4261	somewhat, but if your program doesn't otherwise depend on stdio and your
		4262	libc allows it, this avoids linking in the stdio library which is quite
		4263	big.
		4264
		4265	Note that error messages might become less precise when this option is
		4266	enabled.
		4267
		4268	=item EV_NSIG
		4269
		4270	The highest supported signal number, +1 (or, the number of
		4271	signals): Normally, libev tries to deduce the maximum number of signals
		4272	automatically, but sometimes this fails, in which case it can be
		4273	specified. Also, using a lower number than detected (C<32> should be
		4274	good for about any system in existence) can save some memory, as libev
		4275	statically allocates some 12-24 bytes per signal number.
3356		4276
3357	=item EV_PID_HASHSIZE	4277	=item EV_PID_HASHSIZE
3358		4278
3359	C<ev_child> watchers use a small hash table to distribute workload by	4279	C<ev_child> watchers use a small hash table to distribute workload by
3360	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4280	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3361	than enough. If you need to manage thousands of children you might want to	4281	usually more than enough. If you need to manage thousands of children you
3362	increase this value (I<must> be a power of two).	4282	might want to increase this value (I<must> be a power of two).
3363		4283
3364	=item EV_INOTIFY_HASHSIZE	4284	=item EV_INOTIFY_HASHSIZE
3365		4285
3366	C<ev_stat> watchers use a small hash table to distribute workload by	4286	C<ev_stat> watchers use a small hash table to distribute workload by
3367	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4287	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3368	usually more than enough. If you need to manage thousands of C<ev_stat>	4288	disabled), usually more than enough. If you need to manage thousands of
3369	watchers you might want to increase this value (I<must> be a power of	4289	C<ev_stat> watchers you might want to increase this value (I<must> be a
3370	two).	4290	power of two).
3371		4291
3372	=item EV_USE_4HEAP	4292	=item EV_USE_4HEAP
3373		4293
3374	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4294	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3375	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4295	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3376	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4296	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3377	faster performance with many (thousands) of watchers.	4297	faster performance with many (thousands) of watchers.
3378		4298
3379	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4299	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3380	(disabled).	4300	will be C<0>.
3381		4301
3382	=item EV_HEAP_CACHE_AT	4302	=item EV_HEAP_CACHE_AT
3383		4303
3384	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4304	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3385	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4305	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3386	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4306	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3387	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4307	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3388	but avoids random read accesses on heap changes. This improves performance	4308	but avoids random read accesses on heap changes. This improves performance
3389	noticeably with many (hundreds) of watchers.	4309	noticeably with many (hundreds) of watchers.
3390		4310
3391	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4311	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3392	(disabled).	4312	will be C<0>.
3393		4313
3394	=item EV_VERIFY	4314	=item EV_VERIFY
3395		4315
3396	Controls how much internal verification (see C<ev_loop_verify ()>) will	4316	Controls how much internal verification (see C<ev_verify ()>) will
3397	be done: If set to C<0>, no internal verification code will be compiled	4317	be done: If set to C<0>, no internal verification code will be compiled
3398	in. If set to C<1>, then verification code will be compiled in, but not	4318	in. If set to C<1>, then verification code will be compiled in, but not
3399	called. If set to C<2>, then the internal verification code will be	4319	called. If set to C<2>, then the internal verification code will be
3400	called once per loop, which can slow down libev. If set to C<3>, then the	4320	called once per loop, which can slow down libev. If set to C<3>, then the
3401	verification code will be called very frequently, which will slow down	4321	verification code will be called very frequently, which will slow down
3402	libev considerably.	4322	libev considerably.
3403		4323
3404	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4324	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3405	C<0>.	4325	will be C<0>.
3406		4326
3407	=item EV_COMMON	4327	=item EV_COMMON
3408		4328
3409	By default, all watchers have a C<void *data> member. By redefining	4329	By default, all watchers have a C<void *data> member. By redefining
3410	this macro to a something else you can include more and other types of	4330	this macro to something else you can include more and other types of
3411	members. You have to define it each time you include one of the files,	4331	members. You have to define it each time you include one of the files,
3412	though, and it must be identical each time.	4332	though, and it must be identical each time.
3413		4333
3414	For example, the perl EV module uses something like this:	4334	For example, the perl EV module uses something like this:
3415		4335
…		…
3468	file.	4388	file.
3469		4389
3470	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4390	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3471	that everybody includes and which overrides some configure choices:	4391	that everybody includes and which overrides some configure choices:
3472		4392
3473	#define EV_MINIMAL 1	4393	#define EV_FEATURES 8
3474	#define EV_USE_POLL 0	4394	#define EV_USE_SELECT 1
3475	#define EV_MULTIPLICITY 0
3476	#define EV_PERIODIC_ENABLE 0	4395	#define EV_PREPARE_ENABLE 1
		4396	#define EV_IDLE_ENABLE 1
3477	#define EV_STAT_ENABLE 0	4397	#define EV_SIGNAL_ENABLE 1
3478	#define EV_FORK_ENABLE 0	4398	#define EV_CHILD_ENABLE 1
		4399	#define EV_USE_STDEXCEPT 0
3479	#define EV_CONFIG_H <config.h>	4400	#define EV_CONFIG_H <config.h>
3480	#define EV_MINPRI 0
3481	#define EV_MAXPRI 0
3482		4401
3483	#include "ev++.h"	4402	#include "ev++.h"
3484		4403
3485	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4404	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3486		4405
…		…
3546	default loop and triggering an C<ev_async> watcher from the default loop	4465	default loop and triggering an C<ev_async> watcher from the default loop
3547	watcher callback into the event loop interested in the signal.	4466	watcher callback into the event loop interested in the signal.
3548		4467
3549	=back	4468	=back
3550		4469
		4470	=head4 THREAD LOCKING EXAMPLE
		4471
		4472	Here is a fictitious example of how to run an event loop in a different
		4473	thread than where callbacks are being invoked and watchers are
		4474	created/added/removed.
		4475
		4476	For a real-world example, see the C<EV::Loop::Async> perl module,
		4477	which uses exactly this technique (which is suited for many high-level
		4478	languages).
		4479
		4480	The example uses a pthread mutex to protect the loop data, a condition
		4481	variable to wait for callback invocations, an async watcher to notify the
		4482	event loop thread and an unspecified mechanism to wake up the main thread.
		4483
		4484	First, you need to associate some data with the event loop:
		4485
		4486	typedef struct {
		4487	mutex_t lock; /* global loop lock */
		4488	ev_async async_w;
		4489	thread_t tid;
		4490	cond_t invoke_cv;
		4491	} userdata;
		4492
		4493	void prepare_loop (EV_P)
		4494	{
		4495	// for simplicity, we use a static userdata struct.
		4496	static userdata u;
		4497
		4498	ev_async_init (&u->async_w, async_cb);
		4499	ev_async_start (EV_A_ &u->async_w);
		4500
		4501	pthread_mutex_init (&u->lock, 0);
		4502	pthread_cond_init (&u->invoke_cv, 0);
		4503
		4504	// now associate this with the loop
		4505	ev_set_userdata (EV_A_ u);
		4506	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4507	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4508
		4509	// then create the thread running ev_loop
		4510	pthread_create (&u->tid, 0, l_run, EV_A);
		4511	}
		4512
		4513	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4514	solely to wake up the event loop so it takes notice of any new watchers
		4515	that might have been added:
		4516
		4517	static void
		4518	async_cb (EV_P_ ev_async *w, int revents)
		4519	{
		4520	// just used for the side effects
		4521	}
		4522
		4523	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4524	protecting the loop data, respectively.
		4525
		4526	static void
		4527	l_release (EV_P)
		4528	{
		4529	userdata *u = ev_userdata (EV_A);
		4530	pthread_mutex_unlock (&u->lock);
		4531	}
		4532
		4533	static void
		4534	l_acquire (EV_P)
		4535	{
		4536	userdata *u = ev_userdata (EV_A);
		4537	pthread_mutex_lock (&u->lock);
		4538	}
		4539
		4540	The event loop thread first acquires the mutex, and then jumps straight
		4541	into C<ev_run>:
		4542
		4543	void *
		4544	l_run (void *thr_arg)
		4545	{
		4546	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4547
		4548	l_acquire (EV_A);
		4549	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4550	ev_run (EV_A_ 0);
		4551	l_release (EV_A);
		4552
		4553	return 0;
		4554	}
		4555
		4556	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4557	signal the main thread via some unspecified mechanism (signals? pipe
		4558	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4559	have been called (in a while loop because a) spurious wakeups are possible
		4560	and b) skipping inter-thread-communication when there are no pending
		4561	watchers is very beneficial):
		4562
		4563	static void
		4564	l_invoke (EV_P)
		4565	{
		4566	userdata *u = ev_userdata (EV_A);
		4567
		4568	while (ev_pending_count (EV_A))
		4569	{
		4570	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4571	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4572	}
		4573	}
		4574
		4575	Now, whenever the main thread gets told to invoke pending watchers, it
		4576	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4577	thread to continue:
		4578
		4579	static void
		4580	real_invoke_pending (EV_P)
		4581	{
		4582	userdata *u = ev_userdata (EV_A);
		4583
		4584	pthread_mutex_lock (&u->lock);
		4585	ev_invoke_pending (EV_A);
		4586	pthread_cond_signal (&u->invoke_cv);
		4587	pthread_mutex_unlock (&u->lock);
		4588	}
		4589
		4590	Whenever you want to start/stop a watcher or do other modifications to an
		4591	event loop, you will now have to lock:
		4592
		4593	ev_timer timeout_watcher;
		4594	userdata *u = ev_userdata (EV_A);
		4595
		4596	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4597
		4598	pthread_mutex_lock (&u->lock);
		4599	ev_timer_start (EV_A_ &timeout_watcher);
		4600	ev_async_send (EV_A_ &u->async_w);
		4601	pthread_mutex_unlock (&u->lock);
		4602
		4603	Note that sending the C<ev_async> watcher is required because otherwise
		4604	an event loop currently blocking in the kernel will have no knowledge
		4605	about the newly added timer. By waking up the loop it will pick up any new
		4606	watchers in the next event loop iteration.
		4607
3551	=head3 COROUTINES	4608	=head3 COROUTINES
3552		4609
3553	Libev is very accommodating to coroutines ("cooperative threads"):	4610	Libev is very accommodating to coroutines ("cooperative threads"):
3554	libev fully supports nesting calls to its functions from different	4611	libev fully supports nesting calls to its functions from different
3555	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4612	coroutines (e.g. you can call C<ev_run> on the same loop from two
3556	different coroutines, and switch freely between both coroutines running the	4613	different coroutines, and switch freely between both coroutines running
3557	loop, as long as you don't confuse yourself). The only exception is that	4614	the loop, as long as you don't confuse yourself). The only exception is
3558	you must not do this from C<ev_periodic> reschedule callbacks.	4615	that you must not do this from C<ev_periodic> reschedule callbacks.
3559		4616
3560	Care has been taken to ensure that libev does not keep local state inside	4617	Care has been taken to ensure that libev does not keep local state inside
3561	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4618	C<ev_run>, and other calls do not usually allow for coroutine switches as
3562	they do not clal any callbacks.	4619	they do not call any callbacks.
3563		4620
3564	=head2 COMPILER WARNINGS	4621	=head2 COMPILER WARNINGS
3565		4622
3566	Depending on your compiler and compiler settings, you might get no or a	4623	Depending on your compiler and compiler settings, you might get no or a
3567	lot of warnings when compiling libev code. Some people are apparently	4624	lot of warnings when compiling libev code. Some people are apparently
…		…
3577	maintainable.	4634	maintainable.
3578		4635
3579	And of course, some compiler warnings are just plain stupid, or simply	4636	And of course, some compiler warnings are just plain stupid, or simply
3580	wrong (because they don't actually warn about the condition their message	4637	wrong (because they don't actually warn about the condition their message
3581	seems to warn about). For example, certain older gcc versions had some	4638	seems to warn about). For example, certain older gcc versions had some
3582	warnings that resulted an extreme number of false positives. These have	4639	warnings that resulted in an extreme number of false positives. These have
3583	been fixed, but some people still insist on making code warn-free with	4640	been fixed, but some people still insist on making code warn-free with
3584	such buggy versions.	4641	such buggy versions.
3585		4642
3586	While libev is written to generate as few warnings as possible,	4643	While libev is written to generate as few warnings as possible,
3587	"warn-free" code is not a goal, and it is recommended not to build libev	4644	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3601	==2274== definitely lost: 0 bytes in 0 blocks.	4658	==2274== definitely lost: 0 bytes in 0 blocks.
3602	==2274== possibly lost: 0 bytes in 0 blocks.	4659	==2274== possibly lost: 0 bytes in 0 blocks.
3603	==2274== still reachable: 256 bytes in 1 blocks.	4660	==2274== still reachable: 256 bytes in 1 blocks.
3604		4661
3605	Then there is no memory leak, just as memory accounted to global variables	4662	Then there is no memory leak, just as memory accounted to global variables
3606	is not a memleak - the memory is still being refernced, and didn't leak.	4663	is not a memleak - the memory is still being referenced, and didn't leak.
3607		4664
3608	Similarly, under some circumstances, valgrind might report kernel bugs	4665	Similarly, under some circumstances, valgrind might report kernel bugs
3609	as if it were a bug in libev (e.g. in realloc or in the poll backend,	4666	as if it were a bug in libev (e.g. in realloc or in the poll backend,
3610	although an acceptable workaround has been found here), or it might be	4667	although an acceptable workaround has been found here), or it might be
3611	confused.	4668	confused.
…		…
3623	I suggest using suppression lists.	4680	I suggest using suppression lists.
3624		4681
3625		4682
3626	=head1 PORTABILITY NOTES	4683	=head1 PORTABILITY NOTES
3627		4684
		4685	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4686
		4687	GNU/Linux is the only common platform that supports 64 bit file/large file
		4688	interfaces but I<disables> them by default.
		4689
		4690	That means that libev compiled in the default environment doesn't support
		4691	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4692
		4693	Unfortunately, many programs try to work around this GNU/Linux issue
		4694	by enabling the large file API, which makes them incompatible with the
		4695	standard libev compiled for their system.
		4696
		4697	Likewise, libev cannot enable the large file API itself as this would
		4698	suddenly make it incompatible to the default compile time environment,
		4699	i.e. all programs not using special compile switches.
		4700
		4701	=head2 OS/X AND DARWIN BUGS
		4702
		4703	The whole thing is a bug if you ask me - basically any system interface
		4704	you touch is broken, whether it is locales, poll, kqueue or even the
		4705	OpenGL drivers.
		4706
		4707	=head3 C<kqueue> is buggy
		4708
		4709	The kqueue syscall is broken in all known versions - most versions support
		4710	only sockets, many support pipes.
		4711
		4712	Libev tries to work around this by not using C<kqueue> by default on this
		4713	rotten platform, but of course you can still ask for it when creating a
		4714	loop - embedding a socket-only kqueue loop into a select-based one is
		4715	probably going to work well.
		4716
		4717	=head3 C<poll> is buggy
		4718
		4719	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4720	implementation by something calling C<kqueue> internally around the 10.5.6
		4721	release, so now C<kqueue> I<and> C<poll> are broken.
		4722
		4723	Libev tries to work around this by not using C<poll> by default on
		4724	this rotten platform, but of course you can still ask for it when creating
		4725	a loop.
		4726
		4727	=head3 C<select> is buggy
		4728
		4729	All that's left is C<select>, and of course Apple found a way to fuck this
		4730	one up as well: On OS/X, C<select> actively limits the number of file
		4731	descriptors you can pass in to 1024 - your program suddenly crashes when
		4732	you use more.
		4733
		4734	There is an undocumented "workaround" for this - defining
		4735	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4736	work on OS/X.
		4737
		4738	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4739
		4740	=head3 C<errno> reentrancy
		4741
		4742	The default compile environment on Solaris is unfortunately so
		4743	thread-unsafe that you can't even use components/libraries compiled
		4744	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4745	defined by default. A valid, if stupid, implementation choice.
		4746
		4747	If you want to use libev in threaded environments you have to make sure
		4748	it's compiled with C<_REENTRANT> defined.
		4749
		4750	=head3 Event port backend
		4751
		4752	The scalable event interface for Solaris is called "event
		4753	ports". Unfortunately, this mechanism is very buggy in all major
		4754	releases. If you run into high CPU usage, your program freezes or you get
		4755	a large number of spurious wakeups, make sure you have all the relevant
		4756	and latest kernel patches applied. No, I don't know which ones, but there
		4757	are multiple ones to apply, and afterwards, event ports actually work
		4758	great.
		4759
		4760	If you can't get it to work, you can try running the program by setting
		4761	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4762	C<select> backends.
		4763
		4764	=head2 AIX POLL BUG
		4765
		4766	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4767	this by trying to avoid the poll backend altogether (i.e. it's not even
		4768	compiled in), which normally isn't a big problem as C<select> works fine
		4769	with large bitsets on AIX, and AIX is dead anyway.
		4770
3628	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4771	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4772
		4773	=head3 General issues
3629		4774
3630	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4775	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3631	requires, and its I/O model is fundamentally incompatible with the POSIX	4776	requires, and its I/O model is fundamentally incompatible with the POSIX
3632	model. Libev still offers limited functionality on this platform in	4777	model. Libev still offers limited functionality on this platform in
3633	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4778	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3634	descriptors. This only applies when using Win32 natively, not when using	4779	descriptors. This only applies when using Win32 natively, not when using
3635	e.g. cygwin.	4780	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4781	as every compielr comes with a slightly differently broken/incompatible
		4782	environment.
3636		4783
3637	Lifting these limitations would basically require the full	4784	Lifting these limitations would basically require the full
3638	re-implementation of the I/O system. If you are into these kinds of	4785	re-implementation of the I/O system. If you are into this kind of thing,
3639	things, then note that glib does exactly that for you in a very portable	4786	then note that glib does exactly that for you in a very portable way (note
3640	way (note also that glib is the slowest event library known to man).	4787	also that glib is the slowest event library known to man).
3641		4788
3642	There is no supported compilation method available on windows except	4789	There is no supported compilation method available on windows except
3643	embedding it into other applications.	4790	embedding it into other applications.
		4791
		4792	Sensible signal handling is officially unsupported by Microsoft - libev
		4793	tries its best, but under most conditions, signals will simply not work.
3644		4794
3645	Not a libev limitation but worth mentioning: windows apparently doesn't	4795	Not a libev limitation but worth mentioning: windows apparently doesn't
3646	accept large writes: instead of resulting in a partial write, windows will	4796	accept large writes: instead of resulting in a partial write, windows will
3647	either accept everything or return C<ENOBUFS> if the buffer is too large,	4797	either accept everything or return C<ENOBUFS> if the buffer is too large,
3648	so make sure you only write small amounts into your sockets (less than a	4798	so make sure you only write small amounts into your sockets (less than a
…		…
3653	the abysmal performance of winsockets, using a large number of sockets	4803	the abysmal performance of winsockets, using a large number of sockets
3654	is not recommended (and not reasonable). If your program needs to use	4804	is not recommended (and not reasonable). If your program needs to use
3655	more than a hundred or so sockets, then likely it needs to use a totally	4805	more than a hundred or so sockets, then likely it needs to use a totally
3656	different implementation for windows, as libev offers the POSIX readiness	4806	different implementation for windows, as libev offers the POSIX readiness
3657	notification model, which cannot be implemented efficiently on windows	4807	notification model, which cannot be implemented efficiently on windows
3658	(Microsoft monopoly games).	4808	(due to Microsoft monopoly games).
3659		4809
3660	A typical way to use libev under windows is to embed it (see the embedding	4810	A typical way to use libev under windows is to embed it (see the embedding
3661	section for details) and use the following F<evwrap.h> header file instead	4811	section for details) and use the following F<evwrap.h> header file instead
3662	of F<ev.h>:	4812	of F<ev.h>:
3663		4813
…		…
3670	you do I<not> compile the F<ev.c> or any other embedded source files!):	4820	you do I<not> compile the F<ev.c> or any other embedded source files!):
3671		4821
3672	#include "evwrap.h"	4822	#include "evwrap.h"
3673	#include "ev.c"	4823	#include "ev.c"
3674		4824
3675	=over 4
3676
3677	=item The winsocket select function	4825	=head3 The winsocket C<select> function
3678		4826
3679	The winsocket C<select> function doesn't follow POSIX in that it	4827	The winsocket C<select> function doesn't follow POSIX in that it
3680	requires socket I<handles> and not socket I<file descriptors> (it is	4828	requires socket I<handles> and not socket I<file descriptors> (it is
3681	also extremely buggy). This makes select very inefficient, and also	4829	also extremely buggy). This makes select very inefficient, and also
3682	requires a mapping from file descriptors to socket handles (the Microsoft	4830	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3691	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4839	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3692		4840
3693	Note that winsockets handling of fd sets is O(n), so you can easily get a	4841	Note that winsockets handling of fd sets is O(n), so you can easily get a
3694	complexity in the O(n²) range when using win32.	4842	complexity in the O(n²) range when using win32.
3695		4843
3696	=item Limited number of file descriptors	4844	=head3 Limited number of file descriptors
3697		4845
3698	Windows has numerous arbitrary (and low) limits on things.	4846	Windows has numerous arbitrary (and low) limits on things.
3699		4847
3700	Early versions of winsocket's select only supported waiting for a maximum	4848	Early versions of winsocket's select only supported waiting for a maximum
3701	of C<64> handles (probably owning to the fact that all windows kernels	4849	of C<64> handles (probably owning to the fact that all windows kernels
3702	can only wait for C<64> things at the same time internally; Microsoft	4850	can only wait for C<64> things at the same time internally; Microsoft
3703	recommends spawning a chain of threads and wait for 63 handles and the	4851	recommends spawning a chain of threads and wait for 63 handles and the
3704	previous thread in each. Great).	4852	previous thread in each. Sounds great!).
3705		4853
3706	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4854	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3707	to some high number (e.g. C<2048>) before compiling the winsocket select	4855	to some high number (e.g. C<2048>) before compiling the winsocket select
3708	call (which might be in libev or elsewhere, for example, perl does its own	4856	call (which might be in libev or elsewhere, for example, perl and many
3709	select emulation on windows).	4857	other interpreters do their own select emulation on windows).
3710		4858
3711	Another limit is the number of file descriptors in the Microsoft runtime	4859	Another limit is the number of file descriptors in the Microsoft runtime
3712	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4860	libraries, which by default is C<64> (there must be a hidden I<64>
3713	or something like this inside Microsoft). You can increase this by calling	4861	fetish or something like this inside Microsoft). You can increase this
3714	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4862	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3715	arbitrary limit), but is broken in many versions of the Microsoft runtime	4863	(another arbitrary limit), but is broken in many versions of the Microsoft
3716	libraries.
3717
3718	This might get you to about C<512> or C<2048> sockets (depending on	4864	runtime libraries. This might get you to about C<512> or C<2048> sockets
3719	windows version and/or the phase of the moon). To get more, you need to	4865	(depending on windows version and/or the phase of the moon). To get more,
3720	wrap all I/O functions and provide your own fd management, but the cost of	4866	you need to wrap all I/O functions and provide your own fd management, but
3721	calling select (O(n²)) will likely make this unworkable.	4867	the cost of calling select (O(n²)) will likely make this unworkable.
3722
3723	=back
3724		4868
3725	=head2 PORTABILITY REQUIREMENTS	4869	=head2 PORTABILITY REQUIREMENTS
3726		4870
3727	In addition to a working ISO-C implementation and of course the	4871	In addition to a working ISO-C implementation and of course the
3728	backend-specific APIs, libev relies on a few additional extensions:	4872	backend-specific APIs, libev relies on a few additional extensions:
…		…
3735	Libev assumes not only that all watcher pointers have the same internal	4879	Libev assumes not only that all watcher pointers have the same internal
3736	structure (guaranteed by POSIX but not by ISO C for example), but it also	4880	structure (guaranteed by POSIX but not by ISO C for example), but it also
3737	assumes that the same (machine) code can be used to call any watcher	4881	assumes that the same (machine) code can be used to call any watcher
3738	callback: The watcher callbacks have different type signatures, but libev	4882	callback: The watcher callbacks have different type signatures, but libev
3739	calls them using an C<ev_watcher *> internally.	4883	calls them using an C<ev_watcher *> internally.
		4884
		4885	=item pointer accesses must be thread-atomic
		4886
		4887	Accessing a pointer value must be atomic, it must both be readable and
		4888	writable in one piece - this is the case on all current architectures.
3740		4889
3741	=item C<sig_atomic_t volatile> must be thread-atomic as well	4890	=item C<sig_atomic_t volatile> must be thread-atomic as well
3742		4891
3743	The type C<sig_atomic_t volatile> (or whatever is defined as	4892	The type C<sig_atomic_t volatile> (or whatever is defined as
3744	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	4893	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
3767	watchers.	4916	watchers.
3768		4917
3769	=item C<double> must hold a time value in seconds with enough accuracy	4918	=item C<double> must hold a time value in seconds with enough accuracy
3770		4919
3771	The type C<double> is used to represent timestamps. It is required to	4920	The type C<double> is used to represent timestamps. It is required to
3772	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4921	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3773	enough for at least into the year 4000. This requirement is fulfilled by	4922	good enough for at least into the year 4000 with millisecond accuracy
		4923	(the design goal for libev). This requirement is overfulfilled by
3774	implementations implementing IEEE 754 (basically all existing ones).	4924	implementations using IEEE 754, which is basically all existing ones. With
		4925	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
3775		4926
3776	=back	4927	=back
3777		4928
3778	If you know of other additional requirements drop me a note.	4929	If you know of other additional requirements drop me a note.
3779		4930
…		…
3847	involves iterating over all running async watchers or all signal numbers.	4998	involves iterating over all running async watchers or all signal numbers.
3848		4999
3849	=back	5000	=back
3850		5001
3851		5002
		5003	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5004
		5005	The major version 4 introduced some incompatible changes to the API.
		5006
		5007	At the moment, the C<ev.h> header file provides compatibility definitions
		5008	for all changes, so most programs should still compile. The compatibility
		5009	layer might be removed in later versions of libev, so better update to the
		5010	new API early than late.
		5011
		5012	=over 4
		5013
		5014	=item C<EV_COMPAT3> backwards compatibility mechanism
		5015
		5016	The backward compatibility mechanism can be controlled by
		5017	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5018	section.
		5019
		5020	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5021
		5022	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5023
		5024	ev_loop_destroy (EV_DEFAULT_UC);
		5025	ev_loop_fork (EV_DEFAULT);
		5026
		5027	=item function/symbol renames
		5028
		5029	A number of functions and symbols have been renamed:
		5030
		5031	ev_loop => ev_run
		5032	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5033	EVLOOP_ONESHOT => EVRUN_ONCE
		5034
		5035	ev_unloop => ev_break
		5036	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5037	EVUNLOOP_ONE => EVBREAK_ONE
		5038	EVUNLOOP_ALL => EVBREAK_ALL
		5039
		5040	EV_TIMEOUT => EV_TIMER
		5041
		5042	ev_loop_count => ev_iteration
		5043	ev_loop_depth => ev_depth
		5044	ev_loop_verify => ev_verify
		5045
		5046	Most functions working on C<struct ev_loop> objects don't have an
		5047	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5048	associated constants have been renamed to not collide with the C<struct
		5049	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5050	as all other watcher types. Note that C<ev_loop_fork> is still called
		5051	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5052	typedef.
		5053
		5054	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5055
		5056	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5057	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5058	and work, but the library code will of course be larger.
		5059
		5060	=back
		5061
		5062
		5063	=head1 GLOSSARY
		5064
		5065	=over 4
		5066
		5067	=item active
		5068
		5069	A watcher is active as long as it has been started and not yet stopped.
		5070	See L<WATCHER STATES> for details.
		5071
		5072	=item application
		5073
		5074	In this document, an application is whatever is using libev.
		5075
		5076	=item backend
		5077
		5078	The part of the code dealing with the operating system interfaces.
		5079
		5080	=item callback
		5081
		5082	The address of a function that is called when some event has been
		5083	detected. Callbacks are being passed the event loop, the watcher that
		5084	received the event, and the actual event bitset.
		5085
		5086	=item callback/watcher invocation
		5087
		5088	The act of calling the callback associated with a watcher.
		5089
		5090	=item event
		5091
		5092	A change of state of some external event, such as data now being available
		5093	for reading on a file descriptor, time having passed or simply not having
		5094	any other events happening anymore.
		5095
		5096	In libev, events are represented as single bits (such as C<EV_READ> or
		5097	C<EV_TIMER>).
		5098
		5099	=item event library
		5100
		5101	A software package implementing an event model and loop.
		5102
		5103	=item event loop
		5104
		5105	An entity that handles and processes external events and converts them
		5106	into callback invocations.
		5107
		5108	=item event model
		5109
		5110	The model used to describe how an event loop handles and processes
		5111	watchers and events.
		5112
		5113	=item pending
		5114
		5115	A watcher is pending as soon as the corresponding event has been
		5116	detected. See L<WATCHER STATES> for details.
		5117
		5118	=item real time
		5119
		5120	The physical time that is observed. It is apparently strictly monotonic :)
		5121
		5122	=item wall-clock time
		5123
		5124	The time and date as shown on clocks. Unlike real time, it can actually
		5125	be wrong and jump forwards and backwards, e.g. when the you adjust your
		5126	clock.
		5127
		5128	=item watcher
		5129
		5130	A data structure that describes interest in certain events. Watchers need
		5131	to be started (attached to an event loop) before they can receive events.
		5132
		5133	=back
		5134
3852	=head1 AUTHOR	5135	=head1 AUTHOR
3853		5136
3854	Marc Lehmann <libev@schmorp.de>.	5137	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5138	Magnusson and Emanuele Giaquinta.
3855		5139

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