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…		…
8		8
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
		13
		14	#include <stdio.h> // for puts
13		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_TYPE	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
…		…
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
28		30
29	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_run's to stop iterating
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_break (EV_A_ EVBREAK_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_run to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_break (EV_A_ EVBREAK_ONE);
40	}	42	}
41		43
42	int	44	int
43	main (void)	45	main (void)
44	{	46	{
45	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
46	ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = EV_DEFAULT;
47		49
48	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
…		…
54	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
57		59
58	// now wait for events to arrive	60	// now wait for events to arrive
59	ev_loop (loop, 0);	61	ev_run (loop, 0);
60		62
61	// unloop was called, so exit	63	// unloop was called, so exit
62	return 0;	64	return 0;
63	}	65	}
64		66
65	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
66		70
67	The newest version of this document is also available as an html-formatted	71	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	72	web page you might find easier to navigate when reading it for the first
69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.	73	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		74
		75	While this document tries to be as complete as possible in documenting
		76	libev, its usage and the rationale behind its design, it is not a tutorial
		77	on event-based programming, nor will it introduce event-based programming
		78	with libev.
		79
		80	Familiarity with event based programming techniques in general is assumed
		81	throughout this document.
		82
		83	=head1 WHAT TO READ WHEN IN A HURRY
		84
		85	This manual tries to be very detailed, but unfortunately, this also makes
		86	it very long. If you just want to know the basics of libev, I suggest
		87	reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and
		88	look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and
		89	C<ev_timer> sections in L<WATCHER TYPES>.
		90
		91	=head1 ABOUT LIBEV
70		92
71	Libev is an event loop: you register interest in certain events (such as a	93	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	94	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	95	these event sources and provide your program with events.
74		96
…		…
84	=head2 FEATURES	106	=head2 FEATURES
85		107
86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	108	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	109	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	110	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	111	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
90	with customised rescheduling (C<ev_periodic>), synchronous signals	112	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
91	(C<ev_signal>), process status change events (C<ev_child>), and event	113	timers (C<ev_timer>), absolute timers with customised rescheduling
92	watchers dealing with the event loop mechanism itself (C<ev_idle>,	114	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
93	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	115	change events (C<ev_child>), and event watchers dealing with the event
94	file watchers (C<ev_stat>) and even limited support for fork events	116	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
95	(C<ev_fork>).	117	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		118	limited support for fork events (C<ev_fork>).
96		119
97	It also is quite fast (see this	120	It also is quite fast (see this
98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	121	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
99	for example).	122	for example).
100		123
…		…
103	Libev is very configurable. In this manual the default (and most common)	126	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	127	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	128	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	129	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	130	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<ev_loop *>) will not have	131	name C<loop> (which is always of type C<struct ev_loop *>) will not have
109	this argument.	132	this argument.
110		133
111	=head2 TIME REPRESENTATION	134	=head2 TIME REPRESENTATION
112		135
113	Libev represents time as a single floating point number, representing the	136	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	137	the (fractional) number of seconds since the (POSIX) epoch (in practice
115	the beginning of 1970, details are complicated, don't ask). This type is	138	somewhere near the beginning of 1970, details are complicated, don't
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	139	ask). This type is called C<ev_tstamp>, which is what you should use
117	to the C<double> type in C, and when you need to do any calculations on	140	too. It usually aliases to the C<double> type in C. When you need to do
118	it, you should treat it as some floating point value. Unlike the name	141	any calculations on it, you should treat it as some floating point value.
		142
119	component C<stamp> might indicate, it is also used for time differences	143	Unlike the name component C<stamp> might indicate, it is also used for
120	throughout libev.	144	time differences (e.g. delays) throughout libev.
121		145
122	=head1 ERROR HANDLING	146	=head1 ERROR HANDLING
123		147
124	Libev knows three classes of errors: operating system errors, usage errors	148	Libev knows three classes of errors: operating system errors, usage errors
125	and internal errors (bugs).	149	and internal errors (bugs).
…		…
149		173
150	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
151		175
152	Returns the current time as libev would use it. Please note that the	176	Returns the current time as libev would use it. Please note that the
153	C<ev_now> function is usually faster and also often returns the timestamp	177	C<ev_now> function is usually faster and also often returns the timestamp
154	you actually want to know.	178	you actually want to know. Also interesting is the combination of
		179	C<ev_update_now> and C<ev_now>.
155		180
156	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
157		182
158	Sleep for the given interval: The current thread will be blocked until	183	Sleep for the given interval: The current thread will be blocked until
159	either it is interrupted or the given time interval has passed. Basically	184	either it is interrupted or the given time interval has passed. Basically
…		…
176	as this indicates an incompatible change. Minor versions are usually	201	as this indicates an incompatible change. Minor versions are usually
177	compatible to older versions, so a larger minor version alone is usually	202	compatible to older versions, so a larger minor version alone is usually
178	not a problem.	203	not a problem.
179		204
180	Example: Make sure we haven't accidentally been linked against the wrong	205	Example: Make sure we haven't accidentally been linked against the wrong
181	version.	206	version (note, however, that this will not detect other ABI mismatches,
		207	such as LFS or reentrancy).
182		208
183	assert (("libev version mismatch",	209	assert (("libev version mismatch",
184	ev_version_major () == EV_VERSION_MAJOR	210	ev_version_major () == EV_VERSION_MAJOR
185	&& ev_version_minor () >= EV_VERSION_MINOR));	211	&& ev_version_minor () >= EV_VERSION_MINOR));
186		212
…		…
197	assert (("sorry, no epoll, no sex",	223	assert (("sorry, no epoll, no sex",
198	ev_supported_backends () & EVBACKEND_EPOLL));	224	ev_supported_backends () & EVBACKEND_EPOLL));
199		225
200	=item unsigned int ev_recommended_backends ()	226	=item unsigned int ev_recommended_backends ()
201		227
202	Return the set of all backends compiled into this binary of libev and also	228	Return the set of all backends compiled into this binary of libev and
203	recommended for this platform. This set is often smaller than the one	229	also recommended for this platform, meaning it will work for most file
		230	descriptor types. This set is often smaller than the one returned by
204	returned by C<ev_supported_backends>, as for example kqueue is broken on	231	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
205	most BSDs and will not be auto-detected unless you explicitly request it	232	and will not be auto-detected unless you explicitly request it (assuming
206	(assuming you know what you are doing). This is the set of backends that	233	you know what you are doing). This is the set of backends that libev will
207	libev will probe for if you specify no backends explicitly.	234	probe for if you specify no backends explicitly.
208		235
209	=item unsigned int ev_embeddable_backends ()	236	=item unsigned int ev_embeddable_backends ()
210		237
211	Returns the set of backends that are embeddable in other event loops. This	238	Returns the set of backends that are embeddable in other event loops. This
212	is the theoretical, all-platform, value. To find which backends	239	value is platform-specific but can include backends not available on the
213	might be supported on the current system, you would need to look at	240	current system. To find which embeddable backends might be supported on
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	241	the current system, you would need to look at C<ev_embeddable_backends ()
215	recommended ones.	242	& ev_supported_backends ()>, likewise for recommended ones.
216		243
217	See the description of C<ev_embed> watchers for more info.	244	See the description of C<ev_embed> watchers for more info.
218		245
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	246	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
220		247
221	Sets the allocation function to use (the prototype is similar - the	248	Sets the allocation function to use (the prototype is similar - the
222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	249	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
223	used to allocate and free memory (no surprises here). If it returns zero	250	used to allocate and free memory (no surprises here). If it returns zero
224	when memory needs to be allocated (C<size != 0>), the library might abort	251	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	277	}
251		278
252	...	279	...
253	ev_set_allocator (persistent_realloc);	280	ev_set_allocator (persistent_realloc);
254		281
255	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	282	=item ev_set_syserr_cb (void (*cb)(const char *msg))
256		283
257	Set the callback function to call on a retryable system call error (such	284	Set the callback function to call on a retryable system call error (such
258	as failed select, poll, epoll_wait). The message is a printable string	285	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	286	indicating the system call or subsystem causing the problem. If this
260	callback is set, then libev will expect it to remedy the situation, no	287	callback is set, then libev will expect it to remedy the situation, no
…		…
272	}	299	}
273		300
274	...	301	...
275	ev_set_syserr_cb (fatal_error);	302	ev_set_syserr_cb (fatal_error);
276		303
		304	=item ev_feed_signal (int signum)
		305
		306	This function can be used to "simulate" a signal receive. It is completely
		307	safe to call this function at any time, from any context, including signal
		308	handlers or random threads.
		309
		310	Its main use is to customise signal handling in your process, especially
		311	in the presence of threads. For example, you could block signals
		312	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		313	creating any loops), and in one thread, use C<sigwait> or any other
		314	mechanism to wait for signals, then "deliver" them to libev by calling
		315	C<ev_feed_signal>.
		316
277	=back	317	=back
278		318
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	319	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
280		320
281	An event loop is described by a C<struct ev_loop *> (the C<struct>	321	An event loop is described by a C<struct ev_loop *> (the C<struct> is
282	is I<not> optional in this case, as there is also an C<ev_loop>	322	I<not> optional in this case unless libev 3 compatibility is disabled, as
283	I<function>).	323	libev 3 had an C<ev_loop> function colliding with the struct name).
284		324
285	The library knows two types of such loops, the I<default> loop, which	325	The library knows two types of such loops, the I<default> loop, which
286	supports signals and child events, and dynamically created loops which do	326	supports child process events, and dynamically created event loops which
287	not.	327	do not.
288		328
289	=over 4	329	=over 4
290		330
291	=item struct ev_loop *ev_default_loop (unsigned int flags)	331	=item struct ev_loop *ev_default_loop (unsigned int flags)
292		332
293	This will initialise the default event loop if it hasn't been initialised	333	This returns the "default" event loop object, which is what you should
294	yet and return it. If the default loop could not be initialised, returns	334	normally use when you just need "the event loop". Event loop objects and
295	false. If it already was initialised it simply returns it (and ignores the	335	the C<flags> parameter are described in more detail in the entry for
296	flags. If that is troubling you, check C<ev_backend ()> afterwards).	336	C<ev_loop_new>.
		337
		338	If the default loop is already initialised then this function simply
		339	returns it (and ignores the flags. If that is troubling you, check
		340	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		341	flags, which should almost always be C<0>, unless the caller is also the
		342	one calling C<ev_run> or otherwise qualifies as "the main program".
297		343
298	If you don't know what event loop to use, use the one returned from this	344	If you don't know what event loop to use, use the one returned from this
299	function.	345	function (or via the C<EV_DEFAULT> macro).
300		346
301	Note that this function is I<not> thread-safe, so if you want to use it	347	Note that this function is I<not> thread-safe, so if you want to use it
302	from multiple threads, you have to lock (note also that this is unlikely,	348	from multiple threads, you have to employ some kind of mutex (note also
303	as loops cannot be shared easily between threads anyway).	349	that this case is unlikely, as loops cannot be shared easily between
		350	threads anyway).
304		351
305	The default loop is the only loop that can handle C<ev_signal> and	352	The default loop is the only loop that can handle C<ev_child> watchers,
306	C<ev_child> watchers, and to do this, it always registers a handler	353	and to do this, it always registers a handler for C<SIGCHLD>. If this is
307	for C<SIGCHLD>. If this is a problem for your application you can either	354	a problem for your application you can either create a dynamic loop with
308	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	355	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
309	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	356	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
310	C<ev_default_init>.	357
		358	Example: This is the most typical usage.
		359
		360	if (!ev_default_loop (0))
		361	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		362
		363	Example: Restrict libev to the select and poll backends, and do not allow
		364	environment settings to be taken into account:
		365
		366	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		367
		368	=item struct ev_loop *ev_loop_new (unsigned int flags)
		369
		370	This will create and initialise a new event loop object. If the loop
		371	could not be initialised, returns false.
		372
		373	This function is thread-safe, and one common way to use libev with
		374	threads is indeed to create one loop per thread, and using the default
		375	loop in the "main" or "initial" thread.
311		376
312	The flags argument can be used to specify special behaviour or specific	377	The flags argument can be used to specify special behaviour or specific
313	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	378	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
314		379
315	The following flags are supported:	380	The following flags are supported:
…		…
330	useful to try out specific backends to test their performance, or to work	395	useful to try out specific backends to test their performance, or to work
331	around bugs.	396	around bugs.
332		397
333	=item C<EVFLAG_FORKCHECK>	398	=item C<EVFLAG_FORKCHECK>
334		399
335	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	400	Instead of calling C<ev_loop_fork> manually after a fork, you can also
336	a fork, you can also make libev check for a fork in each iteration by	401	make libev check for a fork in each iteration by enabling this flag.
337	enabling this flag.
338		402
339	This works by calling C<getpid ()> on every iteration of the loop,	403	This works by calling C<getpid ()> on every iteration of the loop,
340	and thus this might slow down your event loop if you do a lot of loop	404	and thus this might slow down your event loop if you do a lot of loop
341	iterations and little real work, but is usually not noticeable (on my	405	iterations and little real work, but is usually not noticeable (on my
342	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	406	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
…		…
348	flag.	412	flag.
349		413
350	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	414	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
351	environment variable.	415	environment variable.
352		416
		417	=item C<EVFLAG_NOINOTIFY>
		418
		419	When this flag is specified, then libev will not attempt to use the
		420	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
		421	testing, this flag can be useful to conserve inotify file descriptors, as
		422	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		423
		424	=item C<EVFLAG_SIGNALFD>
		425
		426	When this flag is specified, then libev will attempt to use the
		427	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
		428	delivers signals synchronously, which makes it both faster and might make
		429	it possible to get the queued signal data. It can also simplify signal
		430	handling with threads, as long as you properly block signals in your
		431	threads that are not interested in handling them.
		432
		433	Signalfd will not be used by default as this changes your signal mask, and
		434	there are a lot of shoddy libraries and programs (glib's threadpool for
		435	example) that can't properly initialise their signal masks.
		436
		437	=item C<EVFLAG_NOSIGMASK>
		438
		439	When this flag is specified, then libev will avoid to modify the signal
		440	mask. Specifically, this means you ahve to make sure signals are unblocked
		441	when you want to receive them.
		442
		443	This behaviour is useful when you want to do your own signal handling, or
		444	want to handle signals only in specific threads and want to avoid libev
		445	unblocking the signals.
		446
		447	It's also required by POSIX in a threaded program, as libev calls
		448	C<sigprocmask>, whose behaviour is officially unspecified.
		449
		450	This flag's behaviour will become the default in future versions of libev.
		451
353	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	452	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
354		453
355	This is your standard select(2) backend. Not I<completely> standard, as	454	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,	455	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	456	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	480	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
382	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	481	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
383		482
384	=item C<EVBACKEND_EPOLL> (value 4, Linux)	483	=item C<EVBACKEND_EPOLL> (value 4, Linux)
385		484
		485	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		486	kernels).
		487
386	For few fds, this backend is a bit little slower than poll and select,	488	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	489	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),	490	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).	491	epoll scales either O(1) or O(active_fds).
390		492
391	The epoll mechanism deserves honorable mention as the most misdesigned	493	The epoll mechanism deserves honorable mention as the most misdesigned
392	of the more advanced event mechanisms: mere annoyances include silently	494	of the more advanced event mechanisms: mere annoyances include silently
393	dropping file descriptors, requiring a system call per change per file	495	dropping file descriptors, requiring a system call per change per file
394	descriptor (and unnecessary guessing of parameters), problems with dup and	496	descriptor (and unnecessary guessing of parameters), problems with dup,
		497	returning before the timeout value, resulting in additional iterations
		498	(and only giving 5ms accuracy while select on the same platform gives
395	so on. The biggest issue is fork races, however - if a program forks then	499	0.1ms) and so on. The biggest issue is fork races, however - if a program
396	I<both> parent and child process have to recreate the epoll set, which can	500	forks then I<both> parent and child process have to recreate the epoll
397	take considerable time (one syscall per file descriptor) and is of course	501	set, which can take considerable time (one syscall per file descriptor)
398	hard to detect.	502	and is of course hard to detect.
399		503
400	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	504	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
401	of course I<doesn't>, and epoll just loves to report events for totally	505	of course I<doesn't>, and epoll just loves to report events for totally
402	I<different> file descriptors (even already closed ones, so one cannot	506	I<different> file descriptors (even already closed ones, so one cannot
403	even remove them from the set) than registered in the set (especially	507	even remove them from the set) than registered in the set (especially
404	on SMP systems). Libev tries to counter these spurious notifications by	508	on SMP systems). Libev tries to counter these spurious notifications by
405	employing an additional generation counter and comparing that against the	509	employing an additional generation counter and comparing that against the
406	events to filter out spurious ones, recreating the set when required.	510	events to filter out spurious ones, recreating the set when required. Last
		511	not least, it also refuses to work with some file descriptors which work
		512	perfectly fine with C<select> (files, many character devices...).
		513
		514	Epoll is truly the train wreck analog among event poll mechanisms,
		515	a frankenpoll, cobbled together in a hurry, no thought to design or
		516	interaction with others.
407		517
408	While stopping, setting and starting an I/O watcher in the same iteration	518	While stopping, setting and starting an I/O watcher in the same iteration
409	will result in some caching, there is still a system call per such	519	will result in some caching, there is still a system call per such
410	incident (because the same I<file descriptor> could point to a different	520	incident (because the same I<file descriptor> could point to a different
411	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	521	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
418	starting a watcher (without re-setting it) also usually doesn't cause	528	starting a watcher (without re-setting it) also usually doesn't cause
419	extra overhead. A fork can both result in spurious notifications as well	529	extra overhead. A fork can both result in spurious notifications as well
420	as in libev having to destroy and recreate the epoll object, which can	530	as in libev having to destroy and recreate the epoll object, which can
421	take considerable time and thus should be avoided.	531	take considerable time and thus should be avoided.
422		532
423	All this means that, in practise, C<EVBACKEND_SELECT> is as fast or faster	533	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
424	then epoll for maybe up to a hundred file descriptors. So sad.	534	faster than epoll for maybe up to a hundred file descriptors, depending on
		535	the usage. So sad.
425		536
426	While nominally embeddable in other event loops, this feature is broken in	537	While nominally embeddable in other event loops, this feature is broken in
427	all kernel versions tested so far.	538	all kernel versions tested so far.
428		539
429	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	540	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
…		…
457		568
458	While nominally embeddable in other event loops, this doesn't work	569	While nominally embeddable in other event loops, this doesn't work
459	everywhere, so you might need to test for this. And since it is broken	570	everywhere, so you might need to test for this. And since it is broken
460	almost everywhere, you should only use it when you have a lot of sockets	571	almost everywhere, you should only use it when you have a lot of sockets
461	(for which it usually works), by embedding it into another event loop	572	(for which it usually works), by embedding it into another event loop
462	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,	573	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
463	using it only for sockets.	574	also broken on OS X)) and, did I mention it, using it only for sockets.
464		575
465	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	576	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
466	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with	577	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
467	C<NOTE_EOF>.	578	C<NOTE_EOF>.
468		579
…		…
476	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	587	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
477		588
478	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	589	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
479	it's really slow, but it still scales very well (O(active_fds)).	590	it's really slow, but it still scales very well (O(active_fds)).
480		591
481	Please note that Solaris event ports can deliver a lot of spurious
482	notifications, so you need to use non-blocking I/O or other means to avoid
483	blocking when no data (or space) is available.
484
485	While this backend scales well, it requires one system call per active	592	While this backend scales well, it requires one system call per active
486	file descriptor per loop iteration. For small and medium numbers of file	593	file descriptor per loop iteration. For small and medium numbers of file
487	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	594	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
488	might perform better.	595	might perform better.
489		596
490	On the positive side, with the exception of the spurious readiness	597	On the positive side, this backend actually performed fully to
491	notifications, this backend actually performed fully to specification
492	in all tests and is fully embeddable, which is a rare feat among the	598	specification in all tests and is fully embeddable, which is a rare feat
493	OS-specific backends (I vastly prefer correctness over speed hacks).	599	among the OS-specific backends (I vastly prefer correctness over speed
		600	hacks).
		601
		602	On the negative side, the interface is I<bizarre> - so bizarre that
		603	even sun itself gets it wrong in their code examples: The event polling
		604	function sometimes returning events to the caller even though an error
		605	occurred, but with no indication whether it has done so or not (yes, it's
		606	even documented that way) - deadly for edge-triggered interfaces where
		607	you absolutely have to know whether an event occurred or not because you
		608	have to re-arm the watcher.
		609
		610	Fortunately libev seems to be able to work around these idiocies.
494		611
495	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	612	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
496	C<EVBACKEND_POLL>.	613	C<EVBACKEND_POLL>.
497		614
498	=item C<EVBACKEND_ALL>	615	=item C<EVBACKEND_ALL>
499		616
500	Try all backends (even potentially broken ones that wouldn't be tried	617	Try all backends (even potentially broken ones that wouldn't be tried
501	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	618	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
502	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	619	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
503		620
504	It is definitely not recommended to use this flag.	621	It is definitely not recommended to use this flag, use whatever
		622	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		623	at all.
		624
		625	=item C<EVBACKEND_MASK>
		626
		627	Not a backend at all, but a mask to select all backend bits from a
		628	C<flags> value, in case you want to mask out any backends from a flags
		629	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
505		630
506	=back	631	=back
507		632
508	If one or more of these are or'ed into the flags value, then only these	633	If one or more of the backend flags are or'ed into the flags value,
509	backends will be tried (in the reverse order as listed here). If none are	634	then only these backends will be tried (in the reverse order as listed
510	specified, all backends in C<ev_recommended_backends ()> will be tried.	635	here). If none are specified, all backends in C<ev_recommended_backends
511		636	()> will be tried.
512	Example: This is the most typical usage.
513
514	if (!ev_default_loop (0))
515	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
516
517	Example: Restrict libev to the select and poll backends, and do not allow
518	environment settings to be taken into account:
519
520	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
521
522	Example: Use whatever libev has to offer, but make sure that kqueue is
523	used if available (warning, breaks stuff, best use only with your own
524	private event loop and only if you know the OS supports your types of
525	fds):
526
527	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
528
529	=item struct ev_loop *ev_loop_new (unsigned int flags)
530
531	Similar to C<ev_default_loop>, but always creates a new event loop that is
532	always distinct from the default loop. Unlike the default loop, it cannot
533	handle signal and child watchers, and attempts to do so will be greeted by
534	undefined behaviour (or a failed assertion if assertions are enabled).
535
536	Note that this function I<is> thread-safe, and the recommended way to use
537	libev with threads is indeed to create one loop per thread, and using the
538	default loop in the "main" or "initial" thread.
539		637
540	Example: Try to create a event loop that uses epoll and nothing else.	638	Example: Try to create a event loop that uses epoll and nothing else.
541		639
542	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	640	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
543	if (!epoller)	641	if (!epoller)
544	fatal ("no epoll found here, maybe it hides under your chair");	642	fatal ("no epoll found here, maybe it hides under your chair");
545		643
		644	Example: Use whatever libev has to offer, but make sure that kqueue is
		645	used if available.
		646
		647	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		648
546	=item ev_default_destroy ()	649	=item ev_loop_destroy (loop)
547		650
548	Destroys the default loop again (frees all memory and kernel state	651	Destroys an event loop object (frees all memory and kernel state
549	etc.). None of the active event watchers will be stopped in the normal	652	etc.). None of the active event watchers will be stopped in the normal
550	sense, so e.g. C<ev_is_active> might still return true. It is your	653	sense, so e.g. C<ev_is_active> might still return true. It is your
551	responsibility to either stop all watchers cleanly yourself I<before>	654	responsibility to either stop all watchers cleanly yourself I<before>
552	calling this function, or cope with the fact afterwards (which is usually	655	calling this function, or cope with the fact afterwards (which is usually
553	the easiest thing, you can just ignore the watchers and/or C<free ()> them	656	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
555		658
556	Note that certain global state, such as signal state (and installed signal	659	Note that certain global state, such as signal state (and installed signal
557	handlers), will not be freed by this function, and related watchers (such	660	handlers), will not be freed by this function, and related watchers (such
558	as signal and child watchers) would need to be stopped manually.	661	as signal and child watchers) would need to be stopped manually.
559		662
560	In general it is not advisable to call this function except in the	663	This function is normally used on loop objects allocated by
561	rare occasion where you really need to free e.g. the signal handling	664	C<ev_loop_new>, but it can also be used on the default loop returned by
		665	C<ev_default_loop>, in which case it is not thread-safe.
		666
		667	Note that it is not advisable to call this function on the default loop
		668	except in the rare occasion where you really need to free its resources.
562	pipe fds. If you need dynamically allocated loops it is better to use	669	If you need dynamically allocated loops it is better to use C<ev_loop_new>
563	C<ev_loop_new> and C<ev_loop_destroy>).	670	and C<ev_loop_destroy>.
564		671
565	=item ev_loop_destroy (loop)	672	=item ev_loop_fork (loop)
566		673
567	Like C<ev_default_destroy>, but destroys an event loop created by an
568	earlier call to C<ev_loop_new>.
569
570	=item ev_default_fork ()
571
572	This function sets a flag that causes subsequent C<ev_loop> iterations	674	This function sets a flag that causes subsequent C<ev_run> iterations to
573	to reinitialise the kernel state for backends that have one. Despite the	675	reinitialise the kernel state for backends that have one. Despite the
574	name, you can call it anytime, but it makes most sense after forking, in	676	name, you can call it anytime, but it makes most sense after forking, in
575	the child process (or both child and parent, but that again makes little	677	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
576	sense). You I<must> call it in the child before using any of the libev	678	child before resuming or calling C<ev_run>.
577	functions, and it will only take effect at the next C<ev_loop> iteration.	679
		680	Again, you I<have> to call it on I<any> loop that you want to re-use after
		681	a fork, I<even if you do not plan to use the loop in the parent>. This is
		682	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		683	during fork.
578		684
579	On the other hand, you only need to call this function in the child	685	On the other hand, you only need to call this function in the child
580	process if and only if you want to use the event library in the child. If	686	process if and only if you want to use the event loop in the child. If
581	you just fork+exec, you don't have to call it at all.	687	you just fork+exec or create a new loop in the child, you don't have to
		688	call it at all (in fact, C<epoll> is so badly broken that it makes a
		689	difference, but libev will usually detect this case on its own and do a
		690	costly reset of the backend).
582		691
583	The function itself is quite fast and it's usually not a problem to call	692	The function itself is quite fast and it's usually not a problem to call
584	it just in case after a fork. To make this easy, the function will fit in	693	it just in case after a fork.
585	quite nicely into a call to C<pthread_atfork>:
586		694
		695	Example: Automate calling C<ev_loop_fork> on the default loop when
		696	using pthreads.
		697
		698	static void
		699	post_fork_child (void)
		700	{
		701	ev_loop_fork (EV_DEFAULT);
		702	}
		703
		704	...
587	pthread_atfork (0, 0, ev_default_fork);	705	pthread_atfork (0, 0, post_fork_child);
588
589	=item ev_loop_fork (loop)
590
591	Like C<ev_default_fork>, but acts on an event loop created by
592	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
593	after fork that you want to re-use in the child, and how you do this is
594	entirely your own problem.
595		706
596	=item int ev_is_default_loop (loop)	707	=item int ev_is_default_loop (loop)
597		708
598	Returns true when the given loop is, in fact, the default loop, and false	709	Returns true when the given loop is, in fact, the default loop, and false
599	otherwise.	710	otherwise.
600		711
601	=item unsigned int ev_loop_count (loop)	712	=item unsigned int ev_iteration (loop)
602		713
603	Returns the count of loop iterations for the loop, which is identical to	714	Returns the current iteration count for the event loop, which is identical
604	the number of times libev did poll for new events. It starts at C<0> and	715	to the number of times libev did poll for new events. It starts at C<0>
605	happily wraps around with enough iterations.	716	and happily wraps around with enough iterations.
606		717
607	This value can sometimes be useful as a generation counter of sorts (it	718	This value can sometimes be useful as a generation counter of sorts (it
608	"ticks" the number of loop iterations), as it roughly corresponds with	719	"ticks" the number of loop iterations), as it roughly corresponds with
609	C<ev_prepare> and C<ev_check> calls.	720	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		721	prepare and check phases.
		722
		723	=item unsigned int ev_depth (loop)
		724
		725	Returns the number of times C<ev_run> was entered minus the number of
		726	times C<ev_run> was exited normally, in other words, the recursion depth.
		727
		728	Outside C<ev_run>, this number is zero. In a callback, this number is
		729	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		730	in which case it is higher.
		731
		732	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
		733	throwing an exception etc.), doesn't count as "exit" - consider this
		734	as a hint to avoid such ungentleman-like behaviour unless it's really
		735	convenient, in which case it is fully supported.
610		736
611	=item unsigned int ev_backend (loop)	737	=item unsigned int ev_backend (loop)
612		738
613	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	739	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
614	use.	740	use.
…		…
623		749
624	=item ev_now_update (loop)	750	=item ev_now_update (loop)
625		751
626	Establishes the current time by querying the kernel, updating the time	752	Establishes the current time by querying the kernel, updating the time
627	returned by C<ev_now ()> in the progress. This is a costly operation and	753	returned by C<ev_now ()> in the progress. This is a costly operation and
628	is usually done automatically within C<ev_loop ()>.	754	is usually done automatically within C<ev_run ()>.
629		755
630	This function is rarely useful, but when some event callback runs for a	756	This function is rarely useful, but when some event callback runs for a
631	very long time without entering the event loop, updating libev's idea of	757	very long time without entering the event loop, updating libev's idea of
632	the current time is a good idea.	758	the current time is a good idea.
633		759
634	See also "The special problem of time updates" in the C<ev_timer> section.	760	See also L<The special problem of time updates> in the C<ev_timer> section.
635		761
		762	=item ev_suspend (loop)
		763
		764	=item ev_resume (loop)
		765
		766	These two functions suspend and resume an event loop, for use when the
		767	loop is not used for a while and timeouts should not be processed.
		768
		769	A typical use case would be an interactive program such as a game: When
		770	the user presses C<^Z> to suspend the game and resumes it an hour later it
		771	would be best to handle timeouts as if no time had actually passed while
		772	the program was suspended. This can be achieved by calling C<ev_suspend>
		773	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		774	C<ev_resume> directly afterwards to resume timer processing.
		775
		776	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		777	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		778	will be rescheduled (that is, they will lose any events that would have
		779	occurred while suspended).
		780
		781	After calling C<ev_suspend> you B<must not> call I<any> function on the
		782	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		783	without a previous call to C<ev_suspend>.
		784
		785	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		786	event loop time (see C<ev_now_update>).
		787
636	=item ev_loop (loop, int flags)	788	=item ev_run (loop, int flags)
637		789
638	Finally, this is it, the event handler. This function usually is called	790	Finally, this is it, the event handler. This function usually is called
639	after you initialised all your watchers and you want to start handling	791	after you have initialised all your watchers and you want to start
640	events.	792	handling events. It will ask the operating system for any new events, call
		793	the watcher callbacks, an then repeat the whole process indefinitely: This
		794	is why event loops are called I<loops>.
641		795
642	If the flags argument is specified as C<0>, it will not return until	796	If the flags argument is specified as C<0>, it will keep handling events
643	either no event watchers are active anymore or C<ev_unloop> was called.	797	until either no event watchers are active anymore or C<ev_break> was
		798	called.
644		799
645	Please note that an explicit C<ev_unloop> is usually better than	800	Please note that an explicit C<ev_break> is usually better than
646	relying on all watchers to be stopped when deciding when a program has	801	relying on all watchers to be stopped when deciding when a program has
647	finished (especially in interactive programs), but having a program	802	finished (especially in interactive programs), but having a program
648	that automatically loops as long as it has to and no longer by virtue	803	that automatically loops as long as it has to and no longer by virtue
649	of relying on its watchers stopping correctly, that is truly a thing of	804	of relying on its watchers stopping correctly, that is truly a thing of
650	beauty.	805	beauty.
651		806
		807	This function is also I<mostly> exception-safe - you can break out of
		808	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		809	exception and so on. This does not decrement the C<ev_depth> value, nor
		810	will it clear any outstanding C<EVBREAK_ONE> breaks.
		811
652	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	812	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
653	those events and any already outstanding ones, but will not block your	813	those events and any already outstanding ones, but will not wait and
654	process in case there are no events and will return after one iteration of	814	block your process in case there are no events and will return after one
655	the loop.	815	iteration of the loop. This is sometimes useful to poll and handle new
		816	events while doing lengthy calculations, to keep the program responsive.
656		817
657	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	818	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
658	necessary) and will handle those and any already outstanding ones. It	819	necessary) and will handle those and any already outstanding ones. It
659	will block your process until at least one new event arrives (which could	820	will block your process until at least one new event arrives (which could
660	be an event internal to libev itself, so there is no guarantee that a	821	be an event internal to libev itself, so there is no guarantee that a
661	user-registered callback will be called), and will return after one	822	user-registered callback will be called), and will return after one
662	iteration of the loop.	823	iteration of the loop.
663		824
664	This is useful if you are waiting for some external event in conjunction	825	This is useful if you are waiting for some external event in conjunction
665	with something not expressible using other libev watchers (i.e. "roll your	826	with something not expressible using other libev watchers (i.e. "roll your
666	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	827	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
667	usually a better approach for this kind of thing.	828	usually a better approach for this kind of thing.
668		829
669	Here are the gory details of what C<ev_loop> does:	830	Here are the gory details of what C<ev_run> does:
670		831
		832	- Increment loop depth.
		833	- Reset the ev_break status.
671	- Before the first iteration, call any pending watchers.	834	- Before the first iteration, call any pending watchers.
		835	LOOP:
672	* If EVFLAG_FORKCHECK was used, check for a fork.	836	- If EVFLAG_FORKCHECK was used, check for a fork.
673	- If a fork was detected (by any means), queue and call all fork watchers.	837	- If a fork was detected (by any means), queue and call all fork watchers.
674	- Queue and call all prepare watchers.	838	- Queue and call all prepare watchers.
		839	- If ev_break was called, goto FINISH.
675	- If we have been forked, detach and recreate the kernel state	840	- If we have been forked, detach and recreate the kernel state
676	as to not disturb the other process.	841	as to not disturb the other process.
677	- Update the kernel state with all outstanding changes.	842	- Update the kernel state with all outstanding changes.
678	- Update the "event loop time" (ev_now ()).	843	- Update the "event loop time" (ev_now ()).
679	- Calculate for how long to sleep or block, if at all	844	- Calculate for how long to sleep or block, if at all
680	(active idle watchers, EVLOOP_NONBLOCK or not having	845	(active idle watchers, EVRUN_NOWAIT or not having
681	any active watchers at all will result in not sleeping).	846	any active watchers at all will result in not sleeping).
682	- Sleep if the I/O and timer collect interval say so.	847	- Sleep if the I/O and timer collect interval say so.
		848	- Increment loop iteration counter.
683	- Block the process, waiting for any events.	849	- Block the process, waiting for any events.
684	- Queue all outstanding I/O (fd) events.	850	- Queue all outstanding I/O (fd) events.
685	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	851	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
686	- Queue all expired timers.	852	- Queue all expired timers.
687	- Queue all expired periodics.	853	- Queue all expired periodics.
688	- Unless any events are pending now, queue all idle watchers.	854	- Queue all idle watchers with priority higher than that of pending events.
689	- Queue all check watchers.	855	- Queue all check watchers.
690	- Call all queued watchers in reverse order (i.e. check watchers first).	856	- Call all queued watchers in reverse order (i.e. check watchers first).
691	Signals and child watchers are implemented as I/O watchers, and will	857	Signals and child watchers are implemented as I/O watchers, and will
692	be handled here by queueing them when their watcher gets executed.	858	be handled here by queueing them when their watcher gets executed.
693	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	859	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
694	were used, or there are no active watchers, return, otherwise	860	were used, or there are no active watchers, goto FINISH, otherwise
695	continue with step *.	861	continue with step LOOP.
		862	FINISH:
		863	- Reset the ev_break status iff it was EVBREAK_ONE.
		864	- Decrement the loop depth.
		865	- Return.
696		866
697	Example: Queue some jobs and then loop until no events are outstanding	867	Example: Queue some jobs and then loop until no events are outstanding
698	anymore.	868	anymore.
699		869
700	... queue jobs here, make sure they register event watchers as long	870	... queue jobs here, make sure they register event watchers as long
701	... as they still have work to do (even an idle watcher will do..)	871	... as they still have work to do (even an idle watcher will do..)
702	ev_loop (my_loop, 0);	872	ev_run (my_loop, 0);
703	... jobs done or somebody called unloop. yeah!	873	... jobs done or somebody called unloop. yeah!
704		874
705	=item ev_unloop (loop, how)	875	=item ev_break (loop, how)
706		876
707	Can be used to make a call to C<ev_loop> return early (but only after it	877	Can be used to make a call to C<ev_run> return early (but only after it
708	has processed all outstanding events). The C<how> argument must be either	878	has processed all outstanding events). The C<how> argument must be either
709	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	879	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
710	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	880	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
711		881
712	This "unloop state" will be cleared when entering C<ev_loop> again.	882	This "break state" will be cleared on the next call to C<ev_run>.
713		883
714	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	884	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		885	which case it will have no effect.
715		886
716	=item ev_ref (loop)	887	=item ev_ref (loop)
717		888
718	=item ev_unref (loop)	889	=item ev_unref (loop)
719		890
720	Ref/unref can be used to add or remove a reference count on the event	891	Ref/unref can be used to add or remove a reference count on the event
721	loop: Every watcher keeps one reference, and as long as the reference	892	loop: Every watcher keeps one reference, and as long as the reference
722	count is nonzero, C<ev_loop> will not return on its own.	893	count is nonzero, C<ev_run> will not return on its own.
723		894
724	If you have a watcher you never unregister that should not keep C<ev_loop>	895	This is useful when you have a watcher that you never intend to
725	from returning, call ev_unref() after starting, and ev_ref() before	896	unregister, but that nevertheless should not keep C<ev_run> from
		897	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
726	stopping it.	898	before stopping it.
727		899
728	As an example, libev itself uses this for its internal signal pipe: It is	900	As an example, libev itself uses this for its internal signal pipe: It
729	not visible to the libev user and should not keep C<ev_loop> from exiting	901	is not visible to the libev user and should not keep C<ev_run> from
730	if no event watchers registered by it are active. It is also an excellent	902	exiting if no event watchers registered by it are active. It is also an
731	way to do this for generic recurring timers or from within third-party	903	excellent way to do this for generic recurring timers or from within
732	libraries. Just remember to I<unref after start> and I<ref before stop>	904	third-party libraries. Just remember to I<unref after start> and I<ref
733	(but only if the watcher wasn't active before, or was active before,	905	before stop> (but only if the watcher wasn't active before, or was active
734	respectively).	906	before, respectively. Note also that libev might stop watchers itself
		907	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		908	in the callback).
735		909
736	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	910	Example: Create a signal watcher, but keep it from keeping C<ev_run>
737	running when nothing else is active.	911	running when nothing else is active.
738		912
739	ev_signal exitsig;	913	ev_signal exitsig;
740	ev_signal_init (&exitsig, sig_cb, SIGINT);	914	ev_signal_init (&exitsig, sig_cb, SIGINT);
741	ev_signal_start (loop, &exitsig);	915	ev_signal_start (loop, &exitsig);
742	evf_unref (loop);	916	ev_unref (loop);
743		917
744	Example: For some weird reason, unregister the above signal handler again.	918	Example: For some weird reason, unregister the above signal handler again.
745		919
746	ev_ref (loop);	920	ev_ref (loop);
747	ev_signal_stop (loop, &exitsig);	921	ev_signal_stop (loop, &exitsig);
…		…
768		942
769	By setting a higher I<io collect interval> you allow libev to spend more	943	By setting a higher I<io collect interval> you allow libev to spend more
770	time collecting I/O events, so you can handle more events per iteration,	944	time collecting I/O events, so you can handle more events per iteration,
771	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	945	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
772	C<ev_timer>) will be not affected. Setting this to a non-null value will	946	C<ev_timer>) will be not affected. Setting this to a non-null value will
773	introduce an additional C<ev_sleep ()> call into most loop iterations.	947	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		948	sleep time ensures that libev will not poll for I/O events more often then
		949	once per this interval, on average.
774		950
775	Likewise, by setting a higher I<timeout collect interval> you allow libev	951	Likewise, by setting a higher I<timeout collect interval> you allow libev
776	to spend more time collecting timeouts, at the expense of increased	952	to spend more time collecting timeouts, at the expense of increased
777	latency/jitter/inexactness (the watcher callback will be called	953	latency/jitter/inexactness (the watcher callback will be called
778	later). C<ev_io> watchers will not be affected. Setting this to a non-null	954	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
780		956
781	Many (busy) programs can usually benefit by setting the I/O collect	957	Many (busy) programs can usually benefit by setting the I/O collect
782	interval to a value near C<0.1> or so, which is often enough for	958	interval to a value near C<0.1> or so, which is often enough for
783	interactive servers (of course not for games), likewise for timeouts. It	959	interactive servers (of course not for games), likewise for timeouts. It
784	usually doesn't make much sense to set it to a lower value than C<0.01>,	960	usually doesn't make much sense to set it to a lower value than C<0.01>,
785	as this approaches the timing granularity of most systems.	961	as this approaches the timing granularity of most systems. Note that if
		962	you do transactions with the outside world and you can't increase the
		963	parallelity, then this setting will limit your transaction rate (if you
		964	need to poll once per transaction and the I/O collect interval is 0.01,
		965	then you can't do more than 100 transactions per second).
786		966
787	Setting the I<timeout collect interval> can improve the opportunity for	967	Setting the I<timeout collect interval> can improve the opportunity for
788	saving power, as the program will "bundle" timer callback invocations that	968	saving power, as the program will "bundle" timer callback invocations that
789	are "near" in time together, by delaying some, thus reducing the number of	969	are "near" in time together, by delaying some, thus reducing the number of
790	times the process sleeps and wakes up again. Another useful technique to	970	times the process sleeps and wakes up again. Another useful technique to
791	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	971	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
792	they fire on, say, one-second boundaries only.	972	they fire on, say, one-second boundaries only.
793		973
		974	Example: we only need 0.1s timeout granularity, and we wish not to poll
		975	more often than 100 times per second:
		976
		977	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		978	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		979
		980	=item ev_invoke_pending (loop)
		981
		982	This call will simply invoke all pending watchers while resetting their
		983	pending state. Normally, C<ev_run> does this automatically when required,
		984	but when overriding the invoke callback this call comes handy. This
		985	function can be invoked from a watcher - this can be useful for example
		986	when you want to do some lengthy calculation and want to pass further
		987	event handling to another thread (you still have to make sure only one
		988	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		989
		990	=item int ev_pending_count (loop)
		991
		992	Returns the number of pending watchers - zero indicates that no watchers
		993	are pending.
		994
		995	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		996
		997	This overrides the invoke pending functionality of the loop: Instead of
		998	invoking all pending watchers when there are any, C<ev_run> will call
		999	this callback instead. This is useful, for example, when you want to
		1000	invoke the actual watchers inside another context (another thread etc.).
		1001
		1002	If you want to reset the callback, use C<ev_invoke_pending> as new
		1003	callback.
		1004
		1005	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		1006
		1007	Sometimes you want to share the same loop between multiple threads. This
		1008	can be done relatively simply by putting mutex_lock/unlock calls around
		1009	each call to a libev function.
		1010
		1011	However, C<ev_run> can run an indefinite time, so it is not feasible
		1012	to wait for it to return. One way around this is to wake up the event
		1013	loop via C<ev_break> and C<av_async_send>, another way is to set these
		1014	I<release> and I<acquire> callbacks on the loop.
		1015
		1016	When set, then C<release> will be called just before the thread is
		1017	suspended waiting for new events, and C<acquire> is called just
		1018	afterwards.
		1019
		1020	Ideally, C<release> will just call your mutex_unlock function, and
		1021	C<acquire> will just call the mutex_lock function again.
		1022
		1023	While event loop modifications are allowed between invocations of
		1024	C<release> and C<acquire> (that's their only purpose after all), no
		1025	modifications done will affect the event loop, i.e. adding watchers will
		1026	have no effect on the set of file descriptors being watched, or the time
		1027	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		1028	to take note of any changes you made.
		1029
		1030	In theory, threads executing C<ev_run> will be async-cancel safe between
		1031	invocations of C<release> and C<acquire>.
		1032
		1033	See also the locking example in the C<THREADS> section later in this
		1034	document.
		1035
		1036	=item ev_set_userdata (loop, void *data)
		1037
		1038	=item void *ev_userdata (loop)
		1039
		1040	Set and retrieve a single C<void *> associated with a loop. When
		1041	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		1042	C<0>.
		1043
		1044	These two functions can be used to associate arbitrary data with a loop,
		1045	and are intended solely for the C<invoke_pending_cb>, C<release> and
		1046	C<acquire> callbacks described above, but of course can be (ab-)used for
		1047	any other purpose as well.
		1048
794	=item ev_loop_verify (loop)	1049	=item ev_verify (loop)
795		1050
796	This function only does something when C<EV_VERIFY> support has been	1051	This function only does something when C<EV_VERIFY> support has been
797	compiled in, which is the default for non-minimal builds. It tries to go	1052	compiled in, which is the default for non-minimal builds. It tries to go
798	through all internal structures and checks them for validity. If anything	1053	through all internal structures and checks them for validity. If anything
799	is found to be inconsistent, it will print an error message to standard	1054	is found to be inconsistent, it will print an error message to standard
…		…
810		1065
811	In the following description, uppercase C<TYPE> in names stands for the	1066	In the following description, uppercase C<TYPE> in names stands for the
812	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1067	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
813	watchers and C<ev_io_start> for I/O watchers.	1068	watchers and C<ev_io_start> for I/O watchers.
814		1069
815	A watcher is a structure that you create and register to record your	1070	A watcher is an opaque structure that you allocate and register to record
816	interest in some event. For instance, if you want to wait for STDIN to	1071	your interest in some event. To make a concrete example, imagine you want
817	become readable, you would create an C<ev_io> watcher for that:	1072	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1073	for that:
818		1074
819	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1075	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
820	{	1076	{
821	ev_io_stop (w);	1077	ev_io_stop (w);
822	ev_unloop (loop, EVUNLOOP_ALL);	1078	ev_break (loop, EVBREAK_ALL);
823	}	1079	}
824		1080
825	struct ev_loop *loop = ev_default_loop (0);	1081	struct ev_loop *loop = ev_default_loop (0);
826		1082
827	ev_io stdin_watcher;	1083	ev_io stdin_watcher;
828		1084
829	ev_init (&stdin_watcher, my_cb);	1085	ev_init (&stdin_watcher, my_cb);
830	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1086	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
831	ev_io_start (loop, &stdin_watcher);	1087	ev_io_start (loop, &stdin_watcher);
832		1088
833	ev_loop (loop, 0);	1089	ev_run (loop, 0);
834		1090
835	As you can see, you are responsible for allocating the memory for your	1091	As you can see, you are responsible for allocating the memory for your
836	watcher structures (and it is I<usually> a bad idea to do this on the	1092	watcher structures (and it is I<usually> a bad idea to do this on the
837	stack).	1093	stack).
838		1094
839	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1095	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
840	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1096	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
841		1097
842	Each watcher structure must be initialised by a call to C<ev_init	1098	Each watcher structure must be initialised by a call to C<ev_init (watcher
843	(watcher *, callback)>, which expects a callback to be provided. This	1099	*, callback)>, which expects a callback to be provided. This callback is
844	callback gets invoked each time the event occurs (or, in the case of I/O	1100	invoked each time the event occurs (or, in the case of I/O watchers, each
845	watchers, each time the event loop detects that the file descriptor given	1101	time the event loop detects that the file descriptor given is readable
846	is readable and/or writable).	1102	and/or writable).
847		1103
848	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1104	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
849	macro to configure it, with arguments specific to the watcher type. There	1105	macro to configure it, with arguments specific to the watcher type. There
850	is also a macro to combine initialisation and setting in one call: C<<	1106	is also a macro to combine initialisation and setting in one call: C<<
851	ev_TYPE_init (watcher *, callback, ...) >>.	1107	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
874	=item C<EV_WRITE>	1130	=item C<EV_WRITE>
875		1131
876	The file descriptor in the C<ev_io> watcher has become readable and/or	1132	The file descriptor in the C<ev_io> watcher has become readable and/or
877	writable.	1133	writable.
878		1134
879	=item C<EV_TIMEOUT>	1135	=item C<EV_TIMER>
880		1136
881	The C<ev_timer> watcher has timed out.	1137	The C<ev_timer> watcher has timed out.
882		1138
883	=item C<EV_PERIODIC>	1139	=item C<EV_PERIODIC>
884		1140
…		…
902		1158
903	=item C<EV_PREPARE>	1159	=item C<EV_PREPARE>
904		1160
905	=item C<EV_CHECK>	1161	=item C<EV_CHECK>
906		1162
907	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1163	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
908	to gather new events, and all C<ev_check> watchers are invoked just after	1164	to gather new events, and all C<ev_check> watchers are invoked just after
909	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1165	C<ev_run> has gathered them, but before it invokes any callbacks for any
910	received events. Callbacks of both watcher types can start and stop as	1166	received events. Callbacks of both watcher types can start and stop as
911	many watchers as they want, and all of them will be taken into account	1167	many watchers as they want, and all of them will be taken into account
912	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1168	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
913	C<ev_loop> from blocking).	1169	C<ev_run> from blocking).
914		1170
915	=item C<EV_EMBED>	1171	=item C<EV_EMBED>
916		1172
917	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1173	The embedded event loop specified in the C<ev_embed> watcher needs attention.
918		1174
919	=item C<EV_FORK>	1175	=item C<EV_FORK>
920		1176
921	The event loop has been resumed in the child process after fork (see	1177	The event loop has been resumed in the child process after fork (see
922	C<ev_fork>).	1178	C<ev_fork>).
923		1179
		1180	=item C<EV_CLEANUP>
		1181
		1182	The event loop is about to be destroyed (see C<ev_cleanup>).
		1183
924	=item C<EV_ASYNC>	1184	=item C<EV_ASYNC>
925		1185
926	The given async watcher has been asynchronously notified (see C<ev_async>).	1186	The given async watcher has been asynchronously notified (see C<ev_async>).
		1187
		1188	=item C<EV_CUSTOM>
		1189
		1190	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1191	by libev users to signal watchers (e.g. via C<ev_feed_event>).
927		1192
928	=item C<EV_ERROR>	1193	=item C<EV_ERROR>
929		1194
930	An unspecified error has occurred, the watcher has been stopped. This might	1195	An unspecified error has occurred, the watcher has been stopped. This might
931	happen because the watcher could not be properly started because libev	1196	happen because the watcher could not be properly started because libev
…		…
969		1234
970	ev_io w;	1235	ev_io w;
971	ev_init (&w, my_cb);	1236	ev_init (&w, my_cb);
972	ev_io_set (&w, STDIN_FILENO, EV_READ);	1237	ev_io_set (&w, STDIN_FILENO, EV_READ);
973		1238
974	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1239	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
975		1240
976	This macro initialises the type-specific parts of a watcher. You need to	1241	This macro initialises the type-specific parts of a watcher. You need to
977	call C<ev_init> at least once before you call this macro, but you can	1242	call C<ev_init> at least once before you call this macro, but you can
978	call C<ev_TYPE_set> any number of times. You must not, however, call this	1243	call C<ev_TYPE_set> any number of times. You must not, however, call this
979	macro on a watcher that is active (it can be pending, however, which is a	1244	macro on a watcher that is active (it can be pending, however, which is a
…		…
992		1257
993	Example: Initialise and set an C<ev_io> watcher in one step.	1258	Example: Initialise and set an C<ev_io> watcher in one step.
994		1259
995	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1260	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
996		1261
997	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1262	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
998		1263
999	Starts (activates) the given watcher. Only active watchers will receive	1264	Starts (activates) the given watcher. Only active watchers will receive
1000	events. If the watcher is already active nothing will happen.	1265	events. If the watcher is already active nothing will happen.
1001		1266
1002	Example: Start the C<ev_io> watcher that is being abused as example in this	1267	Example: Start the C<ev_io> watcher that is being abused as example in this
1003	whole section.	1268	whole section.
1004		1269
1005	ev_io_start (EV_DEFAULT_UC, &w);	1270	ev_io_start (EV_DEFAULT_UC, &w);
1006		1271
1007	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1272	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1008		1273
1009	Stops the given watcher if active, and clears the pending status (whether	1274	Stops the given watcher if active, and clears the pending status (whether
1010	the watcher was active or not).	1275	the watcher was active or not).
1011		1276
1012	It is possible that stopped watchers are pending - for example,	1277	It is possible that stopped watchers are pending - for example,
…		…
1037	=item ev_cb_set (ev_TYPE *watcher, callback)	1302	=item ev_cb_set (ev_TYPE *watcher, callback)
1038		1303
1039	Change the callback. You can change the callback at virtually any time	1304	Change the callback. You can change the callback at virtually any time
1040	(modulo threads).	1305	(modulo threads).
1041		1306
1042	=item ev_set_priority (ev_TYPE *watcher, priority)	1307	=item ev_set_priority (ev_TYPE *watcher, int priority)
1043		1308
1044	=item int ev_priority (ev_TYPE *watcher)	1309	=item int ev_priority (ev_TYPE *watcher)
1045		1310
1046	Set and query the priority of the watcher. The priority is a small	1311	Set and query the priority of the watcher. The priority is a small
1047	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1312	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1048	(default: C<-2>). Pending watchers with higher priority will be invoked	1313	(default: C<-2>). Pending watchers with higher priority will be invoked
1049	before watchers with lower priority, but priority will not keep watchers	1314	before watchers with lower priority, but priority will not keep watchers
1050	from being executed (except for C<ev_idle> watchers).	1315	from being executed (except for C<ev_idle> watchers).
1051		1316
1052	This means that priorities are I<only> used for ordering callback
1053	invocation after new events have been received. This is useful, for
1054	example, to reduce latency after idling, or more often, to bind two
1055	watchers on the same event and make sure one is called first.
1056
1057	If you need to suppress invocation when higher priority events are pending	1317	If you need to suppress invocation when higher priority events are pending
1058	you need to look at C<ev_idle> watchers, which provide this functionality.	1318	you need to look at C<ev_idle> watchers, which provide this functionality.
1059		1319
1060	You I<must not> change the priority of a watcher as long as it is active or	1320	You I<must not> change the priority of a watcher as long as it is active or
1061	pending.	1321	pending.
1062
1063	The default priority used by watchers when no priority has been set is
1064	always C<0>, which is supposed to not be too high and not be too low :).
1065		1322
1066	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1323	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1067	fine, as long as you do not mind that the priority value you query might	1324	fine, as long as you do not mind that the priority value you query might
1068	or might not have been clamped to the valid range.	1325	or might not have been clamped to the valid range.
		1326
		1327	The default priority used by watchers when no priority has been set is
		1328	always C<0>, which is supposed to not be too high and not be too low :).
		1329
		1330	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
		1331	priorities.
1069		1332
1070	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1333	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1071		1334
1072	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1335	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1073	C<loop> nor C<revents> need to be valid as long as the watcher callback	1336	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1081	watcher isn't pending it does nothing and returns C<0>.	1344	watcher isn't pending it does nothing and returns C<0>.
1082		1345
1083	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1346	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1084	callback to be invoked, which can be accomplished with this function.	1347	callback to be invoked, which can be accomplished with this function.
1085		1348
		1349	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1350
		1351	Feeds the given event set into the event loop, as if the specified event
		1352	had happened for the specified watcher (which must be a pointer to an
		1353	initialised but not necessarily started event watcher). Obviously you must
		1354	not free the watcher as long as it has pending events.
		1355
		1356	Stopping the watcher, letting libev invoke it, or calling
		1357	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1358	not started in the first place.
		1359
		1360	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1361	functions that do not need a watcher.
		1362
1086	=back	1363	=back
1087		1364
		1365	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
		1366	OWN COMPOSITE WATCHERS> idioms.
1088		1367
1089	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1368	=head2 WATCHER STATES
1090		1369
1091	Each watcher has, by default, a member C<void *data> that you can change	1370	There are various watcher states mentioned throughout this manual -
1092	and read at any time: libev will completely ignore it. This can be used	1371	active, pending and so on. In this section these states and the rules to
1093	to associate arbitrary data with your watcher. If you need more data and	1372	transition between them will be described in more detail - and while these
1094	don't want to allocate memory and store a pointer to it in that data	1373	rules might look complicated, they usually do "the right thing".
1095	member, you can also "subclass" the watcher type and provide your own
1096	data:
1097		1374
1098	struct my_io	1375	=over 4
		1376
		1377	=item initialiased
		1378
		1379	Before a watcher can be registered with the event looop it has to be
		1380	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1381	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1382
		1383	In this state it is simply some block of memory that is suitable for use
		1384	in an event loop. It can be moved around, freed, reused etc. at will.
		1385
		1386	=item started/running/active
		1387
		1388	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1389	property of the event loop, and is actively waiting for events. While in
		1390	this state it cannot be accessed (except in a few documented ways), moved,
		1391	freed or anything else - the only legal thing is to keep a pointer to it,
		1392	and call libev functions on it that are documented to work on active watchers.
		1393
		1394	=item pending
		1395
		1396	If a watcher is active and libev determines that an event it is interested
		1397	in has occurred (such as a timer expiring), it will become pending. It will
		1398	stay in this pending state until either it is stopped or its callback is
		1399	about to be invoked, so it is not normally pending inside the watcher
		1400	callback.
		1401
		1402	The watcher might or might not be active while it is pending (for example,
		1403	an expired non-repeating timer can be pending but no longer active). If it
		1404	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1405	but it is still property of the event loop at this time, so cannot be
		1406	moved, freed or reused. And if it is active the rules described in the
		1407	previous item still apply.
		1408
		1409	It is also possible to feed an event on a watcher that is not active (e.g.
		1410	via C<ev_feed_event>), in which case it becomes pending without being
		1411	active.
		1412
		1413	=item stopped
		1414
		1415	A watcher can be stopped implicitly by libev (in which case it might still
		1416	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1417	latter will clear any pending state the watcher might be in, regardless
		1418	of whether it was active or not, so stopping a watcher explicitly before
		1419	freeing it is often a good idea.
		1420
		1421	While stopped (and not pending) the watcher is essentially in the
		1422	initialised state, that is it can be reused, moved, modified in any way
		1423	you wish.
		1424
		1425	=back
		1426
		1427	=head2 WATCHER PRIORITY MODELS
		1428
		1429	Many event loops support I<watcher priorities>, which are usually small
		1430	integers that influence the ordering of event callback invocation
		1431	between watchers in some way, all else being equal.
		1432
		1433	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1434	description for the more technical details such as the actual priority
		1435	range.
		1436
		1437	There are two common ways how these these priorities are being interpreted
		1438	by event loops:
		1439
		1440	In the more common lock-out model, higher priorities "lock out" invocation
		1441	of lower priority watchers, which means as long as higher priority
		1442	watchers receive events, lower priority watchers are not being invoked.
		1443
		1444	The less common only-for-ordering model uses priorities solely to order
		1445	callback invocation within a single event loop iteration: Higher priority
		1446	watchers are invoked before lower priority ones, but they all get invoked
		1447	before polling for new events.
		1448
		1449	Libev uses the second (only-for-ordering) model for all its watchers
		1450	except for idle watchers (which use the lock-out model).
		1451
		1452	The rationale behind this is that implementing the lock-out model for
		1453	watchers is not well supported by most kernel interfaces, and most event
		1454	libraries will just poll for the same events again and again as long as
		1455	their callbacks have not been executed, which is very inefficient in the
		1456	common case of one high-priority watcher locking out a mass of lower
		1457	priority ones.
		1458
		1459	Static (ordering) priorities are most useful when you have two or more
		1460	watchers handling the same resource: a typical usage example is having an
		1461	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1462	timeouts. Under load, data might be received while the program handles
		1463	other jobs, but since timers normally get invoked first, the timeout
		1464	handler will be executed before checking for data. In that case, giving
		1465	the timer a lower priority than the I/O watcher ensures that I/O will be
		1466	handled first even under adverse conditions (which is usually, but not
		1467	always, what you want).
		1468
		1469	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1470	will only be executed when no same or higher priority watchers have
		1471	received events, they can be used to implement the "lock-out" model when
		1472	required.
		1473
		1474	For example, to emulate how many other event libraries handle priorities,
		1475	you can associate an C<ev_idle> watcher to each such watcher, and in
		1476	the normal watcher callback, you just start the idle watcher. The real
		1477	processing is done in the idle watcher callback. This causes libev to
		1478	continuously poll and process kernel event data for the watcher, but when
		1479	the lock-out case is known to be rare (which in turn is rare :), this is
		1480	workable.
		1481
		1482	Usually, however, the lock-out model implemented that way will perform
		1483	miserably under the type of load it was designed to handle. In that case,
		1484	it might be preferable to stop the real watcher before starting the
		1485	idle watcher, so the kernel will not have to process the event in case
		1486	the actual processing will be delayed for considerable time.
		1487
		1488	Here is an example of an I/O watcher that should run at a strictly lower
		1489	priority than the default, and which should only process data when no
		1490	other events are pending:
		1491
		1492	ev_idle idle; // actual processing watcher
		1493	ev_io io; // actual event watcher
		1494
		1495	static void
		1496	io_cb (EV_P_ ev_io *w, int revents)
1099	{	1497	{
1100	ev_io io;	1498	// stop the I/O watcher, we received the event, but
1101	int otherfd;	1499	// are not yet ready to handle it.
1102	void *somedata;	1500	ev_io_stop (EV_A_ w);
1103	struct whatever *mostinteresting;	1501
		1502	// start the idle watcher to handle the actual event.
		1503	// it will not be executed as long as other watchers
		1504	// with the default priority are receiving events.
		1505	ev_idle_start (EV_A_ &idle);
1104	};	1506	}
1105		1507
1106	...	1508	static void
1107	struct my_io w;	1509	idle_cb (EV_P_ ev_idle *w, int revents)
1108	ev_io_init (&w.io, my_cb, fd, EV_READ);
1109
1110	And since your callback will be called with a pointer to the watcher, you
1111	can cast it back to your own type:
1112
1113	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1114	{	1510	{
1115	struct my_io *w = (struct my_io *)w_;	1511	// actual processing
1116	...	1512	read (STDIN_FILENO, ...);
		1513
		1514	// have to start the I/O watcher again, as
		1515	// we have handled the event
		1516	ev_io_start (EV_P_ &io);
1117	}	1517	}
1118		1518
1119	More interesting and less C-conformant ways of casting your callback type	1519	// initialisation
1120	instead have been omitted.	1520	ev_idle_init (&idle, idle_cb);
		1521	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1522	ev_io_start (EV_DEFAULT_ &io);
1121		1523
1122	Another common scenario is to use some data structure with multiple	1524	In the "real" world, it might also be beneficial to start a timer, so that
1123	embedded watchers:	1525	low-priority connections can not be locked out forever under load. This
1124		1526	enables your program to keep a lower latency for important connections
1125	struct my_biggy	1527	during short periods of high load, while not completely locking out less
1126	{	1528	important ones.
1127	int some_data;
1128	ev_timer t1;
1129	ev_timer t2;
1130	}
1131
1132	In this case getting the pointer to C<my_biggy> is a bit more
1133	complicated: Either you store the address of your C<my_biggy> struct
1134	in the C<data> member of the watcher (for woozies), or you need to use
1135	some pointer arithmetic using C<offsetof> inside your watchers (for real
1136	programmers):
1137
1138	#include <stddef.h>
1139
1140	static void
1141	t1_cb (EV_P_ ev_timer *w, int revents)
1142	{
1143	struct my_biggy big = (struct my_biggy *
1144	(((char *)w) - offsetof (struct my_biggy, t1));
1145	}
1146
1147	static void
1148	t2_cb (EV_P_ ev_timer *w, int revents)
1149	{
1150	struct my_biggy big = (struct my_biggy *
1151	(((char *)w) - offsetof (struct my_biggy, t2));
1152	}
1153		1529
1154		1530
1155	=head1 WATCHER TYPES	1531	=head1 WATCHER TYPES
1156		1532
1157	This section describes each watcher in detail, but will not repeat	1533	This section describes each watcher in detail, but will not repeat
…		…
1181	In general you can register as many read and/or write event watchers per	1557	In general you can register as many read and/or write event watchers per
1182	fd as you want (as long as you don't confuse yourself). Setting all file	1558	fd as you want (as long as you don't confuse yourself). Setting all file
1183	descriptors to non-blocking mode is also usually a good idea (but not	1559	descriptors to non-blocking mode is also usually a good idea (but not
1184	required if you know what you are doing).	1560	required if you know what you are doing).
1185		1561
1186	If you cannot use non-blocking mode, then force the use of a
1187	known-to-be-good backend (at the time of this writing, this includes only
1188	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1189
1190	Another thing you have to watch out for is that it is quite easy to	1562	Another thing you have to watch out for is that it is quite easy to
1191	receive "spurious" readiness notifications, that is your callback might	1563	receive "spurious" readiness notifications, that is, your callback might
1192	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1564	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1193	because there is no data. Not only are some backends known to create a	1565	because there is no data. It is very easy to get into this situation even
1194	lot of those (for example Solaris ports), it is very easy to get into	1566	with a relatively standard program structure. Thus it is best to always
1195	this situation even with a relatively standard program structure. Thus	1567	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1196	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1197	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1568	preferable to a program hanging until some data arrives.
1198		1569
1199	If you cannot run the fd in non-blocking mode (for example you should	1570	If you cannot run the fd in non-blocking mode (for example you should
1200	not play around with an Xlib connection), then you have to separately	1571	not play around with an Xlib connection), then you have to separately
1201	re-test whether a file descriptor is really ready with a known-to-be good	1572	re-test whether a file descriptor is really ready with a known-to-be good
1202	interface such as poll (fortunately in our Xlib example, Xlib already	1573	interface such as poll (fortunately in the case of Xlib, it already does
1203	does this on its own, so its quite safe to use). Some people additionally	1574	this on its own, so its quite safe to use). Some people additionally
1204	use C<SIGALRM> and an interval timer, just to be sure you won't block	1575	use C<SIGALRM> and an interval timer, just to be sure you won't block
1205	indefinitely.	1576	indefinitely.
1206		1577
1207	But really, best use non-blocking mode.	1578	But really, best use non-blocking mode.
1208		1579
…		…
1236		1607
1237	There is no workaround possible except not registering events	1608	There is no workaround possible except not registering events
1238	for potentially C<dup ()>'ed file descriptors, or to resort to	1609	for potentially C<dup ()>'ed file descriptors, or to resort to
1239	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1610	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1240		1611
		1612	=head3 The special problem of files
		1613
		1614	Many people try to use C<select> (or libev) on file descriptors
		1615	representing files, and expect it to become ready when their program
		1616	doesn't block on disk accesses (which can take a long time on their own).
		1617
		1618	However, this cannot ever work in the "expected" way - you get a readiness
		1619	notification as soon as the kernel knows whether and how much data is
		1620	there, and in the case of open files, that's always the case, so you
		1621	always get a readiness notification instantly, and your read (or possibly
		1622	write) will still block on the disk I/O.
		1623
		1624	Another way to view it is that in the case of sockets, pipes, character
		1625	devices and so on, there is another party (the sender) that delivers data
		1626	on its own, but in the case of files, there is no such thing: the disk
		1627	will not send data on its own, simply because it doesn't know what you
		1628	wish to read - you would first have to request some data.
		1629
		1630	Since files are typically not-so-well supported by advanced notification
		1631	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1632	to files, even though you should not use it. The reason for this is
		1633	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1634	usually a tty, often a pipe, but also sometimes files or special devices
		1635	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1636	F</dev/urandom>), and even though the file might better be served with
		1637	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1638	it "just works" instead of freezing.
		1639
		1640	So avoid file descriptors pointing to files when you know it (e.g. use
		1641	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1642	when you rarely read from a file instead of from a socket, and want to
		1643	reuse the same code path.
		1644
1241	=head3 The special problem of fork	1645	=head3 The special problem of fork
1242		1646
1243	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1647	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1244	useless behaviour. Libev fully supports fork, but needs to be told about	1648	useless behaviour. Libev fully supports fork, but needs to be told about
1245	it in the child.	1649	it in the child if you want to continue to use it in the child.
1246		1650
1247	To support fork in your programs, you either have to call	1651	To support fork in your child processes, you have to call C<ev_loop_fork
1248	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1652	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1249	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1653	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1250	C<EVBACKEND_POLL>.
1251		1654
1252	=head3 The special problem of SIGPIPE	1655	=head3 The special problem of SIGPIPE
1253		1656
1254	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1657	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1255	when writing to a pipe whose other end has been closed, your program gets	1658	when writing to a pipe whose other end has been closed, your program gets
…		…
1258		1661
1259	So when you encounter spurious, unexplained daemon exits, make sure you	1662	So when you encounter spurious, unexplained daemon exits, make sure you
1260	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1663	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1261	somewhere, as that would have given you a big clue).	1664	somewhere, as that would have given you a big clue).
1262		1665
		1666	=head3 The special problem of accept()ing when you can't
		1667
		1668	Many implementations of the POSIX C<accept> function (for example,
		1669	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1670	connection from the pending queue in all error cases.
		1671
		1672	For example, larger servers often run out of file descriptors (because
		1673	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1674	rejecting the connection, leading to libev signalling readiness on
		1675	the next iteration again (the connection still exists after all), and
		1676	typically causing the program to loop at 100% CPU usage.
		1677
		1678	Unfortunately, the set of errors that cause this issue differs between
		1679	operating systems, there is usually little the app can do to remedy the
		1680	situation, and no known thread-safe method of removing the connection to
		1681	cope with overload is known (to me).
		1682
		1683	One of the easiest ways to handle this situation is to just ignore it
		1684	- when the program encounters an overload, it will just loop until the
		1685	situation is over. While this is a form of busy waiting, no OS offers an
		1686	event-based way to handle this situation, so it's the best one can do.
		1687
		1688	A better way to handle the situation is to log any errors other than
		1689	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1690	messages, and continue as usual, which at least gives the user an idea of
		1691	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1692	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1693	usage.
		1694
		1695	If your program is single-threaded, then you could also keep a dummy file
		1696	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1697	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1698	close that fd, and create a new dummy fd. This will gracefully refuse
		1699	clients under typical overload conditions.
		1700
		1701	The last way to handle it is to simply log the error and C<exit>, as
		1702	is often done with C<malloc> failures, but this results in an easy
		1703	opportunity for a DoS attack.
1263		1704
1264	=head3 Watcher-Specific Functions	1705	=head3 Watcher-Specific Functions
1265		1706
1266	=over 4	1707	=over 4
1267		1708
…		…
1299	...	1740	...
1300	struct ev_loop *loop = ev_default_init (0);	1741	struct ev_loop *loop = ev_default_init (0);
1301	ev_io stdin_readable;	1742	ev_io stdin_readable;
1302	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1743	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1303	ev_io_start (loop, &stdin_readable);	1744	ev_io_start (loop, &stdin_readable);
1304	ev_loop (loop, 0);	1745	ev_run (loop, 0);
1305		1746
1306		1747
1307	=head2 C<ev_timer> - relative and optionally repeating timeouts	1748	=head2 C<ev_timer> - relative and optionally repeating timeouts
1308		1749
1309	Timer watchers are simple relative timers that generate an event after a	1750	Timer watchers are simple relative timers that generate an event after a
…		…
1314	year, it will still time out after (roughly) one hour. "Roughly" because	1755	year, it will still time out after (roughly) one hour. "Roughly" because
1315	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1756	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1316	monotonic clock option helps a lot here).	1757	monotonic clock option helps a lot here).
1317		1758
1318	The callback is guaranteed to be invoked only I<after> its timeout has	1759	The callback is guaranteed to be invoked only I<after> its timeout has
1319	passed, but if multiple timers become ready during the same loop iteration	1760	passed (not I<at>, so on systems with very low-resolution clocks this
1320	then order of execution is undefined.	1761	might introduce a small delay). If multiple timers become ready during the
		1762	same loop iteration then the ones with earlier time-out values are invoked
		1763	before ones of the same priority with later time-out values (but this is
		1764	no longer true when a callback calls C<ev_run> recursively).
1321		1765
1322	=head3 Be smart about timeouts	1766	=head3 Be smart about timeouts
1323		1767
1324	Many real-world problems involve some kind of timeout, usually for error	1768	Many real-world problems involve some kind of timeout, usually for error
1325	recovery. A typical example is an HTTP request - if the other side hangs,	1769	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1369	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>	1813	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
1370	member and C<ev_timer_again>.	1814	member and C<ev_timer_again>.
1371		1815
1372	At start:	1816	At start:
1373		1817
1374	ev_timer_init (timer, callback);	1818	ev_init (timer, callback);
1375	timer->repeat = 60.;	1819	timer->repeat = 60.;
1376	ev_timer_again (loop, timer);	1820	ev_timer_again (loop, timer);
1377		1821
1378	Each time there is some activity:	1822	Each time there is some activity:
1379		1823
…		…
1411	ev_tstamp timeout = last_activity + 60.;	1855	ev_tstamp timeout = last_activity + 60.;
1412		1856
1413	// if last_activity + 60. is older than now, we did time out	1857	// if last_activity + 60. is older than now, we did time out
1414	if (timeout < now)	1858	if (timeout < now)
1415	{	1859	{
1416	// timeout occured, take action	1860	// timeout occurred, take action
1417	}	1861	}
1418	else	1862	else
1419	{	1863	{
1420	// callback was invoked, but there was some activity, re-arm	1864	// callback was invoked, but there was some activity, re-arm
1421	// the watcher to fire in last_activity + 60, which is	1865	// the watcher to fire in last_activity + 60, which is
1422	// guaranteed to be in the future, so "again" is positive:	1866	// guaranteed to be in the future, so "again" is positive:
1423	w->again = timeout - now;	1867	w->repeat = timeout - now;
1424	ev_timer_again (EV_A_ w);	1868	ev_timer_again (EV_A_ w);
1425	}	1869	}
1426	}	1870	}
1427		1871
1428	To summarise the callback: first calculate the real timeout (defined	1872	To summarise the callback: first calculate the real timeout (defined
…		…
1441		1885
1442	To start the timer, simply initialise the watcher and set C<last_activity>	1886	To start the timer, simply initialise the watcher and set C<last_activity>
1443	to the current time (meaning we just have some activity :), then call the	1887	to the current time (meaning we just have some activity :), then call the
1444	callback, which will "do the right thing" and start the timer:	1888	callback, which will "do the right thing" and start the timer:
1445		1889
1446	ev_timer_init (timer, callback);	1890	ev_init (timer, callback);
1447	last_activity = ev_now (loop);	1891	last_activity = ev_now (loop);
1448	callback (loop, timer, EV_TIMEOUT);	1892	callback (loop, timer, EV_TIMER);
1449		1893
1450	And when there is some activity, simply store the current time in	1894	And when there is some activity, simply store the current time in
1451	C<last_activity>, no libev calls at all:	1895	C<last_activity>, no libev calls at all:
1452		1896
1453	last_actiivty = ev_now (loop);	1897	last_activity = ev_now (loop);
1454		1898
1455	This technique is slightly more complex, but in most cases where the	1899	This technique is slightly more complex, but in most cases where the
1456	time-out is unlikely to be triggered, much more efficient.	1900	time-out is unlikely to be triggered, much more efficient.
1457		1901
1458	Changing the timeout is trivial as well (if it isn't hard-coded in the	1902	Changing the timeout is trivial as well (if it isn't hard-coded in the
…		…
1496		1940
1497	=head3 The special problem of time updates	1941	=head3 The special problem of time updates
1498		1942
1499	Establishing the current time is a costly operation (it usually takes at	1943	Establishing the current time is a costly operation (it usually takes at
1500	least two system calls): EV therefore updates its idea of the current	1944	least two system calls): EV therefore updates its idea of the current
1501	time only before and after C<ev_loop> collects new events, which causes a	1945	time only before and after C<ev_run> collects new events, which causes a
1502	growing difference between C<ev_now ()> and C<ev_time ()> when handling	1946	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1503	lots of events in one iteration.	1947	lots of events in one iteration.
1504		1948
1505	The relative timeouts are calculated relative to the C<ev_now ()>	1949	The relative timeouts are calculated relative to the C<ev_now ()>
1506	time. This is usually the right thing as this timestamp refers to the time	1950	time. This is usually the right thing as this timestamp refers to the time
…		…
1512		1956
1513	If the event loop is suspended for a long time, you can also force an	1957	If the event loop is suspended for a long time, you can also force an
1514	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1958	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1515	()>.	1959	()>.
1516		1960
		1961	=head3 The special problems of suspended animation
		1962
		1963	When you leave the server world it is quite customary to hit machines that
		1964	can suspend/hibernate - what happens to the clocks during such a suspend?
		1965
		1966	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1967	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1968	to run until the system is suspended, but they will not advance while the
		1969	system is suspended. That means, on resume, it will be as if the program
		1970	was frozen for a few seconds, but the suspend time will not be counted
		1971	towards C<ev_timer> when a monotonic clock source is used. The real time
		1972	clock advanced as expected, but if it is used as sole clocksource, then a
		1973	long suspend would be detected as a time jump by libev, and timers would
		1974	be adjusted accordingly.
		1975
		1976	I would not be surprised to see different behaviour in different between
		1977	operating systems, OS versions or even different hardware.
		1978
		1979	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1980	time jump in the monotonic clocks and the realtime clock. If the program
		1981	is suspended for a very long time, and monotonic clock sources are in use,
		1982	then you can expect C<ev_timer>s to expire as the full suspension time
		1983	will be counted towards the timers. When no monotonic clock source is in
		1984	use, then libev will again assume a timejump and adjust accordingly.
		1985
		1986	It might be beneficial for this latter case to call C<ev_suspend>
		1987	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1988	deterministic behaviour in this case (you can do nothing against
		1989	C<SIGSTOP>).
		1990
1517	=head3 Watcher-Specific Functions and Data Members	1991	=head3 Watcher-Specific Functions and Data Members
1518		1992
1519	=over 4	1993	=over 4
1520		1994
1521	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1995	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1544	If the timer is started but non-repeating, stop it (as if it timed out).	2018	If the timer is started but non-repeating, stop it (as if it timed out).
1545		2019
1546	If the timer is repeating, either start it if necessary (with the	2020	If the timer is repeating, either start it if necessary (with the
1547	C<repeat> value), or reset the running timer to the C<repeat> value.	2021	C<repeat> value), or reset the running timer to the C<repeat> value.
1548		2022
1549	This sounds a bit complicated, see "Be smart about timeouts", above, for a	2023	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1550	usage example.	2024	usage example.
		2025
		2026	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2027
		2028	Returns the remaining time until a timer fires. If the timer is active,
		2029	then this time is relative to the current event loop time, otherwise it's
		2030	the timeout value currently configured.
		2031
		2032	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2033	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2034	will return C<4>. When the timer expires and is restarted, it will return
		2035	roughly C<7> (likely slightly less as callback invocation takes some time,
		2036	too), and so on.
1551		2037
1552	=item ev_tstamp repeat [read-write]	2038	=item ev_tstamp repeat [read-write]
1553		2039
1554	The current C<repeat> value. Will be used each time the watcher times out	2040	The current C<repeat> value. Will be used each time the watcher times out
1555	or C<ev_timer_again> is called, and determines the next timeout (if any),	2041	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1581	}	2067	}
1582		2068
1583	ev_timer mytimer;	2069	ev_timer mytimer;
1584	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2070	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1585	ev_timer_again (&mytimer); /* start timer */	2071	ev_timer_again (&mytimer); /* start timer */
1586	ev_loop (loop, 0);	2072	ev_run (loop, 0);
1587		2073
1588	// and in some piece of code that gets executed on any "activity":	2074	// and in some piece of code that gets executed on any "activity":
1589	// reset the timeout to start ticking again at 10 seconds	2075	// reset the timeout to start ticking again at 10 seconds
1590	ev_timer_again (&mytimer);	2076	ev_timer_again (&mytimer);
1591		2077
…		…
1593	=head2 C<ev_periodic> - to cron or not to cron?	2079	=head2 C<ev_periodic> - to cron or not to cron?
1594		2080
1595	Periodic watchers are also timers of a kind, but they are very versatile	2081	Periodic watchers are also timers of a kind, but they are very versatile
1596	(and unfortunately a bit complex).	2082	(and unfortunately a bit complex).
1597		2083
1598	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2084	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1599	but on wall clock time (absolute time). You can tell a periodic watcher	2085	relative time, the physical time that passes) but on wall clock time
1600	to trigger after some specific point in time. For example, if you tell a	2086	(absolute time, the thing you can read on your calender or clock). The
1601	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	2087	difference is that wall clock time can run faster or slower than real
1602	+ 10.>, that is, an absolute time not a delay) and then reset your system	2088	time, and time jumps are not uncommon (e.g. when you adjust your
1603	clock to January of the previous year, then it will take more than year	2089	wrist-watch).
1604	to trigger the event (unlike an C<ev_timer>, which would still trigger
1605	roughly 10 seconds later as it uses a relative timeout).
1606		2090
		2091	You can tell a periodic watcher to trigger after some specific point
		2092	in time: for example, if you tell a periodic watcher to trigger "in 10
		2093	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2094	not a delay) and then reset your system clock to January of the previous
		2095	year, then it will take a year or more to trigger the event (unlike an
		2096	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2097	it, as it uses a relative timeout).
		2098
1607	C<ev_periodic>s can also be used to implement vastly more complex timers,	2099	C<ev_periodic> watchers can also be used to implement vastly more complex
1608	such as triggering an event on each "midnight, local time", or other	2100	timers, such as triggering an event on each "midnight, local time", or
1609	complicated rules.	2101	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2102	those cannot react to time jumps.
1610		2103
1611	As with timers, the callback is guaranteed to be invoked only when the	2104	As with timers, the callback is guaranteed to be invoked only when the
1612	time (C<at>) has passed, but if multiple periodic timers become ready	2105	point in time where it is supposed to trigger has passed. If multiple
1613	during the same loop iteration, then order of execution is undefined.	2106	timers become ready during the same loop iteration then the ones with
		2107	earlier time-out values are invoked before ones with later time-out values
		2108	(but this is no longer true when a callback calls C<ev_run> recursively).
1614		2109
1615	=head3 Watcher-Specific Functions and Data Members	2110	=head3 Watcher-Specific Functions and Data Members
1616		2111
1617	=over 4	2112	=over 4
1618		2113
1619	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2114	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1620		2115
1621	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2116	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1622		2117
1623	Lots of arguments, lets sort it out... There are basically three modes of	2118	Lots of arguments, let's sort it out... There are basically three modes of
1624	operation, and we will explain them from simplest to most complex:	2119	operation, and we will explain them from simplest to most complex:
1625		2120
1626	=over 4	2121	=over 4
1627		2122
1628	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2123	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1629		2124
1630	In this configuration the watcher triggers an event after the wall clock	2125	In this configuration the watcher triggers an event after the wall clock
1631	time C<at> has passed. It will not repeat and will not adjust when a time	2126	time C<offset> has passed. It will not repeat and will not adjust when a
1632	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2127	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1633	only run when the system clock reaches or surpasses this time.	2128	will be stopped and invoked when the system clock reaches or surpasses
		2129	this point in time.
1634		2130
1635	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2131	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1636		2132
1637	In this mode the watcher will always be scheduled to time out at the next	2133	In this mode the watcher will always be scheduled to time out at the next
1638	C<at + N * interval> time (for some integer N, which can also be negative)	2134	C<offset + N * interval> time (for some integer N, which can also be
1639	and then repeat, regardless of any time jumps.	2135	negative) and then repeat, regardless of any time jumps. The C<offset>
		2136	argument is merely an offset into the C<interval> periods.
1640		2137
1641	This can be used to create timers that do not drift with respect to the	2138	This can be used to create timers that do not drift with respect to the
1642	system clock, for example, here is a C<ev_periodic> that triggers each	2139	system clock, for example, here is an C<ev_periodic> that triggers each
1643	hour, on the hour:	2140	hour, on the hour (with respect to UTC):
1644		2141
1645	ev_periodic_set (&periodic, 0., 3600., 0);	2142	ev_periodic_set (&periodic, 0., 3600., 0);
1646		2143
1647	This doesn't mean there will always be 3600 seconds in between triggers,	2144	This doesn't mean there will always be 3600 seconds in between triggers,
1648	but only that the callback will be called when the system time shows a	2145	but only that the callback will be called when the system time shows a
1649	full hour (UTC), or more correctly, when the system time is evenly divisible	2146	full hour (UTC), or more correctly, when the system time is evenly divisible
1650	by 3600.	2147	by 3600.
1651		2148
1652	Another way to think about it (for the mathematically inclined) is that	2149	Another way to think about it (for the mathematically inclined) is that
1653	C<ev_periodic> will try to run the callback in this mode at the next possible	2150	C<ev_periodic> will try to run the callback in this mode at the next possible
1654	time where C<time = at (mod interval)>, regardless of any time jumps.	2151	time where C<time = offset (mod interval)>, regardless of any time jumps.
1655		2152
1656	For numerical stability it is preferable that the C<at> value is near	2153	For numerical stability it is preferable that the C<offset> value is near
1657	C<ev_now ()> (the current time), but there is no range requirement for	2154	C<ev_now ()> (the current time), but there is no range requirement for
1658	this value, and in fact is often specified as zero.	2155	this value, and in fact is often specified as zero.
1659		2156
1660	Note also that there is an upper limit to how often a timer can fire (CPU	2157	Note also that there is an upper limit to how often a timer can fire (CPU
1661	speed for example), so if C<interval> is very small then timing stability	2158	speed for example), so if C<interval> is very small then timing stability
1662	will of course deteriorate. Libev itself tries to be exact to be about one	2159	will of course deteriorate. Libev itself tries to be exact to be about one
1663	millisecond (if the OS supports it and the machine is fast enough).	2160	millisecond (if the OS supports it and the machine is fast enough).
1664		2161
1665	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2162	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1666		2163
1667	In this mode the values for C<interval> and C<at> are both being	2164	In this mode the values for C<interval> and C<offset> are both being
1668	ignored. Instead, each time the periodic watcher gets scheduled, the	2165	ignored. Instead, each time the periodic watcher gets scheduled, the
1669	reschedule callback will be called with the watcher as first, and the	2166	reschedule callback will be called with the watcher as first, and the
1670	current time as second argument.	2167	current time as second argument.
1671		2168
1672	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2169	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1673	ever, or make ANY event loop modifications whatsoever>.	2170	or make ANY other event loop modifications whatsoever, unless explicitly
		2171	allowed by documentation here>.
1674		2172
1675	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2173	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1676	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2174	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1677	only event loop modification you are allowed to do).	2175	only event loop modification you are allowed to do).
1678		2176
…		…
1708	a different time than the last time it was called (e.g. in a crond like	2206	a different time than the last time it was called (e.g. in a crond like
1709	program when the crontabs have changed).	2207	program when the crontabs have changed).
1710		2208
1711	=item ev_tstamp ev_periodic_at (ev_periodic *)	2209	=item ev_tstamp ev_periodic_at (ev_periodic *)
1712		2210
1713	When active, returns the absolute time that the watcher is supposed to	2211	When active, returns the absolute time that the watcher is supposed
1714	trigger next.	2212	to trigger next. This is not the same as the C<offset> argument to
		2213	C<ev_periodic_set>, but indeed works even in interval and manual
		2214	rescheduling modes.
1715		2215
1716	=item ev_tstamp offset [read-write]	2216	=item ev_tstamp offset [read-write]
1717		2217
1718	When repeating, this contains the offset value, otherwise this is the	2218	When repeating, this contains the offset value, otherwise this is the
1719	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2219	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2220	although libev might modify this value for better numerical stability).
1720		2221
1721	Can be modified any time, but changes only take effect when the periodic	2222	Can be modified any time, but changes only take effect when the periodic
1722	timer fires or C<ev_periodic_again> is being called.	2223	timer fires or C<ev_periodic_again> is being called.
1723		2224
1724	=item ev_tstamp interval [read-write]	2225	=item ev_tstamp interval [read-write]
…		…
1740	Example: Call a callback every hour, or, more precisely, whenever the	2241	Example: Call a callback every hour, or, more precisely, whenever the
1741	system time is divisible by 3600. The callback invocation times have	2242	system time is divisible by 3600. The callback invocation times have
1742	potentially a lot of jitter, but good long-term stability.	2243	potentially a lot of jitter, but good long-term stability.
1743		2244
1744	static void	2245	static void
1745	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2246	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1746	{	2247	{
1747	... its now a full hour (UTC, or TAI or whatever your clock follows)	2248	... its now a full hour (UTC, or TAI or whatever your clock follows)
1748	}	2249	}
1749		2250
1750	ev_periodic hourly_tick;	2251	ev_periodic hourly_tick;
…		…
1773		2274
1774	=head2 C<ev_signal> - signal me when a signal gets signalled!	2275	=head2 C<ev_signal> - signal me when a signal gets signalled!
1775		2276
1776	Signal watchers will trigger an event when the process receives a specific	2277	Signal watchers will trigger an event when the process receives a specific
1777	signal one or more times. Even though signals are very asynchronous, libev	2278	signal one or more times. Even though signals are very asynchronous, libev
1778	will try it's best to deliver signals synchronously, i.e. as part of the	2279	will try its best to deliver signals synchronously, i.e. as part of the
1779	normal event processing, like any other event.	2280	normal event processing, like any other event.
1780		2281
1781	If you want signals asynchronously, just use C<sigaction> as you would	2282	If you want signals to be delivered truly asynchronously, just use
1782	do without libev and forget about sharing the signal. You can even use	2283	C<sigaction> as you would do without libev and forget about sharing
1783	C<ev_async> from a signal handler to synchronously wake up an event loop.	2284	the signal. You can even use C<ev_async> from a signal handler to
		2285	synchronously wake up an event loop.
1784		2286
1785	You can configure as many watchers as you like per signal. Only when the	2287	You can configure as many watchers as you like for the same signal, but
		2288	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2289	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2290	C<SIGINT> in both the default loop and another loop at the same time. At
		2291	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2292
1786	first watcher gets started will libev actually register a signal handler	2293	When the first watcher gets started will libev actually register something
1787	with the kernel (thus it coexists with your own signal handlers as long as	2294	with the kernel (thus it coexists with your own signal handlers as long as
1788	you don't register any with libev for the same signal). Similarly, when	2295	you don't register any with libev for the same signal).
1789	the last signal watcher for a signal is stopped, libev will reset the
1790	signal handler to SIG_DFL (regardless of what it was set to before).
1791		2296
1792	If possible and supported, libev will install its handlers with	2297	If possible and supported, libev will install its handlers with
1793	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2298	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1794	interrupted. If you have a problem with system calls getting interrupted by	2299	not be unduly interrupted. If you have a problem with system calls getting
1795	signals you can block all signals in an C<ev_check> watcher and unblock	2300	interrupted by signals you can block all signals in an C<ev_check> watcher
1796	them in an C<ev_prepare> watcher.	2301	and unblock them in an C<ev_prepare> watcher.
		2302
		2303	=head3 The special problem of inheritance over fork/execve/pthread_create
		2304
		2305	Both the signal mask (C<sigprocmask>) and the signal disposition
		2306	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2307	stopping it again), that is, libev might or might not block the signal,
		2308	and might or might not set or restore the installed signal handler (but
		2309	see C<EVFLAG_NOSIGMASK>).
		2310
		2311	While this does not matter for the signal disposition (libev never
		2312	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2313	C<execve>), this matters for the signal mask: many programs do not expect
		2314	certain signals to be blocked.
		2315
		2316	This means that before calling C<exec> (from the child) you should reset
		2317	the signal mask to whatever "default" you expect (all clear is a good
		2318	choice usually).
		2319
		2320	The simplest way to ensure that the signal mask is reset in the child is
		2321	to install a fork handler with C<pthread_atfork> that resets it. That will
		2322	catch fork calls done by libraries (such as the libc) as well.
		2323
		2324	In current versions of libev, the signal will not be blocked indefinitely
		2325	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2326	the window of opportunity for problems, it will not go away, as libev
		2327	I<has> to modify the signal mask, at least temporarily.
		2328
		2329	So I can't stress this enough: I<If you do not reset your signal mask when
		2330	you expect it to be empty, you have a race condition in your code>. This
		2331	is not a libev-specific thing, this is true for most event libraries.
		2332
		2333	=head3 The special problem of threads signal handling
		2334
		2335	POSIX threads has problematic signal handling semantics, specifically,
		2336	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2337	threads in a process block signals, which is hard to achieve.
		2338
		2339	When you want to use sigwait (or mix libev signal handling with your own
		2340	for the same signals), you can tackle this problem by globally blocking
		2341	all signals before creating any threads (or creating them with a fully set
		2342	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2343	loops. Then designate one thread as "signal receiver thread" which handles
		2344	these signals. You can pass on any signals that libev might be interested
		2345	in by calling C<ev_feed_signal>.
1797		2346
1798	=head3 Watcher-Specific Functions and Data Members	2347	=head3 Watcher-Specific Functions and Data Members
1799		2348
1800	=over 4	2349	=over 4
1801		2350
…		…
1817	Example: Try to exit cleanly on SIGINT.	2366	Example: Try to exit cleanly on SIGINT.
1818		2367
1819	static void	2368	static void
1820	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2369	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1821	{	2370	{
1822	ev_unloop (loop, EVUNLOOP_ALL);	2371	ev_break (loop, EVBREAK_ALL);
1823	}	2372	}
1824		2373
1825	ev_signal signal_watcher;	2374	ev_signal signal_watcher;
1826	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2375	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1827	ev_signal_start (loop, &signal_watcher);	2376	ev_signal_start (loop, &signal_watcher);
…		…
1833	some child status changes (most typically when a child of yours dies or	2382	some child status changes (most typically when a child of yours dies or
1834	exits). It is permissible to install a child watcher I<after> the child	2383	exits). It is permissible to install a child watcher I<after> the child
1835	has been forked (which implies it might have already exited), as long	2384	has been forked (which implies it might have already exited), as long
1836	as the event loop isn't entered (or is continued from a watcher), i.e.,	2385	as the event loop isn't entered (or is continued from a watcher), i.e.,
1837	forking and then immediately registering a watcher for the child is fine,	2386	forking and then immediately registering a watcher for the child is fine,
1838	but forking and registering a watcher a few event loop iterations later is	2387	but forking and registering a watcher a few event loop iterations later or
1839	not.	2388	in the next callback invocation is not.
1840		2389
1841	Only the default event loop is capable of handling signals, and therefore	2390	Only the default event loop is capable of handling signals, and therefore
1842	you can only register child watchers in the default event loop.	2391	you can only register child watchers in the default event loop.
1843		2392
		2393	Due to some design glitches inside libev, child watchers will always be
		2394	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2395	libev)
		2396
1844	=head3 Process Interaction	2397	=head3 Process Interaction
1845		2398
1846	Libev grabs C<SIGCHLD> as soon as the default event loop is	2399	Libev grabs C<SIGCHLD> as soon as the default event loop is
1847	initialised. This is necessary to guarantee proper behaviour even if	2400	initialised. This is necessary to guarantee proper behaviour even if the
1848	the first child watcher is started after the child exits. The occurrence	2401	first child watcher is started after the child exits. The occurrence
1849	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2402	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1850	synchronously as part of the event loop processing. Libev always reaps all	2403	synchronously as part of the event loop processing. Libev always reaps all
1851	children, even ones not watched.	2404	children, even ones not watched.
1852		2405
1853	=head3 Overriding the Built-In Processing	2406	=head3 Overriding the Built-In Processing
…		…
1863	=head3 Stopping the Child Watcher	2416	=head3 Stopping the Child Watcher
1864		2417
1865	Currently, the child watcher never gets stopped, even when the	2418	Currently, the child watcher never gets stopped, even when the
1866	child terminates, so normally one needs to stop the watcher in the	2419	child terminates, so normally one needs to stop the watcher in the
1867	callback. Future versions of libev might stop the watcher automatically	2420	callback. Future versions of libev might stop the watcher automatically
1868	when a child exit is detected.	2421	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2422	problem).
1869		2423
1870	=head3 Watcher-Specific Functions and Data Members	2424	=head3 Watcher-Specific Functions and Data Members
1871		2425
1872	=over 4	2426	=over 4
1873		2427
…		…
2009	the process. The exception are C<ev_stat> watchers - those call C<stat	2563	the process. The exception are C<ev_stat> watchers - those call C<stat
2010	()>, which is a synchronous operation.	2564	()>, which is a synchronous operation.
2011		2565
2012	For local paths, this usually doesn't matter: unless the system is very	2566	For local paths, this usually doesn't matter: unless the system is very
2013	busy or the intervals between stat's are large, a stat call will be fast,	2567	busy or the intervals between stat's are large, a stat call will be fast,
2014	as the path data is suually in memory already (except when starting the	2568	as the path data is usually in memory already (except when starting the
2015	watcher).	2569	watcher).
2016		2570
2017	For networked file systems, calling C<stat ()> can block an indefinite	2571	For networked file systems, calling C<stat ()> can block an indefinite
2018	time due to network issues, and even under good conditions, a stat call	2572	time due to network issues, and even under good conditions, a stat call
2019	often takes multiple milliseconds.	2573	often takes multiple milliseconds.
…		…
2176		2730
2177	=head3 Watcher-Specific Functions and Data Members	2731	=head3 Watcher-Specific Functions and Data Members
2178		2732
2179	=over 4	2733	=over 4
2180		2734
2181	=item ev_idle_init (ev_signal *, callback)	2735	=item ev_idle_init (ev_idle *, callback)
2182		2736
2183	Initialises and configures the idle watcher - it has no parameters of any	2737	Initialises and configures the idle watcher - it has no parameters of any
2184	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2738	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
2185	believe me.	2739	believe me.
2186		2740
…		…
2199	// no longer anything immediate to do.	2753	// no longer anything immediate to do.
2200	}	2754	}
2201		2755
2202	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2756	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2203	ev_idle_init (idle_watcher, idle_cb);	2757	ev_idle_init (idle_watcher, idle_cb);
2204	ev_idle_start (loop, idle_cb);	2758	ev_idle_start (loop, idle_watcher);
2205		2759
2206		2760
2207	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2761	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2208		2762
2209	Prepare and check watchers are usually (but not always) used in pairs:	2763	Prepare and check watchers are usually (but not always) used in pairs:
2210	prepare watchers get invoked before the process blocks and check watchers	2764	prepare watchers get invoked before the process blocks and check watchers
2211	afterwards.	2765	afterwards.
2212		2766
2213	You I<must not> call C<ev_loop> or similar functions that enter	2767	You I<must not> call C<ev_run> or similar functions that enter
2214	the current event loop from either C<ev_prepare> or C<ev_check>	2768	the current event loop from either C<ev_prepare> or C<ev_check>
2215	watchers. Other loops than the current one are fine, however. The	2769	watchers. Other loops than the current one are fine, however. The
2216	rationale behind this is that you do not need to check for recursion in	2770	rationale behind this is that you do not need to check for recursion in
2217	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2771	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2218	C<ev_check> so if you have one watcher of each kind they will always be	2772	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2302	struct pollfd fds [nfd];	2856	struct pollfd fds [nfd];
2303	// actual code will need to loop here and realloc etc.	2857	// actual code will need to loop here and realloc etc.
2304	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2858	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2305		2859
2306	/* the callback is illegal, but won't be called as we stop during check */	2860	/* the callback is illegal, but won't be called as we stop during check */
2307	ev_timer_init (&tw, 0, timeout * 1e-3);	2861	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2308	ev_timer_start (loop, &tw);	2862	ev_timer_start (loop, &tw);
2309		2863
2310	// create one ev_io per pollfd	2864	// create one ev_io per pollfd
2311	for (int i = 0; i < nfd; ++i)	2865	for (int i = 0; i < nfd; ++i)
2312	{	2866	{
…		…
2386		2940
2387	if (timeout >= 0)	2941	if (timeout >= 0)
2388	// create/start timer	2942	// create/start timer
2389		2943
2390	// poll	2944	// poll
2391	ev_loop (EV_A_ 0);	2945	ev_run (EV_A_ 0);
2392		2946
2393	// stop timer again	2947	// stop timer again
2394	if (timeout >= 0)	2948	if (timeout >= 0)
2395	ev_timer_stop (EV_A_ &to);	2949	ev_timer_stop (EV_A_ &to);
2396		2950
…		…
2425	some fds have to be watched and handled very quickly (with low latency),	2979	some fds have to be watched and handled very quickly (with low latency),
2426	and even priorities and idle watchers might have too much overhead. In	2980	and even priorities and idle watchers might have too much overhead. In
2427	this case you would put all the high priority stuff in one loop and all	2981	this case you would put all the high priority stuff in one loop and all
2428	the rest in a second one, and embed the second one in the first.	2982	the rest in a second one, and embed the second one in the first.
2429		2983
2430	As long as the watcher is active, the callback will be invoked every time	2984	As long as the watcher is active, the callback will be invoked every
2431	there might be events pending in the embedded loop. The callback must then	2985	time there might be events pending in the embedded loop. The callback
2432	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2986	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2433	their callbacks (you could also start an idle watcher to give the embedded	2987	sweep and invoke their callbacks (the callback doesn't need to invoke the
2434	loop strictly lower priority for example). You can also set the callback	2988	C<ev_embed_sweep> function directly, it could also start an idle watcher
2435	to C<0>, in which case the embed watcher will automatically execute the	2989	to give the embedded loop strictly lower priority for example).
2436	embedded loop sweep.
2437		2990
2438	As long as the watcher is started it will automatically handle events. The	2991	You can also set the callback to C<0>, in which case the embed watcher
2439	callback will be invoked whenever some events have been handled. You can	2992	will automatically execute the embedded loop sweep whenever necessary.
2440	set the callback to C<0> to avoid having to specify one if you are not
2441	interested in that.
2442		2993
2443	Also, there have not currently been made special provisions for forking:	2994	Fork detection will be handled transparently while the C<ev_embed> watcher
2444	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2995	is active, i.e., the embedded loop will automatically be forked when the
2445	but you will also have to stop and restart any C<ev_embed> watchers	2996	embedding loop forks. In other cases, the user is responsible for calling
2446	yourself - but you can use a fork watcher to handle this automatically,	2997	C<ev_loop_fork> on the embedded loop.
2447	and future versions of libev might do just that.
2448		2998
2449	Unfortunately, not all backends are embeddable: only the ones returned by	2999	Unfortunately, not all backends are embeddable: only the ones returned by
2450	C<ev_embeddable_backends> are, which, unfortunately, does not include any	3000	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2451	portable one.	3001	portable one.
2452		3002
…		…
2478	if you do not want that, you need to temporarily stop the embed watcher).	3028	if you do not want that, you need to temporarily stop the embed watcher).
2479		3029
2480	=item ev_embed_sweep (loop, ev_embed *)	3030	=item ev_embed_sweep (loop, ev_embed *)
2481		3031
2482	Make a single, non-blocking sweep over the embedded loop. This works	3032	Make a single, non-blocking sweep over the embedded loop. This works
2483	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3033	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2484	appropriate way for embedded loops.	3034	appropriate way for embedded loops.
2485		3035
2486	=item struct ev_loop *other [read-only]	3036	=item struct ev_loop *other [read-only]
2487		3037
2488	The embedded event loop.	3038	The embedded event loop.
…		…
2546	event loop blocks next and before C<ev_check> watchers are being called,	3096	event loop blocks next and before C<ev_check> watchers are being called,
2547	and only in the child after the fork. If whoever good citizen calling	3097	and only in the child after the fork. If whoever good citizen calling
2548	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3098	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2549	handlers will be invoked, too, of course.	3099	handlers will be invoked, too, of course.
2550		3100
		3101	=head3 The special problem of life after fork - how is it possible?
		3102
		3103	Most uses of C<fork()> consist of forking, then some simple calls to set
		3104	up/change the process environment, followed by a call to C<exec()>. This
		3105	sequence should be handled by libev without any problems.
		3106
		3107	This changes when the application actually wants to do event handling
		3108	in the child, or both parent in child, in effect "continuing" after the
		3109	fork.
		3110
		3111	The default mode of operation (for libev, with application help to detect
		3112	forks) is to duplicate all the state in the child, as would be expected
		3113	when I<either> the parent I<or> the child process continues.
		3114
		3115	When both processes want to continue using libev, then this is usually the
		3116	wrong result. In that case, usually one process (typically the parent) is
		3117	supposed to continue with all watchers in place as before, while the other
		3118	process typically wants to start fresh, i.e. without any active watchers.
		3119
		3120	The cleanest and most efficient way to achieve that with libev is to
		3121	simply create a new event loop, which of course will be "empty", and
		3122	use that for new watchers. This has the advantage of not touching more
		3123	memory than necessary, and thus avoiding the copy-on-write, and the
		3124	disadvantage of having to use multiple event loops (which do not support
		3125	signal watchers).
		3126
		3127	When this is not possible, or you want to use the default loop for
		3128	other reasons, then in the process that wants to start "fresh", call
		3129	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3130	Destroying the default loop will "orphan" (not stop) all registered
		3131	watchers, so you have to be careful not to execute code that modifies
		3132	those watchers. Note also that in that case, you have to re-register any
		3133	signal watchers.
		3134
2551	=head3 Watcher-Specific Functions and Data Members	3135	=head3 Watcher-Specific Functions and Data Members
2552		3136
2553	=over 4	3137	=over 4
2554		3138
2555	=item ev_fork_init (ev_signal *, callback)	3139	=item ev_fork_init (ev_fork *, callback)
2556		3140
2557	Initialises and configures the fork watcher - it has no parameters of any	3141	Initialises and configures the fork watcher - it has no parameters of any
2558	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3142	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2559	believe me.	3143	really.
2560		3144
2561	=back	3145	=back
2562		3146
2563		3147
		3148	=head2 C<ev_cleanup> - even the best things end
		3149
		3150	Cleanup watchers are called just before the event loop is being destroyed
		3151	by a call to C<ev_loop_destroy>.
		3152
		3153	While there is no guarantee that the event loop gets destroyed, cleanup
		3154	watchers provide a convenient method to install cleanup hooks for your
		3155	program, worker threads and so on - you just to make sure to destroy the
		3156	loop when you want them to be invoked.
		3157
		3158	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3159	all other watchers, they do not keep a reference to the event loop (which
		3160	makes a lot of sense if you think about it). Like all other watchers, you
		3161	can call libev functions in the callback, except C<ev_cleanup_start>.
		3162
		3163	=head3 Watcher-Specific Functions and Data Members
		3164
		3165	=over 4
		3166
		3167	=item ev_cleanup_init (ev_cleanup *, callback)
		3168
		3169	Initialises and configures the cleanup watcher - it has no parameters of
		3170	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3171	pointless, I assure you.
		3172
		3173	=back
		3174
		3175	Example: Register an atexit handler to destroy the default loop, so any
		3176	cleanup functions are called.
		3177
		3178	static void
		3179	program_exits (void)
		3180	{
		3181	ev_loop_destroy (EV_DEFAULT_UC);
		3182	}
		3183
		3184	...
		3185	atexit (program_exits);
		3186
		3187
2564	=head2 C<ev_async> - how to wake up another event loop	3188	=head2 C<ev_async> - how to wake up an event loop
2565		3189
2566	In general, you cannot use an C<ev_loop> from multiple threads or other	3190	In general, you cannot use an C<ev_run> from multiple threads or other
2567	asynchronous sources such as signal handlers (as opposed to multiple event	3191	asynchronous sources such as signal handlers (as opposed to multiple event
2568	loops - those are of course safe to use in different threads).	3192	loops - those are of course safe to use in different threads).
2569		3193
2570	Sometimes, however, you need to wake up another event loop you do not	3194	Sometimes, however, you need to wake up an event loop you do not control,
2571	control, for example because it belongs to another thread. This is what	3195	for example because it belongs to another thread. This is what C<ev_async>
2572	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3196	watchers do: as long as the C<ev_async> watcher is active, you can signal
2573	can signal it by calling C<ev_async_send>, which is thread- and signal	3197	it by calling C<ev_async_send>, which is thread- and signal safe.
2574	safe.
2575		3198
2576	This functionality is very similar to C<ev_signal> watchers, as signals,	3199	This functionality is very similar to C<ev_signal> watchers, as signals,
2577	too, are asynchronous in nature, and signals, too, will be compressed	3200	too, are asynchronous in nature, and signals, too, will be compressed
2578	(i.e. the number of callback invocations may be less than the number of	3201	(i.e. the number of callback invocations may be less than the number of
2579	C<ev_async_sent> calls).	3202	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
		3203	of "global async watchers" by using a watcher on an otherwise unused
		3204	signal, and C<ev_feed_signal> to signal this watcher from another thread,
		3205	even without knowing which loop owns the signal.
2580		3206
2581	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3207	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
2582	just the default loop.	3208	just the default loop.
2583		3209
2584	=head3 Queueing	3210	=head3 Queueing
2585		3211
2586	C<ev_async> does not support queueing of data in any way. The reason	3212	C<ev_async> does not support queueing of data in any way. The reason
2587	is that the author does not know of a simple (or any) algorithm for a	3213	is that the author does not know of a simple (or any) algorithm for a
2588	multiple-writer-single-reader queue that works in all cases and doesn't	3214	multiple-writer-single-reader queue that works in all cases and doesn't
2589	need elaborate support such as pthreads.	3215	need elaborate support such as pthreads or unportable memory access
		3216	semantics.
2590		3217
2591	That means that if you want to queue data, you have to provide your own	3218	That means that if you want to queue data, you have to provide your own
2592	queue. But at least I can tell you how to implement locking around your	3219	queue. But at least I can tell you how to implement locking around your
2593	queue:	3220	queue:
2594		3221
…		…
2683	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3310	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2684	C<ev_feed_event>, this call is safe to do from other threads, signal or	3311	C<ev_feed_event>, this call is safe to do from other threads, signal or
2685	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3312	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2686	section below on what exactly this means).	3313	section below on what exactly this means).
2687		3314
		3315	Note that, as with other watchers in libev, multiple events might get
		3316	compressed into a single callback invocation (another way to look at this
		3317	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3318	reset when the event loop detects that).
		3319
2688	This call incurs the overhead of a system call only once per loop iteration,	3320	This call incurs the overhead of a system call only once per event loop
2689	so while the overhead might be noticeable, it doesn't apply to repeated	3321	iteration, so while the overhead might be noticeable, it doesn't apply to
2690	calls to C<ev_async_send>.	3322	repeated calls to C<ev_async_send> for the same event loop.
2691		3323
2692	=item bool = ev_async_pending (ev_async *)	3324	=item bool = ev_async_pending (ev_async *)
2693		3325
2694	Returns a non-zero value when C<ev_async_send> has been called on the	3326	Returns a non-zero value when C<ev_async_send> has been called on the
2695	watcher but the event has not yet been processed (or even noted) by the	3327	watcher but the event has not yet been processed (or even noted) by the
…		…
2698	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3330	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2699	the loop iterates next and checks for the watcher to have become active,	3331	the loop iterates next and checks for the watcher to have become active,
2700	it will reset the flag again. C<ev_async_pending> can be used to very	3332	it will reset the flag again. C<ev_async_pending> can be used to very
2701	quickly check whether invoking the loop might be a good idea.	3333	quickly check whether invoking the loop might be a good idea.
2702		3334
2703	Not that this does I<not> check whether the watcher itself is pending, only	3335	Not that this does I<not> check whether the watcher itself is pending,
2704	whether it has been requested to make this watcher pending.	3336	only whether it has been requested to make this watcher pending: there
		3337	is a time window between the event loop checking and resetting the async
		3338	notification, and the callback being invoked.
2705		3339
2706	=back	3340	=back
2707		3341
2708		3342
2709	=head1 OTHER FUNCTIONS	3343	=head1 OTHER FUNCTIONS
…		…
2726		3360
2727	If C<timeout> is less than 0, then no timeout watcher will be	3361	If C<timeout> is less than 0, then no timeout watcher will be
2728	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3362	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2729	repeat = 0) will be started. C<0> is a valid timeout.	3363	repeat = 0) will be started. C<0> is a valid timeout.
2730		3364
2731	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3365	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2732	passed an C<revents> set like normal event callbacks (a combination of	3366	passed an C<revents> set like normal event callbacks (a combination of
2733	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3367	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2734	value passed to C<ev_once>. Note that it is possible to receive I<both>	3368	value passed to C<ev_once>. Note that it is possible to receive I<both>
2735	a timeout and an io event at the same time - you probably should give io	3369	a timeout and an io event at the same time - you probably should give io
2736	events precedence.	3370	events precedence.
2737		3371
2738	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3372	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2739		3373
2740	static void stdin_ready (int revents, void *arg)	3374	static void stdin_ready (int revents, void *arg)
2741	{	3375	{
2742	if (revents & EV_READ)	3376	if (revents & EV_READ)
2743	/* stdin might have data for us, joy! */;	3377	/* stdin might have data for us, joy! */;
2744	else if (revents & EV_TIMEOUT)	3378	else if (revents & EV_TIMER)
2745	/* doh, nothing entered */;	3379	/* doh, nothing entered */;
2746	}	3380	}
2747		3381
2748	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3382	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2749		3383
2750	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2751
2752	Feeds the given event set into the event loop, as if the specified event
2753	had happened for the specified watcher (which must be a pointer to an
2754	initialised but not necessarily started event watcher).
2755
2756	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3384	=item ev_feed_fd_event (loop, int fd, int revents)
2757		3385
2758	Feed an event on the given fd, as if a file descriptor backend detected	3386	Feed an event on the given fd, as if a file descriptor backend detected
2759	the given events it.	3387	the given events it.
2760		3388
2761	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3389	=item ev_feed_signal_event (loop, int signum)
2762		3390
2763	Feed an event as if the given signal occurred (C<loop> must be the default	3391	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
2764	loop!).	3392	which is async-safe.
2765		3393
2766	=back	3394	=back
		3395
		3396
		3397	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3398
		3399	This section explains some common idioms that are not immediately
		3400	obvious. Note that examples are sprinkled over the whole manual, and this
		3401	section only contains stuff that wouldn't fit anywhere else.
		3402
		3403	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3404
		3405	Each watcher has, by default, a C<void *data> member that you can read
		3406	or modify at any time: libev will completely ignore it. This can be used
		3407	to associate arbitrary data with your watcher. If you need more data and
		3408	don't want to allocate memory separately and store a pointer to it in that
		3409	data member, you can also "subclass" the watcher type and provide your own
		3410	data:
		3411
		3412	struct my_io
		3413	{
		3414	ev_io io;
		3415	int otherfd;
		3416	void *somedata;
		3417	struct whatever *mostinteresting;
		3418	};
		3419
		3420	...
		3421	struct my_io w;
		3422	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3423
		3424	And since your callback will be called with a pointer to the watcher, you
		3425	can cast it back to your own type:
		3426
		3427	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3428	{
		3429	struct my_io *w = (struct my_io *)w_;
		3430	...
		3431	}
		3432
		3433	More interesting and less C-conformant ways of casting your callback
		3434	function type instead have been omitted.
		3435
		3436	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3437
		3438	Another common scenario is to use some data structure with multiple
		3439	embedded watchers, in effect creating your own watcher that combines
		3440	multiple libev event sources into one "super-watcher":
		3441
		3442	struct my_biggy
		3443	{
		3444	int some_data;
		3445	ev_timer t1;
		3446	ev_timer t2;
		3447	}
		3448
		3449	In this case getting the pointer to C<my_biggy> is a bit more
		3450	complicated: Either you store the address of your C<my_biggy> struct in
		3451	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3452	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3453	real programmers):
		3454
		3455	#include <stddef.h>
		3456
		3457	static void
		3458	t1_cb (EV_P_ ev_timer *w, int revents)
		3459	{
		3460	struct my_biggy big = (struct my_biggy *)
		3461	(((char *)w) - offsetof (struct my_biggy, t1));
		3462	}
		3463
		3464	static void
		3465	t2_cb (EV_P_ ev_timer *w, int revents)
		3466	{
		3467	struct my_biggy big = (struct my_biggy *)
		3468	(((char *)w) - offsetof (struct my_biggy, t2));
		3469	}
		3470
		3471	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3472
		3473	Often (especially in GUI toolkits) there are places where you have
		3474	I<modal> interaction, which is most easily implemented by recursively
		3475	invoking C<ev_run>.
		3476
		3477	This brings the problem of exiting - a callback might want to finish the
		3478	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3479	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3480	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3481	other combination: In these cases, C<ev_break> will not work alone.
		3482
		3483	The solution is to maintain "break this loop" variable for each C<ev_run>
		3484	invocation, and use a loop around C<ev_run> until the condition is
		3485	triggered, using C<EVRUN_ONCE>:
		3486
		3487	// main loop
		3488	int exit_main_loop = 0;
		3489
		3490	while (!exit_main_loop)
		3491	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3492
		3493	// in a model watcher
		3494	int exit_nested_loop = 0;
		3495
		3496	while (!exit_nested_loop)
		3497	ev_run (EV_A_ EVRUN_ONCE);
		3498
		3499	To exit from any of these loops, just set the corresponding exit variable:
		3500
		3501	// exit modal loop
		3502	exit_nested_loop = 1;
		3503
		3504	// exit main program, after modal loop is finished
		3505	exit_main_loop = 1;
		3506
		3507	// exit both
		3508	exit_main_loop = exit_nested_loop = 1;
		3509
		3510	=head2 THREAD LOCKING EXAMPLE
		3511
		3512	Here is a fictitious example of how to run an event loop in a different
		3513	thread from where callbacks are being invoked and watchers are
		3514	created/added/removed.
		3515
		3516	For a real-world example, see the C<EV::Loop::Async> perl module,
		3517	which uses exactly this technique (which is suited for many high-level
		3518	languages).
		3519
		3520	The example uses a pthread mutex to protect the loop data, a condition
		3521	variable to wait for callback invocations, an async watcher to notify the
		3522	event loop thread and an unspecified mechanism to wake up the main thread.
		3523
		3524	First, you need to associate some data with the event loop:
		3525
		3526	typedef struct {
		3527	mutex_t lock; /* global loop lock */
		3528	ev_async async_w;
		3529	thread_t tid;
		3530	cond_t invoke_cv;
		3531	} userdata;
		3532
		3533	void prepare_loop (EV_P)
		3534	{
		3535	// for simplicity, we use a static userdata struct.
		3536	static userdata u;
		3537
		3538	ev_async_init (&u->async_w, async_cb);
		3539	ev_async_start (EV_A_ &u->async_w);
		3540
		3541	pthread_mutex_init (&u->lock, 0);
		3542	pthread_cond_init (&u->invoke_cv, 0);
		3543
		3544	// now associate this with the loop
		3545	ev_set_userdata (EV_A_ u);
		3546	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3547	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3548
		3549	// then create the thread running ev_loop
		3550	pthread_create (&u->tid, 0, l_run, EV_A);
		3551	}
		3552
		3553	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3554	solely to wake up the event loop so it takes notice of any new watchers
		3555	that might have been added:
		3556
		3557	static void
		3558	async_cb (EV_P_ ev_async *w, int revents)
		3559	{
		3560	// just used for the side effects
		3561	}
		3562
		3563	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3564	protecting the loop data, respectively.
		3565
		3566	static void
		3567	l_release (EV_P)
		3568	{
		3569	userdata *u = ev_userdata (EV_A);
		3570	pthread_mutex_unlock (&u->lock);
		3571	}
		3572
		3573	static void
		3574	l_acquire (EV_P)
		3575	{
		3576	userdata *u = ev_userdata (EV_A);
		3577	pthread_mutex_lock (&u->lock);
		3578	}
		3579
		3580	The event loop thread first acquires the mutex, and then jumps straight
		3581	into C<ev_run>:
		3582
		3583	void *
		3584	l_run (void *thr_arg)
		3585	{
		3586	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3587
		3588	l_acquire (EV_A);
		3589	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3590	ev_run (EV_A_ 0);
		3591	l_release (EV_A);
		3592
		3593	return 0;
		3594	}
		3595
		3596	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3597	signal the main thread via some unspecified mechanism (signals? pipe
		3598	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3599	have been called (in a while loop because a) spurious wakeups are possible
		3600	and b) skipping inter-thread-communication when there are no pending
		3601	watchers is very beneficial):
		3602
		3603	static void
		3604	l_invoke (EV_P)
		3605	{
		3606	userdata *u = ev_userdata (EV_A);
		3607
		3608	while (ev_pending_count (EV_A))
		3609	{
		3610	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3611	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3612	}
		3613	}
		3614
		3615	Now, whenever the main thread gets told to invoke pending watchers, it
		3616	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3617	thread to continue:
		3618
		3619	static void
		3620	real_invoke_pending (EV_P)
		3621	{
		3622	userdata *u = ev_userdata (EV_A);
		3623
		3624	pthread_mutex_lock (&u->lock);
		3625	ev_invoke_pending (EV_A);
		3626	pthread_cond_signal (&u->invoke_cv);
		3627	pthread_mutex_unlock (&u->lock);
		3628	}
		3629
		3630	Whenever you want to start/stop a watcher or do other modifications to an
		3631	event loop, you will now have to lock:
		3632
		3633	ev_timer timeout_watcher;
		3634	userdata *u = ev_userdata (EV_A);
		3635
		3636	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3637
		3638	pthread_mutex_lock (&u->lock);
		3639	ev_timer_start (EV_A_ &timeout_watcher);
		3640	ev_async_send (EV_A_ &u->async_w);
		3641	pthread_mutex_unlock (&u->lock);
		3642
		3643	Note that sending the C<ev_async> watcher is required because otherwise
		3644	an event loop currently blocking in the kernel will have no knowledge
		3645	about the newly added timer. By waking up the loop it will pick up any new
		3646	watchers in the next event loop iteration.
		3647
		3648	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3649
		3650	While the overhead of a callback that e.g. schedules a thread is small, it
		3651	is still an overhead. If you embed libev, and your main usage is with some
		3652	kind of threads or coroutines, you might want to customise libev so that
		3653	doesn't need callbacks anymore.
		3654
		3655	Imagine you have coroutines that you can switch to using a function
		3656	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3657	and that due to some magic, the currently active coroutine is stored in a
		3658	global called C<current_coro>. Then you can build your own "wait for libev
		3659	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3660	the differing C<;> conventions):
		3661
		3662	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3663	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3664
		3665	That means instead of having a C callback function, you store the
		3666	coroutine to switch to in each watcher, and instead of having libev call
		3667	your callback, you instead have it switch to that coroutine.
		3668
		3669	A coroutine might now wait for an event with a function called
		3670	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3671	matter when, or whether the watcher is active or not when this function is
		3672	called):
		3673
		3674	void
		3675	wait_for_event (ev_watcher *w)
		3676	{
		3677	ev_cb_set (w) = current_coro;
		3678	switch_to (libev_coro);
		3679	}
		3680
		3681	That basically suspends the coroutine inside C<wait_for_event> and
		3682	continues the libev coroutine, which, when appropriate, switches back to
		3683	this or any other coroutine. I am sure if you sue this your own :)
		3684
		3685	You can do similar tricks if you have, say, threads with an event queue -
		3686	instead of storing a coroutine, you store the queue object and instead of
		3687	switching to a coroutine, you push the watcher onto the queue and notify
		3688	any waiters.
		3689
		3690	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3691	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3692
		3693	// my_ev.h
		3694	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3695	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3696	#include "../libev/ev.h"
		3697
		3698	// my_ev.c
		3699	#define EV_H "my_ev.h"
		3700	#include "../libev/ev.c"
		3701
		3702	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3703	F<my_ev.c> into your project. When properly specifying include paths, you
		3704	can even use F<ev.h> as header file name directly.
2767		3705
2768		3706
2769	=head1 LIBEVENT EMULATION	3707	=head1 LIBEVENT EMULATION
2770		3708
2771	Libev offers a compatibility emulation layer for libevent. It cannot	3709	Libev offers a compatibility emulation layer for libevent. It cannot
2772	emulate the internals of libevent, so here are some usage hints:	3710	emulate the internals of libevent, so here are some usage hints:
2773		3711
2774	=over 4	3712	=over 4
		3713
		3714	=item * Only the libevent-1.4.1-beta API is being emulated.
		3715
		3716	This was the newest libevent version available when libev was implemented,
		3717	and is still mostly unchanged in 2010.
2775		3718
2776	=item * Use it by including <event.h>, as usual.	3719	=item * Use it by including <event.h>, as usual.
2777		3720
2778	=item * The following members are fully supported: ev_base, ev_callback,	3721	=item * The following members are fully supported: ev_base, ev_callback,
2779	ev_arg, ev_fd, ev_res, ev_events.	3722	ev_arg, ev_fd, ev_res, ev_events.
…		…
2785	=item * Priorities are not currently supported. Initialising priorities	3728	=item * Priorities are not currently supported. Initialising priorities
2786	will fail and all watchers will have the same priority, even though there	3729	will fail and all watchers will have the same priority, even though there
2787	is an ev_pri field.	3730	is an ev_pri field.
2788		3731
2789	=item * In libevent, the last base created gets the signals, in libev, the	3732	=item * In libevent, the last base created gets the signals, in libev, the
2790	first base created (== the default loop) gets the signals.	3733	base that registered the signal gets the signals.
2791		3734
2792	=item * Other members are not supported.	3735	=item * Other members are not supported.
2793		3736
2794	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3737	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2795	to use the libev header file and library.	3738	to use the libev header file and library.
…		…
2814	Care has been taken to keep the overhead low. The only data member the C++	3757	Care has been taken to keep the overhead low. The only data member the C++
2815	classes add (compared to plain C-style watchers) is the event loop pointer	3758	classes add (compared to plain C-style watchers) is the event loop pointer
2816	that the watcher is associated with (or no additional members at all if	3759	that the watcher is associated with (or no additional members at all if
2817	you disable C<EV_MULTIPLICITY> when embedding libev).	3760	you disable C<EV_MULTIPLICITY> when embedding libev).
2818		3761
2819	Currently, functions, and static and non-static member functions can be	3762	Currently, functions, static and non-static member functions and classes
2820	used as callbacks. Other types should be easy to add as long as they only	3763	with C<operator ()> can be used as callbacks. Other types should be easy
2821	need one additional pointer for context. If you need support for other	3764	to add as long as they only need one additional pointer for context. If
2822	types of functors please contact the author (preferably after implementing	3765	you need support for other types of functors please contact the author
2823	it).	3766	(preferably after implementing it).
2824		3767
2825	Here is a list of things available in the C<ev> namespace:	3768	Here is a list of things available in the C<ev> namespace:
2826		3769
2827	=over 4	3770	=over 4
2828		3771
…		…
2846		3789
2847	=over 4	3790	=over 4
2848		3791
2849	=item ev::TYPE::TYPE ()	3792	=item ev::TYPE::TYPE ()
2850		3793
2851	=item ev::TYPE::TYPE (struct ev_loop *)	3794	=item ev::TYPE::TYPE (loop)
2852		3795
2853	=item ev::TYPE::~TYPE	3796	=item ev::TYPE::~TYPE
2854		3797
2855	The constructor (optionally) takes an event loop to associate the watcher	3798	The constructor (optionally) takes an event loop to associate the watcher
2856	with. If it is omitted, it will use C<EV_DEFAULT>.	3799	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2888		3831
2889	myclass obj;	3832	myclass obj;
2890	ev::io iow;	3833	ev::io iow;
2891	iow.set <myclass, &myclass::io_cb> (&obj);	3834	iow.set <myclass, &myclass::io_cb> (&obj);
2892		3835
		3836	=item w->set (object *)
		3837
		3838	This is a variation of a method callback - leaving out the method to call
		3839	will default the method to C<operator ()>, which makes it possible to use
		3840	functor objects without having to manually specify the C<operator ()> all
		3841	the time. Incidentally, you can then also leave out the template argument
		3842	list.
		3843
		3844	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3845	int revents)>.
		3846
		3847	See the method-C<set> above for more details.
		3848
		3849	Example: use a functor object as callback.
		3850
		3851	struct myfunctor
		3852	{
		3853	void operator() (ev::io &w, int revents)
		3854	{
		3855	...
		3856	}
		3857	}
		3858
		3859	myfunctor f;
		3860
		3861	ev::io w;
		3862	w.set (&f);
		3863
2893	=item w->set<function> (void *data = 0)	3864	=item w->set<function> (void *data = 0)
2894		3865
2895	Also sets a callback, but uses a static method or plain function as	3866	Also sets a callback, but uses a static method or plain function as
2896	callback. The optional C<data> argument will be stored in the watcher's	3867	callback. The optional C<data> argument will be stored in the watcher's
2897	C<data> member and is free for you to use.	3868	C<data> member and is free for you to use.
…		…
2903	Example: Use a plain function as callback.	3874	Example: Use a plain function as callback.
2904		3875
2905	static void io_cb (ev::io &w, int revents) { }	3876	static void io_cb (ev::io &w, int revents) { }
2906	iow.set <io_cb> ();	3877	iow.set <io_cb> ();
2907		3878
2908	=item w->set (struct ev_loop *)	3879	=item w->set (loop)
2909		3880
2910	Associates a different C<struct ev_loop> with this watcher. You can only	3881	Associates a different C<struct ev_loop> with this watcher. You can only
2911	do this when the watcher is inactive (and not pending either).	3882	do this when the watcher is inactive (and not pending either).
2912		3883
2913	=item w->set ([arguments])	3884	=item w->set ([arguments])
2914		3885
2915	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3886	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
2916	called at least once. Unlike the C counterpart, an active watcher gets	3887	method or a suitable start method must be called at least once. Unlike the
2917	automatically stopped and restarted when reconfiguring it with this	3888	C counterpart, an active watcher gets automatically stopped and restarted
2918	method.	3889	when reconfiguring it with this method.
2919		3890
2920	=item w->start ()	3891	=item w->start ()
2921		3892
2922	Starts the watcher. Note that there is no C<loop> argument, as the	3893	Starts the watcher. Note that there is no C<loop> argument, as the
2923	constructor already stores the event loop.	3894	constructor already stores the event loop.
2924		3895
		3896	=item w->start ([arguments])
		3897
		3898	Instead of calling C<set> and C<start> methods separately, it is often
		3899	convenient to wrap them in one call. Uses the same type of arguments as
		3900	the configure C<set> method of the watcher.
		3901
2925	=item w->stop ()	3902	=item w->stop ()
2926		3903
2927	Stops the watcher if it is active. Again, no C<loop> argument.	3904	Stops the watcher if it is active. Again, no C<loop> argument.
2928		3905
2929	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3906	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2941		3918
2942	=back	3919	=back
2943		3920
2944	=back	3921	=back
2945		3922
2946	Example: Define a class with an IO and idle watcher, start one of them in	3923	Example: Define a class with two I/O and idle watchers, start the I/O
2947	the constructor.	3924	watchers in the constructor.
2948		3925
2949	class myclass	3926	class myclass
2950	{	3927	{
2951	ev::io io ; void io_cb (ev::io &w, int revents);	3928	ev::io io ; void io_cb (ev::io &w, int revents);
		3929	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
2952	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3930	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2953		3931
2954	myclass (int fd)	3932	myclass (int fd)
2955	{	3933	{
2956	io .set <myclass, &myclass::io_cb > (this);	3934	io .set <myclass, &myclass::io_cb > (this);
		3935	io2 .set <myclass, &myclass::io2_cb > (this);
2957	idle.set <myclass, &myclass::idle_cb> (this);	3936	idle.set <myclass, &myclass::idle_cb> (this);
2958		3937
2959	io.start (fd, ev::READ);	3938	io.set (fd, ev::WRITE); // configure the watcher
		3939	io.start (); // start it whenever convenient
		3940
		3941	io2.start (fd, ev::READ); // set + start in one call
2960	}	3942	}
2961	};	3943	};
2962		3944
2963		3945
2964	=head1 OTHER LANGUAGE BINDINGS	3946	=head1 OTHER LANGUAGE BINDINGS
…		…
2983	L<http://software.schmorp.de/pkg/EV>.	3965	L<http://software.schmorp.de/pkg/EV>.
2984		3966
2985	=item Python	3967	=item Python
2986		3968
2987	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3969	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2988	seems to be quite complete and well-documented. Note, however, that the	3970	seems to be quite complete and well-documented.
2989	patch they require for libev is outright dangerous as it breaks the ABI
2990	for everybody else, and therefore, should never be applied in an installed
2991	libev (if python requires an incompatible ABI then it needs to embed
2992	libev).
2993		3971
2994	=item Ruby	3972	=item Ruby
2995		3973
2996	Tony Arcieri has written a ruby extension that offers access to a subset	3974	Tony Arcieri has written a ruby extension that offers access to a subset
2997	of the libev API and adds file handle abstractions, asynchronous DNS and	3975	of the libev API and adds file handle abstractions, asynchronous DNS and
2998	more on top of it. It can be found via gem servers. Its homepage is at	3976	more on top of it. It can be found via gem servers. Its homepage is at
2999	L<http://rev.rubyforge.org/>.	3977	L<http://rev.rubyforge.org/>.
3000		3978
		3979	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3980	makes rev work even on mingw.
		3981
		3982	=item Haskell
		3983
		3984	A haskell binding to libev is available at
		3985	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3986
3001	=item D	3987	=item D
3002		3988
3003	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3989	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3004	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3990	be found at L<http://proj.llucax.com.ar/wiki/evd>.
3005		3991
3006	=item Ocaml	3992	=item Ocaml
3007		3993
3008	Erkki Seppala has written Ocaml bindings for libev, to be found at	3994	Erkki Seppala has written Ocaml bindings for libev, to be found at
3009	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	3995	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3996
		3997	=item Lua
		3998
		3999	Brian Maher has written a partial interface to libev for lua (at the
		4000	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		4001	L<http://github.com/brimworks/lua-ev>.
3010		4002
3011	=back	4003	=back
3012		4004
3013		4005
3014	=head1 MACRO MAGIC	4006	=head1 MACRO MAGIC
…		…
3028	loop argument"). The C<EV_A> form is used when this is the sole argument,	4020	loop argument"). The C<EV_A> form is used when this is the sole argument,
3029	C<EV_A_> is used when other arguments are following. Example:	4021	C<EV_A_> is used when other arguments are following. Example:
3030		4022
3031	ev_unref (EV_A);	4023	ev_unref (EV_A);
3032	ev_timer_add (EV_A_ watcher);	4024	ev_timer_add (EV_A_ watcher);
3033	ev_loop (EV_A_ 0);	4025	ev_run (EV_A_ 0);
3034		4026
3035	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4027	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3036	which is often provided by the following macro.	4028	which is often provided by the following macro.
3037		4029
3038	=item C<EV_P>, C<EV_P_>	4030	=item C<EV_P>, C<EV_P_>
…		…
3078	}	4070	}
3079		4071
3080	ev_check check;	4072	ev_check check;
3081	ev_check_init (&check, check_cb);	4073	ev_check_init (&check, check_cb);
3082	ev_check_start (EV_DEFAULT_ &check);	4074	ev_check_start (EV_DEFAULT_ &check);
3083	ev_loop (EV_DEFAULT_ 0);	4075	ev_run (EV_DEFAULT_ 0);
3084		4076
3085	=head1 EMBEDDING	4077	=head1 EMBEDDING
3086		4078
3087	Libev can (and often is) directly embedded into host	4079	Libev can (and often is) directly embedded into host
3088	applications. Examples of applications that embed it include the Deliantra	4080	applications. Examples of applications that embed it include the Deliantra
…		…
3168	libev.m4	4160	libev.m4
3169		4161
3170	=head2 PREPROCESSOR SYMBOLS/MACROS	4162	=head2 PREPROCESSOR SYMBOLS/MACROS
3171		4163
3172	Libev can be configured via a variety of preprocessor symbols you have to	4164	Libev can be configured via a variety of preprocessor symbols you have to
3173	define before including any of its files. The default in the absence of	4165	define before including (or compiling) any of its files. The default in
3174	autoconf is documented for every option.	4166	the absence of autoconf is documented for every option.
		4167
		4168	Symbols marked with "(h)" do not change the ABI, and can have different
		4169	values when compiling libev vs. including F<ev.h>, so it is permissible
		4170	to redefine them before including F<ev.h> without breaking compatibility
		4171	to a compiled library. All other symbols change the ABI, which means all
		4172	users of libev and the libev code itself must be compiled with compatible
		4173	settings.
3175		4174
3176	=over 4	4175	=over 4
3177		4176
		4177	=item EV_COMPAT3 (h)
		4178
		4179	Backwards compatibility is a major concern for libev. This is why this
		4180	release of libev comes with wrappers for the functions and symbols that
		4181	have been renamed between libev version 3 and 4.
		4182
		4183	You can disable these wrappers (to test compatibility with future
		4184	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4185	sources. This has the additional advantage that you can drop the C<struct>
		4186	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4187	typedef in that case.
		4188
		4189	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4190	and in some even more future version the compatibility code will be
		4191	removed completely.
		4192
3178	=item EV_STANDALONE	4193	=item EV_STANDALONE (h)
3179		4194
3180	Must always be C<1> if you do not use autoconf configuration, which	4195	Must always be C<1> if you do not use autoconf configuration, which
3181	keeps libev from including F<config.h>, and it also defines dummy	4196	keeps libev from including F<config.h>, and it also defines dummy
3182	implementations for some libevent functions (such as logging, which is not	4197	implementations for some libevent functions (such as logging, which is not
3183	supported). It will also not define any of the structs usually found in	4198	supported). It will also not define any of the structs usually found in
3184	F<event.h> that are not directly supported by the libev core alone.	4199	F<event.h> that are not directly supported by the libev core alone.
3185		4200
		4201	In standalone mode, libev will still try to automatically deduce the
		4202	configuration, but has to be more conservative.
		4203
3186	=item EV_USE_MONOTONIC	4204	=item EV_USE_MONOTONIC
3187		4205
3188	If defined to be C<1>, libev will try to detect the availability of the	4206	If defined to be C<1>, libev will try to detect the availability of the
3189	monotonic clock option at both compile time and runtime. Otherwise no use	4207	monotonic clock option at both compile time and runtime. Otherwise no
3190	of the monotonic clock option will be attempted. If you enable this, you	4208	use of the monotonic clock option will be attempted. If you enable this,
3191	usually have to link against librt or something similar. Enabling it when	4209	you usually have to link against librt or something similar. Enabling it
3192	the functionality isn't available is safe, though, although you have	4210	when the functionality isn't available is safe, though, although you have
3193	to make sure you link against any libraries where the C<clock_gettime>	4211	to make sure you link against any libraries where the C<clock_gettime>
3194	function is hiding in (often F<-lrt>).	4212	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
3195		4213
3196	=item EV_USE_REALTIME	4214	=item EV_USE_REALTIME
3197		4215
3198	If defined to be C<1>, libev will try to detect the availability of the	4216	If defined to be C<1>, libev will try to detect the availability of the
3199	real-time clock option at compile time (and assume its availability at	4217	real-time clock option at compile time (and assume its availability
3200	runtime if successful). Otherwise no use of the real-time clock option will	4218	at runtime if successful). Otherwise no use of the real-time clock
3201	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	4219	option will be attempted. This effectively replaces C<gettimeofday>
3202	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	4220	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
3203	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	4221	correctness. See the note about libraries in the description of
		4222	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		4223	C<EV_USE_CLOCK_SYSCALL>.
		4224
		4225	=item EV_USE_CLOCK_SYSCALL
		4226
		4227	If defined to be C<1>, libev will try to use a direct syscall instead
		4228	of calling the system-provided C<clock_gettime> function. This option
		4229	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		4230	unconditionally pulls in C<libpthread>, slowing down single-threaded
		4231	programs needlessly. Using a direct syscall is slightly slower (in
		4232	theory), because no optimised vdso implementation can be used, but avoids
		4233	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		4234	higher, as it simplifies linking (no need for C<-lrt>).
3204		4235
3205	=item EV_USE_NANOSLEEP	4236	=item EV_USE_NANOSLEEP
3206		4237
3207	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	4238	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
3208	and will use it for delays. Otherwise it will use C<select ()>.	4239	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3224		4255
3225	=item EV_SELECT_USE_FD_SET	4256	=item EV_SELECT_USE_FD_SET
3226		4257
3227	If defined to C<1>, then the select backend will use the system C<fd_set>	4258	If defined to C<1>, then the select backend will use the system C<fd_set>
3228	structure. This is useful if libev doesn't compile due to a missing	4259	structure. This is useful if libev doesn't compile due to a missing
3229	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	4260	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3230	exotic systems. This usually limits the range of file descriptors to some	4261	on exotic systems. This usually limits the range of file descriptors to
3231	low limit such as 1024 or might have other limitations (winsocket only	4262	some low limit such as 1024 or might have other limitations (winsocket
3232	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	4263	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3233	influence the size of the C<fd_set> used.	4264	configures the maximum size of the C<fd_set>.
3234		4265
3235	=item EV_SELECT_IS_WINSOCKET	4266	=item EV_SELECT_IS_WINSOCKET
3236		4267
3237	When defined to C<1>, the select backend will assume that	4268	When defined to C<1>, the select backend will assume that
3238	select/socket/connect etc. don't understand file descriptors but	4269	select/socket/connect etc. don't understand file descriptors but
…		…
3240	be used is the winsock select). This means that it will call	4271	be used is the winsock select). This means that it will call
3241	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4272	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3242	it is assumed that all these functions actually work on fds, even	4273	it is assumed that all these functions actually work on fds, even
3243	on win32. Should not be defined on non-win32 platforms.	4274	on win32. Should not be defined on non-win32 platforms.
3244		4275
3245	=item EV_FD_TO_WIN32_HANDLE	4276	=item EV_FD_TO_WIN32_HANDLE(fd)
3246		4277
3247	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4278	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3248	file descriptors to socket handles. When not defining this symbol (the	4279	file descriptors to socket handles. When not defining this symbol (the
3249	default), then libev will call C<_get_osfhandle>, which is usually	4280	default), then libev will call C<_get_osfhandle>, which is usually
3250	correct. In some cases, programs use their own file descriptor management,	4281	correct. In some cases, programs use their own file descriptor management,
3251	in which case they can provide this function to map fds to socket handles.	4282	in which case they can provide this function to map fds to socket handles.
		4283
		4284	=item EV_WIN32_HANDLE_TO_FD(handle)
		4285
		4286	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4287	using the standard C<_open_osfhandle> function. For programs implementing
		4288	their own fd to handle mapping, overwriting this function makes it easier
		4289	to do so. This can be done by defining this macro to an appropriate value.
		4290
		4291	=item EV_WIN32_CLOSE_FD(fd)
		4292
		4293	If programs implement their own fd to handle mapping on win32, then this
		4294	macro can be used to override the C<close> function, useful to unregister
		4295	file descriptors again. Note that the replacement function has to close
		4296	the underlying OS handle.
3252		4297
3253	=item EV_USE_POLL	4298	=item EV_USE_POLL
3254		4299
3255	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4300	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3256	backend. Otherwise it will be enabled on non-win32 platforms. It	4301	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3303	as well as for signal and thread safety in C<ev_async> watchers.	4348	as well as for signal and thread safety in C<ev_async> watchers.
3304		4349
3305	In the absence of this define, libev will use C<sig_atomic_t volatile>	4350	In the absence of this define, libev will use C<sig_atomic_t volatile>
3306	(from F<signal.h>), which is usually good enough on most platforms.	4351	(from F<signal.h>), which is usually good enough on most platforms.
3307		4352
3308	=item EV_H	4353	=item EV_H (h)
3309		4354
3310	The name of the F<ev.h> header file used to include it. The default if	4355	The name of the F<ev.h> header file used to include it. The default if
3311	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4356	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3312	used to virtually rename the F<ev.h> header file in case of conflicts.	4357	used to virtually rename the F<ev.h> header file in case of conflicts.
3313		4358
3314	=item EV_CONFIG_H	4359	=item EV_CONFIG_H (h)
3315		4360
3316	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4361	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3317	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4362	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3318	C<EV_H>, above.	4363	C<EV_H>, above.
3319		4364
3320	=item EV_EVENT_H	4365	=item EV_EVENT_H (h)
3321		4366
3322	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4367	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3323	of how the F<event.h> header can be found, the default is C<"event.h">.	4368	of how the F<event.h> header can be found, the default is C<"event.h">.
3324		4369
3325	=item EV_PROTOTYPES	4370	=item EV_PROTOTYPES (h)
3326		4371
3327	If defined to be C<0>, then F<ev.h> will not define any function	4372	If defined to be C<0>, then F<ev.h> will not define any function
3328	prototypes, but still define all the structs and other symbols. This is	4373	prototypes, but still define all the structs and other symbols. This is
3329	occasionally useful if you want to provide your own wrapper functions	4374	occasionally useful if you want to provide your own wrapper functions
3330	around libev functions.	4375	around libev functions.
…		…
3352	fine.	4397	fine.
3353		4398
3354	If your embedding application does not need any priorities, defining these	4399	If your embedding application does not need any priorities, defining these
3355	both to C<0> will save some memory and CPU.	4400	both to C<0> will save some memory and CPU.
3356		4401
3357	=item EV_PERIODIC_ENABLE	4402	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4403	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4404	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3358		4405
3359	If undefined or defined to be C<1>, then periodic timers are supported. If	4406	If undefined or defined to be C<1> (and the platform supports it), then
3360	defined to be C<0>, then they are not. Disabling them saves a few kB of	4407	the respective watcher type is supported. If defined to be C<0>, then it
3361	code.	4408	is not. Disabling watcher types mainly saves code size.
3362		4409
3363	=item EV_IDLE_ENABLE	4410	=item EV_FEATURES
3364
3365	If undefined or defined to be C<1>, then idle watchers are supported. If
3366	defined to be C<0>, then they are not. Disabling them saves a few kB of
3367	code.
3368
3369	=item EV_EMBED_ENABLE
3370
3371	If undefined or defined to be C<1>, then embed watchers are supported. If
3372	defined to be C<0>, then they are not. Embed watchers rely on most other
3373	watcher types, which therefore must not be disabled.
3374
3375	=item EV_STAT_ENABLE
3376
3377	If undefined or defined to be C<1>, then stat watchers are supported. If
3378	defined to be C<0>, then they are not.
3379
3380	=item EV_FORK_ENABLE
3381
3382	If undefined or defined to be C<1>, then fork watchers are supported. If
3383	defined to be C<0>, then they are not.
3384
3385	=item EV_ASYNC_ENABLE
3386
3387	If undefined or defined to be C<1>, then async watchers are supported. If
3388	defined to be C<0>, then they are not.
3389
3390	=item EV_MINIMAL
3391		4411
3392	If you need to shave off some kilobytes of code at the expense of some	4412	If you need to shave off some kilobytes of code at the expense of some
3393	speed, define this symbol to C<1>. Currently this is used to override some	4413	speed (but with the full API), you can define this symbol to request
3394	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4414	certain subsets of functionality. The default is to enable all features
3395	much smaller 2-heap for timer management over the default 4-heap.	4415	that can be enabled on the platform.
		4416
		4417	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4418	with some broad features you want) and then selectively re-enable
		4419	additional parts you want, for example if you want everything minimal,
		4420	but multiple event loop support, async and child watchers and the poll
		4421	backend, use this:
		4422
		4423	#define EV_FEATURES 0
		4424	#define EV_MULTIPLICITY 1
		4425	#define EV_USE_POLL 1
		4426	#define EV_CHILD_ENABLE 1
		4427	#define EV_ASYNC_ENABLE 1
		4428
		4429	The actual value is a bitset, it can be a combination of the following
		4430	values:
		4431
		4432	=over 4
		4433
		4434	=item C<1> - faster/larger code
		4435
		4436	Use larger code to speed up some operations.
		4437
		4438	Currently this is used to override some inlining decisions (enlarging the
		4439	code size by roughly 30% on amd64).
		4440
		4441	When optimising for size, use of compiler flags such as C<-Os> with
		4442	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4443	assertions.
		4444
		4445	=item C<2> - faster/larger data structures
		4446
		4447	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4448	hash table sizes and so on. This will usually further increase code size
		4449	and can additionally have an effect on the size of data structures at
		4450	runtime.
		4451
		4452	=item C<4> - full API configuration
		4453
		4454	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4455	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4456
		4457	=item C<8> - full API
		4458
		4459	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4460	details on which parts of the API are still available without this
		4461	feature, and do not complain if this subset changes over time.
		4462
		4463	=item C<16> - enable all optional watcher types
		4464
		4465	Enables all optional watcher types. If you want to selectively enable
		4466	only some watcher types other than I/O and timers (e.g. prepare,
		4467	embed, async, child...) you can enable them manually by defining
		4468	C<EV_watchertype_ENABLE> to C<1> instead.
		4469
		4470	=item C<32> - enable all backends
		4471
		4472	This enables all backends - without this feature, you need to enable at
		4473	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4474
		4475	=item C<64> - enable OS-specific "helper" APIs
		4476
		4477	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4478	default.
		4479
		4480	=back
		4481
		4482	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4483	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4484	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4485	watchers, timers and monotonic clock support.
		4486
		4487	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4488	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4489	your program might be left out as well - a binary starting a timer and an
		4490	I/O watcher then might come out at only 5Kb.
		4491
		4492	=item EV_AVOID_STDIO
		4493
		4494	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4495	functions (printf, scanf, perror etc.). This will increase the code size
		4496	somewhat, but if your program doesn't otherwise depend on stdio and your
		4497	libc allows it, this avoids linking in the stdio library which is quite
		4498	big.
		4499
		4500	Note that error messages might become less precise when this option is
		4501	enabled.
		4502
		4503	=item EV_NSIG
		4504
		4505	The highest supported signal number, +1 (or, the number of
		4506	signals): Normally, libev tries to deduce the maximum number of signals
		4507	automatically, but sometimes this fails, in which case it can be
		4508	specified. Also, using a lower number than detected (C<32> should be
		4509	good for about any system in existence) can save some memory, as libev
		4510	statically allocates some 12-24 bytes per signal number.
3396		4511
3397	=item EV_PID_HASHSIZE	4512	=item EV_PID_HASHSIZE
3398		4513
3399	C<ev_child> watchers use a small hash table to distribute workload by	4514	C<ev_child> watchers use a small hash table to distribute workload by
3400	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4515	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3401	than enough. If you need to manage thousands of children you might want to	4516	usually more than enough. If you need to manage thousands of children you
3402	increase this value (I<must> be a power of two).	4517	might want to increase this value (I<must> be a power of two).
3403		4518
3404	=item EV_INOTIFY_HASHSIZE	4519	=item EV_INOTIFY_HASHSIZE
3405		4520
3406	C<ev_stat> watchers use a small hash table to distribute workload by	4521	C<ev_stat> watchers use a small hash table to distribute workload by
3407	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4522	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3408	usually more than enough. If you need to manage thousands of C<ev_stat>	4523	disabled), usually more than enough. If you need to manage thousands of
3409	watchers you might want to increase this value (I<must> be a power of	4524	C<ev_stat> watchers you might want to increase this value (I<must> be a
3410	two).	4525	power of two).
3411		4526
3412	=item EV_USE_4HEAP	4527	=item EV_USE_4HEAP
3413		4528
3414	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4529	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3415	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4530	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3416	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4531	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3417	faster performance with many (thousands) of watchers.	4532	faster performance with many (thousands) of watchers.
3418		4533
3419	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4534	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3420	(disabled).	4535	will be C<0>.
3421		4536
3422	=item EV_HEAP_CACHE_AT	4537	=item EV_HEAP_CACHE_AT
3423		4538
3424	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4539	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3425	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4540	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3426	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4541	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3427	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4542	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3428	but avoids random read accesses on heap changes. This improves performance	4543	but avoids random read accesses on heap changes. This improves performance
3429	noticeably with many (hundreds) of watchers.	4544	noticeably with many (hundreds) of watchers.
3430		4545
3431	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4546	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3432	(disabled).	4547	will be C<0>.
3433		4548
3434	=item EV_VERIFY	4549	=item EV_VERIFY
3435		4550
3436	Controls how much internal verification (see C<ev_loop_verify ()>) will	4551	Controls how much internal verification (see C<ev_verify ()>) will
3437	be done: If set to C<0>, no internal verification code will be compiled	4552	be done: If set to C<0>, no internal verification code will be compiled
3438	in. If set to C<1>, then verification code will be compiled in, but not	4553	in. If set to C<1>, then verification code will be compiled in, but not
3439	called. If set to C<2>, then the internal verification code will be	4554	called. If set to C<2>, then the internal verification code will be
3440	called once per loop, which can slow down libev. If set to C<3>, then the	4555	called once per loop, which can slow down libev. If set to C<3>, then the
3441	verification code will be called very frequently, which will slow down	4556	verification code will be called very frequently, which will slow down
3442	libev considerably.	4557	libev considerably.
3443		4558
3444	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4559	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3445	C<0>.	4560	will be C<0>.
3446		4561
3447	=item EV_COMMON	4562	=item EV_COMMON
3448		4563
3449	By default, all watchers have a C<void *data> member. By redefining	4564	By default, all watchers have a C<void *data> member. By redefining
3450	this macro to a something else you can include more and other types of	4565	this macro to something else you can include more and other types of
3451	members. You have to define it each time you include one of the files,	4566	members. You have to define it each time you include one of the files,
3452	though, and it must be identical each time.	4567	though, and it must be identical each time.
3453		4568
3454	For example, the perl EV module uses something like this:	4569	For example, the perl EV module uses something like this:
3455		4570
…		…
3508	file.	4623	file.
3509		4624
3510	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4625	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3511	that everybody includes and which overrides some configure choices:	4626	that everybody includes and which overrides some configure choices:
3512		4627
3513	#define EV_MINIMAL 1	4628	#define EV_FEATURES 8
3514	#define EV_USE_POLL 0	4629	#define EV_USE_SELECT 1
3515	#define EV_MULTIPLICITY 0
3516	#define EV_PERIODIC_ENABLE 0	4630	#define EV_PREPARE_ENABLE 1
		4631	#define EV_IDLE_ENABLE 1
3517	#define EV_STAT_ENABLE 0	4632	#define EV_SIGNAL_ENABLE 1
3518	#define EV_FORK_ENABLE 0	4633	#define EV_CHILD_ENABLE 1
		4634	#define EV_USE_STDEXCEPT 0
3519	#define EV_CONFIG_H <config.h>	4635	#define EV_CONFIG_H <config.h>
3520	#define EV_MINPRI 0
3521	#define EV_MAXPRI 0
3522		4636
3523	#include "ev++.h"	4637	#include "ev++.h"
3524		4638
3525	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4639	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3526		4640
3527	#include "ev_cpp.h"	4641	#include "ev_cpp.h"
3528	#include "ev.c"	4642	#include "ev.c"
3529		4643
3530	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4644	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3531		4645
3532	=head2 THREADS AND COROUTINES	4646	=head2 THREADS AND COROUTINES
3533		4647
3534	=head3 THREADS	4648	=head3 THREADS
3535		4649
…		…
3586	default loop and triggering an C<ev_async> watcher from the default loop	4700	default loop and triggering an C<ev_async> watcher from the default loop
3587	watcher callback into the event loop interested in the signal.	4701	watcher callback into the event loop interested in the signal.
3588		4702
3589	=back	4703	=back
3590		4704
		4705	See also L<THREAD LOCKING EXAMPLE>.
		4706
3591	=head3 COROUTINES	4707	=head3 COROUTINES
3592		4708
3593	Libev is very accommodating to coroutines ("cooperative threads"):	4709	Libev is very accommodating to coroutines ("cooperative threads"):
3594	libev fully supports nesting calls to its functions from different	4710	libev fully supports nesting calls to its functions from different
3595	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4711	coroutines (e.g. you can call C<ev_run> on the same loop from two
3596	different coroutines, and switch freely between both coroutines running the	4712	different coroutines, and switch freely between both coroutines running
3597	loop, as long as you don't confuse yourself). The only exception is that	4713	the loop, as long as you don't confuse yourself). The only exception is
3598	you must not do this from C<ev_periodic> reschedule callbacks.	4714	that you must not do this from C<ev_periodic> reschedule callbacks.
3599		4715
3600	Care has been taken to ensure that libev does not keep local state inside	4716	Care has been taken to ensure that libev does not keep local state inside
3601	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4717	C<ev_run>, and other calls do not usually allow for coroutine switches as
3602	they do not call any callbacks.	4718	they do not call any callbacks.
3603		4719
3604	=head2 COMPILER WARNINGS	4720	=head2 COMPILER WARNINGS
3605		4721
3606	Depending on your compiler and compiler settings, you might get no or a	4722	Depending on your compiler and compiler settings, you might get no or a
…		…
3617	maintainable.	4733	maintainable.
3618		4734
3619	And of course, some compiler warnings are just plain stupid, or simply	4735	And of course, some compiler warnings are just plain stupid, or simply
3620	wrong (because they don't actually warn about the condition their message	4736	wrong (because they don't actually warn about the condition their message
3621	seems to warn about). For example, certain older gcc versions had some	4737	seems to warn about). For example, certain older gcc versions had some
3622	warnings that resulted an extreme number of false positives. These have	4738	warnings that resulted in an extreme number of false positives. These have
3623	been fixed, but some people still insist on making code warn-free with	4739	been fixed, but some people still insist on making code warn-free with
3624	such buggy versions.	4740	such buggy versions.
3625		4741
3626	While libev is written to generate as few warnings as possible,	4742	While libev is written to generate as few warnings as possible,
3627	"warn-free" code is not a goal, and it is recommended not to build libev	4743	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3663	I suggest using suppression lists.	4779	I suggest using suppression lists.
3664		4780
3665		4781
3666	=head1 PORTABILITY NOTES	4782	=head1 PORTABILITY NOTES
3667		4783
		4784	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4785
		4786	GNU/Linux is the only common platform that supports 64 bit file/large file
		4787	interfaces but I<disables> them by default.
		4788
		4789	That means that libev compiled in the default environment doesn't support
		4790	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4791
		4792	Unfortunately, many programs try to work around this GNU/Linux issue
		4793	by enabling the large file API, which makes them incompatible with the
		4794	standard libev compiled for their system.
		4795
		4796	Likewise, libev cannot enable the large file API itself as this would
		4797	suddenly make it incompatible to the default compile time environment,
		4798	i.e. all programs not using special compile switches.
		4799
		4800	=head2 OS/X AND DARWIN BUGS
		4801
		4802	The whole thing is a bug if you ask me - basically any system interface
		4803	you touch is broken, whether it is locales, poll, kqueue or even the
		4804	OpenGL drivers.
		4805
		4806	=head3 C<kqueue> is buggy
		4807
		4808	The kqueue syscall is broken in all known versions - most versions support
		4809	only sockets, many support pipes.
		4810
		4811	Libev tries to work around this by not using C<kqueue> by default on this
		4812	rotten platform, but of course you can still ask for it when creating a
		4813	loop - embedding a socket-only kqueue loop into a select-based one is
		4814	probably going to work well.
		4815
		4816	=head3 C<poll> is buggy
		4817
		4818	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4819	implementation by something calling C<kqueue> internally around the 10.5.6
		4820	release, so now C<kqueue> I<and> C<poll> are broken.
		4821
		4822	Libev tries to work around this by not using C<poll> by default on
		4823	this rotten platform, but of course you can still ask for it when creating
		4824	a loop.
		4825
		4826	=head3 C<select> is buggy
		4827
		4828	All that's left is C<select>, and of course Apple found a way to fuck this
		4829	one up as well: On OS/X, C<select> actively limits the number of file
		4830	descriptors you can pass in to 1024 - your program suddenly crashes when
		4831	you use more.
		4832
		4833	There is an undocumented "workaround" for this - defining
		4834	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4835	work on OS/X.
		4836
		4837	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4838
		4839	=head3 C<errno> reentrancy
		4840
		4841	The default compile environment on Solaris is unfortunately so
		4842	thread-unsafe that you can't even use components/libraries compiled
		4843	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4844	defined by default. A valid, if stupid, implementation choice.
		4845
		4846	If you want to use libev in threaded environments you have to make sure
		4847	it's compiled with C<_REENTRANT> defined.
		4848
		4849	=head3 Event port backend
		4850
		4851	The scalable event interface for Solaris is called "event
		4852	ports". Unfortunately, this mechanism is very buggy in all major
		4853	releases. If you run into high CPU usage, your program freezes or you get
		4854	a large number of spurious wakeups, make sure you have all the relevant
		4855	and latest kernel patches applied. No, I don't know which ones, but there
		4856	are multiple ones to apply, and afterwards, event ports actually work
		4857	great.
		4858
		4859	If you can't get it to work, you can try running the program by setting
		4860	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4861	C<select> backends.
		4862
		4863	=head2 AIX POLL BUG
		4864
		4865	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4866	this by trying to avoid the poll backend altogether (i.e. it's not even
		4867	compiled in), which normally isn't a big problem as C<select> works fine
		4868	with large bitsets on AIX, and AIX is dead anyway.
		4869
3668	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4870	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4871
		4872	=head3 General issues
3669		4873
3670	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4874	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3671	requires, and its I/O model is fundamentally incompatible with the POSIX	4875	requires, and its I/O model is fundamentally incompatible with the POSIX
3672	model. Libev still offers limited functionality on this platform in	4876	model. Libev still offers limited functionality on this platform in
3673	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4877	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3674	descriptors. This only applies when using Win32 natively, not when using	4878	descriptors. This only applies when using Win32 natively, not when using
3675	e.g. cygwin.	4879	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4880	as every compielr comes with a slightly differently broken/incompatible
		4881	environment.
3676		4882
3677	Lifting these limitations would basically require the full	4883	Lifting these limitations would basically require the full
3678	re-implementation of the I/O system. If you are into these kinds of	4884	re-implementation of the I/O system. If you are into this kind of thing,
3679	things, then note that glib does exactly that for you in a very portable	4885	then note that glib does exactly that for you in a very portable way (note
3680	way (note also that glib is the slowest event library known to man).	4886	also that glib is the slowest event library known to man).
3681		4887
3682	There is no supported compilation method available on windows except	4888	There is no supported compilation method available on windows except
3683	embedding it into other applications.	4889	embedding it into other applications.
		4890
		4891	Sensible signal handling is officially unsupported by Microsoft - libev
		4892	tries its best, but under most conditions, signals will simply not work.
3684		4893
3685	Not a libev limitation but worth mentioning: windows apparently doesn't	4894	Not a libev limitation but worth mentioning: windows apparently doesn't
3686	accept large writes: instead of resulting in a partial write, windows will	4895	accept large writes: instead of resulting in a partial write, windows will
3687	either accept everything or return C<ENOBUFS> if the buffer is too large,	4896	either accept everything or return C<ENOBUFS> if the buffer is too large,
3688	so make sure you only write small amounts into your sockets (less than a	4897	so make sure you only write small amounts into your sockets (less than a
…		…
3693	the abysmal performance of winsockets, using a large number of sockets	4902	the abysmal performance of winsockets, using a large number of sockets
3694	is not recommended (and not reasonable). If your program needs to use	4903	is not recommended (and not reasonable). If your program needs to use
3695	more than a hundred or so sockets, then likely it needs to use a totally	4904	more than a hundred or so sockets, then likely it needs to use a totally
3696	different implementation for windows, as libev offers the POSIX readiness	4905	different implementation for windows, as libev offers the POSIX readiness
3697	notification model, which cannot be implemented efficiently on windows	4906	notification model, which cannot be implemented efficiently on windows
3698	(Microsoft monopoly games).	4907	(due to Microsoft monopoly games).
3699		4908
3700	A typical way to use libev under windows is to embed it (see the embedding	4909	A typical way to use libev under windows is to embed it (see the embedding
3701	section for details) and use the following F<evwrap.h> header file instead	4910	section for details) and use the following F<evwrap.h> header file instead
3702	of F<ev.h>:	4911	of F<ev.h>:
3703		4912
…		…
3710	you do I<not> compile the F<ev.c> or any other embedded source files!):	4919	you do I<not> compile the F<ev.c> or any other embedded source files!):
3711		4920
3712	#include "evwrap.h"	4921	#include "evwrap.h"
3713	#include "ev.c"	4922	#include "ev.c"
3714		4923
3715	=over 4
3716
3717	=item The winsocket select function	4924	=head3 The winsocket C<select> function
3718		4925
3719	The winsocket C<select> function doesn't follow POSIX in that it	4926	The winsocket C<select> function doesn't follow POSIX in that it
3720	requires socket I<handles> and not socket I<file descriptors> (it is	4927	requires socket I<handles> and not socket I<file descriptors> (it is
3721	also extremely buggy). This makes select very inefficient, and also	4928	also extremely buggy). This makes select very inefficient, and also
3722	requires a mapping from file descriptors to socket handles (the Microsoft	4929	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3731	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4938	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3732		4939
3733	Note that winsockets handling of fd sets is O(n), so you can easily get a	4940	Note that winsockets handling of fd sets is O(n), so you can easily get a
3734	complexity in the O(n²) range when using win32.	4941	complexity in the O(n²) range when using win32.
3735		4942
3736	=item Limited number of file descriptors	4943	=head3 Limited number of file descriptors
3737		4944
3738	Windows has numerous arbitrary (and low) limits on things.	4945	Windows has numerous arbitrary (and low) limits on things.
3739		4946
3740	Early versions of winsocket's select only supported waiting for a maximum	4947	Early versions of winsocket's select only supported waiting for a maximum
3741	of C<64> handles (probably owning to the fact that all windows kernels	4948	of C<64> handles (probably owning to the fact that all windows kernels
3742	can only wait for C<64> things at the same time internally; Microsoft	4949	can only wait for C<64> things at the same time internally; Microsoft
3743	recommends spawning a chain of threads and wait for 63 handles and the	4950	recommends spawning a chain of threads and wait for 63 handles and the
3744	previous thread in each. Great).	4951	previous thread in each. Sounds great!).
3745		4952
3746	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4953	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3747	to some high number (e.g. C<2048>) before compiling the winsocket select	4954	to some high number (e.g. C<2048>) before compiling the winsocket select
3748	call (which might be in libev or elsewhere, for example, perl does its own	4955	call (which might be in libev or elsewhere, for example, perl and many
3749	select emulation on windows).	4956	other interpreters do their own select emulation on windows).
3750		4957
3751	Another limit is the number of file descriptors in the Microsoft runtime	4958	Another limit is the number of file descriptors in the Microsoft runtime
3752	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4959	libraries, which by default is C<64> (there must be a hidden I<64>
3753	or something like this inside Microsoft). You can increase this by calling	4960	fetish or something like this inside Microsoft). You can increase this
3754	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4961	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3755	arbitrary limit), but is broken in many versions of the Microsoft runtime	4962	(another arbitrary limit), but is broken in many versions of the Microsoft
3756	libraries.
3757
3758	This might get you to about C<512> or C<2048> sockets (depending on	4963	runtime libraries. This might get you to about C<512> or C<2048> sockets
3759	windows version and/or the phase of the moon). To get more, you need to	4964	(depending on windows version and/or the phase of the moon). To get more,
3760	wrap all I/O functions and provide your own fd management, but the cost of	4965	you need to wrap all I/O functions and provide your own fd management, but
3761	calling select (O(n²)) will likely make this unworkable.	4966	the cost of calling select (O(n²)) will likely make this unworkable.
3762
3763	=back
3764		4967
3765	=head2 PORTABILITY REQUIREMENTS	4968	=head2 PORTABILITY REQUIREMENTS
3766		4969
3767	In addition to a working ISO-C implementation and of course the	4970	In addition to a working ISO-C implementation and of course the
3768	backend-specific APIs, libev relies on a few additional extensions:	4971	backend-specific APIs, libev relies on a few additional extensions:
…		…
3775	Libev assumes not only that all watcher pointers have the same internal	4978	Libev assumes not only that all watcher pointers have the same internal
3776	structure (guaranteed by POSIX but not by ISO C for example), but it also	4979	structure (guaranteed by POSIX but not by ISO C for example), but it also
3777	assumes that the same (machine) code can be used to call any watcher	4980	assumes that the same (machine) code can be used to call any watcher
3778	callback: The watcher callbacks have different type signatures, but libev	4981	callback: The watcher callbacks have different type signatures, but libev
3779	calls them using an C<ev_watcher *> internally.	4982	calls them using an C<ev_watcher *> internally.
		4983
		4984	=item pointer accesses must be thread-atomic
		4985
		4986	Accessing a pointer value must be atomic, it must both be readable and
		4987	writable in one piece - this is the case on all current architectures.
3780		4988
3781	=item C<sig_atomic_t volatile> must be thread-atomic as well	4989	=item C<sig_atomic_t volatile> must be thread-atomic as well
3782		4990
3783	The type C<sig_atomic_t volatile> (or whatever is defined as	4991	The type C<sig_atomic_t volatile> (or whatever is defined as
3784	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	4992	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
3807	watchers.	5015	watchers.
3808		5016
3809	=item C<double> must hold a time value in seconds with enough accuracy	5017	=item C<double> must hold a time value in seconds with enough accuracy
3810		5018
3811	The type C<double> is used to represent timestamps. It is required to	5019	The type C<double> is used to represent timestamps. It is required to
3812	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5020	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3813	enough for at least into the year 4000. This requirement is fulfilled by	5021	good enough for at least into the year 4000 with millisecond accuracy
		5022	(the design goal for libev). This requirement is overfulfilled by
3814	implementations implementing IEEE 754 (basically all existing ones).	5023	implementations using IEEE 754, which is basically all existing ones. With
		5024	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
3815		5025
3816	=back	5026	=back
3817		5027
3818	If you know of other additional requirements drop me a note.	5028	If you know of other additional requirements drop me a note.
3819		5029
…		…
3887	involves iterating over all running async watchers or all signal numbers.	5097	involves iterating over all running async watchers or all signal numbers.
3888		5098
3889	=back	5099	=back
3890		5100
3891		5101
		5102	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5103
		5104	The major version 4 introduced some incompatible changes to the API.
		5105
		5106	At the moment, the C<ev.h> header file provides compatibility definitions
		5107	for all changes, so most programs should still compile. The compatibility
		5108	layer might be removed in later versions of libev, so better update to the
		5109	new API early than late.
		5110
		5111	=over 4
		5112
		5113	=item C<EV_COMPAT3> backwards compatibility mechanism
		5114
		5115	The backward compatibility mechanism can be controlled by
		5116	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5117	section.
		5118
		5119	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5120
		5121	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5122
		5123	ev_loop_destroy (EV_DEFAULT_UC);
		5124	ev_loop_fork (EV_DEFAULT);
		5125
		5126	=item function/symbol renames
		5127
		5128	A number of functions and symbols have been renamed:
		5129
		5130	ev_loop => ev_run
		5131	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5132	EVLOOP_ONESHOT => EVRUN_ONCE
		5133
		5134	ev_unloop => ev_break
		5135	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5136	EVUNLOOP_ONE => EVBREAK_ONE
		5137	EVUNLOOP_ALL => EVBREAK_ALL
		5138
		5139	EV_TIMEOUT => EV_TIMER
		5140
		5141	ev_loop_count => ev_iteration
		5142	ev_loop_depth => ev_depth
		5143	ev_loop_verify => ev_verify
		5144
		5145	Most functions working on C<struct ev_loop> objects don't have an
		5146	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5147	associated constants have been renamed to not collide with the C<struct
		5148	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5149	as all other watcher types. Note that C<ev_loop_fork> is still called
		5150	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5151	typedef.
		5152
		5153	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5154
		5155	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5156	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5157	and work, but the library code will of course be larger.
		5158
		5159	=back
		5160
		5161
		5162	=head1 GLOSSARY
		5163
		5164	=over 4
		5165
		5166	=item active
		5167
		5168	A watcher is active as long as it has been started and not yet stopped.
		5169	See L<WATCHER STATES> for details.
		5170
		5171	=item application
		5172
		5173	In this document, an application is whatever is using libev.
		5174
		5175	=item backend
		5176
		5177	The part of the code dealing with the operating system interfaces.
		5178
		5179	=item callback
		5180
		5181	The address of a function that is called when some event has been
		5182	detected. Callbacks are being passed the event loop, the watcher that
		5183	received the event, and the actual event bitset.
		5184
		5185	=item callback/watcher invocation
		5186
		5187	The act of calling the callback associated with a watcher.
		5188
		5189	=item event
		5190
		5191	A change of state of some external event, such as data now being available
		5192	for reading on a file descriptor, time having passed or simply not having
		5193	any other events happening anymore.
		5194
		5195	In libev, events are represented as single bits (such as C<EV_READ> or
		5196	C<EV_TIMER>).
		5197
		5198	=item event library
		5199
		5200	A software package implementing an event model and loop.
		5201
		5202	=item event loop
		5203
		5204	An entity that handles and processes external events and converts them
		5205	into callback invocations.
		5206
		5207	=item event model
		5208
		5209	The model used to describe how an event loop handles and processes
		5210	watchers and events.
		5211
		5212	=item pending
		5213
		5214	A watcher is pending as soon as the corresponding event has been
		5215	detected. See L<WATCHER STATES> for details.
		5216
		5217	=item real time
		5218
		5219	The physical time that is observed. It is apparently strictly monotonic :)
		5220
		5221	=item wall-clock time
		5222
		5223	The time and date as shown on clocks. Unlike real time, it can actually
		5224	be wrong and jump forwards and backwards, e.g. when the you adjust your
		5225	clock.
		5226
		5227	=item watcher
		5228
		5229	A data structure that describes interest in certain events. Watchers need
		5230	to be started (attached to an event loop) before they can receive events.
		5231
		5232	=back
		5233
3892	=head1 AUTHOR	5234	=head1 AUTHOR
3893		5235
3894	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5236	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5237	Magnusson and Emanuele Giaquinta.
3895		5238

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