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Revision 1.350 by sf-exg, Mon Jan 10 08:36:41 2011 UTC

…		…
8		8
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
		13
		14	#include <stdio.h> // for puts
13		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_TYPE	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
…		…
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
28		30
29	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_run's to stop iterating
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_break (EV_A_ EVBREAK_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_run to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_break (EV_A_ EVBREAK_ONE);
40	}	42	}
41		43
42	int	44	int
43	main (void)	45	main (void)
44	{	46	{
45	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
46	ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = EV_DEFAULT;
47		49
48	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
…		…
54	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
57		59
58	// now wait for events to arrive	60	// now wait for events to arrive
59	ev_loop (loop, 0);	61	ev_run (loop, 0);
60		62
61	// unloop was called, so exit	63	// unloop was called, so exit
62	return 0;	64	return 0;
63	}	65	}
64		66
65	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
66		70
67	The newest version of this document is also available as an html-formatted	71	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	72	web page you might find easier to navigate when reading it for the first
69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.	73	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		74
		75	While this document tries to be as complete as possible in documenting
		76	libev, its usage and the rationale behind its design, it is not a tutorial
		77	on event-based programming, nor will it introduce event-based programming
		78	with libev.
		79
		80	Familiarity with event based programming techniques in general is assumed
		81	throughout this document.
		82
		83	=head1 WHAT TO READ WHEN IN A HURRY
		84
		85	This manual tries to be very detailed, but unfortunately, this also makes
		86	it very long. If you just want to know the basics of libev, I suggest
		87	reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and
		88	look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and
		89	C<ev_timer> sections in L<WATCHER TYPES>.
		90
		91	=head1 ABOUT LIBEV
70		92
71	Libev is an event loop: you register interest in certain events (such as a	93	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	94	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	95	these event sources and provide your program with events.
74		96
…		…
84	=head2 FEATURES	106	=head2 FEATURES
85		107
86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	108	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	109	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	110	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	111	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
90	with customised rescheduling (C<ev_periodic>), synchronous signals	112	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
91	(C<ev_signal>), process status change events (C<ev_child>), and event	113	timers (C<ev_timer>), absolute timers with customised rescheduling
92	watchers dealing with the event loop mechanism itself (C<ev_idle>,	114	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
93	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	115	change events (C<ev_child>), and event watchers dealing with the event
94	file watchers (C<ev_stat>) and even limited support for fork events	116	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
95	(C<ev_fork>).	117	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		118	limited support for fork events (C<ev_fork>).
96		119
97	It also is quite fast (see this	120	It also is quite fast (see this
98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	121	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
99	for example).	122	for example).
100		123
…		…
103	Libev is very configurable. In this manual the default (and most common)	126	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	127	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	128	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	129	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	130	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<ev_loop *>) will not have	131	name C<loop> (which is always of type C<struct ev_loop *>) will not have
109	this argument.	132	this argument.
110		133
111	=head2 TIME REPRESENTATION	134	=head2 TIME REPRESENTATION
112		135
113	Libev represents time as a single floating point number, representing the	136	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	137	the (fractional) number of seconds since the (POSIX) epoch (in practice
115	the beginning of 1970, details are complicated, don't ask). This type is	138	somewhere near the beginning of 1970, details are complicated, don't
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	139	ask). This type is called C<ev_tstamp>, which is what you should use
117	to the C<double> type in C, and when you need to do any calculations on	140	too. It usually aliases to the C<double> type in C. When you need to do
118	it, you should treat it as some floating point value. Unlike the name	141	any calculations on it, you should treat it as some floating point value.
		142
119	component C<stamp> might indicate, it is also used for time differences	143	Unlike the name component C<stamp> might indicate, it is also used for
120	throughout libev.	144	time differences (e.g. delays) throughout libev.
121		145
122	=head1 ERROR HANDLING	146	=head1 ERROR HANDLING
123		147
124	Libev knows three classes of errors: operating system errors, usage errors	148	Libev knows three classes of errors: operating system errors, usage errors
125	and internal errors (bugs).	149	and internal errors (bugs).
…		…
149		173
150	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
151		175
152	Returns the current time as libev would use it. Please note that the	176	Returns the current time as libev would use it. Please note that the
153	C<ev_now> function is usually faster and also often returns the timestamp	177	C<ev_now> function is usually faster and also often returns the timestamp
154	you actually want to know.	178	you actually want to know. Also interesting is the combination of
		179	C<ev_update_now> and C<ev_now>.
155		180
156	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
157		182
158	Sleep for the given interval: The current thread will be blocked until	183	Sleep for the given interval: The current thread will be blocked until
159	either it is interrupted or the given time interval has passed. Basically	184	either it is interrupted or the given time interval has passed. Basically
…		…
176	as this indicates an incompatible change. Minor versions are usually	201	as this indicates an incompatible change. Minor versions are usually
177	compatible to older versions, so a larger minor version alone is usually	202	compatible to older versions, so a larger minor version alone is usually
178	not a problem.	203	not a problem.
179		204
180	Example: Make sure we haven't accidentally been linked against the wrong	205	Example: Make sure we haven't accidentally been linked against the wrong
181	version.	206	version (note, however, that this will not detect other ABI mismatches,
		207	such as LFS or reentrancy).
182		208
183	assert (("libev version mismatch",	209	assert (("libev version mismatch",
184	ev_version_major () == EV_VERSION_MAJOR	210	ev_version_major () == EV_VERSION_MAJOR
185	&& ev_version_minor () >= EV_VERSION_MINOR));	211	&& ev_version_minor () >= EV_VERSION_MINOR));
186		212
…		…
197	assert (("sorry, no epoll, no sex",	223	assert (("sorry, no epoll, no sex",
198	ev_supported_backends () & EVBACKEND_EPOLL));	224	ev_supported_backends () & EVBACKEND_EPOLL));
199		225
200	=item unsigned int ev_recommended_backends ()	226	=item unsigned int ev_recommended_backends ()
201		227
202	Return the set of all backends compiled into this binary of libev and also	228	Return the set of all backends compiled into this binary of libev and
203	recommended for this platform. This set is often smaller than the one	229	also recommended for this platform, meaning it will work for most file
		230	descriptor types. This set is often smaller than the one returned by
204	returned by C<ev_supported_backends>, as for example kqueue is broken on	231	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
205	most BSDs and will not be auto-detected unless you explicitly request it	232	and will not be auto-detected unless you explicitly request it (assuming
206	(assuming you know what you are doing). This is the set of backends that	233	you know what you are doing). This is the set of backends that libev will
207	libev will probe for if you specify no backends explicitly.	234	probe for if you specify no backends explicitly.
208		235
209	=item unsigned int ev_embeddable_backends ()	236	=item unsigned int ev_embeddable_backends ()
210		237
211	Returns the set of backends that are embeddable in other event loops. This	238	Returns the set of backends that are embeddable in other event loops. This
212	is the theoretical, all-platform, value. To find which backends	239	value is platform-specific but can include backends not available on the
213	might be supported on the current system, you would need to look at	240	current system. To find which embeddable backends might be supported on
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	241	the current system, you would need to look at C<ev_embeddable_backends ()
215	recommended ones.	242	& ev_supported_backends ()>, likewise for recommended ones.
216		243
217	See the description of C<ev_embed> watchers for more info.	244	See the description of C<ev_embed> watchers for more info.
218		245
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	246	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
220		247
221	Sets the allocation function to use (the prototype is similar - the	248	Sets the allocation function to use (the prototype is similar - the
222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	249	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
223	used to allocate and free memory (no surprises here). If it returns zero	250	used to allocate and free memory (no surprises here). If it returns zero
224	when memory needs to be allocated (C<size != 0>), the library might abort	251	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	277	}
251		278
252	...	279	...
253	ev_set_allocator (persistent_realloc);	280	ev_set_allocator (persistent_realloc);
254		281
255	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	282	=item ev_set_syserr_cb (void (*cb)(const char *msg))
256		283
257	Set the callback function to call on a retryable system call error (such	284	Set the callback function to call on a retryable system call error (such
258	as failed select, poll, epoll_wait). The message is a printable string	285	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	286	indicating the system call or subsystem causing the problem. If this
260	callback is set, then libev will expect it to remedy the situation, no	287	callback is set, then libev will expect it to remedy the situation, no
…		…
272	}	299	}
273		300
274	...	301	...
275	ev_set_syserr_cb (fatal_error);	302	ev_set_syserr_cb (fatal_error);
276		303
		304	=item ev_feed_signal (int signum)
		305
		306	This function can be used to "simulate" a signal receive. It is completely
		307	safe to call this function at any time, from any context, including signal
		308	handlers or random threads.
		309
		310	Its main use is to customise signal handling in your process, especially
		311	in the presence of threads. For example, you could block signals
		312	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		313	creating any loops), and in one thread, use C<sigwait> or any other
		314	mechanism to wait for signals, then "deliver" them to libev by calling
		315	C<ev_feed_signal>.
		316
277	=back	317	=back
278		318
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	319	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
280		320
281	An event loop is described by a C<struct ev_loop *> (the C<struct>	321	An event loop is described by a C<struct ev_loop *> (the C<struct> is
282	is I<not> optional in this case, as there is also an C<ev_loop>	322	I<not> optional in this case unless libev 3 compatibility is disabled, as
283	I<function>).	323	libev 3 had an C<ev_loop> function colliding with the struct name).
284		324
285	The library knows two types of such loops, the I<default> loop, which	325	The library knows two types of such loops, the I<default> loop, which
286	supports signals and child events, and dynamically created loops which do	326	supports child process events, and dynamically created event loops which
287	not.	327	do not.
288		328
289	=over 4	329	=over 4
290		330
291	=item struct ev_loop *ev_default_loop (unsigned int flags)	331	=item struct ev_loop *ev_default_loop (unsigned int flags)
292		332
293	This will initialise the default event loop if it hasn't been initialised	333	This returns the "default" event loop object, which is what you should
294	yet and return it. If the default loop could not be initialised, returns	334	normally use when you just need "the event loop". Event loop objects and
295	false. If it already was initialised it simply returns it (and ignores the	335	the C<flags> parameter are described in more detail in the entry for
296	flags. If that is troubling you, check C<ev_backend ()> afterwards).	336	C<ev_loop_new>.
		337
		338	If the default loop is already initialised then this function simply
		339	returns it (and ignores the flags. If that is troubling you, check
		340	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		341	flags, which should almost always be C<0>, unless the caller is also the
		342	one calling C<ev_run> or otherwise qualifies as "the main program".
297		343
298	If you don't know what event loop to use, use the one returned from this	344	If you don't know what event loop to use, use the one returned from this
299	function.	345	function (or via the C<EV_DEFAULT> macro).
300		346
301	Note that this function is I<not> thread-safe, so if you want to use it	347	Note that this function is I<not> thread-safe, so if you want to use it
302	from multiple threads, you have to lock (note also that this is unlikely,	348	from multiple threads, you have to employ some kind of mutex (note also
303	as loops cannot bes hared easily between threads anyway).	349	that this case is unlikely, as loops cannot be shared easily between
		350	threads anyway).
304		351
305	The default loop is the only loop that can handle C<ev_signal> and	352	The default loop is the only loop that can handle C<ev_child> watchers,
306	C<ev_child> watchers, and to do this, it always registers a handler	353	and to do this, it always registers a handler for C<SIGCHLD>. If this is
307	for C<SIGCHLD>. If this is a problem for your application you can either	354	a problem for your application you can either create a dynamic loop with
308	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	355	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
309	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	356	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
310	C<ev_default_init>.	357
		358	Example: This is the most typical usage.
		359
		360	if (!ev_default_loop (0))
		361	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		362
		363	Example: Restrict libev to the select and poll backends, and do not allow
		364	environment settings to be taken into account:
		365
		366	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		367
		368	=item struct ev_loop *ev_loop_new (unsigned int flags)
		369
		370	This will create and initialise a new event loop object. If the loop
		371	could not be initialised, returns false.
		372
		373	This function is thread-safe, and one common way to use libev with
		374	threads is indeed to create one loop per thread, and using the default
		375	loop in the "main" or "initial" thread.
311		376
312	The flags argument can be used to specify special behaviour or specific	377	The flags argument can be used to specify special behaviour or specific
313	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	378	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
314		379
315	The following flags are supported:	380	The following flags are supported:
…		…
330	useful to try out specific backends to test their performance, or to work	395	useful to try out specific backends to test their performance, or to work
331	around bugs.	396	around bugs.
332		397
333	=item C<EVFLAG_FORKCHECK>	398	=item C<EVFLAG_FORKCHECK>
334		399
335	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	400	Instead of calling C<ev_loop_fork> manually after a fork, you can also
336	a fork, you can also make libev check for a fork in each iteration by	401	make libev check for a fork in each iteration by enabling this flag.
337	enabling this flag.
338		402
339	This works by calling C<getpid ()> on every iteration of the loop,	403	This works by calling C<getpid ()> on every iteration of the loop,
340	and thus this might slow down your event loop if you do a lot of loop	404	and thus this might slow down your event loop if you do a lot of loop
341	iterations and little real work, but is usually not noticeable (on my	405	iterations and little real work, but is usually not noticeable (on my
342	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	406	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
…		…
348	flag.	412	flag.
349		413
350	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	414	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
351	environment variable.	415	environment variable.
352		416
		417	=item C<EVFLAG_NOINOTIFY>
		418
		419	When this flag is specified, then libev will not attempt to use the
		420	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
		421	testing, this flag can be useful to conserve inotify file descriptors, as
		422	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		423
		424	=item C<EVFLAG_SIGNALFD>
		425
		426	When this flag is specified, then libev will attempt to use the
		427	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
		428	delivers signals synchronously, which makes it both faster and might make
		429	it possible to get the queued signal data. It can also simplify signal
		430	handling with threads, as long as you properly block signals in your
		431	threads that are not interested in handling them.
		432
		433	Signalfd will not be used by default as this changes your signal mask, and
		434	there are a lot of shoddy libraries and programs (glib's threadpool for
		435	example) that can't properly initialise their signal masks.
		436
		437	=item C<EVFLAG_NOSIGMASK>
		438
		439	When this flag is specified, then libev will avoid to modify the signal
		440	mask. Specifically, this means you ahve to make sure signals are unblocked
		441	when you want to receive them.
		442
		443	This behaviour is useful when you want to do your own signal handling, or
		444	want to handle signals only in specific threads and want to avoid libev
		445	unblocking the signals.
		446
		447	This flag's behaviour will become the default in future versions of libev.
		448
353	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	449	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
354		450
355	This is your standard select(2) backend. Not I<completely> standard, as	451	This is your standard select(2) backend. Not I<completely> standard, as
356	libev tries to roll its own fd_set with no limits on the number of fds,	452	libev tries to roll its own fd_set with no limits on the number of fds,
357	but if that fails, expect a fairly low limit on the number of fds when	453	but if that fails, expect a fairly low limit on the number of fds when
…		…
381	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and	477	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
382	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	478	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
383		479
384	=item C<EVBACKEND_EPOLL> (value 4, Linux)	480	=item C<EVBACKEND_EPOLL> (value 4, Linux)
385		481
		482	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		483	kernels).
		484
386	For few fds, this backend is a bit little slower than poll and select,	485	For few fds, this backend is a bit little slower than poll and select,
387	but it scales phenomenally better. While poll and select usually scale	486	but it scales phenomenally better. While poll and select usually scale
388	like O(total_fds) where n is the total number of fds (or the highest fd),	487	like O(total_fds) where n is the total number of fds (or the highest fd),
389	epoll scales either O(1) or O(active_fds). The epoll design has a number	488	epoll scales either O(1) or O(active_fds).
390	of shortcomings, such as silently dropping events in some hard-to-detect	489
391	cases and requiring a system call per fd change, no fork support and bad	490	The epoll mechanism deserves honorable mention as the most misdesigned
392	support for dup.	491	of the more advanced event mechanisms: mere annoyances include silently
		492	dropping file descriptors, requiring a system call per change per file
		493	descriptor (and unnecessary guessing of parameters), problems with dup,
		494	returning before the timeout value, resulting in additional iterations
		495	(and only giving 5ms accuracy while select on the same platform gives
		496	0.1ms) and so on. The biggest issue is fork races, however - if a program
		497	forks then I<both> parent and child process have to recreate the epoll
		498	set, which can take considerable time (one syscall per file descriptor)
		499	and is of course hard to detect.
		500
		501	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		502	of course I<doesn't>, and epoll just loves to report events for totally
		503	I<different> file descriptors (even already closed ones, so one cannot
		504	even remove them from the set) than registered in the set (especially
		505	on SMP systems). Libev tries to counter these spurious notifications by
		506	employing an additional generation counter and comparing that against the
		507	events to filter out spurious ones, recreating the set when required. Last
		508	not least, it also refuses to work with some file descriptors which work
		509	perfectly fine with C<select> (files, many character devices...).
		510
		511	Epoll is truly the train wreck analog among event poll mechanisms.
393		512
394	While stopping, setting and starting an I/O watcher in the same iteration	513	While stopping, setting and starting an I/O watcher in the same iteration
395	will result in some caching, there is still a system call per such incident	514	will result in some caching, there is still a system call per such
396	(because the fd could point to a different file description now), so its	515	incident (because the same I<file descriptor> could point to a different
397	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	516	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
398	very well if you register events for both fds.	517	file descriptors might not work very well if you register events for both
399		518	file descriptors.
400	Please note that epoll sometimes generates spurious notifications, so you
401	need to use non-blocking I/O or other means to avoid blocking when no data
402	(or space) is available.
403		519
404	Best performance from this backend is achieved by not unregistering all	520	Best performance from this backend is achieved by not unregistering all
405	watchers for a file descriptor until it has been closed, if possible,	521	watchers for a file descriptor until it has been closed, if possible,
406	i.e. keep at least one watcher active per fd at all times. Stopping and	522	i.e. keep at least one watcher active per fd at all times. Stopping and
407	starting a watcher (without re-setting it) also usually doesn't cause	523	starting a watcher (without re-setting it) also usually doesn't cause
408	extra overhead.	524	extra overhead. A fork can both result in spurious notifications as well
		525	as in libev having to destroy and recreate the epoll object, which can
		526	take considerable time and thus should be avoided.
		527
		528	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		529	faster than epoll for maybe up to a hundred file descriptors, depending on
		530	the usage. So sad.
409		531
410	While nominally embeddable in other event loops, this feature is broken in	532	While nominally embeddable in other event loops, this feature is broken in
411	all kernel versions tested so far.	533	all kernel versions tested so far.
412		534
413	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	535	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
414	C<EVBACKEND_POLL>.	536	C<EVBACKEND_POLL>.
415		537
416	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	538	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
417		539
418	Kqueue deserves special mention, as at the time of this writing, it was	540	Kqueue deserves special mention, as at the time of this writing, it
419	broken on all BSDs except NetBSD (usually it doesn't work reliably with	541	was broken on all BSDs except NetBSD (usually it doesn't work reliably
420	anything but sockets and pipes, except on Darwin, where of course it's	542	with anything but sockets and pipes, except on Darwin, where of course
421	completely useless). For this reason it's not being "auto-detected" unless	543	it's completely useless). Unlike epoll, however, whose brokenness
422	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or	544	is by design, these kqueue bugs can (and eventually will) be fixed
423	libev was compiled on a known-to-be-good (-enough) system like NetBSD.	545	without API changes to existing programs. For this reason it's not being
		546	"auto-detected" unless you explicitly specify it in the flags (i.e. using
		547	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		548	system like NetBSD.
424		549
425	You still can embed kqueue into a normal poll or select backend and use it	550	You still can embed kqueue into a normal poll or select backend and use it
426	only for sockets (after having made sure that sockets work with kqueue on	551	only for sockets (after having made sure that sockets work with kqueue on
427	the target platform). See C<ev_embed> watchers for more info.	552	the target platform). See C<ev_embed> watchers for more info.
428		553
429	It scales in the same way as the epoll backend, but the interface to the	554	It scales in the same way as the epoll backend, but the interface to the
430	kernel is more efficient (which says nothing about its actual speed, of	555	kernel is more efficient (which says nothing about its actual speed, of
431	course). While stopping, setting and starting an I/O watcher does never	556	course). While stopping, setting and starting an I/O watcher does never
432	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	557	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
433	two event changes per incident. Support for C<fork ()> is very bad and it	558	two event changes per incident. Support for C<fork ()> is very bad (but
434	drops fds silently in similarly hard-to-detect cases.	559	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		560	cases
435		561
436	This backend usually performs well under most conditions.	562	This backend usually performs well under most conditions.
437		563
438	While nominally embeddable in other event loops, this doesn't work	564	While nominally embeddable in other event loops, this doesn't work
439	everywhere, so you might need to test for this. And since it is broken	565	everywhere, so you might need to test for this. And since it is broken
440	almost everywhere, you should only use it when you have a lot of sockets	566	almost everywhere, you should only use it when you have a lot of sockets
441	(for which it usually works), by embedding it into another event loop	567	(for which it usually works), by embedding it into another event loop
442	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,	568	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
443	using it only for sockets.	569	also broken on OS X)) and, did I mention it, using it only for sockets.
444		570
445	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	571	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
446	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with	572	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
447	C<NOTE_EOF>.	573	C<NOTE_EOF>.
448		574
…		…
468	might perform better.	594	might perform better.
469		595
470	On the positive side, with the exception of the spurious readiness	596	On the positive side, with the exception of the spurious readiness
471	notifications, this backend actually performed fully to specification	597	notifications, this backend actually performed fully to specification
472	in all tests and is fully embeddable, which is a rare feat among the	598	in all tests and is fully embeddable, which is a rare feat among the
473	OS-specific backends.	599	OS-specific backends (I vastly prefer correctness over speed hacks).
474		600
475	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	601	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
476	C<EVBACKEND_POLL>.	602	C<EVBACKEND_POLL>.
477		603
478	=item C<EVBACKEND_ALL>	604	=item C<EVBACKEND_ALL>
479		605
480	Try all backends (even potentially broken ones that wouldn't be tried	606	Try all backends (even potentially broken ones that wouldn't be tried
481	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	607	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
482	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	608	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
483		609
484	It is definitely not recommended to use this flag.	610	It is definitely not recommended to use this flag, use whatever
		611	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		612	at all.
		613
		614	=item C<EVBACKEND_MASK>
		615
		616	Not a backend at all, but a mask to select all backend bits from a
		617	C<flags> value, in case you want to mask out any backends from a flags
		618	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
485		619
486	=back	620	=back
487		621
488	If one or more of these are or'ed into the flags value, then only these	622	If one or more of the backend flags are or'ed into the flags value,
489	backends will be tried (in the reverse order as listed here). If none are	623	then only these backends will be tried (in the reverse order as listed
490	specified, all backends in C<ev_recommended_backends ()> will be tried.	624	here). If none are specified, all backends in C<ev_recommended_backends
491		625	()> will be tried.
492	Example: This is the most typical usage.
493
494	if (!ev_default_loop (0))
495	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
496
497	Example: Restrict libev to the select and poll backends, and do not allow
498	environment settings to be taken into account:
499
500	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
501
502	Example: Use whatever libev has to offer, but make sure that kqueue is
503	used if available (warning, breaks stuff, best use only with your own
504	private event loop and only if you know the OS supports your types of
505	fds):
506
507	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
508
509	=item struct ev_loop *ev_loop_new (unsigned int flags)
510
511	Similar to C<ev_default_loop>, but always creates a new event loop that is
512	always distinct from the default loop. Unlike the default loop, it cannot
513	handle signal and child watchers, and attempts to do so will be greeted by
514	undefined behaviour (or a failed assertion if assertions are enabled).
515
516	Note that this function I<is> thread-safe, and the recommended way to use
517	libev with threads is indeed to create one loop per thread, and using the
518	default loop in the "main" or "initial" thread.
519		626
520	Example: Try to create a event loop that uses epoll and nothing else.	627	Example: Try to create a event loop that uses epoll and nothing else.
521		628
522	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	629	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
523	if (!epoller)	630	if (!epoller)
524	fatal ("no epoll found here, maybe it hides under your chair");	631	fatal ("no epoll found here, maybe it hides under your chair");
525		632
		633	Example: Use whatever libev has to offer, but make sure that kqueue is
		634	used if available.
		635
		636	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		637
526	=item ev_default_destroy ()	638	=item ev_loop_destroy (loop)
527		639
528	Destroys the default loop again (frees all memory and kernel state	640	Destroys an event loop object (frees all memory and kernel state
529	etc.). None of the active event watchers will be stopped in the normal	641	etc.). None of the active event watchers will be stopped in the normal
530	sense, so e.g. C<ev_is_active> might still return true. It is your	642	sense, so e.g. C<ev_is_active> might still return true. It is your
531	responsibility to either stop all watchers cleanly yourself I<before>	643	responsibility to either stop all watchers cleanly yourself I<before>
532	calling this function, or cope with the fact afterwards (which is usually	644	calling this function, or cope with the fact afterwards (which is usually
533	the easiest thing, you can just ignore the watchers and/or C<free ()> them	645	the easiest thing, you can just ignore the watchers and/or C<free ()> them
534	for example).	646	for example).
535		647
536	Note that certain global state, such as signal state, will not be freed by	648	Note that certain global state, such as signal state (and installed signal
537	this function, and related watchers (such as signal and child watchers)	649	handlers), will not be freed by this function, and related watchers (such
538	would need to be stopped manually.	650	as signal and child watchers) would need to be stopped manually.
539		651
540	In general it is not advisable to call this function except in the	652	This function is normally used on loop objects allocated by
541	rare occasion where you really need to free e.g. the signal handling	653	C<ev_loop_new>, but it can also be used on the default loop returned by
		654	C<ev_default_loop>, in which case it is not thread-safe.
		655
		656	Note that it is not advisable to call this function on the default loop
		657	except in the rare occasion where you really need to free its resources.
542	pipe fds. If you need dynamically allocated loops it is better to use	658	If you need dynamically allocated loops it is better to use C<ev_loop_new>
543	C<ev_loop_new> and C<ev_loop_destroy>).	659	and C<ev_loop_destroy>.
544		660
545	=item ev_loop_destroy (loop)	661	=item ev_loop_fork (loop)
546		662
547	Like C<ev_default_destroy>, but destroys an event loop created by an
548	earlier call to C<ev_loop_new>.
549
550	=item ev_default_fork ()
551
552	This function sets a flag that causes subsequent C<ev_loop> iterations	663	This function sets a flag that causes subsequent C<ev_run> iterations to
553	to reinitialise the kernel state for backends that have one. Despite the	664	reinitialise the kernel state for backends that have one. Despite the
554	name, you can call it anytime, but it makes most sense after forking, in	665	name, you can call it anytime, but it makes most sense after forking, in
555	the child process (or both child and parent, but that again makes little	666	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
556	sense). You I<must> call it in the child before using any of the libev	667	child before resuming or calling C<ev_run>.
557	functions, and it will only take effect at the next C<ev_loop> iteration.	668
		669	Again, you I<have> to call it on I<any> loop that you want to re-use after
		670	a fork, I<even if you do not plan to use the loop in the parent>. This is
		671	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		672	during fork.
558		673
559	On the other hand, you only need to call this function in the child	674	On the other hand, you only need to call this function in the child
560	process if and only if you want to use the event library in the child. If	675	process if and only if you want to use the event loop in the child. If
561	you just fork+exec, you don't have to call it at all.	676	you just fork+exec or create a new loop in the child, you don't have to
		677	call it at all (in fact, C<epoll> is so badly broken that it makes a
		678	difference, but libev will usually detect this case on its own and do a
		679	costly reset of the backend).
562		680
563	The function itself is quite fast and it's usually not a problem to call	681	The function itself is quite fast and it's usually not a problem to call
564	it just in case after a fork. To make this easy, the function will fit in	682	it just in case after a fork.
565	quite nicely into a call to C<pthread_atfork>:
566		683
		684	Example: Automate calling C<ev_loop_fork> on the default loop when
		685	using pthreads.
		686
		687	static void
		688	post_fork_child (void)
		689	{
		690	ev_loop_fork (EV_DEFAULT);
		691	}
		692
		693	...
567	pthread_atfork (0, 0, ev_default_fork);	694	pthread_atfork (0, 0, post_fork_child);
568
569	=item ev_loop_fork (loop)
570
571	Like C<ev_default_fork>, but acts on an event loop created by
572	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
573	after fork that you want to re-use in the child, and how you do this is
574	entirely your own problem.
575		695
576	=item int ev_is_default_loop (loop)	696	=item int ev_is_default_loop (loop)
577		697
578	Returns true when the given loop is, in fact, the default loop, and false	698	Returns true when the given loop is, in fact, the default loop, and false
579	otherwise.	699	otherwise.
580		700
581	=item unsigned int ev_loop_count (loop)	701	=item unsigned int ev_iteration (loop)
582		702
583	Returns the count of loop iterations for the loop, which is identical to	703	Returns the current iteration count for the event loop, which is identical
584	the number of times libev did poll for new events. It starts at C<0> and	704	to the number of times libev did poll for new events. It starts at C<0>
585	happily wraps around with enough iterations.	705	and happily wraps around with enough iterations.
586		706
587	This value can sometimes be useful as a generation counter of sorts (it	707	This value can sometimes be useful as a generation counter of sorts (it
588	"ticks" the number of loop iterations), as it roughly corresponds with	708	"ticks" the number of loop iterations), as it roughly corresponds with
589	C<ev_prepare> and C<ev_check> calls.	709	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		710	prepare and check phases.
		711
		712	=item unsigned int ev_depth (loop)
		713
		714	Returns the number of times C<ev_run> was entered minus the number of
		715	times C<ev_run> was exited normally, in other words, the recursion depth.
		716
		717	Outside C<ev_run>, this number is zero. In a callback, this number is
		718	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		719	in which case it is higher.
		720
		721	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
		722	throwing an exception etc.), doesn't count as "exit" - consider this
		723	as a hint to avoid such ungentleman-like behaviour unless it's really
		724	convenient, in which case it is fully supported.
590		725
591	=item unsigned int ev_backend (loop)	726	=item unsigned int ev_backend (loop)
592		727
593	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	728	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
594	use.	729	use.
…		…
603		738
604	=item ev_now_update (loop)	739	=item ev_now_update (loop)
605		740
606	Establishes the current time by querying the kernel, updating the time	741	Establishes the current time by querying the kernel, updating the time
607	returned by C<ev_now ()> in the progress. This is a costly operation and	742	returned by C<ev_now ()> in the progress. This is a costly operation and
608	is usually done automatically within C<ev_loop ()>.	743	is usually done automatically within C<ev_run ()>.
609		744
610	This function is rarely useful, but when some event callback runs for a	745	This function is rarely useful, but when some event callback runs for a
611	very long time without entering the event loop, updating libev's idea of	746	very long time without entering the event loop, updating libev's idea of
612	the current time is a good idea.	747	the current time is a good idea.
613		748
614	See also "The special problem of time updates" in the C<ev_timer> section.	749	See also L<The special problem of time updates> in the C<ev_timer> section.
615		750
		751	=item ev_suspend (loop)
		752
		753	=item ev_resume (loop)
		754
		755	These two functions suspend and resume an event loop, for use when the
		756	loop is not used for a while and timeouts should not be processed.
		757
		758	A typical use case would be an interactive program such as a game: When
		759	the user presses C<^Z> to suspend the game and resumes it an hour later it
		760	would be best to handle timeouts as if no time had actually passed while
		761	the program was suspended. This can be achieved by calling C<ev_suspend>
		762	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		763	C<ev_resume> directly afterwards to resume timer processing.
		764
		765	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		766	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		767	will be rescheduled (that is, they will lose any events that would have
		768	occurred while suspended).
		769
		770	After calling C<ev_suspend> you B<must not> call I<any> function on the
		771	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		772	without a previous call to C<ev_suspend>.
		773
		774	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		775	event loop time (see C<ev_now_update>).
		776
616	=item ev_loop (loop, int flags)	777	=item ev_run (loop, int flags)
617		778
618	Finally, this is it, the event handler. This function usually is called	779	Finally, this is it, the event handler. This function usually is called
619	after you initialised all your watchers and you want to start handling	780	after you have initialised all your watchers and you want to start
620	events.	781	handling events. It will ask the operating system for any new events, call
		782	the watcher callbacks, an then repeat the whole process indefinitely: This
		783	is why event loops are called I<loops>.
621		784
622	If the flags argument is specified as C<0>, it will not return until	785	If the flags argument is specified as C<0>, it will keep handling events
623	either no event watchers are active anymore or C<ev_unloop> was called.	786	until either no event watchers are active anymore or C<ev_break> was
		787	called.
624		788
625	Please note that an explicit C<ev_unloop> is usually better than	789	Please note that an explicit C<ev_break> is usually better than
626	relying on all watchers to be stopped when deciding when a program has	790	relying on all watchers to be stopped when deciding when a program has
627	finished (especially in interactive programs), but having a program	791	finished (especially in interactive programs), but having a program
628	that automatically loops as long as it has to and no longer by virtue	792	that automatically loops as long as it has to and no longer by virtue
629	of relying on its watchers stopping correctly, that is truly a thing of	793	of relying on its watchers stopping correctly, that is truly a thing of
630	beauty.	794	beauty.
631		795
		796	This function is also I<mostly> exception-safe - you can break out of
		797	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		798	exception and so on. This does not decrement the C<ev_depth> value, nor
		799	will it clear any outstanding C<EVBREAK_ONE> breaks.
		800
632	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	801	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
633	those events and any already outstanding ones, but will not block your	802	those events and any already outstanding ones, but will not wait and
634	process in case there are no events and will return after one iteration of	803	block your process in case there are no events and will return after one
635	the loop.	804	iteration of the loop. This is sometimes useful to poll and handle new
		805	events while doing lengthy calculations, to keep the program responsive.
636		806
637	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	807	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
638	necessary) and will handle those and any already outstanding ones. It	808	necessary) and will handle those and any already outstanding ones. It
639	will block your process until at least one new event arrives (which could	809	will block your process until at least one new event arrives (which could
640	be an event internal to libev itself, so there is no guarentee that a	810	be an event internal to libev itself, so there is no guarantee that a
641	user-registered callback will be called), and will return after one	811	user-registered callback will be called), and will return after one
642	iteration of the loop.	812	iteration of the loop.
643		813
644	This is useful if you are waiting for some external event in conjunction	814	This is useful if you are waiting for some external event in conjunction
645	with something not expressible using other libev watchers (i.e. "roll your	815	with something not expressible using other libev watchers (i.e. "roll your
646	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	816	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
647	usually a better approach for this kind of thing.	817	usually a better approach for this kind of thing.
648		818
649	Here are the gory details of what C<ev_loop> does:	819	Here are the gory details of what C<ev_run> does:
650		820
		821	- Increment loop depth.
		822	- Reset the ev_break status.
651	- Before the first iteration, call any pending watchers.	823	- Before the first iteration, call any pending watchers.
		824	LOOP:
652	* If EVFLAG_FORKCHECK was used, check for a fork.	825	- If EVFLAG_FORKCHECK was used, check for a fork.
653	- If a fork was detected (by any means), queue and call all fork watchers.	826	- If a fork was detected (by any means), queue and call all fork watchers.
654	- Queue and call all prepare watchers.	827	- Queue and call all prepare watchers.
		828	- If ev_break was called, goto FINISH.
655	- If we have been forked, detach and recreate the kernel state	829	- If we have been forked, detach and recreate the kernel state
656	as to not disturb the other process.	830	as to not disturb the other process.
657	- Update the kernel state with all outstanding changes.	831	- Update the kernel state with all outstanding changes.
658	- Update the "event loop time" (ev_now ()).	832	- Update the "event loop time" (ev_now ()).
659	- Calculate for how long to sleep or block, if at all	833	- Calculate for how long to sleep or block, if at all
660	(active idle watchers, EVLOOP_NONBLOCK or not having	834	(active idle watchers, EVRUN_NOWAIT or not having
661	any active watchers at all will result in not sleeping).	835	any active watchers at all will result in not sleeping).
662	- Sleep if the I/O and timer collect interval say so.	836	- Sleep if the I/O and timer collect interval say so.
		837	- Increment loop iteration counter.
663	- Block the process, waiting for any events.	838	- Block the process, waiting for any events.
664	- Queue all outstanding I/O (fd) events.	839	- Queue all outstanding I/O (fd) events.
665	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	840	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
666	- Queue all expired timers.	841	- Queue all expired timers.
667	- Queue all expired periodics.	842	- Queue all expired periodics.
668	- Unless any events are pending now, queue all idle watchers.	843	- Queue all idle watchers with priority higher than that of pending events.
669	- Queue all check watchers.	844	- Queue all check watchers.
670	- Call all queued watchers in reverse order (i.e. check watchers first).	845	- Call all queued watchers in reverse order (i.e. check watchers first).
671	Signals and child watchers are implemented as I/O watchers, and will	846	Signals and child watchers are implemented as I/O watchers, and will
672	be handled here by queueing them when their watcher gets executed.	847	be handled here by queueing them when their watcher gets executed.
673	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	848	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
674	were used, or there are no active watchers, return, otherwise	849	were used, or there are no active watchers, goto FINISH, otherwise
675	continue with step *.	850	continue with step LOOP.
		851	FINISH:
		852	- Reset the ev_break status iff it was EVBREAK_ONE.
		853	- Decrement the loop depth.
		854	- Return.
676		855
677	Example: Queue some jobs and then loop until no events are outstanding	856	Example: Queue some jobs and then loop until no events are outstanding
678	anymore.	857	anymore.
679		858
680	... queue jobs here, make sure they register event watchers as long	859	... queue jobs here, make sure they register event watchers as long
681	... as they still have work to do (even an idle watcher will do..)	860	... as they still have work to do (even an idle watcher will do..)
682	ev_loop (my_loop, 0);	861	ev_run (my_loop, 0);
683	... jobs done or somebody called unloop. yeah!	862	... jobs done or somebody called unloop. yeah!
684		863
685	=item ev_unloop (loop, how)	864	=item ev_break (loop, how)
686		865
687	Can be used to make a call to C<ev_loop> return early (but only after it	866	Can be used to make a call to C<ev_run> return early (but only after it
688	has processed all outstanding events). The C<how> argument must be either	867	has processed all outstanding events). The C<how> argument must be either
689	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	868	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
690	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	869	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
691		870
692	This "unloop state" will be cleared when entering C<ev_loop> again.	871	This "break state" will be cleared on the next call to C<ev_run>.
693		872
694	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	873	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		874	which case it will have no effect.
695		875
696	=item ev_ref (loop)	876	=item ev_ref (loop)
697		877
698	=item ev_unref (loop)	878	=item ev_unref (loop)
699		879
700	Ref/unref can be used to add or remove a reference count on the event	880	Ref/unref can be used to add or remove a reference count on the event
701	loop: Every watcher keeps one reference, and as long as the reference	881	loop: Every watcher keeps one reference, and as long as the reference
702	count is nonzero, C<ev_loop> will not return on its own.	882	count is nonzero, C<ev_run> will not return on its own.
703		883
704	If you have a watcher you never unregister that should not keep C<ev_loop>	884	This is useful when you have a watcher that you never intend to
705	from returning, call ev_unref() after starting, and ev_ref() before	885	unregister, but that nevertheless should not keep C<ev_run> from
		886	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
706	stopping it.	887	before stopping it.
707		888
708	As an example, libev itself uses this for its internal signal pipe: It is	889	As an example, libev itself uses this for its internal signal pipe: It
709	not visible to the libev user and should not keep C<ev_loop> from exiting	890	is not visible to the libev user and should not keep C<ev_run> from
710	if no event watchers registered by it are active. It is also an excellent	891	exiting if no event watchers registered by it are active. It is also an
711	way to do this for generic recurring timers or from within third-party	892	excellent way to do this for generic recurring timers or from within
712	libraries. Just remember to I<unref after start> and I<ref before stop>	893	third-party libraries. Just remember to I<unref after start> and I<ref
713	(but only if the watcher wasn't active before, or was active before,	894	before stop> (but only if the watcher wasn't active before, or was active
714	respectively).	895	before, respectively. Note also that libev might stop watchers itself
		896	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		897	in the callback).
715		898
716	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	899	Example: Create a signal watcher, but keep it from keeping C<ev_run>
717	running when nothing else is active.	900	running when nothing else is active.
718		901
719	ev_signal exitsig;	902	ev_signal exitsig;
720	ev_signal_init (&exitsig, sig_cb, SIGINT);	903	ev_signal_init (&exitsig, sig_cb, SIGINT);
721	ev_signal_start (loop, &exitsig);	904	ev_signal_start (loop, &exitsig);
722	evf_unref (loop);	905	ev_unref (loop);
723		906
724	Example: For some weird reason, unregister the above signal handler again.	907	Example: For some weird reason, unregister the above signal handler again.
725		908
726	ev_ref (loop);	909	ev_ref (loop);
727	ev_signal_stop (loop, &exitsig);	910	ev_signal_stop (loop, &exitsig);
…		…
748		931
749	By setting a higher I<io collect interval> you allow libev to spend more	932	By setting a higher I<io collect interval> you allow libev to spend more
750	time collecting I/O events, so you can handle more events per iteration,	933	time collecting I/O events, so you can handle more events per iteration,
751	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	934	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
752	C<ev_timer>) will be not affected. Setting this to a non-null value will	935	C<ev_timer>) will be not affected. Setting this to a non-null value will
753	introduce an additional C<ev_sleep ()> call into most loop iterations.	936	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		937	sleep time ensures that libev will not poll for I/O events more often then
		938	once per this interval, on average.
754		939
755	Likewise, by setting a higher I<timeout collect interval> you allow libev	940	Likewise, by setting a higher I<timeout collect interval> you allow libev
756	to spend more time collecting timeouts, at the expense of increased	941	to spend more time collecting timeouts, at the expense of increased
757	latency/jitter/inexactness (the watcher callback will be called	942	latency/jitter/inexactness (the watcher callback will be called
758	later). C<ev_io> watchers will not be affected. Setting this to a non-null	943	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
760		945
761	Many (busy) programs can usually benefit by setting the I/O collect	946	Many (busy) programs can usually benefit by setting the I/O collect
762	interval to a value near C<0.1> or so, which is often enough for	947	interval to a value near C<0.1> or so, which is often enough for
763	interactive servers (of course not for games), likewise for timeouts. It	948	interactive servers (of course not for games), likewise for timeouts. It
764	usually doesn't make much sense to set it to a lower value than C<0.01>,	949	usually doesn't make much sense to set it to a lower value than C<0.01>,
765	as this approaches the timing granularity of most systems.	950	as this approaches the timing granularity of most systems. Note that if
		951	you do transactions with the outside world and you can't increase the
		952	parallelity, then this setting will limit your transaction rate (if you
		953	need to poll once per transaction and the I/O collect interval is 0.01,
		954	then you can't do more than 100 transactions per second).
766		955
767	Setting the I<timeout collect interval> can improve the opportunity for	956	Setting the I<timeout collect interval> can improve the opportunity for
768	saving power, as the program will "bundle" timer callback invocations that	957	saving power, as the program will "bundle" timer callback invocations that
769	are "near" in time together, by delaying some, thus reducing the number of	958	are "near" in time together, by delaying some, thus reducing the number of
770	times the process sleeps and wakes up again. Another useful technique to	959	times the process sleeps and wakes up again. Another useful technique to
771	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	960	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
772	they fire on, say, one-second boundaries only.	961	they fire on, say, one-second boundaries only.
773		962
		963	Example: we only need 0.1s timeout granularity, and we wish not to poll
		964	more often than 100 times per second:
		965
		966	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		967	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		968
		969	=item ev_invoke_pending (loop)
		970
		971	This call will simply invoke all pending watchers while resetting their
		972	pending state. Normally, C<ev_run> does this automatically when required,
		973	but when overriding the invoke callback this call comes handy. This
		974	function can be invoked from a watcher - this can be useful for example
		975	when you want to do some lengthy calculation and want to pass further
		976	event handling to another thread (you still have to make sure only one
		977	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		978
		979	=item int ev_pending_count (loop)
		980
		981	Returns the number of pending watchers - zero indicates that no watchers
		982	are pending.
		983
		984	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		985
		986	This overrides the invoke pending functionality of the loop: Instead of
		987	invoking all pending watchers when there are any, C<ev_run> will call
		988	this callback instead. This is useful, for example, when you want to
		989	invoke the actual watchers inside another context (another thread etc.).
		990
		991	If you want to reset the callback, use C<ev_invoke_pending> as new
		992	callback.
		993
		994	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		995
		996	Sometimes you want to share the same loop between multiple threads. This
		997	can be done relatively simply by putting mutex_lock/unlock calls around
		998	each call to a libev function.
		999
		1000	However, C<ev_run> can run an indefinite time, so it is not feasible
		1001	to wait for it to return. One way around this is to wake up the event
		1002	loop via C<ev_break> and C<av_async_send>, another way is to set these
		1003	I<release> and I<acquire> callbacks on the loop.
		1004
		1005	When set, then C<release> will be called just before the thread is
		1006	suspended waiting for new events, and C<acquire> is called just
		1007	afterwards.
		1008
		1009	Ideally, C<release> will just call your mutex_unlock function, and
		1010	C<acquire> will just call the mutex_lock function again.
		1011
		1012	While event loop modifications are allowed between invocations of
		1013	C<release> and C<acquire> (that's their only purpose after all), no
		1014	modifications done will affect the event loop, i.e. adding watchers will
		1015	have no effect on the set of file descriptors being watched, or the time
		1016	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		1017	to take note of any changes you made.
		1018
		1019	In theory, threads executing C<ev_run> will be async-cancel safe between
		1020	invocations of C<release> and C<acquire>.
		1021
		1022	See also the locking example in the C<THREADS> section later in this
		1023	document.
		1024
		1025	=item ev_set_userdata (loop, void *data)
		1026
		1027	=item void *ev_userdata (loop)
		1028
		1029	Set and retrieve a single C<void *> associated with a loop. When
		1030	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		1031	C<0>.
		1032
		1033	These two functions can be used to associate arbitrary data with a loop,
		1034	and are intended solely for the C<invoke_pending_cb>, C<release> and
		1035	C<acquire> callbacks described above, but of course can be (ab-)used for
		1036	any other purpose as well.
		1037
774	=item ev_loop_verify (loop)	1038	=item ev_verify (loop)
775		1039
776	This function only does something when C<EV_VERIFY> support has been	1040	This function only does something when C<EV_VERIFY> support has been
777	compiled in, which is the default for non-minimal builds. It tries to go	1041	compiled in, which is the default for non-minimal builds. It tries to go
778	through all internal structures and checks them for validity. If anything	1042	through all internal structures and checks them for validity. If anything
779	is found to be inconsistent, it will print an error message to standard	1043	is found to be inconsistent, it will print an error message to standard
…		…
790		1054
791	In the following description, uppercase C<TYPE> in names stands for the	1055	In the following description, uppercase C<TYPE> in names stands for the
792	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1056	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
793	watchers and C<ev_io_start> for I/O watchers.	1057	watchers and C<ev_io_start> for I/O watchers.
794		1058
795	A watcher is a structure that you create and register to record your	1059	A watcher is an opaque structure that you allocate and register to record
796	interest in some event. For instance, if you want to wait for STDIN to	1060	your interest in some event. To make a concrete example, imagine you want
797	become readable, you would create an C<ev_io> watcher for that:	1061	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1062	for that:
798		1063
799	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1064	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
800	{	1065	{
801	ev_io_stop (w);	1066	ev_io_stop (w);
802	ev_unloop (loop, EVUNLOOP_ALL);	1067	ev_break (loop, EVBREAK_ALL);
803	}	1068	}
804		1069
805	struct ev_loop *loop = ev_default_loop (0);	1070	struct ev_loop *loop = ev_default_loop (0);
806		1071
807	ev_io stdin_watcher;	1072	ev_io stdin_watcher;
808		1073
809	ev_init (&stdin_watcher, my_cb);	1074	ev_init (&stdin_watcher, my_cb);
810	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1075	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
811	ev_io_start (loop, &stdin_watcher);	1076	ev_io_start (loop, &stdin_watcher);
812		1077
813	ev_loop (loop, 0);	1078	ev_run (loop, 0);
814		1079
815	As you can see, you are responsible for allocating the memory for your	1080	As you can see, you are responsible for allocating the memory for your
816	watcher structures (and it is I<usually> a bad idea to do this on the	1081	watcher structures (and it is I<usually> a bad idea to do this on the
817	stack).	1082	stack).
818		1083
819	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1084	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
820	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1085	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
821		1086
822	Each watcher structure must be initialised by a call to C<ev_init	1087	Each watcher structure must be initialised by a call to C<ev_init (watcher
823	(watcher *, callback)>, which expects a callback to be provided. This	1088	*, callback)>, which expects a callback to be provided. This callback is
824	callback gets invoked each time the event occurs (or, in the case of I/O	1089	invoked each time the event occurs (or, in the case of I/O watchers, each
825	watchers, each time the event loop detects that the file descriptor given	1090	time the event loop detects that the file descriptor given is readable
826	is readable and/or writable).	1091	and/or writable).
827		1092
828	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1093	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
829	macro to configure it, with arguments specific to the watcher type. There	1094	macro to configure it, with arguments specific to the watcher type. There
830	is also a macro to combine initialisation and setting in one call: C<<	1095	is also a macro to combine initialisation and setting in one call: C<<
831	ev_TYPE_init (watcher *, callback, ...) >>.	1096	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
854	=item C<EV_WRITE>	1119	=item C<EV_WRITE>
855		1120
856	The file descriptor in the C<ev_io> watcher has become readable and/or	1121	The file descriptor in the C<ev_io> watcher has become readable and/or
857	writable.	1122	writable.
858		1123
859	=item C<EV_TIMEOUT>	1124	=item C<EV_TIMER>
860		1125
861	The C<ev_timer> watcher has timed out.	1126	The C<ev_timer> watcher has timed out.
862		1127
863	=item C<EV_PERIODIC>	1128	=item C<EV_PERIODIC>
864		1129
…		…
882		1147
883	=item C<EV_PREPARE>	1148	=item C<EV_PREPARE>
884		1149
885	=item C<EV_CHECK>	1150	=item C<EV_CHECK>
886		1151
887	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1152	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
888	to gather new events, and all C<ev_check> watchers are invoked just after	1153	to gather new events, and all C<ev_check> watchers are invoked just after
889	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1154	C<ev_run> has gathered them, but before it invokes any callbacks for any
890	received events. Callbacks of both watcher types can start and stop as	1155	received events. Callbacks of both watcher types can start and stop as
891	many watchers as they want, and all of them will be taken into account	1156	many watchers as they want, and all of them will be taken into account
892	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1157	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
893	C<ev_loop> from blocking).	1158	C<ev_run> from blocking).
894		1159
895	=item C<EV_EMBED>	1160	=item C<EV_EMBED>
896		1161
897	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1162	The embedded event loop specified in the C<ev_embed> watcher needs attention.
898		1163
899	=item C<EV_FORK>	1164	=item C<EV_FORK>
900		1165
901	The event loop has been resumed in the child process after fork (see	1166	The event loop has been resumed in the child process after fork (see
902	C<ev_fork>).	1167	C<ev_fork>).
903		1168
		1169	=item C<EV_CLEANUP>
		1170
		1171	The event loop is about to be destroyed (see C<ev_cleanup>).
		1172
904	=item C<EV_ASYNC>	1173	=item C<EV_ASYNC>
905		1174
906	The given async watcher has been asynchronously notified (see C<ev_async>).	1175	The given async watcher has been asynchronously notified (see C<ev_async>).
		1176
		1177	=item C<EV_CUSTOM>
		1178
		1179	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1180	by libev users to signal watchers (e.g. via C<ev_feed_event>).
907		1181
908	=item C<EV_ERROR>	1182	=item C<EV_ERROR>
909		1183
910	An unspecified error has occurred, the watcher has been stopped. This might	1184	An unspecified error has occurred, the watcher has been stopped. This might
911	happen because the watcher could not be properly started because libev	1185	happen because the watcher could not be properly started because libev
…		…
949		1223
950	ev_io w;	1224	ev_io w;
951	ev_init (&w, my_cb);	1225	ev_init (&w, my_cb);
952	ev_io_set (&w, STDIN_FILENO, EV_READ);	1226	ev_io_set (&w, STDIN_FILENO, EV_READ);
953		1227
954	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1228	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
955		1229
956	This macro initialises the type-specific parts of a watcher. You need to	1230	This macro initialises the type-specific parts of a watcher. You need to
957	call C<ev_init> at least once before you call this macro, but you can	1231	call C<ev_init> at least once before you call this macro, but you can
958	call C<ev_TYPE_set> any number of times. You must not, however, call this	1232	call C<ev_TYPE_set> any number of times. You must not, however, call this
959	macro on a watcher that is active (it can be pending, however, which is a	1233	macro on a watcher that is active (it can be pending, however, which is a
…		…
972		1246
973	Example: Initialise and set an C<ev_io> watcher in one step.	1247	Example: Initialise and set an C<ev_io> watcher in one step.
974		1248
975	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1249	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
976		1250
977	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1251	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
978		1252
979	Starts (activates) the given watcher. Only active watchers will receive	1253	Starts (activates) the given watcher. Only active watchers will receive
980	events. If the watcher is already active nothing will happen.	1254	events. If the watcher is already active nothing will happen.
981		1255
982	Example: Start the C<ev_io> watcher that is being abused as example in this	1256	Example: Start the C<ev_io> watcher that is being abused as example in this
983	whole section.	1257	whole section.
984		1258
985	ev_io_start (EV_DEFAULT_UC, &w);	1259	ev_io_start (EV_DEFAULT_UC, &w);
986		1260
987	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1261	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
988		1262
989	Stops the given watcher if active, and clears the pending status (whether	1263	Stops the given watcher if active, and clears the pending status (whether
990	the watcher was active or not).	1264	the watcher was active or not).
991		1265
992	It is possible that stopped watchers are pending - for example,	1266	It is possible that stopped watchers are pending - for example,
…		…
1017	=item ev_cb_set (ev_TYPE *watcher, callback)	1291	=item ev_cb_set (ev_TYPE *watcher, callback)
1018		1292
1019	Change the callback. You can change the callback at virtually any time	1293	Change the callback. You can change the callback at virtually any time
1020	(modulo threads).	1294	(modulo threads).
1021		1295
1022	=item ev_set_priority (ev_TYPE *watcher, priority)	1296	=item ev_set_priority (ev_TYPE *watcher, int priority)
1023		1297
1024	=item int ev_priority (ev_TYPE *watcher)	1298	=item int ev_priority (ev_TYPE *watcher)
1025		1299
1026	Set and query the priority of the watcher. The priority is a small	1300	Set and query the priority of the watcher. The priority is a small
1027	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1301	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1028	(default: C<-2>). Pending watchers with higher priority will be invoked	1302	(default: C<-2>). Pending watchers with higher priority will be invoked
1029	before watchers with lower priority, but priority will not keep watchers	1303	before watchers with lower priority, but priority will not keep watchers
1030	from being executed (except for C<ev_idle> watchers).	1304	from being executed (except for C<ev_idle> watchers).
1031		1305
1032	This means that priorities are I<only> used for ordering callback
1033	invocation after new events have been received. This is useful, for
1034	example, to reduce latency after idling, or more often, to bind two
1035	watchers on the same event and make sure one is called first.
1036
1037	If you need to suppress invocation when higher priority events are pending	1306	If you need to suppress invocation when higher priority events are pending
1038	you need to look at C<ev_idle> watchers, which provide this functionality.	1307	you need to look at C<ev_idle> watchers, which provide this functionality.
1039		1308
1040	You I<must not> change the priority of a watcher as long as it is active or	1309	You I<must not> change the priority of a watcher as long as it is active or
1041	pending.	1310	pending.
1042
1043	The default priority used by watchers when no priority has been set is
1044	always C<0>, which is supposed to not be too high and not be too low :).
1045		1311
1046	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1312	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1047	fine, as long as you do not mind that the priority value you query might	1313	fine, as long as you do not mind that the priority value you query might
1048	or might not have been clamped to the valid range.	1314	or might not have been clamped to the valid range.
		1315
		1316	The default priority used by watchers when no priority has been set is
		1317	always C<0>, which is supposed to not be too high and not be too low :).
		1318
		1319	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
		1320	priorities.
1049		1321
1050	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1322	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1051		1323
1052	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1324	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1053	C<loop> nor C<revents> need to be valid as long as the watcher callback	1325	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1061	watcher isn't pending it does nothing and returns C<0>.	1333	watcher isn't pending it does nothing and returns C<0>.
1062		1334
1063	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1335	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1064	callback to be invoked, which can be accomplished with this function.	1336	callback to be invoked, which can be accomplished with this function.
1065		1337
		1338	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1339
		1340	Feeds the given event set into the event loop, as if the specified event
		1341	had happened for the specified watcher (which must be a pointer to an
		1342	initialised but not necessarily started event watcher). Obviously you must
		1343	not free the watcher as long as it has pending events.
		1344
		1345	Stopping the watcher, letting libev invoke it, or calling
		1346	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1347	not started in the first place.
		1348
		1349	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1350	functions that do not need a watcher.
		1351
1066	=back	1352	=back
1067
1068		1353
1069	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1354	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1070		1355
1071	Each watcher has, by default, a member C<void *data> that you can change	1356	Each watcher has, by default, a member C<void *data> that you can change
1072	and read at any time: libev will completely ignore it. This can be used	1357	and read at any time: libev will completely ignore it. This can be used
…		…
1118	#include <stddef.h>	1403	#include <stddef.h>
1119		1404
1120	static void	1405	static void
1121	t1_cb (EV_P_ ev_timer *w, int revents)	1406	t1_cb (EV_P_ ev_timer *w, int revents)
1122	{	1407	{
1123	struct my_biggy big = (struct my_biggy *	1408	struct my_biggy big = (struct my_biggy *)
1124	(((char *)w) - offsetof (struct my_biggy, t1));	1409	(((char *)w) - offsetof (struct my_biggy, t1));
1125	}	1410	}
1126		1411
1127	static void	1412	static void
1128	t2_cb (EV_P_ ev_timer *w, int revents)	1413	t2_cb (EV_P_ ev_timer *w, int revents)
1129	{	1414	{
1130	struct my_biggy big = (struct my_biggy *	1415	struct my_biggy big = (struct my_biggy *)
1131	(((char *)w) - offsetof (struct my_biggy, t2));	1416	(((char *)w) - offsetof (struct my_biggy, t2));
1132	}	1417	}
		1418
		1419	=head2 WATCHER STATES
		1420
		1421	There are various watcher states mentioned throughout this manual -
		1422	active, pending and so on. In this section these states and the rules to
		1423	transition between them will be described in more detail - and while these
		1424	rules might look complicated, they usually do "the right thing".
		1425
		1426	=over 4
		1427
		1428	=item initialiased
		1429
		1430	Before a watcher can be registered with the event looop it has to be
		1431	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1432	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1433
		1434	In this state it is simply some block of memory that is suitable for use
		1435	in an event loop. It can be moved around, freed, reused etc. at will.
		1436
		1437	=item started/running/active
		1438
		1439	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1440	property of the event loop, and is actively waiting for events. While in
		1441	this state it cannot be accessed (except in a few documented ways), moved,
		1442	freed or anything else - the only legal thing is to keep a pointer to it,
		1443	and call libev functions on it that are documented to work on active watchers.
		1444
		1445	=item pending
		1446
		1447	If a watcher is active and libev determines that an event it is interested
		1448	in has occurred (such as a timer expiring), it will become pending. It will
		1449	stay in this pending state until either it is stopped or its callback is
		1450	about to be invoked, so it is not normally pending inside the watcher
		1451	callback.
		1452
		1453	The watcher might or might not be active while it is pending (for example,
		1454	an expired non-repeating timer can be pending but no longer active). If it
		1455	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1456	but it is still property of the event loop at this time, so cannot be
		1457	moved, freed or reused. And if it is active the rules described in the
		1458	previous item still apply.
		1459
		1460	It is also possible to feed an event on a watcher that is not active (e.g.
		1461	via C<ev_feed_event>), in which case it becomes pending without being
		1462	active.
		1463
		1464	=item stopped
		1465
		1466	A watcher can be stopped implicitly by libev (in which case it might still
		1467	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1468	latter will clear any pending state the watcher might be in, regardless
		1469	of whether it was active or not, so stopping a watcher explicitly before
		1470	freeing it is often a good idea.
		1471
		1472	While stopped (and not pending) the watcher is essentially in the
		1473	initialised state, that is it can be reused, moved, modified in any way
		1474	you wish.
		1475
		1476	=back
		1477
		1478	=head2 WATCHER PRIORITY MODELS
		1479
		1480	Many event loops support I<watcher priorities>, which are usually small
		1481	integers that influence the ordering of event callback invocation
		1482	between watchers in some way, all else being equal.
		1483
		1484	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1485	description for the more technical details such as the actual priority
		1486	range.
		1487
		1488	There are two common ways how these these priorities are being interpreted
		1489	by event loops:
		1490
		1491	In the more common lock-out model, higher priorities "lock out" invocation
		1492	of lower priority watchers, which means as long as higher priority
		1493	watchers receive events, lower priority watchers are not being invoked.
		1494
		1495	The less common only-for-ordering model uses priorities solely to order
		1496	callback invocation within a single event loop iteration: Higher priority
		1497	watchers are invoked before lower priority ones, but they all get invoked
		1498	before polling for new events.
		1499
		1500	Libev uses the second (only-for-ordering) model for all its watchers
		1501	except for idle watchers (which use the lock-out model).
		1502
		1503	The rationale behind this is that implementing the lock-out model for
		1504	watchers is not well supported by most kernel interfaces, and most event
		1505	libraries will just poll for the same events again and again as long as
		1506	their callbacks have not been executed, which is very inefficient in the
		1507	common case of one high-priority watcher locking out a mass of lower
		1508	priority ones.
		1509
		1510	Static (ordering) priorities are most useful when you have two or more
		1511	watchers handling the same resource: a typical usage example is having an
		1512	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1513	timeouts. Under load, data might be received while the program handles
		1514	other jobs, but since timers normally get invoked first, the timeout
		1515	handler will be executed before checking for data. In that case, giving
		1516	the timer a lower priority than the I/O watcher ensures that I/O will be
		1517	handled first even under adverse conditions (which is usually, but not
		1518	always, what you want).
		1519
		1520	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1521	will only be executed when no same or higher priority watchers have
		1522	received events, they can be used to implement the "lock-out" model when
		1523	required.
		1524
		1525	For example, to emulate how many other event libraries handle priorities,
		1526	you can associate an C<ev_idle> watcher to each such watcher, and in
		1527	the normal watcher callback, you just start the idle watcher. The real
		1528	processing is done in the idle watcher callback. This causes libev to
		1529	continuously poll and process kernel event data for the watcher, but when
		1530	the lock-out case is known to be rare (which in turn is rare :), this is
		1531	workable.
		1532
		1533	Usually, however, the lock-out model implemented that way will perform
		1534	miserably under the type of load it was designed to handle. In that case,
		1535	it might be preferable to stop the real watcher before starting the
		1536	idle watcher, so the kernel will not have to process the event in case
		1537	the actual processing will be delayed for considerable time.
		1538
		1539	Here is an example of an I/O watcher that should run at a strictly lower
		1540	priority than the default, and which should only process data when no
		1541	other events are pending:
		1542
		1543	ev_idle idle; // actual processing watcher
		1544	ev_io io; // actual event watcher
		1545
		1546	static void
		1547	io_cb (EV_P_ ev_io *w, int revents)
		1548	{
		1549	// stop the I/O watcher, we received the event, but
		1550	// are not yet ready to handle it.
		1551	ev_io_stop (EV_A_ w);
		1552
		1553	// start the idle watcher to handle the actual event.
		1554	// it will not be executed as long as other watchers
		1555	// with the default priority are receiving events.
		1556	ev_idle_start (EV_A_ &idle);
		1557	}
		1558
		1559	static void
		1560	idle_cb (EV_P_ ev_idle *w, int revents)
		1561	{
		1562	// actual processing
		1563	read (STDIN_FILENO, ...);
		1564
		1565	// have to start the I/O watcher again, as
		1566	// we have handled the event
		1567	ev_io_start (EV_P_ &io);
		1568	}
		1569
		1570	// initialisation
		1571	ev_idle_init (&idle, idle_cb);
		1572	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1573	ev_io_start (EV_DEFAULT_ &io);
		1574
		1575	In the "real" world, it might also be beneficial to start a timer, so that
		1576	low-priority connections can not be locked out forever under load. This
		1577	enables your program to keep a lower latency for important connections
		1578	during short periods of high load, while not completely locking out less
		1579	important ones.
1133		1580
1134		1581
1135	=head1 WATCHER TYPES	1582	=head1 WATCHER TYPES
1136		1583
1137	This section describes each watcher in detail, but will not repeat	1584	This section describes each watcher in detail, but will not repeat
…		…
1163	descriptors to non-blocking mode is also usually a good idea (but not	1610	descriptors to non-blocking mode is also usually a good idea (but not
1164	required if you know what you are doing).	1611	required if you know what you are doing).
1165		1612
1166	If you cannot use non-blocking mode, then force the use of a	1613	If you cannot use non-blocking mode, then force the use of a
1167	known-to-be-good backend (at the time of this writing, this includes only	1614	known-to-be-good backend (at the time of this writing, this includes only
1168	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).	1615	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1616	descriptors for which non-blocking operation makes no sense (such as
		1617	files) - libev doesn't guarantee any specific behaviour in that case.
1169		1618
1170	Another thing you have to watch out for is that it is quite easy to	1619	Another thing you have to watch out for is that it is quite easy to
1171	receive "spurious" readiness notifications, that is your callback might	1620	receive "spurious" readiness notifications, that is your callback might
1172	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1621	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1173	because there is no data. Not only are some backends known to create a	1622	because there is no data. Not only are some backends known to create a
…		…
1238		1687
1239	So when you encounter spurious, unexplained daemon exits, make sure you	1688	So when you encounter spurious, unexplained daemon exits, make sure you
1240	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1689	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1241	somewhere, as that would have given you a big clue).	1690	somewhere, as that would have given you a big clue).
1242		1691
		1692	=head3 The special problem of accept()ing when you can't
		1693
		1694	Many implementations of the POSIX C<accept> function (for example,
		1695	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1696	connection from the pending queue in all error cases.
		1697
		1698	For example, larger servers often run out of file descriptors (because
		1699	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1700	rejecting the connection, leading to libev signalling readiness on
		1701	the next iteration again (the connection still exists after all), and
		1702	typically causing the program to loop at 100% CPU usage.
		1703
		1704	Unfortunately, the set of errors that cause this issue differs between
		1705	operating systems, there is usually little the app can do to remedy the
		1706	situation, and no known thread-safe method of removing the connection to
		1707	cope with overload is known (to me).
		1708
		1709	One of the easiest ways to handle this situation is to just ignore it
		1710	- when the program encounters an overload, it will just loop until the
		1711	situation is over. While this is a form of busy waiting, no OS offers an
		1712	event-based way to handle this situation, so it's the best one can do.
		1713
		1714	A better way to handle the situation is to log any errors other than
		1715	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1716	messages, and continue as usual, which at least gives the user an idea of
		1717	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1718	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1719	usage.
		1720
		1721	If your program is single-threaded, then you could also keep a dummy file
		1722	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1723	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1724	close that fd, and create a new dummy fd. This will gracefully refuse
		1725	clients under typical overload conditions.
		1726
		1727	The last way to handle it is to simply log the error and C<exit>, as
		1728	is often done with C<malloc> failures, but this results in an easy
		1729	opportunity for a DoS attack.
1243		1730
1244	=head3 Watcher-Specific Functions	1731	=head3 Watcher-Specific Functions
1245		1732
1246	=over 4	1733	=over 4
1247		1734
…		…
1279	...	1766	...
1280	struct ev_loop *loop = ev_default_init (0);	1767	struct ev_loop *loop = ev_default_init (0);
1281	ev_io stdin_readable;	1768	ev_io stdin_readable;
1282	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1769	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1283	ev_io_start (loop, &stdin_readable);	1770	ev_io_start (loop, &stdin_readable);
1284	ev_loop (loop, 0);	1771	ev_run (loop, 0);
1285		1772
1286		1773
1287	=head2 C<ev_timer> - relative and optionally repeating timeouts	1774	=head2 C<ev_timer> - relative and optionally repeating timeouts
1288		1775
1289	Timer watchers are simple relative timers that generate an event after a	1776	Timer watchers are simple relative timers that generate an event after a
…		…
1294	year, it will still time out after (roughly) one hour. "Roughly" because	1781	year, it will still time out after (roughly) one hour. "Roughly" because
1295	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1782	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1296	monotonic clock option helps a lot here).	1783	monotonic clock option helps a lot here).
1297		1784
1298	The callback is guaranteed to be invoked only I<after> its timeout has	1785	The callback is guaranteed to be invoked only I<after> its timeout has
1299	passed, but if multiple timers become ready during the same loop iteration	1786	passed (not I<at>, so on systems with very low-resolution clocks this
1300	then order of execution is undefined.	1787	might introduce a small delay). If multiple timers become ready during the
		1788	same loop iteration then the ones with earlier time-out values are invoked
		1789	before ones of the same priority with later time-out values (but this is
		1790	no longer true when a callback calls C<ev_run> recursively).
1301		1791
1302	=head3 Be smart about timeouts	1792	=head3 Be smart about timeouts
1303		1793
1304	Many real-world problems involve some kind of timeout, usually for error	1794	Many real-world problems involve some kind of timeout, usually for error
1305	recovery. A typical example is an HTTP request - if the other side hangs,	1795	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1349	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>	1839	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
1350	member and C<ev_timer_again>.	1840	member and C<ev_timer_again>.
1351		1841
1352	At start:	1842	At start:
1353		1843
1354	ev_timer_init (timer, callback);	1844	ev_init (timer, callback);
1355	timer->repeat = 60.;	1845	timer->repeat = 60.;
1356	ev_timer_again (loop, timer);	1846	ev_timer_again (loop, timer);
1357		1847
1358	Each time there is some activity:	1848	Each time there is some activity:
1359		1849
…		…
1391	ev_tstamp timeout = last_activity + 60.;	1881	ev_tstamp timeout = last_activity + 60.;
1392		1882
1393	// if last_activity + 60. is older than now, we did time out	1883	// if last_activity + 60. is older than now, we did time out
1394	if (timeout < now)	1884	if (timeout < now)
1395	{	1885	{
1396	// timeout occured, take action	1886	// timeout occurred, take action
1397	}	1887	}
1398	else	1888	else
1399	{	1889	{
1400	// callback was invoked, but there was some activity, re-arm	1890	// callback was invoked, but there was some activity, re-arm
1401	// the watcher to fire in last_activity + 60, which is	1891	// the watcher to fire in last_activity + 60, which is
1402	// guaranteed to be in the future, so "again" is positive:	1892	// guaranteed to be in the future, so "again" is positive:
1403	w->again = timeout - now;	1893	w->repeat = timeout - now;
1404	ev_timer_again (EV_A_ w);	1894	ev_timer_again (EV_A_ w);
1405	}	1895	}
1406	}	1896	}
1407		1897
1408	To summarise the callback: first calculate the real timeout (defined	1898	To summarise the callback: first calculate the real timeout (defined
…		…
1421		1911
1422	To start the timer, simply initialise the watcher and set C<last_activity>	1912	To start the timer, simply initialise the watcher and set C<last_activity>
1423	to the current time (meaning we just have some activity :), then call the	1913	to the current time (meaning we just have some activity :), then call the
1424	callback, which will "do the right thing" and start the timer:	1914	callback, which will "do the right thing" and start the timer:
1425		1915
1426	ev_timer_init (timer, callback);	1916	ev_init (timer, callback);
1427	last_activity = ev_now (loop);	1917	last_activity = ev_now (loop);
1428	callback (loop, timer, EV_TIMEOUT);	1918	callback (loop, timer, EV_TIMER);
1429		1919
1430	And when there is some activity, simply store the current time in	1920	And when there is some activity, simply store the current time in
1431	C<last_activity>, no libev calls at all:	1921	C<last_activity>, no libev calls at all:
1432		1922
1433	last_actiivty = ev_now (loop);	1923	last_activity = ev_now (loop);
1434		1924
1435	This technique is slightly more complex, but in most cases where the	1925	This technique is slightly more complex, but in most cases where the
1436	time-out is unlikely to be triggered, much more efficient.	1926	time-out is unlikely to be triggered, much more efficient.
1437		1927
1438	Changing the timeout is trivial as well (if it isn't hard-coded in the	1928	Changing the timeout is trivial as well (if it isn't hard-coded in the
…		…
1476		1966
1477	=head3 The special problem of time updates	1967	=head3 The special problem of time updates
1478		1968
1479	Establishing the current time is a costly operation (it usually takes at	1969	Establishing the current time is a costly operation (it usually takes at
1480	least two system calls): EV therefore updates its idea of the current	1970	least two system calls): EV therefore updates its idea of the current
1481	time only before and after C<ev_loop> collects new events, which causes a	1971	time only before and after C<ev_run> collects new events, which causes a
1482	growing difference between C<ev_now ()> and C<ev_time ()> when handling	1972	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1483	lots of events in one iteration.	1973	lots of events in one iteration.
1484		1974
1485	The relative timeouts are calculated relative to the C<ev_now ()>	1975	The relative timeouts are calculated relative to the C<ev_now ()>
1486	time. This is usually the right thing as this timestamp refers to the time	1976	time. This is usually the right thing as this timestamp refers to the time
…		…
1492		1982
1493	If the event loop is suspended for a long time, you can also force an	1983	If the event loop is suspended for a long time, you can also force an
1494	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1984	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1495	()>.	1985	()>.
1496		1986
		1987	=head3 The special problems of suspended animation
		1988
		1989	When you leave the server world it is quite customary to hit machines that
		1990	can suspend/hibernate - what happens to the clocks during such a suspend?
		1991
		1992	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1993	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1994	to run until the system is suspended, but they will not advance while the
		1995	system is suspended. That means, on resume, it will be as if the program
		1996	was frozen for a few seconds, but the suspend time will not be counted
		1997	towards C<ev_timer> when a monotonic clock source is used. The real time
		1998	clock advanced as expected, but if it is used as sole clocksource, then a
		1999	long suspend would be detected as a time jump by libev, and timers would
		2000	be adjusted accordingly.
		2001
		2002	I would not be surprised to see different behaviour in different between
		2003	operating systems, OS versions or even different hardware.
		2004
		2005	The other form of suspend (job control, or sending a SIGSTOP) will see a
		2006	time jump in the monotonic clocks and the realtime clock. If the program
		2007	is suspended for a very long time, and monotonic clock sources are in use,
		2008	then you can expect C<ev_timer>s to expire as the full suspension time
		2009	will be counted towards the timers. When no monotonic clock source is in
		2010	use, then libev will again assume a timejump and adjust accordingly.
		2011
		2012	It might be beneficial for this latter case to call C<ev_suspend>
		2013	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		2014	deterministic behaviour in this case (you can do nothing against
		2015	C<SIGSTOP>).
		2016
1497	=head3 Watcher-Specific Functions and Data Members	2017	=head3 Watcher-Specific Functions and Data Members
1498		2018
1499	=over 4	2019	=over 4
1500		2020
1501	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2021	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1524	If the timer is started but non-repeating, stop it (as if it timed out).	2044	If the timer is started but non-repeating, stop it (as if it timed out).
1525		2045
1526	If the timer is repeating, either start it if necessary (with the	2046	If the timer is repeating, either start it if necessary (with the
1527	C<repeat> value), or reset the running timer to the C<repeat> value.	2047	C<repeat> value), or reset the running timer to the C<repeat> value.
1528		2048
1529	This sounds a bit complicated, see "Be smart about timeouts", above, for a	2049	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1530	usage example.	2050	usage example.
		2051
		2052	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2053
		2054	Returns the remaining time until a timer fires. If the timer is active,
		2055	then this time is relative to the current event loop time, otherwise it's
		2056	the timeout value currently configured.
		2057
		2058	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2059	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2060	will return C<4>. When the timer expires and is restarted, it will return
		2061	roughly C<7> (likely slightly less as callback invocation takes some time,
		2062	too), and so on.
1531		2063
1532	=item ev_tstamp repeat [read-write]	2064	=item ev_tstamp repeat [read-write]
1533		2065
1534	The current C<repeat> value. Will be used each time the watcher times out	2066	The current C<repeat> value. Will be used each time the watcher times out
1535	or C<ev_timer_again> is called, and determines the next timeout (if any),	2067	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1561	}	2093	}
1562		2094
1563	ev_timer mytimer;	2095	ev_timer mytimer;
1564	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2096	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1565	ev_timer_again (&mytimer); /* start timer */	2097	ev_timer_again (&mytimer); /* start timer */
1566	ev_loop (loop, 0);	2098	ev_run (loop, 0);
1567		2099
1568	// and in some piece of code that gets executed on any "activity":	2100	// and in some piece of code that gets executed on any "activity":
1569	// reset the timeout to start ticking again at 10 seconds	2101	// reset the timeout to start ticking again at 10 seconds
1570	ev_timer_again (&mytimer);	2102	ev_timer_again (&mytimer);
1571		2103
…		…
1573	=head2 C<ev_periodic> - to cron or not to cron?	2105	=head2 C<ev_periodic> - to cron or not to cron?
1574		2106
1575	Periodic watchers are also timers of a kind, but they are very versatile	2107	Periodic watchers are also timers of a kind, but they are very versatile
1576	(and unfortunately a bit complex).	2108	(and unfortunately a bit complex).
1577		2109
1578	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2110	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1579	but on wall clock time (absolute time). You can tell a periodic watcher	2111	relative time, the physical time that passes) but on wall clock time
1580	to trigger after some specific point in time. For example, if you tell a	2112	(absolute time, the thing you can read on your calender or clock). The
1581	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	2113	difference is that wall clock time can run faster or slower than real
1582	+ 10.>, that is, an absolute time not a delay) and then reset your system	2114	time, and time jumps are not uncommon (e.g. when you adjust your
1583	clock to January of the previous year, then it will take more than year	2115	wrist-watch).
1584	to trigger the event (unlike an C<ev_timer>, which would still trigger
1585	roughly 10 seconds later as it uses a relative timeout).
1586		2116
		2117	You can tell a periodic watcher to trigger after some specific point
		2118	in time: for example, if you tell a periodic watcher to trigger "in 10
		2119	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2120	not a delay) and then reset your system clock to January of the previous
		2121	year, then it will take a year or more to trigger the event (unlike an
		2122	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2123	it, as it uses a relative timeout).
		2124
1587	C<ev_periodic>s can also be used to implement vastly more complex timers,	2125	C<ev_periodic> watchers can also be used to implement vastly more complex
1588	such as triggering an event on each "midnight, local time", or other	2126	timers, such as triggering an event on each "midnight, local time", or
1589	complicated rules.	2127	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2128	those cannot react to time jumps.
1590		2129
1591	As with timers, the callback is guaranteed to be invoked only when the	2130	As with timers, the callback is guaranteed to be invoked only when the
1592	time (C<at>) has passed, but if multiple periodic timers become ready	2131	point in time where it is supposed to trigger has passed. If multiple
1593	during the same loop iteration, then order of execution is undefined.	2132	timers become ready during the same loop iteration then the ones with
		2133	earlier time-out values are invoked before ones with later time-out values
		2134	(but this is no longer true when a callback calls C<ev_run> recursively).
1594		2135
1595	=head3 Watcher-Specific Functions and Data Members	2136	=head3 Watcher-Specific Functions and Data Members
1596		2137
1597	=over 4	2138	=over 4
1598		2139
1599	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2140	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1600		2141
1601	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2142	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1602		2143
1603	Lots of arguments, lets sort it out... There are basically three modes of	2144	Lots of arguments, let's sort it out... There are basically three modes of
1604	operation, and we will explain them from simplest to most complex:	2145	operation, and we will explain them from simplest to most complex:
1605		2146
1606	=over 4	2147	=over 4
1607		2148
1608	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2149	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1609		2150
1610	In this configuration the watcher triggers an event after the wall clock	2151	In this configuration the watcher triggers an event after the wall clock
1611	time C<at> has passed. It will not repeat and will not adjust when a time	2152	time C<offset> has passed. It will not repeat and will not adjust when a
1612	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2153	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1613	only run when the system clock reaches or surpasses this time.	2154	will be stopped and invoked when the system clock reaches or surpasses
		2155	this point in time.
1614		2156
1615	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2157	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1616		2158
1617	In this mode the watcher will always be scheduled to time out at the next	2159	In this mode the watcher will always be scheduled to time out at the next
1618	C<at + N * interval> time (for some integer N, which can also be negative)	2160	C<offset + N * interval> time (for some integer N, which can also be
1619	and then repeat, regardless of any time jumps.	2161	negative) and then repeat, regardless of any time jumps. The C<offset>
		2162	argument is merely an offset into the C<interval> periods.
1620		2163
1621	This can be used to create timers that do not drift with respect to the	2164	This can be used to create timers that do not drift with respect to the
1622	system clock, for example, here is a C<ev_periodic> that triggers each	2165	system clock, for example, here is an C<ev_periodic> that triggers each
1623	hour, on the hour:	2166	hour, on the hour (with respect to UTC):
1624		2167
1625	ev_periodic_set (&periodic, 0., 3600., 0);	2168	ev_periodic_set (&periodic, 0., 3600., 0);
1626		2169
1627	This doesn't mean there will always be 3600 seconds in between triggers,	2170	This doesn't mean there will always be 3600 seconds in between triggers,
1628	but only that the callback will be called when the system time shows a	2171	but only that the callback will be called when the system time shows a
1629	full hour (UTC), or more correctly, when the system time is evenly divisible	2172	full hour (UTC), or more correctly, when the system time is evenly divisible
1630	by 3600.	2173	by 3600.
1631		2174
1632	Another way to think about it (for the mathematically inclined) is that	2175	Another way to think about it (for the mathematically inclined) is that
1633	C<ev_periodic> will try to run the callback in this mode at the next possible	2176	C<ev_periodic> will try to run the callback in this mode at the next possible
1634	time where C<time = at (mod interval)>, regardless of any time jumps.	2177	time where C<time = offset (mod interval)>, regardless of any time jumps.
1635		2178
1636	For numerical stability it is preferable that the C<at> value is near	2179	For numerical stability it is preferable that the C<offset> value is near
1637	C<ev_now ()> (the current time), but there is no range requirement for	2180	C<ev_now ()> (the current time), but there is no range requirement for
1638	this value, and in fact is often specified as zero.	2181	this value, and in fact is often specified as zero.
1639		2182
1640	Note also that there is an upper limit to how often a timer can fire (CPU	2183	Note also that there is an upper limit to how often a timer can fire (CPU
1641	speed for example), so if C<interval> is very small then timing stability	2184	speed for example), so if C<interval> is very small then timing stability
1642	will of course deteriorate. Libev itself tries to be exact to be about one	2185	will of course deteriorate. Libev itself tries to be exact to be about one
1643	millisecond (if the OS supports it and the machine is fast enough).	2186	millisecond (if the OS supports it and the machine is fast enough).
1644		2187
1645	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2188	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1646		2189
1647	In this mode the values for C<interval> and C<at> are both being	2190	In this mode the values for C<interval> and C<offset> are both being
1648	ignored. Instead, each time the periodic watcher gets scheduled, the	2191	ignored. Instead, each time the periodic watcher gets scheduled, the
1649	reschedule callback will be called with the watcher as first, and the	2192	reschedule callback will be called with the watcher as first, and the
1650	current time as second argument.	2193	current time as second argument.
1651		2194
1652	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2195	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1653	ever, or make ANY event loop modifications whatsoever>.	2196	or make ANY other event loop modifications whatsoever, unless explicitly
		2197	allowed by documentation here>.
1654		2198
1655	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2199	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1656	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2200	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1657	only event loop modification you are allowed to do).	2201	only event loop modification you are allowed to do).
1658		2202
…		…
1688	a different time than the last time it was called (e.g. in a crond like	2232	a different time than the last time it was called (e.g. in a crond like
1689	program when the crontabs have changed).	2233	program when the crontabs have changed).
1690		2234
1691	=item ev_tstamp ev_periodic_at (ev_periodic *)	2235	=item ev_tstamp ev_periodic_at (ev_periodic *)
1692		2236
1693	When active, returns the absolute time that the watcher is supposed to	2237	When active, returns the absolute time that the watcher is supposed
1694	trigger next.	2238	to trigger next. This is not the same as the C<offset> argument to
		2239	C<ev_periodic_set>, but indeed works even in interval and manual
		2240	rescheduling modes.
1695		2241
1696	=item ev_tstamp offset [read-write]	2242	=item ev_tstamp offset [read-write]
1697		2243
1698	When repeating, this contains the offset value, otherwise this is the	2244	When repeating, this contains the offset value, otherwise this is the
1699	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2245	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2246	although libev might modify this value for better numerical stability).
1700		2247
1701	Can be modified any time, but changes only take effect when the periodic	2248	Can be modified any time, but changes only take effect when the periodic
1702	timer fires or C<ev_periodic_again> is being called.	2249	timer fires or C<ev_periodic_again> is being called.
1703		2250
1704	=item ev_tstamp interval [read-write]	2251	=item ev_tstamp interval [read-write]
…		…
1720	Example: Call a callback every hour, or, more precisely, whenever the	2267	Example: Call a callback every hour, or, more precisely, whenever the
1721	system time is divisible by 3600. The callback invocation times have	2268	system time is divisible by 3600. The callback invocation times have
1722	potentially a lot of jitter, but good long-term stability.	2269	potentially a lot of jitter, but good long-term stability.
1723		2270
1724	static void	2271	static void
1725	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2272	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1726	{	2273	{
1727	... its now a full hour (UTC, or TAI or whatever your clock follows)	2274	... its now a full hour (UTC, or TAI or whatever your clock follows)
1728	}	2275	}
1729		2276
1730	ev_periodic hourly_tick;	2277	ev_periodic hourly_tick;
…		…
1753		2300
1754	=head2 C<ev_signal> - signal me when a signal gets signalled!	2301	=head2 C<ev_signal> - signal me when a signal gets signalled!
1755		2302
1756	Signal watchers will trigger an event when the process receives a specific	2303	Signal watchers will trigger an event when the process receives a specific
1757	signal one or more times. Even though signals are very asynchronous, libev	2304	signal one or more times. Even though signals are very asynchronous, libev
1758	will try it's best to deliver signals synchronously, i.e. as part of the	2305	will try its best to deliver signals synchronously, i.e. as part of the
1759	normal event processing, like any other event.	2306	normal event processing, like any other event.
1760		2307
1761	If you want signals asynchronously, just use C<sigaction> as you would	2308	If you want signals to be delivered truly asynchronously, just use
1762	do without libev and forget about sharing the signal. You can even use	2309	C<sigaction> as you would do without libev and forget about sharing
1763	C<ev_async> from a signal handler to synchronously wake up an event loop.	2310	the signal. You can even use C<ev_async> from a signal handler to
		2311	synchronously wake up an event loop.
1764		2312
1765	You can configure as many watchers as you like per signal. Only when the	2313	You can configure as many watchers as you like for the same signal, but
		2314	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2315	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2316	C<SIGINT> in both the default loop and another loop at the same time. At
		2317	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2318
1766	first watcher gets started will libev actually register a signal handler	2319	When the first watcher gets started will libev actually register something
1767	with the kernel (thus it coexists with your own signal handlers as long as	2320	with the kernel (thus it coexists with your own signal handlers as long as
1768	you don't register any with libev for the same signal). Similarly, when	2321	you don't register any with libev for the same signal).
1769	the last signal watcher for a signal is stopped, libev will reset the
1770	signal handler to SIG_DFL (regardless of what it was set to before).
1771		2322
1772	If possible and supported, libev will install its handlers with	2323	If possible and supported, libev will install its handlers with
1773	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2324	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1774	interrupted. If you have a problem with system calls getting interrupted by	2325	not be unduly interrupted. If you have a problem with system calls getting
1775	signals you can block all signals in an C<ev_check> watcher and unblock	2326	interrupted by signals you can block all signals in an C<ev_check> watcher
1776	them in an C<ev_prepare> watcher.	2327	and unblock them in an C<ev_prepare> watcher.
		2328
		2329	=head3 The special problem of inheritance over fork/execve/pthread_create
		2330
		2331	Both the signal mask (C<sigprocmask>) and the signal disposition
		2332	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2333	stopping it again), that is, libev might or might not block the signal,
		2334	and might or might not set or restore the installed signal handler.
		2335
		2336	While this does not matter for the signal disposition (libev never
		2337	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2338	C<execve>), this matters for the signal mask: many programs do not expect
		2339	certain signals to be blocked.
		2340
		2341	This means that before calling C<exec> (from the child) you should reset
		2342	the signal mask to whatever "default" you expect (all clear is a good
		2343	choice usually).
		2344
		2345	The simplest way to ensure that the signal mask is reset in the child is
		2346	to install a fork handler with C<pthread_atfork> that resets it. That will
		2347	catch fork calls done by libraries (such as the libc) as well.
		2348
		2349	In current versions of libev, the signal will not be blocked indefinitely
		2350	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2351	the window of opportunity for problems, it will not go away, as libev
		2352	I<has> to modify the signal mask, at least temporarily.
		2353
		2354	So I can't stress this enough: I<If you do not reset your signal mask when
		2355	you expect it to be empty, you have a race condition in your code>. This
		2356	is not a libev-specific thing, this is true for most event libraries.
		2357
		2358	=head3 The special problem of threads signal handling
		2359
		2360	POSIX threads has problematic signal handling semantics, specifically,
		2361	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2362	threads in a process block signals, which is hard to achieve.
		2363
		2364	When you want to use sigwait (or mix libev signal handling with your own
		2365	for the same signals), you can tackle this problem by globally blocking
		2366	all signals before creating any threads (or creating them with a fully set
		2367	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2368	loops. Then designate one thread as "signal receiver thread" which handles
		2369	these signals. You can pass on any signals that libev might be interested
		2370	in by calling C<ev_feed_signal>.
1777		2371
1778	=head3 Watcher-Specific Functions and Data Members	2372	=head3 Watcher-Specific Functions and Data Members
1779		2373
1780	=over 4	2374	=over 4
1781		2375
…		…
1797	Example: Try to exit cleanly on SIGINT.	2391	Example: Try to exit cleanly on SIGINT.
1798		2392
1799	static void	2393	static void
1800	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2394	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1801	{	2395	{
1802	ev_unloop (loop, EVUNLOOP_ALL);	2396	ev_break (loop, EVBREAK_ALL);
1803	}	2397	}
1804		2398
1805	ev_signal signal_watcher;	2399	ev_signal signal_watcher;
1806	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2400	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1807	ev_signal_start (loop, &signal_watcher);	2401	ev_signal_start (loop, &signal_watcher);
…		…
1813	some child status changes (most typically when a child of yours dies or	2407	some child status changes (most typically when a child of yours dies or
1814	exits). It is permissible to install a child watcher I<after> the child	2408	exits). It is permissible to install a child watcher I<after> the child
1815	has been forked (which implies it might have already exited), as long	2409	has been forked (which implies it might have already exited), as long
1816	as the event loop isn't entered (or is continued from a watcher), i.e.,	2410	as the event loop isn't entered (or is continued from a watcher), i.e.,
1817	forking and then immediately registering a watcher for the child is fine,	2411	forking and then immediately registering a watcher for the child is fine,
1818	but forking and registering a watcher a few event loop iterations later is	2412	but forking and registering a watcher a few event loop iterations later or
1819	not.	2413	in the next callback invocation is not.
1820		2414
1821	Only the default event loop is capable of handling signals, and therefore	2415	Only the default event loop is capable of handling signals, and therefore
1822	you can only register child watchers in the default event loop.	2416	you can only register child watchers in the default event loop.
1823		2417
		2418	Due to some design glitches inside libev, child watchers will always be
		2419	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2420	libev)
		2421
1824	=head3 Process Interaction	2422	=head3 Process Interaction
1825		2423
1826	Libev grabs C<SIGCHLD> as soon as the default event loop is	2424	Libev grabs C<SIGCHLD> as soon as the default event loop is
1827	initialised. This is necessary to guarantee proper behaviour even if	2425	initialised. This is necessary to guarantee proper behaviour even if the
1828	the first child watcher is started after the child exits. The occurrence	2426	first child watcher is started after the child exits. The occurrence
1829	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2427	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1830	synchronously as part of the event loop processing. Libev always reaps all	2428	synchronously as part of the event loop processing. Libev always reaps all
1831	children, even ones not watched.	2429	children, even ones not watched.
1832		2430
1833	=head3 Overriding the Built-In Processing	2431	=head3 Overriding the Built-In Processing
…		…
1843	=head3 Stopping the Child Watcher	2441	=head3 Stopping the Child Watcher
1844		2442
1845	Currently, the child watcher never gets stopped, even when the	2443	Currently, the child watcher never gets stopped, even when the
1846	child terminates, so normally one needs to stop the watcher in the	2444	child terminates, so normally one needs to stop the watcher in the
1847	callback. Future versions of libev might stop the watcher automatically	2445	callback. Future versions of libev might stop the watcher automatically
1848	when a child exit is detected.	2446	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2447	problem).
1849		2448
1850	=head3 Watcher-Specific Functions and Data Members	2449	=head3 Watcher-Specific Functions and Data Members
1851		2450
1852	=over 4	2451	=over 4
1853		2452
…		…
1910		2509
1911		2510
1912	=head2 C<ev_stat> - did the file attributes just change?	2511	=head2 C<ev_stat> - did the file attributes just change?
1913		2512
1914	This watches a file system path for attribute changes. That is, it calls	2513	This watches a file system path for attribute changes. That is, it calls
1915	C<stat> regularly (or when the OS says it changed) and sees if it changed	2514	C<stat> on that path in regular intervals (or when the OS says it changed)
1916	compared to the last time, invoking the callback if it did.	2515	and sees if it changed compared to the last time, invoking the callback if
		2516	it did.
1917		2517
1918	The path does not need to exist: changing from "path exists" to "path does	2518	The path does not need to exist: changing from "path exists" to "path does
1919	not exist" is a status change like any other. The condition "path does	2519	not exist" is a status change like any other. The condition "path does not
1920	not exist" is signified by the C<st_nlink> field being zero (which is	2520	exist" (or more correctly "path cannot be stat'ed") is signified by the
1921	otherwise always forced to be at least one) and all the other fields of	2521	C<st_nlink> field being zero (which is otherwise always forced to be at
1922	the stat buffer having unspecified contents.	2522	least one) and all the other fields of the stat buffer having unspecified
		2523	contents.
1923		2524
1924	The path I<should> be absolute and I<must not> end in a slash. If it is	2525	The path I<must not> end in a slash or contain special components such as
		2526	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1925	relative and your working directory changes, the behaviour is undefined.	2527	your working directory changes, then the behaviour is undefined.
1926		2528
1927	Since there is no standard kernel interface to do this, the portable	2529	Since there is no portable change notification interface available, the
1928	implementation simply calls C<stat (2)> regularly on the path to see if	2530	portable implementation simply calls C<stat(2)> regularly on the path
1929	it changed somehow. You can specify a recommended polling interval for	2531	to see if it changed somehow. You can specify a recommended polling
1930	this case. If you specify a polling interval of C<0> (highly recommended!)	2532	interval for this case. If you specify a polling interval of C<0> (highly
1931	then a I<suitable, unspecified default> value will be used (which	2533	recommended!) then a I<suitable, unspecified default> value will be used
1932	you can expect to be around five seconds, although this might change	2534	(which you can expect to be around five seconds, although this might
1933	dynamically). Libev will also impose a minimum interval which is currently	2535	change dynamically). Libev will also impose a minimum interval which is
1934	around C<0.1>, but thats usually overkill.	2536	currently around C<0.1>, but that's usually overkill.
1935		2537
1936	This watcher type is not meant for massive numbers of stat watchers,	2538	This watcher type is not meant for massive numbers of stat watchers,
1937	as even with OS-supported change notifications, this can be	2539	as even with OS-supported change notifications, this can be
1938	resource-intensive.	2540	resource-intensive.
1939		2541
1940	At the time of this writing, the only OS-specific interface implemented	2542	At the time of this writing, the only OS-specific interface implemented
1941	is the Linux inotify interface (implementing kqueue support is left as	2543	is the Linux inotify interface (implementing kqueue support is left as an
1942	an exercise for the reader. Note, however, that the author sees no way	2544	exercise for the reader. Note, however, that the author sees no way of
1943	of implementing C<ev_stat> semantics with kqueue).	2545	implementing C<ev_stat> semantics with kqueue, except as a hint).
1944		2546
1945	=head3 ABI Issues (Largefile Support)	2547	=head3 ABI Issues (Largefile Support)
1946		2548
1947	Libev by default (unless the user overrides this) uses the default	2549	Libev by default (unless the user overrides this) uses the default
1948	compilation environment, which means that on systems with large file	2550	compilation environment, which means that on systems with large file
1949	support disabled by default, you get the 32 bit version of the stat	2551	support disabled by default, you get the 32 bit version of the stat
1950	structure. When using the library from programs that change the ABI to	2552	structure. When using the library from programs that change the ABI to
1951	use 64 bit file offsets the programs will fail. In that case you have to	2553	use 64 bit file offsets the programs will fail. In that case you have to
1952	compile libev with the same flags to get binary compatibility. This is	2554	compile libev with the same flags to get binary compatibility. This is
1953	obviously the case with any flags that change the ABI, but the problem is	2555	obviously the case with any flags that change the ABI, but the problem is
1954	most noticeably disabled with ev_stat and large file support.	2556	most noticeably displayed with ev_stat and large file support.
1955		2557
1956	The solution for this is to lobby your distribution maker to make large	2558	The solution for this is to lobby your distribution maker to make large
1957	file interfaces available by default (as e.g. FreeBSD does) and not	2559	file interfaces available by default (as e.g. FreeBSD does) and not
1958	optional. Libev cannot simply switch on large file support because it has	2560	optional. Libev cannot simply switch on large file support because it has
1959	to exchange stat structures with application programs compiled using the	2561	to exchange stat structures with application programs compiled using the
1960	default compilation environment.	2562	default compilation environment.
1961		2563
1962	=head3 Inotify and Kqueue	2564	=head3 Inotify and Kqueue
1963		2565
1964	When C<inotify (7)> support has been compiled into libev (generally	2566	When C<inotify (7)> support has been compiled into libev and present at
1965	only available with Linux 2.6.25 or above due to bugs in earlier	2567	runtime, it will be used to speed up change detection where possible. The
1966	implementations) and present at runtime, it will be used to speed up	2568	inotify descriptor will be created lazily when the first C<ev_stat>
1967	change detection where possible. The inotify descriptor will be created	2569	watcher is being started.
1968	lazily when the first C<ev_stat> watcher is being started.
1969		2570
1970	Inotify presence does not change the semantics of C<ev_stat> watchers	2571	Inotify presence does not change the semantics of C<ev_stat> watchers
1971	except that changes might be detected earlier, and in some cases, to avoid	2572	except that changes might be detected earlier, and in some cases, to avoid
1972	making regular C<stat> calls. Even in the presence of inotify support	2573	making regular C<stat> calls. Even in the presence of inotify support
1973	there are many cases where libev has to resort to regular C<stat> polling,	2574	there are many cases where libev has to resort to regular C<stat> polling,
1974	but as long as the path exists, libev usually gets away without polling.	2575	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2576	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2577	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2578	xfs are fully working) libev usually gets away without polling.
1975		2579
1976	There is no support for kqueue, as apparently it cannot be used to	2580	There is no support for kqueue, as apparently it cannot be used to
1977	implement this functionality, due to the requirement of having a file	2581	implement this functionality, due to the requirement of having a file
1978	descriptor open on the object at all times, and detecting renames, unlinks	2582	descriptor open on the object at all times, and detecting renames, unlinks
1979	etc. is difficult.	2583	etc. is difficult.
1980		2584
		2585	=head3 C<stat ()> is a synchronous operation
		2586
		2587	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2588	the process. The exception are C<ev_stat> watchers - those call C<stat
		2589	()>, which is a synchronous operation.
		2590
		2591	For local paths, this usually doesn't matter: unless the system is very
		2592	busy or the intervals between stat's are large, a stat call will be fast,
		2593	as the path data is usually in memory already (except when starting the
		2594	watcher).
		2595
		2596	For networked file systems, calling C<stat ()> can block an indefinite
		2597	time due to network issues, and even under good conditions, a stat call
		2598	often takes multiple milliseconds.
		2599
		2600	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2601	paths, although this is fully supported by libev.
		2602
1981	=head3 The special problem of stat time resolution	2603	=head3 The special problem of stat time resolution
1982		2604
1983	The C<stat ()> system call only supports full-second resolution portably, and	2605	The C<stat ()> system call only supports full-second resolution portably,
1984	even on systems where the resolution is higher, most file systems still	2606	and even on systems where the resolution is higher, most file systems
1985	only support whole seconds.	2607	still only support whole seconds.
1986		2608
1987	That means that, if the time is the only thing that changes, you can	2609	That means that, if the time is the only thing that changes, you can
1988	easily miss updates: on the first update, C<ev_stat> detects a change and	2610	easily miss updates: on the first update, C<ev_stat> detects a change and
1989	calls your callback, which does something. When there is another update	2611	calls your callback, which does something. When there is another update
1990	within the same second, C<ev_stat> will be unable to detect unless the	2612	within the same second, C<ev_stat> will be unable to detect unless the
…		…
2133		2755
2134	=head3 Watcher-Specific Functions and Data Members	2756	=head3 Watcher-Specific Functions and Data Members
2135		2757
2136	=over 4	2758	=over 4
2137		2759
2138	=item ev_idle_init (ev_signal *, callback)	2760	=item ev_idle_init (ev_idle *, callback)
2139		2761
2140	Initialises and configures the idle watcher - it has no parameters of any	2762	Initialises and configures the idle watcher - it has no parameters of any
2141	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2763	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
2142	believe me.	2764	believe me.
2143		2765
…		…
2156	// no longer anything immediate to do.	2778	// no longer anything immediate to do.
2157	}	2779	}
2158		2780
2159	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2781	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2160	ev_idle_init (idle_watcher, idle_cb);	2782	ev_idle_init (idle_watcher, idle_cb);
2161	ev_idle_start (loop, idle_cb);	2783	ev_idle_start (loop, idle_watcher);
2162		2784
2163		2785
2164	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2786	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2165		2787
2166	Prepare and check watchers are usually (but not always) used in pairs:	2788	Prepare and check watchers are usually (but not always) used in pairs:
2167	prepare watchers get invoked before the process blocks and check watchers	2789	prepare watchers get invoked before the process blocks and check watchers
2168	afterwards.	2790	afterwards.
2169		2791
2170	You I<must not> call C<ev_loop> or similar functions that enter	2792	You I<must not> call C<ev_run> or similar functions that enter
2171	the current event loop from either C<ev_prepare> or C<ev_check>	2793	the current event loop from either C<ev_prepare> or C<ev_check>
2172	watchers. Other loops than the current one are fine, however. The	2794	watchers. Other loops than the current one are fine, however. The
2173	rationale behind this is that you do not need to check for recursion in	2795	rationale behind this is that you do not need to check for recursion in
2174	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2796	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2175	C<ev_check> so if you have one watcher of each kind they will always be	2797	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2259	struct pollfd fds [nfd];	2881	struct pollfd fds [nfd];
2260	// actual code will need to loop here and realloc etc.	2882	// actual code will need to loop here and realloc etc.
2261	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2883	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2262		2884
2263	/* the callback is illegal, but won't be called as we stop during check */	2885	/* the callback is illegal, but won't be called as we stop during check */
2264	ev_timer_init (&tw, 0, timeout * 1e-3);	2886	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2265	ev_timer_start (loop, &tw);	2887	ev_timer_start (loop, &tw);
2266		2888
2267	// create one ev_io per pollfd	2889	// create one ev_io per pollfd
2268	for (int i = 0; i < nfd; ++i)	2890	for (int i = 0; i < nfd; ++i)
2269	{	2891	{
…		…
2343		2965
2344	if (timeout >= 0)	2966	if (timeout >= 0)
2345	// create/start timer	2967	// create/start timer
2346		2968
2347	// poll	2969	// poll
2348	ev_loop (EV_A_ 0);	2970	ev_run (EV_A_ 0);
2349		2971
2350	// stop timer again	2972	// stop timer again
2351	if (timeout >= 0)	2973	if (timeout >= 0)
2352	ev_timer_stop (EV_A_ &to);	2974	ev_timer_stop (EV_A_ &to);
2353		2975
…		…
2382	some fds have to be watched and handled very quickly (with low latency),	3004	some fds have to be watched and handled very quickly (with low latency),
2383	and even priorities and idle watchers might have too much overhead. In	3005	and even priorities and idle watchers might have too much overhead. In
2384	this case you would put all the high priority stuff in one loop and all	3006	this case you would put all the high priority stuff in one loop and all
2385	the rest in a second one, and embed the second one in the first.	3007	the rest in a second one, and embed the second one in the first.
2386		3008
2387	As long as the watcher is active, the callback will be invoked every time	3009	As long as the watcher is active, the callback will be invoked every
2388	there might be events pending in the embedded loop. The callback must then	3010	time there might be events pending in the embedded loop. The callback
2389	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	3011	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2390	their callbacks (you could also start an idle watcher to give the embedded	3012	sweep and invoke their callbacks (the callback doesn't need to invoke the
2391	loop strictly lower priority for example). You can also set the callback	3013	C<ev_embed_sweep> function directly, it could also start an idle watcher
2392	to C<0>, in which case the embed watcher will automatically execute the	3014	to give the embedded loop strictly lower priority for example).
2393	embedded loop sweep.
2394		3015
2395	As long as the watcher is started it will automatically handle events. The	3016	You can also set the callback to C<0>, in which case the embed watcher
2396	callback will be invoked whenever some events have been handled. You can	3017	will automatically execute the embedded loop sweep whenever necessary.
2397	set the callback to C<0> to avoid having to specify one if you are not
2398	interested in that.
2399		3018
2400	Also, there have not currently been made special provisions for forking:	3019	Fork detection will be handled transparently while the C<ev_embed> watcher
2401	when you fork, you not only have to call C<ev_loop_fork> on both loops,	3020	is active, i.e., the embedded loop will automatically be forked when the
2402	but you will also have to stop and restart any C<ev_embed> watchers	3021	embedding loop forks. In other cases, the user is responsible for calling
2403	yourself - but you can use a fork watcher to handle this automatically,	3022	C<ev_loop_fork> on the embedded loop.
2404	and future versions of libev might do just that.
2405		3023
2406	Unfortunately, not all backends are embeddable: only the ones returned by	3024	Unfortunately, not all backends are embeddable: only the ones returned by
2407	C<ev_embeddable_backends> are, which, unfortunately, does not include any	3025	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2408	portable one.	3026	portable one.
2409		3027
…		…
2435	if you do not want that, you need to temporarily stop the embed watcher).	3053	if you do not want that, you need to temporarily stop the embed watcher).
2436		3054
2437	=item ev_embed_sweep (loop, ev_embed *)	3055	=item ev_embed_sweep (loop, ev_embed *)
2438		3056
2439	Make a single, non-blocking sweep over the embedded loop. This works	3057	Make a single, non-blocking sweep over the embedded loop. This works
2440	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3058	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2441	appropriate way for embedded loops.	3059	appropriate way for embedded loops.
2442		3060
2443	=item struct ev_loop *other [read-only]	3061	=item struct ev_loop *other [read-only]
2444		3062
2445	The embedded event loop.	3063	The embedded event loop.
…		…
2503	event loop blocks next and before C<ev_check> watchers are being called,	3121	event loop blocks next and before C<ev_check> watchers are being called,
2504	and only in the child after the fork. If whoever good citizen calling	3122	and only in the child after the fork. If whoever good citizen calling
2505	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3123	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2506	handlers will be invoked, too, of course.	3124	handlers will be invoked, too, of course.
2507		3125
		3126	=head3 The special problem of life after fork - how is it possible?
		3127
		3128	Most uses of C<fork()> consist of forking, then some simple calls to set
		3129	up/change the process environment, followed by a call to C<exec()>. This
		3130	sequence should be handled by libev without any problems.
		3131
		3132	This changes when the application actually wants to do event handling
		3133	in the child, or both parent in child, in effect "continuing" after the
		3134	fork.
		3135
		3136	The default mode of operation (for libev, with application help to detect
		3137	forks) is to duplicate all the state in the child, as would be expected
		3138	when I<either> the parent I<or> the child process continues.
		3139
		3140	When both processes want to continue using libev, then this is usually the
		3141	wrong result. In that case, usually one process (typically the parent) is
		3142	supposed to continue with all watchers in place as before, while the other
		3143	process typically wants to start fresh, i.e. without any active watchers.
		3144
		3145	The cleanest and most efficient way to achieve that with libev is to
		3146	simply create a new event loop, which of course will be "empty", and
		3147	use that for new watchers. This has the advantage of not touching more
		3148	memory than necessary, and thus avoiding the copy-on-write, and the
		3149	disadvantage of having to use multiple event loops (which do not support
		3150	signal watchers).
		3151
		3152	When this is not possible, or you want to use the default loop for
		3153	other reasons, then in the process that wants to start "fresh", call
		3154	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3155	Destroying the default loop will "orphan" (not stop) all registered
		3156	watchers, so you have to be careful not to execute code that modifies
		3157	those watchers. Note also that in that case, you have to re-register any
		3158	signal watchers.
		3159
2508	=head3 Watcher-Specific Functions and Data Members	3160	=head3 Watcher-Specific Functions and Data Members
2509		3161
2510	=over 4	3162	=over 4
2511		3163
2512	=item ev_fork_init (ev_signal *, callback)	3164	=item ev_fork_init (ev_fork *, callback)
2513		3165
2514	Initialises and configures the fork watcher - it has no parameters of any	3166	Initialises and configures the fork watcher - it has no parameters of any
2515	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3167	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2516	believe me.	3168	really.
2517		3169
2518	=back	3170	=back
2519		3171
2520		3172
		3173	=head2 C<ev_cleanup> - even the best things end
		3174
		3175	Cleanup watchers are called just before the event loop is being destroyed
		3176	by a call to C<ev_loop_destroy>.
		3177
		3178	While there is no guarantee that the event loop gets destroyed, cleanup
		3179	watchers provide a convenient method to install cleanup hooks for your
		3180	program, worker threads and so on - you just to make sure to destroy the
		3181	loop when you want them to be invoked.
		3182
		3183	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3184	all other watchers, they do not keep a reference to the event loop (which
		3185	makes a lot of sense if you think about it). Like all other watchers, you
		3186	can call libev functions in the callback, except C<ev_cleanup_start>.
		3187
		3188	=head3 Watcher-Specific Functions and Data Members
		3189
		3190	=over 4
		3191
		3192	=item ev_cleanup_init (ev_cleanup *, callback)
		3193
		3194	Initialises and configures the cleanup watcher - it has no parameters of
		3195	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3196	pointless, I assure you.
		3197
		3198	=back
		3199
		3200	Example: Register an atexit handler to destroy the default loop, so any
		3201	cleanup functions are called.
		3202
		3203	static void
		3204	program_exits (void)
		3205	{
		3206	ev_loop_destroy (EV_DEFAULT_UC);
		3207	}
		3208
		3209	...
		3210	atexit (program_exits);
		3211
		3212
2521	=head2 C<ev_async> - how to wake up another event loop	3213	=head2 C<ev_async> - how to wake up an event loop
2522		3214
2523	In general, you cannot use an C<ev_loop> from multiple threads or other	3215	In general, you cannot use an C<ev_run> from multiple threads or other
2524	asynchronous sources such as signal handlers (as opposed to multiple event	3216	asynchronous sources such as signal handlers (as opposed to multiple event
2525	loops - those are of course safe to use in different threads).	3217	loops - those are of course safe to use in different threads).
2526		3218
2527	Sometimes, however, you need to wake up another event loop you do not	3219	Sometimes, however, you need to wake up an event loop you do not control,
2528	control, for example because it belongs to another thread. This is what	3220	for example because it belongs to another thread. This is what C<ev_async>
2529	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3221	watchers do: as long as the C<ev_async> watcher is active, you can signal
2530	can signal it by calling C<ev_async_send>, which is thread- and signal	3222	it by calling C<ev_async_send>, which is thread- and signal safe.
2531	safe.
2532		3223
2533	This functionality is very similar to C<ev_signal> watchers, as signals,	3224	This functionality is very similar to C<ev_signal> watchers, as signals,
2534	too, are asynchronous in nature, and signals, too, will be compressed	3225	too, are asynchronous in nature, and signals, too, will be compressed
2535	(i.e. the number of callback invocations may be less than the number of	3226	(i.e. the number of callback invocations may be less than the number of
2536	C<ev_async_sent> calls).	3227	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
		3228	of "global async watchers" by using a watcher on an otherwise unused
		3229	signal, and C<ev_feed_signal> to signal this watcher from another thread,
		3230	even without knowing which loop owns the signal.
2537		3231
2538	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3232	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
2539	just the default loop.	3233	just the default loop.
2540		3234
2541	=head3 Queueing	3235	=head3 Queueing
2542		3236
2543	C<ev_async> does not support queueing of data in any way. The reason	3237	C<ev_async> does not support queueing of data in any way. The reason
2544	is that the author does not know of a simple (or any) algorithm for a	3238	is that the author does not know of a simple (or any) algorithm for a
2545	multiple-writer-single-reader queue that works in all cases and doesn't	3239	multiple-writer-single-reader queue that works in all cases and doesn't
2546	need elaborate support such as pthreads.	3240	need elaborate support such as pthreads or unportable memory access
		3241	semantics.
2547		3242
2548	That means that if you want to queue data, you have to provide your own	3243	That means that if you want to queue data, you have to provide your own
2549	queue. But at least I can tell you how to implement locking around your	3244	queue. But at least I can tell you how to implement locking around your
2550	queue:	3245	queue:
2551		3246
…		…
2629	=over 4	3324	=over 4
2630		3325
2631	=item ev_async_init (ev_async *, callback)	3326	=item ev_async_init (ev_async *, callback)
2632		3327
2633	Initialises and configures the async watcher - it has no parameters of any	3328	Initialises and configures the async watcher - it has no parameters of any
2634	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3329	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2635	trust me.	3330	trust me.
2636		3331
2637	=item ev_async_send (loop, ev_async *)	3332	=item ev_async_send (loop, ev_async *)
2638		3333
2639	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3334	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2640	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3335	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2641	C<ev_feed_event>, this call is safe to do from other threads, signal or	3336	C<ev_feed_event>, this call is safe to do from other threads, signal or
2642	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3337	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2643	section below on what exactly this means).	3338	section below on what exactly this means).
2644		3339
		3340	Note that, as with other watchers in libev, multiple events might get
		3341	compressed into a single callback invocation (another way to look at this
		3342	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3343	reset when the event loop detects that).
		3344
2645	This call incurs the overhead of a system call only once per loop iteration,	3345	This call incurs the overhead of a system call only once per event loop
2646	so while the overhead might be noticeable, it doesn't apply to repeated	3346	iteration, so while the overhead might be noticeable, it doesn't apply to
2647	calls to C<ev_async_send>.	3347	repeated calls to C<ev_async_send> for the same event loop.
2648		3348
2649	=item bool = ev_async_pending (ev_async *)	3349	=item bool = ev_async_pending (ev_async *)
2650		3350
2651	Returns a non-zero value when C<ev_async_send> has been called on the	3351	Returns a non-zero value when C<ev_async_send> has been called on the
2652	watcher but the event has not yet been processed (or even noted) by the	3352	watcher but the event has not yet been processed (or even noted) by the
…		…
2655	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3355	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2656	the loop iterates next and checks for the watcher to have become active,	3356	the loop iterates next and checks for the watcher to have become active,
2657	it will reset the flag again. C<ev_async_pending> can be used to very	3357	it will reset the flag again. C<ev_async_pending> can be used to very
2658	quickly check whether invoking the loop might be a good idea.	3358	quickly check whether invoking the loop might be a good idea.
2659		3359
2660	Not that this does I<not> check whether the watcher itself is pending, only	3360	Not that this does I<not> check whether the watcher itself is pending,
2661	whether it has been requested to make this watcher pending.	3361	only whether it has been requested to make this watcher pending: there
		3362	is a time window between the event loop checking and resetting the async
		3363	notification, and the callback being invoked.
2662		3364
2663	=back	3365	=back
2664		3366
2665		3367
2666	=head1 OTHER FUNCTIONS	3368	=head1 OTHER FUNCTIONS
…		…
2683		3385
2684	If C<timeout> is less than 0, then no timeout watcher will be	3386	If C<timeout> is less than 0, then no timeout watcher will be
2685	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3387	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2686	repeat = 0) will be started. C<0> is a valid timeout.	3388	repeat = 0) will be started. C<0> is a valid timeout.
2687		3389
2688	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3390	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2689	passed an C<revents> set like normal event callbacks (a combination of	3391	passed an C<revents> set like normal event callbacks (a combination of
2690	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3392	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2691	value passed to C<ev_once>. Note that it is possible to receive I<both>	3393	value passed to C<ev_once>. Note that it is possible to receive I<both>
2692	a timeout and an io event at the same time - you probably should give io	3394	a timeout and an io event at the same time - you probably should give io
2693	events precedence.	3395	events precedence.
2694		3396
2695	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3397	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2696		3398
2697	static void stdin_ready (int revents, void *arg)	3399	static void stdin_ready (int revents, void *arg)
2698	{	3400	{
2699	if (revents & EV_READ)	3401	if (revents & EV_READ)
2700	/* stdin might have data for us, joy! */;	3402	/* stdin might have data for us, joy! */;
2701	else if (revents & EV_TIMEOUT)	3403	else if (revents & EV_TIMER)
2702	/* doh, nothing entered */;	3404	/* doh, nothing entered */;
2703	}	3405	}
2704		3406
2705	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3407	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2706		3408
2707	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2708
2709	Feeds the given event set into the event loop, as if the specified event
2710	had happened for the specified watcher (which must be a pointer to an
2711	initialised but not necessarily started event watcher).
2712
2713	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3409	=item ev_feed_fd_event (loop, int fd, int revents)
2714		3410
2715	Feed an event on the given fd, as if a file descriptor backend detected	3411	Feed an event on the given fd, as if a file descriptor backend detected
2716	the given events it.	3412	the given events it.
2717		3413
2718	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3414	=item ev_feed_signal_event (loop, int signum)
2719		3415
2720	Feed an event as if the given signal occurred (C<loop> must be the default	3416	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
2721	loop!).	3417	which is async-safe.
		3418
		3419	=back
		3420
		3421
		3422	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3423
		3424	This section explains some common idioms that are not immediately
		3425	obvious. Note that examples are sprinkled over the whole manual, and this
		3426	section only contains stuff that wouldn't fit anywhere else.
		3427
		3428	=over 4
		3429
		3430	=item Model/nested event loop invocations and exit conditions.
		3431
		3432	Often (especially in GUI toolkits) there are places where you have
		3433	I<modal> interaction, which is most easily implemented by recursively
		3434	invoking C<ev_run>.
		3435
		3436	This brings the problem of exiting - a callback might want to finish the
		3437	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3438	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3439	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3440	other combination: In these cases, C<ev_break> will not work alone.
		3441
		3442	The solution is to maintain "break this loop" variable for each C<ev_run>
		3443	invocation, and use a loop around C<ev_run> until the condition is
		3444	triggered, using C<EVRUN_ONCE>:
		3445
		3446	// main loop
		3447	int exit_main_loop = 0;
		3448
		3449	while (!exit_main_loop)
		3450	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3451
		3452	// in a model watcher
		3453	int exit_nested_loop = 0;
		3454
		3455	while (!exit_nested_loop)
		3456	ev_run (EV_A_ EVRUN_ONCE);
		3457
		3458	To exit from any of these loops, just set the corresponding exit variable:
		3459
		3460	// exit modal loop
		3461	exit_nested_loop = 1;
		3462
		3463	// exit main program, after modal loop is finished
		3464	exit_main_loop = 1;
		3465
		3466	// exit both
		3467	exit_main_loop = exit_nested_loop = 1;
2722		3468
2723	=back	3469	=back
2724		3470
2725		3471
2726	=head1 LIBEVENT EMULATION	3472	=head1 LIBEVENT EMULATION
2727		3473
2728	Libev offers a compatibility emulation layer for libevent. It cannot	3474	Libev offers a compatibility emulation layer for libevent. It cannot
2729	emulate the internals of libevent, so here are some usage hints:	3475	emulate the internals of libevent, so here are some usage hints:
2730		3476
2731	=over 4	3477	=over 4
		3478
		3479	=item * Only the libevent-1.4.1-beta API is being emulated.
		3480
		3481	This was the newest libevent version available when libev was implemented,
		3482	and is still mostly unchanged in 2010.
2732		3483
2733	=item * Use it by including <event.h>, as usual.	3484	=item * Use it by including <event.h>, as usual.
2734		3485
2735	=item * The following members are fully supported: ev_base, ev_callback,	3486	=item * The following members are fully supported: ev_base, ev_callback,
2736	ev_arg, ev_fd, ev_res, ev_events.	3487	ev_arg, ev_fd, ev_res, ev_events.
…		…
2742	=item * Priorities are not currently supported. Initialising priorities	3493	=item * Priorities are not currently supported. Initialising priorities
2743	will fail and all watchers will have the same priority, even though there	3494	will fail and all watchers will have the same priority, even though there
2744	is an ev_pri field.	3495	is an ev_pri field.
2745		3496
2746	=item * In libevent, the last base created gets the signals, in libev, the	3497	=item * In libevent, the last base created gets the signals, in libev, the
2747	first base created (== the default loop) gets the signals.	3498	base that registered the signal gets the signals.
2748		3499
2749	=item * Other members are not supported.	3500	=item * Other members are not supported.
2750		3501
2751	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3502	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2752	to use the libev header file and library.	3503	to use the libev header file and library.
…		…
2771	Care has been taken to keep the overhead low. The only data member the C++	3522	Care has been taken to keep the overhead low. The only data member the C++
2772	classes add (compared to plain C-style watchers) is the event loop pointer	3523	classes add (compared to plain C-style watchers) is the event loop pointer
2773	that the watcher is associated with (or no additional members at all if	3524	that the watcher is associated with (or no additional members at all if
2774	you disable C<EV_MULTIPLICITY> when embedding libev).	3525	you disable C<EV_MULTIPLICITY> when embedding libev).
2775		3526
2776	Currently, functions, and static and non-static member functions can be	3527	Currently, functions, static and non-static member functions and classes
2777	used as callbacks. Other types should be easy to add as long as they only	3528	with C<operator ()> can be used as callbacks. Other types should be easy
2778	need one additional pointer for context. If you need support for other	3529	to add as long as they only need one additional pointer for context. If
2779	types of functors please contact the author (preferably after implementing	3530	you need support for other types of functors please contact the author
2780	it).	3531	(preferably after implementing it).
2781		3532
2782	Here is a list of things available in the C<ev> namespace:	3533	Here is a list of things available in the C<ev> namespace:
2783		3534
2784	=over 4	3535	=over 4
2785		3536
…		…
2803		3554
2804	=over 4	3555	=over 4
2805		3556
2806	=item ev::TYPE::TYPE ()	3557	=item ev::TYPE::TYPE ()
2807		3558
2808	=item ev::TYPE::TYPE (struct ev_loop *)	3559	=item ev::TYPE::TYPE (loop)
2809		3560
2810	=item ev::TYPE::~TYPE	3561	=item ev::TYPE::~TYPE
2811		3562
2812	The constructor (optionally) takes an event loop to associate the watcher	3563	The constructor (optionally) takes an event loop to associate the watcher
2813	with. If it is omitted, it will use C<EV_DEFAULT>.	3564	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2845		3596
2846	myclass obj;	3597	myclass obj;
2847	ev::io iow;	3598	ev::io iow;
2848	iow.set <myclass, &myclass::io_cb> (&obj);	3599	iow.set <myclass, &myclass::io_cb> (&obj);
2849		3600
		3601	=item w->set (object *)
		3602
		3603	This is a variation of a method callback - leaving out the method to call
		3604	will default the method to C<operator ()>, which makes it possible to use
		3605	functor objects without having to manually specify the C<operator ()> all
		3606	the time. Incidentally, you can then also leave out the template argument
		3607	list.
		3608
		3609	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3610	int revents)>.
		3611
		3612	See the method-C<set> above for more details.
		3613
		3614	Example: use a functor object as callback.
		3615
		3616	struct myfunctor
		3617	{
		3618	void operator() (ev::io &w, int revents)
		3619	{
		3620	...
		3621	}
		3622	}
		3623
		3624	myfunctor f;
		3625
		3626	ev::io w;
		3627	w.set (&f);
		3628
2850	=item w->set<function> (void *data = 0)	3629	=item w->set<function> (void *data = 0)
2851		3630
2852	Also sets a callback, but uses a static method or plain function as	3631	Also sets a callback, but uses a static method or plain function as
2853	callback. The optional C<data> argument will be stored in the watcher's	3632	callback. The optional C<data> argument will be stored in the watcher's
2854	C<data> member and is free for you to use.	3633	C<data> member and is free for you to use.
…		…
2860	Example: Use a plain function as callback.	3639	Example: Use a plain function as callback.
2861		3640
2862	static void io_cb (ev::io &w, int revents) { }	3641	static void io_cb (ev::io &w, int revents) { }
2863	iow.set <io_cb> ();	3642	iow.set <io_cb> ();
2864		3643
2865	=item w->set (struct ev_loop *)	3644	=item w->set (loop)
2866		3645
2867	Associates a different C<struct ev_loop> with this watcher. You can only	3646	Associates a different C<struct ev_loop> with this watcher. You can only
2868	do this when the watcher is inactive (and not pending either).	3647	do this when the watcher is inactive (and not pending either).
2869		3648
2870	=item w->set ([arguments])	3649	=item w->set ([arguments])
2871		3650
2872	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3651	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
2873	called at least once. Unlike the C counterpart, an active watcher gets	3652	method or a suitable start method must be called at least once. Unlike the
2874	automatically stopped and restarted when reconfiguring it with this	3653	C counterpart, an active watcher gets automatically stopped and restarted
2875	method.	3654	when reconfiguring it with this method.
2876		3655
2877	=item w->start ()	3656	=item w->start ()
2878		3657
2879	Starts the watcher. Note that there is no C<loop> argument, as the	3658	Starts the watcher. Note that there is no C<loop> argument, as the
2880	constructor already stores the event loop.	3659	constructor already stores the event loop.
2881		3660
		3661	=item w->start ([arguments])
		3662
		3663	Instead of calling C<set> and C<start> methods separately, it is often
		3664	convenient to wrap them in one call. Uses the same type of arguments as
		3665	the configure C<set> method of the watcher.
		3666
2882	=item w->stop ()	3667	=item w->stop ()
2883		3668
2884	Stops the watcher if it is active. Again, no C<loop> argument.	3669	Stops the watcher if it is active. Again, no C<loop> argument.
2885		3670
2886	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3671	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2898		3683
2899	=back	3684	=back
2900		3685
2901	=back	3686	=back
2902		3687
2903	Example: Define a class with an IO and idle watcher, start one of them in	3688	Example: Define a class with two I/O and idle watchers, start the I/O
2904	the constructor.	3689	watchers in the constructor.
2905		3690
2906	class myclass	3691	class myclass
2907	{	3692	{
2908	ev::io io ; void io_cb (ev::io &w, int revents);	3693	ev::io io ; void io_cb (ev::io &w, int revents);
		3694	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
2909	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3695	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2910		3696
2911	myclass (int fd)	3697	myclass (int fd)
2912	{	3698	{
2913	io .set <myclass, &myclass::io_cb > (this);	3699	io .set <myclass, &myclass::io_cb > (this);
		3700	io2 .set <myclass, &myclass::io2_cb > (this);
2914	idle.set <myclass, &myclass::idle_cb> (this);	3701	idle.set <myclass, &myclass::idle_cb> (this);
2915		3702
2916	io.start (fd, ev::READ);	3703	io.set (fd, ev::WRITE); // configure the watcher
		3704	io.start (); // start it whenever convenient
		3705
		3706	io2.start (fd, ev::READ); // set + start in one call
2917	}	3707	}
2918	};	3708	};
2919		3709
2920		3710
2921	=head1 OTHER LANGUAGE BINDINGS	3711	=head1 OTHER LANGUAGE BINDINGS
…		…
2940	L<http://software.schmorp.de/pkg/EV>.	3730	L<http://software.schmorp.de/pkg/EV>.
2941		3731
2942	=item Python	3732	=item Python
2943		3733
2944	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3734	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2945	seems to be quite complete and well-documented. Note, however, that the	3735	seems to be quite complete and well-documented.
2946	patch they require for libev is outright dangerous as it breaks the ABI
2947	for everybody else, and therefore, should never be applied in an installed
2948	libev (if python requires an incompatible ABI then it needs to embed
2949	libev).
2950		3736
2951	=item Ruby	3737	=item Ruby
2952		3738
2953	Tony Arcieri has written a ruby extension that offers access to a subset	3739	Tony Arcieri has written a ruby extension that offers access to a subset
2954	of the libev API and adds file handle abstractions, asynchronous DNS and	3740	of the libev API and adds file handle abstractions, asynchronous DNS and
2955	more on top of it. It can be found via gem servers. Its homepage is at	3741	more on top of it. It can be found via gem servers. Its homepage is at
2956	L<http://rev.rubyforge.org/>.	3742	L<http://rev.rubyforge.org/>.
2957		3743
		3744	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3745	makes rev work even on mingw.
		3746
		3747	=item Haskell
		3748
		3749	A haskell binding to libev is available at
		3750	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3751
2958	=item D	3752	=item D
2959		3753
2960	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3754	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2961	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3755	be found at L<http://proj.llucax.com.ar/wiki/evd>.
2962		3756
2963	=item Ocaml	3757	=item Ocaml
2964		3758
2965	Erkki Seppala has written Ocaml bindings for libev, to be found at	3759	Erkki Seppala has written Ocaml bindings for libev, to be found at
2966	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	3760	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3761
		3762	=item Lua
		3763
		3764	Brian Maher has written a partial interface to libev for lua (at the
		3765	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3766	L<http://github.com/brimworks/lua-ev>.
2967		3767
2968	=back	3768	=back
2969		3769
2970		3770
2971	=head1 MACRO MAGIC	3771	=head1 MACRO MAGIC
…		…
2985	loop argument"). The C<EV_A> form is used when this is the sole argument,	3785	loop argument"). The C<EV_A> form is used when this is the sole argument,
2986	C<EV_A_> is used when other arguments are following. Example:	3786	C<EV_A_> is used when other arguments are following. Example:
2987		3787
2988	ev_unref (EV_A);	3788	ev_unref (EV_A);
2989	ev_timer_add (EV_A_ watcher);	3789	ev_timer_add (EV_A_ watcher);
2990	ev_loop (EV_A_ 0);	3790	ev_run (EV_A_ 0);
2991		3791
2992	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3792	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2993	which is often provided by the following macro.	3793	which is often provided by the following macro.
2994		3794
2995	=item C<EV_P>, C<EV_P_>	3795	=item C<EV_P>, C<EV_P_>
…		…
3035	}	3835	}
3036		3836
3037	ev_check check;	3837	ev_check check;
3038	ev_check_init (&check, check_cb);	3838	ev_check_init (&check, check_cb);
3039	ev_check_start (EV_DEFAULT_ &check);	3839	ev_check_start (EV_DEFAULT_ &check);
3040	ev_loop (EV_DEFAULT_ 0);	3840	ev_run (EV_DEFAULT_ 0);
3041		3841
3042	=head1 EMBEDDING	3842	=head1 EMBEDDING
3043		3843
3044	Libev can (and often is) directly embedded into host	3844	Libev can (and often is) directly embedded into host
3045	applications. Examples of applications that embed it include the Deliantra	3845	applications. Examples of applications that embed it include the Deliantra
…		…
3072		3872
3073	#define EV_STANDALONE 1	3873	#define EV_STANDALONE 1
3074	#include "ev.h"	3874	#include "ev.h"
3075		3875
3076	Both header files and implementation files can be compiled with a C++	3876	Both header files and implementation files can be compiled with a C++
3077	compiler (at least, thats a stated goal, and breakage will be treated	3877	compiler (at least, that's a stated goal, and breakage will be treated
3078	as a bug).	3878	as a bug).
3079		3879
3080	You need the following files in your source tree, or in a directory	3880	You need the following files in your source tree, or in a directory
3081	in your include path (e.g. in libev/ when using -Ilibev):	3881	in your include path (e.g. in libev/ when using -Ilibev):
3082		3882
…		…
3125	libev.m4	3925	libev.m4
3126		3926
3127	=head2 PREPROCESSOR SYMBOLS/MACROS	3927	=head2 PREPROCESSOR SYMBOLS/MACROS
3128		3928
3129	Libev can be configured via a variety of preprocessor symbols you have to	3929	Libev can be configured via a variety of preprocessor symbols you have to
3130	define before including any of its files. The default in the absence of	3930	define before including (or compiling) any of its files. The default in
3131	autoconf is documented for every option.	3931	the absence of autoconf is documented for every option.
		3932
		3933	Symbols marked with "(h)" do not change the ABI, and can have different
		3934	values when compiling libev vs. including F<ev.h>, so it is permissible
		3935	to redefine them before including F<ev.h> without breaking compatibility
		3936	to a compiled library. All other symbols change the ABI, which means all
		3937	users of libev and the libev code itself must be compiled with compatible
		3938	settings.
3132		3939
3133	=over 4	3940	=over 4
3134		3941
		3942	=item EV_COMPAT3 (h)
		3943
		3944	Backwards compatibility is a major concern for libev. This is why this
		3945	release of libev comes with wrappers for the functions and symbols that
		3946	have been renamed between libev version 3 and 4.
		3947
		3948	You can disable these wrappers (to test compatibility with future
		3949	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		3950	sources. This has the additional advantage that you can drop the C<struct>
		3951	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		3952	typedef in that case.
		3953
		3954	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		3955	and in some even more future version the compatibility code will be
		3956	removed completely.
		3957
3135	=item EV_STANDALONE	3958	=item EV_STANDALONE (h)
3136		3959
3137	Must always be C<1> if you do not use autoconf configuration, which	3960	Must always be C<1> if you do not use autoconf configuration, which
3138	keeps libev from including F<config.h>, and it also defines dummy	3961	keeps libev from including F<config.h>, and it also defines dummy
3139	implementations for some libevent functions (such as logging, which is not	3962	implementations for some libevent functions (such as logging, which is not
3140	supported). It will also not define any of the structs usually found in	3963	supported). It will also not define any of the structs usually found in
3141	F<event.h> that are not directly supported by the libev core alone.	3964	F<event.h> that are not directly supported by the libev core alone.
3142		3965
		3966	In standalone mode, libev will still try to automatically deduce the
		3967	configuration, but has to be more conservative.
		3968
3143	=item EV_USE_MONOTONIC	3969	=item EV_USE_MONOTONIC
3144		3970
3145	If defined to be C<1>, libev will try to detect the availability of the	3971	If defined to be C<1>, libev will try to detect the availability of the
3146	monotonic clock option at both compile time and runtime. Otherwise no use	3972	monotonic clock option at both compile time and runtime. Otherwise no
3147	of the monotonic clock option will be attempted. If you enable this, you	3973	use of the monotonic clock option will be attempted. If you enable this,
3148	usually have to link against librt or something similar. Enabling it when	3974	you usually have to link against librt or something similar. Enabling it
3149	the functionality isn't available is safe, though, although you have	3975	when the functionality isn't available is safe, though, although you have
3150	to make sure you link against any libraries where the C<clock_gettime>	3976	to make sure you link against any libraries where the C<clock_gettime>
3151	function is hiding in (often F<-lrt>).	3977	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
3152		3978
3153	=item EV_USE_REALTIME	3979	=item EV_USE_REALTIME
3154		3980
3155	If defined to be C<1>, libev will try to detect the availability of the	3981	If defined to be C<1>, libev will try to detect the availability of the
3156	real-time clock option at compile time (and assume its availability at	3982	real-time clock option at compile time (and assume its availability
3157	runtime if successful). Otherwise no use of the real-time clock option will	3983	at runtime if successful). Otherwise no use of the real-time clock
3158	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3984	option will be attempted. This effectively replaces C<gettimeofday>
3159	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3985	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
3160	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3986	correctness. See the note about libraries in the description of
		3987	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3988	C<EV_USE_CLOCK_SYSCALL>.
		3989
		3990	=item EV_USE_CLOCK_SYSCALL
		3991
		3992	If defined to be C<1>, libev will try to use a direct syscall instead
		3993	of calling the system-provided C<clock_gettime> function. This option
		3994	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3995	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3996	programs needlessly. Using a direct syscall is slightly slower (in
		3997	theory), because no optimised vdso implementation can be used, but avoids
		3998	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3999	higher, as it simplifies linking (no need for C<-lrt>).
3161		4000
3162	=item EV_USE_NANOSLEEP	4001	=item EV_USE_NANOSLEEP
3163		4002
3164	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	4003	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
3165	and will use it for delays. Otherwise it will use C<select ()>.	4004	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3181		4020
3182	=item EV_SELECT_USE_FD_SET	4021	=item EV_SELECT_USE_FD_SET
3183		4022
3184	If defined to C<1>, then the select backend will use the system C<fd_set>	4023	If defined to C<1>, then the select backend will use the system C<fd_set>
3185	structure. This is useful if libev doesn't compile due to a missing	4024	structure. This is useful if libev doesn't compile due to a missing
3186	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	4025	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3187	exotic systems. This usually limits the range of file descriptors to some	4026	on exotic systems. This usually limits the range of file descriptors to
3188	low limit such as 1024 or might have other limitations (winsocket only	4027	some low limit such as 1024 or might have other limitations (winsocket
3189	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	4028	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3190	influence the size of the C<fd_set> used.	4029	configures the maximum size of the C<fd_set>.
3191		4030
3192	=item EV_SELECT_IS_WINSOCKET	4031	=item EV_SELECT_IS_WINSOCKET
3193		4032
3194	When defined to C<1>, the select backend will assume that	4033	When defined to C<1>, the select backend will assume that
3195	select/socket/connect etc. don't understand file descriptors but	4034	select/socket/connect etc. don't understand file descriptors but
…		…
3197	be used is the winsock select). This means that it will call	4036	be used is the winsock select). This means that it will call
3198	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4037	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3199	it is assumed that all these functions actually work on fds, even	4038	it is assumed that all these functions actually work on fds, even
3200	on win32. Should not be defined on non-win32 platforms.	4039	on win32. Should not be defined on non-win32 platforms.
3201		4040
3202	=item EV_FD_TO_WIN32_HANDLE	4041	=item EV_FD_TO_WIN32_HANDLE(fd)
3203		4042
3204	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4043	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3205	file descriptors to socket handles. When not defining this symbol (the	4044	file descriptors to socket handles. When not defining this symbol (the
3206	default), then libev will call C<_get_osfhandle>, which is usually	4045	default), then libev will call C<_get_osfhandle>, which is usually
3207	correct. In some cases, programs use their own file descriptor management,	4046	correct. In some cases, programs use their own file descriptor management,
3208	in which case they can provide this function to map fds to socket handles.	4047	in which case they can provide this function to map fds to socket handles.
		4048
		4049	=item EV_WIN32_HANDLE_TO_FD(handle)
		4050
		4051	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4052	using the standard C<_open_osfhandle> function. For programs implementing
		4053	their own fd to handle mapping, overwriting this function makes it easier
		4054	to do so. This can be done by defining this macro to an appropriate value.
		4055
		4056	=item EV_WIN32_CLOSE_FD(fd)
		4057
		4058	If programs implement their own fd to handle mapping on win32, then this
		4059	macro can be used to override the C<close> function, useful to unregister
		4060	file descriptors again. Note that the replacement function has to close
		4061	the underlying OS handle.
3209		4062
3210	=item EV_USE_POLL	4063	=item EV_USE_POLL
3211		4064
3212	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4065	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3213	backend. Otherwise it will be enabled on non-win32 platforms. It	4066	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3260	as well as for signal and thread safety in C<ev_async> watchers.	4113	as well as for signal and thread safety in C<ev_async> watchers.
3261		4114
3262	In the absence of this define, libev will use C<sig_atomic_t volatile>	4115	In the absence of this define, libev will use C<sig_atomic_t volatile>
3263	(from F<signal.h>), which is usually good enough on most platforms.	4116	(from F<signal.h>), which is usually good enough on most platforms.
3264		4117
3265	=item EV_H	4118	=item EV_H (h)
3266		4119
3267	The name of the F<ev.h> header file used to include it. The default if	4120	The name of the F<ev.h> header file used to include it. The default if
3268	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4121	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3269	used to virtually rename the F<ev.h> header file in case of conflicts.	4122	used to virtually rename the F<ev.h> header file in case of conflicts.
3270		4123
3271	=item EV_CONFIG_H	4124	=item EV_CONFIG_H (h)
3272		4125
3273	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4126	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3274	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4127	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3275	C<EV_H>, above.	4128	C<EV_H>, above.
3276		4129
3277	=item EV_EVENT_H	4130	=item EV_EVENT_H (h)
3278		4131
3279	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4132	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3280	of how the F<event.h> header can be found, the default is C<"event.h">.	4133	of how the F<event.h> header can be found, the default is C<"event.h">.
3281		4134
3282	=item EV_PROTOTYPES	4135	=item EV_PROTOTYPES (h)
3283		4136
3284	If defined to be C<0>, then F<ev.h> will not define any function	4137	If defined to be C<0>, then F<ev.h> will not define any function
3285	prototypes, but still define all the structs and other symbols. This is	4138	prototypes, but still define all the structs and other symbols. This is
3286	occasionally useful if you want to provide your own wrapper functions	4139	occasionally useful if you want to provide your own wrapper functions
3287	around libev functions.	4140	around libev functions.
…		…
3309	fine.	4162	fine.
3310		4163
3311	If your embedding application does not need any priorities, defining these	4164	If your embedding application does not need any priorities, defining these
3312	both to C<0> will save some memory and CPU.	4165	both to C<0> will save some memory and CPU.
3313		4166
3314	=item EV_PERIODIC_ENABLE	4167	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4168	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4169	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3315		4170
3316	If undefined or defined to be C<1>, then periodic timers are supported. If	4171	If undefined or defined to be C<1> (and the platform supports it), then
3317	defined to be C<0>, then they are not. Disabling them saves a few kB of	4172	the respective watcher type is supported. If defined to be C<0>, then it
3318	code.	4173	is not. Disabling watcher types mainly saves code size.
3319		4174
3320	=item EV_IDLE_ENABLE	4175	=item EV_FEATURES
3321
3322	If undefined or defined to be C<1>, then idle watchers are supported. If
3323	defined to be C<0>, then they are not. Disabling them saves a few kB of
3324	code.
3325
3326	=item EV_EMBED_ENABLE
3327
3328	If undefined or defined to be C<1>, then embed watchers are supported. If
3329	defined to be C<0>, then they are not. Embed watchers rely on most other
3330	watcher types, which therefore must not be disabled.
3331
3332	=item EV_STAT_ENABLE
3333
3334	If undefined or defined to be C<1>, then stat watchers are supported. If
3335	defined to be C<0>, then they are not.
3336
3337	=item EV_FORK_ENABLE
3338
3339	If undefined or defined to be C<1>, then fork watchers are supported. If
3340	defined to be C<0>, then they are not.
3341
3342	=item EV_ASYNC_ENABLE
3343
3344	If undefined or defined to be C<1>, then async watchers are supported. If
3345	defined to be C<0>, then they are not.
3346
3347	=item EV_MINIMAL
3348		4176
3349	If you need to shave off some kilobytes of code at the expense of some	4177	If you need to shave off some kilobytes of code at the expense of some
3350	speed, define this symbol to C<1>. Currently this is used to override some	4178	speed (but with the full API), you can define this symbol to request
3351	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4179	certain subsets of functionality. The default is to enable all features
3352	much smaller 2-heap for timer management over the default 4-heap.	4180	that can be enabled on the platform.
		4181
		4182	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4183	with some broad features you want) and then selectively re-enable
		4184	additional parts you want, for example if you want everything minimal,
		4185	but multiple event loop support, async and child watchers and the poll
		4186	backend, use this:
		4187
		4188	#define EV_FEATURES 0
		4189	#define EV_MULTIPLICITY 1
		4190	#define EV_USE_POLL 1
		4191	#define EV_CHILD_ENABLE 1
		4192	#define EV_ASYNC_ENABLE 1
		4193
		4194	The actual value is a bitset, it can be a combination of the following
		4195	values:
		4196
		4197	=over 4
		4198
		4199	=item C<1> - faster/larger code
		4200
		4201	Use larger code to speed up some operations.
		4202
		4203	Currently this is used to override some inlining decisions (enlarging the
		4204	code size by roughly 30% on amd64).
		4205
		4206	When optimising for size, use of compiler flags such as C<-Os> with
		4207	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4208	assertions.
		4209
		4210	=item C<2> - faster/larger data structures
		4211
		4212	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4213	hash table sizes and so on. This will usually further increase code size
		4214	and can additionally have an effect on the size of data structures at
		4215	runtime.
		4216
		4217	=item C<4> - full API configuration
		4218
		4219	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4220	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4221
		4222	=item C<8> - full API
		4223
		4224	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4225	details on which parts of the API are still available without this
		4226	feature, and do not complain if this subset changes over time.
		4227
		4228	=item C<16> - enable all optional watcher types
		4229
		4230	Enables all optional watcher types. If you want to selectively enable
		4231	only some watcher types other than I/O and timers (e.g. prepare,
		4232	embed, async, child...) you can enable them manually by defining
		4233	C<EV_watchertype_ENABLE> to C<1> instead.
		4234
		4235	=item C<32> - enable all backends
		4236
		4237	This enables all backends - without this feature, you need to enable at
		4238	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4239
		4240	=item C<64> - enable OS-specific "helper" APIs
		4241
		4242	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4243	default.
		4244
		4245	=back
		4246
		4247	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4248	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4249	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4250	watchers, timers and monotonic clock support.
		4251
		4252	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4253	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4254	your program might be left out as well - a binary starting a timer and an
		4255	I/O watcher then might come out at only 5Kb.
		4256
		4257	=item EV_AVOID_STDIO
		4258
		4259	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4260	functions (printf, scanf, perror etc.). This will increase the code size
		4261	somewhat, but if your program doesn't otherwise depend on stdio and your
		4262	libc allows it, this avoids linking in the stdio library which is quite
		4263	big.
		4264
		4265	Note that error messages might become less precise when this option is
		4266	enabled.
		4267
		4268	=item EV_NSIG
		4269
		4270	The highest supported signal number, +1 (or, the number of
		4271	signals): Normally, libev tries to deduce the maximum number of signals
		4272	automatically, but sometimes this fails, in which case it can be
		4273	specified. Also, using a lower number than detected (C<32> should be
		4274	good for about any system in existence) can save some memory, as libev
		4275	statically allocates some 12-24 bytes per signal number.
3353		4276
3354	=item EV_PID_HASHSIZE	4277	=item EV_PID_HASHSIZE
3355		4278
3356	C<ev_child> watchers use a small hash table to distribute workload by	4279	C<ev_child> watchers use a small hash table to distribute workload by
3357	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4280	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3358	than enough. If you need to manage thousands of children you might want to	4281	usually more than enough. If you need to manage thousands of children you
3359	increase this value (I<must> be a power of two).	4282	might want to increase this value (I<must> be a power of two).
3360		4283
3361	=item EV_INOTIFY_HASHSIZE	4284	=item EV_INOTIFY_HASHSIZE
3362		4285
3363	C<ev_stat> watchers use a small hash table to distribute workload by	4286	C<ev_stat> watchers use a small hash table to distribute workload by
3364	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4287	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3365	usually more than enough. If you need to manage thousands of C<ev_stat>	4288	disabled), usually more than enough. If you need to manage thousands of
3366	watchers you might want to increase this value (I<must> be a power of	4289	C<ev_stat> watchers you might want to increase this value (I<must> be a
3367	two).	4290	power of two).
3368		4291
3369	=item EV_USE_4HEAP	4292	=item EV_USE_4HEAP
3370		4293
3371	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4294	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3372	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4295	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3373	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4296	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3374	faster performance with many (thousands) of watchers.	4297	faster performance with many (thousands) of watchers.
3375		4298
3376	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4299	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3377	(disabled).	4300	will be C<0>.
3378		4301
3379	=item EV_HEAP_CACHE_AT	4302	=item EV_HEAP_CACHE_AT
3380		4303
3381	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4304	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3382	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4305	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3383	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4306	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3384	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4307	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3385	but avoids random read accesses on heap changes. This improves performance	4308	but avoids random read accesses on heap changes. This improves performance
3386	noticeably with many (hundreds) of watchers.	4309	noticeably with many (hundreds) of watchers.
3387		4310
3388	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4311	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3389	(disabled).	4312	will be C<0>.
3390		4313
3391	=item EV_VERIFY	4314	=item EV_VERIFY
3392		4315
3393	Controls how much internal verification (see C<ev_loop_verify ()>) will	4316	Controls how much internal verification (see C<ev_verify ()>) will
3394	be done: If set to C<0>, no internal verification code will be compiled	4317	be done: If set to C<0>, no internal verification code will be compiled
3395	in. If set to C<1>, then verification code will be compiled in, but not	4318	in. If set to C<1>, then verification code will be compiled in, but not
3396	called. If set to C<2>, then the internal verification code will be	4319	called. If set to C<2>, then the internal verification code will be
3397	called once per loop, which can slow down libev. If set to C<3>, then the	4320	called once per loop, which can slow down libev. If set to C<3>, then the
3398	verification code will be called very frequently, which will slow down	4321	verification code will be called very frequently, which will slow down
3399	libev considerably.	4322	libev considerably.
3400		4323
3401	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4324	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3402	C<0>.	4325	will be C<0>.
3403		4326
3404	=item EV_COMMON	4327	=item EV_COMMON
3405		4328
3406	By default, all watchers have a C<void *data> member. By redefining	4329	By default, all watchers have a C<void *data> member. By redefining
3407	this macro to a something else you can include more and other types of	4330	this macro to something else you can include more and other types of
3408	members. You have to define it each time you include one of the files,	4331	members. You have to define it each time you include one of the files,
3409	though, and it must be identical each time.	4332	though, and it must be identical each time.
3410		4333
3411	For example, the perl EV module uses something like this:	4334	For example, the perl EV module uses something like this:
3412		4335
…		…
3465	file.	4388	file.
3466		4389
3467	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4390	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3468	that everybody includes and which overrides some configure choices:	4391	that everybody includes and which overrides some configure choices:
3469		4392
3470	#define EV_MINIMAL 1	4393	#define EV_FEATURES 8
3471	#define EV_USE_POLL 0	4394	#define EV_USE_SELECT 1
3472	#define EV_MULTIPLICITY 0
3473	#define EV_PERIODIC_ENABLE 0	4395	#define EV_PREPARE_ENABLE 1
		4396	#define EV_IDLE_ENABLE 1
3474	#define EV_STAT_ENABLE 0	4397	#define EV_SIGNAL_ENABLE 1
3475	#define EV_FORK_ENABLE 0	4398	#define EV_CHILD_ENABLE 1
		4399	#define EV_USE_STDEXCEPT 0
3476	#define EV_CONFIG_H <config.h>	4400	#define EV_CONFIG_H <config.h>
3477	#define EV_MINPRI 0
3478	#define EV_MAXPRI 0
3479		4401
3480	#include "ev++.h"	4402	#include "ev++.h"
3481		4403
3482	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4404	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3483		4405
…		…
3543	default loop and triggering an C<ev_async> watcher from the default loop	4465	default loop and triggering an C<ev_async> watcher from the default loop
3544	watcher callback into the event loop interested in the signal.	4466	watcher callback into the event loop interested in the signal.
3545		4467
3546	=back	4468	=back
3547		4469
		4470	=head4 THREAD LOCKING EXAMPLE
		4471
		4472	Here is a fictitious example of how to run an event loop in a different
		4473	thread than where callbacks are being invoked and watchers are
		4474	created/added/removed.
		4475
		4476	For a real-world example, see the C<EV::Loop::Async> perl module,
		4477	which uses exactly this technique (which is suited for many high-level
		4478	languages).
		4479
		4480	The example uses a pthread mutex to protect the loop data, a condition
		4481	variable to wait for callback invocations, an async watcher to notify the
		4482	event loop thread and an unspecified mechanism to wake up the main thread.
		4483
		4484	First, you need to associate some data with the event loop:
		4485
		4486	typedef struct {
		4487	mutex_t lock; /* global loop lock */
		4488	ev_async async_w;
		4489	thread_t tid;
		4490	cond_t invoke_cv;
		4491	} userdata;
		4492
		4493	void prepare_loop (EV_P)
		4494	{
		4495	// for simplicity, we use a static userdata struct.
		4496	static userdata u;
		4497
		4498	ev_async_init (&u->async_w, async_cb);
		4499	ev_async_start (EV_A_ &u->async_w);
		4500
		4501	pthread_mutex_init (&u->lock, 0);
		4502	pthread_cond_init (&u->invoke_cv, 0);
		4503
		4504	// now associate this with the loop
		4505	ev_set_userdata (EV_A_ u);
		4506	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4507	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4508
		4509	// then create the thread running ev_loop
		4510	pthread_create (&u->tid, 0, l_run, EV_A);
		4511	}
		4512
		4513	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4514	solely to wake up the event loop so it takes notice of any new watchers
		4515	that might have been added:
		4516
		4517	static void
		4518	async_cb (EV_P_ ev_async *w, int revents)
		4519	{
		4520	// just used for the side effects
		4521	}
		4522
		4523	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4524	protecting the loop data, respectively.
		4525
		4526	static void
		4527	l_release (EV_P)
		4528	{
		4529	userdata *u = ev_userdata (EV_A);
		4530	pthread_mutex_unlock (&u->lock);
		4531	}
		4532
		4533	static void
		4534	l_acquire (EV_P)
		4535	{
		4536	userdata *u = ev_userdata (EV_A);
		4537	pthread_mutex_lock (&u->lock);
		4538	}
		4539
		4540	The event loop thread first acquires the mutex, and then jumps straight
		4541	into C<ev_run>:
		4542
		4543	void *
		4544	l_run (void *thr_arg)
		4545	{
		4546	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4547
		4548	l_acquire (EV_A);
		4549	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4550	ev_run (EV_A_ 0);
		4551	l_release (EV_A);
		4552
		4553	return 0;
		4554	}
		4555
		4556	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4557	signal the main thread via some unspecified mechanism (signals? pipe
		4558	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4559	have been called (in a while loop because a) spurious wakeups are possible
		4560	and b) skipping inter-thread-communication when there are no pending
		4561	watchers is very beneficial):
		4562
		4563	static void
		4564	l_invoke (EV_P)
		4565	{
		4566	userdata *u = ev_userdata (EV_A);
		4567
		4568	while (ev_pending_count (EV_A))
		4569	{
		4570	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4571	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4572	}
		4573	}
		4574
		4575	Now, whenever the main thread gets told to invoke pending watchers, it
		4576	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4577	thread to continue:
		4578
		4579	static void
		4580	real_invoke_pending (EV_P)
		4581	{
		4582	userdata *u = ev_userdata (EV_A);
		4583
		4584	pthread_mutex_lock (&u->lock);
		4585	ev_invoke_pending (EV_A);
		4586	pthread_cond_signal (&u->invoke_cv);
		4587	pthread_mutex_unlock (&u->lock);
		4588	}
		4589
		4590	Whenever you want to start/stop a watcher or do other modifications to an
		4591	event loop, you will now have to lock:
		4592
		4593	ev_timer timeout_watcher;
		4594	userdata *u = ev_userdata (EV_A);
		4595
		4596	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4597
		4598	pthread_mutex_lock (&u->lock);
		4599	ev_timer_start (EV_A_ &timeout_watcher);
		4600	ev_async_send (EV_A_ &u->async_w);
		4601	pthread_mutex_unlock (&u->lock);
		4602
		4603	Note that sending the C<ev_async> watcher is required because otherwise
		4604	an event loop currently blocking in the kernel will have no knowledge
		4605	about the newly added timer. By waking up the loop it will pick up any new
		4606	watchers in the next event loop iteration.
		4607
3548	=head3 COROUTINES	4608	=head3 COROUTINES
3549		4609
3550	Libev is very accommodating to coroutines ("cooperative threads"):	4610	Libev is very accommodating to coroutines ("cooperative threads"):
3551	libev fully supports nesting calls to its functions from different	4611	libev fully supports nesting calls to its functions from different
3552	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4612	coroutines (e.g. you can call C<ev_run> on the same loop from two
3553	different coroutines, and switch freely between both coroutines running the	4613	different coroutines, and switch freely between both coroutines running
3554	loop, as long as you don't confuse yourself). The only exception is that	4614	the loop, as long as you don't confuse yourself). The only exception is
3555	you must not do this from C<ev_periodic> reschedule callbacks.	4615	that you must not do this from C<ev_periodic> reschedule callbacks.
3556		4616
3557	Care has been taken to ensure that libev does not keep local state inside	4617	Care has been taken to ensure that libev does not keep local state inside
3558	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4618	C<ev_run>, and other calls do not usually allow for coroutine switches as
3559	they do not clal any callbacks.	4619	they do not call any callbacks.
3560		4620
3561	=head2 COMPILER WARNINGS	4621	=head2 COMPILER WARNINGS
3562		4622
3563	Depending on your compiler and compiler settings, you might get no or a	4623	Depending on your compiler and compiler settings, you might get no or a
3564	lot of warnings when compiling libev code. Some people are apparently	4624	lot of warnings when compiling libev code. Some people are apparently
…		…
3574	maintainable.	4634	maintainable.
3575		4635
3576	And of course, some compiler warnings are just plain stupid, or simply	4636	And of course, some compiler warnings are just plain stupid, or simply
3577	wrong (because they don't actually warn about the condition their message	4637	wrong (because they don't actually warn about the condition their message
3578	seems to warn about). For example, certain older gcc versions had some	4638	seems to warn about). For example, certain older gcc versions had some
3579	warnings that resulted an extreme number of false positives. These have	4639	warnings that resulted in an extreme number of false positives. These have
3580	been fixed, but some people still insist on making code warn-free with	4640	been fixed, but some people still insist on making code warn-free with
3581	such buggy versions.	4641	such buggy versions.
3582		4642
3583	While libev is written to generate as few warnings as possible,	4643	While libev is written to generate as few warnings as possible,
3584	"warn-free" code is not a goal, and it is recommended not to build libev	4644	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3598	==2274== definitely lost: 0 bytes in 0 blocks.	4658	==2274== definitely lost: 0 bytes in 0 blocks.
3599	==2274== possibly lost: 0 bytes in 0 blocks.	4659	==2274== possibly lost: 0 bytes in 0 blocks.
3600	==2274== still reachable: 256 bytes in 1 blocks.	4660	==2274== still reachable: 256 bytes in 1 blocks.
3601		4661
3602	Then there is no memory leak, just as memory accounted to global variables	4662	Then there is no memory leak, just as memory accounted to global variables
3603	is not a memleak - the memory is still being refernced, and didn't leak.	4663	is not a memleak - the memory is still being referenced, and didn't leak.
3604		4664
3605	Similarly, under some circumstances, valgrind might report kernel bugs	4665	Similarly, under some circumstances, valgrind might report kernel bugs
3606	as if it were a bug in libev (e.g. in realloc or in the poll backend,	4666	as if it were a bug in libev (e.g. in realloc or in the poll backend,
3607	although an acceptable workaround has been found here), or it might be	4667	although an acceptable workaround has been found here), or it might be
3608	confused.	4668	confused.
…		…
3620	I suggest using suppression lists.	4680	I suggest using suppression lists.
3621		4681
3622		4682
3623	=head1 PORTABILITY NOTES	4683	=head1 PORTABILITY NOTES
3624		4684
		4685	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4686
		4687	GNU/Linux is the only common platform that supports 64 bit file/large file
		4688	interfaces but I<disables> them by default.
		4689
		4690	That means that libev compiled in the default environment doesn't support
		4691	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4692
		4693	Unfortunately, many programs try to work around this GNU/Linux issue
		4694	by enabling the large file API, which makes them incompatible with the
		4695	standard libev compiled for their system.
		4696
		4697	Likewise, libev cannot enable the large file API itself as this would
		4698	suddenly make it incompatible to the default compile time environment,
		4699	i.e. all programs not using special compile switches.
		4700
		4701	=head2 OS/X AND DARWIN BUGS
		4702
		4703	The whole thing is a bug if you ask me - basically any system interface
		4704	you touch is broken, whether it is locales, poll, kqueue or even the
		4705	OpenGL drivers.
		4706
		4707	=head3 C<kqueue> is buggy
		4708
		4709	The kqueue syscall is broken in all known versions - most versions support
		4710	only sockets, many support pipes.
		4711
		4712	Libev tries to work around this by not using C<kqueue> by default on this
		4713	rotten platform, but of course you can still ask for it when creating a
		4714	loop - embedding a socket-only kqueue loop into a select-based one is
		4715	probably going to work well.
		4716
		4717	=head3 C<poll> is buggy
		4718
		4719	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4720	implementation by something calling C<kqueue> internally around the 10.5.6
		4721	release, so now C<kqueue> I<and> C<poll> are broken.
		4722
		4723	Libev tries to work around this by not using C<poll> by default on
		4724	this rotten platform, but of course you can still ask for it when creating
		4725	a loop.
		4726
		4727	=head3 C<select> is buggy
		4728
		4729	All that's left is C<select>, and of course Apple found a way to fuck this
		4730	one up as well: On OS/X, C<select> actively limits the number of file
		4731	descriptors you can pass in to 1024 - your program suddenly crashes when
		4732	you use more.
		4733
		4734	There is an undocumented "workaround" for this - defining
		4735	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4736	work on OS/X.
		4737
		4738	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4739
		4740	=head3 C<errno> reentrancy
		4741
		4742	The default compile environment on Solaris is unfortunately so
		4743	thread-unsafe that you can't even use components/libraries compiled
		4744	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4745	defined by default. A valid, if stupid, implementation choice.
		4746
		4747	If you want to use libev in threaded environments you have to make sure
		4748	it's compiled with C<_REENTRANT> defined.
		4749
		4750	=head3 Event port backend
		4751
		4752	The scalable event interface for Solaris is called "event
		4753	ports". Unfortunately, this mechanism is very buggy in all major
		4754	releases. If you run into high CPU usage, your program freezes or you get
		4755	a large number of spurious wakeups, make sure you have all the relevant
		4756	and latest kernel patches applied. No, I don't know which ones, but there
		4757	are multiple ones to apply, and afterwards, event ports actually work
		4758	great.
		4759
		4760	If you can't get it to work, you can try running the program by setting
		4761	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4762	C<select> backends.
		4763
		4764	=head2 AIX POLL BUG
		4765
		4766	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4767	this by trying to avoid the poll backend altogether (i.e. it's not even
		4768	compiled in), which normally isn't a big problem as C<select> works fine
		4769	with large bitsets on AIX, and AIX is dead anyway.
		4770
3625	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4771	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4772
		4773	=head3 General issues
3626		4774
3627	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4775	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3628	requires, and its I/O model is fundamentally incompatible with the POSIX	4776	requires, and its I/O model is fundamentally incompatible with the POSIX
3629	model. Libev still offers limited functionality on this platform in	4777	model. Libev still offers limited functionality on this platform in
3630	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4778	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3631	descriptors. This only applies when using Win32 natively, not when using	4779	descriptors. This only applies when using Win32 natively, not when using
3632	e.g. cygwin.	4780	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4781	as every compielr comes with a slightly differently broken/incompatible
		4782	environment.
3633		4783
3634	Lifting these limitations would basically require the full	4784	Lifting these limitations would basically require the full
3635	re-implementation of the I/O system. If you are into these kinds of	4785	re-implementation of the I/O system. If you are into this kind of thing,
3636	things, then note that glib does exactly that for you in a very portable	4786	then note that glib does exactly that for you in a very portable way (note
3637	way (note also that glib is the slowest event library known to man).	4787	also that glib is the slowest event library known to man).
3638		4788
3639	There is no supported compilation method available on windows except	4789	There is no supported compilation method available on windows except
3640	embedding it into other applications.	4790	embedding it into other applications.
		4791
		4792	Sensible signal handling is officially unsupported by Microsoft - libev
		4793	tries its best, but under most conditions, signals will simply not work.
3641		4794
3642	Not a libev limitation but worth mentioning: windows apparently doesn't	4795	Not a libev limitation but worth mentioning: windows apparently doesn't
3643	accept large writes: instead of resulting in a partial write, windows will	4796	accept large writes: instead of resulting in a partial write, windows will
3644	either accept everything or return C<ENOBUFS> if the buffer is too large,	4797	either accept everything or return C<ENOBUFS> if the buffer is too large,
3645	so make sure you only write small amounts into your sockets (less than a	4798	so make sure you only write small amounts into your sockets (less than a
…		…
3650	the abysmal performance of winsockets, using a large number of sockets	4803	the abysmal performance of winsockets, using a large number of sockets
3651	is not recommended (and not reasonable). If your program needs to use	4804	is not recommended (and not reasonable). If your program needs to use
3652	more than a hundred or so sockets, then likely it needs to use a totally	4805	more than a hundred or so sockets, then likely it needs to use a totally
3653	different implementation for windows, as libev offers the POSIX readiness	4806	different implementation for windows, as libev offers the POSIX readiness
3654	notification model, which cannot be implemented efficiently on windows	4807	notification model, which cannot be implemented efficiently on windows
3655	(Microsoft monopoly games).	4808	(due to Microsoft monopoly games).
3656		4809
3657	A typical way to use libev under windows is to embed it (see the embedding	4810	A typical way to use libev under windows is to embed it (see the embedding
3658	section for details) and use the following F<evwrap.h> header file instead	4811	section for details) and use the following F<evwrap.h> header file instead
3659	of F<ev.h>:	4812	of F<ev.h>:
3660		4813
…		…
3667	you do I<not> compile the F<ev.c> or any other embedded source files!):	4820	you do I<not> compile the F<ev.c> or any other embedded source files!):
3668		4821
3669	#include "evwrap.h"	4822	#include "evwrap.h"
3670	#include "ev.c"	4823	#include "ev.c"
3671		4824
3672	=over 4
3673
3674	=item The winsocket select function	4825	=head3 The winsocket C<select> function
3675		4826
3676	The winsocket C<select> function doesn't follow POSIX in that it	4827	The winsocket C<select> function doesn't follow POSIX in that it
3677	requires socket I<handles> and not socket I<file descriptors> (it is	4828	requires socket I<handles> and not socket I<file descriptors> (it is
3678	also extremely buggy). This makes select very inefficient, and also	4829	also extremely buggy). This makes select very inefficient, and also
3679	requires a mapping from file descriptors to socket handles (the Microsoft	4830	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3688	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4839	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3689		4840
3690	Note that winsockets handling of fd sets is O(n), so you can easily get a	4841	Note that winsockets handling of fd sets is O(n), so you can easily get a
3691	complexity in the O(n²) range when using win32.	4842	complexity in the O(n²) range when using win32.
3692		4843
3693	=item Limited number of file descriptors	4844	=head3 Limited number of file descriptors
3694		4845
3695	Windows has numerous arbitrary (and low) limits on things.	4846	Windows has numerous arbitrary (and low) limits on things.
3696		4847
3697	Early versions of winsocket's select only supported waiting for a maximum	4848	Early versions of winsocket's select only supported waiting for a maximum
3698	of C<64> handles (probably owning to the fact that all windows kernels	4849	of C<64> handles (probably owning to the fact that all windows kernels
3699	can only wait for C<64> things at the same time internally; Microsoft	4850	can only wait for C<64> things at the same time internally; Microsoft
3700	recommends spawning a chain of threads and wait for 63 handles and the	4851	recommends spawning a chain of threads and wait for 63 handles and the
3701	previous thread in each. Great).	4852	previous thread in each. Sounds great!).
3702		4853
3703	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4854	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3704	to some high number (e.g. C<2048>) before compiling the winsocket select	4855	to some high number (e.g. C<2048>) before compiling the winsocket select
3705	call (which might be in libev or elsewhere, for example, perl does its own	4856	call (which might be in libev or elsewhere, for example, perl and many
3706	select emulation on windows).	4857	other interpreters do their own select emulation on windows).
3707		4858
3708	Another limit is the number of file descriptors in the Microsoft runtime	4859	Another limit is the number of file descriptors in the Microsoft runtime
3709	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4860	libraries, which by default is C<64> (there must be a hidden I<64>
3710	or something like this inside Microsoft). You can increase this by calling	4861	fetish or something like this inside Microsoft). You can increase this
3711	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4862	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3712	arbitrary limit), but is broken in many versions of the Microsoft runtime	4863	(another arbitrary limit), but is broken in many versions of the Microsoft
3713	libraries.
3714
3715	This might get you to about C<512> or C<2048> sockets (depending on	4864	runtime libraries. This might get you to about C<512> or C<2048> sockets
3716	windows version and/or the phase of the moon). To get more, you need to	4865	(depending on windows version and/or the phase of the moon). To get more,
3717	wrap all I/O functions and provide your own fd management, but the cost of	4866	you need to wrap all I/O functions and provide your own fd management, but
3718	calling select (O(n²)) will likely make this unworkable.	4867	the cost of calling select (O(n²)) will likely make this unworkable.
3719
3720	=back
3721		4868
3722	=head2 PORTABILITY REQUIREMENTS	4869	=head2 PORTABILITY REQUIREMENTS
3723		4870
3724	In addition to a working ISO-C implementation and of course the	4871	In addition to a working ISO-C implementation and of course the
3725	backend-specific APIs, libev relies on a few additional extensions:	4872	backend-specific APIs, libev relies on a few additional extensions:
…		…
3732	Libev assumes not only that all watcher pointers have the same internal	4879	Libev assumes not only that all watcher pointers have the same internal
3733	structure (guaranteed by POSIX but not by ISO C for example), but it also	4880	structure (guaranteed by POSIX but not by ISO C for example), but it also
3734	assumes that the same (machine) code can be used to call any watcher	4881	assumes that the same (machine) code can be used to call any watcher
3735	callback: The watcher callbacks have different type signatures, but libev	4882	callback: The watcher callbacks have different type signatures, but libev
3736	calls them using an C<ev_watcher *> internally.	4883	calls them using an C<ev_watcher *> internally.
		4884
		4885	=item pointer accesses must be thread-atomic
		4886
		4887	Accessing a pointer value must be atomic, it must both be readable and
		4888	writable in one piece - this is the case on all current architectures.
3737		4889
3738	=item C<sig_atomic_t volatile> must be thread-atomic as well	4890	=item C<sig_atomic_t volatile> must be thread-atomic as well
3739		4891
3740	The type C<sig_atomic_t volatile> (or whatever is defined as	4892	The type C<sig_atomic_t volatile> (or whatever is defined as
3741	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	4893	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
3764	watchers.	4916	watchers.
3765		4917
3766	=item C<double> must hold a time value in seconds with enough accuracy	4918	=item C<double> must hold a time value in seconds with enough accuracy
3767		4919
3768	The type C<double> is used to represent timestamps. It is required to	4920	The type C<double> is used to represent timestamps. It is required to
3769	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4921	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3770	enough for at least into the year 4000. This requirement is fulfilled by	4922	good enough for at least into the year 4000 with millisecond accuracy
		4923	(the design goal for libev). This requirement is overfulfilled by
3771	implementations implementing IEEE 754 (basically all existing ones).	4924	implementations using IEEE 754, which is basically all existing ones. With
		4925	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
3772		4926
3773	=back	4927	=back
3774		4928
3775	If you know of other additional requirements drop me a note.	4929	If you know of other additional requirements drop me a note.
3776		4930
…		…
3844	involves iterating over all running async watchers or all signal numbers.	4998	involves iterating over all running async watchers or all signal numbers.
3845		4999
3846	=back	5000	=back
3847		5001
3848		5002
		5003	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5004
		5005	The major version 4 introduced some incompatible changes to the API.
		5006
		5007	At the moment, the C<ev.h> header file provides compatibility definitions
		5008	for all changes, so most programs should still compile. The compatibility
		5009	layer might be removed in later versions of libev, so better update to the
		5010	new API early than late.
		5011
		5012	=over 4
		5013
		5014	=item C<EV_COMPAT3> backwards compatibility mechanism
		5015
		5016	The backward compatibility mechanism can be controlled by
		5017	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5018	section.
		5019
		5020	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5021
		5022	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5023
		5024	ev_loop_destroy (EV_DEFAULT_UC);
		5025	ev_loop_fork (EV_DEFAULT);
		5026
		5027	=item function/symbol renames
		5028
		5029	A number of functions and symbols have been renamed:
		5030
		5031	ev_loop => ev_run
		5032	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5033	EVLOOP_ONESHOT => EVRUN_ONCE
		5034
		5035	ev_unloop => ev_break
		5036	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5037	EVUNLOOP_ONE => EVBREAK_ONE
		5038	EVUNLOOP_ALL => EVBREAK_ALL
		5039
		5040	EV_TIMEOUT => EV_TIMER
		5041
		5042	ev_loop_count => ev_iteration
		5043	ev_loop_depth => ev_depth
		5044	ev_loop_verify => ev_verify
		5045
		5046	Most functions working on C<struct ev_loop> objects don't have an
		5047	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5048	associated constants have been renamed to not collide with the C<struct
		5049	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5050	as all other watcher types. Note that C<ev_loop_fork> is still called
		5051	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5052	typedef.
		5053
		5054	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5055
		5056	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5057	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5058	and work, but the library code will of course be larger.
		5059
		5060	=back
		5061
		5062
		5063	=head1 GLOSSARY
		5064
		5065	=over 4
		5066
		5067	=item active
		5068
		5069	A watcher is active as long as it has been started and not yet stopped.
		5070	See L<WATCHER STATES> for details.
		5071
		5072	=item application
		5073
		5074	In this document, an application is whatever is using libev.
		5075
		5076	=item backend
		5077
		5078	The part of the code dealing with the operating system interfaces.
		5079
		5080	=item callback
		5081
		5082	The address of a function that is called when some event has been
		5083	detected. Callbacks are being passed the event loop, the watcher that
		5084	received the event, and the actual event bitset.
		5085
		5086	=item callback/watcher invocation
		5087
		5088	The act of calling the callback associated with a watcher.
		5089
		5090	=item event
		5091
		5092	A change of state of some external event, such as data now being available
		5093	for reading on a file descriptor, time having passed or simply not having
		5094	any other events happening anymore.
		5095
		5096	In libev, events are represented as single bits (such as C<EV_READ> or
		5097	C<EV_TIMER>).
		5098
		5099	=item event library
		5100
		5101	A software package implementing an event model and loop.
		5102
		5103	=item event loop
		5104
		5105	An entity that handles and processes external events and converts them
		5106	into callback invocations.
		5107
		5108	=item event model
		5109
		5110	The model used to describe how an event loop handles and processes
		5111	watchers and events.
		5112
		5113	=item pending
		5114
		5115	A watcher is pending as soon as the corresponding event has been
		5116	detected. See L<WATCHER STATES> for details.
		5117
		5118	=item real time
		5119
		5120	The physical time that is observed. It is apparently strictly monotonic :)
		5121
		5122	=item wall-clock time
		5123
		5124	The time and date as shown on clocks. Unlike real time, it can actually
		5125	be wrong and jump forwards and backwards, e.g. when the you adjust your
		5126	clock.
		5127
		5128	=item watcher
		5129
		5130	A data structure that describes interest in certain events. Watchers need
		5131	to be started (attached to an event loop) before they can receive events.
		5132
		5133	=back
		5134
3849	=head1 AUTHOR	5135	=head1 AUTHOR
3850		5136
3851	Marc Lehmann <libev@schmorp.de>.	5137	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5138	Magnusson and Emanuele Giaquinta.
3852		5139

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