ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.198 by root, Thu Oct 23 06:30:48 2008 UTC vs.
Revision 1.402 by root, Wed Apr 18 06:09:29 2012 UTC

…		…
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
		14	#include <stdio.h> // for puts
		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
18		20
19	// all watcher callbacks have a similar signature	21	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	22	// this callback is called when data is readable on stdin
…		…
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
28		30
29	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_run's to stop iterating
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_break (EV_A_ EVBREAK_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_run to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_break (EV_A_ EVBREAK_ONE);
40	}	42	}
41		43
42	int	44	int
43	main (void)	45	main (void)
44	{	46	{
45	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
46	ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = EV_DEFAULT;
47		49
48	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
…		…
54	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
57		59
58	// now wait for events to arrive	60	// now wait for events to arrive
59	ev_loop (loop, 0);	61	ev_run (loop, 0);
60		62
61	// unloop was called, so exit	63	// break was called, so exit
62	return 0;	64	return 0;
63	}	65	}
64		66
65	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
66		70
67	The newest version of this document is also available as an html-formatted	71	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	72	web page you might find easier to navigate when reading it for the first
69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.	73	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		74
		75	While this document tries to be as complete as possible in documenting
		76	libev, its usage and the rationale behind its design, it is not a tutorial
		77	on event-based programming, nor will it introduce event-based programming
		78	with libev.
		79
		80	Familiarity with event based programming techniques in general is assumed
		81	throughout this document.
		82
		83	=head1 WHAT TO READ WHEN IN A HURRY
		84
		85	This manual tries to be very detailed, but unfortunately, this also makes
		86	it very long. If you just want to know the basics of libev, I suggest
		87	reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and
		88	look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and
		89	C<ev_timer> sections in L<WATCHER TYPES>.
		90
		91	=head1 ABOUT LIBEV
70		92
71	Libev is an event loop: you register interest in certain events (such as a	93	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	94	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	95	these event sources and provide your program with events.
74		96
…		…
84	=head2 FEATURES	106	=head2 FEATURES
85		107
86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	108	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	109	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	110	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	111	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
90	with customised rescheduling (C<ev_periodic>), synchronous signals	112	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
91	(C<ev_signal>), process status change events (C<ev_child>), and event	113	timers (C<ev_timer>), absolute timers with customised rescheduling
92	watchers dealing with the event loop mechanism itself (C<ev_idle>,	114	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
93	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	115	change events (C<ev_child>), and event watchers dealing with the event
94	file watchers (C<ev_stat>) and even limited support for fork events	116	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
95	(C<ev_fork>).	117	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		118	limited support for fork events (C<ev_fork>).
96		119
97	It also is quite fast (see this	120	It also is quite fast (see this
98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	121	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
99	for example).	122	for example).
100		123
…		…
103	Libev is very configurable. In this manual the default (and most common)	126	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	127	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	128	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	129	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	130	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<ev_loop *>) will not have	131	name C<loop> (which is always of type C<struct ev_loop *>) will not have
109	this argument.	132	this argument.
110		133
111	=head2 TIME REPRESENTATION	134	=head2 TIME REPRESENTATION
112		135
113	Libev represents time as a single floating point number, representing the	136	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	137	the (fractional) number of seconds since the (POSIX) epoch (in practice
115	the beginning of 1970, details are complicated, don't ask). This type is	138	somewhere near the beginning of 1970, details are complicated, don't
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	139	ask). This type is called C<ev_tstamp>, which is what you should use
117	to the C<double> type in C, and when you need to do any calculations on	140	too. It usually aliases to the C<double> type in C. When you need to do
118	it, you should treat it as some floating point value. Unlike the name	141	any calculations on it, you should treat it as some floating point value.
		142
119	component C<stamp> might indicate, it is also used for time differences	143	Unlike the name component C<stamp> might indicate, it is also used for
120	throughout libev.	144	time differences (e.g. delays) throughout libev.
121		145
122	=head1 ERROR HANDLING	146	=head1 ERROR HANDLING
123		147
124	Libev knows three classes of errors: operating system errors, usage errors	148	Libev knows three classes of errors: operating system errors, usage errors
125	and internal errors (bugs).	149	and internal errors (bugs).
…		…
149		173
150	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
151		175
152	Returns the current time as libev would use it. Please note that the	176	Returns the current time as libev would use it. Please note that the
153	C<ev_now> function is usually faster and also often returns the timestamp	177	C<ev_now> function is usually faster and also often returns the timestamp
154	you actually want to know.	178	you actually want to know. Also interesting is the combination of
		179	C<ev_now_update> and C<ev_now>.
155		180
156	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
157		182
158	Sleep for the given interval: The current thread will be blocked until	183	Sleep for the given interval: The current thread will be blocked
159	either it is interrupted or the given time interval has passed. Basically	184	until either it is interrupted or the given time interval has
		185	passed (approximately - it might return a bit earlier even if not
		186	interrupted). Returns immediately if C<< interval <= 0 >>.
		187
160	this is a sub-second-resolution C<sleep ()>.	188	Basically this is a sub-second-resolution C<sleep ()>.
		189
		190	The range of the C<interval> is limited - libev only guarantees to work
		191	with sleep times of up to one day (C<< interval <= 86400 >>).
161		192
162	=item int ev_version_major ()	193	=item int ev_version_major ()
163		194
164	=item int ev_version_minor ()	195	=item int ev_version_minor ()
165		196
…		…
176	as this indicates an incompatible change. Minor versions are usually	207	as this indicates an incompatible change. Minor versions are usually
177	compatible to older versions, so a larger minor version alone is usually	208	compatible to older versions, so a larger minor version alone is usually
178	not a problem.	209	not a problem.
179		210
180	Example: Make sure we haven't accidentally been linked against the wrong	211	Example: Make sure we haven't accidentally been linked against the wrong
181	version.	212	version (note, however, that this will not detect other ABI mismatches,
		213	such as LFS or reentrancy).
182		214
183	assert (("libev version mismatch",	215	assert (("libev version mismatch",
184	ev_version_major () == EV_VERSION_MAJOR	216	ev_version_major () == EV_VERSION_MAJOR
185	&& ev_version_minor () >= EV_VERSION_MINOR));	217	&& ev_version_minor () >= EV_VERSION_MINOR));
186		218
…		…
197	assert (("sorry, no epoll, no sex",	229	assert (("sorry, no epoll, no sex",
198	ev_supported_backends () & EVBACKEND_EPOLL));	230	ev_supported_backends () & EVBACKEND_EPOLL));
199		231
200	=item unsigned int ev_recommended_backends ()	232	=item unsigned int ev_recommended_backends ()
201		233
202	Return the set of all backends compiled into this binary of libev and also	234	Return the set of all backends compiled into this binary of libev and
203	recommended for this platform. This set is often smaller than the one	235	also recommended for this platform, meaning it will work for most file
		236	descriptor types. This set is often smaller than the one returned by
204	returned by C<ev_supported_backends>, as for example kqueue is broken on	237	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
205	most BSDs and will not be auto-detected unless you explicitly request it	238	and will not be auto-detected unless you explicitly request it (assuming
206	(assuming you know what you are doing). This is the set of backends that	239	you know what you are doing). This is the set of backends that libev will
207	libev will probe for if you specify no backends explicitly.	240	probe for if you specify no backends explicitly.
208		241
209	=item unsigned int ev_embeddable_backends ()	242	=item unsigned int ev_embeddable_backends ()
210		243
211	Returns the set of backends that are embeddable in other event loops. This	244	Returns the set of backends that are embeddable in other event loops. This
212	is the theoretical, all-platform, value. To find which backends	245	value is platform-specific but can include backends not available on the
213	might be supported on the current system, you would need to look at	246	current system. To find which embeddable backends might be supported on
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	247	the current system, you would need to look at C<ev_embeddable_backends ()
215	recommended ones.	248	& ev_supported_backends ()>, likewise for recommended ones.
216		249
217	See the description of C<ev_embed> watchers for more info.	250	See the description of C<ev_embed> watchers for more info.
218		251
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	252	=item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())
220		253
221	Sets the allocation function to use (the prototype is similar - the	254	Sets the allocation function to use (the prototype is similar - the
222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	255	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
223	used to allocate and free memory (no surprises here). If it returns zero	256	used to allocate and free memory (no surprises here). If it returns zero
224	when memory needs to be allocated (C<size != 0>), the library might abort	257	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	283	}
251		284
252	...	285	...
253	ev_set_allocator (persistent_realloc);	286	ev_set_allocator (persistent_realloc);
254		287
255	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	288	=item ev_set_syserr_cb (void (*cb)(const char *msg) throw ())
256		289
257	Set the callback function to call on a retryable system call error (such	290	Set the callback function to call on a retryable system call error (such
258	as failed select, poll, epoll_wait). The message is a printable string	291	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	292	indicating the system call or subsystem causing the problem. If this
260	callback is set, then libev will expect it to remedy the situation, no	293	callback is set, then libev will expect it to remedy the situation, no
…		…
272	}	305	}
273		306
274	...	307	...
275	ev_set_syserr_cb (fatal_error);	308	ev_set_syserr_cb (fatal_error);
276		309
		310	=item ev_feed_signal (int signum)
		311
		312	This function can be used to "simulate" a signal receive. It is completely
		313	safe to call this function at any time, from any context, including signal
		314	handlers or random threads.
		315
		316	Its main use is to customise signal handling in your process, especially
		317	in the presence of threads. For example, you could block signals
		318	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		319	creating any loops), and in one thread, use C<sigwait> or any other
		320	mechanism to wait for signals, then "deliver" them to libev by calling
		321	C<ev_feed_signal>.
		322
277	=back	323	=back
278		324
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	325	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
280		326
281	An event loop is described by a C<ev_loop *>. The library knows two	327	An event loop is described by a C<struct ev_loop *> (the C<struct> is
282	types of such loops, the I<default> loop, which supports signals and child	328	I<not> optional in this case unless libev 3 compatibility is disabled, as
283	events, and dynamically created loops which do not.	329	libev 3 had an C<ev_loop> function colliding with the struct name).
		330
		331	The library knows two types of such loops, the I<default> loop, which
		332	supports child process events, and dynamically created event loops which
		333	do not.
284		334
285	=over 4	335	=over 4
286		336
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	337	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		338
289	This will initialise the default event loop if it hasn't been initialised	339	This returns the "default" event loop object, which is what you should
290	yet and return it. If the default loop could not be initialised, returns	340	normally use when you just need "the event loop". Event loop objects and
291	false. If it already was initialised it simply returns it (and ignores the	341	the C<flags> parameter are described in more detail in the entry for
292	flags. If that is troubling you, check C<ev_backend ()> afterwards).	342	C<ev_loop_new>.
		343
		344	If the default loop is already initialised then this function simply
		345	returns it (and ignores the flags. If that is troubling you, check
		346	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		347	flags, which should almost always be C<0>, unless the caller is also the
		348	one calling C<ev_run> or otherwise qualifies as "the main program".
293		349
294	If you don't know what event loop to use, use the one returned from this	350	If you don't know what event loop to use, use the one returned from this
295	function.	351	function (or via the C<EV_DEFAULT> macro).
296		352
297	Note that this function is I<not> thread-safe, so if you want to use it	353	Note that this function is I<not> thread-safe, so if you want to use it
298	from multiple threads, you have to lock (note also that this is unlikely,	354	from multiple threads, you have to employ some kind of mutex (note also
299	as loops cannot bes hared easily between threads anyway).	355	that this case is unlikely, as loops cannot be shared easily between
		356	threads anyway).
300		357
301	The default loop is the only loop that can handle C<ev_signal> and	358	The default loop is the only loop that can handle C<ev_child> watchers,
302	C<ev_child> watchers, and to do this, it always registers a handler	359	and to do this, it always registers a handler for C<SIGCHLD>. If this is
303	for C<SIGCHLD>. If this is a problem for your application you can either	360	a problem for your application you can either create a dynamic loop with
304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	361	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
305	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	362	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
306	C<ev_default_init>.	363
		364	Example: This is the most typical usage.
		365
		366	if (!ev_default_loop (0))
		367	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		368
		369	Example: Restrict libev to the select and poll backends, and do not allow
		370	environment settings to be taken into account:
		371
		372	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		373
		374	=item struct ev_loop *ev_loop_new (unsigned int flags)
		375
		376	This will create and initialise a new event loop object. If the loop
		377	could not be initialised, returns false.
		378
		379	This function is thread-safe, and one common way to use libev with
		380	threads is indeed to create one loop per thread, and using the default
		381	loop in the "main" or "initial" thread.
307		382
308	The flags argument can be used to specify special behaviour or specific	383	The flags argument can be used to specify special behaviour or specific
309	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	384	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
310		385
311	The following flags are supported:	386	The following flags are supported:
…		…
326	useful to try out specific backends to test their performance, or to work	401	useful to try out specific backends to test their performance, or to work
327	around bugs.	402	around bugs.
328		403
329	=item C<EVFLAG_FORKCHECK>	404	=item C<EVFLAG_FORKCHECK>
330		405
331	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	406	Instead of calling C<ev_loop_fork> manually after a fork, you can also
332	a fork, you can also make libev check for a fork in each iteration by	407	make libev check for a fork in each iteration by enabling this flag.
333	enabling this flag.
334		408
335	This works by calling C<getpid ()> on every iteration of the loop,	409	This works by calling C<getpid ()> on every iteration of the loop,
336	and thus this might slow down your event loop if you do a lot of loop	410	and thus this might slow down your event loop if you do a lot of loop
337	iterations and little real work, but is usually not noticeable (on my	411	iterations and little real work, but is usually not noticeable (on my
338	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	412	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
…		…
344	flag.	418	flag.
345		419
346	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	420	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
347	environment variable.	421	environment variable.
348		422
		423	=item C<EVFLAG_NOINOTIFY>
		424
		425	When this flag is specified, then libev will not attempt to use the
		426	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
		427	testing, this flag can be useful to conserve inotify file descriptors, as
		428	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		429
		430	=item C<EVFLAG_SIGNALFD>
		431
		432	When this flag is specified, then libev will attempt to use the
		433	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
		434	delivers signals synchronously, which makes it both faster and might make
		435	it possible to get the queued signal data. It can also simplify signal
		436	handling with threads, as long as you properly block signals in your
		437	threads that are not interested in handling them.
		438
		439	Signalfd will not be used by default as this changes your signal mask, and
		440	there are a lot of shoddy libraries and programs (glib's threadpool for
		441	example) that can't properly initialise their signal masks.
		442
		443	=item C<EVFLAG_NOSIGMASK>
		444
		445	When this flag is specified, then libev will avoid to modify the signal
		446	mask. Specifically, this means you have to make sure signals are unblocked
		447	when you want to receive them.
		448
		449	This behaviour is useful when you want to do your own signal handling, or
		450	want to handle signals only in specific threads and want to avoid libev
		451	unblocking the signals.
		452
		453	It's also required by POSIX in a threaded program, as libev calls
		454	C<sigprocmask>, whose behaviour is officially unspecified.
		455
		456	This flag's behaviour will become the default in future versions of libev.
		457
349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	458	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
350		459
351	This is your standard select(2) backend. Not I<completely> standard, as	460	This is your standard select(2) backend. Not I<completely> standard, as
352	libev tries to roll its own fd_set with no limits on the number of fds,	461	libev tries to roll its own fd_set with no limits on the number of fds,
353	but if that fails, expect a fairly low limit on the number of fds when	462	but if that fails, expect a fairly low limit on the number of fds when
…		…
377	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and	486	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
378	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	487	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
379		488
380	=item C<EVBACKEND_EPOLL> (value 4, Linux)	489	=item C<EVBACKEND_EPOLL> (value 4, Linux)
381		490
		491	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		492	kernels).
		493
382	For few fds, this backend is a bit little slower than poll and select,	494	For few fds, this backend is a bit little slower than poll and select, but
383	but it scales phenomenally better. While poll and select usually scale	495	it scales phenomenally better. While poll and select usually scale like
384	like O(total_fds) where n is the total number of fds (or the highest fd),	496	O(total_fds) where total_fds is the total number of fds (or the highest
385	epoll scales either O(1) or O(active_fds). The epoll design has a number	497	fd), epoll scales either O(1) or O(active_fds).
386	of shortcomings, such as silently dropping events in some hard-to-detect	498
387	cases and requiring a system call per fd change, no fork support and bad	499	The epoll mechanism deserves honorable mention as the most misdesigned
388	support for dup.	500	of the more advanced event mechanisms: mere annoyances include silently
		501	dropping file descriptors, requiring a system call per change per file
		502	descriptor (and unnecessary guessing of parameters), problems with dup,
		503	returning before the timeout value, resulting in additional iterations
		504	(and only giving 5ms accuracy while select on the same platform gives
		505	0.1ms) and so on. The biggest issue is fork races, however - if a program
		506	forks then I<both> parent and child process have to recreate the epoll
		507	set, which can take considerable time (one syscall per file descriptor)
		508	and is of course hard to detect.
		509
		510	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
		511	but of course I<doesn't>, and epoll just loves to report events for
		512	totally I<different> file descriptors (even already closed ones, so
		513	one cannot even remove them from the set) than registered in the set
		514	(especially on SMP systems). Libev tries to counter these spurious
		515	notifications by employing an additional generation counter and comparing
		516	that against the events to filter out spurious ones, recreating the set
		517	when required. Epoll also erroneously rounds down timeouts, but gives you
		518	no way to know when and by how much, so sometimes you have to busy-wait
		519	because epoll returns immediately despite a nonzero timeout. And last
		520	not least, it also refuses to work with some file descriptors which work
		521	perfectly fine with C<select> (files, many character devices...).
		522
		523	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		524	cobbled together in a hurry, no thought to design or interaction with
		525	others. Oh, the pain, will it ever stop...
389		526
390	While stopping, setting and starting an I/O watcher in the same iteration	527	While stopping, setting and starting an I/O watcher in the same iteration
391	will result in some caching, there is still a system call per such incident	528	will result in some caching, there is still a system call per such
392	(because the fd could point to a different file description now), so its	529	incident (because the same I<file descriptor> could point to a different
393	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	530	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
394	very well if you register events for both fds.	531	file descriptors might not work very well if you register events for both
395		532	file descriptors.
396	Please note that epoll sometimes generates spurious notifications, so you
397	need to use non-blocking I/O or other means to avoid blocking when no data
398	(or space) is available.
399		533
400	Best performance from this backend is achieved by not unregistering all	534	Best performance from this backend is achieved by not unregistering all
401	watchers for a file descriptor until it has been closed, if possible,	535	watchers for a file descriptor until it has been closed, if possible,
402	i.e. keep at least one watcher active per fd at all times. Stopping and	536	i.e. keep at least one watcher active per fd at all times. Stopping and
403	starting a watcher (without re-setting it) also usually doesn't cause	537	starting a watcher (without re-setting it) also usually doesn't cause
404	extra overhead.	538	extra overhead. A fork can both result in spurious notifications as well
		539	as in libev having to destroy and recreate the epoll object, which can
		540	take considerable time and thus should be avoided.
		541
		542	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		543	faster than epoll for maybe up to a hundred file descriptors, depending on
		544	the usage. So sad.
405		545
406	While nominally embeddable in other event loops, this feature is broken in	546	While nominally embeddable in other event loops, this feature is broken in
407	all kernel versions tested so far.	547	all kernel versions tested so far.
408		548
409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	549	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
410	C<EVBACKEND_POLL>.	550	C<EVBACKEND_POLL>.
411		551
412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	552	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
413		553
414	Kqueue deserves special mention, as at the time of this writing, it was	554	Kqueue deserves special mention, as at the time of this writing, it
415	broken on all BSDs except NetBSD (usually it doesn't work reliably with	555	was broken on all BSDs except NetBSD (usually it doesn't work reliably
416	anything but sockets and pipes, except on Darwin, where of course it's	556	with anything but sockets and pipes, except on Darwin, where of course
417	completely useless). For this reason it's not being "auto-detected" unless	557	it's completely useless). Unlike epoll, however, whose brokenness
418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or	558	is by design, these kqueue bugs can (and eventually will) be fixed
419	libev was compiled on a known-to-be-good (-enough) system like NetBSD.	559	without API changes to existing programs. For this reason it's not being
		560	"auto-detected" unless you explicitly specify it in the flags (i.e. using
		561	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		562	system like NetBSD.
420		563
421	You still can embed kqueue into a normal poll or select backend and use it	564	You still can embed kqueue into a normal poll or select backend and use it
422	only for sockets (after having made sure that sockets work with kqueue on	565	only for sockets (after having made sure that sockets work with kqueue on
423	the target platform). See C<ev_embed> watchers for more info.	566	the target platform). See C<ev_embed> watchers for more info.
424		567
425	It scales in the same way as the epoll backend, but the interface to the	568	It scales in the same way as the epoll backend, but the interface to the
426	kernel is more efficient (which says nothing about its actual speed, of	569	kernel is more efficient (which says nothing about its actual speed, of
427	course). While stopping, setting and starting an I/O watcher does never	570	course). While stopping, setting and starting an I/O watcher does never
428	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	571	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
429	two event changes per incident. Support for C<fork ()> is very bad and it	572	two event changes per incident. Support for C<fork ()> is very bad (you
		573	might have to leak fd's on fork, but it's more sane than epoll) and it
430	drops fds silently in similarly hard-to-detect cases.	574	drops fds silently in similarly hard-to-detect cases
431		575
432	This backend usually performs well under most conditions.	576	This backend usually performs well under most conditions.
433		577
434	While nominally embeddable in other event loops, this doesn't work	578	While nominally embeddable in other event loops, this doesn't work
435	everywhere, so you might need to test for this. And since it is broken	579	everywhere, so you might need to test for this. And since it is broken
436	almost everywhere, you should only use it when you have a lot of sockets	580	almost everywhere, you should only use it when you have a lot of sockets
437	(for which it usually works), by embedding it into another event loop	581	(for which it usually works), by embedding it into another event loop
438	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,	582	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
439	using it only for sockets.	583	also broken on OS X)) and, did I mention it, using it only for sockets.
440		584
441	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	585	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
442	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with	586	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
443	C<NOTE_EOF>.	587	C<NOTE_EOF>.
444		588
…		…
452	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	596	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
453		597
454	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	598	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
455	it's really slow, but it still scales very well (O(active_fds)).	599	it's really slow, but it still scales very well (O(active_fds)).
456		600
457	Please note that Solaris event ports can deliver a lot of spurious
458	notifications, so you need to use non-blocking I/O or other means to avoid
459	blocking when no data (or space) is available.
460
461	While this backend scales well, it requires one system call per active	601	While this backend scales well, it requires one system call per active
462	file descriptor per loop iteration. For small and medium numbers of file	602	file descriptor per loop iteration. For small and medium numbers of file
463	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	603	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
464	might perform better.	604	might perform better.
465		605
466	On the positive side, with the exception of the spurious readiness	606	On the positive side, this backend actually performed fully to
467	notifications, this backend actually performed fully to specification
468	in all tests and is fully embeddable, which is a rare feat among the	607	specification in all tests and is fully embeddable, which is a rare feat
469	OS-specific backends.	608	among the OS-specific backends (I vastly prefer correctness over speed
		609	hacks).
		610
		611	On the negative side, the interface is I<bizarre> - so bizarre that
		612	even sun itself gets it wrong in their code examples: The event polling
		613	function sometimes returns events to the caller even though an error
		614	occurred, but with no indication whether it has done so or not (yes, it's
		615	even documented that way) - deadly for edge-triggered interfaces where you
		616	absolutely have to know whether an event occurred or not because you have
		617	to re-arm the watcher.
		618
		619	Fortunately libev seems to be able to work around these idiocies.
470		620
471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	621	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
472	C<EVBACKEND_POLL>.	622	C<EVBACKEND_POLL>.
473		623
474	=item C<EVBACKEND_ALL>	624	=item C<EVBACKEND_ALL>
475		625
476	Try all backends (even potentially broken ones that wouldn't be tried	626	Try all backends (even potentially broken ones that wouldn't be tried
477	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	627	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
478	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	628	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
479		629
480	It is definitely not recommended to use this flag.	630	It is definitely not recommended to use this flag, use whatever
		631	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		632	at all.
		633
		634	=item C<EVBACKEND_MASK>
		635
		636	Not a backend at all, but a mask to select all backend bits from a
		637	C<flags> value, in case you want to mask out any backends from a flags
		638	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
481		639
482	=back	640	=back
483		641
484	If one or more of these are or'ed into the flags value, then only these	642	If one or more of the backend flags are or'ed into the flags value,
485	backends will be tried (in the reverse order as listed here). If none are	643	then only these backends will be tried (in the reverse order as listed
486	specified, all backends in C<ev_recommended_backends ()> will be tried.	644	here). If none are specified, all backends in C<ev_recommended_backends
487		645	()> will be tried.
488	Example: This is the most typical usage.
489
490	if (!ev_default_loop (0))
491	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
492
493	Example: Restrict libev to the select and poll backends, and do not allow
494	environment settings to be taken into account:
495
496	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
497
498	Example: Use whatever libev has to offer, but make sure that kqueue is
499	used if available (warning, breaks stuff, best use only with your own
500	private event loop and only if you know the OS supports your types of
501	fds):
502
503	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
504
505	=item struct ev_loop *ev_loop_new (unsigned int flags)
506
507	Similar to C<ev_default_loop>, but always creates a new event loop that is
508	always distinct from the default loop. Unlike the default loop, it cannot
509	handle signal and child watchers, and attempts to do so will be greeted by
510	undefined behaviour (or a failed assertion if assertions are enabled).
511
512	Note that this function I<is> thread-safe, and the recommended way to use
513	libev with threads is indeed to create one loop per thread, and using the
514	default loop in the "main" or "initial" thread.
515		646
516	Example: Try to create a event loop that uses epoll and nothing else.	647	Example: Try to create a event loop that uses epoll and nothing else.
517		648
518	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	649	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
519	if (!epoller)	650	if (!epoller)
520	fatal ("no epoll found here, maybe it hides under your chair");	651	fatal ("no epoll found here, maybe it hides under your chair");
521		652
		653	Example: Use whatever libev has to offer, but make sure that kqueue is
		654	used if available.
		655
		656	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		657
522	=item ev_default_destroy ()	658	=item ev_loop_destroy (loop)
523		659
524	Destroys the default loop again (frees all memory and kernel state	660	Destroys an event loop object (frees all memory and kernel state
525	etc.). None of the active event watchers will be stopped in the normal	661	etc.). None of the active event watchers will be stopped in the normal
526	sense, so e.g. C<ev_is_active> might still return true. It is your	662	sense, so e.g. C<ev_is_active> might still return true. It is your
527	responsibility to either stop all watchers cleanly yourself I<before>	663	responsibility to either stop all watchers cleanly yourself I<before>
528	calling this function, or cope with the fact afterwards (which is usually	664	calling this function, or cope with the fact afterwards (which is usually
529	the easiest thing, you can just ignore the watchers and/or C<free ()> them	665	the easiest thing, you can just ignore the watchers and/or C<free ()> them
530	for example).	666	for example).
531		667
532	Note that certain global state, such as signal state, will not be freed by	668	Note that certain global state, such as signal state (and installed signal
533	this function, and related watchers (such as signal and child watchers)	669	handlers), will not be freed by this function, and related watchers (such
534	would need to be stopped manually.	670	as signal and child watchers) would need to be stopped manually.
535		671
536	In general it is not advisable to call this function except in the	672	This function is normally used on loop objects allocated by
537	rare occasion where you really need to free e.g. the signal handling	673	C<ev_loop_new>, but it can also be used on the default loop returned by
		674	C<ev_default_loop>, in which case it is not thread-safe.
		675
		676	Note that it is not advisable to call this function on the default loop
		677	except in the rare occasion where you really need to free its resources.
538	pipe fds. If you need dynamically allocated loops it is better to use	678	If you need dynamically allocated loops it is better to use C<ev_loop_new>
539	C<ev_loop_new> and C<ev_loop_destroy>).	679	and C<ev_loop_destroy>.
540		680
541	=item ev_loop_destroy (loop)	681	=item ev_loop_fork (loop)
542		682
543	Like C<ev_default_destroy>, but destroys an event loop created by an
544	earlier call to C<ev_loop_new>.
545
546	=item ev_default_fork ()
547
548	This function sets a flag that causes subsequent C<ev_loop> iterations	683	This function sets a flag that causes subsequent C<ev_run> iterations to
549	to reinitialise the kernel state for backends that have one. Despite the	684	reinitialise the kernel state for backends that have one. Despite the
550	name, you can call it anytime, but it makes most sense after forking, in	685	name, you can call it anytime, but it makes most sense after forking, in
551	the child process (or both child and parent, but that again makes little	686	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
552	sense). You I<must> call it in the child before using any of the libev	687	child before resuming or calling C<ev_run>.
553	functions, and it will only take effect at the next C<ev_loop> iteration.	688
		689	Again, you I<have> to call it on I<any> loop that you want to re-use after
		690	a fork, I<even if you do not plan to use the loop in the parent>. This is
		691	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		692	during fork.
554		693
555	On the other hand, you only need to call this function in the child	694	On the other hand, you only need to call this function in the child
556	process if and only if you want to use the event library in the child. If	695	process if and only if you want to use the event loop in the child. If
557	you just fork+exec, you don't have to call it at all.	696	you just fork+exec or create a new loop in the child, you don't have to
		697	call it at all (in fact, C<epoll> is so badly broken that it makes a
		698	difference, but libev will usually detect this case on its own and do a
		699	costly reset of the backend).
558		700
559	The function itself is quite fast and it's usually not a problem to call	701	The function itself is quite fast and it's usually not a problem to call
560	it just in case after a fork. To make this easy, the function will fit in	702	it just in case after a fork.
561	quite nicely into a call to C<pthread_atfork>:
562		703
		704	Example: Automate calling C<ev_loop_fork> on the default loop when
		705	using pthreads.
		706
		707	static void
		708	post_fork_child (void)
		709	{
		710	ev_loop_fork (EV_DEFAULT);
		711	}
		712
		713	...
563	pthread_atfork (0, 0, ev_default_fork);	714	pthread_atfork (0, 0, post_fork_child);
564
565	=item ev_loop_fork (loop)
566
567	Like C<ev_default_fork>, but acts on an event loop created by
568	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
569	after fork that you want to re-use in the child, and how you do this is
570	entirely your own problem.
571		715
572	=item int ev_is_default_loop (loop)	716	=item int ev_is_default_loop (loop)
573		717
574	Returns true when the given loop is, in fact, the default loop, and false	718	Returns true when the given loop is, in fact, the default loop, and false
575	otherwise.	719	otherwise.
576		720
577	=item unsigned int ev_loop_count (loop)	721	=item unsigned int ev_iteration (loop)
578		722
579	Returns the count of loop iterations for the loop, which is identical to	723	Returns the current iteration count for the event loop, which is identical
580	the number of times libev did poll for new events. It starts at C<0> and	724	to the number of times libev did poll for new events. It starts at C<0>
581	happily wraps around with enough iterations.	725	and happily wraps around with enough iterations.
582		726
583	This value can sometimes be useful as a generation counter of sorts (it	727	This value can sometimes be useful as a generation counter of sorts (it
584	"ticks" the number of loop iterations), as it roughly corresponds with	728	"ticks" the number of loop iterations), as it roughly corresponds with
585	C<ev_prepare> and C<ev_check> calls.	729	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		730	prepare and check phases.
		731
		732	=item unsigned int ev_depth (loop)
		733
		734	Returns the number of times C<ev_run> was entered minus the number of
		735	times C<ev_run> was exited normally, in other words, the recursion depth.
		736
		737	Outside C<ev_run>, this number is zero. In a callback, this number is
		738	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		739	in which case it is higher.
		740
		741	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
		742	throwing an exception etc.), doesn't count as "exit" - consider this
		743	as a hint to avoid such ungentleman-like behaviour unless it's really
		744	convenient, in which case it is fully supported.
586		745
587	=item unsigned int ev_backend (loop)	746	=item unsigned int ev_backend (loop)
588		747
589	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	748	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
590	use.	749	use.
…		…
599		758
600	=item ev_now_update (loop)	759	=item ev_now_update (loop)
601		760
602	Establishes the current time by querying the kernel, updating the time	761	Establishes the current time by querying the kernel, updating the time
603	returned by C<ev_now ()> in the progress. This is a costly operation and	762	returned by C<ev_now ()> in the progress. This is a costly operation and
604	is usually done automatically within C<ev_loop ()>.	763	is usually done automatically within C<ev_run ()>.
605		764
606	This function is rarely useful, but when some event callback runs for a	765	This function is rarely useful, but when some event callback runs for a
607	very long time without entering the event loop, updating libev's idea of	766	very long time without entering the event loop, updating libev's idea of
608	the current time is a good idea.	767	the current time is a good idea.
609		768
610	See also "The special problem of time updates" in the C<ev_timer> section.	769	See also L<The special problem of time updates> in the C<ev_timer> section.
611		770
		771	=item ev_suspend (loop)
		772
		773	=item ev_resume (loop)
		774
		775	These two functions suspend and resume an event loop, for use when the
		776	loop is not used for a while and timeouts should not be processed.
		777
		778	A typical use case would be an interactive program such as a game: When
		779	the user presses C<^Z> to suspend the game and resumes it an hour later it
		780	would be best to handle timeouts as if no time had actually passed while
		781	the program was suspended. This can be achieved by calling C<ev_suspend>
		782	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		783	C<ev_resume> directly afterwards to resume timer processing.
		784
		785	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		786	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		787	will be rescheduled (that is, they will lose any events that would have
		788	occurred while suspended).
		789
		790	After calling C<ev_suspend> you B<must not> call I<any> function on the
		791	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		792	without a previous call to C<ev_suspend>.
		793
		794	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		795	event loop time (see C<ev_now_update>).
		796
612	=item ev_loop (loop, int flags)	797	=item bool ev_run (loop, int flags)
613		798
614	Finally, this is it, the event handler. This function usually is called	799	Finally, this is it, the event handler. This function usually is called
615	after you initialised all your watchers and you want to start handling	800	after you have initialised all your watchers and you want to start
616	events.	801	handling events. It will ask the operating system for any new events, call
		802	the watcher callbacks, and then repeat the whole process indefinitely: This
		803	is why event loops are called I<loops>.
617		804
618	If the flags argument is specified as C<0>, it will not return until	805	If the flags argument is specified as C<0>, it will keep handling events
619	either no event watchers are active anymore or C<ev_unloop> was called.	806	until either no event watchers are active anymore or C<ev_break> was
		807	called.
620		808
		809	The return value is false if there are no more active watchers (which
		810	usually means "all jobs done" or "deadlock"), and true in all other cases
		811	(which usually means " you should call C<ev_run> again").
		812
621	Please note that an explicit C<ev_unloop> is usually better than	813	Please note that an explicit C<ev_break> is usually better than
622	relying on all watchers to be stopped when deciding when a program has	814	relying on all watchers to be stopped when deciding when a program has
623	finished (especially in interactive programs), but having a program	815	finished (especially in interactive programs), but having a program
624	that automatically loops as long as it has to and no longer by virtue	816	that automatically loops as long as it has to and no longer by virtue
625	of relying on its watchers stopping correctly, that is truly a thing of	817	of relying on its watchers stopping correctly, that is truly a thing of
626	beauty.	818	beauty.
627		819
		820	This function is I<mostly> exception-safe - you can break out of a
		821	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		822	exception and so on. This does not decrement the C<ev_depth> value, nor
		823	will it clear any outstanding C<EVBREAK_ONE> breaks.
		824
628	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	825	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
629	those events and any already outstanding ones, but will not block your	826	those events and any already outstanding ones, but will not wait and
630	process in case there are no events and will return after one iteration of	827	block your process in case there are no events and will return after one
631	the loop.	828	iteration of the loop. This is sometimes useful to poll and handle new
		829	events while doing lengthy calculations, to keep the program responsive.
632		830
633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	831	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
634	necessary) and will handle those and any already outstanding ones. It	832	necessary) and will handle those and any already outstanding ones. It
635	will block your process until at least one new event arrives (which could	833	will block your process until at least one new event arrives (which could
636	be an event internal to libev itself, so there is no guarentee that a	834	be an event internal to libev itself, so there is no guarantee that a
637	user-registered callback will be called), and will return after one	835	user-registered callback will be called), and will return after one
638	iteration of the loop.	836	iteration of the loop.
639		837
640	This is useful if you are waiting for some external event in conjunction	838	This is useful if you are waiting for some external event in conjunction
641	with something not expressible using other libev watchers (i.e. "roll your	839	with something not expressible using other libev watchers (i.e. "roll your
642	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	840	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
643	usually a better approach for this kind of thing.	841	usually a better approach for this kind of thing.
644		842
645	Here are the gory details of what C<ev_loop> does:	843	Here are the gory details of what C<ev_run> does (this is for your
		844	understanding, not a guarantee that things will work exactly like this in
		845	future versions):
646		846
		847	- Increment loop depth.
		848	- Reset the ev_break status.
647	- Before the first iteration, call any pending watchers.	849	- Before the first iteration, call any pending watchers.
		850	LOOP:
648	* If EVFLAG_FORKCHECK was used, check for a fork.	851	- If EVFLAG_FORKCHECK was used, check for a fork.
649	- If a fork was detected (by any means), queue and call all fork watchers.	852	- If a fork was detected (by any means), queue and call all fork watchers.
650	- Queue and call all prepare watchers.	853	- Queue and call all prepare watchers.
		854	- If ev_break was called, goto FINISH.
651	- If we have been forked, detach and recreate the kernel state	855	- If we have been forked, detach and recreate the kernel state
652	as to not disturb the other process.	856	as to not disturb the other process.
653	- Update the kernel state with all outstanding changes.	857	- Update the kernel state with all outstanding changes.
654	- Update the "event loop time" (ev_now ()).	858	- Update the "event loop time" (ev_now ()).
655	- Calculate for how long to sleep or block, if at all	859	- Calculate for how long to sleep or block, if at all
656	(active idle watchers, EVLOOP_NONBLOCK or not having	860	(active idle watchers, EVRUN_NOWAIT or not having
657	any active watchers at all will result in not sleeping).	861	any active watchers at all will result in not sleeping).
658	- Sleep if the I/O and timer collect interval say so.	862	- Sleep if the I/O and timer collect interval say so.
		863	- Increment loop iteration counter.
659	- Block the process, waiting for any events.	864	- Block the process, waiting for any events.
660	- Queue all outstanding I/O (fd) events.	865	- Queue all outstanding I/O (fd) events.
661	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	866	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
662	- Queue all expired timers.	867	- Queue all expired timers.
663	- Queue all expired periodics.	868	- Queue all expired periodics.
664	- Unless any events are pending now, queue all idle watchers.	869	- Queue all idle watchers with priority higher than that of pending events.
665	- Queue all check watchers.	870	- Queue all check watchers.
666	- Call all queued watchers in reverse order (i.e. check watchers first).	871	- Call all queued watchers in reverse order (i.e. check watchers first).
667	Signals and child watchers are implemented as I/O watchers, and will	872	Signals and child watchers are implemented as I/O watchers, and will
668	be handled here by queueing them when their watcher gets executed.	873	be handled here by queueing them when their watcher gets executed.
669	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	874	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
670	were used, or there are no active watchers, return, otherwise	875	were used, or there are no active watchers, goto FINISH, otherwise
671	continue with step *.	876	continue with step LOOP.
		877	FINISH:
		878	- Reset the ev_break status iff it was EVBREAK_ONE.
		879	- Decrement the loop depth.
		880	- Return.
672		881
673	Example: Queue some jobs and then loop until no events are outstanding	882	Example: Queue some jobs and then loop until no events are outstanding
674	anymore.	883	anymore.
675		884
676	... queue jobs here, make sure they register event watchers as long	885	... queue jobs here, make sure they register event watchers as long
677	... as they still have work to do (even an idle watcher will do..)	886	... as they still have work to do (even an idle watcher will do..)
678	ev_loop (my_loop, 0);	887	ev_run (my_loop, 0);
679	... jobs done or somebody called unloop. yeah!	888	... jobs done or somebody called break. yeah!
680		889
681	=item ev_unloop (loop, how)	890	=item ev_break (loop, how)
682		891
683	Can be used to make a call to C<ev_loop> return early (but only after it	892	Can be used to make a call to C<ev_run> return early (but only after it
684	has processed all outstanding events). The C<how> argument must be either	893	has processed all outstanding events). The C<how> argument must be either
685	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	894	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
686	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	895	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
687		896
688	This "unloop state" will be cleared when entering C<ev_loop> again.	897	This "break state" will be cleared on the next call to C<ev_run>.
689		898
690	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	899	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		900	which case it will have no effect.
691		901
692	=item ev_ref (loop)	902	=item ev_ref (loop)
693		903
694	=item ev_unref (loop)	904	=item ev_unref (loop)
695		905
696	Ref/unref can be used to add or remove a reference count on the event	906	Ref/unref can be used to add or remove a reference count on the event
697	loop: Every watcher keeps one reference, and as long as the reference	907	loop: Every watcher keeps one reference, and as long as the reference
698	count is nonzero, C<ev_loop> will not return on its own.	908	count is nonzero, C<ev_run> will not return on its own.
699		909
700	If you have a watcher you never unregister that should not keep C<ev_loop>	910	This is useful when you have a watcher that you never intend to
701	from returning, call ev_unref() after starting, and ev_ref() before	911	unregister, but that nevertheless should not keep C<ev_run> from
		912	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
702	stopping it.	913	before stopping it.
703		914
704	As an example, libev itself uses this for its internal signal pipe: It is	915	As an example, libev itself uses this for its internal signal pipe: It
705	not visible to the libev user and should not keep C<ev_loop> from exiting	916	is not visible to the libev user and should not keep C<ev_run> from
706	if no event watchers registered by it are active. It is also an excellent	917	exiting if no event watchers registered by it are active. It is also an
707	way to do this for generic recurring timers or from within third-party	918	excellent way to do this for generic recurring timers or from within
708	libraries. Just remember to I<unref after start> and I<ref before stop>	919	third-party libraries. Just remember to I<unref after start> and I<ref
709	(but only if the watcher wasn't active before, or was active before,	920	before stop> (but only if the watcher wasn't active before, or was active
710	respectively).	921	before, respectively. Note also that libev might stop watchers itself
		922	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		923	in the callback).
711		924
712	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	925	Example: Create a signal watcher, but keep it from keeping C<ev_run>
713	running when nothing else is active.	926	running when nothing else is active.
714		927
715	ev_signal exitsig;	928	ev_signal exitsig;
716	ev_signal_init (&exitsig, sig_cb, SIGINT);	929	ev_signal_init (&exitsig, sig_cb, SIGINT);
717	ev_signal_start (loop, &exitsig);	930	ev_signal_start (loop, &exitsig);
718	evf_unref (loop);	931	ev_unref (loop);
719		932
720	Example: For some weird reason, unregister the above signal handler again.	933	Example: For some weird reason, unregister the above signal handler again.
721		934
722	ev_ref (loop);	935	ev_ref (loop);
723	ev_signal_stop (loop, &exitsig);	936	ev_signal_stop (loop, &exitsig);
…		…
743	overhead for the actual polling but can deliver many events at once.	956	overhead for the actual polling but can deliver many events at once.
744		957
745	By setting a higher I<io collect interval> you allow libev to spend more	958	By setting a higher I<io collect interval> you allow libev to spend more
746	time collecting I/O events, so you can handle more events per iteration,	959	time collecting I/O events, so you can handle more events per iteration,
747	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	960	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
748	C<ev_timer>) will be not affected. Setting this to a non-null value will	961	C<ev_timer>) will not be affected. Setting this to a non-null value will
749	introduce an additional C<ev_sleep ()> call into most loop iterations.	962	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		963	sleep time ensures that libev will not poll for I/O events more often then
		964	once per this interval, on average (as long as the host time resolution is
		965	good enough).
750		966
751	Likewise, by setting a higher I<timeout collect interval> you allow libev	967	Likewise, by setting a higher I<timeout collect interval> you allow libev
752	to spend more time collecting timeouts, at the expense of increased	968	to spend more time collecting timeouts, at the expense of increased
753	latency/jitter/inexactness (the watcher callback will be called	969	latency/jitter/inexactness (the watcher callback will be called
754	later). C<ev_io> watchers will not be affected. Setting this to a non-null	970	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
756		972
757	Many (busy) programs can usually benefit by setting the I/O collect	973	Many (busy) programs can usually benefit by setting the I/O collect
758	interval to a value near C<0.1> or so, which is often enough for	974	interval to a value near C<0.1> or so, which is often enough for
759	interactive servers (of course not for games), likewise for timeouts. It	975	interactive servers (of course not for games), likewise for timeouts. It
760	usually doesn't make much sense to set it to a lower value than C<0.01>,	976	usually doesn't make much sense to set it to a lower value than C<0.01>,
761	as this approaches the timing granularity of most systems.	977	as this approaches the timing granularity of most systems. Note that if
		978	you do transactions with the outside world and you can't increase the
		979	parallelity, then this setting will limit your transaction rate (if you
		980	need to poll once per transaction and the I/O collect interval is 0.01,
		981	then you can't do more than 100 transactions per second).
762		982
763	Setting the I<timeout collect interval> can improve the opportunity for	983	Setting the I<timeout collect interval> can improve the opportunity for
764	saving power, as the program will "bundle" timer callback invocations that	984	saving power, as the program will "bundle" timer callback invocations that
765	are "near" in time together, by delaying some, thus reducing the number of	985	are "near" in time together, by delaying some, thus reducing the number of
766	times the process sleeps and wakes up again. Another useful technique to	986	times the process sleeps and wakes up again. Another useful technique to
767	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	987	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
768	they fire on, say, one-second boundaries only.	988	they fire on, say, one-second boundaries only.
769		989
		990	Example: we only need 0.1s timeout granularity, and we wish not to poll
		991	more often than 100 times per second:
		992
		993	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		994	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		995
		996	=item ev_invoke_pending (loop)
		997
		998	This call will simply invoke all pending watchers while resetting their
		999	pending state. Normally, C<ev_run> does this automatically when required,
		1000	but when overriding the invoke callback this call comes handy. This
		1001	function can be invoked from a watcher - this can be useful for example
		1002	when you want to do some lengthy calculation and want to pass further
		1003	event handling to another thread (you still have to make sure only one
		1004	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		1005
		1006	=item int ev_pending_count (loop)
		1007
		1008	Returns the number of pending watchers - zero indicates that no watchers
		1009	are pending.
		1010
		1011	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		1012
		1013	This overrides the invoke pending functionality of the loop: Instead of
		1014	invoking all pending watchers when there are any, C<ev_run> will call
		1015	this callback instead. This is useful, for example, when you want to
		1016	invoke the actual watchers inside another context (another thread etc.).
		1017
		1018	If you want to reset the callback, use C<ev_invoke_pending> as new
		1019	callback.
		1020
		1021	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
		1022
		1023	Sometimes you want to share the same loop between multiple threads. This
		1024	can be done relatively simply by putting mutex_lock/unlock calls around
		1025	each call to a libev function.
		1026
		1027	However, C<ev_run> can run an indefinite time, so it is not feasible
		1028	to wait for it to return. One way around this is to wake up the event
		1029	loop via C<ev_break> and C<ev_async_send>, another way is to set these
		1030	I<release> and I<acquire> callbacks on the loop.
		1031
		1032	When set, then C<release> will be called just before the thread is
		1033	suspended waiting for new events, and C<acquire> is called just
		1034	afterwards.
		1035
		1036	Ideally, C<release> will just call your mutex_unlock function, and
		1037	C<acquire> will just call the mutex_lock function again.
		1038
		1039	While event loop modifications are allowed between invocations of
		1040	C<release> and C<acquire> (that's their only purpose after all), no
		1041	modifications done will affect the event loop, i.e. adding watchers will
		1042	have no effect on the set of file descriptors being watched, or the time
		1043	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		1044	to take note of any changes you made.
		1045
		1046	In theory, threads executing C<ev_run> will be async-cancel safe between
		1047	invocations of C<release> and C<acquire>.
		1048
		1049	See also the locking example in the C<THREADS> section later in this
		1050	document.
		1051
		1052	=item ev_set_userdata (loop, void *data)
		1053
		1054	=item void *ev_userdata (loop)
		1055
		1056	Set and retrieve a single C<void *> associated with a loop. When
		1057	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		1058	C<0>.
		1059
		1060	These two functions can be used to associate arbitrary data with a loop,
		1061	and are intended solely for the C<invoke_pending_cb>, C<release> and
		1062	C<acquire> callbacks described above, but of course can be (ab-)used for
		1063	any other purpose as well.
		1064
770	=item ev_loop_verify (loop)	1065	=item ev_verify (loop)
771		1066
772	This function only does something when C<EV_VERIFY> support has been	1067	This function only does something when C<EV_VERIFY> support has been
773	compiled in. which is the default for non-minimal builds. It tries to go	1068	compiled in, which is the default for non-minimal builds. It tries to go
774	through all internal structures and checks them for validity. If anything	1069	through all internal structures and checks them for validity. If anything
775	is found to be inconsistent, it will print an error message to standard	1070	is found to be inconsistent, it will print an error message to standard
776	error and call C<abort ()>.	1071	error and call C<abort ()>.
777		1072
778	This can be used to catch bugs inside libev itself: under normal	1073	This can be used to catch bugs inside libev itself: under normal
…		…
782	=back	1077	=back
783		1078
784		1079
785	=head1 ANATOMY OF A WATCHER	1080	=head1 ANATOMY OF A WATCHER
786		1081
		1082	In the following description, uppercase C<TYPE> in names stands for the
		1083	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		1084	watchers and C<ev_io_start> for I/O watchers.
		1085
787	A watcher is a structure that you create and register to record your	1086	A watcher is an opaque structure that you allocate and register to record
788	interest in some event. For instance, if you want to wait for STDIN to	1087	your interest in some event. To make a concrete example, imagine you want
789	become readable, you would create an C<ev_io> watcher for that:	1088	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1089	for that:
790		1090
791	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1091	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
792	{	1092	{
793	ev_io_stop (w);	1093	ev_io_stop (w);
794	ev_unloop (loop, EVUNLOOP_ALL);	1094	ev_break (loop, EVBREAK_ALL);
795	}	1095	}
796		1096
797	struct ev_loop *loop = ev_default_loop (0);	1097	struct ev_loop *loop = ev_default_loop (0);
		1098
798	ev_io stdin_watcher;	1099	ev_io stdin_watcher;
		1100
799	ev_init (&stdin_watcher, my_cb);	1101	ev_init (&stdin_watcher, my_cb);
800	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1102	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
801	ev_io_start (loop, &stdin_watcher);	1103	ev_io_start (loop, &stdin_watcher);
		1104
802	ev_loop (loop, 0);	1105	ev_run (loop, 0);
803		1106
804	As you can see, you are responsible for allocating the memory for your	1107	As you can see, you are responsible for allocating the memory for your
805	watcher structures (and it is usually a bad idea to do this on the stack,	1108	watcher structures (and it is I<usually> a bad idea to do this on the
806	although this can sometimes be quite valid).	1109	stack).
807		1110
		1111	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		1112	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
		1113
808	Each watcher structure must be initialised by a call to C<ev_init	1114	Each watcher structure must be initialised by a call to C<ev_init (watcher
809	(watcher *, callback)>, which expects a callback to be provided. This	1115	*, callback)>, which expects a callback to be provided. This callback is
810	callback gets invoked each time the event occurs (or, in the case of I/O	1116	invoked each time the event occurs (or, in the case of I/O watchers, each
811	watchers, each time the event loop detects that the file descriptor given	1117	time the event loop detects that the file descriptor given is readable
812	is readable and/or writable).	1118	and/or writable).
813		1119
814	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1120	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
815	with arguments specific to this watcher type. There is also a macro	1121	macro to configure it, with arguments specific to the watcher type. There
816	to combine initialisation and setting in one call: C<< ev_<type>_init	1122	is also a macro to combine initialisation and setting in one call: C<<
817	(watcher *, callback, ...) >>.	1123	ev_TYPE_init (watcher *, callback, ...) >>.
818		1124
819	To make the watcher actually watch out for events, you have to start it	1125	To make the watcher actually watch out for events, you have to start it
820	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	1126	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
821	*) >>), and you can stop watching for events at any time by calling the	1127	*) >>), and you can stop watching for events at any time by calling the
822	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1128	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
823		1129
824	As long as your watcher is active (has been started but not stopped) you	1130	As long as your watcher is active (has been started but not stopped) you
825	must not touch the values stored in it. Most specifically you must never	1131	must not touch the values stored in it. Most specifically you must never
826	reinitialise it or call its C<set> macro.	1132	reinitialise it or call its C<ev_TYPE_set> macro.
827		1133
828	Each and every callback receives the event loop pointer as first, the	1134	Each and every callback receives the event loop pointer as first, the
829	registered watcher structure as second, and a bitset of received events as	1135	registered watcher structure as second, and a bitset of received events as
830	third argument.	1136	third argument.
831		1137
…		…
840	=item C<EV_WRITE>	1146	=item C<EV_WRITE>
841		1147
842	The file descriptor in the C<ev_io> watcher has become readable and/or	1148	The file descriptor in the C<ev_io> watcher has become readable and/or
843	writable.	1149	writable.
844		1150
845	=item C<EV_TIMEOUT>	1151	=item C<EV_TIMER>
846		1152
847	The C<ev_timer> watcher has timed out.	1153	The C<ev_timer> watcher has timed out.
848		1154
849	=item C<EV_PERIODIC>	1155	=item C<EV_PERIODIC>
850		1156
…		…
868		1174
869	=item C<EV_PREPARE>	1175	=item C<EV_PREPARE>
870		1176
871	=item C<EV_CHECK>	1177	=item C<EV_CHECK>
872		1178
873	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1179	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
874	to gather new events, and all C<ev_check> watchers are invoked just after	1180	to gather new events, and all C<ev_check> watchers are invoked just after
875	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1181	C<ev_run> has gathered them, but before it invokes any callbacks for any
876	received events. Callbacks of both watcher types can start and stop as	1182	received events. Callbacks of both watcher types can start and stop as
877	many watchers as they want, and all of them will be taken into account	1183	many watchers as they want, and all of them will be taken into account
878	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1184	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
879	C<ev_loop> from blocking).	1185	C<ev_run> from blocking).
880		1186
881	=item C<EV_EMBED>	1187	=item C<EV_EMBED>
882		1188
883	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1189	The embedded event loop specified in the C<ev_embed> watcher needs attention.
884		1190
885	=item C<EV_FORK>	1191	=item C<EV_FORK>
886		1192
887	The event loop has been resumed in the child process after fork (see	1193	The event loop has been resumed in the child process after fork (see
888	C<ev_fork>).	1194	C<ev_fork>).
889		1195
		1196	=item C<EV_CLEANUP>
		1197
		1198	The event loop is about to be destroyed (see C<ev_cleanup>).
		1199
890	=item C<EV_ASYNC>	1200	=item C<EV_ASYNC>
891		1201
892	The given async watcher has been asynchronously notified (see C<ev_async>).	1202	The given async watcher has been asynchronously notified (see C<ev_async>).
		1203
		1204	=item C<EV_CUSTOM>
		1205
		1206	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1207	by libev users to signal watchers (e.g. via C<ev_feed_event>).
893		1208
894	=item C<EV_ERROR>	1209	=item C<EV_ERROR>
895		1210
896	An unspecified error has occurred, the watcher has been stopped. This might	1211	An unspecified error has occurred, the watcher has been stopped. This might
897	happen because the watcher could not be properly started because libev	1212	happen because the watcher could not be properly started because libev
…		…
912		1227
913	=back	1228	=back
914		1229
915	=head2 GENERIC WATCHER FUNCTIONS	1230	=head2 GENERIC WATCHER FUNCTIONS
916		1231
917	In the following description, C<TYPE> stands for the watcher type,
918	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
919
920	=over 4	1232	=over 4
921		1233
922	=item C<ev_init> (ev_TYPE *watcher, callback)	1234	=item C<ev_init> (ev_TYPE *watcher, callback)
923		1235
924	This macro initialises the generic portion of a watcher. The contents	1236	This macro initialises the generic portion of a watcher. The contents
…		…
938		1250
939	ev_io w;	1251	ev_io w;
940	ev_init (&w, my_cb);	1252	ev_init (&w, my_cb);
941	ev_io_set (&w, STDIN_FILENO, EV_READ);	1253	ev_io_set (&w, STDIN_FILENO, EV_READ);
942		1254
943	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1255	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
944		1256
945	This macro initialises the type-specific parts of a watcher. You need to	1257	This macro initialises the type-specific parts of a watcher. You need to
946	call C<ev_init> at least once before you call this macro, but you can	1258	call C<ev_init> at least once before you call this macro, but you can
947	call C<ev_TYPE_set> any number of times. You must not, however, call this	1259	call C<ev_TYPE_set> any number of times. You must not, however, call this
948	macro on a watcher that is active (it can be pending, however, which is a	1260	macro on a watcher that is active (it can be pending, however, which is a
…		…
961		1273
962	Example: Initialise and set an C<ev_io> watcher in one step.	1274	Example: Initialise and set an C<ev_io> watcher in one step.
963		1275
964	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1276	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
965		1277
966	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1278	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
967		1279
968	Starts (activates) the given watcher. Only active watchers will receive	1280	Starts (activates) the given watcher. Only active watchers will receive
969	events. If the watcher is already active nothing will happen.	1281	events. If the watcher is already active nothing will happen.
970		1282
971	Example: Start the C<ev_io> watcher that is being abused as example in this	1283	Example: Start the C<ev_io> watcher that is being abused as example in this
972	whole section.	1284	whole section.
973		1285
974	ev_io_start (EV_DEFAULT_UC, &w);	1286	ev_io_start (EV_DEFAULT_UC, &w);
975		1287
976	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1288	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
977		1289
978	Stops the given watcher if active, and clears the pending status (whether	1290	Stops the given watcher if active, and clears the pending status (whether
979	the watcher was active or not).	1291	the watcher was active or not).
980		1292
981	It is possible that stopped watchers are pending - for example,	1293	It is possible that stopped watchers are pending - for example,
…		…
1006	=item ev_cb_set (ev_TYPE *watcher, callback)	1318	=item ev_cb_set (ev_TYPE *watcher, callback)
1007		1319
1008	Change the callback. You can change the callback at virtually any time	1320	Change the callback. You can change the callback at virtually any time
1009	(modulo threads).	1321	(modulo threads).
1010		1322
1011	=item ev_set_priority (ev_TYPE *watcher, priority)	1323	=item ev_set_priority (ev_TYPE *watcher, int priority)
1012		1324
1013	=item int ev_priority (ev_TYPE *watcher)	1325	=item int ev_priority (ev_TYPE *watcher)
1014		1326
1015	Set and query the priority of the watcher. The priority is a small	1327	Set and query the priority of the watcher. The priority is a small
1016	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1328	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1017	(default: C<-2>). Pending watchers with higher priority will be invoked	1329	(default: C<-2>). Pending watchers with higher priority will be invoked
1018	before watchers with lower priority, but priority will not keep watchers	1330	before watchers with lower priority, but priority will not keep watchers
1019	from being executed (except for C<ev_idle> watchers).	1331	from being executed (except for C<ev_idle> watchers).
1020		1332
1021	This means that priorities are I<only> used for ordering callback
1022	invocation after new events have been received. This is useful, for
1023	example, to reduce latency after idling, or more often, to bind two
1024	watchers on the same event and make sure one is called first.
1025
1026	If you need to suppress invocation when higher priority events are pending	1333	If you need to suppress invocation when higher priority events are pending
1027	you need to look at C<ev_idle> watchers, which provide this functionality.	1334	you need to look at C<ev_idle> watchers, which provide this functionality.
1028		1335
1029	You I<must not> change the priority of a watcher as long as it is active or	1336	You I<must not> change the priority of a watcher as long as it is active or
1030	pending.	1337	pending.
1031		1338
		1339	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1340	fine, as long as you do not mind that the priority value you query might
		1341	or might not have been clamped to the valid range.
		1342
1032	The default priority used by watchers when no priority has been set is	1343	The default priority used by watchers when no priority has been set is
1033	always C<0>, which is supposed to not be too high and not be too low :).	1344	always C<0>, which is supposed to not be too high and not be too low :).
1034		1345
1035	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1346	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1036	fine, as long as you do not mind that the priority value you query might	1347	priorities.
1037	or might not have been adjusted to be within valid range.
1038		1348
1039	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1349	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1040		1350
1041	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1351	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1042	C<loop> nor C<revents> need to be valid as long as the watcher callback	1352	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1050	watcher isn't pending it does nothing and returns C<0>.	1360	watcher isn't pending it does nothing and returns C<0>.
1051		1361
1052	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1362	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1053	callback to be invoked, which can be accomplished with this function.	1363	callback to be invoked, which can be accomplished with this function.
1054		1364
		1365	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1366
		1367	Feeds the given event set into the event loop, as if the specified event
		1368	had happened for the specified watcher (which must be a pointer to an
		1369	initialised but not necessarily started event watcher). Obviously you must
		1370	not free the watcher as long as it has pending events.
		1371
		1372	Stopping the watcher, letting libev invoke it, or calling
		1373	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1374	not started in the first place.
		1375
		1376	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1377	functions that do not need a watcher.
		1378
1055	=back	1379	=back
1056		1380
		1381	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
		1382	OWN COMPOSITE WATCHERS> idioms.
1057		1383
1058	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1384	=head2 WATCHER STATES
1059		1385
1060	Each watcher has, by default, a member C<void *data> that you can change	1386	There are various watcher states mentioned throughout this manual -
1061	and read at any time: libev will completely ignore it. This can be used	1387	active, pending and so on. In this section these states and the rules to
1062	to associate arbitrary data with your watcher. If you need more data and	1388	transition between them will be described in more detail - and while these
1063	don't want to allocate memory and store a pointer to it in that data	1389	rules might look complicated, they usually do "the right thing".
1064	member, you can also "subclass" the watcher type and provide your own
1065	data:
1066		1390
1067	struct my_io	1391	=over 4
		1392
		1393	=item initialiased
		1394
		1395	Before a watcher can be registered with the event loop it has to be
		1396	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1397	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1398
		1399	In this state it is simply some block of memory that is suitable for
		1400	use in an event loop. It can be moved around, freed, reused etc. at
		1401	will - as long as you either keep the memory contents intact, or call
		1402	C<ev_TYPE_init> again.
		1403
		1404	=item started/running/active
		1405
		1406	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1407	property of the event loop, and is actively waiting for events. While in
		1408	this state it cannot be accessed (except in a few documented ways), moved,
		1409	freed or anything else - the only legal thing is to keep a pointer to it,
		1410	and call libev functions on it that are documented to work on active watchers.
		1411
		1412	=item pending
		1413
		1414	If a watcher is active and libev determines that an event it is interested
		1415	in has occurred (such as a timer expiring), it will become pending. It will
		1416	stay in this pending state until either it is stopped or its callback is
		1417	about to be invoked, so it is not normally pending inside the watcher
		1418	callback.
		1419
		1420	The watcher might or might not be active while it is pending (for example,
		1421	an expired non-repeating timer can be pending but no longer active). If it
		1422	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1423	but it is still property of the event loop at this time, so cannot be
		1424	moved, freed or reused. And if it is active the rules described in the
		1425	previous item still apply.
		1426
		1427	It is also possible to feed an event on a watcher that is not active (e.g.
		1428	via C<ev_feed_event>), in which case it becomes pending without being
		1429	active.
		1430
		1431	=item stopped
		1432
		1433	A watcher can be stopped implicitly by libev (in which case it might still
		1434	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1435	latter will clear any pending state the watcher might be in, regardless
		1436	of whether it was active or not, so stopping a watcher explicitly before
		1437	freeing it is often a good idea.
		1438
		1439	While stopped (and not pending) the watcher is essentially in the
		1440	initialised state, that is, it can be reused, moved, modified in any way
		1441	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1442	it again).
		1443
		1444	=back
		1445
		1446	=head2 WATCHER PRIORITY MODELS
		1447
		1448	Many event loops support I<watcher priorities>, which are usually small
		1449	integers that influence the ordering of event callback invocation
		1450	between watchers in some way, all else being equal.
		1451
		1452	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1453	description for the more technical details such as the actual priority
		1454	range.
		1455
		1456	There are two common ways how these these priorities are being interpreted
		1457	by event loops:
		1458
		1459	In the more common lock-out model, higher priorities "lock out" invocation
		1460	of lower priority watchers, which means as long as higher priority
		1461	watchers receive events, lower priority watchers are not being invoked.
		1462
		1463	The less common only-for-ordering model uses priorities solely to order
		1464	callback invocation within a single event loop iteration: Higher priority
		1465	watchers are invoked before lower priority ones, but they all get invoked
		1466	before polling for new events.
		1467
		1468	Libev uses the second (only-for-ordering) model for all its watchers
		1469	except for idle watchers (which use the lock-out model).
		1470
		1471	The rationale behind this is that implementing the lock-out model for
		1472	watchers is not well supported by most kernel interfaces, and most event
		1473	libraries will just poll for the same events again and again as long as
		1474	their callbacks have not been executed, which is very inefficient in the
		1475	common case of one high-priority watcher locking out a mass of lower
		1476	priority ones.
		1477
		1478	Static (ordering) priorities are most useful when you have two or more
		1479	watchers handling the same resource: a typical usage example is having an
		1480	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1481	timeouts. Under load, data might be received while the program handles
		1482	other jobs, but since timers normally get invoked first, the timeout
		1483	handler will be executed before checking for data. In that case, giving
		1484	the timer a lower priority than the I/O watcher ensures that I/O will be
		1485	handled first even under adverse conditions (which is usually, but not
		1486	always, what you want).
		1487
		1488	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1489	will only be executed when no same or higher priority watchers have
		1490	received events, they can be used to implement the "lock-out" model when
		1491	required.
		1492
		1493	For example, to emulate how many other event libraries handle priorities,
		1494	you can associate an C<ev_idle> watcher to each such watcher, and in
		1495	the normal watcher callback, you just start the idle watcher. The real
		1496	processing is done in the idle watcher callback. This causes libev to
		1497	continuously poll and process kernel event data for the watcher, but when
		1498	the lock-out case is known to be rare (which in turn is rare :), this is
		1499	workable.
		1500
		1501	Usually, however, the lock-out model implemented that way will perform
		1502	miserably under the type of load it was designed to handle. In that case,
		1503	it might be preferable to stop the real watcher before starting the
		1504	idle watcher, so the kernel will not have to process the event in case
		1505	the actual processing will be delayed for considerable time.
		1506
		1507	Here is an example of an I/O watcher that should run at a strictly lower
		1508	priority than the default, and which should only process data when no
		1509	other events are pending:
		1510
		1511	ev_idle idle; // actual processing watcher
		1512	ev_io io; // actual event watcher
		1513
		1514	static void
		1515	io_cb (EV_P_ ev_io *w, int revents)
1068	{	1516	{
1069	ev_io io;	1517	// stop the I/O watcher, we received the event, but
1070	int otherfd;	1518	// are not yet ready to handle it.
1071	void *somedata;	1519	ev_io_stop (EV_A_ w);
1072	struct whatever *mostinteresting;	1520
		1521	// start the idle watcher to handle the actual event.
		1522	// it will not be executed as long as other watchers
		1523	// with the default priority are receiving events.
		1524	ev_idle_start (EV_A_ &idle);
1073	};	1525	}
1074		1526
1075	...	1527	static void
1076	struct my_io w;	1528	idle_cb (EV_P_ ev_idle *w, int revents)
1077	ev_io_init (&w.io, my_cb, fd, EV_READ);
1078
1079	And since your callback will be called with a pointer to the watcher, you
1080	can cast it back to your own type:
1081
1082	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1083	{	1529	{
1084	struct my_io *w = (struct my_io *)w_;	1530	// actual processing
1085	...	1531	read (STDIN_FILENO, ...);
		1532
		1533	// have to start the I/O watcher again, as
		1534	// we have handled the event
		1535	ev_io_start (EV_P_ &io);
1086	}	1536	}
1087		1537
1088	More interesting and less C-conformant ways of casting your callback type	1538	// initialisation
1089	instead have been omitted.	1539	ev_idle_init (&idle, idle_cb);
		1540	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1541	ev_io_start (EV_DEFAULT_ &io);
1090		1542
1091	Another common scenario is to use some data structure with multiple	1543	In the "real" world, it might also be beneficial to start a timer, so that
1092	embedded watchers:	1544	low-priority connections can not be locked out forever under load. This
1093		1545	enables your program to keep a lower latency for important connections
1094	struct my_biggy	1546	during short periods of high load, while not completely locking out less
1095	{	1547	important ones.
1096	int some_data;
1097	ev_timer t1;
1098	ev_timer t2;
1099	}
1100
1101	In this case getting the pointer to C<my_biggy> is a bit more
1102	complicated: Either you store the address of your C<my_biggy> struct
1103	in the C<data> member of the watcher (for woozies), or you need to use
1104	some pointer arithmetic using C<offsetof> inside your watchers (for real
1105	programmers):
1106
1107	#include <stddef.h>
1108
1109	static void
1110	t1_cb (EV_P_ ev_timer *w, int revents)
1111	{
1112	struct my_biggy big = (struct my_biggy *
1113	(((char *)w) - offsetof (struct my_biggy, t1));
1114	}
1115
1116	static void
1117	t2_cb (EV_P_ ev_timer *w, int revents)
1118	{
1119	struct my_biggy big = (struct my_biggy *
1120	(((char *)w) - offsetof (struct my_biggy, t2));
1121	}
1122		1548
1123		1549
1124	=head1 WATCHER TYPES	1550	=head1 WATCHER TYPES
1125		1551
1126	This section describes each watcher in detail, but will not repeat	1552	This section describes each watcher in detail, but will not repeat
…		…
1150	In general you can register as many read and/or write event watchers per	1576	In general you can register as many read and/or write event watchers per
1151	fd as you want (as long as you don't confuse yourself). Setting all file	1577	fd as you want (as long as you don't confuse yourself). Setting all file
1152	descriptors to non-blocking mode is also usually a good idea (but not	1578	descriptors to non-blocking mode is also usually a good idea (but not
1153	required if you know what you are doing).	1579	required if you know what you are doing).
1154		1580
1155	If you cannot use non-blocking mode, then force the use of a
1156	known-to-be-good backend (at the time of this writing, this includes only
1157	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1158
1159	Another thing you have to watch out for is that it is quite easy to	1581	Another thing you have to watch out for is that it is quite easy to
1160	receive "spurious" readiness notifications, that is your callback might	1582	receive "spurious" readiness notifications, that is, your callback might
1161	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1583	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1162	because there is no data. Not only are some backends known to create a	1584	because there is no data. It is very easy to get into this situation even
1163	lot of those (for example Solaris ports), it is very easy to get into	1585	with a relatively standard program structure. Thus it is best to always
1164	this situation even with a relatively standard program structure. Thus	1586	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1165	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1166	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1587	preferable to a program hanging until some data arrives.
1167		1588
1168	If you cannot run the fd in non-blocking mode (for example you should	1589	If you cannot run the fd in non-blocking mode (for example you should
1169	not play around with an Xlib connection), then you have to separately	1590	not play around with an Xlib connection), then you have to separately
1170	re-test whether a file descriptor is really ready with a known-to-be good	1591	re-test whether a file descriptor is really ready with a known-to-be good
1171	interface such as poll (fortunately in our Xlib example, Xlib already	1592	interface such as poll (fortunately in the case of Xlib, it already does
1172	does this on its own, so its quite safe to use). Some people additionally	1593	this on its own, so its quite safe to use). Some people additionally
1173	use C<SIGALRM> and an interval timer, just to be sure you won't block	1594	use C<SIGALRM> and an interval timer, just to be sure you won't block
1174	indefinitely.	1595	indefinitely.
1175		1596
1176	But really, best use non-blocking mode.	1597	But really, best use non-blocking mode.
1177		1598
…		…
1205		1626
1206	There is no workaround possible except not registering events	1627	There is no workaround possible except not registering events
1207	for potentially C<dup ()>'ed file descriptors, or to resort to	1628	for potentially C<dup ()>'ed file descriptors, or to resort to
1208	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1629	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1209		1630
		1631	=head3 The special problem of files
		1632
		1633	Many people try to use C<select> (or libev) on file descriptors
		1634	representing files, and expect it to become ready when their program
		1635	doesn't block on disk accesses (which can take a long time on their own).
		1636
		1637	However, this cannot ever work in the "expected" way - you get a readiness
		1638	notification as soon as the kernel knows whether and how much data is
		1639	there, and in the case of open files, that's always the case, so you
		1640	always get a readiness notification instantly, and your read (or possibly
		1641	write) will still block on the disk I/O.
		1642
		1643	Another way to view it is that in the case of sockets, pipes, character
		1644	devices and so on, there is another party (the sender) that delivers data
		1645	on its own, but in the case of files, there is no such thing: the disk
		1646	will not send data on its own, simply because it doesn't know what you
		1647	wish to read - you would first have to request some data.
		1648
		1649	Since files are typically not-so-well supported by advanced notification
		1650	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1651	to files, even though you should not use it. The reason for this is
		1652	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1653	usually a tty, often a pipe, but also sometimes files or special devices
		1654	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1655	F</dev/urandom>), and even though the file might better be served with
		1656	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1657	it "just works" instead of freezing.
		1658
		1659	So avoid file descriptors pointing to files when you know it (e.g. use
		1660	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1661	when you rarely read from a file instead of from a socket, and want to
		1662	reuse the same code path.
		1663
1210	=head3 The special problem of fork	1664	=head3 The special problem of fork
1211		1665
1212	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1666	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1213	useless behaviour. Libev fully supports fork, but needs to be told about	1667	useless behaviour. Libev fully supports fork, but needs to be told about
1214	it in the child.	1668	it in the child if you want to continue to use it in the child.
1215		1669
1216	To support fork in your programs, you either have to call	1670	To support fork in your child processes, you have to call C<ev_loop_fork
1217	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1671	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1218	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1672	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1219	C<EVBACKEND_POLL>.
1220		1673
1221	=head3 The special problem of SIGPIPE	1674	=head3 The special problem of SIGPIPE
1222		1675
1223	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1676	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1224	when writing to a pipe whose other end has been closed, your program gets	1677	when writing to a pipe whose other end has been closed, your program gets
…		…
1227		1680
1228	So when you encounter spurious, unexplained daemon exits, make sure you	1681	So when you encounter spurious, unexplained daemon exits, make sure you
1229	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1682	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1230	somewhere, as that would have given you a big clue).	1683	somewhere, as that would have given you a big clue).
1231		1684
		1685	=head3 The special problem of accept()ing when you can't
		1686
		1687	Many implementations of the POSIX C<accept> function (for example,
		1688	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1689	connection from the pending queue in all error cases.
		1690
		1691	For example, larger servers often run out of file descriptors (because
		1692	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1693	rejecting the connection, leading to libev signalling readiness on
		1694	the next iteration again (the connection still exists after all), and
		1695	typically causing the program to loop at 100% CPU usage.
		1696
		1697	Unfortunately, the set of errors that cause this issue differs between
		1698	operating systems, there is usually little the app can do to remedy the
		1699	situation, and no known thread-safe method of removing the connection to
		1700	cope with overload is known (to me).
		1701
		1702	One of the easiest ways to handle this situation is to just ignore it
		1703	- when the program encounters an overload, it will just loop until the
		1704	situation is over. While this is a form of busy waiting, no OS offers an
		1705	event-based way to handle this situation, so it's the best one can do.
		1706
		1707	A better way to handle the situation is to log any errors other than
		1708	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1709	messages, and continue as usual, which at least gives the user an idea of
		1710	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1711	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1712	usage.
		1713
		1714	If your program is single-threaded, then you could also keep a dummy file
		1715	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1716	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1717	close that fd, and create a new dummy fd. This will gracefully refuse
		1718	clients under typical overload conditions.
		1719
		1720	The last way to handle it is to simply log the error and C<exit>, as
		1721	is often done with C<malloc> failures, but this results in an easy
		1722	opportunity for a DoS attack.
1232		1723
1233	=head3 Watcher-Specific Functions	1724	=head3 Watcher-Specific Functions
1234		1725
1235	=over 4	1726	=over 4
1236		1727
…		…
1268	...	1759	...
1269	struct ev_loop *loop = ev_default_init (0);	1760	struct ev_loop *loop = ev_default_init (0);
1270	ev_io stdin_readable;	1761	ev_io stdin_readable;
1271	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1762	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1272	ev_io_start (loop, &stdin_readable);	1763	ev_io_start (loop, &stdin_readable);
1273	ev_loop (loop, 0);	1764	ev_run (loop, 0);
1274		1765
1275		1766
1276	=head2 C<ev_timer> - relative and optionally repeating timeouts	1767	=head2 C<ev_timer> - relative and optionally repeating timeouts
1277		1768
1278	Timer watchers are simple relative timers that generate an event after a	1769	Timer watchers are simple relative timers that generate an event after a
…		…
1283	year, it will still time out after (roughly) one hour. "Roughly" because	1774	year, it will still time out after (roughly) one hour. "Roughly" because
1284	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1775	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1285	monotonic clock option helps a lot here).	1776	monotonic clock option helps a lot here).
1286		1777
1287	The callback is guaranteed to be invoked only I<after> its timeout has	1778	The callback is guaranteed to be invoked only I<after> its timeout has
1288	passed, but if multiple timers become ready during the same loop iteration	1779	passed (not I<at>, so on systems with very low-resolution clocks this
1289	then order of execution is undefined.	1780	might introduce a small delay, see "the special problem of being too
		1781	early", below). If multiple timers become ready during the same loop
		1782	iteration then the ones with earlier time-out values are invoked before
		1783	ones of the same priority with later time-out values (but this is no
		1784	longer true when a callback calls C<ev_run> recursively).
1290		1785
1291	=head3 Be smart about timeouts	1786	=head3 Be smart about timeouts
1292		1787
1293	Many real-world problems invole some kind of time-out, usually for error	1788	Many real-world problems involve some kind of timeout, usually for error
1294	recovery. A typical example is an HTTP request - if the other side hangs,	1789	recovery. A typical example is an HTTP request - if the other side hangs,
1295	you want to raise some error after a while.	1790	you want to raise some error after a while.
1296		1791
1297	Here are some ways on how to handle this problem, from simple and	1792	What follows are some ways to handle this problem, from obvious and
1298	inefficient to very efficient.	1793	inefficient to smart and efficient.
1299		1794
1300	In the following examples a 60 second activity timeout is assumed - a	1795	In the following, a 60 second activity timeout is assumed - a timeout that
1301	timeout that gets reset to 60 seconds each time some data ("a lifesign")	1796	gets reset to 60 seconds each time there is activity (e.g. each time some
1302	was received.	1797	data or other life sign was received).
1303		1798
1304	=over 4	1799	=over 4
1305		1800
1306	=item 1. Use a timer and stop, reinitialise, start it on activity.	1801	=item 1. Use a timer and stop, reinitialise and start it on activity.
1307		1802
1308	This is the most obvious, but not the most simple way: In the beginning,	1803	This is the most obvious, but not the most simple way: In the beginning,
1309	start the watcher:	1804	start the watcher:
1310		1805
1311	ev_timer_init (timer, callback, 60., 0.);	1806	ev_timer_init (timer, callback, 60., 0.);
1312	ev_timer_start (loop, timer);	1807	ev_timer_start (loop, timer);
1313		1808
1314	Then, each time there is some activity, C<ev_timer_stop> the timer,	1809	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
1315	initialise it again, and start it:	1810	and start it again:
1316		1811
1317	ev_timer_stop (loop, timer);	1812	ev_timer_stop (loop, timer);
1318	ev_timer_set (timer, 60., 0.);	1813	ev_timer_set (timer, 60., 0.);
1319	ev_timer_start (loop, timer);	1814	ev_timer_start (loop, timer);
1320		1815
1321	This is relatively simple to implement, but means that each time there	1816	This is relatively simple to implement, but means that each time there is
1322	is some activity, libev will first have to remove the timer from it's	1817	some activity, libev will first have to remove the timer from its internal
1323	internal data strcuture and then add it again.	1818	data structure and then add it again. Libev tries to be fast, but it's
		1819	still not a constant-time operation.
1324		1820
1325	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.	1821	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
1326		1822
1327	This is the easiest way, and involves using C<ev_timer_again> instead of	1823	This is the easiest way, and involves using C<ev_timer_again> instead of
1328	C<ev_timer_start>.	1824	C<ev_timer_start>.
1329		1825
1330	For this, configure an C<ev_timer> with a C<repeat> value of C<60> and	1826	To implement this, configure an C<ev_timer> with a C<repeat> value
1331	then call C<ev_timer_again> at start and each time you successfully read	1827	of C<60> and then call C<ev_timer_again> at start and each time you
1332	or write some data. If you go into an idle state where you do not expect	1828	successfully read or write some data. If you go into an idle state where
1333	data to travel on the socket, you can C<ev_timer_stop> the timer, and	1829	you do not expect data to travel on the socket, you can C<ev_timer_stop>
1334	C<ev_timer_again> will automatically restart it if need be.	1830	the timer, and C<ev_timer_again> will automatically restart it if need be.
1335		1831
1336	That means you can ignore the C<after> value and C<ev_timer_start>	1832	That means you can ignore both the C<ev_timer_start> function and the
1337	altogether and only ever use the C<repeat> value and C<ev_timer_again>.	1833	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1834	member and C<ev_timer_again>.
1338		1835
1339	At start:	1836	At start:
1340		1837
1341	ev_timer_init (timer, callback, 0., 60.);	1838	ev_init (timer, callback);
		1839	timer->repeat = 60.;
1342	ev_timer_again (loop, timer);	1840	ev_timer_again (loop, timer);
1343		1841
1344	Each time you receive some data:	1842	Each time there is some activity:
1345		1843
1346	ev_timer_again (loop, timer);	1844	ev_timer_again (loop, timer);
1347		1845
1348	It is even possible to change the time-out on the fly:	1846	It is even possible to change the time-out on the fly, regardless of
		1847	whether the watcher is active or not:
1349		1848
1350	timer->repeat = 30.;	1849	timer->repeat = 30.;
1351	ev_timer_again (loop, timer);	1850	ev_timer_again (loop, timer);
1352		1851
1353	This is slightly more efficient then stopping/starting the timer each time	1852	This is slightly more efficient then stopping/starting the timer each time
1354	you want to modify its timeout value, as libev does not have to completely	1853	you want to modify its timeout value, as libev does not have to completely
1355	remove and re-insert the timer from/into it's internal data structure.	1854	remove and re-insert the timer from/into its internal data structure.
		1855
		1856	It is, however, even simpler than the "obvious" way to do it.
1356		1857
1357	=item 3. Let the timer time out, but then re-arm it as required.	1858	=item 3. Let the timer time out, but then re-arm it as required.
1358		1859
1359	This method is more tricky, but usually most efficient: Most timeouts are	1860	This method is more tricky, but usually most efficient: Most timeouts are
1360	relatively long compared to the loop iteration time - in our example,	1861	relatively long compared to the intervals between other activity - in
1361	within 60 seconds, there are usually many I/O events with associated	1862	our example, within 60 seconds, there are usually many I/O events with
1362	activity resets.	1863	associated activity resets.
1363		1864
1364	In this case, it would be more efficient to leave the C<ev_timer> alone,	1865	In this case, it would be more efficient to leave the C<ev_timer> alone,
1365	but remember the time of last activity, and check for a real timeout only	1866	but remember the time of last activity, and check for a real timeout only
1366	within the callback:	1867	within the callback:
1367		1868
		1869	ev_tstamp timeout = 60.;
1368	ev_tstamp last_activity; // time of last activity	1870	ev_tstamp last_activity; // time of last activity
		1871	ev_timer timer;
1369		1872
1370	static void	1873	static void
1371	callback (EV_P_ ev_timer *w, int revents)	1874	callback (EV_P_ ev_timer *w, int revents)
1372	{	1875	{
1373	ev_tstamp now = ev_now (EV_A);	1876	// calculate when the timeout would happen
1374	ev_tstamp timeout = last_activity + 60.;	1877	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1375		1878
1376	// if last_activity is older than now - timeout, we did time out	1879	// if negative, it means we the timeout already occured
1377	if (timeout < now)	1880	if (after < 0.)
1378	{	1881	{
1379	// timeout occured, take action	1882	// timeout occurred, take action
1380	}	1883	}
1381	else	1884	else
1382	{	1885	{
1383	// callback was invoked, but there was some activity, re-arm	1886	// callback was invoked, but there was some recent
1384	// to fire in last_activity + 60.	1887	// activity. simply restart the timer to time out
1385	w->again = timeout - now;	1888	// after "after" seconds, which is the earliest time
		1889	// the timeout can occur.
		1890	ev_timer_set (w, after, 0.);
1386	ev_timer_again (EV_A_ w);	1891	ev_timer_start (EV_A_ w);
1387	}	1892	}
1388	}	1893	}
1389		1894
1390	To summarise the callback: first calculate the real time-out (defined as	1895	To summarise the callback: first calculate in how many seconds the
1391	"60 seconds after the last activity"), then check if that time has been	1896	timeout will occur (by calculating the absolute time when it would occur,
1392	reached, which means there was a real timeout. Otherwise the callback was	1897	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1393	invoked too early (timeout is in the future), so re-schedule the timer to	1898	(EV_A)> from that).
1394	fire at that future time.
1395		1899
1396	Note how C<ev_timer_again> is used, taking advantage of the	1900	If this value is negative, then we are already past the timeout, i.e. we
1397	C<ev_timer_again> optimisation when the timer is already running.	1901	timed out, and need to do whatever is needed in this case.
1398		1902
		1903	Otherwise, we now the earliest time at which the timeout would trigger,
		1904	and simply start the timer with this timeout value.
		1905
		1906	In other words, each time the callback is invoked it will check whether
		1907	the timeout cocured. If not, it will simply reschedule itself to check
		1908	again at the earliest time it could time out. Rinse. Repeat.
		1909
1399	This scheme causes more callback invocations (about one every 60 seconds),	1910	This scheme causes more callback invocations (about one every 60 seconds
1400	but virtually no calls to libev to change the timeout.	1911	minus half the average time between activity), but virtually no calls to
		1912	libev to change the timeout.
1401		1913
1402	To start the timer, simply intiialise the watcher and C<last_activity>,	1914	To start the machinery, simply initialise the watcher and set
1403	then call the callback:	1915	C<last_activity> to the current time (meaning there was some activity just
		1916	now), then call the callback, which will "do the right thing" and start
		1917	the timer:
1404		1918
		1919	last_activity = ev_now (EV_A);
1405	ev_timer_init (timer, callback);	1920	ev_init (&timer, callback);
		1921	callback (EV_A_ &timer, 0);
		1922
		1923	When there is some activity, simply store the current time in
		1924	C<last_activity>, no libev calls at all:
		1925
		1926	if (activity detected)
1406	last_activity = ev_now (loop);	1927	last_activity = ev_now (EV_A);
1407	callback (loop, timer, EV_TIMEOUT);
1408		1928
1409	And when there is some activity, simply remember the time in	1929	When your timeout value changes, then the timeout can be changed by simply
1410	C<last_activity>:	1930	providing a new value, stopping the timer and calling the callback, which
		1931	will agaion do the right thing (for example, time out immediately :).
1411		1932
1412	last_actiivty = ev_now (loop);	1933	timeout = new_value;
		1934	ev_timer_stop (EV_A_ &timer);
		1935	callback (EV_A_ &timer, 0);
1413		1936
1414	This technique is slightly more complex, but in most cases where the	1937	This technique is slightly more complex, but in most cases where the
1415	time-out is unlikely to be triggered, much more efficient.	1938	time-out is unlikely to be triggered, much more efficient.
1416		1939
		1940	=item 4. Wee, just use a double-linked list for your timeouts.
		1941
		1942	If there is not one request, but many thousands (millions...), all
		1943	employing some kind of timeout with the same timeout value, then one can
		1944	do even better:
		1945
		1946	When starting the timeout, calculate the timeout value and put the timeout
		1947	at the I<end> of the list.
		1948
		1949	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1950	the list is expected to fire (for example, using the technique #3).
		1951
		1952	When there is some activity, remove the timer from the list, recalculate
		1953	the timeout, append it to the end of the list again, and make sure to
		1954	update the C<ev_timer> if it was taken from the beginning of the list.
		1955
		1956	This way, one can manage an unlimited number of timeouts in O(1) time for
		1957	starting, stopping and updating the timers, at the expense of a major
		1958	complication, and having to use a constant timeout. The constant timeout
		1959	ensures that the list stays sorted.
		1960
1417	=back	1961	=back
1418		1962
		1963	So which method the best?
		1964
		1965	Method #2 is a simple no-brain-required solution that is adequate in most
		1966	situations. Method #3 requires a bit more thinking, but handles many cases
		1967	better, and isn't very complicated either. In most case, choosing either
		1968	one is fine, with #3 being better in typical situations.
		1969
		1970	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1971	rather complicated, but extremely efficient, something that really pays
		1972	off after the first million or so of active timers, i.e. it's usually
		1973	overkill :)
		1974
		1975	=head3 The special problem of being too early
		1976
		1977	If you ask a timer to call your callback after three seconds, then
		1978	you expect it to be invoked after three seconds - but of course, this
		1979	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		1980	guaranteed to any precision by libev - imagine somebody suspending the
		1981	process with a STOP signal for a few hours for example.
		1982
		1983	So, libev tries to invoke your callback as soon as possible I<after> the
		1984	delay has occurred, but cannot guarantee this.
		1985
		1986	A less obvious failure mode is calling your callback too early: many event
		1987	loops compare timestamps with a "elapsed delay >= requested delay", but
		1988	this can cause your callback to be invoked much earlier than you would
		1989	expect.
		1990
		1991	To see why, imagine a system with a clock that only offers full second
		1992	resolution (think windows if you can't come up with a broken enough OS
		1993	yourself). If you schedule a one-second timer at the time 500.9, then the
		1994	event loop will schedule your timeout to elapse at a system time of 500
		1995	(500.9 truncated to the resolution) + 1, or 501.
		1996
		1997	If an event library looks at the timeout 0.1s later, it will see "501 >=
		1998	501" and invoke the callback 0.1s after it was started, even though a
		1999	one-second delay was requested - this is being "too early", despite best
		2000	intentions.
		2001
		2002	This is the reason why libev will never invoke the callback if the elapsed
		2003	delay equals the requested delay, but only when the elapsed delay is
		2004	larger than the requested delay. In the example above, libev would only invoke
		2005	the callback at system time 502, or 1.1s after the timer was started.
		2006
		2007	So, while libev cannot guarantee that your callback will be invoked
		2008	exactly when requested, it I<can> and I<does> guarantee that the requested
		2009	delay has actually elapsed, or in other words, it always errs on the "too
		2010	late" side of things.
		2011
1419	=head3 The special problem of time updates	2012	=head3 The special problem of time updates
1420		2013
1421	Establishing the current time is a costly operation (it usually takes at	2014	Establishing the current time is a costly operation (it usually takes
1422	least two system calls): EV therefore updates its idea of the current	2015	at least one system call): EV therefore updates its idea of the current
1423	time only before and after C<ev_loop> collects new events, which causes a	2016	time only before and after C<ev_run> collects new events, which causes a
1424	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2017	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1425	lots of events in one iteration.	2018	lots of events in one iteration.
1426		2019
1427	The relative timeouts are calculated relative to the C<ev_now ()>	2020	The relative timeouts are calculated relative to the C<ev_now ()>
1428	time. This is usually the right thing as this timestamp refers to the time	2021	time. This is usually the right thing as this timestamp refers to the time
…		…
1434		2027
1435	If the event loop is suspended for a long time, you can also force an	2028	If the event loop is suspended for a long time, you can also force an
1436	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2029	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1437	()>.	2030	()>.
1438		2031
		2032	=head3 The special problem of unsynchronised clocks
		2033
		2034	Modern systems have a variety of clocks - libev itself uses the normal
		2035	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2036	jumps).
		2037
		2038	Neither of these clocks is synchronised with each other or any other clock
		2039	on the system, so C<ev_time ()> might return a considerably different time
		2040	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2041	a call to C<gettimeofday> might return a second count that is one higher
		2042	than a directly following call to C<time>.
		2043
		2044	The moral of this is to only compare libev-related timestamps with
		2045	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2046	a second or so.
		2047
		2048	One more problem arises due to this lack of synchronisation: if libev uses
		2049	the system monotonic clock and you compare timestamps from C<ev_time>
		2050	or C<ev_now> from when you started your timer and when your callback is
		2051	invoked, you will find that sometimes the callback is a bit "early".
		2052
		2053	This is because C<ev_timer>s work in real time, not wall clock time, so
		2054	libev makes sure your callback is not invoked before the delay happened,
		2055	I<measured according to the real time>, not the system clock.
		2056
		2057	If your timeouts are based on a physical timescale (e.g. "time out this
		2058	connection after 100 seconds") then this shouldn't bother you as it is
		2059	exactly the right behaviour.
		2060
		2061	If you want to compare wall clock/system timestamps to your timers, then
		2062	you need to use C<ev_periodic>s, as these are based on the wall clock
		2063	time, where your comparisons will always generate correct results.
		2064
		2065	=head3 The special problems of suspended animation
		2066
		2067	When you leave the server world it is quite customary to hit machines that
		2068	can suspend/hibernate - what happens to the clocks during such a suspend?
		2069
		2070	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		2071	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		2072	to run until the system is suspended, but they will not advance while the
		2073	system is suspended. That means, on resume, it will be as if the program
		2074	was frozen for a few seconds, but the suspend time will not be counted
		2075	towards C<ev_timer> when a monotonic clock source is used. The real time
		2076	clock advanced as expected, but if it is used as sole clocksource, then a
		2077	long suspend would be detected as a time jump by libev, and timers would
		2078	be adjusted accordingly.
		2079
		2080	I would not be surprised to see different behaviour in different between
		2081	operating systems, OS versions or even different hardware.
		2082
		2083	The other form of suspend (job control, or sending a SIGSTOP) will see a
		2084	time jump in the monotonic clocks and the realtime clock. If the program
		2085	is suspended for a very long time, and monotonic clock sources are in use,
		2086	then you can expect C<ev_timer>s to expire as the full suspension time
		2087	will be counted towards the timers. When no monotonic clock source is in
		2088	use, then libev will again assume a timejump and adjust accordingly.
		2089
		2090	It might be beneficial for this latter case to call C<ev_suspend>
		2091	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		2092	deterministic behaviour in this case (you can do nothing against
		2093	C<SIGSTOP>).
		2094
1439	=head3 Watcher-Specific Functions and Data Members	2095	=head3 Watcher-Specific Functions and Data Members
1440		2096
1441	=over 4	2097	=over 4
1442		2098
1443	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2099	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1456	keep up with the timer (because it takes longer than those 10 seconds to	2112	keep up with the timer (because it takes longer than those 10 seconds to
1457	do stuff) the timer will not fire more than once per event loop iteration.	2113	do stuff) the timer will not fire more than once per event loop iteration.
1458		2114
1459	=item ev_timer_again (loop, ev_timer *)	2115	=item ev_timer_again (loop, ev_timer *)
1460		2116
1461	This will act as if the timer timed out and restart it again if it is	2117	This will act as if the timer timed out, and restarts it again if it is
1462	repeating. The exact semantics are:	2118	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2119	timeout to the C<repeat> value and calling C<ev_timer_start>.
1463		2120
		2121	The exact semantics are as in the following rules, all of which will be
		2122	applied to the watcher:
		2123
		2124	=over 4
		2125
1464	If the timer is pending, its pending status is cleared.	2126	=item If the timer is pending, the pending status is always cleared.
1465		2127
1466	If the timer is started but non-repeating, stop it (as if it timed out).	2128	=item If the timer is started but non-repeating, stop it (as if it timed
		2129	out, without invoking it).
1467		2130
1468	If the timer is repeating, either start it if necessary (with the	2131	=item If the timer is repeating, make the C<repeat> value the new timeout
1469	C<repeat> value), or reset the running timer to the C<repeat> value.	2132	and start the timer, if necessary.
1470		2133
		2134	=back
		2135
1471	This sounds a bit complicated, see "Be smart about timeouts", above, for a	2136	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1472	usage example.	2137	usage example.
		2138
		2139	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2140
		2141	Returns the remaining time until a timer fires. If the timer is active,
		2142	then this time is relative to the current event loop time, otherwise it's
		2143	the timeout value currently configured.
		2144
		2145	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2146	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2147	will return C<4>. When the timer expires and is restarted, it will return
		2148	roughly C<7> (likely slightly less as callback invocation takes some time,
		2149	too), and so on.
1473		2150
1474	=item ev_tstamp repeat [read-write]	2151	=item ev_tstamp repeat [read-write]
1475		2152
1476	The current C<repeat> value. Will be used each time the watcher times out	2153	The current C<repeat> value. Will be used each time the watcher times out
1477	or C<ev_timer_again> is called, and determines the next timeout (if any),	2154	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1503	}	2180	}
1504		2181
1505	ev_timer mytimer;	2182	ev_timer mytimer;
1506	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2183	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1507	ev_timer_again (&mytimer); /* start timer */	2184	ev_timer_again (&mytimer); /* start timer */
1508	ev_loop (loop, 0);	2185	ev_run (loop, 0);
1509		2186
1510	// and in some piece of code that gets executed on any "activity":	2187	// and in some piece of code that gets executed on any "activity":
1511	// reset the timeout to start ticking again at 10 seconds	2188	// reset the timeout to start ticking again at 10 seconds
1512	ev_timer_again (&mytimer);	2189	ev_timer_again (&mytimer);
1513		2190
…		…
1515	=head2 C<ev_periodic> - to cron or not to cron?	2192	=head2 C<ev_periodic> - to cron or not to cron?
1516		2193
1517	Periodic watchers are also timers of a kind, but they are very versatile	2194	Periodic watchers are also timers of a kind, but they are very versatile
1518	(and unfortunately a bit complex).	2195	(and unfortunately a bit complex).
1519		2196
1520	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2197	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1521	but on wall clock time (absolute time). You can tell a periodic watcher	2198	relative time, the physical time that passes) but on wall clock time
1522	to trigger after some specific point in time. For example, if you tell a	2199	(absolute time, the thing you can read on your calender or clock). The
1523	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	2200	difference is that wall clock time can run faster or slower than real
1524	+ 10.>, that is, an absolute time not a delay) and then reset your system	2201	time, and time jumps are not uncommon (e.g. when you adjust your
1525	clock to January of the previous year, then it will take more than year	2202	wrist-watch).
1526	to trigger the event (unlike an C<ev_timer>, which would still trigger
1527	roughly 10 seconds later as it uses a relative timeout).
1528		2203
		2204	You can tell a periodic watcher to trigger after some specific point
		2205	in time: for example, if you tell a periodic watcher to trigger "in 10
		2206	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2207	not a delay) and then reset your system clock to January of the previous
		2208	year, then it will take a year or more to trigger the event (unlike an
		2209	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2210	it, as it uses a relative timeout).
		2211
1529	C<ev_periodic>s can also be used to implement vastly more complex timers,	2212	C<ev_periodic> watchers can also be used to implement vastly more complex
1530	such as triggering an event on each "midnight, local time", or other	2213	timers, such as triggering an event on each "midnight, local time", or
1531	complicated rules.	2214	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2215	those cannot react to time jumps.
1532		2216
1533	As with timers, the callback is guaranteed to be invoked only when the	2217	As with timers, the callback is guaranteed to be invoked only when the
1534	time (C<at>) has passed, but if multiple periodic timers become ready	2218	point in time where it is supposed to trigger has passed. If multiple
1535	during the same loop iteration, then order of execution is undefined.	2219	timers become ready during the same loop iteration then the ones with
		2220	earlier time-out values are invoked before ones with later time-out values
		2221	(but this is no longer true when a callback calls C<ev_run> recursively).
1536		2222
1537	=head3 Watcher-Specific Functions and Data Members	2223	=head3 Watcher-Specific Functions and Data Members
1538		2224
1539	=over 4	2225	=over 4
1540		2226
1541	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2227	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1542		2228
1543	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2229	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1544		2230
1545	Lots of arguments, lets sort it out... There are basically three modes of	2231	Lots of arguments, let's sort it out... There are basically three modes of
1546	operation, and we will explain them from simplest to most complex:	2232	operation, and we will explain them from simplest to most complex:
1547		2233
1548	=over 4	2234	=over 4
1549		2235
1550	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2236	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1551		2237
1552	In this configuration the watcher triggers an event after the wall clock	2238	In this configuration the watcher triggers an event after the wall clock
1553	time C<at> has passed. It will not repeat and will not adjust when a time	2239	time C<offset> has passed. It will not repeat and will not adjust when a
1554	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2240	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1555	only run when the system clock reaches or surpasses this time.	2241	will be stopped and invoked when the system clock reaches or surpasses
		2242	this point in time.
1556		2243
1557	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2244	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1558		2245
1559	In this mode the watcher will always be scheduled to time out at the next	2246	In this mode the watcher will always be scheduled to time out at the next
1560	C<at + N * interval> time (for some integer N, which can also be negative)	2247	C<offset + N * interval> time (for some integer N, which can also be
1561	and then repeat, regardless of any time jumps.	2248	negative) and then repeat, regardless of any time jumps. The C<offset>
		2249	argument is merely an offset into the C<interval> periods.
1562		2250
1563	This can be used to create timers that do not drift with respect to the	2251	This can be used to create timers that do not drift with respect to the
1564	system clock, for example, here is a C<ev_periodic> that triggers each	2252	system clock, for example, here is an C<ev_periodic> that triggers each
1565	hour, on the hour:	2253	hour, on the hour (with respect to UTC):
1566		2254
1567	ev_periodic_set (&periodic, 0., 3600., 0);	2255	ev_periodic_set (&periodic, 0., 3600., 0);
1568		2256
1569	This doesn't mean there will always be 3600 seconds in between triggers,	2257	This doesn't mean there will always be 3600 seconds in between triggers,
1570	but only that the callback will be called when the system time shows a	2258	but only that the callback will be called when the system time shows a
1571	full hour (UTC), or more correctly, when the system time is evenly divisible	2259	full hour (UTC), or more correctly, when the system time is evenly divisible
1572	by 3600.	2260	by 3600.
1573		2261
1574	Another way to think about it (for the mathematically inclined) is that	2262	Another way to think about it (for the mathematically inclined) is that
1575	C<ev_periodic> will try to run the callback in this mode at the next possible	2263	C<ev_periodic> will try to run the callback in this mode at the next possible
1576	time where C<time = at (mod interval)>, regardless of any time jumps.	2264	time where C<time = offset (mod interval)>, regardless of any time jumps.
1577		2265
1578	For numerical stability it is preferable that the C<at> value is near	2266	The C<interval> I<MUST> be positive, and for numerical stability, the
1579	C<ev_now ()> (the current time), but there is no range requirement for	2267	interval value should be higher than C<1/8192> (which is around 100
1580	this value, and in fact is often specified as zero.	2268	microseconds) and C<offset> should be higher than C<0> and should have
		2269	at most a similar magnitude as the current time (say, within a factor of
		2270	ten). Typical values for offset are, in fact, C<0> or something between
		2271	C<0> and C<interval>, which is also the recommended range.
1581		2272
1582	Note also that there is an upper limit to how often a timer can fire (CPU	2273	Note also that there is an upper limit to how often a timer can fire (CPU
1583	speed for example), so if C<interval> is very small then timing stability	2274	speed for example), so if C<interval> is very small then timing stability
1584	will of course deteriorate. Libev itself tries to be exact to be about one	2275	will of course deteriorate. Libev itself tries to be exact to be about one
1585	millisecond (if the OS supports it and the machine is fast enough).	2276	millisecond (if the OS supports it and the machine is fast enough).
1586		2277
1587	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2278	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1588		2279
1589	In this mode the values for C<interval> and C<at> are both being	2280	In this mode the values for C<interval> and C<offset> are both being
1590	ignored. Instead, each time the periodic watcher gets scheduled, the	2281	ignored. Instead, each time the periodic watcher gets scheduled, the
1591	reschedule callback will be called with the watcher as first, and the	2282	reschedule callback will be called with the watcher as first, and the
1592	current time as second argument.	2283	current time as second argument.
1593		2284
1594	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2285	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1595	ever, or make ANY event loop modifications whatsoever>.	2286	or make ANY other event loop modifications whatsoever, unless explicitly
		2287	allowed by documentation here>.
1596		2288
1597	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2289	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1598	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2290	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1599	only event loop modification you are allowed to do).	2291	only event loop modification you are allowed to do).
1600		2292
…		…
1630	a different time than the last time it was called (e.g. in a crond like	2322	a different time than the last time it was called (e.g. in a crond like
1631	program when the crontabs have changed).	2323	program when the crontabs have changed).
1632		2324
1633	=item ev_tstamp ev_periodic_at (ev_periodic *)	2325	=item ev_tstamp ev_periodic_at (ev_periodic *)
1634		2326
1635	When active, returns the absolute time that the watcher is supposed to	2327	When active, returns the absolute time that the watcher is supposed
1636	trigger next.	2328	to trigger next. This is not the same as the C<offset> argument to
		2329	C<ev_periodic_set>, but indeed works even in interval and manual
		2330	rescheduling modes.
1637		2331
1638	=item ev_tstamp offset [read-write]	2332	=item ev_tstamp offset [read-write]
1639		2333
1640	When repeating, this contains the offset value, otherwise this is the	2334	When repeating, this contains the offset value, otherwise this is the
1641	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2335	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2336	although libev might modify this value for better numerical stability).
1642		2337
1643	Can be modified any time, but changes only take effect when the periodic	2338	Can be modified any time, but changes only take effect when the periodic
1644	timer fires or C<ev_periodic_again> is being called.	2339	timer fires or C<ev_periodic_again> is being called.
1645		2340
1646	=item ev_tstamp interval [read-write]	2341	=item ev_tstamp interval [read-write]
…		…
1662	Example: Call a callback every hour, or, more precisely, whenever the	2357	Example: Call a callback every hour, or, more precisely, whenever the
1663	system time is divisible by 3600. The callback invocation times have	2358	system time is divisible by 3600. The callback invocation times have
1664	potentially a lot of jitter, but good long-term stability.	2359	potentially a lot of jitter, but good long-term stability.
1665		2360
1666	static void	2361	static void
1667	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2362	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1668	{	2363	{
1669	... its now a full hour (UTC, or TAI or whatever your clock follows)	2364	... its now a full hour (UTC, or TAI or whatever your clock follows)
1670	}	2365	}
1671		2366
1672	ev_periodic hourly_tick;	2367	ev_periodic hourly_tick;
…		…
1695		2390
1696	=head2 C<ev_signal> - signal me when a signal gets signalled!	2391	=head2 C<ev_signal> - signal me when a signal gets signalled!
1697		2392
1698	Signal watchers will trigger an event when the process receives a specific	2393	Signal watchers will trigger an event when the process receives a specific
1699	signal one or more times. Even though signals are very asynchronous, libev	2394	signal one or more times. Even though signals are very asynchronous, libev
1700	will try it's best to deliver signals synchronously, i.e. as part of the	2395	will try its best to deliver signals synchronously, i.e. as part of the
1701	normal event processing, like any other event.	2396	normal event processing, like any other event.
1702		2397
1703	If you want signals asynchronously, just use C<sigaction> as you would	2398	If you want signals to be delivered truly asynchronously, just use
1704	do without libev and forget about sharing the signal. You can even use	2399	C<sigaction> as you would do without libev and forget about sharing
1705	C<ev_async> from a signal handler to synchronously wake up an event loop.	2400	the signal. You can even use C<ev_async> from a signal handler to
		2401	synchronously wake up an event loop.
1706		2402
1707	You can configure as many watchers as you like per signal. Only when the	2403	You can configure as many watchers as you like for the same signal, but
		2404	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2405	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2406	C<SIGINT> in both the default loop and another loop at the same time. At
		2407	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2408
1708	first watcher gets started will libev actually register a signal handler	2409	When the first watcher gets started will libev actually register something
1709	with the kernel (thus it coexists with your own signal handlers as long as	2410	with the kernel (thus it coexists with your own signal handlers as long as
1710	you don't register any with libev for the same signal). Similarly, when	2411	you don't register any with libev for the same signal).
1711	the last signal watcher for a signal is stopped, libev will reset the
1712	signal handler to SIG_DFL (regardless of what it was set to before).
1713		2412
1714	If possible and supported, libev will install its handlers with	2413	If possible and supported, libev will install its handlers with
1715	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2414	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1716	interrupted. If you have a problem with system calls getting interrupted by	2415	not be unduly interrupted. If you have a problem with system calls getting
1717	signals you can block all signals in an C<ev_check> watcher and unblock	2416	interrupted by signals you can block all signals in an C<ev_check> watcher
1718	them in an C<ev_prepare> watcher.	2417	and unblock them in an C<ev_prepare> watcher.
		2418
		2419	=head3 The special problem of inheritance over fork/execve/pthread_create
		2420
		2421	Both the signal mask (C<sigprocmask>) and the signal disposition
		2422	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2423	stopping it again), that is, libev might or might not block the signal,
		2424	and might or might not set or restore the installed signal handler (but
		2425	see C<EVFLAG_NOSIGMASK>).
		2426
		2427	While this does not matter for the signal disposition (libev never
		2428	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2429	C<execve>), this matters for the signal mask: many programs do not expect
		2430	certain signals to be blocked.
		2431
		2432	This means that before calling C<exec> (from the child) you should reset
		2433	the signal mask to whatever "default" you expect (all clear is a good
		2434	choice usually).
		2435
		2436	The simplest way to ensure that the signal mask is reset in the child is
		2437	to install a fork handler with C<pthread_atfork> that resets it. That will
		2438	catch fork calls done by libraries (such as the libc) as well.
		2439
		2440	In current versions of libev, the signal will not be blocked indefinitely
		2441	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2442	the window of opportunity for problems, it will not go away, as libev
		2443	I<has> to modify the signal mask, at least temporarily.
		2444
		2445	So I can't stress this enough: I<If you do not reset your signal mask when
		2446	you expect it to be empty, you have a race condition in your code>. This
		2447	is not a libev-specific thing, this is true for most event libraries.
		2448
		2449	=head3 The special problem of threads signal handling
		2450
		2451	POSIX threads has problematic signal handling semantics, specifically,
		2452	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2453	threads in a process block signals, which is hard to achieve.
		2454
		2455	When you want to use sigwait (or mix libev signal handling with your own
		2456	for the same signals), you can tackle this problem by globally blocking
		2457	all signals before creating any threads (or creating them with a fully set
		2458	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2459	loops. Then designate one thread as "signal receiver thread" which handles
		2460	these signals. You can pass on any signals that libev might be interested
		2461	in by calling C<ev_feed_signal>.
1719		2462
1720	=head3 Watcher-Specific Functions and Data Members	2463	=head3 Watcher-Specific Functions and Data Members
1721		2464
1722	=over 4	2465	=over 4
1723		2466
…		…
1739	Example: Try to exit cleanly on SIGINT.	2482	Example: Try to exit cleanly on SIGINT.
1740		2483
1741	static void	2484	static void
1742	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2485	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1743	{	2486	{
1744	ev_unloop (loop, EVUNLOOP_ALL);	2487	ev_break (loop, EVBREAK_ALL);
1745	}	2488	}
1746		2489
1747	ev_signal signal_watcher;	2490	ev_signal signal_watcher;
1748	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2491	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1749	ev_signal_start (loop, &signal_watcher);	2492	ev_signal_start (loop, &signal_watcher);
…		…
1755	some child status changes (most typically when a child of yours dies or	2498	some child status changes (most typically when a child of yours dies or
1756	exits). It is permissible to install a child watcher I<after> the child	2499	exits). It is permissible to install a child watcher I<after> the child
1757	has been forked (which implies it might have already exited), as long	2500	has been forked (which implies it might have already exited), as long
1758	as the event loop isn't entered (or is continued from a watcher), i.e.,	2501	as the event loop isn't entered (or is continued from a watcher), i.e.,
1759	forking and then immediately registering a watcher for the child is fine,	2502	forking and then immediately registering a watcher for the child is fine,
1760	but forking and registering a watcher a few event loop iterations later is	2503	but forking and registering a watcher a few event loop iterations later or
1761	not.	2504	in the next callback invocation is not.
1762		2505
1763	Only the default event loop is capable of handling signals, and therefore	2506	Only the default event loop is capable of handling signals, and therefore
1764	you can only register child watchers in the default event loop.	2507	you can only register child watchers in the default event loop.
1765		2508
		2509	Due to some design glitches inside libev, child watchers will always be
		2510	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2511	libev)
		2512
1766	=head3 Process Interaction	2513	=head3 Process Interaction
1767		2514
1768	Libev grabs C<SIGCHLD> as soon as the default event loop is	2515	Libev grabs C<SIGCHLD> as soon as the default event loop is
1769	initialised. This is necessary to guarantee proper behaviour even if	2516	initialised. This is necessary to guarantee proper behaviour even if the
1770	the first child watcher is started after the child exits. The occurrence	2517	first child watcher is started after the child exits. The occurrence
1771	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2518	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1772	synchronously as part of the event loop processing. Libev always reaps all	2519	synchronously as part of the event loop processing. Libev always reaps all
1773	children, even ones not watched.	2520	children, even ones not watched.
1774		2521
1775	=head3 Overriding the Built-In Processing	2522	=head3 Overriding the Built-In Processing
…		…
1785	=head3 Stopping the Child Watcher	2532	=head3 Stopping the Child Watcher
1786		2533
1787	Currently, the child watcher never gets stopped, even when the	2534	Currently, the child watcher never gets stopped, even when the
1788	child terminates, so normally one needs to stop the watcher in the	2535	child terminates, so normally one needs to stop the watcher in the
1789	callback. Future versions of libev might stop the watcher automatically	2536	callback. Future versions of libev might stop the watcher automatically
1790	when a child exit is detected.	2537	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2538	problem).
1791		2539
1792	=head3 Watcher-Specific Functions and Data Members	2540	=head3 Watcher-Specific Functions and Data Members
1793		2541
1794	=over 4	2542	=over 4
1795		2543
…		…
1852		2600
1853		2601
1854	=head2 C<ev_stat> - did the file attributes just change?	2602	=head2 C<ev_stat> - did the file attributes just change?
1855		2603
1856	This watches a file system path for attribute changes. That is, it calls	2604	This watches a file system path for attribute changes. That is, it calls
1857	C<stat> regularly (or when the OS says it changed) and sees if it changed	2605	C<stat> on that path in regular intervals (or when the OS says it changed)
1858	compared to the last time, invoking the callback if it did.	2606	and sees if it changed compared to the last time, invoking the callback if
		2607	it did.
1859		2608
1860	The path does not need to exist: changing from "path exists" to "path does	2609	The path does not need to exist: changing from "path exists" to "path does
1861	not exist" is a status change like any other. The condition "path does	2610	not exist" is a status change like any other. The condition "path does not
1862	not exist" is signified by the C<st_nlink> field being zero (which is	2611	exist" (or more correctly "path cannot be stat'ed") is signified by the
1863	otherwise always forced to be at least one) and all the other fields of	2612	C<st_nlink> field being zero (which is otherwise always forced to be at
1864	the stat buffer having unspecified contents.	2613	least one) and all the other fields of the stat buffer having unspecified
		2614	contents.
1865		2615
1866	The path I<should> be absolute and I<must not> end in a slash. If it is	2616	The path I<must not> end in a slash or contain special components such as
		2617	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1867	relative and your working directory changes, the behaviour is undefined.	2618	your working directory changes, then the behaviour is undefined.
1868		2619
1869	Since there is no standard kernel interface to do this, the portable	2620	Since there is no portable change notification interface available, the
1870	implementation simply calls C<stat (2)> regularly on the path to see if	2621	portable implementation simply calls C<stat(2)> regularly on the path
1871	it changed somehow. You can specify a recommended polling interval for	2622	to see if it changed somehow. You can specify a recommended polling
1872	this case. If you specify a polling interval of C<0> (highly recommended!)	2623	interval for this case. If you specify a polling interval of C<0> (highly
1873	then a I<suitable, unspecified default> value will be used (which	2624	recommended!) then a I<suitable, unspecified default> value will be used
1874	you can expect to be around five seconds, although this might change	2625	(which you can expect to be around five seconds, although this might
1875	dynamically). Libev will also impose a minimum interval which is currently	2626	change dynamically). Libev will also impose a minimum interval which is
1876	around C<0.1>, but thats usually overkill.	2627	currently around C<0.1>, but that's usually overkill.
1877		2628
1878	This watcher type is not meant for massive numbers of stat watchers,	2629	This watcher type is not meant for massive numbers of stat watchers,
1879	as even with OS-supported change notifications, this can be	2630	as even with OS-supported change notifications, this can be
1880	resource-intensive.	2631	resource-intensive.
1881		2632
1882	At the time of this writing, the only OS-specific interface implemented	2633	At the time of this writing, the only OS-specific interface implemented
1883	is the Linux inotify interface (implementing kqueue support is left as	2634	is the Linux inotify interface (implementing kqueue support is left as an
1884	an exercise for the reader. Note, however, that the author sees no way	2635	exercise for the reader. Note, however, that the author sees no way of
1885	of implementing C<ev_stat> semantics with kqueue).	2636	implementing C<ev_stat> semantics with kqueue, except as a hint).
1886		2637
1887	=head3 ABI Issues (Largefile Support)	2638	=head3 ABI Issues (Largefile Support)
1888		2639
1889	Libev by default (unless the user overrides this) uses the default	2640	Libev by default (unless the user overrides this) uses the default
1890	compilation environment, which means that on systems with large file	2641	compilation environment, which means that on systems with large file
1891	support disabled by default, you get the 32 bit version of the stat	2642	support disabled by default, you get the 32 bit version of the stat
1892	structure. When using the library from programs that change the ABI to	2643	structure. When using the library from programs that change the ABI to
1893	use 64 bit file offsets the programs will fail. In that case you have to	2644	use 64 bit file offsets the programs will fail. In that case you have to
1894	compile libev with the same flags to get binary compatibility. This is	2645	compile libev with the same flags to get binary compatibility. This is
1895	obviously the case with any flags that change the ABI, but the problem is	2646	obviously the case with any flags that change the ABI, but the problem is
1896	most noticeably disabled with ev_stat and large file support.	2647	most noticeably displayed with ev_stat and large file support.
1897		2648
1898	The solution for this is to lobby your distribution maker to make large	2649	The solution for this is to lobby your distribution maker to make large
1899	file interfaces available by default (as e.g. FreeBSD does) and not	2650	file interfaces available by default (as e.g. FreeBSD does) and not
1900	optional. Libev cannot simply switch on large file support because it has	2651	optional. Libev cannot simply switch on large file support because it has
1901	to exchange stat structures with application programs compiled using the	2652	to exchange stat structures with application programs compiled using the
1902	default compilation environment.	2653	default compilation environment.
1903		2654
1904	=head3 Inotify and Kqueue	2655	=head3 Inotify and Kqueue
1905		2656
1906	When C<inotify (7)> support has been compiled into libev (generally	2657	When C<inotify (7)> support has been compiled into libev and present at
1907	only available with Linux 2.6.25 or above due to bugs in earlier	2658	runtime, it will be used to speed up change detection where possible. The
1908	implementations) and present at runtime, it will be used to speed up	2659	inotify descriptor will be created lazily when the first C<ev_stat>
1909	change detection where possible. The inotify descriptor will be created	2660	watcher is being started.
1910	lazily when the first C<ev_stat> watcher is being started.
1911		2661
1912	Inotify presence does not change the semantics of C<ev_stat> watchers	2662	Inotify presence does not change the semantics of C<ev_stat> watchers
1913	except that changes might be detected earlier, and in some cases, to avoid	2663	except that changes might be detected earlier, and in some cases, to avoid
1914	making regular C<stat> calls. Even in the presence of inotify support	2664	making regular C<stat> calls. Even in the presence of inotify support
1915	there are many cases where libev has to resort to regular C<stat> polling,	2665	there are many cases where libev has to resort to regular C<stat> polling,
1916	but as long as the path exists, libev usually gets away without polling.	2666	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2667	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2668	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2669	xfs are fully working) libev usually gets away without polling.
1917		2670
1918	There is no support for kqueue, as apparently it cannot be used to	2671	There is no support for kqueue, as apparently it cannot be used to
1919	implement this functionality, due to the requirement of having a file	2672	implement this functionality, due to the requirement of having a file
1920	descriptor open on the object at all times, and detecting renames, unlinks	2673	descriptor open on the object at all times, and detecting renames, unlinks
1921	etc. is difficult.	2674	etc. is difficult.
1922		2675
		2676	=head3 C<stat ()> is a synchronous operation
		2677
		2678	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2679	the process. The exception are C<ev_stat> watchers - those call C<stat
		2680	()>, which is a synchronous operation.
		2681
		2682	For local paths, this usually doesn't matter: unless the system is very
		2683	busy or the intervals between stat's are large, a stat call will be fast,
		2684	as the path data is usually in memory already (except when starting the
		2685	watcher).
		2686
		2687	For networked file systems, calling C<stat ()> can block an indefinite
		2688	time due to network issues, and even under good conditions, a stat call
		2689	often takes multiple milliseconds.
		2690
		2691	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2692	paths, although this is fully supported by libev.
		2693
1923	=head3 The special problem of stat time resolution	2694	=head3 The special problem of stat time resolution
1924		2695
1925	The C<stat ()> system call only supports full-second resolution portably, and	2696	The C<stat ()> system call only supports full-second resolution portably,
1926	even on systems where the resolution is higher, most file systems still	2697	and even on systems where the resolution is higher, most file systems
1927	only support whole seconds.	2698	still only support whole seconds.
1928		2699
1929	That means that, if the time is the only thing that changes, you can	2700	That means that, if the time is the only thing that changes, you can
1930	easily miss updates: on the first update, C<ev_stat> detects a change and	2701	easily miss updates: on the first update, C<ev_stat> detects a change and
1931	calls your callback, which does something. When there is another update	2702	calls your callback, which does something. When there is another update
1932	within the same second, C<ev_stat> will be unable to detect unless the	2703	within the same second, C<ev_stat> will be unable to detect unless the
…		…
2075		2846
2076	=head3 Watcher-Specific Functions and Data Members	2847	=head3 Watcher-Specific Functions and Data Members
2077		2848
2078	=over 4	2849	=over 4
2079		2850
2080	=item ev_idle_init (ev_signal *, callback)	2851	=item ev_idle_init (ev_idle *, callback)
2081		2852
2082	Initialises and configures the idle watcher - it has no parameters of any	2853	Initialises and configures the idle watcher - it has no parameters of any
2083	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2854	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
2084	believe me.	2855	believe me.
2085		2856
…		…
2098	// no longer anything immediate to do.	2869	// no longer anything immediate to do.
2099	}	2870	}
2100		2871
2101	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2872	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2102	ev_idle_init (idle_watcher, idle_cb);	2873	ev_idle_init (idle_watcher, idle_cb);
2103	ev_idle_start (loop, idle_cb);	2874	ev_idle_start (loop, idle_watcher);
2104		2875
2105		2876
2106	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2877	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2107		2878
2108	Prepare and check watchers are usually (but not always) used in pairs:	2879	Prepare and check watchers are usually (but not always) used in pairs:
2109	prepare watchers get invoked before the process blocks and check watchers	2880	prepare watchers get invoked before the process blocks and check watchers
2110	afterwards.	2881	afterwards.
2111		2882
2112	You I<must not> call C<ev_loop> or similar functions that enter	2883	You I<must not> call C<ev_run> or similar functions that enter
2113	the current event loop from either C<ev_prepare> or C<ev_check>	2884	the current event loop from either C<ev_prepare> or C<ev_check>
2114	watchers. Other loops than the current one are fine, however. The	2885	watchers. Other loops than the current one are fine, however. The
2115	rationale behind this is that you do not need to check for recursion in	2886	rationale behind this is that you do not need to check for recursion in
2116	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2887	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2117	C<ev_check> so if you have one watcher of each kind they will always be	2888	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2201	struct pollfd fds [nfd];	2972	struct pollfd fds [nfd];
2202	// actual code will need to loop here and realloc etc.	2973	// actual code will need to loop here and realloc etc.
2203	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2974	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2204		2975
2205	/* the callback is illegal, but won't be called as we stop during check */	2976	/* the callback is illegal, but won't be called as we stop during check */
2206	ev_timer_init (&tw, 0, timeout * 1e-3);	2977	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2207	ev_timer_start (loop, &tw);	2978	ev_timer_start (loop, &tw);
2208		2979
2209	// create one ev_io per pollfd	2980	// create one ev_io per pollfd
2210	for (int i = 0; i < nfd; ++i)	2981	for (int i = 0; i < nfd; ++i)
2211	{	2982	{
…		…
2285		3056
2286	if (timeout >= 0)	3057	if (timeout >= 0)
2287	// create/start timer	3058	// create/start timer
2288		3059
2289	// poll	3060	// poll
2290	ev_loop (EV_A_ 0);	3061	ev_run (EV_A_ 0);
2291		3062
2292	// stop timer again	3063	// stop timer again
2293	if (timeout >= 0)	3064	if (timeout >= 0)
2294	ev_timer_stop (EV_A_ &to);	3065	ev_timer_stop (EV_A_ &to);
2295		3066
…		…
2324	some fds have to be watched and handled very quickly (with low latency),	3095	some fds have to be watched and handled very quickly (with low latency),
2325	and even priorities and idle watchers might have too much overhead. In	3096	and even priorities and idle watchers might have too much overhead. In
2326	this case you would put all the high priority stuff in one loop and all	3097	this case you would put all the high priority stuff in one loop and all
2327	the rest in a second one, and embed the second one in the first.	3098	the rest in a second one, and embed the second one in the first.
2328		3099
2329	As long as the watcher is active, the callback will be invoked every time	3100	As long as the watcher is active, the callback will be invoked every
2330	there might be events pending in the embedded loop. The callback must then	3101	time there might be events pending in the embedded loop. The callback
2331	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	3102	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2332	their callbacks (you could also start an idle watcher to give the embedded	3103	sweep and invoke their callbacks (the callback doesn't need to invoke the
2333	loop strictly lower priority for example). You can also set the callback	3104	C<ev_embed_sweep> function directly, it could also start an idle watcher
2334	to C<0>, in which case the embed watcher will automatically execute the	3105	to give the embedded loop strictly lower priority for example).
2335	embedded loop sweep.
2336		3106
2337	As long as the watcher is started it will automatically handle events. The	3107	You can also set the callback to C<0>, in which case the embed watcher
2338	callback will be invoked whenever some events have been handled. You can	3108	will automatically execute the embedded loop sweep whenever necessary.
2339	set the callback to C<0> to avoid having to specify one if you are not
2340	interested in that.
2341		3109
2342	Also, there have not currently been made special provisions for forking:	3110	Fork detection will be handled transparently while the C<ev_embed> watcher
2343	when you fork, you not only have to call C<ev_loop_fork> on both loops,	3111	is active, i.e., the embedded loop will automatically be forked when the
2344	but you will also have to stop and restart any C<ev_embed> watchers	3112	embedding loop forks. In other cases, the user is responsible for calling
2345	yourself - but you can use a fork watcher to handle this automatically,	3113	C<ev_loop_fork> on the embedded loop.
2346	and future versions of libev might do just that.
2347		3114
2348	Unfortunately, not all backends are embeddable: only the ones returned by	3115	Unfortunately, not all backends are embeddable: only the ones returned by
2349	C<ev_embeddable_backends> are, which, unfortunately, does not include any	3116	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2350	portable one.	3117	portable one.
2351		3118
…		…
2377	if you do not want that, you need to temporarily stop the embed watcher).	3144	if you do not want that, you need to temporarily stop the embed watcher).
2378		3145
2379	=item ev_embed_sweep (loop, ev_embed *)	3146	=item ev_embed_sweep (loop, ev_embed *)
2380		3147
2381	Make a single, non-blocking sweep over the embedded loop. This works	3148	Make a single, non-blocking sweep over the embedded loop. This works
2382	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3149	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2383	appropriate way for embedded loops.	3150	appropriate way for embedded loops.
2384		3151
2385	=item struct ev_loop *other [read-only]	3152	=item struct ev_loop *other [read-only]
2386		3153
2387	The embedded event loop.	3154	The embedded event loop.
…		…
2445	event loop blocks next and before C<ev_check> watchers are being called,	3212	event loop blocks next and before C<ev_check> watchers are being called,
2446	and only in the child after the fork. If whoever good citizen calling	3213	and only in the child after the fork. If whoever good citizen calling
2447	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3214	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2448	handlers will be invoked, too, of course.	3215	handlers will be invoked, too, of course.
2449		3216
		3217	=head3 The special problem of life after fork - how is it possible?
		3218
		3219	Most uses of C<fork()> consist of forking, then some simple calls to set
		3220	up/change the process environment, followed by a call to C<exec()>. This
		3221	sequence should be handled by libev without any problems.
		3222
		3223	This changes when the application actually wants to do event handling
		3224	in the child, or both parent in child, in effect "continuing" after the
		3225	fork.
		3226
		3227	The default mode of operation (for libev, with application help to detect
		3228	forks) is to duplicate all the state in the child, as would be expected
		3229	when I<either> the parent I<or> the child process continues.
		3230
		3231	When both processes want to continue using libev, then this is usually the
		3232	wrong result. In that case, usually one process (typically the parent) is
		3233	supposed to continue with all watchers in place as before, while the other
		3234	process typically wants to start fresh, i.e. without any active watchers.
		3235
		3236	The cleanest and most efficient way to achieve that with libev is to
		3237	simply create a new event loop, which of course will be "empty", and
		3238	use that for new watchers. This has the advantage of not touching more
		3239	memory than necessary, and thus avoiding the copy-on-write, and the
		3240	disadvantage of having to use multiple event loops (which do not support
		3241	signal watchers).
		3242
		3243	When this is not possible, or you want to use the default loop for
		3244	other reasons, then in the process that wants to start "fresh", call
		3245	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3246	Destroying the default loop will "orphan" (not stop) all registered
		3247	watchers, so you have to be careful not to execute code that modifies
		3248	those watchers. Note also that in that case, you have to re-register any
		3249	signal watchers.
		3250
2450	=head3 Watcher-Specific Functions and Data Members	3251	=head3 Watcher-Specific Functions and Data Members
2451		3252
2452	=over 4	3253	=over 4
2453		3254
2454	=item ev_fork_init (ev_signal *, callback)	3255	=item ev_fork_init (ev_fork *, callback)
2455		3256
2456	Initialises and configures the fork watcher - it has no parameters of any	3257	Initialises and configures the fork watcher - it has no parameters of any
2457	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3258	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2458	believe me.	3259	really.
2459		3260
2460	=back	3261	=back
2461		3262
2462		3263
		3264	=head2 C<ev_cleanup> - even the best things end
		3265
		3266	Cleanup watchers are called just before the event loop is being destroyed
		3267	by a call to C<ev_loop_destroy>.
		3268
		3269	While there is no guarantee that the event loop gets destroyed, cleanup
		3270	watchers provide a convenient method to install cleanup hooks for your
		3271	program, worker threads and so on - you just to make sure to destroy the
		3272	loop when you want them to be invoked.
		3273
		3274	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3275	all other watchers, they do not keep a reference to the event loop (which
		3276	makes a lot of sense if you think about it). Like all other watchers, you
		3277	can call libev functions in the callback, except C<ev_cleanup_start>.
		3278
		3279	=head3 Watcher-Specific Functions and Data Members
		3280
		3281	=over 4
		3282
		3283	=item ev_cleanup_init (ev_cleanup *, callback)
		3284
		3285	Initialises and configures the cleanup watcher - it has no parameters of
		3286	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3287	pointless, I assure you.
		3288
		3289	=back
		3290
		3291	Example: Register an atexit handler to destroy the default loop, so any
		3292	cleanup functions are called.
		3293
		3294	static void
		3295	program_exits (void)
		3296	{
		3297	ev_loop_destroy (EV_DEFAULT_UC);
		3298	}
		3299
		3300	...
		3301	atexit (program_exits);
		3302
		3303
2463	=head2 C<ev_async> - how to wake up another event loop	3304	=head2 C<ev_async> - how to wake up an event loop
2464		3305
2465	In general, you cannot use an C<ev_loop> from multiple threads or other	3306	In general, you cannot use an C<ev_loop> from multiple threads or other
2466	asynchronous sources such as signal handlers (as opposed to multiple event	3307	asynchronous sources such as signal handlers (as opposed to multiple event
2467	loops - those are of course safe to use in different threads).	3308	loops - those are of course safe to use in different threads).
2468		3309
2469	Sometimes, however, you need to wake up another event loop you do not	3310	Sometimes, however, you need to wake up an event loop you do not control,
2470	control, for example because it belongs to another thread. This is what	3311	for example because it belongs to another thread. This is what C<ev_async>
2471	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3312	watchers do: as long as the C<ev_async> watcher is active, you can signal
2472	can signal it by calling C<ev_async_send>, which is thread- and signal	3313	it by calling C<ev_async_send>, which is thread- and signal safe.
2473	safe.
2474		3314
2475	This functionality is very similar to C<ev_signal> watchers, as signals,	3315	This functionality is very similar to C<ev_signal> watchers, as signals,
2476	too, are asynchronous in nature, and signals, too, will be compressed	3316	too, are asynchronous in nature, and signals, too, will be compressed
2477	(i.e. the number of callback invocations may be less than the number of	3317	(i.e. the number of callback invocations may be less than the number of
2478	C<ev_async_sent> calls).	3318	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
2479		3319	of "global async watchers" by using a watcher on an otherwise unused
2480	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3320	signal, and C<ev_feed_signal> to signal this watcher from another thread,
2481	just the default loop.	3321	even without knowing which loop owns the signal.
2482		3322
2483	=head3 Queueing	3323	=head3 Queueing
2484		3324
2485	C<ev_async> does not support queueing of data in any way. The reason	3325	C<ev_async> does not support queueing of data in any way. The reason
2486	is that the author does not know of a simple (or any) algorithm for a	3326	is that the author does not know of a simple (or any) algorithm for a
2487	multiple-writer-single-reader queue that works in all cases and doesn't	3327	multiple-writer-single-reader queue that works in all cases and doesn't
2488	need elaborate support such as pthreads.	3328	need elaborate support such as pthreads or unportable memory access
		3329	semantics.
2489		3330
2490	That means that if you want to queue data, you have to provide your own	3331	That means that if you want to queue data, you have to provide your own
2491	queue. But at least I can tell you how to implement locking around your	3332	queue. But at least I can tell you how to implement locking around your
2492	queue:	3333	queue:
2493		3334
…		…
2571	=over 4	3412	=over 4
2572		3413
2573	=item ev_async_init (ev_async *, callback)	3414	=item ev_async_init (ev_async *, callback)
2574		3415
2575	Initialises and configures the async watcher - it has no parameters of any	3416	Initialises and configures the async watcher - it has no parameters of any
2576	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3417	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2577	trust me.	3418	trust me.
2578		3419
2579	=item ev_async_send (loop, ev_async *)	3420	=item ev_async_send (loop, ev_async *)
2580		3421
2581	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3422	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2582	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3423	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3424	returns.
		3425
2583	C<ev_feed_event>, this call is safe to do from other threads, signal or	3426	Unlike C<ev_feed_event>, this call is safe to do from other threads,
2584	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3427	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
2585	section below on what exactly this means).	3428	embedding section below on what exactly this means).
2586		3429
2587	This call incurs the overhead of a system call only once per loop iteration,	3430	Note that, as with other watchers in libev, multiple events might get
2588	so while the overhead might be noticeable, it doesn't apply to repeated	3431	compressed into a single callback invocation (another way to look at
2589	calls to C<ev_async_send>.	3432	this is that C<ev_async> watchers are level-triggered: they are set on
		3433	C<ev_async_send>, reset when the event loop detects that).
		3434
		3435	This call incurs the overhead of at most one extra system call per event
		3436	loop iteration, if the event loop is blocked, and no syscall at all if
		3437	the event loop (or your program) is processing events. That means that
		3438	repeated calls are basically free (there is no need to avoid calls for
		3439	performance reasons) and that the overhead becomes smaller (typically
		3440	zero) under load.
2590		3441
2591	=item bool = ev_async_pending (ev_async *)	3442	=item bool = ev_async_pending (ev_async *)
2592		3443
2593	Returns a non-zero value when C<ev_async_send> has been called on the	3444	Returns a non-zero value when C<ev_async_send> has been called on the
2594	watcher but the event has not yet been processed (or even noted) by the	3445	watcher but the event has not yet been processed (or even noted) by the
…		…
2597	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3448	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2598	the loop iterates next and checks for the watcher to have become active,	3449	the loop iterates next and checks for the watcher to have become active,
2599	it will reset the flag again. C<ev_async_pending> can be used to very	3450	it will reset the flag again. C<ev_async_pending> can be used to very
2600	quickly check whether invoking the loop might be a good idea.	3451	quickly check whether invoking the loop might be a good idea.
2601		3452
2602	Not that this does I<not> check whether the watcher itself is pending, only	3453	Not that this does I<not> check whether the watcher itself is pending,
2603	whether it has been requested to make this watcher pending.	3454	only whether it has been requested to make this watcher pending: there
		3455	is a time window between the event loop checking and resetting the async
		3456	notification, and the callback being invoked.
2604		3457
2605	=back	3458	=back
2606		3459
2607		3460
2608	=head1 OTHER FUNCTIONS	3461	=head1 OTHER FUNCTIONS
…		…
2625		3478
2626	If C<timeout> is less than 0, then no timeout watcher will be	3479	If C<timeout> is less than 0, then no timeout watcher will be
2627	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3480	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2628	repeat = 0) will be started. C<0> is a valid timeout.	3481	repeat = 0) will be started. C<0> is a valid timeout.
2629		3482
2630	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3483	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2631	passed an C<revents> set like normal event callbacks (a combination of	3484	passed an C<revents> set like normal event callbacks (a combination of
2632	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3485	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2633	value passed to C<ev_once>. Note that it is possible to receive I<both>	3486	value passed to C<ev_once>. Note that it is possible to receive I<both>
2634	a timeout and an io event at the same time - you probably should give io	3487	a timeout and an io event at the same time - you probably should give io
2635	events precedence.	3488	events precedence.
2636		3489
2637	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3490	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2638		3491
2639	static void stdin_ready (int revents, void *arg)	3492	static void stdin_ready (int revents, void *arg)
2640	{	3493	{
2641	if (revents & EV_READ)	3494	if (revents & EV_READ)
2642	/* stdin might have data for us, joy! */;	3495	/* stdin might have data for us, joy! */;
2643	else if (revents & EV_TIMEOUT)	3496	else if (revents & EV_TIMER)
2644	/* doh, nothing entered */;	3497	/* doh, nothing entered */;
2645	}	3498	}
2646		3499
2647	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3500	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2648		3501
2649	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2650
2651	Feeds the given event set into the event loop, as if the specified event
2652	had happened for the specified watcher (which must be a pointer to an
2653	initialised but not necessarily started event watcher).
2654
2655	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3502	=item ev_feed_fd_event (loop, int fd, int revents)
2656		3503
2657	Feed an event on the given fd, as if a file descriptor backend detected	3504	Feed an event on the given fd, as if a file descriptor backend detected
2658	the given events it.	3505	the given events.
2659		3506
2660	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3507	=item ev_feed_signal_event (loop, int signum)
2661		3508
2662	Feed an event as if the given signal occurred (C<loop> must be the default	3509	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
2663	loop!).	3510	which is async-safe.
2664		3511
2665	=back	3512	=back
		3513
		3514
		3515	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3516
		3517	This section explains some common idioms that are not immediately
		3518	obvious. Note that examples are sprinkled over the whole manual, and this
		3519	section only contains stuff that wouldn't fit anywhere else.
		3520
		3521	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3522
		3523	Each watcher has, by default, a C<void *data> member that you can read
		3524	or modify at any time: libev will completely ignore it. This can be used
		3525	to associate arbitrary data with your watcher. If you need more data and
		3526	don't want to allocate memory separately and store a pointer to it in that
		3527	data member, you can also "subclass" the watcher type and provide your own
		3528	data:
		3529
		3530	struct my_io
		3531	{
		3532	ev_io io;
		3533	int otherfd;
		3534	void *somedata;
		3535	struct whatever *mostinteresting;
		3536	};
		3537
		3538	...
		3539	struct my_io w;
		3540	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3541
		3542	And since your callback will be called with a pointer to the watcher, you
		3543	can cast it back to your own type:
		3544
		3545	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3546	{
		3547	struct my_io *w = (struct my_io *)w_;
		3548	...
		3549	}
		3550
		3551	More interesting and less C-conformant ways of casting your callback
		3552	function type instead have been omitted.
		3553
		3554	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3555
		3556	Another common scenario is to use some data structure with multiple
		3557	embedded watchers, in effect creating your own watcher that combines
		3558	multiple libev event sources into one "super-watcher":
		3559
		3560	struct my_biggy
		3561	{
		3562	int some_data;
		3563	ev_timer t1;
		3564	ev_timer t2;
		3565	}
		3566
		3567	In this case getting the pointer to C<my_biggy> is a bit more
		3568	complicated: Either you store the address of your C<my_biggy> struct in
		3569	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3570	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3571	real programmers):
		3572
		3573	#include <stddef.h>
		3574
		3575	static void
		3576	t1_cb (EV_P_ ev_timer *w, int revents)
		3577	{
		3578	struct my_biggy big = (struct my_biggy *)
		3579	(((char *)w) - offsetof (struct my_biggy, t1));
		3580	}
		3581
		3582	static void
		3583	t2_cb (EV_P_ ev_timer *w, int revents)
		3584	{
		3585	struct my_biggy big = (struct my_biggy *)
		3586	(((char *)w) - offsetof (struct my_biggy, t2));
		3587	}
		3588
		3589	=head2 AVOIDING FINISHING BEFORE RETURNING
		3590
		3591	Often you have structures like this in event-based programs:
		3592
		3593	callback ()
		3594	{
		3595	free (request);
		3596	}
		3597
		3598	request = start_new_request (..., callback);
		3599
		3600	The intent is to start some "lengthy" operation. The C<request> could be
		3601	used to cancel the operation, or do other things with it.
		3602
		3603	It's not uncommon to have code paths in C<start_new_request> that
		3604	immediately invoke the callback, for example, to report errors. Or you add
		3605	some caching layer that finds that it can skip the lengthy aspects of the
		3606	operation and simply invoke the callback with the result.
		3607
		3608	The problem here is that this will happen I<before> C<start_new_request>
		3609	has returned, so C<request> is not set.
		3610
		3611	Even if you pass the request by some safer means to the callback, you
		3612	might want to do something to the request after starting it, such as
		3613	canceling it, which probably isn't working so well when the callback has
		3614	already been invoked.
		3615
		3616	A common way around all these issues is to make sure that
		3617	C<start_new_request> I<always> returns before the callback is invoked. If
		3618	C<start_new_request> immediately knows the result, it can artificially
		3619	delay invoking the callback by e.g. using a C<prepare> or C<idle> watcher
		3620	for example, or more sneakily, by reusing an existing (stopped) watcher
		3621	and pushing it into the pending queue:
		3622
		3623	ev_set_cb (watcher, callback);
		3624	ev_feed_event (EV_A_ watcher, 0);
		3625
		3626	This way, C<start_new_request> can safely return before the callback is
		3627	invoked, while not delaying callback invocation too much.
		3628
		3629	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3630
		3631	Often (especially in GUI toolkits) there are places where you have
		3632	I<modal> interaction, which is most easily implemented by recursively
		3633	invoking C<ev_run>.
		3634
		3635	This brings the problem of exiting - a callback might want to finish the
		3636	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3637	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3638	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3639	other combination: In these cases, C<ev_break> will not work alone.
		3640
		3641	The solution is to maintain "break this loop" variable for each C<ev_run>
		3642	invocation, and use a loop around C<ev_run> until the condition is
		3643	triggered, using C<EVRUN_ONCE>:
		3644
		3645	// main loop
		3646	int exit_main_loop = 0;
		3647
		3648	while (!exit_main_loop)
		3649	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3650
		3651	// in a modal watcher
		3652	int exit_nested_loop = 0;
		3653
		3654	while (!exit_nested_loop)
		3655	ev_run (EV_A_ EVRUN_ONCE);
		3656
		3657	To exit from any of these loops, just set the corresponding exit variable:
		3658
		3659	// exit modal loop
		3660	exit_nested_loop = 1;
		3661
		3662	// exit main program, after modal loop is finished
		3663	exit_main_loop = 1;
		3664
		3665	// exit both
		3666	exit_main_loop = exit_nested_loop = 1;
		3667
		3668	=head2 THREAD LOCKING EXAMPLE
		3669
		3670	Here is a fictitious example of how to run an event loop in a different
		3671	thread from where callbacks are being invoked and watchers are
		3672	created/added/removed.
		3673
		3674	For a real-world example, see the C<EV::Loop::Async> perl module,
		3675	which uses exactly this technique (which is suited for many high-level
		3676	languages).
		3677
		3678	The example uses a pthread mutex to protect the loop data, a condition
		3679	variable to wait for callback invocations, an async watcher to notify the
		3680	event loop thread and an unspecified mechanism to wake up the main thread.
		3681
		3682	First, you need to associate some data with the event loop:
		3683
		3684	typedef struct {
		3685	mutex_t lock; /* global loop lock */
		3686	ev_async async_w;
		3687	thread_t tid;
		3688	cond_t invoke_cv;
		3689	} userdata;
		3690
		3691	void prepare_loop (EV_P)
		3692	{
		3693	// for simplicity, we use a static userdata struct.
		3694	static userdata u;
		3695
		3696	ev_async_init (&u->async_w, async_cb);
		3697	ev_async_start (EV_A_ &u->async_w);
		3698
		3699	pthread_mutex_init (&u->lock, 0);
		3700	pthread_cond_init (&u->invoke_cv, 0);
		3701
		3702	// now associate this with the loop
		3703	ev_set_userdata (EV_A_ u);
		3704	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3705	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3706
		3707	// then create the thread running ev_run
		3708	pthread_create (&u->tid, 0, l_run, EV_A);
		3709	}
		3710
		3711	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3712	solely to wake up the event loop so it takes notice of any new watchers
		3713	that might have been added:
		3714
		3715	static void
		3716	async_cb (EV_P_ ev_async *w, int revents)
		3717	{
		3718	// just used for the side effects
		3719	}
		3720
		3721	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3722	protecting the loop data, respectively.
		3723
		3724	static void
		3725	l_release (EV_P)
		3726	{
		3727	userdata *u = ev_userdata (EV_A);
		3728	pthread_mutex_unlock (&u->lock);
		3729	}
		3730
		3731	static void
		3732	l_acquire (EV_P)
		3733	{
		3734	userdata *u = ev_userdata (EV_A);
		3735	pthread_mutex_lock (&u->lock);
		3736	}
		3737
		3738	The event loop thread first acquires the mutex, and then jumps straight
		3739	into C<ev_run>:
		3740
		3741	void *
		3742	l_run (void *thr_arg)
		3743	{
		3744	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3745
		3746	l_acquire (EV_A);
		3747	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3748	ev_run (EV_A_ 0);
		3749	l_release (EV_A);
		3750
		3751	return 0;
		3752	}
		3753
		3754	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3755	signal the main thread via some unspecified mechanism (signals? pipe
		3756	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3757	have been called (in a while loop because a) spurious wakeups are possible
		3758	and b) skipping inter-thread-communication when there are no pending
		3759	watchers is very beneficial):
		3760
		3761	static void
		3762	l_invoke (EV_P)
		3763	{
		3764	userdata *u = ev_userdata (EV_A);
		3765
		3766	while (ev_pending_count (EV_A))
		3767	{
		3768	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3769	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3770	}
		3771	}
		3772
		3773	Now, whenever the main thread gets told to invoke pending watchers, it
		3774	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3775	thread to continue:
		3776
		3777	static void
		3778	real_invoke_pending (EV_P)
		3779	{
		3780	userdata *u = ev_userdata (EV_A);
		3781
		3782	pthread_mutex_lock (&u->lock);
		3783	ev_invoke_pending (EV_A);
		3784	pthread_cond_signal (&u->invoke_cv);
		3785	pthread_mutex_unlock (&u->lock);
		3786	}
		3787
		3788	Whenever you want to start/stop a watcher or do other modifications to an
		3789	event loop, you will now have to lock:
		3790
		3791	ev_timer timeout_watcher;
		3792	userdata *u = ev_userdata (EV_A);
		3793
		3794	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3795
		3796	pthread_mutex_lock (&u->lock);
		3797	ev_timer_start (EV_A_ &timeout_watcher);
		3798	ev_async_send (EV_A_ &u->async_w);
		3799	pthread_mutex_unlock (&u->lock);
		3800
		3801	Note that sending the C<ev_async> watcher is required because otherwise
		3802	an event loop currently blocking in the kernel will have no knowledge
		3803	about the newly added timer. By waking up the loop it will pick up any new
		3804	watchers in the next event loop iteration.
		3805
		3806	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3807
		3808	While the overhead of a callback that e.g. schedules a thread is small, it
		3809	is still an overhead. If you embed libev, and your main usage is with some
		3810	kind of threads or coroutines, you might want to customise libev so that
		3811	doesn't need callbacks anymore.
		3812
		3813	Imagine you have coroutines that you can switch to using a function
		3814	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3815	and that due to some magic, the currently active coroutine is stored in a
		3816	global called C<current_coro>. Then you can build your own "wait for libev
		3817	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3818	the differing C<;> conventions):
		3819
		3820	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3821	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3822
		3823	That means instead of having a C callback function, you store the
		3824	coroutine to switch to in each watcher, and instead of having libev call
		3825	your callback, you instead have it switch to that coroutine.
		3826
		3827	A coroutine might now wait for an event with a function called
		3828	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3829	matter when, or whether the watcher is active or not when this function is
		3830	called):
		3831
		3832	void
		3833	wait_for_event (ev_watcher *w)
		3834	{
		3835	ev_cb_set (w) = current_coro;
		3836	switch_to (libev_coro);
		3837	}
		3838
		3839	That basically suspends the coroutine inside C<wait_for_event> and
		3840	continues the libev coroutine, which, when appropriate, switches back to
		3841	this or any other coroutine.
		3842
		3843	You can do similar tricks if you have, say, threads with an event queue -
		3844	instead of storing a coroutine, you store the queue object and instead of
		3845	switching to a coroutine, you push the watcher onto the queue and notify
		3846	any waiters.
		3847
		3848	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3849	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3850
		3851	// my_ev.h
		3852	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3853	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3854	#include "../libev/ev.h"
		3855
		3856	// my_ev.c
		3857	#define EV_H "my_ev.h"
		3858	#include "../libev/ev.c"
		3859
		3860	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3861	F<my_ev.c> into your project. When properly specifying include paths, you
		3862	can even use F<ev.h> as header file name directly.
2666		3863
2667		3864
2668	=head1 LIBEVENT EMULATION	3865	=head1 LIBEVENT EMULATION
2669		3866
2670	Libev offers a compatibility emulation layer for libevent. It cannot	3867	Libev offers a compatibility emulation layer for libevent. It cannot
2671	emulate the internals of libevent, so here are some usage hints:	3868	emulate the internals of libevent, so here are some usage hints:
2672		3869
2673	=over 4	3870	=over 4
		3871
		3872	=item * Only the libevent-1.4.1-beta API is being emulated.
		3873
		3874	This was the newest libevent version available when libev was implemented,
		3875	and is still mostly unchanged in 2010.
2674		3876
2675	=item * Use it by including <event.h>, as usual.	3877	=item * Use it by including <event.h>, as usual.
2676		3878
2677	=item * The following members are fully supported: ev_base, ev_callback,	3879	=item * The following members are fully supported: ev_base, ev_callback,
2678	ev_arg, ev_fd, ev_res, ev_events.	3880	ev_arg, ev_fd, ev_res, ev_events.
…		…
2684	=item * Priorities are not currently supported. Initialising priorities	3886	=item * Priorities are not currently supported. Initialising priorities
2685	will fail and all watchers will have the same priority, even though there	3887	will fail and all watchers will have the same priority, even though there
2686	is an ev_pri field.	3888	is an ev_pri field.
2687		3889
2688	=item * In libevent, the last base created gets the signals, in libev, the	3890	=item * In libevent, the last base created gets the signals, in libev, the
2689	first base created (== the default loop) gets the signals.	3891	base that registered the signal gets the signals.
2690		3892
2691	=item * Other members are not supported.	3893	=item * Other members are not supported.
2692		3894
2693	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3895	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2694	to use the libev header file and library.	3896	to use the libev header file and library.
2695		3897
2696	=back	3898	=back
2697		3899
2698	=head1 C++ SUPPORT	3900	=head1 C++ SUPPORT
		3901
		3902	=head2 C API
		3903
		3904	The normal C API should work fine when used from C++: both ev.h and the
		3905	libev sources can be compiled as C++. Therefore, code that uses the C API
		3906	will work fine.
		3907
		3908	Proper exception specifications might have to be added to callbacks passed
		3909	to libev: exceptions may be thrown only from watcher callbacks, all
		3910	other callbacks (allocator, syserr, loop acquire/release and periodioc
		3911	reschedule callbacks) must not throw exceptions, and might need a C<throw
		3912	()> specification. If you have code that needs to be compiled as both C
		3913	and C++ you can use the C<EV_THROW> macro for this:
		3914
		3915	static void
		3916	fatal_error (const char *msg) EV_THROW
		3917	{
		3918	perror (msg);
		3919	abort ();
		3920	}
		3921
		3922	...
		3923	ev_set_syserr_cb (fatal_error);
		3924
		3925	The only API functions that can currently throw exceptions are C<ev_run>,
		3926	C<ev_inoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		3927	because it runs cleanup watchers).
		3928
		3929	Throwing exceptions in watcher callbacks is only supported if libev itself
		3930	is compiled with a C++ compiler or your C and C++ environments allow
		3931	throwing exceptions through C libraries (most do).
		3932
		3933	=head2 C++ API
2699		3934
2700	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3935	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2701	you to use some convenience methods to start/stop watchers and also change	3936	you to use some convenience methods to start/stop watchers and also change
2702	the callback model to a model using method callbacks on objects.	3937	the callback model to a model using method callbacks on objects.
2703		3938
…		…
2713	Care has been taken to keep the overhead low. The only data member the C++	3948	Care has been taken to keep the overhead low. The only data member the C++
2714	classes add (compared to plain C-style watchers) is the event loop pointer	3949	classes add (compared to plain C-style watchers) is the event loop pointer
2715	that the watcher is associated with (or no additional members at all if	3950	that the watcher is associated with (or no additional members at all if
2716	you disable C<EV_MULTIPLICITY> when embedding libev).	3951	you disable C<EV_MULTIPLICITY> when embedding libev).
2717		3952
2718	Currently, functions, and static and non-static member functions can be	3953	Currently, functions, static and non-static member functions and classes
2719	used as callbacks. Other types should be easy to add as long as they only	3954	with C<operator ()> can be used as callbacks. Other types should be easy
2720	need one additional pointer for context. If you need support for other	3955	to add as long as they only need one additional pointer for context. If
2721	types of functors please contact the author (preferably after implementing	3956	you need support for other types of functors please contact the author
2722	it).	3957	(preferably after implementing it).
		3958
		3959	For all this to work, your C++ compiler either has to use the same calling
		3960	conventions as your C compiler (for static member functions), or you have
		3961	to embed libev and compile libev itself as C++.
2723		3962
2724	Here is a list of things available in the C<ev> namespace:	3963	Here is a list of things available in the C<ev> namespace:
2725		3964
2726	=over 4	3965	=over 4
2727		3966
…		…
2737	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	3976	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
2738		3977
2739	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	3978	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
2740	the same name in the C<ev> namespace, with the exception of C<ev_signal>	3979	the same name in the C<ev> namespace, with the exception of C<ev_signal>
2741	which is called C<ev::sig> to avoid clashes with the C<signal> macro	3980	which is called C<ev::sig> to avoid clashes with the C<signal> macro
2742	defines by many implementations.	3981	defined by many implementations.
2743		3982
2744	All of those classes have these methods:	3983	All of those classes have these methods:
2745		3984
2746	=over 4	3985	=over 4
2747		3986
2748	=item ev::TYPE::TYPE ()	3987	=item ev::TYPE::TYPE ()
2749		3988
2750	=item ev::TYPE::TYPE (struct ev_loop *)	3989	=item ev::TYPE::TYPE (loop)
2751		3990
2752	=item ev::TYPE::~TYPE	3991	=item ev::TYPE::~TYPE
2753		3992
2754	The constructor (optionally) takes an event loop to associate the watcher	3993	The constructor (optionally) takes an event loop to associate the watcher
2755	with. If it is omitted, it will use C<EV_DEFAULT>.	3994	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2787		4026
2788	myclass obj;	4027	myclass obj;
2789	ev::io iow;	4028	ev::io iow;
2790	iow.set <myclass, &myclass::io_cb> (&obj);	4029	iow.set <myclass, &myclass::io_cb> (&obj);
2791		4030
		4031	=item w->set (object *)
		4032
		4033	This is a variation of a method callback - leaving out the method to call
		4034	will default the method to C<operator ()>, which makes it possible to use
		4035	functor objects without having to manually specify the C<operator ()> all
		4036	the time. Incidentally, you can then also leave out the template argument
		4037	list.
		4038
		4039	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		4040	int revents)>.
		4041
		4042	See the method-C<set> above for more details.
		4043
		4044	Example: use a functor object as callback.
		4045
		4046	struct myfunctor
		4047	{
		4048	void operator() (ev::io &w, int revents)
		4049	{
		4050	...
		4051	}
		4052	}
		4053
		4054	myfunctor f;
		4055
		4056	ev::io w;
		4057	w.set (&f);
		4058
2792	=item w->set<function> (void *data = 0)	4059	=item w->set<function> (void *data = 0)
2793		4060
2794	Also sets a callback, but uses a static method or plain function as	4061	Also sets a callback, but uses a static method or plain function as
2795	callback. The optional C<data> argument will be stored in the watcher's	4062	callback. The optional C<data> argument will be stored in the watcher's
2796	C<data> member and is free for you to use.	4063	C<data> member and is free for you to use.
…		…
2802	Example: Use a plain function as callback.	4069	Example: Use a plain function as callback.
2803		4070
2804	static void io_cb (ev::io &w, int revents) { }	4071	static void io_cb (ev::io &w, int revents) { }
2805	iow.set <io_cb> ();	4072	iow.set <io_cb> ();
2806		4073
2807	=item w->set (struct ev_loop *)	4074	=item w->set (loop)
2808		4075
2809	Associates a different C<struct ev_loop> with this watcher. You can only	4076	Associates a different C<struct ev_loop> with this watcher. You can only
2810	do this when the watcher is inactive (and not pending either).	4077	do this when the watcher is inactive (and not pending either).
2811		4078
2812	=item w->set ([arguments])	4079	=item w->set ([arguments])
2813		4080
2814	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4081	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
2815	called at least once. Unlike the C counterpart, an active watcher gets	4082	method or a suitable start method must be called at least once. Unlike the
2816	automatically stopped and restarted when reconfiguring it with this	4083	C counterpart, an active watcher gets automatically stopped and restarted
2817	method.	4084	when reconfiguring it with this method.
2818		4085
2819	=item w->start ()	4086	=item w->start ()
2820		4087
2821	Starts the watcher. Note that there is no C<loop> argument, as the	4088	Starts the watcher. Note that there is no C<loop> argument, as the
2822	constructor already stores the event loop.	4089	constructor already stores the event loop.
2823		4090
		4091	=item w->start ([arguments])
		4092
		4093	Instead of calling C<set> and C<start> methods separately, it is often
		4094	convenient to wrap them in one call. Uses the same type of arguments as
		4095	the configure C<set> method of the watcher.
		4096
2824	=item w->stop ()	4097	=item w->stop ()
2825		4098
2826	Stops the watcher if it is active. Again, no C<loop> argument.	4099	Stops the watcher if it is active. Again, no C<loop> argument.
2827		4100
2828	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4101	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2840		4113
2841	=back	4114	=back
2842		4115
2843	=back	4116	=back
2844		4117
2845	Example: Define a class with an IO and idle watcher, start one of them in	4118	Example: Define a class with two I/O and idle watchers, start the I/O
2846	the constructor.	4119	watchers in the constructor.
2847		4120
2848	class myclass	4121	class myclass
2849	{	4122	{
2850	ev::io io ; void io_cb (ev::io &w, int revents);	4123	ev::io io ; void io_cb (ev::io &w, int revents);
		4124	ev::io io2 ; void io2_cb (ev::io &w, int revents);
2851	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4125	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2852		4126
2853	myclass (int fd)	4127	myclass (int fd)
2854	{	4128	{
2855	io .set <myclass, &myclass::io_cb > (this);	4129	io .set <myclass, &myclass::io_cb > (this);
		4130	io2 .set <myclass, &myclass::io2_cb > (this);
2856	idle.set <myclass, &myclass::idle_cb> (this);	4131	idle.set <myclass, &myclass::idle_cb> (this);
2857		4132
2858	io.start (fd, ev::READ);	4133	io.set (fd, ev::WRITE); // configure the watcher
		4134	io.start (); // start it whenever convenient
		4135
		4136	io2.start (fd, ev::READ); // set + start in one call
2859	}	4137	}
2860	};	4138	};
2861		4139
2862		4140
2863	=head1 OTHER LANGUAGE BINDINGS	4141	=head1 OTHER LANGUAGE BINDINGS
…		…
2882	L<http://software.schmorp.de/pkg/EV>.	4160	L<http://software.schmorp.de/pkg/EV>.
2883		4161
2884	=item Python	4162	=item Python
2885		4163
2886	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	4164	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2887	seems to be quite complete and well-documented. Note, however, that the	4165	seems to be quite complete and well-documented.
2888	patch they require for libev is outright dangerous as it breaks the ABI
2889	for everybody else, and therefore, should never be applied in an installed
2890	libev (if python requires an incompatible ABI then it needs to embed
2891	libev).
2892		4166
2893	=item Ruby	4167	=item Ruby
2894		4168
2895	Tony Arcieri has written a ruby extension that offers access to a subset	4169	Tony Arcieri has written a ruby extension that offers access to a subset
2896	of the libev API and adds file handle abstractions, asynchronous DNS and	4170	of the libev API and adds file handle abstractions, asynchronous DNS and
2897	more on top of it. It can be found via gem servers. Its homepage is at	4171	more on top of it. It can be found via gem servers. Its homepage is at
2898	L<http://rev.rubyforge.org/>.	4172	L<http://rev.rubyforge.org/>.
2899		4173
		4174	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		4175	makes rev work even on mingw.
		4176
		4177	=item Haskell
		4178
		4179	A haskell binding to libev is available at
		4180	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		4181
2900	=item D	4182	=item D
2901		4183
2902	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4184	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2903	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4185	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
		4186
		4187	=item Ocaml
		4188
		4189	Erkki Seppala has written Ocaml bindings for libev, to be found at
		4190	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		4191
		4192	=item Lua
		4193
		4194	Brian Maher has written a partial interface to libev for lua (at the
		4195	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		4196	L<http://github.com/brimworks/lua-ev>.
2904		4197
2905	=back	4198	=back
2906		4199
2907		4200
2908	=head1 MACRO MAGIC	4201	=head1 MACRO MAGIC
…		…
2922	loop argument"). The C<EV_A> form is used when this is the sole argument,	4215	loop argument"). The C<EV_A> form is used when this is the sole argument,
2923	C<EV_A_> is used when other arguments are following. Example:	4216	C<EV_A_> is used when other arguments are following. Example:
2924		4217
2925	ev_unref (EV_A);	4218	ev_unref (EV_A);
2926	ev_timer_add (EV_A_ watcher);	4219	ev_timer_add (EV_A_ watcher);
2927	ev_loop (EV_A_ 0);	4220	ev_run (EV_A_ 0);
2928		4221
2929	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4222	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2930	which is often provided by the following macro.	4223	which is often provided by the following macro.
2931		4224
2932	=item C<EV_P>, C<EV_P_>	4225	=item C<EV_P>, C<EV_P_>
…		…
2945	suitable for use with C<EV_A>.	4238	suitable for use with C<EV_A>.
2946		4239
2947	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4240	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2948		4241
2949	Similar to the other two macros, this gives you the value of the default	4242	Similar to the other two macros, this gives you the value of the default
2950	loop, if multiple loops are supported ("ev loop default").	4243	loop, if multiple loops are supported ("ev loop default"). The default loop
		4244	will be initialised if it isn't already initialised.
		4245
		4246	For non-multiplicity builds, these macros do nothing, so you always have
		4247	to initialise the loop somewhere.
2951		4248
2952	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4249	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
2953		4250
2954	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4251	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
2955	default loop has been initialised (C<UC> == unchecked). Their behaviour	4252	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
2972	}	4269	}
2973		4270
2974	ev_check check;	4271	ev_check check;
2975	ev_check_init (&check, check_cb);	4272	ev_check_init (&check, check_cb);
2976	ev_check_start (EV_DEFAULT_ &check);	4273	ev_check_start (EV_DEFAULT_ &check);
2977	ev_loop (EV_DEFAULT_ 0);	4274	ev_run (EV_DEFAULT_ 0);
2978		4275
2979	=head1 EMBEDDING	4276	=head1 EMBEDDING
2980		4277
2981	Libev can (and often is) directly embedded into host	4278	Libev can (and often is) directly embedded into host
2982	applications. Examples of applications that embed it include the Deliantra	4279	applications. Examples of applications that embed it include the Deliantra
…		…
3009		4306
3010	#define EV_STANDALONE 1	4307	#define EV_STANDALONE 1
3011	#include "ev.h"	4308	#include "ev.h"
3012		4309
3013	Both header files and implementation files can be compiled with a C++	4310	Both header files and implementation files can be compiled with a C++
3014	compiler (at least, thats a stated goal, and breakage will be treated	4311	compiler (at least, that's a stated goal, and breakage will be treated
3015	as a bug).	4312	as a bug).
3016		4313
3017	You need the following files in your source tree, or in a directory	4314	You need the following files in your source tree, or in a directory
3018	in your include path (e.g. in libev/ when using -Ilibev):	4315	in your include path (e.g. in libev/ when using -Ilibev):
3019		4316
…		…
3062	libev.m4	4359	libev.m4
3063		4360
3064	=head2 PREPROCESSOR SYMBOLS/MACROS	4361	=head2 PREPROCESSOR SYMBOLS/MACROS
3065		4362
3066	Libev can be configured via a variety of preprocessor symbols you have to	4363	Libev can be configured via a variety of preprocessor symbols you have to
3067	define before including any of its files. The default in the absence of	4364	define before including (or compiling) any of its files. The default in
3068	autoconf is documented for every option.	4365	the absence of autoconf is documented for every option.
		4366
		4367	Symbols marked with "(h)" do not change the ABI, and can have different
		4368	values when compiling libev vs. including F<ev.h>, so it is permissible
		4369	to redefine them before including F<ev.h> without breaking compatibility
		4370	to a compiled library. All other symbols change the ABI, which means all
		4371	users of libev and the libev code itself must be compiled with compatible
		4372	settings.
3069		4373
3070	=over 4	4374	=over 4
3071		4375
		4376	=item EV_COMPAT3 (h)
		4377
		4378	Backwards compatibility is a major concern for libev. This is why this
		4379	release of libev comes with wrappers for the functions and symbols that
		4380	have been renamed between libev version 3 and 4.
		4381
		4382	You can disable these wrappers (to test compatibility with future
		4383	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4384	sources. This has the additional advantage that you can drop the C<struct>
		4385	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4386	typedef in that case.
		4387
		4388	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4389	and in some even more future version the compatibility code will be
		4390	removed completely.
		4391
3072	=item EV_STANDALONE	4392	=item EV_STANDALONE (h)
3073		4393
3074	Must always be C<1> if you do not use autoconf configuration, which	4394	Must always be C<1> if you do not use autoconf configuration, which
3075	keeps libev from including F<config.h>, and it also defines dummy	4395	keeps libev from including F<config.h>, and it also defines dummy
3076	implementations for some libevent functions (such as logging, which is not	4396	implementations for some libevent functions (such as logging, which is not
3077	supported). It will also not define any of the structs usually found in	4397	supported). It will also not define any of the structs usually found in
3078	F<event.h> that are not directly supported by the libev core alone.	4398	F<event.h> that are not directly supported by the libev core alone.
3079		4399
		4400	In standalone mode, libev will still try to automatically deduce the
		4401	configuration, but has to be more conservative.
		4402
		4403	=item EV_USE_FLOOR
		4404
		4405	If defined to be C<1>, libev will use the C<floor ()> function for its
		4406	periodic reschedule calculations, otherwise libev will fall back on a
		4407	portable (slower) implementation. If you enable this, you usually have to
		4408	link against libm or something equivalent. Enabling this when the C<floor>
		4409	function is not available will fail, so the safe default is to not enable
		4410	this.
		4411
3080	=item EV_USE_MONOTONIC	4412	=item EV_USE_MONOTONIC
3081		4413
3082	If defined to be C<1>, libev will try to detect the availability of the	4414	If defined to be C<1>, libev will try to detect the availability of the
3083	monotonic clock option at both compile time and runtime. Otherwise no use	4415	monotonic clock option at both compile time and runtime. Otherwise no
3084	of the monotonic clock option will be attempted. If you enable this, you	4416	use of the monotonic clock option will be attempted. If you enable this,
3085	usually have to link against librt or something similar. Enabling it when	4417	you usually have to link against librt or something similar. Enabling it
3086	the functionality isn't available is safe, though, although you have	4418	when the functionality isn't available is safe, though, although you have
3087	to make sure you link against any libraries where the C<clock_gettime>	4419	to make sure you link against any libraries where the C<clock_gettime>
3088	function is hiding in (often F<-lrt>).	4420	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
3089		4421
3090	=item EV_USE_REALTIME	4422	=item EV_USE_REALTIME
3091		4423
3092	If defined to be C<1>, libev will try to detect the availability of the	4424	If defined to be C<1>, libev will try to detect the availability of the
3093	real-time clock option at compile time (and assume its availability at	4425	real-time clock option at compile time (and assume its availability
3094	runtime if successful). Otherwise no use of the real-time clock option will	4426	at runtime if successful). Otherwise no use of the real-time clock
3095	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	4427	option will be attempted. This effectively replaces C<gettimeofday>
3096	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	4428	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
3097	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	4429	correctness. See the note about libraries in the description of
		4430	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		4431	C<EV_USE_CLOCK_SYSCALL>.
		4432
		4433	=item EV_USE_CLOCK_SYSCALL
		4434
		4435	If defined to be C<1>, libev will try to use a direct syscall instead
		4436	of calling the system-provided C<clock_gettime> function. This option
		4437	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		4438	unconditionally pulls in C<libpthread>, slowing down single-threaded
		4439	programs needlessly. Using a direct syscall is slightly slower (in
		4440	theory), because no optimised vdso implementation can be used, but avoids
		4441	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		4442	higher, as it simplifies linking (no need for C<-lrt>).
3098		4443
3099	=item EV_USE_NANOSLEEP	4444	=item EV_USE_NANOSLEEP
3100		4445
3101	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	4446	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
3102	and will use it for delays. Otherwise it will use C<select ()>.	4447	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3118		4463
3119	=item EV_SELECT_USE_FD_SET	4464	=item EV_SELECT_USE_FD_SET
3120		4465
3121	If defined to C<1>, then the select backend will use the system C<fd_set>	4466	If defined to C<1>, then the select backend will use the system C<fd_set>
3122	structure. This is useful if libev doesn't compile due to a missing	4467	structure. This is useful if libev doesn't compile due to a missing
3123	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	4468	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3124	exotic systems. This usually limits the range of file descriptors to some	4469	on exotic systems. This usually limits the range of file descriptors to
3125	low limit such as 1024 or might have other limitations (winsocket only	4470	some low limit such as 1024 or might have other limitations (winsocket
3126	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	4471	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3127	influence the size of the C<fd_set> used.	4472	configures the maximum size of the C<fd_set>.
3128		4473
3129	=item EV_SELECT_IS_WINSOCKET	4474	=item EV_SELECT_IS_WINSOCKET
3130		4475
3131	When defined to C<1>, the select backend will assume that	4476	When defined to C<1>, the select backend will assume that
3132	select/socket/connect etc. don't understand file descriptors but	4477	select/socket/connect etc. don't understand file descriptors but
…		…
3134	be used is the winsock select). This means that it will call	4479	be used is the winsock select). This means that it will call
3135	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4480	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3136	it is assumed that all these functions actually work on fds, even	4481	it is assumed that all these functions actually work on fds, even
3137	on win32. Should not be defined on non-win32 platforms.	4482	on win32. Should not be defined on non-win32 platforms.
3138		4483
3139	=item EV_FD_TO_WIN32_HANDLE	4484	=item EV_FD_TO_WIN32_HANDLE(fd)
3140		4485
3141	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4486	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3142	file descriptors to socket handles. When not defining this symbol (the	4487	file descriptors to socket handles. When not defining this symbol (the
3143	default), then libev will call C<_get_osfhandle>, which is usually	4488	default), then libev will call C<_get_osfhandle>, which is usually
3144	correct. In some cases, programs use their own file descriptor management,	4489	correct. In some cases, programs use their own file descriptor management,
3145	in which case they can provide this function to map fds to socket handles.	4490	in which case they can provide this function to map fds to socket handles.
		4491
		4492	=item EV_WIN32_HANDLE_TO_FD(handle)
		4493
		4494	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4495	using the standard C<_open_osfhandle> function. For programs implementing
		4496	their own fd to handle mapping, overwriting this function makes it easier
		4497	to do so. This can be done by defining this macro to an appropriate value.
		4498
		4499	=item EV_WIN32_CLOSE_FD(fd)
		4500
		4501	If programs implement their own fd to handle mapping on win32, then this
		4502	macro can be used to override the C<close> function, useful to unregister
		4503	file descriptors again. Note that the replacement function has to close
		4504	the underlying OS handle.
3146		4505
3147	=item EV_USE_POLL	4506	=item EV_USE_POLL
3148		4507
3149	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4508	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3150	backend. Otherwise it will be enabled on non-win32 platforms. It	4509	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3186	If defined to be C<1>, libev will compile in support for the Linux inotify	4545	If defined to be C<1>, libev will compile in support for the Linux inotify
3187	interface to speed up C<ev_stat> watchers. Its actual availability will	4546	interface to speed up C<ev_stat> watchers. Its actual availability will
3188	be detected at runtime. If undefined, it will be enabled if the headers	4547	be detected at runtime. If undefined, it will be enabled if the headers
3189	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4548	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3190		4549
		4550	=item EV_NO_SMP
		4551
		4552	If defined to be C<1>, libev will assume that memory is always coherent
		4553	between threads, that is, threads can be used, but threads never run on
		4554	different cpus (or different cpu cores). This reduces dependencies
		4555	and makes libev faster.
		4556
		4557	=item EV_NO_THREADS
		4558
		4559	If defined to be C<1>, libev will assume that it will never be called
		4560	from different threads, which is a stronger assumption than C<EV_NO_SMP>,
		4561	above. This reduces dependencies and makes libev faster.
		4562
3191	=item EV_ATOMIC_T	4563	=item EV_ATOMIC_T
3192		4564
3193	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4565	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3194	access is atomic with respect to other threads or signal contexts. No such	4566	access is atomic and serialised with respect to other threads or signal
3195	type is easily found in the C language, so you can provide your own type	4567	contexts. No such type is easily found in the C language, so you can
3196	that you know is safe for your purposes. It is used both for signal handler "locking"	4568	provide your own type that you know is safe for your purposes. It is used
3197	as well as for signal and thread safety in C<ev_async> watchers.	4569	both for signal handler "locking" as well as for signal and thread safety
		4570	in C<ev_async> watchers.
3198		4571
3199	In the absence of this define, libev will use C<sig_atomic_t volatile>	4572	In the absence of this define, libev will use C<sig_atomic_t volatile>
3200	(from F<signal.h>), which is usually good enough on most platforms.	4573	(from F<signal.h>), which is usually good enough on most platforms,
		4574	although strictly speaking using a type that also implies a memory fence
		4575	is required.
3201		4576
3202	=item EV_H	4577	=item EV_H (h)
3203		4578
3204	The name of the F<ev.h> header file used to include it. The default if	4579	The name of the F<ev.h> header file used to include it. The default if
3205	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4580	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3206	used to virtually rename the F<ev.h> header file in case of conflicts.	4581	used to virtually rename the F<ev.h> header file in case of conflicts.
3207		4582
3208	=item EV_CONFIG_H	4583	=item EV_CONFIG_H (h)
3209		4584
3210	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4585	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3211	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4586	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3212	C<EV_H>, above.	4587	C<EV_H>, above.
3213		4588
3214	=item EV_EVENT_H	4589	=item EV_EVENT_H (h)
3215		4590
3216	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4591	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3217	of how the F<event.h> header can be found, the default is C<"event.h">.	4592	of how the F<event.h> header can be found, the default is C<"event.h">.
3218		4593
3219	=item EV_PROTOTYPES	4594	=item EV_PROTOTYPES (h)
3220		4595
3221	If defined to be C<0>, then F<ev.h> will not define any function	4596	If defined to be C<0>, then F<ev.h> will not define any function
3222	prototypes, but still define all the structs and other symbols. This is	4597	prototypes, but still define all the structs and other symbols. This is
3223	occasionally useful if you want to provide your own wrapper functions	4598	occasionally useful if you want to provide your own wrapper functions
3224	around libev functions.	4599	around libev functions.
…		…
3229	will have the C<struct ev_loop *> as first argument, and you can create	4604	will have the C<struct ev_loop *> as first argument, and you can create
3230	additional independent event loops. Otherwise there will be no support	4605	additional independent event loops. Otherwise there will be no support
3231	for multiple event loops and there is no first event loop pointer	4606	for multiple event loops and there is no first event loop pointer
3232	argument. Instead, all functions act on the single default loop.	4607	argument. Instead, all functions act on the single default loop.
3233		4608
		4609	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4610	default loop when multiplicity is switched off - you always have to
		4611	initialise the loop manually in this case.
		4612
3234	=item EV_MINPRI	4613	=item EV_MINPRI
3235		4614
3236	=item EV_MAXPRI	4615	=item EV_MAXPRI
3237		4616
3238	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4617	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3246	fine.	4625	fine.
3247		4626
3248	If your embedding application does not need any priorities, defining these	4627	If your embedding application does not need any priorities, defining these
3249	both to C<0> will save some memory and CPU.	4628	both to C<0> will save some memory and CPU.
3250		4629
3251	=item EV_PERIODIC_ENABLE	4630	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4631	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4632	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3252		4633
3253	If undefined or defined to be C<1>, then periodic timers are supported. If	4634	If undefined or defined to be C<1> (and the platform supports it), then
3254	defined to be C<0>, then they are not. Disabling them saves a few kB of	4635	the respective watcher type is supported. If defined to be C<0>, then it
3255	code.	4636	is not. Disabling watcher types mainly saves code size.
3256		4637
3257	=item EV_IDLE_ENABLE	4638	=item EV_FEATURES
3258
3259	If undefined or defined to be C<1>, then idle watchers are supported. If
3260	defined to be C<0>, then they are not. Disabling them saves a few kB of
3261	code.
3262
3263	=item EV_EMBED_ENABLE
3264
3265	If undefined or defined to be C<1>, then embed watchers are supported. If
3266	defined to be C<0>, then they are not. Embed watchers rely on most other
3267	watcher types, which therefore must not be disabled.
3268
3269	=item EV_STAT_ENABLE
3270
3271	If undefined or defined to be C<1>, then stat watchers are supported. If
3272	defined to be C<0>, then they are not.
3273
3274	=item EV_FORK_ENABLE
3275
3276	If undefined or defined to be C<1>, then fork watchers are supported. If
3277	defined to be C<0>, then they are not.
3278
3279	=item EV_ASYNC_ENABLE
3280
3281	If undefined or defined to be C<1>, then async watchers are supported. If
3282	defined to be C<0>, then they are not.
3283
3284	=item EV_MINIMAL
3285		4639
3286	If you need to shave off some kilobytes of code at the expense of some	4640	If you need to shave off some kilobytes of code at the expense of some
3287	speed, define this symbol to C<1>. Currently this is used to override some	4641	speed (but with the full API), you can define this symbol to request
3288	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4642	certain subsets of functionality. The default is to enable all features
3289	much smaller 2-heap for timer management over the default 4-heap.	4643	that can be enabled on the platform.
		4644
		4645	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4646	with some broad features you want) and then selectively re-enable
		4647	additional parts you want, for example if you want everything minimal,
		4648	but multiple event loop support, async and child watchers and the poll
		4649	backend, use this:
		4650
		4651	#define EV_FEATURES 0
		4652	#define EV_MULTIPLICITY 1
		4653	#define EV_USE_POLL 1
		4654	#define EV_CHILD_ENABLE 1
		4655	#define EV_ASYNC_ENABLE 1
		4656
		4657	The actual value is a bitset, it can be a combination of the following
		4658	values (by default, all of these are enabled):
		4659
		4660	=over 4
		4661
		4662	=item C<1> - faster/larger code
		4663
		4664	Use larger code to speed up some operations.
		4665
		4666	Currently this is used to override some inlining decisions (enlarging the
		4667	code size by roughly 30% on amd64).
		4668
		4669	When optimising for size, use of compiler flags such as C<-Os> with
		4670	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4671	assertions.
		4672
		4673	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4674	(e.g. gcc with C<-Os>).
		4675
		4676	=item C<2> - faster/larger data structures
		4677
		4678	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4679	hash table sizes and so on. This will usually further increase code size
		4680	and can additionally have an effect on the size of data structures at
		4681	runtime.
		4682
		4683	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4684	(e.g. gcc with C<-Os>).
		4685
		4686	=item C<4> - full API configuration
		4687
		4688	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4689	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4690
		4691	=item C<8> - full API
		4692
		4693	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4694	details on which parts of the API are still available without this
		4695	feature, and do not complain if this subset changes over time.
		4696
		4697	=item C<16> - enable all optional watcher types
		4698
		4699	Enables all optional watcher types. If you want to selectively enable
		4700	only some watcher types other than I/O and timers (e.g. prepare,
		4701	embed, async, child...) you can enable them manually by defining
		4702	C<EV_watchertype_ENABLE> to C<1> instead.
		4703
		4704	=item C<32> - enable all backends
		4705
		4706	This enables all backends - without this feature, you need to enable at
		4707	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4708
		4709	=item C<64> - enable OS-specific "helper" APIs
		4710
		4711	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4712	default.
		4713
		4714	=back
		4715
		4716	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4717	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4718	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4719	watchers, timers and monotonic clock support.
		4720
		4721	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4722	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4723	your program might be left out as well - a binary starting a timer and an
		4724	I/O watcher then might come out at only 5Kb.
		4725
		4726	=item EV_API_STATIC
		4727
		4728	If this symbol is defined (by default it is not), then all identifiers
		4729	will have static linkage. This means that libev will not export any
		4730	identifiers, and you cannot link against libev anymore. This can be useful
		4731	when you embed libev, only want to use libev functions in a single file,
		4732	and do not want its identifiers to be visible.
		4733
		4734	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4735	wants to use libev.
		4736
		4737	This option only works when libev is compiled with a C compiler, as C++
		4738	doesn't support the required declaration syntax.
		4739
		4740	=item EV_AVOID_STDIO
		4741
		4742	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4743	functions (printf, scanf, perror etc.). This will increase the code size
		4744	somewhat, but if your program doesn't otherwise depend on stdio and your
		4745	libc allows it, this avoids linking in the stdio library which is quite
		4746	big.
		4747
		4748	Note that error messages might become less precise when this option is
		4749	enabled.
		4750
		4751	=item EV_NSIG
		4752
		4753	The highest supported signal number, +1 (or, the number of
		4754	signals): Normally, libev tries to deduce the maximum number of signals
		4755	automatically, but sometimes this fails, in which case it can be
		4756	specified. Also, using a lower number than detected (C<32> should be
		4757	good for about any system in existence) can save some memory, as libev
		4758	statically allocates some 12-24 bytes per signal number.
3290		4759
3291	=item EV_PID_HASHSIZE	4760	=item EV_PID_HASHSIZE
3292		4761
3293	C<ev_child> watchers use a small hash table to distribute workload by	4762	C<ev_child> watchers use a small hash table to distribute workload by
3294	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4763	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3295	than enough. If you need to manage thousands of children you might want to	4764	usually more than enough. If you need to manage thousands of children you
3296	increase this value (I<must> be a power of two).	4765	might want to increase this value (I<must> be a power of two).
3297		4766
3298	=item EV_INOTIFY_HASHSIZE	4767	=item EV_INOTIFY_HASHSIZE
3299		4768
3300	C<ev_stat> watchers use a small hash table to distribute workload by	4769	C<ev_stat> watchers use a small hash table to distribute workload by
3301	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4770	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3302	usually more than enough. If you need to manage thousands of C<ev_stat>	4771	disabled), usually more than enough. If you need to manage thousands of
3303	watchers you might want to increase this value (I<must> be a power of	4772	C<ev_stat> watchers you might want to increase this value (I<must> be a
3304	two).	4773	power of two).
3305		4774
3306	=item EV_USE_4HEAP	4775	=item EV_USE_4HEAP
3307		4776
3308	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4777	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3309	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4778	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3310	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4779	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3311	faster performance with many (thousands) of watchers.	4780	faster performance with many (thousands) of watchers.
3312		4781
3313	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4782	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3314	(disabled).	4783	will be C<0>.
3315		4784
3316	=item EV_HEAP_CACHE_AT	4785	=item EV_HEAP_CACHE_AT
3317		4786
3318	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4787	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3319	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4788	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3320	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4789	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3321	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4790	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3322	but avoids random read accesses on heap changes. This improves performance	4791	but avoids random read accesses on heap changes. This improves performance
3323	noticeably with many (hundreds) of watchers.	4792	noticeably with many (hundreds) of watchers.
3324		4793
3325	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4794	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3326	(disabled).	4795	will be C<0>.
3327		4796
3328	=item EV_VERIFY	4797	=item EV_VERIFY
3329		4798
3330	Controls how much internal verification (see C<ev_loop_verify ()>) will	4799	Controls how much internal verification (see C<ev_verify ()>) will
3331	be done: If set to C<0>, no internal verification code will be compiled	4800	be done: If set to C<0>, no internal verification code will be compiled
3332	in. If set to C<1>, then verification code will be compiled in, but not	4801	in. If set to C<1>, then verification code will be compiled in, but not
3333	called. If set to C<2>, then the internal verification code will be	4802	called. If set to C<2>, then the internal verification code will be
3334	called once per loop, which can slow down libev. If set to C<3>, then the	4803	called once per loop, which can slow down libev. If set to C<3>, then the
3335	verification code will be called very frequently, which will slow down	4804	verification code will be called very frequently, which will slow down
3336	libev considerably.	4805	libev considerably.
3337		4806
3338	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4807	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3339	C<0>.	4808	will be C<0>.
3340		4809
3341	=item EV_COMMON	4810	=item EV_COMMON
3342		4811
3343	By default, all watchers have a C<void *data> member. By redefining	4812	By default, all watchers have a C<void *data> member. By redefining
3344	this macro to a something else you can include more and other types of	4813	this macro to something else you can include more and other types of
3345	members. You have to define it each time you include one of the files,	4814	members. You have to define it each time you include one of the files,
3346	though, and it must be identical each time.	4815	though, and it must be identical each time.
3347		4816
3348	For example, the perl EV module uses something like this:	4817	For example, the perl EV module uses something like this:
3349		4818
…		…
3402	file.	4871	file.
3403		4872
3404	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4873	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3405	that everybody includes and which overrides some configure choices:	4874	that everybody includes and which overrides some configure choices:
3406		4875
3407	#define EV_MINIMAL 1	4876	#define EV_FEATURES 8
3408	#define EV_USE_POLL 0	4877	#define EV_USE_SELECT 1
3409	#define EV_MULTIPLICITY 0
3410	#define EV_PERIODIC_ENABLE 0	4878	#define EV_PREPARE_ENABLE 1
		4879	#define EV_IDLE_ENABLE 1
3411	#define EV_STAT_ENABLE 0	4880	#define EV_SIGNAL_ENABLE 1
3412	#define EV_FORK_ENABLE 0	4881	#define EV_CHILD_ENABLE 1
		4882	#define EV_USE_STDEXCEPT 0
3413	#define EV_CONFIG_H <config.h>	4883	#define EV_CONFIG_H <config.h>
3414	#define EV_MINPRI 0
3415	#define EV_MAXPRI 0
3416		4884
3417	#include "ev++.h"	4885	#include "ev++.h"
3418		4886
3419	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4887	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3420		4888
3421	#include "ev_cpp.h"	4889	#include "ev_cpp.h"
3422	#include "ev.c"	4890	#include "ev.c"
3423		4891
3424	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4892	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3425		4893
3426	=head2 THREADS AND COROUTINES	4894	=head2 THREADS AND COROUTINES
3427		4895
3428	=head3 THREADS	4896	=head3 THREADS
3429		4897
…		…
3480	default loop and triggering an C<ev_async> watcher from the default loop	4948	default loop and triggering an C<ev_async> watcher from the default loop
3481	watcher callback into the event loop interested in the signal.	4949	watcher callback into the event loop interested in the signal.
3482		4950
3483	=back	4951	=back
3484		4952
		4953	See also L<THREAD LOCKING EXAMPLE>.
		4954
3485	=head3 COROUTINES	4955	=head3 COROUTINES
3486		4956
3487	Libev is very accommodating to coroutines ("cooperative threads"):	4957	Libev is very accommodating to coroutines ("cooperative threads"):
3488	libev fully supports nesting calls to its functions from different	4958	libev fully supports nesting calls to its functions from different
3489	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4959	coroutines (e.g. you can call C<ev_run> on the same loop from two
3490	different coroutines, and switch freely between both coroutines running the	4960	different coroutines, and switch freely between both coroutines running
3491	loop, as long as you don't confuse yourself). The only exception is that	4961	the loop, as long as you don't confuse yourself). The only exception is
3492	you must not do this from C<ev_periodic> reschedule callbacks.	4962	that you must not do this from C<ev_periodic> reschedule callbacks.
3493		4963
3494	Care has been taken to ensure that libev does not keep local state inside	4964	Care has been taken to ensure that libev does not keep local state inside
3495	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4965	C<ev_run>, and other calls do not usually allow for coroutine switches as
3496	they do not clal any callbacks.	4966	they do not call any callbacks.
3497		4967
3498	=head2 COMPILER WARNINGS	4968	=head2 COMPILER WARNINGS
3499		4969
3500	Depending on your compiler and compiler settings, you might get no or a	4970	Depending on your compiler and compiler settings, you might get no or a
3501	lot of warnings when compiling libev code. Some people are apparently	4971	lot of warnings when compiling libev code. Some people are apparently
…		…
3511	maintainable.	4981	maintainable.
3512		4982
3513	And of course, some compiler warnings are just plain stupid, or simply	4983	And of course, some compiler warnings are just plain stupid, or simply
3514	wrong (because they don't actually warn about the condition their message	4984	wrong (because they don't actually warn about the condition their message
3515	seems to warn about). For example, certain older gcc versions had some	4985	seems to warn about). For example, certain older gcc versions had some
3516	warnings that resulted an extreme number of false positives. These have	4986	warnings that resulted in an extreme number of false positives. These have
3517	been fixed, but some people still insist on making code warn-free with	4987	been fixed, but some people still insist on making code warn-free with
3518	such buggy versions.	4988	such buggy versions.
3519		4989
3520	While libev is written to generate as few warnings as possible,	4990	While libev is written to generate as few warnings as possible,
3521	"warn-free" code is not a goal, and it is recommended not to build libev	4991	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3535	==2274== definitely lost: 0 bytes in 0 blocks.	5005	==2274== definitely lost: 0 bytes in 0 blocks.
3536	==2274== possibly lost: 0 bytes in 0 blocks.	5006	==2274== possibly lost: 0 bytes in 0 blocks.
3537	==2274== still reachable: 256 bytes in 1 blocks.	5007	==2274== still reachable: 256 bytes in 1 blocks.
3538		5008
3539	Then there is no memory leak, just as memory accounted to global variables	5009	Then there is no memory leak, just as memory accounted to global variables
3540	is not a memleak - the memory is still being refernced, and didn't leak.	5010	is not a memleak - the memory is still being referenced, and didn't leak.
3541		5011
3542	Similarly, under some circumstances, valgrind might report kernel bugs	5012	Similarly, under some circumstances, valgrind might report kernel bugs
3543	as if it were a bug in libev (e.g. in realloc or in the poll backend,	5013	as if it were a bug in libev (e.g. in realloc or in the poll backend,
3544	although an acceptable workaround has been found here), or it might be	5014	although an acceptable workaround has been found here), or it might be
3545	confused.	5015	confused.
…		…
3557	I suggest using suppression lists.	5027	I suggest using suppression lists.
3558		5028
3559		5029
3560	=head1 PORTABILITY NOTES	5030	=head1 PORTABILITY NOTES
3561		5031
		5032	=head2 GNU/LINUX 32 BIT LIMITATIONS
		5033
		5034	GNU/Linux is the only common platform that supports 64 bit file/large file
		5035	interfaces but I<disables> them by default.
		5036
		5037	That means that libev compiled in the default environment doesn't support
		5038	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		5039
		5040	Unfortunately, many programs try to work around this GNU/Linux issue
		5041	by enabling the large file API, which makes them incompatible with the
		5042	standard libev compiled for their system.
		5043
		5044	Likewise, libev cannot enable the large file API itself as this would
		5045	suddenly make it incompatible to the default compile time environment,
		5046	i.e. all programs not using special compile switches.
		5047
		5048	=head2 OS/X AND DARWIN BUGS
		5049
		5050	The whole thing is a bug if you ask me - basically any system interface
		5051	you touch is broken, whether it is locales, poll, kqueue or even the
		5052	OpenGL drivers.
		5053
		5054	=head3 C<kqueue> is buggy
		5055
		5056	The kqueue syscall is broken in all known versions - most versions support
		5057	only sockets, many support pipes.
		5058
		5059	Libev tries to work around this by not using C<kqueue> by default on this
		5060	rotten platform, but of course you can still ask for it when creating a
		5061	loop - embedding a socket-only kqueue loop into a select-based one is
		5062	probably going to work well.
		5063
		5064	=head3 C<poll> is buggy
		5065
		5066	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		5067	implementation by something calling C<kqueue> internally around the 10.5.6
		5068	release, so now C<kqueue> I<and> C<poll> are broken.
		5069
		5070	Libev tries to work around this by not using C<poll> by default on
		5071	this rotten platform, but of course you can still ask for it when creating
		5072	a loop.
		5073
		5074	=head3 C<select> is buggy
		5075
		5076	All that's left is C<select>, and of course Apple found a way to fuck this
		5077	one up as well: On OS/X, C<select> actively limits the number of file
		5078	descriptors you can pass in to 1024 - your program suddenly crashes when
		5079	you use more.
		5080
		5081	There is an undocumented "workaround" for this - defining
		5082	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		5083	work on OS/X.
		5084
		5085	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		5086
		5087	=head3 C<errno> reentrancy
		5088
		5089	The default compile environment on Solaris is unfortunately so
		5090	thread-unsafe that you can't even use components/libraries compiled
		5091	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		5092	defined by default. A valid, if stupid, implementation choice.
		5093
		5094	If you want to use libev in threaded environments you have to make sure
		5095	it's compiled with C<_REENTRANT> defined.
		5096
		5097	=head3 Event port backend
		5098
		5099	The scalable event interface for Solaris is called "event
		5100	ports". Unfortunately, this mechanism is very buggy in all major
		5101	releases. If you run into high CPU usage, your program freezes or you get
		5102	a large number of spurious wakeups, make sure you have all the relevant
		5103	and latest kernel patches applied. No, I don't know which ones, but there
		5104	are multiple ones to apply, and afterwards, event ports actually work
		5105	great.
		5106
		5107	If you can't get it to work, you can try running the program by setting
		5108	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		5109	C<select> backends.
		5110
		5111	=head2 AIX POLL BUG
		5112
		5113	AIX unfortunately has a broken C<poll.h> header. Libev works around
		5114	this by trying to avoid the poll backend altogether (i.e. it's not even
		5115	compiled in), which normally isn't a big problem as C<select> works fine
		5116	with large bitsets on AIX, and AIX is dead anyway.
		5117
3562	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5118	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		5119
		5120	=head3 General issues
3563		5121
3564	Win32 doesn't support any of the standards (e.g. POSIX) that libev	5122	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3565	requires, and its I/O model is fundamentally incompatible with the POSIX	5123	requires, and its I/O model is fundamentally incompatible with the POSIX
3566	model. Libev still offers limited functionality on this platform in	5124	model. Libev still offers limited functionality on this platform in
3567	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5125	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3568	descriptors. This only applies when using Win32 natively, not when using	5126	descriptors. This only applies when using Win32 natively, not when using
3569	e.g. cygwin.	5127	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		5128	as every compiler comes with a slightly differently broken/incompatible
		5129	environment.
3570		5130
3571	Lifting these limitations would basically require the full	5131	Lifting these limitations would basically require the full
3572	re-implementation of the I/O system. If you are into these kinds of	5132	re-implementation of the I/O system. If you are into this kind of thing,
3573	things, then note that glib does exactly that for you in a very portable	5133	then note that glib does exactly that for you in a very portable way (note
3574	way (note also that glib is the slowest event library known to man).	5134	also that glib is the slowest event library known to man).
3575		5135
3576	There is no supported compilation method available on windows except	5136	There is no supported compilation method available on windows except
3577	embedding it into other applications.	5137	embedding it into other applications.
		5138
		5139	Sensible signal handling is officially unsupported by Microsoft - libev
		5140	tries its best, but under most conditions, signals will simply not work.
3578		5141
3579	Not a libev limitation but worth mentioning: windows apparently doesn't	5142	Not a libev limitation but worth mentioning: windows apparently doesn't
3580	accept large writes: instead of resulting in a partial write, windows will	5143	accept large writes: instead of resulting in a partial write, windows will
3581	either accept everything or return C<ENOBUFS> if the buffer is too large,	5144	either accept everything or return C<ENOBUFS> if the buffer is too large,
3582	so make sure you only write small amounts into your sockets (less than a	5145	so make sure you only write small amounts into your sockets (less than a
…		…
3587	the abysmal performance of winsockets, using a large number of sockets	5150	the abysmal performance of winsockets, using a large number of sockets
3588	is not recommended (and not reasonable). If your program needs to use	5151	is not recommended (and not reasonable). If your program needs to use
3589	more than a hundred or so sockets, then likely it needs to use a totally	5152	more than a hundred or so sockets, then likely it needs to use a totally
3590	different implementation for windows, as libev offers the POSIX readiness	5153	different implementation for windows, as libev offers the POSIX readiness
3591	notification model, which cannot be implemented efficiently on windows	5154	notification model, which cannot be implemented efficiently on windows
3592	(Microsoft monopoly games).	5155	(due to Microsoft monopoly games).
3593		5156
3594	A typical way to use libev under windows is to embed it (see the embedding	5157	A typical way to use libev under windows is to embed it (see the embedding
3595	section for details) and use the following F<evwrap.h> header file instead	5158	section for details) and use the following F<evwrap.h> header file instead
3596	of F<ev.h>:	5159	of F<ev.h>:
3597		5160
…		…
3604	you do I<not> compile the F<ev.c> or any other embedded source files!):	5167	you do I<not> compile the F<ev.c> or any other embedded source files!):
3605		5168
3606	#include "evwrap.h"	5169	#include "evwrap.h"
3607	#include "ev.c"	5170	#include "ev.c"
3608		5171
3609	=over 4
3610
3611	=item The winsocket select function	5172	=head3 The winsocket C<select> function
3612		5173
3613	The winsocket C<select> function doesn't follow POSIX in that it	5174	The winsocket C<select> function doesn't follow POSIX in that it
3614	requires socket I<handles> and not socket I<file descriptors> (it is	5175	requires socket I<handles> and not socket I<file descriptors> (it is
3615	also extremely buggy). This makes select very inefficient, and also	5176	also extremely buggy). This makes select very inefficient, and also
3616	requires a mapping from file descriptors to socket handles (the Microsoft	5177	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3625	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	5186	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3626		5187
3627	Note that winsockets handling of fd sets is O(n), so you can easily get a	5188	Note that winsockets handling of fd sets is O(n), so you can easily get a
3628	complexity in the O(n²) range when using win32.	5189	complexity in the O(n²) range when using win32.
3629		5190
3630	=item Limited number of file descriptors	5191	=head3 Limited number of file descriptors
3631		5192
3632	Windows has numerous arbitrary (and low) limits on things.	5193	Windows has numerous arbitrary (and low) limits on things.
3633		5194
3634	Early versions of winsocket's select only supported waiting for a maximum	5195	Early versions of winsocket's select only supported waiting for a maximum
3635	of C<64> handles (probably owning to the fact that all windows kernels	5196	of C<64> handles (probably owning to the fact that all windows kernels
3636	can only wait for C<64> things at the same time internally; Microsoft	5197	can only wait for C<64> things at the same time internally; Microsoft
3637	recommends spawning a chain of threads and wait for 63 handles and the	5198	recommends spawning a chain of threads and wait for 63 handles and the
3638	previous thread in each. Great).	5199	previous thread in each. Sounds great!).
3639		5200
3640	Newer versions support more handles, but you need to define C<FD_SETSIZE>	5201	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3641	to some high number (e.g. C<2048>) before compiling the winsocket select	5202	to some high number (e.g. C<2048>) before compiling the winsocket select
3642	call (which might be in libev or elsewhere, for example, perl does its own	5203	call (which might be in libev or elsewhere, for example, perl and many
3643	select emulation on windows).	5204	other interpreters do their own select emulation on windows).
3644		5205
3645	Another limit is the number of file descriptors in the Microsoft runtime	5206	Another limit is the number of file descriptors in the Microsoft runtime
3646	libraries, which by default is C<64> (there must be a hidden I<64> fetish	5207	libraries, which by default is C<64> (there must be a hidden I<64>
3647	or something like this inside Microsoft). You can increase this by calling	5208	fetish or something like this inside Microsoft). You can increase this
3648	C<_setmaxstdio>, which can increase this limit to C<2048> (another	5209	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3649	arbitrary limit), but is broken in many versions of the Microsoft runtime	5210	(another arbitrary limit), but is broken in many versions of the Microsoft
3650	libraries.
3651
3652	This might get you to about C<512> or C<2048> sockets (depending on	5211	runtime libraries. This might get you to about C<512> or C<2048> sockets
3653	windows version and/or the phase of the moon). To get more, you need to	5212	(depending on windows version and/or the phase of the moon). To get more,
3654	wrap all I/O functions and provide your own fd management, but the cost of	5213	you need to wrap all I/O functions and provide your own fd management, but
3655	calling select (O(n²)) will likely make this unworkable.	5214	the cost of calling select (O(n²)) will likely make this unworkable.
3656
3657	=back
3658		5215
3659	=head2 PORTABILITY REQUIREMENTS	5216	=head2 PORTABILITY REQUIREMENTS
3660		5217
3661	In addition to a working ISO-C implementation and of course the	5218	In addition to a working ISO-C implementation and of course the
3662	backend-specific APIs, libev relies on a few additional extensions:	5219	backend-specific APIs, libev relies on a few additional extensions:
…		…
3669	Libev assumes not only that all watcher pointers have the same internal	5226	Libev assumes not only that all watcher pointers have the same internal
3670	structure (guaranteed by POSIX but not by ISO C for example), but it also	5227	structure (guaranteed by POSIX but not by ISO C for example), but it also
3671	assumes that the same (machine) code can be used to call any watcher	5228	assumes that the same (machine) code can be used to call any watcher
3672	callback: The watcher callbacks have different type signatures, but libev	5229	callback: The watcher callbacks have different type signatures, but libev
3673	calls them using an C<ev_watcher *> internally.	5230	calls them using an C<ev_watcher *> internally.
		5231
		5232	=item pointer accesses must be thread-atomic
		5233
		5234	Accessing a pointer value must be atomic, it must both be readable and
		5235	writable in one piece - this is the case on all current architectures.
3674		5236
3675	=item C<sig_atomic_t volatile> must be thread-atomic as well	5237	=item C<sig_atomic_t volatile> must be thread-atomic as well
3676		5238
3677	The type C<sig_atomic_t volatile> (or whatever is defined as	5239	The type C<sig_atomic_t volatile> (or whatever is defined as
3678	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5240	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
3701	watchers.	5263	watchers.
3702		5264
3703	=item C<double> must hold a time value in seconds with enough accuracy	5265	=item C<double> must hold a time value in seconds with enough accuracy
3704		5266
3705	The type C<double> is used to represent timestamps. It is required to	5267	The type C<double> is used to represent timestamps. It is required to
3706	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5268	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3707	enough for at least into the year 4000. This requirement is fulfilled by	5269	good enough for at least into the year 4000 with millisecond accuracy
		5270	(the design goal for libev). This requirement is overfulfilled by
3708	implementations implementing IEEE 754 (basically all existing ones).	5271	implementations using IEEE 754, which is basically all existing ones.
		5272
		5273	With IEEE 754 doubles, you get microsecond accuracy until at least the
		5274	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5275	is either obsolete or somebody patched it to use C<long double> or
		5276	something like that, just kidding).
3709		5277
3710	=back	5278	=back
3711		5279
3712	If you know of other additional requirements drop me a note.	5280	If you know of other additional requirements drop me a note.
3713		5281
…		…
3775	=item Processing ev_async_send: O(number_of_async_watchers)	5343	=item Processing ev_async_send: O(number_of_async_watchers)
3776		5344
3777	=item Processing signals: O(max_signal_number)	5345	=item Processing signals: O(max_signal_number)
3778		5346
3779	Sending involves a system call I<iff> there were no other C<ev_async_send>	5347	Sending involves a system call I<iff> there were no other C<ev_async_send>
3780	calls in the current loop iteration. Checking for async and signal events	5348	calls in the current loop iteration and the loop is currently
		5349	blocked. Checking for async and signal events involves iterating over all
3781	involves iterating over all running async watchers or all signal numbers.	5350	running async watchers or all signal numbers.
3782		5351
3783	=back	5352	=back
3784		5353
3785		5354
		5355	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5356
		5357	The major version 4 introduced some incompatible changes to the API.
		5358
		5359	At the moment, the C<ev.h> header file provides compatibility definitions
		5360	for all changes, so most programs should still compile. The compatibility
		5361	layer might be removed in later versions of libev, so better update to the
		5362	new API early than late.
		5363
		5364	=over 4
		5365
		5366	=item C<EV_COMPAT3> backwards compatibility mechanism
		5367
		5368	The backward compatibility mechanism can be controlled by
		5369	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5370	section.
		5371
		5372	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5373
		5374	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5375
		5376	ev_loop_destroy (EV_DEFAULT_UC);
		5377	ev_loop_fork (EV_DEFAULT);
		5378
		5379	=item function/symbol renames
		5380
		5381	A number of functions and symbols have been renamed:
		5382
		5383	ev_loop => ev_run
		5384	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5385	EVLOOP_ONESHOT => EVRUN_ONCE
		5386
		5387	ev_unloop => ev_break
		5388	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5389	EVUNLOOP_ONE => EVBREAK_ONE
		5390	EVUNLOOP_ALL => EVBREAK_ALL
		5391
		5392	EV_TIMEOUT => EV_TIMER
		5393
		5394	ev_loop_count => ev_iteration
		5395	ev_loop_depth => ev_depth
		5396	ev_loop_verify => ev_verify
		5397
		5398	Most functions working on C<struct ev_loop> objects don't have an
		5399	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5400	associated constants have been renamed to not collide with the C<struct
		5401	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5402	as all other watcher types. Note that C<ev_loop_fork> is still called
		5403	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5404	typedef.
		5405
		5406	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5407
		5408	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5409	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5410	and work, but the library code will of course be larger.
		5411
		5412	=back
		5413
		5414
		5415	=head1 GLOSSARY
		5416
		5417	=over 4
		5418
		5419	=item active
		5420
		5421	A watcher is active as long as it has been started and not yet stopped.
		5422	See L<WATCHER STATES> for details.
		5423
		5424	=item application
		5425
		5426	In this document, an application is whatever is using libev.
		5427
		5428	=item backend
		5429
		5430	The part of the code dealing with the operating system interfaces.
		5431
		5432	=item callback
		5433
		5434	The address of a function that is called when some event has been
		5435	detected. Callbacks are being passed the event loop, the watcher that
		5436	received the event, and the actual event bitset.
		5437
		5438	=item callback/watcher invocation
		5439
		5440	The act of calling the callback associated with a watcher.
		5441
		5442	=item event
		5443
		5444	A change of state of some external event, such as data now being available
		5445	for reading on a file descriptor, time having passed or simply not having
		5446	any other events happening anymore.
		5447
		5448	In libev, events are represented as single bits (such as C<EV_READ> or
		5449	C<EV_TIMER>).
		5450
		5451	=item event library
		5452
		5453	A software package implementing an event model and loop.
		5454
		5455	=item event loop
		5456
		5457	An entity that handles and processes external events and converts them
		5458	into callback invocations.
		5459
		5460	=item event model
		5461
		5462	The model used to describe how an event loop handles and processes
		5463	watchers and events.
		5464
		5465	=item pending
		5466
		5467	A watcher is pending as soon as the corresponding event has been
		5468	detected. See L<WATCHER STATES> for details.
		5469
		5470	=item real time
		5471
		5472	The physical time that is observed. It is apparently strictly monotonic :)
		5473
		5474	=item wall-clock time
		5475
		5476	The time and date as shown on clocks. Unlike real time, it can actually
		5477	be wrong and jump forwards and backwards, e.g. when you adjust your
		5478	clock.
		5479
		5480	=item watcher
		5481
		5482	A data structure that describes interest in certain events. Watchers need
		5483	to be started (attached to an event loop) before they can receive events.
		5484
		5485	=back
		5486
3786	=head1 AUTHOR	5487	=head1 AUTHOR
3787		5488
3788	Marc Lehmann <libev@schmorp.de>.	5489	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5490	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
3789		5491

Diff Legend

–	Removed lines
+	Added lines
<	Changed lines
>	Changed lines