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…		…
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
		14	#include <stdio.h> // for puts
		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
18		20
19	// all watcher callbacks have a similar signature	21	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	22	// this callback is called when data is readable on stdin
21	static void	23	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	25	{
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_ struct 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	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = EV_DEFAULT;
47		49
48	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
…		…
54	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
57		59
58	// now wait for events to arrive	60	// now wait for events to arrive
59	ev_loop (loop, 0);	61	ev_run (loop, 0);
60		62
61	// unloop was called, so exit	63	// unloop was called, so exit
62	return 0;	64	return 0;
63	}	65	}
64		66
65	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
66		70
67	The newest version of this document is also available as an html-formatted	71	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	72	web page you might find easier to navigate when reading it for the first
69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.	73	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		74
		75	While this document tries to be as complete as possible in documenting
		76	libev, its usage and the rationale behind its design, it is not a tutorial
		77	on event-based programming, nor will it introduce event-based programming
		78	with libev.
		79
		80	Familiarity with event based programming techniques in general is assumed
		81	throughout this document.
		82
		83	=head1 WHAT TO READ WHEN IN A HURRY
		84
		85	This manual tries to be very detailed, but unfortunately, this also makes
		86	it very long. If you just want to know the basics of libev, I suggest
		87	reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and
		88	look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and
		89	C<ev_timer> sections in L<WATCHER TYPES>.
		90
		91	=head1 ABOUT LIBEV
70		92
71	Libev is an event loop: you register interest in certain events (such as a	93	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	94	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	95	these event sources and provide your program with events.
74		96
…		…
84	=head2 FEATURES	106	=head2 FEATURES
85		107
86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	108	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	109	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	110	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	111	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
90	with customised rescheduling (C<ev_periodic>), synchronous signals	112	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
91	(C<ev_signal>), process status change events (C<ev_child>), and event	113	timers (C<ev_timer>), absolute timers with customised rescheduling
92	watchers dealing with the event loop mechanism itself (C<ev_idle>,	114	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
93	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	115	change events (C<ev_child>), and event watchers dealing with the event
94	file watchers (C<ev_stat>) and even limited support for fork events	116	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
95	(C<ev_fork>).	117	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		118	limited support for fork events (C<ev_fork>).
96		119
97	It also is quite fast (see this	120	It also is quite fast (see this
98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	121	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
99	for example).	122	for example).
100		123
…		…
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	131	name C<loop> (which is always of type C<struct ev_loop *>) will not have
109	this argument.	132	this argument.
110		133
111	=head2 TIME REPRESENTATION	134	=head2 TIME REPRESENTATION
112		135
113	Libev represents time as a single floating point number, representing the	136	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	137	the (fractional) number of seconds since the (POSIX) epoch (in practice
115	the beginning of 1970, details are complicated, don't ask). This type is	138	somewhere near the beginning of 1970, details are complicated, don't
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	139	ask). This type is called C<ev_tstamp>, which is what you should use
117	to the C<double> type in C, and when you need to do any calculations on	140	too. It usually aliases to the C<double> type in C. When you need to do
118	it, you should treat it as some floating point value. Unlike the name	141	any calculations on it, you should treat it as some floating point value.
		142
119	component C<stamp> might indicate, it is also used for time differences	143	Unlike the name component C<stamp> might indicate, it is also used for
120	throughout libev.	144	time differences (e.g. delays) throughout libev.
121		145
122	=head1 ERROR HANDLING	146	=head1 ERROR HANDLING
123		147
124	Libev knows three classes of errors: operating system errors, usage errors	148	Libev knows three classes of errors: operating system errors, usage errors
125	and internal errors (bugs).	149	and internal errors (bugs).
…		…
149		173
150	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
151		175
152	Returns the current time as libev would use it. Please note that the	176	Returns the current time as libev would use it. Please note that the
153	C<ev_now> function is usually faster and also often returns the timestamp	177	C<ev_now> function is usually faster and also often returns the timestamp
154	you actually want to know.	178	you actually want to know. Also interesting is the combination of
		179	C<ev_update_now> and C<ev_now>.
155		180
156	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
157		182
158	Sleep for the given interval: The current thread will be blocked until	183	Sleep for the given interval: The current thread will be blocked until
159	either it is interrupted or the given time interval has passed. Basically	184	either it is interrupted or the given time interval has passed. Basically
…		…
176	as this indicates an incompatible change. Minor versions are usually	201	as this indicates an incompatible change. Minor versions are usually
177	compatible to older versions, so a larger minor version alone is usually	202	compatible to older versions, so a larger minor version alone is usually
178	not a problem.	203	not a problem.
179		204
180	Example: Make sure we haven't accidentally been linked against the wrong	205	Example: Make sure we haven't accidentally been linked against the wrong
181	version.	206	version (note, however, that this will not detect other ABI mismatches,
		207	such as LFS or reentrancy).
182		208
183	assert (("libev version mismatch",	209	assert (("libev version mismatch",
184	ev_version_major () == EV_VERSION_MAJOR	210	ev_version_major () == EV_VERSION_MAJOR
185	&& ev_version_minor () >= EV_VERSION_MINOR));	211	&& ev_version_minor () >= EV_VERSION_MINOR));
186		212
…		…
197	assert (("sorry, no epoll, no sex",	223	assert (("sorry, no epoll, no sex",
198	ev_supported_backends () & EVBACKEND_EPOLL));	224	ev_supported_backends () & EVBACKEND_EPOLL));
199		225
200	=item unsigned int ev_recommended_backends ()	226	=item unsigned int ev_recommended_backends ()
201		227
202	Return the set of all backends compiled into this binary of libev and also	228	Return the set of all backends compiled into this binary of libev and
203	recommended for this platform. This set is often smaller than the one	229	also recommended for this platform, meaning it will work for most file
		230	descriptor types. This set is often smaller than the one returned by
204	returned by C<ev_supported_backends>, as for example kqueue is broken on	231	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
205	most BSDs and will not be auto-detected unless you explicitly request it	232	and will not be auto-detected unless you explicitly request it (assuming
206	(assuming you know what you are doing). This is the set of backends that	233	you know what you are doing). This is the set of backends that libev will
207	libev will probe for if you specify no backends explicitly.	234	probe for if you specify no backends explicitly.
208		235
209	=item unsigned int ev_embeddable_backends ()	236	=item unsigned int ev_embeddable_backends ()
210		237
211	Returns the set of backends that are embeddable in other event loops. This	238	Returns the set of backends that are embeddable in other event loops. This
212	is the theoretical, all-platform, value. To find which backends	239	value is platform-specific but can include backends not available on the
213	might be supported on the current system, you would need to look at	240	current system. To find which embeddable backends might be supported on
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	241	the current system, you would need to look at C<ev_embeddable_backends ()
215	recommended ones.	242	& ev_supported_backends ()>, likewise for recommended ones.
216		243
217	See the description of C<ev_embed> watchers for more info.	244	See the description of C<ev_embed> watchers for more info.
218		245
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	246	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
220		247
…		…
250	}	277	}
251		278
252	...	279	...
253	ev_set_allocator (persistent_realloc);	280	ev_set_allocator (persistent_realloc);
254		281
255	=item ev_set_syserr_cb (void (*cb)(const char *msg));	282	=item ev_set_syserr_cb (void (*cb)(const char *msg))
256		283
257	Set the callback function to call on a retryable system call error (such	284	Set the callback function to call on a retryable system call error (such
258	as failed select, poll, epoll_wait). The message is a printable string	285	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	286	indicating the system call or subsystem causing the problem. If this
260	callback is set, then libev will expect it to remedy the situation, no	287	callback is set, then libev will expect it to remedy the situation, no
…		…
274	...	301	...
275	ev_set_syserr_cb (fatal_error);	302	ev_set_syserr_cb (fatal_error);
276		303
277	=back	304	=back
278		305
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	306	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
280		307
281	An event loop is described by a C<struct ev_loop *>. The library knows two	308	An event loop is described by a C<struct ev_loop *> (the C<struct> is
282	types of such loops, the I<default> loop, which supports signals and child	309	I<not> optional in this case unless libev 3 compatibility is disabled, as
283	events, and dynamically created loops which do not.	310	libev 3 had an C<ev_loop> function colliding with the struct name).
		311
		312	The library knows two types of such loops, the I<default> loop, which
		313	supports child process events, and dynamically created event loops which
		314	do not.
284		315
285	=over 4	316	=over 4
286		317
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	318	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		319
289	This will initialise the default event loop if it hasn't been initialised	320	This returns the "default" event loop object, which is what you should
290	yet and return it. If the default loop could not be initialised, returns	321	normally use when you just need "the event loop". Event loop objects and
291	false. If it already was initialised it simply returns it (and ignores the	322	the C<flags> parameter are described in more detail in the entry for
292	flags. If that is troubling you, check C<ev_backend ()> afterwards).	323	C<ev_loop_new>.
		324
		325	If the default loop is already initialised then this function simply
		326	returns it (and ignores the flags. If that is troubling you, check
		327	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		328	flags, which should almost always be C<0>, unless the caller is also the
		329	one calling C<ev_run> or otherwise qualifies as "the main program".
293		330
294	If you don't know what event loop to use, use the one returned from this	331	If you don't know what event loop to use, use the one returned from this
295	function.	332	function (or via the C<EV_DEFAULT> macro).
296		333
297	Note that this function is I<not> thread-safe, so if you want to use it	334	Note that this function is I<not> thread-safe, so if you want to use it
298	from multiple threads, you have to lock (note also that this is unlikely,	335	from multiple threads, you have to employ some kind of mutex (note also
299	as loops cannot bes hared easily between threads anyway).	336	that this case is unlikely, as loops cannot be shared easily between
		337	threads anyway).
300		338
301	The default loop is the only loop that can handle C<ev_signal> and	339	The default loop is the only loop that can handle C<ev_child> watchers,
302	C<ev_child> watchers, and to do this, it always registers a handler	340	and to do this, it always registers a handler for C<SIGCHLD>. If this is
303	for C<SIGCHLD>. If this is a problem for your application you can either	341	a problem for your application you can either create a dynamic loop with
304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	342	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
305	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	343	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
306	C<ev_default_init>.	344
		345	Example: This is the most typical usage.
		346
		347	if (!ev_default_loop (0))
		348	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		349
		350	Example: Restrict libev to the select and poll backends, and do not allow
		351	environment settings to be taken into account:
		352
		353	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		354
		355	=item struct ev_loop *ev_loop_new (unsigned int flags)
		356
		357	This will create and initialise a new event loop object. If the loop
		358	could not be initialised, returns false.
		359
		360	Note that this function I<is> thread-safe, and one common way to use
		361	libev with threads is indeed to create one loop per thread, and using the
		362	default loop in the "main" or "initial" thread.
307		363
308	The flags argument can be used to specify special behaviour or specific	364	The flags argument can be used to specify special behaviour or specific
309	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	365	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
310		366
311	The following flags are supported:	367	The following flags are supported:
…		…
326	useful to try out specific backends to test their performance, or to work	382	useful to try out specific backends to test their performance, or to work
327	around bugs.	383	around bugs.
328		384
329	=item C<EVFLAG_FORKCHECK>	385	=item C<EVFLAG_FORKCHECK>
330		386
331	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	387	Instead of calling C<ev_loop_fork> manually after a fork, you can also
332	a fork, you can also make libev check for a fork in each iteration by	388	make libev check for a fork in each iteration by enabling this flag.
333	enabling this flag.
334		389
335	This works by calling C<getpid ()> on every iteration of the loop,	390	This works by calling C<getpid ()> on every iteration of the loop,
336	and thus this might slow down your event loop if you do a lot of loop	391	and thus this might slow down your event loop if you do a lot of loop
337	iterations and little real work, but is usually not noticeable (on my	392	iterations and little real work, but is usually not noticeable (on my
338	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	393	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
…		…
344	flag.	399	flag.
345		400
346	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	401	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
347	environment variable.	402	environment variable.
348		403
		404	=item C<EVFLAG_NOINOTIFY>
		405
		406	When this flag is specified, then libev will not attempt to use the
		407	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and
		408	testing, this flag can be useful to conserve inotify file descriptors, as
		409	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		410
		411	=item C<EVFLAG_SIGNALFD>
		412
		413	When this flag is specified, then libev will attempt to use the
		414	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API
		415	delivers signals synchronously, which makes it both faster and might make
		416	it possible to get the queued signal data. It can also simplify signal
		417	handling with threads, as long as you properly block signals in your
		418	threads that are not interested in handling them.
		419
		420	Signalfd will not be used by default as this changes your signal mask, and
		421	there are a lot of shoddy libraries and programs (glib's threadpool for
		422	example) that can't properly initialise their signal masks.
		423
349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	424	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
350		425
351	This is your standard select(2) backend. Not I<completely> standard, as	426	This is your standard select(2) backend. Not I<completely> standard, as
352	libev tries to roll its own fd_set with no limits on the number of fds,	427	libev tries to roll its own fd_set with no limits on the number of fds,
353	but if that fails, expect a fairly low limit on the number of fds when	428	but if that fails, expect a fairly low limit on the number of fds when
…		…
359	writing a server, you should C<accept ()> in a loop to accept as many	434	writing a server, you should C<accept ()> in a loop to accept as many
360	connections as possible during one iteration. You might also want to have	435	connections as possible during one iteration. You might also want to have
361	a look at C<ev_set_io_collect_interval ()> to increase the amount of	436	a look at C<ev_set_io_collect_interval ()> to increase the amount of
362	readiness notifications you get per iteration.	437	readiness notifications you get per iteration.
363		438
		439	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		440	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		441	C<exceptfds> set on that platform).
		442
364	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	443	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
365		444
366	And this is your standard poll(2) backend. It's more complicated	445	And this is your standard poll(2) backend. It's more complicated
367	than select, but handles sparse fds better and has no artificial	446	than select, but handles sparse fds better and has no artificial
368	limit on the number of fds you can use (except it will slow down	447	limit on the number of fds you can use (except it will slow down
369	considerably with a lot of inactive fds). It scales similarly to select,	448	considerably with a lot of inactive fds). It scales similarly to select,
370	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for	449	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
371	performance tips.	450	performance tips.
372		451
		452	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		453	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		454
373	=item C<EVBACKEND_EPOLL> (value 4, Linux)	455	=item C<EVBACKEND_EPOLL> (value 4, Linux)
		456
		457	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		458	kernels).
374		459
375	For few fds, this backend is a bit little slower than poll and select,	460	For few fds, this backend is a bit little slower than poll and select,
376	but it scales phenomenally better. While poll and select usually scale	461	but it scales phenomenally better. While poll and select usually scale
377	like O(total_fds) where n is the total number of fds (or the highest fd),	462	like O(total_fds) where n is the total number of fds (or the highest fd),
378	epoll scales either O(1) or O(active_fds). The epoll design has a number	463	epoll scales either O(1) or O(active_fds).
379	of shortcomings, such as silently dropping events in some hard-to-detect	464
380	cases and requiring a system call per fd change, no fork support and bad	465	The epoll mechanism deserves honorable mention as the most misdesigned
381	support for dup.	466	of the more advanced event mechanisms: mere annoyances include silently
		467	dropping file descriptors, requiring a system call per change per file
		468	descriptor (and unnecessary guessing of parameters), problems with dup,
		469	returning before the timeout value, resulting in additional iterations
		470	(and only giving 5ms accuracy while select on the same platform gives
		471	0.1ms) and so on. The biggest issue is fork races, however - if a program
		472	forks then I<both> parent and child process have to recreate the epoll
		473	set, which can take considerable time (one syscall per file descriptor)
		474	and is of course hard to detect.
		475
		476	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		477	of course I<doesn't>, and epoll just loves to report events for totally
		478	I<different> file descriptors (even already closed ones, so one cannot
		479	even remove them from the set) than registered in the set (especially
		480	on SMP systems). Libev tries to counter these spurious notifications by
		481	employing an additional generation counter and comparing that against the
		482	events to filter out spurious ones, recreating the set when required. Last
		483	not least, it also refuses to work with some file descriptors which work
		484	perfectly fine with C<select> (files, many character devices...).
		485
		486	Epoll is truly the train wreck analog among event poll mechanisms.
382		487
383	While stopping, setting and starting an I/O watcher in the same iteration	488	While stopping, setting and starting an I/O watcher in the same iteration
384	will result in some caching, there is still a system call per such incident	489	will result in some caching, there is still a system call per such
385	(because the fd could point to a different file description now), so its	490	incident (because the same I<file descriptor> could point to a different
386	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	491	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
387	very well if you register events for both fds.	492	file descriptors might not work very well if you register events for both
388		493	file descriptors.
389	Please note that epoll sometimes generates spurious notifications, so you
390	need to use non-blocking I/O or other means to avoid blocking when no data
391	(or space) is available.
392		494
393	Best performance from this backend is achieved by not unregistering all	495	Best performance from this backend is achieved by not unregistering all
394	watchers for a file descriptor until it has been closed, if possible, i.e.	496	watchers for a file descriptor until it has been closed, if possible,
395	keep at least one watcher active per fd at all times.	497	i.e. keep at least one watcher active per fd at all times. Stopping and
		498	starting a watcher (without re-setting it) also usually doesn't cause
		499	extra overhead. A fork can both result in spurious notifications as well
		500	as in libev having to destroy and recreate the epoll object, which can
		501	take considerable time and thus should be avoided.
		502
		503	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		504	faster than epoll for maybe up to a hundred file descriptors, depending on
		505	the usage. So sad.
396		506
397	While nominally embeddable in other event loops, this feature is broken in	507	While nominally embeddable in other event loops, this feature is broken in
398	all kernel versions tested so far.	508	all kernel versions tested so far.
		509
		510	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		511	C<EVBACKEND_POLL>.
399		512
400	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	513	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
401		514
402	Kqueue deserves special mention, as at the time of this writing, it	515	Kqueue deserves special mention, as at the time of this writing, it
403	was broken on all BSDs except NetBSD (usually it doesn't work reliably	516	was broken on all BSDs except NetBSD (usually it doesn't work reliably
404	with anything but sockets and pipes, except on Darwin, where of course	517	with anything but sockets and pipes, except on Darwin, where of course
405	it's completely useless). For this reason it's not being "auto-detected"	518	it's completely useless). Unlike epoll, however, whose brokenness
		519	is by design, these kqueue bugs can (and eventually will) be fixed
		520	without API changes to existing programs. For this reason it's not being
406	unless you explicitly specify it explicitly in the flags (i.e. using	521	"auto-detected" unless you explicitly specify it in the flags (i.e. using
407	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	522	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
408	system like NetBSD.	523	system like NetBSD.
409		524
410	You still can embed kqueue into a normal poll or select backend and use it	525	You still can embed kqueue into a normal poll or select backend and use it
411	only for sockets (after having made sure that sockets work with kqueue on	526	only for sockets (after having made sure that sockets work with kqueue on
…		…
413		528
414	It scales in the same way as the epoll backend, but the interface to the	529	It scales in the same way as the epoll backend, but the interface to the
415	kernel is more efficient (which says nothing about its actual speed, of	530	kernel is more efficient (which says nothing about its actual speed, of
416	course). While stopping, setting and starting an I/O watcher does never	531	course). While stopping, setting and starting an I/O watcher does never
417	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	532	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
418	two event changes per incident, support for C<fork ()> is very bad and it	533	two event changes per incident. Support for C<fork ()> is very bad (but
419	drops fds silently in similarly hard-to-detect cases.	534	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		535	cases
420		536
421	This backend usually performs well under most conditions.	537	This backend usually performs well under most conditions.
422		538
423	While nominally embeddable in other event loops, this doesn't work	539	While nominally embeddable in other event loops, this doesn't work
424	everywhere, so you might need to test for this. And since it is broken	540	everywhere, so you might need to test for this. And since it is broken
425	almost everywhere, you should only use it when you have a lot of sockets	541	almost everywhere, you should only use it when you have a lot of sockets
426	(for which it usually works), by embedding it into another event loop	542	(for which it usually works), by embedding it into another event loop
427	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	543	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
428	sockets.	544	also broken on OS X)) and, did I mention it, using it only for sockets.
		545
		546	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		547	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		548	C<NOTE_EOF>.
429		549
430	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	550	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
431		551
432	This is not implemented yet (and might never be, unless you send me an	552	This is not implemented yet (and might never be, unless you send me an
433	implementation). According to reports, C</dev/poll> only supports sockets	553	implementation). According to reports, C</dev/poll> only supports sockets
…		…
446	While this backend scales well, it requires one system call per active	566	While this backend scales well, it requires one system call per active
447	file descriptor per loop iteration. For small and medium numbers of file	567	file descriptor per loop iteration. For small and medium numbers of file
448	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	568	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
449	might perform better.	569	might perform better.
450		570
451	On the positive side, ignoring the spurious readiness notifications, this	571	On the positive side, with the exception of the spurious readiness
452	backend actually performed to specification in all tests and is fully	572	notifications, this backend actually performed fully to specification
453	embeddable, which is a rare feat among the OS-specific backends.	573	in all tests and is fully embeddable, which is a rare feat among the
		574	OS-specific backends (I vastly prefer correctness over speed hacks).
		575
		576	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		577	C<EVBACKEND_POLL>.
454		578
455	=item C<EVBACKEND_ALL>	579	=item C<EVBACKEND_ALL>
456		580
457	Try all backends (even potentially broken ones that wouldn't be tried	581	Try all backends (even potentially broken ones that wouldn't be tried
458	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	582	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
460		584
461	It is definitely not recommended to use this flag.	585	It is definitely not recommended to use this flag.
462		586
463	=back	587	=back
464		588
465	If one or more of these are or'ed into the flags value, then only these	589	If one or more of the backend flags are or'ed into the flags value,
466	backends will be tried (in the reverse order as listed here). If none are	590	then only these backends will be tried (in the reverse order as listed
467	specified, all backends in C<ev_recommended_backends ()> will be tried.	591	here). If none are specified, all backends in C<ev_recommended_backends
468		592	()> will be tried.
469	The most typical usage is like this:
470
471	if (!ev_default_loop (0))
472	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
473
474	Restrict libev to the select and poll backends, and do not allow
475	environment settings to be taken into account:
476
477	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
478
479	Use whatever libev has to offer, but make sure that kqueue is used if
480	available (warning, breaks stuff, best use only with your own private
481	event loop and only if you know the OS supports your types of fds):
482
483	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
484
485	=item struct ev_loop *ev_loop_new (unsigned int flags)
486
487	Similar to C<ev_default_loop>, but always creates a new event loop that is
488	always distinct from the default loop. Unlike the default loop, it cannot
489	handle signal and child watchers, and attempts to do so will be greeted by
490	undefined behaviour (or a failed assertion if assertions are enabled).
491
492	Note that this function I<is> thread-safe, and the recommended way to use
493	libev with threads is indeed to create one loop per thread, and using the
494	default loop in the "main" or "initial" thread.
495		593
496	Example: Try to create a event loop that uses epoll and nothing else.	594	Example: Try to create a event loop that uses epoll and nothing else.
497		595
498	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	596	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
499	if (!epoller)	597	if (!epoller)
500	fatal ("no epoll found here, maybe it hides under your chair");	598	fatal ("no epoll found here, maybe it hides under your chair");
501		599
		600	Example: Use whatever libev has to offer, but make sure that kqueue is
		601	used if available.
		602
		603	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		604
502	=item ev_default_destroy ()	605	=item ev_loop_destroy (loop)
503		606
504	Destroys the default loop again (frees all memory and kernel state	607	Destroys an event loop object (frees all memory and kernel state
505	etc.). None of the active event watchers will be stopped in the normal	608	etc.). None of the active event watchers will be stopped in the normal
506	sense, so e.g. C<ev_is_active> might still return true. It is your	609	sense, so e.g. C<ev_is_active> might still return true. It is your
507	responsibility to either stop all watchers cleanly yourself I<before>	610	responsibility to either stop all watchers cleanly yourself I<before>
508	calling this function, or cope with the fact afterwards (which is usually	611	calling this function, or cope with the fact afterwards (which is usually
509	the easiest thing, you can just ignore the watchers and/or C<free ()> them	612	the easiest thing, you can just ignore the watchers and/or C<free ()> them
510	for example).	613	for example).
511		614
512	Note that certain global state, such as signal state, will not be freed by	615	Note that certain global state, such as signal state (and installed signal
513	this function, and related watchers (such as signal and child watchers)	616	handlers), will not be freed by this function, and related watchers (such
514	would need to be stopped manually.	617	as signal and child watchers) would need to be stopped manually.
515		618
516	In general it is not advisable to call this function except in the	619	This function is normally used on loop objects allocated by
517	rare occasion where you really need to free e.g. the signal handling	620	C<ev_loop_new>, but it can also be used on the default loop returned by
		621	C<ev_default_loop>, in which case it is not thread-safe.
		622
		623	Note that it is not advisable to call this function on the default loop
		624	except in the rare occasion where you really need to free it's resources.
518	pipe fds. If you need dynamically allocated loops it is better to use	625	If you need dynamically allocated loops it is better to use C<ev_loop_new>
519	C<ev_loop_new> and C<ev_loop_destroy>).	626	and C<ev_loop_destroy>.
520		627
521	=item ev_loop_destroy (loop)	628	=item ev_loop_fork (loop)
522		629
523	Like C<ev_default_destroy>, but destroys an event loop created by an
524	earlier call to C<ev_loop_new>.
525
526	=item ev_default_fork ()
527
528	This function sets a flag that causes subsequent C<ev_loop> iterations	630	This function sets a flag that causes subsequent C<ev_run> iterations to
529	to reinitialise the kernel state for backends that have one. Despite the	631	reinitialise the kernel state for backends that have one. Despite the
530	name, you can call it anytime, but it makes most sense after forking, in	632	name, you can call it anytime, but it makes most sense after forking, in
531	the child process (or both child and parent, but that again makes little	633	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
532	sense). You I<must> call it in the child before using any of the libev	634	child before resuming or calling C<ev_run>.
533	functions, and it will only take effect at the next C<ev_loop> iteration.	635
		636	Again, you I<have> to call it on I<any> loop that you want to re-use after
		637	a fork, I<even if you do not plan to use the loop in the parent>. This is
		638	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		639	during fork.
534		640
535	On the other hand, you only need to call this function in the child	641	On the other hand, you only need to call this function in the child
536	process if and only if you want to use the event library in the child. If	642	process if and only if you want to use the event loop in the child. If
537	you just fork+exec, you don't have to call it at all.	643	you just fork+exec or create a new loop in the child, you don't have to
		644	call it at all (in fact, C<epoll> is so badly broken that it makes a
		645	difference, but libev will usually detect this case on its own and do a
		646	costly reset of the backend).
538		647
539	The function itself is quite fast and it's usually not a problem to call	648	The function itself is quite fast and it's usually not a problem to call
540	it just in case after a fork. To make this easy, the function will fit in	649	it just in case after a fork.
541	quite nicely into a call to C<pthread_atfork>:
542		650
		651	Example: Automate calling C<ev_loop_fork> on the default loop when
		652	using pthreads.
		653
		654	static void
		655	post_fork_child (void)
		656	{
		657	ev_loop_fork (EV_DEFAULT);
		658	}
		659
		660	...
543	pthread_atfork (0, 0, ev_default_fork);	661	pthread_atfork (0, 0, post_fork_child);
544
545	=item ev_loop_fork (loop)
546
547	Like C<ev_default_fork>, but acts on an event loop created by
548	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
549	after fork, and how you do this is entirely your own problem.
550		662
551	=item int ev_is_default_loop (loop)	663	=item int ev_is_default_loop (loop)
552		664
553	Returns true when the given loop actually is the default loop, false otherwise.	665	Returns true when the given loop is, in fact, the default loop, and false
		666	otherwise.
554		667
555	=item unsigned int ev_loop_count (loop)	668	=item unsigned int ev_iteration (loop)
556		669
557	Returns the count of loop iterations for the loop, which is identical to	670	Returns the current iteration count for the event loop, which is identical
558	the number of times libev did poll for new events. It starts at C<0> and	671	to the number of times libev did poll for new events. It starts at C<0>
559	happily wraps around with enough iterations.	672	and happily wraps around with enough iterations.
560		673
561	This value can sometimes be useful as a generation counter of sorts (it	674	This value can sometimes be useful as a generation counter of sorts (it
562	"ticks" the number of loop iterations), as it roughly corresponds with	675	"ticks" the number of loop iterations), as it roughly corresponds with
563	C<ev_prepare> and C<ev_check> calls.	676	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		677	prepare and check phases.
		678
		679	=item unsigned int ev_depth (loop)
		680
		681	Returns the number of times C<ev_run> was entered minus the number of
		682	times C<ev_run> was exited, in other words, the recursion depth.
		683
		684	Outside C<ev_run>, this number is zero. In a callback, this number is
		685	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		686	in which case it is higher.
		687
		688	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread
		689	etc.), doesn't count as "exit" - consider this as a hint to avoid such
		690	ungentleman-like behaviour unless it's really convenient.
564		691
565	=item unsigned int ev_backend (loop)	692	=item unsigned int ev_backend (loop)
566		693
567	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	694	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
568	use.	695	use.
…		…
573	received events and started processing them. This timestamp does not	700	received events and started processing them. This timestamp does not
574	change as long as callbacks are being processed, and this is also the base	701	change as long as callbacks are being processed, and this is also the base
575	time used for relative timers. You can treat it as the timestamp of the	702	time used for relative timers. You can treat it as the timestamp of the
576	event occurring (or more correctly, libev finding out about it).	703	event occurring (or more correctly, libev finding out about it).
577		704
		705	=item ev_now_update (loop)
		706
		707	Establishes the current time by querying the kernel, updating the time
		708	returned by C<ev_now ()> in the progress. This is a costly operation and
		709	is usually done automatically within C<ev_run ()>.
		710
		711	This function is rarely useful, but when some event callback runs for a
		712	very long time without entering the event loop, updating libev's idea of
		713	the current time is a good idea.
		714
		715	See also L<The special problem of time updates> in the C<ev_timer> section.
		716
		717	=item ev_suspend (loop)
		718
		719	=item ev_resume (loop)
		720
		721	These two functions suspend and resume an event loop, for use when the
		722	loop is not used for a while and timeouts should not be processed.
		723
		724	A typical use case would be an interactive program such as a game: When
		725	the user presses C<^Z> to suspend the game and resumes it an hour later it
		726	would be best to handle timeouts as if no time had actually passed while
		727	the program was suspended. This can be achieved by calling C<ev_suspend>
		728	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		729	C<ev_resume> directly afterwards to resume timer processing.
		730
		731	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		732	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		733	will be rescheduled (that is, they will lose any events that would have
		734	occurred while suspended).
		735
		736	After calling C<ev_suspend> you B<must not> call I<any> function on the
		737	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		738	without a previous call to C<ev_suspend>.
		739
		740	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		741	event loop time (see C<ev_now_update>).
		742
578	=item ev_loop (loop, int flags)	743	=item ev_run (loop, int flags)
579		744
580	Finally, this is it, the event handler. This function usually is called	745	Finally, this is it, the event handler. This function usually is called
581	after you initialised all your watchers and you want to start handling	746	after you have initialised all your watchers and you want to start
582	events.	747	handling events. It will ask the operating system for any new events, call
		748	the watcher callbacks, an then repeat the whole process indefinitely: This
		749	is why event loops are called I<loops>.
583		750
584	If the flags argument is specified as C<0>, it will not return until	751	If the flags argument is specified as C<0>, it will keep handling events
585	either no event watchers are active anymore or C<ev_unloop> was called.	752	until either no event watchers are active anymore or C<ev_break> was
		753	called.
586		754
587	Please note that an explicit C<ev_unloop> is usually better than	755	Please note that an explicit C<ev_break> is usually better than
588	relying on all watchers to be stopped when deciding when a program has	756	relying on all watchers to be stopped when deciding when a program has
589	finished (especially in interactive programs), but having a program that	757	finished (especially in interactive programs), but having a program
590	automatically loops as long as it has to and no longer by virtue of	758	that automatically loops as long as it has to and no longer by virtue
591	relying on its watchers stopping correctly is a thing of beauty.	759	of relying on its watchers stopping correctly, that is truly a thing of
		760	beauty.
592		761
593	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	762	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
594	those events and any outstanding ones, but will not block your process in	763	those events and any already outstanding ones, but will not wait and
595	case there are no events and will return after one iteration of the loop.	764	block your process in case there are no events and will return after one
		765	iteration of the loop. This is sometimes useful to poll and handle new
		766	events while doing lengthy calculations, to keep the program responsive.
596		767
597	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	768	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
598	necessary) and will handle those and any outstanding ones. It will block	769	necessary) and will handle those and any already outstanding ones. It
599	your process until at least one new event arrives, and will return after	770	will block your process until at least one new event arrives (which could
600	one iteration of the loop. This is useful if you are waiting for some	771	be an event internal to libev itself, so there is no guarantee that a
601	external event in conjunction with something not expressible using other	772	user-registered callback will be called), and will return after one
		773	iteration of the loop.
		774
		775	This is useful if you are waiting for some external event in conjunction
		776	with something not expressible using other libev watchers (i.e. "roll your
602	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	777	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
603	usually a better approach for this kind of thing.	778	usually a better approach for this kind of thing.
604		779
605	Here are the gory details of what C<ev_loop> does:	780	Here are the gory details of what C<ev_run> does:
606		781
		782	- Increment loop depth.
		783	- Reset the ev_break status.
607	- Before the first iteration, call any pending watchers.	784	- Before the first iteration, call any pending watchers.
		785	LOOP:
608	* If EVFLAG_FORKCHECK was used, check for a fork.	786	- If EVFLAG_FORKCHECK was used, check for a fork.
609	- If a fork was detected (by any means), queue and call all fork watchers.	787	- If a fork was detected (by any means), queue and call all fork watchers.
610	- Queue and call all prepare watchers.	788	- Queue and call all prepare watchers.
		789	- If ev_break was called, goto FINISH.
611	- If we have been forked, detach and recreate the kernel state	790	- If we have been forked, detach and recreate the kernel state
612	as to not disturb the other process.	791	as to not disturb the other process.
613	- Update the kernel state with all outstanding changes.	792	- Update the kernel state with all outstanding changes.
614	- Update the "event loop time" (ev_now ()).	793	- Update the "event loop time" (ev_now ()).
615	- Calculate for how long to sleep or block, if at all	794	- Calculate for how long to sleep or block, if at all
616	(active idle watchers, EVLOOP_NONBLOCK or not having	795	(active idle watchers, EVRUN_NOWAIT or not having
617	any active watchers at all will result in not sleeping).	796	any active watchers at all will result in not sleeping).
618	- Sleep if the I/O and timer collect interval say so.	797	- Sleep if the I/O and timer collect interval say so.
		798	- Increment loop iteration counter.
619	- Block the process, waiting for any events.	799	- Block the process, waiting for any events.
620	- Queue all outstanding I/O (fd) events.	800	- Queue all outstanding I/O (fd) events.
621	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	801	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
622	- Queue all outstanding timers.	802	- Queue all expired timers.
623	- Queue all outstanding periodics.	803	- Queue all expired periodics.
624	- Unless any events are pending now, queue all idle watchers.	804	- Queue all idle watchers with priority higher than that of pending events.
625	- Queue all check watchers.	805	- Queue all check watchers.
626	- Call all queued watchers in reverse order (i.e. check watchers first).	806	- Call all queued watchers in reverse order (i.e. check watchers first).
627	Signals and child watchers are implemented as I/O watchers, and will	807	Signals and child watchers are implemented as I/O watchers, and will
628	be handled here by queueing them when their watcher gets executed.	808	be handled here by queueing them when their watcher gets executed.
629	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	809	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
630	were used, or there are no active watchers, return, otherwise	810	were used, or there are no active watchers, goto FINISH, otherwise
631	continue with step *.	811	continue with step LOOP.
		812	FINISH:
		813	- Reset the ev_break status iff it was EVBREAK_ONE.
		814	- Decrement the loop depth.
		815	- Return.
632		816
633	Example: Queue some jobs and then loop until no events are outstanding	817	Example: Queue some jobs and then loop until no events are outstanding
634	anymore.	818	anymore.
635		819
636	... queue jobs here, make sure they register event watchers as long	820	... queue jobs here, make sure they register event watchers as long
637	... as they still have work to do (even an idle watcher will do..)	821	... as they still have work to do (even an idle watcher will do..)
638	ev_loop (my_loop, 0);	822	ev_run (my_loop, 0);
639	... jobs done or somebody called unloop. yeah!	823	... jobs done or somebody called unloop. yeah!
640		824
641	=item ev_unloop (loop, how)	825	=item ev_break (loop, how)
642		826
643	Can be used to make a call to C<ev_loop> return early (but only after it	827	Can be used to make a call to C<ev_run> return early (but only after it
644	has processed all outstanding events). The C<how> argument must be either	828	has processed all outstanding events). The C<how> argument must be either
645	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	829	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
646	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	830	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
647		831
648	This "unloop state" will be cleared when entering C<ev_loop> again.	832	This "break state" will be cleared when entering C<ev_run> again.
		833
		834	It is safe to call C<ev_break> from outside any C<ev_run> calls, too.
649		835
650	=item ev_ref (loop)	836	=item ev_ref (loop)
651		837
652	=item ev_unref (loop)	838	=item ev_unref (loop)
653		839
654	Ref/unref can be used to add or remove a reference count on the event	840	Ref/unref can be used to add or remove a reference count on the event
655	loop: Every watcher keeps one reference, and as long as the reference	841	loop: Every watcher keeps one reference, and as long as the reference
656	count is nonzero, C<ev_loop> will not return on its own. If you have	842	count is nonzero, C<ev_run> will not return on its own.
657	a watcher you never unregister that should not keep C<ev_loop> from	843
658	returning, ev_unref() after starting, and ev_ref() before stopping it. For	844	This is useful when you have a watcher that you never intend to
		845	unregister, but that nevertheless should not keep C<ev_run> from
		846	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
		847	before stopping it.
		848
659	example, libev itself uses this for its internal signal pipe: It is not	849	As an example, libev itself uses this for its internal signal pipe: It
660	visible to the libev user and should not keep C<ev_loop> from exiting if	850	is not visible to the libev user and should not keep C<ev_run> from
661	no event watchers registered by it are active. It is also an excellent	851	exiting if no event watchers registered by it are active. It is also an
662	way to do this for generic recurring timers or from within third-party	852	excellent way to do this for generic recurring timers or from within
663	libraries. Just remember to I<unref after start> and I<ref before stop>	853	third-party libraries. Just remember to I<unref after start> and I<ref
664	(but only if the watcher wasn't active before, or was active before,	854	before stop> (but only if the watcher wasn't active before, or was active
665	respectively).	855	before, respectively. Note also that libev might stop watchers itself
		856	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		857	in the callback).
666		858
667	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	859	Example: Create a signal watcher, but keep it from keeping C<ev_run>
668	running when nothing else is active.	860	running when nothing else is active.
669		861
670	struct ev_signal exitsig;	862	ev_signal exitsig;
671	ev_signal_init (&exitsig, sig_cb, SIGINT);	863	ev_signal_init (&exitsig, sig_cb, SIGINT);
672	ev_signal_start (loop, &exitsig);	864	ev_signal_start (loop, &exitsig);
673	evf_unref (loop);	865	evf_unref (loop);
674		866
675	Example: For some weird reason, unregister the above signal handler again.	867	Example: For some weird reason, unregister the above signal handler again.
…		…
689	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	881	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
690	allows libev to delay invocation of I/O and timer/periodic callbacks	882	allows libev to delay invocation of I/O and timer/periodic callbacks
691	to increase efficiency of loop iterations (or to increase power-saving	883	to increase efficiency of loop iterations (or to increase power-saving
692	opportunities).	884	opportunities).
693		885
694	The background is that sometimes your program runs just fast enough to	886	The idea is that sometimes your program runs just fast enough to handle
695	handle one (or very few) event(s) per loop iteration. While this makes	887	one (or very few) event(s) per loop iteration. While this makes the
696	the program responsive, it also wastes a lot of CPU time to poll for new	888	program responsive, it also wastes a lot of CPU time to poll for new
697	events, especially with backends like C<select ()> which have a high	889	events, especially with backends like C<select ()> which have a high
698	overhead for the actual polling but can deliver many events at once.	890	overhead for the actual polling but can deliver many events at once.
699		891
700	By setting a higher I<io collect interval> you allow libev to spend more	892	By setting a higher I<io collect interval> you allow libev to spend more
701	time collecting I/O events, so you can handle more events per iteration,	893	time collecting I/O events, so you can handle more events per iteration,
702	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	894	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
703	C<ev_timer>) will be not affected. Setting this to a non-null value will	895	C<ev_timer>) will be not affected. Setting this to a non-null value will
704	introduce an additional C<ev_sleep ()> call into most loop iterations.	896	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		897	sleep time ensures that libev will not poll for I/O events more often then
		898	once per this interval, on average.
705		899
706	Likewise, by setting a higher I<timeout collect interval> you allow libev	900	Likewise, by setting a higher I<timeout collect interval> you allow libev
707	to spend more time collecting timeouts, at the expense of increased	901	to spend more time collecting timeouts, at the expense of increased
708	latency (the watcher callback will be called later). C<ev_io> watchers	902	latency/jitter/inexactness (the watcher callback will be called
709	will not be affected. Setting this to a non-null value will not introduce	903	later). C<ev_io> watchers will not be affected. Setting this to a non-null
710	any overhead in libev.	904	value will not introduce any overhead in libev.
711		905
712	Many (busy) programs can usually benefit by setting the I/O collect	906	Many (busy) programs can usually benefit by setting the I/O collect
713	interval to a value near C<0.1> or so, which is often enough for	907	interval to a value near C<0.1> or so, which is often enough for
714	interactive servers (of course not for games), likewise for timeouts. It	908	interactive servers (of course not for games), likewise for timeouts. It
715	usually doesn't make much sense to set it to a lower value than C<0.01>,	909	usually doesn't make much sense to set it to a lower value than C<0.01>,
716	as this approaches the timing granularity of most systems.	910	as this approaches the timing granularity of most systems. Note that if
		911	you do transactions with the outside world and you can't increase the
		912	parallelity, then this setting will limit your transaction rate (if you
		913	need to poll once per transaction and the I/O collect interval is 0.01,
		914	then you can't do more than 100 transactions per second).
717		915
718	Setting the I<timeout collect interval> can improve the opportunity for	916	Setting the I<timeout collect interval> can improve the opportunity for
719	saving power, as the program will "bundle" timer callback invocations that	917	saving power, as the program will "bundle" timer callback invocations that
720	are "near" in time together, by delaying some, thus reducing the number of	918	are "near" in time together, by delaying some, thus reducing the number of
721	times the process sleeps and wakes up again. Another useful technique to	919	times the process sleeps and wakes up again. Another useful technique to
722	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	920	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
723	they fire on, say, one-second boundaries only.	921	they fire on, say, one-second boundaries only.
724		922
		923	Example: we only need 0.1s timeout granularity, and we wish not to poll
		924	more often than 100 times per second:
		925
		926	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		927	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		928
		929	=item ev_invoke_pending (loop)
		930
		931	This call will simply invoke all pending watchers while resetting their
		932	pending state. Normally, C<ev_run> does this automatically when required,
		933	but when overriding the invoke callback this call comes handy. This
		934	function can be invoked from a watcher - this can be useful for example
		935	when you want to do some lengthy calculation and want to pass further
		936	event handling to another thread (you still have to make sure only one
		937	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		938
		939	=item int ev_pending_count (loop)
		940
		941	Returns the number of pending watchers - zero indicates that no watchers
		942	are pending.
		943
		944	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		945
		946	This overrides the invoke pending functionality of the loop: Instead of
		947	invoking all pending watchers when there are any, C<ev_run> will call
		948	this callback instead. This is useful, for example, when you want to
		949	invoke the actual watchers inside another context (another thread etc.).
		950
		951	If you want to reset the callback, use C<ev_invoke_pending> as new
		952	callback.
		953
		954	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		955
		956	Sometimes you want to share the same loop between multiple threads. This
		957	can be done relatively simply by putting mutex_lock/unlock calls around
		958	each call to a libev function.
		959
		960	However, C<ev_run> can run an indefinite time, so it is not feasible
		961	to wait for it to return. One way around this is to wake up the event
		962	loop via C<ev_break> and C<av_async_send>, another way is to set these
		963	I<release> and I<acquire> callbacks on the loop.
		964
		965	When set, then C<release> will be called just before the thread is
		966	suspended waiting for new events, and C<acquire> is called just
		967	afterwards.
		968
		969	Ideally, C<release> will just call your mutex_unlock function, and
		970	C<acquire> will just call the mutex_lock function again.
		971
		972	While event loop modifications are allowed between invocations of
		973	C<release> and C<acquire> (that's their only purpose after all), no
		974	modifications done will affect the event loop, i.e. adding watchers will
		975	have no effect on the set of file descriptors being watched, or the time
		976	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		977	to take note of any changes you made.
		978
		979	In theory, threads executing C<ev_run> will be async-cancel safe between
		980	invocations of C<release> and C<acquire>.
		981
		982	See also the locking example in the C<THREADS> section later in this
		983	document.
		984
		985	=item ev_set_userdata (loop, void *data)
		986
		987	=item ev_userdata (loop)
		988
		989	Set and retrieve a single C<void *> associated with a loop. When
		990	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		991	C<0.>
		992
		993	These two functions can be used to associate arbitrary data with a loop,
		994	and are intended solely for the C<invoke_pending_cb>, C<release> and
		995	C<acquire> callbacks described above, but of course can be (ab-)used for
		996	any other purpose as well.
		997
725	=item ev_loop_verify (loop)	998	=item ev_verify (loop)
726		999
727	This function only does something when C<EV_VERIFY> support has been	1000	This function only does something when C<EV_VERIFY> support has been
728	compiled in. It tries to go through all internal structures and checks	1001	compiled in, which is the default for non-minimal builds. It tries to go
729	them for validity. If anything is found to be inconsistent, it will print	1002	through all internal structures and checks them for validity. If anything
730	an error message to standard error and call C<abort ()>.	1003	is found to be inconsistent, it will print an error message to standard
		1004	error and call C<abort ()>.
731		1005
732	This can be used to catch bugs inside libev itself: under normal	1006	This can be used to catch bugs inside libev itself: under normal
733	circumstances, this function will never abort as of course libev keeps its	1007	circumstances, this function will never abort as of course libev keeps its
734	data structures consistent.	1008	data structures consistent.
735		1009
736	=back	1010	=back
737		1011
738		1012
739	=head1 ANATOMY OF A WATCHER	1013	=head1 ANATOMY OF A WATCHER
740		1014
		1015	In the following description, uppercase C<TYPE> in names stands for the
		1016	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		1017	watchers and C<ev_io_start> for I/O watchers.
		1018
741	A watcher is a structure that you create and register to record your	1019	A watcher is an opaque structure that you allocate and register to record
742	interest in some event. For instance, if you want to wait for STDIN to	1020	your interest in some event. To make a concrete example, imagine you want
743	become readable, you would create an C<ev_io> watcher for that:	1021	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1022	for that:
744		1023
745	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1024	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
746	{	1025	{
747	ev_io_stop (w);	1026	ev_io_stop (w);
748	ev_unloop (loop, EVUNLOOP_ALL);	1027	ev_break (loop, EVBREAK_ALL);
749	}	1028	}
750		1029
751	struct ev_loop *loop = ev_default_loop (0);	1030	struct ev_loop *loop = ev_default_loop (0);
		1031
752	struct ev_io stdin_watcher;	1032	ev_io stdin_watcher;
		1033
753	ev_init (&stdin_watcher, my_cb);	1034	ev_init (&stdin_watcher, my_cb);
754	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1035	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
755	ev_io_start (loop, &stdin_watcher);	1036	ev_io_start (loop, &stdin_watcher);
		1037
756	ev_loop (loop, 0);	1038	ev_run (loop, 0);
757		1039
758	As you can see, you are responsible for allocating the memory for your	1040	As you can see, you are responsible for allocating the memory for your
759	watcher structures (and it is usually a bad idea to do this on the stack,	1041	watcher structures (and it is I<usually> a bad idea to do this on the
760	although this can sometimes be quite valid).	1042	stack).
761		1043
		1044	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		1045	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
		1046
762	Each watcher structure must be initialised by a call to C<ev_init	1047	Each watcher structure must be initialised by a call to C<ev_init (watcher
763	(watcher *, callback)>, which expects a callback to be provided. This	1048	*, callback)>, which expects a callback to be provided. This callback is
764	callback gets invoked each time the event occurs (or, in the case of I/O	1049	invoked each time the event occurs (or, in the case of I/O watchers, each
765	watchers, each time the event loop detects that the file descriptor given	1050	time the event loop detects that the file descriptor given is readable
766	is readable and/or writable).	1051	and/or writable).
767		1052
768	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1053	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
769	with arguments specific to this watcher type. There is also a macro	1054	macro to configure it, with arguments specific to the watcher type. There
770	to combine initialisation and setting in one call: C<< ev_<type>_init	1055	is also a macro to combine initialisation and setting in one call: C<<
771	(watcher *, callback, ...) >>.	1056	ev_TYPE_init (watcher *, callback, ...) >>.
772		1057
773	To make the watcher actually watch out for events, you have to start it	1058	To make the watcher actually watch out for events, you have to start it
774	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	1059	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
775	*) >>), and you can stop watching for events at any time by calling the	1060	*) >>), and you can stop watching for events at any time by calling the
776	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1061	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
777		1062
778	As long as your watcher is active (has been started but not stopped) you	1063	As long as your watcher is active (has been started but not stopped) you
779	must not touch the values stored in it. Most specifically you must never	1064	must not touch the values stored in it. Most specifically you must never
780	reinitialise it or call its C<set> macro.	1065	reinitialise it or call its C<ev_TYPE_set> macro.
781		1066
782	Each and every callback receives the event loop pointer as first, the	1067	Each and every callback receives the event loop pointer as first, the
783	registered watcher structure as second, and a bitset of received events as	1068	registered watcher structure as second, and a bitset of received events as
784	third argument.	1069	third argument.
785		1070
…		…
794	=item C<EV_WRITE>	1079	=item C<EV_WRITE>
795		1080
796	The file descriptor in the C<ev_io> watcher has become readable and/or	1081	The file descriptor in the C<ev_io> watcher has become readable and/or
797	writable.	1082	writable.
798		1083
799	=item C<EV_TIMEOUT>	1084	=item C<EV_TIMER>
800		1085
801	The C<ev_timer> watcher has timed out.	1086	The C<ev_timer> watcher has timed out.
802		1087
803	=item C<EV_PERIODIC>	1088	=item C<EV_PERIODIC>
804		1089
…		…
822		1107
823	=item C<EV_PREPARE>	1108	=item C<EV_PREPARE>
824		1109
825	=item C<EV_CHECK>	1110	=item C<EV_CHECK>
826		1111
827	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1112	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
828	to gather new events, and all C<ev_check> watchers are invoked just after	1113	to gather new events, and all C<ev_check> watchers are invoked just after
829	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1114	C<ev_run> has gathered them, but before it invokes any callbacks for any
830	received events. Callbacks of both watcher types can start and stop as	1115	received events. Callbacks of both watcher types can start and stop as
831	many watchers as they want, and all of them will be taken into account	1116	many watchers as they want, and all of them will be taken into account
832	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1117	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
833	C<ev_loop> from blocking).	1118	C<ev_run> from blocking).
834		1119
835	=item C<EV_EMBED>	1120	=item C<EV_EMBED>
836		1121
837	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1122	The embedded event loop specified in the C<ev_embed> watcher needs attention.
838		1123
839	=item C<EV_FORK>	1124	=item C<EV_FORK>
840		1125
841	The event loop has been resumed in the child process after fork (see	1126	The event loop has been resumed in the child process after fork (see
842	C<ev_fork>).	1127	C<ev_fork>).
843		1128
		1129	=item C<EV_CLEANUP>
		1130
		1131	The event loop is about to be destroyed (see C<ev_cleanup>).
		1132
844	=item C<EV_ASYNC>	1133	=item C<EV_ASYNC>
845		1134
846	The given async watcher has been asynchronously notified (see C<ev_async>).	1135	The given async watcher has been asynchronously notified (see C<ev_async>).
		1136
		1137	=item C<EV_CUSTOM>
		1138
		1139	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1140	by libev users to signal watchers (e.g. via C<ev_feed_event>).
847		1141
848	=item C<EV_ERROR>	1142	=item C<EV_ERROR>
849		1143
850	An unspecified error has occurred, the watcher has been stopped. This might	1144	An unspecified error has occurred, the watcher has been stopped. This might
851	happen because the watcher could not be properly started because libev	1145	happen because the watcher could not be properly started because libev
852	ran out of memory, a file descriptor was found to be closed or any other	1146	ran out of memory, a file descriptor was found to be closed or any other
		1147	problem. Libev considers these application bugs.
		1148
853	problem. You best act on it by reporting the problem and somehow coping	1149	You best act on it by reporting the problem and somehow coping with the
854	with the watcher being stopped.	1150	watcher being stopped. Note that well-written programs should not receive
		1151	an error ever, so when your watcher receives it, this usually indicates a
		1152	bug in your program.
855		1153
856	Libev will usually signal a few "dummy" events together with an error,	1154	Libev will usually signal a few "dummy" events together with an error, for
857	for example it might indicate that a fd is readable or writable, and if	1155	example it might indicate that a fd is readable or writable, and if your
858	your callbacks is well-written it can just attempt the operation and cope	1156	callbacks is well-written it can just attempt the operation and cope with
859	with the error from read() or write(). This will not work in multi-threaded	1157	the error from read() or write(). This will not work in multi-threaded
860	programs, though, so beware.	1158	programs, though, as the fd could already be closed and reused for another
		1159	thing, so beware.
861		1160
862	=back	1161	=back
863		1162
864	=head2 GENERIC WATCHER FUNCTIONS	1163	=head2 GENERIC WATCHER FUNCTIONS
865
866	In the following description, C<TYPE> stands for the watcher type,
867	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
868		1164
869	=over 4	1165	=over 4
870		1166
871	=item C<ev_init> (ev_TYPE *watcher, callback)	1167	=item C<ev_init> (ev_TYPE *watcher, callback)
872		1168
…		…
878	which rolls both calls into one.	1174	which rolls both calls into one.
879		1175
880	You can reinitialise a watcher at any time as long as it has been stopped	1176	You can reinitialise a watcher at any time as long as it has been stopped
881	(or never started) and there are no pending events outstanding.	1177	(or never started) and there are no pending events outstanding.
882		1178
883	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1179	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
884	int revents)>.	1180	int revents)>.
885		1181
		1182	Example: Initialise an C<ev_io> watcher in two steps.
		1183
		1184	ev_io w;
		1185	ev_init (&w, my_cb);
		1186	ev_io_set (&w, STDIN_FILENO, EV_READ);
		1187
886	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1188	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
887		1189
888	This macro initialises the type-specific parts of a watcher. You need to	1190	This macro initialises the type-specific parts of a watcher. You need to
889	call C<ev_init> at least once before you call this macro, but you can	1191	call C<ev_init> at least once before you call this macro, but you can
890	call C<ev_TYPE_set> any number of times. You must not, however, call this	1192	call C<ev_TYPE_set> any number of times. You must not, however, call this
891	macro on a watcher that is active (it can be pending, however, which is a	1193	macro on a watcher that is active (it can be pending, however, which is a
892	difference to the C<ev_init> macro).	1194	difference to the C<ev_init> macro).
893		1195
894	Although some watcher types do not have type-specific arguments	1196	Although some watcher types do not have type-specific arguments
895	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	1197	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
896		1198
		1199	See C<ev_init>, above, for an example.
		1200
897	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1201	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
898		1202
899	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1203	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
900	calls into a single call. This is the most convenient method to initialise	1204	calls into a single call. This is the most convenient method to initialise
901	a watcher. The same limitations apply, of course.	1205	a watcher. The same limitations apply, of course.
902		1206
		1207	Example: Initialise and set an C<ev_io> watcher in one step.
		1208
		1209	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1210
903	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1211	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
904		1212
905	Starts (activates) the given watcher. Only active watchers will receive	1213	Starts (activates) the given watcher. Only active watchers will receive
906	events. If the watcher is already active nothing will happen.	1214	events. If the watcher is already active nothing will happen.
907		1215
		1216	Example: Start the C<ev_io> watcher that is being abused as example in this
		1217	whole section.
		1218
		1219	ev_io_start (EV_DEFAULT_UC, &w);
		1220
908	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1221	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
909		1222
910	Stops the given watcher again (if active) and clears the pending	1223	Stops the given watcher if active, and clears the pending status (whether
		1224	the watcher was active or not).
		1225
911	status. It is possible that stopped watchers are pending (for example,	1226	It is possible that stopped watchers are pending - for example,
912	non-repeating timers are being stopped when they become pending), but	1227	non-repeating timers are being stopped when they become pending - but
913	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1228	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
914	you want to free or reuse the memory used by the watcher it is therefore a	1229	pending. If you want to free or reuse the memory used by the watcher it is
915	good idea to always call its C<ev_TYPE_stop> function.	1230	therefore a good idea to always call its C<ev_TYPE_stop> function.
916		1231
917	=item bool ev_is_active (ev_TYPE *watcher)	1232	=item bool ev_is_active (ev_TYPE *watcher)
918		1233
919	Returns a true value iff the watcher is active (i.e. it has been started	1234	Returns a true value iff the watcher is active (i.e. it has been started
920	and not yet been stopped). As long as a watcher is active you must not modify	1235	and not yet been stopped). As long as a watcher is active you must not modify
…		…
936	=item ev_cb_set (ev_TYPE *watcher, callback)	1251	=item ev_cb_set (ev_TYPE *watcher, callback)
937		1252
938	Change the callback. You can change the callback at virtually any time	1253	Change the callback. You can change the callback at virtually any time
939	(modulo threads).	1254	(modulo threads).
940		1255
941	=item ev_set_priority (ev_TYPE *watcher, priority)	1256	=item ev_set_priority (ev_TYPE *watcher, int priority)
942		1257
943	=item int ev_priority (ev_TYPE *watcher)	1258	=item int ev_priority (ev_TYPE *watcher)
944		1259
945	Set and query the priority of the watcher. The priority is a small	1260	Set and query the priority of the watcher. The priority is a small
946	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1261	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
947	(default: C<-2>). Pending watchers with higher priority will be invoked	1262	(default: C<-2>). Pending watchers with higher priority will be invoked
948	before watchers with lower priority, but priority will not keep watchers	1263	before watchers with lower priority, but priority will not keep watchers
949	from being executed (except for C<ev_idle> watchers).	1264	from being executed (except for C<ev_idle> watchers).
950		1265
951	This means that priorities are I<only> used for ordering callback
952	invocation after new events have been received. This is useful, for
953	example, to reduce latency after idling, or more often, to bind two
954	watchers on the same event and make sure one is called first.
955
956	If you need to suppress invocation when higher priority events are pending	1266	If you need to suppress invocation when higher priority events are pending
957	you need to look at C<ev_idle> watchers, which provide this functionality.	1267	you need to look at C<ev_idle> watchers, which provide this functionality.
958		1268
959	You I<must not> change the priority of a watcher as long as it is active or	1269	You I<must not> change the priority of a watcher as long as it is active or
960	pending.	1270	pending.
961		1271
		1272	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1273	fine, as long as you do not mind that the priority value you query might
		1274	or might not have been clamped to the valid range.
		1275
962	The default priority used by watchers when no priority has been set is	1276	The default priority used by watchers when no priority has been set is
963	always C<0>, which is supposed to not be too high and not be too low :).	1277	always C<0>, which is supposed to not be too high and not be too low :).
964		1278
965	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1279	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
966	fine, as long as you do not mind that the priority value you query might	1280	priorities.
967	or might not have been adjusted to be within valid range.
968		1281
969	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1282	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
970		1283
971	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1284	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
972	C<loop> nor C<revents> need to be valid as long as the watcher callback	1285	C<loop> nor C<revents> need to be valid as long as the watcher callback
973	can deal with that fact.	1286	can deal with that fact, as both are simply passed through to the
		1287	callback.
974		1288
975	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1289	=item int ev_clear_pending (loop, ev_TYPE *watcher)
976		1290
977	If the watcher is pending, this function returns clears its pending status	1291	If the watcher is pending, this function clears its pending status and
978	and returns its C<revents> bitset (as if its callback was invoked). If the	1292	returns its C<revents> bitset (as if its callback was invoked). If the
979	watcher isn't pending it does nothing and returns C<0>.	1293	watcher isn't pending it does nothing and returns C<0>.
980		1294
		1295	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1296	callback to be invoked, which can be accomplished with this function.
		1297
		1298	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1299
		1300	Feeds the given event set into the event loop, as if the specified event
		1301	had happened for the specified watcher (which must be a pointer to an
		1302	initialised but not necessarily started event watcher). Obviously you must
		1303	not free the watcher as long as it has pending events.
		1304
		1305	Stopping the watcher, letting libev invoke it, or calling
		1306	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1307	not started in the first place.
		1308
		1309	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1310	functions that do not need a watcher.
		1311
981	=back	1312	=back
982		1313
983
984	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1314	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
985		1315
986	Each watcher has, by default, a member C<void *data> that you can change	1316	Each watcher has, by default, a member C<void *data> that you can change
987	and read at any time, libev will completely ignore it. This can be used	1317	and read at any time: libev will completely ignore it. This can be used
988	to associate arbitrary data with your watcher. If you need more data and	1318	to associate arbitrary data with your watcher. If you need more data and
989	don't want to allocate memory and store a pointer to it in that data	1319	don't want to allocate memory and store a pointer to it in that data
990	member, you can also "subclass" the watcher type and provide your own	1320	member, you can also "subclass" the watcher type and provide your own
991	data:	1321	data:
992		1322
993	struct my_io	1323	struct my_io
994	{	1324	{
995	struct ev_io io;	1325	ev_io io;
996	int otherfd;	1326	int otherfd;
997	void *somedata;	1327	void *somedata;
998	struct whatever *mostinteresting;	1328	struct whatever *mostinteresting;
999	}	1329	};
		1330
		1331	...
		1332	struct my_io w;
		1333	ev_io_init (&w.io, my_cb, fd, EV_READ);
1000		1334
1001	And since your callback will be called with a pointer to the watcher, you	1335	And since your callback will be called with a pointer to the watcher, you
1002	can cast it back to your own type:	1336	can cast it back to your own type:
1003		1337
1004	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1338	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1005	{	1339	{
1006	struct my_io *w = (struct my_io *)w_;	1340	struct my_io *w = (struct my_io *)w_;
1007	...	1341	...
1008	}	1342	}
1009		1343
1010	More interesting and less C-conformant ways of casting your callback type	1344	More interesting and less C-conformant ways of casting your callback type
1011	instead have been omitted.	1345	instead have been omitted.
1012		1346
1013	Another common scenario is having some data structure with multiple	1347	Another common scenario is to use some data structure with multiple
1014	watchers:	1348	embedded watchers:
1015		1349
1016	struct my_biggy	1350	struct my_biggy
1017	{	1351	{
1018	int some_data;	1352	int some_data;
1019	ev_timer t1;	1353	ev_timer t1;
1020	ev_timer t2;	1354	ev_timer t2;
1021	}	1355	}
1022		1356
1023	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1357	In this case getting the pointer to C<my_biggy> is a bit more
1024	you need to use C<offsetof>:	1358	complicated: Either you store the address of your C<my_biggy> struct
		1359	in the C<data> member of the watcher (for woozies), or you need to use
		1360	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1361	programmers):
1025		1362
1026	#include <stddef.h>	1363	#include <stddef.h>
1027		1364
1028	static void	1365	static void
1029	t1_cb (EV_P_ struct ev_timer *w, int revents)	1366	t1_cb (EV_P_ ev_timer *w, int revents)
1030	{	1367	{
1031	struct my_biggy big = (struct my_biggy *	1368	struct my_biggy big = (struct my_biggy *)
1032	(((char *)w) - offsetof (struct my_biggy, t1));	1369	(((char *)w) - offsetof (struct my_biggy, t1));
1033	}	1370	}
1034		1371
1035	static void	1372	static void
1036	t2_cb (EV_P_ struct ev_timer *w, int revents)	1373	t2_cb (EV_P_ ev_timer *w, int revents)
1037	{	1374	{
1038	struct my_biggy big = (struct my_biggy *	1375	struct my_biggy big = (struct my_biggy *)
1039	(((char *)w) - offsetof (struct my_biggy, t2));	1376	(((char *)w) - offsetof (struct my_biggy, t2));
1040	}	1377	}
		1378
		1379	=head2 WATCHER STATES
		1380
		1381	There are various watcher states mentioned throughout this manual -
		1382	active, pending and so on. In this section these states and the rules to
		1383	transition between them will be described in more detail - and while these
		1384	rules might look complicated, they usually do "the right thing".
		1385
		1386	=over 4
		1387
		1388	=item initialiased
		1389
		1390	Before a watcher can be registered with the event looop it has to be
		1391	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1392	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1393
		1394	In this state it is simply some block of memory that is suitable for use
		1395	in an event loop. It can be moved around, freed, reused etc. at will.
		1396
		1397	=item started/running/active
		1398
		1399	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1400	property of the event loop, and is actively waiting for events. While in
		1401	this state it cannot be accessed (except in a few documented ways), moved,
		1402	freed or anything else - the only legal thing is to keep a pointer to it,
		1403	and call libev functions on it that are documented to work on active watchers.
		1404
		1405	=item pending
		1406
		1407	If a watcher is active and libev determines that an event it is interested
		1408	in has occurred (such as a timer expiring), it will become pending. It will
		1409	stay in this pending state until either it is stopped or its callback is
		1410	about to be invoked, so it is not normally pending inside the watcher
		1411	callback.
		1412
		1413	The watcher might or might not be active while it is pending (for example,
		1414	an expired non-repeating timer can be pending but no longer active). If it
		1415	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1416	but it is still property of the event loop at this time, so cannot be
		1417	moved, freed or reused. And if it is active the rules described in the
		1418	previous item still apply.
		1419
		1420	It is also possible to feed an event on a watcher that is not active (e.g.
		1421	via C<ev_feed_event>), in which case it becomes pending without being
		1422	active.
		1423
		1424	=item stopped
		1425
		1426	A watcher can be stopped implicitly by libev (in which case it might still
		1427	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1428	latter will clear any pending state the watcher might be in, regardless
		1429	of whether it was active or not, so stopping a watcher explicitly before
		1430	freeing it is often a good idea.
		1431
		1432	While stopped (and not pending) the watcher is essentially in the
		1433	initialised state, that is it can be reused, moved, modified in any way
		1434	you wish.
		1435
		1436	=back
		1437
		1438	=head2 WATCHER PRIORITY MODELS
		1439
		1440	Many event loops support I<watcher priorities>, which are usually small
		1441	integers that influence the ordering of event callback invocation
		1442	between watchers in some way, all else being equal.
		1443
		1444	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1445	description for the more technical details such as the actual priority
		1446	range.
		1447
		1448	There are two common ways how these these priorities are being interpreted
		1449	by event loops:
		1450
		1451	In the more common lock-out model, higher priorities "lock out" invocation
		1452	of lower priority watchers, which means as long as higher priority
		1453	watchers receive events, lower priority watchers are not being invoked.
		1454
		1455	The less common only-for-ordering model uses priorities solely to order
		1456	callback invocation within a single event loop iteration: Higher priority
		1457	watchers are invoked before lower priority ones, but they all get invoked
		1458	before polling for new events.
		1459
		1460	Libev uses the second (only-for-ordering) model for all its watchers
		1461	except for idle watchers (which use the lock-out model).
		1462
		1463	The rationale behind this is that implementing the lock-out model for
		1464	watchers is not well supported by most kernel interfaces, and most event
		1465	libraries will just poll for the same events again and again as long as
		1466	their callbacks have not been executed, which is very inefficient in the
		1467	common case of one high-priority watcher locking out a mass of lower
		1468	priority ones.
		1469
		1470	Static (ordering) priorities are most useful when you have two or more
		1471	watchers handling the same resource: a typical usage example is having an
		1472	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1473	timeouts. Under load, data might be received while the program handles
		1474	other jobs, but since timers normally get invoked first, the timeout
		1475	handler will be executed before checking for data. In that case, giving
		1476	the timer a lower priority than the I/O watcher ensures that I/O will be
		1477	handled first even under adverse conditions (which is usually, but not
		1478	always, what you want).
		1479
		1480	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1481	will only be executed when no same or higher priority watchers have
		1482	received events, they can be used to implement the "lock-out" model when
		1483	required.
		1484
		1485	For example, to emulate how many other event libraries handle priorities,
		1486	you can associate an C<ev_idle> watcher to each such watcher, and in
		1487	the normal watcher callback, you just start the idle watcher. The real
		1488	processing is done in the idle watcher callback. This causes libev to
		1489	continuously poll and process kernel event data for the watcher, but when
		1490	the lock-out case is known to be rare (which in turn is rare :), this is
		1491	workable.
		1492
		1493	Usually, however, the lock-out model implemented that way will perform
		1494	miserably under the type of load it was designed to handle. In that case,
		1495	it might be preferable to stop the real watcher before starting the
		1496	idle watcher, so the kernel will not have to process the event in case
		1497	the actual processing will be delayed for considerable time.
		1498
		1499	Here is an example of an I/O watcher that should run at a strictly lower
		1500	priority than the default, and which should only process data when no
		1501	other events are pending:
		1502
		1503	ev_idle idle; // actual processing watcher
		1504	ev_io io; // actual event watcher
		1505
		1506	static void
		1507	io_cb (EV_P_ ev_io *w, int revents)
		1508	{
		1509	// stop the I/O watcher, we received the event, but
		1510	// are not yet ready to handle it.
		1511	ev_io_stop (EV_A_ w);
		1512
		1513	// start the idle watcher to handle the actual event.
		1514	// it will not be executed as long as other watchers
		1515	// with the default priority are receiving events.
		1516	ev_idle_start (EV_A_ &idle);
		1517	}
		1518
		1519	static void
		1520	idle_cb (EV_P_ ev_idle *w, int revents)
		1521	{
		1522	// actual processing
		1523	read (STDIN_FILENO, ...);
		1524
		1525	// have to start the I/O watcher again, as
		1526	// we have handled the event
		1527	ev_io_start (EV_P_ &io);
		1528	}
		1529
		1530	// initialisation
		1531	ev_idle_init (&idle, idle_cb);
		1532	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1533	ev_io_start (EV_DEFAULT_ &io);
		1534
		1535	In the "real" world, it might also be beneficial to start a timer, so that
		1536	low-priority connections can not be locked out forever under load. This
		1537	enables your program to keep a lower latency for important connections
		1538	during short periods of high load, while not completely locking out less
		1539	important ones.
1041		1540
1042		1541
1043	=head1 WATCHER TYPES	1542	=head1 WATCHER TYPES
1044		1543
1045	This section describes each watcher in detail, but will not repeat	1544	This section describes each watcher in detail, but will not repeat
…		…
1069	In general you can register as many read and/or write event watchers per	1568	In general you can register as many read and/or write event watchers per
1070	fd as you want (as long as you don't confuse yourself). Setting all file	1569	fd as you want (as long as you don't confuse yourself). Setting all file
1071	descriptors to non-blocking mode is also usually a good idea (but not	1570	descriptors to non-blocking mode is also usually a good idea (but not
1072	required if you know what you are doing).	1571	required if you know what you are doing).
1073		1572
1074	If you must do this, then force the use of a known-to-be-good backend	1573	If you cannot use non-blocking mode, then force the use of a
1075	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1574	known-to-be-good backend (at the time of this writing, this includes only
1076	C<EVBACKEND_POLL>).	1575	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1576	descriptors for which non-blocking operation makes no sense (such as
		1577	files) - libev doesn't guarantee any specific behaviour in that case.
1077		1578
1078	Another thing you have to watch out for is that it is quite easy to	1579	Another thing you have to watch out for is that it is quite easy to
1079	receive "spurious" readiness notifications, that is your callback might	1580	receive "spurious" readiness notifications, that is your callback might
1080	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1581	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1081	because there is no data. Not only are some backends known to create a	1582	because there is no data. Not only are some backends known to create a
1082	lot of those (for example Solaris ports), it is very easy to get into	1583	lot of those (for example Solaris ports), it is very easy to get into
1083	this situation even with a relatively standard program structure. Thus	1584	this situation even with a relatively standard program structure. Thus
1084	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1585	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1085	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1586	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1086		1587
1087	If you cannot run the fd in non-blocking mode (for example you should not	1588	If you cannot run the fd in non-blocking mode (for example you should
1088	play around with an Xlib connection), then you have to separately re-test	1589	not play around with an Xlib connection), then you have to separately
1089	whether a file descriptor is really ready with a known-to-be good interface	1590	re-test whether a file descriptor is really ready with a known-to-be good
1090	such as poll (fortunately in our Xlib example, Xlib already does this on	1591	interface such as poll (fortunately in our Xlib example, Xlib already
1091	its own, so its quite safe to use).	1592	does this on its own, so its quite safe to use). Some people additionally
		1593	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1594	indefinitely.
		1595
		1596	But really, best use non-blocking mode.
1092		1597
1093	=head3 The special problem of disappearing file descriptors	1598	=head3 The special problem of disappearing file descriptors
1094		1599
1095	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1600	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1096	descriptor (either by calling C<close> explicitly or by any other means,	1601	descriptor (either due to calling C<close> explicitly or any other means,
1097	such as C<dup>). The reason is that you register interest in some file	1602	such as C<dup2>). The reason is that you register interest in some file
1098	descriptor, but when it goes away, the operating system will silently drop	1603	descriptor, but when it goes away, the operating system will silently drop
1099	this interest. If another file descriptor with the same number then is	1604	this interest. If another file descriptor with the same number then is
1100	registered with libev, there is no efficient way to see that this is, in	1605	registered with libev, there is no efficient way to see that this is, in
1101	fact, a different file descriptor.	1606	fact, a different file descriptor.
1102		1607
…		…
1133	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1638	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1134	C<EVBACKEND_POLL>.	1639	C<EVBACKEND_POLL>.
1135		1640
1136	=head3 The special problem of SIGPIPE	1641	=head3 The special problem of SIGPIPE
1137		1642
1138	While not really specific to libev, it is easy to forget about SIGPIPE:	1643	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1139	when writing to a pipe whose other end has been closed, your program gets	1644	when writing to a pipe whose other end has been closed, your program gets
1140	send a SIGPIPE, which, by default, aborts your program. For most programs	1645	sent a SIGPIPE, which, by default, aborts your program. For most programs
1141	this is sensible behaviour, for daemons, this is usually undesirable.	1646	this is sensible behaviour, for daemons, this is usually undesirable.
1142		1647
1143	So when you encounter spurious, unexplained daemon exits, make sure you	1648	So when you encounter spurious, unexplained daemon exits, make sure you
1144	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1649	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1145	somewhere, as that would have given you a big clue).	1650	somewhere, as that would have given you a big clue).
1146		1651
		1652	=head3 The special problem of accept()ing when you can't
		1653
		1654	Many implementations of the POSIX C<accept> function (for example,
		1655	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1656	connection from the pending queue in all error cases.
		1657
		1658	For example, larger servers often run out of file descriptors (because
		1659	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1660	rejecting the connection, leading to libev signalling readiness on
		1661	the next iteration again (the connection still exists after all), and
		1662	typically causing the program to loop at 100% CPU usage.
		1663
		1664	Unfortunately, the set of errors that cause this issue differs between
		1665	operating systems, there is usually little the app can do to remedy the
		1666	situation, and no known thread-safe method of removing the connection to
		1667	cope with overload is known (to me).
		1668
		1669	One of the easiest ways to handle this situation is to just ignore it
		1670	- when the program encounters an overload, it will just loop until the
		1671	situation is over. While this is a form of busy waiting, no OS offers an
		1672	event-based way to handle this situation, so it's the best one can do.
		1673
		1674	A better way to handle the situation is to log any errors other than
		1675	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1676	messages, and continue as usual, which at least gives the user an idea of
		1677	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1678	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1679	usage.
		1680
		1681	If your program is single-threaded, then you could also keep a dummy file
		1682	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1683	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1684	close that fd, and create a new dummy fd. This will gracefully refuse
		1685	clients under typical overload conditions.
		1686
		1687	The last way to handle it is to simply log the error and C<exit>, as
		1688	is often done with C<malloc> failures, but this results in an easy
		1689	opportunity for a DoS attack.
1147		1690
1148	=head3 Watcher-Specific Functions	1691	=head3 Watcher-Specific Functions
1149		1692
1150	=over 4	1693	=over 4
1151		1694
1152	=item ev_io_init (ev_io *, callback, int fd, int events)	1695	=item ev_io_init (ev_io *, callback, int fd, int events)
1153		1696
1154	=item ev_io_set (ev_io *, int fd, int events)	1697	=item ev_io_set (ev_io *, int fd, int events)
1155		1698
1156	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1699	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1157	receive events for and events is either C<EV_READ>, C<EV_WRITE> or	1700	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1158	C<EV_READ | EV_WRITE> to receive the given events.	1701	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1159		1702
1160	=item int fd [read-only]	1703	=item int fd [read-only]
1161		1704
1162	The file descriptor being watched.	1705	The file descriptor being watched.
1163		1706
…		…
1172	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1715	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1173	readable, but only once. Since it is likely line-buffered, you could	1716	readable, but only once. Since it is likely line-buffered, you could
1174	attempt to read a whole line in the callback.	1717	attempt to read a whole line in the callback.
1175		1718
1176	static void	1719	static void
1177	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1720	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1178	{	1721	{
1179	ev_io_stop (loop, w);	1722	ev_io_stop (loop, w);
1180	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1723	.. read from stdin here (or from w->fd) and handle any I/O errors
1181	}	1724	}
1182		1725
1183	...	1726	...
1184	struct ev_loop *loop = ev_default_init (0);	1727	struct ev_loop *loop = ev_default_init (0);
1185	struct ev_io stdin_readable;	1728	ev_io stdin_readable;
1186	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1729	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1187	ev_io_start (loop, &stdin_readable);	1730	ev_io_start (loop, &stdin_readable);
1188	ev_loop (loop, 0);	1731	ev_run (loop, 0);
1189		1732
1190		1733
1191	=head2 C<ev_timer> - relative and optionally repeating timeouts	1734	=head2 C<ev_timer> - relative and optionally repeating timeouts
1192		1735
1193	Timer watchers are simple relative timers that generate an event after a	1736	Timer watchers are simple relative timers that generate an event after a
1194	given time, and optionally repeating in regular intervals after that.	1737	given time, and optionally repeating in regular intervals after that.
1195		1738
1196	The timers are based on real time, that is, if you register an event that	1739	The timers are based on real time, that is, if you register an event that
1197	times out after an hour and you reset your system clock to January last	1740	times out after an hour and you reset your system clock to January last
1198	year, it will still time out after (roughly) and hour. "Roughly" because	1741	year, it will still time out after (roughly) one hour. "Roughly" because
1199	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1742	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1200	monotonic clock option helps a lot here).	1743	monotonic clock option helps a lot here).
1201		1744
1202	The callback is guaranteed to be invoked only after its timeout has passed,	1745	The callback is guaranteed to be invoked only I<after> its timeout has
1203	but if multiple timers become ready during the same loop iteration then	1746	passed (not I<at>, so on systems with very low-resolution clocks this
1204	order of execution is undefined.	1747	might introduce a small delay). If multiple timers become ready during the
		1748	same loop iteration then the ones with earlier time-out values are invoked
		1749	before ones of the same priority with later time-out values (but this is
		1750	no longer true when a callback calls C<ev_run> recursively).
		1751
		1752	=head3 Be smart about timeouts
		1753
		1754	Many real-world problems involve some kind of timeout, usually for error
		1755	recovery. A typical example is an HTTP request - if the other side hangs,
		1756	you want to raise some error after a while.
		1757
		1758	What follows are some ways to handle this problem, from obvious and
		1759	inefficient to smart and efficient.
		1760
		1761	In the following, a 60 second activity timeout is assumed - a timeout that
		1762	gets reset to 60 seconds each time there is activity (e.g. each time some
		1763	data or other life sign was received).
		1764
		1765	=over 4
		1766
		1767	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1768
		1769	This is the most obvious, but not the most simple way: In the beginning,
		1770	start the watcher:
		1771
		1772	ev_timer_init (timer, callback, 60., 0.);
		1773	ev_timer_start (loop, timer);
		1774
		1775	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1776	and start it again:
		1777
		1778	ev_timer_stop (loop, timer);
		1779	ev_timer_set (timer, 60., 0.);
		1780	ev_timer_start (loop, timer);
		1781
		1782	This is relatively simple to implement, but means that each time there is
		1783	some activity, libev will first have to remove the timer from its internal
		1784	data structure and then add it again. Libev tries to be fast, but it's
		1785	still not a constant-time operation.
		1786
		1787	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1788
		1789	This is the easiest way, and involves using C<ev_timer_again> instead of
		1790	C<ev_timer_start>.
		1791
		1792	To implement this, configure an C<ev_timer> with a C<repeat> value
		1793	of C<60> and then call C<ev_timer_again> at start and each time you
		1794	successfully read or write some data. If you go into an idle state where
		1795	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1796	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1797
		1798	That means you can ignore both the C<ev_timer_start> function and the
		1799	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1800	member and C<ev_timer_again>.
		1801
		1802	At start:
		1803
		1804	ev_init (timer, callback);
		1805	timer->repeat = 60.;
		1806	ev_timer_again (loop, timer);
		1807
		1808	Each time there is some activity:
		1809
		1810	ev_timer_again (loop, timer);
		1811
		1812	It is even possible to change the time-out on the fly, regardless of
		1813	whether the watcher is active or not:
		1814
		1815	timer->repeat = 30.;
		1816	ev_timer_again (loop, timer);
		1817
		1818	This is slightly more efficient then stopping/starting the timer each time
		1819	you want to modify its timeout value, as libev does not have to completely
		1820	remove and re-insert the timer from/into its internal data structure.
		1821
		1822	It is, however, even simpler than the "obvious" way to do it.
		1823
		1824	=item 3. Let the timer time out, but then re-arm it as required.
		1825
		1826	This method is more tricky, but usually most efficient: Most timeouts are
		1827	relatively long compared to the intervals between other activity - in
		1828	our example, within 60 seconds, there are usually many I/O events with
		1829	associated activity resets.
		1830
		1831	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1832	but remember the time of last activity, and check for a real timeout only
		1833	within the callback:
		1834
		1835	ev_tstamp last_activity; // time of last activity
		1836
		1837	static void
		1838	callback (EV_P_ ev_timer *w, int revents)
		1839	{
		1840	ev_tstamp now = ev_now (EV_A);
		1841	ev_tstamp timeout = last_activity + 60.;
		1842
		1843	// if last_activity + 60. is older than now, we did time out
		1844	if (timeout < now)
		1845	{
		1846	// timeout occurred, take action
		1847	}
		1848	else
		1849	{
		1850	// callback was invoked, but there was some activity, re-arm
		1851	// the watcher to fire in last_activity + 60, which is
		1852	// guaranteed to be in the future, so "again" is positive:
		1853	w->repeat = timeout - now;
		1854	ev_timer_again (EV_A_ w);
		1855	}
		1856	}
		1857
		1858	To summarise the callback: first calculate the real timeout (defined
		1859	as "60 seconds after the last activity"), then check if that time has
		1860	been reached, which means something I<did>, in fact, time out. Otherwise
		1861	the callback was invoked too early (C<timeout> is in the future), so
		1862	re-schedule the timer to fire at that future time, to see if maybe we have
		1863	a timeout then.
		1864
		1865	Note how C<ev_timer_again> is used, taking advantage of the
		1866	C<ev_timer_again> optimisation when the timer is already running.
		1867
		1868	This scheme causes more callback invocations (about one every 60 seconds
		1869	minus half the average time between activity), but virtually no calls to
		1870	libev to change the timeout.
		1871
		1872	To start the timer, simply initialise the watcher and set C<last_activity>
		1873	to the current time (meaning we just have some activity :), then call the
		1874	callback, which will "do the right thing" and start the timer:
		1875
		1876	ev_init (timer, callback);
		1877	last_activity = ev_now (loop);
		1878	callback (loop, timer, EV_TIMER);
		1879
		1880	And when there is some activity, simply store the current time in
		1881	C<last_activity>, no libev calls at all:
		1882
		1883	last_activity = ev_now (loop);
		1884
		1885	This technique is slightly more complex, but in most cases where the
		1886	time-out is unlikely to be triggered, much more efficient.
		1887
		1888	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1889	callback :) - just change the timeout and invoke the callback, which will
		1890	fix things for you.
		1891
		1892	=item 4. Wee, just use a double-linked list for your timeouts.
		1893
		1894	If there is not one request, but many thousands (millions...), all
		1895	employing some kind of timeout with the same timeout value, then one can
		1896	do even better:
		1897
		1898	When starting the timeout, calculate the timeout value and put the timeout
		1899	at the I<end> of the list.
		1900
		1901	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1902	the list is expected to fire (for example, using the technique #3).
		1903
		1904	When there is some activity, remove the timer from the list, recalculate
		1905	the timeout, append it to the end of the list again, and make sure to
		1906	update the C<ev_timer> if it was taken from the beginning of the list.
		1907
		1908	This way, one can manage an unlimited number of timeouts in O(1) time for
		1909	starting, stopping and updating the timers, at the expense of a major
		1910	complication, and having to use a constant timeout. The constant timeout
		1911	ensures that the list stays sorted.
		1912
		1913	=back
		1914
		1915	So which method the best?
		1916
		1917	Method #2 is a simple no-brain-required solution that is adequate in most
		1918	situations. Method #3 requires a bit more thinking, but handles many cases
		1919	better, and isn't very complicated either. In most case, choosing either
		1920	one is fine, with #3 being better in typical situations.
		1921
		1922	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1923	rather complicated, but extremely efficient, something that really pays
		1924	off after the first million or so of active timers, i.e. it's usually
		1925	overkill :)
1205		1926
1206	=head3 The special problem of time updates	1927	=head3 The special problem of time updates
1207		1928
1208	Requesting the current time is a costly operation (it usually takes at	1929	Establishing the current time is a costly operation (it usually takes at
1209	least two syscalls): EV therefore updates it's idea of the current time	1930	least two system calls): EV therefore updates its idea of the current
1210	only before and after C<ev_loop> polls for new events, which causes the	1931	time only before and after C<ev_run> collects new events, which causes a
1211	difference between C<ev_now ()> and C<ev_time ()>.	1932	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1933	lots of events in one iteration.
1212		1934
1213	The relative timeouts are calculated relative to the C<ev_now ()>	1935	The relative timeouts are calculated relative to the C<ev_now ()>
1214	time. This is usually the right thing as this timestamp refers to the time	1936	time. This is usually the right thing as this timestamp refers to the time
1215	of the event triggering whatever timeout you are modifying/starting. If	1937	of the event triggering whatever timeout you are modifying/starting. If
1216	you suspect event processing to be delayed and you I<need> to base the	1938	you suspect event processing to be delayed and you I<need> to base the
1217	timeout on the current time, use something like this to adjust for this:	1939	timeout on the current time, use something like this to adjust for this:
1218		1940
1219	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1941	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1220		1942
		1943	If the event loop is suspended for a long time, you can also force an
		1944	update of the time returned by C<ev_now ()> by calling C<ev_now_update
		1945	()>.
		1946
		1947	=head3 The special problems of suspended animation
		1948
		1949	When you leave the server world it is quite customary to hit machines that
		1950	can suspend/hibernate - what happens to the clocks during such a suspend?
		1951
		1952	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1953	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1954	to run until the system is suspended, but they will not advance while the
		1955	system is suspended. That means, on resume, it will be as if the program
		1956	was frozen for a few seconds, but the suspend time will not be counted
		1957	towards C<ev_timer> when a monotonic clock source is used. The real time
		1958	clock advanced as expected, but if it is used as sole clocksource, then a
		1959	long suspend would be detected as a time jump by libev, and timers would
		1960	be adjusted accordingly.
		1961
		1962	I would not be surprised to see different behaviour in different between
		1963	operating systems, OS versions or even different hardware.
		1964
		1965	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1966	time jump in the monotonic clocks and the realtime clock. If the program
		1967	is suspended for a very long time, and monotonic clock sources are in use,
		1968	then you can expect C<ev_timer>s to expire as the full suspension time
		1969	will be counted towards the timers. When no monotonic clock source is in
		1970	use, then libev will again assume a timejump and adjust accordingly.
		1971
		1972	It might be beneficial for this latter case to call C<ev_suspend>
		1973	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1974	deterministic behaviour in this case (you can do nothing against
		1975	C<SIGSTOP>).
		1976
1221	=head3 Watcher-Specific Functions and Data Members	1977	=head3 Watcher-Specific Functions and Data Members
1222		1978
1223	=over 4	1979	=over 4
1224		1980
1225	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1981	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1248	If the timer is started but non-repeating, stop it (as if it timed out).	2004	If the timer is started but non-repeating, stop it (as if it timed out).
1249		2005
1250	If the timer is repeating, either start it if necessary (with the	2006	If the timer is repeating, either start it if necessary (with the
1251	C<repeat> value), or reset the running timer to the C<repeat> value.	2007	C<repeat> value), or reset the running timer to the C<repeat> value.
1252		2008
1253	This sounds a bit complicated, but here is a useful and typical	2009	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1254	example: Imagine you have a TCP connection and you want a so-called idle	2010	usage example.
1255	timeout, that is, you want to be called when there have been, say, 60
1256	seconds of inactivity on the socket. The easiest way to do this is to
1257	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1258	C<ev_timer_again> each time you successfully read or write some data. If
1259	you go into an idle state where you do not expect data to travel on the
1260	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1261	automatically restart it if need be.
1262		2011
1263	That means you can ignore the C<after> value and C<ev_timer_start>	2012	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1264	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1265		2013
1266	ev_timer_init (timer, callback, 0., 5.);	2014	Returns the remaining time until a timer fires. If the timer is active,
1267	ev_timer_again (loop, timer);	2015	then this time is relative to the current event loop time, otherwise it's
1268	...	2016	the timeout value currently configured.
1269	timer->again = 17.;
1270	ev_timer_again (loop, timer);
1271	...
1272	timer->again = 10.;
1273	ev_timer_again (loop, timer);
1274		2017
1275	This is more slightly efficient then stopping/starting the timer each time	2018	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1276	you want to modify its timeout value.	2019	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2020	will return C<4>. When the timer expires and is restarted, it will return
		2021	roughly C<7> (likely slightly less as callback invocation takes some time,
		2022	too), and so on.
1277		2023
1278	=item ev_tstamp repeat [read-write]	2024	=item ev_tstamp repeat [read-write]
1279		2025
1280	The current C<repeat> value. Will be used each time the watcher times out	2026	The current C<repeat> value. Will be used each time the watcher times out
1281	or C<ev_timer_again> is called and determines the next timeout (if any),	2027	or C<ev_timer_again> is called, and determines the next timeout (if any),
1282	which is also when any modifications are taken into account.	2028	which is also when any modifications are taken into account.
1283		2029
1284	=back	2030	=back
1285		2031
1286	=head3 Examples	2032	=head3 Examples
1287		2033
1288	Example: Create a timer that fires after 60 seconds.	2034	Example: Create a timer that fires after 60 seconds.
1289		2035
1290	static void	2036	static void
1291	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2037	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1292	{	2038	{
1293	.. one minute over, w is actually stopped right here	2039	.. one minute over, w is actually stopped right here
1294	}	2040	}
1295		2041
1296	struct ev_timer mytimer;	2042	ev_timer mytimer;
1297	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	2043	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1298	ev_timer_start (loop, &mytimer);	2044	ev_timer_start (loop, &mytimer);
1299		2045
1300	Example: Create a timeout timer that times out after 10 seconds of	2046	Example: Create a timeout timer that times out after 10 seconds of
1301	inactivity.	2047	inactivity.
1302		2048
1303	static void	2049	static void
1304	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2050	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1305	{	2051	{
1306	.. ten seconds without any activity	2052	.. ten seconds without any activity
1307	}	2053	}
1308		2054
1309	struct ev_timer mytimer;	2055	ev_timer mytimer;
1310	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2056	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1311	ev_timer_again (&mytimer); /* start timer */	2057	ev_timer_again (&mytimer); /* start timer */
1312	ev_loop (loop, 0);	2058	ev_run (loop, 0);
1313		2059
1314	// and in some piece of code that gets executed on any "activity":	2060	// and in some piece of code that gets executed on any "activity":
1315	// reset the timeout to start ticking again at 10 seconds	2061	// reset the timeout to start ticking again at 10 seconds
1316	ev_timer_again (&mytimer);	2062	ev_timer_again (&mytimer);
1317		2063
…		…
1319	=head2 C<ev_periodic> - to cron or not to cron?	2065	=head2 C<ev_periodic> - to cron or not to cron?
1320		2066
1321	Periodic watchers are also timers of a kind, but they are very versatile	2067	Periodic watchers are also timers of a kind, but they are very versatile
1322	(and unfortunately a bit complex).	2068	(and unfortunately a bit complex).
1323		2069
1324	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2070	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1325	but on wall clock time (absolute time). You can tell a periodic watcher	2071	relative time, the physical time that passes) but on wall clock time
1326	to trigger after some specific point in time. For example, if you tell a	2072	(absolute time, the thing you can read on your calender or clock). The
1327	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	2073	difference is that wall clock time can run faster or slower than real
1328	+ 10.>, that is, an absolute time not a delay) and then reset your system	2074	time, and time jumps are not uncommon (e.g. when you adjust your
1329	clock to January of the previous year, then it will take more than year	2075	wrist-watch).
1330	to trigger the event (unlike an C<ev_timer>, which would still trigger
1331	roughly 10 seconds later as it uses a relative timeout).
1332		2076
		2077	You can tell a periodic watcher to trigger after some specific point
		2078	in time: for example, if you tell a periodic watcher to trigger "in 10
		2079	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2080	not a delay) and then reset your system clock to January of the previous
		2081	year, then it will take a year or more to trigger the event (unlike an
		2082	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2083	it, as it uses a relative timeout).
		2084
1333	C<ev_periodic>s can also be used to implement vastly more complex timers,	2085	C<ev_periodic> watchers can also be used to implement vastly more complex
1334	such as triggering an event on each "midnight, local time", or other	2086	timers, such as triggering an event on each "midnight, local time", or
1335	complicated, rules.	2087	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2088	those cannot react to time jumps.
1336		2089
1337	As with timers, the callback is guaranteed to be invoked only when the	2090	As with timers, the callback is guaranteed to be invoked only when the
1338	time (C<at>) has passed, but if multiple periodic timers become ready	2091	point in time where it is supposed to trigger has passed. If multiple
1339	during the same loop iteration then order of execution is undefined.	2092	timers become ready during the same loop iteration then the ones with
		2093	earlier time-out values are invoked before ones with later time-out values
		2094	(but this is no longer true when a callback calls C<ev_run> recursively).
1340		2095
1341	=head3 Watcher-Specific Functions and Data Members	2096	=head3 Watcher-Specific Functions and Data Members
1342		2097
1343	=over 4	2098	=over 4
1344		2099
1345	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2100	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1346		2101
1347	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2102	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1348		2103
1349	Lots of arguments, lets sort it out... There are basically three modes of	2104	Lots of arguments, let's sort it out... There are basically three modes of
1350	operation, and we will explain them from simplest to complex:	2105	operation, and we will explain them from simplest to most complex:
1351		2106
1352	=over 4	2107	=over 4
1353		2108
1354	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2109	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1355		2110
1356	In this configuration the watcher triggers an event after the wall clock	2111	In this configuration the watcher triggers an event after the wall clock
1357	time C<at> has passed and doesn't repeat. It will not adjust when a time	2112	time C<offset> has passed. It will not repeat and will not adjust when a
1358	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2113	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1359	run when the system time reaches or surpasses this time.	2114	will be stopped and invoked when the system clock reaches or surpasses
		2115	this point in time.
1360		2116
1361	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2117	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1362		2118
1363	In this mode the watcher will always be scheduled to time out at the next	2119	In this mode the watcher will always be scheduled to time out at the next
1364	C<at + N * interval> time (for some integer N, which can also be negative)	2120	C<offset + N * interval> time (for some integer N, which can also be
1365	and then repeat, regardless of any time jumps.	2121	negative) and then repeat, regardless of any time jumps. The C<offset>
		2122	argument is merely an offset into the C<interval> periods.
1366		2123
1367	This can be used to create timers that do not drift with respect to system	2124	This can be used to create timers that do not drift with respect to the
1368	time, for example, here is a C<ev_periodic> that triggers each hour, on	2125	system clock, for example, here is an C<ev_periodic> that triggers each
1369	the hour:	2126	hour, on the hour (with respect to UTC):
1370		2127
1371	ev_periodic_set (&periodic, 0., 3600., 0);	2128	ev_periodic_set (&periodic, 0., 3600., 0);
1372		2129
1373	This doesn't mean there will always be 3600 seconds in between triggers,	2130	This doesn't mean there will always be 3600 seconds in between triggers,
1374	but only that the callback will be called when the system time shows a	2131	but only that the callback will be called when the system time shows a
1375	full hour (UTC), or more correctly, when the system time is evenly divisible	2132	full hour (UTC), or more correctly, when the system time is evenly divisible
1376	by 3600.	2133	by 3600.
1377		2134
1378	Another way to think about it (for the mathematically inclined) is that	2135	Another way to think about it (for the mathematically inclined) is that
1379	C<ev_periodic> will try to run the callback in this mode at the next possible	2136	C<ev_periodic> will try to run the callback in this mode at the next possible
1380	time where C<time = at (mod interval)>, regardless of any time jumps.	2137	time where C<time = offset (mod interval)>, regardless of any time jumps.
1381		2138
1382	For numerical stability it is preferable that the C<at> value is near	2139	For numerical stability it is preferable that the C<offset> value is near
1383	C<ev_now ()> (the current time), but there is no range requirement for	2140	C<ev_now ()> (the current time), but there is no range requirement for
1384	this value, and in fact is often specified as zero.	2141	this value, and in fact is often specified as zero.
1385		2142
1386	Note also that there is an upper limit to how often a timer can fire (CPU	2143	Note also that there is an upper limit to how often a timer can fire (CPU
1387	speed for example), so if C<interval> is very small then timing stability	2144	speed for example), so if C<interval> is very small then timing stability
1388	will of course deteriorate. Libev itself tries to be exact to be about one	2145	will of course deteriorate. Libev itself tries to be exact to be about one
1389	millisecond (if the OS supports it and the machine is fast enough).	2146	millisecond (if the OS supports it and the machine is fast enough).
1390		2147
1391	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2148	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1392		2149
1393	In this mode the values for C<interval> and C<at> are both being	2150	In this mode the values for C<interval> and C<offset> are both being
1394	ignored. Instead, each time the periodic watcher gets scheduled, the	2151	ignored. Instead, each time the periodic watcher gets scheduled, the
1395	reschedule callback will be called with the watcher as first, and the	2152	reschedule callback will be called with the watcher as first, and the
1396	current time as second argument.	2153	current time as second argument.
1397		2154
1398	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2155	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1399	ever, or make ANY event loop modifications whatsoever>.	2156	or make ANY other event loop modifications whatsoever, unless explicitly
		2157	allowed by documentation here>.
1400		2158
1401	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2159	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1402	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2160	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1403	only event loop modification you are allowed to do).	2161	only event loop modification you are allowed to do).
1404		2162
1405	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	2163	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1406	*w, ev_tstamp now)>, e.g.:	2164	*w, ev_tstamp now)>, e.g.:
1407		2165
		2166	static ev_tstamp
1408	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	2167	my_rescheduler (ev_periodic *w, ev_tstamp now)
1409	{	2168	{
1410	return now + 60.;	2169	return now + 60.;
1411	}	2170	}
1412		2171
1413	It must return the next time to trigger, based on the passed time value	2172	It must return the next time to trigger, based on the passed time value
…		…
1433	a different time than the last time it was called (e.g. in a crond like	2192	a different time than the last time it was called (e.g. in a crond like
1434	program when the crontabs have changed).	2193	program when the crontabs have changed).
1435		2194
1436	=item ev_tstamp ev_periodic_at (ev_periodic *)	2195	=item ev_tstamp ev_periodic_at (ev_periodic *)
1437		2196
1438	When active, returns the absolute time that the watcher is supposed to	2197	When active, returns the absolute time that the watcher is supposed
1439	trigger next.	2198	to trigger next. This is not the same as the C<offset> argument to
		2199	C<ev_periodic_set>, but indeed works even in interval and manual
		2200	rescheduling modes.
1440		2201
1441	=item ev_tstamp offset [read-write]	2202	=item ev_tstamp offset [read-write]
1442		2203
1443	When repeating, this contains the offset value, otherwise this is the	2204	When repeating, this contains the offset value, otherwise this is the
1444	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2205	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2206	although libev might modify this value for better numerical stability).
1445		2207
1446	Can be modified any time, but changes only take effect when the periodic	2208	Can be modified any time, but changes only take effect when the periodic
1447	timer fires or C<ev_periodic_again> is being called.	2209	timer fires or C<ev_periodic_again> is being called.
1448		2210
1449	=item ev_tstamp interval [read-write]	2211	=item ev_tstamp interval [read-write]
1450		2212
1451	The current interval value. Can be modified any time, but changes only	2213	The current interval value. Can be modified any time, but changes only
1452	take effect when the periodic timer fires or C<ev_periodic_again> is being	2214	take effect when the periodic timer fires or C<ev_periodic_again> is being
1453	called.	2215	called.
1454		2216
1455	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2217	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1456		2218
1457	The current reschedule callback, or C<0>, if this functionality is	2219	The current reschedule callback, or C<0>, if this functionality is
1458	switched off. Can be changed any time, but changes only take effect when	2220	switched off. Can be changed any time, but changes only take effect when
1459	the periodic timer fires or C<ev_periodic_again> is being called.	2221	the periodic timer fires or C<ev_periodic_again> is being called.
1460		2222
1461	=back	2223	=back
1462		2224
1463	=head3 Examples	2225	=head3 Examples
1464		2226
1465	Example: Call a callback every hour, or, more precisely, whenever the	2227	Example: Call a callback every hour, or, more precisely, whenever the
1466	system clock is divisible by 3600. The callback invocation times have	2228	system time is divisible by 3600. The callback invocation times have
1467	potentially a lot of jitter, but good long-term stability.	2229	potentially a lot of jitter, but good long-term stability.
1468		2230
1469	static void	2231	static void
1470	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2232	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1471	{	2233	{
1472	... its now a full hour (UTC, or TAI or whatever your clock follows)	2234	... its now a full hour (UTC, or TAI or whatever your clock follows)
1473	}	2235	}
1474		2236
1475	struct ev_periodic hourly_tick;	2237	ev_periodic hourly_tick;
1476	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2238	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1477	ev_periodic_start (loop, &hourly_tick);	2239	ev_periodic_start (loop, &hourly_tick);
1478		2240
1479	Example: The same as above, but use a reschedule callback to do it:	2241	Example: The same as above, but use a reschedule callback to do it:
1480		2242
1481	#include <math.h>	2243	#include <math.h>
1482		2244
1483	static ev_tstamp	2245	static ev_tstamp
1484	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2246	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1485	{	2247	{
1486	return fmod (now, 3600.) + 3600.;	2248	return now + (3600. - fmod (now, 3600.));
1487	}	2249	}
1488		2250
1489	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2251	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1490		2252
1491	Example: Call a callback every hour, starting now:	2253	Example: Call a callback every hour, starting now:
1492		2254
1493	struct ev_periodic hourly_tick;	2255	ev_periodic hourly_tick;
1494	ev_periodic_init (&hourly_tick, clock_cb,	2256	ev_periodic_init (&hourly_tick, clock_cb,
1495	fmod (ev_now (loop), 3600.), 3600., 0);	2257	fmod (ev_now (loop), 3600.), 3600., 0);
1496	ev_periodic_start (loop, &hourly_tick);	2258	ev_periodic_start (loop, &hourly_tick);
1497		2259
1498		2260
…		…
1501	Signal watchers will trigger an event when the process receives a specific	2263	Signal watchers will trigger an event when the process receives a specific
1502	signal one or more times. Even though signals are very asynchronous, libev	2264	signal one or more times. Even though signals are very asynchronous, libev
1503	will try it's best to deliver signals synchronously, i.e. as part of the	2265	will try it's best to deliver signals synchronously, i.e. as part of the
1504	normal event processing, like any other event.	2266	normal event processing, like any other event.
1505		2267
		2268	If you want signals to be delivered truly asynchronously, just use
		2269	C<sigaction> as you would do without libev and forget about sharing
		2270	the signal. You can even use C<ev_async> from a signal handler to
		2271	synchronously wake up an event loop.
		2272
1506	You can configure as many watchers as you like per signal. Only when the	2273	You can configure as many watchers as you like for the same signal, but
		2274	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2275	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2276	C<SIGINT> in both the default loop and another loop at the same time. At
		2277	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2278
1507	first watcher gets started will libev actually register a signal watcher	2279	When the first watcher gets started will libev actually register something
1508	with the kernel (thus it coexists with your own signal handlers as long	2280	with the kernel (thus it coexists with your own signal handlers as long as
1509	as you don't register any with libev). Similarly, when the last signal	2281	you don't register any with libev for the same signal).
1510	watcher for a signal is stopped libev will reset the signal handler to
1511	SIG_DFL (regardless of what it was set to before).
1512		2282
1513	If possible and supported, libev will install its handlers with	2283	If possible and supported, libev will install its handlers with
1514	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2284	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1515	interrupted. If you have a problem with system calls getting interrupted by	2285	not be unduly interrupted. If you have a problem with system calls getting
1516	signals you can block all signals in an C<ev_check> watcher and unblock	2286	interrupted by signals you can block all signals in an C<ev_check> watcher
1517	them in an C<ev_prepare> watcher.	2287	and unblock them in an C<ev_prepare> watcher.
		2288
		2289	=head3 The special problem of inheritance over fork/execve/pthread_create
		2290
		2291	Both the signal mask (C<sigprocmask>) and the signal disposition
		2292	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2293	stopping it again), that is, libev might or might not block the signal,
		2294	and might or might not set or restore the installed signal handler.
		2295
		2296	While this does not matter for the signal disposition (libev never
		2297	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2298	C<execve>), this matters for the signal mask: many programs do not expect
		2299	certain signals to be blocked.
		2300
		2301	This means that before calling C<exec> (from the child) you should reset
		2302	the signal mask to whatever "default" you expect (all clear is a good
		2303	choice usually).
		2304
		2305	The simplest way to ensure that the signal mask is reset in the child is
		2306	to install a fork handler with C<pthread_atfork> that resets it. That will
		2307	catch fork calls done by libraries (such as the libc) as well.
		2308
		2309	In current versions of libev, the signal will not be blocked indefinitely
		2310	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2311	the window of opportunity for problems, it will not go away, as libev
		2312	I<has> to modify the signal mask, at least temporarily.
		2313
		2314	So I can't stress this enough: I<If you do not reset your signal mask when
		2315	you expect it to be empty, you have a race condition in your code>. This
		2316	is not a libev-specific thing, this is true for most event libraries.
1518		2317
1519	=head3 Watcher-Specific Functions and Data Members	2318	=head3 Watcher-Specific Functions and Data Members
1520		2319
1521	=over 4	2320	=over 4
1522		2321
…		…
1533		2332
1534	=back	2333	=back
1535		2334
1536	=head3 Examples	2335	=head3 Examples
1537		2336
1538	Example: Try to exit cleanly on SIGINT and SIGTERM.	2337	Example: Try to exit cleanly on SIGINT.
1539		2338
1540	static void	2339	static void
1541	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2340	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1542	{	2341	{
1543	ev_unloop (loop, EVUNLOOP_ALL);	2342	ev_break (loop, EVBREAK_ALL);
1544	}	2343	}
1545		2344
1546	struct ev_signal signal_watcher;	2345	ev_signal signal_watcher;
1547	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2346	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1548	ev_signal_start (loop, &sigint_cb);	2347	ev_signal_start (loop, &signal_watcher);
1549		2348
1550		2349
1551	=head2 C<ev_child> - watch out for process status changes	2350	=head2 C<ev_child> - watch out for process status changes
1552		2351
1553	Child watchers trigger when your process receives a SIGCHLD in response to	2352	Child watchers trigger when your process receives a SIGCHLD in response to
1554	some child status changes (most typically when a child of yours dies). It	2353	some child status changes (most typically when a child of yours dies or
1555	is permissible to install a child watcher I<after> the child has been	2354	exits). It is permissible to install a child watcher I<after> the child
1556	forked (which implies it might have already exited), as long as the event	2355	has been forked (which implies it might have already exited), as long
1557	loop isn't entered (or is continued from a watcher).	2356	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2357	forking and then immediately registering a watcher for the child is fine,
		2358	but forking and registering a watcher a few event loop iterations later or
		2359	in the next callback invocation is not.
1558		2360
1559	Only the default event loop is capable of handling signals, and therefore	2361	Only the default event loop is capable of handling signals, and therefore
1560	you can only register child watchers in the default event loop.	2362	you can only register child watchers in the default event loop.
1561		2363
		2364	Due to some design glitches inside libev, child watchers will always be
		2365	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2366	libev)
		2367
1562	=head3 Process Interaction	2368	=head3 Process Interaction
1563		2369
1564	Libev grabs C<SIGCHLD> as soon as the default event loop is	2370	Libev grabs C<SIGCHLD> as soon as the default event loop is
1565	initialised. This is necessary to guarantee proper behaviour even if	2371	initialised. This is necessary to guarantee proper behaviour even if the
1566	the first child watcher is started after the child exits. The occurrence	2372	first child watcher is started after the child exits. The occurrence
1567	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2373	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1568	synchronously as part of the event loop processing. Libev always reaps all	2374	synchronously as part of the event loop processing. Libev always reaps all
1569	children, even ones not watched.	2375	children, even ones not watched.
1570		2376
1571	=head3 Overriding the Built-In Processing	2377	=head3 Overriding the Built-In Processing
…		…
1581	=head3 Stopping the Child Watcher	2387	=head3 Stopping the Child Watcher
1582		2388
1583	Currently, the child watcher never gets stopped, even when the	2389	Currently, the child watcher never gets stopped, even when the
1584	child terminates, so normally one needs to stop the watcher in the	2390	child terminates, so normally one needs to stop the watcher in the
1585	callback. Future versions of libev might stop the watcher automatically	2391	callback. Future versions of libev might stop the watcher automatically
1586	when a child exit is detected.	2392	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2393	problem).
1587		2394
1588	=head3 Watcher-Specific Functions and Data Members	2395	=head3 Watcher-Specific Functions and Data Members
1589		2396
1590	=over 4	2397	=over 4
1591		2398
…		…
1623	its completion.	2430	its completion.
1624		2431
1625	ev_child cw;	2432	ev_child cw;
1626		2433
1627	static void	2434	static void
1628	child_cb (EV_P_ struct ev_child *w, int revents)	2435	child_cb (EV_P_ ev_child *w, int revents)
1629	{	2436	{
1630	ev_child_stop (EV_A_ w);	2437	ev_child_stop (EV_A_ w);
1631	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2438	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1632	}	2439	}
1633		2440
…		…
1648		2455
1649		2456
1650	=head2 C<ev_stat> - did the file attributes just change?	2457	=head2 C<ev_stat> - did the file attributes just change?
1651		2458
1652	This watches a file system path for attribute changes. That is, it calls	2459	This watches a file system path for attribute changes. That is, it calls
1653	C<stat> regularly (or when the OS says it changed) and sees if it changed	2460	C<stat> on that path in regular intervals (or when the OS says it changed)
1654	compared to the last time, invoking the callback if it did.	2461	and sees if it changed compared to the last time, invoking the callback if
		2462	it did.
1655		2463
1656	The path does not need to exist: changing from "path exists" to "path does	2464	The path does not need to exist: changing from "path exists" to "path does
1657	not exist" is a status change like any other. The condition "path does	2465	not exist" is a status change like any other. The condition "path does not
1658	not exist" is signified by the C<st_nlink> field being zero (which is	2466	exist" (or more correctly "path cannot be stat'ed") is signified by the
1659	otherwise always forced to be at least one) and all the other fields of	2467	C<st_nlink> field being zero (which is otherwise always forced to be at
1660	the stat buffer having unspecified contents.	2468	least one) and all the other fields of the stat buffer having unspecified
		2469	contents.
1661		2470
1662	The path I<should> be absolute and I<must not> end in a slash. If it is	2471	The path I<must not> end in a slash or contain special components such as
		2472	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1663	relative and your working directory changes, the behaviour is undefined.	2473	your working directory changes, then the behaviour is undefined.
1664		2474
1665	Since there is no standard to do this, the portable implementation simply	2475	Since there is no portable change notification interface available, the
1666	calls C<stat (2)> regularly on the path to see if it changed somehow. You	2476	portable implementation simply calls C<stat(2)> regularly on the path
1667	can specify a recommended polling interval for this case. If you specify	2477	to see if it changed somehow. You can specify a recommended polling
1668	a polling interval of C<0> (highly recommended!) then a I<suitable,	2478	interval for this case. If you specify a polling interval of C<0> (highly
1669	unspecified default> value will be used (which you can expect to be around	2479	recommended!) then a I<suitable, unspecified default> value will be used
1670	five seconds, although this might change dynamically). Libev will also	2480	(which you can expect to be around five seconds, although this might
1671	impose a minimum interval which is currently around C<0.1>, but thats	2481	change dynamically). Libev will also impose a minimum interval which is
1672	usually overkill.	2482	currently around C<0.1>, but that's usually overkill.
1673		2483
1674	This watcher type is not meant for massive numbers of stat watchers,	2484	This watcher type is not meant for massive numbers of stat watchers,
1675	as even with OS-supported change notifications, this can be	2485	as even with OS-supported change notifications, this can be
1676	resource-intensive.	2486	resource-intensive.
1677		2487
1678	At the time of this writing, only the Linux inotify interface is	2488	At the time of this writing, the only OS-specific interface implemented
1679	implemented (implementing kqueue support is left as an exercise for the	2489	is the Linux inotify interface (implementing kqueue support is left as an
1680	reader, note, however, that the author sees no way of implementing ev_stat	2490	exercise for the reader. Note, however, that the author sees no way of
1681	semantics with kqueue). Inotify will be used to give hints only and should	2491	implementing C<ev_stat> semantics with kqueue, except as a hint).
1682	not change the semantics of C<ev_stat> watchers, which means that libev
1683	sometimes needs to fall back to regular polling again even with inotify,
1684	but changes are usually detected immediately, and if the file exists there
1685	will be no polling.
1686		2492
1687	=head3 ABI Issues (Largefile Support)	2493	=head3 ABI Issues (Largefile Support)
1688		2494
1689	Libev by default (unless the user overrides this) uses the default	2495	Libev by default (unless the user overrides this) uses the default
1690	compilation environment, which means that on systems with large file	2496	compilation environment, which means that on systems with large file
1691	support disabled by default, you get the 32 bit version of the stat	2497	support disabled by default, you get the 32 bit version of the stat
1692	structure. When using the library from programs that change the ABI to	2498	structure. When using the library from programs that change the ABI to
1693	use 64 bit file offsets the programs will fail. In that case you have to	2499	use 64 bit file offsets the programs will fail. In that case you have to
1694	compile libev with the same flags to get binary compatibility. This is	2500	compile libev with the same flags to get binary compatibility. This is
1695	obviously the case with any flags that change the ABI, but the problem is	2501	obviously the case with any flags that change the ABI, but the problem is
1696	most noticeably disabled with ev_stat and large file support.	2502	most noticeably displayed with ev_stat and large file support.
1697		2503
1698	The solution for this is to lobby your distribution maker to make large	2504	The solution for this is to lobby your distribution maker to make large
1699	file interfaces available by default (as e.g. FreeBSD does) and not	2505	file interfaces available by default (as e.g. FreeBSD does) and not
1700	optional. Libev cannot simply switch on large file support because it has	2506	optional. Libev cannot simply switch on large file support because it has
1701	to exchange stat structures with application programs compiled using the	2507	to exchange stat structures with application programs compiled using the
1702	default compilation environment.	2508	default compilation environment.
1703		2509
1704	=head3 Inotify	2510	=head3 Inotify and Kqueue
1705		2511
1706	When C<inotify (7)> support has been compiled into libev (generally only	2512	When C<inotify (7)> support has been compiled into libev and present at
1707	available on Linux) and present at runtime, it will be used to speed up	2513	runtime, it will be used to speed up change detection where possible. The
1708	change detection where possible. The inotify descriptor will be created lazily	2514	inotify descriptor will be created lazily when the first C<ev_stat>
1709	when the first C<ev_stat> watcher is being started.	2515	watcher is being started.
1710		2516
1711	Inotify presence does not change the semantics of C<ev_stat> watchers	2517	Inotify presence does not change the semantics of C<ev_stat> watchers
1712	except that changes might be detected earlier, and in some cases, to avoid	2518	except that changes might be detected earlier, and in some cases, to avoid
1713	making regular C<stat> calls. Even in the presence of inotify support	2519	making regular C<stat> calls. Even in the presence of inotify support
1714	there are many cases where libev has to resort to regular C<stat> polling.	2520	there are many cases where libev has to resort to regular C<stat> polling,
		2521	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2522	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2523	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2524	xfs are fully working) libev usually gets away without polling.
1715		2525
1716	(There is no support for kqueue, as apparently it cannot be used to	2526	There is no support for kqueue, as apparently it cannot be used to
1717	implement this functionality, due to the requirement of having a file	2527	implement this functionality, due to the requirement of having a file
1718	descriptor open on the object at all times).	2528	descriptor open on the object at all times, and detecting renames, unlinks
		2529	etc. is difficult.
		2530
		2531	=head3 C<stat ()> is a synchronous operation
		2532
		2533	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2534	the process. The exception are C<ev_stat> watchers - those call C<stat
		2535	()>, which is a synchronous operation.
		2536
		2537	For local paths, this usually doesn't matter: unless the system is very
		2538	busy or the intervals between stat's are large, a stat call will be fast,
		2539	as the path data is usually in memory already (except when starting the
		2540	watcher).
		2541
		2542	For networked file systems, calling C<stat ()> can block an indefinite
		2543	time due to network issues, and even under good conditions, a stat call
		2544	often takes multiple milliseconds.
		2545
		2546	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2547	paths, although this is fully supported by libev.
1719		2548
1720	=head3 The special problem of stat time resolution	2549	=head3 The special problem of stat time resolution
1721		2550
1722	The C<stat ()> system call only supports full-second resolution portably, and	2551	The C<stat ()> system call only supports full-second resolution portably,
1723	even on systems where the resolution is higher, many file systems still	2552	and even on systems where the resolution is higher, most file systems
1724	only support whole seconds.	2553	still only support whole seconds.
1725		2554
1726	That means that, if the time is the only thing that changes, you can	2555	That means that, if the time is the only thing that changes, you can
1727	easily miss updates: on the first update, C<ev_stat> detects a change and	2556	easily miss updates: on the first update, C<ev_stat> detects a change and
1728	calls your callback, which does something. When there is another update	2557	calls your callback, which does something. When there is another update
1729	within the same second, C<ev_stat> will be unable to detect it as the stat	2558	within the same second, C<ev_stat> will be unable to detect unless the
1730	data does not change.	2559	stat data does change in other ways (e.g. file size).
1731		2560
1732	The solution to this is to delay acting on a change for slightly more	2561	The solution to this is to delay acting on a change for slightly more
1733	than a second (or till slightly after the next full second boundary), using	2562	than a second (or till slightly after the next full second boundary), using
1734	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2563	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1735	ev_timer_again (loop, w)>).	2564	ev_timer_again (loop, w)>).
…		…
1755	C<path>. The C<interval> is a hint on how quickly a change is expected to	2584	C<path>. The C<interval> is a hint on how quickly a change is expected to
1756	be detected and should normally be specified as C<0> to let libev choose	2585	be detected and should normally be specified as C<0> to let libev choose
1757	a suitable value. The memory pointed to by C<path> must point to the same	2586	a suitable value. The memory pointed to by C<path> must point to the same
1758	path for as long as the watcher is active.	2587	path for as long as the watcher is active.
1759		2588
1760	The callback will receive C<EV_STAT> when a change was detected, relative	2589	The callback will receive an C<EV_STAT> event when a change was detected,
1761	to the attributes at the time the watcher was started (or the last change	2590	relative to the attributes at the time the watcher was started (or the
1762	was detected).	2591	last change was detected).
1763		2592
1764	=item ev_stat_stat (loop, ev_stat *)	2593	=item ev_stat_stat (loop, ev_stat *)
1765		2594
1766	Updates the stat buffer immediately with new values. If you change the	2595	Updates the stat buffer immediately with new values. If you change the
1767	watched path in your callback, you could call this function to avoid	2596	watched path in your callback, you could call this function to avoid
…		…
1850		2679
1851		2680
1852	=head2 C<ev_idle> - when you've got nothing better to do...	2681	=head2 C<ev_idle> - when you've got nothing better to do...
1853		2682
1854	Idle watchers trigger events when no other events of the same or higher	2683	Idle watchers trigger events when no other events of the same or higher
1855	priority are pending (prepare, check and other idle watchers do not	2684	priority are pending (prepare, check and other idle watchers do not count
1856	count).	2685	as receiving "events").
1857		2686
1858	That is, as long as your process is busy handling sockets or timeouts	2687	That is, as long as your process is busy handling sockets or timeouts
1859	(or even signals, imagine) of the same or higher priority it will not be	2688	(or even signals, imagine) of the same or higher priority it will not be
1860	triggered. But when your process is idle (or only lower-priority watchers	2689	triggered. But when your process is idle (or only lower-priority watchers
1861	are pending), the idle watchers are being called once per event loop	2690	are pending), the idle watchers are being called once per event loop
…		…
1872		2701
1873	=head3 Watcher-Specific Functions and Data Members	2702	=head3 Watcher-Specific Functions and Data Members
1874		2703
1875	=over 4	2704	=over 4
1876		2705
1877	=item ev_idle_init (ev_signal *, callback)	2706	=item ev_idle_init (ev_idle *, callback)
1878		2707
1879	Initialises and configures the idle watcher - it has no parameters of any	2708	Initialises and configures the idle watcher - it has no parameters of any
1880	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2709	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1881	believe me.	2710	believe me.
1882		2711
…		…
1886		2715
1887	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2716	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1888	callback, free it. Also, use no error checking, as usual.	2717	callback, free it. Also, use no error checking, as usual.
1889		2718
1890	static void	2719	static void
1891	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2720	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1892	{	2721	{
1893	free (w);	2722	free (w);
1894	// now do something you wanted to do when the program has	2723	// now do something you wanted to do when the program has
1895	// no longer anything immediate to do.	2724	// no longer anything immediate to do.
1896	}	2725	}
1897		2726
1898	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2727	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1899	ev_idle_init (idle_watcher, idle_cb);	2728	ev_idle_init (idle_watcher, idle_cb);
1900	ev_idle_start (loop, idle_cb);	2729	ev_idle_start (loop, idle_watcher);
1901		2730
1902		2731
1903	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2732	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1904		2733
1905	Prepare and check watchers are usually (but not always) used in tandem:	2734	Prepare and check watchers are usually (but not always) used in pairs:
1906	prepare watchers get invoked before the process blocks and check watchers	2735	prepare watchers get invoked before the process blocks and check watchers
1907	afterwards.	2736	afterwards.
1908		2737
1909	You I<must not> call C<ev_loop> or similar functions that enter	2738	You I<must not> call C<ev_run> or similar functions that enter
1910	the current event loop from either C<ev_prepare> or C<ev_check>	2739	the current event loop from either C<ev_prepare> or C<ev_check>
1911	watchers. Other loops than the current one are fine, however. The	2740	watchers. Other loops than the current one are fine, however. The
1912	rationale behind this is that you do not need to check for recursion in	2741	rationale behind this is that you do not need to check for recursion in
1913	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2742	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1914	C<ev_check> so if you have one watcher of each kind they will always be	2743	C<ev_check> so if you have one watcher of each kind they will always be
1915	called in pairs bracketing the blocking call.	2744	called in pairs bracketing the blocking call.
1916		2745
1917	Their main purpose is to integrate other event mechanisms into libev and	2746	Their main purpose is to integrate other event mechanisms into libev and
1918	their use is somewhat advanced. This could be used, for example, to track	2747	their use is somewhat advanced. They could be used, for example, to track
1919	variable changes, implement your own watchers, integrate net-snmp or a	2748	variable changes, implement your own watchers, integrate net-snmp or a
1920	coroutine library and lots more. They are also occasionally useful if	2749	coroutine library and lots more. They are also occasionally useful if
1921	you cache some data and want to flush it before blocking (for example,	2750	you cache some data and want to flush it before blocking (for example,
1922	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2751	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1923	watcher).	2752	watcher).
1924		2753
1925	This is done by examining in each prepare call which file descriptors need	2754	This is done by examining in each prepare call which file descriptors
1926	to be watched by the other library, registering C<ev_io> watchers for	2755	need to be watched by the other library, registering C<ev_io> watchers
1927	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2756	for them and starting an C<ev_timer> watcher for any timeouts (many
1928	provide just this functionality). Then, in the check watcher you check for	2757	libraries provide exactly this functionality). Then, in the check watcher,
1929	any events that occurred (by checking the pending status of all watchers	2758	you check for any events that occurred (by checking the pending status
1930	and stopping them) and call back into the library. The I/O and timer	2759	of all watchers and stopping them) and call back into the library. The
1931	callbacks will never actually be called (but must be valid nevertheless,	2760	I/O and timer callbacks will never actually be called (but must be valid
1932	because you never know, you know?).	2761	nevertheless, because you never know, you know?).
1933		2762
1934	As another example, the Perl Coro module uses these hooks to integrate	2763	As another example, the Perl Coro module uses these hooks to integrate
1935	coroutines into libev programs, by yielding to other active coroutines	2764	coroutines into libev programs, by yielding to other active coroutines
1936	during each prepare and only letting the process block if no coroutines	2765	during each prepare and only letting the process block if no coroutines
1937	are ready to run (it's actually more complicated: it only runs coroutines	2766	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1940	loop from blocking if lower-priority coroutines are active, thus mapping	2769	loop from blocking if lower-priority coroutines are active, thus mapping
1941	low-priority coroutines to idle/background tasks).	2770	low-priority coroutines to idle/background tasks).
1942		2771
1943	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2772	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1944	priority, to ensure that they are being run before any other watchers	2773	priority, to ensure that they are being run before any other watchers
		2774	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2775
1945	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2776	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1946	too) should not activate ("feed") events into libev. While libev fully	2777	activate ("feed") events into libev. While libev fully supports this, they
1947	supports this, they might get executed before other C<ev_check> watchers	2778	might get executed before other C<ev_check> watchers did their job. As
1948	did their job. As C<ev_check> watchers are often used to embed other	2779	C<ev_check> watchers are often used to embed other (non-libev) event
1949	(non-libev) event loops those other event loops might be in an unusable	2780	loops those other event loops might be in an unusable state until their
1950	state until their C<ev_check> watcher ran (always remind yourself to	2781	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1951	coexist peacefully with others).	2782	others).
1952		2783
1953	=head3 Watcher-Specific Functions and Data Members	2784	=head3 Watcher-Specific Functions and Data Members
1954		2785
1955	=over 4	2786	=over 4
1956		2787
…		…
1958		2789
1959	=item ev_check_init (ev_check *, callback)	2790	=item ev_check_init (ev_check *, callback)
1960		2791
1961	Initialises and configures the prepare or check watcher - they have no	2792	Initialises and configures the prepare or check watcher - they have no
1962	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2793	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1963	macros, but using them is utterly, utterly and completely pointless.	2794	macros, but using them is utterly, utterly, utterly and completely
		2795	pointless.
1964		2796
1965	=back	2797	=back
1966		2798
1967	=head3 Examples	2799	=head3 Examples
1968		2800
…		…
1981		2813
1982	static ev_io iow [nfd];	2814	static ev_io iow [nfd];
1983	static ev_timer tw;	2815	static ev_timer tw;
1984		2816
1985	static void	2817	static void
1986	io_cb (ev_loop *loop, ev_io *w, int revents)	2818	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1987	{	2819	{
1988	}	2820	}
1989		2821
1990	// create io watchers for each fd and a timer before blocking	2822	// create io watchers for each fd and a timer before blocking
1991	static void	2823	static void
1992	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2824	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1993	{	2825	{
1994	int timeout = 3600000;	2826	int timeout = 3600000;
1995	struct pollfd fds [nfd];	2827	struct pollfd fds [nfd];
1996	// actual code will need to loop here and realloc etc.	2828	// actual code will need to loop here and realloc etc.
1997	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2829	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1998		2830
1999	/* the callback is illegal, but won't be called as we stop during check */	2831	/* the callback is illegal, but won't be called as we stop during check */
2000	ev_timer_init (&tw, 0, timeout * 1e-3);	2832	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2001	ev_timer_start (loop, &tw);	2833	ev_timer_start (loop, &tw);
2002		2834
2003	// create one ev_io per pollfd	2835	// create one ev_io per pollfd
2004	for (int i = 0; i < nfd; ++i)	2836	for (int i = 0; i < nfd; ++i)
2005	{	2837	{
…		…
2012	}	2844	}
2013	}	2845	}
2014		2846
2015	// stop all watchers after blocking	2847	// stop all watchers after blocking
2016	static void	2848	static void
2017	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2849	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2018	{	2850	{
2019	ev_timer_stop (loop, &tw);	2851	ev_timer_stop (loop, &tw);
2020		2852
2021	for (int i = 0; i < nfd; ++i)	2853	for (int i = 0; i < nfd; ++i)
2022	{	2854	{
…		…
2061	}	2893	}
2062		2894
2063	// do not ever call adns_afterpoll	2895	// do not ever call adns_afterpoll
2064		2896
2065	Method 4: Do not use a prepare or check watcher because the module you	2897	Method 4: Do not use a prepare or check watcher because the module you
2066	want to embed is too inflexible to support it. Instead, you can override	2898	want to embed is not flexible enough to support it. Instead, you can
2067	their poll function. The drawback with this solution is that the main	2899	override their poll function. The drawback with this solution is that the
2068	loop is now no longer controllable by EV. The C<Glib::EV> module does	2900	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2069	this.	2901	this approach, effectively embedding EV as a client into the horrible
		2902	libglib event loop.
2070		2903
2071	static gint	2904	static gint
2072	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2905	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2073	{	2906	{
2074	int got_events = 0;	2907	int got_events = 0;
…		…
2078		2911
2079	if (timeout >= 0)	2912	if (timeout >= 0)
2080	// create/start timer	2913	// create/start timer
2081		2914
2082	// poll	2915	// poll
2083	ev_loop (EV_A_ 0);	2916	ev_run (EV_A_ 0);
2084		2917
2085	// stop timer again	2918	// stop timer again
2086	if (timeout >= 0)	2919	if (timeout >= 0)
2087	ev_timer_stop (EV_A_ &to);	2920	ev_timer_stop (EV_A_ &to);
2088		2921
…		…
2105	prioritise I/O.	2938	prioritise I/O.
2106		2939
2107	As an example for a bug workaround, the kqueue backend might only support	2940	As an example for a bug workaround, the kqueue backend might only support
2108	sockets on some platform, so it is unusable as generic backend, but you	2941	sockets on some platform, so it is unusable as generic backend, but you
2109	still want to make use of it because you have many sockets and it scales	2942	still want to make use of it because you have many sockets and it scales
2110	so nicely. In this case, you would create a kqueue-based loop and embed it	2943	so nicely. In this case, you would create a kqueue-based loop and embed
2111	into your default loop (which might use e.g. poll). Overall operation will	2944	it into your default loop (which might use e.g. poll). Overall operation
2112	be a bit slower because first libev has to poll and then call kevent, but	2945	will be a bit slower because first libev has to call C<poll> and then
2113	at least you can use both at what they are best.	2946	C<kevent>, but at least you can use both mechanisms for what they are
		2947	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2114		2948
2115	As for prioritising I/O: rarely you have the case where some fds have	2949	As for prioritising I/O: under rare circumstances you have the case where
2116	to be watched and handled very quickly (with low latency), and even	2950	some fds have to be watched and handled very quickly (with low latency),
2117	priorities and idle watchers might have too much overhead. In this case	2951	and even priorities and idle watchers might have too much overhead. In
2118	you would put all the high priority stuff in one loop and all the rest in	2952	this case you would put all the high priority stuff in one loop and all
2119	a second one, and embed the second one in the first.	2953	the rest in a second one, and embed the second one in the first.
2120		2954
2121	As long as the watcher is active, the callback will be invoked every time	2955	As long as the watcher is active, the callback will be invoked every
2122	there might be events pending in the embedded loop. The callback must then	2956	time there might be events pending in the embedded loop. The callback
2123	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2957	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2124	their callbacks (you could also start an idle watcher to give the embedded	2958	sweep and invoke their callbacks (the callback doesn't need to invoke the
2125	loop strictly lower priority for example). You can also set the callback	2959	C<ev_embed_sweep> function directly, it could also start an idle watcher
2126	to C<0>, in which case the embed watcher will automatically execute the	2960	to give the embedded loop strictly lower priority for example).
2127	embedded loop sweep.
2128		2961
2129	As long as the watcher is started it will automatically handle events. The	2962	You can also set the callback to C<0>, in which case the embed watcher
2130	callback will be invoked whenever some events have been handled. You can	2963	will automatically execute the embedded loop sweep whenever necessary.
2131	set the callback to C<0> to avoid having to specify one if you are not
2132	interested in that.
2133		2964
2134	Also, there have not currently been made special provisions for forking:	2965	Fork detection will be handled transparently while the C<ev_embed> watcher
2135	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2966	is active, i.e., the embedded loop will automatically be forked when the
2136	but you will also have to stop and restart any C<ev_embed> watchers	2967	embedding loop forks. In other cases, the user is responsible for calling
2137	yourself.	2968	C<ev_loop_fork> on the embedded loop.
2138		2969
2139	Unfortunately, not all backends are embeddable, only the ones returned by	2970	Unfortunately, not all backends are embeddable: only the ones returned by
2140	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2971	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2141	portable one.	2972	portable one.
2142		2973
2143	So when you want to use this feature you will always have to be prepared	2974	So when you want to use this feature you will always have to be prepared
2144	that you cannot get an embeddable loop. The recommended way to get around	2975	that you cannot get an embeddable loop. The recommended way to get around
2145	this is to have a separate variables for your embeddable loop, try to	2976	this is to have a separate variables for your embeddable loop, try to
2146	create it, and if that fails, use the normal loop for everything.	2977	create it, and if that fails, use the normal loop for everything.
		2978
		2979	=head3 C<ev_embed> and fork
		2980
		2981	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2982	automatically be applied to the embedded loop as well, so no special
		2983	fork handling is required in that case. When the watcher is not running,
		2984	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2985	as applicable.
2147		2986
2148	=head3 Watcher-Specific Functions and Data Members	2987	=head3 Watcher-Specific Functions and Data Members
2149		2988
2150	=over 4	2989	=over 4
2151		2990
…		…
2160	if you do not want that, you need to temporarily stop the embed watcher).	2999	if you do not want that, you need to temporarily stop the embed watcher).
2161		3000
2162	=item ev_embed_sweep (loop, ev_embed *)	3001	=item ev_embed_sweep (loop, ev_embed *)
2163		3002
2164	Make a single, non-blocking sweep over the embedded loop. This works	3003	Make a single, non-blocking sweep over the embedded loop. This works
2165	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3004	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2166	appropriate way for embedded loops.	3005	appropriate way for embedded loops.
2167		3006
2168	=item struct ev_loop *other [read-only]	3007	=item struct ev_loop *other [read-only]
2169		3008
2170	The embedded event loop.	3009	The embedded event loop.
…		…
2179	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	3018	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2180	used).	3019	used).
2181		3020
2182	struct ev_loop *loop_hi = ev_default_init (0);	3021	struct ev_loop *loop_hi = ev_default_init (0);
2183	struct ev_loop *loop_lo = 0;	3022	struct ev_loop *loop_lo = 0;
2184	struct ev_embed embed;	3023	ev_embed embed;
2185		3024
2186	// see if there is a chance of getting one that works	3025	// see if there is a chance of getting one that works
2187	// (remember that a flags value of 0 means autodetection)	3026	// (remember that a flags value of 0 means autodetection)
2188	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3027	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2189	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3028	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2203	kqueue implementation). Store the kqueue/socket-only event loop in	3042	kqueue implementation). Store the kqueue/socket-only event loop in
2204	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3043	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2205		3044
2206	struct ev_loop *loop = ev_default_init (0);	3045	struct ev_loop *loop = ev_default_init (0);
2207	struct ev_loop *loop_socket = 0;	3046	struct ev_loop *loop_socket = 0;
2208	struct ev_embed embed;	3047	ev_embed embed;
2209		3048
2210	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3049	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2211	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3050	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2212	{	3051	{
2213	ev_embed_init (&embed, 0, loop_socket);	3052	ev_embed_init (&embed, 0, loop_socket);
…		…
2228	event loop blocks next and before C<ev_check> watchers are being called,	3067	event loop blocks next and before C<ev_check> watchers are being called,
2229	and only in the child after the fork. If whoever good citizen calling	3068	and only in the child after the fork. If whoever good citizen calling
2230	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3069	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2231	handlers will be invoked, too, of course.	3070	handlers will be invoked, too, of course.
2232		3071
		3072	=head3 The special problem of life after fork - how is it possible?
		3073
		3074	Most uses of C<fork()> consist of forking, then some simple calls to set
		3075	up/change the process environment, followed by a call to C<exec()>. This
		3076	sequence should be handled by libev without any problems.
		3077
		3078	This changes when the application actually wants to do event handling
		3079	in the child, or both parent in child, in effect "continuing" after the
		3080	fork.
		3081
		3082	The default mode of operation (for libev, with application help to detect
		3083	forks) is to duplicate all the state in the child, as would be expected
		3084	when I<either> the parent I<or> the child process continues.
		3085
		3086	When both processes want to continue using libev, then this is usually the
		3087	wrong result. In that case, usually one process (typically the parent) is
		3088	supposed to continue with all watchers in place as before, while the other
		3089	process typically wants to start fresh, i.e. without any active watchers.
		3090
		3091	The cleanest and most efficient way to achieve that with libev is to
		3092	simply create a new event loop, which of course will be "empty", and
		3093	use that for new watchers. This has the advantage of not touching more
		3094	memory than necessary, and thus avoiding the copy-on-write, and the
		3095	disadvantage of having to use multiple event loops (which do not support
		3096	signal watchers).
		3097
		3098	When this is not possible, or you want to use the default loop for
		3099	other reasons, then in the process that wants to start "fresh", call
		3100	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3101	Destroying the default loop will "orphan" (not stop) all registered
		3102	watchers, so you have to be careful not to execute code that modifies
		3103	those watchers. Note also that in that case, you have to re-register any
		3104	signal watchers.
		3105
2233	=head3 Watcher-Specific Functions and Data Members	3106	=head3 Watcher-Specific Functions and Data Members
2234		3107
2235	=over 4	3108	=over 4
2236		3109
2237	=item ev_fork_init (ev_signal *, callback)	3110	=item ev_fork_init (ev_fork *, callback)
2238		3111
2239	Initialises and configures the fork watcher - it has no parameters of any	3112	Initialises and configures the fork watcher - it has no parameters of any
2240	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3113	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2241	believe me.	3114	really.
2242		3115
2243	=back	3116	=back
2244		3117
2245		3118
		3119	=head2 C<ev_cleanup> - even the best things end
		3120
		3121	Cleanup watchers are called just before the event loop is being destroyed
		3122	by a call to C<ev_loop_destroy>.
		3123
		3124	While there is no guarantee that the event loop gets destroyed, cleanup
		3125	watchers provide a convenient method to install cleanup hooks for your
		3126	program, worker threads and so on - you just to make sure to destroy the
		3127	loop when you want them to be invoked.
		3128
		3129	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3130	all other watchers, they do not keep a reference to the event loop (which
		3131	makes a lot of sense if you think about it). Like all other watchers, you
		3132	can call libev functions in the callback, except C<ev_cleanup_start>.
		3133
		3134	=head3 Watcher-Specific Functions and Data Members
		3135
		3136	=over 4
		3137
		3138	=item ev_cleanup_init (ev_cleanup *, callback)
		3139
		3140	Initialises and configures the cleanup watcher - it has no parameters of
		3141	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3142	pointless, I assure you.
		3143
		3144	=back
		3145
		3146	Example: Register an atexit handler to destroy the default loop, so any
		3147	cleanup functions are called.
		3148
		3149	static void
		3150	program_exits (void)
		3151	{
		3152	ev_loop_destroy (EV_DEFAULT_UC);
		3153	}
		3154
		3155	...
		3156	atexit (program_exits);
		3157
		3158
2246	=head2 C<ev_async> - how to wake up another event loop	3159	=head2 C<ev_async> - how to wake up an event loop
2247		3160
2248	In general, you cannot use an C<ev_loop> from multiple threads or other	3161	In general, you cannot use an C<ev_run> from multiple threads or other
2249	asynchronous sources such as signal handlers (as opposed to multiple event	3162	asynchronous sources such as signal handlers (as opposed to multiple event
2250	loops - those are of course safe to use in different threads).	3163	loops - those are of course safe to use in different threads).
2251		3164
2252	Sometimes, however, you need to wake up another event loop you do not	3165	Sometimes, however, you need to wake up an event loop you do not control,
2253	control, for example because it belongs to another thread. This is what	3166	for example because it belongs to another thread. This is what C<ev_async>
2254	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3167	watchers do: as long as the C<ev_async> watcher is active, you can signal
2255	can signal it by calling C<ev_async_send>, which is thread- and signal	3168	it by calling C<ev_async_send>, which is thread- and signal safe.
2256	safe.
2257		3169
2258	This functionality is very similar to C<ev_signal> watchers, as signals,	3170	This functionality is very similar to C<ev_signal> watchers, as signals,
2259	too, are asynchronous in nature, and signals, too, will be compressed	3171	too, are asynchronous in nature, and signals, too, will be compressed
2260	(i.e. the number of callback invocations may be less than the number of	3172	(i.e. the number of callback invocations may be less than the number of
2261	C<ev_async_sent> calls).	3173	C<ev_async_sent> calls).
…		…
2266	=head3 Queueing	3178	=head3 Queueing
2267		3179
2268	C<ev_async> does not support queueing of data in any way. The reason	3180	C<ev_async> does not support queueing of data in any way. The reason
2269	is that the author does not know of a simple (or any) algorithm for a	3181	is that the author does not know of a simple (or any) algorithm for a
2270	multiple-writer-single-reader queue that works in all cases and doesn't	3182	multiple-writer-single-reader queue that works in all cases and doesn't
2271	need elaborate support such as pthreads.	3183	need elaborate support such as pthreads or unportable memory access
		3184	semantics.
2272		3185
2273	That means that if you want to queue data, you have to provide your own	3186	That means that if you want to queue data, you have to provide your own
2274	queue. But at least I can tell you would implement locking around your	3187	queue. But at least I can tell you how to implement locking around your
2275	queue:	3188	queue:
2276		3189
2277	=over 4	3190	=over 4
2278		3191
2279	=item queueing from a signal handler context	3192	=item queueing from a signal handler context
2280		3193
2281	To implement race-free queueing, you simply add to the queue in the signal	3194	To implement race-free queueing, you simply add to the queue in the signal
2282	handler but you block the signal handler in the watcher callback. Here is an example that does that for	3195	handler but you block the signal handler in the watcher callback. Here is
2283	some fictitious SIGUSR1 handler:	3196	an example that does that for some fictitious SIGUSR1 handler:
2284		3197
2285	static ev_async mysig;	3198	static ev_async mysig;
2286		3199
2287	static void	3200	static void
2288	sigusr1_handler (void)	3201	sigusr1_handler (void)
…		…
2354	=over 4	3267	=over 4
2355		3268
2356	=item ev_async_init (ev_async *, callback)	3269	=item ev_async_init (ev_async *, callback)
2357		3270
2358	Initialises and configures the async watcher - it has no parameters of any	3271	Initialises and configures the async watcher - it has no parameters of any
2359	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3272	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2360	believe me.	3273	trust me.
2361		3274
2362	=item ev_async_send (loop, ev_async *)	3275	=item ev_async_send (loop, ev_async *)
2363		3276
2364	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3277	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2365	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3278	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2366	C<ev_feed_event>, this call is safe to do in other threads, signal or	3279	C<ev_feed_event>, this call is safe to do from other threads, signal or
2367	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3280	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2368	section below on what exactly this means).	3281	section below on what exactly this means).
2369		3282
		3283	Note that, as with other watchers in libev, multiple events might get
		3284	compressed into a single callback invocation (another way to look at this
		3285	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3286	reset when the event loop detects that).
		3287
2370	This call incurs the overhead of a system call only once per loop iteration,	3288	This call incurs the overhead of a system call only once per event loop
2371	so while the overhead might be noticeable, it doesn't apply to repeated	3289	iteration, so while the overhead might be noticeable, it doesn't apply to
2372	calls to C<ev_async_send>.	3290	repeated calls to C<ev_async_send> for the same event loop.
2373		3291
2374	=item bool = ev_async_pending (ev_async *)	3292	=item bool = ev_async_pending (ev_async *)
2375		3293
2376	Returns a non-zero value when C<ev_async_send> has been called on the	3294	Returns a non-zero value when C<ev_async_send> has been called on the
2377	watcher but the event has not yet been processed (or even noted) by the	3295	watcher but the event has not yet been processed (or even noted) by the
…		…
2380	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3298	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2381	the loop iterates next and checks for the watcher to have become active,	3299	the loop iterates next and checks for the watcher to have become active,
2382	it will reset the flag again. C<ev_async_pending> can be used to very	3300	it will reset the flag again. C<ev_async_pending> can be used to very
2383	quickly check whether invoking the loop might be a good idea.	3301	quickly check whether invoking the loop might be a good idea.
2384		3302
2385	Not that this does I<not> check whether the watcher itself is pending, only	3303	Not that this does I<not> check whether the watcher itself is pending,
2386	whether it has been requested to make this watcher pending.	3304	only whether it has been requested to make this watcher pending: there
		3305	is a time window between the event loop checking and resetting the async
		3306	notification, and the callback being invoked.
2387		3307
2388	=back	3308	=back
2389		3309
2390		3310
2391	=head1 OTHER FUNCTIONS	3311	=head1 OTHER FUNCTIONS
…		…
2395	=over 4	3315	=over 4
2396		3316
2397	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3317	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2398		3318
2399	This function combines a simple timer and an I/O watcher, calls your	3319	This function combines a simple timer and an I/O watcher, calls your
2400	callback on whichever event happens first and automatically stop both	3320	callback on whichever event happens first and automatically stops both
2401	watchers. This is useful if you want to wait for a single event on an fd	3321	watchers. This is useful if you want to wait for a single event on an fd
2402	or timeout without having to allocate/configure/start/stop/free one or	3322	or timeout without having to allocate/configure/start/stop/free one or
2403	more watchers yourself.	3323	more watchers yourself.
2404		3324
2405	If C<fd> is less than 0, then no I/O watcher will be started and events	3325	If C<fd> is less than 0, then no I/O watcher will be started and the
2406	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	3326	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2407	C<events> set will be created and started.	3327	the given C<fd> and C<events> set will be created and started.
2408		3328
2409	If C<timeout> is less than 0, then no timeout watcher will be	3329	If C<timeout> is less than 0, then no timeout watcher will be
2410	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3330	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2411	repeat = 0) will be started. While C<0> is a valid timeout, it is of	3331	repeat = 0) will be started. C<0> is a valid timeout.
2412	dubious value.
2413		3332
2414	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3333	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2415	passed an C<revents> set like normal event callbacks (a combination of	3334	passed an C<revents> set like normal event callbacks (a combination of
2416	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3335	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2417	value passed to C<ev_once>:	3336	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3337	a timeout and an io event at the same time - you probably should give io
		3338	events precedence.
		3339
		3340	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2418		3341
2419	static void stdin_ready (int revents, void *arg)	3342	static void stdin_ready (int revents, void *arg)
2420	{	3343	{
		3344	if (revents & EV_READ)
		3345	/* stdin might have data for us, joy! */;
2421	if (revents & EV_TIMEOUT)	3346	else if (revents & EV_TIMER)
2422	/* doh, nothing entered */;	3347	/* doh, nothing entered */;
2423	else if (revents & EV_READ)
2424	/* stdin might have data for us, joy! */;
2425	}	3348	}
2426		3349
2427	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3350	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2428		3351
2429	=item ev_feed_event (ev_loop *, watcher *, int revents)
2430
2431	Feeds the given event set into the event loop, as if the specified event
2432	had happened for the specified watcher (which must be a pointer to an
2433	initialised but not necessarily started event watcher).
2434
2435	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3352	=item ev_feed_fd_event (loop, int fd, int revents)
2436		3353
2437	Feed an event on the given fd, as if a file descriptor backend detected	3354	Feed an event on the given fd, as if a file descriptor backend detected
2438	the given events it.	3355	the given events it.
2439		3356
2440	=item ev_feed_signal_event (ev_loop *loop, int signum)	3357	=item ev_feed_signal_event (loop, int signum)
2441		3358
2442	Feed an event as if the given signal occurred (C<loop> must be the default	3359	Feed an event as if the given signal occurred (C<loop> must be the default
2443	loop!).	3360	loop!).
2444		3361
2445	=back	3362	=back
…		…
2525		3442
2526	=over 4	3443	=over 4
2527		3444
2528	=item ev::TYPE::TYPE ()	3445	=item ev::TYPE::TYPE ()
2529		3446
2530	=item ev::TYPE::TYPE (struct ev_loop *)	3447	=item ev::TYPE::TYPE (loop)
2531		3448
2532	=item ev::TYPE::~TYPE	3449	=item ev::TYPE::~TYPE
2533		3450
2534	The constructor (optionally) takes an event loop to associate the watcher	3451	The constructor (optionally) takes an event loop to associate the watcher
2535	with. If it is omitted, it will use C<EV_DEFAULT>.	3452	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2567		3484
2568	myclass obj;	3485	myclass obj;
2569	ev::io iow;	3486	ev::io iow;
2570	iow.set <myclass, &myclass::io_cb> (&obj);	3487	iow.set <myclass, &myclass::io_cb> (&obj);
2571		3488
		3489	=item w->set (object *)
		3490
		3491	This is a variation of a method callback - leaving out the method to call
		3492	will default the method to C<operator ()>, which makes it possible to use
		3493	functor objects without having to manually specify the C<operator ()> all
		3494	the time. Incidentally, you can then also leave out the template argument
		3495	list.
		3496
		3497	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3498	int revents)>.
		3499
		3500	See the method-C<set> above for more details.
		3501
		3502	Example: use a functor object as callback.
		3503
		3504	struct myfunctor
		3505	{
		3506	void operator() (ev::io &w, int revents)
		3507	{
		3508	...
		3509	}
		3510	}
		3511
		3512	myfunctor f;
		3513
		3514	ev::io w;
		3515	w.set (&f);
		3516
2572	=item w->set<function> (void *data = 0)	3517	=item w->set<function> (void *data = 0)
2573		3518
2574	Also sets a callback, but uses a static method or plain function as	3519	Also sets a callback, but uses a static method or plain function as
2575	callback. The optional C<data> argument will be stored in the watcher's	3520	callback. The optional C<data> argument will be stored in the watcher's
2576	C<data> member and is free for you to use.	3521	C<data> member and is free for you to use.
2577		3522
2578	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3523	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2579		3524
2580	See the method-C<set> above for more details.	3525	See the method-C<set> above for more details.
2581		3526
2582	Example:	3527	Example: Use a plain function as callback.
2583		3528
2584	static void io_cb (ev::io &w, int revents) { }	3529	static void io_cb (ev::io &w, int revents) { }
2585	iow.set <io_cb> ();	3530	iow.set <io_cb> ();
2586		3531
2587	=item w->set (struct ev_loop *)	3532	=item w->set (loop)
2588		3533
2589	Associates a different C<struct ev_loop> with this watcher. You can only	3534	Associates a different C<struct ev_loop> with this watcher. You can only
2590	do this when the watcher is inactive (and not pending either).	3535	do this when the watcher is inactive (and not pending either).
2591		3536
2592	=item w->set ([arguments])	3537	=item w->set ([arguments])
2593		3538
2594	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3539	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
2595	called at least once. Unlike the C counterpart, an active watcher gets	3540	method or a suitable start method must be called at least once. Unlike the
2596	automatically stopped and restarted when reconfiguring it with this	3541	C counterpart, an active watcher gets automatically stopped and restarted
2597	method.	3542	when reconfiguring it with this method.
2598		3543
2599	=item w->start ()	3544	=item w->start ()
2600		3545
2601	Starts the watcher. Note that there is no C<loop> argument, as the	3546	Starts the watcher. Note that there is no C<loop> argument, as the
2602	constructor already stores the event loop.	3547	constructor already stores the event loop.
2603		3548
		3549	=item w->start ([arguments])
		3550
		3551	Instead of calling C<set> and C<start> methods separately, it is often
		3552	convenient to wrap them in one call. Uses the same type of arguments as
		3553	the configure C<set> method of the watcher.
		3554
2604	=item w->stop ()	3555	=item w->stop ()
2605		3556
2606	Stops the watcher if it is active. Again, no C<loop> argument.	3557	Stops the watcher if it is active. Again, no C<loop> argument.
2607		3558
2608	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3559	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2620		3571
2621	=back	3572	=back
2622		3573
2623	=back	3574	=back
2624		3575
2625	Example: Define a class with an IO and idle watcher, start one of them in	3576	Example: Define a class with two I/O and idle watchers, start the I/O
2626	the constructor.	3577	watchers in the constructor.
2627		3578
2628	class myclass	3579	class myclass
2629	{	3580	{
2630	ev::io io; void io_cb (ev::io &w, int revents);	3581	ev::io io ; void io_cb (ev::io &w, int revents);
		3582	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
2631	ev:idle idle void idle_cb (ev::idle &w, int revents);	3583	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2632		3584
2633	myclass (int fd)	3585	myclass (int fd)
2634	{	3586	{
2635	io .set <myclass, &myclass::io_cb > (this);	3587	io .set <myclass, &myclass::io_cb > (this);
		3588	io2 .set <myclass, &myclass::io2_cb > (this);
2636	idle.set <myclass, &myclass::idle_cb> (this);	3589	idle.set <myclass, &myclass::idle_cb> (this);
2637		3590
2638	io.start (fd, ev::READ);	3591	io.set (fd, ev::WRITE); // configure the watcher
		3592	io.start (); // start it whenever convenient
		3593
		3594	io2.start (fd, ev::READ); // set + start in one call
2639	}	3595	}
2640	};	3596	};
2641		3597
2642		3598
2643	=head1 OTHER LANGUAGE BINDINGS	3599	=head1 OTHER LANGUAGE BINDINGS
…		…
2652	=item Perl	3608	=item Perl
2653		3609
2654	The EV module implements the full libev API and is actually used to test	3610	The EV module implements the full libev API and is actually used to test
2655	libev. EV is developed together with libev. Apart from the EV core module,	3611	libev. EV is developed together with libev. Apart from the EV core module,
2656	there are additional modules that implement libev-compatible interfaces	3612	there are additional modules that implement libev-compatible interfaces
2657	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3613	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2658	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3614	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3615	and C<EV::Glib>).
2659		3616
2660	It can be found and installed via CPAN, its homepage is at	3617	It can be found and installed via CPAN, its homepage is at
2661	L<http://software.schmorp.de/pkg/EV>.	3618	L<http://software.schmorp.de/pkg/EV>.
2662		3619
2663	=item Python	3620	=item Python
2664		3621
2665	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3622	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2666	seems to be quite complete and well-documented. Note, however, that the	3623	seems to be quite complete and well-documented.
2667	patch they require for libev is outright dangerous as it breaks the ABI
2668	for everybody else, and therefore, should never be applied in an installed
2669	libev (if python requires an incompatible ABI then it needs to embed
2670	libev).
2671		3624
2672	=item Ruby	3625	=item Ruby
2673		3626
2674	Tony Arcieri has written a ruby extension that offers access to a subset	3627	Tony Arcieri has written a ruby extension that offers access to a subset
2675	of the libev API and adds file handle abstractions, asynchronous DNS and	3628	of the libev API and adds file handle abstractions, asynchronous DNS and
2676	more on top of it. It can be found via gem servers. Its homepage is at	3629	more on top of it. It can be found via gem servers. Its homepage is at
2677	L<http://rev.rubyforge.org/>.	3630	L<http://rev.rubyforge.org/>.
2678		3631
		3632	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3633	makes rev work even on mingw.
		3634
		3635	=item Haskell
		3636
		3637	A haskell binding to libev is available at
		3638	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3639
2679	=item D	3640	=item D
2680		3641
2681	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3642	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2682	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3643	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3644
		3645	=item Ocaml
		3646
		3647	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3648	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3649
		3650	=item Lua
		3651
		3652	Brian Maher has written a partial interface to libev for lua (at the
		3653	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3654	L<http://github.com/brimworks/lua-ev>.
2683		3655
2684	=back	3656	=back
2685		3657
2686		3658
2687	=head1 MACRO MAGIC	3659	=head1 MACRO MAGIC
…		…
2701	loop argument"). The C<EV_A> form is used when this is the sole argument,	3673	loop argument"). The C<EV_A> form is used when this is the sole argument,
2702	C<EV_A_> is used when other arguments are following. Example:	3674	C<EV_A_> is used when other arguments are following. Example:
2703		3675
2704	ev_unref (EV_A);	3676	ev_unref (EV_A);
2705	ev_timer_add (EV_A_ watcher);	3677	ev_timer_add (EV_A_ watcher);
2706	ev_loop (EV_A_ 0);	3678	ev_run (EV_A_ 0);
2707		3679
2708	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3680	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2709	which is often provided by the following macro.	3681	which is often provided by the following macro.
2710		3682
2711	=item C<EV_P>, C<EV_P_>	3683	=item C<EV_P>, C<EV_P_>
…		…
2751	}	3723	}
2752		3724
2753	ev_check check;	3725	ev_check check;
2754	ev_check_init (&check, check_cb);	3726	ev_check_init (&check, check_cb);
2755	ev_check_start (EV_DEFAULT_ &check);	3727	ev_check_start (EV_DEFAULT_ &check);
2756	ev_loop (EV_DEFAULT_ 0);	3728	ev_run (EV_DEFAULT_ 0);
2757		3729
2758	=head1 EMBEDDING	3730	=head1 EMBEDDING
2759		3731
2760	Libev can (and often is) directly embedded into host	3732	Libev can (and often is) directly embedded into host
2761	applications. Examples of applications that embed it include the Deliantra	3733	applications. Examples of applications that embed it include the Deliantra
…		…
2788		3760
2789	#define EV_STANDALONE 1	3761	#define EV_STANDALONE 1
2790	#include "ev.h"	3762	#include "ev.h"
2791		3763
2792	Both header files and implementation files can be compiled with a C++	3764	Both header files and implementation files can be compiled with a C++
2793	compiler (at least, thats a stated goal, and breakage will be treated	3765	compiler (at least, that's a stated goal, and breakage will be treated
2794	as a bug).	3766	as a bug).
2795		3767
2796	You need the following files in your source tree, or in a directory	3768	You need the following files in your source tree, or in a directory
2797	in your include path (e.g. in libev/ when using -Ilibev):	3769	in your include path (e.g. in libev/ when using -Ilibev):
2798		3770
…		…
2841	libev.m4	3813	libev.m4
2842		3814
2843	=head2 PREPROCESSOR SYMBOLS/MACROS	3815	=head2 PREPROCESSOR SYMBOLS/MACROS
2844		3816
2845	Libev can be configured via a variety of preprocessor symbols you have to	3817	Libev can be configured via a variety of preprocessor symbols you have to
2846	define before including any of its files. The default in the absence of	3818	define before including (or compiling) any of its files. The default in
2847	autoconf is noted for every option.	3819	the absence of autoconf is documented for every option.
		3820
		3821	Symbols marked with "(h)" do not change the ABI, and can have different
		3822	values when compiling libev vs. including F<ev.h>, so it is permissible
		3823	to redefine them before including F<ev.h> without breaking compatibility
		3824	to a compiled library. All other symbols change the ABI, which means all
		3825	users of libev and the libev code itself must be compiled with compatible
		3826	settings.
2848		3827
2849	=over 4	3828	=over 4
2850		3829
		3830	=item EV_COMPAT3 (h)
		3831
		3832	Backwards compatibility is a major concern for libev. This is why this
		3833	release of libev comes with wrappers for the functions and symbols that
		3834	have been renamed between libev version 3 and 4.
		3835
		3836	You can disable these wrappers (to test compatibility with future
		3837	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		3838	sources. This has the additional advantage that you can drop the C<struct>
		3839	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		3840	typedef in that case.
		3841
		3842	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		3843	and in some even more future version the compatibility code will be
		3844	removed completely.
		3845
2851	=item EV_STANDALONE	3846	=item EV_STANDALONE (h)
2852		3847
2853	Must always be C<1> if you do not use autoconf configuration, which	3848	Must always be C<1> if you do not use autoconf configuration, which
2854	keeps libev from including F<config.h>, and it also defines dummy	3849	keeps libev from including F<config.h>, and it also defines dummy
2855	implementations for some libevent functions (such as logging, which is not	3850	implementations for some libevent functions (such as logging, which is not
2856	supported). It will also not define any of the structs usually found in	3851	supported). It will also not define any of the structs usually found in
2857	F<event.h> that are not directly supported by the libev core alone.	3852	F<event.h> that are not directly supported by the libev core alone.
2858		3853
		3854	In standalone mode, libev will still try to automatically deduce the
		3855	configuration, but has to be more conservative.
		3856
2859	=item EV_USE_MONOTONIC	3857	=item EV_USE_MONOTONIC
2860		3858
2861	If defined to be C<1>, libev will try to detect the availability of the	3859	If defined to be C<1>, libev will try to detect the availability of the
2862	monotonic clock option at both compile time and runtime. Otherwise no use	3860	monotonic clock option at both compile time and runtime. Otherwise no
2863	of the monotonic clock option will be attempted. If you enable this, you	3861	use of the monotonic clock option will be attempted. If you enable this,
2864	usually have to link against librt or something similar. Enabling it when	3862	you usually have to link against librt or something similar. Enabling it
2865	the functionality isn't available is safe, though, although you have	3863	when the functionality isn't available is safe, though, although you have
2866	to make sure you link against any libraries where the C<clock_gettime>	3864	to make sure you link against any libraries where the C<clock_gettime>
2867	function is hiding in (often F<-lrt>).	3865	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2868		3866
2869	=item EV_USE_REALTIME	3867	=item EV_USE_REALTIME
2870		3868
2871	If defined to be C<1>, libev will try to detect the availability of the	3869	If defined to be C<1>, libev will try to detect the availability of the
2872	real-time clock option at compile time (and assume its availability at	3870	real-time clock option at compile time (and assume its availability
2873	runtime if successful). Otherwise no use of the real-time clock option will	3871	at runtime if successful). Otherwise no use of the real-time clock
2874	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3872	option will be attempted. This effectively replaces C<gettimeofday>
2875	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3873	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2876	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3874	correctness. See the note about libraries in the description of
		3875	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3876	C<EV_USE_CLOCK_SYSCALL>.
		3877
		3878	=item EV_USE_CLOCK_SYSCALL
		3879
		3880	If defined to be C<1>, libev will try to use a direct syscall instead
		3881	of calling the system-provided C<clock_gettime> function. This option
		3882	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3883	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3884	programs needlessly. Using a direct syscall is slightly slower (in
		3885	theory), because no optimised vdso implementation can be used, but avoids
		3886	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3887	higher, as it simplifies linking (no need for C<-lrt>).
2877		3888
2878	=item EV_USE_NANOSLEEP	3889	=item EV_USE_NANOSLEEP
2879		3890
2880	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3891	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2881	and will use it for delays. Otherwise it will use C<select ()>.	3892	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2897		3908
2898	=item EV_SELECT_USE_FD_SET	3909	=item EV_SELECT_USE_FD_SET
2899		3910
2900	If defined to C<1>, then the select backend will use the system C<fd_set>	3911	If defined to C<1>, then the select backend will use the system C<fd_set>
2901	structure. This is useful if libev doesn't compile due to a missing	3912	structure. This is useful if libev doesn't compile due to a missing
2902	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3913	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2903	exotic systems. This usually limits the range of file descriptors to some	3914	on exotic systems. This usually limits the range of file descriptors to
2904	low limit such as 1024 or might have other limitations (winsocket only	3915	some low limit such as 1024 or might have other limitations (winsocket
2905	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3916	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2906	influence the size of the C<fd_set> used.	3917	configures the maximum size of the C<fd_set>.
2907		3918
2908	=item EV_SELECT_IS_WINSOCKET	3919	=item EV_SELECT_IS_WINSOCKET
2909		3920
2910	When defined to C<1>, the select backend will assume that	3921	When defined to C<1>, the select backend will assume that
2911	select/socket/connect etc. don't understand file descriptors but	3922	select/socket/connect etc. don't understand file descriptors but
…		…
2913	be used is the winsock select). This means that it will call	3924	be used is the winsock select). This means that it will call
2914	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3925	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2915	it is assumed that all these functions actually work on fds, even	3926	it is assumed that all these functions actually work on fds, even
2916	on win32. Should not be defined on non-win32 platforms.	3927	on win32. Should not be defined on non-win32 platforms.
2917		3928
2918	=item EV_FD_TO_WIN32_HANDLE	3929	=item EV_FD_TO_WIN32_HANDLE(fd)
2919		3930
2920	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3931	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
2921	file descriptors to socket handles. When not defining this symbol (the	3932	file descriptors to socket handles. When not defining this symbol (the
2922	default), then libev will call C<_get_osfhandle>, which is usually	3933	default), then libev will call C<_get_osfhandle>, which is usually
2923	correct. In some cases, programs use their own file descriptor management,	3934	correct. In some cases, programs use their own file descriptor management,
2924	in which case they can provide this function to map fds to socket handles.	3935	in which case they can provide this function to map fds to socket handles.
		3936
		3937	=item EV_WIN32_HANDLE_TO_FD(handle)
		3938
		3939	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3940	using the standard C<_open_osfhandle> function. For programs implementing
		3941	their own fd to handle mapping, overwriting this function makes it easier
		3942	to do so. This can be done by defining this macro to an appropriate value.
		3943
		3944	=item EV_WIN32_CLOSE_FD(fd)
		3945
		3946	If programs implement their own fd to handle mapping on win32, then this
		3947	macro can be used to override the C<close> function, useful to unregister
		3948	file descriptors again. Note that the replacement function has to close
		3949	the underlying OS handle.
2925		3950
2926	=item EV_USE_POLL	3951	=item EV_USE_POLL
2927		3952
2928	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3953	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2929	backend. Otherwise it will be enabled on non-win32 platforms. It	3954	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
2976	as well as for signal and thread safety in C<ev_async> watchers.	4001	as well as for signal and thread safety in C<ev_async> watchers.
2977		4002
2978	In the absence of this define, libev will use C<sig_atomic_t volatile>	4003	In the absence of this define, libev will use C<sig_atomic_t volatile>
2979	(from F<signal.h>), which is usually good enough on most platforms.	4004	(from F<signal.h>), which is usually good enough on most platforms.
2980		4005
2981	=item EV_H	4006	=item EV_H (h)
2982		4007
2983	The name of the F<ev.h> header file used to include it. The default if	4008	The name of the F<ev.h> header file used to include it. The default if
2984	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4009	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2985	used to virtually rename the F<ev.h> header file in case of conflicts.	4010	used to virtually rename the F<ev.h> header file in case of conflicts.
2986		4011
2987	=item EV_CONFIG_H	4012	=item EV_CONFIG_H (h)
2988		4013
2989	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4014	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2990	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4015	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2991	C<EV_H>, above.	4016	C<EV_H>, above.
2992		4017
2993	=item EV_EVENT_H	4018	=item EV_EVENT_H (h)
2994		4019
2995	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4020	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2996	of how the F<event.h> header can be found, the default is C<"event.h">.	4021	of how the F<event.h> header can be found, the default is C<"event.h">.
2997		4022
2998	=item EV_PROTOTYPES	4023	=item EV_PROTOTYPES (h)
2999		4024
3000	If defined to be C<0>, then F<ev.h> will not define any function	4025	If defined to be C<0>, then F<ev.h> will not define any function
3001	prototypes, but still define all the structs and other symbols. This is	4026	prototypes, but still define all the structs and other symbols. This is
3002	occasionally useful if you want to provide your own wrapper functions	4027	occasionally useful if you want to provide your own wrapper functions
3003	around libev functions.	4028	around libev functions.
…		…
3022	When doing priority-based operations, libev usually has to linearly search	4047	When doing priority-based operations, libev usually has to linearly search
3023	all the priorities, so having many of them (hundreds) uses a lot of space	4048	all the priorities, so having many of them (hundreds) uses a lot of space
3024	and time, so using the defaults of five priorities (-2 .. +2) is usually	4049	and time, so using the defaults of five priorities (-2 .. +2) is usually
3025	fine.	4050	fine.
3026		4051
3027	If your embedding application does not need any priorities, defining these both to	4052	If your embedding application does not need any priorities, defining these
3028	C<0> will save some memory and CPU.	4053	both to C<0> will save some memory and CPU.
3029		4054
3030	=item EV_PERIODIC_ENABLE	4055	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4056	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4057	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3031		4058
3032	If undefined or defined to be C<1>, then periodic timers are supported. If	4059	If undefined or defined to be C<1> (and the platform supports it), then
3033	defined to be C<0>, then they are not. Disabling them saves a few kB of	4060	the respective watcher type is supported. If defined to be C<0>, then it
3034	code.	4061	is not. Disabling watcher types mainly saves code size.
3035		4062
3036	=item EV_IDLE_ENABLE	4063	=item EV_FEATURES
3037
3038	If undefined or defined to be C<1>, then idle watchers are supported. If
3039	defined to be C<0>, then they are not. Disabling them saves a few kB of
3040	code.
3041
3042	=item EV_EMBED_ENABLE
3043
3044	If undefined or defined to be C<1>, then embed watchers are supported. If
3045	defined to be C<0>, then they are not.
3046
3047	=item EV_STAT_ENABLE
3048
3049	If undefined or defined to be C<1>, then stat watchers are supported. If
3050	defined to be C<0>, then they are not.
3051
3052	=item EV_FORK_ENABLE
3053
3054	If undefined or defined to be C<1>, then fork watchers are supported. If
3055	defined to be C<0>, then they are not.
3056
3057	=item EV_ASYNC_ENABLE
3058
3059	If undefined or defined to be C<1>, then async watchers are supported. If
3060	defined to be C<0>, then they are not.
3061
3062	=item EV_MINIMAL
3063		4064
3064	If you need to shave off some kilobytes of code at the expense of some	4065	If you need to shave off some kilobytes of code at the expense of some
3065	speed, define this symbol to C<1>. Currently this is used to override some	4066	speed (but with the full API), you can define this symbol to request
3066	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4067	certain subsets of functionality. The default is to enable all features
3067	much smaller 2-heap for timer management over the default 4-heap.	4068	that can be enabled on the platform.
		4069
		4070	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4071	with some broad features you want) and then selectively re-enable
		4072	additional parts you want, for example if you want everything minimal,
		4073	but multiple event loop support, async and child watchers and the poll
		4074	backend, use this:
		4075
		4076	#define EV_FEATURES 0
		4077	#define EV_MULTIPLICITY 1
		4078	#define EV_USE_POLL 1
		4079	#define EV_CHILD_ENABLE 1
		4080	#define EV_ASYNC_ENABLE 1
		4081
		4082	The actual value is a bitset, it can be a combination of the following
		4083	values:
		4084
		4085	=over 4
		4086
		4087	=item C<1> - faster/larger code
		4088
		4089	Use larger code to speed up some operations.
		4090
		4091	Currently this is used to override some inlining decisions (enlarging the
		4092	code size by roughly 30% on amd64).
		4093
		4094	When optimising for size, use of compiler flags such as C<-Os> with
		4095	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4096	assertions.
		4097
		4098	=item C<2> - faster/larger data structures
		4099
		4100	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4101	hash table sizes and so on. This will usually further increase code size
		4102	and can additionally have an effect on the size of data structures at
		4103	runtime.
		4104
		4105	=item C<4> - full API configuration
		4106
		4107	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4108	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4109
		4110	=item C<8> - full API
		4111
		4112	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4113	details on which parts of the API are still available without this
		4114	feature, and do not complain if this subset changes over time.
		4115
		4116	=item C<16> - enable all optional watcher types
		4117
		4118	Enables all optional watcher types. If you want to selectively enable
		4119	only some watcher types other than I/O and timers (e.g. prepare,
		4120	embed, async, child...) you can enable them manually by defining
		4121	C<EV_watchertype_ENABLE> to C<1> instead.
		4122
		4123	=item C<32> - enable all backends
		4124
		4125	This enables all backends - without this feature, you need to enable at
		4126	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4127
		4128	=item C<64> - enable OS-specific "helper" APIs
		4129
		4130	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4131	default.
		4132
		4133	=back
		4134
		4135	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4136	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4137	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4138	watchers, timers and monotonic clock support.
		4139
		4140	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4141	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4142	your program might be left out as well - a binary starting a timer and an
		4143	I/O watcher then might come out at only 5Kb.
		4144
		4145	=item EV_AVOID_STDIO
		4146
		4147	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4148	functions (printf, scanf, perror etc.). This will increase the code size
		4149	somewhat, but if your program doesn't otherwise depend on stdio and your
		4150	libc allows it, this avoids linking in the stdio library which is quite
		4151	big.
		4152
		4153	Note that error messages might become less precise when this option is
		4154	enabled.
		4155
		4156	=item EV_NSIG
		4157
		4158	The highest supported signal number, +1 (or, the number of
		4159	signals): Normally, libev tries to deduce the maximum number of signals
		4160	automatically, but sometimes this fails, in which case it can be
		4161	specified. Also, using a lower number than detected (C<32> should be
		4162	good for about any system in existence) can save some memory, as libev
		4163	statically allocates some 12-24 bytes per signal number.
3068		4164
3069	=item EV_PID_HASHSIZE	4165	=item EV_PID_HASHSIZE
3070		4166
3071	C<ev_child> watchers use a small hash table to distribute workload by	4167	C<ev_child> watchers use a small hash table to distribute workload by
3072	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4168	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3073	than enough. If you need to manage thousands of children you might want to	4169	usually more than enough. If you need to manage thousands of children you
3074	increase this value (I<must> be a power of two).	4170	might want to increase this value (I<must> be a power of two).
3075		4171
3076	=item EV_INOTIFY_HASHSIZE	4172	=item EV_INOTIFY_HASHSIZE
3077		4173
3078	C<ev_stat> watchers use a small hash table to distribute workload by	4174	C<ev_stat> watchers use a small hash table to distribute workload by
3079	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4175	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3080	usually more than enough. If you need to manage thousands of C<ev_stat>	4176	disabled), usually more than enough. If you need to manage thousands of
3081	watchers you might want to increase this value (I<must> be a power of	4177	C<ev_stat> watchers you might want to increase this value (I<must> be a
3082	two).	4178	power of two).
3083		4179
3084	=item EV_USE_4HEAP	4180	=item EV_USE_4HEAP
3085		4181
3086	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4182	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3087	timer and periodics heap, libev uses a 4-heap when this symbol is defined	4183	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3088	to C<1>. The 4-heap uses more complicated (longer) code but has	4184	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3089	noticeably faster performance with many (thousands) of watchers.	4185	faster performance with many (thousands) of watchers.
3090		4186
3091	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4187	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3092	(disabled).	4188	will be C<0>.
3093		4189
3094	=item EV_HEAP_CACHE_AT	4190	=item EV_HEAP_CACHE_AT
3095		4191
3096	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4192	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3097	timer and periodics heap, libev can cache the timestamp (I<at>) within	4193	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3098	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4194	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3099	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4195	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3100	but avoids random read accesses on heap changes. This improves performance	4196	but avoids random read accesses on heap changes. This improves performance
3101	noticeably with with many (hundreds) of watchers.	4197	noticeably with many (hundreds) of watchers.
3102		4198
3103	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4199	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3104	(disabled).	4200	will be C<0>.
3105		4201
3106	=item EV_VERIFY	4202	=item EV_VERIFY
3107		4203
3108	Controls how much internal verification (see C<ev_loop_verify ()>) will	4204	Controls how much internal verification (see C<ev_verify ()>) will
3109	be done: If set to C<0>, no internal verification code will be compiled	4205	be done: If set to C<0>, no internal verification code will be compiled
3110	in. If set to C<1>, then verification code will be compiled in, but not	4206	in. If set to C<1>, then verification code will be compiled in, but not
3111	called. If set to C<2>, then the internal verification code will be	4207	called. If set to C<2>, then the internal verification code will be
3112	called once per loop, which can slow down libev. If set to C<3>, then the	4208	called once per loop, which can slow down libev. If set to C<3>, then the
3113	verification code will be called very frequently, which will slow down	4209	verification code will be called very frequently, which will slow down
3114	libev considerably.	4210	libev considerably.
3115		4211
3116	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4212	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3117	C<0.>	4213	will be C<0>.
3118		4214
3119	=item EV_COMMON	4215	=item EV_COMMON
3120		4216
3121	By default, all watchers have a C<void *data> member. By redefining	4217	By default, all watchers have a C<void *data> member. By redefining
3122	this macro to a something else you can include more and other types of	4218	this macro to something else you can include more and other types of
3123	members. You have to define it each time you include one of the files,	4219	members. You have to define it each time you include one of the files,
3124	though, and it must be identical each time.	4220	though, and it must be identical each time.
3125		4221
3126	For example, the perl EV module uses something like this:	4222	For example, the perl EV module uses something like this:
3127		4223
…		…
3139	and the way callbacks are invoked and set. Must expand to a struct member	4235	and the way callbacks are invoked and set. Must expand to a struct member
3140	definition and a statement, respectively. See the F<ev.h> header file for	4236	definition and a statement, respectively. See the F<ev.h> header file for
3141	their default definitions. One possible use for overriding these is to	4237	their default definitions. One possible use for overriding these is to
3142	avoid the C<struct ev_loop *> as first argument in all cases, or to use	4238	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3143	method calls instead of plain function calls in C++.	4239	method calls instead of plain function calls in C++.
		4240
		4241	=back
3144		4242
3145	=head2 EXPORTED API SYMBOLS	4243	=head2 EXPORTED API SYMBOLS
3146		4244
3147	If you need to re-export the API (e.g. via a DLL) and you need a list of	4245	If you need to re-export the API (e.g. via a DLL) and you need a list of
3148	exported symbols, you can use the provided F<Symbol.*> files which list	4246	exported symbols, you can use the provided F<Symbol.*> files which list
…		…
3178	file.	4276	file.
3179		4277
3180	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4278	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3181	that everybody includes and which overrides some configure choices:	4279	that everybody includes and which overrides some configure choices:
3182		4280
3183	#define EV_MINIMAL 1	4281	#define EV_FEATURES 8
3184	#define EV_USE_POLL 0	4282	#define EV_USE_SELECT 1
3185	#define EV_MULTIPLICITY 0
3186	#define EV_PERIODIC_ENABLE 0	4283	#define EV_PREPARE_ENABLE 1
		4284	#define EV_IDLE_ENABLE 1
3187	#define EV_STAT_ENABLE 0	4285	#define EV_SIGNAL_ENABLE 1
3188	#define EV_FORK_ENABLE 0	4286	#define EV_CHILD_ENABLE 1
		4287	#define EV_USE_STDEXCEPT 0
3189	#define EV_CONFIG_H <config.h>	4288	#define EV_CONFIG_H <config.h>
3190	#define EV_MINPRI 0
3191	#define EV_MAXPRI 0
3192		4289
3193	#include "ev++.h"	4290	#include "ev++.h"
3194		4291
3195	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4292	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3196		4293
3197	#include "ev_cpp.h"	4294	#include "ev_cpp.h"
3198	#include "ev.c"	4295	#include "ev.c"
3199		4296
		4297	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3200		4298
3201	=head1 THREADS AND COROUTINES	4299	=head2 THREADS AND COROUTINES
3202		4300
3203	=head2 THREADS	4301	=head3 THREADS
3204		4302
3205	Libev itself is completely thread-safe, but it uses no locking. This	4303	All libev functions are reentrant and thread-safe unless explicitly
		4304	documented otherwise, but libev implements no locking itself. This means
3206	means that you can use as many loops as you want in parallel, as long as	4305	that you can use as many loops as you want in parallel, as long as there
3207	only one thread ever calls into one libev function with the same loop	4306	are no concurrent calls into any libev function with the same loop
3208	parameter.	4307	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		4308	of course): libev guarantees that different event loops share no data
		4309	structures that need any locking.
3209		4310
3210	Or put differently: calls with different loop parameters can be done in	4311	Or to put it differently: calls with different loop parameters can be done
3211	parallel from multiple threads, calls with the same loop parameter must be	4312	concurrently from multiple threads, calls with the same loop parameter
3212	done serially (but can be done from different threads, as long as only one	4313	must be done serially (but can be done from different threads, as long as
3213	thread ever is inside a call at any point in time, e.g. by using a mutex	4314	only one thread ever is inside a call at any point in time, e.g. by using
3214	per loop).	4315	a mutex per loop).
		4316
		4317	Specifically to support threads (and signal handlers), libev implements
		4318	so-called C<ev_async> watchers, which allow some limited form of
		4319	concurrency on the same event loop, namely waking it up "from the
		4320	outside".
3215		4321
3216	If you want to know which design (one loop, locking, or multiple loops	4322	If you want to know which design (one loop, locking, or multiple loops
3217	without or something else still) is best for your problem, then I cannot	4323	without or something else still) is best for your problem, then I cannot
3218	help you. I can give some generic advice however:	4324	help you, but here is some generic advice:
3219		4325
3220	=over 4	4326	=over 4
3221		4327
3222	=item * most applications have a main thread: use the default libev loop	4328	=item * most applications have a main thread: use the default libev loop
3223	in that thread, or create a separate thread running only the default loop.	4329	in that thread, or create a separate thread running only the default loop.
…		…
3235		4341
3236	Choosing a model is hard - look around, learn, know that usually you can do	4342	Choosing a model is hard - look around, learn, know that usually you can do
3237	better than you currently do :-)	4343	better than you currently do :-)
3238		4344
3239	=item * often you need to talk to some other thread which blocks in the	4345	=item * often you need to talk to some other thread which blocks in the
		4346	event loop.
		4347
3240	event loop - C<ev_async> watchers can be used to wake them up from other	4348	C<ev_async> watchers can be used to wake them up from other threads safely
3241	threads safely (or from signal contexts...).	4349	(or from signal contexts...).
		4350
		4351	An example use would be to communicate signals or other events that only
		4352	work in the default loop by registering the signal watcher with the
		4353	default loop and triggering an C<ev_async> watcher from the default loop
		4354	watcher callback into the event loop interested in the signal.
3242		4355
3243	=back	4356	=back
3244		4357
		4358	=head4 THREAD LOCKING EXAMPLE
		4359
		4360	Here is a fictitious example of how to run an event loop in a different
		4361	thread than where callbacks are being invoked and watchers are
		4362	created/added/removed.
		4363
		4364	For a real-world example, see the C<EV::Loop::Async> perl module,
		4365	which uses exactly this technique (which is suited for many high-level
		4366	languages).
		4367
		4368	The example uses a pthread mutex to protect the loop data, a condition
		4369	variable to wait for callback invocations, an async watcher to notify the
		4370	event loop thread and an unspecified mechanism to wake up the main thread.
		4371
		4372	First, you need to associate some data with the event loop:
		4373
		4374	typedef struct {
		4375	mutex_t lock; /* global loop lock */
		4376	ev_async async_w;
		4377	thread_t tid;
		4378	cond_t invoke_cv;
		4379	} userdata;
		4380
		4381	void prepare_loop (EV_P)
		4382	{
		4383	// for simplicity, we use a static userdata struct.
		4384	static userdata u;
		4385
		4386	ev_async_init (&u->async_w, async_cb);
		4387	ev_async_start (EV_A_ &u->async_w);
		4388
		4389	pthread_mutex_init (&u->lock, 0);
		4390	pthread_cond_init (&u->invoke_cv, 0);
		4391
		4392	// now associate this with the loop
		4393	ev_set_userdata (EV_A_ u);
		4394	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4395	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4396
		4397	// then create the thread running ev_loop
		4398	pthread_create (&u->tid, 0, l_run, EV_A);
		4399	}
		4400
		4401	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4402	solely to wake up the event loop so it takes notice of any new watchers
		4403	that might have been added:
		4404
		4405	static void
		4406	async_cb (EV_P_ ev_async *w, int revents)
		4407	{
		4408	// just used for the side effects
		4409	}
		4410
		4411	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4412	protecting the loop data, respectively.
		4413
		4414	static void
		4415	l_release (EV_P)
		4416	{
		4417	userdata *u = ev_userdata (EV_A);
		4418	pthread_mutex_unlock (&u->lock);
		4419	}
		4420
		4421	static void
		4422	l_acquire (EV_P)
		4423	{
		4424	userdata *u = ev_userdata (EV_A);
		4425	pthread_mutex_lock (&u->lock);
		4426	}
		4427
		4428	The event loop thread first acquires the mutex, and then jumps straight
		4429	into C<ev_run>:
		4430
		4431	void *
		4432	l_run (void *thr_arg)
		4433	{
		4434	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4435
		4436	l_acquire (EV_A);
		4437	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4438	ev_run (EV_A_ 0);
		4439	l_release (EV_A);
		4440
		4441	return 0;
		4442	}
		4443
		4444	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4445	signal the main thread via some unspecified mechanism (signals? pipe
		4446	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4447	have been called (in a while loop because a) spurious wakeups are possible
		4448	and b) skipping inter-thread-communication when there are no pending
		4449	watchers is very beneficial):
		4450
		4451	static void
		4452	l_invoke (EV_P)
		4453	{
		4454	userdata *u = ev_userdata (EV_A);
		4455
		4456	while (ev_pending_count (EV_A))
		4457	{
		4458	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4459	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4460	}
		4461	}
		4462
		4463	Now, whenever the main thread gets told to invoke pending watchers, it
		4464	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4465	thread to continue:
		4466
		4467	static void
		4468	real_invoke_pending (EV_P)
		4469	{
		4470	userdata *u = ev_userdata (EV_A);
		4471
		4472	pthread_mutex_lock (&u->lock);
		4473	ev_invoke_pending (EV_A);
		4474	pthread_cond_signal (&u->invoke_cv);
		4475	pthread_mutex_unlock (&u->lock);
		4476	}
		4477
		4478	Whenever you want to start/stop a watcher or do other modifications to an
		4479	event loop, you will now have to lock:
		4480
		4481	ev_timer timeout_watcher;
		4482	userdata *u = ev_userdata (EV_A);
		4483
		4484	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4485
		4486	pthread_mutex_lock (&u->lock);
		4487	ev_timer_start (EV_A_ &timeout_watcher);
		4488	ev_async_send (EV_A_ &u->async_w);
		4489	pthread_mutex_unlock (&u->lock);
		4490
		4491	Note that sending the C<ev_async> watcher is required because otherwise
		4492	an event loop currently blocking in the kernel will have no knowledge
		4493	about the newly added timer. By waking up the loop it will pick up any new
		4494	watchers in the next event loop iteration.
		4495
3245	=head2 COROUTINES	4496	=head3 COROUTINES
3246		4497
3247	Libev is much more accommodating to coroutines ("cooperative threads"):	4498	Libev is very accommodating to coroutines ("cooperative threads"):
3248	libev fully supports nesting calls to it's functions from different	4499	libev fully supports nesting calls to its functions from different
3249	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4500	coroutines (e.g. you can call C<ev_run> on the same loop from two
3250	different coroutines and switch freely between both coroutines running the	4501	different coroutines, and switch freely between both coroutines running
3251	loop, as long as you don't confuse yourself). The only exception is that	4502	the loop, as long as you don't confuse yourself). The only exception is
3252	you must not do this from C<ev_periodic> reschedule callbacks.	4503	that you must not do this from C<ev_periodic> reschedule callbacks.
3253		4504
3254	Care has been invested into making sure that libev does not keep local	4505	Care has been taken to ensure that libev does not keep local state inside
3255	state inside C<ev_loop>, and other calls do not usually allow coroutine	4506	C<ev_run>, and other calls do not usually allow for coroutine switches as
3256	switches.	4507	they do not call any callbacks.
3257		4508
		4509	=head2 COMPILER WARNINGS
3258		4510
3259	=head1 COMPLEXITIES	4511	Depending on your compiler and compiler settings, you might get no or a
		4512	lot of warnings when compiling libev code. Some people are apparently
		4513	scared by this.
3260		4514
3261	In this section the complexities of (many of) the algorithms used inside	4515	However, these are unavoidable for many reasons. For one, each compiler
3262	libev will be explained. For complexity discussions about backends see the	4516	has different warnings, and each user has different tastes regarding
3263	documentation for C<ev_default_init>.	4517	warning options. "Warn-free" code therefore cannot be a goal except when
		4518	targeting a specific compiler and compiler-version.
3264		4519
3265	All of the following are about amortised time: If an array needs to be	4520	Another reason is that some compiler warnings require elaborate
3266	extended, libev needs to realloc and move the whole array, but this	4521	workarounds, or other changes to the code that make it less clear and less
3267	happens asymptotically never with higher number of elements, so O(1) might	4522	maintainable.
3268	mean it might do a lengthy realloc operation in rare cases, but on average
3269	it is much faster and asymptotically approaches constant time.
3270		4523
3271	=over 4	4524	And of course, some compiler warnings are just plain stupid, or simply
		4525	wrong (because they don't actually warn about the condition their message
		4526	seems to warn about). For example, certain older gcc versions had some
		4527	warnings that resulted in an extreme number of false positives. These have
		4528	been fixed, but some people still insist on making code warn-free with
		4529	such buggy versions.
3272		4530
3273	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	4531	While libev is written to generate as few warnings as possible,
		4532	"warn-free" code is not a goal, and it is recommended not to build libev
		4533	with any compiler warnings enabled unless you are prepared to cope with
		4534	them (e.g. by ignoring them). Remember that warnings are just that:
		4535	warnings, not errors, or proof of bugs.
3274		4536
3275	This means that, when you have a watcher that triggers in one hour and
3276	there are 100 watchers that would trigger before that then inserting will
3277	have to skip roughly seven (C<ld 100>) of these watchers.
3278		4537
3279	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	4538	=head2 VALGRIND
3280		4539
3281	That means that changing a timer costs less than removing/adding them	4540	Valgrind has a special section here because it is a popular tool that is
3282	as only the relative motion in the event queue has to be paid for.	4541	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3283		4542
3284	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	4543	If you think you found a bug (memory leak, uninitialised data access etc.)
		4544	in libev, then check twice: If valgrind reports something like:
3285		4545
3286	These just add the watcher into an array or at the head of a list.	4546	==2274== definitely lost: 0 bytes in 0 blocks.
		4547	==2274== possibly lost: 0 bytes in 0 blocks.
		4548	==2274== still reachable: 256 bytes in 1 blocks.
3287		4549
3288	=item Stopping check/prepare/idle/fork/async watchers: O(1)	4550	Then there is no memory leak, just as memory accounted to global variables
		4551	is not a memleak - the memory is still being referenced, and didn't leak.
3289		4552
3290	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	4553	Similarly, under some circumstances, valgrind might report kernel bugs
		4554	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		4555	although an acceptable workaround has been found here), or it might be
		4556	confused.
3291		4557
3292	These watchers are stored in lists then need to be walked to find the	4558	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3293	correct watcher to remove. The lists are usually short (you don't usually	4559	make it into some kind of religion.
3294	have many watchers waiting for the same fd or signal).
3295		4560
3296	=item Finding the next timer in each loop iteration: O(1)	4561	If you are unsure about something, feel free to contact the mailing list
		4562	with the full valgrind report and an explanation on why you think this
		4563	is a bug in libev (best check the archives, too :). However, don't be
		4564	annoyed when you get a brisk "this is no bug" answer and take the chance
		4565	of learning how to interpret valgrind properly.
3297		4566
3298	By virtue of using a binary or 4-heap, the next timer is always found at a	4567	If you need, for some reason, empty reports from valgrind for your project
3299	fixed position in the storage array.	4568	I suggest using suppression lists.
3300		4569
3301	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3302		4570
3303	A change means an I/O watcher gets started or stopped, which requires	4571	=head1 PORTABILITY NOTES
3304	libev to recalculate its status (and possibly tell the kernel, depending
3305	on backend and whether C<ev_io_set> was used).
3306		4572
3307	=item Activating one watcher (putting it into the pending state): O(1)	4573	=head2 GNU/LINUX 32 BIT LIMITATIONS
3308		4574
3309	=item Priority handling: O(number_of_priorities)	4575	GNU/Linux is the only common platform that supports 64 bit file/large file
		4576	interfaces but I<disables> them by default.
3310		4577
3311	Priorities are implemented by allocating some space for each	4578	That means that libev compiled in the default environment doesn't support
3312	priority. When doing priority-based operations, libev usually has to	4579	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
3313	linearly search all the priorities, but starting/stopping and activating
3314	watchers becomes O(1) w.r.t. priority handling.
3315		4580
3316	=item Sending an ev_async: O(1)	4581	Unfortunately, many programs try to work around this GNU/Linux issue
		4582	by enabling the large file API, which makes them incompatible with the
		4583	standard libev compiled for their system.
3317		4584
3318	=item Processing ev_async_send: O(number_of_async_watchers)	4585	Likewise, libev cannot enable the large file API itself as this would
		4586	suddenly make it incompatible to the default compile time environment,
		4587	i.e. all programs not using special compile switches.
3319		4588
3320	=item Processing signals: O(max_signal_number)	4589	=head2 OS/X AND DARWIN BUGS
3321		4590
3322	Sending involves a system call I<iff> there were no other C<ev_async_send>	4591	The whole thing is a bug if you ask me - basically any system interface
3323	calls in the current loop iteration. Checking for async and signal events	4592	you touch is broken, whether it is locales, poll, kqueue or even the
3324	involves iterating over all running async watchers or all signal numbers.	4593	OpenGL drivers.
3325		4594
3326	=back	4595	=head3 C<kqueue> is buggy
3327		4596
		4597	The kqueue syscall is broken in all known versions - most versions support
		4598	only sockets, many support pipes.
3328		4599
		4600	Libev tries to work around this by not using C<kqueue> by default on this
		4601	rotten platform, but of course you can still ask for it when creating a
		4602	loop - embedding a socket-only kqueue loop into a select-based one is
		4603	probably going to work well.
		4604
		4605	=head3 C<poll> is buggy
		4606
		4607	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4608	implementation by something calling C<kqueue> internally around the 10.5.6
		4609	release, so now C<kqueue> I<and> C<poll> are broken.
		4610
		4611	Libev tries to work around this by not using C<poll> by default on
		4612	this rotten platform, but of course you can still ask for it when creating
		4613	a loop.
		4614
		4615	=head3 C<select> is buggy
		4616
		4617	All that's left is C<select>, and of course Apple found a way to fuck this
		4618	one up as well: On OS/X, C<select> actively limits the number of file
		4619	descriptors you can pass in to 1024 - your program suddenly crashes when
		4620	you use more.
		4621
		4622	There is an undocumented "workaround" for this - defining
		4623	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4624	work on OS/X.
		4625
		4626	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4627
		4628	=head3 C<errno> reentrancy
		4629
		4630	The default compile environment on Solaris is unfortunately so
		4631	thread-unsafe that you can't even use components/libraries compiled
		4632	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4633	defined by default. A valid, if stupid, implementation choice.
		4634
		4635	If you want to use libev in threaded environments you have to make sure
		4636	it's compiled with C<_REENTRANT> defined.
		4637
		4638	=head3 Event port backend
		4639
		4640	The scalable event interface for Solaris is called "event
		4641	ports". Unfortunately, this mechanism is very buggy in all major
		4642	releases. If you run into high CPU usage, your program freezes or you get
		4643	a large number of spurious wakeups, make sure you have all the relevant
		4644	and latest kernel patches applied. No, I don't know which ones, but there
		4645	are multiple ones to apply, and afterwards, event ports actually work
		4646	great.
		4647
		4648	If you can't get it to work, you can try running the program by setting
		4649	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4650	C<select> backends.
		4651
		4652	=head2 AIX POLL BUG
		4653
		4654	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4655	this by trying to avoid the poll backend altogether (i.e. it's not even
		4656	compiled in), which normally isn't a big problem as C<select> works fine
		4657	with large bitsets on AIX, and AIX is dead anyway.
		4658
3329	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4659	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4660
		4661	=head3 General issues
3330		4662
3331	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4663	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3332	requires, and its I/O model is fundamentally incompatible with the POSIX	4664	requires, and its I/O model is fundamentally incompatible with the POSIX
3333	model. Libev still offers limited functionality on this platform in	4665	model. Libev still offers limited functionality on this platform in
3334	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4666	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3335	descriptors. This only applies when using Win32 natively, not when using	4667	descriptors. This only applies when using Win32 natively, not when using
3336	e.g. cygwin.	4668	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4669	as every compielr comes with a slightly differently broken/incompatible
		4670	environment.
3337		4671
3338	Lifting these limitations would basically require the full	4672	Lifting these limitations would basically require the full
3339	re-implementation of the I/O system. If you are into these kinds of	4673	re-implementation of the I/O system. If you are into this kind of thing,
3340	things, then note that glib does exactly that for you in a very portable	4674	then note that glib does exactly that for you in a very portable way (note
3341	way (note also that glib is the slowest event library known to man).	4675	also that glib is the slowest event library known to man).
3342		4676
3343	There is no supported compilation method available on windows except	4677	There is no supported compilation method available on windows except
3344	embedding it into other applications.	4678	embedding it into other applications.
		4679
		4680	Sensible signal handling is officially unsupported by Microsoft - libev
		4681	tries its best, but under most conditions, signals will simply not work.
3345		4682
3346	Not a libev limitation but worth mentioning: windows apparently doesn't	4683	Not a libev limitation but worth mentioning: windows apparently doesn't
3347	accept large writes: instead of resulting in a partial write, windows will	4684	accept large writes: instead of resulting in a partial write, windows will
3348	either accept everything or return C<ENOBUFS> if the buffer is too large,	4685	either accept everything or return C<ENOBUFS> if the buffer is too large,
3349	so make sure you only write small amounts into your sockets (less than a	4686	so make sure you only write small amounts into your sockets (less than a
3350	megabyte seems safe, but thsi apparently depends on the amount of memory	4687	megabyte seems safe, but this apparently depends on the amount of memory
3351	available).	4688	available).
3352		4689
3353	Due to the many, low, and arbitrary limits on the win32 platform and	4690	Due to the many, low, and arbitrary limits on the win32 platform and
3354	the abysmal performance of winsockets, using a large number of sockets	4691	the abysmal performance of winsockets, using a large number of sockets
3355	is not recommended (and not reasonable). If your program needs to use	4692	is not recommended (and not reasonable). If your program needs to use
3356	more than a hundred or so sockets, then likely it needs to use a totally	4693	more than a hundred or so sockets, then likely it needs to use a totally
3357	different implementation for windows, as libev offers the POSIX readiness	4694	different implementation for windows, as libev offers the POSIX readiness
3358	notification model, which cannot be implemented efficiently on windows	4695	notification model, which cannot be implemented efficiently on windows
3359	(Microsoft monopoly games).	4696	(due to Microsoft monopoly games).
3360		4697
3361	A typical way to use libev under windows is to embed it (see the embedding	4698	A typical way to use libev under windows is to embed it (see the embedding
3362	section for details) and use the following F<evwrap.h> header file instead	4699	section for details) and use the following F<evwrap.h> header file instead
3363	of F<ev.h>:	4700	of F<ev.h>:
3364		4701
…		…
3366	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	4703	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3367		4704
3368	#include "ev.h"	4705	#include "ev.h"
3369		4706
3370	And compile the following F<evwrap.c> file into your project (make sure	4707	And compile the following F<evwrap.c> file into your project (make sure
3371	you do I<not> compile the F<ev.c> or any other embedded soruce files!):	4708	you do I<not> compile the F<ev.c> or any other embedded source files!):
3372		4709
3373	#include "evwrap.h"	4710	#include "evwrap.h"
3374	#include "ev.c"	4711	#include "ev.c"
3375		4712
3376	=over 4
3377
3378	=item The winsocket select function	4713	=head3 The winsocket C<select> function
3379		4714
3380	The winsocket C<select> function doesn't follow POSIX in that it	4715	The winsocket C<select> function doesn't follow POSIX in that it
3381	requires socket I<handles> and not socket I<file descriptors> (it is	4716	requires socket I<handles> and not socket I<file descriptors> (it is
3382	also extremely buggy). This makes select very inefficient, and also	4717	also extremely buggy). This makes select very inefficient, and also
3383	requires a mapping from file descriptors to socket handles (the Microsoft	4718	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3392	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4727	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3393		4728
3394	Note that winsockets handling of fd sets is O(n), so you can easily get a	4729	Note that winsockets handling of fd sets is O(n), so you can easily get a
3395	complexity in the O(n²) range when using win32.	4730	complexity in the O(n²) range when using win32.
3396		4731
3397	=item Limited number of file descriptors	4732	=head3 Limited number of file descriptors
3398		4733
3399	Windows has numerous arbitrary (and low) limits on things.	4734	Windows has numerous arbitrary (and low) limits on things.
3400		4735
3401	Early versions of winsocket's select only supported waiting for a maximum	4736	Early versions of winsocket's select only supported waiting for a maximum
3402	of C<64> handles (probably owning to the fact that all windows kernels	4737	of C<64> handles (probably owning to the fact that all windows kernels
3403	can only wait for C<64> things at the same time internally; Microsoft	4738	can only wait for C<64> things at the same time internally; Microsoft
3404	recommends spawning a chain of threads and wait for 63 handles and the	4739	recommends spawning a chain of threads and wait for 63 handles and the
3405	previous thread in each. Great).	4740	previous thread in each. Sounds great!).
3406		4741
3407	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4742	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3408	to some high number (e.g. C<2048>) before compiling the winsocket select	4743	to some high number (e.g. C<2048>) before compiling the winsocket select
3409	call (which might be in libev or elsewhere, for example, perl does its own	4744	call (which might be in libev or elsewhere, for example, perl and many
3410	select emulation on windows).	4745	other interpreters do their own select emulation on windows).
3411		4746
3412	Another limit is the number of file descriptors in the Microsoft runtime	4747	Another limit is the number of file descriptors in the Microsoft runtime
3413	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4748	libraries, which by default is C<64> (there must be a hidden I<64>
3414	or something like this inside Microsoft). You can increase this by calling	4749	fetish or something like this inside Microsoft). You can increase this
3415	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4750	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3416	arbitrary limit), but is broken in many versions of the Microsoft runtime	4751	(another arbitrary limit), but is broken in many versions of the Microsoft
3417	libraries.
3418
3419	This might get you to about C<512> or C<2048> sockets (depending on	4752	runtime libraries. This might get you to about C<512> or C<2048> sockets
3420	windows version and/or the phase of the moon). To get more, you need to	4753	(depending on windows version and/or the phase of the moon). To get more,
3421	wrap all I/O functions and provide your own fd management, but the cost of	4754	you need to wrap all I/O functions and provide your own fd management, but
3422	calling select (O(n²)) will likely make this unworkable.	4755	the cost of calling select (O(n²)) will likely make this unworkable.
3423		4756
3424	=back
3425
3426
3427	=head1 PORTABILITY REQUIREMENTS	4757	=head2 PORTABILITY REQUIREMENTS
3428		4758
3429	In addition to a working ISO-C implementation, libev relies on a few	4759	In addition to a working ISO-C implementation and of course the
3430	additional extensions:	4760	backend-specific APIs, libev relies on a few additional extensions:
3431		4761
3432	=over 4	4762	=over 4
3433		4763
3434	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	4764	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3435	calling conventions regardless of C<ev_watcher_type *>.	4765	calling conventions regardless of C<ev_watcher_type *>.
…		…
3438	structure (guaranteed by POSIX but not by ISO C for example), but it also	4768	structure (guaranteed by POSIX but not by ISO C for example), but it also
3439	assumes that the same (machine) code can be used to call any watcher	4769	assumes that the same (machine) code can be used to call any watcher
3440	callback: The watcher callbacks have different type signatures, but libev	4770	callback: The watcher callbacks have different type signatures, but libev
3441	calls them using an C<ev_watcher *> internally.	4771	calls them using an C<ev_watcher *> internally.
3442		4772
		4773	=item pointer accesses must be thread-atomic
		4774
		4775	Accessing a pointer value must be atomic, it must both be readable and
		4776	writable in one piece - this is the case on all current architectures.
		4777
3443	=item C<sig_atomic_t volatile> must be thread-atomic as well	4778	=item C<sig_atomic_t volatile> must be thread-atomic as well
3444		4779
3445	The type C<sig_atomic_t volatile> (or whatever is defined as	4780	The type C<sig_atomic_t volatile> (or whatever is defined as
3446	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	4781	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3447	threads. This is not part of the specification for C<sig_atomic_t>, but is	4782	threads. This is not part of the specification for C<sig_atomic_t>, but is
3448	believed to be sufficiently portable.	4783	believed to be sufficiently portable.
3449		4784
3450	=item C<sigprocmask> must work in a threaded environment	4785	=item C<sigprocmask> must work in a threaded environment
3451		4786
…		…
3460	except the initial one, and run the default loop in the initial thread as	4795	except the initial one, and run the default loop in the initial thread as
3461	well.	4796	well.
3462		4797
3463	=item C<long> must be large enough for common memory allocation sizes	4798	=item C<long> must be large enough for common memory allocation sizes
3464		4799
3465	To improve portability and simplify using libev, libev uses C<long>	4800	To improve portability and simplify its API, libev uses C<long> internally
3466	internally instead of C<size_t> when allocating its data structures. On	4801	instead of C<size_t> when allocating its data structures. On non-POSIX
3467	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4802	systems (Microsoft...) this might be unexpectedly low, but is still at
3468	is still at least 31 bits everywhere, which is enough for hundreds of	4803	least 31 bits everywhere, which is enough for hundreds of millions of
3469	millions of watchers.	4804	watchers.
3470		4805
3471	=item C<double> must hold a time value in seconds with enough accuracy	4806	=item C<double> must hold a time value in seconds with enough accuracy
3472		4807
3473	The type C<double> is used to represent timestamps. It is required to	4808	The type C<double> is used to represent timestamps. It is required to
3474	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4809	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3475	enough for at least into the year 4000. This requirement is fulfilled by	4810	good enough for at least into the year 4000 with millisecond accuracy
		4811	(the design goal for libev). This requirement is overfulfilled by
3476	implementations implementing IEEE 754 (basically all existing ones).	4812	implementations using IEEE 754, which is basically all existing ones. With
		4813	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
3477		4814
3478	=back	4815	=back
3479		4816
3480	If you know of other additional requirements drop me a note.	4817	If you know of other additional requirements drop me a note.
3481		4818
3482		4819
3483	=head1 COMPILER WARNINGS	4820	=head1 ALGORITHMIC COMPLEXITIES
3484		4821
3485	Depending on your compiler and compiler settings, you might get no or a	4822	In this section the complexities of (many of) the algorithms used inside
3486	lot of warnings when compiling libev code. Some people are apparently	4823	libev will be documented. For complexity discussions about backends see
3487	scared by this.	4824	the documentation for C<ev_default_init>.
3488		4825
3489	However, these are unavoidable for many reasons. For one, each compiler	4826	All of the following are about amortised time: If an array needs to be
3490	has different warnings, and each user has different tastes regarding	4827	extended, libev needs to realloc and move the whole array, but this
3491	warning options. "Warn-free" code therefore cannot be a goal except when	4828	happens asymptotically rarer with higher number of elements, so O(1) might
3492	targeting a specific compiler and compiler-version.	4829	mean that libev does a lengthy realloc operation in rare cases, but on
		4830	average it is much faster and asymptotically approaches constant time.
3493		4831
3494	Another reason is that some compiler warnings require elaborate	4832	=over 4
3495	workarounds, or other changes to the code that make it less clear and less
3496	maintainable.
3497		4833
3498	And of course, some compiler warnings are just plain stupid, or simply	4834	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3499	wrong (because they don't actually warn about the condition their message
3500	seems to warn about).
3501		4835
3502	While libev is written to generate as few warnings as possible,	4836	This means that, when you have a watcher that triggers in one hour and
3503	"warn-free" code is not a goal, and it is recommended not to build libev	4837	there are 100 watchers that would trigger before that, then inserting will
3504	with any compiler warnings enabled unless you are prepared to cope with	4838	have to skip roughly seven (C<ld 100>) of these watchers.
3505	them (e.g. by ignoring them). Remember that warnings are just that:
3506	warnings, not errors, or proof of bugs.
3507		4839
		4840	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3508		4841
3509	=head1 VALGRIND	4842	That means that changing a timer costs less than removing/adding them,
		4843	as only the relative motion in the event queue has to be paid for.
3510		4844
3511	Valgrind has a special section here because it is a popular tool that is	4845	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3512	highly useful, but valgrind reports are very hard to interpret.
3513		4846
3514	If you think you found a bug (memory leak, uninitialised data access etc.)	4847	These just add the watcher into an array or at the head of a list.
3515	in libev, then check twice: If valgrind reports something like:
3516		4848
3517	==2274== definitely lost: 0 bytes in 0 blocks.	4849	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3518	==2274== possibly lost: 0 bytes in 0 blocks.
3519	==2274== still reachable: 256 bytes in 1 blocks.
3520		4850
3521	Then there is no memory leak. Similarly, under some circumstances,	4851	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3522	valgrind might report kernel bugs as if it were a bug in libev, or it
3523	might be confused (it is a very good tool, but only a tool).
3524		4852
3525	If you are unsure about something, feel free to contact the mailing list	4853	These watchers are stored in lists, so they need to be walked to find the
3526	with the full valgrind report and an explanation on why you think this is	4854	correct watcher to remove. The lists are usually short (you don't usually
3527	a bug in libev. However, don't be annoyed when you get a brisk "this is	4855	have many watchers waiting for the same fd or signal: one is typical, two
3528	no bug" answer and take the chance of learning how to interpret valgrind	4856	is rare).
3529	properly.
3530		4857
3531	If you need, for some reason, empty reports from valgrind for your project	4858	=item Finding the next timer in each loop iteration: O(1)
3532	I suggest using suppression lists.
3533		4859
		4860	By virtue of using a binary or 4-heap, the next timer is always found at a
		4861	fixed position in the storage array.
		4862
		4863	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4864
		4865	A change means an I/O watcher gets started or stopped, which requires
		4866	libev to recalculate its status (and possibly tell the kernel, depending
		4867	on backend and whether C<ev_io_set> was used).
		4868
		4869	=item Activating one watcher (putting it into the pending state): O(1)
		4870
		4871	=item Priority handling: O(number_of_priorities)
		4872
		4873	Priorities are implemented by allocating some space for each
		4874	priority. When doing priority-based operations, libev usually has to
		4875	linearly search all the priorities, but starting/stopping and activating
		4876	watchers becomes O(1) with respect to priority handling.
		4877
		4878	=item Sending an ev_async: O(1)
		4879
		4880	=item Processing ev_async_send: O(number_of_async_watchers)
		4881
		4882	=item Processing signals: O(max_signal_number)
		4883
		4884	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4885	calls in the current loop iteration. Checking for async and signal events
		4886	involves iterating over all running async watchers or all signal numbers.
		4887
		4888	=back
		4889
		4890
		4891	=head1 PORTING FROM LIBEV 3.X TO 4.X
		4892
		4893	The major version 4 introduced some incompatible changes to the API.
		4894
		4895	At the moment, the C<ev.h> header file provides compatibility definitions
		4896	for all changes, so most programs should still compile. The compatibility
		4897	layer might be removed in later versions of libev, so better update to the
		4898	new API early than late.
		4899
		4900	=over 4
		4901
		4902	=item C<EV_COMPAT3> backwards compatibility mechanism
		4903
		4904	The backward compatibility mechanism can be controlled by
		4905	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		4906	section.
		4907
		4908	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		4909
		4910	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		4911
		4912	ev_loop_destroy (EV_DEFAULT_UC);
		4913	ev_loop_fork (EV_DEFAULT);
		4914
		4915	=item function/symbol renames
		4916
		4917	A number of functions and symbols have been renamed:
		4918
		4919	ev_loop => ev_run
		4920	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		4921	EVLOOP_ONESHOT => EVRUN_ONCE
		4922
		4923	ev_unloop => ev_break
		4924	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		4925	EVUNLOOP_ONE => EVBREAK_ONE
		4926	EVUNLOOP_ALL => EVBREAK_ALL
		4927
		4928	EV_TIMEOUT => EV_TIMER
		4929
		4930	ev_loop_count => ev_iteration
		4931	ev_loop_depth => ev_depth
		4932	ev_loop_verify => ev_verify
		4933
		4934	Most functions working on C<struct ev_loop> objects don't have an
		4935	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		4936	associated constants have been renamed to not collide with the C<struct
		4937	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		4938	as all other watcher types. Note that C<ev_loop_fork> is still called
		4939	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		4940	typedef.
		4941
		4942	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		4943
		4944	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		4945	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		4946	and work, but the library code will of course be larger.
		4947
		4948	=back
		4949
		4950
		4951	=head1 GLOSSARY
		4952
		4953	=over 4
		4954
		4955	=item active
		4956
		4957	A watcher is active as long as it has been started and not yet stopped.
		4958	See L<WATCHER STATES> for details.
		4959
		4960	=item application
		4961
		4962	In this document, an application is whatever is using libev.
		4963
		4964	=item backend
		4965
		4966	The part of the code dealing with the operating system interfaces.
		4967
		4968	=item callback
		4969
		4970	The address of a function that is called when some event has been
		4971	detected. Callbacks are being passed the event loop, the watcher that
		4972	received the event, and the actual event bitset.
		4973
		4974	=item callback/watcher invocation
		4975
		4976	The act of calling the callback associated with a watcher.
		4977
		4978	=item event
		4979
		4980	A change of state of some external event, such as data now being available
		4981	for reading on a file descriptor, time having passed or simply not having
		4982	any other events happening anymore.
		4983
		4984	In libev, events are represented as single bits (such as C<EV_READ> or
		4985	C<EV_TIMER>).
		4986
		4987	=item event library
		4988
		4989	A software package implementing an event model and loop.
		4990
		4991	=item event loop
		4992
		4993	An entity that handles and processes external events and converts them
		4994	into callback invocations.
		4995
		4996	=item event model
		4997
		4998	The model used to describe how an event loop handles and processes
		4999	watchers and events.
		5000
		5001	=item pending
		5002
		5003	A watcher is pending as soon as the corresponding event has been
		5004	detected. See L<WATCHER STATES> for details.
		5005
		5006	=item real time
		5007
		5008	The physical time that is observed. It is apparently strictly monotonic :)
		5009
		5010	=item wall-clock time
		5011
		5012	The time and date as shown on clocks. Unlike real time, it can actually
		5013	be wrong and jump forwards and backwards, e.g. when the you adjust your
		5014	clock.
		5015
		5016	=item watcher
		5017
		5018	A data structure that describes interest in certain events. Watchers need
		5019	to be started (attached to an event loop) before they can receive events.
		5020
		5021	=back
3534		5022
3535	=head1 AUTHOR	5023	=head1 AUTHOR
3536		5024
3537	Marc Lehmann <libev@schmorp.de>.	5025	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5026	Magnusson and Emanuele Giaquinta.
3538		5027

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