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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 ABOUT LIBEV
70		84
71	Libev is an event loop: you register interest in certain events (such as a	85	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	86	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	87	these event sources and provide your program with events.
74		88
…		…
84	=head2 FEATURES	98	=head2 FEATURES
85		99
86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	100	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	101	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	102	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	103	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
90	with customised rescheduling (C<ev_periodic>), synchronous signals	104	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	105	timers (C<ev_timer>), absolute timers with customised rescheduling
92	watchers dealing with the event loop mechanism itself (C<ev_idle>,	106	(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	107	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	108	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
95	(C<ev_fork>).	109	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		110	limited support for fork events (C<ev_fork>).
96		111
97	It also is quite fast (see this	112	It also is quite fast (see this
98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	113	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
99	for example).	114	for example).
100		115
…		…
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	123	name C<loop> (which is always of type C<struct ev_loop *>) will not have
109	this argument.	124	this argument.
110		125
111	=head2 TIME REPRESENTATION	126	=head2 TIME REPRESENTATION
112		127
113	Libev represents time as a single floating point number, representing the	128	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	129	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	130	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	131	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	132	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	133	any calculations on it, you should treat it as some floating point value.
		134
119	component C<stamp> might indicate, it is also used for time differences	135	Unlike the name component C<stamp> might indicate, it is also used for
120	throughout libev.	136	time differences (e.g. delays) throughout libev.
121		137
122	=head1 ERROR HANDLING	138	=head1 ERROR HANDLING
123		139
124	Libev knows three classes of errors: operating system errors, usage errors	140	Libev knows three classes of errors: operating system errors, usage errors
125	and internal errors (bugs).	141	and internal errors (bugs).
…		…
149		165
150	=item ev_tstamp ev_time ()	166	=item ev_tstamp ev_time ()
151		167
152	Returns the current time as libev would use it. Please note that the	168	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	169	C<ev_now> function is usually faster and also often returns the timestamp
154	you actually want to know.	170	you actually want to know. Also interesting is the combination of
		171	C<ev_update_now> and C<ev_now>.
155		172
156	=item ev_sleep (ev_tstamp interval)	173	=item ev_sleep (ev_tstamp interval)
157		174
158	Sleep for the given interval: The current thread will be blocked until	175	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	176	either it is interrupted or the given time interval has passed. Basically
…		…
176	as this indicates an incompatible change. Minor versions are usually	193	as this indicates an incompatible change. Minor versions are usually
177	compatible to older versions, so a larger minor version alone is usually	194	compatible to older versions, so a larger minor version alone is usually
178	not a problem.	195	not a problem.
179		196
180	Example: Make sure we haven't accidentally been linked against the wrong	197	Example: Make sure we haven't accidentally been linked against the wrong
181	version.	198	version (note, however, that this will not detect other ABI mismatches,
		199	such as LFS or reentrancy).
182		200
183	assert (("libev version mismatch",	201	assert (("libev version mismatch",
184	ev_version_major () == EV_VERSION_MAJOR	202	ev_version_major () == EV_VERSION_MAJOR
185	&& ev_version_minor () >= EV_VERSION_MINOR));	203	&& ev_version_minor () >= EV_VERSION_MINOR));
186		204
…		…
197	assert (("sorry, no epoll, no sex",	215	assert (("sorry, no epoll, no sex",
198	ev_supported_backends () & EVBACKEND_EPOLL));	216	ev_supported_backends () & EVBACKEND_EPOLL));
199		217
200	=item unsigned int ev_recommended_backends ()	218	=item unsigned int ev_recommended_backends ()
201		219
202	Return the set of all backends compiled into this binary of libev and also	220	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	221	also recommended for this platform, meaning it will work for most file
		222	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	223	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	224	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	225	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.	226	probe for if you specify no backends explicitly.
208		227
209	=item unsigned int ev_embeddable_backends ()	228	=item unsigned int ev_embeddable_backends ()
210		229
211	Returns the set of backends that are embeddable in other event loops. This	230	Returns the set of backends that are embeddable in other event loops. This
212	is the theoretical, all-platform, value. To find which backends	231	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	232	current system. To find which embeddable backends might be supported on
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	233	the current system, you would need to look at C<ev_embeddable_backends ()
215	recommended ones.	234	& ev_supported_backends ()>, likewise for recommended ones.
216		235
217	See the description of C<ev_embed> watchers for more info.	236	See the description of C<ev_embed> watchers for more info.
218		237
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	238	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
220		239
221	Sets the allocation function to use (the prototype is similar - the	240	Sets the allocation function to use (the prototype is similar - the
222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	241	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
223	used to allocate and free memory (no surprises here). If it returns zero	242	used to allocate and free memory (no surprises here). If it returns zero
224	when memory needs to be allocated (C<size != 0>), the library might abort	243	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	269	}
251		270
252	...	271	...
253	ev_set_allocator (persistent_realloc);	272	ev_set_allocator (persistent_realloc);
254		273
255	=item ev_set_syserr_cb (void (*cb)(const char *msg));	274	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
256		275
257	Set the callback function to call on a retryable system call error (such	276	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	277	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	278	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	279	callback is set, then libev will expect it to remedy the situation, no
…		…
274	...	293	...
275	ev_set_syserr_cb (fatal_error);	294	ev_set_syserr_cb (fatal_error);
276		295
277	=back	296	=back
278		297
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	298	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
280		299
281	An event loop is described by a C<struct ev_loop *>. The library knows two	300	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	301	I<not> optional in this case unless libev 3 compatibility is disabled, as
283	events, and dynamically created loops which do not.	302	libev 3 had an C<ev_loop> function colliding with the struct name).
		303
		304	The library knows two types of such loops, the I<default> loop, which
		305	supports signals and child events, and dynamically created event loops
		306	which do not.
284		307
285	=over 4	308	=over 4
286		309
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	310	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		311
289	This will initialise the default event loop if it hasn't been initialised	312	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	313	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	314	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).	315	C<ev_loop_new>.
		316
		317	If the default loop is already initialised then this function simply
		318	returns it (and ignores the flags. If that is troubling you, check
		319	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		320	flags, which should almost always be C<0>, unless the caller is also the
		321	one calling C<ev_run> or otherwise qualifies as "the main program".
293		322
294	If you don't know what event loop to use, use the one returned from this	323	If you don't know what event loop to use, use the one returned from this
295	function.	324	function (or via the C<EV_DEFAULT> macro).
296		325
297	Note that this function is I<not> thread-safe, so if you want to use it	326	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,	327	from multiple threads, you have to employ some kind of mutex (note also
299	as loops cannot bes hared easily between threads anyway).	328	that this case is unlikely, as loops cannot be shared easily between
		329	threads anyway).
300		330
301	The default loop is the only loop that can handle C<ev_signal> and	331	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	332	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	333	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	334	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	335	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
306	C<ev_default_init>.	336
		337	Example: This is the most typical usage.
		338
		339	if (!ev_default_loop (0))
		340	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		341
		342	Example: Restrict libev to the select and poll backends, and do not allow
		343	environment settings to be taken into account:
		344
		345	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		346
		347	=item struct ev_loop *ev_loop_new (unsigned int flags)
		348
		349	This will create and initialise a new event loop object. If the loop
		350	could not be initialised, returns false.
		351
		352	Note that this function I<is> thread-safe, and one common way to use
		353	libev with threads is indeed to create one loop per thread, and using the
		354	default loop in the "main" or "initial" thread.
307		355
308	The flags argument can be used to specify special behaviour or specific	356	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>).	357	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
310		358
311	The following flags are supported:	359	The following flags are supported:
…		…
326	useful to try out specific backends to test their performance, or to work	374	useful to try out specific backends to test their performance, or to work
327	around bugs.	375	around bugs.
328		376
329	=item C<EVFLAG_FORKCHECK>	377	=item C<EVFLAG_FORKCHECK>
330		378
331	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	379	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	380	make libev check for a fork in each iteration by enabling this flag.
333	enabling this flag.
334		381
335	This works by calling C<getpid ()> on every iteration of the loop,	382	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	383	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	384	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	385	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
…		…
344	flag.	391	flag.
345		392
346	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	393	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
347	environment variable.	394	environment variable.
348		395
		396	=item C<EVFLAG_NOINOTIFY>
		397
		398	When this flag is specified, then libev will not attempt to use the
		399	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and
		400	testing, this flag can be useful to conserve inotify file descriptors, as
		401	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		402
		403	=item C<EVFLAG_SIGNALFD>
		404
		405	When this flag is specified, then libev will attempt to use the
		406	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API
		407	delivers signals synchronously, which makes it both faster and might make
		408	it possible to get the queued signal data. It can also simplify signal
		409	handling with threads, as long as you properly block signals in your
		410	threads that are not interested in handling them.
		411
		412	Signalfd will not be used by default as this changes your signal mask, and
		413	there are a lot of shoddy libraries and programs (glib's threadpool for
		414	example) that can't properly initialise their signal masks.
		415
349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	416	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
350		417
351	This is your standard select(2) backend. Not I<completely> standard, as	418	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,	419	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	420	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	426	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	427	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	428	a look at C<ev_set_io_collect_interval ()> to increase the amount of
362	readiness notifications you get per iteration.	429	readiness notifications you get per iteration.
363		430
		431	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		432	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		433	C<exceptfds> set on that platform).
		434
364	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	435	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
365		436
366	And this is your standard poll(2) backend. It's more complicated	437	And this is your standard poll(2) backend. It's more complicated
367	than select, but handles sparse fds better and has no artificial	438	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	439	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,	440	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	441	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
371	performance tips.	442	performance tips.
372		443
		444	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		445	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		446
373	=item C<EVBACKEND_EPOLL> (value 4, Linux)	447	=item C<EVBACKEND_EPOLL> (value 4, Linux)
		448
		449	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		450	kernels).
374		451
375	For few fds, this backend is a bit little slower than poll and select,	452	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	453	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),	454	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	455	epoll scales either O(1) or O(active_fds).
379	of shortcomings, such as silently dropping events in some hard-to-detect	456
380	cases and requiring a system call per fd change, no fork support and bad	457	The epoll mechanism deserves honorable mention as the most misdesigned
381	support for dup.	458	of the more advanced event mechanisms: mere annoyances include silently
		459	dropping file descriptors, requiring a system call per change per file
		460	descriptor (and unnecessary guessing of parameters), problems with dup and
		461	so on. The biggest issue is fork races, however - if a program forks then
		462	I<both> parent and child process have to recreate the epoll set, which can
		463	take considerable time (one syscall per file descriptor) and is of course
		464	hard to detect.
		465
		466	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		467	of course I<doesn't>, and epoll just loves to report events for totally
		468	I<different> file descriptors (even already closed ones, so one cannot
		469	even remove them from the set) than registered in the set (especially
		470	on SMP systems). Libev tries to counter these spurious notifications by
		471	employing an additional generation counter and comparing that against the
		472	events to filter out spurious ones, recreating the set when required. Last
		473	not least, it also refuses to work with some file descriptors which work
		474	perfectly fine with C<select> (files, many character devices...).
382		475
383	While stopping, setting and starting an I/O watcher in the same iteration	476	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	477	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	478	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	479	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
387	very well if you register events for both fds.	480	file descriptors might not work very well if you register events for both
388		481	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		482
393	Best performance from this backend is achieved by not unregistering all	483	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.	484	watchers for a file descriptor until it has been closed, if possible,
395	keep at least one watcher active per fd at all times.	485	i.e. keep at least one watcher active per fd at all times. Stopping and
		486	starting a watcher (without re-setting it) also usually doesn't cause
		487	extra overhead. A fork can both result in spurious notifications as well
		488	as in libev having to destroy and recreate the epoll object, which can
		489	take considerable time and thus should be avoided.
		490
		491	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		492	faster than epoll for maybe up to a hundred file descriptors, depending on
		493	the usage. So sad.
396		494
397	While nominally embeddable in other event loops, this feature is broken in	495	While nominally embeddable in other event loops, this feature is broken in
398	all kernel versions tested so far.	496	all kernel versions tested so far.
		497
		498	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		499	C<EVBACKEND_POLL>.
399		500
400	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	501	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
401		502
402	Kqueue deserves special mention, as at the time of this writing, it	503	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	504	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	505	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"	506	it's completely useless). Unlike epoll, however, whose brokenness
		507	is by design, these kqueue bugs can (and eventually will) be fixed
		508	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	509	"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)	510	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
408	system like NetBSD.	511	system like NetBSD.
409		512
410	You still can embed kqueue into a normal poll or select backend and use it	513	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	514	only for sockets (after having made sure that sockets work with kqueue on
…		…
413		516
414	It scales in the same way as the epoll backend, but the interface to the	517	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	518	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	519	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	520	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	521	two event changes per incident. Support for C<fork ()> is very bad (but
419	drops fds silently in similarly hard-to-detect cases.	522	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		523	cases
420		524
421	This backend usually performs well under most conditions.	525	This backend usually performs well under most conditions.
422		526
423	While nominally embeddable in other event loops, this doesn't work	527	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	528	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	529	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	530	(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	531	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
428	sockets.	532	also broken on OS X)) and, did I mention it, using it only for sockets.
		533
		534	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		535	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		536	C<NOTE_EOF>.
429		537
430	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	538	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
431		539
432	This is not implemented yet (and might never be, unless you send me an	540	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	541	implementation). According to reports, C</dev/poll> only supports sockets
…		…
446	While this backend scales well, it requires one system call per active	554	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	555	file descriptor per loop iteration. For small and medium numbers of file
448	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	556	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
449	might perform better.	557	might perform better.
450		558
451	On the positive side, ignoring the spurious readiness notifications, this	559	On the positive side, with the exception of the spurious readiness
452	backend actually performed to specification in all tests and is fully	560	notifications, this backend actually performed fully to specification
453	embeddable, which is a rare feat among the OS-specific backends.	561	in all tests and is fully embeddable, which is a rare feat among the
		562	OS-specific backends (I vastly prefer correctness over speed hacks).
		563
		564	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		565	C<EVBACKEND_POLL>.
454		566
455	=item C<EVBACKEND_ALL>	567	=item C<EVBACKEND_ALL>
456		568
457	Try all backends (even potentially broken ones that wouldn't be tried	569	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	570	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
460		572
461	It is definitely not recommended to use this flag.	573	It is definitely not recommended to use this flag.
462		574
463	=back	575	=back
464		576
465	If one or more of these are or'ed into the flags value, then only these	577	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	578	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.	579	here). If none are specified, all backends in C<ev_recommended_backends
468		580	()> 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		581
496	Example: Try to create a event loop that uses epoll and nothing else.	582	Example: Try to create a event loop that uses epoll and nothing else.
497		583
498	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	584	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
499	if (!epoller)	585	if (!epoller)
500	fatal ("no epoll found here, maybe it hides under your chair");	586	fatal ("no epoll found here, maybe it hides under your chair");
501		587
		588	Example: Use whatever libev has to offer, but make sure that kqueue is
		589	used if available.
		590
		591	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		592
502	=item ev_default_destroy ()	593	=item ev_loop_destroy (loop)
503		594
504	Destroys the default loop again (frees all memory and kernel state	595	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	596	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	597	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>	598	responsibility to either stop all watchers cleanly yourself I<before>
508	calling this function, or cope with the fact afterwards (which is usually	599	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	600	the easiest thing, you can just ignore the watchers and/or C<free ()> them
510	for example).	601	for example).
511		602
512	Note that certain global state, such as signal state, will not be freed by	603	Note that certain global state, such as signal state (and installed signal
513	this function, and related watchers (such as signal and child watchers)	604	handlers), will not be freed by this function, and related watchers (such
514	would need to be stopped manually.	605	as signal and child watchers) would need to be stopped manually.
515		606
516	In general it is not advisable to call this function except in the	607	This function is normally used on loop objects allocated by
517	rare occasion where you really need to free e.g. the signal handling	608	C<ev_loop_new>, but it can also be used on the default loop returned by
		609	C<ev_default_loop>, in which case it is not thread-safe.
		610
		611	Note that it is not advisable to call this function on the default loop
		612	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	613	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>).	614	and C<ev_loop_destroy>.
520		615
521	=item ev_loop_destroy (loop)	616	=item ev_loop_fork (loop)
522		617
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	618	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	619	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	620	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	621	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	622	child before resuming or calling C<ev_run>.
533	functions, and it will only take effect at the next C<ev_loop> iteration.	623
		624	Again, you I<have> to call it on I<any> loop that you want to re-use after
		625	a fork, I<even if you do not plan to use the loop in the parent>. This is
		626	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		627	during fork.
534		628
535	On the other hand, you only need to call this function in the child	629	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	630	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.	631	you just fork+exec or create a new loop in the child, you don't have to
		632	call it at all (in fact, C<epoll> is so badly broken that it makes a
		633	difference, but libev will usually detect this case on its own and do a
		634	costly reset of the backend).
538		635
539	The function itself is quite fast and it's usually not a problem to call	636	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	637	it just in case after a fork.
541	quite nicely into a call to C<pthread_atfork>:
542		638
		639	Example: Automate calling C<ev_loop_fork> on the default loop when
		640	using pthreads.
		641
		642	static void
		643	post_fork_child (void)
		644	{
		645	ev_loop_fork (EV_DEFAULT);
		646	}
		647
		648	...
543	pthread_atfork (0, 0, ev_default_fork);	649	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		650
551	=item int ev_is_default_loop (loop)	651	=item int ev_is_default_loop (loop)
552		652
553	Returns true when the given loop actually is the default loop, false otherwise.	653	Returns true when the given loop is, in fact, the default loop, and false
		654	otherwise.
554		655
555	=item unsigned int ev_loop_count (loop)	656	=item unsigned int ev_iteration (loop)
556		657
557	Returns the count of loop iterations for the loop, which is identical to	658	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	659	to the number of times libev did poll for new events. It starts at C<0>
559	happily wraps around with enough iterations.	660	and happily wraps around with enough iterations.
560		661
561	This value can sometimes be useful as a generation counter of sorts (it	662	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	663	"ticks" the number of loop iterations), as it roughly corresponds with
563	C<ev_prepare> and C<ev_check> calls.	664	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		665	prepare and check phases.
		666
		667	=item unsigned int ev_depth (loop)
		668
		669	Returns the number of times C<ev_run> was entered minus the number of
		670	times C<ev_run> was exited, in other words, the recursion depth.
		671
		672	Outside C<ev_run>, this number is zero. In a callback, this number is
		673	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		674	in which case it is higher.
		675
		676	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread
		677	etc.), doesn't count as "exit" - consider this as a hint to avoid such
		678	ungentleman-like behaviour unless it's really convenient.
564		679
565	=item unsigned int ev_backend (loop)	680	=item unsigned int ev_backend (loop)
566		681
567	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	682	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
568	use.	683	use.
…		…
577		692
578	=item ev_now_update (loop)	693	=item ev_now_update (loop)
579		694
580	Establishes the current time by querying the kernel, updating the time	695	Establishes the current time by querying the kernel, updating the time
581	returned by C<ev_now ()> in the progress. This is a costly operation and	696	returned by C<ev_now ()> in the progress. This is a costly operation and
582	is usually done automatically within C<ev_loop ()>.	697	is usually done automatically within C<ev_run ()>.
583		698
584	This function is rarely useful, but when some event callback runs for a	699	This function is rarely useful, but when some event callback runs for a
585	very long time without entering the event loop, updating libev's idea of	700	very long time without entering the event loop, updating libev's idea of
586	the current time is a good idea.	701	the current time is a good idea.
587		702
588	See also "The special problem of time updates" in the C<ev_timer> section.	703	See also L<The special problem of time updates> in the C<ev_timer> section.
589		704
		705	=item ev_suspend (loop)
		706
		707	=item ev_resume (loop)
		708
		709	These two functions suspend and resume an event loop, for use when the
		710	loop is not used for a while and timeouts should not be processed.
		711
		712	A typical use case would be an interactive program such as a game: When
		713	the user presses C<^Z> to suspend the game and resumes it an hour later it
		714	would be best to handle timeouts as if no time had actually passed while
		715	the program was suspended. This can be achieved by calling C<ev_suspend>
		716	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		717	C<ev_resume> directly afterwards to resume timer processing.
		718
		719	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		720	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		721	will be rescheduled (that is, they will lose any events that would have
		722	occurred while suspended).
		723
		724	After calling C<ev_suspend> you B<must not> call I<any> function on the
		725	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		726	without a previous call to C<ev_suspend>.
		727
		728	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		729	event loop time (see C<ev_now_update>).
		730
590	=item ev_loop (loop, int flags)	731	=item ev_run (loop, int flags)
591		732
592	Finally, this is it, the event handler. This function usually is called	733	Finally, this is it, the event handler. This function usually is called
593	after you initialised all your watchers and you want to start handling	734	after you have initialised all your watchers and you want to start
594	events.	735	handling events. It will ask the operating system for any new events, call
		736	the watcher callbacks, an then repeat the whole process indefinitely: This
		737	is why event loops are called I<loops>.
595		738
596	If the flags argument is specified as C<0>, it will not return until	739	If the flags argument is specified as C<0>, it will keep handling events
597	either no event watchers are active anymore or C<ev_unloop> was called.	740	until either no event watchers are active anymore or C<ev_break> was
		741	called.
598		742
599	Please note that an explicit C<ev_unloop> is usually better than	743	Please note that an explicit C<ev_break> is usually better than
600	relying on all watchers to be stopped when deciding when a program has	744	relying on all watchers to be stopped when deciding when a program has
601	finished (especially in interactive programs), but having a program that	745	finished (especially in interactive programs), but having a program
602	automatically loops as long as it has to and no longer by virtue of	746	that automatically loops as long as it has to and no longer by virtue
603	relying on its watchers stopping correctly is a thing of beauty.	747	of relying on its watchers stopping correctly, that is truly a thing of
		748	beauty.
604		749
605	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	750	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
606	those events and any outstanding ones, but will not block your process in	751	those events and any already outstanding ones, but will not wait and
607	case there are no events and will return after one iteration of the loop.	752	block your process in case there are no events and will return after one
		753	iteration of the loop. This is sometimes useful to poll and handle new
		754	events while doing lengthy calculations, to keep the program responsive.
608		755
609	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	756	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
610	necessary) and will handle those and any outstanding ones. It will block	757	necessary) and will handle those and any already outstanding ones. It
611	your process until at least one new event arrives, and will return after	758	will block your process until at least one new event arrives (which could
612	one iteration of the loop. This is useful if you are waiting for some	759	be an event internal to libev itself, so there is no guarantee that a
613	external event in conjunction with something not expressible using other	760	user-registered callback will be called), and will return after one
		761	iteration of the loop.
		762
		763	This is useful if you are waiting for some external event in conjunction
		764	with something not expressible using other libev watchers (i.e. "roll your
614	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	765	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
615	usually a better approach for this kind of thing.	766	usually a better approach for this kind of thing.
616		767
617	Here are the gory details of what C<ev_loop> does:	768	Here are the gory details of what C<ev_run> does:
618		769
		770	- Increment loop depth.
		771	- Reset the ev_break status.
619	- Before the first iteration, call any pending watchers.	772	- Before the first iteration, call any pending watchers.
		773	LOOP:
620	* If EVFLAG_FORKCHECK was used, check for a fork.	774	- If EVFLAG_FORKCHECK was used, check for a fork.
621	- If a fork was detected (by any means), queue and call all fork watchers.	775	- If a fork was detected (by any means), queue and call all fork watchers.
622	- Queue and call all prepare watchers.	776	- Queue and call all prepare watchers.
		777	- If ev_break was called, goto FINISH.
623	- If we have been forked, detach and recreate the kernel state	778	- If we have been forked, detach and recreate the kernel state
624	as to not disturb the other process.	779	as to not disturb the other process.
625	- Update the kernel state with all outstanding changes.	780	- Update the kernel state with all outstanding changes.
626	- Update the "event loop time" (ev_now ()).	781	- Update the "event loop time" (ev_now ()).
627	- Calculate for how long to sleep or block, if at all	782	- Calculate for how long to sleep or block, if at all
628	(active idle watchers, EVLOOP_NONBLOCK or not having	783	(active idle watchers, EVRUN_NOWAIT or not having
629	any active watchers at all will result in not sleeping).	784	any active watchers at all will result in not sleeping).
630	- Sleep if the I/O and timer collect interval say so.	785	- Sleep if the I/O and timer collect interval say so.
		786	- Increment loop iteration counter.
631	- Block the process, waiting for any events.	787	- Block the process, waiting for any events.
632	- Queue all outstanding I/O (fd) events.	788	- Queue all outstanding I/O (fd) events.
633	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	789	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
634	- Queue all outstanding timers.	790	- Queue all expired timers.
635	- Queue all outstanding periodics.	791	- Queue all expired periodics.
636	- Unless any events are pending now, queue all idle watchers.	792	- Queue all idle watchers with priority higher than that of pending events.
637	- Queue all check watchers.	793	- Queue all check watchers.
638	- Call all queued watchers in reverse order (i.e. check watchers first).	794	- Call all queued watchers in reverse order (i.e. check watchers first).
639	Signals and child watchers are implemented as I/O watchers, and will	795	Signals and child watchers are implemented as I/O watchers, and will
640	be handled here by queueing them when their watcher gets executed.	796	be handled here by queueing them when their watcher gets executed.
641	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	797	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
642	were used, or there are no active watchers, return, otherwise	798	were used, or there are no active watchers, goto FINISH, otherwise
643	continue with step *.	799	continue with step LOOP.
		800	FINISH:
		801	- Reset the ev_break status iff it was EVBREAK_ONE.
		802	- Decrement the loop depth.
		803	- Return.
644		804
645	Example: Queue some jobs and then loop until no events are outstanding	805	Example: Queue some jobs and then loop until no events are outstanding
646	anymore.	806	anymore.
647		807
648	... queue jobs here, make sure they register event watchers as long	808	... queue jobs here, make sure they register event watchers as long
649	... as they still have work to do (even an idle watcher will do..)	809	... as they still have work to do (even an idle watcher will do..)
650	ev_loop (my_loop, 0);	810	ev_run (my_loop, 0);
651	... jobs done or somebody called unloop. yeah!	811	... jobs done or somebody called unloop. yeah!
652		812
653	=item ev_unloop (loop, how)	813	=item ev_break (loop, how)
654		814
655	Can be used to make a call to C<ev_loop> return early (but only after it	815	Can be used to make a call to C<ev_run> return early (but only after it
656	has processed all outstanding events). The C<how> argument must be either	816	has processed all outstanding events). The C<how> argument must be either
657	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	817	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
658	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	818	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
659		819
660	This "unloop state" will be cleared when entering C<ev_loop> again.	820	This "unloop state" will be cleared when entering C<ev_run> again.
		821
		822	It is safe to call C<ev_break> from outside any C<ev_run> calls. ##TODO##
661		823
662	=item ev_ref (loop)	824	=item ev_ref (loop)
663		825
664	=item ev_unref (loop)	826	=item ev_unref (loop)
665		827
666	Ref/unref can be used to add or remove a reference count on the event	828	Ref/unref can be used to add or remove a reference count on the event
667	loop: Every watcher keeps one reference, and as long as the reference	829	loop: Every watcher keeps one reference, and as long as the reference
668	count is nonzero, C<ev_loop> will not return on its own. If you have	830	count is nonzero, C<ev_run> will not return on its own.
669	a watcher you never unregister that should not keep C<ev_loop> from	831
670	returning, ev_unref() after starting, and ev_ref() before stopping it. For	832	This is useful when you have a watcher that you never intend to
		833	unregister, but that nevertheless should not keep C<ev_run> from
		834	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
		835	before stopping it.
		836
671	example, libev itself uses this for its internal signal pipe: It is not	837	As an example, libev itself uses this for its internal signal pipe: It
672	visible to the libev user and should not keep C<ev_loop> from exiting if	838	is not visible to the libev user and should not keep C<ev_run> from
673	no event watchers registered by it are active. It is also an excellent	839	exiting if no event watchers registered by it are active. It is also an
674	way to do this for generic recurring timers or from within third-party	840	excellent way to do this for generic recurring timers or from within
675	libraries. Just remember to I<unref after start> and I<ref before stop>	841	third-party libraries. Just remember to I<unref after start> and I<ref
676	(but only if the watcher wasn't active before, or was active before,	842	before stop> (but only if the watcher wasn't active before, or was active
677	respectively).	843	before, respectively. Note also that libev might stop watchers itself
		844	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		845	in the callback).
678		846
679	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	847	Example: Create a signal watcher, but keep it from keeping C<ev_run>
680	running when nothing else is active.	848	running when nothing else is active.
681		849
682	struct ev_signal exitsig;	850	ev_signal exitsig;
683	ev_signal_init (&exitsig, sig_cb, SIGINT);	851	ev_signal_init (&exitsig, sig_cb, SIGINT);
684	ev_signal_start (loop, &exitsig);	852	ev_signal_start (loop, &exitsig);
685	evf_unref (loop);	853	evf_unref (loop);
686		854
687	Example: For some weird reason, unregister the above signal handler again.	855	Example: For some weird reason, unregister the above signal handler again.
…		…
701	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	869	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
702	allows libev to delay invocation of I/O and timer/periodic callbacks	870	allows libev to delay invocation of I/O and timer/periodic callbacks
703	to increase efficiency of loop iterations (or to increase power-saving	871	to increase efficiency of loop iterations (or to increase power-saving
704	opportunities).	872	opportunities).
705		873
706	The background is that sometimes your program runs just fast enough to	874	The idea is that sometimes your program runs just fast enough to handle
707	handle one (or very few) event(s) per loop iteration. While this makes	875	one (or very few) event(s) per loop iteration. While this makes the
708	the program responsive, it also wastes a lot of CPU time to poll for new	876	program responsive, it also wastes a lot of CPU time to poll for new
709	events, especially with backends like C<select ()> which have a high	877	events, especially with backends like C<select ()> which have a high
710	overhead for the actual polling but can deliver many events at once.	878	overhead for the actual polling but can deliver many events at once.
711		879
712	By setting a higher I<io collect interval> you allow libev to spend more	880	By setting a higher I<io collect interval> you allow libev to spend more
713	time collecting I/O events, so you can handle more events per iteration,	881	time collecting I/O events, so you can handle more events per iteration,
714	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	882	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
715	C<ev_timer>) will be not affected. Setting this to a non-null value will	883	C<ev_timer>) will be not affected. Setting this to a non-null value will
716	introduce an additional C<ev_sleep ()> call into most loop iterations.	884	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		885	sleep time ensures that libev will not poll for I/O events more often then
		886	once per this interval, on average.
717		887
718	Likewise, by setting a higher I<timeout collect interval> you allow libev	888	Likewise, by setting a higher I<timeout collect interval> you allow libev
719	to spend more time collecting timeouts, at the expense of increased	889	to spend more time collecting timeouts, at the expense of increased
720	latency (the watcher callback will be called later). C<ev_io> watchers	890	latency/jitter/inexactness (the watcher callback will be called
721	will not be affected. Setting this to a non-null value will not introduce	891	later). C<ev_io> watchers will not be affected. Setting this to a non-null
722	any overhead in libev.	892	value will not introduce any overhead in libev.
723		893
724	Many (busy) programs can usually benefit by setting the I/O collect	894	Many (busy) programs can usually benefit by setting the I/O collect
725	interval to a value near C<0.1> or so, which is often enough for	895	interval to a value near C<0.1> or so, which is often enough for
726	interactive servers (of course not for games), likewise for timeouts. It	896	interactive servers (of course not for games), likewise for timeouts. It
727	usually doesn't make much sense to set it to a lower value than C<0.01>,	897	usually doesn't make much sense to set it to a lower value than C<0.01>,
728	as this approaches the timing granularity of most systems.	898	as this approaches the timing granularity of most systems. Note that if
		899	you do transactions with the outside world and you can't increase the
		900	parallelity, then this setting will limit your transaction rate (if you
		901	need to poll once per transaction and the I/O collect interval is 0.01,
		902	then you can't do more than 100 transactions per second).
729		903
730	Setting the I<timeout collect interval> can improve the opportunity for	904	Setting the I<timeout collect interval> can improve the opportunity for
731	saving power, as the program will "bundle" timer callback invocations that	905	saving power, as the program will "bundle" timer callback invocations that
732	are "near" in time together, by delaying some, thus reducing the number of	906	are "near" in time together, by delaying some, thus reducing the number of
733	times the process sleeps and wakes up again. Another useful technique to	907	times the process sleeps and wakes up again. Another useful technique to
734	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	908	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
735	they fire on, say, one-second boundaries only.	909	they fire on, say, one-second boundaries only.
736		910
		911	Example: we only need 0.1s timeout granularity, and we wish not to poll
		912	more often than 100 times per second:
		913
		914	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		915	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		916
		917	=item ev_invoke_pending (loop)
		918
		919	This call will simply invoke all pending watchers while resetting their
		920	pending state. Normally, C<ev_run> does this automatically when required,
		921	but when overriding the invoke callback this call comes handy. This
		922	function can be invoked from a watcher - this can be useful for example
		923	when you want to do some lengthy calculation and want to pass further
		924	event handling to another thread (you still have to make sure only one
		925	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		926
		927	=item int ev_pending_count (loop)
		928
		929	Returns the number of pending watchers - zero indicates that no watchers
		930	are pending.
		931
		932	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		933
		934	This overrides the invoke pending functionality of the loop: Instead of
		935	invoking all pending watchers when there are any, C<ev_run> will call
		936	this callback instead. This is useful, for example, when you want to
		937	invoke the actual watchers inside another context (another thread etc.).
		938
		939	If you want to reset the callback, use C<ev_invoke_pending> as new
		940	callback.
		941
		942	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		943
		944	Sometimes you want to share the same loop between multiple threads. This
		945	can be done relatively simply by putting mutex_lock/unlock calls around
		946	each call to a libev function.
		947
		948	However, C<ev_run> can run an indefinite time, so it is not feasible
		949	to wait for it to return. One way around this is to wake up the event
		950	loop via C<ev_break> and C<av_async_send>, another way is to set these
		951	I<release> and I<acquire> callbacks on the loop.
		952
		953	When set, then C<release> will be called just before the thread is
		954	suspended waiting for new events, and C<acquire> is called just
		955	afterwards.
		956
		957	Ideally, C<release> will just call your mutex_unlock function, and
		958	C<acquire> will just call the mutex_lock function again.
		959
		960	While event loop modifications are allowed between invocations of
		961	C<release> and C<acquire> (that's their only purpose after all), no
		962	modifications done will affect the event loop, i.e. adding watchers will
		963	have no effect on the set of file descriptors being watched, or the time
		964	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		965	to take note of any changes you made.
		966
		967	In theory, threads executing C<ev_run> will be async-cancel safe between
		968	invocations of C<release> and C<acquire>.
		969
		970	See also the locking example in the C<THREADS> section later in this
		971	document.
		972
		973	=item ev_set_userdata (loop, void *data)
		974
		975	=item ev_userdata (loop)
		976
		977	Set and retrieve a single C<void *> associated with a loop. When
		978	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		979	C<0.>
		980
		981	These two functions can be used to associate arbitrary data with a loop,
		982	and are intended solely for the C<invoke_pending_cb>, C<release> and
		983	C<acquire> callbacks described above, but of course can be (ab-)used for
		984	any other purpose as well.
		985
737	=item ev_loop_verify (loop)	986	=item ev_verify (loop)
738		987
739	This function only does something when C<EV_VERIFY> support has been	988	This function only does something when C<EV_VERIFY> support has been
740	compiled in. It tries to go through all internal structures and checks	989	compiled in, which is the default for non-minimal builds. It tries to go
741	them for validity. If anything is found to be inconsistent, it will print	990	through all internal structures and checks them for validity. If anything
742	an error message to standard error and call C<abort ()>.	991	is found to be inconsistent, it will print an error message to standard
		992	error and call C<abort ()>.
743		993
744	This can be used to catch bugs inside libev itself: under normal	994	This can be used to catch bugs inside libev itself: under normal
745	circumstances, this function will never abort as of course libev keeps its	995	circumstances, this function will never abort as of course libev keeps its
746	data structures consistent.	996	data structures consistent.
747		997
748	=back	998	=back
749		999
750		1000
751	=head1 ANATOMY OF A WATCHER	1001	=head1 ANATOMY OF A WATCHER
752		1002
		1003	In the following description, uppercase C<TYPE> in names stands for the
		1004	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		1005	watchers and C<ev_io_start> for I/O watchers.
		1006
753	A watcher is a structure that you create and register to record your	1007	A watcher is an opaque structure that you allocate and register to record
754	interest in some event. For instance, if you want to wait for STDIN to	1008	your interest in some event. To make a concrete example, imagine you want
755	become readable, you would create an C<ev_io> watcher for that:	1009	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1010	for that:
756		1011
757	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1012	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
758	{	1013	{
759	ev_io_stop (w);	1014	ev_io_stop (w);
760	ev_unloop (loop, EVUNLOOP_ALL);	1015	ev_break (loop, EVBREAK_ALL);
761	}	1016	}
762		1017
763	struct ev_loop *loop = ev_default_loop (0);	1018	struct ev_loop *loop = ev_default_loop (0);
		1019
764	struct ev_io stdin_watcher;	1020	ev_io stdin_watcher;
		1021
765	ev_init (&stdin_watcher, my_cb);	1022	ev_init (&stdin_watcher, my_cb);
766	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1023	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
767	ev_io_start (loop, &stdin_watcher);	1024	ev_io_start (loop, &stdin_watcher);
		1025
768	ev_loop (loop, 0);	1026	ev_run (loop, 0);
769		1027
770	As you can see, you are responsible for allocating the memory for your	1028	As you can see, you are responsible for allocating the memory for your
771	watcher structures (and it is usually a bad idea to do this on the stack,	1029	watcher structures (and it is I<usually> a bad idea to do this on the
772	although this can sometimes be quite valid).	1030	stack).
773		1031
		1032	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		1033	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
		1034
774	Each watcher structure must be initialised by a call to C<ev_init	1035	Each watcher structure must be initialised by a call to C<ev_init (watcher
775	(watcher *, callback)>, which expects a callback to be provided. This	1036	*, callback)>, which expects a callback to be provided. This callback is
776	callback gets invoked each time the event occurs (or, in the case of I/O	1037	invoked each time the event occurs (or, in the case of I/O watchers, each
777	watchers, each time the event loop detects that the file descriptor given	1038	time the event loop detects that the file descriptor given is readable
778	is readable and/or writable).	1039	and/or writable).
779		1040
780	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1041	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
781	with arguments specific to this watcher type. There is also a macro	1042	macro to configure it, with arguments specific to the watcher type. There
782	to combine initialisation and setting in one call: C<< ev_<type>_init	1043	is also a macro to combine initialisation and setting in one call: C<<
783	(watcher *, callback, ...) >>.	1044	ev_TYPE_init (watcher *, callback, ...) >>.
784		1045
785	To make the watcher actually watch out for events, you have to start it	1046	To make the watcher actually watch out for events, you have to start it
786	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	1047	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
787	*) >>), and you can stop watching for events at any time by calling the	1048	*) >>), and you can stop watching for events at any time by calling the
788	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1049	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
789		1050
790	As long as your watcher is active (has been started but not stopped) you	1051	As long as your watcher is active (has been started but not stopped) you
791	must not touch the values stored in it. Most specifically you must never	1052	must not touch the values stored in it. Most specifically you must never
792	reinitialise it or call its C<set> macro.	1053	reinitialise it or call its C<ev_TYPE_set> macro.
793		1054
794	Each and every callback receives the event loop pointer as first, the	1055	Each and every callback receives the event loop pointer as first, the
795	registered watcher structure as second, and a bitset of received events as	1056	registered watcher structure as second, and a bitset of received events as
796	third argument.	1057	third argument.
797		1058
…		…
806	=item C<EV_WRITE>	1067	=item C<EV_WRITE>
807		1068
808	The file descriptor in the C<ev_io> watcher has become readable and/or	1069	The file descriptor in the C<ev_io> watcher has become readable and/or
809	writable.	1070	writable.
810		1071
811	=item C<EV_TIMEOUT>	1072	=item C<EV_TIMER>
812		1073
813	The C<ev_timer> watcher has timed out.	1074	The C<ev_timer> watcher has timed out.
814		1075
815	=item C<EV_PERIODIC>	1076	=item C<EV_PERIODIC>
816		1077
…		…
834		1095
835	=item C<EV_PREPARE>	1096	=item C<EV_PREPARE>
836		1097
837	=item C<EV_CHECK>	1098	=item C<EV_CHECK>
838		1099
839	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1100	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
840	to gather new events, and all C<ev_check> watchers are invoked just after	1101	to gather new events, and all C<ev_check> watchers are invoked just after
841	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1102	C<ev_run> has gathered them, but before it invokes any callbacks for any
842	received events. Callbacks of both watcher types can start and stop as	1103	received events. Callbacks of both watcher types can start and stop as
843	many watchers as they want, and all of them will be taken into account	1104	many watchers as they want, and all of them will be taken into account
844	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1105	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
845	C<ev_loop> from blocking).	1106	C<ev_run> from blocking).
846		1107
847	=item C<EV_EMBED>	1108	=item C<EV_EMBED>
848		1109
849	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1110	The embedded event loop specified in the C<ev_embed> watcher needs attention.
850		1111
851	=item C<EV_FORK>	1112	=item C<EV_FORK>
852		1113
853	The event loop has been resumed in the child process after fork (see	1114	The event loop has been resumed in the child process after fork (see
854	C<ev_fork>).	1115	C<ev_fork>).
855		1116
		1117	=item C<EV_CLEANUP>
		1118
		1119	The event loop is abotu to be destroyed (see C<ev_cleanup>).
		1120
856	=item C<EV_ASYNC>	1121	=item C<EV_ASYNC>
857		1122
858	The given async watcher has been asynchronously notified (see C<ev_async>).	1123	The given async watcher has been asynchronously notified (see C<ev_async>).
		1124
		1125	=item C<EV_CUSTOM>
		1126
		1127	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1128	by libev users to signal watchers (e.g. via C<ev_feed_event>).
859		1129
860	=item C<EV_ERROR>	1130	=item C<EV_ERROR>
861		1131
862	An unspecified error has occurred, the watcher has been stopped. This might	1132	An unspecified error has occurred, the watcher has been stopped. This might
863	happen because the watcher could not be properly started because libev	1133	happen because the watcher could not be properly started because libev
864	ran out of memory, a file descriptor was found to be closed or any other	1134	ran out of memory, a file descriptor was found to be closed or any other
		1135	problem. Libev considers these application bugs.
		1136
865	problem. You best act on it by reporting the problem and somehow coping	1137	You best act on it by reporting the problem and somehow coping with the
866	with the watcher being stopped.	1138	watcher being stopped. Note that well-written programs should not receive
		1139	an error ever, so when your watcher receives it, this usually indicates a
		1140	bug in your program.
867		1141
868	Libev will usually signal a few "dummy" events together with an error,	1142	Libev will usually signal a few "dummy" events together with an error, for
869	for example it might indicate that a fd is readable or writable, and if	1143	example it might indicate that a fd is readable or writable, and if your
870	your callbacks is well-written it can just attempt the operation and cope	1144	callbacks is well-written it can just attempt the operation and cope with
871	with the error from read() or write(). This will not work in multi-threaded	1145	the error from read() or write(). This will not work in multi-threaded
872	programs, though, so beware.	1146	programs, though, as the fd could already be closed and reused for another
		1147	thing, so beware.
873		1148
874	=back	1149	=back
875		1150
		1151	=head2 WATCHER STATES
		1152
		1153	There are various watcher states mentioned throughout this manual -
		1154	active, pending and so on. In this section these states and the rules to
		1155	transition between them will be described in more detail - and while these
		1156	rules might look complicated, they usually do "the right thing".
		1157
		1158	=over 4
		1159
		1160	=item initialiased
		1161
		1162	Before a watcher can be registered with the event looop it has to be
		1163	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1164	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1165
		1166	In this state it is simply some block of memory that is suitable for use
		1167	in an event loop. It can be moved around, freed, reused etc. at will.
		1168
		1169	=item started/running/active
		1170
		1171	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1172	property of the event loop, and is actively waiting for events. While in
		1173	this state it cannot be accessed (except in a few documented ways), moved,
		1174	freed or anything else - the only legal thing is to keep a pointer to it,
		1175	and call libev functions on it that are documented to work on active watchers.
		1176
		1177	=item pending
		1178
		1179	If a watcher is active and libev determines that an event it is interested
		1180	in has occurred (such as a timer expiring), it will become pending. It will
		1181	stay in this pending state until either it is stopped or its callback is
		1182	about to be invoked, so it is not normally pending inside the watcher
		1183	callback.
		1184
		1185	The watcher might or might not be active while it is pending (for example,
		1186	an expired non-repeating timer can be pending but no longer active). If it
		1187	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1188	but it is still property of the event loop at this time, so cannot be
		1189	moved, freed or reused. And if it is active the rules described in the
		1190	previous item still apply.
		1191
		1192	It is also possible to feed an event on a watcher that is not active (e.g.
		1193	via C<ev_feed_event>), in which case it becomes pending without being
		1194	active.
		1195
		1196	=item stopped
		1197
		1198	A watcher can be stopped implicitly by libev (in which case it might still
		1199	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1200	latter will clear any pending state the watcher might be in, regardless
		1201	of whether it was active or not, so stopping a watcher explicitly before
		1202	freeing it is often a good idea.
		1203
		1204	While stopped (and not pending) the watcher is essentially in the
		1205	initialised state, that is it can be reused, moved, modified in any way
		1206	you wish.
		1207
		1208	=back
		1209
876	=head2 GENERIC WATCHER FUNCTIONS	1210	=head2 GENERIC WATCHER FUNCTIONS
877
878	In the following description, C<TYPE> stands for the watcher type,
879	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
880		1211
881	=over 4	1212	=over 4
882		1213
883	=item C<ev_init> (ev_TYPE *watcher, callback)	1214	=item C<ev_init> (ev_TYPE *watcher, callback)
884		1215
…		…
890	which rolls both calls into one.	1221	which rolls both calls into one.
891		1222
892	You can reinitialise a watcher at any time as long as it has been stopped	1223	You can reinitialise a watcher at any time as long as it has been stopped
893	(or never started) and there are no pending events outstanding.	1224	(or never started) and there are no pending events outstanding.
894		1225
895	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1226	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
896	int revents)>.	1227	int revents)>.
897		1228
		1229	Example: Initialise an C<ev_io> watcher in two steps.
		1230
		1231	ev_io w;
		1232	ev_init (&w, my_cb);
		1233	ev_io_set (&w, STDIN_FILENO, EV_READ);
		1234
898	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1235	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
899		1236
900	This macro initialises the type-specific parts of a watcher. You need to	1237	This macro initialises the type-specific parts of a watcher. You need to
901	call C<ev_init> at least once before you call this macro, but you can	1238	call C<ev_init> at least once before you call this macro, but you can
902	call C<ev_TYPE_set> any number of times. You must not, however, call this	1239	call C<ev_TYPE_set> any number of times. You must not, however, call this
903	macro on a watcher that is active (it can be pending, however, which is a	1240	macro on a watcher that is active (it can be pending, however, which is a
904	difference to the C<ev_init> macro).	1241	difference to the C<ev_init> macro).
905		1242
906	Although some watcher types do not have type-specific arguments	1243	Although some watcher types do not have type-specific arguments
907	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	1244	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
908		1245
		1246	See C<ev_init>, above, for an example.
		1247
909	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1248	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
910		1249
911	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1250	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
912	calls into a single call. This is the most convenient method to initialise	1251	calls into a single call. This is the most convenient method to initialise
913	a watcher. The same limitations apply, of course.	1252	a watcher. The same limitations apply, of course.
914		1253
		1254	Example: Initialise and set an C<ev_io> watcher in one step.
		1255
		1256	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1257
915	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1258	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
916		1259
917	Starts (activates) the given watcher. Only active watchers will receive	1260	Starts (activates) the given watcher. Only active watchers will receive
918	events. If the watcher is already active nothing will happen.	1261	events. If the watcher is already active nothing will happen.
919		1262
		1263	Example: Start the C<ev_io> watcher that is being abused as example in this
		1264	whole section.
		1265
		1266	ev_io_start (EV_DEFAULT_UC, &w);
		1267
920	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1268	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
921		1269
922	Stops the given watcher again (if active) and clears the pending	1270	Stops the given watcher if active, and clears the pending status (whether
		1271	the watcher was active or not).
		1272
923	status. It is possible that stopped watchers are pending (for example,	1273	It is possible that stopped watchers are pending - for example,
924	non-repeating timers are being stopped when they become pending), but	1274	non-repeating timers are being stopped when they become pending - but
925	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1275	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
926	you want to free or reuse the memory used by the watcher it is therefore a	1276	pending. If you want to free or reuse the memory used by the watcher it is
927	good idea to always call its C<ev_TYPE_stop> function.	1277	therefore a good idea to always call its C<ev_TYPE_stop> function.
928		1278
929	=item bool ev_is_active (ev_TYPE *watcher)	1279	=item bool ev_is_active (ev_TYPE *watcher)
930		1280
931	Returns a true value iff the watcher is active (i.e. it has been started	1281	Returns a true value iff the watcher is active (i.e. it has been started
932	and not yet been stopped). As long as a watcher is active you must not modify	1282	and not yet been stopped). As long as a watcher is active you must not modify
…		…
948	=item ev_cb_set (ev_TYPE *watcher, callback)	1298	=item ev_cb_set (ev_TYPE *watcher, callback)
949		1299
950	Change the callback. You can change the callback at virtually any time	1300	Change the callback. You can change the callback at virtually any time
951	(modulo threads).	1301	(modulo threads).
952		1302
953	=item ev_set_priority (ev_TYPE *watcher, priority)	1303	=item ev_set_priority (ev_TYPE *watcher, int priority)
954		1304
955	=item int ev_priority (ev_TYPE *watcher)	1305	=item int ev_priority (ev_TYPE *watcher)
956		1306
957	Set and query the priority of the watcher. The priority is a small	1307	Set and query the priority of the watcher. The priority is a small
958	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1308	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
959	(default: C<-2>). Pending watchers with higher priority will be invoked	1309	(default: C<-2>). Pending watchers with higher priority will be invoked
960	before watchers with lower priority, but priority will not keep watchers	1310	before watchers with lower priority, but priority will not keep watchers
961	from being executed (except for C<ev_idle> watchers).	1311	from being executed (except for C<ev_idle> watchers).
962		1312
963	This means that priorities are I<only> used for ordering callback
964	invocation after new events have been received. This is useful, for
965	example, to reduce latency after idling, or more often, to bind two
966	watchers on the same event and make sure one is called first.
967
968	If you need to suppress invocation when higher priority events are pending	1313	If you need to suppress invocation when higher priority events are pending
969	you need to look at C<ev_idle> watchers, which provide this functionality.	1314	you need to look at C<ev_idle> watchers, which provide this functionality.
970		1315
971	You I<must not> change the priority of a watcher as long as it is active or	1316	You I<must not> change the priority of a watcher as long as it is active or
972	pending.	1317	pending.
973		1318
		1319	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1320	fine, as long as you do not mind that the priority value you query might
		1321	or might not have been clamped to the valid range.
		1322
974	The default priority used by watchers when no priority has been set is	1323	The default priority used by watchers when no priority has been set is
975	always C<0>, which is supposed to not be too high and not be too low :).	1324	always C<0>, which is supposed to not be too high and not be too low :).
976		1325
977	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1326	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
978	fine, as long as you do not mind that the priority value you query might	1327	priorities.
979	or might not have been adjusted to be within valid range.
980		1328
981	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1329	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
982		1330
983	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1331	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
984	C<loop> nor C<revents> need to be valid as long as the watcher callback	1332	C<loop> nor C<revents> need to be valid as long as the watcher callback
985	can deal with that fact.	1333	can deal with that fact, as both are simply passed through to the
		1334	callback.
986		1335
987	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1336	=item int ev_clear_pending (loop, ev_TYPE *watcher)
988		1337
989	If the watcher is pending, this function returns clears its pending status	1338	If the watcher is pending, this function clears its pending status and
990	and returns its C<revents> bitset (as if its callback was invoked). If the	1339	returns its C<revents> bitset (as if its callback was invoked). If the
991	watcher isn't pending it does nothing and returns C<0>.	1340	watcher isn't pending it does nothing and returns C<0>.
992		1341
		1342	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1343	callback to be invoked, which can be accomplished with this function.
		1344
		1345	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1346
		1347	Feeds the given event set into the event loop, as if the specified event
		1348	had happened for the specified watcher (which must be a pointer to an
		1349	initialised but not necessarily started event watcher). Obviously you must
		1350	not free the watcher as long as it has pending events.
		1351
		1352	Stopping the watcher, letting libev invoke it, or calling
		1353	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1354	not started in the first place.
		1355
		1356	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1357	functions that do not need a watcher.
		1358
993	=back	1359	=back
994		1360
995		1361
996	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1362	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
997		1363
998	Each watcher has, by default, a member C<void *data> that you can change	1364	Each watcher has, by default, a member C<void *data> that you can change
999	and read at any time, libev will completely ignore it. This can be used	1365	and read at any time: libev will completely ignore it. This can be used
1000	to associate arbitrary data with your watcher. If you need more data and	1366	to associate arbitrary data with your watcher. If you need more data and
1001	don't want to allocate memory and store a pointer to it in that data	1367	don't want to allocate memory and store a pointer to it in that data
1002	member, you can also "subclass" the watcher type and provide your own	1368	member, you can also "subclass" the watcher type and provide your own
1003	data:	1369	data:
1004		1370
1005	struct my_io	1371	struct my_io
1006	{	1372	{
1007	struct ev_io io;	1373	ev_io io;
1008	int otherfd;	1374	int otherfd;
1009	void *somedata;	1375	void *somedata;
1010	struct whatever *mostinteresting;	1376	struct whatever *mostinteresting;
1011	};	1377	};
1012		1378
…		…
1015	ev_io_init (&w.io, my_cb, fd, EV_READ);	1381	ev_io_init (&w.io, my_cb, fd, EV_READ);
1016		1382
1017	And since your callback will be called with a pointer to the watcher, you	1383	And since your callback will be called with a pointer to the watcher, you
1018	can cast it back to your own type:	1384	can cast it back to your own type:
1019		1385
1020	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1386	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1021	{	1387	{
1022	struct my_io *w = (struct my_io *)w_;	1388	struct my_io *w = (struct my_io *)w_;
1023	...	1389	...
1024	}	1390	}
1025		1391
…		…
1036	ev_timer t2;	1402	ev_timer t2;
1037	}	1403	}
1038		1404
1039	In this case getting the pointer to C<my_biggy> is a bit more	1405	In this case getting the pointer to C<my_biggy> is a bit more
1040	complicated: Either you store the address of your C<my_biggy> struct	1406	complicated: Either you store the address of your C<my_biggy> struct
1041	in the C<data> member of the watcher, or you need to use some pointer	1407	in the C<data> member of the watcher (for woozies), or you need to use
1042	arithmetic using C<offsetof> inside your watchers:	1408	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1409	programmers):
1043		1410
1044	#include <stddef.h>	1411	#include <stddef.h>
1045		1412
1046	static void	1413	static void
1047	t1_cb (EV_P_ struct ev_timer *w, int revents)	1414	t1_cb (EV_P_ ev_timer *w, int revents)
1048	{	1415	{
1049	struct my_biggy big = (struct my_biggy *	1416	struct my_biggy big = (struct my_biggy *)
1050	(((char *)w) - offsetof (struct my_biggy, t1));	1417	(((char *)w) - offsetof (struct my_biggy, t1));
1051	}	1418	}
1052		1419
1053	static void	1420	static void
1054	t2_cb (EV_P_ struct ev_timer *w, int revents)	1421	t2_cb (EV_P_ ev_timer *w, int revents)
1055	{	1422	{
1056	struct my_biggy big = (struct my_biggy *	1423	struct my_biggy big = (struct my_biggy *)
1057	(((char *)w) - offsetof (struct my_biggy, t2));	1424	(((char *)w) - offsetof (struct my_biggy, t2));
1058	}	1425	}
		1426
		1427	=head2 WATCHER PRIORITY MODELS
		1428
		1429	Many event loops support I<watcher priorities>, which are usually small
		1430	integers that influence the ordering of event callback invocation
		1431	between watchers in some way, all else being equal.
		1432
		1433	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1434	description for the more technical details such as the actual priority
		1435	range.
		1436
		1437	There are two common ways how these these priorities are being interpreted
		1438	by event loops:
		1439
		1440	In the more common lock-out model, higher priorities "lock out" invocation
		1441	of lower priority watchers, which means as long as higher priority
		1442	watchers receive events, lower priority watchers are not being invoked.
		1443
		1444	The less common only-for-ordering model uses priorities solely to order
		1445	callback invocation within a single event loop iteration: Higher priority
		1446	watchers are invoked before lower priority ones, but they all get invoked
		1447	before polling for new events.
		1448
		1449	Libev uses the second (only-for-ordering) model for all its watchers
		1450	except for idle watchers (which use the lock-out model).
		1451
		1452	The rationale behind this is that implementing the lock-out model for
		1453	watchers is not well supported by most kernel interfaces, and most event
		1454	libraries will just poll for the same events again and again as long as
		1455	their callbacks have not been executed, which is very inefficient in the
		1456	common case of one high-priority watcher locking out a mass of lower
		1457	priority ones.
		1458
		1459	Static (ordering) priorities are most useful when you have two or more
		1460	watchers handling the same resource: a typical usage example is having an
		1461	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1462	timeouts. Under load, data might be received while the program handles
		1463	other jobs, but since timers normally get invoked first, the timeout
		1464	handler will be executed before checking for data. In that case, giving
		1465	the timer a lower priority than the I/O watcher ensures that I/O will be
		1466	handled first even under adverse conditions (which is usually, but not
		1467	always, what you want).
		1468
		1469	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1470	will only be executed when no same or higher priority watchers have
		1471	received events, they can be used to implement the "lock-out" model when
		1472	required.
		1473
		1474	For example, to emulate how many other event libraries handle priorities,
		1475	you can associate an C<ev_idle> watcher to each such watcher, and in
		1476	the normal watcher callback, you just start the idle watcher. The real
		1477	processing is done in the idle watcher callback. This causes libev to
		1478	continuously poll and process kernel event data for the watcher, but when
		1479	the lock-out case is known to be rare (which in turn is rare :), this is
		1480	workable.
		1481
		1482	Usually, however, the lock-out model implemented that way will perform
		1483	miserably under the type of load it was designed to handle. In that case,
		1484	it might be preferable to stop the real watcher before starting the
		1485	idle watcher, so the kernel will not have to process the event in case
		1486	the actual processing will be delayed for considerable time.
		1487
		1488	Here is an example of an I/O watcher that should run at a strictly lower
		1489	priority than the default, and which should only process data when no
		1490	other events are pending:
		1491
		1492	ev_idle idle; // actual processing watcher
		1493	ev_io io; // actual event watcher
		1494
		1495	static void
		1496	io_cb (EV_P_ ev_io *w, int revents)
		1497	{
		1498	// stop the I/O watcher, we received the event, but
		1499	// are not yet ready to handle it.
		1500	ev_io_stop (EV_A_ w);
		1501
		1502	// start the idle watcher to handle the actual event.
		1503	// it will not be executed as long as other watchers
		1504	// with the default priority are receiving events.
		1505	ev_idle_start (EV_A_ &idle);
		1506	}
		1507
		1508	static void
		1509	idle_cb (EV_P_ ev_idle *w, int revents)
		1510	{
		1511	// actual processing
		1512	read (STDIN_FILENO, ...);
		1513
		1514	// have to start the I/O watcher again, as
		1515	// we have handled the event
		1516	ev_io_start (EV_P_ &io);
		1517	}
		1518
		1519	// initialisation
		1520	ev_idle_init (&idle, idle_cb);
		1521	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1522	ev_io_start (EV_DEFAULT_ &io);
		1523
		1524	In the "real" world, it might also be beneficial to start a timer, so that
		1525	low-priority connections can not be locked out forever under load. This
		1526	enables your program to keep a lower latency for important connections
		1527	during short periods of high load, while not completely locking out less
		1528	important ones.
1059		1529
1060		1530
1061	=head1 WATCHER TYPES	1531	=head1 WATCHER TYPES
1062		1532
1063	This section describes each watcher in detail, but will not repeat	1533	This section describes each watcher in detail, but will not repeat
…		…
1087	In general you can register as many read and/or write event watchers per	1557	In general you can register as many read and/or write event watchers per
1088	fd as you want (as long as you don't confuse yourself). Setting all file	1558	fd as you want (as long as you don't confuse yourself). Setting all file
1089	descriptors to non-blocking mode is also usually a good idea (but not	1559	descriptors to non-blocking mode is also usually a good idea (but not
1090	required if you know what you are doing).	1560	required if you know what you are doing).
1091		1561
1092	If you must do this, then force the use of a known-to-be-good backend	1562	If you cannot use non-blocking mode, then force the use of a
1093	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1563	known-to-be-good backend (at the time of this writing, this includes only
1094	C<EVBACKEND_POLL>).	1564	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1565	descriptors for which non-blocking operation makes no sense (such as
		1566	files) - libev doesn't guarantee any specific behaviour in that case.
1095		1567
1096	Another thing you have to watch out for is that it is quite easy to	1568	Another thing you have to watch out for is that it is quite easy to
1097	receive "spurious" readiness notifications, that is your callback might	1569	receive "spurious" readiness notifications, that is your callback might
1098	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1570	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1099	because there is no data. Not only are some backends known to create a	1571	because there is no data. Not only are some backends known to create a
1100	lot of those (for example Solaris ports), it is very easy to get into	1572	lot of those (for example Solaris ports), it is very easy to get into
1101	this situation even with a relatively standard program structure. Thus	1573	this situation even with a relatively standard program structure. Thus
1102	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1574	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1103	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1575	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1104		1576
1105	If you cannot run the fd in non-blocking mode (for example you should not	1577	If you cannot run the fd in non-blocking mode (for example you should
1106	play around with an Xlib connection), then you have to separately re-test	1578	not play around with an Xlib connection), then you have to separately
1107	whether a file descriptor is really ready with a known-to-be good interface	1579	re-test whether a file descriptor is really ready with a known-to-be good
1108	such as poll (fortunately in our Xlib example, Xlib already does this on	1580	interface such as poll (fortunately in our Xlib example, Xlib already
1109	its own, so its quite safe to use).	1581	does this on its own, so its quite safe to use). Some people additionally
		1582	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1583	indefinitely.
		1584
		1585	But really, best use non-blocking mode.
1110		1586
1111	=head3 The special problem of disappearing file descriptors	1587	=head3 The special problem of disappearing file descriptors
1112		1588
1113	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1589	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1114	descriptor (either by calling C<close> explicitly or by any other means,	1590	descriptor (either due to calling C<close> explicitly or any other means,
1115	such as C<dup>). The reason is that you register interest in some file	1591	such as C<dup2>). The reason is that you register interest in some file
1116	descriptor, but when it goes away, the operating system will silently drop	1592	descriptor, but when it goes away, the operating system will silently drop
1117	this interest. If another file descriptor with the same number then is	1593	this interest. If another file descriptor with the same number then is
1118	registered with libev, there is no efficient way to see that this is, in	1594	registered with libev, there is no efficient way to see that this is, in
1119	fact, a different file descriptor.	1595	fact, a different file descriptor.
1120		1596
…		…
1151	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1627	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1152	C<EVBACKEND_POLL>.	1628	C<EVBACKEND_POLL>.
1153		1629
1154	=head3 The special problem of SIGPIPE	1630	=head3 The special problem of SIGPIPE
1155		1631
1156	While not really specific to libev, it is easy to forget about SIGPIPE:	1632	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1157	when writing to a pipe whose other end has been closed, your program gets	1633	when writing to a pipe whose other end has been closed, your program gets
1158	send a SIGPIPE, which, by default, aborts your program. For most programs	1634	sent a SIGPIPE, which, by default, aborts your program. For most programs
1159	this is sensible behaviour, for daemons, this is usually undesirable.	1635	this is sensible behaviour, for daemons, this is usually undesirable.
1160		1636
1161	So when you encounter spurious, unexplained daemon exits, make sure you	1637	So when you encounter spurious, unexplained daemon exits, make sure you
1162	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1638	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1163	somewhere, as that would have given you a big clue).	1639	somewhere, as that would have given you a big clue).
1164		1640
		1641	=head3 The special problem of accept()ing when you can't
		1642
		1643	Many implementations of the POSIX C<accept> function (for example,
		1644	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1645	connection from the pending queue in all error cases.
		1646
		1647	For example, larger servers often run out of file descriptors (because
		1648	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1649	rejecting the connection, leading to libev signalling readiness on
		1650	the next iteration again (the connection still exists after all), and
		1651	typically causing the program to loop at 100% CPU usage.
		1652
		1653	Unfortunately, the set of errors that cause this issue differs between
		1654	operating systems, there is usually little the app can do to remedy the
		1655	situation, and no known thread-safe method of removing the connection to
		1656	cope with overload is known (to me).
		1657
		1658	One of the easiest ways to handle this situation is to just ignore it
		1659	- when the program encounters an overload, it will just loop until the
		1660	situation is over. While this is a form of busy waiting, no OS offers an
		1661	event-based way to handle this situation, so it's the best one can do.
		1662
		1663	A better way to handle the situation is to log any errors other than
		1664	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1665	messages, and continue as usual, which at least gives the user an idea of
		1666	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1667	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1668	usage.
		1669
		1670	If your program is single-threaded, then you could also keep a dummy file
		1671	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1672	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1673	close that fd, and create a new dummy fd. This will gracefully refuse
		1674	clients under typical overload conditions.
		1675
		1676	The last way to handle it is to simply log the error and C<exit>, as
		1677	is often done with C<malloc> failures, but this results in an easy
		1678	opportunity for a DoS attack.
1165		1679
1166	=head3 Watcher-Specific Functions	1680	=head3 Watcher-Specific Functions
1167		1681
1168	=over 4	1682	=over 4
1169		1683
1170	=item ev_io_init (ev_io *, callback, int fd, int events)	1684	=item ev_io_init (ev_io *, callback, int fd, int events)
1171		1685
1172	=item ev_io_set (ev_io *, int fd, int events)	1686	=item ev_io_set (ev_io *, int fd, int events)
1173		1687
1174	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1688	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1175	receive events for and events is either C<EV_READ>, C<EV_WRITE> or	1689	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1176	C<EV_READ | EV_WRITE> to receive the given events.	1690	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1177		1691
1178	=item int fd [read-only]	1692	=item int fd [read-only]
1179		1693
1180	The file descriptor being watched.	1694	The file descriptor being watched.
1181		1695
…		…
1190	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1704	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1191	readable, but only once. Since it is likely line-buffered, you could	1705	readable, but only once. Since it is likely line-buffered, you could
1192	attempt to read a whole line in the callback.	1706	attempt to read a whole line in the callback.
1193		1707
1194	static void	1708	static void
1195	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1709	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1196	{	1710	{
1197	ev_io_stop (loop, w);	1711	ev_io_stop (loop, w);
1198	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1712	.. read from stdin here (or from w->fd) and handle any I/O errors
1199	}	1713	}
1200		1714
1201	...	1715	...
1202	struct ev_loop *loop = ev_default_init (0);	1716	struct ev_loop *loop = ev_default_init (0);
1203	struct ev_io stdin_readable;	1717	ev_io stdin_readable;
1204	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1718	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1205	ev_io_start (loop, &stdin_readable);	1719	ev_io_start (loop, &stdin_readable);
1206	ev_loop (loop, 0);	1720	ev_run (loop, 0);
1207		1721
1208		1722
1209	=head2 C<ev_timer> - relative and optionally repeating timeouts	1723	=head2 C<ev_timer> - relative and optionally repeating timeouts
1210		1724
1211	Timer watchers are simple relative timers that generate an event after a	1725	Timer watchers are simple relative timers that generate an event after a
1212	given time, and optionally repeating in regular intervals after that.	1726	given time, and optionally repeating in regular intervals after that.
1213		1727
1214	The timers are based on real time, that is, if you register an event that	1728	The timers are based on real time, that is, if you register an event that
1215	times out after an hour and you reset your system clock to January last	1729	times out after an hour and you reset your system clock to January last
1216	year, it will still time out after (roughly) and hour. "Roughly" because	1730	year, it will still time out after (roughly) one hour. "Roughly" because
1217	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1731	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1218	monotonic clock option helps a lot here).	1732	monotonic clock option helps a lot here).
1219		1733
1220	The callback is guaranteed to be invoked only after its timeout has passed,	1734	The callback is guaranteed to be invoked only I<after> its timeout has
1221	but if multiple timers become ready during the same loop iteration then	1735	passed (not I<at>, so on systems with very low-resolution clocks this
1222	order of execution is undefined.	1736	might introduce a small delay). If multiple timers become ready during the
		1737	same loop iteration then the ones with earlier time-out values are invoked
		1738	before ones of the same priority with later time-out values (but this is
		1739	no longer true when a callback calls C<ev_run> recursively).
		1740
		1741	=head3 Be smart about timeouts
		1742
		1743	Many real-world problems involve some kind of timeout, usually for error
		1744	recovery. A typical example is an HTTP request - if the other side hangs,
		1745	you want to raise some error after a while.
		1746
		1747	What follows are some ways to handle this problem, from obvious and
		1748	inefficient to smart and efficient.
		1749
		1750	In the following, a 60 second activity timeout is assumed - a timeout that
		1751	gets reset to 60 seconds each time there is activity (e.g. each time some
		1752	data or other life sign was received).
		1753
		1754	=over 4
		1755
		1756	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1757
		1758	This is the most obvious, but not the most simple way: In the beginning,
		1759	start the watcher:
		1760
		1761	ev_timer_init (timer, callback, 60., 0.);
		1762	ev_timer_start (loop, timer);
		1763
		1764	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1765	and start it again:
		1766
		1767	ev_timer_stop (loop, timer);
		1768	ev_timer_set (timer, 60., 0.);
		1769	ev_timer_start (loop, timer);
		1770
		1771	This is relatively simple to implement, but means that each time there is
		1772	some activity, libev will first have to remove the timer from its internal
		1773	data structure and then add it again. Libev tries to be fast, but it's
		1774	still not a constant-time operation.
		1775
		1776	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1777
		1778	This is the easiest way, and involves using C<ev_timer_again> instead of
		1779	C<ev_timer_start>.
		1780
		1781	To implement this, configure an C<ev_timer> with a C<repeat> value
		1782	of C<60> and then call C<ev_timer_again> at start and each time you
		1783	successfully read or write some data. If you go into an idle state where
		1784	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1785	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1786
		1787	That means you can ignore both the C<ev_timer_start> function and the
		1788	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1789	member and C<ev_timer_again>.
		1790
		1791	At start:
		1792
		1793	ev_init (timer, callback);
		1794	timer->repeat = 60.;
		1795	ev_timer_again (loop, timer);
		1796
		1797	Each time there is some activity:
		1798
		1799	ev_timer_again (loop, timer);
		1800
		1801	It is even possible to change the time-out on the fly, regardless of
		1802	whether the watcher is active or not:
		1803
		1804	timer->repeat = 30.;
		1805	ev_timer_again (loop, timer);
		1806
		1807	This is slightly more efficient then stopping/starting the timer each time
		1808	you want to modify its timeout value, as libev does not have to completely
		1809	remove and re-insert the timer from/into its internal data structure.
		1810
		1811	It is, however, even simpler than the "obvious" way to do it.
		1812
		1813	=item 3. Let the timer time out, but then re-arm it as required.
		1814
		1815	This method is more tricky, but usually most efficient: Most timeouts are
		1816	relatively long compared to the intervals between other activity - in
		1817	our example, within 60 seconds, there are usually many I/O events with
		1818	associated activity resets.
		1819
		1820	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1821	but remember the time of last activity, and check for a real timeout only
		1822	within the callback:
		1823
		1824	ev_tstamp last_activity; // time of last activity
		1825
		1826	static void
		1827	callback (EV_P_ ev_timer *w, int revents)
		1828	{
		1829	ev_tstamp now = ev_now (EV_A);
		1830	ev_tstamp timeout = last_activity + 60.;
		1831
		1832	// if last_activity + 60. is older than now, we did time out
		1833	if (timeout < now)
		1834	{
		1835	// timeout occurred, take action
		1836	}
		1837	else
		1838	{
		1839	// callback was invoked, but there was some activity, re-arm
		1840	// the watcher to fire in last_activity + 60, which is
		1841	// guaranteed to be in the future, so "again" is positive:
		1842	w->repeat = timeout - now;
		1843	ev_timer_again (EV_A_ w);
		1844	}
		1845	}
		1846
		1847	To summarise the callback: first calculate the real timeout (defined
		1848	as "60 seconds after the last activity"), then check if that time has
		1849	been reached, which means something I<did>, in fact, time out. Otherwise
		1850	the callback was invoked too early (C<timeout> is in the future), so
		1851	re-schedule the timer to fire at that future time, to see if maybe we have
		1852	a timeout then.
		1853
		1854	Note how C<ev_timer_again> is used, taking advantage of the
		1855	C<ev_timer_again> optimisation when the timer is already running.
		1856
		1857	This scheme causes more callback invocations (about one every 60 seconds
		1858	minus half the average time between activity), but virtually no calls to
		1859	libev to change the timeout.
		1860
		1861	To start the timer, simply initialise the watcher and set C<last_activity>
		1862	to the current time (meaning we just have some activity :), then call the
		1863	callback, which will "do the right thing" and start the timer:
		1864
		1865	ev_init (timer, callback);
		1866	last_activity = ev_now (loop);
		1867	callback (loop, timer, EV_TIMER);
		1868
		1869	And when there is some activity, simply store the current time in
		1870	C<last_activity>, no libev calls at all:
		1871
		1872	last_activity = ev_now (loop);
		1873
		1874	This technique is slightly more complex, but in most cases where the
		1875	time-out is unlikely to be triggered, much more efficient.
		1876
		1877	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1878	callback :) - just change the timeout and invoke the callback, which will
		1879	fix things for you.
		1880
		1881	=item 4. Wee, just use a double-linked list for your timeouts.
		1882
		1883	If there is not one request, but many thousands (millions...), all
		1884	employing some kind of timeout with the same timeout value, then one can
		1885	do even better:
		1886
		1887	When starting the timeout, calculate the timeout value and put the timeout
		1888	at the I<end> of the list.
		1889
		1890	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1891	the list is expected to fire (for example, using the technique #3).
		1892
		1893	When there is some activity, remove the timer from the list, recalculate
		1894	the timeout, append it to the end of the list again, and make sure to
		1895	update the C<ev_timer> if it was taken from the beginning of the list.
		1896
		1897	This way, one can manage an unlimited number of timeouts in O(1) time for
		1898	starting, stopping and updating the timers, at the expense of a major
		1899	complication, and having to use a constant timeout. The constant timeout
		1900	ensures that the list stays sorted.
		1901
		1902	=back
		1903
		1904	So which method the best?
		1905
		1906	Method #2 is a simple no-brain-required solution that is adequate in most
		1907	situations. Method #3 requires a bit more thinking, but handles many cases
		1908	better, and isn't very complicated either. In most case, choosing either
		1909	one is fine, with #3 being better in typical situations.
		1910
		1911	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1912	rather complicated, but extremely efficient, something that really pays
		1913	off after the first million or so of active timers, i.e. it's usually
		1914	overkill :)
1223		1915
1224	=head3 The special problem of time updates	1916	=head3 The special problem of time updates
1225		1917
1226	Establishing the current time is a costly operation (it usually takes at	1918	Establishing the current time is a costly operation (it usually takes at
1227	least two system calls): EV therefore updates its idea of the current	1919	least two system calls): EV therefore updates its idea of the current
1228	time only before and after C<ev_loop> polls for new events, which causes	1920	time only before and after C<ev_run> collects new events, which causes a
1229	a growing difference between C<ev_now ()> and C<ev_time ()> when handling	1921	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1230	lots of events.	1922	lots of events in one iteration.
1231		1923
1232	The relative timeouts are calculated relative to the C<ev_now ()>	1924	The relative timeouts are calculated relative to the C<ev_now ()>
1233	time. This is usually the right thing as this timestamp refers to the time	1925	time. This is usually the right thing as this timestamp refers to the time
1234	of the event triggering whatever timeout you are modifying/starting. If	1926	of the event triggering whatever timeout you are modifying/starting. If
1235	you suspect event processing to be delayed and you I<need> to base the	1927	you suspect event processing to be delayed and you I<need> to base the
…		…
1239		1931
1240	If the event loop is suspended for a long time, you can also force an	1932	If the event loop is suspended for a long time, you can also force an
1241	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1933	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1242	()>.	1934	()>.
1243		1935
		1936	=head3 The special problems of suspended animation
		1937
		1938	When you leave the server world it is quite customary to hit machines that
		1939	can suspend/hibernate - what happens to the clocks during such a suspend?
		1940
		1941	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1942	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1943	to run until the system is suspended, but they will not advance while the
		1944	system is suspended. That means, on resume, it will be as if the program
		1945	was frozen for a few seconds, but the suspend time will not be counted
		1946	towards C<ev_timer> when a monotonic clock source is used. The real time
		1947	clock advanced as expected, but if it is used as sole clocksource, then a
		1948	long suspend would be detected as a time jump by libev, and timers would
		1949	be adjusted accordingly.
		1950
		1951	I would not be surprised to see different behaviour in different between
		1952	operating systems, OS versions or even different hardware.
		1953
		1954	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1955	time jump in the monotonic clocks and the realtime clock. If the program
		1956	is suspended for a very long time, and monotonic clock sources are in use,
		1957	then you can expect C<ev_timer>s to expire as the full suspension time
		1958	will be counted towards the timers. When no monotonic clock source is in
		1959	use, then libev will again assume a timejump and adjust accordingly.
		1960
		1961	It might be beneficial for this latter case to call C<ev_suspend>
		1962	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1963	deterministic behaviour in this case (you can do nothing against
		1964	C<SIGSTOP>).
		1965
1244	=head3 Watcher-Specific Functions and Data Members	1966	=head3 Watcher-Specific Functions and Data Members
1245		1967
1246	=over 4	1968	=over 4
1247		1969
1248	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1970	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1271	If the timer is started but non-repeating, stop it (as if it timed out).	1993	If the timer is started but non-repeating, stop it (as if it timed out).
1272		1994
1273	If the timer is repeating, either start it if necessary (with the	1995	If the timer is repeating, either start it if necessary (with the
1274	C<repeat> value), or reset the running timer to the C<repeat> value.	1996	C<repeat> value), or reset the running timer to the C<repeat> value.
1275		1997
1276	This sounds a bit complicated, but here is a useful and typical	1998	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1277	example: Imagine you have a TCP connection and you want a so-called idle	1999	usage example.
1278	timeout, that is, you want to be called when there have been, say, 60
1279	seconds of inactivity on the socket. The easiest way to do this is to
1280	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1281	C<ev_timer_again> each time you successfully read or write some data. If
1282	you go into an idle state where you do not expect data to travel on the
1283	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1284	automatically restart it if need be.
1285		2000
1286	That means you can ignore the C<after> value and C<ev_timer_start>	2001	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1287	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1288		2002
1289	ev_timer_init (timer, callback, 0., 5.);	2003	Returns the remaining time until a timer fires. If the timer is active,
1290	ev_timer_again (loop, timer);	2004	then this time is relative to the current event loop time, otherwise it's
1291	...	2005	the timeout value currently configured.
1292	timer->again = 17.;
1293	ev_timer_again (loop, timer);
1294	...
1295	timer->again = 10.;
1296	ev_timer_again (loop, timer);
1297		2006
1298	This is more slightly efficient then stopping/starting the timer each time	2007	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1299	you want to modify its timeout value.	2008	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2009	will return C<4>. When the timer expires and is restarted, it will return
		2010	roughly C<7> (likely slightly less as callback invocation takes some time,
		2011	too), and so on.
1300		2012
1301	=item ev_tstamp repeat [read-write]	2013	=item ev_tstamp repeat [read-write]
1302		2014
1303	The current C<repeat> value. Will be used each time the watcher times out	2015	The current C<repeat> value. Will be used each time the watcher times out
1304	or C<ev_timer_again> is called and determines the next timeout (if any),	2016	or C<ev_timer_again> is called, and determines the next timeout (if any),
1305	which is also when any modifications are taken into account.	2017	which is also when any modifications are taken into account.
1306		2018
1307	=back	2019	=back
1308		2020
1309	=head3 Examples	2021	=head3 Examples
1310		2022
1311	Example: Create a timer that fires after 60 seconds.	2023	Example: Create a timer that fires after 60 seconds.
1312		2024
1313	static void	2025	static void
1314	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2026	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1315	{	2027	{
1316	.. one minute over, w is actually stopped right here	2028	.. one minute over, w is actually stopped right here
1317	}	2029	}
1318		2030
1319	struct ev_timer mytimer;	2031	ev_timer mytimer;
1320	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	2032	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1321	ev_timer_start (loop, &mytimer);	2033	ev_timer_start (loop, &mytimer);
1322		2034
1323	Example: Create a timeout timer that times out after 10 seconds of	2035	Example: Create a timeout timer that times out after 10 seconds of
1324	inactivity.	2036	inactivity.
1325		2037
1326	static void	2038	static void
1327	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2039	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1328	{	2040	{
1329	.. ten seconds without any activity	2041	.. ten seconds without any activity
1330	}	2042	}
1331		2043
1332	struct ev_timer mytimer;	2044	ev_timer mytimer;
1333	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2045	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1334	ev_timer_again (&mytimer); /* start timer */	2046	ev_timer_again (&mytimer); /* start timer */
1335	ev_loop (loop, 0);	2047	ev_run (loop, 0);
1336		2048
1337	// and in some piece of code that gets executed on any "activity":	2049	// and in some piece of code that gets executed on any "activity":
1338	// reset the timeout to start ticking again at 10 seconds	2050	// reset the timeout to start ticking again at 10 seconds
1339	ev_timer_again (&mytimer);	2051	ev_timer_again (&mytimer);
1340		2052
…		…
1342	=head2 C<ev_periodic> - to cron or not to cron?	2054	=head2 C<ev_periodic> - to cron or not to cron?
1343		2055
1344	Periodic watchers are also timers of a kind, but they are very versatile	2056	Periodic watchers are also timers of a kind, but they are very versatile
1345	(and unfortunately a bit complex).	2057	(and unfortunately a bit complex).
1346		2058
1347	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2059	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1348	but on wall clock time (absolute time). You can tell a periodic watcher	2060	relative time, the physical time that passes) but on wall clock time
1349	to trigger after some specific point in time. For example, if you tell a	2061	(absolute time, the thing you can read on your calender or clock). The
1350	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	2062	difference is that wall clock time can run faster or slower than real
1351	+ 10.>, that is, an absolute time not a delay) and then reset your system	2063	time, and time jumps are not uncommon (e.g. when you adjust your
1352	clock to January of the previous year, then it will take more than year	2064	wrist-watch).
1353	to trigger the event (unlike an C<ev_timer>, which would still trigger
1354	roughly 10 seconds later as it uses a relative timeout).
1355		2065
		2066	You can tell a periodic watcher to trigger after some specific point
		2067	in time: for example, if you tell a periodic watcher to trigger "in 10
		2068	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2069	not a delay) and then reset your system clock to January of the previous
		2070	year, then it will take a year or more to trigger the event (unlike an
		2071	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2072	it, as it uses a relative timeout).
		2073
1356	C<ev_periodic>s can also be used to implement vastly more complex timers,	2074	C<ev_periodic> watchers can also be used to implement vastly more complex
1357	such as triggering an event on each "midnight, local time", or other	2075	timers, such as triggering an event on each "midnight, local time", or
1358	complicated, rules.	2076	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2077	those cannot react to time jumps.
1359		2078
1360	As with timers, the callback is guaranteed to be invoked only when the	2079	As with timers, the callback is guaranteed to be invoked only when the
1361	time (C<at>) has passed, but if multiple periodic timers become ready	2080	point in time where it is supposed to trigger has passed. If multiple
1362	during the same loop iteration then order of execution is undefined.	2081	timers become ready during the same loop iteration then the ones with
		2082	earlier time-out values are invoked before ones with later time-out values
		2083	(but this is no longer true when a callback calls C<ev_run> recursively).
1363		2084
1364	=head3 Watcher-Specific Functions and Data Members	2085	=head3 Watcher-Specific Functions and Data Members
1365		2086
1366	=over 4	2087	=over 4
1367		2088
1368	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2089	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1369		2090
1370	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2091	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1371		2092
1372	Lots of arguments, lets sort it out... There are basically three modes of	2093	Lots of arguments, let's sort it out... There are basically three modes of
1373	operation, and we will explain them from simplest to complex:	2094	operation, and we will explain them from simplest to most complex:
1374		2095
1375	=over 4	2096	=over 4
1376		2097
1377	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2098	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1378		2099
1379	In this configuration the watcher triggers an event after the wall clock	2100	In this configuration the watcher triggers an event after the wall clock
1380	time C<at> has passed and doesn't repeat. It will not adjust when a time	2101	time C<offset> has passed. It will not repeat and will not adjust when a
1381	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2102	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1382	run when the system time reaches or surpasses this time.	2103	will be stopped and invoked when the system clock reaches or surpasses
		2104	this point in time.
1383		2105
1384	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2106	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1385		2107
1386	In this mode the watcher will always be scheduled to time out at the next	2108	In this mode the watcher will always be scheduled to time out at the next
1387	C<at + N * interval> time (for some integer N, which can also be negative)	2109	C<offset + N * interval> time (for some integer N, which can also be
1388	and then repeat, regardless of any time jumps.	2110	negative) and then repeat, regardless of any time jumps. The C<offset>
		2111	argument is merely an offset into the C<interval> periods.
1389		2112
1390	This can be used to create timers that do not drift with respect to system	2113	This can be used to create timers that do not drift with respect to the
1391	time, for example, here is a C<ev_periodic> that triggers each hour, on	2114	system clock, for example, here is an C<ev_periodic> that triggers each
1392	the hour:	2115	hour, on the hour (with respect to UTC):
1393		2116
1394	ev_periodic_set (&periodic, 0., 3600., 0);	2117	ev_periodic_set (&periodic, 0., 3600., 0);
1395		2118
1396	This doesn't mean there will always be 3600 seconds in between triggers,	2119	This doesn't mean there will always be 3600 seconds in between triggers,
1397	but only that the callback will be called when the system time shows a	2120	but only that the callback will be called when the system time shows a
1398	full hour (UTC), or more correctly, when the system time is evenly divisible	2121	full hour (UTC), or more correctly, when the system time is evenly divisible
1399	by 3600.	2122	by 3600.
1400		2123
1401	Another way to think about it (for the mathematically inclined) is that	2124	Another way to think about it (for the mathematically inclined) is that
1402	C<ev_periodic> will try to run the callback in this mode at the next possible	2125	C<ev_periodic> will try to run the callback in this mode at the next possible
1403	time where C<time = at (mod interval)>, regardless of any time jumps.	2126	time where C<time = offset (mod interval)>, regardless of any time jumps.
1404		2127
1405	For numerical stability it is preferable that the C<at> value is near	2128	For numerical stability it is preferable that the C<offset> value is near
1406	C<ev_now ()> (the current time), but there is no range requirement for	2129	C<ev_now ()> (the current time), but there is no range requirement for
1407	this value, and in fact is often specified as zero.	2130	this value, and in fact is often specified as zero.
1408		2131
1409	Note also that there is an upper limit to how often a timer can fire (CPU	2132	Note also that there is an upper limit to how often a timer can fire (CPU
1410	speed for example), so if C<interval> is very small then timing stability	2133	speed for example), so if C<interval> is very small then timing stability
1411	will of course deteriorate. Libev itself tries to be exact to be about one	2134	will of course deteriorate. Libev itself tries to be exact to be about one
1412	millisecond (if the OS supports it and the machine is fast enough).	2135	millisecond (if the OS supports it and the machine is fast enough).
1413		2136
1414	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2137	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1415		2138
1416	In this mode the values for C<interval> and C<at> are both being	2139	In this mode the values for C<interval> and C<offset> are both being
1417	ignored. Instead, each time the periodic watcher gets scheduled, the	2140	ignored. Instead, each time the periodic watcher gets scheduled, the
1418	reschedule callback will be called with the watcher as first, and the	2141	reschedule callback will be called with the watcher as first, and the
1419	current time as second argument.	2142	current time as second argument.
1420		2143
1421	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2144	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1422	ever, or make ANY event loop modifications whatsoever>.	2145	or make ANY other event loop modifications whatsoever, unless explicitly
		2146	allowed by documentation here>.
1423		2147
1424	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2148	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1425	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2149	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1426	only event loop modification you are allowed to do).	2150	only event loop modification you are allowed to do).
1427		2151
1428	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	2152	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1429	*w, ev_tstamp now)>, e.g.:	2153	*w, ev_tstamp now)>, e.g.:
1430		2154
		2155	static ev_tstamp
1431	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	2156	my_rescheduler (ev_periodic *w, ev_tstamp now)
1432	{	2157	{
1433	return now + 60.;	2158	return now + 60.;
1434	}	2159	}
1435		2160
1436	It must return the next time to trigger, based on the passed time value	2161	It must return the next time to trigger, based on the passed time value
…		…
1456	a different time than the last time it was called (e.g. in a crond like	2181	a different time than the last time it was called (e.g. in a crond like
1457	program when the crontabs have changed).	2182	program when the crontabs have changed).
1458		2183
1459	=item ev_tstamp ev_periodic_at (ev_periodic *)	2184	=item ev_tstamp ev_periodic_at (ev_periodic *)
1460		2185
1461	When active, returns the absolute time that the watcher is supposed to	2186	When active, returns the absolute time that the watcher is supposed
1462	trigger next.	2187	to trigger next. This is not the same as the C<offset> argument to
		2188	C<ev_periodic_set>, but indeed works even in interval and manual
		2189	rescheduling modes.
1463		2190
1464	=item ev_tstamp offset [read-write]	2191	=item ev_tstamp offset [read-write]
1465		2192
1466	When repeating, this contains the offset value, otherwise this is the	2193	When repeating, this contains the offset value, otherwise this is the
1467	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2194	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2195	although libev might modify this value for better numerical stability).
1468		2196
1469	Can be modified any time, but changes only take effect when the periodic	2197	Can be modified any time, but changes only take effect when the periodic
1470	timer fires or C<ev_periodic_again> is being called.	2198	timer fires or C<ev_periodic_again> is being called.
1471		2199
1472	=item ev_tstamp interval [read-write]	2200	=item ev_tstamp interval [read-write]
1473		2201
1474	The current interval value. Can be modified any time, but changes only	2202	The current interval value. Can be modified any time, but changes only
1475	take effect when the periodic timer fires or C<ev_periodic_again> is being	2203	take effect when the periodic timer fires or C<ev_periodic_again> is being
1476	called.	2204	called.
1477		2205
1478	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2206	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1479		2207
1480	The current reschedule callback, or C<0>, if this functionality is	2208	The current reschedule callback, or C<0>, if this functionality is
1481	switched off. Can be changed any time, but changes only take effect when	2209	switched off. Can be changed any time, but changes only take effect when
1482	the periodic timer fires or C<ev_periodic_again> is being called.	2210	the periodic timer fires or C<ev_periodic_again> is being called.
1483		2211
1484	=back	2212	=back
1485		2213
1486	=head3 Examples	2214	=head3 Examples
1487		2215
1488	Example: Call a callback every hour, or, more precisely, whenever the	2216	Example: Call a callback every hour, or, more precisely, whenever the
1489	system clock is divisible by 3600. The callback invocation times have	2217	system time is divisible by 3600. The callback invocation times have
1490	potentially a lot of jitter, but good long-term stability.	2218	potentially a lot of jitter, but good long-term stability.
1491		2219
1492	static void	2220	static void
1493	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2221	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1494	{	2222	{
1495	... its now a full hour (UTC, or TAI or whatever your clock follows)	2223	... its now a full hour (UTC, or TAI or whatever your clock follows)
1496	}	2224	}
1497		2225
1498	struct ev_periodic hourly_tick;	2226	ev_periodic hourly_tick;
1499	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2227	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1500	ev_periodic_start (loop, &hourly_tick);	2228	ev_periodic_start (loop, &hourly_tick);
1501		2229
1502	Example: The same as above, but use a reschedule callback to do it:	2230	Example: The same as above, but use a reschedule callback to do it:
1503		2231
1504	#include <math.h>	2232	#include <math.h>
1505		2233
1506	static ev_tstamp	2234	static ev_tstamp
1507	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2235	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1508	{	2236	{
1509	return fmod (now, 3600.) + 3600.;	2237	return now + (3600. - fmod (now, 3600.));
1510	}	2238	}
1511		2239
1512	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2240	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1513		2241
1514	Example: Call a callback every hour, starting now:	2242	Example: Call a callback every hour, starting now:
1515		2243
1516	struct ev_periodic hourly_tick;	2244	ev_periodic hourly_tick;
1517	ev_periodic_init (&hourly_tick, clock_cb,	2245	ev_periodic_init (&hourly_tick, clock_cb,
1518	fmod (ev_now (loop), 3600.), 3600., 0);	2246	fmod (ev_now (loop), 3600.), 3600., 0);
1519	ev_periodic_start (loop, &hourly_tick);	2247	ev_periodic_start (loop, &hourly_tick);
1520		2248
1521		2249
…		…
1524	Signal watchers will trigger an event when the process receives a specific	2252	Signal watchers will trigger an event when the process receives a specific
1525	signal one or more times. Even though signals are very asynchronous, libev	2253	signal one or more times. Even though signals are very asynchronous, libev
1526	will try it's best to deliver signals synchronously, i.e. as part of the	2254	will try it's best to deliver signals synchronously, i.e. as part of the
1527	normal event processing, like any other event.	2255	normal event processing, like any other event.
1528		2256
		2257	If you want signals to be delivered truly asynchronously, just use
		2258	C<sigaction> as you would do without libev and forget about sharing
		2259	the signal. You can even use C<ev_async> from a signal handler to
		2260	synchronously wake up an event loop.
		2261
1529	You can configure as many watchers as you like per signal. Only when the	2262	You can configure as many watchers as you like for the same signal, but
		2263	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2264	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2265	C<SIGINT> in both the default loop and another loop at the same time. At
		2266	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2267
1530	first watcher gets started will libev actually register a signal watcher	2268	When the first watcher gets started will libev actually register something
1531	with the kernel (thus it coexists with your own signal handlers as long	2269	with the kernel (thus it coexists with your own signal handlers as long as
1532	as you don't register any with libev). Similarly, when the last signal	2270	you don't register any with libev for the same signal).
1533	watcher for a signal is stopped libev will reset the signal handler to
1534	SIG_DFL (regardless of what it was set to before).
1535		2271
1536	If possible and supported, libev will install its handlers with	2272	If possible and supported, libev will install its handlers with
1537	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2273	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1538	interrupted. If you have a problem with system calls getting interrupted by	2274	not be unduly interrupted. If you have a problem with system calls getting
1539	signals you can block all signals in an C<ev_check> watcher and unblock	2275	interrupted by signals you can block all signals in an C<ev_check> watcher
1540	them in an C<ev_prepare> watcher.	2276	and unblock them in an C<ev_prepare> watcher.
		2277
		2278	=head3 The special problem of inheritance over fork/execve/pthread_create
		2279
		2280	Both the signal mask (C<sigprocmask>) and the signal disposition
		2281	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2282	stopping it again), that is, libev might or might not block the signal,
		2283	and might or might not set or restore the installed signal handler.
		2284
		2285	While this does not matter for the signal disposition (libev never
		2286	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2287	C<execve>), this matters for the signal mask: many programs do not expect
		2288	certain signals to be blocked.
		2289
		2290	This means that before calling C<exec> (from the child) you should reset
		2291	the signal mask to whatever "default" you expect (all clear is a good
		2292	choice usually).
		2293
		2294	The simplest way to ensure that the signal mask is reset in the child is
		2295	to install a fork handler with C<pthread_atfork> that resets it. That will
		2296	catch fork calls done by libraries (such as the libc) as well.
		2297
		2298	In current versions of libev, the signal will not be blocked indefinitely
		2299	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2300	the window of opportunity for problems, it will not go away, as libev
		2301	I<has> to modify the signal mask, at least temporarily.
		2302
		2303	So I can't stress this enough: I<If you do not reset your signal mask when
		2304	you expect it to be empty, you have a race condition in your code>. This
		2305	is not a libev-specific thing, this is true for most event libraries.
1541		2306
1542	=head3 Watcher-Specific Functions and Data Members	2307	=head3 Watcher-Specific Functions and Data Members
1543		2308
1544	=over 4	2309	=over 4
1545		2310
…		…
1556		2321
1557	=back	2322	=back
1558		2323
1559	=head3 Examples	2324	=head3 Examples
1560		2325
1561	Example: Try to exit cleanly on SIGINT and SIGTERM.	2326	Example: Try to exit cleanly on SIGINT.
1562		2327
1563	static void	2328	static void
1564	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2329	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1565	{	2330	{
1566	ev_unloop (loop, EVUNLOOP_ALL);	2331	ev_break (loop, EVBREAK_ALL);
1567	}	2332	}
1568		2333
1569	struct ev_signal signal_watcher;	2334	ev_signal signal_watcher;
1570	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2335	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1571	ev_signal_start (loop, &sigint_cb);	2336	ev_signal_start (loop, &signal_watcher);
1572		2337
1573		2338
1574	=head2 C<ev_child> - watch out for process status changes	2339	=head2 C<ev_child> - watch out for process status changes
1575		2340
1576	Child watchers trigger when your process receives a SIGCHLD in response to	2341	Child watchers trigger when your process receives a SIGCHLD in response to
1577	some child status changes (most typically when a child of yours dies). It	2342	some child status changes (most typically when a child of yours dies or
1578	is permissible to install a child watcher I<after> the child has been	2343	exits). It is permissible to install a child watcher I<after> the child
1579	forked (which implies it might have already exited), as long as the event	2344	has been forked (which implies it might have already exited), as long
1580	loop isn't entered (or is continued from a watcher).	2345	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2346	forking and then immediately registering a watcher for the child is fine,
		2347	but forking and registering a watcher a few event loop iterations later or
		2348	in the next callback invocation is not.
1581		2349
1582	Only the default event loop is capable of handling signals, and therefore	2350	Only the default event loop is capable of handling signals, and therefore
1583	you can only register child watchers in the default event loop.	2351	you can only register child watchers in the default event loop.
1584		2352
		2353	Due to some design glitches inside libev, child watchers will always be
		2354	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2355	libev)
		2356
1585	=head3 Process Interaction	2357	=head3 Process Interaction
1586		2358
1587	Libev grabs C<SIGCHLD> as soon as the default event loop is	2359	Libev grabs C<SIGCHLD> as soon as the default event loop is
1588	initialised. This is necessary to guarantee proper behaviour even if	2360	initialised. This is necessary to guarantee proper behaviour even if the
1589	the first child watcher is started after the child exits. The occurrence	2361	first child watcher is started after the child exits. The occurrence
1590	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2362	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1591	synchronously as part of the event loop processing. Libev always reaps all	2363	synchronously as part of the event loop processing. Libev always reaps all
1592	children, even ones not watched.	2364	children, even ones not watched.
1593		2365
1594	=head3 Overriding the Built-In Processing	2366	=head3 Overriding the Built-In Processing
…		…
1604	=head3 Stopping the Child Watcher	2376	=head3 Stopping the Child Watcher
1605		2377
1606	Currently, the child watcher never gets stopped, even when the	2378	Currently, the child watcher never gets stopped, even when the
1607	child terminates, so normally one needs to stop the watcher in the	2379	child terminates, so normally one needs to stop the watcher in the
1608	callback. Future versions of libev might stop the watcher automatically	2380	callback. Future versions of libev might stop the watcher automatically
1609	when a child exit is detected.	2381	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2382	problem).
1610		2383
1611	=head3 Watcher-Specific Functions and Data Members	2384	=head3 Watcher-Specific Functions and Data Members
1612		2385
1613	=over 4	2386	=over 4
1614		2387
…		…
1646	its completion.	2419	its completion.
1647		2420
1648	ev_child cw;	2421	ev_child cw;
1649		2422
1650	static void	2423	static void
1651	child_cb (EV_P_ struct ev_child *w, int revents)	2424	child_cb (EV_P_ ev_child *w, int revents)
1652	{	2425	{
1653	ev_child_stop (EV_A_ w);	2426	ev_child_stop (EV_A_ w);
1654	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2427	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1655	}	2428	}
1656		2429
…		…
1671		2444
1672		2445
1673	=head2 C<ev_stat> - did the file attributes just change?	2446	=head2 C<ev_stat> - did the file attributes just change?
1674		2447
1675	This watches a file system path for attribute changes. That is, it calls	2448	This watches a file system path for attribute changes. That is, it calls
1676	C<stat> regularly (or when the OS says it changed) and sees if it changed	2449	C<stat> on that path in regular intervals (or when the OS says it changed)
1677	compared to the last time, invoking the callback if it did.	2450	and sees if it changed compared to the last time, invoking the callback if
		2451	it did.
1678		2452
1679	The path does not need to exist: changing from "path exists" to "path does	2453	The path does not need to exist: changing from "path exists" to "path does
1680	not exist" is a status change like any other. The condition "path does	2454	not exist" is a status change like any other. The condition "path does not
1681	not exist" is signified by the C<st_nlink> field being zero (which is	2455	exist" (or more correctly "path cannot be stat'ed") is signified by the
1682	otherwise always forced to be at least one) and all the other fields of	2456	C<st_nlink> field being zero (which is otherwise always forced to be at
1683	the stat buffer having unspecified contents.	2457	least one) and all the other fields of the stat buffer having unspecified
		2458	contents.
1684		2459
1685	The path I<should> be absolute and I<must not> end in a slash. If it is	2460	The path I<must not> end in a slash or contain special components such as
		2461	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1686	relative and your working directory changes, the behaviour is undefined.	2462	your working directory changes, then the behaviour is undefined.
1687		2463
1688	Since there is no standard to do this, the portable implementation simply	2464	Since there is no portable change notification interface available, the
1689	calls C<stat (2)> regularly on the path to see if it changed somehow. You	2465	portable implementation simply calls C<stat(2)> regularly on the path
1690	can specify a recommended polling interval for this case. If you specify	2466	to see if it changed somehow. You can specify a recommended polling
1691	a polling interval of C<0> (highly recommended!) then a I<suitable,	2467	interval for this case. If you specify a polling interval of C<0> (highly
1692	unspecified default> value will be used (which you can expect to be around	2468	recommended!) then a I<suitable, unspecified default> value will be used
1693	five seconds, although this might change dynamically). Libev will also	2469	(which you can expect to be around five seconds, although this might
1694	impose a minimum interval which is currently around C<0.1>, but thats	2470	change dynamically). Libev will also impose a minimum interval which is
1695	usually overkill.	2471	currently around C<0.1>, but that's usually overkill.
1696		2472
1697	This watcher type is not meant for massive numbers of stat watchers,	2473	This watcher type is not meant for massive numbers of stat watchers,
1698	as even with OS-supported change notifications, this can be	2474	as even with OS-supported change notifications, this can be
1699	resource-intensive.	2475	resource-intensive.
1700		2476
1701	At the time of this writing, only the Linux inotify interface is	2477	At the time of this writing, the only OS-specific interface implemented
1702	implemented (implementing kqueue support is left as an exercise for the	2478	is the Linux inotify interface (implementing kqueue support is left as an
1703	reader, note, however, that the author sees no way of implementing ev_stat	2479	exercise for the reader. Note, however, that the author sees no way of
1704	semantics with kqueue). Inotify will be used to give hints only and should	2480	implementing C<ev_stat> semantics with kqueue, except as a hint).
1705	not change the semantics of C<ev_stat> watchers, which means that libev
1706	sometimes needs to fall back to regular polling again even with inotify,
1707	but changes are usually detected immediately, and if the file exists there
1708	will be no polling.
1709		2481
1710	=head3 ABI Issues (Largefile Support)	2482	=head3 ABI Issues (Largefile Support)
1711		2483
1712	Libev by default (unless the user overrides this) uses the default	2484	Libev by default (unless the user overrides this) uses the default
1713	compilation environment, which means that on systems with large file	2485	compilation environment, which means that on systems with large file
1714	support disabled by default, you get the 32 bit version of the stat	2486	support disabled by default, you get the 32 bit version of the stat
1715	structure. When using the library from programs that change the ABI to	2487	structure. When using the library from programs that change the ABI to
1716	use 64 bit file offsets the programs will fail. In that case you have to	2488	use 64 bit file offsets the programs will fail. In that case you have to
1717	compile libev with the same flags to get binary compatibility. This is	2489	compile libev with the same flags to get binary compatibility. This is
1718	obviously the case with any flags that change the ABI, but the problem is	2490	obviously the case with any flags that change the ABI, but the problem is
1719	most noticeably disabled with ev_stat and large file support.	2491	most noticeably displayed with ev_stat and large file support.
1720		2492
1721	The solution for this is to lobby your distribution maker to make large	2493	The solution for this is to lobby your distribution maker to make large
1722	file interfaces available by default (as e.g. FreeBSD does) and not	2494	file interfaces available by default (as e.g. FreeBSD does) and not
1723	optional. Libev cannot simply switch on large file support because it has	2495	optional. Libev cannot simply switch on large file support because it has
1724	to exchange stat structures with application programs compiled using the	2496	to exchange stat structures with application programs compiled using the
1725	default compilation environment.	2497	default compilation environment.
1726		2498
1727	=head3 Inotify	2499	=head3 Inotify and Kqueue
1728		2500
1729	When C<inotify (7)> support has been compiled into libev (generally only	2501	When C<inotify (7)> support has been compiled into libev and present at
1730	available on Linux) and present at runtime, it will be used to speed up	2502	runtime, it will be used to speed up change detection where possible. The
1731	change detection where possible. The inotify descriptor will be created lazily	2503	inotify descriptor will be created lazily when the first C<ev_stat>
1732	when the first C<ev_stat> watcher is being started.	2504	watcher is being started.
1733		2505
1734	Inotify presence does not change the semantics of C<ev_stat> watchers	2506	Inotify presence does not change the semantics of C<ev_stat> watchers
1735	except that changes might be detected earlier, and in some cases, to avoid	2507	except that changes might be detected earlier, and in some cases, to avoid
1736	making regular C<stat> calls. Even in the presence of inotify support	2508	making regular C<stat> calls. Even in the presence of inotify support
1737	there are many cases where libev has to resort to regular C<stat> polling.	2509	there are many cases where libev has to resort to regular C<stat> polling,
		2510	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2511	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2512	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2513	xfs are fully working) libev usually gets away without polling.
1738		2514
1739	(There is no support for kqueue, as apparently it cannot be used to	2515	There is no support for kqueue, as apparently it cannot be used to
1740	implement this functionality, due to the requirement of having a file	2516	implement this functionality, due to the requirement of having a file
1741	descriptor open on the object at all times).	2517	descriptor open on the object at all times, and detecting renames, unlinks
		2518	etc. is difficult.
		2519
		2520	=head3 C<stat ()> is a synchronous operation
		2521
		2522	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2523	the process. The exception are C<ev_stat> watchers - those call C<stat
		2524	()>, which is a synchronous operation.
		2525
		2526	For local paths, this usually doesn't matter: unless the system is very
		2527	busy or the intervals between stat's are large, a stat call will be fast,
		2528	as the path data is usually in memory already (except when starting the
		2529	watcher).
		2530
		2531	For networked file systems, calling C<stat ()> can block an indefinite
		2532	time due to network issues, and even under good conditions, a stat call
		2533	often takes multiple milliseconds.
		2534
		2535	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2536	paths, although this is fully supported by libev.
1742		2537
1743	=head3 The special problem of stat time resolution	2538	=head3 The special problem of stat time resolution
1744		2539
1745	The C<stat ()> system call only supports full-second resolution portably, and	2540	The C<stat ()> system call only supports full-second resolution portably,
1746	even on systems where the resolution is higher, many file systems still	2541	and even on systems where the resolution is higher, most file systems
1747	only support whole seconds.	2542	still only support whole seconds.
1748		2543
1749	That means that, if the time is the only thing that changes, you can	2544	That means that, if the time is the only thing that changes, you can
1750	easily miss updates: on the first update, C<ev_stat> detects a change and	2545	easily miss updates: on the first update, C<ev_stat> detects a change and
1751	calls your callback, which does something. When there is another update	2546	calls your callback, which does something. When there is another update
1752	within the same second, C<ev_stat> will be unable to detect it as the stat	2547	within the same second, C<ev_stat> will be unable to detect unless the
1753	data does not change.	2548	stat data does change in other ways (e.g. file size).
1754		2549
1755	The solution to this is to delay acting on a change for slightly more	2550	The solution to this is to delay acting on a change for slightly more
1756	than a second (or till slightly after the next full second boundary), using	2551	than a second (or till slightly after the next full second boundary), using
1757	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2552	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1758	ev_timer_again (loop, w)>).	2553	ev_timer_again (loop, w)>).
…		…
1778	C<path>. The C<interval> is a hint on how quickly a change is expected to	2573	C<path>. The C<interval> is a hint on how quickly a change is expected to
1779	be detected and should normally be specified as C<0> to let libev choose	2574	be detected and should normally be specified as C<0> to let libev choose
1780	a suitable value. The memory pointed to by C<path> must point to the same	2575	a suitable value. The memory pointed to by C<path> must point to the same
1781	path for as long as the watcher is active.	2576	path for as long as the watcher is active.
1782		2577
1783	The callback will receive C<EV_STAT> when a change was detected, relative	2578	The callback will receive an C<EV_STAT> event when a change was detected,
1784	to the attributes at the time the watcher was started (or the last change	2579	relative to the attributes at the time the watcher was started (or the
1785	was detected).	2580	last change was detected).
1786		2581
1787	=item ev_stat_stat (loop, ev_stat *)	2582	=item ev_stat_stat (loop, ev_stat *)
1788		2583
1789	Updates the stat buffer immediately with new values. If you change the	2584	Updates the stat buffer immediately with new values. If you change the
1790	watched path in your callback, you could call this function to avoid	2585	watched path in your callback, you could call this function to avoid
…		…
1873		2668
1874		2669
1875	=head2 C<ev_idle> - when you've got nothing better to do...	2670	=head2 C<ev_idle> - when you've got nothing better to do...
1876		2671
1877	Idle watchers trigger events when no other events of the same or higher	2672	Idle watchers trigger events when no other events of the same or higher
1878	priority are pending (prepare, check and other idle watchers do not	2673	priority are pending (prepare, check and other idle watchers do not count
1879	count).	2674	as receiving "events").
1880		2675
1881	That is, as long as your process is busy handling sockets or timeouts	2676	That is, as long as your process is busy handling sockets or timeouts
1882	(or even signals, imagine) of the same or higher priority it will not be	2677	(or even signals, imagine) of the same or higher priority it will not be
1883	triggered. But when your process is idle (or only lower-priority watchers	2678	triggered. But when your process is idle (or only lower-priority watchers
1884	are pending), the idle watchers are being called once per event loop	2679	are pending), the idle watchers are being called once per event loop
…		…
1895		2690
1896	=head3 Watcher-Specific Functions and Data Members	2691	=head3 Watcher-Specific Functions and Data Members
1897		2692
1898	=over 4	2693	=over 4
1899		2694
1900	=item ev_idle_init (ev_signal *, callback)	2695	=item ev_idle_init (ev_idle *, callback)
1901		2696
1902	Initialises and configures the idle watcher - it has no parameters of any	2697	Initialises and configures the idle watcher - it has no parameters of any
1903	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2698	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1904	believe me.	2699	believe me.
1905		2700
…		…
1909		2704
1910	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2705	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1911	callback, free it. Also, use no error checking, as usual.	2706	callback, free it. Also, use no error checking, as usual.
1912		2707
1913	static void	2708	static void
1914	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2709	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1915	{	2710	{
1916	free (w);	2711	free (w);
1917	// now do something you wanted to do when the program has	2712	// now do something you wanted to do when the program has
1918	// no longer anything immediate to do.	2713	// no longer anything immediate to do.
1919	}	2714	}
1920		2715
1921	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2716	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1922	ev_idle_init (idle_watcher, idle_cb);	2717	ev_idle_init (idle_watcher, idle_cb);
1923	ev_idle_start (loop, idle_cb);	2718	ev_idle_start (loop, idle_watcher);
1924		2719
1925		2720
1926	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2721	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1927		2722
1928	Prepare and check watchers are usually (but not always) used in tandem:	2723	Prepare and check watchers are usually (but not always) used in pairs:
1929	prepare watchers get invoked before the process blocks and check watchers	2724	prepare watchers get invoked before the process blocks and check watchers
1930	afterwards.	2725	afterwards.
1931		2726
1932	You I<must not> call C<ev_loop> or similar functions that enter	2727	You I<must not> call C<ev_run> or similar functions that enter
1933	the current event loop from either C<ev_prepare> or C<ev_check>	2728	the current event loop from either C<ev_prepare> or C<ev_check>
1934	watchers. Other loops than the current one are fine, however. The	2729	watchers. Other loops than the current one are fine, however. The
1935	rationale behind this is that you do not need to check for recursion in	2730	rationale behind this is that you do not need to check for recursion in
1936	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2731	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1937	C<ev_check> so if you have one watcher of each kind they will always be	2732	C<ev_check> so if you have one watcher of each kind they will always be
1938	called in pairs bracketing the blocking call.	2733	called in pairs bracketing the blocking call.
1939		2734
1940	Their main purpose is to integrate other event mechanisms into libev and	2735	Their main purpose is to integrate other event mechanisms into libev and
1941	their use is somewhat advanced. This could be used, for example, to track	2736	their use is somewhat advanced. They could be used, for example, to track
1942	variable changes, implement your own watchers, integrate net-snmp or a	2737	variable changes, implement your own watchers, integrate net-snmp or a
1943	coroutine library and lots more. They are also occasionally useful if	2738	coroutine library and lots more. They are also occasionally useful if
1944	you cache some data and want to flush it before blocking (for example,	2739	you cache some data and want to flush it before blocking (for example,
1945	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2740	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1946	watcher).	2741	watcher).
1947		2742
1948	This is done by examining in each prepare call which file descriptors need	2743	This is done by examining in each prepare call which file descriptors
1949	to be watched by the other library, registering C<ev_io> watchers for	2744	need to be watched by the other library, registering C<ev_io> watchers
1950	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2745	for them and starting an C<ev_timer> watcher for any timeouts (many
1951	provide just this functionality). Then, in the check watcher you check for	2746	libraries provide exactly this functionality). Then, in the check watcher,
1952	any events that occurred (by checking the pending status of all watchers	2747	you check for any events that occurred (by checking the pending status
1953	and stopping them) and call back into the library. The I/O and timer	2748	of all watchers and stopping them) and call back into the library. The
1954	callbacks will never actually be called (but must be valid nevertheless,	2749	I/O and timer callbacks will never actually be called (but must be valid
1955	because you never know, you know?).	2750	nevertheless, because you never know, you know?).
1956		2751
1957	As another example, the Perl Coro module uses these hooks to integrate	2752	As another example, the Perl Coro module uses these hooks to integrate
1958	coroutines into libev programs, by yielding to other active coroutines	2753	coroutines into libev programs, by yielding to other active coroutines
1959	during each prepare and only letting the process block if no coroutines	2754	during each prepare and only letting the process block if no coroutines
1960	are ready to run (it's actually more complicated: it only runs coroutines	2755	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1963	loop from blocking if lower-priority coroutines are active, thus mapping	2758	loop from blocking if lower-priority coroutines are active, thus mapping
1964	low-priority coroutines to idle/background tasks).	2759	low-priority coroutines to idle/background tasks).
1965		2760
1966	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2761	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1967	priority, to ensure that they are being run before any other watchers	2762	priority, to ensure that they are being run before any other watchers
		2763	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2764
1968	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2765	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1969	too) should not activate ("feed") events into libev. While libev fully	2766	activate ("feed") events into libev. While libev fully supports this, they
1970	supports this, they might get executed before other C<ev_check> watchers	2767	might get executed before other C<ev_check> watchers did their job. As
1971	did their job. As C<ev_check> watchers are often used to embed other	2768	C<ev_check> watchers are often used to embed other (non-libev) event
1972	(non-libev) event loops those other event loops might be in an unusable	2769	loops those other event loops might be in an unusable state until their
1973	state until their C<ev_check> watcher ran (always remind yourself to	2770	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1974	coexist peacefully with others).	2771	others).
1975		2772
1976	=head3 Watcher-Specific Functions and Data Members	2773	=head3 Watcher-Specific Functions and Data Members
1977		2774
1978	=over 4	2775	=over 4
1979		2776
…		…
1981		2778
1982	=item ev_check_init (ev_check *, callback)	2779	=item ev_check_init (ev_check *, callback)
1983		2780
1984	Initialises and configures the prepare or check watcher - they have no	2781	Initialises and configures the prepare or check watcher - they have no
1985	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2782	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1986	macros, but using them is utterly, utterly and completely pointless.	2783	macros, but using them is utterly, utterly, utterly and completely
		2784	pointless.
1987		2785
1988	=back	2786	=back
1989		2787
1990	=head3 Examples	2788	=head3 Examples
1991		2789
…		…
2004		2802
2005	static ev_io iow [nfd];	2803	static ev_io iow [nfd];
2006	static ev_timer tw;	2804	static ev_timer tw;
2007		2805
2008	static void	2806	static void
2009	io_cb (ev_loop *loop, ev_io *w, int revents)	2807	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2010	{	2808	{
2011	}	2809	}
2012		2810
2013	// create io watchers for each fd and a timer before blocking	2811	// create io watchers for each fd and a timer before blocking
2014	static void	2812	static void
2015	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2813	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2016	{	2814	{
2017	int timeout = 3600000;	2815	int timeout = 3600000;
2018	struct pollfd fds [nfd];	2816	struct pollfd fds [nfd];
2019	// actual code will need to loop here and realloc etc.	2817	// actual code will need to loop here and realloc etc.
2020	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2818	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2021		2819
2022	/* the callback is illegal, but won't be called as we stop during check */	2820	/* the callback is illegal, but won't be called as we stop during check */
2023	ev_timer_init (&tw, 0, timeout * 1e-3);	2821	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2024	ev_timer_start (loop, &tw);	2822	ev_timer_start (loop, &tw);
2025		2823
2026	// create one ev_io per pollfd	2824	// create one ev_io per pollfd
2027	for (int i = 0; i < nfd; ++i)	2825	for (int i = 0; i < nfd; ++i)
2028	{	2826	{
…		…
2035	}	2833	}
2036	}	2834	}
2037		2835
2038	// stop all watchers after blocking	2836	// stop all watchers after blocking
2039	static void	2837	static void
2040	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2838	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2041	{	2839	{
2042	ev_timer_stop (loop, &tw);	2840	ev_timer_stop (loop, &tw);
2043		2841
2044	for (int i = 0; i < nfd; ++i)	2842	for (int i = 0; i < nfd; ++i)
2045	{	2843	{
…		…
2084	}	2882	}
2085		2883
2086	// do not ever call adns_afterpoll	2884	// do not ever call adns_afterpoll
2087		2885
2088	Method 4: Do not use a prepare or check watcher because the module you	2886	Method 4: Do not use a prepare or check watcher because the module you
2089	want to embed is too inflexible to support it. Instead, you can override	2887	want to embed is not flexible enough to support it. Instead, you can
2090	their poll function. The drawback with this solution is that the main	2888	override their poll function. The drawback with this solution is that the
2091	loop is now no longer controllable by EV. The C<Glib::EV> module does	2889	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2092	this.	2890	this approach, effectively embedding EV as a client into the horrible
		2891	libglib event loop.
2093		2892
2094	static gint	2893	static gint
2095	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2894	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2096	{	2895	{
2097	int got_events = 0;	2896	int got_events = 0;
…		…
2101		2900
2102	if (timeout >= 0)	2901	if (timeout >= 0)
2103	// create/start timer	2902	// create/start timer
2104		2903
2105	// poll	2904	// poll
2106	ev_loop (EV_A_ 0);	2905	ev_run (EV_A_ 0);
2107		2906
2108	// stop timer again	2907	// stop timer again
2109	if (timeout >= 0)	2908	if (timeout >= 0)
2110	ev_timer_stop (EV_A_ &to);	2909	ev_timer_stop (EV_A_ &to);
2111		2910
…		…
2128	prioritise I/O.	2927	prioritise I/O.
2129		2928
2130	As an example for a bug workaround, the kqueue backend might only support	2929	As an example for a bug workaround, the kqueue backend might only support
2131	sockets on some platform, so it is unusable as generic backend, but you	2930	sockets on some platform, so it is unusable as generic backend, but you
2132	still want to make use of it because you have many sockets and it scales	2931	still want to make use of it because you have many sockets and it scales
2133	so nicely. In this case, you would create a kqueue-based loop and embed it	2932	so nicely. In this case, you would create a kqueue-based loop and embed
2134	into your default loop (which might use e.g. poll). Overall operation will	2933	it into your default loop (which might use e.g. poll). Overall operation
2135	be a bit slower because first libev has to poll and then call kevent, but	2934	will be a bit slower because first libev has to call C<poll> and then
2136	at least you can use both at what they are best.	2935	C<kevent>, but at least you can use both mechanisms for what they are
		2936	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2137		2937
2138	As for prioritising I/O: rarely you have the case where some fds have	2938	As for prioritising I/O: under rare circumstances you have the case where
2139	to be watched and handled very quickly (with low latency), and even	2939	some fds have to be watched and handled very quickly (with low latency),
2140	priorities and idle watchers might have too much overhead. In this case	2940	and even priorities and idle watchers might have too much overhead. In
2141	you would put all the high priority stuff in one loop and all the rest in	2941	this case you would put all the high priority stuff in one loop and all
2142	a second one, and embed the second one in the first.	2942	the rest in a second one, and embed the second one in the first.
2143		2943
2144	As long as the watcher is active, the callback will be invoked every time	2944	As long as the watcher is active, the callback will be invoked every
2145	there might be events pending in the embedded loop. The callback must then	2945	time there might be events pending in the embedded loop. The callback
2146	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2946	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2147	their callbacks (you could also start an idle watcher to give the embedded	2947	sweep and invoke their callbacks (the callback doesn't need to invoke the
2148	loop strictly lower priority for example). You can also set the callback	2948	C<ev_embed_sweep> function directly, it could also start an idle watcher
2149	to C<0>, in which case the embed watcher will automatically execute the	2949	to give the embedded loop strictly lower priority for example).
2150	embedded loop sweep.
2151		2950
2152	As long as the watcher is started it will automatically handle events. The	2951	You can also set the callback to C<0>, in which case the embed watcher
2153	callback will be invoked whenever some events have been handled. You can	2952	will automatically execute the embedded loop sweep whenever necessary.
2154	set the callback to C<0> to avoid having to specify one if you are not
2155	interested in that.
2156		2953
2157	Also, there have not currently been made special provisions for forking:	2954	Fork detection will be handled transparently while the C<ev_embed> watcher
2158	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2955	is active, i.e., the embedded loop will automatically be forked when the
2159	but you will also have to stop and restart any C<ev_embed> watchers	2956	embedding loop forks. In other cases, the user is responsible for calling
2160	yourself.	2957	C<ev_loop_fork> on the embedded loop.
2161		2958
2162	Unfortunately, not all backends are embeddable, only the ones returned by	2959	Unfortunately, not all backends are embeddable: only the ones returned by
2163	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2960	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2164	portable one.	2961	portable one.
2165		2962
2166	So when you want to use this feature you will always have to be prepared	2963	So when you want to use this feature you will always have to be prepared
2167	that you cannot get an embeddable loop. The recommended way to get around	2964	that you cannot get an embeddable loop. The recommended way to get around
2168	this is to have a separate variables for your embeddable loop, try to	2965	this is to have a separate variables for your embeddable loop, try to
2169	create it, and if that fails, use the normal loop for everything.	2966	create it, and if that fails, use the normal loop for everything.
		2967
		2968	=head3 C<ev_embed> and fork
		2969
		2970	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2971	automatically be applied to the embedded loop as well, so no special
		2972	fork handling is required in that case. When the watcher is not running,
		2973	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2974	as applicable.
2170		2975
2171	=head3 Watcher-Specific Functions and Data Members	2976	=head3 Watcher-Specific Functions and Data Members
2172		2977
2173	=over 4	2978	=over 4
2174		2979
…		…
2183	if you do not want that, you need to temporarily stop the embed watcher).	2988	if you do not want that, you need to temporarily stop the embed watcher).
2184		2989
2185	=item ev_embed_sweep (loop, ev_embed *)	2990	=item ev_embed_sweep (loop, ev_embed *)
2186		2991
2187	Make a single, non-blocking sweep over the embedded loop. This works	2992	Make a single, non-blocking sweep over the embedded loop. This works
2188	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2993	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2189	appropriate way for embedded loops.	2994	appropriate way for embedded loops.
2190		2995
2191	=item struct ev_loop *other [read-only]	2996	=item struct ev_loop *other [read-only]
2192		2997
2193	The embedded event loop.	2998	The embedded event loop.
…		…
2202	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	3007	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2203	used).	3008	used).
2204		3009
2205	struct ev_loop *loop_hi = ev_default_init (0);	3010	struct ev_loop *loop_hi = ev_default_init (0);
2206	struct ev_loop *loop_lo = 0;	3011	struct ev_loop *loop_lo = 0;
2207	struct ev_embed embed;	3012	ev_embed embed;
2208		3013
2209	// see if there is a chance of getting one that works	3014	// see if there is a chance of getting one that works
2210	// (remember that a flags value of 0 means autodetection)	3015	// (remember that a flags value of 0 means autodetection)
2211	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3016	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2212	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3017	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2226	kqueue implementation). Store the kqueue/socket-only event loop in	3031	kqueue implementation). Store the kqueue/socket-only event loop in
2227	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3032	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2228		3033
2229	struct ev_loop *loop = ev_default_init (0);	3034	struct ev_loop *loop = ev_default_init (0);
2230	struct ev_loop *loop_socket = 0;	3035	struct ev_loop *loop_socket = 0;
2231	struct ev_embed embed;	3036	ev_embed embed;
2232		3037
2233	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3038	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2234	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3039	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2235	{	3040	{
2236	ev_embed_init (&embed, 0, loop_socket);	3041	ev_embed_init (&embed, 0, loop_socket);
…		…
2251	event loop blocks next and before C<ev_check> watchers are being called,	3056	event loop blocks next and before C<ev_check> watchers are being called,
2252	and only in the child after the fork. If whoever good citizen calling	3057	and only in the child after the fork. If whoever good citizen calling
2253	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3058	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2254	handlers will be invoked, too, of course.	3059	handlers will be invoked, too, of course.
2255		3060
		3061	=head3 The special problem of life after fork - how is it possible?
		3062
		3063	Most uses of C<fork()> consist of forking, then some simple calls to set
		3064	up/change the process environment, followed by a call to C<exec()>. This
		3065	sequence should be handled by libev without any problems.
		3066
		3067	This changes when the application actually wants to do event handling
		3068	in the child, or both parent in child, in effect "continuing" after the
		3069	fork.
		3070
		3071	The default mode of operation (for libev, with application help to detect
		3072	forks) is to duplicate all the state in the child, as would be expected
		3073	when I<either> the parent I<or> the child process continues.
		3074
		3075	When both processes want to continue using libev, then this is usually the
		3076	wrong result. In that case, usually one process (typically the parent) is
		3077	supposed to continue with all watchers in place as before, while the other
		3078	process typically wants to start fresh, i.e. without any active watchers.
		3079
		3080	The cleanest and most efficient way to achieve that with libev is to
		3081	simply create a new event loop, which of course will be "empty", and
		3082	use that for new watchers. This has the advantage of not touching more
		3083	memory than necessary, and thus avoiding the copy-on-write, and the
		3084	disadvantage of having to use multiple event loops (which do not support
		3085	signal watchers).
		3086
		3087	When this is not possible, or you want to use the default loop for
		3088	other reasons, then in the process that wants to start "fresh", call
		3089	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3090	Destroying the default loop will "orphan" (not stop) all registered
		3091	watchers, so you have to be careful not to execute code that modifies
		3092	those watchers. Note also that in that case, you have to re-register any
		3093	signal watchers.
		3094
2256	=head3 Watcher-Specific Functions and Data Members	3095	=head3 Watcher-Specific Functions and Data Members
2257		3096
2258	=over 4	3097	=over 4
2259		3098
2260	=item ev_fork_init (ev_signal *, callback)	3099	=item ev_fork_init (ev_fork *, callback)
2261		3100
2262	Initialises and configures the fork watcher - it has no parameters of any	3101	Initialises and configures the fork watcher - it has no parameters of any
2263	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3102	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2264	believe me.	3103	believe me.
2265		3104
2266	=back	3105	=back
2267		3106
2268		3107
		3108	=head2 C<ev_cleanup> - even the best things end
		3109
		3110	Cleanup watchers are called just before the event loop they are registered
		3111	with is being destroyed.
		3112
		3113	While there is no guarantee that the event loop gets destroyed, cleanup
		3114	watchers provide a convenient method to install cleanup hooks for your
		3115	program, worker threads and so on - you just to make sure to destroy the
		3116	loop when you want them to be invoked.
		3117
		3118	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3119	all other watchers, they do not keep a reference to the event loop (which
		3120	makes a lot of sense if you think about it). Like all other watchers, you
		3121	can call libev functions in the callback, except C<ev_cleanup_start>.
		3122
		3123	=head3 Watcher-Specific Functions and Data Members
		3124
		3125	=over 4
		3126
		3127	=item ev_cleanup_init (ev_cleanup *, callback)
		3128
		3129	Initialises and configures the cleanup watcher - it has no parameters of
		3130	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3131	pointless, believe me.
		3132
		3133	=back
		3134
		3135	Example: Register an atexit handler to destroy the default loop, so any
		3136	cleanup functions are called.
		3137
		3138	static void
		3139	program_exits (void)
		3140	{
		3141	ev_loop_destroy (EV_DEFAULT_UC);
		3142	}
		3143
		3144	...
		3145	atexit (program_exits);
		3146
		3147
2269	=head2 C<ev_async> - how to wake up another event loop	3148	=head2 C<ev_async> - how to wake up an event loop
2270		3149
2271	In general, you cannot use an C<ev_loop> from multiple threads or other	3150	In general, you cannot use an C<ev_run> from multiple threads or other
2272	asynchronous sources such as signal handlers (as opposed to multiple event	3151	asynchronous sources such as signal handlers (as opposed to multiple event
2273	loops - those are of course safe to use in different threads).	3152	loops - those are of course safe to use in different threads).
2274		3153
2275	Sometimes, however, you need to wake up another event loop you do not	3154	Sometimes, however, you need to wake up an event loop you do not control,
2276	control, for example because it belongs to another thread. This is what	3155	for example because it belongs to another thread. This is what C<ev_async>
2277	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3156	watchers do: as long as the C<ev_async> watcher is active, you can signal
2278	can signal it by calling C<ev_async_send>, which is thread- and signal	3157	it by calling C<ev_async_send>, which is thread- and signal safe.
2279	safe.
2280		3158
2281	This functionality is very similar to C<ev_signal> watchers, as signals,	3159	This functionality is very similar to C<ev_signal> watchers, as signals,
2282	too, are asynchronous in nature, and signals, too, will be compressed	3160	too, are asynchronous in nature, and signals, too, will be compressed
2283	(i.e. the number of callback invocations may be less than the number of	3161	(i.e. the number of callback invocations may be less than the number of
2284	C<ev_async_sent> calls).	3162	C<ev_async_sent> calls).
…		…
2289	=head3 Queueing	3167	=head3 Queueing
2290		3168
2291	C<ev_async> does not support queueing of data in any way. The reason	3169	C<ev_async> does not support queueing of data in any way. The reason
2292	is that the author does not know of a simple (or any) algorithm for a	3170	is that the author does not know of a simple (or any) algorithm for a
2293	multiple-writer-single-reader queue that works in all cases and doesn't	3171	multiple-writer-single-reader queue that works in all cases and doesn't
2294	need elaborate support such as pthreads.	3172	need elaborate support such as pthreads or unportable memory access
		3173	semantics.
2295		3174
2296	That means that if you want to queue data, you have to provide your own	3175	That means that if you want to queue data, you have to provide your own
2297	queue. But at least I can tell you would implement locking around your	3176	queue. But at least I can tell you how to implement locking around your
2298	queue:	3177	queue:
2299		3178
2300	=over 4	3179	=over 4
2301		3180
2302	=item queueing from a signal handler context	3181	=item queueing from a signal handler context
2303		3182
2304	To implement race-free queueing, you simply add to the queue in the signal	3183	To implement race-free queueing, you simply add to the queue in the signal
2305	handler but you block the signal handler in the watcher callback. Here is an example that does that for	3184	handler but you block the signal handler in the watcher callback. Here is
2306	some fictitious SIGUSR1 handler:	3185	an example that does that for some fictitious SIGUSR1 handler:
2307		3186
2308	static ev_async mysig;	3187	static ev_async mysig;
2309		3188
2310	static void	3189	static void
2311	sigusr1_handler (void)	3190	sigusr1_handler (void)
…		…
2377	=over 4	3256	=over 4
2378		3257
2379	=item ev_async_init (ev_async *, callback)	3258	=item ev_async_init (ev_async *, callback)
2380		3259
2381	Initialises and configures the async watcher - it has no parameters of any	3260	Initialises and configures the async watcher - it has no parameters of any
2382	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3261	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2383	believe me.	3262	trust me.
2384		3263
2385	=item ev_async_send (loop, ev_async *)	3264	=item ev_async_send (loop, ev_async *)
2386		3265
2387	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3266	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2388	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3267	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2389	C<ev_feed_event>, this call is safe to do in other threads, signal or	3268	C<ev_feed_event>, this call is safe to do from other threads, signal or
2390	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3269	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2391	section below on what exactly this means).	3270	section below on what exactly this means).
2392		3271
		3272	Note that, as with other watchers in libev, multiple events might get
		3273	compressed into a single callback invocation (another way to look at this
		3274	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3275	reset when the event loop detects that).
		3276
2393	This call incurs the overhead of a system call only once per loop iteration,	3277	This call incurs the overhead of a system call only once per event loop
2394	so while the overhead might be noticeable, it doesn't apply to repeated	3278	iteration, so while the overhead might be noticeable, it doesn't apply to
2395	calls to C<ev_async_send>.	3279	repeated calls to C<ev_async_send> for the same event loop.
2396		3280
2397	=item bool = ev_async_pending (ev_async *)	3281	=item bool = ev_async_pending (ev_async *)
2398		3282
2399	Returns a non-zero value when C<ev_async_send> has been called on the	3283	Returns a non-zero value when C<ev_async_send> has been called on the
2400	watcher but the event has not yet been processed (or even noted) by the	3284	watcher but the event has not yet been processed (or even noted) by the
…		…
2403	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3287	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2404	the loop iterates next and checks for the watcher to have become active,	3288	the loop iterates next and checks for the watcher to have become active,
2405	it will reset the flag again. C<ev_async_pending> can be used to very	3289	it will reset the flag again. C<ev_async_pending> can be used to very
2406	quickly check whether invoking the loop might be a good idea.	3290	quickly check whether invoking the loop might be a good idea.
2407		3291
2408	Not that this does I<not> check whether the watcher itself is pending, only	3292	Not that this does I<not> check whether the watcher itself is pending,
2409	whether it has been requested to make this watcher pending.	3293	only whether it has been requested to make this watcher pending: there
		3294	is a time window between the event loop checking and resetting the async
		3295	notification, and the callback being invoked.
2410		3296
2411	=back	3297	=back
2412		3298
2413		3299
2414	=head1 OTHER FUNCTIONS	3300	=head1 OTHER FUNCTIONS
…		…
2418	=over 4	3304	=over 4
2419		3305
2420	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3306	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2421		3307
2422	This function combines a simple timer and an I/O watcher, calls your	3308	This function combines a simple timer and an I/O watcher, calls your
2423	callback on whichever event happens first and automatically stop both	3309	callback on whichever event happens first and automatically stops both
2424	watchers. This is useful if you want to wait for a single event on an fd	3310	watchers. This is useful if you want to wait for a single event on an fd
2425	or timeout without having to allocate/configure/start/stop/free one or	3311	or timeout without having to allocate/configure/start/stop/free one or
2426	more watchers yourself.	3312	more watchers yourself.
2427		3313
2428	If C<fd> is less than 0, then no I/O watcher will be started and events	3314	If C<fd> is less than 0, then no I/O watcher will be started and the
2429	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	3315	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2430	C<events> set will be created and started.	3316	the given C<fd> and C<events> set will be created and started.
2431		3317
2432	If C<timeout> is less than 0, then no timeout watcher will be	3318	If C<timeout> is less than 0, then no timeout watcher will be
2433	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3319	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2434	repeat = 0) will be started. While C<0> is a valid timeout, it is of	3320	repeat = 0) will be started. C<0> is a valid timeout.
2435	dubious value.
2436		3321
2437	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3322	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2438	passed an C<revents> set like normal event callbacks (a combination of	3323	passed an C<revents> set like normal event callbacks (a combination of
2439	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3324	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2440	value passed to C<ev_once>:	3325	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3326	a timeout and an io event at the same time - you probably should give io
		3327	events precedence.
		3328
		3329	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2441		3330
2442	static void stdin_ready (int revents, void *arg)	3331	static void stdin_ready (int revents, void *arg)
2443	{	3332	{
		3333	if (revents & EV_READ)
		3334	/* stdin might have data for us, joy! */;
2444	if (revents & EV_TIMEOUT)	3335	else if (revents & EV_TIMER)
2445	/* doh, nothing entered */;	3336	/* doh, nothing entered */;
2446	else if (revents & EV_READ)
2447	/* stdin might have data for us, joy! */;
2448	}	3337	}
2449		3338
2450	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3339	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2451		3340
2452	=item ev_feed_event (ev_loop *, watcher *, int revents)
2453
2454	Feeds the given event set into the event loop, as if the specified event
2455	had happened for the specified watcher (which must be a pointer to an
2456	initialised but not necessarily started event watcher).
2457
2458	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3341	=item ev_feed_fd_event (loop, int fd, int revents)
2459		3342
2460	Feed an event on the given fd, as if a file descriptor backend detected	3343	Feed an event on the given fd, as if a file descriptor backend detected
2461	the given events it.	3344	the given events it.
2462		3345
2463	=item ev_feed_signal_event (ev_loop *loop, int signum)	3346	=item ev_feed_signal_event (loop, int signum)
2464		3347
2465	Feed an event as if the given signal occurred (C<loop> must be the default	3348	Feed an event as if the given signal occurred (C<loop> must be the default
2466	loop!).	3349	loop!).
2467		3350
2468	=back	3351	=back
…		…
2548		3431
2549	=over 4	3432	=over 4
2550		3433
2551	=item ev::TYPE::TYPE ()	3434	=item ev::TYPE::TYPE ()
2552		3435
2553	=item ev::TYPE::TYPE (struct ev_loop *)	3436	=item ev::TYPE::TYPE (loop)
2554		3437
2555	=item ev::TYPE::~TYPE	3438	=item ev::TYPE::~TYPE
2556		3439
2557	The constructor (optionally) takes an event loop to associate the watcher	3440	The constructor (optionally) takes an event loop to associate the watcher
2558	with. If it is omitted, it will use C<EV_DEFAULT>.	3441	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2590		3473
2591	myclass obj;	3474	myclass obj;
2592	ev::io iow;	3475	ev::io iow;
2593	iow.set <myclass, &myclass::io_cb> (&obj);	3476	iow.set <myclass, &myclass::io_cb> (&obj);
2594		3477
		3478	=item w->set (object *)
		3479
		3480	This is a variation of a method callback - leaving out the method to call
		3481	will default the method to C<operator ()>, which makes it possible to use
		3482	functor objects without having to manually specify the C<operator ()> all
		3483	the time. Incidentally, you can then also leave out the template argument
		3484	list.
		3485
		3486	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3487	int revents)>.
		3488
		3489	See the method-C<set> above for more details.
		3490
		3491	Example: use a functor object as callback.
		3492
		3493	struct myfunctor
		3494	{
		3495	void operator() (ev::io &w, int revents)
		3496	{
		3497	...
		3498	}
		3499	}
		3500
		3501	myfunctor f;
		3502
		3503	ev::io w;
		3504	w.set (&f);
		3505
2595	=item w->set<function> (void *data = 0)	3506	=item w->set<function> (void *data = 0)
2596		3507
2597	Also sets a callback, but uses a static method or plain function as	3508	Also sets a callback, but uses a static method or plain function as
2598	callback. The optional C<data> argument will be stored in the watcher's	3509	callback. The optional C<data> argument will be stored in the watcher's
2599	C<data> member and is free for you to use.	3510	C<data> member and is free for you to use.
2600		3511
2601	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3512	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2602		3513
2603	See the method-C<set> above for more details.	3514	See the method-C<set> above for more details.
2604		3515
2605	Example:	3516	Example: Use a plain function as callback.
2606		3517
2607	static void io_cb (ev::io &w, int revents) { }	3518	static void io_cb (ev::io &w, int revents) { }
2608	iow.set <io_cb> ();	3519	iow.set <io_cb> ();
2609		3520
2610	=item w->set (struct ev_loop *)	3521	=item w->set (loop)
2611		3522
2612	Associates a different C<struct ev_loop> with this watcher. You can only	3523	Associates a different C<struct ev_loop> with this watcher. You can only
2613	do this when the watcher is inactive (and not pending either).	3524	do this when the watcher is inactive (and not pending either).
2614		3525
2615	=item w->set ([arguments])	3526	=item w->set ([arguments])
2616		3527
2617	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3528	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
2618	called at least once. Unlike the C counterpart, an active watcher gets	3529	method or a suitable start method must be called at least once. Unlike the
2619	automatically stopped and restarted when reconfiguring it with this	3530	C counterpart, an active watcher gets automatically stopped and restarted
2620	method.	3531	when reconfiguring it with this method.
2621		3532
2622	=item w->start ()	3533	=item w->start ()
2623		3534
2624	Starts the watcher. Note that there is no C<loop> argument, as the	3535	Starts the watcher. Note that there is no C<loop> argument, as the
2625	constructor already stores the event loop.	3536	constructor already stores the event loop.
2626		3537
		3538	=item w->start ([arguments])
		3539
		3540	Instead of calling C<set> and C<start> methods separately, it is often
		3541	convenient to wrap them in one call. Uses the same type of arguments as
		3542	the configure C<set> method of the watcher.
		3543
2627	=item w->stop ()	3544	=item w->stop ()
2628		3545
2629	Stops the watcher if it is active. Again, no C<loop> argument.	3546	Stops the watcher if it is active. Again, no C<loop> argument.
2630		3547
2631	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3548	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2643		3560
2644	=back	3561	=back
2645		3562
2646	=back	3563	=back
2647		3564
2648	Example: Define a class with an IO and idle watcher, start one of them in	3565	Example: Define a class with two I/O and idle watchers, start the I/O
2649	the constructor.	3566	watchers in the constructor.
2650		3567
2651	class myclass	3568	class myclass
2652	{	3569	{
2653	ev::io io; void io_cb (ev::io &w, int revents);	3570	ev::io io ; void io_cb (ev::io &w, int revents);
		3571	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
2654	ev:idle idle void idle_cb (ev::idle &w, int revents);	3572	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2655		3573
2656	myclass (int fd)	3574	myclass (int fd)
2657	{	3575	{
2658	io .set <myclass, &myclass::io_cb > (this);	3576	io .set <myclass, &myclass::io_cb > (this);
		3577	io2 .set <myclass, &myclass::io2_cb > (this);
2659	idle.set <myclass, &myclass::idle_cb> (this);	3578	idle.set <myclass, &myclass::idle_cb> (this);
2660		3579
2661	io.start (fd, ev::READ);	3580	io.set (fd, ev::WRITE); // configure the watcher
		3581	io.start (); // start it whenever convenient
		3582
		3583	io2.start (fd, ev::READ); // set + start in one call
2662	}	3584	}
2663	};	3585	};
2664		3586
2665		3587
2666	=head1 OTHER LANGUAGE BINDINGS	3588	=head1 OTHER LANGUAGE BINDINGS
…		…
2675	=item Perl	3597	=item Perl
2676		3598
2677	The EV module implements the full libev API and is actually used to test	3599	The EV module implements the full libev API and is actually used to test
2678	libev. EV is developed together with libev. Apart from the EV core module,	3600	libev. EV is developed together with libev. Apart from the EV core module,
2679	there are additional modules that implement libev-compatible interfaces	3601	there are additional modules that implement libev-compatible interfaces
2680	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3602	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2681	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3603	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3604	and C<EV::Glib>).
2682		3605
2683	It can be found and installed via CPAN, its homepage is at	3606	It can be found and installed via CPAN, its homepage is at
2684	L<http://software.schmorp.de/pkg/EV>.	3607	L<http://software.schmorp.de/pkg/EV>.
2685		3608
2686	=item Python	3609	=item Python
2687		3610
2688	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3611	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2689	seems to be quite complete and well-documented. Note, however, that the	3612	seems to be quite complete and well-documented.
2690	patch they require for libev is outright dangerous as it breaks the ABI
2691	for everybody else, and therefore, should never be applied in an installed
2692	libev (if python requires an incompatible ABI then it needs to embed
2693	libev).
2694		3613
2695	=item Ruby	3614	=item Ruby
2696		3615
2697	Tony Arcieri has written a ruby extension that offers access to a subset	3616	Tony Arcieri has written a ruby extension that offers access to a subset
2698	of the libev API and adds file handle abstractions, asynchronous DNS and	3617	of the libev API and adds file handle abstractions, asynchronous DNS and
2699	more on top of it. It can be found via gem servers. Its homepage is at	3618	more on top of it. It can be found via gem servers. Its homepage is at
2700	L<http://rev.rubyforge.org/>.	3619	L<http://rev.rubyforge.org/>.
2701		3620
		3621	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3622	makes rev work even on mingw.
		3623
		3624	=item Haskell
		3625
		3626	A haskell binding to libev is available at
		3627	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3628
2702	=item D	3629	=item D
2703		3630
2704	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3631	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2705	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3632	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3633
		3634	=item Ocaml
		3635
		3636	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3637	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3638
		3639	=item Lua
		3640
		3641	Brian Maher has written a partial interface to libev for lua (at the
		3642	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3643	L<http://github.com/brimworks/lua-ev>.
2706		3644
2707	=back	3645	=back
2708		3646
2709		3647
2710	=head1 MACRO MAGIC	3648	=head1 MACRO MAGIC
…		…
2724	loop argument"). The C<EV_A> form is used when this is the sole argument,	3662	loop argument"). The C<EV_A> form is used when this is the sole argument,
2725	C<EV_A_> is used when other arguments are following. Example:	3663	C<EV_A_> is used when other arguments are following. Example:
2726		3664
2727	ev_unref (EV_A);	3665	ev_unref (EV_A);
2728	ev_timer_add (EV_A_ watcher);	3666	ev_timer_add (EV_A_ watcher);
2729	ev_loop (EV_A_ 0);	3667	ev_run (EV_A_ 0);
2730		3668
2731	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3669	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2732	which is often provided by the following macro.	3670	which is often provided by the following macro.
2733		3671
2734	=item C<EV_P>, C<EV_P_>	3672	=item C<EV_P>, C<EV_P_>
…		…
2774	}	3712	}
2775		3713
2776	ev_check check;	3714	ev_check check;
2777	ev_check_init (&check, check_cb);	3715	ev_check_init (&check, check_cb);
2778	ev_check_start (EV_DEFAULT_ &check);	3716	ev_check_start (EV_DEFAULT_ &check);
2779	ev_loop (EV_DEFAULT_ 0);	3717	ev_run (EV_DEFAULT_ 0);
2780		3718
2781	=head1 EMBEDDING	3719	=head1 EMBEDDING
2782		3720
2783	Libev can (and often is) directly embedded into host	3721	Libev can (and often is) directly embedded into host
2784	applications. Examples of applications that embed it include the Deliantra	3722	applications. Examples of applications that embed it include the Deliantra
…		…
2811		3749
2812	#define EV_STANDALONE 1	3750	#define EV_STANDALONE 1
2813	#include "ev.h"	3751	#include "ev.h"
2814		3752
2815	Both header files and implementation files can be compiled with a C++	3753	Both header files and implementation files can be compiled with a C++
2816	compiler (at least, thats a stated goal, and breakage will be treated	3754	compiler (at least, that's a stated goal, and breakage will be treated
2817	as a bug).	3755	as a bug).
2818		3756
2819	You need the following files in your source tree, or in a directory	3757	You need the following files in your source tree, or in a directory
2820	in your include path (e.g. in libev/ when using -Ilibev):	3758	in your include path (e.g. in libev/ when using -Ilibev):
2821		3759
…		…
2864	libev.m4	3802	libev.m4
2865		3803
2866	=head2 PREPROCESSOR SYMBOLS/MACROS	3804	=head2 PREPROCESSOR SYMBOLS/MACROS
2867		3805
2868	Libev can be configured via a variety of preprocessor symbols you have to	3806	Libev can be configured via a variety of preprocessor symbols you have to
2869	define before including any of its files. The default in the absence of	3807	define before including (or compiling) any of its files. The default in
2870	autoconf is noted for every option.	3808	the absence of autoconf is documented for every option.
		3809
		3810	Symbols marked with "(h)" do not change the ABI, and can have different
		3811	values when compiling libev vs. including F<ev.h>, so it is permissible
		3812	to redefine them before including F<ev.h> without breaking compatibility
		3813	to a compiled library. All other symbols change the ABI, which means all
		3814	users of libev and the libev code itself must be compiled with compatible
		3815	settings.
2871		3816
2872	=over 4	3817	=over 4
2873		3818
		3819	=item EV_COMPAT3 (h)
		3820
		3821	Backwards compatibility is a major concern for libev. This is why this
		3822	release of libev comes with wrappers for the functions and symbols that
		3823	have been renamed between libev version 3 and 4.
		3824
		3825	You can disable these wrappers (to test compatibility with future
		3826	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		3827	sources. This has the additional advantage that you can drop the C<struct>
		3828	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		3829	typedef in that case.
		3830
		3831	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		3832	and in some even more future version the compatibility code will be
		3833	removed completely.
		3834
2874	=item EV_STANDALONE	3835	=item EV_STANDALONE (h)
2875		3836
2876	Must always be C<1> if you do not use autoconf configuration, which	3837	Must always be C<1> if you do not use autoconf configuration, which
2877	keeps libev from including F<config.h>, and it also defines dummy	3838	keeps libev from including F<config.h>, and it also defines dummy
2878	implementations for some libevent functions (such as logging, which is not	3839	implementations for some libevent functions (such as logging, which is not
2879	supported). It will also not define any of the structs usually found in	3840	supported). It will also not define any of the structs usually found in
2880	F<event.h> that are not directly supported by the libev core alone.	3841	F<event.h> that are not directly supported by the libev core alone.
2881		3842
		3843	In standalone mode, libev will still try to automatically deduce the
		3844	configuration, but has to be more conservative.
		3845
2882	=item EV_USE_MONOTONIC	3846	=item EV_USE_MONOTONIC
2883		3847
2884	If defined to be C<1>, libev will try to detect the availability of the	3848	If defined to be C<1>, libev will try to detect the availability of the
2885	monotonic clock option at both compile time and runtime. Otherwise no use	3849	monotonic clock option at both compile time and runtime. Otherwise no
2886	of the monotonic clock option will be attempted. If you enable this, you	3850	use of the monotonic clock option will be attempted. If you enable this,
2887	usually have to link against librt or something similar. Enabling it when	3851	you usually have to link against librt or something similar. Enabling it
2888	the functionality isn't available is safe, though, although you have	3852	when the functionality isn't available is safe, though, although you have
2889	to make sure you link against any libraries where the C<clock_gettime>	3853	to make sure you link against any libraries where the C<clock_gettime>
2890	function is hiding in (often F<-lrt>).	3854	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2891		3855
2892	=item EV_USE_REALTIME	3856	=item EV_USE_REALTIME
2893		3857
2894	If defined to be C<1>, libev will try to detect the availability of the	3858	If defined to be C<1>, libev will try to detect the availability of the
2895	real-time clock option at compile time (and assume its availability at	3859	real-time clock option at compile time (and assume its availability
2896	runtime if successful). Otherwise no use of the real-time clock option will	3860	at runtime if successful). Otherwise no use of the real-time clock
2897	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3861	option will be attempted. This effectively replaces C<gettimeofday>
2898	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3862	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2899	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3863	correctness. See the note about libraries in the description of
		3864	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3865	C<EV_USE_CLOCK_SYSCALL>.
		3866
		3867	=item EV_USE_CLOCK_SYSCALL
		3868
		3869	If defined to be C<1>, libev will try to use a direct syscall instead
		3870	of calling the system-provided C<clock_gettime> function. This option
		3871	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3872	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3873	programs needlessly. Using a direct syscall is slightly slower (in
		3874	theory), because no optimised vdso implementation can be used, but avoids
		3875	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3876	higher, as it simplifies linking (no need for C<-lrt>).
2900		3877
2901	=item EV_USE_NANOSLEEP	3878	=item EV_USE_NANOSLEEP
2902		3879
2903	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3880	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2904	and will use it for delays. Otherwise it will use C<select ()>.	3881	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2920		3897
2921	=item EV_SELECT_USE_FD_SET	3898	=item EV_SELECT_USE_FD_SET
2922		3899
2923	If defined to C<1>, then the select backend will use the system C<fd_set>	3900	If defined to C<1>, then the select backend will use the system C<fd_set>
2924	structure. This is useful if libev doesn't compile due to a missing	3901	structure. This is useful if libev doesn't compile due to a missing
2925	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3902	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2926	exotic systems. This usually limits the range of file descriptors to some	3903	on exotic systems. This usually limits the range of file descriptors to
2927	low limit such as 1024 or might have other limitations (winsocket only	3904	some low limit such as 1024 or might have other limitations (winsocket
2928	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3905	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2929	influence the size of the C<fd_set> used.	3906	configures the maximum size of the C<fd_set>.
2930		3907
2931	=item EV_SELECT_IS_WINSOCKET	3908	=item EV_SELECT_IS_WINSOCKET
2932		3909
2933	When defined to C<1>, the select backend will assume that	3910	When defined to C<1>, the select backend will assume that
2934	select/socket/connect etc. don't understand file descriptors but	3911	select/socket/connect etc. don't understand file descriptors but
…		…
2936	be used is the winsock select). This means that it will call	3913	be used is the winsock select). This means that it will call
2937	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3914	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2938	it is assumed that all these functions actually work on fds, even	3915	it is assumed that all these functions actually work on fds, even
2939	on win32. Should not be defined on non-win32 platforms.	3916	on win32. Should not be defined on non-win32 platforms.
2940		3917
2941	=item EV_FD_TO_WIN32_HANDLE	3918	=item EV_FD_TO_WIN32_HANDLE(fd)
2942		3919
2943	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3920	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
2944	file descriptors to socket handles. When not defining this symbol (the	3921	file descriptors to socket handles. When not defining this symbol (the
2945	default), then libev will call C<_get_osfhandle>, which is usually	3922	default), then libev will call C<_get_osfhandle>, which is usually
2946	correct. In some cases, programs use their own file descriptor management,	3923	correct. In some cases, programs use their own file descriptor management,
2947	in which case they can provide this function to map fds to socket handles.	3924	in which case they can provide this function to map fds to socket handles.
		3925
		3926	=item EV_WIN32_HANDLE_TO_FD(handle)
		3927
		3928	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3929	using the standard C<_open_osfhandle> function. For programs implementing
		3930	their own fd to handle mapping, overwriting this function makes it easier
		3931	to do so. This can be done by defining this macro to an appropriate value.
		3932
		3933	=item EV_WIN32_CLOSE_FD(fd)
		3934
		3935	If programs implement their own fd to handle mapping on win32, then this
		3936	macro can be used to override the C<close> function, useful to unregister
		3937	file descriptors again. Note that the replacement function has to close
		3938	the underlying OS handle.
2948		3939
2949	=item EV_USE_POLL	3940	=item EV_USE_POLL
2950		3941
2951	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3942	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2952	backend. Otherwise it will be enabled on non-win32 platforms. It	3943	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
2999	as well as for signal and thread safety in C<ev_async> watchers.	3990	as well as for signal and thread safety in C<ev_async> watchers.
3000		3991
3001	In the absence of this define, libev will use C<sig_atomic_t volatile>	3992	In the absence of this define, libev will use C<sig_atomic_t volatile>
3002	(from F<signal.h>), which is usually good enough on most platforms.	3993	(from F<signal.h>), which is usually good enough on most platforms.
3003		3994
3004	=item EV_H	3995	=item EV_H (h)
3005		3996
3006	The name of the F<ev.h> header file used to include it. The default if	3997	The name of the F<ev.h> header file used to include it. The default if
3007	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	3998	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3008	used to virtually rename the F<ev.h> header file in case of conflicts.	3999	used to virtually rename the F<ev.h> header file in case of conflicts.
3009		4000
3010	=item EV_CONFIG_H	4001	=item EV_CONFIG_H (h)
3011		4002
3012	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4003	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3013	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4004	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3014	C<EV_H>, above.	4005	C<EV_H>, above.
3015		4006
3016	=item EV_EVENT_H	4007	=item EV_EVENT_H (h)
3017		4008
3018	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4009	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3019	of how the F<event.h> header can be found, the default is C<"event.h">.	4010	of how the F<event.h> header can be found, the default is C<"event.h">.
3020		4011
3021	=item EV_PROTOTYPES	4012	=item EV_PROTOTYPES (h)
3022		4013
3023	If defined to be C<0>, then F<ev.h> will not define any function	4014	If defined to be C<0>, then F<ev.h> will not define any function
3024	prototypes, but still define all the structs and other symbols. This is	4015	prototypes, but still define all the structs and other symbols. This is
3025	occasionally useful if you want to provide your own wrapper functions	4016	occasionally useful if you want to provide your own wrapper functions
3026	around libev functions.	4017	around libev functions.
…		…
3045	When doing priority-based operations, libev usually has to linearly search	4036	When doing priority-based operations, libev usually has to linearly search
3046	all the priorities, so having many of them (hundreds) uses a lot of space	4037	all the priorities, so having many of them (hundreds) uses a lot of space
3047	and time, so using the defaults of five priorities (-2 .. +2) is usually	4038	and time, so using the defaults of five priorities (-2 .. +2) is usually
3048	fine.	4039	fine.
3049		4040
3050	If your embedding application does not need any priorities, defining these both to	4041	If your embedding application does not need any priorities, defining these
3051	C<0> will save some memory and CPU.	4042	both to C<0> will save some memory and CPU.
3052		4043
3053	=item EV_PERIODIC_ENABLE	4044	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4045	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4046	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3054		4047
3055	If undefined or defined to be C<1>, then periodic timers are supported. If	4048	If undefined or defined to be C<1> (and the platform supports it), then
3056	defined to be C<0>, then they are not. Disabling them saves a few kB of	4049	the respective watcher type is supported. If defined to be C<0>, then it
3057	code.	4050	is not. Disabling watcher types mainly saves code size.
3058		4051
3059	=item EV_IDLE_ENABLE	4052	=item EV_FEATURES
3060
3061	If undefined or defined to be C<1>, then idle watchers are supported. If
3062	defined to be C<0>, then they are not. Disabling them saves a few kB of
3063	code.
3064
3065	=item EV_EMBED_ENABLE
3066
3067	If undefined or defined to be C<1>, then embed watchers are supported. If
3068	defined to be C<0>, then they are not.
3069
3070	=item EV_STAT_ENABLE
3071
3072	If undefined or defined to be C<1>, then stat watchers are supported. If
3073	defined to be C<0>, then they are not.
3074
3075	=item EV_FORK_ENABLE
3076
3077	If undefined or defined to be C<1>, then fork watchers are supported. If
3078	defined to be C<0>, then they are not.
3079
3080	=item EV_ASYNC_ENABLE
3081
3082	If undefined or defined to be C<1>, then async watchers are supported. If
3083	defined to be C<0>, then they are not.
3084
3085	=item EV_MINIMAL
3086		4053
3087	If you need to shave off some kilobytes of code at the expense of some	4054	If you need to shave off some kilobytes of code at the expense of some
3088	speed, define this symbol to C<1>. Currently this is used to override some	4055	speed (but with the full API), you can define this symbol to request
3089	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4056	certain subsets of functionality. The default is to enable all features
3090	much smaller 2-heap for timer management over the default 4-heap.	4057	that can be enabled on the platform.
		4058
		4059	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4060	with some broad features you want) and then selectively re-enable
		4061	additional parts you want, for example if you want everything minimal,
		4062	but multiple event loop support, async and child watchers and the poll
		4063	backend, use this:
		4064
		4065	#define EV_FEATURES 0
		4066	#define EV_MULTIPLICITY 1
		4067	#define EV_USE_POLL 1
		4068	#define EV_CHILD_ENABLE 1
		4069	#define EV_ASYNC_ENABLE 1
		4070
		4071	The actual value is a bitset, it can be a combination of the following
		4072	values:
		4073
		4074	=over 4
		4075
		4076	=item C<1> - faster/larger code
		4077
		4078	Use larger code to speed up some operations.
		4079
		4080	Currently this is used to override some inlining decisions (enlarging the
		4081	code size by roughly 30% on amd64).
		4082
		4083	When optimising for size, use of compiler flags such as C<-Os> with
		4084	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4085	assertions.
		4086
		4087	=item C<2> - faster/larger data structures
		4088
		4089	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4090	hash table sizes and so on. This will usually further increase code size
		4091	and can additionally have an effect on the size of data structures at
		4092	runtime.
		4093
		4094	=item C<4> - full API configuration
		4095
		4096	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4097	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4098
		4099	=item C<8> - full API
		4100
		4101	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4102	details on which parts of the API are still available without this
		4103	feature, and do not complain if this subset changes over time.
		4104
		4105	=item C<16> - enable all optional watcher types
		4106
		4107	Enables all optional watcher types. If you want to selectively enable
		4108	only some watcher types other than I/O and timers (e.g. prepare,
		4109	embed, async, child...) you can enable them manually by defining
		4110	C<EV_watchertype_ENABLE> to C<1> instead.
		4111
		4112	=item C<32> - enable all backends
		4113
		4114	This enables all backends - without this feature, you need to enable at
		4115	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4116
		4117	=item C<64> - enable OS-specific "helper" APIs
		4118
		4119	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4120	default.
		4121
		4122	=back
		4123
		4124	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4125	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4126	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4127	watchers, timers and monotonic clock support.
		4128
		4129	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4130	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4131	your program might be left out as well - a binary starting a timer and an
		4132	I/O watcher then might come out at only 5Kb.
		4133
		4134	=item EV_AVOID_STDIO
		4135
		4136	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4137	functions (printf, scanf, perror etc.). This will increase the code size
		4138	somewhat, but if your program doesn't otherwise depend on stdio and your
		4139	libc allows it, this avoids linking in the stdio library which is quite
		4140	big.
		4141
		4142	Note that error messages might become less precise when this option is
		4143	enabled.
		4144
		4145	=item EV_NSIG
		4146
		4147	The highest supported signal number, +1 (or, the number of
		4148	signals): Normally, libev tries to deduce the maximum number of signals
		4149	automatically, but sometimes this fails, in which case it can be
		4150	specified. Also, using a lower number than detected (C<32> should be
		4151	good for about any system in existence) can save some memory, as libev
		4152	statically allocates some 12-24 bytes per signal number.
3091		4153
3092	=item EV_PID_HASHSIZE	4154	=item EV_PID_HASHSIZE
3093		4155
3094	C<ev_child> watchers use a small hash table to distribute workload by	4156	C<ev_child> watchers use a small hash table to distribute workload by
3095	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4157	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3096	than enough. If you need to manage thousands of children you might want to	4158	usually more than enough. If you need to manage thousands of children you
3097	increase this value (I<must> be a power of two).	4159	might want to increase this value (I<must> be a power of two).
3098		4160
3099	=item EV_INOTIFY_HASHSIZE	4161	=item EV_INOTIFY_HASHSIZE
3100		4162
3101	C<ev_stat> watchers use a small hash table to distribute workload by	4163	C<ev_stat> watchers use a small hash table to distribute workload by
3102	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4164	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3103	usually more than enough. If you need to manage thousands of C<ev_stat>	4165	disabled), usually more than enough. If you need to manage thousands of
3104	watchers you might want to increase this value (I<must> be a power of	4166	C<ev_stat> watchers you might want to increase this value (I<must> be a
3105	two).	4167	power of two).
3106		4168
3107	=item EV_USE_4HEAP	4169	=item EV_USE_4HEAP
3108		4170
3109	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4171	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3110	timer and periodics heap, libev uses a 4-heap when this symbol is defined	4172	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3111	to C<1>. The 4-heap uses more complicated (longer) code but has	4173	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3112	noticeably faster performance with many (thousands) of watchers.	4174	faster performance with many (thousands) of watchers.
3113		4175
3114	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4176	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3115	(disabled).	4177	will be C<0>.
3116		4178
3117	=item EV_HEAP_CACHE_AT	4179	=item EV_HEAP_CACHE_AT
3118		4180
3119	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4181	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3120	timer and periodics heap, libev can cache the timestamp (I<at>) within	4182	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3121	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4183	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3122	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4184	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3123	but avoids random read accesses on heap changes. This improves performance	4185	but avoids random read accesses on heap changes. This improves performance
3124	noticeably with with many (hundreds) of watchers.	4186	noticeably with many (hundreds) of watchers.
3125		4187
3126	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4188	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3127	(disabled).	4189	will be C<0>.
3128		4190
3129	=item EV_VERIFY	4191	=item EV_VERIFY
3130		4192
3131	Controls how much internal verification (see C<ev_loop_verify ()>) will	4193	Controls how much internal verification (see C<ev_verify ()>) will
3132	be done: If set to C<0>, no internal verification code will be compiled	4194	be done: If set to C<0>, no internal verification code will be compiled
3133	in. If set to C<1>, then verification code will be compiled in, but not	4195	in. If set to C<1>, then verification code will be compiled in, but not
3134	called. If set to C<2>, then the internal verification code will be	4196	called. If set to C<2>, then the internal verification code will be
3135	called once per loop, which can slow down libev. If set to C<3>, then the	4197	called once per loop, which can slow down libev. If set to C<3>, then the
3136	verification code will be called very frequently, which will slow down	4198	verification code will be called very frequently, which will slow down
3137	libev considerably.	4199	libev considerably.
3138		4200
3139	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4201	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3140	C<0.>	4202	will be C<0>.
3141		4203
3142	=item EV_COMMON	4204	=item EV_COMMON
3143		4205
3144	By default, all watchers have a C<void *data> member. By redefining	4206	By default, all watchers have a C<void *data> member. By redefining
3145	this macro to a something else you can include more and other types of	4207	this macro to something else you can include more and other types of
3146	members. You have to define it each time you include one of the files,	4208	members. You have to define it each time you include one of the files,
3147	though, and it must be identical each time.	4209	though, and it must be identical each time.
3148		4210
3149	For example, the perl EV module uses something like this:	4211	For example, the perl EV module uses something like this:
3150		4212
…		…
3162	and the way callbacks are invoked and set. Must expand to a struct member	4224	and the way callbacks are invoked and set. Must expand to a struct member
3163	definition and a statement, respectively. See the F<ev.h> header file for	4225	definition and a statement, respectively. See the F<ev.h> header file for
3164	their default definitions. One possible use for overriding these is to	4226	their default definitions. One possible use for overriding these is to
3165	avoid the C<struct ev_loop *> as first argument in all cases, or to use	4227	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3166	method calls instead of plain function calls in C++.	4228	method calls instead of plain function calls in C++.
		4229
		4230	=back
3167		4231
3168	=head2 EXPORTED API SYMBOLS	4232	=head2 EXPORTED API SYMBOLS
3169		4233
3170	If you need to re-export the API (e.g. via a DLL) and you need a list of	4234	If you need to re-export the API (e.g. via a DLL) and you need a list of
3171	exported symbols, you can use the provided F<Symbol.*> files which list	4235	exported symbols, you can use the provided F<Symbol.*> files which list
…		…
3201	file.	4265	file.
3202		4266
3203	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4267	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3204	that everybody includes and which overrides some configure choices:	4268	that everybody includes and which overrides some configure choices:
3205		4269
3206	#define EV_MINIMAL 1	4270	#define EV_FEATURES 8
3207	#define EV_USE_POLL 0	4271	#define EV_USE_SELECT 1
3208	#define EV_MULTIPLICITY 0
3209	#define EV_PERIODIC_ENABLE 0	4272	#define EV_PREPARE_ENABLE 1
		4273	#define EV_IDLE_ENABLE 1
3210	#define EV_STAT_ENABLE 0	4274	#define EV_SIGNAL_ENABLE 1
3211	#define EV_FORK_ENABLE 0	4275	#define EV_CHILD_ENABLE 1
		4276	#define EV_USE_STDEXCEPT 0
3212	#define EV_CONFIG_H <config.h>	4277	#define EV_CONFIG_H <config.h>
3213	#define EV_MINPRI 0
3214	#define EV_MAXPRI 0
3215		4278
3216	#include "ev++.h"	4279	#include "ev++.h"
3217		4280
3218	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4281	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3219		4282
3220	#include "ev_cpp.h"	4283	#include "ev_cpp.h"
3221	#include "ev.c"	4284	#include "ev.c"
3222		4285
		4286	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3223		4287
3224	=head1 THREADS AND COROUTINES	4288	=head2 THREADS AND COROUTINES
3225		4289
3226	=head2 THREADS	4290	=head3 THREADS
3227		4291
3228	Libev itself is completely thread-safe, but it uses no locking. This	4292	All libev functions are reentrant and thread-safe unless explicitly
		4293	documented otherwise, but libev implements no locking itself. This means
3229	means that you can use as many loops as you want in parallel, as long as	4294	that you can use as many loops as you want in parallel, as long as there
3230	only one thread ever calls into one libev function with the same loop	4295	are no concurrent calls into any libev function with the same loop
3231	parameter.	4296	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		4297	of course): libev guarantees that different event loops share no data
		4298	structures that need any locking.
3232		4299
3233	Or put differently: calls with different loop parameters can be done in	4300	Or to put it differently: calls with different loop parameters can be done
3234	parallel from multiple threads, calls with the same loop parameter must be	4301	concurrently from multiple threads, calls with the same loop parameter
3235	done serially (but can be done from different threads, as long as only one	4302	must be done serially (but can be done from different threads, as long as
3236	thread ever is inside a call at any point in time, e.g. by using a mutex	4303	only one thread ever is inside a call at any point in time, e.g. by using
3237	per loop).	4304	a mutex per loop).
		4305
		4306	Specifically to support threads (and signal handlers), libev implements
		4307	so-called C<ev_async> watchers, which allow some limited form of
		4308	concurrency on the same event loop, namely waking it up "from the
		4309	outside".
3238		4310
3239	If you want to know which design (one loop, locking, or multiple loops	4311	If you want to know which design (one loop, locking, or multiple loops
3240	without or something else still) is best for your problem, then I cannot	4312	without or something else still) is best for your problem, then I cannot
3241	help you. I can give some generic advice however:	4313	help you, but here is some generic advice:
3242		4314
3243	=over 4	4315	=over 4
3244		4316
3245	=item * most applications have a main thread: use the default libev loop	4317	=item * most applications have a main thread: use the default libev loop
3246	in that thread, or create a separate thread running only the default loop.	4318	in that thread, or create a separate thread running only the default loop.
…		…
3258		4330
3259	Choosing a model is hard - look around, learn, know that usually you can do	4331	Choosing a model is hard - look around, learn, know that usually you can do
3260	better than you currently do :-)	4332	better than you currently do :-)
3261		4333
3262	=item * often you need to talk to some other thread which blocks in the	4334	=item * often you need to talk to some other thread which blocks in the
		4335	event loop.
		4336
3263	event loop - C<ev_async> watchers can be used to wake them up from other	4337	C<ev_async> watchers can be used to wake them up from other threads safely
3264	threads safely (or from signal contexts...).	4338	(or from signal contexts...).
		4339
		4340	An example use would be to communicate signals or other events that only
		4341	work in the default loop by registering the signal watcher with the
		4342	default loop and triggering an C<ev_async> watcher from the default loop
		4343	watcher callback into the event loop interested in the signal.
3265		4344
3266	=back	4345	=back
3267		4346
		4347	=head4 THREAD LOCKING EXAMPLE
		4348
		4349	Here is a fictitious example of how to run an event loop in a different
		4350	thread than where callbacks are being invoked and watchers are
		4351	created/added/removed.
		4352
		4353	For a real-world example, see the C<EV::Loop::Async> perl module,
		4354	which uses exactly this technique (which is suited for many high-level
		4355	languages).
		4356
		4357	The example uses a pthread mutex to protect the loop data, a condition
		4358	variable to wait for callback invocations, an async watcher to notify the
		4359	event loop thread and an unspecified mechanism to wake up the main thread.
		4360
		4361	First, you need to associate some data with the event loop:
		4362
		4363	typedef struct {
		4364	mutex_t lock; /* global loop lock */
		4365	ev_async async_w;
		4366	thread_t tid;
		4367	cond_t invoke_cv;
		4368	} userdata;
		4369
		4370	void prepare_loop (EV_P)
		4371	{
		4372	// for simplicity, we use a static userdata struct.
		4373	static userdata u;
		4374
		4375	ev_async_init (&u->async_w, async_cb);
		4376	ev_async_start (EV_A_ &u->async_w);
		4377
		4378	pthread_mutex_init (&u->lock, 0);
		4379	pthread_cond_init (&u->invoke_cv, 0);
		4380
		4381	// now associate this with the loop
		4382	ev_set_userdata (EV_A_ u);
		4383	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4384	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4385
		4386	// then create the thread running ev_loop
		4387	pthread_create (&u->tid, 0, l_run, EV_A);
		4388	}
		4389
		4390	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4391	solely to wake up the event loop so it takes notice of any new watchers
		4392	that might have been added:
		4393
		4394	static void
		4395	async_cb (EV_P_ ev_async *w, int revents)
		4396	{
		4397	// just used for the side effects
		4398	}
		4399
		4400	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4401	protecting the loop data, respectively.
		4402
		4403	static void
		4404	l_release (EV_P)
		4405	{
		4406	userdata *u = ev_userdata (EV_A);
		4407	pthread_mutex_unlock (&u->lock);
		4408	}
		4409
		4410	static void
		4411	l_acquire (EV_P)
		4412	{
		4413	userdata *u = ev_userdata (EV_A);
		4414	pthread_mutex_lock (&u->lock);
		4415	}
		4416
		4417	The event loop thread first acquires the mutex, and then jumps straight
		4418	into C<ev_run>:
		4419
		4420	void *
		4421	l_run (void *thr_arg)
		4422	{
		4423	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4424
		4425	l_acquire (EV_A);
		4426	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4427	ev_run (EV_A_ 0);
		4428	l_release (EV_A);
		4429
		4430	return 0;
		4431	}
		4432
		4433	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4434	signal the main thread via some unspecified mechanism (signals? pipe
		4435	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4436	have been called (in a while loop because a) spurious wakeups are possible
		4437	and b) skipping inter-thread-communication when there are no pending
		4438	watchers is very beneficial):
		4439
		4440	static void
		4441	l_invoke (EV_P)
		4442	{
		4443	userdata *u = ev_userdata (EV_A);
		4444
		4445	while (ev_pending_count (EV_A))
		4446	{
		4447	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4448	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4449	}
		4450	}
		4451
		4452	Now, whenever the main thread gets told to invoke pending watchers, it
		4453	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4454	thread to continue:
		4455
		4456	static void
		4457	real_invoke_pending (EV_P)
		4458	{
		4459	userdata *u = ev_userdata (EV_A);
		4460
		4461	pthread_mutex_lock (&u->lock);
		4462	ev_invoke_pending (EV_A);
		4463	pthread_cond_signal (&u->invoke_cv);
		4464	pthread_mutex_unlock (&u->lock);
		4465	}
		4466
		4467	Whenever you want to start/stop a watcher or do other modifications to an
		4468	event loop, you will now have to lock:
		4469
		4470	ev_timer timeout_watcher;
		4471	userdata *u = ev_userdata (EV_A);
		4472
		4473	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4474
		4475	pthread_mutex_lock (&u->lock);
		4476	ev_timer_start (EV_A_ &timeout_watcher);
		4477	ev_async_send (EV_A_ &u->async_w);
		4478	pthread_mutex_unlock (&u->lock);
		4479
		4480	Note that sending the C<ev_async> watcher is required because otherwise
		4481	an event loop currently blocking in the kernel will have no knowledge
		4482	about the newly added timer. By waking up the loop it will pick up any new
		4483	watchers in the next event loop iteration.
		4484
3268	=head2 COROUTINES	4485	=head3 COROUTINES
3269		4486
3270	Libev is much more accommodating to coroutines ("cooperative threads"):	4487	Libev is very accommodating to coroutines ("cooperative threads"):
3271	libev fully supports nesting calls to it's functions from different	4488	libev fully supports nesting calls to its functions from different
3272	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4489	coroutines (e.g. you can call C<ev_run> on the same loop from two
3273	different coroutines and switch freely between both coroutines running the	4490	different coroutines, and switch freely between both coroutines running
3274	loop, as long as you don't confuse yourself). The only exception is that	4491	the loop, as long as you don't confuse yourself). The only exception is
3275	you must not do this from C<ev_periodic> reschedule callbacks.	4492	that you must not do this from C<ev_periodic> reschedule callbacks.
3276		4493
3277	Care has been invested into making sure that libev does not keep local	4494	Care has been taken to ensure that libev does not keep local state inside
3278	state inside C<ev_loop>, and other calls do not usually allow coroutine	4495	C<ev_run>, and other calls do not usually allow for coroutine switches as
3279	switches.	4496	they do not call any callbacks.
3280		4497
		4498	=head2 COMPILER WARNINGS
3281		4499
3282	=head1 COMPLEXITIES	4500	Depending on your compiler and compiler settings, you might get no or a
		4501	lot of warnings when compiling libev code. Some people are apparently
		4502	scared by this.
3283		4503
3284	In this section the complexities of (many of) the algorithms used inside	4504	However, these are unavoidable for many reasons. For one, each compiler
3285	libev will be explained. For complexity discussions about backends see the	4505	has different warnings, and each user has different tastes regarding
3286	documentation for C<ev_default_init>.	4506	warning options. "Warn-free" code therefore cannot be a goal except when
		4507	targeting a specific compiler and compiler-version.
3287		4508
3288	All of the following are about amortised time: If an array needs to be	4509	Another reason is that some compiler warnings require elaborate
3289	extended, libev needs to realloc and move the whole array, but this	4510	workarounds, or other changes to the code that make it less clear and less
3290	happens asymptotically never with higher number of elements, so O(1) might	4511	maintainable.
3291	mean it might do a lengthy realloc operation in rare cases, but on average
3292	it is much faster and asymptotically approaches constant time.
3293		4512
3294	=over 4	4513	And of course, some compiler warnings are just plain stupid, or simply
		4514	wrong (because they don't actually warn about the condition their message
		4515	seems to warn about). For example, certain older gcc versions had some
		4516	warnings that resulted in an extreme number of false positives. These have
		4517	been fixed, but some people still insist on making code warn-free with
		4518	such buggy versions.
3295		4519
3296	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	4520	While libev is written to generate as few warnings as possible,
		4521	"warn-free" code is not a goal, and it is recommended not to build libev
		4522	with any compiler warnings enabled unless you are prepared to cope with
		4523	them (e.g. by ignoring them). Remember that warnings are just that:
		4524	warnings, not errors, or proof of bugs.
3297		4525
3298	This means that, when you have a watcher that triggers in one hour and
3299	there are 100 watchers that would trigger before that then inserting will
3300	have to skip roughly seven (C<ld 100>) of these watchers.
3301		4526
3302	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	4527	=head2 VALGRIND
3303		4528
3304	That means that changing a timer costs less than removing/adding them	4529	Valgrind has a special section here because it is a popular tool that is
3305	as only the relative motion in the event queue has to be paid for.	4530	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3306		4531
3307	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	4532	If you think you found a bug (memory leak, uninitialised data access etc.)
		4533	in libev, then check twice: If valgrind reports something like:
3308		4534
3309	These just add the watcher into an array or at the head of a list.	4535	==2274== definitely lost: 0 bytes in 0 blocks.
		4536	==2274== possibly lost: 0 bytes in 0 blocks.
		4537	==2274== still reachable: 256 bytes in 1 blocks.
3310		4538
3311	=item Stopping check/prepare/idle/fork/async watchers: O(1)	4539	Then there is no memory leak, just as memory accounted to global variables
		4540	is not a memleak - the memory is still being referenced, and didn't leak.
3312		4541
3313	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	4542	Similarly, under some circumstances, valgrind might report kernel bugs
		4543	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		4544	although an acceptable workaround has been found here), or it might be
		4545	confused.
3314		4546
3315	These watchers are stored in lists then need to be walked to find the	4547	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3316	correct watcher to remove. The lists are usually short (you don't usually	4548	make it into some kind of religion.
3317	have many watchers waiting for the same fd or signal).
3318		4549
3319	=item Finding the next timer in each loop iteration: O(1)	4550	If you are unsure about something, feel free to contact the mailing list
		4551	with the full valgrind report and an explanation on why you think this
		4552	is a bug in libev (best check the archives, too :). However, don't be
		4553	annoyed when you get a brisk "this is no bug" answer and take the chance
		4554	of learning how to interpret valgrind properly.
3320		4555
3321	By virtue of using a binary or 4-heap, the next timer is always found at a	4556	If you need, for some reason, empty reports from valgrind for your project
3322	fixed position in the storage array.	4557	I suggest using suppression lists.
3323		4558
3324	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3325		4559
3326	A change means an I/O watcher gets started or stopped, which requires	4560	=head1 PORTABILITY NOTES
3327	libev to recalculate its status (and possibly tell the kernel, depending
3328	on backend and whether C<ev_io_set> was used).
3329		4561
3330	=item Activating one watcher (putting it into the pending state): O(1)	4562	=head2 GNU/LINUX 32 BIT LIMITATIONS
3331		4563
3332	=item Priority handling: O(number_of_priorities)	4564	GNU/Linux is the only common platform that supports 64 bit file/large file
		4565	interfaces but I<disables> them by default.
3333		4566
3334	Priorities are implemented by allocating some space for each	4567	That means that libev compiled in the default environment doesn't support
3335	priority. When doing priority-based operations, libev usually has to	4568	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
3336	linearly search all the priorities, but starting/stopping and activating
3337	watchers becomes O(1) w.r.t. priority handling.
3338		4569
3339	=item Sending an ev_async: O(1)	4570	Unfortunately, many programs try to work around this GNU/Linux issue
		4571	by enabling the large file API, which makes them incompatible with the
		4572	standard libev compiled for their system.
3340		4573
3341	=item Processing ev_async_send: O(number_of_async_watchers)	4574	Likewise, libev cannot enable the large file API itself as this would
		4575	suddenly make it incompatible to the default compile time environment,
		4576	i.e. all programs not using special compile switches.
3342		4577
3343	=item Processing signals: O(max_signal_number)	4578	=head2 OS/X AND DARWIN BUGS
3344		4579
3345	Sending involves a system call I<iff> there were no other C<ev_async_send>	4580	The whole thing is a bug if you ask me - basically any system interface
3346	calls in the current loop iteration. Checking for async and signal events	4581	you touch is broken, whether it is locales, poll, kqueue or even the
3347	involves iterating over all running async watchers or all signal numbers.	4582	OpenGL drivers.
3348		4583
3349	=back	4584	=head3 C<kqueue> is buggy
3350		4585
		4586	The kqueue syscall is broken in all known versions - most versions support
		4587	only sockets, many support pipes.
3351		4588
		4589	Libev tries to work around this by not using C<kqueue> by default on this
		4590	rotten platform, but of course you can still ask for it when creating a
		4591	loop - embedding a socket-only kqueue loop into a select-based one is
		4592	probably going to work well.
		4593
		4594	=head3 C<poll> is buggy
		4595
		4596	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4597	implementation by something calling C<kqueue> internally around the 10.5.6
		4598	release, so now C<kqueue> I<and> C<poll> are broken.
		4599
		4600	Libev tries to work around this by not using C<poll> by default on
		4601	this rotten platform, but of course you can still ask for it when creating
		4602	a loop.
		4603
		4604	=head3 C<select> is buggy
		4605
		4606	All that's left is C<select>, and of course Apple found a way to fuck this
		4607	one up as well: On OS/X, C<select> actively limits the number of file
		4608	descriptors you can pass in to 1024 - your program suddenly crashes when
		4609	you use more.
		4610
		4611	There is an undocumented "workaround" for this - defining
		4612	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4613	work on OS/X.
		4614
		4615	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4616
		4617	=head3 C<errno> reentrancy
		4618
		4619	The default compile environment on Solaris is unfortunately so
		4620	thread-unsafe that you can't even use components/libraries compiled
		4621	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4622	defined by default. A valid, if stupid, implementation choice.
		4623
		4624	If you want to use libev in threaded environments you have to make sure
		4625	it's compiled with C<_REENTRANT> defined.
		4626
		4627	=head3 Event port backend
		4628
		4629	The scalable event interface for Solaris is called "event
		4630	ports". Unfortunately, this mechanism is very buggy in all major
		4631	releases. If you run into high CPU usage, your program freezes or you get
		4632	a large number of spurious wakeups, make sure you have all the relevant
		4633	and latest kernel patches applied. No, I don't know which ones, but there
		4634	are multiple ones to apply, and afterwards, event ports actually work
		4635	great.
		4636
		4637	If you can't get it to work, you can try running the program by setting
		4638	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4639	C<select> backends.
		4640
		4641	=head2 AIX POLL BUG
		4642
		4643	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4644	this by trying to avoid the poll backend altogether (i.e. it's not even
		4645	compiled in), which normally isn't a big problem as C<select> works fine
		4646	with large bitsets on AIX, and AIX is dead anyway.
		4647
3352	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4648	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4649
		4650	=head3 General issues
3353		4651
3354	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4652	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3355	requires, and its I/O model is fundamentally incompatible with the POSIX	4653	requires, and its I/O model is fundamentally incompatible with the POSIX
3356	model. Libev still offers limited functionality on this platform in	4654	model. Libev still offers limited functionality on this platform in
3357	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4655	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3358	descriptors. This only applies when using Win32 natively, not when using	4656	descriptors. This only applies when using Win32 natively, not when using
3359	e.g. cygwin.	4657	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4658	as every compielr comes with a slightly differently broken/incompatible
		4659	environment.
3360		4660
3361	Lifting these limitations would basically require the full	4661	Lifting these limitations would basically require the full
3362	re-implementation of the I/O system. If you are into these kinds of	4662	re-implementation of the I/O system. If you are into this kind of thing,
3363	things, then note that glib does exactly that for you in a very portable	4663	then note that glib does exactly that for you in a very portable way (note
3364	way (note also that glib is the slowest event library known to man).	4664	also that glib is the slowest event library known to man).
3365		4665
3366	There is no supported compilation method available on windows except	4666	There is no supported compilation method available on windows except
3367	embedding it into other applications.	4667	embedding it into other applications.
		4668
		4669	Sensible signal handling is officially unsupported by Microsoft - libev
		4670	tries its best, but under most conditions, signals will simply not work.
3368		4671
3369	Not a libev limitation but worth mentioning: windows apparently doesn't	4672	Not a libev limitation but worth mentioning: windows apparently doesn't
3370	accept large writes: instead of resulting in a partial write, windows will	4673	accept large writes: instead of resulting in a partial write, windows will
3371	either accept everything or return C<ENOBUFS> if the buffer is too large,	4674	either accept everything or return C<ENOBUFS> if the buffer is too large,
3372	so make sure you only write small amounts into your sockets (less than a	4675	so make sure you only write small amounts into your sockets (less than a
3373	megabyte seems safe, but thsi apparently depends on the amount of memory	4676	megabyte seems safe, but this apparently depends on the amount of memory
3374	available).	4677	available).
3375		4678
3376	Due to the many, low, and arbitrary limits on the win32 platform and	4679	Due to the many, low, and arbitrary limits on the win32 platform and
3377	the abysmal performance of winsockets, using a large number of sockets	4680	the abysmal performance of winsockets, using a large number of sockets
3378	is not recommended (and not reasonable). If your program needs to use	4681	is not recommended (and not reasonable). If your program needs to use
3379	more than a hundred or so sockets, then likely it needs to use a totally	4682	more than a hundred or so sockets, then likely it needs to use a totally
3380	different implementation for windows, as libev offers the POSIX readiness	4683	different implementation for windows, as libev offers the POSIX readiness
3381	notification model, which cannot be implemented efficiently on windows	4684	notification model, which cannot be implemented efficiently on windows
3382	(Microsoft monopoly games).	4685	(due to Microsoft monopoly games).
3383		4686
3384	A typical way to use libev under windows is to embed it (see the embedding	4687	A typical way to use libev under windows is to embed it (see the embedding
3385	section for details) and use the following F<evwrap.h> header file instead	4688	section for details) and use the following F<evwrap.h> header file instead
3386	of F<ev.h>:	4689	of F<ev.h>:
3387		4690
…		…
3389	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	4692	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3390		4693
3391	#include "ev.h"	4694	#include "ev.h"
3392		4695
3393	And compile the following F<evwrap.c> file into your project (make sure	4696	And compile the following F<evwrap.c> file into your project (make sure
3394	you do I<not> compile the F<ev.c> or any other embedded soruce files!):	4697	you do I<not> compile the F<ev.c> or any other embedded source files!):
3395		4698
3396	#include "evwrap.h"	4699	#include "evwrap.h"
3397	#include "ev.c"	4700	#include "ev.c"
3398		4701
3399	=over 4
3400
3401	=item The winsocket select function	4702	=head3 The winsocket C<select> function
3402		4703
3403	The winsocket C<select> function doesn't follow POSIX in that it	4704	The winsocket C<select> function doesn't follow POSIX in that it
3404	requires socket I<handles> and not socket I<file descriptors> (it is	4705	requires socket I<handles> and not socket I<file descriptors> (it is
3405	also extremely buggy). This makes select very inefficient, and also	4706	also extremely buggy). This makes select very inefficient, and also
3406	requires a mapping from file descriptors to socket handles (the Microsoft	4707	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3415	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4716	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3416		4717
3417	Note that winsockets handling of fd sets is O(n), so you can easily get a	4718	Note that winsockets handling of fd sets is O(n), so you can easily get a
3418	complexity in the O(n²) range when using win32.	4719	complexity in the O(n²) range when using win32.
3419		4720
3420	=item Limited number of file descriptors	4721	=head3 Limited number of file descriptors
3421		4722
3422	Windows has numerous arbitrary (and low) limits on things.	4723	Windows has numerous arbitrary (and low) limits on things.
3423		4724
3424	Early versions of winsocket's select only supported waiting for a maximum	4725	Early versions of winsocket's select only supported waiting for a maximum
3425	of C<64> handles (probably owning to the fact that all windows kernels	4726	of C<64> handles (probably owning to the fact that all windows kernels
3426	can only wait for C<64> things at the same time internally; Microsoft	4727	can only wait for C<64> things at the same time internally; Microsoft
3427	recommends spawning a chain of threads and wait for 63 handles and the	4728	recommends spawning a chain of threads and wait for 63 handles and the
3428	previous thread in each. Great).	4729	previous thread in each. Sounds great!).
3429		4730
3430	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4731	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3431	to some high number (e.g. C<2048>) before compiling the winsocket select	4732	to some high number (e.g. C<2048>) before compiling the winsocket select
3432	call (which might be in libev or elsewhere, for example, perl does its own	4733	call (which might be in libev or elsewhere, for example, perl and many
3433	select emulation on windows).	4734	other interpreters do their own select emulation on windows).
3434		4735
3435	Another limit is the number of file descriptors in the Microsoft runtime	4736	Another limit is the number of file descriptors in the Microsoft runtime
3436	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4737	libraries, which by default is C<64> (there must be a hidden I<64>
3437	or something like this inside Microsoft). You can increase this by calling	4738	fetish or something like this inside Microsoft). You can increase this
3438	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4739	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3439	arbitrary limit), but is broken in many versions of the Microsoft runtime	4740	(another arbitrary limit), but is broken in many versions of the Microsoft
3440	libraries.
3441
3442	This might get you to about C<512> or C<2048> sockets (depending on	4741	runtime libraries. This might get you to about C<512> or C<2048> sockets
3443	windows version and/or the phase of the moon). To get more, you need to	4742	(depending on windows version and/or the phase of the moon). To get more,
3444	wrap all I/O functions and provide your own fd management, but the cost of	4743	you need to wrap all I/O functions and provide your own fd management, but
3445	calling select (O(n²)) will likely make this unworkable.	4744	the cost of calling select (O(n²)) will likely make this unworkable.
3446		4745
3447	=back
3448
3449
3450	=head1 PORTABILITY REQUIREMENTS	4746	=head2 PORTABILITY REQUIREMENTS
3451		4747
3452	In addition to a working ISO-C implementation, libev relies on a few	4748	In addition to a working ISO-C implementation and of course the
3453	additional extensions:	4749	backend-specific APIs, libev relies on a few additional extensions:
3454		4750
3455	=over 4	4751	=over 4
3456		4752
3457	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	4753	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3458	calling conventions regardless of C<ev_watcher_type *>.	4754	calling conventions regardless of C<ev_watcher_type *>.
…		…
3464	calls them using an C<ev_watcher *> internally.	4760	calls them using an C<ev_watcher *> internally.
3465		4761
3466	=item C<sig_atomic_t volatile> must be thread-atomic as well	4762	=item C<sig_atomic_t volatile> must be thread-atomic as well
3467		4763
3468	The type C<sig_atomic_t volatile> (or whatever is defined as	4764	The type C<sig_atomic_t volatile> (or whatever is defined as
3469	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	4765	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3470	threads. This is not part of the specification for C<sig_atomic_t>, but is	4766	threads. This is not part of the specification for C<sig_atomic_t>, but is
3471	believed to be sufficiently portable.	4767	believed to be sufficiently portable.
3472		4768
3473	=item C<sigprocmask> must work in a threaded environment	4769	=item C<sigprocmask> must work in a threaded environment
3474		4770
…		…
3483	except the initial one, and run the default loop in the initial thread as	4779	except the initial one, and run the default loop in the initial thread as
3484	well.	4780	well.
3485		4781
3486	=item C<long> must be large enough for common memory allocation sizes	4782	=item C<long> must be large enough for common memory allocation sizes
3487		4783
3488	To improve portability and simplify using libev, libev uses C<long>	4784	To improve portability and simplify its API, libev uses C<long> internally
3489	internally instead of C<size_t> when allocating its data structures. On	4785	instead of C<size_t> when allocating its data structures. On non-POSIX
3490	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4786	systems (Microsoft...) this might be unexpectedly low, but is still at
3491	is still at least 31 bits everywhere, which is enough for hundreds of	4787	least 31 bits everywhere, which is enough for hundreds of millions of
3492	millions of watchers.	4788	watchers.
3493		4789
3494	=item C<double> must hold a time value in seconds with enough accuracy	4790	=item C<double> must hold a time value in seconds with enough accuracy
3495		4791
3496	The type C<double> is used to represent timestamps. It is required to	4792	The type C<double> is used to represent timestamps. It is required to
3497	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4793	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3498	enough for at least into the year 4000. This requirement is fulfilled by	4794	good enough for at least into the year 4000 with millisecond accuracy
		4795	(the design goal for libev). This requirement is overfulfilled by
3499	implementations implementing IEEE 754 (basically all existing ones).	4796	implementations using IEEE 754, which is basically all existing ones. With
		4797	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
3500		4798
3501	=back	4799	=back
3502		4800
3503	If you know of other additional requirements drop me a note.	4801	If you know of other additional requirements drop me a note.
3504		4802
3505		4803
3506	=head1 COMPILER WARNINGS	4804	=head1 ALGORITHMIC COMPLEXITIES
3507		4805
3508	Depending on your compiler and compiler settings, you might get no or a	4806	In this section the complexities of (many of) the algorithms used inside
3509	lot of warnings when compiling libev code. Some people are apparently	4807	libev will be documented. For complexity discussions about backends see
3510	scared by this.	4808	the documentation for C<ev_default_init>.
3511		4809
3512	However, these are unavoidable for many reasons. For one, each compiler	4810	All of the following are about amortised time: If an array needs to be
3513	has different warnings, and each user has different tastes regarding	4811	extended, libev needs to realloc and move the whole array, but this
3514	warning options. "Warn-free" code therefore cannot be a goal except when	4812	happens asymptotically rarer with higher number of elements, so O(1) might
3515	targeting a specific compiler and compiler-version.	4813	mean that libev does a lengthy realloc operation in rare cases, but on
		4814	average it is much faster and asymptotically approaches constant time.
3516		4815
3517	Another reason is that some compiler warnings require elaborate	4816	=over 4
3518	workarounds, or other changes to the code that make it less clear and less
3519	maintainable.
3520		4817
3521	And of course, some compiler warnings are just plain stupid, or simply	4818	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3522	wrong (because they don't actually warn about the condition their message
3523	seems to warn about).
3524		4819
3525	While libev is written to generate as few warnings as possible,	4820	This means that, when you have a watcher that triggers in one hour and
3526	"warn-free" code is not a goal, and it is recommended not to build libev	4821	there are 100 watchers that would trigger before that, then inserting will
3527	with any compiler warnings enabled unless you are prepared to cope with	4822	have to skip roughly seven (C<ld 100>) of these watchers.
3528	them (e.g. by ignoring them). Remember that warnings are just that:
3529	warnings, not errors, or proof of bugs.
3530		4823
		4824	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3531		4825
3532	=head1 VALGRIND	4826	That means that changing a timer costs less than removing/adding them,
		4827	as only the relative motion in the event queue has to be paid for.
3533		4828
3534	Valgrind has a special section here because it is a popular tool that is	4829	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3535	highly useful, but valgrind reports are very hard to interpret.
3536		4830
3537	If you think you found a bug (memory leak, uninitialised data access etc.)	4831	These just add the watcher into an array or at the head of a list.
3538	in libev, then check twice: If valgrind reports something like:
3539		4832
3540	==2274== definitely lost: 0 bytes in 0 blocks.	4833	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3541	==2274== possibly lost: 0 bytes in 0 blocks.
3542	==2274== still reachable: 256 bytes in 1 blocks.
3543		4834
3544	Then there is no memory leak. Similarly, under some circumstances,	4835	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3545	valgrind might report kernel bugs as if it were a bug in libev, or it
3546	might be confused (it is a very good tool, but only a tool).
3547		4836
3548	If you are unsure about something, feel free to contact the mailing list	4837	These watchers are stored in lists, so they need to be walked to find the
3549	with the full valgrind report and an explanation on why you think this is	4838	correct watcher to remove. The lists are usually short (you don't usually
3550	a bug in libev. However, don't be annoyed when you get a brisk "this is	4839	have many watchers waiting for the same fd or signal: one is typical, two
3551	no bug" answer and take the chance of learning how to interpret valgrind	4840	is rare).
3552	properly.
3553		4841
3554	If you need, for some reason, empty reports from valgrind for your project	4842	=item Finding the next timer in each loop iteration: O(1)
3555	I suggest using suppression lists.
3556		4843
		4844	By virtue of using a binary or 4-heap, the next timer is always found at a
		4845	fixed position in the storage array.
		4846
		4847	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4848
		4849	A change means an I/O watcher gets started or stopped, which requires
		4850	libev to recalculate its status (and possibly tell the kernel, depending
		4851	on backend and whether C<ev_io_set> was used).
		4852
		4853	=item Activating one watcher (putting it into the pending state): O(1)
		4854
		4855	=item Priority handling: O(number_of_priorities)
		4856
		4857	Priorities are implemented by allocating some space for each
		4858	priority. When doing priority-based operations, libev usually has to
		4859	linearly search all the priorities, but starting/stopping and activating
		4860	watchers becomes O(1) with respect to priority handling.
		4861
		4862	=item Sending an ev_async: O(1)
		4863
		4864	=item Processing ev_async_send: O(number_of_async_watchers)
		4865
		4866	=item Processing signals: O(max_signal_number)
		4867
		4868	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4869	calls in the current loop iteration. Checking for async and signal events
		4870	involves iterating over all running async watchers or all signal numbers.
		4871
		4872	=back
		4873
		4874
		4875	=head1 PORTING FROM LIBEV 3.X TO 4.X
		4876
		4877	The major version 4 introduced some minor incompatible changes to the API.
		4878
		4879	At the moment, the C<ev.h> header file tries to implement superficial
		4880	compatibility, so most programs should still compile. Those might be
		4881	removed in later versions of libev, so better update early than late.
		4882
		4883	=over 4
		4884
		4885	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		4886
		4887	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		4888
		4889	ev_loop_destroy (EV_DEFAULT_UC);
		4890	ev_loop_fork (EV_DEFAULT);
		4891
		4892	=item function/symbol renames
		4893
		4894	A number of functions and symbols have been renamed:
		4895
		4896	ev_loop => ev_run
		4897	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		4898	EVLOOP_ONESHOT => EVRUN_ONCE
		4899
		4900	ev_unloop => ev_break
		4901	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		4902	EVUNLOOP_ONE => EVBREAK_ONE
		4903	EVUNLOOP_ALL => EVBREAK_ALL
		4904
		4905	EV_TIMEOUT => EV_TIMER
		4906
		4907	ev_loop_count => ev_iteration
		4908	ev_loop_depth => ev_depth
		4909	ev_loop_verify => ev_verify
		4910
		4911	Most functions working on C<struct ev_loop> objects don't have an
		4912	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		4913	associated constants have been renamed to not collide with the C<struct
		4914	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		4915	as all other watcher types. Note that C<ev_loop_fork> is still called
		4916	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		4917	typedef.
		4918
		4919	=item C<EV_COMPAT3> backwards compatibility mechanism
		4920
		4921	The backward compatibility mechanism can be controlled by
		4922	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		4923	section.
		4924
		4925	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		4926
		4927	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		4928	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		4929	and work, but the library code will of course be larger.
		4930
		4931	=back
		4932
		4933
		4934	=head1 GLOSSARY
		4935
		4936	=over 4
		4937
		4938	=item active
		4939
		4940	A watcher is active as long as it has been started and not yet stopped.
		4941	See L<WATCHER STATES> for details.
		4942
		4943	=item application
		4944
		4945	In this document, an application is whatever is using libev.
		4946
		4947	=item backend
		4948
		4949	The part of the code dealing with the operating system interfaces.
		4950
		4951	=item callback
		4952
		4953	The address of a function that is called when some event has been
		4954	detected. Callbacks are being passed the event loop, the watcher that
		4955	received the event, and the actual event bitset.
		4956
		4957	=item callback/watcher invocation
		4958
		4959	The act of calling the callback associated with a watcher.
		4960
		4961	=item event
		4962
		4963	A change of state of some external event, such as data now being available
		4964	for reading on a file descriptor, time having passed or simply not having
		4965	any other events happening anymore.
		4966
		4967	In libev, events are represented as single bits (such as C<EV_READ> or
		4968	C<EV_TIMER>).
		4969
		4970	=item event library
		4971
		4972	A software package implementing an event model and loop.
		4973
		4974	=item event loop
		4975
		4976	An entity that handles and processes external events and converts them
		4977	into callback invocations.
		4978
		4979	=item event model
		4980
		4981	The model used to describe how an event loop handles and processes
		4982	watchers and events.
		4983
		4984	=item pending
		4985
		4986	A watcher is pending as soon as the corresponding event has been
		4987	detected. See L<WATCHER STATES> for details.
		4988
		4989	=item real time
		4990
		4991	The physical time that is observed. It is apparently strictly monotonic :)
		4992
		4993	=item wall-clock time
		4994
		4995	The time and date as shown on clocks. Unlike real time, it can actually
		4996	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4997	clock.
		4998
		4999	=item watcher
		5000
		5001	A data structure that describes interest in certain events. Watchers need
		5002	to be started (attached to an event loop) before they can receive events.
		5003
		5004	=back
3557		5005
3558	=head1 AUTHOR	5006	=head1 AUTHOR
3559		5007
3560	Marc Lehmann <libev@schmorp.de>.	5008	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3561		5009

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