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…		…
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
		14	#include <stdio.h> // for puts
		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
18		20
19	// all watcher callbacks have a similar signature	21	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	22	// this callback is called when data is readable on stdin
21	static void	23	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	25	{
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
28		30
29	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_run's to stop iterating
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_break (EV_A_ EVBREAK_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_run to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_break (EV_A_ EVBREAK_ONE);
40	}	42	}
41		43
42	int	44	int
43	main (void)	45	main (void)
44	{	46	{
45	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
46	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = EV_DEFAULT;
47		49
48	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
…		…
54	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
57		59
58	// now wait for events to arrive	60	// now wait for events to arrive
59	ev_loop (loop, 0);	61	ev_run (loop, 0);
60		62
61	// unloop was called, so exit	63	// unloop was called, so exit
62	return 0;	64	return 0;
63	}	65	}
64		66
65	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
66		70
67	The newest version of this document is also available as an html-formatted	71	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	72	web page you might find easier to navigate when reading it for the first
69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.	73	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		74
		75	While this document tries to be as complete as possible in documenting
		76	libev, its usage and the rationale behind its design, it is not a tutorial
		77	on event-based programming, nor will it introduce event-based programming
		78	with libev.
		79
		80	Familiarity with event based programming techniques in general is assumed
		81	throughout this document.
		82
		83	=head1 WHAT TO READ WHEN IN A HURRY
		84
		85	This manual tries to be very detailed, but unfortunately, this also makes
		86	it very long. If you just want to know the basics of libev, I suggest
		87	reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and
		88	look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and
		89	C<ev_timer> sections in L<WATCHER TYPES>.
		90
		91	=head1 ABOUT LIBEV
70		92
71	Libev is an event loop: you register interest in certain events (such as a	93	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	94	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	95	these event sources and provide your program with events.
74		96
…		…
84	=head2 FEATURES	106	=head2 FEATURES
85		107
86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	108	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	109	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	110	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	111	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
90	with customised rescheduling (C<ev_periodic>), synchronous signals	112	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
91	(C<ev_signal>), process status change events (C<ev_child>), and event	113	timers (C<ev_timer>), absolute timers with customised rescheduling
92	watchers dealing with the event loop mechanism itself (C<ev_idle>,	114	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
93	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	115	change events (C<ev_child>), and event watchers dealing with the event
94	file watchers (C<ev_stat>) and even limited support for fork events	116	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
95	(C<ev_fork>).	117	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		118	limited support for fork events (C<ev_fork>).
96		119
97	It also is quite fast (see this	120	It also is quite fast (see this
98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	121	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
99	for example).	122	for example).
100		123
…		…
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	131	name C<loop> (which is always of type C<struct ev_loop *>) will not have
109	this argument.	132	this argument.
110		133
111	=head2 TIME REPRESENTATION	134	=head2 TIME REPRESENTATION
112		135
113	Libev represents time as a single floating point number, representing the	136	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	137	the (fractional) number of seconds since the (POSIX) epoch (in practice
115	the beginning of 1970, details are complicated, don't ask). This type is	138	somewhere near the beginning of 1970, details are complicated, don't
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	139	ask). This type is called C<ev_tstamp>, which is what you should use
117	to the C<double> type in C, and when you need to do any calculations on	140	too. It usually aliases to the C<double> type in C. When you need to do
118	it, you should treat it as some floating point value. Unlike the name	141	any calculations on it, you should treat it as some floating point value.
		142
119	component C<stamp> might indicate, it is also used for time differences	143	Unlike the name component C<stamp> might indicate, it is also used for
120	throughout libev.	144	time differences (e.g. delays) throughout libev.
121		145
122	=head1 ERROR HANDLING	146	=head1 ERROR HANDLING
123		147
124	Libev knows three classes of errors: operating system errors, usage errors	148	Libev knows three classes of errors: operating system errors, usage errors
125	and internal errors (bugs).	149	and internal errors (bugs).
…		…
149		173
150	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
151		175
152	Returns the current time as libev would use it. Please note that the	176	Returns the current time as libev would use it. Please note that the
153	C<ev_now> function is usually faster and also often returns the timestamp	177	C<ev_now> function is usually faster and also often returns the timestamp
154	you actually want to know.	178	you actually want to know. Also interesting is the combination of
		179	C<ev_update_now> and C<ev_now>.
155		180
156	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
157		182
158	Sleep for the given interval: The current thread will be blocked until	183	Sleep for the given interval: The current thread will be blocked until
159	either it is interrupted or the given time interval has passed. Basically	184	either it is interrupted or the given time interval has passed. Basically
…		…
176	as this indicates an incompatible change. Minor versions are usually	201	as this indicates an incompatible change. Minor versions are usually
177	compatible to older versions, so a larger minor version alone is usually	202	compatible to older versions, so a larger minor version alone is usually
178	not a problem.	203	not a problem.
179		204
180	Example: Make sure we haven't accidentally been linked against the wrong	205	Example: Make sure we haven't accidentally been linked against the wrong
181	version.	206	version (note, however, that this will not detect other ABI mismatches,
		207	such as LFS or reentrancy).
182		208
183	assert (("libev version mismatch",	209	assert (("libev version mismatch",
184	ev_version_major () == EV_VERSION_MAJOR	210	ev_version_major () == EV_VERSION_MAJOR
185	&& ev_version_minor () >= EV_VERSION_MINOR));	211	&& ev_version_minor () >= EV_VERSION_MINOR));
186		212
…		…
197	assert (("sorry, no epoll, no sex",	223	assert (("sorry, no epoll, no sex",
198	ev_supported_backends () & EVBACKEND_EPOLL));	224	ev_supported_backends () & EVBACKEND_EPOLL));
199		225
200	=item unsigned int ev_recommended_backends ()	226	=item unsigned int ev_recommended_backends ()
201		227
202	Return the set of all backends compiled into this binary of libev and also	228	Return the set of all backends compiled into this binary of libev and
203	recommended for this platform. This set is often smaller than the one	229	also recommended for this platform, meaning it will work for most file
		230	descriptor types. This set is often smaller than the one returned by
204	returned by C<ev_supported_backends>, as for example kqueue is broken on	231	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
205	most BSDs and will not be auto-detected unless you explicitly request it	232	and will not be auto-detected unless you explicitly request it (assuming
206	(assuming you know what you are doing). This is the set of backends that	233	you know what you are doing). This is the set of backends that libev will
207	libev will probe for if you specify no backends explicitly.	234	probe for if you specify no backends explicitly.
208		235
209	=item unsigned int ev_embeddable_backends ()	236	=item unsigned int ev_embeddable_backends ()
210		237
211	Returns the set of backends that are embeddable in other event loops. This	238	Returns the set of backends that are embeddable in other event loops. This
212	is the theoretical, all-platform, value. To find which backends	239	value is platform-specific but can include backends not available on the
213	might be supported on the current system, you would need to look at	240	current system. To find which embeddable backends might be supported on
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	241	the current system, you would need to look at C<ev_embeddable_backends ()
215	recommended ones.	242	& ev_supported_backends ()>, likewise for recommended ones.
216		243
217	See the description of C<ev_embed> watchers for more info.	244	See the description of C<ev_embed> watchers for more info.
218		245
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	246	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
220		247
221	Sets the allocation function to use (the prototype is similar - the	248	Sets the allocation function to use (the prototype is similar - the
222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	249	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
223	used to allocate and free memory (no surprises here). If it returns zero	250	used to allocate and free memory (no surprises here). If it returns zero
224	when memory needs to be allocated (C<size != 0>), the library might abort	251	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	277	}
251		278
252	...	279	...
253	ev_set_allocator (persistent_realloc);	280	ev_set_allocator (persistent_realloc);
254		281
255	=item ev_set_syserr_cb (void (*cb)(const char *msg));	282	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
256		283
257	Set the callback function to call on a retryable system call error (such	284	Set the callback function to call on a retryable system call error (such
258	as failed select, poll, epoll_wait). The message is a printable string	285	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	286	indicating the system call or subsystem causing the problem. If this
260	callback is set, then libev will expect it to remedy the situation, no	287	callback is set, then libev will expect it to remedy the situation, no
…		…
274	...	301	...
275	ev_set_syserr_cb (fatal_error);	302	ev_set_syserr_cb (fatal_error);
276		303
277	=back	304	=back
278		305
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	306	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
280		307
281	An event loop is described by a C<struct ev_loop *>. The library knows two	308	An event loop is described by a C<struct ev_loop *> (the C<struct> is
282	types of such loops, the I<default> loop, which supports signals and child	309	I<not> optional in this case unless libev 3 compatibility is disabled, as
283	events, and dynamically created loops which do not.	310	libev 3 had an C<ev_loop> function colliding with the struct name).
		311
		312	The library knows two types of such loops, the I<default> loop, which
		313	supports child process events, and dynamically created event loops which
		314	do not.
284		315
285	=over 4	316	=over 4
286		317
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	318	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		319
289	This will initialise the default event loop if it hasn't been initialised	320	This returns the "default" event loop object, which is what you should
290	yet and return it. If the default loop could not be initialised, returns	321	normally use when you just need "the event loop". Event loop objects and
291	false. If it already was initialised it simply returns it (and ignores the	322	the C<flags> parameter are described in more detail in the entry for
292	flags. If that is troubling you, check C<ev_backend ()> afterwards).	323	C<ev_loop_new>.
		324
		325	If the default loop is already initialised then this function simply
		326	returns it (and ignores the flags. If that is troubling you, check
		327	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		328	flags, which should almost always be C<0>, unless the caller is also the
		329	one calling C<ev_run> or otherwise qualifies as "the main program".
293		330
294	If you don't know what event loop to use, use the one returned from this	331	If you don't know what event loop to use, use the one returned from this
295	function.	332	function (or via the C<EV_DEFAULT> macro).
296		333
297	Note that this function is I<not> thread-safe, so if you want to use it	334	Note that this function is I<not> thread-safe, so if you want to use it
298	from multiple threads, you have to lock (note also that this is unlikely,	335	from multiple threads, you have to employ some kind of mutex (note also
299	as loops cannot bes hared easily between threads anyway).	336	that this case is unlikely, as loops cannot be shared easily between
		337	threads anyway).
300		338
301	The default loop is the only loop that can handle C<ev_signal> and	339	The default loop is the only loop that can handle C<ev_child> watchers,
302	C<ev_child> watchers, and to do this, it always registers a handler	340	and to do this, it always registers a handler for C<SIGCHLD>. If this is
303	for C<SIGCHLD>. If this is a problem for your application you can either	341	a problem for your application you can either create a dynamic loop with
304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	342	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
305	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	343	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
306	C<ev_default_init>.	344
		345	Example: This is the most typical usage.
		346
		347	if (!ev_default_loop (0))
		348	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		349
		350	Example: Restrict libev to the select and poll backends, and do not allow
		351	environment settings to be taken into account:
		352
		353	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		354
		355	=item struct ev_loop *ev_loop_new (unsigned int flags)
		356
		357	This will create and initialise a new event loop object. If the loop
		358	could not be initialised, returns false.
		359
		360	Note that this function I<is> thread-safe, and one common way to use
		361	libev with threads is indeed to create one loop per thread, and using the
		362	default loop in the "main" or "initial" thread.
307		363
308	The flags argument can be used to specify special behaviour or specific	364	The flags argument can be used to specify special behaviour or specific
309	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	365	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
310		366
311	The following flags are supported:	367	The following flags are supported:
…		…
326	useful to try out specific backends to test their performance, or to work	382	useful to try out specific backends to test their performance, or to work
327	around bugs.	383	around bugs.
328		384
329	=item C<EVFLAG_FORKCHECK>	385	=item C<EVFLAG_FORKCHECK>
330		386
331	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	387	Instead of calling C<ev_loop_fork> manually after a fork, you can also
332	a fork, you can also make libev check for a fork in each iteration by	388	make libev check for a fork in each iteration by enabling this flag.
333	enabling this flag.
334		389
335	This works by calling C<getpid ()> on every iteration of the loop,	390	This works by calling C<getpid ()> on every iteration of the loop,
336	and thus this might slow down your event loop if you do a lot of loop	391	and thus this might slow down your event loop if you do a lot of loop
337	iterations and little real work, but is usually not noticeable (on my	392	iterations and little real work, but is usually not noticeable (on my
338	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	393	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
…		…
344	flag.	399	flag.
345		400
346	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	401	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
347	environment variable.	402	environment variable.
348		403
		404	=item C<EVFLAG_NOINOTIFY>
		405
		406	When this flag is specified, then libev will not attempt to use the
		407	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and
		408	testing, this flag can be useful to conserve inotify file descriptors, as
		409	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		410
		411	=item C<EVFLAG_SIGNALFD>
		412
		413	When this flag is specified, then libev will attempt to use the
		414	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API
		415	delivers signals synchronously, which makes it both faster and might make
		416	it possible to get the queued signal data. It can also simplify signal
		417	handling with threads, as long as you properly block signals in your
		418	threads that are not interested in handling them.
		419
		420	Signalfd will not be used by default as this changes your signal mask, and
		421	there are a lot of shoddy libraries and programs (glib's threadpool for
		422	example) that can't properly initialise their signal masks.
		423
349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	424	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
350		425
351	This is your standard select(2) backend. Not I<completely> standard, as	426	This is your standard select(2) backend. Not I<completely> standard, as
352	libev tries to roll its own fd_set with no limits on the number of fds,	427	libev tries to roll its own fd_set with no limits on the number of fds,
353	but if that fails, expect a fairly low limit on the number of fds when	428	but if that fails, expect a fairly low limit on the number of fds when
…		…
377	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and	452	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
378	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	453	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
379		454
380	=item C<EVBACKEND_EPOLL> (value 4, Linux)	455	=item C<EVBACKEND_EPOLL> (value 4, Linux)
381		456
		457	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		458	kernels).
		459
382	For few fds, this backend is a bit little slower than poll and select,	460	For few fds, this backend is a bit little slower than poll and select,
383	but it scales phenomenally better. While poll and select usually scale	461	but it scales phenomenally better. While poll and select usually scale
384	like O(total_fds) where n is the total number of fds (or the highest fd),	462	like O(total_fds) where n is the total number of fds (or the highest fd),
385	epoll scales either O(1) or O(active_fds). The epoll design has a number	463	epoll scales either O(1) or O(active_fds).
386	of shortcomings, such as silently dropping events in some hard-to-detect	464
387	cases and requiring a system call per fd change, no fork support and bad	465	The epoll mechanism deserves honorable mention as the most misdesigned
388	support for dup.	466	of the more advanced event mechanisms: mere annoyances include silently
		467	dropping file descriptors, requiring a system call per change per file
		468	descriptor (and unnecessary guessing of parameters), problems with dup,
		469	returning before the timeout value requiring additional iterations and so
		470	on. The biggest issue is fork races, however - if a program forks then
		471	I<both> parent and child process have to recreate the epoll set, which can
		472	take considerable time (one syscall per file descriptor) and is of course
		473	hard to detect.
		474
		475	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		476	of course I<doesn't>, and epoll just loves to report events for totally
		477	I<different> file descriptors (even already closed ones, so one cannot
		478	even remove them from the set) than registered in the set (especially
		479	on SMP systems). Libev tries to counter these spurious notifications by
		480	employing an additional generation counter and comparing that against the
		481	events to filter out spurious ones, recreating the set when required. Last
		482	not least, it also refuses to work with some file descriptors which work
		483	perfectly fine with C<select> (files, many character devices...).
389		484
390	While stopping, setting and starting an I/O watcher in the same iteration	485	While stopping, setting and starting an I/O watcher in the same iteration
391	will result in some caching, there is still a system call per such incident	486	will result in some caching, there is still a system call per such
392	(because the fd could point to a different file description now), so its	487	incident (because the same I<file descriptor> could point to a different
393	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	488	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
394	very well if you register events for both fds.	489	file descriptors might not work very well if you register events for both
395		490	file descriptors.
396	Please note that epoll sometimes generates spurious notifications, so you
397	need to use non-blocking I/O or other means to avoid blocking when no data
398	(or space) is available.
399		491
400	Best performance from this backend is achieved by not unregistering all	492	Best performance from this backend is achieved by not unregistering all
401	watchers for a file descriptor until it has been closed, if possible, i.e.	493	watchers for a file descriptor until it has been closed, if possible,
402	keep at least one watcher active per fd at all times.	494	i.e. keep at least one watcher active per fd at all times. Stopping and
		495	starting a watcher (without re-setting it) also usually doesn't cause
		496	extra overhead. A fork can both result in spurious notifications as well
		497	as in libev having to destroy and recreate the epoll object, which can
		498	take considerable time and thus should be avoided.
		499
		500	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		501	faster than epoll for maybe up to a hundred file descriptors, depending on
		502	the usage. So sad.
403		503
404	While nominally embeddable in other event loops, this feature is broken in	504	While nominally embeddable in other event loops, this feature is broken in
405	all kernel versions tested so far.	505	all kernel versions tested so far.
406		506
407	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	507	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
…		…
410	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	510	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
411		511
412	Kqueue deserves special mention, as at the time of this writing, it	512	Kqueue deserves special mention, as at the time of this writing, it
413	was broken on all BSDs except NetBSD (usually it doesn't work reliably	513	was broken on all BSDs except NetBSD (usually it doesn't work reliably
414	with anything but sockets and pipes, except on Darwin, where of course	514	with anything but sockets and pipes, except on Darwin, where of course
415	it's completely useless). For this reason it's not being "auto-detected"	515	it's completely useless). Unlike epoll, however, whose brokenness
		516	is by design, these kqueue bugs can (and eventually will) be fixed
		517	without API changes to existing programs. For this reason it's not being
416	unless you explicitly specify it explicitly in the flags (i.e. using	518	"auto-detected" unless you explicitly specify it in the flags (i.e. using
417	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	519	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
418	system like NetBSD.	520	system like NetBSD.
419		521
420	You still can embed kqueue into a normal poll or select backend and use it	522	You still can embed kqueue into a normal poll or select backend and use it
421	only for sockets (after having made sure that sockets work with kqueue on	523	only for sockets (after having made sure that sockets work with kqueue on
…		…
423		525
424	It scales in the same way as the epoll backend, but the interface to the	526	It scales in the same way as the epoll backend, but the interface to the
425	kernel is more efficient (which says nothing about its actual speed, of	527	kernel is more efficient (which says nothing about its actual speed, of
426	course). While stopping, setting and starting an I/O watcher does never	528	course). While stopping, setting and starting an I/O watcher does never
427	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	529	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
428	two event changes per incident, support for C<fork ()> is very bad and it	530	two event changes per incident. Support for C<fork ()> is very bad (but
429	drops fds silently in similarly hard-to-detect cases.	531	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		532	cases
430		533
431	This backend usually performs well under most conditions.	534	This backend usually performs well under most conditions.
432		535
433	While nominally embeddable in other event loops, this doesn't work	536	While nominally embeddable in other event loops, this doesn't work
434	everywhere, so you might need to test for this. And since it is broken	537	everywhere, so you might need to test for this. And since it is broken
435	almost everywhere, you should only use it when you have a lot of sockets	538	almost everywhere, you should only use it when you have a lot of sockets
436	(for which it usually works), by embedding it into another event loop	539	(for which it usually works), by embedding it into another event loop
437	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	540	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
438	sockets.	541	also broken on OS X)) and, did I mention it, using it only for sockets.
439		542
440	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	543	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
441	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with	544	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
442	C<NOTE_EOF>.	545	C<NOTE_EOF>.
443		546
…		…
460	While this backend scales well, it requires one system call per active	563	While this backend scales well, it requires one system call per active
461	file descriptor per loop iteration. For small and medium numbers of file	564	file descriptor per loop iteration. For small and medium numbers of file
462	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	565	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
463	might perform better.	566	might perform better.
464		567
465	On the positive side, ignoring the spurious readiness notifications, this	568	On the positive side, with the exception of the spurious readiness
466	backend actually performed to specification in all tests and is fully	569	notifications, this backend actually performed fully to specification
467	embeddable, which is a rare feat among the OS-specific backends.	570	in all tests and is fully embeddable, which is a rare feat among the
		571	OS-specific backends (I vastly prefer correctness over speed hacks).
468		572
469	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	573	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
470	C<EVBACKEND_POLL>.	574	C<EVBACKEND_POLL>.
471		575
472	=item C<EVBACKEND_ALL>	576	=item C<EVBACKEND_ALL>
…		…
477		581
478	It is definitely not recommended to use this flag.	582	It is definitely not recommended to use this flag.
479		583
480	=back	584	=back
481		585
482	If one or more of these are or'ed into the flags value, then only these	586	If one or more of the backend flags are or'ed into the flags value,
483	backends will be tried (in the reverse order as listed here). If none are	587	then only these backends will be tried (in the reverse order as listed
484	specified, all backends in C<ev_recommended_backends ()> will be tried.	588	here). If none are specified, all backends in C<ev_recommended_backends
485		589	()> will be tried.
486	The most typical usage is like this:
487
488	if (!ev_default_loop (0))
489	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
490
491	Restrict libev to the select and poll backends, and do not allow
492	environment settings to be taken into account:
493
494	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
495
496	Use whatever libev has to offer, but make sure that kqueue is used if
497	available (warning, breaks stuff, best use only with your own private
498	event loop and only if you know the OS supports your types of fds):
499
500	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
501
502	=item struct ev_loop *ev_loop_new (unsigned int flags)
503
504	Similar to C<ev_default_loop>, but always creates a new event loop that is
505	always distinct from the default loop. Unlike the default loop, it cannot
506	handle signal and child watchers, and attempts to do so will be greeted by
507	undefined behaviour (or a failed assertion if assertions are enabled).
508
509	Note that this function I<is> thread-safe, and the recommended way to use
510	libev with threads is indeed to create one loop per thread, and using the
511	default loop in the "main" or "initial" thread.
512		590
513	Example: Try to create a event loop that uses epoll and nothing else.	591	Example: Try to create a event loop that uses epoll and nothing else.
514		592
515	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	593	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
516	if (!epoller)	594	if (!epoller)
517	fatal ("no epoll found here, maybe it hides under your chair");	595	fatal ("no epoll found here, maybe it hides under your chair");
518		596
		597	Example: Use whatever libev has to offer, but make sure that kqueue is
		598	used if available.
		599
		600	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		601
519	=item ev_default_destroy ()	602	=item ev_loop_destroy (loop)
520		603
521	Destroys the default loop again (frees all memory and kernel state	604	Destroys an event loop object (frees all memory and kernel state
522	etc.). None of the active event watchers will be stopped in the normal	605	etc.). None of the active event watchers will be stopped in the normal
523	sense, so e.g. C<ev_is_active> might still return true. It is your	606	sense, so e.g. C<ev_is_active> might still return true. It is your
524	responsibility to either stop all watchers cleanly yourself I<before>	607	responsibility to either stop all watchers cleanly yourself I<before>
525	calling this function, or cope with the fact afterwards (which is usually	608	calling this function, or cope with the fact afterwards (which is usually
526	the easiest thing, you can just ignore the watchers and/or C<free ()> them	609	the easiest thing, you can just ignore the watchers and/or C<free ()> them
527	for example).	610	for example).
528		611
529	Note that certain global state, such as signal state, will not be freed by	612	Note that certain global state, such as signal state (and installed signal
530	this function, and related watchers (such as signal and child watchers)	613	handlers), will not be freed by this function, and related watchers (such
531	would need to be stopped manually.	614	as signal and child watchers) would need to be stopped manually.
532		615
533	In general it is not advisable to call this function except in the	616	This function is normally used on loop objects allocated by
534	rare occasion where you really need to free e.g. the signal handling	617	C<ev_loop_new>, but it can also be used on the default loop returned by
		618	C<ev_default_loop>, in which case it is not thread-safe.
		619
		620	Note that it is not advisable to call this function on the default loop
		621	except in the rare occasion where you really need to free it's resources.
535	pipe fds. If you need dynamically allocated loops it is better to use	622	If you need dynamically allocated loops it is better to use C<ev_loop_new>
536	C<ev_loop_new> and C<ev_loop_destroy>).	623	and C<ev_loop_destroy>.
537		624
538	=item ev_loop_destroy (loop)	625	=item ev_loop_fork (loop)
539		626
540	Like C<ev_default_destroy>, but destroys an event loop created by an
541	earlier call to C<ev_loop_new>.
542
543	=item ev_default_fork ()
544
545	This function sets a flag that causes subsequent C<ev_loop> iterations	627	This function sets a flag that causes subsequent C<ev_run> iterations to
546	to reinitialise the kernel state for backends that have one. Despite the	628	reinitialise the kernel state for backends that have one. Despite the
547	name, you can call it anytime, but it makes most sense after forking, in	629	name, you can call it anytime, but it makes most sense after forking, in
548	the child process (or both child and parent, but that again makes little	630	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
549	sense). You I<must> call it in the child before using any of the libev	631	child before resuming or calling C<ev_run>.
550	functions, and it will only take effect at the next C<ev_loop> iteration.	632
		633	Again, you I<have> to call it on I<any> loop that you want to re-use after
		634	a fork, I<even if you do not plan to use the loop in the parent>. This is
		635	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		636	during fork.
551		637
552	On the other hand, you only need to call this function in the child	638	On the other hand, you only need to call this function in the child
553	process if and only if you want to use the event library in the child. If	639	process if and only if you want to use the event loop in the child. If
554	you just fork+exec, you don't have to call it at all.	640	you just fork+exec or create a new loop in the child, you don't have to
		641	call it at all (in fact, C<epoll> is so badly broken that it makes a
		642	difference, but libev will usually detect this case on its own and do a
		643	costly reset of the backend).
555		644
556	The function itself is quite fast and it's usually not a problem to call	645	The function itself is quite fast and it's usually not a problem to call
557	it just in case after a fork. To make this easy, the function will fit in	646	it just in case after a fork.
558	quite nicely into a call to C<pthread_atfork>:
559		647
		648	Example: Automate calling C<ev_loop_fork> on the default loop when
		649	using pthreads.
		650
		651	static void
		652	post_fork_child (void)
		653	{
		654	ev_loop_fork (EV_DEFAULT);
		655	}
		656
		657	...
560	pthread_atfork (0, 0, ev_default_fork);	658	pthread_atfork (0, 0, post_fork_child);
561
562	=item ev_loop_fork (loop)
563
564	Like C<ev_default_fork>, but acts on an event loop created by
565	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
566	after fork, and how you do this is entirely your own problem.
567		659
568	=item int ev_is_default_loop (loop)	660	=item int ev_is_default_loop (loop)
569		661
570	Returns true when the given loop actually is the default loop, false otherwise.	662	Returns true when the given loop is, in fact, the default loop, and false
		663	otherwise.
571		664
572	=item unsigned int ev_loop_count (loop)	665	=item unsigned int ev_iteration (loop)
573		666
574	Returns the count of loop iterations for the loop, which is identical to	667	Returns the current iteration count for the event loop, which is identical
575	the number of times libev did poll for new events. It starts at C<0> and	668	to the number of times libev did poll for new events. It starts at C<0>
576	happily wraps around with enough iterations.	669	and happily wraps around with enough iterations.
577		670
578	This value can sometimes be useful as a generation counter of sorts (it	671	This value can sometimes be useful as a generation counter of sorts (it
579	"ticks" the number of loop iterations), as it roughly corresponds with	672	"ticks" the number of loop iterations), as it roughly corresponds with
580	C<ev_prepare> and C<ev_check> calls.	673	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		674	prepare and check phases.
		675
		676	=item unsigned int ev_depth (loop)
		677
		678	Returns the number of times C<ev_run> was entered minus the number of
		679	times C<ev_run> was exited, in other words, the recursion depth.
		680
		681	Outside C<ev_run>, this number is zero. In a callback, this number is
		682	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		683	in which case it is higher.
		684
		685	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread
		686	etc.), doesn't count as "exit" - consider this as a hint to avoid such
		687	ungentleman-like behaviour unless it's really convenient.
581		688
582	=item unsigned int ev_backend (loop)	689	=item unsigned int ev_backend (loop)
583		690
584	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	691	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
585	use.	692	use.
…		…
594		701
595	=item ev_now_update (loop)	702	=item ev_now_update (loop)
596		703
597	Establishes the current time by querying the kernel, updating the time	704	Establishes the current time by querying the kernel, updating the time
598	returned by C<ev_now ()> in the progress. This is a costly operation and	705	returned by C<ev_now ()> in the progress. This is a costly operation and
599	is usually done automatically within C<ev_loop ()>.	706	is usually done automatically within C<ev_run ()>.
600		707
601	This function is rarely useful, but when some event callback runs for a	708	This function is rarely useful, but when some event callback runs for a
602	very long time without entering the event loop, updating libev's idea of	709	very long time without entering the event loop, updating libev's idea of
603	the current time is a good idea.	710	the current time is a good idea.
604		711
605	See also "The special problem of time updates" in the C<ev_timer> section.	712	See also L<The special problem of time updates> in the C<ev_timer> section.
606		713
		714	=item ev_suspend (loop)
		715
		716	=item ev_resume (loop)
		717
		718	These two functions suspend and resume an event loop, for use when the
		719	loop is not used for a while and timeouts should not be processed.
		720
		721	A typical use case would be an interactive program such as a game: When
		722	the user presses C<^Z> to suspend the game and resumes it an hour later it
		723	would be best to handle timeouts as if no time had actually passed while
		724	the program was suspended. This can be achieved by calling C<ev_suspend>
		725	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		726	C<ev_resume> directly afterwards to resume timer processing.
		727
		728	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		729	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		730	will be rescheduled (that is, they will lose any events that would have
		731	occurred while suspended).
		732
		733	After calling C<ev_suspend> you B<must not> call I<any> function on the
		734	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		735	without a previous call to C<ev_suspend>.
		736
		737	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		738	event loop time (see C<ev_now_update>).
		739
607	=item ev_loop (loop, int flags)	740	=item ev_run (loop, int flags)
608		741
609	Finally, this is it, the event handler. This function usually is called	742	Finally, this is it, the event handler. This function usually is called
610	after you initialised all your watchers and you want to start handling	743	after you have initialised all your watchers and you want to start
611	events.	744	handling events. It will ask the operating system for any new events, call
		745	the watcher callbacks, an then repeat the whole process indefinitely: This
		746	is why event loops are called I<loops>.
612		747
613	If the flags argument is specified as C<0>, it will not return until	748	If the flags argument is specified as C<0>, it will keep handling events
614	either no event watchers are active anymore or C<ev_unloop> was called.	749	until either no event watchers are active anymore or C<ev_break> was
		750	called.
615		751
616	Please note that an explicit C<ev_unloop> is usually better than	752	Please note that an explicit C<ev_break> is usually better than
617	relying on all watchers to be stopped when deciding when a program has	753	relying on all watchers to be stopped when deciding when a program has
618	finished (especially in interactive programs), but having a program that	754	finished (especially in interactive programs), but having a program
619	automatically loops as long as it has to and no longer by virtue of	755	that automatically loops as long as it has to and no longer by virtue
620	relying on its watchers stopping correctly is a thing of beauty.	756	of relying on its watchers stopping correctly, that is truly a thing of
		757	beauty.
621		758
622	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	759	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
623	those events and any outstanding ones, but will not block your process in	760	those events and any already outstanding ones, but will not wait and
624	case there are no events and will return after one iteration of the loop.	761	block your process in case there are no events and will return after one
		762	iteration of the loop. This is sometimes useful to poll and handle new
		763	events while doing lengthy calculations, to keep the program responsive.
625		764
626	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	765	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
627	necessary) and will handle those and any outstanding ones. It will block	766	necessary) and will handle those and any already outstanding ones. It
628	your process until at least one new event arrives, and will return after	767	will block your process until at least one new event arrives (which could
629	one iteration of the loop. This is useful if you are waiting for some	768	be an event internal to libev itself, so there is no guarantee that a
630	external event in conjunction with something not expressible using other	769	user-registered callback will be called), and will return after one
		770	iteration of the loop.
		771
		772	This is useful if you are waiting for some external event in conjunction
		773	with something not expressible using other libev watchers (i.e. "roll your
631	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	774	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
632	usually a better approach for this kind of thing.	775	usually a better approach for this kind of thing.
633		776
634	Here are the gory details of what C<ev_loop> does:	777	Here are the gory details of what C<ev_run> does:
635		778
		779	- Increment loop depth.
		780	- Reset the ev_break status.
636	- Before the first iteration, call any pending watchers.	781	- Before the first iteration, call any pending watchers.
		782	LOOP:
637	* If EVFLAG_FORKCHECK was used, check for a fork.	783	- If EVFLAG_FORKCHECK was used, check for a fork.
638	- If a fork was detected (by any means), queue and call all fork watchers.	784	- If a fork was detected (by any means), queue and call all fork watchers.
639	- Queue and call all prepare watchers.	785	- Queue and call all prepare watchers.
		786	- If ev_break was called, goto FINISH.
640	- If we have been forked, detach and recreate the kernel state	787	- If we have been forked, detach and recreate the kernel state
641	as to not disturb the other process.	788	as to not disturb the other process.
642	- Update the kernel state with all outstanding changes.	789	- Update the kernel state with all outstanding changes.
643	- Update the "event loop time" (ev_now ()).	790	- Update the "event loop time" (ev_now ()).
644	- Calculate for how long to sleep or block, if at all	791	- Calculate for how long to sleep or block, if at all
645	(active idle watchers, EVLOOP_NONBLOCK or not having	792	(active idle watchers, EVRUN_NOWAIT or not having
646	any active watchers at all will result in not sleeping).	793	any active watchers at all will result in not sleeping).
647	- Sleep if the I/O and timer collect interval say so.	794	- Sleep if the I/O and timer collect interval say so.
		795	- Increment loop iteration counter.
648	- Block the process, waiting for any events.	796	- Block the process, waiting for any events.
649	- Queue all outstanding I/O (fd) events.	797	- Queue all outstanding I/O (fd) events.
650	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	798	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
651	- Queue all outstanding timers.	799	- Queue all expired timers.
652	- Queue all outstanding periodics.	800	- Queue all expired periodics.
653	- Unless any events are pending now, queue all idle watchers.	801	- Queue all idle watchers with priority higher than that of pending events.
654	- Queue all check watchers.	802	- Queue all check watchers.
655	- Call all queued watchers in reverse order (i.e. check watchers first).	803	- Call all queued watchers in reverse order (i.e. check watchers first).
656	Signals and child watchers are implemented as I/O watchers, and will	804	Signals and child watchers are implemented as I/O watchers, and will
657	be handled here by queueing them when their watcher gets executed.	805	be handled here by queueing them when their watcher gets executed.
658	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	806	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
659	were used, or there are no active watchers, return, otherwise	807	were used, or there are no active watchers, goto FINISH, otherwise
660	continue with step *.	808	continue with step LOOP.
		809	FINISH:
		810	- Reset the ev_break status iff it was EVBREAK_ONE.
		811	- Decrement the loop depth.
		812	- Return.
661		813
662	Example: Queue some jobs and then loop until no events are outstanding	814	Example: Queue some jobs and then loop until no events are outstanding
663	anymore.	815	anymore.
664		816
665	... queue jobs here, make sure they register event watchers as long	817	... queue jobs here, make sure they register event watchers as long
666	... as they still have work to do (even an idle watcher will do..)	818	... as they still have work to do (even an idle watcher will do..)
667	ev_loop (my_loop, 0);	819	ev_run (my_loop, 0);
668	... jobs done or somebody called unloop. yeah!	820	... jobs done or somebody called unloop. yeah!
669		821
670	=item ev_unloop (loop, how)	822	=item ev_break (loop, how)
671		823
672	Can be used to make a call to C<ev_loop> return early (but only after it	824	Can be used to make a call to C<ev_run> return early (but only after it
673	has processed all outstanding events). The C<how> argument must be either	825	has processed all outstanding events). The C<how> argument must be either
674	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	826	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
675	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	827	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
676		828
677	This "unloop state" will be cleared when entering C<ev_loop> again.	829	This "break state" will be cleared when entering C<ev_run> again.
		830
		831	It is safe to call C<ev_break> from outside any C<ev_run> calls, too.
678		832
679	=item ev_ref (loop)	833	=item ev_ref (loop)
680		834
681	=item ev_unref (loop)	835	=item ev_unref (loop)
682		836
683	Ref/unref can be used to add or remove a reference count on the event	837	Ref/unref can be used to add or remove a reference count on the event
684	loop: Every watcher keeps one reference, and as long as the reference	838	loop: Every watcher keeps one reference, and as long as the reference
685	count is nonzero, C<ev_loop> will not return on its own. If you have	839	count is nonzero, C<ev_run> will not return on its own.
686	a watcher you never unregister that should not keep C<ev_loop> from	840
687	returning, ev_unref() after starting, and ev_ref() before stopping it. For	841	This is useful when you have a watcher that you never intend to
		842	unregister, but that nevertheless should not keep C<ev_run> from
		843	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
		844	before stopping it.
		845
688	example, libev itself uses this for its internal signal pipe: It is not	846	As an example, libev itself uses this for its internal signal pipe: It
689	visible to the libev user and should not keep C<ev_loop> from exiting if	847	is not visible to the libev user and should not keep C<ev_run> from
690	no event watchers registered by it are active. It is also an excellent	848	exiting if no event watchers registered by it are active. It is also an
691	way to do this for generic recurring timers or from within third-party	849	excellent way to do this for generic recurring timers or from within
692	libraries. Just remember to I<unref after start> and I<ref before stop>	850	third-party libraries. Just remember to I<unref after start> and I<ref
693	(but only if the watcher wasn't active before, or was active before,	851	before stop> (but only if the watcher wasn't active before, or was active
694	respectively).	852	before, respectively. Note also that libev might stop watchers itself
		853	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		854	in the callback).
695		855
696	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	856	Example: Create a signal watcher, but keep it from keeping C<ev_run>
697	running when nothing else is active.	857	running when nothing else is active.
698		858
699	struct ev_signal exitsig;	859	ev_signal exitsig;
700	ev_signal_init (&exitsig, sig_cb, SIGINT);	860	ev_signal_init (&exitsig, sig_cb, SIGINT);
701	ev_signal_start (loop, &exitsig);	861	ev_signal_start (loop, &exitsig);
702	evf_unref (loop);	862	evf_unref (loop);
703		863
704	Example: For some weird reason, unregister the above signal handler again.	864	Example: For some weird reason, unregister the above signal handler again.
…		…
718	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	878	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
719	allows libev to delay invocation of I/O and timer/periodic callbacks	879	allows libev to delay invocation of I/O and timer/periodic callbacks
720	to increase efficiency of loop iterations (or to increase power-saving	880	to increase efficiency of loop iterations (or to increase power-saving
721	opportunities).	881	opportunities).
722		882
723	The background is that sometimes your program runs just fast enough to	883	The idea is that sometimes your program runs just fast enough to handle
724	handle one (or very few) event(s) per loop iteration. While this makes	884	one (or very few) event(s) per loop iteration. While this makes the
725	the program responsive, it also wastes a lot of CPU time to poll for new	885	program responsive, it also wastes a lot of CPU time to poll for new
726	events, especially with backends like C<select ()> which have a high	886	events, especially with backends like C<select ()> which have a high
727	overhead for the actual polling but can deliver many events at once.	887	overhead for the actual polling but can deliver many events at once.
728		888
729	By setting a higher I<io collect interval> you allow libev to spend more	889	By setting a higher I<io collect interval> you allow libev to spend more
730	time collecting I/O events, so you can handle more events per iteration,	890	time collecting I/O events, so you can handle more events per iteration,
731	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	891	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
732	C<ev_timer>) will be not affected. Setting this to a non-null value will	892	C<ev_timer>) will be not affected. Setting this to a non-null value will
733	introduce an additional C<ev_sleep ()> call into most loop iterations.	893	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		894	sleep time ensures that libev will not poll for I/O events more often then
		895	once per this interval, on average.
734		896
735	Likewise, by setting a higher I<timeout collect interval> you allow libev	897	Likewise, by setting a higher I<timeout collect interval> you allow libev
736	to spend more time collecting timeouts, at the expense of increased	898	to spend more time collecting timeouts, at the expense of increased
737	latency (the watcher callback will be called later). C<ev_io> watchers	899	latency/jitter/inexactness (the watcher callback will be called
738	will not be affected. Setting this to a non-null value will not introduce	900	later). C<ev_io> watchers will not be affected. Setting this to a non-null
739	any overhead in libev.	901	value will not introduce any overhead in libev.
740		902
741	Many (busy) programs can usually benefit by setting the I/O collect	903	Many (busy) programs can usually benefit by setting the I/O collect
742	interval to a value near C<0.1> or so, which is often enough for	904	interval to a value near C<0.1> or so, which is often enough for
743	interactive servers (of course not for games), likewise for timeouts. It	905	interactive servers (of course not for games), likewise for timeouts. It
744	usually doesn't make much sense to set it to a lower value than C<0.01>,	906	usually doesn't make much sense to set it to a lower value than C<0.01>,
745	as this approaches the timing granularity of most systems.	907	as this approaches the timing granularity of most systems. Note that if
		908	you do transactions with the outside world and you can't increase the
		909	parallelity, then this setting will limit your transaction rate (if you
		910	need to poll once per transaction and the I/O collect interval is 0.01,
		911	then you can't do more than 100 transactions per second).
746		912
747	Setting the I<timeout collect interval> can improve the opportunity for	913	Setting the I<timeout collect interval> can improve the opportunity for
748	saving power, as the program will "bundle" timer callback invocations that	914	saving power, as the program will "bundle" timer callback invocations that
749	are "near" in time together, by delaying some, thus reducing the number of	915	are "near" in time together, by delaying some, thus reducing the number of
750	times the process sleeps and wakes up again. Another useful technique to	916	times the process sleeps and wakes up again. Another useful technique to
751	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	917	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
752	they fire on, say, one-second boundaries only.	918	they fire on, say, one-second boundaries only.
753		919
		920	Example: we only need 0.1s timeout granularity, and we wish not to poll
		921	more often than 100 times per second:
		922
		923	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		924	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		925
		926	=item ev_invoke_pending (loop)
		927
		928	This call will simply invoke all pending watchers while resetting their
		929	pending state. Normally, C<ev_run> does this automatically when required,
		930	but when overriding the invoke callback this call comes handy. This
		931	function can be invoked from a watcher - this can be useful for example
		932	when you want to do some lengthy calculation and want to pass further
		933	event handling to another thread (you still have to make sure only one
		934	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		935
		936	=item int ev_pending_count (loop)
		937
		938	Returns the number of pending watchers - zero indicates that no watchers
		939	are pending.
		940
		941	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		942
		943	This overrides the invoke pending functionality of the loop: Instead of
		944	invoking all pending watchers when there are any, C<ev_run> will call
		945	this callback instead. This is useful, for example, when you want to
		946	invoke the actual watchers inside another context (another thread etc.).
		947
		948	If you want to reset the callback, use C<ev_invoke_pending> as new
		949	callback.
		950
		951	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		952
		953	Sometimes you want to share the same loop between multiple threads. This
		954	can be done relatively simply by putting mutex_lock/unlock calls around
		955	each call to a libev function.
		956
		957	However, C<ev_run> can run an indefinite time, so it is not feasible
		958	to wait for it to return. One way around this is to wake up the event
		959	loop via C<ev_break> and C<av_async_send>, another way is to set these
		960	I<release> and I<acquire> callbacks on the loop.
		961
		962	When set, then C<release> will be called just before the thread is
		963	suspended waiting for new events, and C<acquire> is called just
		964	afterwards.
		965
		966	Ideally, C<release> will just call your mutex_unlock function, and
		967	C<acquire> will just call the mutex_lock function again.
		968
		969	While event loop modifications are allowed between invocations of
		970	C<release> and C<acquire> (that's their only purpose after all), no
		971	modifications done will affect the event loop, i.e. adding watchers will
		972	have no effect on the set of file descriptors being watched, or the time
		973	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		974	to take note of any changes you made.
		975
		976	In theory, threads executing C<ev_run> will be async-cancel safe between
		977	invocations of C<release> and C<acquire>.
		978
		979	See also the locking example in the C<THREADS> section later in this
		980	document.
		981
		982	=item ev_set_userdata (loop, void *data)
		983
		984	=item ev_userdata (loop)
		985
		986	Set and retrieve a single C<void *> associated with a loop. When
		987	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		988	C<0.>
		989
		990	These two functions can be used to associate arbitrary data with a loop,
		991	and are intended solely for the C<invoke_pending_cb>, C<release> and
		992	C<acquire> callbacks described above, but of course can be (ab-)used for
		993	any other purpose as well.
		994
754	=item ev_loop_verify (loop)	995	=item ev_verify (loop)
755		996
756	This function only does something when C<EV_VERIFY> support has been	997	This function only does something when C<EV_VERIFY> support has been
757	compiled in. It tries to go through all internal structures and checks	998	compiled in, which is the default for non-minimal builds. It tries to go
758	them for validity. If anything is found to be inconsistent, it will print	999	through all internal structures and checks them for validity. If anything
759	an error message to standard error and call C<abort ()>.	1000	is found to be inconsistent, it will print an error message to standard
		1001	error and call C<abort ()>.
760		1002
761	This can be used to catch bugs inside libev itself: under normal	1003	This can be used to catch bugs inside libev itself: under normal
762	circumstances, this function will never abort as of course libev keeps its	1004	circumstances, this function will never abort as of course libev keeps its
763	data structures consistent.	1005	data structures consistent.
764		1006
765	=back	1007	=back
766		1008
767		1009
768	=head1 ANATOMY OF A WATCHER	1010	=head1 ANATOMY OF A WATCHER
769		1011
		1012	In the following description, uppercase C<TYPE> in names stands for the
		1013	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		1014	watchers and C<ev_io_start> for I/O watchers.
		1015
770	A watcher is a structure that you create and register to record your	1016	A watcher is an opaque structure that you allocate and register to record
771	interest in some event. For instance, if you want to wait for STDIN to	1017	your interest in some event. To make a concrete example, imagine you want
772	become readable, you would create an C<ev_io> watcher for that:	1018	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1019	for that:
773		1020
774	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1021	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
775	{	1022	{
776	ev_io_stop (w);	1023	ev_io_stop (w);
777	ev_unloop (loop, EVUNLOOP_ALL);	1024	ev_break (loop, EVBREAK_ALL);
778	}	1025	}
779		1026
780	struct ev_loop *loop = ev_default_loop (0);	1027	struct ev_loop *loop = ev_default_loop (0);
		1028
781	struct ev_io stdin_watcher;	1029	ev_io stdin_watcher;
		1030
782	ev_init (&stdin_watcher, my_cb);	1031	ev_init (&stdin_watcher, my_cb);
783	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1032	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
784	ev_io_start (loop, &stdin_watcher);	1033	ev_io_start (loop, &stdin_watcher);
		1034
785	ev_loop (loop, 0);	1035	ev_run (loop, 0);
786		1036
787	As you can see, you are responsible for allocating the memory for your	1037	As you can see, you are responsible for allocating the memory for your
788	watcher structures (and it is usually a bad idea to do this on the stack,	1038	watcher structures (and it is I<usually> a bad idea to do this on the
789	although this can sometimes be quite valid).	1039	stack).
790		1040
		1041	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		1042	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
		1043
791	Each watcher structure must be initialised by a call to C<ev_init	1044	Each watcher structure must be initialised by a call to C<ev_init (watcher
792	(watcher *, callback)>, which expects a callback to be provided. This	1045	*, callback)>, which expects a callback to be provided. This callback is
793	callback gets invoked each time the event occurs (or, in the case of I/O	1046	invoked each time the event occurs (or, in the case of I/O watchers, each
794	watchers, each time the event loop detects that the file descriptor given	1047	time the event loop detects that the file descriptor given is readable
795	is readable and/or writable).	1048	and/or writable).
796		1049
797	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1050	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
798	with arguments specific to this watcher type. There is also a macro	1051	macro to configure it, with arguments specific to the watcher type. There
799	to combine initialisation and setting in one call: C<< ev_<type>_init	1052	is also a macro to combine initialisation and setting in one call: C<<
800	(watcher *, callback, ...) >>.	1053	ev_TYPE_init (watcher *, callback, ...) >>.
801		1054
802	To make the watcher actually watch out for events, you have to start it	1055	To make the watcher actually watch out for events, you have to start it
803	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	1056	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
804	*) >>), and you can stop watching for events at any time by calling the	1057	*) >>), and you can stop watching for events at any time by calling the
805	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1058	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
806		1059
807	As long as your watcher is active (has been started but not stopped) you	1060	As long as your watcher is active (has been started but not stopped) you
808	must not touch the values stored in it. Most specifically you must never	1061	must not touch the values stored in it. Most specifically you must never
809	reinitialise it or call its C<set> macro.	1062	reinitialise it or call its C<ev_TYPE_set> macro.
810		1063
811	Each and every callback receives the event loop pointer as first, the	1064	Each and every callback receives the event loop pointer as first, the
812	registered watcher structure as second, and a bitset of received events as	1065	registered watcher structure as second, and a bitset of received events as
813	third argument.	1066	third argument.
814		1067
…		…
823	=item C<EV_WRITE>	1076	=item C<EV_WRITE>
824		1077
825	The file descriptor in the C<ev_io> watcher has become readable and/or	1078	The file descriptor in the C<ev_io> watcher has become readable and/or
826	writable.	1079	writable.
827		1080
828	=item C<EV_TIMEOUT>	1081	=item C<EV_TIMER>
829		1082
830	The C<ev_timer> watcher has timed out.	1083	The C<ev_timer> watcher has timed out.
831		1084
832	=item C<EV_PERIODIC>	1085	=item C<EV_PERIODIC>
833		1086
…		…
851		1104
852	=item C<EV_PREPARE>	1105	=item C<EV_PREPARE>
853		1106
854	=item C<EV_CHECK>	1107	=item C<EV_CHECK>
855		1108
856	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1109	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
857	to gather new events, and all C<ev_check> watchers are invoked just after	1110	to gather new events, and all C<ev_check> watchers are invoked just after
858	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1111	C<ev_run> has gathered them, but before it invokes any callbacks for any
859	received events. Callbacks of both watcher types can start and stop as	1112	received events. Callbacks of both watcher types can start and stop as
860	many watchers as they want, and all of them will be taken into account	1113	many watchers as they want, and all of them will be taken into account
861	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1114	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
862	C<ev_loop> from blocking).	1115	C<ev_run> from blocking).
863		1116
864	=item C<EV_EMBED>	1117	=item C<EV_EMBED>
865		1118
866	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1119	The embedded event loop specified in the C<ev_embed> watcher needs attention.
867		1120
868	=item C<EV_FORK>	1121	=item C<EV_FORK>
869		1122
870	The event loop has been resumed in the child process after fork (see	1123	The event loop has been resumed in the child process after fork (see
871	C<ev_fork>).	1124	C<ev_fork>).
872		1125
		1126	=item C<EV_CLEANUP>
		1127
		1128	The event loop is about to be destroyed (see C<ev_cleanup>).
		1129
873	=item C<EV_ASYNC>	1130	=item C<EV_ASYNC>
874		1131
875	The given async watcher has been asynchronously notified (see C<ev_async>).	1132	The given async watcher has been asynchronously notified (see C<ev_async>).
		1133
		1134	=item C<EV_CUSTOM>
		1135
		1136	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1137	by libev users to signal watchers (e.g. via C<ev_feed_event>).
876		1138
877	=item C<EV_ERROR>	1139	=item C<EV_ERROR>
878		1140
879	An unspecified error has occurred, the watcher has been stopped. This might	1141	An unspecified error has occurred, the watcher has been stopped. This might
880	happen because the watcher could not be properly started because libev	1142	happen because the watcher could not be properly started because libev
881	ran out of memory, a file descriptor was found to be closed or any other	1143	ran out of memory, a file descriptor was found to be closed or any other
		1144	problem. Libev considers these application bugs.
		1145
882	problem. You best act on it by reporting the problem and somehow coping	1146	You best act on it by reporting the problem and somehow coping with the
883	with the watcher being stopped.	1147	watcher being stopped. Note that well-written programs should not receive
		1148	an error ever, so when your watcher receives it, this usually indicates a
		1149	bug in your program.
884		1150
885	Libev will usually signal a few "dummy" events together with an error,	1151	Libev will usually signal a few "dummy" events together with an error, for
886	for example it might indicate that a fd is readable or writable, and if	1152	example it might indicate that a fd is readable or writable, and if your
887	your callbacks is well-written it can just attempt the operation and cope	1153	callbacks is well-written it can just attempt the operation and cope with
888	with the error from read() or write(). This will not work in multi-threaded	1154	the error from read() or write(). This will not work in multi-threaded
889	programs, though, so beware.	1155	programs, though, as the fd could already be closed and reused for another
		1156	thing, so beware.
890		1157
891	=back	1158	=back
892		1159
893	=head2 GENERIC WATCHER FUNCTIONS	1160	=head2 GENERIC WATCHER FUNCTIONS
894
895	In the following description, C<TYPE> stands for the watcher type,
896	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
897		1161
898	=over 4	1162	=over 4
899		1163
900	=item C<ev_init> (ev_TYPE *watcher, callback)	1164	=item C<ev_init> (ev_TYPE *watcher, callback)
901		1165
…		…
907	which rolls both calls into one.	1171	which rolls both calls into one.
908		1172
909	You can reinitialise a watcher at any time as long as it has been stopped	1173	You can reinitialise a watcher at any time as long as it has been stopped
910	(or never started) and there are no pending events outstanding.	1174	(or never started) and there are no pending events outstanding.
911		1175
912	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1176	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
913	int revents)>.	1177	int revents)>.
914		1178
		1179	Example: Initialise an C<ev_io> watcher in two steps.
		1180
		1181	ev_io w;
		1182	ev_init (&w, my_cb);
		1183	ev_io_set (&w, STDIN_FILENO, EV_READ);
		1184
915	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1185	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
916		1186
917	This macro initialises the type-specific parts of a watcher. You need to	1187	This macro initialises the type-specific parts of a watcher. You need to
918	call C<ev_init> at least once before you call this macro, but you can	1188	call C<ev_init> at least once before you call this macro, but you can
919	call C<ev_TYPE_set> any number of times. You must not, however, call this	1189	call C<ev_TYPE_set> any number of times. You must not, however, call this
920	macro on a watcher that is active (it can be pending, however, which is a	1190	macro on a watcher that is active (it can be pending, however, which is a
921	difference to the C<ev_init> macro).	1191	difference to the C<ev_init> macro).
922		1192
923	Although some watcher types do not have type-specific arguments	1193	Although some watcher types do not have type-specific arguments
924	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	1194	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
925		1195
		1196	See C<ev_init>, above, for an example.
		1197
926	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1198	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
927		1199
928	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1200	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
929	calls into a single call. This is the most convenient method to initialise	1201	calls into a single call. This is the most convenient method to initialise
930	a watcher. The same limitations apply, of course.	1202	a watcher. The same limitations apply, of course.
931		1203
		1204	Example: Initialise and set an C<ev_io> watcher in one step.
		1205
		1206	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1207
932	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1208	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
933		1209
934	Starts (activates) the given watcher. Only active watchers will receive	1210	Starts (activates) the given watcher. Only active watchers will receive
935	events. If the watcher is already active nothing will happen.	1211	events. If the watcher is already active nothing will happen.
936		1212
		1213	Example: Start the C<ev_io> watcher that is being abused as example in this
		1214	whole section.
		1215
		1216	ev_io_start (EV_DEFAULT_UC, &w);
		1217
937	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1218	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
938		1219
939	Stops the given watcher again (if active) and clears the pending	1220	Stops the given watcher if active, and clears the pending status (whether
		1221	the watcher was active or not).
		1222
940	status. It is possible that stopped watchers are pending (for example,	1223	It is possible that stopped watchers are pending - for example,
941	non-repeating timers are being stopped when they become pending), but	1224	non-repeating timers are being stopped when they become pending - but
942	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1225	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
943	you want to free or reuse the memory used by the watcher it is therefore a	1226	pending. If you want to free or reuse the memory used by the watcher it is
944	good idea to always call its C<ev_TYPE_stop> function.	1227	therefore a good idea to always call its C<ev_TYPE_stop> function.
945		1228
946	=item bool ev_is_active (ev_TYPE *watcher)	1229	=item bool ev_is_active (ev_TYPE *watcher)
947		1230
948	Returns a true value iff the watcher is active (i.e. it has been started	1231	Returns a true value iff the watcher is active (i.e. it has been started
949	and not yet been stopped). As long as a watcher is active you must not modify	1232	and not yet been stopped). As long as a watcher is active you must not modify
…		…
965	=item ev_cb_set (ev_TYPE *watcher, callback)	1248	=item ev_cb_set (ev_TYPE *watcher, callback)
966		1249
967	Change the callback. You can change the callback at virtually any time	1250	Change the callback. You can change the callback at virtually any time
968	(modulo threads).	1251	(modulo threads).
969		1252
970	=item ev_set_priority (ev_TYPE *watcher, priority)	1253	=item ev_set_priority (ev_TYPE *watcher, int priority)
971		1254
972	=item int ev_priority (ev_TYPE *watcher)	1255	=item int ev_priority (ev_TYPE *watcher)
973		1256
974	Set and query the priority of the watcher. The priority is a small	1257	Set and query the priority of the watcher. The priority is a small
975	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1258	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
976	(default: C<-2>). Pending watchers with higher priority will be invoked	1259	(default: C<-2>). Pending watchers with higher priority will be invoked
977	before watchers with lower priority, but priority will not keep watchers	1260	before watchers with lower priority, but priority will not keep watchers
978	from being executed (except for C<ev_idle> watchers).	1261	from being executed (except for C<ev_idle> watchers).
979		1262
980	This means that priorities are I<only> used for ordering callback
981	invocation after new events have been received. This is useful, for
982	example, to reduce latency after idling, or more often, to bind two
983	watchers on the same event and make sure one is called first.
984
985	If you need to suppress invocation when higher priority events are pending	1263	If you need to suppress invocation when higher priority events are pending
986	you need to look at C<ev_idle> watchers, which provide this functionality.	1264	you need to look at C<ev_idle> watchers, which provide this functionality.
987		1265
988	You I<must not> change the priority of a watcher as long as it is active or	1266	You I<must not> change the priority of a watcher as long as it is active or
989	pending.	1267	pending.
990		1268
		1269	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1270	fine, as long as you do not mind that the priority value you query might
		1271	or might not have been clamped to the valid range.
		1272
991	The default priority used by watchers when no priority has been set is	1273	The default priority used by watchers when no priority has been set is
992	always C<0>, which is supposed to not be too high and not be too low :).	1274	always C<0>, which is supposed to not be too high and not be too low :).
993		1275
994	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1276	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
995	fine, as long as you do not mind that the priority value you query might	1277	priorities.
996	or might not have been adjusted to be within valid range.
997		1278
998	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1279	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
999		1280
1000	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1281	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1001	C<loop> nor C<revents> need to be valid as long as the watcher callback	1282	C<loop> nor C<revents> need to be valid as long as the watcher callback
1002	can deal with that fact.	1283	can deal with that fact, as both are simply passed through to the
		1284	callback.
1003		1285
1004	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1286	=item int ev_clear_pending (loop, ev_TYPE *watcher)
1005		1287
1006	If the watcher is pending, this function returns clears its pending status	1288	If the watcher is pending, this function clears its pending status and
1007	and returns its C<revents> bitset (as if its callback was invoked). If the	1289	returns its C<revents> bitset (as if its callback was invoked). If the
1008	watcher isn't pending it does nothing and returns C<0>.	1290	watcher isn't pending it does nothing and returns C<0>.
1009		1291
		1292	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1293	callback to be invoked, which can be accomplished with this function.
		1294
		1295	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1296
		1297	Feeds the given event set into the event loop, as if the specified event
		1298	had happened for the specified watcher (which must be a pointer to an
		1299	initialised but not necessarily started event watcher). Obviously you must
		1300	not free the watcher as long as it has pending events.
		1301
		1302	Stopping the watcher, letting libev invoke it, or calling
		1303	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1304	not started in the first place.
		1305
		1306	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1307	functions that do not need a watcher.
		1308
1010	=back	1309	=back
1011		1310
1012
1013	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1311	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1014		1312
1015	Each watcher has, by default, a member C<void *data> that you can change	1313	Each watcher has, by default, a member C<void *data> that you can change
1016	and read at any time, libev will completely ignore it. This can be used	1314	and read at any time: libev will completely ignore it. This can be used
1017	to associate arbitrary data with your watcher. If you need more data and	1315	to associate arbitrary data with your watcher. If you need more data and
1018	don't want to allocate memory and store a pointer to it in that data	1316	don't want to allocate memory and store a pointer to it in that data
1019	member, you can also "subclass" the watcher type and provide your own	1317	member, you can also "subclass" the watcher type and provide your own
1020	data:	1318	data:
1021		1319
1022	struct my_io	1320	struct my_io
1023	{	1321	{
1024	struct ev_io io;	1322	ev_io io;
1025	int otherfd;	1323	int otherfd;
1026	void *somedata;	1324	void *somedata;
1027	struct whatever *mostinteresting;	1325	struct whatever *mostinteresting;
1028	};	1326	};
1029		1327
…		…
1032	ev_io_init (&w.io, my_cb, fd, EV_READ);	1330	ev_io_init (&w.io, my_cb, fd, EV_READ);
1033		1331
1034	And since your callback will be called with a pointer to the watcher, you	1332	And since your callback will be called with a pointer to the watcher, you
1035	can cast it back to your own type:	1333	can cast it back to your own type:
1036		1334
1037	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1335	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1038	{	1336	{
1039	struct my_io *w = (struct my_io *)w_;	1337	struct my_io *w = (struct my_io *)w_;
1040	...	1338	...
1041	}	1339	}
1042		1340
…		…
1053	ev_timer t2;	1351	ev_timer t2;
1054	}	1352	}
1055		1353
1056	In this case getting the pointer to C<my_biggy> is a bit more	1354	In this case getting the pointer to C<my_biggy> is a bit more
1057	complicated: Either you store the address of your C<my_biggy> struct	1355	complicated: Either you store the address of your C<my_biggy> struct
1058	in the C<data> member of the watcher, or you need to use some pointer	1356	in the C<data> member of the watcher (for woozies), or you need to use
1059	arithmetic using C<offsetof> inside your watchers:	1357	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1358	programmers):
1060		1359
1061	#include <stddef.h>	1360	#include <stddef.h>
1062		1361
1063	static void	1362	static void
1064	t1_cb (EV_P_ struct ev_timer *w, int revents)	1363	t1_cb (EV_P_ ev_timer *w, int revents)
1065	{	1364	{
1066	struct my_biggy big = (struct my_biggy *	1365	struct my_biggy big = (struct my_biggy *)
1067	(((char *)w) - offsetof (struct my_biggy, t1));	1366	(((char *)w) - offsetof (struct my_biggy, t1));
1068	}	1367	}
1069		1368
1070	static void	1369	static void
1071	t2_cb (EV_P_ struct ev_timer *w, int revents)	1370	t2_cb (EV_P_ ev_timer *w, int revents)
1072	{	1371	{
1073	struct my_biggy big = (struct my_biggy *	1372	struct my_biggy big = (struct my_biggy *)
1074	(((char *)w) - offsetof (struct my_biggy, t2));	1373	(((char *)w) - offsetof (struct my_biggy, t2));
1075	}	1374	}
		1375
		1376	=head2 WATCHER STATES
		1377
		1378	There are various watcher states mentioned throughout this manual -
		1379	active, pending and so on. In this section these states and the rules to
		1380	transition between them will be described in more detail - and while these
		1381	rules might look complicated, they usually do "the right thing".
		1382
		1383	=over 4
		1384
		1385	=item initialiased
		1386
		1387	Before a watcher can be registered with the event looop it has to be
		1388	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1389	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1390
		1391	In this state it is simply some block of memory that is suitable for use
		1392	in an event loop. It can be moved around, freed, reused etc. at will.
		1393
		1394	=item started/running/active
		1395
		1396	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1397	property of the event loop, and is actively waiting for events. While in
		1398	this state it cannot be accessed (except in a few documented ways), moved,
		1399	freed or anything else - the only legal thing is to keep a pointer to it,
		1400	and call libev functions on it that are documented to work on active watchers.
		1401
		1402	=item pending
		1403
		1404	If a watcher is active and libev determines that an event it is interested
		1405	in has occurred (such as a timer expiring), it will become pending. It will
		1406	stay in this pending state until either it is stopped or its callback is
		1407	about to be invoked, so it is not normally pending inside the watcher
		1408	callback.
		1409
		1410	The watcher might or might not be active while it is pending (for example,
		1411	an expired non-repeating timer can be pending but no longer active). If it
		1412	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1413	but it is still property of the event loop at this time, so cannot be
		1414	moved, freed or reused. And if it is active the rules described in the
		1415	previous item still apply.
		1416
		1417	It is also possible to feed an event on a watcher that is not active (e.g.
		1418	via C<ev_feed_event>), in which case it becomes pending without being
		1419	active.
		1420
		1421	=item stopped
		1422
		1423	A watcher can be stopped implicitly by libev (in which case it might still
		1424	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1425	latter will clear any pending state the watcher might be in, regardless
		1426	of whether it was active or not, so stopping a watcher explicitly before
		1427	freeing it is often a good idea.
		1428
		1429	While stopped (and not pending) the watcher is essentially in the
		1430	initialised state, that is it can be reused, moved, modified in any way
		1431	you wish.
		1432
		1433	=back
		1434
		1435	=head2 WATCHER PRIORITY MODELS
		1436
		1437	Many event loops support I<watcher priorities>, which are usually small
		1438	integers that influence the ordering of event callback invocation
		1439	between watchers in some way, all else being equal.
		1440
		1441	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1442	description for the more technical details such as the actual priority
		1443	range.
		1444
		1445	There are two common ways how these these priorities are being interpreted
		1446	by event loops:
		1447
		1448	In the more common lock-out model, higher priorities "lock out" invocation
		1449	of lower priority watchers, which means as long as higher priority
		1450	watchers receive events, lower priority watchers are not being invoked.
		1451
		1452	The less common only-for-ordering model uses priorities solely to order
		1453	callback invocation within a single event loop iteration: Higher priority
		1454	watchers are invoked before lower priority ones, but they all get invoked
		1455	before polling for new events.
		1456
		1457	Libev uses the second (only-for-ordering) model for all its watchers
		1458	except for idle watchers (which use the lock-out model).
		1459
		1460	The rationale behind this is that implementing the lock-out model for
		1461	watchers is not well supported by most kernel interfaces, and most event
		1462	libraries will just poll for the same events again and again as long as
		1463	their callbacks have not been executed, which is very inefficient in the
		1464	common case of one high-priority watcher locking out a mass of lower
		1465	priority ones.
		1466
		1467	Static (ordering) priorities are most useful when you have two or more
		1468	watchers handling the same resource: a typical usage example is having an
		1469	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1470	timeouts. Under load, data might be received while the program handles
		1471	other jobs, but since timers normally get invoked first, the timeout
		1472	handler will be executed before checking for data. In that case, giving
		1473	the timer a lower priority than the I/O watcher ensures that I/O will be
		1474	handled first even under adverse conditions (which is usually, but not
		1475	always, what you want).
		1476
		1477	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1478	will only be executed when no same or higher priority watchers have
		1479	received events, they can be used to implement the "lock-out" model when
		1480	required.
		1481
		1482	For example, to emulate how many other event libraries handle priorities,
		1483	you can associate an C<ev_idle> watcher to each such watcher, and in
		1484	the normal watcher callback, you just start the idle watcher. The real
		1485	processing is done in the idle watcher callback. This causes libev to
		1486	continuously poll and process kernel event data for the watcher, but when
		1487	the lock-out case is known to be rare (which in turn is rare :), this is
		1488	workable.
		1489
		1490	Usually, however, the lock-out model implemented that way will perform
		1491	miserably under the type of load it was designed to handle. In that case,
		1492	it might be preferable to stop the real watcher before starting the
		1493	idle watcher, so the kernel will not have to process the event in case
		1494	the actual processing will be delayed for considerable time.
		1495
		1496	Here is an example of an I/O watcher that should run at a strictly lower
		1497	priority than the default, and which should only process data when no
		1498	other events are pending:
		1499
		1500	ev_idle idle; // actual processing watcher
		1501	ev_io io; // actual event watcher
		1502
		1503	static void
		1504	io_cb (EV_P_ ev_io *w, int revents)
		1505	{
		1506	// stop the I/O watcher, we received the event, but
		1507	// are not yet ready to handle it.
		1508	ev_io_stop (EV_A_ w);
		1509
		1510	// start the idle watcher to handle the actual event.
		1511	// it will not be executed as long as other watchers
		1512	// with the default priority are receiving events.
		1513	ev_idle_start (EV_A_ &idle);
		1514	}
		1515
		1516	static void
		1517	idle_cb (EV_P_ ev_idle *w, int revents)
		1518	{
		1519	// actual processing
		1520	read (STDIN_FILENO, ...);
		1521
		1522	// have to start the I/O watcher again, as
		1523	// we have handled the event
		1524	ev_io_start (EV_P_ &io);
		1525	}
		1526
		1527	// initialisation
		1528	ev_idle_init (&idle, idle_cb);
		1529	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1530	ev_io_start (EV_DEFAULT_ &io);
		1531
		1532	In the "real" world, it might also be beneficial to start a timer, so that
		1533	low-priority connections can not be locked out forever under load. This
		1534	enables your program to keep a lower latency for important connections
		1535	during short periods of high load, while not completely locking out less
		1536	important ones.
1076		1537
1077		1538
1078	=head1 WATCHER TYPES	1539	=head1 WATCHER TYPES
1079		1540
1080	This section describes each watcher in detail, but will not repeat	1541	This section describes each watcher in detail, but will not repeat
…		…
1104	In general you can register as many read and/or write event watchers per	1565	In general you can register as many read and/or write event watchers per
1105	fd as you want (as long as you don't confuse yourself). Setting all file	1566	fd as you want (as long as you don't confuse yourself). Setting all file
1106	descriptors to non-blocking mode is also usually a good idea (but not	1567	descriptors to non-blocking mode is also usually a good idea (but not
1107	required if you know what you are doing).	1568	required if you know what you are doing).
1108		1569
1109	If you must do this, then force the use of a known-to-be-good backend	1570	If you cannot use non-blocking mode, then force the use of a
1110	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1571	known-to-be-good backend (at the time of this writing, this includes only
1111	C<EVBACKEND_POLL>).	1572	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1573	descriptors for which non-blocking operation makes no sense (such as
		1574	files) - libev doesn't guarantee any specific behaviour in that case.
1112		1575
1113	Another thing you have to watch out for is that it is quite easy to	1576	Another thing you have to watch out for is that it is quite easy to
1114	receive "spurious" readiness notifications, that is your callback might	1577	receive "spurious" readiness notifications, that is your callback might
1115	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1578	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1116	because there is no data. Not only are some backends known to create a	1579	because there is no data. Not only are some backends known to create a
1117	lot of those (for example Solaris ports), it is very easy to get into	1580	lot of those (for example Solaris ports), it is very easy to get into
1118	this situation even with a relatively standard program structure. Thus	1581	this situation even with a relatively standard program structure. Thus
1119	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1582	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1120	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1583	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1121		1584
1122	If you cannot run the fd in non-blocking mode (for example you should not	1585	If you cannot run the fd in non-blocking mode (for example you should
1123	play around with an Xlib connection), then you have to separately re-test	1586	not play around with an Xlib connection), then you have to separately
1124	whether a file descriptor is really ready with a known-to-be good interface	1587	re-test whether a file descriptor is really ready with a known-to-be good
1125	such as poll (fortunately in our Xlib example, Xlib already does this on	1588	interface such as poll (fortunately in our Xlib example, Xlib already
1126	its own, so its quite safe to use).	1589	does this on its own, so its quite safe to use). Some people additionally
		1590	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1591	indefinitely.
		1592
		1593	But really, best use non-blocking mode.
1127		1594
1128	=head3 The special problem of disappearing file descriptors	1595	=head3 The special problem of disappearing file descriptors
1129		1596
1130	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1597	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1131	descriptor (either by calling C<close> explicitly or by any other means,	1598	descriptor (either due to calling C<close> explicitly or any other means,
1132	such as C<dup>). The reason is that you register interest in some file	1599	such as C<dup2>). The reason is that you register interest in some file
1133	descriptor, but when it goes away, the operating system will silently drop	1600	descriptor, but when it goes away, the operating system will silently drop
1134	this interest. If another file descriptor with the same number then is	1601	this interest. If another file descriptor with the same number then is
1135	registered with libev, there is no efficient way to see that this is, in	1602	registered with libev, there is no efficient way to see that this is, in
1136	fact, a different file descriptor.	1603	fact, a different file descriptor.
1137		1604
…		…
1168	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1635	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1169	C<EVBACKEND_POLL>.	1636	C<EVBACKEND_POLL>.
1170		1637
1171	=head3 The special problem of SIGPIPE	1638	=head3 The special problem of SIGPIPE
1172		1639
1173	While not really specific to libev, it is easy to forget about SIGPIPE:	1640	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1174	when writing to a pipe whose other end has been closed, your program gets	1641	when writing to a pipe whose other end has been closed, your program gets
1175	send a SIGPIPE, which, by default, aborts your program. For most programs	1642	sent a SIGPIPE, which, by default, aborts your program. For most programs
1176	this is sensible behaviour, for daemons, this is usually undesirable.	1643	this is sensible behaviour, for daemons, this is usually undesirable.
1177		1644
1178	So when you encounter spurious, unexplained daemon exits, make sure you	1645	So when you encounter spurious, unexplained daemon exits, make sure you
1179	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1646	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1180	somewhere, as that would have given you a big clue).	1647	somewhere, as that would have given you a big clue).
1181		1648
		1649	=head3 The special problem of accept()ing when you can't
		1650
		1651	Many implementations of the POSIX C<accept> function (for example,
		1652	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1653	connection from the pending queue in all error cases.
		1654
		1655	For example, larger servers often run out of file descriptors (because
		1656	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1657	rejecting the connection, leading to libev signalling readiness on
		1658	the next iteration again (the connection still exists after all), and
		1659	typically causing the program to loop at 100% CPU usage.
		1660
		1661	Unfortunately, the set of errors that cause this issue differs between
		1662	operating systems, there is usually little the app can do to remedy the
		1663	situation, and no known thread-safe method of removing the connection to
		1664	cope with overload is known (to me).
		1665
		1666	One of the easiest ways to handle this situation is to just ignore it
		1667	- when the program encounters an overload, it will just loop until the
		1668	situation is over. While this is a form of busy waiting, no OS offers an
		1669	event-based way to handle this situation, so it's the best one can do.
		1670
		1671	A better way to handle the situation is to log any errors other than
		1672	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1673	messages, and continue as usual, which at least gives the user an idea of
		1674	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1675	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1676	usage.
		1677
		1678	If your program is single-threaded, then you could also keep a dummy file
		1679	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1680	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1681	close that fd, and create a new dummy fd. This will gracefully refuse
		1682	clients under typical overload conditions.
		1683
		1684	The last way to handle it is to simply log the error and C<exit>, as
		1685	is often done with C<malloc> failures, but this results in an easy
		1686	opportunity for a DoS attack.
1182		1687
1183	=head3 Watcher-Specific Functions	1688	=head3 Watcher-Specific Functions
1184		1689
1185	=over 4	1690	=over 4
1186		1691
1187	=item ev_io_init (ev_io *, callback, int fd, int events)	1692	=item ev_io_init (ev_io *, callback, int fd, int events)
1188		1693
1189	=item ev_io_set (ev_io *, int fd, int events)	1694	=item ev_io_set (ev_io *, int fd, int events)
1190		1695
1191	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1696	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1192	receive events for and events is either C<EV_READ>, C<EV_WRITE> or	1697	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1193	C<EV_READ | EV_WRITE> to receive the given events.	1698	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1194		1699
1195	=item int fd [read-only]	1700	=item int fd [read-only]
1196		1701
1197	The file descriptor being watched.	1702	The file descriptor being watched.
1198		1703
…		…
1207	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1712	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1208	readable, but only once. Since it is likely line-buffered, you could	1713	readable, but only once. Since it is likely line-buffered, you could
1209	attempt to read a whole line in the callback.	1714	attempt to read a whole line in the callback.
1210		1715
1211	static void	1716	static void
1212	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1717	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1213	{	1718	{
1214	ev_io_stop (loop, w);	1719	ev_io_stop (loop, w);
1215	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1720	.. read from stdin here (or from w->fd) and handle any I/O errors
1216	}	1721	}
1217		1722
1218	...	1723	...
1219	struct ev_loop *loop = ev_default_init (0);	1724	struct ev_loop *loop = ev_default_init (0);
1220	struct ev_io stdin_readable;	1725	ev_io stdin_readable;
1221	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1726	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1222	ev_io_start (loop, &stdin_readable);	1727	ev_io_start (loop, &stdin_readable);
1223	ev_loop (loop, 0);	1728	ev_run (loop, 0);
1224		1729
1225		1730
1226	=head2 C<ev_timer> - relative and optionally repeating timeouts	1731	=head2 C<ev_timer> - relative and optionally repeating timeouts
1227		1732
1228	Timer watchers are simple relative timers that generate an event after a	1733	Timer watchers are simple relative timers that generate an event after a
1229	given time, and optionally repeating in regular intervals after that.	1734	given time, and optionally repeating in regular intervals after that.
1230		1735
1231	The timers are based on real time, that is, if you register an event that	1736	The timers are based on real time, that is, if you register an event that
1232	times out after an hour and you reset your system clock to January last	1737	times out after an hour and you reset your system clock to January last
1233	year, it will still time out after (roughly) and hour. "Roughly" because	1738	year, it will still time out after (roughly) one hour. "Roughly" because
1234	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1739	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1235	monotonic clock option helps a lot here).	1740	monotonic clock option helps a lot here).
1236		1741
1237	The callback is guaranteed to be invoked only after its timeout has passed,	1742	The callback is guaranteed to be invoked only I<after> its timeout has
1238	but if multiple timers become ready during the same loop iteration then	1743	passed (not I<at>, so on systems with very low-resolution clocks this
1239	order of execution is undefined.	1744	might introduce a small delay). If multiple timers become ready during the
		1745	same loop iteration then the ones with earlier time-out values are invoked
		1746	before ones of the same priority with later time-out values (but this is
		1747	no longer true when a callback calls C<ev_run> recursively).
		1748
		1749	=head3 Be smart about timeouts
		1750
		1751	Many real-world problems involve some kind of timeout, usually for error
		1752	recovery. A typical example is an HTTP request - if the other side hangs,
		1753	you want to raise some error after a while.
		1754
		1755	What follows are some ways to handle this problem, from obvious and
		1756	inefficient to smart and efficient.
		1757
		1758	In the following, a 60 second activity timeout is assumed - a timeout that
		1759	gets reset to 60 seconds each time there is activity (e.g. each time some
		1760	data or other life sign was received).
		1761
		1762	=over 4
		1763
		1764	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1765
		1766	This is the most obvious, but not the most simple way: In the beginning,
		1767	start the watcher:
		1768
		1769	ev_timer_init (timer, callback, 60., 0.);
		1770	ev_timer_start (loop, timer);
		1771
		1772	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1773	and start it again:
		1774
		1775	ev_timer_stop (loop, timer);
		1776	ev_timer_set (timer, 60., 0.);
		1777	ev_timer_start (loop, timer);
		1778
		1779	This is relatively simple to implement, but means that each time there is
		1780	some activity, libev will first have to remove the timer from its internal
		1781	data structure and then add it again. Libev tries to be fast, but it's
		1782	still not a constant-time operation.
		1783
		1784	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1785
		1786	This is the easiest way, and involves using C<ev_timer_again> instead of
		1787	C<ev_timer_start>.
		1788
		1789	To implement this, configure an C<ev_timer> with a C<repeat> value
		1790	of C<60> and then call C<ev_timer_again> at start and each time you
		1791	successfully read or write some data. If you go into an idle state where
		1792	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1793	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1794
		1795	That means you can ignore both the C<ev_timer_start> function and the
		1796	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1797	member and C<ev_timer_again>.
		1798
		1799	At start:
		1800
		1801	ev_init (timer, callback);
		1802	timer->repeat = 60.;
		1803	ev_timer_again (loop, timer);
		1804
		1805	Each time there is some activity:
		1806
		1807	ev_timer_again (loop, timer);
		1808
		1809	It is even possible to change the time-out on the fly, regardless of
		1810	whether the watcher is active or not:
		1811
		1812	timer->repeat = 30.;
		1813	ev_timer_again (loop, timer);
		1814
		1815	This is slightly more efficient then stopping/starting the timer each time
		1816	you want to modify its timeout value, as libev does not have to completely
		1817	remove and re-insert the timer from/into its internal data structure.
		1818
		1819	It is, however, even simpler than the "obvious" way to do it.
		1820
		1821	=item 3. Let the timer time out, but then re-arm it as required.
		1822
		1823	This method is more tricky, but usually most efficient: Most timeouts are
		1824	relatively long compared to the intervals between other activity - in
		1825	our example, within 60 seconds, there are usually many I/O events with
		1826	associated activity resets.
		1827
		1828	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1829	but remember the time of last activity, and check for a real timeout only
		1830	within the callback:
		1831
		1832	ev_tstamp last_activity; // time of last activity
		1833
		1834	static void
		1835	callback (EV_P_ ev_timer *w, int revents)
		1836	{
		1837	ev_tstamp now = ev_now (EV_A);
		1838	ev_tstamp timeout = last_activity + 60.;
		1839
		1840	// if last_activity + 60. is older than now, we did time out
		1841	if (timeout < now)
		1842	{
		1843	// timeout occurred, take action
		1844	}
		1845	else
		1846	{
		1847	// callback was invoked, but there was some activity, re-arm
		1848	// the watcher to fire in last_activity + 60, which is
		1849	// guaranteed to be in the future, so "again" is positive:
		1850	w->repeat = timeout - now;
		1851	ev_timer_again (EV_A_ w);
		1852	}
		1853	}
		1854
		1855	To summarise the callback: first calculate the real timeout (defined
		1856	as "60 seconds after the last activity"), then check if that time has
		1857	been reached, which means something I<did>, in fact, time out. Otherwise
		1858	the callback was invoked too early (C<timeout> is in the future), so
		1859	re-schedule the timer to fire at that future time, to see if maybe we have
		1860	a timeout then.
		1861
		1862	Note how C<ev_timer_again> is used, taking advantage of the
		1863	C<ev_timer_again> optimisation when the timer is already running.
		1864
		1865	This scheme causes more callback invocations (about one every 60 seconds
		1866	minus half the average time between activity), but virtually no calls to
		1867	libev to change the timeout.
		1868
		1869	To start the timer, simply initialise the watcher and set C<last_activity>
		1870	to the current time (meaning we just have some activity :), then call the
		1871	callback, which will "do the right thing" and start the timer:
		1872
		1873	ev_init (timer, callback);
		1874	last_activity = ev_now (loop);
		1875	callback (loop, timer, EV_TIMER);
		1876
		1877	And when there is some activity, simply store the current time in
		1878	C<last_activity>, no libev calls at all:
		1879
		1880	last_activity = ev_now (loop);
		1881
		1882	This technique is slightly more complex, but in most cases where the
		1883	time-out is unlikely to be triggered, much more efficient.
		1884
		1885	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1886	callback :) - just change the timeout and invoke the callback, which will
		1887	fix things for you.
		1888
		1889	=item 4. Wee, just use a double-linked list for your timeouts.
		1890
		1891	If there is not one request, but many thousands (millions...), all
		1892	employing some kind of timeout with the same timeout value, then one can
		1893	do even better:
		1894
		1895	When starting the timeout, calculate the timeout value and put the timeout
		1896	at the I<end> of the list.
		1897
		1898	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1899	the list is expected to fire (for example, using the technique #3).
		1900
		1901	When there is some activity, remove the timer from the list, recalculate
		1902	the timeout, append it to the end of the list again, and make sure to
		1903	update the C<ev_timer> if it was taken from the beginning of the list.
		1904
		1905	This way, one can manage an unlimited number of timeouts in O(1) time for
		1906	starting, stopping and updating the timers, at the expense of a major
		1907	complication, and having to use a constant timeout. The constant timeout
		1908	ensures that the list stays sorted.
		1909
		1910	=back
		1911
		1912	So which method the best?
		1913
		1914	Method #2 is a simple no-brain-required solution that is adequate in most
		1915	situations. Method #3 requires a bit more thinking, but handles many cases
		1916	better, and isn't very complicated either. In most case, choosing either
		1917	one is fine, with #3 being better in typical situations.
		1918
		1919	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1920	rather complicated, but extremely efficient, something that really pays
		1921	off after the first million or so of active timers, i.e. it's usually
		1922	overkill :)
1240		1923
1241	=head3 The special problem of time updates	1924	=head3 The special problem of time updates
1242		1925
1243	Establishing the current time is a costly operation (it usually takes at	1926	Establishing the current time is a costly operation (it usually takes at
1244	least two system calls): EV therefore updates its idea of the current	1927	least two system calls): EV therefore updates its idea of the current
1245	time only before and after C<ev_loop> polls for new events, which causes	1928	time only before and after C<ev_run> collects new events, which causes a
1246	a growing difference between C<ev_now ()> and C<ev_time ()> when handling	1929	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1247	lots of events.	1930	lots of events in one iteration.
1248		1931
1249	The relative timeouts are calculated relative to the C<ev_now ()>	1932	The relative timeouts are calculated relative to the C<ev_now ()>
1250	time. This is usually the right thing as this timestamp refers to the time	1933	time. This is usually the right thing as this timestamp refers to the time
1251	of the event triggering whatever timeout you are modifying/starting. If	1934	of the event triggering whatever timeout you are modifying/starting. If
1252	you suspect event processing to be delayed and you I<need> to base the	1935	you suspect event processing to be delayed and you I<need> to base the
…		…
1256		1939
1257	If the event loop is suspended for a long time, you can also force an	1940	If the event loop is suspended for a long time, you can also force an
1258	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1941	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1259	()>.	1942	()>.
1260		1943
		1944	=head3 The special problems of suspended animation
		1945
		1946	When you leave the server world it is quite customary to hit machines that
		1947	can suspend/hibernate - what happens to the clocks during such a suspend?
		1948
		1949	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1950	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1951	to run until the system is suspended, but they will not advance while the
		1952	system is suspended. That means, on resume, it will be as if the program
		1953	was frozen for a few seconds, but the suspend time will not be counted
		1954	towards C<ev_timer> when a monotonic clock source is used. The real time
		1955	clock advanced as expected, but if it is used as sole clocksource, then a
		1956	long suspend would be detected as a time jump by libev, and timers would
		1957	be adjusted accordingly.
		1958
		1959	I would not be surprised to see different behaviour in different between
		1960	operating systems, OS versions or even different hardware.
		1961
		1962	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1963	time jump in the monotonic clocks and the realtime clock. If the program
		1964	is suspended for a very long time, and monotonic clock sources are in use,
		1965	then you can expect C<ev_timer>s to expire as the full suspension time
		1966	will be counted towards the timers. When no monotonic clock source is in
		1967	use, then libev will again assume a timejump and adjust accordingly.
		1968
		1969	It might be beneficial for this latter case to call C<ev_suspend>
		1970	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1971	deterministic behaviour in this case (you can do nothing against
		1972	C<SIGSTOP>).
		1973
1261	=head3 Watcher-Specific Functions and Data Members	1974	=head3 Watcher-Specific Functions and Data Members
1262		1975
1263	=over 4	1976	=over 4
1264		1977
1265	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1978	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1288	If the timer is started but non-repeating, stop it (as if it timed out).	2001	If the timer is started but non-repeating, stop it (as if it timed out).
1289		2002
1290	If the timer is repeating, either start it if necessary (with the	2003	If the timer is repeating, either start it if necessary (with the
1291	C<repeat> value), or reset the running timer to the C<repeat> value.	2004	C<repeat> value), or reset the running timer to the C<repeat> value.
1292		2005
1293	This sounds a bit complicated, but here is a useful and typical	2006	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1294	example: Imagine you have a TCP connection and you want a so-called idle	2007	usage example.
1295	timeout, that is, you want to be called when there have been, say, 60
1296	seconds of inactivity on the socket. The easiest way to do this is to
1297	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1298	C<ev_timer_again> each time you successfully read or write some data. If
1299	you go into an idle state where you do not expect data to travel on the
1300	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1301	automatically restart it if need be.
1302		2008
1303	That means you can ignore the C<after> value and C<ev_timer_start>	2009	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1304	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1305		2010
1306	ev_timer_init (timer, callback, 0., 5.);	2011	Returns the remaining time until a timer fires. If the timer is active,
1307	ev_timer_again (loop, timer);	2012	then this time is relative to the current event loop time, otherwise it's
1308	...	2013	the timeout value currently configured.
1309	timer->again = 17.;
1310	ev_timer_again (loop, timer);
1311	...
1312	timer->again = 10.;
1313	ev_timer_again (loop, timer);
1314		2014
1315	This is more slightly efficient then stopping/starting the timer each time	2015	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1316	you want to modify its timeout value.	2016	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2017	will return C<4>. When the timer expires and is restarted, it will return
		2018	roughly C<7> (likely slightly less as callback invocation takes some time,
		2019	too), and so on.
1317		2020
1318	=item ev_tstamp repeat [read-write]	2021	=item ev_tstamp repeat [read-write]
1319		2022
1320	The current C<repeat> value. Will be used each time the watcher times out	2023	The current C<repeat> value. Will be used each time the watcher times out
1321	or C<ev_timer_again> is called and determines the next timeout (if any),	2024	or C<ev_timer_again> is called, and determines the next timeout (if any),
1322	which is also when any modifications are taken into account.	2025	which is also when any modifications are taken into account.
1323		2026
1324	=back	2027	=back
1325		2028
1326	=head3 Examples	2029	=head3 Examples
1327		2030
1328	Example: Create a timer that fires after 60 seconds.	2031	Example: Create a timer that fires after 60 seconds.
1329		2032
1330	static void	2033	static void
1331	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2034	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1332	{	2035	{
1333	.. one minute over, w is actually stopped right here	2036	.. one minute over, w is actually stopped right here
1334	}	2037	}
1335		2038
1336	struct ev_timer mytimer;	2039	ev_timer mytimer;
1337	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	2040	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1338	ev_timer_start (loop, &mytimer);	2041	ev_timer_start (loop, &mytimer);
1339		2042
1340	Example: Create a timeout timer that times out after 10 seconds of	2043	Example: Create a timeout timer that times out after 10 seconds of
1341	inactivity.	2044	inactivity.
1342		2045
1343	static void	2046	static void
1344	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2047	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1345	{	2048	{
1346	.. ten seconds without any activity	2049	.. ten seconds without any activity
1347	}	2050	}
1348		2051
1349	struct ev_timer mytimer;	2052	ev_timer mytimer;
1350	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2053	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1351	ev_timer_again (&mytimer); /* start timer */	2054	ev_timer_again (&mytimer); /* start timer */
1352	ev_loop (loop, 0);	2055	ev_run (loop, 0);
1353		2056
1354	// and in some piece of code that gets executed on any "activity":	2057	// and in some piece of code that gets executed on any "activity":
1355	// reset the timeout to start ticking again at 10 seconds	2058	// reset the timeout to start ticking again at 10 seconds
1356	ev_timer_again (&mytimer);	2059	ev_timer_again (&mytimer);
1357		2060
…		…
1359	=head2 C<ev_periodic> - to cron or not to cron?	2062	=head2 C<ev_periodic> - to cron or not to cron?
1360		2063
1361	Periodic watchers are also timers of a kind, but they are very versatile	2064	Periodic watchers are also timers of a kind, but they are very versatile
1362	(and unfortunately a bit complex).	2065	(and unfortunately a bit complex).
1363		2066
1364	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2067	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1365	but on wall clock time (absolute time). You can tell a periodic watcher	2068	relative time, the physical time that passes) but on wall clock time
1366	to trigger after some specific point in time. For example, if you tell a	2069	(absolute time, the thing you can read on your calender or clock). The
1367	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	2070	difference is that wall clock time can run faster or slower than real
1368	+ 10.>, that is, an absolute time not a delay) and then reset your system	2071	time, and time jumps are not uncommon (e.g. when you adjust your
1369	clock to January of the previous year, then it will take more than year	2072	wrist-watch).
1370	to trigger the event (unlike an C<ev_timer>, which would still trigger
1371	roughly 10 seconds later as it uses a relative timeout).
1372		2073
		2074	You can tell a periodic watcher to trigger after some specific point
		2075	in time: for example, if you tell a periodic watcher to trigger "in 10
		2076	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2077	not a delay) and then reset your system clock to January of the previous
		2078	year, then it will take a year or more to trigger the event (unlike an
		2079	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2080	it, as it uses a relative timeout).
		2081
1373	C<ev_periodic>s can also be used to implement vastly more complex timers,	2082	C<ev_periodic> watchers can also be used to implement vastly more complex
1374	such as triggering an event on each "midnight, local time", or other	2083	timers, such as triggering an event on each "midnight, local time", or
1375	complicated, rules.	2084	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2085	those cannot react to time jumps.
1376		2086
1377	As with timers, the callback is guaranteed to be invoked only when the	2087	As with timers, the callback is guaranteed to be invoked only when the
1378	time (C<at>) has passed, but if multiple periodic timers become ready	2088	point in time where it is supposed to trigger has passed. If multiple
1379	during the same loop iteration then order of execution is undefined.	2089	timers become ready during the same loop iteration then the ones with
		2090	earlier time-out values are invoked before ones with later time-out values
		2091	(but this is no longer true when a callback calls C<ev_run> recursively).
1380		2092
1381	=head3 Watcher-Specific Functions and Data Members	2093	=head3 Watcher-Specific Functions and Data Members
1382		2094
1383	=over 4	2095	=over 4
1384		2096
1385	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2097	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1386		2098
1387	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2099	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1388		2100
1389	Lots of arguments, lets sort it out... There are basically three modes of	2101	Lots of arguments, let's sort it out... There are basically three modes of
1390	operation, and we will explain them from simplest to complex:	2102	operation, and we will explain them from simplest to most complex:
1391		2103
1392	=over 4	2104	=over 4
1393		2105
1394	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2106	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1395		2107
1396	In this configuration the watcher triggers an event after the wall clock	2108	In this configuration the watcher triggers an event after the wall clock
1397	time C<at> has passed and doesn't repeat. It will not adjust when a time	2109	time C<offset> has passed. It will not repeat and will not adjust when a
1398	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2110	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1399	run when the system time reaches or surpasses this time.	2111	will be stopped and invoked when the system clock reaches or surpasses
		2112	this point in time.
1400		2113
1401	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2114	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1402		2115
1403	In this mode the watcher will always be scheduled to time out at the next	2116	In this mode the watcher will always be scheduled to time out at the next
1404	C<at + N * interval> time (for some integer N, which can also be negative)	2117	C<offset + N * interval> time (for some integer N, which can also be
1405	and then repeat, regardless of any time jumps.	2118	negative) and then repeat, regardless of any time jumps. The C<offset>
		2119	argument is merely an offset into the C<interval> periods.
1406		2120
1407	This can be used to create timers that do not drift with respect to system	2121	This can be used to create timers that do not drift with respect to the
1408	time, for example, here is a C<ev_periodic> that triggers each hour, on	2122	system clock, for example, here is an C<ev_periodic> that triggers each
1409	the hour:	2123	hour, on the hour (with respect to UTC):
1410		2124
1411	ev_periodic_set (&periodic, 0., 3600., 0);	2125	ev_periodic_set (&periodic, 0., 3600., 0);
1412		2126
1413	This doesn't mean there will always be 3600 seconds in between triggers,	2127	This doesn't mean there will always be 3600 seconds in between triggers,
1414	but only that the callback will be called when the system time shows a	2128	but only that the callback will be called when the system time shows a
1415	full hour (UTC), or more correctly, when the system time is evenly divisible	2129	full hour (UTC), or more correctly, when the system time is evenly divisible
1416	by 3600.	2130	by 3600.
1417		2131
1418	Another way to think about it (for the mathematically inclined) is that	2132	Another way to think about it (for the mathematically inclined) is that
1419	C<ev_periodic> will try to run the callback in this mode at the next possible	2133	C<ev_periodic> will try to run the callback in this mode at the next possible
1420	time where C<time = at (mod interval)>, regardless of any time jumps.	2134	time where C<time = offset (mod interval)>, regardless of any time jumps.
1421		2135
1422	For numerical stability it is preferable that the C<at> value is near	2136	For numerical stability it is preferable that the C<offset> value is near
1423	C<ev_now ()> (the current time), but there is no range requirement for	2137	C<ev_now ()> (the current time), but there is no range requirement for
1424	this value, and in fact is often specified as zero.	2138	this value, and in fact is often specified as zero.
1425		2139
1426	Note also that there is an upper limit to how often a timer can fire (CPU	2140	Note also that there is an upper limit to how often a timer can fire (CPU
1427	speed for example), so if C<interval> is very small then timing stability	2141	speed for example), so if C<interval> is very small then timing stability
1428	will of course deteriorate. Libev itself tries to be exact to be about one	2142	will of course deteriorate. Libev itself tries to be exact to be about one
1429	millisecond (if the OS supports it and the machine is fast enough).	2143	millisecond (if the OS supports it and the machine is fast enough).
1430		2144
1431	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2145	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1432		2146
1433	In this mode the values for C<interval> and C<at> are both being	2147	In this mode the values for C<interval> and C<offset> are both being
1434	ignored. Instead, each time the periodic watcher gets scheduled, the	2148	ignored. Instead, each time the periodic watcher gets scheduled, the
1435	reschedule callback will be called with the watcher as first, and the	2149	reschedule callback will be called with the watcher as first, and the
1436	current time as second argument.	2150	current time as second argument.
1437		2151
1438	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2152	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1439	ever, or make ANY event loop modifications whatsoever>.	2153	or make ANY other event loop modifications whatsoever, unless explicitly
		2154	allowed by documentation here>.
1440		2155
1441	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2156	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1442	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2157	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1443	only event loop modification you are allowed to do).	2158	only event loop modification you are allowed to do).
1444		2159
1445	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	2160	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1446	*w, ev_tstamp now)>, e.g.:	2161	*w, ev_tstamp now)>, e.g.:
1447		2162
		2163	static ev_tstamp
1448	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	2164	my_rescheduler (ev_periodic *w, ev_tstamp now)
1449	{	2165	{
1450	return now + 60.;	2166	return now + 60.;
1451	}	2167	}
1452		2168
1453	It must return the next time to trigger, based on the passed time value	2169	It must return the next time to trigger, based on the passed time value
…		…
1473	a different time than the last time it was called (e.g. in a crond like	2189	a different time than the last time it was called (e.g. in a crond like
1474	program when the crontabs have changed).	2190	program when the crontabs have changed).
1475		2191
1476	=item ev_tstamp ev_periodic_at (ev_periodic *)	2192	=item ev_tstamp ev_periodic_at (ev_periodic *)
1477		2193
1478	When active, returns the absolute time that the watcher is supposed to	2194	When active, returns the absolute time that the watcher is supposed
1479	trigger next.	2195	to trigger next. This is not the same as the C<offset> argument to
		2196	C<ev_periodic_set>, but indeed works even in interval and manual
		2197	rescheduling modes.
1480		2198
1481	=item ev_tstamp offset [read-write]	2199	=item ev_tstamp offset [read-write]
1482		2200
1483	When repeating, this contains the offset value, otherwise this is the	2201	When repeating, this contains the offset value, otherwise this is the
1484	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2202	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2203	although libev might modify this value for better numerical stability).
1485		2204
1486	Can be modified any time, but changes only take effect when the periodic	2205	Can be modified any time, but changes only take effect when the periodic
1487	timer fires or C<ev_periodic_again> is being called.	2206	timer fires or C<ev_periodic_again> is being called.
1488		2207
1489	=item ev_tstamp interval [read-write]	2208	=item ev_tstamp interval [read-write]
1490		2209
1491	The current interval value. Can be modified any time, but changes only	2210	The current interval value. Can be modified any time, but changes only
1492	take effect when the periodic timer fires or C<ev_periodic_again> is being	2211	take effect when the periodic timer fires or C<ev_periodic_again> is being
1493	called.	2212	called.
1494		2213
1495	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2214	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1496		2215
1497	The current reschedule callback, or C<0>, if this functionality is	2216	The current reschedule callback, or C<0>, if this functionality is
1498	switched off. Can be changed any time, but changes only take effect when	2217	switched off. Can be changed any time, but changes only take effect when
1499	the periodic timer fires or C<ev_periodic_again> is being called.	2218	the periodic timer fires or C<ev_periodic_again> is being called.
1500		2219
1501	=back	2220	=back
1502		2221
1503	=head3 Examples	2222	=head3 Examples
1504		2223
1505	Example: Call a callback every hour, or, more precisely, whenever the	2224	Example: Call a callback every hour, or, more precisely, whenever the
1506	system clock is divisible by 3600. The callback invocation times have	2225	system time is divisible by 3600. The callback invocation times have
1507	potentially a lot of jitter, but good long-term stability.	2226	potentially a lot of jitter, but good long-term stability.
1508		2227
1509	static void	2228	static void
1510	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2229	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1511	{	2230	{
1512	... its now a full hour (UTC, or TAI or whatever your clock follows)	2231	... its now a full hour (UTC, or TAI or whatever your clock follows)
1513	}	2232	}
1514		2233
1515	struct ev_periodic hourly_tick;	2234	ev_periodic hourly_tick;
1516	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2235	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1517	ev_periodic_start (loop, &hourly_tick);	2236	ev_periodic_start (loop, &hourly_tick);
1518		2237
1519	Example: The same as above, but use a reschedule callback to do it:	2238	Example: The same as above, but use a reschedule callback to do it:
1520		2239
1521	#include <math.h>	2240	#include <math.h>
1522		2241
1523	static ev_tstamp	2242	static ev_tstamp
1524	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2243	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1525	{	2244	{
1526	return fmod (now, 3600.) + 3600.;	2245	return now + (3600. - fmod (now, 3600.));
1527	}	2246	}
1528		2247
1529	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2248	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1530		2249
1531	Example: Call a callback every hour, starting now:	2250	Example: Call a callback every hour, starting now:
1532		2251
1533	struct ev_periodic hourly_tick;	2252	ev_periodic hourly_tick;
1534	ev_periodic_init (&hourly_tick, clock_cb,	2253	ev_periodic_init (&hourly_tick, clock_cb,
1535	fmod (ev_now (loop), 3600.), 3600., 0);	2254	fmod (ev_now (loop), 3600.), 3600., 0);
1536	ev_periodic_start (loop, &hourly_tick);	2255	ev_periodic_start (loop, &hourly_tick);
1537		2256
1538		2257
…		…
1541	Signal watchers will trigger an event when the process receives a specific	2260	Signal watchers will trigger an event when the process receives a specific
1542	signal one or more times. Even though signals are very asynchronous, libev	2261	signal one or more times. Even though signals are very asynchronous, libev
1543	will try it's best to deliver signals synchronously, i.e. as part of the	2262	will try it's best to deliver signals synchronously, i.e. as part of the
1544	normal event processing, like any other event.	2263	normal event processing, like any other event.
1545		2264
		2265	If you want signals to be delivered truly asynchronously, just use
		2266	C<sigaction> as you would do without libev and forget about sharing
		2267	the signal. You can even use C<ev_async> from a signal handler to
		2268	synchronously wake up an event loop.
		2269
1546	You can configure as many watchers as you like per signal. Only when the	2270	You can configure as many watchers as you like for the same signal, but
		2271	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2272	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2273	C<SIGINT> in both the default loop and another loop at the same time. At
		2274	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2275
1547	first watcher gets started will libev actually register a signal watcher	2276	When the first watcher gets started will libev actually register something
1548	with the kernel (thus it coexists with your own signal handlers as long	2277	with the kernel (thus it coexists with your own signal handlers as long as
1549	as you don't register any with libev). Similarly, when the last signal	2278	you don't register any with libev for the same signal).
1550	watcher for a signal is stopped libev will reset the signal handler to
1551	SIG_DFL (regardless of what it was set to before).
1552		2279
1553	If possible and supported, libev will install its handlers with	2280	If possible and supported, libev will install its handlers with
1554	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2281	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1555	interrupted. If you have a problem with system calls getting interrupted by	2282	not be unduly interrupted. If you have a problem with system calls getting
1556	signals you can block all signals in an C<ev_check> watcher and unblock	2283	interrupted by signals you can block all signals in an C<ev_check> watcher
1557	them in an C<ev_prepare> watcher.	2284	and unblock them in an C<ev_prepare> watcher.
		2285
		2286	=head3 The special problem of inheritance over fork/execve/pthread_create
		2287
		2288	Both the signal mask (C<sigprocmask>) and the signal disposition
		2289	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2290	stopping it again), that is, libev might or might not block the signal,
		2291	and might or might not set or restore the installed signal handler.
		2292
		2293	While this does not matter for the signal disposition (libev never
		2294	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2295	C<execve>), this matters for the signal mask: many programs do not expect
		2296	certain signals to be blocked.
		2297
		2298	This means that before calling C<exec> (from the child) you should reset
		2299	the signal mask to whatever "default" you expect (all clear is a good
		2300	choice usually).
		2301
		2302	The simplest way to ensure that the signal mask is reset in the child is
		2303	to install a fork handler with C<pthread_atfork> that resets it. That will
		2304	catch fork calls done by libraries (such as the libc) as well.
		2305
		2306	In current versions of libev, the signal will not be blocked indefinitely
		2307	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2308	the window of opportunity for problems, it will not go away, as libev
		2309	I<has> to modify the signal mask, at least temporarily.
		2310
		2311	So I can't stress this enough: I<If you do not reset your signal mask when
		2312	you expect it to be empty, you have a race condition in your code>. This
		2313	is not a libev-specific thing, this is true for most event libraries.
1558		2314
1559	=head3 Watcher-Specific Functions and Data Members	2315	=head3 Watcher-Specific Functions and Data Members
1560		2316
1561	=over 4	2317	=over 4
1562		2318
…		…
1573		2329
1574	=back	2330	=back
1575		2331
1576	=head3 Examples	2332	=head3 Examples
1577		2333
1578	Example: Try to exit cleanly on SIGINT and SIGTERM.	2334	Example: Try to exit cleanly on SIGINT.
1579		2335
1580	static void	2336	static void
1581	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2337	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1582	{	2338	{
1583	ev_unloop (loop, EVUNLOOP_ALL);	2339	ev_break (loop, EVBREAK_ALL);
1584	}	2340	}
1585		2341
1586	struct ev_signal signal_watcher;	2342	ev_signal signal_watcher;
1587	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2343	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1588	ev_signal_start (loop, &sigint_cb);	2344	ev_signal_start (loop, &signal_watcher);
1589		2345
1590		2346
1591	=head2 C<ev_child> - watch out for process status changes	2347	=head2 C<ev_child> - watch out for process status changes
1592		2348
1593	Child watchers trigger when your process receives a SIGCHLD in response to	2349	Child watchers trigger when your process receives a SIGCHLD in response to
1594	some child status changes (most typically when a child of yours dies). It	2350	some child status changes (most typically when a child of yours dies or
1595	is permissible to install a child watcher I<after> the child has been	2351	exits). It is permissible to install a child watcher I<after> the child
1596	forked (which implies it might have already exited), as long as the event	2352	has been forked (which implies it might have already exited), as long
1597	loop isn't entered (or is continued from a watcher).	2353	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2354	forking and then immediately registering a watcher for the child is fine,
		2355	but forking and registering a watcher a few event loop iterations later or
		2356	in the next callback invocation is not.
1598		2357
1599	Only the default event loop is capable of handling signals, and therefore	2358	Only the default event loop is capable of handling signals, and therefore
1600	you can only register child watchers in the default event loop.	2359	you can only register child watchers in the default event loop.
1601		2360
		2361	Due to some design glitches inside libev, child watchers will always be
		2362	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2363	libev)
		2364
1602	=head3 Process Interaction	2365	=head3 Process Interaction
1603		2366
1604	Libev grabs C<SIGCHLD> as soon as the default event loop is	2367	Libev grabs C<SIGCHLD> as soon as the default event loop is
1605	initialised. This is necessary to guarantee proper behaviour even if	2368	initialised. This is necessary to guarantee proper behaviour even if the
1606	the first child watcher is started after the child exits. The occurrence	2369	first child watcher is started after the child exits. The occurrence
1607	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2370	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1608	synchronously as part of the event loop processing. Libev always reaps all	2371	synchronously as part of the event loop processing. Libev always reaps all
1609	children, even ones not watched.	2372	children, even ones not watched.
1610		2373
1611	=head3 Overriding the Built-In Processing	2374	=head3 Overriding the Built-In Processing
…		…
1621	=head3 Stopping the Child Watcher	2384	=head3 Stopping the Child Watcher
1622		2385
1623	Currently, the child watcher never gets stopped, even when the	2386	Currently, the child watcher never gets stopped, even when the
1624	child terminates, so normally one needs to stop the watcher in the	2387	child terminates, so normally one needs to stop the watcher in the
1625	callback. Future versions of libev might stop the watcher automatically	2388	callback. Future versions of libev might stop the watcher automatically
1626	when a child exit is detected.	2389	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2390	problem).
1627		2391
1628	=head3 Watcher-Specific Functions and Data Members	2392	=head3 Watcher-Specific Functions and Data Members
1629		2393
1630	=over 4	2394	=over 4
1631		2395
…		…
1663	its completion.	2427	its completion.
1664		2428
1665	ev_child cw;	2429	ev_child cw;
1666		2430
1667	static void	2431	static void
1668	child_cb (EV_P_ struct ev_child *w, int revents)	2432	child_cb (EV_P_ ev_child *w, int revents)
1669	{	2433	{
1670	ev_child_stop (EV_A_ w);	2434	ev_child_stop (EV_A_ w);
1671	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2435	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1672	}	2436	}
1673		2437
…		…
1688		2452
1689		2453
1690	=head2 C<ev_stat> - did the file attributes just change?	2454	=head2 C<ev_stat> - did the file attributes just change?
1691		2455
1692	This watches a file system path for attribute changes. That is, it calls	2456	This watches a file system path for attribute changes. That is, it calls
1693	C<stat> regularly (or when the OS says it changed) and sees if it changed	2457	C<stat> on that path in regular intervals (or when the OS says it changed)
1694	compared to the last time, invoking the callback if it did.	2458	and sees if it changed compared to the last time, invoking the callback if
		2459	it did.
1695		2460
1696	The path does not need to exist: changing from "path exists" to "path does	2461	The path does not need to exist: changing from "path exists" to "path does
1697	not exist" is a status change like any other. The condition "path does	2462	not exist" is a status change like any other. The condition "path does not
1698	not exist" is signified by the C<st_nlink> field being zero (which is	2463	exist" (or more correctly "path cannot be stat'ed") is signified by the
1699	otherwise always forced to be at least one) and all the other fields of	2464	C<st_nlink> field being zero (which is otherwise always forced to be at
1700	the stat buffer having unspecified contents.	2465	least one) and all the other fields of the stat buffer having unspecified
		2466	contents.
1701		2467
1702	The path I<should> be absolute and I<must not> end in a slash. If it is	2468	The path I<must not> end in a slash or contain special components such as
		2469	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1703	relative and your working directory changes, the behaviour is undefined.	2470	your working directory changes, then the behaviour is undefined.
1704		2471
1705	Since there is no standard to do this, the portable implementation simply	2472	Since there is no portable change notification interface available, the
1706	calls C<stat (2)> regularly on the path to see if it changed somehow. You	2473	portable implementation simply calls C<stat(2)> regularly on the path
1707	can specify a recommended polling interval for this case. If you specify	2474	to see if it changed somehow. You can specify a recommended polling
1708	a polling interval of C<0> (highly recommended!) then a I<suitable,	2475	interval for this case. If you specify a polling interval of C<0> (highly
1709	unspecified default> value will be used (which you can expect to be around	2476	recommended!) then a I<suitable, unspecified default> value will be used
1710	five seconds, although this might change dynamically). Libev will also	2477	(which you can expect to be around five seconds, although this might
1711	impose a minimum interval which is currently around C<0.1>, but thats	2478	change dynamically). Libev will also impose a minimum interval which is
1712	usually overkill.	2479	currently around C<0.1>, but that's usually overkill.
1713		2480
1714	This watcher type is not meant for massive numbers of stat watchers,	2481	This watcher type is not meant for massive numbers of stat watchers,
1715	as even with OS-supported change notifications, this can be	2482	as even with OS-supported change notifications, this can be
1716	resource-intensive.	2483	resource-intensive.
1717		2484
1718	At the time of this writing, only the Linux inotify interface is	2485	At the time of this writing, the only OS-specific interface implemented
1719	implemented (implementing kqueue support is left as an exercise for the	2486	is the Linux inotify interface (implementing kqueue support is left as an
1720	reader, note, however, that the author sees no way of implementing ev_stat	2487	exercise for the reader. Note, however, that the author sees no way of
1721	semantics with kqueue). Inotify will be used to give hints only and should	2488	implementing C<ev_stat> semantics with kqueue, except as a hint).
1722	not change the semantics of C<ev_stat> watchers, which means that libev
1723	sometimes needs to fall back to regular polling again even with inotify,
1724	but changes are usually detected immediately, and if the file exists there
1725	will be no polling.
1726		2489
1727	=head3 ABI Issues (Largefile Support)	2490	=head3 ABI Issues (Largefile Support)
1728		2491
1729	Libev by default (unless the user overrides this) uses the default	2492	Libev by default (unless the user overrides this) uses the default
1730	compilation environment, which means that on systems with large file	2493	compilation environment, which means that on systems with large file
1731	support disabled by default, you get the 32 bit version of the stat	2494	support disabled by default, you get the 32 bit version of the stat
1732	structure. When using the library from programs that change the ABI to	2495	structure. When using the library from programs that change the ABI to
1733	use 64 bit file offsets the programs will fail. In that case you have to	2496	use 64 bit file offsets the programs will fail. In that case you have to
1734	compile libev with the same flags to get binary compatibility. This is	2497	compile libev with the same flags to get binary compatibility. This is
1735	obviously the case with any flags that change the ABI, but the problem is	2498	obviously the case with any flags that change the ABI, but the problem is
1736	most noticeably disabled with ev_stat and large file support.	2499	most noticeably displayed with ev_stat and large file support.
1737		2500
1738	The solution for this is to lobby your distribution maker to make large	2501	The solution for this is to lobby your distribution maker to make large
1739	file interfaces available by default (as e.g. FreeBSD does) and not	2502	file interfaces available by default (as e.g. FreeBSD does) and not
1740	optional. Libev cannot simply switch on large file support because it has	2503	optional. Libev cannot simply switch on large file support because it has
1741	to exchange stat structures with application programs compiled using the	2504	to exchange stat structures with application programs compiled using the
1742	default compilation environment.	2505	default compilation environment.
1743		2506
1744	=head3 Inotify	2507	=head3 Inotify and Kqueue
1745		2508
1746	When C<inotify (7)> support has been compiled into libev (generally only	2509	When C<inotify (7)> support has been compiled into libev and present at
1747	available on Linux) and present at runtime, it will be used to speed up	2510	runtime, it will be used to speed up change detection where possible. The
1748	change detection where possible. The inotify descriptor will be created lazily	2511	inotify descriptor will be created lazily when the first C<ev_stat>
1749	when the first C<ev_stat> watcher is being started.	2512	watcher is being started.
1750		2513
1751	Inotify presence does not change the semantics of C<ev_stat> watchers	2514	Inotify presence does not change the semantics of C<ev_stat> watchers
1752	except that changes might be detected earlier, and in some cases, to avoid	2515	except that changes might be detected earlier, and in some cases, to avoid
1753	making regular C<stat> calls. Even in the presence of inotify support	2516	making regular C<stat> calls. Even in the presence of inotify support
1754	there are many cases where libev has to resort to regular C<stat> polling.	2517	there are many cases where libev has to resort to regular C<stat> polling,
		2518	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2519	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2520	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2521	xfs are fully working) libev usually gets away without polling.
1755		2522
1756	(There is no support for kqueue, as apparently it cannot be used to	2523	There is no support for kqueue, as apparently it cannot be used to
1757	implement this functionality, due to the requirement of having a file	2524	implement this functionality, due to the requirement of having a file
1758	descriptor open on the object at all times).	2525	descriptor open on the object at all times, and detecting renames, unlinks
		2526	etc. is difficult.
		2527
		2528	=head3 C<stat ()> is a synchronous operation
		2529
		2530	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2531	the process. The exception are C<ev_stat> watchers - those call C<stat
		2532	()>, which is a synchronous operation.
		2533
		2534	For local paths, this usually doesn't matter: unless the system is very
		2535	busy or the intervals between stat's are large, a stat call will be fast,
		2536	as the path data is usually in memory already (except when starting the
		2537	watcher).
		2538
		2539	For networked file systems, calling C<stat ()> can block an indefinite
		2540	time due to network issues, and even under good conditions, a stat call
		2541	often takes multiple milliseconds.
		2542
		2543	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2544	paths, although this is fully supported by libev.
1759		2545
1760	=head3 The special problem of stat time resolution	2546	=head3 The special problem of stat time resolution
1761		2547
1762	The C<stat ()> system call only supports full-second resolution portably, and	2548	The C<stat ()> system call only supports full-second resolution portably,
1763	even on systems where the resolution is higher, many file systems still	2549	and even on systems where the resolution is higher, most file systems
1764	only support whole seconds.	2550	still only support whole seconds.
1765		2551
1766	That means that, if the time is the only thing that changes, you can	2552	That means that, if the time is the only thing that changes, you can
1767	easily miss updates: on the first update, C<ev_stat> detects a change and	2553	easily miss updates: on the first update, C<ev_stat> detects a change and
1768	calls your callback, which does something. When there is another update	2554	calls your callback, which does something. When there is another update
1769	within the same second, C<ev_stat> will be unable to detect it as the stat	2555	within the same second, C<ev_stat> will be unable to detect unless the
1770	data does not change.	2556	stat data does change in other ways (e.g. file size).
1771		2557
1772	The solution to this is to delay acting on a change for slightly more	2558	The solution to this is to delay acting on a change for slightly more
1773	than a second (or till slightly after the next full second boundary), using	2559	than a second (or till slightly after the next full second boundary), using
1774	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2560	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1775	ev_timer_again (loop, w)>).	2561	ev_timer_again (loop, w)>).
…		…
1795	C<path>. The C<interval> is a hint on how quickly a change is expected to	2581	C<path>. The C<interval> is a hint on how quickly a change is expected to
1796	be detected and should normally be specified as C<0> to let libev choose	2582	be detected and should normally be specified as C<0> to let libev choose
1797	a suitable value. The memory pointed to by C<path> must point to the same	2583	a suitable value. The memory pointed to by C<path> must point to the same
1798	path for as long as the watcher is active.	2584	path for as long as the watcher is active.
1799		2585
1800	The callback will receive C<EV_STAT> when a change was detected, relative	2586	The callback will receive an C<EV_STAT> event when a change was detected,
1801	to the attributes at the time the watcher was started (or the last change	2587	relative to the attributes at the time the watcher was started (or the
1802	was detected).	2588	last change was detected).
1803		2589
1804	=item ev_stat_stat (loop, ev_stat *)	2590	=item ev_stat_stat (loop, ev_stat *)
1805		2591
1806	Updates the stat buffer immediately with new values. If you change the	2592	Updates the stat buffer immediately with new values. If you change the
1807	watched path in your callback, you could call this function to avoid	2593	watched path in your callback, you could call this function to avoid
…		…
1890		2676
1891		2677
1892	=head2 C<ev_idle> - when you've got nothing better to do...	2678	=head2 C<ev_idle> - when you've got nothing better to do...
1893		2679
1894	Idle watchers trigger events when no other events of the same or higher	2680	Idle watchers trigger events when no other events of the same or higher
1895	priority are pending (prepare, check and other idle watchers do not	2681	priority are pending (prepare, check and other idle watchers do not count
1896	count).	2682	as receiving "events").
1897		2683
1898	That is, as long as your process is busy handling sockets or timeouts	2684	That is, as long as your process is busy handling sockets or timeouts
1899	(or even signals, imagine) of the same or higher priority it will not be	2685	(or even signals, imagine) of the same or higher priority it will not be
1900	triggered. But when your process is idle (or only lower-priority watchers	2686	triggered. But when your process is idle (or only lower-priority watchers
1901	are pending), the idle watchers are being called once per event loop	2687	are pending), the idle watchers are being called once per event loop
…		…
1912		2698
1913	=head3 Watcher-Specific Functions and Data Members	2699	=head3 Watcher-Specific Functions and Data Members
1914		2700
1915	=over 4	2701	=over 4
1916		2702
1917	=item ev_idle_init (ev_signal *, callback)	2703	=item ev_idle_init (ev_idle *, callback)
1918		2704
1919	Initialises and configures the idle watcher - it has no parameters of any	2705	Initialises and configures the idle watcher - it has no parameters of any
1920	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2706	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1921	believe me.	2707	believe me.
1922		2708
…		…
1926		2712
1927	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2713	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1928	callback, free it. Also, use no error checking, as usual.	2714	callback, free it. Also, use no error checking, as usual.
1929		2715
1930	static void	2716	static void
1931	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2717	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1932	{	2718	{
1933	free (w);	2719	free (w);
1934	// now do something you wanted to do when the program has	2720	// now do something you wanted to do when the program has
1935	// no longer anything immediate to do.	2721	// no longer anything immediate to do.
1936	}	2722	}
1937		2723
1938	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2724	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1939	ev_idle_init (idle_watcher, idle_cb);	2725	ev_idle_init (idle_watcher, idle_cb);
1940	ev_idle_start (loop, idle_cb);	2726	ev_idle_start (loop, idle_watcher);
1941		2727
1942		2728
1943	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2729	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1944		2730
1945	Prepare and check watchers are usually (but not always) used in tandem:	2731	Prepare and check watchers are usually (but not always) used in pairs:
1946	prepare watchers get invoked before the process blocks and check watchers	2732	prepare watchers get invoked before the process blocks and check watchers
1947	afterwards.	2733	afterwards.
1948		2734
1949	You I<must not> call C<ev_loop> or similar functions that enter	2735	You I<must not> call C<ev_run> or similar functions that enter
1950	the current event loop from either C<ev_prepare> or C<ev_check>	2736	the current event loop from either C<ev_prepare> or C<ev_check>
1951	watchers. Other loops than the current one are fine, however. The	2737	watchers. Other loops than the current one are fine, however. The
1952	rationale behind this is that you do not need to check for recursion in	2738	rationale behind this is that you do not need to check for recursion in
1953	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2739	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1954	C<ev_check> so if you have one watcher of each kind they will always be	2740	C<ev_check> so if you have one watcher of each kind they will always be
1955	called in pairs bracketing the blocking call.	2741	called in pairs bracketing the blocking call.
1956		2742
1957	Their main purpose is to integrate other event mechanisms into libev and	2743	Their main purpose is to integrate other event mechanisms into libev and
1958	their use is somewhat advanced. This could be used, for example, to track	2744	their use is somewhat advanced. They could be used, for example, to track
1959	variable changes, implement your own watchers, integrate net-snmp or a	2745	variable changes, implement your own watchers, integrate net-snmp or a
1960	coroutine library and lots more. They are also occasionally useful if	2746	coroutine library and lots more. They are also occasionally useful if
1961	you cache some data and want to flush it before blocking (for example,	2747	you cache some data and want to flush it before blocking (for example,
1962	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2748	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1963	watcher).	2749	watcher).
1964		2750
1965	This is done by examining in each prepare call which file descriptors need	2751	This is done by examining in each prepare call which file descriptors
1966	to be watched by the other library, registering C<ev_io> watchers for	2752	need to be watched by the other library, registering C<ev_io> watchers
1967	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2753	for them and starting an C<ev_timer> watcher for any timeouts (many
1968	provide just this functionality). Then, in the check watcher you check for	2754	libraries provide exactly this functionality). Then, in the check watcher,
1969	any events that occurred (by checking the pending status of all watchers	2755	you check for any events that occurred (by checking the pending status
1970	and stopping them) and call back into the library. The I/O and timer	2756	of all watchers and stopping them) and call back into the library. The
1971	callbacks will never actually be called (but must be valid nevertheless,	2757	I/O and timer callbacks will never actually be called (but must be valid
1972	because you never know, you know?).	2758	nevertheless, because you never know, you know?).
1973		2759
1974	As another example, the Perl Coro module uses these hooks to integrate	2760	As another example, the Perl Coro module uses these hooks to integrate
1975	coroutines into libev programs, by yielding to other active coroutines	2761	coroutines into libev programs, by yielding to other active coroutines
1976	during each prepare and only letting the process block if no coroutines	2762	during each prepare and only letting the process block if no coroutines
1977	are ready to run (it's actually more complicated: it only runs coroutines	2763	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1980	loop from blocking if lower-priority coroutines are active, thus mapping	2766	loop from blocking if lower-priority coroutines are active, thus mapping
1981	low-priority coroutines to idle/background tasks).	2767	low-priority coroutines to idle/background tasks).
1982		2768
1983	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2769	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1984	priority, to ensure that they are being run before any other watchers	2770	priority, to ensure that they are being run before any other watchers
		2771	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2772
1985	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2773	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1986	too) should not activate ("feed") events into libev. While libev fully	2774	activate ("feed") events into libev. While libev fully supports this, they
1987	supports this, they might get executed before other C<ev_check> watchers	2775	might get executed before other C<ev_check> watchers did their job. As
1988	did their job. As C<ev_check> watchers are often used to embed other	2776	C<ev_check> watchers are often used to embed other (non-libev) event
1989	(non-libev) event loops those other event loops might be in an unusable	2777	loops those other event loops might be in an unusable state until their
1990	state until their C<ev_check> watcher ran (always remind yourself to	2778	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1991	coexist peacefully with others).	2779	others).
1992		2780
1993	=head3 Watcher-Specific Functions and Data Members	2781	=head3 Watcher-Specific Functions and Data Members
1994		2782
1995	=over 4	2783	=over 4
1996		2784
…		…
1998		2786
1999	=item ev_check_init (ev_check *, callback)	2787	=item ev_check_init (ev_check *, callback)
2000		2788
2001	Initialises and configures the prepare or check watcher - they have no	2789	Initialises and configures the prepare or check watcher - they have no
2002	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2790	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
2003	macros, but using them is utterly, utterly and completely pointless.	2791	macros, but using them is utterly, utterly, utterly and completely
		2792	pointless.
2004		2793
2005	=back	2794	=back
2006		2795
2007	=head3 Examples	2796	=head3 Examples
2008		2797
…		…
2021		2810
2022	static ev_io iow [nfd];	2811	static ev_io iow [nfd];
2023	static ev_timer tw;	2812	static ev_timer tw;
2024		2813
2025	static void	2814	static void
2026	io_cb (ev_loop *loop, ev_io *w, int revents)	2815	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2027	{	2816	{
2028	}	2817	}
2029		2818
2030	// create io watchers for each fd and a timer before blocking	2819	// create io watchers for each fd and a timer before blocking
2031	static void	2820	static void
2032	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2821	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2033	{	2822	{
2034	int timeout = 3600000;	2823	int timeout = 3600000;
2035	struct pollfd fds [nfd];	2824	struct pollfd fds [nfd];
2036	// actual code will need to loop here and realloc etc.	2825	// actual code will need to loop here and realloc etc.
2037	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2826	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2038		2827
2039	/* the callback is illegal, but won't be called as we stop during check */	2828	/* the callback is illegal, but won't be called as we stop during check */
2040	ev_timer_init (&tw, 0, timeout * 1e-3);	2829	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2041	ev_timer_start (loop, &tw);	2830	ev_timer_start (loop, &tw);
2042		2831
2043	// create one ev_io per pollfd	2832	// create one ev_io per pollfd
2044	for (int i = 0; i < nfd; ++i)	2833	for (int i = 0; i < nfd; ++i)
2045	{	2834	{
…		…
2052	}	2841	}
2053	}	2842	}
2054		2843
2055	// stop all watchers after blocking	2844	// stop all watchers after blocking
2056	static void	2845	static void
2057	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2846	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2058	{	2847	{
2059	ev_timer_stop (loop, &tw);	2848	ev_timer_stop (loop, &tw);
2060		2849
2061	for (int i = 0; i < nfd; ++i)	2850	for (int i = 0; i < nfd; ++i)
2062	{	2851	{
…		…
2101	}	2890	}
2102		2891
2103	// do not ever call adns_afterpoll	2892	// do not ever call adns_afterpoll
2104		2893
2105	Method 4: Do not use a prepare or check watcher because the module you	2894	Method 4: Do not use a prepare or check watcher because the module you
2106	want to embed is too inflexible to support it. Instead, you can override	2895	want to embed is not flexible enough to support it. Instead, you can
2107	their poll function. The drawback with this solution is that the main	2896	override their poll function. The drawback with this solution is that the
2108	loop is now no longer controllable by EV. The C<Glib::EV> module does	2897	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2109	this.	2898	this approach, effectively embedding EV as a client into the horrible
		2899	libglib event loop.
2110		2900
2111	static gint	2901	static gint
2112	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2902	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2113	{	2903	{
2114	int got_events = 0;	2904	int got_events = 0;
…		…
2118		2908
2119	if (timeout >= 0)	2909	if (timeout >= 0)
2120	// create/start timer	2910	// create/start timer
2121		2911
2122	// poll	2912	// poll
2123	ev_loop (EV_A_ 0);	2913	ev_run (EV_A_ 0);
2124		2914
2125	// stop timer again	2915	// stop timer again
2126	if (timeout >= 0)	2916	if (timeout >= 0)
2127	ev_timer_stop (EV_A_ &to);	2917	ev_timer_stop (EV_A_ &to);
2128		2918
…		…
2145	prioritise I/O.	2935	prioritise I/O.
2146		2936
2147	As an example for a bug workaround, the kqueue backend might only support	2937	As an example for a bug workaround, the kqueue backend might only support
2148	sockets on some platform, so it is unusable as generic backend, but you	2938	sockets on some platform, so it is unusable as generic backend, but you
2149	still want to make use of it because you have many sockets and it scales	2939	still want to make use of it because you have many sockets and it scales
2150	so nicely. In this case, you would create a kqueue-based loop and embed it	2940	so nicely. In this case, you would create a kqueue-based loop and embed
2151	into your default loop (which might use e.g. poll). Overall operation will	2941	it into your default loop (which might use e.g. poll). Overall operation
2152	be a bit slower because first libev has to poll and then call kevent, but	2942	will be a bit slower because first libev has to call C<poll> and then
2153	at least you can use both at what they are best.	2943	C<kevent>, but at least you can use both mechanisms for what they are
		2944	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2154		2945
2155	As for prioritising I/O: rarely you have the case where some fds have	2946	As for prioritising I/O: under rare circumstances you have the case where
2156	to be watched and handled very quickly (with low latency), and even	2947	some fds have to be watched and handled very quickly (with low latency),
2157	priorities and idle watchers might have too much overhead. In this case	2948	and even priorities and idle watchers might have too much overhead. In
2158	you would put all the high priority stuff in one loop and all the rest in	2949	this case you would put all the high priority stuff in one loop and all
2159	a second one, and embed the second one in the first.	2950	the rest in a second one, and embed the second one in the first.
2160		2951
2161	As long as the watcher is active, the callback will be invoked every time	2952	As long as the watcher is active, the callback will be invoked every
2162	there might be events pending in the embedded loop. The callback must then	2953	time there might be events pending in the embedded loop. The callback
2163	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2954	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2164	their callbacks (you could also start an idle watcher to give the embedded	2955	sweep and invoke their callbacks (the callback doesn't need to invoke the
2165	loop strictly lower priority for example). You can also set the callback	2956	C<ev_embed_sweep> function directly, it could also start an idle watcher
2166	to C<0>, in which case the embed watcher will automatically execute the	2957	to give the embedded loop strictly lower priority for example).
2167	embedded loop sweep.
2168		2958
2169	As long as the watcher is started it will automatically handle events. The	2959	You can also set the callback to C<0>, in which case the embed watcher
2170	callback will be invoked whenever some events have been handled. You can	2960	will automatically execute the embedded loop sweep whenever necessary.
2171	set the callback to C<0> to avoid having to specify one if you are not
2172	interested in that.
2173		2961
2174	Also, there have not currently been made special provisions for forking:	2962	Fork detection will be handled transparently while the C<ev_embed> watcher
2175	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2963	is active, i.e., the embedded loop will automatically be forked when the
2176	but you will also have to stop and restart any C<ev_embed> watchers	2964	embedding loop forks. In other cases, the user is responsible for calling
2177	yourself.	2965	C<ev_loop_fork> on the embedded loop.
2178		2966
2179	Unfortunately, not all backends are embeddable, only the ones returned by	2967	Unfortunately, not all backends are embeddable: only the ones returned by
2180	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2968	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2181	portable one.	2969	portable one.
2182		2970
2183	So when you want to use this feature you will always have to be prepared	2971	So when you want to use this feature you will always have to be prepared
2184	that you cannot get an embeddable loop. The recommended way to get around	2972	that you cannot get an embeddable loop. The recommended way to get around
2185	this is to have a separate variables for your embeddable loop, try to	2973	this is to have a separate variables for your embeddable loop, try to
2186	create it, and if that fails, use the normal loop for everything.	2974	create it, and if that fails, use the normal loop for everything.
		2975
		2976	=head3 C<ev_embed> and fork
		2977
		2978	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2979	automatically be applied to the embedded loop as well, so no special
		2980	fork handling is required in that case. When the watcher is not running,
		2981	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2982	as applicable.
2187		2983
2188	=head3 Watcher-Specific Functions and Data Members	2984	=head3 Watcher-Specific Functions and Data Members
2189		2985
2190	=over 4	2986	=over 4
2191		2987
…		…
2200	if you do not want that, you need to temporarily stop the embed watcher).	2996	if you do not want that, you need to temporarily stop the embed watcher).
2201		2997
2202	=item ev_embed_sweep (loop, ev_embed *)	2998	=item ev_embed_sweep (loop, ev_embed *)
2203		2999
2204	Make a single, non-blocking sweep over the embedded loop. This works	3000	Make a single, non-blocking sweep over the embedded loop. This works
2205	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3001	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2206	appropriate way for embedded loops.	3002	appropriate way for embedded loops.
2207		3003
2208	=item struct ev_loop *other [read-only]	3004	=item struct ev_loop *other [read-only]
2209		3005
2210	The embedded event loop.	3006	The embedded event loop.
…		…
2219	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	3015	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2220	used).	3016	used).
2221		3017
2222	struct ev_loop *loop_hi = ev_default_init (0);	3018	struct ev_loop *loop_hi = ev_default_init (0);
2223	struct ev_loop *loop_lo = 0;	3019	struct ev_loop *loop_lo = 0;
2224	struct ev_embed embed;	3020	ev_embed embed;
2225		3021
2226	// see if there is a chance of getting one that works	3022	// see if there is a chance of getting one that works
2227	// (remember that a flags value of 0 means autodetection)	3023	// (remember that a flags value of 0 means autodetection)
2228	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3024	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2229	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3025	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2243	kqueue implementation). Store the kqueue/socket-only event loop in	3039	kqueue implementation). Store the kqueue/socket-only event loop in
2244	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3040	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2245		3041
2246	struct ev_loop *loop = ev_default_init (0);	3042	struct ev_loop *loop = ev_default_init (0);
2247	struct ev_loop *loop_socket = 0;	3043	struct ev_loop *loop_socket = 0;
2248	struct ev_embed embed;	3044	ev_embed embed;
2249		3045
2250	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3046	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2251	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3047	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2252	{	3048	{
2253	ev_embed_init (&embed, 0, loop_socket);	3049	ev_embed_init (&embed, 0, loop_socket);
…		…
2268	event loop blocks next and before C<ev_check> watchers are being called,	3064	event loop blocks next and before C<ev_check> watchers are being called,
2269	and only in the child after the fork. If whoever good citizen calling	3065	and only in the child after the fork. If whoever good citizen calling
2270	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3066	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2271	handlers will be invoked, too, of course.	3067	handlers will be invoked, too, of course.
2272		3068
		3069	=head3 The special problem of life after fork - how is it possible?
		3070
		3071	Most uses of C<fork()> consist of forking, then some simple calls to set
		3072	up/change the process environment, followed by a call to C<exec()>. This
		3073	sequence should be handled by libev without any problems.
		3074
		3075	This changes when the application actually wants to do event handling
		3076	in the child, or both parent in child, in effect "continuing" after the
		3077	fork.
		3078
		3079	The default mode of operation (for libev, with application help to detect
		3080	forks) is to duplicate all the state in the child, as would be expected
		3081	when I<either> the parent I<or> the child process continues.
		3082
		3083	When both processes want to continue using libev, then this is usually the
		3084	wrong result. In that case, usually one process (typically the parent) is
		3085	supposed to continue with all watchers in place as before, while the other
		3086	process typically wants to start fresh, i.e. without any active watchers.
		3087
		3088	The cleanest and most efficient way to achieve that with libev is to
		3089	simply create a new event loop, which of course will be "empty", and
		3090	use that for new watchers. This has the advantage of not touching more
		3091	memory than necessary, and thus avoiding the copy-on-write, and the
		3092	disadvantage of having to use multiple event loops (which do not support
		3093	signal watchers).
		3094
		3095	When this is not possible, or you want to use the default loop for
		3096	other reasons, then in the process that wants to start "fresh", call
		3097	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3098	Destroying the default loop will "orphan" (not stop) all registered
		3099	watchers, so you have to be careful not to execute code that modifies
		3100	those watchers. Note also that in that case, you have to re-register any
		3101	signal watchers.
		3102
2273	=head3 Watcher-Specific Functions and Data Members	3103	=head3 Watcher-Specific Functions and Data Members
2274		3104
2275	=over 4	3105	=over 4
2276		3106
2277	=item ev_fork_init (ev_signal *, callback)	3107	=item ev_fork_init (ev_fork *, callback)
2278		3108
2279	Initialises and configures the fork watcher - it has no parameters of any	3109	Initialises and configures the fork watcher - it has no parameters of any
2280	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3110	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2281	believe me.	3111	really.
2282		3112
2283	=back	3113	=back
2284		3114
2285		3115
		3116	=head2 C<ev_cleanup> - even the best things end
		3117
		3118	Cleanup watchers are called just before the event loop is being destroyed
		3119	by a call to C<ev_loop_destroy>.
		3120
		3121	While there is no guarantee that the event loop gets destroyed, cleanup
		3122	watchers provide a convenient method to install cleanup hooks for your
		3123	program, worker threads and so on - you just to make sure to destroy the
		3124	loop when you want them to be invoked.
		3125
		3126	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3127	all other watchers, they do not keep a reference to the event loop (which
		3128	makes a lot of sense if you think about it). Like all other watchers, you
		3129	can call libev functions in the callback, except C<ev_cleanup_start>.
		3130
		3131	=head3 Watcher-Specific Functions and Data Members
		3132
		3133	=over 4
		3134
		3135	=item ev_cleanup_init (ev_cleanup *, callback)
		3136
		3137	Initialises and configures the cleanup watcher - it has no parameters of
		3138	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3139	pointless, I assure you.
		3140
		3141	=back
		3142
		3143	Example: Register an atexit handler to destroy the default loop, so any
		3144	cleanup functions are called.
		3145
		3146	static void
		3147	program_exits (void)
		3148	{
		3149	ev_loop_destroy (EV_DEFAULT_UC);
		3150	}
		3151
		3152	...
		3153	atexit (program_exits);
		3154
		3155
2286	=head2 C<ev_async> - how to wake up another event loop	3156	=head2 C<ev_async> - how to wake up an event loop
2287		3157
2288	In general, you cannot use an C<ev_loop> from multiple threads or other	3158	In general, you cannot use an C<ev_run> from multiple threads or other
2289	asynchronous sources such as signal handlers (as opposed to multiple event	3159	asynchronous sources such as signal handlers (as opposed to multiple event
2290	loops - those are of course safe to use in different threads).	3160	loops - those are of course safe to use in different threads).
2291		3161
2292	Sometimes, however, you need to wake up another event loop you do not	3162	Sometimes, however, you need to wake up an event loop you do not control,
2293	control, for example because it belongs to another thread. This is what	3163	for example because it belongs to another thread. This is what C<ev_async>
2294	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3164	watchers do: as long as the C<ev_async> watcher is active, you can signal
2295	can signal it by calling C<ev_async_send>, which is thread- and signal	3165	it by calling C<ev_async_send>, which is thread- and signal safe.
2296	safe.
2297		3166
2298	This functionality is very similar to C<ev_signal> watchers, as signals,	3167	This functionality is very similar to C<ev_signal> watchers, as signals,
2299	too, are asynchronous in nature, and signals, too, will be compressed	3168	too, are asynchronous in nature, and signals, too, will be compressed
2300	(i.e. the number of callback invocations may be less than the number of	3169	(i.e. the number of callback invocations may be less than the number of
2301	C<ev_async_sent> calls).	3170	C<ev_async_sent> calls).
…		…
2306	=head3 Queueing	3175	=head3 Queueing
2307		3176
2308	C<ev_async> does not support queueing of data in any way. The reason	3177	C<ev_async> does not support queueing of data in any way. The reason
2309	is that the author does not know of a simple (or any) algorithm for a	3178	is that the author does not know of a simple (or any) algorithm for a
2310	multiple-writer-single-reader queue that works in all cases and doesn't	3179	multiple-writer-single-reader queue that works in all cases and doesn't
2311	need elaborate support such as pthreads.	3180	need elaborate support such as pthreads or unportable memory access
		3181	semantics.
2312		3182
2313	That means that if you want to queue data, you have to provide your own	3183	That means that if you want to queue data, you have to provide your own
2314	queue. But at least I can tell you would implement locking around your	3184	queue. But at least I can tell you how to implement locking around your
2315	queue:	3185	queue:
2316		3186
2317	=over 4	3187	=over 4
2318		3188
2319	=item queueing from a signal handler context	3189	=item queueing from a signal handler context
2320		3190
2321	To implement race-free queueing, you simply add to the queue in the signal	3191	To implement race-free queueing, you simply add to the queue in the signal
2322	handler but you block the signal handler in the watcher callback. Here is an example that does that for	3192	handler but you block the signal handler in the watcher callback. Here is
2323	some fictitious SIGUSR1 handler:	3193	an example that does that for some fictitious SIGUSR1 handler:
2324		3194
2325	static ev_async mysig;	3195	static ev_async mysig;
2326		3196
2327	static void	3197	static void
2328	sigusr1_handler (void)	3198	sigusr1_handler (void)
…		…
2394	=over 4	3264	=over 4
2395		3265
2396	=item ev_async_init (ev_async *, callback)	3266	=item ev_async_init (ev_async *, callback)
2397		3267
2398	Initialises and configures the async watcher - it has no parameters of any	3268	Initialises and configures the async watcher - it has no parameters of any
2399	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3269	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2400	believe me.	3270	trust me.
2401		3271
2402	=item ev_async_send (loop, ev_async *)	3272	=item ev_async_send (loop, ev_async *)
2403		3273
2404	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3274	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2405	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3275	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2406	C<ev_feed_event>, this call is safe to do in other threads, signal or	3276	C<ev_feed_event>, this call is safe to do from other threads, signal or
2407	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3277	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2408	section below on what exactly this means).	3278	section below on what exactly this means).
2409		3279
		3280	Note that, as with other watchers in libev, multiple events might get
		3281	compressed into a single callback invocation (another way to look at this
		3282	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3283	reset when the event loop detects that).
		3284
2410	This call incurs the overhead of a system call only once per loop iteration,	3285	This call incurs the overhead of a system call only once per event loop
2411	so while the overhead might be noticeable, it doesn't apply to repeated	3286	iteration, so while the overhead might be noticeable, it doesn't apply to
2412	calls to C<ev_async_send>.	3287	repeated calls to C<ev_async_send> for the same event loop.
2413		3288
2414	=item bool = ev_async_pending (ev_async *)	3289	=item bool = ev_async_pending (ev_async *)
2415		3290
2416	Returns a non-zero value when C<ev_async_send> has been called on the	3291	Returns a non-zero value when C<ev_async_send> has been called on the
2417	watcher but the event has not yet been processed (or even noted) by the	3292	watcher but the event has not yet been processed (or even noted) by the
…		…
2420	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3295	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2421	the loop iterates next and checks for the watcher to have become active,	3296	the loop iterates next and checks for the watcher to have become active,
2422	it will reset the flag again. C<ev_async_pending> can be used to very	3297	it will reset the flag again. C<ev_async_pending> can be used to very
2423	quickly check whether invoking the loop might be a good idea.	3298	quickly check whether invoking the loop might be a good idea.
2424		3299
2425	Not that this does I<not> check whether the watcher itself is pending, only	3300	Not that this does I<not> check whether the watcher itself is pending,
2426	whether it has been requested to make this watcher pending.	3301	only whether it has been requested to make this watcher pending: there
		3302	is a time window between the event loop checking and resetting the async
		3303	notification, and the callback being invoked.
2427		3304
2428	=back	3305	=back
2429		3306
2430		3307
2431	=head1 OTHER FUNCTIONS	3308	=head1 OTHER FUNCTIONS
…		…
2435	=over 4	3312	=over 4
2436		3313
2437	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3314	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2438		3315
2439	This function combines a simple timer and an I/O watcher, calls your	3316	This function combines a simple timer and an I/O watcher, calls your
2440	callback on whichever event happens first and automatically stop both	3317	callback on whichever event happens first and automatically stops both
2441	watchers. This is useful if you want to wait for a single event on an fd	3318	watchers. This is useful if you want to wait for a single event on an fd
2442	or timeout without having to allocate/configure/start/stop/free one or	3319	or timeout without having to allocate/configure/start/stop/free one or
2443	more watchers yourself.	3320	more watchers yourself.
2444		3321
2445	If C<fd> is less than 0, then no I/O watcher will be started and events	3322	If C<fd> is less than 0, then no I/O watcher will be started and the
2446	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	3323	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2447	C<events> set will be created and started.	3324	the given C<fd> and C<events> set will be created and started.
2448		3325
2449	If C<timeout> is less than 0, then no timeout watcher will be	3326	If C<timeout> is less than 0, then no timeout watcher will be
2450	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3327	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2451	repeat = 0) will be started. While C<0> is a valid timeout, it is of	3328	repeat = 0) will be started. C<0> is a valid timeout.
2452	dubious value.
2453		3329
2454	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3330	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2455	passed an C<revents> set like normal event callbacks (a combination of	3331	passed an C<revents> set like normal event callbacks (a combination of
2456	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3332	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2457	value passed to C<ev_once>:	3333	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3334	a timeout and an io event at the same time - you probably should give io
		3335	events precedence.
		3336
		3337	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2458		3338
2459	static void stdin_ready (int revents, void *arg)	3339	static void stdin_ready (int revents, void *arg)
2460	{	3340	{
		3341	if (revents & EV_READ)
		3342	/* stdin might have data for us, joy! */;
2461	if (revents & EV_TIMEOUT)	3343	else if (revents & EV_TIMER)
2462	/* doh, nothing entered */;	3344	/* doh, nothing entered */;
2463	else if (revents & EV_READ)
2464	/* stdin might have data for us, joy! */;
2465	}	3345	}
2466		3346
2467	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3347	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2468		3348
2469	=item ev_feed_event (ev_loop *, watcher *, int revents)
2470
2471	Feeds the given event set into the event loop, as if the specified event
2472	had happened for the specified watcher (which must be a pointer to an
2473	initialised but not necessarily started event watcher).
2474
2475	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3349	=item ev_feed_fd_event (loop, int fd, int revents)
2476		3350
2477	Feed an event on the given fd, as if a file descriptor backend detected	3351	Feed an event on the given fd, as if a file descriptor backend detected
2478	the given events it.	3352	the given events it.
2479		3353
2480	=item ev_feed_signal_event (ev_loop *loop, int signum)	3354	=item ev_feed_signal_event (loop, int signum)
2481		3355
2482	Feed an event as if the given signal occurred (C<loop> must be the default	3356	Feed an event as if the given signal occurred (C<loop> must be the default
2483	loop!).	3357	loop!).
2484		3358
2485	=back	3359	=back
…		…
2565		3439
2566	=over 4	3440	=over 4
2567		3441
2568	=item ev::TYPE::TYPE ()	3442	=item ev::TYPE::TYPE ()
2569		3443
2570	=item ev::TYPE::TYPE (struct ev_loop *)	3444	=item ev::TYPE::TYPE (loop)
2571		3445
2572	=item ev::TYPE::~TYPE	3446	=item ev::TYPE::~TYPE
2573		3447
2574	The constructor (optionally) takes an event loop to associate the watcher	3448	The constructor (optionally) takes an event loop to associate the watcher
2575	with. If it is omitted, it will use C<EV_DEFAULT>.	3449	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2607		3481
2608	myclass obj;	3482	myclass obj;
2609	ev::io iow;	3483	ev::io iow;
2610	iow.set <myclass, &myclass::io_cb> (&obj);	3484	iow.set <myclass, &myclass::io_cb> (&obj);
2611		3485
		3486	=item w->set (object *)
		3487
		3488	This is a variation of a method callback - leaving out the method to call
		3489	will default the method to C<operator ()>, which makes it possible to use
		3490	functor objects without having to manually specify the C<operator ()> all
		3491	the time. Incidentally, you can then also leave out the template argument
		3492	list.
		3493
		3494	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3495	int revents)>.
		3496
		3497	See the method-C<set> above for more details.
		3498
		3499	Example: use a functor object as callback.
		3500
		3501	struct myfunctor
		3502	{
		3503	void operator() (ev::io &w, int revents)
		3504	{
		3505	...
		3506	}
		3507	}
		3508
		3509	myfunctor f;
		3510
		3511	ev::io w;
		3512	w.set (&f);
		3513
2612	=item w->set<function> (void *data = 0)	3514	=item w->set<function> (void *data = 0)
2613		3515
2614	Also sets a callback, but uses a static method or plain function as	3516	Also sets a callback, but uses a static method or plain function as
2615	callback. The optional C<data> argument will be stored in the watcher's	3517	callback. The optional C<data> argument will be stored in the watcher's
2616	C<data> member and is free for you to use.	3518	C<data> member and is free for you to use.
2617		3519
2618	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3520	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2619		3521
2620	See the method-C<set> above for more details.	3522	See the method-C<set> above for more details.
2621		3523
2622	Example:	3524	Example: Use a plain function as callback.
2623		3525
2624	static void io_cb (ev::io &w, int revents) { }	3526	static void io_cb (ev::io &w, int revents) { }
2625	iow.set <io_cb> ();	3527	iow.set <io_cb> ();
2626		3528
2627	=item w->set (struct ev_loop *)	3529	=item w->set (loop)
2628		3530
2629	Associates a different C<struct ev_loop> with this watcher. You can only	3531	Associates a different C<struct ev_loop> with this watcher. You can only
2630	do this when the watcher is inactive (and not pending either).	3532	do this when the watcher is inactive (and not pending either).
2631		3533
2632	=item w->set ([arguments])	3534	=item w->set ([arguments])
2633		3535
2634	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3536	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
2635	called at least once. Unlike the C counterpart, an active watcher gets	3537	method or a suitable start method must be called at least once. Unlike the
2636	automatically stopped and restarted when reconfiguring it with this	3538	C counterpart, an active watcher gets automatically stopped and restarted
2637	method.	3539	when reconfiguring it with this method.
2638		3540
2639	=item w->start ()	3541	=item w->start ()
2640		3542
2641	Starts the watcher. Note that there is no C<loop> argument, as the	3543	Starts the watcher. Note that there is no C<loop> argument, as the
2642	constructor already stores the event loop.	3544	constructor already stores the event loop.
2643		3545
		3546	=item w->start ([arguments])
		3547
		3548	Instead of calling C<set> and C<start> methods separately, it is often
		3549	convenient to wrap them in one call. Uses the same type of arguments as
		3550	the configure C<set> method of the watcher.
		3551
2644	=item w->stop ()	3552	=item w->stop ()
2645		3553
2646	Stops the watcher if it is active. Again, no C<loop> argument.	3554	Stops the watcher if it is active. Again, no C<loop> argument.
2647		3555
2648	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3556	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2660		3568
2661	=back	3569	=back
2662		3570
2663	=back	3571	=back
2664		3572
2665	Example: Define a class with an IO and idle watcher, start one of them in	3573	Example: Define a class with two I/O and idle watchers, start the I/O
2666	the constructor.	3574	watchers in the constructor.
2667		3575
2668	class myclass	3576	class myclass
2669	{	3577	{
2670	ev::io io; void io_cb (ev::io &w, int revents);	3578	ev::io io ; void io_cb (ev::io &w, int revents);
		3579	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
2671	ev:idle idle void idle_cb (ev::idle &w, int revents);	3580	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2672		3581
2673	myclass (int fd)	3582	myclass (int fd)
2674	{	3583	{
2675	io .set <myclass, &myclass::io_cb > (this);	3584	io .set <myclass, &myclass::io_cb > (this);
		3585	io2 .set <myclass, &myclass::io2_cb > (this);
2676	idle.set <myclass, &myclass::idle_cb> (this);	3586	idle.set <myclass, &myclass::idle_cb> (this);
2677		3587
2678	io.start (fd, ev::READ);	3588	io.set (fd, ev::WRITE); // configure the watcher
		3589	io.start (); // start it whenever convenient
		3590
		3591	io2.start (fd, ev::READ); // set + start in one call
2679	}	3592	}
2680	};	3593	};
2681		3594
2682		3595
2683	=head1 OTHER LANGUAGE BINDINGS	3596	=head1 OTHER LANGUAGE BINDINGS
…		…
2692	=item Perl	3605	=item Perl
2693		3606
2694	The EV module implements the full libev API and is actually used to test	3607	The EV module implements the full libev API and is actually used to test
2695	libev. EV is developed together with libev. Apart from the EV core module,	3608	libev. EV is developed together with libev. Apart from the EV core module,
2696	there are additional modules that implement libev-compatible interfaces	3609	there are additional modules that implement libev-compatible interfaces
2697	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3610	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2698	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3611	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3612	and C<EV::Glib>).
2699		3613
2700	It can be found and installed via CPAN, its homepage is at	3614	It can be found and installed via CPAN, its homepage is at
2701	L<http://software.schmorp.de/pkg/EV>.	3615	L<http://software.schmorp.de/pkg/EV>.
2702		3616
2703	=item Python	3617	=item Python
2704		3618
2705	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3619	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2706	seems to be quite complete and well-documented. Note, however, that the	3620	seems to be quite complete and well-documented.
2707	patch they require for libev is outright dangerous as it breaks the ABI
2708	for everybody else, and therefore, should never be applied in an installed
2709	libev (if python requires an incompatible ABI then it needs to embed
2710	libev).
2711		3621
2712	=item Ruby	3622	=item Ruby
2713		3623
2714	Tony Arcieri has written a ruby extension that offers access to a subset	3624	Tony Arcieri has written a ruby extension that offers access to a subset
2715	of the libev API and adds file handle abstractions, asynchronous DNS and	3625	of the libev API and adds file handle abstractions, asynchronous DNS and
2716	more on top of it. It can be found via gem servers. Its homepage is at	3626	more on top of it. It can be found via gem servers. Its homepage is at
2717	L<http://rev.rubyforge.org/>.	3627	L<http://rev.rubyforge.org/>.
2718		3628
		3629	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3630	makes rev work even on mingw.
		3631
		3632	=item Haskell
		3633
		3634	A haskell binding to libev is available at
		3635	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3636
2719	=item D	3637	=item D
2720		3638
2721	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3639	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2722	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3640	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3641
		3642	=item Ocaml
		3643
		3644	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3645	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3646
		3647	=item Lua
		3648
		3649	Brian Maher has written a partial interface to libev for lua (at the
		3650	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3651	L<http://github.com/brimworks/lua-ev>.
2723		3652
2724	=back	3653	=back
2725		3654
2726		3655
2727	=head1 MACRO MAGIC	3656	=head1 MACRO MAGIC
…		…
2741	loop argument"). The C<EV_A> form is used when this is the sole argument,	3670	loop argument"). The C<EV_A> form is used when this is the sole argument,
2742	C<EV_A_> is used when other arguments are following. Example:	3671	C<EV_A_> is used when other arguments are following. Example:
2743		3672
2744	ev_unref (EV_A);	3673	ev_unref (EV_A);
2745	ev_timer_add (EV_A_ watcher);	3674	ev_timer_add (EV_A_ watcher);
2746	ev_loop (EV_A_ 0);	3675	ev_run (EV_A_ 0);
2747		3676
2748	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3677	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2749	which is often provided by the following macro.	3678	which is often provided by the following macro.
2750		3679
2751	=item C<EV_P>, C<EV_P_>	3680	=item C<EV_P>, C<EV_P_>
…		…
2791	}	3720	}
2792		3721
2793	ev_check check;	3722	ev_check check;
2794	ev_check_init (&check, check_cb);	3723	ev_check_init (&check, check_cb);
2795	ev_check_start (EV_DEFAULT_ &check);	3724	ev_check_start (EV_DEFAULT_ &check);
2796	ev_loop (EV_DEFAULT_ 0);	3725	ev_run (EV_DEFAULT_ 0);
2797		3726
2798	=head1 EMBEDDING	3727	=head1 EMBEDDING
2799		3728
2800	Libev can (and often is) directly embedded into host	3729	Libev can (and often is) directly embedded into host
2801	applications. Examples of applications that embed it include the Deliantra	3730	applications. Examples of applications that embed it include the Deliantra
…		…
2828		3757
2829	#define EV_STANDALONE 1	3758	#define EV_STANDALONE 1
2830	#include "ev.h"	3759	#include "ev.h"
2831		3760
2832	Both header files and implementation files can be compiled with a C++	3761	Both header files and implementation files can be compiled with a C++
2833	compiler (at least, thats a stated goal, and breakage will be treated	3762	compiler (at least, that's a stated goal, and breakage will be treated
2834	as a bug).	3763	as a bug).
2835		3764
2836	You need the following files in your source tree, or in a directory	3765	You need the following files in your source tree, or in a directory
2837	in your include path (e.g. in libev/ when using -Ilibev):	3766	in your include path (e.g. in libev/ when using -Ilibev):
2838		3767
…		…
2881	libev.m4	3810	libev.m4
2882		3811
2883	=head2 PREPROCESSOR SYMBOLS/MACROS	3812	=head2 PREPROCESSOR SYMBOLS/MACROS
2884		3813
2885	Libev can be configured via a variety of preprocessor symbols you have to	3814	Libev can be configured via a variety of preprocessor symbols you have to
2886	define before including any of its files. The default in the absence of	3815	define before including (or compiling) any of its files. The default in
2887	autoconf is noted for every option.	3816	the absence of autoconf is documented for every option.
		3817
		3818	Symbols marked with "(h)" do not change the ABI, and can have different
		3819	values when compiling libev vs. including F<ev.h>, so it is permissible
		3820	to redefine them before including F<ev.h> without breaking compatibility
		3821	to a compiled library. All other symbols change the ABI, which means all
		3822	users of libev and the libev code itself must be compiled with compatible
		3823	settings.
2888		3824
2889	=over 4	3825	=over 4
2890		3826
		3827	=item EV_COMPAT3 (h)
		3828
		3829	Backwards compatibility is a major concern for libev. This is why this
		3830	release of libev comes with wrappers for the functions and symbols that
		3831	have been renamed between libev version 3 and 4.
		3832
		3833	You can disable these wrappers (to test compatibility with future
		3834	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		3835	sources. This has the additional advantage that you can drop the C<struct>
		3836	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		3837	typedef in that case.
		3838
		3839	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		3840	and in some even more future version the compatibility code will be
		3841	removed completely.
		3842
2891	=item EV_STANDALONE	3843	=item EV_STANDALONE (h)
2892		3844
2893	Must always be C<1> if you do not use autoconf configuration, which	3845	Must always be C<1> if you do not use autoconf configuration, which
2894	keeps libev from including F<config.h>, and it also defines dummy	3846	keeps libev from including F<config.h>, and it also defines dummy
2895	implementations for some libevent functions (such as logging, which is not	3847	implementations for some libevent functions (such as logging, which is not
2896	supported). It will also not define any of the structs usually found in	3848	supported). It will also not define any of the structs usually found in
2897	F<event.h> that are not directly supported by the libev core alone.	3849	F<event.h> that are not directly supported by the libev core alone.
2898		3850
		3851	In standalone mode, libev will still try to automatically deduce the
		3852	configuration, but has to be more conservative.
		3853
2899	=item EV_USE_MONOTONIC	3854	=item EV_USE_MONOTONIC
2900		3855
2901	If defined to be C<1>, libev will try to detect the availability of the	3856	If defined to be C<1>, libev will try to detect the availability of the
2902	monotonic clock option at both compile time and runtime. Otherwise no use	3857	monotonic clock option at both compile time and runtime. Otherwise no
2903	of the monotonic clock option will be attempted. If you enable this, you	3858	use of the monotonic clock option will be attempted. If you enable this,
2904	usually have to link against librt or something similar. Enabling it when	3859	you usually have to link against librt or something similar. Enabling it
2905	the functionality isn't available is safe, though, although you have	3860	when the functionality isn't available is safe, though, although you have
2906	to make sure you link against any libraries where the C<clock_gettime>	3861	to make sure you link against any libraries where the C<clock_gettime>
2907	function is hiding in (often F<-lrt>).	3862	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2908		3863
2909	=item EV_USE_REALTIME	3864	=item EV_USE_REALTIME
2910		3865
2911	If defined to be C<1>, libev will try to detect the availability of the	3866	If defined to be C<1>, libev will try to detect the availability of the
2912	real-time clock option at compile time (and assume its availability at	3867	real-time clock option at compile time (and assume its availability
2913	runtime if successful). Otherwise no use of the real-time clock option will	3868	at runtime if successful). Otherwise no use of the real-time clock
2914	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3869	option will be attempted. This effectively replaces C<gettimeofday>
2915	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3870	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2916	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3871	correctness. See the note about libraries in the description of
		3872	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3873	C<EV_USE_CLOCK_SYSCALL>.
		3874
		3875	=item EV_USE_CLOCK_SYSCALL
		3876
		3877	If defined to be C<1>, libev will try to use a direct syscall instead
		3878	of calling the system-provided C<clock_gettime> function. This option
		3879	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3880	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3881	programs needlessly. Using a direct syscall is slightly slower (in
		3882	theory), because no optimised vdso implementation can be used, but avoids
		3883	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3884	higher, as it simplifies linking (no need for C<-lrt>).
2917		3885
2918	=item EV_USE_NANOSLEEP	3886	=item EV_USE_NANOSLEEP
2919		3887
2920	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3888	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2921	and will use it for delays. Otherwise it will use C<select ()>.	3889	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2937		3905
2938	=item EV_SELECT_USE_FD_SET	3906	=item EV_SELECT_USE_FD_SET
2939		3907
2940	If defined to C<1>, then the select backend will use the system C<fd_set>	3908	If defined to C<1>, then the select backend will use the system C<fd_set>
2941	structure. This is useful if libev doesn't compile due to a missing	3909	structure. This is useful if libev doesn't compile due to a missing
2942	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3910	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2943	exotic systems. This usually limits the range of file descriptors to some	3911	on exotic systems. This usually limits the range of file descriptors to
2944	low limit such as 1024 or might have other limitations (winsocket only	3912	some low limit such as 1024 or might have other limitations (winsocket
2945	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3913	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2946	influence the size of the C<fd_set> used.	3914	configures the maximum size of the C<fd_set>.
2947		3915
2948	=item EV_SELECT_IS_WINSOCKET	3916	=item EV_SELECT_IS_WINSOCKET
2949		3917
2950	When defined to C<1>, the select backend will assume that	3918	When defined to C<1>, the select backend will assume that
2951	select/socket/connect etc. don't understand file descriptors but	3919	select/socket/connect etc. don't understand file descriptors but
…		…
2953	be used is the winsock select). This means that it will call	3921	be used is the winsock select). This means that it will call
2954	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3922	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2955	it is assumed that all these functions actually work on fds, even	3923	it is assumed that all these functions actually work on fds, even
2956	on win32. Should not be defined on non-win32 platforms.	3924	on win32. Should not be defined on non-win32 platforms.
2957		3925
2958	=item EV_FD_TO_WIN32_HANDLE	3926	=item EV_FD_TO_WIN32_HANDLE(fd)
2959		3927
2960	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3928	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
2961	file descriptors to socket handles. When not defining this symbol (the	3929	file descriptors to socket handles. When not defining this symbol (the
2962	default), then libev will call C<_get_osfhandle>, which is usually	3930	default), then libev will call C<_get_osfhandle>, which is usually
2963	correct. In some cases, programs use their own file descriptor management,	3931	correct. In some cases, programs use their own file descriptor management,
2964	in which case they can provide this function to map fds to socket handles.	3932	in which case they can provide this function to map fds to socket handles.
		3933
		3934	=item EV_WIN32_HANDLE_TO_FD(handle)
		3935
		3936	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3937	using the standard C<_open_osfhandle> function. For programs implementing
		3938	their own fd to handle mapping, overwriting this function makes it easier
		3939	to do so. This can be done by defining this macro to an appropriate value.
		3940
		3941	=item EV_WIN32_CLOSE_FD(fd)
		3942
		3943	If programs implement their own fd to handle mapping on win32, then this
		3944	macro can be used to override the C<close> function, useful to unregister
		3945	file descriptors again. Note that the replacement function has to close
		3946	the underlying OS handle.
2965		3947
2966	=item EV_USE_POLL	3948	=item EV_USE_POLL
2967		3949
2968	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3950	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2969	backend. Otherwise it will be enabled on non-win32 platforms. It	3951	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3016	as well as for signal and thread safety in C<ev_async> watchers.	3998	as well as for signal and thread safety in C<ev_async> watchers.
3017		3999
3018	In the absence of this define, libev will use C<sig_atomic_t volatile>	4000	In the absence of this define, libev will use C<sig_atomic_t volatile>
3019	(from F<signal.h>), which is usually good enough on most platforms.	4001	(from F<signal.h>), which is usually good enough on most platforms.
3020		4002
3021	=item EV_H	4003	=item EV_H (h)
3022		4004
3023	The name of the F<ev.h> header file used to include it. The default if	4005	The name of the F<ev.h> header file used to include it. The default if
3024	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4006	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3025	used to virtually rename the F<ev.h> header file in case of conflicts.	4007	used to virtually rename the F<ev.h> header file in case of conflicts.
3026		4008
3027	=item EV_CONFIG_H	4009	=item EV_CONFIG_H (h)
3028		4010
3029	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4011	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3030	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4012	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3031	C<EV_H>, above.	4013	C<EV_H>, above.
3032		4014
3033	=item EV_EVENT_H	4015	=item EV_EVENT_H (h)
3034		4016
3035	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4017	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3036	of how the F<event.h> header can be found, the default is C<"event.h">.	4018	of how the F<event.h> header can be found, the default is C<"event.h">.
3037		4019
3038	=item EV_PROTOTYPES	4020	=item EV_PROTOTYPES (h)
3039		4021
3040	If defined to be C<0>, then F<ev.h> will not define any function	4022	If defined to be C<0>, then F<ev.h> will not define any function
3041	prototypes, but still define all the structs and other symbols. This is	4023	prototypes, but still define all the structs and other symbols. This is
3042	occasionally useful if you want to provide your own wrapper functions	4024	occasionally useful if you want to provide your own wrapper functions
3043	around libev functions.	4025	around libev functions.
…		…
3062	When doing priority-based operations, libev usually has to linearly search	4044	When doing priority-based operations, libev usually has to linearly search
3063	all the priorities, so having many of them (hundreds) uses a lot of space	4045	all the priorities, so having many of them (hundreds) uses a lot of space
3064	and time, so using the defaults of five priorities (-2 .. +2) is usually	4046	and time, so using the defaults of five priorities (-2 .. +2) is usually
3065	fine.	4047	fine.
3066		4048
3067	If your embedding application does not need any priorities, defining these both to	4049	If your embedding application does not need any priorities, defining these
3068	C<0> will save some memory and CPU.	4050	both to C<0> will save some memory and CPU.
3069		4051
3070	=item EV_PERIODIC_ENABLE	4052	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4053	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4054	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3071		4055
3072	If undefined or defined to be C<1>, then periodic timers are supported. If	4056	If undefined or defined to be C<1> (and the platform supports it), then
3073	defined to be C<0>, then they are not. Disabling them saves a few kB of	4057	the respective watcher type is supported. If defined to be C<0>, then it
3074	code.	4058	is not. Disabling watcher types mainly saves code size.
3075		4059
3076	=item EV_IDLE_ENABLE	4060	=item EV_FEATURES
3077
3078	If undefined or defined to be C<1>, then idle watchers are supported. If
3079	defined to be C<0>, then they are not. Disabling them saves a few kB of
3080	code.
3081
3082	=item EV_EMBED_ENABLE
3083
3084	If undefined or defined to be C<1>, then embed watchers are supported. If
3085	defined to be C<0>, then they are not.
3086
3087	=item EV_STAT_ENABLE
3088
3089	If undefined or defined to be C<1>, then stat watchers are supported. If
3090	defined to be C<0>, then they are not.
3091
3092	=item EV_FORK_ENABLE
3093
3094	If undefined or defined to be C<1>, then fork watchers are supported. If
3095	defined to be C<0>, then they are not.
3096
3097	=item EV_ASYNC_ENABLE
3098
3099	If undefined or defined to be C<1>, then async watchers are supported. If
3100	defined to be C<0>, then they are not.
3101
3102	=item EV_MINIMAL
3103		4061
3104	If you need to shave off some kilobytes of code at the expense of some	4062	If you need to shave off some kilobytes of code at the expense of some
3105	speed, define this symbol to C<1>. Currently this is used to override some	4063	speed (but with the full API), you can define this symbol to request
3106	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4064	certain subsets of functionality. The default is to enable all features
3107	much smaller 2-heap for timer management over the default 4-heap.	4065	that can be enabled on the platform.
		4066
		4067	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4068	with some broad features you want) and then selectively re-enable
		4069	additional parts you want, for example if you want everything minimal,
		4070	but multiple event loop support, async and child watchers and the poll
		4071	backend, use this:
		4072
		4073	#define EV_FEATURES 0
		4074	#define EV_MULTIPLICITY 1
		4075	#define EV_USE_POLL 1
		4076	#define EV_CHILD_ENABLE 1
		4077	#define EV_ASYNC_ENABLE 1
		4078
		4079	The actual value is a bitset, it can be a combination of the following
		4080	values:
		4081
		4082	=over 4
		4083
		4084	=item C<1> - faster/larger code
		4085
		4086	Use larger code to speed up some operations.
		4087
		4088	Currently this is used to override some inlining decisions (enlarging the
		4089	code size by roughly 30% on amd64).
		4090
		4091	When optimising for size, use of compiler flags such as C<-Os> with
		4092	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4093	assertions.
		4094
		4095	=item C<2> - faster/larger data structures
		4096
		4097	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4098	hash table sizes and so on. This will usually further increase code size
		4099	and can additionally have an effect on the size of data structures at
		4100	runtime.
		4101
		4102	=item C<4> - full API configuration
		4103
		4104	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4105	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4106
		4107	=item C<8> - full API
		4108
		4109	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4110	details on which parts of the API are still available without this
		4111	feature, and do not complain if this subset changes over time.
		4112
		4113	=item C<16> - enable all optional watcher types
		4114
		4115	Enables all optional watcher types. If you want to selectively enable
		4116	only some watcher types other than I/O and timers (e.g. prepare,
		4117	embed, async, child...) you can enable them manually by defining
		4118	C<EV_watchertype_ENABLE> to C<1> instead.
		4119
		4120	=item C<32> - enable all backends
		4121
		4122	This enables all backends - without this feature, you need to enable at
		4123	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4124
		4125	=item C<64> - enable OS-specific "helper" APIs
		4126
		4127	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4128	default.
		4129
		4130	=back
		4131
		4132	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4133	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4134	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4135	watchers, timers and monotonic clock support.
		4136
		4137	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4138	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4139	your program might be left out as well - a binary starting a timer and an
		4140	I/O watcher then might come out at only 5Kb.
		4141
		4142	=item EV_AVOID_STDIO
		4143
		4144	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4145	functions (printf, scanf, perror etc.). This will increase the code size
		4146	somewhat, but if your program doesn't otherwise depend on stdio and your
		4147	libc allows it, this avoids linking in the stdio library which is quite
		4148	big.
		4149
		4150	Note that error messages might become less precise when this option is
		4151	enabled.
		4152
		4153	=item EV_NSIG
		4154
		4155	The highest supported signal number, +1 (or, the number of
		4156	signals): Normally, libev tries to deduce the maximum number of signals
		4157	automatically, but sometimes this fails, in which case it can be
		4158	specified. Also, using a lower number than detected (C<32> should be
		4159	good for about any system in existence) can save some memory, as libev
		4160	statically allocates some 12-24 bytes per signal number.
3108		4161
3109	=item EV_PID_HASHSIZE	4162	=item EV_PID_HASHSIZE
3110		4163
3111	C<ev_child> watchers use a small hash table to distribute workload by	4164	C<ev_child> watchers use a small hash table to distribute workload by
3112	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4165	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3113	than enough. If you need to manage thousands of children you might want to	4166	usually more than enough. If you need to manage thousands of children you
3114	increase this value (I<must> be a power of two).	4167	might want to increase this value (I<must> be a power of two).
3115		4168
3116	=item EV_INOTIFY_HASHSIZE	4169	=item EV_INOTIFY_HASHSIZE
3117		4170
3118	C<ev_stat> watchers use a small hash table to distribute workload by	4171	C<ev_stat> watchers use a small hash table to distribute workload by
3119	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4172	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3120	usually more than enough. If you need to manage thousands of C<ev_stat>	4173	disabled), usually more than enough. If you need to manage thousands of
3121	watchers you might want to increase this value (I<must> be a power of	4174	C<ev_stat> watchers you might want to increase this value (I<must> be a
3122	two).	4175	power of two).
3123		4176
3124	=item EV_USE_4HEAP	4177	=item EV_USE_4HEAP
3125		4178
3126	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4179	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3127	timer and periodics heap, libev uses a 4-heap when this symbol is defined	4180	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3128	to C<1>. The 4-heap uses more complicated (longer) code but has	4181	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3129	noticeably faster performance with many (thousands) of watchers.	4182	faster performance with many (thousands) of watchers.
3130		4183
3131	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4184	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3132	(disabled).	4185	will be C<0>.
3133		4186
3134	=item EV_HEAP_CACHE_AT	4187	=item EV_HEAP_CACHE_AT
3135		4188
3136	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4189	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3137	timer and periodics heap, libev can cache the timestamp (I<at>) within	4190	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3138	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4191	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3139	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4192	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3140	but avoids random read accesses on heap changes. This improves performance	4193	but avoids random read accesses on heap changes. This improves performance
3141	noticeably with with many (hundreds) of watchers.	4194	noticeably with many (hundreds) of watchers.
3142		4195
3143	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4196	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3144	(disabled).	4197	will be C<0>.
3145		4198
3146	=item EV_VERIFY	4199	=item EV_VERIFY
3147		4200
3148	Controls how much internal verification (see C<ev_loop_verify ()>) will	4201	Controls how much internal verification (see C<ev_verify ()>) will
3149	be done: If set to C<0>, no internal verification code will be compiled	4202	be done: If set to C<0>, no internal verification code will be compiled
3150	in. If set to C<1>, then verification code will be compiled in, but not	4203	in. If set to C<1>, then verification code will be compiled in, but not
3151	called. If set to C<2>, then the internal verification code will be	4204	called. If set to C<2>, then the internal verification code will be
3152	called once per loop, which can slow down libev. If set to C<3>, then the	4205	called once per loop, which can slow down libev. If set to C<3>, then the
3153	verification code will be called very frequently, which will slow down	4206	verification code will be called very frequently, which will slow down
3154	libev considerably.	4207	libev considerably.
3155		4208
3156	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4209	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3157	C<0.>	4210	will be C<0>.
3158		4211
3159	=item EV_COMMON	4212	=item EV_COMMON
3160		4213
3161	By default, all watchers have a C<void *data> member. By redefining	4214	By default, all watchers have a C<void *data> member. By redefining
3162	this macro to a something else you can include more and other types of	4215	this macro to something else you can include more and other types of
3163	members. You have to define it each time you include one of the files,	4216	members. You have to define it each time you include one of the files,
3164	though, and it must be identical each time.	4217	though, and it must be identical each time.
3165		4218
3166	For example, the perl EV module uses something like this:	4219	For example, the perl EV module uses something like this:
3167		4220
…		…
3179	and the way callbacks are invoked and set. Must expand to a struct member	4232	and the way callbacks are invoked and set. Must expand to a struct member
3180	definition and a statement, respectively. See the F<ev.h> header file for	4233	definition and a statement, respectively. See the F<ev.h> header file for
3181	their default definitions. One possible use for overriding these is to	4234	their default definitions. One possible use for overriding these is to
3182	avoid the C<struct ev_loop *> as first argument in all cases, or to use	4235	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3183	method calls instead of plain function calls in C++.	4236	method calls instead of plain function calls in C++.
		4237
		4238	=back
3184		4239
3185	=head2 EXPORTED API SYMBOLS	4240	=head2 EXPORTED API SYMBOLS
3186		4241
3187	If you need to re-export the API (e.g. via a DLL) and you need a list of	4242	If you need to re-export the API (e.g. via a DLL) and you need a list of
3188	exported symbols, you can use the provided F<Symbol.*> files which list	4243	exported symbols, you can use the provided F<Symbol.*> files which list
…		…
3218	file.	4273	file.
3219		4274
3220	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4275	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3221	that everybody includes and which overrides some configure choices:	4276	that everybody includes and which overrides some configure choices:
3222		4277
3223	#define EV_MINIMAL 1	4278	#define EV_FEATURES 8
3224	#define EV_USE_POLL 0	4279	#define EV_USE_SELECT 1
3225	#define EV_MULTIPLICITY 0
3226	#define EV_PERIODIC_ENABLE 0	4280	#define EV_PREPARE_ENABLE 1
		4281	#define EV_IDLE_ENABLE 1
3227	#define EV_STAT_ENABLE 0	4282	#define EV_SIGNAL_ENABLE 1
3228	#define EV_FORK_ENABLE 0	4283	#define EV_CHILD_ENABLE 1
		4284	#define EV_USE_STDEXCEPT 0
3229	#define EV_CONFIG_H <config.h>	4285	#define EV_CONFIG_H <config.h>
3230	#define EV_MINPRI 0
3231	#define EV_MAXPRI 0
3232		4286
3233	#include "ev++.h"	4287	#include "ev++.h"
3234		4288
3235	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4289	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3236		4290
3237	#include "ev_cpp.h"	4291	#include "ev_cpp.h"
3238	#include "ev.c"	4292	#include "ev.c"
3239		4293
		4294	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3240		4295
3241	=head1 THREADS AND COROUTINES	4296	=head2 THREADS AND COROUTINES
3242		4297
3243	=head2 THREADS	4298	=head3 THREADS
3244		4299
3245	Libev itself is thread-safe (unless the opposite is specifically	4300	All libev functions are reentrant and thread-safe unless explicitly
3246	documented for a function), but it uses no locking itself. This means that	4301	documented otherwise, but libev implements no locking itself. This means
3247	you can use as many loops as you want in parallel, as long as only one	4302	that you can use as many loops as you want in parallel, as long as there
3248	thread ever calls into one libev function with the same loop parameter:	4303	are no concurrent calls into any libev function with the same loop
		4304	parameter (C<ev_default_*> calls have an implicit default loop parameter,
3249	libev guarentees that different event loops share no data structures that	4305	of course): libev guarantees that different event loops share no data
3250	need locking.	4306	structures that need any locking.
3251		4307
3252	Or to put it differently: calls with different loop parameters can be done	4308	Or to put it differently: calls with different loop parameters can be done
3253	concurrently from multiple threads, calls with the same loop parameter	4309	concurrently from multiple threads, calls with the same loop parameter
3254	must be done serially (but can be done from different threads, as long as	4310	must be done serially (but can be done from different threads, as long as
3255	only one thread ever is inside a call at any point in time, e.g. by using	4311	only one thread ever is inside a call at any point in time, e.g. by using
3256	a mutex per loop).	4312	a mutex per loop).
3257		4313
3258	Specifically to support threads (and signal handlers), libev implements	4314	Specifically to support threads (and signal handlers), libev implements
3259	so-called C<ev_async> watchers, which allow some limited form of	4315	so-called C<ev_async> watchers, which allow some limited form of
3260	concurrency on the same event loop.	4316	concurrency on the same event loop, namely waking it up "from the
		4317	outside".
3261		4318
3262	If you want to know which design (one loop, locking, or multiple loops	4319	If you want to know which design (one loop, locking, or multiple loops
3263	without or something else still) is best for your problem, then I cannot	4320	without or something else still) is best for your problem, then I cannot
3264	help you. I can give some generic advice however:	4321	help you, but here is some generic advice:
3265		4322
3266	=over 4	4323	=over 4
3267		4324
3268	=item * most applications have a main thread: use the default libev loop	4325	=item * most applications have a main thread: use the default libev loop
3269	in that thread, or create a separate thread running only the default loop.	4326	in that thread, or create a separate thread running only the default loop.
…		…
3293	default loop and triggering an C<ev_async> watcher from the default loop	4350	default loop and triggering an C<ev_async> watcher from the default loop
3294	watcher callback into the event loop interested in the signal.	4351	watcher callback into the event loop interested in the signal.
3295		4352
3296	=back	4353	=back
3297		4354
		4355	=head4 THREAD LOCKING EXAMPLE
		4356
		4357	Here is a fictitious example of how to run an event loop in a different
		4358	thread than where callbacks are being invoked and watchers are
		4359	created/added/removed.
		4360
		4361	For a real-world example, see the C<EV::Loop::Async> perl module,
		4362	which uses exactly this technique (which is suited for many high-level
		4363	languages).
		4364
		4365	The example uses a pthread mutex to protect the loop data, a condition
		4366	variable to wait for callback invocations, an async watcher to notify the
		4367	event loop thread and an unspecified mechanism to wake up the main thread.
		4368
		4369	First, you need to associate some data with the event loop:
		4370
		4371	typedef struct {
		4372	mutex_t lock; /* global loop lock */
		4373	ev_async async_w;
		4374	thread_t tid;
		4375	cond_t invoke_cv;
		4376	} userdata;
		4377
		4378	void prepare_loop (EV_P)
		4379	{
		4380	// for simplicity, we use a static userdata struct.
		4381	static userdata u;
		4382
		4383	ev_async_init (&u->async_w, async_cb);
		4384	ev_async_start (EV_A_ &u->async_w);
		4385
		4386	pthread_mutex_init (&u->lock, 0);
		4387	pthread_cond_init (&u->invoke_cv, 0);
		4388
		4389	// now associate this with the loop
		4390	ev_set_userdata (EV_A_ u);
		4391	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4392	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4393
		4394	// then create the thread running ev_loop
		4395	pthread_create (&u->tid, 0, l_run, EV_A);
		4396	}
		4397
		4398	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4399	solely to wake up the event loop so it takes notice of any new watchers
		4400	that might have been added:
		4401
		4402	static void
		4403	async_cb (EV_P_ ev_async *w, int revents)
		4404	{
		4405	// just used for the side effects
		4406	}
		4407
		4408	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4409	protecting the loop data, respectively.
		4410
		4411	static void
		4412	l_release (EV_P)
		4413	{
		4414	userdata *u = ev_userdata (EV_A);
		4415	pthread_mutex_unlock (&u->lock);
		4416	}
		4417
		4418	static void
		4419	l_acquire (EV_P)
		4420	{
		4421	userdata *u = ev_userdata (EV_A);
		4422	pthread_mutex_lock (&u->lock);
		4423	}
		4424
		4425	The event loop thread first acquires the mutex, and then jumps straight
		4426	into C<ev_run>:
		4427
		4428	void *
		4429	l_run (void *thr_arg)
		4430	{
		4431	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4432
		4433	l_acquire (EV_A);
		4434	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4435	ev_run (EV_A_ 0);
		4436	l_release (EV_A);
		4437
		4438	return 0;
		4439	}
		4440
		4441	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4442	signal the main thread via some unspecified mechanism (signals? pipe
		4443	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4444	have been called (in a while loop because a) spurious wakeups are possible
		4445	and b) skipping inter-thread-communication when there are no pending
		4446	watchers is very beneficial):
		4447
		4448	static void
		4449	l_invoke (EV_P)
		4450	{
		4451	userdata *u = ev_userdata (EV_A);
		4452
		4453	while (ev_pending_count (EV_A))
		4454	{
		4455	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4456	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4457	}
		4458	}
		4459
		4460	Now, whenever the main thread gets told to invoke pending watchers, it
		4461	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4462	thread to continue:
		4463
		4464	static void
		4465	real_invoke_pending (EV_P)
		4466	{
		4467	userdata *u = ev_userdata (EV_A);
		4468
		4469	pthread_mutex_lock (&u->lock);
		4470	ev_invoke_pending (EV_A);
		4471	pthread_cond_signal (&u->invoke_cv);
		4472	pthread_mutex_unlock (&u->lock);
		4473	}
		4474
		4475	Whenever you want to start/stop a watcher or do other modifications to an
		4476	event loop, you will now have to lock:
		4477
		4478	ev_timer timeout_watcher;
		4479	userdata *u = ev_userdata (EV_A);
		4480
		4481	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4482
		4483	pthread_mutex_lock (&u->lock);
		4484	ev_timer_start (EV_A_ &timeout_watcher);
		4485	ev_async_send (EV_A_ &u->async_w);
		4486	pthread_mutex_unlock (&u->lock);
		4487
		4488	Note that sending the C<ev_async> watcher is required because otherwise
		4489	an event loop currently blocking in the kernel will have no knowledge
		4490	about the newly added timer. By waking up the loop it will pick up any new
		4491	watchers in the next event loop iteration.
		4492
3298	=head2 COROUTINES	4493	=head3 COROUTINES
3299		4494
3300	Libev is much more accommodating to coroutines ("cooperative threads"):	4495	Libev is very accommodating to coroutines ("cooperative threads"):
3301	libev fully supports nesting calls to it's functions from different	4496	libev fully supports nesting calls to its functions from different
3302	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4497	coroutines (e.g. you can call C<ev_run> on the same loop from two
3303	different coroutines and switch freely between both coroutines running the	4498	different coroutines, and switch freely between both coroutines running
3304	loop, as long as you don't confuse yourself). The only exception is that	4499	the loop, as long as you don't confuse yourself). The only exception is
3305	you must not do this from C<ev_periodic> reschedule callbacks.	4500	that you must not do this from C<ev_periodic> reschedule callbacks.
3306		4501
3307	Care has been taken to ensure that libev does not keep local state inside	4502	Care has been taken to ensure that libev does not keep local state inside
3308	C<ev_loop>, and other calls do not usually allow coroutine switches.	4503	C<ev_run>, and other calls do not usually allow for coroutine switches as
		4504	they do not call any callbacks.
3309		4505
		4506	=head2 COMPILER WARNINGS
3310		4507
3311	=head1 COMPLEXITIES	4508	Depending on your compiler and compiler settings, you might get no or a
		4509	lot of warnings when compiling libev code. Some people are apparently
		4510	scared by this.
3312		4511
3313	In this section the complexities of (many of) the algorithms used inside	4512	However, these are unavoidable for many reasons. For one, each compiler
3314	libev will be explained. For complexity discussions about backends see the	4513	has different warnings, and each user has different tastes regarding
3315	documentation for C<ev_default_init>.	4514	warning options. "Warn-free" code therefore cannot be a goal except when
		4515	targeting a specific compiler and compiler-version.
3316		4516
3317	All of the following are about amortised time: If an array needs to be	4517	Another reason is that some compiler warnings require elaborate
3318	extended, libev needs to realloc and move the whole array, but this	4518	workarounds, or other changes to the code that make it less clear and less
3319	happens asymptotically never with higher number of elements, so O(1) might	4519	maintainable.
3320	mean it might do a lengthy realloc operation in rare cases, but on average
3321	it is much faster and asymptotically approaches constant time.
3322		4520
3323	=over 4	4521	And of course, some compiler warnings are just plain stupid, or simply
		4522	wrong (because they don't actually warn about the condition their message
		4523	seems to warn about). For example, certain older gcc versions had some
		4524	warnings that resulted in an extreme number of false positives. These have
		4525	been fixed, but some people still insist on making code warn-free with
		4526	such buggy versions.
3324		4527
3325	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	4528	While libev is written to generate as few warnings as possible,
		4529	"warn-free" code is not a goal, and it is recommended not to build libev
		4530	with any compiler warnings enabled unless you are prepared to cope with
		4531	them (e.g. by ignoring them). Remember that warnings are just that:
		4532	warnings, not errors, or proof of bugs.
3326		4533
3327	This means that, when you have a watcher that triggers in one hour and
3328	there are 100 watchers that would trigger before that then inserting will
3329	have to skip roughly seven (C<ld 100>) of these watchers.
3330		4534
3331	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	4535	=head2 VALGRIND
3332		4536
3333	That means that changing a timer costs less than removing/adding them	4537	Valgrind has a special section here because it is a popular tool that is
3334	as only the relative motion in the event queue has to be paid for.	4538	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3335		4539
3336	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	4540	If you think you found a bug (memory leak, uninitialised data access etc.)
		4541	in libev, then check twice: If valgrind reports something like:
3337		4542
3338	These just add the watcher into an array or at the head of a list.	4543	==2274== definitely lost: 0 bytes in 0 blocks.
		4544	==2274== possibly lost: 0 bytes in 0 blocks.
		4545	==2274== still reachable: 256 bytes in 1 blocks.
3339		4546
3340	=item Stopping check/prepare/idle/fork/async watchers: O(1)	4547	Then there is no memory leak, just as memory accounted to global variables
		4548	is not a memleak - the memory is still being referenced, and didn't leak.
3341		4549
3342	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	4550	Similarly, under some circumstances, valgrind might report kernel bugs
		4551	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		4552	although an acceptable workaround has been found here), or it might be
		4553	confused.
3343		4554
3344	These watchers are stored in lists then need to be walked to find the	4555	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3345	correct watcher to remove. The lists are usually short (you don't usually	4556	make it into some kind of religion.
3346	have many watchers waiting for the same fd or signal).
3347		4557
3348	=item Finding the next timer in each loop iteration: O(1)	4558	If you are unsure about something, feel free to contact the mailing list
		4559	with the full valgrind report and an explanation on why you think this
		4560	is a bug in libev (best check the archives, too :). However, don't be
		4561	annoyed when you get a brisk "this is no bug" answer and take the chance
		4562	of learning how to interpret valgrind properly.
3349		4563
3350	By virtue of using a binary or 4-heap, the next timer is always found at a	4564	If you need, for some reason, empty reports from valgrind for your project
3351	fixed position in the storage array.	4565	I suggest using suppression lists.
3352		4566
3353	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3354		4567
3355	A change means an I/O watcher gets started or stopped, which requires	4568	=head1 PORTABILITY NOTES
3356	libev to recalculate its status (and possibly tell the kernel, depending
3357	on backend and whether C<ev_io_set> was used).
3358		4569
3359	=item Activating one watcher (putting it into the pending state): O(1)	4570	=head2 GNU/LINUX 32 BIT LIMITATIONS
3360		4571
3361	=item Priority handling: O(number_of_priorities)	4572	GNU/Linux is the only common platform that supports 64 bit file/large file
		4573	interfaces but I<disables> them by default.
3362		4574
3363	Priorities are implemented by allocating some space for each	4575	That means that libev compiled in the default environment doesn't support
3364	priority. When doing priority-based operations, libev usually has to	4576	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
3365	linearly search all the priorities, but starting/stopping and activating
3366	watchers becomes O(1) w.r.t. priority handling.
3367		4577
3368	=item Sending an ev_async: O(1)	4578	Unfortunately, many programs try to work around this GNU/Linux issue
		4579	by enabling the large file API, which makes them incompatible with the
		4580	standard libev compiled for their system.
3369		4581
3370	=item Processing ev_async_send: O(number_of_async_watchers)	4582	Likewise, libev cannot enable the large file API itself as this would
		4583	suddenly make it incompatible to the default compile time environment,
		4584	i.e. all programs not using special compile switches.
3371		4585
3372	=item Processing signals: O(max_signal_number)	4586	=head2 OS/X AND DARWIN BUGS
3373		4587
3374	Sending involves a system call I<iff> there were no other C<ev_async_send>	4588	The whole thing is a bug if you ask me - basically any system interface
3375	calls in the current loop iteration. Checking for async and signal events	4589	you touch is broken, whether it is locales, poll, kqueue or even the
3376	involves iterating over all running async watchers or all signal numbers.	4590	OpenGL drivers.
3377		4591
3378	=back	4592	=head3 C<kqueue> is buggy
3379		4593
		4594	The kqueue syscall is broken in all known versions - most versions support
		4595	only sockets, many support pipes.
3380		4596
		4597	Libev tries to work around this by not using C<kqueue> by default on this
		4598	rotten platform, but of course you can still ask for it when creating a
		4599	loop - embedding a socket-only kqueue loop into a select-based one is
		4600	probably going to work well.
		4601
		4602	=head3 C<poll> is buggy
		4603
		4604	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4605	implementation by something calling C<kqueue> internally around the 10.5.6
		4606	release, so now C<kqueue> I<and> C<poll> are broken.
		4607
		4608	Libev tries to work around this by not using C<poll> by default on
		4609	this rotten platform, but of course you can still ask for it when creating
		4610	a loop.
		4611
		4612	=head3 C<select> is buggy
		4613
		4614	All that's left is C<select>, and of course Apple found a way to fuck this
		4615	one up as well: On OS/X, C<select> actively limits the number of file
		4616	descriptors you can pass in to 1024 - your program suddenly crashes when
		4617	you use more.
		4618
		4619	There is an undocumented "workaround" for this - defining
		4620	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4621	work on OS/X.
		4622
		4623	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4624
		4625	=head3 C<errno> reentrancy
		4626
		4627	The default compile environment on Solaris is unfortunately so
		4628	thread-unsafe that you can't even use components/libraries compiled
		4629	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4630	defined by default. A valid, if stupid, implementation choice.
		4631
		4632	If you want to use libev in threaded environments you have to make sure
		4633	it's compiled with C<_REENTRANT> defined.
		4634
		4635	=head3 Event port backend
		4636
		4637	The scalable event interface for Solaris is called "event
		4638	ports". Unfortunately, this mechanism is very buggy in all major
		4639	releases. If you run into high CPU usage, your program freezes or you get
		4640	a large number of spurious wakeups, make sure you have all the relevant
		4641	and latest kernel patches applied. No, I don't know which ones, but there
		4642	are multiple ones to apply, and afterwards, event ports actually work
		4643	great.
		4644
		4645	If you can't get it to work, you can try running the program by setting
		4646	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4647	C<select> backends.
		4648
		4649	=head2 AIX POLL BUG
		4650
		4651	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4652	this by trying to avoid the poll backend altogether (i.e. it's not even
		4653	compiled in), which normally isn't a big problem as C<select> works fine
		4654	with large bitsets on AIX, and AIX is dead anyway.
		4655
3381	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4656	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4657
		4658	=head3 General issues
3382		4659
3383	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4660	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3384	requires, and its I/O model is fundamentally incompatible with the POSIX	4661	requires, and its I/O model is fundamentally incompatible with the POSIX
3385	model. Libev still offers limited functionality on this platform in	4662	model. Libev still offers limited functionality on this platform in
3386	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4663	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3387	descriptors. This only applies when using Win32 natively, not when using	4664	descriptors. This only applies when using Win32 natively, not when using
3388	e.g. cygwin.	4665	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4666	as every compielr comes with a slightly differently broken/incompatible
		4667	environment.
3389		4668
3390	Lifting these limitations would basically require the full	4669	Lifting these limitations would basically require the full
3391	re-implementation of the I/O system. If you are into these kinds of	4670	re-implementation of the I/O system. If you are into this kind of thing,
3392	things, then note that glib does exactly that for you in a very portable	4671	then note that glib does exactly that for you in a very portable way (note
3393	way (note also that glib is the slowest event library known to man).	4672	also that glib is the slowest event library known to man).
3394		4673
3395	There is no supported compilation method available on windows except	4674	There is no supported compilation method available on windows except
3396	embedding it into other applications.	4675	embedding it into other applications.
		4676
		4677	Sensible signal handling is officially unsupported by Microsoft - libev
		4678	tries its best, but under most conditions, signals will simply not work.
3397		4679
3398	Not a libev limitation but worth mentioning: windows apparently doesn't	4680	Not a libev limitation but worth mentioning: windows apparently doesn't
3399	accept large writes: instead of resulting in a partial write, windows will	4681	accept large writes: instead of resulting in a partial write, windows will
3400	either accept everything or return C<ENOBUFS> if the buffer is too large,	4682	either accept everything or return C<ENOBUFS> if the buffer is too large,
3401	so make sure you only write small amounts into your sockets (less than a	4683	so make sure you only write small amounts into your sockets (less than a
3402	megabyte seems safe, but thsi apparently depends on the amount of memory	4684	megabyte seems safe, but this apparently depends on the amount of memory
3403	available).	4685	available).
3404		4686
3405	Due to the many, low, and arbitrary limits on the win32 platform and	4687	Due to the many, low, and arbitrary limits on the win32 platform and
3406	the abysmal performance of winsockets, using a large number of sockets	4688	the abysmal performance of winsockets, using a large number of sockets
3407	is not recommended (and not reasonable). If your program needs to use	4689	is not recommended (and not reasonable). If your program needs to use
3408	more than a hundred or so sockets, then likely it needs to use a totally	4690	more than a hundred or so sockets, then likely it needs to use a totally
3409	different implementation for windows, as libev offers the POSIX readiness	4691	different implementation for windows, as libev offers the POSIX readiness
3410	notification model, which cannot be implemented efficiently on windows	4692	notification model, which cannot be implemented efficiently on windows
3411	(Microsoft monopoly games).	4693	(due to Microsoft monopoly games).
3412		4694
3413	A typical way to use libev under windows is to embed it (see the embedding	4695	A typical way to use libev under windows is to embed it (see the embedding
3414	section for details) and use the following F<evwrap.h> header file instead	4696	section for details) and use the following F<evwrap.h> header file instead
3415	of F<ev.h>:	4697	of F<ev.h>:
3416		4698
…		…
3418	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	4700	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3419		4701
3420	#include "ev.h"	4702	#include "ev.h"
3421		4703
3422	And compile the following F<evwrap.c> file into your project (make sure	4704	And compile the following F<evwrap.c> file into your project (make sure
3423	you do I<not> compile the F<ev.c> or any other embedded soruce files!):	4705	you do I<not> compile the F<ev.c> or any other embedded source files!):
3424		4706
3425	#include "evwrap.h"	4707	#include "evwrap.h"
3426	#include "ev.c"	4708	#include "ev.c"
3427		4709
3428	=over 4
3429
3430	=item The winsocket select function	4710	=head3 The winsocket C<select> function
3431		4711
3432	The winsocket C<select> function doesn't follow POSIX in that it	4712	The winsocket C<select> function doesn't follow POSIX in that it
3433	requires socket I<handles> and not socket I<file descriptors> (it is	4713	requires socket I<handles> and not socket I<file descriptors> (it is
3434	also extremely buggy). This makes select very inefficient, and also	4714	also extremely buggy). This makes select very inefficient, and also
3435	requires a mapping from file descriptors to socket handles (the Microsoft	4715	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3444	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4724	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3445		4725
3446	Note that winsockets handling of fd sets is O(n), so you can easily get a	4726	Note that winsockets handling of fd sets is O(n), so you can easily get a
3447	complexity in the O(n²) range when using win32.	4727	complexity in the O(n²) range when using win32.
3448		4728
3449	=item Limited number of file descriptors	4729	=head3 Limited number of file descriptors
3450		4730
3451	Windows has numerous arbitrary (and low) limits on things.	4731	Windows has numerous arbitrary (and low) limits on things.
3452		4732
3453	Early versions of winsocket's select only supported waiting for a maximum	4733	Early versions of winsocket's select only supported waiting for a maximum
3454	of C<64> handles (probably owning to the fact that all windows kernels	4734	of C<64> handles (probably owning to the fact that all windows kernels
3455	can only wait for C<64> things at the same time internally; Microsoft	4735	can only wait for C<64> things at the same time internally; Microsoft
3456	recommends spawning a chain of threads and wait for 63 handles and the	4736	recommends spawning a chain of threads and wait for 63 handles and the
3457	previous thread in each. Great).	4737	previous thread in each. Sounds great!).
3458		4738
3459	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4739	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3460	to some high number (e.g. C<2048>) before compiling the winsocket select	4740	to some high number (e.g. C<2048>) before compiling the winsocket select
3461	call (which might be in libev or elsewhere, for example, perl does its own	4741	call (which might be in libev or elsewhere, for example, perl and many
3462	select emulation on windows).	4742	other interpreters do their own select emulation on windows).
3463		4743
3464	Another limit is the number of file descriptors in the Microsoft runtime	4744	Another limit is the number of file descriptors in the Microsoft runtime
3465	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4745	libraries, which by default is C<64> (there must be a hidden I<64>
3466	or something like this inside Microsoft). You can increase this by calling	4746	fetish or something like this inside Microsoft). You can increase this
3467	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4747	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3468	arbitrary limit), but is broken in many versions of the Microsoft runtime	4748	(another arbitrary limit), but is broken in many versions of the Microsoft
3469	libraries.
3470
3471	This might get you to about C<512> or C<2048> sockets (depending on	4749	runtime libraries. This might get you to about C<512> or C<2048> sockets
3472	windows version and/or the phase of the moon). To get more, you need to	4750	(depending on windows version and/or the phase of the moon). To get more,
3473	wrap all I/O functions and provide your own fd management, but the cost of	4751	you need to wrap all I/O functions and provide your own fd management, but
3474	calling select (O(n²)) will likely make this unworkable.	4752	the cost of calling select (O(n²)) will likely make this unworkable.
3475		4753
3476	=back
3477
3478
3479	=head1 PORTABILITY REQUIREMENTS	4754	=head2 PORTABILITY REQUIREMENTS
3480		4755
3481	In addition to a working ISO-C implementation, libev relies on a few	4756	In addition to a working ISO-C implementation and of course the
3482	additional extensions:	4757	backend-specific APIs, libev relies on a few additional extensions:
3483		4758
3484	=over 4	4759	=over 4
3485		4760
3486	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	4761	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3487	calling conventions regardless of C<ev_watcher_type *>.	4762	calling conventions regardless of C<ev_watcher_type *>.
…		…
3490	structure (guaranteed by POSIX but not by ISO C for example), but it also	4765	structure (guaranteed by POSIX but not by ISO C for example), but it also
3491	assumes that the same (machine) code can be used to call any watcher	4766	assumes that the same (machine) code can be used to call any watcher
3492	callback: The watcher callbacks have different type signatures, but libev	4767	callback: The watcher callbacks have different type signatures, but libev
3493	calls them using an C<ev_watcher *> internally.	4768	calls them using an C<ev_watcher *> internally.
3494		4769
		4770	=item pointer accesses must be thread-atomic
		4771
		4772	Accessing a pointer value must be atomic, it must both be readable and
		4773	writable in one piece - this is the case on all current architectures.
		4774
3495	=item C<sig_atomic_t volatile> must be thread-atomic as well	4775	=item C<sig_atomic_t volatile> must be thread-atomic as well
3496		4776
3497	The type C<sig_atomic_t volatile> (or whatever is defined as	4777	The type C<sig_atomic_t volatile> (or whatever is defined as
3498	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	4778	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3499	threads. This is not part of the specification for C<sig_atomic_t>, but is	4779	threads. This is not part of the specification for C<sig_atomic_t>, but is
3500	believed to be sufficiently portable.	4780	believed to be sufficiently portable.
3501		4781
3502	=item C<sigprocmask> must work in a threaded environment	4782	=item C<sigprocmask> must work in a threaded environment
3503		4783
…		…
3512	except the initial one, and run the default loop in the initial thread as	4792	except the initial one, and run the default loop in the initial thread as
3513	well.	4793	well.
3514		4794
3515	=item C<long> must be large enough for common memory allocation sizes	4795	=item C<long> must be large enough for common memory allocation sizes
3516		4796
3517	To improve portability and simplify using libev, libev uses C<long>	4797	To improve portability and simplify its API, libev uses C<long> internally
3518	internally instead of C<size_t> when allocating its data structures. On	4798	instead of C<size_t> when allocating its data structures. On non-POSIX
3519	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4799	systems (Microsoft...) this might be unexpectedly low, but is still at
3520	is still at least 31 bits everywhere, which is enough for hundreds of	4800	least 31 bits everywhere, which is enough for hundreds of millions of
3521	millions of watchers.	4801	watchers.
3522		4802
3523	=item C<double> must hold a time value in seconds with enough accuracy	4803	=item C<double> must hold a time value in seconds with enough accuracy
3524		4804
3525	The type C<double> is used to represent timestamps. It is required to	4805	The type C<double> is used to represent timestamps. It is required to
3526	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4806	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3527	enough for at least into the year 4000. This requirement is fulfilled by	4807	good enough for at least into the year 4000 with millisecond accuracy
		4808	(the design goal for libev). This requirement is overfulfilled by
3528	implementations implementing IEEE 754 (basically all existing ones).	4809	implementations using IEEE 754, which is basically all existing ones. With
		4810	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
3529		4811
3530	=back	4812	=back
3531		4813
3532	If you know of other additional requirements drop me a note.	4814	If you know of other additional requirements drop me a note.
3533		4815
3534		4816
3535	=head1 COMPILER WARNINGS	4817	=head1 ALGORITHMIC COMPLEXITIES
3536		4818
3537	Depending on your compiler and compiler settings, you might get no or a	4819	In this section the complexities of (many of) the algorithms used inside
3538	lot of warnings when compiling libev code. Some people are apparently	4820	libev will be documented. For complexity discussions about backends see
3539	scared by this.	4821	the documentation for C<ev_default_init>.
3540		4822
3541	However, these are unavoidable for many reasons. For one, each compiler	4823	All of the following are about amortised time: If an array needs to be
3542	has different warnings, and each user has different tastes regarding	4824	extended, libev needs to realloc and move the whole array, but this
3543	warning options. "Warn-free" code therefore cannot be a goal except when	4825	happens asymptotically rarer with higher number of elements, so O(1) might
3544	targeting a specific compiler and compiler-version.	4826	mean that libev does a lengthy realloc operation in rare cases, but on
		4827	average it is much faster and asymptotically approaches constant time.
3545		4828
3546	Another reason is that some compiler warnings require elaborate	4829	=over 4
3547	workarounds, or other changes to the code that make it less clear and less
3548	maintainable.
3549		4830
3550	And of course, some compiler warnings are just plain stupid, or simply	4831	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3551	wrong (because they don't actually warn about the condition their message
3552	seems to warn about).
3553		4832
3554	While libev is written to generate as few warnings as possible,	4833	This means that, when you have a watcher that triggers in one hour and
3555	"warn-free" code is not a goal, and it is recommended not to build libev	4834	there are 100 watchers that would trigger before that, then inserting will
3556	with any compiler warnings enabled unless you are prepared to cope with	4835	have to skip roughly seven (C<ld 100>) of these watchers.
3557	them (e.g. by ignoring them). Remember that warnings are just that:
3558	warnings, not errors, or proof of bugs.
3559		4836
		4837	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3560		4838
3561	=head1 VALGRIND	4839	That means that changing a timer costs less than removing/adding them,
		4840	as only the relative motion in the event queue has to be paid for.
3562		4841
3563	Valgrind has a special section here because it is a popular tool that is	4842	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3564	highly useful, but valgrind reports are very hard to interpret.
3565		4843
3566	If you think you found a bug (memory leak, uninitialised data access etc.)	4844	These just add the watcher into an array or at the head of a list.
3567	in libev, then check twice: If valgrind reports something like:
3568		4845
3569	==2274== definitely lost: 0 bytes in 0 blocks.	4846	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3570	==2274== possibly lost: 0 bytes in 0 blocks.
3571	==2274== still reachable: 256 bytes in 1 blocks.
3572		4847
3573	Then there is no memory leak. Similarly, under some circumstances,	4848	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3574	valgrind might report kernel bugs as if it were a bug in libev, or it
3575	might be confused (it is a very good tool, but only a tool).
3576		4849
3577	If you are unsure about something, feel free to contact the mailing list	4850	These watchers are stored in lists, so they need to be walked to find the
3578	with the full valgrind report and an explanation on why you think this is	4851	correct watcher to remove. The lists are usually short (you don't usually
3579	a bug in libev. However, don't be annoyed when you get a brisk "this is	4852	have many watchers waiting for the same fd or signal: one is typical, two
3580	no bug" answer and take the chance of learning how to interpret valgrind	4853	is rare).
3581	properly.
3582		4854
3583	If you need, for some reason, empty reports from valgrind for your project	4855	=item Finding the next timer in each loop iteration: O(1)
3584	I suggest using suppression lists.
3585		4856
		4857	By virtue of using a binary or 4-heap, the next timer is always found at a
		4858	fixed position in the storage array.
		4859
		4860	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4861
		4862	A change means an I/O watcher gets started or stopped, which requires
		4863	libev to recalculate its status (and possibly tell the kernel, depending
		4864	on backend and whether C<ev_io_set> was used).
		4865
		4866	=item Activating one watcher (putting it into the pending state): O(1)
		4867
		4868	=item Priority handling: O(number_of_priorities)
		4869
		4870	Priorities are implemented by allocating some space for each
		4871	priority. When doing priority-based operations, libev usually has to
		4872	linearly search all the priorities, but starting/stopping and activating
		4873	watchers becomes O(1) with respect to priority handling.
		4874
		4875	=item Sending an ev_async: O(1)
		4876
		4877	=item Processing ev_async_send: O(number_of_async_watchers)
		4878
		4879	=item Processing signals: O(max_signal_number)
		4880
		4881	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4882	calls in the current loop iteration. Checking for async and signal events
		4883	involves iterating over all running async watchers or all signal numbers.
		4884
		4885	=back
		4886
		4887
		4888	=head1 PORTING FROM LIBEV 3.X TO 4.X
		4889
		4890	The major version 4 introduced some incompatible changes to the API.
		4891
		4892	At the moment, the C<ev.h> header file provides compatibility definitions
		4893	for all changes, so most programs should still compile. The compatibility
		4894	layer might be removed in later versions of libev, so better update to the
		4895	new API early than late.
		4896
		4897	=over 4
		4898
		4899	=item C<EV_COMPAT3> backwards compatibility mechanism
		4900
		4901	The backward compatibility mechanism can be controlled by
		4902	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		4903	section.
		4904
		4905	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		4906
		4907	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		4908
		4909	ev_loop_destroy (EV_DEFAULT_UC);
		4910	ev_loop_fork (EV_DEFAULT);
		4911
		4912	=item function/symbol renames
		4913
		4914	A number of functions and symbols have been renamed:
		4915
		4916	ev_loop => ev_run
		4917	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		4918	EVLOOP_ONESHOT => EVRUN_ONCE
		4919
		4920	ev_unloop => ev_break
		4921	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		4922	EVUNLOOP_ONE => EVBREAK_ONE
		4923	EVUNLOOP_ALL => EVBREAK_ALL
		4924
		4925	EV_TIMEOUT => EV_TIMER
		4926
		4927	ev_loop_count => ev_iteration
		4928	ev_loop_depth => ev_depth
		4929	ev_loop_verify => ev_verify
		4930
		4931	Most functions working on C<struct ev_loop> objects don't have an
		4932	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		4933	associated constants have been renamed to not collide with the C<struct
		4934	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		4935	as all other watcher types. Note that C<ev_loop_fork> is still called
		4936	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		4937	typedef.
		4938
		4939	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		4940
		4941	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		4942	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		4943	and work, but the library code will of course be larger.
		4944
		4945	=back
		4946
		4947
		4948	=head1 GLOSSARY
		4949
		4950	=over 4
		4951
		4952	=item active
		4953
		4954	A watcher is active as long as it has been started and not yet stopped.
		4955	See L<WATCHER STATES> for details.
		4956
		4957	=item application
		4958
		4959	In this document, an application is whatever is using libev.
		4960
		4961	=item backend
		4962
		4963	The part of the code dealing with the operating system interfaces.
		4964
		4965	=item callback
		4966
		4967	The address of a function that is called when some event has been
		4968	detected. Callbacks are being passed the event loop, the watcher that
		4969	received the event, and the actual event bitset.
		4970
		4971	=item callback/watcher invocation
		4972
		4973	The act of calling the callback associated with a watcher.
		4974
		4975	=item event
		4976
		4977	A change of state of some external event, such as data now being available
		4978	for reading on a file descriptor, time having passed or simply not having
		4979	any other events happening anymore.
		4980
		4981	In libev, events are represented as single bits (such as C<EV_READ> or
		4982	C<EV_TIMER>).
		4983
		4984	=item event library
		4985
		4986	A software package implementing an event model and loop.
		4987
		4988	=item event loop
		4989
		4990	An entity that handles and processes external events and converts them
		4991	into callback invocations.
		4992
		4993	=item event model
		4994
		4995	The model used to describe how an event loop handles and processes
		4996	watchers and events.
		4997
		4998	=item pending
		4999
		5000	A watcher is pending as soon as the corresponding event has been
		5001	detected. See L<WATCHER STATES> for details.
		5002
		5003	=item real time
		5004
		5005	The physical time that is observed. It is apparently strictly monotonic :)
		5006
		5007	=item wall-clock time
		5008
		5009	The time and date as shown on clocks. Unlike real time, it can actually
		5010	be wrong and jump forwards and backwards, e.g. when the you adjust your
		5011	clock.
		5012
		5013	=item watcher
		5014
		5015	A data structure that describes interest in certain events. Watchers need
		5016	to be started (attached to an event loop) before they can receive events.
		5017
		5018	=back
3586		5019
3587	=head1 AUTHOR	5020	=head1 AUTHOR
3588		5021
3589	Marc Lehmann <libev@schmorp.de>.	5022	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5023	Magnusson and Emanuele Giaquinta.
3590		5024

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