ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.184 by root, Tue Sep 23 09:11:14 2008 UTC vs.
Revision 1.346 by root, Wed Nov 10 14:50:54 2010 UTC

…		…
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
		14	#include <stdio.h> // for puts
		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
18		20
19	// all watcher callbacks have a similar signature	21	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	22	// this callback is called when data is readable on stdin
21	static void	23	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	25	{
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
28		30
29	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_run's to stop iterating
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_break (EV_A_ EVBREAK_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_run to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_break (EV_A_ EVBREAK_ONE);
40	}	42	}
41		43
42	int	44	int
43	main (void)	45	main (void)
44	{	46	{
45	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
46	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = EV_DEFAULT;
47		49
48	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
…		…
54	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
57		59
58	// now wait for events to arrive	60	// now wait for events to arrive
59	ev_loop (loop, 0);	61	ev_run (loop, 0);
60		62
61	// unloop was called, so exit	63	// unloop was called, so exit
62	return 0;	64	return 0;
63	}	65	}
64		66
65	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
66		70
67	The newest version of this document is also available as an html-formatted	71	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	72	web page you might find easier to navigate when reading it for the first
69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.	73	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		74
		75	While this document tries to be as complete as possible in documenting
		76	libev, its usage and the rationale behind its design, it is not a tutorial
		77	on event-based programming, nor will it introduce event-based programming
		78	with libev.
		79
		80	Familiarity with event based programming techniques in general is assumed
		81	throughout this document.
		82
		83	=head1 WHAT TO READ WHEN IN A HURRY
		84
		85	This manual tries to be very detailed, but unfortunately, this also makes
		86	it very long. If you just want to know the basics of libev, I suggest
		87	reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and
		88	look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and
		89	C<ev_timer> sections in L<WATCHER TYPES>.
		90
		91	=head1 ABOUT LIBEV
70		92
71	Libev is an event loop: you register interest in certain events (such as a	93	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	94	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	95	these event sources and provide your program with events.
74		96
…		…
84	=head2 FEATURES	106	=head2 FEATURES
85		107
86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	108	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	109	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	110	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	111	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
90	with customised rescheduling (C<ev_periodic>), synchronous signals	112	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
91	(C<ev_signal>), process status change events (C<ev_child>), and event	113	timers (C<ev_timer>), absolute timers with customised rescheduling
92	watchers dealing with the event loop mechanism itself (C<ev_idle>,	114	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
93	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	115	change events (C<ev_child>), and event watchers dealing with the event
94	file watchers (C<ev_stat>) and even limited support for fork events	116	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
95	(C<ev_fork>).	117	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		118	limited support for fork events (C<ev_fork>).
96		119
97	It also is quite fast (see this	120	It also is quite fast (see this
98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	121	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
99	for example).	122	for example).
100		123
…		…
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	131	name C<loop> (which is always of type C<struct ev_loop *>) will not have
109	this argument.	132	this argument.
110		133
111	=head2 TIME REPRESENTATION	134	=head2 TIME REPRESENTATION
112		135
113	Libev represents time as a single floating point number, representing the	136	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	137	the (fractional) number of seconds since the (POSIX) epoch (in practice
115	the beginning of 1970, details are complicated, don't ask). This type is	138	somewhere near the beginning of 1970, details are complicated, don't
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	139	ask). This type is called C<ev_tstamp>, which is what you should use
117	to the C<double> type in C, and when you need to do any calculations on	140	too. It usually aliases to the C<double> type in C. When you need to do
118	it, you should treat it as some floating point value. Unlike the name	141	any calculations on it, you should treat it as some floating point value.
		142
119	component C<stamp> might indicate, it is also used for time differences	143	Unlike the name component C<stamp> might indicate, it is also used for
120	throughout libev.	144	time differences (e.g. delays) throughout libev.
121		145
122	=head1 ERROR HANDLING	146	=head1 ERROR HANDLING
123		147
124	Libev knows three classes of errors: operating system errors, usage errors	148	Libev knows three classes of errors: operating system errors, usage errors
125	and internal errors (bugs).	149	and internal errors (bugs).
…		…
149		173
150	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
151		175
152	Returns the current time as libev would use it. Please note that the	176	Returns the current time as libev would use it. Please note that the
153	C<ev_now> function is usually faster and also often returns the timestamp	177	C<ev_now> function is usually faster and also often returns the timestamp
154	you actually want to know.	178	you actually want to know. Also interesting is the combination of
		179	C<ev_update_now> and C<ev_now>.
155		180
156	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
157		182
158	Sleep for the given interval: The current thread will be blocked until	183	Sleep for the given interval: The current thread will be blocked until
159	either it is interrupted or the given time interval has passed. Basically	184	either it is interrupted or the given time interval has passed. Basically
…		…
176	as this indicates an incompatible change. Minor versions are usually	201	as this indicates an incompatible change. Minor versions are usually
177	compatible to older versions, so a larger minor version alone is usually	202	compatible to older versions, so a larger minor version alone is usually
178	not a problem.	203	not a problem.
179		204
180	Example: Make sure we haven't accidentally been linked against the wrong	205	Example: Make sure we haven't accidentally been linked against the wrong
181	version.	206	version (note, however, that this will not detect other ABI mismatches,
		207	such as LFS or reentrancy).
182		208
183	assert (("libev version mismatch",	209	assert (("libev version mismatch",
184	ev_version_major () == EV_VERSION_MAJOR	210	ev_version_major () == EV_VERSION_MAJOR
185	&& ev_version_minor () >= EV_VERSION_MINOR));	211	&& ev_version_minor () >= EV_VERSION_MINOR));
186		212
…		…
197	assert (("sorry, no epoll, no sex",	223	assert (("sorry, no epoll, no sex",
198	ev_supported_backends () & EVBACKEND_EPOLL));	224	ev_supported_backends () & EVBACKEND_EPOLL));
199		225
200	=item unsigned int ev_recommended_backends ()	226	=item unsigned int ev_recommended_backends ()
201		227
202	Return the set of all backends compiled into this binary of libev and also	228	Return the set of all backends compiled into this binary of libev and
203	recommended for this platform. This set is often smaller than the one	229	also recommended for this platform, meaning it will work for most file
		230	descriptor types. This set is often smaller than the one returned by
204	returned by C<ev_supported_backends>, as for example kqueue is broken on	231	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
205	most BSDs and will not be auto-detected unless you explicitly request it	232	and will not be auto-detected unless you explicitly request it (assuming
206	(assuming you know what you are doing). This is the set of backends that	233	you know what you are doing). This is the set of backends that libev will
207	libev will probe for if you specify no backends explicitly.	234	probe for if you specify no backends explicitly.
208		235
209	=item unsigned int ev_embeddable_backends ()	236	=item unsigned int ev_embeddable_backends ()
210		237
211	Returns the set of backends that are embeddable in other event loops. This	238	Returns the set of backends that are embeddable in other event loops. This
212	is the theoretical, all-platform, value. To find which backends	239	value is platform-specific but can include backends not available on the
213	might be supported on the current system, you would need to look at	240	current system. To find which embeddable backends might be supported on
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	241	the current system, you would need to look at C<ev_embeddable_backends ()
215	recommended ones.	242	& ev_supported_backends ()>, likewise for recommended ones.
216		243
217	See the description of C<ev_embed> watchers for more info.	244	See the description of C<ev_embed> watchers for more info.
218		245
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	246	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
220		247
…		…
250	}	277	}
251		278
252	...	279	...
253	ev_set_allocator (persistent_realloc);	280	ev_set_allocator (persistent_realloc);
254		281
255	=item ev_set_syserr_cb (void (*cb)(const char *msg));	282	=item ev_set_syserr_cb (void (*cb)(const char *msg))
256		283
257	Set the callback function to call on a retryable system call error (such	284	Set the callback function to call on a retryable system call error (such
258	as failed select, poll, epoll_wait). The message is a printable string	285	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	286	indicating the system call or subsystem causing the problem. If this
260	callback is set, then libev will expect it to remedy the situation, no	287	callback is set, then libev will expect it to remedy the situation, no
…		…
274	...	301	...
275	ev_set_syserr_cb (fatal_error);	302	ev_set_syserr_cb (fatal_error);
276		303
277	=back	304	=back
278		305
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	306	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
280		307
281	An event loop is described by a C<struct ev_loop *>. The library knows two	308	An event loop is described by a C<struct ev_loop *> (the C<struct> is
282	types of such loops, the I<default> loop, which supports signals and child	309	I<not> optional in this case unless libev 3 compatibility is disabled, as
283	events, and dynamically created loops which do not.	310	libev 3 had an C<ev_loop> function colliding with the struct name).
		311
		312	The library knows two types of such loops, the I<default> loop, which
		313	supports child process events, and dynamically created event loops which
		314	do not.
284		315
285	=over 4	316	=over 4
286		317
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	318	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		319
289	This will initialise the default event loop if it hasn't been initialised	320	This returns the "default" event loop object, which is what you should
290	yet and return it. If the default loop could not be initialised, returns	321	normally use when you just need "the event loop". Event loop objects and
291	false. If it already was initialised it simply returns it (and ignores the	322	the C<flags> parameter are described in more detail in the entry for
292	flags. If that is troubling you, check C<ev_backend ()> afterwards).	323	C<ev_loop_new>.
		324
		325	If the default loop is already initialised then this function simply
		326	returns it (and ignores the flags. If that is troubling you, check
		327	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		328	flags, which should almost always be C<0>, unless the caller is also the
		329	one calling C<ev_run> or otherwise qualifies as "the main program".
293		330
294	If you don't know what event loop to use, use the one returned from this	331	If you don't know what event loop to use, use the one returned from this
295	function.	332	function (or via the C<EV_DEFAULT> macro).
296		333
297	Note that this function is I<not> thread-safe, so if you want to use it	334	Note that this function is I<not> thread-safe, so if you want to use it
298	from multiple threads, you have to lock (note also that this is unlikely,	335	from multiple threads, you have to employ some kind of mutex (note also
299	as loops cannot bes hared easily between threads anyway).	336	that this case is unlikely, as loops cannot be shared easily between
		337	threads anyway).
300		338
301	The default loop is the only loop that can handle C<ev_signal> and	339	The default loop is the only loop that can handle C<ev_child> watchers,
302	C<ev_child> watchers, and to do this, it always registers a handler	340	and to do this, it always registers a handler for C<SIGCHLD>. If this is
303	for C<SIGCHLD>. If this is a problem for your application you can either	341	a problem for your application you can either create a dynamic loop with
304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	342	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
305	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	343	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
306	C<ev_default_init>.	344
		345	Example: This is the most typical usage.
		346
		347	if (!ev_default_loop (0))
		348	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		349
		350	Example: Restrict libev to the select and poll backends, and do not allow
		351	environment settings to be taken into account:
		352
		353	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		354
		355	=item struct ev_loop *ev_loop_new (unsigned int flags)
		356
		357	This will create and initialise a new event loop object. If the loop
		358	could not be initialised, returns false.
		359
		360	This function is thread-safe, and one common way to use libev with
		361	threads is indeed to create one loop per thread, and using the default
		362	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 its 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 its 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, resulting in additional iterations
		470	(and only giving 5ms accuracy while select on the same platform gives
		471	0.1ms) and so on. The biggest issue is fork races, however - if a program
		472	forks then I<both> parent and child process have to recreate the epoll
		473	set, which can take considerable time (one syscall per file descriptor)
		474	and is of course hard to detect.
		475
		476	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		477	of course I<doesn't>, and epoll just loves to report events for totally
		478	I<different> file descriptors (even already closed ones, so one cannot
		479	even remove them from the set) than registered in the set (especially
		480	on SMP systems). Libev tries to counter these spurious notifications by
		481	employing an additional generation counter and comparing that against the
		482	events to filter out spurious ones, recreating the set when required. Last
		483	not least, it also refuses to work with some file descriptors which work
		484	perfectly fine with C<select> (files, many character devices...).
		485
		486	Epoll is truly the train wreck analog among event poll mechanisms.
389		487
390	While stopping, setting and starting an I/O watcher in the same iteration	488	While stopping, setting and starting an I/O watcher in the same iteration
391	will result in some caching, there is still a system call per such incident	489	will result in some caching, there is still a system call per such
392	(because the fd could point to a different file description now), so its	490	incident (because the same I<file descriptor> could point to a different
393	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	491	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
394	very well if you register events for both fds.	492	file descriptors might not work very well if you register events for both
395		493	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		494
400	Best performance from this backend is achieved by not unregistering all	495	Best performance from this backend is achieved by not unregistering all
401	watchers for a file descriptor until it has been closed, if possible,	496	watchers for a file descriptor until it has been closed, if possible,
402	i.e. keep at least one watcher active per fd at all times. Stopping and	497	i.e. keep at least one watcher active per fd at all times. Stopping and
403	starting a watcher (without re-setting it) also usually doesn't cause	498	starting a watcher (without re-setting it) also usually doesn't cause
404	extra overhead.	499	extra overhead. A fork can both result in spurious notifications as well
		500	as in libev having to destroy and recreate the epoll object, which can
		501	take considerable time and thus should be avoided.
		502
		503	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		504	faster than epoll for maybe up to a hundred file descriptors, depending on
		505	the usage. So sad.
405		506
406	While nominally embeddable in other event loops, this feature is broken in	507	While nominally embeddable in other event loops, this feature is broken in
407	all kernel versions tested so far.	508	all kernel versions tested so far.
408		509
409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	510	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
410	C<EVBACKEND_POLL>.	511	C<EVBACKEND_POLL>.
411		512
412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	513	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
413		514
414	Kqueue deserves special mention, as at the time of this writing, it was	515	Kqueue deserves special mention, as at the time of this writing, it
415	broken on all BSDs except NetBSD (usually it doesn't work reliably with	516	was broken on all BSDs except NetBSD (usually it doesn't work reliably
416	anything but sockets and pipes, except on Darwin, where of course it's	517	with anything but sockets and pipes, except on Darwin, where of course
417	completely useless). For this reason it's not being "auto-detected" unless	518	it's completely useless). Unlike epoll, however, whose brokenness
418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or	519	is by design, these kqueue bugs can (and eventually will) be fixed
419	libev was compiled on a known-to-be-good (-enough) system like NetBSD.	520	without API changes to existing programs. For this reason it's not being
		521	"auto-detected" unless you explicitly specify it in the flags (i.e. using
		522	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		523	system like NetBSD.
420		524
421	You still can embed kqueue into a normal poll or select backend and use it	525	You still can embed kqueue into a normal poll or select backend and use it
422	only for sockets (after having made sure that sockets work with kqueue on	526	only for sockets (after having made sure that sockets work with kqueue on
423	the target platform). See C<ev_embed> watchers for more info.	527	the target platform). See C<ev_embed> watchers for more info.
424		528
425	It scales in the same way as the epoll backend, but the interface to the	529	It scales in the same way as the epoll backend, but the interface to the
426	kernel is more efficient (which says nothing about its actual speed, of	530	kernel is more efficient (which says nothing about its actual speed, of
427	course). While stopping, setting and starting an I/O watcher does never	531	course). While stopping, setting and starting an I/O watcher does never
428	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	532	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
429	two event changes per incident. Support for C<fork ()> is very bad and it	533	two event changes per incident. Support for C<fork ()> is very bad (but
430	drops fds silently in similarly hard-to-detect cases.	534	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		535	cases
431		536
432	This backend usually performs well under most conditions.	537	This backend usually performs well under most conditions.
433		538
434	While nominally embeddable in other event loops, this doesn't work	539	While nominally embeddable in other event loops, this doesn't work
435	everywhere, so you might need to test for this. And since it is broken	540	everywhere, so you might need to test for this. And since it is broken
436	almost everywhere, you should only use it when you have a lot of sockets	541	almost everywhere, you should only use it when you have a lot of sockets
437	(for which it usually works), by embedding it into another event loop	542	(for which it usually works), by embedding it into another event loop
438	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,	543	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
439	using it only for sockets.	544	also broken on OS X)) and, did I mention it, using it only for sockets.
440		545
441	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	546	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
442	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with	547	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
443	C<NOTE_EOF>.	548	C<NOTE_EOF>.
444		549
…		…
464	might perform better.	569	might perform better.
465		570
466	On the positive side, with the exception of the spurious readiness	571	On the positive side, with the exception of the spurious readiness
467	notifications, this backend actually performed fully to specification	572	notifications, this backend actually performed fully to specification
468	in all tests and is fully embeddable, which is a rare feat among the	573	in all tests and is fully embeddable, which is a rare feat among the
469	OS-specific backends.	574	OS-specific backends (I vastly prefer correctness over speed hacks).
470		575
471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	576	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
472	C<EVBACKEND_POLL>.	577	C<EVBACKEND_POLL>.
473		578
474	=item C<EVBACKEND_ALL>	579	=item C<EVBACKEND_ALL>
…		…
479		584
480	It is definitely not recommended to use this flag.	585	It is definitely not recommended to use this flag.
481		586
482	=back	587	=back
483		588
484	If one or more of these are or'ed into the flags value, then only these	589	If one or more of the backend flags are or'ed into the flags value,
485	backends will be tried (in the reverse order as listed here). If none are	590	then only these backends will be tried (in the reverse order as listed
486	specified, all backends in C<ev_recommended_backends ()> will be tried.	591	here). If none are specified, all backends in C<ev_recommended_backends
487		592	()> will be tried.
488	Example: This is the most typical usage.
489
490	if (!ev_default_loop (0))
491	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
492
493	Example: Restrict libev to the select and poll backends, and do not allow
494	environment settings to be taken into account:
495
496	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
497
498	Example: Use whatever libev has to offer, but make sure that kqueue is
499	used if available (warning, breaks stuff, best use only with your own
500	private event loop and only if you know the OS supports your types of
501	fds):
502
503	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
504
505	=item struct ev_loop *ev_loop_new (unsigned int flags)
506
507	Similar to C<ev_default_loop>, but always creates a new event loop that is
508	always distinct from the default loop. Unlike the default loop, it cannot
509	handle signal and child watchers, and attempts to do so will be greeted by
510	undefined behaviour (or a failed assertion if assertions are enabled).
511
512	Note that this function I<is> thread-safe, and the recommended way to use
513	libev with threads is indeed to create one loop per thread, and using the
514	default loop in the "main" or "initial" thread.
515		593
516	Example: Try to create a event loop that uses epoll and nothing else.	594	Example: Try to create a event loop that uses epoll and nothing else.
517		595
518	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	596	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
519	if (!epoller)	597	if (!epoller)
520	fatal ("no epoll found here, maybe it hides under your chair");	598	fatal ("no epoll found here, maybe it hides under your chair");
521		599
		600	Example: Use whatever libev has to offer, but make sure that kqueue is
		601	used if available.
		602
		603	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		604
522	=item ev_default_destroy ()	605	=item ev_loop_destroy (loop)
523		606
524	Destroys the default loop again (frees all memory and kernel state	607	Destroys an event loop object (frees all memory and kernel state
525	etc.). None of the active event watchers will be stopped in the normal	608	etc.). None of the active event watchers will be stopped in the normal
526	sense, so e.g. C<ev_is_active> might still return true. It is your	609	sense, so e.g. C<ev_is_active> might still return true. It is your
527	responsibility to either stop all watchers cleanly yourself I<before>	610	responsibility to either stop all watchers cleanly yourself I<before>
528	calling this function, or cope with the fact afterwards (which is usually	611	calling this function, or cope with the fact afterwards (which is usually
529	the easiest thing, you can just ignore the watchers and/or C<free ()> them	612	the easiest thing, you can just ignore the watchers and/or C<free ()> them
530	for example).	613	for example).
531		614
532	Note that certain global state, such as signal state, will not be freed by	615	Note that certain global state, such as signal state (and installed signal
533	this function, and related watchers (such as signal and child watchers)	616	handlers), will not be freed by this function, and related watchers (such
534	would need to be stopped manually.	617	as signal and child watchers) would need to be stopped manually.
535		618
536	In general it is not advisable to call this function except in the	619	This function is normally used on loop objects allocated by
537	rare occasion where you really need to free e.g. the signal handling	620	C<ev_loop_new>, but it can also be used on the default loop returned by
		621	C<ev_default_loop>, in which case it is not thread-safe.
		622
		623	Note that it is not advisable to call this function on the default loop
		624	except in the rare occasion where you really need to free its resources.
538	pipe fds. If you need dynamically allocated loops it is better to use	625	If you need dynamically allocated loops it is better to use C<ev_loop_new>
539	C<ev_loop_new> and C<ev_loop_destroy>).	626	and C<ev_loop_destroy>.
540		627
541	=item ev_loop_destroy (loop)	628	=item ev_loop_fork (loop)
542		629
543	Like C<ev_default_destroy>, but destroys an event loop created by an
544	earlier call to C<ev_loop_new>.
545
546	=item ev_default_fork ()
547
548	This function sets a flag that causes subsequent C<ev_loop> iterations	630	This function sets a flag that causes subsequent C<ev_run> iterations to
549	to reinitialise the kernel state for backends that have one. Despite the	631	reinitialise the kernel state for backends that have one. Despite the
550	name, you can call it anytime, but it makes most sense after forking, in	632	name, you can call it anytime, but it makes most sense after forking, in
551	the child process (or both child and parent, but that again makes little	633	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
552	sense). You I<must> call it in the child before using any of the libev	634	child before resuming or calling C<ev_run>.
553	functions, and it will only take effect at the next C<ev_loop> iteration.	635
		636	Again, you I<have> to call it on I<any> loop that you want to re-use after
		637	a fork, I<even if you do not plan to use the loop in the parent>. This is
		638	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		639	during fork.
554		640
555	On the other hand, you only need to call this function in the child	641	On the other hand, you only need to call this function in the child
556	process if and only if you want to use the event library in the child. If	642	process if and only if you want to use the event loop in the child. If
557	you just fork+exec, you don't have to call it at all.	643	you just fork+exec or create a new loop in the child, you don't have to
		644	call it at all (in fact, C<epoll> is so badly broken that it makes a
		645	difference, but libev will usually detect this case on its own and do a
		646	costly reset of the backend).
558		647
559	The function itself is quite fast and it's usually not a problem to call	648	The function itself is quite fast and it's usually not a problem to call
560	it just in case after a fork. To make this easy, the function will fit in	649	it just in case after a fork.
561	quite nicely into a call to C<pthread_atfork>:
562		650
		651	Example: Automate calling C<ev_loop_fork> on the default loop when
		652	using pthreads.
		653
		654	static void
		655	post_fork_child (void)
		656	{
		657	ev_loop_fork (EV_DEFAULT);
		658	}
		659
		660	...
563	pthread_atfork (0, 0, ev_default_fork);	661	pthread_atfork (0, 0, post_fork_child);
564
565	=item ev_loop_fork (loop)
566
567	Like C<ev_default_fork>, but acts on an event loop created by
568	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
569	after fork that you want to re-use in the child, and how you do this is
570	entirely your own problem.
571		662
572	=item int ev_is_default_loop (loop)	663	=item int ev_is_default_loop (loop)
573		664
574	Returns true when the given loop is, in fact, the default loop, and false	665	Returns true when the given loop is, in fact, the default loop, and false
575	otherwise.	666	otherwise.
576		667
577	=item unsigned int ev_loop_count (loop)	668	=item unsigned int ev_iteration (loop)
578		669
579	Returns the count of loop iterations for the loop, which is identical to	670	Returns the current iteration count for the event loop, which is identical
580	the number of times libev did poll for new events. It starts at C<0> and	671	to the number of times libev did poll for new events. It starts at C<0>
581	happily wraps around with enough iterations.	672	and happily wraps around with enough iterations.
582		673
583	This value can sometimes be useful as a generation counter of sorts (it	674	This value can sometimes be useful as a generation counter of sorts (it
584	"ticks" the number of loop iterations), as it roughly corresponds with	675	"ticks" the number of loop iterations), as it roughly corresponds with
585	C<ev_prepare> and C<ev_check> calls.	676	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		677	prepare and check phases.
		678
		679	=item unsigned int ev_depth (loop)
		680
		681	Returns the number of times C<ev_run> was entered minus the number of
		682	times C<ev_run> was exited normally, in other words, the recursion depth.
		683
		684	Outside C<ev_run>, this number is zero. In a callback, this number is
		685	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		686	in which case it is higher.
		687
		688	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
		689	throwing an exception etc.), doesn't count as "exit" - consider this
		690	as a hint to avoid such ungentleman-like behaviour unless it's really
		691	convenient, in which case it is fully supported.
586		692
587	=item unsigned int ev_backend (loop)	693	=item unsigned int ev_backend (loop)
588		694
589	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	695	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
590	use.	696	use.
…		…
599		705
600	=item ev_now_update (loop)	706	=item ev_now_update (loop)
601		707
602	Establishes the current time by querying the kernel, updating the time	708	Establishes the current time by querying the kernel, updating the time
603	returned by C<ev_now ()> in the progress. This is a costly operation and	709	returned by C<ev_now ()> in the progress. This is a costly operation and
604	is usually done automatically within C<ev_loop ()>.	710	is usually done automatically within C<ev_run ()>.
605		711
606	This function is rarely useful, but when some event callback runs for a	712	This function is rarely useful, but when some event callback runs for a
607	very long time without entering the event loop, updating libev's idea of	713	very long time without entering the event loop, updating libev's idea of
608	the current time is a good idea.	714	the current time is a good idea.
609		715
610	See also "The special problem of time updates" in the C<ev_timer> section.	716	See also L<The special problem of time updates> in the C<ev_timer> section.
611		717
		718	=item ev_suspend (loop)
		719
		720	=item ev_resume (loop)
		721
		722	These two functions suspend and resume an event loop, for use when the
		723	loop is not used for a while and timeouts should not be processed.
		724
		725	A typical use case would be an interactive program such as a game: When
		726	the user presses C<^Z> to suspend the game and resumes it an hour later it
		727	would be best to handle timeouts as if no time had actually passed while
		728	the program was suspended. This can be achieved by calling C<ev_suspend>
		729	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		730	C<ev_resume> directly afterwards to resume timer processing.
		731
		732	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		733	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		734	will be rescheduled (that is, they will lose any events that would have
		735	occurred while suspended).
		736
		737	After calling C<ev_suspend> you B<must not> call I<any> function on the
		738	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		739	without a previous call to C<ev_suspend>.
		740
		741	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		742	event loop time (see C<ev_now_update>).
		743
612	=item ev_loop (loop, int flags)	744	=item ev_run (loop, int flags)
613		745
614	Finally, this is it, the event handler. This function usually is called	746	Finally, this is it, the event handler. This function usually is called
615	after you initialised all your watchers and you want to start handling	747	after you have initialised all your watchers and you want to start
616	events.	748	handling events. It will ask the operating system for any new events, call
		749	the watcher callbacks, an then repeat the whole process indefinitely: This
		750	is why event loops are called I<loops>.
617		751
618	If the flags argument is specified as C<0>, it will not return until	752	If the flags argument is specified as C<0>, it will keep handling events
619	either no event watchers are active anymore or C<ev_unloop> was called.	753	until either no event watchers are active anymore or C<ev_break> was
		754	called.
620		755
621	Please note that an explicit C<ev_unloop> is usually better than	756	Please note that an explicit C<ev_break> is usually better than
622	relying on all watchers to be stopped when deciding when a program has	757	relying on all watchers to be stopped when deciding when a program has
623	finished (especially in interactive programs), but having a program	758	finished (especially in interactive programs), but having a program
624	that automatically loops as long as it has to and no longer by virtue	759	that automatically loops as long as it has to and no longer by virtue
625	of relying on its watchers stopping correctly, that is truly a thing of	760	of relying on its watchers stopping correctly, that is truly a thing of
626	beauty.	761	beauty.
627		762
		763	This function is also I<mostly> exception-safe - you can break out of
		764	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		765	exception and so on. This does not decrement the C<ev_depth> value, nor
		766	will it clear any outstanding C<EVBREAK_ONE> breaks.
		767
628	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	768	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
629	those events and any already outstanding ones, but will not block your	769	those events and any already outstanding ones, but will not wait and
630	process in case there are no events and will return after one iteration of	770	block your process in case there are no events and will return after one
631	the loop.	771	iteration of the loop. This is sometimes useful to poll and handle new
		772	events while doing lengthy calculations, to keep the program responsive.
632		773
633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	774	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
634	necessary) and will handle those and any already outstanding ones. It	775	necessary) and will handle those and any already outstanding ones. It
635	will block your process until at least one new event arrives (which could	776	will block your process until at least one new event arrives (which could
636	be an event internal to libev itself, so there is no guarentee that a	777	be an event internal to libev itself, so there is no guarantee that a
637	user-registered callback will be called), and will return after one	778	user-registered callback will be called), and will return after one
638	iteration of the loop.	779	iteration of the loop.
639		780
640	This is useful if you are waiting for some external event in conjunction	781	This is useful if you are waiting for some external event in conjunction
641	with something not expressible using other libev watchers (i.e. "roll your	782	with something not expressible using other libev watchers (i.e. "roll your
642	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	783	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
643	usually a better approach for this kind of thing.	784	usually a better approach for this kind of thing.
644		785
645	Here are the gory details of what C<ev_loop> does:	786	Here are the gory details of what C<ev_run> does:
646		787
		788	- Increment loop depth.
		789	- Reset the ev_break status.
647	- Before the first iteration, call any pending watchers.	790	- Before the first iteration, call any pending watchers.
		791	LOOP:
648	* If EVFLAG_FORKCHECK was used, check for a fork.	792	- If EVFLAG_FORKCHECK was used, check for a fork.
649	- If a fork was detected (by any means), queue and call all fork watchers.	793	- If a fork was detected (by any means), queue and call all fork watchers.
650	- Queue and call all prepare watchers.	794	- Queue and call all prepare watchers.
		795	- If ev_break was called, goto FINISH.
651	- If we have been forked, detach and recreate the kernel state	796	- If we have been forked, detach and recreate the kernel state
652	as to not disturb the other process.	797	as to not disturb the other process.
653	- Update the kernel state with all outstanding changes.	798	- Update the kernel state with all outstanding changes.
654	- Update the "event loop time" (ev_now ()).	799	- Update the "event loop time" (ev_now ()).
655	- Calculate for how long to sleep or block, if at all	800	- Calculate for how long to sleep or block, if at all
656	(active idle watchers, EVLOOP_NONBLOCK or not having	801	(active idle watchers, EVRUN_NOWAIT or not having
657	any active watchers at all will result in not sleeping).	802	any active watchers at all will result in not sleeping).
658	- Sleep if the I/O and timer collect interval say so.	803	- Sleep if the I/O and timer collect interval say so.
		804	- Increment loop iteration counter.
659	- Block the process, waiting for any events.	805	- Block the process, waiting for any events.
660	- Queue all outstanding I/O (fd) events.	806	- Queue all outstanding I/O (fd) events.
661	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	807	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
662	- Queue all expired timers.	808	- Queue all expired timers.
663	- Queue all expired periodics.	809	- Queue all expired periodics.
664	- Unless any events are pending now, queue all idle watchers.	810	- Queue all idle watchers with priority higher than that of pending events.
665	- Queue all check watchers.	811	- Queue all check watchers.
666	- Call all queued watchers in reverse order (i.e. check watchers first).	812	- Call all queued watchers in reverse order (i.e. check watchers first).
667	Signals and child watchers are implemented as I/O watchers, and will	813	Signals and child watchers are implemented as I/O watchers, and will
668	be handled here by queueing them when their watcher gets executed.	814	be handled here by queueing them when their watcher gets executed.
669	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	815	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
670	were used, or there are no active watchers, return, otherwise	816	were used, or there are no active watchers, goto FINISH, otherwise
671	continue with step *.	817	continue with step LOOP.
		818	FINISH:
		819	- Reset the ev_break status iff it was EVBREAK_ONE.
		820	- Decrement the loop depth.
		821	- Return.
672		822
673	Example: Queue some jobs and then loop until no events are outstanding	823	Example: Queue some jobs and then loop until no events are outstanding
674	anymore.	824	anymore.
675		825
676	... queue jobs here, make sure they register event watchers as long	826	... queue jobs here, make sure they register event watchers as long
677	... as they still have work to do (even an idle watcher will do..)	827	... as they still have work to do (even an idle watcher will do..)
678	ev_loop (my_loop, 0);	828	ev_run (my_loop, 0);
679	... jobs done or somebody called unloop. yeah!	829	... jobs done or somebody called unloop. yeah!
680		830
681	=item ev_unloop (loop, how)	831	=item ev_break (loop, how)
682		832
683	Can be used to make a call to C<ev_loop> return early (but only after it	833	Can be used to make a call to C<ev_run> return early (but only after it
684	has processed all outstanding events). The C<how> argument must be either	834	has processed all outstanding events). The C<how> argument must be either
685	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	835	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
686	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	836	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
687		837
688	This "unloop state" will be cleared when entering C<ev_loop> again.	838	This "break state" will be cleared on the next call to C<ev_run>.
		839
		840	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		841	which case it will have no effect.
689		842
690	=item ev_ref (loop)	843	=item ev_ref (loop)
691		844
692	=item ev_unref (loop)	845	=item ev_unref (loop)
693		846
694	Ref/unref can be used to add or remove a reference count on the event	847	Ref/unref can be used to add or remove a reference count on the event
695	loop: Every watcher keeps one reference, and as long as the reference	848	loop: Every watcher keeps one reference, and as long as the reference
696	count is nonzero, C<ev_loop> will not return on its own.	849	count is nonzero, C<ev_run> will not return on its own.
697		850
698	If you have a watcher you never unregister that should not keep C<ev_loop>	851	This is useful when you have a watcher that you never intend to
699	from returning, call ev_unref() after starting, and ev_ref() before	852	unregister, but that nevertheless should not keep C<ev_run> from
		853	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
700	stopping it.	854	before stopping it.
701		855
702	As an example, libev itself uses this for its internal signal pipe: It is	856	As an example, libev itself uses this for its internal signal pipe: It
703	not visible to the libev user and should not keep C<ev_loop> from exiting	857	is not visible to the libev user and should not keep C<ev_run> from
704	if no event watchers registered by it are active. It is also an excellent	858	exiting if no event watchers registered by it are active. It is also an
705	way to do this for generic recurring timers or from within third-party	859	excellent way to do this for generic recurring timers or from within
706	libraries. Just remember to I<unref after start> and I<ref before stop>	860	third-party libraries. Just remember to I<unref after start> and I<ref
707	(but only if the watcher wasn't active before, or was active before,	861	before stop> (but only if the watcher wasn't active before, or was active
708	respectively).	862	before, respectively. Note also that libev might stop watchers itself
		863	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		864	in the callback).
709		865
710	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	866	Example: Create a signal watcher, but keep it from keeping C<ev_run>
711	running when nothing else is active.	867	running when nothing else is active.
712		868
713	struct ev_signal exitsig;	869	ev_signal exitsig;
714	ev_signal_init (&exitsig, sig_cb, SIGINT);	870	ev_signal_init (&exitsig, sig_cb, SIGINT);
715	ev_signal_start (loop, &exitsig);	871	ev_signal_start (loop, &exitsig);
716	evf_unref (loop);	872	evf_unref (loop);
717		873
718	Example: For some weird reason, unregister the above signal handler again.	874	Example: For some weird reason, unregister the above signal handler again.
…		…
742		898
743	By setting a higher I<io collect interval> you allow libev to spend more	899	By setting a higher I<io collect interval> you allow libev to spend more
744	time collecting I/O events, so you can handle more events per iteration,	900	time collecting I/O events, so you can handle more events per iteration,
745	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	901	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
746	C<ev_timer>) will be not affected. Setting this to a non-null value will	902	C<ev_timer>) will be not affected. Setting this to a non-null value will
747	introduce an additional C<ev_sleep ()> call into most loop iterations.	903	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		904	sleep time ensures that libev will not poll for I/O events more often then
		905	once per this interval, on average.
748		906
749	Likewise, by setting a higher I<timeout collect interval> you allow libev	907	Likewise, by setting a higher I<timeout collect interval> you allow libev
750	to spend more time collecting timeouts, at the expense of increased	908	to spend more time collecting timeouts, at the expense of increased
751	latency/jitter/inexactness (the watcher callback will be called	909	latency/jitter/inexactness (the watcher callback will be called
752	later). C<ev_io> watchers will not be affected. Setting this to a non-null	910	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
754		912
755	Many (busy) programs can usually benefit by setting the I/O collect	913	Many (busy) programs can usually benefit by setting the I/O collect
756	interval to a value near C<0.1> or so, which is often enough for	914	interval to a value near C<0.1> or so, which is often enough for
757	interactive servers (of course not for games), likewise for timeouts. It	915	interactive servers (of course not for games), likewise for timeouts. It
758	usually doesn't make much sense to set it to a lower value than C<0.01>,	916	usually doesn't make much sense to set it to a lower value than C<0.01>,
759	as this approaches the timing granularity of most systems.	917	as this approaches the timing granularity of most systems. Note that if
		918	you do transactions with the outside world and you can't increase the
		919	parallelity, then this setting will limit your transaction rate (if you
		920	need to poll once per transaction and the I/O collect interval is 0.01,
		921	then you can't do more than 100 transactions per second).
760		922
761	Setting the I<timeout collect interval> can improve the opportunity for	923	Setting the I<timeout collect interval> can improve the opportunity for
762	saving power, as the program will "bundle" timer callback invocations that	924	saving power, as the program will "bundle" timer callback invocations that
763	are "near" in time together, by delaying some, thus reducing the number of	925	are "near" in time together, by delaying some, thus reducing the number of
764	times the process sleeps and wakes up again. Another useful technique to	926	times the process sleeps and wakes up again. Another useful technique to
765	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	927	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
766	they fire on, say, one-second boundaries only.	928	they fire on, say, one-second boundaries only.
767		929
		930	Example: we only need 0.1s timeout granularity, and we wish not to poll
		931	more often than 100 times per second:
		932
		933	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		934	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		935
		936	=item ev_invoke_pending (loop)
		937
		938	This call will simply invoke all pending watchers while resetting their
		939	pending state. Normally, C<ev_run> does this automatically when required,
		940	but when overriding the invoke callback this call comes handy. This
		941	function can be invoked from a watcher - this can be useful for example
		942	when you want to do some lengthy calculation and want to pass further
		943	event handling to another thread (you still have to make sure only one
		944	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		945
		946	=item int ev_pending_count (loop)
		947
		948	Returns the number of pending watchers - zero indicates that no watchers
		949	are pending.
		950
		951	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		952
		953	This overrides the invoke pending functionality of the loop: Instead of
		954	invoking all pending watchers when there are any, C<ev_run> will call
		955	this callback instead. This is useful, for example, when you want to
		956	invoke the actual watchers inside another context (another thread etc.).
		957
		958	If you want to reset the callback, use C<ev_invoke_pending> as new
		959	callback.
		960
		961	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		962
		963	Sometimes you want to share the same loop between multiple threads. This
		964	can be done relatively simply by putting mutex_lock/unlock calls around
		965	each call to a libev function.
		966
		967	However, C<ev_run> can run an indefinite time, so it is not feasible
		968	to wait for it to return. One way around this is to wake up the event
		969	loop via C<ev_break> and C<av_async_send>, another way is to set these
		970	I<release> and I<acquire> callbacks on the loop.
		971
		972	When set, then C<release> will be called just before the thread is
		973	suspended waiting for new events, and C<acquire> is called just
		974	afterwards.
		975
		976	Ideally, C<release> will just call your mutex_unlock function, and
		977	C<acquire> will just call the mutex_lock function again.
		978
		979	While event loop modifications are allowed between invocations of
		980	C<release> and C<acquire> (that's their only purpose after all), no
		981	modifications done will affect the event loop, i.e. adding watchers will
		982	have no effect on the set of file descriptors being watched, or the time
		983	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		984	to take note of any changes you made.
		985
		986	In theory, threads executing C<ev_run> will be async-cancel safe between
		987	invocations of C<release> and C<acquire>.
		988
		989	See also the locking example in the C<THREADS> section later in this
		990	document.
		991
		992	=item ev_set_userdata (loop, void *data)
		993
		994	=item void *ev_userdata (loop)
		995
		996	Set and retrieve a single C<void *> associated with a loop. When
		997	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		998	C<0>.
		999
		1000	These two functions can be used to associate arbitrary data with a loop,
		1001	and are intended solely for the C<invoke_pending_cb>, C<release> and
		1002	C<acquire> callbacks described above, but of course can be (ab-)used for
		1003	any other purpose as well.
		1004
768	=item ev_loop_verify (loop)	1005	=item ev_verify (loop)
769		1006
770	This function only does something when C<EV_VERIFY> support has been	1007	This function only does something when C<EV_VERIFY> support has been
771	compiled in. which is the default for non-minimal builds. It tries to go	1008	compiled in, which is the default for non-minimal builds. It tries to go
772	through all internal structures and checks them for validity. If anything	1009	through all internal structures and checks them for validity. If anything
773	is found to be inconsistent, it will print an error message to standard	1010	is found to be inconsistent, it will print an error message to standard
774	error and call C<abort ()>.	1011	error and call C<abort ()>.
775		1012
776	This can be used to catch bugs inside libev itself: under normal	1013	This can be used to catch bugs inside libev itself: under normal
…		…
780	=back	1017	=back
781		1018
782		1019
783	=head1 ANATOMY OF A WATCHER	1020	=head1 ANATOMY OF A WATCHER
784		1021
		1022	In the following description, uppercase C<TYPE> in names stands for the
		1023	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		1024	watchers and C<ev_io_start> for I/O watchers.
		1025
785	A watcher is a structure that you create and register to record your	1026	A watcher is an opaque structure that you allocate and register to record
786	interest in some event. For instance, if you want to wait for STDIN to	1027	your interest in some event. To make a concrete example, imagine you want
787	become readable, you would create an C<ev_io> watcher for that:	1028	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1029	for that:
788		1030
789	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1031	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
790	{	1032	{
791	ev_io_stop (w);	1033	ev_io_stop (w);
792	ev_unloop (loop, EVUNLOOP_ALL);	1034	ev_break (loop, EVBREAK_ALL);
793	}	1035	}
794		1036
795	struct ev_loop *loop = ev_default_loop (0);	1037	struct ev_loop *loop = ev_default_loop (0);
		1038
796	struct ev_io stdin_watcher;	1039	ev_io stdin_watcher;
		1040
797	ev_init (&stdin_watcher, my_cb);	1041	ev_init (&stdin_watcher, my_cb);
798	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1042	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
799	ev_io_start (loop, &stdin_watcher);	1043	ev_io_start (loop, &stdin_watcher);
		1044
800	ev_loop (loop, 0);	1045	ev_run (loop, 0);
801		1046
802	As you can see, you are responsible for allocating the memory for your	1047	As you can see, you are responsible for allocating the memory for your
803	watcher structures (and it is usually a bad idea to do this on the stack,	1048	watcher structures (and it is I<usually> a bad idea to do this on the
804	although this can sometimes be quite valid).	1049	stack).
805		1050
		1051	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		1052	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
		1053
806	Each watcher structure must be initialised by a call to C<ev_init	1054	Each watcher structure must be initialised by a call to C<ev_init (watcher
807	(watcher *, callback)>, which expects a callback to be provided. This	1055	*, callback)>, which expects a callback to be provided. This callback is
808	callback gets invoked each time the event occurs (or, in the case of I/O	1056	invoked each time the event occurs (or, in the case of I/O watchers, each
809	watchers, each time the event loop detects that the file descriptor given	1057	time the event loop detects that the file descriptor given is readable
810	is readable and/or writable).	1058	and/or writable).
811		1059
812	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1060	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
813	with arguments specific to this watcher type. There is also a macro	1061	macro to configure it, with arguments specific to the watcher type. There
814	to combine initialisation and setting in one call: C<< ev_<type>_init	1062	is also a macro to combine initialisation and setting in one call: C<<
815	(watcher *, callback, ...) >>.	1063	ev_TYPE_init (watcher *, callback, ...) >>.
816		1064
817	To make the watcher actually watch out for events, you have to start it	1065	To make the watcher actually watch out for events, you have to start it
818	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	1066	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
819	*) >>), and you can stop watching for events at any time by calling the	1067	*) >>), and you can stop watching for events at any time by calling the
820	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1068	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
821		1069
822	As long as your watcher is active (has been started but not stopped) you	1070	As long as your watcher is active (has been started but not stopped) you
823	must not touch the values stored in it. Most specifically you must never	1071	must not touch the values stored in it. Most specifically you must never
824	reinitialise it or call its C<set> macro.	1072	reinitialise it or call its C<ev_TYPE_set> macro.
825		1073
826	Each and every callback receives the event loop pointer as first, the	1074	Each and every callback receives the event loop pointer as first, the
827	registered watcher structure as second, and a bitset of received events as	1075	registered watcher structure as second, and a bitset of received events as
828	third argument.	1076	third argument.
829		1077
…		…
838	=item C<EV_WRITE>	1086	=item C<EV_WRITE>
839		1087
840	The file descriptor in the C<ev_io> watcher has become readable and/or	1088	The file descriptor in the C<ev_io> watcher has become readable and/or
841	writable.	1089	writable.
842		1090
843	=item C<EV_TIMEOUT>	1091	=item C<EV_TIMER>
844		1092
845	The C<ev_timer> watcher has timed out.	1093	The C<ev_timer> watcher has timed out.
846		1094
847	=item C<EV_PERIODIC>	1095	=item C<EV_PERIODIC>
848		1096
…		…
866		1114
867	=item C<EV_PREPARE>	1115	=item C<EV_PREPARE>
868		1116
869	=item C<EV_CHECK>	1117	=item C<EV_CHECK>
870		1118
871	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1119	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
872	to gather new events, and all C<ev_check> watchers are invoked just after	1120	to gather new events, and all C<ev_check> watchers are invoked just after
873	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1121	C<ev_run> has gathered them, but before it invokes any callbacks for any
874	received events. Callbacks of both watcher types can start and stop as	1122	received events. Callbacks of both watcher types can start and stop as
875	many watchers as they want, and all of them will be taken into account	1123	many watchers as they want, and all of them will be taken into account
876	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1124	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
877	C<ev_loop> from blocking).	1125	C<ev_run> from blocking).
878		1126
879	=item C<EV_EMBED>	1127	=item C<EV_EMBED>
880		1128
881	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1129	The embedded event loop specified in the C<ev_embed> watcher needs attention.
882		1130
883	=item C<EV_FORK>	1131	=item C<EV_FORK>
884		1132
885	The event loop has been resumed in the child process after fork (see	1133	The event loop has been resumed in the child process after fork (see
886	C<ev_fork>).	1134	C<ev_fork>).
887		1135
		1136	=item C<EV_CLEANUP>
		1137
		1138	The event loop is about to be destroyed (see C<ev_cleanup>).
		1139
888	=item C<EV_ASYNC>	1140	=item C<EV_ASYNC>
889		1141
890	The given async watcher has been asynchronously notified (see C<ev_async>).	1142	The given async watcher has been asynchronously notified (see C<ev_async>).
		1143
		1144	=item C<EV_CUSTOM>
		1145
		1146	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1147	by libev users to signal watchers (e.g. via C<ev_feed_event>).
891		1148
892	=item C<EV_ERROR>	1149	=item C<EV_ERROR>
893		1150
894	An unspecified error has occurred, the watcher has been stopped. This might	1151	An unspecified error has occurred, the watcher has been stopped. This might
895	happen because the watcher could not be properly started because libev	1152	happen because the watcher could not be properly started because libev
896	ran out of memory, a file descriptor was found to be closed or any other	1153	ran out of memory, a file descriptor was found to be closed or any other
		1154	problem. Libev considers these application bugs.
		1155
897	problem. You best act on it by reporting the problem and somehow coping	1156	You best act on it by reporting the problem and somehow coping with the
898	with the watcher being stopped.	1157	watcher being stopped. Note that well-written programs should not receive
		1158	an error ever, so when your watcher receives it, this usually indicates a
		1159	bug in your program.
899		1160
900	Libev will usually signal a few "dummy" events together with an error, for	1161	Libev will usually signal a few "dummy" events together with an error, for
901	example it might indicate that a fd is readable or writable, and if your	1162	example it might indicate that a fd is readable or writable, and if your
902	callbacks is well-written it can just attempt the operation and cope with	1163	callbacks is well-written it can just attempt the operation and cope with
903	the error from read() or write(). This will not work in multi-threaded	1164	the error from read() or write(). This will not work in multi-threaded
…		…
906		1167
907	=back	1168	=back
908		1169
909	=head2 GENERIC WATCHER FUNCTIONS	1170	=head2 GENERIC WATCHER FUNCTIONS
910		1171
911	In the following description, C<TYPE> stands for the watcher type,
912	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
913
914	=over 4	1172	=over 4
915		1173
916	=item C<ev_init> (ev_TYPE *watcher, callback)	1174	=item C<ev_init> (ev_TYPE *watcher, callback)
917		1175
918	This macro initialises the generic portion of a watcher. The contents	1176	This macro initialises the generic portion of a watcher. The contents
…		…
923	which rolls both calls into one.	1181	which rolls both calls into one.
924		1182
925	You can reinitialise a watcher at any time as long as it has been stopped	1183	You can reinitialise a watcher at any time as long as it has been stopped
926	(or never started) and there are no pending events outstanding.	1184	(or never started) and there are no pending events outstanding.
927		1185
928	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1186	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
929	int revents)>.	1187	int revents)>.
930		1188
931	Example: Initialise an C<ev_io> watcher in two steps.	1189	Example: Initialise an C<ev_io> watcher in two steps.
932		1190
933	ev_io w;	1191	ev_io w;
934	ev_init (&w, my_cb);	1192	ev_init (&w, my_cb);
935	ev_io_set (&w, STDIN_FILENO, EV_READ);	1193	ev_io_set (&w, STDIN_FILENO, EV_READ);
936		1194
937	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1195	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
938		1196
939	This macro initialises the type-specific parts of a watcher. You need to	1197	This macro initialises the type-specific parts of a watcher. You need to
940	call C<ev_init> at least once before you call this macro, but you can	1198	call C<ev_init> at least once before you call this macro, but you can
941	call C<ev_TYPE_set> any number of times. You must not, however, call this	1199	call C<ev_TYPE_set> any number of times. You must not, however, call this
942	macro on a watcher that is active (it can be pending, however, which is a	1200	macro on a watcher that is active (it can be pending, however, which is a
…		…
955		1213
956	Example: Initialise and set an C<ev_io> watcher in one step.	1214	Example: Initialise and set an C<ev_io> watcher in one step.
957		1215
958	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1216	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
959		1217
960	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1218	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
961		1219
962	Starts (activates) the given watcher. Only active watchers will receive	1220	Starts (activates) the given watcher. Only active watchers will receive
963	events. If the watcher is already active nothing will happen.	1221	events. If the watcher is already active nothing will happen.
964		1222
965	Example: Start the C<ev_io> watcher that is being abused as example in this	1223	Example: Start the C<ev_io> watcher that is being abused as example in this
966	whole section.	1224	whole section.
967		1225
968	ev_io_start (EV_DEFAULT_UC, &w);	1226	ev_io_start (EV_DEFAULT_UC, &w);
969		1227
970	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1228	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
971		1229
972	Stops the given watcher again (if active) and clears the pending	1230	Stops the given watcher if active, and clears the pending status (whether
		1231	the watcher was active or not).
		1232
973	status. It is possible that stopped watchers are pending (for example,	1233	It is possible that stopped watchers are pending - for example,
974	non-repeating timers are being stopped when they become pending), but	1234	non-repeating timers are being stopped when they become pending - but
975	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1235	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
976	you want to free or reuse the memory used by the watcher it is therefore a	1236	pending. If you want to free or reuse the memory used by the watcher it is
977	good idea to always call its C<ev_TYPE_stop> function.	1237	therefore a good idea to always call its C<ev_TYPE_stop> function.
978		1238
979	=item bool ev_is_active (ev_TYPE *watcher)	1239	=item bool ev_is_active (ev_TYPE *watcher)
980		1240
981	Returns a true value iff the watcher is active (i.e. it has been started	1241	Returns a true value iff the watcher is active (i.e. it has been started
982	and not yet been stopped). As long as a watcher is active you must not modify	1242	and not yet been stopped). As long as a watcher is active you must not modify
…		…
998	=item ev_cb_set (ev_TYPE *watcher, callback)	1258	=item ev_cb_set (ev_TYPE *watcher, callback)
999		1259
1000	Change the callback. You can change the callback at virtually any time	1260	Change the callback. You can change the callback at virtually any time
1001	(modulo threads).	1261	(modulo threads).
1002		1262
1003	=item ev_set_priority (ev_TYPE *watcher, priority)	1263	=item ev_set_priority (ev_TYPE *watcher, int priority)
1004		1264
1005	=item int ev_priority (ev_TYPE *watcher)	1265	=item int ev_priority (ev_TYPE *watcher)
1006		1266
1007	Set and query the priority of the watcher. The priority is a small	1267	Set and query the priority of the watcher. The priority is a small
1008	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1268	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1009	(default: C<-2>). Pending watchers with higher priority will be invoked	1269	(default: C<-2>). Pending watchers with higher priority will be invoked
1010	before watchers with lower priority, but priority will not keep watchers	1270	before watchers with lower priority, but priority will not keep watchers
1011	from being executed (except for C<ev_idle> watchers).	1271	from being executed (except for C<ev_idle> watchers).
1012		1272
1013	This means that priorities are I<only> used for ordering callback
1014	invocation after new events have been received. This is useful, for
1015	example, to reduce latency after idling, or more often, to bind two
1016	watchers on the same event and make sure one is called first.
1017
1018	If you need to suppress invocation when higher priority events are pending	1273	If you need to suppress invocation when higher priority events are pending
1019	you need to look at C<ev_idle> watchers, which provide this functionality.	1274	you need to look at C<ev_idle> watchers, which provide this functionality.
1020		1275
1021	You I<must not> change the priority of a watcher as long as it is active or	1276	You I<must not> change the priority of a watcher as long as it is active or
1022	pending.	1277	pending.
1023		1278
		1279	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1280	fine, as long as you do not mind that the priority value you query might
		1281	or might not have been clamped to the valid range.
		1282
1024	The default priority used by watchers when no priority has been set is	1283	The default priority used by watchers when no priority has been set is
1025	always C<0>, which is supposed to not be too high and not be too low :).	1284	always C<0>, which is supposed to not be too high and not be too low :).
1026		1285
1027	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1286	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1028	fine, as long as you do not mind that the priority value you query might	1287	priorities.
1029	or might not have been adjusted to be within valid range.
1030		1288
1031	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1289	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1032		1290
1033	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1291	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1034	C<loop> nor C<revents> need to be valid as long as the watcher callback	1292	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1042	watcher isn't pending it does nothing and returns C<0>.	1300	watcher isn't pending it does nothing and returns C<0>.
1043		1301
1044	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1302	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1045	callback to be invoked, which can be accomplished with this function.	1303	callback to be invoked, which can be accomplished with this function.
1046		1304
		1305	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1306
		1307	Feeds the given event set into the event loop, as if the specified event
		1308	had happened for the specified watcher (which must be a pointer to an
		1309	initialised but not necessarily started event watcher). Obviously you must
		1310	not free the watcher as long as it has pending events.
		1311
		1312	Stopping the watcher, letting libev invoke it, or calling
		1313	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1314	not started in the first place.
		1315
		1316	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1317	functions that do not need a watcher.
		1318
1047	=back	1319	=back
1048
1049		1320
1050	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1321	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1051		1322
1052	Each watcher has, by default, a member C<void *data> that you can change	1323	Each watcher has, by default, a member C<void *data> that you can change
1053	and read at any time: libev will completely ignore it. This can be used	1324	and read at any time: libev will completely ignore it. This can be used
…		…
1056	member, you can also "subclass" the watcher type and provide your own	1327	member, you can also "subclass" the watcher type and provide your own
1057	data:	1328	data:
1058		1329
1059	struct my_io	1330	struct my_io
1060	{	1331	{
1061	struct ev_io io;	1332	ev_io io;
1062	int otherfd;	1333	int otherfd;
1063	void *somedata;	1334	void *somedata;
1064	struct whatever *mostinteresting;	1335	struct whatever *mostinteresting;
1065	};	1336	};
1066		1337
…		…
1069	ev_io_init (&w.io, my_cb, fd, EV_READ);	1340	ev_io_init (&w.io, my_cb, fd, EV_READ);
1070		1341
1071	And since your callback will be called with a pointer to the watcher, you	1342	And since your callback will be called with a pointer to the watcher, you
1072	can cast it back to your own type:	1343	can cast it back to your own type:
1073		1344
1074	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1345	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1075	{	1346	{
1076	struct my_io *w = (struct my_io *)w_;	1347	struct my_io *w = (struct my_io *)w_;
1077	...	1348	...
1078	}	1349	}
1079		1350
…		…
1097	programmers):	1368	programmers):
1098		1369
1099	#include <stddef.h>	1370	#include <stddef.h>
1100		1371
1101	static void	1372	static void
1102	t1_cb (EV_P_ struct ev_timer *w, int revents)	1373	t1_cb (EV_P_ ev_timer *w, int revents)
1103	{	1374	{
1104	struct my_biggy big = (struct my_biggy *	1375	struct my_biggy big = (struct my_biggy *)
1105	(((char *)w) - offsetof (struct my_biggy, t1));	1376	(((char *)w) - offsetof (struct my_biggy, t1));
1106	}	1377	}
1107		1378
1108	static void	1379	static void
1109	t2_cb (EV_P_ struct ev_timer *w, int revents)	1380	t2_cb (EV_P_ ev_timer *w, int revents)
1110	{	1381	{
1111	struct my_biggy big = (struct my_biggy *	1382	struct my_biggy big = (struct my_biggy *)
1112	(((char *)w) - offsetof (struct my_biggy, t2));	1383	(((char *)w) - offsetof (struct my_biggy, t2));
1113	}	1384	}
		1385
		1386	=head2 WATCHER STATES
		1387
		1388	There are various watcher states mentioned throughout this manual -
		1389	active, pending and so on. In this section these states and the rules to
		1390	transition between them will be described in more detail - and while these
		1391	rules might look complicated, they usually do "the right thing".
		1392
		1393	=over 4
		1394
		1395	=item initialiased
		1396
		1397	Before a watcher can be registered with the event looop it has to be
		1398	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1399	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1400
		1401	In this state it is simply some block of memory that is suitable for use
		1402	in an event loop. It can be moved around, freed, reused etc. at will.
		1403
		1404	=item started/running/active
		1405
		1406	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1407	property of the event loop, and is actively waiting for events. While in
		1408	this state it cannot be accessed (except in a few documented ways), moved,
		1409	freed or anything else - the only legal thing is to keep a pointer to it,
		1410	and call libev functions on it that are documented to work on active watchers.
		1411
		1412	=item pending
		1413
		1414	If a watcher is active and libev determines that an event it is interested
		1415	in has occurred (such as a timer expiring), it will become pending. It will
		1416	stay in this pending state until either it is stopped or its callback is
		1417	about to be invoked, so it is not normally pending inside the watcher
		1418	callback.
		1419
		1420	The watcher might or might not be active while it is pending (for example,
		1421	an expired non-repeating timer can be pending but no longer active). If it
		1422	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1423	but it is still property of the event loop at this time, so cannot be
		1424	moved, freed or reused. And if it is active the rules described in the
		1425	previous item still apply.
		1426
		1427	It is also possible to feed an event on a watcher that is not active (e.g.
		1428	via C<ev_feed_event>), in which case it becomes pending without being
		1429	active.
		1430
		1431	=item stopped
		1432
		1433	A watcher can be stopped implicitly by libev (in which case it might still
		1434	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1435	latter will clear any pending state the watcher might be in, regardless
		1436	of whether it was active or not, so stopping a watcher explicitly before
		1437	freeing it is often a good idea.
		1438
		1439	While stopped (and not pending) the watcher is essentially in the
		1440	initialised state, that is it can be reused, moved, modified in any way
		1441	you wish.
		1442
		1443	=back
		1444
		1445	=head2 WATCHER PRIORITY MODELS
		1446
		1447	Many event loops support I<watcher priorities>, which are usually small
		1448	integers that influence the ordering of event callback invocation
		1449	between watchers in some way, all else being equal.
		1450
		1451	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1452	description for the more technical details such as the actual priority
		1453	range.
		1454
		1455	There are two common ways how these these priorities are being interpreted
		1456	by event loops:
		1457
		1458	In the more common lock-out model, higher priorities "lock out" invocation
		1459	of lower priority watchers, which means as long as higher priority
		1460	watchers receive events, lower priority watchers are not being invoked.
		1461
		1462	The less common only-for-ordering model uses priorities solely to order
		1463	callback invocation within a single event loop iteration: Higher priority
		1464	watchers are invoked before lower priority ones, but they all get invoked
		1465	before polling for new events.
		1466
		1467	Libev uses the second (only-for-ordering) model for all its watchers
		1468	except for idle watchers (which use the lock-out model).
		1469
		1470	The rationale behind this is that implementing the lock-out model for
		1471	watchers is not well supported by most kernel interfaces, and most event
		1472	libraries will just poll for the same events again and again as long as
		1473	their callbacks have not been executed, which is very inefficient in the
		1474	common case of one high-priority watcher locking out a mass of lower
		1475	priority ones.
		1476
		1477	Static (ordering) priorities are most useful when you have two or more
		1478	watchers handling the same resource: a typical usage example is having an
		1479	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1480	timeouts. Under load, data might be received while the program handles
		1481	other jobs, but since timers normally get invoked first, the timeout
		1482	handler will be executed before checking for data. In that case, giving
		1483	the timer a lower priority than the I/O watcher ensures that I/O will be
		1484	handled first even under adverse conditions (which is usually, but not
		1485	always, what you want).
		1486
		1487	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1488	will only be executed when no same or higher priority watchers have
		1489	received events, they can be used to implement the "lock-out" model when
		1490	required.
		1491
		1492	For example, to emulate how many other event libraries handle priorities,
		1493	you can associate an C<ev_idle> watcher to each such watcher, and in
		1494	the normal watcher callback, you just start the idle watcher. The real
		1495	processing is done in the idle watcher callback. This causes libev to
		1496	continuously poll and process kernel event data for the watcher, but when
		1497	the lock-out case is known to be rare (which in turn is rare :), this is
		1498	workable.
		1499
		1500	Usually, however, the lock-out model implemented that way will perform
		1501	miserably under the type of load it was designed to handle. In that case,
		1502	it might be preferable to stop the real watcher before starting the
		1503	idle watcher, so the kernel will not have to process the event in case
		1504	the actual processing will be delayed for considerable time.
		1505
		1506	Here is an example of an I/O watcher that should run at a strictly lower
		1507	priority than the default, and which should only process data when no
		1508	other events are pending:
		1509
		1510	ev_idle idle; // actual processing watcher
		1511	ev_io io; // actual event watcher
		1512
		1513	static void
		1514	io_cb (EV_P_ ev_io *w, int revents)
		1515	{
		1516	// stop the I/O watcher, we received the event, but
		1517	// are not yet ready to handle it.
		1518	ev_io_stop (EV_A_ w);
		1519
		1520	// start the idle watcher to handle the actual event.
		1521	// it will not be executed as long as other watchers
		1522	// with the default priority are receiving events.
		1523	ev_idle_start (EV_A_ &idle);
		1524	}
		1525
		1526	static void
		1527	idle_cb (EV_P_ ev_idle *w, int revents)
		1528	{
		1529	// actual processing
		1530	read (STDIN_FILENO, ...);
		1531
		1532	// have to start the I/O watcher again, as
		1533	// we have handled the event
		1534	ev_io_start (EV_P_ &io);
		1535	}
		1536
		1537	// initialisation
		1538	ev_idle_init (&idle, idle_cb);
		1539	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1540	ev_io_start (EV_DEFAULT_ &io);
		1541
		1542	In the "real" world, it might also be beneficial to start a timer, so that
		1543	low-priority connections can not be locked out forever under load. This
		1544	enables your program to keep a lower latency for important connections
		1545	during short periods of high load, while not completely locking out less
		1546	important ones.
1114		1547
1115		1548
1116	=head1 WATCHER TYPES	1549	=head1 WATCHER TYPES
1117		1550
1118	This section describes each watcher in detail, but will not repeat	1551	This section describes each watcher in detail, but will not repeat
…		…
1144	descriptors to non-blocking mode is also usually a good idea (but not	1577	descriptors to non-blocking mode is also usually a good idea (but not
1145	required if you know what you are doing).	1578	required if you know what you are doing).
1146		1579
1147	If you cannot use non-blocking mode, then force the use of a	1580	If you cannot use non-blocking mode, then force the use of a
1148	known-to-be-good backend (at the time of this writing, this includes only	1581	known-to-be-good backend (at the time of this writing, this includes only
1149	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).	1582	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1583	descriptors for which non-blocking operation makes no sense (such as
		1584	files) - libev doesn't guarantee any specific behaviour in that case.
1150		1585
1151	Another thing you have to watch out for is that it is quite easy to	1586	Another thing you have to watch out for is that it is quite easy to
1152	receive "spurious" readiness notifications, that is your callback might	1587	receive "spurious" readiness notifications, that is your callback might
1153	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1588	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1154	because there is no data. Not only are some backends known to create a	1589	because there is no data. Not only are some backends known to create a
…		…
1219		1654
1220	So when you encounter spurious, unexplained daemon exits, make sure you	1655	So when you encounter spurious, unexplained daemon exits, make sure you
1221	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1656	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1222	somewhere, as that would have given you a big clue).	1657	somewhere, as that would have given you a big clue).
1223		1658
		1659	=head3 The special problem of accept()ing when you can't
		1660
		1661	Many implementations of the POSIX C<accept> function (for example,
		1662	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1663	connection from the pending queue in all error cases.
		1664
		1665	For example, larger servers often run out of file descriptors (because
		1666	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1667	rejecting the connection, leading to libev signalling readiness on
		1668	the next iteration again (the connection still exists after all), and
		1669	typically causing the program to loop at 100% CPU usage.
		1670
		1671	Unfortunately, the set of errors that cause this issue differs between
		1672	operating systems, there is usually little the app can do to remedy the
		1673	situation, and no known thread-safe method of removing the connection to
		1674	cope with overload is known (to me).
		1675
		1676	One of the easiest ways to handle this situation is to just ignore it
		1677	- when the program encounters an overload, it will just loop until the
		1678	situation is over. While this is a form of busy waiting, no OS offers an
		1679	event-based way to handle this situation, so it's the best one can do.
		1680
		1681	A better way to handle the situation is to log any errors other than
		1682	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1683	messages, and continue as usual, which at least gives the user an idea of
		1684	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1685	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1686	usage.
		1687
		1688	If your program is single-threaded, then you could also keep a dummy file
		1689	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1690	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1691	close that fd, and create a new dummy fd. This will gracefully refuse
		1692	clients under typical overload conditions.
		1693
		1694	The last way to handle it is to simply log the error and C<exit>, as
		1695	is often done with C<malloc> failures, but this results in an easy
		1696	opportunity for a DoS attack.
1224		1697
1225	=head3 Watcher-Specific Functions	1698	=head3 Watcher-Specific Functions
1226		1699
1227	=over 4	1700	=over 4
1228		1701
…		…
1249	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1722	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1250	readable, but only once. Since it is likely line-buffered, you could	1723	readable, but only once. Since it is likely line-buffered, you could
1251	attempt to read a whole line in the callback.	1724	attempt to read a whole line in the callback.
1252		1725
1253	static void	1726	static void
1254	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1727	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1255	{	1728	{
1256	ev_io_stop (loop, w);	1729	ev_io_stop (loop, w);
1257	.. read from stdin here (or from w->fd) and handle any I/O errors	1730	.. read from stdin here (or from w->fd) and handle any I/O errors
1258	}	1731	}
1259		1732
1260	...	1733	...
1261	struct ev_loop *loop = ev_default_init (0);	1734	struct ev_loop *loop = ev_default_init (0);
1262	struct ev_io stdin_readable;	1735	ev_io stdin_readable;
1263	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1736	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1264	ev_io_start (loop, &stdin_readable);	1737	ev_io_start (loop, &stdin_readable);
1265	ev_loop (loop, 0);	1738	ev_run (loop, 0);
1266		1739
1267		1740
1268	=head2 C<ev_timer> - relative and optionally repeating timeouts	1741	=head2 C<ev_timer> - relative and optionally repeating timeouts
1269		1742
1270	Timer watchers are simple relative timers that generate an event after a	1743	Timer watchers are simple relative timers that generate an event after a
…		…
1275	year, it will still time out after (roughly) one hour. "Roughly" because	1748	year, it will still time out after (roughly) one hour. "Roughly" because
1276	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1749	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1277	monotonic clock option helps a lot here).	1750	monotonic clock option helps a lot here).
1278		1751
1279	The callback is guaranteed to be invoked only I<after> its timeout has	1752	The callback is guaranteed to be invoked only I<after> its timeout has
1280	passed, but if multiple timers become ready during the same loop iteration	1753	passed (not I<at>, so on systems with very low-resolution clocks this
1281	then order of execution is undefined.	1754	might introduce a small delay). If multiple timers become ready during the
		1755	same loop iteration then the ones with earlier time-out values are invoked
		1756	before ones of the same priority with later time-out values (but this is
		1757	no longer true when a callback calls C<ev_run> recursively).
		1758
		1759	=head3 Be smart about timeouts
		1760
		1761	Many real-world problems involve some kind of timeout, usually for error
		1762	recovery. A typical example is an HTTP request - if the other side hangs,
		1763	you want to raise some error after a while.
		1764
		1765	What follows are some ways to handle this problem, from obvious and
		1766	inefficient to smart and efficient.
		1767
		1768	In the following, a 60 second activity timeout is assumed - a timeout that
		1769	gets reset to 60 seconds each time there is activity (e.g. each time some
		1770	data or other life sign was received).
		1771
		1772	=over 4
		1773
		1774	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1775
		1776	This is the most obvious, but not the most simple way: In the beginning,
		1777	start the watcher:
		1778
		1779	ev_timer_init (timer, callback, 60., 0.);
		1780	ev_timer_start (loop, timer);
		1781
		1782	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1783	and start it again:
		1784
		1785	ev_timer_stop (loop, timer);
		1786	ev_timer_set (timer, 60., 0.);
		1787	ev_timer_start (loop, timer);
		1788
		1789	This is relatively simple to implement, but means that each time there is
		1790	some activity, libev will first have to remove the timer from its internal
		1791	data structure and then add it again. Libev tries to be fast, but it's
		1792	still not a constant-time operation.
		1793
		1794	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1795
		1796	This is the easiest way, and involves using C<ev_timer_again> instead of
		1797	C<ev_timer_start>.
		1798
		1799	To implement this, configure an C<ev_timer> with a C<repeat> value
		1800	of C<60> and then call C<ev_timer_again> at start and each time you
		1801	successfully read or write some data. If you go into an idle state where
		1802	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1803	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1804
		1805	That means you can ignore both the C<ev_timer_start> function and the
		1806	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1807	member and C<ev_timer_again>.
		1808
		1809	At start:
		1810
		1811	ev_init (timer, callback);
		1812	timer->repeat = 60.;
		1813	ev_timer_again (loop, timer);
		1814
		1815	Each time there is some activity:
		1816
		1817	ev_timer_again (loop, timer);
		1818
		1819	It is even possible to change the time-out on the fly, regardless of
		1820	whether the watcher is active or not:
		1821
		1822	timer->repeat = 30.;
		1823	ev_timer_again (loop, timer);
		1824
		1825	This is slightly more efficient then stopping/starting the timer each time
		1826	you want to modify its timeout value, as libev does not have to completely
		1827	remove and re-insert the timer from/into its internal data structure.
		1828
		1829	It is, however, even simpler than the "obvious" way to do it.
		1830
		1831	=item 3. Let the timer time out, but then re-arm it as required.
		1832
		1833	This method is more tricky, but usually most efficient: Most timeouts are
		1834	relatively long compared to the intervals between other activity - in
		1835	our example, within 60 seconds, there are usually many I/O events with
		1836	associated activity resets.
		1837
		1838	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1839	but remember the time of last activity, and check for a real timeout only
		1840	within the callback:
		1841
		1842	ev_tstamp last_activity; // time of last activity
		1843
		1844	static void
		1845	callback (EV_P_ ev_timer *w, int revents)
		1846	{
		1847	ev_tstamp now = ev_now (EV_A);
		1848	ev_tstamp timeout = last_activity + 60.;
		1849
		1850	// if last_activity + 60. is older than now, we did time out
		1851	if (timeout < now)
		1852	{
		1853	// timeout occurred, take action
		1854	}
		1855	else
		1856	{
		1857	// callback was invoked, but there was some activity, re-arm
		1858	// the watcher to fire in last_activity + 60, which is
		1859	// guaranteed to be in the future, so "again" is positive:
		1860	w->repeat = timeout - now;
		1861	ev_timer_again (EV_A_ w);
		1862	}
		1863	}
		1864
		1865	To summarise the callback: first calculate the real timeout (defined
		1866	as "60 seconds after the last activity"), then check if that time has
		1867	been reached, which means something I<did>, in fact, time out. Otherwise
		1868	the callback was invoked too early (C<timeout> is in the future), so
		1869	re-schedule the timer to fire at that future time, to see if maybe we have
		1870	a timeout then.
		1871
		1872	Note how C<ev_timer_again> is used, taking advantage of the
		1873	C<ev_timer_again> optimisation when the timer is already running.
		1874
		1875	This scheme causes more callback invocations (about one every 60 seconds
		1876	minus half the average time between activity), but virtually no calls to
		1877	libev to change the timeout.
		1878
		1879	To start the timer, simply initialise the watcher and set C<last_activity>
		1880	to the current time (meaning we just have some activity :), then call the
		1881	callback, which will "do the right thing" and start the timer:
		1882
		1883	ev_init (timer, callback);
		1884	last_activity = ev_now (loop);
		1885	callback (loop, timer, EV_TIMER);
		1886
		1887	And when there is some activity, simply store the current time in
		1888	C<last_activity>, no libev calls at all:
		1889
		1890	last_activity = ev_now (loop);
		1891
		1892	This technique is slightly more complex, but in most cases where the
		1893	time-out is unlikely to be triggered, much more efficient.
		1894
		1895	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1896	callback :) - just change the timeout and invoke the callback, which will
		1897	fix things for you.
		1898
		1899	=item 4. Wee, just use a double-linked list for your timeouts.
		1900
		1901	If there is not one request, but many thousands (millions...), all
		1902	employing some kind of timeout with the same timeout value, then one can
		1903	do even better:
		1904
		1905	When starting the timeout, calculate the timeout value and put the timeout
		1906	at the I<end> of the list.
		1907
		1908	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1909	the list is expected to fire (for example, using the technique #3).
		1910
		1911	When there is some activity, remove the timer from the list, recalculate
		1912	the timeout, append it to the end of the list again, and make sure to
		1913	update the C<ev_timer> if it was taken from the beginning of the list.
		1914
		1915	This way, one can manage an unlimited number of timeouts in O(1) time for
		1916	starting, stopping and updating the timers, at the expense of a major
		1917	complication, and having to use a constant timeout. The constant timeout
		1918	ensures that the list stays sorted.
		1919
		1920	=back
		1921
		1922	So which method the best?
		1923
		1924	Method #2 is a simple no-brain-required solution that is adequate in most
		1925	situations. Method #3 requires a bit more thinking, but handles many cases
		1926	better, and isn't very complicated either. In most case, choosing either
		1927	one is fine, with #3 being better in typical situations.
		1928
		1929	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1930	rather complicated, but extremely efficient, something that really pays
		1931	off after the first million or so of active timers, i.e. it's usually
		1932	overkill :)
1282		1933
1283	=head3 The special problem of time updates	1934	=head3 The special problem of time updates
1284		1935
1285	Establishing the current time is a costly operation (it usually takes at	1936	Establishing the current time is a costly operation (it usually takes at
1286	least two system calls): EV therefore updates its idea of the current	1937	least two system calls): EV therefore updates its idea of the current
1287	time only before and after C<ev_loop> collects new events, which causes a	1938	time only before and after C<ev_run> collects new events, which causes a
1288	growing difference between C<ev_now ()> and C<ev_time ()> when handling	1939	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1289	lots of events in one iteration.	1940	lots of events in one iteration.
1290		1941
1291	The relative timeouts are calculated relative to the C<ev_now ()>	1942	The relative timeouts are calculated relative to the C<ev_now ()>
1292	time. This is usually the right thing as this timestamp refers to the time	1943	time. This is usually the right thing as this timestamp refers to the time
…		…
1298		1949
1299	If the event loop is suspended for a long time, you can also force an	1950	If the event loop is suspended for a long time, you can also force an
1300	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1951	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1301	()>.	1952	()>.
1302		1953
		1954	=head3 The special problems of suspended animation
		1955
		1956	When you leave the server world it is quite customary to hit machines that
		1957	can suspend/hibernate - what happens to the clocks during such a suspend?
		1958
		1959	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1960	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1961	to run until the system is suspended, but they will not advance while the
		1962	system is suspended. That means, on resume, it will be as if the program
		1963	was frozen for a few seconds, but the suspend time will not be counted
		1964	towards C<ev_timer> when a monotonic clock source is used. The real time
		1965	clock advanced as expected, but if it is used as sole clocksource, then a
		1966	long suspend would be detected as a time jump by libev, and timers would
		1967	be adjusted accordingly.
		1968
		1969	I would not be surprised to see different behaviour in different between
		1970	operating systems, OS versions or even different hardware.
		1971
		1972	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1973	time jump in the monotonic clocks and the realtime clock. If the program
		1974	is suspended for a very long time, and monotonic clock sources are in use,
		1975	then you can expect C<ev_timer>s to expire as the full suspension time
		1976	will be counted towards the timers. When no monotonic clock source is in
		1977	use, then libev will again assume a timejump and adjust accordingly.
		1978
		1979	It might be beneficial for this latter case to call C<ev_suspend>
		1980	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1981	deterministic behaviour in this case (you can do nothing against
		1982	C<SIGSTOP>).
		1983
1303	=head3 Watcher-Specific Functions and Data Members	1984	=head3 Watcher-Specific Functions and Data Members
1304		1985
1305	=over 4	1986	=over 4
1306		1987
1307	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1988	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1330	If the timer is started but non-repeating, stop it (as if it timed out).	2011	If the timer is started but non-repeating, stop it (as if it timed out).
1331		2012
1332	If the timer is repeating, either start it if necessary (with the	2013	If the timer is repeating, either start it if necessary (with the
1333	C<repeat> value), or reset the running timer to the C<repeat> value.	2014	C<repeat> value), or reset the running timer to the C<repeat> value.
1334		2015
1335	This sounds a bit complicated, but here is a useful and typical	2016	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1336	example: Imagine you have a TCP connection and you want a so-called idle	2017	usage example.
1337	timeout, that is, you want to be called when there have been, say, 60
1338	seconds of inactivity on the socket. The easiest way to do this is to
1339	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1340	C<ev_timer_again> each time you successfully read or write some data. If
1341	you go into an idle state where you do not expect data to travel on the
1342	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1343	automatically restart it if need be.
1344		2018
1345	That means you can ignore the C<after> value and C<ev_timer_start>	2019	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1346	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1347		2020
1348	ev_timer_init (timer, callback, 0., 5.);	2021	Returns the remaining time until a timer fires. If the timer is active,
1349	ev_timer_again (loop, timer);	2022	then this time is relative to the current event loop time, otherwise it's
1350	...	2023	the timeout value currently configured.
1351	timer->again = 17.;
1352	ev_timer_again (loop, timer);
1353	...
1354	timer->again = 10.;
1355	ev_timer_again (loop, timer);
1356		2024
1357	This is more slightly efficient then stopping/starting the timer each time	2025	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1358	you want to modify its timeout value.	2026	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
1359		2027	will return C<4>. When the timer expires and is restarted, it will return
1360	Note, however, that it is often even more efficient to remember the	2028	roughly C<7> (likely slightly less as callback invocation takes some time,
1361	time of the last activity and let the timer time-out naturally. In the	2029	too), and so on.
1362	callback, you then check whether the time-out is real, or, if there was
1363	some activity, you reschedule the watcher to time-out in "last_activity +
1364	timeout - ev_now ()" seconds.
1365		2030
1366	=item ev_tstamp repeat [read-write]	2031	=item ev_tstamp repeat [read-write]
1367		2032
1368	The current C<repeat> value. Will be used each time the watcher times out	2033	The current C<repeat> value. Will be used each time the watcher times out
1369	or C<ev_timer_again> is called, and determines the next timeout (if any),	2034	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1374	=head3 Examples	2039	=head3 Examples
1375		2040
1376	Example: Create a timer that fires after 60 seconds.	2041	Example: Create a timer that fires after 60 seconds.
1377		2042
1378	static void	2043	static void
1379	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2044	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1380	{	2045	{
1381	.. one minute over, w is actually stopped right here	2046	.. one minute over, w is actually stopped right here
1382	}	2047	}
1383		2048
1384	struct ev_timer mytimer;	2049	ev_timer mytimer;
1385	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	2050	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1386	ev_timer_start (loop, &mytimer);	2051	ev_timer_start (loop, &mytimer);
1387		2052
1388	Example: Create a timeout timer that times out after 10 seconds of	2053	Example: Create a timeout timer that times out after 10 seconds of
1389	inactivity.	2054	inactivity.
1390		2055
1391	static void	2056	static void
1392	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2057	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1393	{	2058	{
1394	.. ten seconds without any activity	2059	.. ten seconds without any activity
1395	}	2060	}
1396		2061
1397	struct ev_timer mytimer;	2062	ev_timer mytimer;
1398	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2063	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1399	ev_timer_again (&mytimer); /* start timer */	2064	ev_timer_again (&mytimer); /* start timer */
1400	ev_loop (loop, 0);	2065	ev_run (loop, 0);
1401		2066
1402	// and in some piece of code that gets executed on any "activity":	2067	// and in some piece of code that gets executed on any "activity":
1403	// reset the timeout to start ticking again at 10 seconds	2068	// reset the timeout to start ticking again at 10 seconds
1404	ev_timer_again (&mytimer);	2069	ev_timer_again (&mytimer);
1405		2070
…		…
1407	=head2 C<ev_periodic> - to cron or not to cron?	2072	=head2 C<ev_periodic> - to cron or not to cron?
1408		2073
1409	Periodic watchers are also timers of a kind, but they are very versatile	2074	Periodic watchers are also timers of a kind, but they are very versatile
1410	(and unfortunately a bit complex).	2075	(and unfortunately a bit complex).
1411		2076
1412	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2077	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1413	but on wall clock time (absolute time). You can tell a periodic watcher	2078	relative time, the physical time that passes) but on wall clock time
1414	to trigger after some specific point in time. For example, if you tell a	2079	(absolute time, the thing you can read on your calender or clock). The
1415	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	2080	difference is that wall clock time can run faster or slower than real
1416	+ 10.>, that is, an absolute time not a delay) and then reset your system	2081	time, and time jumps are not uncommon (e.g. when you adjust your
1417	clock to January of the previous year, then it will take more than year	2082	wrist-watch).
1418	to trigger the event (unlike an C<ev_timer>, which would still trigger
1419	roughly 10 seconds later as it uses a relative timeout).
1420		2083
		2084	You can tell a periodic watcher to trigger after some specific point
		2085	in time: for example, if you tell a periodic watcher to trigger "in 10
		2086	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2087	not a delay) and then reset your system clock to January of the previous
		2088	year, then it will take a year or more to trigger the event (unlike an
		2089	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2090	it, as it uses a relative timeout).
		2091
1421	C<ev_periodic>s can also be used to implement vastly more complex timers,	2092	C<ev_periodic> watchers can also be used to implement vastly more complex
1422	such as triggering an event on each "midnight, local time", or other	2093	timers, such as triggering an event on each "midnight, local time", or
1423	complicated rules.	2094	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2095	those cannot react to time jumps.
1424		2096
1425	As with timers, the callback is guaranteed to be invoked only when the	2097	As with timers, the callback is guaranteed to be invoked only when the
1426	time (C<at>) has passed, but if multiple periodic timers become ready	2098	point in time where it is supposed to trigger has passed. If multiple
1427	during the same loop iteration, then order of execution is undefined.	2099	timers become ready during the same loop iteration then the ones with
		2100	earlier time-out values are invoked before ones with later time-out values
		2101	(but this is no longer true when a callback calls C<ev_run> recursively).
1428		2102
1429	=head3 Watcher-Specific Functions and Data Members	2103	=head3 Watcher-Specific Functions and Data Members
1430		2104
1431	=over 4	2105	=over 4
1432		2106
1433	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2107	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1434		2108
1435	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2109	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1436		2110
1437	Lots of arguments, lets sort it out... There are basically three modes of	2111	Lots of arguments, let's sort it out... There are basically three modes of
1438	operation, and we will explain them from simplest to most complex:	2112	operation, and we will explain them from simplest to most complex:
1439		2113
1440	=over 4	2114	=over 4
1441		2115
1442	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2116	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1443		2117
1444	In this configuration the watcher triggers an event after the wall clock	2118	In this configuration the watcher triggers an event after the wall clock
1445	time C<at> has passed. It will not repeat and will not adjust when a time	2119	time C<offset> has passed. It will not repeat and will not adjust when a
1446	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2120	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1447	only run when the system clock reaches or surpasses this time.	2121	will be stopped and invoked when the system clock reaches or surpasses
		2122	this point in time.
1448		2123
1449	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2124	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1450		2125
1451	In this mode the watcher will always be scheduled to time out at the next	2126	In this mode the watcher will always be scheduled to time out at the next
1452	C<at + N * interval> time (for some integer N, which can also be negative)	2127	C<offset + N * interval> time (for some integer N, which can also be
1453	and then repeat, regardless of any time jumps.	2128	negative) and then repeat, regardless of any time jumps. The C<offset>
		2129	argument is merely an offset into the C<interval> periods.
1454		2130
1455	This can be used to create timers that do not drift with respect to the	2131	This can be used to create timers that do not drift with respect to the
1456	system clock, for example, here is a C<ev_periodic> that triggers each	2132	system clock, for example, here is an C<ev_periodic> that triggers each
1457	hour, on the hour:	2133	hour, on the hour (with respect to UTC):
1458		2134
1459	ev_periodic_set (&periodic, 0., 3600., 0);	2135	ev_periodic_set (&periodic, 0., 3600., 0);
1460		2136
1461	This doesn't mean there will always be 3600 seconds in between triggers,	2137	This doesn't mean there will always be 3600 seconds in between triggers,
1462	but only that the callback will be called when the system time shows a	2138	but only that the callback will be called when the system time shows a
1463	full hour (UTC), or more correctly, when the system time is evenly divisible	2139	full hour (UTC), or more correctly, when the system time is evenly divisible
1464	by 3600.	2140	by 3600.
1465		2141
1466	Another way to think about it (for the mathematically inclined) is that	2142	Another way to think about it (for the mathematically inclined) is that
1467	C<ev_periodic> will try to run the callback in this mode at the next possible	2143	C<ev_periodic> will try to run the callback in this mode at the next possible
1468	time where C<time = at (mod interval)>, regardless of any time jumps.	2144	time where C<time = offset (mod interval)>, regardless of any time jumps.
1469		2145
1470	For numerical stability it is preferable that the C<at> value is near	2146	For numerical stability it is preferable that the C<offset> value is near
1471	C<ev_now ()> (the current time), but there is no range requirement for	2147	C<ev_now ()> (the current time), but there is no range requirement for
1472	this value, and in fact is often specified as zero.	2148	this value, and in fact is often specified as zero.
1473		2149
1474	Note also that there is an upper limit to how often a timer can fire (CPU	2150	Note also that there is an upper limit to how often a timer can fire (CPU
1475	speed for example), so if C<interval> is very small then timing stability	2151	speed for example), so if C<interval> is very small then timing stability
1476	will of course deteriorate. Libev itself tries to be exact to be about one	2152	will of course deteriorate. Libev itself tries to be exact to be about one
1477	millisecond (if the OS supports it and the machine is fast enough).	2153	millisecond (if the OS supports it and the machine is fast enough).
1478		2154
1479	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2155	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1480		2156
1481	In this mode the values for C<interval> and C<at> are both being	2157	In this mode the values for C<interval> and C<offset> are both being
1482	ignored. Instead, each time the periodic watcher gets scheduled, the	2158	ignored. Instead, each time the periodic watcher gets scheduled, the
1483	reschedule callback will be called with the watcher as first, and the	2159	reschedule callback will be called with the watcher as first, and the
1484	current time as second argument.	2160	current time as second argument.
1485		2161
1486	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2162	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1487	ever, or make ANY event loop modifications whatsoever>.	2163	or make ANY other event loop modifications whatsoever, unless explicitly
		2164	allowed by documentation here>.
1488		2165
1489	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2166	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1490	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2167	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1491	only event loop modification you are allowed to do).	2168	only event loop modification you are allowed to do).
1492		2169
1493	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	2170	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1494	*w, ev_tstamp now)>, e.g.:	2171	*w, ev_tstamp now)>, e.g.:
1495		2172
		2173	static ev_tstamp
1496	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	2174	my_rescheduler (ev_periodic *w, ev_tstamp now)
1497	{	2175	{
1498	return now + 60.;	2176	return now + 60.;
1499	}	2177	}
1500		2178
1501	It must return the next time to trigger, based on the passed time value	2179	It must return the next time to trigger, based on the passed time value
…		…
1521	a different time than the last time it was called (e.g. in a crond like	2199	a different time than the last time it was called (e.g. in a crond like
1522	program when the crontabs have changed).	2200	program when the crontabs have changed).
1523		2201
1524	=item ev_tstamp ev_periodic_at (ev_periodic *)	2202	=item ev_tstamp ev_periodic_at (ev_periodic *)
1525		2203
1526	When active, returns the absolute time that the watcher is supposed to	2204	When active, returns the absolute time that the watcher is supposed
1527	trigger next.	2205	to trigger next. This is not the same as the C<offset> argument to
		2206	C<ev_periodic_set>, but indeed works even in interval and manual
		2207	rescheduling modes.
1528		2208
1529	=item ev_tstamp offset [read-write]	2209	=item ev_tstamp offset [read-write]
1530		2210
1531	When repeating, this contains the offset value, otherwise this is the	2211	When repeating, this contains the offset value, otherwise this is the
1532	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2212	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2213	although libev might modify this value for better numerical stability).
1533		2214
1534	Can be modified any time, but changes only take effect when the periodic	2215	Can be modified any time, but changes only take effect when the periodic
1535	timer fires or C<ev_periodic_again> is being called.	2216	timer fires or C<ev_periodic_again> is being called.
1536		2217
1537	=item ev_tstamp interval [read-write]	2218	=item ev_tstamp interval [read-write]
1538		2219
1539	The current interval value. Can be modified any time, but changes only	2220	The current interval value. Can be modified any time, but changes only
1540	take effect when the periodic timer fires or C<ev_periodic_again> is being	2221	take effect when the periodic timer fires or C<ev_periodic_again> is being
1541	called.	2222	called.
1542		2223
1543	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2224	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1544		2225
1545	The current reschedule callback, or C<0>, if this functionality is	2226	The current reschedule callback, or C<0>, if this functionality is
1546	switched off. Can be changed any time, but changes only take effect when	2227	switched off. Can be changed any time, but changes only take effect when
1547	the periodic timer fires or C<ev_periodic_again> is being called.	2228	the periodic timer fires or C<ev_periodic_again> is being called.
1548		2229
…		…
1553	Example: Call a callback every hour, or, more precisely, whenever the	2234	Example: Call a callback every hour, or, more precisely, whenever the
1554	system time is divisible by 3600. The callback invocation times have	2235	system time is divisible by 3600. The callback invocation times have
1555	potentially a lot of jitter, but good long-term stability.	2236	potentially a lot of jitter, but good long-term stability.
1556		2237
1557	static void	2238	static void
1558	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2239	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1559	{	2240	{
1560	... its now a full hour (UTC, or TAI or whatever your clock follows)	2241	... its now a full hour (UTC, or TAI or whatever your clock follows)
1561	}	2242	}
1562		2243
1563	struct ev_periodic hourly_tick;	2244	ev_periodic hourly_tick;
1564	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2245	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1565	ev_periodic_start (loop, &hourly_tick);	2246	ev_periodic_start (loop, &hourly_tick);
1566		2247
1567	Example: The same as above, but use a reschedule callback to do it:	2248	Example: The same as above, but use a reschedule callback to do it:
1568		2249
1569	#include <math.h>	2250	#include <math.h>
1570		2251
1571	static ev_tstamp	2252	static ev_tstamp
1572	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2253	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1573	{	2254	{
1574	return now + (3600. - fmod (now, 3600.));	2255	return now + (3600. - fmod (now, 3600.));
1575	}	2256	}
1576		2257
1577	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2258	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1578		2259
1579	Example: Call a callback every hour, starting now:	2260	Example: Call a callback every hour, starting now:
1580		2261
1581	struct ev_periodic hourly_tick;	2262	ev_periodic hourly_tick;
1582	ev_periodic_init (&hourly_tick, clock_cb,	2263	ev_periodic_init (&hourly_tick, clock_cb,
1583	fmod (ev_now (loop), 3600.), 3600., 0);	2264	fmod (ev_now (loop), 3600.), 3600., 0);
1584	ev_periodic_start (loop, &hourly_tick);	2265	ev_periodic_start (loop, &hourly_tick);
1585		2266
1586		2267
1587	=head2 C<ev_signal> - signal me when a signal gets signalled!	2268	=head2 C<ev_signal> - signal me when a signal gets signalled!
1588		2269
1589	Signal watchers will trigger an event when the process receives a specific	2270	Signal watchers will trigger an event when the process receives a specific
1590	signal one or more times. Even though signals are very asynchronous, libev	2271	signal one or more times. Even though signals are very asynchronous, libev
1591	will try it's best to deliver signals synchronously, i.e. as part of the	2272	will try its best to deliver signals synchronously, i.e. as part of the
1592	normal event processing, like any other event.	2273	normal event processing, like any other event.
1593		2274
1594	If you want signals asynchronously, just use C<sigaction> as you would	2275	If you want signals to be delivered truly asynchronously, just use
1595	do without libev and forget about sharing the signal. You can even use	2276	C<sigaction> as you would do without libev and forget about sharing
1596	C<ev_async> from a signal handler to synchronously wake up an event loop.	2277	the signal. You can even use C<ev_async> from a signal handler to
		2278	synchronously wake up an event loop.
1597		2279
1598	You can configure as many watchers as you like per signal. Only when the	2280	You can configure as many watchers as you like for the same signal, but
		2281	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2282	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2283	C<SIGINT> in both the default loop and another loop at the same time. At
		2284	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2285
1599	first watcher gets started will libev actually register a signal handler	2286	When the first watcher gets started will libev actually register something
1600	with the kernel (thus it coexists with your own signal handlers as long as	2287	with the kernel (thus it coexists with your own signal handlers as long as
1601	you don't register any with libev for the same signal). Similarly, when	2288	you don't register any with libev for the same signal).
1602	the last signal watcher for a signal is stopped, libev will reset the
1603	signal handler to SIG_DFL (regardless of what it was set to before).
1604		2289
1605	If possible and supported, libev will install its handlers with	2290	If possible and supported, libev will install its handlers with
1606	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2291	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1607	interrupted. If you have a problem with system calls getting interrupted by	2292	not be unduly interrupted. If you have a problem with system calls getting
1608	signals you can block all signals in an C<ev_check> watcher and unblock	2293	interrupted by signals you can block all signals in an C<ev_check> watcher
1609	them in an C<ev_prepare> watcher.	2294	and unblock them in an C<ev_prepare> watcher.
		2295
		2296	=head3 The special problem of inheritance over fork/execve/pthread_create
		2297
		2298	Both the signal mask (C<sigprocmask>) and the signal disposition
		2299	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2300	stopping it again), that is, libev might or might not block the signal,
		2301	and might or might not set or restore the installed signal handler.
		2302
		2303	While this does not matter for the signal disposition (libev never
		2304	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2305	C<execve>), this matters for the signal mask: many programs do not expect
		2306	certain signals to be blocked.
		2307
		2308	This means that before calling C<exec> (from the child) you should reset
		2309	the signal mask to whatever "default" you expect (all clear is a good
		2310	choice usually).
		2311
		2312	The simplest way to ensure that the signal mask is reset in the child is
		2313	to install a fork handler with C<pthread_atfork> that resets it. That will
		2314	catch fork calls done by libraries (such as the libc) as well.
		2315
		2316	In current versions of libev, the signal will not be blocked indefinitely
		2317	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2318	the window of opportunity for problems, it will not go away, as libev
		2319	I<has> to modify the signal mask, at least temporarily.
		2320
		2321	So I can't stress this enough: I<If you do not reset your signal mask when
		2322	you expect it to be empty, you have a race condition in your code>. This
		2323	is not a libev-specific thing, this is true for most event libraries.
1610		2324
1611	=head3 Watcher-Specific Functions and Data Members	2325	=head3 Watcher-Specific Functions and Data Members
1612		2326
1613	=over 4	2327	=over 4
1614		2328
…		…
1625		2339
1626	=back	2340	=back
1627		2341
1628	=head3 Examples	2342	=head3 Examples
1629		2343
1630	Example: Try to exit cleanly on SIGINT and SIGTERM.	2344	Example: Try to exit cleanly on SIGINT.
1631		2345
1632	static void	2346	static void
1633	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2347	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1634	{	2348	{
1635	ev_unloop (loop, EVUNLOOP_ALL);	2349	ev_break (loop, EVBREAK_ALL);
1636	}	2350	}
1637		2351
1638	struct ev_signal signal_watcher;	2352	ev_signal signal_watcher;
1639	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2353	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1640	ev_signal_start (loop, &sigint_cb);	2354	ev_signal_start (loop, &signal_watcher);
1641		2355
1642		2356
1643	=head2 C<ev_child> - watch out for process status changes	2357	=head2 C<ev_child> - watch out for process status changes
1644		2358
1645	Child watchers trigger when your process receives a SIGCHLD in response to	2359	Child watchers trigger when your process receives a SIGCHLD in response to
1646	some child status changes (most typically when a child of yours dies or	2360	some child status changes (most typically when a child of yours dies or
1647	exits). It is permissible to install a child watcher I<after> the child	2361	exits). It is permissible to install a child watcher I<after> the child
1648	has been forked (which implies it might have already exited), as long	2362	has been forked (which implies it might have already exited), as long
1649	as the event loop isn't entered (or is continued from a watcher), i.e.,	2363	as the event loop isn't entered (or is continued from a watcher), i.e.,
1650	forking and then immediately registering a watcher for the child is fine,	2364	forking and then immediately registering a watcher for the child is fine,
1651	but forking and registering a watcher a few event loop iterations later is	2365	but forking and registering a watcher a few event loop iterations later or
1652	not.	2366	in the next callback invocation is not.
1653		2367
1654	Only the default event loop is capable of handling signals, and therefore	2368	Only the default event loop is capable of handling signals, and therefore
1655	you can only register child watchers in the default event loop.	2369	you can only register child watchers in the default event loop.
1656		2370
		2371	Due to some design glitches inside libev, child watchers will always be
		2372	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2373	libev)
		2374
1657	=head3 Process Interaction	2375	=head3 Process Interaction
1658		2376
1659	Libev grabs C<SIGCHLD> as soon as the default event loop is	2377	Libev grabs C<SIGCHLD> as soon as the default event loop is
1660	initialised. This is necessary to guarantee proper behaviour even if	2378	initialised. This is necessary to guarantee proper behaviour even if the
1661	the first child watcher is started after the child exits. The occurrence	2379	first child watcher is started after the child exits. The occurrence
1662	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2380	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1663	synchronously as part of the event loop processing. Libev always reaps all	2381	synchronously as part of the event loop processing. Libev always reaps all
1664	children, even ones not watched.	2382	children, even ones not watched.
1665		2383
1666	=head3 Overriding the Built-In Processing	2384	=head3 Overriding the Built-In Processing
…		…
1676	=head3 Stopping the Child Watcher	2394	=head3 Stopping the Child Watcher
1677		2395
1678	Currently, the child watcher never gets stopped, even when the	2396	Currently, the child watcher never gets stopped, even when the
1679	child terminates, so normally one needs to stop the watcher in the	2397	child terminates, so normally one needs to stop the watcher in the
1680	callback. Future versions of libev might stop the watcher automatically	2398	callback. Future versions of libev might stop the watcher automatically
1681	when a child exit is detected.	2399	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2400	problem).
1682		2401
1683	=head3 Watcher-Specific Functions and Data Members	2402	=head3 Watcher-Specific Functions and Data Members
1684		2403
1685	=over 4	2404	=over 4
1686		2405
…		…
1718	its completion.	2437	its completion.
1719		2438
1720	ev_child cw;	2439	ev_child cw;
1721		2440
1722	static void	2441	static void
1723	child_cb (EV_P_ struct ev_child *w, int revents)	2442	child_cb (EV_P_ ev_child *w, int revents)
1724	{	2443	{
1725	ev_child_stop (EV_A_ w);	2444	ev_child_stop (EV_A_ w);
1726	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2445	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1727	}	2446	}
1728		2447
…		…
1743		2462
1744		2463
1745	=head2 C<ev_stat> - did the file attributes just change?	2464	=head2 C<ev_stat> - did the file attributes just change?
1746		2465
1747	This watches a file system path for attribute changes. That is, it calls	2466	This watches a file system path for attribute changes. That is, it calls
1748	C<stat> regularly (or when the OS says it changed) and sees if it changed	2467	C<stat> on that path in regular intervals (or when the OS says it changed)
1749	compared to the last time, invoking the callback if it did.	2468	and sees if it changed compared to the last time, invoking the callback if
		2469	it did.
1750		2470
1751	The path does not need to exist: changing from "path exists" to "path does	2471	The path does not need to exist: changing from "path exists" to "path does
1752	not exist" is a status change like any other. The condition "path does	2472	not exist" is a status change like any other. The condition "path does not
1753	not exist" is signified by the C<st_nlink> field being zero (which is	2473	exist" (or more correctly "path cannot be stat'ed") is signified by the
1754	otherwise always forced to be at least one) and all the other fields of	2474	C<st_nlink> field being zero (which is otherwise always forced to be at
1755	the stat buffer having unspecified contents.	2475	least one) and all the other fields of the stat buffer having unspecified
		2476	contents.
1756		2477
1757	The path I<should> be absolute and I<must not> end in a slash. If it is	2478	The path I<must not> end in a slash or contain special components such as
		2479	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1758	relative and your working directory changes, the behaviour is undefined.	2480	your working directory changes, then the behaviour is undefined.
1759		2481
1760	Since there is no standard kernel interface to do this, the portable	2482	Since there is no portable change notification interface available, the
1761	implementation simply calls C<stat (2)> regularly on the path to see if	2483	portable implementation simply calls C<stat(2)> regularly on the path
1762	it changed somehow. You can specify a recommended polling interval for	2484	to see if it changed somehow. You can specify a recommended polling
1763	this case. If you specify a polling interval of C<0> (highly recommended!)	2485	interval for this case. If you specify a polling interval of C<0> (highly
1764	then a I<suitable, unspecified default> value will be used (which	2486	recommended!) then a I<suitable, unspecified default> value will be used
1765	you can expect to be around five seconds, although this might change	2487	(which you can expect to be around five seconds, although this might
1766	dynamically). Libev will also impose a minimum interval which is currently	2488	change dynamically). Libev will also impose a minimum interval which is
1767	around C<0.1>, but thats usually overkill.	2489	currently around C<0.1>, but that's usually overkill.
1768		2490
1769	This watcher type is not meant for massive numbers of stat watchers,	2491	This watcher type is not meant for massive numbers of stat watchers,
1770	as even with OS-supported change notifications, this can be	2492	as even with OS-supported change notifications, this can be
1771	resource-intensive.	2493	resource-intensive.
1772		2494
1773	At the time of this writing, the only OS-specific interface implemented	2495	At the time of this writing, the only OS-specific interface implemented
1774	is the Linux inotify interface (implementing kqueue support is left as	2496	is the Linux inotify interface (implementing kqueue support is left as an
1775	an exercise for the reader. Note, however, that the author sees no way	2497	exercise for the reader. Note, however, that the author sees no way of
1776	of implementing C<ev_stat> semantics with kqueue).	2498	implementing C<ev_stat> semantics with kqueue, except as a hint).
1777		2499
1778	=head3 ABI Issues (Largefile Support)	2500	=head3 ABI Issues (Largefile Support)
1779		2501
1780	Libev by default (unless the user overrides this) uses the default	2502	Libev by default (unless the user overrides this) uses the default
1781	compilation environment, which means that on systems with large file	2503	compilation environment, which means that on systems with large file
1782	support disabled by default, you get the 32 bit version of the stat	2504	support disabled by default, you get the 32 bit version of the stat
1783	structure. When using the library from programs that change the ABI to	2505	structure. When using the library from programs that change the ABI to
1784	use 64 bit file offsets the programs will fail. In that case you have to	2506	use 64 bit file offsets the programs will fail. In that case you have to
1785	compile libev with the same flags to get binary compatibility. This is	2507	compile libev with the same flags to get binary compatibility. This is
1786	obviously the case with any flags that change the ABI, but the problem is	2508	obviously the case with any flags that change the ABI, but the problem is
1787	most noticeably disabled with ev_stat and large file support.	2509	most noticeably displayed with ev_stat and large file support.
1788		2510
1789	The solution for this is to lobby your distribution maker to make large	2511	The solution for this is to lobby your distribution maker to make large
1790	file interfaces available by default (as e.g. FreeBSD does) and not	2512	file interfaces available by default (as e.g. FreeBSD does) and not
1791	optional. Libev cannot simply switch on large file support because it has	2513	optional. Libev cannot simply switch on large file support because it has
1792	to exchange stat structures with application programs compiled using the	2514	to exchange stat structures with application programs compiled using the
1793	default compilation environment.	2515	default compilation environment.
1794		2516
1795	=head3 Inotify and Kqueue	2517	=head3 Inotify and Kqueue
1796		2518
1797	When C<inotify (7)> support has been compiled into libev (generally only	2519	When C<inotify (7)> support has been compiled into libev and present at
1798	available with Linux) and present at runtime, it will be used to speed up	2520	runtime, it will be used to speed up change detection where possible. The
1799	change detection where possible. The inotify descriptor will be created lazily	2521	inotify descriptor will be created lazily when the first C<ev_stat>
1800	when the first C<ev_stat> watcher is being started.	2522	watcher is being started.
1801		2523
1802	Inotify presence does not change the semantics of C<ev_stat> watchers	2524	Inotify presence does not change the semantics of C<ev_stat> watchers
1803	except that changes might be detected earlier, and in some cases, to avoid	2525	except that changes might be detected earlier, and in some cases, to avoid
1804	making regular C<stat> calls. Even in the presence of inotify support	2526	making regular C<stat> calls. Even in the presence of inotify support
1805	there are many cases where libev has to resort to regular C<stat> polling,	2527	there are many cases where libev has to resort to regular C<stat> polling,
1806	but as long as the path exists, libev usually gets away without polling.	2528	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2529	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2530	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2531	xfs are fully working) libev usually gets away without polling.
1807		2532
1808	There is no support for kqueue, as apparently it cannot be used to	2533	There is no support for kqueue, as apparently it cannot be used to
1809	implement this functionality, due to the requirement of having a file	2534	implement this functionality, due to the requirement of having a file
1810	descriptor open on the object at all times, and detecting renames, unlinks	2535	descriptor open on the object at all times, and detecting renames, unlinks
1811	etc. is difficult.	2536	etc. is difficult.
1812		2537
		2538	=head3 C<stat ()> is a synchronous operation
		2539
		2540	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2541	the process. The exception are C<ev_stat> watchers - those call C<stat
		2542	()>, which is a synchronous operation.
		2543
		2544	For local paths, this usually doesn't matter: unless the system is very
		2545	busy or the intervals between stat's are large, a stat call will be fast,
		2546	as the path data is usually in memory already (except when starting the
		2547	watcher).
		2548
		2549	For networked file systems, calling C<stat ()> can block an indefinite
		2550	time due to network issues, and even under good conditions, a stat call
		2551	often takes multiple milliseconds.
		2552
		2553	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2554	paths, although this is fully supported by libev.
		2555
1813	=head3 The special problem of stat time resolution	2556	=head3 The special problem of stat time resolution
1814		2557
1815	The C<stat ()> system call only supports full-second resolution portably, and	2558	The C<stat ()> system call only supports full-second resolution portably,
1816	even on systems where the resolution is higher, most file systems still	2559	and even on systems where the resolution is higher, most file systems
1817	only support whole seconds.	2560	still only support whole seconds.
1818		2561
1819	That means that, if the time is the only thing that changes, you can	2562	That means that, if the time is the only thing that changes, you can
1820	easily miss updates: on the first update, C<ev_stat> detects a change and	2563	easily miss updates: on the first update, C<ev_stat> detects a change and
1821	calls your callback, which does something. When there is another update	2564	calls your callback, which does something. When there is another update
1822	within the same second, C<ev_stat> will be unable to detect unless the	2565	within the same second, C<ev_stat> will be unable to detect unless the
…		…
1965		2708
1966	=head3 Watcher-Specific Functions and Data Members	2709	=head3 Watcher-Specific Functions and Data Members
1967		2710
1968	=over 4	2711	=over 4
1969		2712
1970	=item ev_idle_init (ev_signal *, callback)	2713	=item ev_idle_init (ev_idle *, callback)
1971		2714
1972	Initialises and configures the idle watcher - it has no parameters of any	2715	Initialises and configures the idle watcher - it has no parameters of any
1973	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2716	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1974	believe me.	2717	believe me.
1975		2718
…		…
1979		2722
1980	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2723	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1981	callback, free it. Also, use no error checking, as usual.	2724	callback, free it. Also, use no error checking, as usual.
1982		2725
1983	static void	2726	static void
1984	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2727	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1985	{	2728	{
1986	free (w);	2729	free (w);
1987	// now do something you wanted to do when the program has	2730	// now do something you wanted to do when the program has
1988	// no longer anything immediate to do.	2731	// no longer anything immediate to do.
1989	}	2732	}
1990		2733
1991	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2734	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1992	ev_idle_init (idle_watcher, idle_cb);	2735	ev_idle_init (idle_watcher, idle_cb);
1993	ev_idle_start (loop, idle_cb);	2736	ev_idle_start (loop, idle_watcher);
1994		2737
1995		2738
1996	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2739	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1997		2740
1998	Prepare and check watchers are usually (but not always) used in pairs:	2741	Prepare and check watchers are usually (but not always) used in pairs:
1999	prepare watchers get invoked before the process blocks and check watchers	2742	prepare watchers get invoked before the process blocks and check watchers
2000	afterwards.	2743	afterwards.
2001		2744
2002	You I<must not> call C<ev_loop> or similar functions that enter	2745	You I<must not> call C<ev_run> or similar functions that enter
2003	the current event loop from either C<ev_prepare> or C<ev_check>	2746	the current event loop from either C<ev_prepare> or C<ev_check>
2004	watchers. Other loops than the current one are fine, however. The	2747	watchers. Other loops than the current one are fine, however. The
2005	rationale behind this is that you do not need to check for recursion in	2748	rationale behind this is that you do not need to check for recursion in
2006	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2749	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2007	C<ev_check> so if you have one watcher of each kind they will always be	2750	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2077		2820
2078	static ev_io iow [nfd];	2821	static ev_io iow [nfd];
2079	static ev_timer tw;	2822	static ev_timer tw;
2080		2823
2081	static void	2824	static void
2082	io_cb (ev_loop *loop, ev_io *w, int revents)	2825	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2083	{	2826	{
2084	}	2827	}
2085		2828
2086	// create io watchers for each fd and a timer before blocking	2829	// create io watchers for each fd and a timer before blocking
2087	static void	2830	static void
2088	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2831	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2089	{	2832	{
2090	int timeout = 3600000;	2833	int timeout = 3600000;
2091	struct pollfd fds [nfd];	2834	struct pollfd fds [nfd];
2092	// actual code will need to loop here and realloc etc.	2835	// actual code will need to loop here and realloc etc.
2093	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2836	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2094		2837
2095	/* the callback is illegal, but won't be called as we stop during check */	2838	/* the callback is illegal, but won't be called as we stop during check */
2096	ev_timer_init (&tw, 0, timeout * 1e-3);	2839	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2097	ev_timer_start (loop, &tw);	2840	ev_timer_start (loop, &tw);
2098		2841
2099	// create one ev_io per pollfd	2842	// create one ev_io per pollfd
2100	for (int i = 0; i < nfd; ++i)	2843	for (int i = 0; i < nfd; ++i)
2101	{	2844	{
…		…
2108	}	2851	}
2109	}	2852	}
2110		2853
2111	// stop all watchers after blocking	2854	// stop all watchers after blocking
2112	static void	2855	static void
2113	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2856	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2114	{	2857	{
2115	ev_timer_stop (loop, &tw);	2858	ev_timer_stop (loop, &tw);
2116		2859
2117	for (int i = 0; i < nfd; ++i)	2860	for (int i = 0; i < nfd; ++i)
2118	{	2861	{
…		…
2175		2918
2176	if (timeout >= 0)	2919	if (timeout >= 0)
2177	// create/start timer	2920	// create/start timer
2178		2921
2179	// poll	2922	// poll
2180	ev_loop (EV_A_ 0);	2923	ev_run (EV_A_ 0);
2181		2924
2182	// stop timer again	2925	// stop timer again
2183	if (timeout >= 0)	2926	if (timeout >= 0)
2184	ev_timer_stop (EV_A_ &to);	2927	ev_timer_stop (EV_A_ &to);
2185		2928
…		…
2214	some fds have to be watched and handled very quickly (with low latency),	2957	some fds have to be watched and handled very quickly (with low latency),
2215	and even priorities and idle watchers might have too much overhead. In	2958	and even priorities and idle watchers might have too much overhead. In
2216	this case you would put all the high priority stuff in one loop and all	2959	this case you would put all the high priority stuff in one loop and all
2217	the rest in a second one, and embed the second one in the first.	2960	the rest in a second one, and embed the second one in the first.
2218		2961
2219	As long as the watcher is active, the callback will be invoked every time	2962	As long as the watcher is active, the callback will be invoked every
2220	there might be events pending in the embedded loop. The callback must then	2963	time there might be events pending in the embedded loop. The callback
2221	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2964	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2222	their callbacks (you could also start an idle watcher to give the embedded	2965	sweep and invoke their callbacks (the callback doesn't need to invoke the
2223	loop strictly lower priority for example). You can also set the callback	2966	C<ev_embed_sweep> function directly, it could also start an idle watcher
2224	to C<0>, in which case the embed watcher will automatically execute the	2967	to give the embedded loop strictly lower priority for example).
2225	embedded loop sweep.
2226		2968
2227	As long as the watcher is started it will automatically handle events. The	2969	You can also set the callback to C<0>, in which case the embed watcher
2228	callback will be invoked whenever some events have been handled. You can	2970	will automatically execute the embedded loop sweep whenever necessary.
2229	set the callback to C<0> to avoid having to specify one if you are not
2230	interested in that.
2231		2971
2232	Also, there have not currently been made special provisions for forking:	2972	Fork detection will be handled transparently while the C<ev_embed> watcher
2233	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2973	is active, i.e., the embedded loop will automatically be forked when the
2234	but you will also have to stop and restart any C<ev_embed> watchers	2974	embedding loop forks. In other cases, the user is responsible for calling
2235	yourself - but you can use a fork watcher to handle this automatically,	2975	C<ev_loop_fork> on the embedded loop.
2236	and future versions of libev might do just that.
2237		2976
2238	Unfortunately, not all backends are embeddable: only the ones returned by	2977	Unfortunately, not all backends are embeddable: only the ones returned by
2239	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2978	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2240	portable one.	2979	portable one.
2241		2980
2242	So when you want to use this feature you will always have to be prepared	2981	So when you want to use this feature you will always have to be prepared
2243	that you cannot get an embeddable loop. The recommended way to get around	2982	that you cannot get an embeddable loop. The recommended way to get around
2244	this is to have a separate variables for your embeddable loop, try to	2983	this is to have a separate variables for your embeddable loop, try to
2245	create it, and if that fails, use the normal loop for everything.	2984	create it, and if that fails, use the normal loop for everything.
		2985
		2986	=head3 C<ev_embed> and fork
		2987
		2988	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2989	automatically be applied to the embedded loop as well, so no special
		2990	fork handling is required in that case. When the watcher is not running,
		2991	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2992	as applicable.
2246		2993
2247	=head3 Watcher-Specific Functions and Data Members	2994	=head3 Watcher-Specific Functions and Data Members
2248		2995
2249	=over 4	2996	=over 4
2250		2997
…		…
2259	if you do not want that, you need to temporarily stop the embed watcher).	3006	if you do not want that, you need to temporarily stop the embed watcher).
2260		3007
2261	=item ev_embed_sweep (loop, ev_embed *)	3008	=item ev_embed_sweep (loop, ev_embed *)
2262		3009
2263	Make a single, non-blocking sweep over the embedded loop. This works	3010	Make a single, non-blocking sweep over the embedded loop. This works
2264	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3011	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2265	appropriate way for embedded loops.	3012	appropriate way for embedded loops.
2266		3013
2267	=item struct ev_loop *other [read-only]	3014	=item struct ev_loop *other [read-only]
2268		3015
2269	The embedded event loop.	3016	The embedded event loop.
…		…
2278	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	3025	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2279	used).	3026	used).
2280		3027
2281	struct ev_loop *loop_hi = ev_default_init (0);	3028	struct ev_loop *loop_hi = ev_default_init (0);
2282	struct ev_loop *loop_lo = 0;	3029	struct ev_loop *loop_lo = 0;
2283	struct ev_embed embed;	3030	ev_embed embed;
2284		3031
2285	// see if there is a chance of getting one that works	3032	// see if there is a chance of getting one that works
2286	// (remember that a flags value of 0 means autodetection)	3033	// (remember that a flags value of 0 means autodetection)
2287	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3034	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2288	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3035	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2302	kqueue implementation). Store the kqueue/socket-only event loop in	3049	kqueue implementation). Store the kqueue/socket-only event loop in
2303	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3050	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2304		3051
2305	struct ev_loop *loop = ev_default_init (0);	3052	struct ev_loop *loop = ev_default_init (0);
2306	struct ev_loop *loop_socket = 0;	3053	struct ev_loop *loop_socket = 0;
2307	struct ev_embed embed;	3054	ev_embed embed;
2308		3055
2309	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3056	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2310	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3057	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2311	{	3058	{
2312	ev_embed_init (&embed, 0, loop_socket);	3059	ev_embed_init (&embed, 0, loop_socket);
…		…
2327	event loop blocks next and before C<ev_check> watchers are being called,	3074	event loop blocks next and before C<ev_check> watchers are being called,
2328	and only in the child after the fork. If whoever good citizen calling	3075	and only in the child after the fork. If whoever good citizen calling
2329	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3076	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2330	handlers will be invoked, too, of course.	3077	handlers will be invoked, too, of course.
2331		3078
		3079	=head3 The special problem of life after fork - how is it possible?
		3080
		3081	Most uses of C<fork()> consist of forking, then some simple calls to set
		3082	up/change the process environment, followed by a call to C<exec()>. This
		3083	sequence should be handled by libev without any problems.
		3084
		3085	This changes when the application actually wants to do event handling
		3086	in the child, or both parent in child, in effect "continuing" after the
		3087	fork.
		3088
		3089	The default mode of operation (for libev, with application help to detect
		3090	forks) is to duplicate all the state in the child, as would be expected
		3091	when I<either> the parent I<or> the child process continues.
		3092
		3093	When both processes want to continue using libev, then this is usually the
		3094	wrong result. In that case, usually one process (typically the parent) is
		3095	supposed to continue with all watchers in place as before, while the other
		3096	process typically wants to start fresh, i.e. without any active watchers.
		3097
		3098	The cleanest and most efficient way to achieve that with libev is to
		3099	simply create a new event loop, which of course will be "empty", and
		3100	use that for new watchers. This has the advantage of not touching more
		3101	memory than necessary, and thus avoiding the copy-on-write, and the
		3102	disadvantage of having to use multiple event loops (which do not support
		3103	signal watchers).
		3104
		3105	When this is not possible, or you want to use the default loop for
		3106	other reasons, then in the process that wants to start "fresh", call
		3107	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3108	Destroying the default loop will "orphan" (not stop) all registered
		3109	watchers, so you have to be careful not to execute code that modifies
		3110	those watchers. Note also that in that case, you have to re-register any
		3111	signal watchers.
		3112
2332	=head3 Watcher-Specific Functions and Data Members	3113	=head3 Watcher-Specific Functions and Data Members
2333		3114
2334	=over 4	3115	=over 4
2335		3116
2336	=item ev_fork_init (ev_signal *, callback)	3117	=item ev_fork_init (ev_fork *, callback)
2337		3118
2338	Initialises and configures the fork watcher - it has no parameters of any	3119	Initialises and configures the fork watcher - it has no parameters of any
2339	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3120	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2340	believe me.	3121	really.
2341		3122
2342	=back	3123	=back
2343		3124
2344		3125
		3126	=head2 C<ev_cleanup> - even the best things end
		3127
		3128	Cleanup watchers are called just before the event loop is being destroyed
		3129	by a call to C<ev_loop_destroy>.
		3130
		3131	While there is no guarantee that the event loop gets destroyed, cleanup
		3132	watchers provide a convenient method to install cleanup hooks for your
		3133	program, worker threads and so on - you just to make sure to destroy the
		3134	loop when you want them to be invoked.
		3135
		3136	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3137	all other watchers, they do not keep a reference to the event loop (which
		3138	makes a lot of sense if you think about it). Like all other watchers, you
		3139	can call libev functions in the callback, except C<ev_cleanup_start>.
		3140
		3141	=head3 Watcher-Specific Functions and Data Members
		3142
		3143	=over 4
		3144
		3145	=item ev_cleanup_init (ev_cleanup *, callback)
		3146
		3147	Initialises and configures the cleanup watcher - it has no parameters of
		3148	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3149	pointless, I assure you.
		3150
		3151	=back
		3152
		3153	Example: Register an atexit handler to destroy the default loop, so any
		3154	cleanup functions are called.
		3155
		3156	static void
		3157	program_exits (void)
		3158	{
		3159	ev_loop_destroy (EV_DEFAULT_UC);
		3160	}
		3161
		3162	...
		3163	atexit (program_exits);
		3164
		3165
2345	=head2 C<ev_async> - how to wake up another event loop	3166	=head2 C<ev_async> - how to wake up an event loop
2346		3167
2347	In general, you cannot use an C<ev_loop> from multiple threads or other	3168	In general, you cannot use an C<ev_run> from multiple threads or other
2348	asynchronous sources such as signal handlers (as opposed to multiple event	3169	asynchronous sources such as signal handlers (as opposed to multiple event
2349	loops - those are of course safe to use in different threads).	3170	loops - those are of course safe to use in different threads).
2350		3171
2351	Sometimes, however, you need to wake up another event loop you do not	3172	Sometimes, however, you need to wake up an event loop you do not control,
2352	control, for example because it belongs to another thread. This is what	3173	for example because it belongs to another thread. This is what C<ev_async>
2353	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3174	watchers do: as long as the C<ev_async> watcher is active, you can signal
2354	can signal it by calling C<ev_async_send>, which is thread- and signal	3175	it by calling C<ev_async_send>, which is thread- and signal safe.
2355	safe.
2356		3176
2357	This functionality is very similar to C<ev_signal> watchers, as signals,	3177	This functionality is very similar to C<ev_signal> watchers, as signals,
2358	too, are asynchronous in nature, and signals, too, will be compressed	3178	too, are asynchronous in nature, and signals, too, will be compressed
2359	(i.e. the number of callback invocations may be less than the number of	3179	(i.e. the number of callback invocations may be less than the number of
2360	C<ev_async_sent> calls).	3180	C<ev_async_sent> calls).
…		…
2365	=head3 Queueing	3185	=head3 Queueing
2366		3186
2367	C<ev_async> does not support queueing of data in any way. The reason	3187	C<ev_async> does not support queueing of data in any way. The reason
2368	is that the author does not know of a simple (or any) algorithm for a	3188	is that the author does not know of a simple (or any) algorithm for a
2369	multiple-writer-single-reader queue that works in all cases and doesn't	3189	multiple-writer-single-reader queue that works in all cases and doesn't
2370	need elaborate support such as pthreads.	3190	need elaborate support such as pthreads or unportable memory access
		3191	semantics.
2371		3192
2372	That means that if you want to queue data, you have to provide your own	3193	That means that if you want to queue data, you have to provide your own
2373	queue. But at least I can tell you how to implement locking around your	3194	queue. But at least I can tell you how to implement locking around your
2374	queue:	3195	queue:
2375		3196
2376	=over 4	3197	=over 4
2377		3198
2378	=item queueing from a signal handler context	3199	=item queueing from a signal handler context
2379		3200
2380	To implement race-free queueing, you simply add to the queue in the signal	3201	To implement race-free queueing, you simply add to the queue in the signal
2381	handler but you block the signal handler in the watcher callback. Here is an example that does that for	3202	handler but you block the signal handler in the watcher callback. Here is
2382	some fictitious SIGUSR1 handler:	3203	an example that does that for some fictitious SIGUSR1 handler:
2383		3204
2384	static ev_async mysig;	3205	static ev_async mysig;
2385		3206
2386	static void	3207	static void
2387	sigusr1_handler (void)	3208	sigusr1_handler (void)
…		…
2453	=over 4	3274	=over 4
2454		3275
2455	=item ev_async_init (ev_async *, callback)	3276	=item ev_async_init (ev_async *, callback)
2456		3277
2457	Initialises and configures the async watcher - it has no parameters of any	3278	Initialises and configures the async watcher - it has no parameters of any
2458	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3279	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2459	trust me.	3280	trust me.
2460		3281
2461	=item ev_async_send (loop, ev_async *)	3282	=item ev_async_send (loop, ev_async *)
2462		3283
2463	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3284	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2464	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3285	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2465	C<ev_feed_event>, this call is safe to do from other threads, signal or	3286	C<ev_feed_event>, this call is safe to do from other threads, signal or
2466	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3287	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2467	section below on what exactly this means).	3288	section below on what exactly this means).
2468		3289
		3290	Note that, as with other watchers in libev, multiple events might get
		3291	compressed into a single callback invocation (another way to look at this
		3292	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3293	reset when the event loop detects that).
		3294
2469	This call incurs the overhead of a system call only once per loop iteration,	3295	This call incurs the overhead of a system call only once per event loop
2470	so while the overhead might be noticeable, it doesn't apply to repeated	3296	iteration, so while the overhead might be noticeable, it doesn't apply to
2471	calls to C<ev_async_send>.	3297	repeated calls to C<ev_async_send> for the same event loop.
2472		3298
2473	=item bool = ev_async_pending (ev_async *)	3299	=item bool = ev_async_pending (ev_async *)
2474		3300
2475	Returns a non-zero value when C<ev_async_send> has been called on the	3301	Returns a non-zero value when C<ev_async_send> has been called on the
2476	watcher but the event has not yet been processed (or even noted) by the	3302	watcher but the event has not yet been processed (or even noted) by the
…		…
2479	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3305	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2480	the loop iterates next and checks for the watcher to have become active,	3306	the loop iterates next and checks for the watcher to have become active,
2481	it will reset the flag again. C<ev_async_pending> can be used to very	3307	it will reset the flag again. C<ev_async_pending> can be used to very
2482	quickly check whether invoking the loop might be a good idea.	3308	quickly check whether invoking the loop might be a good idea.
2483		3309
2484	Not that this does I<not> check whether the watcher itself is pending, only	3310	Not that this does I<not> check whether the watcher itself is pending,
2485	whether it has been requested to make this watcher pending.	3311	only whether it has been requested to make this watcher pending: there
		3312	is a time window between the event loop checking and resetting the async
		3313	notification, and the callback being invoked.
2486		3314
2487	=back	3315	=back
2488		3316
2489		3317
2490	=head1 OTHER FUNCTIONS	3318	=head1 OTHER FUNCTIONS
…		…
2494	=over 4	3322	=over 4
2495		3323
2496	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3324	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2497		3325
2498	This function combines a simple timer and an I/O watcher, calls your	3326	This function combines a simple timer and an I/O watcher, calls your
2499	callback on whichever event happens first and automatically stop both	3327	callback on whichever event happens first and automatically stops both
2500	watchers. This is useful if you want to wait for a single event on an fd	3328	watchers. This is useful if you want to wait for a single event on an fd
2501	or timeout without having to allocate/configure/start/stop/free one or	3329	or timeout without having to allocate/configure/start/stop/free one or
2502	more watchers yourself.	3330	more watchers yourself.
2503		3331
2504	If C<fd> is less than 0, then no I/O watcher will be started and events	3332	If C<fd> is less than 0, then no I/O watcher will be started and the
2505	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	3333	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2506	C<events> set will be created and started.	3334	the given C<fd> and C<events> set will be created and started.
2507		3335
2508	If C<timeout> is less than 0, then no timeout watcher will be	3336	If C<timeout> is less than 0, then no timeout watcher will be
2509	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3337	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2510	repeat = 0) will be started. While C<0> is a valid timeout, it is of	3338	repeat = 0) will be started. C<0> is a valid timeout.
2511	dubious value.
2512		3339
2513	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3340	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2514	passed an C<revents> set like normal event callbacks (a combination of	3341	passed an C<revents> set like normal event callbacks (a combination of
2515	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3342	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2516	value passed to C<ev_once>:	3343	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3344	a timeout and an io event at the same time - you probably should give io
		3345	events precedence.
		3346
		3347	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2517		3348
2518	static void stdin_ready (int revents, void *arg)	3349	static void stdin_ready (int revents, void *arg)
2519	{	3350	{
		3351	if (revents & EV_READ)
		3352	/* stdin might have data for us, joy! */;
2520	if (revents & EV_TIMEOUT)	3353	else if (revents & EV_TIMER)
2521	/* doh, nothing entered */;	3354	/* doh, nothing entered */;
2522	else if (revents & EV_READ)
2523	/* stdin might have data for us, joy! */;
2524	}	3355	}
2525		3356
2526	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3357	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2527		3358
2528	=item ev_feed_event (ev_loop *, watcher *, int revents)
2529
2530	Feeds the given event set into the event loop, as if the specified event
2531	had happened for the specified watcher (which must be a pointer to an
2532	initialised but not necessarily started event watcher).
2533
2534	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3359	=item ev_feed_fd_event (loop, int fd, int revents)
2535		3360
2536	Feed an event on the given fd, as if a file descriptor backend detected	3361	Feed an event on the given fd, as if a file descriptor backend detected
2537	the given events it.	3362	the given events it.
2538		3363
2539	=item ev_feed_signal_event (ev_loop *loop, int signum)	3364	=item ev_feed_signal_event (loop, int signum)
2540		3365
2541	Feed an event as if the given signal occurred (C<loop> must be the default	3366	Feed an event as if the given signal occurred (C<loop> must be the default
2542	loop!).	3367	loop!).
2543		3368
2544	=back	3369	=back
2545		3370
2546		3371
		3372	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3373
		3374	This section explains some common idioms that are not immediately
		3375	obvious. Note that examples are sprinkled over the whole manual, and this
		3376	section only contains stuff that wouldn't fit anywhere else.
		3377
		3378	=over 4
		3379
		3380	=item Model/nested event loop invocations and exit conditions.
		3381
		3382	Often (especially in GUI toolkits) there are places where you have
		3383	I<modal> interaction, which is most easily implemented by recursively
		3384	invoking C<ev_run>.
		3385
		3386	This brings the problem of exiting - a callback might want to finish the
		3387	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3388	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3389	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3390	other combination: In these cases, C<ev_break> will not work alone.
		3391
		3392	The solution is to maintain "break this loop" variable for each C<ev_run>
		3393	invocation, and use a loop around C<ev_run> until the condition is
		3394	triggered, using C<EVRUN_ONCE>:
		3395
		3396	// main loop
		3397	int exit_main_loop = 0;
		3398
		3399	while (!exit_main_loop)
		3400	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3401
		3402	// in a model watcher
		3403	int exit_nested_loop = 0;
		3404
		3405	while (!exit_nested_loop)
		3406	ev_run (EV_A_ EVRUN_ONCE);
		3407
		3408	To exit from any of these loops, just set the corresponding exit variable:
		3409
		3410	// exit modal loop
		3411	exit_nested_loop = 1;
		3412
		3413	// exit main program, after modal loop is finished
		3414	exit_main_loop = 1;
		3415
		3416	// exit both
		3417	exit_main_loop = exit_nested_loop = 1;
		3418
		3419	=back
		3420
		3421
2547	=head1 LIBEVENT EMULATION	3422	=head1 LIBEVENT EMULATION
2548		3423
2549	Libev offers a compatibility emulation layer for libevent. It cannot	3424	Libev offers a compatibility emulation layer for libevent. It cannot
2550	emulate the internals of libevent, so here are some usage hints:	3425	emulate the internals of libevent, so here are some usage hints:
2551		3426
2552	=over 4	3427	=over 4
		3428
		3429	=item * Only the libevent-1.4.1-beta API is being emulated.
		3430
		3431	This was the newest libevent version available when libev was implemented,
		3432	and is still mostly uncanged in 2010.
2553		3433
2554	=item * Use it by including <event.h>, as usual.	3434	=item * Use it by including <event.h>, as usual.
2555		3435
2556	=item * The following members are fully supported: ev_base, ev_callback,	3436	=item * The following members are fully supported: ev_base, ev_callback,
2557	ev_arg, ev_fd, ev_res, ev_events.	3437	ev_arg, ev_fd, ev_res, ev_events.
…		…
2563	=item * Priorities are not currently supported. Initialising priorities	3443	=item * Priorities are not currently supported. Initialising priorities
2564	will fail and all watchers will have the same priority, even though there	3444	will fail and all watchers will have the same priority, even though there
2565	is an ev_pri field.	3445	is an ev_pri field.
2566		3446
2567	=item * In libevent, the last base created gets the signals, in libev, the	3447	=item * In libevent, the last base created gets the signals, in libev, the
2568	first base created (== the default loop) gets the signals.	3448	base that registered the signal gets the signals.
2569		3449
2570	=item * Other members are not supported.	3450	=item * Other members are not supported.
2571		3451
2572	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3452	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2573	to use the libev header file and library.	3453	to use the libev header file and library.
…		…
2592	Care has been taken to keep the overhead low. The only data member the C++	3472	Care has been taken to keep the overhead low. The only data member the C++
2593	classes add (compared to plain C-style watchers) is the event loop pointer	3473	classes add (compared to plain C-style watchers) is the event loop pointer
2594	that the watcher is associated with (or no additional members at all if	3474	that the watcher is associated with (or no additional members at all if
2595	you disable C<EV_MULTIPLICITY> when embedding libev).	3475	you disable C<EV_MULTIPLICITY> when embedding libev).
2596		3476
2597	Currently, functions, and static and non-static member functions can be	3477	Currently, functions, static and non-static member functions and classes
2598	used as callbacks. Other types should be easy to add as long as they only	3478	with C<operator ()> can be used as callbacks. Other types should be easy
2599	need one additional pointer for context. If you need support for other	3479	to add as long as they only need one additional pointer for context. If
2600	types of functors please contact the author (preferably after implementing	3480	you need support for other types of functors please contact the author
2601	it).	3481	(preferably after implementing it).
2602		3482
2603	Here is a list of things available in the C<ev> namespace:	3483	Here is a list of things available in the C<ev> namespace:
2604		3484
2605	=over 4	3485	=over 4
2606		3486
…		…
2624		3504
2625	=over 4	3505	=over 4
2626		3506
2627	=item ev::TYPE::TYPE ()	3507	=item ev::TYPE::TYPE ()
2628		3508
2629	=item ev::TYPE::TYPE (struct ev_loop *)	3509	=item ev::TYPE::TYPE (loop)
2630		3510
2631	=item ev::TYPE::~TYPE	3511	=item ev::TYPE::~TYPE
2632		3512
2633	The constructor (optionally) takes an event loop to associate the watcher	3513	The constructor (optionally) takes an event loop to associate the watcher
2634	with. If it is omitted, it will use C<EV_DEFAULT>.	3514	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2666		3546
2667	myclass obj;	3547	myclass obj;
2668	ev::io iow;	3548	ev::io iow;
2669	iow.set <myclass, &myclass::io_cb> (&obj);	3549	iow.set <myclass, &myclass::io_cb> (&obj);
2670		3550
		3551	=item w->set (object *)
		3552
		3553	This is a variation of a method callback - leaving out the method to call
		3554	will default the method to C<operator ()>, which makes it possible to use
		3555	functor objects without having to manually specify the C<operator ()> all
		3556	the time. Incidentally, you can then also leave out the template argument
		3557	list.
		3558
		3559	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3560	int revents)>.
		3561
		3562	See the method-C<set> above for more details.
		3563
		3564	Example: use a functor object as callback.
		3565
		3566	struct myfunctor
		3567	{
		3568	void operator() (ev::io &w, int revents)
		3569	{
		3570	...
		3571	}
		3572	}
		3573
		3574	myfunctor f;
		3575
		3576	ev::io w;
		3577	w.set (&f);
		3578
2671	=item w->set<function> (void *data = 0)	3579	=item w->set<function> (void *data = 0)
2672		3580
2673	Also sets a callback, but uses a static method or plain function as	3581	Also sets a callback, but uses a static method or plain function as
2674	callback. The optional C<data> argument will be stored in the watcher's	3582	callback. The optional C<data> argument will be stored in the watcher's
2675	C<data> member and is free for you to use.	3583	C<data> member and is free for you to use.
…		…
2681	Example: Use a plain function as callback.	3589	Example: Use a plain function as callback.
2682		3590
2683	static void io_cb (ev::io &w, int revents) { }	3591	static void io_cb (ev::io &w, int revents) { }
2684	iow.set <io_cb> ();	3592	iow.set <io_cb> ();
2685		3593
2686	=item w->set (struct ev_loop *)	3594	=item w->set (loop)
2687		3595
2688	Associates a different C<struct ev_loop> with this watcher. You can only	3596	Associates a different C<struct ev_loop> with this watcher. You can only
2689	do this when the watcher is inactive (and not pending either).	3597	do this when the watcher is inactive (and not pending either).
2690		3598
2691	=item w->set ([arguments])	3599	=item w->set ([arguments])
2692		3600
2693	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3601	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
2694	called at least once. Unlike the C counterpart, an active watcher gets	3602	method or a suitable start method must be called at least once. Unlike the
2695	automatically stopped and restarted when reconfiguring it with this	3603	C counterpart, an active watcher gets automatically stopped and restarted
2696	method.	3604	when reconfiguring it with this method.
2697		3605
2698	=item w->start ()	3606	=item w->start ()
2699		3607
2700	Starts the watcher. Note that there is no C<loop> argument, as the	3608	Starts the watcher. Note that there is no C<loop> argument, as the
2701	constructor already stores the event loop.	3609	constructor already stores the event loop.
2702		3610
		3611	=item w->start ([arguments])
		3612
		3613	Instead of calling C<set> and C<start> methods separately, it is often
		3614	convenient to wrap them in one call. Uses the same type of arguments as
		3615	the configure C<set> method of the watcher.
		3616
2703	=item w->stop ()	3617	=item w->stop ()
2704		3618
2705	Stops the watcher if it is active. Again, no C<loop> argument.	3619	Stops the watcher if it is active. Again, no C<loop> argument.
2706		3620
2707	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3621	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2719		3633
2720	=back	3634	=back
2721		3635
2722	=back	3636	=back
2723		3637
2724	Example: Define a class with an IO and idle watcher, start one of them in	3638	Example: Define a class with two I/O and idle watchers, start the I/O
2725	the constructor.	3639	watchers in the constructor.
2726		3640
2727	class myclass	3641	class myclass
2728	{	3642	{
2729	ev::io io ; void io_cb (ev::io &w, int revents);	3643	ev::io io ; void io_cb (ev::io &w, int revents);
		3644	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
2730	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3645	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2731		3646
2732	myclass (int fd)	3647	myclass (int fd)
2733	{	3648	{
2734	io .set <myclass, &myclass::io_cb > (this);	3649	io .set <myclass, &myclass::io_cb > (this);
		3650	io2 .set <myclass, &myclass::io2_cb > (this);
2735	idle.set <myclass, &myclass::idle_cb> (this);	3651	idle.set <myclass, &myclass::idle_cb> (this);
2736		3652
2737	io.start (fd, ev::READ);	3653	io.set (fd, ev::WRITE); // configure the watcher
		3654	io.start (); // start it whenever convenient
		3655
		3656	io2.start (fd, ev::READ); // set + start in one call
2738	}	3657	}
2739	};	3658	};
2740		3659
2741		3660
2742	=head1 OTHER LANGUAGE BINDINGS	3661	=head1 OTHER LANGUAGE BINDINGS
…		…
2761	L<http://software.schmorp.de/pkg/EV>.	3680	L<http://software.schmorp.de/pkg/EV>.
2762		3681
2763	=item Python	3682	=item Python
2764		3683
2765	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3684	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2766	seems to be quite complete and well-documented. Note, however, that the	3685	seems to be quite complete and well-documented.
2767	patch they require for libev is outright dangerous as it breaks the ABI
2768	for everybody else, and therefore, should never be applied in an installed
2769	libev (if python requires an incompatible ABI then it needs to embed
2770	libev).
2771		3686
2772	=item Ruby	3687	=item Ruby
2773		3688
2774	Tony Arcieri has written a ruby extension that offers access to a subset	3689	Tony Arcieri has written a ruby extension that offers access to a subset
2775	of the libev API and adds file handle abstractions, asynchronous DNS and	3690	of the libev API and adds file handle abstractions, asynchronous DNS and
2776	more on top of it. It can be found via gem servers. Its homepage is at	3691	more on top of it. It can be found via gem servers. Its homepage is at
2777	L<http://rev.rubyforge.org/>.	3692	L<http://rev.rubyforge.org/>.
2778		3693
		3694	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3695	makes rev work even on mingw.
		3696
		3697	=item Haskell
		3698
		3699	A haskell binding to libev is available at
		3700	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3701
2779	=item D	3702	=item D
2780		3703
2781	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3704	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2782	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3705	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3706
		3707	=item Ocaml
		3708
		3709	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3710	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3711
		3712	=item Lua
		3713
		3714	Brian Maher has written a partial interface to libev for lua (at the
		3715	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3716	L<http://github.com/brimworks/lua-ev>.
2783		3717
2784	=back	3718	=back
2785		3719
2786		3720
2787	=head1 MACRO MAGIC	3721	=head1 MACRO MAGIC
…		…
2801	loop argument"). The C<EV_A> form is used when this is the sole argument,	3735	loop argument"). The C<EV_A> form is used when this is the sole argument,
2802	C<EV_A_> is used when other arguments are following. Example:	3736	C<EV_A_> is used when other arguments are following. Example:
2803		3737
2804	ev_unref (EV_A);	3738	ev_unref (EV_A);
2805	ev_timer_add (EV_A_ watcher);	3739	ev_timer_add (EV_A_ watcher);
2806	ev_loop (EV_A_ 0);	3740	ev_run (EV_A_ 0);
2807		3741
2808	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3742	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2809	which is often provided by the following macro.	3743	which is often provided by the following macro.
2810		3744
2811	=item C<EV_P>, C<EV_P_>	3745	=item C<EV_P>, C<EV_P_>
…		…
2851	}	3785	}
2852		3786
2853	ev_check check;	3787	ev_check check;
2854	ev_check_init (&check, check_cb);	3788	ev_check_init (&check, check_cb);
2855	ev_check_start (EV_DEFAULT_ &check);	3789	ev_check_start (EV_DEFAULT_ &check);
2856	ev_loop (EV_DEFAULT_ 0);	3790	ev_run (EV_DEFAULT_ 0);
2857		3791
2858	=head1 EMBEDDING	3792	=head1 EMBEDDING
2859		3793
2860	Libev can (and often is) directly embedded into host	3794	Libev can (and often is) directly embedded into host
2861	applications. Examples of applications that embed it include the Deliantra	3795	applications. Examples of applications that embed it include the Deliantra
…		…
2888		3822
2889	#define EV_STANDALONE 1	3823	#define EV_STANDALONE 1
2890	#include "ev.h"	3824	#include "ev.h"
2891		3825
2892	Both header files and implementation files can be compiled with a C++	3826	Both header files and implementation files can be compiled with a C++
2893	compiler (at least, thats a stated goal, and breakage will be treated	3827	compiler (at least, that's a stated goal, and breakage will be treated
2894	as a bug).	3828	as a bug).
2895		3829
2896	You need the following files in your source tree, or in a directory	3830	You need the following files in your source tree, or in a directory
2897	in your include path (e.g. in libev/ when using -Ilibev):	3831	in your include path (e.g. in libev/ when using -Ilibev):
2898		3832
…		…
2941	libev.m4	3875	libev.m4
2942		3876
2943	=head2 PREPROCESSOR SYMBOLS/MACROS	3877	=head2 PREPROCESSOR SYMBOLS/MACROS
2944		3878
2945	Libev can be configured via a variety of preprocessor symbols you have to	3879	Libev can be configured via a variety of preprocessor symbols you have to
2946	define before including any of its files. The default in the absence of	3880	define before including (or compiling) any of its files. The default in
2947	autoconf is documented for every option.	3881	the absence of autoconf is documented for every option.
		3882
		3883	Symbols marked with "(h)" do not change the ABI, and can have different
		3884	values when compiling libev vs. including F<ev.h>, so it is permissible
		3885	to redefine them before including F<ev.h> without breaking compatibility
		3886	to a compiled library. All other symbols change the ABI, which means all
		3887	users of libev and the libev code itself must be compiled with compatible
		3888	settings.
2948		3889
2949	=over 4	3890	=over 4
2950		3891
		3892	=item EV_COMPAT3 (h)
		3893
		3894	Backwards compatibility is a major concern for libev. This is why this
		3895	release of libev comes with wrappers for the functions and symbols that
		3896	have been renamed between libev version 3 and 4.
		3897
		3898	You can disable these wrappers (to test compatibility with future
		3899	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		3900	sources. This has the additional advantage that you can drop the C<struct>
		3901	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		3902	typedef in that case.
		3903
		3904	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		3905	and in some even more future version the compatibility code will be
		3906	removed completely.
		3907
2951	=item EV_STANDALONE	3908	=item EV_STANDALONE (h)
2952		3909
2953	Must always be C<1> if you do not use autoconf configuration, which	3910	Must always be C<1> if you do not use autoconf configuration, which
2954	keeps libev from including F<config.h>, and it also defines dummy	3911	keeps libev from including F<config.h>, and it also defines dummy
2955	implementations for some libevent functions (such as logging, which is not	3912	implementations for some libevent functions (such as logging, which is not
2956	supported). It will also not define any of the structs usually found in	3913	supported). It will also not define any of the structs usually found in
2957	F<event.h> that are not directly supported by the libev core alone.	3914	F<event.h> that are not directly supported by the libev core alone.
2958		3915
		3916	In standalone mode, libev will still try to automatically deduce the
		3917	configuration, but has to be more conservative.
		3918
2959	=item EV_USE_MONOTONIC	3919	=item EV_USE_MONOTONIC
2960		3920
2961	If defined to be C<1>, libev will try to detect the availability of the	3921	If defined to be C<1>, libev will try to detect the availability of the
2962	monotonic clock option at both compile time and runtime. Otherwise no use	3922	monotonic clock option at both compile time and runtime. Otherwise no
2963	of the monotonic clock option will be attempted. If you enable this, you	3923	use of the monotonic clock option will be attempted. If you enable this,
2964	usually have to link against librt or something similar. Enabling it when	3924	you usually have to link against librt or something similar. Enabling it
2965	the functionality isn't available is safe, though, although you have	3925	when the functionality isn't available is safe, though, although you have
2966	to make sure you link against any libraries where the C<clock_gettime>	3926	to make sure you link against any libraries where the C<clock_gettime>
2967	function is hiding in (often F<-lrt>).	3927	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2968		3928
2969	=item EV_USE_REALTIME	3929	=item EV_USE_REALTIME
2970		3930
2971	If defined to be C<1>, libev will try to detect the availability of the	3931	If defined to be C<1>, libev will try to detect the availability of the
2972	real-time clock option at compile time (and assume its availability at	3932	real-time clock option at compile time (and assume its availability
2973	runtime if successful). Otherwise no use of the real-time clock option will	3933	at runtime if successful). Otherwise no use of the real-time clock
2974	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3934	option will be attempted. This effectively replaces C<gettimeofday>
2975	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3935	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2976	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3936	correctness. See the note about libraries in the description of
		3937	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3938	C<EV_USE_CLOCK_SYSCALL>.
		3939
		3940	=item EV_USE_CLOCK_SYSCALL
		3941
		3942	If defined to be C<1>, libev will try to use a direct syscall instead
		3943	of calling the system-provided C<clock_gettime> function. This option
		3944	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3945	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3946	programs needlessly. Using a direct syscall is slightly slower (in
		3947	theory), because no optimised vdso implementation can be used, but avoids
		3948	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3949	higher, as it simplifies linking (no need for C<-lrt>).
2977		3950
2978	=item EV_USE_NANOSLEEP	3951	=item EV_USE_NANOSLEEP
2979		3952
2980	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3953	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2981	and will use it for delays. Otherwise it will use C<select ()>.	3954	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2997		3970
2998	=item EV_SELECT_USE_FD_SET	3971	=item EV_SELECT_USE_FD_SET
2999		3972
3000	If defined to C<1>, then the select backend will use the system C<fd_set>	3973	If defined to C<1>, then the select backend will use the system C<fd_set>
3001	structure. This is useful if libev doesn't compile due to a missing	3974	structure. This is useful if libev doesn't compile due to a missing
3002	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3975	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3003	exotic systems. This usually limits the range of file descriptors to some	3976	on exotic systems. This usually limits the range of file descriptors to
3004	low limit such as 1024 or might have other limitations (winsocket only	3977	some low limit such as 1024 or might have other limitations (winsocket
3005	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3978	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3006	influence the size of the C<fd_set> used.	3979	configures the maximum size of the C<fd_set>.
3007		3980
3008	=item EV_SELECT_IS_WINSOCKET	3981	=item EV_SELECT_IS_WINSOCKET
3009		3982
3010	When defined to C<1>, the select backend will assume that	3983	When defined to C<1>, the select backend will assume that
3011	select/socket/connect etc. don't understand file descriptors but	3984	select/socket/connect etc. don't understand file descriptors but
…		…
3013	be used is the winsock select). This means that it will call	3986	be used is the winsock select). This means that it will call
3014	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3987	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3015	it is assumed that all these functions actually work on fds, even	3988	it is assumed that all these functions actually work on fds, even
3016	on win32. Should not be defined on non-win32 platforms.	3989	on win32. Should not be defined on non-win32 platforms.
3017		3990
3018	=item EV_FD_TO_WIN32_HANDLE	3991	=item EV_FD_TO_WIN32_HANDLE(fd)
3019		3992
3020	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3993	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3021	file descriptors to socket handles. When not defining this symbol (the	3994	file descriptors to socket handles. When not defining this symbol (the
3022	default), then libev will call C<_get_osfhandle>, which is usually	3995	default), then libev will call C<_get_osfhandle>, which is usually
3023	correct. In some cases, programs use their own file descriptor management,	3996	correct. In some cases, programs use their own file descriptor management,
3024	in which case they can provide this function to map fds to socket handles.	3997	in which case they can provide this function to map fds to socket handles.
		3998
		3999	=item EV_WIN32_HANDLE_TO_FD(handle)
		4000
		4001	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4002	using the standard C<_open_osfhandle> function. For programs implementing
		4003	their own fd to handle mapping, overwriting this function makes it easier
		4004	to do so. This can be done by defining this macro to an appropriate value.
		4005
		4006	=item EV_WIN32_CLOSE_FD(fd)
		4007
		4008	If programs implement their own fd to handle mapping on win32, then this
		4009	macro can be used to override the C<close> function, useful to unregister
		4010	file descriptors again. Note that the replacement function has to close
		4011	the underlying OS handle.
3025		4012
3026	=item EV_USE_POLL	4013	=item EV_USE_POLL
3027		4014
3028	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4015	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3029	backend. Otherwise it will be enabled on non-win32 platforms. It	4016	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3076	as well as for signal and thread safety in C<ev_async> watchers.	4063	as well as for signal and thread safety in C<ev_async> watchers.
3077		4064
3078	In the absence of this define, libev will use C<sig_atomic_t volatile>	4065	In the absence of this define, libev will use C<sig_atomic_t volatile>
3079	(from F<signal.h>), which is usually good enough on most platforms.	4066	(from F<signal.h>), which is usually good enough on most platforms.
3080		4067
3081	=item EV_H	4068	=item EV_H (h)
3082		4069
3083	The name of the F<ev.h> header file used to include it. The default if	4070	The name of the F<ev.h> header file used to include it. The default if
3084	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4071	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3085	used to virtually rename the F<ev.h> header file in case of conflicts.	4072	used to virtually rename the F<ev.h> header file in case of conflicts.
3086		4073
3087	=item EV_CONFIG_H	4074	=item EV_CONFIG_H (h)
3088		4075
3089	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4076	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3090	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4077	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3091	C<EV_H>, above.	4078	C<EV_H>, above.
3092		4079
3093	=item EV_EVENT_H	4080	=item EV_EVENT_H (h)
3094		4081
3095	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4082	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3096	of how the F<event.h> header can be found, the default is C<"event.h">.	4083	of how the F<event.h> header can be found, the default is C<"event.h">.
3097		4084
3098	=item EV_PROTOTYPES	4085	=item EV_PROTOTYPES (h)
3099		4086
3100	If defined to be C<0>, then F<ev.h> will not define any function	4087	If defined to be C<0>, then F<ev.h> will not define any function
3101	prototypes, but still define all the structs and other symbols. This is	4088	prototypes, but still define all the structs and other symbols. This is
3102	occasionally useful if you want to provide your own wrapper functions	4089	occasionally useful if you want to provide your own wrapper functions
3103	around libev functions.	4090	around libev functions.
…		…
3125	fine.	4112	fine.
3126		4113
3127	If your embedding application does not need any priorities, defining these	4114	If your embedding application does not need any priorities, defining these
3128	both to C<0> will save some memory and CPU.	4115	both to C<0> will save some memory and CPU.
3129		4116
3130	=item EV_PERIODIC_ENABLE	4117	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4118	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4119	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3131		4120
3132	If undefined or defined to be C<1>, then periodic timers are supported. If	4121	If undefined or defined to be C<1> (and the platform supports it), then
3133	defined to be C<0>, then they are not. Disabling them saves a few kB of	4122	the respective watcher type is supported. If defined to be C<0>, then it
3134	code.	4123	is not. Disabling watcher types mainly saves code size.
3135		4124
3136	=item EV_IDLE_ENABLE	4125	=item EV_FEATURES
3137
3138	If undefined or defined to be C<1>, then idle watchers are supported. If
3139	defined to be C<0>, then they are not. Disabling them saves a few kB of
3140	code.
3141
3142	=item EV_EMBED_ENABLE
3143
3144	If undefined or defined to be C<1>, then embed watchers are supported. If
3145	defined to be C<0>, then they are not. Embed watchers rely on most other
3146	watcher types, which therefore must not be disabled.
3147
3148	=item EV_STAT_ENABLE
3149
3150	If undefined or defined to be C<1>, then stat watchers are supported. If
3151	defined to be C<0>, then they are not.
3152
3153	=item EV_FORK_ENABLE
3154
3155	If undefined or defined to be C<1>, then fork watchers are supported. If
3156	defined to be C<0>, then they are not.
3157
3158	=item EV_ASYNC_ENABLE
3159
3160	If undefined or defined to be C<1>, then async watchers are supported. If
3161	defined to be C<0>, then they are not.
3162
3163	=item EV_MINIMAL
3164		4126
3165	If you need to shave off some kilobytes of code at the expense of some	4127	If you need to shave off some kilobytes of code at the expense of some
3166	speed, define this symbol to C<1>. Currently this is used to override some	4128	speed (but with the full API), you can define this symbol to request
3167	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4129	certain subsets of functionality. The default is to enable all features
3168	much smaller 2-heap for timer management over the default 4-heap.	4130	that can be enabled on the platform.
		4131
		4132	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4133	with some broad features you want) and then selectively re-enable
		4134	additional parts you want, for example if you want everything minimal,
		4135	but multiple event loop support, async and child watchers and the poll
		4136	backend, use this:
		4137
		4138	#define EV_FEATURES 0
		4139	#define EV_MULTIPLICITY 1
		4140	#define EV_USE_POLL 1
		4141	#define EV_CHILD_ENABLE 1
		4142	#define EV_ASYNC_ENABLE 1
		4143
		4144	The actual value is a bitset, it can be a combination of the following
		4145	values:
		4146
		4147	=over 4
		4148
		4149	=item C<1> - faster/larger code
		4150
		4151	Use larger code to speed up some operations.
		4152
		4153	Currently this is used to override some inlining decisions (enlarging the
		4154	code size by roughly 30% on amd64).
		4155
		4156	When optimising for size, use of compiler flags such as C<-Os> with
		4157	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4158	assertions.
		4159
		4160	=item C<2> - faster/larger data structures
		4161
		4162	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4163	hash table sizes and so on. This will usually further increase code size
		4164	and can additionally have an effect on the size of data structures at
		4165	runtime.
		4166
		4167	=item C<4> - full API configuration
		4168
		4169	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4170	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4171
		4172	=item C<8> - full API
		4173
		4174	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4175	details on which parts of the API are still available without this
		4176	feature, and do not complain if this subset changes over time.
		4177
		4178	=item C<16> - enable all optional watcher types
		4179
		4180	Enables all optional watcher types. If you want to selectively enable
		4181	only some watcher types other than I/O and timers (e.g. prepare,
		4182	embed, async, child...) you can enable them manually by defining
		4183	C<EV_watchertype_ENABLE> to C<1> instead.
		4184
		4185	=item C<32> - enable all backends
		4186
		4187	This enables all backends - without this feature, you need to enable at
		4188	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4189
		4190	=item C<64> - enable OS-specific "helper" APIs
		4191
		4192	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4193	default.
		4194
		4195	=back
		4196
		4197	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4198	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4199	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4200	watchers, timers and monotonic clock support.
		4201
		4202	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4203	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4204	your program might be left out as well - a binary starting a timer and an
		4205	I/O watcher then might come out at only 5Kb.
		4206
		4207	=item EV_AVOID_STDIO
		4208
		4209	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4210	functions (printf, scanf, perror etc.). This will increase the code size
		4211	somewhat, but if your program doesn't otherwise depend on stdio and your
		4212	libc allows it, this avoids linking in the stdio library which is quite
		4213	big.
		4214
		4215	Note that error messages might become less precise when this option is
		4216	enabled.
		4217
		4218	=item EV_NSIG
		4219
		4220	The highest supported signal number, +1 (or, the number of
		4221	signals): Normally, libev tries to deduce the maximum number of signals
		4222	automatically, but sometimes this fails, in which case it can be
		4223	specified. Also, using a lower number than detected (C<32> should be
		4224	good for about any system in existence) can save some memory, as libev
		4225	statically allocates some 12-24 bytes per signal number.
3169		4226
3170	=item EV_PID_HASHSIZE	4227	=item EV_PID_HASHSIZE
3171		4228
3172	C<ev_child> watchers use a small hash table to distribute workload by	4229	C<ev_child> watchers use a small hash table to distribute workload by
3173	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4230	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3174	than enough. If you need to manage thousands of children you might want to	4231	usually more than enough. If you need to manage thousands of children you
3175	increase this value (I<must> be a power of two).	4232	might want to increase this value (I<must> be a power of two).
3176		4233
3177	=item EV_INOTIFY_HASHSIZE	4234	=item EV_INOTIFY_HASHSIZE
3178		4235
3179	C<ev_stat> watchers use a small hash table to distribute workload by	4236	C<ev_stat> watchers use a small hash table to distribute workload by
3180	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4237	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3181	usually more than enough. If you need to manage thousands of C<ev_stat>	4238	disabled), usually more than enough. If you need to manage thousands of
3182	watchers you might want to increase this value (I<must> be a power of	4239	C<ev_stat> watchers you might want to increase this value (I<must> be a
3183	two).	4240	power of two).
3184		4241
3185	=item EV_USE_4HEAP	4242	=item EV_USE_4HEAP
3186		4243
3187	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4244	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3188	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4245	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3189	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4246	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3190	faster performance with many (thousands) of watchers.	4247	faster performance with many (thousands) of watchers.
3191		4248
3192	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4249	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3193	(disabled).	4250	will be C<0>.
3194		4251
3195	=item EV_HEAP_CACHE_AT	4252	=item EV_HEAP_CACHE_AT
3196		4253
3197	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4254	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3198	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4255	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3199	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4256	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3200	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4257	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3201	but avoids random read accesses on heap changes. This improves performance	4258	but avoids random read accesses on heap changes. This improves performance
3202	noticeably with many (hundreds) of watchers.	4259	noticeably with many (hundreds) of watchers.
3203		4260
3204	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4261	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3205	(disabled).	4262	will be C<0>.
3206		4263
3207	=item EV_VERIFY	4264	=item EV_VERIFY
3208		4265
3209	Controls how much internal verification (see C<ev_loop_verify ()>) will	4266	Controls how much internal verification (see C<ev_verify ()>) will
3210	be done: If set to C<0>, no internal verification code will be compiled	4267	be done: If set to C<0>, no internal verification code will be compiled
3211	in. If set to C<1>, then verification code will be compiled in, but not	4268	in. If set to C<1>, then verification code will be compiled in, but not
3212	called. If set to C<2>, then the internal verification code will be	4269	called. If set to C<2>, then the internal verification code will be
3213	called once per loop, which can slow down libev. If set to C<3>, then the	4270	called once per loop, which can slow down libev. If set to C<3>, then the
3214	verification code will be called very frequently, which will slow down	4271	verification code will be called very frequently, which will slow down
3215	libev considerably.	4272	libev considerably.
3216		4273
3217	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4274	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3218	C<0>.	4275	will be C<0>.
3219		4276
3220	=item EV_COMMON	4277	=item EV_COMMON
3221		4278
3222	By default, all watchers have a C<void *data> member. By redefining	4279	By default, all watchers have a C<void *data> member. By redefining
3223	this macro to a something else you can include more and other types of	4280	this macro to something else you can include more and other types of
3224	members. You have to define it each time you include one of the files,	4281	members. You have to define it each time you include one of the files,
3225	though, and it must be identical each time.	4282	though, and it must be identical each time.
3226		4283
3227	For example, the perl EV module uses something like this:	4284	For example, the perl EV module uses something like this:
3228		4285
…		…
3240	and the way callbacks are invoked and set. Must expand to a struct member	4297	and the way callbacks are invoked and set. Must expand to a struct member
3241	definition and a statement, respectively. See the F<ev.h> header file for	4298	definition and a statement, respectively. See the F<ev.h> header file for
3242	their default definitions. One possible use for overriding these is to	4299	their default definitions. One possible use for overriding these is to
3243	avoid the C<struct ev_loop *> as first argument in all cases, or to use	4300	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3244	method calls instead of plain function calls in C++.	4301	method calls instead of plain function calls in C++.
		4302
		4303	=back
3245		4304
3246	=head2 EXPORTED API SYMBOLS	4305	=head2 EXPORTED API SYMBOLS
3247		4306
3248	If you need to re-export the API (e.g. via a DLL) and you need a list of	4307	If you need to re-export the API (e.g. via a DLL) and you need a list of
3249	exported symbols, you can use the provided F<Symbol.*> files which list	4308	exported symbols, you can use the provided F<Symbol.*> files which list
…		…
3279	file.	4338	file.
3280		4339
3281	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4340	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3282	that everybody includes and which overrides some configure choices:	4341	that everybody includes and which overrides some configure choices:
3283		4342
3284	#define EV_MINIMAL 1	4343	#define EV_FEATURES 8
3285	#define EV_USE_POLL 0	4344	#define EV_USE_SELECT 1
3286	#define EV_MULTIPLICITY 0
3287	#define EV_PERIODIC_ENABLE 0	4345	#define EV_PREPARE_ENABLE 1
		4346	#define EV_IDLE_ENABLE 1
3288	#define EV_STAT_ENABLE 0	4347	#define EV_SIGNAL_ENABLE 1
3289	#define EV_FORK_ENABLE 0	4348	#define EV_CHILD_ENABLE 1
		4349	#define EV_USE_STDEXCEPT 0
3290	#define EV_CONFIG_H <config.h>	4350	#define EV_CONFIG_H <config.h>
3291	#define EV_MINPRI 0
3292	#define EV_MAXPRI 0
3293		4351
3294	#include "ev++.h"	4352	#include "ev++.h"
3295		4353
3296	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4354	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3297		4355
3298	#include "ev_cpp.h"	4356	#include "ev_cpp.h"
3299	#include "ev.c"	4357	#include "ev.c"
3300		4358
		4359	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3301		4360
3302	=head1 THREADS AND COROUTINES	4361	=head2 THREADS AND COROUTINES
3303		4362
3304	=head2 THREADS	4363	=head3 THREADS
3305		4364
3306	Libev itself is thread-safe (unless the opposite is specifically	4365	All libev functions are reentrant and thread-safe unless explicitly
3307	documented for a function), but it uses no locking itself. This means that	4366	documented otherwise, but libev implements no locking itself. This means
3308	you can use as many loops as you want in parallel, as long as only one	4367	that you can use as many loops as you want in parallel, as long as there
3309	thread ever calls into one libev function with the same loop parameter:	4368	are no concurrent calls into any libev function with the same loop
		4369	parameter (C<ev_default_*> calls have an implicit default loop parameter,
3310	libev guarantees that different event loops share no data structures that	4370	of course): libev guarantees that different event loops share no data
3311	need locking.	4371	structures that need any locking.
3312		4372
3313	Or to put it differently: calls with different loop parameters can be done	4373	Or to put it differently: calls with different loop parameters can be done
3314	concurrently from multiple threads, calls with the same loop parameter	4374	concurrently from multiple threads, calls with the same loop parameter
3315	must be done serially (but can be done from different threads, as long as	4375	must be done serially (but can be done from different threads, as long as
3316	only one thread ever is inside a call at any point in time, e.g. by using	4376	only one thread ever is inside a call at any point in time, e.g. by using
3317	a mutex per loop).	4377	a mutex per loop).
3318		4378
3319	Specifically to support threads (and signal handlers), libev implements	4379	Specifically to support threads (and signal handlers), libev implements
3320	so-called C<ev_async> watchers, which allow some limited form of	4380	so-called C<ev_async> watchers, which allow some limited form of
3321	concurrency on the same event loop.	4381	concurrency on the same event loop, namely waking it up "from the
		4382	outside".
3322		4383
3323	If you want to know which design (one loop, locking, or multiple loops	4384	If you want to know which design (one loop, locking, or multiple loops
3324	without or something else still) is best for your problem, then I cannot	4385	without or something else still) is best for your problem, then I cannot
3325	help you. I can give some generic advice however:	4386	help you, but here is some generic advice:
3326		4387
3327	=over 4	4388	=over 4
3328		4389
3329	=item * most applications have a main thread: use the default libev loop	4390	=item * most applications have a main thread: use the default libev loop
3330	in that thread, or create a separate thread running only the default loop.	4391	in that thread, or create a separate thread running only the default loop.
…		…
3354	default loop and triggering an C<ev_async> watcher from the default loop	4415	default loop and triggering an C<ev_async> watcher from the default loop
3355	watcher callback into the event loop interested in the signal.	4416	watcher callback into the event loop interested in the signal.
3356		4417
3357	=back	4418	=back
3358		4419
		4420	=head4 THREAD LOCKING EXAMPLE
		4421
		4422	Here is a fictitious example of how to run an event loop in a different
		4423	thread than where callbacks are being invoked and watchers are
		4424	created/added/removed.
		4425
		4426	For a real-world example, see the C<EV::Loop::Async> perl module,
		4427	which uses exactly this technique (which is suited for many high-level
		4428	languages).
		4429
		4430	The example uses a pthread mutex to protect the loop data, a condition
		4431	variable to wait for callback invocations, an async watcher to notify the
		4432	event loop thread and an unspecified mechanism to wake up the main thread.
		4433
		4434	First, you need to associate some data with the event loop:
		4435
		4436	typedef struct {
		4437	mutex_t lock; /* global loop lock */
		4438	ev_async async_w;
		4439	thread_t tid;
		4440	cond_t invoke_cv;
		4441	} userdata;
		4442
		4443	void prepare_loop (EV_P)
		4444	{
		4445	// for simplicity, we use a static userdata struct.
		4446	static userdata u;
		4447
		4448	ev_async_init (&u->async_w, async_cb);
		4449	ev_async_start (EV_A_ &u->async_w);
		4450
		4451	pthread_mutex_init (&u->lock, 0);
		4452	pthread_cond_init (&u->invoke_cv, 0);
		4453
		4454	// now associate this with the loop
		4455	ev_set_userdata (EV_A_ u);
		4456	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4457	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4458
		4459	// then create the thread running ev_loop
		4460	pthread_create (&u->tid, 0, l_run, EV_A);
		4461	}
		4462
		4463	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4464	solely to wake up the event loop so it takes notice of any new watchers
		4465	that might have been added:
		4466
		4467	static void
		4468	async_cb (EV_P_ ev_async *w, int revents)
		4469	{
		4470	// just used for the side effects
		4471	}
		4472
		4473	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4474	protecting the loop data, respectively.
		4475
		4476	static void
		4477	l_release (EV_P)
		4478	{
		4479	userdata *u = ev_userdata (EV_A);
		4480	pthread_mutex_unlock (&u->lock);
		4481	}
		4482
		4483	static void
		4484	l_acquire (EV_P)
		4485	{
		4486	userdata *u = ev_userdata (EV_A);
		4487	pthread_mutex_lock (&u->lock);
		4488	}
		4489
		4490	The event loop thread first acquires the mutex, and then jumps straight
		4491	into C<ev_run>:
		4492
		4493	void *
		4494	l_run (void *thr_arg)
		4495	{
		4496	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4497
		4498	l_acquire (EV_A);
		4499	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4500	ev_run (EV_A_ 0);
		4501	l_release (EV_A);
		4502
		4503	return 0;
		4504	}
		4505
		4506	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4507	signal the main thread via some unspecified mechanism (signals? pipe
		4508	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4509	have been called (in a while loop because a) spurious wakeups are possible
		4510	and b) skipping inter-thread-communication when there are no pending
		4511	watchers is very beneficial):
		4512
		4513	static void
		4514	l_invoke (EV_P)
		4515	{
		4516	userdata *u = ev_userdata (EV_A);
		4517
		4518	while (ev_pending_count (EV_A))
		4519	{
		4520	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4521	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4522	}
		4523	}
		4524
		4525	Now, whenever the main thread gets told to invoke pending watchers, it
		4526	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4527	thread to continue:
		4528
		4529	static void
		4530	real_invoke_pending (EV_P)
		4531	{
		4532	userdata *u = ev_userdata (EV_A);
		4533
		4534	pthread_mutex_lock (&u->lock);
		4535	ev_invoke_pending (EV_A);
		4536	pthread_cond_signal (&u->invoke_cv);
		4537	pthread_mutex_unlock (&u->lock);
		4538	}
		4539
		4540	Whenever you want to start/stop a watcher or do other modifications to an
		4541	event loop, you will now have to lock:
		4542
		4543	ev_timer timeout_watcher;
		4544	userdata *u = ev_userdata (EV_A);
		4545
		4546	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4547
		4548	pthread_mutex_lock (&u->lock);
		4549	ev_timer_start (EV_A_ &timeout_watcher);
		4550	ev_async_send (EV_A_ &u->async_w);
		4551	pthread_mutex_unlock (&u->lock);
		4552
		4553	Note that sending the C<ev_async> watcher is required because otherwise
		4554	an event loop currently blocking in the kernel will have no knowledge
		4555	about the newly added timer. By waking up the loop it will pick up any new
		4556	watchers in the next event loop iteration.
		4557
3359	=head2 COROUTINES	4558	=head3 COROUTINES
3360		4559
3361	Libev is much more accommodating to coroutines ("cooperative threads"):	4560	Libev is very accommodating to coroutines ("cooperative threads"):
3362	libev fully supports nesting calls to it's functions from different	4561	libev fully supports nesting calls to its functions from different
3363	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4562	coroutines (e.g. you can call C<ev_run> on the same loop from two
3364	different coroutines and switch freely between both coroutines running the	4563	different coroutines, and switch freely between both coroutines running
3365	loop, as long as you don't confuse yourself). The only exception is that	4564	the loop, as long as you don't confuse yourself). The only exception is
3366	you must not do this from C<ev_periodic> reschedule callbacks.	4565	that you must not do this from C<ev_periodic> reschedule callbacks.
3367		4566
3368	Care has been taken to ensure that libev does not keep local state inside	4567	Care has been taken to ensure that libev does not keep local state inside
3369	C<ev_loop>, and other calls do not usually allow coroutine switches.	4568	C<ev_run>, and other calls do not usually allow for coroutine switches as
		4569	they do not call any callbacks.
3370		4570
		4571	=head2 COMPILER WARNINGS
3371		4572
3372	=head1 COMPLEXITIES	4573	Depending on your compiler and compiler settings, you might get no or a
		4574	lot of warnings when compiling libev code. Some people are apparently
		4575	scared by this.
3373		4576
3374	In this section the complexities of (many of) the algorithms used inside	4577	However, these are unavoidable for many reasons. For one, each compiler
3375	libev will be explained. For complexity discussions about backends see the	4578	has different warnings, and each user has different tastes regarding
3376	documentation for C<ev_default_init>.	4579	warning options. "Warn-free" code therefore cannot be a goal except when
		4580	targeting a specific compiler and compiler-version.
3377		4581
3378	All of the following are about amortised time: If an array needs to be	4582	Another reason is that some compiler warnings require elaborate
3379	extended, libev needs to realloc and move the whole array, but this	4583	workarounds, or other changes to the code that make it less clear and less
3380	happens asymptotically never with higher number of elements, so O(1) might	4584	maintainable.
3381	mean it might do a lengthy realloc operation in rare cases, but on average
3382	it is much faster and asymptotically approaches constant time.
3383		4585
3384	=over 4	4586	And of course, some compiler warnings are just plain stupid, or simply
		4587	wrong (because they don't actually warn about the condition their message
		4588	seems to warn about). For example, certain older gcc versions had some
		4589	warnings that resulted in an extreme number of false positives. These have
		4590	been fixed, but some people still insist on making code warn-free with
		4591	such buggy versions.
3385		4592
3386	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	4593	While libev is written to generate as few warnings as possible,
		4594	"warn-free" code is not a goal, and it is recommended not to build libev
		4595	with any compiler warnings enabled unless you are prepared to cope with
		4596	them (e.g. by ignoring them). Remember that warnings are just that:
		4597	warnings, not errors, or proof of bugs.
3387		4598
3388	This means that, when you have a watcher that triggers in one hour and
3389	there are 100 watchers that would trigger before that then inserting will
3390	have to skip roughly seven (C<ld 100>) of these watchers.
3391		4599
3392	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	4600	=head2 VALGRIND
3393		4601
3394	That means that changing a timer costs less than removing/adding them	4602	Valgrind has a special section here because it is a popular tool that is
3395	as only the relative motion in the event queue has to be paid for.	4603	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3396		4604
3397	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	4605	If you think you found a bug (memory leak, uninitialised data access etc.)
		4606	in libev, then check twice: If valgrind reports something like:
3398		4607
3399	These just add the watcher into an array or at the head of a list.	4608	==2274== definitely lost: 0 bytes in 0 blocks.
		4609	==2274== possibly lost: 0 bytes in 0 blocks.
		4610	==2274== still reachable: 256 bytes in 1 blocks.
3400		4611
3401	=item Stopping check/prepare/idle/fork/async watchers: O(1)	4612	Then there is no memory leak, just as memory accounted to global variables
		4613	is not a memleak - the memory is still being referenced, and didn't leak.
3402		4614
3403	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	4615	Similarly, under some circumstances, valgrind might report kernel bugs
		4616	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		4617	although an acceptable workaround has been found here), or it might be
		4618	confused.
3404		4619
3405	These watchers are stored in lists then need to be walked to find the	4620	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3406	correct watcher to remove. The lists are usually short (you don't usually	4621	make it into some kind of religion.
3407	have many watchers waiting for the same fd or signal).
3408		4622
3409	=item Finding the next timer in each loop iteration: O(1)	4623	If you are unsure about something, feel free to contact the mailing list
		4624	with the full valgrind report and an explanation on why you think this
		4625	is a bug in libev (best check the archives, too :). However, don't be
		4626	annoyed when you get a brisk "this is no bug" answer and take the chance
		4627	of learning how to interpret valgrind properly.
3410		4628
3411	By virtue of using a binary or 4-heap, the next timer is always found at a	4629	If you need, for some reason, empty reports from valgrind for your project
3412	fixed position in the storage array.	4630	I suggest using suppression lists.
3413		4631
3414	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3415		4632
3416	A change means an I/O watcher gets started or stopped, which requires	4633	=head1 PORTABILITY NOTES
3417	libev to recalculate its status (and possibly tell the kernel, depending
3418	on backend and whether C<ev_io_set> was used).
3419		4634
3420	=item Activating one watcher (putting it into the pending state): O(1)	4635	=head2 GNU/LINUX 32 BIT LIMITATIONS
3421		4636
3422	=item Priority handling: O(number_of_priorities)	4637	GNU/Linux is the only common platform that supports 64 bit file/large file
		4638	interfaces but I<disables> them by default.
3423		4639
3424	Priorities are implemented by allocating some space for each	4640	That means that libev compiled in the default environment doesn't support
3425	priority. When doing priority-based operations, libev usually has to	4641	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
3426	linearly search all the priorities, but starting/stopping and activating
3427	watchers becomes O(1) with respect to priority handling.
3428		4642
3429	=item Sending an ev_async: O(1)	4643	Unfortunately, many programs try to work around this GNU/Linux issue
		4644	by enabling the large file API, which makes them incompatible with the
		4645	standard libev compiled for their system.
3430		4646
3431	=item Processing ev_async_send: O(number_of_async_watchers)	4647	Likewise, libev cannot enable the large file API itself as this would
		4648	suddenly make it incompatible to the default compile time environment,
		4649	i.e. all programs not using special compile switches.
3432		4650
3433	=item Processing signals: O(max_signal_number)	4651	=head2 OS/X AND DARWIN BUGS
3434		4652
3435	Sending involves a system call I<iff> there were no other C<ev_async_send>	4653	The whole thing is a bug if you ask me - basically any system interface
3436	calls in the current loop iteration. Checking for async and signal events	4654	you touch is broken, whether it is locales, poll, kqueue or even the
3437	involves iterating over all running async watchers or all signal numbers.	4655	OpenGL drivers.
3438		4656
3439	=back	4657	=head3 C<kqueue> is buggy
3440		4658
		4659	The kqueue syscall is broken in all known versions - most versions support
		4660	only sockets, many support pipes.
3441		4661
		4662	Libev tries to work around this by not using C<kqueue> by default on this
		4663	rotten platform, but of course you can still ask for it when creating a
		4664	loop - embedding a socket-only kqueue loop into a select-based one is
		4665	probably going to work well.
		4666
		4667	=head3 C<poll> is buggy
		4668
		4669	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4670	implementation by something calling C<kqueue> internally around the 10.5.6
		4671	release, so now C<kqueue> I<and> C<poll> are broken.
		4672
		4673	Libev tries to work around this by not using C<poll> by default on
		4674	this rotten platform, but of course you can still ask for it when creating
		4675	a loop.
		4676
		4677	=head3 C<select> is buggy
		4678
		4679	All that's left is C<select>, and of course Apple found a way to fuck this
		4680	one up as well: On OS/X, C<select> actively limits the number of file
		4681	descriptors you can pass in to 1024 - your program suddenly crashes when
		4682	you use more.
		4683
		4684	There is an undocumented "workaround" for this - defining
		4685	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4686	work on OS/X.
		4687
		4688	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4689
		4690	=head3 C<errno> reentrancy
		4691
		4692	The default compile environment on Solaris is unfortunately so
		4693	thread-unsafe that you can't even use components/libraries compiled
		4694	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4695	defined by default. A valid, if stupid, implementation choice.
		4696
		4697	If you want to use libev in threaded environments you have to make sure
		4698	it's compiled with C<_REENTRANT> defined.
		4699
		4700	=head3 Event port backend
		4701
		4702	The scalable event interface for Solaris is called "event
		4703	ports". Unfortunately, this mechanism is very buggy in all major
		4704	releases. If you run into high CPU usage, your program freezes or you get
		4705	a large number of spurious wakeups, make sure you have all the relevant
		4706	and latest kernel patches applied. No, I don't know which ones, but there
		4707	are multiple ones to apply, and afterwards, event ports actually work
		4708	great.
		4709
		4710	If you can't get it to work, you can try running the program by setting
		4711	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4712	C<select> backends.
		4713
		4714	=head2 AIX POLL BUG
		4715
		4716	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4717	this by trying to avoid the poll backend altogether (i.e. it's not even
		4718	compiled in), which normally isn't a big problem as C<select> works fine
		4719	with large bitsets on AIX, and AIX is dead anyway.
		4720
3442	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4721	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4722
		4723	=head3 General issues
3443		4724
3444	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4725	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3445	requires, and its I/O model is fundamentally incompatible with the POSIX	4726	requires, and its I/O model is fundamentally incompatible with the POSIX
3446	model. Libev still offers limited functionality on this platform in	4727	model. Libev still offers limited functionality on this platform in
3447	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4728	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3448	descriptors. This only applies when using Win32 natively, not when using	4729	descriptors. This only applies when using Win32 natively, not when using
3449	e.g. cygwin.	4730	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4731	as every compielr comes with a slightly differently broken/incompatible
		4732	environment.
3450		4733
3451	Lifting these limitations would basically require the full	4734	Lifting these limitations would basically require the full
3452	re-implementation of the I/O system. If you are into these kinds of	4735	re-implementation of the I/O system. If you are into this kind of thing,
3453	things, then note that glib does exactly that for you in a very portable	4736	then note that glib does exactly that for you in a very portable way (note
3454	way (note also that glib is the slowest event library known to man).	4737	also that glib is the slowest event library known to man).
3455		4738
3456	There is no supported compilation method available on windows except	4739	There is no supported compilation method available on windows except
3457	embedding it into other applications.	4740	embedding it into other applications.
		4741
		4742	Sensible signal handling is officially unsupported by Microsoft - libev
		4743	tries its best, but under most conditions, signals will simply not work.
3458		4744
3459	Not a libev limitation but worth mentioning: windows apparently doesn't	4745	Not a libev limitation but worth mentioning: windows apparently doesn't
3460	accept large writes: instead of resulting in a partial write, windows will	4746	accept large writes: instead of resulting in a partial write, windows will
3461	either accept everything or return C<ENOBUFS> if the buffer is too large,	4747	either accept everything or return C<ENOBUFS> if the buffer is too large,
3462	so make sure you only write small amounts into your sockets (less than a	4748	so make sure you only write small amounts into your sockets (less than a
…		…
3467	the abysmal performance of winsockets, using a large number of sockets	4753	the abysmal performance of winsockets, using a large number of sockets
3468	is not recommended (and not reasonable). If your program needs to use	4754	is not recommended (and not reasonable). If your program needs to use
3469	more than a hundred or so sockets, then likely it needs to use a totally	4755	more than a hundred or so sockets, then likely it needs to use a totally
3470	different implementation for windows, as libev offers the POSIX readiness	4756	different implementation for windows, as libev offers the POSIX readiness
3471	notification model, which cannot be implemented efficiently on windows	4757	notification model, which cannot be implemented efficiently on windows
3472	(Microsoft monopoly games).	4758	(due to Microsoft monopoly games).
3473		4759
3474	A typical way to use libev under windows is to embed it (see the embedding	4760	A typical way to use libev under windows is to embed it (see the embedding
3475	section for details) and use the following F<evwrap.h> header file instead	4761	section for details) and use the following F<evwrap.h> header file instead
3476	of F<ev.h>:	4762	of F<ev.h>:
3477		4763
…		…
3484	you do I<not> compile the F<ev.c> or any other embedded source files!):	4770	you do I<not> compile the F<ev.c> or any other embedded source files!):
3485		4771
3486	#include "evwrap.h"	4772	#include "evwrap.h"
3487	#include "ev.c"	4773	#include "ev.c"
3488		4774
3489	=over 4
3490
3491	=item The winsocket select function	4775	=head3 The winsocket C<select> function
3492		4776
3493	The winsocket C<select> function doesn't follow POSIX in that it	4777	The winsocket C<select> function doesn't follow POSIX in that it
3494	requires socket I<handles> and not socket I<file descriptors> (it is	4778	requires socket I<handles> and not socket I<file descriptors> (it is
3495	also extremely buggy). This makes select very inefficient, and also	4779	also extremely buggy). This makes select very inefficient, and also
3496	requires a mapping from file descriptors to socket handles (the Microsoft	4780	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3505	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4789	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3506		4790
3507	Note that winsockets handling of fd sets is O(n), so you can easily get a	4791	Note that winsockets handling of fd sets is O(n), so you can easily get a
3508	complexity in the O(n²) range when using win32.	4792	complexity in the O(n²) range when using win32.
3509		4793
3510	=item Limited number of file descriptors	4794	=head3 Limited number of file descriptors
3511		4795
3512	Windows has numerous arbitrary (and low) limits on things.	4796	Windows has numerous arbitrary (and low) limits on things.
3513		4797
3514	Early versions of winsocket's select only supported waiting for a maximum	4798	Early versions of winsocket's select only supported waiting for a maximum
3515	of C<64> handles (probably owning to the fact that all windows kernels	4799	of C<64> handles (probably owning to the fact that all windows kernels
3516	can only wait for C<64> things at the same time internally; Microsoft	4800	can only wait for C<64> things at the same time internally; Microsoft
3517	recommends spawning a chain of threads and wait for 63 handles and the	4801	recommends spawning a chain of threads and wait for 63 handles and the
3518	previous thread in each. Great).	4802	previous thread in each. Sounds great!).
3519		4803
3520	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4804	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3521	to some high number (e.g. C<2048>) before compiling the winsocket select	4805	to some high number (e.g. C<2048>) before compiling the winsocket select
3522	call (which might be in libev or elsewhere, for example, perl does its own	4806	call (which might be in libev or elsewhere, for example, perl and many
3523	select emulation on windows).	4807	other interpreters do their own select emulation on windows).
3524		4808
3525	Another limit is the number of file descriptors in the Microsoft runtime	4809	Another limit is the number of file descriptors in the Microsoft runtime
3526	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4810	libraries, which by default is C<64> (there must be a hidden I<64>
3527	or something like this inside Microsoft). You can increase this by calling	4811	fetish or something like this inside Microsoft). You can increase this
3528	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4812	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3529	arbitrary limit), but is broken in many versions of the Microsoft runtime	4813	(another arbitrary limit), but is broken in many versions of the Microsoft
3530	libraries.
3531
3532	This might get you to about C<512> or C<2048> sockets (depending on	4814	runtime libraries. This might get you to about C<512> or C<2048> sockets
3533	windows version and/or the phase of the moon). To get more, you need to	4815	(depending on windows version and/or the phase of the moon). To get more,
3534	wrap all I/O functions and provide your own fd management, but the cost of	4816	you need to wrap all I/O functions and provide your own fd management, but
3535	calling select (O(n²)) will likely make this unworkable.	4817	the cost of calling select (O(n²)) will likely make this unworkable.
3536		4818
3537	=back
3538
3539
3540	=head1 PORTABILITY REQUIREMENTS	4819	=head2 PORTABILITY REQUIREMENTS
3541		4820
3542	In addition to a working ISO-C implementation, libev relies on a few	4821	In addition to a working ISO-C implementation and of course the
3543	additional extensions:	4822	backend-specific APIs, libev relies on a few additional extensions:
3544		4823
3545	=over 4	4824	=over 4
3546		4825
3547	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	4826	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3548	calling conventions regardless of C<ev_watcher_type *>.	4827	calling conventions regardless of C<ev_watcher_type *>.
…		…
3550	Libev assumes not only that all watcher pointers have the same internal	4829	Libev assumes not only that all watcher pointers have the same internal
3551	structure (guaranteed by POSIX but not by ISO C for example), but it also	4830	structure (guaranteed by POSIX but not by ISO C for example), but it also
3552	assumes that the same (machine) code can be used to call any watcher	4831	assumes that the same (machine) code can be used to call any watcher
3553	callback: The watcher callbacks have different type signatures, but libev	4832	callback: The watcher callbacks have different type signatures, but libev
3554	calls them using an C<ev_watcher *> internally.	4833	calls them using an C<ev_watcher *> internally.
		4834
		4835	=item pointer accesses must be thread-atomic
		4836
		4837	Accessing a pointer value must be atomic, it must both be readable and
		4838	writable in one piece - this is the case on all current architectures.
3555		4839
3556	=item C<sig_atomic_t volatile> must be thread-atomic as well	4840	=item C<sig_atomic_t volatile> must be thread-atomic as well
3557		4841
3558	The type C<sig_atomic_t volatile> (or whatever is defined as	4842	The type C<sig_atomic_t volatile> (or whatever is defined as
3559	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	4843	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
3573	except the initial one, and run the default loop in the initial thread as	4857	except the initial one, and run the default loop in the initial thread as
3574	well.	4858	well.
3575		4859
3576	=item C<long> must be large enough for common memory allocation sizes	4860	=item C<long> must be large enough for common memory allocation sizes
3577		4861
3578	To improve portability and simplify using libev, libev uses C<long>	4862	To improve portability and simplify its API, libev uses C<long> internally
3579	internally instead of C<size_t> when allocating its data structures. On	4863	instead of C<size_t> when allocating its data structures. On non-POSIX
3580	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4864	systems (Microsoft...) this might be unexpectedly low, but is still at
3581	is still at least 31 bits everywhere, which is enough for hundreds of	4865	least 31 bits everywhere, which is enough for hundreds of millions of
3582	millions of watchers.	4866	watchers.
3583		4867
3584	=item C<double> must hold a time value in seconds with enough accuracy	4868	=item C<double> must hold a time value in seconds with enough accuracy
3585		4869
3586	The type C<double> is used to represent timestamps. It is required to	4870	The type C<double> is used to represent timestamps. It is required to
3587	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4871	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3588	enough for at least into the year 4000. This requirement is fulfilled by	4872	good enough for at least into the year 4000 with millisecond accuracy
		4873	(the design goal for libev). This requirement is overfulfilled by
3589	implementations implementing IEEE 754 (basically all existing ones).	4874	implementations using IEEE 754, which is basically all existing ones. With
		4875	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
3590		4876
3591	=back	4877	=back
3592		4878
3593	If you know of other additional requirements drop me a note.	4879	If you know of other additional requirements drop me a note.
3594		4880
3595		4881
3596	=head1 COMPILER WARNINGS	4882	=head1 ALGORITHMIC COMPLEXITIES
3597		4883
3598	Depending on your compiler and compiler settings, you might get no or a	4884	In this section the complexities of (many of) the algorithms used inside
3599	lot of warnings when compiling libev code. Some people are apparently	4885	libev will be documented. For complexity discussions about backends see
3600	scared by this.	4886	the documentation for C<ev_default_init>.
3601		4887
3602	However, these are unavoidable for many reasons. For one, each compiler	4888	All of the following are about amortised time: If an array needs to be
3603	has different warnings, and each user has different tastes regarding	4889	extended, libev needs to realloc and move the whole array, but this
3604	warning options. "Warn-free" code therefore cannot be a goal except when	4890	happens asymptotically rarer with higher number of elements, so O(1) might
3605	targeting a specific compiler and compiler-version.	4891	mean that libev does a lengthy realloc operation in rare cases, but on
		4892	average it is much faster and asymptotically approaches constant time.
3606		4893
3607	Another reason is that some compiler warnings require elaborate	4894	=over 4
3608	workarounds, or other changes to the code that make it less clear and less
3609	maintainable.
3610		4895
3611	And of course, some compiler warnings are just plain stupid, or simply	4896	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3612	wrong (because they don't actually warn about the condition their message
3613	seems to warn about).
3614		4897
3615	While libev is written to generate as few warnings as possible,	4898	This means that, when you have a watcher that triggers in one hour and
3616	"warn-free" code is not a goal, and it is recommended not to build libev	4899	there are 100 watchers that would trigger before that, then inserting will
3617	with any compiler warnings enabled unless you are prepared to cope with	4900	have to skip roughly seven (C<ld 100>) of these watchers.
3618	them (e.g. by ignoring them). Remember that warnings are just that:
3619	warnings, not errors, or proof of bugs.
3620		4901
		4902	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3621		4903
3622	=head1 VALGRIND	4904	That means that changing a timer costs less than removing/adding them,
		4905	as only the relative motion in the event queue has to be paid for.
3623		4906
3624	Valgrind has a special section here because it is a popular tool that is	4907	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3625	highly useful, but valgrind reports are very hard to interpret.
3626		4908
3627	If you think you found a bug (memory leak, uninitialised data access etc.)	4909	These just add the watcher into an array or at the head of a list.
3628	in libev, then check twice: If valgrind reports something like:
3629		4910
3630	==2274== definitely lost: 0 bytes in 0 blocks.	4911	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3631	==2274== possibly lost: 0 bytes in 0 blocks.
3632	==2274== still reachable: 256 bytes in 1 blocks.
3633		4912
3634	Then there is no memory leak. Similarly, under some circumstances,	4913	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3635	valgrind might report kernel bugs as if it were a bug in libev, or it
3636	might be confused (it is a very good tool, but only a tool).
3637		4914
3638	If you are unsure about something, feel free to contact the mailing list	4915	These watchers are stored in lists, so they need to be walked to find the
3639	with the full valgrind report and an explanation on why you think this is	4916	correct watcher to remove. The lists are usually short (you don't usually
3640	a bug in libev. However, don't be annoyed when you get a brisk "this is	4917	have many watchers waiting for the same fd or signal: one is typical, two
3641	no bug" answer and take the chance of learning how to interpret valgrind	4918	is rare).
3642	properly.
3643		4919
3644	If you need, for some reason, empty reports from valgrind for your project	4920	=item Finding the next timer in each loop iteration: O(1)
3645	I suggest using suppression lists.
3646		4921
		4922	By virtue of using a binary or 4-heap, the next timer is always found at a
		4923	fixed position in the storage array.
		4924
		4925	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4926
		4927	A change means an I/O watcher gets started or stopped, which requires
		4928	libev to recalculate its status (and possibly tell the kernel, depending
		4929	on backend and whether C<ev_io_set> was used).
		4930
		4931	=item Activating one watcher (putting it into the pending state): O(1)
		4932
		4933	=item Priority handling: O(number_of_priorities)
		4934
		4935	Priorities are implemented by allocating some space for each
		4936	priority. When doing priority-based operations, libev usually has to
		4937	linearly search all the priorities, but starting/stopping and activating
		4938	watchers becomes O(1) with respect to priority handling.
		4939
		4940	=item Sending an ev_async: O(1)
		4941
		4942	=item Processing ev_async_send: O(number_of_async_watchers)
		4943
		4944	=item Processing signals: O(max_signal_number)
		4945
		4946	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4947	calls in the current loop iteration. Checking for async and signal events
		4948	involves iterating over all running async watchers or all signal numbers.
		4949
		4950	=back
		4951
		4952
		4953	=head1 PORTING FROM LIBEV 3.X TO 4.X
		4954
		4955	The major version 4 introduced some incompatible changes to the API.
		4956
		4957	At the moment, the C<ev.h> header file provides compatibility definitions
		4958	for all changes, so most programs should still compile. The compatibility
		4959	layer might be removed in later versions of libev, so better update to the
		4960	new API early than late.
		4961
		4962	=over 4
		4963
		4964	=item C<EV_COMPAT3> backwards compatibility mechanism
		4965
		4966	The backward compatibility mechanism can be controlled by
		4967	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		4968	section.
		4969
		4970	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		4971
		4972	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		4973
		4974	ev_loop_destroy (EV_DEFAULT_UC);
		4975	ev_loop_fork (EV_DEFAULT);
		4976
		4977	=item function/symbol renames
		4978
		4979	A number of functions and symbols have been renamed:
		4980
		4981	ev_loop => ev_run
		4982	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		4983	EVLOOP_ONESHOT => EVRUN_ONCE
		4984
		4985	ev_unloop => ev_break
		4986	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		4987	EVUNLOOP_ONE => EVBREAK_ONE
		4988	EVUNLOOP_ALL => EVBREAK_ALL
		4989
		4990	EV_TIMEOUT => EV_TIMER
		4991
		4992	ev_loop_count => ev_iteration
		4993	ev_loop_depth => ev_depth
		4994	ev_loop_verify => ev_verify
		4995
		4996	Most functions working on C<struct ev_loop> objects don't have an
		4997	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		4998	associated constants have been renamed to not collide with the C<struct
		4999	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5000	as all other watcher types. Note that C<ev_loop_fork> is still called
		5001	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5002	typedef.
		5003
		5004	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5005
		5006	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5007	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5008	and work, but the library code will of course be larger.
		5009
		5010	=back
		5011
		5012
		5013	=head1 GLOSSARY
		5014
		5015	=over 4
		5016
		5017	=item active
		5018
		5019	A watcher is active as long as it has been started and not yet stopped.
		5020	See L<WATCHER STATES> for details.
		5021
		5022	=item application
		5023
		5024	In this document, an application is whatever is using libev.
		5025
		5026	=item backend
		5027
		5028	The part of the code dealing with the operating system interfaces.
		5029
		5030	=item callback
		5031
		5032	The address of a function that is called when some event has been
		5033	detected. Callbacks are being passed the event loop, the watcher that
		5034	received the event, and the actual event bitset.
		5035
		5036	=item callback/watcher invocation
		5037
		5038	The act of calling the callback associated with a watcher.
		5039
		5040	=item event
		5041
		5042	A change of state of some external event, such as data now being available
		5043	for reading on a file descriptor, time having passed or simply not having
		5044	any other events happening anymore.
		5045
		5046	In libev, events are represented as single bits (such as C<EV_READ> or
		5047	C<EV_TIMER>).
		5048
		5049	=item event library
		5050
		5051	A software package implementing an event model and loop.
		5052
		5053	=item event loop
		5054
		5055	An entity that handles and processes external events and converts them
		5056	into callback invocations.
		5057
		5058	=item event model
		5059
		5060	The model used to describe how an event loop handles and processes
		5061	watchers and events.
		5062
		5063	=item pending
		5064
		5065	A watcher is pending as soon as the corresponding event has been
		5066	detected. See L<WATCHER STATES> for details.
		5067
		5068	=item real time
		5069
		5070	The physical time that is observed. It is apparently strictly monotonic :)
		5071
		5072	=item wall-clock time
		5073
		5074	The time and date as shown on clocks. Unlike real time, it can actually
		5075	be wrong and jump forwards and backwards, e.g. when the you adjust your
		5076	clock.
		5077
		5078	=item watcher
		5079
		5080	A data structure that describes interest in certain events. Watchers need
		5081	to be started (attached to an event loop) before they can receive events.
		5082
		5083	=back
3647		5084
3648	=head1 AUTHOR	5085	=head1 AUTHOR
3649		5086
3650	Marc Lehmann <libev@schmorp.de>.	5087	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5088	Magnusson and Emanuele Giaquinta.
3651		5089

Diff Legend

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